Human oocytes express murine retroviral equivalents

Unfertilized human oocytes expressed a gp70-related epitope as observed when staining section immunocytochemically with a panel of monoclonal antibodies against gp70 of murine leukemia virus. Some oocytes also expressed virus-like particles at the cell membrane. Follicular fluids, corresponding to these oocytes, contained p30- and gp70-related antigens, reverse transcriptase, and an increased titer of interferon. The three- to four-cell human cleavage stages did not contain the gp70-related epitope. It is concluded that human oocytes, but not early cleavage stages, express products that suggest the presence of an active endogenous retrovirus genome.

Preparation of human chromosomes for high resolution scanning electron microscopy

The addition of ethidium bromide during the last 2.5-3 h of lymphocyte culturing restricted chromosome contraction and preserved the banding structure in scanning electron microscopy. Treatment of the chromosomes with trypsin and use of impregnation with osmium tetroxide and thiocarbohydrazide resulted in a structural preservation of high resolution quality.

A retroviral gp70-related protein is expressed at specific stages during mouse oocyte maturation and in preimplantation embryos

Mouse monoclonal antibodies directed against different epitopes of the murine leukemia virus envelope protein gp70 were used to study the expression of retroviral related env proteins during mouse oocyte maturation, fertilization and blastocyst formation. A gp70-related antigen was detected with immunohistochemistry in growing oocytes but not in primordial and primary non-growing oocytes. Atretic oocytes were also negative. Both parthenogenetically activated and fertilized oocytes were positive. Two-cell stages showed a patchy distribution of the antigen. Later preimplantation stages were negative except for a markedly positive period during compaction of the morula and adhesion of the blastocyst.