ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb07515.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb07516.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract–Detergent‐solubilized tyrosine hydroxylase from the caudate nucleus of the sheep was purified 3‐fold by affinity chromatography on 3‐iodotyrosine modified agarose. Supplementation of the standard assay with 1 mM Fe2+resulted in only slight stimulation of the enzymic activity. The enzyme was, however, markedly inhibited by certain complexing agents specific for either Fe2+or Fe3+. Double reciprocal plots of the kinetic data for a representative complexing agent, bathophenanthroline, showed the inhibition to be competitive with O2(apparentKm0.15 mM) and noncompetitive with eitherl‐tyrosine or the synthetic tetrahydropterin cofactor DMPH4(apparentKm's 0.12 and 0.29 mM, respectively). The combined inhibition and kinetics studies strongly suggest that brain tyrosine hydroxylase is an iron enzyme. Furthermore, the prosthetic iron very likely participates directly in catalytic function, presumably by binding molecular oxygen.The activity of ammonium sulphate‐precipitated enzyme was found to be stimulated 2‐fold by Fe2+, catalase or peroxidase, while untreated enzyme was markedly less affected by these agents. Since the only ostensible difference between the two preparations was the extensive aggregation present in the former case, the change in physical state evoked by ammonium sulphate precipitation appeared to be somehow related to this peculiar property

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb07517.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract–In control rats and in rats rendered epileptic by insertion of cobalt slivers into the cerebral cortex, total free fatty acids, free cholesterol, esterified cholesterol, triglycerides and phospholipids were measured in normal and lesion areas of cerebral cortex. The cortical lipid profile of the adult rat resembled that of the whole brain of very young rats rather than that of adult whole brain, with the principal differences from whole adult brain being lower total lipid content, increased proportions of phosphatidyl choline in the phospholipid fraction, and higher levels of cholesterol esters. Cobalt‐induced epilepsy was associated with significant changes in cerebral cortical lipids in the area of the lesion and in the non‐necrotic tissue adjacent to the lesion. The total lipid in the area of the lesion decreased sharply as a result of reductions in free cholesterol and total phospholipids. The levels of cholesterol esters and triglycerides increased in the area of the lesion, and cholesterol esters were also increased in the adjacent tissue. In addition there were decreases in the proportion of phosphatidyl ethanolamine in the phospholipids from the lesion site and adjacent tissue and decreases in the proportions of oleic, arachidonic and nervonic acids (unsaturated acids), and an increase in the proportions of lignoceric acid in the phospholipids. In the site of the lesion only, we observed a decrease in phospholipid palmitic acid and an appreciable increase in the proportions of an unidentified long‐chained fat

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb07518.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—A procedure is described for the preparation from rat brain of myelin having the same degree of purity at all ages. Such a procedure is essential for the study of myelin composition during development. Microsomal contamination was successfully eliminated by adjusting the method to maintain a constant amount of brain per unit volume in the initial density gradient step, and by including two osmotic shocks and two low‐speed centrifugation steps. Myelin prepared in this way from animals ranging from 15 days to 14months of age had a total ATPase activity of 0.3‐2.0 μmol of Pi.h−1.mg−1dry wt of myelin, representing 0.1‐1.2 per cent recovery of the total homogenate activity; a Na+, K+‐ ATPase activity of 0.1‐1.6 μfnol of Pi.h−1.mg−1dry wt, representing 0.04‐1.5 per cent recovery; a nucleic acid content of 0.2‐0.7 per cent of myelin dry wt, representing 0.2‐2.0 per cent recovery; and a ganglioside NANA content of 0.04‐0.07 per cent of myelin dry wt. representing 0.2‐4.6 per cent recovery. The myelin prepared from 20‐day animals had the highest content of the first three constituents; otherwise the values of the four constituents were relatively constant per unit weight of myelin. The amounts of nucleic acid and ganglioside recovered in the myelin fractions increased wit

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb07519.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—Myelin was isolated from rat brains during development by a procedure giving fractions of constant purity at all ages. The lipid composition of these fractions and of whole brains of littermates was determined. The amount of myelin recovered per brain was a nearly linear function of the logarithm of age from the youngest (15 days) to the oldest (425 days) animals studied. With the exception of the earliest age point, the isolated myelin accounted for approximately 40 per cent of total brain galactolipid, evidence that a constant fraction (calculated to be 60 per cent) of myelin was recovered at all ages. Although the lipid‐protein ratio of the myelin was constant with age, marked changes were seen in the amounts of cerebroside, sulphatide, phosphatidylcholine and desmosterol. The total galactolipid increased from 21 per cent of the total lipid at age 15 days to about 31 per cent at maturity. Phosphatidylcholine decreased from 17 to 11 per cent during the same period. Desmosterol decreased from 2.5 per cent of the total sterol to 0.2‐0.3 per cent. All of these changes were complete between 2 and 5 months of age; no other ‘lower phase’ lipids showed significant changes with age. Although qualitatively similar to those reported by others, the changes differed in magnitude, with more stability in the levels of cholesterol and phosphatidalethanolamine with development. A sensitive indicator of the maturation of myelin was the mole ratio galactolipid/phosphatidylcholine, which varied from 1.2 at age 15 days to 2.8 at maturity. The maximum rate of myelination occurred at 20 days of postnatal age when myelin was deposited at the rate of 3.5 mg day−1brain−1. However, at this age the rat brain had only 15 per cent of its eventual complement of myelin. The rate of accumulation of cerebroside in the whole brain paralleled that of myelin, and was the only lipid to show this relationship. Myelin deposition appeared to be almost solely responsible for the continued increase in brain weight after about 10

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb07520.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—Interactive effects of puromycin and cycloheximide on brain polyribosomes and cortical electrical activity were investigated. The time courses of action of the drugs on these parameters, in comparison to their inhibitory actions on protein synthesis, were also observed. The results indicate that the disruption of brain polyribosomes by cycloheximide was independent of its inhibition of protein synthesis, whereas the two processes were closely linked in the case of puromycin. For both the disruption of polyribosomes and the alteration of electrical activity, the order in which the drugs were administered was critical, with preadministration of cycloheximide having a protective effect. In contrast to the massive effect of cycloheximide on brain polyribosomes, the drug had no such effect on polyribosomes from live

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb07521.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—Rats were exposed to 5.6% oxygen environments for up to 2 h. The accumulation of brain DOPA and 5‐hydroxytryptophan at 30 min after decarboxylase inhibition was used to estimate cerebral tryosine and tryptophan hydroxylase activity, respectively,in vivo.There was a continuing decrease in tryosine hydroxylase activity during the 2 h in whole brain as well as five brain regions. Tryptophan hydroxylase activity declined during the 1st h, but then increased towards control levels during the 2nd h. There was an increase in brain tryptophan during the 2nd h as well. In whole brain and the five brain regions, there was no significant change in the levels of noradrenaline, dopamine or 5‐hydroxytrypamine. During a 1 h exposure to 5.6% oxygen, there was decreased accumulation of noradrenaline, dopamine and 5‐hydroxytryptamine after MAO inhibition and decreased accumulation of homovanillic acid and 5‐hydroxyindoleacetic acid after probenecid administration. The dercreased synthesis and metabolism of the monoamines is most likely attributable to insufficient brain tissue oxygen as a substrate for the two hydroxylas

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb07522.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—Differential and gradient centrifugation revealed that 90 per cent of the 5‐HT, dopamine and noradrenaline in the CNS of the fresh water mussel was bound to particles; 60‐70 per cent of the bound monoamines appeared in the mitochondrial and 15‐20 per cent in the microsomal fraction. Spectrofluorimetric assay and electron microscopic analysis of the subfractions obtained by separation of the mitochondrial fraction on sucrose density gradients showed that the nerve endings and their dense‐core vesicles were concentrated in fractions with high relative specific activity of the three monoamines. This supports the proposed function of these monoamines as interneuronal mediators. Osmotic shock treatment resulted in the formation of a synaptosomal subfraction of low density displaying a high relative specific activity for 5‐HT. From the results obtained one cannot draw clear‐cut conclusions regarding the participation of subcellular particles in the storage of serotonin detectable in the perikarya by means of histoche

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb07523.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—Seventeen monkeys (M. nemestrinaandM. fascicularis) aged 10 months to about 5 yr were divided into two groups and fed either an adequate protein diet (20% casein) or a low‐protein diet (2% casein). The diets were supplied to the animals in restricted amount (200 g/animal in two daily rations). In one experiment, the malnourished animals were initially fed a diet containiing 8 per cent protein and the protein content of the diet was gradually reduced over a period of 9 months, to 2 per cent. After about 3 months on the 2 per cent protein diet, the malnourished monkeys showed growth failure, severe anorexia, peri‐ocular oedema, tremors of the head and limbs, atrophy of several visceral organs, fatty liver, hypoalbuminaemia, and depressed serum levels of many essential amino acids with an elevation of the ratio of non‐essential to essential amino acids. These features are consistent with protein‐calorie malnutrition. Examination of the brains revealed significant alterations in the levels of glycerophosphoethanolamine (—40 per cent), glutamic acid (—25 per cent), histidine (+230 per cent), homocamosine (+185 per cent), 3‐methyl‐histidine (+147 per cent), lysine (+55 per cent), phenylalanine (+33 per cent) and tyrosine (+26 per cent) in comparison to findings on the well‐fed monkeys. The possible implications of elevated cerebral contents of homocarnosine in malnourished monkeys are discussed in the light of several reported human cases in whom neurological disorders are associated with increased histidine‐containing dipeptides in the brain,

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb07524.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY