bluuebunny/crossref_metadata_2025_split huggingface dataset:
GUANYLATE CYCLASES IN CNS: ENZYMATIC CHARACTERISTICS OF SOLUBLE AND PARTICULATE ENZYMES FROM MOUSE CEREBELLUM AND RETINA
Authors: Troyer Edward W. , Hall Isabelle A. , Ferrendelli James A. 
Published: October 2006

AbstractGuanylate cyclase activity is present in both soluble and particulate fractions of homogenates of mouse cerebellum and retina. Soluble guanylate cyclases in cerebellum and retina have an apparent Km for GTP of approx 40 and 70 μM, respectively; are stimulated by Ca2+ and Mg2+ in the presence of low Mn2+; and do not respond to NaN3, NH2OH or detergent. The particulate guanylate cyclase found in brain has an apparent Km GTP of 237 7mu;M, is not stimulated by Ca2+ or Mg2+ in the presence of low Mn2+, but is stimulated by NaN3, NH2OH, and detergent. In particulate fractions of normal retina, guanylate cyclase has two apparent Km GTP values (42 and 225 μM); has higher activity at low concentrations of Mn2+ (0.5 mM) than at high concentrations (5.0 mM); is inhibited by Ca2+; and does not respond to NaN3, NH2OH, or detergent. Retinas essentially devoid of photoreceptor cells (from mice with photoreceptor dystrophy) have soluble guanylate cyclase activity which is similar to that in normal retina, but have only 4% as much particulate guanylate cyclase activity. This residual particulate guanylate cyclase has an apparent Km GTP value of 392 μM and other properties similar to particulate guanylate cyclase from brain. These data indicate the presence of three distinguishable guanylate cyclases in CNS: (1) a soluble enzyme present in both brain and retina: (2) a particulate enzyme which is also present in brain and in the inner or neural retina: and (3) another particulate enzyme which is apparently unique and confined to retinal photoreceptor cells.
A COMPARISON OF GABA AND β‐ALANINE TRANSPORT AND GABA MEMBRANE BINDING IN THE RAT BRAIN1
Authors: Hitzemann R. J. , Loh H. H. 
Published: October 2006

Abstract—It was found that rat brain nerve endings contain a high affinity and Na‐ dependent transport system for [3H]β‐alanine ([3H]β‐ala). As determined from Michaelis‐Menten plots, the [3H]β‐ala Km was 2.8 × 10‐5 M and the Vmax was 0.29 nmol/mg protein/5 min. Under similar incubation conditions the [3H]GABA Km was 3.8 x 10‐6M and the Vmax was 6.3 nmol/mg protein/5 min. The [3H]β‐ala and [3H]GABA transport systems were further characterized by determining the IC50 values for a number of compounds. The compounds tested were GABA, β‐ala, l‐2,4‐diaminobutyric acid. DL‐3‐hyd‐roxy‐GABA, β‐guanidopropionic acid, strychnine, γ‐guanidobutyric acid, imidazole‐4‐acetic acid, DL‐proline, bicuculline, L‐serine, glycine, l‐α‐ala and taurine. DABA, dl‐3‐hydroxy‐GABA, β‐guanidopro‐pionic acid and γ‐guanidobutyric acid were more potent inhibitors of [3H]GABA than [3H]β‐ala transport. Strychnine, imidazole‐4‐acetic acid, proline and glycine were between 2 and 6 times more potent inhibitors of [3H]β‐ala than [3H]GABA transport. β‐Ala, bicuculline, serine, α‐alanine and taurine were all markedly more potent (12–150 times) inhibitors of [3H]β‐ala than [3H]GABA transport. IC50 values were also determined for the above compounds for the sodium‐dependent and the sodium‐independent binding of [3H]GABA to both fresh and frozen brain membranes. In general, the potency of these compounds to inhibit either sodium‐independent or sodium‐dependent binding was greater in fresh tissue. It was also observed that the neurophysiologically‘glycine‐like’amino acids were more potent inhibitors in the presence of NaCl. No significant correlations were found between [3H]GABA binding under any condition and [3H]GABA or [3H]β‐ala transport into nerve endings.
CHANGES IN FATTY ACID COMPOSITION OF HUMAN BRAIN MYELIN LIPIDS DURING MATURATION1
Authors: Svennerholm L. , Vanier M.‐T. , Jungbjer B. 
Published: October 2006

Abstract— The variation with age of the fatty acid composition of the major lipids in human brain myelin was compared with that of cerebral white matter from the same region. The myelin was isolated from the semiovale centre of the cerebrum of 27 subjects neonatal to old aged. The phospholipid, cholesterol and galactolipid concentrations were determined in all the samples, as were the proportions of the major phospholipid classes. The proportions of cholesterol and especially of the galactolipids increased in myelin during the first 6 months, and in cerebral white matter up to 2 years. During this period the individual phospholipids also varied substantially. Serine phosphoglycerides and especially sphingomyelins increased, and choline phosphoglycerides decreased.The fatty acid patterns of ethanolamine phosphoglycerides (EPG) and sphingomyelins underwent the largest changes. The proportions of saturated fatty acids in EPG diminished rapidly, and there was an increase of monoenoic acids. Fatty acids of the linoleic acid series showed a peak between 4 and 12 months, after which time their proportion slowly diminished to old age. The major fatty acid of this series was docosatetraenoic acid, 22:4 (n‐6), which constituted more than 25% of total fatty acids at the maximum level. The fatty acid changes were larger in cerebral white matter, but from 2 years of age the EPG fatty acid pattern in myelin was similar to that in white matter. The fatty acid changes in serine and choline phosphoglycerides of myelin with maturation were much less striking than in EPG but of a similar type.In myelin sphingomyelin the proportion of saturated long‐chain fatty acids, C16‐C22, diminished, while that of monoenoic acids increased and continued to do so up to old age. From 2 years of age the fatty acid patterns in myelin and cerebral white matter were quite similar. Also the fatty acid patterns of cerebrosides and sulphatides in cerebral white matter and myelin were the same except for the first 2 months of life. The same fatty acid changes occurred in cerebrosides and sulphatides as in the sphingomyelins, i.e. increased proportions of unsaturated (monoenoic) acids. The proportions of 24:1 and 24h:1 and of the odd‐numbered fatty acids 25:1 and 23h:1 continued to increase to old age.The variations of the individual lipid fatty acid patterns were small except in the youngest age classes, in which the variations were presumably ascribable to the difficulty in determining the gestational age.
REGIONAL BIOSYNTHESIS OF ACETYLCHOLINE IN BRAIN FOLLOWING FORCED ORAL CHRONIC BARBITONE TREATMENT TO RAT
Authors: Nordberg Agneta , Wahlström G. 
Published: October 2006

Abstract—Rats received a solution of sodium barbitone as their only drinking fluid for 33 and 42–44 weeks. In three groups (A3, A12 and A30) the barbitone solution was withheld and replaced by water 3, 12 and 30 days respectively before death. Two other groups consisted of animals drinking barbitone until death (B) and untreated controls (C). Abstinence convulsions were recorded by jiggle cages.Thirty nmol of tritium‐labelled choline ([3H]Ch) were injected i.v. and the rats were killed by decapitation 1 min later. A significantly higher content of tritium‐labelled acetylcholine ([3H]ACh) was found in the cerebellum + medulla oblongata + midbrain of rats receiving barbitone until death (group B) (+22%) and abstinent for 3 days (+54%) (group A3) compared with group C. The [3H]ACh content was also significantly increased in the hippocampus + cortex of rats abstinent for 3 days (+23%). In the striatum no significant effect on [3H]ACh content was found in any of the groups. The ratio [3H]ACh/[3H]Ch was significantly increased in the cerebellum + medulla oblongata + midbrain of rats in group B and A3 and in the hippocampus + cortex in group A3. These results might indicate an increased turnover of ACh.The effect of long‐term barbitone treatment on the enzyme activities of brain choline acetyltransferase and acetylcholinesterase was also studied but no significant effect was found.
CELLULAR DISTRIBUTION OF 16S ACETYLCHOLINESTERASE
Authors: Fernandez Hugo L. , Duell Myron J. , Festoff Barry W. 
Published: October 2006

Abstract—Multiple molecular forms of acetylcholinesterase (AChE; EC 3.1.1.7), in crude extracts of various tissues from the rat, were distinguished by velocity sedimentation analysis on linear sucrose gradients. Skeletal muscle samples containing end‐plate regions showed three different forms of AChE with apparent sedimentation coefficients of 16, 10 and 4s. The 16s form was not detected in non‐innervated regions of skeletal muscle, large intestine smooth muscle, whole brain tissue, red blood cells or plasma. Spinal cord, a predominantly motor cranial nerve and mixed (sensory and motor) peripheral nerves contained 16, 10, 6.5 and 4S AChE. Ventral motor roots, supplying the sciatic nerve, contained these four forms of the enzyme, while corresponding dorsal sensory roots were devoid of the 16S form. The 16s‐AChE confined to ventral roots can be attributed totally to motor neurons and not to Schwann cells composing these roots. Whether the 16s‐AChE presently found in motor nerves has chemical identity with that found at motor end‐plates is the basis of future experiments.
5‐HYDROXYTRYPTOPHYL PEPTIDES: POTENT INHIBITORS OF A STORAGE COMPARTMENT OF SEROTONIN1
Authors: Tamir Hadassah , Wilchek Meir 
Published: October 2006

Abstract—Several analogues of 5‐hydroxytryptophan were tested for their ability to inhibit the binding of serotonin to serotonin‐binding protein (SBP), a protein found within serotonergic neurons which has a high affinity for serotonin. An N‐substituted dipeptide, N‐acetyl‐5‐hydroxytryptophan‐5‐hydroxytryptophan amide, was found to be an inhibitor of this binding. The inhibition (50% at 1.0 μM) was specific, since it did not affect other known sites of serotonin binding. The binding of serotonin to its membrane receptor was not affected by the dipeptide (up to 10 μM). Uptake of serotonin by synaptosomes was only slightly affected (9% at 10 μM), and aromatic‐L‐amino‐acid carboxy‐lyase(EC 4.1.1.28) and amine: oxygen oxidoreductase (deaminating) (flavin‐containing) (EC 1.4.3.4) were not inhibited (10 μM and 5 mM respectively), The peptide was not hydrolyzed by honiogenates of brain or myenteric plexus. The 14C‐labelled dipeptide was shown to be taken up by synaptosomes. However, the uptake of the peptide was not affected either by drugs that inhibit serotonin uptake or by serotonin itself although the uptake was abolished by excess 5‐hydroxytryptophan. Intraventricular injection of N‐acetyl dipeptide caused a biphasic effect depending on dose. Lower doses (10nmol) induced a decrease in serotonin brain levels (40%). Higher doses (300 nmol) caused a 95% increase in serotonin levels.It is suggested that 5‐hydroxytryptophyl peptides may be used as potent specific inhibitors of SBP, a storage compartment of serotonin.
BRAIN TISSUE AND PLASMA ASSAY OF L‐DOPA AND α‐METHYLDOPA METABOLITES BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY WITH ELECTROCHEMICAL DETECTION
Authors: Freed Curt R. , Asmus Paul A. 
Published: October 2006

AbstractUsing reverse phase high‐performance liquid chromatography and electrochemical detection with mobile phases composed of simple acids, we have developed an assay technique to measure multiple catecholamines and their catechol metabolites in plasma or brain tissue with sensitivity to the picomole level. Ion‐pairing chromatography with nitric or trichloroacetic acid as the mobile phase permits separation and quantitation of norepinephrine, α‐methylnorepinephrine, epinephrine, dopamine, α‐methyldopamine, l‐DOPA, α‐methyldopa, carbidopa, and DOPAC. Alumina extraction selectively isolates catechols which are then separated on a reverse‐phase column and measured by a commercially available electrochemical detector. This method has been applied to measurement of L‐DOPA metabolites in patients with Parkinson's disease treated with L‐DOPA and carbidopa and to measurement of catecholamines in rat hypothalamus in the course of studies on L‐DOPA and α‐methyldopa metabolism. Dihydroxybenzylamine is added as an internal standard and standard curves are linear over two orders of magnitude in concentration with coefficients of variation averaging 3.1%. Quantitation is routinely done to 20 pmol with absolute sensitivity possible to 0.5 pmol.
DETERMINATION OF SOME MOLECULAR PARAMETERS OF TRYPTOPHAN HYDROXYLASE FROM RAT MIDBRAIN AND MURINE MAST CELL
Authors: Kuhn Donald M. , Rosenberg Robert C. , Lovenberg Walter 
Published: October 2006

Abstract—The molecular parameters of tryptophan hydroxylase (EC 1.14.16.4) from rat midbrain and murine mast cell were determined by gel filtration and sucrose density gradient ultracentrifugation. The enzyme from rat midbrain has a calculated molecular weight of 220, 000, a Stokes radius of 55.6 Å, a frictional ratio of 1.28, and a sedimentation coefficient of 9.63 S. The mast cell enzyme has a calculated molecular weight of 144, 000, a Stokes radius of 50.3 Å, a frictional ratio of 1.35, and a sedimentation coefficient of 6.97 S. It appears that the tryptophan hydroxylase species from rat midbrain and murine mast cell represent distinct molecular entities.
INHIBITION OF GUINEA‐PIG BRAIN TYROSINE HYDROXYLASE BY CATECHOLS AND BIOPTERIN
Authors: Mann S. P. , Gordon J. I. 
Published: October 2006

Abstract—The inhibition by catechols and biopterin of tyrosine hydroxylase from guineapig caudate nuclei has been examined. Inhibitory constants of 10–20 μm were obtained for dopamine and noradrena‐line and 150–250 μmfor l‐DOPA and dihydroxyphenylacetic acid. When examined under similar conditions homovanillic acid was found not to be inhibitory. Using an acetone dried powder as the source of tyrosine hydroxylase no change in Km or Vmax was observed when cyclic AMP or Ca2+ were added to the medium. Enzyme mechanisms and a possible explanation of the mechanisms controlling catechol synthesis are discussed.
BASAL, DOPAMINE‐ AND OCTOPAMINE‐STIMULATED ADENYLATE CYCLASE ACTIVITY IN THE BRAIN OF THE MOTH, MAMESTRA CONFIGURATA, DURING ITS METAMORPHOSIS1
Authors: Bodnaryk Robert P. 
Published: October 2006

Abstract—The specific activities of basal, dopamine‐ and octopamine‐stimulated adenylate cyclase in the brain of the moth, Mamestra configurata, increased by an order of magnitude or more during the transition from pupal to adult brain. Increases in adenylate cyclase activity outpaced increases in brain weight and protein content by a wide margin, especially during the last 10 days of metamorphosis when most of the change in enzyme activity occurred.The greatly enhanced adenylate cyclase activity appears to reflect increased demands placed on the adult brain as an integrative centre, especially in the integration of sensory input from the eyes and antennae. Growth of the optic lobes during brain development contributed a substantial proportion of basal (33%), dopamine‐sensitive (21%) and octopamine‐sensitive (37%) adenylate cyclase activity to the adult brain. High levels of octopamine and the presence of active octopamine‐sensitive adenylate cyclase suggest a cyclic AMP‐mediated physiological function for octopamine in the optic lobes of the insect brain, probably as a neurotransmitter or neuromodulator.
Transport and Turnover of Acetylcholinesterase and Choline Acetyltransferase in Rat Sciatic Nerve and Skeletal Muscle
Authors: Wooten G. Frederick , Cheng Chuan‐Huan 
Published: October 2006

Abstract:We studied the axonal transport and turnover of acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) activities in rat sciatic nerve and skeletal muscle. AChE activity accumulated proximal to a sciatic nerve ligation rapidly and linearly for 4‐6 h, and ChAT accumulated much more slowly, but linearly, for at least 4 days. In the nerve segment distal to a ligation, AChE activity accumulated rapidly and linearly for 3‐4 h, while no change was found for ChAT for up to 48 h. Only 13% of total AChE activity in rat sciatic nerve moved in the rapidly transported phase. The absolute rate of rapid orthograde axonal transport of AChE activity was estimated to be approximately 390 mm per day and for retrograde transport approximately 230 mm per day. ChAT transport occurred only in the orthograde direction and at a rate of approximately 1‐2 mm per day. It is suggested that previous investigations of turnover of AChE and ChAT activities in skeletal muscle over‐estimated the true rate of turnover. We estimate that the theoretical minimal rate of turnover for total AChE and ChAT activities in skeletal muscle were 200 days and 950 days, respectively.
Regulation of Muscarinic Receptor‐Mediated Cyclic GMP Synthesis by Cultured Mouse Neuroblastoma Cells
Authors: El‐Fakahany Esam , Richelson Elliott 
Published: October 2006

Abstract:Mouse neuroblastoma clone N1E‐115 has muscarinic acetylcholine receptors that mediate cyclic GMP synthesis. This receptor‐mediated response is not significantly higher than background until the cells have been maintained in the stationary phase for at least 1 week. The basis of the influence of time in culture on the cyclic GMP response was investigated. The relative amount of cyclic GMP synthesized by intact cells was measured by radioactively labeling the GTP pool with [3H]guanine, incubating cells with agonists, and then chromatographically isolating [3H]cyclic GMP. Carbamylcholine‐, ionophore X‐537A‐, and sodium azide‐induced cyclic GMP formation increased with time in culture to a maximum of 13‐, 9‐, and 2.5‐fold above basal, respectively. There was no change in the number or the apparent affinity of the muscarinic receptors as measured by [3H]quinuclidinyl benzylate ([3H]QNB) binding. In addition, there was no change in the apparent affinity of the receptors for agonist as measured by the ability of carbamylcholine to displace the specific binding of [3H]QNB. Guanylate cyclase activity per milligram protein and per cell in‐creased six‐ and sevenfold, respectively, from day 0 to day 22. However, this increase in guanylate cyclase appeared to precede the marked increase in sensitivity of the cells to agonists. These data suggest that, in addition to guanylate cyclase and muscarinic receptors, there is another factor which is responsible for the development of this muscarinic receptor‐mediated response.
Asparagine as Precursor for Transmitter Aspartate in Corticostriatal Fibres
Authors: Reubi J. C. , Toggenburger G. , Cuénod M. 
Published: October 2006

Abstract:The role of asparagine as precursor for the neurotransmitter aspartate was investigated in rat striatum in vitro.14C‐asparagine incubated with striatal slices is converted to a great extent to 14C‐aspartate which is released in a calcium‐dependent manner by high KCl. Furthermore, a frontoparietal cortex ablation of two weeks produces a decrease of more than 70% in the striatal release of newly synthetized 14C‐aspartate, whereas the striatal GABA release is unaffected. This suggests that asparagine is a possible pre‐cursor in vitro for transmitter aspartate in the striatum. This reaction is dependent on intact corticostriatal fibres.
Lysosomal Acid Hydrolases in Developing Huml Brain Regions
Authors: Sinha L. , Sinha A. K. 
Published: October 2006

Abstract:β‐D‐Glucosidase, β‐D‐glucosaminidase, acid phosphatase, and β‐D‐galactosidase were monitored in the human foetal brain at different gestaional periods. Glucosidase specific activity in all brain regions exhibits two peaks, at 8 g and 32 g foetal weights. Acid phosphatase exhibits very high specific activity in all brain regions at 5 g, but the cerebellar activity forms a peak at 220 g foetal weight, the midbrain at 135 g, and the spinal activity at 760 g. β‐D‐Glucosaminidase has a peak at 220 g and 660 g in the midbrain, and β‐D‐galactosidase specific activity is highest in the cortex and cerebellum in late gestation (neuronal differentiation phase). The midbrain medulla and the spinal cord show peak activity at 8 g and 220 g foetal weight. The results suggest an inter‐ and intraregional heterogeneity of acquisition for these enzymes in human brain ontogeny.
Immunocytochemical Localization of (Na+,K+)‐ATPase in the Goldfish Optic Nerve
Authors: Schwartz Michal , Ernst Stephen A. , Siegel George J. , Agranoff Bernard W. 
Published: October 2006

Abstract:Antiserum to the catalytic subunit of goldfish brain (Na+,K+)‐ATPase has been employed at the electron microscopic level by means of the peroxidase‐antiperoxidase immunohistochemical method. In optic nerve, an‐tigenic sites are restricted to the nodes of Ranvier. No reaction product is detected in underlying internodal neurolemma. Outgrowing neurites for cultured retinal explants devoid of glial ensheathment exhibit a continuous distribution of the enzyme subunit. Antibodies against eel electroplax (Na+, K+)‐ATPase cross‐react with the goldfish brain enzyme and show a similar immunocytochemical distribution pattern.
Acetylcholine Releases ATP from Varicosities Isolated from Guinea Pig Myenteric Plexus
Authors: White Thomas D. , Al‐Humayyd Mohammed 
Published: October 2006

Abstract:The effects of cholinergic agonists and antagonists on the release of ATP from isolated myenteric varicosities were studied using a firefly luciferin‐luciferase technique. In a previous study, acetylcholine and nicotine released ATP from isolated myenteric varicosities, whereas the muscarinic agonist bethanechol did not. In the present study, release of ATP by acetylcholine was shown to be Ca2+dependent. d‐Tubocurarine competitively antagonized the release of ATP by either acetylcholine or nicotine. Maximal release of ATP by acetylcholine (10‐3M) was approximately 24% that observed with the depolarizing drug veratridine (5 x 105M), suggesting either that not all of the varicosities capable of releasing ATP possess nicotinic receptors or that acetyl‐choline does not depolarize the varicosities to the degree that veratridine does. Tetrodotoxin slightly but significantly reduced ATP release induced by acetylcholine or nicotine, indicating some involvement of Na+ channels in the release process. Finally, 6‐hydroxydopamine pre‐treatment produced a 48% reduction in the acetylcholine‐evoked release of ATP, suggesting that much, but possibly not all, of the ATP release occurs from noradrenergic varicosities present in the preparation.
Determination of Some Molecular Parameters of Tyrosine Hydroxylase From Rat Adrenal, Rat Striatum, and Human Pheochromocytoma
Authors: Rosenberg Robert C. , Lovenberg Walter 
Published: October 2006

Abstract:The molecular parameters of tyrosine hydroxylase (EC 1.14.16.2) from rat adrenal, rat striatum, and human pheochromocytoma were determined by combined gel filtration and sucrose gradient ultracentrifugation. The enzyme from rat adrenal has a calculated molecular weight of 228,000, a Stokes radius of 60.9 Å, a sedimentation coefficient of 9.10S, and a frictional ratio of 1.39. The enzyme from rat striatum has a calculated molecular weight of 210,000, a Stokes radius of 54.3 Å, a sedimentation coefficient of 9.38S, and a frictional ratio of 1.28. Tyrosine hydroxylase from human pheochromocytoma tissue has a calculated molecular weight of 255,000, a Stokes radius of 68.2 Å, a sedimentation coefficient of 9.08S, and a frictional ratio of 1.50. These results indicate that the tyrosine hydroxylases from central and peripheral tissue in the rat are quite similar although the human enzyme appears to be significantly larger.