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Biomedical subjects

H Borg

Publications and source records attributed to H Borg.

29 records · Page 2Linked to original sources
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↗