glycogen and Hypoxia-Ischemia--Brain

Damage to the choroid plexus in 1-day-old Wistar rats subjected to hypoxia was investigated. The mRNA and protein expression of hypoxia-inducible factor-1alpha (HIF-1alpha), endothelial, neuronal, inducible nitric oxide synthase (eNOS, nNOS, iNOS), and vascular endothelial growth factor (VEGF) along with nitric oxide (NO) production and VEGF concentration was up-regulated significantly in hypoxic rats. Ultrastructurally, the choroid plexus epithelial cells showed massive accumulation of glycogen. A striking feature was the extrusion of cytoplasmic fragments from the apical cell surfaces into the ventricular lumen following the hypoxic insult. Intraventricular macrophages showed increased expression of complement type 3 receptors, major histocompatibility complex class I and II antigens, and ED1 antigens. Following an intravenous injection of horseradish peroxidase (HRP), a large number of intraventricular macrophages were labeled suggesting enhanced leakage of the tracer from the blood vessels in the choroid plexus connective tissue stroma into the ventricular lumen. We suggest that increased production of NO in hypoxia is linked to the structural alteration of the choroid plexus, and along with VEGF, may lead to increased vascular permeability. Melatonin treatment reduced VEGF and NO levels as well as leakage of HRP suggesting its potential value in ameliorating damage in choroid plexus pathologies.

Topics: Age Factors; Animals; Animals, Newborn; Antigens, Surface; Capillary Permeability; Choroid Plexus; Epithelial Cells; Glycogen; Horseradish Peroxidase; Hypoxia-Inducible Factor 1, alpha Subunit; Hypoxia-Ischemia, Brain; Isoenzymes; Lateral Ventricles; Macrophages; Melatonin; Nitric Oxide; Nitric Oxide Synthase; Rats; Rats, Wistar; RNA, Messenger; Treatment Outcome; Up-Regulation; Vascular Endothelial Growth Factor A

The purpose of this study was to determine whether oxygen treatment could attenuate the alterations in cerebral energy metabolism found in the brain following hypoxia-ischemia.. Seven-day-old rat pups were subjected to unilateral carotid artery ligation followed by 2 hrs of hypoxia (8% oxygen at 37 degrees C). The concentrations of high-energy phosphate compounds and glycolytic intermediates and the activity of Na+/K+-adenosine triphosphatase were measured at 4-72 hrs of recovery. Brain weight was used to determine the severity of the brain injury at 2 wks after insult.. Experimental setting.. Rat pups.. Pups were treated with 100% oxygen 1 hr after the insult at 2.5 atmospheres absolute (hyperbaric oxygen) or at normobaric pressure for a duration of 2 hrs.. During the initial period of recovery from hypoxia-ischemia, values of adenosine triphosphate and phosphocreatine remained at levels below normal, whereas the levels of glucose and other glycolytic intermediates were elevated. Hyperbaric oxygen and normobaric oxygen both attenuated brain injury, restored the levels of adenosine triphosphate and phosphocreatine, decreased the levels of the glycolytic intermediates, and increased the utilization of energy.. These results suggest that oxygen treatment during the initial period of recovery from a hypoxia-ischemic insult is able to attenuate energy deficits in the brain, which ultimately leads to a reduction in brain injury.

Topics: Adenine Nucleotides; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Analysis of Variance; Animals; Animals, Newborn; Energy Metabolism; Glycogen; Hypoxia-Ischemia, Brain; Oxygen Inhalation Therapy; Random Allocation; Rats; Rats, Sprague-Dawley

Increasing evidence indicates that fetal metabolic stress may result in a variety of post-natal perturbations during brain development. The goal of the study was to determine the duration of hypoxia/ischemia that would elicit a demonstrable regional depression of metabolism in the fetal brain and further to examine several end-points to determine if the metabolic stress affects the developing brain. The uterine artery and uterine branch of the ovarian artery were occluded with aneurysm clamps for a period of 45 min, the clips removed and the metabolites in five regions of the perinatal brain were measured at 0, 2 and 6 h of reflow. Regional P-creatine, ATP and glucose levels were significantly depleted at the end of the 45 min occlusion. The levels of glycogen and glutamate at the end of the occlusion indicated a decreasing trend which was not significant. The concentration of citrate remained essentially unchanged at the end of the occlusion. To ensure that the insult was not lethal to the tissue, the recovery of the metabolites was examined at 2 and 6 h of reflow and generally the concentrations of the high-energy phosphates and glucose were normal or near-normal by 6 h of reperfusion in the five regions of the brain examined. The changes in the metabolites indicate that 45 min of hypoxia/ischemia is an appropriate model for studying neonatal development after fetal metabolic stress.

