bluuebunny/crossref_metadata_2025_split huggingface dataset:
RNA POLYMERASE ACTIVITY IN VARIOUS CLASSES OF NUCLEI FROM DIFFERENT REGIONS OF RAT BRAIN DURING POSTNATAL DEVELOPMENT
Authors: Giuffrida Anna M. , Cox D. , Mathias A. P. 
Published: October 2006

Abstract—The changes in the wet weight and the numbers of cell nuclei recovered from the cerebral hemispheres, the cerebellum and the brain stem of rats from the period of 5–30 days after birth have been determined. In parallel a study has been made of the RNA polymerase activity, both in the unfractionated nuclei from these regions and in the nuclei separated by zonal centrifugation. In general there is a considerable decline in activity during this period, which occurs in all class of nuclei although not to the same extent. The most dense nuclei from the cerebellum retain relatively high activity at 20 days after birth, possibly due to the contribution of the microneuronal nuclei.
PROPERTIES OF PARTIALLY PURIFIED PIG BRAIN STEM TRYPTOPHAN HYDROXYLASE
Authors: Youdim M. B. H. , Hamon M. , Bourgoin S. 
Published: October 2006

Abstract—Tryptophan hydroxylase form pig brain has been purified using a method which involved sonic disintegration of a whole homogenate, ammonium sulphate fractionation, hydroxylapatite fractionation, column chromatography on Sephadex G‐100 or G‐200 and finally electrophoresis on poly‐acrylamide gel. The enzyme was stabilized during purification by tryptophan and dithiothreitol. The partially purified enzyme has a molecular weight of 55,000‐60,000 as measured by gel‐filtration. The Km of the soluble partially purified enzyme was 0‐4 mm, which differed significantly from that of the particulate enzyme (0·02mm). Enzyme activity was not stimulated by ferrous ion. However, it was inhibited by the chelating agents 8‐hydroxyquinoline, O‐phenanthroline and EDTA. In contrast to dopamine, high concentration of tryptophan (10 mm), 5‐hydroxytryptamine, tryptamine and tyramine at 0‐5 mm concentration did not inhibit the enzyme in the presence of dimethyltetrahydropterin (DMPH4). A number of monoamine oxidase inhibitors, phenelzine, pheniprazine and chlorgyline at 1 mm strongly inhibit the formation of 5‐hydroxytryptamine. Evidence is presented for the presence of an endogenous inhibitor of tryptophan hydroxylase.
CARBOHYDRATE AND ENERGY METABOLISM IN PERINATAL RAT BRAIN: RELATION TO SURVIVAL IN ANOXIA
Authors: Duffy T. E. , Kohle S. J. , Vannucci R. C. 
Published: October 2006

Abstract—The ability of rats of different ages to survive exposure to anoxia was correlated with rates of high energy phosphate consumption (metabolic rates) of the fore‐brain. Fetal rats at term, delivered by hysterotomy following maternal decapitation, survived in nitrogen at 37°C twice as long as 1‐day‐old neo‐nates, 5 times longer than 7‐day‐old rats, and 45 times longer than adults. During ischemia induced by decapitation, the cerebral concentrations of the labile energy reserves (ATP, ADP, P‐creatine, glucose and glycogen) and of lactate were determined in fetuses, 1‐ and 7‐day post‐natal animals. From the changes, the cerebral energy use rates were calculated to be 1·57 mmol/kg/min in fetuses, 1·33 mmol/kg/min in 1‐day‐olds and 2·58 mmol/kg/min in 7‐day‐olds. Maximal rates of lactate accumulation during ischemia, as a measure of glycolytic capacity, were comparable in fetuses and neonates, but were about twice as great in 7‐day‐old rats. It is concluded that in post‐natal animals survival in anoxia and cerebral energy consumption are inversely, and nearly quantitatively, related. However, the reduced cerebral energy requirement cannot entirely account for the greater anoxic resistance of fetuses.
SYNTHESIS, SUBCELLULAR DISTRIBUTION AND TURNOVER OF DOPAMINE β‐HYDROXYLASE IN ORGAN CULTURES OF SYMPATHETIC GANGLIA AND ADRENAL MEDULLAE
Authors: Gagnon C. , Schatz R. , Otten U. , Thoenen H. 
Published: October 2006

Abstract—The synthesis, subcellular distribution and turnover of dopamine β‐hydroxylase was studied in organ cultures of rat adrenal medullae and superior cervical ganglia. After exposure to [3H]leucine for 1 or 3 h, the tissues were homogenized at various time intervals and the amount of labelled dopamine β‐hydroxylase in different subcellular fractions (cytosol, soluble and membrane‐bound fraction of catecholamine storage vesicles) was determined by immunoprecipitation and subsequent electrophoresis. In cultured adrenal medullae, induction of dopamine β‐hydroxylase initiated in vivo by administration of reserpine affected both soluble and membrane‐bound pools of dopamine β‐hydroxylase to a similar extent after pulse‐labelling for 1 or 3 h. The half‐lives of dopamine β‐hydroxylase, which amounted to 6 h for the cytosol, 7.5 h for the soluble vesicular and 32 h for the membrane‐bound vesicular pools were not altered by pretreatment with reserpine. In superior cervical ganglia the half‐lives of the soluble pools were 2–3 times longer than in the adrenal medulla, whereas the half‐life of the membrane‐bound fraction was the same as in the adrenal medulla. In both organs the most heavily labelled fraction (both after a pulse of 1 or 3 h) was always that of the vesicular membrane, suggesting that newly‐synthesized dopamine β‐hydroxylase is immediately incorporated into the storage vesicles and not via release into the cytosol from the site of synthesis. The fact that the half‐life of membrane‐bound dopamine β‐hydroxylase is markedly longer than that of the two soluble pools suggests that the single pools are not only independently supplied by newly‐synthesized DBH but there is also no appreciable subsequent exchange between soluble and membrane‐bound pools.
EFFECT OF LITHIUM ON DOPAMINE UPTAKE BY BRAIN SYNAPTOSOMES
Authors: Stefanini E. , Argiolas A. , Gessa G. L. , Fadda F. 
Published: October 2006

Abstract—Lithium chloride exerts two opposite effects on dopamine uptake by synaptosomes isolated from rat caudate nucleus. Added in vitro, it inhibits dopamine uptake; whereas administered chronically in vivo, it enhances dopamine uptake in vitro. Thus, in vitro, 1, 2.5, 5 and 10meqiv.l−1 of lithium chloride decrease [3H]dopamine uptake by 13, 17, 25 and 31%, respectively. Synaptosomes isolated from rats treated with lithium chloride for 20 days, show a 23% increase in [3H]dopamine uptake with respect to synaptosomes isolated from control rats. It is suggested that chronic lithium treatment stimulates a compensatory mechanism which overcomes its direct inhibitory effect on [3H]dopamine uptake.
INCREASED SYNTHESIS OF DOPAMINE β‐HYDROXYLASE IN CULTURED RAT ADRENAL EDULLAE AFTER IN VIVO ADMINISTRATION OF RESERPINE
Authors: Gagnon C. , Otten U. , Thoenen H. 
Published: October 2006

Abstract— The present experiments were designed to provide direct evidence that the increase in dopamine β‐hydroxylase (DBH) activity after treatment with reserpme results from an augmented synthesis of new enzyme protein. After in vivo experiments had shown that DBH could not be labelled to a sufficient extent even after administration of high doses (8.3 mCi/kg) of [3H]leucine we took advantage of earlier observations that neuronally‐mediated enzyme induction initiated in vivo progresses in organ cultures of adrenal medullae in a similar manner as in vivo. With that system it was possible to achieve a sufficient labelling of DBH molecules and to provide evidence that the increase in DBH activity produced by reserpine was really due to a specific increase in DBH synthesis. The fact that the half‐life of DBH was identical in organ cultures of controls and reserpine‐treated animals eliminated the possibility that the increased labelling of DBH after reserpine results from a slower rate of degradation.Both the experiments in vivo and in organ culture showed very clearly that the immunoprecipitation of labelled molecules has to be followed by additional purification by gel electrophoresis since in spite of the use of monospecific antibodies and careful washing of the immunoprecipitates contaminating coprecipitated labelled molecules accounted for up to 96% of the total precipitated radioactivity in whole adrenals (in vivo experiments) and up to 80% in adrenal medulla (organ culture experiments). The coprecipitation of contaminants most probably results from the addition of carrier proteins, used in order to make the precipitation of the small amounts of labelled proteins visible.
DEFICIENCY OF A Ca2+‐ATPase IN BRAINS OF SEIZURE PRONE MICE
Authors: Rosenblatt D. E. , Lauter C. J. , Trams E. G. 
Published: October 2006

