The Crosstalk between Melatonin and Sex Steroid Hormones.

Melatonin, an indolamine mainly released from the pineal gland, is associated with many biological functions, namely, the modulation of circadian and seasonal rhythms, sleep inducer, regulator of energy metabolism, antioxidant, and anticarcinogenic. Although several pieces of evidence also recognize the influence of melatonin in the reproductive physiology, the crosstalk between melatonin and sex hormones is not clear. Here, we review the effects of sex differences in the circulating levels of melatonin and update the current knowledge on the link between sex hormones and melatonin. Furthermore, we explore the effects of melatonin on gonadal steroidogenesis and hormonal control in females. The literature review shows that despite the strong evidence that sex differences impact on the circadian profiles of melatonin, reports are still considerably ambiguous, and these differences may arise from several factors, like the use of contraceptive pills, hormonal status, and sleep deprivation. Furthermore, there has been an inconclusive debate about the characteristics of the reciprocal relationship between melatonin and reproductive hormones. In this regard, there is evidence for the role of melatonin in gonadal steroidogenesis brought about by research that shows that melatonin affects multiple transduction pathways that modulate Sertoli cell physiology and consequently spermatogenesis, and also estrogen and progesterone production. From the outcome of our research, it is possible to conclude that understanding the correlation between melatonin and reproductive hormones is crucial for the correction of several complications occurring during pregnancy, like preeclampsia, and for the control of climacteric symptoms.

Evolution of placentation in cattle and antelopes.

Bovids have enjoyed great evolutionary success as evidenced by the large number of extant species. Several important domestic animals are from this family. They derive from both subfamilies: cattle and their kin belong to Bovinae and sheep and goats to Antilopinae. The premise of this review, therefore, is that evolution of reproduction and placentation is best understood in a context that includes antelope-like bovines and antelopes. Many key features of placentation, including hormone secretion, had evolved before bovids emerged as a distinct group. Variation nevertheless occurs. Most striking is the difference in fusion of the binucleate trophoblast cell with uterine epithelium that yields a transient trinucleate cell in bovines and many antelopes, but a more persistent syncytium in wildebeest, sheep and goat. There is considerable variation in placentome number and villus branching within the placentome. Many antelopes have right-sided implantation in a bicornuate uterus whilst others have a uterus duplex. Finally, there has been continued evolution of placental hormones with tandem duplication of PAG genes in cattle, differences in glycosylation of placental lactogen and the emergence of placental growth hormone in sheep and goats. The selection pressures driving this evolution are unknown though maternal-fetal competition for nutrients is an attractive hypothesis.

Evolution of placentation in cattle and antelope

Bovids have enjoyed great evolutionary success as evidenced by the large number of extant species. Several important domestic animals are from this family. They derive from both subfamilies: cattle and their kin belong to Bovinae and sheep and goats to Antilopinae. The premise of this review, therefore, is that evolution of reproduction and placentation is best understood in a context that includes antelope-like bovines and antelopes. Many key features of placentation, including hormone secretion, had evolved before bovids emerged as a distinct group. Variation nevertheless occurs. Most striking is the difference in fusion of the binucleate trophoblast cell with uterine epithelium that yields a transient trinucleate cell in bovines and many antelopes, but a more persistent syncytium in wildebeest, sheep and goat. There is considerable variation in placentome number and villus branching within the placentome. Many antelopes have right-sided implantation in a bicornuate uterus whilst others have a uterus duplex. Finally, there has been continued evolution of placental hormones with tandem duplication of PAG genes in cattle, differences in glycosylation of placental lactogen and the emergence of placental growth hormone in sheep and goats. The selection pressures driving this evolution are unknown though maternal-fetal competition for nutrients is an attractive hypothesis.

Evolution of placentation in cattle and antelope

Bovids have enjoyed great evolutionary success as evidenced by the large number of extant species. Several important domestic animals are from this family. They derive from both subfamilies: cattle and their kin belong to Bovinae and sheep and goats to Antilopinae. The premise of this review, therefore, is that evolution of reproduction and placentation is best understood in a context that includes antelope-like bovines and antelopes. Many key features of placentation, including hormone secretion, had evolved before bovids emerged as a distinct group. Variation nevertheless occurs. Most striking is the difference in fusion of the binucleate trophoblast cell with uterine epithelium that yields a transient trinucleate cell in bovines and many antelopes, but a more persistent syncytium in wildebeest, sheep and goat. There is considerable variation in placentome number and villus branching within the placentome. Many antelopes have right-sided implantation in a bicornuate uterus whilst others have a uterus duplex. Finally, there has been continued evolution of placental hormones with tandem duplication of PAG genes in cattle, differences in glycosylation of placental lactogen and the emergence of placental growth hormone in sheep and goats. The selection pressures driving this evolution are unknown though maternal-fetal competition for nutrients is an attractive hypothesis.(AU)

Modulation of uterine function by endocrine and paracri ne factors in ruminants

Uterine adenogenesis in the neonate is critical as uterine glands are essential for pregnancy in adult ruminants. The uterus is stimulated by estrogens (E2) and progesterone (P4) that prepare it to respond to biochemical signals from the conceptus (embryo/fetus and placenta). Interferon ta u (IFNT) is responsible for pregnancy recognition and modification of uterine gene expression including sensitivity to placental lactogen and placental growth hormone that stimulate development and gene expression by epithelial cells of uterine glands. P4 is permissive for most actions of IFNT. Novel genes are expressed by uterine luminal and superficial glandular epithelia in response to P4 and IFNT as those cells are in direct contact with conceptus trophectoderm. But, uterine glandular epithelium and stromal cells respond to P4 and IFNT by expressing classical interferon stimulat ed genes. Uterine receptivity to implantation requires loss of expression of receptors for P4 and E2 by uterine epithelia. P4 stimulates P4 receptor-positive st romal cells to express fibroblast growth factor 10 (FGF10) and hepatocyte growth factor (HGF) that act via their re spective receptors on uterine epithelia and trophectoderm to regulate cellular functions and gene expression. FGF10 and IFNT are hypothesized to activate complementary cell signaling pathways that modulate expression of genes for implantation, modify phenotype of uterine stromal cells, silence expression of genes for P4 and E2 receptors, signal pregnancy recognition, suppress genes for immune recognition, alter membrane permeability to enhance conceptus-maternal exchange of factors, increase endometrial vascularity, and activate genes for transport of nutrients into the uterine lumen. Those actions are essential for a successful outcome of pregnancy.(AU)

Modulation of uterine function by endocrine and paracri ne factors in ruminants

Uterine adenogenesis in the neonate is critical as uterine glands are essential for pregnancy in adult ruminants. The uterus is stimulated by estrogens (E2) and progesterone (P4) that prepare it to respond to biochemical signals from the conceptus (embryo/fetus and placenta). Interferon ta u (IFNT) is responsible for pregnancy recognition and modification of uterine gene expression including sensitivity to placental lactogen and placental growth hormone that stimulate development and gene expression by epithelial cells of uterine glands. P4 is permissive for most actions of IFNT. Novel genes are expressed by uterine luminal and superficial glandular epithelia in response to P4 and IFNT as those cells are in direct contact with conceptus trophectoderm. But, uterine glandular epithelium and stromal cells respond to P4 and IFNT by expressing classical interferon stimulat ed genes. Uterine receptivity to implantation requires loss of expression of receptors for P4 and E2 by uterine epithelia. P4 stimulates P4 receptor-positive st romal cells to express fibroblast growth factor 10 (FGF10) and hepatocyte growth factor (HGF) that act via their re spective receptors on uterine epithelia and trophectoderm to regulate cellular functions and gene expression. FGF10 and IFNT are hypothesized to activate complementary cell signaling pathways that modulate expression of genes for implantation, modify phenotype of uterine stromal cells, silence expression of genes for P4 and E2 receptors, signal pregnancy recognition, suppress genes for immune recognition, alter membrane permeability to enhance conceptus-maternal exchange of factors, increase endometrial vascularity, and activate genes for transport of nutrients into the uterine lumen. Those actions are essential for a successful outcome of pregnancy.