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Biomedical subjects

B Wilke

Publications and source records attributed to B Wilke.

34 records · Page 2Linked to original sources
PubMed1981

Characterization of insulin biosynthesis and secretion of pancreatic islets prepared from hyperglycaemic sand rats. II. Investigations of islets after different periods of cultivation.

Cultivation of pancreatic islets of sand rats in the presence of high glucose led to a very high insulin release and to strongly diminished insulin contents independent of the metabolic stage of the sand rats. Changes in the [3H]-leucine incorporation into (pro)insulin were not found in dependence of cultivation.

Animals↗
PubMed1981

Influence of culture conditions on B-cell functions in vitro.

Isolated pancreatic islets from Wistar rats were maintained in vitro at 37 degrees C for 12 days in TCM 199 containing 10 mmol/l glucose and supplemented with 10% serum. 10 mmol/l glucose completely prevented the diminution of insulin content independent of the type of serum (fetal calf serum; serum from newborn calfs; horse serum), whereas the insulin biosynthesis as well as the insulin release were modulated by the kind of serum. Fetal calf serum can be replaced by horse serum.

Animals↗
PubMed1980

Changes in glucose-stimulated insulin secretion after long-term treatment of C57BL mice with glibenclamide.

An insulin response to increased glucose concentrations could not be found in vivo and in vitro after long-term treatment of C57BL/KsJ and C57BL/6J mice with Glibenclamide. This missing stimulation of insulin secretion was not the result of an exhaustion of the islets or a disturbed (pro)insulin biosynthesis as demonstrated by measurements of insulin content of the islets and by in vitro (pro)insulin biosynthesis experiments. In the presence of glucose (15 mmol/l) theophylline increased the insulin secretion of isolated islets of Glibenclamide-treated mice to values similar to control islets. The insulin response to an i.p. glucose loading was found to be normal in comparison with control mice 1-2 weeks after the Glibenclamide treatment had been finished.

Animals↗
PubMed1980

The influence of cultivation on (pro-)insulin biosynthesis and secretion of isolated pancreatic islets of C57BL-mice, long-term treated with glibenclamide in vivo.

Long-term treatment of C57Bl/KsJ and C57Bl/6J mice with glibenclamide in vivo caused a diminished response of insulin to high glucose concentrations (20 mmol/l). Islets of those mice were investigated to answer the question whether it is possible to overcome this diminution of glucose sensitivity by cultivation in presence of high glucose (20 mmol/l). The insulin release of islets of glibenclamide treated mice was significantly lowered also in the first 48 h of cultivation. In the following short-term incubation (2 h) no differences in the glucose stimulated insulin secretion could be seen. The second cultivation period (48-96 h) confirmed these results. Both groups of islets (controls and glibenclamide treated) reached comparable values in insulin release. Cultivation of islets of glibenclamide treated mice in presence of 20 mmol/l glucose for at least 2 days led to a restoration of the glucose sensitivity of insulin release. Insulin biosynthesis, judged by measuring 3H-leucine incorporation into (pro-)insulin, was largely unaffected. In all experimental conditions the insulin content was comparable to that of controls.

Animals↗
PubMed1979

Studies on (pro)insulin biosynthesis and secretion of pancreatic islets of sand rats (Psammomys obesus) after different feeding conditions.

It was possible to induce different metabolic states in sand rats of our breeding colony or in newly caught Egyptian sand rats, respectively, by feeding a pellet diet or vegetable diet (green cabbage). Newly captured sand rats fed only on native food were used as reference group (group C). Plasma IRI-level and glucose in vivo and [3H]-leucine incorporation into proinsulin and insulin, insulin secretion and insulin content in vitro were investigated. Sand rats fed on pellet chow and ad libitum (group B) developed a hyperinsulinism and showed higher sensitivity of [3H]-leucine incorporation into proinsulin and insulin to glucose (maximal stimulation at 3 mM) and increased incorporation rates in vitro. Restriction of pellet food to 35-40 kcal/animal/day (group A) lead to changes of all parameters, which were investigated in the same direction as in group B, but to a much smaller extent. Newly captured sand rats, which were fed green cabbage for 4 to 6 weeks divided into two groups: One group (group D1) was comparable to the normal group (C) in IRI levels, glucose levels, glucose sensitivity and amount of [3H]-leucine incorporation. The other group (group D2) tended to group A. Marked changes in insulin content and insulin secretion of isolated pancreatic islets could not be found in any group.

Animals↗
PubMed1978

Influence of pilocarpine pretreatment on (pro)insulin biosynthesis of isolated islets of rats.

3[H]-Leucine incorporation into (pro)insulin and insulin secretion was investigated using islets prepared by collagenase digestion from pancreata of rats pretreated with the cholimimetic agent pilocarpine or with saline (controls). Under the influence of pilocarpine pretreatment the [3H]-leucine incorporation into islet proteins with insulin immunoreactivity is enhanced at 6 mM glucose in the incubation medium of the islets but the incorporated radioactivity at 18 mM glucose is independent of the pretreatment of the animals. Only small or no changes were found regarding insulin secretion. It is concluded that an influence of pilocarpine pretreatment should be taken into consideration using such islets for studies on the regulation of (pro)insulin biosynthesis.

Animals↗
PubMed1977

Studies on the (pro) insulin biosynthesis of islets of Langerhans of sand rats (Psammomys obesus).

By feeding a regular laboratory chow, sand rats (Psammomys obesus) from our breeding colony gained different body weights, though they received approximately the same quantity of calories. Sand rats, reaching a body weight above 160 g (group B) showed significantly increased blood glucose values in contrast to the animals with a body weight under 160 g (group A). Isolated pancreatic islets of these two groups of sand rats were incubated with [3H]-leucine to study the incorporation of this amino acid into proinsulin and insulin. The incorporation into proteins of pancreatic islets of sand rats of group B was stimulated by 0.45 mg and 3.0 mg/ml glucose. In group A there was no further stimulation from 0.45 mg to 3.0 mg/ml glucose. Insulin secretion could be stimulated by glucose in both groups, but the stimulation was stronger in group B than in group A.

Animals↗
PubMed1976

[(Pro)insulin biosynthesis of isolated islands of Langerhans in the sand rat and Wistar rat].

Sand rats develop a diabetes-like syndrome, connected with temporary hyperinsulinism, when fed a rat laboratory chow diet. The conversion of proinsulin to insulin is not disturbed in these animals. Sand rat islets do not secrete newly synthesized (pro) insulin preferentially. Time course and glucose response of [3H]-leucine incorporation are different between islets of sand rats and Wistar rats.

Animals↗
PubMedDate not supplied

Syngeneic transplantation of rat pancreatic islets into the spleen. Light and electron microscopical findings.

An islet transplantation model was established with the two congeneic Lewis rat strains LEW.1W and LEW.1A, which were made diabetic by a single i.p. injection of 50 mg/kg b.w. streptozotocin. Isolated neonatal islets of the two strains served as a graft. Syngeneic transplantation into the spleen resulted in permanent graft survival and in normoglycemia of streptozotocin diabetic rats of the two strains. 200 days after transplantation functionally intact islets were demonstrable in the spleen by histological, histochemical and electron microscopical investigations. Histochemical findings indicate an activation of interdigitating reticular cells in the white pulp and of macrophages in the red pulp of the spleen as consequences of the islet transplantation. In addition a few electron microscopical findings concerning possible interactions between host plasma cells, lymphocytes and transplanted beta cells of islets are described and discussed.

Animals↗
PubMedDate not supplied

[Determination of the irritating potential of environmental substances in an epidermal cell suspension in vitro].

A simple in vitro screening method was established, which allows estimation of the effect of environmental products on cell alteration or irritative potential. Primary cell suspensions, prepared from the epidermis of guinea pig ears through trypsination (0.2%) over night at 4 degrees C, were used. The cell suspension (3 mill./ml) and test substances were mixed in equal portions (500 microliters) and incubated at room temperature for approximately 90 min. The degree of cell alteration was determined by the trypan blue exclusion test. Chemically defined substances as well as disinfectants were employed. The cell alteration was clearly dependent upon substance concentration as well as incubation time. On the basis of the mean alteration time (AT50) measured in vitro, and the mean irritation time (IT50) determined in the patch test in vivo, the substances were ranked according to strength of cell alteration or irritative potency in vitro and in vivo. A good correlation (Spearman's rank correlation, rs = 0.76) was found between the in vitro and in vivo results. Thus, this method is suited for the screening of chemical products especially in industrial laboratories.

Adolescent↗