bluuebunny/crossref_metadata_2025 huggingface dataset:
CHANGES WITHIN METABOLIC COMPARTMENTS IN THE BRAINS OF YOUNG RATS INGESTING LEAD
Authors: Patel A. J. , Michaelson I. A. , Cremer J. E. , Balázs R.
Published: October 2006

—[2‐14C]Glucose and [3H]acetate were injected simultaneously into 19‐day‐old rats suckling from mothers fed either a normal diet or a diet containing 4·5% lead acetate. Changes in the rate of conversion of both precursors into amino acids associated with the tricarboxylic acid cycle were observed.

[I4C]Glucose. In the brain of young rats ingesting lead, the specific radioactivity of glutamate, aspartate, γ‐aminobutyrate and glutamine were all significantly lowered relative to that of glucose. Glutamine labelling was the most affected.

[3H]Acetate. In comparison with controls, the total amount of 3H in either water or acid‐soluble constituents of the brain was the same, but the 3H content of the amino acids was significantly reduced in the lead‐treated rats. In both groups, glutamine had the highest specific radioactivity but the time courses of the labelling of glutamine were different. In the control the peak incorporation was reached during the first 5 min, whereas in the experimental animals this occurred at about 10 min after the injection of the precursor, and the specific radioactivity even at that time was less than in controls. When compared with controls, the depression in the labelling of glutamine was accompanied at 5 min by an increase in the specific radioactivity of aspartate. In the lead‐treated rats the labelling of GABA was also slowed and the time course seemed to follow that of glutamine rather than glutamate. In spite of the differences in the metabolism of [3H]acetate, metabolic compartmentation of glutamate, assessed by a glutamine : glutamate specific radioactivity ratio higher than 1, was evident even in the brain of the lead‐treated animals, although the values of the ratio at 5 and 10 min were less than in controls. There was no evidence of a diminished supply of substrates to the brain in lead intoxication. The overall changes would be consistent with a retardation in the biochemical maturation of the brain in terms of development of glucose metabolism and metabolic compartmentation.
REGULATION OF CATECHOLAMINE SYNTHESIS IN RAT BRAIN SYNAPTOSOMES1
Authors: Patrick R. L. , Barchas J. D.
Published: October 2006

Abstract— Catecholamine synthesis in synaptosomal preparations of rat striatum, cortex and brain stem was investigated. The striatum had much higher activity than either the cortex or brain stem. Equilibration of labelled tyrosine between tissue and incubation medium was completed within 2 min. The apparent Km of tyrosine hydroxylase (EC 1.14.3a) and of the overall catecholamine synthetic pathway were both approximately 5 ± 10−6m for tyrosine. The following amines were found to inhibit striatal dopamine synthesis: dopamine, 25% inhibition at 5 ± 10−7m; noradrenaline, 25% inhibition at 5 ± 10−6m;and serotonin, 30% inhibition at 10−5m. The catecholamine‐induced inhibition of synthesis was antagonized by pre‐incubation with cocaine. Increasing the potassium concentration from 5 to 55 mm caused a release of amines into the medium which was accompanied by a 40% increase in dopamine synthesis, when synthesis was measured during the first 5 min of exposure to elevated potassium. These results indicate that synaptosomal catecholamine synthesis is inhibited by increases in intra‐synaptosomal amine levels, and that short‐term exposure to depolarizing concentrations of potassium can increase synthesis.
STABILITY OF THE BRAIN FATTY ACID PATTERN IN ADULT RATS DURING EXTREME STARVATION1
Authors: Joel C. D. , Ellis C. A. , Lace J. K. , Joel P. B. , Swanson M. R. , Stroemer J. R.
Published: October 2006

Abstract— Adult rats were denied food for 7 days. As compared with a control group, this severe starvation reduced the mean total body weight by 44 per cent, the weight of the diaphragm by 33 per cent and liver by 67 per cent, the total lipid content of the diaphragm by 57 per cent and liver by 69 per cent, and the total lipid phosphorus content of the diaphragm by 19 per cent and liver by 68 per cent. The decrease in lipid phosphorus contents indicates that the diaphragm and liver catabolized membrane phospholipids as well as triglycerides. In contrast, the fresh weight of the brain and the total lipid content of the brain were not significantly altered by starvation. The fatty acid patterns of the total lipid of the diaphragm and liver (determined by GLC) were grossly altered by starvation. In the brain, however, 17 of the 21 fatty acids measured did not change significantly (P > 0.05) and the remaining four changed, with borderline statistical significance, by only 2 to 13 per cent. There was no significant effect of starvation of the pattern of the brain polyunsaturated fatty acids when measured by alkali isomerization. In contrast to the liver and diaphragm, the brain is apparently unable to utilize its lipids appreciably as an energy source. Presumably the lipids of the brain are preserved to permit this organ to function properly, even in the last stages of starvation.
THE METABOLISM OF [1‐14C]ARACHIDONIC ACID IN THE NEUTRAL GLYCERIDES AND PHOSPHOGLYCERIDES OF MOUSE BRAIN1
Authors: Yau T. M. , Sun Grace Y.
Published: October 2006

