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  • Blackwell Publishing Ltd  (15,605)
  • 1970-1974  (15,605)
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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Birth 1 (1974), S. 0 
    ISSN: 1523-536X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Birth 1 (1974), S. 0 
    ISSN: 1523-536X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Birth 1 (1974), S. 0 
    ISSN: 1523-536X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Birth 1 (1974), S. 0 
    ISSN: 1523-536X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Birth 1 (1974), S. 0 
    ISSN: 1523-536X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Birth 1 (1974), S. 0 
    ISSN: 1523-536X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Birth 1 (1974), S. 0 
    ISSN: 1523-536X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 8
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Apomorphine (A) inhibited dopamine deamination by rat brain mitochondria, but did not influence catechol-O-methyltransferase (COMT) activity by brain homogenates. The administration of apomorphine (10mg/kg i.p.) to normal rats increased brain dopamine (DA) by 34 per cent and decreased homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC) by 60 per cent. In rats treated with reserpine 15 min prior to A, the latter prevented the rise of cerebral HVA and DOPAC and the depletion of DA produced by the former. Finally, A decreased the L-DOPA-induced accumulation of HVA and DOPAC in the rat basal ganglia. These results indicate that A inhibits DA deamination by monoamine oxidase.This inhibition seems to be specific since apomorphine did not influence 5-HIAA levels in normal rats and prevented neither central 5-HT depletion nor 5-HIAA rise induced by reserpine.
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  • 9
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The ACh content of the rat hippocampus, visual cortex, auditory cortex and corpus striatum was estimated as so-called free, labile-bound and stable bound acetylcholine at different times after the learning of a brightness discrimination.In the hippocampal region the free acetylcholine was highly increased immediately after the training, whereas the stable bound ACh and the labile-bound fraction rose 70 min and 4 h respectively-after completion of training.Only small alterations of the ACh fractions were observed in the visual and auditory cortices. In the corpus striatum no changes appeared.
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  • 10
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The activity of cyclic AMP phosphodiesterase of rat cerebral homogenates increased several-fold between 1 and 60 days of age. Enzyme activity in the cerebellum, on the other hand, did not increase during this period. A kinetic analysis of the phosphodiesterase activity revealed evidence for multiple forms of the enzyme and indicated that the postnatal increase in phosphodiesterase activity of rat cerebrum was due almost exclusively to the high Km enzyme. In cerebellum, the ratio of the high and low Km enzyme remained fairly constant during ontogenetic development.Physical separation of the phosphodiesterases contained in 100,000 g soluble supernatant fractions of sonicated brain homogenates by polyacrylamide disc gel electrophoresis confirmed the presence of multiple enzyme forms. In adult rats we found six distinct peaks of phosphodiesterase activity (designated I to VI according to the order in which they were eluted from the column) in cerebellum and 4 forms of the enzyme (Peaks I through IV) in cerebrum. Brains of newborn rats had a different pattern and ratio of phosphodiesterase activities. For example, Peak I phosphodiesterase was undetectable in cerebrum or cerebellum of newborn rats. Moreover, in the cerebellum of newborn rats Peak II was the dominant peak whereas in the cerebellum of adult rats Peak III was the largest peak. A comparison of the multiple forms of phosphodiesterase from the cerebrum of newborn and adult animals suggested that the postnatal increase in phosphodiesterase activity previously seen in crude homogenates was due largely to an increase in a high K, Peak II phosphodiesterase. The ratios of activities of the other peaks and their sensitivities to an activator of phosphodiesterase were similar in newborn and adult rats.An endogenous heat-stable activator of phosphodiesterase was found in cerebrum, cerebellum and brain stem. In newborn rats, the cerebellum contained several-fold less activity of this activator than did cerebrum or brain stem. However, the activity of this activator increased with age in the cerebellum and would appear to have decreased postnatally in cerebrum and brain stem.These results suggest that some multiple forms of phosphodiesterase can develop independently and that changes in activities of these phosphodiesterases may occur by increases in the quantity of enzyme or by changes in the quantity of an endogenous activator of phosphodiesterase.
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  • 11
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Choline acetyltransferase (EC 2.3.1.6) catalyses the following reversible reaction: acetyl coenzyme A + choline acetylcholine + coenzyme A. Enzyme activity in the atria and ventricles of guinea-pig heart varied independently of the biochemically related carnitine acetyltransferase (EC 2.3.1.7). Choline acelyltransferase activity was greatest in right atrium, intermediate in right ventricle and left atrium and lowest in left ventricle (405. 2-33. 177 and I 33 nmol min-1 g-1, respectively). Carnitine acetyltransferasc activity was greatest in the right and left ventricle and least in the right and left atria (8-86. 8-27, 3-18 and 2-38 mmol min-1g-1. respectively). Carnitine acelyltransferase activity was 800- to 6000-fold greater than that of the choline acetyltransferase. depending on the chamber. Bromoacctylcholine inhibited acetylcholine. but not acetylcarnitine biosynthesis in vitro. Contrariwise, acetylcarnitine inhibited carnitine, but not choline acetyltransferase. These results demonstrate the feasibility and specificity of measuring the differences in choline acetyltransferase activity in dialysed homogenates prepared from the four chambers of the heart.
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  • 12
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The effects of divalent metal ions, sulfhydryl reagents, carbonyl trapping reagents, substrate analogs, and organic solvents on purified mouse brain 4-aminobutyrate-2-ketoglutarate transaminase (EC 2.6.1.19) and the subunit structure of this enzyme were studied. Of the metal ions tested, Hg2+ was found to be the most potent inhibitor inhibiting the enzyme 50 percent at a concentration of 0-7 μM. The order of decreasing inhibitory potency for the divalent metal ions was: Hg2+± Cd2+± Zn2+± Cu2+± Co2+± Ba2+± Sr2+± Ni2+± Mn2+± Ca2+± Mg2+. p-Chloromercuribenzoale was the most potent inhibitor among the sulfhydryl reagents tested inhibiting the enzyme to the extent of 50 per cent at 0-5 μM 3-Mercaptopropionic acid was found to be a competitive inhibitor for GABA and non-competitive for 2-ketoglutarate. The Ki, value was estimated to be 13 μM. Aminooxyacetic acid was the most potent inhibitor of the carbonyl trapping agents with a K, value of 0-06 μM. being competitive with GABA and non-competitive with 2-ketoglutarate. Hydroxylamine and hydrazine were the next most potent compounds in this group. Of a series of substrate analogs and metabolites tested, only acetic acid, propionic acid, butyric acid, glutamic acid, adipic acid, pimelic acid and 2-ketoadipic acid inhibited the enzyme to a significant extent. Dioxan inhibited the enzyme 50 per cent at a concentration of 5 per cent (v/v) whereas methanol and ethanol only inhibited 5-10 per cent at 10 per cent (v/v) concentration.A spectrum of the native enzyme at pH 7-2 showed maxima at 278 nm. 330 nm and 411 nm. Treatment of the enzyme with aminooxyacetic acid or 3-mercaptopropionic acid caused the maximum at 411 nm to disappear.Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the enzyme revealed two protein bands. The molecular weights of these two subunits were determined to be 53.000 and 58,000, respectively.
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  • 13
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 14
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 15
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 16
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —The effects of various cations and cholinergic ligands on the rate of α-bungarotoxin-acetylcholine receptor complex formation has been studied by means of a DEAE-cellulose disk assay technique. The reaction rate is reduced to one half the initial rate in the presence of 2·5 · 10−6m acetyleholine. a value close to the observed KD of ACh measured by equilibrium dialysis. Inhibition constants of about 5 mM were obtained for most monovalent cations whereas divalent cations gave inhibition constants of 0·05-0·2 mm. The rate and extent of toxin-receptor complex formation was also investigated as a function of hydrogen ion concentration; the rate of formation reaches a maximum at pH 7·5 and a group with a pK about 6 inhibits toxin binding to the receptor when protonated.These data can be correlated with the observed effects of inorganic cations on the binding of cholinergic ligands in vivo at the neuromuscular junction. Given the affinities of the individual cations, it is possible to predict how the apparent affinity of a cation-sensitive cholinergic ligand will change with variations of buffer composition.
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  • 17
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —Acute injections of LSD (2 × 500 μg/kg) to rats resulted in evidence of a reduced 5-hydroxytryptamine (5-HT) turnover in all brain areas studied. In contrast, a much smaller dose of LSD (20 μg/kg) repeated daily for 1 month produced a significantly reduced turnover only in the midbrain area. The pons/medulla and forebrain areas showed small and not statistically significant increases in 5-HT turnover.
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  • 18
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —An electrophoretic investigation in acrylamide gels of 5-hydroxytryptophan decarboxylase, obtained mostly from mouse, rat, and beef brain and also from beef and human liver, showed electrophoretic differences between species. With the exception of the rat, only one molecular species was found (the same in beef brain and liver). In the rat, polymers form spontaneously and are, at least in part, disaggregated by urea and by triton. Mouse-rat or beef-rat molecular hybrids form in the admixtures. No electrophoretic differences were found in five mice strains that were investigated. Techniques of electrophoretic analysis and of assay of 5-hydroxytryptophan decarboxylase are described, which can be easily applied to other enzymes, provided a substrate is available in radioactive form.
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  • 19
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —[14C]-Glutamate and [14C]-glutamine were incorporated into calf brain tRNA in the presence of homologous aminoacyl-tRNA synthetases. When the tRNAs were then deaminoacylated and chromatographed, a number of radioactive products were found in addition to the original amino acids. One of the products of glutamate transformation was identified to be glutamine. Formation of the radioactive products of glutamate in the presence and absence of tRNA indicated that glutamine was produced from glutamate at the level of the free amino acid followed by the incorporation of both substances into tRNA. Examination of the products of deaminoacylation of glutaminyl-tRNA showed that glutamine underwent structural alterations at the level of the aminoacyl-tRNAs to give rise to a cyclic derivative of glutarimide. This reaction was specific for glutamine, and constituted approximately 15 per cent of the total radioactivity in the deaminoacylation products of glutaminyl-tRNA.
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  • 20
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —The redistribution of rapidly migrating [3H]leucine-labelled proteins was studied using double ligatures applied to the vagus nerve and single ligatures, applied to the hypoglossal nerves. Rapidly migrating proteins accumulating for 16 h proximal to a distal ligature of the cervical vagus redistributed to give a retrograde accumulation distal to a second ligature. Within 6 h a substantial redistribution occurred indicating a rapid retrograde transport. After 21 h there was a further accumulation with 70 per cent of the labelled material accumulating at the distal end of the isolated nerve segment and 16 per cent accumulating at the proximal end. It was shown that about a half of the retrograde accumulation was dependent on the distal accumulation zone. Rapidly migrating proteins accumulated distal to a ligature applied to the hypoglossal nerve 16 h after labelling of the nerve cell bodies indicating that a rapid retrograde transport of labelled macromolecules occurs from the peripheral parts of the nerve in the tongue. Labelled proteins accumulated proximal to ligatures and transections of both the hypoglossal and vagus nerve when applied 16 h after labelling of the nerve cell bodies, indicating the presence of axonal proteins, migrating at a rate of transport intermediate to that of rapidly and slowly migrating proteins.
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  • 21
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —The influence of insulin-induced hypoglycemia upon carbohydrate substrates, amino acids and ammonia in the brain was studied in lightly anaesthetized rats, and the changes observed were related to the blood glucose concentration and to the EEG. Calculations from glucose concentrations in tissue, CSF and blood indicated the presence of appreciable amounts of free intracellular glucose at blood glucose concentrations above 3 μmol/g. When the blood glucose concentration fell below 3 μmol/g, there was no calculated intracellular glucose and decreases in the concentrations of glycogen, G-6-P, pyruvate, lactate and of citric acid cycle intermediates were observed. At blood glucose levels of below 1 μmol/g the tissue was virtually depleted of glycogen, G-6-P, pyruvate and lactate.When the blood glucose concentration was reduced below about 2·5 μmol/g there were progressive increases in aspartate and progressive decreases in alanine, GABA, glutamine and glutamate, and at blood glucose concentrations below 2 μmol/g the ammonia concentration increased. It is suggested that most of the changes observed can be explained as a result of a decreased availability of pyruvate and of NADH. The decrease in the concentration of free NADH was reflected in reductions of the lactate/pyruvate and malate/oxaloacetate ratios at an unchanged intracellular pH.Slow wave activity appeared in the EEG when the hypoglycemia gave rise to reduction of the intracellular glucose concentration to zero. Convulsive activity continued until carbohydrate stores in the form of glycogen and G-6-P were depleted. When this occurred the EEG became isoelectric. In all convulsive animals the concentration of the nervous system activity inhibitor, GABA, was decreased and stimulant, aspartate, was increased.
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  • 22
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —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.
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  • 23
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —Au cours d'une période de stimulation, la réponse électrophysiologique de l'organe électrique évolue en trois phases successives: décroissance, palier, décroissance. Le taux d'acétylcholine (ACh) totale baisse durant la première décroissance. Il augmente pendant le palier, pouvant atteindre et même dépasser sa valeur initiale. Une nouvelle baisse de ce taux coïncide avec la dernière phase décroissante. Ces premières variations du taux d'ACh ne concernent que le compartiment libre’ ou disponible qui est défini dans le texte. Les corrélations décrites entre l'évolution de la décharge et celles de l'ACh ont été observées constamment dans différentes conditions de stimulation, in vivo et in vitro, aux fréquences de 1, 5 et 10/s. Une réduction de la température abrège et abaisse le palier de la réponse électrophysiologique, elle diminue la remontée de l'ACh disponible. Les premières variations de l'ACh disponible évoluent en fonction du temps selon un mode relativement indépendant de la fréquence de stimulation entre 1 et 10/s. Après une incubation en présence d'acétate 14C-1 qui est incorporé dans la moitié acétyl de l'ACh, le tissu est stimulé au contact du précurseur hautement radioactif. Dans ces conditions, les premières variations d'ACh disponible s'effectuent sans changement de sa radioactivité spécifique: le taux du transmetteur et sa radioactivitéévoluent parallèlement. L'ACh synthétisée pendant le palier doit par conséquent provenir d'un compartiment en équilibre avec l'ACh disponible ou du médiateur récemment libéré.Après la deuxième décroissance, la radioactivité spécifique de l'ACh disponible s'élève, traduisant l'épuisement du pool précurseur et l'incorporation de l'acétate très radioactif présent dans l'espace extracellulaire. A cette phase d'épuisement succède une utilisation de l'ACh vésiculaire stable, ou liée, qui semble alimenter le compartiment disponible. Le nombre des vésicules synaptiques comptées sur des micrographies électroniques peut alors diminuer. Si la stimulation est poursuivie encore plus longtemps, le nombre des vésicules retrouve ou même dépasse sa valeur initiale mais le taux d'ACh liée reste bas. Nous avons évalué la concentration de l'ACh dans les terminaisons nerveuses et celle de ses produits d'hydrolyse dans la fente synaptique. Cette dernière concentration, très élevée après un seul influx, pourrait être un des éléments essentiels du couplage entre la vitesse de synthèse de l'ACh disponible et celle de son utilisation.〈section xml:id="abs1-2"〉〈title type="main"〉Abstract—During a period of stimulation the electrophysiological response of the electric organ shows three successive phases: decrease, plateau and late decrease. The level of total acetylcholine (ACh) diminishes during the first decrease. It increases during the plateau phase, where it may reach or even exceed the initial value. A new diminution of the ACh level coincides with the last decreasing phase. The first changes in ACh only concern the ‘free’ or available compartment, which is defined in the text. The correlations between the changes of ACh and those of the electrophysiological discharge have been consistently observed under various conditions of stimulation, in vivo and in vitro, at frequencies of 1, 5 and 10/s. When the temperature is reduced, the plateau of the response becomes lower and shorter, and the corresponding increase in ACh is smaller. The time course of the first changes in the available ACh was not modified by the frequency of stimulation between 1 and 10/s. After an incubation with [1-14C]acetate, which is incorporated in the acetyl moiety of ACh, the tissue was stimulated in the presence of the highly radioactive precursor. Under these conditions, the first variations in the available ACh are not accompanied by any change in its specific radioactivity (RA.S), variations of the radioactive and non-radioactive transmitter being parallel. The ACh synthesized during the plateau should therefore originate either from a pool in equilibrium with the available ACh, or from the recently released transmitter. Following the second fall of the available ACh, its specific radioactivity increases indicating a greater incorporation of the highly radioactive acetate of the extracellular space in a diminished precursor pool. After this phase, bound (stable vesicular) ACh is utilized and appears to supply the available compartment. The number of synaptic vesicles counted in electron micrographs may diminish at this stage. If stimulation is still continued, the vesicles recover or even exceed their initial number whereas bound ACh remains at a low level. An estimate has been made of the concentration of ACh in nerve terminals and its hydrolysis products in the synaptic cleft. The latter concentration, very high after only one impulse, may be of importance for the coupling of the speed of synthesis and utilization of available ACh.
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  • 24
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —Intact and dissociated dorsal root ganglia from 8-day chick embryos were examined for their ability to incorporate radio-precursors into RNA and protein in unsupplemented medium or in medium supplemented with Nerve Growth Factor, insulin, Concanavalin A, fetal calf serum, or several combinations of such agents. In the absence of any agent, incorporation into RNA and protein declined with time. All four agents maintained or improved the initial incorporation rates, and optimal doses were determined in each case. Different combinations of two agents led to potentiated, full or partially additive, or inhibited effects; in particular, NGF promoted incorporation even in conjunction with insulin (additive) or serum (potentiating). Several differences were noted between the responses of intact and of dissociated ganglia.
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  • 25
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —Mercuric chloride, silver acetate and cupric sulphate (0·1 mm) completely inhibited purified choline acetyltransferase from bovine caudate nuclei. At the same concentration cadmium chloride and zinc acetate gave a 50 per cent inhibition. Potassium and sodium salts more than doubled the enzymatic activity while creatinine hydrochloride more than tripled it. Guanidine hydrochloride was less effective than creatinine hydrochloride but more effective than KCl and NaCl. Sodium chloride and creatinine hydrochloride had a synergistic effect on the enzyme.When ammonium sulphate was used to fractionate the choline acetyltransferase that had been extracted from bovine caudate nuclei, the enzyme aggregated into different molecular sizes as determined by exclusion chromatography on Bio-gel A-1·5 m. The molecular weight of the largest aggregate was at least 106 daltons. The initial tissue extract contained only one molecular species of ChAc as did a partially purified preparation in which ammonium sulphate was not used in the purification.
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  • 26
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The ATP concentration in infant rat cerebral cortex slices which were incubated aerobically with glucose (5 mm) as substrate was much higher than in those from the adult. The higher ATP concentration in slices from young rat was also obtained when they were incubated aerobically with pyruvate (10 mm), dl-lactate (20 mm) and dl-3-nydroxybutyrate (20 mm) However, when the slices were incubated anaerobically with glucose, the ATP concentration was very low. Thus, the formation of ATP in the slices from the young rat was thought to be mainly due to their oxidative metabolism, as in those from the adult. The amounts of glycolytic key enzymes in rat cerebral cortex (hexokinase. phosphofructokinase and pyruvate kinase) increased with age. Glycolysis was actually shown to be less active in the cerebral slices from young rats than from the adult. In addition it is known that the tricarboxylic acid cycle enzymes in rat cerebrum also increase with age. Consequently, the activity with respect to ATP formation must be lower in the cerebral cortex slices from young rats than from the adult. The fact that ATP was nevertheless higher in the slices from young rats may be explained by a lower rate of degradation. Developmental increases in the amounts of Na+-K+-ATPase and Mg2+ -ATPase in rat cerebral cortex were greater than those of the glycolytic key enzymes. These are discussed in relation to the observation that the rate of aerobic glycolysis in slices from cerebral cortex of young rats was not increased by d-glutamate (5 mm) and high potassium (50 mm).
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  • 27
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The in vitro biosynthesis of thyrotropin releasing factor (TRF) by hypothalamic and forebrain fragments from adult newts (Triturus viridescens) was studied by incubating the fragments in the presence of the radioactive amino acid precursors of thyrotropin releasing factor (TRF). The synthesized product was identified by successive chromatography and electrophoresis. A purification scheme was developed which can be applied to the processing of multiple samples labelled with l-[3H]proline and yields a TRF peak which, when derivatized with 1-fluoro-2,4-dinitrobenzene and applied to electrophoresis in acid buffer, yields a single radioactive peak corresponding to the migration of the Nim-Dnp derivative made from standard synthetic [3H]TRF. Both forebrain and hypothalamic fragments of the adult newt are capable of synthesizing a product which migrates with standard TRF after application of this purification scheme. Hypothalamic and forebrain fragments were also assayed for biological activity of TRF and it was determined that one newt hypothalamus contains approximately 200 pg TRF and that an equal amount of TRF is present in a forebrain piece of comparable size. It is concluded that newt TRF is identical to mammalian TRF (pGlu-His-Pro-NH2) and that the storage and synthesis of this substance is not confined to the hypothalamus in this species.
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  • 28
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The activity and kinetic characteristics of tRNA methyltransferases were measured with enzyme preparations obtained from neonatal and adult mouse brain tissue. Both neonatal and mature brain enzyme preparations were shown to contain a considerable amount of protein methylase activity which could interfere with the measurement of the tRNA methyltransferases. When increasing amounts of the unfractionated enzymes from young and adult neural tissue were added to reaction mixtures, the saturation kinetics were found to be considerably different. However, fractionation of the samples by precipitation at pH 5 resulted in an increase in the enzyme activity of preparations obtained from adult brain. Although the precipitation at pH 5 allowed a quantitative recovery of the enzyme activity of immature brain samples, this partial purification step led to an apparent activation of the tRNA methyltransferases in adult preparations. This activation was shown to be independent of differential changes in the thermolability of the enzymes but rather to be associated with an increase in the sites methylated and the measured affinity of the adult enzyme preparations with the tRNA substrate. Nicotinamide, a potent inhibitor of tRNA methyltransferase activity in other tissues, was shown to be ineffective in modulating brain tRNA methyltransferase activity. The results are discussed in light of the possible modulation of the activity of specific enzyme species and the alterations in the synthesis of nucleic acid precursors during neural development.
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  • 29
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Levels of ATP, ADP, phosphocreatine, glycogen, glucose, lactic acid and inorganic phosphate in the rabbit brain were determined after cerebral hypothermia to 24, 22, 20, 18 and 16°C brain temperature. Hypothermia was induced by isolated head perfusion by means of an extracorporeal device including a donor animal of the same species. In two experiments brains were cooled to 24 and 16°C, followed by rewarming to nearly normothermic values before brain biopsy was performed. In all experiments the electrical activity of the cerebral cortex was recorded intermittently.No metabolic disturbances could be observed in 25 out of a total number of 26 experiments. Only one experiment showed a marked decrease in cerebral content of high-energy phosphates, glycogen and glucose and a corresponding increase of lactic acid and inorganic phosphate. These metabolic changes were caused in our opinion by convulsive activity of the brain induced by hypothermia. This was recorded in an electrocorticogram at a brain temperature ranging from 18·9 to 17·8°C over a 150 s period, 5 min before this brain was removed from the animal. These findings demonstrate that hypothermia per se to 24–16°C under our experimental conditions does not cause damage to the rabbit brain, generally, but under special conditions can provoke an increase in energy requirement which exceeds the energy available.
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  • 30
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 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.
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  • 31
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The effect of phenothiazines either alone or in combination with physostigmine on whole brain acetylcholine concn and cholinesterase activity has been investigated in male rats. Phenothiazines (chlorpromazine, trifluperazine and thioridazine) when injected alone had no significant effect on brain acetylcholine concentration. Pretreatment with chlorpromazine and thioridazine significantly enhanced the physostigmine-induced increase in brain acetylcholine concn and inhibition of cholinesterase activity. However, trifluperazine had no significant effect on the physostigmine-induced increase in brain acetylcholine concentration and inhibition of cholinesterase activity. The potentiation of the physostigmine-induced increase in brain acetylcholine concn by phenothiazines may be due to (1) increased acetylcholine turnover secondary to the blockade of dopamine receptors by neuroleptic drugs and.
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  • 32
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Three dietary levels of essential fatty acids, 30, 0-75 and 007 calorie-%, with a linoleic: linolenic acid ratio of 4:1, were fed to rats for two generations. In the third generation the weight of the cerebrum and the concentration of its lipids and the fatty acid composition of phosphoglycerides were determined from term to 120 days of age. The cerebral weights and the concentrations of phospholipids, cholesterol and cerebrosides differed only slightly between the three dietary groups. The accretion of fatty acids of the linoleic acid series was independent of the dietary essential fatty acid level while the accretion of fatty acids of the linolenic acid series was markedly reduced in the groups with low essential fatty acid supply. The sum of the total polyunsaturated fatty acids in ethanolamine phosphoglycerides differed only slightly between the groups. The proportion of the major polyunsaturated fatty acid of the linoleic acid series was equal between the groups while that of 22:6 (n-3) was much lower in the groups fed 007 calorie % essential fatty acids. In these latter groups the relative concentrations of 22:5 (n-6), 20:3 (n-9) and 22:3 (n-9) were increased. The differences in the fatty acid composition were dependent on the age of the rats. They were largest in newborn rats and diminished with age after weaning.
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  • 33
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 34
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The cerebral ventricles of spinal-sectioned cats were perfused with artificial cerebrospinal fluid after the intraventricular administration of [3H]DOPA or [3H]tyrosine. Endogenously synthesized [3H]dopamine or [3H]norepinephrine were identified in the perfusate. Electrical stimulation of catecholaminergic nerve tracts in the hypothalamus increased the efflux of both catecholamines. The addition of d-amphetamine to the perfusing cerebrospinal fluid caused a large increase in [3H]dopamine and a small increase in [3H]norepinephrine appearing in the perfusate. Most of the endogenously synthesized [3H]catecholamines detected in the perfusate following stimuli originated from structures bordering the lateral cerebral ventricle. Thus, norepinephrine and dopamine can be synthesized in and released from catecholaminergic nerve terminals in structures bordering the cerebral ventricles.
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  • 35
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The combination of l-DOPA and pargyline caused a decrease in level of aspartate and an increase in that of glutamine in vivo in cerebral cortex, cerebellum, brain stem, hypothalamus, neostriatum and cervical cord of rat. There was also a decreased incorporation of radioactivity from [1-14C]acetate into amino acids in vivo, most notably in cerebellum and brain stem. The labelling of glutamine was especially affected. In addition, cortical slices were prepared from guinea pigs which had been pretreated with pargyline. These slices were incubated with and without 1 mm l-DOPA in media containing [1-14C]acetate. Pargyline alone caused a stimulation of the labelling of glutamate and aspartate but not glutamine and GABA; the levels of aspartate and GABA were greater than in control slices. The addition of l-DOPA to slices from pargylinized animals caused a severe decrease in glutamine labelling but not in that of glutamate or aspartate; the level of glutamine was increased while that of glutamate was decreased. The results are discussed in terms of the known biochemical and morphological compartmentation of amino acids in brain. It is suggested that catecholamines, in the process of functioning as transmitters, may also function as metabolic regulators of other transmitters, e.g. amino acids, as well as of the energy required for balanced neuronal function.
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  • 36
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 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.
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  • 37
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Mannose was transferred from GDP-[14C]mannose by homogenates of embryonic chick and adult rat brain to mannolipids with properties identical to manriosyl-phosphoryl-dihydropolyisoprenols. Embryonic chick brain formed six-fold larger quantities of mannolipid than adult rat brain. The reaction was stimulated by Mn2+ ions and Triton X-100 but inhibited by EDTA. Phosphoenolpyruvic acid had no effect on the reaction. A crude mitochondrial fraction was two to three times more active than the microsomal fraction. All radioactivity in the mannolipid could be displaced by the addition of non-radioactive GDP-mannose. The endogenous lipid acceptor in brain was readily labelled in vivo by injection of [3H]mevalonate into the amniotic sac of 7-day-old embryos. The mannolipid formed had the properties of an acidic phospholipid on column and TLC, was stable to dilute alkali but readily cleaved by dilute acid. Synthesis was markedly stimulated by the addition of pig liver or calf brain dolichol phosphate in the presence of Triton X-100 and Mn2+. The mannolipid so formed displayed chemical characteristics identical to the endogenous lipid acceptor. Incubation of the purified radioactive mannolipid with the ‘post-nuclear’ fraction from 14-day-old embryonic chick brain in the presence of EDTA and Triton X-100 resulted in the transfer of 40-50 per cent of the radioactive mannose to protein and 40-45 per cent to water soluble compounds. The efficiency of transfer of radioactivity from endogenously formed mannolipid with or without the addition of dolichol phosphate was similar to exogenously added highly purified mannolipid. These results are compatible with the hypothesis that synthesis of the mannose core of brain glycoproteins involves the synthesis first of mannosyl-phosphoryl-dolichols followed by transfer of the mannose to glycoprotein.
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  • 38
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Rat brain particulate fractions were shown to acylate [32P]1-alkyl-sn-glycero-3-phosphorylethanolamine (GPE). While the main product is 1-alkyl-2-acyl GPE, about 12 per cent of the radioactivity was also found in 1-alkenyl-2-acyl GPE. The acyl transferase activity was completely dependent on added ATP and CoA and it was localized mainly in the microsomal fraction. A comparative study of acyl transferase activities to 1-alkyl-, 1-alkenyl-, and 1-acyl GPE by crude mitochondrial fraction and microsomes of 10, 16 and 22-day-old rat brains showed a progressive increase in activity with development. In the 22-day-old rat brain the order of activity towards the three substrates is as follows: 1-acyl GPE ± 1-alkenyl GPE ± 1-alkyl GPE with a crude mitochondrial fraction and 1-acyl GPE ± 1-alkyl GPE ± 1-alkenyl GPE with microsomes.
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  • 39
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 40
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 41
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    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 42
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 43
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    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 44
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 45
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 46
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The effect of acute hypercapnia upon the energy state of the brain in sustained hyperammonaemia was evaluated in lightly (N2O) anaesthetized rats. No significant changes occurred in the high energy phosphates (phosphocreatine, ATP, ADP, and AMP) despite a fourfold increase in the ammonia content and a 50 per cent reduction in the total α-ketoglutarate content. It is concluded that brain tissue maintains energy homeostasis in hypercapnic hyperammonaemia.
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  • 47
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Catecholamine synthesis in synaptosomal preparations of rat striatum, cortex and brain stem was investigated. The striatum had much higher activity than either the cortex or brain stem. Equilibration of labelled tyrosine between tissue and incubation medium was completed within 2 min. The apparent Km of tyrosine hydroxylase (EC 1.14.3a) and of the overall catecholamine synthetic pathway were both approximately 5 ± 10−6m for tyrosine. The following amines were found to inhibit striatal dopamine synthesis: dopamine, 25% inhibition at 5 ± 10−7m; noradrenaline, 25% inhibition at 5 ± 10−6m;and serotonin, 30% inhibition at 10−5m. The catecholamine-induced inhibition of synthesis was antagonized by pre-incubation with cocaine. Increasing the potassium concentration from 5 to 55 mm caused a release of amines into the medium which was accompanied by a 40% increase in dopamine synthesis, when synthesis was measured during the first 5 min of exposure to elevated potassium. These results indicate that synaptosomal catecholamine synthesis is inhibited by increases in intra-synaptosomal amine levels, and that short-term exposure to depolarizing concentrations of potassium can increase synthesis.
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  • 48
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Adult rats were denied food for 7 days. As compared with a control group, this severe starvation reduced the mean total body weight by 44 per cent, the weight of the diaphragm by 33 per cent and liver by 67 per cent, the total lipid content of the diaphragm by 57 per cent and liver by 69 per cent, and the total lipid phosphorus content of the diaphragm by 19 per cent and liver by 68 per cent. The decrease in lipid phosphorus contents indicates that the diaphragm and liver catabolized membrane phospholipids as well as triglycerides. In contrast, the fresh weight of the brain and the total lipid content of the brain were not significantly altered by starvation. The fatty acid patterns of the total lipid of the diaphragm and liver (determined by GLC) were grossly altered by starvation. In the brain, however, 17 of the 21 fatty acids measured did not change significantly (P 〉 0.05) and the remaining four changed, with borderline statistical significance, by only 2 to 13 per cent. There was no significant effect of starvation of the pattern of the brain polyunsaturated fatty acids when measured by alkali isomerization. In contrast to the liver and diaphragm, the brain is apparently unable to utilize its lipids appreciably as an energy source. Presumably the lipids of the brain are preserved to permit this organ to function properly, even in the last stages of starvation.
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  • 49
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Acetylcholine, its precursor (choline), and the enzymes of its biosynthesis and degradation (choline acetyltransferase and acetylcholinesterase, respectively) have been studied and quantified in extracts of several regions of the nervous system of the lobster and in single, isolated axons of identified efferent excitatory, efferent inhibitory and afferent sensory neurons. The choline acetyltransferase is a soluble enzyme similar to that from other species. The predominant acetylcholine-hydrolysing enzyme is largely membrane-bound and has been characterized as a specific acetylcholinesterase. A single peak of acetylcholinesterase activity can be detected upon velocity sedimentation analysis of Triton X-100-treated extracts of all regions of the nervous system. Choline acetyltransferase distribution parallels that of sensory neural elements, and its specific activity shows nearly a 500-fold difference from the richest to the poorest neural source. Acetylcholinesterase levels span only a 23-fold range, and activity is found in all neural regions, including those free of known sensory components. A radiochemical microassay for choline and acetylcholine in the range of 20–2000 pmol is described in detail. All 3 types of axons contain comparable levels of choline (ca. 2 pmol/μg protein), but acetylcholine is asymmetrically distributed. Efferent axons contain no detectable acetylcholine, while sensory axons from abdominal muscle receptor organs have an average of 1·9 pmol/μg protein. Choline acetyltransferase is similarly distributed; sensory axons show at least 500-fold greater activity than efferent axons. Acetylcholinesterase is nearly uniformly distributed among the three types of fibres. These results are discussed in terms of a general view of transmitter accumulation in single neurons.
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  • 50
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Visible lesions from monkeys with acute experimental allergic encephalomyelitis (EAE) induced by injection of purified myelin basic protein were assayed for acid proteinase, for a neutral proteinase at pH 6·5, and one lesion was measured for cathepsin A. Acid proteinase was increased to 152–176 per cent of levels in normal-appearing brain areas, neutral proteinase increased to 220–258 per cent, and the one lesion assayed for cathepsin A was 840 per cent of control. These enzymes were measured in the brain stem of Lewis rats with acute EAE as a result of basic protein injection and compared to Freund's adjuvant-injected controls. Acid proteinase was increased significantly to an average level of 128 per cent of control, the increase in neutral proteinase was not significant, and cathepsin A levels were 258 per cent of control, a highly significant increase. The rise in cathepsin A levels was not seen until the onset of paralytic symptoms. The brain stem of Wistar rats treated with whole spinal cord which show EAE in a milder form than the Lewis rat did not contain significantly higher enzyme levels than the control. The increases in acid proteinase and cathepsin A in brain stems were compared to levels of these enzymes in lymph nodes of EAE, Freund's adjuvant-injected controls and uninjected controls. The level of acid proteinase of lymph nodes/g protein did not change appreciably in the course of EAE development in the Lewis and Wistar rats and was about 3–4 times the activity in the brain stem. The cathepsin A in the inguinal lymph nodes of Wistar and Lewis rats injected with whole spinal cord in Freund's adjuvant increases to a level 2× that of the lymph nodes of the uninjected control. The cathepsin A levels in these activated lymph nodes was 6–8 × that of the control brain stem. The lymph nodes of Lewis and Wistar rats injected with Freund's adjuvant alone showed the same increase in cathepsin A as those from rats injected with spinal cord. The brain stem of rats undergoing severe demyelination as a result of chronic administration of triethyl tin did not show the enzyme increases. These results are compatible with the theory that proteolytic enzyme increases in EAE (and probably multiple sclerosis) are due to the invasion of mononuclear cells, some of which are probably lymphocytes. Whether or not these enzymes participate in the actual dissolution of myelin is unknown.
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  • 51
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    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Two basic peptides (B1 and B2) were derived from bovine spinal cord following in situ proteolysis at 37°C for 10–24 h. These peptides do not arise as degradation products from the A1 protein as shown by amino acid composition and end group analysis; rather they appear to originate from some larger basic protein in the spinal cord having similarities to the P2 protein, a basic protein found in peripheral nerve myelin. The peptides were purified following defatting, acid extraction, and ammonium sulphate fractionation, by chromatography on Amberlite IRC-50 resin using guanidinium chloride. The peptides, found generally in a 4:1 ratio of B1 to B2, appeared homogeneous on gel electrophoresis and immunodiffusion. Approximately 25–60 mg of peptides was obtained per 100 g wet spinal cord.In contrast to the basic A1 protein from myelin, neither of these peptides nor their pepsin digests were encephalitogenic. They do not cross-react immunologically with the basic A1 protein, but cross-react with each other. These peptides further differ from the A1 protein in their tryptic peptide map, size (B1, 63 residues; B2, 54 residues), and composition particularly the high lysine: arginine ratio, and low histidine content. Like the A1 protein, however, they contain a tryptophan residue and a blocked NH2-terminal amino acid; peptide Bl has COOH-terminal valine. It was concluded that the basic peptides represent a fragment of a hitherto unidentified protein(s) of the nervous system.
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  • 52
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    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The influx and efflux of [3H]GABA were investigated in synaptosomes. Two efflux components were detected. The first, termed spontaneous efflux, was not affected by the external sodium chloride concentration. The second, termed GABA-stimulated efflux, was observed when low levels of GABA were added to the incubation medium and was found to require external sodium chloride. The rate of spontaneous efflux at 0°C was about 37 per cent of the rate at 27°C but both GABA-stimulated efflux and GABA influx were completely inhibited at 0°C. The stimulation of efflux by external GABA followed simple Michaelis–Menten kinetics with respect to external GABA. The concentration of external GABA required for half-maximal stimulation was 4·9 ± 1·4 μm and the Vmax for efflux was 1·0 ± 0·6 nmol. min-1.mg-1 of protein. A similar stimulation of efflux was observed with GABA analogue l-2,4-diamino-butyric acid which is a competitive inhibitor of influx. The concentration of external l-2,4-diaminobutyric acid required for half-maximal stimulation of efflux was 51 ± 12 μm and the Vmax for efflux was 0·8 ± 0·5 nmol.min-1.mg-1 of protein. Since the sodium-dependency, temperature sensitivity, and kinetic properties of the GABA-stimulated efflux system were similar to the influx system, GABA-stimulated efflux was attributed to carrier-mediated exchange diffusion. Measurement of efflux and influx in the same preparation showed there was a net efflux when total fluxes were considered and that the exchange ratio (influx to GABA-stimulated efflux) was 0·9 when carrier-mediated fluxes were considered. The effect of the temperature of the fluid used to rinse synaptosomes collected on filters in influx experiments was investigated. There was no detectable difference in measured values of influx between samples rinsed with cold fluid (0°C) and warm fluid (27°C). The endogenous GABA content of synaptosomes was found to be 20·3 ± 2·5 nmol GABA per mg of protein. From this value, the cytoplasmic concentration of GABA in synaptosomes was estimated to be a maximum of 40 mm. About 5 per cent of total cerebral cortical GABA was found in the synaptosomal fraction.
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  • 53
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— A segment, defined by gross anatomic boundaries, which comprises most of the sciatic nerve was dissected from rabbits aged from birth to 1 yr. The mean and standard deviation of the variance determined for the weights of pairs of nerve units removed from single animals of an age group did not exceed 2·7 per cent and 12·3 per cent respectively of the average weight of the two nerve units which were the values determined for a group of newborn animals. During the period from birth to one year of age, the weight and length of the nerve unit increased 47- and 6-fold respectively while the animal's weight increased 78-fold. Whereas the nerve unit length increased little after 8 weeks, its weight and that of the whole animal continued to increase up to 1 year. Estimations of nucleic acids in the nerve unit from adult animals gave values of 54 μg DNA-P and 25 μg RNA-P per g fresh weight. During the period birth to 1 yr the absolute amount of DNA in the nerve unit increased 11-fold, 71 per cent of this having occurred by 6 weeks of age. The absolute amount of RNA increased 11 -fold by 8 weeks of age and remained constant thereafter. During the period birth to 1 yr, the proportion of the nerve constituents accounted for by lipid-free solids remained constant at 10 per cent, while lipids increased from 5 to 18 per cent and tissue water declined from 84 to 71 per cent. Changes in some lipid classes were examined also. Increases of absolute content in the nerve unit over the first year and concentrations on a fresh weight basis attained in year-old animals were as follows: cholesterol, 132-fold and 86 mg/g; triglyceride 554-fold and 43·2 mg/g; total phospholipid, 85-fold and 61 mg/g; cerebroside 205-fold and 28 μmol/g; sulphatide, 154-fold and 10 μmol/g; monogalactosyl diglyceride, 31-fold and 0·6 μmol/g. The ratio cholesterol/phospholipid/galactolipid in whole nerve units from adult animals was 2·0/2·1/1·0 and the change in this ratio in the first year was compatible with enrichment of myelin in galactolipid during myelination. The ratio of cerebroside to sulphatide increased from 2·0 to 2·6 during this period. Increases in absolute content and concentrations attained for sialic acid-containing components representing cell surface constituents were as follows: ganglioside sialic acid, 33-fold, and 83 μg/g; glycoprotein sialic acid, 57-fold and 371 μg/g. The quantitative pattern of ganglioside fractions separated by thin-layer chromatography in one direction resembled that of whole brain and was the same at all ages studied. The changes reported reflect a composite picture of changes in a variety of cell membranes indicative of marked variation during development in quantity and composition of membranes.
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  • 54
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    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The content of several amino acids was measured in five discrete regions of the central nervous system of the developing rat, using a [3H]dansylation assay procedure. Both regional differences in amino acid content and regional differences in rate of change of amino acids during maturation were found. Particularly prominent were the maturational changes and high adult contents of glutamic acid in the cerebral cortex, GABA in the hypothalamus, and aspartic acid in the medulla.
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  • 55
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    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— δ-Aminolevulinic acid (δ-ALA) was taken up by rabbit brain cortical slices to a concentration greater than that in the surrounding medium. The process responsible for this accumulation of δ-ALA shows many of the properties characteristic of an active transport system. δ-ALA is taken up by a system which exhibits some allosteric kinetic properties, and is specific to a relatively high degree.
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  • 56
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Previous suggestions that the K+-dependent uptake of chloride by mammalian cerebral cortex is localized to cortical astrocytes has been investigated in two lines of neural cells in tissue culture. Hamster astrocytes and mouse neuroblastoma cells were each cultured on small glass cover slips in Eagle's (astrocytes) or Dulbecco's (neuroblastoma) supplemented media. At 48 h, cultures were incubated at 37°C for 1–60 min in the presence of 36Cl plus [3H]inulin (as a measure of extracellular space). In media containing approximately 140 mm chloride, the rate of uptake of 36Cl by the astrocytes was a function of the concentration of K+ (range 5–54 mm) in the medium, and the uptake was characterized by saturation kinetics and an apparent Km of 38·5 mm. The uptake was temperature and apparently energy dependent, significantly inhibited by 5 or 10 mm Br-, I-, SCN- or ClO4-, and competitively inhibited by 10 mm acetazolamide (Ki= 27·1 mm). None of these characteristics were observed with neuroblastoma cultures studied under similar conditions. In chloride-free media, the cellular K/Na ratio of the astrocytes shifted from the usual value of 4·55 to a value of 0·29, the culture medium became more alkaline than normal, and the cells spontaneously sloughed from the cover slips but remained normally viable. Our observations are the first to provide direct support for previous suggestions that there is a mediated, K+-dependent coupled cation, chloride and fluid uptake by mammalian cerebrocortical glia and that this uptake is an enzymatically catalysed process. The observations have been discussed in terms of a presumed central role for astrocytes in modulating the external ionic milieu of the neurons they surround and in terms of implications for epilepsy, stroke and cortical edema.
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  • 57
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Isolated neuronal cell bodies and astroglia of young (15–20-day-old) rat brains were both found to contain small concentrations of a variety of glycosphingolipids, including glucosylceramide, galactosylceramide, sulphatide, dihexosylceramide and gangliosides. These sphingolipids, plus sphingomyelin, were isolated, quantitated and their fatty acid and long chain base patterns determined. These data were compared to similar data obtained on these lipids isolated from whole brain and myelin of rats of the same age range.Glucosylceramide was found in an amount equal to galactosylceramide in neurons, and accounted for 35 per cent of the total monohexosylceramide in astroglia. Dihexosylceramide was present in nearly the same amount as sulphatide in both cell types.The sphingolipids of each cell type had characteristic fatty acid patterns. Generally the whole brain fatty acid patterns resembled those of astroglial lipids rather than neuronal lipids. In no case did the cell sphingolipid fatty acids resemble those of myelin. However, the galactosylceramide and sulphatides of both cells had unsubstituted and α-hydroxy acids, both of which had appreciable quantities of C24 acids.The ganglioside fatty acids of each cell type were similar and not unusual, but were quite different from those of glucosylceramide and dihexosylceramide; the latter having appreciable quantities of 16:0 and acids longer than 18:0. The ganglioside patterns of these cells were similar and only slightly different from that of whole brain. Long chain bases of sphingolipids were mainly C18-sphingosine in both cell types, and those of ganglioside and sphingomyelin contained small amounts of C20-sphingosine.
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  • 58
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— A small basic protein (mol.wt. 12,000), referred to as the P2 protein, was extracted with dilute acid from delipidated bovine root myelin and purified by ion exchange chromatography on cellulose phosphate. It appeared homogeneous on polyacrylamide gel electrophoresis. The P2 protein had a distinctly different amino acid composition than the larger basic protein (mol.wt. 18,000), referred to as the P1 protein, that is also present in peripheral nerve myelin. It contained relatively more hydrophobic residues and much less histidine and proline. The P2 protein conjugated with peroxidase was bound by lymph node cells and infiltrates in rabbits sensitized with whole bovine root myelin. No binding was evident with the bovine central nervous system myelin basic protein. Chemically and immunologically, the P2 protein appears to be specific to peripheral nervous system myelin. The isolated P2 protein produced mild clinical symptoms of experimental allergic neuritis, but no histological evidence of disease. It was suggested that the P2 protein is an important antigen for experimental allergic neuritis, and that its antigenic determinants are likely to be conformation-dependent.
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  • 59
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The suitability of radioactively labeled proline as a marker of axonally transported protein in the goldfish visual system is further investigated and compared with another amino acid, leucine, in double-label experiments. Intraocularly injected proline is incorporated into protein in the eye S times more efficiently than is leucine, while local labeling of brain protein from precursor which has left the eye and entered the blood, (observed in the ipsilateral optic tectum) is five- to eight-fold less from proline than from leucine. The difference is attributed to the superior transport of leucine, an essential amino acid, into the brain from the blood. Once in the brain, the apparent rates of incorporation of the two amino acids are similar. Proline- or leucine-labeled, axonally transported proteins have a longer apparent half-life in the brain than do proteins labeled from intracranial injection of the precursors. By either route, proline-labeled proteins have a longer apparent half-life than leucine-labeled proteins. It is proposed that proline, released from protein breakdown is reutilized to a greater extent than is leucine.
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  • 60
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The isolation of brain actomyosin-like protein (neurostenin) with a Ca2+ -sensitive component is described. The addition of 1 mm EGTA results in approximately 50 per cent reduction in MgATPase activity. The inhibition can be released by a free Ca2+ concentration of 10−6m. Dialysis of the protein complex against low ionic strength medium followed by centrifugation results in a loss of Ca2+ sensitivity in the pelleted protein. Ca2+ sensitivity can be restored by reprecipitating this desensitized complex in the presence of the 70.000 g supernatant. The protection of sulphhydryl groups during desensitization and reconstitution procedures is essential. This Ca2+ regulatory property is similar, in these respects, to other actomyosin-like proteins.
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  • 61
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Phenylethanolamine and octopamine have been detected in the developing rat brain. Maximum concentration of these amines occurs early in development (16-17 days of gestation). At this developmental stage, the brain concentration of these amines is higher than that of norepinephrine. There is a sharp decline in the phenylethanolamine and octopamine concentrations on day 18 of gestation to approximately those of the adult. This decrease coincides with an increase in-monoamine oxidase activity of fetal brain, with an increase in the activities of tyrosine hydroxylase and dopamine-β-hydroxylase, and with the appearance of a saturable active uptake mechanism for norepinephrine. The administration of iproniazid, a monoamine oxidase inhibitor, to pregnant rats produced an increase in phenylethanolamine, octopamine and norepinephrine concentrations in the fetal rat brain at 16 days of gestation. p-Chlorophenylalanine, an inhibitor of phenylalanine hydroxylase, decreased fetal brain norepinephrine; this drug increased brain levels of phenylethanolamine and octopamine. The combined administration of iproniazid, p-chlorophenylalanine and phenylalanine to pregnant rats resulted in increased concentrations of octopamine and in a several-fold increase of phenylethanolamine levels; norepinephrine concentrations were sharply reduced. The possible significance of these findings in relation to pathological conditions such as phenylketonuria is discussed.
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  • 62
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— A subcellular fraction (called the 0·85-fraction) was isolated from the brains of Jimpy mice by a procedure for obtaining myelin of high purity from immature normal brains. The yield of this fraction obtained from 17-day-old Jimpy mice was only 5 per cent of that from age matched controls. In the electron microscope, the O·85-fractions obtained from 9- and 17-day-old control mice showed many multilayered whorls of myelin, whereas the corresponding fraction from the Jimpy mice was free of multilayered structures which could be recognized as myelin. Basic proteins, proteolipid protein and galactocerebrosides could not be detected in the 0·85-fraction from Jimpy mice although they were major components of the 0·85-fractions from both 9- and 17-day-old control mice. The specific activity of 2′,3′-cyclic nucleotide 3′- phosphohydrolase in the Jimpy 0·85-fraction was only 15 per cent of the value for controls. These results can be explained either by the 0·85-fraction from Jimpy brain being a very abnormal ‘myelin’ or by its being primarily non-myelin contaminants. Little or none of the major glycoprotein found in normal myelin fractions was found in the 0·85-fraction from Jimpy brains. This finding is strong evidence indicating that the glycoprotein is closely associated with normal myelin in situ.
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  • 63
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Le métabolisme du'calcium a étéétudié dans l'organe électrique de la Torpille, au repos et en activité, in vivo et in vitro, en mesurant le calcium total et en utilisant du 45Ca. Lorsque le tissu est mis en présence de fortes concentrations de calcium, un échange complet s'effectue entre le calcium cellulaire et celui du milieu d'incubation. En présence de faibles concentrations, le tissu retient son calcium qui, dans ce cas, séchange mal avec l'extérieur. La stimulation cause une augmentation nette du calcium cellulaire et accélère son échange avec le milieu extérieur. Cette entrée de calcium concerne principalement les terminaisons nerveuses présynaptiques car on l'observe aussi lorsque la transmission est bloquée par le curare qui agit au niveaja des électroplaques. Il semble que le calcium influence la répartition intracellulaire du transmetteur. En effet, l'entrée présynaptique de calcium s'accompagne d'une diminution de l'ACh ‘liée’ (vésiculaire). Lorsque le tissu est incubé dans une solution exempte de calcium, surtout en présence d'EDTA, la réponse électrophysiologique disparaît; le taux d'ACh ‘libre’ (disponible) diminue alors, mais son ‘turnover’ augmente. Le calcium extracellulaire est donc nécessaire au maintien du compartiment d'ACh immédiatement disponible.
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  • 64
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 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.
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  • 65
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The turnover of the different histone components from brain nuclei was studied after the administration of l-[3H]lysine and l-[14C-methyl]methionine to newborn rats. The radioactivities of the different histone subfractions as well as other proteins were determined over a 280-day period. Biphasic type decay curves (3H and 14C) were obtained for total brain histones and all the subfractions. From 6 to 40 days of age the half life of total brain histones was 19 days. After reaching brain maturity the half life was 132 days. The lysine rich histone (F1) was found to turnover the fastest of all the histones, having half lives of 13 and 112 days, respectively. The decay curve for the slightly lysine rich histones (F2a2, F2b) gave half lives of 25 days up to 40 days of age and 189 days after reaching brain maturity. The arginine rich histones (F2a1, F3) gave a half life of 32 days up to 40 days of age, while no turnover was observed after maturity. The turnover rates of the methyl groups and/or methionyl residues did not vary significantly from the turnover rates of the lysyl residues in the F2 and F3 histones. The lysine-rich histones did not contain significant amounts of methionyl residues or methyl groups.Amino acid analysis of the brain histones revealed that about 3·6 per cent of the lysyl residues in the slightly lysine rich histones were methylated, mainly as ε-N-dimethyllysine. About 13 per cent of the lysyl residues in the arginine rich histones were methylated, mainly as ε-N-monomethyllysine and ε-N-dimethyllysine.
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  • 66
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The turnover of brain norepinephrine (NE) and dopamine (DA) was studied in five groups of male Sprague-Dawley rats under different conditions of alcohol treatment: no treatment, acute treatment while intoxicated, acute treatment subsequent to elimination of alcohol from the blood, alcohol-dependence while still intoxicated and alcohol-dependence during a withdrawal syndrome. Turnover was determined from the rate of depletion of brain catecholamine levels after inhibition of tyrosine hydroxylase. In rats given a single dose of alcohol, NE turnover was increased, while DA turnover was unaffected during the few first hours after treatment. After that time the turnover of both NE and DA was reduced. In alcohol-dependent rats, whether intoxicated or undergoing a withdrawal syndrome, the turnover of NE was increased, while that of DA was decreased. These data suggest that catecholamines may mediate some of the symptoms of the alcohol withdrawal syndrome in the rat.
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  • 67
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 22 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The NH2-terminal amino acids of Wolfgram and Folch-Lees proteolipids of bovine and human CNS myelin were determined using the cyanate method (Starke & Smyth, 1963) followed by direct amino acid analysis of the products. Glycine predominated in every case and was recovered in amounts similar to the results described by Whikehart & Lees (1973), who used a dansylation technique followed by thin layer chromatography of the DNS-amino acids. In the present study substantial amounts of glutamic acid, serine, alanine and aspartic acid were also recovered, plus traces of other amino acids. Few differences were observed between Wolfgram and Folch-Lees proteolipids. The end group products of purified W1 proteolipid of bovine Wolfgram fraction, of diazometholysed Folch-Lees proteolipid, and of a sample of phosphatidyl serine had essentially the same composition. The similarity of these results, especially for both fractionated and unfractionated Wolfgram proteolipid, may be evidence that the observed products are derived from phosphoglycerides present in proteolipid rather than from the actual NH2-terminals of the protein.
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  • 68
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The distribution of DBH activity between soluble and sedimentable fractions of hypotonic homogenates was examined in rat sympathetic ganglia and nerves after interruption of axonal transport. Local application of colchicine to superior cervical ganglia caused an increase mainly in particulate DBH activity, which was presumably bound to membranes. Likewise, in sciatic nerves, particulate DBH activity accumulated on both sides of a ligature and disappeared from a region well below a ligature much faster than did soluble activity. On the other hand, 18 h after simultaneous application of two ligatures to the nerve, neither total DBH activity nor subcellular distribution of this activity changed in the isolated nerve region. More detailed analysis showed that ligation affected the distribution of DBH activity within a fraction that sedimented at 140,000 g after homogenization of nerves in isotonic sucrose. Just above a ligature, osmotically releasable DBH activity was a smaller proportion of the sedimentable activity than in control nerves. However, as compared to controls, osmotically releasable DBH activity was a larger proportion of the activity in the sedimentable fraction from a region well below a ligature. A model was developed which accounts for some of these results by postulating that DBH is associated with different compartments in sciatic nerve which have different rates of transport and different proportions of soluble and bound enzyme.
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  • 69
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The accumulation, metabolism and stimulated-induced release of 5-HT in the nervous system of the snail was studied. When nervous tissue was incubated at 24°C in a medium containing [14C]5-HT or [3H]tryptophan, tissue: medium ratios of about 25:1 and 4:1 respectively were obtained after 45 min incubation.The process responsible for [14C]5-HT accumulation showed properties of an active transport system: it was temperature sensitive and was greatly inhibited by dinitrophenol and ouabain. Furthermore, the accumulation process was inhibited by imipramine and desipramine.Of a number of analogues of indole, N-acetyl-5-HT and 5-hydroxytryptophan were the most potent in the inhibition of the accumulation of [14C]5-HT. The presence of a large molar excess of amino acids had little effect.A small amount (less than 14 per cent) of the accumulated [14C]5-HT was metabolized to form 5-hydroxyindole acetic acid, even after long periods (2 h) of incubation. The accumulated [3H]tryptophan was metabolized to form 5-hydroxytryptophan and 5-HT; the content of formed [3H]5-HT increased with incubation time whilst the [3H]5-hydroxytryptophan remained more or less constant.The presence of p-chlorophenylalanine in the incubation medium did not interfere with the accumulation of [3H]tryptophan, though it inhibited the formation of [3H]5-hydroxytryptophan and to a greater extent [3H]5-HT.A rapid efflux of the accumulated [14C]5-HT from snail nervous tissue was observed on electrical stimulation. Slower release resulted when the Ca2+ ion content of the incubation medium was replaced by Mg2+ ions. There is also a slight efflux of radioactive substances following electrical stimulation in tissues previously incubated in [3H]tryptophan. Most of this radioactivity was attributed to the formed [3H]5-HT.The data support the idea that 5-HT is a transmitter-substance in the snail Helix pomatia, and that re-uptake of the substance is a method of inactivating the released amine.
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  • 70
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Lipid composition has been determined in brain frontal lobe gray and white matter from a 5-month-old patient who died from Menkes' disease, and from a normal control patient of the same age.Total cholesterol and the amount of cholesterol esters were significantly increased in the case of Menkes' disease, whereas the values for free cholesterol were nearly unchanged.In white matter a decrease in total galactolipids was observed in the pathological brain.The values for total phospholipids were unchanged for the tissues, but the ratio between phosphatidylcholines and phosphatidylethanolamines (including ethanolamineplasmalogens) in white matter from the patient seemed increased. The fatty acid pattern of phosphatidylethanolamines (including ethanolamineplasmalogens), phosphatidylcholines and sphingomyelin were similar to those of the normal control. Phosphatidylethanolamines from pathological tissues contained 25–30 per cent polyunsaturated fatty acids with four, five or six double bonds.
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  • 71
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Young rat cerebral-cortex slices were incubated with 32Pi in the absence and presence of ACh plus eserine, norepinephrine, dopamine or serotonin for 1 h. their cellular and subcellular fractions were isolated, and the specific radioactivities of the various phospholipids determined.In the neuronal- and astroglial-enriched fractions ACh plus eserine increased the 32P-labelling of phosphatidyl inositol (PhI) phosphatidic acid (PhA) and phosphatidylcholine (PhC) by increments which ranged from 108 per cent for PhI to 30 per cent for PhC and in the presence of norepinephrine or dopamine these increments ranged from 180 per cent for PhI to 29 per cent for PhC.In the subcellular fractions ACh plus eserine exerted maximal stimulatory effect on the labelling of the synaptosomal phospholipids, which was 88 per cent for PhI and 79 per cent for PhA, followed by those of microsomes, mitochondria and nuclei.ACh plus eserine exerted no effect on [l4C]glucose incorporation, but inhibited the incorporation of [14C]glycerol into phospholipids by amounts which ranged from 30 per cent for PhI to 3 per cent for PhE.Although the rate of incorporation of 32Pi into phospholipids of 0.2 mm slices was higher than that of the 0.5 mm slices the stimulatory effect of ACh plus eserine on the 32Pi incorporation into the lipids of the latter was higher.When neuronal- and astroglial enriched fractions were first isolated from the cerebra then incubated with 32Pi or [14C]choline, labelling of phospholipids in the neuronal fraction was higher than that of the astroglial fraction; however, ACh plus eserine had no effect on the incorporation of 32Pi into the lipids of either fraction.ACh plus eserine stimulated the activity of phosphatidic acid phosphatase in the various subcellular fractions by increments which ranged from 13 per cent in nuclei to 37 per cent in microsomes.It was concluded that the nonspecific localization of the neurotransmitter effect could be due to the widespread distribution of the enzymes which appear to be responsive to cholinergic and adrenergic neurotransmitters.
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  • 72
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 22 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— In order to evaluate whether porta-caval anastomosis, and the accompanying hyperammonemia, affect the balance between production and utilization of ATP in the brain, organic phosphates and carbohydrate substrates were measured in control and shunted rats exposed to hypoxia (arterial Po2 about 30 mm Hg). In the shunted animals the cortical ammonia content was about 2.5 times that measured in the controls, and there was a marked accumulation of glutamine. The intracellular lactate concentration was identical in the control and the shunted groups, and the pattern of change in carbohydrate substrates was similar. There were no significant differences in ATP, ADP or AMP between the groups but the shunted group showed a significantly lower phosphocreatine content. However, the fall in phosphocreatine in the shunted group could be related to a decrease in the sum of phosphocreatine and creatine. It is concluded that the shunting procedure does not disturb the balance between energy production and energy utilization in the brain.
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  • 73
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —A hexokinase has been isolated from brain tissue on Sephadex G-100 and DEAE cellulose which is similar to yeast enzyme in stimulating the AMP-aminohydrolase activity of rat brain soluble fractions. This effect of hexokinase is influenced neither by N-acetyl-glucosamine nor noradrenaline. An isoenzyme of hexokinase isolated from brain tissue on DEAE cellulose, having properties similar to that of the muscle enzyme, has no effect on AMP-aminohydrolase activity. The activating effect of yeast hexokinase is not due to its oligomeric structure. Enzyme subunits obtained by the treatment of native yeast enzyme by urea also activate AMP-aminohydrolase of rat brain soluble fractions.
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  • 74
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    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —Rat brain contains the enzyme which forms sulphate conjugates of phenols, phenolsulphotransferase (EC 2.8.2.1), but the physiological role of the enzyme is unclear. The enzyme is unevenly distributed in rat brain, with the activity 13 times higher in the hypothalamus than in the cerebellum. Phenolsulphotransferase does not seem to be primarily located in glial cells. Cultured cells (type C6 astrocytoma) derived from rat glia had less than 1 per cent of the phenolsulphotransferase activity of whole rat brain. Sulphate conjugation of neutral compounds may be important in their removal from brain. The pineal and pituitary glands, areas outside the blood-brain barrier had very low phenolsulphotransferase activity. The activity of the enzyme in brain varied widely among different species: rabbit and rat had much higher levels of activity than mouse or frog; the activity in human brain was intermediate. Phenolsulphotransferase also occurred in other organs, including liver, heart, testes, lung, spleen, salivary glands, and intact or decentralized superior cervical ganglion. There was no correlation of enzyme activity with adrenergic or cholinergic innervation, or with the known roles of various tissues in drug metabolism or detoxification. The enzyme activity does not seem to be under neuronal control since ganglionectomy did not affect the phenolsulphotransferase activity of salivary glands. The precise localization of phenolsulphotransferase remains to be established, as well as the physiological importance of sulphate conjugation of phenols in brain and other organs.
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  • 75
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —Injection of a soluble protein fraction from mouse brain into rabbits gave rise to an antibody which was specific for galactocerebroside. The antigen had the following characteristics: (1) it was present in the soluble fraction of a mouse brain homogenate but absent from the soluble fraction of homogenates of mouse liver, spleen, kidney and testis; (2) it was non-dialysable; (3) it voided from a Sephadex G200 column; (4) on immunodiffusion with antibody directed against it, it gave a sharp single precipitin band; (5) it bound to DEAE cellulose column and was eluted with high salt. Given these characteristics the antigen might have been identified as a ‘brain specific protein’. However, the lipid nature of the antigen was revealed when it was found that it was not destroyed by Pronase digestion and could be quantitatively extracted with chloroform-methanol. The antigen has been identified as a galaetocerebroside and is 100 times more abundant in the myelin fraction than in the soluble fraction of the mouse brain homogenates. The antigen could have been falsely identified as a ‘brain specific protein’ if the antigenicity and macromolecular behaviour of lipids was overlooked.
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