摘要:

Abstract—Previously reported interspecies correlations of cerebral cortical oxygen consumption (as a function of average species body weight) and of cerebral cortical chloride content and acetylcholinesterase activity (as functions of average species brain weight) were confirmed by selected repetitions of the determinations and were further validated by inclusion of data from samples of cerebral cortex of the fin whale (Balaenoptera physalus) and the sperm whale (Physeter catodon). Despite the fact that the samples of whale brain were obtained at 15–22 h after death and were preserved only by simply freezing on dry ice, no evidence of significant postmortem autolysis was obtained by examination of gangliosides, myelin basic proteins, acidic and amide residues of total isolated proteins, and lipid composition of cerebral cortical samples. The chloride content of whale cerebral cortex was 65.1 (± 12) μequiv./g, and the activity of acetylcholinesterase was 0.78 (± 0.28) μmol of acetylthiocholine hydrolysed min‐1g‐1, with no differences in these values between the two species. The two interspecies correlations yielded regression curves with calculated slopes for chloride of +9.07 (± 0.37) and for acetylcholinesterase of ‐0–204 (± 0.006), each correlating significantly as functions of species brain weight atP200 g) samples of whale (and beef) brain, subsequently prepared slices of whale cerebral cortex respired at a rate of 20.6 (± 1.8) μmol of O2taken up h‐1g‐1, also 50 per cent of the value of 40.7 predicted by extrapolation for fresh (unfrozen) slices. When plotted as a function of species body weight, the data for oxygen consumption by previously frozen cortical slices paralleled the regression curve for fresh slices previously characterized by the expression, R = 5.4 W‐0.1. The data obtained for the two species of great whales (brain weights, 6800–7800 g; body weights, 3–53 ± 104kg) served to ‘anchor’ with more certainty the upper limits of the three interspecies correlations re‐examined here and thus provided a better basis for predicting by extrapolation nor

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12125.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—The question of a constant density of glial cells in mammalian cerebral cortex regardless of species was examined by surveying the cortical activities of two enzymes primarily localized to dial cells. The cortical activity of butyrylcholinesterase (EC 3.1.1.8) was essentially constant at a rate of approx. 0.1 μmol of butyrylthiocholine hydrolysed min‐1g‐1over the range of species from rat (brain wt., 1.6 g) to fin whale and sperm whale (brain wt., 6800 and 7800 g, respectively). Over the same range the activity of cortical acetylcholinesterase, a neuronal enzyme, decreases by a factor of 7. Thus, butyrylcholinesterase ranged from<2 per cent (in small rodent brains) to approximately 10 per cent (in whale brain) of the cortical acetylcholinesterase activity. The cortical activity of carbonic anhydrase (EC 4.2.1.1) was constant at a rate of 6.2 (± 0.25) μmol of CO2evolved min‐1g‐1over the range of species from guinea‐pig (brain wt., 4.75 g) to fin whale (brain wt., 6800 g). These data obtained by assaying the dehydration reaction were confirmed by limited assays of the esterase activity of the enzyme (withp‐nitrophenylacetate as substrate) and agreed with limited, previously reported data for the hydration reaction. Thus, the circumstantial evidence strongly favoured a relative constancy of cortical glial cell density regardless of species.The rates of anaerobic glycolysis in the cerebral cortex of various species were also investigated. For six species from mouse (brain wt., 0.4 g) to beef (brain wt., 380 g) cortical anaerobic glycolysis varied only slightly in the range of 50–62 μmol of CO2evolved h‐1g‐l, whereas cortical oxygen consumption for the same range of species decreased by a factor of 3. Previously frozen samples of beef cortex glycolysed at 35 per Cent of the rate of fresh (unfrozen) samples. Since identical rates were obtained for previously frozen samples of fin whale cerebral cortex, we concluded that the relative constancy of cortical anaerobic glycolysis could be extended to the range from mouse to whale and that this aspect of cortical metabolism is probably primarily glial in localization. Some implications of the latter conclusion for the proposed role of astrocytes as modulators of neuronal activ

