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  • Author: K. M. Battye x
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A. W. N. Cameron, K. M. Battye and A. O. Trounson

Summary. The timing of ovulation in feral goats treated with 1200 i.u. PMSG ± 50 μg GnRH was studied by repeated laparoscopy. Experiment 1 established that superovulation began as early as 30 h after withdrawal of progestagen-impregnated sponges and was not completed at 54 h if goats received PMSG alone. GnRH synchronized ovulation, leading to 91% of ovulations appearing between 36 and 48 h after sponges were withdrawn. Experiment 2 established that superovulation continued until up to 77 h in goats treated only with PMSG. The stress of repeated laparoscopy appeared to delay or abolish ovulation in some females. The mean (±s.e.) ovulation rate was greater in goats treated with GnRH (12·7 ± 1·3) than in those that received PMSG only (9·7 ± 1·1; P < 0·05). Out of 47 of the females in Exp. 1, 43 had one or more corpora lutea at laparoscopy 24 h after withdrawal of progestagen. These early corpora lutea were associated with an increased concentration of plasma progesterone during the periovulatory period. Experiment 3 provided evidence that these corpora lutea arose before the withdrawal of progestagen-impregnated sponges.

Keywords: goats; PMSG; ovulation; laparoscopy; progesterone

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K. M. Battye, R. J. Fairclough, A. W. N. Cameron and A. O. Trounson

Summary. Feral does of various ages were treated with intravaginal progestagen sponges for 16 days to synchronize oestrus. On Day 2 before sponge removal the goats were given 1200 i.u. PMSG to induce superovulation: 6 of the goats were also injected every 12 h with flunixin meglumine, a prostaglandin (PG) synthetase inhibitor, from Day 3 to 7 of the synchronized oestrous cycle. Jugular blood samples were collected from all females into heparinized syringes at daily intervals over the 2 days before sponge removal, twice daily for the next 2 days, then at hourly intervals from 09:00 to 17:00 h for 2 days and then twice daily for a further 2 days, for measurement of plasma progesterone and the PGF metabolite 13,14-dihydro-15-keto-PGF (PGFM) by radioimmunoassay. Intermittent surges in plasma PGFM concentrations were observed in hourly samples collected from 4/4 untreated females but in only 2/6 of the inhibitor-treated females(P < 0·05), and the peak plasma PGFM concentrations were reduced in these 2 inhibitor-treated goats compared with the control goats. The corpora lutea (CL) of the inhibitor-treated females appeared to be functional as indicated by the plasma progesterone profile and endoscopic examination of CL. In the control females, however, there was evidence of premature regression of CL. These results suggest that the premature release of PGF-2α may be the cause of premature regression of CL in nanny goats induced to superovulate.

Keywords: corpus luteum; goat; prostaglandin; superovulation; progesterone

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K. M. Battye, A. J. Ammit, C. O'Neill and G. Evans

Summary. Embryos were collected from superovulated ewes on Day 2 (2–8 cell), Day 4 (8–16 cell) and Day 6 (morula/early blastocyst). Two embryos were cultured in 1 ml of one of four media: (i) Ham's F10 + 4mg bovine serum albumin (BSA)/ml, (ii) synthetic oviduct fluid medium + 20% human serum, (iii) Quinn's human tubal fluid medium (HTF) + 3 mg BSA/ml or (iv) HTF + 10% acid-treated fetal calf serum for 24 h. They were transferred to fresh media of the same type and their further development was monitored. A quantitative bioassay and radioimmunoassay was used to measure the concentration of platelet-activating factor (PAF, 1-o-alkyl-2-acetyl-snglyceryl-3-phosphocholine) produced. Following extraction and partial purification, 21/95 (22·1%) of the embryo-conditioned media samples had PAF concentrations greater than that measured in corresponding control media. This was designated as embryo-derived PAF and the corresponding cultures were termed 'PAF-positive'. PAF was produced by embryos at all three developmental stages examined and in each of the four media used, and the average amount of PAF produced was 60·9 ± 9·8 pmol/embryo/24 h. However, neither the developmental stage of the embryo, nor the type of media affected the proportion of PAF-positive cultures nor the amount of PAF produced during culture. Thus, it is demonstrated for the first time that early ovine embryos can secrete PAF in vitro, and that there is considerable variability in their capacity for PAF secretion.

Keywords: platelet-activating factor; embryo; in vitro; sheep

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K. M. Battye, T. J. Parkinson, L. J. Jenner, G. Evans, C. O'Neill and G. E. Lamming

In sheep, the presence of an embryo in utero on the 12th to 13th day after oestrus prevents luteolysis. These studies investigated whether platelet-activating factor (PAF) could exert an antiluteolytic function, either alone or in combination with interferon. The intrauterine administration of 250 μg PAF per horn per day, administered through indwelling cannulae into the uterus as injections twice a day (n = 12) or by continuous infusion (n = 4) failed to extend luteal function compared with controls (n = 8). When indwelling cannulae were used to administer (i) 125 μg PAF per uterine horn, as a bolus infusion twice a day (n = 5), (ii) continuous infusion of 500 μg bovine recombinant α1-interferon each day (brIFN, n = 5), (iii) 125 μg PAF per horn twice a day, plus 500 μg brIFN per day (n = 8), or (iv) vehicle (n = 5), the luteal phase was significantly longer in co-infused (iii) than in control (iv) animals. These findings indicate that pharmacological doses of PAF may act synergistically with interferons to prevent luteolysis.