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J. Barrett, D. H. Abbott and L. M. George

Subordinate female marmoset monkeys remain anovulatory and have low plasma concentrations of luteinizing hormone (LH) when maintained with their dominant females. Olfactory cues from the dominant female have been implicated in maintaining this reproductive suppression. Subordinate females that received either ablation of the vomeronasal organ (an accessory olfactory organ; n = 3), ablation of the main olfactory epithelium (n = 4), or both lesions (n = 5) did not ovulate in the following 7 weeks while housed with their dominant female. Plasma LH concentrations following either or both lesions were similar to pre-lesion concentrations. Olfactory lesions (verified by histological and behavioural trials) did not impair reproductive activity, as olfactory-lesioned dominant females underwent ovarian cycles of similar duration to intact dominant females. Lesioned subordinate females (n = 6), maintained in visual-only contact with their dominant female and group ovulated 29.1 ± 9.3 days (mean ± sem) after physical separation from their dominant females; this first onset of ovulation was significantly delayed (P < 0.05) compared with intact subordinate females completely isolated from their dominant females and group (10.8 ± 1.3 days, n = 8). Behavioural and visual cues together with olfaction all appear to play important roles in maintaining the suppression of ovulation in subordinate female marmoset monkeys.

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J. Barrett, D. H. Abbott and L. M. George

Summary. Pheromonal signals from the dominant female marmoset monkey were implicated in maintaining the suppression of LH secretion and ovulation in socially subordinate females. When subordinate, and reproductively suppressed, female marmoset monkeys were removed from their group without scent contact with their dominant females, subordinate females in control group 1 (N = 8) and control group 2 (N = 5), ovulated 10·8 ± 1·4 days and 10·4 ± 0·8 days respectively (mean ± s.e.m.) after separation. Subordinate females (N = 8) removed from their dominant female and group, but maintained in scent contact only with their dominant females, showed a delay in the onset of ovulation (31·0 ± 6·4 days) compared with control groups 1 and 2. Plasma LH concentrations of subordinate females during the scent transfer phase were lower than in controls without scent transfer and comparable to those seen whilst the females were subordinates in groups. Contact of subordinate females with olfactory stimuli from dominant females therefore maintains the suppression of both LH secretion and ovulation in socially subordinate female marmosets. Such pheromonal cues provide evidence of a quantifiable link between dominant female marmosets and the maintenance of physiological suppression of reproduction in their female subordinates.

Keywords: marmoset; reproductive suppression; pheromones; ovulation; progesterone

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Rajani M George, Katherine L Hahn, Alan Rawls, Robert S Viger and Jeanne Wilson-Rawls

Notch2 and Notch3 and genes of the Notch signaling network are dynamically expressed in developing follicles, where they are essential for granulosa cell proliferation and meiotic maturation. Notch receptors, ligands, and downstream effector genes are also expressed in testicular Leydig cells, predicting a potential role in regulating steroidogenesis. In this study, we sought to determine if Notch signaling in small follicles regulates the proliferation response of granulosa cells to FSH and represses the up-regulation steroidogenic gene expression that occurs in response to FSH as the follicle grows. Inhibition of Notch signaling in small preantral follicles led to the up-regulation of the expression of genes in the steroid biosynthetic pathway. Similarly, progesterone secretion by MA-10 Leydig cells was significantly inhibited by constitutively active Notch. Together, these data indicated that Notch signaling inhibits steroidogenesis. GATA4 has been shown to be a positive regulator of steroidogenic genes, including STAR protein, P450 aromatase, and 3B-hydroxysteroid dehydrogenase. We observed that Notch downstream effectors HEY1, HEY2, and HEYL are able to differentially regulate these GATA4-dependent promoters. These data are supported by the presence of HEY/HES binding sites in these promoters. These studies indicate that Notch signaling has a role in the complex regulation of the steroidogenic pathway.

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J. B. Carroll, D. H. Abbott, L. M. George, J. E. Hindle and R. D. Martin

Summary. A non-invasive study of urinary hormones in 6 captive female Goeldi's monkeys provided accurate information on reproductive function. Conjugated oestrone accounted for 80–85% of the urinary oestrone and oestradiol measured. Radioimmunoassay measurements of conjugated oestrone provided a reliable indicator of cyclic ovarian function (mean cycle length: 24·1 ± 0·9 days; n = 9) and pregnancy (gestation: 145, 155 days; n = 2). Measurements of urinary progesterone and pregnanediol glucuronide were only reliable as indicators of ovarian cyclicity. Elevations in urinary conjugated oestrone coincided with luteal-phase elevations of urinary progesterone and pregnanediol glucuronide. Urinary LH concentrations provided no indication of pituitary activity. However, the frequencies of female sexual solicitations of males were maximal when oestrone conjugate concentrations rose, suggesting a peri-ovulatory period. Ovulation was suppressed in 1 of 3 subordinate females housed in male–female–female trios.

Keywords: monkey; oestrogen; progesterone; pregnanediol glucuronide, LH; ovarian cycle; pregnancy; urinary hormones

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Elaine M Carnevale, Marco A Coutinho da Silva, Lisa J Maclellan, George E Seidel Jr and Edward L Squires

Parentage identification was used to test the developmental competence of oocytes cultured under different conditions and fertilized in vivo after oocyte transfer. Oocytes were collected transvaginally from follicles of estrous mares approximately 22 h after administration of human chorionic gonadotropin. Oocytes were cultured for approximately 16 h in one of three media, with or without addition of hormones and growth factors. Groups of three or four oocytes, cultured in different media, were transferred into the oviduct contralateral to a recipient’s own ovulation. Recipients were inseminated with semen from two different stallions at 15 h before and 2.5 h after oocyte transfer. Sixteen days after transfer, embryos were recovered from uteri and submitted for parentage testing. The percentage of oocytes resulting in embryonic vesicles was nearly identical (P > 0.05) for transferred oocytes (32/44, 73%) versus ovulated oocytes of recipients (9/13, 69%). More (P < 0.01) oocytes were fertilized by sperm inseminated before (35/38, 92%) versus after (3/38, 8%) oocyte transfer. Tissue culture medium (TCM)-199 was superior to equine maturation medium I (EMMI; a SOF-based medium) for culturing oocytes (P < 0.05), although addition of hormones and growth factors during culture did not improve (P > 0.05) development of embryos.

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Marco A Coutinho da Silva, George E Seidel Jr, Edward L Squires, James K Graham and Elaine M Carnevale

The effects of semen extender components on the ability of stallion sperm to bind to the zona pellucida (ZP) and the suitability of using bovine ZP for a ZP-binding assay for stallion sperm were investigated in a series of experiments. In Experiment I, binding of stallion sperm to both bovine and equine ZP was significantly increased when a skim milk-based extender (EZM) was used. In Experiment II, a threefold increase in sperm binding to ZP was observed when sperm were diluted in EZM compared with diluents, which contained no milk (TALP, LAC, and EmCare). In Experiment III, centrifuging the sperm through Percoll did not increase sperm binding to the ZP but did remove any positive effect of EZM on sperm–ZP binding. In Experiment IV, exposure of either sperm or ZP to EZM before co-incubation did not increase sperm binding to ZP. In Experiment V, sperm diluted in TALP containing skim milk, EZM, or INRA96 bound more efficiently to the ZP than sperm diluted in TALP without milk proteins. In Experiment VI, sodium caseinate, native phosphocaseinate, and caseinoglycopeptide increased sperm binding to the ZP. In conclusion, diluents containing milk or milk proteins markedly enhanced the number of sperm bound to both equine and bovine ZP.