bluuebunny/crossref_metadata_2025 huggingface dataset:
PURIFICATION AND PROPERTIES OF HUMAN BRAIN α‐L‐FUCOSIDASE
Authors: ALHADEFF J. A. , JANOWSKY A. J.
Published: October 2006

Abstract—

Human brain α‐L‐fucosidase has been extracted and the soluble portion has been purified 9388‐fold with 25% yield by a two‐step affinity chromatographic procedure utilizing agarose‐epsilon‐aminocaproyl‐fucosamine. Isoelectric focusing revealed that all seven isoelectric forms of the enzyme were purified. Trace amounts of eight glycosidases, with hexosaminidase being the largest contaminant (1% by activity) were found in the purified α‐L‐fucosidase preparation. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis indicated the presence of a single subunit of molecular weight 51,000 ± 2500. The purified enzyme has a pH optimum of 4.7 with a suggested second optimum of 6.6. The apparent Michaelis constant and maximal velocity of the purified enzyme with respect to the p‐nitrophenyl substrate are 0.44 mM and 10.7 μmol/min/mg protein, respectively. Ag2+ and Hg2+ completely inactivated the enzyme at concentrations of 0.1‐0.3 mM. Antibodies made previously against purified human liver α‐L‐fucosidase cross‐reacted with the purified brain α‐L‐fucosidase and gave a single precipitin line coincident with that from purified liver α‐L‐fucosidase. From all our studies it appears that at least the soluble portion of brain α‐L‐fucosidase is identical to human liver α‐L‐fucosidase.
CHARACTERIZATION OF PUTATIVE AMINO ACID TRANSMITTER RELEASE FROM SLICES OF RAT DENTATE GYRUS
Authors: Nadler J. V. , White W. F. , Vaca K. W. , Redburn Dianna A. , Cotman C. W.
Published: October 2006

Abstract— Superfused slices of the rat dentate gyrus were employed to study the release of GABA, glutamate and aspartate, which are considered strong neurotransmitter candidates in this region. The introduction of Ca2+ to a Ca2+‐free superfusion medium containing a depolarizing agent augmented the efflux of all three amino acids. The response to application of Ca2+ nearly always occurred within 30 s, the shortest interval tested in these studies. The efflux rate reached a peak within 90 s and then declined to a level slightly greater than the prestimulation baseline. The failure to maintain the maximal rate with continued exposure to Ca2+ and depolarizing influences appeared not to result from a reduction in Ca2+ permeability caused by continuous depolarization. Ca2+ also stimulated the efflux of exogenously loaded radiolabeled GABA, glutamate and aspartate, but not proline. Exogenously loaded GABA was more readily released than endogenous GABA. Otherwise the effects of various treatments on their efflux rates were qualitatively similar.

Mg2+ inhibited Ca2+‐dependent efflux. Ba2+, but not Mg2+, stimulated amino acid efflux in the absence of Ca2+. Extracellular Na+ was not required to support Ca2+‐dependent efflux. Addition of Ca2+ to a Ca2+‐free medium in the absence of a depolarizing agent released GABA from the slices, but not glutamate or aspartate.

K+‐enriched medium and the depolarizing alkaloid, veratridine, stimulated both Ca2+‐dependent and Ca2+‐independent release processes. Na+‐free medium enhanced the Ca2+‐independent releasing action of elevated K+. Ca2+‐independent release was inhibited by raising the Mg2+ concentration by 15 or 30 mM and appeared to be inhibited by Ca2+ as well. Amino acid output in the absence of Ca2+ is probably not directly related to transmission and is considered to result partially from a general increase in membrane permeability induced by depolarization in a Ca2+‐free medium and partially from stimulation of carrier‐mediated amino acid efflux.

These results support previously suggested transmitter roles for GABA, glutamate and aspartate in the rat dentate gyrus.
STUDIES OF THE INTER‐RELATIONSHIP BETWEEN CEREBROSPINAL FLUID AND PLASMA AMINO ACID CONCENTRATIONS IN NORMAL INDIVIDUALS
Authors: McGale E. H. F. , Pye I. F. , Stonier C. , Hutchinson E. C. , Aber G. M.
Published: October 2006

Abstract— —The concentration of free amino acids has been determined in lumbar CSF in 37 fasting normal subjects. The values obtained have been compared with the concentration of the same amino acids measured in venous plasma collected simultaneously and with ventricular CSF amino acid concentrations. Twenty‐three amino acids have been identified and quantitated in CSF and plasma. Trace quantities of eight other amino acids have been also detected.

The concentration of 13 amino acids in CSF has been shown to be directly related to the plasma concentration. No such relationship was noted for the other 7 amino acids. Significant variations in the concentration of individual amino acids relating to both age and sex have been noted. A large number of unidentified ninhydrin positive compounds have been found in CSF. Preliminary studies have identified one of these as ɛ‐aminobutyric acid (GABA).
SYNAPTIC AND NON‐SYNAPTIC MITOCHONDRIA FROM RAT BRAIN: ISOLATION AND CHARACTERIZATION
Authors: Lai J. C. K. , Walsh Julia M. , Dennis S. C. , Clark J. B.
Published: October 2006

Abstract— A method has been developed where by three distinct populations of metabolically active, well coupled and relatively pure mitochondria from rat brain may be prepared. Two mitochondrial populations are derived from synaptozomes and the third consists of ‘free’ (i.e. non‐synaptic) mitochondria. These mitochondrial populations have been characterized with respect to both enzyme content and ability to oxidize substrates. The results indicate that these mitochondrial populations are heterogeneous with respect to maximal activities of certain enzymes concerned with the citric acid cycle and glutamate and 4‐aminobutyrate metabolism as well as their ability to utilize various substrates. The data reported here also confirm that brain mitochondria are very heterogeneous and suggest that synaptic mitochondria may contain at least two sub‐populations. The relations between the heterogeneity of brain mitochondria and the metabolic compartmentation of the citric acid cycle and related metabolites such as glutamate, aspartate and 4‐aminobutyrate are briefly discussed in the light of two proposed models of metabolic compartmentation in the mammalian brain.
RAT BRAIN SYNAPTIC VESICLES: UPTAKE SPECIFICITIES OF [3H]NOREPINEPHRINE AND [3H]SEROTONIN IN PREPARATIONS FROM WHOLE BRAIN AND BRAIN REGIONS1
Authors: Slotkin Theodore A. , Seidler Frederic J. , Whitmore William L. , Lau Christopher , Salvaggio Maria , Kirksey Donny F.
Published: October 2006

A fraction containing neurotransmitter storage vesicles was isolated from rat whole brain and brain regions, and the uptakes of [3H]norepinephrine and [3H]serotonin were determined in vitro. Norepinephrine uptake in vesicle preparations from corpus striatum was higher than in prep arations from cerebral cortex, and uptake in vesicles from the remainder (midbrain + brainstem + cerebellum) was intermediate. The Km for norepinephrine uptake was the same in the three brain regions, but the regions differed in maximal uptake capacity by factors which paralleled total catecholamine concentration rather than content of norepinephrine alone. Intracisternal administration of 6‐hydroxydopamine, but not of 5,6‐dihydroxytryptamine, reduced vesicular norepinephrine uptake, and pretreat‐ment with desmethylimipramine (which protects specifically norepinephrine neurons but not dopamine neurons from the 6‐hydroxydopamine) only partially prevented the loss of vesicular norepinephrine uptake. These studies indicate that uptake of norepinephrine by rat brain vesicle preparations occurs in vesicles from norepinephrine and dopamine neurons, but probably not in vesicles from serotonin neurons. Uptake of serotonin by brain vesicle preparations exhibited time, temperature and ATP‐Mg2+ requirements nearly identical to those of norepinephrine uptake. The affinity of serotonin uptake matched that of serotonin for inhibition of norepinephrine uptake, and the maximal capacity was the same for serotonin as for norepinephrine. Norepinephrine, dopamine and reserpine inhibited serotonin uptake in a purely competitive fashion, with Kis similar to those for inhibition of norepinephrine uptake. Whereas 5,6‐dihydroxytryptamine treatment reduced synaptosomal serotonin uptake but not vesicular serotonin uptake, 6‐hydroxydopamine reduced vesicular serotonin uptake in the absence of reductions in synaptosomal serotonin uptake. Thus, in this preparation, serotonin appears to be taken up in vitro into catecholamine vesicles, rather than into serotonin vesicles.
CEREBRAL METABOLIC AND CIRCULATORY CHANGES INDUCED BY HYPOXIA IN STARVED RATS
Authors: Berntman L. , Siesjou B. K.
Published: October 2006

In order to study cerebral metabolic and circulatory effects of hypoxia under conditions of restricted glucose supply, the arterial Po2, was reduced to 25–30mm Hg in artificially ventilated and lightly anaesthetized rats that were starved for 24 or 48 h prior to experiments. Arterial glucose concentrations, that were initially around 6μmol g‐1, were significantly reduced after 15min of hypoxia, and decreased to 50o of control after 30min.

In animals studied after 30min of hypoxia (24 h of starvation), cerebral blood flow had increased 4‐fold and there was a moderate (25%) rise in cerebral oxygen consumption. During the course of hypoxia, cerebral cortical concentrations of glucose fell to low values. In spite of this, concentrations of pyruvate and lactate rose with time, and the sum of citric acid cycle intermediates (citrate, α‐ketoglutarate, fumarate. malate and oxaloacetate) increased. Changes in amino acids were dominated by a fall in aspartate and a rise in alanine concentration. There was a moderate reduction in phosphocreatine and a slight rise in ADP concentration, but concentrations at ATP and AMP were unchanged. The changes observed are similar to those previously obtained in fed animals. It is concluded that even if blood glucose concentrations fall to 3μmol g‐1, and cerebral energy flux is maintained, substrate supply is sufficient to cover the energy requirements of the tissue.

Hypoxia was accompanied by increases in the lactate/pyruvate and β‐hydroxybutyrate acetoacetate ratios of blood. In the tissue, NADH/NAD+ ratios derived from the lactate, malate and β‐hydroxybutyrate dehydrogenase systems rose, while that derived from the glutamate dehydrogenase reaction fell. It is concluded that the latter system is not well suited for estimating mitochondrial redox changes in brain tissue.
PROLIDASE ACTIVITY IN BRAIN: COMPARISON WITH OTHER ORGANS
Authors: Hui K. S. , Lajtha A.
Published: October 2006

Abstract—

Prolidase (imidodipeptidase, EC 3.4.3.7) activity in brain was assayed spectrophotometrically, and the validity of the assay was confirmed by microchromatographic analysis of the dansyl derivatives of the reaction products. The ratio of the activity of prolidase from brain on Ala‐Pro, Gly‐Pro, and Pro‐Pro was similar to that of the highly purified intestinal mucosal prolidase. The size and polarity of the amino acid side chain (R) of the N‐terminal amino acid and whether the terminal amino and carboxy groups are free or blocked are important factors in determining prolidase substrate activity. Using Ala‐Pro as substrate, we found prolidase activity in all rat tissues we investigated, with highest activity in kidney and lowest in plasma; 33 mmol of Ala‐Pro was hydrolyzed per mg of protein per min by brain tissue, which is 20% of the activity for kidney and 23% of that for intestinal mucosa. The specific activity of prolidase was higher in the sciatic nerve than in brain or spinal cord, and activity was higher in the distal portion.
EFFECT OF 1‐AMINOCYCLOPENTANE‐1‐CARBOXYLIC ACID (CYCLOLEUCINE) ON DEVELOPING RAT CENTRAL NERVOUS SYSTEM PHOSPHOLIPIDS
Authors: Ramsey Robert B. , Fischer Vernon W.
Published: October 2006

Abstract—

Treatment of developing rats with 1‐amino‐cyclopentane carboxylic acid (cycloleucine) resulted in changes in brain and spinal cord phospholipid content and fatty acid composition. General findings were a decrease in ethanolamine phospholipid content, and relative increase in the saturated fatty acid content of ethanolamine phospholipid. In all the different cycloleucine experiments conducted, there was consistently less fatty aldehyde present in the methylated ethanolamine phospholipid fatty acid‐fatty aldehyde fractions than in corresponding controls. In some experiments fatty aldehyde was almost completely absent, suggesting the presence of little plasmalogen. Changes in fatty acids of phosphatidyl choline, the other phospholipid examined in this manner, were generally minor. Administration of massive amounts of sodium propionate in addition to cycloleucine did not result in an appreciable odd‐chain fatty acid increase in the CNS.

Examination of the spinal cords by electron microscopy demonstrated considerable myelin splitting in one set of animals. No other ultrastructural changes were evident.

The suitability of this drug to produce a neurological condition and pathological state similar to that seen in B12‐deficient subacute combined degeneration is discussed.
DISTRIBUTION OF VASOACTIVE INTESTINAL POLYPEPTIDE (VIP) IN THE PORCINE CENTRAL NERVOUS SYSTEM
Authors: Fahrenkrug J. , de Muckadell O. B. Schaffalitzky
Published: October 2006

Abstract—

A sensitive and specific radioimmunoassay for vasoactive intestinal polypeptide (VIP) has been used to determine the regional distribution of the peptide in the porcine CNS. The hippocampus and cerebral cortex contained the highest concentration of VIP, while lower but significant amounts were present in the hypothalamus and neurohypophysis. The immunoreactive VIP in the brain appeared to be identical with the octacosapeptide originally isolated from porcine small intestine, since it was found to have identical chromatographic properties. to dilute in parallel with the standard curves and to react equally with six different VIP antisera independent of extraction procedure used.
EFFECTS OF INSULIN AND STREPTOZOTOCIN–NDUCED DIABETES ON BRAIN TRYPTOPHAN AND SEROTONIN METABOLISM IN RATS
Authors: Mackenzie R. G. , Trulson M. E.
Published: October 2006

Abstract—

Previous work by other authors has shown hat insulin administration increases brain tryptophan levels and serotonin (5–HT) metabolism. The present study partially replicates these results and tests whether these effects could be due to insulin‐induced hypoglycemic stress, since stressers such as immobilization or food deprivation also increase brain tryptophan and 5‐HT metabolism. Ingestion of a dextrose solution by rats administered insulin (2 I.U./kg) prevents the extreme fall in blood glucose concentration and rise in plasma corticosterone following insulin injections alone. This treatment, however, produces a larger increase in brain tryptophan (30%) than insulin‐injected rats allowed only tap water. The greater accumulation of brain tryptophan may reflect an additive effect of the endogenously released insulin to that exogenously administered, since ingestion of the dextrose solution could trigger insulin secretion. In addition, brain tryptophan and 5‐HT metabolism were measured in streptozotocin‐diabetic rats maintained on several different feeding schedules to control for the effects of hyperphagia. All groups of diabetics showed significant decreases of approx 30% in brain tryptophan concentrations, while 5‐HT metabolism was unchanged. This deficit in brain tryptophan is reversed within 2 h after insulin administration (2 I.U./kg). These results indicate that changes in brain tryptophan and 5‐HT metabolism following insulin injections are not due to hypoglycemic stress, and that brain tryptophan is low in diabetics but increases above normal after administration of insulin. The results are discussed with respect to the effects of insulin on plasma levels of the neutral amino acids and a possible direct effect of insulin on the uptake of tryptophan by brain.
PROTEIN AND GLYCOPROTEIN COMPOSITION OF MYELIN AND MYELIN SUBFRACTIONS FROM BRAINS OF ‘QUAKING’ MICE
Authors: Matthieu Jean‐Marie , Koellreutter Brigitte , Joyet Marie‐Louise
Published: October 2006

Abstract— Quaking mutants in mice are known to be affected by an arrest of myelinogenesis and to have a purified myelin which is more dense than that of controls. Their myelin has been shown to demonstrate a striking decrease in proteolipid protein, a lesser decrease in the small myelin basic protein and changes in glycoproteins comprising reduction in the major peak and shift of this peak towards a higher apparent molecular weight. The possibility that these findings might reflect merely contamination of myelin with other membranes was tested by subfractionation. Light myelin (floats on 0.62 m‐sucrose) is generally accepted as more compact and mature than the heavier subfraction (floating on 0.85 m‐sucrose). The changes previously found were present in both subfractions and even more marked in the light myelin. These results indicate that the anomalies of myelin proteins and glycoproteins were not caused by contaminants and are present in compact myelin as well as in membranes which are transitional between the glial plasma membrane and the myelin sheath. Therefore, we suggest that the Quaking mutation results in dysmyelination rather than hypomyelination.
STALOSYLGALACTOSYL CERAMTDE AS A SPECIFIC MARKER FOR HUMAN MYELIN AND OLIGODENDROGLIAL PERIKARYA: GANGLIOSIDES OF HUMAN MYELIN, OLIGODENDROGLIA AND NEURONS
Authors: Yu Robert K. , Iqbal Khalid
Published: October 2006

Abstract—

Gangliosides were isolated from human brain myelin, oligodendroglia, and neurons. Quantitative analysis revealed the following ganglioside contents: myelin, 2.0; neurons, 1.3; and oligodendroglia, 0.35 μg ganglioside sialic acid per mg protein. Myclin had a relatively simple ganglioside pattern with GM4and GM1as the predominant ganglioside species. The ganglioside pattern of oligodendroglia was quite complex and it resembled that of whole white matter rather than that of myelin. A high concentration of GM4was found in oligodendroglial fractions in addition to GM1, GD1a, GD1b, and GT1b. The usually‐ minor brain gangliosides GM3, GM2, and GM3were also enriched in oligodendroglia. The neuronal ganglioside pattern was generally similar to the pattern of whole gray matter. Both neurons and whole gray matter contained very low amounts of GM4. These results indicate that GM4is specifically localized in myelin and oligodendroglia of the CNS. Evidence is also presented that myelin, but not oligodendroglia, is the major reservoir of human white matter GM1and GM4.
EFFECT OF PHENYL AND PHENOLIC ACIDS ON MEVALONATE‐5‐PHOSPHATE KINASE AND MEVALONATE‐5‐PYROPHOSPHATE DECARBOXYLASE OF THE RAT BRAIN
Authors: Bhat Charavu Shama , Ramasarma T.
Published: October 2006

Abstract— Phenyl and phenolic acids are known to inhibit metabolism of mevalonate in rat brain. The site of inhibition has been found to be mevalonate‐5‐pyrophosphate decarboxylase. Phenolic acids also inhibited mevalonate‐5‐phosphate kinase on preincubation. The kinetics showed that p‐coumaric acid and isoferulic acid were competing with substrates, mevalonate‐5‐phosphate or mevalonate‐5‐pyre phosphate, whereas others showed an uncompetitive type of inhibition. Chlorophenoxyisobutyrate, a hypocholesterolaemic drug, had no effect on these enzymes. An improved method for the synthesis of mevalonate‐5‐phosphate and mevalonate‐5‐pyrophosphate, labeled at carbon‐1, is described.
ROLE OF ADENOSINE 3′, 5′‐MONOPHOSPHATE IN THE REGULATION OF CIRCADIAN OSCILLATION OF SEROTONIN N‐ACETYLTRANSFERASE ACTIVITY IN CULTURED CHICKEN PINEAL GLAND
Authors: Deguchi Takeo
Published: October 2006

—When pineal glands of 10–12‐day‐old chicks were organ‐cultured in darkness, serotonin N‐acetyltransferase activity was low during the daytime, increased at midnight and then decreased to the daytime level the next morning. The pattern of increase and decrease of enzyme activity in cultured pineal glands was comparable to the circadian rhythm of N‐acetyltransferase activity in vivo. When pineal glands were kept at a low temperature for 5 h prior to culture, the phase of autonomous rhythm of enzyme activity was delayed. When chicken pineal glands were cultured during the daytime for 6 h, derivatives of adenosine 3′, 5′‐monophosphate (cyclic AMP), cholera toxin, a high concentration of KCl and phosphodiesterase inhibitors increased N‐acetyltransferase activity 3–7‐fold, indicating an involvement of cyclic AMP in the regulation of N‐acetyltransferase activity in chicken pineal gland as has been shown in rat pineal gland. When pineal glands were cultured at night in darkness, cholera toxin or a high KCl did not enhance the night‐time increase of the enzyme activity. Derivatives of cyclic AMP or phosphodiesterase inhibitors enhanced the autonomous night‐time increase of N‐acetyltransferase activity in an additive or more than additive manner in cultured pineal glands. These observations suggest that adenylate cyclase of pinealocytes is inactive during daytime, but is activated at night in darkness, which is transduced to the synthesis of N‐acetyltransferase molecules. Catecholamines suppressed the basal level and the nocturnal increase of N‐acetyltransferase activity via α‐adrenergic receptor. The nocturnal increase of enzyme activity was prevented by cycloheximide or actinomycin D. Cocaine, which stabilizes cell membrane potential or light exposure, blocked the nighttime increase of N‐acetyltransferase activity in cultured chicken pineal glands.
The Development of Enzymes of Energy Metabolism in the Brain of a Precocial (Guinea Pig) and Non‐Precocial (Rat) Species
Authors: Booth R. F. G. , Patel T. B. , Clark J. B.
Published: October 2006

Abstract: Key enzymes of ketone body metabolism (3‐hydroxybutyrate de‐hydrogenase, 3‐oxo‐acid: CoA transferase, acetoacetyl‐CoA thiolase) and glucose metabolism (hexokinase, lactate dehydrogenase, pyruvate dehydrogenase, citrate synthase) have been measured in the brains of foetal, neonatal and adult guinea pigs and compared to those in the brains of neonatal and adult rats. The activities of the guinea pig brain ketone‐body‐metabolising enzymes remain relatively low in activity throughout the foetal and neonatal periods, with only slight increases occurring at birth. This contrasts with the rat brain, where three‐ to fourfold increases in activity occur during the suckling period (0–21 days post partum), followed by a corresponding decrease in the adult. The activities of the hexokinase (mitochondrial and cytosolic), pyruvate dehydrogenase, lactate dehydrogenase and citrate synthase of guinea pig brain show marked increases in the last 10–15 days before birth, so that at birth the guinea pig possesses activities of these enzymes similar to the adult state. This contrasts with the rat brain where these enzymes develop during the late suckling period (10–15 days after birth). The development of the enzymes of aerobic glycolytic metabolism correlate with the onset of neurological competence in the two species, the guinea pig being a “precocial” species born neurologically competent and the rat being a “non‐precocial” species born neurologically immature. The results are discussed with respect to the enzymatic activities required for the energy metabolism of a fully developed, neurologically competent mammalian brain and its relative sensitivity to hypoxia.
Biphasic and Opposite Effects of Dopamine and Apomorphine on Endogenous GABA Release in the Rat Substantia Nigra
Authors: van der Heyden J. A. M. , Venema K. , Korf J.
Published: October 2006

Abstract: A push‐pull cannula technique was used to study the in vivo release of endogenous GABA in the rat substantia nigra. Intranigral application of both dopamine (DA) and apomorphine produced biphasic changes in the rate of endogenous GABA release. The presence of 10 μM‐DA in the perfusion medium increased GABA release (140%). At 25 μM‐DA, both stimulation and inhibition of the nigral GABA release were observed. Higher concentrations of DA produced a decrease of the GABA release (50%). A small amount of apomorphine (10 μM in the perfusion medium) resulted in a decrease in GABA release (75%). Application of 25 μM‐apomorphine produces opposite effects, similar to those observed after addition of 25 μM‐DA. We observed an enhanced GABA release from the substantia nigra at 100 μM‐apomorphine in the perfusion medium (360%). The presence of 5 μM‐haloperidol produced a small decrease in the rate of GABA release (80%). Both the inhibitory effect of 25 μM‐DA and the excitatory effect of 100 μM‐apomorphine could be blocked by haloperidol added to the perfusion medium. Dibutyryl cyclic AMP (1.5 mM) and 2‐amino‐6, 7‐dihydroxyl(1, 2, 3, 4) tetrahydronapthalene (ADTN) (50 μM) added to the perfusion medium produced an inhibition of nigral GABA release (55% and 35% respectively) similar to that observed after addition of 50 μM‐DA. The amounts of lysine and ethanolamine (measured with GABA concurrently) released into the perfusion medium did not change in most of the experiments. The changes in the rates of release of these compounds that were observed in some experiments were either in the same or in the opposite direction of the change in GABA release. These results suggest that dopaminergic processes within the substantia nigra affect GABA‐ergic neurotransmission and that DA and apomorphine have different effects on GABA release.
Taurine in Developing Rhesus Monkey Brain
Authors: Sturman J. A. , Rassin D. K. , Gaull G. E. , Cote L. J.
Published: October 2006

The concentrations of taurine in all regions of fetal and neonatal rhesus monkey brain are greater than in the same regions of adult monkey brain. [35S]Taurine injected into pregnant rhesus monkeys is accumulated by the fetus. This process occurs rapidly in most tissues, but occurs slowly in fetal brain. Neonatal rhesus monkey brain also accumulates [35S]taurine slowly compared with other tissues after i.v. injection, and continues to accumulate [35S]taurine for a long period of time. These results suggest that the accumulation and exchange of taurine in developing rhesus monkey brain is slow, as found in neonatal rats, and that if there is a period of development at which rapid exchange of brain taurine occurs in the rhesus monkey, it is before the rapid brain growth spurt.
Long‐chain Fatty Acid:CoA Ligase in Rat Brain in vitro: A Comparison of Activities with Oleic and cis‐Vaccenic Acids
Authors: Murphy M. G. , Spence M. W.
Published: October 2006

Long‐chain fatty acid:CoA ligase (EC 6.2.1.3) has been examined in vitro with brain preparations from 12‐ to 16‐day‐old rats using oleic (18: 1[n‐9]) and cis‐vaccenic (18: 1[n‐7]) acids. A novel assay system, which permits measurement of product as [14C]fatty acyl‐[3H]CoA, [14C]fatty acyl‐CoA, or fatty acyl‐[3H]CoA, was used. With the double‐label assay, reaction conditions were established that gave a molar ratio of [3H]CoA to [14C]fatty acid in the product of 1.06 ± 0.12 (mean ±s.d., n= 14). This indicates that the method is specific for the fatty acid added to the incubation mixture. The assay is sensitive to the formation of approximately 0.02 nmol fatty acyl‐CoA. With oleic acid, specific activity of the ligase was highest in a microsomal fraction (3.91 ± 0.55 nmol oleoyl‐CoA formed/min/mg protein; n= 16). Optimal activity was obtained at concentrations of fatty acid, CoA, ATP and Mg2+ of 50 μM, 50 μM, 10 mm, and 8 mm, respectively. The apparent Kms (approximate) for oleic acid and coenzyme A were 20 and 6 μM, respectively. With cis‐vaccenic acid (18:1[n‐7]), a naturally occurring isomer of oleate, the maximum reaction rate was higher than that with oleate, as were the apparent Kms for both fatty acid (105 μM) and coenzyme A (23 μM).
Effect of Thyrotropin‐Releasing Hormone (TRH) on Local Cerebral Glucose Utilization, by the Autoradiographic 2‐Deoxy[14C]glucose Method, in Conscious and Pentobarbitalized Rats
Authors: Nagai Y. , Narumi S. , Nagawa Y. , Sakuradat O. , Uenot H. , Ishii S.
Published: October 2006

Effects of TRH and pentobarbital alone, and in combination, on local cerebral glucose utilization of rats were studied by the autoradiographic 2‐deoxy[14C] glucose method. TRH (5 mg/kg i.v.) reduced the rate of cerebral glucose utilization slightly in the whole brain. Locally, significant depression was observed in the following structures: frontal and visual cortices, hippocampus Ammon's horn and dentate gyrus, medial and lateral geniculate bodies, nucleus accumbens, caudate‐putamen, substantia nigra, pontine gray matter, superior colliculus, superior olivary nucleus, vestibular nucleus, lateral lemniscus and cerebellar cortex. Pentobarbital (30 mg/kg i.v.) produced a marked and diffuse reduction in the rate of glucose utilization throughout the brain. TRH given 15 min after the administration of pentobarbital markedly shortened the pentobarbital sleeping time and caused some reversal of the depression in local cerebral glucose utilization produced by pentobarbital. These effects were almost completely abolished by pretreatment with intracerebroventricular injection of atropine methyl bromide (20 μg/rat). These results indicate that although TRH acts to cause a reduction in the rate of cerebral glucose utilization, it reverses the depression induced by pentobarbital, via a cholinergic mechanism, in a number of structures, some of which are related to monoaminergic systems and the reticulo‐thalamo‐cortical activating system. Nagai Y. et al. Effect of thyrotropin‐releasing hormone (TRH) on local cerebral glucose utilization, by the autoradiographic 2‐deoxy[14C]glucose method, in conscious and pentobarbitalized rats. J. Neurochem.35, 963‐971 (1980).
Halothane Increases Membrane Fluidity and Stimulates Sphingomyelin Degradation by Membrane‐Bound Neutral Sphingomyelinase of Synaptosomal Plasma Membranes from Calf Brain Already at Clinical Concentrations
Authors: Pellkofer R. , Sandhoff K.
Published: October 2006

Abstract: High concentrations of halothane stimulate the degradation of sphingomyelin by neutral sphingomyelinase bound to synaptosomal plasma membranes (SYM) from calf brain up to 50‐fold, and increase membrane fluidity dramatically as measured by fluorescence depolarisation of incorporated 1,6‐diphenylhexatriene (DPH). To investigate the effects of low concentrations of halothane clinical conditions of anaesthesia were simulated in vitro by gassing a suspension of SYM with a gas mixture of 1.5 and 3% (by vol.) of [14C]halothane in N2 at 37°C. The uptake of halothane into SYM as determined by radioactivity measurements was 31 and 73 mmol per mol membrane lipid or 4 and 9 mg per g membrane, respectively. The same concentrations of halothane in the membrane suspensions increased membrane fluidity of SYM significantly as shown by measurements of fluorescence depolarisation of in‐corporated DPH. At halothane concentrations corresponding to 1.5 and 3% (by vol.) in the gas phase the degradation of sphingomyelin by membrane‐bound neutral sphingomyelinase of SYM was stimulated by 11 and 57% of controls, respectively. These results are discussed in relation to the anaesthetic potential of halothane. Key words: Synaptosomal plasma membranes‐Membrane‐bound neutral sphingomyelinase‐Membrane fluidity‐Halothane‐Clinical concentrations.
Increased Incorporation of [3H]Fucose into Chick Brain Glycoproteins Following Training on a Passive Avoidance Task
Authors: Sukumar Robert , Rose Steven P. R. , Burgoyne Robert D.
Published: October 2006

Abstract: Incorporation of [1H]fucose into the TCA‐precipitable material from the particulate and soluble fractions of different regions of the brain in the 1‐day‐old chick was measured following training on a passive avoidance task. A significant increase in the level of incorporation of [3H]fucose into the particulate fraction of the anterior forebrain roof was observed in the trained birds as compared with untrained controls. The percentage increases in radioactivity in the particulate fraction of the anterior forebrain roof were 29% (p < 0.01), 16% (p < 0.01), and 26% (p < 0.01) in the trained birds as compared with controls, 30 min, 3 h, and 24 h following learning, respectively, but had returned to control levels after 48 h. These results suggest either increased production of glycoproteins or increased fucosylation of preexisting proteins following training, and suggest one of the possible localized neurochemical changes associated with the learning of the passive avoidance response.
Dopamine and Norepinephrine in Discrete Areas of the Copper‐Deficient Rat Brain1
Authors: O'Dell B. L. , Feller D. J.
Published: October 2006

Abstract: Copper deficiency was induced in post‐weaning rats by feeding the dams a low copper diet during gestation and lactation. In confirmation of an earlier study, both dopamine and norepinephrine concentrations in the total brain were approximately 30% lower in deficient than in control rats. Doparnine in the corpus striaturm was depressed nearly 60%, but the concentration of norepinephrine in the hypothalamus was unchanged. Tyrosine concentrations in the striatum, hypothalamus, and total brain were not affected by copper deficiency, suggesting a catalytic defect rather than lack of substrate. Copper repletion restored norepinephrine level in total brain but did not affect the low level of dopamine. The results suggest that copper deficiency depresses a catalytic function of the adrenergic pathways and, further, adversely affects a structural component of the dopaminergic system during development.
In Vivo Release of Endogenous γ‐Aminobutyric Acid from Rat Striatum: Effects of Muscimol, Oxotremorine, and Morphine
Authors: van der Heyden J. A. M. , Venema K. , Korf J.
Published: October 2006

Abstract: A push‐pull cannula technique was used to study the in vivo release of endogenous GABA from the striaturn of chloral hydrate anaesthesized rats. The GABA in the perfusate was isolated with hplc and fluorimetrically detected (detection limit 0.6 pmol, signalhoke = 3). The mean resting release of GABA under steady state conditions was 1.62 ± 0.09 pmo/min (n = 180, ± s.E.M.). GABA release was increased after addition of depolarizing amounts of potassium to the perfusion medium. Inhibition of GABA synthesis with 3‐mercaptopropionic acid (MPA, 0.5 mM) or blockade of the neuronal activity with tetrodotoxin (TTX, 0.2 μM) diminished the spontaneous release of GABA. MPA, but not TTX, reduced the potassium‐induced increase in GABA release. Striatal GABA release was decreased by local application of muscimol (l0 μM) but enhanced by picrotoxin (100 μM); the latter counteracted the effect of muscimol. Intrastriatally applied serotonin (100 μM) did not affect the rate of endogenous GABA release. Oxotremorine (25 μM) added to the perfusion medium slightly increased the striatal GABA release. This effect was blocked both by locally applied atropine (100 μM) and haloperidol (5 μM). The latter two drugs did not themselves affect the rate of GABA release. Perfusion with morphine (100 μM) inhibited striatal GABA release. This effect was not influenced by haloperidol, but was no longer observed in the presence of nalorphine (10 μM) which itself did not alter GABA release. These results indicate that GABA released from the striatum is, at least in part, of neuronal origin and that the spontaneous GABA release can be affected by various neuromodulators (including GABA, enkephalins, and acetylcholine).
Acetylcholine Turnover and Compartmentation in Rat Brain Synaptosomes
Authors: Jope Richard S.
Published: October 2006

Abstract: The turnover of acetylcholine (ACh) in rat brain synaptosomes and its compartmentation in the labile bound and stable bound pools were investigated. The P2 fraction from rat brain was subjected to three sequential incubations, each terminated by centrifugation followed by determination of ACh concentrations by gas chromatography‐mass spectrometry (GCMS): (1) Depletion phase: Incubation of synaptosomes at 37°C for 10 min in Na+‐free buffer containing 35 mM‐KCl reduced the content of both labile bound and stable bound ACh by 40%. (2) Synthesis phase: Incubation at 37°C with 2 μM‐[2H4]choline resulted in accumulation of labeled and unlabeled ACh in both compartments. Addition of an anticholinesterase had little effect on stable bound ACh but greatly increased the content of labile bound ACh. This excess accumulated ACh was probably due to inhibition of intracellular acetylcholinesterase (AChE), because negligible uptake of ACh from the medium was observed. The effects on ACh synthesis of altered cation concentrations and metabolic inhibitors were examined. (3) Release phase: The tissue was incubated in the presence of 35 mM‐KCl, 40 μM‐paraoxon, and 20 μM‐hemicholinium‐3 (HC‐3) (to inhibit further synthesis of ACh). Measurements of the compartmental localization of ACh at several time points indicated that ACh was being released from the labile bound fraction. In support of this conclusion, 20 mM‐Mg2+ reduced ACh release and increased the labile bound ACh concentration.
Oxygen Dependence of Glucose and Acetylcholine Metabolism in Slices and Synaptosomes from Rat Brain
Authors: Ksiezak Hanna J. , Gibson Gary E.
Published: October 2006

Abstract: Previous studies have shown that a reduction in the O2 tension of the blood from 120 torr to 57 torr (hypoxic hypoxia) decreases brain acetylcholine (ACh) synthesis. To determine if this decrease is due to a direct impairment of ACh metabolism or to an indirect effect mediated by other neurotransmitter systems, we studied ACh formation in rat brain slices and synaptosomes. At O2 tensions ranging from 760 to less than 1 torr, 14CO2 production and [14C]ACh synthesis from [U‐14C]glucose, the levels of lactate and ATP, and the ATP/ADP ratio were determined. In slices, the first decreases were observed in the rate of 14CO2 production and [14C]ACh synthesis at an O2 tension of 152 torr. The ATP level started to decline at 53–38 torr, and a reduction in the ATP/ADP ratio was first found at and below 19 torr. Lactate formation was maximally stimulated at 38–19 torr. Synaptosomes responded differently than brain slices to reduced O2 tensions. In synaptosomes, 14CO2 production and [14C]ACh synthesis from [U‐14C]glucose, the levels of lactate and ATP, and the ATP/ADP ratio were unaltered if a minimum O2 tension of 19 torr was maintained. Despite the difference in sensitivities to decreases in O2 levels, there is a curvilinear relationship between [U‐14C]glucose decarboxylation and [14C]ACh synthesis at various O2 tensions for both tissue preparations with a high coefficient of determination (R2= 0.970). The difference in the metabolic sensitivity of slices and synaptosomes to a reduced O2 level may be explained by the greater distance O2 must diffuse in slices. The results are discussed in comparison with hypoxia in vivo.
Benzodiazepine Receptors on Primary Cultures of Mouse Astrocytes
Authors: Tardy M , Costa M. F , Rolland B , Fages C , Gonnard P
Published: October 2006

Abstract: Benzodiazepines bind to glial membranes on a single type of site, with a high affinity (KD= 5 × 10−9 M) on about 100 fmol of sites per mg protein. The number of binding sites is increased when the membranes are treated with Triton X‐100. Antiepileptic drugs such as clonazepam and phenobarbital and hypnotic drugs such as Ro‐11‐3128 and Ro‐11‐6896 are able in pharmacological concentrations to displace [3H]flunitrazepam from its glial binding sites.
Stimulation of Fructose‐1,6‐Biphosphatase Activity and Synthesis in the Cerebral Cortex of Rats Submitted to the Convulsant Methionine Sulfoximine
Authors: Hevor Tobias , Gayet Jacques
Published: October 2006

Abstract: Purification of rat cerebral cortex fructose‐ l,6‐biphosphatase (FBPase) was performed by substrate elution from phosphocellulose, followed by Sephadex G‐200 column filtration. The purified enzyme exhibited an optimum at pH 7.5, and its catalytic properties were very similar to those of the purified whole‐brain enzyme previously prepared by Majumder and Eisenberg in 1977. The isolated preparation was electrophoretically homogeneous. The molecular weight of the enzyme subunit was 40,000; the hydrophobic amino acids predominated with 592 residues, and tryptophan was not detected. Expressed as μmol fructose‐1,6‐biphosphate hydrolysed per g brain tissue wet weight per min, FBPase activity increased twofold 24 h after an intrapentoned injection of 100 mg per kg body weight of the convulsant methionine sulfoximine (MSO); the increase of the rate of incorporation of [1‐14C]valine into brain FBPase was 2.8‐fold under the same experimental conditions. A rabbit specific antiserum against rat cerebral cortex FBPase was prepared, and immunotitration studies confirmed both an increase in the number of molecules and the activation of brain FBPase, 24 h after administration of MSO. The increase of the number of brain FBPase molecules, induced by MSO, was due to an increase in synthesis of the enzyme, as shown by a double‐label valine incorporation study.
Ontogeny of Histaminergic Neurotransmission in the Rat Brain: Concomitant Development of Neuronal Histamine, H‐1 Receptors, and H‐1 Receptor‐Mediated Stimulation of Phospholipid Turnover
Authors: Subramanian N. , Whitmore W. L. , Seidler F. J. , Slotkin T. A.
Published: October 2006

Abstract: The ontogeny of histaminergic neurotransmission in the rat brain was studied by assessing development of histamine levels in brain regions, along with H‐1 receptor binding of [3H]mepyramine and H‐1 receptor‐mediated cellular events. In the hypothalamus, which is rich in histaminergic innervation, levels of the amine were low at birth, increased sharply at 8 days of age, and reached adult concentrations shortly thereafter; this pattern is typical of most neurotransmitters. In contrast, regions poor in neuronal histamine showed an initially high histamine level and a subsequent decline with development, as is known to occur during general growth of tissues. The developmental profile of H‐1 receptor binding sites resembled that of the neuronal histamine pool, and the increases with age resulted from changes in the number of binding sites without alterations in Kd. Cellular responses to H‐1 receptor activation were assessed by determining the stimulation of phospholipid turnover evoked by intracisternally administered histamine, a process that has been shown to involve only the neuronal compartment. Again, the developmental profile was superimposable upon that of H‐1 receptor binding and that of hypothalamic histamine levels. These studies indicate that ontogeny of histaminergic neurotransmission is a coordinated process, with simultaneous development of neuronal histamine, its key biosynthetic enzyme, and H‐1 receptors coupled directly to cellular events.
Cellular Localization and Regulation of Glutamine Synthetase in Primary Cultures of Brain Cells from Newborn Mice
Authors: Hallermayer Klaus , Harmening Christine , Hamprecht Bernd
Published: October 2006

Abstract: The cellular distribution of glutamine synthetase was determined by indirect immunofluorescence in cultures of dissociated brain cells from newborn mice. The enzyme could be detected in about 40% of all cells, among which cells with astrocytic morphology were clearly identified. Treatment with the glucocorticoid dexamethasone led to a strong increase in the number of positively stained cells. Enzyme induction by dexamethasone was maximal after 36 h and at a concentration of 0.1 μM. Under these conditions glutamine synthetase specific activity was elevated about sixfold. Steroid hormones other than corticosteroids had no effect. The basal activity in these cultures was near that found in brains of newborn mice, but far below the activity in adult brains, showing that in culture the normal development of these cells is disturbed. A comparison of glial and neuronal cell lines showed that glutamine synthetase is present in both types of cell lines at a very low specific activity. Inducibility of this enzyme by dexamethasone was found in glial but not in neuronal cell lines.
The Interaction of Dithiothreitol and Acetyl Coenzyme A in a Radiochemical Assay for Rat Brain ATP:Citrate Oxaloacetate Lyase
Authors: Simpson J.
Published: October 2006

Abstract: [14C]Acetyl‐CoA was found to react spontaneously with dithiothreitol to give a relatively apolar product which was readily extractable into a butanol‐toluene scintillant. This technique was used in a rapid, reproducible assay for rat brain ATP:citrate lyase using [1,5‐14C]citrate as substrate. The tissue extract, a 14,000 g supernatant, exhibited a lyase activity of approximately 7 nmol acetyl‐CoA produced/min per mg supernatant protein, and was inhibited ≥79% by α‐ketoglutaric acid (10 mm), Cu2+ (1 mm)and Zn2+(1 mm). [14C]Oxaloacetate, [14C]malate and endogenous citrate synthase were found not to interfere significantly with lyase estimations, but NADH was required in the reaction mixture to inhibit acetyl‐CoA hydrolase activity.
Increased Nervous System‐Specific Enolases in Rat Plasma and Cerebrospinal Fluid in Bilirubin Encephalopathy Detected by an Enzyme Immunoassay
Authors: Semba Reiji , Kato Kanefusa
Published: October 2006

Abstract: Three forms of enolase isozymes (αα, αγ, and γγ), including nervous system‐specific forms, were measured in the cerebrospinal fluid and the blood plasma of jaundiced or nonjaundiced infant rats by means of enzyme immunoassay systems capable of detecting each form of enolase at the 1 amol (10−18 mol) level. Average enolase levels in cerebrospinal fluid in normal rat were 2.0, 0.2 and 0.1 pmol/ml for αα, αγ, and γγ forms, respectively. Levels of αγ and γγ forms (nervous system‐specific enolases; NSE) in jaundiced rats, which suffer Purkinje cell degeneration due to the inborn hyperbilirubinemia, were three to four times as high as the normal values. When kernicterus was induced in jaundiced rats by an injection of bucolome, the NSE level in cerebrospinal fluid was elevated up to more than 30‐fold the control, together with a significantly higher level of αγ form in blood plasma. These results suggest that assays of NSE in the cerebrospinal fluid or the blood plasma are helpful in detecting neuronal damage in the central nervous system.
Kinetics of Neutral Amino Acid Transport Through the Blood‐Brain Barrier of the Newborn Rabbit
Authors: Pardridge William M. , Mietus Lawrence J.
Published: October 2006

Abstract: Since protein synthesis in the developing brain may, under certain conditions, be limited by amino acid availability, the present studies were undertaken to characterize the kinetics of large neutral amino acid transport through the blood‐brain barrier (BBB) of the newborn rabbit. The Km, Vmax, and KD of the transport of eight amino acids were determined by a nonlinear regression analysis of data obtained with the carotid injection technique. Compared with kinetic parameters observed for the adult rat, the Km, Vmax, and KD of amino acid transport were all two‐ to threefold higher in the newborn. Albumin was found to bind tryptophan actively in vitro, but had no inhibitory effect on tryptophan transport through the newborn BBB. Glutamine was transported through the BBB of the newborn at rates severalfold higher than are seen in the adult rat. However, glutamine transport was not inhibited by high concentrations of N‐methylaminoisobutyric acid (NMAIB), a model amino acid that is specific for the alanine‐preferring or A‐system present in peripheral tissues. In conclusion, these studies show that the BBB neutral amino acid transport system of the newborn rabbit has a lower affinity and higher capacity than does the BBB of the adult rat. Under conditions of high plasma amino acids, the increased capacity of the newborn transport system allows for a higher rate of amino acid transport into brain than would occur via the lower capacity system present in the adult rat brain.