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1.
Ovarian follicular dynamics of cattle were examined during the estrous cycle, early pregnancy and in response to PMSG. Number and size of follicles were monitored by ultrasonographic examinations. During the estrous cycle, distinct periods of follicular dominance (measured by the increase in difference in size between the largest and second largest follicle) occurred in both the luteal (Days 6-8) and proestrus (18-22) phases of the estrous cycle (two follicular waves). Associated with the well timed development of the first dominant follicle was a change in distribution of follicle numbers in small (less than 5 mm; increased on Days 2-4), medium (6-8 mm; increased on Days 3-5) and large (greater than or equal to 9 mm; increased on Days 6-9) follicular size classes. Follicular development was greater on the ovary bearing the CL for the period that the CL was present. The dominant follicle formed during the first follicular wave was capable of ovulating (6 of 8 heifers) following an injection of a synthetic analogue of prostaglandin F-2 alpha on Day 9 of the estrous cycle. During early pregnancy (Days 6-34), follicular development (size of largest follicle, number of follicles and total accumulated size of all follicles) on the ovary bearing the CL was suppressed between Days 24 and 34 of pregnancy. This was a local effect in that follicular development was sustained on the contralateral ovary. Therefore, the CL or conceptus may be regulating follicular development in a manner to help prevent luteolysis. Associated with the injection of PMSG was an initial increase in the number of small follicles followed by their recruitment into medium and large size classes leading to ovulation. Number of follicles greater than 5 mm on the Day of estrus was related (r = .97) to the number of subsequent embryos and oocytes collected. Ultrasonography is a valuable technique to monitor ovarian follicular dynamics in cattle, and can thereby be used to infer changes in physiological and endocrine states.  相似文献   

2.
Effects of recombinant bovine somatotropin (rbST) on ovarian and uterine function and the production of components of the insulin-like growth factor (IGF) system were examined during the period of maternal recognition of pregnancy in cattle. Lactating dairy cows were treated with 25 mg/d rbST (n = 8) or saline (n = 8) for 16 d after estrus. Ovaries, uteri, and conceptuses were collected on Day 17 after estrus. The length (millimeters) of the conceptus was recorded. The concentration of IGF-I and the content of IGF-binding proteins (BP) in uterine flushings were determined. Corpora lutea (CL) were weighed, and the number of follicles (⩾2 mm in diameter) were counted. Follicular fluid from the largest and second-largest follicles was assayed for the concentration of IGF-I, IGFBP, progesterone, and estradiol. The length of the conceptus and the total amount of IGF-I in uterine fluid were similar for rbST and control. Recombinant bST increased 1) the weight of the CL, 2) the number of largest follicles (10 to 15 mm in diameter), 3) the concentration of IGF-I in the follicular fluid, 4) the follicular fluid content of IGFBP of the largest estrogenic follicle, and 5) the quantity of IGFBP in uterine flushings. The concentration of progesterone in the follicular fluid tended to be increased in rbST-treated cows, whereas the concentration of estradiol was similar to that of control cows. The concentration of progesterone in plasma was similar for rbST compared with control. In conclusion, the administration of rbST in lactating dairy cows for 16 d after estrus did not alter the growth of the conceptus collected on Day 17. The greatest responses to rbST were found within the ovary, where rbST increased the weight of the CL and altered the amount of IGF-I and IGFBP in the follicular fluid.  相似文献   

