RESUMO
The present study investigated the pituitary oestrogen (ER) and progesterone (PR) receptor concentrations in ewes during the oestrous cycle in the breeding season (n = 19), and in anoestrous ewes treated with gonadotrophin-releasing hormone (GnRH) (n = 11) and anoestrous ewes treated with progesterone + GnRH (n = 11). The pituitary ER and PR concentrations at the expected time of ovulation and in the early and late luteal phases were measured by binding assay. The pattern of pituitary ER and PR concentrations in the progesterone + GnRH-treated ewes resembled the pattern found during the normal oestrous cycle, with ER and PR concentrations decreasing from the time of ovulation to the early luteal phase. In contrast, in ewes treated with GnRH alone, ER and PR concentrations increased in the early luteal phase, which may increase the inhibitory effects of steroid hormones on luteinising hormone secretion, ultimately leading to the development of subnormal luteal phases.
Assuntos
Cruzamento/métodos , Corpo Lúteo/fisiologia , Estro/fisiologia , Hipófise/metabolismo , Receptores de Estrogênio/metabolismo , Receptores de Progesterona/metabolismo , Ovinos , Análise de Variância , Animais , Corpo Lúteo/efeitos dos fármacos , Estro/metabolismo , Feminino , Hormônio Liberador de Gonadotropina/farmacologia , Hipófise/efeitos dos fármacos , Progesterona/farmacologia , Ligação ProteicaRESUMO
Two experiments were performed to determine the endocrine and ovarian changes in medroxyprogesterone acetate (MAP)-primed ewes after ram introduction. Experiment 1 was performed during the mid-breeding season with 71 ewes primed with an intravaginal MAP sponge for 12 days. While the control (C) ewes (n = 35) were in permanent contact with rams, the ram effect (RE) ewes (n = 36) were isolated for 34 days prior to contact with rams. At sponge withdrawal, all ewes were joined with eight sexually experienced marking Corriedale rams and estrus was recorded over the next 4 days. The ovaries were observed by laparoscopy 4-6 days after estrus. Four weeks later, pregnancy was determined by transrectal ultrasonography. In eight ewes from each group, ovaries were ultrasonographically scanned; FSH, LH, and estradiol-17beta were measured every 12 hours until ovulation or 96 hours after estrus. The response to the rams was not affected by the fact that ewes had been kept or not in close contact with males before teasing. No differences were found in FSH, LH, estradiol-17beta concentrations, growth of the ovulatory follicle, onset of estrus, ovulation rate, or pregnancy rate. Experiment 2 was performed with 14 ewes during the nonbreeding season. Ewes were isolated from rams for 1 month, and received a 6-day MAP priming. Ovaries were ultrasonographically scanned every 12 hours, and FSH, LH, estradiol-17beta, and progesterone were measured. Ewes that ovulated and came into estrus had higher FSH and estradiol-17beta levels before introduction of the rams than did ewes that had a silent ovulation. The endocrine pattern of the induced follicular phase of ewes that came into estrus was more similar to a normal follicular phase, than in ewes that had a silent ovulation. The follicle that finally ovulated tended to emerge earlier and in a more synchronized fashion in those ewes that did come into estrus. All ewes that ovulated had an LH surge and reached higher maximum FSH levels than ewes that did not ovulate, none of which had an LH surge. We conclude that (a) the effect of ram introduction in cyclic ewes treated with MAP may vary depending on the time of the breeding season at which teasing is performed; (b) patterns of FSH, and estradiol-17beta concentrations, as indicators of activity of the reproductive axis, may be used to classify depth of anestrus; and (c) the endocrine pattern of the induced follicular phase, which is related to the depth of anestrus, may be reflected in the behavioral responses to MAP priming and the ram effect.
Assuntos
Cruzamento , Anticoncepcionais Femininos/farmacologia , Estro/efeitos dos fármacos , Acetato de Medroxiprogesterona/farmacologia , Ovário/efeitos dos fármacos , Animais , Estradiol/sangue , Feminino , Hormônio Foliculoestimulante/sangue , Hormônio Luteinizante/sangue , Masculino , Ovário/diagnóstico por imagem , Gravidez , Ovinos , UltrassonografiaRESUMO
This study investigated if ewes expected to have subnormal luteal phases (SNLP) present a different pattern of uterine oestrogen receptor (ER) and progesterone receptor (PR) expression at the expected time of premature luteolysis. The concentrations of uterine ER, PR and ERalpha mRNA, and the steroid ovarian hormone were determined in anoestrous ewes treated with either gonadotrophin-releasing hormone (GnRH) to develop a SNLP (n = 16), or progesterone + GnRH to develop a normal luteal phase (NLP; n = 16). The ER, PR and ERalpha mRNA concentrations were measured using binding and solution hybridisation assays, while the hormone level concentration was measured by radioimmunoassay. In all ewes, a luteinising hormone- and follicle-stimulating hormone-synchronised surge was found. The SNLP group had lower preovulatory oestradiol levels than the NLP group. On Day 5, the SNLP group had lower progesterone levels, and higher uterine ER, PR and ERalpha mRNA concentrations than the NLP group. While in the SNLP group the receptor expression increased from Days 1 to 5, in the NLP group the receptor expression decreased. The results suggest that the induction of steroid receptor expression in the uterus and the hormonal environment found in the experimental SNLP group at the expected time of premature luteolysis may be involved in the mechanisms causing SNLP.
Assuntos
Corpo Lúteo/fisiologia , Estradiol/sangue , Progesterona/sangue , Receptores de Esteroides/análise , Ovinos/fisiologia , Útero/química , Animais , Receptor alfa de Estrogênio/genética , Feminino , Hormônio Foliculoestimulante/sangue , Expressão Gênica , Hormônio Liberador de Gonadotropina/administração & dosagem , Hormônio Luteinizante/sangue , Luteólise , Progesterona/administração & dosagem , RNA Mensageiro/análise , Receptores de Estrogênio/análise , Receptores de Progesterona/análiseRESUMO
This study tested whether the effects of a short period of nutritional supplementation given to ewes during the luteal phase on follicle development and ovulation rate is associated with an increase in circulating concentrations of FSH, glucose or metabolic hormones. Oestrus was synchronised with two prostaglandin injections given 9 days apart and the supplement consisted of corn grain and soybean meal. Corriedale ewes with low body condition were randomly assigned to 2 groups: the control group (C; n = 10) received a maintenance diet while the short-term supplemented group (STS; n = 10) received double the maintenance diet over days 9 to 14 of the oestrous cycle (day 0 = ovulation). Ovaries were examined daily by ultrasound and blood was sampled three times a day during the inter-ovulatory interval for measuring reproductive and metabolic hormones. On days 9, 11 and 14 of the oestrous cycle, half of the ewes from each group (n = 5) were bled intensively to determine the concentrations of glucose, insulin, IGF-I and leptin. Plasma FSH, progesterone, oestradiol and androstenedione concentrations were similar among groups. Dietary supplementation increased plasma insulin concentrations from the first to the sixth day of supplementation and increased glucose concentrations on the third day, compared with control ewes. Plasma leptin concentrations were higher in STS ewes from the second to the fifth day of supplementation. The pattern of IGF-I concentrations was similar among groups. In STS ewes, the nutritional treatment prolonged the lifespan of the last non-ovulatory follicle, so fewer follicular waves developed during the cycle. In STS ewes, increased concentrations of glucose, insulin and leptin one day before ovulatory wave emergence were associated with increased numbers of follicles growing from 2 to 3 mm and with stimulation of the dominant follicle to grow for a longer period. We suggest that the mechanism by which short-term nutritional supplementation affects follicle development does not involve an increase in FSH concentrations, but may involve responses to increased concentrations of glucose, insulin and leptin, acting directly at the ovarian level. This effect is acute, since concentrations of all three substances decrease after reaching peak values on the third day of supplementation. The status of follicle development at the time of maximum concentrations of glucose and metabolic hormones may be one of the factors that determines whether ovulation rate increases or not.
Assuntos
Fenômenos Fisiológicos da Nutrição Animal , Suplementos Nutricionais , Insulina/sangue , Folículo Ovariano/fisiologia , Ovulação/fisiologia , Ovinos/metabolismo , Animais , Glicemia/análise , Feminino , Hormônio Foliculoestimulante/sangue , Fator de Crescimento Insulin-Like I/análise , Leptina/sangue , Folículo Ovariano/diagnóstico por imagem , Fatores de Tempo , UltrassonografiaRESUMO
The present review summarises knowledge of the reproductive response of anoestrous ewes to the introduction of rams - in other words, the ram effect. The ovarian and endocrine response, the factors that determine whether ewes will respond or not (associated with both the stimulus and the receptivity of the ewes) and some aspects of practical management are discussed. Information on the use of the ram effect to stimulate post-partum, prepubertal and cyclic ewes is also given. New insights are provided on ovarian response patterns, including recently collected information on luteal responses. The existence of delayed ovulation (5-7 days after the introduction of the rams) followed by luteal phases of normal or short length, luteal cysts and luteinised follicles is reported after scanning the ovaries with ultrasound. Endocrine parameters for depth of anoestrus, such as LH pulsatility and FSH concentrations, and how the concentrations of these hormones should be considered are discussed. Particular attention is paid to the observation of spontaneous, higher LH pulsatility and higher FSH concentrations in anoestrous ewes that respond to rams with luteal phases than in those that fail to respond. The use of progestogen priming and single progestogen administration and the possible advantages for synchronisation of oestrus are also discussed. Other factors that should be considered before the ram effect is applied, such as the strength of the stimulus and some practical considerations, are also included.
Assuntos
Anestro/fisiologia , Sincronização do Estro/métodos , Comportamento Sexual Animal , Carneiro Doméstico/fisiologia , Anestro/efeitos dos fármacos , Anestro/metabolismo , Animais , Feminino , Hormônio Foliculoestimulante/sangue , Hormônio Foliculoestimulante/metabolismo , Hormônio Luteinizante/sangue , Hormônio Luteinizante/metabolismo , Masculino , Progesterona/farmacologiaRESUMO
The effect of plane of nutrition on progesterone receptor (PR) and estrogen receptor alpha (ERalpha) expression in ovine endometrium was investigated. Rasa Aragonesa ewes (n=26) were fed diets to provide either 1.5 (Group C) or 0.5 (Group L) times the daily maintenance requirement and were slaughtered at Days 5 or 10 of the estrous cycle (Day 0=estrus). PR and ERalpha immunoreactivity were analyzed in eight endometrial cell compartments, defined by cell type and location. Group L had less PR immunostaining on Day 5 (P<0.05), which is consistent with lesser endometrial content of progesterone found in such animals. Most cell types of Group C had down regulation of PR at Day 10, but in Group L, this pattern was observed only in three cell compartments. The lesser PR contents found at Day 5 in Group L ewes may explain the lack of inhibition of PR. No effect of treatment or day of the estrous cycle was observed in ERalpha. Results indicate that endometrial PR is affected in a cell type, in specific manner, by plane of nutrition.
Assuntos
Endométrio/metabolismo , Estado Nutricional/fisiologia , Receptores de Estrogênio/biossíntese , Receptores de Progesterona/biossíntese , Ovinos/metabolismo , Animais , Receptor alfa de Estrogênio , Feminino , Imuno-Histoquímica , MasculinoRESUMO
The objective of this study was to assess the accuracy of estimating the size and number of corpora lutea (CL) and ovarian follicles by ultrasonography (US) of the ewe in standing position. US observations were compared with those made at subsequent postmortem examination of the ovaries. Corriedale ewes (n=50) of unknown reproductive history and at random stages of the oestrus cycle were used for the study. Transrectal US was performed using a 7.5 MHz transducer with the ewe in standing position. The ewes were slaughtered 12 h after the US examination and the ovaries collected, dissected and the number and size of the CL and follicles evaluated. CL were classified as functional or non-functional on the basis of their colour and follicles were classified by size (2, 3, 4 and > or =5 mm). Accuracy of US was assessed by calculating its positive predictive value and sensitivity. The data were evaluated by Pearson correlation and linear regression analysis. The predictive value and sensitivity of US was 100% for the presence and 96% for the absence of CL. In four out of five ewes with double ovulations, the presence of both CL was correctly diagnosed by US. For functional CL, the sensitivity of US was 100%. The regression coefficient for CL diameter was significant (P< or =0.001; r2=0.4; n=35). The size of 85 of 117 follicles was accurately determined. The correlation between numbers of follicles counted by US and postmortem increased with size of follicle from r=0.44 (P< or =0.01) for 2 mm to r=0.85 (P< or =0.001) for >or =5 mm diameter follicles. The regression between the diameter of follicles determined by the two methods was significant (P< or =0.001; r2=0.8; n=117). The predictive value of US for the number of follicles was high (98-100%) for all follicle sizes except for 3 mm diameter follicles (predictive value 71%). Similarly, the sensitivity was high for all sizes of follicles (90-95%) except for those of 2 mm diameter (62%). It was concluded that ultrasound scanning provides a highly accurate method for determining the number of CL and follicles > or =4 mm diameter but that its predictive value and sensitivity are lower for smaller diameter follicles. The regression equation for diameter measured by US on that evaluated postmortem explained more of the variation for follicles than for CL.
Assuntos
Ovário/diagnóstico por imagem , Ovinos/anatomia & histologia , Ultrassonografia/veterinária , Animais , Corpo Lúteo/diagnóstico por imagem , Feminino , Modelos Lineares , Folículo Ovariano/diagnóstico por imagem , Reto , Sensibilidade e Especificidade , Ultrassonografia/métodosRESUMO
The aim of this study was to compare the response of cortisol in sheep of different sex and gonadal status to adrenal cortex stimulation by an ACTH analogue in the breeding and non-breeding season. Twenty-four adult Corriedale sheep were used in the non-breeding season, and 19 in the breeding season. Three weeks prior to the first trial (non-breeding season), six rams and six ewes were gonadectomised. In each trial, blood was obtained every 15min for 9h and the animals received 0.5mg of ACTH (Tetracosactid, Synacthen Depot i.m., after 1.5h of sampling. Sampling began at 10:00a.m. in the non-breeding season and at 9:00a.m. in the breeding season. Three main effects (sex, gonadal status and season) were evaluated, each with two levels (male and female, intact and gonadectomised, breeding and non-breeding season, respectively). In both seasons, the females showed higher cortisol levels after ACTH than males (P<0.001), though the difference seemed less marked in the non-breeding season. The cortisol response in the ewes was not affected by season. The rams, however, showed a lower response in the breeding season (P<0.03). Gonadectomy reduced the response in the ewes (P<0.001) but had no effect in the rams. Nevertheless, gonadectomy also eliminated the differences between the ewes and the rams, such that the intact rams had lower levels of cortisol compared to the intact females, with those of the gonadectomised animals of both sexes being intermediate between the gonad-intact groups. The results of this study confirm sex differences in ACTH induced cortisol secretion in intact sheep in vivo. Furthermore, by applying exogenous ACTH we have directly stimulated the adrenal cortex, indicating the existence of sex differences also at this level. The circulating gonadal steroids, which are responsible at least in part for the sex differences in the responses to stress, may influence cortisol secretion from the adrenal gland by direct action at the cortex.
Assuntos
Hormônio Adrenocorticotrópico/análogos & derivados , Cruzamento , Hidrocortisona/metabolismo , Ovinos/fisiologia , Córtex Suprarrenal/efeitos dos fármacos , Córtex Suprarrenal/fisiologia , Animais , Peso Corporal , Cosintropina/farmacologia , Feminino , Cinética , Masculino , Orquiectomia , Ovariectomia , Análise de Regressão , Estações do Ano , Testosterona/sangueRESUMO
To evaluate the effects of incorporating medroxyprogesterone acetate (MAP) in an Ovsynch protocol, cyclic lactating dairy cows were assigned randomly to two groups (control and MAP, n=8 each). Ovsynch treatment (Day 0: GnRH, Day 7: PG, Day 9: GnRH) was initiated at random stages of the estrous cycle (control) and an intravaginal polyurethane sponge impregnated with 300mg of MAP was inserted intravaginally in the MAP group at Day 0 and removed at Day 7 of the Ovsynch protocol (MAP treatment). Ovaries were scanned daily from Day 0 until the second GnRH treatment on Day 9 and from then every 6h for 36 h. Milk samples were collected three times weekly starting 17 days before the initiation of treatment to determine the stage of the cycle at the beginning of the Ovsynch protocol. Blood samples were collected to monitor estradiol (E2), progesterone (P4), LH, and 15-ketodihydro-PGF(2alpha) (PGFM) by RIA. Response to the first GnRH treatment varied with the stage of the cycle at the time of initiation of treatment, as cows in metestrous and late diestrous did not ovulate. In cows ovulating, growth rate of the new follicle was not affected by the addition of MAP. No treatment differences were found in E2 concentrations which reached a maximum at Day 9, consistent with the maximum follicular size. At Day 7, cows with luteal concentrations of P4 had increased concentrations of PGFM, but cows with basal P4 did not show an active release of prostaglandins. There were no treatment differences in the ovulatory response to the second GnRH-induced ovulation, with 11 of the 16 cows ovulating between 16 and 32 h. The addition of MAP to the Ovsynch protocol could not mimic the normal high progesterone levels needed to prevent premature ovulations in those cows with premature CL regression.
Assuntos
Bovinos/fisiologia , Dinoprosta/análogos & derivados , Hormônio Liberador de Gonadotropina/administração & dosagem , Hormônios/sangue , Lactação , Acetato de Medroxiprogesterona/administração & dosagem , Folículo Ovariano/fisiologia , Prostaglandinas F Sintéticas/administração & dosagem , Administração Intravaginal , Animais , Dinoprosta/sangue , Estradiol/sangue , Ciclo Estral , Feminino , Cinética , Hormônio Luteinizante/sangue , Indução da Ovulação/veterinária , Progesterona/sangueRESUMO
The objective of this work was to investigate the effect of progesterone (P) and gonadotropin-releasing hormone (GnRH) treatment on estrogen receptor (ER) and P receptor (PR) concentrations in the pituitary gland and uterus of anestrous ewes. Ewes were either not treated (group C, n = 4); were treated with 0.33 g P-controlled internal drug release (P-CIDR) for 10 days (group P, n = 4), with GnRH, 6.7 ng i.v. injections every 2 h for 18 h followed by a 4 microg bolus administration of Receptal at 20 h (group GnRH, n = 4), or with a combination of the P and GnRH treatment (group P + GnRH, n = 3). Ewes were humanely killed either at the beginning of the experiment (group C), when the CIDR was removed (group P), or 24 h after the GnRH bolus treatment (groups GnRH and P + GnRH). Progesterone treatment increased serum P concentrations, indicating that the treatment was effective. All GnRH treated ewes had similar luteinizing hormone (LH) surges, which lasted 8 h. At slaughter, estradiol (E2) concentrations in the GnRH group were higher than in groups C, P, and P + GnRH. Treatment with GnRH increased more than 10-fold the content of ER and PR in the pituitary gland without altering steroid receptor concentrations in the uterus. When GnRH was combined with P the uterine receptor contents were higher than with P treatment alone. The treatment with P decreased ER and PR content in the uterus, but had no effect on the pituitary gland. The results show that regulation by P and GnRH of ER and PR content in anestrous ewes is tissue-specific.
Assuntos
Anestro , Hormônio Liberador de Gonadotropina/farmacologia , Progesterona/farmacologia , Receptores de Estrogênio/análise , Receptores de Progesterona/análise , Ovinos/metabolismo , Animais , Feminino , Tamanho do Órgão , Folículo Ovariano/anatomia & histologia , Ovário/anatomia & histologia , Hipófise/anatomia & histologia , Hipófise/química , Hipófise/efeitos dos fármacos , Útero/anatomia & histologia , Útero/química , Útero/efeitos dos fármacosRESUMO
This study characterized endometrial expression of mRNAs of oestrogen and progesterone receptors (ER, PR) and insulin-like growth factor-I (IGF-I) during the oestrous cycle. Seven Holstein heifers that showed standing oestrus on the same day (day 0) were selected and blood samples for oestradiol (E2) and progesterone (P4) determinations by RIA were taken daily until day 23. Endometrial samples were taken by transcervical biopsies on days 0, 5, 12 and 19 for mRNA determination by solution hybridization. The highest endometrial mRNA levels of ERalpha and PR were observed at oestrus and a decline was observed already at day 5, which then decreased progressively at the end of the luteal phase. IGF-I mRNA levels were higher at day 0 and 5 than at day 12. At day 19, mRNA levels of ERalpha, PR and IGF-I were the lowest in heifers that were at the end of their luteal phase (n=4), but were high again in heifers which P4 levels were basal (n=3). The temporal changes in mRNA endometrial expression of ERalpha, PR and IGF-I and their relation to the changes in steroid concentrations during the bovine oestrus cycle are described.
Assuntos
Bovinos/fisiologia , Endométrio/metabolismo , Ciclo Estral/metabolismo , Fator de Crescimento Insulin-Like I/metabolismo , Receptores de Estrogênio/metabolismo , Receptores de Progesterona/metabolismo , Animais , Northern Blotting , Estradiol/sangue , Receptor alfa de Estrogênio , Feminino , Regulação da Expressão Gênica/fisiologia , Fator de Crescimento Insulin-Like I/genética , Ovário/metabolismo , Progesterona/sangue , RNA Mensageiro/metabolismo , Receptores de Estrogênio/genética , Receptores de Progesterona/genética , Fatores de TempoRESUMO
Plasma FSH, LH, estradiol (E2) and progesterone (P4) profiles and patterns of follicular growth and regression by ultrasonography were determined after E2 treatment (1 microg/kg) in anestrous ewes. Fifteen ewes were treated with one (group I, n=7) or two (group II, n=4) i.m. injections of E2 with a 24h interval, or two oil injections with a 24h interval (group C, n=4). Blood samples for E2, P4, FSH and LH determinations were collected daily 4 days before the initiation of the treatment (day 0), when bleeding increased to every 2h starting 2h before treatment until 56h after the first injection and from then on every 6h until day 8, and twice per day till the end of the experiment (day 9). During the experimental period (days -4 to 9), transrectal ultrasonic examinations were carried out daily using a 7.5 MHz linear array probe. Number and size of follicles > or =3mm in diameter were recorded. No estrous was detected before, during or after treatment. LH and FSH surges were observed 10-18h after the first E2 injection. The second E2 injection stimulated another release of LH but no surges. E2 inhibited FSH levels before the surge and the second E2 injection induced a longer inhibition. No ovulation was detected by ultrasonography during the experimental period and P4 levels remained low (<0.7 nmol/l) before, during and after the treatment in all ewes. There was an effect of E2 treatment on the diameter of the largest follicle, a decrease could be observed 3 days after the first injection in both ewes of groups I and II. The E2-treated groups had a higher frequency of ewes showing wave emergence on day 3 (day 1.5+/-1,2.4+/-0.4 and 2.5+/-0.5 for control, groups I and II). LH and FSH surges were observed after E2 treatment, but were not able to provoke ovulation neither luteinization. In contrast, the treatment was associated with the regression of the largest follicle and with emergence of a new follicular wave on day 3.
Assuntos
Anestro , Estradiol/farmacologia , Gonadotropinas/sangue , Folículo Ovariano/fisiologia , Ovinos/fisiologia , Animais , Estradiol/administração & dosagem , Estradiol/sangue , Feminino , Hormônio Foliculoestimulante/sangue , Hormônio Luteinizante/sangue , Folículo Ovariano/diagnóstico por imagem , Progesterona/sangue , UltrassonografiaRESUMO
The aim of this study was to evaluate the effect of the length of a progestagen treatment (12 d vs. 6 d) on follicular dynamics, estrus synchronization and pregnancy rate using medroxyprogesterone acetate (MAP) with or without an eCG dose at the end of MAP treatment. One hundred sixty Polwarth ewes were divided into four equal groups: long-term treated (LT, n=40); short-term treated (ST, n=40); long-term treated plus eCG (LTeCG, n=40); and short-term treated plus eCG (STeCG, n=40). Five ewes of each group were separated to undergo daily transrectal ultrasonography, and blood samples were taken for hormone determination. Until 96 h after sponge withdrawal the number of ewes in estrus was higher in both long-term-treated groups than in both short-term-treated groups but at the end of the observational period (144 h) no significant differences were found among groups. The pregnancy rate was higher in the ST group (87%) than in the other groups (LT, 63%; LTeCG, 67%; and STeCG, 58%; P< or =0.03). The ovulatory follicle emerged before sponge withdrawal in long-term-treated ewes (-3.8+/-0.4 d and -2.2+/-0.8 d for LT and LTeCG, respectively), whereas in short-term-treated ewes it emerges around sponge removal (0.4+/-1.1 d and 0.5+/-0.5 d for ST and STeCG, respectively; P< or =0.01). The ovulatory follicle in the LT group had a longer lifespan and attained a larger (P< or =0.05) maximum diameter than in the ST group. We conclude: a) that the lower pregnancy rate observed after long-term progestagen treatment was related to a slower follicular turnover that promoted the ovulation of persistent dominant follicles; (b) that short-term treatment resulted in a higher pregnancy rate probably due to the ovulation of newly recruited growing follicles; and (c) treatment with eCG had no advantage in association with long-term treatment and had a deleterious effect in combination with short-term treatment with MAP.
Assuntos
Folículo Ovariano/efeitos dos fármacos , Folículo Ovariano/fisiologia , Congêneres da Progesterona/administração & dosagem , Ovinos/fisiologia , Administração Intravaginal , Animais , Gonadotropina Coriônica/administração & dosagem , Estradiol/sangue , Sincronização do Estro , Feminino , Acetato de Medroxiprogesterona/administração & dosagem , Folículo Ovariano/diagnóstico por imagem , Indução da Ovulação , Gravidez , Estações do Ano , Fatores de Tempo , UltrassonografiaRESUMO
Regulation of the uterine expression of estrogen and progesterone receptors was studied in 20 three-month-old lambs that were not treated or treated with estradiol- 17beta. Determinations of receptors were performed by binding assays in the nuclear and cytosolic fractions, receptor mRNAs by solution hybridization, and estrogen receptor protein by an enzyme-immunoassay. Estradiol treatment decreased the receptor binding capacity of both receptors and the levels of immunoreactive estrogen receptor 12 h after injection in the absence of decreased receptor mRNAs, suggesting that the initial decrease is due to degradation of the proteins or that mRNAs are translated into new receptor proteins at a reduced rate. The mRNA levels increased after estradiol treatment suggesting that the replenishment phase consists of synthesis of new receptors rather than recycling of inactivated receptors.
Assuntos
Estradiol/farmacologia , Expressão Gênica/efeitos dos fármacos , Receptores de Estrogênio/genética , Receptores de Progesterona/genética , Ovinos/metabolismo , Útero/metabolismo , Animais , Núcleo Celular/química , Citosol/química , Feminino , RNA Mensageiro/análise , Receptores de Estrogênio/análise , Receptores de Estrogênio/metabolismo , Receptores de Progesterona/análise , Receptores de Progesterona/metabolismo , Útero/química , Útero/ultraestruturaRESUMO
The aim of the present study was to determine whether pre- and post-pubertal young rams on different grazing regimes, resulting in differences in live weight (LW), would show corresponding differences in testicular growth or testicular morphometry that could influence the reproductive traits of these rams upon reaching adulthood. Forty-one spring-born Corriedale rams were reared on either native pasture (low feeding level, Group L, n=22) or improved pasture (higher feeding level, Group H, n=19) from 1 to 7 months of age. Thereafter, half the animals in the native-pasture group were placed on improved pasture and vice versa, thus creating an additional four differential-grazing treatment groups (Groups LL, n=11; LH, n=11; HL, n=10; and HH, n=9). Animals were managed in this way until 18 months of age. Half the animals from each group were then castrated and their testes were subjected to morphometric analysis. The remaining animals (Groups LL, n=6; LH, n=6; HL, n=5; and HH, n=4) were managed together until 30 months of age (from 18 to 27 months on native pastures and from 27 to 30 months of age on improved pastures, at a stocking rate of two to three rams per hectare), whereupon they were also castrated for testicular morphometry. LW and scrotal circumference (SC) were recorded every 60 days. The stereological analysis of testicular parenchyma included counts of elongated spermatids and Sertoli cells. Differences (P<0.001) in LW were observed between feeding levels, even at 30 months of age. Differences (P<0.001) in SC existing at the end of the differential treatment (18 months of age) disappeared (n.s.) soon after. Most differences (P<0.05) in testicular morphometry existing at the end of the differential treatments were no longer significant 1 year later. It is concluded that changes in grazing management during pre- and post-pubertal periods can induce short-lived differences in testicular post-natal growth in Corriedale rams but do not influence testicular morphology or function later in life.
Assuntos
Ração Animal , Criação de Animais Domésticos , Ovinos/crescimento & desenvolvimento , Testículo/crescimento & desenvolvimento , Animais , Peso Corporal , Castração/veterinária , Processamento de Imagem Assistida por Computador , Masculino , Distribuição Aleatória , Escroto/fisiologia , Células de Sertoli , Ovinos/fisiologia , Espermátides/fisiologia , Estatísticas não Paramétricas , Testículo/anatomia & histologia , UruguaiRESUMO
The effects of estradiol-17beta (E2) on the expression of estrogen receptor alpha (ERalpha) in stromal and epithelial cells of endometrium in prepubertal lambs were investigated. Twenty three-month-old lambs were treated or not treated with one, two or three i.m. injections of E2 (1 microg x kg(-1)) in corn oil at intervals of 24 h. Lambs were slaughtered 12 or 24 h after the last injection. An immunohistochemical technique was used to visualize ERalpha immunostaining which was then analyzed quantitatively by a computer imaging analysis system. Seven endometrial compartments defined by cell type and location were analyzed separately. Positive staining of ERalpha was seen in the nuclei of stromal and epithelial cells. Glandular epithelium located next to the myometrium was stained more intensely than that next to the luminal epithelium and this phenomenon was maintained during treatment. Significantly less immunostaining was found in stromal cells 12 and 24 h after the first injection compared to the control group. A similar pattern was found in the glandular epithelium, although the decrease was more pronounced and the restoration of ERalpha was faster. This study shows that E2 treatment down regulates ERalpha in the endometrium temporarily in both stromal and epithelial cells, but the characteristics of this effect seems to be cell type specific.
Assuntos
Endométrio/metabolismo , Estradiol/farmacologia , Receptores de Estrogênio/efeitos dos fármacos , Ovinos/metabolismo , Animais , Regulação para Baixo/efeitos dos fármacos , Endométrio/citologia , Endométrio/efeitos dos fármacos , Células Epiteliais/metabolismo , Receptor alfa de Estrogênio , Feminino , Processamento de Imagem Assistida por Computador , Imuno-Histoquímica/veterinária , Receptores de Estrogênio/metabolismo , Células Estromais/metabolismoRESUMO
The present study was conducted: (a) to determine the degree of seasonal variation in testis stereology in Corriedale rams between autumn and winter; (b) to test the hypothesis that testis stereology of Corriedale rams grazing native pastures during autumn and winter would differ from those of Corriedale rams grazing sown pastures and supplemented with grain during the same period; and (c) to determine whether Sertoli cell numbers differ in adult rams between the breeding season (autumn) and the following non-breeding season (winter). Twenty experimental animals were studied. Six rams (autumn control group, C-A) that had been grazing on native pasture (stocking rate = 2-3 animals ha(-1)) were castrated at the beginning of the experiment (March, early autumn). Seven rams (winter control group, C-W) continued to graze on native pasture at the same stocking rate until the end of the experiment (August, late winter). Another seven rams (treated group, T) grazed on improved pasture (stocking rate = 1-2 animals ha(-1)) and were supplemented with 1 kg grain ram(-1) day(-1) until the end of the experiment. Live weight, scrotal circumference, serum testosterone concentration and selected testicular stereological parameters were measured. The treatment did not impede the winter reduction in testicular activity and reduced its magnitude slightly (group T) compared with controls (group C-W). Sertoli cell numbers were higher in autumn (group C-A) than in winter, both on native (group C-W) and sown pastures (group T). Diminishing Sertoli cell numbers between autumn and the following winter suggest the occurrence of that Sertoli cell death during this period. The results indicate that, although the reproductive activity of Corriedale rams is moderately seasonal, a restricted change in grazing and grain supplementation can only modify it to a limited extent.
Assuntos
Criação de Animais Domésticos , Ovinos/fisiologia , Testículo/anatomia & histologia , Fenômenos Fisiológicos da Nutrição Animal , Animais , Castração/veterinária , Processamento de Imagem Assistida por Computador , Masculino , Fotoperíodo , Radioimunoensaio/veterinária , Distribuição Aleatória , Análise de Regressão , Estações do Ano , Células de Sertoli/fisiologia , Células de Sertoli/ultraestrutura , Ovinos/anatomia & histologia , Contagem de Espermatozoides/veterinária , Espermátides/fisiologia , Testosterona/sangue , UruguaiRESUMO
The goal of the present study was to determine whether ACTH and progesterone have any effect on LH secretion and pulse frequency in recently castrated rams. Six 2-year-old Corriedale rams were castrated in the winter. The day before castration, blood samples were taken in order to establish the precastration LH levels. The rams were divided into an untreated group (group U: n = 2) and a treated group (group T: n = 4). The first treatment consisted of the i.v. administration of 0.5 mg of ACTH on day 20 post-castration, immediately after the first sample had been taken. During the second treatment, subcutaneous progesterone implants were given to group T for 5 days. Control samplings were performed one week before each treatment. Prior to castration, the testosterone levels were low, while after castration they were below the detection limit of the assay. Cortisol and progesterone concentrations were basal before castration in all of the animals and after castration in group U and also in the control samplings for group T. ACTH treatment caused a significant increase in both cortisol and progesterone levels for 3 h (P < 0.001). Progesterone implants raised progesterone levels in group T, but cortisol levels remained basal. Before castration, all animals had low LH levels and hardly any pulse activity was seen. After castration, both the number of LH pulses and the mean LH production increased significantly in all of the animals (P < 0.01). During the ACTH trial, LH pulse frequency was significantly reduced for the first 4 h following ACTH administration (P = 0.013), however, no such differences occurred in the prior control period. No effect was seen on mean LH concentration during the ACTH treatment. Progesterone treatment did not have any effect on either the number of LH pulses nor on LH concentrations (P > 0.05).
Assuntos
Hormônio Adrenocorticotrópico/farmacologia , Hormônio Luteinizante/metabolismo , Orquiectomia/veterinária , Progesterona/farmacologia , Ovinos/fisiologia , Animais , Anti-Inflamatórios/sangue , Anticorpos Monoclonais , Hidrocortisona/sangue , Hormônio Luteinizante/sangue , Masculino , Progesterona/sangue , Radioimunoensaio/veterinária , Testosterona/sangue , UruguaiRESUMO
One hundred eighty-nine Corriedale ewes were used during the non-breeding season to study the "ram effect" stimulus after priming with progestogens. Intravaginal sponges containing either medroxyprogesterone acetate (MAP group, n = 49), fluorogestone acetate (FGA group, n = 49), or progesterone devices (CIDR group, n = 46) were inserted on Day-6 (Day 0 = introduction of the rams). Forty-five ewes were untreated and kept as a control group. On Day 0 the sponges were removed and rams provided with marking harnesses for oestrous detection were placed with the ewes. Onset of estrus was monitored until Day 25, and conception was determined by transrectal ultrasonography. Ewes came into heat during 4 periods: Days 0-3, 5-7, 17-20, and 21-23. The overall number of oestrus ewes were 29%, 53%, 35%, and 50% for the control, MAP, FGA, and CIDR groups, respectively (MAP and CIDR > control, p < 0.05). Control ewes presented oestrus only on Days 17-20 and 21-23. Oestrus in the progestogen-primed ewes was concentrated during Days 0-3 and 17-20, and some ewes came into oestrus on Days 5-7. There were no differences between different primings neither in oestrous response nor in conception rate. The conception rate from matings occurring on Days 0-3 was higher than on those occurring on Days 17-20. We conclude that MAP, FGA, and CIDR is equally effective in improving the response to the ram effect, and the pattern of oestrus in primed ewes was different than previously reported.
Assuntos
Cruzamento , Estro/fisiologia , Congêneres da Progesterona/administração & dosagem , Progesterona/administração & dosagem , Ovinos/fisiologia , Administração Intravaginal , Animais , Feminino , Fertilização/fisiologia , Acetato de Fluorogestona/administração & dosagem , Masculino , Medroxiprogesterona/administração & dosagem , Progesterona/fisiologiaRESUMO
Nineteen Corriedale ewes were treated with an im dose of a PGF2alpha during the luteal phase to synchronize estrus. After ovulation had been detected by using ultrasonography (Day 0); the ewes were randomly assigned to 2 different groups. In 11 ewes a CIDR, which had previously been used for 10 d, was inserted on the fourth day after ovulation. The ewes then received a dose of PGF2alpha on Day 5 to induce luteolysis. The CIDR remained in place until the end of the experiment (Day 9). Control ewes (n = 8) received no treatment. Blood samples were taken daily for estradiol, progesterone and FSH determinations. In the untreated ewes, 2 follicular waves were detected in all of the animals throughout the monitoring period, with a mean wave interval of 4.5 d. The total number of follicles which were > or =2 mm decreased from Day 0 to Day 4 (8.8+/-1.0 to 5.3+/-0.6; P< or =0.05) and then increased at Day 7 (7.5+/-0.9; P< or =0.05). The growth profiles of both the largest and the second largest follicles of Wave 1 showed significant divergence, while no divergence was observed in Wave 2. Serum estradiol concentrations decreased significantly from the day before to the day of ovulation and then increased again during the growing phase of the largest follicle of Wave 1. Concentrations of FSH were high on the day of emergence of both waves, but while a significant decline was observed after emergence in Wave 1, the levels remained high in Wave 2. In 8 of the 11 treated ewes, the largest follicle of Wave 1 was still present on the ninth day after ovulation (persistent follicle). In the other 3 ewes, the largest follicle of Wave 1 was already regressing on the day that the treatment was administered, and the largest follicle that was present on Day 9 originated from Wave 2 (nonpersistent follicle). In persistent follicle ewes, the largest follicle of Wave 1 prolonged its lifespan significantly, attaining the maximum diameter (Day 8.1+/-0.8) later than in untreated (Day 3.0+/-0.4) and nonpersisted follicle ewes (Day 2.0+/-0.6). The total number of follicles decreased in persistent follicle ewes between Day 0 and Day 4 (7.9+/-1.5 to 4.5+/-0.5, respectively; P< or =0.05) and remained low until the end of the experiment. Progesterone concentrations (nmol/L) between Days 6 and 9 were significantly different between untreated and persistent follicle ewes (12.8+/-1.0 vs. 9.4+/-1.0, P< or =0.02). The present study confirms that the largest follicle of Wave 1 is dominant in the ewe and that subluteal progesterone concentrations can prolong its lifespan and extend this dominance.