ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1978.tb07028.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1978.tb07029.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Abstract—Intravenous injection of a sonicated dispersion of bovine brain phospholipids results in a significant change in both NaF‐dependent and dopamine dependent adenylate cyclase activity. High dosage of phospholipids inhibits the dopamine dependent, but not the NaF dependent, adenylate cyclase activity. The stimulation of cyclase activity is accompanied by an increased level of cAMP in mice brains. Treatment with haloperidol abolishes the increase in cAMP. Among individual phospholipids, phosphatidylserine is the most active component for inducing the activation of DA‐dependent adenylate cyclase act

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1978.tb07030.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Abstract—The kinetics of washout of radioactive calcium (45Ca) from nerves of the larger legs ofLibinia emarginataequilibrated in various solutions of artificial sea water (ASW) containing 1, 11, 22 or 44 mM‐Ca was followed. In every case two components were found when the period of washout was not more than 30 min. The washout of14C labelled inulin and sucrose gave one and two components respectively; these substances were considered to exist in the extracellular regions of nerve fibers. Comparison of the total calcium of the nerves determined spectrophotometrically and by measurement of radioactivity indicated that the exchangeability of calcium in the nerves in ASW containing 44 and 22 mM‐Ca was 100%. In the case of nerves equilibrated in 11 mM‐CaASW, two groups of nerves, one (group A) containing a high concentration of Ca (13.6μmol/g) and the other (group B) containing a low concentration (7.3μmol/g), were detected Several factors which could account for the accumulation of Ca in nerve fibers in group A were considered. The electrolyte data relating to group A nerve fibers indicated that Ca accumulation may be due to the presence of a high concentration of sodium in those fibers. However, the exchangeability of Ca for group A was about 47%; and in group B fibers, it was 61%. The exchangeability was less than 41% in the case of nerves equilibrated in 1 mM‐CaASW. The kinetic parameters of45Ca washout from the nerve fibers have been used to develop a model for the distribution of calcium among the different compartments of the n

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1978.tb07031.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Abstract—Choline acetyltransferase from bovine brain caudate nucleus has been purified to a specific activity of 25–30μmol ACh formed per min and mg protein. Disc electrophoresis at pH 9.5 of the purified enzyme showed two protein bands localized close to each other. We were not able to show if ChAT was linked to one or both bands. In SDS disc electrophoresis the enzyme preparation showed one major and one minor protein band with molecular weights of 69,000 and 34,000, respectively. Heterogeneity of the enzyme preparation was also demonstrated by immunodiffusion and immunoelectrophoresis. After ammonium sulphate precipitation no aggregation of the enzyme could be detected by gelfiltration on Ultrogel AC‐34 whilst a high molecular weight fraction was occasionally observed by gelfiltration on Sephadex G‐200. The enzyme was, however, separated into two molecular forms (A and B) on CM‐Sephadex chromatography. Both molecular forms had the same S220wbut differed in heat stability and affinity for acetyl‐CoA. Both forms were inactivated by an antibody preparation raised against either a purified preparation of ChAT, or A and B separately. The highly purified enzyme preparation was inactivated more than 98% by immunoprecipitation. The antibody crossreacted with ChATs from several mammalian species, but only slightly with ChAT from pigeon. The results of binding studies with affinity columns, suggest that the enzyme contains a hydrophobic lobe and a dinucleotide fold, and that a free purine rather than a free ribosyl ring of acetyl‐CoA is important for the binding of the substrate to the active site. The hydrophobic lobe may be the same as the din

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1978.tb07032.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Abstract—The accumulation of labelledd‐aspartate into crude synaptosomal fraction (P2) prepared from the rat cerebral cortex proceeded by a ‘high affinity’ system (Km= 15.1μmThe maximal velocity ofd‐aspartate uptake was higher than that of the ‘high affinity’ component ofl‐aspartate uptake and almost equal to that ofl‐glutamate under the same incubation conditions. Negligible metabolism of labelledd‐aspartate was observed in the P2fraction. These findings are in accord with those which have been reported for rat cerebral cortical slices. The following observations were made ond‐aspartate uptake into rat cerebral P2fraction. (1) The requirement of sodium is almost absolute and obligatory. (2) The affinity of the carrier for the substrate is increased by increasing sodium concentration in the medium, but the maximal velocity is not altered. (3) It is suggested that sodium ion is co‐transported mole for mole with the substrate molecule. (4) Omission of potassium from the medium inhibits the uptake competitively. (5) Ouabain is a competitive inhibitor on the uptake. (6) Whereas thallium, rubidium and ammonium are efficient substitutes for potassium in exhibiting Na–K ATPase activity of the P2fraction, the uptake is activated only by rubidium in the absence of potassium. These observations were in common with the uptake ofl‐aspartate as well as ofl‐ andd‐glutamate, but not with GABA uptake. The requirement of sodium for the uptake ofd‐glutamate was indicated to be higher than that in the uptake of the other amino acids. Mutual inhibitions of the uptake amongl‐ andd‐isomers of glutamate and aspartate suggested that a common carrier is involved in the transport. Mechanisms of the transport of these amino acids in the crud

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1978.tb07033.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Abstract—Chicken sciatic nerves undergo demyelination following intraneural injection of diphtheria toxin due to a lesion at the site of injection. Paresis occurs after 1 week and lasts for approx 3 weeks; at the height of the lesion we injected [14C]Ieucine into the ventral horn cells of the spinal cord and followed the axonal transport of fast flowing labelled proteins down the sciatic nerve fibres making measurements of flow rates at two different times. The results showed the fast flowing labelled proteins were blocked at the demyelination site. We measured total protein in the nerves and examined them histologically to confirm the lesion. Further studies are in progress on the post synaptic muscle cells and the impaired nerve

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1978.tb07034.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Abstract—Cerebral blood flow (CBF) and the cerebral metabolic rates for oxygen, glucose, acetoacetate, β‐hydroxybutyrate and lactate were measured in 1‐ to 5‐day old Beagle dogs under nitrous oxide anesthesia. CBF was determined by133Xe washout with mechanically integrated blood samples withdrawn simultaneously from a femoral artery and from the posterior one‐third of the superior sagittal sinus. CBF and CMRO2in normocapnia (PaCO240 × 1 mm Hg) were 48 × 5 ml/100 g/min and 2.15 ml/100 g/min, respectively. There was a positive, linear relationship between CBF and PaCO2, calculated for PaCO2values ranging from 26 to 70 mm Hg. Induced hypocapnia (PaCO231 × 1 mm Hg) or hypercapnia (PaCO258 × 2 mm Hg) did not alter the CMRO2. Glucose and acetoacetate were taken up by the brain at all PaCO2levels examined; however, the cerebral uptake of glucose always exceeded the combined uptake of ketone bodies by more than a factor of ten. The cerebral metabolic rate for glucose (94.6 × 3.6μmol/100 g/min) more than accounted for overall cerebral oxygen consumption, and yielded an oxygen:glucose ratio (mol:mol) of 5.1. Thus, as in adult animals, PaCO2is an important regulator of cerebral blood flow in puppies, and glucose is the major substrate for oxidative energy production in the immature brain. The oxidation of ketone bodies by the newborn dog brain accounts for not more than 6% of thein vivocerebral ox

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1978.tb07035.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Abstract—The turnover of acetylcholine in whole mouse brainin vivohas been determined using [U‐14C]glucose as a precursor of the acetyl moiety. The standard requirements for the measurement of turnover were met: the injection did not change the concentrations of precursor or product, the amount of radioactivity in the brain was proportional to the amount injected, and the relationship between the specific activity of glucose and that of acetylcholine was typical of a precursor and a product. The value for acetylcholine turnover was 64 pmol/min per mg protein, approx 6.4 nmol/min per g brain. Treatment with amobarbital (0.16 mmol/kg) decreased the incorporation of glucose into acetylcholine by 73 × 7%, and treatment with atropine increased it by 18 × 6%. These values agree with those using choline as a precursor, supporting the validity of the values for turnover obtained with either labelled precursor.The specific activity of acetylcholine was higher than that of pyruvate at all times in mouse brainin vivoand in rat brain slicesin vitro. These observations demonstrate compartmentation of glucose metabolism with respect to acetylcholine synthesis in the brain. They agree with observations by others of compartmentation of acetyl metabolism. They provide an explanation for the close linkage which has been observed between carbohydrate catabolism and acetylcholine synthesis in th

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1978.tb07036.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Abstract—In the presence of ATP, Mg2+and CoA, mouse brain synaptosomes actively catalyze the transfer of arachidonate to 1‐acyl‐phosphoglycerides. The enzymic acylation process was inhibited greatly by 0.1 mm‐PCMB (parachloromercuric benzoate), and only partially by 0.1 mm‐DNP (2,4‐dini‐trophenol) and 0.001% (w/v) oligomycin. Arachidonoyl transfer to 1‐acyl‐glycerophosphorylcholines and 1‐acyl‐glycerophosphorylinositols was negligibly affected by 1 mm‐NaF and 10 mm‐glucose. Among the different 1‐acyl‐phosphoglycerides used as acceptor molecules, the relative order for arachidonoyl transfer activity was: 1‐acyl‐glycerophosphorylinositols>1‐acyl‐glycerophosphorylcholines>l‐acyl‐glycerophosphorylethanolamines. The ester linkage at the C‐1 position of the 1‐acyl‐phosphoglycerides also appears necessary for activity for no arachidonoyl transfer activity was observed when 1‐alkenyl‐glycerophosphorylethanolamines were used as the acceptor molecules. Arachidonate transfer to 1‐acyl‐glycerophosphorylinositols was optimal at low acceptor concentrations (10–30μm) whereas the transfer to 1‐acyl‐glycerophosphorylcholines occurred over a much broader range of acceptor concentrations (30–80μm). At optimal acceptor concentration, maximal transfer activity was observed at arachidonate concentration of 50–80μm. The newly synthesized phosphoglycerides were found distributed in the subsynaptic components with sp

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1978.tb07037.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY