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  • 1
    Electronic Resource
    Electronic Resource
    Direct effects of progesterone on rat islets of Langerhans in vivo and in tissue culture (1977)
    Springer
    Diabetologia 13 (1977), S. 579-583 
    Details
    ISSN: 1432-0428
    Keywords: Isolated islets ; tissue culture ; insulin secretion ; progesterone ; oestradiol ; adenylate cyclase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Progesterone and oestradiol did not alter rates of insulin secretion from isolated rat islets of Langerhans during a 60 min period of incubation in vitro. However, islets isolated from rats which had been injected daily for 15 days with progesterone (5 mg) and oestradiol (5 μg) showed enhanced rates of insulin secretion in response to stimulation by 20 mmol/l glucose or 6 and 20 mmol/l glucose plus 5 mmol/l theophylline. Islets from rats which had been injected with the slow-releasing depot progesterone derivative, hydroxyprogesterone hexanoate, 3 times in 15 days, also showed enhanced rates of insulin release in the absence of any alteration in adenylate cyclase activity. In neither experiment could increased food intake, blood glucose levels or islet insulin content account for the observed changes. The possibility of a direct effect of progesterone on the secretory process was investigated in islets which had been cultured for 20 h with progesterone and oestradiol; these islets were then subjected to a variety of stimuli for secretion. They responded significantly more to glucose (6 or 20 mmol/l) in the presence of theophylline (5 mmol/l), while their insulin content was not significantly different from control islets cultured for a similar period. Islets cultured for 20 h in the presence of progesterone and oestradiol did not show any change in their adenylate cyclase activities. Similarly, direct addition of progesterone and oestradiol to islet homogenates did not alter the adenylate cyclase activity during a 30 minute incubation. These results suggest that progesterone and oestradiol affect insulin secretion directly, by a mechanism which does not involve activation of adenylate cyclase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01236310
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Biochemical and ultrastructural changes in A and B cells of the islets of Langerhans of mice infected with EMC virus (1979)
    Springer
    Diabetologia 17 (1979), S. 51-57 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01222978
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Role of microtubules in the intracellular transport of growth hormone (1978)
    Springer
    Cell & tissue research 190 (1978), S. 163-171 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00210045
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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