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  • 1
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effects of several γ-aminobutyric acid (GABA)-ergic drugs on sodium-dependent high-affinity choline uptake (HACU) were investigated in the hippocampus. HACU was measured in vitro after in vivo administration of the drug to mice. HACU was inhibited by those drugs that enhance GABA transmission. The convulsant 3-mercaptopropionic acid, which decreases GABA levels, stimulated HACU. From these results and previous find ings, it appears that GABA mediates a tonic inhibitory effect on the septal-hippocampal cholinergic system.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 65 (1995), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Protein tyrosine kinases that are known to have major roles in the control of cell growth and transformation are abundant and have numerous phosphoprotein substrates in the adult CNS. Although less well characterized than serine/threonine kinases, tyrosine kinases are also concentrated in the synapse. The effect of genistein, a selective inhibitor of tyrosine kinase activity, was examined on the in vitro release of endogenous dopamine (DA) from superfused mouse striatal slices. Fractional release of DA was significantly increased over basal release levels by genistein (100 and 200 µM). The effect was concentration dependent and rapidly reversible on washout of the kinase inhibitor. No significant change from basal release levels was observed with two structural analogues of genistein that do not inhibit tyrosine kinase activity at the same concentration. We have previously described alterations in basal and evoked DA release from the striatum of the weaver (wv/wv) mutant mouse, and genotypic differences in fractional release were also observed with genistein stimulation. The total evoked release was 25–50% greater from the wv/wv striatum. These results suggest a modulatory role for tyrosine kinase activity in neurotransmitter release and perhaps an alteration of kinase-regulated mechanisms in the DA-deficient wv/wv striatum.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Mice of different ages and homozygous or heterozygous for the weaver gene (wv) were used to study the time course for the effect of the weaver gene on several striatal dopaminergic parameters. Dopamine uptake was decreased in the homozygous weaver at all ages examined. The deficit in uptake at the earliest age studied, postnatal day 3, was approximately 50% and increased to greater than 70% at older ages. In control mice, dopamine uptake reached a maximum by postnatal day 22, but in homozygous weaver mice, development of uptake activity was curtailed by postnatal day 7. Dopamine content and tyrosine hydroxylase activity were significantly decreased in the homozygous weaver at all ages studied except postnatal days 7 and 10. The magnitude of the deficit in dopamine content ranged from approximately 40% at postnatal days 3 and 5 to about 70% in adults (6 months to 1 year of age). The magnitude of the deficit in tyrosine hydroxylase activity ranged from 40 to 70%. In general, no major differences between heterozygotes and controls were observed for any of the dopaminergic parameters investigated. The results of the present investigation indicate that neurochemical alterations can be observed in the striata of weaver mice as early as postnatal day 3 and raise the possibility that the striatal dopamine transporter may be an early target of the weaver mutation.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 57 (1991), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: : The weaver mutant mouse has a genetically determined defect in the nigrostriatal dopaminergic system. The present study was undertaken to test the hypothesis that in the weaver mutant mouse, striatal nerve terminals undergo compensatory changes in response to this deficiency. To test this hypothesis, we studied the basal and stimulated release of dopamine from striatal slices of weaver mutant mice and matched controls. By using a superfusion system and concentrating the superfusate by passage over alumina, resting dopamine release could be determined in the weaver mutant despite the fact that striatal tissue content of dopamine in these mice is reduced by 〉75% compared with control mice. Fractional resting release of dopamine in weaver striatal slices was significantly elevated compared with that in controls, suggesting that the release mechanisms in the weaver may be adapting to overcome the dopamine deficit. Potassium-evoked release (24 and 48 mM potassium) was not significantly different between the two genotypes. In contrast, amphetamine-evoked release (1 μM) was significantly greater in the weaver mice than in controls. In both genotypes, release evoked by amphetamine was completely inhibited by cocaine, implicating the dopamine uptake carrier in this release process. These findings suggest that fundamental differences in dopamine release mechanisms exist between weaver and control mice and support the hypothesis that compensatory mechanisms may develop in neurons in response to dopamine deficits.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 64 (1995), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The weaver mutant mouse (wv/wv) has an ∼70% loss of nigrostriatal dopamine (DA) neurons, but the fractional DA release evoked by amphetamine (but not a high potassium level) has been shown to be greater from striatal slices of the weaver compared with +/+ mice. In the present work we tested the hypothesis that fractional DA release from weaver striatum would be greater when release was mediated by the DA transporter. Serotonin (5-HT)-stimulated fractional DA release was greater from weaver than from +/+ striatum. The release evoked by 5-HT in the presence of 10 µM nomifensine (an antagonist of the DA transporter) was less than in its absence, but the difference between weaver and +/+ striatum remained. In the presence of nomifensine, 1-(m-chlorophenyl)biguanide, classified as a 5-HT3 agonist, also induced a greater fractional release from weaver compared with +/+ striatum. When veratridine was used at a low concentration (1 µM), the fractional evoked release of DA was higher from the weaver in the presence and absence of nomifensine. These findings suggest that the reason for the difference in the responsiveness of the two genotypes to these release-inducing agents is not related to DA transporter function.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 5 (1989), S. 0 
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Increasing the ploughing depth and ploughing in grassland has been common in Germany during the past 20 years. Incubation studies were conducted with topsoils from luvisols and gleysols at different times after change of management in order to assess its influence on nitrogen mineralization and its kinetic parameters.The results show that deep ploughing slows the mineralization of nitrogen. The difference between earlier (1967–72) and more recently (1980–82) deepened topsoil has become smaller after a further three years of cultivation, however. The preceding crops (wheat or sugar beet), the amount of N fertilizer as well as clay and nitrogen contents cause a variation in N mineralization. The results indicate a continuing approach of an‘equilibrium’organic matter and nitrogen content. The enrichment capacity of intensively managed soils may be replenished within 10 years.Gleysols formerly under grass mineralize more nitrogen than‘traditionally’ploughed soils, even 27 years after the ploughing-in. While nitrogen from easily decomposable materials decreases within the first 10 years, the resistant fraction is a long-lasting determinant for N mineralization. Both processes need to be considered when applying fertilizer to minimize nitrate leaching.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 53 (2002), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: This paper describes the movement of anions and cations through soils at the regional scale using block-scale and regional simulations of one-dimensional ion transport through cultivated soils. The simulations were based on field experiments in a region of about 10 km2 in Lower Saxony, Germany. Transport was modelled with the convection–dispersion equation, and the cation exchange was described using the Gapon equation. We evaluated the spatial variation of cation exchange parameters, obtained estimates valid at the block scale, and simulated the one-dimensional transport of anions and cations. The movement of anions and cations was simulated over blocks using effective transport parameters calculated from local transport parameters. The approach led to a good agreement between measured and predicted concentrations of Br–, Na+, K+, Ca2+ and Mg2+ on four different 1 ha blocks. However, the mean concentrations of K+ in the soil solution in the uppermost horizons could not be described satisfactorily by the model. For the regional simulations, transport and exchange parameters were estimated by block kriging. All variograms of the exchange parameters were spatially structured with correlation lengths varying from 100 m to 300 m. Results of the regional simulations imply that Cl– and K+ were transported substantially deeper in the southern part than in the northern part of the area. The transport depth of the ions strongly depended on the pore water velocities. The simulation of solute transport to the water table showed the influence of the depth of water table on the estimated travel times, superimposing the influence of the transport parameters in the region. The results of the regional simulations also emphasize the importance of careful fertilization, especially in regions with shallow water tables such as in the north of the area.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 30 (1978), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 18 (1971), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The effects of high circulating concentrations of several amino acids on the free amino acids of rat brain were measured, to see whether or not the results followed any consistent pattern. High circulating concentrations of large, neutral amino acids (phenylalanine, valine or isoleucine) caused significantly decreased values only of other large, neutral amino acids in the brains. High circulating concentrations of the basic amino acids lysine or arginine caused significantly decreased values only of each other. The data suggest that there are separate systems for the transport of neutral and basic amino acids across the blood-brain barrier. The effects of valine and lysine on the uptake by brain and the con-vulsant action of allylglycine (a neutral amino acid) were consistent with the concept of separate systems for the transport of amino acids across the blood-brain barrier. Valine inhibited the uptake by brain and the convulsant action of allylglycine in mice, but lysine did not. The data suggest that allylglycine and valine are transported into the brain by a common mechanism that does not transport lysine.
    Type of Medium: Electronic Resource
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