bluuebunny/crossref_metadata_2025 huggingface dataset:
BIOCHEMICAL CORRELATES OF TRANSMISSION MEDIATED BY GLUTAMATE AND ASPARTATE
Authors: Nadler J. V. , White W. F. , Vaca K. W. , Perry B. W. , Cotman C. W.
Published: December 2006

Abstract— Glutamate and aspartate probably serve as transmitters of hippocampal perforant path and commissural afferents, respectively. We therefore used slices of hippocampal regions to evaluate certain biochemical properties as markers for sites of transmission mediated by these amino acids. In these studies content and accumulation of glutamate and aspartate were compared with their Ca2+‐dependent effluxes.

Hippocampal regions varied little in their contents of glutamate and aspartate, but slices of regio superior and dentate gyrus accumulated and released more of each than slices of regio inferior. A commissurotomy or bilateral entorhinal lesion altered Ca2+‐dependent efflux and accumulation in the same direction, but did not affect the glutamate or aspartate content of any hippocampal region. Elimination of hippocampal mossy fibers reduced the Ca2+‐dependent efflux of glutamate and probably aspartate from slices of dentate gyrus, but not of regio inferior, where most mossy fiber synapses are located. The mossy fibers appeared relatively deficient in aspartate in both strains tested, but only in Purdue‐Wistar rats were they enriched in glutamate. Removal of the perforant path input to the fascia dentata did not significantly change the activity of any of the enzymes most actively involved in glutamate synthesis.

These results suggest that accumulation or high affinity transport of glutamate or aspartate can be employed to localize afferents which use these amino acids as transmitters, although it is not so reliable or selective a marker as Ca2+‐dependent efflux. Enrichment in either glutamate or aspartate content or in the activity of enzymes which synthesize them is not a reliable marker. Neither amino acid is likely to be used as a transmitter by the hippocampal mossy fibers.
A COMPARISON OF THE AXONAL TRANSPORT OF TAURINE AND PROTEINS IN THE GOLDFISH VISUAL SYSTEM
Authors: Ingoglia N. A. , Sturman J. A. , Rassin D. K. , Lindquist T. D.
Published: December 2006

Abstract— Radioactive cystathionine, a metabolic precursor of taurine, was injected into the right eye of goldfish. At various times after injection the retina and both optic tecta were extracted with trichloroacetic acid (TCA) and the amount and nature of the radioactivity was determined. Radioactive taurine and inorganic sulfate were present in the TCA‐soluble extract of retina and radioactive taurine and a small amount of inorganic sulfate was found in the contralateral optic tectum. That taurine is migrating intraaxonally and is not diffusing in extraaxonal spaces is suggested from experiments in which the migration of taurine was compared with that of [14C]mannitol, used here as a marker of extracellular diffusion. In the time studied (up to 15 h) mannitol did not migrate to the tectum, whereas taurine was detectable in the tectum as early as 8 h after injection. Since intra‐axonal diffusion of amino acids and other small molecules in this system has been ruled out, it is likely that taurine is being transported axonally.

The axonal transport of taurine was found to be similar to the fast component of protein transport because: (1) their rates of transport are similar, (2) the transport of both is blocked by the protein synthesis inhibitor cycloheximide, (3) vinblastine, which disrupts neurotubules, appears to have similar effects on both protein and taurine transport, and (4) both rapidly transported proteins and taurine remain mostly intra‐axonal once they have been transported to the tectum. Taurine and proteins differ in that rapidly transported proteins are primarily paniculate in nature and localized to a large extent in nerve endings, while taurine is primarily in a soluble fraction and is present in nerve endings only in trace amounts.

We suggest that taurine may be loosely linked to a newly synthesized protein in the soma and is then transported along with that protein on a similar conveying mechanism in the axoplasm.
DEMONSTRATION OF HIGH AFFINITY HEXOSE UPTAKE IN CEREBRAL CORTEX SLICES
Authors: Fletcher A. M. , Bachelard H. S.
Published: December 2006

Abstract— The high‐affinity glucose transport system (Km 0.2–0.4 mm), previously detected in synaptosome preparations, has now been demonstrated to be present in slices of the cerebral cortex incubated in vitro. The kinetic properties of this undirectional uptake process in slices were similar to those exhibited by synaptosomes. The results are discussed with respect to the possible sites of the high affinity and low affinity glucose transport processes in the brain.
DISSOCIATION OF THE REGULATION OF FATTY ACID SYNTHESIS AND CYCLIC AMP LEVELS IN CULTURED GLIAL AND NEURONAL CELLS1
Authors: Volpe J. J. , Marasa J. C.
Published: December 2006

Abstract— Cultured C‐6 glia and neuroblastoma were utilized to investigate the relation of rates of fatty acid synthesis (from 3H2O) to levels of cyclic AMP under conditions of short‐term and long‐term regulation. The data demonstrate a consistent dissociation of alterations in rates of fatty acid synthesis and levels of cyclic AMP. Thus, marked alterations in the rate of fatty acid synthesis occurred when serum or albumin‐bound palmitic acid was present in the culture medium, but there were no accompanying alterations in levels of cyclic AMP. Similarly, when high intracellular and/or extracellular levels of cyclic AMP were induced by exposure of the cells to dibutyryl cyclic AMP or isoproterenol, no change in the rate of fatty acid synthesis occurred. Although the data raise serious doubt about an important role for cyclic AMP in the regulation of fatty acid synthesis, they do not rule out such a role. The findings do indicate that any such role must involve alterations in compartmentalization, metabolism or binding of the mononucleotide within the cell.
EVALUATION OF IN SITU FREEZING OF CAT BRAIN BY NADH FLUORESCENCE
Authors: Welsh F. A. , Rieder W.
Published: December 2006

Abstract— Cat brain was frozen in situ with liquid nitrogen. In order to locate areas with ischemic artifact, frozen brain slices were surveyed for regions of increased NADH fluorescence. In addition, levels of ATP, phosphocreatine, lactate, and NADH were determined in various brain regions. High levels of ATP and phosphocreatine, and low levels of lactate and NADH were present in all brain regions except the depths of some cortical sulci. These regions of ischemic change were easily detected by virtue of increased NADH fluorescence in frozen brain slices. Deep brain structures such as basal ganglia and hippocampus showed neither high tissue fluorescence nor ischemic changes of the metabolites measured. Therefore, in situ freezing of cat brain adequately preserves metabolite levels in most regions.
EFFECT OF OLIGEMIA ON REGIONAL METABOLITE LEVELS IN CAT BRAIN
Authors: Welsh F. A. , O'Connor M. J. , Marcy V. R.
Published: December 2006

Abstract— Incomplete cerebral ischemia (oligemia) was produced in cat by carotid occlusion combined with arterial hypotension. Lowering arterial pressure to 50–60 Torr for 20 min caused marked alterations of the ATP, phosphocreatine, and lactate content of subcortical white matter. In contrast, metabolite levels in cerebral cortex and caudate nucleus were only moderately perturbed from control values. More severe oligemia resulted when arterial pressure was lowered to 30 Torr for 20 min following carotid occlusion. Metabolite levels in cortex, caudate nucleus, and white matter were greatly altered from control. In the gray matter there was regional heterogeneity of metabolic alteration, as evidenced from the pattern of NADH tissue fluorescence. The cortex contained micro‐patches (0.1mm) of increased NADH, which frequently exhibited a columnar orientation.

These findings demonstrate two distinct types of cerebral inhomogeneity of metabolic failure with reduced blood flow; white matter fails before gray matter, and there is micro‐heterogeneity of metabolic failure in the gray matter.
THE DISTRIBUTION OF CYCLIC NUCLEOTIDE PHOSPHODIESTERASE IN THE HYPOTHALAMUS
Authors: Howlet Allyn C. , Breckenridge Bruce McL.
Published: December 2006

Abstract— Quantitative measurements of capacities of microgram‐sized samples of tissue to hydrolyze adenosine 3′,5′‐phosphate (cyclic AMP) and guanosine 3′,5′‐phosphate (cyclic GMP) have been made in 32 discrete regions of the rabbit hypothalamus. The capacities to hydrolyze the two cyclic nucleotides were found to be distributed over a 3‐fold range and to vary in parallel from region to region. Notable exceptions, however, were observed. A positive association was found between the capacity to hydrolyze cyclic AMP and the reported density of catecholaminergic innervation. No clear relationship was observed between the distributions of the cyclic nucleotide phosphodiesterase activities and that of other enzymes and neurotransmitters.
Dopamine Metabolism and Receptor Function After Acute and Chronic Ethanol
Authors: Reggiani A. , Barbaccia M. L. , Spano P. F. , Trabucchi M.
Published: December 2006

Abstract: Acute ethanol treatment in rats elicits a selective increase in dihydroxyphenylacetic acid (DOPAC) content in striatum. In contrast, striatal DOPAC concentration does not differ from normal values after chronic ethanol treatment. Chronic administration of ethanol however causes a selective increase of specific [3H]spiroperidol binding and met‐enkephalin content in the striatum. Kinetic analysis of [3H]spiroperidol binding data shows that after chronic ethanol treatment there is a significant increase in the affinity constant rather than in the number of binding sites for the ligand. Our results support the hypothesis that dopaminergic mechanisms at both pre‐ and postsynaptic level may be involved in the mediation of some of the central effects observed after ethanol consumption.
Localization of Hexokinase in Neural Tissue: Immunofluorescence Studies on the Developing Cerebellum and Retina of the Rat
Authors: Simurda Maryanne , Wilson John E.
Published: December 2006

Abstract: Antiserum against purified rat brain hexokinase (ATP: D‐hexose 6‐phosphotransferase, EC 2.7.1.1) has been used in a study of the distribution of hexokinase during the postnatal development of rat cerebellum and retina. The cells of the external germinal layer of the cerebellum exhibit little or no fluorescence. The Purkinje cells exhibit a transient increase in hexokinase levels between 2 and 8 days postnatally, followed by a precipitous decrease (8–12 days) to the relatively low levels found in the mature Purkinje cell. Development of the intensely fluorescent cerebellar glomeruli in the granule cell layer is readily followed during the 3rd and 4th weeks postnatally. With respect to postnatal changes in hexokinase distribution of the retina, perhaps most notable is the observation that even the cytoplasmic protrusions which represent the precursors of the photoreceptor segments are richly endowed with hexokinase. Biochemical differentiation of the photoreceptor segments into hexokinase‐rich inner segments and hexokinase‐poor outer segments is readily observed long before the growth of the photoreceptor segments has been completed.
Effects of Branched‐Chain L‐Amino Acids, L‐Phenylalanine, and L‐Methionine on the Transport of L‐Glutamine in Rat Brain Cortex In Vitro. Influence of Cations
Authors: Benjamin A. M. , Verjee Z. H. , Quastel J. H.
Published: December 2006

Abstract: Uptake of L‐glutamine (2 mM) by rat brain cortex slices against a concentration gradient is markedly inhibited (40%) by branched‐chain Lamino acids (1 mM), L‐phenylalanine (1 mM), or L‐methionine (1 mM); that of L‐asparagine (2 mM) is much less affected by these amino acids. Other amino acids investigated have little or no effect on cerebral L‐glutamine uptake. The suppressions of L‐glutamine uptake by the inhibitory amino acids are apparently blocked by high [K+], which itself has little or no effect on glutamine uptake. This abolition of suppression is partly explained by high [K+] retention of endogenous glutamine; in the absence of Ca2+ such retention disappears. The inhibitory amino acids (1 mM) also enhance the release of endogenous glutamine, exogenous glutamine with which slices have been loaded, or glutamine synthesized in the slices from exogenous glutamate. The enhanced release of endogenous glutamine is diminished by high [K+]. The suppression of glutamine uptake by the branched‐chain amino acids is independent of the concentration of glutamine at low concentrations (0.25–0.5 mM), indicating non‐competition, but is reduced with high concentration of glutamine. The inhibition by L‐phenylalanine is noncompetitive. L‐Glutamine (2 mM) exerts no inhibition of the cerebral uptakes of the branched‐chain L‐amino acids or Lphenylalanine (0.25–2 mM). The inhibitory amino acids are as active in suppressing L‐glutamine uptake with immature rat brain slices as with adult, although the uptake, against a gradient, of L‐glutamine in the infant rat brain is about one‐half that in the adult. They are also just as inhibitory on the concentrative uptake of L‐glutamine by a crude synaptosomal preparation derived from rat brain cortex. Such a nerve ending preparation takes up L‐glutamine (0.25 mM), against a gradient, at about ninefold the rate at which it is taken up by cortex slices (for equal amounts of protein), and the uptake process is markedly suppressed by high [K+] in contrast to the effects of high [K+] with slices. The possible physiological and pathological consequences of the suppression of glutamine uptake are discussed.
The Synthesis and Possible Transport of Specific Proteins by Cells Associated with Brain Capillaries
Authors: White Fredric P.
Published: December 2006

Abstract: Vinblastine causes alterations in the subcellular distribution of certain proteins synthesized by telencephalon slices. Proteins in various subcellular fractions were separated according to their molecular weight by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis, and radioactive proteins were determined by autofluorography. A microvascular fraction contained very high amounts of radioactivity in proteins with a molecular weight of 71,000. At least one of these proteins accumulated in the microvascular fraction when the telencephalon slices were incubated in vinblastine. At the same time these proteins became depleted in a myelinated axon fraction, microsomal fraction, and soluble/cytosol fraction. Vinblastine also affected the subcellular distribution of some proteins with a molecular weight below 27,000, but unlike the proteins of mol. wt. 71,000 none of these were synthesized at very high rates. Vinblastine did not effect the synthesis of protein in telencephalon slices, nor did it alter the subcellular fractionation of particles and organelles from slices. It is suggested that a non‐neuronal vinblastine‐sensitive protein translocation system is functioning within the cells of the microvascular network in telencephalon slices, and that at least one protein of 71,000 molecular weight and one protein with a molecular weight below 27,000 are transported on this system.
Stimulation of Ornithine Decarboxylase Activity in Neural Cell Culture: Potential Role of Insulin
Authors: Parker Keith , Vernadakis Antonia
Published: December 2006

Abstract: Age‐dependent decreases in the levels of ornithine decarboxylase activity were observed in the optic lobes, cerebral hemispheres, and midbrain‐diencephalon of 6–17‐day‐old chick embryos. In dissociated cell cultures from chick embryonic brains a similar pattern of declining ornithine decarboxylase activity with time in culture was observed. Ornithine decarboxylase activity in the dissociated brain cell cultures was stimulated by changing the culture medium. The peak stimulatory effect was shown to occur 12 h after changing the medium. Although serum‐free medium stimulated ornithine decarboxylase activity slightly, the presence of serum in the medium was the primary stimulatory factor. Both fetal calf serum and heat‐inactivated fetal calf serum produced dose‐dependent stimulation of ornithine decarboxylase activity. Dialyzed fetal calf sera stimulated ornithine decarboxylase, but to a lower level than that produced by nondialyzed sera. Insulin (0.5–10 μg/ml) stimulated ornithine decarboxylase activity in a dose‐dependent manner in serum free medium. In addition, 102 M‐L‐asparagine stimulated ornithine decarboxylase activity in serum‐free medium.
Effects of Detergents, Proteins, and Lipids on 2′:3′‐Cyclic‐Nucleotide 3′‐Phosphodiesterase Activity
Authors: Clapshaw Patric A. , Seifert Wilfried
Published: December 2006

Abstract: The myelin marker 2′:3′‐cyclic‐nucleotide 3′‐phosphodiesterase (CNPase) was isolated to a lipid‐ and phosphate‐free stage. The effects of exogenously added lipids were tested on this preparation and compared to the known stimulation of the enzyme by detergents and proteins. CNPase could be stimulated 2–3 fold by these various agents which appeared to be additive in their effect. Enzyme‐protein and enzyme‐lipid interactions and possible medical use of the improved assay conditions for CNPase employed in the study are discussed.
Riboflavin Homeostasis in the Central Nervous System
Authors: Spector Reynold
Published: December 2006

Abstract: The mechanisms by which riboflavin, which is not synthesized in mammals, enters and leaves brain, CSF, and choroid plexus were investigated by injecting [14C]riboflavin intravenously or intraventricularly. Tracer amounts of [14C]riboflavin with or without FMN were infused intravenously at a constant rate into normal, starved, or probenecid‐pretreated rabbits. At 3 h, [14C]riboflavin readily entered choroid plexus and brain, and, to a much lesser extent, CSF. Over 85% of the [14C]riboflavin in brain and choroid plexus was present as [14C]FMN and [14C]FAD. The addition of 0.2 mmol/kg FMN to the infusate markedly depressed the relative entry of [14C]riboflavin into brain, choroid plexus, and, less so, CSF, whereas starvation increased the relative entry of [14C]riboflavin into brain and choroid plexus. After intraventricular injection (2 h), most of the [14C]riboflavin was extremely rapidly cleared from CSF into blood. Some of the [14C]riboflavin entered brain, where over 85% of the 14C was present as [14C]FMN plus [14C]FAD. The addition of 1.23μmol FAD (which was rapidly hydrolyzed to riboflavin) to the injectate decreased the clearance of [14C]riboflavin from CSF and the phosphorylation of [14C]riboflavin in brain. Probenecid in the injectate also decreased the clearance of [14C]riboflavin from CSF. These results show that the control of entry and exit of riboflavin is the mechanism, at least in part, by which total riboflavin levels in brain cells and CSF are regulated. Penetration of riboflavin through the blood‐brain barrier, saturable efflux of riboflavin from CSF, and saturable entry of riboflavin into brain cells are three distinct parts of the homeostatic system for total riboflavin in the central nervous system.
Metabolic Disposition of Glucose Carbon by Sensory Ganglia of 15‐Day‐old Chicken Embryos, with New Dynamic Models of Carbohydrate Metabolism
Authors: Larrabee Martin G.
Published: December 2006

Abstract: Dorsal root ganglia from the lumbar region of chicken embryos 14–16 days old were incubated at 37° in modified McCoy's culture medium containing [l‐11Cjglucose or [6‐11C]glucose and sometimes 32Pi A volume of 10 μl of medium was used for four ganglia (dry weight approx. 90 μg). The output of 14CO2 was measured continuously. Incorporation of 14C into tissue constituents and into products released to the medium was measured after incubation for 3–17 h. Among nine radioactive components resolved in paper chromato‐grams of ganglion constituents, the most 14C was found in lipids and on materials remaining at the origin. Only the lipids and the origin materials were detectably labeled by 32Pi. Only relatively small amounts of 14C from [6‐14C]glucose were found in chromatographic regions that should contain intermediates of the pentose cycle. At least five labeled products were released to the bathing medium. Among these, the largest amount of 14C was found in lactic acid. A second component released, possibly alanine, also received considerable 14C. No 32P was detected in products in the medium. The rate of glucose uptake remained relatively constant as the concentration of glucose in the medium declined nearly 10‐fold during prolonged experiments. Two new dynamic models of glucose metabolism successfully explained the time courses and magnitudes of previously reported 14CO2 outputs from [l‐14C]glucose, [2‐14C]‐glucose, and [6‐14C]glucose. These models are based on the assumption that glucose carbon was delayed on its way to CO2 in a pool of intermediates early in the metabolic chain and in a second pool either in or before the citric acid cycle. Both models assigned the pentose cycle to one cellular compartment, and incorporation into slowly‐turning‐over substances to another cellular compartment. According to both models, not more than one‐half of the glyceraldehyde‐P produced by the pentose cycle was converted to fruc‐tose‐6‐P, while at least half of this and other fructose‐6‐P from the pentose cycle was recycled into it. These conclusions differ from those from a previous model, which assumed that glucose carbon was delayed in a pool related to the pentose cycle: that model had suggested full recycling of both the glyceraldehyde‐P and the fructose‐6‐P produced by the pentose cycle. In the citric acid cycle the efficiency of recycling was over 80%, according to all models. All models demonstrated the large differences that can occur in the metabolic handling of carbons 1, 2, and 6 of glucose. These differences need consideration in any description of the partitioning of glucose metabolism between alternative pathways.
Axonal Transport of the Ca2+‐Dependent Protein Modulator of 3′:5′‐Cyclic‐AMP Phosphodiesterase in the Rabbit Visual System
Authors: Erickson Paul F. , Seamon Kenneth B. , Moore Blake W. , Lasher Robert S. , Minier Lee N.
Published: December 2006

Abstract: Water‐soluble proteins were extracted from individual retinas, optic nerves, combined optic tracts and lateral geniculate bodies, and superior colliculi of rabbits at 1, 3, and 18 days after injection of [3H]leucine into the right eye. The Ca2+‐dependent protein modulator of 3′:5′‐cyclic‐AMP phos‐phodiesterase (calmodulin) was isolated from these samples by a two‐step polyacrylamide gel electrophoresis procedure. An analysis of the radioactivity incorporated into the total soluble proteins and the calmodulin revealed that most of the calmodulin was axonally transported at a slow rate (2–4 mm/day) and represented about 0.45% of the total transported soluble protein.
Acetyl‐CoA Synthesizing Enzymes in Cholinergic Nerve Terminals
Authors: Sterri Sigrun H. , Fonnum Frode
Published: December 2006

Abstract: The activities of five enzymes involved in acetyl‐CoA synthesis, pyruvate dehydrogenase complex, ATP citrate lyase, carnitine acetyl‐transferase, acetyl‐CoA synthetase, and citrate synthase, were determined in normal nucleus interpeduncularis and nucleus interpeduncularis in which cholinergic terminals were removed following lesion of the habenulo‐interpeduncular tract. The activities of aspartate transaminase, fumarase, and GABA transaminase also were determined to compare the effect of lesion on other mitochondrial enzymes which are not linked to the biosynthesis of ACh. In normal nucleus interpeduncularis the activities of carnitine acetyltransferase and pyruvate dehydrogenase complex were higher than the activity of ChAT (choline acetyltransferase), whereas the activities of acetyl‐CoA synthetase and citrate synthase were considerably lower than that of ChAT. The effect of the lesion separated the enzymes into two groups: the activities of pyruvate dehydrogenase complex, carnitine acetyltransferase, fumarase and aspartate transaminase decreased by 30–409%, whereas the activities of the other enzymes decreased 5–15%. ChAT activity was in all cases less than 159% of normal. It could be concluded that none of the acetyl‐CoA synthesizing enzymes decreased to the degree that ChAT did. Only pyruvate dehydrogenase complex and carnitine acetyltransferase seem to be localized in cholinergic terminals to a significant degree. ATP citrate lyase as well as acetyl‐CoA synthetase seem to have less significance in supporting acetyl‐CoA formation in cholinergic nerve terminals.
Activity of Erythrocyte Na,K‐ATPase in Manic Patients
Authors: Akagawa Kimio , Watanabe Masayuki , Tsukada Yasuzo
Published: December 2006

Abstract: Erythrocyte membrane Na,K‐ATPase activity of manic patients was studied. The activity of patients in acute manic phase was higher than that of normal controls, while that of patients in normal phase was not. Even in the same patient, the activity in acute phase was higher than that in normal phase. Mg‐ATPase activities did not differ between controls and patients. These findings clearly indicate a possible correlation between change in clinical phase in manic patients and change ot erythrocyte membrane Na,K‐ATPase activity.
Cyclic AMP‐Dependent Protein Kinase Activity in Human Brain Across Age
Authors: Schmidt M. J. , Truex L. L. , Ghetti B. , Routtenberg A.
Published: December 2006

Abstract: Cyclic AMP‐dependent protein kinase activity was measured in the cerebral cortex of humans 2 days to 83 years of age and in the cortex of F344 rats 3, 22, or 30 months of age. Protein kinase activity was detected in the human brain, but no age‐related differences in activity were observed in the presence or absence of cyclic AMP. Age differences were also not seen in protein kinase in the rat cerebral cortex. Enzyme activities in rat and human brain were similar.
Lipid Composition of the Brain in the Vitamin B12‐Deficient Fruit Bat (Rousettus aegyptiacus) with Neurological Impairment
Authors: van der Westhuyzen Justin , Cantrill Richard C. , Fernandes‐Costa F. , Metz Jack
Published: December 2006

Abstract: The Egyptian fruit bat Rousettus aegyptiacus develops severe vitamin B12 deficiency when fed a diet of fresh peeled fruit and water. In a group of bats fed this diet, B12 concentrations in the serum and brain were low, and neurological impairment, evidenced by deficient or absent hindlimb groping or grasping ability and climbing difficulties, was manifest. Control bats fed the identical diet supplemented with B12 showed no such changes. Fatty acid analysis of whole brain homogenates showed a higher level of 20:4 in the deficient group. Phosphatidylcholine showed a marginally higher percentage of 18:3. The total percentage of branched chain fatty acids of phos‐phatidylethanolamine was four times higher in deficient brains, comprising 2% of the total. Sphingomyelin showed a slightly higher percentage of 15:0, and a significantly lower percentage of long chain fatty acids C‐24 and longer (p < 0.01). The compositions of nonhydroxy fatty acids in cerebroside were unchanged. Examination of phospholipids showed that 8.9 ± 0.4% of total phosphorus was present as sphingomyelin in deficient bats, compared with 11.9 ± 1.2% in control animals (p < 0.05). There were no statistically significant differences in the concentrations of total brain lipid, protein, phospholipid, glycosphingolipid, cholesterol and plasmalogen between B12‐deficient and control bats.
The PO Protein of Chick Sciatic Nerve Myelin: Purification and Partial Characterization
Authors: Mezei C. , Verpoorte J. A.
Published: December 2006

Abstract: The PO protein of the myelin of chick sciatic nerve was isolated and purified by propanoic acid extraction of peripheral nervous system (PNS) myelin, delipidation, Sepharose CL‐6B chromatography in the presence of sodium dodecyl sulfate (SDS), and preparative SDS‐polyacrylamide gel electro‐phoresis (PAGE). Approximately 15% of the PO protein in the sciatic nerve myelin was recovered in a homogeneous state. The purified protein monomer has an apparent molecular weight of 32.1K as determined by gel electrophoresis. The PO protein undergoes extensive aggregation during exhaustive dialysis and freeze‐drying and yields stable dimers, trimers, and tetramers. The aggregation of the PO protein after freeze‐drying is independent of the presence of a reducing agent (2‐mercaptoethanol) in the solubilizing medium. The PO protein is a glycoprotein. The amino acid composition of the chick PO protein indicates a definite species difference when compared with mammalian PO proteins although the NH2‐terminal isoleucine residue seems to have been retained during evolution.
Evidence for Two Cholesterol Ester Hydrolases in Human Cerebrospinal Fluid
Authors: Johnson Ronald C. , Shah Shantilal N.
Published: December 2006

Abstract: In the present study, the properties, such as pH optima, detergent requirement, and effects of various lipids, of cholesterol ester hydrolase in human cerebrospinal fluid (CSF) were examined, and the activity levels of the enzyme in CSF from multiple sclerosis (MS) patients and non‐MS individuals were compared. Our data indicate that the enzyme in CSF exhibits two pH optima: pH 6.0 in the presence of Triton X‐100 and pH 7.0 in the presence of sodium taurocholate. Both phosphatidylethanolamine (PE) and phosphatidylserine (PS) enhanced the hydrolase activity at pH 6.0. The activity at pH 7.0, on the other hand, was enhanced slightly in the presence of PE but was inhibited in the presence of PS. These data suggest the presence of two cholesterol ester hydrolases in CSF and also indicate that the activity at pH 6.0 may be due to microsomal enzyme in brain and that at pH 7.0 may be due to myelin enzyme. The hydrolase activity at pH 7.0 was significantly lower in CSF from MS patients. The activity at pH 6.0 in CSF from MS and non‐MS patients, however, did not differ significantly. This indicates that the reduction in pH 7.0 hydrolase activity in CSF may be related to demyelination.
Developmental Changes in Brain Glucose, Glycogen, Phosphocreatine, and ATP Levels in DBA/2J and C57BL/6J Mice, and Audiogenic Seizures
Authors: Schreiber Robert A.
Published: December 2006

Abstract. Brains of rodents are primarily dependent on ketone bodies as a source of hydrogen for NADH and of acetyl‐CoA during the perinatal period characterized by suckling. A mouse dam begins to wean her pups at about 14 days of age (DOA), the same age at which the brain reaches near‐adult size and begins to shift to dependence on carbohydrate‐derived sources of acetyl‐CoA for normal function. Also at this time, the ear canals open, and mice of some strains become susceptible to audiogenic seizures (AGS). There may be a genetically determined derangement in the orderly transition from one source of brain energy to the other in AGS‐prone mice, with a concomitant brief (days) reduction in the in situ energy reserve during the transition. In mice with a decreased energy reserve, a large energy expenditure within a short period of time (s), such as that induced by a substantial acoustic stimulus to newly opened acoustic pathways, might briefly lead to CNS disorganization before body energy repletion processes may occur, resulting in the onset of an AGS. Since glucose, glycogen, ATP, and phosphocreatine provide the bulk of the brain energy reserve, a developmental study was performed to measure the concentrations of these metabolites in brain tissues of DBA/2J mice (genetically/developmentally susceptible to AGS: onset at 12–14 DOA, peak at 18–21 DOA, rapid decline until 30 DOA, essentially lost by 42 DOA) and in C57BL/6J mice (not developmentally susceptible to AGS). Samples of frontal, temporal, cerebellar, and diencephalic regions were taken from mice 0–44 DOA and assayed. With the exception of higher glycogen levels in both DBA and C57 mice in cerebellar and diencephalic samples 0–16 DOA, no regional differences were found. A decrease in glycogen in all regions was observed in DBA mice 16–30 DOA, which was the inverse of susceptibility to AGS in these mice. This dip was not found in C57 mice. ATP levels were elevated in DBA mice 14–18 DOA, and glucose levels were decreased in DBA mice 24–40 DOA. These data lend support to the hypothesis that lowered brain energy reserves, or lowered access to brain reserves, underlies susceptibility to AGS.
Investigations on Myelination In Vitro: Regulation of 2′,3′‐Cyclic Nucleotide 3′‐Phosphohydrolase by Thyroid Hormone in Cultures of Dissociated Brain Cells from Embryonic Mice
Authors: Bhat Narayan R. , Shanker Gouri , Pieringer Ronald A.
Published: December 2006

Abstract: The direct influence of l‐3,3′,5‐triiodothyronine (T3) on the development of 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase (EC 3.1.4.37, CNPase) is demonstrated by using an in vitro culture system of dissociated embryonic mouse brain cells. Serum from a thyroidectomized calf, which contained low levels of T3 (31 ng/100 ml), and thyroxine, T4 (<1 μg/ml), was used in the culture medium in place of normal calf serum (T3, 103 ng/100 ml; T4, 5.7 μg/ml) to render the culture responsive to exogenously added T3. The lower levels of enzyme activity observed in the presence of such a deficient medium could be restored to normal values by T3 supplementation. Half‐maximal effect was obtained with 2.5 ± 10−9m‐T3. Three days of hormone treatment resulted in the maximal stimulation of CNPase. T4 was less effective in inducing CNPase activity and the inactive analog of the hormone, reverse T3 (3,3′,5′‐T3) was ineffective. The morphological appearance of the cells was characterized by deformed (smaller size and less in number) reaggregates in the cultures, lacking hormone.
Neurite‐Promoting Factor in Conditioned Medium from RN22 Schwannoma Cultures: Bioassay, Fractionation, and Properties
Authors: Manthorpe Marston , Varon Silvio , Adler Ruben
Published: December 2006

Abstract: On polyornithine (PORN) substrata dissociated 8‐day chick embryo ciliary ganglionic neurons will survive if the culture medium is supplemented with Ciliary Neuronotrophic Factor. However, neuritic growth will not occur unless the substratum is derivatized with a PORN‐bindable Neurite Promoting Factor (PNPF). In this preliminary study we report that soluble PNPF can be (1) assayed by a convenient in vitro system; (2) obtained in relatively large amounts from serum‐free media conditioned over RN22 Schwannoma cultures; (3) concentrated by using Amicon XM100 ultrafiltration; and (4) separated from nearly all of the non‐active protein by using ion‐exchange chromatography. The partially purified PNPF can be concentrated using XM100 and is heat‐ and protease‐sensitive. In the course of these fractionation studies we observed in some cases a concentration‐dependent interference with the expression of PNPF activity in the bioassay; we propose graphical methods to permit the simultaneous determination of PNPF and the extent of such interference. Different treatments that affected the interference property did not always affect PNPF activity in a reciprocal manner, leaving open the possibility that the interference with PNPF activity results from reversible alteration of the PNPF molecule, or that there exists a separate interfering agent.
Inhibition of Calcium‐Dependent ATPase from Sarcoplasmic Reticulum by a New Class of Indolizidine Alkaloids, Pumiliotoxins A, B, and 251D
Authors: Tamburini R. , Albuquerque E. X. , Daly J. W. , Kauffman F. C.
Published: December 2006

Abstract: Pumiliotoxins (PTX) A, B, and 251D, members of a new class of indolizidine alkaloids isolated from the skin of poison frogs of the family Dendrobatidae, inhibit Ca2+‐ATPase activity in sarcoplasmic reticulum vesicles from frog and rat hind‐limb muscles. PTX‐B and PTX‐A appear to be relatively specific inhibitors of Ca2+‐ATPase; PTX‐A is much less potent than PTX‐B. PTX‐251D is a potent inhibitor of Ca2+‐ATPase, and was also found to inhibit Na+, K+, and Mg2+‐ATPases in rat brain synaptosomes. Caffeine and verapamil, two drugs known to affect calcium translocation, are very weak inhibitors of the Ca2+‐ATPase. The K, values for inhibition of the Ca2+‐ATPase of rat and frog sarcoplasmic reticulum by PTX‐B were comparable and ranged between 22 and 36 μM. Inhibition of calcium‐dependent ATPase in sarcoplasmic reticulum by pumiliotoxin‐B is noncompetitive with calcium and is not readily reversible. Based on structure‐activity profiles, it is concluded that inhibition of Ca2+‐ATPase by the indolizidine alkaloids is responsible for the alkaloidelicited prolongation of twitch in intact muscle.
Arylsulphatase C and Estrone Sulphatase of Sheep Hypothalamus, Preoptic Area, and Midbrain: Separation by Hydrophobic Interaction Chromatography and Evidence for Differences in Their Lipid Environment
Authors: Mathew Joy , Balasubramanian A. S.
Published: December 2006

Abstract: Arylsulphatase C and estrone sulphatase activities of sheep hypothalamus‐preoptic area‐midbrain were examined for their susceptibility to phospholipase action. Russel's viper phospholipase A could completely inactivate estrone sulphatase without affecting arylsulphatase C. The latter was partially inactivated by S. aureus phospholipase C but not by C. welchi phospholipase C. Both arylsulphatase C and estrone sulphatase were inactivated to different extents by sodium deoxycholate, which is known to activate the intrinsic phospholipases of brain. Hydrophobic interaction chromatography on phenyl‐Sepharose resulted in the differential elution of arylsulphatase C and estrone sulphatase. The results suggest that one enzyme is not responsible for arylsulphatase C and estrone sulphatase activities.
Receptors for Vasoactive Intestinal Polypeptide on Isolated Synaptosomes from Rat Cerebral Cortex. Heterogeneity of Binding and Desensitization of Receptors
Authors: Staun‐Olsen Poul , Ottesen Bent , Bartels Paul D. , Nielsen Morten H. , Gammeltoft Steen , Fahrenkrug Jan
Published: December 2006

Abstract: Vasoactive intestinal polypeptide (VIP) is a neuropeptide that causes neurone excitation in the brain cortex. VIP receptors were studied in subcellular fractions isolated from rat cerebral cortex. The receptor binding of 125I‐VIP was greatest in the synaptosomal fraction at membrane protein concentrations of 50–100 μg/ml, a temperature of 37°C, and a pH from 7.4 to 7.7. Under these conditions the concomitant proteolytic degradation of 125I‐VIP was approximately 10% after 60 min of incubation. The binding of 60 pmoI/L 125I‐VIP reached steady‐state after 60 min and was maintained up to 240 min. At steady‐state, the receptor‐bound 125I‐VIP was displaced by unlabelled VIP with half‐maximal inhibition (IC50) at a concentration of approximately 3 nmol/L. The binding of 125I‐VIP in the concentration range of 10 pmol/L to 6 nmol/L was superimposable on the VIP displacement curve. The Scatchard plot was curvilinear with upward concavity, which can be interpreted to represent two classes of receptors with KD of 2.5 and 125 nmol/L, one class of receptors with negative cooperative interactions, or heterogeneity of the 125I‐ VIP preparation. The total amount of receptors was 9.5 pmol/mg of membrane protein. Secretin displaced receptor‐bound 125I‐VIP with an IC50 of 0.3 μmol/L, whereas glucagon snowed no inhibition up to 1 μmol/L. The dissociation of receptor‐bound 125I‐VIP was biexponential with rate constants (k2) of 4.1 – 10−3 and 0.18 min−1 corresponding to half‐times of approximately 170 and 4 min, respectively. The size of the two components was dependent on the duration of the 125I‐VIP association period. Initially, both components increased; at steady‐state, the rapid component declined, whereas the slow component increased to approximately 70% after 120 min. The association rate constants (k1) were estimated from the initial velocities as 106 and 4. 106 L. mol−1. min−1, and a calculation of the KD as k2/k1 gave values of 4.1 and 45 nmol/L, respectively. In conclusion, the presence of receptors for VIP on synaptosomes from the cerebral cortex supports the role of VIP as a neurotransmitter in the brain. The receptor binding was heterogeneous, suggesting the presence of two classes of receptors. The binding kinetics showed a time‐dependent transition of VIP receptors from a low‐ to a high‐affinity state, which may be interpreted as desensitisation of synapses to the action of VIP.
Effect of Age on Variables Influencing the Supply of Tryptophan to the Brain
Authors: Sarna G. S. , Tricklebank M. D. , Kantamaneni B. D. , Hunt A. , Patel A. J. , Curzon G.
Published: December 2006

Abstract: The relations of plasma concentrations of substances claimed to influence brain tryptophan concentration (total tryptophan, free tryptophan, large neutral amino acids) with the concentrations of tryptophan, 5‐hydroxytryptamine (5‐HT), and 5‐hydroxyindoleacetic acid (5‐HIAA) in the forebrain were investigated in rats of different ages (from 8 days to 16 months after birth). In brain, tryptophan fell by 46%, whereas 5‐HT rose by 20% between 8 and 40/42 days after birth. Thereafter, the levels of both tryptophan and 5‐HT remained essentially constant. Brain 5‐HIAA showed a more complex pattern, rising by 63% between 8 and 19 days, falling between 19 and 40/42 days, and then gradually rising until values at 16 months were significantly higher than those at 40/42 days. In plasma, the concentrations of free fatty acids, free and total tryptophan, and large neutral amino acids all decreased between 8 and 19 days and thereafter either remained constant or increased slowly, the exception being total tryptophan values, which showed large increases between 28/30 and 60/70 days. Also, the unidirectional uptake of tryptophan from blood to brain was determined using a carotid artery injection technique. Uptake values obtained using a tracer concentration of tryptophan in the injection solution decreased progressively with age. Kinetic analysis of the data in terms of the Michaelis‐Menten equation for carrier‐mediated transport indicated significantly lower values for Vmax and KD (a component for nonsaturable transport) in 6‐month‐old rats as compared to 19‐day‐old suckling rats, whereas Km values were the same at both ages. Detailed analysis of these results indicated that the age‐related changes in brain tryptophan were largely explicable in terms of plasma free tryptophan in association with blood‐brain transport characteristics; moderate differences in concentration of amino acids competing for transport were without apparent effect between 19 days and 16 months. The larger differences between 8 and 19 days after birth could be important.
Effects of Nutritional Rehabilitation on the Content and Lipid Composition of Brain Gray and White Matter of Neonatally Undernourished Rats
Authors: Reddy T. Sanjeeva , Rajalakshmi R. , Ramakrishnan C. V.
Published: December 2006

Abstract: Neonatal undernutrition affects the content and lipid concentrations of gray and white matter. Nutritional rehabilitation reverses the deficit observed in gray matter. In the case of white matter the lipid concentration but not the content comes back to normal.
High Specific Binding of [3H]GABA and [3H]Muscimol to Membranes from Dendrodendritic Synaptosomes of the Rat Olfactory Bulb
Authors: Quinn Michael R. , Cagan Robert H.
Published: December 2006

Abstract: Olfactory bulbs contain dendrodendritic synapses, which occur between granule cells and mitral cells, and γ‐aminobutyric acid (GABA) is thought to act as an inhibitory neurotransmitter at these synapses. Synaptosomes derived from the dendrodendritic synapses of the olfactory bulb were shown previously to contain considerable L‐glutamate decarboxylase activity. The subcellular distribution and binding parameters of [3H]GABA and [3H]muscimol binding sites have now been determined in the rat olfactory bulb. Of all fractions examined, crude synaptic membranes (CSM) prepared from the dendrodendritic synaptosomes were shown to have the highest specific binding activity and accounted for nearly all of the total binding activity for both ligands. The specific binding activities for [3H]GABA and for [3H]muscimol were greatly increased after treating the CSM with 0.05% Triton X‐100. Binding was shown to be Na+‐independent, reversible, pharmacologically specific, and saturable. High‐ and low‐affinity sites were detected for both ligands, and both classes of sites had appreciably lower KD values for muscimol (KD1= 3.1 nM, KD2= 25.1 nM) than for GABA (KD1= 8.6 nM; KD2= 63.7 nM). The amounts of the high‐affinity binding sites for muscimol and GABA were similar (Bmax= 1.7 and 1.5 pmol/mg protein, respectively). The results of the present experiments indicate that the GABA and muscimol binding sites represent the GABA postsynaptic receptor, presumably on mitral cell dendrites, and provide further support for the hypothesis that GABA functions as a neurotransmitter at the dendrodendritic synapses in the olfactory bulb.
Acetylcholine Release from Isolated Synaptic Vesicles Related to Ionic Permeability Changes: Continuous Detection with a Chemiluminescent Method
Authors: Diebler M. F.
Published: December 2006

Abstract: The effect of ionic permeability changes on acetylcholine (ACh) release from isolated cholinergic synaptic vesicles of Torpedo was studied using a chemiluminescent method for continuous ACh detection. Vesicles rendered freely permeable to potassium by valinomycin lost most of their ACh content in K+ media, if the accompanying anion was permeant; it thus appeared that ACh leakage occurred as the result of internal osmotic changes. Upon addition of ionophores that catalyse monovalent cation/H+ exchange (gramicidin D or a mixture of valinomycin plus protonophore FCCP), a rapid but transient ACh release was observed. Surprisingly, nigericin which also catalyses K+/H+ exchange, had no effect on ACh release. The divalent cation ionophore A23187 promoted ACh release only when calcium (and not magnesium) was introduced into the external medium in a millimolar concentration range. As the simultaneous addition of the protonophore FCCP and A23187 decreased this calcium‐dependent ACh leakage, a releasing effect of A23187 through Ca2+/H+ exchange is suspected. The present results emphasise the role of internal protons for ACh retention inside synaptic vesicles.
Biochemical Characterisation and Localization in Brain of a Human Brain‐Leucocyte Membrane Glycoprotein Recognised by a Monoclonal Antibody
Authors: McKenzie Judith L. , Dalchau Rosemarie , Fabre John W.
Published: December 2006

Abstract: The F10‐44‐2 monoclonal antibody was originally shown to interact with a determinant found predominantly in human brain and leucocytes. In this study we demonstrate by quantitative absorption analysis with homogenates of the head of the caudate nucleus, putamen, thalamus, cerebral grey matter, cerebral white matter, corpus callosum and cerebellar folia that the determinant is restricted to the white matter of the CNS. Immunofluorescence studies on frozen sections of the above brain subregions confirm the absorption analyses, showing staining only of white matter. In addition, and unexpectedly, we found very bright staining around blood vessels, particularly in the cerebellum. Biochemical studies established that the molecule in white matter bearing the F10‐44‐2 determinants is a sialylated membrane glycoprotein with an apparent molecular weight of 90,000, which is similar to but slightly smaller than the T lymphocyte form of the antigen. Developmental studies comparing 16‐week foetal and adult cerebrum showed a fivefold increase in F10‐44‐2 antigen content. Thus, in the human CNS, the F10‐44‐2 antigen is a medium‐sized glycoprotein which is restricted to white matter and shows a marked increase in concentration during development. No such molecule has been described previously.