bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Jejunoileal Bypass on Plasma and Brain Amino Acids in the Rat
Authors: Herlin Per M. , James J. Howard , Joffe Stephen N. , Kulneff‐Herlin Agneta E. A. , Fischer Josef E.
Published: October 2006

Abstract: Liver failure and coma are serious complications of Jejunoileal bypass (JIB) in man. Rats underwent either a 90–95% JIB or a sham operation. Six weeks later all animals were sacrificed, and plasma and brain amino acids were determined. In the plasma of rats with JIB compared with sham operation, the concentrations of valine, leucine, isoleucine, lysine, tryptophan, and tyrosine were significantly lower, while in the brain, phenylalanine, tyrosine, histidine, and glutamine were significantly higher. These changes in the brain are similar to those resulting from portalsystemic shunting in the rat.
Inhibition of Aldehyde Dehydrogenases in Rat Brain and Liver by Disulfiram and Coprine
Authors: Pettersson Hans , Tottmar Olof
Published: October 2006

Abstract: Rats were treated with either coprine or disulfiram and the inhibition of aldehyde dehydrogenase (ALDH) in liver and brain mitochondria was measured with acetaldehyde, 3,4‐dihydroxyphenylacetaldehyde (DOPAL), and succinate semialdehyde at different concentrations. The inhibition pattern was similar for both inhibitors, but the degree of inhibition was lower with disulfiram. The ALDH activity both in the liver and the brain was inhibited at low concentrations of acetaldehyde and DOPAL, but not with succinate semialdehyde. The high‐Km enzyme activities with acetaldehyde were not inhibited in liver and brain. The activity at high concentration of DOPAL was inhibited in the liver, but only slightly affected in the brain, suggesting the presence of a brain enzyme with an intermediate Km value for DOPAL. In contrast with the results observed in viva, it was found that the high‐Km activities with acetaldehyde and DOPAL in brain mitochondrial preparations were more sensitive to the inhibitors in vitro than the low‐Km activities. Kinetic studies on ALDH preparations from brain and liver mitochondria suggested that acetaldehyde and DOPAL are metabolized by the same low‐Km ALDH.
Estimation of the Turnover of 3‐Methoxytyramine in the Rat Striatum by HPLC with Electrochemical Detection: Implications for the Sequence in the Cerebral Metabolism of Dopamine
Authors: Westerink B. H. C. , Spaan S. J.
Published: October 2006

Abstract: A highly sensitive method for the determination of 3‐methoxytyramine (3‐MT) in nervous tissue is described. The method is based on a rapidly performed isolation of 3‐MT on small columns of Sephadex G 10, followed by reverse‐phase high‐performance liquid chromatography in conjunction with a rotating disk electrochemical detector. The detection limit of the assay (0.5–1 pmol/tissue sample) is about 10% of control value for microwave‐killed rats. 3‐MT as well as dopamine could be quantified in the same chromatographic run. Inhibition of catechol‐O‐methyl transferase with tropolone resulted in an exponential decline of 3‐MT. From this exponential decline a turnover rate for 3‐MT of 1.9 nmol/g/h was calculated. In the same group of rats the turnover rate of homovanillic acid was 9.1 nmol/g/h. From these data it is concluded that in the rat striatum about 80% of homovanillic acid is formed from 3,4‐dihydroxyphenylacetic acid and 20% from 3‐MT.
Activation of Cyclic AMP‐Generating Systems in Brain Membranes and Slices by the Diterpene Forskolin: Augmentation of Receptor‐Mediated Responses
Authors: Daly J. W. , Padgett W. , Seamon K. B.
Published: October 2006

Abstract: The diterpene forskolin markedly activates adenylate cyclase in membranes from various rat brain regions and elicits marked accumulations of radioactive cyclic AMP in adenine‐labeled slices from cerebral cortex, cerebellum, hippocampus, striatum, superior colliculi, hypothalamus, thalamus, and medulla‐pens. In cerebral cortical slices, forskolin has half‐maximal effects at 20–30 μm on cyclic AMP levels, both alone and in the presence of the phosphodiesterase inhibitor ZK 62771. The presence of a very low dose of forskolin (1 μm) can augment the response of brain cyclic AMP‐generating systems to norepinephrine, isoproterenol, histamine, serotonin, dopamine, adenosine, prostaglandin E2, and vasoactive intestinal peptide. Forskolin does not augment responses to combinations of histamine‐norepinephrine, adenosine‐norepinephrine, or histamine‐adenosine. For norepinephrine and isoproterenol in rat cerebral cortical slices and for histamine in guinea pig cerebral cortical slices, the presence of 1 μm‐forskolin augments the apparent efficacy of the amine, whereas for adenosine, prostaglandin E2, and vasoactive intestinal peptide, the major effect of 1 μm‐forskolin is to increase the apparent potency of the stimulatory agent. In rat striatal slices, forskolin reveals a significant response of cyclic AMP systems to dopamine and augments the dopamine‐elicited activation of adenylate cyclase in rat striatal membranes. The activation of cyclic AMP systems by forskolin is rapid and reversible, and appears to involve both direct activation of adenylate cyclase and facilitation and/or enhancement of receptor‐mediated activation of the enzyme.
Biosynthesis of Biopterin by Rat Brain
Authors: Kapatos Gregory , Katoh Setsuko , Kaufman Seymour
Published: October 2006

Abstract: A method for the determination of [14C]biopterin biosynthesis from [14C]guanosine‐5′‐triphosphate by a desalted preparation from rat striatum, based on sequential reverse‐phase and cation‐exchange high performance liquid chromatography, is described. Synthesis of reduced forms of biopterin by this striatal extract was found to be dependent on enzymatic activity, guanosine‐5′‐triphosphate, magnesium ions, and a reduced pyridine nucleotide. As demonstrated by the technique of isotope dilution, isotope trapping, 6‐lactyl‐7,8‐dihydropterin (sepiapterin) was found to be an intermediate in biopterin biosynthesis that is catalyzed by the striatal extract. Rat brain was also shown to synthesize biopterin in vivo from intraventricularly administered [14C]guanosine or sepiapterin. Intraventricular injection of sepiapterin increased dihydro‐ and 5,6,7,8‐tetrahydrobiopterin levels in rat brain by more than eightfold. The temporal relationship between the appearance of dihydro‐ and 5,6,7,8‐tetrahydrobiopterin following intraventricular injection of sepiapterin suggests that dihydrobiopterin is the immediate product of sepiapterin reduction which is then reduced further to the functional cofactor 5,6,7,8‐tetra‐hydrobiopterin. Therefore, in contrast to previous reports, the biosynthesis of biopterin by rat brain does not appear to differ from that occurring in other, nonneural tissues.
Use of β‐Methylene‐D,L‐Aspartate to Assess the Role of Aspartate Aminotransferase in Cerebral Oxidative Metabolism
Authors: Fitzpatrick S. M. , Cooper A. J. L. , Duffy T. E.
Published: October 2006

Abstract: Several inhibitors of aspartate aminotransferase, a key enzyme of the malate‐aspartate shuttle, were investigated for their effects on cerebral oxidative metabolism in vitro. β‐Methylene‐D,L‐aspartate (2 mM), aminooxyacetate (0.1 mM), and D,L‐vinylglycine (20 mM) all significantly reduced the activity of aspartate aminotransferase and the rate of oxygen consumption of rat cerebral cortex slices respiring on glucose. In the presence of β‐methyleneaspartate, a one‐to‐one correlation was found between the degree of inhibition of tissue respiration and the degree of inhibition of transaminase activity. Slices of rat liver incubated in the presence of glucose and β‐methyleneaspartate showed a similar oneto‐one relationship between inhibition of oxygen cornsumption and inhibition of aspartate aminotransferase activity, whereas with rat kidney cortex slices, the inhibition of aspartate aminotransferase activity was greater than the inhibition of oxygen consumption. Structural analogs of β‐methyleneaspartate (D,L‐β‐methyl‐D,L‐aspartate, ‐γ‐methyl‐D,L‐glutamate, and α‐methyl‐D,L‐didehydroglutamate) that did not inhibit the activity of aspartate aminotransferase similarly did not inhibit the rate of oxygen consumption by cerebral cortex slices. In the presence of β‐methyleneaspartate, pyruvate oxidation by cerebral cortex slices was inhibited to almost the same extent as was glucose oxidation, and the oxidation of succinate was decreased by approximately 20%. The artificial electron acceptor phenazine methosulfate (0.1 mM) only partially overcame the β‐methyleneaspartate‐mediated inhibition of respiration with glucose as substrate. The content of ATP and phosphocreatine declined steadily in slices incubated with glucose and β‐methyleneaspartate. At 1 h the concentration of lactate and the lactate/ pyruvate ratio, an indicator of the cytoplasmic redox state, increased threefold, whereas the concentrations of malate, citrate, and aspartate decreased. The findings are interpreted in the context of the hypothesis that enzymes common to the malate‐aspartate shuttle and the tricarboxylic acid cycle are physically complexed in brain, so that inhibition of aspartate aminotransferase, a component of the complex, impedes the flow of carbon through both metabolic pathways. The operation of the malateaspartate shuttle may provide a link between cerebral glycolysis (a continued need for NAD+) and the tricarboxylic acid cycle (supply of oxaloacetate) that is vulnerable to several metabolic disturbances that impair brain function.
45Ca2+ Uptake into Rat Whole Brain Synaptosomes Unaltered by Dihydropyridine Calcium Antagonists
Authors: Daniell Laura C. , Barr Edward M. , Leslie Steven W.
Published: October 2006

Abstract: Voltage‐dependent 45Ca2+ uptake into rat whole brain synaptosomes was measured after 3‐s KClinduced depolarization to investigate possible inhibitory effects of calcium antagonists, nitrendipine, nimodipine, and nisoldipine. At a Ca2+ concentration of 1.2 mM, nitrendipine, in concentrations ranging from 0.1 nM to 10 μM, had no effect on 45Ca2+ uptake. When the Ca2+ concentration was lowered to 0.06 and 0.12 μM, nitrendipine, 10 μM, inhibited 45Ca2+ uptake in response to 109 mM KC1 depolarization. However, in a separate concentration response study, nitrendipine, nimodipine, and nisoldipine, 0.1 μM to 10 μM, failed to alter the uptake of 45Ca2+ (0.06 mM Ca2+) into 30 mM KCl‐depolarized synaptosomes. The high concentrations of these agents required to depress 45Ca2+ uptake indicate that the dihydropyridine calcium antagonists are considerably less potent in brain tissue than in peripheral tissue.
Glycolysis and Epilepsy‐Induced Changes in Cerebrocortical NAD/NADH Redox State
Authors: Dóra Eörs
Published: October 2006

Abstract: The effects of topical inhibition of glycolysis on epilepsy‐induced changes of cortical vascular volume (CVV) and fluorescence of reduced nicotinamide adenine dinucleotide (NADH) were investigated in chloralose‐anaesthetized cats. CVV and NADH fluorescence were measured by a microscope fluororeflectometer. It was found that 30 min of superfusion of the brain cortex with artificial cerebrospinal fluid (CSF) containing 0.5 mM sodium iodoacetate (IAA) resulted in a 16.4 ± 0.8% increase in CVV, and 6.6 ± 0.5% in NADH oxidation. IAA did not alter the electrical activity of the brain cortex. Epileptic seizures in the nonsuperfused brain cortex and following 30 min superfusion of the brain cortex with mock CSF resulted in changes (not significantly different) in CVV and NAD/NADH redox state. They increased CVV and NAD reduction by 28–32% and 7–10%, respectively. Following 0.5 mM IAA treatment of the brain cortex, epileptic seizures led to greatly reduced vascular responses and induced NADH oxidation instead of NAD reduction. Since the topical inhibition of glycolysis reversed the direction of NAD/NADH redox responses accompanying epilepsy, it may be suggested that the relative rate of substrate mobilization as compared with the rate of mitochondrial electron transport is the factor that determines the actual change in NAD‐NADH ratio during excessive brain activations. However, contrary to the situation in vitro (isolated mitochondria), the NAD/NADH redox state of the intact brain cortex is not shifted toward oxidation but to reduction during increased electrical activity.
The Presence of Zinc‐Binding Proteins in Brain
Authors: Itoh Masatoshi , Ebadi Manuchair , Swanson Stanley
Published: October 2006

