Stages Of Human Embryonic Development Research Articles

Blastocyst formation rate after ICSI with extreme oligozoospermic samples

Objective: Male factor infertility is believed to have an impact not only on fertilisation rate but also on the early stages of human embryonic development. Several studies support a paternal influence on blastocyst formation when comparing ICSI and IVF cycles: the blastocyst formation rate being consistently lower in ICSI cycles than in IVF cycles. In the present study the blastocyst formation rate using extreme oligozoospermic samples for ICSI was evaluated.

Localization of Retinoic Acid Receptors in Anterior Human Embryo

Retinoic acid receptors (RARs) are nuclear transcription factors that are activated by all-trans-retinoic acid or 9-cis-retinoic acid and are found in all tissues but predominantly in developing fetus, dividing tumor cells, and adult skin. Three forms of these receptors, α, β, and γ, have been described. In this paper we report the presence of RARα and β determined by hybridization with anti-sense messenger RNA, and histochemical localization of the three forms of RARs using monospecific polyclonal antibodies in various tissues of early human embryos. In a 54-day-old embryo, RARα was expressed primarily in the liver and the brain, with somewhat lesser expression in the intestine. RARβ was the highest in the brain, followed by a restricted expression in the intestine and the liver. Other organs, i.e., adrenal, kidney, and testis, did not show measurable amounts of RARβ. The immunohistochemical localization in anterior sections of a 43-day-old embryo indicated that RARα was present in the neuroepithelial cells and in cells lining the primitive pharyngeal sac, dorsal aorta, and pericardium. RARβ was somewhat less prevalent in same tissues, whereas the expression of RARγ was the lowest of the tree RARs in any tissues examined. Results indicated that RARα and β appear at early stages of human embryonic development and their expression is restricted to certain types of tissues.

Ontogeny of human natural killer (NK) cells: fetal NK cells mediate cytolytic function and express cytoplasmic CD3 epsilon,delta proteins.

Natural killer (NK) cells have been defined as CD3 epsilon-, CD16+ and/or CD56+ lymphocytes that mediate major histocompatibility complex (MHC)-unrestricted cytotoxicity against certain tumors and virus-infected cells. Unlike T lymphocytes, NK cells do not rearrange or productively express T cell antigen receptor genes. Moreover, NK cells from adults have been reported to not express CD3 gamma, delta, or epsilon proteins on the cell surface or in the cytoplasm. Nonetheless, NK cells have been shown to share a number of antigenic and functional similarities to T cells that suggest the possibility of common origins. In this report, we demonstrate that functional NK cells exist in liver at early stages of human embryonic development. Freshly isolated fetal NK cells mediated MHC-unrestricted cytotoxicity against NK-sensitive targets and acquired the ability to lyse NK-resistant tumors after overnight culture in interleukin 2. Unlike adult NK cells, freshly isolated fetal liver NK cells and clones derived from these cells, as well as a subset of cord blood NK cells, express substantial levels of CD3 delta and CD3 epsilon proteins in the cytoplasm. Expression of CD3 epsilon and CD3 delta transcripts and cytoplasmic proteins in fetal NK clones was confirmed by polymerase chain reaction and Western blot analysis. These findings support the concept that NK and T cells may arise from a common progenitor that expresses components of the CD3 complex. Alternatively, it is possible that the cytoplasmic CD3 delta, epsilon+ fetal NK cells represent a distinct subpopulation of NK cells that is predominant in the fetus, but replaced by the cytoplasmic CD3 delta,epsilon- adult NK cell population after embryogenesis.

Prenatal diagnosis of genetic disorders in preimplantation embryos: invasive and non-invasive approaches

The purpose of this article is to analyse the various non-invasive and invasive methods that offer the opportunity of prenatal diagnosis of selected inherited disorders at the preimplantation stages of human embryonic development and to discuss the advantages and ethical problems associated with such procedures. These investigations should also provide important information on the development of the human embryo and its hormonal and immunological relationship with the mother.