bluuebunny/crossref_metadata_2025_split huggingface dataset:
MOLECULAR CHARACTERIZATION OF CHOLINE ACETYLTRANSFERASE FROM BOVINE BRAIN CAUDATE NUCLEUS AND SOME IMMUNOLOGICAL PROPERTIES OF THE HIGHLY PURIFIED ENZYME
Authors: Malthe‐Sosrenssen D. , Lea T. , Fonnum F. , Eskeland T. 
Published: October 2006

Abstract—Choline acetyltransferase from bovine brain caudate nucleus has been purified to a specific activity of 25–30 μmol ACh formed per min and mg protein. Disc electrophoresis at pH 9.5 of the purified enzyme showed two protein bands localized close to each other. We were not able to show if ChAT was linked to one or both bands. In SDS disc electrophoresis the enzyme preparation showed one major and one minor protein band with molecular weights of 69,000 and 34,000, respectively. Heterogeneity of the enzyme preparation was also demonstrated by immunodiffusion and immunoelectrophoresis. After ammonium sulphate precipitation no aggregation of the enzyme could be detected by gelfiltration on Ultrogel AC‐34 whilst a high molecular weight fraction was occasionally observed by gelfiltration on Sephadex G‐200. The enzyme was, however, separated into two molecular forms (A and B) on CM‐Sephadex chromatography. Both molecular forms had the same S220w but differed in heat stability and affinity for acetyl‐CoA. Both forms were inactivated by an antibody preparation raised against either a purified preparation of ChAT, or A and B separately. The highly purified enzyme preparation was inactivated more than 98% by immunoprecipitation. The antibody crossreacted with ChATs from several mammalian species, but only slightly with ChAT from pigeon. The results of binding studies with affinity columns, suggest that the enzyme contains a hydrophobic lobe and a dinucleotide fold, and that a free purine rather than a free ribosyl ring of acetyl‐CoA is important for the binding of the substrate to the active site. The hydrophobic lobe may be the same as the dinucleotide fold.
REGIONAL AND SUBCELLULAR DISTRIBUTION OF HOMOCARNOSINE–CARNOSINE SYNTHETASE IN THE CENTRAL NERVOUS SYSTEM OF RATS
Authors: Ng R. H. , Marshall F. D. 
Published: October 2006

Abstract—Homocarnosine–carnosine synthetase and carnosinase were assayed in homogenates, 100,000 g supernatants, and ammonium sulfate fractions of the supernatants from nine regions of the central nervous system (CNS), as well as subcellular fractions of whole brains. The enzymes were detected in all CNS regions tested, with olfactory bulbs having the highest activities of both enzymes. In the subcellular fractions, the synthetase was found mainly in the cell‐sap; carnosinase was detected in all fractions, the highest activity being in the mitochondria. The synthetases from olfactory bulbs, cerebellum and spinal cord have similar Km's for β‐alanine and GABA.
DEVELOPMENTAL CHANGES OF ENZYMES ASSOCIATED WITH ENERGY METABOLISM AND THE SYNTHESIS OF SOME NEUROTRANSMITTERS IN DISCRETE AREAS OF HUMAN NEOCORTEX
Authors: Diebler M. F. , Farkas‐Bargeton E. , Wehrlé R. 
Published: October 2006

Abstract—Developmental changes in pyruvate kinase (PK), lactate dehydrogenase (LDH), α‐glycerophosphate dehydrogenase (α‐GPD), glucose‐6‐phosphate dehydrogenase (G6P), succinate dehydrogenase (SDH), glutamate dehydrogenase (GDH), choline acetyltransferase (CAT), glutamate decarboxylase (GAD), activities were measured in early autopsy material in the following areas of human neocortex: area 4 (motor cortex), area 17 (visual cortex), area 40 (gyrus supramarginalis, associative cortex). Changes with age were analysed from 8 fetal weeks to adult age. The important points emerging from this study are: 1. Enzymes associated with glycolytic pathways show a high activity in early fetal period, decline through to the end of the active phase of neurogenesis and then, rise continuously to the end of the first year of life. 2. G6P, an enzyme associated with the oxidative segment of the pentose phosphate pathway, shows a high activity at 8 fetal weeks and, gradually declines through to the end of the active phase of neurogenesis; it then either does not change significantly (motor cortex) or increases slightly. 3. Enzymes related to the tricarboxylic pathway have a low level of activity throughout the first half of gestation, and then rise markedly during the last fetal months and the first year after birth. SDH increase is of much higher magnitude (× 10) than that observed for glycolytic enzymes (×4). For the enzymes of oxidative metabolism, motor cortex is the most advanced area, while associative cortex matures more slowly. 4. CAT activity at 8 fetal weeks is high in visual cortex and declines to the fifth month. After that time, there is a continuous rise until the age of 11 years. Although the time pattern in reaching the adult value is different in motor and associative cortex, there exists a continuous increase from fetal onset to adult level in both areas. Developmental changes in GAD activity are very unusual. The development of activity lags behind that of CAT and commences after birth. After a steady rise in the first year of life, the activity decreases after this age.
PROPERTIES OF A PUTATIVE MUSCARINIC CHOLTNERGIC RECEPTOR FROM DROSOPHILA MELANOGASTER
Authors: Haim N. , Nahum S. , Dudai Y. 
Published: October 2006

Abstract—The powerful muscarinic antagonist [3H]quinuclidinyl benzilate (QNB) specifically binds to homogenates of Drosophila melanogaster head at a level of 65 ± 6 fmol/mg protein, with an apparent dissociation constant of 0.15–0.7 nM. The half‐life of the ligand‐receptor complex at 25°C is 30–40 min. Binding is inhibited by low concentrations of muscarinic ligands but not by low concentrations of nicotinic ligands, anticholinesterases or non‐cholinergic drugs. Binding‐sites are membrane bound and are inactivated by trypsin and by Triton X‐100. Part of the activity (<20%) is released into a high speed supernatant by 2 M‐NaCI. The gene coding for the putative muscarinic receptor in Drosophila is apparently not located adjacent to the gene for acetylcholinesterase
PARTIAL PURIFICATION OF DROSOPHILA GLUTAMATE DECARBOXYLASE1
Authors: Chude Obi , Roberts Eugene , Wu Jang‐Yen 
Published: October 2006

Abstract— A 600‐fold purification of l‐glutamatc decarboxylasc from Drosophila melanogaster Oregon R Wild Type has been achieved. The purification procedures involve the initial homogenization of whole flies in dilute potassium phosphate buffer containing dithiothreitol and phenylmethyl sulfonyl fluoride as protectors, followed by a series of column chromatography with hydroxylapatite, Sephadex G‐150 and DEAE‐Sephadex. The purified enzyme has an apparent Km of 11 mm for l‐glutamate and requires a 40mm‐K+ for maximum activity.The purified enzyme shows only 1 pH optimum around pH 7.5, while crude preparations of the inset display 2 pH optima, pH 4.8–5.2. and 7.5. The significance and possible application of this study are also discussed.
EFFECT OF CONCUSSIVE HEAD INJURY ON CENTRAL CATECHOLAMINE LEVELS AND SYNTHESIS RATES IN RAT BRAIN REGIONS 1
Authors: Huger F. , Patrick G. 
Published: October 2006

Abstract—Unanesthetized male Sprague‐Dawley rats were subjected to head injury using a unique acceleration‐deceleration model designed to mimic the most prevalent form of clinical head injury. Endogenous tyrosine, dopamine and norepinephrine were determined fluorometrically and catecholamine synthesis rates were determined by a radioisotopic method. These values were determined in four brain regions: cortex‐striatum, midbrain‐hypothalamus, medulla‐pons, and cerebellum, and were performed at 5 min, 15 min, 1 h, and 2h post‐trauma. Dopamine levels were elevated in the medulla pons region at 5 min after trauma and in the midbrain‐hypothalamus at the 15 min and 1 h time periods. This increase in dopamine levels may reflect disruption of dopamine beta hydroxylase activity. Norepinephrine synthesis rate in the cerebellum was elevated at 2 h after trauma. Changes in the other parameters were observed but appeared to be related to stress, and the effect of stress in this model is discussed.
ACTH‐SENSITIVE PROTEIN KINASE FROM RAT BRAIN MEMBRANES
Authors: Zwiers H. , Tonnaer J. , Wiegant V. M. , ScHotman P. , Gispen W. H. 
Published: October 2006

Abstract—The protein kinase which in rat brain synaptosomal plasma membranes is responsible for the phosphorylation of a protein band B‐50 (MW 48, 000) was inhibited by the behaviorally active peptide ACTH1–24 and not stimulated by cAMP. Treatment with 0.5% Triton X‐100 in 75 mM‐KCl solubilized 15% of the total B‐50 protein kinase activity and preserved the sensitivity of the enzyme to ACTH1–24. The rate of endogenous phosphorylation of protein band B‐50 was different in intact SPM, solubilized fraction and residue. cAMP stimulated the endogenous phosphorylation of the solubilized fraction in a rather general manner. The solubilized membrane material also phosphorylated B‐50 proteins which were previously extracted from membranes. Column chromatography of the solubilized material over DEAE‐cellulose pointed to the presence of multiple protein kinase activities from rat brain synaptosomal plasma membranes, one of which was the ACTH‐sensitive B‐50 protein kinase.
Isolation and Characterization of Brain Endothelial Cells: Morphology and Enzyme Activity
Authors: Williams Stuart K. , Gillis John F. , Matthews† Maureen A. , Wagnert Roger C. , Bitensky Mark W. 
Published: October 2006

AbstractMicrovessels were isolated from rat brain using a double collagenase treatment which removed the endothelial basement membranes. The isolate was characterized by intact luminal and abluminal membranes and an absence of pericytes and astrocyte membranes. Minimal contamination by 5′‐nucleotidase, an enzyme believed exclusively localized within the plasma membranes of neuroglia, established the purity of the isolated microvessels. Enrichment of alkaline phosphatase and ‐γ‐glutamyl transpeptidase activity in microvessel preparations supports the endothelial localization of these enzymes.
Uptake of l‐[35S]Cystine by Isolated Rat Brain Capillaries
Authors: Hwang Shing Mei , Weiss Steven , Segal Stanton 
Published: October 2006

AbstractAdult rat brain capillaries were isolated by a simplified procedure and showed an enrichment of the marker enzyme, γ‐glutamyltranspeptidase. The uptake of [35S]cystine at 37°C by this preparation can be divided into two components, a sodium‐ and energy‐dependent transport process for the free amino acid pool, with an apparent Km of 36 μm, and a binding process, with an apparent Km of 1.13 mm. Chemical analysis of the amino acid pool indicates that cystine is the major form of intracapillary 35S. Cystine transport was not inhibited by lysine, but glycine, α‐methylaminoisobutyric acid and β‐2‐aminobicyclo‐[2,2,1]‐heptane‐2‐carboxylic acid were inhibitory to a small extent.
Transient Formation of Superoxide Radicals in Polyunsaturated Fatty Acid‐Induced Brain Swelling
Authors: Chan Pak Hoo , Fishman Robert A. 
Published: October 2006

Abstract:The involvement of superoxide free radicals and lipid peroxidation in brain swelling induced by free fatty acids has been studied in brain slices and homogenates. The polyunsaturated fatty acids linoleic acid (18:2), linolenic acid (18:3), arachidonic acid (20:4), and docosahexaenoic acid (22:6) caused brain swelling concomitant with increases in superoxide and membrane lipid peroxidation. Palmitic acid (16:0) and oleic acid (18:1) had no such effect. Furthermore, superoxide formation was stimulated by NADPH and scavenged by the addition of exogenous superoxide dismutase in cortical slice homogenates. These in vitro data support the hypothesis that both superoxide radicals and lipid peroxidation are involved in the mechanism of polyunsaturated fatty acid‐induced brain edema.
Regional Distribution of Glutathione Peroxidase in the Adult Rat Brain
Authors: Brannan Timothy S. , Maker Howard S. , Weiss Cipora , Cohen Gerald 
Published: October 2006

Abstract:Glutathione peroxidase activity was measured in 10 areas of perfused adult rat brain with the use of a fluorometric assay coupled to NADPH oxidation. The caudate‐putamen and the substantia nigra had the highest activities. Cortical areas and several nuclear areas had somewhat lower activity. Activity was lowest in a white matter structure (corpus callosum). High activity of glutathione peroxidase may be related to the need to reduce hydrogen peroxide arising in the course of monoamine metabolism.
A Sensitive Radiometric Assay for Ornithine Aminotransferase: Regional and Subcellular Distributions in Rat Brain
Authors: Wong P. T.‐H. , McGeer E. G. , McGeer P. L. 
Published: October 2006

Abstract: A radiometric assay for ornithine aminotransferase was developed using [1‐14C]α‐ketoglutarate as the labeled substrate and glutamate decarboxylation as a linking step. This assay gives near total measurement of ornithine aminotransferase activities that are, respectively, about 1.5 and 10 times larger than those obtained by the spectrophotometric assay and the radiometric assay using [1‐14C]ornithine. It is also the most sensitive of the three assay procedures.Consistent with previous reports, brain ornithine aminotransferase was found to be present predominantly in synaptosomes. Regional distribution of the enzyme correlated with that of the high‐affinity uptake of glutamate, but not with the distribution of glutamate decarboxylase. Ornithine aminotransferase may be responsible for the synthesis of glutamate in glutamatergic neurons but it is clearly not localized exclusively in such neurons.
Serotonin‐Elicited Amplification of Adenylate Cyclase Activity in Hippocampal Membranes from Adult Rat
Authors: Barbaccia M. L. , Brunelle N. , Chuang D.‐M. , Costa E. 
Published: October 2006

Abstract:The activity of the adenylate cyclase located in membranes prepared from hippocampus of adult rat can be stimulated by serotonin (5‐HT) (Ka= 4 x 10‐7M). The maximal effect is obtained with 10 μM 5‐HT. Freezing of the tissue decreases the 5‐HT stimulation; this stimulation is optimal in the presence of 82.5 mM Tris‐maleate buffer (pH 7.4) and 50 μM GTP. The adenylate cyclase activity of membranes prepared from cortex, hypothalamus, and colliculi of adult rats is not significantly stimulated by 5‐HT. Dopamine (DA) also stimulates adenylate cyclase located in hippocampal membranes; its effect can be blocked by haloperidol (10‐6 M), which fails to inhibit 5‐HT stimulation. Moreover, p‐chlorophenylalanine treatment for 2 weeks or selective lesion of 5‐HT axons afferent to the hippocampus increases the Vmax of 5‐HT stimulation, but fails to change that of DA stimulation. The 5‐HT stimulation can be inhibited by metergoline, spiroperidol, and pizotyline (10‐6 M), but not by the same concentrations of mianserin, ketanserine, alprenolol, phenoxybenzamine, and mepyramine. The 5‐HT stimulation of adenylate cyclase of hippocampal membranes can be mimicked by tryptamine, 5‐methoxytryptamine, bufotenine, and to a lesser extent by LSD; N‐methyltryptamine, N‐methyltryptophan, and 5‐hydroxytryptophan are inactive. Studies with kainic acid suggest that the 5‐HT recognition site (5‐HT1) linked to adenylate cyclase is located on the membrane of intrinsic hippocampal neurons.
Distribution of Glucose‐ 1,6‐Bisphosphate and IMP‐Activated Glucose Bisphosphatase in Brain and Retina
Authors: Yip Vera , Carter Joyce G. , Dick Evan , Rose Zelda B. , Lowry Oliver H. 
Published: October 2006

Abstract:The activity of glucose‐1,6‐bisphosphatase and the level of its substrate were measured in 16 gray areas and four fiber areas of mouse brain and 10 layers or sublayers of monkey retina. Because of the low activity of the enzyme and the small sample sizes, it was necessary to develop a method with two different amplification steps (overall amplification about 106). The enzyme ranged in activity 100‐fold from a low in monkey retina photoreceptor cells to a high in the pyramidal layer of the hippocampus. However, in gray areas of the brain proper the range was only about fourfold. This, together with its requirement for IMP, suggests that the enzyme has a widespread metabolic function related to states of increased neuronal activity. Glucose‐1,6‐bisphosphate levels varied from 80 to 960 μmol/kg dry weight in different areas of mouse brain and from 44 to 200 μmol/kg dry weight in different layers of monkey retina. In general, the glucose bisphosphate levels correlated positively with the bisphosphatase activities; however, the three areas with the highest enzyme concentrations did not fit this pattern.
m‐Octopamine: Normal Occurrence with p‐Octopamine in Mammalian Sympathetic Nerves
Authors: Ibrahim K. E. , Couch M. W. , Williams C. M. , Fregly M. J. , Midgley J. M. 
Published: October 2006

Abstract:The development of a radiochemical enzyme assay for p‐octopamine in 1969 led to its identification in a large number of invertebrate nerve systems and in mammalian sympathetic nerves. The original method by which p‐octopamine was measured has now been found to be nonspecific; however, modifications of this procedure can determine both m‐ and p‐octopamine. We recently developed a new specific method for the unequivocal identification and quantitative determination in tissue of the six octopamine and synephrine isomers. With this method—negative chemical ionization gas chromatography‐mass spectrometry—the more physiologically active m‐octopamine has been found in association with p‐octopamine in 10 organs of the rat. m‐Octopamine is present in concentrations equal to those of p‐octopamine in heart, spleen, and liver and in concentrations from 30 to 60% of p‐octopamine in adrenals, vas deferens, brain, kidney, large intestine, bladder, and lungs. In vivo inhibition of monoamine oxidase markedly increased the concentrations of both m‐ and p‐octopamine in all organs examined. Both amines were virtually absent from all organs except the adrenals following chemical sympathectomy with 6‐hydroxydopamine, thereby establishing that m‐ and p‐octopamine are localized within sympathetic nerve endings.
Brain α‐Ketoglutarate Dehydrogenase Complex: Kinetic Properties, Regional Distribution, and Effects of Inhibitors
Authors: Lai James C. K. , Cooper Arthur J. L. 
Published: October 2006

Abstract The substrate and cofactor requirements and some kinetic properties of the α‐ketoglutarate dehydrogenase complex (KGDHC; EC 1.2.4.2, EC 2.3.1.61, and EC 1.6.4.3) in purified rat brain mitochondria were studied. Brain mitochondrial KGDHC showed absolute requirement for α‐ketoglutarate, CoA and NAD, and only partial requirement for added thiamine pyrophosphate, but no requirement for Mg2+ under the assay conditions employed in this study. The pH optimum was between 7.2 and 7.4, but, at pH values below 7.0 or above 7.8, KGDHC activity decreased markedly. KGDHC activity in various brain regions followed the rank order: cerebral cortex > cerebellum ≧ midbrain > striatum = hippocampus > hypothalamus > pons and medulla > olfactory bulb. Significant inhibition of brain mitochondrial KGDHC was noted at pathological concentrations of ammonia (0.2–2 mM). However, the purified bovine heart KGDHC and KGDHC activity in isolated rat heart mitochondria were much less sensitive to inhibition. At 5 mM both β‐methylene‐D,L‐aspartate and D,L‐vinylglycine (inhibitors of cerebral glucose oxidation) inhibited the purified heart but not the brain mitochondrial enzyme complex. At approximately 10 μM, calcium slightly stimulated (by 10–15%) the brain mitochondrial KGDHC.At concentrations above 100 μM, calcium (IC50= 1 mM) inhibited both brain mitochondrial and purified heart KGDHC. The present results suggest that some of the kinetic properties of the rat brain mitochondrial KGDHC differ from those of the purified bovine heart and rat heart mitochondrial enzyme complexes. They also suggest that the inhibition of KGDHC by ammonia and the consequent effect on the citric acid cycle fluxes may be of pathophysiological and/or pathogenetic importance in hyperammonemia and in diseases (e.g., hepatic encephalopathy, inborn errors of urea metabolism, Reye's syndrome) where hyperammonemia is a consistent feature. Brain accumulation of calcium occurs in a number of pathological conditions. Therefore, it is possible that such a calcium accumulation may have a deleterious effect on KGDHC activity.
Effects of Nucleus Basalis Lesions on the Muscarinic and Nicotinic Modulation of [3H] Acetylcholine Release in the Rat Cerebral Cortex
Authors: Meyer Edwin M. , W. Arendash Gary , Judkins Jennifer H. , Ying Lily , Wade Cathy , Ken William R. 
Published: October 2006

Abstract:Presynaptic muscarinic and nicotinic receptors in the cerebral cortex reportedly inhibit and increase acetyl‐choline (ACh) release, respectively. In this study, we investigated whether these receptors reside on cholinergic nerve terminals projecting to the cerebral cortex from the nucleus basalis magnocellularis (nbm). Adult male rats received unilateral infusions of ibotenic acid (5 μg/1 μl) in the nbm. Two weeks later, cerebral cortical cholinergic markers (choline acetyltransferase activity, high‐affinity choline uptake, and coupled ACh synthesis) were significantly reduced in synaptosomes prepared from the lesioned hemispheres compared to contralateral controls. The depolarization‐induced release of [3H]ACh from these synaptosomes was also reduced in the lesioned hemispheres, reflecting the reduced synthesis of transmitter. However, the nbm lesions had no effect on the inhibition of release induced by 100 μM oxotremorine. Synaptosomal [3H]ACh release was not altered by nicotine or the nicotinic agonists anabaseine and 2‐(3‐pyridyl)‐l, 4, 5, 6‐tetrahydropyrimdine. Nicotine (10–100 μM) did increase [3H]ACh release in control and lesioned hemispheres in cortical minces, but to a similar extent. These results suggest that neither muscarinic nor nicotinic receptors modulating ACh release reside on nbm‐cholinergic terminals.
Presence of Kynurenic Acid in the Mammalian Brain
Authors: Moroni F. , Russi P. , Lombardi G. , Beni M. , Carlà V. 
Published: October 2006

AbstractKynurenic acid, a tryptophan metabolite able to antagonize the actions of the excitatory amino acids, has been identified and measured for the first time in the brain of mice, rats, guinea pigs, and humans by using an HPLC method. Its content was 5.8 ± 0.9 in mouse brain, 17.8 ± 2.0 in rat brain, 16.2 ± 1.5 in guinea pig brain, 26.8 ± 2.9 in rabbit brain, and 150 ± 30 in human cortex (pmol/g wet wt, mean ± SE). The regional distribution of this molecule was uneven. In rats, guinea pigs, and rabbits, the brainstem was the area richest in this compound. Tryptophan administration (100–300 mg/kg, i.p.) to rats resulted in a significant increase of the brain content of kynurenic acid. Similarly, 1 h after probenecid administration (200 mg/kg, i.p.), the brain content of kynurenate increased by fourfold, thus suggesting that its turnover rate is relatively fast.