Search Results

You are looking at 1 - 10 of 34 items for

  • Author: F. W. Bazer x
  • All content x
Clear All Modify Search
Free access

J. L. Vallet and F. W. Bazer

Summary. In Exp. 1, endometrium was collected from Day-15 cyclic ewes and effects of oTP-1, oxytocin and oTP-1 + oxytocin, in various temporal relationships, on phosphatidylinositol (PI) turnover were determined. Co-treatment of endometrium with oTP-1 and oxytocin inhibited stimulatory effects of oxytocin, while treatment with oTP-1 before and during oxytocin administration had no effect. Turnover of PI was unaffected by oTP-1 alone. In Exp. 2, ovariectomized ewes were treated with progesterone (50 mg/day) for 10 days and then oestrogen (100 μg/day) for 2 days and endometrium was collected. Oxytocin stimulated PI turnover in endometrium, but oTP-1 had no effect alone or in combination with oxytocin. In Exp. 3, ovariectomized ewes were treated with corn oil (1 ml/day), oestrogen (50 μg/day), progesterone (50 mg/day) or progesterone + oestrogen for 10 days and endometrium was collected. Oxytocin stimulated PI turnover only in ewes that received progesterone. oTP-1 alone had no effect on PI turnover, while co-treatment of endometrium with oxytocin and oTP-1 stimulated PI turnover in ewes treated with progesterone, but not progesterone and oestrogen. Pretreatment of endometrium with oTP-1 stimulated PI turnover when ewes were treated with progesterone or progesterone + oestrogen. Pretreatment of endometrium with oxytocin and then treatment with oTP-1 inhibited PI turnover compared to treatment with oxytocin alone. In Exp. 4, ovariectomized ewes were treated as in Exp. 2. Catheters were placed into the uterine horns and ewes received oTP-1 into one horn and serum into the other twice daily on Days 10–12 of steroid treatment. Endometrium collected on Day 13 was used to measure PI turnover and received either no treatment or oxytocin. Oxytocin stimulated PI turnover in endometrium of these ewes and in-vivo treatment of the ewes with oTP-1 had no effect on PI turnover. These results indicate that antiluteolytic effects of oTP-1 are not mediated by inhibiting effects of oxytocin on phosphatidylinositol turnover if oxytocin receptors are present and that uterine responsiveness to oxytocin is progesterone dependent.

Keywords: sheep; conceptus; ovine trophoblast protein-1; phosphatidylinositol turnover; oxytocin

Free access

R. M. Roberts and F. W. Bazer

The likely functions of uterine secretions, often termed histotroph, in the nurture of the early conceptus are reviewed. Particular emphasis has been placed on the pig in which the uterus synthesizes and secretes large amounts of protein in response to progesterone. In this species, which possesses a non-invasive, diffuse type of epitheliochorial placentation, the secretions provide a sustained embryotrophic environment which is distinct from that of serum. A group of basic proteins dominates these uterine secretions after Day 11 of pregnancy and its best characterized member is uteroferrin, an iron-containing acid phosphatase with a deep purple colour. Evidence has accumulated to suggest that uteroferrin, rather than functioning as an acid phosphatase, is involved in transporting iron to the conceptus. Three basic polypeptides which are found noncovalently associated with uteroferrin have been shown to be antigenically closely related to one another and to have arisen by post-translational processing from a common precursor molecule. Their function is unknown. A group of basic protease inhibitors has been identified which bear considerable sequence homology to bovine pancreatic trypsin inhibitor (aprotinin) and may control intrauterine proteolytic events initiated by the conceptuses. The last basic protein so far characterized is lysozyme which is presumed to have an antibacterial role. Finally, two low molecular weight (M r ∼ 18 000) acidic polypeptides have been purified and have sequence homology to a plasma retinol binding protein. Like uteroferrin, these proteins may be responsible for transport of an essential nutrient to the conceptus.

Free access

R. M. Eley, W. W. Thatcher, and F. W. Bazer

Summary. The action of oestrone sulphate on luteal function was tested in cyclic beef heifers. Once daily injection of 28 or 56 mg oestrone sulphate in corn oil beginning on Day 10 of the cycle had a significant luteolytic effect as compared to corn oil-treated controls.

Free access

R. M. Eley, W. W. Thatcher, and F. W. Bazer

Summary. Conceptus (placental membranes, fetal fluids and fetus) development was characterized between Days 27 and 111 of gestation. Progestagens, oestrone, oestradiol, oestrone sulphate and prostaglandins (PG) F were measured in maternal plasma and allantoic and amniotic fluids. Protein concentrations are described for fetal fluids. The early increase in placental membrane weight from 1·12 g (27 days) to 58·45 g (50 days) was associated with oestrogen production presumably of conceptus origin. Oestrogens increased significantly in allantoic and amniotic fluids throughout the period studied with oestrone being the primary free oestrogen, rising from 2 pg/ml (Day 33) to 144 ng/ml by 111 days in allantoic fluid. Changes in plasma oestrogens of the maternal circulation were not detected until after Day 70 at which time oestrone concentration was greater than that of oestradiol. Fetal fluid concentrations of progestagens, oestrone sulphate and PGF were not related to maternal plasma levels and a sequestration of these hormones by the allantois is postulated.

Free access

M. T. Zavyt, R. M. Roberts, and F. W. Bazer

Summary. The activities of uteroferrin, measured as acid phosphatase (AP), and an aminoacylpeptidase (AA) were measured in uterine flushings collected from gilts on Days 6, 8, 10, 12, 14, 15, 16 and 18 of the oestrous cycle and pregnancy (N = 37). Changes in AP (P < 0·05) were associated with day for both specific and total AP in non-pregnant and pregnant gilts. For pregnant and non-pregnant gilts, AP activity was greatest between Days 14 and 16 and then decreased to Day 18.

The AA specific activity increased (P < 0·01) between Days 10 and 12 of the oestrous cycle and pregnancy, but neither effects of pregnancy nor day by pregnancy status interaction were detected. The AA total activity was greater for pregnant gilts (P < 0·01). These data suggest an inhibitory effect of oestrogens of blastocyst origin on synthesis and/or secretion of uteroferrin, but not AA.

Free access

S. M. M. Basha, F. W. Bazer, and R. M. Roberts

Summary. Endometrial explants were removed from uteri of animals pregnant and pseudopregnant (5 mg oestradiol valerate on Days 11–15) for 60 days, from the gravid and non-gravid horns of unilaterally pregnant pigs at Day 60 of pregnancy and from non-pregnant animals at Day 12 of the oestrous cycle. The tissues were cultured in the presence of l-[35S]methionine for 24 h, and the tissues and medium were then analysed separately by two-dimensional polyacrylamide gel electrophoresis. Radioactive polypeptides were identified by autoradiography of dried gels. Tissues from all except the cyclic animals released an identical group of polypeptides into the culture medium: the major radioactive products were 4 acidic polypeptides of low molecular weight and several basic proteins, which included the purple phosphatase uteroferrin, and lysozyme. In separate experiments explants from 3 unilaterally pregnant pigs were cultured with l-[3H]leucine, and, on a fresh weight basis, the tissue from the non-gravid horn released significantly less radioactive macromolecular material into the medium in 24 h than did tissue from gravid horns. It therefore appears that although the nature of the secretion produced by the pregnant uterus is a consequence of maternal hormonal regulation alone, the tissue underlying a conceptus is quantitatively more active than that from unoccupied regions of a uterus.

Free access

K. H. Young, R. R. Kraeling, and F. W. Bazer

Summary. Hypoprolactinaemia was induced by bromocriptine (CB154; 100 mg/day) which decreased circulating prolactin by 40% (P < 0·06), but did not affect conceptus survival at Day 25 when administered on Days 10–16 when compared to saline:ethanol-treated control gilts. Bromocriptine or vehicle was administered to cyclic gilts on Days 10–11, oestradiol valerate was injected on Day 11 and uterine flushings were collected on Day 12. Total recoverable protein and uteroferrin in uterine flushings were not affected by treatment. However, leucine aminopeptidase activity (P < 0·02) and total recoverable Ca2+ Na +, K+ and Cl (P < 0·05) were decreased in uterine flushings of gilts that received bromocriptine, suggesting that hypoprolactinaemia decreased general secretory activity of the endometrial epithelium and modulated ionic changes, respectively, in the uterine environment of pigs.

Subcutaneous administration of pig prolactin (1 mg/12h) increased (P < 0·001) serum prolactin 4·5-fold. The interaction between hyperprolactinaemia and progesterone, without oestrogen, on components of uterine flushings were determined using gilts that received progesterone (200 mg/day) and prolactin or saline on Days 4–14 after ovariectomy on Day 4. On Day 15, there were no differences (P > 0·05) in any of the uterine secretory components measured. Hyperprolactinaemia (1 mg pig prolactin on Days 6–11) enhanced overall uterine secretory response on Day 12 to oestradiol (5 mg) administered on Day 11 compared to gilts that received 1 ml saline on Days 6–11 of the oestrous cycle. Total recoverable protein and leucine aminopeptidase activity were greater (P < 0·05) for oestradiol-treated gilts, but effects of prolactin were not significant. Total recoverable glucose (P < 0·01), PGF-2α (P < 0·02), uteroferrin (P < 0·01) and specific activity of uteroferrin (P < 0·001) were increased by prolactin and oestradiol, but not oestradiol alone. Calcium (P < 0·05), chloride (P < 0·05) and potassium (P < 0·01) were increased in response to oestradiol. These results indicate an interaction between oestradiol and prolactin, but not progesterone and prolactin, which enhances secretion of some products of the pig uterine endometrium.

Keywords: prolactin; endometrium; secretion; pig; pregnancy

Free access

P. J. Hansen, F. W. Bazer, and R. M. Roberts

Summary. In one experiment, ovariectomized gilts were treated with corn oil (vehicle), progesterone, oestradiol-17β or both steroids. While oestradiol treatment did not stimulate enzyme activity in uterine flushings relative to vehicle-treated animals, gilts treated with progesterone had elevated amounts of all enzymes measured. Progesterone was less effective when co-administered with oestradiol-17β. Enzymes were not equally stimulated by progesterone. For example, there was a 909-fold increase in acid phosphatase activity in uterine flushings and a 304-fold increase in β-N-acetylglucosaminidase, but only a 10-fold increase in β-glucosidase. Endometrial explants from gilts synthesized and secreted radiolabelled β-N-acetylglucosaminidase, suggesting that at least some lysosomal enzymes enter the uterus through secretory processes. In other experiments, changes in β-N-acetylglucosaminidase in uterine fluids of mares and ewes treated with hormonal regimens similar to those given to the gilts were evaluated. Treatment with the combination of progesterone and oestrogen stimulated accumulation of the enzyme relative to that in vehicle-treated animals. The biochemical properties of porcine β-N-acetylglucosaminidase were examined in detail. Properties of the uterine enzyme were similar to reported values for lysosomal hexosaminidase. These included molecular weight (82 000–89 000), pH optimum (pH 4·4), presence of two isomers (isoelectric points of 5·5 and 8·0) and ability to hydrolyse substrates for glucosaminidase and galactosaminidase. We conclude that steroids induce the accumulation of lysosomal enzymes in the uterine lumen. The degree of stimulation differed between enzymes, suggesting that those enzymes stimulated to the greatest extent may play an important role in pregnancy.

Free access

K. L. Adams, F. W. Bazer, and R. M. Roberts

Summary. A retinol binding protein(s) of molecular weight about 17 000 has been demonstrated in uterine secretions from pigs in the luteal phase of the oestrous cycle. This protein was induced in ovariectomized sows treated with progesterone or progesterone plus oestradiol, but not in sows given oestradiol or corn oil. The vitamin A content of secretions from progesterone-treated animals also increased relative to those in controls. The apparent K d of the binding protein for retinol was 2·6 × 10−6 m. The protein had some affinity for retinoic acid and oleic acid, but did not bind retinyl esters or retinal. The protein probably comprises 5% or less of the total fraction of low molecular weight proteins induced by progesterone. A similar protein was found in allantoic fluid of pregnant animals, suggesting that, like uteroferrin, it serves to transport a water-insoluble nutrient from the maternal uterine endometrium to the conceptus.

Free access

J. D. Godkin, F. W. Bazer, and R. M. Roberts

Summary. Primary cell cultures were established from cells derived from dissociated Day-14 and -16 sheep and pig blastocysts. The appearance of cells in culture from both species was similar. Cultures contained a variety of cells with distinct morphologies, some were small and compact and formed clumps and multiple layers while others were large, flat and formed a monolayer. Within 4 h of culturing small floating fluid-filled spheres of cells were observed in the medium; some of these increased in size to > 1 cm diameter over 1–2 weeks. In addition, fluid-filled domes of cells arose from the underlying monolayer. Contractile cells became evident after about 8 days and some became organized into large patches of contracting tissue. Two-dimensional polyacrylamide gel electrophoresis and fluorography were performed on proteins released into the medium by confluent monolayers, floating spheres and floating cells that failed to attach during the first 24 h. All cultures produced as major products proteins with electrophoretic mobilities identical to certain fetal plasma proteins. In general, cultures did not produce proteins characteristic of short-term cultures of whole conceptuses harvested at Days 14–16. In cultures established from sheep blastocysts only the cells that failed to attach produced ovine trophoblast protein-1, a major ploypeptide produced by the trophectoderm of the sheep conceptus between Days 13 and 21 of pregnancy.