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12126.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—The arylsulphatase A and B patterns of human tissues and leucocytes have been established by isoelectric focussing. Assay conditions, which enable an evaluation of these patterns as quantitatively as possible, have been studied. The dependences of the enzyme patterns on the origin of the tissues and on the storage conditions have been determined. The arylsulphatase A obtained by isoelectric focussing exhibits cerebroside sulphatase activity in the presence of detergents. A purified preparation of the arylsulphatase B likewise shows a significant, although low, cerebroside sulphatase activity. In cases of the conventional types of metachromatic leucodystrophy the arylsulphatase A activity is missing, while in an atypical form of this disease (‘ML Variant’ according to Austinet al. (1965) the arylsulphatase A, B and C activities are deficient. In both forms, however, residual activities of the deficient enzymes could be detected which showed isoelectric points identical to those of the normal enzymes.The following nomenclature is proposed: ‘Variant B’ for the conventional type, in which the arylsulphatase B activity is present, and ‘Variant O’ for the exceptional cases, in which all arylsulphatase activities are deficient. The significance of the cerebroside sulphatase activity of arylsulphatase B for a possible residual turnover of cerebroside sulphates in the conventional type of the disease

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12127.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—The effect of phenylalanine and phenylpyruvate on the metabolism of pyruvate by homogenates of human brain was investigated. In the presence of 5 mM pyruvate as substrate homogenates of human cerebral cortex fixed about 1 μmol of H14CO3‐‐per g of tissue in 30 min. Phenylpyruvate at a concentration of 5 raw inhibited the fixation of H14CO3‐‐by homogenates of human brain by approximately 50 per cent, whereas 5 mM phenylalanine had no effect. The inhibition of pyruvate carboxylation by phenylpyruvate was dependent upon the concentration of the inhibitor. The activity of pyruvate carboxylase (EC 6.4.1.1) in human cerebral cortex was 02–0.4 units, with aKmfor pyruvate of about 0.2 mM. Homogenates of human cerebral cortex decarboxylated [1‐14C]pyruvate to14CO2at a rate of about 5 μmol per g of tissue per 15 min, with a 20–50 per cent reduction in the presence of 5 mM phenylpyruvate; phenylalanine at the same concentration had no effect. The possible toxic effect of phenylpyruvate on the metabolism of pyruvate in the brains of untreated phenylketonuric pati

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12128.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—Choline acetyltransferase (EC 2.3.1.6) was partially purified from human caudate nucleus and putamen, human sciatic nerve, rabbit and rat brain, and rabbit sciatic nerve. Kinetic constants were determined under the same conditions for all six extracts. ExtrapolatedKmvalues were between 6.6 and 18 μM for acetyl‐CoA and between 0.4 and 1.2 mM for choline. Product inhibition patterns indicated that ChAc from both central and peripheral nervous tissues of man and the rabbit obeys a Theorell‐Chance mechanism. Kinetic parameters suggest a possible influence on ACh synthesis of thein vivoconcentration ratio, CoA/acet

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12129.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—Male rats of the Sprague‐Dawley strain were weaned at 21–23 days of age and littermates were assigned to enriched or deprived environments. At days 7, 20 and 35 following separation of littermates, the brain RNA from 3 out of each group of 12 enriched or deprived rats was pulse‐labelled with [5‐3H]uridine, while the remaining rats in each group were used as a source of unlabelled competitor RNA. The RNA was used in DNA:RNA hybridization studies involving simultaneous competition between labelled RNA and varying amounts of unlabelled competitor RNA from the brains of enriched or deprived rats. The number of groups of enriched and deprived rats studied was 2 each at day 7 and at day 20, while 3 groups were employed at the 35‐day interval. No significant qualitative differences were found between RNA from the brains of enriched and de

