摘要:

Abstract—Various parameters of thein vitroincorporation of [14C]amino acids into protein by cell nuclei isolated and purified from rat brain and liver were investigated. Nuclei purified through 2.2msucrose solution were capable of amino acid incorporationin vitro; and washing procedure to eliminate hypertonic sucrose before incubation was essential since sucrose in high concentration was inhibitory. Microbial contamination was found to be a serious source of error and the use of sterile conditions for incubation were necessary to obtain reproducible and valid results. Using completely sterile conditions, Na+, K+, RNase, DNase, puromycin, cycloheximide and chloramphenicol were without any effect on the ability of brain and liver nuclei to incorporate labelled amino acids into protein. Results of time‐course and preincubation experiments revealed that some factors essential for amino acid incorporation pass out of the nucleus into the medium. In addition, approximately 15 per cent of the labelled nuclear proteins with higher specific radioactivity was recovered in the incubation medium. Incorporation of [14C]leucine was proportional to the concentration of labelled amino acid and to the number of nuclei, and it is suggested that carefully controlled conditions of incubation are essential to obtain valid comparisons between different types of nuclei in terms of their relative abilities to incorporate amino acidsin vitro.No evidence was obtained indicating isotope dilution phenomenon in these experiments. Whether or notin vitroincorporation of amino acid by nuclei represents protein synthesis is discus

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb03809.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—The specific radioactivity of acetylcholine liberated from the surface of the rabbit occipital cortex has been compared with that of the underlying cortical synaptosomal and vesicular acetylcholine at varying times after the administration of [N‐Me‐3H]choline. Choline was administered by diffusion from solutions placed in cups formed by Perspex cylinders applied to the surface of the cortex. Acetylcholine was collected by diffusion into these cups. The specific radioactivity of the acetylcholine declined progressively. The effect of stimulation of afferent cholinergic pathways was to cause a fall in the specific radioactivity of the released acetylcholine. However this was always higher than that of the synaptosomal or vesicular acetylcholine as represented by fractions P2and D of the authors’fractionation scheme. It is concluded that acetylcholine released from the cortex must come from a store or stores more recently synthesized than the endogenous acetylcholine of these subcellular fr

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb03810.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—Two groups of totally adrenalectomized male rats (220‐260 g) were injected intraperitoneally with different amounts of [1,2‐3H] corticosterone. One group received 1 μg of hormone (50 μCi/μg), and the other received 20 μg (2·5 μCiμg). All animals were decapitated at 15 min and various tissues including the pituitary, cerebellum, pons‐medulla, cerebral cortex, hypothalamus, septal area, and hippocampus were assayed for radioactivity and protein content. In the 1‐μg group, the hippocampus contained more cpm/mg of protein (P<0·05) than all the other areas including the hypothalamus. The septal area and pituitary gland values were higher (P<0·05) than all the other areas except the hippocampus. In the 20‐μg group there was a significant reduction (P<0·05) in the values (cpm/mg of protein) for the hippocampus, septal area and cerebral cortex, but no change in the values for the pituitary, hypothalamus, and pons‐medulla. These data suggest that the hippocampus and septal area are primary target sites for corticosterone because they take up more hormone than other nervous tissue loci and demonstrate a limited capacity for hormonal uptake. The pituitary gland tends to concentrate the hormone but does not demonstrate a limited capacity for uptake. The hypothalamus does not concentrate the hormone or demonstrate a limited capacity for uptake, and the data suggest that it is not a primary targe

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb03811.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—Approximately 70 per cent of the total AChE of bovine brain tissue was solubilized by repeated homogenization and centrifugation in 0.32msucrose containing EDTA. After ammonium sulphate fractionation, application of the enzyme preparation to an agarose affinity gel column effected a 700‐fold purification. Subsequent molecular filtration separated three active forms of AChE with molecular weights of 130,000, 270,000 and 390,000 with an average specific activity of 575 mmol of acetylthiocholine hydrolysed/mg of protein/h. The complete procedure represented an approximate 23,000‐fold purification of the enzyme from that in the original tissue homogenate. The three forms of AChE exhibited certain differences in properties, including apparentKmvalues, pH optima and sensitivity to inhibitory agents. Ancillary studies on less purified enzyme preparations by use of polyacrylamide gel electrophoresis and isoelectric focusing techniques also suggested that brain AChE exists in multiple

