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  • 1
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 219 (1968), S. 857-858 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Extracts of mouse islets were made in 0-25 M sucrose, 1 mM EDTA, pH 7-0, by ultrasonic disintegration7 (80-180 islets in 0.2-0.3 ml.). Glucose-6-phosphatase activity was measured by the release of phosphate during 2 h of incubation at 37 C of 20 µl.. of islet homogenate with 20 µl. of ...
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Diabetologia 19 (1980), S. 391-396 
    ISSN: 1432-0428
    Schlagwort(e): Growth hormone ; hypophysectomy ; plasma growth hormone ; plasma insulin, insulin release ; perifusion ; cultured rat islets
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Growth hormone injected intravenously in the rat elicited a 6-fold spike change in immunoreactive insulin with little variation in glucose. Subcutaneous administration of growth hormone for 4 days augmented by 56% the insulin-secretory response to glucose of isolated islets from hypophysectomised rats but not the response of control rat islets. When islets were cultured in the presence of growth hormone, the glucose-induced insulin release was increased by 35% in batch incubations of islets from both normal and hypophysectomised rats and by 70–110% in perifused islets. Thus the capacity for stimulated release of insulin is limited by hypophysectomy, and growth hormone is capable of directly influencing the secretory function of the β- cell.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1432-0428
    Schlagwort(e): Islets of Langerhans ; insulin ; glucose ; phosphoenolpyruvate ; substrate-site ; methylxanthines ; cyclic AMP ; calcium ; mitochondria ; fructose 1,6-diphosphate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 45Ca2+-accumulation by a mitochondrial fraction from isolated rat pancreatic islets was strongly stimulated by ATP. The ATP-dependent uptake was inhibited by phosphoenolpyruvate in a dose-dependent manner over a wide variety of conditions. Inhibition by phosphoenolpyruvate was noncompetitive with respect to calcium, competitive with respect to magnesium, and antagonised by high Mg-ATP2− concentrations; fructose 1,6-diphosphate also decreased 45Ca2+-uptake. Other glucose metabolites were either less effective or ineffective in diminishing mitochondrial 45Ca2+-accumulation. The ATP-dependent uptake was also inhibited by xanthine derivatives (caffeine and 3-isobutyl-l-methylxanthine) which potentiate the effects of glucose on insulin secretion. Cyclic AMP had no effect. It is thought that the rate of insulin secretion is a function of the cytosolic calcium concentration in the B-cell. These data show that phosphoenolpyruvate, fructose 1,6-diphosphate and methylxanthines might influence exocytosis by direct effects on mitochondrial calcium accumulation, and thus the intracellular distribution of calcium.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Diabetologia 22 (1982), S. 300-300 
    ISSN: 1432-0428
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Diabetologia 22 (1982), S. 134-137 
    ISSN: 1432-0428
    Schlagwort(e): Insulin release ; insulin biosynthesis ; growth hormone ; calmodulin ; cyclic AMP ; islet glucose metabolism ; hypophysectomy ; cultured islets
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effects on islet function of addition to the culture medium of rat growth hormone was studied in 4-day cultured islets of Langerhans from normal and hypophysectomised rats. In islets from hypophysectomised rats, rates of insulin release were 34% lower than in control rat islets; rates of insulin plus proinsulin and total protein biosynthesis were also lower by 48% and 16% respectively. The rates of glucose oxidation and the islet content of cyclic AMP were unchanged in islets from hypophysectomised rats but the islet content of calmodulin was decreased by 68%. The presence of rat growth hormone during the culture period restored the secretory response of hypophysectomised rat islets to that seen in control islets cultured without growth hormone but had only a marginal effect on the rate of insulin plus proinsulin biosynthesis, and no significant effect on islet calmodulin content. Glucose oxidation was increased by the presence of growth hormone during the culture period in both control (73% increase) and hypophysectomised (38% increase) rat islets. Addition of growth hormone to the culture medium also enhanced rates of insulin release and biosynthesis in control islets by 116% and 20% respectively. It is suggested that these changes arise primarily from modification of the synthesis of specific islet proteins.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1432-0428
    Schlagwort(e): Alloxan ; dehydrouramil ; 5-hydroxy-pseudouric acid ; diabetes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effects on islet morphology and blood glucose concentration of intravenous administration of alloxan to rats have been compared with those of two new diabetogenic agents, 5-hydroxy-pseudouric acid (5-HPUA) and dehydrouramil hydrate hydrochloride (DHU). Administration of alloxan (0.35 mmol/kg) caused a classical triphasic change in blood glucose characterised by initial hyperglycaemia, subsequent hypoglycaemia and a delayed persistent hyperglycaemia. In contrast, 5-HPUA and DHU elicited persistent hyperglycaemia as early as 30 min after administration. Morphological evidence for degranulation, pyknosis, necrosis and widening of pericapillary spaces was obtained with all three agents. However, both 5-HPUA and DHU elicit considerably more rapid and extensive changes than alloxan, with evidence for extensive pyknosis occurring as early as 15 min after administration of DHU and 5-HPUA compared with 24 h for alloxan. The more marked potency of DHU and 5-HPUA may be at least partially attributable to the greater stability of these agents compared with alloxan, since solutions of DHU or 5-HPUA kept for 15 min prior to administration retained full diabetogenic activity, whereas similar treatment of alloxan solution completely abolished its diabetogenic activity. Since both 5-HPUA and DHU are potential metabolites of uric acid, their marked diabetogenic potency raises the possibility of a role for uric acid metabolites in the pathogenesis of diabetes mellitus.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Diabetologia 29 (1986), S. 119-121 
    ISSN: 1432-0428
    Schlagwort(e): Insulin release ; insulin biosynthesis ; dexamethasone ; prednisolone ; hydrocortisone ; aldosterone ; cultured islets
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effect of additions to the culture medium of some natural or synthetic corticosteroid hormones was studied in cultured rat islets of Langerhans. The steroids decreased glucose-induced insulin release. The extent of inhibition by dexamethasone was 18–55%, prednisolone 23%, hydrocortisone 21% and aldosterone 18%. None of them affected the basal secretion of insulin or had any effect on diameter or insulin content of the islet. The inhibitory action of dexamethasone on insulin release was observed in the range 63 nmol/l to 6.3 μmol/l. At 6.3 μmol/l during two h, dexamethasone (a) inhibited insulin response to glucose concentrations above 5 mmol/l (b) caused a delay in the first phase and markedly reduced the second phase of insulin release of perifused islets, and (c) decreased the incorporation of [H3]-leucine into total islet proteins without affecting [H3]-leucine-incorporation into insulin plus proinsulin. It is suggested that steroids, by directly acting on the islets of Langerhans, may modulate the insulin-release response to secretagogues.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1432-0428
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Diabetologia 19 (1980), S. 114-117 
    ISSN: 1432-0428
    Schlagwort(e): Insulin secretion ; human islets of Langerhans ; pancreatic β-cell ; tissue culture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Islets of Langerhans were isolated by collagenase digestion from the pancreas of a 39 year-old female renal transplant donor. The islets were subjected to three consecutive periods of tissue culture, after each of which they were incubated in vitro with various agents whose effects on insulin release from islets of laboratory animals have previously been established. After the first culture period, the basal insulin secretion rate of 5.2 μU/islet/h seen with 2 mmol/l glucose was increased approx. 5-fold on raising the glucose concentration to 20 mmol/l. The islets retained the insulin-secretory response to 20 mmol/l glucose throughout the period of study. Insulin secretion was also stimulated by mannose, leucine, α-ketoisocaproate, dihydroxyacetone and 3-hydroxybutyrate, but not by fructose or N-acetyl-glucosamine. Fructose however increased insulin release in the presence of 4 mmol/l glucose. Caffeine elicited insulin release in the absence of glucose and enhanced insulin release in response to 10 mmol/l glucose. Glucose-stimulated insulin release was inhibited by trifluoperazine (25 μmol/l).
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Diabetologia 20 (1981), S. 642-646 
    ISSN: 1432-0428
    Schlagwort(e): Enkephalin ; insulin secretion ; islets of Langerhans ; naloxone ; islet culture ; DAMME
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Rat islets of Langerhans were maintained for 2 days in tissue culture. Following the culture period, the insulin secretory responses of the islets on incubation in bicarbonate medium were measured. The enkephalin analogue D-ala2, MePhe4, Met(0)-ol (DAMME), 8.3×10-8mol/l, augmented insulin release stimulated by glucose (5 or 7 mmol/l) by 76% and 47% respectively; increased insulin release stimulated by α-ketoisocaproate (7.5 mmol/l) by 23%; and enhanced insulin release in the presence of glibenclamide (10 μg/ml) plus glucose (3.3 mmol/l) by 38%. Insulin release in the presence of glucose at 2 or 12 mmol/l was not affected by DAMME (8.3×10-8mol/l). The potentiatory effect of DAMME on insulin release in the presence of glucose (5 mmol/l) was blocked by naloxone (11 μmol/l): naloxone alone did not affect glucose-stimulated insulin release. A high concentration (3.3×10-6mol/l) of DAMME did not modify glucose-stimulated insulin release. Inhibition of glucose-stimulated insulin release by trifluoperazine, an inhibitor of calmodulin, was not overcome by DAMME. Insulin secretory responses were not enhanced by exposure of the islets to DAMME (8.3×10-8mol/l) during the culture period. It is concluded that insulin release from isolated islets is capable of being influenced by an opioid peptide.
    Materialart: Digitale Medien
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