摘要:

Abstract:The terminal phosphate group of ATP was transferred to ADP by an enzyme present in the soluble core proteins of adrenal medulla catecholamine storage vesicles. It was purified 10–30‐fold by DEAE Sephadex chromatography (Fraction I). The enzyme required divalent metal ions for activation; Mn2+was almost as effective as Mg2+, but Ca2+was only a weak activator. Activation by Mg2+took place over a very narrow concentration range (0.5–3 mm). The specificity of the enzyme activity to nucleoside triphosphates was broad, to the nucleoside diphosphates narrow, favouring adenosine diphosphate. In dependence on the pH the activity increased from pH 4 to pH 7 and remained constantly high between pH 7 and 9. The Arrhenius plot was linear between 5 and 70°C, with an activation energy of 11.1 kcal/mol. The phosphoryl group transfer reaction depended on the function of thiol groups;p‐hydroxymercuribenzoate inhibited 50% of the enzyme activity; dithioerythritol reactivated it completely. Gel electrophoresis revealed that in Fraction I, a protein of molecular weight about 45,000, was enriched compared with the total soluble proteins. The enzyme‐enriched Fraction I differed significantly in its relative amino acid composition from that of the total soluble proteins; in general, the acidic amino acids were reduced and the more basic acid

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb10811.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:The nuclear mitochondrial and synaptosomal fractions of rat brain were each found to contain some 25–30% of the total aldehyde dehydrogenase activity. The cytoplasmic fraction had a very low total aldehyde dehydrogenase activity. There were differences in the distribution of the activity when different aldehydes were used as substrates, suggesting the presence of isoenzymes in the various subcellular compartments. When rats were treated intra‐cisternally with 6‐hydroxydopamine there was no change in brain aldehyde dehydrogenase activity, although the noradrenaline content and the activities of tyrosine hydroxylase and dopamine‐β‐hydroxylase were markedly decreased. Treatment with 6‐hydroxydopamine also had no significant effect on the aldehyde dehydrogenase activity in retinal homogenates. The results suggest that the aldehyde dehydrogenase activity in rat brain is predominantly outside the catecholaminergic ner

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb10812.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:The dopamine (DA)‐containing nerve terminals in the caudate nucleus arise from cell bodies located in the substantia nigra (pars compacta), and it is possible thatp‐tyramine‐ andm‐tyramine‐containing neurons may also exist in this nucleus. We have studied the effects of unilateral electrolytic lesions of the pars compacta in rat on levels of DA,p‐tyramine,m‐tyramine, and homovanillic acid in the caudate nucleus after various survival times. At 12 and 24 h following lesioning the ipsilateral level ofp‐tyramine was significantly reduced compared with the contralateral side, whereas the concentrations ofm‐tyramine, DA, and homovanillic acid were significantly increased. Thus, in the short term, the lesion results in an increase in DA turnover, which is accompanied by an increase inm‐tyramine levels and a decrease inp‐tyramine levels. Similar changes occur following pharmacological treatments (chlorpromazine,d‐amphetamine,l‐DOPA) that increase DA turnover. At survival times of 2, 11, and 25 days, the ipsilateral concentrations ofm‐tyramine, DA, and homovanillic acid were reduced along withp‐tyramine. These longer‐term alterations in amine levels are most likely a consequence of degeneration of nigro‐striatal axons. Placement of a lesion 1 mm dorsal to the usual position centering on the pars compacta produced different biochemical changes from those seen after the pars compacta lesion. One day following this lesion the concentration ofp‐tyramine was slightly reduced; DA was unaffected, but the concentration ofm‐tyramine was profoundly increased, even more so than after the pars compacta lesion. This could indicate the existence of specificm‐tyramine‐containing cell bodies located dorsal to the substantia nigra. The results suggest thatp‐ andm‐tyramine in the caudate nucleus originate from neurons in or close to the substantia nigra. The results in the short term following the lesion support the observation that there is an inverse relationship betweenp‐tyramine conce

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb10813.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:Fractions of neurospecific S‐100 protein were purified from bovine brain and their physicochemical properties were studied. Conformational changes caused by the binding of calcium to S‐100 protein fractions were detected by means of differential and fluorescence spectroscopy. Fractions demonstrating opposite shifts of their spectra also differ in the distribution in double‐phase system. The number of calcium‐binding centers and their association constants were determined by means of equilibrium dialysis and gel filtration. The nature of the differences in the interaction of various S‐100 protein fractions with calcium is

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb10814.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:Phosphate‐activated glutaminase (EC 3.5.1.2) in synaptosomal preparations is inhibited 40–60% by the sulphydryl group reagentN‐ethylmaleimide (NEM), forming the basis for distinction between NEM‐sensitive and NEM‐insensitive glutaminases. The NEM effect cannot be explained by differential effects on distinct glutaminases because other glutaminases have not been detected, and the synaptosomal glutaminase activity can be fully accounted for by the activity of phosphate‐activated glutaminase. By fractionation of mitochondria isolated from synaptosomal preparations, which are preincubated with and without NEM, both NEM‐sensitive and NEM‐insensitive glutaminases are found to be localized to the inner mitochondrial membrane. Variations in pH (7.0–7.6) and the phosphate concentration (5–10 mM) affect chiefly NEM‐sensitive glutaminase, demonstrating that this glutaminase may be subject to regulation by compounds in the cytosol having restricted permeability to the inner mitochondrial membrane. Sincep‐hydroxymercuribenzoate, which is known to be impermeable to the inner mitochondrial membrane, inhibits glutaminase similarly to NEM, phosphate‐activated glutaminase is assumed to be compartmentalized within the inner mitochondrial membrane. Thus, NEM‐sensitive glutaminase is localized to the outer face and NEM‐insensitive glutaminase to the inner region of this membrane and proba

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb10815.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:Glycoproteins from central nervous system myelin were evaluated for developmental alterations in their carbohydrate composition by autoradiographic analysis of radioiodinated lectin binding after separation by high‐resolution sodium dodecyl sulfate‐pore gradient slab gel electrophoresis (SDS‐PGE). Sixteen lectin‐binding components were assessed in highly purified myelin preparations from 15‐day, 18‐day, and adult rat brains, using the lectinsTriticum vulgaris(wheat germ agglutinin) andUlex europeus(gorse agglutinin I). Developmental changes in lectin binding for individual glycoproteins were evaluated semiquantitatively by comparing densitometric scans of the auto radiographs. Both increases and decreases in lectin binding for individual components were observed as a consequence of development, as well as the appearance and disappearance of lectin binding to three low‐molecular‐weight components. No changes in electrophoretic mobility and hence glycoprotein molecular weight were observed in any components when using these lectins. These developmental changes in lectin binding suggest that increases in glycoprotein (receptor) density occur, as well as an elaboration of oligosaccharide branching for individual glycoproteins. In addition, the appearance of a new glycoprotein in the adult myelin membrane could imply a new functional role not present in the immature membrane. These observations suggest that dynamic alterations of myelin‐associated glycoproteins occur during development. Such developmental regulation of membrane glycoproteins increases the significance of their potential role in myelination and m

