bluuebunny/crossref_metadata_2025_split huggingface dataset:
INCORPORATION OF [14C]GLUCOSAMINE INTO SYNAPTOSOMES IN VITRO1
Authors: Festoff B. W. , Appel S. H. , Day E. 
Published: October 2006

Abstract— Synaptosomes isolated from rat cerebral cortex by zonal centrifugation in‐corporated radioactive glucosamine into macromolecules in vitro as glucosamine, galactosamine, N‐acetylneuraminic acid, and glucuronic acid. The largest percentage of incorporated radioactivity was recovered in the particulate fraction in which radioactive carbohydrates were bound in covalent linkage requiring acid hydrolysis or enzymatic digestion for release. Less than 20 per cent of the particulate radioactivity represented incorporation into gangliosides. Some 20 per cent of the radioactivity was incorporated into proteins as glucosamine, identified in hydrolysates by paper chromatography and by the amino acid analyser. After incubation, radioactivity was demonstrable in the proteins as sialic acid by paper chromatography and specific enzymic digestion; and as glucuronic acid by chromatography, electrophoresis, and digestion with hyaluronidase.Incorporation of carbohydrate was stimulated by sodium and potassium at concentrations demonstrated to enhance incorporation of amino acids, and involved the macro‐molecules of all subsynaptosomal fractions. Significant incorporation of radioactivity was found in the synaptic plasma membrane. The synthesis of glycoproteins was suggested by simultaneous incorporation of [14C]glucosamine and [3H]leucine into glycopeptides subsequently hydrolysed and subjected to polyacrylamide gel electrophoresis and two‐dimensional paper chromatography and electrophoresis. Such studies demonstrated that amino acids and carbohydrates may be incorporated into glycoproteins of the synaptic membrane and suggest the possibility of local synthesis as well as modification of material brought to the nerve ending by axoplasmic flow.
HIGH‐AFFINITY TRANSPORT AND PHOSPHORYLATION OF 2‐DEOXY‐d‐GLUCOSE IN SYNAPTOSOMES1,2
Authors: Diamond I. , Fishman R. A. 
Published: October 2006

Abstract2‐Deoxy‐d‐glucose (2 DG) entered synaptosomes (from rat brain) by a high‐affinity, Na+‐independent glucose transport system with a Km, of 0.24 mM. 3‐O‐methyl‐glucose, D‐glucose, and phloretin were competitive inhibitors of 2‐DG transport with Ki's of 7 mM, 64 μM, and 0·75 μM, respectively. Insulin was without effect. 2‐DG uptake was also saturable at high substrate concentrations with an apparent low affinity Km, of 75 mM, where the Kl, for glucose was 17.5 mM. We are not certain whether the rate‐limiting step for the low‐affinity uptake system is attributable to transport or phosphorylation. However, the high‐affinity glucose transport system probably is a special property of neuronal cell membranes and could be useful in helping to distinguish separated neurons from glial cells.
OPTIMAL FREEZING CONDITIONS FOR CEREBRAL METABOLITES IN RATS
Authors: Pontén U. , Ratcheson R. A. , Salford L. G. , Siesjö B. K. 
Published: October 2006

Abstract— Optimal freezing conditions for metabolites were evaluated in 250‐450 g rats. As a standard procedure, the brains were frozen in such a way that the blood pressure and arterial oxygenation were upheld during the freezing. The progression of the freezing front was determined by means of implanted thermocouples, and the interruption of the circulation by means of injections of carbon particles into the blood stream. The freezing gave rise to a rapid interruption of the circulation in the superficial cortical layer first reached by the freezing front well before the temperature reached 0°C. In deeper regions the progression of the freezing front was slower and interruption of the circulation occurred simultaneously with the freezing of the tissue. Measurements of labile cerebral metabolites, including phosphocreatine, ATP, ADP, AMP and lactate, failed to show signs of autolysis in the part of cortex which became unperfused at temperatures above zero. Since the energy state was identical in superficial cortical areas and in areas that did not freeze until after 40–90 s, it is concluded that the freezing technique gives optimal conditions for metabolites also in deep cerebral structures.Decapitation of unanaesthetized animals gave rise to large autolytic changes in the cerebral cortex. In unanaesthetized animals that were immersed in liquid nitrogen the changes were less marked and mainly affected the concentrations of phosphocreatine, ADP and lactate. When paralysed animals that were anaesthetized with N2O were immersed in liquid nitrogen the only significant change from the control was a decrease in phosphocreatine content. The virtual absence of autolytic changes in this group of animals was not related to the anaesthesia since more pronounced changes were observed in phenobarbitone‐anaesthetized rats immersed in the coolant. These differences could be explained by the fact that spontaneously breathing animals immersed in liquid nitrogen developed arterial hypoxia much faster than paralysed animals. It is concluded that an optimal metabolite pattern can only be obtained in anaesthetized animals, frozen with a method that was described by Kerr almost 40 years ago (Kerr, 1935). If unanaesthetized animals must be used, greater attention should be paid to the oxygenation of the blood during the freezing than to such factors as speed of freezing or depth of anaesthesia.
THE BIOSYNTHESIS AND CONCENTRATION OF GALACTOSYL DIGLYCERIDE IN GLIAL AND NEURONAL ENRICHED FRACTIONS OF ACTIVELY MYELINATING RAT BRAIN
Authors: Deshmukh D. S. , Flynn T. J. , Pieringer R. A. 
Published: October 2006

Abstract—In continuation of our studies on the association of the galactosyl diglycerides of brain with myelination, we have measured the biosynthesis and concentration of these glyceride glycolipids, in oligodendroglial, astroglial, neuronal, and myelin enriched fractions from brains of rats of postnatal age 16, 19 and 29 days. The relative purity of cell fractions and myelin derived from 50 to 60 brains of each age‐group was checked by phase contrast microscopy and 2′,3′‐cyclic nucleotide‐3′‐phosphohydrolase activity. The relative purity was comparable to that reported by other investigators for cell fractions from bovine brain. Of the three cell types, the oligodendroglia had the highest and the neurons had the lowest capacity to enzymatically synthesize and to accumulate monogalactosyl diglyceride. The amount of monogalactosyl diglyceride found in myelin compared to that found in oligodendroglial fraction greatly increased during development between 16 and 29 days of age. The biosynthesis of galactosyl ceramide but not glucosyl ceramide was highest in oligodendroglial enriched cell fraction. However, ceramide glucosyl‐transferase activity, which was greatly affected by the method used for cellular separation, was highest in a microsomal fraction derived from grey matter. Our results support the contention that the oligodendroglial cells are the site of synthesis of myelin constituents of the central nervous system, and that there is a temporal relationship between this site of synthesis and the site of deposition (myelin).
ACTIVATION OF HEXOSE MONOPHOSPHATE PATHWAY IN BRAIN BY ELECTRICAL STIMULATION IN VITRO
Authors: Kimura H. , Naito K. , Nakagawa K. , Kuriyama K. 
Published: October 2006

Abstract— The incubation of cerebral cortical slices for 15 min in Krebs‐Ringer‐tris (pH 7.6) solution at 37°C with [1‐14C]glucose or [6‐14C]glucose as substrates yielded a C‐1:C‐6 14CO2 ratio of 1.21, whereas this ratio increased to 3.01 after the application of electrical stimulation (ES). Tissue levels of 6‐phosphoglu‐conate (6PG) and glucose 6‐phosphate (G6P), intermediary metabolites of hexose monophosphate (HMP) pathway, were 7 and 180 nmol/g tissue following 15 min incubation, and increased by 33 and 45 per cent respectively following the application of ES. Activities of 6‐phosphogluconate dehydrogenase (6PGDH, 6‐phospho‐d‐gluconate: NADP+ 2‐oxidoreductase, EC 1.1.1.44) and glucose‐6‐phosphate dehydrogenase (G6PDH, d‐glucose‐6‐phosphate: NADP+ 1‐oxidoreductase, EC 1.1.1.49), important enzymes in regulating the activity of HMP pathway, in cerebral cortical slices were 689 and 907 pmol/mg protein/min and were increased by 66 and 25 per cent respectively by the application of ES. Synaptosomal G6PDH and 6PGDH activities were maximally activated by the addition of 40 mm‐Na+ to the reaction mixture, whereas no activation by Na+ was observed in microsomal G6PDH and 6PGDH. Amobarbital inhibited more strongly the Embden–Meyerhof (EM) pathway than the HMP pathway, while imipramine had a stronger inhibitory effect on HMP pathway than on EM pathway in the electrically stimulated cerebral tissues.The present results indicate that the HMP shunt pathway in the cerebral cortex is activated by the application of ES in vitro, possibly at synaptic regions and may play an important metabolic and functional role in the brain.
THE RELATIONSHIP BETWEEN NORADRENALINE TURNOVER IN CEREBRAL CORTEX AND ELECTRICAL SELF‐STIMULATION THROUGH ELECTRODES IN THE REGION OF LOCUS COERULEUS
Authors: Anlezark G. M. , Walter D. S. , Arbuthnott G. W. , Crow T. J. , Eccleston D. 
Published: October 2006

Abstract—Rats allowed to stimulate themselves through electrodes implanted in the region of the noradrenaline‐containing cells of the locus coeruleus had increased concentrations in the cerebral cortex of 4‐hydroxy‐3‐methoxy‐phenylglycol (a noradrenaline metabolite). In a group of animals stimulated under anaesthesia a rise was present if, and only if, the electrodes had previously supported self‐stimulation behaviour. It is concluded that the increase in cortical 4‐hydroxy‐3‐methoxy‐phenylglycol reflects an increase in noradrenaline turnover which results from self‐stimulation through electrodes in the region of the locus coeruleus. The results constitute further evidence for the involvement of a specific catecholamine‐containing pathway, the coerulo‐cortical noradrenergic system, in central reward mechanisms.
ELEVATED EXTRACELLULAR POTASSIUM AS A STIMULUS FOR RELEASING [3H]NOREPINEPHRINE AND [14C]α‐AMINOISOBUTYRATE FROM NEOCORTICAL SLICES. SPECIFICITY AND CALCIUM DEPENDENCY OF THE PROCESS
Authors: Vargas Olga , Orrego F. 
Published: October 2006

Abstract—The effect of short (4–6 min)‘pulses’ of elevated extracellular potassium ions K0, in the 10–50 mm range, on the efflux of [3H]norepinephrine [3H]NE) and [14C]α‐aminoisobutyrate (AIB) has been studied in a superfused neocortical thin slice system. At all the concentrations tested high K0 increases the efflux of both NE and AIB, although thc effects on the former are greater. In the absence of calcium ions, or in the presence of 8 mm‐MnCl2, the potassium‐stimulated release of both NE and AIB is severely depressed. However, potassium induced NE release is proportional to extracellular calcium ions in the 0–1.5 mm range, while that of AIB does not continue to increase above 0.2 mm‐calcium. This permissive role of calcium in amino acid efflux is interpreted as due to changes in the inactivation of membrane sodium conductance.
NEONATAL ASPHYXIA IN THE RAT: GREATER VULNERABILITY OF MALES AND PERSISTENT EFFECTS ON BRAIN MONOAMINE SYNTHESIS
Authors: Simon Nicole , Volicer L. 
Published: October 2006

Abstract—In the rat, neonatal asphyxia produced by suffocation did not leave permanent visible lesions in thc brain, nor did it result in permanent motor impairment, although a delay in the development of some reflexes was observed. A transient retardation of body and brain growth, which was more pronounced in males, was found. By 5‐6 weeks of age, body and brain weights of asphyxiated rats were no longer significantly different from control animals. However, an increase in brain norepinephrine synthesis was found to persist after maturation. An alteration of serotonin metabolism was found after maturation only in asphyxiated males. The possibility that neonatal asphyxia in the rat is a model for abnormal development of monoamine metabolism, relevant to early childhood behavior disorders such as infantile autism or the syndrome of minimal brain dysfunction, is discussed.
QUANTITATION OF ACTIN IN DEVELOPING BRAIN1
Authors: Pardee J. D. , Bamburg J. R. 
Published: October 2006

AbstractActin levels in the soluble fraction of chick embryo brain sonicates have been quantitated by polyacrylamide gel electrophoresis. Brain actin concentrations remained constant at 8.10 ± 0.9% in developing cnibryos but dropped to 6.0 ± 0.9% in adult brain. Over 80% of the total brain protein was solubilized by the sonication procedure and actin was not detected in the remaining insoluble fraction.
N‐ACETYLNEURAMINIC ACID MOLECULES AS POSSIBLE SEROTONIN BINDING SITES1
Authors: OCHOA E. L. M. , BANGHAM A. D. 
Published: October 2006

Abstract5‐Hydroxytryptamine (5‐HT), but not acetylcholine, carbamylcholine or L‐D‐noradrenaline, binds to ox brain ganglioside micelles, to phosphatidylcholine smectic mesophases (liposomes) containing gangliosides and to the glycoprotein fetuin, through the negatively charged N‐acctylneuraminic acid (NeuNAc) residues. The 5‐HT binding to NeuNAc is reversible, saturable, prodeeds in a 1: 1 fashion and can be specifically blocked by 7‐methyltryptamine. Thc affinity constant at equilibrium for the reaction is of the order of 102 1. mol‐1. No special ganglioside was identified as specifically associating with the amine. A terminal NeuNAc in the gangliosides is not a prerequisite for binding, although it seems important for binding 5‐HT in entire mcmbrane preparations (MARCHBANKS, 1966) or for bringing about the 5‐HT induced contraction of smooth muscle cells (WOOLLCY & GOMML 1964a). It is proposed that in 5‐HT target cells, NeuNAc residues, probably attached to membrane surface glycoprotein(s) are involved in thc mechanism of action of the drug.
DECREASE OF HOMOVANILLIC, DIHYDROXYPHENYLACETIC ACID AND CYCLIC‐ADENOSINE‐3′,5′‐MONOPHOSPHATE CONTENT IN THE RAT CAUDATE NUCLEUS INDUCED BY THE ACUTE ADMINISTRATION OF AN AMINOACID MIXTURE LACKING TYROSINE AND PHENYLALANINE1
Authors: Biggio. G. , Porceddu M. L. , Gessa G. L. 
Published: October 2006

AbstractThe oral administration of an aminoacid mixture lacking tyrosine and phenylalanine induces, in rats, a profound depletion of tyrosine in serum and in brain. Brain tyrosine is maximally depleted by 73%, 2 h after treatment, when there is a concomitant decrease in the levels of HVA (by 50%), DOPAC (by 30%) and c‐AMP (by 28%) in the basal ganglia. However, 4 to 8 h after treatment, when brain tyrosine is still depleted by 47 and 28%, respectively, DA metabolites and c‐AMP levels have returned to normal. Our findings indicate that striatal tyrosine hydroxylase is fully saturated in v i m by the concentrations of tyrosine normally present in the basal ganglia. The results also suggest indirectly that decreased DA turnover results in decreased nerve activity, as judged by the decreased cyclic AMP levels.
LOCALIZATION OF HEXOKINASE IN NEURAL TISSUE: LIGHT MICROSCOPIC STUDIES WITH IMMUNOFLUORESCENCE AND HISTOCHEMICAL PROCEDURES
Authors: Wilkin G. P. , Wilson J. E. 
Published: October 2006

Abstract— The distribution of hexokinase (ATP: D‐hexose 6‐phosphotransferase, EC 2.7.1.1) in rat cerebellum, retina, hippocampus, choroid plexus and ependymal cells of the cerebral ventricles, and dorsal root ganglion has been determined, at the light microscopic level, by both immunofluorescence and a histochemical procedure using nitro blue tetrazolium. With the exception of an artifactual staining of the outer photoreceptor segments of retina when the histochemical procedure was used, both methods gave comparable results, from which the following conclusions are drawn:

The cytoplasm of neuronal cell bodies clearly contained hexokinase, although the relative levels varied markedly among different types of neurons; such variations have previously been detected by direct assay of hexokinase in dissected neuronal cell bodies (Kato & Lowry, 1973a).
Glial cells contained readily detectable levels of hexokinase: the immunofluorescence technique revealed spidery glial processes within the myelinated tracts; in other areas, glial cell cytoplasms were indistinguishable from surrounding neuropil, indicating comparable levels of hexokinase; the satellite glia of dorsal root ganglia actually contained higher levels than did adjacent large neurons. The present results, therefore, do not support previous suggestions that glia are characteristically low and neurons characteristically high in hexokinase content.
Hexokinase was distributed throughout neuropil areas, with a somewhat speckled appearance suggesting the existence of small localizations of relatively higher activity, the nature of which could not be determined at this level of resolution; the hexokinase level in neuropil was clearly higher than that of white fiber tracts, in agreement with previous direct biochemical measurements (Buellet al., 1958)
No detectable levels of hexokinase were found in cell nuclei.
Regions expected to be rich in nerve terminals (e.g. the cerebellar glomeruli, the plexiform layers of retina) showed relatively high hexokinase levels compared to the cytoplasm of adjacent neuronal perikarya, in agreement with previous subcellular fractionation experiments which indicated relatively high levels of hexokinase in nerve endings (Wilson, 1972). Considered along with the‘high affinity’glucose transport system in nerve endings (Diamond & Fishman, 1973), these results suggest nerve terminals are well adapted for the'efficient acquisition and introduction of glucose into metabolism.
In addition, high levels of hexokinase were observed in the inner photoreceptor segments of retina, and in the ependymal and choroid plexus cells of the ventricles.
THE DISTRIBUTION OF ACETYL‐CoA IN SPECIFIC AREAS OF THE CNS OF THE RAT AS MEASURED BY A MODIFICATION OF A RADIO‐ENZYMATIC ASSAY FOR ACETYLCHOLINE AND CHOLINE1
Authors: Shea P. A. , Aprison M. H. 
Published: October 2006

Abstract—A rapid and sensitive enzymatic assay for measuring picomole quantities of acetyl‐CoA, acetylcholine (ACh), and choline from the same tissue extract has been developed. After ACh and choline were extracted into 15% 1 N formic acid/85% acetone, the pellet was further extracted with 5% trichloroacetic acid (TCA) to remove the remaining acetyl‐CoA. The two extraction solvents were pooled and lipids, organic solvents, and TCA were removed first by a heptane‐chloroform wash followed by an ether extraction. In the acetyl‐CoA assay, endogenous ACh and choline were removed by extractions with sodium tetraphenylboron in butenenitrile prior to the enzymatic reactions. The acetyl‐CoA remaining in the aqueous phase was then converted enzymatically to labelled ACh in the presence of [Me‐14C]choline using choline acetyltransferase. The unreacted labelled precursor was converted to choline phosphate by the enzyme choline kinase. The [14C]ACh formed from acetyl‐CoA was extracted into sodium tetraphenylboron in butenenitrile and a portion of the organic phase containing the [14C]ACh was counted in a scintillation counter. Acetylcholine and choline were assayed from the same tissue extracts by a modification of the procedure by SHEA & APRISON (1973). Acetyl‐CoA levels in rat whole brain when killed by the near‐freezing procedure were found to be 5.50 ± 0.2 nmol/g. The content of acetyl‐CoA was the same whether the rats were killed by the near‐freezing method or by total freezing in liquid nitrogen. The levels of acetyl‐CoA did not change with time after death when the tissue was maintained at a temperature of −10°C. In the same tissue extracts from rat whole brain killed by the near‐freezing method, the content of ACh was 20.6 ± 0.7 nmol/g and choline 58.2 ± 1.2 nmol/g. Although reproducible, the level reported for choline is high when assayed under this condition. The content of choline however after total freezing was found to be 25.2 ± 2.0 nmol/g. The sensitivity (d. p. m. of sample twice blank) is 10 pmol for the acetyl‐CoA assay and 25 pmol for the ACh and choline assays. The regional distribution of these three compounds in the brain of rats as well as the content of acetyl‐CoA in heart, liver and kidney are presented.
CEREBRAL ENERGY METABOLISM DURING TRANSIENT ISCHEMIA AND RECOVERY IN THE GERBIL1
Authors: Levy D. E. , Duffy T. E. 
Published: October 2006

Abstract—Energy metabolism was studied in the cerebral cortex of gerbils during and following ischemia induced by 1 h of unilateral carotid artery occlusion. An aneurysm clip was applied to the right common carotid artery of 50‐70 g gerbils under brief halothane anesthesia, and the clip was removed 1 h later. Clinical state (gait, responsiveness, seizures) was evaluated during carotid occlusion, and 40% of the animals showed clinical evidence of stroke. Cortical energy stores (2 ATP + ADP + P‐creatine) were more than half depleted in the ipsilateral cortex of clinically‐affected gerbils, and glucose fell by 75%; lactate rose over 7‐fold in the same specimens. After release of the carotid clip, clinical state improved, and biochemical abnormalities partially resolved. However, even after 24 h, the concentration of ATP and the total pool of adenine nucleotides remained subnormal. Metabolic activity in the ischemic cortex, assessed as the utilization of high‐energy phosphates following decapitation, was normal after 1 h of recovery and decreased (‐50%) after 24 h but was increased by more than 50% after 4 h. Cerebral glucose utilization, evaluated from autoradiographs prepared after intravenous administration of 2‐[1‐14C]deoxyglucose, was also increased in the cortex, hippocampus, and thalamus after 4 h of recovery. This post‐ischemic hypermetabolism in tissue damaged by ischemia may identify a critical period for cell repair, when therapy could be decisive.