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  • 1
    ISSN: 1432-0428
    Keywords: Diabetes mellitus ; insulin resistance ; insulin receptor ; Rabson-Mendenhall syndrome ; insertion mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have studied the structure and function of the insulin receptor in a patient (PK) with severe insulin resistance and Rabson-Mendenhall syndrome. Insulin binding to cultured fibroblasts from PK was almost not detectable and insulin-induced insulin receptor autophosphorylation and glucose uptake was abolished. The structure of the receptor gene was analysed by sequencing amplified products of the 22 exons with the flanking intron regions directly as well as after subcloning in pUCBM20 plasmids. Two mutant alleles of the insulin receptor gene were detected. One allele contains in-frame 12 additional base pairs in exon 3 coding for the amino acids Leu-His-Leu-Val located between Asp-261 and Leu-262 in the receptor's extracellular domain, being the first report of an insertion mutation of the insulin receptor gene. In the other allele Arg-86 in exon 2 is changed into a stop codon. Therefore, PK is compound heterozygous at the insulin receptor locus. Direct cDNA sequencing indicates that both mutant alleles are expressed in the patient's fibroblasts. Studies of the parents' fibroblasts revealed that PK inherited the insertion mutation from the father and the nonsense mutation from the mother. Insulin binding to fibroblasts of the mother was reduced (63 % of control cells) and hormone binding to the father's cells shows a larger reduction (37 % of control cells), but less severe than the patient's cells (11 % of control). This investigation provides further evidence that the Rabson-Mendenhall syndrome is causally related to mutations in the insulin receptor gene.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0428
    Keywords: Lipodystrophic diabetes mellitus ; insulin resistance ; insulin receptor ; IGF-I receptor ; polymorphisms ; Seip-Berardinelli syndrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Lipodystrophic diabetes mellitus of the Seip-Berardinelli type is a syndrome associated with insulin resistance and recessive inheritance. We have examined whether mutations in the insulin receptor are pathogenetic factors in this syndrome. Fibroblasts from three different patients with Seip-Berardinelli's lipodystrophy were tested for insulin binding, and insulin-stimulated receptor autophosphorylation. In addition, the coding region of both alleles of the insulin receptor gene was sequenced. No abnormalities in the number of high affinity insulin binding sites, and in-sulinstimulated receptor autophosphorylation were detected. The insulin receptor related insulin-like growth factor I receptor also showed no functional changes. DNA sequence analysis of the amplified exons of the insulin receptor gene showed a silent mutation in patient 1 at codon Ser339, changing AGT to AGC. In patient 2 a heterozygous Met for Val substitution at position 985 was detected, which is a rare polymorphism. In patient 3 no mutations, other than described polymorphisms, were observed. These findings demonstrate that the primary genetic lesion in Seip-Berardinelli's lipodystrophy is outside the insulin receptor gene and that an involvement of the insulin-like growth factor I receptor is also unlikely.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 37 (1994), S. 1169-1170 
    ISSN: 1432-0428
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0428
    Keywords: Amylin ; islet amyloid polypeptide ; glucose production ; glucose uptake ; in vivo ; clamp ; counterregulatory hormones ; insulin action ; insulin receptor ; diabetes mellitus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Amylin is a polypeptide of 37 amino acids, predominantly synthesized in pancreatic Beta cells. The peptide was suggested to be dysregulated in Type 2 (non-insulin-dependent) diabetes mellitus and it antagonized certain actions of insulin in vitro in rat muscle. This led to speculation that amylin is involved in the pathogenesis of Type 2 diabetes. We have examined the in vivo effects of rat amylin, amidated at the carboxy-terminus, on insulin-mediated carbohydrate metabolism in conscious rats, using the hyperinsulinaemic (±1 nmol/l) euglycaemic (6 mmol/l) clamp technique combined with [3-3H]-glucose infusion. Basal plasma amylin levels were ≤75 pmol/l. Applied amylin levels of 220±75 pmol/l (infusion rate of 12.5 pmol/min) antagonized only the insulin action on liver, resulting in a 100% increase of hepatic glucose output. Amylin levels of 4750±750 pmol/l (infusion rate of 125 pmol/min) induced a 250% increase of insulin-inhibited hepatic glucose output and, in addition, a 30% decrease of insulin-stimulated peripheral glucose uptake. Amylin did not affect: 1) the metabolic clearance rate of insulin, 2) the levels of plasma glucagon, epinephrine, norepinephrine, and corticosterone, 3) in vitro insulin binding and insulin-stimulated receptor autophosphorylation. This suggests that amylin antagonizes insulin action via binding to a yet unknown receptor. In conclusion: amylin causes in vivo insulin resistance and the liver seems the predominant organ regulated by this hormone. The in vivo effects of amylin mimic the pathophysiological abnormalities of insulin action in Type 2 diabetes.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular histology 24 (1992), S. 833-841 
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This study describes the presence of CD15 in dorsal root ganglia neurons in five experimental conditions: chemically defined medium and the same medium with added nerve growth factor, retinoic acid or antibodies against insulin or tyrosine phosphate. Positive astrocyte controls were used to differentiate the monoclonal antibodies that did not react with CD15. Those monoclonal antibodies which detected CD15 in this positive control were also used to study CD15 positivity in dorsal root ganglion cells. This study shows: (i) masking of the CD15 antibody, which influences the detection capacity of the monoclonal antibodies used; (ii) that CD15 discerns two subpopulations of DRG neurons: a CD15-positive and a CD15-negative population; (iii) that CD15 expression is not involved in the outgrowth of protrusions or the wrapping by non-neuronal cells of DRG neurons.
    Type of Medium: Electronic Resource
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