Reproduction, Fertility and Development
Number 7 2017
A unique approach to managing coyote (Canis latrans) depredation is the development of a one-time deliverable chemical sterilant. We hypothesised that exposure to a high dose of a gonadotrophin-releasing hormone (GnRH) agonist would cause prolonged suppression of the reproductive axis. The results of the present study suggest that a plasma concentration of 100 pg mL–1 deslorelin must be maintained and that elevations beyond this threshold are likely to be unimportant.
Progesterone, which is essential for pregnancy in mammals, is synthesised from cholesterol in the corpus luteum (CL). We investigated the involvement of cholesterol uptake receptors and efflux transporters in bovine CL regression (luteolysis), and found that the expression of scavenger receptor B1, a cholesterol uptake receptor, decreased during luteolysis. The decline in cholesterol uptake may reduce progesterone production in the CL during luteolysis.
Histone H3 phosphorylation is essential for chromatin condensation, which is a prerequisite for accurate chromosome separation in mitosis or meiosis. The present study demonstrates that p21-activated kinase 1 (Pak1) activity is required for histone H3 phosphorylation and consequent chromatin condensation in mouse oocytes upon the resumption of meiotic progression.
A valid biomarker for sperm molecular characterisation was found in Japanese black cattle. The distribution of acrosomal tyrosine-phosphorylated proteins largely differs among individual bulls. The grades of acrosomal freezability and results of AI with cryopreserved spermatozoa can be predicted by assessing the distribution of acrosomal tyrosine-phosphorylated proteins in spermatozoa before cryopreservation.
Despite evidence of the presence of PGI2 in mammalian oviducts, its role in development of early embryos is largely unknown. We revealed that supplementation of PGI2 analog enhanced early development of IVP porcine embryos through activation of AKT cascade. These results indicate that iloprost can be a useful IVC supplement for production of IVP early porcine embryos with high quality.
Spermatozoa maturation is a necessary step for the best success in artificial reproduction. This study focused on the role of calcium ions in the acquisition of testicular sturgeon sperm to be able to swim: our results show that an influx of Ca2+ ions is required for finalisation of this maturation process.
The reproductive tract secretes molecules collectively known as embryokines that regulate embryonic growth and development. In this study we tested four growth factors expressed in the endometrium for actions on the bovine preimplantation embryo. All four molecules affected embryonic development or gene expression and may therefore function in the endometrium as embryokines.
Transgenerational food restriction and overweightAdverse environmental factors during gestation, such as under- or overnutrition, may predispose individuals to certain diseases later in life by altering their fetal programming. The present study investigated whether prenatal 40% food restriction was able to induce weight, metabolic and neuroimmune disturbances in the next two generations, even if they were normally fed. We showed a transgenerational transmission effect for overweight over two generations, associated with changes in immune and inflammatory patterns, revealing the severe impact of undernutrition over generations.
This study looked at how off-feed incidents or competition for feed can affect hormonal regulation of luteal function and early pregnancy in pigs. We found no effect of a day’s fasting on LH secretion, but progesterone secretion was reduced and fewer piglets were born at subsequent farrowing. Malnutrition in group-housed sows or in periods of hot weather can potentially reduce ovarian progesterone output and fertility.
Stem cell factor (SCF) and epidermal growth factor (EGF) play key roles in ovarian folliculogenesis. Herein we report that SCF promotes cat follicle growth by upregulating c-kit mRNA expression and AKT phosphorylation. EGF suppresses the stimulating effect of SCF, leading to a downregulation of FSH receptor mRNA expression. The ability to grow premature follicles in vitro could become a pivotal tool for preserving fertility in animal disease models and endangered felids.
Diabetes mellitus (DM) has been associated with male reproductive impairment but the underlying mechanisms are poorly understood owing to the diversity of factors involved in the disease. In this study we focused on the in vitro effects of high glucose levels, the primary recognised signature of DM, on spermatogenesis. We found that while mouse testicular luminal area was decreased, Sertoli cell number was increased. These findings suggest an impairment of Sertoli cell function in high-glucose conditions that may impact spermatogenesis.
The effect of birth type (single, twin, triplet) and co-twin sex on in vitro developmental competence of oocytes from 6 to 8-week old lambs significantly increased blastocyst development rates for lambs born with a female co-twin compared with a male co-twin. This indicates a female co-twin enhancement effect on oocyte development. Selection of lambs for embryo production programs based on co-twin sex is warranted.
Using a hamster model, we found significant changes in mitochondrial number, structure and function as well as fecundity, ova production and follicular number in aged compared to younger animals. Old hamsters had decreased fertility rates, smaller litters, and decreased numbers of preantral follicles and MII oocytes. In addition, old ova contained large areas of collapsed, non-luminal cytoplasmic lamellae. Finally, old hamster ova contained higher levels of reactive oxygen species, lower mitochondrial membrane potential and decreased mitochondrial numbers, all of which could be contributing to the age-related decline in mammalian fertility rates.
Poor egg quality underlies reproductive aging in mice and in women. Oocyte maturation is a critical stage in determining the quality of eggs and hence embryonic potential. We demonstrated that putrescine supplementation during in vitro maturation of aged mouse oocytes resulted in healthier embryos. Peri-ovulatory putrescine supplementation may be an effective therapy in reproductive aging.
Mammalian males do not produce equal numbers of X- and Y-chromosome-bearing sperm, but factors influencing the variation are unknown. We show that sperm sex ratios and ejaculate traits vary with mating rate in laboratory mice, and hypothesise that males that mate frequently are usually more attractive, and would be advantaged by producing sons that inherit their attractiveness.
Germinal vesicle oocytes are susceptible to heat stress. The present study demonstrated that the physiological IGF-I concentration of 12.5 ng/ml was able to revert the deleterious effects of heat shock on bovine GV oocyte cellular function and ability to became a blastocyst. This thermoprotective role of IGF1 warrants further in vivo IGF1 manipulation to improve dairy cow fertility during summer.
The use of sex-sorted fresh spermatozoa has the potential to yield higher pregnancy rates than sex-sorted frozen spermatozoa. This study sought to characterise the in vitro quality of X and Y sex-sorted bull spermatozoa and identified the need for tailored diluents for fresh sex-sorted spermatozoa to avoid head-to-head agglutination. The use of fresh sex-sorted spermatozoa, when managed correctly, has enormous potential in the dairy industry.
Androgens (male steroids) interact with the key regulator of female reproduction, FSH, but the nature of their interaction is not clear. Examination of mutant androgen-insensitive mice with and without the expression of human transgenic FSH (Tg-FSH) revealed that subfertility in androgen-insensitive mice is rescued by the presence of Tg-FSH. These findings demonstrate that androgens and FSH actions interact in a synergistic manner to maintain optimal female fertility.
This work demonstrates that it is necessary for progressive sperm motility that flagellar proteins, like ODF1, maintain reduced cysteines after epididymal transit. To determine how oxidative changes in flagellar proteins affect sperm motility, a sulfhydryl blocker was used; sperm progressive motility was abolished without affecting the level of ATP. Incomplete oxidation in flagellar proteins of asthenozoospermic samples was also observed. Inadequate maturation or an unbalanced thiol status leads to non-progressive motility.
We present a new hypothesis of the molecular mechanisms responsible for implantation, which could provide an important basis for further understanding of embryo implantation. Our study shows that spontaneous elimination of GRIM-19 is required for endometrial receptivity and the embryo implantation process. Our results demonstrate the involvement of GRIM-19 in the embryo implantation process by regulating adhesion, apoptosis and immune tolerance.