Reproduction, Fertility and Development
Volume 25 Number 3 2013
RESEARCH FRONT: Oocyte Meiosis
Since 1935, the general acceptance of the hypothesis is that a mural granulosa origin oocyte maturation inhibitor (OMI) arrests mammalian oocyte maturation. Many studies have focused on identifying the arrester for a long time, and until recently showed that natriuretic peptide precursor C-promoted cGMP by its receptor NPR2 is essential to block oocyte maturation through diffusing into the oocyte and inhibiting phosphodiesterase 3A activity and cAMP hydrolysis. Thus, NPPC may be the OMI, and also the decrease of its function by LH is required for oocyte maturation.
The errors during division of the germ cells may generate embryonic aneuploidy which results in spontaneous abortions or genetic diseases like Down Syndrome. In many cells aneuploidy is prevented through the function of the mechanism called spindle assembly checkpoint (SAC), which existence in the mammalian oocytes was debatable for a long time until recently. This review summarises the current knowledge on the SAC function in mammalian oocytes with the special reference to the SAC efficiency and discusses a possible clinically relevant interference between the SAC and the oocyte-specific cell cycle control mechanism.
Meiosis, the division of the female gamete, is a complex, tightly orchestrated process. This review describes the latest knowledge regarding the roles of major kinases, regulatory proteins, as well as the involvement of protein degradation in meiosis, and highlights the differences and similarities with the somatic cell division, mitosis.
RD12300Knockdown of UCHL5IP causes abnormalities in γ-tubulin localisation, spindle organisation and chromosome alignment in mouse oocyte meiotic maturation
In mammals, meiosis is a necessary step to produce spermatozoa or oocytes for sexual reproduction, and γ-tubulin localises at the spindle poles to promote microtubule nucleation, which is critical for meiosis procession. In this research, we focussed on the protein UCHL5IP, one of the subunits of augmin, which is important for γ-tubulin localisation in mitosis, to explore its function in oocyte meiotic maturation. Knockdown of UCHL5IP disrupted γ-tubulin localisation and led to chromosome misalignment and spindle defects. Our research reveals the functions of UCHL5IP in mouse oocyte maturation and promotes understanding of the regulation of meiosis.
Proper cell cycle generates life and requires accurate chromatin structure control both in DNA and histone. Here we have identified a histone trimethyltransferase, Suv4-20h, is essential for early meiotic progression in mouse oocyte. This work indicates that histone epigenetic modifications in mammals are crucial for proper meiotic progression.
Implantation of the embryo is a crucial step in the reproductive process. Our research focused on the dialogues between blastocyst and endometrium and more particularly on the expression of Luteinising Hormone and Luteinising Hormone Receptor at the time of implantation in mice. Better understanding of these proteins interactions could improve our understanding of implantation and might have a major impact on infertility by the validation of a mouse model.
RD11284Effect of duration of the growing phase of ovulatory follicles on oocyte competence in superstimulated cattle
How can we improve oocyte competence after superstimulation? To answer this question, we tested two durations (4 and 7 days) of follicular growth with or without FSH support at end of the treatment (i.e. FSH starvation). The duration of follicular growth did not affect oocyte competence; however, FSH starvation compromised ovulation capability. Therefore, follicular age does not alter oocyte competence but follicles are dependent of gonadotropins to ovulate.
RD11295Effect of feeding level on luteal function and progesterone concentration in the vena cava during early pregnancy in gilts
High feed levels are generally reported to reduce systemic progesterone in gilts, but conclusions about the effects on embryo survival are inconsistent. This paper shows that progesterone in utero–ovarian venous blood (local circulation), is pulsatile and much higher than systemic progesterone, and is increased on a higher feed level. This differential effect of feed level on local versus systemic circulation may explain the inconsistent findings between studies in regards to embryo survival.
Ovulation is essential for reproduction. It is induced by a sequence of events that allows pregnancy to occur. The objective of this study was to understand where the hormone angiotensin II fits into this cascade of events. We conclude that angiotensin II is a key hormone for ovulation, acting as one of the earliest players of this process and eliciting increases in progesterone and prostaglandin secretion that are important for ovulation.
RD12127Spermatogenesis is seasonal in the large hairy armadillo, Chaetophractus villosus (Dasypodidae, Xenarthra, Mammalia)
Armadillo reproduction differs between species: in one species, females deliver only twins, yet in another embryos undergo developmental arrest. The big hairy armadillo, Chaetophractus villosus, is one of the most widespread throughout South America. Herein, we describe spermatogenesis in this species, demonstrating a block in sperm production from mid-May to July (mid–end autumn), evidence of seasonal reproduction. The findings of the present study may contribute towards the reproductive control of a species that causes agricultural damage and is a reservoir for Chagas disease and Trichinella infection.
RD12029Structure, histochemistry and ultrastructure of the male reproductive accessory glands in the neotropical flat-faced fruit-eating bat Artibeus planirostris (Chiroptera: Phyllostomidae)
Several factors influence the Chiroptera reproduction, thus bats evolved different reproductive features. This study aimed to characterise the reproductive accessory glands (RAGs) in a neotropical bat. The RAGs are composed by prostatic complex, paraurethral and bulbourethral glands, but no seminal vesicles. Morphological data demonstrated the holocrine nature of the ventral prostate, which never having been described previously for this gland. Our findings demonstrate the wide discrepancy of RAGs between Artibeus planirostris and other mammals in terms of their morphological composition.
RD11287Expression patterns of activin, inhibin and follistatin variants in the adult male mouse reproductive tract suggest important roles in the epididymis and vas deferens
Activin is an important regulator of growth and immune responses. In the adult mouse, an inverse relationship was found between the production of activin and its binding protein follistatin in different regions of the male reproductive tract. This suggests that a reciprocal regulatory relationship involving activin and follistatin controls reproductive development, fertility and resistance to infectious disease in the male reproductive tract.
RD12055Factors affecting reproductive performance of white-tailed deer subjected to fixed-time artificial insemination or natural mating
In recent years the use of artificial insemination in white-tailed deer hunting ranches has markedly increased, because producers obtain higher prices with high-scoring bucks. The main objective of this study was to compare the efficacy of two insemination techniques in these animals. Results indicate that insemination of frozen–thawed semen via the cervix would be advantageous for use in white-tailed deer because it is easier, faster, more cost effective and less invasive than uterine insemination using surgery.