bluuebunny/crossref_metadata_2025 huggingface dataset:
IN VIVO METABOLISM OF 3‐KETOCERAMIDE IN RAT BRAIN1
Authors: Shoyama Yukihiro , Kishimoto Yasuo
Published: October 2006

Abstract—

Eight hours after intracerebral injection of a double‐labeled 3‐ketoceramide4, [1‐14C]lignoceroyl 3‐keto [1‐3H]sphingosine, various brain sphingolipids were isolated. Free ceramide and the ceramide portions of nonhydroxy cerebroside and sphingomyelin were further fractionated into subgroups containing longer‐chain or shorter‐chain fatty acids. Nonhydroxy ceramide, nonhydroxy cerebroside and sphingomyelin containing longer‐chain fatty acids had significant quantities of radioactivity with 3H/14C ratios similar to each other but lower than that of the injected material. The sphingolipids containing shorter‐chain fatty acids were also significantly labeled; however, the 3H/14C ratios were much higher than that of the injected material. Hydroxy‐ceramide and sulfatides contained very little radioactivity. However, hydroxy‐cerebroside contained an amount of radioactivity comparable to that of the longer‐chain nonhydroxy cerebroside with a similar 3H/14C ratio. It is proposed that the injected 3‐ketoceramide was converted into ceramide, cerebroside, and sphingomyelin and that the fatty acids of these lipids were partly replaced by other fatty acids during the metabolic conversions.
THE STABILITY OF VITAMIN B6 ACCUMULATION AND PYRIDOXAL KINASE ACTIVITY IN RABBIT BRAIN AND CHOROID PLEXUS
Authors: Spector Reynold , Shikuma Stanley N.
Published: October 2006

The effects of changes in the concentrations of pyridoxal phosphate and blogenic amines in brain on: (I) pyridoxal kinase (EC 2.7.1.35) activity in brain and choroid plexus; and (2) vitamin B6 accumulation by brain slices and isolated, intact choroid plexuses were studied. New Zealand white rabbits were treated parenterally with 200 mg/kg pyridoxine‐HCl for 3 days or 120 mg/kg 4‐deoxypyridoxine HCI or 5 mg/kg reserpine I day before death. After these treatments the mean concentration of pyridoxal phosphate in brain was elevated by 39% by pyridoxine and decreased by 57% by 4‐deoxypyridoxine. Reserpine had no effect. However, the ability of brain slices and isolated, intact choroid plexuses from the treated rabbits to accumulate [3H] vitamin B6 (with [3H]pyridoxine in the medium) was not different from untreated controls. Also, the specific activity of pyridoxal kinase in brain and choroid plexus of treated rabbits was not different from controls. These results show that vitamin B6 accumulation and pyridoxal kinase activity in brain and choroid plexus are independent of both pyridoxal phosphate and reserpine‐sensitive biogenic amine concentrations in brain. In vitro studies with pyridoxal kinase showed that. in both choroid plexus and brain. pyridoxal kinase was a single enzyme with a molecular weight of 43.000 and a Km, for pyridoxine of 2.0 μM Crude and partially‐purified pyridoxal kinase from brain was not inhibited by biogenic amines (1 mM) or pyridoxal phosphate (5 μM). These in vitro data are consistent with the lack of effect of changes in pyridoxal phosphate and biogenic amine concentrations (in brain) on pyridoxal kinase activity in brain in vivo.
SYNAPTOSOMAL TYROSINE HYDROXYLATION IN THE RAT BRAIN: COMPARISON OF ACTIVITY FROM HIPPOCAMPUS AND HYPOTHALAMUS WITH ACTIVITY FROM STRIATUM
Authors: Boarder Michael R. , Fillenz Marianne
Published: October 2006

Abstract— A modified tritium release assay for the measurement of synaptosomal tyrosine hydroxyl‐ation. with a sensitivity suitable for use on areas of the rat brain with a low density of catecholamine terminals. is described. The apparent Km, for tyrosine hydroxylase in the hippocampus was 9.3 μM. in the hypothalamus 6.1 μM and in the striatum 9.9 μM Preparations from all three regions showed a pH optimum of 6.0–6.2, and the activities were reduced to a small % of control by synaptosomal disruption. 3‐iodotyrosine. noradrenaline and reserpine. Membrane depolarization at a pH of 6.1 did not elevate tyrosine hydroxylation rates in any of the regions studied, although striatal tyrosine hy‐droxylation rates were elevated at a pH of 7.2 by 55 mM‐K+. The addition of dibutyryl cyclic AMP (0.5 mM) to the medium produced a 20‐30% elevation of the rates of hydroxylation in all three regions studied: addition of tetrahydrobiopterin (0.2 mM) elevated hydroxylation rates in the hypothalamus and striatum. These results indicate that many characteristics of tyrosine hydroxylase from the three regions are similar. In each case the enzyme is apparently sensitive to end‐product inhibition and to cyclic AMP activation.
THE HEXOSE MONOPHOSPHATE PATHWAY IN ETHYLNITROSOUREA INDUCED TUMORS OF THE NERVOUS SYSTEM
Authors: Coleman Mary Thoesen , Allen Norman
Published: October 2006

Abstract—

Respiration studies in vitro, in which tissue slices were incubated with [1‐14C]glucose or [6‐14C]glucose and 14CO2 collected, resulted in C‐1/C‐6 14CO2 ratios that were higher in slices of tumor and newborn brain than in slices of adult brain. In adult brain, the C‐1/C‐6 14CO2 ratio averaged close to unity. In slices of tumor and newborn brain however, the mean C‐1/C‐6 ratio was greater than three. Addition of phenazine methosulfate (PMS) increased conversion of [1‐14C]glucose to 14CO2 in slices of normal adult brain 5‐fold, and in slices of newborn brain and tumor, approx 12‐fold. Injection of animals with 6‐aminonicotinamide (6‐AN) decreased conversion of [1‐14C]glucose in slices of normal brain 30% but decreased conversion in tumor slices by 80%. Evidence supports the presence of an active hexose monophosphate pathway (HMP) in tumors of the nervous system regulated in part by available NADP+ levels. Inhibition by 6‐AN was more effective in tumors than in normal adult brain.
STIMULATION OF BRAIN ACETYL‐CoA HYDROLASE BY ATP AND ATP ANALOGUES
Authors: Matsuda T. , Yonehara N. , Ichida S. , Yoshida H.
Published: October 2006

Abstract—

The effects of ATP and ATP analogues on the brain acetyl‐CoA hydrolase (EC 3.1.2.1) were studied. The enzyme was stimulated reversibly by ATP‐Mg2+ the presence of Mg2+ being absolutely required for the stimulation. The stimulatory effect of ATP was highly specific since adenine nucleotides other than ATP had no stimulatory effects and nucleoside triphosphates other than ATP stimulated the enzyme much less than ATP in the following order: ATP > ITP CTP, UTP GTP. A phosphate modified analogue of ATP, AMP‐PNP had a similar stimulatory effect to that of ATP. Other ATP analogues such as AMP‐PCP and AMPCPP showed less stimulatory effect than ATP. The order of the stimulatory effects of these ATP analogues was: ATP > AMP‐PNP > AMP‐PCP > AMPCPP. The concentrations needed for half‐maximal stimulation of ATP, AMP‐PNP and AMP‐PCP were approx 0.11 mm, 0.22 mm, and 0.22 mm, respectively. Double reciprocal plots demonstrated that ATP as well as AMP‐PNP produced a significant decrease in the apparent Km, value for acetyl‐CoA and an increase in Vmax indicating that these nucleotides increased the affinity for acetyl‐CoA through binding at a site other than the catalytic site. The data described above suggest that the rate of hydrolysis of acetyl‐CoA may be regulated by the concentration of ATP in the micro‐environment of the enzyme.
PLASMALOGENASE ACTIVITIES IN THE BRAINS OF JIMPY AND QUAKING MICE
Authors: V.Dorman Robert , Freysz Louis , Mandel Paul , Horrocks Lloyd A.
Published: October 2006

Abstract—

The activity of plasmalogenase, which hydrolyzes the vinyl ether linkage of the plasmalogen molecule, increased markedly in control mouse brains during the period of most active myelin deposition. Only a slight increase in plasmalogenase activity was found in brains from jimpy mice. At all ages studied, the jimpy mouse brains had less plasmalogenase activity than the littermate control brains and this disparity increased with increasing age. By 25 days of age the jimpy brains contained only 43% of the activity observed in control brains. Adult quaking mouse brains also had significantly less plasmalogenase activity when compared to littermate controls. Thus, the plasmalogenase activities correlate well with the degree of myelination.
SULPHOLIPID METABOLISM IN DEVELOPING CHICKEN RETINA1
Authors: Dreyfus H. , Pieringer J. A. , Farooqui A. A. , Harth S. , Rebel G. , Sarlieve L. L.
Published: October 2006

Abstract—

Glycolipid analysis of chicken retina and brain indicated the presence of cerebroside, cerebroside 3‐sulphate and sulphogalactosylglycerolipid In retina, the ratio of cerebroside to cerebroside 3‐sulphate was approximately half compared to brain. During chicken retina ontogenesis the ratio of cerebroside 3‐sulphate to sulphogalactosylglycerolipid increased rapidly and in the adult animal, the amount of cerebroside 3‐sulphate was 14 times higher than that of sulphogalactosylglycerolipid.

The activity of PAPS: cerebroside sulphotransferase and arylsulphatase A in developing chicken retina indicated that the general ontogenic profiles of retinal PAPS: cerebroside sulphotransferase and arylsulphatase A were similar to those obtained for the brain. Both the enzymes showed the highest activity just before hatching. The significance of occurrence of sulpholipids in retina is discussed.
NOREPINEPHRINE‐STIMULATED BREAKDOWN OF TRIPHOSPHOINOSITIDE OF RABBIT IRIS SMOOTH MUSCLE: EFFECTS OF SURGICAL SYMPATHETIC DENERVATION AND IN VIVO ELECTRICAL STIMULATION OF THE SYMPATHETIC NERVE OF THE EYE
Authors: Abdel‐Latif A. A. , Green K. , Smith J. P. , McPherson J. C. , Matheny J. L.
Published: October 2006

Abstract— Paired iris smooth muscles from rabbits were prelabelled either in vitro by incubation for 30 min at 37°C in an iso‐osmotic salt medium containing glucose, inositol, cytidine and 32Pi, or in vivo by administration of the isotope intracamerally into each eye 1 h before death. One of the pair was then incubated at 37°C for 10 min in an unlabelled medium containing 10 mm of 2‐deoxyglucose and the other was incubated in the presence of norepinephrine (NE) or other adrenergic agents. Triphosphoinositide (TPI) was found to contain more 32P than any other phospholipid (almost 39% of total lipid radioactivity) in both the in vitro and in vivo experiments. NE (50 μm) increased the loss of 32P from TPI (the TPI effect') by 28–30% in the 32P‐labelled muscle. The TPI effect was accompanied by a significant increase in 32P labelling of phosphatidic acid (PA) and phosphatidylinositol (PI) but not phosphatidylcoholine. In this tissue the TPI effect was found to be mediated through α‐adrenergic receptors. At 14 days after surgical sympathetic denervation, incorporation of 32P into phospholipids of the denervated muscle increased by an average of 6% over that of the normal muscle. The increase in TPI, PI and PA was 7%, 4% and 9% of that of the control respectively. There was little change in phospholipid content of the denervated muscle. The increase in sensitivity to NE (12.5 μm) caused by denervation produced about 18% increase in the TPI effect and a 25% increase in the 32P labelling of PA, but not PI. In view of our previous findings on the requirement of the TPI effect for Ca2+, this observation could suggest that an increase in Ca2+ influx, following the interaction between the neurotransmitter and its receptor could stimulate TPI‐phosphodiesterase, thus leading to increased PA via increased diglyceride. This denervation‐induced supersensitivity to NE appears to be postsynaptic in nature. 32Pi was injected intracamerally into each eye 1 h before electrical stimulation of one of the sympathetic trunks. After stimulation for 30 min there was a significant loss of 32P from TPI and a significant increase in the labelling of PI and PA of the stimulated muscle. It is concluded that TPI and its enzymes could play an important role in neurotransmission at the neuromuscular junction of smooth muscle.
CONCOMITANT ELEVATION OF TYROSINE HYDROXYLASE AND DOPAMINE BETA‐HYDROXYLASE BY CYCLIC AMP IN CULTURED MOUSE NEUROBLASTOMA CELLS1
Authors: Waymire Jack C. , Gilmer‐Waymire Katrina , Boehme Richard E.
Published: October 2006

Abstract—

The effects of cyclic AMP analogues and of phosphodiesterase inhibitors were investigated in neuroblastoma cells (NBD‐2) cloned from the C‐1300 tumor. 8Br‐cAMP and phosphodiesterase inhibitors that elevated cAMP induced large (greater than 15 fold) and specific increases in tyrosine hydroxylase and dopamine beta‐hydroxylase activity. In contrast, catechol O‐methyltransferase, monoamine oxidase and aromatic‐l‐amino‐acid decarboxylase were unaffected by the cAMP altering drugs. Similarly, AChE was unaffected and only a small increase in choline acetyltransferase (3 fold) was observed. The increases in tyrosine hydroxylase and dopamine beta‐hydroxylase were similar with respect to dose response relationships and with respect to time course of onset.

Only those phosphodiesterase inhibitors that elevated cAMP (papaverine and Ro20‐1724 as opposed to theophylline) were effective in elevating tyrosine hydroxylase and dopamine beta‐hydroxylase. Further, the doses optimal for elevating cAMP coincided with the optimal doses for elevating the two enzymes. Theophylline had no influence either upon NBD‐2 cell cAMP levels or upon tyrosine hydroxylase and dopamine beta‐hydroxylase activity.

The changes in protein synthesis rates produced by the cAMP altering drugs were temporally distinct from the changes in either tyrosine hydroxylase or dopamine beta‐hydroxylase. These results suggest that the intracellular messenger compound cAMP is involved in the specific regulation of both tyrosine hydroxylase and dopamine beta‐hydroxylase in adrenergic cells.
A MODEL OF HIGH AFFINITY GLUTAMIC ACID TRANSPORT BY CORTICAL SYNAPTOSOMES FROM THE LONG‐EVANS RAT
Authors: Wheeler D. D. , Hollingsworth R. G.
Published: October 2006

Abstract— The initial velocity of uptake of L‐glutamic acid by cortical synaptosomes from the Long‐Evans rat has been measured as a function of sodium and glutamic acid concentration. These data were then fitted to the rate equation from each of several possible models, and the model giving minimum error identified. The major predictions from the best fit model are as follows: (1) The order of combination with the carrier should be sodium, sodium, glutamic acid. (2) Uptake should be 100% dependent on the presence of sodium in the incubation medium. (3) At a finite concentration of sodium, Vmx should be independent of the sodium concentration, which implies that translocation of the carrier across the membrane is independent of the sodium concentration. (4) Lineweaver‐Burk plots should be linear with slopes depending on the sodium Concentration. (5) There should be co‐transport of two sodium ions with each glutamic acid molecule. (6) The dependence of Kt, on the sodium concentration should have the following form: Kt= A/[Na]2+ 8/[Na] +C, where A, B, and C are constants. The results differ substantially from those previously reported for Sprague‐Dawley rats. Kt, is 2–5 times less than that for Sprfague‐Dawley rats, and the relation of sodium to Kt, is basically different. We also find a coupling ratio of two, whereas previous studies found a coupling ratio of one. Thus the results raise the possibility that there are fundamental differences between Sprague‐Dawley and Long‐Evans rats with regard to the mechanism by which sodium participates in amino acid transport.
ALTERATION OF TRICARBOXYLIC ACID CYCLE METABOLISM IN RAT BRAIN SLICES BY HALOTHANE
Authors: Cheng Sze‐Chuh , Brunner Edward A.
Published: October 2006

Abstract—

Metabolism of [2‐14C]pyruvate, [1‐14C]acetate and [5‐14C]citrate in the rat cerebral cortex slices was studied in the presence of halothane. Metabolites assayed include acetylcholine (ACh), citrate, glutamate, glutamine, γ‐aminobutyrate (GABA) and aspartate. The trichloroacetic acid soluble extract, the trichloroacetic acid insoluble precipitate and its lipid extract were also studied.

In control experiments, pyruvate preferentially labelled ACh, citrate, glutamate, GABA and aspartate. Acetate labeled ACh, but to a lesser extent than pyruvate. Acetate also labeled lipids and glutamine. Citrate labeled lipids but not ACh and served as a preferential precursor for glutamine. These data support a three‐compartment model for cerebral tricarboxylic acid cycle metabolism.

Halothane caused increases in GABA and aspartate contents and a decrease in ACh content. It has no effect on the contents of citrate, glutamate and glutamine.

Halothane preferentially inhibited the metabolic transfer of radioactivity from pyruvate into almost all metabolites, an effect probably not related to pyruvate permeability. This is interpreted as halothane depression of the‘large metabolic compartment’ which includes the nerve endings.

Halothane increased the metabolic transfer of radioactivity from acetate into lipids but did not alter such a transfer into the trichloracetic acid extract.

Halothane increased the metabolic transfer of radioactivity from citrate into the trichloroacetic acid precipitate, lipids and especially glutamine. Transfer of citrate radioactivity into GABA was somewhat decreased.

The differential effects of halothane on acetate and citrate utilization suggest that the ‘small metabolic compartment’ should be subdivided. Therefore, at least three metabolic compartments are demonstrated.

Halothane did not interfere with the dicarboxylic acid portion of the tricarboxylic acid cycle.
THE FLUOROMETRIC DETERMINATION OF 5‐METHOXYTRYPTAMINE IN MAMMALIAN TISSUES AND FLUIDS
Authors: Prozialeck Walter C. , Boehme D. H. , Vogel Wolfgang H.
Published: October 2006

Abstract— Using a sensitive and specific fluorometric procedure involving selective extraction, reaction of the extracts with o‐phthalaldehyde (OP), separation of the OP derivatives by TLC, and determination of fluorescent characteristics and intensities, we have detected and measured 5‐methoxytryptamine, (5‐MT) in various central and peripheral tissues and fluids of the rat, dog, baboon, and man.

Distribution of 5‐MT in peripheral tissues of the rat seemed to parallel that of 5‐HT, with highest levels being found in the gastrointestinal (GI) tract and Harderian gland, regions that are rich in 5‐HT and have been reported to contain systems capable of methylating 5‐HT. 5‐MT was detected in the lung, plasma, kidney, spleen, and heart of the rat. 5‐MT was present in the CNS of all species examined. No marked interspecies differences were observed. In the rat CNS, the regional distribution of 5‐MT did not parallel that of 5‐HT indicating that the systems for the synthesis, uptake, or transport of 5‐MT might be different than for 5‐HT. Pretreatment of rats with iproniazid resulted in a 50% increase in whole brain 5‐MT. Reserpine pretreatment had no effect, indicating that the storage or release mechanisms for 5‐MT are different than for the conventional amine transmitters. 5‐MT was detected in human CSF and urine but not in plasma. These data indicate that 5‐MT, a compound with potent pharmacological properties, is more widely distributed in the mammalian body than had previously been supposed.
THE METABOLISM OF LEUCINE BY DEVELOPING RAT BRAIN: EFFECT OF LEUCINE AND 2‐OXO‐4‐METHYLVALERATE ON LIPID SYNTHESIS FROM GLUCOSE AND KETONE BODIES
Authors: Patel M. S. , Owen O. E.
Published: October 2006

Abstract— The oxidation of l‐[U‐14C]leucine and l‐[l‐14C]leucine at varying concentrations from 0.1 to 5mM to CO2 and the incorporation into cerebral lipids and proteins by brain slices from 1‐week old rats were markedly stimulated by glucose. Although the addition of S mM‐dl‐3‐hydroxybutyrate had no effect on the metabolism of [U‐14C]leucine by brain slices from suckling rats, the stimulatory effects of glucose on the metabolism of l‐[U‐14C]leucine were markedly reduced in the presence of dl‐3‐hydroxybutyrate. The stimulatory effect of glucose on leucine oxidation was, however, not observed in adult rat brain. Furthermore, the incorporation of leucine‐carbon into cerebral lipids and proteins was also very low in the adult brain. The incorporation of l‐[U‐14C]leucine into cerebral lipids by cortex slices was higher during the first 2 postnatal weeks, which then declined to the adult level. During this time span, the oxidation of l‐[U‐14C]leucine to CO2 remained relatively unchanged. The incorporation in vivo of D‐3‐hydroxy[3‐14C]butyrate into cerebral lipids was markedly decreased by acute hyperleucinemia induced by injecting leucine into 9‐day old rats. In in vitro experiments, 5 mM‐leucine had no effect on the oxidation of [U‐14C]glucose to CO2 or its incorporation into lipids by brain slices from 1‐week old rats. However, 5 mM‐leucine inhibited the oxidation of d‐3‐hydroxy‐[3‐14C]butyrate, [3‐14C]acetoacetate and [1‐14C]acetate to CO2 by brain slices, but their incorporation into cerebral lipids was not affected by leucine. In contrast 2‐oxo‐4‐methylvalerate, a deaminated metabolite of leucine, markedly inhibited both the oxidation to CO2 and the incorporation into lipids of labelled glucose, ketone bodies and acetate by cortex slices from 1‐week old rats. These findings suggest that the reduction in the incorporation in vivo of d‐3‐hydroxy[3‐14C]butyrate into cerebral lipids in rats injected with leucine is most likely caused by 2‐oxo‐4‐methylvalerate formed from leucine. Since the concentrations of leucine and 2‐oxo‐4‐methylvalerate in plasma of untreated patients with maple‐syrup urine disease are markedly elevated, our findings are compatible with the possibility that an alteration in the metabolism of glucose and ketone bodies in the brain may contribute to the pathophysiology of this disease.
NET PRODUCTION OF γ‐AMINOBUTYRIC ACID IN ASTROCYTES IN PRIMARY CULTURES DETERMINED BY A SENSITIVE MASS SPECTROMETRIC METHOD
Authors: Wu P. H. , Durden D. A. , Hertz L.
Published: October 2006

Abstract—

A sensitive and specific high resolution mass spectrometric method, using a deuterium labelled internal standard, was developed for the quantitation of GABA in biological materials. GABA was converted to the DNS‐γ‐butyrolactam, isolated by thin layer chromatography and quantitated by the integrated ion current procedure. The method was used to measure the GABA content of cultured astrocytes (0.0545 nmol/mg protein, depending upon the culturing conditions), of fresh media (0.02–0.04 μM) and of conditioned media (after culturing in the absence of added GABA: 0.02–1.8 μM, depending upon the culturing conditions). An estimate of the rate of GABA production was obtained from the concentration in conditioned media and in the cells when GABA degradation was inhibited by AOAA (13 μM). The production of GABA was negligible in the cells grown under ordinary conditions but increased to 0.3 nmol/h per mg protein in cells which had been grown in the presence of 0.25 mM‐ dibutyryl cyclic AMP for 1 week. This value is of the same order of magnitude as the GAD activity observed in extraneurónal tissue. However, the GABA production measured mass spectrometrically was much lower than that of labelled GABA from [U‐14C]glutamate. The latter value was non‐reproducible and varied from one batch of radioactive glutamate to another.
THE CHARACTERIZATIO OF MONOAMINE OXIDASE IN CULTURED MAMMALIAN CELLS
Authors: Powell J. F. , Craig I. W.
Published: October 2006

Abstract—

The expression of monoamine oxidase (MAO) in a variety of mammalian cells has been investigated employing tryptamine as substrate. The enzyme present in those cell lines having sufficient activity for detailed analysis exhibited a monophasic response to the inhibitor clorgyline. On this basis the cell lines examined were found to express only A, or only B, type activity. Hypoxanthineguanine phosphoribosyl transferase (HGPRT) deficient derivatives of both MAO type A, or MAOtype B, expressing cells were examined. The HGPRT status of the cells appeared to have little influence on the expression of the enzyme.
LOCATING THE MAJOR GLYCOPROTEIN (Po PROTEIN) IN THE X‐RAY PROFILE OF FROG SCIATIC‐NERVE MYELIN
Authors: Blaurock A. E. , Nelander J. C.
Published: October 2006

Some detailed X‐ray profiles have been put forward for frog sciatic‐nerve myelin in the past 8 y. In this paper we interpret one of these. Much of the myelin protein is located in the extracellular half of the membrane. On the basis of a chemical analysis and other recently published data indicating the sidedness of some myelin proteins, we suggest that the major glycoprotein (Po protein) is inserted into the extracellular half of the myelin bilayer and that it extends into the extracellular space. Our interpretation is consistent with known physical properties of the Po protein. Other myelin proteins have not yet been located.

Electron densities and average hydrophobicities of some myelin proteins have been calculated, as well as electron densities and scattering powers of some myelin lipids.
FREE 3‐METHOXY‐4‐HYDROXYPHENYLETHYLENEGLYCOL IN THE CENTRAL NERVOUS SYSTEM OF THE RAT: SEMI‐AUTOMATED FLUOROMETRIC ASSAY, TURNOVER AND EFFECTS OF DRUGS
Authors: Adégr J.‐P. , Korf J.
Published: October 2006

A semi‐automated fluorometric assay technique for free 3‐methoxy‐4‐hydroxyphenylethyl‐eneglycol (MOPEG) in rat brain and spinal cord is described.

The method is based on a simple manually‐performed two‐step purification procedure using column chromatography on Sephadex G 10 and DEAE‐Sephadex A 25 (borate form) respectively. After isolation MOPEG is converted into a fluorophore in a continuous flow system using ethylene diamine condensation in the presence of an oxidant. The MOPEG assay is highly sensitive (detection limit 2 ng/sample) and linear, with an overall recovery of approx 75%.

Specificity is demonstrated by testing a number of compounds and confirmed by gas chromatography‐mass spectrometry analysis. Treatment with clozapine and haloperidol (both neuroleptics), reser‐pine (impairing intraneuronal storage) or phenoxybenzamine (α‐adrenoceptor blocking agent) increased the content of MOPEG both in brain and spinal cord. Cerebral levels of MOPEG were decreased after injection of a single dose of the tricyclic antidepressant desipramine and after chronic destruction of the locus coeruleus by electrolytic lesion or by the administration of the neurotoxic drug 6‐hydroxy‐dopamine. Animals killed by microwave irradiation did not show lower MOPEG contents in brain than decapitated animals.

These results indicate that MOPEG is a measure for changes in central noradrenaline turnover and that drugs affect MOPEG in the brain and spinal cord similarly. Fractional rate constants of MOPEG in the rat brain and spinal cord were estimated with the exponential decline curves produced by treatment with pargyline. Turnover rates of 193 pmol/g/h and 167 pmol/g/h in the brain and spinal cord respectively were calculated.
THE EFFECT OF DELTA‐AMINOLAEVULINIC ACID ON THE UPTAKE AND EFFLUX OF [3H]GABA IN RAT BRAIN SYNAPTOSOMES
Authors: Brennan M. J. W. , Cantrill R. C.
Published: October 2006

§‐Aminolaevulinic acid (§‐ALA) is an omega amino acid which can be considered as an analogue of γ‐aminobutyric acid (GABA). We have examined the effect of §‐ALA on [3H]GABA uptake and release in the synaptosome fraction of rat cerebral cortex and report:

(1) High concentrations of §‐ALA (0.75‐5 mM) stimulated [3H]GABA release very markedly, the stimulation with 1mM and 5mM‐§‐ALA exceeding the maximum obtainable with unlabelled GABA;

(2) Low concentrations of §‐ALA (0.1‐0.5 mM) produced little stimulation of [3H]GABA efflux, less than that produced by similar concentrations of unlabelled GABA;

(3) 0.1 mM‐§‐ALA reduced the stimulation of [3H]GABA efflux elicited by 55 mM‐K+ and the combination of 1 mM‐§‐ALA and 55mM‐K+ produced a lower stimulation of efflux than 1 mM‐§‐ALA alone;

(4) §‐ALA inhibits [3H]GABA uptake in a linearly competitive fashion and inhibition is maximal at 0.5 mM‐§‐ALA.

These results are discussed in relation to the neuronal high affinity GABA transport mechanism and inhibition of the synaptosomal Na+ and K+ ‐dependent ATPase. It is also postulated that §‐ALA increases the chloride conductance of the synaptosomal membrane, possibly by acting on presynaptic GABA receptors.
CHARACTERIZATION OF TAURINE UPTAKE BY NEURONAL AND GLIAL CELLS IN CULTURE
Authors: Borg J. , Balcar V. J. , Mark J. , Mandel P.
Published: October 2006

Uptake of [35S]taurine was studied in parallel on glial and neuronal cells maintained in continuous culture, including transformed neuronal cells. Both glial and neuronal taurine uptake systems were concentrative, highly sodium‐dependent and inhibited by closely related structural analogues such as hypotaurine, β‐alanine and GABA. Strychnine was found to be a potent inhibitor of taurine uptake, especially in the glial cells, while parachloromercuriphenylsulphonate was more efficient on the neuronal clones. In contrast with uptake by neuroblastoma cells, the glial transport was dependent on the presence of calcium in the incubation medium.
Evolution du taux de quelques acides aminés libres cérébraux au cours de l'encéphalopathie hépatique chez le rat porteur dune anastomose porto‐cave Brain amino acids changes during hepatic encephalopathy in the rat with portocaval anastomosis
Authors: Tangapregassom M. J. , Lantin N. , Salomon F. , Bismuth H. , Grange D.
Published: October 2006

The free amino acid contents of rat brain have been estimated in animals with portocaval shunt and sham operated up to 1, 2, 3, 5 and 6 weeks after operation. The cyclic amino acid levels (Phe, Tyr and His) were consistently raised from the first to the last weeks. The aliphatic amino acid contents (Ala, Gly, GABA, Lys and Arg) were not found to be significantly different from those of sham operated animals during the first 3 weeks, but they dropped significantly during the 5th and 6th postoperative weeks. Consideration is given to the possibility that the increase of brain cyclic amino acids and delayed fall of aliphatic amino acid contents may explain other results (i.e. drop of sleep and pain thresholds) which have been described in animals with a similar portocaval shunt.
INTERACTION OF LEUCINE, GLUCOSE, AND KETONE METABOLISM IN RAT BRAIN IN VITRO
Authors: Palaiologos G. , Koivisto V. A. , Felig P.
Published: October 2006

Brain cortex slices from fed, 48 h and 120 h fasted rats were incubated and 14CO2 was measured from (a) [U‐14C]glucose (5 mm) either alone or in the presence of l‐lcucine (0.1 or 1 mm), and (b) [U‐14C]leucine or [l‐14C]leucine at 0.1 or 1 mm with or without glucose (5 mm). In other experiments, sodium dl‐3‐hydroxybutyrate (3‐OHB) or acetoacetate (AcAc) at 1 or 5 mm were added in the above incubation mixture. The rate of conversion of [U14C]glucose to CO2 was decreased 20% by leucine at 1 mm and 30–50% by 3‐OHB at 1 or 5 mm but not by leucine at 0.1 mm. The effects of 3‐OHB and of leucine (1 mm) were not additive. The effects of leucine were similar in the fed and fasted rats. The rate of conversion of [U‐14C]leucine or [l‐,4C]leucine to 14CO2 at 0.1 mm and 1.0 mm was increased by glucose (35%) in the fed or fasted rats. Ketone bodies in the absence of glucose had no effect on leucine oxidation. However, the stimulatory effect of glucose on the rate of conversion of leucine to CO2 was inhibited by 3‐OHB at 5 mm. These results suggest that (a) leucine in increased concentrations (1 mm) may reduce glucose oxidation by brain cortex while itself becoming an oxidative fuel for brain, and (b) leucine oxidation by brain may be influenced by the prevailing glucose and ketone concentrations.
THE COMPLEX BINDING OF γ‐AMINOBUTYRIC ACID TO A RAT BRAIN SYNAPTIC MEMBRANE PREPARATION
Authors: Winkler M. H. , Nicklas W. J. , Berl S.
Published: October 2006

The association of γ‐aminobutyric acid (GABA) with rat brain synaptic membranes is complex and involves more than one set of binding sites. This fact is suggested by the form of experimentally determined binding curves and confirmed by the destruction of one set of homogenous sites by covalent modifications with iodine. The difference in binding of GABA by two sets of membranes which have been exhaustively iodinated in the presence and absence of an excess of GABA corresponds to 1/6 of the binding expressed by uniodinated membranes after equilibration with 0.25 μm‐GABA. This difference appears to be the result of the expression of a homogeneous set of independent sites, each of which contains an iodinatable'residue that is protected by bound GABA.

Examination of the factors leading to the retention of radioactive ligand by a synaptic membrane preparation is suggestive of a method for determining the maximum number of binding sites for a given ligand and for evaluating solution space without displacing the bound species or adding a presumably inert tracer. Three additional measurements of retention of high ligand concentration are shown to be sufficient for the determination. Employment of the method facilitates the investigation of the interaction of the membrane preparations with individual agonists and antagonists.
THE ACTIVITY OF PARTIAL REACTIONS IN THE CHAIN ELONGATION OF PALMITOYL‐CoA AND STEAROYL‐CoA BY MOUSE BRAIN MICROSOMES
Authors: Bernert John T. , Bourre Jean‐Marie , Baumann Nicole A. , Sprecher Howard
Published: October 2006

Partial reactions in the overall chain elongation of palmitoyl‐CoA and stearoyl‐CoA by mouse brain microsomes have been analyzed. The rate of the initial condensation reaction between palmitoyl‐CoA and malonyl‐CoA was more than 5 times greater than the rate obtained with stearoyl‐CoA, and in both cases good agreement between condensation and overall chain elongation rates was observed.

By contrast, both β‐hydroxyoctadecanoyl‐CoA and β‐hydroxyeicosanoyl‐CoA were quite rapidly dehydrated by brain microsomes at similar rates. Similar results were obtained with 2‐trans‐octadecenoyl‐CoA and 2‐trans‐eicosenoyl‐CoA in which both substrates were rapidly reduced at nearly the same rate in the presence of NADPH. In all cases, intermediate reactions subsequent to condensation were much more rapid than overall chain elongation. These results suggest that the mechanism of malonyl‐CoA‐dependent fatty acid chain elongation in brain microsomes is similar to that observed in other tissues, and are consistent with an overall regulation of chain elongation mediated primarily by the initial condensation reaction.
BIOPTERIN V. DE NOVO SYNTHESIS OF DIHYDROBIOPTERIN: EVIDENCE FOR ITS QUINONOID STRUCTURE AND LACK OF DEPENDENCE OF ITS REDUCTION TO TETRAHYDROBIOPTERIN ON DIHYDROFOLATE REDUCTASE
Authors: Gál E. M. , Bybee J. A. , Sherman A. D.
Published: October 2006

Samples of quinonoid‐l‐erythrodihydrobiopterin (q‐BH2) and quinonoid‐6‐methyl‐dihydro‐pterin (q‐6‐MPH2) were prepared by oxidation of l‐erythro‐5,6,7,8‐tetrahydrobiopterin (BH4) and 5,6,7,8‐tetrahydro‐6‐methylpterin (6‐MPH4) and separated from D‐erythro‐7,8‐dihydrobiopterin (7,8‐BH2) and 6‐methyl‐7,8‐dihydropterin (7,8‐6‐MPH2) as well as from the tetrahydropterins on phosphocellulose column by high‐pressure liquid chromatography. The quinonoid dihydropterins were identified and quantitated by scan of their ultraviolet absorption and fluorescence emission spectra through their rearrangement to their 7,8‐tautomer and also by gas chromatography of their rapidly synthesized trimethylsilyl derivative. Identification was also achieved by the enzymatic reduction of [3H]q‐BH2to [3H]BH4 by dihydrofolate reductase (DHFR). Direct proof for the enzymatic synthesis of the q‐BH2 from GTP or from 2‐amino‐6‐(5′‐triphosphoribosyl)‐amino‐5‐ or ‐6‐formamido‐6‐hydroxypyrimi‐dine (FPyd‐P3) was obtained by isolation of the compound which was identical in all respects to the q‐BH2 obtained by chemical synthesis from BH4. The reduction of enzymatically synthesized q‐BH2 by dihydropteridine reductase (DHPR) to BH4 was not inhibited by methotrexate (MTX). When the enzymatically synthesized q‐BH2 was converted to 7,8‐BH2, it was reduced only by DHFR. This reduction, however, was inhibited by MTX. On the biosynthetic pathway from GTP to dihydrobiopterin, the enzyme responsible for the appearance of the quinonoid structure is the d‐erythro‐dihydroneopterin triphosphate synthetase, the product of which (quinonoid d‐erythro‐dihydroneopterin triphosphate) is converted to quinonoid dihydrobiopterin by l‐erythro‐dihydrobiopterin synthetase. Experiments in vivo established that DHFR does not participate in the reduction of dihydrobiopterin to tetra‐hydrobiopterin when the former is synthesized from GTP de novo. MTX at 5 × 10−6M exerted no inhibition on the reduction of the biosynthetic dihydrobiopterin to tetrahydrobiopterin in vivo, yet completely inhibited the reduction of intraventricularly injected tritiated dihydrofolate ([3H]FH2) to tritiated tetrahydrofolate ([3H]FH4).
DEVELOPMENTAL CHANGES OF MYELIN PROTEINS IN THE CHICK PERIPHERAL NERVE
Authors: Uyemura K. , Horie K. , Kitamura K. , Suzuki M. , Uehara S.
Published: October 2006

Abstract— Developmental changes of myelin proteins in chick sciatic nerve were studied at the stage of myelination by sodium dodecylsulfate (SDS)‐polyacrylamide gel electrophoresis. The myelin of adult hen peripheral nervous system (PNS) contained two glycoproteins (BR‐P0 and PASII), both of which are unique to PNS myelin, in addition to the basic encephalitogenic protein, BP, which is common to CNS and PNS myelin. The other basic protein (BF‐P2) found in the PNS of other species was not definitely detectable in hen PNS. At the early stages of myelination (from 14 to 18 embryonic days) the amounts of myelin proteins increased rapidly in parallel with the increase in number of layers of the myelin sheath of the PNS. At 14 embryonic days high molecular weight proteins were dominant, while myelin specific proteins were barely detectable in the PNS myelin fraction. At 18 embryonic days, however, BR‐PO, BP and PASII proteins became the main protein components of the PNS myelin, whereas high molecular weight proteins decreased in quantitative importance during development. At the early stage of myelination other glycoproteins were also detectable in the PNS myelin. Radioactive fucose was actively incorporated into the two glycoproteins, BR‐P0 and PASII, at the early stage of myelination in vivo. These results suggested that myelin proteins especially glycoproteins, may play an important role in PNS myelin formation.
SOLUBLE AND MEMBRANE LECTIN‐BINDING GLYCOPROTEINS OF THE CHROMAFFIN GRANULE
Authors: Cahill Anne L. , Morris S. J.
Published: October 2006

Abstract— Fluorescein isothiocyanate‐labelled lectins were used to identify lectin‐binding glycoproteins of the chromaffin granule after electrophoresis of the membrane and soluble granule proteins on sodium dodecyl sulphate polyacrylamide slab gels. The glycoprotein nature of all lectin‐binding bands was confirmed by staining the gels for carbohydrates, and the specificity of the lectin‐binding was demonstrated by hapten sugar inhibition of binding. In samples of granule membrane proteins reduced with dithiothreitol 10 concanavalin A (Con A), 5 wheat germ agglutinin, 8 Ricinus communis agglutinin‐60, and 7 Ricinus communis agglutinin‐120 (RCA‐120) binding glycoproteins were identified. Molecular weights of these glycoproteins varied from 20,000 to 200,000 daltons. All but two of the Con A‐binding bands and one of the RCA‐120 binding bands appeared to react with more than one lectin, suggesting possible carbohydrate heterogeneity in these membrane glycoproteins. The band identified as dopamine β‐hydroxylase reacted most intensely with all four lectin tested, and in the soluble core material this enzyme was the sole significant lectin binding glycoprotein.
DIFFERENCES IN THE SUBCELLULAR AND SUBSYNAPTOSOMAL DISTRIBUTION OF THE PUTATIVE ENDOPLASMIC RETICULUM MARKERS, NADPH‐CYTOCHROME c REDUCTASE, ESTRONE SULFATE SULFOHYDROLASE AND CDP‐CHOLINE DIACYLGLYCEROL CHOLINEPHOSPHOTRANSFERASE IN RAT BRAIN
Authors: Possmayer Fred , Kleine Leonard , Duwe Gail , Stewart‐DeHaan P. Jill , Wong Tanya , MacPherson Catherine F. C. , Harding Paul G. R.
Published: October 2006

Abstract— A comprehensive study has been undertaken on the subcellular and subsynaptosomal distribution of a number of markers for subcellular organelles in preparations from rat brain. Although the activity of most enzymatic markers was decreased by freezing and storage at ‐ 70oC, no significant changes were noted in the distribution of these activities. This demonstrates that contamination of brain fractions by subcellular organelles can be accurately assessed after freezing and thawing. A marked discrepancy was noted between the distribution of three putative markers for endoplasmic reticulum. CDP‐choline‐diacylglycerol cholinephosphotransferase (EC 2.7.8.1) activity was mainly limited to the microsomal fraction and was present to a lesser extent in the synaptosomal fraction than the other putative markers for endoplasmic reticulum. Estrone sulfate sulfohydrolase (EC 3.1.6.2) activity demonstrated a bimodal distribution between the crude nuclear and microsomal fractions. However, considerable activity was associated with the synaptosomal fraction. NADPH‐cytochrome c reductase (EC 2.3.1.15) activity sedimented in the microsomal and the synaptosomal fractions. Calculations based on the relative specific activities of the microsomal and synaptic plasma membrane fraction indicated that the contamination of the synaptic plasma membranes by endoplasmic reticulum was 44.5% (NADPH‐cytochrome c reductase), 38.0% (estrone sulfatase) and 9.0% (cholinephosphotransferase). Since it is believed that virtually all of the synthesis of phosphatidylcholine by cholinephosphotransferase occurs in the neuronal and glial cell bodies, it was concluded that cholinephosphotransferase is a satisfactory marker for the endoplasmic reticulum derived from these sources. The results suggest that NADPH‐cytochrome c reductase and estrone sulfatase may be present in the smooth endoplasmic reticulum system responsible for the fast transport of macromolecules along the axon to the nerve endings as well as in the endoplasmic reticulum of the cell bodies. The possible relation between that portion of the smooth endoplasmic reticulum involved in fast axonal transport and the GERL (Golgi, Endoplasmic Reticulum, Lysosomes) complex discovered by Novikoff and his coworkers (Novikoff, 1976) is discussed.
CATECHOLAMINE SECRETION BY HAMSTER ADRENAL CELLS1
Authors: Liang Bruce T. , Perlman Robert L.
Published: October 2006

Abstract— Suspensions of isolated adrenal cells were prepared by digesting hamster adrenal glands with collagenase, and the secretion of catecholamine from these cells was studied. Acetylcholine (ACh) produces a dose‐dependent increase in catecholamine secretion; half‐maximal secretion is produced by 3 μm‐ACh, and maximal secretion by 100 μm‐ACh. The cholinergic receptor in these cells appears to be nicotinic, since catecholamine secretion is stimulated by the nicotinic agonists nicotine and dimeth‐ylphenylpiperaziniurn, but not by the muscarinic agonists pilocarpine or oxotremorine. ACh‐induced catecholamine secretion is inhibited by hexamethonium, tubocurarine, and atropine, but is not inhibited by α‐bungarotoxin. ACh‐induced catecholamine secretion is dependent upon the presence of extracellular Ca2+, and appears to occur by exocytosis, since the release of catecholamine is accompanied by the release of dopamine β‐monooxygenase, but not of lactate dehydrogenase. These biochemical studies complement the morphological evidence for exocytosis in hamster adrenal glands, and indicate that catecholamine secretion from hamster chromaffin cells is similar to that from chromaffin cells of other species.
MUSCARINIC CHOLINERGIC AND PREGANGLIONIC PHYSIOLOGICAL STIMULATION INCREASE CYCLIC GMP LEVELS IN GUINEA‐PIG SUPERIOR CERVICAL GANGLIA1
Authors: Wamsley James K. , West James R. , Black Asa C. , Williams Terence H.
Published: October 2006

Abstract— Incubation of guinea‐pig superior cervical ganglia in 500μ4mUm‐carbachol for 2min increased cyclic GMP levels 530% over control values. The increase was blocked by prior incubation in 300μmatropine. No increase in cyclic GMP levels after incubation in 100 μm‐l‐norepinephrine was observed. Preganglionic physiological stimulation for 8 min at 10 Hz increased cyclic GMP levels 180% over control values. We conclude that both muscarinic cholinergic and preganglionic physiological stimulation increase cyclic GMP levels in guinea pig superior cervical ganglia, while norepinephrine has no effect.
THE EFFECT OF FASTING ON THE METABOLISM OF 5‐HYDROXYTRYPTAMINE AND DOPAMINE IN THE BRAIN OF THE MOUSE
Authors: Fuenmayor L. D.
Published: October 2006

Abstract— The turnover of 5‐hydroxytryptamine in the forebrain and of dopamine in the striatum was studied in mice fasted for 20 h. Such mice showed an increased tissue concentration of 5‐hydroxyindoleacetic acid in the forebrain and an increased accumulation of this acid after probenecid. Fasted mice also showed a higher concentration of homovanillic acid in the striatum than fed mice. However, the administration of probenecid produced a smaller increase in homovanillic acid concentration in fasted than in fed mice. The decay of dopamine following α‐methyl‐p‐tyrosine was reduced in fasted mice at 2 h, but not at 1 h or 6 h after administration of the inhibitor. The possibility that fasting increases the activity of some dopaminergic neurones while decreasing the activity of others is considered. The existence of a pool of homovanillic acid at a site within the striatum where the probenecid‐sensitive transport is not effective is postulated.
DIFFERENT TURNOVER RATES OF BRAIN RIBOSOMAL RIBONUCLEIC ACIDS IN MALE AND FEMALE RATS
Authors: Novaković Milka B. , Petrović S. L. , Rakić L. M. , Ivanuš J. J.
Published: October 2006

Abstract— Following a single intracranial injection of [5‐3H]orotic acid, the decay dynamics were determined for rRNAs of whole brain in male and female Wistar‐inbred albino rats aged 2.5‐3.5 months. The turnover rate for male brain rRNAs was significantly lower than in females (mean half‐lives being, respectively, 12.2 ± 2.2 (S.D.M.) days, and 7.4 ± 1.3 days in four regression measurements). This difference was apparently not related to the turnover rate of acid‐soluble brain nucleotides, which turned over much faster and at a similar rate in rats of both sexes; it also could not be connected with brain levels of rRNAs or DNAs, which were quite similar For males and females. The results are discussed in terms of possible sex hormone determination of brain RNA metabolic patterns especially in males.
NICOTINAMIDE DEAMIDASE RELEASED BY NEUROBLASTOMA CELL CULTURES1
Authors: Wintzerith Marguerite , Dierich A. , Mandel P.
Published: October 2006

Abstract— An enzymic activity which catalyses the deamidation of nicotinamide to nicotinic acid has been found in the growth media of neuroblasts and glioblasts cultivated in vitro. Some properties of the crude nicotinamide deamidase from the growth medium of neuroblastoma M1 cells have been studied.
CONGENITAL HYPOMYELINOGENESIS (BORDER DISEASE) OF LAMBS: POSTNATAL NEUROCHEMICAL RECOVERY IN THE CENTRAL NERVOUS SYSTEM
Authors: Sweasey D. , Patterson D. S. P.
Published: October 2006

Abstract— In a neurochemical study of experimental Border Disease in lambs it was found that the fresh weights of four parts of the CNS (cerebrum, cerebellum, brain stem and spinal cord) from clinically affected lambs were significantly smaller than those of controls at birth but by 20 weeks of age the cerebrum, cerebellum and brain stem had reached near normal weights. The spinal cord was still considerably smaller, however. Clinical symptoms of the disease (muscular spasms and‘hairy’birthcoat) had disappeared during this period, accompanied by a regression in the neurochemical abnormalities seen at birth. Thus the deficiency of myelin lipids was partially made up by the rapid deposition of cerebrosides and by 20 weeks differences in the fatty acid composition of this lipid fraction were no longer apparent. Myelin degeneration as indicated by the presence of elevated levels of esterified cholesterol was apparently absent at 20 weeks of age and this was parallelled by a fall in the level of‘anti‐myelin’antibodies in the sera of affected lambs. The altered distribution of copper in spinal cord myelin seen at birth had also become nearly normal at the end of the period.