bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxygen Affinity of Tyrosine and Tryptophan Hydroxylases in Synaptosomes
Authors: Katz Ira R. 
Published: October 2006

Abstract: Tyrosine and tryptophan hydroxylase activities were studied in a synaptosome‐enriched (P2) preparation from the rat striatum. Care was taken to avoid the potential diffusional artifacts to which measures of oxygenase activities in respiring tissue are, in general, subject. Tyrosine hydroxylase exhibited a Km for oxygen of 2 to 3 mm Hg under a variety of conditions. Tryptophan hydroxylase exhibited a Km of 3 to 4 mm Hg at C.S.F. levels of tryptophan (10 μm). The Km increased to 8 to 10 mm Hg at 2 μm tryptophan. These values are all consistent with some degree of unsaturation with respect to oxygen in vivo.
5′‐Nucleotidase in Rat Brain Myelin
Authors: Cammer W. , Sirota S. R. , Zimmerman T. R. , Norton W. T. 
Published: October 2006

AbstractRat brain myelin showed substantial activity of 5′‐nucleotidase. The specific activity in myelin was enriched two‐ to threefold over that in rat brain homogenates, and the total activity in myelin accounted for approximately 24% of the activity in the homogenates. The 5′‐nucleotidase in the homogenates and in isolated myelin had optimum activity at pH 7.5‐9.0, was stimulated by Mg2+ and Mn2+, and was inhibited by Co2+, Zn2+, EDTA, and EGTA. 5′‐AMP, 5′‐UMP, and 5′‐CMP were the preferred substrates, and 5′‐GMP was hydrolyzed at approximately one‐half the rate of the other mononucleotides. The very low rates of cleavage of β‐glycerophosphate and 2′‐AMP ruled out any significant contribution of nonspecific phosphatase to the observed 5′‐nucleotidase activity in myelin. The 5′‐nucleotidase was inhibited by concanavalin A and was protected by α‐methyl‐d‐mannoside against inhibition by that lectin, suggesting that this enzyme in the CNS is a glycoprotein. It is concluded from these data, and from histochemical observations made in other laboratories, that the myelin sheath is one major locus of 5′‐nucleotidase in the rat brain.
Ultraviolet Irradiation Produces Loss of Saxitoxin Binding to Sodium Channels in Rat Synaptosomes
Authors: Weigele John B. , Barchi Robert L. 
Published: October 2006

AbstractUltraviolet irradiation (UV) has been shown to cause an electrophysiologically measured inactivation of the rapid, transient sodium conductance system in nerve. Tritiated saxitoxin ([3H]STX) was used as a structural probe to assess the possibility of a corresponding perturbation in the conformation of the STX binding site. UV irradiation caused an irreversible decrease in the total number of high‐affinity [3H]STX binding sites in rat synaptosomes, while the dissociation constant of the remaining sites did not change. The receptor loss followed first‐order kinetics, and the rate of loss was independent of temperature. The action spectrum for binding loss indicated a peak in spectral sensitivity near 280 nm. A22Na flux assay in irradiated synaptosomes directly demonstrated that [3H]STX binding sites and veratridinestimulated, STX‐blocked 22Na efflux had similar sensitivities to UV radiation. We conclude that the UV inactivation of functional channels includes a modification of the STX binding‐site structure.
Subcellular Distribution and Developmental Change of 2′,3′‐Cyclic Nucleotide 3′‐Phosphohydrolase in the Central Nervous System of the Myelin‐Deficient Shiverer Mutant Mice
Authors: Mikoshiba Katsuhiko , Nagaike Kazuhiro , Tsukada Yasuzo 
Published: October 2006

Abstract Shiverer is an autosomal recessive mutant characterized by dysmyelination in the central nervous system. The myelin in the shiverer is devoid of the major dense line. The pattern of increase of 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase (CNPase) in the various parts of the central nervous system during postnatal development was identical with that of controls. Subcellular fractionation of the brain from shiverer showed that the recovery of CNPase activity of the P2A was only 14% of the control, but those of P2B and P3 were several times higher than the controls. The specific activity of CNPase of the purified myelin and P2A from shiverer did not differ significantly from that of the controls. The combined P2 and P3(P2+ P3) fraction was subjected to linear sucrose density gradient (0.32‐1.3 m) centrifugation. By measuring CNPase activities of the fractions obtained after centrifugation, shiverer showed two peaks of CNPase activities in the sucrose gradient, although that of the control showed a single peak. The main peak obtained from shiverer was found in the region of higher sucrose concentration than that of the control, while a small peak was found in the region of lower sucrose concentration.
Turnover Numbers of γ‐Aminobutyrate Aminotransferase in Some Regions of Rat Brain
Authors: Ossola Lucienne , Maitre Michel , Blinderman Jean‐Marc , Mandel Paul 
Published: October 2006

Abstract:Using a radioimmunoassay to measure GABA (γ‐aminobutyric acid) transaminase in brain tissue homogenate, we have determined the turnover number of the enzyme in various regions of the rat brain. These numbers are not constant and vary from 3.5 to 30.6 s‐1 according to the regions studied, the highest numbers being found in regions rich in white matter. The significance of these results is discussed.
Lipid Requirement for Long‐lived Morphine‐dependent Activations of Adenylate Cyclase of Neuroblastoma × Glioma Hybrid Cells
Authors: Wilkening Douglas , Nirenberg Marshall 
Published: October 2006

Abstract:Morphine or norepinephrine at 10 μM inhibit adenylate cyclase of NG108‐15 neuroblastoma × glioma hybrid cells and gradually, over a period of 12 h or more, elicit a compensatory, persistent increase in adenylate cyclase activity. The cells are then dependent upon the receptor ligand for maintenance of normal cyclic AMP levels. Serum lipids or linoleic acid are required for the full expression of the long‐lived morphine‐dependent increase in adenylate cyclase activity, but serum lipids are not required for inhibition of the enzyme by morphine. Serum lipids are also not required for the full expression of the norepinephrine‐dependent increase in adenylate cyclase activity. In the NG108‐15 model system, therefore, the acquisition of dependence upon morphine can be dissociated from the inhibition of adenylate cyclase by morphine as well as from the acquisition of dependence upon another receptor ligand, norepinephrine.
Purification and Characterization of Rat Pheochromocytoma Dopamine β‐Hydroxylase
Authors: Fong Jim C. , Shenkman Louis , Goldstein Menek 
Published: October 2006

Abstract:Dopamine β‐hydroxylase (DβH) was purified from rat adrenal pheochromocytoma tumors by a procedure that requires only a few purification steps. Tumors obtained from a small number of rats yield sufficient quantities of pure DβH to raise antibodies to DβH in guinea pigs. The specificity of the antiserum was demonstrated by immunoelectrophoretic and Ouchterlony immunodiffusion analysis, as well as by the specific inhibition of DβH activity. Enzyme inhibition studies revealed complete cross‐reactivity between the rat pheochromocytoma antiserum and rat adrenal DβH, but interspecies cross‐reactivity was almost nonexistent. The molecular parameters and the kinetic properties of rat pheochromocytoma DβH are similar to those reported for bovine adrenal, human plasma, and human pheochromocytoma DβH.
Regional and Subcellular Distribution of ATP‐Citrate Lyase and Other Enzymes of Acetyl‐CoA Metabolism in Rat Brain
Authors: Szutowicz A. , Lysiak W. Z. 
Published: October 2006

Abstract:The activities of ATP‐citrate lyase in frog, guinea pig, mouse, rat, and human brain vary from 18 to 30 μmol/h/g of tissue, being several times higher than choline acetyltransferase activity. Activities of pyruvate dehydrogenase and acetyl coenzyme A synthetase in rat brain are 206 and 18.4 μmol/h/g of tissue, respectively. Over 70% of the activities of both choline acetyltransferase and ATP‐citrate lyase in secondary fractions are found in synaptosomes. Their preferential localization in synaptosomes and synaptoplasm is supported by RSA values above 2. Acetyl CoA synthetase activity is located mainly in whole brain mitochondria (RSA, 2.33) and its activity in synaptoplasm is low (RSA, 0.25). The activities of pyruvate dehydrogenase, citrate synthase, and carnitine acetyltransferase are present mainly in fractions C and Bp. No pyruvate dehydrogenase activity is found in synaptoplasm. Striatum, cerebral cortex, and cerebellum contain similar activities of pyruvate dehydrogenase, citrate synthase, carnitine acetyltransferase, fatty acid synthetase, and acetyl‐CoA hydrolase. Activities of acetyl CoA synthetase, choline acetyltransferase and ATP‐citrate lyase in cerebellum are about 10 and 4 times lower, respectively, than in other parts of the brain. These data indicate preferential localization of ATP‐citrate lyase in cholinergic nerve endings, and indicate that this enzyme is not a rate limiting step in the synthesis of the acetyl moiety of ACh in brain.
Surface Proteins of Cultured Mouse Cerebellar Cells
Authors: Rohrer Hermann , Schachner Melitta 
Published: October 2006

