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  • 1
    Electronic Resource
    Electronic Resource
    Localisation of islet amyloid polypeptide and its carboxy terminal flanking peptide in islets of diabetic man and monkey (1991)
    Springer
    Diabetologia 34 (1991), S. 449-451 
    Details
    ISSN: 1432-0428
    Keywords: Islet amyloid polypeptide ; islet amyloid ; Type 2 (non-insulin-dependent) diabetes mellitus ; Beta cell ; pancreas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Islet amyloid polypeptide is a normal constituent of islet Beta cells and is derived from a larger precursor by removal of flanking peptides at the carboxy (C) and amino (N) terminals. The role of these flanking peptides in the formation of amyloid in Type 2 (non-insulin-dependent) diabetes mellitus and in insulinomas is unknown. The C-terminal flanking peptide of islet amyloid polypeptide was localised by immunocytochemistry in human and monkey pancreatic islets from Type 2 diabetic and non-diabetic individuals by use of specific polyclonal antisera. Immunoreactivity for the C-terminal peptide was found in insulincontaining cells in both diabetic and non-diabetic tissue: no antibody binding was detected in islet amyloid of Type 2 diabetic man or of monkeys although a positive reaction occurred with antisera for islet amyloid polypeptide. The C-terminal peptide was localised by immunogold electron microscopy in the insulin granules in both diabetic and nondiabetic individuals but, unlike islet amyloid polypeptide, was not detected in lysosomes. The absence of immunoreactivity for the C-terminal peptide in amyloid suggests that incomplete cleavage of this flanking peptide from islet amyloid polypeptide is not a factor in the formation of islet amyloid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00403186
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Chronic overproduction of islet amyloid polypeptide/amylin in transgenic mice: lysosomal localization of human islet amyloid polypeptide and lack of marked hyperglycaemia or hyperinsulinaemia (1993)
    Springer
    Diabetologia 36 (1993), S. 1258-1265 
    Details
    ISSN: 1432-0428
    Keywords: Islet amyloid polypeptide ; amylin ; transgenic mouse ; islet beta cell ; islet amyloid ; glucose metabolism ; insulin resistance ; Type 2 (non-insulin-dependent) diabetes mellitus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Type 2 (non-insulin-dependent) diabetes mellitus is characterised by hyperglycaemia, peripheral insulin resistance, impaired insulin secretion and pancreatic islet amyloid formation. The major constituent of islet amyloid is islet amyloid polypeptide (amylin). Islet amyloid polypeptide is synthesized by islet beta cells and co-secreted with insulin. The ability of islet amyloid polypeptide to form amyloid fibrils is related to its species-specific amino acid sequence. Islet amyloid associated with diabetes is only found in man, monkeys, cats and racoons. Pharmacological doses of islet amyloid polypeptide have been shown to inhibit insulin secretion as well as insulin action on peripheral tissues (insulin resistance). To examine the role of islet amyloid polypeptide in the pathogenesis of Type 2 diabetes, we have generated transgenic mice with the gene encoding either human islet amyloid polypeptide (which can form amyloid) or rat islet amyloid polypeptide, under control of an insulin promoter. Transgenic islet amyloid polypeptide mRNA was detected in the pancreas in all transgenic mice. Plasma islet amyloid polypeptide levels were significantly elevated (up to 15-fold) in three out of five transgenic lines, but elevated glucose levels, hyperinsulinaemia and obesity were not observed. This suggests that insulin resistance is not induced by chronic hypersecretion of islet amyloid polypeptide. Islet amyloid polypeptide immunoreactivity was localized to beta-cell secretory granules in all mice. Islet amyloid polypeptide immunoreactivity in beta-cell lysosomes was seen only in mice with the human islet amyloid polypeptide gene, as in human beta cells, and might represent an initial step in intracellular formation of amyloid fibrils. These transgenic mice provide a unique model with which to examine the physiological function of islet amyloid polypeptide and to study intracellular and extracellular handling of human islet amyloid polypeptide in pancreatic islets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00400803
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Granule populations in oxytocin and abnormal perikarya of the supraoptic nucleus of homozygous Brattleboro rats: Effects of colchicine administration (1985)
    Springer
    Cell & tissue research 241 (1985), S. 435-444 
    Details
    ISSN: 1432-0878
    Keywords: Neurosecretory granules ; Supraoptic nucleus ; Colchicine ; Oxytocin neurones ; Co-transmission ; Brattleboro rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Magnocellular neurones in the supraoptic nucleus of the homozygous Brattleboro rat, which are unable to produce vasopressin, were investigated by immunocytochemistry to identify both the oxytocin cells and the abnormal neurones, which in normal animals would produce vasopressin. The abnormal cell profiles were significantly more rounded than those of the oxytocin cells. Both cell types showed evidence of hyperactivity, but the Golgi apparatus was more extensive in the oxytocin cells, probably as a result of the failure of the abnormal cells to produce vasopressin and its neurophysin and the resultant reduction in hormone packaging. Neurosecretory granules (NSG) 160 nm in diameter were found in the oxytocin perikarya but were absent from the abnormal cell bodies. In addition, a population of small dense granules (SDG) 100 nm in diameter was observed in both types of neurone, in numbers equal to the NSG in oxytocin cells. Injection of a low, non-lethal dose of the axonal transport inhibitor colchicine resulted in a rapid and equal accumulation of both NSG and SDG in oxytocin perikarya and of SDG in the abnormal perikarya after one day. The effects of colchicine were reversed 2–3 days after administration. The SDG, which may contain a co-transmitter or co-hormone substance, are thus produced at a similar rate to NSG, and appear to be transported from the perikarya for subsequent release at the nerve endings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217191
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Improved visualization of the immunoreactive hypothalamo-neurohypophysial system by use of immuno-gold techniques (1986)
    Springer
    Cell & tissue research 243 (1986), S. 193-204 
    Details
    ISSN: 1432-0878
    Keywords: Hypothalamo-neurohypophysial system ; Supraoptic nucleus ; Neurosecretory granules ; Neurophysins ; Lysosomes ; Immuno-gold techniques ; Double-immunolabeling ; Monoclonal antibodies ; Murids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural post-embedding immuno-gold techniques were applied to the supraoptic nucleus and the neurohypophysis of mice and rats. The primary antibodies were three different monoclonal antineurophysins, used in protein A-gold and immunoglobulin-gold procedures. Conventional plastic embedding as well as hydrophilic media (L.R. White) were used; non-osmicated and osmicated tissues were immunolabeled; sodium metaperiodate oxidation was used, but was not essential for immunolabeling. Vasopressinergic and oxytocinergic NSGs were identified by the specific immunoreactivity of their respective neurophysins on adjacent thin sections, and by sequential double labeling on the same thin section using two different antibodies associated with gold probes of different diameters. The immunoidentification indicates that vasopressin NSGs can additionally be differentiated as larger, with more electron-dense matrix, and susceptible to damage by sodium metaperiodate. The only organelles consistently labeled were neurosecretory granules (NSGs), either intact or within lysosomal configurations. Some lysosomal dense bodies were immunoreactive even when discrete NSGs were no longer morphologically recognisable within them. Labeled NSGs were located within neuronal cell bodies, along axonal shafts and within axonal swellings and endings; occasionally immunoreactive NSGs were observed within synaptic boutons. Labeling intensity was semi-quantitatively gauged by counting gold particles in relation to numbers of NSGs per axonal varicosity. The precise localisation achieved with particulate immunogold labeling surpasses that previously obtained with diffuse electron-dense immunoreaction products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221868
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    Paper (German National Licenses)
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