phosphocreatine and Brain-Ischemia

Creatine (Cr) is essential in safeguarding ATP levels and in moving ATP from its production site (mitochondria) to the cytoplasmic regions where it is used. Moreover, it has effects unrelated to energy metabolism, such as free radical scavenging, antiapoptotic action, and protection against excitotoxicity. Recent research has studied Cr-derived compounds (Cr benzyl ester and phos-pho-Cr-magnesium complex) that reproduce the neuroprotective effects of Cr while better crossing the neuronal plasma membrane and, hopefully, the blood-brain barrier (BBB). Intracellular levels of Cr can be increased by incubation with Cr or some of its derivatives, and this increase is protective against anoxic or ischemic damage. A large amount of experimental evidence shows that pretreatment with Cr is capable of reducing the damage induced by ischemia or anoxia in both heart and brain, and that such treatment may also be useful even after stroke or myocardial infarction (MI) has already occurred. Cr has been safely administered to patients affected by several neurological diseases, yet it has never been tested in human brain ischemia, the condition where its rationale is strongest. Phosphocreatine (PCr) has been administered after human MI, where it proved to be safe and probably helpful. Cr should be tested in the prophylactic protection against human brain ischemia and either Cr or PCr should be further tested in MI. Moreover, Cr- or PCr-derived drugs should be developed in order to overcome these molecules' limitations in crossing the BBB and the cell plasma membrane.

Topics: Blood-Brain Barrier; Brain Ischemia; Cardiotonic Agents; Creatine; Female; Forecasting; Humans; In Vitro Techniques; Male; Myocardial Infarction; Myocardial Ischemia; Neuroprotective Agents; Phosphocreatine; Stroke; Treatment Outcome

Phosphocreatine can to some extent compensate for the lack of ATP synthesis that is caused in the brain by deprivation of oxygen or glucose. Treatment of in vitro rat hippocampal slices with creatine increases the neuronal store of phosphocreatine. In this way it increases the resistance of the tissue to anoxic or ischemic damage. In in vitro brain slices pretreatment with creatine delays anoxic depolarization (AD) and prevents the irreversible loss of evoked potentials that is caused by transient anoxia, although it seems so far not to be active against milder, not AD-mediated, damage. Although creatine crosses poorly the blood-brain barrier, its administration in vivo at high doses through the intracerebroventricular or the intraperitoneal way causes an increase of cerebral phosphocreatine that has been shown to be of therapeutic value in vitro. Accordingly, preliminary data show that creatine pretreatment decreases ischemic damage in vivo.

Topics: Adenosine Triphosphate; Animals; Blood-Brain Barrier; Brain Ischemia; Creatine; Glucose; Hippocampus; Hypoxia, Brain; Neurons; Neuroprotective Agents; Oxygen; Phosphocreatine

Serum metabonomic profiles of the model of focal cerebral ischemia reperfusion is established with the suture-occluded method by Longa to study the effect of ginsenosides. In this study, 48 rats were randomly divided into six groups: sham-operated group, pathological model group, positive drug group(6 mg·kg~(-1)·d~(-1)) and high, medium, low-dose ginsenosides groups(200, 100, 50 mg·kg~(-1)·d~(-1)). They are given intragastric administration respectively with same amount of 0.5% CMC-Na,nimodipine and ginsenoside for 5 days. At 2 h after the final administration, the model was established with the suture-occluded method, and free radical-scavenging activity changes of ginsenoside were observed by maillard reaction, and Longa was possible used as a renoprotective agent-occluded method. At the end of 24 h after the reperfusion, the hemolymph of rats in each group was collected, and the ~1H-NMR spectrum was collected after being treated by certain methods, and analyzed by principal component analysis(PCA). Compared with sham-operated group, pathological model group showed significant increases in the levels of lactate, glutamate, taurine, choline, glucose and methionine, but decreases in the levels of 3-hydroxybutyrate and phosphocreatine/creatine in serum. After treatment with ginsenosides, lipid, 3-hydroxybutyrate and phosphocreatine/creatine were increased in the serum of ginsenosides group rats, but with decreases in lactate and glutamate. The results showed that ginsenosides could regulate metabolic disorders in rats with focal cerebral ischemia reperfusion, and promote a recovery in the process of metabolism. It's helpful to promote the metabolic changes in rats with focal cerebral ischemia reperfusion via ~1H-NMR, and lay a foundation to develop ginsenosides as a new drug to treat ischemic cerebral paralysis.

Topics: 3-Hydroxybutyric Acid; Animals; Brain Ischemia; Creatine; Ginsenosides; Hemolymph; Metabolome; Phosphocreatine; Proton Magnetic Resonance Spectroscopy; Random Allocation; Rats; Reperfusion Injury

To observe the efficacy of phosphocreatine pre-administration (PCr-PA) on X-linked inhibitor of apoptosis protein (XIAP), the second mitochondia-derived activator of caspase (Smac) and apoptosis in the ischemic penumbra of rats with focal cerebral ischemia-reperfusion injury (CIRI).. A total of 60 healthy male Sprague Dawley (SD) rats were randomly divided into three groups (n=20): group A (the sham operation group), group B <intraperitoneally injected with 20 mg/kg (10 mg/ml) of saline before preparing the ischemia-reperfusion (IR) model>, and group C <intraperitoneally injected with 20 mg/kg (10 mg/ml) of PCr immediately before preparing the IR model>. After 24 h for reperfusion, the neurological function was evaluated and the tissue was sampled to detect expression of XIAP, Smac and caspase-3 positive cells in the ischemic penumbra so as to observe the apoptosis.. Compared with group B, neurological deficit scores, numbers of apoptotic cells, expression of Smac,caspase-9 and the numbers of Caspase-3 positive cells were decreased while expression of XIAP were increased in the ischemic penumbra of group C.. Phosphocreatine pre-administration may elicit neuroprotective effects in the brain by increasing expression of X-linked inhibitor of apoptosis protein, reducing expression of second mitochondia-derived activator of caspase, and inhibiting the apoptosis in the ischemic penumbra.

Topics: Animals; Apoptosis; Apoptosis Regulatory Proteins; Brain Ischemia; Cardiotonic Agents; Caspase 3; Disease Models, Animal; Drug Evaluation, Preclinical; Humans; Intracellular Signaling Peptides and Proteins; Male; Mitochondrial Proteins; Neuroprotective Agents; Phosphocreatine; Random Allocation; Rats; Rats, Sprague-Dawley; Reperfusion Injury; X-Linked Inhibitor of Apoptosis Protein

The study aims to characterize age-associated changes in skeletal muscle bioenergetics by evaluating the response to ischemia-reperfusion in the skeletal muscle of the Goto-Kakizaki (GK) rats, a rat model of non-obese type 2 diabetes (T2D). (31)P magnetic resonance spectroscopy (MRS) and blood oxygen level-dependent (BOLD) MRI was performed on the hindlimb of young (12 weeks) and adult (20 weeks) GK and Wistar (control) rats. (31)P-MRS and BOLD-MRI data were acquired continuously during an ischemia and reperfusion protocol to quantify changes in phosphate metabolites and muscle oxygenation. The time constant of phosphocreatine recovery, an index of mitochondrial oxidative capacity, was not statistically different between GK rats (60.8 ± 13.9 sec in young group, 83.7 ± 13.0 sec in adult group) and their age-matched controls (62.4 ± 11.6 sec in young group, 77.5 ± 7.1 sec in adult group). During ischemia, baseline-normalized BOLD-MRI signal was significantly lower in GK rats than in their age-matched controls. These results suggest that insulin resistance leads to alterations in tissue metabolism without impaired mitochondrial oxidative capacity in GK rats.

Topics: Animals; Brain Ischemia; Diabetes Mellitus, Type 2; Disease Models, Animal; Hydrogen-Ion Concentration; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Male; Mitochondria; Muscle, Skeletal; Phosphocreatine; Phosphorus Radioisotopes; Rats; Reperfusion Injury

Rapid advances in imaging technologies have pushed novel spectroscopic modalities such as Fourier transform infrared spectroscopy (FTIR) and X-ray absorption spectroscopy (XAS) at the sulfur K-edge to the forefront of direct in situ investigation of brain biochemistry. However, few studies have examined the extent to which sample preparation artifacts confound results. Previous investigations using traditional analyses, such as tissue dissection, homogenization, and biochemical assay, conducted extensive research to identify biochemical alterations that occur ex vivo during sample preparation. In particular, altered metabolism and oxidative stress may be caused by animal death. These processes were a concern for studies using biochemical assays, and protocols were developed to minimize their occurrence. In this investigation, a similar approach was taken to identify the biochemical alterations that are detectable by two in situ spectroscopic methods (FTIR, XAS) that occur as a consequence of ischemic conditions created during humane animal killing. FTIR and XAS are well suited to study markers of altered metabolism such as lactate and creatine (FTIR) and markers of oxidative stress such as aggregated proteins (FTIR) and altered thiol redox (XAS). The results are in accordance with previous investigations using biochemical assays and demonstrate that the time between animal death and tissue dissection results in ischemic conditions that alter brain metabolism and initiate oxidative stress. Therefore, future in situ biospectroscopic investigations utilizing FTIR and XAS must take into consideration that brain tissue dissected from a healthy animal does not truly reflect the in vivo condition, but rather reflects a state of mild ischemia. If studies require the levels of metabolites (lactate, creatine) and markers of oxidative stress (thiol redox) to be preserved as close as possible to the in vivo condition, then rapid freezing of brain tissue via decapitation into liquid nitrogen, followed by chiseling the brain out at dry ice temperatures is required.

Topics: Animals; Brain Ischemia; Cerebellum; Creatine; Decapitation; Dissection; Disulfides; Freezing; Lactic Acid; Nitrogen; Oxidative Stress; Phosphocreatine; Protein Aggregates; Rats; Spectroscopy, Fourier Transform Infrared; Sulfhydryl Compounds; Time Factors; White Matter; X-Ray Absorption Spectroscopy

Clinical effectiveness of metabolic support in surgical treatment of patients, suffering stenotic affection of carotid arteries, was estimated. Neoton intraoperative injection inside internal carotid artery have promoted improvement of metabolism in ischemized brain tissues, reduction of metabolic acidosis severity, and preservation of normal bioelectrical activity of the brain. Expediency of prolongation of clinical investigation for intraoperative prophylaxis of reperfusional brain tissue damage, while surgical treatment of patients, suffering stenotic affection of carotid arteries, using metabolic support, was discussed.

Topics: Acidosis; Brain; Brain Ischemia; Cardiotonic Agents; Carotid Artery, Internal; Carotid Stenosis; Catheters, Indwelling; Electroencephalography; Endarterectomy, Carotid; Female; Humans; Lactic Acid; Male; Middle Aged; Phosphocreatine

Phosphocreatine is a major cellular source of high energy phosphates, which is crucial to maintain cell viability under conditions of impaired metabolic states, such as decreased oxygen and energy availability (i.e., ischemia). Many methods exist for the bulk analysis of phosphocreatine and its dephosphorylated product creatine; however, no method exists to image the distribution of creatine or phosphocreatine at the cellular level. In this study, Fourier transform infrared (FTIR) spectroscopic imaging has revealed the ex vivo development of creatine microdeposits in situ in the brain region most affected by the disease, the cerebellum of cerebral malaria (CM) diseased mice; however, such deposits were also observed at significantly lower levels in the brains of control mice and mice with severe malaria. In addition, the number of deposits was observed to increase in a time-dependent manner during dehydration post tissue cutting. This challenges the hypotheses in recent reports of FTIR spectroscopic imaging where creatine microdeposits found in situ within thin sections from epileptic, Alzheimer's (AD), and amlyoid lateral sclerosis (ALS) diseased brains were proposed to be disease specific markers and/or postulated to contribute to the brain pathogenesis. As such, a detailed investigation was undertaken, which has established that the creatine microdeposits exist as the highly soluble HCl salt or zwitterion and are an ex-vivo tissue processing artifact and, hence, have no effect on disease pathogenesis. They occur as a result of creatine crystallization during dehydration (i.e., air-drying) of thin sections of brain tissue. As ischemia and decreased aerobic (oxidative metabolism) are common to many brain disorders, regions of elevated creatine-to-phosphocreatine ratio are likely to promote crystal formation during tissue dehydration (due to the lower water solubility of creatine relative to phosphocreatine). The results of this study have demonstrated that although the deposits do not occur in vivo, and do not directly play any role in disease pathogenesis, increased levels of creatine deposits within air-dried tissue sections serve as a highly valuable marker for the identification of tissue regions with an altered metabolic status. In this study, the location of crystalline creatine deposits were used to identify whether an altered metabolic state exists within the molecular and granular layers of the cerebellum during CM, which complements the recent

Topics: Animals; Biomarkers; Brain; Brain Ischemia; Creatine; Malaria, Cerebral; Mice; Phosphocreatine; Spectroscopy, Fourier Transform Infrared

The influence of creatine or its derivates on the cell energy potential may be one of the possibl approaches to induce neuroprotection. Effect of creamide (creatinylglycine ethylic ether fumarate) on the brain injury was studied in the experimental model of the brain ischemia/reperfusion in rats. The experiments were carried out in 14-20 weeks old male Wistar rats weighing 240-300 g, anesthetized by chloral hydrate (430 mg/kg). Creamide was administered intravenously at the doses of 50, 70, 140, and 280 mg/kg. For comparison phosphocreatine was used at the dose of 255 mg/kg. Creamide and phosphocreatine were administered intravenously (in volume of 1 ml within 5 min) 30 min before cerebral middle artery occlusion. Focal cerebral ischemia for 30 min was produced by endovascular suture occlusion with the subsequent 48 h reperfusion period. Creamide administration resulted in dose-dependent decrease of brain ischemic injury. Creamide administered at the doses of 140 and 280 mg/kg was more effective as compared with phosphocreatine (255 mg/kg). The data obtained open new perspectives for further research and development of new creatine-derived drugs with neuroprotective action.

Topics: Animals; Brain; Brain Ischemia; Disease Models, Animal; Dose-Response Relationship, Drug; Infarction, Middle Cerebral Artery; Injections, Intravenous; Male; Neuroprotective Agents; Phosphocreatine; Rats; Rats, Wistar; Reperfusion Injury; Time Factors

Phosphocreatine (PCr) is an endogenous compound containing high-energy phosphate bonds. It has been confirmed that PCr is effective in preventing and treating cardiac and renal ischemia-reperfusion injury. In this study, rat cerebral ischemia-reperfusion injury models were constructed. Apoptotic cells in the cortex region were measured by TUNEL method. Malondialdehyde (MDA) content was detected by chromatometry, and calmodulin (CaM) activity was detected by ELISA. Compared with sham-operated group (sham group), TUNEL-positive cells, MDA, and level of CaM activity increased in ischemia-reperfusion group (I/R group) and PCr preconditioning group (PCr group); compared with I/R group, TUNEL-positive cells, MDA content, and level of CaM activity decreased in PCr group. This study indicated that PCr can decrease the morphological damage and the neuron apoptosis of the ischemia-reperfusion injury brain through attenuating abnormalities of calcium balance and production of oxygen free radicals.

Topics: Animals; Apoptosis; Brain; Brain Ischemia; Calmodulin; Enzyme-Linked Immunosorbent Assay; In Situ Nick-End Labeling; Ischemic Preconditioning; Male; Malondialdehyde; Phosphocreatine; Rats; Rats, Wistar; Reperfusion Injury

The neuroprotective effects of ethyl pyruvate (EP), a stable derivative of pyruvate, on energy metabolism of rat brain exposed to ischemia-reperfusion stress were investigated by (31)P-nuclear magnetic resonance ((31)P-NMR) spectroscopy. Recovery level of phosphocreatine after ischemia was significantly greater when superfused with artificial cerebrospinal fluid (ACSF) with 2 mM EP than when superfused with ACSF without EP. EP was neuroprotective against ischemia only when administered before the ischemic exposure. Intracellular pH during ischemia was less acidic when superfused ahead of time with EP. EP did not show neuroprotective effects in neuron-rich slices pretreated with 100 microM fluorocitrate, a selective glial poison. It was suggested that both the administration of EP before ischemic exposure and the presence of astrocytes are required for EP to exert neuroprotective effects. We suggest the potential involvement of multiple mechanisms of action, such as less acidic intracellular pH, glial production of lactate, and radical scavenging ability.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Electron Spin Resonance Spectroscopy; Energy Metabolism; Hydrogen-Ion Concentration; In Vitro Techniques; Intracellular Fluid; Magnetic Resonance Spectroscopy; Male; Neuroprotective Agents; Phosphocreatine; Pyruvates; Rats; Reperfusion Injury

Phosphorylated fructose compounds have been reported to lessen neuronal injury in in vitro models of hypoxia and in vivo models of ischemia. Although a variety of mechanisms have been proposed to account for this finding, it is unknown if intracellular uptake and incorporation of these compounds into the glycolytic pathway contribute to the benefit. We evaluated phosphorylated fructose administration in an adult rat model of transient, near-complete cerebral ischemia to determine its impact on brain metabolism before, during, and after ischemia. Fifty-four pentobarbital anesthetized rats were randomly assigned to receive IV infusions of either fructose-1,6-bisphosphate, fructose-2,6-bisphosphate, or 0.9% saline. After 2 hours of infusion, 18 rats (6/treatment group) were subjected to brain harvesting before any ischemia, 18 additional rats had brain harvesting at the completion of 10 minutes of forebrain ischemia (2-vessel occlusion plus induced hypotension), and 18 rats had harvesting after ischemia and 15 minutes of reperfusion. Cortical brain samples were analyzed for ATP, ADP, AMP, phosphocreatine, glucose, and glycogen. When compared with placebo, neither phosphorylated fructose compound altered preischemic, intraischemic, or postischemic concentrations of brain high-energy phosphates, glucose, glycogen, or lactate, nor did they influence the intraischemic metabolism of endogenous brain glucose or glycogen. On the basis of these results, we conclude that mechanisms other than augmented carbohydrate metabolism are responsible for previous reports of neuronal protection by the bisphosphonates.

Topics: Adenine Nucleotides; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Anesthesia; Anesthetics; Animals; Blood Glucose; Brain Chemistry; Brain Ischemia; Carbohydrate Metabolism; Cerebrovascular Circulation; Electroencephalography; Fructosediphosphates; Glycogen; Hemodynamics; Lactic Acid; Phosphocreatine; Prosencephalon; Rats; Rats, Sprague-Dawley; Reperfusion Injury

Phosphocreatine-Mg-complex acetate (PCr-Mg-CPLX) is a creatine-derived compound that in previous in vitro research was able to increase neuronal creatine independently of the creatine transporter, thus providing hope to cure the hereditary syndrome of creatine transporter deficiency. In previous research we showed that it reproduces in vitro the known neuroprotective effect of creatine against anoxic damage. In the present paper we investigated if PCr-Mg-CPLX reproduces this neuroprotective effect in vivo, too. We used a mouse model of transient middle cerebral artery occlusion. Mice received PCr-Mg-CPLX or a mixture of the two separate compounds phosphocreatine (PCr) and MgSO(4), or vehicle. The injections were done 60 min and 30 min before ischemia. Forty-eight hours after ischemia neurological damage was evaluated with Clark's behavioural tests, then the infarct volume was measured. PCr-Mg-CPLX reduced the infarct volume by 48%, an effect that was not duplicated by the separate administration of PCr and MgSO(4) and the neurological damage was decreased in a statistically significant way. We conclude that PCr-Mg-CPLX affords in vivo neuroprotection when administered before ischemia. These results are comparable to previous research on creatine administration in experimental stroke. PCr-Mg-CPLX maintains creatine-like neuroprotective effects in vivo as well as in vitro. Our study suggests that PCr-Mg-CPLX might have a therapeutic role in the treatment of hereditary creatine transporter deficiency and of conditions where there is a high risk of impending stroke or cerebral ischemic damage, like high-risk transient ischemic attacks, open heart surgery, and carotid surgery.

Topics: Animals; Brain Infarction; Brain Ischemia; Creatine; Cytoprotection; Disease Models, Animal; Infarction, Middle Cerebral Artery; Magnesium; Male; Membrane Transport Proteins; Mice; Nerve Degeneration; Neuroprotective Agents; Phosphocreatine; Treatment Outcome

Stroke leads to energy failure and subsequent neuronal cell loss. Creatine and phosphocreatine constitute a cellular energy buffering and transport system, and dietary creatine supplementation was shown to protect neurons in several models of neurodegeneration. Although creatine has recently been found to reduce infarct size after cerebral ischemia in mice, the mechanisms of neuroprotection remained unclear. We provide evidence for augmented cerebral blood flow (CBF) after stroke in creatine-treated mice using a magnetic resonance imaging (MRI)-based technique of CBF measurement (flow-sensitive alternating inversion recovery-MRI). Moreover, improved vasodilatory responses were detected in isolated middle cerebral arteries obtained from creatine-treated animals. After 3 weeks of dietary creatine supplementation, minor changes in brain creatine, phosphocreatine, adenosine triphosphate, adenosine diphosphate and adenosine monophosphate levels were detected, which did not reach statistical significance. However, we found a 40% reduction in infarct volume after transient focal cerebral ischemia. Our data suggest that creatine-mediated neuroprotection can occur independent of changes in the bioenergetic status of brain tissue, but may involve improved cerebrovascular function.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Cerebrovascular Circulation; Creatine; Disease Models, Animal; Magnetic Resonance Imaging; Male; Mice; Phosphocreatine

Vasoconstriction is known to occur in cerebral arterioles during ischemia and considered to be distinct from vasospasm seen after subarachnoid hemorrhage. To elucidate the mechanism and functional significance underlying ischemic vasoconstriction, we investigated the relationship between arteriolar constriction and tissue energy metabolism during bilateral common carotid artery occlusion in gerbils. Using video microscopy and microspectroscopy, the arteriolar caliber, the total hemoglobin (Hb) content, and the redox state of cytochrome oxidase (cyt.aa3) were monitored in the cerebral cortex in vivo. After in situ freezing of the brain, adenine nucleotides, creatine phosphate (P-Cr), and lactate levels were analyzed using high-performance liquid chromatography in vitro. Tissue damage was also assessed immunohistochemically using antibodies against microtubule-associated proteins. There was a slight reduction of the diameter of pial arterioles during the initial 1 min of ischemia. A rapid decline of total Hb and reduction of cyt.aa3 were observed with rapid decreases of P-Cr and ATP in the cortical tissue during the initial 0.5 min, but all of them showed tendencies to return toward preischemic levels at 0.5-1 min. Beyond 1.5 min, extensive vasoconstriction occurred together with further decline of total Hb, reduction of cyt.aa3, and decreases of ATP and P-Cr. Neuronal damage developed in the cerebral cortex immunohistochemically beyond 3 min. The present investigation demonstrated two phases of vasoconstriction with the possibilities that the immediate vasoconstriction likely contributed to transient improvement of cortical oxygen/energy metabolism, and the second extensive vasoconstriction was an index of tissue energy failure and imminent neuronal damage.

Topics: Adenosine Triphosphate; Animals; Arterioles; Brain Ischemia; Carotid Artery, Common; Cerebral Cortex; Cerebrovascular Circulation; Electron Transport Complex IV; Energy Metabolism; Gerbillinae; Hemoglobins; Immunohistochemistry; Lactic Acid; Male; Microscopy, Video; Oxygen Consumption; Phosphocreatine; Vasoconstriction

To observe the effect of salvianolic acid B (SalB) on high energy phosphate and activity of ATPase of cerebral ischemia in mice, and to study the role of SalB on hydrocephalus further.. NIH mice were divided into four groups randomly: Sham-operated group, cerebral ischemia group, SalB-treated group and Nimodipine (Nim)-collated group. In Sal B-treated group, mice were injected with SalB (22.5 mg x kg(-1)) in vena caudalis at 30 min before the experiment. In Nim-collated group, Nim (0.03 mg x kg(-1)) was injected into tail vein at the same time, while the mice in Sham-operated group and cerebral ischemia group were injected the same volume normal saline. The acute cerebral ischemia model was established by ligating bilateral common carotid arteries for 30 min in mice, then the mice were killed and the content of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), phosphocreatine (PCr) were observed, and the cerebral energy charge (EC) was computed. At the same time, activity of Na(+) -K(+) -ATPase and Ca2(+) -ATPase, content of water in brain tissue were measured.. Compared with cerebral ischemia group, EC and content of ATP, ADP, PCr in SalB-treated group heightened evidently (P < 0.01). Moreover, activity of Na(+)-K+ ATPase and Ca2+ ATPase in SalB-treated group had a remarkable increase (P < 0.01). But the content of water in brain tissue decreased markedly (P < 0.05).. The mechanism that SalB can relieve content of water in brain tissue of cerebral ischemia in mice, may be associated with improving the content of high-energy phosphoric acid compounds and enhancing the activity of ATPase.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphatases; Adenosine Triphosphate; Animals; Benzofurans; Brain; Brain Ischemia; Calcium-Transporting ATPases; Energy Metabolism; Male; Mice; Phosphocreatine; Plants, Medicinal; Random Allocation; Salvia miltiorrhiza; Sodium-Potassium-Exchanging ATPase; Water

Mice pathological model of acute cerebral ischemia was established. In order to observe the effect of salvianolic acid B (Sal B) on brain energy metabolism and hydrocephalus in the brain of mice at different ischemic times, the energy charge (EC), content of phosphocreatine (PCr), level of lactic acid (Lac), activity of Na+ -K+ -ATPase, brain index and water content of brain were measured at 6, 12, 18, 24, and 30 min, separately after ligating bilateral common carotid arteries in mice. NIH mice were randomly divided into sham-operated group (sham), cerebral ischemia group (ischemia), Sal B-treated group (Sal B) and nimodipine-collated group (Nim). At 6 min after cerebral ischemia, EC, content of PCr and activity of Na +-K -ATPase began to decrease, while level of Lac, brain index and water content of brain increased gradually. However, Sal B (22.5 mg x kg(-1) improved pathophysiological changes at different ischemic times. Especially at 30 min after cerebral ischemia in Sal B group, EC (P < 0.01), content of PCr (P < 0.01 and activity of Na+ -K+ -ATPase ( < 0.05) increased significantly. Meanwhile, level of Lac (P < 0.01, brain index (P < 0.01) and water content of brain (P < 0.05) were lower obviously than those of cerebral ischemia group. Sal B could alleviate hydrocephalus by the improvement of energy metabolism in mice with acute cerebral ischemia, that provides scientific evidence that Sal B can be used for the clinical application of ischemic diseases.

