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  • 1
    ISSN: 1432-0428
    Keywords: Glucose infusion ; in vivo insulin secretion ; in vitro insulin secretion ; beta-cell sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We investigated the importance of the level and the duration of glucose stimulation on the in vivo and in vitro insulin response to glucose in normal rats previously submitted to hyperglycaemia. Rats were made hyperglycaemic by a 48-h glucose infusion. Glucose-induced insulin secretion was investigated in vivo by a 20-min hyperglycaemic clamp and in vitro by the isolated perfused pancreas technique, 3 h after the end of the in vivo glucose infusion. In glucose-infused rats, as compared to controls, in vivo incremental plasma insulin values above baseline integrated over the 20-min hyperglycaemic clamp (ΔI) were five times higher during 8 mmol/l glucose clamp, only two times higher in 11 mmol/l glucose clamp and no different in 16.5 mmol/l. Compared to the controls, in vitro incremental plasma insulin concentration above baseline integrated over a 20-min period (ΔI) in glucose-infused rats was 16 times higher in response to 2.8 mmol/l glucose, two times higher in response to 5.5 mmol/l, similar in response to 8.3 mmol/l and significantly lower in response to 16.5 mmol/l. In conclusion, our data suggest that a 48-h hyperglycaemic period results in an increased response of the pancreatic beta cell to low glucose. The response is immediately maximal and can not be increased with higher glucose concentrations. This situation could explain the apparent minimal effect of high concentrations on in vitro insulin secretion in previously hyperglycaemic rats and may provide insights into the sequence of events leading to the impairment of beta-cell function in Type 2 (non-insulin-dependent) diabetes mellitus.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 56 (1991), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Spoilage bacteria of cod fillets were desorbed off the fillet surface by ultrasonication. Catalase activity of these bacteria was determined using the disc flotation method after selective heat inactivation of the endogenous cod catalase and then correlated with the colony forming units. The method was applied to cod fillets from ten retail sources with satisfactory results.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The pineal organ of fish contains photoreceptor cells with structural and functional analogies to retinal photoreceptors. In these cells, the light/dark (LD) cycle influences the production of melatonin by controlling the activity of one of its synthetizing enzymes, serotonin N-acetyltransferase (NAT). The daily rhythm in NAT activity is generated endogenously in the pike but not in the trout pineal. We report here that in addition to the LD information, chemical factors are also involved in the control of melatonin production. Adenosine and two of its analogs stimulated or inhibited NAT activity and melatonin release in cultured pike and trout pineals, depending on the experimental conditions. It is believed that the nucleoside, produced locally, exerts a modulatory role on the neurohormonal output via still enigmatic mechanisms, involving a transmembranous carrier. Nocturnal melatonin production in cultured pike pineals was inhibited by α-adrenergic agonists and stimulated by a β-adrenergic agonist. No effect could be induced in trout pineals cultured under similar conditions. Because melatonin production by pineal photoreceptors is apparently regulated by both light and chemical inputs, we propose they might be multieffector cells.
    Type of Medium: Electronic Resource
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