Search Results

You are looking at 1 - 4 of 4 items for

  • Author: F. Grasso x
Clear All Modify Search
Free access

M. A. Fortier, L. A. Guilbault and F. Grasso

Summary. Epithelial and stromal cells were isolated from endometrium of cyclic heifers by enzymic dispersion. These cells exhibited specific morphological and functional properties. Epithelial cells appeared cuboidal or columnal and showed contact inhibition as they reached confluence. Stromal cells were fibroblast-like and enlarged at the time of confluence after which they overgrew in multiple layers. The presence of specific receptors for PGE-2 and β-adrenergic catecholamines (isoproterenol) was estimated by activation of adenylate cyclase. Stromal cells had more adenylate cyclase activity (P < 0·01) than did epithelial cells before (basal) and after stimulation with guanosine triphosphate (GTP) and PGE-2. However, epithelial cells were much more responsive to isoproterenol (P < 0·01). Treatment of cultured cells with indomethacin to block PG synthesis increased the sensitivity and maximal response to PGE-2 in stromal (P < 0·01) but not in epithelial (P > 0·1) cells. The latter result suggested autologous desensitization of the PGE-2 response resulting from synthesis of PGs in cultured cells. Both cell types synthesized PGs in culture: PGF-2α was synthesized in greater quantity in epithelial than in stromal cells (P < 0·05) while stromal cells synthesized more PGE-2 than did epithelial cells (P < 0·001). Endometrial cells separated in this way should prove useful for study of their specific role in the processes of implantation and maternal recognition of pregnancy.

Keywords: cattle; endometrium; cell culture; adenylate cyclase; prostaglandins

Free access

L. A. Guilbault, G. L. Roy, F. Grasso and P. Matton

Summary. Luteolysis was induced by an injection of 500 μg cloprostenol (a prostaglandin (PG) analogue) in pregnant (P) Holstein heifers on Days 17 or 24 of gestation and in non-pregnant (NP) Holstein heifers on Day 17 of the oestrous cycle (oestrus = Day 0). Heifers in Groups P-17 (N = 8) and P-24 (N = 8) were inseminated twice whereas those in Group NP-17 (N = 8) were not inseminated. Immediately after PG injection, embryos were recovered by uterine flushing (400 ml) to confirm pregnancy in Groups P-17 and P-24. Uterine flushing with an equivalent volume of physiological saline was also done in Group NP-17. The interval from PG injection to oestrus and to the peak of luteinizing hormone (LH) as well as profile of increase in plasma oestradiol concentrations during that period did not differ (P > 0·1) among the groups. However, the proportion of heifers exhibiting abnormal luteal phases (primarily of short duration) during the oestrous cycle after PG injection was greater (P < 0·01) in Group P-24 than in Groups NP-17 +P-17 pooled (6/8 vs 3/16). These results suggest that the previous presence of a conceptus did not have any effect on the onset of oestrus, or on plasma concentrations of oestradiol and LH after PG-induced luteolysis on Days 17 or 24 of gestation. However, luteal function during the subsequent oestrous cycle was impaired if heifers were 24 days pregnant when luteolysis was induced.

Keywords: pregnancy; luteolysis; conceptus; ovary; cattle

Free access

J. G. Lussier, P. Matton, L. A. Guilbault, F. Grasso, R. J. Mapletoft and T. D. Carruthers

The effects of charcoal-extracted bovine follicular fluid (BFF) on endocrine profiles and follicular development in intact and hemiovariectomized postpubertal heifers were examined. Oestrus-synchronized heifers received Norgestomet implants on day 1 and 7 of treatment and were then injected s.c. with 11 ml saline (control) or 11 ml BFF twice a day for 12 days. The ovary bearing the largest follicle (OV1) was removed on day 7 and the remaining ovary (OV2) was collected on day 13. Follicles were observed by daily ultrasonography and were classified according to diameter (size 1: 2–3 mm; size 2: 4–6 mm; size 3: 7–10 mm; size 4: > 10 mm). After ovariectomy they were classified by diameter and histologically as normal or atretic. Intact control heifers had increased numbers of size 4 follicles on OV1 on days 6 and 7; no increase was observed in BFF-treated heifers (P < 0.03). In BFF-treated heifers, the mean basal LH concentration was higher (P < 0.05) and that of FSH was lower (P < 0.04) than in controls. FSH concentrations in BFF-treated heifers decreased from 0.60 ± 0.08 ng ml−1 (day 1) to 0.22 ± 0.05 ng ml−1 (day 7; P < 0.04). The concentration of oestradiol increased in control heifers, but not in BFF-treated heifers (P < 0.001). After hemicastration, OV2 underwent compensatory hypertrophy in control heifers, with an increase in the number of size 2, 3 and 4 follicles (P < 0.05), whereas BFF-treated heifers did not. Thus, total follicular volume was much lower in BFF-treated than in control heifers on day 13 (92.2 ± 15.4 versus 1393.8 ± 276.6 mm3; P < 0.0002). A transient increase in FSH (P < 0.006) and oestradiol (P < 0.01) concentrations occurred after hemiovariectomy in control but not in BFF-treated animals. In control heifers, an analysis of temporal relationships showed negative correlations between the volume of size 3 and size 4 follicles, and between FSH concentrations and the volume of size 3 and 4 follicles. A positive correlation was found between the mean diameter of the largest follicle and the concentration of oestradiol, whereas negative relationships were found between the concentrations of FSH and oestradiol, and between FSH and the mean diameter of the largest follicle. Analysis of the histological data showed that the number and volume of follicles > 8.57 mm was lower in the BFF-treated OV1 ovary, whereas no differences were found for follicles ≤ 8.57 mm. An absence of or a lower number and volume of follicles ≥ 3.68 mm was observed in BFF-treated OV2 compared with controls. We showed that: (i) compensatory hypertrophy in the remaining ovary occurs in heifers when the ovary bearing the largest follicle is removed; (ii) treatment with BFF decreases the FSH concentration and follicular development in intact postpubertal heifers, and prevents compensatory FSH increase and follicular growth after unilateral ovariectomy; and (iii) the histological population of follicles < 3.68 mm in diameter are not altered following 12 days of BFF treatment. Our results suggest that follicular development beyond 3–4 mm in cattle depends on an adequate circulating concentration of FSH.

Free access

L. A. Guilbault, F. Grasso, J. G. Lussier, P. Rouillier and P. Matton

Summary. Dairy heifers were superovulated in the presence (dominant group, N = 8) or absence (non-dominant group, N = 6) of a dominant follicle at the start of a superovulatory treatment on Days 7–12 of the oestrous cycle (Day 0 = oestrus). Daily ultrasonographic observations of ovaries (recorded on videotape) starting on Day 3 were used to assess the presence or absence of a dominant follicle (diameter > 9 mm, in a growing phase or at a stable diameter for < 4 days) and to monitor follicular development before and during treatment. The number of CL estimated by ultrasonography (7·1 ± 1·8 vs 13·5 ± 1·4) or by rectal palpation (6·9 ± 2·0 vs 16·3 ± 1·6) and mean progesterone concentrations (32·5 ± 19 vs 80·7 ± 16 ng/ml) after treatment were lower (P < 0·01) in the dominant than in the non-dominant group. Based on number of CL, two populations of heifers were identified in the dominant group, i.e. those that had a high (dominant–high, N = 4; > 7 CL) or a low (dominant–low, N = 4; < 7 CL) response to treatment. During treatment, the increases in number of follicles 7–10 mm and > 10 mm in diameter occurred sooner and were of higher magnitude in the non-dominant than in the dominant–high or dominant–low groups (P < 0·01). At the expected time of ovulation 6–7 days after the start of treatment, there was a rapid decrease in number of follicles 7–10 mm and > 10 mm in diameter in the dominant–high and non-dominant groups but not in the dominant–low group. Compared with the dominant–high group, differences in profiles of changes in diameter of largest (F1) and second largest (F2) follicles indicated that emergence of the dominant F1 follicle before treatment was delayed by 1–2 days in the dominant–low group. These results suggest that the presence of a dominant follicle before superovulation treatment may decrease the superovulatory response and/or alter the maturation process of growing follicles during treatment, especially when emergence of the dominant F1 follicle occurred within 3 days of the start of treatment.

Keywords: follicle; dominance; superovulation; ultrasonography; cattle