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Biological Control of Vertebrates
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Biological and Ecological Systems, 2020
Biological controls that inhibit reproduction or development are an attractive target for pest control. Virally vectored immunocontraception (VVIC) aimed to use a genetically engineered transmissible agent to deliver an immunocontraceptive antigen to a pest species. Infection with the recombinant organism would stimulate an immune response to the immunocontraceptive antigen which would block fertility. Potential antigens include components of sperm, the zona pellucida surrounding the egg or peptide hormones such as gonadotrophin-releasing hormone. Direct injection of such antigens is already used in some wildlife population control programs (Naz and Saver 2016). However, direct injection is not feasible for control of widespread invasive species such as rabbits, mice and foxes.
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.
Biological Responses in Context
Published in Arthur T. Johnson, Biology for Engineers, 2019
There is a complex interplay of different hormones in the female, and this is often unique to a particular species or class of species. For instance, humans and many other primates undergo a menstrual cycle, wherein the egg is matured, and the uterine lining is prepared for implantation of the fertilized egg. Hormones participating in this process are gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), estrogens, and progesterone. Others, such as oxytocin and prostaglandins, play a role in the birth process. Other mammals have an estrus cycle different from the menstrual cycle. Birds, amphibians, and insects undergo different processes. The common characteristic of these cycles, however, is the preparation of the egg (or eggs) for fertilization.
The combined effects of noise and vibration stress on sex hormone levels, fertility capacity, and the protective role of cinnamon extract in rats: an experimental study
Published in Archives of Environmental & Occupational Health, 2022
Hamideh Pirami, Ali Khavanin, Farshad Nadri, Ali Tajpoor, Younes Mehrifar, Zohreh Mazaheri Tirani
The gonadotropin releasing hormone (GnRH) is secreted in the hypothalamus and stimulates the release of LH and FSH from the anterior pituitary gland. LH is the main stimulus for testosterone secretion and FSH mainly stimulates spermatogenesis.51 Stress can reduce GnRH release by affecting the hypothalamus and reducing LH and FSH secretion. On the other hand, stress reduces the pituitary's ability to respond to GnRH. The results of the present study confirmed that stress can inhibit GnRH release by activating inhibitory pathways connected to GnRH nerve endings in the median eminence, thereby reducing LH and FSH secretion.52
How the quest to improve sheep reproduction provided insight into oocyte control of follicular development
Published in Journal of the Royal Society of New Zealand, 2018
Ovarian follicular growth and ovulation is controlled by complex communication among the hypothalamus, pituitary, ovary and uterus (Figure 2). The hypothalamus secretes gonadotrophin releasing hormone (GnRH), which acts on the pituitary to cause synthesis and release of the gonadotrophins, follicle stimulating hormone (FSH) and luteinising hormone (LH) (Clarke & Arbabi 2016). In turn, FSH and LH act on cells in the ovarian follicle to support its growth and maturation (Webb & Campbell 2007). Initially, FSH acts on granulosa cells to stimulate proliferation and differentiation. LH stimulates production of androstenedione from the theca that then is used as a substrate by granulosa cells to produce oestradiol. As the follicle grows, increased amounts of inhibin are also produced by the granulosa cells and, together with oestradiol, these feedback to the pituitary to inhibit FSH synthesis and release (Webb & Campbell 2007). Oestradiol, as well as progesterone produced by the corpus luteum, also inhibit GnRH release from the hypothalamus, suppressing the release of the gonadotrophins (Goodman et al. 2002). However, as the follicle continues to grow, the granulosa cells mature and they begin to express LH receptors (LHR). FSH concentrations fall during selection of the follicles that will go on to ovulation. Follicles that are mature enough to express LHR on the granulosa cells are able to survive through the additional support of LH, as FSH concentrations are suppressed. Less mature gonadotrophin dependent follicles, that have yet to express LHR on the granulosa cells, die in this environment. The mature follicles continue to grow and synthesise increasing levels of oestradiol (Webb & Campbell 2007). During the follicular phase, following the regression of the corpus luteum triggered by release of prostaglandin F2α from the uterus (Niswender et al. 2000), oestradiol reaches a critical threshold. At this stage, oestradiol actually switches from negative to positive feedback, causing the release of the preovulatory gonadotrophin surge (Caraty et al. 1995), and ovulation of the mature follicle(s) (usually one or two in sheep).