title: One-step versus two-step culture of mouse preimplantation embryos: is there a difference?
abstract: BACKGROUND
  A comparison has been made of the development of mouse zygotes in either one-step or two-step culture systems.
  
  
  METHODS
  Embryo culture, blastocyst cell counts and embryo transfer were done.
  
  
  RESULTS
  No significant differences were observed in the proportions of blastocysts, rates of hatching, numbers of cells in the inner cell mass (ICM) and trophectoderm (TE) that developed in protocols: one-step culture in potassium-enriched simplex optimized medium supplemented with glucose and amino acids (KSOMg(AA)), two-step culture in KSOMg(AA)/KSOMg(AA), and two-step culture in G1.2/G2.2. No gross abnormalities were observed in the fetuses that developed from zygotes in the one-step protocol using KSOMg(AA) and a two-step protocol using G1.2/G2.2. The body weights of these two groups of fetuses were not significantly different and no developmental abnormalities were observed. No significant differences were observed in the proportions of blastocysts, rates of hatching, numbers of cells in the ICM and TE that developed in protocols: one-step culture in KSOMg(AA), two-step culture in KSOMg(AA)/KSOMg(AA), and two-step culture in DM2/DM1. EDTA is not toxic to the initial cleavage stages of development at a concentration of 0.01 mmol/l in KSOMg(AA).
  
  
  CONCLUSIONS
  Two-step culture protocols are sufficient for the support of preimplantation mouse development in vitro but they are not necessary.
authors.affiliation: Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 02115 Beth Israel Deaconess Hospital, Boston, MA 02115, USA. john_biggers@hms.harvard.edu
authors.forename: J D
authors.initials: JD
authors.lastname: Biggers
authors.forename: L K
authors.initials: LK
authors.lastname: McGinnis
authors.forename: J A
authors.initials: JA
authors.lastname: Lawitts
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology* / Q000378:metabolism*; D001835:Body Weight; D018929:Cell Culture Techniques / Q000379:methods; D003470:Culture Media / Q000494:pharmacology; D004475:Ectoderm / Q000166:cytology; D004492:Edetic Acid / Q000494:pharmacology; D046149:Embryo Culture Techniques; D004624:Embryo Transfer; D047108:Embryonic Development; D005260:Female; D005307:Fertilization in Vitro; D051379:Mice; D011188:Potassium / Q000494:pharmacology; D013997:Time Factors; D015053:Zygote
chemical_list: D003470:Culture Media; D004492:Edetic Acid; D011188:Potassium