bluuebunny/crossref_metadata_2025 huggingface dataset:
Intrauterine Malnutrition and the Brain: Effects on Enzymes and Free Amino Acids Related to Glutamate Metabolism
Authors: Prasad C. , Agarwal K. N.
Published: October 2006

Abstract: The effect of feeding pregnant rats with wheat and Bengal gram (black chick pea) diets during the later part of pregnancy on brain growth, enzymes, and free amino acids of glutamate metabolism in 1‐day‐old rats was investigated. These diets did not induce growth dissociation, and the body and brain weights were equally affected. The concentrations of DNA, RNA, protein, and free α‐amino nitrogen in brain decreased significantly and the activities of glutamine synthetase, glutamine transferase, glutaminase 1, glutaminase 11, and glutamate decarboxylase and the concentrations of free amino acids, glutamic acid, glutamine, alanine, and GABA were also decreased. The concentration of aspartic acid, however, was increased. Wheat and Bengal gram diets fortified with lysine and with methionine, cystine, and tryptophan respectively showed various beneficial effects on the changes observed in the brain. A 20% casein diet induced higher body and brain weights and better brain protein and free α‐amino nitrogen concentrations than those observed on a 10% casein diet.
Acetylcholinesterase in Mouse Neuroblastoma Cells: Intracellular and Released Enzyme
Authors: Kimhi Yosef , Mahler Alexandra , Saya Danielle
Published: October 2006

Abstract: Mouse neuroblastoma cells in cultures release acetylcholinesterase into the growth medium. The released enzyme, as well as the intracellular activity, separate on a density gradient into two molecular forms, sedimenting as 4.5S and 10.5S entities. The relative amounts of these forms are different in the two cases: whereas the slower sedimenting form is the major one in the cellular extract, the 10.5S form predominates in the released activity. The cellular and released proteins were labelled by [3H]diisopropylphosphofluoridate and analysed on polyacrylamide‐SDS gels. The results suggest that the intracellular as well as the extracellular molecules are oligomers of similar subunits.
Determination of GAB A Levels by a [3H]Muscimol Radioreceptor Assay
Authors: Bernasconi R. , Bittiger H. , Heid J. , Martin P.
Published: October 2006

Abstract: A [3H]muscimol radioreceptor assay was used to measure the levels of GAB A in mouse brain. The method is based on the competitive inhibition of [3H]muscimol binding to the GABA receptor by GABA extracted from tissue. The specificity and accuracy of the method was established by comparative measurements of GABA levels by gas chromatography. GABA levels obtained by radioreceptor assay (R) and gas chromatography (GC) in different areas of mouse brain were (in μmol/g tissue ± S.E.M.): cerebral cortex 1.41 ± 0.06 (R), 1.50 ± 0.03 (GC); corpus striatum 1.70 ± 0.05 (R), 1.66 ± 0.01 (GC); cerebellum 1.15 ± 0.04 (R), 1.11 ± 0.07 (GC); hippocampus 1.35 ± 0.04 (R), 1.43 ± 0.04 (GC). The sensitivity of the assay was 5 pmol of GABA, which is sufficient to measure GABA levels in brain. The technique described is simple and rapid and it can be used for unpurified tissue extracts.
Sound Stimulates Labeling of Polyphosphoinositides in the Auditory Organ of the Noctuid Moth
Authors: Kilian Patricia L. , Schacht Jochen
Published: October 2006

Abstract: The Noctuid moth possesses a simple auditory structure suitable for the investigation of biochemical correlates of sound stimulation in vivo. Stimulation with pulsed tones increased 32P incorporation into polyphos‐phoinositides but not into ATP or other lipids. The effect was seen in the scoloparium (sensory structure) but hot in the nodular sclerite, an adjacent nonsensory tissue. It was also not seen when the stimulus was a continuous tone, leading to adaptation of the action potential.
Studies of Pargyline‐Monoamine Oxidase Binding Using a Spin Label Probe Analog
Authors: Buckman Trent , Eiduson Samuel
Published: October 2006

Abstract: Analogs of the monoamine oxidase (MAO) inhibitor pargyline with a nitroxide free radical moiety attached through an ether linkage to the para position on the benzene ring have been prepared and reacted with solubilized MAO preparations from rat and beef brain and pig liver. These compounds behave as normal irreversible inhibitors of catalytic activity, with some preference for B‐type enzyme. When the reaction was monitored by electron spin resonance (ESR), line broadening effects indicative of binding and with an apparent relation to substrate specificity of the preparation were observed. In addition, there was a slow decrease in intensity of the ESR spectra, which could be retarded by the addition of other MAO inhibitors or increased O2 and enhanced by flavin reduction. It appears to be related to development of the irreversible phase of MAO inhibition. Signal recovery with added O2 and studies of a model reaction with free flavin, suggest the signal loss to be a line broadening effect due to interaction with an enzyme‐generated paramagnetic species rather than to direct reduction of the nitroxide radical.
Effect of Inhibitors of GABA Transaminase on the Synthesis, Binding, Uptake and Metabolism of GABA
Authors: Löscher W.
Published: October 2006

Abstract: Four catalytic inhibitors of GABA aminotransferase (gabaculine, γ‐acetylenic GABA, γ‐vinyl GABA, ethanolamine O‐sulphate) as well as aminooxyacetic acid and valproate were studied for effects on neurochemical assays for GABA synthesis, receptor binding, uptake and metabolism in mouse and rat brain preparations. Gabaculine did not interfere with GABA synthesis as reflected by the activity of glutamate decarboxylase (GAD), it was only a weak inhibitor (IC50= 0.94 mM) of GABA receptor binding sites but was a moderately potent inhibitor of GABA uptake (IC50= 81 μM) and very potent (IC50= 1.8 μM) with respect to inhibition of the GABA‐metabolizing enzyme GABA aminotransferase (GABA‐T). γ‐Acetylenic GABA was a weak inhibitor of GAD and GABA binding (IC50 > 1 mM), but virtually equipotent to inhibit uptake and metabolism of GABA (IC50 560 and 150 μM, respectively). This was very similar to γ‐vinyl GABA, except that this drug did not decrease GAD activity. Ethanolamine O‐sulphate was found to show virtually no inhibition of GAD and GABA uptake, but was a fairly potent inhibitor of GABA binding (IC50= 67 μM) and in this respect, 500 times more potent than as an inhibitor of GABA‐T. Aminooxyacetic acid was a powerful inhibitor of both GAD and GABA‐T (IC50 14 and 2.7 μM, respectively), but had very little affinity to receptor and uptake sites for GABA. Valproate showed no effects on GABA neurochemical assays which could be related to anticonvulsant action. The present results suggest that the anticonvulsant properties of the four catalytic inhibitors of GABA‐T tested are at least in part mediated through a direct influence on GABA receptors and uptake sites.
The Influence of Hypoxia on the Concentrations of Cyclic Nucleotides in the Rat Brain
Authors: Folbergrová J. , Nilsson B. , Sakabe T. , Siesjö B. K.
Published: October 2006

Abstract: In order to study the influence of hypoxia on cyclic nucleotides in the brain, we reduced arterial Po, for 15–30 min in lightly anaesthetised and artificially ventilated rats to obtain values ranging from about 45 to about 10 mm Hg. In an additional group (arterial Po2 18–22 mm Hg), the tissue hypoxia was aggravated by moderate arterial hypotension (mean arterial blood pressure about 80 mm Hg). In all animals, electrocortical activity was recorded. Cyclic GMP concentrations in cerebral cortex were unchanged in all groups but one. In that group, in which tissue hypoxia was severe enough to induce a suppression‐burst EEG pattern and a measurable reduction in the adenylate energy charge, cyclic GMP concentrations were slightly increased (p < 0.05). Cyclic AMP concentrations remained unaltered at all degrees of hypoxia studied. It is concluded that changes in cyclic nucleotides in brain tissue occur first at such severe degrees of hypoxia of the duration studied that function and metabolism are profoundly altered.
Kinetic Characterization of Ca2+ Transport in Synaptic Membranes
Authors: Javors M. A. , Bowden C. L. , Ross D. H.
Published: October 2006

Abstract: Lysed synaptosomal membranes were prepared from brain cortices of HA/ICR Swiss mice, and the ATP‐stimulated Ca2+ uptake, Ca2+‐stimulated Mg2+ ‐dependent ATPase activity, and the Ca2+‐stimulated acyl phosphorylation of these membranes were studied. The Km values for free calcium concentrations ([Ca2+]f) for these processes were 0.50 μM, 0.40 μM, and 0.31 μM, respectively. Two kinetically distinct binding sites for ATP were observed for the ATP‐stimulated Ca2+ uptake and the Ca2+‐stimulated Mg2+‐ATPase activity. The high‐affinity Km values for ATP for these two processes were 16.3 μM, and 28 μM, respectively. These results indicate that the processes studied operate in similar physiological concentration ranges for the substrates [Ca2+]f and ATP under identical assay conditions and, further, that these processes may be functionally coupled in the membrane.
Brain Regional Distribution of Glutamic Acid Decarboxylase, Choline Acetyltransferase, and Acetylcholinesterase in the Rat: Effects of Chronic Manganese Chloride Administration after Two Years
Authors: Lai James C. K , Leung Thomas K. C , Lim Louis
Published: October 2006

Abstract: Rats were treated chronically with manganese chloride from conception onward for a period of over 2 years in order to study the effects of manganese and aging on the activities of glutamic acid decarboxylase (GAD), choline acetyltransferase (ChAT), and acetylcholinesterase (AChE) in hypothalamus, cerebellum, pons and medulla, striatum, midbrain, and cerebral cortex (which included the hippocampus). Manganese‐treated 2‐month‐old and 24‐ to 28‐month‐old rats and age‐matched controls were studied. In control rats during aging the activities of GAD decreased in hypothalamus (19%), pons and medulla (28%), and midbrain (22%) whereas the activities of AChE decreased in all regions (20–48%), particularly in the striatum (44–48%). Changes in ChAT activities in aging were observed only in one region—a decrease (23%) in the striatum. Life‐long treatment with manganese appeared to abolish partially the decreases in aging in AChE activities in hypothalamus, cerebellum and striatum, and striatal ChAT activity. Manganese treatment also seemed to abolish the age‐related decreases in GAD activities, since GAD activities in various brain regions of manganese‐treated senescent rats were not significantly different from those of control young rats. These results are discussed in relation to other metabolic changes associated with aging and manganese toxicity.
The Interaction of Transport and Metabolism on Brain Glucose Utilization: A Reevaluation of the Lumped Constant
Authors: Crane Paul D , Pardridge William M , Braun Leon D , Nyerges Anthony M , Oldendorf William H
Published: October 2006

Abstract: The relative cerebral cortical metabolism of glucose (GLU) and 2‐deoxy‐D‐glucose (DG) was measured in vivo in control and insulin‐treated hypoglycemic rats. The ratio of the utilization rate constants for the two hexoses, i.e., KDG/KCLU is defined as the Hexose Utilization Index (HUI). The HUI was found to be invariant in rats whose cerebral glucose content exceeded 1 μmo1.g−1 wet weight (HUI = 0.48 ± 0.07). Severe hypoglycemia (plasma glucose <2 mM) effected a shift in the HUI to 1.04 ± 0.21. The results are consistent with a model in which the interpretation of the HUI is determined by the rate of transport into brain, or subsequent phosphorylation, as the rate‐limiting step for hexose utilization.
Changes in Regional Brain Levels of Amino Acid Putative Neurotransmitters After Prolonged Treatment with t he Anticonvulsant Drugs Diphenylhydantoin, Phenobarbitone, Sodium Valproate, Ethosuximide, and Sulthiame in the Rat
Authors: Patsalos P. N. , Lascelles P. T.
Published: October 2006

