PARENT SESSION

(T350) THE DISTRIBUTION OF POLYMERIZED ACTIN AND NUCLEI WHEN HAMSTER BLASTOCYSTS EXPRESS TROPHECTODERM PROJECTIONS IN UTERO.

Harris, Keith¹, Calderon, Jesus¹, Gonzales, David¹, ¹ Arizona State University West, Glendale, Arizona

ABSTRACT- This study was designed to compare the distribution of polymerized F-actin in the preimplantation hamster embryo. Three structures of the preimplantation embryo were compared with a confocal microscope; the inner-cell-mass (ICM), trophectoderm, and trophectoderm projections (TEP). TEPs emanate from the trophectoderm as filopodia-like appendages that undergo extension, retraction, and angular movement (Blandau, 1949; Blandau and Rumery, 1957; Gonzales et al., 1996a; and Gonzales et al., 1996b). This phenomenon has been demonstrated in the guinea pig (Graf von Spee, 1883; Blandau 1949), mouse (Cole, 1967), hamster (Gonzales, 1996a), equine, bovine and human embryos (Gonzales, 1996b). Taken together these authors collectively suggest that TEPs may be involved in zona escape, endogenous movement in polycoital animals, initial contact with maternal epithelia, and implantation. The distribution of FITC-labeled phalloidin in the trophectoderm, TEPs, and ICM were compared independently by ANOVA. The fluorescence intensity was greatest in the TEPs, second in trophectoderm and least in the ICM of in vivo developed preimplantation embryos flushed from the uterus with an isotonic fixative. There was a significant difference between the fluorescence within each structure (p value < 0.0001). In addition, we have demonstrated by nuclear stain that there was at least one nucleus associated with a single TEP. This data is consistent with the hypothesis that TEP movement is generated by polymerized actin.

KEY WORDS: trophectoderm, actin, filopodia