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  • Blackwell Publishing Ltd  (5,190)
  • Nature Publishing Group  (3,625)
  • 1975-1979  (8,815)
  • 1970-1974
  • 1977  (8,815)
Collection
Years
  • 1975-1979  (8,815)
  • 1970-1974
Year
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Birth 4 (1977), 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 4 (1977), S. 0 
    ISSN: 1523-536X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Birth 4 (1977), S. 0 
    ISSN: 1523-536X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Birth 4 (1977), 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 4 (1977), S. 0 
    ISSN: 1523-536X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Birth 4 (1977), S. 0 
    ISSN: 1523-536X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 7
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The effect of diazepam and pentobarbital on γ-aminobutyric acid (GABA) levels, the aminooxyacetic acid (AOAA)-induced accumulation of GABA, and the in vitro activity of l-glutamate 1-carboxyl-lyase (EC 4.1.1.15) [GAD] were studied in various regions of rat brain. Diazepam increased GABA levels in the substantia nigra, diminished the AOAA-induced accumulation of GABA in the caudate nucleus, cingulate, parietal and entorhinal cortex and had no effect on GABA accumulation in the pyriform and cerebellar cortex. After pentobarbital, GABA levels were elevated in the caudate nucleus but decreased in the parietal and pyriform cortex; the AOAA-induced accumulation of GABA also diminished in all cortical regions studied. No correlation was found between the apparent changes in GABA synthesis, as estimated by accumulation after inhibition of 4-aminobutyrate-2-oxoglu-tarate (EC 2.6.1.19) [GABA-T] with AOAA, and the changes in GABA levels induced by these drugs. The reduction in AOAA-induced GABA accumulation after diazepam and pentobarbital treatment was most pronounced in regions which showed the greatest accumulation of GABA after AOAA administration. Neither diazepam nor pentobarbital administration affected the activity of GAD in homogenates of cingulate cortex. Chlorpromazine, at a dose which decreased spontaneous activity, enhanced the AOAA-induced GABA accumulation in the cingulate cortex, suggesting that drug-induced sedation is not necessarily associated with decreased GABA synthesis. While regional differences were observed in the effects of diazepam and pentobarbital on GABA synthesis, both agents appear to inhibit GABA synthesis in vivo and both do so, in at least some brain areas, at subsedative doses.
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  • 8
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Up to approx 3 pmol of acetylcholine (ACh)/h/cell body was synthesized by perikarya of large spinal neurons isolated in bulk fractions from bovine ventral spinal cord. Many of the cell bodies are probably derived from motoneurons. A medium of low ionic strength and pH was used to minimize losses of soluble acetyl CoA:choline-o-acetyltransferase (ChAc; EC 2.3.1.6) from the neurons, whose permeability properties were altered. Such a medium also increased the retention of other soluble proteins by the cell bodies. The maximal rate of hydrolysis of ACh by the isolated neurons exceeded that of its synthesis by a factor of at least 100. It was estimated that ChAc and acetylcholinesterase (AChE; EC 3.1.1.7) each represent less than 0.01% by weight of the total protein in these cell bodies and that as little as 10% of each enzyme in the ventral spinal cord is located within the large neuronal somata and their proximal processes.
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  • 9
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— 3,3′,5-Triiodothyronine (T3) inhibited L-[14C]leucine uptake into synaptosomes. Inhibition was competitive with a Ki of 3.1 × 10−5m. Hofstee plot revealed an inverted hyperbolic curve suggestive of a two carrier or carrier plus diffusion mediated system for amino acid uptake. Both the carrier mediated and diffusional components were inhibited by thyroid analogues. l-Thyroxine and analogues inhibited the incorporation of l-[14C] leucine into cerebral synaptosome protein. At 50 μm, the triiodo-compounds were more inhibitory than tetraiodo-〉3,5-triiodo-l-thyronine 〉3,3′,5-triiodothyropro-pionic〉 l-thyroxine 〉3,5-diiodo-l-tyrosine. Thyroid analogue inhibition was not seen in liver or brain mitochondrial protein synthesis. 3,3′,5-Triiodothyronine had no effect on respiratory control or 2,4-DNP stimulated synaptosome respiration supported by malate plus pyruvate. Ouabain did not inhibit [14C]leucine uptake into adult synaptosomes. There was synergistic inhibition of synaptosome protein synthesis by thyroid analogues in the presence of 0.2 mm-ouabain. 3,3′,5-Triiodothyronine had no effect on synaptosome fraction ATPase or Na-K ATPase. Addition of T3 induced further inhibition of synaptosome protein synthesis in the presence of either chloramphenicol (100μm) or cycloheximide (50μg/ml). [14C]Glycine uptake and incorporation into synaptosome protein was inhibited by 3,3′,5-triiodothyronine. There was no inhibition of [14C]proline uptake or incorporation.The above evidence and kinetic data strongly favor a selective competitive block in amino acid transport at the synaptosome membrane leading to a decreased rate of protein synthesis.
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  • 10
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The structural requirements for amino acid inhibition of Na+-dependent proline uptake by rat brain synaptosomal fractions were investigated. It is shown that the amino group has to be in the α-position to strongly inhibit proline uptake. Hydroxyamino acids are less potent inhibitors than the parent amino acids. Amino acids with net positive or negative charges on their molecules exert no effect, whereas elimination of the net charge results in compounds with profound inhibitory effects. Blocking of the carboxyl group reduces the inhibition, but does not abolish it. Since acetylation of the α-amino group results in elimination of the inhibitory effect whereas N-methylation does not, it is concluded that in the interaction of an amino acid with the proline transport site the positive charge on the amino group plays the most critical role.
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  • 11
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Rapid axoplasmic transport was studied in dystrophic mice of the 129/ReJ-dy strain. Proteins transported in vivo through α-motoneurons of the sciatic nerve were labeled by injections of [3H] or [35S] amino acids into the ventral horn of the lumbar spinal cord. Following an 18 h incubation, axoplasmic transport was quantitated by summing the radioactivity in the 10 mm length of sciatic nerve proximal to a ligation. Although the amount of transported radioactivity was small, transport appeared depressed when adult dystrophic mice were compared to controls. Transport was also studied in the sensory fibers of the sciatic nerve under in vitro conditions, resulting in high levels of transported radioactivity. In this system transport was strongly depressed. The severity of the deficiency varied with age, being small in animals with early clinical signs and becoming maximal (80–90%) in animals over 60 days of age. Proteins transported by adult dy/dy and +/+ animals were compared by gel electrophoresis using double-label techniques. Transport of nearly all proteins was depressed in dy/dy mice, although the possibility exists that small differences occur. The data suggest that the dystrophic state produces a significant deficiency in rapid axoplasmic transport in both motor and sensory fibers, and may interfere with transport processes in all neurons. Since rapid axoplasmic transport has been associated with membranes, the data are consistent with a general alteration of cellular membranes in dystrophic animals.
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  • 12
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The experiments reported here confirm that glutamate can penetrate the inner membrane of isolated rat brain non-synaptosomal mitochondria, either on a glutamate-hydroxyl antiporter or on a glutamate-aspartate antiporter.An inhibition of respiratory activity of mitochondria with glutamate as substrate was obtained in the presence of avenaciolide or N-ethylmaleimide. Swelling of the mitochondria in iso-osmotic NH4+-l-glutamate was inhibited in the presence of avenaciolide and N-ethylmaleimide, but mersalyl, kainic acid, glisoxepide and amino-oxyacetic acid had no effect on the glutamate-hydroxyl exchange. Glutamate induced the reduction of intramitochondrial NAD(P), as estimated by double-beam spectrophotometry, and this reduction was inhibited on the one hand by N-ethylmaleimide, avenaciolide or fuscine, on the other hand by aminooxyacetic acid. A direct estimation of the penetration of l-[14C]glutamate into brain mitochondria was performed by using the centrifugation-stop procedure. This penetration followed saturation kinetics, with a mean apparent Km of 1.56 MM at pH 7.4 and at 20°C, the value of Knax was 4.34 nmol per min per mg protein in the same conditions. IV-Ethylmaleimide slowed down the initial rate of glutamate penetration, and this inhibition appeared to be non-competitive with a Ki of 0.7 Mm -at pH 7.4 and at 20°C. The entry of glutamate was pH-dependent and it increased 2-fold in the pH range of 7.4 to 6.4. A temperature-dependence of glutamate transport was also shown between 2 and 25°C; the Arrhenius plot was a straight line, with a calculated EA of 12.8 kCal per mol of glutamate and a Q10 of 2.16. The activity of γ-glutamyl transpeptidase was practically absent in these rat brain mitochondria.Oxidation of extramitochondrial NADH by the‘malate-aspartate shuttle’reconstituted in vitro was followed in rat brain non-synaptosomal mitochondria. In the absence of extramitochondrial malate or glutamate the ‘shuttle’ did not function, and in the absence of extramitochondrial aspartate the rate of NADH oxidation was low. Glutamine or γ-aminobutyrate did not replace glutamate efficiently. A high inhibition of the‘malate-aspartate shuttle’occurred in the presence of avenaciolide or mersalyl, and a moderate one in the presence of n-ethylmaleimide, glisoxepide or n-butylmalonate.Glutaminase activity in intact brain mitochondria was inhibited in the presence of extramitochondrial glutamate.
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  • 13
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The effects of lithium chloride in vitro and in vivo were investigated on Na-K ATPase and Mg ATPase activities in synaptic plasma membrane, mitochondrial and synaptic vesicle fractions prepared from rat brain. In vitro, lithium chloride (10−3-10−8m) had no effect on ATPase activity in any of the fractions studied. Lithium chloride given chronically by i.p. injection (30 mg/rat/day) for 9 days had little effect on synaptic plasma membrane ATPases. Dietary administration of lithium chloride (60 mmol/kg food) produced a small but significant increase in synaptic plasma membrane Mg ATPase activity after 3 weeks administration and mitochondrial Mg ATPase activity after 1 week. There was no effect on synaptic plasma membrane Na-K ATPase activity. Salt supplementation reduced the toxic effects of lithium administration and it is suggested that toxicity may account for some of the previously reported changes in synaptic membrane ATPases produced by lithium.
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  • 14
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The surface properties of isolated rat brain myelin have been investigated by the method of particle microelectrophoresis. The mobility has been measured as a function of ionic strength and composition of the buffer, the results suggesting the presence of areas of non-ionogenic material. Antisera against ganglioside and myelin produce a fall in mobility whereas antiproteolipid apoprotein produces a slight increase but antibasic protein and anticerebroside sera had no effect on mobility. Of the lipases studied only phospholipase D produced a clear increase in mobility. From this preliminary study some indications of the asymmetric disposition of components in the myelin sheath may be derived. The ganglioside appears to be wholly located at intraperiod line interface, along with some fraction of the galactocerebroside and phosphatidylcholine. There appears to be few amino groups, but SH groups are present.
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  • 15
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— A microsomal fraction prepared from rat dorsal spinal nerve roots accumulated 45Ca by a temperature–and ATP-dependent mechanism. Uptake, which was maximal at pH 7.2–7.4, was potentiated 4-fold by 8 mm-oxalate and was linear over a 20 min incubation period. Ca uptake was not inhibited by sodium azide or by oligomycin and only slightly by ruthenium red suggesting that it was not of mitochondrial origin. On a sucrose density gradient the microsomal fraction equilibrated at between 0.25 m- and 0.65 m-sucrose but, using a discontinuous gradient over this range, no fraction enriched in Ca-accumulating activity could be separated. The possibility is discussed that the Ca-accumulating microsomes may be derived from smooth endoplasmic reticulum.
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  • 16
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Specific antibodies were raised in rabbits to acetylcholinesterase (AChE) from bovine caudate nucleus and the‘native’(14S + 18S) and globular (11S) forms of AChE from eel electric tissue. All AChE preparations were purified by affinity chromatography to a specific activity of 100–400 mmol acetylthiocholine hydrolyzed/mg protein/h. Antigenic specificities of the different enzyme forms were studied by immunodiffusion, Immunoelectrophoresis and micro-complement fixation. Minor differences in antigenic determinants were observed between the different molecular forms of electric tissue AChE. In crossover experiments using both eel AChE and bovine caudate AChE antisera there was complete absence of cross reactivity between the mammalian brain AChE and the different molecular forms of the electric tissue enzyme. Brain AChE activity was inhibited up to 50% in the presence of its antiserum.
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  • 17
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 18
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 19
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 20
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 21
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 22
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: γ-Glutamylation of p-tyramine, noradrenaline, dopamine and serotonin in rat brains was demonstrated by intraventricular injections of the radioactive amines and isolation of the γ-glutamylamines from the acidic extract of the rat brains. Formation of these γ-glutamylamines was proved to be catalysed by γ-glutamyltranspeptidase prepared from both rat kidney and brain. However, these compounds were degraded by γ-glutamylcyclotransferase of rat brain, but not by the emzyme of rat kidney.
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  • 23
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Homogenates of male rat hypothalami were fractionated by means of differential centrifugation, and α-melanocyte-stimulating hormone (α-MSH) in the various fractions was quantified by radioimmunoassay. Of the total quantity of α-MSH in the homogenate, 36% was recovered in the 11,500 g pellet and 31% sedimented between 11,500 and 105,000 g. α-MSH was not detected in the 105,000 g supernatant fluid. When the 900 g supernatant fluid was fractionated on continuous sucrose density gradients at non-equilibrium conditions, two populations of particles containing α-MSH were observed. When fractionated at equilibrium conditions, the two populations were recovered in a single band. These sedimentation characteristics indicate that the particles that contain α-MSH differ in size but are similar in density. After hypo-osmotic shock, the large particles containing α-MSH were not demonstrable, whereas the small particles appeared to be resistant to such treatment. In their sedimentation, the particles containing α-MSH were indistinguishable from particles containing thyrotropin releasing hormone (TRH) but were separable from those that contained luteinizing hormone releasing hormone (LHRH). It is suggested that the large particles containing α-MSH are synaptosomes.
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  • 24
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The neurotransmitter acetylcholine regulates cAMP concentrations in mouse neuroblastoma cells (clone NS20). In these cells, the action of acetylcholine appears to be specific: it does not alter basal concentrations of cAMP, but prevents the elevation of cAMP which is mediated by either adenosine or prostaglandin E1. The receptor for acetylcholine which is involved in this phenomenon has been identified as muscarinic. Pilocarpine and carbamylcholine, but not acetate or choline, will substitute for acetylcholine. Furthermore, the action of 10 μM-carbbamylcholine is blocked by ≥ nM concentrations of atropine, isopropamide or 3-quinuclidinylbenzilate, but not by mM concentrations of d-tubocurarine or hexamethonium.Of eight cholinergic antagonists tested, decamethonium and succinylcholine were the only two which were able to substitute for acetylcholine. These two antagonists are known to cause depolarization of post-synaptic cells. Decamethonium and succinylcholine appear to interact with the same muscarinic receptor, as their actions are also blockèd by low concentrations of 3-quinuclidinylbenzilate. In addition to these two depolarizing antagonists, the ionophores, valinomycin, A23187 and X537A, were also found to prevent elevation of cAMP concentrations. The involvement of specific membrane depolarization as being the active agent by which acetylcholine inhibits elevation of cAMP concentrations is discussed.
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  • 25
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Tyrosine hydroxylase activity correlated significantly with norepinephrine concentration and turnover, when results from regions containing predominantly noradrenergic terminals were compared, and with dopamine concentration and turnover when results from regions containing predominantly dopaminergic terminals were compared. Regions containing dopamine or norepinephrine cell bodies were characterized by higher tyrosine hydroxylase activities as compared to regions containing mostly nerve terminals. Higher levels of tyrosine hydroxylase activity and transmitter turnover were observed in regions containing dopaminergic terminals than in regions containing norepinephrine terminals. These findings are consistent with the view that tyrosine hydroxylase activity is linked to rates of catecholamine utilization by neurons in the CNS.
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  • 26
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Subacute methyl mercury (MeHg) intoxication was induced in adult rats following the daily intragastric administration of 1 mg MeHg/100 g body weight. Decreased [14C]leucine incorporation into cerebral and cerebellar slice protein was found. Weight loss occurred during the latent and neurotoxic phases but pair feeding did not reveal a significant defect in amino acid incorporation into slice protein. There was no decline in synaptosome protein synthesis in vitro during the latent phase but a significant decline in cerebellar and cerebral synaptosome synthesis was found during the neurotoxic phase. MeHg in vitro inhibited cerebral slice and synaptosome protein synthesis at half maximal concentrations of 7.5 and 12.5 μM respectively. Inhibition of synthesis in synaptosomes was non-competitive with K1 of 4 × 10−6M. MeHg had no effect on [14C]leucine or [14C]proline uptake into synaptosomes. There was no significant inhibition of synaptosome basal ATPase or Na + K ATPase at concentrations of MeHg (12 μM) giving half maximal inhibition of protein synthesis. No preferential inhibition of the chloramphenicol (55S) or cycloheximide sensitive components of synaptosome fraction protein synthesis was found, suggesting that the inhibition is common to both mitochondrial and extramitochondrial protein synthesizing systems. Addition of nucleotides and/or atractylate failed to influence protein synthesis and did not reverse the MeHg inhibition. Mannitol, as a replacement for the predominant cation species of the incubation medium, gave 40% inhibition of protein synthesis in the control but protected against further inhibition by MeHg.
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  • 27
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Epileptic seizures were induced electrically in rats paralyzed and ventilated with oxygen. Dissociation of brain polysomes and increase in ribosomal dimers were observed after multiple (25 or more) seizures, but were not seen after shorter treatments (up to 10 seizures). Polysomal dissociation and dimer formation occurred in vivo and were accompanied by decreased amino acid incorporation into brain proteins in cell-free systems in vitro. These events paralleled changes in brain energy reserves rather than changes in behavior.
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  • 28
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The toxicity of trimethyltin chloride and triethyltin sulphate on animal tissues was assessed by their effects on isolated phrenic nerve-diaphragm preparations. Studies by electron microscopy show that the inhibitory effects of these compounds on the muscular contractility of this tissue are associated with (a) the disruption of mitochondria and disorganisation of muscle fibres and (b) the depletion of neuromicrotubules in the axons of nerves innervating the muscle. The neurotoxie effect of triethyltin sulphate on neuromicrotubules is further substantiated by its inhibition (in a concentration-dependent manner) of the specific colchicine-binding activity of the crude and purified tubulin preparations derived from brain tissue. In addition, both triethyltin sulphate and trimethyltin chloride at a concentration greater than 100 μM completely prevent the normal in vitro assembly of microtubules from tubulin.
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  • 29
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A semi-automated fluorimetric assay technique for the concurrent estimations of noradrenaline, dopamine, 3, 4-dihydroxyphenylacetic acid, homovanillic acid and 3-methoxytyramine is described. The method is based on a rapid manually performed isolation of the catecholamines and metabolites on small columns of Sephadex G10, followed by automated fluorimetric dection in continuous flow systems. Samples containing no more that 2-5 ng (NA, DA, DOPAC or HVA) or 10 ng 3-MT could be reproducibly measured. The small Sephadex G10 columns has proven to be an excellent alternative to the currently used columns of alumina or ion-exchange resins.
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  • 30
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The depolarization-induced, calcium-dependent release of [3H]ACh from hippocampal synaptosomes was studied in a superfusion system. Release increased, with increasing depolarization. Barium and strontium effectively substituted for calcium during the depolarization, but magnesium inhibited the release. Releasable [3H]ACh is derived from the sodium-dependent component of the [3H]choline uptake which points out the physiologic importance of sodium-dependent choline transport. It is concluded that [3H]ACh release in this system has the same properties as neurotransmitter release in many other systems.Previous studies have shown that treatments which alter the activity of cholinergic neurons in vivo result in parallel changes in sodium-dependent choline uptake in vitro. When synaptosomes were utilized from animals treated to reduce cholinergic activity, there was a reduced release following the reduced uptake. Conversely, when synaptosomes were taken from animals treated to increase sodium-dependent choline uptake, there was an increase in the release. It is concluded that the changes in sodium-dependent choline uptake in vitro consequent to changes in neuronal activity in vivo result in parallel changes in releasable ACh.A comparison was made between the effect of a number of ions and agents on release and their effect on the in vitro, depolarization-induced activation of sodium-dependent choline uptake. Barium and strontium, ions which substitute for calcium in the release process, support the in vitro activation of uptake. Vinblastine and Bay a 1040, compounds which block release, prevented the in vitro activation of sodium-dependent choline uptake. However, magnesium blocked release in a dose-dependent manner, but did not block the activation of uptake in vitro. Rather, magnesium substituted for calcium and supported the activation of uptake in a dose-dependent fashion. It is concluded that acetylcholine release is not necessary for the activation of choline uptake.
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  • 31
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 32
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 33
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    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), 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— Slices of cerebellum from Purkinje cell-deficient, neurologically mutant ‘nervous’ mice or normal littermates synthesized cyclic AMP and cyclic GMP during in vitro incubations. Resting levels of cyclic AMP were the same in the two groups, but accumulations in the presence of kainic acid, a glutamic acid analogue, or norepinephrine were significantly greater in the ‘nervous’ mice. Resting levels of cyclic GMP were lower in the ‘nervous’ mice, but the elevations produced by kainic acid were the same in both groups. Adenylate and guanylate cyclase activities in the cerebellum were not affected by the mutation. These findings indicate that cyclic nucleotide synthesis in the cerebellum does not occur solely in the Purkinje cell population.
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  • 35
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Using the method of least squares, a logistic curve was fitted to the data points for DNA content in neonatal rat cerebellum versus postnatal age (day 0 is the day of birth). The resultant equation was differentiated to give an expression for the rate of cerebellar DNA accumulation in units of ng/h per mg wet cerebellum. The DNA accumulation rate in control rats increased from 77.0 at 2 days of age to a maximum of 108 at 7 days of age and declined thereafter to a minimum of 16.3 on day 15. Thyroxine treatment significantly (P 〈 0.05) increased the rate to 89.8 (117% of control) at 2 days of age, and a significant elevation was maintained to 6 days of age at which time a maximum rate of 115 (114% of control) was attained. The rate was significantly decreased below control at 9 and 12 days of age, and reached a minimum of 9.22 on day 15.The developmental pattern for the activity of cerebellar thymidylate synthetase (EC 2.1.1.6), in units of pmol/h per mg wet cerebellum, closely paralleled the pattern for DNA accumulation rate in both control and thyroxine-treated animals. In controls, thymidylate synthetase activity increased from 98.6 at 2 days of age to a maximum of 125 at 7 days of age and declined thereafter to a minimum of 30.0 at 15 days of age. In thyroxine-treated animals, the activity was significantly increased to 118 (122% of control) at 4 days of age and remained significantly elevated through 6 days of age at which time a maximum activity of 154 (115% of control) was attained; thereafter, the activity was significantly decreased below control and reached a minimum of 16.9 (56.3% of control) on day 15. The developmental pattern for the activity of cerebellar thymidine kinase (EC 2.7.1.21) did not parallel the DNA accumulation rate quite so closely, in neither treated nor control animals, as did the pattern for thymidylate synthetase activity.These data suggest that thymidylate synthetase activity in the developing rat cerebellum may be more important for maintenance of replicative DNA synthesis than is thymidine kinase activity. In addition, the thyroxine-induced acceleration of the increase and subsequent decline in rate of DNA accumulation and in the activities of thymidylate synthetase and thymidine kinase in developing rat cerebella is probably the result of alterations in the number of external granular cells undergoing replicative DNA synthesis.
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  • 36
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Endogenous protein phosphorylation has been studied during in vitro polymerization of microtubules by incubating a purified tubulin preparation at 37°C in the presence of radioactive ATP. At optimal conditions the rate of phosphorylation was found to follow the course of polymerization by a shift to a lower rate at the polymerization plateau.Zn2+ at 0.5 mm was shown to stimulate phosphorylation, mainly of tubulin-associated proteins (mol wt 110,000 and 175,000,) and to a lesser extent of tubulin. The effect occurred at Zn2+-concentrations which induce formation of tubulin sheet polymers, which suggests that the state of aggregation of tubulin is of importance for the phosphorylation. In contrast to Zn2+, Mg2+ only increased phosphorylation of the high molecular weight proteins, and to a lesser degree. The stimulation by Zn2+ or Mg2+ was potentiated by cyclic AMP or cyclic GMP.A low concentration of Zn2+ (5 μm) or cyclic GMP at 10 μm inhibited phosphorylation, possibly by interaction with a co-existing protein phosphatase.
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  • 37
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— [2-14C]Propionate injected into rats was metabolized into [14C]glucose and 14C-labelled aspartate, glutamate, glutamine and alanine. The results are consistent with the conversion of propionate into succinate and the oxidation of succinate into oxaloacetate, the precursor of labelled amino acids and the substrate for gluconeogenesis.The ratio of the specific radioactivity of glutamine to glutamate was greater than 1 during the 30 min period in the brain, indicating that propionate taken up by the brain was metabolized mainly in the ‘small glutamate compartment’ in the brain. The results, therefore, support the previous conclusion (Gaitonde, 1975) that the labelling of amino acids by [14C]propionate formed from [U-14C〉]-threonine in thiamin-deficient rats was metabolized in the ‘large glutamate compartment’ of the brain.The specific radioactivity ratio of glutamine to glutamate in the liver was less than 1 during the 10 min period but greater than 1 at 30min. These findings which gave evidence against metabolic compartments of glutamate in the liver, were interpreted as indicative of the entry of blood-borne [14C]glutamine synthesized in other tissues, e.g. brain. The labelling of amino acids when compared to that after injection of [U-14C]glucose showed that [2-14C]propionate was quantitatively a better source of amino acids in the liver. The concentration of some amino acids in the brain and liver was less in the adult than in the young rats, except for alanine and glutathione, where the liver content was more than double that in the adult.
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  • 38
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The uptake of D-glucosamine by rat brain synaptosomes is studied as a function of time, temperature and synaptosomal protein and substrate concentrations. The rate of D-glucosamine uptake, after correcting for simple diffusion, obeys Michaelis-Menten kinetics. The apparent kinetic constants for the uptake process are Km= 2.5 0.8 mm, Vmax= 3.7 ± 1.2 nmol/mg protein/min. D-Glucose, D-mannose, 2-deoxy-D-glucose and 3-0-methyl-o-glucose are potent inhibitors of D-glucosamine uptake. 2-Deoxy-D-glucose and D-glucosamine inhibit the uptake of one another in a simple competitive manner, indicating their sharing of a common transport system. Cytochalasin B, phloretin and phloridzin are powerful competitive inhibitors of D-glucosamine uptake with apparent inhibitor constants (K1) of 7.0 × 10-5, 2.3 × 10-3 and 0.4 mM, respectively. The uptake is unaffected by Na+, Li+ and Mg2+, partially inhibited by NH4+, Mn2+ and Ca2+, and slightly stimulated by PO4-ions. D-Glucosamine uptake is also sensitive to inhibition by several sulfhydryl reagents, thus implying the involvement of sulfhydryl groups in the transport process. The apparent affinity constants for synaptosomal transport for both D-glucosamine and 2-deoxy-D-glucose are about 4 times greater in 7-day-old than in the adult rat brains.
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  • 39
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— We have investigated the in vivo synthesis of stable RNA in the rat nodose ganglia following unilateral vagotomy. Incorporation of precursor into rRNA, and possibly tRNA, in the injured ganglion increases rapidly after vagotomy, reaching twice the normal value at 2 days post-crush. In contrast to this, incorporation within the uninjured colateral ganglion decreases to about 65% of normal values after 4 days. But, by 7 days, both ganglia appear to be returning to their normal levels. One phase of DNA synthesis is detected in the injured ganglion, at days 1 and 2. while two phases are found in the contralateral ganglion, at days 2 and 34.
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  • 40
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The synthesis of rapidly-labelled RNA was studied in the nodose ganglia following unilateral vagotomy. Early changes were detected in the electrophoretic patterns of RNA from both ganglia following a crush of the right vagus. The right ganglionic response is characterized by two phases, the first involving rapid processing of rRNA with associated changes in ‘message-like’ RNA (mlRNA). A second change, detected by 14 days, appears to involve an increase in the heterodispersity of mlRNA and decreased processing of rRNA. The left ganglion follows a very similar response to that of the right with the exception of the changes in rRNA. However, the left response lags behind that of the right by at least 1 day. We conclude that extensive changes in gene expression are occurring in both ganglia. The similarity of the responses of both ganglia suggests that axon regeneration (in the right) and collateral sprouting (in the left) may produce analogous changes in gene expression, but not in rRNA synthesis.
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  • 41
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— l-Glutamic acid decarboxylase (GAD) was isolated from bovine cerebellum and purified approx 32-fold by a combination of DEAE-Sephadex chromatography and gel filtration. This preparation was purified electrophoretically. Rabbit antiserum against the electrophoretically purified bovine GAD was found to react with the decarboxylase of bovine cerebellum and mouse brain. Examination of GAD enzyme specific activity at various postnatal ages of developing mouse brain showed that an initial rise in GAD activity occurs at 6 days postnatally. followed by a rapid increase in enzymatic activity which reaches a maximum at 28 days postnatally. Quantitative immunoprecipitation of mouse GAD by rabbit anti-GAD antisera indicated that the amount of GAD per brain increases 10-fold over the period between 1 and 28 days postnatally. This increase coincides closely with the GAD enzyme activity profile. Therefore, the increase in GAD enzyme specific activity during the postnatal development of mouse brain represents an increase in the absolute amount of GAD enzyme protein.
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  • 42
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Closely related changes in the levels of acetylcholine (ACh) and adenosine triphosphate (ATP) in the electric organ of Torpedo exist during rest and synaptic activity. The present work clarifies these relations by showing:〈list xml:id="l1" style="custom"〉1That both substances are involved in an oscillatory process induced by nerve stimulation.2Both substances are present in synaptic vesicles; the size of the bound pool of ACh is Ca2-dependent and is large when Ca2+ is low. Free ACh and transmission are restored when Ca2+ is present in the incubation medium.3The amount of ATP in the tissue is also Ca2+-dependent but is low when Ca2+ is omitted. The addition of Ca2+ to the physiological medium restores the amount of ATP in the tissue.4There is a postsynaptic release of ATP triggered by transmitter depolarization. This release was measured after single nerve impulses.5When added to the incubation medium, nucleotides strongly inhibit transmitter release. It is suggested that the postsynaptic release of ATP regulates transmitter release.
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  • 43
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Rat pups were reared in litters of 20 and litters of 6 to study effects of malnutrition on cerebellar development. Cell production and cell content were determined by assaying for DNA, as a measure of cell number, and RNA and protein, as indicators of cell constituents. By comparing DNA contents at 3, 4, 8, 11, 14, 17, 21, and 28 days after birth, we concluded that (a) there is little nutritional reserve at birth since significant differences appear by day 4, (b) most relative differences between groups appeared by day 8, with absolute differences increasing to day 21, and (c) there is partial recovery of cell number and cell constituents in the malnourished rats between 21 and 28 days.Areal measurements of histological preparations showed that malnutrition resulted in less total area in cerebellar midsagittal sections at days 8, 11. and 14. In malnourished animals, the germinal matrix area of the cerebellum, the external granular layer, was smaller on the 8th postnatal day, the same on the eleventh day, and larger on the fourteenth day when compared with that of well fed animals. At all three ages alterations could be discerned in the distribution of cells between the mitotic external mantle and nonmitotic internal matrix portions of the external granular layer.Further studies involving exchanging animals between large and small litters at various ages indicated that the time around days 4 to 8 is most sensitive to malnutrition. The results suggest a process in which malnutrition exerts its maximum effect by a slowing of cell production in the external granular layer in the initial exponential growth phase. It is likely that an adaptation occurs immediately in the external granular layer which subsequently permits a partial recovery of cerebellar growth between days 21 and 28.
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  • 44
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Rats were exposed to 5 atmospheres absolute of oxygen, and [1-14C]acetate was injected into the jugular vein either before or at the onset of electroencephalogram-defined convulsions. Levels of 14C observed 2.2 min after the injection were reduced in the total lipids of brain and elevated in the blood of convulsed rats when compared to the nonconvulsed controls. These differences between convulsed and nonconvulsed animals were less pronounced when measured 15 and 60 min after injection. Convulsions did not change the amount of 14C incorporated into the total lipids of plasma during the 60 min period studied. Six fractions obtained from total lipid extracts of brain by TEAE-cellulose showed similar 14C distributions in convulsed and control animals. The results suggest that oxygen-induced convulsions cause an impaired utilization of systemically administered acetate for fatty acid incorporation into the lipids of brain.
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  • 45
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The ganglioside content and composition of brains from twenty-five human fetuses, three new-born babies and ten children, were studied. The ages ranged from 13 weeks gestation to 26 months postpartum. Each brain was divided into forebrain. cerebellum and brain stem. The concentration of total gangliosides rose to a plateau at different stages of development in the different parts, whereas the total amount reached a constant value at 9 months of age in each part. The developmental profile of individual gangliosides differed in the different parts of the brain. Thus, in the forebrain GD1a. and in the cerebellum GD1a rose to become the major gangliosides. The brain stem showed little change in its ganglioside pattern during the developmental period studied. The possible significance of these charges in the gangliosides during development is discussed.
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  • 46
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Dopamine, norepinephrine, carbamylcholine and PGE1 (prostaglandin E1). increased cyclic AMP concentrations in slices of bovine superior cervical ganglia. PGF1α was less effective and neither PGE2 nor PGF2α had any effect. Dopamine and PGE, alone or in combination, did not modify low Km cyclic AMP phosphodiesterase activity. Combinations of dopamine and PGE, showed a marked synergistic effect, increasing ganglionic cyclic AMP to a much greater extent than that observed when the two compounds were tested alone. Norepinephrine (10 μM), which increased cyclic AMP as much as 10 μm-dopamine, showed no synergistic effect when tested in the presence of PGE1 or other PGs. Phentolamine, fluphenazine and triflupromazine blocked the dopamine effect without suppressing its synergism with PGE1 Adenylate cyclase of synaptosomes isolated from the ganglia under a variety of experimental conditions appeared to be as responsive to PGE1 as the slices, but it was poorly stimulated by dopamine and was not synergistically modulated by dopamine in the presence of PGE1These and other data are interpreted as indicating the presence of both a PGE1-sensitive and a PGE1-modulated dopamine-sensitive adenylate cyclase in the cervical ganglion. These adenylate cyclases are tentatively assigned to pre- and post-synaptic structures respectively.
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  • 47
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Oligodendroglia were isolated from fresh and frozen human autopsied brains by a modification of our technique for isolation of neuronal perikarya and astroglia (Iqbal & Tellez-Nagel, 1972). Cerebral white matter was minced in a hypertonic hexose-Ficoll buffered medium, passed through successive screens of decreasing pore size, and the cells were then separated on a discontinuous sucrose density gradient using low speed centrifugation. Cells could also be isolated by substituting sucrose for hexoses in the cell isolation medium. About 95% of the isolated cells had morphology characteristic of oligodendroglia. The usual contaminants in this fraction were capillary fragments, red blood cells, and a few astrocytes. Free myelin was only sparsely seen. About 5–10% of the isolated oligodendroglia had one or more loops of loose membranes extending from the cell plasma membrane. These membraneous loops resembled myelin. The ultrastructural preservation of the cells was poor. The average yield per gram of wet tissue was 52 million cells amounting to 2.4 mg protein, 283 μg DNA, and 94 μg RNA. The protein, DNA, and RNA contents per average cell were 47, 5.3, and 1.8 pg respectively. About 50% of the tissue DNA was recovered as isolated cells, suggesting a larger proportion of oligodendroglia to astroglia, the other principal cell type in human white matter.Comparison of the total protein profiles of the isolated oligodendroglia with those of the purified human myelin on sodium dodecyl sulfate-polyacrylamide gels revealed the presence of all human myelin constituent proteins in the isolated cells except the intermediate (or DM-20) myelin proteins. Densitometry of the gels stained with Fast Green showed that the ratio of protein bands corresponding to myelin encephalitogenic basic protein (BP) to myelin proteolipid protein (PLP) in the isolated cells was three-fold as high as in purified human myelin. The oligodendroglial BP which constituted about 14% of the total cell protein contents, also coelectrophoresed with the myelin BP on pH 4.3 polyacrylamide gels. Furthermore, the two dimensional peptide maps of the tryptic digest of the cell BP labelled with 125I were also identical to the similarly treated myelin BP. The data suggest that the BP can be used as a chemical marker for oligodendroglia.
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  • 48
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Uptake of 2-deoxy-d-glucose (2-DG) was investigated in capillaries isolated from rat brain. A high affinity, carrier-mediated transport system was defined with an apparent Km for 2-DG of 93 μM. Uptake was temperature-dependent and markedly inhibited by phloretin and selected hexose isomers. The apparent Ki for d-glucose inhibition of 2-DG uptake was 98 μM. Essentially all of the 2-DG retained by the capillary preparation could be released by sonication and 95% was recovered as free unphosphorylated 2-DG. Uptake was not sodium-dependent and not altered by insulin. These results suggest that movement of glucose across the blood-brain barrier through endothelial cells probably is not rate-limiting unless blood glucose levels are extremely low.
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  • 49
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The cholesterol ester hydrolase of rat brain, localized almost exclusively in the myelin sheath, has been solubilized from the acidic high-molecular-weight protein fraction of purified myelin. Solubilization required both high ionic strength and an amphoteric detergent, Miranol H2M. Solubilized preparations with apparent purification factors of 300–500 fold over the starting homogenate still contained approx 25% lipid but were retarded on the Sephadex G-200 column. The enzyme was reversibly precipitated when the concentration of either Miranol H2M or KCI was lowered below certain critical levels. The soluble enzyme was characterized for the pH optimum, linearity against incubation time and enzyme protein, and apparent Km. Activity was dependent on the presence of exogenously added lipid. Phosphatidylserine at optimum concentrations stimulated the hydrolytic activity 25-Fold. Effects of other lipids, bile salts, cations, heating and potential inhibitors were examined. β-Naphthyl oleate was a competitive inhibitor but both β-naphthyl acetate and cholesteryl butyrate were non-competitive inhibitors. These results suggested a heterogenous nature of the rat myelin cholesterol ester hydrolase, possibly with different specificities with respect to the chain length of the acyl group of substrates.
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  • 50
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The enzyme in rat brain responsible for the de-acetylation of N-acetyl-aspartic acid has been partially purified. In contrast to the enzyme from hog kidney which is stable at 70°C, it rapidly denatures above 57°C. The rat brain enzyme has the same Km for its substrate and the same solubility in ammonium sulphate solution as the hog kidney enzyme. Results of migration on starch gel electro-phoreses and isoelectric focusing indicate a pI for the amidohydrolase of 5.1. A variety of potential substrates, modulators, and inhibitors have been examined.
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  • 51
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The activities of each enzyme associated with the pentose phosphate pathway as well as the non-enzymatic intermediates in this pathway were measured in synaptosomes isolated from rat cerebral cortex. The specific activities of transketolase (EC 2.2.1.1) and transaldolase (EC 2.2.1.2) were significantly lower in synaptosomes than cerebral cortex; however, the specific activities of glucose-6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), ribosephosphate isomerase (EC 5.3.1.6) and ribulosephosphate epimerase (EC 5.1.3.1.) were comparable in homogenates of synaptosomal fractions and cerebral cortex. Concentrations of most intermediates of the pentose pathway were also similar in extracts of synaptosomes and brain homogenates.Six hours after treatment of rats with the nicotinamide analog, 6-aminonicotinamide (6-AN), 6-phosphogluconate levels in synaptosomes were increased 5-fold; however, glucose-6-phosphate levels remained unchanged. During a 30 min in uitro incubation 6-phosphogluconate levels increased approx 2-fold in synaptosomes obtained from 6-AN treated rats but did not change in synaptosomes from untreated rats. During the same period glucose-6-phosphate levels decreased in synaptosomes from both control and 6-AN treated rats. The conversion of both [1-14C]glucose and [6-14C]glucose to 14CO2 was depressed in synaptosomes from 6-AN treated rats; however, the ratio of the two isotopes converted to 14CO2 was essentially the same. It is concluded that the pentose phosphate pathway is active in nerve endings both in vivo and in vitro.
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  • 52
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— We have in the present study investigated the properties of mevalonate kinase, phosphomevalonate kinase and pyrophosphomevalonate decarboxylase in the 105,000 g supernatant fractions from rat brain, and determined whether the activities of these enzymes change during brain development. All three enzymes in brain showed a specific requirement for ATP for optimal activity. The presence of Mg2+ as divalent cation was also required for optimal activity of mevalonate kinase and phosphomevalonate kinase. Both Mg2+ and Mn2+ were equally effective divalent metal ions for pyrophosphomevalonate decarboxylase in brain. Mevalonate kinase as well as phosphomevalonate kinase were active in a broad pH range of 6.5–8 while the pH curve for pyrophosphomevalonate decarboxylase showed a peak activity at approx 6. No age-dependent change occurred in the activities of mevalonate kinase and phosphomevalonate kinase in developing brain, whereas pyrophosphomevalonate decarboxylase activity in brain increased during the 1st week after birth, reached a peak value at about the 8th day of age and declined slowly thereafter. The Km for brain mevalonate kinase in 2, 13 and 52 day old rats were 312, 400 and 434 μM, respectively. The Vmax for the kinase in 2, 13 and 52 day old rats were in the range of 45–52 nmol/h/mg protein, respectively. This suggests that, like in liver (Ramachandran & Shah, 1976), pyrophosphomevalonate decarboxylase in brain may also be one regulatory step for cholesterol synthesis.
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  • 53
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The uniformity and speed of inactivation of mouse brain adenylate cyclase, guanylate cyclase and cyclic nucleotide phosphodiesterase were measured after 6 kW microwave irradiation (MWR). Inactivation of enzymes was uniform throughout the brain during heating and 100% loss of activity was evident after 300 ms. MWR. For comparison of effects of inactivation times on levels of cyclic nucleotides measured in regional brain areas, cyclic AMP and cyclic GMP were estimated after 1.5 kW MWR requiring 4 s of heating and 6 kW MWR requiring 300 ms. Except for corpus striatum, uniformly lower levels of cyclic AMP were measured following 300 ms vs. 4s MWR. There was no change in cyclic GMP levels in regional brain areas after 4s vs. 300 ms MWR. Cyclic AMP and cyclic GMP were measured from the same regional brain tissue samples after 300 ms and ratios calculated. The finding of much lower cyclic AMP:cyclic GMP ratios than had previously been reported suggests that slow inactivation times provide for the measurement of regional brain cyclic nucleotide values which are not consistent with the in-vivo state.
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  • 54
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The localization of an acid lipase-esterase which cleaves the fluorogenic substrate 4-methyl-umbelliferyl oleate at pH 5 was studied, because previous experiments has shown this activity to be reduced in the plaques of multiple sclerosis. In the human cerebellum, quantitative histochemical methods showed the activity to be relatively low in the molecular layer, compared to the granule cell layer; but the underlying white matter was the most active. In the human spinal cord, anterior horn cell bodies were richest in acid lipase, but white matter was, on a dry weight basis, as active as neuropil. Oligodendrocytes obtained in bulk from bovine white matter according to Poduslo & Norton (1972) had a specific activity up to 20 times greater than the crude myelin fraction. While it remains possible that in myelin the enzyme is in an inactive or inhibited state, the results indicate that the enzyme is localized in oligodendroglial cell bodies and suggest its use as a marker.
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  • 55
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Uptake kinetics of l-glutamate in cultured, normal glia cells obtained from the brain hemispheres of newborn mice were measured together with the activities of the glutamate metabolizing enzymes, glutamic-oxaloacetate-transaminase, glutamate dehydrogenase and glutamine synthetase. During 3 weeks of culturing, the activities of the enzymes rose from low neonatal values toward the levels in the adult brain (206, 12.3 and 25.9 nmol. min−1. mg−1 cell protein for the three enzymes, respectively). The uptake kinetics indicated an unsaturable component together with an uptake following Michaelis-Menten kinetics with a Km of 220 μm and a Vmax of 7.9 nmol. min−1. mg−1 cell protein. The saturable glutamate uptake was inhibited by d-glutamate, l-aspartate and α-aminoadipate whereas l-glutamine, GABA and glutarate had no effect. The uptake which was Ca2+-independent had a Km for sodium of 18mm and it was stimulated by an increase in the external potassium concentration from 5 to 10 and 25 mm. The results suggest that glia cells are important for the uptake of glutamate from synaptic clefts and for the subsequent metabolism of glutamate.
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  • 56
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— MAO of human brain and liver mitochondria was solubilized by a procedure that preserved the substrate and inhibitor selectivities of the original mitochondrial preparation. Techniques that are designed to separate proteins on the basis of molecular size or net surface charge did not yield a physical separation of enzymically active A and B forms, even in the presence of ionic detergents or with limited proteolysis. However, sulfhydryl inhibitors, inorganic salts, ionic detergents, heat treatment, and sonication all tended to cause selective inactivation of serotonin-metabolizing activity in solubilized preparations. Experiments with selectively inhibited (membrane-bound or solubilized) MAO supported the concept of at least two independent kinds of substrate binding site, only one of which metabolizes serotonin (A type) and another (B type) which has a very strong affinity for β-phenethylamine. l-Norepinephrine, tryptamine, dopamine, and tyramine could be classified as common substrates. The lowest Km values were found for tryptamine at A sites and for β-phenethylamine at B sites. Results of this study suggest that the different MAO sites could be part of the same large molecular complex, which may normally be embedded in the outer mitochondrial membrane so that A sites are more dependent on their lipid environment within this membrane.
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  • 57
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Crude or purified rat brain choline acetyltransferase (ChAc) is activated by anions. Among anions, Cl− is the most effective and may promote an up to 60 fold increase in Vmax. In the absence of Cl−, at low ionic strength, acetylcholine (ACh) is a good ChAc inhibitor (Ki= 0.310 mm). The ACh inhibition becomes negligible when Cl− is increased to 145 mm (ACh Ki= 45 mm). These results are discussed in terms of regulation of ACh synthesis by nerve terminals. It is proposed that ChAc is part of a presynaptic membrane bound multienzymatic complex under direct control of the ion fluxes promoted by nerve impulses.
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  • 58
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— We describe an α-bungarotoxin binding component from Dromphila melanoyaster that has the properties expected of an acetylcholine receptor. Toxin binding to a paniculate form of this component has been shown to be proportional to amount of extract, to be saturable and to be destroyed by heat. Localization studies using 125I-α-bungarotoxin binding to frozen sections has shown toxin binding to be restricted to synaptic areas of the Drosophila CNS. We have also shown that this toxinbinding component can be treated with Triton X-100 without significantly altering its toxin-binding and pharmacological specificity. The ability of preincubation with cholinergic ligands to block labeled α-bungarotoxin binding to both particulate and detergent treated extracts has been studied. The nicotinic agents nicotine, d-tubocurarine, and acetylcholine are the most effective blocking agents. All of the muscarinic agents tested and the nicotinic agent decamethonium were less effective than acetylcholine in preventing α-bungarotoxin binding.
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  • 59
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— An assay method based on the use of specific oxidases has been used to search for D-amino acids in the organs of Octopus vulgaris. A high concentration of D-aspartate has been detected in the central brain and in the optic lobes but not in non-nervous organs.Other D-amino acids appear to be absent from brain and from other tissues.
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  • 60
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Abstract-We have previously described a 5-fluorodeox yuridine (FUdR) resistant neuroblastoma variant, possessing normal levels of ATP: thymidine-5-phosphotransferase (EC 2.7.1.21) [trivial name: thymidine kinase (TK)] but an 8-fold elevation in methy1enetetrahydrofolate:dUrd-5′P C-methyltransferase (EC 2.l.l.b) [trivial name: thymidylate synthetase (TS)] relative to the drug-sensitive parental clone. This variant possesses elevated levels of the parental TS species, 30% of which is uninhibitable by in vivo pulses of FUdR, suggesting the subcellular compartmentalization of this enzyme. We contrast this variant with a second FUdR resistant clone isolated from an ethyl-methane-sulfonate mutagenized population of the parental clone. This variant displays a 96% reduction in TK specific activity, despite normal FUdR and thymidine uptake rates, demonstrating the independence of thymidine phosphorylation and uptake. Grown without drug, its resistance declines (half-life of 15 cell divisions) with its TK specific activity rising to a plateau of 16% of the parental level after 56 cell divisions. Thymidine (1.0μM) protects the TK+ but not the TK- variants from FUdR induced growth inhibition but is without effect on TS specific activity. Unlike Tetrahymena (DICKENS et al., 1975), neuroblastoma TS activities appear not to be regulated by adenosine or guanosine cyclic nucleotide levels.
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  • 61
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— A method has been developed for the simultaneous measurement of the rates of glucose consumption in the various structural and functional components of the brain in vivo. The method can be applied to most laboratory animals in the conscious state. It is based on the use of 2-deoxy-D-[14C]glucose ([14C]DG) as a tracer for the exchange of glucose between plasma and brain and its phosphorylation by hexokinase in the tissues. [14C]DG is used because the label in its product, [14C]deoxyglucose-6-phosphate, is essentially trapped in the tissue over the time course of the measurement. A model has been designed based on the assumptions of a steady state for glucose consumption, a first order equilibration of the free [14C]DG pool in the tissue with the plasma level, and relative rates of phosphorylation of [14C]DG and glucose determined by their relative concentrations in the precursor pools and their respective kinetic constants for the hexokinase reaction. An operational equation based on this model has been derived in terms of determinable variables. A pulse of [14C]DG is administered intravenously and the arterial plasma [14C]DG and glucose concentrations monitored for a preset time between 30 and 45min. At the prescribed time, the head is removed and frozen in liquid N2-chilled Freon XII, and the brain sectioned for autoradiography. Local tissue concentrations of [14C]DG are determined by quantitative autoradiography. Local cerebral glucose consumption is calculated by the equation on the basis of these measured values.The method has been applied to normal albino rats in the conscious state and under thiopental anesthesia. The results demonstrate that the local rates of glucose consumption in the brain fall into two distinct distributions, one for gray matter and the other for white matter. In the conscious rat the values in the gray matter vary widely from structure to structure (54-197 μmol/100 g/min) with the highest values in structures related to auditory function, e.g. medial geniculate body, superior olive, inferior colliculus, and auditory cortex. The values in white matter are more uniform (i.e. 33–40 μmo1/100 g/min) at levels approximately one-fourth to one-half those of gray matter. Heterogeneous rates of glucose consumption are frequently seen within specific structures, often revealing a pattern of cytoarchitecture. Thiopental anesthesia markedly depresses the rates of glucose utilization throughout the brain, particularly in gray matter, and metabolic rate throughout gray matter becomes more uniform at a lower level.
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  • 62
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Cortical slices from rat brain were incubated in Krebs-Ringer phosphate medium. Activity of the pyruvate dehydrogenase complex (PDH) was measured in homogenates of the incubated tissue. Increasing the extracellular KCI concentration from 5 to 75 mM caused a dose-dependent increase in activity of this rate-limiting mitochondrial enzyme. The increase in PDH activity, produced by high concentration of KCI. was associated with a decrease in the tissue content of ATP. Omission of calcium, or replacement of sodium by choline, reduced, and addition of ouabain prevented, the activation of the enzyme in the depolarized tissue.The mechanism by which extracellular potassium can affect PDH activity is unknown. However, it is most likely that the alterations in enzyme activity are related to changes in properties of cell membranes during depolarization leading to intracellular events directly affecting the enzyme complex. These could include alterations in the concentrations of adenine nucleotides or free calcium ions in the cell.
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  • 63
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Injections of dexamethasone (0.1 mg/kg/day, s.c.) on the first 2–3 days of life increased the phenylethanolamine-N-methyltransferase (PNMT) activity and epinephrine content of the superior cervical ganglion (SCG) and stellate ganglion of neonatal rats; the dopamine content was unaltered while norepinephrine was slightly reduced in these ganglia. Dexamethasone did not alter the PNMT activity or epinephrine content of the salivary glands or heart. The PNMT activity and epinephrine content of the SCG remained elevated for 10–14 days. Pretreatment with 6-hydroxydopamine did not alter the dexamethasone effects.Injections of adrenocorticotrophic hormone (ACTH) (25 munits/rat twice a day) or exposure to a cold stress (4°C, 3 times a day) on the first 2–3 days of life, elevated the plasma concentration of corticosterone, and also increased the PNMT activity and epinephrine content in SCG of neonatal rats. Injecting pregnant rats with dexamethasone or ACTH, or exposing them to cold or restraint stress on the last 3 days of gestation increased the PNMT activity and epinephrine content in the SCG of their pups. These results indicate that the actions of dexamethasone on neonatal sympathetic ganglia may be mimicked by increasing the plasma concentration of endogenous adrenocortical steroids.
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  • 64
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Cat geniohyoid muscle samples containing endplate regions, when incubated in vitro at 37°C in phosphate buffer (pH 73, release acetylcholinesterase (AChE; EC 3.1.1.7) to the bathing medium. By treating the muscle samples with collagenase (EC 3.4.4.19), it was confirmed that most of the AChE released came from the endplates. Enzyme liberation was studied 10 days after either local injection of 10mM-cokhicine into the hypoglossal nerve or following nerve transection. Results showed that the rate of release is increased by denervation, but is not affected by axoplasmic transport blockage. It is postulated that the cellular contact between nerve and muscle—altered by denervation but not by interruption of axoplasmic transport—is an essential factor in maintaining the localization of end-plate AChE within the synaptic cleft substance. This does not invalidate the possible participation of ACh and muscle activity in such enzyme localization.
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  • 65
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Rats were subjected to cerebral compression ischaemia for 15min and were subsequently recirculated with blood for periods up to 3 h. In vivo incorporation of intravenously administered L-[1–14C]valine into total brain proteins was found to be severely inhibited (about 20% of controls) after 45 min of recirculation. After 3 h, protein synthesis had increased, the specific radioactivity of proteins then being about 40% of controls. The post-ischaemic inhibition of protein synthesis was accompanied by a breakdown in polyribosomes and a concomitant increase in ribosomal subunits. In vitro incorporation of L-[1–14C]phenylalanine by a postmitochondrial supernatant system derived from animals subjected to 15 min ischaemia and 15 min recirculation was also severely reduced and showed, in contrast to control animals, no response to the addition of a specific inhibitor of polypeptide chain initiation (Poly(I)). Together with the in vivo accumulation of ribosomal subunits this indicates a block in peptide chain initiation during the early stages of recirculation.Polyribosomes from animals subjected to 15 min ischaemia without recirculation showed a normal rate of in vitro protein synthesis which was inhibited by Poly(I) to a similar extent as polyribosomes from control animals. These results suggest that the post-ischaemic inhibition in chain initiation develops during the early stages of recirculation rather than during the ischaemic period itself.
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  • 66
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Cyclic AMP was found to accumulate in rabbit vagus nerve after stimulation of specific β-adrenoceptors. The increase in cyclic AMP content by either isoproterenol or epinephrine was inhibited by the β-adrenoceptor antagonists sotalol and propranolol. α-Adrenoceptor agonists and antagonists, indirect sympathomimetics and theophylline had no effect on the accumulation of cyclic AMP in vagus nerve. The cyclic AMP increase caused by either β-adrenoceptor agents or adenosine was found to have no effect on resting potentials, action potentials or on post-tetanic hyperpolarization.
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  • 67
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Tryptophan uptake was studied in brain slices and synaptosomes prepared from regions known to vary in the numbers of serotoninergic cell bodies and nerve endings that they contain. The rate of tryptophan uptake was highest in hypothalamus for both types of preparation. Differences among the regions were much more pronounced in isolated nerve endings (synaptosomes). Loading with tryptophan did not affect the uptake into tissue slices. Tryptophan accumulation in hypothalamus synaptosomes was reduced after intraventricular injection of 5,7–dihydroxytryptamine whereas no change was observed in synaptosomes prepared from cerebellum under the same conditions; accumulation by synaptosomes prepared from the hypothalamic and hippocampal regions was reduced after raphe lesions.
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  • 68
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Choline kinase (ATP:cholinephosphotransferase; EC 2.7.1.32) activity was measured in preparations of lumbar spinal cord from rats ranging in development from 12 days of gestation to 46 days of age. The enzyme activity was measured with a radiochemical assay procedure suitable for whole tissue preparations which are rich in ATP-metabolizing enzymes. Total choline kinase activity was further differentiated into hemicholinium-3 (HC-3) sensitive and HC-3 insensitive components. The specific activity of choline kinase (unhibited) increased 3-fold during the prenatal period and subsequently decreased to relatively low levels by birth. There was no significant change in choline kinase activity throughout the postnatal period. The ontogenetic patterns for the HC-3 sensitive and HC-3 insensitive components of choline kinase activity had transient peaks in activity during the prenatal period; however, these peaks in specific activity for the 2 components were 2–3 days out of phase temporally. HC-3 insensitive activity reached a peak at 18 days of gestation while the HC-3 sensitive activity peaked at 2CL21 days of gestation. In the 10-day-old rat, the apparent choline Km values were 0.56 and 0.16 MM for the total activity, 0.58 and 0.13 mM for the HC-3 insensitive activity, and 0.47 for the HC-3 sensitive activity.
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  • 69
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The effects of brief exposures of a number of depolarizing agents on 24Na+ influx and on the Na+, K+ and ATP contents of synaptosomes were studied using a Millipore filtration technique to terminate the reaction. When synaptosomes were incubated in normal medium, there was a rapid influx of 24Na+ and a gain in Na’contents; neither the 24Na+ influx nor the Na+ gain were blocked by tetrodotoxin suggesting that this Na+ entry did not involve Na+-channels.Veratridine markedly increased the rate of 24Na+ influx into synaptosomes and also increased the Na+ content and decreased the K+ content of synaptosomes within the first 10s of exposure. The normal ion contents were reversed by 1 min. The effects of veratridine on Na+ influx and on synaptosomal ion contents were prevented by tetrodotoxin and required Na+ in the medium.The ionophores gramicidin D and valinomycin also rapidly reversed the Na+ and K+ contents of synaptosomes, but these effects could not be blocked by tetrodotoxin. The reducing effect of gramicidin D on synaptosomal K+ content required Na’in the medium, whereas valinomycin caused a fall in the K+ content of synaptosomes in a Na+-free medium.Veratridine and gramicidin D, at concentrations known to reverse the synaptosomal ion contents, did not affect synaptosomal ATP levels. In contrast, valinomycin and NaCN caused an abrupt fall in synaptosomal ATP levels.The above findings suggest that veratridine quickly alters synaptosomal Na+ and K+ contents by opening Na +-channels in the presynaptic membrane, and provide direct evidence for the existence of Na+-channels in synaptosomes. In contrast, gramicidin D and valinomycin appear to act independently of Na +-channels, possibly by their ionophoric effects and, in the case of valinomycin, by diminishing synaptosomal ATP contents and hence diminishing Na+-pump activity.The rapid reversals of Na+ and K+ contents by these drugs could affect the resting membrane potentials, Na+-Ca2+ exchange across the synaptosomal membrane, and the release, synthesis and uptake of neurotransmitters by synaptosomes.
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  • 70
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Partly purified chromaffin granules were incubated in vitro with Ca2+ (with trace amounts of 45Ca2+) in concentrations ranging from 4 μm to 1 mm. After incubation the granules were washed with media containing EDTA and then subjected to density gradient centrifugation (1.3 to 2.0 m-sucrose solutions) in order to characterize the particles which had taken up 45Ca2+. By using marker enzymes and various inhibitors of Ca2+ uptake into such cell particles as mitochondria it was established that under the conditions of the experiments chromaffin granules took up Ca2+ from the incubation medium. To characterize this uptake a simplified density gradient procedure was tested and found to be suitable. The uptake of Ca2+ into chromaffin granules was strongly dependent on temperature. It was not activated by ATP. The uptake was linear up to 10 min. At high calcium concentrations (above 200 μm) the rate of uptake levelled off. The uptake at 37°C was 1 nmol Ca2+/mg protein/min at a Ca2+ concentration of 500 μm. Mg2+ had no influence on Ca2+ uptake, whereas Sr2+ (1 mm) inhibited it. The methods established in this study should prove useful for a further characterization of this Ca2+ uptake into chromaffin granules which is likely to represent a useful model for the Ca2+ uptake occurring in the intact gland.
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  • 71
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Pyridoxine (50mg/kg, per os) given for 7 consecutive days did not modify the content of dopamine, noradrenaline, and serotonin in the neostriatum of the brain 3, 6 and 18 h after the last dose, but significantly increased DOPA/5HTP decarboxylase activity in both the neostriatum and liver. The administration of l-DOPA and pyridoxine (100 and 50mg/kg, per os, respectively) together for 7 days increased DOPA/5HTP decarboxylase activity in the brain to the same extent as did l-DOPA and pyridoxine given individually. Liver DOPA/5HTP decarboxylase activity remained normal when both drugs were administered together. However it decreased significantly after l-DOPA administration for 7 days but not after pyridoxine treatment. In cats under treatment with l-DOPA for 7 days, actinomycin D given for the final 3 days prevented the increased DOPA/5HTP decarboxylase activity induced by l-DOPA in the neostriatum and mesencephalon but had no effect on the enzymatic activity in the liver. These findings indicate that differences exist between brain and liver DOPA/SHTP decarboxylase activity in uivo. In addition, denatured supernatant from livers of animals treated with l-DOPA contained a dialysable compound which inhibits DOPA/SHTP decarboxylase activity in the supernatant from livers of untreated cats. In animals who received pyridoxine along with l-DOPA, no such inhibitor was found. These results may explain the mechanism by which l-DOPA exerts its beneficial effects and why pyridoxine administered with l-DOPA reduces the therapeutic effectiveness of l-DOPA in Parkinson's disease. These findings are consistent with the possibility that a tetrahydro-isoquinoline derivative formed in vivo in the liver after l-DOPA therapy for 7 days might affect DOPA/5HTP decarboxylase activity in the liver but not in brain. A tetrahydroisoquinoline derivative did not appear to be formed when l-DOPA and pyridoxine were administrated together suggesting that pyridoxine protected the enzyme and favored a more rapid degradation of l-DOPA peripherally with less l-DOPA available for the CNS.
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  • 72
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— A homogeneous preparation of proteolipid protein (PLP) from rat brain myelin was isolated by preparative gel electrophoresis in sodium dodecyl sulfate and chemically characterized. The results of amino acid and N-terminal amino acid analyses are reported. The same preparation of myelin PLP was used to produce specific precipitating antibodies. Rabbit and goat antisera to myelin PLP each gave a single precipitin line with purified PLP dissolved in Triton X-100. Under identical conditions, no precipitation was observed with antiserum to myelin basic protein or with control serum. Immunofluorescence localization employing antiserum to PLP demonstrated bright specific fluorescence restricted to the myelin sheaths of axons in all anatomical areas of the rat brain examined. Neuronal cell bodies and their dendrites were completely negative with respect to the presence of proteolipid protein. PLP could not be localized in the cell bodies or fibrous processes in any of the glial elements in the adult rat brain. However, myelin PLP was clearly visible in the cytoplasm and processes of actively myelinating oligodendrocytes in the corpus callosum in the brains of 10-day-old rats.
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  • 73
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The polyamines spermidine and spermine were measured in brain regions from adult male rats aged 2, 10 and 20 months. Spermine levels displayed marked constancy in all brain regions studied across all ages. However, spermidine concentrations, as expressed per microgram DNA, significantly increased as a function of age in the hypothalamus, corpus striatum and medulla oblongata-pons. Similar trends with age of increased spermidine steady-state levels, but not reaching statistical significance, were observed in the cerebral cortex, midbrain and hippocampus. An absolute decline with age in DNA levels was observed only in the hippocampus. Total RNA levels, as expressed per DNA, tended to decline in all brain regions between 2 and 10 months with a reversal in this trend between 10 and 20 months in all regions except the corpus striatum. Perhaps the increased steady-state levels of spermidine, which may represent significantly increased turnover rates of this polyamine, are compensatory responses to a decreased turnover of RNA. Alternatively, the observed changes in the spermidine to spermine ratio with age may reflect changes in neuronal-glial relationships within brain regions.
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  • 74
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— A procedure is described for the preparation of free and bound polysomes from whole homogenate of rat brain tissue. Brain is homogenized in a sucrose-polysome buffer medium high in KCl (250 mm). After a 12-min centrifugation at 135,000 g, the free polysomes in the supernatant are decanted and saved, while the membrane bound polysomes in the pellet are resuspended in homogenizing medium, homogenized in the presence of detergent (Triton X-100), centrifuged for 5min at 1470 g to remove nuclei, decanted, treated with deoxycholate and centrifuged for 10 min at 24,000 g to remove deoxycholate-insoluble material. Polysomes in the two supernatants are harvested by centrifugation through sucrose gradients prepared in high KCl polysome buffer, and with or without cell sap. Free and bound polysomes prepared in this manner are undegraded, equally active in cell-free protein synthesis, and largely free of the usual contaminants. Cross-contamination is minimal (〉10%). The recovery of polysomes is at least 95%. The distribution of ribosomes and polysomes in rat brain is 58% free and 42% membrane-bound. The distribution of rat brain RNA is 65% ribosomal and 35% non-ribosomal. Conditions are described for the visualization and analysis of the entire complement of free and bound ribosomes. The size fractionation procedure is rapid and reproducible, requires much less ultracentrifugation than the density-gradient technique, and provides a nearly quantitative means of isolating undegraded free and bound polysomes of rat brain tissue.
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  • 75
    ISSN: 1471-4159