| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Articles |
a Center for Animal Biotechnology and Genomics, Albert B. Alkek Institute of Biosciences and Technology, Texas A&M University System Health Science Center, and Department of Animal Science, Texas A&M University,College Station, Texas 77843-2471
b Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel
c Institute of Animal Science, Agricultural Research Organization, Volcani Center, Bet Dagan 50650, Israel
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
(IFN), placental lactogen (PL), and growth hormone (GH) on endometrial function. In the first study, administration of IFN to cyclic ewes for one period (Days 11–15) resulted in an interestrous interval (IEI) of ~30 days, whereas administration for two periods (Days 11–15 and Days 21–25) extended the IEI to greater than 50 days. Administration of IFN from Days 11 to 15 and of PL or GH from Days 21 to 25 failed to extend the IEI more than for IFN alone. In the second study, effects of IFN, PL, and GH on endometrial differentiation and function were determined in ovariectomized ewes receiving ovarian steroid replacement therapy. Endometrial expression of mRNAs for estrogen receptor (ER), progesterone receptor (PR), and oxytocin receptor (OTR) were not affected by PL or GH treatment; however, uterine milk protein mRNA levels and stratum spongiosum gland density were increased by both PL and GH treatments. Collectively, results indicated that 1) PL and GH do not regulate endometrial PR, ER, and OTR expression or affect corpus luteum life span; 2) down-regulation of epithelial PR expression is requisite for progesterone induction of secretory gene expression in uterine glandular epithelium; 3) effects of PL and GH on endometrial function require IFN; and 4) PL and GH regulate endometrial gland proliferation and perhaps differentiated function.
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
), placental lactogen (PL), placental GH, and progesterone [1–3]. Establishment of pregnancy in ruminants requires that the preimplantation embryo enter a receptive uterus and develop sufficiently to synthesize and release IFN, the pregnancy recognition signal, at the appropriate time and in appropriate amounts [1,2, 4]. Ovine IFN prevents development of the endometrial luteolytic mechanism by acting on the endometrial luminal (LE) and superficial glandular epithelium (GE) to suppress transcription of the estrogen receptor (ER) and oxytocin receptor (OTR) genes [5, 6]. These actions of IFN maintain function of the corpus luteum (CL) by preventing endometrial OTR formation and, therefore, oxytocin-induced release of luteolytic pulses of prostaglandin F2
(PGF).
Interestrous intervals of 30–35 days result when conceptuses are flushed from the uterus of ewes on Day 16 [7] or after intrauterine infusions of either highly purified native ovine IFN [8] or recombinant ovine IFN [9] into the uterus of cyclic ewes between Days 11 and 15 after onset of estrus. Endometrial OTR mRNA and protein were found to increase between Days 30 and 70 in pregnant ewes [10]. Injection of oxytocin at different stages of pregnancy in the ewe produces a small increase in peripheral PGF metabolite concentrations in early pregnancy, and this response increases significantly from midgestation onward [11]. Collectively, available evidence indicates that the endometrial luteolytic mechanism is reactivated between 20 and 30 days postestrus and must be abrogated by the conceptus to prolong CL function until Day 50 when the placenta begins to produce progesterone [12].
After pregnancy recognition, maintenance of pregnancy requires reciprocal communication between the conceptus and endometrium during implantation and synepitheliochorial placentation. In sheep, superficial implantation and placentation is a lengthy process that begins on Days 15–16 and is not completed until Days 50–60 of pregnancy [13]. During this period, the ovine placenta produces PL and GH. The placentae of a number of other species, including rodents, humans, and nonhuman primates, also secrete hormones structurally related to pituitary GH and PRL that are termed PLs [1, 14, 15]. Ovine PL is a nonglycosylated 22-kDa protein [16] produced by binucleate cells of the conceptus trophectoderm beginning on Day 16 of pregnancy [17]. PL is detected in maternal serum by Day 50, and peak levels occur between Days 120 and 130 of gestation [18–20]. In the sheep uterus, prolactin receptor (PRL-R) expression is specifically restricted to the GE and increases during pregnancy [21]. This receptor transduces signals by PRL and PL, because bovine PL can activate signal transduction through the long form of the PRL-R [22]. The ovine placenta also expresses GH between Days 35 and 70 [23]. Expression of the GH receptor (GH-R) has not been reported for the ovine uterus, but the endometrial epithelium and vasculature of the bovine uterus express GH-R mRNA and protein [24]. In sheep, it has been proposed that PLs are involved in the regulation of fetal growth and metabolism [25], development of the maternal mammary gland [26], and modulation of maternal intermediary metabolism [20]. However, specific biological actions of PL and placental GH on ovine uterine function have not been reported. But in other species, lactogenic hormones, including PRL and PL, are reported to play a role in pregnancy by direct actions on the endometrium [27–29].
Ovine PL may be critical to maintenance of pregnancy, because lactogenic hormones influence steroidogenesis in the CL, transport of water by placental membranes, endometrial proliferation, endometrial progesterone receptor (PR) gene expression, protein synthesis and secretion by endometrial epithelium, exocrine secretion of PGF in pigs, and mammary growth and lactation [20, 25–29]. During the first 60 days of pregnancy, the ovine uterus grows substantially in order to accommodate rapid conceptus development and growth. In addition to placentomal development in the caruncular areas of the endometrium and changes in vascularity, the intercaruncular endometrial glands grow substantially in length and width during pregnancy in ewes [13]. These uterine glands synthesize, secrete, or transport a variety of enzymes, growth factors, cytokines, lymphokines, hormones, transport proteins, and other substances that are collectively termed histotroph [30–32]. Available evidence strongly supports the idea that secretions from the endometrial epithelia influence conceptus development, onset of pregnancy recognition signals, and growth of the fetus and placenta in both the pig and sheep (see [30–32]). It is possible that PL and placental GH regulate endometrial gland function since the GE of the ruminant uterus expresses receptors for both of these hormones [21, 24].
