bluuebunny/crossref_metadata_2025_split huggingface dataset:
BIOCHEMTCAL CHANGES IN THE BRAIN OF EXPERIMENTAL ANIMALS IN RESPONSE TO ELEVATED PLASMA HOMOCYSTINE AND METHIONINE
Authors: Tudball N. , Griffiths R. 
Published: October 2006

AbstractThe effects of high plasma concentrations of homocystine and methionine on the free amino acids of brain have been examined. Incorporation of the label from [35S]methionine into the free amino acid pools of rabbit brain was enhanced in response to high plasma homocystine or high plasma homocystine and mcthionine. Under comparable conditions a marked decrease in the incorporation of the label from [14C]glycine into the free pool was observed. The corresponding incorporation of 35S and 14C into brain proteins parallelled the results obtained with incorporation into the free pools of amino acids. Amino acid analyses of the free amino acid pools of rabbit brain revealed a general decrease in the concentration of amino acids in response to high plasma homocystine or high plasma homocystine and methionine. Inhibition of protein synthesis which occurs under the above experimental conditions is a general phenomenon. myelin and other brain fractions being equally affected. The decrease in concentration of brain amino acids also results in a diminution in concentration of the neurotransmitters GABA, dopamine and noradrenaline. The possible relationship of the observed changes to homocystinuria is discussed.
INFLUENCE OF NEONATAL HYPOTHYROIDISM UPON TRANSCRIPTION IN ISOLATED RAT BRAIN AND LIVER NUCLEI
Authors: Krawiec L. , Montalbano C. A. , Gömez C. J. 
Published: October 2006

AbstractThe optimum conditions for measuring the transcriptional activity of endogenous RNA polymerase I and I1 were established in low ionic strength incubation mixtures for liver and cerebrum cell nuclei. Both activities were estimated in the presence of Mg2+ for RNA polymerase 1 and Mn2+ for RNA polymerase I1 under conditions in which the nuclear morphology is prcscrvcd. The UMPIGMP incorporation ratio was used to determine the type of RNA synthesized and the results were confirmed employing specific inhibitors of RNA synthesis, such as a‐Amanitin and Actinomycin‐D. Neonatal thyroidectomy in the rat diminished the normal growth of body and liver more than the cerebral growth. The transcriptional capacity in the presence of Mg2+ in cerebral cell nuclei was not changed by the absence of thyroid function during postnatal development. Contrariwise, the activity the presence of Mn2+ was transicntly diminished between the 10th and 13th day of life. When the assays were performed at high ionic strength there were no differences between normal and hypothyroid animals. In liver, thyroid deficiency affected in an early and permanent way the transcription of an AU‐rich RNA. The endogenous activity measured at high ionic strength and that tested in the presence of Mg2+ were altered from the 20th day onward.
OCCURRENCE OF γ‐GLUTAMYLHISTIDINE IN BOVINE BRAIN
Authors: Kakimoto Y. , Konishi H. 
Published: October 2006

Abstractγ‐Glutamylhistidine was purified from 7.5 kg of bovine brain. ldentification was based on the comparison with the synthetized compound. γ‐Glutamyllysine and γ‐glutamylarginine were not detected. The present study added another γ‐glutamyl amino acid 10 the list of the previously known 10 γ‐glutamyl compounds.
SDS GEL ELECTROPHORESIS OF RAPIDLY TRANSPORTED PROTEINS IN GARFISH OLFACTORY NERVE
Authors: Cancalon P. , Elam J. S. , Beidler L. M. 
Published: October 2006

Abstract— Proteins undergoing rapid axonal transport in the garfish olfactory nerve were examined by sodium dodecyl sulphate gel electrophoresis. The distribution of polypeptides and the extent of their labeling by transported molecules was determined in several nerve subfractions including: total particulate, total membrane, mitochondrial and two membrane subfractions rich in axolemma. The polypeptide composition of the various fractions was found to be relatively similar, with each showing a major protein with an estimated MW of 58,000. Specific differences in the concentrations of certain proteins were noted between fractions, including differences between the lower and higher density axolemma rich subfractions. Axonally transported radioactivity was predominantly localized among high molecular weight proteins, with all fractions, except mitochondrial pellet, displaying a major peak of radioactivity centered at 126,000‐MW. Several major proteins including the 58,000‐MW band were labeled by rapid transport to a much smaller extent. Certain labeled peaks were found to be concentrated in individual fractions, particularly a polypeptide (MW 35,000) more predominantly found in the lower density axolemma rich fraction.Systemic labeling of the nerve is found to give a general distribution of radioactivity on gels, which is clearly different from the pattern obtained after axonal transport labeling.
MYELIN BASIC PROTEIN PHOSPHATASE ACTIVITY IN RAT BRAIN
Authors: McNamara J. O. , Appel S. H. 
Published: October 2006

Abstract— Previous work from this and other laboratories has demonstrated phosphorylation of myelin BP in vivo and in vitro. The rapid turnover of BP phosphate has suggested the presence of a phosphatase. The present studies have identified two BP phosphatases. One is present in the cytosol of rat brain homogenate. It has the highest specific activity (37 pmol/min/mg) and total activity of BP phosphatase present in any subcellular fraction. The partially purified cytosol enzyme can readily dephosphorylate soluble 32P‐labelled BP but is only half as effective in dephosphorylating membrane‐bound BP. Conversely, the phosphatase which remains associated with highly purified myelin is 2.3 times as effective on BP in the membrane (7.2 pmol/min/mg) as on soluble BP (3.2 pmol/min/mg). The myelin phosphatase is tightly bound to the membrane and cannot be removed with concentrated salt solutions. During development the specific activity of the cytosol phosphatase remains constant. The specific activity of the myelin phosphatase, however, is twice as high during the period of maximum myelin formation (6.8 pmol/min/mg at 18 days) as it is in adult myelin (3.2 pmol/min/mg at 12 weeks).In order to compare enzyme effectiveness under the various conditions employed in these studies, we have assumed that both soluble and particulate substrates are phosphorylated at equivalent sites on the polypeptide. We have further assumed that soluble and/or particulate substrates are dephosphorylated at equivalent sites on the polypeptide chain and that the various particulate and soluble enzymes have comparable access to the substrate. Within the limitations of these assumptions, our data suggest myelin phosphatase may play a significant role in phosphate turnover of BP.
INCREASE IN THE APPARENT AChE ACTIVITY IN THE MOUSE DIAPHRAGM INDUCED BY PROTEOLYTIC TREATMENT
Authors: Sketeij J. , Brzin M. 
Published: October 2006

Abstract— Isolated endplate regions from the mouse diaphragm were treated with different agents before or after homogenization in order to solubilize junctional AChE and study the effect of solubilization on its apparent activity. Total AChE activity (solubilized + nonsolubilized) of samples treated with collagenase or papain before homogenization was nearly twice as high as in control samples. If collagenase was added after homogenization no increase in apparent activity was observed although in both cases about 70–80% of AChE activity was solubilized. The access of ACh to the membrane‐bound enzyme is probably not a limiting factor in the AChE assay as is the case in the electric organ homogenates. Both 1 m‐NaCl and Triton X‐100 were quite ineffective as solubilizers when applied before homogenization and had an insignificant effect on the apparent AChE activity.The increase in apparent AChE activity cannot be explained either by a de novo synthesis or by the change in kinetic properties of different species of AChE, or by the release of AChE possibly sequestrated in the membrane vesicles. The possibility is discussed that a part of junctional AChE is inactivated at the beginning of homogenization while it can be preserved by previous solubilization, or that proteolytic treatment may activate some ‘silent’ AChE sites in motor endplates.However, the mere fact that the difference does exist suggests that all AChE activity present in intact motor endplates may not be measurable after homogenization.
REGULATION OF THE LEVEL OF ENDOGENOUS PHOSPHORYLATION OF SPECIFIC BRAIN PROTEINS BY DIPHENYLHYDANTOIN1
Authors: Delorenzo R. J. , Emple G. P. , Glaser G. H. 
Published: October 2006

Abstract—Diphenylhydantoin (DPH) in therapeutic concentrations caused a decrease in the net level of endogenous phosphorylation of two specific proteins from rat brain cerebri, while not significantly affecting the phosphorylation of other protein substrates. The apparent molecular weights of the DPH‐ specific substrate proteins were 60‐63,000 and 49‐52,000, and were designated proteins DPH‐L and DPH‐M, respectively. DPH decreased both the initial rate and the net level of [32P] phosphate incorporation from [γ‐32P] ATP into proteins DPH‐L and DPH‐M. The concentrations of DPH required to produce a half maximal decrease in the levels of phosphorylation of proteins DPH‐L and DPH‐M was 3 × 10‐4 and 8 × 10 ‐4 M, respectively. The effects of DPH on the incorporation of [32P] phosphate into these specific brain proteins were independent of the concentration of ATP over a wide range of ATP concentrations. The DPH‐specific proteins were demonstrated to be present in synaptosomal preparations. The results are compatible with the hypothesis that some of the stabilizing actions of DPH on neuronal tissue and seizure discharge may be mediated by the effect of this anticonvulsant on the phosphorylation of specific brain protein substrates.
NUCLEAR DNA‐DEPENDENT DNA POLYMERASES IN HUMAN BRAIN
Authors: Viola M. V. , Norton P. , Cole Margery L. 
Published: October 2006

Abstract—DNA‐dependent DNA polymerases were partially purified from nuclei of cells from the occipital lobe of human brain. The purification procedure included successive DEAE‐cellulose and phosphocellulose column chromatography, gel filtration and sucrose density gradient centrifugation steps. Four enzymes corresponding to DNA polymerases‐α, β, γ, and terminal deoxynucleotidyl transferase were found. Brain DNA polymerases could be differentiated from one another by size, template preferences and sensitivity to sulfhydryl blocking agents.
AXONAL TRANSPORT OF [35S] SULPHATE IN RETINAL GANGLION CELLS OF THE RABBIT
Authors: KARLSSON J. ‐O. , LINDE A. 
Published: October 2006

Abstract—A rapid axonal transport of 35SO4 in axons of retinal ganglion cells of the rabbit was demonstrated after intraocular administration of the isotope. Transported radioactivity accumulated in the nerve terminals up to 2 days following isotope injection. No evidence for a slow transport of labelled material was found. A considerable part of transported radioactivity had solubility characteristics of glycosaminoglycans, primarily chondroitin sulphate.
METHYL MERCURY INHIBITION OF SYNAPTOSOME AND BRAIN SLICE PROTEIN SYNTHESIS: IN VIVO AND IN VITRO STUDIES
Authors: VERITY M. A. , BROWN W. J. , CHEUNG M. , CZER G. 
Published: October 2006

Abstract—Subacute methyl mercury (MeHg) intoxication was induced in adult rats following the daily intragastric administration of 1 mg MeHg/100 g body weight. Decreased [14C]leucine incorporation into cerebral and cerebellar slice protein was found. Weight loss occurred during the latent and neurotoxic phases but pair feeding did not reveal a significant defect in amino acid incorporation into slice protein. There was no decline in synaptosome protein synthesis in vitro during the latent phase but a significant decline in cerebellar and cerebral synaptosome synthesis was found during the neurotoxic phase. MeHg in vitro inhibited cerebral slice and synaptosome protein synthesis at half maximal concentrations of 7.5 and 12.5 μM respectively. Inhibition of synthesis in synaptosomes was non‐competitive with K1 of 4 × 10−6M. MeHg had no effect on [14C]leucine or [14C]proline uptake into synaptosomes. There was no significant inhibition of synaptosome basal ATPase or Na + K ATPase at concentrations of MeHg (12 μM) giving half maximal inhibition of protein synthesis. No preferential inhibition of the chloramphenicol (55S) or cycloheximide sensitive components of synaptosome fraction protein synthesis was found, suggesting that the inhibition is common to both mitochondrial and extramitochondrial protein synthesizing systems. Addition of nucleotides and/or atractylate failed to influence protein synthesis and did not reverse the MeHg inhibition. Mannitol, as a replacement for the predominant cation species of the incubation medium, gave 40% inhibition of protein synthesis in the control but protected against further inhibition by MeHg.
HIGH AFFINITY UPTAKE SYSTEMS FOR TAURINE IN TISSUE SLICES AND SYNAPTOSOMAL FRACTIONS PREPARED FROM VARIOUS REGIONS OF THE RAT CENTRAL NERVOUS SYSTEM. CORRECTION OF TRANSPORT DATA BY DIFFERENT EXPERIMENTAL PROCEDURES
Authors: Lombardini J. B. 
Published: October 2006

Abstract— —The uptake of taurine into tissue slices of specific regions of the rat central nervous system (CNS) was compared with the uptake of taurine into synaptosomal fractions prepared from the corresponding regions. Two different techniques for performing control experiments were also compared: procedure I, correction for the uptake of taurine obtained from duplicate incubations but at 2°c and procedure II, correction of taurine uptake into extracellular or extrasynaptosomal space measured by inulin uptake experiments plus correction for diffusion (non‐saturable) processes.Kinetic analyses of the uptake data in tissue slices utilizing the procedure I correction technique indicate that six regions of the rat CNS (spinal cord, diencephalon, cortex, striatum, hippocampus, and midbrain) possess high affinity uptake systems (Km values approx 60 μM or less). The Km value for the cerebellum (105.4 ± 15.7 μM) is intermediate between a high and low affinity uptake system while the Km value for the pons‐medulla (210.0 12.4 μM) is considered to be low affinity. When procedure II techniques were utilized for correcting the uptake data all eight regions demonstrated high affinity uptake systems (11.8–73.2μM).Synaptosomal fractions prepared from the spinal cord, pons‐medulla, diencephalon, and midbrain demonstrate high affinity uptake systems (procedure I) for taurine (10.3–47.2 μM) while the hippocampus, cortex, striatum, and cerebellum have intermediate (but still high affinity) values (59.4–96.4 μM). High affinity uptake systems (8.2–79.8 μM) were obtained for all eight regions of the rat CNS when procedure II was utilized for correction of the data.
METABOLITES AND ENZYMES OF THE PENTOSE PHOSPHATE PATHWAY IN ISOLATED NERVE ENDINGS1
Authors: Kauffman F. C. , Harkonen M. H. A. 
Published: October 2006

Abstract— The activities of each enzyme associated with the pentose phosphate pathway as well as the non‐enzymatic intermediates in this pathway were measured in synaptosomes isolated from rat cerebral cortex. The specific activities of transketolase (EC 2.2.1.1) and transaldolase (EC 2.2.1.2) were significantly lower in synaptosomes than cerebral cortex; however, the specific activities of glucose‐6‐phosphate dehydrogenase (EC 1.1.1.49), 6‐phosphogluconate dehydrogenase (EC 1.1.1.44), ribosephosphate isomerase (EC 5.3.1.6) and ribulosephosphate epimerase (EC 5.1.3.1.) were comparable in homogenates of synaptosomal fractions and cerebral cortex. Concentrations of most intermediates of the pentose pathway were also similar in extracts of synaptosomes and brain homogenates.Six hours after treatment of rats with the nicotinamide analog, 6‐aminonicotinamide (6‐AN), 6‐phosphogluconate levels in synaptosomes were increased 5‐fold; however, glucose‐6‐phosphate levels remained unchanged. During a 30 min in uitro incubation 6‐phosphogluconate levels increased approx 2‐fold in synaptosomes obtained from 6‐AN treated rats but did not change in synaptosomes from untreated rats. During the same period glucose‐6‐phosphate levels decreased in synaptosomes from both control and 6‐AN treated rats. The conversion of both [1‐14C]glucose and [6‐14C]glucose to 14CO2 was depressed in synaptosomes from 6‐AN treated rats; however, the ratio of the two isotopes converted to 14CO2 was essentially the same. It is concluded that the pentose phosphate pathway is active in nerve endings both in vivo and in vitro.
ACETYL‐CoA SYNTHESIZING ENZYME ACTIVITIES IN SINGLE NERVE CELL BODIES OF RABBIT
Authors: Hayashi Hideaki , Kato Takahiko 
Published: October 2006

AbstractActivities of five enzymes (pyruvate dehydrogenase complex; citrate synthase, EC 4.1.3.7; carnitine acetyltransferase, EC 2.3.1.7; acetyl‐CoA synthetase, EC 6.2.1.1; and ATP citrate lyase, EC 4.1.3.8) were determined in cell bodies of anterior horn cells and dorsal root ganglion cells from the rabbit. For comparison, molecular layer, granular layer and white matter from rabbit and mouse cerebella and cerebral cortex and striatum from the mouse were analyzed. Samples (3–85 ng dry weight) were assayed in 180 to 370 ml of assay reagents containing CoASH and other substrates in excess. By using ‘CoA cycling’, the assay systems were devised to amplify and measure small amounts of acetyl‐CoA formed during the enzyme reactions. Carnitine acetyltransferase was the most active enzyme in single nerve cell bodies and all layer samples, except for rabbit and mouse cerebellar white matter. Citrate synthetase was the lowest in single cell bodies. The activities of carnitine acetyltransferase and acetyl‐CoA synthetase (656 and 89.8 mmoles of acetyl‐CoA formed/kg of dry weight/h at 38°C) from dorsal root ganglion cells were about 2‐fold higher than those from anterior horn cells. The activity of ATP citrate lyase (134mmol of acetyl‐CoA formed/kg of dry weight/h at 38°C) from anterior horn cells was approximately twice that from dorsal root ganglion cells. The activity of this enzyme was distributed in a wider range in anterior horn cells than dorsal root ganglion cells. The second highest activity (80.0 mmol of acetyl‐CoA formed/kg of dry weight/h at 38°C) of ATP citrate lyase was found in striatum where cholinergic interneurones are abundant. Relatively higher activities of this enzyme were found in cerebellar granular layer and white matter which are known to contain the cholinergic mossy fibers. These results suggested that cholinergic neurones contain higher activity of ATP citrate lyase which is thought to supply acetyl‐CoA to choline acetyltransferase (EC 2.3.1.6) as a substrate to form acetylcholine.
α‐DIFLUOROMETHYL DOPA, A NEW ENZYME‐ACTIVATED IRREVERSIBLE INHIBITOR OF AROMATIC L‐AMINO ACID DECARBOXYLASE
Authors: Palfreyman M. G. , Danzin C. , Bey P. , Jung M. J. , Ribereau‐Gayon G. , Aubry M. , Vevert J. P. , Sjoerdsma A. 
Published: October 2006

AbstractDL‐x‐Difluoromethyl DOPA (DFMD, RMI 71801), an enzyme‐activated irreversible inhibitor of aromatic L‐amino acid decarboxylase in vitro, produces a rapid, long‐lasting and dose‐dependent inhibition of aromatic L‐amino acid decarboxylase in peripheral tissues of mice when administered i.p. or orally. Doses of 500 mg/kg i.p. produce only very slight inhibition of the enzyme activity in mouse brain whilst inhibiting the enzyme activity of peripheral tissues by more than 90%. With L‐[3H]‐DOPA co‐administration brain concentrations of L‐[3H]DOPA and 3H‐catecholamines are increased 3‐ to 8‐fold concomitant with a decrease in the peripheral decarboxylation of L‐[3H]DOPA. Under these conditions it is clear that the slight inhibition of enzyme activity in the brain is totally inadequate to inhibit the decarboxylation of L‐DOPA in this organ. Similarly, the decarboxylation of exogenously supplied 5‐hydroxytryptophan is inhibited peripherally with a consequent increase in brain serotonin concentrations. DFMD is another example of an enzyme‐activated irreversible inhibitor which due to its novel and specific mechanism of action, may offer advantages over existing decarboxylase inhibitors.
MECHANISM OF ACTION OF NOTEXIN AND NOTECHIS 11‐5 ON SYNAPTOSOMES
Authors: Sen I. , Baba A. , Schulz R. A. , Cooper J. R. 
Published: October 2006

AbstractThe neurochemical activity of notexin and notechis II‐5 was investigated using a synaptosomal preparation of rat cerebral cortices. In preparations preincubated with [3H]choline in order to label acetylcholine, the toxins caused a rapid release of the transmitter which was calcium‐dependent. The toxins were also potent inhibitors of high affinity choline uptake. Both agents produced a marked depolarization of the synaptosomal preparation as measured by a fluorescent dye and at high concentrations lysed the preparation. At a concentration of 0.1 μM, notexin and notechis II‐5 caused a 50% increase in the efflux of lactate dehydrogenase activity. These results, together with electron microscopic observations, indicated that the toxins disrupt the synaptosomal membranes presumably by their inherent phospholipase activity. The release of acetylcholine and inhibition of choline uptake, together with the depolarization of synaptosomal membranes noted in this study, could explain the observed electrophysiological effects of these toxins.
CHOLINE ACETYLTRANSFERASE AND THE HIGH AFFINITY UPTAKE OF CHOLINE IN CORPUS STRIATUM OF RESERPINISED RATS1
Authors: Burgess E. J. , Atterwill C. K. , Prince A. K. 
Published: October 2006

AbstractRats treated with reserpine show increased Vmax for the high affinity uptake of choline into small slices of corpus striatum. The choline acetyltransferase activity of whole homogenates of striatum is also increased. These changes are consistent with increased cholinergic neuronal activity in the striatum and seem likely to be adaptations mediating increased rates of synthesis of acetylcholine. The maximal increases found occurred concurrently, consistent with coupling of the high affinity uptake of choline and its acetylation in cholinergic nerve terminals of the rat. That increased high affinity uptake is accompanied by increased choline acetyltransferase activity, suggests the input of choline is not the sole determinant of rates of synthesis of acetylcholine, in spite of the large Vmas for striatal choline acetyltransferase, compared with that for high affinity uptake. These results seem best explained by kinetic coupling, in the rat, of the high affinity uptake of choline with a limited pool of choline acetyltransferase preferentially localised at the nerve terminal plasma membrane.
ISOLATION AND PURIFICATION OF CHOLINERGIC RECEPTOR PROTEOLIPIDS FROM RAT GASTROCNEMIUS TISSUE1
Authors: Taylor Richard F. 
Published: October 2006

AbstractFour organic solvent extraction methods have been used to isolate receptor proteolipids from rat gastrocnemius tissue. The resulting proteolipids have high binding capacities and specificities for a number of cholinergic ligands including acetylcholine, α‐bungarotoxin. tubocurarine and deca‐methonium. The proteolipids have been purified by repeated Sephadex LH‐20, Sepharose‐CL and affinity chromatography in organic solvent systems. Protein, carbohydrate and lipid phosphorous analysis of the receptors throughout the purification procedure show that the relative proportions of these components varied with extraction method. The purified receptor proteolipid resulting from wet tissue extraction has been characterized as a somatic, nicotinic cholinergic receptor by its specificity and binding kinetics toward a variety of drugs and toxins. The presence of carbohydrate in the receptor proteolipid preparations throughout the purification procedure may indicate that the cholinergic receptor from rat gastrocnemius tissue is a glycoproteolipid.