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  • 1
    ISSN: 0196-9781
    Keywords: Immunohistochemistry ; Mammals ; Peptide histidine isoleucine (PHI) ; Vasoactive intestinal peptide (VIP)
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0309-1651
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Glutamate uptake ; Glutamate analogues ; Sodium dependency ; Glutamate release ; Cultured astrocytes ; Cultured neurons ; Brain regions ; Granule cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The uptake of L-glutamate was studied in astrocytes cultured from different brain areas of newborn rats as well as in two different cultures of neurons obtained from mouse brain. Both astrocytes and neurons exhibited high-affinity glutamate uptake with Km values ranging from 34 [μM to 82 μM. Vmax values for astrocytes cultured from the different brain regions were: prefrontal cortex: 13.9; occipital cortex: 11.4; neostriatum: 27.3 and cerebellum: 5.8 nmol · min−1 · mg−1 cell protein. For cerebellar granule cells and cerebral cortical neurons the Vmax values were found to be 10.2 and 5.9 nmol · min−1 · mg−1 cell protein, respectively. The effect on L-glutamate uptake in astrocytes cultured from prefrontal cortex and in cultured cerebellar granule cells of a series of compounds structurally related to glutamate was studied, and detailed kinetic analyses of the inhibitory patterns of three potent inhibitors were performed. L-aspartate and L-aspartate-β-hydroxamate were found to be competitive inhibitors of L-glutamate uptake in both cell types with Ki values for astrocytes of 60 μM and 91 [μM, respectively, and for granule cells of 48 μM and 72 μM, respectively. D-aspartate was found to be a mixed-type noncompetitive inhibitor of L-glutamate uptake in astrocytes (K;: 106 μM), but in granule cells this compound showed simple competitive inhibition with a Ki of 49 μM. Sodium dependency of L-glutamate uptake in both cell types was studied at a series of Lglutamate and Na+ concentrations. It was found that the uptake of glutamate in astrocytes is coupled with one Na+ ion in contrast to two Na+ ions in granule cells. The Km value for sodium was found to be 15 mM in both cell types. It was shown that release of exogenously supplied [3H] -L-glutamate from cerebel lar granule cells could be stimulated in a Ca2+-dependent manner by high concentrations (55 mM) of K+. In contrast to this no K+-induced release of glutamate could be demonstrated in cultured astrocytes.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2307
    Keywords: Key words Western blotting ; Fusion protein ; FLI1 ; Ewing’s sarcoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We applied Western blotting, using an antibody against the carboxy terminal of the FLI1 protein, for detection of the 68-kDa EWS/FLI1 fusion protein in cultured Ewing’s sarcoma cells and in four surgical biopsies of Ewing’s sarcoma. Of six different human cell lines, the 68-kDa fusion protein was identified only in Ewing’s sarcoma cells carrying the t(11;22)(q24;q12) translocation. The four samples from Ewing’s sarcoma patients were also found to contain the 68-kDa fusion protein. The lowest detection level for total protein loaded on the gel was 0.3 μg. When whole Ewing’s sarcoma cells were used for Western blotting without prior protein extraction, the lowest detection level was 1,300 cells. It will be possible to use Western blotting for detection of the EWS/FLI1 fusion protein in the diagnosis of Ewing’s sarcoma in surgical biopsy specimens, and possibly also in fine-needle aspirates. As the method is not dependent on the quality of mRNA in the sample and involves no risk of contamination, it will be a powerful complement to the reverse-transcription polymerase chain reaction (RT-PCR).
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0428
    Keywords: Key words Islets of Langerhans ; glucose ; tolbutamide ; [Ca2 + ]i-oscillations ; insulin secretion.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Plasma insulin levels in healthy subjects oscillate and non-insulin-dependent diabetic patients display an irregular pattern of such oscillations. Since an increase in cytoplasmic free Ca2 + concentration ([Ca2 + ]i) in the pancreatic beta cell is the major stimulus for insulin release, this study was undertaken to investigate the dynamics of electrical activity, [Ca2 + ]i-changes and insulin release, in stimulated islets from subjects of varying glucose tolerance. In four patients it was possible to investigate more than one of these three parameters. Stimulation of pancreatic islets with glucose and tolbutamide sometimes resulted in the appearance of oscillations in [Ca2 + ]i, lasting 2–3 min. Such oscillations were observed even in some islets from patients with impaired glucose tolerance. In one islet from a diabetic patient there was no response to glucose, whereas that islet displayed [Ca2 + ]i-oscillations in response to tolbutamide, suggesting that sulphonylurea treatment can mimic the complex pattern of glucose-induced [Ca2 + ]i-oscillations. We also, for the first time, made patch-clamp recordings of membrane currents in beta-cells in situ in the islet. Stimulation with glucose and tolbutamide resulted in depolarization and appearance of action potentials. The islet preparations responded to stimulation with a number of different secretagogues with release of insulin. The present study shows that human islets can respond to stimulation with glucose and sulphonylurea with oscillations in [Ca2 + ]i, which is the signal probably underlying the oscillations in plasma insulin levels observed in healthy subjects. Interestingly, even subjects with impaired glucose tolerance had islets that responded with oscillations in [Ca2 + ]i upon glucose stimulation, although it is not known to what extent the response of these islets was representative of most islets in these patients. [Diabetologia (1994) 37: 1121–1131]
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0428
    Keywords: Islets of Langerhans ; glucose ; tolbutamide ; [Ca2+]i-oscillations ; insulin secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Plasma insulin levels in healthy subjects oscillate and non-insulin-dependent diabetic patients display an irregular pattern of such oscillations. Since an increase in cytoplasmic free Ca2+ concentration ([Ca2+]i) in the pancreatic beta cell is the major stimulus for insulin release, this study was undertaken to investigate the dynamics of electrical activity, [Ca2+]i-changes and insulin release, in stimulated islets from subjects of varying glucose tolerance. In four patients it was possible to investigate more than one of these three parameters. Stimulation of pancreatic islets with glucose and tolbutamide sometimes resulted in the appearance of oscillations in [Ca2+]i, lasting 2–3 min. Such oscillations were observed even in some islets from patients with impaired glucose tolerance. In one islet from a diabetic patient there was no response to glucose, whereas that islet displayed [Ca2+]i-oscillations in response to tolbutamide, suggesting that sulphonylurea treatment can mimic the complex pattern of glucose-induced [Ca2+]i-oscillations. We also, for the first time, made patch-clamp recordings of membrane currents in beta-cells in situ in the islet. Stimulation with glucose and tolbutamide resulted in depolarization and appearance of action potentials. The islet preparations responded to stimulation with a number of different secretagogues with release of insulin. The present study shows that human islets can respond to stimulation with glucose and sulphonylurea with oscillations in [Ca2+]i, which is the signal probably underlying the oscillations in plasma insulin levels observed in healthy subjects. Interestingly, even subjects with impaired glucose tolerance had islets that responded with oscillations in [Ca2+]i upon glucose stimulation, although it is not known to what extent the response of these islets was representative of most islets in these patients.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Two groups of GABA (γ-aminobutyric acid) analogues, one comprising derivatives of β-proline and the other compounds structurally related to nipecotic acid, were investigated as potential inhibitors of high-affinity GABA transport in neurons and glial cells, as well as displacers of GABA receptor binding. In addition to cis-4-hydroxynipecotic acid, which is known as a potent inhibitor of GABA uptake, homo-β-proline was the only compound which proved to be a potent inhibitor of glial as well as neuronal GABA uptake. IC50 values for GABA uptake into glial cells and brain cortex “prisms” were 20 and 75 μM, respectively, and the IC50 value obtained for GABA uptake into cultured neurons was 10 μM. A kinetic analysis of the action of homo-β-proline on GABA uptake into cultured astrocytes and neurons showed that this compound acts as a competitive inhibitor of GABA uptake in both cell types. From the apparent Km values, Ki values for homo-β-proline of 16 and 6 μM could be calculated for glial and neuronal uptake, respectively. This mechanism of action strongly suggests that homo-β-proline interacts with the GABA carriers. Furthermore, homo-β-proline also displaced GABA from its receptor with an IC50 value of 0.3 μM. The cis-4-hydroxynipecotic acid analogues, cis- and trans-4-mercaptonipecotic acid, had no inhibitory effect on glial or neuronal GABA uptake. Other SH reagents, PCMB, NEM and DTNB, were shown to be relatively weak inhibitors of GABA uptake into cultured astrocytes, suggesting that SH groups are not directly involved in the interaction between GABA and its transport carrier.
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  • 8
    ISSN: 0014-4827
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0014-5793
    Keywords: ATP-regulated K^+ channel ; Pancreatic β-cell ; Sulfhydryl reagent ; Thimerosal
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0014-5793
    Keywords: Pancreatic B-cell ; Phospholipase C-system ; Stimulus-secretion coupling, Ca^2^+-oscillation ; Voltage-dependent Ca^2-channel
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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