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Biomedical subjects

F W Bazer

Publications and source records attributed to F W Bazer.

At least 91 records · Page 5Linked to original sources
PubMed1997

Interferon tau: a novel pregnancy recognition signal.

PROBLEM: Trophectoderm of ruminant conceptuses (embryo and associated membranes) secretes tau interferons (IFNtau) as the pregnancy recognition signal. How does it act? METHOD: Review of current data. RESULTS: IFNtau acts on uterine epithelium to suppress transcription of the genes for estrogen receptor and oxytocin receptor. This blocks development of the uterine luteolytic mechanism and, therefore, release of luteolytic pulses of prostaglandin F2alpha, but it has no effect on expression of the progesterone receptor. Maintenance of progesterone secretion by the corpus luteum ensures establishment and maintenance of pregnancy. Secretion of IFNtau on days 12-15 for sheep and days 14-17 for cows and goats is essential for pregnancy recognition. CONCLUSION: We propose that IFNtau affects endometrial gene expression by activating the Jak/Stat pathway, which results in formation of the ISGF3alpha transcription factor complex. ISGF3alpha binds to interferon-stimulated response elements and activates transcription of interferon-responsive genes such as interferon regulatory factor-1 (IRF-1) which, in turn, activates expression of the negative-acting transcription factor IRF-2. Pregnancy (or intrauterine injection of roIFNtau) results in a transient increase in endometrial IRF-1 expression followed 36-48 hr later by a sustained increase in IRF-2. We propose that IRF-2, or an IFNtau-induced negative regulatory factor like IRF-2, suppresses expression of the estrogen receptor gene and directly or indirectly blocks expression of the gene for oxytocin receptor to abrogate the uterine luteolytic mechanism and ensure the establishment of pregnancy.

Animals↗
PubMed1997

Extracellular matrix and the implantation cascade in pigs.

The structural and functional alterations of uterine epithelial cells that permit the apical-apical union of conceptus and uterine epithelium are complex and are likely to involve many different adhesion molecules with distinct but inter-related functions. A number of changes in the molecular composition at the apical surface of uterine epithelial cells associated with the transition from the pre-receptive to the receptive state in the pig uterus are reviewed. Molecules that function in the adhesion cascade resulting in implantation are represented by a variety of adhesion systems. However, integrins are probably the dominant adhesion systems because their capacity to mediate adhesion is linked to their activation by engaging other surface molecules.

Animals↗
PubMed1996

Biochemical and immunological properties of related small ruminant trophoblast interferons.

The objectives of this study were 1) to evaluate the biochemical and immunological properties of caprine interferon tau (cIFNtau), 2) to determine if intrauterine injection of recombinant ovine interferon tau (roIFNtau) extends CL life span in goats, and 3) to evaluate potential side effects of intramuscular (i.m.) administration roIFNtau. Caprine IFNtau was purified, and its effects on lymphocyte proliferation were evaluated. Incorporation of 3H-thymidine into newly synthesized DNA was suppressed (P<0.05) by cIFNtau. Spanish goats were also fitted with bilateral uterine catheters at Day 7 or 8 postestrus. The goats received twice-daily intrauterine injections of 100 microg roIFNtau (n = 4) or caprine serum proteins (n = 4) from Days 14 to 18 postestrus. Intrauterine injection of roIFNtau extended CL life span compared with that of control goats (26.4 +/- 1.7 vs 17.8 +/- 1.9 d, respectively; P<0.01). Potential side effects of intramuscular injections of roIFNtau were also evaluated. Goats received 0, 1, 2 or 4 mg of roIFNt on Days 10, 13, 16 or 19 of the estrous cycle. Treatment of goats with roIFN resulted in hyperthermia (P<0.01), with rectal temperatures of 40.5 degrees C recorded after 4 h and returning to normal (38.5 degrees C) after 24 h. Concomitant with the increase in rectal temperatures was a decrease (P<0.01) in plasma progesterone concentrations. Therefore, the tau interferons of goats and sheep have similar biological properties and roIFNtau has side effects associated with other classes of interferons.

Journal Article↗
PubMed1996

Developmentally regulated expression of interleukin-1 beta by peri-implantation conceptuses in swine.

