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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 40 (1983), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Cultured astrocytes, transformed by Herpesvirus, were used as a model system to study several aspects of the control of glycogenolysis. Adrenergic agonists such as norepinephrine and isoproterenol caused an immediate and dose-dependent increase in the intracellular levels of cyclic AMP. Concomitant with the initial phase of cyclic AMP increase, conversion of phosphorylase b to a and glycogenolysis were observed. The elevation of cyclic AMP, phosphorylase conversion, and glycogenolysis were simultaneously blocked by β-adrenergic blockers, but not by α-adrenergic blocking agents. Repeated administration of norepinephrine caused an attenuated response in both cyclic AMP accumulation and glycogenolysis. Glycogen degradation is also partially regulated by glucose availability. In the presence of glucose, norepinephrine-induced glycogenolysis is blocked, despite elevations in cyclic AMP. The direct role of glucose is postulated, since glucose analogs mimic the effects of glucose.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 40 (1983), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Glycogen metabolism was studied in primary and Herpesvirus-transformed cultures of neonatal rat brain astrocytes. A small fraction of the glucose consumed was coaserved in glycogen in both the primary and the transformed astrocytic cell cultures. After addition of culture medium containing 5.5 mM glucose, glycogen increased to maximal levels within 2.5 h, the approximate time at which half of the medium glucose was consumed, and rapidly declined thereafter in both the primary and transformed astrocytic cultures. Maximum levels of glycogen were apparently related to the cell density of the Herpesvirus-transformed cultures, but primary cultures did not show this behavior. At any given cell density, maximal levels of glycogen were dependent on the concentration of extracellular glucose. Administration of glucose caused a transient activation of glycogen synthase a and a rapid inactivation of glycogen phosphorylase a.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 16 (1969), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —The levels of ATP, phosphocreatine, glucose, glucose-6-P., lactate, and glycogen have been measured in brains and spinal cords of lamprey larvae. Levels of glycogen in the brains were high, sometimes exceeding 100 m-moles of glycosyl units/kg wet weight. Isolated brains incubated in oxygenated saline exhibited the same levels of ATP and phosphocreatine as brains of intact animals. The level of glucose in tissue water of isolated brains approximated that found in the medium, except at low concentrations where the brains maintained levels of glucose many times that of the medium. It is demonstrated that under metabolic stress lamprey brains produce glucose by the breakdown of glycogen and the probable action of a glucose-6-phosphatase. The hypothesis is proposed that cells of the brain exchange glucose by this mechanism.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 20 (1973), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The turnover of cerebral glycogen in mice has been investigated by using [U-14C]glucose as a precursor. The time required for turnover of total glycogen and limit dextrin has been determined in normal animals and animals given phenobarbital or hydrocortisone. In all 3 groups, the turnover time for limit dextrin was twice that of total glycogen. Phenobarbital increased the time for turnover of total glycogen and limit dextrin approximately 2-fold, whereas hydrocortisone diminished the turnover time of both fractions to one-half. The accumulation of glycogen during phenobarbital anesthesia (2·5-fold) is attributed to the decrease in rate of phosphorolysis rather than elevated glycogenesis. The ratio of phosphorylase a to total phosphorylase was significantly decreased in the brains of phenobarbital-treated mice, while the ratio of glycogen synthetase I to total synthetase activity was not affected. The administration of hydrocortisone had no effect on either the phosphorylase or synthetase of mouse brain. A mathematical model was devised to determine the rate constants for incorporation of labelled glucose into brain glycogen and the subsequent loss of radioactivity. Metabolite levels and enzyme activities have been correlated with the observed changes in glycogen turnover.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The effects of maximal electroshock (MES) and phenytoin on metabolites and cyclic nucleotides in layers of frozen-dried cerebellum have been investigated. The four layers (molecular, Purkinje-cell rich, granular and white matter) had remarkably homogeneous distributions of P-creatine, ATP, glucose, glycogen, lactate, GABA and the cyclic nucleotides. MES caused dramatic decreases in P-creatine, ATP, and glucose at 10 s after treatment, followed by a decrease in glycogen at 30 s. Lactate levels were elevated, and GABA was unchanged. Cyclic AMP concentrations were increased at 10s and cyclic GMP at 30 s. Phenytoin modified most of the MES induced changes in all the layers, although white matter was less affected by MES and/or phenytoin. Lactate concentrations were increased by MES and these effects were not altered when phenytoin was administered. The most dramatic effects of phenytoin were on the changes in cyclic nucleotides. Cyclic AMP concentrations were elevated after MES but the values returned to normal more rapidly when phenytoin was present. The drug almost obliterated the MES induced changes in cyclic GMP. The possible relationship of cyclic nucleotide concentrations and the modulation of seizure activity is discussed.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Levels of glucose, lactate, GABA and cyclic nucleotides were examined in discrete layers of the cerebellum and cerebral cortex of mice following treatment with the anticonvulsant, sodium valproate, and/or the convulsant, isoniazid. The concentrations of the metabolites were essentially uniform among the layers of each region, whether from control or from drug-treated mice. Metabolite concentrations in the isoniazid-treated mice were determined either 30 min after administration (preconvulsive state), or immediatley after the onset of seizures. Glucose and lactate, two markers of energy status in the brain, were only minimally affected by drug treatment. However, the levels of GABA and cyclic nucleotides were markedly different from control values in the drug-treated animals. In the preconvulsive state, GABA levels in cerebellar layers were depressed and the cyclic nucleotides were elevated in most layers of both regions. At the onset of seizures, the reduction of GABA and the elevation of cyclic AMP in both regions was more pronounced than during the preconvulsive state. While the concentration of cyclic GMP remained elevated in the cerebellar layers at the onset of seizures, the level in the cerebral cortex returned to control values. Valproate elevated GABA in all the layers of both regions and decreased the cyclic GMP in the cerebellar layers. Generally, when valproate was administered in combination with isoniazid, it dampened the isoniazid induced changes in the metabolites. The events leading up to a seizure as well as those that sustain it may be reflected by the disparate responses of the metabolites in the cerebellum and cerebral cortex.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 26 (1976), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: -Eight metabolites were measured in the post-ischemic period following either 1 or 3 h of unilateral ischemia in the gerbil cerebral cortex. The levels of ATP, P-creatine, glucose, glycogen and GABA were essentially restored by 1 h after ischemia. In the 3 h ischemic animals. glycogen continued to increase to greater than control values aftcr 5 and 20 h of recirculation. The Icvels of glutamate were unchanged during the ischemic episode, but decreased to 60% of control at Smin and 1 h after either period of ischemia. The concentrations of cyclic AMP, which were 4-to 5-fold elevated during ischemia. increased an additional 6-fold 5 min after recirculation in both groups. Arter 1 h of recovery. the levels were not different from control values. After the 1 h ischemic period, lactate levels recovered between 5 and 20 h of recirculation. In the 3 h ischemic animals. lactate concentrations were still elevated even after 20 h of recirculation. These data suggest that with the exception of lactate. recovery of metabolites is not sevcrely compromiscd by either 1 or 3 h of ischemia. Furthermore, the changes in glycogen. glutamate and cyclic AMP after recirculation suggest that the recovery process is not just a rcversal of the changes observed during ischemia.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract—The accumulation of adenosine-3′,5′-cyclic monophosphate (cyclic AMP) has been investigated in murine brain following electroconvulsive shock and decapitation. Animals were made hypothermic (20°C) to minimize the freezing time of the brain and to delay metabolic events. Cyclic AMP concentrations were decreased in the cerebral cortex of hypothermic rats and mice. Furthermore, the changes in cyclic AMP elicited by electroconvulsive shock and decapitation were delayed. In hypothermic animals, the metabolic rate as determined by high energy phosphate use was decreased to 65% of control values. The interconversions of the active and inactive forms of glycogen phosphorylase and glycogen synthase were sufficiently retarded in hypothermic animals to correlate with changes in cyclic AMP concentrations. The conversion of phosphorylase b to a and synthase a to b occurred when cyclic AMP concentrations had increased from 2 to 5 μmol/kg, following either electroconvulsive shock or decapitation. The results indicate that cyclic AMP plays a role in regulation of glycogen metabolism in cerebral cortex.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: –Adenosine 3′,5′-cyclic monophosphate (cyclic AMP) levels increase about 5-fold in the cerebral cortex and 2-fold in the cerebellum following electroconvulsive shock (ECS). The peak levels of cyclic AMP occur at 45 s after ECS in the cerebral cortex, and at 15 s in the cerebellum. In the cerebral cortex, ECS produces twice the cyclic AMP accumulation as does decapitation in a comparable time period; however, the relative effect of a number of neurotropic agents on the cyclic AMP accumulation is essentially the same, whether stimulated by decapitation or by ECS. In the cerebellum, the levels of guanosine 3′,5′-cyclic monophosphate (cyclic GMP) also increase following ECS. The cyclic GMP levels are greatest at 60 s after ECS during the postictal depression. An association between elevated cerebellar cyclic GMP and depression seems unlikely, since CNS depressants either lowered or had no effect on cyclic GMP levels. From these results, cyclic nucleotide profiles following treatments such as ECS or decapitation may be useful in elucidating the molecular events involved in seizures, brain injury and ischemia.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 32 (1976), S. 732-734 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Cortical glycogen levels decreased after both 1 and 3 h of unilateral ischemia. After 1 h of recirculation, the levels of glycogen were restored to control values in both groups. Subsequently, glycogen increased above normal levels after 1 week of recirculation in the 1 h ischemic groups, and after 5 h in the 3 h ischemic group. Thus, the onset of the excess glycogen accumulation appears to be dependent on the intensity of the ischemic insult.
    Type of Medium: Electronic Resource
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