Bioscientifica Proceedings

The cervids represent a complex assemblage of taxa characterized by extreme diversity in morphology, physiology, ecology and geographical distribution. Farmed species (for example red deer and fallow deer) are usually the common larger-bodied, gregarious and monotocous species that express marked reproductive seasonality in their temperate environment. Their commercial importance has facilitated considerable research into reproductive physiology and the development of assisted...

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...

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Summary. Identical twin pairs of dairy cows (one twin being placed with 4 calves for multiple suckling while the other was machine milked) were used to study the hormonal changes associated with anoestrus. Experiments were conducted to examine the effect of multiple suckling on the interval to first oestrus post partum, concentrations of LH and progesterone post partum, and the LH response to LH-RH or oestradiol-17β. The effects of hormo...

Melatonin, which is synthesized at night by the pineal gland, is present in the cerebrospinal fluid (CSF), but its entry site and its role in this compartment are not known. Using several approaches, we tested the hypothesis that melatonin enters the CSF through the pineal recess, an evagination of the third ventricle. CSF melatonin concentrations are higher near the pineal gland than in the anterior part of the third ventricle, and decrease markedly (80%) after sealing of...

In sheep, as in other mammals, ovarian follicular growth is regulated mainly by intraovarian growth factors during early development with pituitary hormones increasingly important during the final phases to ovulation. Most follicles are present as primordial structures and these express many hundreds of genes that fulfil an array of housekeeping and signalling functions. Once growth has been initiated, at least two oocyte-derived growth factors, namely growth differentiation f...

In ruminants, more than 30% of the embryonic losses observed after artificial insemination (AI) have an early origin, coincident with a marked elongation of the trophoblast which occurs before implantation. Several observations provide clear evidence that early elongation of the conceptus relies on cell multiplication, cell growth and cell shape remodeling. Recent results indicating an intense multiplication of a non-fully differentiated trophoblast, which still expresses ...

Summary. Numerous biological and practical lessons associated with the use of sexed semen have been learnt in the 15 years since it was released onto the commercial market. Over this time, concerns regarding the safety of sex-sorted spermatozoa have been largely allayed through the birth of several million pre-sexed calves, but the major issue that remains is that of reduced fertility. Numerous studies have demonstrated that the process of flow cytometric sort...

Ruminant placentae produce at least two distinct subclasses of the growth hormone/prolactin gene family, the placental lactogens and prolactin-related proteins. Placental lactogens have been purified from cattle, goat and sheep placentae, and the amino acid sequences of bovine and ovine placental lactogen are known. Bovine and ovine placental lactogens are structurally more similar to prolactin than they are to growth hormone. In addition, six unique mRNAs have been described ...

Determining the stage- and tissue-specific patterns of gene expression shown by the embryo and fetus will provide information about the control of normal development. Identification of alterations in these patterns associated with specific abnormal phenotypes will also be informative regarding the underlying molecular mechanisms. In addition, qualitative and quantitative changes in gene expression that deviate from the norm may provide a potential marker system for predicting ...