Abstract– Ca2+‐stimulated ATPase activity was studied in membrane enriched preparations from the brains of audiogenic seizure‐prone (DBA) and control (C57 and C3H) mice. The animals ranged in age from 7 to 60 days. Na+, K + ‐ATPase, 5′‐nucleotidase and p‐nitrophenylphosphatase were assayed to evaluate membrane integrity.Ca2+‐ATPase was significantly lower in DBA mice; notably during the period of maximal seizure sensitivity. Mg2+ ‐ATPase somewhat followed the pattern shown by Ca2+ ‐ATPase. Na+, K+ ‐ATPase in DBA did not differ significantly from controls and there were no differences in either 5′‐nucleotidase or p‐nitrophenylphosphatase activities.Ca2+‐ATPase kinetics experiments showed even more clearly the difference between DBA and control preparations. Vmax was consistently lower in DBA than in controls. The Km values appeared to fall into groupings suggestive of sequential synthesis of isozymes. Differences in the patterns of DBA and C57 just prior to the time of maximal seizure sensitivity are interpreted as reflecting failure to synthesize an isozyme or delay of its synthesis. The genesis of seizures through such an enzymatic defect may be related to the action of translocated ATP on the plasma membrane.
CHARACTERIZATION OF A RAT BRAIN CATHEPTIC CARBOXYPEPTIDASE (CATHEPSIN A) INACTIVATING ANGIOTENSIN‐II
Authors: Grynbaum Alice , Marks N. 
Published: October 2006

Abstract—Catheptic carboxypeptidase (cathepsin A) is present in lysosomal‐enriched fractions of rat brain at levels approximately 5‐fold that of cathepsin B1 and of the classical carboxypeptidase A but lower than that of cathepsin C and carboxypeptidase B. Cathepsin A was purified 40‐fold by extraction of calf brain with an acetate buffer containing 0.5% desoxycholate followed by heat treatment, salt precipitation and chromatography on DEAE‐Sephadex. Purification revealed the presence of two distinct isoenzymatic forms of high mol. wt that were very stable when frozen in the presence of sucrose and KCl. Among N‐protected dipeptides used as substrates the highest activity was given by Z‐Glu‐Tyr and Z‐Phe‐Tyr at a pH optimum of 5.5, Km1.1 mm and Vmax 0.5 μmol (Tyr)/mg protein per min. Brain cathepsin A was completely inhibited by low concentrations of DFP and PCMB but unaffected by thiols, EDTA and specific inhibitors of other cathepsins (pepstatin and chymostatin). The carboxypeptidase A‐like specificity of cathepsin A was confirmed by breakdown of Ile5‐angiotensin with release of C‐terminal Phe. Cathepsin A may play a role in the turnover of selected hormonal peptides containing C‐terminal neutral amino acids and in the sequential breakdown of proteins associated with degenerative conditions such as demyelination.
UNESTERIFIED FATTY ACIDS IN RAT CEREBRAL CORTEX: THEIR ASSOCIATION WITH PROTEOLIPIDS
Authors: Lunt G. G. , James J. E. 
Published: October 2006

Abstract—Proteolipids isolated from rat cerebral cortex have unesterified fatty acids associated with them. The fatty acids may be divided into two pools on the basis of their susceptibility to methylation by diazomethane. The fatty acid composition of the two pools is different. Proteolipid fractions separated by chromatography on Sephadex LH 20 have varying amounts of unesterified fatty acids associated with them and the composition of the fatty acids is different for each proteolipid fraction.
STUDIES ON FUNCTIONAL AND METABOLIC ROLE OF UREA CYCLE INTERMEDIATES IN BRAIN
Authors: Sadasivudu B. , Rao T. Indira 
Published: October 2006

Abstract— The distribution of argininosuccinate synthetase, argininosuccinase and arginase, and the synthesis of urea in cerebullum. cerebral cortex and brain stem have been studied. Cerebral cortex had high levels of argininosuccinate synthetase and argininosuccinase. and a high ability to synthesize urea from aspartic acid and citrulline. Of the three regions, cerebullum had the highest arginase activity. The activities of the enzymes transamidinase and ornithine aminotransferase in the metabolism of arginine and ornithine in pathways other than urea formation have been studied in the three regions of the rat brain. The activity of creatine phosphokinase in all regions was the same: carbamylphosphatase activity was highest in cerebullum. Cerebral cortex had a high activity of aspartic acid transcarba‐mylase. The brain stem, among the three regions, had the lowest activities of glutamine synthetase and glutaminase. The activities of these enzymes in the different regions are discussed in relation to urea production and the utilization of the urea cycle intermediates.Intraperitoneal injection of high amounts of citrulline brought about a rise in the glutamine synthetase activity of cerebellum and brain stem and a rise in ornithine aminotransferase in cerebral cortex and liver. These results are discussed in relation to the mechanism of action of citrulline in alleviating the toxicity in hyperammonaemic states.
EFFECT OF COPPER DEFICIENCY ON THE CONCENTRATIONS OF CATECHOLAMINES AND RELATED ENZYME ACTIVITIES IN THE RAT BRAIN1
Authors: Morgan R. F. , O'Dell B. L. 
Published: October 2006

Abstract—Immature rats were made copper deficient by feeding them a low (< 1 p. p. m.) copper diet. During the gestation and lactation periods their dams consumed the same diet. Controls received a dietary supplement of 10 p. p. m. copper. At approx 7 weeks of age, the deficient animals exhibited signs of neurological dysfunction and gross lesions of the brain. Cytochrome oxidase activity and copper content of the liver and brain were used as criteria of copper status and confirmed the existence of severe deficiency. The whole brains minus cerebella of the deficient animals contained approx 30% less dopamine and norepinephrine than those of the controls. The tyrosine hydroxylase activity was depressed more than 25% in the copper deficient brains while the superoxide dismutase activity was lowered more than 35%. There was a high correlation between the chief criterion of copper status, liver cytochrome oxidase activity, and the brain concentrations of dopamine, norepinephrine and tyrosine hydroxylase activity. The decrease in activity of tyrosine hydroxylase was sufficient to account for the lowered concentrations of the catecholamines.
STUDIES OF THE UPTAKE AND RELEASE OF [3H]β‐ALANINE BY FROG SPINAL SLICES
Authors: Adair R. , Davidoff R. A. 
Published: October 2006

Abstract— [3H]β‐Alanine was accumulated by frog spinal cord slices by two transport components with estimated Km values of 31 M (‘high‐affinity’) and 11 HIM (‘low affinity’) respectively. The high affinity uptake exhibited sodium ion and energy dependence, temperature sensitivity, had a very low Vmax (10.4 nmol/g/min) compared to GABA and glycine, was competitively inhibited by GABA (Kt 2 M), and was significantly reduced by the presence of glycine and of taurine in the incubating medium.When slices preloaded with [3H]β‐alanine were superfused with medium containing depolarizing concentrations of potassium ions, there was a small, but consistent, increase in [3H]β‐alanine efflux: 1.4 times prestimulation rates in 40 mM potassium. When the superfusate was altered by omission of calcium and addition of concentrations of magnesium (10 mm), manganese (1 mM), and cobalt (1 mM) ions sufficient to block reflex transmission in the isolated in vitro frog cord, the potassium‐evoked release was not blocked. Release was decreased by lanthanum ions (1 mM). Release of [3H]GABA and [3H]glycine in parallel experiments was inhibited by magnesium, manganese, cobalt and lanthanum. Veratridine significantly increased the release of [3H]GABA and [3H]glycine but not of [3H]β‐alanine.These observations demonstrate the non‐specificity of β‐alanine uptake and the unconventional nature of the calcium‐dependence of β‐alanine release and therefore do not lend support to the hypothesis that β‐alanine functions as a neurotransmitter in frog spinal cord.
CADMIUM ALTERS BEHAVIOUR AND THE BIOSYNTHETIC CAPACITY FOR CATECHOLAMINES AND SEROTONIN IN NEONATAL RAT BRAIN1
Authors: Rastogi R. B. , Merali Z. , Singhal R. L. 
Published: October 2006

Abstract— Daily exposure to cadmium (10 μg/100g) for 30 days since birth significantly increased spontaneous locomotor activity as well as striatal tyrosine hydroxylase and mid‐brain tryptophan hydroxylase. The endogenous levels of norepinephrine, dopamine and serotonin failed to change in various brain regions of cadmium‐treated rats. In contrast, the concentration of 5‐hydroxyindoleacetic acid tended to rise but was significantly different from controls only in the mid‐brain region. The data suggest that cadmium treatment in early life increased the synthesis and physiological utilization of these putative transmitters which in turn probably altered locomotor performance.Increasing the dose of cadmium to 100 μg/100 g for 30 days decreased body weight (by 19%) and produced slight increases in the turnover of brain amines. However, the rise was not dose‐dependent. Furthermore, the locomotor activity remained the same as that seen in rats treated with the low dose of cadmium. The levels of dopamine in hypothalamus and that of norepinephrine in several brain regions examined were enhanced. This could in part, be attributed to decreased (12%) activity of catechol‐O‐methyl transferase enzyme. Administration of the high dose of cadmium produced significant increases in 5‐hydroxyindoleacetic acid level. Data suggest that cadmium acts at some step in the sequence of intracellular events that leads to increased synthesis and presumably turnover of brain catecholamines and serotonin. Since high dosage of this heavy metal failed to produce a dose‐dependent change in locomotor activity, it is not possible to impute any casual role for these amines in the production of hyperactivity seen in cadmium‐treated rats.
RAPID EFFECTS OF VERATRIDINE, TETRODOTOXIN, GRAMICIDIN D, VALINOMYCIN AND NaCN ON THE NA+, K+ AND ATP CONTENTS OF SYNAPTOSOMES
Authors: Li P. P. , White T. D. 
Published: October 2006

Abstract— The effects of brief exposures of a number of depolarizing agents on 24Na+ influx and on the Na+, K+ and ATP contents of synaptosomes were studied using a Millipore filtration technique to terminate the reaction. When synaptosomes were incubated in normal medium, there was a rapid influx of 24Na+ and a gain in Na’contents; neither the 24Na+ influx nor the Na+ gain were blocked by tetrodotoxin suggesting that this Na+ entry did not involve Na+‐channels.Veratridine markedly increased the rate of 24Na+ influx into synaptosomes and also increased the Na+ content and decreased the K+ content of synaptosomes within the first 10s of exposure. The normal ion contents were reversed by 1 min. The effects of veratridine on Na+ influx and on synaptosomal ion contents were prevented by tetrodotoxin and required Na+ in the medium.The ionophores gramicidin D and valinomycin also rapidly reversed the Na+ and K+ contents of synaptosomes, but these effects could not be blocked by tetrodotoxin. The reducing effect of gramicidin D on synaptosomal K+ content required Na’in the medium, whereas valinomycin caused a fall in the K+ content of synaptosomes in a Na+‐free medium.Veratridine and gramicidin D, at concentrations known to reverse the synaptosomal ion contents, did not affect synaptosomal ATP levels. In contrast, valinomycin and NaCN caused an abrupt fall in synaptosomal ATP levels.The above findings suggest that veratridine quickly alters synaptosomal Na+ and K+ contents by opening Na +‐channels in the presynaptic membrane, and provide direct evidence for the existence of Na+‐channels in synaptosomes. In contrast, gramicidin D and valinomycin appear to act independently of Na +‐channels, possibly by their ionophoric effects and, in the case of valinomycin, by diminishing synaptosomal ATP contents and hence diminishing Na+‐pump activity.The rapid reversals of Na+ and K+ contents by these drugs could affect the resting membrane potentials, Na+‐Ca2+ exchange across the synaptosomal membrane, and the release, synthesis and uptake of neurotransmitters by synaptosomes.
A MODIFIED PROCEDURE FOR ISOLATION OF ASTROCYTE‐ AND NEURON‐ENRICHED FRACTIONS FROM RAT BRAIN
Authors: Farooq Muhammad , Norton William T. 
Published: October 2006

AbstractOur previously published method for isolation of neurons with extensive processes (Farooqet al., 1977) has been modified to permit the isolation of both astrocyte‐ and neuron‐enriched fractions. Rat cerebral tissue is incubated with acetylated trypsin and disrupted. The cell suspension is separated first by differential centrifugation and then by gradient centrifugation on discontinuous Ficoll gradients. The method is reproducible and is applicable equally well to immature and adult animals. The yield of astrocytes of 57% particle purity, and higher weight purity, is 4–7 × 106 cells/brain, amounting to 1.5–2.0 mg of protein. The astrocytes appear to be a mixture of fibrous and protoplasmic types. The yield of neurons of 90% particle purity is 10–14 × 106 cells/brain, amounting to 2.4–3.0 mg of protein. A total yield of neurons of 28–37 × 106 cells/brain can be obtained at 70% purity. These preparations have been characterized by light microscopy and protein, RNA and DNA content.
THE EFFECT OF BROMOCRIPTINE ON RAT STRIATAL ADENYLATE CYCLASE AND RAT BRAIN MONOAMINE METABOLISM
Authors: Markstein R. , Herrling P. L. , Asper H. R. Buurki. H. , Ruch W. 
Published: October 2006

AbstractIn slices and homogenate from rat brain striatum bromocriptine in marked contrast to DA. NA and apomorphine. had no stimulatory effect on adenylate cyclase activity, but antagonised the stimulatory effects of both NA and DA.Bromocriptine (10 mg/kg s.c.) decreased the turnover of DA in striatum and limbic structures 3h after drug administration. However, an increase in the turnover of NA in the brain stem and that of 5‐HT in the cortex was observed 4h following treatment with bromocriptine. Possible modes of action of bromocriptine are discussed.
CALCIUM UPTAKE AND EXCHANGE IN LEG NERVES OF THE CRAB ‘LIBINIA EMARGINATA’
Authors: Bianchi C. Paul , Lakshminarayanaiah N. 
Published: October 2006

Abstract—The kinetics of washout of radioactive calcium (45Ca) from nerves of the larger legs of Libinia emarginata equilibrated in various solutions of artificial sea water (ASW) containing 1, 11, 22 or 44 mM‐Ca was followed. In every case two components were found when the period of washout was not more than 30 min. The washout of 14C labelled inulin and sucrose gave one and two components respectively; these substances were considered to exist in the extracellular regions of nerve fibers. Comparison of the total calcium of the nerves determined spectrophotometrically and by measurement of radioactivity indicated that the exchangeability of calcium in the nerves in ASW containing 44 and 22 mM‐Ca was 100%. In the case of nerves equilibrated in 11 mM‐CaASW, two groups of nerves, one (group A) containing a high concentration of Ca (13.6 μmol/g) and the other (group B) containing a low concentration (7.3 μmol/g), were detected Several factors which could account for the accumulation of Ca in nerve fibers in group A were considered. The electrolyte data relating to group A nerve fibers indicated that Ca accumulation may be due to the presence of a high concentration of sodium in those fibers. However, the exchangeability of Ca for group A was about 47%; and in group B fibers, it was 61%. The exchangeability was less than 41% in the case of nerves equilibrated in 1 mM‐CaASW. The kinetic parameters of 45Ca washout from the nerve fibers have been used to develop a model for the distribution of calcium among the different compartments of the nerve fibers.