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Elimination of spontaneous and chemically induced chromosome aberrations in mice during early embryogenesis
Abstract:
NMRI mice (female female) were treated with 0.25 mg/kg body weight Trenimon (2,3,5-triethyleneiminobenzoquinone-1,4) in the preovulatory phase just before ovulation. Then they were mated with untreated males. The female mice were dissected 45 h after application of this mutagen. The preimplantation embryos, being in a 2-cell stage, were flushed out of the oviduct and cultured in vitro for 60 h. Of the cultured embryos 87.7% reached the blastocysts stage in the control series, whereas only 49.7% did so in the experiments. Some of the females were dissected on the 14th day post conception (p.c.) and the number of dead and living implants was determined. Furthermore, the 9.5- and 13.5-day-old embryos were cytologically investigated, to determine the frequency of chromosomal aberrations. Of the unfertilized oocytes 76.2% deriving from mice treated with 0.25 mg/kg Trenimon, were aberrant in the stage of metaphase II (Röhrborn and Hansmann, 1971). Comparing Röhrborn's and Hansmann's results (1971) to our own findings a continuous elimination of chromosome aberration is clearly to be seen during early embryogenesis. The biological selection takes place in the pre- as well as in the early and late postimplantative phase.
Insights
Trenimon, a mutagen, significantly reduced embryo development in mice by causing chromosomal aberrations. These genetic defects were eliminated throughout early embryogenesis, indicating biological selection against affected embryos.
Area of Science:
- Reproductive toxicology
- Developmental biology
- Genetics
Background:
- Mutagenic agents can impact reproductive outcomes.
- Chromosomal aberrations are a known consequence of exposure to certain chemicals.
- Early embryogenesis involves critical stages sensitive to genetic damage.
Purpose of the Study:
- To investigate the effects of Trenimon on preimplantation mouse embryos.
- To assess the frequency of chromosomal aberrations induced by Trenimon.
- To determine the impact of Trenimon on early embryonic development and survival.
Main Methods:
- NMRI mice were treated with Trenimon (2,3,5-triethyleneiminobenzoquinone-1,4) before ovulation.
- Preimplantation embryos (2-cell stage) were collected and cultured in vitro.
- Embryos and unfertilized oocytes were analyzed for chromosomal aberrations.
- Implant survival rates were determined at day 14 post-conception.
Main Results:
- Trenimon treatment reduced the blastocyst formation rate from 87.7% (control) to 49.7%.
- 76.2% of unfertilized oocytes from treated mice showed metaphase II aberrations.
- A continuous elimination of chromosome aberrations was observed during early embryogenesis.
- Biological selection against aberrant embryos occurred during pre- and post-implantation stages.
Conclusions:
- Trenimon induces significant chromosomal aberrations in mouse oocytes and embryos.
- Early embryogenesis involves a selection process that eliminates chromosomally abnormal embryos.
- The study highlights the detrimental effects of mutagens on reproductive success and embryonic development.