Bioscientifica Proceedings

Summary. In Exp. 1, sheep fetuses (2 male and 3 female) were gonadectomized between Days 70 and 120 of gestation and their blood LH and FSH levels were compared to those of control animals (4 male, 6 female) at regular times during the first year after birth. In Exp. 2. fetuses (3 male and 5 female) were gonadectomized between Days 50 and 60 of gestation and gonadotrophin levels at Day 90 of gestation were compared to those of control fetuses of the same age. ...

Summary. An inadequate luteal phase occurs in domestic ruminants in several physiological situations (e.g. puberty, post partum), and also following the induction of ovulation in anoestrous ewes with GnRH treatment. The induced corpora lutea (CL) initially developed, but then regressed rapidly after Day 4, unless the animals had been primed with progesterone before GnRH therapy or hysterectomized. Significant increases in prostaglandin F-2α metab...

In domestic ruminants the parenchyma of the corpus luteum consists of two subpopulations of steroidogenic cells commonly referred to as small and large luteal cells. These cells differ not only in size and structural characteristics, but also in functional properties. During the mid-luteal phase of the oestrous cycle approximately 60% of the corpus luteum is occupied by steroidogenic cells. Although the steroidogenic capacity of these cells declines as pregnancy advances, ...

We have investigated whether the maternal melatonin rhythm provides the fetus with either a circadian or seasonal ‘signal’ during development. Our findings provide evidence that melatonin can generate and entrain the early evening peak in the daily rhythm of fetal breathing movements. In contrast, daily variations in maternal and fetal prolactin concentrations are present in pinealectomized ewes, are altered by changes in the time of onset of darkness, but are unal...

During early pregnancy the bovine embryo must produce a protein called interferon τ which inhibits the development of the luteolytic mechanism. Failure to inhibit luteolysis is the major cause of pregnancy loss in cows. The embryo must produce sufficient quantities of interferon τ by about day 16 to prevent luteolysis. Its ability to achieve this is largely dependent on the pattern of maternal progesterone production. A late rise in progesterone after ovulation or po...

The ovine conceptus releases interferon-τ (IFNT), which prevents upregulation of the endometrial estrogen receptor (ESR1) and, consequently, oxytocin receptor (OXTR), thereby disrupting pulsatile release of prostaglandin F2α (PGF) in response to oxytocin. IFNT, through paracrine action on the endometrium, protects the corpus luteum (CL) during maternal recognition of pregnancy. Pregnancy also induces IFN stimulated genes (ISGs) in peripheral blood mononuclear cells (...

Summary. Transcriptome studies of the bovine endometrium during early pregnancy and during the estrous cycle have been performed using DNA microarrays and RNA sequencing to identify genes associated with establishment and maintenance of pregnancy. The results of these studies are reviewed and the identified differentially expressed genes (DEG) are compared to define the overlaps between studies and technical platforms. Good overlaps were found for upregulated ...

In mammals, testicular differentiation is initiated by SRY (the sex-determining region of the Y chromosome) gene expression in Sertoli cell precursors, followed by upregulation of the SOX9 gene (SRY-related HMG box gene 9). Subsequently, differentiated testis produces two hormones that induce sexual differentiation of the internal and external genital tract. Knowledge of the molecular mechanisms involved in gonadal differentiation has increased greatly over the past deca...

Timing of conceptus growth and attachment to the uterine luminal epithelium is regulated by progesterone secretion from the corpus luteum and by expression of progesterone receptor in the uterine epithelia and stroma. Conceptus growth and uterine attachment are temporally associated with the disappearance of progesterone receptors from uterine epithelia. While the loss of progesterone receptor from the endometrial epithelia on day 10 of the oestrous cycle and pregnancy h...

In the wild, the pig adapts her reproductive functions according to the seasonal changes in the environment, such as the ambient temperature and availability of food. Like in other short day seasonal breeders, breeding season is favoured in the mid winter in order to provide the offspring with the best chances to survive four months later Seasonal changes in environment are perceived mainly by the ability of the pig to recognise seasonal changes in photoperiod. This info...