3.
This study aimed to investigate the intra- and interovarian relationships among the corpus luteum (CL), the largest follicle (LF) and follicular population in non-pregnant and between the conceptus and ovarian structures in pregnant ewes. In experiment 1, the follicular and luteal structures were examined in 538 reproductive systems of non-pregnant Awassi ewes. The follicular population was categorised into small (SF), medium (MF) and large (LF) groups. Inter-relationships between CL and follicular population and between LF and subordinate follicles were determined. In experiment 2, the location and number of conceptuses were identified and correlated with the ovarian structures in 58 reproductive systems of pregnant ewes. Effects of pregnancy status, stage of pregnancy, pregnancy side and conceptual number on follicular population were determined. The results showed that the right ovary was more active than the left ovary. CL had intraovarian positive effect on the number of medium and large follicles. LF had no local suppressive effect on the subordinate follicles. Side and stage of pregnancy and the conceptual number did not affect the follicular population. Accordingly, it can be concluded that the LF has no local suppressive effect on the subordinate follicles. The CL has intraovarian positive effect on the follicular population. Follicular population does not show remarkable changes during the first term of pregnancy. The present study probably provides information which may help in the understanding of the ovarian dynamics during pregnancy in sheep.  相似文献   

4.
The aim of the study was to investigate the histological characteristics and steroid concentrations in follicular fluid of different populations of follicles at different stages of development, during pregnancy and the oestrous cycle in cows. Follicles from ovaries collected at a slaughterhouse were allocated into three size categories (small, 2–5.9 mm; medium, 6–13.9 mm; and large, 14–20 mm) in pregnant and non-pregnant cows. Slices were stained with HE and PAS for histological analysis. Follicular fluid was pooled according to size and pregnancy status and estradiol, testosterone and progesterone concentrations in follicular fluid were determined by RIA. Characteristics of healthy follicles did not differ, regardless of follicle size or pregnancy status. Total histological atresia was significantly higher in pregnant cows than in non-pregnant cows (p < 0.05). Estradiol increased and testosterone decreased significantly, while follicles increased in size, in both non-pregnant and pregnant cows (p < 0.05). Nonpregnant cows had the highest estradiol values in follicles of all sizes. Medium and large follicles from pregnant cows showed the lowest testosterone concentration (p < 0.05). Progesterone levels increased with follicle size only in non-pregnant animals. In large follicles, progesterone concentration was significantly higher in non-pregnant cows than in pregnant cows (p < 0.05). Considering steroid concentration and histological findings, most large follicles might be atretic during pregnancy in cattle.  相似文献   

5.
Follicular development was examined by transrectal ultrasound scanning in 12 heifers during 51 oestrous cycles. Internal diameters of largest and second largest follicles and the number of smaller ovarian vesicles were determined. Diameters of dominant follicles showed inverse growth pattern to the second largest follicles and numbers of smaller follicles (greater than or equal to 5 mm). There was an increase in diameters of the largest follicles from beginning of dioestrous to day 9 and from time of luteolysis to ovulation, which was coincident which a decrease in diameters of the second largest follicles and numbers of smaller ovarian vesicles. Smaller follicles increased in count and diameter, when the dominant follicle achieved its largest dimension and started to regress. The cyclic corpus luteum had no local influence on diameters of the largest and second largest follicles in the ovary bearing the corpus luteum versus the contralateral ovary. Internal diameters of oestrous follicles measured 14.7 +/- 2.6 mm in heifers and 15.3 +/- 2.9 mm in cows at the day of oestrous (p greater than 0.05; t-test). Dioestrous follicles with similar size were detected during various stages of the oestrous cycle. The diameter of the dominant follicle is not an accurate criterion for determining the stage of the oestrous cycle.  相似文献   

6.
Ovarian follicular growth, function and turnover in cattle: a review   总被引：3，自引：0，他引：3  
Studies in cattle assessing changes in number and size of antral follicles, concentrations of estradiol, androgens and progesterone in serum and follicular fluid, and numbers of gonadotropin receptors per follicle during repetitive estrous cycles and postpartum anestrus are reviewed. The rate of growth of small follicles (1 to 3 mm) into larger follicles increases as the estrous cycle progresses from d 1 to 18 (d 0 = estrus). Size of the largest antral follicle present on the ovary also increases with advancement of the estrous cycle. Most large follicles (greater than 10 mm) persist on the ovarian surface for 5 d or more between d 3 and 13 of the bovine estrous cycle. After d 13, most of these large follicles are replaced more frequently by new growing follicles (turnover) with an increased probability for recruitment of the ovulatory follicle after d 18. More research is needed to determine the time required for growth of bovine follicles from small to large antral size and evoke recruitment of the ovulatory follicle. Factors that regulate selection of the ovulatory follicle are unknown but may involve increased frequency of LH pulses in blood, altered blood flow and(or) changes in intrafollicular steroids and proteins. Quantitative evaluation of ovarian follicles indicated occurrence of consistent short-term changes in fluid estradiol and numbers of luteinizing hormone receptors in cells of large follicles only during the pre-ovulatory period. Presumably, low concentrations of follicular estradiol found during most of the estrous cycle are not due to a lack of aromatizable precursor or follicle-stimulating hormone receptors. Follicular fluid concentrations of progesterone increase only near the time of ovulation. Little is known about changes in follicular growth, turnover and function during postpartum anestrus in cattle. However, preliminary data suggest that the steroidogenic capacity of large follicles changes markedly during the postpartum period.  相似文献   

7.
Comparisons of numbers of antral ovarian follicles and corpora lutea (CL), of blood hormone concentrations, and of follicular fluid steroid concentrations and IGFBP activity were conducted between cows selected (twinner) and unselected (control) for twin births to elucidate genetic differences in the regulation of ovarian follicular development. Ovarian follicular development was synchronized among cows by a single i.m. injection of PGF2alpha on d 18 of the estrous cycle; six cows per population were slaughtered at 0, 24, 48, and 72 h after PGF2alpha. Jugular vein blood was collected from each animal at PGF2alpha injection and at 24-h intervals until slaughter. Ovaries of twinner cows contained more small (< or = 5 mm in diameter, P < 0.05), medium (5.1 to 9.9 mm, P < 0.05), and large (> or = 10.0 mm, P < 0.01) follicles and more (P < 0.01) CL than ovaries of controls. Follicular fluid concentrations of estradiol, androstenedione, testosterone, and progesterone reflected the stage of follicular development and were similar for twinner and control follicles at the same stage. Earlier initiation of follicular development and/or selection of twin-dominant follicles in some twinner cows resulted in greater concentrations of estradiol in plasma at 0, 24, and 48 h and of estradiol, androstenedione, and testosterone in follicular fluid of large follicles at 0 h after PGF2alpha for twinner vs. control cows (follicular status x time x population, P < 0.01). Binding activities of IGFBP-5 and -4 were absent or reduced (P < 0.01) in follicular fluid of developing medium and large estro-gen-active (estradiol:progesterone ratio > 1) follicles but increased with atresia. Only preovulatory Graafian follicles lacked IGFBP-2 binding, suggesting a possible role for IGFBP-2 in selection of the dominant follicle. Concentrations of IGF-I were twofold greater (P < 0.01), but GH (P = 0.10) and cholesterol (P < 0.05) were less in blood of twinners. Three generations of selection of cattle for twin ovulations and births enhanced ovarian follicular development as manifested by increased numbers of follicles within a follicular wave and subsequent selection of twin dominant follicles. Because gonadotropin secretion and ovarian steroidogenesis were similar for control and twinner cattle, enhanced follicular development in twinners may result from decreased inhibition by the dominant follicle(s), increased ovarian sensitivity to gonadotropins, and/or increased intragonadal stimulation, possibly by increased IGF-I.  相似文献   

8.
To investigate some biochemical changes during bovine follicle development, ovaries were obtained from cyclic heifers (7 to 11 heifers/d on each day of the 21-d estrous cycle; N = 152). Follicular fluid from the two largest follicles from both ovaries and a pool from small follicles (N = 30/cow) were collected from each animal and analyzed for ionic, enzymatic and endocrine changes in relation to day of the estrous cycle, follicle size, rank and atretic or growing status. Follicular fluid alkaline phosphatase activity and ascorbate concentrations were highest in all follicular sizes during the earlier portion of the estrous cycle (d 1 to 12; P less than .05), then decreased to the lowest levels (d 13 to 21). As follicular size (diameter) increased lactate dehydrogenase (LDH), acid and alkaline phosphatase activity was reduced in follicular fluid (P less than .05). Alkaline phosphatase and LDH activity tended to be increased in atretic follicles (P less than .10), and was correlated with increased progesterone and androgen concentrations of follicular fluid (r = .4, P less than .05). Both albumin and total protein concentrations decreased as follicular diameter increased (P less than .05). Sodium concentrations in follicular fluid were greater in growing-antral than atretic follicles, and increased with follicular enlargement (P less than .05). Follicular potassium concentrations increased as the estrous cycle progressed (P less than .05), and tended to be elevated in atretic follicles (nonsignificant). Both Ca and Mg concentrations increased with follicular enlargement (P less than .05). Dehydroepiandrosterone and testosterone were the predominant androgens in follicular fluid (androstenedione, the lowest concentration); their concentration decreased with follicle development (P less than .05), but were quite variable. Estradiol was increased in growing follicles (P less than .01). Estrone and estradiol concentrations increased as ovulation approached, particularly in small follicles (less than or equal to 4 mm diameter). Changes of biochemical components found in follicular fluid that relate to the growth and atresia process may provide a more sensitive and accurate method to classify follicle status, and thus aid in understanding the complexity of events associated with maturation of the bovine follicle and oocyte.  相似文献   

9.
Factors that affect ovarian follicular dynamics in cattle.   总被引：1，自引：0，他引：1  
Studies of ovarian follicular dynamics in cattle may lead to methods for improving fertility, for synchronizing estrus with more precision, and for enhancing superovulatory responses. Within an estrous cycle, two or three large (> 10 mm) follicles develop during consecutive waves of follicular growth. The last wave provides the ovulatory follicle, whereas preceding wave(s) provide follicles that undergo atresia. The life span of large follicles seems to depend on the pulsatile secretion of LH; decreased frequency of LH pulses results in atresia of large follicles. Aromatase activity in the walls of the largest follicles is greatest during the first 8 d of the estrous cycle and decreases by d 12. Steroidogenesis of the largest and second-largest ovarian follicles differs on d 5, 8, and 12 of the estrous cycle. Follicular dynamics are altered by negative energy balance and lactation. The number of large follicles and concentration of estradiol during the preovulatory period differs between postpartum lactating and nonlactating cows. Dietary fats stimulate follicular growth when they are fed to increase energy balance. Administration of bovine somatotropin decreases energy balance and has a differential effect on ovarian follicular responses; growth of the largest follicle does not change, but growth of the second-largest follicle is stimulated by somatotropin. Studies of follicular dynamics in lactating cows demonstrate changes in ovarian function associated with energy balance that may be related to inefficient reproductive performance of cows producing high yields of milk.  相似文献   

10.
We investigated the effects of twice-weekly follicular punctures of ovaries with or without corpus luteum (CL) on follicular and luteal dynamics. A cross-over design was used, with each cow (seven Japanese Black beef cows) being assigned to one of the three groups at 2-month intervals. Follicular punctures were performed twice weekly for three consecutive weeks until day 20 (oestrus = day 0). All visible follicles (diameter >3 mm) in the ovaries bearing CL (ipsilateral group) or those in the contralateral ovaries (contralateral group) were aspirated. As a control, all visible follicles in both ovaries were aspirated (bilateral group). Follicular development, CL formation and progesterone concentrations in each cow were monitored from days 0 to 30. Follicular growth profiles in the punctured ovaries during/after puncture treatment were similar, irrespective of the presence of follicles in the unpunctured ovary and the CL in the punctured or unpunctured ovaries. After puncture, two cows (28.6%) each in the ipsilateral and bilateral groups did not exhibit behavioural oestrus until day 30, whereas all cows in the contralateral group exhibited oestrus. CL growth and increase in progesterone concentrations after the last follicular puncture in the bilateral group were delayed when compared with those in the ipsilateral group. Our results indicate that the presence of follicles in the unpunctured ovary and the CL in the punctured or unpunctured ovaries does not significantly influence follicular growth in punctured ovaries during/after puncture treatment. However, follicular puncture in ovaries bearing CL may disturb or delay oestrus occurrence after treatment.  相似文献   

11.
Relatively few studies have been reported regarding the reproductive physiology of female Thai native cattle. Therefore, the objective of the present study was to evaluate the follicular dynamics and concentrations of follicle stimulating hormone (FSH), estradiol (E2) and progesterone (P4) during the estrous cycle in Thai native heifers (TNH) and to compare obtained results with those of European and Indian cattle breeds previously reported. For the detection of estrus, ovaries of all 20 heifers were examined twice daily (12 h intervals) by ultrasonography for three consecutive estrous cycles. From data of 60 estrous cycles (n = 60 estrous cycles from 20 heifers), it was found that 14 (70%) and 6 heifers (30%) had two (42 estrous cycles collected from 14 heifers) and three follicular waves (18 estrous cycles collected from 6 heifers), respectively. The days when estrus was detected, interovulatory intervals, life‐spans of corpus lutea (CL), and days for growing and regression of CLs were shorter in the two follicular waves than those in the three follicular waves (P < 0.05). In both two and thre follicular waves, larger maximum diameters and higher growth rates of the dominant follicle (DF) in an ovulatory wave were observed than those of the preceding waves without ovulation (P < 0.05). There was a progressive increase in follicular size and FSH and E2 production during follicular growth in each follicular wave. In addition, the FSH and E2 peak concentrations during the ovulatory wave were higher than those of the anovulation waves (P < 0.05). Moreover, although the ovarian follicular dynamic patterns in Thai native heifers were similar to those previously reported for European and Indian cattle breeds, the diameter of the largest preovulatory follicle (OF), subordinate follicles (SF) and CLs were smaller than those in European and Indian cattle breeds. In conclusion, when compared with European and some breeds of Indian cattle, the length of interovulatory intervals was shorter, and the sizes of dominant SF and CLs were smaller in Thai native heifers.  相似文献   

12.
“Within follicle” regulations may be important for the fine tuning of gonadotrophin action in ovarian follicles. While numerous growth factors, steroids or proteins which are present in follicular fluid have been shown to have the ability of positively or negatively affecting follicle function, the net effet of follicular fluid of the dominant follicle on its function is unclear.

A bioassay measuring aromatase activity of follicular walls was used (1) to check whether follicular fluid from dominant follicles can alter aromatase activity (2), to check how follicle size, atresia and specific gonadotrophins alter the effects of follicular fluid (3), to identify the nature (steroid or protein) of the active compound(s), and (4) to check whether the inhibition is specific of aromatase. Dominant follicular fluid had the ability to reduce aromatase activity. This effect was dose dependent and was obvious whether or not a protease inhibitor was added to the incubation medium. There was no difference in the magnitude of the inhibitory effect of follicular fluid when FSH (2 ng/ml) or no FSH was added to the incubation medium. LH, however, could potentialise the inhibitory effects of follicular fluid. Dominant follicular fluid was more potent to inhibit aromatase than follicular fluid from atretic follicles. Medium conditioned by granulosa cells, but not by theca cells could inhibit aromatase activity when added to the incubation medium. Charcoal treatment of dominant follicular fluid did not remove its inhibitory potential. Fractionation of dominant follicular fluid by a desalting column demonstrated that the inhibition was related to a compound(s) > 10 kDa. Finally, the effect of dominant follicular fluid on aromatase appears specific of this enzyme as follicular fluid does not affect androgen output by thecal shells or progesterone output by luteal cells.

Further research is required to check whether the activity observed in dominant follicular fluid is related to compounds known to affect aromatase activity (inhibin, mullerian inhibiting substance, heat shock protein 90, superoxyde dismutase) or to another peptide/protein.  相似文献   


13.
Ovarian morphology and follicular systems in yaks of different ages   总被引：5，自引：0，他引：5  
Forty-five female yaks of different ages with known reproductive histories were used to determine the morphology and follicular systems of their ovaries. The histological structure of the ovaries in each age group was found to be similar and resembled that of cattle and buffalo. The atresia of primordial follicles took one form (oocyte atresia); that of growing follicles could be divided into two stages (early and late); and that of Graafian follicular were classified as early, definite and late stage. The details of the several types of atresia are described herein. The average total numbers of primordial follicles per ovary pair in 1-month-old calves, 1-year-old heifers, 2-year-old heifers and 7-10-year-old cows were 53,500 +/- 6300, 32,870 +/- 4500, 22,850 +/- 2800 and 9500 +/- 1200, respectively; those of growing follicles were 210 +/- 76, 815 +/- 95, 895 +/- 142 and 445 +/- 88, respectively; and those of Graafian follicles were 36.5 +/- 14.2, 41.7 +/- 12.3, 37.8 +/- 9.8 and 42.5 +/- 14.5, respectively. The percentage of atretic primordial follicles per ovary pair in 1-month-old calves, 1-year-old heifers, 2-year-old heifers and 7 to 10 year-old cows were 51.6, 55.5, 56.7 and 47.4%, respectively. The average total numbers of atretic growing follicles per ovary pair were 119.5 +/- 21.5, 605.5 +/- 74.3, 721.6 +/- 78.5 and 275.8 +/- 66.3, respectively; those of atretic Graafian follicles were 22.1 +/- 5.6, 21.2 +/- 7.6, 21.5 +/- 4.7 and 25.3 +/- 6.7, respectively.  相似文献   

14.
The size of the ovary varies substantially among cattle. This variation may influence the potential of the ovary to produce follicles. In the present study, we examined whether a relationship exists between the weight of the ovary and the number of antral follicles >or=1 mm. Paired ovaries were obtained from Holstein x Japanese Black F1 heifers. Follicles were classified into three size categories (small: 1.0-<5.0 mm, medium: 5.0-<8.5 mm and large: >or=8.5 mm), and the number of follicles in each category was recorded. Large variations in the weight of ovaries and the number of follicles were observed among animals. Significant positive correlations (r>or=0.4, P<0.001) were found between the weight of intact ovaries and the number of follicles in all three categories for the ovary contralateral to CL (OCC) and in the small follicles for the ovary ipsilateral to CL (OIC). Significant positive correlations (r>0.4, P<0.0001) were also observed between the weight of ovaries devoid of CL and follicles and the number of small and medium follicles in both OIC and OCC, indicating that the correlation is not due to the increase in ovarian weight associated with the increase in follicular number. Paired ovaries contained a similar number of small and medium follicles, and significant positive correlations were observed between them (r>0.6, P<0.0001). There were significant positive correlations between the weight of OCC and the number of small and medium follicles in paired ovaries (r>0.4, P<0.0001). These results suggest that 1) the weight of an ovary reflects the potential of the ovary to produce antral follicles, and 2) a rough estimation of follicular population might be possible by using the weight of the ovary contralateral to CL in heifers.  相似文献   

15.
Changes in sizes and numbers of ovarian antral follicles, uterine size and weight, serum hormones, and frequency and duration of suckling were examined during the postpartum anovulatory period in primiparous, suckled beef cows. Twenty-one anovulatory, suckled cows (n = 4 to 6/d) were slaughtered on d 7, 14, 28 and 42 to 56 after parturition. In addition, a total of 11 postpartum cows that had begun cyclic activity were slaughtered on d 28, 42 or 56. Blood was collected at 10-min intervals for 6 h 1 d before slaughter for measurement of prolactin, cortisol and progesterone in serum. Numbers of medium (4.0 to 7.9 mm) follicles increased fourfold (P less than .05) between d 7 and 42 to 56 in anovulatory cows, whereas numbers of small (1.0 to 3.9 mm) and large (greater than or equal to 8.0 mm) follicles did not change (P greater than .10). Uterine involution was complete by d 28. In anovulatory cows, a higher (P less than .05) proportion of largest (but not second-largest) follicles was opposite the ovary containing the corpus albicans from pregnancy (CAP). In addition, 90% of these largest follicles opposite the CAP had concentrations of estradiol greater than progesterone. In cyclic cows, however, first ovulations occurred with equal frequency on either ovary. Concentrations of prolactin or cortisol in serum or duration of suckling were not associated with changes in uterine or ovarian measurements. In conclusion, growth and function of the largest (but not second-largest) follicle were reduced when located on the ovary containing the CAP.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

16.
The objective of this research was to determine changes in IGF-I levels in serum and follicular fluid, and immunoreactivity of the follicle wall of cows with spontaneous (slaughter specimens) or ACTH-induced follicular cysts, and to compare results to normal cycling (control) cows after selection of the ovulatory follicle. Concentrations of IGF-I in serum did not differ between control and cystic animals (p=0.76). Fluid from the ovulatory follicle in control cows had 41% higher concentrations of IGF-I than that from cystic follicles collected at slaughter (spontaneous cysts; p<0.05) and 70% higher than that in induced follicular cysts (p<0.05). An intense positive immunostaining with anti-IGF-I was observed in granulosa cells (p<0.05) and in the theca interna (p<0.05) of secondary and tertiary follicles in all three groups of animals, but staining was less intense in cystic (p<0.05) and atretic follicles (p<0.05). This study provides evidence to suggest that cystic ovarian disease in cattle is associated with decreased concentrations of IGF-I in follicular fluid, but not in serum, and decreased production of IGF-I in the follicular wall. These data support the notion that IGF-I plays a role in the regulation of folliculogenesis, and may participate in the pathogenesis of cystic ovarian disease in cattle.  相似文献   

17.
The objective of this study was to determine if increased secretion of intraovarian insulin-like growth factor-I (IGF-I), experimentally induced via minipumps, affects follicular function in cattle. Fourteen cycling Holstein cows were divided equally into two groups: Control, osmotic minipumps (containing vehicle) surgically inserted into each ovary, or IGF-I treated, osmotic minipumps as in Controls but pumping 2.0 microg of recombinant human IGF-I per hr for 7 days. All cows were synchronized with prostaglandin F(2alpha) 0.10) between Control and IGF-I-treated cows during Days 2 to 6 of treatment. IGF-I treatment increased (P<0.05) estradiol concentrations in follicular fluid of small follicles, but had no effect (P<0.10) on estradiol concentrations in follicular fluid of large follicles, or on progesterone, androstenedione, or IGF binding protein concentrations in small or large follicles. We conclude that a 7-day infusion of IGF-I directly into the stroma of the ovary altered follicular growth and follicular fluid estradiol concentrations.  相似文献   

18.
The results of continually repeated transrectal palpations, performed in 168 post partum periods, 383 estrous cycles and 178 early pregnancies, were used to describe and to discuss the left-right distribution of ovarian functional structures. In cycling as well as in pregnant cattle, anovulatory interestral follicles and estrous follicles or corpora lutea in the mean were all distributed at 41% and 59% on the left and right ovaries respectively. No signs were found indicating that the position of functional structures would be influenced by local interactions between follicles and corpora lutea. At least for cyclic ovarian activity, and in early pregnancy, the interrelationship observed between the locations of these structures could be put down to the normally increased activity of the right ovary. After delivery, the first follicles preferentially became discernible on the ovary opposite to the previously pregnant uterine horn. But, as from the 4th follicle p.p. onward, the distribution of new ovarian structures again agreed with the one of the ensuing reproductive stages. After calving, probably the position of new follicles is temporally influenced by direct signals from the uterine horns affected differently by pregnancy. Several observations indicate that the factors causing asymmetrical ovarian activity could exert a selective effect on the recruitment of the dominant and solitary interestral follicles from the pool of their minor and less differentiated precursors.  相似文献   

19.
Glucocorticoid (G) directly modulates ovarian functions through binding to G receptor. The actions of G are both agonistic and antagonistic depending on the developmental stage of follicles and corpora lutea (CL). During follicular maturation, G suppresses follicular differentiation by downregulating expression of P450 aromatase and luteinizing hormone (LH) receptor in granulosa cells. During ovulation, G protects the ovulatory follicle from inflammatory damage and promotes luteinization, ensuring a smooth transition of the follicle to CL. Throughout life the ovary is exposed to periodic and sporadic waves of G. The Ovary appears to cope with this situation by locally modulating levels of active G. The primary regulatory mechanism consists of two isoforms of 11β‐hydroxysteroid dehydrogenase (11βHSD) that catalyze conversion between active and inactive G. During follicular maturation the levels of active G are suppressed by the dehydrogenase activity of 11βHSD, whereas during the ovulatory process, levels of active G are further increased by the oxo‐reductase activity of 11βHSD. The expression of these enzymes is under the control of gonadotrpins and local regulatory factors such as cytokines, allowing the mechanism to act in coordination with major reproductive events. Thus the G system is an integral part of ovarian physiology, which ensures that the ovary experiences only beneficial effects of G.  相似文献   

20.
In cattle, sub-luteal circulating progesterone induces an increase in the frequency of LH pulses, prolonged growth of the dominant follicle, increased peripheral estradiol and reduced fertility. The objective of this study was to examine the earliest stages of development of prolonged dominant follicles, to gain insight into the etiology of this aberrant condition. Heifers were treated with an intravaginal progesterone-releasing device (CIDR) from Day 4-8 post-estrus and PGF2alpha was injected on Day 6 and again 12h later (early prolonged dominant group). Follicular phase (CIDR: Day 4-6, with PGF2alpha) and luteal phase (CIDR: Day 4-8, without PGF2alpha) groups served as controls. As expected, peripheral progesterone in heifers of the early prolonged dominant group was intermediate between luteal and follicular phase groups after luteal regression (P<0.05). On Day 7, the frequency of LH pulses was higher in heifers of the follicular phase and early prolonged dominant groups than the luteal phase group (P<0.05). Dominant follicles (n = 4 per group) were collected by ovariectomy on Day 8 and were similar in size among groups (P>0.05). Estradiol and androstenedione concentrations in the follicular fluid at ovariectomy were higher in the follicular phase and early prolonged dominant groups versus the luteal phase group (P<0.01), whereas progesterone did not differ among groups (P>0.05). Granulosa cells and theca interna isolated from dominant follicles were incubated for 3h with or without gonadotropins or frozen for later analysis of mRNA for steroidogenic enzymes. Luteinizing doses (128 ng/ml) of LH and FSH increased secretion of progesterone (P<0.05) but did not affect secretion of estradiol by granulosa cells in all groups. Low (2 or 4 ng/ml) and luteinizing doses of LH increased secretion of androstenedione by theca interna to a similar extent among groups. Expression of mRNA for P450 side chain cleavage (P450scc), 3beta-hydroxysteroid dehydrogenase (3beta-HSD), P450 aromatase (aromatase) and Steroidogenic Acute Regulatory (StAR) protein by granulosa cells did not differ among groups (P>0.05). Levels of mRNA for P450scc, 3beta-HSD, 17alpha-hydroxylase (17alpha-OH) and StAR protein in theca interna were similar in the follicular phase and early prolonged dominant groups (P>0.05), but lower in the luteal phase group (P<0.05-0.1). In summary, the premature follicular luteinization observed in previous studies after prolonged periods of sub-luteal progesterone was absent in early prolonged dominant follicles, exposed to sub-luteal progesterone for 36 h, and their characteristics resembled those of control follicles during the follicular phase.  相似文献   

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