摘要:

Abstract—Frozen and unfrozen bovine brains were used to determine the extent ofin situdegradation of myelin basic protein. The following three parameters were investigated. (1) The time interval between death and sampling of the tissue, (2) the effective temperature of the tissue during this interval, and (3) the effect of freezing and thawing on the subsequent autolysis of myelin basic protein. Polyacrylamide gel electrophoresis was carried out on unfrozen white matter solubilized with phenol‐formic acid–water. The resulting electrophoretic pattern showed no qualitative changes in the myelin basic protein after tissue incubation at 4° or 23°C for up to 24 h. When myelin basic protein was extracted, purified and quantitated, there was no apparent decrease within 24 h of incubation at 23°C. However, if the tissue was frozen and thawed prior to incubation, there was a rapid disappearance of myelin basic protein such that only 10% remained after 24 h of incubation. Basic protein extracted from frozen or unfrozen tissue that had undergone autolysis for up to 24 h was found to be encephalitogenic in guinea pigs. Electron microscopy of frozen and thawed material showed separation and fraying of myelin lamellae. It is postulated that the above morphological changes probably render the basic protein readily accessible to proteolytic

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb06952.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—(1) The sum of the values of total (tissue + medium) amino acid‐Nof glutamate, glutamine, γ‐aminobutyrate, and aspartate (referred to as the glutamate system) and of ammonia‐Nof incubated rat brain cortex slices is approximately constant under a variety of metabolic conditions (presence or absence of glucose or of oxygen or in the presence of metabolic inhibitors such as aminooxyacetate, malonate, methionine sulfoximine, fluoroacetate, ouabain, 2:4 dinitrophenol, or Amytal). Fluctuations in the value of one constituent are compensated by fluctuations in the values of other constituents. The same applies to infant rat brain cortex slices and to rat brain synaptosome preparations. It is suggested that the constancy of the glutamate‐ammonia system implies a coupling of neurons and glia in such a manner that glutamate released from the neurons during excitation is taken up by the glia and there converted to glutamine. The glutamine is returned to the neurons where it is hydrolysed to glutamate and ammonia. The glia, on this view, exercise an important buffering effect on the extracellular content of the excitatory amino acid, glutamate, and possibly on that of other functionally active amino acids emanating from the neurons. (2) The magnitude of the glutamate‐ammonia system in the infant rat brain cortex is about 43% of that in the adult. It is suggested that, with maturity, the development of the glutamate‐ammonia system is linked with the development of the citric acid cycle of operations. (3) The ammonia in the system is tightly linked to the activity of the ATP‐controlled glutamine synthetase. (4) Proteolytic ammonia and amino acids are formed, during the incubation, to values that seem to be independent of a wide variety of metabolic conditions. The total value is approximately 10 μmol/g in the first h of incubation. (5) As the ammonium ion is necessary for the return of glutamate to the neuron in the form of glutamine, it is inferred that the ion plays a functional role in the nervous system by helping to maintain the steady state of glutam

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb06953.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—Radioactively labelled fatty acids were incubated with interfascicular oligodendroglial preparations isolated from 9 month fetal and adult bovine CNS white matter to study their metabolism by these cells. Of the various acids studied, the uptake was greatest for palmitic acid and decreased with decreasing chain length. Laurie acid was converted to the greatest extent to other fatty acids. The incorporation of oleic and linoleic acids in the oligodendroglia from both the fetal and adult brains was higher than that of linolenic acid. Fatty acids underwent chain elongation, desaturation and oxidation. Oleic acid was elongated to nervonic acid. Fatty acids were incorporated into both cerebrosides and phospholipids, with preferential incorporation into ethanolamine phosphoglycerid

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb06954.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—This paper specifies methodology for the sequential determination of manganese and catecholamines in selfsame brain samples and shows correlations between them. Small samples were obtained from five regions of brain of cats that had received either saline or levodopa. The doses of levodopa were varied so that although all animals reacted, some developed dyskinesia while others did not. Each sample was first analyzed nondestructively for manganese and then destructively for dopa and dopamine; thus errors inherent in analysing separate samples, due to the structural heterogeneity of the brain, were avoided. Statistically significant correlations were found (1) between levodopa‐induced dyskinesia and the concentrations of dopamine and manganese in some of the regions analysed, and (2) between the concentrations of dopamine and of manganese in the caudates of the cats receiving the highest doses of levod

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb06955.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—Copper deficiency was produced in developing rats by feeding a low copper diet to rats during gestation and lactation and providing the offspring the same diet. The progeny developed similar to those of an earlier model based on preconception depletion followed by marginal supplementation during gestation. Copper levels were greatly reduced in the brain, iron levels were slightly depressed, and no differences in zinc content were found. Electron microscopic examination of brain tissue revealed the presence of enlarge mitochondria from copper‐deficient animals. Isolated mitochondria from copper‐deficient rats showed a 30% reduction in the rate of both succinate and glutamate oxidation, and for glutamate, the respiratory control ratio (RCR) was decreased by 60%. Difference spectra displayed a four‐fold reduction in cytochromea+a3and slight increases in cytochromeb,c1andc. Enzyme analysis of isolated mitochondria revealed a five‐fold decrease in cytochrome oxidase, slight increases in succinic dehydrogenase and fumarase, and small decreases in hexokinase and monoamine oxidase. No difference in peroxidation of brain lipids was evident. Determination of metabolites from fast frozen tissue suggested that the copper‐deficient brain was in a more reduced state based on a doubling of both the lactate/pyruvate and α‐glycerol‐P/dihydroxyacetone‐Pratios. Creatine‐P, ATP, and ADP level

