The genetic basis of infertility remains unclear in a majority of infertile men. In this study, Y chromosome long arm involving DAZ (Deleted in Azoospermia) was screened in order to evaluate the occurrence of microdeletion in Japanese infertile men. 197 infertile Japanese men with azoospermia and oligozoospermia were analyzed for microdeletions of the Azoospermia factor (AZF) c region of the Y chromosome by using polymerase chain reaction with sequence-tagged site markers. The 16 sets of oligonucleotides primer were synthesized for polymerase chain reaction, and southern blot analysis was also performed. All analyzed infertile men were divided into 5 categories on the basis of sperm concentration: functional azoospermia (A) 28, azoospermia due to obstruction (AO) 20, oligozoospermia I (OI) (less than 1×10⁵/ml) 49, oligozoospermia II (OII) (less than 1×10⁶/ml) 50 and oligozoospermia III (OIII) (less than 1×10⁷/ml) 50. 30 fertile men with sperm concentration of more than 2×10⁷/ml were also analyzed as control. In 15 (7.6%) of 197 infertile men, microdeletions were identified as follow: 1 in category A, 1 in category AO, 6 in category OI, 6 in category OII and 1 in category OIII. On the other hand, no deletion was identified in fertile men. One common region around sY240 was identified through 14 infertile men with microdeletions. This locus might contain specific genes for spermatogenesis. Sperm concentrations of 13 oligozoospermic men with microdeletions were below 1×10⁶/ml. There was no correlation between the severity of spermatogenesis and the extent of microdeletions. These results suggested that genes in the AZFc region of the Y chromosome might be important roles for spermatogenesis.

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Nuclear transfer techniques have been known to be useful for producing cloned embryos in animals. This study was designed to examine the ability of the mouse metaphase oocyte cytoplasm to support mitotic cell cycles under the direction of differentiated somatic cell nuclei of various mammalian species. Monkey amniotic epithelial cells, mouse yolk sac cells and fibroblast cells from mouse, pig and rabbit were used as sources of donor nuclei. Nuclear transfer units produced by fusion of enucleated mouse oocytes and individual somatic cells from all species examined underwent transition to interphase accompanied by nuclear swelling, further progression through the cell cycle, and completion of the first mitosis. Regardless of the species of donor somatic cell used, the fusion rate was uniformity. Reconstructed embryos produced by intraspecies nuclear transfer developed to advanced stages, as the evidenced by continuation of cell proliferation and formation of a blastocoele cavity. On the other hands, reconstructed embryos derived from nuclear transfer of interspecies were did not develop over 8-cell stage. These observations suggest that mechanisms regulating early embryonic development may be conserved among mammalian species and that mouse oocyte cytoplasm might be possible to support the introduced differentiated nucleus regardless of chromosome number, species, or age of the nuclear donor.

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