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Biomedical subjects

H J Hahn

Publications and source records attributed to H J Hahn.

At least 55 records · Page 3Linked to original sources
PubMed1991

Detection of proinsulin, C-peptide, insulin-A-chain, and glicentin in pancreatic islet cells of early human fetogenesis.

The presence of C-peptide, proinsulin, insulin-A-chain, and glicentin in human fetal pancreatic cells by using the PAP-technique was investigated and the results obtained compared with the occurrence of insulin or glucagon immunoreactive cells. In pancreatic sections obtained from 10 weeks old human fetuses we could identify cells reacting with antibodies directed against C-peptide, proinsulin, and insulin-A-chain. The majority of the cells were found in the duct epithelium and their number increased from the 10th to 14th week forming clusters near the ducts. The number and localization of the cells correspond exactly to the insulin positive cells. The presence of proinsulin and insulin-A-chains is a further proof of biological activity already in an early step of fetal development. The presence of glicentin-positive cells in the 10th week of gestational age as well as cells reacting with glucagon antibodies provide evidence for active glucagon biosynthesis. The number of these cells increased markedly in the 14th week of gestational age.

Antibodies↗
PubMed1991

Prospective investigations of long-term normoglycaemic BB/OK-rats: serial determination of glucose tolerance, insulitis, B-cell volume density and pancreatic insulin content.

Pancreatic tissue was obtained by repeated surgical biopsies from BB/OK rats (n = 62), which maintained normoglycaemia up to 250 days. The tissue was used to determine pancreatic insulin content, islet volume density, pancreatic B-cell volume density and the presence of mononuclear cell infiltrations within and around pancreatic islets (insulitis). The BB/OK rats were also characterized by determination of glucose tolerance. In 50 d old BB/OK rats lymphatic infiltration of pancreatic islets are rare. The mean value of relative B-cell volume density amounted to 0.71 +/- 0.05% and the pancreatic insulin content was 21.31 +/- 1.29 pmol/mg wet weight. 70 d old BB/OK rats are characterized by an identical relative B-cell volume density and pancreatic insulin content, although in 70% of the animals an invasion of immunocytes could be observed. At an age of 90 and 120 d the BB/OK rats were characterized by an increased number of islets having insulitis accompanied by a decrease of pancreatic insulin content and B-cell volume density. The individual evaluation of the investigated BB/OK rats revealed in each animal the presence of insulitis accompanied by a decreased B-cell volume density and a diminished pancreatic insulin content. Animals older than 120 d do reenhance the pancreatic insulin content and B-cell volume density attended by an impairment of glucose tolerance. The results suggest that all BB/OK rats are characterized by a spontaneous pancreatic B-cell destruction, which was arrested and/or interrupted in the animals maintaining normoglycaemia up to 250 d.

Aging↗
PubMed1991

The effect of human amniotic fluid in supporting long-term survival of pancreatic islets in tissue culture.

Pancreatic islets obtained from newborn Lewis rats were kept free-floating in TCM 199 either in the presence of 50% human amniotic fluid (HAF), 50% Hank's balanced salt solution (HBSS) or 10% fetal calf serum (FCS) for up to 14 days. The culture, in the presence of HAF, resulted in a good islet viability as demonstrated by islet number, islet insulin content and insulin release into the medium. Contradictory results were obtained when HBSS was used as the medium supplement. Moreover, the islets cultured in HAF-supplemented medium are characterized by a marked replicatory activity as reflected by the incorporation of labeled thymidine into islet DNA and gradual increase in DNA content with the progression of culture time. Even if compared to DNA synthesis of islets cultured under so called standard culture conditions as e.g. supplementation of 10% FCS to the medium, 50% HAF but not yet 10% HAF was found to stimulate the islet replication twofold already after 4 days of culture. It was also demonstrated that FCS has no additional effect on HAF-stimulated DNA synthesis. These findings support the view that HAF-enriched culture medium may have a use in supporting the long-term survival of well preserved endocrine pancreatic tissue.

Amniotic Fluid↗
PubMed1991

Morphology of the endocrine pancreas in cyclosporine-treated glucose-intolerant Wistar rats.

The toxic effect of Cyclosporin A (CS-A) (1.25-50.0 mg/kg body weight) on the endocrine pancreas of Wistar rats was morphologically investigated. The treatment of animals with CS-A doses above 5 mg/kg for 2 weeks resulted in a disturbed glucose tolerance, a reduced B-cell volume density and degranulation, vacuolization and decreased mitotic activity of the B-cells. After withdrawal of the drug the impaired parameters were stepwise normalized, starting with regranulation of pancreatic B-cells, followed by a stimulation of mitotic activity, and increase of B-cell volume density. When continuing the CS-A treatment with doses lower than 5.0 mg/kg for longer periods we observed a decreased body weight gain and reduced pancreatic insulin content.

Animals↗
PubMed1991

The monoclonal antibody RIB5/1--a useful completion of the MRC OX-3 and OX-6 haplotype specificity.

The haplotype binding pattern of a new mAb RIB5/1 against RT1 class II antigens on different tissues of inbred rat strains was investigated using the indirect POD-technique and a cytofluorometric analysis. RIB5/1 binds to a polymorphic determinant of the RT1 class II glycoprotein. Unlike MRC OX-3 (and OX-6), RIB5/1 reacts in optimal dilution with the RT1 haplotypes dvl, a, av, g, 1 but not with u. Therefore, the mAb pair MRC OX-3 (OX-6) and RIB5/1 is applicable for specific immunohistological purposes in chimaeric models with these RT1 haplotypes.

Animals↗
PubMed1990

[Hyperinsulinemia and B-cell proliferation in rats treated postnatally with L-glutamate].

Development of hyperinsulinemia was investigated which appeared late in the obese state in rats postnatally treated with L-glutamate. Insulin concentrations were estimated in the blood plasma of the caval and portal vein, and morphometric and immunohistochemical measurements of cells in the islets of Langerhans were performed, and also glucose tolerance tests. Not earlier than at 3 months hyperinsulinemia is shown in glutamate obese rats (GOR) in the peripheral blood plasma. Also in the portal blood plasma the insulin concentration is higher (167%) in GOR relative to controls. The insulin concentrations in the portal vein rise further in both animal groups whereas insulin concentration in the peripheral blood remains at the different levels in both animal groups. Impaired glucose tolerance was observed for GOR only. Islets of Langerhans in the Pancreas show enlargement and increased proliferation of B-cells in GOR. In contrast the number of D-cells is diminished. The hyperplasia of islets differs remarkably to hypoplasia of other organs in GOR. We conclude that the peripheral hyperinsulinemia is caused by a permanent hypersecretion of insulin.

Animals↗
PubMed1990

Morphological findings in the liver of diabetic rats after intraportal transplantation of neonatal isologous pancreatic islets.

Morphological (light microscopical, immunohistological and electron microscopical) findings in the recipient liver of rats with streptozotocin-induced diabetes, obtained 9 months after intraportal injection of neonatal isologous pancreatic islets, are described and their significance discussed. The results support the assumption of active ingrowth of nonmyelinated nerve fibers into the islet isografts. The hepatocytes surrounding the islet isografts contain--obviously owing to the influence of unusually high and locally variable concentrations of insulin--a focally increased number of enlarged mitochondria, abundant glycogen and a smaller amount of neutral fat droplets. Furthermore, hepatocytes and cells looking like hepatocytes (hepatocyte-like cells) with typically structured cytoplasmic beta (insulin) granules were found bordering the islet isografts. These results could be interpreted as an expression of artificial or nonartificial fusion of beta cells with hepatocytes, i.e. formation of hybrid cells ("in vivo hybridization"). Alternatively, they might reflect insulin uptake and storage in the hepatocytes. In addition, these findings suggest that contact between neonatal islet tissue and liver tissue could be a trigger for the in vivo transformation (modulation) of differentiated cells of similar embryonic development in the adult organism.

Animals↗
PubMed1990

Different lymphocyte subset distribution within "insulitis" islets of normoglycaemic and prediabetic BB/OK rats of similar age.

The fact that insulitis occurs also in normoglycaemic BB rats led us to investigate the phenotypes of lymphocytes invading the pancreatic islets of prediabetic BB/OK rats in comparison to age- and sex-matched normoglycaemic animals in a retrospective analysis. By using a panel of monoclonal antibodies we investigated the number of pan T-cells, T-helper cells, cytotoxic T-cells and NK-cells and determined the number of activated cells by measurement of class I, class II and IL-2 receptor positive cells. The bound primary antibodies were visualized using the APAAP-technique. The prediabetic rats showed a significantly decreased pancreatic insulin content which was drastically reduced at diagnosis of diabetes. This was accompanied by reduction of the B-cell volume density. The prediabetic as well as the long-term normoglycaemic BB rats showed an accumulation of mononuclear cells (all phenotypes investigated) within the pancreatic islets. Concerning the phenotypes of infiltrating cells there was no qualitative difference between long-term normoglycaemic and prediabetic rats but quantitatively an enhanced amount of W3/25+, OX-8+, OX-6+ and ART-18+ cells could be observed in the prediabetic animals. From our results we conclude that an immunological B-cell destructive process occurs also in long-term normoglycaemic BB rats by participation of mononuclear cells qualitatively not different from those observed in prediabetic animals. Activated T-cells (OX-19+, OX-8+, W3/25+) expressing class II antigens (OX-6+) and the IL-2 receptor (ART-18+) seem to play a significant role in the amplified immunological pancreatic B-cell destruction.

Animals↗
PubMed1990

Phenotyping of lymphocytes following transplantation of allogeneic rat pancreatic islets into streptozotocin-diabetic recipients.

We investigated the phenotypes of peripheral and cervical lymphocytes in allografted pancreatic islet recipients during graft rejection. Grafting 2000 pancreatic islets, obtained from LEW.1A rats, into streptozotocin-diabetic non-immunosuppressed LEW.1W rats acute rejection occurred within 7.0 +/- 0.6 days. Neither the T-cells (W3/13+), nor the T helper (W3/25+) or T-suppressor (OX-8+) lymphocytes were markedly altered during rejection crisis in peripheral or cervical lymphocytes. When using monoclonal antibodies detecting activation markers (OX-17 for class II antigens; ART-18 for interleukin-2 receptor) a significant increase of OX-17+ cells and OX-17+ T-lymphocytes could be observed in lymph node lymphocytes from 24 h after transplantation until 7 days, whereas the peripheral lymphocytes behaved inconspicuously. The results underline the uselessness of peripheral lymphocytes to monitor allogeneic destruction of minimal amounts of grafted tissue by using presently known differentiation and activation markers of lymphocytes.

Animals↗
PubMed1990

Human amniotic fluid stimulates DNA synthesis of rat pancreatic islets.

Collagenase isolated pancreatic islets from newborn Lewis rats were used to study the effect of human amniotic fluid (HAF) on DNA synthesis measured as incorporation of 3H-thymidine into islet DNA and as estimation of labeling index. We investigated individual samples of HAF obtained from pregnant women between the 28th and 39th week of gestation. Since there were no significant differences of HAF obtained from different gestational weeks on islet DNA synthesis, the following experiments were carried out with pooled HAF. When islets were cultured for 2 days in TCM 199 containing 10 mmol/l glucose the addition of 50% HAF resulted in a significantly increased DNA synthesis in comparison to islets cultured in TCM 199 supplemented to 50% with Hank's balanced salt solution (HANK). When extending the culture period from 2 to 4 days the stimulatory effect of 50% HAF was well preserved. Islets cultured in HANK are characterized by a declined DNA-content, which was prevented in the presence of HAF. There was a good correlation between incorporation of 3H-thymidine and the percentage of labeled nuclei, estimated on hematoxylin/eosin-stained autoradiograms of islets cultured for 4 days either in TCM 199 alone, in the presence of 50% HANK or 50% HAF, indicating that the measured incorporation of labeled thymidine into islet DNA was representative for islet replication.

Amniotic Fluid↗