bluuebunny/crossref_metadata_2025_split huggingface dataset:
CHOLESTEROL ESTER METABOLIZING ENZYMES IN HUMAN BRAIN: PROPERTIES, SUBCELLULAR DISTRIBUTION AND RELATIVE LEVELS IN VARIOUS DISEASED CONDITIONS
Authors: Johnson Ronald C. , Shah Shantilal N. 
Published: October 2006

AbstractWe have in the present study examined the properties and subcellular distribution of cholesterol ester metabolizing enzymes in human brain, and compared the levels of these enzymes in brains from patients with phenylketonuria (PKU), metachromatic leucodystrophy (MLD), and Down's Syndrome (DS).Cholesterol esterification was optimal at pH 5.6, did not require ATP or CoA as cofactors and was inhibited by detergents (TWEEN‐20 and Triton X‐100) and bile acids (sodium taurocholate and sodium deoxycholate). The specific activity of the cholesterol esterifying enzyme was highest in the mitochondrial fraction. Cholesterol esterifying activity in brains from PKU, MLD, and DS patients was not significantly different.Cholesterol ester hydrolase activity in human brain peaked at two different pHs (4.5 and 6.5). The activity was optimal when the substrate was dispersed in Triton X‐100 and sonicated. The specific activity of the pH 4.5 hydrolase was highest in the mitochondrial fraction, while that of the pH 6.5 hydrolase was highest in myelin. The sulfhydryl group reagent parachloromercuribenzoate (PCMB) inhibited the activity of the hydrolase(s) but diisopropylfluorophosphate (DFP), a typical serine reagent, had no effect on hydrolase(s) activity. Addition of either phosphatidyl serine or phosphatidyl inositol significantly enhanced the hydrolase activity at both pHs.The level of cholesterol ester hydrolase(s) in PKU brains was lower than in the brains from DS patients, and the level of these enzymes in the brains from two patients with metachromatic leucodystrophy was lower than in the brains from PKU patients. It is concluded that the properties and subcellular distribution of cholesterol esterifying enzyme in human brain is similar to that in rat brain (Ero & Suzuki, 1971) but that the hydrolases in human brain differ from that in rat brain in several respects, and that the low levels of hydrolase(s) activity in MLD and PKU brain may be related to reduced myelin content of those brains.
ISOLATION AND CHARACTERIZATION OF DNA‐DEPENDENT RNA POLYMERASE A, B AND C FROM RAT BRAIN NUCLEI1
Authors: Yamamoto H. , Takahashi Y. 
Published: October 2006

Abstract— DNA‐dependent RNA polymerase activities were solubilized from the brain nuclei of young rats. Six forms of RNA polymerases were distinguished on DEAE‐Sephadex A‐25 chromatography and designated A, BI, BII, CI, CII, and Oil by their sensitivities to α‐amanitin. CII enzyme was shown to derive from CIII enzyme by serine‐protease digestion. CI enzyme was also suggested to be a product of a proteolytic process.Using a DNA template, enzyme A was completely resistant to α‐amanitin; BI and BII enzymes were equally sensitive to this toxin (50% inhibition at 0.006 μg/ml); while C enzymes showed intermediate sensitivity (50% inhibition at 30 μg/ml). When poly[d(A‐T)] was used as a template, α‐amanitin sensitivities were altered in A, CI, CII, and CIII enzymes without any change in the BII enzyme. CI, CII and CIII enzymes were greatly stimulated by poly[d(A‐T)], whereas A and BII enzymes were only slightly stimulated. All six forms of RNA polymerases were extensively characterized with respect to their ammonium sulphate optima, effects of divalent metal ions, template requirements and pH optima, using DNA and poly[d(A‐T)] as templates. The results show new findings in several properties and supply basic data for discussion and future studies on RNA metabolism of the brain.
EFFECTS OF KAINIC ACID ON ION DISTRIBUTION AND ATP LEVELS OF STRIATAL SLICES INCUBATED IN VITRO
Authors: Biziere K. , Coyle J. T. 
Published: October 2006

Abstract— To determine the mechanism of neurotoxicity of kainic acid, striatal slices (350μ) were incubated in oxygenated Krebs buffer with kainic acid and other depolarizing agents; and the alterations in the uptake and retention of 22Na+, 86Rb+ (as a measure of K +), 3HzO and the levels of ATP were determined. The excitatory amino acid, L‐glutamate (10 mM) increases striatal slice uptake and retention of Na+, K+ and H2O but decreases ATP levels whereas the neuroexcitant, A'‐methyl aspartate, increases only Na+ and H2O. Veratridine (100μM), which opens electrogenic sodium channels, and ouabain (100μM), which inhibits Na+‐K+ ATPase, both elevate striatal Na+ and H2O but considerably reduce K+ and ATP. The effects of these different depolarizing agents on the parameters examined are consistent with their mechanisms of actions and support the validity of this in vitro method.Although 10mM‐kainate significantly depresses striatal K+ and ATP, lower concentrations of kainate (5mM‐0.1μ) elevate striatal uptake of Na+ but do not markedly affect H2O, K+ or ATP. Kainate (10mM‐lμM) does not exhibit additivity with 10 mM‐glutamate with respect to Na+ permeability but does significantly potentiate glutamate's ATP depleting effects. Injection of 10 nmol of kainate into the striatum in vivo causes a reduction in striatal ATP 1 h afterward which is comparable to that occurring in vitro with 10mM‐kainate alone or with lower concentrations of kainate (≥1/μM) with 10 mM‐glutamate. These results suggest that kainate alone is directly neurotoxic at 10mM or neurotoxic at lower concentrations in combination with the high intrasynaptic levels of glutamate on neurons receiving glutamatergic innervation.
HE TURNOVER RATE OF TUBULIN IN RAT BRAIN
Authors: Forgue S. Thomas , Dahl June L. 
Published: October 2006

AbstractThe turnover rate of tubulin in rat brain was determined from the decay in specific radioactivity of the protein after pulse‐labeling. When precursors were administered by a parenteral route, the shortest half‐life, 9.8 days, was obtained with [14C]NaHCO3; the longer half‐lives obtained with [U‐14C]glucose or [4,5‐3H]leucine suggest significant reutilization of label. Furthermore, with leucine as precursor maximal specific radioactivity of tubulin was not obtained until eight days after administration of label. Labeling and decay kinetics obtained with [4,5‐3H]leucine were markedly different when the isotope was administered directly into the lateral ventricle. The difference between the turnover rates of the ‐α and β subunits of tubulin purified by means of high resolution polyacrylamide gel electrophoresis was not statistically significant. A half‐life for tubulin of 6.2 days was measured by continuous intravenous infusion of [U‐14C]tyrosine.
MECHANISM OF EXTRACELLULAR POTASSIUM STIMULATION OF PROTEIN SYNTHESIS IN THE IN VITRO HIPPOCAMPUS1
Authors: Lipton Peter , Heimbach Catherine J. 
Published: October 2006

AbstractTransverse slices of guinea‐pig hippocampus respond to small increases in extracellular potassium concentration [K +] by showing a marked augmentation in the rate of incorporation of labelled precursor amino acid into protein. We find that this augmentation is manifested equally in superfusing solutions containing low specific activity/high concentration precursor and high specific activity/low concentration precursor. This provides additional evidence that the effect of extracellular [K +] is on the rate of protein synthesis and not on the precursor pool. Extracellular [K +] augments amino acid incorporation normally in the presence of concentrations of α‐amanatin and actinomycin D which are inhibiting RNA synthesis by over 97%. This suggests the effect is exerted post‐transcriptionally. Extracellular [K +] causes an unattenuated increase in protein synthesis in the presence of high Mg2+ (20mm) or low Ca2+ (0 mm) in the superfusate–suggesting this effect of [K +] does not result from an effect on neurotransmitter release. Increases in extracellular [K+] which increase protein synthesis threefold (1.3‐6.4mm‐K +) increase the intracellular [K +]/[Na +] 2‐fold. 3 x 10‐7m‐Ouabain. which lowers incorporation by 40‐50% lowers [K +]/[Na +] by about 50% while having no effect on the uptake of labelled precursor or on the cell concentrations of ATP. These results suggest that protein synthesis in the cell is sensitive to [K. +]/[Na +] and that an alteration in this ratio is the mechanism by which the concentration of extracellular [K +] affects the rate of in vitro hippocampal protein synthesis. This effect of extracellular [K +] on synthesis is not observed in slices from non‐cerebral organs of the guinea pig.
ACTIVITY OF 2′,3′‐CYCLIC‐NUCLEOTIDE 3′‐PHOSPHODIESTERASE IN REGIONS OF RAT BRAIN DURING DEVELOPMENT: QUANTITATIVE RELATIONSHIP TO MYELIN BASIC PROTEIN
Authors: Sprinkle T. J. , Zaruba M. E. , McKhann G. M. 
Published: October 2006

Abstract—2′,3′‐Cyclic‐nucleotide‐3′‐phosphodiesterase activity was examined in several regions of rat brain during development, namely optic nerve, olfactory bulb, cerebrum, cerebellum, midbrain, brain stem, and spinal cord. From 4 to 120 days the total activity increased in all regions, although the specific activity approached a constant value in adults. The developmental profile of the enzyme appeared to correlate with the onset of myelination and with the levels of myelin basic protein as well as the appearance of galactocerebroside sulfotransferase.A correlation coefficient of 0.91 was found between total basic protein, expressed as the per cent of the adult (120 day) value, and total enzyme activity over 12–42 days of age (P < 0.001) from six different brain regions as well as for whole brain.By increasing the sensitivity of the assay with the use of [3H‐8]adenosine 2′,3′‐cyclic monophosphate, we were able to detect activity at birth in both whole brain and spinal cord.
STUDIES ON THE REGULATION OF GABA SYNTHESIS: THE INTERACTION OF ADENINE NUCLEOTIDES AND GLUTAMATE WITH BRAIN GLUTAMATE DECARBOXYLASE
Authors: Seligmann B. , Miller L. P. , Brockman D. E. , Martin D. L. 
Published: October 2006

Abstract—The effects of adenine nucleotides and glutamate on glutamate decarboxylase were studied in a dialyzed, high‐speed supernatant of rat brain. When incubated with 10 μm‐pyridoxal‐P the enzyme was strongly inhibited by ATP, ADP and their Mg2+ complexes at concentrations which were well below tissue levels. The enzyme was not significantly inhibited by 15 mm‐AMP or by 100 μM‐3′‐5’cyclic AMP or 3′‐5’cyclic GMP. Inhibition by the nucleotides cannot be described in conventional steady‐state kinetic terms. Addition of ATP in the presence of pyridoxal‐P resulted in a slow, progressive decrease in the reaction rate which was similar to the inactivation observed when the enzyme was incubated in the absence of pyridoxal‐P. The progressive inactivation in the presence of ATP was minimal at concentrations of glutamate which were well below Km and became much more pronounced at higher glutamate concentrations. Addition of suprasaturating amounts of pyridoxal‐P late in the incubation when the enzyme was almost completely inactivated resulted in an immediate and complete reactivation of the enzyme. Inhibition by ATP could be prevented by addition of saturating amounts of pyridoxal‐P at the start of the reaction and was also relieved by addition of potassium phosphate buffer. The results suggest that inhibition by the nucleotides involves the prior formation of the inactive apoenzyme which results from the glutamate‐promoted dissociation of pyridoxal‐P. In the absence of the nucleotides, the enzyme is normally reactivated by the added pyridoxal‐P. The nucleotides act to block this reassociation of pyridoxal‐P with the apoenzyme thereby producing a progressive inactivation of the enzyme. The implications of these results for the regulation of GABA synthesis are discussed.
IN VIVO METABOLISM OF 3‐KETOCERAMIDE IN RAT BRAIN1
Authors: Shoyama Yukihiro , Kishimoto Yasuo 
Published: October 2006

Abstract—Eight hours after intracerebral injection of a double‐labeled 3‐ketoceramide4, [1‐14C]lignoceroyl 3‐keto [1‐3H]sphingosine, various brain sphingolipids were isolated. Free ceramide and the ceramide portions of nonhydroxy cerebroside and sphingomyelin were further fractionated into subgroups containing longer‐chain or shorter‐chain fatty acids. Nonhydroxy ceramide, nonhydroxy cerebroside and sphingomyelin containing longer‐chain fatty acids had significant quantities of radioactivity with 3H/14C ratios similar to each other but lower than that of the injected material. The sphingolipids containing shorter‐chain fatty acids were also significantly labeled; however, the 3H/14C ratios were much higher than that of the injected material. Hydroxy‐ceramide and sulfatides contained very little radioactivity. However, hydroxy‐cerebroside contained an amount of radioactivity comparable to that of the longer‐chain nonhydroxy cerebroside with a similar 3H/14C ratio. It is proposed that the injected 3‐ketoceramide was converted into ceramide, cerebroside, and sphingomyelin and that the fatty acids of these lipids were partly replaced by other fatty acids during the metabolic conversions.
THE HEXOSE MONOPHOSPHATE PATHWAY IN ETHYLNITROSOUREA INDUCED TUMORS OF THE NERVOUS SYSTEM
Authors: Coleman Mary Thoesen , Allen Norman 
Published: October 2006

Abstract—Respiration studies in vitro, in which tissue slices were incubated with [1‐14C]glucose or [6‐14C]glucose and 14CO2 collected, resulted in C‐1/C‐6 14CO2 ratios that were higher in slices of tumor and newborn brain than in slices of adult brain. In adult brain, the C‐1/C‐6 14CO2 ratio averaged close to unity. In slices of tumor and newborn brain however, the mean C‐1/C‐6 ratio was greater than three. Addition of phenazine methosulfate (PMS) increased conversion of [1‐14C]glucose to 14CO2 in slices of normal adult brain 5‐fold, and in slices of newborn brain and tumor, approx 12‐fold. Injection of animals with 6‐aminonicotinamide (6‐AN) decreased conversion of [1‐14C]glucose in slices of normal brain 30% but decreased conversion in tumor slices by 80%. Evidence supports the presence of an active hexose monophosphate pathway (HMP) in tumors of the nervous system regulated in part by available NADP+ levels. Inhibition by 6‐AN was more effective in tumors than in normal adult brain.
STIMULATION OF BRAIN ACETYL‐CoA HYDROLASE BY ATP AND ATP ANALOGUES
Authors: Matsuda T. , Yonehara N. , Ichida S. , Yoshida H. 
Published: October 2006

Abstract—The effects of ATP and ATP analogues on the brain acetyl‐CoA hydrolase (EC 3.1.2.1) were studied. The enzyme was stimulated reversibly by ATP‐Mg2+ the presence of Mg2+ being absolutely required for the stimulation. The stimulatory effect of ATP was highly specific since adenine nucleotides other than ATP had no stimulatory effects and nucleoside triphosphates other than ATP stimulated the enzyme much less than ATP in the following order: ATP > ITP CTP, UTP GTP. A phosphate modified analogue of ATP, AMP‐PNP had a similar stimulatory effect to that of ATP. Other ATP analogues such as AMP‐PCP and AMPCPP showed less stimulatory effect than ATP. The order of the stimulatory effects of these ATP analogues was: ATP > AMP‐PNP > AMP‐PCP > AMPCPP. The concentrations needed for half‐maximal stimulation of ATP, AMP‐PNP and AMP‐PCP were approx 0.11 mm, 0.22 mm, and 0.22 mm, respectively. Double reciprocal plots demonstrated that ATP as well as AMP‐PNP produced a significant decrease in the apparent Km, value for acetyl‐CoA and an increase in Vmax indicating that these nucleotides increased the affinity for acetyl‐CoA through binding at a site other than the catalytic site. The data described above suggest that the rate of hydrolysis of acetyl‐CoA may be regulated by the concentration of ATP in the micro‐environment of the enzyme.
PLASMALOGENASE ACTIVITIES IN THE BRAINS OF JIMPY AND QUAKING MICE
Authors: V.Dorman Robert , Freysz Louis , Mandel Paul , Horrocks Lloyd A. 
Published: October 2006

Abstract—The activity of plasmalogenase, which hydrolyzes the vinyl ether linkage of the plasmalogen molecule, increased markedly in control mouse brains during the period of most active myelin deposition. Only a slight increase in plasmalogenase activity was found in brains from jimpy mice. At all ages studied, the jimpy mouse brains had less plasmalogenase activity than the littermate control brains and this disparity increased with increasing age. By 25 days of age the jimpy brains contained only 43% of the activity observed in control brains. Adult quaking mouse brains also had significantly less plasmalogenase activity when compared to littermate controls. Thus, the plasmalogenase activities correlate well with the degree of myelination.
SULPHOLIPID METABOLISM IN DEVELOPING CHICKEN RETINA1
Authors: Dreyfus H. , Pieringer J. A. , Farooqui A. A. , Harth S. , Rebel G. , Sarlieve L. L. 
Published: October 2006

Abstract—Glycolipid analysis of chicken retina and brain indicated the presence of cerebroside, cerebroside 3‐sulphate and sulphogalactosylglycerolipid In retina, the ratio of cerebroside to cerebroside 3‐sulphate was approximately half compared to brain. During chicken retina ontogenesis the ratio of cerebroside 3‐sulphate to sulphogalactosylglycerolipid increased rapidly and in the adult animal, the amount of cerebroside 3‐sulphate was 14 times higher than that of sulphogalactosylglycerolipid.The activity of PAPS: cerebroside sulphotransferase and arylsulphatase A in developing chicken retina indicated that the general ontogenic profiles of retinal PAPS: cerebroside sulphotransferase and arylsulphatase A were similar to those obtained for the brain. Both the enzymes showed the highest activity just before hatching. The significance of occurrence of sulpholipids in retina is discussed.
CONCOMITANT ELEVATION OF TYROSINE HYDROXYLASE AND DOPAMINE BETA‐HYDROXYLASE BY CYCLIC AMP IN CULTURED MOUSE NEUROBLASTOMA CELLS1
Authors: Waymire Jack C. , Gilmer‐Waymire Katrina , Boehme Richard E. 
Published: October 2006

Abstract—The effects of cyclic AMP analogues and of phosphodiesterase inhibitors were investigated in neuroblastoma cells (NBD‐2) cloned from the C‐1300 tumor. 8Br‐cAMP and phosphodiesterase inhibitors that elevated cAMP induced large (greater than 15 fold) and specific increases in tyrosine hydroxylase and dopamine beta‐hydroxylase activity. In contrast, catechol O‐methyltransferase, monoamine oxidase and aromatic‐l‐amino‐acid decarboxylase were unaffected by the cAMP altering drugs. Similarly, AChE was unaffected and only a small increase in choline acetyltransferase (3 fold) was observed. The increases in tyrosine hydroxylase and dopamine beta‐hydroxylase were similar with respect to dose response relationships and with respect to time course of onset.Only those phosphodiesterase inhibitors that elevated cAMP (papaverine and Ro20‐1724 as opposed to theophylline) were effective in elevating tyrosine hydroxylase and dopamine beta‐hydroxylase. Further, the doses optimal for elevating cAMP coincided with the optimal doses for elevating the two enzymes. Theophylline had no influence either upon NBD‐2 cell cAMP levels or upon tyrosine hydroxylase and dopamine beta‐hydroxylase activity.The changes in protein synthesis rates produced by the cAMP altering drugs were temporally distinct from the changes in either tyrosine hydroxylase or dopamine beta‐hydroxylase. These results suggest that the intracellular messenger compound cAMP is involved in the specific regulation of both tyrosine hydroxylase and dopamine beta‐hydroxylase in adrenergic cells.
ALTERATION OF TRICARBOXYLIC ACID CYCLE METABOLISM IN RAT BRAIN SLICES BY HALOTHANE
Authors: Cheng Sze‐Chuh , Brunner Edward A. 
Published: October 2006

Abstract—

Metabolism of [2‐14C]pyruvate, [1‐14C]acetate and [5‐14C]citrate in the rat cerebral cortex slices was studied in the presence of halothane. Metabolites assayed include acetylcholine (ACh), citrate, glutamate, glutamine, γ‐aminobutyrate (GABA) and aspartate. The trichloroacetic acid soluble extract, the trichloroacetic acid insoluble precipitate and its lipid extract were also studied.
In control experiments, pyruvate preferentially labelled ACh, citrate, glutamate, GABA and aspartate. Acetate labeled ACh, but to a lesser extent than pyruvate. Acetate also labeled lipids and glutamine. Citrate labeled lipids but not ACh and served as a preferential precursor for glutamine. These data support a three‐compartment model for cerebral tricarboxylic acid cycle metabolism.
Halothane caused increases in GABA and aspartate contents and a decrease in ACh content. It has no effect on the contents of citrate, glutamate and glutamine.
Halothane preferentially inhibited the metabolic transfer of radioactivity from pyruvate into almost all metabolites, an effect probably not related to pyruvate permeability. This is interpreted as halothane depression of the‘large metabolic compartment’ which includes the nerve endings.
Halothane increased the metabolic transfer of radioactivity from acetate into lipids but did not alter such a transfer into the trichloracetic acid extract.
Halothane increased the metabolic transfer of radioactivity from citrate into the trichloroacetic acid precipitate, lipids and especially glutamine. Transfer of citrate radioactivity into GABA was somewhat decreased.
The differential effects of halothane on acetate and citrate utilization suggest that the ‘small metabolic compartment’ should be subdivided. Therefore, at least three metabolic compartments are demonstrated.
Halothane did not interfere with the dicarboxylic acid portion of the tricarboxylic acid cycle.
THE FLUOROMETRIC DETERMINATION OF 5‐METHOXYTRYPTAMINE IN MAMMALIAN TISSUES AND FLUIDS
Authors: Prozialeck Walter C. , Boehme D. H. , Vogel Wolfgang H. 
Published: October 2006

Abstract— Using a sensitive and specific fluorometric procedure involving selective extraction, reaction of the extracts with o‐phthalaldehyde (OP), separation of the OP derivatives by TLC, and determination of fluorescent characteristics and intensities, we have detected and measured 5‐methoxytryptamine, (5‐MT) in various central and peripheral tissues and fluids of the rat, dog, baboon, and man.Distribution of 5‐MT in peripheral tissues of the rat seemed to parallel that of 5‐HT, with highest levels being found in the gastrointestinal (GI) tract and Harderian gland, regions that are rich in 5‐HT and have been reported to contain systems capable of methylating 5‐HT. 5‐MT was detected in the lung, plasma, kidney, spleen, and heart of the rat. 5‐MT was present in the CNS of all species examined. No marked interspecies differences were observed. In the rat CNS, the regional distribution of 5‐MT did not parallel that of 5‐HT indicating that the systems for the synthesis, uptake, or transport of 5‐MT might be different than for 5‐HT. Pretreatment of rats with iproniazid resulted in a 50% increase in whole brain 5‐MT. Reserpine pretreatment had no effect, indicating that the storage or release mechanisms for 5‐MT are different than for the conventional amine transmitters. 5‐MT was detected in human CSF and urine but not in plasma. These data indicate that 5‐MT, a compound with potent pharmacological properties, is more widely distributed in the mammalian body than had previously been supposed.