bluuebunny/crossref_metadata_2025_split huggingface dataset:
LOCALIZATION OF GLUTAMIC ACID DECARBOXYLASE WITHIN LAMINAE OF THE RAT OLFACTORY TUBERCLE
Authors: K.RIEGER NEIL R. , HELLER JOHN S. 
Published: October 2006

Abstract—There are three histological layers within the rat olfactory tubercle: plexiform, pyramidal and polymorphic. We have assayed glutamic acid decarboxylase (GAD) and GABA in homogenates of frozen sections cut parallel to these layers. Consecutive sections (16 μm) were homogenized in groups and assayed for GAD or GABA. Every seventh section was stained with Toluidine Blue to monitor the depth and orientation of the plane of section. Steep variations in GAD activity (up to 6‐fold) were observed as a function of depth in the tubercle. These were paralleled by corresponding but less marked variations in GABA levels. The lowest values were found in the plexiform layer. This suggests that GAD may play a very limited role there. The highest activities were found in sections from the deepest lamina of the polymorphic layer. This is the only lamina of the tubercle that does not receive a dopaminergic input.
Regulation of Rat Pineal Hydroxyindole‐O‐Methyltransferase: Evidence of S‐Adenosylmethionine‐Mediated Glucocorticoid Control
Authors: Sandrock Alfred W. , Leblanc Gabrielle G. , Wong Dona L. , Ciaranello Roland D. 
Published: October 2006

Abstract: Rat pineal hydroxyindole‐O‐methyltransferase is controlled similarly to adrenal medullary phenylethanolamine N‐methyltransferase. S‐adenosylmethionine (SAM), the in vivo cofactor utilized by the enzyme to convert N‐acetylserotonin to melatonin, protects this methyltransferase against tryptic proteolysis in vitro. Furthermore, in vivo studies suggest that the nucleoside itself is controlled by glucocorticoids. Hypophysectomy decreases hydroxyindole‐O‐methyltransferase levels as compared with control animals, while dexamethasone and SAM administration restore enzyme levels toward control values. In vitro proteolytic studies further demonstrate that, although N‐acetylserotonin does not stabilize the enzyme against trypsinization, this substrate acts synergistically with SAM to confer greater stabilization than observed with SAM alone.
Regulation of the Cycle in Chick Pineal Serotonin N‐Acetyltransferase Activity In Vitro by Light
Authors: Wainwright S. D. , Wainwright Lillian K. 
Published: October 2006

AbstractThe diurnal cycle in vivo in the level of serotonin N‐acetyltransferase (NAT) activity found in the pineal gland of chicks kept under diurnal lighting was reproduced in vitro with glands incubated in organ culture under the same diurnal lighting conditions. We have examined the effects of varying the lighting conditions of culture upon development of NAT activity in vitro with pineal glands from birds which were killed at different times during the photoperiod in vivo. The ability of chick pineal glands to develop increased NAT activity in culture during the dark period of a diurnal cycle of illumination was determined primarily by the proportion of the photoperiod in vivo elapsed at the time of sacrifice of the birds. The time of development of maximal NAT activity in cultured chick pineal glands could be advanced or delayed by corresponding changes in time of start of the dark period. However, the ‘settings’of the pineal‘biological clock’remained unchanged. Glands from birds sacrificed in the final 30 min of the photoperiod in vivo developed increased NAT activity without lag when cultured in the light. Similarly, pineal glands cultured under continuous illumination developed an increased photostable NAT activity beginning at the time of the „subjective” end of the photoperiod in vitro. Ability to develop additional NAT activity in the dark was lost rapidly at the „subjective” time in vitro of start of the next photoperiod. The maximal NAT activity developed in the dark consisted of both photolabile and photostable components.
Alterations in γ‐Aminobutyric Acid Receptor Sensitivity Following Acute and Chronic Ethanol Treatments
Authors: Ticku Maharaj K. , Burch Troie 
Published: October 2006

Abstract:The effects of acute and chronic ethanol ingestion on the binding of the inhibitory neurotransmitter 3H‐γ‐aminobutyric acid (GABA) was investigated in inbred strains of mice. Acute effects were analyzed in DBA/2J (alcohol avoiding) and C57BL/6J (alcohol preferring) mice, while chronic effects were analyzed in C57 mice. Acute ethanol (4 g/kg) produced a significant increase in the binding capacity of the low‐affinity γ‐aminobutyric acid binding site in both C57 (12%) and DBA (23%) mice, without significantly altering other binding parameters. The enhanced binding capacity may be responsible for the behavioral depression associated with ethanol use. Chronically treated C57 mice exhibited a decrease in the density of low‐affinity GABA receptor sites. These results suggest the possible involvement of γ‐aminobutyric acid synaptic function in the neuropharmacological effects of ethanol. The possibility that chronic ethanol administration may result in adaptation of γ‐aminobutyric acid receptors to the continuous presence of ethanol‐induced central nervous system depression is discussed.
Regional Protein Synthesis in Rat Brain Following Acute Hemispheric Ischemia
Authors: Dienel G. A. , Pulsinelli W. A. , Duffy T. E. 
Published: October 2006

Abstract:Regional protein synthesis was measured in rat brain at intervals up to 48 h following occlusion of the four major arteries to the brain for either 10 or 30 min. Four‐vessel occlusion produces ischemia in the cerebral hemispheres and oligemia in the midbrain‐diencephalon and brainstem. During the hour following 10 min of ischemia, protein synthesis, measured by incorporation of [14C]valine into protein, was inhibited in the cerebral cortex by 67%. Normal rates of protein synthesis were attained within 4 h of recirculation. In rats subjected to 30 min of ischemia, protein synthesis was inhibited by 83% during the first hour of recirculation in the cortex, caudate‐putamen, and hippocampus. Recovery of protein synthesis in these regions was slow (25–48 h). The midbrain‐diencephalon showed less inhibition, 67%, and faster recovery (by 12 h). Protein synthesis was unaffected in the brainstem. [14C]Autoradiography revealed that the pyramidal neurons of the hippocampus and areas of the caudate and cortex failed to recover normal rates of protein synthesis even after 48 h.The accumulation of TCA‐soluble [14C]valine was enhanced (55–65%) in the cortex, caudate, and hippocampus after 30 min of ischemia; the increase persisted for 12 h. A smaller rise in [14C]valine content (30%) and more rapid normalization of valine accumulation (by 7 h) were observed in the midbraindiencephalon; no changes were found in the brainstem. In the cortex, recovery was more rapid when the duration of ischemia was reduced. Thus, the degree of inhibition of protein synthesis, the accumulation of valine in the tissue, and the length of time required to reestablish normal values for these processes were dependent on both the severity and the duration of the ischemic insult. Restoration of normal rates of protein synthesis after ischemia was slow compared with the normalization of cerebral energy metabolites.
Activity and Isoenzyme Pattern of Lactate Dehydrogenase in Neurons and Astroblasts Cultured from Brains of Chick Embryos
Authors: Tholey G. , Roth‐Schechter B. F. , Mandel P. 
Published: October 2006

Abstract:Primary cultures of neurons and glial cells (astroblasts) prepared from brains of 8‐day‐old and 15‐day‐old chick embryos, respectively, were grown for periods between 3 and 19 days. Specific activity of lactate dehydrogenase (LDH) increased in both types of cultures as a function of time and was always significantly higher in glial cells than in neurons. Glial cell extracts were found to contain predominantly the anaerobic isoenzymatic form of LDH (LDH‐H4), and this pattern did not change over a period of 19 days. Cultured neurons contained predominantly the aerobic isoenzymatic form LDH‐H4, and there was a progressive appearance of all other isoenzymes over an 8‐day period. These results support the hypothesis of a different energy metabolism in neurons and glia.
Anticonvulsant Activity of Muscimol and γ‐Aminobutyric Acid Against Pyridoxal Phosphate‐Induced Epileptic Seizures
Authors: Kouyoumdjian Jean Claude , Ebadi Manuchair 
Published: October 2006

Abstract:The intracerebroventricular injection of pyridoxal phosphate (PLP, 0.125‐1.25 μmol/rat) causes epileptic seizures (4 min → 1 min) that are preventable or reversible by GABA (1 μmol/rat), by muscimol (O.025 μmol/rat), or by diazepam (1.75 μmol/rat). At the peak of PLP‐induced convulsions, the activities of GAD and GABA‐T in 14 regions of rat brain remained unaltered, whereas the concentrations of PLP remained elevated. The PLP‐induced convulsion was blocked by DABA (10 μmol/rat) but was not altered by β‐alanine (50 μmol/rat). The previous in vitro studies have shown that PLP increases the uptake of [3H]GABA into synaptosomes and inhibits the binding of [3H]GABA to synaptic membranes. These data suggest that PLP‐induced convulsion is due to reduced availability of GABA to its recognition sites, rather than to alteration in the activity of GABA metabolizing enzymes, or unavailability of PLP as a coenzyme for GAD and GABA‐T. Since the duration of PLP‐induced epileptic seizures is short and can be prevented by GABA agonists, PLP may be used as a tool to study the nature of GABA‐mediated neuroinhibition and the properties of GABA receptor sites.
Enhancement of Neurite Outgrowth and Aspartate‐Glutamate Uptake Systems in Retinal Explants Cultured with Chick Gizzard Extract
Authors: Kato Satoru , Negishi Koroku , Hayashi Yokichi , Miki Naomasa 
Published: October 2006

Abstract:Chicken gizzard extract promoted a long and radially directed neurite outgrowth from retinal explants of 8‐day‐old chick embryo in cultures of 2–3 days. The neurite outgrowth from retinal explants cultured in the absence of gizzard extract was short and restricted to the explant perimeter. The neurite outgrowth promoted by gizzard extract depended strictly on several factors. (a) Fetal calf serum and polycationic substratum were required in this culture system, (b) Pretreatment of the polyornithine‐coated substratum with gizzard extract allowed the retinal explants to extend neurites even in the absence of gizzard extract in the medium. (c) Maximal neurite outgrowth was observed in retinal explants dissected from 8‐day embryos, but thereafter the explants’response to gizzard extract rapidly declined and was almost lost at the 12th day. As a biochemical parameter of differentiation of cultured neuroretina, uptake systems for neurotransmitter candidates were examined in homogenates of retinal explants cultured in the absence or presence of gizzard extract. After 3 days in culture with gizzard extract, the uptake increased for aspartate and glutamate 1.6‐ to 1.8‐fold and for γ‐aminobutyric acid to a lesser degree when examined at a concentration for high‐affinity uptake (10‐6M). In contrast, the uptake capacity for glycine, choline, and dopamine was not altered in explants cultured with or without gizzard extract. Kinetic analysis showed that the enhanced capacity to accumulate aspartate was not due to an alteration of Km, but to an increase of Vmax. The results suggest that one or several factors in chick gizzard muscle promote not only neurite outgrowth but also the aspartate‐glutamate uptake systems in the developing neuroretina, probably related to ganglion cells.
Differential Changes in Superoxide Dismutase Activity in Brain and Liver of Old Rats and Mice
Authors: Danh Hung Cao , Benedetti Margherita Strolin , Dostert Philippe 
Published: October 2006

Abstract:Superoxide dismutase (SOD) activity was measured in the brain and liver of 24–26‐ and 3‐month‐old rats. No significant age‐related differences in Cu/Zn‐SOD activity were found in any of the tissues studied. A small but significant increase in total SOD activity was observed in the whole brain (10‐20%), cerebral cortex (11%), and hypothalamus (18%) of old rats, whereas a much more important increase in Mn‐SOD activity was found in the whole brain (48%), cerebral cortex (70%), striatum (60%), and hypothalamus (30%). The increase of Mn‐SOD activity in the brain of old rats suggests the enzyme may play an important role in the process of aging. Mn‐SOD is found only in the mitochondrion, which could be an important site of oxygen free radical production, and a significant increase in the enzyme activity was also found in the lung of hypoxic rats. A significant decrease in total SOD and Mn‐SOD activity was observed in the liver of old rats. Preliminary experiments in 23–24‐month‐old mice similarly showed an increase and a decrease in total SOD and Mn‐SOD activity, respectively, in the whole brain and liver. These results suggest that the regulatory mechanisms of Mn‐SOD in the brain and liver vary differentially with age.
In Vivo Elevation of Mouse Brain S‐Adenosyl‐L‐Homocysteine after Treatment with L‐Homocysteine
Authors: Gharib A. , Chabannes B. , Sarda N. , Pachéco H. 
Published: October 2006

Abstract:Intraperitoneal coadministration of adenosine and L‐homocysteine markedly increased S‐adenosyl‐l‐homocysteine in whole mouse brain, but further investigations showed that this elevation could also be produced following administration of l‐homocysteine alone. The noted increase was maximal (+1325%) 10 min after treatment, remaining at about this level for 30‐40 min before returning to control values after 180 min. Cerebral adenosine levels were decreased after treatment with l‐homocysteine, adenosine, or these two substances in combination.
Isolation of PGP 9.5, a New Human Neurone‐Specific Protein Detected by High‐Resolution Two‐Dimensional Electrophoresis
Authors: Doran John F. , Jackson Peter , Kynoch Pamela A. M. , Thompson R. J. 
Published: October 2006

Abstract:Protein gene product (PGP) 9.5 is a new brain‐specific protein originally detected by high‐resolution two‐dimensional electrophoresis of the soluble proteins of human brain and other organs. We have purified this protein from human brain and raised a rabbit antihuman PGP 9.5 antiserum. The protein has a monomer molecular weight of ˜27,000 and is present in brain at concentrations at least 50 times greater than in other organs. Im‐munoperoxidase labelling has localised PGP 9.5 to neurones in the human cerebral cortex with no evidence of staining of glial elements. PGP 9.5 is estimated to be present in brain at concentrations of 200‐500 μg/g wet weight and represents a major protein component of neuronal cytoplasm. This new neurone‐specific cytoplasmic marker may prove useful in studies of neuronal development and in the detection of neuronal damage in disease of the nervous system.
The Enzymes of Acetyl‐CoA Metabolism in Differentiating Cholinergic (S‐20) and Noncholinergic (NIE‐115) Neuroblastoma Cells
Authors: Szutowicz A. , Morrison M. R. , Srere P. A. 
Published: October 2006

Abstract:Dibutyryl cyclic AMP and butyrate inhibited growth of S‐20 (cholinergic) and NIE‐115 (adrenergic) neuroblastoma clones. Both these drugs resulted in a parallel increase of choline acetyltransferase and ATP‐citrate lyase activities in S‐20 neuroblastoma cells. On the other hand, the increase in tyrosine hydroxylase activity in NIE‐115 caused by these drugs was not accompanied by a significant change in ATP‐citrate lyase activity. Both dibutyryl cyclic AMP and butyrate caused a decrease in fatty acid synthetase activity in both cell lines. The activities of pyruvate dehydrogenase, citrate synthase, choline acetyltransferase, and lactate dehydrogenase in both S‐20 and NIE‐115 cells were not significantly influenced by the drugs. ATP‐citrate lyases from S‐20 and NIE‐115 had similar kinetic and immunological properties, and their subunits had the same molecular weight as the rat liver enzyme. These data indicate that the differential regulation of ATP‐citrate lyase activity in cholinergic and adrenergic cells does not result from the existence of different molecular forms of the enzyme in these cell lines. They also provide further evidence to support the hypothesis that ATP‐citrate lyase activity increases during maturation of normal cholinergic neurons and decreases in noncholinergic cells of the brain.
Developmental Regulation of Phenylethanolamine N‐Methyl Transferase in Avian Sympathetic Nerves
Authors: David J.‐C. , Rush R. A. 
Published: October 2006

AbstractThe presence of the catecholamine synthetic enzyme, phenylethanolamine N‐methyl transferase (PNMT), has been detected in the expansor secundariorum, a smooth muscle of the avian wing. The concentration of the enzyme was estimated over a 10‐week time course from 17 days incubation to 9 weeks posthatch and found to increase rapidly up until hatch in parallel with dopamine β‐hydroxylase activity, but then to fall precipitously to very low levels. The time course of the initial increase in activity corresponds to the presence of ingrowing sympathetic nerve fibres, and denervation of the expansor results in loss of >80% of the PNMT activity.It is concluded that during the period of innervation the growing nerves contain the enzyme PNMT and therefore have the capacity to synthesize adrenaline, but that shortly after innervation is complete the capacity to synthesize adrenaline is lost. Several alternate mechanisms are proposed to explain the observations.
Autophosphorylation of Calmodulin‐Kinase II in Synaptic Junctions Modulates Endogenous Kinase Activity
Authors: Shields Steven M. , Vernon Paula J. , Kelly Paul T. 
Published: October 2006

AbstractPrevious studies have purified from bfain a Ca2+/calmodulin‐dependent protein kinase II (designated CaM‐kinase II) that phosphorylates synapsin I, a synaptic vesicle‐associated phosphoprotein. CaM‐kinase II is composed of a major Mr 50K polypeptide and a minor Mr60K polypeptide; both bind calmodulin and are phosphorylated in a Ca2+/calmodulin‐dependent manner. Recent studies have demonstrated that the 50K component of CaM‐kinase II and the major postsynaptic density protein (mPSDp) in brain synaptic junctions (SJs) are virtually identical and that the CaM‐kinase II and SJ 60K polypeptides are highly related. In the present study the photoaffinity analog [α‐32P]8‐azido‐ATP was used to demonstrate that the 60K and 50K polypeptides of SJ‐associated CaM‐kinase II each bind ATP in the presence of Ca2+ plus calmodulin. This result is consistent with the observation that these proteins are phosphorylated in a Ca2+/calmodulin‐dependent manner. Experiments using 32P‐labeled peptides obtained by limited proteolysis of 60K and 50K polypeptides from SJs demonstrated that within each kinase polypeptide the same peptide regions contain both autophosphorylation and 125I‐calmoduhn binding sites. These results suggested that the autophosphorylation of CaM‐kinase II could regulate its capacity to bind calmodulin and, thus, its capacity to phosphorylate substrate proteins. By using 125I‐calmodulin overlay techniques and sodium dodecyl Solfate‐polyacrylamide gel electrophoresis we found that phosphorylated 50K and 60K CaM‐kinase II polypeptides bound more calmodulin (50–70%) than did unphosphorylated kinase polypeptides. Levels of in vitro CaM‐kinase II activity in SJs were measured by phosphorylation of exogenous synapsin I. SJs containing highly phosphorylated CaMkinase II displayed greater activity in phosphorylating synapsin I (300% at 15 nM calmodulin) relative to control SJs that contained unphosphorylated CaM‐kinase II. The CaM‐kinase II activity in phosphorylated SJs was indistinguishable from control SJs at saturating calmodulin concentrations (300–1,000 nM). These findings show that the degree of autophosphorylation of CaM‐kinase II in brain SJs modulates its in vitro activity at low and possibly physiological calmodulin concentrations; such a process may represent a mechanism of regulating this kinase's activity at CNS synapses in situ.
P‐31 Nuclear Magnetic Resonance Analysis of Brain: II. Effects of Oxygen Deprivation on Isolated Perfused and Nonperfused Rat Brain
Authors: Kopp S. J. , Krieglstein J. , Freidank A. , Rachman A. , Seibert A. , Cohen M. M. 
Published: October 2006

AbstractPhosphatic metabolite (perchloric acid extractable) concentrations of cerebral tissues were analyzed by phosphorus‐31 nuclear magnetic resonance (P‐31 NMR) spectfoscopy following external perfusion of the isolated rat brain (30 min or 60 min) under the following conditions: (a) constant perfusion pressure with either fluorocarbon‐or erythrocyte‐based medium, and (b) constant perfusate flow rate (3 ml/min) with the erythrocyte‐based medium. Metabolite concentrations of control perfused brains were compared with those in nonperfused controls to provide a basis for detecting any qualitative or quantitative changes in cerebral metabolite composition. Metabolic responses of perfused brains to ischemia (incomplete ischemia, 83% reduction in flow for 10 min; transient complete ischemia for 1.5 or 2 min) were evaluated immediately after the ischemic episode and at selected time points during reperfusion (3 and 15 min). Alterations in cerebral metabolite levels induced by hypoxia were analyzed using a nonperfused rat brain model. Irrespective of the perfusion method employed, the phosphatic metabolites of control perfused rat brains were identical quantitatively to those of the nonperfused controls. Cerebral ischemia resulted in significantly increased levels of ADP, AMP + IMP, Pi, fructose 1,6‐diphosphate, and glycerol 3‐phosphate (global ischemia only), whereas ATP and phosphocreatine (PCr) levels declined significantly. The magnitude of these changes varied with the severity of the ischemia; however, following 15 min of control reperfusion metabolite levels had reverted to preischemic values. Significant perturbations in tissue phosphoethanolamine (3.848 resonance) content were evident at various time points during ischemia and postischemic recovery, which varied according to the perfusion conditions. In contrast to the changes observed in response to ischemia, hypoxia affected only cerebral high‐energy phosphate levels. ATP and PCr levels were reduced, while a concomitant, essentially equimolar, increase in Pi and ADP was observed. The present studies indicate that in terms of phosphatic metabolites, the control equilibrated isolated perfused rat brain is quantitatively and qualitatively indistinguishable from the non‐perfused rat brain in vivo regardless of the perfusion conditions (constant flow versus constant pressure). The metabolic responses to ischemia and hypoxia, as measured by P‐31 NMR, were consistent with the pattern of changes reported elsewhere. Overall, P‐31 NMR spectroscopic evaluation of the intact rat brain provides a potential experimental context for dynamic measures of cerebral metabolism under exogenously controlled conditions. The results reported herein from brain PCA extracts contribute a spectroscopic reference for understanding and interpreting the metabolic information contained in the P‐31 profiles of the intact brain.
Sidedness of Phosphatidylcholine‐Synthesizing Enzymes in Rat Brain Microsomal Vesicles
Authors: Arienti Giuseppe , Corazzi Lanfranco , Freysz Louis , Binaglia Luciano , Roberti Rita , Porcellati Giuseppe 
Published: October 2006

Abstract:The sidedness of CDP‐choline:1,2‐diradylglycerol choline phosphotransferase (EC 2.7.8.2) and of the choline base‐exchange activity has been studied in rat brain microsomal vesicles. Proteases (trypsin and pronase) and mercury‐dextran have been used as reagents for membrane surface components. All of them could inactivate both enzymes to a good extent, without affecting the morphology or the permeability to sucrose of the vesicles. It is therefore concluded that CDP‐choline:1,2‐diradylglycerol choline phosphotransferase and the choline base‐exchange activity are localized on the outer surface of rat brain microsomal vesicles.