Morphogenetic effects of glucose on mouse islet-cell re-aggregation in culture

The re-aggregation of dispersed islet cells from non-inbred ob/ob-mice was studied by light and electron microscopy. After 3 days of culture, spontaneously formed aggregates with more than 95% beta-cells were up to 0.5 mm in diameter and exhibited a high degree of viability on dye exclusion tests. In comparison with cultures at 1 or 3 mM D-glucose, or 1 mM D-glucose in combination with 19 mM 3-0-methyl-D-glucose, aggregates formed in 20 mM D-glucose were more closely packed, had a smoother circumference with elongated peripheral beta-cells, and exhibited well developed micro-villi in localized intercellular widenings. A stereological analysis of electron micrographs showed that beta-cells aggregated at 20 mM D-glucose exhibited the same individual profile area but a significantly lower form factor, and a significant reduction in granule volume density as compared with aggregates at 3 mM D-glucose. It is concluded that D-glucose has morphogenetic effects on both the cellular and the micro-anatomical level of pseudo-islet structure in culture.     

Diethyldithiocarbamate, but not disulfiram, inhibits alloxan-induced dye accumulation of isolated mouse islet beta-cells

The diabetogenic action of alloxan on pancreatic beta-cells is thought to be mediated by hydroxyl radicals. The initial attack of the radicals is probably at the plasma membrane level. Diethyldithiocarbamate (DDTC) and its dimer disulfiram (Antabuse) have recently been shown to protect against damage by free radical generating agents. The ability of DDTC and disulfiram to inhibit alloxan-induced dye accumulation of isolated ob/ob mice islet beta-cells was therefore studied. Evans blue was used as an indicator of plasma membrane permeability. DDTC (100 microM 1 mM) but not disulfiram (100 microM 1 mM) inhibited alloxan-induced dye uptake of beta-cells. The effect of DDTC on oxygen consumption in a mixture of reduced glutathione (GSH), alloxan and FeSO4 was studied with a Clark-type oxygen electrode. DDTC (20, 100 microM) had no effect on the oxygen consumption of this mixture. It is suggested that the DDTC inhibition of alloxan-induced dye uptake of isolated beta-cells takes place at a step beyond the generation of free radicals.