Planar polarity of the extraembryonic epithelia in the preimplantation porcine conceptus.

The present review deals with the trophoblast structure during the free intrauterine life of the pig blastocyst. The term trophoblast is used here to describe the association of the first extraembryonic cell layers, the trophectoderm and the primitive endoderm that are polarized epithelia, a fact established by ultrastructural and immunocytochemical data. The aim of this synthesis is to gather the relative works dispersed in the litterature and to explain the implication of the planar polarity of these cell layers on their developmental fate and roles.

The acrosome of eutherian mammals.

The acrosome is not just a bag of enzymes, most of which, if not all, are singly non-essential for sperm-oocyte interaction. The Golgi-derived acrosomal cap reveals some extraordinary development and structure particularities. The acrosome of eutherian spermatozoa basically consists of two parts, the anterior and equatorial segments; the present review is devoted to the former, the initial actor in fertilization.

Cellular features of the extra-embryonic endoderm during elongation in the ovine conceptus.

The extraembryonic endoderm of the elongating ovine conceptus was analyzed by scanning and transmission electron microscopy and by whole mount actin staining and immunofluorescence. Morphological and functional differences between the visceral endoderm (VE), the founding cell layer, and the parietal endoderm (PE) are presented. During the elongation process, the PE differentiated to fusiform multinucleated cells aligned parallel to the elongation axis of the conceptus, whereas the VE cells retained the aspect of typical epithelial cells.

Analysis of the nucleolar compartment of the nucleus as an indicator of nuclear reprogramming after nuclear transfer.

When analyzing reprogramming after nuclear transfer, it is interesting to focus on the nucleolar compartment, which is the most morphologically well-defined compartment in the nucleus. As with many messenger RNA-encoding genes, the ribosomal RNA genes are expressed in the nuclei of cells used for nuclear transfer. We suppose that a successful passage from the expression of genes specific to somatic cells to those characteristic of an early embryo implies the transient arrest of any expression under the effect of the oocyte cytoplasm.