Mares have an atypical hormone profile during pregnancy. Systemic progesterone (P4) levels approach zero by day 220 of gestation. Other reduced pregnanes such as 5��-pregnane-3, 20-dione (5��), 5��-pregnane-3��, 20��-diol (����), 3��-hydroxy-5��-pregnan-3-one (3��) and 20��-hydroxy-5��-prenan-3-one (20��), increase to near ��g/mL levels in the peripheral system of the mare until directly before parturition when they decrease. This unusual hormone profile during gestation indicates the possibility that other pregnanes, not P4, are responsible for uterine quiescence and gonadotropin inhibition during pregnancy. Three experiments were conducted to determine if these steroids have biologic activity. Experiment 1 consisted of jugular vein blood samples taken from mares from ten days pre-partum until the foal heat ovulation, approximately 15 days postpartum. Samples were analyzed for luteinizing hormone (LH), follicle stimulating hormone (FSH), and pregnane content. Concentrations of these hormones were analyzed for serial correlations. There was a serial negative correlation with pregnanes and FSH (p=0.0138), which were analyzed on a same day basis, day -5 to day of foaling. There also was a positive correlation with pregnanes and FSH analyzed from day of foaling to 10 days post-foaling (p<0.00l). There was also a significant negative correlation (p=0.0196) between pregnanes and LH, analyzed on a lag basis, day -5 to day of foaling for pregnanes, and day -5 to day of ovulation for LH. There was also a significant negative correlation when pregnanes were analyzed from day of foaling to 10 days post foaling, and LH was analyzed from 10 days before ovulation to day of ovulation (p=0.004). Maximum pre-partum pregnane levels did not affect time to ovulation (p=0.34). In experiment 2 equine anterior pituitary glands were harvested and the cells plated to begin a primary cell culture. After attachment, the cells were divided into treatment groups: P4, 5��, ����, 20��, 3�� or a control and each group subjected to a 1.0nM Gonadotropin Hormone Releasing Hormone (GnRH) challenge. Subsequently cells and medium were collected and analyzed for LH and FSH content using radioimmunoassay (RIA). The cells did exhibit a response to GnRH (p=0.015 between positive and negative controls) and there was a treatment effect for FSH (p=0.0058); only 3�� resulted in significantly more FSH release than the positive control (p=0.043) after stimulation with GnRH. There was no treatment effect on LH (p=0.56). Experiment 3 analyzed the response of equine uterine myometrial tissue to pregnane treatment. Myometrial tissue was harvested and placed in a 37��C Krebs buffered saline bath, connected to a physiograph and repetitive spontaneous smooth muscle contraction was induced with oxytocin. Tissue was then treated with P4, 5��, ����, 20��, 3�� or a control (ethanol). The amplitude and frequency of the spontaneous contractions were measured and compared to the control. There were no differences between post treatment responses of the control and pregnane treated samples in either frequency (p=0.78) or amplitude (p=0.63) of myometrial contractions. From these data we conclude that in vivo there is a significant and differential physiologic relationship between pre-partum pregnanes and gonadotropins. Due to lack of response it is unlikely that pregnanes inhibit pituitary secretion, and thus may exert their effects elsewhere, such as at the hypothalamus. The involvement of pregnanes in modulating myometrial contractions remains unclear. It is likely that P4 does play a role in decreasing myometrial responses to OT, however, that result was inconsistent in this study. / Graduation date: 2003

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 87-111). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 87-111). Also available on the Internet.

Graduation date: 2003

Graduation date: 1993

Graduation date: 1992

Made available in DSpace on 2014-06-11T19:29:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-01-25Bitstream added on 2014-06-13T20:38:40Z : No. of bitstreams: 1 schutzer_cgc_me_botfmvz.pdf: 677570 bytes, checksum: 16ad30b55942fb13d5f50a050990e9ea (MD5) / Universidade Estadual Paulista (UNESP) / O comportamento estacional reprodutivo das éguas constitui um desafio para veterinários e criadores. As éguas apresentam um período de atividade reprodutiva durante o verão e, no inverno, mínimo crescimento folicular e ausência de ovulação (anestro). O presente trabalho teve como objetivo avaliar o efeito de diferentes protocolos envolvendo o uso de luz artificial associado ou não ao implante intra vaginal de progesterona ou a administração de acetato de deslorelina sobre a ocorrência da primeira ovulação da estação de monta de éguas em anestro sazonal. Foram utilizadas 120 éguas em anestro distribuídas aleatoriamente em 8 grupos de tratamento: grupo 1 - Controle, grupo 2 – progesterona (P4), grupo 3 - luz artificial por 35 dias (L35), grupo 4 - luz artificial por 60 dias (L60), grupo 5 - luz artificial por 35 dias e progesterona (L35+P4), grupo 6 - luz artificial por 60 dias e progesterona (L60+P4), grupo 7 - luz artificial por 35 dias e acetato de deslorelina (L35+GnRH), e grupo 8 - luz artificial por 60 dias e acetato de deslorelina (L60+GnRH). Nos grupos onde foi utilizado o dispositivo intra-vaginal com 1,3g de progesterona, após a remoção do implante, as éguas passaram a ser avaliadas diariamente até atingirem folículo(s) com diâmetro de 35 mm em média e edema uterino compatível. Neste momento foi administrado 1500 UI de hCG e 1 mg de acetato de deslorelina associadas, por via intra-muscular, com o objetivo de indução da ovulação e o monitoramento continuou sendo diário até a ovulação, avaliada pela presença de corpo lúteo. A deslorelina foi administrada em todas as éguas dos grupos (L35+GnRH e L60+GnRH) a partir do 36º dia do experimento, de 12 em 12 horas, na dose de 100 μg, até estas atingirem folículo(s) com média de 35 mm de diâmetro e edema uterino compatível, para que pudesse ser induzida a ovulação... / The seasonal behavior of breeding mares is a challenge for veterinarians and farmers. The mares have a period of reproductive activity during the summer and in winter, minimum follicular growth and lack of ovulation (anoestrus). This study aimed to evaluate the effect of different protocols involving the use of artificial light with or without intravaginal progesterone-releasing device or deslorelin acetate on the occurrence of first ovulation in mares in seasonal anestrous. We used 120 mares in anestrous randomly assigned to 8 treatment groups: group 1 - Control, group 2 – progesterone (P4), group 3 - artificial light for 35 days (L35), group 4 - artificial light for 60 days (L60), group 5 - artificial light for 35 days and progesterone (L35+P4), group 6 - artificial light for 60 days and progesterone (L60+P4), group 7 - artificial light for 35 days and deslorelin acetate (L35+GnRH), and group 8 - artificial light for 60 days and deslorelin acetate (L60+GnRH). In groups where the device was used intra-vaginally with 1.3 g of progesterone, after implant removal mares began to be assessed daily until they reach the follicle(s) with a diameter of 35 mm on average and uterine edema compatible. At this time was given 1500 IU of hCG and 1 mg deslorelin acetate associated by intra-muscular, with the aim of ovulation induction and monitoring is continued daily until ovulation, as assessed by the presence of corpus luteum. The deslorelin was administered to all mares of the groups (L35 + GnRH and L60 + GnRH) from the 36o day of the experiment, 12 to 12 hours at a dose of 100 μg until they reach the follicle(s) with an average of 35 mm in diameter and uterine edema compatible, so it could be induced ovulation, or no later than 5 days of treatment for mares who have not reached follicular diameter and uterine ...(Complete abstract click electronic access below)

Orientador: Marco Antonio Alvarenga / Banca: José Antonio Dell'Aqua Júnior / Banca: Marcio Teoro do Carmo / Resumo: O comportamento estacional reprodutivo das éguas constitui um desafio para veterinários e criadores. As éguas apresentam um período de atividade reprodutiva durante o verão e, no inverno, mínimo crescimento folicular e ausência de ovulação (anestro). O presente trabalho teve como objetivo avaliar o efeito de diferentes protocolos envolvendo o uso de luz artificial associado ou não ao implante intra vaginal de progesterona ou a administração de acetato de deslorelina sobre a ocorrência da primeira ovulação da estação de monta de éguas em anestro sazonal. Foram utilizadas 120 éguas em anestro distribuídas aleatoriamente em 8 grupos de tratamento: grupo 1 - Controle, grupo 2 - progesterona (P4), grupo 3 - luz artificial por 35 dias (L35), grupo 4 - luz artificial por 60 dias (L60), grupo 5 - luz artificial por 35 dias e progesterona (L35+P4), grupo 6 - luz artificial por 60 dias e progesterona (L60+P4), grupo 7 - luz artificial por 35 dias e acetato de deslorelina (L35+GnRH), e grupo 8 - luz artificial por 60 dias e acetato de deslorelina (L60+GnRH). Nos grupos onde foi utilizado o dispositivo intra-vaginal com 1,3g de progesterona, após a remoção do implante, as éguas passaram a ser avaliadas diariamente até atingirem folículo(s) com diâmetro de 35 mm em média e edema uterino compatível. Neste momento foi administrado 1500 UI de hCG e 1 mg de acetato de deslorelina associadas, por via intra-muscular, com o objetivo de indução da ovulação e o monitoramento continuou sendo diário até a ovulação, avaliada pela presença de corpo lúteo. A deslorelina foi administrada em todas as éguas dos grupos (L35+GnRH e L60+GnRH) a partir do 36º dia do experimento, de 12 em 12 horas, na dose de 100 μg, até estas atingirem folículo(s) com média de 35 mm de diâmetro e edema uterino compatível, para que pudesse ser induzida a ovulação ...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The seasonal behavior of breeding mares is a challenge for veterinarians and farmers. The mares have a period of reproductive activity during the summer and in winter, minimum follicular growth and lack of ovulation (anoestrus). This study aimed to evaluate the effect of different protocols involving the use of artificial light with or without intravaginal progesterone-releasing device or deslorelin acetate on the occurrence of first ovulation in mares in seasonal anestrous. We used 120 mares in anestrous randomly assigned to 8 treatment groups: group 1 - Control, group 2 - progesterone (P4), group 3 - artificial light for 35 days (L35), group 4 - artificial light for 60 days (L60), group 5 - artificial light for 35 days and progesterone (L35+P4), group 6 - artificial light for 60 days and progesterone (L60+P4), group 7 - artificial light for 35 days and deslorelin acetate (L35+GnRH), and group 8 - artificial light for 60 days and deslorelin acetate (L60+GnRH). In groups where the device was used intra-vaginally with 1.3 g of progesterone, after implant removal mares began to be assessed daily until they reach the follicle(s) with a diameter of 35 mm on average and uterine edema compatible. At this time was given 1500 IU of hCG and 1 mg deslorelin acetate associated by intra-muscular, with the aim of ovulation induction and monitoring is continued daily until ovulation, as assessed by the presence of corpus luteum. The deslorelin was administered to all mares of the groups (L35 + GnRH and L60 + GnRH) from the 36o day of the experiment, 12 to 12 hours at a dose of 100 μg until they reach the follicle(s) with an average of 35 mm in diameter and uterine edema compatible, so it could be induced ovulation, or no later than 5 days of treatment for mares who have not reached follicular diameter and uterine ...(Complete abstract click electronic access below) / Mestre