Biomedical subjects

L J Kulick

Publications and source records attributed to L J Kulick.

10 recordsLinked to original sources

PubMed2001

Follicle selection in cattle: follicle deviation and codominance within sequential waves.

Follicle deviation during bovine follicular waves is characterized by continued growth of a developing dominant follicle and reduction or cessation of growth of subordinate follicles. Characteristics of follicle deviation for waves with a single dominant follicle were compared between wave 1 (begins near ovulation; n = 15) and wave 2 (n = 15). Follicles were defined as F1 (largest), F2, and F3, according to maximum diameter. No mean differences were found between waves for follicle diameters at expected deviation (F1, > or =8.5 mm; Hour 0) or observed deviation or in the interval from follicle emergence at 4.0 mm to deviation. For both waves, circulating FSH continued to decrease (P < 0.05) after Hour 0, estradiol began to increase (P < 0.05) at Hour 0, and immunoreactive inhibin began to decrease (P < 0.05) before Hour 0. A transient elevation in circulating LH reached maximum concentration at Hour 0 (P < 0.01) in both waves and was more prominent (P < 0.0001) for wave 1. Waves with codominant follicles (both follicles >10 mm) were more common (P < 0.02) for wave 1 (35%) than for wave 2 (4%). Codominants (n = 6) were associated with more (P < 0.05) follicles > or=4 mm and a greater concentration (P < 0.04) of circulating estradiol at Hours -48 to -8 than were single dominant follicles (n = 15). A mean transient increase in FSH and LH occurred in the codominant group at Hour -24 and may have interfered with deviation of F2. In codominant waves, deviation of F3 occurred near Hour 0 (F1, approximately 8.5 mm). A second deviation involving F2 occurred in four of six waves a mean of 50 h after the F3 deviation and may have resulted from a greater suppression (P < 0.05) of FSH in the codominant group after Hour 0. In conclusion, follicle or hormone differences were similar for waves 1 and 2, indicating that the deviation mechanisms were the same for both waves. Waves that developed codominant follicles differed in hormone as well as follicle dynamics.

Animals↗

PubMed2000

Follicular and hormonal response to experimental suppression of FSH during follicle deviation in cattle.

A near steroid-free fraction of bovine follicular fluid was used to suppress FSH concentrations at the expected time of follicle deviation or when the largest follicle of Wave 1 reached > or = 8.0 mm (actual mean diameter, 8.4 mm; Hour 0). It was hypothesized that the low concentrations of FSH associated with deviation are inadequate for the smaller follicles but are needed for continued growth of the largest follicle. Control heifers (n=8) received 10 mL of saline, and treated heifers (n=16) received either 8.8 mL or 13.3 mL of the follicular-fluid fraction at Hours 0, 12, and 24. Between Hours -48 and 0, FSH concentrations decreased (P<0.05) and diameters of the 4 largest follicles increased (Hour effect, P<0.0001) similarly between groups. Concentrations of LH in the controls increased (P<0.05) between Hours -24 and -12 and decreased (P<0.05) between Hours 8 and 36, demonstrating a transient LH surge encompassing the expected beginning of deviation. In the treated group, a comparable increase in LH occurred before deviation but a decrease did not occur until after Hour 48. By Hour 4.5, the FSH concentrations in the treated group decreased (P<0.05) to below the concentrations in the controls. Suppressed diameter (P<0.001) of the largest follicle was detected at the first post-treatment examination (Hour 12; 7.5 h after FSH suppression) and was accompanied by reduced (P<0.04) systemic estradiol concentrations. The mean growth rates of the 3 smaller follicles in both the treated and control groups began to decrease at Hours -12 to 24 and were not different between groups during Hours 0 to 36. Concentrations of FSH in the treated group returned to control concentrations by Hour 24 (hour of last treatment). A rebound (P<0.05) in concentrations of FSH to >100% above control concentrations occurred by Hour 48 and was accompanied by resumed growth of the largest follicle in 75% of the heifers between Hours 48 and 72. The results demonstrated that the low concentrations of FSH associated with deviation can be further reduced by treatment with a nonsteroidal factor of follicular origin. Transient reduction of FSH concentrations to below the already low control concentrations inhibited the largest follicle but did not further inhibit the smaller follicles. These results support the hypothesis that the low FSH concentrations associated with follicle deviation are below the minimal requirements of the smaller or subordinate follicles but are needed for continued growth of the largest or dominant follicle in cattle.

Animals↗

PubMed2000

Selection of the dominant follicle in cattle: role of two-way functional coupling between follicle-stimulating hormone and the follicles.

The functional coupling between the declining portion of the FSH surge and the growing follicles of a wave was studied by treating heifers with a minimal dose of estradiol to decrease FSH concentrations without an associated change in LH concentrations. Estradiol treatment when the largest follicle reached >/= 6.0 mm (Hour 0) resulted in depression of both FSH concentrations and diameter of the largest follicle by Hour 8. The smaller follicles were also inhibited. These results supported the hypothesis that FSH continues to be needed by the growing follicles even when the FSH concentrations are decreasing during the declining portion of the FSH surge. Estradiol treatment when the largest follicle was >/= 8.5 mm (expected time of follicular deviation) also resulted in a transient decrease in both FSH concentrations and diameter of the largest follicle, but the diameters of the smaller follicles were not affected. These results supported the hypothesis that the low concentrations of FSH at the expected time of deviation, although inadequate for the smaller follicles, were required for continued growth of the largest follicle. In another study, ablation (Hour 0) of the largest follicle was done at >/= 7.5 mm vs. >/= 8.5 mm. The mean FSH concentrations for the 8.5-mm groups were greater for the ablation group than for the control group at Hours 8 and 12, but there was no difference between the 7.5-mm groups at any hour. These results supported the hypothesis that by the time the largest follicle reaches the expected beginning of deviation it has developed a greater capacity for suppressing FSH. It is postulated that the essence of the selection of a dominant follicle is a close two-way functional coupling between changing FSH concentrations and follicular growth.

Animals↗

PubMed2000

Selection of the dominant follicle in cattle: role of estradiol.

Involvement of estradiol in the deviation in growth rates between the two largest follicles of a wave was studied in 39 heifers. In experiment 1, the largest follicle remained intact in a control group and was ablated in five estradiol-treated groups when the largest follicle reached 8.5 mm or larger (expected beginning of deviation; Hour 0). The ablation groups were given a single injection of 0, 0.004, 0.02, 0.1, or 0.5 mg of estradiol. Blood samples were taken from a jugular vein every hour at Hours 0 to 16. By Hour 8, FSH concentrations were greater (P < 0.05) in the ablation group that received 0 mg of estradiol than in the controls. Among the estradiol groups, that receiving 0.02 mg had the lowest detectable increase in estradiol. In this group, FSH concentrations were not suppressed below the control concentrations, but the increase in FSH concentrations following ablation of the largest follicle was delayed for 2 or 3 h. This delay in the increase of FSH concentrations corresponded to the hours that estradiol was maximal. In experiment 2, blood samples were taken every 4 h from the caudal vena cava cranial to the junction with the ovarian veins in heifers with the largest follicle intact (controls) or ablated at 8.5 mm or larger (Hour 0). Averaged over Hours 4 to 48, estradiol concentrations were higher (P < 0.04) in the controls than in the ablation group. During Hours 0 to 12, estradiol concentrations increased (P < 0.05) in the controls, whereas FSH concentrations decreased (P < 0.05). In the ablation group, estradiol concentrations were lower than in the controls by Hour 4, and FSH concentrations increased (P < 0.05) between Hours 4 and 12. These results support the hypothesis that the largest follicle releases increased estradiol into the blood at the beginning of follicular deviation, and that the released estradiol is involved in the continuing depression of FSH concentrations to below the requirement of the smaller follicles.

Animals↗

PubMed1999

Selection of the dominant follicle in cattle: establishment of follicle deviation in less than 8 hours through depression of FSH concentrations.

Deviation in follicle diameter in cattle is characterized by continued growth of the largest follicle of a follicular wave and a reduction or cessation of growth of the smaller follicles. Deviation begins when the largest follicle reaches about 8.5 mm. Two experiments were done to test the hypothesis that the deviation mechanism is established in < 8 h, as indicated by the temporal relationships between follicle removal and an increase in FSH concentrations (Experiment 1) and between a decrease in FSH concentrations and follicle inhibition (Experiment 2). In Experiment 1, the role of the first follicle to reach 8.5 mm was studied by follicle ablation (Hour 0). The combined mean FSH concentrations for the control group (n = 8) and ablation group before ablation (n = 7) progressively decreased (P < 0.02) over two 8-h intervals before the largest follicle reached > or = 8.5 mm (Hour-16, 1.77 +/- 0.11 ng/mL; Hour 0, 1.49 +/- 0.08 ng/mL). In controls, the concentrations continued to decrease (P < 0.02) until Hour 10 (1.21 +/- 0.09 ng/mL). Ablation of the largest follicle at > or = 8.5 mm resulted in increased (P < 0.02) circulating FSH concentrations between Hours 5 (1.34 +/- 0.04 ng/mL) and 8 (1.61 +/- 0.09 ng/mL). Growth rate of the second-largest follicle between Hours 0 and 8 was greater (P < 0.05) in the ablation group than in the controls, and the second largest follicle became dominant in 7 of 7 heifers following ablation of the largest follicle. In Experiment 2, a minimal single injection of a depressant of FSH concentrations (4.4 mL of steroid-reduced follicular fluid) was given when the largest follicle was a mean of 8.4 mm (Hour 0; controls, n = 4; treated, n = 4). An interaction of group and hour (P < 0.005) for FSH concentrations was attributable to an FSH decrease (P < 0.002) by Hour 6 and an increase (P < 0.002) between Hours 9 and 12 in the treated group. The growth rate of the largest follicle between Hours 0 and 12 was less (P < 0.05) in the treated group (0.2 +/- 0.2 mm/12 h) than in the control group (1.2 +/- 0.4 mm/12 h). The reduced diameter was recorded within 6 h after suppression of FSH concentrations, supporting the hypothesis. Our preferred interpretation is that when the largest follicle reaches a critical diameter of about > or = 8.5 mm, FSH concentrations continue to decrease and become lower than required by the smaller follicles but not the largest follicle. The results further indicate that a close temporal coupling between a change in FSH concentrations and the follicular response could establish the deviation mechanism in < 8 h or before the second largest follicle reaches a similar critical diameter.

Animals↗

PubMed1999

Follicular and hormonal dynamics during the first follicular wave in heifers.

A few days after the first follicular wave emerges as 4-mm follicles, follicular deviation occurs wherein 1 follicle of the wave continues to grow (dominant follicle) while the others regress. The objectives of this study were to characterize follicle growth and associated changes in systemic concentrations of gonadotropins and estradiol at 8-h intervals encompassing the time of follicle deviation. Blood samples from heifers (n = 11) were collected and the ovaries scanned by ultrasound every 8 h from 48 h before to 112 h after the maximal value for the preovulatory LH surge. The follicular wave emerged at 5.8 +/- 5.5 h (mean +/- SEM) after the LH surge, and at this time the future dominant follicle (4.2 +/- 0.8 mm) was larger (P < 0.001) than the future largest subordinate follicle (3.6 +/- 0.1 mm). There was no difference in growth rates between the 2 follicles from emergence to the beginning of the deviation (0.5 mm/8 h for each follicle), indicating that, on average, the future dominant follicle maintained a size advantage over the future subordinate follicle. Deviation occurred when the 2 largest follicles were 8.3 +/- 0.2 and 7.8 +/- 0.2 mm in diameter, at 61.0 +/- 3.7 h after wave emergence. Diameter deviation was manifested between 2 adjacent examinations at 8-h intervals. Mean concentrations of FSH decreased, while mean concentrations of LH increased 24 and 32 h before deviation, respectively, and remained constant (no significant differences) for several 8-h intervals encompassing deviation. In addition to the increase and decrease in circulating estradiol concentrations associated with the preovulatory LH surge, an increase (P < 0.05) occurred between the beginning of deviation and 32 h after deviation. The results supported the hypotheses that deviation occurs rapidly (within 8 h), that elevated systemic LH concentrations are present during deviation, and that deviation is not preceded by an increase in systemic estradiol.

Animals↗

PubMed1998

Pulsatility of systemic FSH and LH concentrations during follicular-wave development in cattle.

Changes in systemic FSH and LH pulsatility in temporal association with follicular-wave emergence and follicle deviation were studied in cattle. Wave emergence was defined as occurring when the future dominant follicle first reached 4 mm, as established retrospectively. Follicle deviation was defined as the beginning of a change in growth rates between the 2 largest follicles and occurred 60.4 +/- 4.2 h after wave emergence. Follicles were tracked by transrectal ultrasound scanning every 8 h, and blood samples for pulse characterization were collected every 20 min from before emergence until after deviation. Pulses were characterized by the Pulsar program applied to each 8-h increment, centered on the hour of follicle scanning in each heifer (n = 6). Pulsatility of FSH was not detected for any of the 8-h increments. The mean FSH concentrations for the 24 samples per 8 h increased (P < 0.05) between 8 h before and 8 h after wave emergence, followed by a decrease 40 to 16 h before deviation. The low mean values continued for 24 h after deviation. Pulses of LH were detected for all 8-h increments. The LH mean of all concentrations per 8 h and pulse frequency increased (P < 0.05) between the hour of wave emergence and 32 h after emergence and then pulse frequency plateaued at a mean interpeak interval of 1.3 h. Increased LH means for all concentrations per 8 h and basal concentration were reached 32 h before deviation. The results indicated that elevated concentrations of LH and reduced concentrations of FSH were present 32 to 16 h before to at least 24 h after the beginning of follicle deviation. However, an abrupt, short-term change in FSH concentrations or in LH pulsatility in close temporal association with follicle deviation that could act as an acute stimulus to initiate deviation was not found.

Animals↗

PubMed1997

Emergence and deviation of follicles during the development of follicular waves in cattle.

The nature of emergence and deviation of follicles during follicular waves in cattle was studied in 3 experiments by re-examining data from previous projects. Wave emergence was defined as the day or examination (when more than 1 examination per day) the future dominant follicle was 4 mm (Day 0 or Examination 0). Deviation was defined as the beginning of the greatest difference in growth rates between the 2 largest follicles and between 2 consecutive examinations. The search for deviation in an individual wave was done retrospectively from the examination with the maximum diameter of the second largest follicle. In Experiment 1, follicles were assessed ultrasonically for 28 waves every 8 h. The number of examinations that encompassed the emergence of all growing 3-mm follicles was 10.0 +/-0.5 (mean +/-SEM; equivalent to 3.3 d) and extended from mean Examination -3.1 +/-0.3 to mean Examination 6.0 +/-0.6. A mean of 24 growing 3-mm follicles was found, and the maximal attained diameters were 4 mm (46%), 5 mm (25%), and >/=6 mm (29%). More (P<0.05) 3-mm follicles at Examinations -2 and -1 grew to >/=6 mm than to 4 or 5 mm, whereas more 3-mm follicles at Examinations 2 to 6 grew to only 4 mm. On average, the future dominant follicle appeared as a 3-mm follicle (Examination -2.1 +/-0.2) 6 and 10 h earlier (P<0.03) than for the largest (Examination -1.4 +/-0.3) and second-largest (Examination -0.8 +/-0.4) future subordinates, respectively. This result supported the hypothesis that the future dominant follicle has, on the average, an early developmental advantage. In Experiment 2 (n=33 waves), data were normalized to the day at the beginning of deviation (Day 2.8 +/-0.2) when the mean diameters of the dominant and largest subordinate follicle were 8.5 +/-0.2 mm and 7.2 +/-0.2 mm, respectively. This result suggests that the follicle selected to become dominant, as manifested by deviation, is the first follicle to develop to a decisive stage. In Experiment 3 (n=19 waves), FSH concentrations were lower (P<0.05) on the day at the beginning of deviation (8.5 +/-0.5 ng/ml) than on the day before (10.1 +/-0.8 ng/ml), with no continuing decrease after deviation. This temporal result suggests that the attainment of approximate basal levels of FSH is a component of the deviation mechanism.

Journal Article↗

PubMed1997

Sampling follicular fluid without altering follicular status in cattle: oestradiol concentrations early in a follicular wave.

A transvaginal, ultrasound-guided in situ technique was developed for sampling follicular fluid from 6.0-12.5 mm follicles in cattle, with minimal interference with the subsequent development of the sampled follicle. Each follicle was sampled only once and the status of the follicle (future dominant or subordinate) was determined retrospectively. A sample (20 microliters) was successfully obtained from 77% of 132 targeted follicles. Reasons for considering an attempt unsuccessful were as follows: (1) ovaries difficult to manipulate in two heifers (eight follicles), (2) samples contaminated with blood (11 samples), and (3) follicles sampled but the antrum subsequently developed an apparent blood clot (11 follicles). Only the 102 successful collections were used in the statistical analyses for evaluating oestradiol concentrations in the follicular fluid and the follicle growth profiles before and after sampling. The follicles were sampled once on days 1, 2, 3, or 4 after the emerging dominant follicle was 4 mm in diameter. On day 1, there were no differences in the oestradiol concentrations among follicles that later became the dominant follicle, largest subordinate follicle, or smaller subordinate follicles (means for diameters, 6.7-6.9 mm; means for oestradiol, 30-42 ng ml-1). The mean diameter of the dominant follicle increased linearly over the 4 days. Concentrations of oestradiol in the dominant follicle increased curvilinearly, resulting from a slower increase between days 1 (mean, 42 ng ml-1) and 2 (110 ng ml-1) than between days 2 and 3 (313 ng ml-1) and 3 and 4 (554 ng ml-1). Neither mean diameter nor mean oestradiol concentration of the largest subordinate follicle increased after day 2. Data were available from 19 follicular waves in which both the dominant and largest subordinate follicles were sampled on the same day. Oestradiol concentrations were not higher in the dominant follicle than in the largest subordinate follicle until the day after the two follicles began to deviate in growth rates (mean day of deviation, 2.5 +/- 0.2 days after emergence). These observations indicate that the future dominant follicle cannot be identified reliably by either its diameter or oestradiol production before the deviation in growth rates between the two largest follicles.

Animals↗

PubMed1996

Relationships between FSH and ovarian follicular waves during the last six months of pregnancy in cattle.

Follicles were monitored daily by ultrasound and blood samples for FSH assay were collected daily from eight heifers from day 90 of pregnancy to the emergence of the first postpartum follicular wave. Follicles > or = 6 mm in diameter emerged in groups or waves in each heifer (P < 0.005). Follicular waves developed rhythmically throughout pregnancy, except that follicles > or = 6 mm were not detected during the last 21.6 +/- 2.4 (mean +/- SEM) days of pregnancy. The characteristics of the first follicular wave after day 90 were similar to previous reports for days 10-100. However, between months 4 (days 90-119) and 5, there was a decrease (P < 0.05) in monthly means for maximum diameter (mm) of largest (21.1 +/- 0.5 versus 9.5 +/- 0.5) and second largest (8.0 +/- 0.3 versus 6.9 +/- 0.2) follicles, duration of the interwave interval (8.1 +/- 0.4 versus 6.6 +/- 0.3 days), and number of follicles per wave (3.7 +/- 0.4 versus 2.5 +/- 0.4). Averaged over all follicular waves during months 4-9, the concentrations of FSH normalized to the emergence of a follicular wave increased (P < 0.05) over the 3 days before emergence, reached peak values on the day of emergence of the future dominant follicle at 4 mm, and decreased (P < 0.05) over the 3 days following emergence. Surges in FSH concentrations occurred throughout pregnancy, but during the last 30 days of pregnancy the number of surges was reduced and each heifer had one or two ineffective surges (no follicular wave detected). The temporal relationship between FSH surges and emergence of waves was closer (P < 0.01) than would be expected if the two events were independent. Surges of FSH occurred rhythmically even when there was no follicular response (no follicle > 5 mm). In association with waves in which the largest follicle reached > or = 10 mm compared with 6-9 mm, there was greater depression in the FSH nadir, longer intervals from FSH peak to nadir, and longer intervals between adjacent FSH peaks and adjacent waves.

Animals↗