摘要:

Abstract—Inorganic phosphate labelled with32P was applied to giant axons excised from squid (Loligo pealeii) by addition of32Pi to the bathing solution, by injection into the axon, or by addition to axoplasm which had been separated from the sheath. The preparations were kept at 10 to 25° for various times up to 4 hr. When32Piwas supplied by way of the bathing solution, axoplasm and sheath were usually separated at the end of incubation before extraction of the lipids. Lipids were extracted with chloroform‐methanol and resolved by paper chromatography.The lipids which became labelled appeared to be the same in sheath and axoplasm. They were identified by cochromatography with known lipids and by chromatography of products formed from them by mild alkaline hydrolysis. They included phosphatidylinositol, phosphatidylethanolamine, phosphatidic acid, and probably somelysophosphatidylethanolamine. Some labelled components remained unidentified.Phosphatidylcholine was apparently present, but did not become significantly labelled either in sheath or in axoplasm, or in a squid's stellate ganglion.There was no evidence that separation from the sheath impaired the capacity of the axoplasm for lipid synth

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1968.tb08953.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—A dual‐channel integrating micro‐flame‐photometer was evaluated for simultaneous analysis of sodium and potassium in aqueous extracts from nanogram samples of frozen‐dried mammalian nervous tissue. Calibrated quartz constriction micropipettes delivered 10−8l. of extraction fluid to a 100 μ platinum‐iridium wire for insertion directly into the flame. Over‐all reproducibility was 4 per cent for twenty samples containing 6.5 × 10−11g K and 2.2 × 10−11g Na. Large amounts of anions decreased the emissions for both sodium and potassium, but no interference between sodium and potassium was found over the range adopted for biological analyses. The micro‐flame‐photometer gave results for a few nanolitres of aqueous extracts of brain homogenates which were within 3‐5 per cent of those obtained on larger volumes with a conventional flame photometer. Macroanalysis and microanalyses of microgram quantities of frozen‐dried tissue sections of cerebral cortex were also in agreement. Nanogram samples from frozen‐dried spinal ganglia of a rabbit gave average values for sodium and potassium (calculated/g wet wt.) which were similar to those for aqueous extracts of rabbit brain homogenates. Samples from peripheral gangliain vivo, 10 minpost mortemand 20 minpost mortemhad significantly different average K/Na ratios of 1

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1968.tb08954.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—Brain sterols from chick embryos (11 and 18 days of incubation) and mature rats, previously injected with [2‐14C]mevalonate, were analysed.Acetate derivatives of the sterols were chromatographed on Silica Gel:Celite:AgNO3columns. Sterol fractions were assayed for radioactivity and the amounts determined by gas chromatography. Sterol structures were elucidated by gas chromatography‐mass spectrometry. The method used allowed the identification of some sterols representing no more than 0‐01 per cent of the total mixture.The following brain sterols were identified: cholesterol, cholestanol, cholest‐5,24‐dien‐3β‐ol (desmosterol); 4,4′‐dimethyl‐cholest‐8‐en‐3β‐ol, 4α‐methyl‐cholest‐8‐en‐3β‐ol, cholest‐8‐en‐3β‐ol, 4,4′‐dimethyl‐choIest‐8,24‐dien‐3β‐ol, 4α‐methyl‐cholest‐8,24‐dien‐3β‐ol, cholest‐8,24‐dien‐3β‐ol and cholest‐7,24‐dien‐3β‐ol. Small amounts of other sterols including polyhydroxy sterols, were also detected. There were no qualitative differences in the sterols detected in developing and mature brain. In the developing chick brain, cholesterol represented approximately 90 per cent of the total sterols. In the mature rat brain, cholesterol accounted for 98 per cent of the sterols.The adult rat brain, as well as the embryonic chick brain, demonstrated the capacity to incorporate mevalonate into cholesterol precursors and cholestanol. The sterols retaining the double bond in the lateral chain, that is, those of the Δ8,24series with 29, 28 and 27 carbon atoms and desmosterol, were highly labelled compared with the other identified intermediates. The possibility, suppo

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1968.tb08955.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—The levels of the main cerebral energy reserves, ATP, P‐creatine, glycogen and glucose, and of several glycolytic intermediates and lactate, were measured in the brains of fish (Carassius auratus), turtle (Pseudemys scripta elegans) and frog (Rana pipiens). The levels of glycogen in these brains were 2‐9 times higher than those reported for mammals. In frog, cerebral glycogen levels were 35 per cent higher during the winter than in spring. The P‐creatine: ATP ratios were 3 instead of the more usual (mammalian) value of 1. The levels of other intermediates were similar to those found in mammalian brain.When anoxia was produced by decapitation, changes in the various substances measured were similar to those in mammalian brain, but were much slower. The initial rate at which high‐energy phosphate was used could be calculated from these changes. Values of 1.1 m‐equiv./kg/min for fish and frog and of 0.46 m‐equiv./kg/min for turtle were found, which are 1/20 and 1/50, respectively, of the rate in mouse brain. The rate of disappearance of high‐energy phosphate reserves followed first‐order kinetics for 4 hr in turtle and for at least an hour in the other species.Changes in metabolites as the experiment progressed were interpreted to indicate a progressively falling intracellular pH, prolonged inhibition of phosphofructokinase, and a long period of hexo

