The Studies That Have Been Done on Folliculogenesis in Ewes - Outline Example

Summary of the studies been done by 3 researchers B.K. Campbell, Helen Picton and Mc Neily on Folliculogenesis in Ewes July 24, Summary of Research A number of researchers have studied the reproduction cycles, and folliculogenesis in Ewes. This document presents the research of Campbell, Pickton, and McNeilly. In a very early research, Cambell (et al. 1989) examined the episodic ovarin inhibin secretion in ewes, and concluded that oestradiol secretion by the ovary is not due to pulses of LH, but brought up by ovarian inhibin secretion. Campbell (et al. 1995; 1997) studied the follicular dynamics, and ovarian steroid secretion of six Finn-Merino Ewes, during the follicular and early luteal phases of the estrous cycle in sheep. Diameter of follicles was measured with serial ultrasound scans, along with gonadotropins and steroids in ovarian venous blood, followed by injection of cloprostenol. Concentration of FSH decreased during follicular growth, while that of LH surged. FSH concentration increased on day 1 and a second batch of follicles with 5 mm diameter emerged. The researchers concluded that preovulatory follicles emerge from large follicle population supported by FSH generation. Building up on this research, Campbell and Baird (1998) examined the antral of follicle development of genetic variation in ovulation rates for different sheep breeds. Two strategies have evolved to help achieve high fertility, the Finnish Landrace and the Fec gene, and these suppress FSH. The research indicated an unidentified gene mutation that brings this effect. An interesting research by Campbell (et al. 2000) helped to develop cortical autograft procedures to restore fertility in aged sheep. The results indicate the FSH helps to modulate folliculogenesis, and it can be used for early follicle and oocyte development. Campbell and Baird (2001) undertook a research to evaluate the local actions, the origin and control of inhibin A in sheep. The research concluded that inhibin A acts as an FSH-responsive marker of granulosa cell differentiation, and that it performs paracrine and autocrine activities. In the same years, Campbell (et al. 2001) examined the role of Booroola gene, an autosomal mutation that influences the ovulation rate, and discovered that it leads to the growth of antral follicles that increases the ovulation rate in sheep. Campbell (et al. 2003) undertook further research on the FecB Booroola gene that acts at the ovary of sheep, and enhances the sensitivity of the ovaries to stimulation. Examining the FecB (Booroola) gene, Campbell (et al. 2009) presented a paper on the mechanism of action of the FecB mutation at a conference in Pune, India. In another research, Campbell (et al. 2007) examined the use of LH on growth of large preovulatory follicles and hormone secretion in Ewes. The study indicated that LH is required for normal ovulatory follicle development and for the luteal function. Campbell published a number of publications (et al. 2004a; 2004b; 2007) along with other researchers on the subject of folliculogenesis in ewes. The research by Picton is discussed in this paper, since she has done some seminal work on folliculogenesis in Ewes. Picton and McNeilly (1991) in a research on eight Welsh Mountain ewes examined the mean and peak concentration of FSH in the luteal phase. Follicle growth and Gonadotrophin secretion was suppressed by adminstering GnRH agonist buserelin for 5 weeks. The results indicated that all ewes grew large follicles, and further that threshold concentration for FSH is present for individual animals. Picton and Gosden (2000a) experimented with the idea of developing mature oocytes from the small follicles. The researchers initiated follicle growth in situ, and isolated the follicles complexes after they grew into the preantral stages. While more research is needed in this field, the authors conclude that it is possible to produce a fertile gamete by retaining cellular interactions. In another paper (Picton, 2000b) investigates the formation of primordial follicle in Ewes, which are important in the formation of mammal gamete production. Oocytes are developed during the foetal development, and while there is a finite number to the development of oocytes, this places a limit on the fecundity of the ovary. Picton (et al. 2007) studied the carbohydrate metabolism of murine ovarian follicles and oocytes, grown in vitro. During the research, oocyte–cumulus complexes (OCCs) and denuded oocytes was been compared with in vivo ovulated control samples. The conclusions indicate that amount of glucose consumed and lactate produced by the cultured follicles increased with the development. The metabolic state of in vitro developed oocytes are impacted when they are stored in the culture period for a longer period. Picton (et al. 1998; 2005; 2012a; 2012b; 2013) published a number of papers, where the subject of folliculogenesis in ewes is examined. The research McNeilly, one of the early researchers, is discussed in this section with the focus on research on folliculogenesis in ewes. McNeilly (et al. 1990) conducted an experiment to understand the pattern and relation between processes such as secretion of estradiol, inhibin, and androstenedione in the ovary and the concentration of PRL, LH, and FSH, during the estrous cycle of sheep. The experiment was run on six Merino sheep, in which the left ovary was transplanted to the neck. The conclusions indicate the secretion of FSH in the estrous cycle was controlled by estradiol. McNeilly (et al. 1992) studied the secretion of inhibin, oestradiol and androstenedione, in oestrous cycle of 24 Scottish Ewes. The conclusions drawn were that large oestrogenic follicles produce oestradiol, and the release of inhibin was small in relation to the follicle size, and produced by non-oestrogenic and small follicles, while the inhibin secretion rate did not vary. McNeilly (et al. 1993) developed a model for folliculogenesis, based on physiological changes during follicle growth. Five classes of follicles were defined, and these are used to integrate the morphological models for folliculogenesis. Further longitudinal research on this model by McNeilly (et al. 2011) by using the knowledge gained from 15 years of research, examined the sequence from formation of follicles to the growth, atresia and development of ovulatory follicles. The updated model integrates the events during folliculogenesis, and the influence on oocyte quality. McNeilly (et al. 2003) in a research concluded the preovulatory follicles, taken from mutant ewes, are prone to secreting the same quantity of oestradiol, androstenedione, and inhibin A, as wild ewes. This produces the same concentrations of FSH and the conclusions drawn are that the Booroola gene mutation does not alter the gonadotrophin secretion but acts on the ovary. References Campbell, A. K., McNeilly. and Baird, D. T., 1989. Episodic ovarian inhibin secretion is not due to LH pulses in anoestrous ewes. Journal of Endocrinology, 123, pp: 173-179. Campbell, B., Scaramuzzi, R., and Webb, R., 1995. Control of antral follicle development and selection in sheep and cattle. Journal of Reproduction Fertility, 49, pp: 335–350. Campbell, B. K., Souza, C. J. and Baird, D. T., 1997. Follicular dynamics and ovarian steroid secretion in sheep during the follicular and early luteal phases of the estrous cycle. Biology of Reproduction, 56 (2), pp. 483-488. Campbell, B. K. and Baird, D. T., 1998. Follicle selection in sheep with breed differences in ovulation rate. Molecular and Cellular Endocrinology, 145 (1-2), pp. 89–95. Campbell, B. K., Telfer, E. E., Webb, R. and Baird, D. T. 2000. Ovarian autografts in sheep as a model for studying folliculogenesis. Molecular and Cellular Endocrinology, 163 (1-2), pp. 131-139. Campbell, B. K., Souza, C. J., MacDougall, C., McNeilly, A. S. and Baird, D. T., 2001. The Booroola (FecB) phenotype is associated with a mutation in the bone morphogenetic receptor type 1 B (BMPR1B) gene. Journal of Endocrinology, 169, R1- R6. Campbell, B. K. and Baird, D. T., 2001. Inhibin A is a follicle stimulating hormone - responsive marker of granulosa cell differentiation, which has both autocrine and paracrine actions in sheep. Journal of Endocrinology, 169, pp: 333-345. Campbell, B. K., Souza, C. J., Baird, D. T. and Webb, R., 2003. The FecB (Booroola) gene acts at the ovary: in vivo evidence. Reproduction, 126, pp. 101-111. Campbell, B. K., Telfer, E. E., Webb, R. and Baird, D. T., 2004a. Evidence of a Role for Follicle-Stimulating Hormone in Controlling the Rate of Preantral Follicle Development in Sheep. Endocrinology, 145 (4), pp: 341-356. Campbell, B. K., Baird, D. T., Souza, C. D. and Telfer, E. E., 2004b. Long-term ovarian function in sheep after ovariectomy and autotransplantation of cryopreserved cortical strips. European Journal of Obstetrics & Gynecology and Reproductive Biology, 113 (5), pp. S55–S59. Campbell, B. K., Kendall, N. R. and Baird, D. T., 2007. The effect of the presence and pattern of luteinizing hormone stimulation on ovulatory follicle development in sheep. Biology of Reproduction, 76 (4), pp: 719-727. Campbell, B. K., Somchit, A., Khalid, M., Kendall, N. R. and Scaramuzzi, R. J.,2007. The effect of short-term nutritional supplementation of ewes with lupin grain(Lupinus luteus), during the luteal phase of the estrous cycle on the number of ovarian follicles and the concentrations of hormones and glucose in plasma and follicular fluid. Theriogenology, 68 (7), pp: 1037-1046. Campbell, B. K., Baird, D. T. and Marsters, P., 2009. The mechanism of action of the FecB (Booroola) mutation. Proceedings of the Helen Newton Turner Memorial International Workshop held in Pune, Maharashtra, India, 10–12 November 2008, pp: 46-56. Campbell, B. K., Scaramuzzi, J., Baird, D. T., Driancourt, M. A., Dupont, J., Fortune, J. E., Gilchrist, R. B., McNatty, K. P., McNeilly, A. S., Monget, P., Webb, R., 2011. Regulation of folliculogenesis and the determination of ovulation rate in ruminants. Reproduction, Fertility and Development, 23 (3), pp: 444-467. Campbell, B. K., Thomas, F.H., Armstrong, D. G. and Telfer, E. E., Effects of IGF-I bioavailability on bovine preantral follicular development in vitro. 2007. Reproduction, 133, pp: 1121-1128. McNeilly, A. S., Mann, G. E., Baird, D. T. and Campbell, B. K., 1990. The Pattern of Ovarian Inhibin, Estradiol, and Androstenedione Secretion during the Estrous Cycle of the Ewe. Endocrinology, 127 (1), pp. 227–235. McNeilly, A. S., Mann, G. E. and Baird, D. T., 1992. Hormone production in vivo and in vitro from follicles at different stages of the oestrous cycle in the sheep. Journal of Endocrinology, 132, pp: 225-234. McNeilly, A. S., Scaramuzzi, R. J., Adams, N. R., Baird, D. T., Campbell, B. K., Downing. J. A. and Findlay, J. K., 1993. A model for follicle selection and the determination of ovulation rate in the ewe. Reproduction, Fertility and Development, 5(5), pp: 459-478. McNeilly, A. S., Souza, C. J., Campbell, B. K. and Baird, D. T., 2003. Bone morphogenetic proteins and folliculogenesis: lessons from the Booroola mutation. Reproduction, 61, pp: 361-370 McNeilly, A. S., Scaramuzzi, R. J., Adams, N. R., Baird, D. T., Campbell, B. K., Driancourt, M. A., Dupont J., Fortune J. E, Gilchrist, R. B., and Martin G. B. 2011. Regulation of folliculogenesis and the determination of ovulation rate in ruminants. Reproduction, Fertility and Development, 23 (3), pp: 444-467 Picton, H. M. and McNeilly, A. S., 1991. Evidence to support a follicle-stimulating hormone threshold theory for follicle selection in ewes chronically treated with gonadotrophin-releasing hormone agonist. Journal of Reproduction and Fertility, 93, pp: 43-51. Picton, H. M., Briggs, D., and Gosden, R., 1998. The molecular basis of oocyte growth and development. Molecular Cell Endocrinology, 145, pp: 27-37. Picton, H. M. and Gosden, R. G., 2000a. In vitro growth of primordial follicles from frozen banked ovarian tissue. Molecular Cell Endocrinology, 166, pp: 27-35. Picton, H. M., 2000b. Activation of follicle development: the primordial follicle. Theriogenology, 55 (6), pp. 1193-1210. Picton, H. M., Harris, S. E., Gopichandran, N., Leese, H. J. and Orsi, N., 2005. Nutrient concentrations in murine follicular fluid and the female reproductive tract. Theriogenology, 64, pp: 992-1006. Picton, H. M., Harris, S. E., Leese, H. J. and Gosden, R. G. 2007. Carbohydrate metabolism by murine ovarian follicles and oocytes grown in vitro. Reproduction, 134, pp. 415-424. Picton, H. M., Fernandex, E. and Dumollard, R., 2012a. Metabolism throughout follicle and oocyte development in mammals. International Journal of Development Biology, 56, pp: 799-808 Picton, H. M., Hemmings, K. E. and Leese, H. J., 2012b. Amino acid turnover by bovine oocytes provides an index of oocyte developmental competence in vitro. Biology Reproduction, 86 (165), pp: 161-112. Read More