Immunolocalization of gastrin-releasing peptide in the bovine uterus and placenta

Gastrin-releasing peptide (GRP), a mammalian homologue of amphibian bombesin, has been suggested to be a novel regulatory peptide in the reproductive tract during pregnancy. In this study, the localization of GRP in the bovine uterus and placenta was demonstrated by immunohistochemistry. Uterine and placental samples were collected from nonpregnant and pregnant specimens, respectively. Tissue sampling was done from the caruncle and intercaruncle of the uterus, and from the placentome (caruncle and cotyledon) and intercotyledon of the placenta. In all the tissues examined, GRP was detected although its immunoreactivity was observed at various degrees. In the uterus, moderate immunoreactivity for GRP was observed in the uterine gland epithelial cells. In the placenta, strong immunoreactivity for GRP was demonstrated in the uterine gland epithelial cells; moderate in superficial epithelial cells; and weak in the trophoblasts, trophoblastic giant cells and cryptal epithelial hybrid cells. In both nonpregnant and pregnant animals, GRP was immunolocalized in the uterine gland secretions and was found predominantly in the supranuclear region of the uterine gland epithelial cells. These findings may suggest that GRP is secreted into the uterine lumen and regulates the intrauterine environment of both the nonpregnant and pregnant bovine by exocrine, autocrine and/or paracrine manner.     

Acute changes in the concentrations of prostaglandin F2α (PGF) and cortisol in uterine and ovarian venous blood during PGF-induced luteolysis in cows

Prostaglandin F2α (PGF) is considered to be the main luteolysin in cattle. We have previously demonstrated that cortisol (Cr) suppresses PGF production in non-pregnant bovine endometrium. This study was carried out to test whether exogenous PGF increases ovarian and/or uterine PGF production and to determine the temporal relationship between PGF and Cr in ovarian and uterine circulations during PGF-induced luteolysis in cows. Catheters were inserted into the ovarian vein (OV), uterine vein (UV) and jugular vein (JV) of 10 cows on Day 9 of the oestrous cycle (Ovulation = Day 0) for frequent blood collection. On Day 10, the cows were divided randomly into two groups and treated with a luteolytic dose of a PGF analogue (cloprostenol) or saline solution. Blood samples were collected at -0.25, 0, 0.25, 0.5, 1 and 2 h and then at 2-h intervals until 12 h after treatment (0 h). The basal concentrations of PGF and Cr in OV and UV plasma were not significantly different. Injection of a PGF analogue induced more than twofold increases in the levels of PGF between 0.25 and 1 h in UV plasma, but not in OV plasma. PGF increased (p < 0.05) the concentrations of Cr in OV, UV and JV plasma between 0.5 and 1 h. The Cr levels in OV, UV and JV plasma were similar. The PGF levels in UV plasma decreased after Cr reached its highest levels. The overall results suggest that the uterus rather than the ovary increases PGF production in response to PGF injection. Based on the temporal changes of PGF and Cr in the ovarian and uterine circulations, Cr may act to reduce uterine PGF production in non-pregnant cows in vivo.     

Regulation of endometrial prostaglandin F(2alpha) synthesis during luteolysis and early pregnancy in cattle

Luteal regression is caused by a pulsatile release of prostaglandin (PG) F(2alpha) from the uterus in the late luteal phase in most mammals including cattle. Although it has been proposed in ruminants that pulsatile PGF(2alpha) secretion is generated by a positive feedback loop between luteal and/or hypophyseal oxytocin and uterine PGF(2alpha), the bovine endometrium may possess other mechanisms for initiation of luteolytic PGF(2alpha) secretion. It has been recently demonstrated that tumor necrosis factor-alpha (TNF-alpha) stimulates PGF(2alpha) output from bovine endometrial tissue not only during the follicular phase but also during the late luteal phase, suggesting that TNF-alpha is a factor in the initiation of luteolysis in cattle. Furthermore, our recent study has shown that IFN-tau suppresses the action of TNF-alpha on PGF(2alpha) synthesis by the bovine endometrium in vitro, suggesting that IFN-tau plays a luteoprotective role by inhibiting TNF-alpha-induced PGF(2alpha) production in early pregnancy. On the other hand, factors other than oxytocin or TNF-alpha have also been suggested to be involved in the regulation of PGF(2alpha) synthesis by bovine endometrium. The purpose of this review is to summarize our current understanding of the endocrine mechanisms that regulate the timing and pattern of uterine PGF(2alpha) secretion during the estrous cycle and early pregnancy.     

Survey of the prevalence and types of infertility in beef cows and heifers

Thirty to 180 days after natural mating to bulls, 8,184 beef cows and heifers were palpated rectally for pregnancy determination. Of these, 7,396 (90%) were pregnant and 815 (10%) were not pregnant. Regarding the nonpregnant cattle, 315 (38.7%) had a normal uterus and a functional corpus luteum, suggesting that they were cycling; the rest had palpable pathologic findings: 455 (55.8%) had ovarian inactivity and uterine atrophy; 16 (2%) had pyometra; 12 (1.5%) had a mummified fetus; 7 (0.9%) had chronic metritis; 6 (0.8%) had an involuting uterus; and 4 (0.5%) had adhesions of the uterus, ovaries, or a combination of both. For the purpose of comparison, the cattle were grouped according to age: group 1-1,035 nulliparous heifers 18 to 24 months of age; group 2-1,137 primiparous heifers 30 to 36 months of age; group 3-5,548 multiparous cows between 4 and 9 years of age; and group 4-464 cows 9 years of age or older. The pregnancy rates were 79.1, 72.2, 96.8, and 78.2, respectively, for these groups. The pregnancy rate for 4- to 9-year-old cows was significantly greater (P less than 0.05) than that for the other age groups.     

Old,new and the newest concepts of inhibition of luteolysis during early pregnancy in pig

In 1977 Bazer and Thatcher proposed that maternal recognition of pregnancy in the pig involves the secretion of PGF(2alpha) towards the uterine lumen (exocrine) rather than towards the uterine venous drainage (endocrine) as occurs in the non-pregnant pig during the mid to late stages of the estrous cycle. The retrograde transfer of PGF(2alpha) from the venous blood and uterine lymph into the uterus and the ability of the uterine vein and artery wall to accumulate PGF(2alpha) could constitute a part of putative mechanism of corpus luteum protection during early pregnancy. A luteotropic/anti-luteolytic effect of PGE(2) in the pig also has been frequently demonstrated and it seems that the most effective agent in changing PGE(2):PGF(2alpha) secretion is estradiol. The role for oxytocin during luteolysis and early pregnancy is controversial. It appears, however, that the main function of this hormone is autocrine and/or paracrine stimulation of PGF(2alpha) secretion. Pig trophoblastic interferons, unlike those of ruminants, do not themselves exert an anti-luteolytic effect in pigs. It is likely, that cytokines and angiogenic growth factors are involved in the initiation of luteolysis and/or maintenance of corpora lutea (CL).A discovery of functional LH receptors in porcine endometrium opened a new possibility for this hormone in luteolysis and perhaps in recognition of pregnancy in pigs. The endogenous LH pulses can provoke prostaglandin secretion from endometrium in pigs. On the other hand prolongation of up-regulation of LH receptors in endometrium of early pregnant gilts can additionally increase angiogenic factor production before the process of implantation is completed. Finally new integrated concepts of luteolysis and inhibition of luteolysis in pigs based on selectively reviewed information are presented.     

A method for the treatment of oviduct obstruction in cattle using CO2 insufflation into the uterus]

The investigations were carried out on 59 cows from Holstein half-breed, establishing that 8 cows suffered salpinx obstruction (5 cases with unilateral obstruction and 3 cases with bilateral obstruction). The authors are using an apparatus made by themselves, for insufflation of air in the obstructed uterus, and which is useful in desobstruction treatment, too. For diagnosis, CO2 was introduced inside of uterus. The authors used for treatment PBS (saline phosphate buffer) in addition with penicillin G, hydrocortisone and trypsin. Before air insufflation in uterus there will be infused 10-20 ml 2% Lidocaton. The cows must be examined in oestrus period, or 2 days after PGF2 alfa administration. The gas must be introduced under rectal palpation, and pressure must not be higher than 500 mm H2O column. If there is a permeable oviduct, after 15-20 sec. from gas introduction, ist is possible to palpate the filled oviduct. From ovary we can perceive a rustle produced by gas crossing in abdominal cavity. In case of salpinx obstruction, the treatment must be start as soon as possible. The utilized liquid for treatment will be introduce by gas pressure, inside of uterus and oviducts. Using this method, it managed the repermeability of oviducts at 3 from 8 treated cows. In each case, there were used 3 treatments at 48 h interval. After the second insemination (I.A.) 2 cows remained pregnant.     

Maintenance of the corpus luteum of early pregnancy in the ewe. III. Differences between pregnant and nonpregnant ewes in luteal responsiveness to prostaglandin F2 alpha

The effects of pregnancy and number of corpora lutea on luteal regression induced with prostaglandin F2 alpha (PGF2 alpha) were examined in 93 ewes. Bred and nonpregnant ewes were assigned randomly to receive a single im injection of PGF2 alpha: 0, 2, 4, 6, 8 or 10 mg/58 kg body weight. Injections were given on d 13 postestrus. The concentration of progesterone in serum 24 h after PGF2 alpha injection was affected by dose (P less than .001). The effect of pregnancy and the interaction of pregnancy with number of corpora lutea on levels of progesterone in serum were significant (P less than .05); therefore, data were partitioned according to pregnancy status and analyzed separately. There was an effect of number of corpora lutea on serum concentration of progesterone in pregnant (P less than .01) but not nonpregnant ewes (P greater than .10). Similar relationships among groups were observed for the concentration of progesterone in luteal tissue. In nonpregnant ewes the minimum dose of PGF2 alpha to produce a significant suppression of progesterone in serum (P less than .05) was 4 mg/58 kg body weight. In pregnant ewes with one or two corpora lutea, the minimum effective doses were 6 and 10 mg/58 kg body weight, respectively. The concentration of 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) in serum was related to the dose of PGF2 alpha injected. There were no differences in the concentration of PGFM in serum between pregnant and nonpregnant ewes either before or after injection. Corpora lutea of early pregnancy appear to be resistant to the luteolytic effect of PGF2 alpha.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of oxytocin, prostaglandin F2 alpha and reproductive tract manipulations on uterine contractility in Holstein cows on days 0 and 7 of the estrous cycle

The influence of various treatments on cattle at the time of natural estrus vs estrus induced by prostaglandin F2 alpha (PGF2 alpha) or at d 7 of the estrous cycle were studied; the latter is when embryo transfer often is performed. Eight lactating and 25 nonlactating, normal cycling cows were tested many times while in estrus and 7 d after estrus. A balloon was positioned in the body of the uterus to record changes in intrauterine pressure following clitoral massage, cervical massage, vaginal distention, electrical stimulation of the cervix and vagina, tailhead rubbing, udder massage and the injection of oxytocin or PGF2 alpha. Blood oxytocin and intramammary pressure were measured. There were no differences between cows in estrus spontaneously or those induced, so these groups were combined. Intravenous oxytocin injections of .5, 1, 2, 4 and 15 IU increased blood levels of oxytocin. Intramammary pressure was increased by all oxytocin doses, but greater than or equal to 2 IU were required to cause substantial changes in uterine contractions. As expected, the peak contractions during control periods for cows in estrus were high, averaging 31 mm Hg vs 11 mm Hg on d 7. None of the manipulations of the reproductive organs caused detectable oxytocin release or increases in intramammary pressure, contrasting to responses to massage of the udder. Clitoral massage increased peak uterine pressure by 32 to 60% in four experiments. It did not induce luteinizing hormone release. The contraction was immediate, was not sustained and could be obtained repeatedly, suggesting a reflex response. Treatment with PGF2 alpha increased intramammary pressure. It increased uterine pressure on d 7, but had no effect at estrus. This contrasts with injected oxytocin, which resulted in the highest amplitude for cows in estrus, although the response on d 7 was greater in proportion to the low activity in controls at that time. It is concluded that manual manipulation of the reproductive tract (other than clitoral massage) has little effect on uterine contractility.     

