bluuebunny/crossref_metadata_2025 huggingface dataset:
OBSERVATIONS ON THE BIOSYNTHESIS OF RAT BRAIN CERAMIDE AND CEREBROSIDE IN VIVO
Authors: Carter T. P. , Kanfer J.
Published: October 2006

Abstract— The incorporation in vivo of l‐[14C]serine into ceramide and cerebroside of young rat brain has been studied. Acid hydrolysis of labelled ceramide and galactosyl‐ceramide followed by selective partitioning of the resulting components indicated that 88 per cent of the radioactivity was present in the long‐chain base portion. At early time points (10 min, 20 min) the precursor was incorporated into ceramide and to a lesser degree into glucosyl‐ceramide. During time intervals of 5 and 10 h, the specific activity values (d.p.m./μmol) for ceramide and glucosyl‐ceramide decreased, while values for galactosyl‐ceramide, containing either unsubstituted fatty acids (NFA) or α‐hydroxy fatty acids (HFA), increased 50 and 30 per cent, respectively. Analysis of labelled ceramide at all time points studied (10 min‐10 h) indicated that l‐[14C]serine was incorporated onto the NFA type. This observation suggests that HFA‐ceramide may not be the physiological precursor of HFA‐galactosyl‐ceramide. In this context, the postulated precursor roles of both ceramide and psychosine in the biosynthesis of brain cerebrosides are discussed.
UTILIZATION OF ACETATE AND PYRUVATE FOR THE SYNTHESIS OF‘TOTAL’,‘BOUND’AND‘FREE’ACETYLCHOLINE IN THE ELECTRIC ORGAN OF TORPEDO
Authors: Israël M. , Tuček S.
Published: October 2006

—Slices of tissue of the electric organ of Torpedo marmorata were incubated in vitro in a salineurea‐sucrose solution containing a labelled precursor of the acetyl moiety of ACh ([1‐14C]glucose, [2‐14C]pyruvate, or [1‐14C]acetate) either alone or in the presence of another unlabelled precursor. The incorporation of 14C from [1‐14C]acetate into ACh was considerably higher than from the other two substrates. The specific radioactivities (SRA) of the‘total',‘bound’and‘free’ACh were compared in experiments with [2‐14C]pyruvate and [1‐14C]acetate. With both precursors, the SRA of the‘bound’ACh were lower than those of‘total’ACh; consequently, the‘free’ACh pool was more labelled than the‘bound’pool. After short incubations with [2‐14C]pyruvate the SRA of'bound’ACh were closer to the SRA of‘total’ACh than with [1‐14C]acetate.

A simple method is described for the labelling of ACh and its separation from other labelled compounds in experiments with the electric organ using [14C]acetate as the labelled precursor.
IN VIVO CHANGES OF CEREBRAL CYCLIC ADENOSINE 3′,5′‐MONOPHOSPHATE INDUCED BY BIOGENIC AMINES: ASSOCIATION WITH PHOSPHORYLASE ACTIVATION
Authors: Edwards C. , Nahorski S. R. , Rogers K. J.
Published: October 2006

—The intravenous injection of adrenaline, isoprenaline and histamine to 4‐6‐day‐old chicks resulted in a rapid increase in the cyclic AMP content of cerebral hemispheres that had been removed and frozen within 0·5 s using a freeze‐blowing technique. Noradrenaline, dopamine, adenosine, 5‐HT and acetylcholine did not significantly alter the nucleotide concentration in vivo. Addition of adrenaline, isoprenaline and histamine to incubated chick cerebral cortex slices also increased the cyclic AMP content of the tissue. Noradrenaline was considerably less potent than these amines and adenosine was ineffective.

Low phosphorylase a levels (16 per cent of total activity) were observed in instantaneously frozen cerebral hemispheres of untreated chicks. The injection of adrenaline, isoprenaline and histamine resulted in a rapid conversion of phosphorylase b to a and a significant fall in tissue glycogen. Administration of noradrenaline was without effect on the relative forms of phosphorylase and also failed to influence cerebral glycogen. Phosphorylase activation was not observed in chick cerebral slices under conditions producing large increases in cyclic AMP.

