Heifers in group Da 17 were ovariectomized 1 day after detection of proestrus; proestrus was defined as the day when any 3 of 4 estrus-like characteristics (i.e., high uterine tone, edematous echotexture, intrauterine fluid collection, mucous discharge) were detected. Days of ovariectomy were selected on the basis of previous studies to represent the growing (D3W1), early-static (D6W1), late-static (D1W2), and regressing (Da 17) phases of the dominant follicle of wave 1 (Fig. 1). The design of the experiment also allowed collection of subordinate follicles of wave 1 and the ovulatory wave; preselection follicles of wave 2; preovulatory dominant follicles; and corpora lutea during metestrus (D3W1, Day 3 after ovulation), early dies-trus (D6W1; Day 6 after ovulation), mid-diestrus (D1W2; mean Day 11 after ovulation), and proestrus (Da 17, mean Day 18 after ovulation; Fig. 1). Regressed corpora lutea of the previous estrous cycle were also collected on D3W1 (n = 3) and D6W1 (n = 2). proventil inhaler
Ovariectomies and Tissue Processing
Heifers were ovariectomized via colpotomy in the standing position, under caudal epidural anesthesia using 2% w:v lidocaine HCl with 0.001% w:v epinephrine. Clen-buterol (6 mg/10 kg BW i.v., Ventipulmin; Boehringer In-gelheim Ltd., ON, Canada) was given 10 min before col-potomy to induce relaxation of the uterine and broad ligament musculature. After manual compression of the mesovarium with a lidocaine-soaked gauze, both ovaries were removed through a single incision in the dorsolateral aspect of the vaginal fornix using a chain ecraseur.