bluuebunny/crossref_metadata_2025_split huggingface dataset:
TRANSPORT AND TURNOVER OF DOPAMINE‐β‐HYDROXYLASE (EC 1.14.2.1) IN SYMPATHETIC NERVES OF THE RAT
Authors: Brimijoin S. 
Published: October 2006

AbstractAxoplasmic transport of dopamine‐β‐hydroxylase (DBH), a marker enzyme for catecholamine storage vesicles, was studied in sympathetic nerves of the rat. At 24 h after ligation of the sciatic nerve, there was a marked accumulation of DBH activity in the first 3 mm proximal to the ligature. Immediately distal to the ligature, a slight accumulation took place. Accumulation proximal to the ligature was a linear function of time for at least 6 h; the velocity of transport was calculated as 4.6 mm/h. Local application of 1 ·l of 0.1 M colchicine, caused a rapid increase in DBH activity in superior cervical ganglia. This increase remained linear for 22 h and its rate indicated a turnover time of 12 h for DBH in these ganglia. After application of colchicine to the ganglia, there was a decrease in DBH activity in the submaxillary salivary glands. The initial rate of this decrease was less than the rate of increase in the ganglia and probably reflected the normal turnover of the enzyme. Our results indicated that the turnover time for DBH in salivary glands ranged between 3.6 and 6.3 days.
KINETICS OF THE SODIUM‐DEPENDENT TRANSPORT OF GAMMA‐AMINOBUTYRIC ACID BY SYNAPTOSOMES
Authors: Martin D. L. 
Published: October 2006

AbstractThe kinetics of transport of gamma‐aminobutyric acid [2,3‐3H] by synaptosomes from rat brain was studied by means of a rapid filtration technique. The rate of uptake was proportional to the protein concentration over the range 0.05—0.2 mg of synaptosomal protein per ml. Although apparent allosteric kinetics were observed with sodium, transport followed simple saturation kinetics with respect to GABA and no heterotropic, cooperative effects of GABA on sodium on kinetics were observed. A minimum of three interacting sodium sites is suggested the basis of Hill plots of the sodium data. Both the apparent Km and Vmax for GABA were functions of the sodium ion concentration but the effect of sodium was considerably greater on Vmax than on the apparent Km The Vmax for GABA was 1.1 ± 0.5 nmol.min−1 mg−1 of protein at 95 mm sodium and decreased to 12 per Cent of this value at 19 mm sodium. The apparent Km for GABA increased from 4.0 ± 1.0 μm at 95 mm sodium to 8.4 ± 2.0 μm at 19 mm sodium. Potassium was a noncompetitive inhibitor with respect to GABA and did not affect the apparent cooperativity observed with sodium. These findings are discussed in terms of models of GABA transport.
DIFFERENTIAL INCORPORATION OF LYSINE INTO RETINAL PROTEIN FRACTIONS FOLLOWING FIRST EXPOSURE TO LIGHT
Authors: Richardson K. , Rose S. P. R. 
Published: October 2006

Abstract—Soluble and insoluble proteins from the retina of dark‐reared rats and from similar rats exposed to light for the first time, were subjected to electrophoresis on polyacrylamide gels. After injection of [3H] or [14C]lysine, using a double‐labelling technique, striking differences were observed in the pattern of incorporation into the forty‐one fractions investigated. After exposure for 1 h significant differences emerged in 13 of these fractions (High Differential Activity fractions) when compared with incorporation in control animals, a finding which persisted, irrespective of the order of labelling. Histochemical examination for acetylcholinesterase and glycoprotein material, showed the presence of these substances in some of the high differential activity fractions, and molecular weight determination was carried out on the insoluble fractions separated on SDS‐gels. It is concluded that the consistent enhancement of incorporation of precursor into retinal proteins which accompanies first exposure to light is a complex response involving a number of particular protein species, rather than a general elevation.
IN VIVO EFFECTS OF AMPHETAMINE ON METABOLITES AND METABOLIC RATE IN BRAIN
Authors: Nahorski S. R. , Rogers K. J. 
Published: October 2006

Abstract—The concentrations of several metabolites, including glucose, glycogen, glucose‐6‐phosphate, lactate, ATP and phosphocreatine have been measured in the brains of mice rapidly frozen at various intervals after the intraperitoneal injection of d‐amphetamine sulphate (5 mg/kg). During the initial 30 min following injection, amphetamine induced a fall in cerebral glycogen and phosphocreatine and an elevation of lactate. Changes in glucose and brain/blood glucose ratios were less marked over this period. The metabolite levels returned to control values at 60 min. The cerebral metabolic rate calculated by the ‘closed system’ technique also showed a biphasic change. An initial depression of energy flux over the first 15 min following amphetamine injection was followed by an increase that appeared to be closely associated with the increase in locomotor activity over this period. The results have been discussed in relation to the known catecholamine‐releasing action of amphetamine, and differential effects on glial cells and neurons have been proposed.
SOME PROPERTIES OF A HOMOCARNOSINE‐CARNOSINE SYNTHETASE ISOLATED FROM RAT BRAIN1
Authors: Skaper S. D. , Das S. , Marshall F. D. 
Published: October 2006

Abstract—An enzyme from rat brain catalysing the synthesis of the histidine‐containing dipeptides carnosine and homocarnosine (l.‐histidine: β‐alanine ligase (AMP) [EC 6.3.2.11]) was purified about 30‐40‐fold from a 100,000 g supernatant. Assays were conducted by measuring the incorporation of L‐[14C]histidine into carnosine and homocarnosine isolated by paper electrophoresis from the incubation mixture. The ratios of specific activities for the formation of carnosine and homocarnosine were not significantly different for the various purification steps. This was taken as evidence of one enzyme synthesizing both dipeptides. In studying the properties of this enzyme, a pH optimum of 7.4 was shown for carnosine synthesis. The concentrations of amino acid substrates giving maximal synthesis of both dipeptides were in the physiological range found for rat brain. An apparent requirement for ATP, Mg2+, and DPN was seen for dipeptide synthesis. A substrate dependent, enzymecatalysed 32PPi‐ATP exchange reaction was observed, suggesting the formation of an aminoacyl‐AMP intermediate. Certain other nucleoside triphosphates could substitute for the ATP; this effect showed a specificity toward the dipeptide being synthesized. The apparent requirement for DPN was quite specific, with a number of related compounds having no effect. The stoichiometry of enzyme‐catalysed carnosine synthesis was studied. A one to one relationship between carnosine formed and ATP hydrolysed was demonstrated. However, the ratio between carnosine synthesized and DPN hydrolysed was about 6 to 1, indicating a catalytic role for the DPN. The breakdown of DPN did not occur with enzyme alone but was dependent on the presence of substrate.
γ‐AMINOBUTYRIC ACID (GABA) IN THE RAT BRAIN: RE‐EVALUATION OF SAMPLING PROCEDURES AND THE POST‐MORTEM INCREASE1
Authors: Alderman J. L. , Shellenberger M. K. 
Published: October 2006

Abstract—GABA levels determined after the brain was removed, then frozen, were found to be generally compatible to levels after the brain was frozen in situ provided removal and freezing were effected in less than 60 s. Optimal GABA values were realized when the brain was removed and frozen in liquid nitrogen within 30 s of death. Beginning at 60 s post‐mortem, GABA levels increased until the 4th min with the greatest rate occurring between 60 and 120 s at 30 μg/g/min. When frozen brains were dissected into regions by a partial thawing technique, post‐mortem increases were not found to occur. Microwave irradiation, investigated as a potential sampling technique for GABA assay, showed considerable variability between samples and was rejected as a practical alternative at this time.
CTP SYNTHETASE ACTIVITY IN NEONATAL AND ADULT RAT BRAIN
Authors: Genchev D. D. , Mandel P. 
Published: October 2006

Abstract—The activity of CTP synthetase (UTP:ammonia ligase (ADP‐forming), EC 6.3.4.2) in adult and new‐born rat brain was determined by an enzyme assay using [14C]UTP as a substrate. The activity was age‐dependent and showed a distinctive distribution pattern between the cerebral hemispheres and cerebellum. The possible correlations between the activity of CTP synthetase and the rate of RNA or lipid biosynthesis, as well as the regulatory importance of the enzyme in the formation of cytidine nucleotides are discussed.
CHOLINE ACETYLTRANSFERASE, ACETYLCHOLINESTERASE AND AROMATIC l‐AMINO ACID DECARBOXYLASE IN SINGLE IDENTIFIED NERVE CELL BODIES FROM SNAIL HELIX ASPERSA
Authors: Emson P. C. , Fonnum F. 
Published: October 2006

Abstract—The distribution of choline acetyltransferase, aromatic l‐amino acid decarboxylase and acetylcholinesterase in the nervous system of Helix aspersa has been studied using homogenates of whole ganglia, microdissection from freeze‐dried sections and dissection of single neurons from fresh tissue. Choline acetyltransferase was found in both the cell body and neuropil layers of all the Helix ganglia. The enzyme was not specifically localized to any ganglion or region of ganglion. Between 10 and 30 per cent of the isolated single cell bodies contained the enzyme. The enzymic activity corresponded to 50–200 mmol ACh/1 cell bodies/h. Choline acetyltransferase is probably a specific marker for cholinergic cells in this species.Aromatic l‐amino acid decarboxylase was more selectivity localized and its distribution corresponded well with that of monoamine containing cells as visualized by the fluorescence histochemical technique. A large proportion of cell bodies were localized in the boundary between the visceral and right parietal ganglia and in the pedal ganglion. The other ganglia contained few such cells. The activity of aromatic l‐amino acid decarboxylase corresponded 10–50 mmol dopamine/1 cell bodies/h. A method was developed to measure the enzyme activity towards 5‐hydroxytryptophan and DOPA in single cells simultaneously. The ratio between the activity towards both substrates did not vary significantly for the different cells. The enzyme is probably a specific marker for monoamine cells, but cannot be used to differentiate between the different monoamine cells.Acetylcholinesterase was uniformly distributed in the ganglia and was probably present in all nerve cells.
MYELIN PROTEINS FROM DIFFERENT REGIONS OF THE CENTRAL NERVOUS SYSTEM
Authors: Lees Marjorie B. , Paxman Sally A. 
Published: October 2006

Abstract—The protein composition of myelin prepared from specific anatomical regions of the bovine brain and spinal cord was studied by a modification of the method of Gonzalez‐Sastre (1970). Spinal cord myelin contained lesser amounts of chloroform‐methanol soluble protein and proteolipid protein and had a lower activity of the enzyme 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase than did myelin from subcortical white matter. There was no difference, however, in the protein composition of myelin from the various levels of the spinal cord. The amino acid composition of both proteolipid and basic protein showed no significant regional differences. Myelin preparations from both brain and spinal cord contained DM‐20 protein.
GP‐350, A SIALOGLYCOPROTEIN FROM CALF BRAIN: ITS SUBCELLULAR LOCALIZATION AND OCCURRENCE IN VARIOUS BRAIN AREAS
Authors: van Nieuw Amerongen A. , Roukema P. A. 
Published: October 2006

Abstract— A membrane‐bound form of GP‐350, a sialoglycoprotein from calf brain has been shown to occur in the crude mitochondrial fraction (P2). After subfractionation on a discontinuous sucrose gradient, consisting of 0.8 and 1.2 m‐sucrose, GP‐350 was immunologically only detectable in the synaptosomal fraction. After further separation of the lysed synaptosomal fraction on a discontinuous sucrose gradient (0.4, 0.8 and 1.2m) GP‐350 could be detected only in the 0.8–1.2 m‐sucrose interface.The membrane‐bound GP‐350 from the cerebellar grey matter was purified and analysed. The amino acid composition and the data obtained for galactose, galactosamine, glucosamine and sialic acid were quite similar to those of the soluble GP‐350, indicating their identity, which was sustained by immunodif‐fusion, immunoelectrophoresis and polyacrylamide gel electrophoresis.The membrane‐bound GP‐350 was isolated from 15 different brain areas. Per g wet wt at least 60 μg (corpora quadrigemina inferior) and at most 470 μg (thalamus) of GP‐350 protein were obtained. Compared to the soluble GP‐350 protein 10–52 per cent could be isolated from the crude mitochondrial fraction. Our results on GP‐350 indicate an association with membranes of nerve endings.
MEASUREMENT OF THE RATE OF GLUCOSE UTILIZATION BY RAT BRAIN IN VIVO
Authors: Hawkins R. A. , Miller A. L. , Cremer Jill E. , Veech R. L. 
Published: October 2006

Abstract— A method is described by which the rate of glucose utilization by whole brain of conscious rats may be measured. The basis is the uptake of 14C derived front [2‐14C] glucose into the acid‐soluble metabolite pool of brain. Catheters are placed in the femoral artery and vein under light ether anesthesia. After full recovery of consciousness a single intravenous injection of [2‐14C] glucose is given and arterial blood samples taken at intervals. Simultaneous with the last sample the brain is removed and frozen within 1 s. The accumulation of 14C into the acid‐soluble metabilite pool is measured and the rate of glucose utilization is calculated according to the equation:
image
The integral is calculated from the plasma glucose specific activity curve and evidence is presented to justify this procedure. The rate of glucose utilization measured by this method was 0·62 μmol/min per g in conscious rats and 0·28 μmol/min per g in sodium pentobarbital anesthetized rats.
CEREBRAL ENERGY METABOLISM DURING EXPERIMENTAL STATUS EPILEPTICUS1
Authors: Duffy T. E. , Howse D. C. , Plum F. 
Published: October 2006

Abstract—The concentration of ATP, ADP, AMP, phosphocreatine and of 5 intermediates of carbohydrate metabolism were determined in rodent brain after single and repeated seizures induced by either electroshock (ES), flurothyl or pentylenetetrazol (PTZ). In paralysed‐ventilated rats, one ES produced a 4–5 fold increase in cortical glycolytic flux (estimated from changes in glucose and lactate), and associated increases in pyruvate and in the lactate/pyruvate ratio. Total high energy phosphates declined during the seizure; a decrease was also calculated in cortical tissue pH and in the cytoplasmic [NAD+]/[NADH] ratio. Similar changes in brain were observed in ventilated mice after ES, but in paralysed animals, no decrease in high energy phosphates occurred during the first seizure. More vigorous and prolonged chemically‐induced seizures in both rats and mice elicited a decrease in the cerebral energy reserves with a rise in lactate and in the lactate/pyruvate ratio. At all times during the seizures the cerebral venous blood had a higher oxygen tension than that of control animals (rats) or was visibly reddened (mice), implying that oxygen availability to brain exceeded metabolic demands. It is proposed that the development of‘non‐hypoxic’cerebral lactacidosis during seizures is part of the overall metabolic response of the brain to an abrupt increase in energy consumption. The response constitutes a homeostatic influence which promotes cerebral vasodilatation, thereby increasing blood flow and the delivery of substrates.With repeated seizures, delivered 2 min apart, glycogen declined progressively, but concentrations of the adenine nucleotides appeared to plateau, suggesting that a new energy balance had been established. However, after 20–25 seizures, the attacks became self‐generating and there was a further reduction in the tissue high energy phosphate stores, a fall in brain glucose and in the brain/blood glucose ratio. It is concluded that the brain possesses a limited capacity to adjust its metabolism to meet the increased energy requirements of single or repeated seizures, but that this mechanism ultimately fails during status epilepticus unless the abnormal electrical discharges, themselves, are brought under control.
THE DISTRIBUTION OF GLUTAMATE DECARBOXYLASE IN RAT TISSUES; ISOTOPIC VS FLUORIMETRIC ASSAYS
Authors: MacDonnell P. , Greengard O. 
Published: October 2006

Abstract—The activity of glutamate decarboxylase (GAD, EC 4.1.1.15) in normal and neoplastic rat tissues was determined by two assay methods, one based on the production of 14CO2 from [14C]glutamic acid and the other on the fluorimetric measurement of γ‐aminobutyric acid (GABA) formation. Activities obtained with the isotopic assay were high in every tissue (ranging from over 800 in liver and brain to 107nmol CO2/min/g in lung). They were drastically diminished by Triton X‐100, by an oxygen‐free atmosphere or by the mitochondrial electron transport inhibitors, rotenone and antimycin A. Activities measured fluorimetrically were significant in only a few tissues and were stimulated by Triton (e.g. from 299 to 569 nmol GABA/min/g brain) but were unaffected by rotenone. For several tissues after Triton treatment the fluorimetric and isotopic assays (in air) gave the same results (i.e. the two end products, CO2 and GABA were in stoichiometric agreement); however, the fluorimetric assay remains the more reliable measure of GAD activity since Triton may not inhibit completely the non‐GAD dependent decarboxylation of glutamate in all types of tissue preparations. The hepatic, renal and mammary tumours tested were devoid of GAD; among non‐neural normal tissues, kidney, liver and, possibly, adrenal gland contained significant GAD activity. In kidney and liver the activity was 15 and 10 per cent of that in brain.
IMMUNOLOGICAL STUDIES OF THE RAT OLFACTORY MARKER PROTEIN1
Authors: Keller Angelica , Margolis F. L. 
Published: October 2006

Abstract— Antisera against the rat olfactory marker protein were prepared by injection of the homogeneous protein into a goat and a rabbit. When the antisera were tested by immunodiffusion against olfactory tissue extracts, many but not all mammalian species cross‐reacted against these antisera. Immunoprecipitin titrations with the goat antiserum generally showed higher cross‐reactivity against olfactory extracts from species more closely related to the rat. Human olfactory bulb extracts and non‐mammalian olfactory tissue extracts did not cross‐react with the antisera by either immunodiffusion tests or immunoprecipitin titrations, however, they did cross‐react when tested by a competitive binding radioimmunoassay using tritium‐labelled purified rat protein and the goat antibody.The olfactory marker protein which is an example of a brain protein specific to one cell, the olfactory chemoreceptor neuron, has a very wide species distribution, being present in rat, mouse, hamster, guinea‐pig, sheep, cow, rabbit, pig, dog, man, frog and garfish. Therefore it presumably plays an important and unique role related to the function of this primary chemosensory neuron.
DECREASED RATE OF GLUCOSE UTILIZATION BY RAT BRAIN IN VIVO AFTER EXPOSURE TO ATMOSPHERES CONTAINING HIGH CONCENTRATIONS OF CO2
Authors: Miller A. L. , Hawkins R. A. , Veech R. L. 
Published: October 2006

Abstract—(1) The effects of exposure of rats to increased atmospheric concentrations of CO2 on brain metabolism in vivo were studied. (2) After 2·5 min exposure to an atmosphere of 20% CO2, the rate of glucose utilization by brain decreased from 0·61 μmol/min per g to 0·32 μmol/min per g and remained between 0·3 and 0·4 μmol/min per g for 60 min, the longest interval studied. O2 utilization, calculated from the arteriovenous difference of O2 across the brain and blood flow, was 3·5 μmol/min per g in controls and was 4·7 μmol/min per g after 5 min in the 20% CO2 atmosphere. (3) The concentrations of glucose, glucose 6‐phosphate and aspartate were increased during the first 10 min of CO2 exposure whereas the concentrations of other glycolytic intermediates, tricarboxylic acid cycle intermediates and glutamate were decreased. The amount of endogenous substrate which disappeared during the first 10 min was sufficient, if used to supplement glucose as a fuel, to maintain the O2 consumption at, or slightly above, the control level. Glutamate and lactate were quantitatively the most important energy sources. (4) The mechanism whereby‘CO2 decreased the rate of glucose utilization is uncertain. The initial rise in glucose 6‐phosphate and fall in fructose 1,6‐diphosphate concentrations suggested that an inhibition of phosphofructokinase was responsible. However, after 60 min in 20% CO2, the concentrations of both of these metabolites returned to normal while the rate of glucose utilization remained depressed.
PROTEIN SYNTHESIS IN CENTRAL NERVOUS TISSUE: STUDIES ON RETINA IN VITRO1
Authors: Parks J. M. , Ames A. , Nesbett F. B. 
Published: October 2006

Abstract—Rabbit retinas were maintained in vitro in medium that resembled CSF but with leucine varied from 2 to 1000μM. Both leucine and threonine were isotopically labelled. When leucine in the medium was 100‐1000μM, leucine was incorporated into protein at 2.03 ± 0.04 (s.E.M.) μmol/g dry wt./h, a turnover per h of 0.55% of the leucine in retinal protein. Incorporation was constant for at least 7 h. It was reduced 34% when the other amino acids were omitted from the medium and 24% when they were increased 15 fold above physiological levels. When medium leucine was reduced to 2 μM with other amino acids constant, 14C‐leucine incorporation fell 70%; without significant change in 3H‐threonine incorporation, indicating a fall in intracellular specific activity of leucine. The intracellular/extracellular concentration ratio of labelled leucine was 4:1 with medium leucine 23 μM. It fell markedly when medium leucine was reduced to 2 μM or increased to 1000 μM. The concentration ratio of labelled threonine was 15:1 with medium leucine at physiological levels but fell to 6:1 when medium leucine was increased to 1000 μM. Decarboxylation removed 1.5% of free intracellular leucine per min and, at physiological concentrations, was 7.7% the rate of protein incorporation. The ratio of protein synthesis/breakdown, estimated from changes in leucine and 7 other essential amino acids in the medium, was nearly unity. The potential of this preparation for study of CNS protein metabolism is discussed.