Abstract: The effect of prolonged treatment (10 days) with the anticonvulsant drugs diphenylhydantoin (DPH), phenobarbitone, sodium valproate, ethosuximide and sulthiame, both singly and in combination, on regional rat brain amino acid neurotransmitter concentrations (GABA, glutamate, aspartate and taurine) were assessed. DPH had a major effect in the cerebellum and hypothalamus in that it significantly reduced cerebellar GABA. taurine and aspartate and hypothalamic GABA and aspartate. Sodium valproate significantly elevated GABA and taurine in most regions. Aspartate and glutamate were less affected. Phenobarbitone significantly elevated GABA concentrations in all brain regions, while taurine concentration was only elevated in the cerebral cortex. Ethosuximide induced changes were small compared to the other anticonvulsants while sulthiame produced complex changes. Anticonvulsant drugs administered in combination resulted in complex changes, suggesting that their mode of action is different.
Alterations in Dihydromorphine Binding in Cerebral Hemispheres of Aged Male Rats
Authors: Messing Rita B. , Vasquez Beatriz J. , Samaniego Bernardo , Jensen Robert A. , Martinez Joe L. , McGaugh James L.
Published: October 2006

Abstract: Equilibrium binding of [3H]dihydromorphine was assayed in brain regions of young and aged male F344 rats. Young rats had significantly higher receptor densities than old rats in the frontal poles, anterior cortex, and striatum. In the frontal poles, the decline in receptor concentration with age was accompanied by a significant increase in the apparent affinity of dihydromorphine for receptors, which may be compensatory for the decrease in Bmax. This pattern of receptor alterations is different than that previously observed in aged female rats. Therefore, processes which underlie synaptic alterations with age may be different in males and females.
Effect of Malnutrition and Subsequent Rehabilitation on the Development of Mouse Brain Myelin
Authors: Yusuf H. K. M. , Haque Z. , Mozaffar Z.
Published: October 2006

Abstract: Malnutrition in mice from birth resulted in myelin of brain having higher than normal molar proportions of cholesterol and phospholipids relative to a molar unit of cerebroside + sulphatide. This was found at all ages between 20 and 60 days, and the molar ratio of these lipids in older animals was comparable to that in the younger controls. The phospholipid and the ganglioside patterns were also immature for age. The phospholipid composition was characterized by lower molar proportions of ethanolamine phosphoglyceride (EPG) and sphingomyelin (SPh) and higher proportion of choline phosphoglyceride (CPG), and the ganglioside pattern was characterized by higher molar proportions of the disialogangliosides GDla and GDlb and markedly lower proportion of the monosialoganglioside GM1. Malnutrition imposed from 30 days of age did not affect the contents of the major lipids (and so their molar ratio), but within the phospholipids there was a small but significant deficit of SPh, which was compensated by a higher content of CPG. The ganglioside pattern was as if the animals were malnourished from birth. Nutritional rehabilitation up to 60 days of age subsequent to malnutrition for the first 30 days fully corrected the ganglioside pattern, but not the molar ratio, of the major lipids (because of persistent deficit in cerebroside + sulphatide) and the composition of the phospholipids (because of small but significant deficit of SPh). The results indicate that malnutrition instituted at any time during the entire programme of myelination can affect one or other aspect of myelin development, and nutritional rehabilitation of animals malnourished in early life cannot fully correct this developmental gap.
In Vitro Synthesis of Human Brain Proteins Including Tubulin and Actin by Purified Postmortem Polysomes
Authors: Marotta Charles A. , Brown Beverly A. , Strocchi Paola , Bird Edward D. , Gilbert Jeffrey M.
Published: October 2006

Abstract: Polysomes were prepared from human brain tissue 2‐6 h postmortem; the polysomes were active in a cell‐free protein synthesis system containing rabbit reticulocyte factors. Protein synthesis was totally dependent upon added MgCl2, ATP, the reticulocyte factor fraction, and the human polysome fraction. Human brain proteins synthesized in the presence of L‐[35S]methionine were analyzed by one‐ and two‐dimensional polyacrylamide gel electrophoresis. Over 250 proteins were synthesized and they extended in size up to 250,000 d; many of the most abundant native human brain proteins were synthesized, including tubulin and actin. It was shown that human brain α and β tubulin and actin isomers synthesized in vitro from human postmortem polysomes have the same apparent molecular weights and isoelectric points as the corresponding proteins synthesized by rat polysomes from fresh cortices. The corresponding tubulin and actin synthesized by human and rat brain polysomes also yield the same radioactive methionine‐containing peptides after digestion with Staphylococcus aureus V8 protease. These analyses indicate that postmortem polysomes contain active messenger RNA which can direct the partial and/or complete synthesis of actin and tubulin subunits and other human brain proteins.
Presence of Kynurenine Hydroxylase in Developing Rat Brain
Authors: Battie Cynthia , Verity M. Anthony
Published: October 2006

Abstract: Kynurenine‐3‐hydroxylase, an enzyme that is part of the degradative pathway for tryptophan, was present in the cerebral cortex of neonatal rats and exhibited a Km, for L‐kynurenine close to that of the liver enzyme. This enzyme was enriched in mitochondrial fractions isolated from cerebral cortices of neonatal rats by Ficoll‐sucrose gradient centrifugation, with some activity also present in synaptosomal fractions probably due to the mitochondrial content of synaptosomes since cytochrome c oxidase, another mitochondrial enzyme, had a similar distribution in the gradient. Kynurenine hydroxylase as well as monoamine oxidase, another mitochondrial enzyme, had increased specific activities in synaptosomal fractions isolated from 14‐day‐old rats compared to fractions from 8‐day‐old rats. Hypothyroidism, induced on the day of birth, resulted in increased activities of kynurenine hydroxylase and monoamine oxidase in synaptosomal fractions isolated from 14‐day‐old rats.
Effects of In Vitro Hypoxia and Lowered pH on Potassium Fluxes and Energy Metabolism in Rat Brain Synaptosomes
Authors: Pastuszko Anna , Wilson David F. , Erecińska Maria , Silver Ian A.
Published: October 2006

Synaptosomes isolated on isosmotic Ficoll density gradients are an effective model for some aspects of neuronal function. They maintain metabolic energy levels ([ATP]/[ADP] [Pi1) and transplasma membrane electrical potentials very similar to those of neurons in the intact brain. The concentration of K+ in the external medium (K+‐sensitive electrode), O2 uptake, and cytochrome c reduction (550 nm minus 540 nm) were simultaneously monitored in synaptosomal suspensions. Oxidative metabolism is the primary source of intrasynaptosomal ATP and at pH 7.4 anaerobiosis results in K+ leakage at 4.5 ± 0.8 nmol/min/mg protein with glucose as substrate and 10.7 T 1.9 nmol/min/mg protein with lactate plus pyruvate (10:1) as substrate. Reintroduction of oxygen initiates complete (ouabain‐sensitive) reuptake of K. at initial rates of 35.4 ± 3.2 nmol/min/mg protein and 18 ± 1.7 nmol K‐/min/mg protein, respectively. The rates of K+ leakage and reuptake fall when the pH is lowered from 7.4 to 6.0 but recover fully if the pH is raised to the original value. The rates of K1 release and uptake decrease when the Na‐ concentration in the medium is decreased and increase when the Ca2‐ concentration is decreased. The intrasynaptosomal [K+] under aerobic conditions was 77.3 ± 3 MM and the calculated K+ diffusion potential was ‐72 mV. Anaerobic incubation of the synaptosomes for up to 20 min and at pH values from 7.4 to 6.0 did not produce irreversible impairment of any of the measured variables. These results suggest that permanent loss of brain function following prolonged hypoxia and ischemia is not due to irreversible damage to the synapses with respect to these parameters but rather to impairment of some other neuronal functions.
An Aminopeptidase from Bovine Brain Which Catalyzes the Hydrolysis of Enkephalin
Authors: Hersh Louis B. , McKelvy Jeffrey F.
Published: October 2006

An aminopeptidase from bovine brain which catalyzes the hydrolysis of the tyrosyl1‐glycine2 bond of methionine5‐enkephalin has been purified to electrophoretic homogeneity. The enzyme also catalyzes the hydrolysis of di‐peptides, tripeptides, and amino acid β‐naphthylamides. The enzyme can be inactivated by dialysis against EDTA, and reconstituted with divalent metal ions. Inhibition of the enzyme is observed in the presence of p‐chloromercuribenzoate and puromycin, the latter compound not being hydro‐lyzed by the enzyme. The enzyme is composed of a single polypeptide chain of molecular weight approx. 100,000. The properties of this enzyme are similar to those reported for other brain aminopeptidases active on enkephalin, although distinct differences are observed.
Glutamate‐Stimulated Phosphorylation of a Specific Protein in P2 Fractions of Rat Cerebral Cortex
Authors: Sieghart Werner
Published: October 2006

Abstract— Incubation of P2 fractions from rat cerebral cortex with 32Pi in the presence of l‐glutamate caused an increased phosphorylation of a protein with apparent molecular weight of 43,000 (P43) as demonstrated by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and autoradiography. This glutamate‐stimulated phosphorylation of P43 was already detectable 10 s after the addition of glutamate and was dependent on the concentration of glutamate in the incubation medium. Other excitatory amino acids such as D‐glutamate, l‐aspartate, d,l‐cysteic acid, l‐cysteinesulfinic acid, and d,l‐α‐aminoadipic acid did not stimulate the phosphorylation of P43. In contrast, α‐ketoglutarate and succinate stimulated the phosphorylation of this protein. Glutamate‐stimulated phosphorylation of P43 seemed not to be mediated by either cAMP or cGMP and was inhibited by the presence of Ca2+ in the incubation medium. Experiments performed with metabolic inhibitors indicated that glutamate‐stimulated protein phosphorylation is localized in mitochondria. This conclusion is supported by the occurrence of glutamate‐stimulated phosphorylation of P43 in mitochondrial fractions from several peripheral tissues. The present results are consistent with the hypothesis that P43 is a component of the pyruvate dehydrogenase complex of mitochondria.
Accumulation of N‐3 Polyunsaturated Fatty Acids by Cultured Human Y79 Retinoblastoma Cells
Authors: Hyman Bradley T. , Spector Arthur A.
Published: October 2006

Abstract: The metabolism of the n‐3 class of polyunsaturated fatty acids, which occur in relatively high quantities in neural tissues, was studied in human Y79 retinoblastoma cells. These cells contained low levels of n‐3 polyunsaturates when grown in culture media supplemented with fetal bovine serum. The cells readily incorporated preformed docosahexaenoic acid (22:6 n‐3) into phospholipids, but human skin fibroblasts did this to a similar extent. When 10 to 30 μmol/ml linolenic acid (18:3 n‐3) was added, the cells also accumulated 22:6 in phospholipids. The capacity to convert appreciable amounts of 18:3 to 22:6 appears to be a unique property of the retinoblastoma cells as compared with other continuously cultured cell lines. More 18:3 than linoleic acid (18:2 n‐6) was incorporated into phospholipids by the retinoblastoma cultures, and 18:3 was channeled to a larger extent into the ethanolamine glycerophospholipid fraction. These findings indicate that retinoblastoma cells handle n‐3 polyunsaturated fatty acids in a manner very similar to neural tissue in vivo. Based on the results obtained with this model system, it appears that three processes may contribute to the accumulation of 22:6 in retina and neural tissue: increased ability to incorporate 18:3, the capacity to convert 18:3 to 22:6, and channeling of 18:3 and its metabolites into ethanolamine glycerophospholipids.
Inhibition of Catecholamine Secretion from Adrenal Medulla Cells by Neurotoxins and Cholinergic Antagonists
Authors: Kilpatrick Daniel L. , Slepetis Ruta , Kirshner Norman
Published: October 2006

Abstract: The effects of several neurotoxins and cholinergic antagonists on the nicotine‐induced secretion of catecholamines by adrenal medulla cells in culture were investigated. Aconitine, veratridine, and batrachotoxin, in the presence of 1 μm‐tetrodotoxin inhibited the nicotine‐stimulated secretion of catecholamines in a dose‐dependent manner in Locke's solution. In Na+‐free sucrose medium, tetrodotoxin was not required to inhibit the stimulatory effects of aconitine, veratridine, and batrachotoxin, and these agents by themselves inhibited the nicotine‐stimulated secretion of catecholamines. Scorpion venom, which also increases the flux of Na+ through tetrodotoxin‐sensitive channels, was not an effective inhibitor of nicotine‐stimulated secretion. Histrionicotoxin, atropine, hexamethonium, and decamethoniun–as well as the Na+‐channel activators–noncompetitively inhibit nicotine‐stimulated secretion. The effects of these agents on nicotine‐stimulated secretion appear similar to their effects on the inhibition of depolarization at the neuromuscular junction. Reversibility studies suggest that the stimulatory and inhibitory sites of the neurotoxins are different, while studies in Na+‐free media suggest that tetrodotoxin‐insensitive sodium channels are not involved in the inhibitory effect of the neurotoxins. A possible site of action for the inhibitory effects of the neurotoxins. A possible site of action for the inhibitory effects of the neurotoxins is the nicotinic‐receptor‐associated ion channel.
Decreases in Amino Acid and Acetylcholine Metabolism During Hypoxia
Authors: Gibson Gary E. , Peterson Christine , Sansone Joseph
Published: October 2006

Abstract: Hypoxia impairs brain function by incompletely defined mechanisms. Mild hypoxia, which impairs memory and judgment, decreases acetylcholine (ACh) synthesis, but not the levels of ATP or the adenylate energy charge. However, the effects of mild hypoxia on the synthesis of the glucosederived amino acids [alanine, aspartate, γ‐amino butyric acid (GABA), glutamate, glutamine, and serine] have not been characterized. Thus, we examined the incorporation of [U‐14C]glucose into these amino acids and ACh during anemic hypoxia (injection of NaNO2), hypoxic hypoxia (15 or 10% O2), and hypoxic hypoxia plus hypercarbia (15 or 10% O2 with 5% CO2). In general, the synthesis of the amino acids and of ACh declined in parallel with each type of hypoxia we studied. For example, anemic hypoxia (75 mg/kg of NaNO2) decreased the incorporation of [U‐14C]glucose into the amino acids and into ACh similarly. [Percent inhibition: ACh (57.4), alanine (34.4), aspartate (49.2), GABA (61.9). glutamine (59.2), glutamate (51.0), and serine (36.7)]. A comparison of several levels (37.5, 75, 150, 225 mg/kg of NaNO2) of anemic hypoxia showed a parallel decrease in the flux of glucose into ACh and into the amino acids whose synthesis depends on mitochondrial oxidation: GABA (r= 0.98), glutamate (r= 0.99), aspartate (r= 0.96), and glutamine (r= 0.97). The synthesis of the amino acids not dependent on mitochondrial oxidation did not correlate as well with changes in ACh metabolism: serine (r= 0.68) and alanine (r= 0.76). The decreases in glucose incorporation into ACh and into the amino acids with hypoxic hypoxia (15% or 10% O2) or hypoxic hypoxia with 5% CO2 were very similar to those with the two lowest levels of anemic hypoxia. Thus, any explanation of the brain's sensitivity to a decrease in oxygen availability must include the alterations in the metabolism of the amino acid neurotransmitters as well as ACh.
Biosynthesis of Galactocerebrosides and Glucocerebrosides in Glial Cell Lines
Authors: Neskovic N. M. , Rebel G. , Harth S. , Mandel P.
Published: October 2006

Abstract: UDP‐galactose:ceramide galactosyltransferase (CGalT, EC 2.4.1.45) and UDP‐glucose:ceramide glucosyltransferase (CGlcT, EC 2.4.1.80) were determined in the glial cell lines G26‐20, G26‐24, C6, and C6TK−. The enzymatic assay for CGalT in cultured glial cells was complicated by a rapid conversion of UDP‐galactose to UDP‐glucose, due to the elevated UDP‐galactose‐4′‐epi‐merase activity in certain glial cell clones. It seems that mechanisms regulating UDP‐galactose‐4′‐epimerase activity and levels of UDP sugars in the glial cell lines differ from those in brain tissue. Compared with the maximum activity of CGalT in the myelinating rat brain, the enzyme activities in the oligodendroglioma clonal cell lines G26–20 and G26–24 were 16–30 times lower. On the other hand, CGalT levels in G26‐20 and G26‐24 cells were comparable to the values found in young rat brain before myelination starts. No CGalT activity could be detected in C6 or C6TK− cells by the method used in this study, whereas CGlcT activity was found in all glial cell lines tested and its levels were close to the values observed in the young rat brain.
Specificity of Endogenous Substrates for Types A and B Monoamine Oxidase in Rat Striatum
Authors: Schoepp Darryle D. , Azzaro Albert J.
Published: October 2006

Abstract: Studies were designed to evaluate specificity of the transmitter amines serotonin (5‐hydroxytryptamine, 5‐HT) and dopamine (DA), as well as the trace amines p‐tyramine (p‐TA) and β‐phenylethylamine (PEA) for types A and B monoamine oxidase (MAO) in rat striatum. 5‐HT was found to be a specific substrate for the type A enzyme. However, the specificity of PEA for the type B enzyme was found to be concentration‐dependent. When low concentrations of PEA and 5‐HT were used to measure type B and type A activities, respectively, both clorgyline and deprenyl were highly selective for the sensitive form of MAO in vivo. However, as the concentration of PEA was increased, the type B inhibitor deprenyl became less effective in preventing deamination of PEA. Conversely, the type A inhibitor clorgyline became more effective in this regard. Kinetic analysis following selective in vivo inhibition showed PEA deamination by both forms of MAO with a 13‐fold greater affinity for the type B enzyme. In vivo dose‐response curves obtained with the common substrates DA and p‐TA showed approximately 20% deamination by the B enzyme. Kinetic values for DA and p‐TA deamination in in vivo‐treated tissue possessing only type A or type B MAO activity, revealed a 2.5‐fold greater affinity for the type A enzyme. These studies show the importance of concentration on substrate specificity in striatal tissue. The results obtained characterize the common substrate properties of DA and p‐TA as well as of PEA in rat striatum. In addition, the presence of regional specificity for 5‐HT deamination by only type A MAO is demonstrated.
Ouabain‐Sensitive and Ouabain‐Resistant Net Uptake of Potassium into Astrocytes and Neurons in Primary Cultures
Authors: Walz Wolfgang , Hertz Leif
Published: October 2006

Abstract: Inhibition of net uptake of 42K by different concentrations of ouabain was studied in primary cultures of astrocytes and in primary cultures of neurons in order to investigate whether there is a pronounced difference between ouabain sensitivity in the two cell types and to determine the genuine magnitudes of the ouabain‐sensitive and the ouabain‐resistant potassium uptakes. In morphologically differentiated astrocytes, obtained after treatment with dibutyryl cyclic AMP (dBcAMP), the sensitivity to ouabain was slightly lower than in neurons, but astrocytes which had not been treated with dBcAMP showed sensitivity similar to the neurons (which likewise were not treated). In the presence of elevated potassium concentrations (12 and 24 mM) ouabain sensitivity was decreased, although only by a factor of 2–3. Accordingly, maximum inhibition of the uptake required under all conditions studied, at most, 1.0 mM ouabain. Like total uptake, this ouabain‐sensitive uptake was several times less intense in neurons than in astrocytes, where it reached its maximum value at an external potassium concentration of 12 mM. Subtraction of the ouabain‐sensitive uptake from the total uptake revealed a considerable ouabain‐resistant uptake. This ouabain‐resistant uptake was studied in detail in the astrocytes, where it was found to increase with increasing potassium concentration over the whole concentration range 3–24 mM and to exceed substantially the maximum amount that can be accumulated by diffusion.
Distribution of myo‐Inositol in the Cat Cochlear Nucleus
Authors: Godfrey Donald A. , Hallcher Loretta M. , Laird Michael H. , Matschinsky Franz M. , Sherman William R.
Published: October 2006

Abstract: The distribution of myo‐inositol, a substance that has been implicated in synaptic transmission, has been mapped within sections of the cat cochlear nucleus as well as some nearby regions. Highest values in the cochlear nucleus were found in regions of granule cells along the periphery of the anteroventral subdivision of the nucleus. Highest values overall were found in the molecular layer of the cerebellar flocculus. A fairly good correlation was found between myo‐inositol levels and activities of the enzymes of acetyl‐choline metabolism in the cat cochlear nucleus, supporting the possibility that myo‐inositol may be involved in cholinergic synaptic transmission. No positive correlation was found between myo‐inositol levels and the levels of glutamate, aspartate, glycine, or γ‐aminobutyric acid (GABA). The most striking gradient of myo‐inositol levels within a region was found in the auditory nerve, where different myo‐inositol levels might be related to nerve fibers innervating different parts of the cochlea. The distribution of scyllo‐inositol, a stereoisomer of myo‐inositol, was also examined, and found to parallel closely the distribution of myo‐inositol, with levels 4–5% as high.
Monoamine Oxidase Activity of Mitochondria Prepared from Rat Liver and Rat Heart
Authors: Harris E. J. , Cooper M. B.
Published: October 2006

Abstract: The effect of agents that change the respiratory state of the mitochondrion on tyramine oxidation was investigated. Neither uncoupler nor ADP and Pt in the presence of substrate produced any change in the rate of tyramine oxidation, as judged by direct measurement of tyramine oxidation or by H2O2 production. We conclude that previously reported depression of monoamine oxidase activity by stimulated respiration was due to oxygen depletion.
Effect of Motor and Premotor Cortex Ablation on Concentrations of Amino Acids, Monoamines, and Acetylcholine and on the Ultrastructure in Rat Striatum. A Confirmation of Glutamate as the Specific Cortico‐Striatal Transmitter
Authors: Hassler R. , Haug P. , Nitsch C. , Kim J. S. , Paik K.
Published: October 2006

Abstract: At 1, 2, and 4 weeks after unilateral premotor and motor cortex ablation in rats, a significant and lasting decrease in glutamate levels in the ipsilateral versus contralateral striatum was observed. A significant corresponding fall in aspartate was seen only after 1 week. In contrast, there was a large increase in the striatal concentrations of lysine, threonine, alanine, and glutamine 1 week after the cortical ablation. This correlates with the extensive glial proliferation in the deafferented ipsilateral striatum. Four weeks after cortical ablation the GABA concentration was significantly increased. There was no decrease in other putative transmitters (dopamine, serotonin, acetyl‐choline, glycine and taurine), nor was a glutamate decrease observed in the hippocampus or in the hypothalamus, which do not receive direct premotor and motor cortical inputs. Both biochemical and morphological evidence for a minor contralateral cortico‐striatal projection was obtained. Correlating with the fall in glutamate, ultrastructural observations indicated the degeneration of two types of striatal synapses, i.e., those of the axo‐spinous type III and of the axo‐dendritic type VII. Frontal cortex ablation clearly affects, in opposite directions, the metabolism of various striatal amino acids but not that of acetylcholine and the monoamine transmitters. The results strongly support the view that glutamate is the transmitter of the cortico‐striatal fibers.
Studies on the Pyruvate Dehydrogenase Complex in Brain with the Arylamine Acetyltransferase‐Coupled Assay
Authors: Ksiezak‐Reding Hanna , Blass John P. , Gibson Gary E.
Published: October 2006

Abstract: A spectrophotometric assay for the brain pyruvate dehydrogenase complex (PDHC) with arylamine acetyltransferase (ArAT; EC 2.3.1.5) to follow the production of acetyl‐CoA has been standardized. Activity was proportional to time and protein. It depended completely on added pyruvate, CoA, NAD, and MgCI2, and partially on thiamine pyrophosphate, Triton X‐100, and a sulfhydryl compound. The activities are the highest in the literature for brain PDHC (50 nmol/min/mg protein) and equal the maximum recorded rates of pyruvate flux for brain in vivo. Activities as low as 0.6 nmol/min could be measured. Use of ArAT of different purities (1–2‐fold and 11–%‐fold) allowed convenient measurement of total PDHC (ArAT‐I) and of the active form of PDHC (ArAT‐II). The proportion of PDHC in the active form was 50% in mouse brain, 30% in rat brain, and 10% in mouse liver. Total PDHC activity was unchanged postmortem during storage of mouse brain in situ at +4°C or at ‐20°C for 3 days or at +20°C for 24 h. The relative specific activity of PDHC in cytoplasmic or synaptoplasmic fractions was less than that of two other mitochondrial enzymes, fumarase (EC 4.2.1.2) and monoamine oxidase (EC 1.4.3.4), which argues strongly against the hypothesis of a cytoplasmic PDHC in cholinergic nerve endings.
Species Differences in the Brain Regional Distribution of Receptor Binding for Thyrotropin‐Releasing Hormone
Authors: Taylor Richard L. , Burt David R.
Published: October 2006

Abstract: A survey of the regional distribution of binding of 1 nM [3H](3‐MeHis2)thyrotropin‐releasing hormone ([3H]MeTRH) to TRH receptors in the brains of eight mammalian species revealed major species differences in both the absolute and relative values of TRH receptor binding in different brain regions. Several brain regions exhibited binding equal to or exceeding that in the anterior pituitary gland of the same species, including the amygdaia in the guinea pig and rat, the hypothalamus in the guinea pig, the nucleus accumbens in the rabbit, and all these and other regions in the cat and dog, for which pituitary binding was exceptionally low. Species could be divided into two groups according to which brain region appeared highest in binding: rabbits, sheep, and cattle had highest binding in the nucleus accumbens/septal area, whereas guinea pigs, rats, dogs, cats, and pigs had highest binding in the amygdala/temporal cortex area. The nucleus accumbens consistently exceeded the caudate‐putamen in receptor binding. For most brain regions, rabbits, rodents, and sheep tended to be higher than carnivores, cattle, or pigs. Further regions that exhibited appreciable binding in most species included the olfactory bulb and tubercle, hippocampus, and various cortical and brain stem areas. In fact, essentially all brain regions appeared to have detectable levels of TRH receptors in at least some species, but no rat peripheral tissues have yet shown detectable receptor binding. The species differences appeared to reflect largely if not entirely differences in receptor density, although this was not tested in every species.
Cortical Substance P‐Like Immunoreactivity in Cases of Alzheimer's Disease and Senile Dementia of the Alzheimer Type
Authors: Crystal Howard A. , Davies Peter
Published: October 2006

Abstract: The concentration of substance P‐like immunoreactive material (SPLI) and somatostatin‐like immunoreactive material (SLI) and the activity of acetyl‐CoA: choline‐O‐acetyltransferase (ChAT; EC 2.3.1.6.) were measured in eight brain regions of 13 normal patients and 12 patients with Alzheimer disease/senile dementia of the Alzheimer type (AD/SDAT). SPLI was significantly lower in five of eight regions in the patients with AD/SDAT. Younger patients with AD/SDAT had significantly lower SLI in the parietal cortex than older patients. ChAT activity and SPLI in the parietal cortex of the presenile patients with ADISDAT were not significantly different from values found in older patients.
The Kinetics of Acetylcholine Turnover in a Resting Cholinergic Nerve Terminal and the Magnitude of the Cytoplasmic Compartment
Authors: Weiler M. , Roed I. S. , Whittaker V. P.
Published: October 2006

Abstract: The magnitude of the cytosolic pool of acetylcholine in the cholinergic electromotor nerve terminals of Torpedo marmorata has been calculated to be 22 ± 3% of the total by comparing the isotopic ratio of acetylcholine with that of choline when slices of electric organ were incubated with 10 μM deuterated choline. The calculation is based on a two‐compartment model that assumes the presence, in unstimulated tissue, of a vesicular pool of acetylcholine that does not exchange, under resting conditions, with a second cytosolic pool; the latter, by contrast, is subject to ‘futile recycling’ and comes into isotopic equilibrium with the tissue choline pool.
Antibodies to Gangliosides and Myelin Autoantigens Are Produced in Mice Following Sciatic Nerve Injury
Authors: Schwartz Michal , Sela Ben Ami , Eshhar Nomi
Published: October 2006

Abstract: Autoimmune response following peripheral nerve injury in mice was investigated in the present work. Antibodies specific to gangliosides and myelin proteinaceous constituents are produced in mice following sciatic nerve cut. Results are discussed with regard to the possible relevance of the immunological response to nerve regeneration.
Effects of N‐Acetyl Aspartate, Aspartate, and Glutamate on cAMP and cGMP Levels in Developing Rat Cerebral Cortex
Authors: Burgal M. , Jordá A. , Grisolía S.
Published: October 2006

Abstract: N‐Acetyl‐aspartate (N‐Ac‐Asp) incubated with minced cerebral cortex caused a dose‐dependent increase in the levels of cAMP and cGMP. This effect was followed during postnatal development. N‐Ac‐Asp elicits the greatest increase in cAMP in 5‐day‐old and in cGMP in 40‐day‐old rats. The levels of cyclic AMP were always higher than those of cGMP. We also studied the effects of L‐aspartate (Asp) and L‐glutamate (Glu) on the levels of cyclic nucleotides in the cerebral cortex minces of rats of different ages, and observed that both amino acids produced the maximum increase in cAMP at 10 days, whereas in the case of cGMP the maximal effect of Asp occurs earlier than 20 days and of Glu after 40 days. In the adult rat, the N‐Ac‐Asp effect on cAMP was greater than that produced by either Asp or Glu, whereas the levels of cGMP were similarly affected by all three. The data show a peak response of cAMP and cGMP to N‐Ac‐Asp, Asp, and Glu during cortical maturation. Because this response varies with postnatal time, N‐Ac‐Asp, Asp, and Glu may act upon different receptor sites.
[3H]Imipramine Is Accumulated but Not Released from Slices of the Rabbit Caudate and Hypothalamus
Authors: Langer S. Z. , Galzin A. M. , Kamal L. A.
Published: October 2006

Abstract: Slices of rabbit caudate and hypothalamus take up and accumulate [3H]imipramine. In superfused slices of both structures electrical stimulation or exposure to tyramine failed to release recently taken up [3H]imipramine. De‐polarization by exposure to 30–60 mm‐potassium caused only a small release of [3H]imipramine that was not concentration‐dependent. The release of [3H]imipramine by high potassium was independent of the presence of calcium ions in the superfusion medium. These results contrasted with those obtained for the release of [3H]dopamine from the caudate and [3H]noradrenaline from the hypothalamus, where tyramine, electrical stimulation, and high potassium caused a significant release of the labeled neurotransmitters. The release of [3H]dopamine from the caudate and [3H]noradrenaline from the hypothalamus elicited by electrical stimulation or high potassium was entirely calcium‐dependent. It is concluded that [3H]imipramine is taken up into the two brain regions and is accumulated in a nonvesicular site from which it is not released by calcium‐dependent depolarizing stimuli.
Succinate Dehydrogenase, Monoamine Oxidase and Glutamine Synthetase in Developing Human Foetal Brain Regions
Authors: Mahajan R. G. , Mandal S. , Sinha A. K. , Mukherjee K. L.
Published: October 2006

Abstract: In human foetal brain ontogeny the cerebral activity of succinate oxidoreductase (EC 1.3.99.1), i.e. succinate dehydrogenase (SDH), is higher than the cerebellar activity. With rise in foetal body weight the activity in all the brain regions gradually declines. SDH in all the brain regions shows two high‐activity periods, one at 20–35 g and another at 110–220 g body weight. The enzyme exhibits a craniocaudal pattern of development. At all times of gestation, l‐glutamate:ammonia ligase (EC 6.3.1.2), i.e. glutamine synthetase, activity in the spinal cord and medulla is higher than in the other three regions. At 190 g body weight glutamine synthetase shows an activity peak in all brain regions. Monoamine:oxygen oxidoreductase (EC 1.4.3.4), i.e. monoamine oxidase (MAO), is present much before the onset of electrical activity. It develops caudocranially and exhibits a biphasic pattern of development in all the regions. It increases considerably in the medulla and the spinal cord towards late gestational periods.
Neural Regulation of Muscle Glucose 6‐Phosphate Dehydrogenase: Effect of Batrachotoxin and Tetrodotoxin
Authors: Max Stephen R. , Deshpande Sharad S. , Albuquerque Edson X.
Published: October 2006

Abstract: We tested the hypothesis that glucose 6‐phosphate dehydrogenase (G6PD) activity in the rat skeletal muscle is regulated by putative axonally derived neurotrophic factors. This was accomplished by comparing the effects of nerve section and subperineural injection of batrachotoxin (BTX) or tetrodotoxin (TTX) on G6PD in rat extensor digitorum longus (EDL) muscle. BTX, an agent known to block nerve impulse conduction and axonal transport, increased G6PD activity to 155% and 163% of control by days 2 and 4 after injection. Denervation of the EDL muscle by section of the peroneal nerve 10–20 mm from its entrance to the muscle caused G6PD activity to increase to 170% of control by day 1 and to 200% and 180% of control by days 2 and 4, respectively. The increase in enzyme activity after denervation and after subperineural injection of BTX was due in part to muscle inactivity resulting from blockade of nerve impulses. This conclusion is based upon the observation that subperineural injection of TTX at an identical site in the peroneal nerve caused a small but significant (30%) increase in G6PD activity after 4 days. Choline acetyltransferase (CAT) activity was assessed as a measure of the efficacy of blockade of slow axonal transport. Decreases in CAT activity following denervation or injection of BTX or TTX were parallel to increases in G6PD activity observed under these conditions. These results argue for a role of axonal transport in neural regulation of muscle G6PD, with a small contribution by neuromuscular activity.