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Biomedical subjects

W Besch

Publications and source records attributed to W Besch.

At least 55 records · Page 3Linked to original sources
PubMed1988

Semisynthetic human insulin: pharmacokinetics and biological potency in healthy subjects in comparison with highly purified porcine insulin.

Pharmacokinetics and the biological activity of a new semisynthetic human insulin (VEB Berlin-Chemie) were investigated in 5 healthy men. Following an overnight fast, 0.2 IU per kg body weight of human and pork insulins (SNC insulin; VEB Berlin-Chemie) were injected subcutaneously into thigh of each individual at a time interval of 8 days. To assess biological potency of both insulins all subjects were twice connected to the BIOSTATOR. A very similar pattern of serum insulin levels (IRI) was observed following subcutaneous injection of human and pork insulin, marked by a sharp initial increase and maximum values reached after 2.5 hours. 8 hours after the insulin administration the original fasting concentrations were nearly attained. According to C-peptide levels, both insulins inhibited endogenous insulin secretion. Evaluation of insulin action was determined by euglycemic clamp technique, provided by the BIOSTATOR, whose function was transformed into a glucose-controlled dextrose infusion system. The amount of glucose delivered by the system in order to keep the blood glucose steady state concentrations at the fasting level was utilized as the measure of biological activity of the injected insulin on glucose metabolism. Maximum values of glucose infusion were achieved between 3 and 4 hr after injection of human and pork insulins. At the end of the study (8 hr) the glucose administration did not return to its initial rate. After administration of both the human and porcine insulins, a marked but similar decrease of FFA concentrations was observed. This indicated a clear-cut inhibition of lipolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1987

5-year follow-up study of C-peptide secretion in newly diagnosed type I diabetics: relations to HLA-phenotype, insulin requirement and metabolic control.

50 HLA-typed insulin-dependent diabetics were studied at the time of diabetes onset and after 1, 2, 3 and 5 years with regard to C-peptide secretion after combined stimulation with glucose and glucagon, insulin requirement and glycaemic control index. The mean decrease of the residual B-cell reserve was observed within two years. C-peptide secretion was correlated with better metabolic control and lower insulin requirement after more than one year of diabetes duration, but had no influence on this at the time of diabetes onset. The C-peptide response sometimes varied between non response and high response in one individual from one investigation to the next. There was no prognostic value of C-peptide secretion at diabetes onset for the further development of B-cell function. We found a significantly longer persistence of B-cell function in patients who were older and in those with mild symptoms at diabetes onset. The presence of HLA B8, DR3 antigens was correlated with severe ketoacidosis at manifestation and a more pronounced destruction of B-cell function.

Adolescent↗
PubMed1987

Generation and partial characterization of monoclonal antibodies reactive with islet cell antigens.

Islet cell antibodies have been detected in more than 60% of newly diagnosed type I diabetics. Their pathogenetic role is still unclear. We have generated monoclonal antibodies (mc-ab) reactive with islet cell antigens by fusing mouse myeloma cells with spleen cells from Balb/c mice immunized with pancreatic islet cells. Hybridomas producing islet cell surface antibodies (ICSA) were detected by indirect immunofluorescence on viable cells from rat islets or rat insulinoma. Cytoplasmic islet cell antibodies (ICA) were detected by indirect immunofluorescence on Bouin-fixed sections of mouse pancreas. The ICSA- and/or ICA-producing hybridomas were cloned twice by limiting dilution. This paper describes six different mc-ab. All hybrid cell lines obtained produced IgM antibodies. Four of them mediate complement-dependent cytotoxicity to viable rat islet cells. In the present study the heterogeneity of circulating ICSA is demonstrated. Also, a monoclonal beta cell surface autoantibody K56aF3 was produced by fusion of spleen cells from a mouse treated with sub-diabetogenic doses of streptozotocin in combination with complete Freund's adjuvant. It was cytotoxic against islet cells up to a dilution of 1:1,000 and it could inhibit the insulin secretion from neonatal rat islets cultured in RPMI 1640 as stimulated by glucose or by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine common with glucose. The latter effect was reversible as indicated by the recovery of insulin secretion in a subsequent culture period without mc-ab. These results suggest that circulating ICSA in type I diabetics may alter beta cell function and thereby contribute to the pathogenesis of type I diabetes.

Animals↗
PubMed1987

Measurement of insulin in human sera using a new RIA kit. 1. Insulin determination in the absence of insulin antibodies--conventional assay and micro modification.

A sensitive and versatile radioimmunoassay (RIA) for insulin was established using human insulin standard, a specific guinea pig anti-insulin antiserum and rabbit anti-guinea pig serum. Radioiodination was performed according to a modified chloramine T method. Tracer preparations were used for as long as 6 weeks after iodination. The standard curve ranges from 0.044 to 1.2 nmol/l. The intra-assay coefficient of variation (CV) was 3-5% and the inter-assay CV was 6-9% in the optimal range between 0.4 and 0.9 nmol/l. The average recovery of human insulin added to plasma or serum samples was 100.2 +/- 2.0% (n = 38) and 100.1 +/- 1.9% (n = 42), respectively. In addition to human insulin, porcine, canine, rabbit and bovine insulin can also be determined but not rat or mouse insulin. The cross-reactivity of the antiserum with porcine proinsulin was found to be 40% on the molar basis. The range of mean fasting plasma insulin concentrations in healthy subjects and under various pathological conditions were estimated.

Humans↗
PubMed1987

Measurement of insulin in human sera using a new RIA kit. 2. Determination of free and total insulin--correlations to insulin antibody levels.

Using the micro-scale modification of a newly developed RIA kit for insulin, we established methods for the determination of free and total insulin in serum of insulin-treated diabetics. Precipitation with polyethylene glycol 6000 or acid alcohol extraction of sera was carried out to remove or to dissociate antibody-bound insulin. Both assays permit precise and accurate measurement of either serum insulin fraction. In 50 diabetic sera with tracer insulin binding of 0-97%, free (after equilibration of the sera at 37 degrees C) and total insulin levels as well as insulin antibody binding parameters were determined. There was a good correlation of free to total insulin levels with maximally 10-fold higher values of total insulin. Both free and total insulin were found to be correlated with the ability of the serum to bind insulin. In detail, binding affinities (i.e. the reciprocal of equilibrium dissociation constants) and binding site concentrations were evaluated which were shown to be positively correlated with free and total insulin levels as well. From these data we conclude that insulin antibodies in the serum may accumulate therapeutic insulin and function as a depot for delivering insulin in insulinopenic episodes (Keilacker et al., 1982 and 1986).

Diabetes Mellitus, Type 1↗
PubMed1987

Cytotoxic activity of sera from diabetic BB rats against BB rat islet--a functional study.

[3H] leucine incorporation into islet proteins, insulin secretion, hormone content (insulin, glucagon) and DNA synthesis were measured in cultured BB rat islets in a study to compare the effect of freshly prepared BB rat serum obtained from non-diabetic and newly diagnosed diabetic BB rats on islet functions. After exposure of isolated BB rat islet to a mixture of tissue culture medium and BB rat serum (1:1) for 24 hr, islet lysis was induced by 40% of the diabetic BB rat sera whereas the remaining 60% of diabetic BB rat sera tested did not influence islet functions as evidenced by insulin net production, glucose-induced insulin release and DNA synthesis measured in a subsequent culture period in TCM 199, 10 mmol/l glucose supplemented with 10% neonatal calf serum or short-term incubations. After exposure of islets to sera with anti-islet cytotoxicity the majority of islet cells were destroyed as indicated by a drastically reduced [3H] leucine incorporation into islet proteins and by a diminution of hormone and DNA content of islets. This toxicity against islets was overcome by heat treatment (58 degrees C, 30 min) of sera. The results indicate that heat-labile components in certain diabetic sera of BB rats can lyse the majority of islet cells in BB rat islets within 24 hr. Our assay may help to dissociate humoral and cellular components which cause the injury of beta cells and the onset of diabetes in BB rats.

Animals↗
PubMed1986

[Do doctors understand their patients?].

The extent to which doctors understand the complaints of their patients has been investigated by comparing patient complaints with the observation and assessment of these by the doctor. This involved questioning 259 patients and 30 doctor. From the 259 patients, three groups (a total of 57 patients) were formed, having common main symptomatologies. The extent to which the complaints of each of these patients corresponded with the clinical assessment was evaluated. The results revealed a close agreement between patient complaints and clinical assessment, not only for those patients with organo-medically diffuse symptoms (feeling of illness, tiredness, nervousness) but also for those with organ-medically clearly defined, localised (cardiac and thoracic pain) and mixed diffuse-localised complaints.

Adolescent↗
PubMed1986

Reversibility of the acute toxic effect of cyclosporin A on pancreatic B cells of Wistar rats.

This study investigated if and to what extent the acute toxic effect of Cyclosporin A on pancreatic Wistar rat B cells is reversible. After 2 weeks of treatment rats developed marked glucose intolerance accompanied by reduced pancreatic insulin content due to a loss of B cells, diminished islet DNA synthesis and decreased B-cell insulin content. Cyclosporin A had accumulated in the pancreas. Three weeks after withdrawal of Cyclosporin A, pancreatic tissue concentrations of Cyclosporin A were still 100 times larger than in serum. Glucose tolerance, however, had already improved, associated with an increase of B-cell insulin content and apparent islet replication, and the insulin response of isolated islets was reduced. Five weeks after the withdrawal of Cyclosporin A, glucose tolerance was normal, but pancreatic insulin content and relative B-cell volume were still diminished in comparison to vehicle-treated controls. Eight weeks after withdrawal, the morphometric parameters had also been normalized. The results suggest that the loss of pancreatic B cells is caused by a toxic destruction, possibly combined with an apparent decrease of replicatory activity. The acute toxic effects of Cyclosporin A in pancreatic B cells are stepwise reversible.

1-Methyl-3-isobutylxanthine↗
PubMed1986

The action of cyclosporin A on the endocrine pancreas in vitro--functional and morphological studies.

We investigated the effect of Cyclosporin A (100 ng/ml - 12000 ng/ml) on functional parameters of the endocrine pancreas in vitro. The insulin secretion of isolated islets in response to a variety of secretory stimulators is characterized by minimal alteration occasionally observed in the presence of very high Cyclosporin A concentrations. Cyclosporin A did not alter the glucose-induced biphasic insulin secretion, nor the arginine-stimulated glucagon secretion of the perfused rat pancreas. Exposure of isolated islets to 2000 ng Cyclosporin A/ml for 3 weeks resulted in a minimal decrease of insulin content and a marked reduction of glucagon content, which were not accompanied by drastic alterations of insulin secretion. Scanning electron micrographs of these Cyclosporin A-treated islets did not differ from cultured control islets. The results let us assume that Cyclosporin A exerts no toxic effects on the endocrine pancreas in vitro, when exposed to concentrations greater than or equal to 2000 ng/ml.

Animals↗
PubMed1986

The role of insulin antibodies in insulin treatment of type I diabetes.

We investigated equilibrium plasma binding patterns of insulin in 45 juvenile diabetics treated with conventional insulin preparations. Insulin binding parameters were evaluated by Scatchard analysis of the binding data. Stable diabetics had significantly lower equilibrium dissociation constants than labile, thus suggesting an enhanced insulin depot effect due to stronger insulin binding. Correlation of insulin binding data with a glycemic control index yielded a positive relationship between insulin antibody binding and the degree of glycemic control. Insulin neutralization as detected by a relationship between maximum binding capacity of high affinity antibodies and insulin requirement could only be found if patients with poor diabetes control were excluded. Similarly, the well-known promoting influence of residual beta-cell functional capacity (assessed by C-peptide levels) on diabetic stability was observed only after exclusion of patients with higher insulin antibody binding. These data suggest that insulin antibodies are influencing insulin treatment of diabetics in a dual way. They may neutralize therapeutic insulin but at the same time they exert an insulin-sparing action by improvement of diabetes control. Occasionally the latter effect may abolish the correlation between diabetes control and beta-cell functional capacity.

Adolescent↗
PubMed1986

The long-term culture of encapsulated pancreatic islets.

A new encapsulation technique, the formation of a polyelectrolyte complex membrane from sodium cellulose sulphate and a polycationic solution (polydimethyldiallylammoniumchloride) can be used for culturing pancreatic islets. After 5 weeks of culture, such encapsulated islets were morphologically well preserved, and parameters of cell viability and functionality such as DNA content and DNA synthesis, insulin content and stimulated insulin release were not different between the encapsulated and non-encapsulated control islets. A lower insulin secretion into the medium of the encapsulated islets during the first 3 weeks of culture can probably be explained by the capsule diameter (4-5 mm) and should be improved using microcapsules with a diameter of less than 1 mm.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Measurement of insulin during isolation and purification from animal pancreas. A comparison of radioimmunoassay, radioreceptor assay and in-vivo bioassay.

For the purpose of monitoring the yield of the insulin extraction procedure from animal pancreas three methods of insulin determination were compared, i.e. the mouse convulsion test, a radioreceptor assay (RRA) on rat fat cells and a radioimmunoassay (RIA) which was especially laid out for high insulin concentrations. In samples containing actually insulin in general all three methods provided comparable results. Notable differences were only found in proinsulin-containing material. Because of its simplicity and high reproducibility as well as the good agreement of its results with those obtained with the other assays, the RIA turned out to be the most suitable assay. On the other hand, the RRA should be useful in detecting molecular differences between the investigated insulin-like preparations and standard insulin.

Animals↗
PubMed1986

Effects of islet cell surface antibodies on isolated neonatal rat islets of Langerhans in vitro.

Islet cell surface antibodies (ICSA) were raised by immunization of rabbits with viable neonatal rat pancreatic islet cell suspensions. By absorption with liver powder and spleen cells unspecific cytotoxic components were removable from the sera. Cytotoxic effect of islet cell antiserum against islet cells was indicated by 51Cr-release. In dependence on serum concentration beta-cell damage induced by ICSA-positive serum was detectable by insulin leakage from neonatal rat islets of Langerhans. The immune cytolytic effect of rabbit anti-rat islet cell surface serum was accompanied by morphological alterations of the islet surface structure as revealed by scanning electron microscopy. Pretreatment of pancreatic islets with cytotoxic islet cell antiserum results in an increased insulin leakage even after the removal of the cytotoxic conditions suggesting the persistence of cell membrane lesions. Insulin secretion of islets of Langerhans first exposed to cytotoxic ICSA-positive serum is still stimulated by 15 mmol/1 glucose plus 0.1 mmol/1 3-isobutyl-1-methylxanthine (IBMX) but taking into account the increased insulin leakage the secretory capacity of these islets is significantly diminished.

Animals↗
PubMed1986

[Insulin and glucagon secretion of the preserved dog pancreas].

Well defined results can be obtained quickly by in vitro test concerning the preservation effect of the preserved dog's pancreas. Clinical and chemical parameters were received during the hypothermic perfusion respectively during the refrigerant storage. The in vitro function tests were carried out after the preservation by insulin and glucagon stimulation. The results showed that the A and B cells of the dog's pancreas are completely able to function after a preservation of 24 hours. Thereby a strong formation of edemas by releasing high enzyme activities is caused during the mechanical perfusion of the organs. The simple refrigerant storage of the pancreata therefore, is the more suitable preservation form for organ transplantations.

Animals↗
PubMed1986

Polyacrylamide gel electrophoretic preparation of labeled and non-labeled peptides for radioimmunoassay.

Radioiodinated polypeptide hormones, such as insulin, glucagon, human growth hormone, and human C-peptide are employed for radioimmunoassays for investigations of hormonal alterations in states of disturbed carbohydrate metabolism. Iodination was performed using chloramine T. Iodination products of these polypeptide hormones and, for preparation of standard material, native human C-peptide from cadaver pancreases were fractionated by polyacrylamide gel electrophoresis at pH 8.9. Disc electrophoresis in 24 cm-long gel rods resulted in stable tracers with high specific activity as well as homogeneous standard material being highly suitable for radioimmunoassays.

C-Peptide↗
PubMed1985

[Does closely monitored control and therapy adjustment improve the prognosis in patients with severe heart insufficiency?].

The one year mortality of patients with severe congestive heart failure ranges between 30 and 70%. The effect was investigated of a stepped care program, including weekly monitoring and frequent adjustment of medical treatment, on the prognosis of 18 consecutive outpatients with severe congestive heart failure (NYHA class III and IV, 60 +/- 3.5 years). The diagnosis of congestive heart failure was proven by an invasively measured cardiac index below 2.5 l/min/m2 or by a left ventricular ejection fraction below 30%. Plasma adrenaline and noradrenaline values and plasma renin activity were substantially increased in all patients compared with 20 normals. 11 of the heart failure patients had coronary heart disease, 10 with a large left ventricular aneurysm, 6 patients had congestive cardiomyopathy and one patient had valvular heart disease with aortic insufficiency. In 9 patients ventricular tachycardias were registered, four had recurrent syncopes, and in 7 other patients atrial fibrillation, atrial flutter and paroxysmal supraventricular tachycardias were found. Medical treatment in all patients included pre- and afterload reduction by vasodilators. 11 patients received digoxin and 8 antiarrhythmic drugs. After a mean follow-up of 25 +/- 3.3 months, the one-year mortality was 7% and the two year mortality 15%. The favorable prognosis in patients in this special care program shows the favorable effects of individualized therapy, of frequent patient monitoring and the influence of strict compliance on survival and symptoms in patients with chronic congestive heart failure.

Adult↗
PubMed1985

Pregnancy-associated changes in the endocrine pancreas of normoglycaemic streptozotocin-treated Wistar rats.

The effect of pregnancy on pancreatic insulin content and relative B-cell volume has been studied in normoglycaemic Wistar rats treated with streptozotocin 14 days before mating. A single intravenous injection of streptozotocin (30 mg/kg body weight) caused a significant reduction of pancreatic insulin content and B-cell volume. The islet insulin content was 60% of control values. However, pregnancy-associated adaptation was preserved in these streptozotocin-treated animals. Plasma insulin levels, pancreatic insulin and B-cell volume were significantly enhanced compared with non-pregnant rats investigated on the same date. The incorporation of [3H]-thymidine into islets from pregnant rats (day 10.5) was higher than that in islets isolated from non-pregnant animals. After delivery insulin content and B-cell volume returned to pre-pregnant values. Also during a longer period after streptozotocin treatment (156 days), no measurable enhancement of B-cell volume and pancreatic insulin content was observed indicating the unresponsiveness of residual B cells to compensate spontaneously for the loss despite persisting normoglycaemia.

Animals↗