Skip navigation. In the book, Moore argues that regulation of sex differentiation in mammals is not controlled by sex hormones secreted by embryonic sex organs gonads , but is controlled by non-hormonal genetic factors. In support of his hypothesis, Moore describes the current literature on sex differentiation , and he reviews experiments on vertebrates and invertebrates and his own work with opossum Didelphis virginiana young. The first section of the book, Moore discusses sex differentiation. He explains that once an organism approaches puberty or the beginning of its reproductive life, hormones secreted by the gonads influence the reproductive system's functions and development of secondary sex characteristics.
However, Moore argues that scientists couldn't describe the physiological control over such development, which despite genetic sex determination , permits gradations of sex characteristics in degrees from typical male to typical female. Born with a normal male twin, a freemartin is a sterile cow that has external female genitalia and internal male gonads. Lillie theorized that the freemartin is a genetic female whose internal sex differentiation was suppressed or antagonized by her twin's release of male hormones via their shared blood circulation.
Lillie's study of freemartins led to the theory that gonadal sex hormones partly caused hermaphroditism.
After s suggestion from Lillie, Moore began his research in to create hermaphrodites in the laboratory to test Lillie's theory. Moore reviews his experiments over the course of thirty years with rats, guinea pigs, and, opossums, studies that led him to conclude that hormones released by the embryonic gonads didn't cause the reproductive system to differentiate from other tissues, and that something else did, an interpretation contrary to Lillie's assertion.
In the third section, Moore reviews experiments in which researchers attempted to modify sexual development using living tissues and hormonal extracts from testes and ovaries. In the analysis of experiments using living tissues, Moore concludes that some animals, such as amphibians and some pigs, could develop just as freemartins in cows do.
He next assesses experiments using hormonal extracts and concludes that while birds , fish , and amphibians , which are all non-placental animals, exhibit gradations of sex differentiation when exposed to hormonal extracts. Moore then describes experiments using hormonal extracts with placental mammals, and he reports that the experiments yielded a variety of atypical conditions.
Bovine Embryonic Development to Implantation
Moore concludes that those results could have been caused by the alteration of the hormones delivered in utero either by some interaction with the mother or because of an injury to the placentas. To investigate such possibilities, Moore began his research on the opossum in , at the Marine Biological Institute. The fourth section details Moore's experiments with opossums and the results from those experiments. Moore claims that he chose the opossum because he could avoid the risk of injuring opossums when he interacted with pregnant opossums while the young were in utero , and because the reproductive systems of opossum young are not differentiated at birth.
Opossums are born after thirteen days of gestation and spend the next sixty-five to seventy days attached to the nipple located in the mother's pouch. In his initial experiments, Moore treated the young with hormonal creams until thirty days after birth.
chapter and author info
Moore concludes from these experiments that androgen cream stimulated the male reproductive system in both sexes, with a slightly greater effect in genetic males than in genetic females. The androgen cream, according to Moore, also stimulated female Mullerian ducts but did not inhibit ovarian development in females. Estrogen treatments, Moore asserts, did not change the differentiation of either sex, but did stimulate the growth of male Wolffian and female ducts in each sex.
Moore also treated opossum young with hormones that stimulate gonads gonadotropins , and he states that such treatment failed to produce appreciable amounts of sex hormones from the gonads.
He concludes that in opossum young, sex differentiation is visible at day thirty but the gonads are incapable of secreting hormones until day seventy in males and day in females, gonadal hormones play a significant role in sex differentiation. Moore then describes the procedures he used to surgically remove the gonads on opossum young without detaching them from the mother's nipples.
He determines that even though the gonads are removed, the reproductive system of the opossum proceeds normally until the stage of development when the male and female systems are established. He cites the experiments as further evidence that the sex differentiation of the opossum does not depend on the hormonal secretion of the ovaries or the testes. In the fifth section, Moore discusses his results and their implications for the study of sex differentiation in vertebrates more generally.
Out of 63 samples, 6 did not yield sufficient RNA and thus could not be analysed further. The primer efficiency was tested by a dilution series and their amplicons were sequenced MWG Operon Eurofins Genomics. There was no significant effect of egg treatment F 2, All samples were run on one plate. The intra-assay coefficient of variation was 7. Brown, C. Maternal triiodothyronine injections cause increases in swimbladder inflation and survival rates in larval striped bass, Morone saxatilis. Radder, R. Maternally derived egg yolk steroid hormones and sex determination: review of a paradox in reptiles.
Maternal hormones in avian eggs. David O. Norris and Kristin H. Groothuis, T. Maternal hormones as a tool to adjust offspring phenotype in avian species.
You and Your Hormones
Gil, D. Hormones in avian eggs: Physiology, ecology and behavior. Study Behav. Del Giudice, M. Fetal programming by maternal stress: Insights from a conflict perspective. Psychoneuroendocrinology 37 , — Braun, T. Early-life glucocorticoid exposure: The hypothalamic-pituitary-adrenal axis, placental function, and longterm disease risk. Schwabl, H.
Yolk is a source of maternal testosterone for developing birds. USA 90 , — Hormone mediated maternal effects in birds: mechanisms matter but what do we know of them? B-Biological Sci. Paitz, R. Embryonic modulation of maternal steroids in European starlings Sturnus vulgaris. Kumar, N. Early embryonic modification of maternal hormones differs systematically among embryos of different laying order: A study in birds. Avian yolk androgens are metabolized instead of taken up by the embryo during the first days of incubation.
Cardio-respiratory development in bird embryos: new insights from a venerable animal model
Evolution and development of fetal membranes and placentation in amniote vertebrates. Pfannkuche, K. Examining a pathway for hormone mediated maternal effects — Yolk testosterone affects androgen receptor expression and endogenous testosterone production in young chicks Gallus gallus domesticus.
Smith, C. Gonadal sex differentiation in chicken embryos: Expression of estrogen receptor and aromatase genes. Steroid Biochem.
- Book Hormones And Embryonic Development Advances In The Biosciences .
- Hormones and Embryonic Development.
- The Blackwell Encyclopedic Dictionary of Marketing (Blackwell Encyclopedia of Management);
- Hormones and Embryonic Development - 1st Edition;
- chapter and author info.
- Looking for other ways to read this??
Yoshida, K. Expression of P 17 alpha hydroxylase and P aromatase genes in the chicken gonad before and after sexual differentiation. Gen Comp Endocrinol , — Woods, J.
Plasma testosterone levels in the chick embryo. Characterizing the distribution of steroid sulfatase during embryonic development: when and where might metabolites of maternal steroids be reactivated? Gasc, J. Androgen target cells in the pituitary of the chick embryo. Endo, D. Estrogen target cells in gonads of the chicken embryo during sexual differentiation.
Andrews, J. Sites of estrogen receptor and aromatase expression in the chicken embryo. Guennoun, R. Brain Res. Albergotti, L.
PLoS One 4 , e—e Pavlik, A. Griffith, O. Comparative genomics of hormonal signaling in the chorioallantoic membrane of oviparous and viviparous amniotes. Grzegorzewska, A.
- MIND GAMES?
- 8.5 Control of the embryonic development!
- Working with interpreters and translators : a guide for speech-language pathologists and audiologists?
- Work Rules!: Insights from Inside Google That Will Transform How You Live and Lead!
Folia Biol. McNatt, L. Cruze, L. Evidence of steroid hormone activity in the chorioallantoic membrane of a Turtle Pseudemys nelsoni. Nowak-Sliwinska, P. The chicken chorioallantoic membrane model in biology, medicine and bioengineering. Angiogenesis 17 , — Byerly, T. Growth of the chick embryo in relation to its food supply. Hsu, T. Kim, S. Interaction of steroid receptor coactivators and estrogen receptors in the human placenta. Filiberto, A. Birthweight is associated with DNA promoter methylation of the glucocorticoid receptor in human placenta. Epigenetics 6 , — Mparmpakas, D.
Differential expression of placental glucocorticoid receptors and growth arrest-specific transcript 5 in term and preterm pregnancies: evidence for involvement of maternal stress. Saif, Z. Identification of eight different isoforms of the glucocorticoid receptor in Guinea pig placenta: Relationship to preterm delivery, sex and betamethasone exposure. PLoS One 11 , e Carere, C. Sexual versus individual differentiation: the controversial role of avian maternal hormones. Trends Endocrinol. Winkler, D. Testosterone in Egg-Yolks - an Ornithologists Perspective.
Mock, D. Auk , — Wilson, A. Selection on mothers and offspring: Whose phenotype is it and does it matter? Evolution N. Manipulative signals in family conflict? On the function of maternal yolk hormones in birds. R Core Team.