Abstract: Zinc is one of the most abundant divalent metal ions in the brain, its concentration being greater than those of copper and manganese. Since free zinc ion is a potent inhibitor of sulfhydryl enzymes, we postulated that zinc in the brain most probably exists bound to macromolecules. As zinc‐binding proteins in brain have not been characterized, we attempted to discover the occurrence and properties of these proteins. By using Sephadex G‐75 column chromatography calibrated with proteins of known molecular weights, and by other techniques, we detected separate zinc‐binding proteins, with apparent estimated molecular weights ranging from 15,000 to 210,000. Unlike the hepatic or renal zinc thioneins, the zinc‐binding proteins in brain are not inducible following administration of zinc. Our interpretation of the results is that the major portion of the existing zinc in the brain is bound, and does not exist in free form.
Estimation of Thy‐1 in Cryostat Sections of Nervous Tissue
Authors: Morris R. J. , Raisman G.
Published: October 2006

Abstract: The conventional assay for measuring cell surface antigens‐the quantitative absorption of antibody by tissue homogenates‐proved inadequate when used to determine the level of Thy‐1 glycoprotein in rat nerves and peripheral ganglia. In this paper we report that the binding of 1251‐labelled Fab fragments of a monoclonal anti‐Thy‐1 antibody to cryostat sections is sufficiently sensitive to give consistent estimates of the Thy‐1 level on single samples of even small nerves. Observed levels of Thy‐1 were generally higher than had previously been thought, and in particular we found no nerves totally lacking the antigen. The lowest levels (6‐10 pmol/mg protein) were in peripheral nerves with a large motor component. Autonomic and sensory nerves had higher levels (15‐20 pmol/mg protein). The highest levels were on the optic nerve (34 pmol/mg protein), superior cervical sympathetic ganglion (40 pmol/mg protein), and the cerebellar vermis (46 pmoles/mg protein; the only brain region examined in this study). From a practical point of view, the cryostat assay has the advantage that measurements of Thy‐1 can be done on sections from the same series as is used for immunohistochemical localisation.
Changes in Muscarinic Binding in Distant Brain Regions Showing Neuronal Losses After Folic Acid Injections into the Substantia Innominata
Authors: Wong P. T.‐H. , McGeer E. G. , Singh K. , McGeer P. L.
Published: October 2006

Injection of folic acid (FA) into the nucleus substantia innominata (NSI) was found to decrease [3H]quinuclidinyl benzilate ([3H]QNB) binding in the frontal cortex, pyriform cortex, amygdala, and the NSI itself without changing the Kd. Binding in the thalamus, caudate nucleus, hippocampus, and substantia nigra was not affected. [3H]Flunitrazepam binding was unchanged in all eight regions studied. Previous work indicates FA injections into the NSI produce epileptiform activity and cause loss of GABAergic and possibly other neurons in the frontal and pyriform cortices, the amygdala, and thalamus. The reductions of [3H]QNB binding in the first three of these regions are interpreted as indicating that many of the neurons lost are cholinoceptive, a finding that supports the previous hypothesis that activation of cholinergic projections from the NSI is an important part of the mechanism of cell loss in these regions.
Effects of Dichloroacetate on Brain Tissue Pyruvate Dehydrogenase
Authors: Evans Owen B.
Published: October 2006

Abstract: The activation of the pyruvate dehydrogenase complex (PDHC) by dichloroacetate (DCA) was studied in brain tissue. Chronic administration of DCA to rats caused no significant change of PDHC activation in brain. DCA brain concentrations were comparable to those of other tissues in which activation is known to occur. No effect of DCA on PDHC could be demonstrated from isolated brain mitochondria, whereas DCA reversed the deactivation of PDHC by ATP, α‐ketoglutarate plus malate, and succinate in liver mitochondria. This study suggests that the regulation of PDHC activation in neural tissue differs from that in other tissues.
Evidence for the Presence of a GTP‐Dependent Regulatory Component of Adenylate Cyclase in Myelin from Rat Brain
Authors: Enomoto Keiichi , Asakawa Takeo
Published: October 2006

Abstract: A GTP‐dependent regulatory component of adenylate cyclase was found in myelin from rat brain. The fraction solubilized from myelin contained a component that reconstituted guanine nucleotide‐responsive adenylate cyclase activity when combined with the catalytic unit of adenylate cyclase prepared from rat brain. Purified myelin demonstrated little adenylate cyclase activity, even in the presence of F− or Mn2+. The reconstituted activity was dependent on the amount of the solubilized myelin fraction and required the presence of 5′‐guanylylimidodiphosphate, a hydrolysis‐resistant analog of GTP. The elution pattern of the component solubilized from myelin in gel filtration was very similar to that of a GTP‐dependent regulatory component from synaptic plasma membranes. The content of the regulatory component‐like activity in myelin was estimated to be 50–60% of that in synaptic plasma membranes. Cholera toxin ADP‐ribosylated proteins having molecular weights of 48,000, 38,000, 23,000, 20,000 and 15,000 and other minor peptides in myelin, some of which were also present in synaptic plasma membranes. We conclude that myelin contained a GTP‐dependent regulatory component of adenylate cyclase despite the apparent lack of adenylate cylcase activity in myelin.
Desensitization to Nicotinic Cholinergic Agonists and K+, Agents That Stimulate Catecholamine Secretion, in Isolated Adrenal Chromaffin Cells
Authors: Boksa P. , Livett B. G.
Published: October 2006

Abstract: Desensitization of catecholamine (CA) release from cultured bovine adrenal chromaffin cells was studied to characterize the phenomenon of desensitization and to attempt an elucidation of the mechanism(s) involved in this phenomenon at the level of the isolated chromaffin cell. Prior exposure of chromaffin cells to nicotinic cholinergic agonists [acetylcholine (ACh) or nicotine] caused a subsequent depression or desensitization of CA release during restimulation of the cells with the same agonists. Rates of development of and recovery from nicotinic desensitization were in the minute time range and the magnitude of nicotinic desensitization of CA release was greater at 37°C than at 23°C. ACh‐ (or nicotine)‐induced desensitization was shown to be the result of two processes: (1) a Ca2+‐dependent component of desensitization, possibly due to a depletion of intracellular CA stores and (2) a Ca2+‐independent, depletion‐independent component of desensitization. Prior exposure of cultured chromaffin cells to an elevated concentration of K+ also resulted in desensitization of K+‐induced CA release in these cells. K+‐induced desensitization was completely Ca2+‐dependent and was shown to be the result, at least in part, of a mechanism that is independent of depletion of CA stores.
Differential Uptake of Lithium Isotopes by Rat Cerebral Cortex and Its Effect on Inositol Phosphate Metabolism
Authors: Sherman William R. , Munsell Ling Y. , Wong Yun‐Hua H.
Published: October 2006

Abstract: Twenty hours following the subcutaneous administration of 5 mEq/kg doses of 6LiCl and 7LiCl to two groups of rats, the cerebral cortex molar ratio of 6Li+/7Li+ is 1.5. The effects of the lithium isotopes on cortex myo‐inositol and myo‐inositol‐1 ‐phosphate levels are the same as we have reported earlier: a Li+ concentration‐dependent lowering of myo‐inositol and increase in myo‐inositol‐1‐phosphate. Thus 6LiCl, when administered at the same dose as 7LiCl, produces the larger effect on inositol metabolism. When the 6LiCl and 7LiCl doses were adjusted to 5 mEq/kg and 7 mEq/kg, respectively, the cortical lithium myo‐inositol and myo‐inositol‐1‐phosphate levels of each group of animals became approximately equal, suggesting that the isotope effect occurs at the level of tissue uptake, but not on inositol phosphate metabolism. The inhibition of myo‐inositol‐1‐phosphatase by the two lithium isotopes in vitro showed no differential effect. The isotope effect on cerebral cortex uptake of lithium is in the same direction as that reported by others for erythrocytes and for the CSF/plasma ratio, but of larger magnitude.
Developmental Changes of Cerebral Cortical [3H]Clonidine Binding in Rats: Influences of Guanine Nucleotide and Cations
Authors: Nomura Yasuyuki , Kawai Masanori , Mita Kayoko , Segawa Tomio
Published: October 2006

Abstract: Cerebral cortical [3H]clonidine binding and influences of GTP and cations were investigated in developing rats. The results from Scatchard plots were compatible with the presence of two populations of binding sites [high‐affinity binding (KD= 0.59 nM) and low‐affinity binding (KD= 7.12 nM)] in 70‐day‐old rats but only high‐affinity binding (KD= 0.27 nM) on day 1. Low‐affinity binding was detectable on day 7. KD values in high‐ and low‐affinity binding were not significantly changed during development after 7 days. Bmax of high‐affinity binding reached a peak on day 15, and the value of low‐affinity binding gradually increased with age. The addition of 10 μM GTP caused a significant reduction in Bmax of high‐affinity binding after day 7. Neither KD nor Bmax of low‐affinity binding was affected by 10 μM GTP during development. NaCl (10 and 100 mM) diminished the binding on days 7 and 70. MnCl2 (0.1 and 1.0 mM) markedly increased the binding on days 15 and 70 but not on day 7. It is suggested that: (1) single binding sites of α2‐adrenoceptors with higher affinity seem to be present on day 1; (2) low‐affinity binding appears on day 7; (3) the number of high‐affinity binding sites reaches a peak on day 15, followed by changes in populations of high‐affinity as well as low‐affinity sites without changing affinity; (4) the regulatory mechanism in α2‐receptors by guanine nucleotide reaches functional maturity between days 1 and 7; and (5) the involvement of Na+ and Mn2+ in α2‐receptor binding becomes functional by days 7 and 15, respectively.
Phospholipid‐Sensitive Ca2+‐Dependent Protein Kinase Preferentially Phosphorylates Serine‐115 of Bovine Myelin Basic Protein
Authors: Scott Turner R. , Chou C.‐H. Jen , Mazzei Gonzalo J. , Dembure Philip , Kuo J. F.
Published: October 2006

Abstract: Phospholipid‐sensitive Ca2+‐dependent protein kinase (PL‐Ca‐PK) and cyclic AMP‐dependent protein kinase (A‐PK) both preferentially phosphorylated serine residues of bovine myelin basic protein (MBP). Tryptic peptide maps of MBP phosphorylated by PL‐Ca‐PK or A‐PK, however, revealed different phosphopeptides, suggesting a difference in the intramolecular substrate specificity for the two enzymes. Serine‐115 of MBP, in the sequence (‐Arg‐Phe‐Ser(115)‐Trp‐), was found to be a preferred and probably major phosphorylation site for PL‐Ca‐PK. Because serine‐115 of bovine MBP corresponds to serine‐113 of rabbit MBP, an in vivo phosphorylation site reported by Martenson et al. (1983), and PL‐Ca‐PK is present at a very high level in brain and myelin, it is suggested that the enzyme may be responsible for the in vivo phosphorylation of this and other sites in MBP.
Inhibition of Fast Axonal Transport by erythro‐9‐[3‐(2‐Hydroxynonyl)]Adenine
Authors: Ekstrom Per , Kanje Martin
Published: October 2006

Abstract: erythro‐9‐[3‐(2‐Hydroxynonyl)]adenine, an inhibitor of protein carboxylmethylation and dynein‐ATPase activity, inhibited fast axonal transport in vitro in frog sciatic nerves. Its site of action might be associated with an ATPase on which transport depends, since specific carboxylmethylation inhibitors lacked effects on transport. The levels of high energy phosphates and protein synthesis were unaffected by the drug at a transport‐inhibiting concentration, making disturbances due to metabolic effects less likely. An erythro‐9‐[3‐(2‐hy‐droxynonyl)]adenine‐sensitive ATPase was looked for in various nerve fractions but has so far not been resolved.
Alterations in Cerebral and Microvascular Prostaglandin Synthesis by Manipulation of Dietary Essential Fatty Acids
Authors: Brown Michael L. , Marshall Lisa A. , Johnston Patricia V.
Published: October 2006

Abstract: Sprague‐Dawley rats were fed one of three purified diets—10% corn oil, 10% hydrogenated coconut oil, or 10% linseed oil—through two generations. At 60–80 days of age the animals were sacrificed. The fatty acyl composition of phosphatidylcholine, phosphatidyletha‐nolamine, plasmalogen phosphatidylethanolamine, and combined phosphatidylinositol/phosphatidylserine from cerebral cortex and isolated cerebral microvessels was determined. Brain slice prostaglandin F2α or microvas‐cular prostacyclin synthesis was also measured. Major changes were noted in the fatty acid profiles, most dramatically in the phosphatidylethanolamine and ethanol‐amine plasmalogen fractions, with an active rise in docosahexaenoic acid resulting from linseed oil feeding. A depression in prostaglandin F2α synthesis was seen in brain slices of hydrogenated coconut oil‐and linseed oil‐fed rats. Such a depression was also observed in micro‐vascular prostaglandin synthesis at basal and stimulated levels but not in control incubations. The potential importance of these findings to cerebral microcirculation and hemostasis is discussed.
Regulation of mRNAs for Three Enzymes in the Glial Cell Model C6 Cell Line
Authors: Kumar Shalini , Weingarten Daniel P. , Callahan John W. , Sachar Kanta , de Vellis Jean
Published: October 2006

Abstract: In the glial cell line C6, regulation of actinomycin D (Act‐D)‐sensitive translatable polysomal mRNAs of three key enzymes—glycerol phosphate dehydrogenase (GPDH; EC 1.1.1.8) and glutamine synthetase (GS) by glucocorticoids and lactate dehydrogenase (LDH; EC 1.1.1.27) by catecholamines—is described. Though the first two enzymes are hydrocortisone (HC)‐inducible, the nature of their response to the hyperacetylating agent sodium butyrate is dramatically different. Furthermore the appearance of GPDH translatable poly (A)+ RNA in HC‐induced cells is inhibited by the presence of cycloheximide (CHX), whereas the induction of GS is unaffected by CHX. These observations necessitate further probing into an existing model system to explain the varied mechanisms of induction of these two enzymes by a single inducer. In combination with the third enzyme whose induction by catecholamines is glial specific, we believe that the C6 cell represents the most appropriate cell line for molecular neurobiologists to study the mechanisms of hormone action in glia.
Sequence of Guinea Pig Myelin Basic Protein
Authors: Deibler Gladys E. , Martenson Russell E. , Krutzsch Henry C. , Kies Marian W.
Published: October 2006

Abstract: This paper proposes a tentative amino acid sequence of guinea pig myelin basic protein obtained by comparison of peptide fragments of the guinea pig and bovine proteins. Analyses of the tryptic peptides confirmed the known sequence differences in the NH2‐terminal half of the molecule and showed that in the COOH‐terminal half of the guinea pig protein Ser131 was missing, Ala136‐His137 was deleted, Leu140 was replaced by the, and an extra Ala was inserted somewhere within sequence 142–151 (tryptic peptide T23). Sequence determination of guinea pig tryptic peptides corresponding to residues 130–134 (T20), 135–138 (T21), and 142–151 (T23) of the bovine protein confirmed the above sequence changes and placed the extra Ala between Gly142 and His143. The sequence of the region corresponding to bovine residues 130–143 is thus Ala‐Asp‐Tyr‐Lys‐Ser‐Lys‐Gly‐Phe‐Lys‐Gly‐Ala‐His. No species differences were observed in the amino acid compositions of the remaining tryptic peptides obtained from the COOH‐terminal half of the molecule. Based upon these results, the guinea pig basic protein contains 167 amino acid residues and has a molecular weight of 18,256.
Muscarinic Receptor Subclasses in the Chick Embryo Retina: Influence of Corticosterone Treatment
Authors: Gremo Fulvia , Marchisio Anna Maria , Vernadakis Antonia
Published: October 2006

Abstract: The present study was performed on retinas of chick embryos receiving at day 8 of incubation an intracerebral injection of 0.02 μg of corticosterone. We had previously shown with the use of [3H]quinuclidinylbenzilate ([3H]QNB) that such treatment induced the appearance of two muscarinic binding sites in the treated retinas, whereas only one was detectable in the controls. In the present study we investigated muscarinic cholinergic receptor subclasses with agonist and antagonist binding. Agonist binding was studied by varying the concentrations of carbachol and acetylcholine (10‐9M‐10‐5M) in the presence of a constant concentration (0.2 nM) of [3H]QNB. Two subpopulations of receptors were revealed, a high‐ and a low‐affinity receptor, in both treated and control retinas. However, in the hormonetreated retinas, the two subpopulations significantly differed from the controls in their affinity and in their relative percentage among the total receptor population. Moreover, using pirenzepine, an antagonist known to have the capacity to distinguish between muscarinic cholinergic subclasses, two receptor subpopulations were found to be present in the hormone‐treated retinas but a single one in the controls. It is suggested that hormone treatment can either induce the appearance of a new subclass of muscarinic cholinergic receptors or favor the maturation of a population of retinal cells having these receptors. Pirenzepine binding in retinas from intact embryos of 7, 9, and 11 days of incubation revealed one receptor subpopulation. Thus, these findings are more consistent with the hypothesis that corticosterone effects the target cells, either inducing changes in muscarinic receptor and/or modifying the receptor environment.
An Excitant Amino Acid Projection from the Medial Prefrontal Cortex to the Anterior Part of Nucleus Accumbens in the Rat
Authors: Christie M. J. , James L. B. , Beart P. M.
Published: October 2006

