摘要:

Abstract:The accumulation of the polyamine spermine into 0.1‐mm prisms of rat cerebral cortex has been investigated at both 37°C and at 4°C. Kinetic analysis of the temperature‐sensitive portion of uptake indicates two high‐aftinity saturable components together with an unsaturable component at high concentrations. The ‘very high’– affinity saturable system (Km= 3.8 nM) was temperature‐ and sodium‐dependent, and significantly reduced by metabolic inhibitors, findings that are consistent with an active transport system for spermine into brain tissue. The ‘high’– affinity saturable component (Km= 0.44 μM) was sodium‐dependent and inhibited by ouabain, but only partially susceptible to inhibition by 2,4‐dinitrophenol and sodium cyanide. The significance of these results with respect to the function of spermine in the central

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb00409.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:The effect of ascorbic acid and noradrenaline on the inhibition of synaptosomal membrane ATPase by vanadate has been studied. Ascorbic acid (2 × 10‐3M) and noradrenaline (10‐4M) partly reversed the inhibition by vanadate (10‐6M); however, when both were administered together the inhibition was completely eliminated. Using electron spin resonance (ESR) spectroscopy, we detected that ascorbic acid (10‐3M) caused a 42% of reduction of vanadate (10‐4M). Noradrenaline (10‐4M) alone also reduced vanadate (10‐4M) partially. When ascorbic acid and noradrenaline were present together all the vanadate was reduced to vanadyl. The concentration of ascorbic acid present in the brain under physiological conditions is identical to that found effective in our experiments. We suggest that ascorbic acid may protect the ATPase, at least in part, from inhibition by vanadate as a consequence of reducing vanadate to vanadyl. In those tissues where noradrenaline is also present a complete reduction of endogenous vanadium c

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb00410.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:5‐Hydroxytryptamine (5‐HT) in mouse brain and spinal cord was assayed in the same samples using a fluorimetric assay and a high pressure liquid chromatographic (HPLC) assay with electrochemical detection. The HPLC assay was able to detect levels of 5‐hydroxytryptamine as low as 0.2‐0.5 pmol. With the column (Vydac cation exchange), solvent system (acetate/citrate buffer, 0.1 or 0.2 M, pH 4.8‐5.2) extraction procedure and electrode potential (+0.55 V) used, the HPLC assay was specific for 5‐HT. When the electrode potential was increased to +0.9 V tryptamine could also be detected, with a longer retention time than 5‐hydroxytryptamine. The percentage increase in mouse brain 5‐hydroxytryptamine after pargyline (75 mg/kg) and pargyline +l‐tryptophan (100 mg/kg) was very similar whether measured by fluorimetry or HPLC, although the fluorimetric assay gave consistently higher absolute values (24–32%) in both control and drug‐treated animals.l‐Tryptophan (25, 50 and 100 mg/kg) also increased brain 5‐hydroxytryptamine with similar percentage increases with either assay method. There was a significant correlation (P<0.001) between the values obtained with the two assay methods. The results confirm the use of HPLC with electrochemical detection as a sensitive and specific assay method for 5‐hydroxytryptamine and indicate its potential use for the assay of tryptamine, and the importance of determining the electroactivity and retention charac

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb00411.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:The cerebellar levels of Protein I, a synapse‐specific neuronal phosphoprotein, have been investigated in the cerebellar mouse mutants staggerer (sg), weaver (wv), nervous (nr), and Purkinje cell degeneration (pcd). The Protein I concentration was reduced by about 66% insgandwvmutants, representing a 90% loss of Protein I per cerebellum. A heterozygote effect was observed in thewvmutant. These results indicate that a great majority of Protein I in the normal cerebellum may be present in the granule cells. innrmutants the cerebellar Protein I concentration was reduced by only 12% in 62‐day‐old mice, suggesting that Purkinje cells contribute little to cerebellar Protein I. However, a greater reduction was observed inpcdmutants, which may reflect on the nature of thepcdmut

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb00412.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:The addition of carbachol to superior cervical ganglia causes a rapid increase in tyrosine hydroxylationin situ.The increase occurs in ganglia from both newborn and adult animals, and in ganglia from animals pretreated with reserpine. The increase is not due to increased transport of the substrate. The increase is dependent upon the presence of calcium, and is additive to the stimulation produced by dibutyryl cyclic AMP. The stimulation seems specific for tyrosine hydroxylation; dopamine β‐hydroxylation is not increased. Preincubation experiments suggest that the carbachol‐induced stimulation is due to a change in the availability of, or the affinity of the enzyme for, reduced pterin cofactor. The stimulation is inhibited by atropine and also by low concentrations of phenoxybenzamine or haloperidol, which suggests that it is caused by an action of carbachol on the interneurons in the gan

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb00413.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:We have investigated the effects of 3,4‐dihydroxyphenylalaninel‐DOPA) and its deuterated analogue on the concentrations of alcoholic metabolites of catecholamines in rat brain by means of gas chromatography/mass spectrometry with selected‐ion monitoring. Whole brain concentrations of the two neutral norepinephrine metabolites, 3‐methoxy‐4‐hydroxyphenylethylene‐glycol (MHPG) and 3,4‐dihydroxyphenylethyleneglycol (DHPG), were significantly increased in a dose‐dependent manner by a single intraperitoneal injection ofl‐DOPA. Both MHPG and DHPG, as well as the corresponding dopamine metabolites, reached a maximum 1 h after injection. Brain MHPG and DHPG concentrations were elevated by 78 and 134%, respectively, 1 h after injection of 150 mg/kgl‐DOPA. Analyses of discrete brain regions revealed that concentrations of the norepinephrine metabolites were elevated uniformly in all regions, except that MHPG showed a greater increase in the cerebellum than in other regions. The latter result appeared to be explained by the finding that 52% of the total MHPG in the cerebellum was unconjugated (compared to 15% in the whole brain).l‐DOPA caused a proportionately greater increase in free MHPG than in total MHPG in the cerebellum and brain stem. By using deuteratedl‐DOPA in place ofl‐DOPA and measuring both the deuterated and nondeuterated norepinephrine metabolites, we demonstrated that virtually all of the increases in MHPG and DHPG were due to the conversion of the exogenousl‐DOPA to norepinephrine. Thus, the effects of norepinephrine metabolism need to be considered in attempts to understand clinical an

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb00414.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:The posterior stomach nerve (PSN) is a crustacean sensory nerve containing about 60 cholinergic neurons, which are devoid of synaptic interactions. Kinetic analysis shows that the PSN takes up [3H]choline by both low‐affinity (Km= 163 μM) and high‐affinity (Na+‐dependent) (Km= 1 μM) processes. The capacity of the high‐affinity system is only about 1% that of the low‐affinity system. The high‐affinity system is not tightly coupled to acetylcholine (ACh) synthesis, and it appears that both ACh and phosphorylcholine are formed from an intracellular pool of choline, which is fed by both uptake systems. There are differences in the rates of [3H]choline uptake and3H metabolite accumulation between regions of the PSN that contain neuronal cell bodies and those that do not. These differences may arise from differences in the relative proportion of neuronal to nonneuronal tissue in each

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb00415.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:We have studied the posttranslational processing of actin molecules synthesized in a cell‐free system. The results of these experiments indicate that during thein vivosynthesis of the actins from rat brain the primary translational products undergo two different and sequential posttranslational modifications. These modifications are accompanied by slight changes in the isoelectric points of the proteins and can be detected by isoelectric focusing analysis. The same posttranslational modifications can be detected during thein vitrosynthesis of chick embryo skeletal muscle actin. The evidence presented suggest that the first posttranslational modification may correspond to the methylation of a histidine residue, and the second modification most likely corresponds to the acetylation of the NH2‐terminal amino acid residues of actin molecu

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb00416.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:In order to study the influence of hypoxia on cyclic nucleotides in the brain, we reduced arterial Po, for 15–30 min in lightly anaesthetised and artificially ventilated rats to obtain values ranging from about 45 to about 10 mm Hg. In an additional group (arterial Po218–22 mm Hg), the tissue hypoxia was aggravated by moderate arterial hypotension (mean arterial blood pressure about 80 mm Hg). In all animals, electrocortical activity was recorded. Cyclic GMP concentrations in cerebral cortex were unchanged in all groups but one. In that group, in which tissue hypoxia was severe enough to induce a suppression‐burst EEG pattern and a measurable reduction in the adenylate energy charge, cyclic GMP concentrations were slightly increased (p<0.05). Cyclic AMP concentrations remained unaltered at all degrees of hypoxia studied. It is concluded that changes in cyclic nucleotides in brain tissue occur first at such severe degrees of hypoxia of the duration studied that function and metabolism are profoundly al

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb00417.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:The subcellular distribution in rat brain cortex of six synaptic membrane antigens (56K, 58K, 62K, 63K, 64K, 66K) was studied by rocket immunoelectrophoresis, using antiserum to a highly purified synaptic plasma membrane fraction. Initial analysis of the insoluble portion of subcellular fractions showed that these antigens were also present in smooth microsomes, rough microsomes, and synaptic vesicles; that only traces were present in synaptic junctions; and that none was present in nuclei, mitochondria, and myelin. A trace amount of activity was also present in synaptic vesicle cytosol, but none in whole brain cytosol. Quantitative measurements of synaptic plasma membranes, smooth microsomes, and synaptic vesicles showed that all six antigens were present in synaptic plasma membranes and smooth microsomes, but that the 66K antigen was absent from synaptic vesicles. The 56K, 58K, 62K, 63K, and 64K antigens were present in highest concentration in synaptic plasma membranes, whereas the 66K antigen content was highest in smooth microsomes. Only the 58K, 62K, and 63K antigens were detectable in the membrane fraction of whole brain. Their enrichments in synaptic plasma membranes were 10.9, 5.4, and 5.9, respectively. We conclude that the 56K, 58K, 62K, 63K and 64K antigens are primary components of synaptic plasma membranes. The presence of synaptic plasma membrane antigens in smooth microsomes and synaptic vesicles probably represents material being actively transported, consistent with the hypothesis that proteins of synaptic plasma membranes and synaptic vesicles are transported via smooth endoplasmic reticulum.

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb00418.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY