bluuebunny/crossref_metadata_2025 huggingface dataset:
Extractability of glycoproteins and mucopolysaccharides of brain
Authors: Margolis R. K. , Margolis R. U.
Published: October 2006

Very little is known about the localization and functions of the glycoproteins and mucopolysaccharides of nervous tissue. There have been two major approaches to the study of these substances in brain. The first involves the isolation of glycopeptides and mucopolysaccharides after digestion of the lipid‐free protein residue from whole brain with proteolytic enzymes (Margolis, 1967; Di Benedettaet al., 1969; Margolis and Margolis, 1970; Katzman, 1972). This approach has the advantage that sufficient tissue is used to permit analysis of the structure and metabolism of the carbohydrate components of these macromolecules. However, any differentiation of the various glycoproteins and mucopolysaccharides based on such features as their anatomical location, association with proteins, lipids or other membrane components, and the properties conferred by their non‐carbohydrate portion, is unavoidably lost as a consequence of the procedures used for their isolation.

On the other hand, several laboratories have attempted to study the glycoproteins and mucopolysaccharides of nervous tissue by treating brain (or subcellular fractions) with various detergents, and then examining the extracts for the pattern of separation obtained by polyacrylamide gel electrophoresis in terms of carbohydrate staining reactions or the incorporation of labelled precursors (Bosmann, Case and Shea, 1970; Duiton and Barondes, 1970; Quarles and Brady, 1971; Waehneldt, Morgan and Gombos, 1971). This approach has the advantages of relatively high sensitivity and the ability to study intact glycoproteins rather than glycopeptides produced by proteolytic enzyme digestion. However, it is presently impossible to identify any of the numerous and often poorly resolved bands thus obtained with glycoproteins or mucopolysaccharides of known structure and chemical composition, or in many cases even to identify the various complex carbohydrates as being glycoproteins, glycolipids or acid mucopolysaccharides.

In an attempt to obtain some indication of the degree of anatomical heterogeneity of these compounds in nervous tissue, we have sequentially treated whole rat brain with several solvents to obtain intact glycoproteins and mucopolysaccharides. After removal of lipids and digestion with pronase, the composition of the glycopeptides and mucopolysaccharides has been analyzed.
BIOSYNTHESIS OF CHOLEST‐5‐ENE‐3β, 24‐DIOL (CEREBROSTEROL) BY BOVINE CEREBRAL CORTICAL MICROSOMES1
Authors: Dhar A. K. , Teng J. I. , Smith Leland L.
Published: October 2006

The presence of cholest‐5‐ene‐3β, 24‐diol (cerebrosterol) in samples of human, bovine, and rabbit brains has been established by isolation of the sterol therefrom and identification by comparison of physical properties. Cholest‐5‐ene‐3β, 24‐diol was present at the level of 66.5 sg/g of dried tissue in human brain, 42.9 μg/g in cattle brain, and 89.5 pg/g in rabbit brain. Cholest‐5‐ene‐3β, 24‐diol was the only readily detectable hydroxycholesterol derivative in these brain tissues and was concentrated in the 105,000 g pellet (microsomal fraction) of both human and bovine cerebral cortex, with no demonstrable amounts of the sterol present in nuclear or mitochondrial fractions. Incubation of [1,2‐3H]‐ or of [4‐14C]‐cholesterol with the 105,000 g microsomal pellet from bovine cerebral cortical homogenates demonstrated 0.1‐0.38 per cent conversions to radioactive cholest‐5‐ene‐3β, 24‐diol, isolated and purified as the 3β, 24‐dibenzoate. The bioconversion required oxygen, and a stimulation of hydroxylation by added NADPH2 was demonstrated. Our observations establish that a sterol 24‐hydroxylase system is present in bovine cerebral cortex.
EFFECTS OF ACETYLCHOLINE ON THE IN CORPORATION OF [32P]ORTHOPHOSPHATE IN VITRO INTO THE PHOSPHOLIPIDS OF SUBSYNAPTOSOMAL MEMBRANES FROM GUINEA‐PIG BRAIN
Authors: Yagihara Y. , Bleasdale J. E. , Hawthorne J. N.
Published: October 2006

‐Synaptosomes prepared from guinea‐pig cerebral cortex were incubated with 32P1 in a medium with or without 10−4 M‐acetylcholine and 10−4 M‐eserine. They were then subjected to osmotic shock and density‐gradient centrifugation for the preparation of subsynaptosomal fractions and the phospholipids of each fraction were separated by two‐dimensional thin‐layer chromatography.

The fraction containing synaptic vesicles and that containing mitochondria were the most highly labelled of the sub‐synaptosomal fractions. Phosphatidic acid followed by phosphatidylinositol had the highest specific activity of the phospholipids studied. Acetylcholine caused a marked increase in the specific activity of the vesicular but not of the mitochondrial phosphatidic acid. Phosphatidylinositol specific activity also increased in the presence of acetylcholine but the increase was more reproducible in the fraction containing microsomal membranes than in the vesicle fraction. The other phospholipids were relatively poorly labelled and no effect of acetylcholine on the incorporation of 32P1 into these lipids could be detected. Acetylcholine also caused a decrease in the amount of phosphatidic acid in the synaptic vesicles.
EXPERIMENTAL MATERNAL HYPERPHENYLALANINEMTA: DISAGGREGATION OF FETAL BRAIN RIBOSOMES
Authors: Copenhaver J. H. , Vacanti J. P. , Carver M. J.
Published: October 2006

Disaggregation of polyribosomal structures has been demonstrated in fetal rat brains following treatment of the maternal animal with para‐chloro‐d,l‐phenylalanine (used primarily to inhibit maternal phenylalanine hydroxylase, EC 1.14.3.1) and with phenylalanine (used to raise the level of circulating phenylalanine in maternal and fetal plasma). Since highly disaggregated polyribosomal systems cannot support normal levels of protein synthesis in vitro, it has been postulated that the composition of the free amino acid pool(s) plays a regulatory role in protein synthesis through the intermediary effect of polyribosomal aggregation‐disaggregation. We believe that a possibly prolonged period of disaggregation of neuronal polyribosomes might disrupt neuronal protein synthesis sufficiently in utero to produce the mental insufficiency observed in the offspring of untreated maternal phenylketonurics.
ACCUMULATION AND METABOLISM OF NOREPINE‐PHRINE IN RAT HYPOTHALAMUS AFTER EXHAUSTIVE STRESS1
Authors: Stone E. A.
Published: October 2006

—Exhaustive stress in rats is followed by a temporary reduction of hypothalamic norepinephrine (NE) together with a persistent increase in turnover during recovery. To test for persistent alterations of NE storage and metabolism produced by stress, rats were subjected to 3 h of forced running and were then injected intraventricularly with [3H]NE or [3H]dopamine (DA). The hypothalamus was assayed for [3H]NE and its metabolites at various intervals after injection. The effects of stress were compared with those of reserpine (7·5 mg/kg) or α‐methyltyrosine (AMT, 300 mg/kg) pretreatment. It was found that the stress‐induced reduction of endogenous NE was not accompanied by a change in the accumulation of exogenous [3H]NE either 10 or 30 min after injection, whereas the NE depletions produced by reserpine or AMT were associated with decreased or increased accumulation, respectively. However, stress did produce an increased accumulation of [3H]NE endogenously synthesized from [3H]DA. These results indicate that exhaustive stress does not adversely affect the storage of NE. They also suggest that stores of NE depleted by stress are replenished chiefly with newly synthesized NE and not through an increased uptake and binding or decreased metabolism of extraneuronal NE. The latter factors may play a role in the maintenance of brain NE stores when biosynthesis is low, i.e. after AMT. The major metabolites of exogenous [3H]NE, at 30 min after injection, were identified as conjugates of 3,4‐dihydroxyphenylglycol (DOPEG) and 3‐methoxy‐4‐hydroxyphenylglycol (MOPEG) in approximately equal amounts. The finding of high levels of conjugated DOPEG confirms a recent report (Slgden and Eccleston, 1971) that this compound is a major metabolite of brain NE. Reserpine produced marked elevations of both conjugates; AMT slightly reduced each. Prior stress increased only conjugated MOPEG, an observation suggesting that CNS levels of this metabolite may reflect NE released by nervous activity.
SIALIC ACID INCORPORATION INTO GANGLIOSIDES AND GLYCOPROTEINS OF THE FISH BRAIN1
Authors: Rösner H. , Wiegandt H. , Rahmann H.
Published: October 2006

—The concentration of lipid‐ and non‐lipid‐bound sialic acid in the optic nerve tract and tectum and in whole brain of fish was estimated. The incorporation of sialic acid into gangliosides and non‐lipid components was studied in fish by intracranial or intraocular application of N‐[3H]acetylmannosamine or N‐[3H]acetylglucosamine. After intracranial injection of N‐[3H]acetylmannosamine autoradiography showed lipid‐ and non‐lipid‐bound radioactivity in the tectum opticum evenly distributed over regions of nerve fibres or perikarya indicating an ubiquitous incorporation of label. Sialic acid incorporation into glycoproteins after intracranial injection of N‐acetylmannosamine always exceeded that into gangliosides. TCA‐precipitable non‐lipid material is labelled from intracranially applied N‐acetylmannosamine in the sialic acid portion and also in nonsialic acid components, whereby the percentage of label in sialic acid increases reaching 90 per cent of the total radioactivity after 90 min. After intraocular application of N‐[3H]acetylmannosamine, sialic acid in gangliosides was generally found to be more highly labelled than in glycoproteins. The ratio of radioactivity in gangliosides and glycoproteins increased with time of incubation and the distance from the eye. TCA‐soluble radioactivity was translocated by fast axonal transport. Cycloheximide inhibited incorporation of N‐acetylmannosamine‐derived radioactivity into gangliosides and proteins but not the transport of TCA‐soluble material, which accumulates in the tectum. After intraocular application of N‐[3H]acetylglucosamine, TCA‐soluble label arrives later in the optic tectum than radioactivity of high molecular weight components. The ratio of lipid to non‐lipid‐bound radioactivity does not change considerably with the time after injection or the distance from the eye. There was no accumulation of TCA‐soluble radioactivity after the inhibition of incorporation into high molecular weight components.
AN ASSAY PROCEDURE FOR TRYPTAMINE IN BRAIN AND SPINAL CORD USING ITS [3H]DANSYL DERIVATIVE
Authors: Snodgrass S. R. , Horn A. S.
Published: October 2006

—The tryptamine content of rat and mouse brain and spinal cord was determined with a radiochemical derivative assay, using [3H]dansyl chloride. The amine was extracted into toluene‐isoamyl alcohol, back‐extracted into dilute acid, then adsorbed onto a non‐ionic polystyrene resin, and dansylated in tetrahydrofuran after elution from the resin. Optimum recoveries were obtained with TCA extracts, although significant losses occurred due to surface adsorption and protein binding. The brain content of tryptamine increased after MAO inhibition and was not significantly further increased when tryptophan loading was combined with inhibition of MAO and/or tryptophan 5‐hydroxylase. The tryptamine concentration of spinal cord exceeded that of brain and increased rapidly after death. Among brain regions tryptamine concentrations were greatest in hypothalamus and striatum and lowest in cerebral cortex and cerebellum.
CHANGES IN CENTRAL NORADRENALINE NEURONSADMINISTRATION AFTER SYSTEMIC 6‐HYDROXYDOPAMINE ADMINISTRATION
Authors: Sachs Charlotte , Jonsson Gösta
Published: October 2006

—Intravenous injection of a large dose of 6‐hydroxydopamine (100 mg/kg) to adult rats caused a significant and long‐lasting reduction (about 30 per cent) of the in oirro uptake of [3H]NA in the cerebral cortex and spinal cord, while no changes were seen in the hypothalamus. The endogenous NA in whole brain was similarly reduced (about 20 per cent). Fluorescence histochemistry revealed catecholamine accumulations which are degenerative signs, induced by 6‐hydroxydopamine, in axons of the dorsal NA bundle innervating the cerebral cortex. It is concluded that the blood–brain barrier in adult rats is not completely protective with respect to the neurotoxic action of systemically injected 6‐hydroxydopamine, which can produce degeneration of a significant number of NA nerve terminals in the cerebral cortex and spinal cord. Previous studies have shown that 6‐hydroxydopamine caused a permanent and selective degeneration of a large number of central NA nerve terminals when injected systemically up to 1 week after birth, due to an incompletely developed blood‐brain barrier. This barrier for 6‐hydroxydopamine develops between the 7th and 9th day after birth (Sachs, 1973). In the present study 6‐hydroxydopamine was found to cause a small transient reduction in [3H]NA uptake in cerebral cortex of rats between 9 and 28 days of age, while in older rats the damage produced by 6‐hydroxydopamine was long‐lasting. Thus, the NA nerves ascending to the cerebral cortex seem to possess a regenerative capacity to a 6‐hydroxydopamine‐induced degeneration up to about 28 days postnatally, but which later disappears or is markedly retarded.
THE EFFECT OF HYPOXIA ON MONOAMINE SYNTHESIS, LEVELS AND METABOLISM IN RAT BRAIN
Authors: Davis J. N. , Carlsson A.
Published: October 2006

Abstract— Rats were exposed to 5.6% oxygen environments for up to 2 h. The accumulation of brain DOPA and 5‐hydroxytryptophan at 30 min after decarboxylase inhibition was used to estimate cerebral tryosine and tryptophan hydroxylase activity, respectively, in vivo. There was a continuing decrease in tryosine hydroxylase activity during the 2 h in whole brain as well as five brain regions. Tryptophan hydroxylase activity declined during the 1st h, but then increased towards control levels during the 2nd h. There was an increase in brain tryptophan during the 2nd h as well. In whole brain and the five brain regions, there was no significant change in the levels of noradrenaline, dopamine or 5‐hydroxytrypamine. During a 1 h exposure to 5.6% oxygen, there was decreased accumulation of noradrenaline, dopamine and 5‐hydroxytryptamine after MAO inhibition and decreased accumulation of homovanillic acid and 5‐hydroxyindoleacetic acid after probenecid administration. The dercreased synthesis and metabolism of the monoamines is most likely attributable to insufficient brain tissue oxygen as a substrate for the two hydroxylase enzymes.
PHOSPHOLIPASE A ACTIVITIES IN NORMAL AND SECTIONED RAT SCIATIC NERVE
Authors: Webster G. R.
Published: October 2006

Abstract— The phospholipase A1 (EC 3.1.1.32) and A2 (EC 3.1.1.4) activities of rat sciatic nerve homogenates have been studied. With phosphatidylcholine as substrate normal nerve had significant activity of both types at pH 5.0. Substantial increases occurred in nerve undergoing Wallerian degeneration after transection, beginning as early as 2 days after operation and rising to eight times normal values by the second week.
INFLUENCE OF POTASSIUM ON THE STEADY‐STATE REDOX POTENTIAL OF THE ELECTRON TRANSPORT CHAIN IN SLICES OF RAT CEREBRAL CORTEX AND THE EFFECT OF OUABAIN
Authors: Bull R. J. , Cummins J. T.
Published: October 2006

Abstract— The concentration dependence of the modifications by potassium of the respiratory intermediates in incubated slices of rat cerebral cortex has been examined in the presence and absence of calcium. In addition to the immediate increase in respiration and the concomitant oxidation of the respiratory intermediates, longer term increases in the steady‐state redox potential were observed at higher potassium concentrations. Addition of calcium to the system did not appreciably alter the immediate effects of potassium, but shifted the redox state of the respiratory intermediates; these changes involved a decrease in reduced intermediate at low concentrations of potassium and a relatively higher level of reduced carriers at high concentrations of potassium. Ouabain (50 μm) inhibited both the initial responses to added potassium and modified the changes in steady‐state levels of reduced intermediate in the absence of calcium. In the presence of calcium, ouabain (50 μm) inhibited the initial oxidation of NAD(P)H observed upon addition of potassium but had no effect on the respiratory response to the addition of low concentrations of potassium. The disassociation of these responses resulted in a large decrease in the steady‐state levels of reduced cytochrome. At 30 mm potassium an oxidation of NAD(P)H was observed which accompanied by an increase in levels of reduced cytochromes. These changes in redox state of the respiratory carriers have been discussed in relation to previous reports dealing with the effects of potassium on aerobic glycolysis and oxygen consumption by brain slices.
METABOLIC CHANGES IN THE BRAINS OF MICE FROZEN IN LIQUID NITROGEN
Authors: Pontén U. , Ratcheson R. A. , Siesjö B. K.
Published: October 2006

Abstract— Autolytic changes in the mouse brain, occurring during immersion of the animal in liquid nitrogen, were evaluated by measuring the tissue concentrations of glucose, lactate, pyruvate, α‐oxoglutarate, phosphocreatine, creatine, ATP, ADP and AMP. The values thus obtained were compared with those obtained in paralysed mice under nitrous oxide anaesthesia, the brains of which were frozen in such a way that arterial blood pressure and oxygénation were upheld during the freezing. Immersion of unanaesthetized mice in liquid nitrogen gave rise to significant alterations in phosphocreatine, creatine, lactate, lactate/pyruvate ratio, ADP and AMP. A comparison with values obtained in paralysed and anaesthetized mice that were frozen by immersion in liquid nitrogen showed that the metabolic changes observed in the unanaesthetized animals could not be caused by an anaesthetic effect on the metabolic pattern. It is concluded that autolysis in the mouse brain occurs during immersion of the animal in a coolant, mainly because arterial hypoxia develops before the tissue is frozen. A comparison with previous results on rat cerebral cortex indicates that mice offer no advantage for studies of cerebral metabolites in unanaesthetized animals. In both species, accurate analyses of labile cerebral metabolites require that the brain is frozen in a way that prevents arterial hypoxia during the fixation of the tissue.
THE EFFECT OF THIAMINE DEFICIENCY ON THE ACETYLCOENZYMEA AND ACETYLCHOLINE LEVELS IN THE RAT BRAIN
Authors: Heinrich C. P. , Stadler H. , Weiser H.
Published: October 2006

Abstract—It is shown that transketolase activities in red blood cells and whole brain of normal and thiamine‐deficient rats correlate well with heart frequencies.

The effect of thiamine depletion on the levels of acetylcoenzyme A (acetyl‐CoA) and acetylcholine (ACh), and on the activities of pyruvate dehydrogenase, choline acetyl‐transferase and acetylcholine esterase was studied in whole brains of thiamine‐deficient, thiamine‐supplementedad libitumand pair‐fed rats. The concentrations of acetyl‐CoA and ACh decreased in thiamine‐deficient brains by 42 and 35 per cent, respectively.

Total pyruvate dehydrogenase activity did not change during vitamin B1deficiency. The ‘resolved’ enzyme, reconstituted with thiamine diphosphate, had an association constant of 5.4 × 10−6m. Choline acetyltransferase and acetylcholine esterase activities remained unchanged in thiamine deficiency.

Possible mechanisms which could explain the reduced Ach levels in vitamin B1deficiency are discussed.
NORADRENALINE NERVE TERMINALS IN THE CEREBRAL CORTEX: EFFECTS ON NORADRENALINE UPTAKE AND STORAGE FOLLOWING AXONAL LESION WITH 6‐HYDROXYDOPAMINE
Authors: Lidbrink P. , Jonsson G.
Published: October 2006

The ascending noradrenaline‐containing neuronal system from the locus coeruleus to the cerebral cortex was unilaterally lesioned by an intracerebral injection of 8 μg 6‐hydroxydopamine in the dorsomedial reticular formation in the caudal mesencephalon. The 6‐hydroxydopamine caused injury to axons of the dorsal catecholamine bundle associated with its specific neurotoxic action, while very limited unspecific tissue necrosis was observed.

Following this treatment the endogenous noradrenaline in the ipsilateral cerebral cortex (neocortex) increased acutely (up to 2 days), as observed both with noradrenaline assay and fluorescence histochemistry. The noradrenaline concentration then gradually decreased to 15 per cent of the contralateral side 15 days after the lesion. At this time interval and up to at least 90 days no fluorescent catecholamine nerve terminals could be detected. The acute noradrenaline increase could be blocked partially by tyrosine hydroxylase inhibition produced by α‐methyl‐p‐tyrosine. The disappearance of endogenous noradrenaline following tyrosine hydroxylase inhibition was also reduced after the 6‐hydroxydopamine lesion.

Studies on the in vitro uptake of [3H]noradrenaline (0.1 μM for 5 min) in slices from the neocortex after the 6‐hydroxydopamine lesion showed a gradual decline in uptake reaching maximal reduction (35‐40 per cent of the contralateral side) after 15 days. No recovery of [3H]noradrenaline uptake was seen up to 90 days after the lesion. The formation of [3H]noradrenaline from [3H]dopamine in vitro was reduced to 15 per cent of the contralateral side after a chronic lesion.

The present results indicate that the disappearance of noradrenaline uptake‐storage mechanisms in the neocortex is due to an anterograde degeneration of axons and nerve terminals of the dorsal catecholamine bundle. The data on endogenous noradrenaline and noradrenaline synthesis suggest that approx. 15 per cent of the noradrenaline nerve terminals in the neocortex remain intact following the lesion, while the [3H]noradrenaline uptake data reflect uptake in other tissue structures in addition to noradrenaline nerve terminals, e.g. dopamine nerve terminals, pericytes and/or glial cells.
TRANSFER RNA AND THE REGULATION OF PROTEIN SYNTHESIS IN RAT CEREBRAL CORTEX DURING NEURAL DEVELOPMENT
Authors: Harris C. L. , Maas J. W.
Published: October 2006

Protein synthesis was measured in ribosomal systems derived from the cerebral cortex of 5‐and 35‐day‐old rats. Under optimal conditions incorporation of radioactive leucine per mg ribosomal protein was four times higher with ribosomes from the younger animals than with ribosomes from the 35‐day‐old rats. This suggests that a decrease in the rate of protein synthesis occurs during neural development. Both ribosomes and the pH enzyme fraction from the cerebral cortex of 35‐day‐old rats had lower activities than preparations from the younger rats. Cerebral cortical ribosomes from 35‐day‐old animals had a lower polyribosome content than similar preparations from 5‐day‐old rats. A three‐fold higher requirement for the pH 5 enzyme fraction was observed with the ribosomal system from 5‐day‐old rats, an observation which correlated with the yields of pH 5 enzyme and ribosomal protein from the younger tissue.

The nature of the changes in the composition of the pH 5 enzyme fraction was investigated. Methylated albumin kiesselguhr (MAK) and Sephadex G‐75 column chromatography showed that RNA from the pH 5 enzyme fraction was heterogeneous, containing tRNA, rRNA, and a small molecular weight RNA. This latter RNA, perhaps a degradation product of rRNA, comprised the greatest portion of RNA from the pH 5 enzyme fraction of cerebral cortex. The data obtained with MAK chromatography were used to estimate the total tRNA content of the cerebral cortex, with no age‐related differences being observed. Since evidence of RNA degradation was seen, tRNA was also isolated by phenol extraction of whole cerebral cortex in the presence of bentonite. Purification of tRNA by NaCl and isopropanol fractionation gave preparations with no detectable rRNA or small molecular weight RNA. With this purification method, the tRNA yield was greater than estimated by the MAK method, demonstrating that losses of tRNA occurred during the cell fractionation steps. With the purification method 1.6 times more tRNA was obtained from the cerebral cortex of 5‐day‐old animals than from the older tissue. This higher level of tRNA in the younger, more active tissue appeared to involve all tRNA species, since in vitro aminoacyiation studies revealed nearly identical acceptance values for 18 individual amino acids. These results suggest that the rate of protein synthesis in cerebral cortex is regulated in part by the total amount of tRNA present to translate the higher level of polysome‐bound mRNA.
β‐NEUROTOXIN REDUCES NEUROTRANSMITTER STORAGE IN BRAIN SYNAPSES
Authors: Wernicke J. F. , Oberjat T. , Howard B. D.
Published: October 2006

β‐neurotoxin, a component of Bungarus multicinctus venom, is known to cause neuromuscular blockade by first increasing the rate of spontaneous ACh release and then inhibiting the nerve impulse‐induced release of ACh. We report that the toxin also affects the storage of several neurotransmitters in rat brain and it is active on synaptosomes and brain minces. Synaptosomes prepared from brain tissue that had been treated with β‐toxin have a reduced ability to accumulate radioactive NE, GABA, serotonin and the ACh precursor, choline. The toxin also causes a release of previously accumulated NE and GABA from synaptosomes, suggesting that the storage process rather than the uptake transport process is affected. The toxin does not contain phospholipase A, phospholipase C, protease or hyaluronidase activity.
PATTERNS OF CHANGES IN BRAIN CARBOHYDRATE METABOLITES, AMINO ACIDS AND ORGANIC PHOSPHATES AT INCREASED CARBON DIOXIDE TENSIONS
Authors: Folbergrovaa Jaroslava , Pontean U. , Siesjou B. K.
Published: October 2006

—In order to study the time course of changes in cerebral metabolites in hypercapnia, anaesthetized and artificially ventilated rats were exposed to 11% CO2 for 5, 15, 45, 90 and 180 min. In addition, the effect of anaesthetic levels of carbon dioxide was studied by exposing animals to 30 and 50% CO2 for 45 min. In none of the groups were there significant changes in ATP, ADP or AMP, and a normal energy state was therefore obtained even in short‐lasting hypercapnia, and at anaesthetic CO2 concentrations (50% CO2). In the group exposed to 11% CO2 for 5 min there was a fall in glycogen but normalization occurred when the hypercapnia was prolonged. There were no changes in fructose 1,6‐diphosphate, dihydroxyacetone phosphate or 3‐phosphoglycerate but decreases in pyruvate, lactate, citrate, α‐oxoglutarate, malate and glutamate at all exposure times. With 30 and 50% CO2 glucose 6‐phosphate accumulated. The results do not support the view that the depletion of pyruvate and of citric acid cycle intermediates is caused by H+‐inhibition of rate‐limiting enzymatic steps like the phosphofructokinase reaction.

The glutamate concentration fell progressively during exposure to 11% CO2. In the 5 and 15 min groups aspartate increased significantly indicating that the initial loss of glutamate was partly due to transamination to aspartate. With prolonged hypercapnia there was a secondary fall in aspartate to subnormal values. At 45 min and thereafter the glutamine concentration increased significantly. However, the sum of glutamate, aspartate and glutamine fell progressively after the initial 5 min period.

Hypercapnia gave rise to similar increases in the lactate/pyruvate and malate/oxaloacetate ratios, and since the calculated NADH/NAD+ ratios remained close to normal in all groups, the results indicate that pH‐dependent shifts occurred in the lactate and malate dehydrogenase equilibria.
PURINE NUCLEOTIDE METABOLISM IN THE CAT BRAIN AFTER ONE HOUR OF COMPLETE ISCHEMIA
Authors: Kleihues P. , Kobayashi K. , Hossmann K.‐A.
Published: October 2006

—Complete cerebral ischemia was produced in normothermic anaesthetized cats by clamping the innominate and the left subclavian arteries combined with lowering the blood pressure. After 1 h of ischemia, ATP was no longer present in detectable amounts. Total adenine nucleotides were reduced to 34 per cent of the normal level. The breakdown of guanine nucleotides was less marked, with small amounts of GTP still being present at the end of the ischemic period. In animals with signs of functional recovery after 3–7 h of recirculation, ATP was resynthesized to 62 per cent of the control level. Total adenine nucleotides increased to 68 per cent and the adenylate energy change—[ATP + 1/2 ADP]/[AMP + ADP + ATP]—was re‐established to within 7 per cent of the pre‐ischemic value. Radiochromatography of nucleotides following intravenous injection of [14C]formate indicated a marked enhancement of postischemic purine de novo synthesis. Purine nucleosides and free bases which accumulated during ischemia, were partially re‐utilized by salvage pathways: adenosine was rephosphorylated to AMP by adenosine kinase (EC 2.7.1.20); inosine and hypoxanthine were re‐used via IMP in a reaction mediated by hypoxanthine phosphoribosyltransferase (EC 2.4.2.8).
CEREBRAL ENERGY STATE IN INSULIN‐INDUCED HYPOGLYCEMIA, RELATED TO BLOOD GLUCOSE AND TO EEG
Authors: Lewis L. D. , Ljunggren B. , Ratcheson R. A. , Siesjö B. K.
Published: October 2006

—Concentrations of phosphocreatine, creatine, ATP, ADP and AMP were measured in the cerebral cortex of rats during insulin‐induced hypoglycemia. Blood glucose concentrations were related to clinical symptoms in unanaesthetized animals and to the EEG pattern in paralysed and lightly anaesthetized animals. There was an excellent correlation between blood glucose concentration and EEG pattern. In animals showing a pronounced slowing of the EEG or convulsive polyspike activity for up to 20 min, there were no changes in any of the phosphates. However, after prolonged convulsive activity some animals showed clear signs of energy failure, and in all animals with an isoelectric EEG there was a major derangement of the energy state. Since the majority of those animals did not show signs of cerebral hypoxia or ischemia it is concluded that hypoglycemic coma is accompanied by substrate deficiency of a degree sufficient to induce energy depletion of brain tissue.
RELEASE OF [3H]GAMMA‐AMINOBUTYRIC ACID FROM GLIAL CELLS IN RAT DORSAL ROOT GANGLIA.
Authors: Minchin M. C. W. , Iversen L. L.
Published: October 2006

Abstract— Desheathed rat dorsal root ganglia were incubated in a medium containing amino‐oxyacetic acid and [3H]GABA. Under these conditions, [3H]GABA is taken up exclusively by the satellite glial cells in the ganglia. Efflux of [3H]GABA from the tissue was measured after passing the ganglia through a series of wash solutions. The spontaneous efflux of radioactivity, mostly [3H]GABA, was more rapid in the absence of amino‐oxyacetic acid in the incubation and wash media.

Raising the potassium concentration in the wash media caused an increase in the efflux of [3H]GABA. This increase was sigmoidally related to the potassium concentration in the wash media, reaching a maximum at 64 mm‐K+. The releasing effect of K+ was inhibited by removing calcium from the media. Reducing the calcium and raising the magnesium concentration in the wash solutions inhibited the increased efflux of [3H]GABA due to 64 mm‐K+ by 48 per cent, while 5 mM‐La3+ and diphenylhydantoin (0·005 and 0·5 mm) had no effect on this increase.

Only a small increase in the efflux of [14C]glutamate was produced by 64 mm‐K+ and it had no effect upon the effluxes of [3H]glycine, [3H]alanine or [3H]leucine. The efflux of lactate dehydrogenase was similarly unaffected by 64 mM‐K+. The results suggest that glial cells in spinal ganglia can respond to depolarizing concentrations of potassium by releasing GABA in a calcium‐dependent process.
ACCUMULATION AND DISAPPEARANCE OF NORADRENALINE AND ITS MAJOR METABOLITES SYNTHESIZED FROM INTRAVENTRICULARLY INJECTED [3H]DOPAMINE IN THE RAT BRAIN
Authors: Braestrup C. , Nielsen M. , Scheel‐Krüger J.
Published: October 2006

Abstract— A new combined ion‐exchange and thin‐layer‐chromatographic procedure is described which separates and measures quantitatively, after intraventricular injection of [3H]dopamine (DA), the rat brain content of labelled noradrenaline (NA) and the following labelled noradrenaline metabolites: free 3‐methoxy‐4‐hydroxyphenylethyleneglycol (MOPEG), conjugated MOPEG, free plus conjugated dihydroxyphenylethyleneglycol (DOPEG), vanillic mandelic acid (VMA) and normetanephrine (NM). Labelled dopamine and its metabolites were also measured. The time‐course study performed from 5 min to 24 h after [3H]DA showed that MOPEG and DOPEG, mainly as conjugates, are major NA metabolites whereas VMA is a very insignificant NA metabolite in the rat brain. A very rapid initial increase of [3H]NM, free MOPEG and conjugated MOPEG was found during the time interval where the [3H]NA biosynthesis is very high (0–15 min). This combined with the finding that these metabolites stabilize at lower levels during the [3H]NA ‘storage phase’ (9–24 h) provides a strong indication that newly synthesized NA preferentially is metabolized. Our measurements of endogenous NA, free MOPEG and conjugated MOPEG provide additional support. The injections of various decreasing doses of [3H]DA (3·08–0·0010 μg) showed that the proportions of total [3H]MOPEG and total [3H]DOPEG to [3H]NA were constant after all [3H]DA doses investigated. This finding indicates that the [3H]NA synthesized in situ behaves as a tracer, even after injections of non‐tracer doses of [3H]DA. The results seem thus to indicate that the present technique provides a powerful tool for the investigations on central noradrenaline metabolism.
GANGLIOSIDE ABNORMALITIES IN MULTIPLE SCLEROSIS
Authors: Yu R. K. , Ledeen R. W. , Eng L. F.
Published: October 2006

Abstract— Gangliosides were isolated from plaque tissue and normal appearing white matter of multiple sclerosis (MS) brain. All four plaques showed decreased ganglioside concn relative to normal human white matter on a wet wt basis, but significant elevation in terms of dry wt. The wet wt and dry wt concn of MS white matter gangliosides showed smaller but statistically significant decreases below normal. Thin‐layer patterns of the plaques showed several departures from normal white matter, including decrease of G4 and G5, and complete loss of G7 (sialosylgalactosylceramide). Most of the plaques had significant elevation of G2A and G3A along with increases of the slower‐migrating polysialogangliosides. An additional ganglioside was present between G2 and G2A which was not seen in normal white matter. The TLC pattern of MS white matter gangliosides was essentially normal. The evidence for a general decrease of acidic lipids within normal appearing white matter is discussed.
EFFECT OF ELECTRICAL STIMULATION ON THE YIELD AND COMPOSITION OF SYNAPTIC VESICLES FROM THE CHOLINERGIC SYNAPSES OF THE ELECTRIC ORGAN OF TORPEDO: A COMBINED BIOCHEMICAL, ELECTROPHYSIOLOGICAL AND MORPHOLOGICAL STUDY
Authors: Zimmermann H. , Whittaker V. P.
Published: October 2006

Abstract— The effect of stimulating the electric organ of Torpedo marmorata, anaesthetized with 0.01% Tricaine methane sulphonate, by means of electrical stimulation (5/s) administered via an electrode placed on the electric lobe has been studied electrophysiologically, biochemically and morphologically. The response of the organ declined to about 50 per cent of its initial value after about 500 stimuli, by a further 10 per cent after another 500 stimuli and then to about 12 per cent of the initial value after a further 1000 stimuli. Thereafter the response fell off progressively. However, even when the response was less than 1 per cent of its initial value, the organ had considerable powers of recuperation during a 30‐s rest period, to 30–50 per cent of its initial value.

The fall in response was accompanied by a reduction in vesicle size and number, an increase in the area of the presynaptic membrane and a fall in the protein, total nucleotide, ATP and acetylcholine content of the vesicle fraction isolated from the stimulated tissue. However, whereas vesicle numbers and the protein and total nucleotide content of the vesicle fraction fell by only about 50 per cent, vesicular ATP and acetylcholine levels were reduced to about 10 per cent. An analysis of the covariance of vesicular ATP and acetylcholine showed an initial loss of an acetylcholine‐rich (relative to ATP) population of vesicles. The early loss of vesicular protein and nucleotide and vesicle numbers as well as the morphological changes seen would be consistent with a loss of vesicles due to fusion with the external membrane. The preferential loss of acetylcholine and ATP from the vesicle fraction indicates that the vesicles surviving the stimulation procedure have been utilized in a number of cycles causing the progressive fall in vesicle volume, and acetylcholine and ATP content.
ENZYMATIC ISOTOPIC ASSAY FOR AND PRESENCE OF β‐PHENYLETHYLAMINE IN BRAIN
Authors: Saavedra J. M.
Published: October 2006

Abstract— An enzymatic isotopic assay for the measurement of β‐phenylethylamine in brain, with a sensitivity of 100‐200 pg, has been developed. With this assay, the endogenous β‐phenylethylamine content (1.5 ng/g) in the rat brain has been determined. Phenylalanine administration increases the brain levels of this amine; inhibition of monoamine oxidase causes a 40‐fold increase in brain β‐phenylethylamine. After a combined treatment with a monoamine oxidase inhibitor and phenylalanine, the β‐phenylethylamine content in the brain increases to about 400‐fold. This increase can be blocked by the central decarboxylase inhibitor NSD‐1055. p‐Chlorophenylalanine also increases β‐phenylethylamipe concentration in the brain, and this effect is potentiated by a simultaneous administration of phenylalanine.
ACID PROTEINASES AND OTHER ACID HYDROLASES IN EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS: PINPOINTING THE SOURCE1
Authors: Hirsch Hilde E. , Parks Mary E.
Published: October 2006

—In Lewis rats with experimental allergic encephalomyelitis (EAE), quantitative histochemical techniques were used to measure the activities of several hydrolytic enzymes, especially acid proteinases, and their levels were correlated with the concentrations of DNA and total lipids. Only those samples which contained lesions (visualized directly or in stained nearby sections) had elevated acid hydrolase activities. A lipase‐esterase hydrolysing a fluorogenic substrate at pH 5.0 was more active in lesions; activity on the same substrate at pH 7.2 was not elevated. β‐Glucuronidase rather than acid proteinase or cathepsin D was the enzyme showing the greatest differences. In a monkey with EAE, studied for comparison, a massive inflammatory lesion appeared to leak β‐glucuronidase to a distance of about 2.5 mm beyond its margin.
GABA CONTENT AND GLUTAMIC ACID DECARBOXYLASE ACTIVITY IN BRAIN OF HUNTINGTON'S CHOREA PATIENTS AND CONTROL SUBJECTS1
Authors: Urquhart Nadine , Perry T. L. , Hansen Shirley , Kennedy Janet
Published: October 2006

—GABA contents are significantly decreased in the caudate nucleus, putamen‐globus pallidus, substantia nigra, and occipital cortex in autopsied brain from Huntington's chorea patients, as compared to values in the same regions from control subjects who have died without neurological disease. Homocarnosine levels are lower in choreic than in control brain, but only in the putamen‐globus pallidus and the cerebellar cortex are the differences significant.

Activity of the enzyme which synthesizes GABA, glutamic acid decarboxylase, is reduced in the brains of some choreic patients, but may be equally low in brain of control subjects, even though the latter exhibit normal brain GABA content. Low glutamic acid decarboxylase activity in autopsied human brain is not uniquely characteristic of Huntington's chorea.

No evidence was found in this study for an inhibitor of glutamic acid decarboxylase in choreic brain, nor for the presence of an isoenzyme with decreased affinity for glutamate. GABA aminotransferase, the enzyme which degrades GABA, was equally active in control and choreic brain; therefore, increased activity of this enzyme cannot account for the low brain GABA levels in Huntington's chorea.
MELANIN FORMATION BY HUMAN BRAIN IN VITRO
Authors: Rodgers A. D. , Curzon G.
Published: October 2006

Abstract— A quantitative radiometric assay utilising incorporation of 14C from labelled precursors as a measure of melanin formation by human brain in vitro is described. The assay was validated by comparison with various criteria of melanin formation.

Catecholamines, DOPA and 5HT were precursors for brain melanin formation. Melanin formation was detected in all brain regions studied and was highest in substantia nigra and striatum.

The assay was used to evaluate various hypotheses of brain melanin formation. No evidence for enzymic activity was found and it is concluded that brain melanin formation may be a largely non‐enzymic process.
THE SUBCELLULAR LOCALIZATION OF CARBAMYLCHOLINE‐STIMULATED PHOSPHATIDYL INOSITOL TURNOVER IN RAT CEREBRAL CORTEX IN VIVO
Authors: Lunt G. G. , Pickard M. R.
Published: October 2006

Abstract— The intraventricular injection of 40 μCi of 32Pi (carrier free) into adult rats resulted in maximum incorporation of 32Pi into the phosphatidyl inositol of the whole cortex after 20 h. A further intraventricular injection of 2 nmol carbamylcholine plus 0.02 nmol eserine resulted in a 23% decrease in the specific activity of phosphatidyl inositol after 20 min. The specific radioactivities of phosphatidyl choline, phosphatidyl ethanolarmine and phosphatidyl serine were not changed. Cerebral cortex from rats treated in this way was subjected to an extensive subcellular fractionation. It was found that the specific radioactivity of the phosphatidyl inositol of the synaptic vesicle fraction showed a reduction of 60%. No other fractions showed effects of this magnitude.
POSTNATAL CHANGES IN THE POTASSIUM‐STIMULATED, CALCIUM‐DEPENDENT RELEASE OF RADIOACTIVE GABA AND GLYCINE FROM SLICES OF RAT CENTRAL NERVOUS TISSUE
Authors: Davies L. P. , Johnston G. A. R. , Stephanson A. L.
Published: October 2006

—Using a simple apparatus designed to perfuse nervous tissue mini‐slices retained on glass fibre filter discs, slices of adult (13 week) rat cerebral cortex and spinal cord were shown to release radioactive GABA and glycine, but not 2‐amino‐isobutyric acid, in response to increased potassium ion concentration of the perfusing medium. A major portion of this potassium‐stimulated release was dependent upon the presence of calcium ions in the perfusing medium. Slices of cerebral cortex and spinal cord from rats of 1 day and 10 days postnatal age showed potassium‐stimulated, calcium‐dependent release of radioactive GABA and glycine respectively. These findings are consistent with other evidence that GABA and glycine are functioning as inhibitory transmitters in rats at least as soon as 1 day after birth.
CARBOHYDRATE AND AMINO ACID METABOLISM IN RAT CEREBRAL CORTEX IN MODERATE AND EXTREME HYPERCAPNIA
Authors: Folbergrová J. , Norberg K. , Quistorff B. , Siesjö B. K.
Published: October 2006

—The time course of changes in glycolytic and citric acid cycle intermediates and in amino acids was studied in acute and steady state hypercapnia. Experiments on unanaesthetized animals exposed to 10% CO2 for 10, 20 and 60s showed that there was a transient decrease in glycogen concentration, progressive increases in glucose‐6‐phosphate and fructose‐6‐phosphate and decreases in pyruvate and lactate. During this time the levels of amino acids and Krebs cycle intermediates did not change, except for a small fall in malate at 60s. The results indicate that there was a decrease in glycolytic flux due to an inhibition of the phosphofructokinase reaction. Since the tissue levels of phosphocreatine, ATP, ADP and AMP were unchanged inhibition of phosphofructokinase was probably due to the fall in pH.

Anaesthetized animals were exposed to about 5% CO2 (for 2, 5, 15, 30 and 60 min) or to about 45% CO2 (for 5 and 15 min). Except for succinate, which increased, all citric acid cycle metabolites analysed (citrate, α‐ketoglutarate, fumarate and malate) decreased with the rise in CO2‐tension. The sum of the amino acids analysed (glutamate, glutamine, aspartate, asparagine, alanine and GABA) decreased at extreme hypercapnia. The results suggest that Krebs cycle intermediates and amino acids are partly used as substrates for energy production when there is reduced pyruvate availability due to hypercapnia.

It is proposed that amino acid carbon is made available for oxidation via transamination (aspartate aminotransferase reaction) and deamination (glutamate dehydrogenase reaction) and that citric acid cycle intermediates are metabolized following a reversal of reactions usually leading to CO2 fixation.
ISOLATION OF HYDROPHOBIC PROTEINS BINDING AMINO ACIDS: γ‐AMINOBUTYRIC ACID BINDING IN THE RAT CEREBRAL CORTEX
Authors: Fiszer de Plazas Sara , Robertis E. De
Published: October 2006

—The binding of [14C]GABA to nerve‐ending membranes isolated from rat cerebral cortex follows a hyperbolic curve saturating at 0·4pmol/μg protein. This binding is about 60% inhibited by chloropromazine, and about 40%, inhibited by bicuculline. A hydrophobic protein fraction binding [14C]GABA was separated from the total. lipid extract of nerve‐ending membranes. The binding follows a hyperbolic curve that saturates at 10·5 pmol of [14C]GABA/μg of protein, with an apparent Kd= 30 μm. The binding is competitively inhibited by bicuculline with a Ki= 273 μm. These results are compared with those previously obtained on a GABA binding protein from crustacean muscle.
ALCOHOL:NAD OXIDOREDUCTASE IN BRAIN OF RATS FROM A COLONY FED DILUTE ETHANOL FOR MANY GENERATIONS1,2
Authors: Rodrigo R. , Egaña Enrique
Published: October 2006

—Alcohol:NAD oxidoreductase (EC 1.1.1.1) was studied in brain cortex, hypothalamus, cerebellum and midbrain of adult and immature rats, and in the whole encephalon of neonatal rats. The rats used in this study were (i) from a colony which has been given 12% (v/v) aqueous ethanol as the only fluid for 54 generations (‘E.F.’ rats); (ii) rats removed from this colony after the forty‐eighth generation and thereafter fed water instead of the alcohol solution (‘E.F./H2O’ rats); and (iii) normal rats. Enzyme activity in the 20,000 g supernatant of tissue homogenates was measured by the method of Raskin and Sokoloff. Activity was found to be highest in neonatal rat brain and to decrease as the age increased. Activity in the hypothalamus of adult E.F. rats was significantly higher than that found in the same region of adult E.F./H2O rats. Immature rat cerebellum alcohol:NAD oxidoreductase activity was higher both in ‘E.F.’ and ‘E.F./H2O’ suggesting a possible genetic change be involved in this CNS region. It may be concluded that, with the exception of neonatal rats, ethanol consumption induces an increase in rat CNS alcohol :NAD oxidoreductase activity.
THE DISPOSITION OF [24‐3H]CEREBROSTEROL IN DEVELOPING RAT BRAIN*
Authors: Lin Y. Y. , Smith L. L.
Published: October 2006

—The uptake into subcellular fractions of developing rat brain in vivo of intracerebrally injected [4‐14C]cholesterol, [24‐3H]cerebrosterol, and [24‐3H]24‐epicerebrosterol was measured for periods up to 30 days following administration. [4‐14C]cholesterol was accumulated rapidly in nuclei, nerve endings, and microsomes, more slowly in myelin and mitochondria. [24‐3H]cerebrosterol was accumulated rapidly in myelin, nerve endings, and microsomes, more slowly in nuclei and mitochondria. The uptake of [24‐3H]24‐epicerebrosterol was essentially the same as that of [24‐3H]cerebrosterol. Ratios of radioactivities of [24‐3H]cerebrosterol and [4‐14C]cholesterol accentuated the early accumulation of [24‐3H]cerebrosterol in myelin, nerve endings, and microsomes, and declining 3H:14C ratios disclosed the rapid elimination of [24‐3H]cerebrosterol and [24‐3H]24‐epicerebrosterol relative to [4‐14C]cholesterol in nerve endings and microsomes. The data suggest that the removal of [24‐3H]cerebrosterol from brain results from an enzymic metabolism of the sterol, therefore that cerebrosterol exists in brain in a dynamic state of biosynthesis and catabolism.