The insulin-secreting and proliferative activity of established islet cells in the presence of sulfonylurea]

Exponentially growing rat islet cells (RINr) and hamster islet cells (HIT T-15) were incubated in presence of tolbutamide (10-1000 microM), gliclazide (0.1-10 microM) or glibenclamide (0.01-10 microM) for 15 hrs. Accumulation of insulin in culture medium was estimated by RIA. Effects of sulfonylureas (SU) on cell proliferation were assessed by 3H-thymidine (3H-T) incorporation into cellular DNA. All of SUs used stimulated insulin production in RIN and HIT cell cultures (with an exception of tolbutamide, which markedly suppressed insulin secretion in HIT cells at 1000 microM). 3H-T incorporation into RIN cells was elevated only in presence of gliclazide (10 microM), whereas tolbutamide at 1000 M significantly inhibited RIN cell proliferation. Gliclazide (0.1 microM) and glibenclamide (0.01-10 microM) enhanced 3H-T incorporation into HIT cells. Further detailed investigations of mechanisms of SU effects on islet cell reproduction will be of use for designing optimal strategy of hypoglycemizing therapy of diabetes mellitus.     

The population structure of rural settlements of Sakha Republic (Yakutia): Migration

Migration and gametic structure have been analyzed in rural population of Sakha Republic (Yakutia). The populations studied differ from one another in the migration rate and direction, which are determined by the socioeconomic development of the regions and ethnic composition of settlements. A high rate of long-distance migrations and a low rate of migrations within uluses (districts) are characteristic of regions with well-developed industry and transportation and are more characteristic of immigrant than indigenous populations. In rural regions, migrations within uluses are more prevalent. The gametic structure of the youngest age group does not always correspond to the migration activity of previous generations. The migration effectiveness values (the correspondence of migration flows to the gametic structure depending on the geographic origin of the gametes) are different for men and women.     

Regulatory light chain influences alterations of myosin head induced by actin.

The effect of magnesium-for-calcium exchange and phosphorylation of regulatory light chain (LC2) on structural organization of rabbit skeletal myosin head was studied by limited tryptic digestion. In the presence of actin, exchange of magnesium bound to LC2 by calcium in dephosphorylated myosin accelerates the digestion of myosin and heavy meromyosin heavy chain and increases the accumulation of a 50 kDa fragment. This effect is significantly diminished in the case of phosphorylated myosin. Thus, both phosphorylation and cation exchange influences the effect of actin binding on the structural organization of myosin head.