Abstract:Surface proteins of cultured monolayer cells from embryonic and early postnatal C57BL/6J mouse cerebella were identified by a lactoperoxidase‐catalysed 131iodine labelling technique. Major iodinated polypeptides have molecular weights of approximately 200, 145, 120, 100, 85, 65, 50, and 30 X 103 (P200, P145, ⃛) as estimated by sodium dodecylsulphate polyacrylamide gel electrophoresis. Membrane glycoproteins, of apparent molecular weights 200, 145, 100, 85, and 50 X 103, are detected by biosynthetic labelling with [3H]fucose. The two major iodinated proteins are the glycoproteins P200 and P145. P145 is released from the cells into the medium together with other surface proteins. No changes in the patterns of labelled cerebellar cell surface proteins are detectable between embryonic day 17 and postnatal day 10. A pattern similar to the one seen with cerebellum is obtained with embryonic day 12 and 17 cerebral cortex. Cultured retinal cells from 2‐day‐old mice, skin fibroblasts, and l‐cells display a distinctly different pattern, which does not contain P145 as a major iodinated component. In granule cell‐enriched fractions of cerebellar cells the two glycoproteins P200 and P145 are proportionately increased, while three proteins, P100, P85, and P50, are more abundant in the glial cell‐enriched fraction. These three polypeptides are also enriched in cells obtained from staggerer mutant mice. An antiserum against 4‐day‐old cerebellar cells (anti‐NS‐4) precipitates the 145 and 200 X 103 molecular weight proteins, from lysates of both embryonic cerebral and postnatal cerebellar cells. From lysates of mouse retinal cells, anti‐NS‐4 antiserum precipitates two proteins with molecular weights of 140 and 210 X 103. Rohrer H. and Schachner M. Surface proteins of cultured mouse cerebellar cells. J. Neurochem.35, 792–803 (1980).
Isolation of Cholinergic Synaptic Vesicles from the Myenteric Plexus of Guinea‐Pig Small Intestine
Authors: Dowe G. H. C. , Kilbinger H. , Whittaker V. P. 
Published: October 2006

Abstract:The acetylcholine‐rich myenteric plexus‐longitudinal muscle preparation of the guinea‐pig small intestine has been subjected to subcellular fractionation using modifications of both classical methods and that originally devised for bulk isolation of cholinergic synaptic vesicles from the electromotor nerve terminals of Torpedo marmorata by means of density gradient centrifugation in a zonal rotor. The latter method gave a vesicle fraction with the highest acetylcholine content so far recorded for a mammalian particulate fraction, 30.9 × S.E.M. 1.8 (5) nmol of acetylcholine × mg of protein−1. Electron‐microscopical examination showed that it consisted of a homogeneous preparation of vesicles of mean spherical diameter 61 ×sd 4 (108) nm, with little or no contamination with other lipoprotein membrane structures, mixed how‐ever with considerable amounts of actomyosin fibrils, presumably derived from the longitudinal muscle. Slab‐gel electrophoresis in sodium dodecyl sulphate showed that, in addition to prominent peaks attributable to actin and myosin, there was a relatively simple pattern of (presumably) vesicle protein among which all the proteins thought to be characteristic of Torpedo synaptic vesicles were present. Dowe G. H. C. et al. Isolation of cholinergic synaptic vesicles from the myenteric plexus of guinea‐pig small intestine. J. Neurochem.35, 993–1003 (1980).
Acetylcholine Synthesizing Enzymes in Frog Skeletal Muscle
Authors: Molenaar P. C. , Polak R. L. 
Published: October 2006

Abstract:Acetylcholine synthesis in homogenates of frog sartorius muscle was measured by a radiometric method with a low blank. Choline acetyltransferase activity was very low (Vmax, 2 nmol g1 h−1, Kmfor choline, approx. 50 μ, m). The enzyme was found only in the endplate area and disappeared after denervation; it was inactivated by 4‐(1‐naphthylvinyl)pyridine. At high substrate concentrations its activity was overshadowed by the acetylcholine‐synthesizing activity of a different enzyme not saturated by 10 mm‐choline. The non‐specific enzyme was present at and away from the endplate area, and it was not affected by denervation.
Phosphorylation of Chromatin Proteins in Cerebral Anoxia and Ischemia
Authors: Yanagihara T. 
Published: October 2006

Abstract:Phosphorylation of nuclear protein was investigated in cerebral anoxia up to 30 min with rabbit brain and in cerebral ischemia up to 6 h with gerbil brain in vitro. Isolated nuclei were incubated in the presence of [γ‐32P]ATP and were then fractionated into the NaCl‐soluble, HCl‐soluble, and phenol‐soluble protein fraction. Each protein fraction was further separated by gel electrophoresis, and profiles of 32P incorporation were evaluated in these pathophysiological conditions. 32P incorporation of the acidic phenol‐soluble nonhistone chromatin protein became significantly suppressed in cerebral anoxia after 15 min, and there were decreases of 32P incorporation in protein with high molecular weight and increase in protein with low molecular weight on gel electrophoresis. With gerbil brain nuclei, 32P incorporation into the NaCl‐soluble and HCl‐soluble fraction was increased without significant de‐crease in the phenol‐soluble fraction after an ischemic period of 3 h. However, further separation of the phenol‐soluble fraction demonstrated decrease of 32P incorporation in protein with high molecular weight and increase in protein with low molecular weight. At present, the significance of these findings, particularly in relation to chromatin template activity or irreversibility of these pathophysiological conditions, is not clear.
Effects of Fetal Treatment with Methylazoxymethanol acetate at Various Gestational Dates on the Neurochemistry of the Adult Neocortex of the Rat
Authors: Johnston M. V. , Carman A. B. , Coyle J. T. 
Published: October 2006

Abstract:The effects of gestational date (13, 14, 15, and 17 days) of administration of methylazoxymethanol acetate (20 mg/kg) on the cortical synaptic chemistry and morphology of the rat has been examined in adult offspring. Treatment at 13 days of gestation (DG) resulted in cortical hypoplasia that affected primarily the deep layers whereas treatment at 14 and 15 days gestation caused a severe hypoplasia of cortical neurons above layer V and a 66 to 77% reduction in cortical mass. The 17‐DG treatment caused only a 20% reduction in cortical weight with effects apparent only in the superficial layers. At no treatment date did the specific activity of glutamate decarboxylase differ significantly from control. In contrast, presynaptic markers for noradrenergic (tyrosine hydroxylase and norepinephrine) and for serotonergic (serotonin) terminals were increased in concentration in direct proportion to the degree of cortical hypoplasia. The specific activity of choline acetyltransferase was significantly increased at all treatment dates but total activity per cortical slab was significantly reduced on treatment days 13–15.
Induction by Hydrocortisone of Glutamine Synthetase in Mouse Primary Astrocyte Cultures
Authors: Juurlink B. H. J. , Schousboe A. , Jørgensen O. S. , Hertz L. 
Published: October 2006

Abstract:Glutaminc synthetase activity was investigated in developing primary astroglial cultures established from newborn mouse cerebral hemispheres. Between the 2nd and 4th week of culture there was little change in activity under our standard culturing conditions; however, when hydrocortiwne (10 μM) was added to the cultures for 48 h, the enzyme activity increased two‐ to fourfold, depending upon the age of the culture, with maximum response in 2‐week‐old cultures. The addition of dibutyryl cyclic AMP (dRcAMP) to the culture medium caused morphological differentiation of the astroglial cells but eliminated the response of the cells to hydrocortisone. Culturing in elevated serum levels, which delays morphological differentiation and inhibits astroglial cytodifferentiation after exposure to dBcAMP, shifted the time of maximal response to hydrocortisone from 2 to 3 weeks and prevented the abolishment of glutamine synthetase induction by dBcAMP. The induction of glutamine synthetase by hydrocortisone was prevented by actinomycin D (0.5 μg/ml), indicating its dependence upon RNA and protein synthesis. The present work thus confirms reports in the literature that hydrocortisone induces glutamine synthetase in neural tissues, but differs from the findings of Moscona and co‐workers in the chick retina that intact tissues are required for the induction to occur.
Differential Solubilization of γ‐Aminobutyric Acid Receptive Sites from Membranes of Mammalian Brain
Authors: Lester Bruce R. , Miller Ann L. , Peck Ernest J. 
Published: October 2006

