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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 25 (1970), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 47 (1992), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The contribution of NMDA and non-NMDA receptors to visual synaptic transmission in the superficial layers of the superior colliculus of the cat has been studied using extracellular recording and iontophoretic techniques. Neuronal responses to natural visual stimulation and the ejection of NMDA and AMPA were observed in the absence and presence of the antagonists CNQX, CPP and AP5. CNQX routinely reduced the responses to visual stimulation at ejection currents which selectively blocked the responses to AMPA but not those to NMDA. Agonist selective ejection currents of CPP and AP5 also reduced visual responses of most SC neurons, but there was a substantial majority whose visual responses were resistant to these antagonists. Neurons with CPP/AP5 resistant visual responses were more commonly found 750–1000 μm from the dorsal surface of the SC. The data indicate that, while non-NMDA receptors are heavily involved in visual synaptic transmission in the superficial SC, the involvement of NMDA receptors varies with recording depth.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The existence of the so-called metabotropic excitatory amino acid receptor has been known for some years. Various functions have been suggested for this receptor, but the lack of selective antagonists for (IS, 3R)-aminocyclopentane dicarboxylic acid (ACPD) has precluded the direct demonstration of a functional role for this receptor in synaptic processes. We describe here a specific antagonism of the excitatory responses of thalamic neurons to ACPD by two novel antagonists, and a parallel antagonism by these compounds of sensory synaptic responses to noxious stimuli of the same neurons. This provides the first direct pharmacological evidence for a functional role of ACPD-sensitive receptors in central neurotransmission, and indicates that these receptors may play an important part in central sensory processes.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Nitric oxide has been identified as having a role in synaptic transmission in the central nervous system. In the ventrobasal complex of the thalamus (VB), the precursor of nitric oxide synthesis, L-arginine, causes enhancement of excitatory amino acid responses and somatosensory transmission. In this study, the nitric oxide donors sodium nitroprusside, 3-morpholinosydnonimine and S-nitrosoglutathione were applied to VB relay neurons by iontophoresis and responses of single neurons were recorded extracellularly. Sodium nitroprusside caused selective inhibition of responses to NMDA, probably mediated by a by-product, ferrocyanide, as described in previous studies. 3-Morpholinosydnonimine and S-nitrosoglutathione, however, caused potentiation of responses to sensory stimuli and to excitatory amino acids. In contrast, glutathione in both its reduced and oxidized forms reduced such responses, and this suggests that the potentiating effect of S-nitrosoglutathione could be due to nitric oxide production. These results are consistent with the hypothesis that nitric oxide may have a local modulatory role in the thalamus. Data are presented which suggest that glutathione may have a negative modulatory influence on neurotransmission and excitatory amino acid responses in the ventrobasal thalamus.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. Diet composition and the production of embryos were measured in Asplanchna girodi and Asplanchna priodonta collected through 3 years in the San Joaquin-Sacramento delta of California. The two species are sympatric in low to moderate densities for 5 months of the year.2. Despite marked differences in the structure of the trophi, both species consumed the same array of prey species. Percentage composition of the diet varied both intra- and interspecifically. The food niches of the two species appear to differ little from one another.3. Individuals of Asplanchna girodi had a larger mean number of prey in the gut per individual than did those of A.priodonta, due to their larger size. Per unit volume, each species prey gathering performance was the same. Asplanchna priodonta produced more embryos per calculated unit volume of prey ingested than did A.girodi.4. During spring, when both species were present in the plankton, A.priodonta did not capture Size Class 2 and 5 animals (volumes 0.09–1.0 μm3×106 and 3.0–3.5 μm3X106 respectively) nor large Synchaeta. Both these prey classes were in the diet during the summer and autumn months. Several hypotheses are examined as possible explanations for this phenomenon.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Three species of root aphid (Pachypappa vesicalis Koch, Pachypappa tremulae L. and Prociphilus (Stagona) xylostei De Geer) were found feeding on Norway spruce [Picea abies (L.) Karsten] that were exposed to elevated concentrations of O3, and/or SO2 in a field manipulation experiment at Liphook, England. The experiment exposed conifer trees to controlled concentrations of these gases between 1987 and 1990. Root-aphid populations feeding on Norway spruce were monitored in autumn 1990, the third year of fumigation and in autumn 1991, 10 months after fumigation had ceased. In 1990 the numbers of aphids in the high-SO2, high-SO2+ O3 and O3 treatments were significantly less than in ambient plots. Although after fumigation had ceased in 1991 the ambient plots still had higher numbers than the treatment plots, most of these differences were no longer statistically significant. In all plots sampled, total numbers of root aphids were higher in 1991 than in 1990. These results indicate that the numbers of root aphids in the experiment were negatively related to pollution levels. This relationship is the same as that shown in controlled laboratory experiments and is the converse of that generally reported in experiments using shoot-feeding aphids.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Exposure of R. crispus and R. obtusifolius to elevated CO2 (600 ppm) resulted in an increased C:N ratio of leaf tissue and greater leaf areas. Larvae of P. nigritarsis mining leaves of R. obtusifolius during exposure produced significantly bigger mines in elevated than in ambient (350 ppm) conditions. There were no significant treatment effects on pupal weight although in both host species mean weight was greater in ambient than in elevated conditions. These results are consistent with the hypothesis that insect herbivores compensate for increased C:N ratios by increased food consumption. This response by herbivores may partially offset predicted increases in plant biomass in a future high CO2 environment.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Excitatory amino acid neurotransmitters, such as l-glutamate, act at several receptors in the brain, which are sometimes referred to as N-methyl-d-aspartate (NMDA) and non-NMDA receptors. Extensive in vitro work indicates that both NMDA receptors and non-NMDA receptors contribute to excitatory postsynaptic potentials (epsps). The contribution of NMDA receptors to epsps in vivo under physiological conditions is, however, almost unknown. The receptors that mediate the epsps evoked in thalamic relay cells by natural stimulation of sensory afferents have been investigated in anaesthetized rats, and we report the first pharmacological characterization of an excitatory amino acid receptor-mediated epsp in vivo involving both non-NMDA receptors and, in particular, NMDA receptors.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The metabotropic excitatory amino acid receptor agonist trans-(±)-1-amino-cyclopentane-1,3-dicarboxylate (t-ACPD) was applied to rat ventrobasal thalamic neurons by iontophoresis. This agonist typically evoked an excitatory response which was slower in onset and of longer duration than responses to the other excitatory amino acid agonists, N-methyl-aspartate, kainate or (R.S)-a-amino-3-hydroxy-5-methyl-4-isoxazolepropionate. Responses to f-ACPD were resistant to the excitatory amino acid antagonists 6-cyano-7-nitroquinoxaline-2,3-dione, 3-((RS)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid and kynurenate. These results suggest that f-ACPD may exert its effects via the so-called ‘metabotropic’ excitatory amino acid receptor. The putative antagonists at this receptor, D-2-amino-4-phosphono-butyrate (D-AP4), L-2-amino-4-phosphono-butyrate (L-AP4) and L-2-amino-3-phosphono-propionate (L-AP3), were able to reduce responses to t-ACPD under certain circumstances. However, such antagonism was always accompanied by similar reductions in excitatory responses to other agonists. These non-selective effects would appear to limit the usefulness of AP4 and AP3 as antagonists of t-ACPD.
    Type of Medium: Electronic Resource
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