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12130.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—2‐Hydroxy‐, 2‐chloro‐, 2‐ and Cmethyl‐GABA are linear competitive inhibitors of GABA uptake in rat brain slices. These analogues are thus potential substrates for the GABA transport system and possible‘false transmitters'. 2‐Hydroxy‐GABA is the most potent inhibitor of GABA uptake yet described. No specific inhibitor of GABA uptake was revealed among

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12131.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—The phospholipid composition of, and the incorporation of labelled phosphorus into the different phospholipids of rat and calf retina have been studied. The influence of various conditions, such as dark and light adaptation, during the preparation of retina, lipid extraction and incubation of retina with radioactive phosphorus was investigated.The phospholipid composition of rat retina did not differ significantly from that of calf retina and the different conditions of preparation and incubation did not modify the distributions.The specific radioactivities of the different phospholipids of calf and rat retina, incubated in the presence of32P, distinguished in both species two groups of components characterized by the rate of labelling. Phosphatidic acid (PA) and inositol glycerophospholipids (PI) belonged to the first group and showed the highest uptake of labelled phosphorus; the second group, comprising choline glycerophospholipids (PC), serine glycerophospholipids (PS), sphingomyelin (SP), ethanolamine glycerophospholipids (PE) and cardiolipin (CL) showed low incorporation activities. Only SP was labelled differently in rat and calf retina. With the exception of PS, there was no evidence for the influence of light on the turnover of individual phospholipids. The finding that PS showed higher specific radioactivities when adaptation and incubation proceeded in the dark, seems to be of interest and needs further stud

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12132.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—Ethyleneglycol‐bis (β‐aminoethyl ether)‐N‐N'‐tetraacetic acid (EGTA) inhibited the incorporation of32Piinto phosphatidylinositol (PI) in rat diaphragm incubated in Ca2+‐free Krebs‐Ringer medium. Only the labelling of the PI was altered, and no effects on the pool size of PI or on the incorporation of32Piinto other phospholipids were observed. The effect of EGTA was concentration‐dependent and appeared to be related to its Caa+‐chelating properties; the inhibition of the incorporation of32Picould be completely reversed by the addition of excess Ca2+but not Mg2+. The inhibitory effect of the EGTA was progressively enhanced by lengthening the preincubation of the tissue with EGTA, an observation suggesting that chelation of intracellular or membrane‐bound Ca2+, rather than extracellular Ca2+, was involved in the effect. In contrast to its inhibition of the incorporation of32PiEGTA enhanced the incorporation of [3H]inositol into PI, but this effect was accompanied by an appreciable increase in total uptake of [3Hlinositol by the tissue. Our results suggest that the level of intracellular Ca2+plays a role in the regulation of the incorporation of32Piinto PI. Addition of unlabelled α‐glycerophosphate to the incubation medium of tissues which had been preincubated with 2‐deoxy‐d‐glucose failed to cause a significant diminution in the inhibition by EGTA of the incorporation of32Piinto PI. This experiment suggests, but does not prove, that the effect of EGTA was not at the level of incorporatio

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12133.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—A 20–30 per cent stimulation of ATPase activity by added NaHCO3was found in homogenates of a variety of mammalian tissues. The subcellular distribution of this (HCO3‐)—stimulated activity was examined in detail using rat cerebral cortex. The stimulation was specific for the HCO3‐ion and was predominantly localized in the mitochondrial subcellular fraction, in which a 2‐fold stimulation by HCO3‐was found. The effect of inhibitors supported the identification as the mitochondrial ATPase. Both sodium azide and thiocyanate were inhibitory. The effects of varying the Mg2+concentration, HCO3‐concentration, and pH were also studied. In the presence of HCO3‐theKmfor ATP was reduced approximately 3‐fold. There was no effect of HCO3‐on the ma + K) ATPase or Mg2+ATPase from the microsomal fraction of rat cerebral cortex. Our findings have been discussed in relation to previous work on HCO3‐stimulation of ATPae activity in subcellular fractions from other tissues, as well as its possible relevance to the known effects of HCO3‐and carbonic anhydras

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12134.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY