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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
    Problems in the use of polycarbonate diffusion chambers for syngeneic pancreatic islet transplantation in rats (1980)
    Springer
    Diabetologia 18 (1980), S. 313-317 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00251012
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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
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Role of zinc and calcium in the formation and storage of insulin in the pancreatic β-cell (1978)
    Springer
    Cell & tissue research 188 (1978), S. 107-118 
    Details
    ISSN: 1432-0878
    Keywords: Pancreatic β-cells (mouse) ; Formation and storage of insulin ; Role of zinc and calcium ; Culture of islets ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The effects of culture of isolated mouse islets of Langerhans for up to 9 days in media which had been depleted of zinc electrochemically or with the chelating agent Tris-(2-aminoethyl) amine, or of calcium, have been compared. 2. An 83% reduction of extracellular zinc concentration did not adversely affect proinsulin biosynthesis, conversion of proinsulin to insulin, or the ability of cells to store newly formed insulin in granules. When incubation media were depleted of both zinc and calcium the β-cells produced abnormally large electron-lucent granules, consistent with the failure of insulin to crystallise within the granule sac. 3. Very similar results, with formation of large electron lucent granules, were obtained after culture of islets in the absence of calcium but in the presence of normal concentrations of zinc. 4. It is suggested that zinc may play a less critical role in the biosynthesis of proinsulin and its conversion to insulin, while calcium may have a more important function in insulin storage, than has sometimes previously been supposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220518
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    Paper (German National Licenses)
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