Tolbutamide stimulates proliferation of pancreatic beta cells in culture.

To investigate the beta-cell cytotrophic action of tolbutamide, pancreatic cells were dissociated from neonatal rat pancreata and then cultured for 10 days in the presence of various concentrations of tolbutamide. After counting insulin-positive beta cells, dose-response curves were plotted and analyzed. Increasing concentrations of tolbutamide cause an increase in beta-cell numbers until a maximum response is reached at a concentration of about 100 micrograms/ml.

Allotransplantation of culture-isolated neonatal rat islet tissue. Absence of MHC class II positive antigen-presenting cells in nonimmunogenic islets.

When highly purified neonatal rat islet tissue, derived after 10 days in vitro, was allografted, it was found to be nonimmunogenic or weakly immunogenic. In contrast, nonislet pancreatic components, derived from the same culture system, transplanted with highly purified islet tissue resulted in rejection in 88% of cases. Extension of the culture period did not result in reduced immunogenicity of the nonislet material.

Proliferation of immunocytochemically identified islet beta cells in culture: effect of growth factors, hormones, and nutrients.

Immunocytochemically identified, differentiated, single beta-cells proliferate to form colonies, which then grow into hillocks and islets. Beta-Cell proliferation is most easily quantified during the first week, when colonies are forming. The experimental objective was stimulation of beta-cell proliferation by culture medium supplementation with growth factors, hormones, or nutrients.

Clonal growth of immunocytochemically identified islet beta and alpha cells in culture.

The proliferative capacity of individual immunocytochemically identified islet beta cells was investigated in tissue culture. The pancreatic digest was filtered through a 20-micron filter to eliminate partially digested tissue fragments and islets; it was then cultured at low density to allow assessment of single cells. The type of cell was identified immunocytochemically by reaction with antibody to insulin or glucagon, and DNA synthesis was estimated from autoradiographs after incorporation of tritiated thymidine.

Cross-reactivity of organs in allograft rejection. Comparison of effect of thyroid allografts on established islet allografts.

The effect of allotransplantation of thyroid or islet allografts into rats with established islet allografts was studied to determine the cross-reactivity of the thyroid and islets in allograft rejection. Islets obtained from cultured neonatal rat (F344) pancreas explants were transplanted bilaterally underneath the kidney capsule of Wistar-Furth rats. After 21 days these allografts did not exhibit signs of rejection.