bluuebunny/crossref_metadata_2025 huggingface dataset:
THE ROLE OF INTRANEURONAL 5‐HT AND OF TRYPTOPHAN HYDROXYLASE ACTIVATION IN THE CONTROL OF 5‐HT SYNTHESIS IN RAT BRAIN SLICES INCUBATED IN K+‐ENRICHED MEDIUM
Authors: Hamon M. , Bourgoin S. , Artaud F. , Glowinski J.
Published: October 2006

Abstract— The incubation of brain stem slices from adult rats in a K+‐enriched medium containing a 5‐HT uptake inhibitor (fluoxetine) significantly increased their capacity to synthesize 5‐HT from tryptophan. The K+‐induced stimulation of 5‐HT synthesis was at least partly dependent on the depletion of the indoleamine in tissues since: (1) a good correlation was found between the respective changes in 5‐HT release and synthesis evoked by high K+ concentrations in the presence of various 5‐HT uptake inhibitors; (2) the modifications in endogenous 5‐HT levels produced by in vim treatments with drugs (reserpine, pargyline) or by incubating slices with 5‐HT altered the stimulating effect of high K+ concentrations and fluoxetine on 5‐HT synthesis; (3) the replacement of Ca2+ by Co2+ (4 mM) or EGTA (0.1 mM) in the incubating medium completely prevented the increased 5‐HT release and synthesis evoked by high K+ concentrations and fluoxetine.

The extraction of tryptophan hydroxylase from incubated tissues revealed that the increased 5‐HT synthesis occurring in K+‐enriched medium was associated with an activation of this enzyme. Kinetic analyses indicated that this activation resulted from an increase in the Vmax of tryptophan hydroxylase, its apparent affinities for both tryptophan and 6‐MPH4 being not significantly affected. In contrast to the tryptophan hydroxylase from tissues incubated in normal physiological medium, the activated enzyme from tissues depolarized by K+ was hardly stimulated by Ca2+‐mediated phosphorylating conditions. This led to the proposition of a hypothetical model by which the Ca2+ influx produced by the neuronal depolarization would trigger the activity of a Ca2+‐dependent protein kinase capable of activating tryptophan hydroxylase. Although this sequence is still largely speculative it must be emphasized that, as expected from such a model, the regional differences in the K+‐evoked activation of tryptophan hydroxylase in slices (cerebral cortex > brain stem > spinal cord) were parallel to those of the Ca2+‐dependent protein phosphorylation (r= 0.92) and those of the activating effect of phosphorylating conditions on soluble tryptophan hydroxylase (r= 0.96).
SEROTONIN AND DOPAMINE METABOLITES IN BRAIN REGIONS AND CEREBROSPINAL FLUID OF A PRIMATE SPECIES: EFFECTS OF KETAMINE AND FLUPHENAZINE
Authors: Bacopoulos N. G. , Redmond D. E. , Roth R. H.
Published: October 2006

Abstract— The concentration of dopamine (DA) and serotonin (5‐HT) metabolites in brain regions was not altered by doses of ketamine (10mg/kg) which induced dissociative anesthesia in a primate species. Cercopithecus aethiops. Fluphenazine (1.0mg/kg) increased homovanillic acid (HVA) content in all brain regions examined. An increase in HVA and 5‐hydroxyindoleacetic acid (5‐HIAA) concentration was observed in cisternal CSF 4 h after ketamine without a concomitant change in the brain concentration of these metabolites.
ON THE ELIMINATION OF CENTRALLY FORMED 5‐HYDROXYINDOLEACETIC ACID BY CEREBROSPINAL FLUID AND URINE
Authors: Aizenstein Moacyr L. , Korf Jakob
Published: October 2006

Abstract— In rats, the release of centrally formed 5‐hydroxyindoleacetic acid (5‐HIAA) into brain and spinal cord perfusates and urine was measured. Data from spinal cord perfusion of anaesthetized rats indicate that more than about 36% of the spinal production (122ng/h) of 5‐HIAA is eliminated via the cerebrospinal fluid (CSF). More than 30% of cerebrally formed 5‐HIAA (265.0 ng/h) was calculated to be released into ventricular‐cisternal perfusates. Of the total amount of 5‐HIAA found in the urine we estimated that about 8% originates in the central nervous system (CNS).

In probenecid treated animals there was a substantial increase in the outflow of 5‐HIAA in both perfusion systems. In the combined perfusion experiments no proportional increase of the cerebral contribution to the cisternal outflow was found after probenecid. Our data indicate that a significant proportion of centrally formed 5‐HIAA is eliminated by the CSF. No evidence was found for an increased contribution of cerebral 5‐HIAA to lumbar CSF after application of the probenecid test. Urinary levels of 5‐HIAA do not reflect quantitatively central 5‐hydroxytryptamine metabolism.
PURIFICATION AND EFFECT OF THE NEUROTOXIN FROM THE SEA ANEMONE PARASICYONIS ACTINOSTOLOIDES
Authors: Ishikawa Y. , Onodera K. , Takeuchi A.
Published: October 2006

— Three toxic components were isolated from the sea anemone, Parasicyonis actinostoloides. Among these components a main component had an effect on the neuromuscular transmission of the crayfish. The component was purified and found to be a basic polypeptide having a molecular weight of about 2000. Amplitudes of excitatory and inhibitory poslsynaptic potentials were increased by the toxin. It was found that the quantum content increased markedly in the excitatory synapse. The action of the toxin remained for a long time after the nerve–muscle preparation was thoroughly washed. These results suggest that the toxin has an effect on the presynaptic nerve.
Nerve Growth Factor: Biological Significance, Measurement and Distribution
Authors: Harper G. P. , Thoenen H.
Published: October 2006

CONCLUSION

NGF proteins probably act as informational molecules transferred from end organs to the neurons of the sympathetic nervous system. The direct demonstration of the NGF content of most end organs requires assays more sensitive than those currently available. The high levels of NGF produced by some organs are probably of some other physiological significance.
Comparative Effects of Ethanol and Malnutrition on the Development of Catecholamine Neurons: Changes in Specific Activities of Enzymes
Authors: Detering Nancy , Edwards Elvira , Ozand Pinar , Karahasan Alp
Published: October 2006

A rat model was developed in which the comparative effects of malnutrition and ethanol on the neurochemical maturation of catecholamine neurons in brain were studied. The animals were offspring of rats optimally nourished (control pups), fed a diet with 35% of the calories supplied by ethanol (EtOH pups), or a diet calorically equivalent to the latter but lacking ethanol (isocaloric = IC pups). These latter two groups were calorically deprived since rats fed the diet containing ethanol ate 40–60% less than the optimally nourished group. The diets were administered to dams either during the last week of gestation (prenatal) or during lactation (postnatal). The protein content per gram wet weight was not significantly different between brains of control and experimental pups. Developmental changes in EtOH pups were noted in the activities of tyrosine hydroxylase (TOH) and dopamine β‐hydroxylase (DBH). The specific activity of TOH was increased in EtOH and IC pups preand postnatally. In the postnatal experimental group TOH activity in the brains of EtOH pups was higher not only when compared with control pups but also with IC pups. Prenatal caloric deprivation or ethanol exposure also caused increased specific activity of DBH in the neonatal rat brain. In contrast, exposure to ethanol postnatally caused a significant and persistent reduction in the specific activity of DBH, not only compared with control pups but also to matched IC pups exposed postnatally to the IC diet. The specific activity of 3,4‐dihydroxyphenylalaninedecarboxylase (DOPADC) was significantly elevated in the brains of prenatal and postnatal EtOH and IC pups, with little difference between the groups. Activities of monoamine oxidase (MAO) or catecholamine‐0‐methyltransferase (COMT) were generally lower in EtOH or IC pups than in control pups, again with little difference between EtOH and IC pups. These results suggest that an impaired metabolism of dopamine and norepinephrine is detectable in the brains of pups as a consequence of malnutrition, ethanol exposure, or both.
The Effect of Reducing Agents on the Apparent Molecular Weight of the Myelin P0 Protein and the Possible Identity of the P0 and “Y” Proteins
Authors: Cammer W. , Sirota S. R. , Norton W. T.
Published: October 2006

During sodium dodecyl sulfate polyacrylamide gel electrophoresis of sciatic nerve myelin proteins, the P0 protein migrated to two different positions on the gels. The distribution of P0 between the two forms depended on the concentration of mercaptoethanol (ME) or dithiothreitol (DTT) in the sample solvent. At >1% ME or 3.5% DTT, P0 was almost entirely in a form with an apparent molecular weight of 30,000, whereas in the absence of ME or DTT all the P0 migrated with an apparent molecular weight of 25,000. The distribution of the P0 protein between the two bands was independent of whether proteinase inhibitors were used during preparation of myelin. Furthermore, in a sample containing the more rapidly migrating form of P00, the P0 could be converted to the slower‐migrating form by addition of mercaptoethanol. These data show that interconversion of the two forms of P0 does not involve proteolytic degradation, but suggest rather that ME cleaves one or more intramolecular disulfide bonds in P0 unfolding the amino acid chain and thereby converting the form with a lower apparent molecular weight to that with a higher apparent molecular weight. We postulate that the “Y” protein band, which has been observed, in variable quantities, migrating slightly ahead of P0, may represent its oxidized form.
Interactions of GM1 Ganglioside with Crude Rat Brain Neuronal Membranes
Authors: Toffano G. , Benvegnù D. , Bonetti A. C. , Facci L. , Leon A. , Orlando P. , Ghidoni R. , Tettamanti G.
Published: October 2006

The binding of GM1, ganglioside to crude preparations of rat brain neuronal membranes was studied, the following results being obtained: (a) the binding process followed a biphasic kinetics, which displayed a break at 0.07–0.08 X 10−6m GM1, concentration; (b) the features of the binding process at GM1, concentrations below the break and, over the break, above 10‐6m appeared to be different. Below the break the process proceeded slowly and brought a stable and irreversible association of GM1, molecules to the membranes. Over 10‐6m the process was much more rapid and caused GM1, molecules to interact in such a way that they were releasable by washing and could exchange with newly added free ganglioside; (c) the two binding processes displayed the characteristics of a saturation phenomenon; (d) in both cases, GM1, taken up was freely available to galactose oxidase, indicating that the oligosaccharide chains protrude from the membrane surface. We postulate that GM1, occurs, below and above the break, in different physical forms, each of them having a different mechanism of interaction with the membrane. Above 10‐6m GM1, interacts as micelles, and the basis of the micelle‐membrane inter action is a fusion process. Below the break, in the 10−8–10−7m range, the binding is the result of hydrophobic interactions between sites on the membrane and the hydrophobic portion of individual ganglioside molecules, most likely in the monomeric form. Toffano G. et al. Interactions of GM1, ganglioside with crude rat brain neuronal membranes. J. Neurochem.35, 861–866 (1980).
Neopterin and Biopterin Levels in Patients with Atypical Forms of Phenylketonuria
Authors: Nixon Jon C. , Lee Ching‐Lun , Milstien† Sheldon , Kaufman Seymour , Bartholomé Klaus
Published: October 2006

The pattern of unconjugated pterins in liver tissue and in urine from patients with atypical forms of phenylketonuria with hyperphenylalaninemia (HPA) has been investigated with a high performance liquid chromatographic technique. Two patients with defects in the biosynthesis of biopterin have been shown to have higher than normal levels of neopterin and lower than normal levels of biopterin. In contrast, a patient with HPA due to a deficiency of dihydropteridine reductase has the reverse urinary pattern, i.e., high biopterin, low neopterin. These results indicate that the ratio of neopterin to biopterin in urine can be of value in discriminating between HPA due to a deficiency of phenylalanine hydroxylase (classic PKU), HPA due to dihydropteridine reductase deficiency, and HPA due to a block in the biosynthesis of biopterin.
Differential Changes in Monoamine Oxidase A and B Activity in the Aging Rat Brain
Authors: Benedetti M. Strolin , Keane P. E.
Published: October 2006

The activity of monoamine oxidase (MAO) was assayed in the brains of young adult (7–8 weeks old) and aging (95–104 weeks old) male Sprague‐Dawley rats. When expressed per milligramme of tissue, total protein content was increased to a similar extent in whole brain and in all seven brain regions of the aging rat, whereas MAO A activity (assayed by using 5‐hydroxytryptamine as substrate) was unchanged in whole brain but increased in the cerebellum, and fell in the brainstem, midbrain, hippocampus, and cortex; and MAO B activity (assayed by using β‐phenylethylamine as substrate) increased in whole brain and all regions, except the brainstem. Age‐related changes in total protein, MAO A, and MAO B were thus independent of each other. Kinetic studies indicated that the Vmax of MAO B was increased in aging rat brain, whereas the Km was unaltered. The increase in MAO B activity was restricted to the extrasynaptosomal mitochondrial fraction of the aging brain, whereas a reduction in MAO A activity was found in the intrasynaptosomal, but not the extrasynaptosomal mitochondrial fraction.
Some Characteristics of the Night N‐Acetyltransferase in the Rat Pineal Gland
Authors: Vaněček Jiří , Illnerová Helena
Published: October 2006

Abstract: Following light on at night experiments, N‐acetyltransferase level declines, at first rapidly and after 20 min more slowly. We partly characterised the night N‐acetyltransferase and the residual N‐acetyltransferase 20 min after light on. Both enzymes had pH optimum 6.8 and were inactivated thermally in vitro with a half time of 8 min. Pre‐treatment with cycloheximide or puromycin did not block the rise in N‐acetyltransferase following isoprotenerol ad‐ministration shortly after light on. We propose that night N‐acetyltransferase is one enzyme. After light on, the enzyme rapidly deactivates to a less active form. Isoprotenerol applied within a short time may partly reactivate the enzyme.
Utilization of Cyclocreatine Phosphate, an Analogue of Creatine Phosphate, by Mouse Brain During Ischemia and Its Sparing Action on Brain Energy Reserves
Authors: Woznicki Dennis T. , Walker James B.
Published: October 2006

Abstract: Brains of mice fed the creatine analogue cyclocreatine accumulated 10 γmol/g fresh wt. of cyclocreatine, of which 93% occurred as the synthetic phosphagen, cyclocreatine‐P (l‐carboxymethyl‐2‐imino‐3‐phosphonoimidazolidine). In brains containing cyclocreatine‐P2‐, creatine‐P (phosphocreatine) levels were lowered 40%; levels of ATP, P1, and glucose were not altered: glutamate levels were lowered 17%: and aspartate levels were lowered 56%, relative to controls. When cyclocreatine was removed from the diet, brain cyclocreatine levels decreased with a half‐life of 17 to 28 days. Ischemia was initiated in brains by decapitation of mice previously injected with the centrally acting muscle relaxant mephenesin. The initial creatine‐P pool of 2‐3 γmol/g was completely depleted within 1 min in ischemic brains of both control and cyclocreatine‐fed mice. In brains of cyclocreatine‐fed mice, the much larger cyclocreatine‐P pool of 9.3 γmol/g decreased to 6 γmol/g after 2 min and to 2.2 γrnol/g after 4 min of ischemia, with a correspondingly increased accumulation of P1. Levels of total cellular ATP were sustained slightly longer during ischemia in brains containing cyclocreatine‐P. Available energy reserves of control brains were almost completely depleted after 2 min of ischemia, whereas generation and utilization of high‐energy phosphate continued for more than 3 min after initiation of ischemia in brains of cyclocreatine‐fed mice. These data suggest that during ischemic episodes cyclocreatine‐P can function as a supplemental reservoir of high‐energy phosphate and prolong the time required to exhaust the available energy stores of ischemic brain.
Energy Metabolism in Rat Brain Synaptosomes from Nembutal‐Anesthetized and Nonanesthetized Animals
Authors: Rafalowska Urszula , Erecińska Maria , Wilson David F.
Published: October 2006

Abstract: Cellular energetic parameters including the intramitochondrial and cytosolic [NAD+]/[NADH] ratios, the cellular [ATP]/[ADP][Pi and [creatine phosphate]/[creatine] ratios, the concentration of cytochrome c and its redox state and the respiratory rate were studied in suspensions of rat brain synapto‐somes isolated from nembutal‐anesthetized and nonanesthetized animals. The ratio of [3‐hydroxybutyrate] to [acetoacetate] was 2.0 in synaptosomes isolated from nonanesthetized rats and 5.55 in those from anesthetized animals. The [lactate]/[pyruvate] ratio was 3.8 in the former and 10.9 in the latter preparation. The [ATP]/[ADP][Pi] was 3838 M−1 in the synaptosomes from anesthetized rats and 840 M−1 in those from nonanesthetized animals and the [creatine phosphate]/[creatine] ratios were 0.79 and 0.39, respectively. Cytochrome c was about 15% reduced in both preparations; however, the mitochon‐drial cytochrome concentration was almost twofold higher in the synaptosomes from nonanesthetized animals. Calculations of the free energy relationships between the mitochondrial redox reactions and ATP synthesis showed that in synaptosomes isolated from the brains of nembutal‐anesthetized rats the first two sites of oxidative phosphorylation were at near‐equilibrium, in agreement with observations for intact cells and tissues. The energetic parameters for synaptosomes from anesthetized rats are very similar to the values for intact whole brain, whereas those for synaptosomes from nonanesthetized rats are lower and suggest that nembutal anesthesia protects against some irreversible damage to the synaptosome during isolation. It is concluded that synaptosomes isolated from brains of nembutal‐anesthetized rats can be used as a convenient model system for studies of neuronal metabolism.
Hydrogen Peroxide Production by Rat Brain In Vivo
Authors: Sinet Pierre M. , Heikkila Richard E. , Cohen Gerald
Published: October 2006

Abstract: H2 O2 production by rat brain in vivo was observed with a method based on the measurement of brain catalase. The administration to the rat of 3‐amino‐1, 2, 4‐triazole, an H2 O2‐ dependent inhibitor of catalase, caused progressive inhibition of brain catalase activity in both the supernatant and pellet fractions of homogenates of the striatum and prefrontal cortex. The prevention of catalase inhibition by prior administration of ethanol confirmed that catalase inhibition in vivo was dependent upon H2 O2. A significant portion of the catalase (30‐33%) appeared in the supernatant fraction from a slow‐speed homogenization procedure and was not significantly contaminated by either erythrocytes or capillaries. In the whole homogenate, less than 6% of the catalase activity was attributed to erythrocytes. Modification of intracellular monoamine oxidase activity by either pargyline or reserpine did not change the rate of inhibition of catalase by aminotriazole. A probable interpretation of these data is that H2 O2 generated by mitochondrial monoamine oxidase does not reach the catalase compartment; the catalase is contained in particles described by other investigators as the microperoxisomes of brain. In studies in vitro, the production of H2 O2 by rat brain mitochondria with either dopamine or serotonin as substrate was confirmed.
Identification and Properties of Methyltransferases That Synthesize Phosphatidylcholine in Rat Brain Synaptosomes
Authors: Crews Fulton T. , Hirata Fusao , Axelrod Julius
Published: October 2006

Abstract: Rat brain was found to enzymatically methylate phospholipids to form phosphatidylcholine with S‐adenosyl‐l‐methionine serving as the methyl donor. Methyltransferase activity was localized in the microsomes and synaptosomes. In synaptosomes, at least two enzymes were found to be involved in the formation of phosphatidylcholine. The first methyltransferase which catalyzes the methylation of phosphatidylethanolamine to form phosphatidyl‐N‐monomethylethanolamine was found to have a pH optimum of 7.5, a low Km for 5‐adenosyl‐l‐methionine and a partial requirement for Mg2. Methyltransferase I is tightly bound to membranes. The second methyltransferase (II) catalyzes the successive methylations of phosphatidyl‐N‐monomethylethanolamine to phosphatidyl‐N, N‐dimethylethanolamine and then to phosphatidylcholine. In contrast to methyltransferase I, methyltransferase II has a pH optimum of 10.5, a high apparent Km for S‐adenosyl‐l‐methionine and no requirement for Mg2. Methyltransferase II is easily solubilized by sonication. The highest specific activity for both enzymes was found in the synaptosomal plasma membrane.
Enhancement by Gangliosides of the Binding of Serotonin to Serotonin Binding Protein
Authors: Tamir Hadassah , Brunner William , Casper Diana , Rapport Maurice M.
Published: October 2006

Abstract: Several gangliosides, especially GD3 (disialosyllactosyl ceramide) in the presence of another lipid (lecithin) were found to enhance the binding of serotonin to serotonin binding protein (SBP) severalfold. In our conditions, this enhancement was linear to a concentration of 2.7 × 10−6I GD3 and a three‐ to fivefold increase in binding capacity of SBP was obtained with 8.8 × 10−6 M. The addition of this ganglioside led to an increase of serotonin binding sites, but not to an increase in the affinity of SBP to serotonin. Optimal binding capacity was found with a ratio of lecithin to ganglioside of 6: 1 (w/w). No binding was found in the absence of either SBP or Fe2+ (binding of serotonin to SBP is dependent on Fe2+). Other glycosphingolipids (sulfatide, GD1a, GD1b, GM1) showed lesser effects at low concentration, whereas asialo‐GM1, cytolipin H, galactocerebroside and GM3 had insignificant effects. Since earlier studies suggested a storage role for serotonin binding protein, the interaction of gangliosides with this protein may regulate the concentration of the biogenic amine in the synapse.
Uptake of Exogenous Glutamate and Aspartate by Circumventricular Organs but Not Other Regions of Brain
Authors: Price Madelon T. , Olney John W. , Lowry Oliver H. , Buchsbaum Susan
Published: October 2006

Abstract: Glutamate (Glu) and aspartate (Asp) concentrations in blood and selected regions of brain were measured at sequential intervals over a 3‐h period following subcutaneous administration of Glu, Asp, or Glu plus Asp (2 mg/g body wt) to 4‐day‐old mouse or rat pups. Marked serum elevations of the administered amino acids (peak values exceeding 200 times control levels) were detected within 1 h. In circumventricular organ (CVO) regions of brain, which are thought to have no blood‐brain barriers, a sharp and steady increase in tissue concentrations of the administered amino acids (peak values 4–10 times higher than control levels) occurred during a 15–120 min interval, whereas no appreciable increases were detected in other brain regions. When 2 mg/g Glu plus 2 mg/g Asp were administered, CVO tissue concentrations of each amino acid rose to approximately the same level obtained when the individual amino acids were given. It is concluded that blood‐brain barriers preventing net entry of Glu or Asp into brain proper are relatively well established by the 4th postnatal day in rodents, but that CVO brain regions lack such barriers; selective access of blood‐borne Glu or Asp to CVO neurons explains why these neurons are selectively destroyed by systemic administration of these neurotoxic amino acids.
Highly Sensitive Assay for Dopamine‐β‐Hydroxylase Activity in Human Cerebrospinal Fluid by High Performance Liquid Chromatography‐Electrochemical Detection: Properties of the Enzyme
Authors: Matsui Hiroaki , Kato Takeshi , Yamamoto Chosabro , Fujita Keisuke , Nagatsu Toshiharu
Published: October 2006

Abstract: This paper describes a new, sensitive assay for dopamine‐β‐hydroxylase (DBH) activity in human cerebrospinal fluid (CSF), serum and brain tissues by high performance liquid chromatography (HPLC) with electrochemical detection (ED). Dopamine (DA) was used as a substrate and was incubated under optimal conditions. Norepinephrine (NE) formed enzymatically from DA was isolated by a double‐column procedure, the first column of Dowex‐50‐H+ and the second column of aluminum oxide. NE was adsorbed on the second aluminum oxide column and then eluted with 0.5 M‐hydrochloric acid and assayed by HPLC‐ED. Epinephrine (EN) was added to each incubation mixture as an internal standard, and this assay was therefore highly reproducible. The peak height in HPLC was linear from 500 fmol to 100 pmol of NE and EN. The lower limit of detection for NE formed enzymatically was about 30 pmol, which indicated that the sensitivity of this procedure was comparable to that of radioassay procedures. We applied the method to measurement of the activity of and examination of some of the characteristics of DBH in human CSF. DBH activity in CSF of Parkinsonian patients was lower than that of control patients. The properties of DBH in human CSF were similar to those in serum and adrenal medulla.
Postnatal Development of Synaptic Glycine Receptors in Normal and Hyperglycinemic Rats
Authors: Benavides J. , López‐Lahoya J. , Valdivieso F. , Ugarte M.
Published: October 2006

Abstract: The postnatal development of glycine synaptic receptors has been studied. Strychnine binding to the synaptic membrane fraction is very low at birth, increases thereafter, and reaches adult values at the 15th day in the brain, and at the 30th day in the spinal cord. Throughout postnatal development, there are more glycine receptors in the spinal cord than in the brain. The development of receptors in the spinal cord displays a pattern similar to that reported previously for the glycine reuptake system in spinal cord slices and in the activity of spinal cord glycine synthase. In rats with experimental hyperglycinemia, strychnine binding to spinal cord glycine receptors increases much more rapidly, reaching a level 1.5 times the control value by day 10. When the hyperglycinemia was induced after the 10th postnatal day, however, no effect on the glycine receptors was observed. This increased number of receptors could be explained by an effect of glycine on the synaptic stabilisation process. No changes in the KD for strychnine were observed either during postnatal development or in hyperglycinemic rats. The KD remained approximately 10 nM in the spinal cord and 50 nM in the brain. Results are discussed with respect to the ontogeny of glycinergic synapses and the pathogenesis of nonketotic hyperglycinemia.
Phosphorylation of Adrenal Medulla Cell Proteins in Conjunction with Stimulation of Catecholamine Secretion
Authors: Amy Christopher M. , Kirshner Norman
Published: October 2006

Abstract: Enhanced phosphorylation of two specific protein bands accompanied catecholamine secretion from cultured bovine adrenal medulla cells stimulated by different secretagogues. Cells preincubated with 32Pi were treated with nicotine, veratridine, Ionomycin, or barium. Each of these secretagogues stimulated the phosphorylation of two protein bands with apparent molecular weights of 60,000 and 95,000. Phosphorylation of the 60,000 M.W. protein band was two‐ to threefold higher than that of the 95,000 M.W. band on stimulation with nicotine, veratridine, or barium, but Ionomycin stimulated phosphorylation of each protein band to the same extent. In general, the increase in phosphorylation was most rapid during the first minute of stimulation and occurred prior to detectable secretion. Phosphorylation reached a relatively constant level within 5 min after onset of stimulation at a time when catecholamine release was still proceeding at a rapid rate. Nicotine‐stimulated phosphorylation and catecholamine secretion were calcium‐dependent and blocked by d‐tubocurarine, whereas tetrodotoxin inhibited veratridine‐stimulated secretion and phosphorylation. We conclude that catecholamine secretion and protein phosphorylation occur under similar conditions and that Ca2+‐dependent incorporation of phosphate into specific proteins may be a link in stimulus‐secretion coupling.
Adenosine and Cyclic AMP in Rat Cerebral Cortical Slices: Effects of Adenosine Uptake Inhibitors and Adenosine Deaminase Inhibitors
Authors: Nimit Y. , Skolnick P. , Daly J. W.
Published: October 2006

Abstract: The endogenous levels of adenosine functionally linked to cyclic AMP systems in rat cerebral cortical slices are regulated by both adenosine deaminase and adenosine uptake systems. 2′‐Deoxycoformycin (2′‐DCF), an adenosine deaminase inhibitor, slightly increased basal, adenosine, and norepinephrine‐elicited accumulations of cyclic AMP, whereas dipyridamole, an uptake inhibitor, had an even greater effect on cyclic AMP accumulations under the same conditions. Combinations of 2′‐DCF and dipyridamole elicited a greater effect than either compound alone. Neither 2′‐DCF nor dipyridamole significantly augmented accumulations of cyclic AMP elicited by a depolarizing agent, veratridine, suggesting that the adenosine “released” during neuronal depolarization of brain slices is not as subject to inactivation by uptake or deamination as endogenous adenosine in control brain slices. The accumulation of cyclic AMP elicited by a combination of norepinephrine and veratridine was greater than additive. The response to a pure β‐adrenergic agonist, isoproterenol, was not potentiated by 2′‐DCF, dipyridamole, or veratridine, consonant with minimal interaction of endogenous adenosine with β‐adrenergic systems.
Brain Carbohydrate Metabolism in Developing Rats During Hypercapnia
Authors: Miller Alexander L. , Corddry David H.
Published: October 2006

Abstract: Brain glucose metabolism was studied in developing rats at ages 10 and 20 days postnatal under normal and hypercapnic conditions. Brains were removed and frozen within 1 s with a freeze‐blowing apparatus. Glucose utilization was measured with [2‐14C]glucose and [3H]deoxyglucose as tracers. Metabolites were determined by standard enzymatic techniques. Data from [3H]deoxyglucose phosphorylation indicated that normal brain glucose utilization increased almost threefold between the 10th and 20th postnatal days. From the relative rates of utilization of the two isotopes in the 20‐day‐old control group, it appeared that about 25% of 14C label derived from metabolism of [2‐14C]glucose was lost from brain (probably as lactate) rather than entering the Krebs cycle. Under hypercapnic conditions (20% CO2‐21% O2‐59% N2), rates of glucose utilization by brain were decreased by one‐half at both ages and there were progressive decreases in the concentrations of many intermediary metabolites. The bases for concluding that these metabolites were used to supplement glucose as a fuel for respiration, rather than being lost by leakage into blood, are discussed. Despite the differences in brain glucose metabolism between 10‐day‐old and 20‐day‐old rats, their responses to hypercapnia are remarkably similar: Rates of glucose utilization are reduced to approximately the same proportion of the original rate by 20% CO2, and endogenous metabolites (particularly glutamate and lactate) appear to be oxidized as replacement fuels.
Protein Synthesis in Rat Brain Microvessels Decreases with Aging
Authors: Gozes Illana , Cronin Brenda L. , Moskowitz Michael A.
Published: October 2006

Abstract: The synthesis of protein by brain microvessels prepared from rats 4, 15, and 21 months of age was examined in organ culture. The rate of [35S]methionine incorporation into trichloroacetic acid‐insoluble protein was lower in the vessels from older animals. These decreases were not dependent on the concentration of added methionine. Differences in protein synthesis could not be accounted for by specific peptidases in the incubation mixture. Polypeptide bands corresponding to actin and to the heavy and light chains of myosin were observed among the newly synthesized proteins following electrophoresis and autoradiography of the incubation mixture on polyacrylamide gels. The pattern of proteins synthesized, however, did not appear to vary significantly between young and old animals. Age‐related decreases in the synthesis of vascular proteins may contribute, in part, to some of the changes in the mechanical and functional properties of blood vessels during aging.
Intracellular Localization of 2′,3′‐Cyclic Nucleotide 3′‐Phosphodiesterase in a Neuronal Cell Line as Examined by Immunofluorescence and Cell Fractionation
Authors: Mülller Hans Werner , Clapshaw Patric A. , Seifert Wilfried
Published: October 2006

Abstract The enzyme 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase (CNPase, EC 3.1.4.37) occurs not only in myelin fractions and glial cells, but can also be shown to be present in a CNS cell line of neuronal origin (B104). Direct immunofluorescence microscopy of B104 cells with fluorescein isothiocyanate‐conjugated rabbit anti‐CNPase antibodies shows a discrete and specific intra‐cytoplasmic location of CNPase. Fractionation of the cells was performed by differential centrifugation of a cell homogenate and continuous sucrose density‐gradient centrifugation. As monitored by marker enzyme activities, CNPase seems to be associated with endoplasmic reticulum membranes.
Determination of the Equilibrium Dissociation Constants and Number of Glycine Binding Sites in Several Areas of the Rat Central Nervous System, Using a Sodium‐Independent System
Authors: Kishimoto Hideji , Simon J. R. , Aprison M. H.
Published: October 2006

Abstract Parameters affecting the binding of [3H]glycine to membrane fractions isolated from the cerebral cortex, midbrain, cerebellum, medulla oblongata, and spinal cord of the rat were investigated in a Na+‐free medium. A [3H]glycine binding assay was established in which the binding was specific, saturable, pH‐sensitive, and reversible. Conditions were chosen in an effort to minimize binding to glycine uptake sites. From data on specific [3H]glycine binding, Scatchard plots were prepared and the KD and Bmax values were calculated. Two glycine binding sites (high and low affinity) were identified only in the medulla (KD: 44, 211 nM; Bmax: 361, 1076 fmol/mg protein) and spinal cord (KD: 19, 104nM;Bmax: 105, 486 fmol/mg protein). The ranges of the KD and Bmax values for the other three areas studied were 59 to 144 nM and 882 to 3401 fmol/mg protein, respectively. When the glycine content of each area, expressed as fmol/neuron, was plotted against the respective K0 (high affinity), a negative correlation was found (r=−0.90; p < 0.05). A similar negative correlation was found between the glycine content and Bmax (r=−0.88; p <0.05). Hill plots indicated a slope of essentially 1.0 for all areas. GABA, taurine, strychnine, diazepam, bicuculline, and imipramine had little or no effect on [3H]glycine binding.
Nature of the Autofluorescent Material in Cerebrocortical Necrosis
Authors: Edwin E. E. , Jackman R.
Published: October 2006

A distinctive autofluorescence under ultraviolet light has been observed in the cerebral cortex of young ruminants suffering from cerebrocortical necrosis. The fluorescence is intimately connected with structural elements of the brain and cannot be extracted into solvents by normal procedures. The work presented here shows it to be associated with a collagen‐like material.
Micro topography of Tyrosine Hydroxylase, Glutamic Acid Decarboxylase, and Choline Acetyltransferase in the Substantia Nigra and Ventral Tegmental Area of Control and Parkinsonian Brains
Authors: Javoy‐Agid F. , Ploska A. , Agid Y.
Published: October 2006

Abstract— Tyrosine hydroxylase (TH), glutamic acid decarboxylase (GAD), and choline acetyl transferase (CAT) were used as markers for catecholamine, γ‐aminobutyric acid, and acetylcholine containing neurons in human mesencephalon. Their rostrocaudal, mediolateral, and dorsoventral distribution was investigated within the substantia nigra pars compacta (SNC) and pars reticulata (SNR) and in the ventral tegmental area (VTA). TH activity was highest in the caudal, medial, and ventral SNC and in the middle of VTA medioventrally. The enzyme activity in SNR was low and uniformly distributed. In SNC as well as SNR, GAD activity was high and greater laterally and in the middle of the rostro‐caudal extent. No particular pattern of distribution was observed in VTA, an area with low GAD content. In the substantia nigra, CAT activity was low. A characteristic medio‐ventral distribution with a peak of high enzyme activity in the middle of the rostrocaudal extent was observed. In VTA, enzyme levels were high and also concentrated medio‐ventrally and in the middle of the area. In parkinsonian brains, the distribution of TH was uniformly affected throughout the rostro‐caudal extent. In VTA the enzyme activity was not as reduced as in SNC and SNR; the CAT pattern was only disrupted in a very localized part of SNC but not in SNR and VTA. In all three areas, GAD activity was reduced to a uniformly low distribution.
The Extraneural Distribution of γ‐Hydroxybutyrate
Authors: Nelson Thomas , Kaufman Elaine , Kline John , Sokoloff Louis
Published: October 2006

Abstract— γ‐Hydroxybutyrate has been found to be widely distributed in both neural and extraneural tissues in the rat. The kidney and brown fat have more than 10 times higher concentrations of y‐hydroxybutyrate than does the brain. This observation suggests that γ‐hydroxybutyrate may participate in the metabolism of many organs, and that GABA may not be the precursor in extraneural tissues.
Uptake of 36Cl and 22Na by the Brain‐Cerebrospinal Fluid System: Comparison of the Permeability of the Blood‐Brain and Blood‐Cerebrospinal Fluid Barriers
Authors: Smith Quentin R. , Johanson Conrad E. , Woodbury Dixon M.
Published: October 2006

Abstract: Transport and permeability properties of the blood‐brain and blood‐CSF barriers were determined by kinetic analysis of radioisotope uptake from the plasma into the CNS of the adult rat. Cerebral cortex and cerebellum uptake curves for 36Cl and 22Na were resolved into two components. The fast component (t½ 0.02–0.05 h, fractional volume 0.04–0.08) is comprised of the vascular compartment and a small perivascular space whereas the slow component (t½ 1.06–1.69 h, fractional volume 0.92–0.96) represents isotope movement across the blood‐brain barrier into the brain extracellular and cellular compartments. Uptake curves of both 36Cl and 22Na into the CSF were also resolved into two components, a fast component (t½ 0.18 h, fractional volume 0.24) and a slow component (t½ 1.2 h, fractional volume 0.76). Evidence suggests that the fast component represents isotope movement across the blood‐CSF barrier, i.e., the choroid plexuses, whereas the CSF slow component probably reflects isotope penetration primarily from the brain extracellular fluid into the CSF. The extracellular fluid volume of the cerebral cortex and cerebellum was estimated as ˜13% from the initial slope of the curve of brain space versus CSF space curve for both 36Cl and 22Na. Like the choroid plexuses, the glial cell compartment of the brain appears to accumulate Cl from 2 to 6 times that predicted for passive distribution. The relative permeability of the blood‐CSF and blood‐brain barriers to 36Cl, 22Na, and [3H]mannitol was determined by calculating permeability surface‐area products (PA). Analysis of the PA values for all three isotopes indicates that the effective permeability of the choroidal epithelium (blood/CSF barrier) is significantly greater than that of the capillary endothelium in the cerebral cortex and cerebellum (blood‐brain barrier).
The Cytoskeleton of Primary Astrocytes in Culture Contains Actin, Glial Fibrillary Acidic Protein, and the Fibroblast‐Type Filament Protein, Vimentin
Authors: Chiu Fung‐Chow , Norton William T. , Fields Kay L.
Published: October 2006

Abstract: Primary astrocytes were cultured from the forebrains of 1‐day‐old rats. Immunofluorescence microscopy showed that approximately 80% of the cells were positive for glial fibrillary acidic protein (GFAP) and >80% were stained with an antiserum to the molecular weight 58,000 fibroblast intermediate filament protein (vimentin). Gel electrophoresis of Triton‐insoluble cytoskeleton preparations from these cultures revealed three major bands having molecular weights of 58,000, 51,000, and 42,000, together with some prominent lower‐molecular‐weight species. The protein of molecular weight 51,000 was not present in preparations from fibroblasts. Each of the three major astrocyte proteins was subjected to limited proteolysis, while two of the proteins were cleaved by cyanogen bromide. The electrophoretic peptide patterns of the 58,000 protein were similar to those of vimentin isolated from NIL‐8 fibroblasts, and the patterns of the 51,000 protein were similar to those of GFAP isolated from rat spinal cord. The patterns of the protein of molecular weight 42,000 resembled those of muscle actin. Rocket immunoelectrophoresis showed that the 51,000 astrocyte protein reacted with an antiserum to bovine GFAP, but the 58,000 and 42,000 proteins failed to react. We conclude that the major proteins of cytoskeleton preparations from cultured primary astrocytes are vimentin (58,000), GFAP (51,000), and actin (42,000), and that our data show no obvious structural relationship among them.
Continuous Determination by a Chemiluminescent Method of Acetylcholine Release and Compartmentation in Torpedo Electric Organ Synaptosomes
Authors: Israël Maurice , Lesbats Bernard
Published: October 2006

Abstract: The detection of acetylcholine (ACh) with a chemiluminescent procedure enables one to follow continuously the release of transmitter from stimulated synaptosomes and to study the compartmentation of ACh in resting and active nerve terminals. A compartment of ACh liberated almost entirely by a single freezing and thawing could be directly measured and compared with a compartment of ACh resistant to several cycles of freezing and thawing but liberated by a detergent (60–70% of the total). It is the compartment liberated by freezing and thawing that is reduced when synaptosomes are stimulated. Up to half the total synaptosomal ACh content is readily releasable provided the calcium entry is maintained, or if a strong releasing agent such as the venom of Glycera convoluta is used. In addition, it is shown that synaptosomes contain only negligible amounts of choline, and that the proportion of the two ACh compartments is not influenced by changing extracellular calcium just before their determination.
Competitive Inhibition of Rat Brain Hexokinase by 2‐Deoxyglucose, Glucosamine, and Metrizamide
Authors: Bertoni John M.
Published: October 2006

Abstract: The effects of metrizamide on the kinetics of rat brain hexokinase were compared in vitro with those of 2‐deoxyglucose and glucosamine. Although metrizamide, 2‐deoxyglucose, and glucosamine are known to be competitive inhibitors of approximately equal potency for glucose of yeast hexokinase (K1 approximately 0.7 mm for all three), metrizamide is a much weaker competitive inhibitor (Ki about 20 mm) of rat brain hexokinase than either 2‐deoxyglucose or glucosamine (Ki about 0.3 mm for both). This indicates a greater active site specificity of rat brain hexokinase than of yeast hexokinase. Rat brain hexokinase activity is enhanced approximately threefold in the presence of 0.05, 0.2, and 0.8 mg/ml bovine serum albumin, while yeast hexokinase is only enhanced by 50% under these conditions. Despite the high Ki value for metrizamide, interference with glucose metabolism may occur whenever metrizamide is present in much higher concentrations than glucose. Myelography in humans is one such situation.
Opiate Receptor‐Mediated Inhibition of Adenylate Cyclase in Rat Striatal Plasma Membranes
Authors: Cooper Dermot M. F. , Londos Constantine , Gill Donald L. , Rodbell Martin
Published: October 2006

Abstract: Plasma membranes from rat striatum contain adenylate cyclase activity that is subject to dual regulation by GTP. Low concentrations (up to 30 nM) of the nucleotide increase activity whereas higher concentrations evoke a steady decline in activity; such behavior characterizes dually regulated adenylate cyclase systems. The opiates, morphine sulfate and D‐Ala‐Met‐enkephalin, produce naloxone‐reversible inhibition of the enzyme that is dependent on “inhibitory concentrations” of GTP (above 50 nM). In the absence of GTP no inhibition is observed. Sodium ions decrease the inhibition of activity promoted by GTP alone, but amplify the degree of inhibition seen in the presence of the opiates and GTP. The potencies of the opiates in mediating these effects mirror their affinities for 8 opiate receptors in striatum. It is suggested that this action of the opiates may represent their primary action in striatum.
Aminergic Receptors in Drosophila melanogaster: Responsiveness of Adenylate Cyclase to Putative Neurotransmitters
Authors: Uzzan Anat , Dudai Yadin
Published: October 2006

Abstract: Adenylate cyclase in Drosophila melanogaster heads is stimulated 5–6‐fold by low concentrations of octopamine. The octopamine stimulation is inhibited by low concentrations of the α‐adrenergic ligands phentolamine and dihydroergotamine and of chlorpromazine, but not by low concentrations of the β‐antagonist propranolol and by the α‐antagonist yohirnbine. d‐Tubocurarine enhances the octopamine effect. Tyramine, norepinephrine, and epinephrine also stimulate the cyclase, probably via the octopamine receptor. Serotonin and dopamine stimulate Drosophila adenylate cyclase 1.3‐1.4‐fold; at least the latter putative neurotransmitter seems to interact with a receptor distinct from the octopamine receptor. Prolonged incubation with dopamine in vitro abolishes adenylate cyclase basal activity as well as responsiveness to guanyl nucleotides, NaF, and putative neurotransmitters.
Effects of Iron Deficiency on Serotonin Uptake In Vitro by Rat Brain Synaptic Vesicles
Authors: Kaladhar M. , Rao B. S. Narasinga
Published: October 2006

Abstract: The effects of moderate and severe degrees of iron deficiency on brain and liver nonhaem iron levels and 5‐hydroxytryptamine (serotonin; 5‐HT) uptake by synaptic vesicles in vitro were investigated in experimental rats. Data obtained suggested that in both moderate and severe forms of iron deficiency, 5‐HT uptake by brain synaptic vesicles is decreased and is accompanied by a reduction in brain and liver nonhaem iron levels. On repletion with iron for 4 weeks, the deficient group of rats showed a normalisation of 5‐HT uptake by synaptic vesicles and liver nonhaem iron content, whereas the brain nonhaem iron concentration still showed a significant deficit. The data thus suggest that changes in the uptake of 5‐HT by brain synaptic vesicles that accompany iron depletion and repletion are more rapid than changes in the total nonhaem iron concentration in the brain. The observation that 5‐HT uptake by brain synaptic vesicles is decreased in iron deficiency suggests a probable role for iron in 5‐HT storage in rat brain.