title: A technique for facile and precise transfer of mouse embryos.
abstract: BACKGROUND
  Successful Embryo Transfer (ET) technique is a fateful step of all efforts to achieve live births from in vitro produced embryos in assisted reproductive techniques or in knockout, transgenic or cloned animal projects. Small reproductive tract of mice and limitation of current techniques may not well satisfy the requirements for mass production of genetically modified mice. Genetic abnormalities of embryos, receptivity and uterine contractions, expulsion of embryos, blood, mucus or bacterial contamination on the transfer pipette tip, technical problems and even animal strain may affect embryo transfer outcome.
  
  
  METHODS
  In this study, two techniques of embryo transfer in mice were compared. In conventional technique the oviduct wall was punctured with a 30-gauge needle and the loaded Pasteur pipette with embryos and medium was inserted into the hole. In new technique, embryos that were loaded in modified micropipette with minimal medium were transferred directly to the oviduct by manual piston micro-pump easily. Embryo viability was evaluated considering the percentage of live healthy newborns.
  
  
  RESULTS
  Results of the two techniques were compared by t-test within the NPAR1WAY procedure of SAS software (ver. 9.2). The average live birth rates in the novel methods was significantly higher (42.4%) than the conventional method (21.7%, p<0.05).
  
  
  CONCLUSIONS
  In conclusion, using new embryo transfer technique improved birth rate by preventing embryos expulsion from the oviduct, saving time and easy transfer of embryos with minimum volume of medium.
authors.affiliation: Reproductive Biotechnology Research Center, Avicenna Research Institute, ACECR, Tehran, Iran ; These authors equally contributed to this work.
authors.forename: Ali
authors.initials: A
authors.lastname: Sarvari
authors.forename: Mohammad Mehdi
authors.initials: MM
authors.lastname: Naderi
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Sadeghi
authors.forename: Mohammad Mehdi
authors.initials: MM
authors.lastname: Akhondi
keywords: Embryo; Embryo transfer; Mice; Micropipette