摘要:

Abstract—l‐Glutamate 1‐carboxy‐lyase (EC 4.1.1.15) (GAD) and 4‐aminobutyrate‐2‐oxo‐glutarate aminotransferase (EC 2.6.1.19) (GABA‐T) have been purified from mouse brain (Wuet al.1973; Schousboeet al., 1973) and their properties have been extensively studied (Wu&Roberts, 1974; Schousboeet al., 1974). The above enzymes were prepared from a water lysate of crude mitochondrial fraction, which accounted for only 25–30% of total GAD or GABA‐T activities in brain. A procedure has been developed which liberates approx 85% of total GAD and GABA‐T activities into supernatant. Two distinct, well‐separated peaks with GAD activity and a single peak with GABA‐T activity were observed when a concentrated extract from brain of adult or newborn mice was chromatographed on Sephadex G‐200 or Bio‐Gel A–1.5 m. The first peak appeared in the void volume and is. therefore. an entity of high molecular weight. The second peak gave elution characteristics which were identical to those of the enzyme that had been purified previously (mol wt = 85,000). These two GAD peaks were also clearly separated on polyacrylamide gel electrophoresis. The GAD activities in the two peaks showed similar pH profiles (optimum, 6.5).Kmvalues (1–2 mM), immunodiffusion patterns and inhibitions by anti‐GAD IgG prepared against GAD purified from synaptosome‐containing crude mitochondrial fraction (60–80%). The physiological implications of high molecular weight and low mo

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb10390.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—The noradrenergic cyclic AMP generating system in slices of the limbic forebrain of rats displays characteristics which are compatible with those of a central NE receptor. The cyclic AMP response to aKmaxconcentration of NE (concentration of NE which elicits maximal increase in the level of cyclic AMP) is significantly enhanced in slices from reserpinized animals, although theKavalue of NE (concentration of NE eliciting half‐maximum response) was not significantly changed. Chemosympathectomy with 6‐hydroxydopamine (6‐OHDA) significantly enhanced the activity of the system to NE and isoproterenol but not to adenosine and reduced theKavalue for NE. The changes in the reactivity of the cyclic AMP generating system following 6‐OHDA administration appear to be related to a decrease in the availability of NE and not to that of other neurotransmitters as protection by desipramine (DMI) of noradrenergic neurons against the neurotoxic action of 6‐OHDA prevented the development of supersensitivity to NE. Conversely, and independent of the actual concentration of NE in brain tissue, a persistent increase in the availability of NE caused by prolonged MAO inhibition lead to a marked decrease in the reactivity of the cyclic AMP generating system. The results provide further evidence for a regulatory mechanism in the CNS involving the noradrenergic receptor that adapts its sensitivity to NE in a manner inversely related to the degree of its stimulation by the ca

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb10391.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—The synthesis of γ‐aminobutyric acid (GABA) in mouse brain was decreased by treatment of the animals with pyridoxal phosphate‐ γ‐glutamylhydrazone, an inhibitor of glutamate decarboxylasein vivo.Under these experimental conditions the following parameters were studied: (1) the incorporation of labeled leucinein vivo, into protein of brain subcellular fractions; (2) the brain polysome profile; (3) the incorporation of labeled leucine into proteinin vitro, in ribosomal preparations isolated from brain tissue. In other experiments, GABA synthesis was also decreased in brain cortex slices by preincubation with aminooxyacetic acid. The incorporation of [3H]leucine or [14C]leucine into protein in these slices was studied, and samples from the proteins were subjected to acrylamide‐sodium dodecylsulfate gel electrophoresis. Radioactivity was counted in slices of the gel. The results of the experimentsin vivoandin vitroindicate that the previously reported decrease of protein synthesis induced by an inhibition of GABA synthesis affects proteins of all subcellular fractions and all populations of protein as separated by gel electrophoresis. The polysome profile from brains of mice with decreased GABA synthesis was similar to that of control mice. This result differs from that found when brain protein synthesis is inhibited by dopamine an

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb10392.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—In the striatum of the newborn rat, the activity of tyrosine hydroxylase, the concentration of dopamine and the activity of the synaptosomal high‐affinity uptake process for dopamine is 10% of that of the adult; there is a linear and closely associated increase in all three parameters during maturation, achieving 75% of adult levels by 4 weeks after birth. In contrast, the specific activity of choline acetyltransferase exhibits a more delayed developmental rise commencing 1 week after birth; the concentration of acetylcholine is disproportionately high in the neonatal striatum and precedes the developmental increase in the activity of choline acetyltransferase. At birth, the specific activity of dopamine‐sensitive adenylate cyclase is 20% of that of the adult striatum and achieves adult activity by 4 weeks after birth. Pretreatment with the neuroleptic, fluphenazinc. does not reduce the striatal content of acetylcholine until 8 days after birth. It is postulated that dopaminergic influences on cholinergic neuronal activity appear when the cholinergic neurons in the striatum cease dividing and start differenti