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb06956.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—Gangliosides were isolated from myelin prepared from mouse brains of different ages (23 to 490 days). Quantitative estimation of lipid‐bound sialic acid levels indicated a gradual increase from 560 μg/g of myelin at 23 days to about 1200 μg/g of myelin at older ages. The major ganglioside in all myelin preparations was the monosialoganglioside G4(GM1). However, considerable amounts of di‐ and trisialo species also were found in myelin from young animals. In contrast to human myelin in which the monosialoganglioside, sialosylgalactosylceramide (G7) was highly enriched (Ledeenet al., 1973), a much smaller enrichment of this ganglioside was noticed in mouse brain myelin. Ganglioside G7was not detectable in myelin until the animals were 35 days old, and showed a slight increase with increasing age after that. The results strongly indicated that the concentration of G7in myelin is species specific and age dependent. The study also demonstrated that the ganglioside accretion in developing mouse brain myelin was attributable to the enrichment of monosialogangliosides G4(GM1), G5(GM2) and G7at the expense of polysialogangl

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb06957.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—We have previously described a 5‐fluorodeoxyuridine (FUdR) resistant variant of mouse neuroblastoma possessing an 8‐fold elevation in methylenetetrahydrofolate: dUrd‐5′‐P C‐methyltransferase (EC2.1.1.b) [trivial name: thymidylate synthetase] specific activity relative to that of the sensitive parental clone. This increased specific activity is not associated with a change in cytoplasmic inhibitors or activators, a decreased degradation rate of the enzyme, or the synthesis of a new species with an increasedVmax, but appears to represent an increased synthesis of the enzyme species found in the sensitive parental clone. More resistant cell populations demonstrate even higher specific activities of this enzyme.The enzymatic activities from both the FUdR sensitive and resistant cells have identical stabilities to sonication, freezing, heat, urea, and sodium dodecyl sulfate, are equally and strongly inhibited by 5‐fluorodeoxyuridine‐5′‐phosphate, and have the same affinity for the substrate 2′‐deoxyuridine‐5′‐phosphate (Km= 1·4 = 10−6m). Both are stimulated by the addition of mercaptans and partially protected from heat denaturation in the presence of substrate.Unlike Don Chinese hamster cells (Conrad&Ruddle1972) an actinomycindpulse of neuroblastoma cells in monolayer culture did not increase the thymidylate synthetase specific activity. Mixed growth of FUdR sensitive and resistant cells

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb06958.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—A method is described for quantifying the GABA distribution in cat spinal cord at 200–500 μn resolution. Isolated spinal cord (L5–S1) was frozen and sectioned at about 150 μm thickness. The frozen tissue section was cut into 200 or 500 μm square blocks. The GABA content of each square tissue block was determined by enzymic micromethods and GABA distribution was mapped quantitatively. Average GABA concentrations were: 0·4 mmol/l. in white matter, 1·2 mmol/l. in ventral horn and 1·7 mmol/l. in dorsal horn. The highest concentrations of GABA (2–3 mmol/l.) were found in the dorsolateral part of dorsal horn. In order to destroy the interneurons of dorsal horn, the blood vessels supplying the dorsal horn of the lumbar enlargement were unilaterally cauterized. Seven to 30 days after operation, both the size of dorsal root potential and the GABA level in the dorsal horn were markedly reduced on the cauterized side. These results suggest that GABA is highly concentrated in the interneurons of dorsal horn and functions as a transmitter of presynapt

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb06959.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—The changes in phospholipids and gangliosides during ontogenesis of chick retina have been compared with those in brain. Three phases of accumulation of ganglioside NeuNAc in the retina were detected. In contrast, brain NeuNAc rapidly increased during embryonic life until hatching, followed by a slower increase up to the adult stage. The phospholipid changes in retina and in brain occur in a‐similar manner to the variations observed for gangliosides, however in retina the changes of phospholipid content are less marked than in brain, during embryonic life. There were marked changes in the retina and brain ganglioside patterns with age. Gd3and Gd1bdecreased rapidly in per cent; correspondingly, Gd1aincreased during embryonic life and became the major ganglioside in place of Gd3. There was a similarity between ganglioside patterns of chick retina and brain. Except for some slight variations during embryonic life, the retinal phospholipid pattern did not change noticea

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb06960.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—Results confirm previous findings that after injecting rats with 50mg/kg tryptophan the percentage increase of 5‐hydroxytryptamine metabolism (as shown by 5‐hydroxyindolylacetic acid changes) is particularly small in the hypothalamus. However, 15–30 min after tryptophan injection (when brain 5‐hydroxytryptamine changes were maximal) percentage 5‐hydroxytryptamine increases in the hypothalamus and in the rest of the brain were comparable. The small 5‐hydroxyindolylacetic acid changes in the hypothalamus are consistent with a long 5‐hydroxytryptamine turnover time therein as indicated by experiments using pargyline or probenecid and by the relatively small increases of 5‐hydroxytryptamine after injecting tryptophan into tranylcypromine treated rats. When 5‐hydroxytryptamine synthesis was partially inhibited byp‐chlorophenylalanine and tryptophan was injected, there was a large percentage rise of hypothalamic 5‐hydroxytryptamine but the concentration found in rats given neither drug was not attained and 5‐hydroxyindolylacetic acid showed little change. Elsewhere in the brain 5‐hydroxytryptamine attained concentrations comparable to those in rats given neither drug and 5‐hydroxyindolylacetic acid rose considerably. Results are discussed in relation to the contributions made to brain 5‐hydroxytryptamine turnover by functiona

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb06961.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY