bluuebunny/crossref_metadata_2025 huggingface dataset:
LIPID COMPOSITION AND METABOLISM OF CULTURED HAMSTER BRAIN ASTROCYTES
Authors: Eichberg J. , Shein H. M. , Hauser G.
Published: October 2006

Abstract— The lipid composition and metabolism of confluent cultures of cells derived from newborn hamster brain and having morphology characteristic of immature astrocytes or spongioblasts was investigated and compared to that of newborn hamster brain dispersions and cloned glioma cells (C6). The cells displayed stable morphology for at least 30 subcultures; thereafter spontaneous transformation occurred. No appreciable changes were observed in either composition or metabolic characteristics of any major neutral lipid or phospholipid class in successive subcultures or following transformation. The overall lipid composition of the hamster astrocyte cultures closely resembled that of newborn hamster brain, but the phospholipid composition showed substantial differences. The cells contained as a percent of lipid P relatively more ethanolamine plasmalogen, choline plasmalogen and sphingomyelin and somewhat less phosphatidylcholine and phosphatidylethanolamine. The phospholipids of the hamster astrocyte and C6 cells were similar. Of the lipid precursors examined, [U‐14C]glucose was incorporated best into all preparations. C6 glioma cells incorporated both [U‐14C]glucose and [1‐14C]acetate most actively. From 69–88% of 32P incorporated into hamster astrocyte phospholipids was present in choline phosphoglycerides, whereas the corresonding figure for hamster brain dispersions was 53%. The ratio of specific activities of phosphatidylcholine to phosphatidylinositol was substantially higher in the cultured cells than in the brain preparations. The small pool of choline plasmalogen in the hamster astrocytes usually achieved the highest specific activity of any phospholipid. When [U‐14C]glucose and [1‐14C]acetate were precursors, the bulk of label in the astrocytes appeared in choline phosphoglycerides and triacyglycerol. Our results indicate that the hamster astrocyte cell line as grown expresses distinctive features of lipid composition and metabolism which are nearly constant through many generations.
ENZYMATIC N‐METHYLATION OF INDOLEAMINES BY MAMMALIAN BRAIN: FACT OR ARTEFACT?
Authors: Gomes U. R. , Neethling A. C. , Shanley B. C.
Published: October 2006

Abstract— Indoleamine‐N‐methyltransferase (INMT) activity in brain and other tissues from various species was investigated. Using conventional radiochemical assay techniques it was found that apparent INMT activity in brain was linear with time and concentration of protein, indoleamine substrate and methyl donor (S‐adenosylmethionine). However, examination of the reaction products by means of exhaustive thin‐layer chromatographic analysis failed to reveal evidence of significant N‐methylation of tryptamine or N‐methyltryptamine by S‐adenosylmethionine. By contrast, with other tissues, notably rabbit lung. N‐methylation of indoleamine was reproducibly demonstrable. The significance of these findings with reference to the transmethylation hypothesis of schizophrenia is discussed.
DIVALENT CATION‐ACTIVATED ECTO‐NUCLEOSIDE TRIPHOSPHATASE ACTIVITY OF NERVOUS SYSTEM CELLS IN TISSUE CULTURE
Authors: Stefanovic V. , Léadig M. , Mandel P.
Published: October 2006

Abstract— Intact neuroblastoma and glial cells in monolayer culture hydrolysed ATP added to their medium. Evidence is presented that ATP is cleaved outside of the permeability barrier of the plasma membrane and the product is liberated in the extracellular medium, i.e. the enzyme is an ecto‐enzyme. Divalent cations such as Mg2+, Ca2+, Mn2+ and Co2+ activate the enzyme. In neuroblastoma cells, Ca2+ is the preferential cation for activation; Mg2+ in glial cells. Substrate specificity was very low when different nucleoside‐5′‐triphosphates were examined. Competition studies have revealed that all of the nucleoside triphosphates are hydrolysed by the same enzyme: divalent cation‐activated ecto‐nucleoside‐5′‐triphosphate phosphohydrolase.

Developmental pattern of the enzyme in several lines was established. The role of enzyme in the transport of divalent cations across the plasma membrane and/or in the physical properties of the membrane is suggested.
Subcellular localization of enzymes oxidizing citrate in the rat brain
Authors: Rafalowska Urszula , Ksieźak Hanna
Published: October 2006

1RSA was calculated as the ratio: percentage of total recovered activity found in fraction to percentage of total protein found in the same fraction.
PROTEIN PHOSPHORYLATION IN VITRO IN BRAIN TUBULIN PREPARATIONS: EFFECTS OF Zn2+ AND CYCLIC NUCLEOTIDES
Authors: Larsson H. , Edström A. , Wallin Margareta
Published: October 2006

Abstract— Endogenous protein phosphorylation has been studied during in vitro polymerization of microtubules by incubating a purified tubulin preparation at 37°C in the presence of radioactive ATP. At optimal conditions the rate of phosphorylation was found to follow the course of polymerization by a shift to a lower rate at the polymerization plateau.

Zn2+ at 0.5 mm was shown to stimulate phosphorylation, mainly of tubulin‐associated proteins (mol wt 110,000 and 175,000,) and to a lesser extent of tubulin. The effect occurred at Zn2+‐concentrations which induce formation of tubulin sheet polymers, which suggests that the state of aggregation of tubulin is of importance for the phosphorylation. In contrast to Zn2+, Mg2+ only increased phosphorylation of the high molecular weight proteins, and to a lesser degree. The stimulation by Zn2+ or Mg2+ was potentiated by cyclic AMP or cyclic GMP.

A low concentration of Zn2+ (5 μm) or cyclic GMP at 10 μm inhibited phosphorylation, possibly by interaction with a co‐existing protein phosphatase.
ACID LIPASE‐ESTERASE (4‐METHYLUMBELLIFERYL OLEATE HYDROLASE) OF WHITE MATTER LOCALIZED IN OLIGODENDROCYTE CELL BODIES1
Authors: Hirsch H. E. , Wernicke J. F. , Myers L. W. , Parks M. E.
Published: October 2006

Abstract— The localization of an acid lipase‐esterase which cleaves the fluorogenic substrate 4‐methyl‐umbelliferyl oleate at pH 5 was studied, because previous experiments has shown this activity to be reduced in the plaques of multiple sclerosis. In the human cerebellum, quantitative histochemical methods showed the activity to be relatively low in the molecular layer, compared to the granule cell layer; but the underlying white matter was the most active. In the human spinal cord, anterior horn cell bodies were richest in acid lipase, but white matter was, on a dry weight basis, as active as neuropil. Oligodendrocytes obtained in bulk from bovine white matter according to Poduslo & Norton (1972) had a specific activity up to 20 times greater than the crude myelin fraction. While it remains possible that in myelin the enzyme is in an inactive or inhibited state, the results indicate that the enzyme is localized in oligodendroglial cell bodies and suggest its use as a marker.
SIALYLTRANSFERASES IN RAT BRAIN: REACTION KINETICS, PRODUCT ANALYSES, AND MULTIPLICITIES OF ENZYME SPECIES
Authors: Ng S.‐S. , Dain J. A.
Published: October 2006

Abstract— The incorporation of NeuNAc from CMP‐NeuNAc into endogenous glycolipids and glyco‐proteins, and exogenously added GM1a (monosialoganglioside) and desialylated fetuin (DS‐fetuin) was studied with particulate preparations from 11 to 15 day old rat cerebra. The apparent +K++m values of the enzyme systems for the different substrates, assayed with 0.5 mg enzyme protein, were: CMP‐NeuNAc, 0.13 mm (same with endogenous and exogenous glycolipid and glycoprotein substrates); GM1a, 0.20 mm; DS‐fetuin, 0.15 mm (or 1.2 mm in terms of acceptor sites). The activities, expressed as nmoles NeuNAc incorporated per 0.5 mg enzyme protein per 30 min incubation at 37°C and pH 6.3, were 0.094, 0.039, 0.17 and 0.64 with the endogenous glycolipids, endogenous glycoproteins, exogenous GM1a and exogenous DS‐fetuin, respectively. Incorporation into endogenous glycolipids was mainly in GM3, while exogenously added GM1a was converted to GD1a. Incorporation into endogenous glycoproteins yields about 20 sialoglycopolypeptides on SDS‐polyacrylamide gel electrophoresis. Neura‐minidase pretreatment of the particulate enzyme preparation decreased sialylation of the higher molecule weight polypeptides but increased sialylation of the lower molecule weight species.

The sialyltransferase activity with the endogenous glycolipid substrates was more heat resistant than the activities with exogenous GM1a. Since more than 60% of the endogenous glycolipid activity was due to the conversion of lactosylceramide to GM3, the sialyltransferase responsible for this reaction appears to be different from the one that acts on GM1a. This was supported by the observation that exogenously added GM1a did not diminish the incorporation of NeuNAc into endogenous lactosylceramide. These two glycolipid sialyltransferase activities were distinguishable from the glycoprotein sialyltransferase activity since exogenous DS‐fetuin did not compete with either the endogenous or the exogenous glycolipids for CMP‐NeuNAc.
IDENTIFICATION OF 5‐HYDROXYTRYPTAMINE BINDING SUBSTANCES FROM RAT BRAIN STEM1
Authors: Johnson David A. , Cho Tae Mook , Loh Horace H.
Published: October 2006

Abstract— Godwin & Sneddon (1975) reported the binding of 5‐hydroxy‐[3H]tryptamine (5‐HT) on a Sephadex LH‐20 column to‘proteolipid material’extracted with n‐butanol from rat brain stem. An examination of this‘proteolipid material’with TLC showed the main constituents to be cerebroside sulfate (CS), monophosphoinositide (PI), and diphosphoinositide. The elution profiles of [3H]5‐HT incubated with purified CS or with a mixture of CS and PI were similar to that of the brain extract on the same column. Because the elution profile of the mixture of CS and PI was more similar to that of the brain extract, it was concluded that what was suggested to be a possible proteolipid‘5‐HT receptor’was mainly two acidic lipids. The elution profile of [3H]5‐HT incubated with purified PI, however, was similar to [3H]5‐HT eluted alone. This suggested that either PI did not bind to 5‐HT or that the PI‐5‐HT complex possesses different Chromatographie behavior than PI. To test this latter possibility, [14C]5‐HT and [3H]PI were incubated then eluted on a Sephadex LH‐20 column with a continuous gradient of increasing polarity. The gradient first eluted PI, then an apparent PI‐5‐HT complex, and finally 5‐HT. This demonstrated that PI will bind to 5‐HT on a Sephadex LH‐20 column and that the PI‐5‐HT complex is probably more polar than PI.
CHANGES IN SPECIFIC ACTIVITY OF DOPAMINE METABOLITES AS EVIDENCE OF A MULTIPLE COMPARTMENTATION OF DOPAMINE IN STRIATAL NEURONS
Authors: Groppetti A. , Algeri S. , Cattabeni F. , Di Giulio A. M. , Galli C. L. , Ponzio F. , Spano P. F.
Published: October 2006

Abstract—

The functional status of dopaminergic nerve terminals has been studied with a method that allows the simultaneous determination of the specific activities of dopamine (DM), tyrosine (Tyr), 3‐methoxytyramine (3‐MT) and 3,4‐dihydroxyphenylacetic acid (DOPAC), after administration of [3H]tyrosine ([3H]Tyr).

Combined fluorimetric, mass fragmentographic and radiometric techniques have been used. [3H]Tyrosine was given intraventricularly to unanaesthetized rats and the animals were killed by exposure for 4 s to high energy microwave radiations.

The specific activities of 3‐MT and DOPAC measured 5 and 20 min after administration of [3H]Tyr, i. e. at time intervals in which the specific activity of DM is rising, are much higher than those their physiological precursor, suggesting that they are generated by more than one DM compartment.

This hypothesis seems to be supported by the finding that in animals killed by decapitation instead of microwave radiations the post mortem accumulation of 3‐MT occurs to a much smaller extent for the radioactive fraction than for the endogenous one, indicating that 3‐MT formed after death may be mainly derived from DM coming from a compartment where this monoamine has been poorly labeled by the radioactive precursor.
INTERRELATION OF PHOSPHOINOSITIDE METABOLISM AND ION TRANSPORT IN CRAB NERVE FIBRES1
Authors: Tret'jak A. G. , Limarenko I. M. , Kossova G. V. , Gulak P. V. , Kozlov Yu. P.
Published: October 2006

Abstract—

The effects of acetylcholine (ACh) on phosphoinositide metabolism and associated changes in nerve fibre membranes of Carcinus maenas and Eriphia spinifrons were studied. It was shown that as the content of triphosphoinositide in ACh‐treated crab nerve fibre decreased, the permeability of the fibres to K+ increased, which led to nerve fibre depolarization. Proserini protected nerve fibres against the effect of ACh. These observations appear to implicate the participation of acetylcholinesterase in triphosphoinositide hydrolysis. Our results indicate that phosphoinositides participate in the control of the permeability of crab nerve fibres to potassium ions.
EFFECTS OF PROTECTION OF BUTYRYLCHOLINESTERASE ON REGENERATION OF GANGLIONIC ACETYLCHOLINESTERASE
Authors: KOELLE WINIFRED ANGENENT , SMYRL ELOISE GABEL , RUCH G. A. , SIDDONS VERA E. , KOELLE G. B.
Published: October 2006

Abstract—

The regeneration of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) was followed in the superior cervical (SCG), stellate (StG), and ciliary (CG) ganglia and inferior oblique (IO) muscle of cats for the 3‐day period following their inactivation by isopropylmethylphosphonofluoridate (sarin; 2.0 μmol/kg intravenously), with and without preservation of over half the butyrylcholinesterase activity by the prior intravenous infusion of 10‐(α‐diethylaminopropionyl) phenothiazine HCl (Astra 1397; 100 or 200 μmol/kg). Rates of regeneration of AChE in the three ganglia exhibited the same sequence as their relative proportions of AChE‐containing cholinergic ganglion cells (SCG < StG < CG); no such difference was found in the rates of butyrylcholinesterase regeneration. The mean AChE levels in all three ganglia were higher at 48 h in the cats that had received Astra 1397 (100 μmol/kg) prior to sarin. This finding is interpreted as evidence that BuChE may function as a precursor in the synthesis of AChE.
CHICK BRAIN CREATINE KINASE ONTOGENY BEFORE THE ADVENT OF CREATINE AND INSULIN
Authors: RAMIREZ O. , TAKAHASHI J. , HERNANDEZ MARGARITA
Published: October 2006

Abstract—

The ontogeny of brain creatine kinase (CK) was studied during chick embryo development. The cytosolic activity increased 270% in 10 h from the 2nd to the 3rd days of incubation; this was followed by a plateau phase throughout development and at the end of incubation there appeared to be another increase of cytosolic and mitochondrial CK activities. Therefore, early embryonic chick brain CK is another‘constitutive’enzyme like the early embryonic chick heart CK since creatine has not been enzymatically detected in the embryo until day 4 of incubation. Insulin does not appear to stimulate the early increase of brain CK activity since the hormone is not present in the embryo until day 5 of incubation. It is likely that CK increase is associated with neuronal multiplication at early stages and possibly to neuronal maturation before hatching.
A COMPARATIVE STUDY OF DIHYDROXYLATED PHENOTHIAZINE DERIVATIVES AS MITOCHONDRIAL INHIBITORS
Authors: Tjioe Sarah A. , Manian A. A. , O'neill J. J.
Published: October 2006

Abstract— —The effects of several dihydroxylated phenothiazine derivatives on brain mitochondrial calcium retention, respiration and ATP synthesis were studied and compared to those of 7,8‐dihydroxy‐chlorpromazine. This compound has previously been shown to disrupt retention of calcium accumulated in the presence of ATP, to inhibit state III and state IV respiration with glutamate as substrate and to inhibit ATP synthesis. It was found that 2,3‐dihydroxypromazine has little effect on mitochondrial calcium retention, but is a potent inhibitor of oxidative phosphorylation. 3,7‐Dihydroxychlorpromazine and 3,8‐dihydroxychlorpromazine produced a relatively slow and incomplete efflux of pre‐accumulated calcium and caused a limited inhibition of respiration. 7,8‐Dihydroxyperphenazine and 7,8‐dihydroxyprochlorperazine promoted an efflux of mitochondrial calcium and inhibited mitochondrial respiration as was seen with 7,8‐dihydroxychlorpromazine. The effects seen with 7,8‐dioxochlorpromazine are also similar to those seen with 7,8‐dihydroxychlorpromazine, suggesting that oxidation products may contribute to the inhibitory effects observed.
THE SYNTHESIS OF MYELIN IN DEVELOPING RAT BRAIN
Authors: Sabri M. I. , Davison A. N.
Published: October 2006

Abstract— —The synthesis of myelin proteins has been studied in the grey and white matter slices of developing rat brain by measuring the incorporation of [3H]lysine and [14C]arginine into polypeptide. The incorporation was sensitive to cycloheximide and puromycin at 1 mM concentration. Developing rat optic nerve slices, free of retinal ganglion cells, were able to synthesize myelin basic and proteolipid proteins, but rat retinal preparation failed to synthesize myelin basic protein. Rabbit retinae were able to synthesize myelin basic and proteolipid proteins. Significant activity of the myelin marker enzyme 2′,3′‐cyclic nucleotide‐2′‐phosphodiesterase has been found in the rabbit retina but not in rat retina. The results presented in this communication suggest that myelin proteins in the rat CNS are synthesized by the oligodendroglial cells and that neurons probably do not participate.
UPTAKE OF CALCIUM BY CHROMAFFIN GRANULES IN VITRO
Authors: Kostron H. , Winkler H. , Geissler D. , König P.
Published: October 2006

Abstract— Partly purified chromaffin granules were incubated in vitro with Ca2+ (with trace amounts of 45Ca2+) in concentrations ranging from 4 μm to 1 mm. After incubation the granules were washed with media containing EDTA and then subjected to density gradient centrifugation (1.3 to 2.0 m‐sucrose solutions) in order to characterize the particles which had taken up 45Ca2+. By using marker enzymes and various inhibitors of Ca2+ uptake into such cell particles as mitochondria it was established that under the conditions of the experiments chromaffin granules took up Ca2+ from the incubation medium. To characterize this uptake a simplified density gradient procedure was tested and found to be suitable. The uptake of Ca2+ into chromaffin granules was strongly dependent on temperature. It was not activated by ATP. The uptake was linear up to 10 min. At high calcium concentrations (above 200 μm) the rate of uptake levelled off. The uptake at 37°C was 1 nmol Ca2+/mg protein/min at a Ca2+ concentration of 500 μm. Mg2+ had no influence on Ca2+ uptake, whereas Sr2+ (1 mm) inhibited it. The methods established in this study should prove useful for a further characterization of this Ca2+ uptake into chromaffin granules which is likely to represent a useful model for the Ca2+ uptake occurring in the intact gland.
BRAIN REGIONAL SPERMIDINE AND SPERMINE LEVELS IN RELATION TO RNA AND DNA IN AGING RAT BRAIN1
Authors: Shaskan E. G.
Published: October 2006

Abstract— The polyamines spermidine and spermine were measured in brain regions from adult male rats aged 2, 10 and 20 months. Spermine levels displayed marked constancy in all brain regions studied across all ages. However, spermidine concentrations, as expressed per microgram DNA, significantly increased as a function of age in the hypothalamus, corpus striatum and medulla oblongata‐pons. Similar trends with age of increased spermidine steady‐state levels, but not reaching statistical significance, were observed in the cerebral cortex, midbrain and hippocampus. An absolute decline with age in DNA levels was observed only in the hippocampus. Total RNA levels, as expressed per DNA, tended to decline in all brain regions between 2 and 10 months with a reversal in this trend between 10 and 20 months in all regions except the corpus striatum. Perhaps the increased steady‐state levels of spermidine, which may represent significantly increased turnover rates of this polyamine, are compensatory responses to a decreased turnover of RNA. Alternatively, the observed changes in the spermidine to spermine ratio with age may reflect changes in neuronal‐glial relationships within brain regions.
QUANTITATIVE ISOLATION AND PROPERTIES OF NEARLY HOMOGENEOUS POPULATIONS OF UNDEGRADED FREE AND BOUND POLYSOMES FROM RAT BRAIN1
Authors: Ramsey J. C. , Steele W. J.
Published: October 2006

Abstract— A procedure is described for the preparation of free and bound polysomes from whole homogenate of rat brain tissue. Brain is homogenized in a sucrose‐polysome buffer medium high in KCl (250 mm). After a 12‐min centrifugation at 135,000 g, the free polysomes in the supernatant are decanted and saved, while the membrane bound polysomes in the pellet are resuspended in homogenizing medium, homogenized in the presence of detergent (Triton X‐100), centrifuged for 5min at 1470 g to remove nuclei, decanted, treated with deoxycholate and centrifuged for 10 min at 24,000 g to remove deoxycholate‐insoluble material. Polysomes in the two supernatants are harvested by centrifugation through sucrose gradients prepared in high KCl polysome buffer, and with or without cell sap. Free and bound polysomes prepared in this manner are undegraded, equally active in cell‐free protein synthesis, and largely free of the usual contaminants. Cross‐contamination is minimal (>10%). The recovery of polysomes is at least 95%. The distribution of ribosomes and polysomes in rat brain is 58% free and 42% membrane‐bound. The distribution of rat brain RNA is 65% ribosomal and 35% non‐ribosomal. Conditions are described for the visualization and analysis of the entire complement of free and bound ribosomes. The size fractionation procedure is rapid and reproducible, requires much less ultracentrifugation than the density‐gradient technique, and provides a nearly quantitative means of isolating undegraded free and bound polysomes of rat brain tissue.
SOLUBILIZATION AND PARTIAL CHARACTERIZATION OF THE S‐100 PROTEIN BINDING ACTIVITY OF SYNAPTOSOMAL PARTICULATE FRACTIONS1
Authors: Donato R.
Published: October 2006

Abstract— Chromatographic evidence is presented that 125I‐labelled S‐100 protein binds to the Triton X‐100 extract of synaptosomal membranes obtained from the cerebral cortex of the adult rat. The interaction is specific and saturable with respect to S‐100 concentration. The binding is time‐ and temperature‐dependent. The affinity of the extract for S‐100 is of the same magnitude as that calculated for whole membranes. Treatment of the extract at high temperatures or with trypsin, phospholipase C and neuraminidase reduces the extent of the interaction, while phospholipase D does not affect it. These results further support the view that S‐100 binds to a highly specific site in nervous membranes.
THE GLUTAMINE TRANSAMINASE‐ω‐AMIDASE SYSTEM IN RAT AND HUMAN BRAIN1
Authors: Cooper A. J. L. , Gross M.
Published: October 2006

Abstract— Glutamine transaminase from rat brain was shown to occur in the mitochondrial fraction, whereas the ω‐amidase was shown to occur in the soluble fraction. Both enzymes were also found to be widely distributed throughout human brain tissue. Specific activities for the glutamine transaminase and ω‐amidase in the parietal cortex of one individual at 5 h post mortem were 8 and 53 μmol per hour per gram of tissue, respectively. Rat brain glutamine transaminase was shown to be identical to that of the liver mitochondrial enzyme. Improved assays for glutamine transaminase and ω‐amidase activities in crude tissue homogenates are described. The possible physiological importance of glutamine transaminase and its potential role in the encephalopathy of hepatic disease are discussed.
THE DE NOVO SYNTHESIS OF TYROSINE HYDROXYLASE IN RAT SUPERIOR CERVICAL GANGLIA IN VITRO: THE EFFECT OF NERVE GROWTH FACTOR
Authors: MacDonnell P. , Tolson N. , Yu M. W. , Guroff G.
Published: October 2006

Abstract— An immunoprecipitation technique has been employed to measure the rate of synthesis of tyrosine hydroxylase in organ cultures of rat superior cervical ganglia and the effect of nerve growth factor on that rate. Ganglia which have been maintained in culture for 16 h without nerve growth factor synthesize tyrosine hydroxylase; the hydroxylase comprises approx 0.2% of the newly synthesized soluble protein. While the total amount of tyrosine hydroxylase synthesized de novo increases in the presence of physiological levels of nerve growth factor, the differential rate of tyrosine hydroxylase synthesis is essentially unchanged. At higher levels of nerve growth factor (3–10 μg/ml) there is a small increase in the differential rate of tyrosine hydroxylase synthesis. The major action of nerve growth factor appears to be on the survival of the tissue, but a small effect on the induction of tyrosine hydroxylase is evident at high levels of nerve growth factor.
PYRUVATE DEHYDROGENASE ACTIVATION IN RAT BRAIN CORTICAL SLICES BY ELEVATED CONCENTRATIONS OF EXTERNAL POTASSIUM IONS
Authors: Kovachich G. B. , Haugaard N.
Published: October 2006

Abstract— Cortical slices from rat brain were incubated in Krebs‐Ringer phosphate medium. Activity of the pyruvate dehydrogenase complex (PDH) was measured in homogenates of the incubated tissue. Increasing the extracellular KCI concentration from 5 to 75 mM caused a dose‐dependent increase in activity of this rate‐limiting mitochondrial enzyme. The increase in PDH activity, produced by high concentration of KCI. was associated with a decrease in the tissue content of ATP. Omission of calcium, or replacement of sodium by choline, reduced, and addition of ouabain prevented, the activation of the enzyme in the depolarized tissue.

The mechanism by which extracellular potassium can affect PDH activity is unknown. However, it is most likely that the alterations in enzyme activity are related to changes in properties of cell membranes during depolarization leading to intracellular events directly affecting the enzyme complex. These could include alterations in the concentrations of adenine nucleotides or free calcium ions in the cell.
EFFECT OF β‐ADRENERGIC DRUGS ON ADENOSINE 3′,5′‐MONOPHOSPHATE IN RABBIT VAGUS NERVE
Authors: Roch P. , Salamin A.
Published: October 2006

Abstract— Cyclic AMP was found to accumulate in rabbit vagus nerve after stimulation of specific β‐adrenoceptors. The increase in cyclic AMP content by either isoproterenol or epinephrine was inhibited by the β‐adrenoceptor antagonists sotalol and propranolol. α‐Adrenoceptor agonists and antagonists, indirect sympathomimetics and theophylline had no effect on the accumulation of cyclic AMP in vagus nerve. The cyclic AMP increase caused by either β‐adrenoceptor agents or adenosine was found to have no effect on resting potentials, action potentials or on post‐tetanic hyperpolarization.
THE DISTRIBUTION AND BIOSYNTHESIS OF THE MYELIN ‐GALACTOLIPIDS IN THE SUBCELLULAR FRACTIONS OF BRAINS OF QUAKING AND NORMAL MICE DURING DEVELOPMENT
Authors: Deshmukh D. S. , Bear W. D.
Published: October 2006

Abstract— The biosynthesis and accumulation of monogalactosyl diglyceride, galacto‐cerebrosides and sulfatides were studied in the brain of quaking mouse during myelination. The specific activity of monogalactosyl diglyceride synthesis of the mutant mouse was reduced to 50% of the control of the same age, comparable to the reduction in the biosynthesis of galactosylcerebrosides and sulfatides. The three galactolipids were largely associated with the myelin and microsomal fractions in the normal and quaking mice at the ages studied. Although the concentrations of microsomal galactolipids (expressed as nmol/g wet wt of brain) were lower in quaking mice than in the controls at all ages, the percentage of total brain monogalactosyl diglyceride recovered in the microsomes of the mutant mouse was always larger than in the microsomes of the controls. Between 16 and 41 days, the monogalactosyl diglyceride content of the control myelin increased 10‐fold, whereas the concentrations in the mutant increased only 2‐fold. In normal animals, the percentage of total myelin galactolipids in the ‘small myelin’ decreased over the age of 1841 days with concomitant increase in the ‘large myelin’. In contrast, in the mutant, large percentages of these compounds remained associated with the small myelin even at late periods of myelin development. These findings indicate that the slow rate of deposition of myelin in the brain of quaking mouse may be due to a defective transport mechanism of the galactolipids from the site of synthesis (microsomes) to the site of deposition (myelin), or to a defect in the mechanism of final myelin assembly, rather than to a lipid‐specific genetic error.
ENERGETICS OF AMINO ACID TRANSPORT INTO BRAIN SLICES: EFFECTS OF K+ DEPLETION AND Rb+ OR Cs+ SUBSTITUTION ON AMINO ACID UPTAKE
Authors: Banay‐Schwartz Miriam , Teller D. N. , Horn Babette , Lajtha A.
Published: October 2006

Abstract— Mouse brain slices were depleted of K+ by three 10‐min incubations‐in oxygenated HEPES‐buffered medium lacking glucose and K+. Addition of K+ or Rb+ (or Cs+, to a smaller degree) with glucose, or with succinate, malate, and pyruvate (SMP) before incubation at 37°C with 14C‐amino acids restored active low‐affinity transport of d‐Glu, α‐aminoisobutyrate (AIB), GABA, Gly, His, Val, Leu, Lys, and Orn. Ouabain at 1–2μm with Rb+ was more inhibitory with SMP than with glucose, suggesting that the glycoside may affect specific energy coupling to transport. Valinomycin, in contrast, showed no specificity of inhibition of amino acid uptake with glucose or SMP and K+ or Rb+. Cs+ partially restored amino acid uptake, but Li+ was less effective than Cs +. NaF at 10 mm with SMP + Rb+, or SMP + K+ did not inhibit amino acid uptake. Therefore, it was possible to dissociate glycolysis and Na+, K + ‐ATPase activity from amino acid transport. The ion replacements for K + that supported active amino acid transport indicate that the specificity of ions in possible ionic gradients for transport energetics should be reexamined.
PURIFICATION AND PROPERTIES OF BRAIN ALKALINE PHOSPHATASE
Authors: Dorai D. Thambi , Bachhawat B. K.
Published: October 2006

Abstract— Alkaline phosphatase from sheep brain has been purified to homogeneity. The method includes butanol extraction, fractional ethanol precipitation, ion‐exchange chromatography on DEAE‐cellulose, and on DEAE‐Sephadex followed by Sephadex G‐200 filtration. By these steps, the enzyme is purified 22,920‐fold with 15% recovery. The homogeneous enzyme is shown to be a sialoglycoprotein in nature. Neuraminidase treatment reduces the electrophoretic mobility of the enzyme. The enzyme shows pyridoxal phosphate phosphatase activity along with p‐nitrophenylphosphate phosphatase activity. Both these compounds behave as mutual alternate competitive substrates. The general properties of the enzyme are described.
PHOSPHORYLATION AND METHYLATION OF CHROMATIN PROTEINS FROM MOUSE BRAIN NUCLEI
Authors: Lee N. M. , Loh H. H.
Published: October 2006

Abstract— Chromatin protein kinase and histone methyltransferase are present in two nuclear populations, neuronal and oligodendroglial. At least 30% of the enzymes are tightly bound to chromatin. The specific activities of both enzymes are higher in neuronal populations than in oligodendroglial. Protein kinase from these nuclear populations phosphorylates endogenous protein; however, the methyltransferase requires exogenous histone as substrate. The methyltransferase from both nuclear populations preferentially methylates lysine‐rich histone.
ISOLATION AND IDENTIFICATION OF γ‐AMINOBUTYRYL‐CYSTATHIONINE FROM HUMAN BRAIN AND CSF
Authors: Perry Thomas L. , Hansen Shirley , Schier Gary M. , Halpern Berthold
Published: October 2006

Abstract— A new dipeptide, γ‐aminobutyryl‐cystathionine, has been identified in human brain and CSF. The compound was isolated from peptide concentrates which were prepared by removing free a‐amino acids from deproteinized brain extracts on a copper Sephadex column. The isolated peptide was shown to be GABA‐Cysta by standard chemical methods, and its identification was confirmed by mass spectrometry. GABA‐Cysta is present in both biopsy and autopsy specimens of adult human brain, its content in some brain areas being as high as 0.090 μrnol/g wet weight. Its concentration in CSF is much lower. What physiologic role this unusual peptide plays in brain remains to be determined.
NICOTINE AND α‐BUNGAROTOXIN BINDING TO AXONAL AND NON‐NEURAL TISSUES1
Authors: Jones S. W. , Galasso R. T. , O'Brien R. D.
Published: October 2006

Abstract— Nicotine binds to homogenates of lobster walking leg nerve (Kd= 1.1 ± 0.3 μm, Bmax= 2.4 ± 0.5 nmol/g wet tissue), horseshoe crab leg nerve (Kd= 0.11 ± 0.06 μm, Bmax= 1.3 ± 0.6nmol/g), and kidney from 18‐month‐old rats (Kd= 0.8 ± 0.2 μm, Bmax= 23 ± 9 nmol/g). The pharmacological sensitivities of nicotine binding to lobster and horseshoe crab leg nerve homogenates are similar to that of the axonal cholinergic binding macromolecule (ACBM) (Denburget al., 1972) of lobster leg. nerve membrane, while the binding to rat kidney is sensitive to α‐bungarotoxin but not atropine or curare. There was no nicotine binding to rat heart or spleen, or to kidney from younger rats; little or no binding to blue crab nerve or to Torpedo electroplax motor nerve; and little binding (around 0.1 nmol/g) to rat liver. [3H]α‐Bungarotoxin bound reversibly (0.17 nmol/g) to lobster leg nerve membrane The implications of these results for the distribution and function of the ACBM, and for the specificity of α‐bungarotoxin, are discussed.
CHOLINE ACETYLTRANSFERASE ACTIVITY IN LARGE VENTRAL SPINAL NEURONS
Authors: Weil David E. , Busby W. H. , McIlwain D. L.
Published: October 2006

Abstract— Up to approx 3 pmol of acetylcholine (ACh)/h/cell body was synthesized by perikarya of large spinal neurons isolated in bulk fractions from bovine ventral spinal cord. Many of the cell bodies are probably derived from motoneurons. A medium of low ionic strength and pH was used to minimize losses of soluble acetyl CoA:choline‐o‐acetyltransferase (ChAc; EC 2.3.1.6) from the neurons, whose permeability properties were altered. Such a medium also increased the retention of other soluble proteins by the cell bodies. The maximal rate of hydrolysis of ACh by the isolated neurons exceeded that of its synthesis by a factor of at least 100. It was estimated that ChAc and acetylcholinesterase (AChE; EC 3.1.1.7) each represent less than 0.01% by weight of the total protein in these cell bodies and that as little as 10% of each enzyme in the ventral spinal cord is located within the large neuronal somata and their proximal processes.
EFFECT OF PRETREATMENT UNDER VARIOUS CATIONIC CONDITIONS ON ACETYLCHOLINE CONTENT AND CHOLINE TRANSPORT IN RAT WHOLE BRAIN SYNAPTOSOMES
Authors: Weiler M. H. , Jope R. S. , Jenden D. J.
Published: October 2006

The effects of different ionic environments were measured on the concentration of acetyl‐choline (ACh) from synaptosomes and their effect on subsequent high affinity choline (Ch) transport and ACh synthesis after resuspension of the synaptosomes in the normal Krebs medium. KCl (40 mM) was used to induce ACh release and reduce synaptosomal ACh content. The effects of Na+ omission, Ca2+ omission, and high Mg2+ on spontaneous (KC1: 4.75 mM) and potassium induced (KC1: 40 mM) ACh release and other cholinergic parameters are presented. The high affinity transport of Ch was more highly correlated with the reciprocal of the ACh level (r= 0.934, P= 9.7 × 10‐4) than with the ACh release rate during preincubation (r= 0.792, P= 3.4 × 10‐2). The results are consistent with the view that the consequences of the various ionic conditions on Ch transport and ACh synthesis are dependent on their effects on intrasynaptosomal ACh levels and only secondarily on synaptosomal ACh release.
GLYCOPROTEIN CHANGES DURING THE DEVELOPMENT OF HUMAN BRAIN
Authors: Federico A. , Benedetta C. Di , Milici N.
Published: October 2006

Brain glycoprotein sugars were studied during human brain development. Marked changes were found in the sugar content of glycopeptides derived from soluble and insoluble glycoproteins, showing a general decrease in the soluble and an increase in the insoluble fraction. The data indicate that changes in glycan moiety and/or in glycoprotein population occur during development. The existence of a‘critical period’in glycoprotein development which coincides with the formation of axonal and synaptic membranes sprouting has been established (Dobbing, 1971).
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

We 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

The 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

Transverse 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.