摘要:

Abstract—A consistent observation in particular regions of brains of persons having died with Huntington's disease (HD) is a reduction in the concentration of γ‐aminobutyric acid (GABA) and a decrease in the activity of its synthetic enzyme, glutamate decarboxylase (EC 4.1.4.15). GABA levels are also reduced in HD cerebrospinal fluids. This study suggests that skin fibroblasts obtained from persons with HD can be used to study their GABA system. A rapid and specific assay for [14C]glutamate– [14C]GABA based on Aminex A‐7 chromatography has been developed. Cell monolayers and homogenates of HD cells convert [14C]glutamate to [14C]GABA. GABA synthesis by HD cell homogenates is pyridoxal dependent and is inhibited by 1 mm‐aminooxyacetic acid. GABA synthesis by HD and control cell homogenates also show the same thermal sensitivity as rat brain GAD. When compared to non‐HD human cells the HD cells reveal disturbances in the non‐neuronal GABA metabolic pathway. Concentrated HD cell homogenates synthesize approx 3 times the amount of GABA as control cells. When diluted both extracts made similar amounts of GABA. Synthesis of GABA by HD cell homogenates is not inhibited by cysteine sulfinate. Decarboxylation of glutamate in these cells is therefore most likely due to glutamate decarboxylase and not cysteine sulfinate decarboxylase. HD cells in monolayer also synthesize 3 times the amount of GABA as compared to control cells. In addition, glutamate upake is altered in HD cells. This report indicates there may be a different pattern of enzyme regulation between HD and

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05234.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—AChE activity and protein content in chicken ALD and PLD muscles was studied during pre‐ and postnatal development. Protein content in both muscles increased whereas AChE activity increased in ALD and decreased in PLD during development. All studied values reached the steady‐state 3 weeks after hatching.Electrophoretic separation of the samples showed three molecular forms of AChE present in both adult ALD and PLD muscles. Two molecular forms in ALD muscle increased slowly, one form quickly. On the other hand, the activity of AChE forms in PLD muscle decreased with different rates. It appears from these results that the multiple molecular forms of AChE in muscles are not of the same physiological impor

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05235.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—In cell cultures of glial character derived from perinatal mouse brain adenosine elicits two effects. (a) At submicromolar concentrations It inhibits the increase in the intracellular level of cyclic AMP caused by β‐adrenoceptor agonists. (b) At concentrations above micromolar it increases the level of cyclic AMP in the cultures. These two effects are mediated by two different adenosine receptors present on the outer surface of the cells. This is concluded from the following evidence. (a) Both effects are antagonized by methylxanthines but not by blockage of adenosine uptake or inhibition of phosphodiesterase activity. (b) In both cases activity depends on the integrity of the ribose moiety of the nucleotide. Substituents of the purine system are tolerated comparatively well. (c) The order of potency of adenosine analogues is different for the two effects. We suggest the name A1 receptors for those that mediate the inhibition and A2 for those that mediate the stimulation of cyclic AMP accumula

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05236.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Suitable preparations forin vitrostudies of the composite glucose and energy metabolism of peripheral nerve axons and Schwann cells have not been available. Methods are described for the preparation and incubation of a defined segment of a rabbit sciatic nerve fascicle, free of epineurial contamination, but with an intact perineurial membrane; removing the perineurium provides in addition an‘endoneurial’preparation. Conditions were selected for incubating each preparation with glucose that maintained stable P‐creatine and ATP concentrations and a stable rate of O2uptake; under these conditions the preparations retained an unaltered EM appearance during a 2‐h incubation. Glucose diffusion into the endoneurial compartment of the fascicle is restricted, possibly by the perineurial membrane, and a higher medium glucose concentration (20 mM) was required to maintain a steady state of energy metabolism in this preparation than in the‘endoneurial’preparation, which was incubated with 5 mwglucose. The‘endoneurial’preparation required 0.50 mm‐myoinositol in the medium to prevent a decrease in tissue free myoinositol and a slow decrease in O2uptake, which occurred when it was omitted. Under the incubation conditions selected the glucose concentrations in the‘endoneurial’preparation and in the endoneurial compartment of the fascicle were reasonably similar, and the preparations had similar rates of respiration, similar estimated rates of glucose utilization, and similar relative rates of respiration and lactate production. The preparations derive the major fraction of their energy requirements from respiration. Their rates of O2uptake are 60% higher than the previous indirect estimate of O2uptake in whole rabbit tibial nervein situ. Constant rates of incorporation of14C from [U‐14C]glucose into CO2and total lipid were observed in the‘endoneurial’preparation after a 15‐min equilibration period. The preparations reported provide suitable tools forin vitrostudies of peripheral nerve meta

