bluuebunny/crossref_metadata_2025_split huggingface dataset:
OBSERVATION ON THE PROPERTIES OF DOPAMINE‐β‐HYDROXYLASE1
Authors: Brown F. C. , Harralson J. D. 
Published: October 2006

Abstract—The activity of dopamine‐β‐hydroxylase is inhibited by copper. It is stimulated by a variety of substances, such as fumarate and sodium chloride, which exert salt‐like effects. Both phenomena are mediated indirectly through an interaction of ascorbate with catalase. The latter is converted to the inactive catalase II, by the autoxidation of ascorbate and other electron donors. Copper accelerates the autoxidation, thereby enhancing the inactivation of catalase. The activity of DβH, which requires catalase, is therefore inhibited. At high ionic strength, i. e. in the presence of high levels of salt, the conversion of catalase to catalase II is prevented, and the DβH reaction proceeds.
POLYADENYLIC ACID‐CONTAINING RNA FROM RAT BRAIN
Authors: DeLarco J. , Abramowitz A. , Bromwell Katherine , Guroff G. 
Published: October 2006

Abstract—A portion of rat brain RNA contains poly(A) sequences and binds to oligo(dT)‐cellulose. Young rats have a greater amount of brain RNA which contains poly(A) than do adult animals. The length of the poly(A) sequence from the brain RNA of young animals was shown to be somewhat longer than that from the RNA of adults. The RNA which bound to the oligo(dT)‐cellulose was found to be large and heterogeneous, and to be almost free of ribosomal or of small mol. wt. RNAs. When the polysomal RNA which bound to the oligo(dT)‐cellulose columns and that which did not were used to prime a cell‐free protein synthesizing system there was a noticeable difference in their‘messenger’activity; the RNA which bound to the oligo(dT)‐cellulose was much more active than the unbound material. However, in the case of the nuclear RNA there was not as great a difference between the material which was bound and that which was not bound.
THE EFFECT OF ELECTRICAL STIMULATION ON THE TURNOVER OF PHOSPHATIDIC ACID IN SYNAPTOSOMES FROM GUINEA‐PIG BRAIN
Authors: Bleasdale J. E. , Hawthorne J. N. 
Published: October 2006

Abstract—Synaptosomes prepared from guinea‐pig cerebral cortex were suspended in a medium containing [32P]orthophosphate and subjected to electrical stimulation. When the synaptosomal phospholipids were subsequently separated, the most highly labelled was phosphatidic acid and electrical stimulation over a 10 min period increased incorporation of 32P1 into this lipid. Stimulated synaptosomes were osmotically lysed and subsynaptosomal fractions isolated. The electrically stimulated increase in phosphatidic acid labelling was localized in a fraction enriched in synaptic vesicles. This phospholipid effect was not merely a reflection of an increased specific radioactivity of synaptosomal ATP, due to the electrically stimulated increase in respiration. The time course of the phosphatidic acid effect suggests that it is synchronous with release of transmitter.
GABA AND ITS RELATED ENZYMES IN THE LOWER AUDITORY SYSTEM OF THE GUINEA PIG1
Authors: Fisher S. K. , Davies W. E. 
Published: October 2006

Abstract—The possible existence of GABA‐transmitter neurons in the lower auditory system of the guinea pig has been investigated by means of three different experimental approaches: (1) the regional distribution of GABA and its related enzymes. (2) the subcellular distribution of glutamate decarboxylase, and (3) the effect of selected nerve lesions on glutamate decarboxylase concentrations in the auditory nuclei. Within the regions investigated considerable variations in glutamate decarboxylase activity and GABA concentration were found, with the highest values observed in the inferior colliculus. The dorsal cochlear nucleus also contained significant amounts of both glutamate decarboxylase and GABA, in addition to high concentrations of GABA transaminase. The subcellular distribution of glutamate decarboxylase was bimodal in both the cochlear nucleus and inferior colliculus with most enzyme activity recovered in the soluble and synaptosomal fractions. Neither end organ (cochlea) nor trapezoid body lesions induced a significant loss of glutamate decarboxylase activity in either the cochlear nucleus or inferior colliculus. The results suggest the presence of short axon GABAergic interneurons in the cochlear nucleus, most of which appear to terminate within the dorsal cochlear nucleus.
STUDIES ON THE SYNTHESIS AND DEGRADATION OF DNA IN DEVELOPING AND OLD CHICK CEREBELLUM
Authors: Rao K. Subba , Shrivastaw K. P. 
Published: October 2006

Abstract—The levels of DNA, RNA, protein and acid and alkaline DNase were studied in developing and old chick cerebellum. The in vitro synthesis of DNA, by both chick cerebrum and cerebellum was also studied, by following the incorporation of [3H]thymidine into DNA. It was observed that the increase in DNA content of chick cerebellum continued well beyond adult stages of life span. Maximal DNA synthesis, as judged by the [3H]thymidine incorporation, was noticed during the early embryonic development but decreased with advancement of age. There was, however, another peak of activity, although smaller, at about 9 months of age. Both cerebrum and cerebellum showed similar patterns. The highest specific activity of acid DNase was also found during the early period of cerebellar development, that is at a time when rapid cellular proliferation was occurring. The activity steadily declined with the aging and in 2‐year‐old cerebellum very little activity could be detected. Alkaline DNase, on the other hand, not only exhibited high activity during the early development but also remained at a significant level even in old cerebellum. It is concluded that acid DNase shows a positive correlation to the early embryonic DNA synthesis but not to the cell increase occurring in old age.
UPTAKE AND RELEASE OF NIPECOTIC ACID BY RAT BRAIN SLICES
Authors: Johnston G. A. R. , Stephanson A. L. , Twitchin B. 
Published: October 2006

Abstract—Nipecotic acid, a potent inhibitor of GABA uptake, is taken up by slices of rat cerebral cortex by a sodium‐dependent, ‘high affinity’ system (Km 11 μM), and can be released from these slices by an increased potassium ion concentration in a calcium‐dependent manner. Nipecotic acid and GABA appear to be taken up by the same osmotically‐sensitive structures. GABA and substances which inhibit GABA uptake also inhibit the uptake of nipecotic acid. GABA can release preloaded nipecotic acid from brain slices, and nipecotic acid can release preloaded GABA. This indicates that GABA and nipecotic acid can be counter‐transported using the same mobile carrier. Nipecotic acid appears to have a higher affinity than GABA for this carrier.
A KINETIC ANALYSIS OF SODIUM DEPENDENT GLUTAMIC ACID TRANSPORT IN PERIPHERAL NERVE
Authors: Wheeler D. D. 
Published: October 2006

Abstract—The kinetics of sodium dependent glutamic acid transport have been studied in desheathed frog sciatic nerve. Initial velocities have been measured as a function of both glulamic acid and sodium concentration. Lineweaver–Burk plots are constructed from these data, and the kinetic constants describing uptake are estimated. Vmax is unaffected by sodium concentration, which implies that translocation is not directly affected by sodium. K1 is sodium dependent, which implies that sodium affects the affinity of the carrier for glutamic acid. Reciprocal plots of velocity vs [Na] or K1 vs 1/[Na] are linear, suggesting that glutamic acid and sodium are co‐transported on a one‐to‐one basis. t, the sodium concentration giving half maximal velocity of uptake, was found to vary from about 57 mm to 48 mm at glutamic acid concentrations of 1.0–10.0 ± 10−6m. A model of a mechanism by which sodium and glutamate could be co‐transported is presented; the model is in very good agreement with the experimental data.
EFFECT OF NEOMYCIN ON PHOSPHOINOSITIDE LABELLING AND CALCIUM BINDING IN GUINEA‐PIG INNER EAR TISSUES IN VIVO AND IN VITRO1
Authors: Orsulakova Angela , Stockhorst Eva , Schacht Jochen 
Published: October 2006

Abstract—Phospholipids of guinea‐pig inner ear tissues were labelled in vivo by perilymphatic perfusion of the cochlea with [32P]orthophosphate or myo‐[3H]inositol. After 20‐40 min the most highly labelled 32P‐lipids were phosphatidylinositol phosphate and diphosphate. Incorporation of [3H]inositol proceeded in the order phosphatidylinositol > phosphatidylinositol phosphate > phosphatidylinositol diphosphate.After treatment of animals with neomycin for 3 weeks, 32P‐incorporation into phosphatidylinositol diphosphate, but not into other lipids, was significantly decreased in the preparations of the organ of Corti and stria vascularis. In homogenates of inner ear tissues, the labelling of the polyphosphoinositides by [γ‐32P]ATP was increased and the hydrolysis of these lipids was blocked in the presence of 10−4m‐neomycin. Neomycin also competitively inhibited the binding of 45Ca2+ to homogenates of these tissues.
GLYCEROL KINASE AND DIHYDROXYACETONE KINASE IN RAT BRAIN
Authors: Jenkins B. T. , Hajra A. K. 
Published: October 2006

Abstract—The enzymatic phosphorylation of glycerol and dihydroxyacetone by ATP to sn‐glycerol‐3‐phosphate and dihydroxyacetone phosphate respectively in various subcellular fractions of rat brain was studied. A sensitive radiochemical assay was used where the labelled phosphorylated products were separated from the radioactive substrates by high voltage paper electrophoresis and the radioactivity in these compounds determined. Using this assay the glycerol kinase (EC 2.7.1.30) activity was found to be associated with the mitochondrial fraction of the brain. Under optimum conditions 2.45 nmol of glycerol was phosphorylated/min per mg of protein. The Km for glycerol was 70 μm at pH 7. This mitochondrial enzyme, like other glycerol kinases from different sources, also phosphorylated dihydroxyacetone. Under optimum conditions 1.7 nmol of dihydroxyacetone phosphate was formed/min per mg of mitochondrial protein. The Km for dihydroxyacetone was 0.6 mm.Glycerol kinase activity was also present in the cytoplasm of brain. However, the specific activity of this enzyme in cytosol is about 15% of the mitochondrial glycerol kinase. Compared to glycerol, dihydroxyacetone was phosphorylated by ATP in cytoplasm at a much higher rate. The pH optimum for this soluble dihydroxyacetone kinase was much lower (pH 6.5) than that of the soluble or mitochondrial glycerol kinase (pH 10.0). Using ammonium sulfate, brain cytoplasm was fractionated to yield a fraction in which the dihydroxyacetone kinase was enriched 2–3 fold with no glycerol kinase activity. Under optimum conditions 1.0 nmol of dihydroxyacetone was phosphorylated/min per mg protein. The Km for dihydroxyacetone was 60 μm. This cytosol fraction was also found to phosphorylate d‐glyceraldehyde and l‐glyceraldehyde at a rate of 30–40% to that of the dihydroxyacetone phosphorylation. The properties and the possible metabolic role of these enzymes in brain are discussed.
NEUROCHEMISTRY OF THE MUCOPOLYSACCHARIDOSES: BRAIN GLYCOSAMINOGLYCANS IN NORMALS AND FOUR TYPES OF MUCOPOLYSACCHARIDOSES
Authors: Constantopoulos G. , Mccomb R. D. , Dekaban A. S. 
Published: October 2006

Abstract—Glycosaminoglycan content, composition and molecular weight distribution were determined in cerebral gray and white matter, liver and spleen from normals and 7 patients with mucopolysaccharidosis; 4 were of Type I (Hurler), one Type II (Hunter), one Type IIIA (Sanfilippo A) and one Type V (Scheie).There was a 3 to 4‐fold increase in glycosaminoglycan content of the brains from patients with mucopolysaccharidosis Type I, II and IIIA, but only a 40% increase in the Type V patient. Partially degraded dermatan sulfate accounted for most of the increase in Types I, II and V. Highly fragmented heparan sulfate was the major glycosaminoglycan in the brain of the Type IIIA patient and was also a sizable component in Types I and II.Remarkably, the changes in the brain glycosaminoglycans of the Type V patient were minimal. He also was of normal intelligence
STIMULATION OF GLYCOGENOLYSIS IN RAT CAUDATE NUCLEUS SLICES BY L‐ISOPROPYLNOREPINEPHERINE, DIBUTYRYL CYCLIC AMP AND 2‐CHLOROADENOSINE
Authors: Wilkening Doug , Makman Maynard H. 
Published: October 2006

Abstract—Dopamine (DA), L‐isópropylnorepinepherine (IPNE), 2‐chloroadenosine (2‐Cl‐Ado), 3‐isobutyl, I‐methylxanthine (IBMX) and N6,O2′‐dibutyryl cyclic AMP have been investigated for their effects on glycogen levels in rat caudate nucleus slices. Incubation of slices with 1 mM‐dibutyryl cyclic AMP, or with 50 μM‐IPNE in the presence of 1mM‐IBMX, or with 5‐500 μM‐2‐Cl‐Ado reduced glycogen levels to about 50% of control. Incubation of slices with 1 mM‐IBMX alone, or with 50μM‐IPNE alone, or with 50μM‐DA either alone or in the presence of 1 mM‐IBMX was without significant effect on glycogen levels. The effect of IPNE + IBMX was completely abolished by the prior addition of 10 μM‐propranolol. The effect of 10 μM‐2‐Cl‐Ado was not effectively prevented by either 100 μM‐theophylline or 100 μM‐cordycepin. The results indicate that the β‐adrenergic adenylate cyclase in the rat caudate nucleus plays a role in the regulation of glycogen metabolism, while the DA‐stimulated adenylate cyclase is not significantly involved. The 2‐Cl‐Ado‐stimulated adenylate cyclase may be involved in the control of glycogen metabolism, but other mechanisms for the 2‐CI‐Ado action, such as interference with allosteric regulatory sites on glycogen phosphorylase, have not been ruled out.
GLYCOSYLTRANSFERASES OF RAT BRAIN THAT MAKE CEREBROSIDES: SUBSTRATE SPECIFICITY, INHIBITORS, AND ABNORMAL PRODUCTS1
Authors: Warren K. R. , Misra R. S. , Arora R. C. , Radin N. S. 
Published: October 2006

AbstractBrain homogenates from young rats were assayed for their ability to synthesize cerebrosides from radioactive UDP‐galactose or UDP‐glucose and ceramide. A comparison of galactose transfer with ceramides made from different 2‐hydroxy acids showed that the shortest one tested (C7) was by far the best acceptor, while the poorest contained 18 carbon atoms; longer fatty acids were better than CIS. Glucosyltransferase, on the other hand, showed rather little chain length specificity or discrimination against hydroxy acid ceramides.Synthetic compounds analogous in structure to ceramides were tested as inhibitors of the sugar transferases. Some were found to act as sugar acceptors themselves, particularly amides of DL‐erythro‐1‐ phenyl‐2‐amino‐1,3‐propanediol. Some amides were good inhibitors of glucosyltransferase, particularly decanoyl norephedrine, decanoyl threo‐1‐phenyl‐2‐amino‐1,3‐propanediol and decenoyl phenylalaninol. The secondary amine analogous to the first of these, N‐decyl norephedrine, was also very effective. No strong inhibitors of galactosyl transferase were found, although octanoyl D‐threo‐p‐nitrophenyla‐ minopropanediol showed promise (42% inhibition at 0.3 mM). Octanoyl phenylalaninol was nearly as good an inhibitor; the inhibition appeared only after a lag period.It is suggested that the glucosyltransferase inhibitors might he useful in therapy of Gaucher's disease, by reducing the degradative load normally falling on glucocerebrosidase.
POTASSIUM‐INDUCED RELEASE OF [3H]GABA AND OF [3H]NORADRENALINE FROM NORMAL AND RESERPINIZED RAT BRAIN CORTEX SLICES. DIFFERENCES IN CALCIUMDEPENDENCY, AND IN SENSITIVITY TO POTASSIUM IONS
Authors: Vargas Olga , DEL Carmen María , de Lorenzo Doria , Saldate María Cristina , Orrego F. 
Published: October 2006

Abstract—The release of [3H]GABA induced by elevated extracellular potassium (K)o, from thin rat brain cortex slices, has been compared with that of [3H]noradrenaline ([3H]NA), released by the same procedures, both from normal slices, and from slices pre‐treated with reserpine and nialamide, [3H]NA being predominantly a vesicular component in the former situation, and a soluble substance in the latter one. 46 mM‐(K)o released considerably more [3H]NA from normal than from drug‐treated slices, while the release of GABA was about two thirds of the latter. When 4min ‘pulses’ of increasing concentrations of potassium were applied, it was observed that the release of GABA and of [3H]NA from drug‐treated slices increased in proportion to (K)o, up to 36‐46 mM and then declined considerably with higher (K)o. The dependency of potassium‐induced release on the concentration of calcium in the medium, indicated that release of [3H]NA from normal slices was proportional to calcium up to 1.5‐2 mM, while that of [3H]NA from drug‐treated slices increased up to 0.5 mM‐Calcium, and then declined with higher concentrations. GABA release also increased up to 0.5 mM‐calcium, but no further changes were observed at higher concentrations. The calcium antagonist D‐600 inhibited high (K)o‐induced release of [3H]NA from normal slices to a greater extent than that of [3H]GABA or of [3H]NA from drug‐treated slices. These results, in which elevated (K)o‐induced release of [3H]GABA resembles considerably that of soluble NA, but differs from that of NA present in synaptic vesicles, suggest that release of [3H]GABA also occurs from the soluble cytoplasmic compartment, and that the partial calcium requirement that is found is unrelated to that of transmitter secretion. These findings are also a further indication of the lack of specificity of elevated (K)o as a stimulus for inducing transmitter secretions.
ACETYLTRIETHYLCHOLINE: A CHOLINERGIC FALSE TRANSMITTER IN CAT SUPERIOR CERVICAL GANGLION AND RAT CEREBRAL CORTEX
Authors: ILSON D. , COLLIER B. , BOKSA P. 
Published: October 2006

Abstract—The accumulation and metabolism of [14C]triethylcholine by cat superior cervical ganglia [rested or stimulated (20 Hz)] and by rat cerebral cortex minces was measured. In ganglia, preganglionic nerve stimulation increased the accumulation (2.4 fold) and the acetylation (5.7 fold) of triethylcholine; however the depletion of the ganglion's acetylcholine content was 9.5 times greater than the amount of acetyltriethylcholine synthesized. In the presence of eserine, neither stimulated nor rested ganglia synthesized any extra (surplus) acetyltriethylcholine. It is concluded that the rate‐limiting step in acetyltriethylcholine synthesis is the acetylation of triethylcholine by choline acetyltransferase. Subsequent preganglionic nerve stimulation of ganglia, which had been stimulated during the exposure to [14C]‐triethylcholine, caused the increased release of only acetyltriethylcholine; the release was frequency‐dependent, required the presence of Ca2+, and was blocked by increasing the ratio of Mg2+/Ca2+ in the perfusion fluid. All of the acetyltriethylcholine which had been accumulated was available for release. Rat cerebral cortex also accumulated triethylcholine and acetylated about 3% of the accumulated choline analogue. Subsequent stimulation by high K+ (46 mM)‐atropine (3 μM) caused the increased release of acetyltriethylcholine from the cortex and this release required the presence of Ca2+. Triethylcholine can therefore form a cholinergic false transmitter in the cat superior cervical ganglion and the rat cerebral cortex.
CORRELATION BETWEEN TYROSINE HYDROXYLASE ACTIVITY AND CATECHOLAMINE CONCENTRATION OR TURNOVER IN BRAIN REGIONS1
Authors: BACOPOULOS N. G. , BHATNAGAR R. K. 
Published: October 2006

Abstract—Tyrosine hydroxylase activity correlated significantly with norepinephrine concentration and turnover, when results from regions containing predominantly noradrenergic terminals were compared, and with dopamine concentration and turnover when results from regions containing predominantly dopaminergic terminals were compared. Regions containing dopamine or norepinephrine cell bodies were characterized by higher tyrosine hydroxylase activities as compared to regions containing mostly nerve terminals. Higher levels of tyrosine hydroxylase activity and transmitter turnover were observed in regions containing dopaminergic terminals than in regions containing norepinephrine terminals. These findings are consistent with the view that tyrosine hydroxylase activity is linked to rates of catecholamine utilization by neurons in the CNS.
SUITABILITY OF DIFFERENT MOLECULAR SPECIES OF 1,2‐DIACYLGLYCEROLS AS SUBSTRATES FOR DIACYLGLYCEROL KINASE IN RAT BRAIN MICROSOMES
Authors: Holub B. J. , Piekarski J. 
Published: October 2006

AbstractThe relative suitability of different molecular species of 1,2‐diacyl‐sn‐glycerols as substrates for the diacylglycerol kinase (ATP: 1,2‐diacyl‐sn‐glycerol phosphotransferase) in rat brain microsomes was investigated. The diacylglycerols tested were a mixture of the 1‐[3H]palmitoyl and 1‐[14C]stearoyl homologues of either the 2‐oleoyl (monoenoic), 2‐linoleoyl (dienoic), 2‐arachidonoyl (tetraenoic), or 2‐docosahexaenoyl (hexaenoic) diacylglycerols with an isotope ratio (3H/14C) approximately equal to 1.00.At substrate concentrations of 0.125 mM and 0.60 mM, only a modest preference of the kinase for total (1‐palmitoyl plus 1‐stearoyl homologues) monoenoic over total hexaenoic species was indicated. The tetraenoic diacylglycerols gave reaction rates which were not significantly different from the monoenes, dienes, or hexaenes when the data were analyzed statistically.No significant enzyme selectivity for either the 1‐palmitoyl or 1‐stearoyl homologues of the various 1‐saturated 2‐unsaturated diacylglycerols was apparent.The present results, together with data on the composition of free 1,2‐diacylglycerols in brain, which reveal a preponderance of tetraenoic molecular species, suggest that the tetraenoic phosphatidic acids (mainly as 1‐stearoyl 2‐arachidonoyl species) are quite possibly the major products of diacylglycerol kinase activity in rat brain under physiological conditions.
LACK OF ENHANCEMENT OF DIMETHYLTRYPTAMINE FORMATION IN RAT BRAIN AND RABBIT LUNG IN VIVO BY METHIONINE OR S‐ADENOSYLMETHIONINE
Authors: Stramentinoli Giorgio , Baldessarini Ross J. 
Published: October 2006

Abstract In vivo conversion of intracisternally administered [14C]tryptamine to [14C]N,N‐dimethyl‐tryptamine (DMT) in rat brain, even in the presence of an excess of substrate and methyl donor appeared to be insignificant, although enzymatically synthesized [14C]DMT was recovered readily after intracranial injection. Authenticity of [14C]DMT was demonstrated by cocrystallization with authentic DMT and oxalic acid to constant specific radioactivity after chromatographic separation of [14C]DMT. In rabbit lung, the apparent Km for S‐adenosylmcthionine (SAMe) (29 μM) with indolethylamine‐N‐methyltransferase was found to be close to endogenous levels of SAMe (34 μM) that are not likely to saturate the enzyme normally. Nevertheless. large doses of L‐methioninc or SAMe failed to increase the in vivo conversion of [14C]N‐methyltryptamine to [14C]DMT in this tissue. The production of [14]DMT was instead markedly irihihitrd by this treatment. possibly due to an effect of S‐adeno‐sylhomocysteine. Our results fail to support the hypothesis that psychotropic effects of methionine or SAMe are due to increased accumulations of pharmacologically active methylated indoleamines.