In vivo meiotic resumption, fertilization and early embryonic development in the bitch

Abstract

Early development in canine species follows a very specific pattern. Oocytes are ovulated at the germinal vesicle stage and meiotic resumption occurs in the oviduct. However, because of difficulties in the accurate determination of ovulation time and in the observation of oocyte nuclear stage by light microscopy, these early events have not been fully described. Moreover, the oocyte stage at which sperm penetration occurs is still uncertain since fertilization of immature oocytes has been reported in vivo and in vitro. The aim of this study was to establish the exact timing of in vivo meiotic resumption, fertilization and early embryo development in the bitch with reference to ovulation. Ovulation was first determined by ultrasonography, artificial inseminations were performed daily and oocytes/embryos were collected between 17 and 138 h after ovulation. After fixation and DNA/tubulin staining, the nuclear stage was observed by confocal microscopy. Of the 195 oocytes/embryos collected from 50 bitches, the germinal vesicle stage was the only one present until 44 h post-ovulation, and the first metaphase II stage was observed for the first time at 54 h. Sperm penetration of immature oocytes appeared to be exceptional (three out of 112 immature oocytes). In most cases, fertilization occurred from 90 h post-ovulation in metaphase II oocytes. Embryonic development was observed up to the eight-cell stage. No significant influence of bitch breed and age on ovulation rate, maturation and developmental kinetics was observed. However, some heterogeneity in the maturation/development process was observed within the cohort of oocytes/embryos collected from one bitch. In conclusion, the most peculiar aspect of the canine species remains oocyte meiotic maturation whereas fertilization follows the same pattern as in other mammals. Reproduction (2005) 130 193-201

Ovarian Follicular Morphometry of South American Fur Seal Pups (Arctophoca australis)

“…In turn, in SAFS the oocyte diameter of type 5 follicles (68.2 6 5.3 lm) was lower than reported in adult domestic dogs when measured without zona pellucida (Reynaud et al, 2005;Diagone et al, 2007;Songsasen et al, 2009), which are the only morphometric references available in a related caniformia species. Thecal and granulosa thickness differences between type 3-4 and type 5 follicles may indicate a process of cellular proliferation and differentiation.…”

The influence of ascorbic acid on in vitro maturation of canine oocytes

“…The oocyte of the domestic dog is unique from that of other mammalian species studied to date. Ovulation occurs either once or twice per year, with the oocyte released at the germinal vesicle stage and then completing nuclear and cytoplasmic maturation within the oviduct, and requires 48-72 h in the oviduct post-ovulation to complete nuclear maturation (Reynaud et al, 2005). From 1976 (Mahi and Yanagimaci, 1976) to date, numerous studies have been conducted to improve success of in vitro maturation (IVM) of bitch oocytes but an efficient protocol for IVM has not been established.…”

Biología Gestacional y Predicción del Parto en la Perra

“…Experiencias in vitro demuestran que los espermatozoides caninos pueden unirse a células epiteliales del útero y del oviducto, prolongando su viabilidad, motilidad e inhibiendo la capacitación espermática (Kawakami et al, 2001;England et al, 2006). En un estudio in vivo se describe que la fecundación ocurre principalmente 90 horas después de la ovulación, cuando los ovocitos han completado su maduración nuclear (Reynaud et al, 2005).…”