Showing papers in "Theriogenology in 1991"

TL;DR: A reliable nonsurgical, follicular aspiration procedure was used for the repeated collection of immature oocytes which could be used successfully for in vitro production of embryos and offers a competitive alternative to conventional superovulation/embryo collection procedures.

TL;DR: Using this model, FSH and basal levels of LH have been shown to be key signals for recruitment, however, in cycling sheep and cattle, the exact recruitment signal is not clear.

TL;DR: Embryos of excellent and good quality gave pregnancy rates of close to sixty percent and calving rates near fifty percent and corresponding results for poorer quality embryos were about twenty percent and slightly below twenty percent, respectively.

TL;DR: Further intensive research efforts are required to develop appropriate freezing and thawing procedures that allow practical application and extend the potential of biotechniques such as embryo micromanipulation, in vitro fertilization, cloning and gene transfer.

TL;DR: The results suggest that the apparent relationship between sex and developmental rate could be used as a method for noninvasive sexing of in vitro fertilized embryos.

TL;DR: A better understanding of the endocrine and paracrine factors controlling the process of follicle selection, growth and atresia is required in order to develop more effective systems of superovulation.

TL;DR: A polymerase chain reaction (PCR)-based method for accurate sex determination of preimplantation bovine embryos based upon examining blood cell DNA from adult males and females, which is extremely accurate, as no single incorrect result has occurred yet.

TL;DR: In this paper, a series of experiments that evaluated spermatozoal motion characteristics, as determined by computerized semen analysis, of extended, cooled stallion semen was conducted. And the results showed that those aliquots utilizing high dilution ratios of extender (>1:2.1, volume of semen: volume of extenders) maintained higher spermato-zoal motility and mean velocity than those using a lower dilution ratio.

TL;DR: Because herd management practices differ and could cause differences in mastitis and reproductive outcomes at the dairies, this preliminary field evidence should be followed by prospective studies of luteal function after clinical coliform mastitis.

TL;DR: The results indicate that response to the resynchronization protocol was altered by the outcome (early embryo death or failed fertilization) of the previous unsuccessful insemination, and support the hypothesis that delayed returns to estrus can be attributable to a pregnancy which was initiated but failed to establish itself.

TL;DR: Methods are described that allow the removal of small biopsies from cattle embryos in less than two minutes without compromising developmental potential, and can be used for sex determination, or indeed for analysis of any production trait marker.

TL;DR: It is suggested that the timing of postbreeding uterine lavage may be more important than the lavage media, with regard to detrimental effects on fertility.

TL;DR: In the in vitro system, LH and FSH accelerated and facilitated meiotic progression, and LH selectively improved cytoplasmic maturation which is required to promote the formation of a male pronucleus.

TL;DR: It appears that final maturation and ovulation of a dominant follicle require an increase in LH pulse frequency, so that androgen and estrogen synthesis are stimulated sufficiently to give rise to a gonadotrophin surge.

TL;DR: It was concluded that SMB did not adversely affect superovulatory response and that E(2) administration resulted in atresia of the antral follicles in the cows with SMB implants.

TL;DR: It is concluded that rapid alternations between long and short days decreased seasonality in the sexual activity of bucks.

TL;DR: The objectives of this study were to determine the time of embryo transport through the mare oviduct, to determine whether equine embryos increase in diameter prior to the Time of Oviductal transport, and to assess the stage of equine embryonic development at the time.

TL;DR: In this article, the authors evaluated the influence of different types of cryoprotectant, cooling rate, container and procedure on the post-thaw viability of sheep embryos.

TL;DR: The process of superovulation has an adverse effect on oocyte maturation as well as sperm transport, both of which are crucial events in the context of adequate embryo production.

TL;DR: There was no significant difference in the oocyte recovery rate between viable and atretic follicles, and a significantly higher proportion of oocytes recovered from viable follicles had granular ooplasm.

TL;DR: In good quality bovine embryos total glucose utilization is low until 16-cell stage, with PPP being the predominant pathway, and PPP activity increases significantly in poor quality embryos and in embryos 24 h in culture.

TL;DR: In heifers in which embryonic death preceded luteal regression, there was ultrasonic evidence of conceptus degeneration, but conceptus fluid and tissue appeared to be maintained, and in all heifer with embryonic death, the conceptus and its breakdown products apparently were eliminated by expulsion through the cervix rather than by resorption.

TL;DR: Ten Gyr cows with a functional corpus luteum were used to evaluate the effects of time and temperature of incubation of blood samples on progesterone (P4) concentrations detected in plasma or serum and sodium fluoride used as anticoagulant prevented the degradation of P4.

TL;DR: The data indicate that scrotal circumference measurements can be a useful tool for selecting and improving semen traits of young Guzerat and Nellore bulls under tropical grazing conditions.

TL;DR: The ability of a moderate number of follicle cells to facilitate sperm penetration of pig follicular oocytes and male pronuclear formation is supported.

TL;DR: The reason for the marked increase in the twinning rate during the warmest months may be explained by greater embryo mortality in the hot vs cool months.

TL;DR: It is suggested that PGE2 impedes uterine involution in the cow, and the ratio of plasma prostaglandin concentration (PGFM/PGEM) was affected by treatment.