title: Maintenance of fertility in cryopreserved Indian gerbil (Tatera indica) spermatozoa.
abstract: This study is the first attempt at sperm cryopreservation, as well as a further examination of frozen sperm fertility by the hamster test, applied to the maintenance of an Indian gerbil (Tatera indica) colony, which is a newly developing experimental animal. The osmotic tolerance of the spermatozoa was initially investigated by subjection to hypertonicity, up to 620mOsm/kg, for 5min at room temperature prior to freezing. Although the percentage of total motile sperm was not affected, that of progressive motile spermatozoa began to drop at 400mOsm/kg, and a significant decrease was observed at 620mOsm/kg (p<0.01). According to these results, the osmolality of the solutions for the freezing experiment, in which 6-22% raffinose was present, was fixed at approximately 400mOsm/kg. Sperm, suspended in a plastic straw, were frozen in liquid nitrogen vapor for 5min, followed by immersion in liquid nitrogen. Motile sperm were recovered from all freezing conditions, and high survival was obtained when sperm were frozen in the presence of 14% and 18% raffinose, with a normalized motility higher than 40%. Fertility of cryopreserved Indian gerbil sperm was examined by the zona-free hamster test. Thawed sperm adhered to 88% of the zona-free hamster oocyte surface, and some oocytes were penetrated and exhibited swollen sperm heads or male pronuclei, which we used to define fertilization. Although the fertilization rate of cryopreserved sperm to zona-free hamster eggs was significantly lower than that of fresh sperm (6% vs. 30%, p<0.01), we demonstrated that thawed Indian gerbil spermatozoa have the ability to maintain their fertility.
authors.affiliation: Department of Bio-resources, Division of Biotechnology, Frontier Science Research Center, University of Miyazaki, Kiyotake, Miyazaki, Japan. ckos@med.miyazaki-u.ac.jp
authors.forename: Chihiro
authors.initials: C
authors.lastname: Koshimoto
authors.forename: Daisuke
authors.initials: D
authors.lastname: Watanabe
authors.forename: Akio
authors.initials: A
authors.lastname: Shinohara
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Morita
mesh_terms: D000818:Animals; D006224:Cricetinae; D015925:Cryopreservation / Q000379:methods*; D005260:Female; D005298:Fertility; D005849:Gerbillinae; D008297:Male; D009995:Osmosis; D012662:Semen Preservation / Q000379:methods*; D013081:Sperm Motility / Q000502:physiology; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000502:physiology