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Reprotoxic and Endocrine Substances
Published in Małgorzata Pośniak, Emerging Chemical Risks in the Work Environment, 2020
Katarzyna Miranowicz-Dzierżawska
Gonads (female – ovaries, male – testicles) perform two functions: (1) endocrine, involving the release of sex hormones and (2) non-endocrine, involving the production of reproductive cells (gametes). Gametogenesis, the process in which reproductive cells (male and female gametes) are formed through precursor cell division and differentiation, as well as endocrine functions of both ovaries and testicles, is dependent on glycoprotein molecules – gonadotropins, synthesized and released from the anterior pituitary lobe: follicle-stimulating hormone (follitropin, FSH), and luteinizing hormone (lutropin, LH). LH and FSH bind to receptors in ovaries and testicles, where they regulate the gonadal function.
Reproduction
Published in Alan G. Heath, Water Pollution and Fish Physiology, 2018
Sex pheromones are secreted externally and affect conspecifics. Some actually serve as hormones within the individual thus coordinating both gametogenesis and spawning behavior. The pheromones may be steroids or prostaglandins and are detected by the olfactory system (Stacey, 1991). Because a number of pollutant chemicals have been shown to reduce the sensitivity of the olfactory system (see Chapter 12), this might be a mechanism by which chemicals could reduce spawning success, although there is currently no experimental evidence on this.
The human embryo in vitro
Published in The New Bioethics, 2022
It is then in Part III, ‘out of liminality’, where McMillan brings forward the lessons that can be learned from Part II. In other words, she considers possible ways the legal problem exposed in Part I can be addressed. In chapter 7, she discusses the three topical issues of in vitro gametogenesis, the fourteen-day rule and partial ectogenesis via artificial womb technologies. Particularly she offers suggestions as what the law could do to address the purgatory, not necessarily what the law should do. While proposing a context-based approach, there is no ultimate solution provided for these three areas. These issues seem to be intentionally left open by the author, whose idea seem to be more leaning towards the provision of a different set of possible questions, particularly at the end of chapter 7, through which she proposes to analyse the legal challenge of Part II. For instance, she provides a set of questions concerning how the law could address the distinction between reproductive and research embryos: ‘Firstly, if there are thresholds within reproductive and/or research processes beyond which embryos or IVG [in vitro gametes] gametes cannot be returned (to another pathway) should we more explicitly delineate ‘research’ embryos from ‘reproductive’ embryos in law? If so, how might this be done? Is the reproductive and therapeutic distinction a clear line in the sand for gamete (and embryo) research, still desirable?’ (p. 204).
Sunni Islamic perspectives on lab-grown sperm and eggs derived from stem cells – in vitro gametogenesis (IVG)
Published in The New Bioethics, 2023
Gamal Serour, Mohammed Ghaly, Shaikh Mohd Saifuddeen, Ayaz Anwar, Noor Munirah Isa, Alexis Heng Boon Chin
One of the most exciting developments in regenerative and reproductive medicine is in vitro gametogenesis (IVG). IVG involves reconstitution of germ cell development from pluripotent stem cells in the laboratory. Studies, mainly in rodents, have shown that IVG can produce functional gametes. Mouse embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have shown to be capable of differentiating into primordial germ cell-like cells (PGCLCs) in vitro (Zhang et al.2020). Later, the PGCLCs can be developed into fully functional sperm and eggs upon transplantation into the appropriate reproductive organs. Hayashi et al. (2012) reported that healthy offspring were produced from stem cell derived oocytes that underwent in vitro fertilization. Studies in 2016 showed that functional mouse oocytes can be generated in vitro from skin cells, without having to be transplanted in the mouse ovaries (Cyranoski 2016). Also in 2016, researchers at the Institute of Zoology of the Chinese Academy of Sciences produced functional sperm from the skin-derived stem cells of mice that was able to generate healthy offspring (Zhou et al.2016). In 2021, scientists successfully reconstituted mouse ovarian follicles in vitro that could be used to generate an appropriate somatic environment to support development of oocytes in culture (Yang and Ng 2021, Yoshino et al.2021). More recently, Lee et al. (2022) developed a different technique involving taking a denucleated egg cell and injecting nuclear DNA from a skin cell. Then the cell was prompted to lose half its chromosomes so that it became a haploid egg cell which can combine with a haploid sperm cell. Yet another recent development is the derivation of functional sperm from rat stem cells that can generate viable offspring, a feat that was previously possible only with mice (Oikawa et al.2022).