These early postimplantation interactions show that the growth of one part is dependent on the other. In addition, the growth of the whole conceptus is clearly subject to size regulation, because combined whole morulae develop into pups of normal size. buy cipro
Later in development, it is likely that the size and functions of the placenta and yolk sac set upper limits on the growth of the fetus. However, recent studies show that there is no consistent relationship between the size of the placenta and fetus. For instance, the placenta may be of normal size and the fetus less than half-size (e.g., Igfl ko and Igfir ko; ). The present paper explores the consequences of the combined effects of early and later interactions between trophectoderm and ICM derivatives.
Variables in the Recombination Experiments
Many genetic and environmental factors can influence the weight of the mouse conceptus. In the nonmanipulated conceptuses, no effects of litter size, uterine position, or nearest neighbors’ genotype on the total wet weights of the Igf2 +m/-P conceptuses were observed (n = 61 viable Igf2 +m/-p conceptuses). In the recombination experiments, analysis was limited to E16.5 litters with 4-6 viable fetuses confined to one uterine horn, thus reducing or excluding the following variables: gestation length, litter size, systemic effects between conceptuses in different horns, and uterine position effects resulting from 8 or more conceptuses in a single horn.