Topics: Animals; Benzofurans; Brain; Brain Ischemia; Drugs, Chinese Herbal; Energy Metabolism; Hydrocephalus; Lactic Acid; Male; Mice; Phosphocreatine; Plants, Medicinal; Random Allocation; Salvia miltiorrhiza; Sodium-Potassium-Exchanging ATPase; Time Factors; Water

An animal model involving stepwise occlusion of the common carotid arteries (sCCAO) in DBA/2 mice is presented in which the right and left carotid arteries were permanently ligated within a time interval of four weeks. Thereafter, cerebral functional and structural parameters were determined at acute (15 min) and subchronic (1 day; 3, 7, and 14 days) time points after sCCAO. Quantitative changes in regional cerebral blood flow (rCBF) as determined by the [14C]iodoantipyrine method, energy state (ATP, phosphocreatine, ADP, AMP, adenosine) as shown by HPLC, brain histopathology, and neuronal densities were measured in both hemispheres. Acute sCCAO was accompanied by a drastic reduction in cerebral energy-rich phosphate concentrations, ATP and phosphocreatine, and in rCBF of more than 50%. In contrast, cortical adenosine increased around five-fold. Subchronic sCCAO, however, was associated with normalization in brain energy metabolites and near-complete restoration of rCBF, except in the caudate nucleus (-40%). No marked signs of necrotic or apoptotic cell destruction were detected. Thus, during the subchronic period, compensatory mechanisms are induced to counteract the drastic changes seen after acute vessel occlusion. In conclusion, this sCCAO mouse model may be useful for long-lasting investigations of stepwise deterioration contributing to chronic cerebrovascular disorders.

Topics: Adenosine; Adenosine Triphosphate; Animals; Biomarkers; Brain Ischemia; Carotid Stenosis; Cerebral Cortex; Cerebrovascular Circulation; Disease Models, Animal; Down-Regulation; Energy Metabolism; Female; Mice; Mice, Inbred DBA; Nerve Degeneration; Neurons; Oxidative Phosphorylation; Phosphocreatine; Up-Regulation

Spreading depression (SD) has been demonstrated following focal ischemia, and the additional workload imposed by SD on a tissue already compromised by a marked reduction in blood flow may contribute to the evolution of irreversible damage in the ischemic penumbra. SD was elicited in one group of rats by injecting KCl directly into a frontal craniectomy and the wave of depolarization was recorded in two craniectomies 3 and 6 mm posterior to the first one. In a second group, the middle cerebral artery was occluded using the monofilament technique and a recording electrode was placed 5 mm lateral to the midline and 0.2 mm posterior to bregma. To determine the metabolic response in the penumbral region of the cortex ipsilateral to the occlusion, brains from both groups were frozen in situ when the deflection of the SD was maximal. The spatial metabolic response of SD in the ischemic cortex was compared to that in the non-ischemic cortex. Coronal sections of the brains were lyophilized, pieces of the dorsolateral cortex were dissected and weighed, and analyzed for ATP, P-creatine, inorganic phosphate (Pi), glucose, glycogen and lactate at varying distances anterior and posterior to the recording electrode. ATP and P-creatine levels were significantly decreased at the wavefront in both groups and the levels recovered after passage of the wavefront in the normal brain, but not in the ischemic brain. Glucose and glycogen levels were significantly decreased and lactate levels significantly increased in the tissue after the passage of the wavefront. While the changes in the glucose-related metabolites persisted during recovery even in anterior portions of the cortex in both groups in the aftermath of the SD, the magnitude of the changes was greater in the penumbra than in the normal cortex. SD appears to impose an equivalent increase in energy demands in control and ischemic brain, but the ability of the penumbra to recover from the insult is compromised. Thus, increasing the energy imbalance in the penumbra after multiple SDs may hasten the deterioration of the energy status of the tissue and eventually contribute to terminal depolarization and cell death, particularly in the penumbra.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Cerebral Cortex; Cerebral Infarction; Cortical Spreading Depression; Energy Metabolism; Glucose; Glycogen; Lactic Acid; Male; Membrane Potentials; Phosphates; Phosphocreatine; Potassium Chloride; Rats; Rats, Wistar; Recovery of Function

The aim of the present study was to establish whether aniracetam is capable of protecting cultured rat astrocytes against ischemic injury. Treatment of the cultures with aniracetam (1, 10 and 100 mM) during 24 h ischemia simulated in vitro significantly decreased the number of apoptotic cells. The antiapoptotic effects of the drug were confirmed by the increase of intracellular ATP and phosphocreatine (PCr) levels and the inhibition of the caspase-3 activity. Aniracetam also attenuated cellular oxidative stress by decreased production of reactive oxygen species (ROS). These effects were associated with the decrease in levels of c-fos and c-jun mRNA in primary astrocyte cultures exposed to 24 h ischemia. When cultured astrocytes were incubated during 24 h simulated ischemia with wortmannin, a phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor or PD98059, a mitogen-activated protein (MAP)/extracellular signal regulated kinase (ERK) (MEK) inhibitor the cell apoptosis was accelerated. This effect was antagonized by adding 100 mM aniracetam to the culture medium. These findings suggest that the protective effect of aniracetam is mediated by PI 3-kinase and MEK pathways in the downstream mechanisms.

Topics: Adenosine Triphosphate; Animals; Apoptosis; Astrocytes; Brain Ischemia; Caspase 3; Caspases; Cerebral Cortex; Fluoresceins; Fluorescent Dyes; Gene Expression Regulation; Genes, fos; Genes, jun; Nerve Tissue Proteins; Nootropic Agents; Phosphocreatine; Pyrrolidinones; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction

Reperfusion injury is believed to contribute to the pathophysiology of ischemic cell death, but the precipitating factors have yet to be completely elucidated. The goal of this study was to examine if reflow-induced secondary energy failure is a component in the events that lead to cell death following increasing periods of middle cerebral artery (MCA) occlusion in Wistar rats. Discrete sections within the MCA distribution were dissected and analyzed for high-energy phosphates and glucose. Regional cerebral blood flow was determined by [14C]-iodoantipyrine technique in representative groups. The levels of ATP + P-creatine were initially depressed at the end of the focal ischemia and the concentrations in the penumbra were unchanged for up to 8 h after 2 h of ischemia which contrasts with response in the ischemic core, striatum, and penumbra where the HEP generally recovered to values near those of control only to decrease with increasing periods of reflow. The possibility of a rebound ischemia in secondary energy failure (SEF) was precluded by regional CBF values and concentrations of glucose that were significantly higher than the threshold for an ischemic effect. The depletion of cellular energy stores following SEF strongly indicates that the evolution of infarct during reflow results from loss of ATP and its synthesis.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Cell Death; Cerebrovascular Circulation; Energy Metabolism; Infarction, Middle Cerebral Artery; Male; Mitochondrial Diseases; Nerve Degeneration; Phosphocreatine; Rats; Rats, Wistar; Reperfusion Injury; Telencephalon

In the immature brain, postischemic metabolism may be influenced beneficially by the effect of inducing hypercarbia or hypothermia. With use of 31P nuclear magnetic resonance spectroscopy, intracellular pH (pHi) and cellular energy metabolites in ex vivo neonatal rat cerebral cortex were measured before, during, and after substrate and oxygen deprivation in in vitro ischemia. Early postischemic hypothermia (fall in temperature -3.2 +/- 1.0 degrees C) delayed the normalization of pHi after ischemia by inducing an acid shift in pHi (P < 0.01). Postischemic hypercarbia (Krebs-Henseleit bicarbonate buffer equilibrated with 10% carbon dioxide in oxygen) and hypothermia induced separate, but potentially additive, reversible decreases in pHi, each of approximately -0.16 pH unit (P < 0.05). When these postischemic perturbations were applied in isolation, there was significant improvement of approximately 20% in the recovery of beta-ATP (P < 0.05). In combination, however, hypercarbia and hypothermia worsened recovery in ATP by approximately 20% (P < 0.05). In control tissue, which had not been exposed to ischemia, ATP content was also significantly reduced by co-administration of the two treatments (P < 0.05), an effect that persisted even after discontinuing the perturbing conditions. Therefore, in this vascular-independent neonatal preparation, early postischemic modulation of metabolism by hypercarbia or hypothermia appears to confer improved bioenergetic recovery, but only if they are not administered together.

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Brain Ischemia; Carbon Dioxide; Energy Metabolism; Hydrogen-Ion Concentration; Hypothermia, Induced; In Vitro Techniques; Intracellular Membranes; Magnetic Resonance Spectroscopy; Phosphocreatine; Rats

Near-infrared spectroscopy (NIRS) is used to monitor cerebral oxygenation during cardiac surgery. However, interpretation of the signals is controversial. The aim of the study was to determine which NIRS variable best correlated with brain damage as assessed by animal behavior and neurohistologic score and to compare the accuracy of NIRS and magnetic resonance spectroscopy (MRS) in predicting brain injury.. Forty 5-week-old piglets underwent 60 minutes of deep hypothermic circulatory arrest (DHCA) at 15 degrees C. Changes in brain adenosine triphosphate (ATP), phosphocreatine (PCr), and intracellular pH (pHi) were determined by MRS and correlated to changes in oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (Hb), and oxidized cytochrome a,a3 (CytOx) NIRS signals. Brains were fixed on day 4 and examined using a neurohistologic score.. Reductions in CytOx and HbO2 values were correlated closely with decreases in ATP, PCr, and pHi. The changes in CytOx and PCr showed the strongest correlation (r = 0.623). Maximal CytOx reduction during DHCA of more than -25 microM * differential pathlength factor (DPF) predicted brain damage with a sensitivity of 100% and a specificity of 75%. The histologic score was also correlated with a decrease in ATP (r = -0.52 for CytOx; r = -0.32 for ATP); HbO2, PCr, and pHi showed no correlations.. Reduction in CytOx correlates with decreased brain energy state and predicts histologic brain injury after DHCA with a high sensitivity. These data suggest that the level of CytOx could be a very important predictor of brain damage during DHCA.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Chemistry; Brain Ischemia; Heart Arrest, Induced; Hydrogen-Ion Concentration; Hypothermia, Induced; Magnetic Resonance Spectroscopy; Monitoring, Intraoperative; Oxygen; Phosphocreatine; Sensitivity and Specificity; Spectroscopy, Near-Infrared; Swine

The present study investigates the interrelation between cerebral energy state and memory capacities in a rat model of stepwise cerebral vessel occlusions. After acute and subchronic permanent vessel occlusions, cortical energy metabolites (ATP, phosphocreatine, ADP, AMP) were detected by high-pressure liquid chromatography (HPLC) analysis, and the effects on learning, memory, and cognitive behavior were evaluated using a hole-board test. The results of the study demonstrated a drastic decrease in energy-rich phosphates by 33% for phosphocreatine and by 44% for ATP after acute vessel occlusions. In addition, rat working and reference memories were strikingly decreased to about 5% of controls. In contrast, two weeks after four-vessel occlusion, the energy state was almost completely restored to control levels. However, a significant decrease in memory capacities was observed in subchronic state. In summary, this study has demonstrated a close linear relationship (p < 0.001) between an impaired cerebral energy state and brain memory dysfunction after acute and permanent cerebral four-vessel occlusion. Thus, this animal model of stepwise reduction of the cerebral blood supply may reflect some clinically relevant processes occurring during cerebrovascular and neurodegenerative diseases.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Carotid Artery, Common; Cerebral Cortex; Cognition; Electrocoagulation; Energy Metabolism; Learning; Male; Phosphocreatine; Rats; Rats, Wistar; Vertebral Artery

The influence of chronic cerebral hypoperfusion on cerebral energy metabolism was studied. The bilateral common carotid arteries of Wistar rats were occluded for 0, 2, 7, and 28 days. Cerebral energy metabolism was evaluated by assaying adenosine triphosphate (ATP), phosphocreatine (PCr), and lactate levels and measuring pyruvate dehydrogenase (PDH) activity (each time point, n = 6). Pathological changes were assessed light-microscopically by Klüver-Barrera staining and immunohistochemical labeling for astroglia (each time point, n = 3). There were no changes in ATP and PCr levels or PDH activity; there was slight but significant transient lactate accumulation at 2 days. Myelin pallor and increase in immuno-reactive astroglia were only observed at 28 days. These results indicate that chronic cerebral hypoperfusion induces delayed white matter changes in the corpus callosum of rat brain, but does not affect energy production.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Carotid Artery, Common; Cerebral Cortex; Corpus Callosum; Corpus Striatum; Energy Metabolism; Lactic Acid; Male; Phosphocreatine; Pyruvate Dehydrogenase Complex; Rats; Rats, Wistar

To investigate the functional significance of anaerobic and aerobic glycolysis on neural activity and levels of high energy phosphates, we tested the effects of glucose, mannose, fructose lactate, and pyruvate on the maintenance of neural activity and on the levels of ATP and creatine-P (CrP) in hippocampal slices. For an index of neural activity, population spikes (PS) evoked in the granule cell layer were monitored. Immediately after deprivation of glucose, the PS amplitude was gradually reduced and extinguished within 30 mm. Replacement of glucose with either lactate or pyruvate resulted in a decay and loss of PS with a similar time-course as observed during glucose deprivation. However, after the complete loss of neural activity for 10-20 min the PS reappeared and recovered to normal levels. The replacement of glucose with either mannose or fructose resulted in a transient decrease of the PS to 80-70% of the original amplitude in 20 mm, followed by recovery. The time-course of the decrease of PS in the mannose-containing medium was slower than that in the medium containing fructose and the time-course of recovery was faster. ATP and CrP were reduced to 90 and 70% of original level in each slice after glucose deprivation for 30 and 100 mm, respectively. In media containing either lactate, pyruvate, mannose, or fructose, the level of ATP and CrP was maintained at the original level. The anaerobic metabolic rate of glucose, mannose and fructose, determined by the rate of lactate production during complete anoxia, was consistent with the order of the decay and recovery of the PS in mannose and fructose-containing medium. The mode of the transient decay or loss of PS with no apparent reduction in the levels of ATP and CrP in each slice, in the presence of either mannose, fructose or lactate, indicates that anaerobic glycolysis is crucial for the maintenance of PS. The results obtained in this experiment are not in accordance with the reports by Schurr and Fowler in which they showed that lactate can support neural activity, although they did not measure the levels of ATP and CrP in slices. The present experiment disclosed that this discrepancy was due to the difference of slice preparation; namely rapidly prepared slice with shorter period anoxia (1 mm after removal of hippocampal tissue block) gives the results mentioned in the present study whereas slowly prepared slices by vibratome or chopper method with longer period of ischemia (5-20 mm), did not sho

Topics: Action Potentials; Adenosine Triphosphate; Animals; Brain Ischemia; Energy Metabolism; Fructose; Glucose; Glycolysis; Guinea Pigs; Hippocampus; Lactic Acid; Mannose; Neurons; Organ Culture Techniques; Phosphocreatine; Pyruvic Acid

Creatine kinase reaction rates were measured by the magnetisation transfer technique in brains of healthy adult and aged rats and in rats with chronic cerebral ischemia and chronic ethanol intoxication. These measurements indicated that the rate constant of the creatine kinase reaction is significantly reduced in the case of severe chronic cerebral ischemia in aged rats. In the adult rats, during chronic ethanol intoxication after 3 weeks of administration of 3 ml of 30% ethanol once a day via a gastric tube, a significant decrease in the pseudo first-order rate constant k(for) of the creatine kinase reaction was also found. In contrast, mild chronic cerebral ischemia in adult rats produced an increase in the reaction rate 4 weeks after occlusion. At the same time, corresponding conventional phosphorus magnetic resonance spectra showed negligible changes in signal intensities.

Topics: Adenosine Triphosphate; Aging; Alcoholic Intoxication; Alcoholism; Animals; Brain; Brain Ischemia; Chronic Disease; Creatine Kinase; Phosphocreatine; Rats; Rats, Wistar

The present study tests the hypothesis that ketamine, a dissociative anesthetic known to be a non-competitive antagonist of the NMDA receptor, will attenuate hypoxic-ischemic damage in neonatal rat brain. Studies were performed in 7-day-old rat pups which were divided into four groups. Animals of the first group, neither ligated nor exposed to hypoxia, served as controls. The second group was exposed to hypoxic-ischemic conditions and sacrificed immediately afterwards. Animals of the third and fourth groups were treated either with saline or ketamine (20 mg/kg, i.p.) in four doses following hypoxia. Hypoxic-ischemic injury to the left cerebral hemisphere was induced by ligation of the left common carotid artery followed by 1 h of hypoxia with 8% oxygen. Measurements of high energy phosphates (ATP and phosphocreatine) and amino acids (glutamate and glutamine) and neuropathological evaluation of the hippocampal formation were used to assess the effects of hypoxia-ischemia. The combination of common carotid artery ligation and exposure to an hypoxic environment caused major alterations in the ipsilateral hemisphere. In contrast, minor alterations in amino acid concentrations were observed after the end of hypoxia in the contralateral hemisphere. These alterations were restored during the early recovery period. Post-treatment with ketamine was associated with partial restoration of energy stores and amino acid content of the left cerebral hemisphere. Limited attenuation of the damage to the hippocampal formation as demonstrated by a reduction in the number of damaged neurons was also observed. These findings demonstrate that systemically administered ketamine after hypoxia offers partial protection to the newborn rat brain against hypoxic-ischemic injury.

Topics: Adenosine Triphosphate; Amino Acids; Animals; Animals, Newborn; Body Weight; Brain; Brain Ischemia; Carotid Artery Diseases; Female; Functional Laterality; Glutamic Acid; Glutamine; Hypoxia, Brain; Ketamine; Male; Neurons; Neuroprotective Agents; Phosphocreatine; Rats; Rats, Wistar; Time Factors

The present study was designed to examine the effects of inhibition of nitric oxide synthase on cerebral energy metabolism after hypoxia-ischemia in newborn piglets. Ten 1- to 3-d-old piglets received N(omega)-nitro-L-arginine (NNLA), an inhibitor of nitric oxide synthase (NNLA-hypoxia, n = 5), or normal saline (hypoxia, n = 5) 1 h before cerebral hypoxia-ischemia. After the infusion, hypoxia-ischemia was induced by bilateral occlusion of the carotid arteries and decreasing FiO2 to 0.07 and maintained for 60 min. Thereafter, animals were resuscitated and ventilated for another 3 h. Using 1H- and 31P-magnetic resonance spectroscopy, cerebral energy metabolism was measured in vivo at 15-min intervals throughout the experiment. Phosphocreatine to inorganic phosphate ratios decreased from 2.74 +/- 0.14 to 0.74 +/- 0.36 (hypoxia group) and 2.32 +/- 0.17 to 0.18 +/- 0.10 (NNLA-hypoxia group) during hypoxia-ischemia. Thereafter, phosphocreatine to inorganic phosphate ratios returned rapidly to baseline values in the hypoxia group, but remained below baseline values in the NNLA-hypoxia group. Intracellular pH decreased during hypoxia-ischemia and returned to baseline values on reperfusion in both groups. Intracellular pH values were lower in the NNLA-hypoxia group (p < 0.001, ANOVA). Lactate was not present during the baseline period. After hypoxia-ischemia, lactate to N-acetylaspartate ratios increased to 1.34 +/- 0.28 (hypoxia group) and 2.22 +/- 0.46 (NNLA-hypoxia group). Lactate had disappeared after 3 h of reperfusion in the hypoxia group, whereas lactate to N-acetylaspartate ratios were 1.37 +/- 1.37 in the NNLA-hypoxia group. ANOVA demonstrated a significant effect of NNLA on lactate to N-acetylaspartate ratios (p < 0.001). Inhibition of nitric oxide synthase by NNLA tended to compromise cerebral energy status during and after cerebral hypoxia-ischemia in newborn piglets.

Topics: Animals; Animals, Newborn; Brain; Brain Ischemia; Cerebrovascular Circulation; Disease Models, Animal; Energy Metabolism; Enzyme Inhibitors; Hydrogen-Ion Concentration; Hypoxia, Brain; Lactic Acid; Magnetic Resonance Spectroscopy; Nitric Oxide Synthase; Nitroarginine; Phosphates; Phosphocreatine; Swine

The objective of this study was to determine whether the duration of an ischemic insult effects the activity of the mitochondrial enzyme pyruvate dehydrogenase (PDH) in relation to the recovery of metabolites and regional cerebral blood flow (rCBF) immediately after ischemia and during reperfusion in gerbil cortex. Cerebral ischemia was induced, using the bilateral carotid artery occlusion method, for 20 or 60 min, followed by reperfusion up to 120 min. Immediately after ischemia PDH activity increased threefold regardless of ischemic duration. In the 60-min ischemic group, PDH remained activated, the recovery of high energy phosphates and the clearance of lactate were poor, and the rCBF was 48% of controls after 20-min reperfusion, decreasing gradually to 26% at 120-min reperfusion. In the 20-min ischemic group, PDH activity normalized quickly, the restoration of energy phosphates was good, there was a quick reduction in lactate within the first 60 min of reperfusion, and the rCBF was 65% of control at 20-min reperfusion, and remained over 48% of control throughout reperfusion. Recovery of metabolism after reperfusion did not parallel the changes in rCBF in either group, most noticeably in the 60-min ischemic group. The slow normalization of PDH activity reflected the poor recovery of metabolites in the 60-min ischemic group, indicating that PDH activity is important in the resynthesis of energy metabolites during reperfusion. In conclusion, prolonging the ischemic insult effected PDH activity during reperfusion, impaired recovery of energy metabolites, and worsened the recovery of rCBF.

Topics: Adenosine Triphosphate; Animals; Brain Chemistry; Brain Ischemia; Cerebrovascular Circulation; Energy Metabolism; Gerbillinae; Lactic Acid; Male; Phosphocreatine; Pyruvate Dehydrogenase Complex; Reperfusion Injury; Time Factors

The cell volume is regulated not only by inorganic ions, but also by organic osmolytes, such as amino acids, methylamines, and polyhydric alcohols (polyols). Using proton nuclear magnetic resonance spectroscopy (1H-NMR), we measured the tissue concentrations of amino acids (alanine, aspartate, gamma-aminobutyric acid (GABA), glutamate, glutamine, N-acetyl-aspartate (NAA), taurine), methylamines (glycerophosphorylcholine (GPC), creatine+phosphocreatine (total creatine, tCr)), and polyols (myo-inositol) in the rat brain after middle cerebral artery occlusion (incomplete focal ischemia) or after decapitation (complete global ischemia). The total osmolytes expressed as a sum of total amino acids, total methylamines, and total polyols were significantly decreased at 24 h of focal ischemia (58.7% of control value, P=0.0025) whereas they were not changed following decapitation. The water content was increased from control value of 77.9%-84.1% after focal ischemia (P<0.0001) but not after decapitation. These results suggest that the brain organic osmolytes are involved in the process of edema formation following focal cerebral ischemia. Further elucidation of the cellular mechanisms regulating these organic osmolytes in cerebral ischemia may promote greater understanding of the pathophysiology involved in the evolution of brain edema.

Topics: Alanine; Amino Acids; Animals; Aspartic Acid; Brain Chemistry; Brain Ischemia; Creatine; Disease Models, Animal; gamma-Aminobutyric Acid; Glutamic Acid; Glutamine; Glycerylphosphorylcholine; Magnetic Resonance Spectroscopy; Male; Methylamines; Phosphocreatine; Rats; Rats, Sprague-Dawley; Taurine

The purpose of this study was to test the hypothesis that hyperglycemia ameliorates changes in brain cell membrane function and preserves cerebral high energy phosphates during hypoxia-ischemia in newborn piglets. A total of 42 ventilated piglets were divided into 4 groups, normoglycemic/normoxic(group 1, n=9), hyperglycemic/normoxic(group 2, n=8), normoglycemic/hypoxic-ischemic(group 3, n=13) and hyperglycemic/hypoxic-ischemic(group 4, n=12) group. Cerebral hypoxia-ischemia was induced by occlusion of bilateral common carotid arteries and simultaneous breathing with 8% oxygen for 30 min. Hyperglycemia (blood glucose 350-400 mg/dl) was maintained for 90 min before and throughout hypoxia-ischemia using modified glucose clamp technique. Changes in cytochrome aa3 were continuously monitored using near infrared spectroscopy. Blood and CSF glucose and lactate were monitored. Na+, K+-ATPase activity, lipid peroxidation products (conjugated dienes), tissue high energy phosphates (ATP and phosphocreatine) levels and brain glucose and lactate levels were determined biochemically in the cerebral cortex. During hypoxia-ischemia, glucose levels in blood and CSF were significantly elevated in hyperglycemic/hypoxic-ischemic group compared with normoglycemic/hypoxic-ischemic group, but lactate levels in blood and CSF were not different between two groups. At the end of hypoxia-ischemia of group 3 and 4, triangle up Cyt aa3, Na+, K+-ATPase activity, ATP and phosphocreatine values in brain were significantly decreased compared with normoxic groups 1 and 2, but were not different between groups 3 and 4. Levels of conjugated dienes and brain lactate were significantly increased in groups 3 and 4 compared with groups 1 and 2, and were significantly elevated in group 4 than in group 3 (0.30+/-0.11 vs. 0.09+/-0.02 micromol g-1 protein, 26.4+/-7.6 vs. 13.1+/-2.6 mmol kg-1, p<0.05). These findings suggest that hyperglycemia does not reduce the changes in brain cell membrane function and does not preserve cerebral high energy phosphates during hypoxia-ischemia in newborn piglets. We speculate that hyperglycemia may be harmful during hypoxia-ischemia due to increased levels of lipid peroxidation in newborn piglet.

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Brain; Brain Ischemia; Cell Membrane; Energy Metabolism; Glucose; Hyperglycemia; Hypoxia; Lactic Acid; Phosphocreatine; Sodium-Potassium-Exchanging ATPase; Spectroscopy, Near-Infrared; Swine

To evaluate the effects of infusion with hyperosmolar solutions, mannitol and glycerol on the recovery of cerebral energy metabolism during ischemia and reperfusion in the gerbil brain.. Sequential changes in cerebral energy metabolism following 90-min ischemia and up to 8 h after reperfusion were measured in 15 gerbils using 31P nuclear magnetic resonance (NMR) spectroscopy after 60-min infusion of 10% glycerol (0.5 g/kg; n=5), or 20% mannitol (1.0 g/kg; n=5), and compared with those gerbils receiving with saline (n=5). Gerbils were anesthetized by intraperitoneal injection of pentobarbital. Forebrain ischemia was induced by clipping of bilateral common carotid arteries for 90 min and reperfused. NMR spectroscopy was measured by a 6.34-Tesla JEOL spectrometer, before administration, 2, 4, 6, and 8 h after 90-min ischemia and reperfusion. Areas of inorganic phosphate (Pi), phosphocreatine (PCr), and beta-ATP peaks were measured to calculate parameters of cerebral energy metabolism, i.e., PCr/Pi and beta-ATP/Pi ratios. Intracellular pH (pHi) was calculated from chemical shifts of Pi relative to PCr.. PHi was higher in the mannitol group than in the glycerol and saline groups (P<0.05) 2 h after reperfusion. PCr/Pi ratio was higher 2, 4, and 8 h after reperfusion (P<0.01, P<0.05, P<0.01) in the mannitol group; and 6 h after reperfusion (P<0.05) in the glycerol group; than in the saline group. Beta-ATP/Pi ratio was higher 2 and 8 h after reperfusion (P<0.05) in the glycerol group; and 2 h after reperfusion (P<0.01) in the mannitol group, than in the saline group.. The mannitol group had improved pHi higher than the glycerol group 2 h after reperfusion (P<0.05), while the glycerol group had improved beta-ATP/Pi ratio higher than the mannitol group 6 h after reperfusion (P<0.05). Both mannitol and glycerol groups had improved parameters of cerebral energy metabolism during ischemia and up to 8 h after reperfusion in the gerbil brain.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Dose-Response Relationship, Drug; Energy Metabolism; Gerbillinae; Glycerol; Hydrogen-Ion Concentration; Hypertonic Solutions; Infusion Pumps; Magnetic Resonance Spectroscopy; Male; Mannitol; Oxygen Consumption; Phosphates; Phosphocreatine; Reperfusion Injury

Creatine kinase reaction rates were measured by magnetisation transfer technique in the brain of healthy adult and aged rats and in the rats with mild or severe chronic cerebral ischemia. These measurements indicated that the rate constant of the creatine kinase reaction is significantly reduced in the case of chronic brain ischemia in aged rats. In contrast, occlusion of both carotid arteries in adult rats produced a slight increase in the reaction rate 4 weeks after occlusion. At the same time, corresponding conventional phosphorus magnetic resonance spectra showed negligible changes in signal intensities.

Topics: Aging; Animals; Brain; Brain Ischemia; Chronic Disease; Kinetics; Nuclear Magnetic Resonance, Biomolecular; Phosphocreatine; Phosphorus; Rats; Rats, Wistar

This study investigated whether both mild and severe hypoxia-ischaemia (HI) caused significant numbers of cells to die by apoptosis in the developing brain in vivo. Newborn piglets were subjected to transient global HI and the fraction of all cells in the cingulate gyrus that were apoptotic or necrotic counted 48 h after resuscitation. The mean (S.D.) proportion of apoptotic cells was 11.9% (6.7%) (sham operated controls 4.1% (2.7%)), while 11.4% (8.4%) were necrotic (controls 0.7% (1.3%)) (P<0.05). Apoptotic and necrotic cell counts were both linearly related to the severity of impaired cerebral energy metabolism measured by magnetic resonance spectroscopy (P<0.05), as shown by: (1) the decline in the ratio of nucleotide triphosphates to the exchangeable phosphate pool during HI; (2) the fall in the ratio of phosphocreatine to inorganic phosphate 8 - 48 h after HI; and (3) an increased ratio of lactate to total creatine at both these times. Thus both apoptosis and necrosis occurred in the cingulate gyrus after both severe and mild HI in vivo in proportion to the severity of the insult.

Topics: Animals; Animals, Newborn; Apoptosis; Brain; Brain Ischemia; Cell Count; Energy Metabolism; Gyrus Cinguli; Hypoxia, Brain; Lactic Acid; Magnetic Resonance Spectroscopy; Necrosis; Phosphocreatine; Swine

The objective of this study was to determine if the pretreatment with a sublethal ischemic insult, which has been shown to protect against delayed neuronal death, effects the recovery of energy metabolites or alters the activity of pyruvate dehydrogenase (PDH) following transient cerebral ischemia. Gerbils were pretreated with a sublethal ischemic insult, 2 min of bilateral common carotid artery occlusion, and 24 h later given a 5-min lethal ischemic insult. Animals were reperfused for 0, 10, or 60 min, or 1, 3 or 7 days. Brain metabolites, ATP, PCr, and lactate, and PDH activity were measured in the cortex and the hippocampal CA1 region. The pretreatment had no effect on ATP and PCr depletion or on lactate accumulation after the 5-min insult, nor on their recovery up to 1 day reperfusion, although there was a difference in the lactate levels of the non-pretreated and the pretreated gerbils after 10 min reperfusion. The pretreatment also had no effect on PDH activity during ischemia and reperfusion in either region. However, at 3 days reperfusion the non-pretreated animals exhibited a secondary decrease in ATP levels in the hippocampus. At 7 days reperfusion, ATP levels in the hippocampus of both the pretreated animals and the non-pretreated animals were significantly decreased compared to controls. Additionally, the level of ATP in the non-pretreated group was significantly lower than that in the pretreated group. The pretreatment with a sublethal ischemic insult did not effect the initial recovery of metabolites or the activity of PDH following transient cerebral ischemia. However, it protected against the secondary decrease of ATP levels in the hippocampus. Thus, the induction of ischemic tolerance is not caused by a reduction in metabolic impairment during the secondary insult.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Cerebral Cortex; Energy Metabolism; Gerbillinae; Hippocampus; Lactates; Male; Mitochondria; Phosphocreatine; Pyruvate Dehydrogenase Complex; Reperfusion Injury; Time Factors

31P, 1H and lactate spectroscopic imaging was used to evaluate' the effects of hypothermia on focal cerebral ischemia produced by middle cerebral artery occlusion. The effects on high energy phosphate metabolism, pH, lactate and NAA were investigated in 24 spontaneously hypertensive rats subjected to either permanent or transient ischemia. Under either normothermic (37.5 degrees C) or hypothermic (32 degrees C) conditions, with permanent 6-h occlusion, there was little difference between groups in either the NMR measurements or the volume of infarction. In animals that underwent 3 h of ischemia followed by 12 h of reperfusion, the ischemic changes in lactate, pH, NAA, and high-energy phosphate returned toward control values, and there was a protective effect of hypothermia (infarct volume of 211 +/- 26 and 40 +/- 14 mm3 in normothermic and hypothermic groups, respectively). Thus, hypothermia did not ameliorate the changes in lactate, pH, NAA, or high energy phosphate levels occurring during ischemia, however, during reperfusion there was an improvement in both the recovery of these metabolites and pathological outcome in hypothermic compared with normothermic animals.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Cerebral Arteries; Hypothermia, Induced; Lactates; Magnetic Resonance Spectroscopy; Male; Phosphocreatine; Rats; Reperfusion; Temperature

To study how neuronal cells are affected by development of chronic cerebral vasospasm after subarachnoid hemorrhage (SAH), the changes in neuronal metabolites during development of vasospasm were evaluated by in vivo localized proton magnetic resonance spectroscopy (MRS) in primates.. SAH was produced by introduction of a blood clot around the right middle cerebral artery and the right side of the circle of Willis. MRS experiments were performed before SAH and on Days 7 and 14 after SAH. Multislice magnetic resonance images were obtained to locate the volume of interest (1.0 cm3) in the bilateral parietal regions. The peak areas for choline compounds, the sum of creatine and phosphocreatine, and N-acetyl-aspartate were calculated.. Angiograms revealed approximately 50% reduction of vessel caliber for the right main cerebral arteries on Day 7. Magnetic resonance imaging revealed no apparent cerebral infarction, even in the spasm-side hemisphere. MRS revealed a significant (P < 0.05) reduction of the N-acetyl-aspartate/creatine and phosphocreatine ratio on Days 7 and 14 and a significant increase in the choline/creatine and phosphocreatine ratio on Day 7, in the spasm-side parietal region. In the sham-operated animals, there were no significant changes in these ratios in the bilateral parietal region on Days 7 and 14 after the operation.. The results suggested that the development of cerebral vasospasm after SAH caused ischemic injury in a subpopulation of neuronal cells, even when no apparent cerebral infarction was shown. Proton MRS may be useful to evaluate how neuronal cells are affected by the ischemic insult during development of vasospasm in clinical situations.

Topics: Animals; Aspartic Acid; Brain; Brain Ischemia; Cerebral Angiography; Cerebrovascular Circulation; Choline; Chronic Disease; Cognition Disorders; Creatinine; Energy Metabolism; Female; Ischemic Attack, Transient; Macaca fascicularis; Magnetic Resonance Imaging; Neurons; Phosphocreatine; Subarachnoid Hemorrhage

To record brain temperature for comparison with rectal and temporalis muscle temperatures in preliminary studies before MR spectroscopy experiments, a thermistor was inserted into the basal ganglia in eight anesthetized, ventilated, and physiologically monitored rats. The rats were placed in an MR spectrometer and subjected to 60 min of global cerebral ischemia and 2 h of reperfusion without radiofrequency (RF) pulsing. Body temperature was maintained at 37.5-38.0 degrees C (normothermia) or 36.5-37.0 degrees C (mild hypothermia). Brain temperature during ischemia, which dropped to 31.9 +/- 0.3 (hypothermia) and 33.6 +/- 0.5 degrees C (normothermia), correlated with temporalis muscle temperature (r2 = 0.92) but not with body or magnet bore temperature measurements. Ischemia reduced brain temperature approximately 1.7 degrees C in rats subjected to mild hypothermia (1 degree reduction of body temperature). Parallel MR spectroscopy experiments showed no significant difference in energy metabolites between normothermic and hypothermic rats during ischemia. However, the metabolic recovery was more extensive 20-60 min after the onset of reperfusion in hypothermic rats, although not thereafter (P < 0.05). Mild hypothermia speeds metabolic recovery temporarily during reperfusion but does not retard energy failure during global ischemia in rats.

Topics: Adenosine Triphosphate; Animals; Aspartic Acid; Body Temperature; Brain; Brain Ischemia; Energy Metabolism; Lactic Acid; Magnetic Resonance Spectroscopy; Male; Phosphocreatine; Rats; Rats, Sprague-Dawley; Reperfusion; Temperature

T2 and diffusion weighted MRI, as well as 31P and 1H MRS were performed in kaolin-induced hydrocephalic rats. Extracellular white matter edema was detected in the early stages of progressive hydrocephalus. Phosphocreatine (PCr)/inorganic phosphate (Pi) ratios in hydrocephalic animals were decreased compared to controls, and lactate was detected during the acute and chronic stages of hydrocephalus. These MR spectroscopic results are indicative of a compromised energy metabolism and suggest the occurrence of cerebral ischemia in experimental hydrocephalus.

Topics: Animals; Brain; Brain Edema; Brain Ischemia; Energy Metabolism; Hydrocephalus; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Male; Phosphates; Phosphocreatine; Rats; Rats, Wistar

Topics: Adenosine Triphosphate; Aspartic Acid; Brain Diseases, Metabolic; Brain Ischemia; Humans; Infant, Newborn; Lactic Acid; Magnetic Resonance Spectroscopy; Male; Phosphocreatine; Thalamus

We quantified the concentration of metabolites observed by proton MRS using the tissue water signal as an internal standard. A phantom containing known concentrations of NAA (10 mM) and Cr (5 mM) was used for the study of methodological accuracy. Clinical utility was evaluated by the measurement of patients with severe stenosis or obstruction of the unilateral internal carotid artery. The concentration of tissue water was compensated using a proton-density weighted image measured with a water bag attached to the head. The calculated concentrations of NAA and Cr in the phantom were 9.2 mM (SD: 1.2) and 5.6 mM (SD: 0.7), respectively. On the ischemic side of the brain, the concentrations of NAA and Cr were lower than on the opposite side, but the concentration of choline (Cho) was almost the same on the two sides. The NAA/Cr ratio showed no statistically significant differences between the two sides, because the concentration of Cr was shown to be decreased in the ischemic area. We consider that quantitative evaluation of proton MRS might reveal changes in single metabolites clearly, thereby facilitating understanding of the results of proton MRS.

Topics: Aspartic Acid; Brain; Brain Ischemia; Chronic Disease; Creatine; Humans; Magnetic Resonance Spectroscopy; Phantoms, Imaging; Phosphocreatine; Sensitivity and Specificity

Isoflurane is an appropriate anesthetic for neuroanesthesia. We evaluated whether the effect of sevoflurane is similar to that of isoflurane or halothane on brain energy metabolism after cerebral ischemia followed by reperfusion using 31P-magnetic resonance spectroscopy. Wistar rats (n = 21) were divided into three groups: isoflurane-, sevoflurane-, or halothane-treated. After anesthesia induction and surgical preparation, each anesthetic concentration was adjusted to 1 minimum alveolar anesthetic concentration. Cerebral ischemia was induced with bilateral carotid occlusion and reduction of mean arterial blood pressure to 30-40 mm Hg by blood withdrawal. Magnetic resonance measurements were performed during ischemia and for 120 min of reperfusion. Intracellular pH in the isoflurane-treated, sevoflurane-treated, and halothane-treated groups decreased to 6.180 +/- 0.149, 6.125 +/- 0.134, and 6.027 +/- 0.157, respectively, at the end of ischemia. There were no differences in the change of phosphorous compounds and intracellular pH between the isoflurane-treated and the sevoflurane-treated groups during ischemia and reperfusion. However, in the halothane-treated group, we observed a significant delay in the recovery of adenosine triphosphate and intracellular pH (0.038 +/- 0.013 pH unit/min compared with 0.064 +/- 0.011 in the isoflurane-treated group and 0.058 +/- 0.008 in the sevoflurane-treated group) until 24 min of reperfusion (P < 0.05). We conclude that sevoflurane has effects similar to isoflurane on brain energy metabolism during and after cerebral ischemia.. It is important to know whether anesthetics adversely effect brain metabolism during ischemia and reperfusion. A new anesthetic, sevoflurane, affected the brain in a manner similar to isoflurane, which has been used for many years as an anesthetic.

Topics: Adenosine Triphosphate; Anesthetics, Inhalation; Animals; Brain; Brain Ischemia; Energy Metabolism; Ethers; Halothane; Hydrogen-Ion Concentration; Isoflurane; Magnetic Resonance Spectroscopy; Male; Methyl Ethers; Phosphates; Phosphocreatine; Rats; Rats, Wistar; Reperfusion; Sevoflurane

We examined the potential importance of dexamethasone-mediated alterations in energy metabolism in providing protection against hypoxic-ischemic brain damage in immature rats. Seven-day-old rats (n = 165) that had been treated with dexamethasone (0.1 mg/kg, i.p.) or vehicle were assigned to control or hypoxic-ischemic groups (unilateral carotid artery occlusion plus 2-3 h of 8% oxygen at normothermia). The systemic availability of alternate fuels such as beta-hydroxybutyrate, lactate, pyruvate, and free fatty acids was not altered by dexamethasone treatment, and, except for glucose, brain levels were also unaffected. At the end of hypoxia, levels of cerebral high-energy phosphates (ATP and phosphocreatine) were decreased in vehicle- but relatively preserved in dexamethasone-treated animals. The local cerebral metabolic rate of glucose utilization (lCMRgl) was decreased modestly under control conditions in dexamethasone-treated animals, whereas cerebral energy use measured in a model of decapitation ischemia did not differ significantly between groups. The lCMRgl increased markedly during hypoxia-ischemia (p < 0.05) and remained elevated throughout ischemia in dexamethasone- but not vehicle-treated groups, indicating an enhanced glycolytic flux with dexamethasone treatment. Thus, dexamethasone likely provides protection against hypoxic-ischemic damage in immature rats by preserving cerebral ATP secondary to a maintenance of glycolytic flux.

Topics: 3-Hydroxybutyric Acid; Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Carotid Arteries; Cerebrovascular Circulation; Dexamethasone; Energy Metabolism; Functional Laterality; Glucose; Hydroxybutyrates; Hypoxia, Brain; Ischemic Attack, Transient; Lactates; Phosphocreatine; Pyruvates; Rats; Rats, Wistar

Acidosis may contribute to ischemic injury by mobilizing iron because the iron chelator deferoxamine improves early metabolic recovery from hyperglycermic ischemia. Mobilized iron may then promote oxygen radical-induced lipid peroxidative injury during reperfusion. We tested the hypothesis that administration of the antioxidant tirilazad at the start of reperfusion improves early metabolic recovery after severe acidotic ischemia and ameliorates depletion of the endogenous antioxidant glutathione.. In anesthetized dogs, arterial glucose concentration was increased to 500 to 600 mg/dL and global incomplete cerebral ischemia was produced for 30 minutes by ventricular fluid infusion to reduce perfusion pressure to 10 to 12 mm Hg. Metabolic recovery and intracellular pH were measured by phosphorus MR spectroscopy. In the first experiment, four groups of eight dogs each received either vehicle or 0.25, 1, or 2.5 mg/kg of tirilizad mesylate at reperfusion. Cerebral blood flow was measured with microspheres. In the second experiment, two groups of eight dogs each each received either vehicle or 2.5 mg/kg of tirilazad at reperfusion, and cortical glutathione was measured at 3 hours of reperfusion.. Cerebral blood flow decreased to approximately 6 mL/min per 100 g and intracellular pH decreased to approximately 5.6 during ischemia in all groups. In the vehicle group, ATP recovery was transient and pH remained less than 6.0. Cerebral blood flow, O2 consumption, and ATP eventually declined to near-zero levels by 3 hours. Recovery was improved by tirilazad posttreatment in a dose-dependent fashion. At the highest dose, cerebral blood flow and O2 consumption were sustained near preischemic levels, and five of eight dogs had recovery of ATP greater than 50% and of pH greater than 6.7. Recovery of ATP and phosphocreatine became significantly greater than that in the vehicle group by 17 minutes of reperfusion despite similar levels of early hyperemia, indicating that the drug was acting before the onset of hypoperfusion. Cortical glutathione concentration in the vehicle group was 27% less than that in the tirilazad group and 34% less than that in nonischemic controls.. Decreased depletion of the endogenous antioxidant glutathione is consistent with tirilazad acting as an antioxidant in vivo. Improvement in high-energy phosphate recovery 17 minutes after starting tirilazad infusion during reperfusion is consistent with an early onset of a functionally significant oxygen radical injury. Thus, severe acidosis appears to contribute to early ischemic injury through an oxygen radical mechanism sufficient to impede metabolic recovery.

Topics: Acidosis; Adenosine Triphosphate; Animals; Antioxidants; Brain; Brain Ischemia; Cerebrovascular Circulation; Dogs; Dose-Response Relationship, Drug; Free Radical Scavengers; Glutathione; Hydrogen-Ion Concentration; Hyperemia; Hyperglycemia; Iron; Lipid Peroxidation; Magnetic Resonance Spectroscopy; Male; Oxygen Consumption; Phosphocreatine; Phosphorus; Pregnatrienes; Reperfusion

To use 1H magnetic resonance spectroscopic imaging to study differences in neuron density (N-acetylaspartate [NAA]), membrane phospholipid metabolites (choline [Cho]), and creatine-containing metabolites (creatine plus phosphocreatine [Cr]) in subjects with Alzheimer's disease (AD), with subcortical ischemic vascular dementia (SIVD), and elderly controls.. Cross-sectional, between groups.. A Veterans Affairs medical center and university memory clinic.. Forty elderly subjects with AD (n = 14), with SIVD (n = 8), and elderly controls (n = 18).. We used 1H magnetic resonance spectroscopic imaging to acquire spectra from a 80 x 100 x 17-mm volume superior to the lateral ventricles. Spectra were analyzed from voxels in anterior, medial, and posterior gray and white matter using nuclear magnetic resonance-1 and the results were compared between groups using repeated measures analysis of variance (ANOVA), Tukey's test, and individual Student's t tests.. Using ANOVA, significantly lower levels of NAA/Cho and NAA/Cr and significantly higher levels of Cho/Cr were observed across both gray and white matter voxels in subjects with AD. Using individual Student's t tests, a significantly lower level of NAA/Cho and a higher level of Cho/Cr were observed in the posterior gray matter in subjects with AD. Using ANOVA in subjects with SIVD, significantly lower gray and white matter NAA/Cr levels were observed. Using Tukey's test, the NAA/Cr level was significantly lower in frontal white matter voxels in subjects with SIVD compared with controls.. Our findings in subjects with AD suggest neuron loss in gray matter, axon loss in white matter, and altered Cho metabolism in posterior brain regions. Our findings in subjects with SIVD are consistent with higher levels of creatine-containing metabolites and/or lower levels of NAA in frontal white matter.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Analysis of Variance; Aspartic Acid; Brain; Brain Ischemia; Cerebral Cortex; Choline; Creatine; Cross-Sectional Studies; Dementia, Vascular; Female; Humans; Magnetic Resonance Spectroscopy; Male; Middle Aged; Nerve Tissue; Phosphocreatine; Protons

In the first weeks of life there are important maturational changes in the central nervous system in many species in energy metabolism, synapse number, and concentration of neuronal excitatory receptors.. Four groups of 10 piglets (aged 1, 2, 4, and 10 weeks) underwent 1 hour of deep hypothermic circulatory arrest at 15 degrees C, with cooling and rewarming on cardiopulmonary bypass. Cerebral blood flow and metabolic rate measurements and electroencephalographic recordings were obtained from 5 animals per group. The remaining animals underwent cerebral magnetic resonance spectroscopy.. Preoperative cerebral blood flow and glucose consumption were higher at 4 and 10 weeks than at 1 and 2 weeks. Cerebral adenosine triphosphate content decreased more rapidly during deep hypothermic circulatory arrest at 4 and 10 weeks. Phosphocreatine recovery was greater at 30 minutes of reperfusion at 10 weeks compared with 1 week. Recovery of cerebral phosphocreatine/ adenosine triphosphate ratio and intracellular pH was remarkably uniform at all ages. Latency to recovery of electroencephalographic activity decreased with increasing age (p = 0.04).. Differences in acute recovery of brain energy metabolism and electroencephalogram after cardiopulmonary bypass and 1 hour of deep hypothermic circulatory arrest in piglets between 1 and 10 weeks of age are small. Further studies are required to correlate these acute findings with subsequent neurologic outcome.

Topics: Adenosine Triphosphate; Aging; Animals; Animals, Newborn; Brain; Brain Ischemia; Cardiopulmonary Bypass; Cerebrovascular Circulation; Electroencephalography; Energy Metabolism; Glucose; Heart Arrest, Induced; Hydrogen-Ion Concentration; Hypothermia, Induced; Magnetic Resonance Spectroscopy; Phosphocreatine; Swine; Swine, Miniature

Dichloroacetate (DCA) activates the pyruvate dehydrogenase complex (PDHC), and improves the recovery of cerebral pH, lactate, ATP, and PCr following reperfusion in animal models of forebrain ischemia. In order to determine whether this results in neuroprotection, rats were administered NaDCA (100 mg/kg or 10mg/kg i.v.) 10 min before 12 min of normothermic forebrain ischemia (bilateral carotid artery occlusion plus systemic hypotension, 45 mmHg). Neuronal injury assessed histopathologically 7 days post-ischemia was significantly reduced in the CA1 region of the hippocampus, the dorsal lateral striatum, and the neocortex, in rats treated with 100 mg/kg NaDCA, but not in rats treated with 10 mg/kg NaDCA.

Topics: Adenosine Triphosphate; Animals; Brain Chemistry; Brain Ischemia; Cerebral Cortex; Dichloroacetic Acid; Hippocampus; Male; Neostriatum; Phosphocreatine; Prosencephalon; Pyruvate Dehydrogenase Complex; Rats; Rats, Sprague-Dawley

Brain 99Tcm-HMPAO single photon emission tomography (SPET) and 1H-MRS (proton magnetic resonance spectroscopy) were used to determine correlations between alterations in regional cerebral blood flow (rCBF) and changes in neuronal metabolites in 21 patients (28 examinations) with ischaemic cerebral infarction examined in different phases. rCBF was determined semi-quantitatively using Lassen's linearization algorithm. SPET provided evidence of the hypoperfused site of necrosis within a few hours after the acute event and alterations in rCBF were detected in both the infarcted and diaschistic areas at all stages. 1H-MRS was used to monitor the concentration of the following metabolites: N-acetyl-aspartate (NAA), creatine and phosphocreatine (CR + PCr), compounds containing choline (Cho) and lactate (Lac). A significant correlation was found between reduction in rCBF and a fall in NAA and Cr + PCr in both the acute and chronic phases, but not during "luxury perfusion' in the subacute phase. The presence of LAC in the infarcted area up to 9 months post-ictus was totally unexpected. Simultaneous SPET and 1H-MRS thus provides additional information regarding the physiopathogenesis of cerebral ictus by clarifying the relation between alterations in rCBF and biochemical neuronal changes. We believe that NAA and Cr + PCr concentrations are the best expression of agreement between flow and metabolism in infarcted areas, particularly with regard to hypoperfused areas not clearly detectable by magnetic resonance imaging in the early post-ictus stage.

Topics: Adult; Aged; Aspartic Acid; Brain Ischemia; Cerebral Infarction; Cerebrovascular Circulation; Choline; Creatine; Female; Humans; Lactates; Lactic Acid; Magnetic Resonance Imaging; Male; Middle Aged; Organotechnetium Compounds; Oximes; Phosphocreatine; Protons; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Unlike adults, hyperglycemia with circulating glucose concentrations of 25-35 mM/L protects the immature brain from hypoxic-ischemic damage. To ascertain the effect of hyperglycemia on cerebral oxidative metabolism during the course of hypoxia-ischemia, 7-day postnatal rats underwent unilateral common carotid artery ligation followed by exposure to 8% O2 for 2 h at 37 degrees C. Experimental animals received 0.2 cc s.c. 50% glucose at the onset of hypoxia-ischemia, and 0.15 cc 25% glucose 1 h later to maintain blood glucose concentrations at 20-25 mM/L for 2 h. Control rat pups received equivalent concentrations or volumes of either mannitol or 1 N saline at the same intervals. The cerebral metabolic rate for glucose (CMRglc) increased from 7.1 (control) to 20.2 mumol 100 g-1 min-1 in hyperglycemic rats during the first hour of hypoxia-ischemia, 79 and 35% greater than the rates for saline-and mannitol-injected animals at the same interval, respectively (p < 0.01). Brain intracellular glucose concentrations were 5.2 and 3.0 mM/kg in the hyperglycemic rat pups at 1 and 2 h of hypoxia-ischemia, respectively; glucose levels were near negligible in mannitol- and saline-treated animals at the same intervals. Brain intracellular lactate concentrations averaged 13.4 and 23.3 mM/kg in hyperglycemic animals at 1 and 2 h of hypoxia-ischemia, respectively, more than twice the concentrations estimated for the saline- and mannitol-treated littermates. Phosphocreatine (PCr) and ATP decreased in all three experimental groups, but were preserved to the greatest extent in hyperglycemic animals. Results indicate that anaerobic glycolytic flux is increased to a greater extent in hyperglycemic immature rats than in normoglycemic littermates subjected to cerebral hypoxia-ischemia, and that the enhanced glycolysis leads to greater intracellular lactate accumulation. Despite cerebral lactosis, energy reserves were better preserved in hyperglycemic animals than in saline-treated controls, thus accounting for the greater resistance of hyperglycemic animals to hypoxic-ischemic brain damage.

