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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.
Culture of Chinese Carp
Published in Karol Opuszynski, Jerome V. Shireman, HERBIVOROUS FISHES: Culture and Use for Weed Management, 2019
Karol Opuszynski, Jerome V. Shireman
The physiological mechanisms that control fish reproduction processes are relatively well known. Because these processes involve both the nervous and endocrine systems, the mechanisms are singly called the neurohormonal mechanism of fish reproduction. Environmental stimuli of reproductive importance (see Chapter 3) or genetically imprinted internal cycles stimulate a portion of the brain called the hypothalamus (Figure 28). The hypothalamus produces gonadotropin-releasing hormone (GnRH) and gonadotropin release-inhibiting factor (GRIF) (dopamine). Gonadotropin-releasing hormone stimulates the pituitary (hypophysis), a small gland located beneath the brain, to produce and release gonadotropic hormones (GtH), which target the gonads (ovaries and testes). Elevated blood levels of GtH cause final maturation of the sex products through local action of the steroid hormones (progesterone stimulates final maturation of the eggs and testosterone stimulates spermiation). Prostaglandins act as local ovarian mediators of the ovulatory action of GtH. They play a role in the final stages of ovulation, including rupture of the follicle and expulsion of the mature oocyte.
Reproduction, development and work
Published in Chris Winder, Neill Stacey, Occupational Toxicology, 2004
However, in the reproductive process specialised cells that contain half the normal complement of genetic material are produced (that is one set of 23 chromosomes, not 23 pairs). These specialised cells are called gametes, are unique to the reproductive organs (gonads), and comprise spermatozoa in the male and ova in the female. The process of producing these cells (that is producing gametes with half the genetic material) is different from mitosis, and is called meiosis.
Spawning time in adult polar cod (Boreogadus saida) altered by crude oil exposure, independent of food availability
Published in Journal of Toxicology and Environmental Health, Part A, 2023
Leah C. Strople, Ireen Vieweg, Fekadu Yadetie, Derrick Kwame Odei, Anders Thorsen, Odd André Karlsen, Anders Goksøyr, Lisbet Sørensen, Antonio Sarno, Bjørn Henrik Hansen, Marianne Frantzen, Øyvind J. Hansen, Velmurugu Puvanendran, Jasmine Nahrgang
Here we tested the hypothesis that in-vivo crude oil exposure would alter the natural reproductive development of sexually mature adult polar cod and that lower food availability may further compromise the reproductive outcome. We exposed polar cod to a water-soluble fraction of crude oil for 131 days starting when polar cod were in a late stage of reproductive development until the post-spawning phase. We assessed somatic indices (gonadosomatic index (GSI) and hepatosomatic index (HSI)), gonad histology (reproductive phase and atresia), steroid hormones levels (E2, T, 11-KT), hepatic mRNA expression, (cytochrome P450 1A (cyp1a), vitellogenin (vtg α), estrogen receptor 1 (esr1), transcriptome response), sperm motility and PAH body burden. Based on previous studies, we predicted an up-regulation in genes involved in hepatic biotransformation, a delay in reproductive development, decreases in steroid hormone levels, a reduction in the expression of genes in the estrogen pathway, decreased sperm motility, and parental transfer of PAHs to eggs.
A suggested bisphenol A metabolite (MBP) interfered with reproductive organ development in the chicken embryo while a human-relevant mixture of phthalate monoesters had no such effects
Published in Journal of Toxicology and Environmental Health, Part A, 2020
Anna Mentor, Carl-Gustaf Bornehag, Maria Jönsson, Anna Mattsson
Representative images of control and MBP-exposed embryos of both sexes are illustrated in Figure 1 and the left and right gonad sizes of all groups are shown in Figure 2. Control females exhibited a large left and a small, largely regressed, right ovary. Control males showed two testes of similar size and shape. The mean left ovary area was significantly smaller in MBP-exposed females than in control females (Figure 2(a)) and in several MBP-exposed individuals the ovary appeared thinner than controls. On average, the right testis was significantly smaller and the left testis significantly larger in MBP-exposed males than in control males (Figure 2(c)). All males exposed to MBP developed a left ovotestis, as assessed by the shape and structure of the left gonad. Four out of 12 MBP-exposed males were feminized to the degree that they were mistaken for females at the visual inspection during the dissection. These were determined to be males by genetic sex determination. In mixture-exposed embryos, the gonads appeared unaffected and the mean gonad area did not differ markedly from that of the control group in either of the sexes.