Fetal anomalies produced subsequent to treatment of zygotes with ethylene oxide or ethyl methanesulfonate are not likely due to the usual genetic causes

Earlier studies in this laboratory revealed that ethylene oxide (EtO) or ethyl methanesulfonate (EMS) induced high frequencies of midgestation and late fetal deaths,and of malformations among some of the surviving fetuses, when female mice were exposed at the time of fertilization of their eggs or during the early pronuclear stage of the zygote. Effects of the two mutagens are virtually identical. Thus, in investigating the mechanisms responsible for the dramatic effects in the early pronuclear zygotes, the two compounds were used interchangeably in the experiments. First, a reciprocal zygote-transfer study was conducted in order to determine whether the effect is directly on the zygotes or indirectly through maternal toxicity. And second, cytogenetic analyses of pronuclear metaphases, early cleavage embryos, and midgestation fetuses were carried out.

The zygote transplantation experiment rules out maternal toxicity as a factor in the fetal maldevelopment. Together with the strict stage specificity observed in the earlier studies, this result points to a genetic cause for the abnormalities. However, the cytogenetic studies failed to show structural or numerical chromosome aberrations. Since intragenic base changes and deletions may also be ruled out, it appears that the lesions in question induced in zygotes by the two mutagens are different from conventional ones and, therefore, could be a novel one in experimental mammalian mutagenesis. Alternatively, the mechanism could invlve a non-mutational ‘imprinting’ process that caused changes in gene expression.     

Cost effectiveness in captive management

The purpose of this paper is to encourage recognition that economic constraints are of paramount importance to all management decisions. An early acceptance of this fact minimizes the disastrous effects of those constraints. Each decision considered, whether research, conservation, education, or management, must be approached with cost effectiveness as a primary component of its developmental phases.     

Androgen-dependent fibrinolytic activity in a murine mammary carcinoma (Shionogi SC-115 cells) in vitro.

Physiological concentrations of dihydrotestosterone (DHT) can specifically induce the release of fibrinolysin from androgen-dependent mammary carcinoma (Shionogi SC-115) cells in vitro. No fibrinolytic activity was observed in cells cultured either in the absence of DHT or presence of pharmacological concentrations of estrogen. Furthermore, an autonomous tumor derived from the Shionogi SC-115 cells produced fibrinolytic activity independent of added DHT or estrogen. These observations suggest a close correlation between fibrinolytic activity of a tumor and its ability to grow in vivo.     

Heat shock protein induction and induced thermal tolerance are independent in adult salamanders

Ectothermic vertebrates become thermally tolerant (heat hardened) after exposure to heat shock. Eukaryotic cells show a similar response. Cellular thermal tolerance is correlated with the induction of heat shock proteins (hsps). We have investigated the relationship between heat hardening in salamanders and the induction of hsps in the tissues of these organisms. Although the synthesis of hsps can be induced in these animals by sublethal heat shocks, conditions required for hsp induction and heat hardening often do not coincide. We conclude that induced thermal tolerance in adult salamanders is independent of hsp induction in their tissues.