bluuebunny/crossref_metadata_2025_split huggingface dataset:
NEUROCHEMICAL AND STRUCTURAL STUDIES ON THE MECHANISM OF ACTION OF HEMICHOLINIUM‐3 IN CENTRAL CHOLINERGIC SYNAPSES
Authors: De Lores Arnaiz Georgina Rodríguez , Zieher L. M. , De Robertis E. 
Published: October 2006

Abstract—The action of hemicholinium‐3 (HC‐3) on the cerebral cortex of the rat was studied after subarachnoidal administration. There was a marked decrease of content of ACh in nerve endings and especially in the fraction containing synaptic vesicles, despite the fact that the number of synaptic vesicles was not reduced, as judged by electron microscopy, by the rate of incorporation of ortho [32P]phosphate, and by the phosphorus content of the phospholipids of the isolated synaptic vesicles. There was a close association of [l4C]HC‐3 and of monoaminoxidase, which indicated that the drug was preferentially bound to mitochondria. Experiments indicating that HC‐3 could be acetylated suggested that this drug may compete with choline not only for entry but also for acetylation.
REVERSIBLE CHANGES IN GLUTAMINE LEVELS IN THE CAT CEREBRAL CORTEX EVOKED BY AFFERENT ELECTRICAL STIMULATION AND BY ADMINISTRATION OF PENTAMETHYLENETETRAZOLE (PENTYLENETETRAZOL)
Authors: DOBKIN J. 
Published: October 2006

Abstract—1. Levels of glutamine and glutamate were measured in cat cerebral cortex rapidly frozen in situ after 30 sec of afferent electrical stimulation (AES) of the contralateral brachial plexus. A substantial decrease in glutamine and a minor one in glutamate were found as compared to the ipsilateral cortex. The fall in glutamine was found to be reversed very shortly after break of the current.2. Glutamine levels of the cortex determined after rapid freezing in situ were found to fluctuate with the diverse stages of periodic convulsions induced by pentylenetetrazol (PTZ): glutamine was substantially decreased during the initial part of the first clonictonic convulsion, it returned to the normal value in its termination stage and remained so at the commencement of the interictal recovery period, dropping again shortly before the onset and in the course of the second convulsion. The second drop in glutamine was accompanied by a decrease of glutamate. In the comatose state which followed convulsions, both glutamine and glutamate were again at their original concentrations.3. The results suggest that the view of the metabolic stability of brain glutamine under cerebral stimulation—based on past reports—should be modified in the sense that glutamine is labilized by excitation, but this effect is obscured by the counteracting process of synthesis de novo.4. The significance of the data reported here, in relation to the incidence and termination of convulsions, as well as the mechanisms which may be involved in the observed fall and restitution of the level of cerebral glutamine, are discussed.
REGIONAL DISTRIBUTION OF COLCHICINE‐BINDING (MICROTUBULAR) PROTEIN IN THE RAT BRAIN1
Authors: Dahl D. R. , Redburn D. A. , Samson F. E. 
Published: October 2006

Abstract—The relative concentrations of microtubular protein (tubulin) in regions of rat brain were determined by taking advantage of its specific property of binding colchicine. In comparison with other tissues, all regions of the brain were rich in tubulin. The cerebral cortex, thalamus and hypothalamus had essentially the same concentration. The cerebellum and brain stem had a lower concentration (about 60 per cent of the cortical level). Although the functional significance of these differences is not clear, they may relate to two proposed functions of microtubules–cytoskeleton and cytoplasmic transport. The complex geometry of neurons and many glial cells with ramified processes must require extensive systems for maintaining shape and an active cytoplasmic transport.
BINDING OF MUSCARONE BY EXTRACTS OF HOUSEFLY BRAIN: RELATIONSHIP TO RECEPTORS FOR ACETYLCHOLINE
Authors: Eldefrawi A. Toppozada , O'Brien R. D. 
Published: October 2006

Abstract—The supernatant fluid fraction isolated by centrifugation from a homogenate of heads of houseflies bound muscarone reversibly, with a binding constant of 2·4 × 10−6m and an amount of 70 nmol/g of protein. Studies with 28 drugs demonstrated strong blockade by the 17 cholinergic agents, suggesting both nicotinic and muscarinic characteristics in the mode of binding. The binding appeared to involve acetylcholine receptors.
PIG BRAIN GLUTAMINASE: PURIFICATION AND IDENTIFICATION OF DIFFERENT ENZYME FORMS
Authors: SVENNEBY G. 
Published: October 2006

Abstract—Pig brain glutaminase (EC 3.5.1.2 L‐glutamine amidohydrolase) has been purified about 5000‐fold from acetone powder. Glutaminase exists in different molecular forms, dependent on the ionic composition of the buffer. The three main forms are similar to those of kidney glutaminase and therefore called the tris‐HCl enzyme, the phosphate enzyme, and the phosphate‐borate enzyme. The sedimentation coefficients, as estimated by sucrose gradient technique, are 7·3, 8·7, and 53, respectively. Glutaminase has a pH optimum of about 9, but the pH curves of the tris‐HCl enzyme and the phosphate‐borate enzyme have different shapes. The apparent pK1 of the tris‐HCl enzyme‐substrate complex is similar to pK2 of inorganic phosphate, the apparent pK2 of both the tris‐HCl and the phosphateborate enzyme complexes is similar to pK2 of glutamine. By use of the electron microscope we were able to see the phosphate‐borate enzyme.
THE INCORPORATION OF ISOTOPIC CARBON 14C INTO THE CEREBRAL GLYCOGEN OF NORMAL AND X‐IRRADIATED RATS
Authors: Lundgren P. R. , Miquel J. 
Published: October 2006

Abstract—Maximal incorporation of 14C from labelled glucose into cerebral glycogen of the rat occurred at 3‐6 h following intravenous injection of the precursor. A reduction of the rate of glycogen breakdown is the most likely cause of the glycogen accumulation observed in rat brain following exposure to 10 krad of X‐radiation.
FURTHER STUDIES ON THE EFFECTS OF BLOCKING AGENTS ON PROTEIN SYNTHESIS IN GOLDFISH BRAIN1
Authors: Lim R. , Brink J. J. , Agranoff B. W. 
Published: October 2006

Abstract— In further experiments on the effects of antibiotic agents on protein synthesis in the goldfish brain, doses of intracranially‐injected puromycin or acetoxycycloheximide higher than those previously employed did not hasten the onset of inhibition of incorporation of intraperitoneally‐injected [3H]leucine into brain protein.The antibiotic‐resistant incorporation was not due to the presence of labelled blood protein in the brain. After the intracranial injection of labelled puromycin, the appearance of radioactivity in the acid‐soluble fraction of brain was blocked by acetoxycycloheximide. Repeated daily intracranial or intraperitoneal injections of puromycin were lethal, and acetoxycycloheximide was not protective, indicating that peptidyl‐puromycin was present in the brain but did not account for the lethality of puromycin. Behavioural experiments argued against but did not totally exclude the possibility that peptidyl‐puromycin was responsible for the amnestic effect of puromycin. Puromycin aminonucleoside, O‐methyl tyrosine and 5‐guanylyl methylenediphosphonate had little or no effect on protein synthesis in brain, but gougerotin was slightly inhibitory.
EFFECTS OF POTASSIUM ON INDICATOR SPACES AND FLUXES IN SLICES OF BRAIN CORTEX FROM ADULT AND NEW‐BORN RATS
Authors: Schousboe A. , Hertz L. 
Published: October 2006

Abstract—Inulin, sucrose and chloride spaces were measured in slices of brain cortex from adult and from new‐born rats incubated in‘balanced', potassium‐rich and sodium‐rich media. The efflux of the radioactive markers was followed in the two first media and the following results were obtained:(1) In brain slices from new‐born rats inulin and sucrose spaces were of identical magnitude (35 per cent). The space magnitude was essentially unaffected by excess potassium. The chloride space was somewhat larger than the inulin (sucrose) space, and the difference increased continuously but relatively slightly with the external potassium concentration. By far the largest amount (i.e. about 90 per cent) of the efflux of radioactive inulin, sucrose and chloride occurred from a rapidly exchanging compartment during incubation in both ‘balanced’ and potassium‐rich media.(2) In brain slices from adult rats the inulin space (35 per cent) was significantly smaller than that of sucrose (50 per cent) and of chloride (65 per cent); it seemed to represent the extracellular space relatively well although 10 per cent of the efflux occurred from a slowly exchanging (probably intracellular) compartment. High concentrations of potassium led to a reduction of the inulin space which was probably a result of the concomitant intracellular swelling. The hyperosmolarity per se did not affect the space magnitude, but an increase of the sodium concentration exerted a competitive inhibition of potassium effects on the inulin space. Of the sucrose efflux, 20 per cent occurred from a slowly exchanging compartment in both ‘balanced’ and potassium‐rich media, and 30 per cent of the chloride exchanged with this compartment when the tissue was incubated in a ‘balanced’ medium. An increase of the external potassium concentration caused a drastic increase of the chloride space and a reduction of the slowly exhanging fraction of chloride efflux to less than 10 per cent.
REGULATION OF PYRUVATE KINASE IN THE RAT CEREBRAL CORTEX1
Authors: Schwark W. S. , Singhal R. L. , Ling G. M. 
Published: October 2006

Abstract—The distribution of pyruvate kinase (ATP: pyruvate phosphotransferase; EC 2.7.1.40) in several areas of the central nervous system, the ontogenic changes in the cerebro‐cortical enzyme, and its modulation by certain metabolites were investigated in the rat. No significant differences in activity of pyruvate kinase in different regions of the nervous system were detected when activity was expressed per g of tissue. Studies on the ontogeny of pyruvate kinase in cerebral cortex revealed extremely low levels of enzymic activity at birth. A two‐fold increase occurred between 1 and 20 days of postnatal age, with a further two‐fold increase between 20 and 60 days of age. l‐Phenylalanine, when added directly into the reaction mixture, produced a dose‐dependent inhibition of cerebro‐cortical pyruvate kinase; a similar inhibition of the enzyme activity was observed with copper. The inhibition by l‐phenylalanine and copper was prevented and reversed by l‐alanine. Although the cerebro‐cortical enzyme was resistant to thermal inactivation at 37°C, incubation of the enzyme preparation at 55°C for 60 min resulted in approximately 60 per cent inhibition of its activity. Preincubation with l‐alanine provided partial protection against thermal inactivation of the enzyme. Although l‐alanine exerted no effect on the non‐competitive inhibition of pyruvate kinase produced by calcium, such inhibition was prevented and reversed by EDTA. The sulphydryl inhibitor, P‐chloromercuribenzoate, produced a dose‐dependent inhibition of cerebro‐cortical pyruvate kinase, whereas addition of penicillamine resulted in a slight activation of the enzyme. Although inhibition of pyruvate kinase by P‐chloromercuribenzoate was unaffected by l‐alanine, penicillamine effectively prevented and reversed the inhibition produced by P‐chloromercuribenzoate.
CHOLINE ACETYLTRANSFERASE AND ACETYLCHOLINESTERASE IN CULTURED BRAIN CELLS FROM CHICK EMBRYOS
Authors: Werner I. , Peterson G. R. , Shuster L. 
Published: October 2006

Abstract—Dissociated cells from brains of 7‐day chick embryos were grown in primary culture for as long as 20 days. Many of the plated cells grew out long processes. Others, which proliferated rapidly, formed a confluent layer of flat cells after 4‐6 days. Total DNA and protein increased five‐fold, and activity of choline acetyltransferase (EC2.3.1.6) increased about 40‐fold in 20 days. Acetylcholinesterase (EC3.1.1.7) increased three‐fold by the fourth day of culture and then declined. The pattern of increase for choline acetyltransferase was similar to that for the in vivo development of the enzyme. l‐Thyroxine, cyclic AMP (adenosine‐3′,5′‐monophosphate) or theophylline promoted increased levels of both enzymes by 30‐200 per cent. l‐Thyroxine also increased the activity of acetylcholinesterase in vivo by 40 per cent. When overgrowth by flat cells was prevented by the addition of 10‐3m‐5‐flourouracil, there was a decrease in the activity of choline acetyltransferase and an increase in the activity of acetylcholinesterase in comparison to control activities. The addition of 10‐3m‐morphine or cocaine produced a 30 per cent elevation in the activity of choline acetyltransferase, but this effect could be mimicked with equimolar concentrations of ammonium ion.
MEMBRANE FRAGMENTS FROM MYELIN TREATED WITH DIFFERENT DETERGENTS
Authors: McIlwain D. L. , Graf L. , Rapport M. M. 
Published: October 2006

Abstract—Bovine CNS myelin treated with cationic, anionic and non‐ionic detergents yielded fragments which did not sediment in water at 56,500 g for 15 min. Substantial chemical and immunological differences were observed among the myelin fragments produced by these detergents. The chemical and immunological characteristics of such membrane products were also dependent upon the concentration of detergent. These and similar findings with other biological membranes emphasize the difficulties in using detergents to obtain and examine proposed subunit structures.
GLYCOL SULPHATE ESTER FORMATION FROM [14C]NORADRENALINE IN BRAIN AND THE INFLUENCE OF A COMT INHIBITOR
Authors: Sugden R. F. , Eccleston D. 
Published: October 2006

Abstract—A method is described allowing the identification and separation of the sulphate esters of the glycol metabolites of [14C]noradrenaline injected into the lateral ventricle of the rat. The esters of both the 3,4‐dihydroxy derivative and the 3‐methoxy‐4‐hydroxy derivative are formed in substantial amounts. It is suggested that the quantity of the former may have been underestimated in the past. Contemporaneous administration of pyrogallol, a catechol‐O‐methyl transferase inhibitor, with [14C] noradrenaline leads to a considerable fall in 3‐methoxy‐4‐hydroxyphenylglycol sulphate without a rise in 3‐4‐dihydroxyphenylglycol sulphate although free 3‐4‐dihydroxyphenylglycol rises significantly. It is proposed that the latter may be an index of intraneuronal metabolism of noradrenaline and 3‐methoxy‐4‐hydroxyphenylglycol that of released amine.
IN VlTRO BINDING OF PHENYLALANYL‐tRNA TO NEONATAL AND ADULT MOUSE BRAIN RIBOSOMES
Authors: Chou L. , Lerner M. P. , Johnson T. C. 
Published: October 2006

Abstract—The ability of brain ribosomes, isolated from mice of various ages, to bind phenylalanyl‐tRNA was measured under various reaction conditions. In the presence of template RNA (polyuridylic acid) the binding could be measured by both enzymic and non‐enzymic assays. In general, the binding requirements for the brain system were similar to those previously described for microbial and eukaryotic systems. Although previous studies have shown that ribosomes obtained from increasingly older mow brain tissue were less active in polyphenylalanine synthesis, no significant differences in phenylalanyl‐tRNA binding to polysome complexes could be detected. The binding of phenylalanyl‐tRNA by ribosomes isolated from both neonatal and mature mouse brain tissue was similar with regard to GTP and polyuridylic acid dependence, magnesium ion concentration and reaction kinetics. Similar binding of phenylalanyl‐tRNA by young and mature brain ribosomes was also measured with ribonucleoprotein particles previously stripped with puromycin. The results are discussed in light of the rapid alteration of macromolecular synthesis during postnatal brain development and the possible role of the interaction between ribosomes and tRNA.
AMINO ACID METABOLISM AND AMMONIA FORMATION IN BRAIN SLICES
Authors: Weil‐Malherbe H. , Gordon J. 
Published: October 2006

AbstractThe formation of ammonia and changes in the contents of free amino acids have been investigated in slices of guinea pig cerebral cortex incubated under the following conditions: (1) aerobically in glucose‐free saline; (2) aerobically in glucose‐free saline containing 10 mM‐bromofuroic acid, an inhibitor of glutamate dehydrogenase (EC 1.4.1.2); (3) aerobically in saline containing 11‐1 mM‐glucose and (4) anaerobically in glucose‐free saline. Ammonia was formed at a steady rate aerobically in glucose‐free medium. The formation of ammonia was largely suppressed in the absence of oxygen or in the presence of glucose whereas the inhibitor of glutamate dehydrogenase produced about 50 per cent inhibition. Other inhibitors of glutamate dehydrogenase exerted a similar effect. Ammonia formation was also inhibited by some inhibitors of aminotransferases but not by others. Inhibition was generally more pronounced during the second and third hour of incubation.With the exception of glutamine which decreased slightly, the contents of all amino acids increased markedly during the anaerobic incubation. During aerobic incubation in a glucose‐free medium, there was an almost complete disappearance of glutamic acid and GABA. Glutamine also decreased, but to a relatively smaller extent. The content of all other amino acids increased during aerobic incubation in glucose‐free medium, although to a lesser extent than under anaerobic conditions. The greater increase of amino acids appearing anaerobically in comparison to the increase or decrease occurring under aerobic conditions corresponded closely to the greater amount of ammonia formed aerobically over that formed anaerobically. This finding is interpreted as indicating a similar degree of proteolysis under anaerobic and aerobic conditions; aerobically, the amino acids are partly metabolized with the concomitant liberation of ammonia.In glucose‐supplemented medium, the content of glutamine was markedly increased. The content of glutamate and aspartate remained unchanged, whereas that of some other amino acids increased but to a lesser extent than in the absence of glucose. Proteolysis in the presence of glucose was estimated at about 65 per cent of that in its absence. In the presence of bromofuroate the rate of disappearance of glutamate was unchanged, but there was a larger increase in the content of aspartate and a smaller decrease of GABA and glutamine. Other changes did not differ significantly from those observed in the absence of bromofuroate. We conclude that the metabolism of amino acids in general and of glutamic acid in particular differs according to whether they are already present within the brain slice or are added to the incubation medium. Only the endogenous amino acids appear to be able to serve as precursors of ammonia and as substrates for energy production.
THE DETERMINATION OF ACETYLCHOLINESTERASE ACTIVITY OF BRAIN SLICES AND ITS SIGNIFICANCE IN STUDIES OF EXTRACELLULAR ACETYLCHOLINESTERASE
Authors: Hobbiger F. , Lancaster R. 
Published: October 2006

AbstractThe AChE activity of single slices obtained from the surface of the temporoparietal region of rat brains was measured colorimetrically under anaerobic conditions with acetylthiocholine as substrate. In intact slices from untreated rats AChE activity was only a small proportion of that of homogenates made from the slices, but this proportion increased with the surface area to weight ratio of slices and with an increase in substrate concentration, intact slices not showing substrate inhibition. The inhibition of AChE determined in slices from rats treated with DFP or paraoxon was less than that in homogenates obtained from the slices. When the access of substrate was limited to the cut surface of a slice, the rate of hydrolysis was four times greater than that observed when access was solely from the uncut surface. It is concluded that under anaerobic conditions the substrate diffuses into slices to a depth which is not constant but a function of both substrate and enzyme concentration. Thus the AChE activity of slices cannot be used as a measure of extracellular AChE.
QUAKING MOUSE: ISOLATION AND CHARACTERIZATION OF MYELIN PROTEIN
Authors: Greenfield S. , Norton W. T. , Morell P. 
Published: October 2006

AbstractA new technique, involving final purification on a continuous CsCl gradient, was utilized for the isolation of cerebral myelin from adult (4‐ to 6‐month‐old) quaking mice, littermate controls and young (10‐day‐old) normal mice. The yield of myelin from either adult quaking or normal young mice was 5‐10 per cent of that from adult controls. After deli‐pidation, myelin proteins were separated by polyacrylamide gel electrophoresis in buffers containing sodium dodecylsulphate. Two gel systems were utilized: (1) a high‐resolution discontinuous electrophoresis system; and (2) a continuous system utilizing gels cross linked with ethylenediacrylate (EDA). The gels from the discontinuous system were stained with Fast Green and quantified by densitometry. The base lability of the EDA‐linked gels permitted direct chemical determination of protein in specific bands.Myelin from brains of normal adult mice contained, as major components, one proteo‐lipid and two basic proteins. There were also a number of high‐molecular‐weight proteins which represented a significant portion of the total. Myelin from quaking mice had qualitatively a similar distribution of proteins but the high‐molecular‐weight fraction comprised a much greater percentage of the total protein. The ratio of basic to proteolipid protein in preparations from quaking mice was considerably higher than that in the myelin from control mice. The distribution pattern of the myelin proteins from 10‐day‐old mice was quantitatively similar to that of quaking mice. Altogether the evidence supports the hypothesis that the quaking mutant provides a model of an immature nervous system with respect to myelination.
EFFECTS OF GLUTAMATE AND OTHER AMINO ACIDS ON THE RETINA1
Authors: Harreveld A. Van , Fifkova Eva 
Published: October 2006

AbstractThe application of unlabelled glutamate to the isolated chicken retina charged with [14C]glutamate caused an increase in the tissue transparency and a release of the label into the superfusion fluid. The processes causing the change in transparency were‘desensitized’by a prolonged application of unlabelled glutamate, whereas the release of the labelled amino acid was relatively unaffected. Mg2+ tended to depress the change in transparency caused by stimulation with unlabelled glutamate but had little effect on the release of labelled glutamate from the retina. The effect of a Ca2+‐free superfusion fluid on the transparency and release of glutamate varied from retina to retina. Aspartate (in higher concentrations) elicited a change in transparency and release of the label in a manner similar to that of glutamate. Glutamine caused a change in transparency accompanied by a release of labelled glutamine and in some experiments the release of a small amount of labelled glutamate. Homocysteic acid elicited marked changes in transparency but no release of labelled glutamate. Pyroglutamate depressed both the change in transparency and the release of labelled glutamate caused by the unlabelled amino acid. Gamma‐aminobutyric acid and glycine had no effect on the transparency of the tissue or on the release of amino acids. We have discussed the possibility that a release of glutamate from the intracellular compartment into the extracellular space is involved in the mechanism of spreading depression.