title: Cytogenetic Alterations in Preimplantation Mice Embryos Following Male Mouse Gonadal Gamma-irradiation: Comparison of Two Methods for Reproductive Toxicity Screening.
abstract: BACKGROUND
  Genome instability is a main cause of chromosomal alterations in both somatic and germ cells when exposed to environmental, physical and chemical genotoxicants. Germ cells especially spermatozoa are more vulnerable to suffering from DNA damaging agents during spermatogenesis and also more potent in transmitting genome instability to next generation.
  
  
  METHODS
  To investigate the effects of γ-rays on inducing abnormalities manifested as numerical Chromosome Aberrations (CA) and Micronucleus (MN) in preimplantation embryos, adult male NMRI mice were irradiated with 4 Gy of γ-rays. They were then mated at weekly intervals with superovulated, non-irradiated female mice in 6 successive weeks. About 68 hr post coitous, four to eight cell embryos were retrieved and fixed on slides using standard methods in order to screen for CA and MN.
  
  
  RESULTS
  In embryos generated from irradiated mice, the frequency of aneuploidy and MN increased dramatically at all post-irradiation sampling times as compared to the control (p<0.01). The frequency of embryos expressed MN was much higher than chromosomally abnormal embryos, although the trend of MN formation was similar to chromosomal abnormalities seen in corresponding sampling times.
  
  
  CONCLUSIONS
  Irradiation of sperms at any stages of spermatogenesis may lead to stable chromosomal abnormalities affecting pairing and disjunction of chromosomes in successive preimplantation embryos that are expressed as MN. Although chromosome analysis of embryos showed various types of chromosomal abnormalities, MN assay provide a simpler and faster technique for investigating the genotoxicity of agents affecting embryos at preimplantation stages.
authors.affiliation: Department of Medical Genetics, National Institute of Genetic Engineering and Biotechnology, Tehran, Iran.
authors.forename: Mahdieh
authors.initials: M
authors.lastname: Salimi
authors.affiliation: Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
authors.forename: Hossein
authors.initials: H
authors.lastname: Mozdarani
authors.affiliation: Department of Science and Research, Azad University and Royan Institute, Tehran, Iran.
authors.forename: Elmina
authors.initials: E
authors.lastname: Nazari
keywords: Chromosomal aberrations; Embryo; Germ cells; Irradiation; Micronuclei