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  • 1
    ISSN: 1432-1106
    Keywords: Cochlea ; Perfusion ; Elevated potassium ; Electrical potentials ; Recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Scala tympani (ST) in guinea pig was perfused with modified Ringer's solutions containing 5–50 mM potassium; tone-induced cochlear responses from the basal turn of ST were compared before, during and after perfusions. The compound nerve action potential (N1) and afterpotential (a/p) amplitudes were reduced, especially above 20 mM; the summating potential (SP) was variable, but its onset shape changed consistently with 13–20 mM levels. However, the cochlear microphonic amplitude (CM) remained substantially unchanged even at the 35 mM level. K+ concentration was monitored in ST with ion-sensitive pipettes. Stable levels were reached within 2 min, but N1 responses continued to fall beyond this time. Recovery to normal K+ levels took place spontaneously and the concentration curve which resulted showed a 2-slope characteristic. These experiments question whether elevated potassium concentration in scala tympani depolarizes the hair cells, and if it does, whether the hair cell resting potential is involved in the generation of the CM.
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  • 2
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: There is evidence from immunohistochemical and in situ hybridization studies for the presence of Group I, II and III metabotropic glutamate receptors (mGluRs) in the rat superficial superior colliculus (SSC). The purpose of this study was to investigate if manipulation of Group III mGluRs affects visual responses in the SSC. Drugs were applied by iontophoresis and single neuron activity was recorded extracellularly. L-AP4 (Group III agonist) resulted in a reduction of visual responses in most neurons, but also a potentiation in others. The effect of L-AP4 is drug- and stereospecific in that application of D-AP4 did not significantly affect visual responses. L-AP4 application also resulted in a potentiation of the response to iontophoretically applied NMDA. The effects of MPPG and CPPG (Group III antagonists) were compared with the effect of L-AP4 in the same neuron and were found to produce the opposite effect to L-AP4. Furthermore, the effect of L-AP4 could be blocked by coapplication of MPPG or CPPG. Presynaptic depression of glutamate release is a possible mechanism by which L-AP4 could reduce visual responses in the SSC whereas the potentiation of visual responses by L-AP4 could be due to a reduction of GABAergic inhibition. The finding that MPPG and CPPG, as well as antagonizing the L-AP4 effect, have a direct effect on visual responses suggests that Group III mGluRs are activated by endogenous transmitter released during visual stimulation.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Child 30 (2004), S. 0 
    ISSN: 1365-2214
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Child 30 (2004), S. 0 
    ISSN: 1365-2214
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Child 30 (2004), S. 0 
    ISSN: 1365-2214
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Child 30 (2004), S. 0 
    ISSN: 1365-2214
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0789
    Keywords: Key words C mineralization ; P fertility ; Mineral N ; Microbial C ; Microbial P
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  This study examines the effect of soil P status and N addition on the decomposition of 14C-labelled glucose to assess the consequences of reduced fertilizer inputs on the functioning of pastoral systems. A contrast in soil P fertility was obtained by selecting two hill pasture soils with different fertilizer history. At the two selected sites, representing low (LF) and high (HF) fertility status, total P concentrations were 640 and 820 mg kg–1 and annual pasture production was 4,868 and 14,120 kg DM ha–1 respectively. Soils were amended with 14C-labelled glucose (2,076 mg C kg–1 soil), with and without the addition of N (207 mg kg–1 soil), and incubated for 168 days. During incubation, the amounts of 14CO2 respired, microbial biomass C and 14C, microbial biomass P, extractable inorganic P (Pi) and net N mineralization were determined periodically. Carbon turnover was greatly influenced by nutrient P availability. The amount of glucose-derived 14CO2 production was high (72%) in the HF and low (67%) in the LF soil, as were microbial biomass C and P concentrations. The 14C that remained in the microbial biomass at the end of the 6-month incubation was higher in the LF soil (15%) than in the HF soil (11%). Fluctuations in Pi in the LF soil during incubation were small compared with those in HF soil, suggesting that P was cycling through microbial biomass. The concentrations of Pi were significantly greater in the HF samples throughout the incubation than in the LF samples. Net N mineralization and nitrification rates were also low in the LF soils, indicating a slow turnover of microorganisms under limited nutrient supply. Addition of N had little effect on biomass 14C and glucose utilization. This suggests that, at limiting P fertility, C turnover is retarded because microbial biomass becomes less efficient in the utilization of substrates.
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  • 8
    ISSN: 1432-0428
    Keywords: Keywords Estradiol, estrone, estriol, insulin resistance, IRS proteins.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Aim/hypothesis. Numerous studies have suggested a relation between sex hormones and insulin sensitivity but the ability of sex hormones to directly influence insulin action in peripheral tissues has not been investigated.¶Methods. We have examined the effects of estriol, estradiol and estrone on insulin action in cultured 3T3-L1 adipocytes, a useful model of adipocytes.¶Results. Treatment of these cells with each of these sex hormones resulted in a statistically significant reduction in the ability of insulin to stimulate glucose transport independently of a reduction in total cellular GLUT-4 content. This diminished ability of insulin to stimulate glucose transport was accompanied by a reduction in the total cellular content of insulin receptor substrates –1 and –2 and the p85α subunit of phosphatidylinositol 3'-kinase. By contrast, cellular content of protein kinase B was unchanged by hormone treatment but the magnitude of insulin-stimulated kinase activity was statistically significantly reduced after incubation with each of the sex hormones tested. We have further shown that treatment of 3T3-L1 adipocytes with these hormones alters the subcellular distribution of insulin receptor substrate proteins such that the particulate and soluble pools of these proteins were differentially affected by hormone treatment.¶Conclusion/interpretation. These data show that sex hormones can directly induce a state of insulin resistance in 3T3-L1 adipocytes in culture. The mechanism of this defect seems to be at least in part due to decreased cellular content and altered subcellular distribution of insulin receptor substrate proteins which in turn results in a reduction in proximal insulin-stimulated signalling cascades. [Diabetologia (2000) 43: 1374–1380]
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  • 9
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Understanding the functional connections between genes, proteins, metabolites and mineral ions is one of biology's greatest challenges in the postgenomic era. We describe here the use of mineral nutrient and trace element profiling as a tool to determine the biological significance of connections ...
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  • 10
    ISSN: 1469-7610
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: Background:  Previous research suggests that the phenotype associated with Asperger's syndrome (AS) includes difficulties in understanding the mental states of others, leading to difficulties in social communication and social relationships. It has also been suggested that the first-degree relatives of those with AS can demonstrate similar difficulties, albeit to a lesser extent. This study examined ‘theory of mind’ (ToM) abilities in the siblings of children with AS relative to a matched control group.Method:  27 children who had a sibling with AS were administered the children's version of the ‘Eyes Test’ (Baron-Cohen, Wheelwright, Stone, & Rutherford, 1999). The control group consisted of 27 children matched for age, sex, and a measure of verbal comprehension, and who did not have a family history of AS/autism.Results:  A significant difference was found between the groups on the Eyes Test, the ‘siblings’ group showing a poorer performance on this measure of social cognition. The difference was more pronounced among female siblings.Discussion:  These results are discussed in terms of the familial distribution of a neuro-cognitive profile associated with AS, which confers varying degrees of social handicap amongst first-degree relatives. The implication of this finding with regard to the autism/AS phenotype is explored, with some discussion of why this neuro-cognitive profile (in combination with corresponding strengths) may have an evolutionary imperative.
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