Dystocia in relationship to size and shape of pelvic opening in Holstein heifers

One hundred twenty-seven Holstein heifers were measured prior to calving to obtain 1) heart girth and 2) the horizontal and vertical pelvic measurement, from which pelvic area was calculated. Dystocia scores were assigned at birth, and the heart girth of the calf and sex of the calf were recorded. There was no difference in the level of dystocia noted in heifers with different pelvic sizes. The major cause of dystocia was size of the calf. A greater proportion of the larger calves was bulls (29% vs 20%). The shape of the pelvic opening may affect dystocia through increased calf size.

Ninety-three pregnant heifers were measured on two or more occasions at approximately 60-day intervals to obtain 1) the heart girth and 2) the horizontal and vertical measurements, from which pelvic area was calculated. These measurements were used to determine heifer growth. The heifer's heart girth grew at a rate of 0.066 cm per day of gestation with a corresponding increase in pelvic area of 2.25 cm² per cm of heart girth, or 0.312 cm per day of gestation.     

Effect of milk production on the incidence of double ovulation in dairy cows

To determine the effect of parity and milk production on the incidence of double ovulation, the synchronization of ovulation, using GnRH and prostaglandin F2 alpha followed by timed AI (Ovsynch), was initiated at a random stage of the estrous cycle in lactating Holstein cows (n = 237). Ovulatory response at 48 h after the second GnRH injection and conception rate at 28 d post AI were determined by transrectal ultrasonography. Ovulation was synchronized in 84% of cows receiving the Ovsynch protocol. Of the synchronized cows, 14.1% exhibited a double ovulation and 47.6% conceived. Conception rate tended to be greater (P = 0.08) for cows exhibiting double (64.0%) rather than single ovulation (45.2%). To determine the effect of milk production on the incidence of double ovulation, cows were classified into low (< or = 40 kg/d) or high (> 40 kg/d) milk production groups based on the average milk production of 40.5 +/- 0.8 kg/d collected 2 d before AI. Although the incidence of double ovulation tended to increase linearly (P = 0.09) with increasing parity, the incidence of double ovulation was nearly 3-fold greater (P < 0.05) for cows in the high (20.2%) than the low (6.9%) milk production group. Furthermore, the increase in the incidence of double ovulation with parity apparently occurred because, within a parity group, the proportion of cows with high milk production was greater for the older cows. Twinning rate of cows that calved (n = 58) was 5.2%. In a secondary objective, cows were retrospectively classified as cystic or normal based on ultrasonographic ovarian morphology at the time of the second GnRH injection. Incidence of ovarian cysts was 11%, and the synchronization and conception rate of cows classified as cystic was 73.1 and 36.8%, respectively, which did not differ from that of normal cows. We conclude that milk production is the primary factor affecting the incidence of double ovulation in lactating dairy cows and may explain the effect of parity on twinning rate. In addition, Ovsynch appears to be an effective method for establishing pregnancy in lactating dairy cows with ovarian cysts.     

Lack of complete regression of the Day 5 corpus luteum after one or two doses of PGF2α in nonlactating Holstein cows

The early corpus luteum (CL) (before Day 6) does not regress after a single PGF_2α treatment. We hypothesized that increasing PGF_2α dose or number of treatments would allow regression of the early CL (Day 5). Nonlactating Holstein cows (N = 22) were synchronized using the Ovsynch protocol. On Day 5 (Day 0 = second GnRH treatment), cows were assigned to: (1) control (N = 5): no further treatment; (2) 1PGF (N = 6): one dose of 25 mg PGF_2α; (3) 2PGF (N = 5): two doses of 25 mg PGF_2α (50 mg) given 8 hours apart (second PGF_2α on Day 5 at the same time as the other PGF_2α treatments); (4) DPGF (N = 6): double dose of 25 mg PGF_2α (50 mg) given on Day 5. Blood samples were collected to monitor progesterone (P4) profiles in two periods. In the first period (0 to 24 hours), there were effects of treatment (P = 0.01), time (P < 0.01), and an interaction of treatment and time (P = 0.02). Group 1PGF versus control was different only at 12 hours (P = 0.02). Cows treated with DPGF were different than control at 4 hours (P = 0.04), 12 hours (P < 0.01), and 24 hours (P < 0.01). Only cows treated with 2PGF had lower P4 than control during the entire period and low P4 (0.37 ± 0.17 ng/mL) at 24 hours, usually indicative of luteolysis. In the second period (Day 5 to 15 of the cycle), there were effects of treatment (P < 0.01), time (P < 0.01), and interaction of treatment and time (P = 0.002). Group 1PGF was not different than control from Day 5 to 13 and P4 was greater than control on Day 14 (P = 0.01) and 15 (P < 0.01). Circulating P4 in DPGF cows was lower than control from Day 7 (P = 0.05) through 12 (P < 0.01). Likewise, there were differences between control and 2PGF from Day 7 to 13, but not on Day 14 and 15. On Day 15, all PGF_2α-treated groups had circulating P4 consistent with an active CL. Ultrasound evaluation confirmed that no CL from any group completely regressed during the experiment and no new ovulations occurred to account for functional CL later in cycle. In summary, a double dose of PGF_2α (twice on Day 5 or 8 hours apart) can dramatically decrease P4, consistent with classical definitions of luteolysis; however, these CL recover and become fully functional. Thus, the Day 5 CL of mature Holstein cows do not regress even to two doses of PGF_2α.     

Distinct regulation by steroids of messenger RNAs for FSHR and CYP19A1 in bovine granulosa cells

Steroidal regulation of gene expression in follicular cells is not completely defined. Granulosa cells from 5 mm bovine follicles were cultured and treated and steady-state mRNA levels determined for FSHR (follicle-stimulating hormone receptor) and CYP19A1 (aromatase). Cells were treated for 5 days with (0.1-300 ng/ml) 17beta-estradiol (E2), testosterone (T), or 5alpha-dihydrotestosterone (DHT). FSHR mRNA was increased by T and DHT but not E2. In contrast, CYP19A1 mRNA was induced by all doses of E2 but only high doses of T and DHT. Similarly, varying treatment duration (1-5 days) showed that FSHR was increased by T and DHT and CYP19A1 mRNA increased by E2 and T at all times. Synergism between steroid hormones and FSH or forskolin was also evaluated. FSH or E2 did not alter FSHR mRNA and did not enhance DHT stimulation of FSHR mRNA. In contrast, DHT alone had no effect on CYP19A1 mRNA but synergized with FSH plus E2 to increase CYP19A1 mRNA, probably due to induction of FSHR by DHT. Effects of E2 and T on CYP19A1 were blocked by ICI 182,780, indicating mediation by estrogen receptors. However, the specific androgen receptor antagonist bicalutamide did not block E2 or T effects on CYP19A1 but did block T and DHT stimulation of FSHR. Thus, FSHR is specifically regulated through androgen receptor, whereas CYP19A1 is regulated by multiple pathways, including estrogen receptors and cAMP/protein kinase A induced by FSHR activation in granulosa cells. These inter- and intracellular regulatory mechanisms may be critical for normal follicle growth and dominant follicle selection.     

Synchronization of emergence of follicular waves in cattle

In Experiment 1, heifers were randomly allocated to a control group (saline, im; n = 6) or a GnRH group (100 microg, im; n = 6). Treatment was given approximately 32 h before ovulation. The GnRH treatment shortened (P < 0.001) the time from treatment to emergence of Wave 1 and to the peak concentration of FSH associated with emergence. Administration of GnRH synchronized (less variability, P < 0.01) the time from treatment to ovulation but did not significantly synchronize follicular wave emergence, and tended (P < 0.06) to synchronize the time to the peak concentration of FSH. The mean number of follicles >5 mm per wave was higher (P < 0.01) in the GnRH group (10.7 +/- 1.3) than in the control group (5.7 +/- 0.8). In Experiment 2, either Folltropin (a porcine pituitary extract) was given or the dominant follicle of Wave 1 was aspirated 5 d after ovulation and the following wave (Wave 2) studied. Folltropin and/or aspiration shortened (<0.05) the time from treatment to emergence of Wave 2 and to the peak concentration of FSH associated with wave emergence, and all treatments synchronized (P < 0.01) wave emergence. Retrospective study indicated that the future dominant follicle could have been collected for experimental purposes with a 100% success rate if the following criteria had been used: 1) diameter of largest follicle 10 mm (largest follicle taken), 8 mm (2 largest follicles taken), or 7 mm (3 largest follicles taken); 2) diameter difference between the 2 largest follicles of 4 mm (largest follicle taken), 3 mm (2 largest follicles taken), or 2 mm (3 largest follicles taken); 3) 2 days after wave emergence (2 or 3 largest follicles taken); or 4) 5 days (largest follicle taken), 4 days (2 largest follicles taken), or 3 days (3 largest follicles taken) after treatment (Folltropin or dominant-follicle aspiration).     

BRCT domains: Easy as one,two, three

BRCA1 C-terminal (BRCT) domains are integral signaling modules in the DNA damage response (DDR). Aside from their established roles as phospho-peptide binding modules, BRCT domains have been implicated in phosphorylation-independent protein interactions, DNA binding and poly(ADP-ribose) (PAR) binding. These numerous functions can be attributed to the diversity in BRCT domain structure and architecture, where domains can exist as isolated single domains or assemble into higher order homo- or hetero-domain complexes. In this review, we incorporate recent structural and biochemical studies to demonstrate how structural features allow single and tandem BRCT domains to attain a high degree of functional diversity.Key words: BRCT domain, DNA repair, phosphorylation, phospho-peptide interaction, protein interaction, DNA binding, DNA damage response     

Acute effects of prostaglandin F(2alpha) on systemic oxytocin and progesterone concentrations during the mid- or late-luteal phase in mares

The acute effects of prostaglandin F(2alpha) (PGF) on circulating oxytocin and progesterone concentrations were characterized in mares during the mid- or late-luteal phase. Pony mares were randomly assigned to the following experimental groups based on treatment with PGF (2.5mg) or saline on Day 8 or Day 13 (Day 0=ovulation): PGF-8, PGF-13, saline-8, or saline-13 (n=7/group). Mares were fitted with indwelling, jugular vein catheters and two blood samples (-5 and 0 min) were collected prior to treatment. Treatments were administered into the jugular vein (0 min) and blood collection continued thereafter at 1 min intervals until 5 min and then at 5 min intervals until 60 min. Based on the combined data of -5 and 0 min samples, mares on Day 8 had greater (P<0.05) oxytocin concentrations than mares on Day 13. On Day 8, PGF treatment resulted in a biphasic pattern of oxytocin release. Oxytocin concentrations increased (P<0.05) 1 min after PGF treatment, decreased (P<0.05) from 1 to 10 min, and increased (P<0.05) from 10 to 30 min. Oxytocin concentrations were greater (P<0.05) from 1 to 3 min in PGF-treated than saline-treated mares and at most sample times from 15 to 60 min. On Day 13, oxytocin concentrations were greater (P<0.05) in PGF-treated than in saline-treated mares for most sample times. Mares treated with PGF on Day 8 had greater (P<0.05) oxytocin concentrations at 25, 30, and 40 min than mares on Day 13. Progesterone concentrations on Day 8 also increased by 1 min after PGF, decreased toward basal concentrations by 2-3 min, and then increased to a maximum 10 min after treatment. Subsequently, circulating progesterone decreased (P<0.05) below pretreatment concentrations by 40-50 min after PGF. In conclusion, treatment with PGF resulted in an immediate and biphasic increase in progesterone concentrations prior to the expected decrease. Treatment of mares with PGF on Day 8 resulted in an overall greater increase in systemic oxytocin concentrations compared to treatment on Day 13, and the increase on Day 8 was biphasic.     

Follicle deviation and intrafollicular and systemic estradiol concentrations in mares.

By definition, follicle deviation begins on the day the two largest follicles of a wave begin to differ in growth rates. The relationships between follicle deviation and intrafollicular and systemic estradiol concentrations were studied in ponies, using a two-follicle model in which all but the two largest follicles were ablated. A 20-microliter sample of follicular fluid was obtained from each of the two follicles by transvaginal ultrasonography. In experiment 1, the two follicles were sampled when the larger follicle reached 15 mm. No differences (p > 0.05) in post-sampling follicle characteristics were found between control (n = 6) and sampled (n = 8) groups except that the growth rate was slower (p < 0.01) in the larger follicle between the day of sampling and the next day (0.7 +/- 0.7 mm per day) than in the controls (3.3 +/- 0.3 mm per day). The growth rates between 2 and 5 days after sampling were not different between groups. Follicular fluid estradiol-17beta concentrations were higher (p < 0.007) in the larger follicle (460 +/- 67 ng/ml; diameter, 16.4 +/- 0.4 mm) than in the smaller follicle (322 +/- 50 ng/ml; diameter, 14.6 +/- 0.6 mm). In experiment 2, the pair of follicles was sampled when the larger follicle reached 15 mm, 20 mm, or 25 mm (n = 5 per group). There were no significant differences among the three groups for day of deviation and diameters of larger and smaller follicles at deviation. The difference in diameter between the larger and smaller follicles was similar for the 15-mm (2.2 +/- 0.9 mm) and 20-mm (3.1 +/- 1.0 mm) groups, but the difference between follicles for the 25-mm group (7.9 +/- 1.2 mm) was greater (p < 0.004) than for the other two groups. In contrast, the differences in estradiol concentrations between the larger and smaller follicles increased (p < 0.0001) progressively for the 15-mm (13.0 +/- 86.8 ng/ml), 20-mm (722.0 +/- 173.8 ng/ml), and 25-mm (1873.5 +/- 310.3 ng/ml) groups. The first significant (p < 0.007) increase in systemic estradiol occurred between the day before and the day of the beginning of deviation. Detection of an increased difference in estradiol concentrations between the two follicles before the detection of a change in differences in diameter suggests, on a temporal basis, that estradiol is a candidate for involvement in the mechanism that leads to follicle-diameter deviation in mares.     

Actions of prostaglandin F2alpha and prolactin on intercellular adhesion molecule-1 expression and monocyte/macrophage accumulation in the rat corpus luteum

Expression of intercellular adhesion molecule-1 (ICAM-1) and the accumulation of monocytes/macrophages are inflammatory events that occur during PRL (PRL)-induced regression of the rat corpus luteum. Here we have compared the ability of prostaglandin F2alpha (PGF) and PRL to induce, in rat corpora lutea, inflammatory events thought to perpetuate luteal regression. Immature rats were ovulated with eCG-hCG and then hypophysectomized (Day 0), which resulted in a single cohort of persistent, functional corpora lutea. On Days 9-11, the rats received twice daily injections of saline, PGF (Lutalyse, 250 microg/injection), or PRL (312 microg/injection) to induce luteal regression. Surprisingly, luteal weight and plasma progestin concentrations (progesterone and 20alpha-dihydroprogesterone) did not differ between PGF-treated rats and controls; whereas both luteal weight and plasma progestins declined significantly in PRL-treated rats. Furthermore, corpora lutea of PGF-treated rats and controls contained relatively minimal ICAM-1 staining and few monocytes/macrophages. In contrast, but as expected, corpora lutea of PRL-treated rats stained intensely for ICAM-1 and contained numerous monocytes/macrophages. In an additional experiment, there was no indication that luteal prostaglandin F2alpha receptor mRNA diminished as a result of hypophysectomy. These findings suggest that prolactin, not PGF, induces the inflammatory events that accompany regression of the rat corpus luteum.