Abstract: High‐affinity uptake of neurotransmitter substrates in synaptosome‐containing homogenates and tissue concentrations of amino acids were examined in subcortical areas 5–6 days after bilateral N‐methyl‐D‐aspartate lesions confined to rat medial prefrontal cortex. D‐[3H]Aspartate (32% of control) and [3H]γ‐aminobutyric acid ([3H]GABA) (60% of control) uptakes were significantly reduced in medial prefrontal cortex, whereas [3H]choline (110% of control) uptake was unchanged, suggesting the production of axon‐sparing lesions. The uptake of D‐[3H]aspartate (76% of control), but not of [3H]GABA or [3H]choline, was significantly reduced in nucleus accumbens, with no concomitant reduction in amino acid concentrations. When examined in serial coronal sections, reduced D‐[3H]aspartate uptake was confined to the most anterior 500 μm of nucleus accumbens (67% of contralateral sample). No significant reductions of uptake or amino acid concentrations were observed in caudate putamen or ventral tegmental area. These results suggest a role for glutamate or aspartate as neurotransmitters in projections from medial prefrontal cortex to anterior nucleus accumbens. Medial prefrontal cortex may represent the major excitatory cortical input to the nucleus accumbens.
Biochemical Characterization of the Nicotinic Cholinergic Receptors in Human Brain: Binding of (—)‐[3H]Nicotine
Authors: Shimohama Shun , Taniguchi Takashi , Fujiwara Motohatsu , Kameyama Masakuni
Published: October 2006

Abstract: (−)‐[3H]Nicotine was found to bind specifically to membranes of human brains obtained at autopsy. The binding was stereospecific, (−)‐nicotine being 40 times more potent than (+)‐nicotine in displacing labeled (−)‐nicotine. Saturation binding studies revealed the presence of two binding sites with dissociation constant (KD) values of 8.1 and 86 nM, and maximum binding capacity (Bmax) values of 36 and 90 fmol/mg protein, respectively. In competition studies, nicotinic agonists were 1,000 times more potent than ganglionic, neuromuscular, and muscarinic blocking drugs in displacing labeled (−)nicotine. IC50 values for cholinergic drugs of (−)[3H]nicotine binding were as follows: (−)‐nicotine, 0.51 nM; acetylcholine, 12.6 nM; (+)‐nicotine, 19.9 nM; cytisine, 27.3 nM; and carbachol, 527 nM. IC50 values of α‐bungarotoxin, hexamethonium, d‐tubocurarine, and atropine were larger than 50 μM. (−)‐[3H]Nicotine binding was highest in the nucleus basalis of Meynert and thalamus and lowest in the cerebral cortex and caudate in the brain regions tested. These results suggest that nicotinic cholinergic receptors are present in human brain and that there are regional differences in the density of these receptors.
Decrease of Choline Acetyltransferase Activity of Rat Cortex Capillaries with Aging
Authors: Santos‐Benito F. F. , Gonzalez J. L.
Published: October 2006

Abstract: Choline acetyltransferase (ChAT) activity was estimated in brain cortex capillaries isolated from 3‐, 12‐, 18‐, and 24‐month‐old rats. Maximum enzymatic activity was found at 12 months (55 ± 0.3 pmol · mg−1 protein · min−1; mean ± SEM) and then it decreased to reach a minimum at 24 months (34 ± 3.1 pmol · mg−1 protein · min−1). A less marked decrease of enzymatic activity was also found in cortex homogenate and in a synaptosomal fraction obtained from the same groups of rats. Loss of ChAT of brain capillaries with aging could be related to a general phenomenon of cortical cholinergic deficit in that condition.
Tetraenoic Species Are Conserved in Muscarinically Enhanced Inositide Turnover
Authors: Van Rooijen Lucio A. A. , Hajra Amiya K. , Agranoff Bernard W.
Published: October 2006

Abstract: Carbamylcholine enhances the labeling of phosphatidate and phosphatidylinositol from 32Pi in nerve endings. Approximately 74% of labeled phosphatidate and 85% of labeled phosphatidylinositol produced on muscarinic stimulation are accounted for by tetraenoic species, as detected by argentation TLC. Incubation of membranes derived from nerve endings with [γ‐32P]ATP under conditions of phosphodiesteratic degradation of endogenous polyphosphoinositides resulted in increased labeling of phosphatidate. Approximately 78% of the newly formed phosphatidate was in a tetraenoic fraction. It is concluded that in muscarinically stimulated nerve endings, the diacylglycerol moiety is conserved following diacylglycerol release from polyphosphoinositides through its resynthesis to inositol lipid via phosphatidate.
Effect of Unilateral Decortication on Choline Acetyltransferase Activity in the Nucleus Basalis and Other Areas of the Rat Brain
Authors: Stephens P. H. , Cuello A. C. , Sofroniew M. V. , Pearson R. C. A. , Tagari P
Published: October 2006

Abstract: Acetyl‐coenzyme A: choline O‐acetyltransferase (EC 2.3.1.6) (ChAT) enzyme activity was measured in the nucleus basalis and other microscopically identified brain areas at various times after unilateral cortical lesions were made in the rat. Initially, a significant decrease in ChAT activity was detected in the nucleus basalis ipsilateral to the lesion. However, after 120 days ChAT activity had apparently recovered, as levels of the enzyme at that time were not significantly different from control values. No changes in ChAT activity could be detected in any of the other brain areas similarly studied. The significance of these findings and their relationship to the morphological changes seen in neurones of the nucleus basalis after cortical lesions are discussed.
Choline Acetyltransferase Activity in the Rat Trigeminal System
Authors: Couture R. , Consolazione A. , Cuello A. Claudio
Published: October 2006

Abstract: Choline acetyltranferase activity was investigated in the superior cervical ganglia and in six microdissected regions of the medulla oblongata of the rat ipsilateral and contralateral to electrolytic lesions of the trigeminal sensory ganglia (Gasserian). Electrolytic lesions of the Gasserian ganglia failed to modify levels of enzymatic activity in all structures studied. This result would be an argument against the existence of a major cholinergic population of sensory neurones in the trigeminal system.
Electrophoretic Analysis of Myelin Proteolipid Protein and Its Deacylated Form
Authors: Bizzozero Oscar A. , Dominguez Francisca , Pasquini Juana M. , Soto Eduardo F.
Published: October 2006

Abstract: Myelin proteolipid protein is known to contain covalently bound fatty acid. To determine the contribution of the fatty acid to the multiple bands observed on sodium dodecyl sulfate–polyacrylamide gel electrophoresis, the electrophoretic parameters of the proteolipid protein were compared with those of the deacylated form. The relative mobility and proportion of each band, as well as the retardation coefficient and free electrophoretic mobility, were not altered by removal of the fatty acid moiety. Furthermore, the acylated and deacylated forms bound the same amounts of sodium dodecyl sulfate. These data demonstrate that the presence of covalently bound fatty acids does not account for the electrophoretic heterogeneity of the proteolipid.
Glucocorticoid‐Mediated Increases in Glycerol Phosphate Dehydrogenase Activity Is Inhibited by the Phorbol Ester Tumor Promoters
Authors: Bressler Joseph P. , Weingarten Daniel , Kornblith Paul L.
Published: October 2006

Abstract: An oligodendroglial specific property, glucocorticoid regulation of glycerol‐3‐phosphate dehydrogenase (GPDH) levels, was inhibited in C6 rat glioma cells when 4β‐phorbol 12‐myristate 13‐acetate (PMA) was added to the cultures. PMA inhibited GPDH induction in both logarithmic‐ and stationary‐phase cells. These events are most likely mediated through the phorbol ester receptor since the ability of various phorbol ester analogs to compete with the ligand [3H]4β‐phorbol 12,13‐dibutyrate for binding to the receptor correlates with the ability the particular analog has to inhibit GPDH induction. Additionally, like tumor promotion in vivo, the inhibition of GPDH induction is reversible. The PMA effect is not restricted to the C6 cell line since PMA also inhibits GPDH inducibility in another rat glioma cell line. This PMA‐mediated event has been partially characterized. PMA did not affect the overall rate of protein or RNA synthesis. It was ineffective in altering both glucocorticoid accumulation to the nucleus and the rate of GPDH degradation. It appears likely that PMA's inhibitory action occurs at the transcriptional or translational level.
Effects of Insulin and Streptozotocin‐Induced Diabetes on Brain Norepinephrine Metabolism in Rats
Authors: Trulson M. E. , Himmel C. D.
Published: October 2006

Administration of insulin (2 IU/kg, i.p.) produced a significant decrease (18%) in forebrain norepinephrine and a significant increase in the major metabolite of norepinephrine, 3‐methoxy‐4‐hydroxyphenyl‐glycol‐sulfate (MOPEG‐SO4, +19%) in rats. Streptozotocin‐induced diabetes produced the opposite effects, resulting in an increase in forebrain norepinephrine (+17%) and a decrease in MOPEG‐SO4 (−26%). In addition, insulin increased (+143%) and diabetes decreased (− 41%) the turnover rate of norepinephrine, as measured by the rate of decrease of norepinephrine following inhibition of tyrosine hydroxylase by α‐methyl‐P‐tyrosine. All of these effects in diabetic rats were reversed by insulin replacement therapy. These data are discussed within the context of mood disorders characteristic of diabetic patients.
Effects of p,p′‐DDT on the Rat Brain Concentrations of Biogenic Amine and Amino Acid Neurotransmitters and Their Association with p,p′‐DDT‐Induced Tremor and Hyperthermia
Authors: Hudson P. M. , Chen P. H. , Tilson H. A. , Hong J. S.
Published: October 2006

Abstract: Male, Fischer strain 344 adult rats were given various doses (25–100 mg/kg) of p,p′‐DDT by oral gavage, and levels of biogenic amines, their metabolites, and amino acid neurotransmitters, tremor activity, and rectal temperature were measured at several intervals (2, 5, 12, and 24 h) after dosing. Dose‐related increases in rectal temperature and in tremor activity were observed at 50–100 mg/kg 12 h after dosing. Tremorigenic doses of DDT increased the 5‐hydroxyindoleacetic acid (5‐HIAA) level in hypothalamus, brainstem, and striatum, whereas doses of 75 and 100 mg/kg increased the 3‐methoxy‐4‐hydroxyphenylglycol (MHPG) level in hypothalamus and brainstem and the 3,4‐dihydroxyphenylacetic acid level in striatum. Six amino acids were assayed in the brainstem, hypothalamus, and striatum; aspartate and glutamate levels were increased only in brainstem at 25–100 mg/kg. No consistent changes in concentrations of taurine, glutamine, glycine, or γ‐aminobutyric acid were observed in any of the regions assayed. Time‐related increases in rectal temperature were seen 2–12 h after dosing, and the presence of tremor was observed 5–12 h after dosing; for both the time of peak effect was at 12 h. The DDT‐induced hyperthermia and tremor were associated with dose‐ and time‐related increases in levels of 5‐HIAA, MHPG, aspartate, and glutamate. It is suggested that an increase in the turnover rate of 5‐hydroxy‐tryptamine (5‐HT) may be responsible for the DDT‐induced hyperthermia, whereas increases in the metabolism of 5‐HT and norepinephrine may be involved in the tremor.
Inactivation of Neurotensin by Rat Brain Synaptic Membranes Partly Occurs Through Cleavage at the Arg8‐Arg9 Peptide Bond by a Metalloendopeptidase
Authors: Checler Frédéric , Vincent J. P. , Kitabgi P.
Published: October 2006

Abstract: One of the primary inactivating cleavages of neurotensin (NT) by rat brain synaptic membranes occurs at the Arg8‐Arg9 peptide bond, leading to the formation of NT1‐8 and NT9‐13. The involvement at this site of a recently purified metalloendopeptidase was demonstrated by the use of its specific inhibitor, N‐[1(R,S)‐carboxy‐2‐phenylethyl]‐alanylalanylphenylalanine‐p‐aminobenzoate, which exerts an inhibition on NT1‐8 formation with an IC50 (0.6 μM) close to its Ki for the purified metalloendopeptidase (1.94 μM). Furthermore, we established the role of a postproline dipeptidyl‐aminopeptidase in the secondary processing of NT9‐13 formation.
Effect of Hypoglycemic Encephalopathy upon Amino Acids, High‐Energy Phosphates, and pHi in the Rat Brain In Vivo: Detection by Sequential 1H and 31P NMR Spectroscopy
Authors: Behar K. L. , den Hollander J. A. , Petroff O. A. C. , Hetherington H. P. , Prichard J. W. , Shulman R. G.
Published: October 2006

Abstract: Metabolic alterations in amino acids, high‐energy phosphates, and intracellular pH during and after insulin hypoglycemia in the rat brain was studied in vivo by 1H and 31P nuclear magnetic resonance (NMR) spectroscopy. Sequential accumulations of 1H and 31P spectra were obtained from a double‐tuned surface coil positioned over the exposed skull of a rat while the electroencephalogram was recorded continuously. The transition to EEG silence was accompanied by rapid declines in phosphocreatine, nucleoside triphosphate, and an increase in inorganic orthophosphate in 31P spectra. In 1H spectra acquired during the same time interval, the resonances of glutamate and glutamine decreased in intensity while a progressive increase in aspartate was observed. Following glucose administration, glutamate and aspartate returned to control levels (recovery half‐time, 8 min); recovery of glutamine was incomplete. An increase in lactate was detected in the 1H spectrum during recovery but it was not associated with any change in the intracellular pH as assessed in the corresponding 31P spectrum. Phosphocreatine returned to control levels following glucose administration, in contrast to nucleoside triphosphate and inorganic orthophosphate which recovered to only 80% and 200% of their control levels, respectively. These results show that the changes in cerebral amino acids and high‐energy phosphates detected by alternating the collection of 1H and 31P spectra allow for a detailed assessment of the metabolic response of the hypoglycemic brain in vivo.
Variables Influencing the Effect of a Meal on Brain Tryptophan
Authors: Sarna G. S. , Kantamaneni B. D. , Curzon G.
Published: October 2006

Abstract: Previous work from our laboratory points to plasma free tryptophan being a useful predictor of brain tryptophan concentration in many circumstances. Other work, in particular various studies on the acute effects of food intake, has emphasized the roles of plasma total tryptophan and of plasma large neutral amino acids that compete with tryptophan for transport to the brain. We have now studied associations between the above variables under different dietary conditions. Rats were allowed to feed for restricted periods during a 12‐h light‐12‐h dark cycle. In the first study, rats were given access to a carbohydrate diet for 2 h midway through the light cycle and following an 18‐h fast. The resultant rise of brain tryptophan was explicable largely by the associated fall in large neutral amino acids. In a second study, rats were adapted to a regimen whereby they were allowed access to the standard laboratory diet for 4 h during the dark cycle for 3 weeks. A postprandial decrease in brain tryptophan was associated with a fall in free tryptophan and of its ratio to competing amino acids. The brain change could be attributed neither to changes in plasma total tryptophan (which increased) nor to changes of its ratio to the competers (which remained unchanged). Results as a whole are thus consistent with changes of plasma free tryptophan and large neutral amino acid concentrations affecting brain tryptophan concentration under different dietary circumstances. It is suggested that these influences serve to maintain brain tryptophan when dietary supplies are defective.
Partial Purification and Properties of Human Brain Aldehyde Dehydrogenases
Authors: Maring Jacques‐Andre , Deitrich Richard A. , Little Roger
Published: October 2006

Abstract: Acetaldehyde and biogenic aldehydes were used as substrates to investigate the subcellular distribution of aldehyde dehydrogenase activity in autopsied human brain. With 10 μM acetaldehyde as substrate, over 50% of the total activity was found in the mitochondrial fraction and 38% was associated with the cytosol. However, with 4 μM 3,4‐dihydroxyphenylacetaldehyde and 10 μM indoleacetaldehyde as substrates, 40–50% of the total activity was found in the soluble fraction, the mitochondrial fraction accounting for only 15–30% of the total activity. These data suggested the presence of distinct aldehyde dehydrogenase isozymes in the different compartments. The mitochondrial and cytosolic fractions were, therefore, subjected to salt fractionation and ion‐exchange chromatography to purify further the isozymes present in both fractions. The kinetic data on the partially purified isozymes revealed the presence of a low Km isozyme in both the mitochondria and the cytosol, with Km values for acetaldehyde of 1.7 μM and 10.2 μM, respectively. However, the cytosolic isozyme exhibited lower Km values for the biogenic aldehydes. Both isozymes were activated by Mg2+ and Ca2+ in phosphate buffers (pH 7.4). Also, high Km isozymes were found in the mitochondria and in the microsomes.