bluuebunny/crossref_metadata_2025 huggingface dataset:
RELEASE OF RADIOACTIVE GLUTAMIC ACID FROM THIN SECTIONS OF GUINEA‐PIG OLFACTORY CORTEX IN VITRO
Authors: Matsui S. , Yamamoto C.
Published: October 2006

Abstract—

Slices from the guinea‐pig olfactory cortex were incubated in the medium containing [14C]glutamate and release of radioactive compounds was subsequently studied in the standard or high potassium media or during repetitive stimulation of the lateral olfactory tract (LOT) while electrical activity of the tissue was monitored. In 50 mm‐potassium concentration, the pre‐ and postsynaptic potentials were completely suppressed and effluxes of total 14C and [14C]glutamate increased. No significant increase in [14C]glutamine was found. When Ca2+ concentration was reduced from 2·4 to 0·12 mm, the postsynaptic potential disappeared and release of [14C]glutamate in 50 mm‐potassium decreased to about a third of that in 2·4 mm‐Ca2+. Repetitive LOT stimulation enhanced release of total 14C in thinner slices but caused no significant increase in [14C]glutamate efflux. These findings were discussed in relation to the possibility that glutamate is a mediator between the LOT fibres and cortical neurons.
ISOLATION AND PARTIAL CHARACTERIZATION OF FRACTIONS ENRICHED IN SYNAPTOSOMES FROM CHICK BRAIN
Authors: Oestreicher A. B. , van Leeuwen C.
Published: October 2006

Abstract—

–From a pool of hemispheres, optic lobes and cerebellum of chick 3 fractions containing synaptosomes have been prepared. They were obtained by subcellular fractionation of a homogenate and centrifugation of a crude mitochondrial suspension on a discontinuous Ficoll density gradient in iso‐osmoticsucrose. The synaptosomal fractions were isolated from bands at the interface of 5–9, 9–12 and 12–16% Ficoll. The characterization of these fractions by marker enzymes, such as lactate dehydrogenase, acetyl‐cholinesterase, monoamine oxidase, acid phosphatase and rotenone‐sensitive and ‐insensitive NADH: cytochrome c reductase is reported. Electron microscopic analyses showed that the first fraction (AB) at the 5–9% Ficoll interface contained myelin and other membrane fragments as well as synaptosomes, the second fraction (C) at the 9–12% Ficoll interface contained mainly synaptosomes, and the third fraction (D) at the 12–16% Ficoll interface contained synaptosomes and free mitochondria. A fourth fraction (E) was obtained as a pellet, and was enriched in free mitochondria. There was fair agreement between the distribution pattern of the marker enzyme activities and the particles of the fractions seen by electron microscopy. The content of glycoprotein‐bound N‐acetylneuraminic acid and total phospholipid of these fractions has been determined. Relative to the mitochondrial fraction (E) the synaptosome fraction contained on basis of particulate protein, respectively, 2–3 times as much protein‐bound N‐acetylneuraminic acid and 10–20 per cent more total phospholipid.
CHEMICAL SPECIFICITY OF DOPAMINE TRANSPORT IN THE NIGRO‐NEOSTRIATAL PROJECTION
Authors: McGeer E. G. , Searl K. , Fibiger H. C.
Published: October 2006

Abstract—

Axoplasmic transport of dopamine in the nigro‐neostriatal system has previously been shown by the specific accumulation of labelled dopamine in the striatum following injections of labelled DOPA or dopamine into the substantia nigra. To test the specificity, 17 different labelled materials (pipecolic acid, inulin, taurine, GABA, glycine, histidine, histamine, serotonin, 5‐HTP, D‐amphetamine, 3‐methoxytyramine, dopamine, tyramine, norepinephrine, octopamine and high and low specificity activity DOPA) were injected into the substantia nigra and the distribution of radioactivity in the brain studied after 6 and 24 h. Only the catecholamines and octopamine gave evidence of specific accumulation in the ipsilateral striatum although some of the other compounds caused diffuse labelling of the striatum along with other brain areas.
THE EFFECT OF INDUCED HYPOTHERMIA UPON OXYGEN CONSUMPTION IN THE RAT BRAIN
Authors: Hägerdal M. , Harp J. , Nilsson L. , Siesjöu B. K.
Published: October 2006

Abstract—

The effect of hypothermia upon cerebral metabolic rate for oxygen (CMRO2) was studied in artificially ventilated rats, anaesthetized with nitrous oxide. Cerebral blood flow was measured with a modification of the Kety and Schmidt technique using 133xenon. CMRO2, was found to decrease linearily with temperature in the temperature range 37°C‐22°C. At normal temperatures CMRO2, fell by about 5 per cent per degree C. At a body temperature of 22°C both cerebral blood flow and CMRO2, were reduced to about 25 per cent of normal.
ON THE SPECIFICITY OF TRYPSIN (EC 3.4.4.4) OF NERVE ENDING PARTICLES TO INHIBIT NOREPINEPHRINE TRANSPORT1,2
Authors: Hitzemann Barbara A. , Hitzemann R. J. , Loh H. H.
Published: October 2006

Abstract—

The Na+ and energy dependent uptake of norepinephrine into cortical rat brain homogenates or purified nerve ending particles (NEP) is reduced by prior trypsin treatment. In contrast, the uptake of dopamine, serotonin, choline and γ‐aminobutyric acid is markedly less sensitive to the effect of trypsin. Kinetic analyses indicate that the trypsin‐induced decrease of norepinephrine uptake is non‐competitive. In the dose range studied, trypsin did not appreciably alter the protein content or morphology of NEP. However, in a dose related fashion, trypsin decreased the glycoprotein content of NEP measured as the loss of protein bound N‐acetylneuraminic acid.
SERUM ‘ANTI‐MYELIN ANTIBODIES’: A SPECTROFLUOROMETRIC ASSAY PROCEDURE1
Authors: Suzuki K. , Bornstein M. B. , Tiffany Carol W.
Published: October 2006

Abstract—

A simple spectrofluorometric procedure has been devised to determine serum antibodies, directed to constituents of the myelin sheath. It is an adaptation of the indirect immunofluorescent technique. A suspension of highly purified bovine myelin is incubated successively with a test rabbit serum and fluoresceinisothiocyanate‐conjugated anti‐rabbit gamma‐globulin. Intensity of fluorescence in the final myelin suspension is determined spectrofluorometrically. Sera from rabbits with experimental allergic encephalomyelitis, induced by whole bovine spinal cord, generally gave fluorescence at least 10 times that of normal rabbit serum. Fluorescence of sera with high demyelinating activity was more intense than that of sera with equivocal demyelinating activity. The assay is specific for immunoglobulins directed to myelin constituents, organ‐specific and species‐independent. Rabbit anti‐galactosylceramide serum with known demyelinating activity gave high fluorescence similar to that in sera of rabbits inoculated with whole spinal cord. Galactosylceramide could absorb a substantial portion of‘anti‐myelin antibodies’of the anti‐galactosylceramide serum but it did not absorb‘anti‐myelin antibodies’of serum of rabbits with whole tissue‐induced experimental allergic encephalomyelitis. This assay system may be useful for further studies of ‘anti‐myelin antibodies’.
POSTNATAL CHANGES IN FREE AMINO ACID, DNA, RNA AND PROTEIN CONCENTRATIONS OF MINIATURE SWINE BRAIN1
Authors: Badger T. M. , Tumbleson M. E.
Published: October 2006

Abstract—

Postnatal developmental characteristics of miniature swine brain were evaluated through the first 9 weeks of age. Differential growth rates of cerebrum, cerebellum and brain stem were defined in terms of DNA, RNA, protein and free amino acid concentrations at ages 5, 21, 35 and 63 days. Within the experimental conditions provided, hyperplasia ceased just prior to ages 21, 35 and 63 days for cerebellum, brain stem and cerebrum, respectively. An additional cerebral growth spurt, observed between weaning at age 35 days and sacrifice at age 63 days, may be indicative of impaired brain development due to inadequate nutrition provided by the dam's milk. Developmental changes in mean concentrations of brain free amino acids varied with anatomical area and differed somewhat from those of other species previously reported. For example, mean cerebral concentrations of aspartic acid, γ‐aminobutyric acid and asparagine + glutamine decreased significantly (P < 0·05) with age and mean glutamic acid concentration was 5 times that of taurine.
CYCLIC NUCLEOTIDE PHOSPHODIESTERASE IN RAT NEOSTRIATUM: PROPERTIES OF THE ENZYME IN CRUDE HOMOGENATES
Authors: Minneman K. P.
Published: October 2006

Abstract—

Homogenates of rat neostriatum hydrolysed cGMP faster than cAMP at both high (100μM) and low (1 μM) substrate concentrations, although the hydrolysis of both nucleotides exhibited similar kinetic properties. Kinetic analysis of the effect of substrate concentration on the rate of cAMP and cGMP hydrolysis gave results characteristic of a negatively cooperative enzyme species, with two apparent Km's for each nucleotide. The ratio between the Vmax, of the high Km, form and the Vmax of the low Km form was similar in various subcellular fractions of neostriatal tissue, in a preparation of synaptic membranes from whole brain, and in homogenates of other brain regions, including both neural‐rich and glial‐rich tissues. In homogenates of neostriatum cAMP could almost completely block cGMP hydrolysis and vice versa. The kinetics of this inhibition were competitive at low (1 μM) substrate concentrations, and non‐competitive at high (100 μM) substrate concentrations. Various phosphodiesterase inhibitors failed to preferentially inhibit the hydrolysis of either nucleotide at high or low nucleotide concentrations.

Preliminary studies of the effect of a Ca2+ dependent endogenous activator preparation on the hydrolysis of cyclic nucleotides in homogenates of rat neostriatum showed a specific activation of cGMP hydrolysis at low nucleotide concentrations. The rate of cGMP hydrolysis at 1 μM substrate concentration was doubled in the presence of the activator preparation and 100μM‐CaCl2, while cGMP hydrolysis at 100 μM or cAMP hydrolysis at both 1 μM and 100μ.M remained unaffected.

These observations raise the possibility that cAMP and cGMP may be hydrolysed by the same enzyme in rat neostriatum and that an endogenous activating factor may determine the relative affinities of the enzyme for the two nucleotides.
CYCLIC NUCLEOTIDE PHOSPHODIESTERASE IN RAT NEOSTRIATUM: MULTIPLE ISOELECTRIC FORMS WITH SIMILAR KINETIC PROPERTIES
Authors: Minneman K. P.
Published: October 2006

Abstract—

Separation of multiple forms of cyclic nucleotide phosphodiesterase from the soluble supernatant fraction of rat neostriatum by isolectric focusing yielded five separate peaks of cyclic nucleotide hydrolysing activity. Each separated enzyme form displayed a complex kinetic pattern for the hydrolysis of both cyclic AMP and cyclic GMP, and there were two apparent Km's for each nucleotide. At 1 μM substrate concentration, four enzyme forms exhibited higher activity with cyclic AMP than with cyclic GMP, while one form yielded higher activity with cyclic GMP than with cyclic AMP. Cyclic AMP and cyclic GMP were both capable of almost complete inhibition of the hydrolysis of the other nucleotide in all the peaks separated by isoelectric focusing; the IC50's for this interaction correlated well with the relative rates of hydrolysis of each nucleotide in each peak. The ratio of activity at 1 μM substrate concentration for the five enzyme forms separated by isoelectric focusing was 10:10:5:15:1 for cyclic AMP hydrolysis; and 6:6:4:8:2 for cyclic GMP hydrolysis; and the isoelectric points of the five peaks were 4.3, 4.45, 4.7, 4.85, and 5.5, respectively. Known phosphodiesterase inhibitors did not preferentially inhibit any of the separated forms of activity for either cyclic AMP or cyclic GMP hydrolysis, at either high (100 μM) or low (1 μM) substrate concentrations. Preliminary examination of the subcellular distribution of the different forms of enzyme activity indicated a different degree of attachment of the various forms to particulate tissue components. Isoelectric focusing of the soluble supernatant of rat cerebellum gave rise to a slightly different pattern of isoelectric forms from the neostriatum, indicating a different cellular distribution of the isoelectric forms of PDE in rat brain.

Polyacrylamide disc gel electrophoresis of the soluble supernatant of rat neostriatum also generated a characteristic pattern of five separate peaks of cyclic nucleotide phosphodiesterase activity, each of which hydrolysed both cyclic AMP and cyclic GMP. Polyacrylamide gel electrophoresis of single enzyme forms previously separated by isoelectric focusing gave single peaks, with a marked correspondence between the enzyme forms produced by isoelectric focusing and those produced by gel electrophoresis, suggesting that both protein separation procedures were isolating the same enzyme forms.

The results indicate the existence of multiple isoelectric forms of cyclic nucleotide phosphodiesterase in the soluble supernatant fraction of rat neostriatum, all of which exhibit similar properties. In this tissue a single kinetic form of this enzyme appears to exist displaying complex kinetic behaviour indicative of negative cooperativity and hydrolysing both cyclic AMP and cyclic GMP, with varying affinities.
THE EFFECTS OF ASPHYXIA ON 5‐HYDROXYTRYPTAMINE METABOLISM IN THE IMMATURE RAT BRAIN
Authors: Tricklebank M. D. , Pickard F. J. , Dobbing J.
Published: October 2006

Abstract—

Fire‐day‐old rats subjected to prolonged asphyxia at 37°C show a slower rate of synthesis of 5‐HT as measured by the accumulation of the amine after inhibition of monoamine oxidase. During recovery from asphyxia 5‐HT synthesis is markedly stimulated when measured over a 50 or 90 min period. No change in 5‐HT synthesis was observed in 5‐day‐old rats during recovery from cold exposure or immobilization. The results indicate that the persistent increase in synthesis that follows resuscitation may be related to asphyxia per se rather than to the stress component of the treatment.
ISOLATION AND RADIOENZYMIC ESTIMATION OF PICOGRAM QUANTITIES OF DOPAMINE AND NOREPINEPHRINE IN BIOLOGICAL SAMPLES
Authors: Gauchy C. , Tassin J. P. , Glowinski J. , Cheramy A.
Published: October 2006

Abstract— A method was developed to measure small amounts of dopamine or norepincphrine in biological samples. It was based on the radioenzymic assay originally described by Engelmanet al. (1968) and improved by other workers: dopamine and norepinephrine are O‐methylated by catechol‐O‐ methyl‐transferase in the presence of [3H]S‐adenosylmethioniiie as la belled methyl donor. O‐Methylated derivatives are extracted and estimated. The optimal conditions for the O‐methylation and the extractions were determined. The most important improvement in the method consisted in the selective isolation of catecholamines on microcolumns of alumina under conditions that allowed their subsequent enzymic assay. The assay described can thus be used on any size of biological sample. The assay was not affected by the prescnce of various agents (tissue extracts, CSF salts and particularly calcium, drugs etc.) which were shown to interfere with the O‐methylation process, and it allowed the measurement of quantities of dopamine and norepinephrine as low as 0.15 and 0.1 pmol respectively, whatever the origin of the sample (CSF superfusates, cerebral tissue).
NEUROCHEMICAL CORRELATES OF BEHAVIOUR–CONTENT OF TRYPTOPHAN, 5‐HYDROXYTRYPTOPHAN, SEROTONIN, 5‐HYDROXYINDOLEACETIC ACID, TYROSINE, DOPAMINE AND NOREPINEPHRINE IN FOUR BRAIN PARTS OF THE PIGEON DURING BEHAVIOURAL DEPRESSION FOLLOWING AN INJECTION OF TRYPTOPHAN1,2
Authors: Smith J. E. , Hingtgen J. N. , Lane J. D. , Aprison M. H.
Published: October 2006

Abstract— Pigeons working on a multiple lixed‐ratio 50, fixed interval 10 schedule of food reinforcement were injected with l‐tryptophan (300mg/kg; I.M.) and killed at various times before, during and after the period of behavioural depression following the administration of this amino acid (0, 25, 50, 90, 170 and 230 min). The levels of tryptophan, 5‐hydroxytryptophan, 5‐hydroxytryptamine, 5‐hydroxyindoleacetic acid, tyrosine, dopamine and norepinephrine were concurrently measured in 4 specific areas of the brain (telencephalon, diencephalon plus mesencephalon, pons plus medulla‐oblongata and cerebellum). The course of the increases in the level of 5‐hydroxytryptamine in the telencephalon, and subsequent return to pre‐injection levels, was temporally related to the onset of the decreased responding and gradual return to normal rates of responding. Changes in dopamine and norepinephrine were not correlated with the onset of and recovery from the decreased response rates. The data in this paper are discussed in terms of (a) the previously reported work with 5‐hydroxytryptophan and (b) the importance of the telencephalic serotonergic system in certain types of behavioural depression.
5‐HYDROXY‐l‐TRYPTOPHAN DECARBOXYLASE ACTIVITY: MICROASSAY AND DISTRIBUTION IN DISCRETE RAT BRAIN NUCLEI
Authors: Saavedra J. M.
Published: October 2006

Abstract— 5‐Hydroxy‐l‐tryptophan decarboxylase (EC 4.1.1.28) activity was measured in discrete regions of the rat brain by means of a sensitive micromethod lhat allows the quantitation of enzyme activity in μg amounts of brain tissue.

A good correlation was obtained between serotonin levels and 5‐hydroxy‐l‐tryptophan decarboxylase activity in all the brain regions examined. Wide differences in enzyme activity were found in the different brain nuclei, with a 20‐fold difference in activity between the most active region (the nucleus raphe dorsalis) and the least active regions (the corpus callosum and the optic tract).
SIMULTANEOUS ISOLATION OF PURIFIED MICROSOMAL and MYELIN FRACTIONS FROM RAT SPINAL CORD
Authors: Toews A. D. , Horrocks L. A. , King J. S.
Published: October 2006

Abstract— The fraction that sediments between 2 × 105g‐min and 6 × 106g‐min from dilute dispersions of rat brain in 0.32 m‐sucrose is a microsomal fraction with very little contamination by myelin. A crude microsomal fraction prepared in the same way from rat spinal cord contains more myelin than microsomes. Centrifugation of the crude microsomal fraction in 0.85 m‐sucrose gave a floating fraction, an infranatant fraction (purified microsomes) and a small pellet. The purified microsomes contained very little myelin as judged by electron microscopy and polyacrylamide gel electrophoresis. The lipid composition resembled that of spinal cord myelin except that the purified microsomes contained relatively less cholesterol and ethanolamine plasmalogens. The content of galactolipids was much greater in spinal cord microsomes than in brain microsomes. The spinal cord CDP‐ethanol‐amine:diglyceride ethanolaminephosphotransferase activity (EC 2.7.8.1) was concentrated in the purified microsomes.

A spinal cord myelin fraction isolated from the 2 × 105g‐min pellet was quite pure as judged by electron microscopy, enzyme activities and polyacrylamide gel electrophoresis. No NADPH‐cyto‐chrome c reductase activity (EC 1.6.2.3) could be detected in the purified myelin. The ethanolaminephosphotransferase specific activity was about 5% of that found in the purified microsomal fraction. The protein content was 25% by weight for spinal cord myelin and 31% for brain myelin. Of the total spinal cord 2′,3′‐cyclic nucleotide‐3′‐phosphohydrolase activity, 16% was lost from the crude myelin during purification, 21% was recovered in the purified myelin, and 11% was found in the floating fraction from the crude microsomes. The purified myelin and microsomal fractions from spinal cord were relatively pure. Additional myelin was recovered in the floating fraction from the crude microsomes.
THE EFFECT OF GRADUAL CHANGES IN TEMPERATURE ON THE RELEASE OF HORMONES FROM NERVE ENDINGS ISOLATED FROM BOVINE NEURAL LOBES1
Authors: Baker Ruth V. , Hope D. B.
Published: October 2006

Abstract— Homogenates of bovine neural lobe tissue were fractionated by differential centrifugation at 20°C or at 4°C and the distribution of activities of vasopressin and oxytocin among the fractions was compared. The ratio of total hormone to protein (mg) in the homogenate was similar at the two temperatures. At 20°C a much smaller proportion of the total hormone was recovered in the soluble fraction (100,000 gav supernatant), than at 4°C with a corresponding increase in recovery in the nerve‐ending fraction (800–3000 g sediment).

Nerve endings isolated at 4°C did not, when incubated, release hormone in response to changes in temperature. Nerve endings isolated at 20°C released hormone when the temperature was reduced below 15°C. Gradual reduction in temperature led to hormone release unaccompanied by lactate dehydrogenase release. Incubation of nerve endings for 10 min at 10°C increased the release of vasopressin and of neurophysin without any increase in lactate dehydrogenase. These results demonstrate that release of vasopressin by cold stimulation occurs by way of exocytosis.
CHOLINE AND ACETYLCHOLINE IN RATS: EFFECT OF DIETARY CHOLINE
Authors: Haubrich D. R. , Wang Pauline F. L. , Chippendale T. , Proctor Elizabeth
Published: October 2006

Abstract– The concentration of free choline in peripheral tissues (duodenum, heart, kidney, liver, stomach and plasma) of rats was found to be related to the amount of free choline in the diet. Under steady‐state conditions, the concentration of free choline in plasma varied from a minimum of approx 6 nmol/ml (in rats fed a choline‐deficient diet) to a maximum value not exceeding 21 nmol/ml. The concentration of plasma choline was elevated above 21 nmol/ml for a short time after parenteral administration of choline chloride or one of its precursors (CDP choline or phosphorylcholine), but was not affected by stress, endocrine manipulations, drug treatments or the time of day when rats were killed.

The metabolism of intravenously administered [methyl‐3H] choline was accelerated in peripheral tissues (except plasma) of choline‐deficient rats, indicating that free choline is not preserved during choline deficiency by a reduction in its rate of turnover. Furthermore, the decrease in concentration of plasma choline that occurred in rats fed a choline‐deficient diet was prevented by addition of deanol (dimethylaminoethanol) to the diet. These results indicate that free choline in peripheral tissues of rats is derived from both free choline in the diet, and from precursors of choline present within the diet.

In contrast to the effects in peripheral tissues, the concentration of free choline in brain was not reduced by dietary deprivation of free choline; however, the increase in free choline that occurred when rats were decapitated was reduced in brains by deficiency of choline, suggesting a decrease in the concentration of esterified forms of cerebral choline.

The concentration of acetylcholine was not reduced in the brain, duodenum, heart, kidney or stomach of 21‐week old rats raised from birth on a choline‐deficient diet, in the duodenum of rats given a choline‐deficient diet for 1, 5 or 11 days, or in brains of rats deprived of free choline for 1 or 11 days. However, the rate of in vivo synthesis of ACh from [methyl‐3H]choline was accelerated in cholinergic tissues that were depleted of free choline (i.e. duodenum, heart and stomach).
STEROID SULFATASE IN BRAIN: COMPARISON OF SULFOHYDROLASE ACTIVITIES FOR VARIOUS STEROID SULFATES IN NORMAL AND PATHOLOGICAL BRAINS, INCLUDING THE VARIOUS FORMS OF METACHROMATIC LEUKODYSTROPHY
Authors: Iwamori M. , Moser H. W. , Kishimoto Y.
Published: October 2006

Abstract– The enzymatic hydrolysis by brain homogenate of the sulfate esters of estrone, pregnenolone, dehydroepiandrosterone, testosterone, cholesterol and p‐nitrophenol was studied. With homogenate of young rat brain, the pH optima of estrone sulfatase4 and arysulfatase C (p‐nitrophenyl sulfate as substrate) were 8.2 and all other steroid sulfatases had pH optima at 6.6. Apparent Kms for these steroid sulfates were widely different. The highest Km value was 32.2 μm for estrone sulfate and the lowest was 0.66 μm for testosterone sulfate; the Km for p‐nitrophenyl sulfate was 30 fold higher than for estrone sulfate. Specific activity was also highest with estrone sulfatase and lowest with testosterone sulfatase; specific activity with aryl sulfatase C was over 3 fold higher than with estrone sulfatase. Estrone sulfatase activity was inhibited noncompetitively by sulfate esters of dehydroepiandrosterone, pregnenolone, and cholesterol; on the other hand, other steroid sulfatases were inhibited by these latter three sulfates competitively. Developmental changes of these sulfohydrolase activities in rat brain were almost identical with the exception of testosterone sulfatase activity; the latter sulfatase had a peak activity at 30 days old, while all other sulfatase had a peak at 20 days old. Thermal stability of all these activities was identical. Testosterone sulfatase activity in neurological mouse mutants, jimpy, msd, and quaking mice, was less than one half of littermate controls, while other steroid sulfatase levels in these mutants' brain were normal. All sulfatase activities were diminished in the brain of a metachromatic leukodystrophy patient with multiple sulfatase deficiency. The brains of classical metachromatic leukodystrophy patients contained normal levels of all steroid sulfatases and arylsulfatase C, with the single exception of testosterone sulfatase which level was less than 50% of control.
THE TOXIC EFFECT OF SODIUM GLUTAMATE ON RAT RETINA: CHANGES IN PUTATIVE TRANSMITTERS AND THEIR CORRESPONDING ENZYMES
Authors: Karlsen R. Lund , Fonnum F.
Published: October 2006

Abstract– Subcutaneous administration of high doses of sodium glutamate to rats during their first week after birth produced an almost total loss of choline acetyltransferase, a 90% reduction in glutamate decarboxylase and 70% reductions in acetylcholinesterase and DOPA decarboxylase activities in the adult retina. In addition there was a 70% decrease in GABA and 35‐55% decrease in aspartate, glutamate, glycine, alanine and glutamine. No reduction in taurine was observed. The results support the view that the enzymes are mainly localized in the interneurons of retina and that taurine is present in the photoreceptor cells.

Glutamate treatment was also followed by a small reduction in choline acetyltransferase and glutamate decarboxylase of the superior colliculus and in choline acetyltransferase of hippocampus, whereas no changes could be detected in the lateral geniculate body of the adult rat. Unilateral enucleation performed on 1‐day‐old animals did not alter choline acetyltransferase, acetylcholinesterase, glutamate decarboxylase and DOPA decarboxylase activities in the superior colliculus and in the lateral geniculate body of the adult rat.
CYCLIC NUCLEOTIDES IN MURINE BRAIN: THE TEMPORAL RELATIONSHIP OF CHANGES INDUCED IN ADENOSINE 3′,5′‐MONOPHOSPHATE AND GUANOSINE 3′,5′‐MONOPHOSPHATE FOLLOWING MAXIMAL ELECTROSHOCK OR DECAPITATION
Authors: Lust W. D. , Goldberg N. D. , Passonneau J. V.
Published: October 2006

–Adenosine 3′,5′‐cyclic monophosphate (cyclic AMP) levels increase about 5‐fold in the cerebral cortex and 2‐fold in the cerebellum following electroconvulsive shock (ECS). The peak levels of cyclic AMP occur at 45 s after ECS in the cerebral cortex, and at 15 s in the cerebellum. In the cerebral cortex, ECS produces twice the cyclic AMP accumulation as does decapitation in a comparable time period; however, the relative effect of a number of neurotropic agents on the cyclic AMP accumulation is essentially the same, whether stimulated by decapitation or by ECS. In the cerebellum, the levels of guanosine 3′,5′‐cyclic monophosphate (cyclic GMP) also increase following ECS. The cyclic GMP levels are greatest at 60 s after ECS during the postictal depression. An association between elevated cerebellar cyclic GMP and depression seems unlikely, since CNS depressants either lowered or had no effect on cyclic GMP levels. From these results, cyclic nucleotide profiles following treatments such as ECS or decapitation may be useful in elucidating the molecular events involved in seizures, brain injury and ischemia.
CYCLOHEXIMIDE ALTERS AXONAL TRANSPORT AND SUBCELLULAR DISTRIBUTION OF DOPAMINE‐β‐HYDROXYLASE ACTIVITY
Authors: Brimijoin S.
Published: October 2006

—Administration of cycloheximide, 10 mg/kg s.c. led within 4 h to an approx 30% reduction of dopamine‐β‐hydroxylase (DBH) activity in the abdominal portion of rat sciatic nerves. At least two more hours elapsed before DBH activity in the distal part of these nerves began to fall. This pattern suggests reduced synthesis or delivery of DBH into axons but continued transport of previously delivered enzyme. Coinciding with the time at which DBH activity began to fall in distal segments of sciatic nerve, there was a marked reduction in the accumulation of DBH activity above a ligature in this region. Between 4 and 8 h after administration of cylcoheximide, 10 mg/kg, accumulation above a ligature was 70% less than in untreated nerves (P < 0.001), a reduction significantly greater (P < 0.05) than the accompanying 28% loss of baseline DBH activity. At the same time, the clearance of DBH activity from nerve regions distal to a ligature was greatly reduced. This pattern is consistent with the depletion of a minor but rapidly transported compartment of DBH. Six hours after administration of cylcoheximide, 10 mg/kg, the apparent subcellular distribution of DBH in distal regions of sciatic nerve was altered by a significant 36% loss in sedimentable DBH activity, with non‐significant changes in othcr fractions. This suggests that rapidly transported DBH, depleted from the nerve by cycloheximide‐induced inhibition of protein synthesis, is more highly associated with intraneuronal particles than is slowly transported or stationary DBH.
THE UPTAKE OF BIOGENIC MONOAMINES BY THE ISOLATED AURICLE OF THE SNAIL (HELIX POMATIA)
Authors: Hiripi L. , Neuhoff V. , Osborne N. N.
Published: October 2006

—The uptake of [3H]5HT, [3H]dopamine, [3H]noradrenaline and [3H]octopamine into the auricle of Helix pomatia was studied.

When tissues were incubated at 25°C in media containing radioactive amines, tissue:medium ratios of about 49:1, 14:1 and 5:1 for 5‐HT, dopamine, noradrenaline, and octopamine respectively were obtained after a 20–30 min incubation time. Tissues incubated at 25°C in media containing radioactive amines for 20–30 mins showed that almost all (96%) the radioactivity was present as unchanged [3H]5‐HT, [3H]dopamine, [3H]octopamine or [3H]noradrenaline.

The high tissue:medium ratios for 5‐HT and dopamine, but not for noradrenaline and octopamine, showed saturation kinetics which were dependent upon temperature and sodium ions. From the Lineweaver–Burk plots, two uptake mechanisms for 5‐HT at 25°C were resolved; the high affinity uptake process having a Km1 value of 6.0 ± 10−8m and a Vm1 value of 0.115 nmol/g/min while the lower affinity process had a Km2 value of 1.04 ± 10−6m and a Vm2 value of 0.66nmol/g/min. At 0°C a single uptake mechanism for 5‐HT occurred which gave a Km value of 5.02 ± 10−8m and a Vm value of 0.0165 nmol/g/min. In the case of dopamine, the Lineweaver–Burk plot at 25°C showed a single uptake process with values for Km and Vm of 1.55 ± 10−7m and 0.086 nmol/g/min respectively. This process did not function at 0°C.

The effect of various agents and ions upon the accumulation processes for all amines was also studied, and the data indicate that the same neurons probably accumulate more than one amine type.

It is concluded that 5‐HT and dopamine uptake in the auricle is a mechanism for inactivating these substances at 25°C and that an uptake mechanism for 5‐HT also functions at 0°C. The results are discussed from the point of view of 5‐HT's being the cardioexcitatory substance in the snail heart.
DARK REARING and VISUAL STIMULATION IN THE RAT: EFFECT ON BRAIN ENZYMES
Authors: Sinha A. K. , Rose S. P. R.
Published: October 2006

Abstract— Enzyme activities in motor and visual cortex and cerebellum of rats reared for 50 days in the dark (D) were compared to levels in normally reared (N) and in dark‐reared littermates exposed to 3 h of visual stimulation (L). Amongst 6 acid hydrolases, two, acid phosphatase and galactosaminadase, showed no effect of dark rearing. In three of the others, glucuronidase, glucosaminidase and galactosidase, activity tended to be lower in D than L. In glucosaminidase, N was similar to D and L above both, while in (total) glucosidase, galactosidase and glucuronidase, N was higher than D and L approached N. There were fewer changes in cerebellum than in cortex.

Visual cortex acetylcholinesterase was 29% higher in L than in D, and 41% higher in L than in N, but there were no significant differences in AChE or BChE in motor cortex or cerebellum. Choline acetyltransferase was higher by 30% in L and D in visual cortex, and 22% in motor cortex. There were no differences in the cerebellum. There were no differences in the levels of activity of glutamate decarboxylase or Na+, K+, Mg2+ ‐ATPase in any region or condition.

The significance of both the apparently transient and more permanent effects of dark rearing and light exposure on the enzymes studied, and discrepancies with other reports of enzyme changes in dark rearing are discussed.
THE ROLE OF LIPIDS IN THE OBSERVED LACK OF PHOSPHATIDYLCHOLINE EXCHANGE IN MYELIN
Authors: Brammer M. J. , Sheltawy A.
Published: October 2006

Abstract— When exchange between liposomal phosphatidylcholine and that in a whole myelin fraction from guinea‐pig brain was studied, very little exchange was observed. In order to investigate the reason for this phenomenon, myelin lipids in the Ca2+ form were prepared and subjected to sonication under the same conditions usually used to study phosphatidylcholine exchange. Despite the high cholesterol content in these extracts, this treatment produced liposomes of a size (12 nm Stoke's radius) similar to that of pure phosphatidylcholine liposomes. In this form, myelin total lipids were capable of undergoing exchange, and this was only demonstrable in the fraction containing phosphatidylcholine and that containing phosphatidylinositol. Since the level of acidic phospholipids in these total lipid extracts is potentially capable of producing 40% inhibition of phosphatidylcholine exchange (Hellingset al, 1974; Brammer & Sheltawy, 1975), control experiments were carried out to ensure that the observed phosphatidylcholine exchange in the myelin lipid extract was not due to the loss of phosphoinositides. This was found to be the case, and it was concluded therefore that total myelin lipids, in the Ca2+ form, are capable of phosphatidylcholine exchange and that the observed lack of it in the whole myelin is due either to the effect of myelin proteins or the compact structure of the myelin membrane.

Calculations based on the difference between the rate of phosphatidylcholine exchange in the myelin liposomes and in the sonicated phosphatidylcholine liposomes indicated that the phosphatidylcholine is asymmetrically distributed in the myelin liposomes. Almost all the phosphatidylcholine seems to be present in the outer half of the bilayer.
THE ACTION OF TRIETHYLTIN ON THE RESPIRATION OF RAT BRAIN CORTEX SLICES
Authors: Lock E. A.
Published: October 2006

Abstract—

Glucose oxidation by rat brain cortex slices is inhibited by low concentrations of triethyltin and this sensitive inhibition is shown to be chloride‐dependent. Pyruvate oxidation is only inhibited at high concentrations of triethyltin whether chloride is present or not. In contrast, the stimulation of both glucose and pyruvate oxidation observed with low concentrations of triethyltin prior to inhibition is chloride‐dependent. The results are discussed in relation to the chloride‐hydroxide exchange reaction known to be mediated across the inner mitochondrial membrane by triethyltin and other organo‐metals.
VARIATIONS AU COURS DES DIX PREMIERS JOURS DE LA VIE POSTNATALE DE L'INCORPORATION IN‐VIVO DE LA L‐[3H]LEUCINE DANS LES PROTEINES DU CERVELET DU RAT NORMAL, HYPO‐ ET HYPERTHYROIDIEN
Authors: Dainat J. , Rebiére A.
Published: October 2006

Résumé—

L'incorporation de la leucine tritié dans les proteines du cerveau et du cervel et de rat est mesuré 30min aprés l'injection intraveineuse de cet acide aminé marqué. Chez les rats normaux la radioactivité spécifique (RAS) et la RAS relative des protéines du cervelet et du cerveau, varient trés fortement d'un jour à l'autre durant les dix premiers jours de la vie postnatale du rat. Ces variations font ressortir un maximum de la RAS et de la RAS relative des proteines à 7 jours, et deux minima à 3 et 6 jours. Chez les animaux hypothyroïdiens, la RAS et la RAS relative des protéines du cervelet ct du cervcau sont inférieures à celles des animaux normaux. La RAS présente un maximum à 7 jours et un minimum à 3 jours. Chez les animaux hyperthyroidiens, la RAS relative des protéines du cervelet sont significativement plus élevées que celles des animaux normaux. Elks passent par deux maxima à 2 et 5 jours et un minimum à 9 jours. Chez les animaux hypothyroydïdiens comme chez les animaux normaux bien qu'a un niveau inférieur, les synthéses protéiques sont plus importantes durant la deuxième semaine postnatale que durant la première. Par contre chez les animaux hyperthyroïdiens les synthèses protéiques sont plus importantes durant la premiere semaine postnatale que durant la seconde. L'évolution des valeurs de la RAS et de la RAS relative des protéines du cervelet est discutee en fonction des phénomenes de croissance et de prolifération cellulaires. Alors que l'hyperthyroïdie avance ces deux processus sans modifier la durée qui les sépare, l'hypothyroidie en modifiant cette durée, entraîne une perturbation dans le déroulement de ces phénoménes.
METABOLIC PROPERTIES OF A PURIFIED PREPARATION OF LARGE FRAGMENTS OF THE CEREBELLAR GLOMERULI: GLUCOSE METABOLISM AND AMINO ACID UPTAKE
Authors: Wilson J. E. , Wilkin G. P. , Balazs R.
Published: October 2006

Abstract—

Glomerulus particle preparations contain large fragments of the cerebellar glomeruli and are composed almost exclusively of well‐defined neuronal processes (Balázs et al., 1975). The metabolic competence of the glomerulus particles was demonstrated by their ability to convert [14C]glucose to 14CO2 and lactate at a linear rate for over 1 h. The preparations also transported deoxyglucose via an high affinity uptake system (KT= 0.2‐0.5 mM).

The kinetics of uptake of various labelled amino acids were also studied. Apparently high affinity uptake systems (KT values about 10‐5 M) were found for thc putative transmitters GABA, glycine, glutamate, and aspartate, but not for leucine, serine, and tyrosine. The maximal velocity of high affinity uptake was the greatest for GABA (about 15 nmol/mg protein per 10 min), while glycine was taken up at about 50%, and aspartate and glutamate at only 13% of the rate obtained with GABA. High affinity uptake of glycine required Na+ (half maximal uptake at 70 mM‐NaCl). Inhibition of glucose transport and glycolysis, electron transport, or oxidative phosphorylation also depressed high affinity uptake of glycine. 2,4‐Diaminobutyric acid was a potent competitive inhibitor of GABA uptake (K1 approx 22 μM), while β‐alanine and glycine had a relatively minor inhibitory effect on the uptake of GABA.
ELECTRICALLY INDUCED RELEASE OF [3H]GABA FROM NEOCORTICAL THIN SLICES. EFFECTS OF STIMULUS WAVEFORM AND OF AMINO‐OXYACETIC ACID
Authors: Orrego F. , Miranda R.
Published: October 2006

Abstract—

The efflux of [3H]GABA or [14C]GABA from superfused neocortical thin slices, held on quick transfer electrodes, has been compared with that of the non‐transmitter amino acid model [14C]α‐ amino‐isobutyrate (AIB), and, to a lesser extent, with [3H]norepinephrine. Electrical stimulation of the slices with sine‐wave current (50 Hz); rectangular, biphasic pulses, (80/s, 3 ms); or rectangular, monophasic pulses (100/s, 5 ms), was unable to release GABA at stimulating potentials that are able to release known transmitter substances. Release of GABA and AIB was only seen with higher applied potentials, when also non‐transmitter amino acids were released. It was also found that amino‐oxyacetic acid(10‐5 M and 5 × 10‐5 M) increased the excitability of the slices, and allowed the release of both GABA and AIB to occur with weaker stimuli. This effect was independent of extracellular calcium.
ANISOMYCIN, ACETOXYCYCLOHEXIMIDE, CYCLOHEXIMIDE, AND PUROMYCIN AS INHIBITORS OF RAT BRAIN ACETYLCHOLINESTERASE IN VITRO1
Authors: Moss D. E. , Fahrnly D.
Published: October 2006

A kinetic analysis of the interaction of anisomycin, acetoxycycloheximide, cycloheximide, and puromycin with acetylcholinesterase (acetylcholine acetyl‐hydrolase, EC 3.1.1.7) in rat brain homogenate shows that all of these protein synthesis inhibitors are also inhibitors or this enzyme. Puromycitl aminonucleoside, a puromycin analog without antibiotic activity, was also found to be an inhibitor of acetylcholinesterase activity much like puromycin. Anisomycin appeared to be a competitive inhibitor whereas all of the other compounds showed mixed inhibition. The apparent 10.5 values for inhibition of rat brain acetylcholinesterase at 50 μM substrate were: anisomycin, 3 mM; acetoxycycloheximide, 1 mM; cycloheximide, 2.2 mM; puromycin, 0.5 mM and puromycin aminonucleoside, 0.6 mM.
REGIONAL AND SUBCELLULAR DISTRIBUTION OF PROTEIN CARBOXYMETHYLASE IN BRAIN AND OTHER TISSUES
Authors: Diliberto E. J. , Axelrod J.
Published: October 2006

Protein carboxymethylase, an enzyme that transfcrs the methyl group of S‐adenosyl‐L‐methionine to carboxyl groups of proteins and endogenous acceptor proteins were examined in nerve and endocrine tissues. The highest protein carboxymethylase activity was found in the brain, followed by the testis, pituitary and heart. On the other hand, the tissue with the highest level of endogenous substrate(s) was the pituitary. The nearly identical specific activity ratio for two different protein substrates in all tissues examined, suggests that one enzyme is responsible for carboxymethylase activity in different tissues. The subcellular distribution of the enzyme in brain showed a high concentration in the soluble fraction, presumably representative of the enzyme in the cytosol of cell bodies. Considerable enzyme activity was also found in brain synaptosomes which was increased by osmotic lysis. Protein carboxymethylase was shown to accumulate proximally to a ligation of the rat sciatic nerve. A possible physiological role for protein carboxymethylase in neuronal function is discussed.
THE DISTRIBUTION AND METABOLISM OF PUTRESCINE, SPERMIDINE AND SPERMINE INJECTED INTO THE CEREBRAL VENTRICLES OF RABBITS
Authors: Halliday C. A. , Shaw G. G.
Published: October 2006

Following the intracerebroventricular injection into rabbits of spermidine or spermine the highest concentrations were initially found in the caudate nucleus, hypothalamus and medulla. Subsequently there was a rapid decline in the amounts present in the caudate nucleus and hypothalamus and, particularly in the case of spermidine, an increase in the conccntration in the lower brain stem and cervical cord. This pattern of changes is consistent with the amines being redistributed by passage in CSF. Intraventricularly injected putrescine followed the same initial distribution pattern but within 2 days it had been largely converted to spermidine and spermine. Synthesized polyamines accumulated in all the regions examined. The time course of synthesis indicated that spermidine was the precursor of spermine. Spermine was also formed from injected spermidine and vice‐versa. These findings concur with the pharmacological and neurotoxic actions of putrescine, spermidine and spermine.
PHARMACOLOGICAL STUDIES ON THE STIMULATION OF THE PHOSPHOLIPASE A2‐ACYLATION SYSTEM OF SYNAPTIC MEMBRANES OF BRAIN, BY NEUROTRANSMITTERS AND OTHER AGONISTS
Authors: Gullis R. J. , Rowe C. E.
Published: October 2006

Methacholine, nicotine and succinylcholine stimulated the phospholipase A2‐acylation system of synaptic membranes isolated from the cerebral cortex of guinea pig. Stimulation by acetylcholine was partially blocked by atropine and by D‐tuberocurarine respectively, indicating both muscarinic and nicotinic stimulation. Muscarinic stimulation by acetylcholine was greater than ‐isotinic stimulation, and stimulation by acetylcholine was completely blocked by a combip, or;. and n‐tuberocurarine.

The phospholipase A2‐acylat tem was stimulated by phenylcphrine., id. Cqxoterenoi. Stimulation by noradrenaline was J‐. tidlr, by phenoxybenzamine and pindalol i:spectively, indicating both 8‐adrenergic and P‐adrenergic ztimulation. n‐Adrenergic stimulation by noradrenaline was greater than P‐adrenergic‐stimulation. 5 ‐mlation by noradrenaline was completely blocked by a combination of phenoxybenzamins and pindalol.

Stimulation of both acylation and phospholipid hydrolysis, by 5‐hydroxytryptamine and histamine were partially blocked by methysergide and diphenhydramine respectively. Stimulation by dopamine was blocked by halopcridol. Stimulation by y‐aminobutyric acid was partially blocked by strychnine and by picrotoxin.

Dichloroisoproterenol, atropine, methysergidr, diphenhydramine, strychnine, picrotoxin and eserine, at relatively high concentrations (1 mM), stimuhted the phospholipase A2‐acylation system.

Synergistic stimulations of both acylatior, and hydrolysis of phosphatidylcholine, were observed by adenosine combined with noradrenaline, 5‐hydroxytryptamine, histamine, dopamine or yaminobutyric acid, respectively.

In the presence of ATP‐MgCI, synergistic stimulations of the hydrolysis of phosphatidyicholine were observed after 30 s by noradrenaline combined with 5‐hydroxytryptamine, histamine, dopamine, aminobutyric acid or carbamoylcholine respectively. In the presence of GTP‐MgC12 synergistic stimulations were obtained by cdrbamoylcholine combined with noradrenaline. 5‐hydroxytryptamine. histamine, dopamine or y‐aminobutyric acid, respectively. In the presence of ATP‐MgC12 plus GTP‐MgC12, stimulation by noradrenaline and one other agonist including 5‐hydroxytryptamine, histamine, dopamine, y‐aminobutyric acid or carbamoylcholine were close to additive.
EFFECT OF ACIDIC DEOXYRIBONUCLEOPROTEINS FROM BRAIN ON DNA SYNTHESIS IN VITRO
Authors: Burdman J. A. , Szijan I.
Published: October 2006

Chromatin acidic proteins extracted from rat brain stimulate in uitro synthesis of DNA with either brain chromatin. native or denatured DNA as template.

The stimulation is due to the presence of nuclease activity within these proteins which increases the priming activity of DNA.