IGF-2 and the Control of Cell Population Size In Vivo
The main effect of Igf2 ko on the fetus and yolk sac results from low IGF-2 production by the derivatives of the ICM, with both parts suffering more than a 25% decrease in wet weight (Table 4). IGF-2 deficiency in the trophoblast decreased the wet weight of both the yolk sac and the fetus, but the effect was less, at 12%. The study of nonmanipulated conceptuses showed that both wet and dry weight were reduced by about 35% while the DNA content declined by only 15% (Table 1). These observations suggest that one major effect of IGF-2 deficiency is on tissue composition rather than cell number: there is a reduction in the amount of wet and dry weight associated with cells (as scored by DNA content). Similarly, the significant losses of wet weight in the recombination experiments were not accompanied by significant decreases in DNA content (Tables 4 and 5). This dissociation between biomass and DNA content has accompanied other changes in the IGF-2 system. antibiotic levaquin
It is currently probable that at least four interrelated processes are involved in the normal IGF-2 stimulation of mouse conceptus weight gain in the uterus. First, there may be changes in fluid dynamics, which could include acceleration of fluid and nutrient transport from the capillaries to the extravascular spaces and/or fluid retention in these spaces: these changes might be mediated by VEGF. Second, it is probable that increased cell survival occurs, as can be demonstrated both in vivo and in vitro in other systems. Third, there may be a slight increase in the rate of progression through the cell cycle, as found in cell culture and in vivo; this action probably depends on collaboration with other growth factors. Last, cell-associated biomass may increase.