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb10816.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:Changes in the activity of pyruvate dehydrogenase [pyruvate: lipoamide oxidoreductase (decarboxylating and acceptor‐acetylating), EC 1.2.4.1, PDH], elicited by inhibition of the phosphorylation of its 40,000 Mrα‐subunit, were compared with changes in pyruvate‐supported calcium accumulation by rat brain mitochondria. Dichloroacetate (DCA) produces concentration‐dependent inhibition of the phosphorylation of intramitochondrial PDH a‐subunit, which is accompanied by stimulation of PDH activity and calcium accumulation. DCA did not affect succinate‐ or ATP‐supported mitochondrial calcium accumulation. The concentration of DCA giving half‐maximal inhibition of the phosphorylation was almost identical to that giving half‐maximal stimulation of PDH activity and calcium accumulation. PDH activity and pyruvate‐supported calcium accumulation showed similar dependence on pyruvate concentration with respective apparent affinities for pyruvate of 40μmand 30μm, and both activities exhibited positive cooperativity. DCA modified only the maximal activity of PDH or the maximal calcium accumulation without changing either the apparent affinities for pyruvate or calcium or the Hill coefficients. These data provide evidence that calcium accumulation by mitochondria is tightly linked to PDH activity and that changes in the phosphorylation of the PDH α‐subunit can be reflected in changes in the calcium‐buffering ability of mitochondria. This suggests a possible mechanism by which a variety of manipulations, such as repetitive synaptic stimulation, can alter the regulation

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb10817.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:This study examined whether the effect of intravenous infusions of either epinephrine or norepinephrine on cerebral metabolic rate for oxygen (CMRo2) in the dog was modified by different anesthetics. Infusions of either epinephrine or norepinephrine at rates of 0.1‐0.25 μ kg−1min−1reversibly increased the CMRo2by 17–23% during anesthesia with cyclopropane 20% and nitrous oxide 50% in oxygen, whereas infusions at rates of 0.1‐25.0 μg‐kg−1‐min−1had no effect in dogs anesthetized with other inhalational or intravenous agents. Cyclopropane/nitrous oxide also increased permeability of the blood‐brain barrier to Evan's blue dye whereas the other anesthetics tested did not. It is concluded that epinephrine and norepinephrine crossed the blood‐brain barrier during cyclopropane anesthesia, accounting for the increase in CMRo2. The authors speculate that cyclopropane may have increased blood‐brain barrier permeability by a direct effect on endothelial cells or by affecting central adrenergic systems and that epinephrine or norepinephrine may increase CMRo2either by a direct action on neuronal receptors or via metabolicall

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb10818.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:The administration of LiCl (3.6 mequiv./kg/day) to adult male rats for 9 days results in an increase in the cerebral cortex level ofmyo‐inositol‐1‐phosphate (M1P) to 4.43 ± 0.52 mmol/kg (dry weight) compared with a control level of 0.24 ± 0.02 mmol/kg. This establishes that the previously observed acute effect of lithium on M1P (Allison et al., 1976) is both prolonged and augmented by repeated doses of lithium. Larger doses of LiCl over a 3–5 day period result in even larger increases in M1P and a 35% decrease in myoinositol. In each case, 90% of the increase is due to thed‐enantiomer, evidence that lithium is largely producing this effect via phospholipase C‐mediated phosphoinositide metabolism. Data are presented showing that lithium is an uncompetitive inhibitor of the hydrolysis of bothd‐ andl

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb10819.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:Regional CNS levels of glucose reserves, glycolytic intermediates, and high‐energy phosphate reserves were measured in insulin‐treated, hypoglycemic rats and correlated with EEG activity. Intravenous administration of insulin to paralyzed, ventilated animals causes concomitant reduction of blood glucose levels and progressive abnormality and eventual loss of EEG activity. In all regions of brain examined, glucose and glycogen levels decrease until they are essentially depleted, and glucose‐6‐phosphate and fructose‐1,6‐biphosphate fall approximately 80%. Pyruvate levels decrease 50% in cerebral cortex and brain stem and a lesser amount in striatum, hippocampus, thalamus, and cerebellum. Lactate levels fall 50–60% in all regions except cerebellum, where no change is observed. ATP and phosphocreatine levels remain normal until the EEG is isoelectric, and then decrease in all regions except cerebellum. These results demonstrate that hypoglycemia does not have a uniform effect on brain glucose and energy metabolism, and cerebellum seems to be relativ

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb10820.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY