title: In vitro fertilization and embryo development of Japanese field voles (Microtus montebelli).
abstract: Optimal conditions for in vitro fertilization of Japanese field voles (Microtus montebelli) were analysed. The medium used was a modified Krebs-Ringer bicarbonate devised for in vitro fertilization in rats. Ovulated eggs and epididymal spermatozoa were co-incubated in vitro at 37 degrees C under 5% CO2 in air for 6 h, and the eggs were fixed with 2.5% (w/v) glutaraldehyde, stained with 0.25% (v/v) acetolacmoid and examined for evidence of fertilization at the pronuclear stage. Although the fertilization rate with spermatozoa preincubated at 1-2 x 10(8) cells ml-1 for 2 h was very low (1-13%), it was significantly increased (43-51%, P < 0.05) when spermatozoa were preincubated at a lower concentration (1-2 x 10(7) cells ml-1). Furthermore, the fertilization rate was significantly higher with 1 mmol hypotaurine l-1 (74.0%) than without hypotaurine (44.4%, P < 0.05). Fertilization rates of spermatozoa preincubated at 1-2 x 10(7) cells ml-1 for 0.5 or 2 h were similar (69.0% and 73.6%), but a longer preincubation (10 h) resulted in a significantly lower fertilization rate (56.8%, P < 0.01). Vole spermatozoa preincubated for 2 h penetrated the zona pellucida 2 h after insemination, and the sperm heads became decondensed 3 h after insemination. At 6 h after insemination, male and female pronuclei were found in most penetrated eggs. When the eggs were left in the fertilization medium without washing and cultured for 96 h after insemination, they developed to two-cell (82.6%), four-cell (60.9%), eight-cell (23.2%) and morula/blastocyst (8.7%) stages in modified Krebs-Ringer bicarbonate supplemented with 1 mmol hypotaurine l-1.
authors.affiliation: Department of Veterinary Anatomy, Faculty of Agriculture, University of Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Wakayama
authors.forename: J
authors.initials: J
authors.lastname: Suto
authors.forename: Y
authors.initials: Y
authors.lastname: Matubara
authors.forename: K
authors.initials: K
authors.lastname: Imamura
authors.forename: K
authors.initials: K
authors.lastname: Fukuta
authors.forename: Y
authors.initials: Y
authors.lastname: Toyoda
authors.forename: M
authors.initials: M
authors.lastname: Kurohmaru
authors.forename: Y
authors.initials: Y
authors.lastname: Hayashi
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000196:embryology*; D005314:Embryonic and Fetal Development; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary*; D008297:Male; D008954:Models, Biological; D013075:Sperm Capacitation; D013084:Sperm-Ovum Interactions