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05237.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Brain RNP particles were characterized to determine whether they play a role in the regulation of brain protein synthesis. RNP particles were isolated from the postribosomal supernatant of cerebral hemispheres of young rabbits, employing conditions which minimize adventitious protein‐RNA interactions. Brain RNP particles consist of a different set of proteins compared to proteins associated with either 40 and 60s ribosomal subunits or polysomal mRNA. Poly(A+)mRNA from brain RNP particles stimulates the incorporation of [35S]methionine in a wheat embryo cell‐free system and codes for a different set of proteins compared to poly(A+)mRNA isolated from polysomes (with some overlap; i.e. mRNA coding for brain‐specific S100 protein is present in both RNP particles and polysomes).Addition of total brain RNP particles to a cell‐free wheat embryo system inhibits the endogenous incorporation of [35S]methionine. Total RNP particles were fractionated by sucrose density gradient centrifugation into a‘light’and a‘heavy’fraction. The light RNP fraction inhibited while the heavy RNP fraction stimulated protein synthesis in the wheat embryo cell‐free system. Analysis of the protein composition of fractionated RNP particles revealed that the light and heavy RNP particles contained different sets of proteins. Together these results suggested that one class of brain RNP particles may contain a translational inhibitor and may be involved in the regulation of protein syn

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05238.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—The incubation of brain stem slices from adult rats in a K+‐enriched medium containing a 5‐HT uptake inhibitor (fluoxetine) significantly increased their capacity to synthesize 5‐HT from tryptophan. The K+‐induced stimulation of 5‐HT synthesis was at least partly dependent on the depletion of the indoleamine in tissues since: (1) a good correlation was found between the respective changes in 5‐HT release and synthesis evoked by high K+concentrations in the presence of various 5‐HT uptake inhibitors; (2) the modifications in endogenous 5‐HT levels produced by in vim treatments with drugs (reserpine, pargyline) or by incubating slices with 5‐HT altered the stimulating effect of high K+concentrations and fluoxetine on 5‐HT synthesis; (3) the replacement of Ca2+by Co2+(4 mM) or EGTA (0.1 mM) in the incubating medium completely prevented the increased 5‐HT release and synthesis evoked by high K+concentrations and fluoxetine.The extraction of tryptophan hydroxylase from incubated tissues revealed that the increased 5‐HT synthesis occurring in K+‐enriched medium was associated with an activation of this enzyme. Kinetic analyses indicated that this activation resulted from an increase in the Vmaxof tryptophan hydroxylase, its apparent affinities for both tryptophan and 6‐MPH4being not significantly affected. In contrast to the tryptophan hydroxylase from tissues incubated in normal physiological medium, the activated enzyme from tissues depolarized by K+was hardly stimulated by Ca2+‐mediated phosphorylating conditions. This led to the proposition of a hypothetical model by which the Ca2+influx produced by the neuronal depolarization would trigger the activity of a Ca2+‐dependent protein kinase capable of activating tryptophan hydroxylase. Although this sequence is still largely speculative it must be emphasized that, as expected from such a model, the regional differences in the K+‐evoked activation of tryptophan hydroxylase in slices (cerebral cortex>brain stem>spinal cord) were parallel to those of the Ca2+‐dependent protein phosphorylation (r= 0.92) and those of the activating effect of phosphorylating conditions on sol

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05239.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Several parameters of GABA Auxes across the synaptosomal membrane were studied using synaptosomes prepared from the brain of immature (8‐day‐old) rats. The following aspects of GABA carrier‐mediated transport were similar in immature and mature synaptosomes: (1) magnitude of [3H]GABA accumulation; (2) GABA homoexchange in normal ionic conditions; (3) GABA homoexchange in the presence of cationic fluxes (Na+and Ca2+influx, K+efflux) characteristic of physiological depolarization. As in adult synaptosomes (Levi&Raiteri, 1978), in these conditions the stoichiometry of GABA homoexchange was in the direction of net outward transport (efflux>influx).The essential differences between the behaviour of 8‐day‐old and adult synaptosomes were the following: (1) β‐alanine (a glial uptake inhibitor) inhibited GABA uptake in immature synaptosomes (the inhibition being greater in crude than in purified preparations) and was without a significant effect in adult synaptosomes. DABA and ACHC (two neuronal uptake inhibitors) depressed GABA uptake more efficiently in purified than in crude immature synaptosomes, but were as effective in crude and purified nerve endings from adult animals. The data suggest a greater uptake of GABA in the‘gliosomes’contaminating the synaptosomal preparations from immature animals. (2) In immature synaptosomes prelabelled with [3H]GABA the specific radioactivity of the GABA released spontaneously or by heteroexchange (with 300 μm‐OH‐GABA) was the same as that present in synaptosomes, while in adult synaptosomes OH‐GABA released GABA with increased specific radioactivity. The data suggest a homogeneous distribution of the [3H]GABA taken up within the endogenous GABA pool in immature, but not in mature synaptosomes. (3) In immature synaptosomes the release of GABA (radioactive and endogenous) induced by depolarization with high KC was not potentiated by Ca2+, unless the synaptosomes had been previously depleted of Na+These data suggest that, although a Ca2+sensitive pool of GABA may be present, this pool is not susceptible to being released in normal conditions, probably because the high intrasynaptosomal Na+level prevents a sufficient depolarization. The possible significance of these findings in terms of functional activity of GABAergic neurotransmission in the im

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05240.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Anterograde and retrograde flux of axonal transported glycoproteins were examined in streptozotocin diabetic rats with 4 weeks’duration of the metabolic derangement.[3H]Fucose and [14C]NeuNAc were injected into the fifth lumbar root ganglion and the accumulation of TCA‐PTA insoluble activity proximal and distal to a sciatic nerve ligature was measured.Accumulation of glycoproteins during 2 h collection periods was decreased distal to a ligature in diabetic animals whereas no abnormality of proximal accumulation was observed. These findings demonstrate an abnormality of the retrograde transport of glycoproteins in early experimental dia

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05241.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—The acylation of lysophosphatidylserine, prepared by snake venom digestion of phosphatidylserine, by rat brain microsomes is described. Acylation was monitored by spectrophotometric assay and by measuring the incorporation of radioactively labelled acyl CoA thioesters. Acylation was time dependent, showed an approximately linear response to enzyme concentration and had a pH optimum of 9.0. Maximum acylation was attained at a concentration of about 100 μM for lysophosphatidylserine and about 40μM for acyl CoA thioesters. Positional distribution studies with [14C]oleoyl CoA and [14C]arachidonoyl CoA showed incorporation was predominantly at position ‐2, but with significant labelling at position–1, particularly with oleoyl CoA, possibly as a result of isomerization of the 1–acyl isomer of lysophosphatidylserine. Both saturated and unsaturated thioesters could serve as acyl group donors. Myristoyl CoA was considerably superior to palmitoyl CoA and stearoyl CoA, which were poor acyl group donors. Some selectivity was shown among the long chain unsaturated thioesters, linoleoyl, linolenoyl and arachidonoyl CoA being the most effective acylating agents. Although docosahexaenoic acid is a major unsaturated fatty acid in brain phosphatidylserine, its CoA ester was a relatively poor acyl group donor. Relative acylation rates remained essentially constant over a wide range of lysophosphatidylserine concentrations. It is concluded that acyl transfer mechanisms are active in brain for the regulation of the fatty acid profile of phosphati

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05242.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—To determine whether changes in cerebral polyamines might mediate previously reported ACTH‐induced changes in brain biochemistry and behavior, the cerebral content of polyamines was examined following ACTH treatment. Male CD‐1 mice were injected daily for 3 days with long‐acting (zinc phosphate) preparations of ACTH1–24(1 μg/g) or ACTH4–10(0.33 μg/g) and killed 24 h after the last injection. Putrescine, spermidine and spermine contents were determined by high pressure liquid chromatography. Putrescine content was significantly elevated in all brain regions by ACTH1–24(approx 50%), and in the telencephalon by ACTH4–10At the dose tested ACTH4–10was less effective than ACTH1–24. Telencephalic spermidine was also elevated (10%)by ACTH1–24, but spermine content was not altered in any brain region. One injection of the long‐acting ACTH1–24preparation elevated telencephalic putrescine (49%) 24 h post‐injection. ACTH1–24(1 μg/g) in saline produced a peak elevation of all three telencephalic polyamines 6 h post‐injection, while in the liver only putrescine was significantly elevated and reached a peak at 10h. Neither plasma polyamine nor ornithine concentrations were significantly altered by any of the treatments. Corticosterone, in both single and multiple injection regimens, failed to alter telencephalic polyamine content. Adrenalectomy, however, prevented the ACTH1–24‐induced increase in telencephalic polyamines. It is concluded that ACTH acts directly in the brain to increase cerebral polyamine concentrations. The possibility that adrenal hormones exert permissi

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05243.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY