R. M. Roberts

Inhibition of uterine prostaglandin-F2α production by bovine conceptus secretory proteins☆

Abstract The effect of bovine conceptus secretory proteins (CSP) on uterine prostaglandin (PG)-F 2α production was evaluated in dairy cattle following injection of estradiol-17β. Intrauterine injections of dialyzed serum proteins (Control, n=5) or CSP (n=5) were administered from days 15 through 18 post-estrus. Following intrauterine treatments on day 18, all cows were injected with E 2 (3 mg) to stimulate uterine PGF 2α production. Plasma concentrations of progesterone (P 4 ) and 15-keto-13,14-dihydro-PGF 2α (PGFM) were determined by RIA. The PGFM responses following E 2 challenge were decreased (p 4 and cycle length responses are discussed. Data suggest that proteins secreted by the bovine conceptus suppress uterine PGF 2α production during pregnancy recognition in the cow.

Conceptus development, uterine response, blood gases and endocrine function of gilts exposed to increased ambient temperature during early pregnancy☆

Fifteen crossbred gilts were used to determine the influence of heat stress during Days 8 to 16 after onset of estrus on the development of conceptuses and uterine and endocrine functions. Ten gilts were bred 12 and 24 h after the onset of estrus (Day 0), and five gilts were nonbred controls. On Day 5, catheters were inserted into the uterine-ovarian vein (UV), saphenous artery (SA) and saphenous vein (SV) of each gilt. An electromagnetic blood flow transducer was implanted around the main uterine artery. Pregnant (n=5) and nonbred (n=5) control gilts were exposed to 21 +/- 1 degrees C, and pregnant heat-stressed gilts (n=5) were exposed to 37 +/- 1 degrees C for 12 h and 32 +/- 1 degrees C for 12 h daily during Days 8 through 16 after estrus. Treatment did not influence the partial pressure of oxygen (PO(2)) and of carbon dioxide (PCO(2)) in the UV, SA and SV blood. Uterine blood flow was not altered by heat stress. On Day 16, total wet weight of conceptuses was reduced in the gilts that were heat-stressed compared with conceptuses from control gilts. Incorporation of (3)H-leucine into macromolecules in vitro by conceptuses from the heat-stressed gilts was reduced compared with control gilts. Concentrations of 15-keto-13, 14-dihydro prostaglandin F(2alpha) (PGFM) in peripheral blood were greater than 1 ng/ml between Days 13 to 16 after estrus in 20% of the pregnant control gilts, 60% of the heat-stressed pregnant gilts, and 100% of the nonbred gilts. Concentrations of estradiol in the SA were affected by treatment. These results indicate that heat stress of gilts between Days 8 to 16 after estrus reduced the amount of conceptus tissue and altered concentrations of estradiol in the peripheral circulation, but uterine blood flow and PO(2) and PCO(2) in blood were not affected.

The role of ovine conceptus secretory proteins in the establishment of pregnancy

Sheep (Ovis aries) that are not pregnant have recurring estrous cycles of about 17 days’ duration during the breeding season, i.e., August through December to January. The first day of behavioral estrus is designated Day 0 with ovulation occurring about 30h after onset of estrus and the ovulatory surge of Luteinizing Hormone (LH). The estrous cycle is characterized by growth (Days 4–12) and then regression (luteolysis) of the corpus luteum (CL). Luteolysis begins on about Day 15 after onset of estrus. Prostaglandin F2-alpha (PGF), produced by the uterine endometrium, is the uterine luteolytic hormone in sheep (1). Beginning on Days 14 to 15 and continuing until the onset of the next period of estrus, PGF is released in a pulsatile manner. About 5 episodes of PGF release per 24h are required for luteolysis (2,3).

Interferon Tau (IFNT)

This article provides a short description of the discovery, mode of action, and characteristics of the interferon tau (IFNT), which is produced in abundance by the trophectoderm of peri-implantation conceptuses from the ruminant species for a restricted period during early pregnancy. These secreted molecules have an antiluteolytic action and help to ensure the continued production of progesterone by the ovary during early pregnancy. Conceivably, they also have other roles, including an ability to adjust the maternal endocrine and perhaps immune systems in the interests of conceptus survival. The emphasis in this article is on the antiluteolytic activity of the IFNT, how the IFNT is distinct from other type I IFNs, and how the IFNT might have evolved for a role in maternal recognition of pregnancy.