Abstract— [1‐14C]Arachidonic acid was incorporated into brain lipids with a half‐life of approx. 5 min. Within 40 min after intra‐cerebral injection, radioactivity was distributed mainly among the diacyl‐sn‐glycero‐3‐phosphorylcholine (45 per cent), diacyl‐sn‐glycero‐3‐phosphorylinositol (22 per cent), diacyl‐sn‐glycero‐3‐phosphorylethanolamine (14 per cent) and triacylglycerols (9 per cent). At comparable times, the proportions of radioactivity distributed in diacyl‐sn‐glycero‐3‐phosphorylserines and alkenylacyl‐sn‐glycero‐3‐phosphorylethanolamines were relatively small. Radioactivity was initially incorporated into the phosphatidio acids and diacylglycerols before labelling of the triacylglycerols and other phosphogly‐cerides. The relative specific activity of diacylglycerols was maximum between 3–6 min after injection. Due to the small level of diacyl‐sn‐3‐phosphorylinositol present in brain, its relative specific radioactivity was higher than other types of brain phosphoglycerides. Results of the experiment thus indicate that labelled arachidonic acid is an excellent precursor for metabolic studies with regard to acyl groups present in the 2‐position of the phosphoglyceride molecules. Furthermore, this labelled precursor is specially useful in studies related to metabolism of diacyl‐sn‐glycero‐3‐phosphorylinositol in brain.
EFFECTS OF UNDER NUTRITION AND PROTEIN DEFICIENCY ON GLUTAMATE DEHYDROGENASE AND DECARBOXYLASE IN RAT BRAIN
Authors: Rajalakshmi R. , Paramhswaran M. , Telang S. D. , Ramakrishnan C. V.
Published: October 2006

Abstract— Studies were made on the effects of undernutrition at different ages during the neonatal period and of the comparative effects of postweaning protein and calorie deficiencies in neonatally undernourished or normally reared animals. Neonatal undernutrition resulted in deficits in body wt, brain wt and the activities of brain glutamate dehydrogenase and glutamate decarboxylase. Percentage deficits in brain wt were maximum in the first week of life but those in brain enzymes were greater in the second week. Rehabilitation of neonatally undernourished animals reversed the deficits in brain wt and brain enzymes. Post‐weaning protein deficiency produced similar deficits in brain enzymes in both neonatally undernourished and normally reared animals. With post‐weaning undernutrition, however, these deficits were found only in animals subjected to neonatal undernutrition as well.
INTERACTION OF CATECHOLAMINE AND AMINO ACID METABOLISM IN BRAIN: EFFECT OF PARGYLINE AND l‐DOPA
Authors: Nicklas W. J. , Berl S. , Clarke D. D.
Published: October 2006

Abstract— The combination of l‐DOPA and pargyline caused a decrease in level of aspartate and an increase in that of glutamine in vivo in cerebral cortex, cerebellum, brain stem, hypothalamus, neostriatum and cervical cord of rat. There was also a decreased incorporation of radioactivity from [1‐14C]acetate into amino acids in vivo, most notably in cerebellum and brain stem. The labelling of glutamine was especially affected. In addition, cortical slices were prepared from guinea pigs which had been pretreated with pargyline. These slices were incubated with and without 1 mm l‐DOPA in media containing [1‐14C]acetate. Pargyline alone caused a stimulation of the labelling of glutamate and aspartate but not glutamine and GABA; the levels of aspartate and GABA were greater than in control slices. The addition of l‐DOPA to slices from pargylinized animals caused a severe decrease in glutamine labelling but not in that of glutamate or aspartate; the level of glutamine was increased while that of glutamate was decreased. The results are discussed in terms of the known biochemical and morphological compartmentation of amino acids in brain. It is suggested that catecholamines, in the process of functioning as transmitters, may also function as metabolic regulators of other transmitters, e.g. amino acids, as well as of the energy required for balanced neuronal function.
CHOLINERGIC STIMULATION OF PHOSPHOLIPID LABELLING FROM [32P]ORTHOPHOSPHATE IN GUINEA‐PIG CORTEX SYNAPTOSOMES IN VITRO: SUBSYNAPTOSOMAL LOCALIZATION
Authors: Schacht J. , Neale Elaine A. , Agranoff B. W.
Published: October 2006

Abstract— Subsynaptosomal localization of stimulation of phospholipid labelling by cholinergic agents was investigated. Synaptosomes prepared from guinea‐pig cortex were incubated with [32P]orthophosphate in the presence or absence of 10−3m carbamylcholine. Following incubation and osmotic shock, lysed synaptosomes were subjected to density gradient fractionation. Subsynaptosomal fractions were examined by electron microscopy and analysed for enzyme activities and 32P‐labelled lipids.

In the absence of carbamylcholine, labelled phosphatidate and phosphatidylinositol were recovered in layers and interfaces A, B, C and D formed over 0.9, 1.1, 1.2 and 1.3 m sucrose, with highest amounts of label in fractions C and D for both lipids. Carbamylcholine induced the greatest increment in these two labelled lipids in fractions A and B. This distribution correlated with the presence of acetylcholinesterase activity and membrane ghosts. No correlation was found among the four fractions between the induced increase in labelling and succinic dehydrogenase activity or with the abundance of mitochondria, synaptic vesicles, or cytoplasmic fragments identified by electron microscopy. In contrast with the increases seen in phosphatidylinositol and phosphatidate labelling, carbamylcholine caused a decrease in 32P‐labelling of the polyphosphoinositides, and this effect was seen primarily in the heavier subsynaptosomal fractions, C and D.
SELECTIVE RETENTION AND FILTRATION OF BRAIN NUCLEIC ACIDS IN AGAROSE GELS
Authors: Petrović S. L. , Ivanuš J. J. , Rakić L. M.
Published: October 2006

Abstract— Total nucleic acids of rat brain have been separated by agarose gel chromatography at 2 m‐NaCl into DNA. transfer RNA plus low molecular weight RNA. and high molecular weight RNA fractions. The DNA fraction contained less than 1 per cent RNA by weight judged by either short‐term or long‐term labelling with ortho[32P]phosphate. The high molecular weight RNA fraction contained 28 s and 18 s ribosomal RNAs and a heterogeneous population of 20‐60 s RNAs, apparent after short‐term labelling and characterized by a high content of nearest‐neighbour‐labelled uridylic acid. The rapidly sedimenting (>30s) portion of these RNAs could be largely separated from ribosomal RNAs by gel filtration using 4% agarose. The ribosomal RNAs could be fully resolved into 28 s and 18 s components by agarose gel chromatography at 0.5 m‐0.6 m‐NaCl, as shown by analysis of their sedimentation and nucleotide composition.
METABOLIC COMPARTMENTATION IN THE BRAIN: EFFECTS OF A CENTRAL NERVOUS SYSTEM DEPRESSANT, 1‐HYDROXY‐3‐AMINO‐PYRROLIDONE‐2
Authors: Mouhler H. , Patel A. J. , Johnson A. L. , Reynolds A. P. , Balazs R.
Published: October 2006

—The effect of 1‐hydroxy‐3‐aminopyrrolidone‐2(HA‐966), a CNS depressant, was studied on the metabolism of [14C]glucose and [3H]acetate in the brain in mice. HA‐966 had a marked effect on glucose metabolism. The conversion of glucose carbon into amino acids associated with the tricarboxylic acid cycle (‘cycle’) was severely reduced, while the concentration of brain glucose was approximately doubled. Relative to the specific radioactivity of glucose in the brain, the specific radioactivity of alanine was 60–70 per cent of the control, indicating a reduction in the rate of glycolysis, and those of the‘cycle’amino acids were also lowered. A reduction in‘cycle’flux of 30–35 per cent was estimated. It was established that the depressed glucose utilization flux was not due to either impaired uptake of glucose from blood to brain or to hypothermia. In contrast to [14C]glucose, there was no change in the labelling of the amino acid fraction from [3H]acetate, which is preferentially metabolized in the 'small’compartment believed to be associated with glia. Thus it seems that CNS depression caused by HA‐966 resulted in a selective decrease in energy production in the‘large’metabolic compartment where glucose is oxidized preferentially and which is believed to be associated with neuronal structures.

The results also suggested that communication between the metabolic compartments mediated via glutamine and GABA was reduced, since the labelling from [3H]acetate of glutamine was increased and that of GABA decreased by HA‐966.
METHYLATED AMINO ACID RESIDUES OF PROTEINS OF BRAIN AND OTHER ORGANS
Authors: Kakimoto Y. , Matsuoka Y. , Miyake M. , Konishi H.
Published: October 2006

—Methods for the determination of methyl‐lysine, methyllarginine and methylhistidine residues of tissue proteins are described. They consist of preliminary purification of basic amino acids, enzymic removal of lysine, arginine and histidine followed by amino acid analysis. Recovery rates and specificities of the method were satisfactory. The contents of methylamino acids in proteins of mammalian organs were determined.

The distribution of proteins containing the methylamino acids in human brain showed that the concentrations of methyl‐lysine and NG,N′G‐dimethylarginine were highest in the gray matter of the cerebellar cortex and relatively high in regions rich in gray matter, while those of NG‐mono‐ and NG,N′G‐dimethylarginine were highest in the white matter. The following findings suggest that most of the NG‐mono‐ and NG,N′G‐dimethylarginine was associated with the myelin basic protein. The distribution of the methylarginine residues of acid‐soluble proteins in bovine brains coincided with the cerebroside pattern. The concentrations of the amino acids in acid‐soluble proteins of rat brain increased concomitantly with the increase of cerebroside. The methylamino acid content in proteins increased during the purification of the myelin basic protein from the white matter of human and bovine brains.

Proteins containing NG,NG‐dimethyiarginine and di‐ and trimethyl‐lysine are concentrated in cell nuclei. The first amino acid was found mainly in nucleoplasmic proteins and the other two were found in histones. The concentration of 3‐methylhistidine residue, highest in muscular proteins, is low in cerebral proteins and is probably derived from proteins of walls of blood vessels in the brain.
ELEVATION OF BRAIN HISTAMINE CONTENT IN PROTEIN‐DEFICIENT RATS1
Authors: Enwonwu Cyril O. , Worthington Bonnie S.
Published: October 2006

—Male rats of the Sprague‐Dawley strain (80–250 g body wt) were fed either an adequate protein diet (18% lactalbumin) or a protein‐deficient diet (0.5% lactalbumin). After 5–8 weeks of receiving the low protein diet, some of the malnourished rats were rehabilitated with an adequate protein diet. The malnourished rats exhibited significant elevations in brain levels of histidine (+415%) and homocarnosine (+100%) in comparison to findings in the control animals of similar age. Associated with the elevated brain levels of histidine in malnutrition was a prominent increase in brain content of histamine (+ 150‐+ 238%). The mean brain histamine levels (ng/g) in the control rats varied from 45.96 to 56.15 in several experiments. In the protein‐deficient rats, values ranged from 115 to 190. Refeeding the malnourished rats with adequate protein diet elicited reversal of histidine and histamine levels to near normal values within 1 week. The increased brain content of histamine in malnutrition was attributed to enhanced rate of production resulting from increased availability of the precursor amino acid, a conclusion consistent with elevation also of the brain content of homocarnosine (γ‐aminobutyryl‐l‐histidine) which is another major route of disposal of histidine in the brain. The relevance of these neurochemical alterations to the behavioural changes often associated with protein malnutrition, deserves some intensive examination.
THE PRESENCE OF CYSTEINE IN FROG MYELIN BASIC PROTEIN
Authors: Martenson R. E. , Deibler Gladys E. , Kramer A. J.
Published: October 2006

—Frog myelin basic protein, when subjected to ion‐exchange chromatography at alkaline pH, underwent conversion to a higher molecular weight form. Treatment of the latter with 2‐mercaptoethanol regenerated the monomeric basic protein. Amino acid analysis of the monomer and the higher molecular weight species after performic acid oxidation demonstrated the presence of approximately 1 mol of cysteic acid per mol of protein of molecular weight 19,700. Treatment of the monomer with the mild oxidizing agent azodicarboxylic acid bis dimethyl amide resulted in its partial conversion to the higher molecular weight form. These studies demonstrate that the frog myelin basic protein, unlike those of all other species hitherto examined, contains a single cysteinyl residue in its polypeptide chain.
THE PROPORTIONATE LOSS OF l‐3,4‐DIHYDROXYPHENYLALANINE AND l‐5‐HYDROXYTRYPTOPHAN DECARBOXYLATING ACTIVITY IN RAT CENTRAL NERVOUS SYSTEM FOLLOWING INTRACISTERNAL ADMINISTRATION OF 5,6‐DIHYDROXYTRYPTAMINE OR 6‐HYDROXYDOPAMINE
Authors: Dairman W. , Horst W. Dale , Marchelle Mary E. , Bautz G.
Published: October 2006

—5,6‐Dihydroxytryptamine or 6‐hydroxydopamine was administered intracisternally to rats to effect a selective destruction of serotonin or catecholamine‐containing neurons. The l‐DOPA and l‐5‐hydroxytryptophan decarboxylating activities of the spinal cord and brain were then determined at several time intervals following this treatment. In both cases the relative loss of l‐DOPA decarboxylating activity was the same as the relative loss of l‐5‐hydroxytryptophan decarboxylating activity. 5,6‐Dihydroxytryptamine treatment had little or no effect on catecholamine‐containing neurons and 6‐hydroxydopamine did not effect serotonin‐containing neurons. These data support the idea that only one decarboxylase is involved in the biosynthesis of both serotonin and catecholamines in the rat CNS.
A SENSITIVE MICROASSAY FOR TRYPTOPHAN HYDROXYLASE IN BRAIN
Authors: Kizer J. S. , Zivin J. A. , Saavedra J. M. , Brownstein M. J.
Published: October 2006

—A specific and sensitive, radioisotopic microassay for tryptophan hydroxylase (EC 1.14.36) is described, which is capable of determining enzymatic activity in as little as 5 μg of crude brainstem homogenate. 5‐Hydroxytryptophan, the immediate product of hydroxylation of tryptophan is enzymatically converted to N‐acetylserotonin. A radioisotopic label is then introduced by the enzymatic methylation of N‐acetylserotonin in the presence of [3H]methyl‐S‐adenosyl‐methionine. The [3H]‐melatonin thus formed is isolated by extraction and counted.

With this assay, the activity in individual hypothalamic nuclei (arcuate nucleus, median eminence, suprachiasmatic nucleus, and medial forebrain bundle) has been measured.
APPEARANCE OF NEWLY SYNTHESIZED PROTEIN IN MYELIN OF YOUNG RATS1
Authors: Benjamins Joyce A. , Jones Marjory , Morell P.
Published: October 2006

Abstract— Seventeen‐day‐old rats were injected intracranially with [3H]leucine, then sacrificed between 1 and 24 h. Myelin was prepared from the brains on discontinuous sucrose gradients and the proteins were separated by discontinuous gel electrophoresis in buffers containing sodium dodecyl sulphate. Proteins were stained with acid Fast Green and the distribution was quantitated by densitometry. The gels were then sliced and the radioactivity in each slice was determined. Between 1 and 24 h, the radioactivity in proteolipid protein increased from 18% to 37% of the total radioactivity in the proteins of isolated myelin. During this same period, the per cent distribution of radioactivity in basic and Wolfgram proteins remained constant while that in the remaining high molecular weight proteins decreased. Similar results were also obtained with [3H]glycine as a precursor. The relative specific activity of all of the myelin proteins increased between 1 and 6 h, then remained constant between 6 and 24 h. At 1 h, proteolipid protein reached only 25% of its maximal (6 h) relative specific radioactivity, while the other two proteins reached 50% of maximum. These results indicate a lag in the appearance of labelled amino acids in proteolipid protein relative to the other myelin proteins.
PROTEIN PATTERNS IN DIFFERENT LOBES AND DURING DEVELOPMENT OF OCTOPUS BRAIN
Authors: Giuditta A. , Cimarra Patrizia , Prozzo Nicola
Published: October 2006

Abstract— Utilizing techniques of continuous and SDS‐electrophoresis we have examined the saline‐soluble and SDS‐soluble (membrane‐bound) proteins extracted from the main lobes of adult octopus brain and from the developing optic lobe of the same species. Several additional protein bands are present among the soluble and the membrane‐bound proteins of the vertical lobe in comparison with the suboesophageal lobe. Since the former contains an essentially homogeneous population of small neurons, while the suboesophageal lobe is rich in large nerve cells, these protein bands have been attributed to the small neuronal type present in the vertical lobe.

In the course of a 10,000‐fold increment in body weight, from 0.4 g to 4 kg, there is a significant increase in the concentration of several soluble proteins extracted from the optic lobe. Three of these proteins increase to a marked degree. Among the membrane‐bound proteins some show a moderate increase with age while other protein components of smaller molecular weight undergo a moderate decrease. The overall tissue concentration of the membrane‐bound proteins increases between 0.4 g and 50 g body weight, slightly declining in animals of larger size.
EFFECTS OF METABOLIC INHIBITORS ON AMINO ACID METABOLISM IN RAT RETINA: A COMPARISON OF AMINO‐OXYACETIC ACID AND ETHANOLAMINE‐O‐SULPHATE
Authors: Starr Michael S.
Published: October 2006

Abstract— The abilities of AOAA and EOS to modify the utilisation of radioactively labelled glucose, acetate, glutamine and GABA were studied in isolated rat retina. AOAA inhibited the activities of GAD and GABA‐T, while EOS inhibited GABA‐T but not GAD. AOAA lowered the free amino acid contents of incubated retinae and suppressed the outflow of amino acids into the incubation medium, while EOS had no effect on either parameter. AOAA strongly inhibited the incorporation of 14C from labelled glucose, acetate and glutamine into GABA, and also suppressed the labelling of glutamate, aspartate and glutamine. These effects were qualitatively similar but quantitatively smaller with EOS. Both compounds markedly decreased the syntheses of aspartate and glutamate from exogenous GABA, while the passage of carbon from GABA to glutamine was much less affected. It is suggested that AOAA and EOS may act predominantly on neurones. It appears that inhibition of GABA‐T alone does not cause a profound disturbance of the metabolism of other amino acids. Other metabolic inhibitors such as ouabain, malonate and fluoroacetate did not greatly affect the metabolism of GABA in rat retina.
THE SUBCELLULAR LOCALIZATION OF Ach SYNTHESIS IN RAT STRIATAL SYNAPTOSOMES INVESTIGATED WITH THE USE OF TRITON X‐100
Authors: Lefresne P. , Guyenet P. , Beaujouan J. C. , Glowinski J.
Published: October 2006

—The regulation of [14C]ACh synthesis was studied in rat striatal synaptosomes incubated in presence of various concentrations of Triton X‐100, using [2‐14C]pyruvate or [6‐14C]glucose as precursors. The progressive rupture of the cytoplasmic and mitochondrial compartments induced by the non‐ionic detergent was followed by studying the release, into the incubating medium, of lactate dehydrogenase and choline acetyltransferase (ChAc) and of fumarate hydratase, respectively. [3H]Choline uptake (1 μm) was measured to determine the activity of the high affinity choline permease. 14CO2 formation from [2‐14C]pyruvate was used as an index of the Krebs cycle activity.

The rate of [14C]ACh synthesis from [2‐14C] pyruvate was dependent on the Triton X‐100 concentration; the ester formation decreased between 0·001% (v/v) and 0·010%, but increased again beyond this concentration of detergent. This last phenomenon was interpreted as the result of an extracellular synthesis of ACh involving pyruvate dehydrogenase and ChAc. At 0·002% Triton X‐100 the 14CO2 formation was not affected, indicating a normal mitochondrial activity. The decrease of [14C]ACh synthesis observed up to this detergent concentration could be correlated to the decline of the highaffinity choline permease activity. In these experimental conditions, the ester synthesis could not be restored by the addition of large amounts of choline in the incubating medium suggesting that the molecules of choline must cross the high‐affinity choline permease system in order to be acetylated. This could indicate a close association between the permease and choline acetyltransferase.
EFFECT OF GTP AND OTHER NUCLEOSIDE TRIPHOSPHATES ON GMP INCORPORATION BY ISOLATED CORTICAL NUCLEI
Authors: Ferchmin P. A. , Morimoto H. , Bennett E. L.
Published: October 2006

—The concentration of GTP was found to be critically important in determining the characteristics of incorporation of GMP by DNA‐dependent RNA polymerase from rat brain nuclei. The linearity of the incorporation rate was related to the log of the GTP concentration. Three hundred μM‐GTP in the presence of the other nucleoside triphosphates (1 mM) was near to the optimal conditions in terms of maximum incorporation and linearity. The concentration of ammonium sulfate was an important factor in determining the maximum GMP and UMP incorporation. The U/G incorporation ratio was less than one at low concentrations of substrate and increased with increasing substrate or ammonium sulfate concentration. α‐Amanitin strongly inhibited the reaction, indicating that RNA polymerase II is the effective enzyme.
THE MECHANISM OF ACTION OF β‐BUNGAROTOXIN
Authors: Wernicke J. F. , Vanker A. D. , Howard B. D.
Published: October 2006

—β‐Bungarotoxin, a presynaptically‐acting polypeptide neurotoxin, caused an efflux from synaptosomes of previously accumulated γ‐aminobutyric acid and 2‐deoxy‐d‐glucose. The toxin‐induced efflux of γ‐aminobutyric acid occurred by a Na+ ‐dependent process while that of 2‐deoxyglucose was Na+ ‐independent. These effects were also produced by treating synaptosomes with low molecular weight compounds, including fatty acids, that inhibit oxidative phosphorylation. After incubation with β‐bungarotoxin, synaptosomes exhibited increased production of 14CO2 from [U‐14C]glucose and decreased ATP levels. β‐Bungarotoxin treatment of various subcellular membrane fractions caused the production of a factor that uncoupled oxidative phosphorylation when added to mitochondria. Mitochondria from toxin‐treated brain tissue exhibited a limitation in the maximal rate of substrate utilization. We conclude that β‐bungarotoxin acts by inhibiting oxidative phosphorylation in the mitochondria of nerve terminals. This inhibition accounts for the observed β‐bungarotoxin effects on synaptosomes and at neuromuscular junctions. We suggest that the effects on energy metabolism result from a phospholipase A activity found to be associated with the toxin.
THE EFFECT OF A LOW PROTEIN DIET AND EXOGENOUS INSULIN ON BRAIN TRYPTOPHAN AND ITS METABOLITES IN THE WEANLING RAT
Authors: Dickerson J. W. T. , Pao S.‐K.
Published: October 2006

—Male Wistar rats aged 24 days were divided into three groups. Two groups were given a high protein (250 g/kg casein) and a low protein (30 g/kg casein) diet respectively. The third group was given an amount of the high protein diet containing the same amount of energy as that consumed by the low protein diet rats. The plasma of the animals on low protein contained 20% of the concentration of tryptophan of animals on the other two diets. In these animals the concentration of tryptophan was reduced in the forebrain, cerebellum and brain stem, and the concentrations of 5‐HT and 5‐hydroxyindoleacetic acid were reduced in the forebrain and brain stem. The low protein diet decreased the total uptake of l‐[G‐3H]tryptophan into the brain and its incorporation into brain protein. Plasma insulin concentrations were reduced in the low protein and ‘restricted high protein’ animals and the plasma corticosterone concentration was raised in the low protein animals. Exogenous insulin did not raise the plasma tryptophan concentration in the low protein animals but it increased the uptake of l‐[G‐3H]tryptophan into the brain and its incorporation into protein. Rehabilitation for 7 days restored the plasma and brain tryptophan concentrations and those of brain 5‐HT and 5‐hydroxyindoleacetic acid to control values.
FRACTIONATION OF SPECIFIC MITOCHONDRIAL AND CYTOPLASMIC tRNAs OBTAINED FROM CALF BRAIN1
Authors: Borkowski T. , Brzuszkiewicz‐Żarnowska H.
Published: October 2006

—Total tRNA fractions were isolated from pure mitochondrial and cytoplasmic calf brain preparations. After incubation with homologous crude preparations of aminoacyl‐tRNA ligases in the presence of [14C]‐glutamic acid, tRNAs were separated chromatographically on BD‐cellulose columns and in reversed phase chromatography systems. In both of the methods used, cytoplasmic tRNA preparations revealed a larger number of radioactivity peaks. In experiments with double labelling, five radioactivity peaks for cytoplasmic glutamyl‐tRNAs corresponded to only three mitochondrial glutamyl‐tRNA fractions. The results imply the presence of isoaccepting species of tRNA in brain.
SYNTHETIC AMINO ACIDS AND THE NATURE OF l‐DOPA TRANSPORT AT THE BLOOD‐BRAIN BARRIER
Authors: Wade L. A. , Katzman R.
Published: October 2006

—The blood‐brain barrier transport of amino acids has been measured using the carotid injection technique in the rat. The synthetic amino acids, 2‐aminobicyclo(2,2,1)heptane‐2‐carboxylic acid (BCH) and α‐(methylamino)isobutyric acid (MeAIB), were model substrates in the Ehrlich cell for the leucine (L) and alanine (A) neutral amino acid transport mechanisms, respectively. The uptake (±)b‐[carboxyl‐14C]BCH at the same rate for the five brain regions tested suggested a similarity between regions for the L transport mechanism. At injectant concentrations of 0·1 mm (similar to naturally occurring aromatic neutral amino acids), BCH was mainly taken up by a saturable mediated transport mechanism (K1, 0·16 mm and Vmax, 0·03/μmol/g per min). At higher concentrations, uptake by a nonsaturable or diffusional mechanism could be demonstrated. When BCH was added as a second amino acid to l‐[3‐14C]DOPA, the saturable component of l‐DOPA transport was significantly inhibited. MeAIB had no measurable effect on the rate of l‐DOPA transport. These results suggested that the mediated transport mechanism for l‐DOPA at the cerebral capillaries is similar to the l‐neutral amino acid transport system.
ARE MYELIN PROTEINS SYNTHESIZED IN RETINAL GANGLION CELLS?1
Authors: Prensky A. L. , Fujimoto Karen , Agrawal H. C.
Published: October 2006

—We studied the incorporation of radioactivity into individual proteins of myelin by sodium dodecyl sulfate polyacrylamide gel electrophoresis after the injection of [3H]tryptophan into the right eye of developing rabbits. We found that the specific activity of basic protein (c.p.m./mg of basic protein) and the specific activity of DM‐20 and proteolipid protein (c.p.m./mg total myelin protein applied to the gel) did not approach the ratio predicted by decussation of the fibres of the rabbit optic nerve. The specific activity of Wolfgram protein, however, approached an expected ratio of 15:1. We therefore concluded that myelin basic protein, DM‐20 and proteolipid protein were probably not synthesized in retinal ganglion cells.
METABOLISM OF A TRYPTOPHAN LOAD IN THE HYPOTHALAMUS AND OTHER BRAIN REGIONS
Authors: Curzon G. , Marsden C. A.
Published: October 2006

Abstract— Results confirm previous findings that after injecting rats with 50mg/kg tryptophan the percentage increase of 5‐hydroxytryptamine metabolism (as shown by 5‐hydroxyindolylacetic acid changes) is particularly small in the hypothalamus. However, 15–30 min after tryptophan injection (when brain 5‐hydroxytryptamine changes were maximal) percentage 5‐hydroxytryptamine increases in the hypothalamus and in the rest of the brain were comparable. The small 5‐hydroxyindolylacetic acid changes in the hypothalamus are consistent with a long 5‐hydroxytryptamine turnover time therein as indicated by experiments using pargyline or probenecid and by the relatively small increases of 5‐hydroxytryptamine after injecting tryptophan into tranylcypromine treated rats. When 5‐hydroxytryptamine synthesis was partially inhibited by p‐chlorophenylalanine and tryptophan was injected, there was a large percentage rise of hypothalamic 5‐hydroxytryptamine but the concentration found in rats given neither drug was not attained and 5‐hydroxyindolylacetic acid showed little change. Elsewhere in the brain 5‐hydroxytryptamine attained concentrations comparable to those in rats given neither drug and 5‐hydroxyindolylacetic acid rose considerably. Results are discussed in relation to the contributions made to brain 5‐hydroxytryptamine turnover by functional and non‐functional metabolism.
DISTRIBUTION OF BIOGENIC AMINES AND RELATED ENZYMES IN THE RAT PITUITARY GLAND
Authors: Saavedra J. M. , Palkovits M. , Kizer J. S. , Brownstein M. , Zivin J. A.
Published: October 2006

Abstract— Biogenic amines and related enzymes were quantitatively measured in the pituitary gland of the rat. The sensitivity of the assays used allows the determinations to be performed in single pituitary lobes. Relatively high values of histamine and serotonin were found in all three lobes, with higher amounts in the posterior and intermediate lobes. Highest catecholamine concentrations were detected in the posterior lobe, and only very low amounts of dopamine were measured in the anterior lobe. Throughout the gland, norepinephrine concentrations were low, about one‐tenth that of dopamine. Tryptamine could not be detected. High levels of A and B monoamine oxidase were found in all three pituitary lobes. Tyrosine hydroxylase activity was measured in the posterior and intermediate lobes, but was not detected in the anterior lobe. Tryptophan hydroxylase was present in all three pituitary lobes. A relatively low catechol‐O‐methyltransferase activity was found in the anterior lobe, and none was detected in the intermediate and posterior lobe. Choline acetyltransferase, dopamine‐β‐hydroxylase and phenylethanolamine‐N‐methyltransferase activities could not be detected.
INTERRELATIONS BETWEEN POLYAMINES AND NUCLEIC ACIDS: CHANGES OF POLYAMINE AND NUCLEIC ACID CONCENTRATIONS IN THE DEVELOPING RAT BRAIN
Authors: Seiler N. , Lamberty Ursula
Published: October 2006

Abstract—

The rat brain concentrations of protein, RNA, DNA, putrescine, and of the polyamines spermidine and spermine, were studied during development. Putrescine formation is apparently controlled by ornithine decarboxylase. Spermidine and spermine concentrations change in inverse directions to their anabolic enzymes. It has been presumed, therefore, that the low concentrations of the polyamine‐synthesizing enzymes in immature brain are compensated for, by high putrescine and S‐adenosylmethionine concentrations.

In agreement with previous findings for fish brain, the changes in RNA and spermidine concentrations were most closely correlated. The functions of DNA: spermine are directly correlated only during the periods of brain maturation, after cell proliferation has nearly ceased.
COMPARATIVE STUDIES ON THE MEMBRANE ACTIONS OF DEPRESSANT DRUGS: THE ROLE OF LIPOPHILICITY IN INHIBITION OF BRAIN SODIUM AND POTASSIUM‐STIMULATED ATPase1
Authors: Roufogalis B. D.
Published: October 2006

Abstract—

Depressant drugs are considered to exert their pharmacological effects as a result of membrane interactions determined by their physico‐chemical properties. In this study, a correlation was found between lipid solubility and potency of various local anaesthetics, antihistamines, tricyclic antidepressants and phenothiazine tranquilizers as inhibitors of the Na, K‐ATPase activity of a microsomal membrane fraction from bovine brain cortex. Depressant drugs such as chlorpromazine, which have the greatest lipid solubilities, were competitive inhibitors of Na activation but noncompetitive toward K activation, whereas drugs such as tetracaine with lower lipid solubilities were competitive inhibitors of K activation but noncompetitive toward Na activation. Drugs with intermediate lipid solubilities were mixed competitive‐noncompetitive inhibitors of both Na and K activation. Both chlorpromazine and tetracaine competitively inhibited cation activation by a heterotropic allosteric mechanism, probably mediated through membrane conformational changes. Whereas quaternization or a decrease in the incubation pH interfered with the ability of chlorpromazine to inhibit Na activation in a competitive fashion, these changes did not affect the ability of tetracaine to compete with K activation. In addition Mn, Ca and phosphatidyl serine were very effective non‐competitive antagonists of chlorpromazine inhibition of Na, K‐ATPase, whereas these agents competitively antagonized tetracaine inhibition to a lesser extent. These data suggest that the more lipid soluble phenothiazines penetrate into and react in hydrophobic areas of the membrane microenvironment, resulting in a membrane perturbation which interferes with Na activation. On the other hand the less lipid soluble local anaesthetics probably act at superficial sites near the membrane surface, resulting in a different membrane perturbation which interferes with the K activation mechanism. It is suggested that lipid solubility may be a significant factor in determining selectivity in the membrane interactions of various pharmacological agents and hence differences in pharmacological activity among different classes of depressant drugs.
RATE OF STEROL FORMATION BY RAT BRAIN GLIA AND NEURONS IN VITRO AND IN VIVO
Authors: Jones J. P. , Nicholas H. J. , Ramsey R. B.
Published: October 2006

Abstract—

The ability of 11‐day‐old rat glial and neuronal cells to biosynthesize sterol was studied as a function of time in vivo and in vitro. The in vitro experiments utilized [2‐14C]mevalonic acid as precursor. Glial‐enriched cell preparations demonstrated a greater ability to incorporate [2‐14C]mevalonic acid into isoprenoid material than did neuronal‐enriched preparations. Approximately 4 h were required for maximal uptake of labelled mevalonate by the glial preparations. Further metabolism of the isoprenoid material, involving squalene turnover and sterol demethylation, was still evident even after 15 h of incubation. In vivo, sterol biosynthesis was studied by intraperitoneal injection of sodium [2‐14C]acetate and [U‐14C]glucose, sacrifice of the animals at 2 or 24 h, subsequent isolation of glial‐ and neuronal‐cell enriched fractions and analysis of labelled isoprenoid material. Glial‐enriched fractions again contained the bulk of the labelled isoprenoid material.
EVIDENCE FOR REVERSIBLE INHIBITION OF BRAIN DOPAMINE‐β‐HYDROXYLASE ACTIVITY IN VIVO BY AMPHETAMINE ANALOGUES1
Authors: Stolk J. M.
Published: October 2006

Abstract—

Rats treated with d‐amphctamine have a decreased ability to convert intracisternally injected radioactive dopamine to noradrenaline. This effect is dose‐related and reversible by increasing the dose of injected dopamine. L‐Amphetamine is equipotent to the d‐isomer, but para‐hydroxyamphetamine reduces noradrenaline formation only slightly. Like the amphetamines, imipramine produces significant inhibition of noradrenaline from labelled dopamine; however, dopamine content after imipramine, but not after the amphetamines, was consistently decreased, suggesting that imipramine's effect on conversion of labelled dopamine to noradrenaline is mediated by interference with membranal transport systems. Conversion of labelled tyrosine to noradrenaline increases after imipramine. In contrast, noradrenaline accumulating from labelled tyrosine is decreased by d‐ or l‐amphetamine. The divergent effects of the amphetamines and imipramine on noradrenaline accumulation from labelled tyrosine suggest that the amphetamines' effect on in vivo dopamine‐β‐hydroxylase activity are not solely attributable to interference with transport and, therefore, suggest a direct effect on the enzyme.
ACTIVITY OF ALDEHYDE DEHYDROGENASE, ALDEHYDE REDUCTASE, AND ACETYLCHOLINE ESTERASE IN STRITATUM OF RATS BEARING ELECTROLYTIC LESIONS OF THE MEDIAL FOREBRAIN BUNDLE
Authors: Duncan R. J. S. , Sourkes T. L. , Dubrovsky B. O. , Quik Maryka
Published: October 2006

Abstract—

A number of enzymes have been measured in the striatum of rats in which the dopamine‐containing nerve terminals had been unilaterally destroyed by means of unipolar electrolytic lesions of the medial fore‐brain bundle. Fourteen and 28 days after such lesions the tyrosine hydroxylase activity of the striatum was reduced to immeasurably low values, but neither aldehyde dehydrogenase, aldehyde reductase, nor acetylcholine esterase was affected when compared with the striatum from the intact side of the same rat or with those from control rats. These results indicate that in the rat the 3 enzymes are not localized with tyrosine hydroxylase, in the dopaminergic nerve terminals of the striatum. This conclusion is supported by a study of the subcellular localization of aldehyde dehydrogenase in rat brain. This enzyme is distributed between the cytosol and the particulate fraction of brain homogenates separated by centrifugal techniques. with no exceptionally high concentration of the enzyme in the synaptosomal fraction. Because neither of the enzymes of post‐deaminative catabolism of dopamine is concentrated in the dopaminergic nerve terminals of the striatum of the rat, it is proposed that in this species the amine is not necessarily taken up by the nerve terminals prior to catabolism.
THE PENETRATION OF THE MEMBRANE OF BRAIN MITOCHONDRIA BY ANIONS
Authors: Minn A. , Gayet J. , Delorme P.
Published: October 2006

Abstract—

The permeability of the membrane of rat brain non‐synaptosomal mitochondria, towards inorganic and substrate anions, was assessed by measuring the rate of swelling that occurred when mitochondria were suspended in an iso‐osmotic solution of a permeant anion, in the presence of a permeant cation such as NH+4 or K+ in the presence or absence of valinomycin. In NH+4‐phosphate swelling was higher than it was in KCI or K+‐phosphate, which showed the prevalence of the mechanism of phosphate transport previously demonstrated in liver mitochondria. The entry of succinate and L‐malate seemed to require the presence in the inner mitochondrial membrane of specific carriers. as previously postulated for liver mitochondria, but the rate of swelling of brain mitochondria was lower than that of liver organelles. In K+‐succinate, in the presence of antimycin, added ATP induced swelling and this was attributable to the simultaneous permeation both of the anion and the cation. Fumarate did not penetrate into brain mitochondria. Practically no swelling was recorded in NH+4 or K+‐citrate, which indicated that this anion penetrated poorly into the isolated brain mitochondria even in the presence of malate. Swelling occurred in NH+4‐L‐glutamate in the presence of rotenone, and the entry of this anion seemed to follow a gradient of concentration although the presence of a specific translocator in the inner mitochondrial membrane might be concerned. The entry of glutamate was independent of that of phosphate and N‐ethylmaleimide appeared to be a specific inhibitor of this entry. Swelling in K+‐L‐glutamate, in the presence of rotenone, was enhanced by the addition of valinomycin or ATP but in the latter case when osmotic equilibrium was reached swelling was not reversed by oligomycin. In conclusion, the lesser extent of swelling of isolated brain mitochondria compared with liver mitochondria could be attributed to the heterogeneity of the populations of these organelles, each population possessing its own characteristics of membrane permeability. Observations of electron micrographs of brain mitochondria incubated in iso‐osmotic substrate anions confirmed the heterogeneous rate of swelling of these particles.
FACTORS INFLUENCING BRAIN AND TISSUE LEVELS OF TRYPTAMINE: SPECIES, DRUGS AND LESIONS
Authors: Sloan J. W. , Martin W. R. , Clements T. H. , Buchwald W. F. , Bridges S. R.
Published: October 2006

Abstract—

With a modification of the spectrophotofluorometric (SPF) method of HESS & UDENFRIEND (1959) (J. Pharmac. exp. Ther.127, 175‐177), brain tryptamine levels in the rat (20.9 ng/g) and guinea‐pig (20.7 ng/g) were found to be less than those in the dog (32.1 ng/g) and cat (52.2 ng/g). Regional distribution studies in the dog and cat showed that tryptamine was present in all major brain regions with highest concentrations in the spinal cord. Blood levels of tryptamine in the guinea‐pig, dog and cat (6‐7 ng/ml) were lower than brain levels. Pargyline significantly increased brain tryptamine in both the dog and cat; whereas, isocarboxazid (after 4 h) increased brain tryptamine levels in the dog but decreased brain levels in the cat. Reserpine (0.5‐1.0 mg/kg per day for 1‐4 days) did not significantly decrease brain, spinal cord or blood tryptamine levels in the dog. Spinal cord transection did not decrease tryptamine levels below the lesion in the chronic spinal dog.
FACTORS INFLUENCING THE EFFLUX OF [3H]GAMMAAMINOBUTYRIC ACID FROM SATELLITE GLIAL CELLS IN RAT SENSORY GANGLIA
Authors: Minchin M. C. W.
Published: October 2006

Abstract—

The spontaneous efflux of [3H]GABA from the satellite glial cells of rat dorsal root ganglia and the efflux evoked by 64 mM‐K+ were studied in the presence of 10‐5M‐amino‐oxyacetic acid and found not to be affected by 10‐4M‐D 600 or by elevated (9.6mM) Ca2+ in the absence of Mg2+. [3H]GABA efflux was increased by replacing sodium ions in the washing medium by choline ions and 64 mM‐K+ failed to increase the efflux further. The drugs veratridine (10‐6 and 10‐4M) and batrachotoxin (10‐8 and 10‐6 M) failed to alter the spontaneous efflux of [3H]GABA from the glial cells.

A variety of compounds, including amino acids, a GABA analogue and a GABA antagonist were tested for their ability to affect [3H]GABA efflux. The results indicated that compounds which inhibit GABA uptake into glial cells were also able to stimulate [3H]GABA efflux from these cells.

The results are discussed with reference to possible mechanisms involved in the release of GABA from glial cells.