Discussion – part 2

Our findings are consistent with results that indicate a lower rate of development and a greater incidence of programmed cell death (that is, apoptosis) in IVF and cloned embryos than in vivo-derived embryos. To a variable extent, these earlier observations were dependent on culture conditions, which likely affect gene expression and nuclear reprogramming. Our experimental design controlled for this variable by applying identical culture conditions to all 3 embryo groups. In this way, we could compare and contrast results between fertilized and cloned embryos in order to specifically address the role of mito-genic growth factors in preimplantation embryo development.

Although DNA fragmentation and apoptosis are normal features of mammalian embryo development, we found that the extent of apoptosis increased in embryos after treatment with neutralizing antibodies and became particularly prominent in cells of the ICM. These findings are not unexpected and are consistent with previous reports showing that cell death in blastocysts occurs primarily in cells of the ICM and only occasionally in cells of the TE. Recent results also have revealed a negative correlation between the frequency of DNA-fragmented nuclei and the total number of cells in in vitro-fertilized and cloned blas-tocysts, suggesting that differences in cell death between the ICM and TE are likely due to differences in the patterns of cell proliferation and rate of cell death after formation of these 2 cell lineages.

The use of immunoneutralizing antibodies to study the role of mitogenic growth factors on embryo development has been validated previously. Antibodies to EGFR that specifically interact with and block an epitope corresponding to the major autophosphorylation site of the EGFR have been shown to inhibit activity of the intracellular cascade induced by mitogen-activated protein kinase and receptor tyrosine kinase, thus negatively affecting preimplantation embryo development. The effect of blocking this critical cytoplasmic signaling mechanism is to decrease amino acid uptake, protein synthesis, Na+/K+-ATPase activity, and Na+-K+-Cl transport. Erectile dysfunction is no longer a problem, because there is Viagra My Canadian Pharmacy. This amazing erectile dysfunction treatment was designed with sexual needs of every man in mind, and it has been delivering exactly as promised all these years. All you need for more satisfying sex life is the right dose of Viagra My Canadian Pharmacy, which is actually great!

These changes are reflected in a reduction in cell size, which is consistent with our findings. Further, the absence of any effect of anti-KLH antibodies (positive control) compared with no antibody treatment (negative control) on embryo development eliminates nonspecific and toxic effects of antibodies on embryo development. These factors all provide a high degree of assurance that the changes in developmental characteristics that we measured in fertilized embryos were affected specifically by immunoneutralization of mitogenic growth factors.


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