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A J Forhead and A L Fowden

Introduction The thyroid hormones, thyroxine (T 4 ) and triiodothyronine (T 3 ), are detectable in the fetal circulation from early in gestation and have important developmental, metabolic, and maturational effects in the fetus in all species

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Juliano C da Silveira, Ana Clara F C M de Ávila, Hannah L Garrett, Jason E Bruemmer, Quinton A Winger and Gerrit J Bouma

reproductive biology, including development and function of the reproductive tracts, germ cell development and maturation, fertilization and early embryo development (reviewed in Luense et al . 2011 , Hilz et al . 2016 ). The recent findings that microRNAs

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Wenxia He, Xiangyan Dai, Xiaowen Chen, Jiangyan He and Zhan Yin

2009 ). Puberty is defined as the period that marks the transition from sexual immaturity to maturity. It has been suggested that the onset of ovary maturation in female zebrafish occurs at around 45 dpf ( Chen & Ge 2013 ). Under standard laboratory

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Sonnet S Jonker, Daniel Kamna, Dan LoTurco, Jenai Kailey and Laura D Brown

and maturation The interaction term between treatment and anatomical location of cell origin was not significant for any myocyte measurement. IUGR reduced cell cycle activity expressed as a percentage of mononucleated myocytes ( P  = 0.0191; Fig

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A L Fowden, D S Gardner, J C Ousey, D A Giussani and A J Forhead

nutrition ( Trahair & Sangild 1997 , Fowden et al. 2001 ). In many fetal tissues, the maturational changes essential for neonatal survival begin before birth and are dependent upon the increase in fetal cortisol concentration towards term ( Fowden

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Joyce Emons, Bas E Dutilh, Eva Decker, Heide Pirzer, Carsten Sticht, Norbert Gretz, Gudrun Rappold, Ewan R Cameron, James C Neil, Gary S Stein, Andre J van Wijnen, Jan Maarten Wit, Janine N Post and Marcel Karperien

increases, but with progression of puberty, the growth rate decelerates due to growth plate maturation, and eventually, at the end of puberty, the growth plate disappears due to epiphyseal fusion. The molecular mechanisms underlying these distinct phases are

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Tong Sun, Wen-Bo Deng, Hong-Lu Diao, Hua Ni, Yu-Yan Bai, Xing-Hong Ma, Li-Bin Xu and Zeng-Ming Yang

during sexual maturation, gonadotropin treatment and luteal development. Materials and Methods Sexual maturation Immature female mice (Kunming White outbred strain, 21 days old) were caged in a controlled

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A Mishra and K P Joy

Introduction In teleosts, meiotic resumption is initiated by the production of an ovarian maturation-inducing substance (MIS) or hormone under a luteinizing hormone (LH) surge. In a majority of fishes, the most potent MIS is the

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Osamu Mizuno, Tsuyoshi Otani, Mariko Shirota and Shuji Sasamoto

The present investigation was performed to elucidate the mechanism of the initiation of follicular maturation after inhibition of ovulation in rats treated with pentobarbitone sodium at 13.30 h and progesterone at 14.00 h on the day of pro-oestrus (day 0 denotes the day of these treatments). Ovulation was completely inhibited and the next spontaneous ovulation occurred on day 5, the expected day of the next oestrus. Follicular responsiveness to injection of human chorionic gonadotrophin (hCG) indicated that preovulatory follicles at the time of treatment with pentobarbitone and progesterone regressed by 05.00 h on day 2. Maturation of a new set of follicles began from 17.00 h on day 2 and all rats were induced to ovulate by hCG injection by 17.00 h on day 3, the number of oocytes ovulated being comparable to normal ovulation.

In the animals receiving pentobarbitone sodium and progesterone treatment, two selective rises in plasma FSH, which had peak levels at 05.00 h on day 1 and 11.00 h on day 2, were observed without a rise in LH. Preovulatory surges of FSH and LH occurred on the afternoon of day 4.

These results suggest that the second rise in FSH was induced by regression of Graafian follicles present at the time of treatment with pentobarbitone sodium and progesterone and that this surge of FSH was responsible for initiation of maturation of a new set of follicles destined to ovulate in the subsequent cycle. The mechanism of induction and the role of the first rise of FSH from the night of day 0 to the morning of day 1 cannot be explained at present.

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J. D. HUNTER

The influence of exogenous gonadotrophic hormones (GTH) on the rate of spermatogenesis and germinal maturation in the testes of hypophysectomized male mice was measured. Liquid emulsion autoradiographic techniques were used to measure the incorporation of tritiated thymidine into germinal DNA to see if exogenous hormones could alter the rate of development of late spermiogenic cell stages (Gude, 1968; Clermont & Trott, 1969).

Two experiments were carried out using hypophysectomized and intact 70-day-old CD-I Charles River albino male mice (10/group). In experiment 1, intact (1A) and hypophysectomized (1B) males were compared with hypophysectomized males injected s.c. on alternate days either with 25 i.u. pregnant mare serum gonadotrophin (PMSG) (Equinex, Ayerst) (group 1C), or with 25 i.u. PMSG plus 25 i.u. human chorionic gonadotrophin (Ayerst) (group 1D). After 2 weeks of hormonal replacement, spermatogenic cells in the S phase (spermatogonia and primary spermatocytes synthesizing DNA) were labelled in vivo by a single