Based on available evidence, our working hypotheses were that 1) PL and/or GH may be the second signal(s) for maintenance of pregnancy that reinforces or extends the effects of the primary signal, IFN, to suppress development of the endometrial luteolytic mechanism and extend life span of the CL to Day 50 and beyond; and 2) ovarian steroids, estrogen and progesterone, and placental polypeptide hormones, including IFN, PL, and/or placental GH, constitute a servomechanism that regulates ovine uterine function. The first series of studies determined effects of intrauterine (IU) administration of recombinant ovine IFN, PL, and/or GH to cyclic ewes on life span of the CL by measuring effects of treatment on interestrous interval. The second series of studies determined effects of ovarian steroids and IU administration of recombinant ovine IFN, PL, and GH on ovine endometrial differentiation and secretory gene expression.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Mature ewes of primarily Rambouillet breeding were observed daily for estrous behavior using vasectomized rams and were assigned to treatments after exhibiting at least two estrous cycles of normal duration (16–18 days). Experimental and surgical procedures complied with the Guide for Care and Use of Agriculture Animals and were approved by the Institutional Agricultural Animal Care and Use Committee of Texas A&M University (Animal Use Protocol 95-30056).
Study 1: Experimental Design and Treatments
Experiment 1
Fifteen cyclic ewes were fitted with uterine catheters on Day 5 of the estrous cycle and assigned randomly (n = 5 ewes per treatment group) to receive daily IU injections of 1) control proteins (6 mg serum proteins per day) from Days 11 to 15, 2) recombinant ovine IFN (roIFN; 2 x 107 antiviral units per day) from Days 11 to 15, or 3) roIFN from Days 11 to 15 followed by roIFN on Days 21–25.
Experiment 2
Twenty-five cyclic ewes were fitted with uterine catheters on Day 5 of the estrous cycle and assigned randomly (n = 5 ewes per treatment group) to receive daily IU injections of 1) control proteins (6 mg serum proteins per day) from Days 11 to 15, 2) roIFN (2 x 107 antiviral units per day) from Days 11 to 15, 3) roIFN from Days 11 to 15 followed by roIFN on Days 21–25, 4) roIFN from Days 11 to 15 followed by recombinant ovine PL (roPL; 200 µg/day) on Days 21–25, or 5) roIFN from Days 11 to 15 followed by recombinant ovine GH (roGH; 200 µg/day) on Days 21–25.
Experiment 3
Twenty cyclic ewes were fitted with uterine catheters on Day 5 of the estrous cycle and assigned randomly (n = 5 ewes per treatment group) to receive daily IU injections of 1) control proteins (6 mg serum proteins per day) from Days 11 to 15, 2) roIFN (2 x 107 antiviral units per day) from Days 11 to 15, 3) roIFN from Days 11 to 15 followed by control proteins (6 mg/day) on Days 21–25, or 4) roIFN from Days 11 to 15 followed by roPL (200 µg/day) on Days 21–25.
Depending on the experiment, uterine horns of each ewe received (at 0700 and 1900 h daily) injections of either control serum proteins (1.5 mg total protein per horn per injection), roIFN (5 x 106 antiviral units per horn per injection), roPL (50 µg/horn per injection), or roGH (50 µg/horn per injection) twice daily as described previously [33]. Administration of roIFN from Days 11 to 15 was previously shown to mimic the antiluteolytic effects of the conceptus during the pregnancy recognition period in terms of suppressing endometrial epithelial ER and OTR gene expression and uterine production of luteolytic pulses of PGF in response to oxytocin [33].
In experiments 1, 2, and 3, ewes were monitored twice daily for estrous behavior using a vasectomized ram. Interestrous interval (IEI) was calculated as the interval between estrus (Day 0) and subsequent return to estrus. If ewes failed to return to estrus by Day 50 after onset of estrus, exogenous PGF (Lutalyse; Pharmacia and UpJohn, Kalamazoo, MI) injections (10 mg, i.m., twice) were used to induce luteolysis.
Study 2: Experimental Design and Treatments
Experiment 4 As illustrated in Figure 1A, 25 cyclic ewes were ovariectomized and fitted with uterine catheters on Day 4 of the estrous cycle (Day 0 = estrus) [33] and assigned (n = 5 ewes per treatment) randomly to receive daily IU injections of protein or i.m. injections of ovarian steroids from Days 4 to 29 as follows: 1) corn oil (CO) and control serum proteins (CX; 200 µg) (CO-CX treatment); 2) 50 mg progesterone (P4) and CX proteins (P-CX treatment); 3) P4 plus 25 µg estradiol-17ß (E2) and CX proteins (P+E-CX treatment); 4) P4 and 200 µg roPL (P-oPL treatment); or 5) P4, E2, and PL (P+E-oPL treatment). The uterine horns of each ewe received twice-daily (0700 and 1900 h) injections of either CX proteins or PL (50 µg protein per horn per injection). Steroid treatments were administered at 0700 h in a total volume of 1 ml corn oil vehicle. All ewes were hysterectomized on Day 30.
|
Experiment 5
As illustrated in Figure 4A, 12 cyclic ewes were ovariectomized and fitted with uterine catheters on Day 5 of the estrous cycle (Day 0 = estrus) and received daily i.m. injections of 50 mg P4 from Days 5 to 25, IU injections of roIFN (2 x 107 antiviral units per day) from Days 11 to 20, and daily IU injections from Days 16 to 24 of either 1) control (CX) serum proteins (200 µg; n = 4 ewes), 2) recombinant PL (200 µg; n = 4 ewes), or 3) recombinant GH (200 µg; n = 4 ewes). The uterine horns of each ewe received twice-daily (0700 and 1900 h) injections of either CX proteins, PL, or GH (50 µg protein per horn per injection). Steroid treatments were administered at 0700 h in a total volume of 1 ml corn oil vehicle. All ewes were hysterectomized on Day 25.
|
At hysterectomy, portions (~1.0 cm) from the middle region of each uterine horn were fixed in fresh 4% paraformaldehyde in PBS (pH 7.0) for 24 h and embedded in Paraplast-Plus (Oxford Labware, St. Louis, MO). From the remainder of each uterine horn, endometrium was dissected from myometrium, frozen separately in liquid nitrogen, and stored at -80°C.
Preparation of Recombinant Ovine IFN, PL, and GH
Recombinant oIFN was produced from a synthetic gene construct in Pichia pastoris and purified at the Fermentation Core Facility, Department of Food Science, University of Nebraska [34, 35]. Recombinant PL and GH were produced in Escherichia coli as described previously [36]. IU protein injections were prepared as described previously [33].
RNA Isolation and Analyses
RNA isolation Total cellular RNA was isolated from frozen endometrium using the Trizol reagent (Gibco-BRL, Grand Island, NY).
Slot-blot hybridization analysis
For each ewe, denatured total cellular RNA (20 µg) was analyzed by slot-blot hybridization using radiolabeled antisense cRNA probes generated by in vitro transcription with [-32P]UTP (Amersham Pharmacia Biotech, Piscataway, NJ) as described previously [33]. Plasmid templates containing cDNAs for the ovine ER [33], ovine PR [33], ovine OTR [37], ovine uterine milk proteins (UTMP) [38], ovine sulfated glycoprotein 1 (SGP-1) [39], ovine osteopontin (OPN) [40], and 18S rRNA (pT718S; Ambion, Austin, TX) were used to produce radiolabeled cRNA probes. Slot blots were quantitated by electronic autoradiography using an Instant Imager (Packard, Meriden, CT).
In Situ Hybridization Analysis
The location of mRNA in uterine tissue sections was determined by in situ hybridization analysis as described previously [33]. Deparaffinized, rehydrated, and deproteinated uterine tissue sections (5–7 µm) were hybridized with radiolabeled antisense or sense ovine UTMP or ovine OPN cRNA probes using in vitro transcription with [-35S]UTP (3000 Ci/mmol; Amersham Pharmacia Biotech). Autoradiographs of slides were prepared using BioMax MR film (Eastman Kodak, Rochester, NY) for a 16-h exposure period. Autoradiography was accomplished using Kodak NTB-2 liquid photographic emulsion [41]. Slides were stored at 4°C for 1–2 wk as judged from autoradiographs, developed in Kodak D-19 developer, counterstained with Harris modified hematoxylin (Fisher Scientific, Fairlawn, NJ), dehydrated through a graded series of alcohol to xylene, and coverslipped.
Immunohistochemistry
Immunoreactive PR and Ki-67 protein were detected in uterine tissue cross sections using specific antisera and a Super ABC rabbit or mouse/rat IgG kit (Biomeda, Foster City, CA) as described previously [33]. Mouse monoclonal antibody to the human PR (MA1-411) [42] was purchased from Affinity Bioreagents (Golden, CO), and human Ki-67 (K72820) from Transduction Laboratories (Lexington, KY). The human PR and Ki-67 antibodies were used at a final concentration of 5 µg/ml. Negative controls included substitution of the primary antibody with purified mouse IgG at the same protein concentration and omission of the primary antibody or biotinylated secondary antibody. Tissue sections from both uterine horns of each ewe were processed as sets within an experiment. Staining intensities and patterns were assessed separately by two observers.
Histology and Morphometry
Embedded tissues were sectioned (5–7 µm), deparaffinized, and stained with Mayer's hematoxylin and eosin for general histomorphological evaluation. Relative endometrial gland density was estimated for the upper and lower portions of the stratum spongiosum by determining the total number of uterine glands in a field at a constant magnification (x40). Gland density estimates were generated for at least 6 nonsequential sections from each uterine horn. A total of 8 fields per section, representing random areas of the intercaruncular endometrium of each tissue section, were evaluated for each uterine horn. An observed gland cross section with an open lumen was counted as a gland. Care was taken to place the field in areas of maximum distance between the borders of the stratum spongiosum and stratum compactum or myometrium. In addition, no overlapping fields were allowed. Intra- and intersection repeatability estimates for determination of gland density by a single observer were 0.85 and 0.8, respectively. Data are presented as gland numbers per field.
Photomicroscopy
Photomicrographs of in situ hybridization and immunohistochemistry slides were taken using a Zeiss Axioplan2 photomicroscope (Carl Zeiss, Thornwood, NY) fitted with a Hamamatsu chilled 3CCD color camera (Hamamatsu Corporation, Bridgewater, NJ). Digital images were captured and/or assembled using Adobe Photoshop 4.0 (Adobe Systems, Seattle, WA) and a MacIntosh PowerMac G3 computer (Apple Computer, Cupertino, CA). Black-and-white prints were electronically printed using a Kodak DS8650 color printer.
Statistical Analyses
All quantitative data were subjected to least-squares analysis of variance (LS-ANOVA) using General Linear Models procedures of the Statistical Analysis System [43]. Analyses of steady state levels of endometrial mRNA measured by slot-blot hybridization included the 18S rRNA data as a covariate in LS-ANOVA to correct for differences in sample loading. For experiment 5, statistical models for analysis of gland density data within endometrial area (stratum compactum, upper stratum spongiosum, lower stratum spongiosum) included main effects of treatment (CX, PL, GH), ewe within treatment, uterine wall location (mesometrial and antimesometrial), and uterine wall location by main effect interactions. Initial analyses indicated that uterine horn, tissue section, and microscopic field within section were not significant sources of variation. In all analyses, error terms used in tests of significance were identified according to the expectation of the mean squares for error. In all experiments, preplanned comparisons were used to determine treatment effects [44]. Data are presented as least-square means with overall SE.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Experiment 1
Control ewes receiving ovine serum proteins had IEI of 20 ± 3 days. As expected, IU administration of roIFN for one period (Days 11–15) extended the IEI to 32 ± 3 days (P < 0.05, IFN-1P vs. control). However, administration of roIFN for two periods (Days 11–15 and 21–25) prolonged the IEI to 55 ± 3 days (P < 0.01, IFN-1P vs. IFN-2P).
Experiment 2
The IEI in control ewes was 17 ± 3.4 days, and ewes receiving roIFN for one period (Days 11–15) had longer IEI as expected (29.8 ± 3.4 days; P < 0.01, control vs. IFN-1P). The IEI for ewes receiving roIFN and roGH (27.6 ± 3.4 days), or roIFN and roPL (26.4 ± 3.4 days), were not different (P > 0.10) from those for ewes receiving roIFN alone between Days 11 and 15. As in experiment 1, ewes receiving two periods of roIFN (Days 11–15 and 21–25) had IEI of 51 ± 3.4 days, which was longer (P < 0.01) than for the other treatment groups.
Experiment 3
The IEI in control ewes was 19 ± 5.3 days. Ewes receiving roIFN on Days 11 to 15 had a longer IEI of 32.5 ± 5.3 days as expected (P < 0.05, control vs. IFN). The IEI for ewes receiving roIFN and serum proteins (23.8 ± 5.3 days), or roIFN and roPL (26.3 ± 5.3 days), were not different (P > 0.10) from that for ewes receiving serum proteins or roIFN alone.
Study 2
Experiment 4: Steady state levels of endometrial mRNAs ER, PR, and OTR mRNAs. Steady state levels of ER, PR, and OTR mRNAs were greatest in endometrium from CO-CX ewes (Fig. 1B). Treatment of CX ewes with P4 decreased ER, PR, and OTR mRNA levels (CO-CX vs. P-CX, P < 0.01). In both CX and PL ewes, E2 increased PR mRNA approximately twofold (P4 vs. P+E, P < 0.01) but had no effect (P > 0.10) on ER or OTR mRNA. Treatment of ewes with PL had no effect (P > 0.10) on ER, PR, or OTR mRNA levels, regardless of steroid treatment.
UTMP, OPN, and SGP-1 mRNAs. Treatment of ewes with P4 increased endometrial UTMP and OPN mRNA levels (CO-CX vs. P-CX, P < 0.01), but had no effect on SGP-1 mRNA (Fig. 1C). Regardless of IU protein treatment, administration of P+E decreased endometrial UTMP and OPN mRNA levels (P4 vs. P+E, P < 0.01). Ovine PL had no effect on UTMP and OPN mRNAs in P4-treated ewes (P-CX vs. P-PL, P > 0.10). SGP-1 mRNA was only increased by PL in P+E-treated ewes (P-CX and P+E-oPL vs. P-oPL and P+E-CX, P < 0.05).
Experiment 4: Localization of UTMP mRNA and PR protein in the uterus UTMP mRNA. UTMP mRNA was detected only in the endometrial glands, particularly GE in the stratum spongiosum (Fig. 2). In CX ewes, P4 treatment appeared to increase UTMP mRNA expression as expected. Consistent with mRNA analyses, administration of P+E appeared to decrease UTMP mRNA expression in GE, although some glands in the stratum spongiosum expressed low levels of UTMP mRNA. There was no effect of PL on UTMP mRNA expression.
|
PR protein. Immunoreactive PR levels were highest in CO-CX ewes, particularly in the stroma, stratum compactum GE, and myometrium (Fig. 3). In endometrium of CO-CX ewes, PR protein was not detectable in LE and deep stratum spongiosum GE. Treatment of ewes with P4 appeared to suppress PR expression in all endometrial cell types, whereas treatment with P+E specifically increased PR in LE, stratum compactum GE, and stratum spongiosum GE, regardless of protein treatment. Effects of E2 on endometrial PR protein expression was most evident in the stratum spongiosum GE. As expected from mRNA analyses, PL had no effect on PR expression.
|
Experiment 5: Steady state levels of endometrial mRNAs ER, PR, and OTR mRNAs. As in experiment 4, IU administration of PL or GH had no effect (P > 0.10) on endometrial levels of ER, PR, or OTR mRNAs compared to those in ewes receiving CX proteins (data not shown).
UTMP, OPN, and SGP-1 mRNAs. As illustrated in Figure 4B, ewes receiving PL and GH had approximately twofold greater endometrial levels of UTMP mRNA than CX ewes (CX vs. PL, P = 0.08; CX vs. GH, P = 0.09). Endometrial OPN mRNA levels were also twofold greater in ewes receiving PL than CX (CX vs. PL, P = 0.09), but GH had no effect on OPN mRNA levels (CX vs. GH, P = 0.88). SGP-1 mRNA levels were low and not affected (P > 0.10) by any treatment (data not shown).
Experiment 5: Localization of UTMP and OPN mRNA in the endometrium, histoarchitecture, and measurements of endometrial gland density The UTMP and OPN mRNAs were located only in the GE (Fig. 5). Although the amount of mRNA for UTMP and OPN per gland did not appear to be affected by treatment, the total number of UTMP and OPN mRNA-positive glands appeared to be greater, particularly in the stratum spongiosum, in uteri of PL- and GH-treated ewes compared to CX ewes. Careful analysis of hematoxylin- and eosin-stained uterine tissue sections further indicated that the number of glands was greater in uteri of PL- and GH-treated ewes. In addition, the glands in the upper stratum spongiosum of GH-treated ewes were consistently larger (Figs. 5 and 6).
|
These histological observations were confirmed by measuring endometrial gland density in stratum compactum and stratum spongiosum in the intercaruncular areas of the endometrium. The stratum spongiosum was divided into upper and lower areas. Endometrial gland density was greater in the lower area of the stratum spongiosum in ewes receiving PL (CX vs. PL, P < 0.01; 52 vs. 110 ± 1.5 glands per field) and GH (CX vs. GH, P < 0.01; 52 vs. 89 ± 1.5 glands per field). In the upper area of the stratum spongiosum, endometrial gland density was lower in GH-treated ewes (CX vs. GH, P = 0.09; 25 vs. 18 ± 0.6 glands per field) and not affected (P = 0.23) by PL. There was no effect of treatment on endometrial gland density in the stratum compactum (data not shown).
Experiment 5: Immunolocalization of Ki-67 and PR protein Ki-67, a marker of cell proliferation [45], detected low levels of perinuclear Ki-67 immunoreactivity in GE but not in other uterine cell types of CX ewes (Fig. 6). The abundance of Ki-67-immunoreactive protein appeared to be greater in the endometrial GE of both PL- and GH-treated ewes. In GH-treated ewes, Ki-67 immunostaining appeared to be greatest in the middle GE. No other effects of PL or GH on Ki-67 staining were detected for any uterine cell type.
|
As in experiment 4, PR protein was abundant in the stroma and myometrium, but not detectable in endometrial LE or GE (data not shown). In some ewes, faint nuclear staining was detected in the very deep endometrial GE nearest the myometrium. In agreement with mRNA analyses, no effects of PL or GH on the distribution or abundance of PR protein in any uterine cell type were detected.
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
to suppress development of the endometrial luteolytic mechanism or extend life span of the CL to Day 50 and beyond. However, these results are the first to demonstrate that IU injections of roIFN for two periods (Days 11–15 and Days 21–25) significantly extend CL life span to greater than 50 days. These results are of interest because a biologically active ovine IFN-like protein was detected in allantoic fluid and chorioallantoic culture medium [46]. For both chorioallantoic culture medium and allantoic fluid, antiviral activity was greatest on Day 25 and decreased linearly to low concentrations by Day 40. Consistent with these results, immunoreactive ovine IFN-like protein was detected by specific RIA in all samples of allantoic fluid taken at Days 30 (228 ± 79 ng/ml), 35 (62 ± 8 ng/ml), and 40 (94 ± 50 ng/ml) of gestation. Immunoreactive oIFN-like protein was detected in chorioallantoic culture medium from Day 25 tissues (162 ± 46 ng/ml), but concentrations on Days 30, 35, and 40 were below 1 ng/ml. Fluorographs of two-dimensional SDS-PAGE analysis of proteins produced de novo and secreted by the chorioallantois in culture provided no evidence for a radiolabeled protein possessing molecular weight and isoelectric point similar to those of native ovine IFN at Days 25, 30, or 35 of gestation; however, the relative insensitivity of this technique must be taken into account. Taken together, results from Ott et al. [46] provide evidence for the presence of an immunoreactive, biologically active ovine IFN-like protein in allantoic fluid and chorioallantoic culture medium between Days 25 and 40 of gestation that may be involved in extending CL function. Low levels of IFN are produced by the placenta until at least Day 24 [47]. Although expression of IFN may be low, it may be adequate to extend CL life span beyond Days 30–35. Results of the present study confirm that ovarian steroids regulate expression of the ER, PR, and/or OTR genes in the endometrium [48–50]. Expression of ER, PR, and OTR mRNAs was greatest in ovariectomized CO-CX ewes. Thus, these hormone receptors may be considered products of default genes, because their expression increases to very high levels in the absence of ovarian sex steroids. Therefore, studies involving long term-ovariectomized ewes should be carefully evaluated as to their physiological significance. Administration of P4 decreased overall levels of endometrial ER, PR, and OTR mRNA expression in experiment 4; however, treatment with P+E increased PR mRNA, but not ER or OTR mRNAs. Previous reports clearly indicate that both the ovine ER and OTR genes are regulated by estrogen in the endometrium [6, 50, 51]; however, those studies utilized cyclic ewes treated for a short period (~10 days) with ovarian hormones and not the longer period (~25 days) used in the present studies. Indeed, exposure of the ovine uterus to P4 for 8–10 days up-regulates endometrial ER and OTR and development of the endometrial luteolytic mechanism, because P4 down-regulates expression of epithelial PR expression so that P4 can no longer inhibit expression of ER and OTR genes in the LE [49, 50, 52, 53]. The negative autoregulation of PR expression in the LE by P4 may be required for uterine receptivity, because this phenomenon occurs before conceptus implantation in all mammalian uteri studied [1, 2, 4].
In the present study, administration of P4 alone for 20 or 25 days down-regulated expression of endometrial PR mRNA in LE and GE regardless of IU protein treatment. However, the PR-negative endometrial GE expressed abundant UTMP and OPN mRNAs. In the ovine uterus, UTMP and OPN mRNAs are expressed predominantly by GE, and their protein products are secreted into the uterine lumen [54, 55]. Long-term treatment with P4 increases endometrial OPN and UTMP expression and secretion [54–56]. The protracted nature of this P4 effect is not typical of genes regulated by PR in a classical transcriptional manner. It appears that down-regulation of PR gene expression in the GE is required for P4 induction of secretory gene expression by the same epithelia, because administration of estrogen with P4 up-regulated PR expression in the endometrial epithelium, which decreased UTMP and OPN mRNA expression by GE as shown in the present study. The contention that epithelial PR down-regulation is required for endometrial gland function during pregnancy is also supported by studies of PR gene expression in cyclic and pregnant ovine endometrium [49, 57]. During early pregnancy, endometrial PR expression can be detected in endometrial LE and GE on Days 9 and 11; it then declines to undetectable levels in the LE on Days 13–19. During the pregnancy recognition period, PR expression is progressively lost from the middle and deep GE. By Day 25 of pregnancy, PR expression is abundant in stroma and myometrium and at very low levels in the very deep GE near the myometrium. Endometrial epithelial PR expression remains undetectable in the endometrial epithelium for the remainder of pregnancy (unpublished results). The down-regulation of PR expression by P4 is likely to be required for the glandular remodeling and differentiation that occur during pregnancy, because activated PR can inhibit cell cycle transition and epithelial proliferation.
In the rabbit and pig, it has been proposed that interactions between lactogenic hormones and ovarian steroids constitute a "servomechanism" that regulates endometrial function [27]. Interactions between PRL and P4 increase endometrial proliferation and uteroglobin secretion in long term-ovariectomized rabbits [27, 58]. In the rabbit uterus, PRL also increases the concentration of endometrial PR and thereby enhances the uterine response to P4 [59]. Chilton and Daniel [59] found that PRL increased the concentration of endometrial PR protein and enhanced the uterine response to P4 in the rabbit. This mechanism does not appear to be present in the ovine uterus, because neither PL nor GH had an effect on endometrial PR or ER gene expression.
Although endometrial glands lack PR expression in ewes, PRL-R gene expression is restricted to GE, increases during early pregnancy, and remains abundant throughout pregnancy [21]. Although GH-R expression in the ovine uterus has not been reported, GH-R expression has been detected in endometrial LE, GE, and vasculature of the pregnant bovine uterus [24]. Thus, the endometrial glands of the ovine uterus may be primary targets for actions of lactogenic and somatogenic hormones from both the pituitary and placenta. Indeed, endometrial remodeling (such as gland and caruncular morphogenesis) and secretory capacity of the uterus (indicated by temporal changes in secretion of ovine UTMP) can be correlated to production of PL and GH by the ovine placenta [13, 54, 56]. In the pig uterus, PRL interacts with estrogen and P4 to increase total recoverable uteroferrin, glucose, and PGF in uterine flushings [28, 60]. Results from experiment 5 indicate that PL and GH have specific paracrine actions on the endometrial GE to stimulate proliferation and/or differentiated function in terms of secretory gene expression.
In experiment 4, PL and GH did not affect endometrial UTMP or OPN mRNA levels when ewes were treated with P4 only. However, UTMP and OPN mRNA levels were increased by PL and/or GH in experiment 5 when ewes were treated with P4 as well as IU injections of roIFN. A comparison of results from these two experiments implies that effects of PL and GH on ovine endometrial function require an effect of IFN on the endometrium. IFN may induce or up-regulate genes involved in signal transduction or protein secretion, including janus kinases (JAKs), signal transducers and activators of transcription (STATs), IFN regulatory factors, or perhaps IFN-regulated proteins such as Mx or ubiquitin cross-reactive protein [61–66]. In experiment 5, PL increased expression of both UTMP and OPN mRNAs in GE, whereas GH increased expression only of UTMP mRNA. Although both PL and GH activate the JAK2-STAT5 and mitogen-activated protein kinase signal transduction pathways [67, 68], individual genes may be regulated differentially by these placental hormones. In this study, PL and GH stimulated endometrial gland proliferation and differentiated function in terms of secretory gene expression. The ability of PRL, PL, and GH to elicit similar effects on the endometrial glands is not surprising given that these hormones constitute a unique hormone family as evidenced by genetic, structural, binding, receptor signal transduction, and function studies [3, 69, 70]. PL is produced by binucleate trophectodermal cells as early as Day 16 and can be detected in the maternal circulation from Day 50 until near the end of pregnancy [18–20]. In contrast, expression of GH by the ovine placenta is restricted to Days 35–70 of gestation [23]. These temporal differences in PL and GH expression by the placenta may determine, in part, the specific roles that each plays with respect to endometrial remodeling and function.
It is difficult to determine whether PL and GH effects were directly on transcription of UTMP and OPN genes, because endometrial gland density and perhaps size were greater in the uteri of PL- and GH-treated ewes. Further research is warranted to assess the apparently diverse effects of PL and GH on GE in the stratum spongiosum. In other epitheliomesenchymal organs, PRL induces mitogenesis and alters postdifferentiation gene expression programs. For instance, in the pigeon crop sac, PRL stimulates proliferation of mitogenically competent germinal layer cells and causes the differentiated cells to enter an altered program of gene expression and phenotypic differentiation leading to production of large volumes of crop milk [67,71, 72]. Hyperprolactinemia causes endometrial hypertrophy and glandular differentiation and alters secretions found in the uterine lumen in both the rabbit and pig [27,28, 58–60]. In ruminants, PL may act on the endometrial GE to stimulate morphogenesis and differentiated function in a manner similar to that observed for PRL in its effects on the pigeon crop sac [71] and mouse mammary gland [73].
Available evidence strongly supports the idea that secretions from the endometrial epithelium influence conceptus development, onset of pregnancy recognition signals, and growth of the fetus and placenta in both the pig and sheep [30–32]. Our working hypothesis is that members of the lactogenic and somatogenic hormone family play key roles in stimulating endometrial gland development and function during pregnancy to facilitate implantation and placentation of the conceptus. Indeed, the pregnant ovine endometrium is sequentially exposed to estrogen, P4, PRL, IFN, PL, and placental GH. These hormones may constitute a servomechanism that activates and maintains endometrial remodeling, secretory function, and uterine growth during gestation. Given that PRL-R gene expression in the endometrial glands increases during pregnancy, pituitary PRL and/or PL may play central roles in endometrial gland remodeling and stimulation of differentiated function necessary for optimal maternal support of conceptus growth and development throughout pregnancy.
|
ACKNOWLEDGMENTS |
|---|
|
FOOTNOTES |
|---|
2 Correspondence: Fuller W. Bazer, Department of Animal Science and Center for Animal Biotechnology and Genomics, Albert B. Alkek Institute of Biosciences and Technology, 442D Kleberg Center, Texas A&M University, College Station, TX 77843-2471. FAX: 409 862 2662; fbazer{at}cvm.tamu.edu
3 Current address: Animal and Veterinary Science Department, 216 Agricultural Sciences Building, University of Idaho, Moscow, ID 83844-2330.
Accepted: July 12, 1999.
Received: April 14, 1999.
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
, E and 13,14-dihydro-15-keto-prostaglandin F2 in cyclic ewes. J Reprod Fertil 1988; 84:493–504. release and endometrial oxytocin receptor concentrations throughout pregnancy in ewes. J Reprod Fertil 1995; 103:233–238. secretion in sheep. J Reprod Fertil 1987; 79:457–467.vß3 integrin expression in the uterus and conceptus during the periimplantation period. Biol Reprod 1999; 61:892–899.This article has been cited by other articles:
|
|
 |
|
  H. Gao, G. Wu, T. E. Spencer, G. A. Johnson, and F. W. Bazer Select Nutrients in the Ovine Uterine Lumen. V. Nitric Oxide Synthase, GTP Cyclohydrolase, and Ornithine Decarboxylase in Ovine Uteri and Peri-Implantation Conceptuses Biol Reprod, July 1, 2009; 81(1): 67 - 76. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Song, M C. Satterfield, J. Kim, F. W Bazer, and T. E Spencer Progesterone and interferon tau regulate leukemia inhibitory factor receptor and IL6ST in the ovine uterus during early pregnancy Reproduction, March 1, 2009; 137(3): 553 - 565. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Gao, G. Wu, T. E. Spencer, G. A. Johnson, and F. W. Bazer Select Nutrients in the Ovine Uterine Lumen. III. Cationic Amino Acid Transporters in the Ovine Uterus and Peri-Implantation Conceptuses Biol Reprod, March 1, 2009; 80(3): 602 - 609. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Gao, G. Wu, T. E. Spencer, G. A. Johnson, and F. W. Bazer Select Nutrients in the Ovine Uterine Lumen. II. Glucose Transporters in the Uterus and Peri-Implantation Conceptuses Biol Reprod, January 1, 2009; 80(1): 94 - 104. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Seo, M. Kim, Y. Choi, C.-K. Lee, and H. Ka Analysis of Lysophosphatidic Acid (LPA) Receptor and LPA-Induced Endometrial Prostaglandin-Endoperoxide Synthase 2 Expression in the Porcine Uterus Endocrinology, December 1, 2008; 149(12): 6166 - 6175. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. A. Dunlap, D. W. Erikson, R. C. Burghardt, F. J. White, K. M. Reed, J. L. Farmer, T. E. Spencer, R. R. Magness, F. W. Bazer, K. J. Bayless, et al. Progesterone and Placentation Increase Secreted Phosphoprotein One (SPP1 or Osteopontin) in Uterine Glands and Stroma for Histotrophic and Hematotrophic Support of Ovine Pregnancy Biol Reprod, November 1, 2008; 79(5): 983 - 990. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Song, M. C. Satterfield, J. Kim, F. W. Bazer, and T. E. Spencer Gastrin-Releasing Peptide (GRP) in the Ovine Uterus: Regulation by Interferon Tau and Progesterone Biol Reprod, August 1, 2008; 79(2): 376 - 386. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. D Wright, R. J Orbus, T. R H Regnault, and R. V Anthony Effects of early gestation GH administration on placental and fetal development in sheep J. Endocrinol., July 1, 2008; 198(1): 91 - 99. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Song, J. Kim, F. W. Bazer, and T. E. Spencer Progesterone and Interferon Tau Regulate Hypoxia-Inducible Factors in the Endometrium of the Ovine Uterus Endocrinology, April 1, 2008; 149(4): 1926 - 1934. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. E Spencer, O. Sandra, and E. Wolf Genes involved in conceptus-endometrial interactions in ruminants: insights from reductionism and thoughts on holistic approaches Reproduction, February 1, 2008; 135(2): 165 - 179. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Wu, F. W. Bazer, T. A. Cudd, W. S. Jobgen, S. W. Kim, A. Lassala, P. Li, J. H. Matis, C. J. Meininger, and T. E. Spencer Pharmacokinetics and Safety of Arginine Supplementation in Animals J. Nutr., June 1, 2007; 137(6): 1673S - 1680S. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Song, F. W Bazer, and T. E Spencer Pregnancy and interferon tau regulate RSAD2 and IFIH1 expression in the ovine uterus Reproduction, January 1, 2007; 133(1): 285 - 295. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. R. Bilby, A. Guzeloglu, L. A. MacLaren, C. R. Staples, and W. W. Thatcher Pregnancy, Bovine Somatotropin, and Dietary n-3 Fatty Acids in Lactating Dairy Cows: II. Endometrial Gene Expression Related to Maintenance of Pregnancy. J Dairy Sci, September 1, 2006; 89(9): 3375 - 3385. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. C. Satterfield, F. W. Bazer, and T. E. Spencer Progesterone Regulation of Preimplantation Conceptus Growth and Galectin 15 (LGALS15) in the Ovine Uterus Biol Reprod, August 1, 2006; 75(2): 289 - 296. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Song, T. E. Spencer, and F. W. Bazer Progesterone and Interferon-{tau} Regulate Cystatin C in the Endometrium Endocrinology, July 1, 2006; 147(7): 3478 - 3483. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Song, F. W. Bazer, G. F. Wagner, and T. E. Spencer Stanniocalcin (STC) in the Endometrial Glands of the Ovine Uterus: Regulation by Progesterone and Placental Hormones Biol Reprod, May 1, 2006; 74(5): 913 - 922. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. A. Gray, C. A. Abbey, P. D. Beremand, Y. Choi, J. L. Farmer, D. L. Adelson, T. L. Thomas, F. W. Bazer, and T. E. Spencer Identification of Endometrial Genes Regulated by Early Pregnancy, Progesterone, and Interferon Tau in the Ovine Uterus Biol Reprod, February 1, 2006; 74(2): 383 - 394. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M.P. Green, L.D. Spate, J.A. Bixby, A.D. Ealy, and R.M. Roberts A Comparison of the Anti-Luteolytic Activities of Recombinant Ovine Interferon-Alpha and -Tau in Sheep Biol Reprod, December 1, 2005; 73(6): 1087 - 1093. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. J. White, J. W. Ross, M. M. Joyce, R. D. Geisert, R. C. Burghardt, and G. A. Johnson Steroid Regulation of Cell Specific Secreted Phosphoprotein 1 (Osteopontin) Expression in the Pregnant Porcine Uterus Biol Reprod, December 1, 2005; 73(6): 1294 - 1301. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Song, T. E. Spencer, and F. W. Bazer Cathepsins in the Ovine Uterus: Regulation by Pregnancy, Progesterone, and Interferon Tau Endocrinology, November 1, 2005; 146(11): 4825 - 4833. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C A. Gray, K. A Dunlap, R. C Burghardt, and T. E Spencer Galectin-15 in ovine uteroplacental tissues Reproduction, August 1, 2005; 130(2): 231 - 240. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. A. Costine, E. K. Inskeep, and M. E. Wilson Growth hormone at breeding modifies conceptus development and postnatal growth in sheep J Anim Sci, April 1, 2005; 83(4): 810 - 815. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. A. Balaguer, R. A. Pershing, C. Rodriguez-Sallaberry, W. W. Thatcher, and L. Badinga Effects of Bovine Somatotropin on Uterine Genes Related to the Prostaglandin Cascade in Lactating Dairy Cows J Dairy Sci, February 1, 2005; 88(2): 543 - 552. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. E Spencer, G. A Johnson, F. W Bazer, and R. C Burghardt Implantation mechanisms: insights from the sheep Reproduction, December 1, 2004; 128(6): 657 - 668. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. R. Bilby, A. Guzeloglu, S. Kamimura, S. M. Pancarci, F. Michel, H. H. Head, and W. W. Thatcher Pregnancy and Bovine Somatotropin in Nonlactating Dairy Cows: I. Ovarian, Conceptus, and Insulin-Like Growth Factor System Responses J Dairy Sci, October 1, 2004; 87(10): 3256 - 3267. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Guzeloglu, T. R. Bilby, A. Meikle, S. Kamimura, A. Kowalski, F. Michel, L. A. MacLaren, and W. W. Thatcher Pregnancy and Bovine Somatotropin in Nonlactating Dairy Cows: II. Endometrial Gene Expression Related to Maintenance of Pregnancy J Dairy Sci, October 1, 2004; 87(10): 3268 - 3279. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C Martin, L Pessemesse, M P de la Llosa-Hermier, J Martal, J Djiane, and M Charlier Interferon-{tau} upregulates prolactin receptor mRNA in the ovine endometrium during the peri-implantation period Reproduction, July 1, 2004; 128(1): 99 - 105. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. E. Spencer, G. A. Johnson, R. C. Burghardt, and F. W. Bazer Progesterone and Placental Hormone Actions on the Uterus: Insights from Domestic Animals Biol Reprod, July 1, 2004; 71(1): 2 - 10. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. A. Gray, D. L. Adelson, F. W. Bazer, R. C. Burghardt, E. N. T. Meeusen, and T. E. Spencer Discovery and characterization of an epithelial-specific galectin in the endometrium that forms crystals in the trophectoderm PNAS, May 25, 2004; 101(21): 7982 - 7987. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. E. Spencer and F. W. Bazer Uterine and placental factors regulating conceptus growth in domestic animals J Anim Sci, January 1, 2004; 82(13_suppl): E4 - 13. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. A. Johnson, R. C. Burghardt, F. W. Bazer, and T. E. Spencer Osteopontin: Roles in Implantation and Placentation Biol Reprod, November 1, 2003; 69(5): 1458 - 1471. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Biener, C. Martin, N. Daniel, S. J. Frank, V. E. Centonze, B. Herman, J. Djiane, and A. Gertler Ovine Placental Lactogen-Induced Heterodimerization of Ovine Growth Hormone and Prolactin Receptors in Living Cells Is Demonstrated by Fluorescence Resonance Energy Transfer Microscopy and Leads to Prolonged Phosphorylation of Signal Transducer and Activator of Transcription (STAT)1 and STAT3 Endocrinology, August 1, 2003; 144(8): 3532 - 3540. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. A. Johnson, R. C. Burghardt, M. M. Joyce, T. E. Spencer, F. W. Bazer, C. A. Gray, and C. Pfarrer Osteopontin Is Synthesized by Uterine Glands and a 45-kDa Cleavage Fragment Is Localized at the Uterine-Placental Interface Throughout Ovine Pregnancy Biol Reprod, July 1, 2003; 69(1): 92 - 98. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Noel, A. Herman, G. A. Johnson, C. A. Gray, M. D. Stewart, F. W. Bazer, A. Gertler, and T. E. Spencer Ovine Placental Lactogen Specifically Binds to Endometrial Glands of the Ovine Uterus Biol Reprod, March 1, 2003; 68(3): 772 - 780. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. D. Carpenter, C. A. Gray, S. Noel, A. Gertler, F. W. Bazer, and T. E. Spencer Prolactin Regulation of Neonatal Ovine Uterine Gland Morphogenesis Endocrinology, January 1, 2003; 144(1): 110 - 120. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. E. Garlow, H. Ka, G. A. Johnson, R. C. Burghardt, L. A. Jaeger, and F. W. Bazer Analysis of Osteopontin at the Maternal-Placental Interface in Pigs Biol Reprod, March 1, 2002; 66(3): 718 - 725. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. A. Gray, F. F. Bartol, B. J. Tarleton, A. A. Wiley, G. A. Johnson, F. W. Bazer, and T. E. Spencer Developmental Biology of Uterine Glands Biol Reprod, November 1, 2001; 65(5): 1311 - 1323. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Ka, L. A. Jaeger, G. A. Johnson, T. E. Spencer, and F. W. Bazer Keratinocyte Growth Factor Is Up-Regulated by Estrogen in the Porcine Uterine Endometrium and Functions in Trophectoderm Cell Proliferation and Differentiation Endocrinology, June 1, 2001; 142(6): 2303 - 2310. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. A. Johnson, M. D. Stewart, C. Allison Gray, Y. Choi, R. C. Burghardt, L.-Y. Yu-Lee, F. W. Bazer, and T. E. Spencer Effects of the Estrous Cycle, Pregnancy, and Interferon Tau on 2',5'-Oligoadenylate Synthetase Expression in the Ovine Uterus Biol Reprod, May 1, 2001; 64(5): 1392 - 1399. [Abstract] [Full Text]
|
|
|
|
|
|
C. Chen, T. E. Spencer, and F. W. Bazer Fibroblast Growth Factor-10: A Stromal Mediator of Epithelial Functionin the Ovine Uterus Biol Reprod, September 1, 2000; 63(3): 959 - 966. [Abstract] [Full Text]
|
|
|
|
|
|
M. D. Stewart, G. A. Johnson, C. A. Gray, R. C. Burghardt, L. A. Schuler, M. M. Joyce, F. W. Bazer, and T. E. Spencer Prolactin Receptor and Uterine Milk Protein Expression in the Ovine Endometrium During the Estrous Cycle and Pregnancy Biol Reprod, June 1, 2000; 62(6): 1779 - 1789. [Abstract] [Full Text]
|
|
|
|
|
|
G. A. Johnson, T. E. Spencer, R. C. Burghardt, K. M. Taylor, C. A. Gray, and F. W. Bazer Progesterone Modulation of Osteopontin Gene Expression in the Ovine Uterus Biol Reprod, May 1, 2000; 62(5): 1315 - 1321. [Abstract] [Full Text]
|
|
|
|
|
|
K. M. Taylor, C. A. Gray, M. M. Joyce, M. D. Stewart, F. W. Bazer, and T. E. Spencer Neonatal Ovine Uterine Development Involves Alterations in Expression of Receptors for Estrogen, Progesterone, and Prolactin Biol Reprod, April 1, 2000; 63(4): 1192 - 1204. [Abstract] [Full Text]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
