Effects on Germ Cells

As previously described for the male reproductive toxicity, the class of toxicants affecting germ cells can alter the structure of genetic material (chromosomal aberrations, alterations in meiosis, DNA synthesis, and replication). Mature oocytes have a DNA repair capacity different from that of mature sperm, but this capacity decreases at the period of meiotic maturation. 

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Risk estimation. Hie estimation of effect per unit of exposure. There are two components estimation of mutagenic effects on germ cells (damage) and estimation of effects on health and welfare of future generations (impact). 

A true test of this model requires selective access to Sertoli cell microtubule networks in vivo, independent of direct effects on germ cells. Such a mechanism precludes toxicant or pharmacologic manipulations of microtubules, which exert effects globally. Cell-type specificity can only be afforded by molecular interventions that are capable of being either delivered or expressed in subsets of cells. 

Another potential risk of the welding of stainless steel, and presumably the inhalation of hexavalent chromium has a geno-toxic effect on germ cells. The adjusted relative risk for spontaneous abortion for pregnancies associated with exposure to paternal stainless-steel welding was 3.5 (Hjollund et al. 2000)... 

Leapfrog, Rana dalmutina, larvae, exposed during formation of gonadal structures 9000 Toxic effect on larval gonad, especially on germ cells of ovarian structure 81... 

A mutagenic effect of ozone on germ cells was suggested by the study of Brinkman et in which female mice exposed to ozone at 0.1-0.2 ppm, 7 h/day, 5 days/week, for 3 weeks before birth, demonstrated a fourfold increase in neonatal mortality. A further report of this study noted increased blepharophimosis and jaw anomalies and a decrease in litter size. An artificial oxidant smog mixture derived from irradiated auto exhaust has also been reported to cause an increase in neonatal mortality in mice. ... 

Chemical mutagenesis in laboratory mammals A bibliography on the effects of chemicals on germ cells (EMIC report)... 

Yan W, Suominen J, Samson M, Jegou B, Toppari J. 2000. Involvement of Bcl-2 family proteins in germ cell apoptosis during testicular development in the rat and pro-survival effect of stem cell factor on germ cells in vitro. Mol. Cell Endocrinol. 165 115-29... 

As explained (section V, A, 2), only DLs induced in postmeiotic stages of male germ cells are free of selective elimination prior to ferilization. Point mutations would be much less likely to have a deleterious effect on the cells in which they arose, and therefore would not be subject to such selection. The failure to recover DL mutation from premeiotic cells would not therefore preclude the production of point mutation in such cells. 

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