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb03812.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—Studies of the brain glycogen concentration in the chick during the perinatal period showed that there was an increase immediately prior to hatching. This was followed by a pronounced decrease between 1 and 2 days after hatching. The decrease was most marked in the cerebellum. During ischaemia, the rate of glycogen depletion was greater in 1‐day‐old chicks than in 2‐ and 7‐day‐old birds. Brain glycogen concentration exhibited a circadian rhythm which was not closely related to changes in motor activity or body temperature. Exposure to a high environmental temperature (40°C) caused a depletion of glycogen, but exposure to a low temperature (2°C) had no effect. Four hours of hyperglycaemia resulted in a lowering of brain glycogen levels whereas hypoglycaemia was w

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb03813.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—In vivostudies have been made of the incorporation of radioactive thymidine into acid insoluble components of control and scrapie‐affected mouse brain. Experiments with hot trichloroacetic acid extracts of brain and with purified preparations of DNA have confirmed that there is an increased rate of DNA synthesis in scrapie brain which is entirely associated with nuclei. No increase was found in the rate of DNA synthesis in cytoplasmic fractions of scrapie brain. Hydroxyapatite chromatography of heat denatured and renatured DNA suggests that in scrapie brain there is a similar increase in the rates of synthesis of the poorly, moderately and highly reiterated (i.e. satellite) species of nuclear DNA. Experiments involving brain dissection indicate that the increased rate of DNA synthesis in scrapie does not take place exclusively in the subependymal layer of the lateral ventricles. From these and previously reported studies using radioautographic techniques it is concluded that the increased DNA synthesis in scrapie brain is not associated specifically with cells undergoing mito

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb03814.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—A method is described for the preparation of relatively pure cholinergic synaptosomes from bovine cervical sympathetic ganglia. After dispersion of the tissue by incubation with collagenase, differential centrifugation yielded a crude synaptosomal fraction (P2), which was further purified by centrifugation on sucrose or Ficoll‐sucrose density gradients. Assay of acetylcholine and choline acetyltransferase, and electron microscopy confirmed that presynaptic nerve endings survived the incubation procedure, appeared in theP2fraction and thereafter sedimented to a density of approx. 1.13 in sucrose and 1.06 in Ficoll‐sucrose. The washedP2fraction had an acetylcholine content of 2.3 nmol/mg of protein, which is at least three times higher than the corresponding fraction from

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb03815.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—Congenital tremor, type AIII, is characterized by partial agenesis of the white matter of the CNS affecting mainly the spinal cord. The percentage water content of the fresh cord is consistently higher than normal and other parts of the CNS are sporadically affected. The total lipid content (mg/g fresh tissue) is markedly decreased in the cord but brain stem and cerebellum are less severely deficient; the cerebrum is barely deficient. Total amounts of cholesterol, cerebroside and phospholipid (mmol/part) are significantly reduced predominantly in cerebellum, brain stem and cord. Total DNA and protein contents are decreased to a significant extent only in spinal cord. Broadly similar lipid changes are found in fixed tissues. The data are consistent with sub‐normal myelination, associated with a deficiency of oligodendrocy

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb03816.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—DOPA and 5‐hydroxytryptophan (5‐HTP) are generally supposed to be decarboxylated in mammalian tissues by a single enzyme, the two activities being present in constant ratio through a variety of purification procedures. It has now been shown that the ratio of activity of the liver enzyme towards the two substrates can be altered by mild treatments, such as might be used in solubilization of brain preparations. DOPA decarboxylase activity was preferentially inactivated by sodium dodecyl sulphate treatment, and 5‐HTP decarboxylation by urea.Previous reports that the two substrates show different pH optima but are mutually competitive, have been confirmed. TheKmof the enzyme towards 5‐HTP was lowest at pH 7.8 (the optimum pH for decarboxylation of this amino acid), but the variation with pH of theKmtowards DOPA was unrelated to the pH optimum for decarboxylation. There appeared to be no relation between the probable ionization state of the substrates and the pH dependence of the enzyme. Studies on the binding characteristics of the enzyme for the two products, dopamine and serotonin, did not show any specific saturable binding.It is proposed that the enzyme has a complex active site, with separate affinity sites for the two substrates, adjacent to a single catal

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb03817.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Abstract—A reduction in central and peripheral synthesis of noradrenaline has been demonstrated in mice hemizygous for the X‐linked brindled (Mobr) mutant in the mouse. The results are consistent with defective hydroxylation of dopamine to NA, arising either as a result of a primary genetic defect in the enzyme dopamine‐β‐hydroxylase or from the presence of a highly specific inhibitor of this enzyme in mutant mice. Associated with this deficiency of noradrenaline are an increase in the activity of tyrosine hydroxylase in the central nervous system and an increase in the active uptake of tyrosine (and other amino acids sharing a common uptake mechanism with tyrosine) across the blood‐bra

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb03818.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY