glycogen and Astrocytoma

Central nervous system space-occupying lesions with clear-cell features encompass a nosologically heterogeneous array, ranging from reactive histiocytic proliferations to neuroepithelial or meningothelial neoplasms of various grades and to metastases. In the face of such differential diagnostic breadth, recognizing cytoplasmic lucency as part of the morphological spectrum of some low grade gliomas will directly have an impact on patient care. We describe a prevailing clear-cell change in an epileptogenic left temporal pleomorphic xanthoastrocytoma surgically resected from a 36-year-old man. Mostly subarachnoid and focally calcified, the tumor was composed of fascicles of moderately atypical spindle cells with optically lucent cytoplasm that tended to intermingle with a desmoplastic mesh of reticulin fibers. Immunohistochemically, coexpression of S100 protein, vimentin, GFAP, and CD34 was noted. Conversely, neither punctate staining for EMA nor positivity for CD68 was seen. Mitotic activity was absent, and the MIB1 labeling index was 2-3% on average. Diastase-sensitive PAS-positive granula indicated clear-cell change to proceed from glycogen storage. Electron microscopy showed tumor cell cytoplasm to be largely obliterated by non-lysosomal-bound pools of glycogen, while hardly any fat vacuole was encountered. Neither ependymal-derived organelles nor annular lamellae suggesting oligodendroglial differentiation were detected. The latter differential diagnosis was further invalidated by lack of codeletion of chromosomal regions 1p36 and 19q13 on molecular genetic testing. By significantly interfering with pattern recognition as an implicit approach in histopathology, clear-cell change in pleomorphic xanthoastrocytoma is likely to suspend its status as a "classic", and to prompt more deductive differential diagnostic strategies to exclude look-alikes, especially clear-cell ependymoma and oligodendroglioma.

Topics: Adult; Antigens, CD34; Astrocytoma; Biomarkers, Tumor; Brain Neoplasms; Diagnosis, Differential; Ependymoma; Glial Fibrillary Acidic Protein; Glycogen; Humans; Immunohistochemistry; Magnetic Resonance Imaging; Male; Microscopy, Electron; Oligodendroglioma; S100 Proteins; Seizures; Vimentin

Abnormal regulation of brain glycogen metabolism is believed to underlie insulin-induced hypoglycaemia, which may be serious or fatal in diabetic patients on insulin therapy. A key regulator of glycogen levels is glycogen targeted protein phosphatase 1 (PP1), which dephosphorylates and activates glycogen synthase (GS) leading to an increase in glycogen synthesis. In this study, we show that the gene PPP1R3F expresses a glycogen-binding protein (R3F) of 82.8 kDa, present at the high levels in rodent brain. R3F binds to PP1 through a classical 'RVxF' binding motif and substitution of Phe39 for Ala in this motif abrogates PP1 binding. A hydrophobic domain at the carboxy-terminus of R3F has similarities to the putative membrane binding domain near the carboxy-terminus of striated muscle glycogen targeting subunit G(M)/R(GL), and R3F is shown to bind not only to glycogen but also to membranes. GS interacts with PP1-R3F and is hyperphosphorylated at glycogen synthase kinase-3 sites (Ser640 and Ser644) when bound to R3F(Phe39Ala). Deprivation of glucose or stimulation with adenosine or noradrenaline leads to an increased phosphorylation of PP1-R3F bound GS at Ser640 and Ser644 curtailing glycogen synthesis and facilitating glycogen degradation to provide glucose in astrocytoma cells. Adenosine stimulation also modulates phosphorylation of R3F at Ser14/Ser18.

Topics: Adenosine; Adrenergic alpha-Agonists; Amino Acid Sequence; Animals; Astrocytoma; Brain; Brain Neoplasms; Carrier Proteins; Cell Line, Tumor; DNA; Extracellular Space; Glucose; Glycogen; Glycogen Synthase; Humans; Immunohistochemistry; Male; Mice; Mice, Inbred C57BL; Molecular Sequence Data; Mutagenesis; Norepinephrine; Phosphoprotein Phosphatases; Phosphorylation; Protein Phosphatase 1; RNA; Signal Transduction; Subcellular Fractions

In this study we report that substance P stimulated [3H]glycogen breakdown and elevation of intracellular Ca2+ concentration in the human astrocytoma cell line UC-11MG. Both effects were dose dependent, and completely blocked by CP-96,345 suggesting the involvement of an NK1 receptor. Our previous studies indicated that norepinephrine and histamine stimulate glycogenolysis via cAMP and Ca2+ respectively. Combined stimulation with substance P and norepinephrine or histamine resulted in additive effects suggesting that there is no interaction between these neurotransmitters in regulating glycogenolysis in these cells. These results confirm that UC-11MG cells are a useful model system to investigate the functional role of neurotransmitter receptors in astroglial cells.

Topics: Astrocytoma; Biphenyl Compounds; Brain Neoplasms; Dose-Response Relationship, Drug; Drug Combinations; Glycogen; Histamine; Humans; Norepinephrine; Receptors, Neurokinin-1; Substance P; Tumor Cells, Cultured

Astrocytes from a variety of sources, including the human UC-11MG astrocytoma line, express receptors for histamine on their plasma membranes, but the function of these receptors is largely unknown. Here we report studies on the effect of histamine on newly synthesized glycogen in the human astrocytoma-derived cell line, UC-11MG. We have found [3H]glycogen hydrolysis with a EC50 of 2 microM and a maximum effect of 30% at 300 microM histamine. The glycogenolytic effect of histamine was completely blocked by the H1 receptor antagonist, mepyramine, and was insensitive to the H2 receptor antagonist, cimetidine. Histamine-induced glycogenolysis was significantly reduced in the absence of extracellular Ca2+ and the residual response could be accounted for by Ca2+ released from intracellular stores. The Ca2+ ionophore, ionomycin, induced a similar concentration-dependent increase in both intracellular Ca2+ concentration and in glycogenolysis. These results suggest that one function of astrocytic histamine receptors in vivo may be the stimulation of glucose release from astrocytes, and that this process is mediated by increased intracellular free Ca2+. The glycogenolytic effect of histamine and other neurotransmitters in different systems, and the possible implication of astrocytic glycogenolysis in the pathophysiology of ischemia are discussed.

Topics: Astrocytoma; Calcium; Dose-Response Relationship, Drug; Egtazic Acid; Glucose; Glycogen; Histamine; Histamine Antagonists; Humans; Intracellular Membranes; Ionomycin; Receptors, Histamine; Tumor Cells, Cultured

The regulation of glycogen metabolism in C-6 astrocytoma and C-1300 neuroblastoma cells in culture has been investigated. Two modes of control of glycogen metabolism appear to be operative. The regulation of intracellular glycogen concentrations and the predominant forms of glycogen phosphorylase and glycogen synthase vary with (a) the available energy supply, and (b) altered intracellular concentration of cyclic adenosine 3':5'-monophosphate (cyclic AMP). Both cell lines respond to glucose in the medium; when glucose levels are high, glycogen is synthesized, glycogen phosphorylase a decreases, and glycogen synthase a increases. When glucose in the medium decreases to a critical level, the phosphorylase a increases and glycogen concentrations in the cells decrease in aprallel with the medium glucose. The critical glucose concentration is 2.5 mM for the astrocytoma cells and 4 mM for the neuroblastoma cells. Insulin promotes the conversion of phosphorylase to the b form and synthase to the a form in both cell lines. All of these changes occur without alteration in the intracellular cyclic AMP concentrations. When cyclic AMP concentrations are increased in either cell line, phosphorylase a is increased, synthase a is decreased, and glycogen concentrations decrease. Isobutyl methylxanthine is effective in promoting glycogenolysis in both cell lines. Norepinephrine is effective with the astrocytoma cells, and prostaglandin E1 is effective with the neuroblastoma cells.

Topics: Astrocytoma; Cell Line; Culture Media; Cyclic AMP; Glucose; Glycogen; Glycogen Synthase; Neoplasms, Experimental; Neuroblastoma; Norepinephrine; Phosphorylases; Prostaglandins E; Time Factors; Xanthines

The effect of the concentration of glucose in the medium on the intracellular concentrations of metabolites of C-6 astrocytoma cells and C-1300 neuroblastoma cells in culture has been investigated. The intracellular concentrations of glucose, glycogen, glucose 6-P and UDP-glucose were measured at intervals after feeding the cells. A rapid increase in glucose and glucose 6-P levels occurred when fresh medium containing 5.5 mM glucose was applied to the cells, followed by slower increases in UDP-glucose andglycogen. When the medium glucose was increased ten-fold, the intracellular concentration of glucose was increased, but the level of glucose 6-P, UDP=-glucose and glycogen were not altered, nor were the rates of accumulation. The addition of insulin to the medium resulted in an increase of intracellular glucose, glucose 6-P and glycogen. The transport of glucose into the cells is not the rate-limiting step of the regulation of metabolite levels in the cells.

Topics: Astrocytoma; Biological Transport, Active; Cells, Cultured; Cyclic AMP; Glucose; Glucosephosphates; Glycogen; Insulin; Neuroblastoma; Neurons; Uridine Diphosphate Glucose

Topics: Amylases; Astrocytoma; Cells, Cultured; Glucose; Glycogen; Methods; Phenobarbital; Sodium Hydroxide

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Astrocytoma; Cell Line; Cells, Cultured; Culture Media; Cyclic AMP; Depression, Chemical; DNA; Fluorometry; Freezing; Glycogen; Neoplasm Proteins; Neoplasms, Nerve Tissue; Norepinephrine; Phosphocreatine; Phosphoric Diester Hydrolases; Phosphorylases; Rats; Staining and Labeling; Stimulation, Chemical; Time Factors

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Astrocytoma; Cell Line; Cyclic AMP; Depression, Chemical; Electrodes; Energy Metabolism; Glycogen; Norepinephrine; Oxygen Consumption; Papaverine; Phosphocreatine; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Phosphorylases; Rats; Time Factors

Topics: Adenosine Triphosphate; Animals; Astrocytoma; Butyrates; Clone Cells; Cyclic AMP; Drug Antagonism; Enzyme Activation; Epinephrine; Glucagon; Glycogen; Histamine; In Vitro Techniques; Norepinephrine; Papaverine; Phosphorus Isotopes; Phosphotransferases; Propranolol; Prostaglandins; Proteins; Rats

Topics: Astrocytoma; Brain Neoplasms; Caudate Nucleus; Cell Nucleus; Child; Endoplasmic Reticulum; Female; Glycogen; Golgi Apparatus; Humans; Inclusion Bodies; Microscopy, Electron; Ribosomes; Tuberous Sclerosis

Topics: Astrocytoma; Brain Neoplasms; Ependymoma; Ganglioneuroma; Glioblastoma; Glycogen; Histocytochemistry; Humans; Medulloblastoma; Neurilemmoma; Oligodendroglioma; Papilloma; Tuberous Sclerosis

Topics: Adenosine Triphosphate; Adult; Aged; Animals; Astrocytoma; Brain; Brain Neoplasms; Cerebral Cortex; Craniopharyngioma; Fluorometry; Frontal Lobe; Glucose; Glycogen; Glycolysis; Humans; In Vitro Techniques; Ischemic Attack, Transient; Mice; Middle Aged; Oxygen Consumption; Parietal Lobe; Phosphocreatine; Spectrophotometry

Topics: Astrocytoma; Brain Neoplasms; Carbohydrate Metabolism; Cerebellar Neoplasms; Ependymoma; Glioma; Glycogen; Glycosaminoglycans; Histocytochemistry; Humans; Lipid Metabolism; Lipids; Medulloblastoma; Meningeal Neoplasms; Meningioma