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Toxic Responses of the Female Reproductive System
Published in Stephen K. Hall, Joana Chakraborty, Randall J. Ruch, Chemical Exposure and Toxic Responses, 2020
Joana Chakraborty, Maureen McCorquodale
The process of germ cell production in the female is called oogenesis. In human females oogenesis starts long before birth. During the development of the ovary, germ cells undergo repeated mitoses. At 2 months gestation, the female embryo contains a large number of germ cells; some are called stem cells and others are called oogonia. Some of these oogonia enter meiosis and become primary oocytes. The primary oocytes do not have the capacity to proliferate. These cells reach the “diplotene” stage of first meiotic prophase before or shortly after birth. Shortly after the onset of the diplotene stage, oocytes embark on a prolonged “quiescent” phase, which lasts until division is resumed during oocyte maturation and shortly before ovulation. Therefore, at the time of birth, the ovaries of a human female will contain a finite number of oocytes. If these oocytes are damaged or lost, for example, due to exposure to hazardous chemicals or radiation, they cannot be replaced from stem cells and as a result the woman will be infertile for the rest of her life. If chemical or radiation injury causes chromosomal damage to the oocytes, this damage will last for a lifetime since there will be no new oocyte formation. At the time of puberty, a pool of primordial follicles grows into a pool of growing follicles. At the onset of this growth, the oocytes start to enlarge. The surrounding follicular cells divide to become several layers thick and secrete a glycoprotein material which forms an acellular layer surrounding the oocytes, called the zona pellucida. The follicular cells are called granulosa cells. Changes occur in the surrounding stromal cells which are now called theca. Some follicles grow to become preantral follicles while others undergo degeneration. This process of degeneration is prevented only if adequate follicle stimulating hormone (FSH) and luteinizing hormone (LH) are available and if the release of these gonadotropic hormones coincides with the development of FSH and LH receptors on the granulosa and thecal cells. Thecal cells divide into two distinct layers: a highly vascularized, glandular layer which is called the theca interna, and a fibrous capsulated area called the theca externa which surrounds the first layer. Granulosa cells start to secrete a fluid. Drops of this fluid coalesce to form follicular fluid within a space called the follicular antrum. At this stage, the granulosa cells surrounding the primary oocytes are called the cumulus oophorus. The primary oocytes remain suspended in the follicular fluid connected only by a thin stalk of cells to the peripheral granulosa cells. These follicles are called antral follicles. With the terminal development of antral follicles in which both theca and granulosa cells can bind LH, the follicles enter into a preovulatory growth phase. During this process the follicles enlarge leading to the expulsion of the oocytes from the follicles. This process is called ovulation. When the secondary oocytes enter into the fallopian tube at the time of ovulation, they are surrounded by layers of granulosa cells, now called corona radiata cells.
Increasing cannabis use and importance as an environmental contaminant mixture and associated risks to exposed biota: A review
Published in Critical Reviews in Environmental Science and Technology, 2022
Emily K. C. Kennedy, Genevieve A. Perono, Dion B. Nemez, Alison C. Holloway, Philippe J. Thomas, Robert Letcher, Chris Marvin, Jorg Stetefeld, Jake Stout, Oliver Peters, Vince Palace, Gregg Tomy
Investigation into the effects of increased cannabis usage on the aquatic environment is a relatively new field of research. By consequence, there are many potential toxicological mechanisms of action that have yet to be explored in aquatic organisms. Endocrine disrupting chemicals are known to adversely affect wild fathead minnow populations (Kidd et al., 2007) and, based on research conducted in other species, cannabinoids and their metabolites have the potential to interfere with a variety of endocrine-related systems. There is evidence that endocannabinoids are involved in many processes related to female and male reproduction. The ECS is expressed across reproductive cells and tissues including the testis, prostate, sperm, ovary, uterus, placenta, and hypothalamic-pituitary-gonadal (HPG) axis; influencing signals mediated by sex hormones like estrogen, androgen and progesterone (Battista et al., 2012; Dobovišek et al., 2016; Gammon et al., 2005; Schuel et al., 2002; Walker et al., 2019). The complex interplay between endogenous endocannabinoids and their receptors are critical for normal reproductive function; these processes, including spermatogenesis, oogenesis, embryonic development, placentation, fertility, and folliculogenesis, may be perturbed in the presence of exogenous ligands such as Δ9-THC and CBD (Amoako et al., 2013; El-Talatini et al., 2009; Grimaldi et al., 2009; Maia et al., 2019; Walker et al., 2019). Additionally, other hormones such as glucocorticoids can modulate the HPG axis (Reviewed in: (Geraghty & Kaufer, 2015), and cannabinoids have been shown to influence glucocorticoid receptor (GR)-mediated signaling making it plausible that cannabinoids can adversely affect reproductive behavior and physiology via GR (Eldridge et al., 1991; Natale et al., 2020; Whirledge & Cidlowski, 2010).