Dynamics of ovarian follicular development in cattle following hysterectomy and during early pregnancy

Three experiments were conducted to evaluate ovarian follicular dynamics and functional activity during pregnancy in cattle. In 11 pregnant Charolais cows of Experiment I, size of largest follicle, number of follicles and accumulated follicle size were reduced by day 27 of pregnancy on the ovary bearing the corpus luteum (CL) but not on the non-CL bearing ovary. In experiment II, local attenuation of ovarian follicular development on the CL bearing ovary of seven pregnant heifers was evident compared to the contralateral ovary without the CL. However, in four hysterectomized heifers, follicular development was sustained on both the CL- and non-CL bearing ovaries when CL maintenance was achieved without presence of the uterus or conceptus. In Experiment III, steroidogenic characteristics of the largest and second largest follicles at 17 d postestrus were evaluated for seven pregnant and six cyclic cattle. Follicle by physiological status interactions were detected for both aromatase activity of the follicle and follicular fluid concentrations of estradiol and progesterone. In cyclic cows, the largest follicle had appreciably more aromatase activity than did the second largest follicle; whereas, aromatase activity of the largest follicle from pregnant cows was less than that of cyclic cows. However, in pregnant cows the second largest follicle became the estrogen-active follicle, and this follicle occurred with a higher frequency on the ovary contralateral to the CL-bearing ovary. These changes in aromatase activity were reflected by parallel changes in estrogen concentrations of follicular fluid. The higher progesterone concentration in follicular fluid of the largest follicle in pregnant cows provided further confirmation of their atretic status. In conclusion, during early pregnancy the conceptus and/or uterus ipsilateral to the conceptus appear to secrete compounds which alter local follicular steroidogenic activity and attenuate subsequent follicular growth between 17 to 34 d of pregnancy on the CL-bearing ovary. This local mechanism acting within the ovary may contribute to the antiluteolytic effects of early pregnancy in cattle.     

Immuno-endocrine mechanisms connected with the creation of corpora lutea persistent in animal ovaries

Factors which induce the corpus luteum persistent (CLP) creation in animal ovaries are located in the hypothalamic-pituitary-ovarian axis and also in the uterus. In cows and likewise in others animals, various mediators of inflammatory reaction are released, mainly proinflammatory cytokines from inflamed uterus into the blood and lymph. Afterwards the cytokines cross the blood-brain barrier, and though the brain mediators alter the hormonal profile and amplitude pulses of the hormones release in the hypothalamus and the pituitary. Until it is known, that cytokines: IL-1, IL-2, IL-6, TNF-alpha and also IFN-alpha, administered into the median eminence, cause an increase in corticotrophin-releasing hormone (CRH) and adrenocorticotropic hormone (ACTH) concentrations and decrease in the pituitary gland hormones secretion. The immune system, represented in the corpora lutea (CL) by numerous macrophages/monocytes, limphocytes and neutrophils plays an important role in the luteolysis process. The stimulating factor of the infiltration of these cells is an increased PRL level. The preovulatory increase in PRL level regulates the number of macrophages in newly-formed CL and later influences the number of these cells in the luteolysis period. The pulsatory release and high levels of the hypophyseal oxytocin (OT) and uterine PGF2alpha ensure the beginning and the normal course of the luteolysis period. The cytokines decrease OT concentration and disorder its pulsatory release from the pituitary. In these circumstances the quantity of the uterine PGF2alpha reaching ovaries, is insufficient to begin luteolysis. In the inflamed uterus, the elevation of PGE2 and PGI2 synthesis takes place. Both prostaglandins cause smooth uterine muscles relaxation and the dilatation of blood and lymph vessels in this organ. In these conditions, the blood and lymph outflow from the uterus is several times slower than in the control animals. The secretion of P4 and E2 from CLP, in comparison with control animals, is significantly lower. Decreased P4 concentration during the luteal phase of the estrous cycle, and E2 in the initiation of the luteolysis period, may cause the insufficient preparation of the endometrium for hypophyseal OT activity. Finally, we can assume that the creation of the CLP in the animal ovary is an exceptionally complex and not yet fully understood process.     

Factors associated with shortened estrous cycles after abortion in beef heifers

Forty-six crossbred Hereford heifers were allotted into five experimental groups. Fenprotalene, a prostaglandin analogue, was administered to induce abortion and (or) to regress the corpus luteum (CL) in four groups of heifers about 75 d after conception. The four groups were 1) pregnant heifers, 2) pregnant heifers with the ovary contralateral to the gravid uterine horn removed 24 h after fenprostalene injection, 3) same as Group 2 but with the ipsilateral, rather than the contralateral, ovary removed and 4) heifers with uterus removed (ovaries intact) about 35 d after conception. A fifth group of nonpregnant heifers received implants containing norgestomet from 10 to 76 d after estrus and were given fenprostalene 24 h before removal of the implant. Average length of the first estrous cycle after the fenprostalene injection was 11.2, 8.3, 9.7 and 19.1 for Groups 1, 2, 3 and 5, respectively. Estrous cycles were longer (P less than .05) in norgestomet-treated heifers. Hysterectomized heifers (Group 4) did not exhibit a second estrus by 50 d after fenprostalene treatment; otherwise, all first estrous cycles after the fenprostalene injection were either "short" (7 to 13 d) or "normal" (17 to 23 d). Twenty-two of 24 heifers that aborted had short estrous cycles and two had normal estrous cycles. Short estrous cycles occurred after abortion regardless of whether the ovary ipsilateral or contralateral to the previously gravid uterine horn ovulated. Early regression of the CL (short luteal phase) did not occur in nonpregnant heifers after long-term progestogen stimulation or after hysterectomy, but it did occur in heifers with a previously gravid uterus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation of leptospires from the genital tracts of Iowa cows

Leptospira interrogans serovar hardjo was recovered from 5 of 11 nonpregnant cows chosen at random from an Iowa slaughterhouse. Isolations were made from the kidney in each instance, the genital tract of 3 cows: uterus from 1 cow, oviduct of another, and oviduct and uterus of a 3rd cow.     

Hormonal control of the bovine oestrous cycle

The role of hormones in controlling the estrous cycle of cows is reviewed in the context of current research, specifically on endocrinal functions. This is central as the follicles grow on the ovaries in response to the pituitary's follicular stimulating hormone. When the ovaries produce sufficient estrogens, an ovulatory surge of luteinizing hormone is released by the pituitary. This causes the ovulation of 1 of the follicles and the growth of a corpus luteum in the follicular cavity. This corpus luteum secretes progesterone for about 2 weeks until its activity is terminated by uterine luteolysin. Control of the estrous cycle thus depends on alternate signals from the pituitary and ovaries with the end of the cycle caused by the nonpregnant uterus.     

Influence of infusion of prostaglandin F2 alpha (PGF 2 alpha) and weaning on surface and histologic populations of ovarian follicles in early postpartum beef cows

Twenty-four beef cows were infused continuously for 11 d (d 2 to 13 after parturition) into the descending aorta with either prostaglandin F2 alpha-Tham salt (PGF2 alpha; 33.5 mg/d; n = 12) or with .9% NaCl (saline; n = 12) vehicle. Cows from each infusion treatment then were assigned to three slaughter groups (G). Cows in G1 and G2 were suckled until slaughter on d 15 and 35, respectively, whereas calves in G3 were weaned on d 31 and cows were slaughtered on d 35 after parturition. Nonatretic and atretic (greater than 4 pycnosis) antral follicles (greater than .15 mm) on ovaries ipsilateral to the previously gravid uterine horn were evaluated by histological techniques. Compared with saline infusion, PGF2 alpha increased mean diameters of the largest (F1) follicles on the ipsilateral (d 15 and 35; P less than .07) and contralateral (d 15; P less than .07) ovaries (surface evaluation) as well as mean diameters of the largest (F1, d 35; P less than .002), second- and third-largest (F2, F3 d 15 and 35; P less than .01) nonatretic follicles (histologic evaluation) in suckled cows. Compared with suckled cows slaughtered on d 35, weaning on d 31 increased the number of medium follicles (3 to 5 mm), diameters of the three largest nonatretic follicles, percentage of large nonatretic follicles (greater than 3.67 mm) and mitotic index of class 3 (.68 to 1.57 mm) follicles in saline-infused cows. In contrast, in PGF2 alpha-infused cows, weaning decreased (P less than .05 to P less than .001) all of these responses. Surface and histologic evaluations of follicular activity indicated that postpartum infusion of PGF2 alpha stimulated development of large follicles. In response to weaning, PGF2 alpha infusion favored development of those large follicles toward ovulation or atresia on nonovulated follicles.     

Clinical and endocrine responses to embryonic and fetal death induced by manual rupture of the amniotic vesicle during early pregnancy in cows

Pregnancy was terminated in 4 cows by manual rupture of the amniotic vesicle on day 41 (n = 1) and day 46 (n = 3) after insemination. Each cow was necropsied 36 days after vesicle rupture, by which time only one cow had come into estrus. Luteal activity, monitored daily by plasma progesterone assay, was still evident in 2 cows 35 days after fetal death; in the remaining 2 cows, regression of the corpus luteum (CL) was achieved at 28 and 32 days, respectively. Uterine release of prostaglandin F2 alpha (PGF2 alpha), measured as the 15-keto metabolite (PGFM) PGF2 alpha, was monitored by a plasma sampling schedule; specimens were obtained every 4 hours. There were no appreciable releases of PGF2 alpha associated with fetal death. The first appreciable PGF2 alpha release in episodic form was seen only in conjunction with CL regression. In all cows, a palpable membrane slip was evident for 18 days after rupture of the amniotic vesicle, although at that time, uterine resilience was diminished in the 2 cows in which the CL subsequently regressed. After 18 days, the uterus was noticeably edematous and fluid-filled in all cows; in 1 of the cows with a regressed CL, the uterus had returned to prepregnancy size and tone by day 33.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of standing estrus and supplemental estradiol on changes in uterine pH during a fixed-time artificial insemination protocol

Cows that exhibit estrus within 24 h of fixed-time AI have elevated concentrations of estradiol and greater pregnancy rates compared with cows not in estrus. Our objective was to determine whether estradiol, estrus, or both had an effect on uterine pH during a fixed-time AI protocol. Beef cows were treated with the CO-Synch protocol (100 mircog of GnRH on d -9; 25 mg of PGF(2alpha) on d -2; and 100 mircog of GnRH on d 0). One-half of the cows received an injection of estradiol cypionate (ECP; 1 mg) 12 h after PGF(2alpha). Cows detected in standing estrus within 24 h of the second GnRH injection were considered to be in standing estrus. Uterine pH was determined in all animals 12, 24, and 48 h after the PGF(2alpha) injection. For Exp. 1, pH was also determined 72 and 96 h after the PGF(2alpha) injection; in Exp. 2, pH was also determined at 54, 60, 66, 72, 78, 84, 90, and 96 h after the PGF(2alpha) injection or until ovulation. A treatment x time interaction (P < 0.01) influenced concentrations of estradiol. All cows had similar (P > 0.15) concentrations of estradiol at the time of ECP administration, but after ECP treatment all cows treated with ECP and control cows that exhibited estrus had greater (P < 0.01) concentrations of estradiol compared with nontreated cows that did not exhibit estrus. In all animals, estradiol diminished 48 h after the PGF(2alpha) (time of the second GnRH injection), but ECP-treated cows, regardless of estrus, had elevated (P < 0.02) concentrations of estradiol compared with control cows. There was a treatment x time interaction (P < 0.001) on uterine pH. All cows had similar uterine pH (P > 0.19) 24 h after the PGF(2alpha) injection. Control cows that did not exhibit estrus had a greater uterine pH compared with control cows that exhibited estrus (P < 0.01) and ECP cows that exhibited estrus (P = 0.05) 48 h after the PGF(2alpha) injection (7.0 +/- 0.1 vs. 6.7 +/- 0.1 and 6.8 +/- 0.1, respectively). Estradiol cypionate-treated cows not exhibiting estrus were intermediate (6.8 +/- 0.1; P > 0.05). All cows had similar uterine pH 72 h after the PGF(2alpha) injection through ovulation (P > 0.06). In summary, uterine pH was similar among all animals that exhibited estrus, regardless of treatment with ECP.     

Cell-specific Distribution of Oestrogen Receptor-alpha in the Bovine Ovary

In this study, the expression of estrogen receptor alpha (ERα) in the bovine ovary is described. ERα was visualized by immunohistochemistry on paraffin sections of ovaries obtained from 11 non‐pregnant and 2 pregnant animals. In general, ERα was not observed in cells of primordial, primary and secondary follicles, whereas weak expression was noticed in cells of healthy and arteric tertiary follicles. In corpora lutea cells the expression of ERα was obvious. Intermediate to high ERα expression was present in thecal cells and in cells of the superficial and deep stroma, tunica albuginea and surface epithelium. Furthermore, the expression of ERα in stroma and tunica albuginea cells was in general, highest in cows with the lowest plasma progesterone levels, and lowest in cows with the highest plasma progesterone levels. Remarkably, the ERα expression in pregnant cows was in general, lower than in non‐pregnant cows with similar plasma progesterone levels. The relatively high expression of ERα in thecal and stromal cells in comparison with that in follicle cells suggests an indirect effect of estrogen on the follicular development. However, the exact function of ERα in the bovine ovary together with the cycle‐dependent variations in ERα expression remain to be elucidated.     

口服促孕散治疗前后持久黄体奶牛B超影像学的研究

为探讨促孕散治疗持久黄体的作用机理,本研究通过直肠检查结合B超直肠检查对持久黄体奶牛做出诊断后口服促孕散,应用B超每3 d对黄体直径、卵泡数量、卵巢长度、卵巢宽度、子宫角纵径和子宫颈纵径进行测量,并统计1次,与用药前进行对比。30头持久黄体奶牛口服促孕散后,治疗有效头数25头,有效率为83.3%。停药后第1天卵巢出现小卵泡和中等卵泡,停药后分别在第10和19天大卵泡数量最多,部分奶牛出现发情并排卵,与用药前卵巢相比,结果发现左、右侧卵巢长在停药后均降低,但差异不显著(P>0.05);左、右卵巢宽在停药后均降低,但差异不显著(P>0.05);子宫颈纵径和子宫角纵径均在停药后升高,但差异不显著(P>0.05)。结果表明,B超是诊断奶牛持久黄体的有效手段,中药促孕散对持久黄体奶牛卵巢和子宫形态等指标具有一定的影响,可以促进黄体的溶解。