Although available data from the mouse model suggest that morphogenesis during preimplantation development is dependent on the expression of embryonic genes, convincing data for human preimplantation embryos are missing. To investigate the expression of genes involved in human preimplantation development we constructed cDNA libraries from human individual blastocysts and screened them for the expression of beta-actin, CD59, homeoboxes OCT-3 and HOXA4, and HLA-G and hMLH-1 genes. Beta-actin, CD59, and OCT-3 were detected by reverse transcription-polymerase chain reaction (RT-PCR), while HOXA4, HLA-G and hMLH-1 were undetected. Sequencing of 48 random clones from two libraries revealed a different identity to the known genes including 99% identity to human histone 3.1 and human ribosome protein S25 complete cDNA. These data demonstrate the feasibility of constructing cDNA libraries from individual human preimplantation embryos and their potential usefulness in the assessment of the relevance of specific gene expression in the failures of preimplantation development.

The transcripts of homeobox genes, HoxA4, HoxA7, HoxB4, and HoxB5, were present in oocytes and cleaving embryos. The pattern of expression of homeobox genes in cultured fibroblasts derived from spontaneously aborted embryos with aneuploidies was different from that in control diploid cells.

The presence of these genes in human preimplantation development suggests expression specific to the blastocyst stage.

The data demonstrate the usefulness of constructing cDNA libraries from individual human blastocysts and their values in the analysis of genetic expression in human preimplantation development.

Plasmid pLD105 isolated from a clinical strain of E. coli determines nitrofuran resistance due to inactivation of low-molecular-weight nitrofuran reductase subunit. pLD105 plasmid belongs to IncF. It is a conjugative plasmid and mobilizes chromosome markers, but is not transmitted to strains containing other plasmids. However, the presence of pLD105 plasmid in the recipient strain does not prevent incorporation of other plasmids, including nonconjugative ones. Transfer of nonconjugative plasmids from the donor to a recipient strain carrying pLD105 was denoted as "reverse donation".