摘要:

Abstract—A simple method is described for the preparation of succinic semialdehyde by the oxidation of 4‐hydroxybutyric acid with dimethyl sulphoxide in the presence of phosphorus pentoxide. The colorimetric estimation of succinic semialdehyde by condensation with 3‐methyl‐2‐benzothiazolinone‐2‐hydrazone is used as an assay for GABA aminotransferase activity in mouse brain. The values obtained for the specific activity of this enzyme in mouse brain using the colorimetric method agree with those obtained by the more conventional is

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01257.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—The distribution of [14C]‐labeIled material into subcellular fractions of 15‐day‐old rat brain was studied as a function of time after intracerebral injection of [2‐14C]mevalonic acid. As previously shown for adult brain, the data indicated the microsomal fraction to be the site of sterol biosynthesis. The synaptosomal fraction exhibited a marked early uptake of [14C]‐nonsaponifiable material. Total radioactivity in both myelin and myelin‐like fractions remained low in comparison to that in the other subcellular fractions at all time periods examined. At 2 h after injection, labelled digitonin‐precipitable material was demonstrable in all subcellular fractions. Examination of the [14C]‐labelled nonsaponifiable material by thin‐layer chromatography indicated the rapid appearance of labelled 4‐desmethyl sterol in all subcellular fractions, with the most rapid appearance in the myelin fraction, followed in decreasing order by microsomal, synaptosomal, and mitochondrial fractions. Examination of [14C] digitonin‐precipitable material from each fraction by the dibromide method demonstrated that although 4‐desmethyl sterol appeared quickly, the formation of cholesterol was slow in all fractions, an effect that had been reporte

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01258.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—The contents and the fatty acid composition of cholesterol esters were analysed in developing rat brain. The total content did not exceed 20 μg/brain throughout development. Elimination of serum by adequate perfusion was essential for accurate results. Two separate events appeared to affect the levels of cholesterol esters in developing rat brain, one probably reflecting general developmental changes and the other apparently related to myelination. On either a unit weight or a whole brain basis, the curves appeared to be a superimposition of the two events. There was an underlying developmental change, which was characterized on a unit weight basis by the highest level of cholesterol esters immediately after birth and a steady decline to the adult level by 30 days of age or which on the basis of whole brain was characterized by a steady increase throughout the development. A period of transient increase was superimposed on this underlying developmental change between the ages of 7 and 27 days and corresponded to the period of active myelination. The major fatty acids of rat brain cholesterol esters were palmitic, palmitoleic, oleic and arachidonic acids. Palmitic and palmitoleic acids decreased in proportion while oleic acid increased, as the animal matured. The fatty acid composition of serum cholesterol esters was distinctly different from that of brain cholesterol esters; those from serum contained much higher proportions of linoleic and arachidonic acids and much less palmitoleic and oleic aci

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01259.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—Three enzymes of cholesterol ester metabolism, a cholesterol‐esterifying enzyme which incorporates free fatty acids into cholesterol esters without participation of CoA, and two cholesterol ester hydrolases with differing pH optima, all showed distinct changes in developing rat brains. The specific activity of the esterifying enzyme was approx. 20 percent of the adult level at birth, increased gradually to the adult level by 20 days of age and remained constant thereafter. The pH 4.2 hydrolase at birth also had a specific activity of about 20 per cent of the adult level but it increased rapidly to reach a peak at 13 days, by which time the activity had increased eight‐fold. The activity declined somewhat thereafter to reach the adult level by 23–30 days. In contrast, there already was 60 per cent of the adult specific activity of the pH 6.6 cholesterol ester hydrolase at birth. The activity remained constant until 12 days and then doubled during the next two weeks, reaching a broad peak, then declining slightly to reach the adult activity by 50 days. Therefore, the developmental changes of both of the hydrolases appeared to be related to the process of myelination. The period of active myelination (10–30 days) was characterized by the sharp rise in the activity of pH 6.6 cholesterol ester hydrolase and by the rapid decrease of pH 4.2 cholesterol ester

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01260.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—Homogenates of rat brain hydrolysed the sulphate esters of dehydroepiandrosterone, oestrone and pregnenolone to free steroids. The pH optimum was 6.6 for all three steroid sulphates. Under similar conditions, cholesterol sulphate was not hydrolysed to a significant extent. Unlike sterol sulphatases (EC 3.1.6.2) from extraneural tissues, most of the activity in brain was found in the crude nuclear fraction. The remainder of the activity was found in the crude mitochondrial fraction and almost none was detected in microsomal or cytosol fractions. Sterol sulphatase activity was present in the foetal brain and increased rapidly with increasing postnatal age to a plateau at approx. 25 days of postnatal age. The enzymic activity did not differ significantly with the sex of the animal. The sulphatase activity was found throughout the brain, with cerebellum and brain stem exhibiting a slightly higher activity per wet wt. of tissue than other regions. Inhibition of enzymic activity occurred in the presence of sodium deoxycholate, Triton X‐100, sodium dodecyl sulphate and inorganic phosphate or sulph

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01261.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—The kinetics of canine hypothalamic tyrosine hydroxylase were studied in the presence of various ions and sulphated mucopolysaccharides. Enzymic activity was dependent on ionic strength, a specific sulphate effect and the presence of the highly sulphated mucopolysaccharide, heparin. Whereas both sulphate and heparin activated tyrosine hydroxylase by increasing Vmaxheparin, but not sulphate, also increased the affinity of the enzyme for the synthetic cofactor, 2‐amino‐4‐hydroxy‐6,7‐dirnethyl‐5,6,7,8‐tetrahydropteridine, by nearly an order of magnitude. Other rnucopolysaccharides, such as chondroitin sulphate and hyaluronic acid, were not effective as activators of tyrosine hydroxylase. The allosteric activation of tyrosine hydroxylase by heparin may serve to ‘sensitize’ the enzyme to low levels of its end prod

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01262.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—The levels of free amino acids in subcellular fractions of guinea pig cerebral cortex have been determined. Putative transmitter amino acids are not bound to synaptic vesicles in a manner analogous to acetylcholine, as shown by the failure of hypo‐osmotic shock to cause a specific release of the excitant and depressant amino ac

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01263.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—Oxygen uptake, ADP/O ratios and respiratory control ratios (RCR) were studied by the oxygen electrode technique in mitochondria prepared from adult and neonatal brains from normal and pyridoxine‐deficient rats. The mitochondria from neonatal brain exhibited decreased rates of substrate oxidation, ADP/O ratios and respiratory control ratios in comparison to those obtained with mitochondria from the respective adult brains. The cytochrome contents of the neonatal brains were also less than those of the adults. Within the neonatal or adult groups, there were no differences in any of the parameters tested between the normal and pyridoxine‐deficient

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01264.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—Octopamine is a normally occurring amine in several species of animals. Particularly high concentrations are found in the crustacean central nerve cord. In the rat it is specifically localized to sympathetic nerve endings, has a subcellular distribution similar to that of norepinephrine, and is asymmetrically distributed in the CNS. It has a turnover rate in heart about six times that of norepinephrine. The physiological role of octopamine has not been established but it appears likely that it is a cotransmitter together with norepinephrine in the peripheral sympathetic nervous syste

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01265.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—A time‐dependent activation of the tris‐HC1 enzyme form of pig brain glutaminase (EC 3.5.1.2, L‐glutamine amidohydrolase) by phosphate, phosphate‐borate and carboxylic acids is described. This time‐dependent activation increases with increased protein concentration and also with temperature. The sedimentation behaviour of the various activated enzyme preparations is described. The Arrhenius plot for the triq‐HC1 enzyme is curved, indicating a reversible equilibrium between two enzyme forms, whereas the plot obtained for the phosphate‐borate enzyme was a straight line. The apparent activationenergy has

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01266.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY