Summary. The

The ultrastructure of the endometrial epithelium of the pig was studied during the estrous cycle and early pregnancy up to implantation. Special attention was given to the luminal epithelium and morphological indications of protein synthesis. Although the general morphology of the luminal and glandular epithelia is similar (both tissues consist of secretory cells and ciliated cells at all the stages studied), it appears that the two epithelia should be considered as two functionally different units in the pre-implantation period. Morphological evidence suggests the presence of at least three different secretory products within luminal epithelial cells; they are released at different times, i.e. at estrus, between day 8 and 10 and after day 11. The glandular epithelium shows release of secretory products from day 10-11. Increasing amounts of glycogen were found within epithelial cells, especially in pregnant gilts from day 12. The possible significance of secretory activity of the epithelium is discussed in relation to the development of the embryos.

No abstract

The differentiation of the jaw adductor muscle of the rosy barb, Barbus conchonius, has been studied during development to determine the relation between fiber type and early muscle activity. First, a morphological description and a functional analysis with electromyography has been made of the jaw adductor of the adult fish. Based on this analysis and on histochemical characteristics, the jaw adductor muscle can be divided into two parts: an aerobic part, which shows contractile activity during respiration, and an anaerobic part, which is silent during respiration. Secondly, the jaw adductor muscle of embryonic and larval specimens of the barb was investigated (immuno)histochemically. From the fourth day after fertilization onwards, deeply located future-red fibers and more superficial future-white fibers can be distinguished histochemically. From the juvenile stage onwards (30 days after fertilization), the histochemical pattern of the jaw adductor is identical to that of the adult. Results are discussed in relation to the start of respiratory and feeding behaviour during development.