Topics: Adenosine Triphosphate; Animals; Body Water; Brain; Brain Ischemia; Carotid Arteries; Glucose; Glycolysis; Hyperglycemia; Hypoxia, Brain; Kinetics; Lactates; Lactic Acid; Ligation; Oxygen; Phosphocreatine; Rats; Rats, Wistar

Pyruvate dehydrogenase (PDH) is one of the mitochondrial enzymes which regulate the glucose metabolism. The purpose of this study is to determine the effect of the duration of cerebral ischemia on PDH activity and the metabolites. Cerebral ischemia was produced by bilateral common carotid artery occlusion in Mongolian Gerbils. 20-minute (1) and 60-minute ischemic groups (2) were made. PDH activity and energy metabolites (ATP, PCr, lactate) were measured in the caudate nucleus and cortex at each time period. 1) 20 min ischemic group: PDH activity significantly increased after 20-min ischemia in both the caudate nucleus and cortex, and decreased to levels less than that of the control after 20 min reperfusion. At 60 and 120 min reperfusion, PHD activity returned to the control levels. ATP and PCr concentrations were significantly depleted after the ischemic insult, returning to 60-80% of the control level after reperfusion. Lactate concentrations increased significantly after ischemia, and were reduced by reperfusion. 2) 60 min ischemic group: PDH activity significantly increased after 60 min ischemia, and decreased but remained higher than the control level after 20 min reperfusion. At 60 and 120 min reperfusion, PDH activity gradually decreased towards control levels. ATP and PCr concentrations were depleted after ischemia, and were gradually restored after 20 min reperfusion, recovering to 50% after 60 min reperfusion. Lactate concentrations increased after the ischemic insult, and became more elevated after reperfusion. These findings indicate that there is a significant difference in the PDH activity and metabolism depending on the duration of ischemia. The data suggest that impaired metabolism and persistent elevation of PDH activity may be caused by damage to the mitochondria allowing the influx of Ca2+ during prolonged ischemia.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Gerbillinae; Lactates; Male; Phosphocreatine; Pyruvate Dehydrogenase Complex; Time Factors

The apparent diffusion coefficient (ADC) of choline-containing compounds (Cho), creatine and phosphocreatine (Cre), N-acetyl-aspartate (NAA), lactate, and water was measured in normal rat brain, and in the ischemic and contralateral region of rat brain approximately 3 and 24 h after induction of focal cerebral ischemia. After 3 h of ischemia, the ADC of Cre and NAA in the ischemic region had significantly decreased by 29% and 19%, respectively (P < 0.05). Lactate ADC was also obtained in the ischemic region. After 24 h of focal ischemia, no ADC values could be measured for NAA, Cre and Cho in the ischemic region because their concentrations had become too low. The ADCs of lactate and water in the ischemic volume were virtually identical at 3 and 24 h after occlusion. The experiments suggest that the ADC decrease of water after induction of ischemia is partly caused by changes in the diffusion characteristics of the intracellular compartment.

Topics: Animals; Aspartic Acid; Brain; Brain Ischemia; Choline; Creatine; Diffusion; Lactic Acid; Magnetic Resonance Spectroscopy; Male; Phosphocreatine; Rats; Rats, Inbred F344; Water

Hyperglycemia increases cerebral damage after transient cerebral ischemia. This study used in vivo 31P nuclear magnetic resonance spectroscopy to determine the relationship of intracellular tissue acidosis and delayed recovery of brain high-energy phosphates to increased damage during the reperfusion period. Mongolian gerbils were subjected to transient bilateral carotid ischemia for 20 min with 2 h reperfusion. All gerbils were pretreated intraperitoneally with equivalent volumes in saline of 0.003 units per kilogram of insulin or vehicle, or with 4 grams of glucose per kilogram. The gerbils were then scanned in a 4.7 Tesla Magnetic Resonance Imager-Spectrometer to determine levels of intracellular pH, inorganic phosphate, adenosine triphosphate, and phosphocreatine. In each group, intracellular pH decreased with ischemia, but most significantly in hyperglycemic animals (6.45 +/- 0.15), in which it had not recovered to preischemic levels by the end of the reperfusion period (6.8 +/- 0.1 vs 7.04 +/- 0.1, p < 0.05). High-energy phosphates phosphocreatine-inorganic phosphate and phosphocreatine-adenosine triphosphate showed partial recovery in all groups throughout the reperfusion period; the recovery was not significantly altered by glucose status. Hyperglycemia worsened pH but not the recovery of high-energy phosphates in animals reperfused after 20 min of transient cerebral ischemia. This sustained acidosis may be a primary event in transient damage in hyperglycemic animals.

Topics: Adenosine Triphosphate; Animals; Arterial Occlusive Diseases; Blood Glucose; Body Weight; Brain Ischemia; Carotid Arteries; Energy Metabolism; Gerbillinae; Glucose; Hydrogen-Ion Concentration; Hyperglycemia; Hypoglycemic Agents; Insulin; Magnetic Resonance Spectroscopy; Male; Phosphates; Phosphocreatine; Reperfusion Injury

Rapid changes in the average water diffusion constant, Dav = 1/3[Dxx+Dyy+Dzz], and in the concentrations of lactate and purine nucleotides and nucleosides were measured upon global ischemia (cardiac arrest) in cat brain, at a combined time resolution of 36 s (n = 7). At this time resolution, the normalized time curves of 1 - Dav and the increase in ATP breakdown product did not coincide, with the changes in Dav being most rapid. The normalized curves of 1 - Dav and the lactate increase coincided for the first 2-2.5 min after which the change in Dav was more rapid. After this time point, an excellent correlation was found between the drop in Dav and the decrease in energy utilization rate, which was calculated from the measured time curves of lactate formation and ATP breakdown, and from the time curve for phosphocreatine use reported in the literature. These results are in agreement with the expected biphasic changes in ion and water homeostasis during ischemia and with the model of diffusional changes being a consequence of a water shift from interstitial to intracellular space.

Topics: Adenosine Triphosphate; Animals; Body Water; Brain; Brain Ischemia; Cats; Diffusion; Energy Metabolism; Heart Arrest; Lactates; Phosphocreatine; Purine Nucleosides; Purine Nucleotides

A 2.9 degrees C reduction in the intraischemic rectal temperature of neonatal piglets is associated with less brain damage compared with animals with normothermic rectal temperatures. This investigation studied one potential mechanism for this observation: better maintenance of energy stores and less brain acidosis secondary to reduced metabolic activity associated with modest hypothermia.. 31P MR spectroscopy was used to study piglets before, during, and after 15 minutes of partial brain ischemia with intraischemic rectal temperatures of either 38.3 +/- 0.4 degrees C (n = 10, normothermic) or 35.4 +/- 0.5 degrees C (n = 10, hypothermic). Animals were followed up for up to 72 hours after ischemia and were evaluated clinically and by brain histology.. Values for pHi remained 0.15 to 0.20 pH units greater in modestly hypothermic than in normothermic piglets during ischemia and the initial 30 minutes after ischemia (P = .049, group effect). Phosphocreatine, beta-ATP, and inorganic phosphorus were similar between groups. The relationship between the intraischemic energy state and subsequent clinical evidence of brain damage (irrespective of group assignment) revealed lower pHi over the last 7 minutes of ischemia for abnormal compared with normal piglets (5.98 +/- 0.22 versus 6.39 +/- 0.24, respectively; P = .002). In contrast, intraischemic beta-ATP (41 +/- 19% versus 57 +/- 21% of control) and inorganic phosphorus (273 +/- 31% versus 224 +/- 92% of control) for abnormal and normal piglets, respectively, did not differ between groups.. Intraischemic modest hypothermia attenuates the severity of brain acidosis during and 30 minutes after ischemia compared with normothermic animals and supports the concept that attenuated brain acidosis is a potential mechanism by which hypothermia may reduce ischemic brain damage.

Topics: Acidosis; Adenosine Triphosphate; Animals; Animals, Newborn; Body Temperature; Brain; Brain Damage, Chronic; Brain Diseases; Brain Ischemia; Energy Metabolism; Follow-Up Studies; Hydrogen-Ion Concentration; Hypothermia, Induced; Magnetic Resonance Spectroscopy; Phosphates; Phosphocreatine; Phosphorus Isotopes; Swine; Time Factors

To evaluate the effect of hypothermic circulatory arrest on brain metabolism, we used 31P-magnetic resonance spectroscopy to monitor brain metabolites in pigs during 2 hours of ischemia and 1 hour of reperfusion. Twenty-eight pigs were divided into five groups. Anesthesia (n = 5) and hypothermic cardiopulmonary bypass groups (n = 5) served as controls. In the circulatory arrest (n = 6), antegrade perfusion (n = 6), and retrograde (n = 6) brain perfusion groups, the bypass flow rate was 60 to 100 ml.kg-1.min-1. In the antegrade group, the brain was perfused via the carotid arteries at a blood flow rate of 180 to 200 ml.min-1 during circulatory arrest at 15 degrees C. In the retrograde group, the brain was perfused through the superior vena cava at a flow rate of 300 to 500 ml.min-1 during circulatory arrest at 15 degrees C. The intracellular pH was 7.1 +/- 0.1 and 7.3 +/- 0.1 in the anesthesia and hypothermic cardiopulmonary bypass groups, respectively. In the circulatory arrest group, the intracellular pH decreased to 6.2 +/- 0.1 and did not recover to its initial value (7.0 +/- 0.1) during reperfusion (p < 0.05 compared with the value obtained from the control groups at the corresponding time). Inorganic phosphate did not return to its initial level during reperfusion. In three animals in this group, levels of high-energy phosphates, adenosine triphosphate and phosphocreatine, recovered partially but did not reach the levels observed before arrest. In the group receiving antegrade perfusion, cerebral metabolites and intracellular pH were unchanged throughout the protocol. During circulatory arrest in the retrograde perfusion group the intracellular pH decreased to 6.4 +/- 0.1 and recovered fully during reperfusion (7.1 +/- 0.1). High-energy phosphates also returned to their initial levels during reperfusion. These studies show that deep hypothermic circulatory arrest with antegrade brain perfusion provides the best brain protection of the options investigated.

Topics: Adenosine Triphosphate; Analysis of Variance; Animals; Aorta, Thoracic; Brain; Brain Ischemia; Heart Arrest, Induced; Hydrogen-Ion Concentration; Hypothermia, Induced; Magnetic Resonance Spectroscopy; Perfusion; Phosphates; Phosphocreatine; Radionuclide Imaging; Swine

The effects of NBP on gasping and brain energy metabolism after complete brain ischemia in mice subjected to decapitation were investigated. The levels of ATP, phosphocreatine (PCr) and lactate were determined by the method of Lowry. The data indicated that NBP at 112.5 or 250 mg.kg-1 sc can significantly prolong the duration of gasping and at the dose of 150 or 200 mg.kg-1 sc reduce the level of lactate and increase the levels of ATP and PCr after complete brain ischemia. The results suggest that NBP may have brain protective action and improve ischemic brain energy metabolism.

Topics: Adenosine Triphosphate; Animals; Anticonvulsants; Benzofurans; Brain; Brain Ischemia; Decerebrate State; Energy Metabolism; Female; Lactates; Male; Mice; Phosphocreatine

In a rat model of intrauterine growth retardation and fetal brain ischemia, the maternal-fetal circulation was obstructed for up to 40 min in 20-day gestational age rats by occluding (restriction) the uterine blood vessels supplying the placenta. After restriction, flow was returned (reperfusion) for designated times. A time-dependent depletion of cerebral pyruvate levels (from 0.2 +/- 0.02 to 0.06 +/- 0.01 mumol/g wet weight) accompanied by an elevation in lactate concentration (from 1.95 +/- 0.03 to 7.00 +/- 0.56 mumol/g wet weight) was observed after 20 min restriction. During 20 min, reperfusion lactate levels continued to increase, then gradually decreased as the reperfusion continued for approximately 2 h. A drastic increase in the lactate/pyruvate ratio (from 10 to 117) suggested that the fetal brain was relying on anaerobic glycolysis to meet its energy demands. In addition, a time-dependent decrease in fetal brain phosphocreatine (PCr) content from 2.54 +/- 0.26 to 1.52 +/- 0.15 mM was observed after 20 min of maternal-fetal blood flow obstruction. ATP levels gradually decreased after 20 min restriction from 1.62 +/- 0.13 to 0.59 +/- 0.09 mM. After 30 min reperfusion ATP, PCr and pyruvate returned to their normal values. These metabolic changes observed are concordant with the ability of the ischemic fetal brain to sustain adequate levels of ATP for energy-requiring cellular processes. The capacity of glucose transporters to facilitate transport of glucose into brain tissue was assessed ex vivo, using [3H]2-deoxyglucose (2D-Glu).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Brain; Brain Chemistry; Brain Ischemia; Deoxyglucose; Energy Metabolism; Female; Glucose; Glycolysis; Kinetics; Lactates; Lactic Acid; Phosphocreatine; Placental Circulation; Pregnancy; Pyruvates; Pyruvic Acid; Rats; Rats, Wistar; Reperfusion

Spatial localization with the spectroscopic imaging technique is normally implemented with the Fourier-transform approach, yielding rectangular voxels, with potentially significant cross-voxel contamination. Multidimensional Fourier-series window (FSW) is an alternate approach that generates single voxels of predetermined shape, with minimal out-of-voxel contamination. The spatial location of the voxel is shifted by means of postacquisition processing. A two-dimensional circular voxel is introduced, which for many in vivo applications is a good match of the region of interest. Phantom images illustrate the spatial distribution of signal intensity within the circular FSW voxels. Phantom spectroscopic studies show excellent spatial localization, with no detectable out-of-voxel contamination. The circular FSW voxel approach is implemented in human and animal model studies, demonstrating the technique's utility. This arbitrary shape approach can be extended to three dimensions, defining, for example, cylinders, spheres, or ellipsoids.

Topics: Adenosine Triphosphate; Animals; Artifacts; Brain Ischemia; Diphosphates; Dogs; Female; Humans; Hydrogen; Leg; Magnetic Resonance Spectroscopy; Models, Structural; Models, Theoretical; Muscle, Skeletal; Organophosphorus Compounds; Phosphates; Phosphocreatine; Phosphorus Isotopes; Potassium Compounds; Spectroscopy, Fourier Transform Infrared

Proton magnetic resonance spectroscopy (1H-MRS) is a non-invasive technique which has proved to be useful for monitoring various brain metabolites (N-acetyl-aspartate, choline, creatine-phosphocreatine, lactate). A total of 18 patients underwent a combined magnetic resonance imaging (MRI)/1H-MRS protocol in order to evaluate the distribution of the metabolites in the various stages of cerebral ischemia. Our results show a marked decrease of N-acetyl-aspartate and a large content of Lactate during the early phases, and a decrease in N-acetyl-aspartate, choline and creatine-phosphocreatine (Cr-PCr) during the chronic phase.

Topics: Adult; Aged; Aspartic Acid; Brain; Brain Ischemia; Case-Control Studies; Choline; Creatine; Female; Humans; Lactates; Lactic Acid; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Male; Middle Aged; Phosphocreatine

Tissue acidosis is believed to be a key element in ischemic injury of neural tissue. The goal of this study was to determine whether persisting postischemic acidosis or the extent of acidosis would affect metabolic recovery following an ischemic event. Intracellular pH (pHi), adenosine triphosphate, phosphocreatine, and lactate levels were measured in the cerebral cortex during the early stages of reperfusion, following either 5 or 10 minutes of global ischemia in both normo- and hyperglycemic gerbils. A total of 130 gerbils were injected with a solution containing 1.5 ml Neutral Red (1%) (+/- 2.5 gm/kg glucose); 30 minutes later, the gerbils were placed under halothane anesthesia, and the carotid arteries were occluded for either 5 or 10 minutes. The brains were frozen in liquid nitrogen at 0, 15, 30, 60, and 120 seconds after reperfusion; they were sectioned and the block face was photographed to determine the pHi by using Neutral Red histophotometry. At the conclusion of the ischemia, the pHi in all groups had decreased significantly from a control value of 7.05 +/- 0.03) (mean +/- standard error of the mean). In normoglycemic brains, the pHi values fell to 6.71 +/- 0.04 and 6.68 +/- 0.11 after 5 and 10 minutes of ischemia, respectively. Hyperglycemic brains were more acidotic; values fell to 6.57 +/- 0.10 and 6.52 +/- 0.24 after 5 and 10 minutes of ischemia, respectively. Lactate levels were approximately fivefold greater than those of control tissue in normoglycemic brains, while lactate levels in hyperglycemic brains were increased eightfold. The adenosine triphosphate and phosphocreatine levels were depleted at the end of ischemia in all groups. After 2 minutes of reflow activity, the pHi levels in both normo- and hyperglycemic brains were restored to those of control values in the '5-minute ischemic group, while the pHi levels remained significantly depressed in the 10-minute ischemic group. Restoration of high-energy phosphates was similar in normoglycemic brains regardless of ischemic duration, recovering to only 20% of the restoration obtained in control tissue at 2 minutes. In hyperglycemic brains, however, there was complete recovery of high-energy phosphates by 2 minutes of reflow activity following 5 minutes of ischemia. Extending the ischemic period to 10 minutes in hyperglycemic brains slowed the rate of metabolic recovery to that observed in normoglycemic brains. The results indicate that the reflow period permits the rapid restoration o

Topics: Acidosis; Adenosine Triphosphate; Animals; Blood Glucose; Brain Ischemia; Cerebral Cortex; Cerebrovascular Circulation; Energy Metabolism; Gerbillinae; Hydrogen-Ion Concentration; Lactates; Male; Phosphocreatine; Reperfusion; Vascular Patency

When carbamazepine (Car) was injected ip 13.0-50.0 mg.kg-1 30 min before inhaling 96% N2 + 4% O2, the survival time of mice was prolonged (from 54 +/- 8 s in control group to 119 +/- 35 s). The survival time of mice subjected to bilateral carotid artery ligation was markedly prolonged by Car (25.0-50.0 mg.kg-1), medians were 4, 6, and 15 min, respectively. Car (25.5-70.0 mg.kg-1) alleviated the reduction of ATP (from 1.0 +/- 0.3 mumol.g-1 in control group to 1.9 +/- 0.5 mumol.g-1) and phosphocreatine (PC) contents (from 0.8 +/- 0.2 mumol.g-1 in control group to 1.2 +/- 0.3 mumol.g-1) and the accumulation of lactic acid (LA) (from 9.6 +/- 1.3 mumol.g-1 in control group to 6.7 +/- 0.7 mumol.g-1) in mouse brain 30 s after decapitation. These results indicated that Car was effective against hypoxia and brain ischemia in mice.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Carbamazepine; Hypoxia; Lactates; Male; Mice; Phosphocreatine

The association between the ultimate brain damage resulting from unilateral hypoxic-ischemic insult (HI) and the changes in high-energy metabolites, measured by noninvasive phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy during the insult, was evaluated in 7-day postnatal rats. When the NMR metabolite levels were integrated over the last 1.5 h out of 2.5 h of HI, there was a significant correlation of both the estimator of phosphorylation potential (P < 0.001) and ATP levels (P < 0.01) with histologic score of damage and area morphometry. In particular, the development of cerebral infarction could be predicted from the NMR evaluation (P < 0.005). These findings suggest that a large disturbance in cellular energy metabolism is a prerequisite for the subsequent neuropathological alterations in this model.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Chemistry; Brain Ischemia; Carotid Artery, Common; Energy Metabolism; Female; Histocytochemistry; Hydrogen-Ion Concentration; Hypoxia, Brain; Magnetic Resonance Spectroscopy; Male; Phosphocreatine; Rats; Rats, Wistar

The time course of the decline in energy levels during an in vitro ischemia-like condition was compared with changes in intracellular Ca2+ concentration ([Ca2+]i) in subregions of the gerbil hippocampal slice [CA1, CA3, and the inner and outer portions of the dentate gyrus (DG)]. Hippocampal transverse slices were loaded with a fluorescent indicator, rhod-2. During the on-line monitoring of [Ca2+]i, the slices were perfused with an in vitro ischemia-like medium (33 degrees C). The slices were collected at several experimental time points, frozen, dried, and dissected into subregions. The contents of adenine nucleotides (ATP, ADP, and AMP) and phosphocreatine (PCr) were measured by HPLC methods. Region-specific and acute [Ca2+]i elevations were observed in CA1 approximately 4 min after onset of the in vitro ischemia-like condition and also in the inner portion of the DG with a delay of 10-40 s. The change in ATP levels was related to the increase in [Ca2+]i. ATP levels in all subregions gradually decreased before the acute [Ca2+]i elevation. Concomitant with the acute [Ca2+]i elevation in CA1 and the inner portion of the DG, ATP levels in the subregions rapidly decreased, whereas declines in levels of high-energy-charge phosphates were gradual in CA3 and the outer portion of the DG, in which the remarkable [Ca2+]i elevation was not observed. These results suggest that ATP depletion observed in CA1 and the inner portion of the DG is due to the region-specific increase in [Ca2+]i, which activates a Ca(2+)-ATP-driven pump and produces a subsequent fall in neuronal ATP content.

Topics: Adenine Nucleotides; Animals; Brain Ischemia; Calcium; Energy Metabolism; Fluorescent Dyes; Gerbillinae; Heterocyclic Compounds, 3-Ring; Hippocampus; In Vitro Techniques; Intracellular Membranes; Male; Osmolar Concentration; Phosphocreatine

We examined metabolic and functional changes when forebrain ischemia was induced in stroke-prone spontaneously hypertensive rats by bilateral carotid artery occlusion. In addition, the protective effect of clentiazem was evaluated in this model.. Rats were anesthetized with urethane. Cerebral blood flow was measured with a laser Doppler flowmeter. Cerebral high-energy phosphates and intracellular pH were measured by phosphorus magnetic resonance spectroscopy. Electroencephalographic activity was evaluated as the summation of its amplitude. These parameters were monitored during a 30-minute period of ischemia and recirculation. Clentiazem was given orally as pretreatment (10 mg/kg twice a day for 3.5 days).. Bilateral carotid occlusion caused a decrease in cerebral blood flow to approximately 5% of the preischemic level and the disappearance of electroencephalographic activity. Occlusion also caused a decrease in ATP and phosphocreatine (to 48.7 +/- 4.3% and 23.7 +/- 2.2% of preischemic levels, respectively) as well as intracellular pH (from 7.3 +/- 0.1 to 6.0 +/- 0.1). During recirculation the reversal of these changes was variable: high-energy phosphates were partially restored, but electroencephalographic activity and intracellular pH showed little improvement. Hypoperfusion (55.7 +/- 11.5% of the preischemic flow) developed after reactive hyperemia. Pretreatment with clentiazem lessened the decrease in cerebral blood flow (control, 4.8 +/- 1.4%; clentiazem, 14.1 +/- 4.1% of the preischemic level; P < .05) and prevented the disappearance of electroencephalographic activity in some rats during ischemia. Clentiazem also prevented postischemic hypoperfusion and accelerated the restoration of high-energy phosphates, intracellular pH, and electroencephalographic activity during recirculation.. Carotid artery occlusion induced stable forebrain ischemia in stroke-prone spontaneously hypertensive rats. Clentiazem improved the metabolic and functional disturbances that occurred in this ischemic model, and its beneficial effect appeared to be due mainly to the relative preservation of cerebral blood flow during carotid occlusion.

Topics: Adenosine Triphosphate; Analysis of Variance; Animals; Antihypertensive Agents; Arterial Occlusive Diseases; Blood Pressure; Brain; Brain Ischemia; Carbon Dioxide; Carotid Artery Diseases; Cerebral Arteries; Cerebral Cortex; Cerebrovascular Circulation; Cerebrovascular Disorders; Diltiazem; Disease Susceptibility; Electroencephalography; Energy Metabolism; Heart Rate; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Male; Oxygen; Partial Pressure; Phosphocreatine; Rats; Rats, Inbred SHR; Regional Blood Flow; Time Factors; Tissue Distribution

We used 31P nuclear magnetic resonance (NMR) spectroscopy to study the effect of moderate hyperglycemia on brain ATP and intracellular pH in a model of severe incomplete forebrain ischemia. Plasma glucose in the hyperglycemic rats was 277 +/- 9 mg/100 ml compared with 115 +/- 10 mg/100 ml in the normoglycemic rats at the onset of ischemia. After 15 min of ischemia, brain ATP levels decreased to 31 +/- 8% in normoglycemic rats vs. 63 +/- 11% in hyperglycemic rats (P < 0.05). Phosphocreatine levels were 31 +/- 9 and 55 +/- 8% for normoglycemic and hyperglycemic rats, respectively. Intracellular pH decreased to the same level (approximately 6.5) in both normoglycemic and hyperglycemic animals after 15 min of ischemia. In summary, we found that moderate hyperglycemia during severe incomplete forebrain ischemia significantly increases ischemic brain ATP levels but does not have a significant effect on intracellular pH. These results support the hypothesis that alterations in brain ATP and adenosine concentrations may be important in the pathogenesis of ischemic tissue injury under moderate hyperglycemic conditions, whereas alterations in tissue pH may be less important.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Hydrogen-Ion Concentration; Hyperglycemia; Intracellular Membranes; Magnetic Resonance Spectroscopy; Male; Phosphocreatine; Phosphorus; Rats; Rats, Sprague-Dawley

The time-course of changes in extracellular glutamate and energy metabolism during 30 or 60 min of complete cerebral ischemia and 60-90 min of reperfusion was investigated by microdialysis and magnetic resonance spectroscopy in parallel groups of rats. During the first 10 min of ischemia, adenosine triphosphate (ATP) was completely depleted, and lactate increased 10-fold; after 30 min, intracellular pH had decreased to 6.33 +/- 0.11. ATP and lactate did not change further between 30 and 60 min of ischemia. Glutamate increased 30-fold between 10 and 30 min of ischemia and continued to increase in the 60-min ischemia group. After 30 min of reperfusion, glutamate had returned to pre-ischemic levels in both groups. The cellular energy state recovered within 50-60 min after 30 min of ischemia but never returned to more than 60% of baseline values after 60 min of ischemia. The continued increase in extracellular glutamate after total depletion of ATP suggests that glutamate release during ischemia is not entirely energy dependent. Ca(2+)-independent glutamate release and failure of energy-dependent glutamate re-uptake mechanisms may result in continued increase in extracellular glutamate. The rapid normalization of extracellular glutamate after 30 and 60 min of ischemia despite differences in the recovery of energy metabolism suggests that the glutamate levels were reduced by an energy-independent mechanism, such as diffusion into the restored circulation.

