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Excessive tissue lactic acidosis is considered to be detrimental to the central nervous system (CNS) and may adversely affect recovery from anoxia, ischemia, trauma and epilepsy. Since astrocytes are believed to play a role in pH regulation in the CNS, we studied the effect of this acid on primary astrocyte cultures. Cells exposed to lactic acid showed(More)
The effect of ATP and other purines on 45Ca uptake was studied in primary cultures of rat astrocytes. Treatment of the cells with ATP for 1 to 30 min brought about an increase in cellular 45Ca. Stimulation of calcium influx by ATP was investigated using a 90 sec exposure to 45Ca and over a concentration range of 0.1 nM to 3 mM; a biphasic dose-response(More)
The effect of ammonia on water space of astrocytes in culture was determined as a means of studying the neurotoxicity of ammonia in fulminant hepatic failure (FHF). Treatment of primary astrocyte cultures obtained from neonatal rat cortices with 10 mM NH4Cl for 4 days resulted in a 29% increase in astrocytic water space, as measured by an isotopic method(More)
To evaluate the astrocytic alterations commonly seen in hepatic encephalopathy and other hyperammonemic states, primary astrocyte cultures derived from neonatal rats were exposed to varying concentrations of ammonia for one to ten days. Ammonia-treated cultures initially showed an increase in basophilia, prominent cytoplasmic processes and increased(More)
Peripheral-type benzodiazepine (BZD) receptors were studied in cultured astrocytes derived from genetically epilepsy-prone and control rats. Scatchard analysis of the binding of [3H]Ro 5-4864 to astrocyte homogenates from epilepsy-prone rats showed 38% fewer BZD receptors (Bmax) as compared to controls. No significant change in affinity (Kd) was observed.(More)
We have carried out studies on the effect of ammonium chloride on the astrocyte benzodiazepine receptor. Scatchard analysis of the binding of [3H]Ro-5-4864 to homogenates prepared from primary astrocyte cultures showed a significant decrease in Kd (27% with 2 mM NH4Cl; 32% with 5 mM NH4Cl; 25% with 10 mM NH4Cl) and Bmax (14% with 10 mM NH4Cl). These(More)
Extracellular adenosine 5'-triphosphate (ATP)-evoked increases in intracellular calcium and the consequent stimulation of calcium-mediated protein phosphorylation systems were investigated in primary cultures of rat cerebral cortical astrocytes. Measurement of calcium responses in fura-2-loaded astrocytes indicated that extracellular ATP stimulated a(More)
The effect of the anticonvulsants diazepam, phenytoin, and valproic acid on calcium, calmodulin-dependent protein phosphorylation in astrocytes was investigated. We found that diazepam inhibited calcium, calmodulin-stimulated phosphorylation in both supernatant and membrane fractions from primary cultures of rat astrocytes, whereas phenytoin and valproic(More)
The distribution of calcium-activated, phospholipid-dependent protein kinase (protein kinase C) in supernatant and particulate fractions of primary cultures of rat astrocytes and its translocation by a phorbol ester were studied. We observed that 91% of protein kinase C activity in astrocytes was in the supernatant fraction, as measured by lysine-rich(More)
Treatment of primary astrocyte cultures with ammonium chloride for one day prior to phosphoprotein labeling resulted in a reduction in phosphate incorporation in a 66-kDa protein. Increasing ammonium chloride concentrations (2, 5, and 10 mM) led to greater reductions in phosphate incorporation in this band. The specificity of the effect was indicated by the(More)