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191.
Improved histological localization of GABA-transaminase activity in rat cerebellar cortex after aldehyde fixation 总被引:1,自引:0,他引:1
Summary A method for the chemical fixation of the enzyme GABA-transaminase in nervous tissue is described. It is shown that after
perfusion with a formaldehyde/glutaraldehyde fixative, activity of the enzyme in cerebellar cortex is demonstrable whilst
cellular morphology is preserved. Results from the improved technique have shown new sites of GABA-transaminase activity in
cerebellar cortex. In view of these results a special function for glial cells in this area of brain has been suggested. 相似文献
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—Purified myelin incorporated l -[14C]leucine and l -[14C]lysine into myelin proteins in an enzymatic process similar to that of renal brush border membranes. The system was not inhibited by cycloheximide or puromycin or by pretreatment with ribonuclease; the reaction was inhibited by cetophenicol. ATP was an effector, shifting the optimal pH from 7.2 to 8.3. In the presence of ATP, myelin was less dense in a sucrose gradient. Ammonia was released from the membrane during the incorporation of amino acids. Myelin preloaded with cold leucine did not incorporate [14C]leucine but did incorporate [14C]lysine; there was no cross inhibition between the two amino acids. The incorporation was into or onto proteins of the Wolfgram proteolipid fraction of myelin. The incorporation was of the high affinity type with a Km of 10?7m and was restricted to the natural amino acids. 相似文献
194.
—Rat pineal serotonin N—acetyltransferase activity increases 30–70-fold at night in the dark and then decreases rapidly when animals are exposed to light. Activity of the enzyme is also stimulated by l -norepinephrine in organ culture. When homogenates of glands stimulated by dark in vivo or NE in vitro are incubated at 37°C, enzyme activity will also rapidly decrease. This decrease can be prevented by one of the cosubstrates of the enzyme, acetyl–CoA. Protection can also be conferred by cysteamine (β-mercaptoethylamine, HS–CH2–CH2–NH2) which is the terminal portion of the CoA molecule. This protection mechanism could be involved in the physiological control of enzyme activity. 相似文献
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