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Biomedical subjects

H Borg

Publications and source records attributed to H Borg.

13 recordsLinked to original sources
PubMed1987

Tissue culture of human fetal pancreas. Effects of human serum on development and endocrine function of isletlike cell clusters.

The human fetal pancreas represents a source of insulin-producing beta-cells with a potential for transplantation to diabetic patients. It has previously been shown that such cells can be viably maintained in tissue culture media containing fetal calf serum (FCS) and that these explants continue to synthesize and release insulin. In this study the effects of human serum (HS) on the growth and function of human fetal pancreatic explants have been compared with those of FCS. For this purpose, pancreatic glands, obtained after prostaglandin-induced abortions, were briefly exposed to collagenase, and the digest was cultured in RPMI-1640 medium plus 10% pooled HS or FCS. The outgrowth of isletlike cell clusters (ICCs) was monitored. In 31 of 58 consecutively explanted glands, development of ICCs was observed. In the presence of FCS the outgrowth of ICC took place on top of a fibroblast monocellular cell layer; HS effected less growth of fibroblasts and increased the formation of ICCs about sevenfold compared with explants from the same glands maintained in FCS. However, in the explant cultures with HS, the cell number per ICC, expressed as DNA content, was reduced by 50%. In both FCS and HS the insulin content of the medium showed great variability and progressively declined from day 2 to day 5. The medium glucagon concentration also decreased but not to the same extent as that of insulin. Immunocytochemical-stained ICCs showed insulin- and glucagon-positive cells scattered among most nonstained, presumably nonendocrine cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood↗
PubMed1985

Evidence for IFN-beta heterogeneity in a substrain of Namalwa cells.

A substrain of Namalwa cells, denoted substrain B, was grown in fermentors up to the 100-L scale, and was induced with Sendai virus to produce interferon (IFN). The titer of the crude IFN varied extensively between different batches; part of the variation was caused by a differential expression of IFN-alpha and IFN-beta. More than 80% of the IFN activity was IFN-beta by several criteria. A two-step purification procedure was developed and the resulting preparation had a specific activity of approximately 10(6) U/mg protein. The IFN-beta type was found to be heterogeneous, and could be separated into several components, which probably represented post-translational modifications of one molecule.

Adsorption↗
PubMed1985

Tissue culture of human fetal pancreas. Development and function of B-cells in vitro and transplantation of explants to nude mice.

The present study evaluates the development and function of human fetal B-cells in vitro with a view to using such cells in future attempts for transplantation of human fetal pancreas to diabetic patients. A method previously described in our laboratory for preparing islets in vitro from the fetal rat pancreas has been applied and modified for use with human fetal pancreas. Pancreatic glands of different gestational ages were obtained from 37 consecutive prostaglandin-induced abortions. After a mild collagenase treatment, the partially disintegrated tissue was maintained in culture for 7 days in tissue culture medium RPMI 1640 plus 20% fetal calf serum to permit cell attachment and out-growth of endocrine cells. In 17 of the 37 consecutively cultured fetal pancreatic glands, islet-like cell clusters were formed. The 20 remaining glands were lost because of either bacterial contamination or lack of viability already before dissection had occurred. Sections of the newly formed cell clusters revealed well-preserved pancreatic cells showing frequent mitotic figures. The tissue exhibited a high rate of (pro)insulin biosynthesis and a modest insulin response to secretory stimuli, suggesting that the mechanism of glucose regulation by the fetal B-cells is not yet fully developed. Electron micrographs showed a large number of granule-containing cells, some of which were identified as B-cells. In nine cases, harvested cell clusters were implanted beneath the kidney capsule of nude mice. When these animals were killed after 2 mo, seven mice showed a considerable growth of the grafts with numerous islet-like structures containing insulin- and glucagon-positive cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Calcium and pancreatic beta-cell function. 6. Glucose and intracellular 45Ca distribution.

Glucose stimulates the uptake of 45Ca into beta-cell-rich pancreatic islets isolated from ob/ob-mice. The distribution of the incorporated radioactivity was analysed by labelling the organelles with 45Ca in their cellular environment. The radioactive content of the organelles was measured after homogenization and fractionation of the islets under conditions preventing 45Ca redistribution. The 45Ca taken up in response to glucose appeared essentially in the secretory granule fraction and in that enriched in mitochondria. Modification of the 45Ca loading procedure, involving reduction of the oxygen tension and incubation volume, resulted in the disappearance of the glucose effect on the mitochondrial fraction whereas part of the stimulatory effect on the secretory granules persisted. Buffering of calcium by the secretory granules and mitochondria may be important for regulating the cytoplasmic Ca2+ involved in stimulus-secretion coupling.

Animals↗
PubMed1977

Purification of human immunoglobulin M by affinity chromatography on protamine-Sepharose.

Human IgM has been isolated from plasma by a simple procedure in high yield. The first step was adsorption to protamine-Sepharose and elution by increasing the ionic strength with NaCl. This was followed by two gel filtration steps resulting in a 98% pure IgM in about 30% yield. A somewhat modified procedure could also be used for purification of IgM from Cohn fraction II + III. The purified IgM was found to have a sedimentation constant in agreement with reported values. In immunoelectrophoresis and isoelectric focusing, purified IgM showed the same behaviour as IgM in plasma. Different fragments of IgM were tested for binding to the protamine-Sepharose adsorbent. IgM and Fab were not bound unlike (FC)5, indicating that the sites responsible for binding are located in the Fc part and that several Fc parts are necessary for sufficiently strong binding for adsorption.

Chromatography, Affinity↗
PubMed1976

Survival of isolated human islets of Langerhans maintained in tissue culture.

Transplantation of human pancreatic islets to diabetic patients may require that donor islets be kept viable in vitro for extended time periods before transfer to the recipient. We have maintained isolated pancreatic islets obtained from the human cadaveric pancreas in tissue culture for 1-3 wk, after which we studied the structure and function of the islets. Electron micrographs of the cultured islets showed a satisfactory preservation of both beta-cells and alpha 2-cells. After culture for 1 wk, the islet oxygen uptake proceeded at a constant rate at a low glucose concentration (3.3 mM) and was significantly enhanced by raising the glucose concentration to 16.7 mM. Likewise, after culture for 1 wk, the islets responded with an increased insulin release when exposed to 16.7 mM glucose with or without added theophylline (10 mM). Islets cultured for 1-3 wk were able to incorporate [3H]leucine into proinsulin, as judged by gel filtration of acid-alcohol extracts. Glucagon release from the cultured islets was reduced significantly by 16.7 mM glucose alone, but stimulated by glucose (16.7 mM) plus theophylline (10 MM). It is concluded that viable pancreatic islets can be isolated from the pancreas of adult human donors and maintained in tissue culture for at least 1 wk without loss of the specific functions of the alpha 2- and beta-cells. It remains to be established whether such islets will survive and remain functionally competent after transplantation to human recipients.

Culture Techniques↗