Topics: Adenosine Triphosphate; Animals; Brain; Creatine; Disease Models, Animal; Female; Fetal Hypoxia; Glucose; Glycogen; Hypoxia-Ischemia, Brain; Lactic Acid; Phosphates; Pregnancy; Rats; Rats, Sprague-Dawley; Severity of Illness Index; Uterus

Hippocampal slices often have more synapses than perfusion-fixed hippocampus, but the cause of this synaptogenesis is unclear. Ultrastructural evidence for synaptogenic triggers during slice preparation was investigated in 21-day-old rats. Slices chopped under warm or chilled conditions and fixed after 0, 5, 25, 60, or 180 minutes of incubation in an interface chamber were compared with hippocampi fixed by perfusion or by immersion of the whole hippocampus. There was no significant synaptogenesis in these slices compared with perfusion-fixed hippocampus, but there were other structural changes during slice preparation and recovery in vitro. Whole hippocampus and slices prepared under warm conditions exhibited an increase in axonal coated vesicles, suggesting widespread neurotransmitter release. Glycogen granules were depleted from astrocytes and neurons in 0-min slices, began to reappear by 1 hour, and had fully recovered by 3 hours. Dendritic microtubules were initially disassembled in slices, but reassembled into normal axial arrays after 5 minutes. Microtubules were short at 5 minutes (12.3 +/- 1.1 microm) but had recovered normal lengths by 3 hours (84.6 +/- 20.0 microm) compared with perfusion-fixed hippocampus (91 +/- 22 microm). Microtubules appeared transiently in 15 +/- 3% and 9 +/- 4% of dendritic spines 5 and 25 minutes after incubation, respectively. Spine microtubules were absent from perfusion-fixed hippocampus and 3-hour slices. Ice-cold dissection and vibratomy in media that blocked activity initially produced less glycogen loss, coated vesicles, and microtubule disassembly. Submersing these slices in normal oxygenated media at 34 degrees C led to glycogen depletion, as well as increased coated vesicles and microtubule disassembly within 1 minute.

Topics: Animals; Culture Media; Dendrites; Dissection; Glycogen; Hippocampus; Hypoxia-Ischemia, Brain; Interneurons; Male; Microscopy, Electron; Microtomy; Microtubules; Nerve Degeneration; Neuroglia; Neuronal Plasticity; Neurons; Organ Culture Techniques; Oxygen; Postmortem Changes; Presynaptic Terminals; Rats; Rats, Long-Evans; Tissue Fixation

Recent studies have shown a protection from cerebral hypoxic-ischemic (HI) brain damage in the immature rat following a prior systemic hypoxic exposure when compared with those not exposed previously. To investigate the mechanism(s) of hypoxic preconditioning, brain glycogen and high-energy phosphate reserves were measured in naïve and preconditioned rat pups subjected to HI. Groups in this study included untouched (naïve) controls, preconditioned controls (i.e., hypoxia only), preconditioned with HI insult, and naïve pups with HI insult. Hypoxic preconditioning was achieved in postnatal-day-6 rats subjected to 8% systemic hypoxia for 2.5 h at 37 degrees C. Twenty-four hours later, they were subjected to unilateral common carotid artery ligation and systemic hypoxia with 8% oxygen at 37 degrees C for 90 min. Animals were allowed to recover from HI for up to 24 h. At specific intervals, animals in each group were frozen in liquid nitrogen for determination of cerebral metabolites. Preconditioned animals showed a significant increase in brain glycogen 24 h following the initial hypoxic exposure, corresponding to the beginning of the HI insult. Measurement at the end of 90 min of HI showed a depletion of high-energy phosphates, ATP and phosphocreatine, in all animals although ATP remained significantly higher in the preconditioned animals. Thus, the energy from increased glycogen following preconditioning slowed high-energy phosphate depletion during HI, thereby allowing for long-term protection.

Topics: Adenosine Triphosphate; Animals; Brain; Energy Metabolism; Glucose; Glycogen; Hypoxia-Ischemia, Brain; Ischemic Preconditioning; Phosphocreatine; Rats; Rats, Wistar