Topics: Adenosine Triphosphate; Amino Acids; Animals; Blood Pressure; Brain Ischemia; Dialysis; Energy Metabolism; Extracellular Space; Glutamates; Glutamic Acid; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Male; Neurotransmitter Agents; Oxygen Consumption; Phosphocreatine; Rats; Rats, Sprague-Dawley

We investigated the temporal relationship of the emergence of biochemical abnormalities to the development of behavioral dysfunction to identify the central factors of ischemic neurological disorders in developing brains. To induce early ischemia, bilateral carotid artery occlusion (BCAO) was surgically performed on 21 cats at the second week of age. BCAO produces histopathological damage, including neuronal loss and thinning of white matter. 31P magnetic resonance spectroscopy was used to monitor brain oxidative metabolism, neuronal membrane growth, and myelination of the prefrontal cortex in the first 3 months. Neurological development was monitored by conducting 25 tests of reflex, motor, sensory, and integrated behavioral function. At 1 month, phosphodiester (PDE) levels, a component of membranes and myelin, were low in animals showing complete ligation. At 2 months, the growth of PDE was low (1/4 to 1/2 of normal) in BCAO animals, whereas normal animals demonstrated a 23% increase. Phosphocreatine (PCr) levels, indicated by PCr/ATP and PCr/inorganic phosphate ratios, were retarded at 2 months in completely ligated animals (1/4 of normal). Neurologically, the completely ligated animals showed retardation of general development. The retardation was most pronounced for integrative functions, including visual function, and became more pronounced later in development. The time course of emergence of the retardation generally coincided with emergence of abnormalities in phosphorous compounds. The simultaneous occurrence of several biochemical and functional abnormalities in development following early ischemic insult suggests a causal relationship between membrane and mitochondrial development and neurological function.

Topics: Adenosine Triphosphate; Aging; Animals; Brain; Brain Ischemia; Carotid Arteries; Cats; Cerebrovascular Circulation; Energy Metabolism; Magnetic Resonance Spectroscopy; Motor Activity; Motor Neurons; Neurons; Neurons, Afferent; Phosphates; Phosphocreatine; Phosphorus; Reflex

Experimental and clinical studies suggest that the calcium channel blocker nimodipine may reduce cerebral ischemic injury. Using rapid acquisition phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy, we examined the effect of nimodipine on cerebral energy metabolism during severe ischemia in gerbils. High-energy phosphates and intracellular pH were characterized at baseline and at 2-min intervals following bilateral common carotid artery (CCA) ligation. Serial forebrain spectroscopy was continued until phosphocreatine (PCr) and adenosine triphosphate (ATP) resonances disappeared. Controls (n = 10) were compared to gerbils receiving intraperitoneal nimodipine 30 min prior to carotid ligation, at the following doses: 0.5 mg/kg (n = 8), 1.0 mg/kg (n = 10), 2.0 mg/kg (n = 8), or 4.0 mg/kg (n = 4). In the control group, PCr and ATP peaks were undetectable after a mean of 5.4 +/- 0.47 min following CCA ligation. Compared with controls, the mean time for depletion of high-energy phosphates following carotid ligation was prolonged at nimodipine doses of 0.5 mg/kg and 1.0 mg/kg, but the differences did not reach statistical significance. In the 2.0 mg/kg group, however, ATP was preserved until 9.8 +/- 1.0 min following the onset of ischemia, significantly longer than the control group (p = 0.005, Mann-Whitney test). Nimodipine had no effect on the time course or severity of intracellular acidosis. In this model of severe ischemia, relatively high doses of nimodipine slowed the depletion of high-energy phosphates without altering intracellular acidosis. This suggests that nimodipine may provide cerebral protection by directly altering ischemic cellular metabolism.

Topics: Acidosis; Adenosine Triphosphate; Animals; Brain Ischemia; Carotid Artery, Common; Energy Metabolism; Gerbillinae; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Male; Nimodipine; Phosphates; Phosphocreatine

The effect of benidipine on experimental cerebral ischemia was investigated in rats subjected to occlusion of the bilateral common carotid arteries. Benidipine (30 micrograms/kg, i.p.) improved neurological symptoms such as ataxia, convulsion and loss of righting reflex, and prolonged survival time after occlusion of the bilateral common carotid arteries. In the nicardipine (100 micrograms/kg, i.p.)-treated group, a similar effect was observed, whereas nifedipine (100, 300 micrograms/kg, i.p.) and verapamil (300 micrograms/kg, i.p.) did not show any beneficial effect in this model. Furthermore, pretreatment with benidipine (30 micrograms/kg, i.p.) suppressed the increase in cerebral water content 3 h after the occlusion. Nicardipine (100 micrograms/kg, i.p.) showed a tendency to reduce the increase in cerebral water content, though the effect was not statistically significant. Nifedipine (100 micrograms/kg, i.p.) produced no improvement. After occlusion of the bilateral common carotid arteries, depletion of adenosine triphosphate (ATP) and phosphocreatine (CP) and an accumulation of lactate occurred in a time-dependent manner. Prophylactic administration of benidipine (30 micrograms/kg, i.p.), 20 min before occlusion, attenuated the depletion of ATP and CP and the accumulation of lactate 3h after the occlusion. Furthermore, post-treatment with benidipine 30 min after occlusion also suppressed these metabolic disorders. In conclusion, the beneficial effects of benidipine in this severe cerebral ischemia model show that the compound has advantages over nicardipine, nifedipine and verapamil. Thus, these results suggest that benidipine may be useful in the treatment of acute ischemic cerebral damage.

Topics: Adenosine Triphosphate; Animals; Behavior, Animal; Brain; Brain Chemistry; Brain Ischemia; Calcium Channel Blockers; Carotid Artery, Common; Dihydropyridines; Lactates; Lactic Acid; Male; Nicardipine; Nifedipine; Phosphocreatine; Potassium; Rats; Rats, Wistar; Sodium; Verapamil

A lactate editing sequence based on the use of spin-locking pulses with surface coils is described. The sequence retains more than 90% of the available lactate magnetization and suppresses at least 95% of the lipid signal in a single scan and ca. 99.5% after a simple two step cycle. The technique allows simultaneous observation of lactate and uncoupled metabolites in the range 2 to 3 ppm. The sequence was combined with two-dimensional spectroscopic imaging to obtain a lactate map of an ischemic rat brain in vivo.

Topics: Animals; Aspartic Acid; Brain; Brain Ischemia; Choline; Creatine; Electron Spin Resonance Spectroscopy; Image Enhancement; Lactates; Lipids; Magnetic Resonance Spectroscopy; Magnetics; Models, Structural; Models, Theoretical; Phosphocreatine; Rats; Signal Processing, Computer-Assisted; Water

Age-related changes in cerebral energy utilization were examined in swine, a species whose maximal rate of development is known to occur in the perinatal period. Interleaved in vivo 31P and 1H nuclear magnetic resonance spectroscopy was used to measure the rates of change in cerebral concentrations of phosphocreatine (PCr), nucleoside triphosphates, and lactate following complete ischemia, induced via cardiac arrest, in a total of 19 newborn, 10-day-old, and 1-month-old piglets. Preischemic concentrations of these three metabolites plus glucose and glycogen were determined in a separate experiment on 12 piglets whose brains were funnel-frozen in situ. The rate constants for the PCr and ATP decline and lactate increase were determined by nonlinear regression fits to the experimental data, assuming first-order kinetics. The rate constants and preischemic metabolite concentrations were used to calculate the initial flux of high-energy phosphate equivalents (approximately P), which was used as an estimate of cerebral energy utilization at the point when ischemia was initiated. Cerebral energy utilization equaled 6.5 +/- 1.9, 9.5 +/- 3.2, and 15.1 +/- 3.2 mumol approximately P/g/min in newborn, 10-day-old, and 1-month-old piglets, respectively. Within each age group the energy utilization rate was not altered by hyperglycemia-induced increases in cerebral energy reserves, but during hypoglycemia cerebral energy utilization rates decrease. The slope of approximately P versus time decreased with the duration of ischemia, indicating that cerebral energy utilization rates decrease after the first few minutes of ischemia. Newborn piglets had higher cerebral energy utilization rates compared with literature values for newborn rats and mice. This is consistent with the concept that newborns from a species with a perinatal stage of maximal growth and development will have higher cerebral energy demands compared with newborns from a species such as rodents, whose maximal growth occurs postnatally. However, this conclusion remains tentative because literature cerebral utilization rates estimated from the initial slope of approximately P-versus-time plots tend to underestimate the true rate, since the assumption of continued linearity may not be valid for the interval chosen.

Topics: Animals; Animals, Newborn; Brain; Brain Ischemia; Energy Metabolism; Glucose; Lactates; Lactic Acid; Magnetic Resonance Spectroscopy; Phosphocreatine; Swine

Postischemic evoked potential recovery correlates with acidosis during ischemia and early reperfusion. Acidosis promotes lipid peroxidation in vitro. We tested the hypothesis that the 21-aminosteroid tirilazad mesylate (U74006F), an inhibitor of lipid peroxidation in vitro, ameliorates somatosensory evoked potential recovery and acidosis during reperfusion after severe incomplete cerebral ischemia.. Cerebral perfusion pressure was reduced to 11 +/- 1 mm Hg (+/- SEM) for 30 minutes by cerebral ventricular fluid infusion in anesthetized dogs. Cerebral intracellular pH and high-energy phosphates were measured by magnetic resonance spectroscopy. Dogs were randomized to receive vehicle (citrate buffer; n = 8) or tirilazad (1 mg/kg; n = 8) before ischemia in a blinded study.. Cerebral blood flow was reduced to 6 +/- 1 mL/min per 100 g during ischemia, resulting in nearly complete loss of high-energy phosphates and an intracellular pH of 6.0-6.1 in both groups. Initial postischemic hyperemia was similar between groups but lasted longer in the vehicle group. Tirilazad accelerated mean recovery time of intracellular pH from 31 +/- 5 to 15 +/- 3 minutes and of inorganic phosphate from 13 +/- 2 to 6 +/- 1 minutes. Recovery of somatosensory evoked potential amplitude was greater with tirilazad (49 +/- 3%) than vehicle (33 +/- 6%). Fractional cortical water content was less with tirilazad (0.819 +/- 0.003) than vehicle (0.831 +/- 0.002).. Tirilazad attenuates cerebral edema and improves somatosensory evoked potential recovery after incomplete ischemia associated with severe acidosis. Accelerated pH and inorganic phosphate recovery indicates that this antioxidant acts during the early minutes of reperfusion.

Topics: Acidosis; Adenosine Triphosphate; Animals; Bicarbonates; Brain; Brain Edema; Brain Ischemia; Cytoplasm; Dogs; Drug Evaluation, Preclinical; Evoked Potentials, Somatosensory; Hydrogen-Ion Concentration; Male; Phosphocreatine; Pregnatrienes; Reactive Oxygen Species; Reperfusion Injury

Ischemia-induced changes in 31P NMR relaxation were examined in 16 piglets. NMR spectra were acquired under control conditions and during complete cerebral ischemia induced via cardiac arrest. Changes in T1 were assessed directly in six animals during control conditions and after 30-45 min of complete ischemia when changes in brain Pi levels had reached a plateau. The T1 for Pi did not change, i.e., 2.3 +/- 0.5 s during control conditions versus 2.4 +/- 1.0 s during ischemia. To evaluate phosphocreatine and ATP, two types of spectra, with a long (25-s) or short (1-s) interpulse delay time, were collected during the first 10 min of ischemia (n = 10). Both types of spectra showed the same time course of changes in phosphocreatine and ATP levels, implying that the T1 relaxation times do not change during ischemia. There were no changes in the linewidths of phosphocreatine, ATP, or Pi during ischemia, implying that the T2* values remain constant. Our results suggest that the 31P T1 and T2* for phosphocreatine, Pi, and ATP do not change during ischemia, and therefore changes in 31P NMR peak intensity accurately reflect changes in metabolite concentrations.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Magnetic Resonance Spectroscopy; Osmolar Concentration; Phosphates; Phosphocreatine; Phosphorus; Swine

Localized proton nuclear magnetic resonance spectroscopy (MRS), obtained with stimulated echo and spin echo sequences, MR imaging (MRI) and MR angiography (MRA) were used to study the brain in 13 children and adolescents with sickle cell disease. Regions of interest (ROI) studied by MRS included regions appearing normal on MRI as well as regions showing complications of sickle cell disease, including focal deep white matter areas of high signal intensity (deep white matter ischemia, DWMI) seen on long TR images, focal atrophic brain areas, and infarcts. The findings in these studies are summarized as follows: Normal-appearing regions on MRI have normal MRS. In ROI including small areas of DWMI, lactate elevation was not detected, but the levels of N-acetyl-aspartate (NAA) appeared slightly elevated. In areas of DWMI 1-2 cm in size, reduced blood flow could be seen on MRA and lactate elevation could be detected with MRS. When blood flow to a DWMI region was normal, NAA was reduced and there was little lactate elevation, as cell death had already occurred. ROI consisting of atrophic tissue had reduced NAA levels but total creatine levels were not changed. Sometimes lipids, presumably from broken cell membrane, could be detected. In regions of past massive stroke, all metabolites were absent except for small amounts of lactate or lipids.

Topics: Adolescent; Adult; Anemia, Sickle Cell; Aspartic Acid; Atrophy; Brain; Brain Ischemia; Cerebral Infarction; Cerebrovascular Disorders; Child; Choline; Creatine; Female; Frontal Lobe; Humans; Hydrogen; Lactates; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Male; Phosphocreatine

1H magnetic resonance spectroscopic imaging has been used to obtain metabolite maps of the rat brain. The spin-echo-based technique has been evaluated with respect to water and lipid suppression and sensitivity. Metabolite maps were constructed for choline, creatine + phosphocreatine, amino acids, N-acetyl aspartate, and lactate. A spatial resolution of 3 x 3 mm (in plane) with 7-mm-thick slices was achieved routinely in 60-min (16 x 16 phase encodings) acquisitions. For higher intensity resonances, metabolite maps could be constructed in as little as 10 min. Results from phantoms and from rats under normal and focal ischemia conditions are presented.

Topics: Amino Acids; Animals; Aspartic Acid; Brain; Brain Ischemia; Choline; Creatine; Glutamates; Glutamic Acid; Magnetic Resonance Spectroscopy; Phosphocreatine; Rats; Rats, Inbred F344

The effects of dichloroacetate (DCA) on brain lactate, intracellular pH (pHi), phosphocreatine (PCr), and ATP during 60 min of complete cerebral ischemia and 2 h of reperfusion were investigated in rats by in vivo 1H and 31P magnetic resonance spectroscopy; brain lactate, water content, cations, and amino acids were measured in vitro after reperfusion. DCA, 100 mg/kg, or saline was infused before or immediately after the ischemic period. Preischemic treatment with DCA did not affect brain lactate or pHi during ischemia, but reduced lactate and increased pHi after 30 min of reperfusion (p < 0.05 vs. controls) and facilitated the recovery of PCr and ATP during reperfusion. Postischemic DCA treatment also reduced brain lactate and increased pHi during reperfusion compared with controls (p < 0.05), but had little effect on PCr, ATP, or Pi during reperfusion. After 30 min of reperfusion, serum lactate was 67% lower in the postischemic DCA group than in controls (p < 0.05). The brain lactate level in vitro was 46% lower in the postischemic DCA group than in controls (p < 0.05). DCA did not affect water content or cation concentrations in either group, but it increased brain glutamate by 40% in the preischemic treatment group (p < 0.05). The potential therapeutic effects of DCA on brain injury after complete ischemia may be mediated by reduced excitotoxin release related to decreased lactic acidosis during reperfusion.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Cations; Dichloroacetic Acid; Disease Models, Animal; Glutamates; Glutamic Acid; Hydrogen-Ion Concentration; Lactates; Lactic Acid; Magnetic Resonance Spectroscopy; Male; Phosphocreatine; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Water

Topics: Aspartic Acid; Brain; Brain Ischemia; Brain Mapping; Choline; Energy Metabolism; Humans; Image Interpretation, Computer-Assisted; Ischemic Attack, Transient; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Male; Middle Aged; Neurotransmitter Agents; Phosphocreatine; Phosphorus; Protons; Regional Blood Flow

Loss of cellular ion homeostasis during anoxia, with rapid downhill fluxes of K+, Ca2+, Na+ and Cl-, is preceded by a slow rise in extracellular K+ concentration (Ke+), probably reflecting early activation of a K+ conductance. It has been proposed that this conductance is activated by either a rise in intracellular calcium concentration (Cai2+), or by a fall in ATP concentration. In a previous study from this laboratory (Folbergrová et al. 1990) we explored whether the early activation of a K+ conductance could be triggered by a rise in Cai2+. To that end, labile metabolites and phosphorylase a, a calcium sensitive enzyme, were measured after 15, 30, 60 and 120 s of complete ischemia ("anoxia"). In the present study, we investigated whether brief anoxia is accompanied by changes in ATP/ADP ratio, or in the phosphate potential, which could cause activation of a K+ conductance. To provide information on this issue, we added a group with 45 s of anoxia to the previously reported groups, and derived changes in intracellular pH (pHi). This allowed calculations of the free concentrations of ADP (ADPf) and AMP (AMPf) from the creatine kinase and adenylate kinase equilibria, and hence the derivation of ATP/ADPf ratios. In performing these calculations we initially assumed that the free intracellular Mg2+ concentration remained unchanged at 1 mM. However we also explored how a change in Mgi2+ of the type described by Brooks and Bachelard (1989) influenced the calculation. The results showed that ADPf must have risen to 150-200% of control within 15 s, and to 330-350% of control within 45 s of anoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Brain Ischemia; Creatine Kinase; Cytosol; Energy Metabolism; Hydrogen-Ion Concentration; Hypoxia; Ion Channels; Male; Phosphocreatine; Phosphorylation; Rats

Tirilazad mesylate (U74006F) has been reported to improve recovery following cerebral ischemia. We conducted a randomized blinded study to determine if the drug would improve immediate metabolic recovery after complete cerebral compression ischemia.. Mongrel dogs were anesthetized with pentobarbital and fentanyl and treated with either vehicle (citrate buffer, n = 8) or tirilazad (1.5 mg/kg i.v. plus 0.18 mg/kg/hr, n = 8). Normothermic complete cerebral compression ischemia was produced for 12 minutes by lateral ventricular fluid infusion to raise intracranial pressure above systolic arterial pressure. Cerebral high-energy phosphate concentrations and intracellular pH were measured by phosphorus magnetic resonance spectroscopy. Cerebral blood flow was measured with radiolabeled microspheres, and oxygen consumption was calculated from sagittal sinus blood samples. Somatosensory evoked potentials were measured throughout the experiment.. During ischemia, both groups demonstrated complete loss of high-energy phosphates and a fall in intracellular pH (vehicle, 5.76 +/- 0.23; tirilazad, 5.79 +/- 0.26; mean +/- SEM). At 180 minutes of reperfusion, there were no differences between groups in recovery of intracellular pH (vehicle, 6.89 +/- 0.07; tirilazad, 6.88 +/- 0.18), phosphocreatine concentration (vehicle, 89 +/- 16%; tirilazad, 94 +/- 24% of baseline value), oxygen consumption (vehicle, 2.6 +/- 0.2 ml/min/100 g; tirilazad, 1.8 +/- 0.5 ml/min/100 g), or somatosensory evoked potential amplitude (vehicle, 11 +/- 6%; tirilazad, 7 +/- 4% of baseline value). Forebrain blood flow fell below baseline levels at 180 minutes of reperfusion in the tirilazad-treated animals but not in the vehicle-treated dogs (vehicle, 28 +/- 4 ml/min/100 g; tirilazad, 18 +/- 5 ml/min/100 g).. We conclude that tirilazad pretreatment does not improve immediate metabolic recovery 3 hours following 12 minutes of normothermic complete ischemia produced by cerebral compression.

Topics: Animals; Brain Ischemia; Cerebrovascular Circulation; Disease Models, Animal; Dogs; Evoked Potentials, Somatosensory; Injections, Intraventricular; Magnetic Resonance Spectroscopy; Oxygen Consumption; Phosphates; Phosphocreatine; Pregnatrienes; Regional Blood Flow; Reperfusion Injury

31P-NMR spectroscopic studies were performed in vivo on brains of rats administered cocaine. Cocaine.HCl (1-5 mg/kg) administered systemically to lightly anesthetized rats resulted in significant and progressive deficits in whole brain intracellular free Mg ([Mg2+]i). Intracellular pH (pHi) also fell in a progressive manner but only after a significant fall in brain [Mg2+]i was noted. Both [Mg2+]i and pHi returned to normal in most rats. Brains of rats that exhibited stroke-like events, however, demonstrated continued intracellular acidosis associated with progressive loss of phosphocreatine and elevation of Pi up until death. These observations are consistent with the tenet that injection of cocaine can result in severe cerebral vasospasm, ischemia and rupture of cerebral blood vessels as a consequence of depletion of brain [Mg2+]i.

Topics: Animals; Brain Chemistry; Brain Ischemia; Cerebrovascular Disorders; Cocaine; Hydrogen-Ion Concentration; Magnesium Deficiency; Magnetic Resonance Spectroscopy; Male; Phosphates; Phosphocreatine; Rats; Rats, Wistar

The effects of high dose allopurinol (ALLOP) pretreatment on the cerebral energy metabolism of unanesthetized 7-day-postnatal rats during exposure to 3 h of cerebral hypoxia-ischemia were serially quantitated using non-invasive 31P NMR spectroscopy. Adenosine triphosphate, integrated over the last 2 h of hypoxia and expressed as a fraction of baseline, was 0.73 +/- 0.16 with ALLOP pretreatment (200 mg/kg s.c.) compared to 0.52 +/- 0.05 for saline pretreatment (P = 0.001). Inorganic phosphate/phosphocreatine (Pi/PCr), integrated over the same time interval, was 2.63 +/- 1.23 relative to baseline with ALLOP versus 5.13 +/- 1.45 for saline-treated pups (P less than 0.0005). We suggest that the neuroprotection achieved with high dose ALLOP pretreatment may be attributed in part to preservation of energy metabolites.

Topics: Adenosine Triphosphate; Allopurinol; Animals; Brain Chemistry; Brain Ischemia; Energy Metabolism; Hypoxia, Brain; In Vitro Techniques; Magnetic Resonance Spectroscopy; Phosphocreatine; Rats; Rats, Wistar; Xanthine Oxidase

After 30 s ischemia induced by decapitation, the contents of ATP and phosphocreatine (PC) in mouse brain reduced, while that of lactic acid (LA) increased. When mexiletine (3.1-50 mg.kg-1) was injected ip 30 min before decapitation, the brain ATP and PC reduction, and LA accumulation were both alleviated in a dose-dependent manner. These findings suggested that mexiletine was effective in ameliorating the energy exhaustion in the ischemic brain.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Dose-Response Relationship, Drug; Energy Metabolism; Lactates; Male; Mexiletine; Mice; Phosphocreatine

Localized water suppressed proton spectroscopy has opened up a new field of pathophysiological studies of severe brain ischemia. The signals obtained with the pulse sequences used so far are both T1 and T2 weighted. In order to evaluate the extent to which changes in metabolite signals during the course of infarction can be explained by changes in T1 and T2 relaxation times, eight patients with acute stroke were studied. STEAM sequences with varying echo delay times and repetition times were used to measure T1 and T2 of N-acetyl-aspartate (NAA), creatine plus phosphocreatine (Cr+PCr) and choline containing compounds (CHO) in a 27-ml voxel located in the affected area of the brain. Ten healthy volunteers served as controls. We found no difference in T1 or T2 of the metabolites between the patients and the normal controls. The T2 of CHO was longer than that of NAA and Cr+PCr. Our results indicate that spectra obtained in brain infarcts and normal tissue with the same acquisition parameters are directly comparable with respect to relative signal intensities as well as signals scaled with internal and external standards.

Topics: Adult; Aged; Aged, 80 and over; Aspartic Acid; Brain Ischemia; Choline; Creatine; Humans; Magnetic Resonance Spectroscopy; Middle Aged; Phosphocreatine

Concentrations of phosphocreatine, creatine, ATP, ADP, AMP, glucose and lactate in the whole brain did not differ between the mice intoxicated with acrylamide and the controls. When the brain was made ischemic, these concentrations changed to the same extent in both groups. The only difference was the lower pyruvate in acrylamide-intoxicated mice under the ischemia. Thus, as far as the whole brain is concerned, acrylamide does not cause gross alterations of energy metabolites, even under ischemia.

Topics: Acrylamide; Acrylamides; Adenosine Triphosphate; Animals; Body Weight; Brain; Brain Ischemia; Energy Metabolism; Glucose; Lactates; Lactic Acid; Male; Mice; Mice, Inbred Strains; Phosphocreatine; Pyruvates; Pyruvic Acid

31-phosphorous magnetic resonance spectroscopy was used in a rat model of 10 min severe incomplete forebrain ischemia (two-vessel occlusion with hypotension) to assess the effect of hyperglycemia on intracellular pH and high energy phosphates during ischemia and early reperfusion. One group (n = 8) with preischemic hyperglycemia (serum glucose 20 mmol.l-1) showed an increased intracellular acidosis (pH 6.35) during ischemia compared to 6.55 in the normoglycemic control group (n = 7, P less than 0.001), but the recovery of phosphocreatine and ATP in early reperfusion was the same in the two groups. Another group (n = 7) was normoglycemic during ischemia, but received an i.v. bolus of glucose during the first minute of reperfusion. In this group the recovery of intracellular pH in early reperfusion was slower than in the control group (0.034 +/- 0.006 pH units per minute compared to 0.052 +/- 0.11 in the controls, +/- s.d. and P less than 0.01).