Interleukin-1 beta (IL-1 beta) is one of the critical inflammatory cytokines involved in many physiological processes. This study investigated the temporal expression of IL-1 beta in pig conceptuses. A human IL-1 beta cDNA probe and a anti-human IL-1 beta antibody were used to examine IL-1 beta gene and protein expression in pig conceptuses on days 11, 12, 13, 14, 15, 20, 30, 45, 60, 75, 90, 105 and 112 of pregnancy using Northern, Slot and Western blot analyses. A human cell line (A375.S2) was used to determine IL-1 activity in pig conceptuses. High levels of IL-1 beta mRNA were detected in days 11, 12 and 13 conceptuses. IL-1 beta protein was also detected in conceptuses on days 11, 12, 13, and 14, but not in conceptuses recovered after day 15 of pregnancy. IL-1 beta biological activity was demonstrated in days 11 and 12 conceptus homogenates, but not in homogenates of days 112 allantochorion. Low levels of IL-1 beta mRNA were detected by Northern blot analysis in Day 15 conceptuses, endometrium and myometrium only when poly(A+) RNA was used. The production of IL-1 beta by peri-implantation pig conceptuses was temporally associated with maternal recognition of pregnancy. The results suggest that conceptus IL-1 beta may be important for conceptus development and establishment of pregnancy.

Animals↗
PubMed1996

Transfer of heterologous immunoglobulin into the uterine lumen of pigs.

Transfer of circulating heterologous immunoglobulin G (IgG) into the uterine lumen of pigs has not been reported. The present study determined if ovine IgG (oIgG) could be transferred into the uterine lumen of pigs. Six gilts (nonparous female pigs) were injected i.v. with either immune sheep serum (25 or 50 ml) to porcine uteroferrin (Uf) or non-immune sheep serum (50 ml) on days 9, 11 and 13 of the estrous cycle. Serum was collected daily from days 9 to 15 and uterine flushings were collected at hysterectomy on day 15. An ELISA detecting oIgG was used to determine levels of oIgG in pig sera and uterine flushings. High oIgG levels in serum (ranging from 87 +/- 11 to 141 +/- 14 micrograms/ml) were maintained by injecting the gilts at 48 h intervals with ovine antiserum to porcine Uf. Serum concentrations of oIgG did not differ (P > 0.05) regardless of whether immune or non-immune sera or different doses of immune serum were injected. oIgG in uterine flushings (2 +/- 1 micrograms/uterine flushing) was detectable when the samples were concentrated 40-fold, but were lower (P < 0.01) than serum levels of oIgG (107 +/- 10 micrograms/ml). Results indicate that small amounts of circulating heterologous IgG can be transferred into the uterine lumen of pigs. However, passive immunization may not result in titers high enough to examine in vivo functions of proteins secreted into the uterine lumen of pigs.

Acid Phosphatase↗
PubMed1996

Effects of interferon-tau and progesterone on oestrogen-stimulated expression of receptors for oestrogen, progesterone and oxytocin in the endometrium of ovariectomized ewes.

The effects of recombinant ovine interferon-tau (IFN-tau) and progesterone on oestrogen-stimulated expression of endometrial receptors for oestrogen (ER), progesterone (PR) and oxytocin (OTR) were determined in ovariectomized ewes. Cyclic ewes (n = 16) were ovariectomized and fitted with uterine catheters on Day 4 of the oestrous cycle (Day O, oestrous) and assigned randomly in 2 x 2-factorial arrangement to receive daily intrauterine injections of either recombinant ovine IFN-tau (roIFN-tau; 2 x 10(7) anti-viral units) or control proteins from Day 11 to Day 15 and 50 mg progesterone from either Day 4 to Day 10 (E-P) or Day 4 to Day 15 (E+P). All ewes received 50 micrograms oestradiol-17 beta on Days 13, 14 and 15 and were hysterectomized on Day 16. In control ewes, endometrial ER mRNA, PR protein and OTR density were greater in E-P- than E+P- treated ewes. In E-P ewes, roIFN-tau decreased oestrogen-stimulated increases in ER and OTR, but not PR expression compared with control ewes. In E+P ewes, endometrial ER mRNA and protein, PR mRNA and protein, and OTR levels were lower in roIFN-tau-treated ewes than control ewes. Immunoreactive ER and PR were absent in the endometrial luminal and superficial glandular epithelium of roIFN-tau compared with control ewes, but were present in the deep glandular epithelium and stroma regardless of steroid or protein treatment. These results indicate that progesterone affects oestrogen-induced increases in endometrial ER, PR and OTR expression in the PR+ deep glandular epithelium and stroma, whereas IFN-tau suppresses oestrogen-induced increases ER, PR and OTR expression in the PR- luminal and superficial glandular epithelium. These combined actions of IFN-tau and progesterone to suppress oestrogen-induced increases in endometrial OTR formation would prevent pulsatile production of luteolytic prostaglandin F2 alpha by the endometrium during early pregnancy.

Animals↗
PubMed1996

Expression of oncofetal fibronectin in porcine conceptuses and uterus throughout gestation.

Oncofetal fibronectin is reportedly expressed specifically by trophoblast tissue and some tumours and speculated to mediate placental attachment. In the present study, a monoclonal antibody (FDC-6) to human oncofetal fibronectin was used to characterize temporal and spatial changes in the expression of oncofetal fibronectin at the fetal-maternal interface of pigs. Conceptus and uterine tissues were collected from gilts throughout normal pregnancy and processed for immunohistochemical characterization. Results indicated that oncofetal fibronectin was constitutively expressed by both porcine conceptus and uterus throughout gestation. The most abundant staining for oncofetal fibronectin was found in the allantochorion and detectable levels of oncofetal fibronectin were also detected in luminal and glandular epithelial cells in the uterus. During the second-half of pregnancy, oncofetal fibronectin was also detected in fibroblast-like cells in the uterine stroma, but not in the stroma of the allantochorion. Owing to the non-invasive nature of the porcine placenta, the abundant expression of oncofetal fibronectin by the trophoblast and uterus may influence attachment between chorion and endometrium during pregnancy. Since attachment is the first step in implantation and placentation in all mammalian species, the pig may represent an excellent animal model to study interactions between trophoblast and endometrium mediated by oncofetal fibronectin.

Animals↗
PubMed1996

High yield expression and secretion of the ovine pregnancy recognition hormone interferon-tau by Pichia pastoris.

The early conceptus (embryo and associated membranes) of domestic ruminats signals its presence to the maternal uterus through production of interferon-tau (IFN-tau). Production of IFN-tau ensures continued production of progesterone, the hormone of pregnancy, by the ovarian corpus luteum. This paper reports the high-level expression and efficient secretion of biologically active recombinant ovine IFN-tau (rOvIFN-tau) by Pichia pastoris. The developed method produces more than 80% pure recombinant ovine IFN-tau, obviating the need for further purification for many purposes. Initial fermentation studies produced IFN-tau at 280 mg/liter and demonstrate the potential of this system for large-scale production of IFN-tau.

Animals↗
PubMed1996

Enzyme-linked immunosorbent assay for ovine interferon-tau.

Ovine interferon-tau (OvIFN-tau) is a trophectoderm secretory protein responsible for maintenance of corpus luteum function during early pregnancy. Methods for its quantitation include an antiviral assay and radioimmunoassay (RIA), both of which have disadvantages. We therefore developed an ELISA for OvIFN-tau that is specific, rapid, and 40-fold more sensitive than the current RIA. It uses a monoclonal antibody (Ab) HL129, which binds both native and recombinant (r) OvIFN-tau. The ELISA accurately detected known amounts of rOvIFN-tau added to yeast and tissue culture medium and to sheep serum at concentrations between 0.005 and 50,000 ng/ml. Inter- and intraassay coefficients of variation were 9.3 +/- 0.8 and 6.1 +/- 1.4%, respectively. Data are given for the reliability and reproducibility of the ELISA for measuring native OvIFN-tau and rOvIFN-tau.

Animals↗
PubMed1996

Effects of recombinant interferon-tau on ovine lentivirus replication.

As a pregnancy recognition signal, sheep trophoblast cells secrete a type I interferon, ovine interferon-tau (OvIFN-tau), which has potent antiviral activity. We studied the effects of a recombinant protein (rOv-IFN-tau) on the replication of ovine lentivirus (OvLV) in goat synovial membrane cells. The amount of provirus DNA, as measured by polymerase chain reaction (PCR), the virus titers, and the number of OvLV-induced syncytia were 76.5%, 82%, and 95%, respectively, lower in cultures treated with rOv-IFN-tau than in placebo-treated controls (p < 0.01). rOv-IFN-tau also reduced OvLV reverse transcriptase activity and protected cells from OvLV-induced cell lysis, but the effect was less dramatic. The antiviral activity increased with the concentration up to a maximum with 256 antiviral units of rOv-IFN-tau per ml.

Animals↗
PubMed1996

Unusual abundance of arginine and ornithine in porcine allantoic fluid.

The concentrations of free arginine, ornithine, and glutamine in porcine allantoic and amniotic fluids were determined on Days 30,35, 40, and 45 of gestation. Arginine and ornithine were the most abundant amino acids in allantoic fluid on Days 35-40 and 45 of gestation, respectively. Arginine and ornithine nitrogen accounted for 40%, 50%, and 55% of the total free alpha-amino acid nitrogen in allantoic fluid on Days 35, 40, and 45 of gestation, respectively. Glutamine was the most abundant amino acid in amniotic fluid during early gestation and was also abundant in allantoic fluid. On Day 45 of gestation, glutamine nitrogen accounted for 41% of the total free alpha-amino acid nitrogen in amniotic fluid. The unusual abundance of arginine (2.5-4.1 mM) and ornithine (1.08-2.52 mM) in allantoic fluid on Days 35-40 of gestation has not been reported for any other biological fluid. These results are novel and interesting with respect to the role of these two basic amino acids in fetal-placental nutrition and metabolism.

Allantoin↗
PubMed1996

Estrogen enhances endometrial estrogen receptor gene expression by a posttranscriptional mechanism in the ovariectomized ewe.

Prior influence of estrogen is required for many physiological effects of steroid hormones. This study addresses positive autoregulation of estrogen receptor gene expression in endometrium. Groups of ovariectomized ewes (n = 6) were treated with a single i.m. injection of 50 micrograms 17 beta-estradiol for 6, 12, 24, or 48 h or of vehicle for 24 h (control) prior to collection of endometrium. Three ewes received a regimen of estradiol-progesterone-estradiol (EPE) designed to mimic the estrous cycle. Northern analysis of endometrial RNA using an ovine estrogen receptor complementary RNA probe indicated that estradiol increased (p < 0.0001) estrogen receptor messenger RNA abundance over time to be 5-fold greater at 24 h postinjection. This effect also occurred after a period of progesterone dominance in EPE ewes (p < 0.05). Ribonuclease protection assays with a complementary RNA probe for the ovine progesterone receptor demonstrated that estradiol treatment increased progesterone receptor messenger RNA abundance at 48 h (p < 0.005). Nuclear runoff analyses indicated that whereas estradiol enhanced the transcription rates of progesterone receptor (p < 0.1) and 28S ribosomal RNA genes (p < 0.002), activity of the estrogen receptor gene was unchanged (p > 0.25). These results suggest that a physiological dose of estradiol, similar to the preovulatory surge of estrogen, up-regulates endometrial estrogen receptor gene expression by a posttranscriptional mechanism.

Amino Acid Sequence↗
PubMed1996

Characterization of a polarized porcine uterine epithelial model system.

A porcine uterine epithelial cell (pUE) culture system that retains structural and functional properties of the surface epithelium in vivo was developed. Uterine luminal epithelial cells were isolated after pancreatin-dispase enzymatic release of epithelium from hysterectomized gilts. Cells were seeded on Millicell filters precoated with Matrigel in 24-well plates and subsequently allowed to proliferate to confluence. Purity of the isolation was confirmed by the presence of > 99% cytokeratin-positive cells. Epithelial cells became polarized in vitro and compared favorably in morphology to uterine epithelial cells in situ once a transepithelial resistance of > 600 omega cm2 was established. Microscopic analysis confirmed the presence of a simple columnar epithelium with prominent microvilli on the apical cell surface and a well-developed junctional complex containing tight junctions, belt and spot desmosomes, and interdigitating lateral cell processes. Indirect immunofluorescence of the tight junction-associated protein, ZO-1, indicated the formation of tight junctional complexes in the subapical region of the polarized cells. Functional polarity of epithelial cultures was also verified by 1) electrical resistance measurements, 2) basal preference for the secretion of prostaglandins F2 alpha and E2, 3) apical preference for the release of 35S-methionine-incorporated secretory proteins, and 4) apically and basally distinct secretory protein profiles. Steroid treatment (estrogen, progesterone, or estrogen plus progesterone) of the polarized pUE cells affected the release of radiolabeled methionine-incorporated secretory proteins. In addition, the protein profiles as compared to samples treated with fetal bovine serum or charcoal/dextran-stripped fetal bovine serum were altered. Steroid treatments did not alter the electrical resistance or the basal preference for prostaglandin secretion. This culture system may be useful for in vitro analysis of maternal recognition of pregnancy paradigms as well as the study of the direct actions of hormones, prostaglandin secretion, and epithelial-stromal interactions.

Animals↗
PubMed1996

Differential expression of beta transforming growth factors (TGF beta 1, TGF beta 2, and TGF beta 3) and their receptors (type I and type II) in peri-implantation porcine conceptuses.

Beta transforming growth factors (TGF beta 1, TGF beta 2, and TGF beta 3) and type I and II TGF beta receptors were immunohistochemically localized in peri-implantation porcine conceptuses (embryos and associated membranes) collected on Day 10 through Day 14 of gestation. Our results indicate specific immunolocalization of TGF beta isoforms and their receptors in conceptuses during these gestational days. In parietal endoderm, TGF beta 1 immunoreactions were weak to undetectable, TGF beta 2 immunoreactions were intense, and TGF beta 3 immunoreactions were intermediate in intensity to TGF beta 2 and TGF beta 1. In contrast to immunoreactions in endoderm, TGF beta 1 and TGF beta 3 immunostaining in trophectoderm (Tr) was intense. Differences in TGF beta 2 immunostaining of Tr were observed from Days 10 to 14 of gestation. A drastic decrease in cytoplasmic immunostaining of ectoderm and mesoderm was detected from Days 12 to 14 for all TGF beta isoforms and type II receptor; however, type I receptor immunoreactions were consistently detected between Days 10 and 14. Concurrent expression of both type I and type II receptors in the peri-implantation conceptuses suggests that porcine conceptuses are capable of binding and responding to TGF beta s during this period. Differential expression of the three TGF beta isoforms suggests different roles for TGF beta s 1, 2, and 3 in conceptus development. Our results suggest possible roles for TGF beta s in early growth and differentiation of the embryo, differentiation of the Tr, and implantation.

Animals↗
PubMed1996

Spatial and temporal analyses of integrin and Muc-1 expression in porcine uterine epithelium and trophectoderm in vivo.

The spatial and temporal expressions of Muc-1, selected integrin subunits, and extracellular matrix components in porcine uterine epithelium from estrous (Days 0, 4, 8, 10-15) and early pregnant (Days 10-15 of pregnancy) gilts and from steroid-treated ovariectomized gilts were analyzed using indirect immunofluorescence analyses on cryosectioned tissues to identify potential components of uterine receptivity. Integrin subunit and extracellular matrix expressions were also examined in Day 11-15 conceptuses. Intense Muc-1 staining was detected on apical uterine epithelium on Day 0 but was absent by Day 10 in both cyclic and pregnant gilts. The result of estrogen treatment (E2; 100 micrograms/day for 10 days) was similar to that of the corn oil vehicle control, while treatment with progesterone (P4; 200 mg/day for 10 days) or E2 + P4 decreased Muc-1 staining in ovariectomized gilts. Immunostaining performed with antibodies directed against integrin subunits (alpha 1, alpha 3, alpha 4, alpha 5, alpha v, beta 1, and beta 3) in uterine epithelium revealed low (integrin subunits alpha 1 alpha 3), high (integrin subunits alpha v and beta 3), or modulated (integrin subunits alpha 4, alpha 5, and beta 1) expression, with the lowest expression on Day 0 and maximum expression by Days 10-15. Additionally, no differences due to pregnancy status were detected in staining of uterine epithelium on Days 10-15. Uterine epithelium from steroid-treated ovariectomized gilts had low expression of alpha 4, alpha 5, and beta 1 subunits in the presence of E2 that increased in response to P4 and E2 + P4 treatments. The expression of integrin subunits alpha 3, alpha v and beta 3 was not affected by sex steroids. Trophectoderm also expressed alpha 1, alpha 4, alpha 5, alpha v, beta 1, and beta 3, integrin subunits. Extracellular matrix constituents (fibronectin, vitronectin, laminin, and collagen type IV) were also examined. Fibronectin and vitronectin were present on trophectoderm, but only vitronectin was detected on uterine epithelium. The alpha 4, alpha 5, alpha v, beta 1, and beta 3 integrin subunits, vitronectin, and fibronectin were detected at sites of attachment between uterine epithelial cells and trophectoderm on Days 12-15 of pregnancy. These studies indicate that down-regulation of Muc-1 coincides with the transition of the prereceptive uterus to the receptive uterus. Additionally, the expression of alpha 4, alpha 5, alpha v, beta 1, and beta 3 integrin subunits along with the extracellular matrix components of fibronectin and vitronectin correlates with the time of implantation in swine.

Animals↗
PubMed1996

Placental interferons.

Trophectoderm of ruminant conceptuses (embryo and associated membranes) secrete tau interferons (IFN tau) as the pregnancy recognition signal. Secretion of IFN tau on gestational days 12-13 for sheep and gestation days 14-17 for cows and goats is critical for pregnancy recognition. IFN tau acts on uterine epithelium to suppress estrogen receptor and oxytocin receptor gene expression, which prevents uterine release of luteolytic pulses of prostaglandin F2 alpha (PGF). Expression of the progesterone receptor (PR) gene in uterine endometrium is not affected by oIFN tau. Maintenance of progesterone secretion by the corpus luteum (CL) ensures establishment of pregnancy. Pig conceptuses secrete both IFN alpha and IFN gamma between days 15-21 of gestation, but their role(s) in early pregnancy is unknown. Estrogen secreted by pig trophoblast between gestational days 11-13 and 15-25 increases endometrial receptors for prolactin and causes exocrine secretion of PGF into the uterine lumen to prevent luteolysis. Shared cell-signaling mechanisms by IFNs and lactogenic hormones through Janus kinases (JAK) 1 and 2 may provide a common pathway to abrogate luteolytic mechanisms to ensure establishment of pregnancy. The role(s) of IFNs produced by human and rodent placentae is not known.

Animals↗
PubMed1996

Ovine interferon tau suppresses transcription of the estrogen receptor and oxytocin receptor genes in the ovine endometrium.

Tau interferons (IFNtau) are a unique subclass of the omega interferons that are transiently produced by the trophectoderm of the conceptus (embryo and associated membranes) during early pregnancy in ruminants. IFNtau acts as an antiestrogen on the endometrium to suppress increases in estrogen receptor (ER) and oxytocin receptor (OTR) gene expression which prevents pulsatile production of prostaglandin F2alpha and regression of the corpus luteum or luteolysis. In this study, steady-state levels of ER mRNA and transcription rates of the ER and OTR genes were two-fold lower in the endometrium of pregnant as compared to cyclic ewes on day 15. Levels of ER mRNA and ER and OTR gene transcription were also two-fold lower in the endometrium of day 15 cyclic ewes receiving intrauterine injections of recombinant ovine IFNtau from day 11 to day 14 compared to control ewes. Results suggest that the antiluteolytic action of IFNtau is to suppress transcription of the ER gene by a negative-acting transcriptional mechanism which prevents estrogen-induced increases in OTR gene expression in the endometrium. The novel antiestrogenic effects of IFNtau, combined with its Type I IFN characteristics and low cytotoxicity, suggest that this trophoblast IFN may have potential value as a chemotherapeutic agent for the treatment of infertility, viral disease and estrogen-dependent malignant disorders.

Animals↗