Biomedical subjects

R M Roberts

Publications and source records attributed to R M Roberts.

At least 199 records · Page 11Linked to original sources

PubMed1985

Differential patterns of secretory protein localization within the pig uterine endometrium.

We have compared the distribution of two of the major secreted proteins of the porcine uterus within the endometrium of ovariectomized pigs which had received hormone replacement therapy for 30 days. The proteins studied, plasmin/trypsin inhibitor (PI) and uteroferrin (Uf), an iron-containing acid phosphatase, were both secreted into the uterine lumen by ovariectomized gilts given progesterone (P4) or P4 and 17 beta-estradiol but not by animals given 17 beta-estradiol alone or corn oil. The two proteins were localized immunocytochemically within the endometrium using an immunoperoxidase procedure. The results confirmed that production of PI and Uf was P4-dependent and demonstrated that the primary site of synthesis of PI was the surface and upper glandular epithelium, while Uf synthesis was confined to the glandular epithelium. A similar localization of PI and of Uf was found in endometrial tissue from pigs at day 13 (late luteal phase) of the estrous cycle. These results suggest that the uterine epithelium of the pig is regionally differentiated with regard to the production of P4-induced proteins.

Acid Phosphatase↗

PubMed1985

In vitro synthesis and secretion of ovine trophoblast protein-1 during the period of maternal recognition of pregnancy.

The trophoblast of the sheep conceptus secretes a low mol wt, acidic polypeptide called ovine trophoblast protein-1 (oTP-1) from days 13-21 of pregnancy. This protein has been proposed to have an antiluteolytic role during pregnancy, since infusion of oTP-1 into the uterine lumen of nonpregnant ewes lengthened their estrous cycles. In the present study, mRNA from day 16 conceptuses was translated using a cell-free wheat germ lysate, and oTP-1 was immunoprecipitated from the translation mixture by means of a specific rabbit antiserum. The predominant protein synthesized under these conditions was oTP-1, which had a mol wt (21,000) higher than that of oTP-1 secreted by intact conceptuses into culture medium (mol wt, 17,000). In a separate experiment, in vitro secretion of oTP-1 from conceptuses on days 13, 17, and 21 of pregnancy was examined. Conceptuses were cultured for 24 h in the presence of [3H]leucine, and oTP-1 was immunoprecipitated from the culture medium. Incorporation of [3H]leucine into secreted macromolecules (mol wt, greater than 3500) increased 12-fold from days 13 to 21, while release of immunoprecipitable 3H-labeled oTP-1 increased 27-fold from days 13 to 17 and declined by over 50% from days 17 to 21. When results were expressed per microgram DNA, secretion of total macromolecules declined from days 13 to 17 and then remained constant until day 21. The pattern of oTP-1 secretion held whether results were expressed per conceptus or per unit DNA. The interestrous intervals for the donor ewes were shorter for ewes which had their conceptuses removed on day 13 than for ewes flushed on day 17 or 21. Thus, the period of oTP-1 synthesis corresponds closely to the time at which the conceptus acts to extend luteal lifespan.

Animals↗

PubMed1985

Appearance of beta-hexosaminidase and other lysosomal-like enzymes in the uterine lumen of gilts, ewes and mares in response to progesterone and oestrogens.

In one experiment, ovariectomized gilts were treated with corn oil (vehicle), progesterone, oestradiol-17 beta 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-17 beta. 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 beta-N-acetylglucosaminidase, but only a 10-fold increase in beta-glucosidase. Endometrial explants from gilts synthesized and secreted radiolabelled beta-N-acetylglucosaminidase, suggesting that at least some lysosomal enzymes enter the uterus through secretory processes. In other experiments, changes in beta-N-acetyglucosaminidase 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 beta-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.

Acetylglucosaminidase↗

PubMed1985

Protein production by cultures established from Day-14-16 sheep and pig conceptuses.

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 greater than 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 polypeptide produced by the trophectoderm of the sheep conceptus between Days 13 and 21 of pregnancy.

Animals↗

PubMed1984

Lysosomal enzyme phosphorylation. Recognition of a protein-dependent determinant allows specific phosphorylation of oligosaccharides present on lysosomal enzymes.

We have investigated the basis for the specific recognition of lysosomal enzymes by UDP-GlcNAc:lysosomal enzyme N-acetylglucosaminylphosphotransferase. This enzyme is responsible for the selective phosphorylation of mannose residues on lysosomal enzymes. Two mammalian lysosomal enzymes, cathepsin D and uteroferrin, and two nonlysosomal glycoproteins were treated with endo-beta-N-acetylglucosaminidase H to remove those high mannose oligosaccharide units which are accessible on the native protein. These proteins were then tested as inhibitors of three different glycosyltransferases. The endo H-treated lysosomal enzymes were shown to be specific inhibitors of the phosphorylation of intact lysosomal enzymes. Proteolytic fragments of cathepsin D, including the entire light chain and heavy chain, did not retain the ability to be recognized by the N-acetylglucosaminylphosphotransferase. These findings indicate that the intact protein portion of lysosomal enzymes contains a specific recognition determinant which leads to high-affinity binding to the N-acetylglucosaminylphosphotransferase. The expression of this determinant appears to be dependent on the conformation of the protein.

Acetylglucosaminidase↗

PubMed1984

Human pulmonary dirofilariasis.

Dirofilaria immitis, the canine heartworm, is a relatively rare, but well-documented cause of human lung disease. The disease presents in man as a solitary, peripheral parenchymal lung nodule which may simulate a peripheral lung neoplasm. This case is the first report of the disease in New Zealand, a country where the parasite has not become established in the dog population. A brief review of the life cycle, epidemiology and clinical data relating to human dirofilariasis is included.

Dirofilariasis↗

PubMed1984

Uteroferrin has N-asparagine-linked high-mannose-type oligosaccharides that contain mannose 6-phosphate.

Uteroferrin is an iron-containing, progesterone-induced, acid phosphatase that is secreted in large amounts by the uterine endometrium of pigs. During pregnancy, it transports iron across the chorioallantois (placenta) for use in fetal hematopoiesis. In this paper, it is reported that uteroferrin synthesized by cultured endometrial explants possesses N-linked, high-mannose, oligosaccharide chains that contain 6- phosphomannose units. The latter is regarded as a possible recognition marker whereby acid hydrolases are targeted to the lysosome. On uteroferrin, however, the majority of the phosphate is in single diester linkages between the mannose and a covering N-acetylglucosamine. It is suggested that uteroferrin is a lysosomal enzyme that has assumed a role in iron transport and metabolism and is secreted because the covering N-acetylglucosamine is not removed.

Acid Phosphatase↗

PubMed1984

Presence of an inhibitor of plasminogen activator in uterine fluid of the western spotted skunk during delayed implantation.

This study was designed to test the hypothesis that protease inhibitors would be present in uterine fluids of the western spotted skunk during the period of delayed implantation but would decline or disappear during implantation. Blood plasma, uterine flushings and medium from endometrial cultures were collected 40-70 days preimplantation (Stage 1), 20-25 days preimplantation (Stage 2), 1-3 days preimplantation (Stage 3) and 1-5 days postimplantation (Stage 4). Protein content of the flushings was low in Stage 1 (12.9 +/- 3.0 micrograms), increased slightly (21.8 +/- 6.4 micrograms) during Stage 2 and increased markedly in Stages 3 (99 +/- 44.8 micrograms) and 4 (256 +/- 150 micrograms). No protease activity was detected in any fluid at any stage. Uterine flushings, however, contained an inhibitor of plasminogen activator (PA) of apparent molecular weight approximately 70,000. The total amount of inhibitor increased as pregnancy progressed, but specific inhibitory activity was highest during Stages 1 and 2 (1.7 and 3.2 units/micrograms protein, respectively) and declined in Stages 3 and 4 (1.2 and 0.6 units/micrograms protein, respectively). The inhibitor was present in medium from uterine cultures but was low in plasma. All of the fluids could inhibit trypsin, but not plasmin. The antitrypsin activity in uterine fluids is attributed to plasma transudate. The results demonstrate an inhibitor of PA in skunk uterine fluids but show no temporal relationship between its presence and the period of obligate delay of implantation.

Animals↗

PubMed1984

Suppression of phytohemagglutinin-stimulated lymphocyte blastogenesis by ovine uterine milk protein.

Two basic glycoproteins (UTM-P) with molecular weights of 57,000 and 59,000 were purified from ovine uterine milk collected on Days 125 and 130 of pregnancy. The UTM-P were evaluated for immunosuppressive activity in phytohemagglutinin (PHA)-treated, mixed lymphocyte (MLC) and resting lymphocyte (RLC) cultures. For PHA and RLC cultures, UTM-P (2.5 to 800 micrograms UTM-P/ml) were added to 1 X 10(6) lymphocytes and 0.8 micrograms of PHA (for PHA cultures only), while for the MLC, UTM-P (50 to 1600 micrograms UTM-P/ml) were added to 5 X 10(5) lymphocytes combined from each of two ewes. Following [3H] thymidine addition, cells were later harvested for determination of thymidine incorporation. Lymphocyte blastogenesis was suppressed by UTM-P in PHA (R2 = 0.32 to 0.92, P less than 0.01 to 0.001), MLC (R2 = 0.8, P less than 0.001) and RLC (R2 = 0.65, P les than 0.01) experiments. To determine reversibility, PHA-treated lymphocytes were incubated with UTM-P for 6, 12 or 24 h, then washed to remove surface UTM-P. Incubation was continued in the presence of PHA as with other experiments. Exposure of lymphocytes to UTM-P for 6 or 12 h did not result in suppression of blastogenesis, whereas exposure for 24 h was sufficient for suppression (P less than 0.01). In an additional experiment, UTM-P were added to PHA-treated cultures at 0, 6, 12 or 24 h. Suppression (P less than 0.01) of blastogenesis was observed for each time period. Immunosuppressive activity was not mediated by overall cytotoxicity and was not affected by routine handling and storage of UTM-P. Data from these experiments provide one explanation for tolerance of the conceptus allograft during defined stages of ovine pregnancy.

Animals↗

PubMed1984

Ovine trophoblast protein 1, an early secreted blastocyst protein, binds specifically to uterine endometrium and affects protein synthesis.

Ovine trophoblastic protein-1 (oTP-1), an early secretory protein of the sheep blastocyst, was purified after culturing day 14-16 conceptuses for 24 h in vitro. The localization of oTP-1 in the pregnant day 16 sheep uterus was determined immunocytochemically. The protein was associated with trophectoderm cells of the elongated blastocyst and with the surface and upper glandular epithelium of the maternal uterus. Receptors that bound oTP-1 with high affinity (Kd = approximately 2 X 10(-10) M) were present in crude membrane preparations derived from homogenates of endometria from day 12 nonpregnant and anestrous ewes. Uterine infusion of 125I-labeled oTP-1 into day 12 nonpregnant ewes showed that the majority of the radioactivity was retained in the uterus, and only very small amounts of intact protein appeared to enter the maternal vasculature. There was no significant association with the corpora lutea, ovaries, or other tissues tested. oTP-1 failed to compete with ovine PRL for rabbit mammary gland receptors or with hCG or bovine LH for sheep luteal cell receptors, and the oTP-1 did not stimulate progesterone production by dispersed luteal cells from day 12 cycling ewes. Incubation of endometrial explants from day 12 nonpregnant ewes with 5 micrograms/ml oTP-1 resulted in increased rates of protein release into the medium. Two-dimensional polyacrylamide gel electrophoresis revealed that the synthesis of six polypeptides was stimulated selectively by the presence of oTP-1. Together these data suggest that oTP-1 acts on the maternal endometrium. It is suggested that the interaction of oTP-1 with uterine endometrium may elicit maternal responses which contribute to the maintenance of pregnancy in the sheep.

Animals↗

PubMed1984

Effect of altered oligosaccharide structure on the cell surface number, distribution and turnover of the high molecular weight acidic glycoproteins of CHO cells.

The influence of altered carbohydrate structure on the surface number, distribution and turnover of plasma membrane glycoproteins has been studied in Chinese hamster ovary (CHO) cells by comparing three lines that are resistant to the cytotoxic effects of wheat germ agglutinin (WGA) with parental CHO cells. The glycoproteins investigated were members of a group of high molecular weight acidic glycoproteins (HMWAG). On parental cells these represent the major surface components that become labelled by lactoperoxidase-catalysed iodination. They are the only plasma membrane glycoproteins that bind WGA. The mutant lines also possess iodinatable surface polypeptides of high molecular weight, but these were less acidic and electrophoretically less diffuse than those from parental cells. These polypeptides in general did not bind [125I]WGA when two-dimensional polyacrylamide gels were overlaid with iodinated lectin. Mutant cells treated with fluorescein-conjugated WGA showed low surface fluorescence. However, the nuclear envelope and a small region in the perinuclear zone fluoresced strongly. Together, these results confirm that the surface glycoproteins of mutant cells had altered carbohydrate structure. Mouse antiserum prepared against the HMWAG, however, bound equally effectively to the mutant lines as to the parental lines. Indirect immunofluorescence experiments showed that the HMWAG had a fairly uniform distribution over the surface, and that internalization induced by second antibody occurred at a similar rate and in a similar manner in all lines, including the mutants. Electron microscopic observations using immunoperoxidase procedures confirmed the similarities in glycoprotein distribution on mutant and parental cells. Two mouse monoclonal antibodies raised against the HMWAG also revealed no difference in the number or topography of surface glycoproteins. Finally, the half-lives of several HMWAG in a parental and a mutant line (15B) maintained on low-serum medium were compared by means of a 125I/131I double-label technique. Half-lives of HMWAG from the former averaged 12 h and from the latter 11 h. It is concluded that the lack of complex termini on oligosaccharides of this particular group of CHO plasma membrane glycoproteins has no effect on their number, distribution or turnover.

Animals↗

PubMed1984

Proteins released by cultured Day 15-16 conceptuses prolong luteal maintenance when introduced into the uterine lumen of cyclic ewes.

Experiments were performed to determine whether proteins, produced and released into the incubation medium by Day 15-16 sheep conceptuses cultured for 24-48 h, could prolong the functional lifespan of the corpus luteum (CL) when infused into the uterine lumen of cyclic ewes. Beginning on Day 12 (oestrus = Day 0) either a concentrated (2 ml) solution of total conceptus culture medium protein (2.2 mg) or diluted sheep serum (2.2 mg protein) was introduced daily via an indwelling catheter into the uterine lumen of 3 ewes for 7 days (Days 12-18). Peripheral blood samples were collected daily for 14 days (Days 12-25). On Day 25 all ewes were laparotomized and ovaries observed to determine whether CL previously marked with India ink were maintained. All controls had ovulated and formed new CL. By contrast none of the conceptus protein-treated ewes had ovulated, and their peripheral progesterone levels remained elevated. One ewe maintained a functional CL until Day 52 when she was hysterectomized. Light microscopy of histological sections prepared from the endometrium revealed glandular development comparable to that in the endometrium of cyclic animals during late dioestrus. The cells of the CL were similar to those from cyclic animals during mid- to late dioestrus. Ovine trophoblast protein ( oTP -1), a major protein secreted by the sheep conceptus between Days 13 and 21 of pregnancy, was purified from conceptus incubation medium and injected (0.2 mg protein/day) into the uterine lumen of 3 animals. Plasma progesterone concentrations indicated that oTP -1-treated animals maintained luteal function 4 days longer than did control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Acid phosphatase and leucine aminopeptidase activity in the uterine flushings of non-pregnant and pregnant gilts.

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 less than 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 less than 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 less than 0.01). These data suggest an inhibitory effect of oestrogens of blastocyst origin on synthesis and/or secretion of uteroferrin, but not AA.

Acid Phosphatase↗

PubMed1984

Role of uteroferrin in placental iron transport: effect of maternal iron treatment on fetal iron and uteroferrin content and neonatal hemoglobin.

Uteroferrin, an Fe-containing, progesterone-induced glycoprotein is involved in maternal to fetal Fe transport in swine. These studies examined the effect of im Fe injection of dam on conceptus and piglet Fe stores. In Exp. I, eight gilts were bred and assigned to either treatment I (no Fe injections) or treatment II (total of 22 mg iron-dextran/kg body weight on d 40, 45, 50, 55 and 60 of gestation) and hysterectomized on d 90 to determine whether Fe injections increased Fe stores in the conceptus. Total Fe in allantoic fluid (P less than .10) as well as uteroferrin concentration (P less than .05) and total uteroferrin (P less than .05) in placentae were greater for gilts in treatment II. In Exp. II, 19 cross-bred sows were bred and assigned to treatments I and II (d 40, 50 and 60 of gestation), as in Exp. I, and treatment III (total of 22 mg iron-dextran/kg body weight on d 90, 100 and 110 of gestation) to determine effects of treatment on hemoglobin (Hb) values of the piglets at 8 +/- 1 h and d 4 postpartum. Piglets from treatment II had higher (P less than .01) Hb at 8 +/- 1 h, but not on d 4 postpartum. Experiment III was a replication of Exp. II except that Hb values were determined at 8 +/- 1 h, d 4 and d 7 postpartum. On d 7, piglets from treatment II had higher (P less than .05) Hb, but differences at 8 +/- 1 h and d 4 were not significant (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Phosphatase↗

PubMed1984

Maternal recognition of pregnancy in cattle.

Nature and potential functions of chemical signals involved in the process of pregnancy recognition in cattle are discussed. The array of prostaglandins, steroid metabolites, and proteins produced by the conceptus and endometrium are described and collated with histological and physiological responses of the uterus and ovary that lead toward maintenance of the corpus luteum. Advances during the last 10 yr partially have identified the conceptus-endometrial-ovarian signal sequence that is associated with maternal recognition of pregnancy in cattle. Final evaluation of the control system should permit investigators to improve embryo survival and augment further the impact of embryo manipulation to improve genetic merit of the cattle population.

Animals↗

PubMed1984

Arterial injuries in extremity shotgun wounds: requisite factors for successful management.

The extremity shotgun wound presents a surgical challenge in the treatment of peripheral arterial trauma. Adherence to specific principles of management is required for optimal limb salvage. Thirty-four vascular injuries in 31 patients were reported. Arteriography is mandatory since the presence of distal palpable pulses was an unreliable indicator of the absence of arterial injury in 13 patients. Intraoperative arteriography was essential to demonstrate distal sequential injuries. Arterial reconstruction was necessary in 28 patients who sustained 31 significant vascular injuries. Autogenous interposition grafts were required in 10 patients. Seventeen patients underwent resection of the injured arterial segment followed by an end-to-end anastomosis. Arteriovenous fistulas were ligated in two patients, while two sidewall injuries were treated with lateral repair. Delay of operative intervention with subsequent infection, failure to reconstruct all vessels injured, and inadequate initial fasciotomy were factors that contributed to an amputation in two patients. Successful management of arterial injuries in extremity shotgun wounds requires attention to the following requisite factors: preoperative and intraoperative arteriography, prompt operative intervention, fracture stabilization, repair of all injured major vessels, use of autogenous graft tissue, venous reconstruction, thorough debridement, and fasciotomy. Twenty-nine of 31 patients retained a functional limb by adhering to these principles of management.

Adult↗

PubMed1983

Biochemical aspects of conceptus--endometrial interactions.

Mammalian conceptuses must provide a chemical signal to the maternal system to insure maintenance of corpus luteum (CL) function and of progesterone production and continuation of uterine endometrial secretory activity. These events insure that the developing conceptus is provided with appropriate nutrients, regulatory enzymes and endocrine state to allow successful establishment and maintenance of pregnancy. Pig blastocysts begin to produce estrogens by Day 11 of pregnancy, which prevents secretion of the uterine luteolytic factor (PGF2 alpha) in an endocrine direction, but allows secretion in an exocrine direction, i.e., into the uterine lumen. Therefore, CL are "protected." Blastocyst estrogens also trigger secretion of a group of proteins, including uteroferrin, an iron transport protein, and a family of protease inhibitors whose biosynthesis within the uterine glandular epithelium is under the control of progesterone. Estrogen also appears to promote accumulation of glucose and fructose within the uterine lumen. A complex in vivo "culture medium" is thereby established to promote conceptus development. Pig blastocysts do not undergo invasive implantation within the uterine lumen although they produce the protease, plasminogen activator. Invasion may be prevented by endometrial secretion of progesterone-induced protease inhibitors which are produced in large amounts. In addition to estrogens of conceptus origin, calcium and prostaglandins PGF2 alpha and E2 may affect the uterine vasculature, water and electrolyte transport, capillary permeability, conceptus steroid production, and related events during pregnancy. The blastocysts of the large domestic animals also secrete proteins which include a large glycoprotein (Mr approximately 600,000) and a small acidic protein (Mr approximately 17,000). The latter has been purified from sheep and named ovine trophoblast protein I. These proteins may play unique roles in early pregnancy with respect to establishment and maintenance of pregnancy in the ewe, sow, mare, and cow.

Animals↗

PubMed1983

Relationship between release of plasminogen activator and estrogen by blastocysts and secretion of plasmin inhibitor by uterine endometrium in the pregnant pig.

Pig blastocysts isolated between Days 10 and 16 of pregnancy release the protease, plasminogen activator (PA), into the medium in a time-dependent manner when cultured in vitro. Production is biphasic. The initial phase (Days 10-12) coincides with the early elongation stages, while release during the second phase (Days 14-16) occurs during a time at which the DNA content of the blastocysts is increasing markedly. Uterine flushings from these pregnant animals contain the zymogen substrate for PA, plasminogen, presumably as a serum transudate. Plasminogen is present in highest amounts at Day 12. The blastocyst, therefore, has the potential ability to generate the broadly specific protease, plasmin, within the uterine lumen. However, during this same period, the endometrium secretes an inhibitor of plasmin into the uterine lumen. In pregnant animals the amount of plasmin inhibitory activity rose 7-fold between Day 10.5, when the blastocysts were spherical, and Day 12, when they had become filamentous. At Day 12 each uterine horn contained about 3 to 4 mg of plasmin inhibitor. A similar release of inhibitor can be initiated in nonpregnant gilts given a single, intramuscular injection of estradiol valerate on Day 11 of the estrous cycle. It is suggested that the initiation of estrogen production by the elongating blastocyst triggers the release of plasmin inhibitor by the maternal endometrium and that the inhibitor serves to prevent a proteolytic cascade of reactions initiated by blastocyst PA, which might otherwise damage the uterine epithelium.

Animals↗