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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 431 (1996), S. 363-370 
    ISSN: 1432-2013
    Keywords: Key words Outwardly rectifying ; Chloride channel ; Regulatory volume decrease ; Pancreatic β-cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The whole-cell patch-clamp recording technique was used to measure volume-activated currents in K+-free solutions in RINm5F and HIT-T15 insulinoma cells and in dispersed rat islet cells. Cell swelling, induced by intracellular hypertonicity or extracellular hypotonicity, caused activation of an outwardly rectifying conductance which could be subsequently inactivated by hypertonic extracellular solutions. The conductance required adenosine 5′-triphosphate (ATP) in the pipette solution but was Ca2+ independent. Na+ and Cl− substitution studies suggested that the swelling-activated current is Cl− selective with a halide permeability sequence of Br 〉 Cl 〉 I. The conductance was reversibly inhibited by the anion channel inhibitors 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS) and by 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB). Further evidence for a volume-activated anion conductance was provided by studies of volume regulation in insulin-secreting cells. When RINm5F cells were exposed to a hypotonic medium, the initial cell swelling was followed by a regulatory volume decrease (RVD). This RVD response was also inhibited by DIDS and by NPPB. These data therefore provide evidence for a volume-activated anion conductance in insulin-secreting cells which could be involved in the RVD following osmotic stress. A possible role for the conductance in hypotonically induced insulin release is also discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 431 (1996), S. 363-370 
    ISSN: 1432-2013
    Keywords: Outwardly rectifying ; Chloride channel ; Regulatory volume decrease ; Pancreaticβ-cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The whole-cell patch-clamp recording technique was used to measure volume-activated currents in K+-free solutions in RINm5F and HIT-T15 insulinoma cells and in dispersed rat islet cells. Cell swelling, induced by intracellular hypertonicity or extracellular hypotonicity, caused activation of an outwardly rectifying conductance which could be subsequently inactivated by hypertonic extracellular solutions. The conductance required adenosine 5′-triphosphate (ATP) in the pipette solution but was Ca2+ independent. Na+ and Cl− substitution studies suggested that the swelling-activated current is Cl− selective with a halide permeability sequence of Br 〉 Cl 〉 1. The conductance was reversibly inhibited by the anion channel inhibitors 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS) and by 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB). Further evidence for a volume-activated anion conductance was provided by studies of volume regulation in insulin-secreting cells. When RINm5F cells were exposed to a hypotonic medium, the initial cell swelling was followed by a regulatory volume decrease (RVD). This RVD response was also inhibited by DIDS and by NPPB. These data therefore provide evidence for a volume-activated anion conductance in insulin-secreting cells which could be involved in the RVD following osmotic stress. A possible role for the conductance in hypotonically induced insulin release is also discussed.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1424
    Keywords: Ca2+-activated K+ channels ; Cell volume ; Regulatory volume decrease ; Tetraethylammonium ; Lacrimal acinar cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The volumes of acinar cells isolated from rat lacrimal gland were measured on computer by video-imaging. Cells were found to swell on exposure to hypotonic solutions; they subsequently exhibited a regulatory volume decrease (RVD). RVD was inhibited in the absence of extracellular Ca2+, and by the K+ channel blocker tetraethylammonium chloride (2 mm TEA+). The possible involvement of K+ channels in RVD was further investigated in cell-attached patches. Exposing the cells to a hypotonic solution activated channels with a conductance of 141±6 pS (n=11). These channels were partially blocked by 0.5 mm TEA+, and channel activation was not observed in the absence of extracellular Ca2+. Experiments in the inside-out patch configuration demonstrated that the channels activated by hypotonie stress were “maxi” Ca2+-activated K+ channels. It is concluded that the opening of these channels plays an important role in RVD, by facilitating K+ loss from the cell.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 80 (1990), S. 673-679 
    ISSN: 1432-2242
    Keywords: Rice ; Tissue culture ; Somaclonal variation ; RFLP ; Methylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Regenerants of rice were examined by RFLP analysis to determine the occurrence and extent of somaclonal variation. DNA polymorphisms were observed both among plants regenerated from different callus cultures as well as among sibling plants derived from a single callus. Regardless of the basal medium, a higher degree of genetic instability was found among plants regenerated from callus cultures maintained for longer incubation periods (67 days) than among those from shorter incubation periods (28 days). Detailed analysis showed that in several regenerants, there was a close correlation among those plants exhibiting DNA rearrangements and those with apparent methylation changes. Such alterations were observed with both structural and housekeeping genes.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 78 (1989), S. 321-328 
    ISSN: 1432-2242
    Keywords: Gene methylation ; Tissue culture ; 5-Azacytidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A major problem associated with cereal biotechnology remains the extreme difficulty of reliably and efficiently regenerating plants from protoplasts. Because of the assumed inverse correlation between levels of the modified nucleotide 5-methylcytosine in a gene and the degree of transcription, we report here on experiments to determine whether exposure of maize and tobacco cultures to the 5-methylcytosine analogue 5-Azacytidine (5-Azt) induces gene de-methylation and, as such, enhances tissue culture response, for example by increasing protoplast division frequency. The results show that whilst 5-Azt may be of use in expanding leaf areas capable of producing callus as well as increasing the amount of callus produced, in all other aspects 5-Azt is strongly inhibitory to growth at all but the lowest concentrations. Molecular analysis shows that no readily discernible changes in gene methylation status can be found, regardless of 5-Azt concentration or the gene probe used. Differences can, however, be found in methylation status between callus and developmentally determined tissues, irrespective of 5-Azt treatment. The results suggest that, apart from a very limited role, 5-Azt has no obvious use in tissue culture.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 237 (1993), S. 311-317 
    ISSN: 1617-4623
    Keywords: PCR ; RAPD ; Somaclonal variation ; Tissue culture ; Transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We investigated the use of the polymerase chain reaction (PCR) and the associated random amplification of polymorphic DNA (RAPD) technique in the analysis of DNA and specific genes in plant cells at different stages of regeneration in in vitro cultures. We demonstrate that both procedures can be used to differentiate reproducibly between closely related species as well as to reveal levels of DNA polymorphism in regenerated plants. We also demonstrate that both procedures, using protocols that we have developed, are applicable at all tissue culture stages, from single isolated protoplasts to regenerated plants. Possible explanations for the variation levels detected in regenerated wheat plants are advanced.
    Type of Medium: Electronic Resource
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