Topics: Acidosis; Adenosine Triphosphate; Animals; Blood Glucose; Brain Ischemia; Hydrogen-Ion Concentration; Hyperglycemia; Magnetic Resonance Spectroscopy; Male; Phosphates; Phosphocreatine; Phosphorus; Rats; Rats, Inbred Strains; Reperfusion; Time Factors

Post-ischemic reperfusion impairment, ("no-reflow phenomenon"), was studied in rats subjected to 8-30 minutes of global brain ischemia. During ischemia, rapid and complete loss of cerebral blood flow, EEG and 31P-high energy phosphates (ATP/PCr) was observed. Brain intravascular perfusion defects were examined by injecting carbon black intravenously in a group of rats with stable cardiopulmonary function and in another group subjected to rapid thoracotomy and intraarterial infusion of the carbon marker. Results indicate that global brain ischemic or non-ischemic control rats given intraarterial carbon black after thoracotomy had varying degrees of vessel filling defects in brain resulting in "pale tissue areas" suggestive of impaired perfusion (no-reflow). All rats given carbon black intravenously whether global brain ischemic or not, showed normal cerebrovascular filling of the carbon black and absence of "pale tissue areas". In addition, post-ischemic cerebral reperfusion following 8-30 minutes global brain ischemia can reverse neuroelectric, energy metabolite and cerebral blood flow loss in rats whose cardiopulmonary function is not compromised. These findings indicate that the "no-reflow phenomenon" is an agonal or post-mortem artifact observed in the presence of cardiopulmonary failure.

Topics: Adenosine Triphosphate; Animals; Artifacts; Brain; Brain Damage, Chronic; Brain Ischemia; Cerebral Arteries; Cerebral Cortex; Cerebrovascular Circulation; Male; Phosphocreatine; Postmortem Changes; Rats; Rats, Inbred Strains; Reperfusion Injury

We measured the parameter lambda, which is the ratio of the distribution spaces of 2-deoxy-D-glucose (DG) and glucose in the brain, in a model of focal cerebral ischemia in the cat. lambda is the parameter in the lumped constant of the [14C]DG technique most susceptible to changes in ischemia. Cats were subjected to occlusion of the middle cerebral artery for a period of 2 h. During the last 60 min of occlusion, [14C]DG was infused in a programmed fashion so as to obtain a stable arterial blood [14C]DG concentration. The brain was funnel-frozen to preserve tissue metabolites and the frozen brain was sampled regionally (4 to 7-mg samples) for local concentrations of glucose, ATP, phosphocreatine (PCr), and lactate. In a separate series of cats, the infusion of [14C]DG was started after 2 h of occlusion and 3 h of recirculation. In both series, lambda declined slightly for increased levels of tissue glucose and increased appreciably as tissue glucose decreased. A similar relationship was observed between lambda and ATP and PCr, although the correlation was not as clear. Since lambda, and hence the lumped constant, increases in ischemia as well as in postischemic tissue, it is important to measure tissue glucose concentration if quantitative values of local cerebral glucose metabolism are desired in this condition.

Topics: Adenosine Triphosphate; Algorithms; Animals; Brain Ischemia; Carbon Radioisotopes; Cats; Cerebrovascular Circulation; Deoxyglucose; Glucose; Lactates; Lactic Acid; Male; Phosphocreatine

Bilateral ischemia has been shown to alter the net brain levels of energy metabolites such as ATP, phosphocreatine, glucose, and glycogen. The amino acid neurotransmitter gamma-aminobutyric acid (GABA) exerts a tonic inhibitory influence on neural activity. The present studies were designed to evaluate the influence of elevated GABA levels on the metabolic sequelae of ischemia. The GABA transaminase inhibitor gamma-vinyl-GABA (GVG; vigabatrin) was administered to Mongolian gerbils before the production of a bilateral ischemic incident. GABA levels were elevated in all regions assayed. Levels of energy metabolites were also increased, an indication of reduced energy utilization. In control animals, in the absence of GVG, 1 min of bilateral ischemia produced decreases in the levels of all metabolites. In animals pretreated with GVG, the effects of 1 min of bilateral ischemia were attenuated. These data suggest that the level of ongoing activity may affect the response to an ischemic insult. Furthermore, GVG may have a clinical indication in reducing the effect of minor ischemic incidents.

Topics: Adenosine Triphosphate; Aminocaproates; Animals; Body Temperature; Brain; Brain Ischemia; Energy Metabolism; GABA Antagonists; gamma-Aminobutyric Acid; Gerbillinae; Glycogen; Phosphocreatine; Tissue Distribution; Vigabatrin

This study investigated the relations between hemorrhagic infarction and occlusion, release, levels of glycemia, brain energy state, and lactate content after cerebrovascular occlusion.. Prospective, controlled laboratory investigation.. One hundred six pentobarbital-anesthetized cats.. The middle cerebral artery was occluded with a Yasargil clip transorbitally either temporarily (0.5, four, and eight hours) or permanently. Normoglycemic and hyperglycemic animals were closely monitored for eight hours. Brain pathology was assessed after two weeks' survival or at the time of spontaneous animal death. Topographic brain metabolite studies were carried out after four hours of middle cerebral artery occlusion.. Morphometric quantitation of cerebral hemorrhage and infarction and fluorometric determinations of blood and brain tissue, glucose, glycogen, lactate, adenosine triphosphate, and phosphocreatine from 16 topographic brain sites were carried out. Twenty-one of 82 (25.6%) animals evaluated neuropathologically showed hemorrhagic infarcts. Occluding the artery in hyperglycemic animals caused fivefold more frequent and 25-fold more extensive hemorrhage into infarcts than in normoglycemic animals. Temporary occlusion with clip release after four hours in hyperglycemic animals caused the most extensive hemorrhage into infarcts. Most hemorrhages into infarcts (81%) took place in animals that died within a few hours after they experienced ischemia and that showed infarction and marked edema of the entire middle cerebral artery territory. Linear regression analyses demonstrated a close relation between hemorrhage into infarcts and near-total energy depletion (adenosine triphosphate, less than 0.3 microM/g; phosphocreatine, less than 0.5 microM/g) in brain sites that showed extremely high tissue lactate concentrations (more than 30 microM/g). The biochemical changes that correlated with hemorrhage into infarcts were more marked than those with infarcts without hemorrhage.. Hyperglycemia and restoration of blood flow to ischemic territories were strong risk factors for hemorrhagic infarct conversion. Concomitant tissue metabolic changes suggest that marked tissue energy depletion accompanied by acidosis damages brain vessels and renders them penetrable for edema fluid and, ultimately, red blood cell extravasation.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Chemistry; Brain Ischemia; Cats; Cerebral Arteries; Cerebral Hemorrhage; Cerebral Infarction; Constriction; Glucose; Hyperglycemia; Lactates; Lactic Acid; Linear Models; Phosphocreatine; Prospective Studies; Risk Factors

The intracerebral injection of the excitotoxins, glutamate (GLU), or its analogues, quisqualic acid (QA) and N-methyl-D-aspartate (NMDA), produces neuropathologic changes which resemble those induced by hypoxic-ischemic injury. We employed proton magnetic resonance spectroscopy to investigate the acute biochemical changes which follow injection of these excitotoxins in the neonatal rat brain. Aspartate and GLU increased in animals injected with GLU or NMDA. Alanine, glycine, and taurine increased with all three excitotoxins. There was no decrease in phosphocreatine (PCr) or glucose and only a modest increase in lactate after excitotoxin injection, but there was substantial change in these metabolites after hypoxia. GABA rose only after hypoxic-ischemic injury. Although NMDA and QA produced morphological changes which resembled those following hypoxic-ischemic injury, the effect of these excitotoxins on levels of PCr, glucose, and excitatory and inhibitory amino acids was considerably different.

Topics: Amino Acids; Animals; Animals, Newborn; Brain; Brain Ischemia; Female; Glucose; Glutamates; Glutamic Acid; Male; N-Methylaspartate; Organ Specificity; Phosphocreatine; Quisqualic Acid; Rats; Rats, Inbred Strains

We used phosphorus-31 nuclear magnetic resonance spectroscopy in a rat model of 10 minutes' severe incomplete forebrain ischemia (two-vessel occlusion with hypotension) to study the effects of preischemic and postischemic treatment with 3 mg/kg i.v. U74006F on the recovery of high-energy phosphates and intracellular pH during early reperfusion. The mean +/- SD time to 85% recovery of phosphocreatine was 14.1 +/- 8.4 minutes in the control group (n = 10) compared with 6.6 +/- 3.5 minutes (p less than 0.05) in the preischemic (n = 8) and 4.2 +/- 1.0 minutes (p less than 0.001) in the postischemic (n = 11) treatment groups. The mean +/- SD time to 80% recovery of adenosine triphosphate was 15.4 +/- 8.5 minutes in the control group compared with 6.3 +/- 1.8 (p less than 0.005) and 5.4 +/- 2.8 (p less than 0.001) minutes in the preischemic and postischemic treatment groups, respectively. There were no differences in intracellular pH between the control and either of the treatment groups. We conclude that U74006F led to quicker recovery of high-energy phosphates during early reperfusion, and this beneficial effect was also seen with postischemic treatment.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Free Radicals; Injections, Intravenous; Lipid Peroxides; Magnetic Resonance Spectroscopy; Male; Phosphates; Phosphocreatine; Pregnatrienes; Prosencephalon; Rats; Rats, Inbred Strains; Time Factors

To investigate the effects of hypothermia on the rate of change and degree of recovery of brain adenosine triphosphate and phosphocreatine concentrations and intracellular pH, we have developed a model that allows phosphorus nuclear magnetic resonance spectroscopy of the intact piglet brain during circulatory arrest.. Three groups of piglets were studied. Three control animals underwent cardiopulmonary bypass at normothermia for 1 hour; five group 1 animals underwent bypass at a brain temperature of 15 degrees C, followed by a period of circulatory arrest such that adenosine triphosphate was absent for 21 minutes, followed by 1 hour of reperfusion; and five group 2 animals underwent bypass at a brain temperature of 37 degrees C, followed by a period of circulatory arrest such that adenosine triphosphate was absent for 21 minutes, followed by reperfusion for 1 hour.. Control animals showed no significant metabolic effects of bypass. Group 1 animals showed a slower decay of the adenosine triphosphate and phosphocreatine concentrations than group 2 animals, consistent with a lower metabolic rate, and had a higher pH at the onset of ischemia. Recovery of the adenosine triphosphate concentration was significantly better in group 1 animals (95%) than in group 2 animals (30%) (p less than 0.02), and recovery of the phosphocreatine concentration was also better in group 1 animals (93%) than in group 2 animals (32%) (p less than 0.02). Intracellular pH recovered in group 1 animals, but not in group 2 animals. Regional biochemical assays of metabolites performed in the group 2 piglets and in five pilot piglets exposed to deep hypothermia generally confirmed the spectroscopic findings but demonstrated considerable regional variation, specially in the group 2 piglets' brains.. We conclude that hypothermia exerts a protective effect on the piglet brain during global ischemia even after the adenosine triphosphate pool has been completely depleted.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Heart Arrest, Induced; Hydrogen-Ion Concentration; Hypothermia, Induced; Phosphocreatine; Swine

Cerebral high-energy metabolites and metabolic end products were measured during and following total cerebral ischemia in the rat. During cerebral ischemia, lactate accumulation was greatest in the hippocampus, followed by the cerebral cortex and striatum. Following reperfusion, the rate of lactate clearance was slower in the hippocampus than in the other two regions. Regional CBF, cerebral plasma volume (CPV), and calculated mean transit time (MTT) were determined following reflow of ischemic tissue. During hyperemia, CPV, used as an indicator of capillary volume, increased concomitantly with CBF while the MTT remained near the control value, suggesting that the linear flow rate through the vasculature was unchanged. During hypoperfusion, CPV returned to control values, but there was a significant increase in MTT that would result from a decreased linear velocity. The finding of normal tissue energy charge, pHi, and concentration of other metabolites during hypoperfusion shows that hypoperfusion does not result in CBF-metabolic mismatch.

Topics: Adenosine Triphosphate; Animals; Blood Flow Velocity; Brain; Brain Ischemia; Cerebral Cortex; Cerebrovascular Circulation; Corpus Striatum; Energy Metabolism; Heart Arrest, Induced; Hippocampus; Lactates; Lactic Acid; Male; Phosphocreatine; Plasma Volume; Rats; Rats, Inbred Strains

Acute, progressive global brain ischemia was induced in awake or anesthetized rats for 5-75 min. Ischemia was achieved with a subclavian-carotid artery occlusion technique (SCOT). After thoracotomy, both subclavian arteries (proximal to their vertebral branches) were tied-off and carotid artery catheter-snares installed. Results show progressive morphological, physiological and neurochemical damage when CBF was reduced from preischemic levels of 115 ml to 0 blood flow. 31P magnetic resonance spectroscopy of high energy phosphate metabolites in vivo showed loss of PCr and beta-ATP signals after 6 min brain ischemia. Energy metabolite levels, EEG and CBF normalized within hours after reperfusion. Degree of neuropathologic damage to hippocampal region appeared linearly related to the ischemic duration of ischemia. Thus, acute global brain ischemia resulted in loss of high energy phosphate metabolites, EEG and neuronal integrity in the hippocampal subfields. Reperfusion following short (5 min) or long (75 min) periods of global brain ischemia induced return of 31P-spectra, EEG and CBF to normal but was unable to reverse all of the neuronal damage at the end of the 72-h observation period.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Cerebral Cortex; Electroencephalography; Hippocampus; Magnetic Resonance Spectroscopy; Male; Nervous System; Phosphocreatine; Phosphorus; Rats; Rats, Inbred Strains; Time Factors

Phosphorus magnetic resonance spectroscopy (31P-MRS) was made to measure changes in brain high energy phosphate compounds, adenosine triphosphate (ATP) and phosphocreatine (PCr), inorganic phosphorus (Pi) and intracellular pH (pHi) during a prolonged period of incomplete brain ischaemia produced, in anaesthetized dogs, by bilateral carotid occlusion together with haemorrhagic hypotension for intervals of up to 300 min. Mean arterial blood pressure (MABP) was lowered in a stepwise fashion, until signs of metabolic decompensation (as estimated by MRS) occurred. At that point MABP was varied against further evidence of metabolic decompensation in an attempt to maintain a more constant degree of insult. At the end of the ischaemic period MABP was restored and the animals observed during a 3 h recovery period. At the end of the recovery period the brains were perfusion-fixed for histological examination. A semi-quantitative method of histological evaluation was used to determine the degree of histological damage. This permitted assignment of an 'ischaemic score' to the tissue sampled from each animal. Comparisons were then made between the magnitude of this 'ischaemic score' and the changes in metabolic and physiological variables (ATP, PCr, pHi and MABP) as well as an estimator of phosphorylation potential (PCr/Pi), which were all measured during the ischaemic insult. Histological examination showed a wide variety of neuronal alterations, including dark and pale type injury, which correlated directly with the metabolic derangements brought about by ischaemia. The degree of damage determined from this histological assessment correlated best with the duration and degree of change in PCr/Pi, supporting the use of this ratio as a critical index of cellular energy state. In particular there was a strong linear relationship between the degree of leucocyte recruitment and changes in PCr/Pi. To summarize, metabolic changes, determined by MRS, correlate with the degree of histological damage, and in turn, the classical descriptions of acute ischaemic neuronal injury appear to be validated by MRS determinations of metabolic changes during ischaemia.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Chemistry; Brain Ischemia; Dogs; Magnetic Resonance Imaging; Phosphates; Phosphocreatine; Phosphorus Isotopes; Shock

Brain oedema is an important aspect of infarction from cerebrovascular occlusion. In a cat stroke model where the middle cerebral artery (MCA) was reversibly or permanently occluded, we analyzed the incidence of fatal hemispheral oedema in 35 normo- (6 mM) and 35 hyperglycaemic (20 mM for 6 hours) animals, with (N = 45) and without (N = 25) restoration of blood flow with clip release at 4 and 8 hrs of occlusion. Fatal hemispheral oedema occurred in 23% of cats (16/70) while hyperglycaemia, for one, and restoration of blood flow, for another, each quadrupled its occurrence. Further, evidence of remote oedema in the form of posterior cingulate cortical pressure atrophy from transtentorial herniation was found in animals that were allowed to survive for 2 weeks and that exhibited infarcts that affected 12 to 95% of the MCA territory. Thus, hemispheral oedema in association with MCA occlusion developed sufficiently markedly as to cause transtentorial herniation in 47% of all cats (33/70). We carried out biochemical analyses in 14 hyper- and 10 normoglycaemic cats after 4 hrs of MCA occlusion for ATP, phosphocreatine (PCr), lactate, glucose and glycogen. The biochemical findings then were correlated with the occurrence of reperfusion oedema following clip release after 4 hrs of occlusion point-by-point in the brains. Linear regression analyses of the brain metabolic and pathologic data revealed highly significant (p less than 0.001) correlations of acute oedema with brain tissue ATP and PCr reductions less than 1.5 microM/g, with lactic acid accumulation greater than 20 microM/g and with the extents of reduction in brain tissue glucose concentrations in the ischaemic territories.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Brain; Brain Edema; Brain Ischemia; Cats; Forecasting; Hyperglycemia; Phosphocreatine; Regression Analysis; Reperfusion

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Energy Metabolism; Magnetic Resonance Spectroscopy; NAD; Phosphocreatine; Phosphorus Radioisotopes; Rats

We used neonatal piglets to determine the influence of plasma glucose concentration on cerebral energy metabolism during and immediately after partial ischemia. We assessed cerebral metabolism using in vivo phosphorus-31 magnetic resonance spectroscopy. Arterial plasma glucose concentration was increased in four piglets by systemic infusions of dextrose in water for comparison with infusions of saline in four controls or decreased in eight piglets by fasting for 24-48 hours for comparison with four fed piglets. Plasma glucose concentration showed a significant linear correlation with intracellular pH (r = -0.7, p less than 0.05). Piglets that developed hypoglycemia during partial ischemia had a smaller reduction in intracellular pH and a larger increase in inorganic phosphate content than piglets that were normoglycemic or hyperglycemic during ischemia. Similar differences persisted during the first 5 minutes of postischemic reperfusion. Subsequently, the cerebral concentrations of phosphorylated compounds returned to normal in all piglets. Our results demonstrate that 1) arterial plasma glucose concentration influences cerebral energy metabolism and intracellular pH during ischemia, 2) neonatal piglets can develop profound brain acidosis, and 3) brain acidosis during ischemia does not influence the restoration of cerebral phosphorylated compounds to control levels during the first 90 minutes after ischemia.

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Blood Glucose; Brain; Brain Ischemia; Carbon Dioxide; Fasting; Hydrogen-Ion Concentration; Intracellular Membranes; Osmolar Concentration; Partial Pressure; Phosphocreatine; Swine

4-(o-Benzylphenoxy)-N-methylbutylamine hydrochloride (bifemelane, CAS 90293-01-9, Celeport) has been reported to exert a protective effect on the brain against ischemic insults. However, the underlying mechanism of this action has not yet been fully elucidated. The effects of bifemelane on the intracellular pH (pHi) and energy metabolism of the ischemic brain were examined in Mongolian gerbils using in vivo 31P nuclear magnetic resonance spectroscopy. Transient global ischemia was produced by clipping both common carotid arteries for 45 min, and the brain was reperfused by releasing the clips. Bifemelane (10 or 20 mg/kg) or normal saline was administered intraperitoneally 30 min prior to the ischemia. During the ischemia, adenosine triphosphate (ATP) and phosphocreatine (PCr) were markedly reduced in association with an increase in inorganic phosphate (Pi) and decrease in pHi in both the control and bifemelane groups. The extents of energy disturbance and intracellular acidosis in the three groups were identical. After reperfusion, ATP, PCr, Pi and pHi recovered towards the pre-ischemic levels in all the groups. In the bifemelane groups, the recovery of pHi was significantly faster than in the control group. Of the two bifemelane groups, the 20 mg/kg group showed more excellent pHi recovery as compared to the 10 mg/kg group. The energy recovery in the three groups were almost identical, although the 20 mg/kg group showed some tendency towards faster recovery as compared to the control group. The present results suggest that bifemelane may accelerate recovery of the pHi after cerebral ischemia. Such an action may contribute to the cerebral protective effects of this drug against ischemic insults.

Topics: Adenosine Triphosphate; Animals; Antidepressive Agents; Benzhydryl Compounds; Blood Gas Analysis; Blood Pressure; Brain Chemistry; Brain Ischemia; Carbon Dioxide; Energy Metabolism; Gerbillinae; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Male; Oxygen; Phosphates; Phosphocreatine

The blockade of postsynaptic receptors for excitatory amino acids is a promising new field for the possible treatment of cerebral ischaemia. The most important receptor seems to be the N-methyl-D-aspartate (NMDA) subtype of the glutamate receptors and MK-801 is a potent non-competitive antagonist to the NMDA receptor. 31P NMR Spectroscopy was used to measure the recovery of intracellular pH and the high energy phosphates Phosphocreatine (PCr) and ATP after ten minutes of temporary global cerebral ischaemia in the rat. Cerebral ischaemia was obtained by combining bilateral carotid ligation and systemic hypotension (2 vessel occlusion model). Two intervention groups with intravenous injection of MK-801 in doses of 0.25 mg/kg and 0.5 mg/kg 15 minutes before onset of ischaemia were compared to a control group. Both intervention groups showed a more rapid recovery of PCr and ATP than the control group, but there were no significant differences for intracellular pH.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Dizocilpine Maleate; Energy Metabolism; Magnetic Resonance Spectroscopy; Male; Phosphocreatine; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate

The brain damage that evolves from perinatal cerebral hypoxia-ischemia may involve lingering disturbances in metabolic activity that proceed into the recovery period. To clarify this issue, we determined the carbohydrate and energy status of cerebral tissue using enzymatic, fluorometric techniques in an experimental model of perinatal hypoxic-ischemic brain damage. Seven-day postnatal rats were subjected to unilateral common carotid artery ligation followed by 3 h of hypoxia with 8% oxygen at 37 degrees C. This insult is known to produce tissue injury (selective neuronal necrosis or infarction) predominantly in the cerebral hemisphere ipsilateral to the carotid artery occlusion in 92% of the animals. Rat pups were quick-frozen in liquid nitrogen at 0, 1, 4, 12, 24, or 72 h of recovery; littermate controls underwent neither ligation nor hypoxia. Glucose in both cerebral hemispheres was nearly completely exhausted during hypoxia-ischemia, with concurrent increases in lactate to 10 mmol/kg. During recovery, glucose promptly increased above control values, suggesting an inhibition of glycolytic flux, as documented in the ipsilateral cerebral hemisphere by measurement of glucose utilization (CMRglc) at 24 h. Tissue lactate declined rapidly during recovery but remained slightly elevated in the ipsilateral hemisphere for 12 h. Phosphocreatine (P approximately Cr) and ATP in the ipsilateral cerebral hemisphere were 14 and 26% of control (p less than 0.001) at the end of hypoxia-ischemia; total adenine nucleotides (ATP + ADP + AMP) also were partially depleted (-46%).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenine Nucleotides; Animals; Animals, Newborn; Body Water; Brain; Brain Ischemia; Carbohydrate Metabolism; Energy Metabolism; Glucose; Glycolysis; Hypoxia, Brain; Phosphocreatine; Rats

The changes in cerebral phosphorus metabolites, intracellular pH, and lactate during 30 min of complete global ischemia and 2 h of reperfusion were monitored by time-shared 1H and 31P in vivo NMR spectroscopy in rats. After the induction of ischemia, intracellular pH decreased from 7.14 +/- 0.01 to 6.32 +/- 0.10, and lactate concentration increased from 1.6 +/- 0.4 to 15.8 +/- 2.5 mumol/g; ATP and phosphocreatine were totally depleted, while inorganic phosphate increased 715 +/- 47%. Within 1 h after blood flow was restored, high-energy phosphates and lactate levels had recovered close to baseline levels. The changes in intracellular pH and lactate levels during ischemia and reperfusion correlated well.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Chemistry; Brain Ischemia; Hydrogen; Hydrogen-Ion Concentration; Lactates; Magnetic Resonance Spectroscopy; Phosphocreatine; Phosphorus; Rats; Rats, Inbred Strains; Time Factors

The neurologic outcomes following incomplete cerebral ischemia in rats treated by fasting, nonfasting, or glucose administration (6 ml/kg of 50% glucose solution intraperitoneal) were compared. Rats were anesthetized with 1.4% inspired isoflurane in air and incomplete ischemia was produced by temporary unilateral carotid occlusion and hypotension of 30 mmHg for 30 min. The rats were recovered and neurologic outcome was scored every 8 h for 3 days using a 6-point scale ranging from 0 (normal) to 5 (death associated with stroke). Brain histopathology was scored using a four-point scale on 19 of 30 rats surviving the 3-day postischemic neurologic examination and was correlated with neurologic deficit scores. Fasted rats had plasma glucose concentrations of 79 +/- 7 mg/100 ml (mean +/- SE) during ischemia and a significantly better neurologic outcome (P less than 0.001) than glucose-loaded rats (plasma glucose = 496 +/- 43 mg/100 ml). Nonfasted rats had blood glucose values (292 +/- 28 mg/100 ml) and deficit scores not significantly different from fasted but better than glucose-loaded rats (P = 0.054). Brain histology showed the greatest neuronal damage in caudate followed by hippocampus and cortical tissue. Histopathologic evaluation showed a correlation of r = 0.87 (P less than 0.01) with neurologic outcome. In separate experiments brain samples were collected at the end of the ischemic period in each of the experimental groups and regional tissue lactate and brain phosphocreatine and adenosinetriphosphate (ATP) concentrations were measured. Ischemic tissue lactate was similar in fasted, nonfasted, and glucose-loaded rats in caudate and hippocampus but was significantly higher in glucose loaded rats in cortical and thalamic tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Fasting; Glucose; Lactates; Lactic Acid; Male; Nervous System; Phosphocreatine; Rats; Rats, Inbred Strains

To investigate the prognostic significance of abnormalities of oxidative phosphorylation, the brains of 61 newborn infants born at 27-42 wk of gestation and suspected of hypoxic-ischemic brain injury were examined by surface-coil phosphorus magnetic resonance spectroscopy. Of these infants, 23 died, and the neurodevelopmental status of the 38 survivors was assessed at 1 y of age. Of the 28 infants whose phosphocreatine/inorganic orthophosphate (PCr/Pi) ratios fell below 95% confidence limits for normal infants, 19 died, and of the nine survivors, seven had serious multiple impairments (sensitivity 74%, specificity 92%, positive predictive value for unfavorable outcome 93%). Of the 12 infants with ATP/total phosphorus ratios below 95% confidence limits 11 died (sensitivity 47%, specificity 97%, positive predictive value 91%). Among the 46 infants with increased cerebral echodensities, PCr/Pi was more likely to be low, and prognosis poor, in infants whose echodensities were diffuse or indicated intraparenchymal hemorrhage than in infants whose echodensities were consistent with periventricular leukomalacia. We conclude that when reduced values for PCr/Pi indicating severely impaired oxidative phosphorylation are found in the brains of infants suspected of hypoxic-ischemic injury, the prognosis for survival without serious multiple impairments is very poor, and that when ATP/total phosphorus is reduced, death is almost inevitable.

