Extracellular matrix degrading proteases from the plasminogen (plg) activator (PA) and the matrix metalloproteinase (MMP) systems have been implicated as important mediators of ovulation and corpus luteum (CL) formation and regression. The aim of this thesis was to investigate the expression and regulation of PAs and MMPs in the ovary and to examine their functional roles for CL formation and function. The expression of membrane-type MMP-1 (MT1-MMP) and its substrate gelatinase A (MMP-2) mRNAs was studied during pregnant mare serum gonadotropin (PMSG)/human chorionic gonadotropin (hCG)-induced ovulation in immature rats. These proteases were coordinately regulated so that both were highly expressed in the theca cells of large preovulatory follicles. This suggests that MT1-MMP activates gelatinase A in preovulatory follicles to degrade the follicular wall during ovulation. In pseudopregnant (psp) rats, MT1-MMP mRNA was expressed in the CL throughout the luteal phase. Tissue inhibitor of metalloproteases type-1 (TIMP-1) mRNA was expressed during CL formation and regression. MMP-2 and collagenase-3 mRNAs were expressed during CL formation and regression, respectively. When the luteal phase was artificially prolonged or shortened, TIMP-1 and collagenase-3 mRNAs were induced only after the serum progesterone levels had decreased, indicating a close association with luteolysis in the rat. In psp mice, the expression of mRNAs coding for both PAs, seven MMPs, and five protease inhibitors was studied. Most of the studied molecules were coordinately expressed during formation or regression of the CL. However, uPA, MT1-MMP, and TIMP-3 mRNAs were expressed throughout the luteal phase. The role of uPA was examined in psp uPA deficient mice. These mice displayed no abnormalities in luteal function or vascularity. The role of uPA is thus either not essential or can be compensated by other proteases in the absence of uPA. In order to control the timing of the CL formation, a mouse model for PMSG/hCG-induced CL formation was developed. Five different protocols were evaluated. One of them provided CL that were stable for six days. In that protocol the mice were treated with prolactin (PRL), twice daily from day 2 of CL life onward. The expression of the steroid acute regulatory protein (StAR) mRNA in the psp CL was also characterized to assess its use as a molecular marker for CL development and regression. It was highly expressed in the forming and functional CL and downregulated at a late stage of CL regression. The functional role of plg and MMPs for CL formation and function was investigated in plg deficient mice treated with the MMP inhibitor galardin (GM6001). Both psp mice and PMSG/hCG +PRL-induced CL formation were used. Several molecular markers for CL development and regression were used to evaluate the health status of the CL. Our data showed that healthy and vascularized CL formed even in plg deficient mice treated with the inhibitor. However, serum progesterone levels were significantly reduced in these mice, an effect that was mainly attributable to the plg deficiency. In conclusion, neither plg nor MMPs, alone or in combination, seem to be essential for the development of a functional CL.

Measurements of ovarian, corpus luteum, follicles of Lithuanian Black and White and German Black and White breed cows made by ultrasound scanner were revised. Effect of different factors, such as age, breed and season determining persistence of corpus luteum was statistically evaluated. Validation of treatment efficacy of persistent corpus luteum was carried out based on testing of progesterone concentration in peripheral blood plasma.

The ovary undergoes cyclic changes in follicular growth and luteogenesis due to the action of gonadotropins and steroids. The ovary and especially the corpus luteum has an exteremely high blood flow. There is a gap in our knowledge about the physiological role of the high blood flow of the corpus luteum. The production of lactate, progesterone and cyclic AMP of follicles and corpora lutea incubated in vitro was analyzed and related to the tissue content of ATP to elucidate possible connections between oxygen and substrate levels and energy consumption, steroid output and LH responsiveness in vitro. It was also considered of interest to investigate if the oxygen tensions needed for ATP and progesterone production of the follicle and the corpus luteum differed. A corpus luteum model using adult pseudopregnant rats was developed and characterized according to criteria for identification of corpora lutea as well as levels of plasma steroids and gonadotropins. In vitro progesterone production was compared to plasma progesterone levels. The absolute blood flow of corpora lutea of different ages and the response to injection of hCG, noradrenaline and antidiuretic hormone was investigated with the microsphere technique. Relative blood flow changes of follicles and corpora lutea during follicular growth and luteogenesis in vivo were studied by injecting radiolabelled microspheres to anaesthetized immature rats at different time periods after injection of an ovulatory dose of pregnant mare serum gonadotropin. This approach was chosen to investigate the possible relation between follicular/luteal blood flow, steroid output and morphology in relation to the endogenous gonadotropin surge, ovulation and luteogenesis. Hormonal stimulation by injection of hCG and noradrenaline increased total ovarian blood flow but no evidence was found for a parallelism between luteotropism and blood flow. The increasing effect of hCG on ovarian blood flow was partly due to a shunting of blood from the uterus towards the ovary. The antidiuretic hormone potently decreased ovarian and uterine blood flow by 80-90% while blood flow of some other organs (e.g. kidney and spleen) were hardly affected. The corpus luteum of pseudopregnancy was found to produce 15“ 20 times more progesterone in vitro as compared to the preovulatory follicle. The steroidogenesis and energy production of corpora lutea was found to be more sensitive to decreases in oxygen tension in terms of tissue ATP levels and LH responsiveness of progesterone production while the follicle could compensate by increasing glycolysis. A parallelism between follicular/luteal blood flow and progesterone production in vivo was found. It was shown that the formation, growth and progesterone production of the corpus luteum was accompanied by an increase in blood flow as well as vascularization as seen under the light microscope. The endogenous gonadotropin surge did not change follicular blood flow due to the development of a follicular oedema. We hypothesize that the corpus luteum function in vivo and in vitro is dependent on higher energy levels than the preovulatory follicle and that the transformation of the follicle to a corpus luteum is supported by a high nutritive blood flow possibly to support a high demand for energy-rich substrates. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1987, härtill 7 uppsatser.</p> / digitalisering@umu

No description available.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 96-109). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 96-109). Also available on the Internet.

Made available in DSpace on 2014-06-11T19:27:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-06-25Bitstream added on 2014-06-13T19:55:44Z : No. of bitstreams: 1 rossetti_rc_me_araca.pdf: 1720798 bytes, checksum: d354f1ca5dc638e7fe69f0547f4aa711 (MD5) / Fundação para o Desenvolvimento da UNESP (FUNDUNESP) / Estratégias farmacológicas são empregadas para reduzir a mortalidade embrionária em fêmeas bovinas. Objetivou se comparar o efeito do Flunixin Meglumine (FM), Somatotropina Recombinante Bovina (bST) e/ou Gonadotrofina Coriônica Humana (hCG) na redução da mortalidade embrionária em vacas Nelore no período compreendido entre o 15º e 19º dias da gestação, baseando se na taxa de concepção aos 40 dias de gestação. A hipótese é que vacas tratadas com FM, bST e/ou hCG, apresentam menor mortalidade embrionária e maiores taxas de concepção. Vacas Nelores (n=975), lactantes, com 35 a 70 dias pós parto, receberam no D 10 um dispositivo intravaginal contendo 1g de Progesterona (DIB®) associado a uma njeção de 2mg de Benzoato de Estradiol (Gonadiol®), via intramuscular (IM). No D 2 o dispositivo foi removido e os animais receberam uma injeção de 112,5Cg de D Cloprostenol (Preloban®); 300UI de Gonadotrofina Coriônica Eqüina (Folligon®) e 1mg de Cipionato de Estradiol (ECP®), todos via IM. Após 48 horas da última injeção (D0), as fêmeas foram submetidas à inseminação artificial em tempo fixo (IATF) e sete dias após foram divididas equitativamente em oito grupos para receberem um dos seguintes tratamentos: não tratadas (Grupo Controle; n= 124); FM no D16 (Grupo FM; n=122); bST no D7 (Grupo bST; n=119); bST no D7 + FM no D16 (Grupo bST + FM; n=121); hCG no D7 (Grupo o hCG; n=124); hCG no D7 + FM no D16 (Grupo hCG + FM; n=124); bST e hCG no D7 (Grupo bS T + hCG; n=120) ou bST e hCG no D7 + FM no D16 (Grupo bS T + hCG +FM; n=121). Utilizou se 2.500UI de hCG (Chorulon®), IM; 500mg de bST (Boostin®), via subcutânea, na fossa ísqueo retal e 2,2mg/Kg de FM (Banamine®), IM. Amostras de sangue foram coletadas no D7 e D16, para mensuração das concentrações plasmáticas de progesterona (P4) por radioimunoensaio. O diagnóstico de gestação foi realizado 40 dias após... / Pharmacologic strategies are employed to reduce the embryonic mortality in bovine females. The aim of the study was to compare the effect of Flunixin Meglumine (FM), Recombinant Bovine Somatotropin (bST) and/or Human Corionic Gonadotropin (hCG) on the reduction of embryonic mortality in Nelore cows in the period between the 15th and 19th days of gestation, based on conception rate at 40 days gestation. The hipothesis is that, cows treated with FM, bST and/or hCG, show lower embryo mortality and greater conception rates. Lactating Nelore cows (n=975), 35 to 70 days postpartum, received on D 10 an intravaginal device containing 1g of Progesterone (DIB®) associated with an injection of 2mg of estradiol benzoate (Gonadiol®), i.m. On D 2 the device was removed and the animals received one injection of 112,5Cg of D Cloprostenol (Preloban®); 300UI of Equine Chorionic Gonadotropin (Folligon®) and 1mg of Estradiol Cipionate (ECP®), all through i.m. route. After 48 hours from the last injection (D0), the cows were submitted to Fixed Timed Artificial Insemination (FTAI) and seven days later were divided equitably in eight groups and received one of the following treatments: untreated (Group Control; n= 124); FM on D16 (Group FM; n=122); bST on D7 Group bST; n=119); bST on D7 + FM on D16 (Group bST+FM; n=121); hCG on D7 (Group hCG; n=124); hCG on D7 + FM on D16 (Group hCG+FM; n=124); bST and hCG on D7 (Group bST+hCG; n=120) or bST and hCG on D7 + FM on D16 (Group bST+ hCG+FM; n=121). Used 2.500UI of hCG (Chorulon®), IM; 500mg of bST (Boostin®), through subcutaneous route, on the ischiorectal fossa and 2,2mg/Kg of FM (Banamine®), i.m. Blood samples were collected on D7 and D16, to measure plasmatic progesterone (P4) concentration through radioimuneassay. Pregnancy diagnosis was performed by ultrasound exam 40 days after FTAI. The variable rate design was analyzed by logistic... (Complete abstract click electronic access below)

Made available in DSpace on 2015-03-26T13:55:29Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2231606 bytes, checksum: b29196071c5e84791111ab5a3acb8e50 (MD5) Previous issue date: 2007-02-27 / Fundação de Amparo a Pesquisa do Estado de Minas Gerais / Ultrasound image attributes, quantified by computer-assisted analysis, are a good indication of corpora lutea (CL) physiological and functional status. However, a standard method to capture and processing images has not been established for bovine. The purposes of this research were to establish a methodology for capture, processing and computer-assisted analysis; to evaluate CL morphological and echotexture changes throughout a natural estrous cycle or a luteolysis induced estrous cycle; and to determine whether computer-assisted analysis is efficient or not for embryo recipient selection. In the first study, evaluations were made of methods to capture images, systems of capture and the minimum representative sample area. For transrectal (TR) images, the minimum established area was 0.25 cm² (4.42% of the major area). A correlation was found in mean pixel values (r = 0.9930; P<0.001) and heterogeneity (r = 0.9861; P<0.001) between images videotaped or direct digitized. In a second study, two experiments were developed: natural estrous cycle and induced luteolysis (day 10) estrous cycle. Echotexture parameters of the CL, in the expt. 1, were analyzed after data adjustment to the onset of luteolysis. In both experiments, mean pixel values did not differ throughout the days of the cycle (P>0.10) and there was no correlation between plasma progesterone and mean pixel value (r = -0.39 and r = -0.28; P>0.10). Pixel heterogeneity varied through the days in a cycle with natural luteolysis (P<0.01), but did not in a luteolysis induced cycle (P>0.10). Correlations were observed between pixel heterogeneity and plasma P4 in both of the experiments (r = - 0.69 and r = -0.48; P<0.05). In a third study, embryo recipients (n=259) were examined by transrectal ultrasonography on the embryo transfer day (ET). The same type of analysis was done to assess image attributes, as previously tested in the 1st and 2nd studies. Good quality embryos (grades 1 and 2) collected after conventional superovulatory treatment (MOET; n=94) or in vitro produced (IVP; 88) were transferred to the recipients. Pregnancy rates were 56.4% and 30.2% for MOET and IVP, respectively. Plasma progesterone concentration values were greater in the recipients later diagnosed as pregnant, than in non-pregnant (5.88±0.77 vs 3.98±0.48 ng/mL, respectively; P<0.05). There was no difference in plasma P4 between pregnant and non pregnant IVP recipients (3.97±0.57 vs 3.52±0.23; P>0.10). Corpus luteum and luteal tissue area did not differ between pregnant and non-pregnant animals. In addition, no difference in mean pixel values (71.80±1.29 vs 71.19±1.14; P>0.10; scale of 0 to 255) and heterogeneity (14.80 vs 14.52; P>0.10) was observed, between pregnant and non pregnant MOET or IVP recipients. Echotexture parameters (mean pixel value and heterogeneity) showed correlations with plasma P4 (0.17 and 0.18, respectively; P<0.01). In conclusion, differences between capture, processing and image analysis methods should be considered in luteal echotexture evaluation; if on one hand, pixel heterogeneity in ultrasound images is a strong indicative of functional status and steroidogenic capacity of luteal gland, on the other hand, mean pixel values are a poor indicator of these characteristics. Finally, in this approach computer-assisted analysis of ultrasound images was not efficient on embryo recipient selection, probably due to other variables which strongly influence overall pregnancy rate. / Atributos de imagens de ultra-som, quantificados por análise computacional, têm o potencial de indicar o status fisiológico e funcional de corpos lúteos (CL). Ainda não foi estabelecido, contudo, um padrão de captura e processamento das imagens para bovinos. Os objetivos desta pesquisa foram estabelecer uma metodologia para aquisição, processamento e análise computacional de imagens; avaliar as mudanças morfológicas e de ecotextura do CL ao longo do ciclo estral natural ou após indução da luteólise; e verificar a eficiência da técnica de análise computacional na seleção e triagem de receptoras de embrião. No primeiro estudo, foram avaliados métodos de geração de imagens, sistemas de captura e área de amostragem mínima representativa. Para imagens geradas por via transretal (TR), a área mínima estabelecida foi de 0,25 cm² (4,42% de variação em relação à maior área). Foi constatada uma correlação nos valores médios de pixel (r=0,99; P<0,001) e heterogeneidade (r=0,99; P<0,001) entre imagens gravadas em fitas VHS e com digitalização direta. No segundo estudo, foram realizados dois experimentos: avaliação do ciclo natural ou após luteólise induzida no 10º dia do ciclo. No experimento 1, os parâmetros de ecotextura do CL foram analisados após o ajuste dos dados para o momento da luteólise. Em ambos os experimentos, o valor médio dos pixels não variou em função dos dias (P>0,10) e não foi observada relação entre a concentração de progesterona [P4] plasmática e este parâmetro (r = -0,39 e r = -0,28; P>0,10). A heterogeneidade variou em função dos dias na luteólise natural (P<0,01), mas não na induzida (P>0,10). Ainda, foram observadas relações entre heterogeneidade e a [P4] plasmática nos dois experimentos (r = -0,69 e r = -0,48; P<0,05). No terceiro estudo, receptoras de embrião (n=259) foram examinadas por ultra-sonografia no dia da transferência de embriões (TE). Foi feito o mesmo tipo de análise dos atributos das imagens previamente testado nos estudos 1 e 2. Foram transferidos embriões de boa qualidade (1 e 2) obtidos por superovulação convencional (TE; n=94) ou produzidos in vitro (PIV; n=88). As taxas de gestação foram de 56,4% e 30,2% para embriões TE e PIV, respectivamente. Nas receptoras TE, os valores de [P4] plasmática foram maiores nos animais posteriormente diagnosticados como gestantes que nos não gestantes (5,88±0,77 vs 3,98±0,48 ng/mL, respectivamente; P<0,05). No entanto, nas receptoras PIV não houve diferenças entre gestantes ou não (3,97±0,57 vs 3,52±0,23; P>0,10). A área do CL e área de tecido luteal entre gestantes e não gestantes não diferiu. Não foram observadas diferenças nos valores médios (71,80±1,29 vs 71,19±1,14; P>0,10; escala de 0 a 255) e na heterogeneidade (14,80 vs 14,52; P>0,10) dos pixels, em receptoras gestantes ou não gestantes, que receberam embriões TE ou PIV. Os parâmetros de ecotextura (média dos pixels e heterogeneidade) apresentaram baixas relações com a [P4] plasmática (0,17 e 0,18; respectivamente; P<0,01). Conclui-se que as diferenças nos métodos de captura, processamento e análise de imagens devem ser consideradas quando se avalia a ecotextura luteal; a heterogeneidade, ao contrário do valor médio, de pixels em imagens ultrasonográficas é indicativo de funcionalidade e capacidade esteroidogênica da glândula luteal; e a análise computacional de imagens não foi eficiente no auxílio à seleção e triagem de receptoras de embriões, possivelmente pela forte influência que outras variáveis exercem sobre a taxa de gestação final.

Orientador: João Carlos Pinheiro Ferreira / Coorientador: Milo C. Wiltbank / Resumo: Em ruminantes a luteólise natural é caraterizada pela liberação de vários pulsos de prostaglandina F2alfa (PGF) produzidos pelo útero. A PGF é o hormônio luteolítico, enquanto a prostaglandina E1 (PGE1) é considerada um mediador luteoprotetor. Em estudos anteriores, infusões com doses baixas de PGF no útero com intervalos de 6 horas (h) resultou em regressão do corpo luteo (CL). A proposta deste experimento é desenvolver um modelo para avaliar o efeito de baixas doses de PGE1, também infundidas no lúmen uterino sobre a resposta luteal à PGF intrauterina (IU). Vacas no dia 10 do ciclo estral receberam infusões IU de salina (0,1 ml de salina + 0,1 ml de DMSO), PGE (2 mg de PGE1 em 0,1ml de DMSO) ou PGF (0,25 mg of PGF em 0,1 ml de salina) em intervalos de 6 h em um desenho experimental 2 X 2. Portanto os animais foram agrupados em quatro tratamentos: SALINA (4 infusões de salina; n=5), PGE (4 infusões de PGE1; n=5), PGF (4 infusões de PGF; n=5) e PGE+PGF (4 infusões de PGE1+PGF; n=5). As concentrações plasmáticas de progesterona (P4) foram dosadas por radioimunoensaio e o volume luteal foi determinado por ultrassonografia transretal. As concentrações circulantes de PGFM e PGEM foram dosadas antes e 10 minutos após as primeiras duas infusões. Biopsias luteais foram coletadas de cada vaca 30 minutos após cada infusão para determiner a expressão de genes em resposta a cada tratamento. As concentrações circulantes de PGFM 10 minutos após as infusões foram maiores em vacas que receb... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

O objetivo deste estudo foi determinar os efeitos da aplicação de hCG no quarto dia após a inseminação a tempo fixo (IATF) sobre o tamanho do corpo lúteo (CL) existente, a indução de CL acessórios, a concentração de progesterona (P4) sérica e taxa de prenhez de vacas de corte em lactação. Nos três experimentos, vacas de corte multíparas (n=569), cruza Bos taurus, com período pós-parto entre 45 e 70 dias, foram sincronizadas com a administração de 2mg de benzoato de estradiol i.m. e a inserção de um dispositivo intravaginal contendo 0,750g de P4 (Dia -9). Sete dias após, administraram-se 150 μg de D-cloprostenol e 0,5 mg de cipionato de estradiol, i.m., no momento da retirada do dispositivo (Dia -2). Sessenta vacas de corte em lactação foram divididas aleatoriamente em dois grupos: hCG (n=30) tratadas com 1500UI i.m. de hCG e Controle (n=30) injetadas com 1,5 mL de solução salina i.m. no dia 4 depois do estro (Dia 0). Realizaram-se coletas sanguíneas dos animais para mensuração da concentração sérica de P4 nos Dias 4, 7, 10 e 14 do ciclo estral. Para acompanhamento da dinâmica ovariana, sessenta animais foram divididos aleatoriamente nos grupos hCG (n=30) ou Controle (n=30) e receberam o mesmo protocolo hormonal como citado anteriormente. No Dia 0, os ovários foram examinados por ultrassonografia transretal para determinar o diâmetro do folículo ovulatório; no Dia 4, o diâmetro do FD e presença do CL e no Dia 7 para mensurar a área luteal do CL e a presença de CL acessório. Quinhentas e sessenta e nove vacas (hCG, n= 269 e Controle, n= 300) foram inseminadas a tempo fixo 52-56 horas depois da retirada dos implantes de P4 e tratadas no Dia 4, conforme o protocolo descrito. O diagnóstico de prenhez foi realizado por ultrassonografia 30 dias após a IATF. Os resultados observados, mostraram que vacas tratadas com hCG no Dia 4 apresentaram maiores concentrações sérica de P4 no Dia 7, comparadas com as do grupo Controle (4,45 vs. 3,37ng/mL, respectivamente; p<0,05), mas níveis semelhantes de P4 nos Dias 10 e 14. Os animais do grupo hCG apresentaram CL com maior (p<0,01) área luteal no Dia 7, em relação ao grupo Controle (3,52 cm² vs. 2,66 cm², respectivamente) e uma incidência de 29,6 % de indução da ovulação do FD presente no Dia 4. Observou-se uma taxa de prenhez maior (p=0,071) no grupo tratado com hCG (53,9%) comparando-se com as vacas não tratadas (46,3%). Conclui-se que a administração de hCG no quarto dia do ciclo estral promove o aumento da área do CL, melhora função luteal, pode induzir a formação de CL acessório e tende a aumentar a taxa de prenhez de vacas de corte em lactação. / The aim of this study was to determine the effects of injection of hCG on the fourth day after the TAI on the size of the existing corpus luteum (CL), the induction of CL accessories, the concentration of progesterone (P4) levels and the possibility of increasing the rate of pregnancy of lactating beef cows subjected to synchronization of estrus and ovulation. Multiparous beef cows (n= 569), Bos taurus crossbreed with postpartum between 45 and 70 days were synchronized by administration of 2mg of estradiol benzoate im and the insertion of an intravaginal device containing 0,750g of P4 (Day -9). Seven days later, were administered 150mg of D- cloprostenol 0.5 mg of estradiol cypionate, im, at the time of device removal (Day -2). Sixty lactating beef cows were randomly divided into two groups: hCG (n= 30) treated with im 1500UI hCG and Control (n= 30) injected with 1.5 ml of saline im on day 4 after estrus (Day 0). There were blood collections of animals for measurement by radioimmunoassay of serum P4 on Days 4, 7, 10 and 14 of the estrous cycle. To evaluate the ovarian dinamics, sixty animals (hCG, n= 30 and Control, n = 30) received the same hormonal protocol and were uniformly distributed into groups according to the diameter of the ovulatory follicles on day 0 (estrus). On Day 0, the ovaries were examined by transrectal ultrasonography to determine the diameter of the ovulatory follicle, on Day 4, the diameter of the dominant follicle (DF) and the presence of CL on Day 7 to measure the area of the luteal CL and the presence of accessory CL. Five hundred and sixty-nine cows (hCG, n= 269 and Control, n= 300) were inseminated at a fixed time 52 to 56 hours after removal of the P4 devices treated on Day 4, according to the protocol described previously. The diagnosis of pregnancy were performed by ultrasonography 30 days after TAI. The results demonstrate that cows treated with hCG on Day 4 showed higher serum concentrations of P4 on Day 7, compared with the control group (4.45 vs. 3.37ng/mL, respectively, (p<0.05), but similar levels of P4 on Days 10 and 14. The animals of hCG group had greater (p<0,01) luteal area on Day 7, compared to the Control group (3.52cm² vs. 2.66cm², respectively) and a 29.6% incidence of induction DF ovulation present on Day 4. We observed a higher rate of pregnancy (p= 0.071) in the group treated with hCG (53.9%) comparing with untreated cows (46.3%). We conclude that administration of hCG on the fourth day of the estrous cycle increase the CL area, improves luteal function, can induce the formation of accessory CL and tends to increase the pregnancy rate of lactating beef cows.