Abstract:Sodium‐dependent (+Na) and sodium‐independent (‐Na) receptive sites for γ‐aminobutyric acid (GABA) residing in or on frozen synaptic plasma membranes (SPM) of bovine cerebral cortex were characterized as to binding constants, pharmacologic specificities, and sodium dependence. The SPM fraction was then treated with various concentrations of Triton X‐100 resulting in the loss of pharmacologic specificity, binding characteristics, and sodium dependence associated with +Na GABA receptive sites in SPM. The resulting junctional complex preparation (JC), i.e., a fraction enriched in junctional complexes, possessed only the pharmacologic specificity and binding constants associated with Na receptive sites whether assayed in the presence or absence of 100 mwNaC1. This is probably due to the detergent dispersal or solubilization of the +Na GABA receptive site. The binding constants, KD and Bmax, for –Na GABA binding in SPM were 170 nM and 4.4 pmol/mg protein, while in JC they were 186 nM and 3.7 pmol/mg protein. Under repeated washing the KD was reduced to 60 ± 6.9 nM and the Bmax was reduced to 2.5 ± 0.5 pmol/mg protein in JC, probably owing to the removal of endogenous ligand or inhibitor, and not to inhibition by residual Triton X‐100. Multiple extraction with 0.1% or 0.5% Triton X‐100 did not alter the KB or Bmax, values for the binding of [3H] GABA to JC. Sodium‐independent GABA binding was lost from JC membranes with the use of sodium deoxycholate, probably through solubilization.
Postnatal Changes in Cathepsin D in Rat Neural Tissue
Authors: Snyder D. Stephen , Whitaker John N. 
Published: October 2006

Abstract:Cathepsin D, an aspartyl endopeptidase, was analyzed in cortex from forebrain and cerebellum, spinal cord, and optic and sciatic nerves, and in the liver of rats from 1 to 120 days of age. Cathepsin D was quantitated in tissue extracts by measurement of enzyme specific activity on a substrate of [methyl‐14C]‐methylated hemoglobin and by radioimmunoassay. Immunocytochemistry was used to ascertain the identity of the mixed cell types that contributed to the cathepsin D detected. As quantitated by radioimmunoassay, immunoreactive cathepsin D varied between 0.2 and 1 ng/μg of total protein. Maximum activity occurred at approximately the 15th postnatal day; the least amount of immunoreactive cathepsin D was found at 30 or 60 days of age. A subsequent increase of varying magnitude occurred at postnatal day 120. There was good correspondence between immunoreactive enzyme and enzyme specific activity, which ranged from 1 to 4 ng/μg of total protein, and the activities determined by the two methods provided similar, but not identical, developmental profiles. Cathepsin D was demonstrated by immunocytochemistry to be present in most neurons, in all choroid plexus epithelium, and in certain oligodendrocytes from the first postnatal day. Cathepsin D was present in oligodendrocytes in cord lateral funiculi and optic nerve by the first postnatal day, and by the sixth postnatal day many oligodendrocytes were abundantly stained. In contrast, oligodendrocytes in the corpus callosum and in the cerebellar white matter did not contain demonstrable cathepsin D until postnatal days 10 and 15, respectively. These results indicate a role for cathepsin D during the postnatal development of rat CNS and suggest that this proteinase may be involved in the steps of myelination.
Amino Acids in the Substantia Nigra of Rats with Striatal Lesions Produced by Kainic Acid
Authors: Korf Jakob , Venema Kor 
Published: October 2006

Abstract:In an attempt to estimate the pool size of glutamate and other amino acids in γ‐aminobutyric acid (GABA)‐containing neurons, we determined the content of 12 amino acids in the bilateral substantia nigra of rats, in which unilateral striatal lesions had been made with kainic acid two weeks earlier. The assay of the amino acids (including glutamate, aspartate, glutamine, asparagine, glycine, and GABA) and ethanolamine was based on HPLC and fluorimetric detection after precolumn derivatization with o‐phthaldialdehyde. The levels of all measured amino acids (except those of tyrosine, threonine, and ethanolamine) were decreased in the affected striatum, but only the levels of aspartate, taurine, and GABA were lowered in the ipsilateral substantia nigra. These results indicate that the pool size of the various amino acids in the striatonigral GABAergic pathway is small compared to their nigral content, and that in addition to GABA a significant fraction of aspartate and taurine may be confined to nerve terminals in the substantia nigra.