Expanded use of artificial insemination (AI) and/or adoption of emerging reproductive technologies for beef heifers and cows require precise methods of estrous-cycle control. New protocols for inducing and synchronizing a fertile estrus in replacement beef heifers and postpartum beef cows in which progestins are used provide new opportunities for beef producers to synchronize estrus and ovulati...

Prolactin (PRL) mRNA concentrations were assessed by nucleic acid hybridization assays in pituitaries of ewes representing the defined stages of the ovine estrous cycle. Concomitantly, pituitary and serum PRL concentrations were measured in these ewes using radioimmunoassays. It was observed that PRL serum, pituitary and mRNA concentrations tended to increase near the time of the gonadotropin p...

Production calendars for most swine farms are based upon the reproductive cycle of sows and gilts. The key reproductive event that determines when females begin their reproductive cycles is the onset of estrus. Estrus normally occurs spontaneously in gilts and mature females that are not pregnant or lactating. Once estrous cycles have begun, they normally occur every 18 to 21 days. From a produ...

The aim of this study is to determine whether sex-related differences exist in the biosynthetic activity of the mitral cells within the mitral layer of the AOB. Possible functional changes over the estrus cycle and the potential effects of castration and androgenization are assessed. Biosynthetic activity was measured using silver staining of the argyrophilic proteins associated with the nucleo...

Two experiments were conducted to determine the day on which the bovine embryo first affects luteal function. Experiment I was to determine the sole effect of flushing the uterine lumen and involved 12 non-inseminated heifers flushed 9, 14 and 16 days after estrus (4 animals per group). The same procedure was used to remove conceptuses from 15 pregnant heifers on days 9 (n = 4), 14 (n = 5) and ...

BACKGROUND AND PURPOSE Exogenous application of estrogens or progesterone ameliorates hypoxic/ischemic cell damage. This study investigates whether values of primary and induced hypoxic tolerance vary endogenously during the estrus cycle in female mice. METHODS Population spike amplitude (PSA) and NADH were measured during hypoxic hypoxia and recovery in hippocampal slices from untreated cont...

An experiment was conducted to determine whether short estrous cycles following abortion of heifers between 70 and 75 d of gestation are due to factors associated with the previous presence of a conceptus or long-term exposure of the uterus and(or) ovaries to a progestogen. Fifty crossbred heifers were randomly allotted at estrus (d 0) to five groups: control (n = 10), pregnant (Preg.; n = 14),...

Apoptosis is associated with the regression of the corpus luteum (CL) in many species. Since caspases play a central role in apoptosis, we studied several initiators (-2, -8, and -9) and the main effector (-3) caspase in the CL during the estrous cycle of the rat. Two different populations of CL (old and new) were identified on ovaries at estrus and diestrus II (DII). Diminished (P < 0.05) lute...

T he estrus cycle of rats and hamsters is regulated by the daily light-dar k cycle . The suprachiasmatic nucleus of the hypothalamus appears t o generate a rhythm with a frequency of approximately one cycle in 24 hours . This rhythm is exactly synchronized with the external light-dark cycle b y impulses received from the eyes through a retinohypothalamic projection . Lesions that destroy the su...

The prolactin secretory activity of anterior pituitary during estrous cycle was determined from 14C-leucine incorporation in vitro into the hormone, using IVCS mice which showed regular 4-day-cycles. Prolactin in the anterior pituitary and in the incubation medium was fractionated by disc electrophoresis on polyacrylamide gel. The synthesis and release of prolactin were significantly lower at e...