Michael T. Zavy

Effect of exogenous progesterone on prostaglandin F2α release and the interestrous interval in the bovine

The present study was developed to determine if administration of progesterone, early in the estrous cycle of the cow, stimulated an advanced pulsatile release of PGF2 alpha from the uterine endometrium resulting in a decreased interestrous interval. Twenty-three cyclic beef cows were randomly assigned to receive either sesame oil or progesterone (100 mg) on Day 1, 2, 3 and 4 of the estrous cycle. Peripheral plasma concentrations of progesterone and the metabolite of prostaglandin F2 alpha, 15-keto-13,14-dihydro-prostaglandin F2 alpha (PGFM) were measured by radioimmunoassay. Administration of exogenous progesterone increased peripheral plasma concentration of progesterone in treated (3.67 ng/ml) compared to control (1.28 ng/ml) cows from Day 2 through 5 of the estrous cycle. Progesterone administration shortened the interestrous interval (16.7 d) compared to controls (21.6 d). The shortened interestrous intervals in treated cows resulted from an earlier decline in peripheral plasma progesterone. Decline of peripheral plasma progesterone concentrations is coincident with an increased pulsatile release of PGFM in both progesterone treated and control cows. Results indicate that administration of exogenous progesterone stimulates an earlier maturation of endometrial development, causing an advanced release of PGF2 alpha which shortens the interestrous interval of the cow.

Characterization of the uterine environment during early conceptus expansion in the bovine

Abstract Fifty-three Angus and Hereford beef cows were utilized to investigate the effect of the conceptus on uterine environment during the period of pregnancy recognition. Blood samples were collected on Days 10, 12, 14, 16 and 18. Cows were randomly assigned to be either mated on the subsequent oestrus or serve as cyclic controls. Blood samples were then collected daily from Day 10 until slaughter on Day 15, 16 or 17 from the initiation of oestrus. Uteri were flushed with physiological saline and flushings analyzed for quantitative and qualitative protein changes, calcium, oestradiol-17β and prostaglandin F content. Endometrial explants of caruncular and intercaruncular tissue, and conceptus tissue recovered from pregnant cows were cultured with [3H]-leucine to determine quantitative and qualitative polypeptide synthesis and release. Plasma progesterone concentrations were similar between pregnant and cyclic cows from Day 10 through 17. Only the uterine content of prostaglandin F significantly increased in the ipsilateral horn of pregnant cows on Days 16 and 17. This increase in prostaglandin content was related to the increase in conceptus length from 25 to 40–80 mm. Conceptus production of bovine trophoblastic protein-1 was also first clearly detectable in fluorographs of medium from conceptuses measuring 25 mm. The complexity of the polypeptides present in the medium increased with conceptus development. Polypeptide synthesis by the endometrium was similar between tissues and days; however, production of two groups of low molecular weight basic polypeptides continued to be intensified on fluorographs from the pregnant horn on Day 17 compared to cyclic cows.

Maternal recognition of pregnancy

Abstract Maternal recognition of pregnancy in domestic farm animals evolved as a physiological mechanism by which the conceptus inhibits luteolysis through alteration in endometrial prostaglandin F2α (PGF2α) synthesis or movement during the establishment of early pregnancy. Luteolysis in ruminants, swine and horses results from the pulsatile release of PGF2α from the endometrium during late diestrous. Current evidence indicates that the timing of luteolysis is controlled by down regulation of nuclear progesterone receptors within the uterine epithelium during mid-luteal phase of the estrous cycle. Loss of progesterone regulation on uterine epithelium may permit the synthesis of oxytocin receptors necessary for establishing luteolytic pulses of PGF2α as proposed for the ewe and cow of allow synthesis of PGF2α essential for regressing the corpus luteum. Mechanism(s) by which the conceptus of each species gains control over the uterine epithelium to protect the corpora lutea from luteolysis, most likely evolved through pathways which were best suited to meet the requirements of placental growth, development and attachment. Ruminants have adapted a specific trophoblast Type I interferon (IFN) to inhibit prostaglandin synthesis and possibly stabilize the uterine environment while trophoblast expansion and attachment occur. Although the pig conceptus secretes a trophobiast IFN, its endometrium is refractory to IFN stimulation of 2′, 5′-oligoadenylate synthetase as occurs in ruminants. Estrogen secretion by the porcine conceptus alters endometrial PGF2α movement and allows estrogen stimulated endometrial growth and secretion necessary for establishment of pregnancy in this polytocous species. The earlier evolution of the horse, which retains a spherical chorio-vitelline placenta during maternal recognition of pregnancy, developed a method of intrauterinc conceptus migration to inhibit luteolysis through secretion of an unknown prostaglandin synthetase inhibitor.

Effect of heat stress on conceptus and uterine secretion in the bovine

This study examined the effects of heat stress on conceptus secretion of bovine trophoblastic proteins (bTP) and the uterine secretory environment on Day 17 of pregnancy. After mating to fertile bulls, cows were placed in an environmental chamber at 21 degrees C, 45% RH on Day 7 and were assigned to one of the following treatments on Day 8: Control (21 degrees C, 45% RH), Treatment 1 (37 degrees C, 30% RH) and Treatment 2 (37 degrees C, 40% RH). Cows were slaughtered on Day 17 and each uterine horn was flushed separately with physiological saline to recover the conceptus and uterine contents. The wet weight of the conceptus was recorded and uterine flushings were analyzed for quantitative and qualitative protein changes, prostaglandin F and calcium concentrations. Conceptus tissue was cultured in vitro with 100 muCi of [(3)H]-leucine and the polypeptides released into the medium were analyzed by 2D-PAGE followed by fluorography. Heat stress increased rectal temperature of cows and reduced conceptus wet weight. Uterine content of protein and calcium were increased in the uterine horn ipsilateral to the CL of heat-stressed cows. Although uterine protein increased in heat-stressed cows, no qualitative difference was observed in the polypeptides present in the uterine lumen. Conceptus synthesis and release of bTP were enhanced in treated cows. These responses indicate that heat stress between Days 8 to 17 of pregnancy altered the uterine environment as well as growth and secretory activity of the conceptus.

Concentrations of insulin-like growth factor-I in serum of sheep with different ovulation rates: Changes during the estrous cycle

Abstract To determine if concentrations of IGF-I in serum are associated with the ovulation rate or if IGF-I concentrations change during an estrous cycle, blood was collected from ewes of three genotypes in two experiments. In Experiment 1, blood was collected once during the mid-luteal phase of an estrous cycle in nulliparous ewes. In Experiment 2, blood was collected every other day from Day 1 to 19 postestrus in primiparous ewes. Three genotypes of ewes were used in both experiments: Dorset × Rambouillet, Finn × Rambouillet and Booroola Merino × Rambouillet. Ovulation rates in Experiment 1 were 1.35, 1.88 and 2.50 for Dorset × Rambouillet (n=17), Finn × Rambouillet (n=49) and Booroola Merino × Rambouillet (n=28) ewes, respectively. IGF-I concentrations in serum were greater (P

Estrogen-induced pseudopregnancy in gilts: Its use in estrus synchronization and subsequent influence on litter response

The effectiveness of using estrogen-induced pseudopregnancy followed by PGF(2alpha) (Lutalyse) treatment to synchronize estrus in gilts and the subsequent effect of pseudopregnancy on litter parameters was examined in two experiments. Experiment 1 consisted of a control (n = 49) group and a pseudopregnant (n = 49) group. Pseudopregnant gilts received PGF(2alpha) between Days 25 and 38 and were bred at the ensuing estrus. Ninety-two percent of the gilts responded to PGF(2alpha) and exhibited estrus in 4.9 +/- 0.2 (Least Square Mean +/- SEM) days. Duration of estrus was longer in pseudopregnant compared to control gilts (2.8 vs 1.7 d, P<0.001). Experiment 2 consisted of a control (n = 24) group and a pseudopregnant (n = 24) group. All pseudopregnant gilts received PGF(2alpha) on Day 38 and 79% responded with a mean onset of estrus at 5.2 +/- 0.2 d. As in Experiment 1, duration of estrus was longer in gilts from the pseudopregnant group (2.2 vs 1.7 d, P<0.005). The percentage of farrowing was similar for both groups in both experiments, and no differences existed in the number of pigs born and those alive at 21 d post partum. Litters from gilts in the pseudopregnant groups were heavier at birth than those in the control group (Experiment 1, 17.21 vs 15.25 kg, P<0.01; Experiment 2, 15.31 vs 13.55 kg, P<0.02) and at 21 d (Experiment 1, 60.81 vs 56.79 kg, P<0.01; Experiment 2, 51.89 vs 46.96 kg, P<0.02). Survival rate at 21 d was higher in offspring from pseudopregnant gilts in both experiments (Experiment 1, 85.3% vs 78.2%, Experiment 2, 91.4% vs 81.2%).

Estrogen administration on days 9 and 10 of gestation does not adversely affect ultrastructural changes of porcine uterine luminal epithelium

Abstract Previously we demonstrated that conceptus mortality in swine is associated with alterations in the uterine epithelial glycocalyx after administration of estradiol valerate (E) on Days 9 and 10 of gestation. The objective of the present study was to examine ultrastructural characteristics of the uterine epithelium following E administration. Gilts received either 5.0 mg (i.m.) of estradiol valerate (n=6) or vehicle (control; n=6) on Days 9 and 10 of gestation. Endometrial tissue was processed for transmission electron microscopy on Days 12, 14, 16, and 18 of pregnancy. On all days studied, surface epithelial cells lining the uterine lumen were characterized by the presence of vesicular nuclei, prominent Golgi complexes, and abundant mitochondria. Glycogen deposition was prominent in both control and E-treated gilts; however, glycogen accumulation was greater in E-treated gilts than in control gilts on Day 12 of pregnancy. In control gilts, clear vesicles were more prominent in the apical aspect of uterine epithelial cells compared with the basal aspect on Day 12 of gestation. Dense bodies were more numerous in the basal region compared with the apical region of the uterine epithelium in control and E-treated gilts. Volume density (VD) of mitochondria was greater on Days 16 and 18 than on Day 12 of gestation in control and E-treated gilts. The VD values of rough endoplasmic reticulum were not different between control and E-treated gilts on Days 12–18 of gestation. The VD value of smooth endoplasmic reticulum was greater in control gilts than in E-treated gilts only on Day 12 of gestation. These ultrastructural changes indicated an earlier increase in synthetic and secretory activity in E-treated gilts compared with control gilts and suggest that embryonic death, previously demonstrated to be associated with alterations in the uterine epithelial glycocalyx, did not result from any dramatic ultrastructural changes in the uterine epithelium.