Topics: Asphyxia Neonatorum; Brain Ischemia; Humans; Hydrogen-Ion Concentration; Infant, Newborn; Magnetic Resonance Spectroscopy; Nervous System; Organophosphorus Compounds; Oxidative Phosphorylation; Phosphates; Phosphocreatine; Phosphorus; Predictive Value of Tests; Prognosis

Effects of S-adenosyl-L-methionine (SAM) on the metabolism in ischemic brain were investigated. The ischemic model employed was an incomplete cerebral ischemia of the spontaneously hypertensive rat (SHR) produced by the occlusion of both common carotid arteries. One hundred mg/kg of SAM was administered (i.p.) 6 times from the beginning of occlusion at 30 min intervals. At 3 hr after the onset of occlusion, animals were killed by microwave irradiation and creatine phosphate (CrP), ATP, glucose, lactate and gamma-aminobutyric acid (GABA) contents in the brain were measured. SAM significantly mitigated both the reductions in CrP, ATP and glucose levels and the increase in GABA level due to the cerebral ischemia. In another set of experiments with the same experimental schedule, water content in the brain was examined. SAM significantly suppressed the increase in water content due to the cerebral ischemia. These results indicate ameliorating effects of SAM on the metabolism in ischemic brain.

Topics: Adenosine Triphosphate; Animals; Blood Glucose; Body Water; Brain; Brain Chemistry; Brain Ischemia; Energy Metabolism; gamma-Aminobutyric Acid; Glucose; Lactates; Male; Phosphocreatine; Rats; Rats, Inbred SHR; S-Adenosylmethionine

The sensitivity of cerebral energy metabolism to ischemic and hypoxic stresses following global cerebral ischemia was evaluated in a cat model using 31P nuclear magnetic resonance (NMR) spectroscopic methods. Complete global cerebral ischemia of 5 to 10 min in length was produced at 1 h intervals by reversible arterial occlusion, permitting continuous monitoring of NMR and EEG. Ischemia appeared to produce slightly more severe energy failure in animals that had previously experienced an ischemic injury. Preischemic hypoxia (5% O2 for 5 min) resulted in minor changes in the levels of phosphocreatine and intracellular inorganic phosphate, which were slightly amplified in animals that previously experienced ischemia.

Topics: Animals; Brain Ischemia; Cats; Electroencephalography; Energy Metabolism; Hydrogen-Ion Concentration; Hypoxia, Brain; Magnetic Resonance Spectroscopy; Phosphates; Phosphocreatine; Phosphorus

The effects of 1 h of complete global ischemia on the recovery of high-energy phosphates, intracellular pH (pHi), and lactate in the cat brain in vivo was investigated by 31P and 1H NMR spectroscopy. Ischemia led to a decrease in creatine phosphate (CrP), nucleoside triphosphates (NTP), and pHi, while inorganic phosphate and lactate increased. Intracellular pH decreased from a control value of 7.07 +/- 0.04 to 6.17 +/- 0.12 after 1 h of ischemia (N = 7). The degree of metabolic recovery after recirculation was variable. In three animals CrP and NTP were detected within 4 min and NTP increased to greater than or equal to 90% of control within 1 h; these levels were maintained for the 3 h of observation. In four other animals, CrP and NTP reached only 20 to 80% of control; however, high-energy phosphates decreased and lactate increased spontaneously between 1 and 2.5 h. Immediately following recirculation, pHi decreased further by an average of 0.3 units. The rate of recovery of cerebral pHi was slower than that of PCr and NTP for the majority of animals. Recovery of pHi was not detected for an average of 32 min after recirculation--by this time, NTP had attained 80 +/- 10% of their preischemic level. Recovery of pHi (and lactate) was not observed in two animals where PCr and NTP recovered transiently to only 30-43% of the preischemic level. Recovery of cerebral pHi was markedly heterogeneous in one animal, since two Pi peaks were detected shortly after recirculation.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Acid-Base Equilibrium; Animals; Brain; Brain Ischemia; Cats; Energy Metabolism; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Nucleotides; Phosphocreatine; Reference Values; Reperfusion; Time Factors

Two simple cerebral ischemic models of mice were used for studying brain energy metabolism and the effects of drugs. Model one is partial occlusion of the left carotid artery and total occlusion of the right one including the vagus. The behavior of the animals appeared splaying of the contralateral extremities, circling around counterclockwise and in a comatose motionless state. Following the designated ischemic time, the animals were put into liquid N2. Model two is decapitation induced ischemia of mouse brain. The whole animal (control) and the severed head were rapidly frozen in liquid nitrogen 0, 10, 30, 60 s after decapitation. Brain samples were powdered at liquid N2 temperature, extracted and determined for ATP, phosphocreatine (Pcr) and lactic acid (LA). The data from model one indicate that after an ischemic period of 10 min, brain LA level increased significantly compared with values from the sham operated group, while no significant alteration was observed in brain ATP, and Pcr level. At 180 min of ischemia, levels of ATP and Pcr were considerably reduced while LA level increased significantly. The degree of symptoms induced by brain ischemia showed good correlation with brain energy metabolism. In model 2 brain LA level was found to be increased, while ATP and Pcr levels decreased after whole brain ischemia. However, brain ATP and Pcr levels were increased and LA level was decreased significantly in the normal and ischemic animal after administration of phenobarbital (225 mg/kg ip). LA level decreased significantly in the unischemic mice treated with Rb1 (100 mg/kg ip). It is indicated that both models of cerebral ischemia were simple and sensitive methods for studying brain ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Ginsenosides; Lactates; Lactic Acid; Male; Mice; Nimodipine; Phenobarbital; Phosphocreatine; Saponins

Local CBF (LCBF) was compared with the corresponding local tissue concentration of ATP, phosphocreatine (PCr), and lactate in anaesthetized baboons subjected to focal ischaemia produced by middle cerebral artery occlusion (MCAO). LCBF hydrogen electrodes were implanted in cortical regions where MCAO had been previously shown to produce severe and penumbral ischaemia and in posterior regions where blood flow is not altered. Metabolites were assayed in small tissue samples collected either by cryoprobe biopsy in the regions where LCBFs were measured (series 1) or by sampling appropriate regions of the rapidly frozen brain (series 2). Subsequent topographical study of brain tissue pH with umbelliferone was performed in this latter series. The results from these two series are compared and discussed in terms of the more appropriate way to perform simultaneous electrode measurements and analysis of tissue samples for studying focal ischaemia in the primate brain. They confirm that the concentrations of ATP and PCr decrease, and that lactate level increases, with decreasing blood flow. These metabolites tended to change more rapidly below a blood flow threshold, rather than showing a steady decrease as the blood flow was reduced, although the variability of the data precluded us from establishing this with confidence. Topographical study of tissue pH often showed sharp boundaries between zones of very low pH and regions with normal pH.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Cerebral Arteries; Cerebrovascular Circulation; Female; Hydrogen-Ion Concentration; Lactates; Lactic Acid; Male; Papio; Phosphocreatine

We investigated the effect of mild whole-body hyperthermia before and after 16 minutes of global cerebral ischemia on metabolic recovery during recirculation in cats using in vivo phosphorus-31 nuclear magnetic resonance spectroscopy. Hyperthermia (temperature 40.6 +/- 0.2 degrees C) was induced greater than or equal to 1 hour before ischemia and was maintained during 1.5-2 hours of recirculation in nine cats; four cats were subjected to hyperthermia without cerebral ischemia, six to hyperthermia during recirculation (after return of intracellular pH to preischemic values), and 14 to normothermic ischemia and recirculation. Our data indicate that preischemic hyperthermia results in an intracellular cerebral pH during recirculation significantly lower than that in normothermic cats. In hyperthermic cats beta-ATP and phosphocreatine (PCr) concentrations and the ratio of PCr to inorganic phosphate failed to return to preischemic levels during recirculation in contrast to normothermic cats. Hyperthermia without ischemia and hyperthermia during recirculation had no significant effect on intracellular pH. Thus, preischemic hyperthermia has a detrimental effect on metabolic recovery after transient global cerebral ischemia.

Topics: Acidosis; Adenosine Triphosphate; Animals; Brain Ischemia; Cats; Fever; Phosphates; Phosphocreatine

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Brain Ischemia; Energy Metabolism; Phosphocreatine

Relative levels of phosphate metabolites in the brain were examined in vivo by 31P magnetic resonance spectroscopy (MRS) in 50 Sprague-Dawley rats before, during, and after induction of focal permanent cerebral ischemia. After acquisition of baseline spectra, rats were subjected to injury within the core of the MR spectrometer, and 31P spectra were collected for 60 min after injury: in 7 rats, permanent, acute focal cerebral ischemia was induced (ischemia group); in 6 rats, mild hypoxia (FiO2 14%) was induced at the time of the ischemic insult and was maintained for 20 min (ischemia-hypoxia group); in 6 rats, mild hypoxia (FiO2 14%) only was induced for 20 min (hypoxia group). Control studies were performed in 25 rats. Cerebral intracellular pH, calculated from the chemical shift of inorganic phosphate (Pi), decreased immediately after injury in the ischemia and ischemia-hypoxia groups. The first 31P spectrum obtained after injury was characterized by an increase in Pi and a decrease in phosphocreatine (PCr) in the ischemia and ischemia-hypoxia groups; these changes in spectra were significantly greater in the ischemia-hypoxia group. No significant changes in adenosine triphosphate (ATP) were found in either group. Within 60 min of occlusion, 31P spectra returned toward baseline spectra in both ischemia-hypoxia and ischemia groups. No significant changes were seen in spectra of rats subjected to hypoxia alone. These results confirm that 31P MRS is a sensitive measure of early changes of high energy metabolites in focal cerebral ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Blood Pressure; Brain; Brain Ischemia; Energy Metabolism; Hydrogen-Ion Concentration; Kinetics; Magnetic Resonance Spectroscopy; Male; Oxygen; Phosphates; Phosphocreatine; Rats; Rats, Inbred Strains

Dihydropyridine calcium channel blockers such as nicardipine are under evaluation for treating acute cerebral ischemia because they may increase cerebral blood flow by causing vasodilation and because they may be cytoprotective in part by limiting production of arachidonic acid metabolites. We demonstrated in a previous study that nicardipine improves postischemic neuronal function, as measured by somatosensory evoked potentials, without reducing the extent of light-microscopic CA-1 hippocampal histologic damage. To characterize further the effect of nicardipine on global ischemic injury, we administered the drug beginning 24 hours before 30 minutes of four-vessel ischemia in Wistar rats. We then measured hippocampal ATP, phosphocreatine, and glucose contents immediately and 2 hours after ischemia, and measured learning ability (working and reference errors) on an eight-arm radial maze beginning 30 days after ischemia. To gain insight into the possible mechanism of action, we measured production of arachidonic acid metabolites (eicosanoids: TXB2 and 6-keto-PGF1 alpha) and hemispheric and hippocampal cerebral blood flow by the [14C]butanol indicator fractionation technique immediately and 2 hours after ischemia. Nicardipine was associated with fewer working errors (p less than 0.02) but no difference in reference errors. The drug had no effect on energy metabolites, cerebral blood flow, or eicosanoids immediately after ischemia, but ATP, phosphocreatine, and cerebral blood flow all returned to normal levels significantly more rapidly during reperfusion in treated rats. Nicardipine improves behavioral, electrophysiologic, and mitochondrial function after ischemia without preventing cellular damage and improves postischemic reperfusion. The drug's positive effect appears to occur during reperfusion.

Topics: Adenosine Triphosphate; Animals; Biomechanical Phenomena; Brain Ischemia; Calcium Channel Blockers; Cerebrovascular Circulation; Eicosanoic Acids; Evoked Potentials, Somatosensory; Glucose; Hippocampus; Learning; Male; Nicardipine; Phosphocreatine; Rats; Rats, Inbred Strains

Progressive cerebral ischemia was induced in seven anesthetized hyperglycemic rats by carotid artery ligation and hemorrhagic hypotension. Phosphorus metabolites, intracellular pH, and lactate in the brain were monitored by 31P and 1H magnetic resonance spectroscopy. Under conditions in which blood flow was low, phosphocreatine (PCr) concentration and intracellular pH decreased and the concentration of lactate increased. The decrease in ATP was approximately one-third that of PCr until only 25% PCr remained, after which ATP was lost more rapidly than PCr. These changes were interpreted in terms of three regions observed by the magnetic resonance coil, one of complete ischemia, one of partial ischemia, and one of perfusion sufficient to maintain normal metabolite levels. The extent of the three regions was estimated quantitatively. Broadening and splitting of the inorganic phosphorus (Pi) peak into two components provided further evidence of distinct populations of cells, one very acidic and another less so. Apparent intracellular buffering capacity was calculated as 23.6 +/- 1.3 mumol lactate/g wet wt/pH.

Topics: Acidosis, Lactic; Adenosine Triphosphate; Animals; Brain Ischemia; Hydrogen; Hydrogen-Ion Concentration; Hyperglycemia; Lactates; Magnetic Resonance Spectroscopy; Phosphocreatine; Phosphorus; Rats; Rats, Inbred Strains

Focal cerebral ischemia in the rat was induced by occlusion of the left middle cerebral artery. The temporal evolution of regional energy metabolism was studied over the 14 days consequent to the induction of ischemia in the frontal, cingulate, parietal, and occipital cortices as well as in the striatum. Regional concentrations of adenosine triphosphate (ATP), phosphocreatine, and lactate and, in addition, glucose and the cerebral/plasma glucose ratio (C/P) were measured in the hemispheres both ipsilateral and contralateral to the occlusion. Two hours after middle cerebral artery occlusion, the biochemical changes were severe in the striatum and moderate in cortical regions. Later on (at 24 and 48 h), an overall aggravated metabolic status was noted while lactate declined and glucose markedly increased. These latter biochemical changes likely indicate a marked inhibition of the rate of glucose utilization. At 48 h, the energy reserves (ATP, phosphocreatine) of parietal cortex no longer equaled those of other cortical regions, but abruptly fell to the levels found in the striatum without any increase in lactate level. Finally, at 7 and 14 days, the levels of the various metabolites in most cortical regions returned toward control values, although signs of a depressed glucose metabolism remained. However, in both striatum and parietal cortex, ATP and phosphocreatine concentrations, although higher than those observed at 48 h, remained significantly decreased. Our present biochemical study permits the classification of these selected brain regions into three categories. First there are those that are outside the area of infarction: the frontal, cingulate, and occipital cortices. These regions show little temporal evolution of brain energy metabolism but, notwithstanding, they are regions in which glucose use would appear to be greatly depressed. Second is a region considered to be the focus of infarction: the striatum. The caudate-putamen is a region with early and profound metabolic disturbances with no final restitution. Last is the region of metabolic penumbra--the parietal cortex, in which there is a time-related exacerbation of the consequences of middle cerebral occlusion in the rat.

Topics: Adenosine Triphosphate; Animals; Blood Glucose; Brain; Brain Ischemia; Energy Metabolism; Lactates; Lactic Acid; Male; Phosphocreatine; Rats; Rats, Inbred F344; Reference Values; Time Factors; Tissue Distribution

Unlike adult rats, glucose supplementation of immature rats does not lead to accentuated hypoxic-ischemic brain damage. To explore the reason for this age-specific paradox, we subjected 7-day postnatal rats to unilateral common carotid artery occlusion followed by a subcutaneous injection of either 0.1 ml 50% glucose or normal saline. They were then exposed to hypoxia with 8% oxygen, during which they received 2.5 microCi 2-[14C]-glucose or were quick-frozen for brain metabolite analysis. During hypoxia-ischemia, glucose transport into the ipsilateral cerebral hemisphere of the hyperglycemic rats was greater (+100-150%) than in normoglycemic animals. However, glucose consumption was similar in the two groups. Glucose concentrations in brain were lower during hypoxia-ischemia in the normoglycemic animals, whereas lactate increased to similar levels in the two groups. The high-energy phosphate reserves, ATP and phosphocreatine, were depleted to a similar extent. Thus, hyperglycemia combined with hypoxia-ischemia, although associated with increased glucose transport into brain, does not lead to enhanced glucose utilization or lactate accumulation by brain over that of hypoxia-ischemia alone.

Topics: Adenine Nucleotides; Animals; Animals, Newborn; Blood Glucose; Brain; Brain Ischemia; Glucose; Hyperglycemia; Hypoxia, Brain; Lactates; Lactic Acid; Phosphocreatine; Pyruvates; Pyruvic Acid; Rats; Rats, Inbred Strains

CBF has been measured with the hydrogen clearance technique in the two cerebral hemispheres of the gerbil under halothane anesthesia. This has been correlated with changes in local pH, tissue lactate, and phosphorus energy metabolites measured in the same animals with 1H and 31P nuclear magnetic resonance spectroscopy. We demonstrate a threshold flow value for the metabolic changes associated with energy failure at a level similar to the values previously reported for electrical failure and tissue water accumulation, but higher than that associated with breakdown of extracellular potassium homeostasis.

Topics: Animals; Aspartic Acid; Brain; Brain Ischemia; Cerebrovascular Circulation; Energy Metabolism; Gerbillinae; Hydrogen; Hydrogen-Ion Concentration; Lactates; Lactic Acid; Magnetic Resonance Spectroscopy; Phosphocreatine; Phosphorus

In order to study the metabolic events surrounding ischemia induced by the graded increase of cerebrospinal fluid (CSF) pressure, the technique of simultaneous phosphorus-31- and hydrogen-1-enhanced nuclear magnetic resonance spectroscopy was applied to five cats as intracranial pressure (ICP) was gradually raised by the instillation of mock CSF. Threshold lactate rose at an average cerebral perfusion pressure (CPP) of 49 torr, and, in general, preceded a threshold decrease in phosphocreatine, which was observed at an average CPP of 29 torr. There was considerable variation among cats in the CPP at which failure of brain energy metabolism occurred, however, suggesting differences in the autoregulatory curves. It is concluded that, with elevated ICP, there is no universally "safe" CPP at which brain energy metabolism may be assumed to be uncompromised.

Topics: Animals; Blood Pressure; Brain; Brain Ischemia; Cats; Female; Hydrogen; Hydrogen-Ion Concentration; Intracranial Pressure; Lactates; Lactic Acid; Magnetic Resonance Spectroscopy; Phosphocreatine; Phosphorus

The objective of this study was to evaluate simultaneous 31P/1H nuclear magnetic resonance (NMR) spectroscopy as a technique for monitoring and correlating changes in brain energy metabolism during hypoxia and ischemia. Five cats were studied with a protocol that involved 20 min of hypoxia (PaO2 20 mm), 60 min of recovery, 10 min of hypoxia with relative ischemia (bilateral carotid occlusion, PaO2 20 mm), and 60 min of recovery. Bifrontal and biparietal electrocorticograms (ECoG) were monitored continuously during the entire protocol. The results demonstrate that the degree of metabolic response is different in individual cats, but a number of quantitative relationships between metabolic parameters are consistently observed for all cats. First, there is agreement between increases in lactate and changes in intracellular pH; the observed relationship corresponds to an in vivo cerebral buffer capacity of 29 mumol/g/pH unit. Second, the delayed recovery of PCr is due to the effect of metabolic acidosis on the creatine kinase equilibrium and not to a delayed recovery of the ATP/ADP ratio. Third, the observed rate of lactate clearance from the cell is zero-order (k = 0.36 mumol/g/min) for lactate levels greater than 5 microns/g and may be composed of both lactate efflux from the cell and lactate oxidation.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Cats; Electroencephalography; Hydrogen; Hypoxia; Lactates; Lactic Acid; Magnetic Resonance Spectroscopy; Male; Phosphocreatine; Phosphorus

Phosphorus-31 magnetic resonance (31P MR) spectroscopy was used to obtain serial in vivo measurements of cerebral adenosine triphosphate (ATP), phosphocreatine (PCr), inorganic phosphate (Pi), and intracellular pH levels in rats during temporary global cerebral ischemia and reperfusion. Three groups of 4 rats each that recovered from permanent bilateral vertebral artery occlusion were placed in a MR spectrometer and subjected to remotely controlled bilateral carotid artery occlusion lasting 6, 15, or 30 minutes followed by 1 hour of reperfusion. Four additional rats that developed systemic hypotension (2 during a 6-minute occlusion and 2 during a 15-minute occlusion) were also studied. 31P MR spectra were obtained in each rat before, during, and after ischemia. Rats in which MR spectra showed metabolic recovery underwent a second occlusion followed by reperfusion and sacrifice. In the 12 normotensive rats, metabolic alterations began within 3 minutes after the onset of global ischemia. By the end of the occlusion period, cerebral ATP had decreased by 20 to 100% in 10 rats and PCr had decreased by 15 to 75% in all 12; Pi increased by 25 to 240%. The mean intracellular pH decreased from 7.33 to 6.9 +/- 0.6. The degree of metabolic deterioration during ischemia was not related to the duration of occlusion. During reperfusion, ATP, PCr, Pi, and intracellular pH returned to normal in 4 rats; 5 rats had partial metabolic recovery, and 3 had minimal or transient metabolic recovery followed by progressive deterioration. All rats that developed systemic hypotension had a decrease in ATP, PCr, and intracellular pH and an increase in Pi during the initial occlusion. Each had transient partial recovery in ATP during reperfusion, and 2 had slight recovery of PCr. The onset of hypotension was followed by depletion of these metabolites, progressive increase in Pi, and progressive intracellular acidosis. All rats that deteriorated metabolically after reversal of carotid occlusion died by the end of the reperfusion period or soon after. The 8 rats that recovered from the first occlusion were subjected to a second period of ischemia, during which each rat showed severe depletion of metabolites. During the second reperfusion, only 1 rat showed significant metabolic recovery, which lasted only 30 minutes and was followed by progressive deterioration. Severe global cerebral ischemia was associated with a progressive decline in both ATP and PCr, whereas less complete ischemia

Topics: Adenosine Triphosphate; Animals; Blood Pressure; Brain Ischemia; Cerebrovascular Circulation; Energy Metabolism; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Male; Phosphates; Phosphocreatine; Rats; Rats, Inbred Strains

Intracellular energy metabolism was studied by phosphorus magnetic resonance spectroscopy in the brains of 27 preterm and term infants with increased echodensities consistent with hypoxic-ischaemic injury and 18 comparable normal infants. In the normal infants the phosphocreatine (PCr)/inorganic orthophosphate (Pi) ratio increased significantly from 0.77 +/- 0.24 (95% confidence limits) at a gestational plus postnatal age of 28 weeks to 1.09 +/- 0.24 at 42 weeks. 9 of the 15 infants with increased echodensities whose PCr/Pi ratios fell below the normal range died; in all 6 survivors cerebral atrophy developed (cysts in brain tissue or microcephaly). In contrast, all 12 infants with increased echodensities whose PCr/Pi ratios remained within the normal range survived, although cerebral atrophy developed in 3 with ratios towards the lower limit of normal.

Topics: Age Factors; Brain; Brain Ischemia; Cerebral Hemorrhage; Energy Metabolism; Female; Follow-Up Studies; Humans; Infant, Newborn; Infant, Premature, Diseases; Magnetic Resonance Spectroscopy; Male; Phosphates; Phosphocreatine; Ultrasonography

Changes in cerebral high-energy phosphate stores and lactate concentration (as evidence for cerebral protection) were studied in dogs treated with etomidate during incomplete global ischemia, which was of a magnitude insufficient to abolish neuronal synaptic activity (as evidenced by electrical activity on EEG). In six dogs the effects of etomidate (5 mg X kg-1) on the rates of adenosine triphosphate (ATP) and phosphocreatine (PCr) depletion and lactate accumulation during 9 min of oligemic hypotension to 31 mmHg were compared with six untreated dogs. In the dogs treated with etomidate the cerebral energy stores of ATP and PCr and the cerebral energy charge were maintained at higher levels than in the untreated dogs, and the cerebral lactate accumulation was significantly less. This effect of etomidate is similar to that of other anesthetics (thiopental and isoflurane) in this model. The authors conclude that in circumstances of ischemia that are insufficient to abolish neuronal synaptic activity, etomidate may improve tolerance of the brain to ischemia by decreasing cerebral metabolism through its suppression of neuronal synaptic activity.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Dogs; Electroencephalography; Energy Metabolism; Etomidate; Hypotension; Lactates; Lactic Acid; Phosphates; Phosphocreatine

The recovery of the EEG and somatosensory evoked responses (SER) as compared with recovery of the cerebral energy state was studied in rats during recirculation following different degrees of brain ischemia with varying tissue lactic acidosis. Reversible complete and incomplete ischemia was induced either by increasing the intracranial pressure (compression ischemia) or by carotid artery clamping combined with arterial hypotension. In incomplete ischemia the degree of tissue lactic acidosis was varied by manipulations of blood and brain glucose levels. Animals with an increase in brain lactate to about 25 mumol X g-1 (whole brain wet weight) during ischemia showed persistent failure of both cerebral energy metabolism and neurophysiologic restitution during the recirculation phase; if less than 20 mumol X g-1 metabolic recovery was almost complete. Despite a similar restitution of tissue energy metabolism in these animals, neurophysiologic recovery was inversely proportional to brain lactate concentrations during ischemia. At similar levels of ischemic tissue lactic acidosis, and despite a similar recovery of cortical energy state, the neurophysiologic restitution was clearly inferior after complete ischemia to that following incomplete ischemia. Three conclusions were drawn: (i) neurophysiologic variables were more sensitive indicators of postischemic persistent cerebral dysfunction than the cerebral energy state; (ii) the degree to which lactate accumulated in the ischemic brain influenced neurophysiologic restitution even if concentrations critical for metabolic recovery were not attained; and (iii) incomplete ischemia was less harmful than complete ischemia provided that tissue lactic acidosis was not excessive.