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb10393.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—The lipid composition and metabolism of confluent cultures of cells derived from newborn hamster brain and having morphology characteristic of immature astrocytes or spongioblasts was investigated and compared to that of newborn hamster brain dispersions and cloned glioma cells (C6). The cells displayed stable morphology for at least 30 subcultures; thereafter spontaneous transformation occurred. No appreciable changes were observed in either composition or metabolic characteristics of any major neutral lipid or phospholipid class in successive subcultures or following transformation. The overall lipid composition of the hamster astrocyte cultures closely resembled that of newborn hamster brain, but the phospholipid composition showed substantial differences. The cells contained as a percent of lipid P relatively more ethanolamine plasmalogen, choline plasmalogen and sphingomyelin and somewhat less phosphatidylcholine and phosphatidylethanolamine. The phospholipids of the hamster astrocyte and C6 cells were similar. Of the lipid precursors examined, [U‐14C]glucose was incorporated best into all preparations. C6 glioma cells incorporated both [U‐14C]glucose and [1‐14C]acetate most actively. From 69–88% of32P incorporated into hamster astrocyte phospholipids was present in choline phosphoglycerides, whereas the corresonding figure for hamster brain dispersions was 53%. The ratio of specific activities of phosphatidylcholine to phosphatidylinositol was substantially higher in the cultured cells than in the brain preparations. The small pool of choline plasmalogen in the hamster astrocytes usually achieved the highest specific activity of any phospholipid. When [U‐14C]glucose and [1‐14C]acetate were precursors, the bulk of label in the astrocytes appeared in choline phosphoglycerides and triacyglycerol. Our results indicate that the hamster astrocyte cell line as grown expresses distinctive features of lipid composition and metabolism which are nearly constant through man

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb10394.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—Proteins undergoing rapid axonal transport in the garfish olfactory nerve were examined by sodium dodecyl sulphate gel electrophoresis. The distribution of polypeptides and the extent of their labeling by transported molecules was determined in several nerve subfractions including: total particulate, total membrane, mitochondrial and two membrane subfractions rich in axolemma. The polypeptide composition of the various fractions was found to be relatively similar, with each showing a major protein with an estimated MW of 58,000. Specific differences in the concentrations of certain proteins were noted between fractions, including differences between the lower and higher density axolemma rich subfractions. Axonally transported radioactivity was predominantly localized among high molecular weight proteins, with all fractions, except mitochondrial pellet, displaying a major peak of radioactivity centered at 126,000‐MW. Several major proteins including the 58,000‐MW band were labeled by rapid transport to a much smaller extent. Certain labeled peaks were found to be concentrated in individual fractions, particularly a polypeptide (MW 35,000) more predominantly found in the lower density axolemma rich fraction.Systemic labeling of the nerve is found to give a general distribution of radioactivity on gels, which is clearly different from the pattern obtained after axonal transport lab

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb10395.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—The content of γ‐aminobutyric acid (GABA), but not glutamate, and the uptake of [3H]GABA by synaptosomes was reduced in the lumbar cord of guinea pigs during experimental allergic encephalomyelitis (EAE)‐induced hind limb paralysis. The decrease in glutamate decarboxylase (GAD) activity in the dorsal and ventral parts of the cord was confined to the lumbar region, and appeared before the onset of motor dysfunction. No change in activity was found in the thoracic cord, motor cortex, cerebellum or striatum. GAD activity remained unchanged in animals which were EAE‐sensitized but did not develop the clinical symptoms. Choline acetyltransferase activity did not change in the cord during p

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb10396.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—Indoleamine‐N‐methyltransferase (INMT) activity in brain and other tissues from various species was investigated. Using conventional radiochemical assay techniques it was found that apparent INMT activity in brain was linear with time and concentration of protein, indoleamine substrate and methyl donor (S‐adenosylmethionine). However, examination of the reaction products by means of exhaustive thin‐layer chromatographic analysis failed to reveal evidence of significantN‐methylation of tryptamine orN‐methyltryptamine byS‐adenosylmethionine. By contrast, with other tissues, notably rabbit lung.N‐methylation of indoleamine was reproducibly demonstrable. The significance of these findings with reference to the transmethylation hypothesis of schizophr

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb10397.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—The distribution of carbonic anhydrase was examined in subcellular fractions of perfused rat brain and compared with those of markers for cytosol (lactic dehydrogenase), mitochondrial matrix (glutamic dehydrogenase), and mitochondrial membranes (succinic dehydrogenase). About half of the total carbonic anhydrase was found in particulate fractions, with the greatest part of this in the crude mitochondrial fraction. This fraction was separated into its components on a discontinuous sucrose gradient either as such or after isotonic mechanical disruption with a French pressure cell, and the resultant fractions were characterized by electron microscopy and by assay of marker enzymes.Carbonic anhydrase was solubilized by mechanical disruption, but not to the same extent as lactic dehydrogenase. The highest specific activity for carbonic anhydrase was found in the myelin fraction of the gradient. A mitochondrial locus for carbonic anhydrase is unlikely, but the presence of the enzyme in synaptosomes remains in question.Addition of soluble carbonic anhydrase did not significantly increase the activity of particulate fractions. Treatment of particulate fractions with detergent was necessary to reveal latent activity; this procedure resulted in a more than ten‐fold increase in the measurable carbonic anhydrase activity of myelin fragme

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb10398.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—Guanylate cyclase activity of dark‐adapted bovine rod outer segments demonstrates a biphasic pattern upon exposure to light. By 10 s of illumination, activity is 20% lower than that observed in dark‐adapted outer segments. Activity subsequently increases and then slowly declines to two‐thirds of the original activity after 10 min of illumination. In the presence of GTP or ATP, hydrolysis of cyclic GMP is rapidly enhanced by exposure of outer segments to light; the magnitude of this effect is dependent on the amount of substrate present. The rapid effects of light on synthesis and degradation of cyclic GMP indicate that these reactions may be involved in the visual process. The concentration of guanosine 3′:5′‐cyclic monophosphate (cyclic GMP) is extraordinarily high in dark‐adapted bovine rod outer segments and is at least 100‐fold that of adenosine 3′:5′‐cyclic monophosphate (cyclic AMP). No significant decrease in the level of cyclic GMP or cyclic AMP was observed however upon exposure of dark‐adapte

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb10399.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY