Thiotepa, a reliable marker for sperm precedence measurement in a polyandrous moth

The determination of paternity of offspring produced by polyandrous females is essential for the understanding of sperm competition mechanisms. The sterile male technique using radiation is one of the most commonly employed methods for this purpose. However, sterilization using radiation is likely to be restricted by the equipment availability and cost. Chemosterilization may thus be a cheaper and easier alternative for sterilizing male insects in sperm competition studies. Here we report a reliable chemomarker, thiotepa (N,N′,N″-triethylenethiophosphoramide), for the study of sperm competition and precedence in a polyandrous moth, Ephestia kuehniella (Lepidoptera: Pyralidae). Dipping heads of male moths in 1% thiotepa aqueous solution for 10 s resulted in complete sterilization, i.e. their sperm still fertilized eggs but those eggs did not hatch. The sterilization treatment did not significantly affect male copulation ability, female fecundity, and sperm transfer, motility and fertilization. Our results indicate that 86% offspring of the twice-copulated females were fathered by the second males and 14% by the first males. Males treated with 5% thiotepa aqueous solution died within 24 h while those treated with 0.5% thiotepa were not fully sterilized.     

Hprt mutant frequency and molecular analysis of Hprt mutations in rats treated with mutagenic carcinogens

Much of the progress in the field of cancer research has come from the increased understanding of the molecular events associated with the initiation and accumulation of mutational events associated with carcinogenesis. Genetic toxicologists have developed a number of in vitro and in vivo non-mammalian and mammalian systems to predict those genetic events required to induce the cancer process. Several model rodent systems have been proposed that have the ability to detect and quantify in vivo somatic mutation in endogenous genes and transgenes and relate the nature of the mutation to the specific type of chemical damage. One such system, the rat lymphocyte hypoxanthine guanine phosphoribosyl transferase (Hprt) assay is described in this review. Data are presented that describe mutant induction and mutational spectra in N-ethyl-N-nitrosourea (ENU), 7,12-dimethylbenzo[a]anthracene (DMBA) and thiotepa (TEPA) treated rats.