Dissertations / Theses on the topic 'Ovulation'

Thesis (M.S.)--University of Missouri-Columbia, 2007.<br>The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 31, 2007) Includes bibliographical references.

El objetivo de esta tesis ha sido estudiar la respuesta directa a la selección por tasa de ovulación en conejo y las respuestas correlacionadas en tamaño de camada y tasas de supervivencia. Los animales pertenecían a una línea de conejos seleccionada por tasa de ovulación durante 10 generaciones. La selección se realizó en base al valor fenotípico de la hembra, que se midió el día 12 de la segunda gestación mediante laparoscopia. Se creó una línea control a partir de la recuperación de aproximadamente 470 embriones de 50 hembras donantes de la generación base. Los embriones fueron vitrificados y almacenados en nitrógeno líquido hasta su transferencia al final del experimento de selección (generación 10 de la línea seleccionada). Se midieron los siguientes caracteres: tamaño de camada (LS), estimada como el número total de gazapos al parto en un máximo de 5 partos; tasa de ovulación (OR), estimada como el número de cuerpos lúteos en los dos ovarios; tasa de ovulación derecha y tasa de ovulación izquierda (ROR y LOR); el número de embriones implantados totales (IE), en el lado derecho (RIE) y en el lado izquierdo (LIE); la diferencia ovulatoria (OD), definida como la diferencia entre ROR y LOR, expresada en valor absoluto; la diferencia de implantación (ID), definida como la diferencia entre RIE y LIE, expresada en valor absoluto; la supervivencia embrionaria (ES), calculada como IE/OR; la supervivencia fetal (FS), calculada como LS/IE; la supervivencia prenatal (PS), calculada como LS/OR. Se utilizó metodología bayesiana para analizar los datos. Las estimas de las heredabilidades de OR, LS, ES, FS y PS fueron 0.16, 0.09, 0.09, 0.24 y 0.14, respectivamente. Las estimas de las correlaciones fenotípicas de OR con LS, ES, FS y PS fueron 0.09, -0.07, -0.26 and -0.28, respectivamente. Las estimas de las correlaciones genéticas de OR con LS y ES tuvieron una baja precisión, y no se pudo concretar su signo. Las estimas de las correlaciones genéticas de OR con FS y PS fueron negativas (probabilidad de ser negativa de 1.00 y 0.98, respectivamente). Las correlaciones fenotípicas y genéticas entre LS y las tasas de supervivencias fueron positivas (probabilidad de ser positivas de 1.00).<br>Laborda Vidal, P. (2011). Selection for ovulation rate in rabbits [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/14121<br>Palancia

Both G and P exhibit anti-inflammatory characteristics in the uterus and since ovulation has been likened to an inflammatory reaction, it is my hypothesis that P and G work in synergy through genomic and nongenomic receptors to regulate ovulation. Therefore, RNase protection assays and in situ hybridisation were developed to examine spatio-temporal expression of genes believed to be crucial to P and G production, metabolism and reception in the rat ovary. Gonadotrophins were shown to up-regulate the expression of StAR, P450scc, 3bHSD and 11bHSD1 and down-regulate 11bHSD2 expression in whole rat ovary and in GC cultures. PR and mRNA was expressed transiently 6h after the LH surge whereas GR mRNA was expressed throughout the cycle. Therefore, genes that regulate the synthesis of P, the activation of G and both genomic receptors were developmentally regulated, being induced by gonadotrophins. In GC cultures, after priming with FSH to induce functional maturity, concurrent addition of the antiprogestin, RU486, inhibited the stimulatory effects of LH on 11bHSD1, StAR, P450scc and 3bHSD mRNA levels, 6h after treatment began. PR gene expression was unaltered. However, with 12h treatment, 11bHSD gene expression had increased and StAR, P450scc and 3bHSD mRNA levels were unchanged with RU486. The previously recognised ability of RU486 to halt ovulation and luteinisation may therefore be due to its effect on the expression of genes regulating P and G. However, nongenomic P action was not ruled out since P bound to a cytosolic protein which showed characteristics of NGPR identified in other species in both mature and immature ovaries. In summary, gonadotrophins act on ovarian GC to induce the expression of genes which aid in the synthesis and activation of P and G. These steroids may act locally through genomic or non-genomic receptors mediating events which lead to follicle rupture. The presence of P, G and their receptors in the ovary after ovulation suggests a role for these anti-inflammatory steroids in the corpus luteum, perhaps remodelling the ruptured ovarian surface.

Superovulatory treatment with exogenous gonadotrophins adversely affects the uterus through the disruption of the delicate balance of ovarian steroid (estrogens, progestins, androgens) secretion rates. To examine the uterine effects of this treatment, 189 animals were given 4, 20 or 40 IU pregnant mare serum gonadotrophin (PMSG) at 28 days of age and sacrificed every 24 h until day 10 (D10) post injection. To study the long term uterine effects, 12 rats were treated with 4 or 40 IU PMSG and killed on D30. The morphological and histological changes of control (4 IU) uteri mimicked those of the adult on a comparable time course from D2 to D5. Administration of superovulatory doses (2 0, 4 0 IU) of PMSG produced stromal hypertrophy by D2 and focal papillary hyperplasia of the luminal epithelia by D3. It is suggested that previous exposure to high levels of estrogen and androgens, secondary to superovulation, are possible causes for this pathology. Levels of 17B-estradiol following 2 0 and 40 IU PMSG treatment were significantly (p<0.005, p<0.05) elevated above those of controls from DI to early D3 and at D2, respectively. Androgen levels of both groups (20 IU, 40 IU) significantly (p<0.05, p<0.005) increased from baseline at DI to maxima by D2 and D3, respectively. In the 20 IU PMSG group, the hyperplasia gradually regressed after D3 and was absent by D10. The hyperplasia in the 40 IU PMSG group, however, had diffused by D6. It is suspected that preceding elevated levels of estrogen may be responsible for this progressive change. At D4, levels of 17B-estradiol reached a maximum, which was significantly (p<0.001) greater than those of controls and 20 IU PMSG treated rats. Between D6 and D10, the hyperplasia partially regressed. Examination of uteri from D30 revealed no evidence of pathology. In addition to these structural effects, superovulation induced secretion of a mucinous substance in both 20 IU and 40 IU PMSG groups at D5-D6 and D6-D7, respectively. These results suggest that abnormal changes in the uterine histology and metabolism may result following administration of superovulatory doses of PMSG. Although these dose-dependent alterations appear reversible, they may interfere with preparations associated with implantation and thus require further investigation.<br>Medicine, Faculty of<br>Obstetrics and Gynaecology, Department of<br>Graduate

Ovulation has been hypothesized as an inflammatory process. Interleukin(IL)-1$\alpha$, IL-1$\beta$ and tumor necrosis factor(TNF)-$\alpha$ are potent cytokines produced from macrophages and various other cell types, and are pivotal components of inflammation. Although previous studies have investigated cytokine activities in the reproductive system, there is little information on their precise localization and activities during the periovulatory period. To investigate the role of cytokines in ovulation, experiments were designed to determine the immunohistochemical localization and time specific production of cytokines IL-1 and TNF-$\alpha$ using a mouse model at 36h, 12h, 6h, 2h before ovulation, and at 6h and 18h after ovulation in vivo. Isolated individual follicles in vitro were used to determine more precise roles of cytokines on follicular development, ovulation and steroidogenesis. From these studies it was found that (1) granulosa cells were the primary sites of IL-1$\alpha$ and TNF-$\alpha$ production from large antral follicles and preovulatory follicles in vivo, (2) production of IL-1$\alpha$ and TNF-$\alpha$ increased as ovulation neared, first appearing in the cumulus cells and expanding to antral and mural granulosa cells, (3) less intense staining of these cytokines in the theca layer of smaller follicles suggests that theca cells may contribute to the production of these cytokines to some extent, (4) but there was no IL-1$\beta$ production, (5) localized and temporal production of cytokines during the periovulatory period suggests precise regulation, (6) decrease of IL-1$\alpha$ in the ovary after gonadotropin injection determined by enzyme linked immunoadsorbent assay suggests that IL-1$\alpha$ production may be under the control of gonadotropins, (7) in follicle culture without bone marrow derived cells, granulosa cells were confirmed as the main source of cytokine production, (8) addition of IL-1$\alpha$ and TNF-$\alpha$ to follicles in culture tend to decrease estradiol production. In conclusion, immunoreactive cytokine production correlated positively with the periovulatory follicular development suggesting their role as ovulatory mediators. It requires further studies on what are the signals for the initiation and termination of cytokine production, how transcription and translation of these cytokines are regulated during the periovulatory period, and how they contribute to the ovulation.

The age at which gilts could be effectively induced into a precocious puberty was assessed by injecting gilts of different ages (100-180 days old) with an exogenous gonadotrophin (PG600). Gilts could be stimulated into puberty as early as 100 days old but they had to be at least 160 days old to maintain cyclicity. Ovulation rate (OR) was found to increase with increasing age. Gilts of two different ages (160, 180 days old at induction) were fed two different diets (lysine:DE (g/MJ DE) ratios 0.3 and 0.9) over a 6 week rearing period. At puberty induction the low protein (LP) gilts were lighter and fatter than their HP counterparts (backfat probes, 12.0 vs 10.4 (P<0.05) respectively; eye muscle depths, 67.4 vs 71.2 respectively (P<0.05)). Response to gonadotrophin injection was significantly reduced in the LP gilts. OR was also significantly lower in the LP gilts (15.9 ± 1.6 vs 21.4 ± 1.4; P<0.01). The factor having most effect on OR was protein gain over the rearing period. In a third experiment, cycling sows of three different parity categories were fed a protein free (PF) diet over one oestrous cycle. PF Sows had a tendency to have reduced follicle counts and reduced subsequent interval from standing oestrus to ovulation (45.2 hours vs 55 hours). The effect of feeding a high fibre diet (50% unmolassed sugar beet pulp) to gilts over the rearing period on reproductive performance was also assessed. In the first experiment gilts exposed to boar stimulation alone only showed puberty response within 40 days and this response was positively correlated with weight. Gilts induced with exogenous gonadotrophin responded within 10 days and showed an OR response to weight. There was no effect of diet on OR. In the second experiment, there again was no effect on OR. Cell counts of the embryos collected from the high fibre gilts and cultured were significantly higher than the controls (198 ± 7 vs 138 ± 9; P<0.005) at 6-7 days; this was taken as an indication that feeding a high fibre diet may improve embryo survival.

The fertility of a couple depends upon several factors in both the male and female. Ovulation induction involves the use of medication to stimulate development of one or more mature follicles in the ovaries of women who have anovulation and infertility. Letrozole, an aromatase inhibitor, has been demonstrated to be effective as an ovulation induction and controlled ovarian hyperstimulation agent.

Ovulation due to hypothetical conspecific male pheromone(s) was examined in the dwarf African clawed frog (Hymenochirus curtipes, Noble, 1924). Oviducts of females were examined for the presence of eggs in untreated females and after exposure to each variable condition. A flow-through water system was constructed, and a total of nine experimental runs performed. Mature, female H. curtipes were exposed to seven different water conditions to discern which stimuli induced ovulation. One ovulation stimulus may be a male pheromone; the cutaneous post-axillary gland of male H. curtipes and the testes have also been suggested as possible organs of pheromone secretion. Therefore, females were exposed to post-axillary gland and testicular homogenates. Females were also exposed to other variable conditions, including plain flowing water, gonadotropin releasing hormone agonist (GnRH-a) in water, and GnRH-a injected males. Ovulation was induced in females exposed to two of the variable conditions: GnRH-a injected males (87%) and uninjected-glandless males (85%). No other treatments induced ovulation at these levels, although GnRH-a in water induced ovulation in females (70%). From the results obtained, it can be concluded that male H. curtipes secrete chemical(s) which stimulate(s) females, though the source and nature of the pheromone has not been identified. While GnRH-a in water can induce ovulation in females, it is not as effective as the pheromone(s) released by male H. curtipes.

Techniques to increase prolificacy in cattle have met with limited success; the aim of these studies was to investigate the potential of actively immunising cattle against certain gonadal hormones, and to examine the physiological basis of these treatments. Eight heifers were immunised against 8mg of a testosterone conjugate in Freund's Incomplete Adjuvant, & nine animals served as controls. These heifers were given one priming and two booster injections at four-month intervals. After the last booster injection, 7/8 animals had become anoestrous, and displayed significantly raised blood progesterone & mean LH concentrations,increased LH pulse frequency, & decreased mean FSH concentrations. Seven months after this treatment, 3/7 anoestrous heifers resumed ovarian cyclicity, with a mean ovulation rate of 2.7+0.7. To determine if the different ovarian responses observed above could be obtained by changes of ovarian steroid feedback seen during the oestrous cycle, groups of 6 heifers were implanted with large,medium or small sized oestradiol capsules during the luteal phase of the cycle. Five control heifers received empty implants. During the luteal phase of the cycle following implantation, all heifers were ovariectomised. The effect of the treatment on ovarian function and gonadotrophin secretion in the presence or absence of progesterone (PRID) was then determined. Increasing physiological concentrations of oestradiol reduced the number of large antral follicles and corpora lutea, but not the total number of antral follicles >lmm diameter. A combination of progesterone and oestradiol were fully effective in maintaining luteal-phase concentrations of LH and FSH, and follicular-phase concentrations of oestradiol alone were able to maintain LH and FSH concentrations within the physiological range. Thus changes of blood steroid levels similar to those seen during the oestrous cycle may interrupt ovarian function. Cattle were therefore immunised against a non-steroidal, partly purified fraction of ovine follicular fluid (PPFF) enriched ininhibin-like activity as measured in vivo and in vitro. Active immunisation against 0.4mg and 4mg ovine PPFF produced 1/5 & 3/5 heifers with multiple ovulations, respectively; this was not associated with changes of FSH secretion. To examine in more detail the endocrine responses to this treatment, and to investigate possible comparative aspects, cows were immunised against 4mg ovine, porcine or equine PPFF. No treatment increased ovulation rate, but the porcine-PPFF immunised heifers showed a 7-fold increase in mean LH secretion that could not be explained by alterations in pulsatile secretion or in steroid feedback. Collectively, these results suggest that the cow does not respond consistently to treatments so far designed to alter gonadotrophin secretion, that inhibin is not a major feedback hormone in this species, and that the heifer may possess an influential intra-ovarian control mechanism which ultimately determines ovulation rate.

The equine breeding industry continues to be somewhat inefficient, even with existing technology. On average, foaling rates are low when compared with that of other livestock. One major contributor is the inability to accurately predict ovulation in mares, which ovulate before the end of estrus, leaving much variability in coordinating insemination. A more efficient, less invasive method that could replace or reduce the need for constant teasing and ultrasonography to evaluate follicular activity is needed. In both dairy cattle and women, a change in body temperature has been shown to occur immediately prior to ovulation. Research on horses has been limited, although one study reported no useable relationship between body temperature and ovulation in mares (Ammons, 1989). The current study utilized thirty-eight mature cycling American Quarter Horse mares, and was conducted from March-August 2004. Each mare was implanted in the nuchal ligament with a microchip that can be used for identification purposes, but is also capable of reporting body temperature. Once an ovulatory follicle (>35mm) was detected using ultrasonography and the mare was exhibiting signs of estrus, the mare's follicle size and temperature were recorded approximately every six hours until ovulation. Not only was the temperature collected using the microchips, but the corresponding rectal temperature was also recorded using a digital thermometer. A significant effect (p<0.05) on body temperature was noted in relation to the presence or absence of an ovulatory follicle (>35mm) under different circumstances. When evaluating the rectal temperatures, no significant difference was found in temperature in relation to the presence or absence of a follicle. However, in the temperatures obtained using the microchip, temperature was higher (p<0.05) with the presence of a follicle of greater than 35mm. This may be due to the extreme sensitivity of the microchip implant and its ability to more closely reflect minute changes in body temperature.

The gonad of the snail Helix aspersa is innervated by a branch of the intestinal nerve. Here it is demonstrated that nerve stimulation causes peristaltic contractions and the acceleration of cilia beating in the proximal part of the hermaphroditic duct. Acetylcholine and serotonin induced peristaltic contractions when applied without nerve stimulation. As well, serotonin induced the acceleration of cilia beating. The neuropeptide FMRFamide caused dilation of the hermaphroditic duct. Pharmacological blocking of acetylcholine and serotonin receptors with concurrent nerve stimulation induced a dilation similar to that caused by FMRFamide application. It is suggested that all three transmitters are released from intestinal nerve terminals to facilitate oocyte transport during ovulation. Nerve stimulation induced an increase in gamete transport rates. Because several candidate chemical messengers failed to induce ovulation when injected into the circulatory system, Helix aspersa appears to initiate ovulation differently from related species. Whereas Aplysia and Lymnaea use hormones, Helix apparently signals ovulation via the intestinal nerve.

[EN] The aim of this thesis was to evaluate the productive performance of a rabbit line (OR-LS) selected by ovulation rate during first 6 generations (period 1), and later by ovulation rate (OR) and litter size (LS) during 11 generations using independent culling levels (Period 2). Genetic parameters, direct response for OR and LS and the correlated response for embryo (ES), foetal (FS) and prenatal survival (PS) were estimated. Also, the correlated response on growth rates (GR), weaning (WW) and marketing weight (MW) were estimated. The objective of chapter 3 was to estimate the genetic parameters of the productive traits and the response to selection by OR and LS of OR-LS line. For traits analysis, Bayesian methods were used. Heritability values of litter size traits were low, 0.10, 0.07, 0.07 and 0.07 for litter size, number of born alive (NBA), number of kits at weaning (NW) and marketing (NM), respectively. Heritability for OR was moderate (0.25), while it was low (0.13 and 0.14) for number of implanted embryos (IE) and number of live foetuses at 12 days of gestation (LF12), respectively. Low heritability values for survival traits were found, 0.09 for embryo survival (ES), 0.16 for foetal survival (FS) and 0.14 for prenatal survival (PS). In the second period, after 11 generations of selection by OR and LS, a genetic response of 0.17 kits per generation for LS was achieved. This response was higher than the obtained in period 1 (0.07 kits per generation), in which just selection by OR was performed. The opposite effect was found for OR; the highest response for OR appeared in the first period (0.24 ova per generation) versus the second period (0.17 ova per generation). This reduction in OR response can be due to the decrease in selection differential during the second period of selection. Since high genetic correlations were obtained for LS and other litter size traits, a positive correlated response was observed for NBA, NW and NM (0.12, 0.12 and 0.11 kits per generation, respectively) in the second period. In the first period, no correlated response on ES was observed and a decrease in FS (-0.04) was found. Nevertheless, in the second period a correlated response on PS appeared due to an improvement in both ES (0.04) and FS (0.03). Summarizing, the improvement in litter size in the second period is due to an increase in ovulation rate as well as an increase in prenatal survival. The objective of chapter 4 was to study the correlated response on growth traits in the OR-LS line in both periods of selection, the selection by OR during six generations and the selection by independent levels by OR and LS during 11 generations. The heritability estimates were low for weaning weight (WW), marketing weight (MW) and growth rate (GR), 0.09, 0.13 and 0.14, respectively. The estimated genetic correlations of WW, GR and MW with LS were around zero and with OR were positive and from low (0.19) to moderate (0.38). The positive moderate genetic correlation estimated between OR and MW could explain the correlated response found in MW. Correlated response on WW could be explained by positive and high genetic correlation between MW and WW. The aim of chapter 5 was to investigate magnitude and timing of embryo and early foetal survival in females with high OR using hormonal treatment as a model for selection by OR. Two groups of females (treated and untreated) were used. Treated females were injected with 50 IU eCG 48 hours before mating. Females were slaughtered at day 18 of gestation. OR, IE, LF12 and LF18 were recorded. Besides, ES (IE/OR), FSLF18 (LF18/IE), FSLF18/LF12 (LF18/LF12) and PSLF18 (LF18/OR) were estimated. Treated females had a higher OR than untreated females. According to the previous results for OR and LF18, treated females showed a lower survival rate from ovulation to 18 d of gestation. Treated females also had lower embryo and foetal survival. Main difference in foetal survival appeared from day 12 to 18 of gestation.<br>[ES] El objetivo de esta tesis fue evaluar el tamaño de camada de una línea de conejo seleccionada por tasa de ovulación durante las primeras seis generaciones (periodo 1) y después por tasa de ovulación (OR) y tamaño de camada (LS) durante 11 generaciones mediante el método de niveles independientes (periodo 2). Se estimaron los parámetros genéticos, así como la respuesta en OR y LS y la respuesta correlacionada en los caracteres reproductivos (capítulo 3). Además, se evaluó la respuesta correlacionada en los caracteres de crecimiento (capítulo 4); peso al destete (WW), peso al sacrificio (MW) y ganancia de peso entre el destete y el sacrificio (GR). Para el análisis de los caracteres se utilizaron métodos bayesianos. El objetivo del capítulo 3 fue estimar los parámetros genéticos de los caracteres reproductivos y la respuesta a la selección. Los valores de heredabilidad de los caracteres del tamaño de camada fueron bajos (alrededor de 0.10). La heredabilidad estimada para OR fue moderada (0.25), mientras que fue baja para el número de embriones implantados (IE) y el número de fetos vivos a los 12 días de gestación (LF12). Se obtuvieron valores bajos de heredabilidad; 0.09 para la supervivencia embrionaria (ES), 0.16 para la supervivencia fetal (FS) y 0.14 para la supervivencia prenatal (PS). En el periodo 2, se obtuvo una respuesta genética de 0.17 gazapos por generación para LS. Esta respuesta fue mayor que la obtenida en el periodo 1. En el caso de la tasa de ovulación, la mayor respuesta en OR se obtuvo en el periodo 1 (0.24 óvulos por generación) versus (0.17 óvulos por generación) en el periodo 2. Esta reducción en la respuesta de OR se puede atribuir a la disminución del diferencial de selección durante el período 2 de selección. De acuerdo con la alta correlación genética entre LS y otros caracteres del tamaño de camada, también se observó una respuesta correlacionada positiva en el número de nacidos vivos (NBA), destetados (NW) y comercializados (NM); 0.12, 0.12 y 0.11 gazapos por generación, respectivamente, en el segundo periodo. En el primer periodo no se observa respuesta correlacionada en la SE y se produce una disminución de la SF (-0.04). Sin embargo, en el segundo periodo se produce una respuesta correlacionada positiva en la SP que se debe a una mejora de la SE (0.04) y SF (0.03). En resumen, la mejora del tamaño de camada en el segundo periodo se debe tanto a un aumento de la tasa de ovulación como a un aumento de la supervivencia prenatal. El objetivo del capítulo 4 fue estudiar la respuesta correlacionada en los caracteres de crecimiento en esta línea. Las estimas de heredabilidad fueron bajas para los caracteres WW (0.09), MW (0.13) y GR (0.14). Las correlaciones genéticas estimadas de LS con WW, MW y GR fueron cercanas a cero; con la tasa de ovulación, las correlaciones fueron positivas y variaban de bajas a moderadas (de 0.19 a 0.38). La correlación genética moderada entre OR y MW podría explicar la respuesta correlacionada observada en MW. La alta correlación entre MW y WW podría explicar la respuesta correlacionada obtenida para WW. Finalmente, el objetivo de capítulo 5 fue estudiar en hembras con alta tasa de ovulación en qué momento se producen las mayores pérdidas fetales y cómo se ve afectado el desarrollo fetal. Para ello, de un total de 51 hembras, 24 hembras fueron pinchadas con 50 UI de eCG 48 horas antes de la cubrición para aumentar la tasa de ovulación. Las hembras fueron sacrificadas a los 18 días de gestación. Se registró OR, IE y el número de fetos vivos a los 12 y 18 días de gestación (LF18). Las hembras tratadas tuvieron una tasa de ovulación mayor que las no tratadas. De acuerdo con los resultados obtenidos para OR y LF18, las hembras tratadas mostraron una supervivencia más baja desde la ovulación hasta los 18 días de gestación y tuvieron una menor supervivencia embrionaria y fetal. Las principales diferencias en l<br>[CAT] L'objectiu d'esta tesi va ser avaluar la millora de la grandària de ventrada d'una línia de conill seleccionada per tasa d'ovulació durant les primeres sis generacions (període 1) i després per tasa d'ovulació (OR) i la grandària de ventrada (LS) durant 11 generacions per mitjà del mètode de nivells independents (període 2). Es van estimar els paràmetres genètics, així com la resposta en OR i LS i la resposta correlacionada en caràcters reproductius (capítol 3). A més, es va estudiar la resposta correlacionada en els caràcters de creixement (capítol 4); pes al deslletament (WW), pes al sacrifici (MW) i guany de pes entre el deslletament y el sacrifici (GR). Per a l'anàlisi dels caràcters es van utilitzar mètodes bayesians. L'objectiu del capítol 3 va ser estimar els paràmetres genètics dels caràcters reproductius i la resposta a la selecció. Els valors d'heretabilitat dels caràcters de la grandària de ventrada van ser baixos (al voltant de 0.10). L'heretabilitat estimada per a OR va ser moderada (0.25), mentres que va ser baixa per al nombre d'embrions implantats (IE) i el nombre de fetus vius als 12 dies de gestació (LF12). Es van obtindre valors baixos d'heretabilitat; 0.09 per a ES, 0.16 per a FS i 0.14 per a PS. En el període 2, es va obtindre una resposta genètica de 0.17 llorigons per generació per a LS. Esta resposta va ser major que l'obtinguda en el període 1. En el cas de la tasa d'ovulació, la major resposta per a OR va ser en el primer període (0.24 òvuls per generació) versus (0.17 òvuls per generació) en el període 2. Esta reducció en la resposta d'OR es pot atribuir a la disminució del diferencial de selecció durant el període 2 de selecció. Donada l'alta correlació genètica entre LS i altres caràcters de la grandària de ventrada, també es va observar una resposta correlacionada positiva en el nombre de nascuts vius (NBA), deslletats (NW) i comercialitzats (NM); 0.12, 0.12 i 0.11 llorigons per generació, respectivament, en el segon període. En el primer període no s'observa resposta correlacionada en la SE i es produeix una disminució de la SF (-0.04). No obstant això, en el segon període es produeix una resposta correlacionada en la SP que es deu a una millora de la SE (0.04) i SF (0.03). En resum, la millora de la grandària de ventrada en el segon període es deu tant a un augment de la tasa d'ovulació com a un augment de la supervivència prenatal. L'objectiu del capítol 4 va ser estudiar la resposta correlacionada en els caràcters de creixement en aquesta línia. Les estimes d'heretabilitat van ser baixes per als caràcters WW (0.09), MW (0.13) i GR (0.14). Les correlacions genètiques estimades de LS amb WW, MW i GR van ser pròximes a zero; amb la tasa d'ovulació, les correlacions van ser positives i variaven de baixes a moderades (de 0.19 a 0.38). La correlació genètica moderada entre OR i MW podria explicar la resposta correlacionada trobada per a MW. D'altra banda, l'alta correlació entre MW i WW podria explicar la resposta correlacionada obtinguda per a WW. Finalment. l'objectiu del capítol 5 va ser estudiar en femelles amb alta tasa d'ovulació en quin moment es van produir les majors pèrdues fetals i com es veu afectat el desenvolupament fetal. Per a això, d'un total de 51 femelles, 24 femelles van ser punxades amb 50 UI d'eCG 48 hores abans del cobriment per a augmentar la tasa d'ovulació. Les femelles van ser sacrificades al 18 dies de gestació. Es va registrar OR, IE i el nombre de fetus vius al 12 i 18 dies de gestació (LF18). Les femelles tractades van tindre una tasa d'ovulació major que les no tractades. D¿acord als resultats obtinguts per OR i LF18, les femelles tractades van mostrar una supervivència més baixa des de l'ovulació fins als 18 dies de gestació i van tindre una menor supervivència embrionària i fetal. Les principals diferències en la supervivència fetal van aparèixer entre els dies 12 i 18 de gestaci<br>Yehia Badawy Elmoghazy, A. (2016). SELECTION FOR OVULATION RATE AND LITTER SIZE IN RABBITS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/73265<br>TESIS

Chez les mammifères, la régulation endocrine de la maturation folliculaire est bien définie mais les mécanismes locaux restent mal connus. Le système interleukine-1 (IL-1a, b, RA, R1 et R2) serait impliqué dans les événements précédant l'ovulation. En utilisant le modèle jument, la localisation et le rôle de l'IL-1 dans le follicule ont été étudiés. Nous avons montré que : Les membres du système IL-1 sont exprimés différemment dans les types cellulaires étudiés (ovocytes, cumulus, granulosa) et au cours du temps. Ceci suggère une régulation du système IL-1 par la LH. In vivo, l'injection d'IL-1b dans un follicule dominant équin induit l'ovulation ainsi que la maturation ovocytaire. Par contre, in vitro, l'IL-1b inhibe la maturation des ovocytes induite par LH ou EGF. Cet effet est levé en présence d'IL-1RA. Ce travail confirme l'implication du système IL-1 dans la physiologie ovarienne chez la jument<br>In domestic mammals, endocrine regulation of the preovulatory maturation is well known but local mechanisms have to be clarified. Interleukin-1 system (IL-1a, b, RA, R1 and R2) could be involved in the events leading to ovulation. The study of IL-1 in equine preovulatory follicle was initiated in this thesis. Main results are : A differential expression of the IL-1 system members was observed between the ovarian cells studied (oocytes, cumulus and granulosa cells) and during the maturation stages. That suggests the IL-1 system regulation by LH. - The intrafollicular injection of IL-1b induced ovulation and in vivo oocyte maturation in the mare. In an other hand, IL-1b inhibited the eLH and EGF-induced in vitro oocyte maturation. This effect was reversed in the presence of IL-1RA in the culture medium. The present work confirms the implication of IL-1 system in equine ovarian physiology

La détermination précise du jour de l'ovulation est considérée par la plupart des auteurs comme l'un des facteurs les plus importants pour fixer le moment optimal d'insémination artificielle chez la chienne. Ceci est particulièrement important lors d'utilisation de semence congelée en raison de la faible durée de survie de la semence congelée/décongelée dans l'appareil génital femelle. Notre étude a tout d'abord tenté de déterminer la technique la plus précise pour identifier la survenue de l'ovulation chez la chienne. Notamment, nous avons souhaité savoir si l'examen échographique des ovaires pouvait être un moyen fiable et précis pour déterminer l'ovulation chez la chienne. Notre but a été de détecter l'ovulation par échographie dans différentes races et d'évaluer les intérêts et la précision de cette technique, en comparaison avec les taux hormonaux autour de l'ovulation. Nos résultats ont confirmé que l'échographie ovarienne était une technique précise de détermination de l'ovulation chez la chienne. Nous avons également démontré que cette technique n'améliorait la détection de l'ovulation que chez 15,3% des chiennes en comparaison des dosages de progestérone sanguine. Au bilan, les concentrations de progestérone plasmatique sont extrêmement constantes au moment de l'ovulation quelle que soit la race et, de ce fait, les dosages de progestérone apparaissent être une méthode suffisamment précise pour déterminer le moment de l'ovulation. Utilisant les échographies ovariennes pour la détection du moment de l'ovulation chez la chienne, nous avons ensuite essayé d'évaluer le déroulement exact de la maturation ovocytaire in vivo chez la chienne, ainsi que le développement embryonnaire précoce. De plus, nous avons cherché à vérifier si, in vivo, les spermatozoïdes canins étaient capables de pénétrer des ovocytes encore à un stade immature. Nous avons démontré que le stade de la vésicule germinative (VG) était le seul présent jusqu'à 44h après l'ovulation. Le premier stade métaphase II n'est observé qu'à partir de 54h. Plusieurs stades de maturation ovcytaire différents sont observés au même moment pour une même chienne. In vivo, la fécondation se produit dans la plupart des cas à partir de 90h post ovulation dans des ovocytes ayant complété leur maturation (métaphase II). La pénétration in vivo d'ovocytes immatures par des spermatozoïdes apparaît extrêmement rare. Ces résultats devraient permettre une amélioration ou une simplification de la pratique vétérinaire quotidienne, notamment lors d'utilisation d'insémination artificielle en semence congelée. De plus une meilleure connaissance des processus impliqués dans la maturation ovocytaire in vivo, la fécondation, et le développement embryonnaire précoce sont des étapes importantes pour améliorer le développement des biotechnologies de la reproduction dans l'espèce canine.

Calcium status is a major factor in the regulation of reproductive activity in the hen. Restriction of dietary calcium (Ca) or vitamin D (D) is assumed to cause cessation of ovulation through decreased plasma calcium concentrations. Several studies suggest that there may be a threshold level of ionized calcium (Cai) below which ovulation will not proceed. The objectives of this thesis were to determine how Cai concentration is involved in the process of ovulation by comparing Ca and D-deficient hens, that had ceased laying, with control birds that were laying normally. A secondary objective was to determine the effects of multiple blood sampling (MBS) on the hen's ovulatory cycle. SCWL hens were divided into three groups-control, Ca-deficient and D-deficient groups and fed respective diets. Control birds were serially sampled every two hrs for 24-26 hrs immediately after oviposition until the next oviposition. Deficient birds, that had ceased laying for 10 to 14 days, were sampled at the same time. MBS was achieved with an indwelling vascular access port. Six birds/experimental group were used. Control birds were bled two weeks later from late afternoon until the following day at the same time. Whole blood was analyzed for Cai. Separated plasma was analyzed for total calcium (Cat), inorganic phosphorus (Pi), estrogen (E₂), progesterone (P₄) and l,25(OH)₂D₃ concentrations. Tibiae were ashed for mineral content. In expt. 1, the effect of MBS on the ovulatory pattern of hormones and ions was observed by sampling control birds twice, using two different time courses. Patterns and concentrations of the hormones and ions, regardless of time course, were similar to previous studies. Overall treatment effects were only significant between treatments with regards to total calcium and estradiol concentrations. The large loss of plasma proteins during the bleeding regime resulted in a steady decline in Cat over the 26 hrs, however, it was still within the physiological range of laying birds. . E₂ concentrations were also affected due to interruption of the laying sequence. However, this can be avoided since some birds continued to lay. In expt. 2, the control group had significantly higher mean plasma Cat and Pi concentrations and bone ash than both the deficient groups. Control and D-deficient groups had similar mean Cai concentrations, however, the ovulatory profile of the control group had a significant cyclic pattern over the 24-26 hrs, whereas, both deficient groups did not vary significantly over the 24 hrs. Plasma Pi concentration in the control group, not previously described, was cyclic in nature, related to the egg laying cycle. Plasma l,25(OH)₂D₃ concentrations were significantly higher in the Ca-deficient group than the control group. D-deficient birds had detectable levels of plasma 1,25(OH)₂D₃, but it was significantly lower than the control group. Plasma E₂ and P₄ concentrations were significantly higher in the control group In conclusion, it would appear that an inter-relationship exists among Cai, Pi and 1,25(0H)₂D₃ and the reproductive hormones. A threshold concentration of Cai may be the trigger for ovulation, perceived at the level of the pituitary, hypothalamus or ovary. A threshold of Pi and a window of l,25(OH)₂D₃ concentration may also have permissive roles in ovulation. In addition, MBS, regardless of time course, can be used as a method for determining ovulatory profiles in individual birds without seriously affecting ionic and hormonal concentrations and patterns.<br>Land and Food Systems, Faculty of<br>Graduate

The role of plasmin and plasminogen activators (PA) in bovine lactation and porcine ovulation has been examined. There is no difference in the activation pattern of plasminogen to plasmin throughout the whole range of somatic cell counts (SCC) and from third to ninth month in lactation. The ratio of (plasminogen + plasmin)/plasmin, which serves as an index of the activation process, was 7.27 during early (first and second month) and 4.23 during late lactation (tenth month) and both values are different (p $<$ 0.01) from all the other ratios throughout the whole range of SCC and from third to ninth month in lactation suggesting limited and increased activation of plasminogen to plasmin during early and late lactation, respectively. Macrophages produce but they do not secrete urokinase-PA, suggesting a minor role in influencing milk plasmin. Somatotropin administration resulted in a suppression of milk plasmin in vivo. Insulin-like growth factor-1 (IGF-1), the most likely mediator of the effects of somatotropin on the bovine mammary gland, inhibited the induction of tissue-PA (t-PA) production which is observed when mammary epithelial cells are cultured in the absence of IGF-1. Plasmin and t-PA increased while PA inhibitor-1 decreased in porcine granulosa, theca interna cells and follicular fluid just prior to the time of expected ovulation suggesting a role for plasmin in follicle rupture.

Clomiphene citrate (CC) has been the first line of treatment for induction of ovulation in patients with anovulatory infertility since 1962. It is administered as a mixture of two geometric isomers, Enclomiphene (En) and Zu-clomiphene (Zu) citrate in the ratio 62%:38%. The En isomer is perceived to be more active. A prediction model of response to CC was developed utilizing physical and biochemical characteristics of patients but this model has not been vahdated in a set of patients independent of those used to develop the model. It examines an existent nomogram for the identification of patient resistant to CC therapy and indicates that the nomogram is not sufficiently sensitive and specific to be useful in clinical practice. It shows that obesity could change the pharmacokinetics of Zu but not En. It provides early indications for a hypothesis that therapeutic outcome may be linked to interindividual variation in the exposure to the metabolite formed by CYP2D6. This may explain the lack of any direct relationship between the concentrations of the parent compound and response.

La détermination précise du jour de l’ovulation est considérée par la plupart des auteurs comme l’un des facteurs les plus importants pour fixer le moment optimal d’insémination artificielle chez la chienne. Ceci est particulièrement important lors d’utilisation de semence congelée en raison de la faible durée de survie de la semence congelée/décongelée dans l’appareil génital femelle. Notre étude a tout d’abord tenté de déterminer la technique la plus précise pour identifier la survenue de l’ovulation chez la chienne. Notamment, nous avons souhaité savoir si l’examen échographique des ovaires pouvait être un moyen fiable et précis pour déterminer l’ovulation chez la chienne. Notre but a été de détecter l’ovulation par échographie dans différentes races et d’évaluer les intérêts et la précision de cette technique, en comparaison avec les taux hormonaux autour de l’ovulation. Nos résultats ont confirmé que l’échographie ovarienne était une technique précise de détermination de l’ovulation chez la chienne. Nous avons également démontré que cette technique n’améliorait la détection de l’ovulation que chez 15,3% des chiennes en comparaison des dosages de progestérone sanguine. Au bilan, les concentrations de progestérone plasmatique sont extrêmement constantes au moment de l’ovulation quelle que soit la race et, de ce fait, les dosages de progestérone apparaissent être une méthode suffisamment précise pour déterminer le moment de l’ovulation. Utilisant les échographies ovariennes pour la détection du moment de l’ovulation chez la chienne, nous avons ensuite essayé d’évaluer le déroulement exact de la maturation ovocytaire in vivo chez la chienne, ainsi que le développement embryonnaire précoce. De plus, nous avons cherché à vérifier si, in vivo, les spermatozoïdes canins étaient capables de pénétrer des ovocytes encore à un stade immature. Nous avons démontré que le stade de la vésicule germinative (VG) était le seul présent jusqu’à 44h après l’ovulation. Le premier stade métaphase II n’est observé qu’à partir de 54h. Plusieurs stades de maturation ovcytaire différents sont observés au même moment pour une même chienne. In vivo, la fécondation se produit dans la plupart des cas à partir de 90h post ovulation dans des ovocytes ayant complété leur maturation (métaphase II). La pénétration in vivo d’ovocytes immatures par des spermatozoïdes apparaît extrêmement rare. Ces résultats devraient permettre une amélioration ou une simplification de la pratique vétérinaire quotidienne, notamment lors d’utilisation d’insémination artificielle en semence congelée. De plus une meilleure connaissance des processus impliqués dans la maturation ovocytaire in vivo, la fécondation, et le développement embryonnaire précoce sont des étapes importantes pour améliorer le développement des biotechnologies de la reproduction dans l’espèce canine.

Detection of oestrus in pigs occurs predominantly through monitoring for the presence of standing heat, the behaviour change indicative of sexual receptivity. Standing heat can be used to identify the oestrus period but is not capable of precisely identifying ovulation and the optimum timing for insemination. As a result, breeding protocols implement double inseminations repeated over the 2-3 day oestrus period to ensure viable spermatozoa are present within the reproductive tract at ovulation. Multiple inseminations result in wasted semen doses and high labour inputs which could be prevented with the development of an accurate oestrus detection tool. This project was focused on investigating and evaluating novel markers that enable rapid identification of ovulation and the optimum time for mating with high precision. There are several physiological changes in sows that could be used as alternative markers. This research focuses on several markers during oestrus: electrical resistance of the reproductive tract, cervical mucus composition, body temperature and quantified behaviour monitoring. Oestrus was clearly distinguished through observation of elevated activity levels and distinctive signal profiles, detected using collar-mounted accelerometers. This technology is a precise potential replacement of existing oestrus detection protocols which could reduce daily labour requirements for this task. Ovulation occurred simultaneously with sharp increases in vaginal electrical resistance (ER), a reduction in cervical mucus pH and sodium levels, increased likelihood of linear cervical mucus patterns and increased vulva temperature. The recommendation from the current study is to conduct inseminations immediately upon observation of any of these markers. Individual markers can enable accurate detection of ovulation status. However, if multiple markers are identified, a more productive and efficient conception outcome is likely leading to more profitable sow management.

Studies to monitor bovine ovarian function with regard to follicular growth and turnover, and corpus luteum (CL) growth and function, were carried out during three different reproductive states: the postpartum anestrus period, early pregnancy and during the artificial control of the estrous cycle with the synthetic progestin norgestomet. Ovarian function was monitored using a combination of ultrasound imaging and progesterone (P₄) profiling. Growth of large antral follicles (> 10mm) was found to commence very early in the postpartum period and ovulation occurred as early as the first week postpartum. Short first postpartum estrous cycles (< 18 days) were observed in a minority of the animals studied (4/10) and the occurance of a short first cycle was not associated with an early ovulation following parturition. Growth of large antral follicles occurred in a wave-like pattern during the postpartum estrous cycles with most cycles being composed of two waves of growth, the second wave resulting in the growth of the ovulatory follicle. A wave-like pattern of growth of large dominant follicles was also seen through the first 60 days of pregnancy. There was no difference between pregnant and non pregnant cows in the size of the dominant follicle found on day 20. In addition no effect of the CL could be found on the side on which the dominant follicle was found, it was as likely to be on the ipsilateral ovary to the CL as on the contra lateral. The gonadotrophin ihibitor norgestomet did not effect follicular dynamics in the presence of the CL, however in the absence of a CL the dominant follicle present was maintained for the duration of the norgestomet treatment and then went on to ovulate upon norgestomet removal. In addition there was no new growth of antral follicles in the absence of a CL. Norgestomet did not effect the temporal relationship between the onset of standing estrus, the LH surge and ovulation. The results of the three studies suggest that a wavelike pattern of growth of large antral follicles is a characteristic of the bovine ovary regardless of the reproductive state.<br>Land and Food Systems, Faculty of<br>Graduate

Chez les ovins allaitants, la prolificité (nombre d’agneaux par mise-bas) est un des leviers technico-économique important pour améliorer la rentabilité d’un élevage. D’un point de vue génétique, ce caractère est très peu héritable, mais des mutations ponctuelles ayant un effet important sur l’augmentation du nombre d’ovulations et de la prolificité ont été identifiées dans quatre gènes dits de fécondité (Fec) et nommés FecB/BMPR1B, FecG/GDF9, FecX/BMP15 et FecL/B4GALNT2. L’objectif de cette thèse est l’identification de mutations de prolificités, nouvelles ou connues, principalement dans les races ovines allaitantes françaises pour lesquelles est posée une hypothèse statistique de ségrégation de telles mutations. En associant des approches de génétique, de génomique à haut-débit, et de biologie moléculaire et fonctionnelle, j’ai identifié cinq mutations à effet majeur associées à la prolificité dans huit populations ovines différentes. Toutes ces mutations affectent les gènes déjà connus, mais deux d’entre-elles sont nouvellement identifiées par cette thèse dans le gène FecX/BMP15. En particulier, la nouvelle mutation FecXN est, à la différence des 9 autres mutations prolifiques connues de BMP15, située dans la partie régulatrice du gène inhibant son expression. Une fois ces mutations identifiées, l’information de fréquence de la présence de chaque mutation dans les populations et de son effet sur la reproduction des brebis doit être prise en compte pour la gestion des schémas de sélection. Dans ce cadre, j’ai particulièrement étudié la mutation FecLL du gène FecL/B4GALNT2 précédemment découverte en race Lacaune et que j’ai mis en évidence dans la race Noire du Velay. La mutation FecLL, connue pour augmenter la prolificité des brebis de +0,45 agneaux par mise-bas, n’a pas d’impact sur le poids de naissance ou la croissance des agnelles porteuses de cette mutation. Cependant, les agnelles porteuses de FecLL présentent une puberté avancée de 2 mois en moyenne. Cette précocité sexuelle n’est pourtant pas expliquée par l’observation de concentrations circulantes plus faibles de deux hormones ovariennes AMH et inhibine A. De façon intéressante pour la pratique de l’insémination animale, les brebis porteuses de FecLL sont plus fertiles que les brebis non mutées en partie grâce à leur meilleure sensibilité à l’hormone PMSG utilisée de façon exogène pour synchroniser les ovulations. L’ensemble de ce travail de thèse apporte de nouveaux éléments pour améliorer la gestion génétique et physiologique des populations ovines allaitantes dans lesquelles ségrégent des mutations à effet majeur sur la prolificité. L’ensemble de ce travail de thèse apporte de nouveaux éléments pour améliorer la gestion génétique et physiologique des populations ovines allaitantes dans lesquelles ségrégent des mutations à effet majeur sur la prolificité<br>In meat sheep, prolificacy (number of lambs per lambing) is one of the most important technicaleconomic levers to improve the breeders’ profitability. From a genetic point of view, this trait is lowly heritable. However, point mutations having a significant effect on increasing ovulation rate and prolificacy have been identified in four fecundity (Fec) genes, named FecB/BMPR1B, FecG/GDF9, FecX/BMP15 and FecL/B4GALNT2. The objective of this thesis was the identification of new or already known prolificacy mutations, mainly in French meat sheep breeds for which the segregation of such mutations was statistically hypothesized. By combining genetics, highthroughput genomics, and molecular and functional biology approaches, I identified five mutations with major effect on prolificacy in eight different sheep populations. All these mutations affect the fecundity genes already known, but two of them in the FecX/BMP15 gene are newly identified by this thesis work. In particular, the new FecXN mutation is, unlike the 9 other known prolific mutations in BMP15, located in the regulatory part of the gene inhibiting its expression. Once these mutations are identified, the information of frequency of the presence of each mutation in the populations and the effect on the reproductive physiology of the ewes must be considered for the management of breeding schemes. In this context, I particularly studied the FecLL mutation of the FecL/B4GALNT2 gene previously discovered in Lacaune sheep and that I also evidenced in the Noire du Velay breed. The FecLL mutation, known to increase the ewe prolificacy by +0.45 lambs per lambing, has no impact on the birth weight or growth rate of ewe lambs carrying this mutation. However, ewe lambs carrying FecLL have an advanced puberty of 2 months on average. This sexual precocity is however not explained by the observation of lower circulating concentrations of two ovarian hormones, AMH and inhibin A. Interestingly for the practice of animal insemination, ewes carrying FecLL are more fertile than non-carrier ewes partly due to their better sensitivity to the PMSG administration used to synchronize ovulations. All of this thesis work brings new elements to improve the genetic and physiological management of meat sheep populations in which a mutation with major effect on prolificacy segregates

In two experiments, immature female Sprague-Dawley rats treated with superovulatory doses of pregnant mare serum gonadotropin (PMSG) were used to study the effects of antiandrogen, hydroxyflutamide, on steroid production, particularly the biologically active androgens, testosterone, 5α-dihydrotestosterone, and androstenedione. In the first experiment, the animals were given either 5 mg hydroxyflutamide or vehicle alone at 30 and 36 h following 40 IU PMSG. Compared to the vehicle group, hydroxyflutamide treatment significantly reduced the percentage of degenerate oocytes recovered from oviducts (p<0.05). Serum levels of aromatizable androgens, testosterone and androstenedione, and their aromatized product, estradiol-17ß significantly decreased (p<0.05) in hydroxyflutamide-treated group; however, the serum concentrations of nonaromatizable androgen, 5α-dihydrotestosterone, was not statistically different between the two groups. In the second experiment, ovaries stimulated with 4 or 40 IU PMSG were obtained 48 h later and cultured in the presence and absence of hydroxyflutamide (10⁻⁵M) and/or testosterone (10⁻⁷ M) to study [4⁻¹⁴C] pregnenolone metabolism to major steroids. In 40 IU stimulated ovaries, hydroxyflutamide significantly decreased the metabolism of pregnenolone to progesterone (p<0.01) and androstenedione (p<0.01) while the production of estradiol-17ß increased significantly (p<0.05); however, pregnenolone conversions to testosterone and 5α-dihydrotestosterone were not statistically different between the untreated and hydroxyflutamide-treated cultures. Testosterone completely reversed the hydroxyflutamide-induced alteration of pregnenolone metabolism. In contrast, there was no difference in the pregnenolone conversion patterns between the untreated and hydroxyflutamide or hydroxyflutamide plus testosterone groups in the culture of ovaries stimulated with 4 IU PMSG. Present results confirm previous reports that antiandrogen, hydroxyflutamide, decreases the percentage of abnormal oocytes recovered from superovulating rats, and indicates that this hydroxyflutamide effect may be partly mediated by altered ovarian steroidogenesis, specifically the reduced hypersecretion of aromatizable androgens, testosterone and androstenedione, and/or estradiol-17ß.<br>Medicine, Faculty of<br>Obstetrics and Gynaecology, Department of<br>Graduate

This study was designed to investigate the locus of action of different gonadotrophins on the stimulation of multiple follicular development and superovulation in heifers. In addition follicular populations and steroiodogenic potential of the follicles (>10 mm diameter) at different stages of the superovulatory treatment were studied. Experiment 1 was carried out to investigate the effect of three gonadotrophins (pregnant mare serum gonadotrophin, PMSG; human menopausal gonadotrophin, hMG-Pergonal 75 i.u. FSH, 75 i.u. LH per ampoule; and urofollitrophin UF-Metrodin 75 i.u. FSH per ampoule) on multiple follicular development and hormonal profiles. Experiments 2 and 3 were designed to study follicular populations and steroiodogenic potential of the follicles in superovulated heifers and to compare these parameters with control heifers.