It is suggested that in vivo phosphorylase activation and subsequent glycogenolysis may occur, at least in part, in glia and that these cells may be damaged during preparation of cerebral slices. The results provide evidence of a metabolic role for cyclic AMP in cerebral tissue.
INFLUENCE OF ANAESTHETICS ON THE BALANCE BETWEEN PRODUCTION AND UTILIZATION OF ENERGY IN THE BRAIN
Authors: Nilsson L. , Siesjö B. K.
Published: October 2006

Abstract— The influence of general anaesthesia upon the metabolic state of the brain was evaluated from the tissue concentrations of ATP, ADP and AMP, and from the concentrations of glycolytic and citric acid cycle intermediates, in immobilized and artificially ventilated rats anaesthetized either with 70% N2O, 1% halothane or 60 mg/kg of pentobarbitone. The results were compared to the results obtained on awake animals in fentanyl‐analgesia. The adenylate energy charge was identical in all groups studied and there were no H+‐independent changes in the phosphocreatine/creatine ratios. In pentobarbitone anaesthesia there was an accumulation of glucose 6‐phosphate and a fall in fructose 1,6‐diphosphate, indicating inhibition of phosphofructokinase. No significant changes in these metabolites were observed with halothane or nitrous oxide anaesthesia and the substrate patterns differed from that obtained with pentobarbitone.

The blood glucose concentrations were higher in the unanaesthetized, immobilized rats given fentanyl than in those anaesthetized. There was a direct relationship between the glucose concentrations in blood and in tissue. The glucose concentration ratios intracellular water to blood were higher in the anaesthetized than in the unanaesthetized animals, increasing with increasing depth of anaesthesia. The intracellular lactate concentrations were lowest in the groups given pentobarbitone and fentanyl citrate, and there was thus no direct relationship between lactate concentration and depth of anaesthesia.
THE TURNOVER OF ISOTOPICALLY LABELLED DNA IN VIVO IN DEVELOPING, ADULT AND SCRAPIE‐AFFECTED MOUSE BRAIN
Authors: Kimberlin R. H. , Shirt D. B. , Collis S. C.
Published: October 2006

Abstract— Tracer experiments using [3H]thymidine have shown that a large proportion of the DNA synthesized in control and scrapie‐affected mouse brain is metabolically unstable. Although the turnover of mitochondrial DNA contributed to the loss of radioactivity from whole brain, it has been shown that 70 per cent of the labelled nuclear DNA was removed between 1 and 21 days after injecting the isotopic precursor. Observations on developing mouse brain, where the rate of DNA synthesis is far higher than that in adult brain, also revealed the existence of metabolically unstable DNA. Similar studies on developing and adult brain using [14C]thymidine indicated that most of the radioactivity lost in vivo was not due to radiation damage to newly labelled DNA molecules. Hydroxyapatite chromatography of heat denatured and renatured DNA from adult brain showed that the rates of turnover of the poorly, moderately and highly reiterated species of nuclear DNA were similar. The results of some dissection experiments have further shown that the observed breakdown of DNA in adult brain was not specifically associated with the turnover of subependymal cells. It is suggested that a metabolically labile fraction of nuclear DNA is present in developing and adult mouse brain and that the amount of tracer incorporated into this fraction is increased in mice infected with scrapie.
IN VITRO EXPERIMENTS ON THE METABOLISM, ACCUMULATION AND RELEASE OF 5‐HT IN THE NERVOUS SYSTEM OF THE SNAIL HELIX POMATIA
Authors: Osborne N. N. , Neuhoff V.
Published: October 2006

Abstract— The accumulation, metabolism and stimulated‐induced release of 5‐HT in the nervous system of the snail was studied. When nervous tissue was incubated at 24°C in a medium containing [14C]5‐HT or [3H]tryptophan, tissue: medium ratios of about 25:1 and 4:1 respectively were obtained after 45 min incubation.

The process responsible for [14C]5‐HT accumulation showed properties of an active transport system: it was temperature sensitive and was greatly inhibited by dinitrophenol and ouabain. Furthermore, the accumulation process was inhibited by imipramine and desipramine.

Of a number of analogues of indole, N‐acetyl‐5‐HT and 5‐hydroxytryptophan were the most potent in the inhibition of the accumulation of [14C]5‐HT. The presence of a large molar excess of amino acids had little effect.

A small amount (less than 14 per cent) of the accumulated [14C]5‐HT was metabolized to form 5‐hydroxyindole acetic acid, even after long periods (2 h) of incubation. The accumulated [3H]tryptophan was metabolized to form 5‐hydroxytryptophan and 5‐HT; the content of formed [3H]5‐HT increased with incubation time whilst the [3H]5‐hydroxytryptophan remained more or less constant.

The presence of p‐chlorophenylalanine in the incubation medium did not interfere with the accumulation of [3H]tryptophan, though it inhibited the formation of [3H]5‐hydroxytryptophan and to a greater extent [3H]5‐HT.

A rapid efflux of the accumulated [14C]5‐HT from snail nervous tissue was observed on electrical stimulation. Slower release resulted when the Ca2+ ion content of the incubation medium was replaced by Mg2+ ions. There is also a slight efflux of radioactive substances following electrical stimulation in tissues previously incubated in [3H]tryptophan. Most of this radioactivity was attributed to the formed [3H]5‐HT.

The data support the idea that 5‐HT is a transmitter‐substance in the snail Helix pomatia, and that re‐uptake of the substance is a method of inactivating the released amine.
REGIONAL CHANGES IN AMINO ACID CONTENT IN DEVELOPING RAT BRAIN1
Authors: Cutler R. W. P. , Dudzinski D. S.
Published: October 2006

Abstract— The content of several amino acids was measured in five discrete regions of the central nervous system of the developing rat, using a [3H]dansylation assay procedure. Both regional differences in amino acid content and regional differences in rate of change of amino acids during maturation were found. Particularly prominent were the maturational changes and high adult contents of glutamic acid in the cerebral cortex, GABA in the hypothalamus, and aspartic acid in the medulla.
RNA METABOLISM IN ISOLATED MOUSE BRAIN NUCLEI DURING EARLY POSTNATAL DEVELOPMENT
Authors: Banks‐Schlegel S. P. , Johnson T. C.
Published: October 2006

—RNA metabolism in isolated brain nuclei has been shown to be dramatically altered during early postnatal brain development. The present study involved an examination of the RNA products synthesized by nuclei at various stages of postnatal neural maturation. In all cases, the majority of the RNA appeared to be heterodisperse, non‐ribosomal and non‐tRNA in nature. In comparison to the RNA isolated from nuclei of neonatal tissue, the RNA from nuclei of 12‐day and 30‐day‐old mouse brain was found to be of smaller molecular weight. Despite the heterodisperse nature of these RNA molecules, the addition of α‐amanitin did not completely inhibit nuclear synthesis.

An investigation of RNA synthesis in isolated neuronal and glial cell nuclei revealed that nucleic acid metabolism in these respective cell populations had different and distinct developmental patterns. Preparations enriched with glial cell nuclei were found to be most active at birth and then decreased in activity (3–4‐fold) during neural maturation. On the other hand, the rate of RNA synthesis in fractions enriched in neuronal cell nuclei was observed to increase dramatically in activity (4–5‐fold) until 14 days of age. From 14 days of age until adulthood, RNA synthetic activity remained essentially the same.
THE EFFECTS OF SOME NEWER ANAESTHETICS ON THE IN VITRO ACTIVITY OF GLUTAMATE DECARBOXYLASE AND GABA TRANSAMINASE IN CRUDE BRAIN EXTRACTS AND ON THE LEVELS OF AMINO ACIDS IN VIVO
Authors: Dye D. J. , Taberner P. V.
Published: October 2006

—The effects of several anaesthetic and hypnotic compounds with well‐defined excitatory side‐effects on glutamate decarboxylase and γ‐aminobutyric acid transaminase activity have been examined. The dissociative anaesthetics ketamine and γ‐hydroxybutyric acid produced competitive inhibition of glutamate decarboxylase with respect to glutamate at concentrations which had no effect on GABA transaminase activity. The inhibitor constant (Ki) values were, ketamine: 13.3 mm, γ‐hydroxybutyric acid; 8.8 mm. The steroid anaesthetic alphaxalone was also a potent competitive inhibitor of glutamate decarboxylase Ki= 4.1 mm). Pentobarbitone, thiopentone and methohexitone non‐competitively inhibited both glutamate decarboxylase and GABA‐transaminase but only at high concentration (> 20 mm). None of the drugs tested produced any significant change in brain GABA or glutamate levels following the injection of an hypnotic or anaesthetic dose. It is proposed that an alteration in the rate of GABA synthesis as a result of the inhibition of glutamate decarboxylase could explain the convulsive properties of the dissociative anaesthetics when given at high doses.
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

—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

—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.
CEREBRAL UPTAKES AND EXCHANGE DIFFUSION IN VITRO OF l‐ AND d‐GLUTAMATES
Authors: Benjamin A. M. , Quastel J. H.
Published: October 2006

Abstract— 1. Whereas exogenous l‐glutamate enters rat brain cortex slices incubated in a glucose‐physiological saline medium by both low affinity (Km= 0.7 mm) and high affinity (Km= 27−30 μM) processes, the uptake of d‐glutamate occurs only by a low affinity (Km= 2mm) system. 2. d‐glutamate appears to release l‐glutamate from incubated rat brain cortex slices only to a very small extent, whether the tissue l‐glutamate is of endogenous or exogenous origin. 3. Competitive inhibition takes place between l‐ and d‐glutamates at the low affinity carrier. This indicates that a common carrier exists for l‐ and d‐glutamates for the low affinity uptake process. 4. Apparently non‐competitive inhibition by d‐glutamate of l‐glutamate uptake occurs at the high affinity carrier, but the affinity of d‐glutamate for this carrier is about 0.4% of that of l‐glutamate. 5. Both d‐, and l‐glutamate exchange freely with labelled d‐glutamate taken up by preliminary incubation of the brain slices with this amino acid. Whereas l‐glutamate exchanges freely with labelled l‐glutamate taken up by preliminary incubation, d‐glutamate shows little or no exchange. 6. The uptake of labelled d‐glutamate by exchange diffusion into brain slices previously loaded with unlabelled d‐glutamate proceeds by a low affinity system. Therefore, the process of exchange diffusion does not necessarily involve a high affinity uptake component. 7. Whereas ouabain suppresses both high and low affinity concentrative uptakes of l‐ and d‐glutamate it has little apparent effect on the exchange diffusion process. 8. Sensitivity to tetrodotoxin of evoked release of l‐ and d‐glutamates, taken up by brain slices by preliminary incubation with these amino acids, indicates that the major proportion of the uptake of exogenous l‐ or d‐glutamate proceeds into non‐neuronal structures (presumably the glia). 9. At 0°C non‐carrier mediated (passive) diffusion of labelled d‐ and l‐glutamate takes place in brain slices.
DNA SYNTHESIS IN NEURONAL, GLIAL AND LIVER NUCLEI ISOLATED FROM THE ADULT GUINEA PIG
Authors: Inoue N. , Suzuki O. , Kato T.
Published: October 2006

Abstract— [3H]Deoxythymidine‐5′‐triphosphate incorporation into P51 (51% neuronal nuclei: 49% glial nuclei), P3 (3% neuronal nuclei: 97% glial nuclei) and liver nuclear preparations, isolated from the adult guinea pig, was determined in the presence of the other three complementary deoxyribonucleo‐tides. The enzymic characteristics of the DNA synthesis reaction were studied and DNA polymerase contents were estimated in neuronal, glial and liver nuclei. (1) Cerebral and liver nuclei exhibited similar enzymic properties for DNA synthesis activities with a few discrepancies. (2) P51 nuclei synthesized DNA 2.4‐fold more actively than P3 nuclei. Liver nuclei carried out the most active DNA synthesis. The proportion of chromatin DNA available as template and primer was estimated by comparison with native calf thymus DNA. The available proportions found, in terms of the total chromatin DNA. were 2.39% for P51 nuclei, 1.38% for P3 nuclei and 37.6% for liver nuclei. (3) Exogenous native and heat‐denatured calf thymus DNA were utilized as template and primer by DNA polymerase in nuclei in different ways depending on the nuclear species. The enzyme was saturated with native DNA by elevating the concentration and the activity reached a plateau. Denatured DNA inhibited the activity at the higher concentrations. (4) From the enzyme activities at a saturation concentration of exogenous DNA, DNA polymerase contents were estimated: P51 nuclei, 39.2 ± 2.6 (s.e.m.) units (fmol of TMP incorporated/30 min at 31°C)/μg of nuclear DNA; P3 nuclei. 24.5 ± 1.6; and liver nuclei, 72.5 ± 8.1; the specific activity obtained on a protein basis was 1.55 times higher with P3 nuclei than with P51 nuclei. (5) Denatured DNA inhibited the nuclear DNA polymerase activity dependent on native DNA. The efficiency of inhibition was in the order: P3 > P51 > liver nuclei.
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.
NUCLEAR‐CYTOSOL INTERACTIONS THAT MODULATE RNA SYNTHESIS AND TRANSCRIPT SIZE OF MOUSE BRAIN NUCLEI
Authors: Weck P. K. , Johnson T. C.
Published: October 2006

Abstract– The addition of a dialyzed cytosol preparation from various types of mouse tissue, guinea‐pig brain, and neuroblastoma cells resulted in an increased incorporation of [3H]GTP into RNA by mouse brain nuclei. In addition to a stimulation of the incorporation of [3H]GTP into RNA. the presence of these cytosol preparations also caused a significant increase in nuclear RNA transcript size. Although all cell cytosols appeared to influence nuclear RNA metabolism to some degree, dialyzed mouse serum had little stimulatory effect on brain nuclear RNA synthesis and failed to cause an increase in RNA product size. The polyanion, heparin, was found to be highly stimulatory to brain nuclear RNA synthesis although the size of the resulting RNA products was not significantly altered. RNA synthesis by neuronal and glial nuclei, isolated from adult brain tissue, showed a differential response to the presence of brain cytosol preparations. In the absence of cytosol, RNA synthesis by neuronal nuclei was more active than that measured in glial nuclei, and when the RNA products were analyzed by sucrose gradient centrifugation, those of glial nuclei were considerably larger than those isolated from neuronal nuclei. The addition of cytosol caused a significant increase in RNA transcript size with neuronal nuclei of adult brain tissue while little, if any, change in the size of the RNA products was measured with nuclei isolated from glial cells. Although an overall increase in product size could be measured in response to the addition of dialyzed cytosol with neuronal nuclei of 2,10, 20‐day old and adult (over 60 days of age) brain tissue, a greater response was measured with nuclei prepared from the brains of more mature animals where the proportion of larger RNA products (>10S) was greatly increased.
CALCIUM UPTAKE INTO RAT PHEOCHROMOCYTOMA CELLS1
Authors: Chalfie M. , Hoadley Deborah , Pastan S. , Perlman R. L.
Published: October 2006

Abstract– The uptake of 45Ca2+ into cell suspensions prepared from a transplantable rat pheochromocytoma was measured. The uptake of Ca2+ into these cells is biphasic; there is a rapid, initial uptake of Ca+, followed by a slower uptake that proceeds at a linear rate for at least 10min at 37°C. The uptake of Ca2+ is a linear function of the external Ca2+ concentration over the range of 0.13‐2.5 mm‐Ca2+ Incubation of the cells in a medium containing 56mm‐K+ results in a 2‐3 fold increase in the uptake of Ca2+ into the cells; 56mm‐K+ increases both phases of Ca2+ uptake. The cells apparently lack a mechanism to inactivate this 56 mm‐K+‐induced increase‐in Ca2+ permeability. Two inhibitors of K+ stimulated catecholamine secretion, diphenylhydantoin and verapamil, both inhibit K +‐stimulated Ca2+ uptake. These results provide a direct demonstration of the stimulus‐coupled uptake of Ca2+ into chromaffin cells, and provide additional evidence for the correlation of Ca2+ uptake with catecholamine secretion by these cells.
CHOLINERGIC SITES IN SKELETAL MUSCLE: INTERACTION WITH CONCANAVALIN A
Authors: Almon R. R. , Appel S. H.
Published: October 2006

Abstract– The interaction of normal and denervated skeletal muscle cholinergic sites with the lectin concanavalin A and concanavalin A‐Sepharose are detailed. Concanavalin A blocks the binding of 125I‐α‐bungarotoxin to both the high and low affinity sets of cholinergic sites described previously. The characteristics of the block of 125I‐α‐bungarotoxin binding to the high affinity set (acetylcholine receptor) is not competitive. The data suggest that the concanavalin binds multivalently to the macro‐molecular complex containing the ACh receptor site and sterically prevents the α‐bungarotoxin binding. The interaction of both sets of cholinergic sites with concanavalin A‐Sepharose was also studied. The macromolecule(s) containing both the high and low affinity sets of sites bind to the concanavalin A‐Sepharose. The data indicate a multivalent association with the affinity resin. Following the affinity procedure, a partial purification in both sets of sites is effected. The equilibrium binding of 125I‐diiodo‐α‐bungarotoxin to the preparations from the affinity procedure (both normal and denervated muscle) was examined. The KD of the α‐bungarotoxin binding to the high affinity sets of sites (acetylcholine receptor) in both normal and denervated preparations changes from ∼10−9mol/l to ∼ 10−10 mol/l following purification. No change in the KD of the α‐bungarotoxin binding to the low affinity set of sites was observed following purification. The 125l‐α‐bungarotoxin binding to the partially purified acetylcholine receptor was blocked by unlabelled α‐bungarotoxin, concanavalin A, d‐tubocurarine and carbamylcholine.
CHARACTERIZATION OF A RAT BRAIN CATHEPTIC CARBOXYPEPTIDASE (CATHEPSIN A) INACTIVATING ANGIOTENSIN‐II
Authors: Grynbaum Alice , Marks N.
Published: October 2006

—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

—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.
ADAPTIVE MECHANISMS OF THE NORADRENERGIC CYCLIC AMP GENERATING SYSTEM IN THE LIMBIC FOREBRAIN OF THE RAT: ADAPTATION TO PERSISTENT CHANGES IN THE AVAILABILITY OF NOREPINEPHRINE (NE)1,2
Authors: Vetulani Jerzy , Stawarz R. J. , Sulser Fridolin
Published: October 2006

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 a Kmax concentration of NE (concentration of NE which elicits maximal increase in the level of cyclic AMP) is significantly enhanced in slices from reserpinized animals, although the Ka value 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 the Ka value 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 catecholamine.
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.
EFFECT OF FATTY‐ACID DOUBLE‐BOND POSITION ON THE SELECTIVITY OF RAT‐BRAIN ENZYMES: THE INCORPORATION OF OLEIC AND CIS‐VACCENIC ACIDS INTO LYSOLECITHIN IN VITRO
Authors: Murphy M. G. , Spenge M. W.
Published: October 2006

Abstract— —Selectivity in the esterification of fatty acids to lysolecithin by rat‐brain enzymes in vitro was investigated using free fatty acids (activation plus esterification) and CoA esters (esterification) of two naturally‐occurring monoenoic fatty‐acid isomers, oleic acid [18:1 (n ‐ 9)] and cis‐vaccenic acid [18:1 (n ‐ 7)]. Esterification of free acids to l‐acyl‐sn‐glycero‐3‐phosphorylcholine (1‐acyl GPC) was dependent on CoA and ATP, and was stimulated by MgCl2 and NaF. Under comparable conditions, fatty‐acid activation (acyl‐CoA synthetase [acid: CoA ligase (AMP)] EC 6.2.1.3.) appeared to be rate‐limiting to 1‐acyl GPC acyltransferase (acyl‐CoA:l‐acylglycero‐3‐phosphocholine O‐acyltrans‐ferase, EC 2.3.1.23.), since rates were always less with free fatty acids than with the CoA esters. A comparison of substrate curves obtained with free fatty acids and CoA esters suggests a preference for oleic acid during activation. Acyltransferase activity with 2‐acyl GPC was similar with both acyl‐CoA isomers, whereas with 1‐acyl GPC, activity with oleoyl‐CoA consistently exceeded that with cis‐vaccenoyl‐CoA. This difference between patterns of selectivity in esterification of positions 1 and 2 of lecithin suggests that separate enzymes catalyze the two reactions. The transfer of the isomers to the 2 position was affected in a similar manner by changes in pH and temperature, as well as in protein, fatty acid (or acyl‐CoA), and 1‐acyl GPC concentrations. Patterns of incorporation with simultaneous incubation of both isomers suggests one enzyme. Differences in acyltransferase activity with the two isomerie acyl‐CoA's were observed in subcellular distribution, activity changes with brain maturation, and loss of activity on preincubation of microsomes at 45C. From these results it is not certain whether oleic and cis‐vaccenic acids are esterified to the 2 position by separate enzymes, or by one enzyme with different affinities for the isomers. However, the investigation clearly indicates that acyltransferases, and possibly acyl‐CoA synthetases in brain possess selectivity related to subtle differences in double‐bond position. These selectivities probably are important in determining the specific fatty‐acid composition of the complex lipids of brain.
THE PERMISSIVE ROLE OF HYPERTHERMIA IN THE DISAGGREGATION OF BRAIN POLYSOMES BY l‐DOPA OR d‐AMPHETAMINE1
Authors: Moskowitz M. A. , Rubin Deborah , Liebschutz J. , Munro H. N. , Nowak T. S. , Wurtman R. J.
Published: October 2006

Abstract— l‐DOPA or d‐amphetamine administration disaggregates brain polyribosomes in animals maintained in an environment warm enough (26°C) so that the drugs concurrently elevate their body temperatures to above 39°C. The production of equivalent hyperthermia (by keeping control rats at ambient temperatures of 40–44° C) does not cause similar disaggregation of brain polysomes. Hence, the role of hyperthermia in the drug‐induced disaggregation is permissive.
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.
THE ENCEPHALITOGENIC ACTIVITY AND MYELIN BASIC PROTEIN CONTENT OF ISOLATED OLIGODENDROGLIA
Authors: McDermott J. R. , Iqbal K. , Wisniewski H. M.
Published: October 2006

Abstract— Oligodendroglia isolated from frozen human brain induced EAE in the guinea pig when injected with Freund's complete adjuvant. An acid extract of the isolated cells was highly encephalitogenic. The disease was clinically and histologically similar to EAE induced with CNS white matter or myelin basic protein(MBP). The isolated cells were essentially myelin‐free but contained a large amount of myelin basic protein as determined by polyacrylamide gel electrophoresis. It was shown that the cells can absorb 125I‐MBP during isolation and the possibility that contamination from extra cellular MBP is responsible for the encephalitogenic activity is considered.