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Abstract: Stereological quantitative methods have revealed the presence of three distinct follicular cell populations (C1–C3) in bovine cumulus–oocyte complexes. Type C3 cells became largely predominant from metestrous to proestrous, with a simultaneously large decrease in the other two cell types. To further characterize these cumulus cell types, cumulus–oocyte complexes from small (1–4mm) and medium (4–8mm) antral follicles (category 1: with a compact multilayered cumulus and a homogeneous ooplasm) were aspirated from ovaries of Holstein–Friesian cows and processed for electron microscopy, ultrastructural cytochemical detection of glycogen and glycoproteins, and immunogold localization of chondroitin sulfate. Each follicular cell type displayed the same ultrastructural characteristics independently of the size of the follicle and the stage of the estrous cycle. Type C1 cells showed morphological characteristics of undifferentiated cells and progressively transformed into type C2 cells. Type C2 cells were characterized by cell extensions, polarized nuclei with evident nucleolar fibrilar centers, steroidogenic characteristics (numerous large lipid droplets, large endoplasmic reticulum vesicles and vacuoles), and synthesis of glycoproteins and chondroitin sulfate by the Golgi apparatus and endoplasmic reticulum. Type C3 cells presented morphologic features of fully differentiated and luteinized cumulus cells. They were characterized by an increase in cytoskeleton filaments, loss of cell extensions and of intercellular junctions, depletion of lipid and glycogen stores, and initiation of glycoprotein and chondroitin sulfate exocytosis. In conclusion, the present study suggests that bovine cumulus cells from small and medium antral follicles follow a complete dynamic functional differentiation process, in which the three cell types seem to correspond to a functional continuum. We identified undifferentiated cells, cells strongly engaged in glycoprotein and proteoglycan synthesis, and cells fully differentiated and secreting. [Copyright &y& Elsevier]

In this chapter, we provide an overview of the basic principles of teratology, beginning with its definition, the critical point for teratogenesis to occur and the most evident etiological agents to improve the understanding of this science.Teratology is a recent science that began in the early twentieth century, and has greatly improved over the recent years with the advancements in molecular biology, toxicology, animal laboratory science, and genetics, as well as the improvement on the knowledge of the environmental influences.Nevertheless, more work is required to reduce the influence of hazardous products that could be deleterious during pregnancy, thus reducing teratogenic defects in the newborn. While some teratogenic defects are attributed to their agents with certainty, the same for a lot of other such defects is lacking, necessitating consistent studies to decipher the influence of various teratogenic agents on their corresponding teratogenic defects. It is here that the laboratory animal science is of great importance both in the present and in the future.