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  • islets of Langerhans  (2)
  • B-cell cytoskeleton  (1)
  • Colchicine, vinblastine  (1)
  • 1
    ISSN: 1432-0428
    Keywords: Diabetes ; EMC virus ; DBA2 mice ; islets of Langerhans ; ultrastructure ; insulin ; glucagon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Infection of DBA2 mice with the M strain of EMC virus was used to study the effects of virusinduced diabetes on the A and B cells of the islets of Langerhans. A transient hypoglycaemia was seen in 48% of mice 2–3 days after infection and probably resulted from increased serum insulin concentrations together with inhibition of glucagon secretion at that time. Islets from hypoglycaemic mice showed no significant alterations from control level in basal or fluoride-stimulated adenylate cyclase activity. Overall, 70% of infected mice became hyperglycaemic with a maximum incidence 6 days after infection. Hyperglycaemia was accompanied by a dramatic reduction in the total pancreatic insulin content and in insulin secretory responses to glucose and theophylline, while A-cell structure and function appeared relatively unaffected in diabetic animals. Basal adenylate cyclase activity was increased in hyperglycaemic mice at 7 days after infection, while fluoride-stimulated adenylate cyclase activity was normal throughout the course of infection. Ultrastructural alterations were observed in a small proportion of B cells from two days after infection and included abnormalities of mitochondrial structure and increased electron opacity of the cytoplasm of affected cells, which subsequently led to complete necrosis. The results suggest that EMC virus specifically affects the B cells of the islets and that disturbances of A cell function may be secondary to B cell damage.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0428
    Keywords: Transplantation ; islets of Langerhans ; streptozotocin diabetes ; diffusion chambers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Islets of Langerhans have been enclosed in polycarbonate diffusion chambers and transplanted intraperitoneally to syngeneic streptozotocin diabetic rats. Direct implantation of 1100–1400 islets in these chambers failed to reverse diabetes during a period of 12 weeks, and viable islet tissue was not recoverable at the end of this period. Islets placed in chambers which had been implanted 3–12 weeks previously similarly failed to lower blood glucose of diabetic recipients, as a result of lack of survival of the islets. Insulin infusion into chambers previously implanted in vivo, I125 insulin diffusion studies in chambers recovered 6–8 weeks after implantation, and scanning electron microscopy of the recovered membranes all indicated that the pores were not totally occluded. The failure of islet transplantation via chambers in this simple syngeneic model has discouraging implications for their use as a means of avoiding allograft rejection.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 40 (1984), S. 1098-1105 
    ISSN: 1420-9071
    Keywords: Insulin secretion ; regulation of ; microtubule-granule interactions ; B-cell cytoskeleton ; exocytosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Conclusions Studies of the role of the microtubule-microfilamentous system in insulin secretion have been widened by continuing experimentation and analysis to provide a comprehensive working hypothesis which embraces ideas of the way in which the polymerization of microtubules and microfilaments may be regulated and how these cytoskeletal components may act together to enhance the process of granule movement. It is also possible to speculate about, but not yet to demonstrate, the way in which the activities of this effector system could be regulated by calcium and by cyclic AMP, which are essentially involved in the regulation of rates of secretion.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 190 (1978), S. 163-171 
    ISSN: 1432-0878
    Keywords: Growth hormone ; Somatotrophs ; Microtubules ; Colchicine, vinblastine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pulse-chase experiments utilising(3H)leucine have been used to study the effects of colchicine and vinblastine on intracellular transport and secretion of newly synthesised growth hormone from rat anterior pituitary fragments. Growth hormone was isolated from medium and fragments by polyacrylamide gel electrophoresis. When colchicine or vinblastine, which disrupt microtubules, were added immediately after pulse labelling, inhibition of the subsequent secretion of newly synthesised growth hormone was detected throughout the succeeding 5 h. Similar inhibition was seen if the drugs were added after a 1 h delay. However, if colchicine or vinblastine were added only after a 2 h chase incubation, then no significant effect on subsequent release of labelled growth hormone was seen. The results suggest that these agents may inhibit the transport of newly formed growth hormone storage granules from the Golgi complex to the cytoplasmic pool. Microtubules do not appear to be involved in the mechanism of the final secretion of newly synthesised hormone by exocytosis.
    Type of Medium: Electronic Resource
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