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1968.tb08956.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—A simple technique was described for isolation of the mitochondrial fraction from central nervous tissue of the rat. The fraction so prepared satisfied structural and functional criteria of intactness and relative homogeneity. Oxidation of various substrates and the influences of inhibitors and experimental conditions were examined. The refractoriness of brain mitochondria to thyroxine was confirmed. Oxidation of glutamate was characterized by a very high degree of respiratory control. There was a pronounced Mg requirement by mitochondria in the aerobic active state, but not in the controlled state. Reverse acceptor control was manifest during succinate oxidation by Mg deficient mitochondri

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1968.tb08957.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—The concentration of methylhistamine in whole brain of guinea pig is 72 ng (about 0‐5 mμ mole/g). The greatest portion is found in the crude mitochondrial frac

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1968.tb08958.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—(1) Animals were exposed to hypoxic environments either by supplying them with breathing mixtures low in oxygen or by exposing them in a decompression chamber to simulated altitude. Both methods of producing hypoxia brought about significant increases in brain GABA levels.(2) Elevated GABA levels occurred in all species tested (mouse, hamster, rat, guinea pig, and rabbit) and reached maximal concentration 60 min after the initiation of breathing the hypoxic mixtures. Extension of the exposure beyond 60 min brought about a gradual decline in GABA level from the maximal value reached.(3) A linear relation was found between the oxygen content of the gas mixture and the elevation of GABA level. For guinea pigs, at least, the critical oxygen content required to prevent elevation of GABA level was 8.1 per cen

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1968.tb08959.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—The lack of information on the mechanism of inactivation of the crustacean neuromuscular inhibitory transmitter compound prompted a study of the disposition of radioactive γ‐aminobutyric acid (GABA) in lobster nerve‐muscle preparations.A specific GABA transport system was found. Radioactive GABA was concentrated by the tissues to levels several times those in the medium, and net uptake could be demonstrated. The process was dependent on sodium ions in the medium; neither lithium nor choline could substitute for sodium. Incubations with increasing GABA concentrations indicated that uptake was a saturable mechanism with an apparentKmof 5.8 × 10−5m.Of many compounds tested, only desmethylimipramine, chlopromazine (and several related compounds), and certain close structural analogues (guanidinoacetic acid, β‐guani‐dinopropionic acid and,β‐hydroxy‐GAB A) were effective inhibitors of uptake. The inhibition with all these compounds, however, was at high concentrations (5 × 10−4to 10−3m) which limited their usefulness for physiological studies.A separate uptake mechanism for glutamate was found in the lobster nerve‐muscle preparations. This process was not described in detail, but certain properties are similar to those of the GABA transport system.The cellular location of the GABA uptake system remains unknown. By analogy with noradrenaline inactivation, however, it is postulated that uptake could serve to terminate the physiological actions of GABA by rapidly removing it from its sites of

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1968.tb08960.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—(1) The effects of thiamine deficiency as produced by pyrithiamine injections have been studied in the weanling mouse. Selected metabolites were measured in extracts from brain and liver of quick‐frozen animals. Pyruvate and α‐oxoglutarate dehydrogenases and transketolase were also measured.(2) In deficient brain, pyruvate and α‐oxoglutarate levels were greatly increased. Xylulose‐5‐P and 6‐P‐gluconate were more than doubled. Lactate, glucose‐6‐P, glucose and P‐creatine were moderately elevated, and ATP was increased a little. Glutamate was depressed.(3) In deficient liver, α‐oxoglutarate was much increased and ATP was twice normal. Glycogen, glucose, glucose‐6‐P, 6‐P‐gluconate, pyruvate, and glutamate were not different from the controls. Lactate was depressed.(4) Pyruvate dehydrogenase activity was reduced to 25 per cent or less in brain and liver. Transketolase and α‐oxoglutarate dehydrogenase activities were reduced to 50 per cent in both organs.(5) Thiamine treatment, within 5 hr, largely reversed the metabolite changes brought on by pyrithiamine in brain. At the same time pyruvate and α‐oxoglutarate dehydrogenase activities were increased 60 per cent or more in both brain and liver. Transketolase activity in liver was only increased 20 per cent at this time, however, and in brain was unchanged.(6) The results are interpreted to indicate that inhibition of pyruvate and α‐oxoglutarate dehydrogenases in brain is sufficient to depressin vivofunction. The same seems true for the inhibition of α‐oxoglutarate dehydrogenase in liver. However, the changes seen in brain 6‐P‐gluconate and xyluIose‐5‐P probably depend on factors other than, or in addition to, the decrease in transketolase activity. It seems worthy of emphasis that in spite of the partial metabolic block

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1968.tb08961.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—The rate of incorporation of [35S]methionine and the turnover rate of proteins in spinal motoneurons were studied in adolescent and old rats. The radioactivity of proteins was estimated by quantitative autoradiography and direct counting of beta radiation from samples of neurons isolated by free hand dissection. Both methods showed that the rate of incorporation into spinal motoneurons was significantly lower in old animals. By measuring the turnover rate of proteins in spinal motoneurons at least two protein components could be distinguished by their different turnover rates. The short‐lived component had an average half‐life of 2‐2‐2‐8 days, the long‐lived protein component had an average half‐life of 27‐38 days. Neither in the short‐lived component, nor in the long‐lived component was it possible to detect a significant difference between ad

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1968.tb08962.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY