bluuebunny/crossref_metadata_2025 huggingface dataset:
Choline Administration Elevates Brain Phosphorylcholine Concentrations
Authors: Millington William R. , Wurtman Richard J.
Published: October 2006

Abstract: The phosphorylcholine concentration of rat brain rises and falls in response to parallel changes in the concentration of circulating choline. A single oral dose of choline chloride (20 mmol/kg) elevated whole‐brain concentrations of both choline and phosphorylcholine 5 h after administration; a greater proportion of exogenously administered choline was retained by the brain in its phosphorylated form than as the free arnine. Striatal phosphorylcholine concentrations were elevated within 2 h of choline administration and continued to be significantly greater than control values for up to 34 h after treatment. The response of striatal choline levels to exogenous choline was of shorter duration than that of phosphorylcholine and was correlated with a significant increase in striatal acetylcholine concentrations. The consumption of a choline‐free diet for 7 days lowered both serum choline and striatal phosphorylcholine concentrations, but had no effect on striatal choline or acetylcholine. These results suggest that choline kinase is unsaturated by its substrate in vivo and may thus serve to modulate the response of brain choline concentrations to alterations in the supply of circulating choline.
Angiotensin Converting Enzyme in Alzheimer's Disease: Increased Activity in Caudate Nucleus and Cortical Areas
Authors: Arregui Alberto , Perry Elaine K. , Rossor Martin , Tomlinson Bernard E.
Published: October 2006

Abstract: The activity of the dipeptidyl carboxypeptidase, angiotensin converting enzyme, was assayed in several brain regions of patients dying with Alzheimer's disease and compared to that of appropriately age‐matched controls. Enzyme activity was found to be elevated by 44% and 41% in the medial hippocampus and parahippocampal gyrus, respectively, and by 27% and 29% in the frontal cortex (area 10 of Brodman) and caudate nucleus, respectively, in Alzheimer's disease patients. Converting enzyme activity did not differ from controls in the nucleus accumbens, substantia nigra, temporal cortex, anterior or posterior hippocampus, amygdala, and septal nuclei.
Effect of Nipecotic Acid, a γ‐Aminobutyric Acid Transport Inhibitor, on the Turnover and Release of γ‐Aminobutyric Acid in Rat Cortical Slices
Authors: Szerb John C.
Published: October 2006

Abstract: To see the effect of a γ‐aminobutyric acid GABA uptake inhibitor on the efflux and content of endogenous and labeled GABA, rat cortical slices were first labeled with [3H]GABA and then superfused in the absence or presence of 1 mM nipecotic acid. Endogenous GABA released or remaining in the slices was measured with high performance liquid chromatography, which was also used to separate [3H]GABA from its metabolites. In the presence of 3 mM K+, nipecotic acid released both endogenous and [3H]GABA, with a specific activity four to five times as high as that present in the slices. The release of labeled metabolite(s) of [3H]GABA was also increased by nipecotic acid. The release of endogenous GABA evoked by 50 mM K+ was enhanced fourfold by nipecotic acid but that of [3H]GABA was only doubled when expressed as fractional release. In a medium containing no Ca2+ and 10 mM Mg2+, the release evoked by 50 mMK+ was nearly suppressed in either the absence or the presence of nipecotic acid. In the absence of nipecotic acid electrical stimulation (bursts of 64 Hz) was ineffective in evoking release of either endogenous or [3H]GABA, but in the presence of nipecotic acid it increased the efflux of endogenous GABA threefold, while having much less effect on that of [3H]GABA. Tetrodotoxin (TTX) abolished the effect of electrical stimulation. Both high K+ and electrical stimulation increased the amount of endogenous GABA remaining in the slices, and this increase was reduced by omission of Ca2+ or by TTX. The results suggest that uptake of GABA released through depolarization is of major importance in removing GABA from extracellular spaces, but the enhancement of spontaneous release by nipecotic acid may involve intracellular heteroexchange. Depolarization in the presence of Ca2+ leads to an increased synthesis of GABA, in excess of its release, but the role of this excess GABA remains to be established.
Serotonin‐Containing Neurones in Vertebrate Retinas
Authors: Osborne N. N. , Nesselhut T. , Nicholas D. A. , Patel S. , Cuello A. C.
Published: October 2006

Abstract: It has been established by a combination of HPLC and electrochemical detection that frog, lizard, goldfish, rabbit, and bovine retinas contain both dopamine and serotonin. Immunohistological and immunoradiographical methods show that serotonin is localised in amacrine perikarya and processes situated in the inner plexiform layers of frog, lizard, and goldfish retinas. The amount of serotonin in the mammalian retina appears to be too low for detection in neurones. The serotonin in the bovine retina is located mainly in the inner nuclear and plexiform layers, suggesting that the amine is present in the same types of cells as found for frog, lizard, and goldfish retinas. Retinas incubated in [3H]serotonin showed that radioactivity is associated with processes in the inner plexiform layer and amacrine perikarya. These results suggest that the neuronal elements that contain endogenous serotonin also have the capacity to accumulate exogenous amine and are consistent with the opinion that serotonin has a neuronal function in retinas of a variety of vertebrates.
Opiate Receptor‐Mediated Inhibition of Catecholamine Release in Primary Cultures of Bovine Adrenal Chromaffin Cells
Authors: Saiani Laura , Guidotti Alessandro
Published: October 2006

Abstract: Primary cultures of chromaffin cells from bovine adrenal medulla were used to evaluate the ability of several opiates to reduce the release of catecholamines induced by stimulation of nicotinic receptors. Etorphine, β‐endorphin, Met‐enkephalin[Arg6,Phe7], and the synthetic peptide [d‐Ala2,Me‐Phe4,Met(O)s‐ol]enkephalin inhibited the acetylcholine‐induced release of catecholamines with an IC30 varying from 10−7 to 1 × 10−6M. The effect was stereospecific because levorphanol (IC30= 7.5 × 10−7M) was approximately two orders of magnitude more potent than dextrorphan. Morphine (μ‐receptor agonist), [d‐Ala2, d‐Leu5]enkephalin (δ‐receptor agonist), ethylketazocine (k‐receptor agonist), and N‐allylnormetazocine (σ‐receptor agonist) were at least 100–1000 times less potent than etorphine. Diprenorphine (IC50= 5 × 10−7M) and naloxone (IC50= 10−6M) antagonized the effect of etorphine. High‐affinity, saturable, and stereospecific binding sites for [3H]etorphine, [3H]dihydromorphine, [3H‐d‐Ala2,d‐Leu5]enkephalin, [3H]ethylketazocine, and for [3H]N‐allylnormetazocine, [3H]diprenorphine, and [3H]naloxone were detected in chromaffin cell membranes and in membranes obtained from adrenal medulla homogenates. However, the number of binding sites for [3H]etorphine and [3H]diprenorphine was 10–70 times higher than the number of sites measured with the other 3H ligands. The rank order of potency of these compounds for the displacement of [3H]etorphine binding correlates (r = 0.90) with the rank order of potency of the same compounds for the inhibition of acetylcholine‐induced catecholamine release. These data suggest that a stereoselective opiate receptor (different from the classic μ‐, δ‐, k‐, or σ‐receptor) with high affinity for etorphine, diprenorphine, β‐endorphin, and Met‐enkephalin[Arg6,Phe7] modulates the function of the nicotinic receptor in adrenal chromaffin cells.
Kinetics of Regional Blood–Brain Barrier Transport and Brain Phosphorylation of Glucose and 2‐Deoxyglucose in the Barbiturate–Anesthetized Rat
Authors: Pardridge William M. , Crane Paul D. , Mietus Lawrence J. , Oldendorf William H.
Published: October 2006

Abstract: Recent studies indicate the lumped constant (LC), which defines the relative rates of brain utilization of glucose and 2‐deoxyglucose (2‐DG), doubles to values > 1.0 under conditions of hypoglycemia. Since changes in the LC should be predictable given the kinetic parameters of blood‐brain barrier (BBB) transport and brain phosphorylation of glucose and 2‐DG, the present studies were designed to measure the necessary kinetic parameters. The carotid injection technique was used to determine cerebral blood flow and the Km, Vmax, and KD of glucose and 2‐DG transport through the BBB in seven brain regions in rats anesthetized with 50 mg/kg i.p. pentobarbital. Regional glucose transport through the BBB was characterized by an average Km= 6.3 mm, average Vmax= 0.53 μmol min−1g−1, and average KD= 0.022 ml min−1g−1. The nonsaturable route of transport of glucose represented on the average 40% of the total glucose influx into brain regions at an arterial glucose concentration of 10 mm. In addition, the rate constants of phosphorylation of glucose and 2‐DG were measured for each region. Substitutions of the measured kinetic parameters for sugar transport and phosphorylation into equations defining the LC confirm the observation that the LC would be expected to vary under extreme conditions such as hypoglycemia and to exceed values of 1.0 under these conditions.
Relationship Between GABA Concentrations in Cerebrospinal Fluid and Seizure Excitability
Authors: Löscher Wolfgang
Published: October 2006

Abstract: Various studies suggest that alterations in GABAergic function may be connected to epileptic seizures. Low CSF GABA levels have been reported in epilepsy and also febrile convulsions of children. In this study the pentet‐razole seizure threshold of dogs was compared with the concentration of GABA in the CSF and blood plasma. A highly significant positive correlation was found between seizure excitability and CSF GABA level, but not between CSF and plasma GABA concentrations.
Na+,K+‐ATPase and Mg2+‐ATPase Activities in Different Regions of Rat Brain During Alloxan Diabetes
Authors: Mayanil C. S. K. , Kazmi S. M. I. , Baquer N. Z.
Published: October 2006

Abstract: The effect of alloxan diabetes on the activities of Na+,K+‐ATPase and Mg2+‐ATPase was studied in three regions of rat brain at various time intervals after the onset of diabetes. It was observed that Na2+,K2+‐ATPase activity increased at early time intervals after diabetes, followed by a recovery to near control levels in all three regions of the brain. There was an overall increase in Mg2+‐ATPase activity in all the regions. A reversal of the effect was observed with insulin administration to the diabetic rats
Maternal Dietary Fat and Polyunsaturated Fatty Acids in the Developing Foetal Rat Brain
Authors: Samulski Marilla A. , Walker Brian L.
Published: October 2006

Abstract: Female rats were fed pursed diets containing 10% safflower oil, which is high in linoleic acid, from approximately 2 weeks prior to mating until the 14th day of gestation. They were then fed purified diets containing safflower oil, soybean oil (containing linoleic and linolenic acids), or hydrogenated coconut oil (essential fatty acid deficient). On days 16, 18, and 21 of gestation, foetuses were removed by caesarean section and the brains were subjected to fatty acid analysis. By day 16 of gestation, the ethanolamine glycerophospholipids and combined serine‐inositol glycerophospholipids were rich in polyunsaturated fatty acids, particularly arachidonic acid. Between days 16 and 21 of gestation, there was a marked increase in the C22‐polyunsaturated acids in these glycerophospholipids, with 225n‐6 deposited in foetuses from dams fed safflower or coconut oils and 22:6n‐3 deposition occurring in the soybean oil group; the effects of essential fatty acid deficiency in this period were minimal. A similar pattern was evident in the choline glycerophospholipids but this fraction contained less of the polyunsaturated acids. The data are consistent with increased placental transfer of highly unsaturated fatty acids or increased foetal synthesis of these compounds during the last week of gestation, with the actual fatty acid pattern reflecting the dietary fat available to the dam.
Effect of Polyunsaturated Fatty Acids on Fetal Mouse Brain Cells in Culture in a Chemically Defined Medium
Authors: Bourre J. M. , Faivre A. , Dumont O. , Nouvelot A. , Loudes C. , Puymirat J. , Tixier‐Vidal A.
Published: October 2006

Abstract: The biochemical and morphological effects of polyunsaturated fatty acids on fetal brain cells grown in a chemically defined medium were studied. Fetal brain cells were dissociated from mouse cerebral hemispheres taken on the 16th day of gestation. After cells had grown in chemically defined medium for 8 days, the proportion of polyunsaturated fatty acids of cultured cells was only one‐half of that observed at day 0 and about 1.5 times less than that of cells grown in serum‐supplemented medium. Fatty acid 20:3(n‐9) was present in cultured cells grown in either chemically defined or serum‐supplemented medium, demonstrating the deficiency of essential fatty acids. The reduced amount of polyunsaturated fatty acids in cells grown in the chemically defined medium was balanced by an increase in monounsaturated fatty acids. The saturated fatty acids were not affected. When added at the seeding time, linoleic, linolenic, arachidonic, or docosahexaenoic acid stimulated the proliferation of small dense cells. Besides, we demonstrate that each of the four fatty acids studied was incorporated into phospholipids. Adding fatty acids of the n‐6 series increased the content of n‐6 fatty acids in the cells, but also provoked an increase in the n‐3 fatty acids. Among several combinations of fatty acids, only 20:4 and 22:6, when added to the culture in a ratio of 2:1, restored a fatty acid profile similar to controls (i.e. in vivo tissue taken at postnatal day 5).
Substrates of Energy Metabolism of the Pituitary and Pineal Glands
Authors: Vannucci Susan , Hawkins Richard
Published: October 2006

Abstract: The capability of the neurohypophysis, the adenohypophysis, and the pineal gland to oxidize nonesterified fatty acids and glucose as energy sources was studied in vivo. Fed and 48‐h‐starved rats had catheters placed in their femoral vessels. After they became conscious, an intravenous injection of one of the following was given: [1‐14C]acetate, [1‐14C]octanoate, [1‐14C]‐palmitate, or [2‐14C]glucose. After 5 min the rats were sacrificed. These metabolites produce [14C]acetyl‐CoA within the mitochondria when they are oxidized as metabolic fuels. On passage through the Krebs cycle a considerable portion of the 14C is trapped in large amino acid pools closely associated with the Krebs cycle; the appearance of 14C in these amino acids was taken as evidence of oxidation. As expected, brain structures behind the blood‐brain barrier (cerebral cortex and caudate) showed considerable labeling of Krebs cycle‐associated amino acids in both nutritional states when [2‐14C]glucose was the substrate. Surprisingly, however, no label was detected in amino acids of the neurohypophysis or the pineal gland in starved rats and very little in fed rats. On the other hand, 14C from acetate and palmitate was extensively incorporated into amino acids of the pineal gland and the neurohypophysis, while little 14C labeling was found in the cerebral cortex and the caudate. Octanoate, which passes the blood‐brain barrier readily, labeled amino acids of all tissues. The experiments demonstrated conclusively that the neural structures studied, which have no blood‐brain barrier, do not rely heavily upon glucose as a fuel for oxidative energy metabolism, in contrast to the rest of the brain. The results also showed that nonesterified fatty acids may supply at least some of their energy requirements.
Purification and Inhibition by Neuropeptides of Angiotensin‐Converting Enzyme from Rat Brain
Authors: Yokosawa Hideyoshi , Ogura Yasuhiko , Ishii Shin‐ichi
Published: October 2006

Abstract: Angiotensin‐converting enzyme was solubilized with papain from a particulate fraction of rat brain and purified to apparent homogeneity by a procedure including DEAE‐cellulose, hydroxylapatite, Sephadex G‐200. Cys(Bzl)‐Pro‐Sepharose, and ricin‐Sepharose chromatography. Bradykinin potentiators, SQ 14,225, and Arg‐Pro‐Pro strongly inhibited the activity of the purified enzyme. whereas Phe‐Ala, phosphoramidon, and pentobarvital expert little inhibitory effect on the activity. Among nuropeptides investigated, substance P, bradykinin, and Leu‐enkephalin (Arg6) exerted strong inhibitory actions on the enzyme. Furthermore, the latter two peptides were shown to be good substrates for the enzyme. Thus, an‐giotensin‐converting enzyme of rat brain is distinct from endogenous enkephalinase and may interact with various neuropeptides located in the brain.
Depolarizing Agents Regulate the Phosphorylation of Myelin Basic Protein in Rat Optic Nerves
Authors: Murray Norman , Steck Andreas J.
Published: October 2006

Abstract: The regulation of the state of phosphorylation of myelin basic protein has been studied in intact rat optic nerves incubated in vitro. For this purpose the endogenous state of phosphorylation was preserved and the “back‐phosphorylation” technique was used to determine the amount of dephosphorylated protein present in extracts of the nerves. Our results indicate that when nerves were incubated in the presence of depolarizing agents, the state of phosphorylation of myelin basic protein was increased. This effect was calcium‐dependent and was partly inhibited by chlorpromazine.
Effect of Oral Administration of Tri‐o‐cresyl Phosphate on In Vitro Phosphorylation of Membrane and Cytosolic Proteins from Chicken Brain
Authors: Patton Suzanne E. , O'Callaghan James P. , Miller Diane B. , Abou‐Donia Mohamed B.
Published: October 2006

Abstract: The effects of a single oral dose of 750 mg/kg tri‐o‐cresyl phosphate (TOCP) on the endogenous phosphorylation of specific brain proteins were assessed in male adult chickens following the development of delayed neurotoxicity. Phosphorylation of crude synaptosomal (P2) membrane and synaptosomal cytosolic proteins was assayed in vitro by using [γ‐32P]ATP as phosphate donor. Following resolution of brain proteins by sodium dodecyl sulfate polyacrylamide gel electrophoresis, specific protein phosphorylation was detected by autoradiography and quantified by microdensitometry. TOCP administration enhanced the phosphorylation of both cytosolic (Mr 65,000 and 55,000) and membrane (20,000) proteins by as much as 146% and 200%, respectively.
Tetanus Toxin Inhibition of K+ ‐Stimulated [3H]GABA Release from Developing Cell Cultures of the Rat Cerebellum
Authors: Pearce Brian R. , Gard Anthony L. , Dutton Gary R.
Published: October 2006

Abstract: The effect of tetanus toxin pretreatment on K+ ‐stimulated [3H]γ‐aminobutyric acid release from neuron‐enriched cerebellar cell cultures at various stages during their development in vitro was assessed. Tetanus toxin had little inhibitory effect on immature (1‐3‐day‐old) cultures, but markedly reduced K+‐evoked [3H]γ‐aminobutyric acid release from 7‐ and 14‐day‐old cultures (∼80% inhibition). It is suggested that cerebellar neurons in culture develop tetanus toxin‐sensitive transmitter release mechanisms similar to their in vivo counterparts.
Glucose Availability to Individual Cerebral Structures Is Correlated to Glucose Metabolism
Authors: Hawkins Richard A. , Mans Anke M. , Davis Donald W. , Hibbard Lyndon S. , Lu Daniel M.
Published: October 2006

Regional cerebral glucose influx was measured using quantitative autoradiography after the intravenous infusion of [2‐14C]glucose for a period of 10 or 20 s. Glucose influx varied considerably among structures over an almost threefold range. When compared with rates of regional glucose utilization, a significant correlation by region was found between glucose influx and utilization, demonstrating that the glucose supply to individual cere bral structures is closely matched to their metabolic needs.
Regulation and Properties of an NADP+ Oxidoreductase Which Functions as a γ‐Hydroxybutyrate Dehydrogenase
Authors: Kaufman E. E. , Relkin N. , Nelson T.
Published: October 2006

A number of naturally occurring biological intermediates have been found to inhibit competitively the activity of a highly purified NADP+‐dependent oxidore‐ductase which catalyzes the simultaneous oxidation of γ‐hydroxybutyrate to succinic semialdehyde, and the reduction of D‐glucuronate to L‐gulonate. Of the inhibitors studied, those with the lowest Ki are the α‐keto analogues of the branched chain or aromatic amino acids. The Vmax and Km for this enzyme are affected by pH; consequently, changes in substrate concentration can markedly alter the pH optimum. The enzyme has been found to be inhibited by reducing agents such as dithiothreitol and mercapto‐ethanol, protected against this inhibition by oxidizing agents such as oxidized glutathione or H2O2, and finally, protected against heat inactivation by the presence of either NADP+ or NADPH.
Effect of Maternal Iron Deficiency in Rat on Serotonin Uptake In Vitro by Brain Synaptic Vesicles in the Offspring
Authors: Kaladhar M. , Rao B. S. Narasinga
Published: October 2006

The effect of maternal dietary iron deficiency on brain synaptic vesicle [3H]serotonin (5‐HT) uptake and iron content in the offspring was examined in rats. Pups born to iron‐deficient mothers revealed significant deficits in vesicular [3H]5‐HT uptake and iron concentration at 21 days of age. These changes were, however, found to be reversible with postweaning iron repletion.
Depolarisation‐Dependent Protein Phosphorylation in Rat Cortical Synaptosomes: Factors Determining the Magnitude of the Response
Authors: Robinson Phillip J. , Dunkley Peter R.
Published: October 2006

Abstract: The sequence of molecular events linking depolarisation‐dependent calcium influx to the release of neurotransmitters from nerve terminals is unknown; however, calcium‐stimulated protein phosphorylation may play a role. In this study the incorporation of phosphate into proteins was investigated using an intact postmitochondrial pellet isolated from rat cerebral cortex. The rate and relative incorporation of label into individual phosphoproteins depended on the prelabelling time and buffer concentrations of calcium and phosphate. After prelabelling for 45 min, depolarisation caused a >20% increase in the labelling of 10 phosphoproteins, and this initial increase was maximal with 41 mM K+ for 5 s, or 30 μM veratridine for 15 s, in the presence of 1 mM calcium. Both agents also led to an initial dephosphorylation of four phosphoproteins. Depolarisation for 5 min led to a significant decrease in the labelling of all phosphoproteins. All of the depolarisation‐stimulated changes in protein phosphorylation were calcium‐dependent. The depolarisation conditions found to optimally alter the phosphorylation of synaptosomal proteins find many parallels in studies on calcium uptake and neurotransmitter release. However, the uniform responses of such a large number of phosphoproteins to the multitude of depolarisation conditions studied suggest that the changes could equally well relate to recovery events such as biosynthesis of neurotransmitters and regulation of intraterminal metabolic activity.
Reductions of Γ‐Aminobutyric Acid and Glutamate Uptake and (Na++ K+)‐ATPase Activity in Brain Slices and Synaptosomes by Arachidonic Acid
Authors: Chan Pak Hoo , Kerlan Randi , Fishman Robert A.
Published: October 2006

Abstract: Arachidonic acid, a major polyunsaturated fatty acid of membrane phospholipids in the CNS, reduced the high‐affinity uptake of glutamate and γ‐aminobutyric acid (GABA) in both rat brain cortical slices and synaptosomes. α‐Aminoisobutyric acid uptake was not affected. Intrasynaptosomal sodium was increased concomitant with decreased (Na++ K+)‐ATPase activity in synaptosomal membranes. The reduction of GABA uptake in synaptosomes could be partially reversed by α‐tocopherol. The inhibition of membrane‐bound (Na++K+)‐ATPase by arachidonic acid was not due to a simple detergent‐like action on membranes, since sodium dodecyl sulfate stimulated the sodium pump activity in synaptosomes. These data indicate that arachidonic acid selectively modifies membrane stability and integrity associated with reductions of GABA and glutamate uptake and of (Na++ K+)‐ATPase activity.
Biochemical Study of Heterosis for Brain Myelin Content in Mice
Authors: Ebato H. , Seyfried T. N. , Yu R. K.
Published: October 2006

Abstract: Heterosis (hybrid vigor) for brain myelin content has been examined in detail in (C57BL/6J × DBA/ 2J)F1 hybrid mice at 17 days of age. The amount of myelin isolated from the F1 hybrid brain is greater than that isolated from either parental strain. In addition, the total protein content in the myelin of the three genotypes showed the following trend: F1 > DBA > C57. However, no discernible differences in myelin protein compositions could be detected by sodium dodecyl sulfate‐poly‐acrylamide gel electrophoresis. Analysis of the whole brain for several myelin‐associated constituents such as GM1 ganglioside, 2′, 3′‐cyclic nucleotide 3′‐phosphohy‐drolase (CNPase), 5′‐nucleotidase and carbonic anhy‐drase indicated that heterosis exists for these components. No heterosis was found for such nonmyelin constituents as gangliosides GDIa, GT, GQ, RNA, DNA and choline acetyltransferase. A developmental study of the whole brain CNPase indicated that the heterotic effect was greatest during the most active period of myelination (17–30 days). We conclude that the heterotic effect is specific for myelin content and is probably the result of an accelerated myelin synthesis. The heterotic effect should have great potential as a new model for studying aspects of myelinogenesis.
Depolarization‐Evoked Release of γ‐Hydroxybutyrate from Rat Brain Slices
Authors: Maitre Michel , Cash Christopher , Weissmann‐Nanopoulos Dinah , Mandel Paul
Published: October 2006

Abstract: The release of γ‐hydroxybutyrate from preloaded rat brain striatal slices was investigated. K+‐induced depolarization caused an efflux of γ‐hydroxybutyrate of about 50 fmol min‐1 mg‐1 (wet weight), but in a Ca2+‐free medium containing Mg2+, the evoked release was reduced by 50–60%. The release was higher when 100 μM veratridine was used as a depolarizing agent. The efflux of γ‐hydroxybutyrate is related to veratridine and K+ concentration, and is strongly inhibited by 10 μM tetrodotoxin. The Ca2+ channel blocker verapamil induces a large decrease in the efflux of γ‐hydroxybutyrate after both K+‐ and veratridine‐induced depolarization. These results are in favour of a possible transmitter function for γ‐hydroxybutyrate in rat striatum.
Changes of Biogenic Amines and Their Metabolites in Postmortem Brains from Patients with Alzheimer‐Type Dementia
Authors: Aral Heii , Kosaka Kenji , Iizuka Reiji
Published: October 2006

Abstract: Noradrenaline (NA), 3,4‐dihydroxyphenyl‐ethylamine (dopamine, DA), 5‐hydroxytryptamine (serotonin, 5‐HT), homovanillic acid (HVA), and 5‐hydroxy‐indoleacetic acid (5‐HIAA) were measured in 22 regions of postmortem brains from four histologically verified cases with Alzheimer‐type dementia (AID) and nine histologically normal controls. Compared with the controls, concentrations of 5‐HT and 5‐HIAA in the ATD brains were significantly reduced in nine regions (superior frontal gyrus, insula, cingulate gyrus, amygdala, putamen, medial and lateral segments of globus pallidus, substantia nigra, lateral nucleus of thalamus) and in eight regions (amygdala, substantia innominata, caudate, putamen, medial and lateral segments of globus pallidus, medial and lateral nuclei of thalamus), respectively. NA concentrations of the ATD brains were significantly reduced in six regions (cingulate gyrus, substantia innominata, putamen, hypothalamus, medial nucleus of thalamus, raphe area). In contrast, significant reductions of DA and HVA concentrations in the ATD brains were found only in putamen and amygdala, respectively. The 5‐HIAA/5‐HT ratio in the ATD brains decreased significantly in locus coeruleus, while the HYA/DA ratio increased significantly in putamen and medial segment of globus pallidus. These findings suggest that the serotonergic and noradrenergic systems are affected, while the dopaminergic system is relatively unaffected in ATD brains.
Malonate, Malonyl‐Coenzyme A, and Acetyl‐Coenzyme A in Developing Rat Brain
Authors: Mitzen Edward J. , Koeppen Arnulf H.
Published: October 2006

Abstract: Free malonate, malonyl‐coenzyme A (malonyl‐CoA), and acetyl‐CoA were assayed in rat brain at developmental ages from the 20th day of gestation to 60 days of postnatal life. The determination of malonate was based on its conversion to malonyl‐CoA and decarboxylation to acetyl‐CoA by enzyme extracts from Pseudo‐monas fluorescens. The resulting acetyl‐CoA reacted with [4‐14C]oxaloacetate to form [5‐14C]citrate, which was isolated by TLC. Malonyl‐CoA in perchloric acid extracts from brain was converted to acetyl‐CoA by rat liver mitochondrial malonyl‐CoA decarboxylase (EC 4.1.1.9). Acetyl‐CoA derived from this step was assayed by a modified CoA‐cycling procedure. Brain acetyl‐CoA was also assayed by CoA cycling. Prenatal brain contained no free malonate but malonyl‐CoA was present. The acetyl‐CoA level was relatively high just prior to birth and declined slightly with growth. Malonate concentrations after birth rose rapidly to reach 192 nmol/g wet weight at 60 days. Adult levels for malonyl‐CoA and acetyl‐CoA were 1.83 and 1.90 nmol/g wet weight, respectively. The origin and natural role of free malonate in brain are not known but deacylation of malonyl‐CoA by reversal of the malonyl‐CoA synthetase reaction is postulated. Rat liver and kidney also contain substantial concentrations of free malonate.
Regional and Subcellular Distribution of Cyanide Metabolizing Enzymes in the Central Nervous System
Authors: Mimori Yasuyo , Nakamura Shigenobu , Kameyama Masakuni
Published: October 2006

Abstract: Activities of cyanide metabolizing enzymes were measured in various subcellular fractions and regions in the central nervous system. Brain rhodanese and liver β‐mercaptopyruvate sulfurtransferase showed a slight decrease in activity after death. The activity of β‐mercaptopyruvate sulfurtransferase was negligible in the rat brain, compared with that of rhodanese. A small amount of thiocyanate was produced from cyanide and β‐mercaptopyruvate in the human brain, probably due to contamination with red blood cells. Rhodanese activity was widely distributed in all the areas of nervous tissue examined. In the rat the olfactory bulb showed the highest rhodanese activity, and high activity was also observed in the thalamus, septum, hippocampus, and dorsal part of the midbrain. Rhodanese activity was low in various parts of the cerebral cortex. The distribution pattern of rhodanese in post‐mortem human brain was essentially similar to that in rat brain. The thalamus, amygdala, centrum semiovale, colliculus superior, and cerebellar cortex showed high rhodanese activity in the human brain. Rhodanese activity was detected in the spinal cord. Anterior horn showed the highest rhodanese activity in the cervical, thoracic, and lumbar cord. Most rhodanese activity in the rat brain was recovered in the mitochondrial fraction with the highest specific activity. Rhodanese activity was lower in spinal cords obtained from autopsied cases with amyotrophic lateral sclerosis than in those of control subjects. A significant decrease in rhodanese was observed in the posterior column of the cervical or thoracic cord, but the activity in the anterior horn did not differ significantly between the two groups.
Effects of Trypsin and Plasmin Treatment of Myelin on the Myelin‐Associated Glycoprotein and Basic Protein
Authors: Inuzuka Takashi , Sato Shuzo , McIntyre Laurence J. , Quarles Richard H.
Published: October 2006

Abstract: Human and rat myelin preparations were incubated with varying concentrations of trypsin and plasmin to determine the effects of these proteolytic enzymes on myelin‐associated glycoprotein (MAG), basic protein, and other myelin proteins and to compare the effects with those of the neutral protease that was reported to be endogenous in myelin. Basic protein was most susceptible to degradation by both trypsin and plasmin, whereas MAG was relatively resistant to their actions. Under the assay conditions used, the highest concentrations of trypsin and plasmin degraded > 80% of the basic protein but < 30% of the MAG, and lower concentrations caused significant loss of basic protein without appreciably affecting MAG. Neither trypsin nor plasmin caused a specific cleavage of MAG to a derivative of MAG (dMAG) in a manner analogous to the endogenous neutral protease. Thus the endogenous protease appears unique in converting human MAG to dMAG much more rapidly than it degrades basic protein. MAG is slowly degraded along with other proteins when myelin is treated with trypsin or plasmin, but it is less susceptible to their action than is basic protein.
Influence of Pathological Concentrations of Ammonia on Metabolic Fate of 14C‐Labeled Glutamate in Astrocytes in Primary Cultures
Authors: Yu Albert C. H. , Schousboe Arne , Hertz Leif
Published: October 2006

Abstract: Rates of glutamine formation and of carbon dioxide production (as an indication of oxidative deamination of glutamate) were determined in primary cultures of astrocytes exposed to 50 μM labeled glutamate in the absence or presence of added ammonia (0.1–3 mM). Glutamine formation (1.7 nmol/min/mg protein) was unaffected by all concentrations of added ammonia. This probably reflects the presence of a low content of ammonia (0.1–0.2 mM), originating from degradation of glutamine, in the cells even in the absence of added ammonia, and it shows that pathophysiological concentrations of ammonia do not increase the formation of glutamine from exogenous glutamate. The carbon dioxide production rate was 5.9 nmol/min/mg protein, i.e., three to four times higher than the rate of glutamine formation. It was significantly reduced (to 3.5 nmol/min/mg protein) in the presence of 1 mM or more of ammonia. This is in keeping with suggestions by others that toxic levels of ammonia affect oxidative metabolism.
Differential Effect of Cerebral Ischemia on Monoamine Content of Discrete Brain Regions of the Mongolian Gerbil (Meriones unguiculatus)
Authors: Matsumoto Masayasu , Kimura Kazufumi , Fujisawa Atsushi , Matsuyama Tomohiro , Fukunaga Ryuzo , Yoneda Shotaro , Wada Hiroshi , Abe Hiroshi
Published: October 2006

Abstract: The effect of bilateral cerebral ischemia on noradrenaline, dopamine, and serotonin concentrations in six brain regions (i.e., the cerebral cortex, striatum, hippocampus, midbrain‐diencephalon, cerebellum, and pons‐medulla oblongata) was examined in the gerbil stroke model. The relative changes in regional cerebral blood flow after bilateral common carotid occlusion were also assessed using the radioactive microsphere technique. At 1 h after bilateral carotid occlusion, a significant decrease of monoamine concentration was observed in the cerebral cortex, striatum, hippocampus, and midbrain‐diencephalon whereas no significant change was detected in the cerebellum and pons‐medulla oblongata. The fall in NA content was most prominent in the cerebral cortex and hippocampus and percentage reductions of dopamine and serotonin were greatest in the striatum and cerebral cortex, respectively. These results suggest that the monoamine neurons in various brain regions might have different vulnerabilities to ischemic insult and show no evidence of transtentorial diaschisis.
3α‐Hydroxysteroid Oxidoreductase in Rat Brain
Authors: Krieger Neil R. , Scott Robert G.
Published: October 2006

Abstract: We describe a simple procedure for the microassay of 3α‐hydroxysteroid oxidoreductase in homogenates of rat brain. This enzyme converts dihydrotestosterone to 3α‐androstandiol. We have mapped the distribution of the enzymatic activity in 14 regions of the rat brain. The highest activities were observed in homogenates of olfactory bulb (51/nmol/mg protein/h) and olfactory tubercle (29 nmol/mg protein/h). Substantially lower values were seen in the other brain regions, including thalamus, caudate nucleus, frontal cortex, hippocampus, hypothalamus, and preoptic area (6–20 nmol/mg protein/ h).
Thyroxine‐Induced Changes in the Development of Neutral α‐Amino Acid Transport Systems of Rat Brain
Authors: Riggs Thomas R. , Pote Kenneth G. , Im Hae‐Sook , Huff Daniel W.
Published: October 2006

Abstract: Transport of representative neutral α‐amino acids was measured in brain slices after injecting thy‐roxine into donor rats of various ages from 1 to 23 days old. The hormone did not alter uptake in slices from 1‐day‐old rats even when treatment was begun on pregnant rats as much as 10 days before delivery. Injecting thy‐roxine until age 6 days, however, decreased the activity of transport system A (the major sodium‐dependent system in most mammalian cells) and caused appearance of a new transport system used by the model amino acids, 2‐aminoisobutyric acid and 2‐(methylamino)isobutyric acid. Uptake at 6 days was similar to that found in slices from older, untreated rats (e.g., those 14 days old). These results strongly suggest that one action of thyroxine is to accelerate the development of neutral α‐amino acid transport systems of brain over the first six days after birth. Thyroxine treatment of rats from birth to age 14 days also appears to increase the activities of both system A and the second transport system used by the two model amino acids in brains from 14‐day‐old rats.
Enzymes of Cerebral GABA Metabolism and Synaptosomal GABA Uptake in Acute Liver Failure in the Rabbit: Evidence for Decreased Cerebral GABA‐Transaminase Activity
Authors: Ferenci P. , Jacobs R. , Pappas S. C. , Schafer D. F. , Jones E. A.
Published: October 2006

Abstract: Measurements of the activities of the two key enzymes in cerebral GABA metabolism—glutamate decarboxylase (GAD) and GABA‐transaminase (GABA‐T)—were performed in normal rabbits and in rabbits with hepatic encephalopathy due to galactosamine‐induced liver failure. Furthermore the uptake of GABA by synaptosomes was studied. Hepatic encephalopathy was associated with a marked decrease in the activity of GAB A‐T. This decrease in activity was already apparent in galactosamine‐treated rabbits before the onset of hepatic encephalopathy. Sera and serum ultrafiltrates of rabbits with hepatic encephalopathy but not of normal rabbits or of rabbits with uremic encephalopathy were shown to inhibit GABA‐T activity in vitro. Cerebral GAD activity and synaptosomal GABA uptake in rabbits with hepatic encephalopathy and in untreated animals were not different. These later findings indicate that hepatic encephalopathy is not associated with alterations of presynaptic GABA nerve terminals in the central nervous system. The demonstration of a decrease in cortical GABA‐T activity provides indirect evidence for decreased GABA turnover in the brains of rabbits with hepatic encephalopathy and thus is compatible with augmented GABA‐ergic inhibitory neurotransmission contributing to the neural inhibition of hepatic encephalopathy.
Effect of Ethylcholine Mustard on Choline Dehydrogenase and Other Enzymes of Choline Metabolism
Authors: Barlow P. , Marchbanks R. M.
Published: October 2006

The effect of ethyl choline mustard (ECMA), an effective irreversible inhibitor of choline transport, was investigated on the enzymes of choline metabolism. ECMA at concentrations of 50 μM hardly affected choline acetyltransferase and caused only a 20% inhibition of choline kinase at a concentration of 1 mM. However, the mustard was an extremely effective inhibitor of choline dehydrogenase, producing 50% inhibition at concentrations of 6 μM. The inhibition was prevented by incubation in the presence of choline or by prior reaction of the mustard with thiosulphate. Separation of the components of the ECMA solution on TLC suggested that only the compound with an aziridine ring was an effective inhibitor of choline dehydrogenase. The inhibition was resistant to the washing out of excess unreacted mustard. The rate constant of inhibition was 395 M'‐1 s‐1. By the use of [3H]ECMA a single polypeptide in the enzyme preparation having a MW of 67,000 was labelled. The labelling was thiosulphate‐sensitive and prevented by incubation with choline. It is concluded that ECMA is an irreversible inhibitor of choline dehydrogenase. It is at least as effective an inhibitor of choline dehydrogenase as of the choline transport system, although it does not appreciably inhibit choline acetyltransferase or choline kinase in the micromolar range.
Nicotinic Stimulation of [3H]Acetylcholine Release from Mouse Cerebral Cortical Synaptosomes
Authors: Rowell Peter P. , Winkler Donald L.
Published: October 2006

The effects of nicotine and 1,1‐dimethyl‐4‐phenylpiperazinium (DMPP) on the release of newly synthesized [3H]acetylcholine in mouse cerebral cortical synaptosomes were examined. Nicotine and DMPP produced increases in [3H]acetylcholine release, over the level of spontaneous release, of 24% and 30%, respectively, of a maximum depolarization‐induced release produced by 50 mM potassium. The maximum effect was achieved at a concentration of 1 × 10‐4M for both agents. The time course of release indicated a slow onset of action, reaching a maximum effect at 15 min of incubation. Both nicotine and DMPP also produced a slightly greater release of total tritium, measured in the absence of cholinesterase inhibition, than of [3H]acetylcholine. The release induced by nicotine was completely antagonized by hexamethonium and was largely (58%) calciumdependent. Nicotine also produced an increase in [3H]choline accumulation into synaptosomes. These results indicate that the nicotinic agonists nicotine and DMPP can produce a moderate enhancement of acetylcholine release by a receptor‐mediated action on cholinergic nerve terminals in the central nervous system.
Biosynthesis of 5‐Aminopentanoic Acid and 2‐Piperidone from Cadaverine and 1‐Piperideine in Mouse
Authors: Callery Patrick S. , Geelhaar Linda A.
Published: October 2006

1‐Piperideine, 5‐aminopentanoic acid, and its lactam, 2‐piperidone, were identified as metabolites of cadaverine in 10,000 g mouse liver supernatants to which diamine oxidase had been added. Both metabolites were also found when the cadaverine metabolite 1‐piperideine was incubated with the preparation which suggested that 1‐piperideine is an intermediate in the formation of 5‐ammopentanoic acid and 2‐piperidone. Identification of the metabolites was based on gas chromatography‐mass spectrometric analysis in comparison to authentic standards. Mouse brain homogenates converted 1‐piperideine to 5‐aminopentanoic acid. The results suggest that the metabolic fate of cadaverine may provide precursors of pharmacologically active analogues of GABA.
Measurement of Prostaglandins in the Cerebrospinal Fluid in Cat, Dog, and Man
Authors: Romero Silvia Divinetz , Chyatte Douglas , Byer David E. , Romero J. Carlos , Yaksh Tony L.
Published: October 2006

Prostaglandins are involved in the modulation of various central functions (neurotransmitters and hypothalamic hormone release, thermoregulation, cerebro‐vascular tone) and their levels increase in pathological situations [subarachnoid hemorrhage (SAH), stroke, convulsive disorders, etc.]. This study, using sensitive and specific antibodies, examined levels of four eicosanoids, Prostaglandins E2 and F2α(PGE2, PGF2α); and the metabolites of PGI2, 6‐keto‐prostaglandin F1α (6‐keto‐PGF1α) and of thromboxane A2, thromboxane B2 (TxB2), in the cerebrospinal fluid (CSF) obtained atraumatically from three species (human, canine, and feline). An assessment of the methodologic procedures (extraction and radioimmunoassay) was carried out. Human lumbar cerebrospinal fluid was shown to contain PGF2α (15–44 pg/ml), 6‐keto‐PGF1α (undetectable to 39 pg/ml), and TxB2 (un‐detectable to 28 pg/ml), whereas PGE2 was undetectable (>18 pg) in all cases. In both animals species the eico‐sanoid concentrations were 3‐to 30‐fold higher than humans for every prostaglandin examined. Although the prostaglandin profile for a given species remained constant (cat, PGE2:6‐keto‐PGF1α:TxB2:PGF2α; dog, TxB2:PGE2:6‐keto‐PGF1α:PGF2α), the absolute levels were found to be lower in the pentobarbital‐anesthetized animals than in conscious cats. The correspondence of the prostaglandin profiles found in cerebrospinal fluid with the profiles reported in the literature in brain homogenates for the same species supports the hypothesis that cerebrospinal fluid levels of prostaglandins reflect the relative rates of synthesis in neural tissue.
Effect of the Jimpy Mutation on Expression of Myelin Proteins in Heterozygous and Hemizygous Mouse Brain
Authors: Kerner Ann‐Louise , Carson John H.
Published: October 2006

The levels of myelin basic protein, proteolipid protein, and 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase (EC 3.1.4.37) in cerebral hemispheres of wild‐type, heterozygous jp/+, and hemizygous jp/Y mice of different ages were determined by radioimmunoassay and immunoblotting. ln jp/Y brain the level of myelin basic protein was 8% that of wild‐type at all ages. All forms of the protein were reduced although the 21.5K Mr form was relatively spared at early ages compared to the 18.5K, 17K, and 14K Mr forms. The level of 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase was. 8% that of wild‐type at all ages, and proteolipid protein was undetectable at any age. These results are consistent with the hypothesis that the jimpy mutation blocks myelin morphogenesis subsequent to incorporation of 21.5K Mr myelin basic protein but prior to incorporation of proteolipid protein. ln jp/+ brain the levels of the three proteins were reduced commensurately to 60–70% those of wild‐type. The deficit was apparent as early as 1.0 days after birth and remained proportionately constant throughout development. These results suggest that in jp/+ mice, X‐chromosome inactivation produces a mosaic population of functionally wild‐type and functionally jimpy oligodendrocytes. The former elaborate normal amounts of myelin but do not completely compensate for the myelin deficit due to the latter.
Effects of Methiothepin and Lysergic Acid Diethylamide on Serotonin Release In Vitro and Serotonin Synthesis In Vivo: Possible Relation to Serotonin Autoreceptor Function
Authors: Pettibone Douglas J. , Pflueger A. Barbara
Published: October 2006

Abstract: An in vitro system characterizing the presyn‐ aptic serotonin (5‐HT) autoreceptor which controls the release of 5‐HT from rat brain slices is described. Using this system, methiothepin (1–10 μM) demonstrated 5‐HT autoreceptor antagonist activity ‐by enhancing 5‐HT release, while several recognized postsynaptic 5‐HT receptor antagonists were inactive: mianserin, cinanserin, cyproheptadine, methysergide. The activity of methiothepin was highest in hypothalamic slices and lowest in striatal slices and was inhibited by the autoreceptor agonists lysergic acid diethylamide (LSD) and 5‐methoxy‐ tryptamine (5‐MT). The reversal of the methiothepin‐enhanced 5‐HT release from hypothalamic slices by LSD was not influenced by 0.3 μM tetrodotoxin. The peripheral administration of LSD to rats has been shown to reduce 5‐HT synthesis and release by a mechanism thought to involve, in part, an autoreceptor‐mediated reduction in impulse flow of 5‐HT neurons. In the present experiments, intraperitoneal injection of methiothepin antagonized the LSD‐induced reduction in hypothalamic 5‐HT synthesis (5‐hydroxytryptophan accumulation) while exerting no influence by itself. Conversely, compounds which were not active as 5‐HT autoreceptor antagonists in vitro (i.e., cyproheptadine, methysergide, cinanserin) did not influence the effect of LSD on 5‐HT synthesis. Further, the reduction in 5‐hydroxytryptophan (5‐HTP) accumulation by LSD showed regional differences in inhibition by methiothepin (hypothalamus > cortex > striatum) which paralleled the autoreceptor antagonist activity of methiothepin in vitro. These data suggest that similar autoreceptor mechanisms control 5‐HT release and synthesis in terminal 5‐HT projection areas and that the reduction in 5‐HT accumulation by LSD and the antagonism by methiothepin may represent a useful biochemical measure of 5‐HT autoreceptor activity in vivo.