Topics: Acidosis; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Brain Ischemia; Cerebral Cortex; Electroencephalography; Energy Metabolism; Evoked Potentials, Somatosensory; Lactates; Male; Phosphocreatine; Rats; Rats, Inbred Strains

The influence of a new eburnamenine derivative RU 24722 [(3 beta, 14 alpha, 16 alpha)-(+/-)-14,15-dihydro-20,21-dinoreburnamenin -14-ol] on post-ischemic EEG recovery was studied in N2O anesthetized rats subjected to 1 min of global-compression cerebral ischemia. RU 24722 was compared with vincamine, dihydroergotoxine mesylate and nicergoline. Treatment with RU 24722 (2 mg/kg i.v.) significantly decreased the EEG recovery time and increased the electrocortical activity during the first phase of the post-ischemic recovery. Vincamine (2 mg/kg i.v.), dihydroergotoxine mesylate (0.5 mg/kg i.v.) and nicergoline (0.5 mg/kg i.v.) were devoid of activity. In an attempt to elucidate its mechanism of action, the influence of RU 24722 on changes in the cerebral metabolic energy reserves was studied in mouse brain after different periods of decapitation ischemia. The changes occurring during the first 10 s of ischemia were used to calculate the baseline cerebral metabolic rate (CMR). The activity of RU 24722 was compared with that of vincamine and pentobarbital. RU 24722 (10 mg/kg i.p.) significantly retarded glucose, phosphocreatine and adenosine triphosphate utilisation and lactate production. Vincamine (10 mg/kg i.p.) had no effect on cerebral energy substrates. Pentobarbital (100 mg/kg i.p.) markedly increased the tissue concentration of glucose and phosphocreatine and decreased lactate levels before and after ischemia. The improvement of EEG recovery suggests that RU 24722 may be therapeutically effective in cerebral insufficiency, and the decreased brain energy demand may be one of the mechanisms by which RU 24722 has a protective effect against cerebral ischemic damage.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Dihydroergotoxine; Electroencephalography; Energy Metabolism; Glucose; Glycogen; Lactates; Lactic Acid; Male; Mice; Nicergoline; Phosphocreatine; Rats; Vasodilator Agents; Vinca Alkaloids; Vincamine

The effects of hypoxic hypoxia on high-energy phosphate metabolites and intracellular pH (pHi) in the brain of the anesthetized infant rabbit were studied in vivo using 31P nuclear magnetic resonance spectroscopy. Five 10- to 16-day-old rabbits were anesthetized with 1.5% halothane. Ventilation was controlled to maintain normocarbia. Inspired O2 fraction was adjusted to produce three states of arterial oxygenation: hyperoxia (PaO2 greater than 250 mm Hg), normoxia (PaO2 approximately 100 mm Hg), and hypoxia (PaO2 25-30 mm Hg). During hypoxia, blood pressure was kept within 20% of control values with a venous infusion of epinephrine. During hyperoxia, the phosphocreatine-to-ATP ratio was 0.86, a value that is 2-2.5 times less than that reported for adults. During normoxia, ATP decreased by 20% and Pi increased by 90% from hyperoxia values. During 60 min of hypoxia, the concentrations of high-energy phosphate metabolites did not change, but intracellular and arterial blood pH (pHa) decreased significantly. When hyperoxia was reestablished, pHi returned to normal and pHa remained low. These results suggest that during periods of hypoxemia, the normotensive infant rabbit maintains intracellular concentrations of cerebral high-energy phosphates better than has been reported for adult animals.

Topics: Adenosine Triphosphate; Anesthesia; Animals; Animals, Newborn; Brain; Brain Ischemia; Energy Metabolism; Extracellular Space; Halothane; Hydrogen-Ion Concentration; Hypoxia; Magnetic Resonance Spectroscopy; Phosphates; Phosphocreatine; Phosphorus; Rabbits

Phosphatic metabolite (perchloric acid extractable) concentrations of cerebral tissues were analyzed by phosphorus-31 nuclear magnetic resonance (P-31 NMR) spectroscopy following external perfusion of the isolated rat brain (30 min or 60 min) under the following conditions: (a) constant perfusion pressure with either fluorocarbon- or erythrocyte-based medium, and (b) constant perfusate flow rate (3 ml/min) with the erythrocyte-based medium. Metabolite concentrations of control perfused brains were compared with those in nonperfused controls to provide a basis for detecting any qualitative or quantitative changes in cerebral metabolite composition. Metabolic responses of perfused brains to ischemia (incomplete ischemia, 83% reduction in flow for 10 min; transient complete ischemia for 1.5 or 2 min) were evaluated immediately after the ischemic episode and at selected time points during reperfusion (3 and 15 min). Alterations in cerebral metabolite levels induced by hypoxia were analyzed using a nonperfused rat brain model. Irrespective of the perfusion method employed, the phosphatic metabolites of control perfused rat brains were identical quantitatively to those of the nonperfused controls. Cerebral ischemia resulted in significantly increased levels of ADP, AMP + IMP, Pi, fructose 1,6-diphosphate, and glycerol 3-phosphate (global ischemia only), whereas ATP and phosphocreatine (PCr) levels declined significantly. The magnitude of these changes varied with the severity of the ischemia; however, following 15 min of control reperfusion metabolite levels had reverted to preischemic values. Significant perturbations in tissue phosphoethanolamine (3.84 delta resonance) content were evident at various time points during ischemia and postischemic recovery, which varied according to the perfusion conditions. In contrast to the changes observed in response to ischemia, hypoxia affected only cerebral high-energy phosphate levels. ATP and PCr levels were reduced, while a concomitant, essentially equimolar, increase in Pi and ADP was observed. The present studies indicate that in terms of phosphatic metabolites, the control equilibrated isolated perfused rat brain is quantitatively and qualitatively indistinguishable from the nonperfused rat brain in vivo regardless of the perfusion conditions (constant flow versus constant pressure). The metabolic responses to ischemia and hypoxia, as measured by P-31 NMR, were consistent with the pattern of changes reported elsewh

Topics: Animals; Brain; Brain Ischemia; Electroencephalography; Energy Metabolism; Erythrocytes; Fluorocarbons; Hypoxia; In Vitro Techniques; Magnetic Resonance Spectroscopy; Male; Nucleotides; Perchlorates; Perfusion; Phosphates; Phosphocreatine; Rats; Rats, Inbred Strains; Sugar Phosphates

Effects of perfluorochemical (PFC) and glycerol on energy metabolism in cerebral ischaemia were examined by the sequential measurements of in vivo 31P-NMR spectrum using topical magnetic resonance (TMR). Experimental cerebral ischaemia was induced in forty-five Wistar rats by a four-vessel occlusion method. The 31P-NMR spectrum and the EEG were monitored during preischaemic and ischaemic periods and after circulation was restored for various periods up to 240 min. There were several peaks in the 31P-NMR spectrum of the preischaemic rat brain; beta-ATP, alpha-ATP, gamma-ATP, phosphocreatine (PCr), phosphodiesters, inorganic phosphate (Pi) and sugar phosphate. As soon as the ischaemia was induced, PCr and ATP decreased and Pi increased. The chemical shift of the increased Pi peak decreased, showing acidosis of the brain tissue. After circulation was restored following the 30 min ischaemia, recovery of the 31P-NMR spectrum occurred within 30 min in all sixteen untreated rats. Recovery of the 31P-NMR spectrum was induced by recirculation only in half of the six rats in the untreated 60 min ischaemia group. None of the six rats in the untreated group showed recovery of the spectrum after 120 min ischaemia. When 20% Fluosol-DA was administered at a dose of 20 ml/kg before the induction of ischaemia, all eight rats showed recovery of the spectrum after 120 min ischaemia. Moreover, four of six rats treated with both PFC and glycerol showed temporary recovery even after 240 min ischaemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Brain Ischemia; Drug Combinations; Electroencephalography; Energy Metabolism; Evoked Potentials; Fluorocarbons; Glycerol; Hydroxyethyl Starch Derivatives; Magnetic Resonance Spectroscopy; NAD; Phosphates; Phosphocreatine; Plasma Substitutes; Rats; Rats, Inbred Strains

The transverse guinea pig hippocampal slice preparation was used to model the metabolic changes which occur in vivo during ischemia and recovery. Perfusing brain slices with medium devoid of glucose and oxygen elicits rapid decreases in phosphocreatine, ATP, intracellular pH, and in the evoked field potential recorded in the dentate gyrus. AMP and creatine rise during this period, while ADP and lactate levels remain unchanged. Cyclic AMP exhibits a transient increase in concentration. With the exception of ADP and lactate, these responses are very similar to those observed during in vivo ischemia. The return of glucose and oxygen to the incubation medium reverses these metabolic and electrophysiological effects and also leads to pronounced elevations in cyclic nucleotide concentrations. Metabolite concentrations approach, but do not reach, in vitro steady state levels during the first 30 min of recovery. Total adenylate and creatine steady state levels are approximately 50% of in vivo concentrations. The results suggest that, although hippocampal slices differ metabolically from in vivo tissue, they exhibit a similar pattern of metabolic responses to ischemic and reflow conditions.

Topics: Adenosine Monophosphate; Adenosine Triphosphate; Animals; Brain Ischemia; Creatine; Cyclic AMP; Cyclic GMP; Evoked Potentials; Glucose; Guinea Pigs; Hippocampus; Hydrogen-Ion Concentration; In Vitro Techniques; Male; Models, Biological; Oxygen; Perfusion; Phosphocreatine

To clarify the changes that occur during marked hypocarbia in the neonate, we measured brain blood flow and metabolite levels after 90 minutes of hyperventilation in neonatal dogs. Brain blood flow decreased significantly in diencephalon, brainstem, and spinal cord but not in cerebral cortex or white matter. There was no substantial change in the electroencephalogram. Lactate concentrations, both in telencephalon and in superior sagittal sinus blood, increased significantly, although there was no alteration in levels of ATP or phosphocreatine. Marked hypocarbia in the neonatal dog produces an elevated brain lactate level that may be related to changes in glycolytic rate rather than to tissue ischemia or hypoxia.

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Blood Glucose; Brain; Brain Ischemia; Carbon Dioxide; Cerebrovascular Circulation; Dogs; Electroencephalography; Energy Metabolism; Female; Hydrogen-Ion Concentration; Hyperventilation; Lactates; Lactic Acid; Male; Phosphocreatine

The energy metabolites in rat brain in vivo were measured by using topical magnetic resonance (TMR) during the whole course of ischemia, in combination with the concomitant monitoring of electroencephalogram (EEG). Immediate loss of high energy phosphorus compounds, phosphocreatine (PCr) and ATP, resulted in the flattening of EEG after the induction of ischemia. PCr and ATP returned to almost normal level 30 min after recirculation of the ischemic brain, but EEG showed no recovery and the abnormality lasted for 12 h. The measurement of in vivo 31P-NMR is essential for the decision of the convalescence of cellular function in the brain.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Brain Death; Brain Ischemia; Cerebral Cortex; Cerebrovascular Circulation; Electroencephalography; Energy Metabolism; Magnetic Resonance Spectroscopy; Neurons; Phosphates; Phosphocreatine; Rats; Rats, Inbred Strains

Topics: 2,3-Diphosphoglycerate; Adenine Nucleotides; Animals; Brain; Brain Ischemia; Diphosphoglyceric Acids; Energy Metabolism; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Phosphates; Phosphocreatine; Rats; Rats, Inbred Strains

The low cerebral energy requirements of most mammals at birth reflect an immaturity of the central nervous system, and it has been suggested that energy demands in fetuses are even less well developed than in newborns. Furthermore, fetal cerebral energy requirements are presumed to be met predominantly or exclusively by anaerobic glycolysis. To clarify these issues, we investigated cerebral oxidative metabolism in 9-, 14-, 16-, and 19-day-old chick embryos and in newly hatched peeps. Animals were decapitated and quick-frozen in liquid Freon 0--5 min post-mortem. Forebrain extracts were prepared and assayed for ATP, phosphocreatine, glucose, and lactate. Alterations in these metabolites post-decapitation were used to calculate cerebral metabolic rates (delta similar to P) and rates of maximal anaerobic glycolysis (delta lactate). Rates of lactate accumulation during cerebral ischemia increased progressively from embryonic day 9 through hatching. Cerebral metabolic rates were not different in 9-, 14-, and 15-day-old embryos, but increased steadily thereafter. The extent to which total cerebral energy utilization could be derived from anaerobic glycolysis (delta lactate/delta similar to P) increased from a low at day 9 (0.29) to a maximum at day 16 (0.78). The data suggest that, despite the low cerebral metabolic activity of the chick embryo, at no time during development is anaerobic glycolysis capable of entirely supporting the energy needs of the developing brain.

Topics: Animals; Brain; Brain Ischemia; Chick Embryo; Chickens; Glucose; Glycolysis; Lactates; Lactic Acid; Oxidation-Reduction; Phosphocreatine

We have used the noninvasive method of 31phosphorus nuclear magnetic resonance (31P NMR) in vivo to follow changes in phosphorous metabolite concentrations and the intracellular pH in the right and left hemispheres and in the cerebellum of gerbil brains after the occlusion of the right carotid artery. Spatial resolution over the brain was possible using surface coils. Ligation, which is know to cause ischaemia in this species in the ipsilateral hemisphere, resulted in the diminution of phosphocreatine and adenine nucleotides and a decrease in tissue pH. Less acidification occurred in the contralateral hemisphere and in the cerebellum. The high-energy metabolite concentrations, phosphocreatine and adenosine triphosphate (ATP), declined in unison in the ischaemic region, in marked contrast to the sequence of events in skeletal muscle, in which phosphocreatine buffers against an immediate fall in ATP concentration. In a separate series of gerbils, 31P NMR spectra were followed for exactly 1 h after carotid ligation. The animals were then sacrificed and brain grey matter specific gravity was rapidly measured to assess the development of oedema. There was a clear correlation between abnormality of spectra and the presence of oedema. It cannot, however, be confidently asserted that a normal spectrum is never seen in oedematous gerbil brains. 31P NMR spectra specific gravity and histological changes shown by light microscopy have been correlated and show that useful signals are received from a depth of at least 4 mm or more from the 10-mm diameter coil.

Topics: Adenine Nucleotides; Animals; Brain Chemistry; Brain Ischemia; Cerebral Cortex; Gerbillinae; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Phosphocreatine; Phosphorus

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Phosphocreatine; Phosphorus Radioisotopes; Rabbits

Microanalysis methods were used to determine the effect of bilateral carotid occlusion on net levels of energy metabolites in discrete cellular regions of the hippocampus and dentate gyrus of the Mongolian gerbil. Glucose, glycogen, ATP and phosphocreatine levels were not decreased after one minute of bilateral occlusion. Three minutes of ischemia, however, produced a dramatic fall in net levels with no further decrease observed at fifteen minutes. Re-establishment of blood flow for five minutes after a fifteen minute ischemic episode resulted in replenishment of metabolites to pre-ischemic levels. Glucose was increased two to three times in sham-operated animals as compared to control (non-operated) animals. The increase was the result of the Na-pentobarbital anesthetic employed. The present data indicate that regions of the hippocampus and dentate gyrus respond in a uniform manner to bilateral occlusion of the carotid arteries. Further, most cells maintained enough viability to resume production of high-energy phosphate and carbohydrate metabolites.

Topics: Adenosine Triphosphate; Animals; Blood Glucose; Brain Ischemia; Dominance, Cerebral; Energy Metabolism; Gerbillinae; Glycogen; Hippocampus; Phosphocreatine

This study explores the influence of severe lactic acidosis in the ischemic rat brain on postischemic recovery of the tissue energy state and neurophysiological parameters. Severe incomplete brain ischemia (cerebral blood flow below 5% of normal) was induced by bilateral carotid artery clamping combined with hypovolemic hypotension. We varied the production of lactate in the tissue by manipulating the blood glucose concentrations. A 30-min period of incomplete ischemia induced in food-deprived animals caused lactate to accumulate to 15-16 mumol g-1 in cortical tissue. Upon recirculation these animals showed: (1) a considerable recovery of the cortical energy state as evaluated from the tissue concentrations of phosphocreatine, ATP, ADP, and AMP; and (2) return of spontaneous electrocortical activity as well as of somatosensory evoked response (SER). In contrast, administration of glucose to food-deprived animals prior to ischemia caused an increase in tissue lactate concentration to about 35 mumol g-1. These animals did not recover energy balance in the tissue and neurophysiological functions did not return. In other experiments the production of lactate during 30 min of complete compression ischemia was increased from about 12 mumol g-1 (normoglycemic animals) to 20-30 mumol g-1 by preischemic hyperglycemia and, in separate animals, combined hypercapnia. The recovery of the cortical energy state upon recirculation was significantly poorer in hyperglycemic animals. It is concluded that a high degree of tissue lactic acidosis during brain ischemia impairs postischemic recovery and that different degrees of tissue lactic acidosis may explain why severe incomplete ischemia, in certain experimental models, is more deleterious than complete brain ischemia.

Topics: Acidosis; Adenosine Triphosphate; Animals; Blood Glucose; Brain; Brain Ischemia; Cerebral Cortex; Electroencephalography; Energy Metabolism; Fasting; Ketone Bodies; Lactates; Male; Phosphocreatine; Rats; Rats, Inbred Strains

Topics: Adenosine Triphosphate; Animals; Aspartic Acid; Brain; Brain Ischemia; Creatine; Energy Metabolism; Glutamates; Mice; Phosphocreatine

Regional cortical levels of organic phosphates and carbohydrates were measured in cat brains, enzymatically inactivated by the technique of "funnel freezing" 1 hour after occlusion of a middle cerebral artery (MCA). Significant metabolic alterations occurred in all hemispheres ipsilateral to the site of occlusion. However, there was marked interindividual variability, with changes ranging from only slight increases in lactate, pyruvate, and adenosine monophosphate (AMP) in small regions of cortex at one extreme, to profound depletion of high-energy phosphates, depression of glucose and pyruvate levels, and increased lactate, adenosine diphosphate (ADP) and AMP levels in much of the hemisphere of the most severely involved animals. In contrast, metabolic changes in the hemisphere contralateral to the site of occlusion were very few or nonexistent. In addition, in all ipsilateral hemispheres there were regions peripheral to the areas of greatest metabolic alteration where there was excessive elevation of glucose levels. The results demonstrate that occlusion of a major cerebral vessel does not produce metabolic changes that are consistent in their distribution or severity. However, the findings of this study probably depict some of the complicated metabolic events that occur clinically during thrombotic or embolic infarction of brain.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Brain Ischemia; Cats; Cerebral Arteries; Freezing; Glycolysis; Lactates; Phosphocreatine; Regional Blood Flow

The bioenergetic mechanisms of vasogenic edema were studied by measuring concentrations of adenosine triphosphate (ATP), phosphocreatine (CrP), and lactate in rapidly frozen edematous white matter in cats. When edema was produced using a cold lesion, it was found that both ATP and CrP were reduced to one-half of control values, and that lactate was elevated. When a correction was applied for dilution, however, it was found that high-energy phosphates were equal to control values, and that lactate was even more significantly elevated. This pattern contrasted with that seen in white-matter ischemia, in which CrP is depressed out of proportion to ATP. Finally, it was found that the white-matter lactate-concentration in the plasma infusion model of edema was increased. It is concluded that vasogenic edema induces an increase in lactate, but does not deplete high-energy phosphate compounds in affected white matter.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Edema; Brain Ischemia; Cats; Cold Temperature; Energy Metabolism; Lactates; Male; Phosphocreatine; Vasomotor System

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Brain; Brain Ischemia; Heart Arrest, Induced; Hydrogen-Ion Concentration; Hypothermia, Induced; Magnetic Resonance Spectroscopy; Phosphates; Phosphocreatine; Phosphorus Isotopes; Rats; Sugar Phosphates

Topics: Adenine Nucleotides; Animals; Brain Ischemia; Cerebral Cortex; Energy Metabolism; Glycogen; Hypoxia; Kinetics; Lactates; Phosphocreatine; Potassium; Pyruvates; Rats

In rats, cerebral perfusion pressure were altered abruptly by aortic transection to determine the production by ischemic brain of adenosine and its metabolites, inosine and hypoxanthine. Brain samples were obtained after 0, 5, 10, 15, 30, and 60 seconds of ischemia. Also measured were ATP, ADP, AMP, phosphocreatine (PCr), lactate, and pyruvate. Blood pressure was monitored continuously, and arterial PO2, PCO2, and pH were measured just prior to induction of ischemia. Adenosine was elevated t 2.30 +/- 0.31 (SE) nmol/g at 5 seconds from a control value of 0.96 +/- 0.07. A significant elevation of adenosine continued to 60 seconds (5.50 +/- 1.24). Furthermore, inosine showed a progressive upward trend during the entire 60 seconds of ischemia, whereas no change in hypoxanthine occurred between the moment of transection (31.81 +/- 2.01 nmol/g) and 60 seconds of ischemia (34.72 +/- 2.93). PCr decreased by 1.24 mumol/g within the first 5 seconds. After the onset of hypotension, significant changes did not occur in AMP and ADP until 30 seconds, and in ATP and pyruvate until 60 seconds after aortic transection; lactate was elevated by 10 seconds. The rapid rise of cerebral adenosine within 5 seconds after the onset of ischemia supports a role for adenosine in the regulation of cerebral blood flow.

Topics: Adenosine; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Cerebrovascular Circulation; Homeostasis; Lactates; Phosphocreatine; Pyruvates; Rats; Time Factors

Bilateral ligation of common carotid arteries sharply decreases volume blood flow and oxygen consumption in the cortex, in diencephalon and midbrain whereas inducing no changes in the cerebellum and medulla oblongata. The same is true for intensity of metabolism of both total and separate fractions of phospholipids. This suggests that the changes of phospholipid metabolism in neural tissue depend on the degree of its blood supply disturbance and duration of the ischemia.

Topics: Adenine Nucleotides; Animals; Brain; Brain Chemistry; Brain Ischemia; Carotid Artery Diseases; Lactates; Male; Oxygen Consumption; Phosphocreatine; Phospholipids; Rats; Time Factors

Pyridoxine (1-8 mmol/l) did not change significantly the cerebral oxygen nor the hypoxic or ischaemic degradation of phosphocreatine and ATP. Glyoxylic acid (1-8 mmol/l), an inhibitor of the citric acid cycle, depressed the electrically stimulated oxygen uptake of brain slices to a lesser extent than did pyridoxylate. Moreover, at concentrations of 0.66 mmol/l, pyridoxylate predominantly delayed the hypoxic or the ischaemic breakdown of creatine phosphate and of ATP compared with glyoxylic acid (0.66 mmol/l). These findings paralleled clearly the prominent hypoxic and post-hypoxic protection afforded by pyridoxylate upon rat brain electrogenesis, reported in the preceding paper.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Cerebral Cortex; Electric Stimulation; Glyoxylates; Hypoxia, Brain; Isonicotinic Acids; Lactates; Oxygen; Phosphates; Phosphocreatine; Pyridoxic Acid; Pyridoxine; Rats

The behaviour of fuels (glycogen, glucose), of glycolytic pathway intermediates (glucose-6-phosphate, pyruvate) and end-product (lactate), as well as the pool of labile phosphates (ATP, ADP, AMP, creatine phosphate) and the energy charge of the brain were studied in the motor area of the cerebral cortex of beagle dogs in hypovolaemic hypotension. These parameters were evaluated after acute hypoxia (obtained by altering the composition of the inhalation mixture), after acute hypoxia plus incomplete ischaemia, after acute hypoxia plus complete ischaemia, during post-hypoxic recovery (3, 15 or 30 min after the restoration of normal ventilation), during post-hypoxic recovery and recirculation. A comparative examination of the different conditions showed that the most dramatic fall in the cerebral energy state took place in hypoxia plus complete ischaemia followed, in the order, by hypoxia plus incomplete ischaemia and simple hypoxia. However, reversal was most difficult in hypoxia plus incomplete ischaemia. The different situations are discussed in this paper with regard to the changes taking place in cerebral biochemical events.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Dogs; Energy Metabolism; Female; Glucose; Glycogen; Hypoxia, Brain; Lactates; Models, Biological; Phosphocreatine; Pyruvates

The effect of (-)eburnamonine, papaverine and UDP-glucose intracarotid perfusion has been evaluated in the brain of beagle dogs during various conditions of cerebral damage (hypoxia, hypoxia plus incomplete ischaemia, hypoxia plus complete ischaemia), and after 3, 15 or 30 min of the post-hypoxic recovery and recirculation. The behaviour of fuels (glycogen, glucose), of glycolytic pathway intermediates (glucose-6-phosphate, pyruvate) and end-product (lactate), of the pool of labile phosphates (ATP, ADP, AMP, creatine phosphate) and the energy charge potential of the brain were evaluated in the motor area of the cerebral cortex. The different pharmacological effects of (-)eburnamonine, papaverine and UDP-glucose are discussed with regard to the biochemical changes taking place during the physiopathological conditions tested.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Dogs; Energy Metabolism; Female; Glucose; Glycogen; Hypoxia, Brain; Lactates; Papaverine; Phosphocreatine; Pyruvates; Uridine Diphosphate Glucose; Uridine Diphosphate Sugars; Vasodilator Agents; Vinca Alkaloids

Effects of controlled hypoxemia on cerebral functional activity were studied in rats using cyclic adenosine monophosphate (cAMP) and aminergic neurotransmitters in the brain tissue as special references. Evidence is presented that: (1) mild hypoxemic stress (PaO2 60 to 40 torr) may activate cerebral glycolysis with no evidence of anaerobic metabolism but that further reduction of PaO2 impairs cellular respiration, as evidenced by accumulation of glycolytic products; (2) glycogenolysis in the brain tissue, leakage of potassium ions from the brain cell, increase in brain water, and suppression of neural functional activity occur concomitant with accumulation of cAMP and prior to the fall of adenosine triphosphate; (3) the diminution of cerebral high-energy phosphates during hypoxia is associated with and may be caused by hypoxemia-induced neuroglycopenia and occurs at PaO2 15 torr; (4) induced hypoxemia per se does not affect the level or aminergic neurotransmitter substances in brain tissue.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Blood Glucose; Brain; Brain Ischemia; Carbon Dioxide; Cyclic AMP; Dopamine; Electroencephalography; Evoked Potentials; Glycogen; Lactates; Male; NAD; Norepinephrine; Oxygen; Phosphocreatine; Pyruvates; Rats; Serotonin