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  • 1990-1994  (4)
  • Nucleotide regulation  (2)
  • Chemical modification  (1)
  • Impaired glucose tolerance  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Nucleotide regulation of a calcium-activated cation channel in the rat insulinoma cell line, CRI-G1 (1994)
    Springer
    The journal of membrane biology 141 (1994), S. 101-112 
    Details
    ISSN: 1432-1424
    Keywords: Rat insulinoma cell line ; CRI-G1 ; Nucleotide regulation ; Calcium-activated nonselective cation channel ; Patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The nucleotide regulation of a calcium-activated nonselective cation (Ca-NS+) channel has been investigated in the rat insulinoma cell line CRI-G1. The activity of the channel is reduced by both AMP and ADP (1–100 μm) in a concentration-dependent manner, with AMP being more potent than ADP. At lower concentrations (0.1–5 μm), both ADP and AMP activate the channel in some patches. Examination of the nucleotide specificity of channel inhibition indicates a high selectivity for AMP over the other nucleotides tested with a rank order of potency of AMP 〉 UMP 〉 CMP ≥GMP. Cyclic nucleotides also modulate channel activity in a complex, concentration-dependent way. Cyclic AMP exhibits a dual effect, predominantly increasing channel activity at low concentrations (0.1–10 μm) and reducing it at higher concentrations (100 μm and 1 mm). Specificity studies indicate that the cyclic nucleotide site mediating inhibition of channel activity exhibits a strong preference for cyclic AMP over cyclic GMP, with cyclic UMP being almost equipotent with cyclic AMP. Cyclic IMP and cyclic CMP are not active at this site. The cyclic nucleotide site mediating activation of the channel shows much less nucleotide specificity than the inhibitory site, with cyclic AMP, cyclic GMP and cyclic IMP being almost equally active.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238244
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of chemical modification of amino and sulfhydryl groups on KATP channel function and sulfonylurea binding in CRI-G1 insulin-secreting cells (1994)
    Springer
    The journal of membrane biology 139 (1994), S. 167-181 
    Details
    ISSN: 1432-1424
    Keywords: KATP channels ; Chemical modification ; Sulfhydryl group ; Basic amino acids ; Pancreatic β-cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The effects of several group-specific chemical reagents were examined upon the activity of the ATP-sensitive potassium (KATP) channel in the CRI-G1 insulin-secreting cell line. Agents which interact with the sulfhydryl moiety (including 1 mM N-ethylmaleimide (NEM), 1 mM 5,5′-dithio-bis-(2-nitrobenzoic acid) (DNTB) and 1 mm o-iodobenzoate) produced an irreversible inhibition of KATP channel activity when applied to the intracellular surface of excised inside-out patches. This inhibition was substantially reduced when attempts were made to eliminate Mg2+ from the intracellular compartment. ATP 50 μm and 100 μm tolbutamide were each shown to protect against the effects of these reagents. The membrane impermeable DNTB was significantly less effective when applied to the external surface of outside-out patches. Agents which interact with peptide terminal amine groups and ɛ amino groups of lysine [1 mm methyl acetimidate and 1 mm trinitrobenzene sulfonic acid (TNBS)] and also the guanido group of arginine (1 mm methyl glyoxal) produced a Mg2+-dependent irreversible inhibition of KATP channel activity which could be prevented by ATP but not tolbutamide. The irreversible activation of the KATP channel produced by the proteolytic enzyme trypsin was prevented only when methyl glyoxal and methyl acetimidate were used in combination to inhibit channel activity. Radioligand binding studies showed that the binding of 3H glibenclamide was unaffected by any of the above agents with the exception of TNBS which completely inhibited binding with a EC50 of 307 ±6 μm. These results provide evidence for the presence of essential sulfhydryl (possibly cysteine), and basic amino acid (possibly lysine and arginine) residues associated with the normal functioning of the KATP channel. Furthermore, we believe that the sulfhydryl group in question is situated at the internal surface of the membrane, possibly near to the channel pore.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232621
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  • 3
    Electronic Resource
    Electronic Resource
    The effects of pyridine nucleotides on the activity of a calcium-activated nonselective cation channel in the rat insulinoma cell line, CRI-G1 (1994)
    Springer
    The journal of membrane biology 142 (1994), S. 299-307 
    Details
    ISSN: 1432-1424
    Keywords: Calcium-activated nonselective channel ; Rat insulinoma cell line ; CRI-G1 ; Pyridine nucleotides β-NAD+-NS+ channel ; Nucleotide regulation ; AMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The activity of a calcium-activated nonselective (Ca-NS+) channel in a rat insulinoma cell line (CRI-G1) is inhibited by pyridine nucleotides in excised patches. The effects of all four pyridine nucleotides tested, β-NAD+, β-NADH, β-NADP+ and β-NADPH were very similar when tested at 0.1 mm, and at 1 mm the phosphorylated forms, β-NADP+ and β-NADPH, appeared to be slightly more potent than β-NAD+ and β-NADH. All the pyridine nucleotides tested reduced both the open state probability of the channel and the number of functional channels observed in a single patch. The application of β-NAD+, but not of the other nucleotides tested, to the cytoplasmic surface of isolated inside-out patches from CRI-G1 cells opened a novel nonselective cation channel (the β-NAD+-NS+ channel). The activity of this new channel is calcium sensitive and may also be inhibited by AMP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233437
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Fetal growth and impaired glucose tolerance in men and women (1993)
    Springer
    Diabetologia 36 (1993), S. 225-228 
    Details
    ISSN: 1432-0428
    Keywords: Impaired glucose tolerance ; non-insulin-dependent diabetes mellitus ; fetal growth ; ponderal index at birth ; placental weight to birthweight ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A follow-up study was carried out to determine whether reduced fetal growth is associated with the development of impaired glucose tolerance in men and women aged 50 years. Standard oral glucose tolerance tests were carried out on 140 men and 126 women born in Preston (Lancashire, UK) between 1935 and 1943, whose size at birth had been measured in detail. Those subjects found to have impaired glucose tolerance or non-insulin-dependent diabetes mellitus had lower birthweight, a smaller head circumference and were thinner at birth. They also had a higher ratio of placental weight to birthweight. The prevalence of impaired glucose tolerance or diabetes fell from 27% in subjects who weighed 2.50 kg (5.5 pounds) or less at birth to 6% in those who weighed more than 3.41 kg (7.5 pounds) (p 〈 0.002 after adjusting for body mass index). Plasma glucose concentrations taken at 2-h in the glucose tolerance test fell progressively as birthweight increased (p 〈 0.004), as did 2-h plasma insulin concentrations (p 〈 0.001). The trends with birthweight were independent of duration of gestation and must therefore be related to reduced rates of fetal growth. These findings confirm the association between impaired glucose tolerance in adult life and low birthweight previously reported in Hertfordshire (UK), and demonstrate it in women as well as men. It is suggested that the association reflects the long-term effects of reduced growth of the endocrine pancreas and other tissues in utero. This may be a consequence of maternal undernutrition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00399954
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    Paper (German National Licenses)
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