摘要:

Abstract—The distribution of [14C]labelled material into subcellular fractions of 30‐day‐old rat brain was studied as a function of time, following intracerebral injection of [2‐14C] mevalonic acid. As in the adult and 15‐day‐old brain, the microsomal fraction was indicated as the site of sterol synthesis. Unlike the 15‐day‐old animal, the myelin fraction from the 30‐day‐old rat was the predominately labelled fraction at 2 weeks after injection of the animal. Significant amounts of [14C]cholesterol were not present until about 4 h after injection. In order to ascertain whether different populations of cholesterol were being labelled, depending on the age of the animal injected, we compared the labelling of myelin and non‐myelin components in animals injected at 15 or at 30 days of age, and sacrificed, respectively, from 14 to 29 days or from 1 to 28 days after injection. Our results indicated that there was an apparent shift of labelled sterol from non‐myelin to myelin fractions at

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01414.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—The effect of neonatal thyroidectomy on the cyclic AMP system in the developing rat brain was examined. Administration of131I at birth led to a 16 per cent reduction in brain weight and a 70 per cent reduction in body weight by 40 days of age. The level of cyclic AMP in the brain increased 5‐fold between birth and 40 days of age and this increase was partially reduced by early thyroidectomy. A similar increase in the activity of adenyl cyclase and phosphodiesterase was observed during development, but thyroidectomy produced no detectable changes in the activity of either enzyme. The activity of the cyclic AMP‐dependent protein kinase was already maximal at birth and also was unaffected by thyroidectomy.Norepinephrine increased levels of cyclic AMP 4‐ to 5‐fold in brain slices prepared from adult rats, but was without effect on slices prepared from newborn or 3‐day‐old rats. The response to norepinephrine in thyroidectomized rats did not differ from that in control rats at any of the ages examined. Our findings indicate that neonatal hypothyroidism does not deleteriously affect the development of the cyclic AMP system in

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01415.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—Aminotransferase activity was measured in various areas of the nervous system of the rat (cortical grey matter, midbrain, corpus callosum, spinal cord and sciatic nerve) and in subcellular fractions of rat brain (nuclei, mitochondria and cytosol). Activity was low or absent in the sciatic nerve relative to that in the other areas, with the exception of incubation of glutamate with oxaloacetate (25 per cent of the activity found in brain) and of asparagine with 2‐oxoglutarate (65 per cent of the activity found in brain). The distribution of enzymic activity was not homogeneous; alanine‐2‐oxoglutarate aminotransferase was highest in cortical grey matter; leucine‐ and GABA‐2‐oxoglutarate aminotransferases were highest in midbrain. Incubation of phenylalanine or tyrosine with 2‐oxoglutarate gave similar activities in grey matter and midbrain. Activity generally was higher in the grey matter than in corpus callosum or spinal cord. However, incubations of methionine with 2‐oxoglutarate, or glutamine with glyoxylate, gave similar activities in the three areas studied from the brain, whereas incubations of glutamate with glyoxylate gave highest activity in the corpus callosum. Only incubations of asparagine with 2‐oxoglutarate, and glutamate with glyoxylate, gave significant activity in the nuclear subcellular fraction. Aminotransferase activity of phenylalanine, tyrosine or GABA with 2‐oxoglutarate, or ornithine or glutamine with glyoxylate, was localized to mitochondria. The remaining reactions studied (glutamate with oxaloacetate; leucine, alanine, methionine or asparagine with 2‐oxoglutarate and glutamate with glyoxylate) demonstrated activity in both the mitochondrial fraction and the solub

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01416.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—The levels of ATP, ADP, AMP and phosphocreatine, of four amino acids, and of 11 intermediates of carbohydrate metabolism in mouse brain were determined after: (1) various degrees of hypoxia; (2) hypoxia combined with anaesthesia; and (3) recovery from severe hypoxia. Glycogen decreased and lactate rose markedly in hypoxia, but levels of ATP and phosphocreatine were normal or near normal even when convulsions and respiratory collapse appeared imminent.During 30 s of complete ischaemia (decapitation) the decline in cerebral ATP and phosphocreatine and the increase in AMP was less in mice previously rendered hypoxic than in control mice. From the changes we calculated that the metabolic rate had decreased by 15 per cent or more during 30 min of hypoxia.Hypoxia was also associated with decreases of cerebral 6‐phosphogluconate and aspartate, and increases in alanine, γ‐aminobutyrate, α‐ketoglutarate, malate, pyruvate, and the lactate :pyruvate ratio. Following recovery in air (10 min), increases were observed in glucose (200 per cent), glucose‐6‐phosphate, phosphocreatine and citrate, and there was a fall in fructose‐1, 6‐diphosphale.Similar measurements were made in samples from cerebral cortex, cerebellum, midbrain and medulla. Severe hypoxia produced significant increases in lactate and decreases in glycogen in all areas; γ‐aminobutyrate levels increased in cerebral cortex and brain stem, but not in cerebellum. No significant changes occurred in ATP and only in cerebral cortex was there a significant fall in phosphocreatine.Phosphocreatine, ATP and glycogen were determined by quantitative histochemical methods in four areas ofmedulla oblongata, including the physiological respiratory centre of the ventromedial portion. After hypoxia, ATP was unchanged throughout and the changes (decreases) in phosphocreatine and glycogen were principally confined to dorsal medulla, notably the lateral zone.Thus there is no evidence that respiratory failure is caused by a ‘power’ failure in the respiratory centre. It is suggested that inextremisa protective mechanism may cause neurons to cease firing before high‐energy phosphate

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01417.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—Murine brains were frozenin situ, either in liquid N2or in Freon‐12 cooled to its freezing point. The effect of these coolants on cooling rates and times in various CNS regions was determined. In addition, levels of ATP, P‐creatine and lactate were measured in selected regions of brains from both intact animals and severed heads frozen in either coolant. For both the intact animals and severed heads, superficial regions of brain cooled to 0°C and deeper regions to 25°C, at the same rate in either liquid N2or Freon. Subsequent cooling was more rapid in liquid N2in both regions. Levels of ATP, P‐creatine and lactate were similar in brains frozen in either coolant, probably because CNS utilization of highenergy phosphates decreased markedly as body temperature fell. In brains of animals frozen intact, levels of ATP and P‐creatine were higher and levels of lactate were lower than those in brains from heads which were severed prior to freezing. This difference may be a result of the marked stimulation which accompanies decapitation and may also reflect continued cerebral circulation in the intact animal for a brief time after immersing the animal in

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01418.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Résumé—Dans le but d'étudier la localisation cytologique de I'AChE dans divers tissus de Gymnote, nous avons préparé un antisérum anti‐AChE en utilisant une préparation commerciale partiellement purifiée, contenant une forme globulaire de l'AChEGp. Cet antisérum réagit dans le test de double diffusion avec l'enzyme purifiéGp, mais également avec la forme globulaire spontanéeGb, ainsi qu'avec les trois espèces ‘natives’ asymétriquesA,CetD. Nous avons mis en évidence l'existence de ces quatres formesGb,A,CetDdans des extraits de cerveau, de moelle épinière et de muscle de Gymnote. La forme globulaireGbest particulièrement abondante dans la moelle épinière et à un moindre degré, dans le cerveau. La distribution des espèes est identique dans le muscle et l'organe électrique. Grâce à notre antisérum, nous avom Iocalisé par immunofluorescence indirecte l'AChE dans les terminaisons nerveuses sur le muscle, dans le cytoplasme de certains neurones situés dans le centre moteur de la décharge (moelle épinière) et au voisinage d

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01419.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—Saxitoxin and tetrodotoxin at low concentrations (10−7‐10−8M) exerted similar inhibitory effects on the increase in lactate production and the redistrjbution of Na+and K+that normally accompany electrical stimulation of rat cerebral cortical slices. In contrast, the toxins exerted dissimilar effects on the production of lactate in response to low concentrations of Ca2+in the medium. Inhibition by tetrodotoxin occurred at a higher concentration of Ca2+and was significantly greater than that produced by saxitoxin at concentrations of Ca2+below 0.75 mM. These differences were not related to differential effects on the redistribution of Na+and K+under such conditions. The toxins had different effects on Ca2+influx. Tetrodotoxin, but not saxitoxin, inhibited the influx of Ca2+in the absence of electrical stimulation. The influx of Ca2+increased when electrical pulses were applied and tetrodotoxin inhibited this increase, whereas saxitoxin potentiated influx of Ca2+during stimulation. Our results suggest that metabolic responses to conditions that increase excitability are not governed solely by changes in the distribution of Na+and K+. The differential effects of the toxins on Ca2+fluxes suggest that one site of Ca2+entry during electrical stimulation may be functionally independent of N

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01420.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—The rate of efflux of45Ca2+from slices of rat cerebral cortex was resolved into two exponential curves which were attributed to an extracellular component and an intracellular or bound component. Electrical stimulation increased efflux of45Ca2+from the more stable pool and the time course for the redistribution of Na+and K+paralleled that for the increased efflux of Ca2+. This effect of stimulationwas dependent on the presence of Na+in the incubation medium. Lack of Na+in the medium during loading of the slices with45Ca2+increased uptake but on subsequent transfer to a medium containing Na+, electrical pulses failed to increase the rate of efflux of45Ca2+. In unstimulated slices, the rate of efflux of45Ca2+was dependent upon the concentration ratio of Na+to Ca2+in the incubation medium. Saxitoxin and tetrodotoxin inhibited the increased efflux of45Ca2+that occurred during electrical stimulation but exerted no effect on Ca2+‐Ca2+exchange. Our results suggest that there is a Na+‐dependent turnover of Ca2+in brain slices which may involve changes in affinity at a common binding site. The possible involvement of such a Na+‐Ca2+interaction in the regulation of neurotransmitter function is di

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01421.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—Labelled fucose administered to ratsin vivowas rapidly incorporated into brain glycoproteins, but not into any other brain constituents, including glycolipids and acid mucopolysaccharides. Maximum incorporation of tritium‐labelled fucose into brain glyco‐proteins occurred 3–6 h after intraperitoneal injection in young or adult rats, and the half‐time for the turnover of glycoprotein‐fucose in young rats was approximately 2 weeks.Within 3 h after the administration of either [1‐3H]fucose or fucose generally labelled with tritium, 75 per cent of the total acid‐soluble radioactivity in plasma and brain was found to be volatile, and by 24 h after injection more than 90 per cent of the acid‐soluble radioactivity was volatile. The tritium in labelled fiicose appears to undergo arapid exchange reaction with hydrogen atoms in body water, although the tritium in fucose glycosidically‐ linked to glycoproteins is biologically stable. The rapid disappearance of labelled free fucose from the plasma and tissues of the rat precludes the possibility of any significant degree of reutilization of labelled precursor, and provides support for other data indicating that the turnover of fucose in brain glycoproteins is relatively slow in comparison to that of hexosamine and sialic acid.Activities of α‐L‐fucosidase in rat brain, with pH optima at 40 and 6.0, had essentially the sameKm(4 × 10−4M and 3.2 × 10−4M, respectively) withp‐nitrophenyl‐α‐L‐fucopyranoside as substrate. Activities of both were competitively inhibited by L‐fucose. However, theKtmeasured at pH 4 (1.9 × 10−2) was almost ten times gre

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01422.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—The content of cerebrosides, sulphatides, gangliosides, cholesterol and phospholipids was evaluated in the brain and spinal cord of rats during the acute and recovery stages of experimental allergic encephalomyelitis (EAE). During the acute stage there was a significant decrease of sulphatides and gangliosides in spinal cord; in brain, only sulphatides were diminished. In the recovery stage, cerebrosides and gangliosides were decreased in the brain, whereas the lipid content of the spinal cord was similar to that in control animals. Cholesterol esters were detected in the brain and spinal cord during both periods. The results show that the changes are not the same for brain and spinal cord during the acute and recovery stages and that glycosphingolipids from either white or grey matter seem to be preferentially altere

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb01423.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY