[Effect of bone marrow cells transplantation on the decidua formation in pseudopregnant rats]

One of the most common causes of the current pregnancy loss is the failure of the decidual reaction of endometrial cells. It is assumed that a partial source of decidual cells in endometrial tissue is bone marrow cells (BMCs). In the present work, we have studied possible effect of BMCs transplantation on the process of decidualization using the model of pseudopregnancy in rats. BMCs were flushed from the rat femurs and tibias. The obtained suspension of single BMCs was injected into one of rat uterine horns on the 5th day of pseudopregnancy. PBS without cells was injected into the contralateral horn served as the control. Rats were sacrificed on the 11th day of pseudopregnancy. Decidua formed in the experimental uterine horn showed an increase in the meso-antimezometral direction of their diameter of about 1.5-2 times as compared with a control horn. The weight of decidual tissue in the experimental horn exceeded 3 times the weight of the control one. The presence of transplanted BMCs in decidual tissue was documented by preliminary double staining of BMCs with membrane dye PKH 26 Red and nuclear dye Hoechst 33342. Histological analysis of decidua sections after transplantation revealed any alterations neither in cell differentiation nor in tissue structure. We conclude that BMCs transplantation stimulates decidualization in animals.

Endometrial stromal beta-catenin is required for steroid-dependent mesenchymal-epithelial cross talk and decidualization

BACKGROUND

Beta-catenin is part of a protein complex associated with adherens junctions. When allowed to accumulate to sufficient levels in its dephosphorylated form, beta-catenin serves as a transcriptional co-activator associated with a number of signaling pathways, including steroid hormone signaling pathways.

METHODS

To investigate the role of beta-catenin in progesterone (P₄) signaling and female reproductive physiology, conditional ablation of Ctnnb1 from the endometrial mesenchymal (i.e. stromal and myometrial), but not epithelial, compartment was accomplished using the Amhr2-Cre mice. Experiments were conducted to assess the ability of mutant female mice to undergo pregnancy and pseudopregnancy by or through oil-induced decidualization. The ability of uteri from mutant female mice to respond to estrogen (E₂) and P₄ was also determined.

RESULTS

Conditional deletion of Ctnnb1 from the mesenchymal compartment of the uterus resulted in infertility stemming, in part, from complete failure of the uterus to decidualize. E₂-stimulated epithelial cell mitosis and edematization were not altered in mutant uteri indicating that the mesenchyme is capable of responding to E₂. However, exposure of ovariectomized mutant female mice to a combined E₂ and P₄ hormone regimen consistent with early pregnancy revealed that mesenchymal beta-catenin is essential for indirectly opposing E₂-induced epithelial proliferation by P₄ and in some mice resulted in development of endometrial metaplasia. Lastly, beta-catenin is also required for the induced expression of genes that are known to play a fundamental role in decidualization such as Ihh, Ptch1, Gli1 and Muc1

CONCLUSIONS

Three salient points derive from these studies. First, the findings demonstrate a mechanistic linkage between the P₄ and beta-catenin signaling pathways. Second, they highlight an under appreciated role for the mesenchymal compartment in indirectly mediating P₄ signaling to the epithelium, a process that intimately involves mesenchymal beta-catenin. Third, the technical feasibility of deleting genes in the mesenchymal compartment of the uterus in an effort to understand decidualization and post-natal interactions with the overlying epithelium has been demonstrated. It is concluded that beta-catenin plays an integral role in selective P₄-directed epithelial-mesenchymal communication in both the estrous cycling and gravid uterus.

Expression of COX-1 and COX-2 in the endometrium of cyclic, pregnant and in a model of pseudopregnant rats and their regulation by sex steroids

BACKGROUND

Cyclooxygenases (COXs) are the rate limiting enzymes in the process of prostaglandins (PGs) synthesis, which are critical regulators of a number of reproductive processes, including ovulation, implantation, decidualization and parturition. The aim of the present study was to investigate the expression and regulation of COX-1 and COX-2 and levels of prostaglandins during rat pregnancy, in a model of pseudopregnancy and estrous cycle.

METHODS

Uteri were collected from the cyclic rats on each day of estrous cycle, after every two days for pregnant (days 2 to 22) and pseudopregnant rats (days 1 to 9). In vitro primary endometrial stromal cells were cultured in the presence of steroid hormones and their respective inhibitors for the possible modulation of COX-1 and COX-2. Endometrial protein extracts were used for western blot analysis and tissue sections were prepared for protein localization using immunofluorescence. Measurements of PGF2alpha and PGE2 metabolites in serum were performed by enzyme immunoassay (EIA).

RESULTS

COX-1 expression was found to be elevated during implantation and parturition, however, the levels of COX-1 decreased during decidualization periods. COX-2 was detected during early pregnancy from day 2 to 5, increased during decidual regression, and was also expressed at the time of parturition. COX-2 protein expression was found to be increased at estrus phase in cyclic rats. Both enzymes were found to be modulated in the endometrium of pseudopregnant rats, suggesting that they are regulated by 17beta-estradiol and progesterone. A significant increase in PGE2 metabolite levels was observed on day 10, 12 and 14 of pregnancy. However, an increase in PGF2alpha metabolite levels was observed only on day 14. The concentration of both these metabolites changed during pseudopregnancy and maximum levels were observed at day 7. Significant increase in PGE2 metabolite was observed at proestrus phase, on the other hand, PGF2alpha metabolite was significantly increased at proestrus and metestrus phase. COX-2 protein was regulated by 17beta-estradiol in cultured endometrial stromal cells which was blocked in the presence of ICI-182,780.

CONCLUSIONS

Taken together, these results suggest that COX-1 and COX-2 could be differentially regulated by steroid hormones and might be the key factors involved in embryo implantation, decidualization, decidua basalis regression and parturition in rats.

3beta-Hydroxysteroid dehydrogenase/5-ene-4-ene isomerase mRNA expression in rat brain: effect of pseudopregnancy and traumatic brain injury

Evidence that endogenous progesterone (PROG) is neuroprotective after traumatic brain injury (TBI) is supported by the findings that pseudopregnant female rats present less edema and achieve better functional recovery than do male rats. PROG in the nervous system may originate from steroidogenic glands or can be locally synthesized. 3beta-Hydroxysteroid dehydrogenase/5-ene-4-ene isomerase (3beta-HSD) is the key enzyme in the biosynthesis of PROG. In the present study, we investigated the effects of pseudopregnancy and TBI on brain 3beta-HSD mRNA expression and on PROG levels. Twenty-four hours after bilateral contusion of the medial prefrontal cortex of rats, 3beta-HSD mRNA expression was analyzed by in situ hybridization while PROG levels were measured by gas chromatography/mass spectrometry. Similar levels of 3beta-HSD mRNA expression were observed in males and pseudopregnant females in the non-injured groups. At this time point, there was a significant decrease in the 3beta-HSD mRNA expression in the contusion site within the frontal cortex in both males and pseudopregnant females. In all other regions analyzed, 3beta-HSD mRNA expression was not affected by TBI and there was no difference between males and pseudopregnant females. The high decrease in the expression of the 3beta-HSD mRNA in the lesion site 24 h after TBI suggests a possible decrease in locally synthesized PROG in lesion site without change in the other brain regions. This decrease has less impact in pseudopregnant females since they have high plasmatic and brain levels of PROG compared to males.

Apoptosis is not altered by clomiphene citrate in pseudopregnant rat uteri

Clomiphene citrate (CC) remains one of the most often prescribed synthetic oestrogens used in the treatment of infertility even though the ensuing pregnancy rates are low. CC alters the uterine environment on most levels. Ovariectomised rats were treated with 5 mg progesterone (P) for 3 days and a 0.5 microg injection of oestrogen (E) on the third day (PP(PE)) thus inducing pseudopregnancy and rendering the uterus receptive to implantation 24 h later. Using this model, we investigated apoptosis in the rat uterus treated with 0.25 mg CC given prior to the PP(PE) treatment. Apoptotic cells in the uterus were localised using TUNEL and visualised with a FITC marker. There was a similar increase in apoptosis in the uterine luminal epithelium in the PP(PE) and CCPP(PE) treated animals; no changes were observed in apoptosis in the other uterine compartments when compared to the control. The CCPP(PE)-treated tissue showed tall epithelial cells with long microvilli while the PP(PE) tissue had short microvilli and low cuboidal epithelium. These results suggest that CC does not disrupt the normal apoptotic activity seen at implantation, but does change the morphology of the luminal epithelium, suggesting that these cellular changes could influence successful implantation.

Expressions of VEGF and its receptors in rat corpus luteum during interferon alpha administration in early and pseudopregnancy

It is accepted that angiogenesis plays an important role in the development of the corpus luteum (CL) and is probably necessary for normal lutein cell function. A number of drugs currently being tested in clinical trials as possible angiogenesis inhibitors were not originally developed with the intention of suppressing tumor angiogenesis. Interferon alpha (IFN-alpha) is one of the notable examples of such 'accidental angiogenesis inhibitors' and daily administration of IFN-alpha is known to suppress tumor growth, tumor vascularization, and down-regulation of various growth factors. We investigated the effects of IFN-alpha treatment on the expression of vascular endothelial growth factor (VEGF), and its receptors KDR and Flt-1, and CD34 in CL during the first week of pseudopregnancy and pregnancy in hormonally induced rat ovaries by immunohistochemistry and Western blot techniques. Basal body temperatures of the drug-treated rats, as an indicator of treatment effect, were determined daily and were increased significantly when compared to controls (38.03 +/- 0.18 vs. 36.6 +/- 0.1 degrees C), respectively. The effect of IFN-alpha treatment was minimal when the entire week was evaluated, however, the expression of VEGF decreased at 3rd, 5th, and 7th days of both pregnancy and pseudopregnancy, when compared to the 1st day, whereas there was not a such alteration in the untreated rats regarding these days. The daily subcutaneous administrations of 672.500 U IFN-alpha2b had minimal effects on the expressions of VEGF, and its two receptors KDR and Flt-1 in either pregnant or pseudopregnant corpora lutea utilizing HSCORE.

Changes of ovarian microvasculature in hCG stimulated rabbits. A scanning electron microscopic study of corrosion casts

The microvasculature of the ovarian cortex was studied by means of scanning electron microscopy of vascular corrosion casts in estrous and hCG stimulated rabbits in order to establish a better understanding of the structural as well as functional vascular changes which accompany the evolution of the luteofollicular complex. According to the various shape and size seven different morphological types of vascular plexuses corresponding respectively to antral follicles (Types 1-2), atretic follicles (Types 3-4), periovulatory follicles (Type 5), growing pseudopregnant corpora lutea (Type 6) and regressing pseudopregnant corpora lutea (Type 7) were identified. Growing to mature cycling type follicles (Types 1-2) showed a gradual enlargement and proliferation of the theca capillaries. These changes, associated with capillary hyper-permeabilization were observed in ovulatory and post-ovulatory follicles (Types 5), after hCG stimulation. The corpus luteum formation (Types 6) was accompanied by additional capillary dilatation, diffuse angiogenetic sprouts and organization of a more conspicuous venous drainage. The regression of the corpus luteum (Type 7) was characterized by the appearance of avascular areas within the glandular tissue and by regression of vascular dilatation. The atretic follicle (Types 3-4) wall showed large interruptions (avascular areas) and focal invasion of the central cavity by newly formed capillaries randomly arranged. The hCG stimulation did not affect consistently the atretic follicle microvasculature. The present observation shows that both thecal capillary vasodilatation and angiogenetic processes support the gradual increase of ovarian blood flow during follicle growth and corpora lutea formation and that microvascular changes of atretic follicles are possibly related to a type of inflammatory reaction since they seem to be a consequence rather than a primary cause of atresia.

Involvement of apoptosis during deciduomal regression in pseudopregnant hamsters effect of progesterone

We determined whether fragmentation of genomic DNA, apoptosis, occurs during deciduomal regression in pseudopregnant hamsters and the effect of progesterone on the apoptotic processes. Artificially induced deciduoma were obtained on different days of pseudopregnancy and separated into mesometrial and antimesometrial tissues. The deciduomal cell cycle progression and population profiles of both sides were compared by flow cytometry. The proportion of sub-G1 peak, which was correlated with the apoptotic cells, were about 10% on day 8 and reached to 40% in both tissues on day 10. Exogenous progesterone treatment by daily injection (2 mg; s.c.) on and after day 8 reduced the percentage of low molecular weight DNA in both tissues on day 10 and day 12 as compared to the nontreated control one, respectively. The appearance of DNA ladder was also delayed at least 24 h by progesterone administration. The intensity of DNA fragmentation was more pronounced in antimesometrial deciduoma. In situ 3'-end labeling of apoptotic cells further substantiated the apoptotic process. The apoptotic cells first appeared in the luminal region in antimesometrial deciduoma on day 8 and spreaded all over the entire deciduomal tissue on day 10. Progesterone treatment stimulated deciduomal proliferating cell nuclear antigen (PCNA) expression, maintained deciduoma until day 14 and retarded the differentiation and regeneration of the uterine epithelium.

Transient induction of polycystic ovary-like syndrome in immature hypothyroid rats

Hypothyroidism in the human female is often associated with ovarian follicular cysts and hyperandrogenism, two cardinal signs of polycystic ovary syndrome. To explore the intraovarian changes that lead to follicular cyst formation in hypothyroidism, we have created a prepubertal hypothyroid rat model. These hypothyroid rats are hyperandrogenic and develop transient ovarian follicular cysts. Hypothyroidism in newborn rats was induced by providing the lactating dams with 0.04% propylthiouracil (PTU)-containing water. Subsequently, female rats were weaned and kept on PTU-containing water. On Day 25 of age, the rats were primed with 15 international units of pregnant mare's serum gonadotropin (PMSG) in 100 microl of phosphate buffered saline. Two days later, to initiate pseudopregnancy, they were injected with five international units of human chorionic gonadotropin (hCG). The animals were sacrificed at appropriate times, and blood and ovaries were collected for analyses. Control experiments were done with euthyroid rats. Two days after PMSG injection, well-developed antral follicles were observed in both the hypothyroid and euthyroid rats. Two days after hCG injection, while the euthyroid rat ovaries, as expected, contained numerous corpora lutea (CL), the hypothyroid rat ovaries still retained antral follicles. Some of these follicles with degenerating oocytes showed signs of luteinization. By 3-4 days post-hCG injection, the hypothyroid rat ovaries developed cystic follicles. By Day 6, however, the hypothyroid rat ovaries were indistinguishable from those of the euthyroid rats. Although serum testosterone concentrations were significantly elevated in the hypothyroid rats on Days 1-3, progesterone concentrations were not significantly different from the euthyroid animals. However, by Days 8-14, the hypothyroid rats had significantly higher serum progesterone concentrations. This model will be useful for investigating the intraovarian biochemical changes that lead to follicular cyst development in response to acute gonadotropin treatment.

Estradiol-mediated suppression of apoptosis in the rabbit corpus luteum is associated with a shift in expression of bcl-2 family members favoring cellular survival

In the rabbit, estradiol is the primary luteotropic hormone. Estradiol withdrawal results in a rapid decline in serum progesterone and eventually in corpus luteum (CL) regression. The objective of this study was to determine whether estradiol modulates luteal cell apoptosis. In the first experiment, rabbits were randomly assigned to one of five experimental groups. An empty capsule (control) or estradiol-filled Silastic capsule was inserted s.c. on Day 0 of pseudopregnancy (day of hCG administration). On Day 11 of pseudopregnancy, some of the group I (control) and group II (estradiol capsule) rabbits were subjected to laparotomy, and one ovary from each rabbit was perfused in vitro to determine progesterone secretion rates. The CL from the contralateral ovary were dissected, snap-frozen, and stored at -70 degrees C until analyzed for internucleosomal DNA cleavage (apoptosis). Estradiol-containing capsules were removed from some of the remaining rabbits on Days 8, 9, and 10 to initiate estradiol deprivation. Rabbits were then subjected to laparotomy 24, 48, or 72 h after capsule removal (groups III, IV, and V, respectively), and ovaries or CL were processed as described above. Deprivation of estradiol for 24 (group III), 48 (group IV), or 72 (group V) h in vivo reduced in vitro progesterone secretion rates by more than 90% as compared to that in ovaries collected from estradiol capsule-intact animals. After in vivo endogenous estradiol suppression, withdrawal of exogenous estradiol resulted in luteal cell apoptosis, which increased in a time-dependent manner. Northern blot analysis revealed an increase in bax mRNA levels and a decrease in bcl-x mRNA levels coincident with luteal cell apoptosis induced by estradiol withdrawal. These data demonstrate that changes in progesterone production caused by estradiol exposure and deprivation are in part related to luteal cell apoptosis, and alterations in the expression of bcl-2 gene family members may be one of the mechanisms by which estradiol exerts its luteotropic effect in the rabbit CL.

The human corpus luteum: reduction in macrophages during simulated maternal recognition of pregnancy

It has been shown that immune cells, particularly macrophages, accumulate in the corpus luteum during luteolysis. This study aimed to investigate the effect of maternal recognition of pregnancy on the localization and numbers of macrophages in the human corpus luteum. Corpora lutea (n = 12) were obtained from normally cycling women at the time of hysterectomy and were dated on the basis of serial urinary luteinizing hormone (LH) estimation. In addition, corpora lutea (n = 4) were collected from women who had received daily doubling doses of human chorionic gonadotrophin (HCG) to mimic the hormonal changes of early pregnancy. Macrophages were localized by immunohistochemistry using an anti-CD68 antibody. Steroidogenic cells, steroidogenic cells of thecal origin and endothelial cells were identified on serial sections by immunohistochemistry for 3beta-hydroxysteroid dehydrogenase, 17alpha-hydroxylase and von Willebrand factor, respectively. The luteal cells capable of responding directly to HCG were identified by isotopic in-situ hybridization for messenger RNA encoding LH/HCG receptors. Macrophages were localized primarily to the vascular connective tissue and theca-lutein areas of the corpus luteum, although some were found in the granulosa-lutein cell layer. Macrophage numbers increased throughout the luteal phase to a maximum in the late-luteal phase (P < 0.05). Luteal 'rescue' with HCG was associated with a marked reduction in the numbers of tissue macrophages when compared with those of the late-luteal phase (P < 0.001). One of the effects of HCG during maternal recognition of pregnancy is to prevent the normal influx of macrophages into the corpus luteum. As LH/HCG receptors localized to the steroidogenic cells, this implies a fundamental role for steroidogenic cell products in the control of macrophage influx into the human corpus luteum.

Reproductive condition and the low-dose endotoxin-induced inflammatory response in rats. Glomerular influx of inflammatory cells and expression of adhesion molecules

These experiments were designed to study the increased sensitivity of pregnant rats to endotoxin. Pregnant (Pr), cyclic (C), and progesterone (P)-treated pseudopregnant rats with or without a decidualized uterus (PSP and DEC rats, respectively) received infusions of an ultra-low dose of endotoxin (1.0 microg/kg BW) and were killed 3 days later. Pr, PSP, and DEC rats were infused on Day 14, C rats on diestrus. Endotoxin-infused rats were compared with saline-infused rats in the same reproductive conditions. The inflammatory reaction of the glomeruli of the kidneys was studied by immunohistochemical methods using 4-microm cryostat sections stained with specific monoclonal antibodies against neutrophils (polymorphonuclear cells, PMNs) and monocytes (MOs), and against the adhesion molecules ICAM-1 and VCAM-1 on the endothelium, and LFA-1, MAC-1, and VLA-4 on the leukocytes. Endotoxin infusion increased glomerular PMN and MO number in Pr, PSP, and DEC rats, all of which have elevated P levels, but not in C rats, which do not. The endotoxin-induced expression of adhesion molecules, associated with this influx of inflammatory cells, varied with the reproductive condition. In C rats there was no increased adhesion molecule expression after endotoxin treatment, in Pr rats there was increased expression of both the combinations ICAM-1/LFA-1 and VCAM-1/VLA-4. DEC rats did not express either of these combinations (although there was expression of ICAM-1); PSP rats expressed the combination ICAM-1/MAC-1. Adhesion molecule expression thus seems to be regulated by ovarian (e.g., P) and placental factors (e.g., of trophoblastic and decidual origin). Because the different combinations of adhesion molecules in the various reproductive conditions after exposure to endotoxin led to more or less the same leukocyte influx under these conditions, the increased sensitivity to endotoxin of pregnant individuals cannot be reduced to differences in leukocyte influx into the glomeruli.

Estrogen withdrawal induces macrophage invasion in the rabbit corpus luteum

Macrophages within the corpus luteum are associated with spontaneous luteal regression in a number of species. However, an understanding of the consequences of macrophage recruitment on the functional capacity and responsiveness of the luteal tissue has remained elusive. Here we investigate the temporal appearance of macrophages and their potential impact in corpora lutea of rabbits, in which a rapid fall in progesterone synthesis and premature regression of the corpus luteum are initiated by withdrawal of the luteotropic hormone estradiol-17beta. Removal of estradiol implants, placed subcutaneously, induced a significant increase in the average number of macrophages per high-power field (hpf) in corpora lutea (p < 0.05) within 72 h. Replacement of the estradiol implants 48 h after their removal resulted in a marginal rebound of plasma progesterone and a variable number of luteal macrophages (range: 6-160 macrophages/hpf) among the 11 rabbits. A third experiment revealed that the relative numbers of macrophages within the corpora lutea have no apparent relationship to rates of progesterone synthesis in vitro: progesterone production (ng/mg tissue) did not differ (p > 0.05) between corpora lutea of estradiol-maintained rabbits and those of estradiol-replaced rabbits despite obvious differences in numbers of luteal macrophages (2 +/- 1 vs. 42 +/- 10 macrophages/hpf, respectively; p < 0.05). We conclude that the entry/recruitment of macrophages into the rabbit corpus luteum is sensitive to the luteotropic hormone estradiol-17beta and that the presence of macrophages does not preclude the continuation of progesterone production in surviving luteal tissue revitalized after estradiol removal/replacement.

The angioarchitecture of estrous, pseudopregnant and pregnant rabbit ovary as seen by scanning electron microscopy of vascular corrosion casts

Ovarian angioarchitecture was studied by scanning electron microscopy of vascular corrosion casts in estrous, pseudopregnant (stimulated with human chorionic gonadotropin) and pregnant rabbits. In all samples, the proper ovarian branch of the ovarian artery (ramus ovaricus) entered the ovarian hilus near the caudal pole of the organ and ran parallel to the major axis of the hilus. The extraovarian venous drainage was formed by several vessels emptying into a distal large vein. The ramus ovaricus exhibited various degrees of coiling and branched in the medulla. The coiling of the ramus ovaricus and its ramifications were maintained in all samples. A venous meshwork and/or flat vein branches closely enveloped the arterial coils found in the hilus and outer medulla. At this level numerous arteriovenous contacts were demonstrated in all samples. The coiled arteries, prior to entering the ovarian cortex, supplied several small peripheral follicles which were drained by the hilar veins. In the cortex the coiled arteries branched in numerous thin, straight or slightly undulated arterioles which supplied developing estrous follicles and pseudopregnant corpora lutea. The arterioles supplying the pregnant corpora lutea were long, large and tightly spiraled. The venous drainage followed the modifications of the arterial supply. These data demonstrate that ovarian cycle and pregnancy induced significant changes in the cortical vessels, which adapted their structure to the temporary functional needs of the recruited follicles or corpora lutea. Hilar and medullary vessels have permanent structures that may represent morphological devices for (a) a continuous control of the blood flow (spiral arteries) and (b) a local recirculation of endocrine products (arteriovenous contacts) comparable to the "countercurrent mechanism" previously shown to operate in ovaries of other species, but not yet found in rabbits.

Prolactin expresses differential effects on apoptotic cell death of luteal cells in vivo and in vitro

PRL surges in female rats have dual effects of luteal function: either inducing luteolysis during the estrous cycle or rescuing and maintaining luteal function during pseudopregnancy. We analyzed these apparent contradictory effects in relation to apoptosis. The detection of fragmented DNA and in situ 3'-end labeling studies were done on corpora lutea (CL) collected from cycling rats at proestrus 1800 h (P1800 specimen) or pseudopregnant rats on day 6 (psp 6). Distinct DNA ladders were observed in P1800 samples as we previously reported, but only slight ones were found in psp 6 specimen. The effect of PRL on the induction of apoptosis was evaluated in vitro with dispersed luteal tissue. CL from cycling rats were exempted from a PRL surge by pre-treating donors with a dopamine agonist. The extent of apoptotic reaction in P1800 specimen depended on the doses of PRL added to the culture medium. In psp 6 specimen, in contrast, PRL suppressed the apoptotic reaction, increased the cell survival rate (MTT assay), and decreased the cell death rate (LDH assay). Furthermore, PRL enhanced 20 alpha-hydroxysteroid dehydrogenase activity in P1800 specimen but suppressed it in psp 6 specimen. In summary, PRL in rats is either an apoptosis-inducer or -suppressor, depending on the functional state of luteal cells.

Leucocyte binding to the uterine epithelial cell surface during lectin-induced decidualization

Intra-uterine injection of the lectin Concanavalin A (ConA) on day 5 of pseudopregnancy induced a rapid and persistent infiltration of leucocytes into the rat uterine stroma. Although the infiltration of leucocytes was seen along the entire length of the uterine horn, areas of stromal oedema, indicative of decidualization (as indicated by a positive Pontamine Sky Blue reaction), were only associated with regions in which leucocytes had crossed the uterine epithelium and were present in the uterine lumen. Ultrastructural evaluation of the interaction of the luminal leucocytes with the apical surface of the uterine epithelium appeared strikingly similar to that of the blastocyst and the uterine epithelium during normal implantation. It is proposed that leucocytes, induced by ConA, may initiate a decidual response in a manner analogous to that of the blastocyst through surface epithelial interaction.

Normal and malignant trophoblasts do not recruit granulated metrial gland cells

A possible relationship between the development of granulated metrial gland (GMG) cells and trophoblast was studied. Trophoblast implanted in ectopic sites (e.g. kidney capsule) did not induce decidua and did not recruit GMG cells. Only when injected in utero did trophoblast lead to the development of decidua and to the recruitment of GMG cells. With malignant trophoblast (choriocarcinoma cells) similar results were obtained as with normal trophoblast both after ectopic or after in utero injection. The presence of decidua, but not the development of a conceptus or the outgrowth of trophoblast, seems to be required for the differentiation of GMG cells.

Effects of splenectomy on luteolysis in pseudopregnant rabbits

The effects of splenectomy on luteolysis in pseudopregnant rabbits were observed. Pseudopregnancy was induced in the rabbits by mating with vasoligated mature males and injection of human chorionic gonadotrophin (D0). In these rabbits, the concentration of serum progesterone increased for 7 days after the induction of pseudopregnancy. In the control group (sham-operation), the concentration of serum progesterone returned to the level of the pre-ovulatory levels by 14 days of pseudopregnancy. On the other hand, in the splenectomized group, in which splenectomy was performed at D7, the serum progesterone concentration was maintained at the level of the functional luteal phase (D7) at least until 21 days of pseudopregnancy. These findings indicate that the spleen is concerned with luteolysis of the rabbit.

Morphometric evidence of changes in the vasculature of the uterine tube of mice induced by the 2-cell embryo on the second day of pregnancy

Some evidence suggests that the uterine tube plays an active role in supporting the development of the preimplantation embryo. To determine whether there were morphological and/or ultrastructural changes in the uterine tube as a consequence of pregnancy, the region of the uterine tube containing 2-cell embryos or oocytes was examined in untreated d 2 pregnant and pseudopregnant mice. The general morphology of the uterine tube was assessed by light and electron microscopy. Qualitative assessment of uterine tube morphology suggested that although the epithelium and muscular layers of the oviduct were similar in pregnancy and pseudopregnancy there were differences in the vasculature between the 2 groups. In transverse sections of the uterine tube, cross-sectional vascular surface area was assessed morphometrically. There was a statistically significant decrease (P < 0.001) in the cross-sectional vascular surface of the oviduct in pregnant mice compared with pseudopregnant mice. This reduction was apparently due to (1) a decrease in the median cross-sectional surface area of small intramural blood vessels, and (2) an apparent collapse of many subepithelial capillaries. Pregnant mice also had fewer fenestrated capillaries whereas such vessels were common in pseudopregnancy. Activated, aggregated platelets were only observed in the capillaries and venules of pregnant, untreated mice. Some animals were treated with 10 micrograms WEB 2086/day on d 1 and d 2, a platelet-activating factor receptor antagonist. This treatment reversed the reduced vascular surface cross-sectional area found in early pregnancy, but had no effect on vascular measurements in pseudopregnancy.

Progesterone facilitates cognitive recovery and reduces secondary neuronal loss caused by cortical contusion injury in male rats

The ability of progesterone to reduce the cerebral edema associated with traumatic brain damage first became apparent when we observed that males had significantly more edema than females after cortical contusion. In addition, edema was almost absent in pseudopregnant female rats, a condition in which progesterone levels are high relative to estrogen. Progesterone injections given after injury also reduced edema and were equally effective in both males and females. The present experiment was done to determine if the progesterone-induced reduction in edema could also prevent secondary neuronal degeneration and reduce the behavioral impairments that accompany contusion of the medial frontal cortex. Progesterone-treated rats were less impaired on a Morris water maze spatial navigation task than rats treated with the oil vehicle. Progesterone-treated rats also showed less neuronal degeneration 21 days after injury in the medial dorsal thalamic nucleus, a structure that has reciprocal connections with the contused area.

Lectin-induced deciduoma formation in the pseudopregnant rat

Decidual cell induction in the pseudopregnant rat was examined in this study using the lectin concanavalin A (ConA). The histochemical binding of the lectin to the uterine cell surface at the time of deciduomatic induction was also studied. ConA was found to induce significant deciduomata (decidual-like tissue) in the uterine horn when injected intraluminally on day 5 of pseudopregnancy (PSP). ConA-induced deciduomata appeared as a series of discrete nodules in the uterine horn, reminiscent of the anatomical appearance of normal embryo implantation sites. Deciduoma induction by ConA was greatly reduced by pre-absorption of the lectin with its competitive sugar. Lectin histochemistry revealed binding of ConA to the cell surface on day 5 of PSP. Pre-absorption of the lectin with its competitive sugar also significantly reduced surface binding of the lectin, and this finding may be correlated with the greatly reduced ability of the pre-absorbed lectin to induce deciduomata. Possible mechanisms for the induction of deciduomata by lectins are considered.

The chronic intracerebroventricular infusion of interleukin-1 beta alters the activity of the hypothalamic-pituitary-gonadal axis of cycling rats. II. Induction of pseudopregnant-like corpora lutea

The acute administration of interleukin-1 beta (IL-1 beta) into the brain ventricles of rats has been shown to cause a significant decrease in plasma LH levels, a phenomenon primarily mediated through inhibition of LHRH release. However, there are no studies of the long-term consequences of IL-1 beta injected intracerebroventricularly on the hypothalamic-pituitary-gonadal axis. In particular, we became interested in determining whether IL-1 beta exerts deleterious effects on reproductive parameters, and to what extent they might be caused by a lowering of circulating gonadotropins. In the present experiments, we therefore investigated the effects of the infusion of IL-1 beta to intact cycling female rats and compared them to those observed in rats injected with a potent LHRH antagonist. Although blockade of LHRH receptors caused a modest and delayed inhibition of progesterone secretion, infusion of IL-1 beta (4 ng/h for 4-6 days) was accompanied by persistent and significant increases in plasma P4 levels. In these rats, the PRL release was erratic, with low values during the morning and generally extremely elevated values during the night. The volume of the corpora lutea-I (CL-I) of rats exposed to IL-1 beta, but not to the vehicle or the LHRH antagonist, was significantly increased, and the lutein cells showed extensive hypertrophy. These results indicate that prolonged infusion of IL-1 beta into the brain of cycling rats blocks luteolysis in newly formed CL. These changes were not present in rats injected with the LHRH antagonist, suggesting that they were not primarily related to decreases in gonadotropin secretion. We propose that the high plasma PRL levels may play a role in the changes in ovarian activity which we observed, through other mechanisms, such as sustained increases in adrenal epinephrine and/or glucocorticoids, may also be involved. These findings indicate a novel role for central IL-1 beta in the prevention of luteolysis and the transformation of the CL of the cycle into a CL of pseudopregnancy.

Changes in rabbit corpus luteum progesterone secretion and cellular morphology following unilateral luteectomy or ovariectomy

The objective of this study was to determine whether removal of corpora lutea (CL) from one ovary (unilateral luteectomy; ULL) or removal of the entire ovary (unilateral ovariectomy; ULO) of pseudopregnant rabbits would cause compensatory growth and progesterone production by the contralateral ovary. Pseudopregnancy was induced in rabbits with hCG (Day 0). On the first day of pseudopregnancy, one group of rabbits received a sham operation (controls), another group underwent ULL, and a third group underwent ULO. On Day 11 of pseudopregnancy, each rabbit underwent laparotomy, the ovarian artery and vein were cannulated, and the ovary(ies) was removed and perfused in vitro for 6 h. The mean CL weight increased by 33% in the ULL group and by 28% in the ULO group as compared to sham-operated controls. Peripheral estradiol and progesterone levels in sham-operated control, ULL, and ULO groups were similar. Ovarian venous estradiol levels were similar in the control and ULL groups, but were significantly increased in the remaining ovary of the ULO group. Both ovarian venous progesterone in vivo and progesterone secretion in vitro increased significantly in contralateral ovaries from ULL and ULO rabbits as compared to sham-operated controls. Progesterone secretion by ovaries perfused in vitro increased significantly in the contralateral ovary of the ULL and ULO groups. Mean number of luteal cells per CL increased significantly in the ULL group, but not in the ULO group. In contrast, luteal cell volume increased significantly in the ULO, but not in the ULL group. The stimuli responsible for increased progesterone production following ULL and ULO result in morphological changes in the remaining CL.(ABSTRACT TRUNCATED AT 250 WORDS)

Leukocyte distribution in the pseudopregnant mouse uterus

Pseudopregnancy, induced by mating females with vasectomized males, is a frequently used model for studying pregnancy-like uterine changes in the absence of an embryo. Leukocytes make a significant contribution to uterine cellularity during pregnancy. The present study was designed to determine whether changes in numbers and distribution of leukocytes in the uterus during pseudopregnancy and following intraluminal injection of a deciduogenic stimulus parallel changes observed during the first eight days of pregnancy. Common leukocyte antigen positive (CLA+) cells, macrophages (F4/80+ cells), and granulocytes were assessed between days 1 and 8 of pseudopregnancy using qualitative and quantitative immunohistochemistry. High numbers of CLA+ leukocytes were present on days 1 and 2. Those were comprised primarily by macrophages, polymorphonuclear leukocytes, and eosinophils. High concentrations of leukocytes were detected in the endometrium, and some granulocytes were observed migrating through the luminal epithelium. Leukocytes, principally macrophages, were reduced in number and were distributed throughout the endometrium on days 3 and 4. Introduction of oil to the uterine lumen on day 4 stimulated primary decidualization. Decidual cells were CLA- and F4/80-, and, as decidualization proceeded, CLA+ and F4/80+ cells decreased in number in the anti-mesometrial uterus and were detected primarily in the deep endometrium. Later, a secondary decidualization zone developed in the mesometrial aspect of the uterus. Unlike the initial decidual reaction, which was relatively free of leukocytes, the secondary decidual zone contained very high numbers of CLA+ and F4/80+ cells. The uninjected uterine horn remained relatively unchanged from days 3 through 8.(ABSTRACT TRUNCATED AT 250 WORDS)

The direct luteotropic effect of tokishakuyakusan in rats

The effect of Tokishakuyakusan (TS) on the corpus luteum function in pseudopregnant rats was examined in vivo. On day 4 of pseudopregnancy (PSP), induced by cervical stimulation, TS (20 micrograms) stimulated the progesterone secretion rate (PSR) in the ovarian venous plasma. There was also a significant increase in the rate of progesterone to 20 alpha-OH-progesterone. However, on day 8 of PSP, there was no apparent change in PSR in the ovarian venous plasma after the administration of TS. These data suggest that the sensitivity to TS of the corpus luteum varies according to its age.

Deciduomal estrogen and progesterone receptors in unilateral pregnant hamsters

Deciduomal reactions in response to artificial stimuli were induced on the tube-ligated uterine horns of unilateral pregnant hamsters. Serum progesterone levels were determined, and the changes of estrogen and progesterone receptors (ER and PR, respectively) were simultaneously studied in the deciduoma. After stimulation on day 4 of pregnancy (D4), the serum progesterone level rose steadily to about 16 ng/ml on D12 and remained at plateau until D14. A sharp increase followed by a rapid fall in progesterone was observed on D15 and D16. The weight of the deciduoma-bearing horn increased more than 5 times to a maximal level on D10. Both deciduomal and myometrial weights were maintained and remained elevated on D16. Histological observation revealed that the maintenance of decidual cells was heterogenous. Cells at antimesometrial site (AMS) started to regress on D10, whereas cells at mesometrial site (MS) remained recognizable on D16. Cytosol ER was detected during the early stage (D6) of decidualization. The cytosol ER in the deciduoma continuously decreased and became undetectable on D10. Nuclear ER was not detected during the time of study. The nuclear and cytosol PR increased and reached a peak level on D8 and D10, respectively. The concentration of PR declined sharply afterward. The PR levels in deciduomal tissues at MS and AMS were separately studied. PR in AMS decreased gradually after D8 to basal level on D14. PR at MS still remained relatively constant on D12 followed by a precipitous decrease. These data show a prolongation of the deciduomal life span and the heterogeneity of deciduomal maintenance and regression in unilateral pregnant hamsters. This strongly suggests a close relationship between the loss of PR and the regression of the deciduoma.

Biochemical evidence for programmed cell death in rabbit uterine epithelium

Uterine epithelial cell proliferation, differentiation, and death are known to be regulated by estrogen and progesterone. The authors investigated a specific pattern of cell death called apoptosis, or programmed cell death, which is biochemically characterized by a specific pattern of DNA degradation. DNA isolated from endometrium of ovariectomized pseudopregnant rabbits showed a pattern of DNA cleavage at internucleosomal locations. In comparison, DNA from the endometrium of non-ovariectomized animals, as well as several other organs, did not exhibit that pattern. This biochemical evidence supports previous and present morphologic data and correlates with it. Under the experimental conditions used, only the uterine epithelial compartment of the endometrium shows apoptotic cell death, which is absent in the stromal compartment.

Quantitative light microscopic analysis of corpus luteum growth during pseudopregnancy in the rabbit

We employed stereological methods at the light-microscope level to examine the mechanism by which corpora lutea (CL) grow during the course of pseudopregnancy in the rabbit. Corpus luteum volume per ovary, the absolute volume of luteal cells per CL, individual luteal cell volume, the number of luteal and endothelial cells per CL, and capillary surface area per CL were examined in rabbits at Days 1, 4, 7, 11, and 18 of pseudopregnancy. Total CL volume increased from 3.7 +/- 0.1 microliter to 30.3 +/- 0.5 microliter over Days 1 to 11 and thereafter decreased to 15.2 +/- 1.1 microliter by Day 18. Stereological analyses showed that the increases in CL volume from Day 1 to Day 11 were due primarily to increases in the volume of individual luteal cells (from 2.6 +/- 0.2 pl on Day 1 to 23.5 +/- 1.7 pl on Day 11, 1 pl = (10 mu)3; r = 0.96), and that the decrease in CL volume after Day 11 resulted largely from a decrease in luteal cell volume (to 12.8 +/- 1.5 pl). In contrast, no change was seen in the number of luteal cells per CL (range 9.1 x 10(5)-12.5 x 10(5)). These data show that CL growth and subsequent regression during pseudopregnancy result primarily from changes in the volume of individual luteal cells, and not from changes in the number of luteal cells. These data support the hypothesis that modulation of progesterone production during pseudopregnancy is due to changes in individual luteal cell volume and not to changes in cell number.

The morphology of cultured cells from the mouse endometrium and decidua

Single cell preparations were obtained from the endometrium of virgin and pseudopregnant mice as well as Day 5 and Day 8 deciduomata and were maintained in culture for periods of one to ten days. Three cell types, believed to be stromal cells, epithelial cells and macrophages, were identified in cultures prepared from virgin and Day 3 pseudopregnant uteri. Two further cell types, believed to represent mesometrial and antimesometrial decidual cells, were identified in cultures of cells from deciduomata. Granulated metrial gland cells were rarely seen, even in cultures of Day 8 deciduomata cells. Morphological changes in the cultured cells occurred with time and this was particularly evident in the cells believed to be derived from endometrial stromal cells and decidual cells. It is suggested that this represents in vitro growth of the cells which is independent of in vitro decidualization.

Rabbit endocervical epithelium: morphometric analysis of secretory cell populations

In this report we quantitated ultrastructural changes in two cytologically distinct secretory cell populations from the rabbit endocervix. Type I and type II cells from estrous animals differ only in the presence of one or more empty cytoplasmic vacuoles in type II cells. Comparing type II cells from 5-day pseudopregnant (PSP) rabbits with type II cells from estrous controls, there is no increase (P greater than .05) in the average vacuole volume. When type I and type II cells from PSP animals are compared to cells from estrous controls, there is a decrease (P less than .01) in the average cell volume, a decrease (P less than .01) in the average nuclear volume, and a decrease (P less than .01) in the average granule volume. This reduction in the granule content of secretory endocervical cells was correlated with a dramatic decrease in protein glycosylation into the microsomal fraction. Serum estradiol concentrations for estrous (13.7 +/- 1.0 pg/ml) and PSP (18.1 +/- 1.5 pg/ml) animals were comparable. However, the 36-fold increase in serum progesterone concentrations for PSP (12.04 +/- 1.7 ng/ml) animals compared to estrous (0.33 +/- 0.1 ng/ml) animals may be responsible for the decrease in protein glycosylation.

Size distribution and hormonal responsiveness of dispersed rabbit luteal cells during pseudopregnancy

Due to the evidence for two distinct steroidogenic cell types in corpora lutea of large domestic animals, cells of the rabbit corpus luteum were characterized with respect to cell diameters, relative abundance, steroidogenic capacity and responsiveness to hormones. Pseudopregnancy was induced in New Zealand rabbits by injection of 30-160 IU pregnant mare's serum gonadotropin (PMSG) followed in 2-4 days by an i.m. injection of 20-35 micrograms gonadotropin-releasing hormone (GnRH). Corpora lutea were obtained 2, 5 and 9 days after injection of GnRH and dissociated into single cell suspensions. Suspended steroidogenic cells were incubated (2 h, 37 degrees C) in medium 199 alone or in medium containing ovine luteinizing hormone (oLH) (100 ng/ml), or isoproterenol (100 microM). Media were collected and assayed for progesterone content. Secretion of progesterone (means +/- SE, n = 4) was stimulated (p less than 0.05) by oLH on each day: Day 2 = 1.7 +/- 0.2-fold; Day 5 = 3.5 +/- 0.4-fold; and Day 9 = 3.1 +/- 0.6-fold stimulation above controls. Isoproterenol also stimulated (p less than 0.05) secretion of progesterone by suspended luteal cells on Days 2 and 9. Microscopic examination of cell suspensions stained for 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) activity provided identification of cells with steroidogenic capacity. The diameters (means +/- SE) for steroidogenic cells increased (p less than 0.05) from Days 2 to 9 (Day 2 = 15.2 +/- 0.2 micron; Day 5 = 22.4 +/- 0.4 micron; Day 9 = 28.3 +/- 1.6 micron). The large cell to small cell ratio increased from 0.01 on Day 2 to 2.03 on Day 9.(ABSTRACT TRUNCATED AT 250 WORDS)

Stage-specific alterations in the apical membrane glycoproteins of endometrial epithelial cells related to implantation in rabbits

The rabbit endometrial epithelium undergoes differentiation prior to the time of blastocyst implantation, including loss of surface negativity and a change in glycocalyx morphology. Nonpregnant (estrous) and pseudopregnant rabbits were used to study specific alterations in proteins and saccharide composition of the luminal epithelial membrane and its glycocalyx related to the acquisition of receptivity to implantation. Pregnant animals were used to study further modification of the luminal surface by implanting blastocysts. The apical surface of luminal epithelial cells was solubilized by a 15-min intraluminal incubation of 1% Triton X-100 containing protease inhibitors. Proteins in extract solutions were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Three new polypeptides (24 kDa, 42 kDa and 58 kDa) were identified in uteri from receptive rabbits. Binding of succinyl Wheat Germ Agglutinin (sWGA) and Ricinus communis Agglutinin (RCA-I) lectins to the 24 kDa and 42 kDa components on Western blots of extracts separated by SDS-PAGE identified them as glycoproteins. Additionally, other polypeptides (26 kDa, 80-86 kDa and 145 kDa) showed changes in affinity for WGA, RCA-I or concanavalin A (Con A), depending on the hormonal state. Correlating with these findings was an increased binding of these lectins to intact nonciliated cells in uteri of receptive rabbits compared to estrous animals; ciliated cells bound Dolichos biflorus Agglutinin (DBA) specifically, regardless of the hormonal condition. Treatment of uteri from estrous animals, or Western blots of proteins from these animals, with neuraminidase prior to lectin exposure suggested the presence of glycoproteins having a sialic acid-D-galactose terminus in nonreceptive rabbits. Reduced binding of lectin to intact cells at implantation sites and to blots of proteins isolated from these sites, compared to nonimplantation sites, was noted. These results provide evidence for stage-specific alterations in protein and saccharide composition of the apical surface of endometrial epithelium prior to implantation, and indicate that implanting blastocysts further modify the luminal surface.

Regeneration of the uterine epithelium in later stages of pseudopregnancy in the rabbit. An ultrastructural study

Morphological changes of the uterine epithelium in later stages of pseudopregnancy in the rabbit have been studied using different morphological methods. The highly proliferated mucosa with numerous symplasms of a pseudopregnant animal returns to the morphology of a nonpregnant animal by apoptosis, moderate necrosis and lytic transformation of symplasms back to typical endometrial cells without desquamation of cells. The first signs of lytic transformation are observed on Day 8 of pseudopregnancy. Enhanced regeneration with apoptosis and lysis of the symplasmic nuclei is observed between Day 14 and Day 16. Full restoration of the epithelium with reappearance of ciliated cells, typical columnar and partly mucified epithelial cells is not completed earlier than Day 24 p. hCG. This epithelium, however, differs clearly from the epithelium of a virgin rabbit due to several residues of epithelial transformation. Thus, from a morphological point of view, pseudopregnancy in the rabbit lasts up to or even longer than Day 28 p. hCG with persisting ultrastructural remnants of the preceding cycle.

Morphology and morphometry of the rabbit uterus during pseudopregnancy

Morphometry was carried out on the luminal epithelium of the rabbit uterus from oestrus to day 21 of pseudopregnancy. This indicated that syncytia increased in size until day 18, after which a rapid reduction occurred with approximate oestrous dimensions being restored on day 21. Involution of syncytia took place in two overlapping stages with reduction in nuclear numbers occurring from day 12 onwards, followed by loss of cytoplasm mainly after day 18. Ciliated cells predominated at oestrus and day 21 but were sparse at other times. When ciliated cells were plentiful, they were concentrated on the tops of the mucosal folds.

An autoradiographic study of rabbit ovarian surface epithelium before and after ovulation

Morphologic studies suggest that the proliferative activity of the ovarian surface epithelium (OSE) may vary during the reproductive life cycle. To further investigate this phenomenon, rabbit ovaries obtained before and after induction of ovulation with human chorionic gonadotropin (hCG) were incubated in medium containing 3H-methylthymidine and processed for autoradiography. Before ovulation, the labeling index (LI) of OSE cells varied from 0.04% to 0.22%. Twelve hours after hCG, the maximal LI (9.02 +/- 0.38%) was seen in OSE cells adjacent to the ovulatory stigma. The LI remained elevated at Days 1 and 5 post-hCG in OSE cells overlying corpora lutea. At Day 12, numerous papillary processes were observed at the apex of each corpus luteum. The maximal LI (16.44 +/- 1.31%) had now shifted to the OSE cells covering these processes. Eighteen days after hCG stimulation, the LI of OSE cells near the corpora lutea had returned to preovulatory levels. A slight increase in the LI of OSE cells not associated with ovulatory sites was also observed after ovulation. This study shows that a significant fraction of OSE cells undergoes DNA synthesis throughout most of the postovulatory period.

Granulated metrial gland cells in the lungs of mice in pregnancy and pseudopregnancy

A study has been made, using light microscopy, of GMG cells in the lungs of pregnant mice and pseudopregnant mice with deciduomata. GMG cells are found in the lungs from Day 8 to Day 17 of pregnancy and are mainly located in the interalveolar septa. The temporal relationship between GMG cells in the lungs and GMG cells in the blood vessels of the decidua basalis and metrial gland suggests that the GMG cells in the lungs are migrants from the uterus. The presence of GMG cells in the lungs is considered in relation to the possibility that a site of functional importance to this cell type is the labyrinthine placenta. GMG cells are found in the uterine blood vessels and lungs of pseudopregnant mice with deciduomata. This finding suggests that the migration of GMG cells is under the influence of the mother rather than under the control of factors derived from the fetal allograft.

Transient development and function of rabbit corpora lutea after hypophysectomy

The requirement of the pituitary gland and the role of 17 beta-estradiol in the early development of the corpus luteum was investigated in rabbits hypophysectomized the day after sterile mating (day 1). Serum progesterone in hypophysectomized rabbits was normal for 2 days after hypophysectomy. Luteal tissue from hypophysectomized and sham-hypophysectomized rabbits had similar wet weight (4.0 +/- 0.4 vs. 5.3 +/- 0.2 mg/corpus luteum) and similar concentrations of available cytoplasmic estrogen receptor (1.2 +/- 0.2 vs. 1.5 +/- 0.3 fmol/micrograms DNA) and luteinizing hormone (LH) receptor (4.0 +/- 0.2 vs. 6.1 +/- 1.4 fmol/micrograms DNA) on day 4 of pseudopregnancy. Serum progesterone in hypophysectomized rabbits began to decline on day 4 and was undetectable by day 6. Estrogen receptor and luteal weight in hypophysectomized animals also declined after day 4 to low values by day 6, and serum estradiol was undetectable. However, if estradiol was administered by Silastic capsule implanted subcutaneously at the time of hypophysectomy or 3 days after hypophysectomy, serum progesterone, luteal weight, estrogen receptor, and LH receptor were maintained on day 6 of pseudopregnancy. These results indicate that after a preovulatory gonadotropin surge, the function of newly formed corpora lutea is normal for 3-4 days in the absence of pituitary hormones. However, by 4 days after ovulation, estradiol is required to sustain the structural and functional integrity of corpora lutea.

The effects of pelvic neurectomy on collagen in the cervix of the pseudopregnant rat

Bilateral section of the pelvic parasympathetic nerves (pelvic-neurectomy) on day 5 of pseudopregnancy had no effect on the wet weight of ovaries, uteri, and/or cervices, but at day 9 serum progesterone was reduced to approximately half that of sham-operated animals. Collagen in the cervix was visualized with picrosirius red staining under polarization microscopy. Pelvic neurectomy decreased the birefringence of Type 1 collagen in the cervix to less than half that of sham operated animals. The decreased birefringence, an index of the organization of collagen fibers, is believed to be attributable to reduced progesterone levels. Alternatively, the pelvic nerve may directly influence mucopolysaccharides or collagenolytic enzymes in the cervix.

Alterations in epithelial glycocalyx of rabbit uteri during early pseudopregnancy and pregnancy, and following ovariectomy

Pseudopregnant, pregnant, and ovariectomized rabbits were utilized to study hormonal mediation of uterine epithelial surface negativity and glycocalyx morphology, and to seek local effects of blastocysts at sites of implantatioN. A loss of surface negativity [polycationic ferritin (PCF) binding] by day 6 of pregnancy or pseudopregnancy was noted, accompanied by alterations in epithelial glycocalyx. Uteri from estrous animals, or ovariectomized animals receiving oil or estradiol injections, bound PCF and exhibited a "globular" glycocalyx. Uteri from day 6 pseudopregnant or pregnant animals, or ovariectomized animals receiving progesterone injections, did not bind PCF or exhibit a globular glycocalyx. Both PCF binding and the globular character of the epithelial glycocalyx were sensitive to neuraminidase and trypsin treatment, suggesting sialoglycoprotein contribution to surface negativity. Implanting blastocysts had no detectable local effect on surface negativity, but did induce local reduction of epithelial glycocalyx at sites of implantation. Results of this study suggest that uterine epithelial glycocalyx alterations during the preimplantation period reflect a general response to progesterone stimulation, primarily qualitative in nature, related to the acquisition of receptivity to ovo-implantation.

Estrogen receptor in rabbit endocervical cells isolated by velocity sedimentation

Three nonciliated rabbit endocervical epithelial cell types were isolated by velocity sedimentation at unit gravity. Cell Types I and II contained heterogeneous secretory granules, whereas Type III cells were characterized by empty cytoplasmic vacuoles. Previous studies had confirmed the ultrastructural and functional integrity of each cell type and suggested hormone dependence of cell population sizes. Since the concentration of total cytosol estrogen receptor in endocervical epithelial cells from progesterone-dominated, 5-day pseudopregnant rabbits was reduced to approximately 23% of the value for estrous rabbits, receptor concentrations were measured in the three nonciliated epithelial cell types from animals in both hormonal states. The results indicate that the reduction in the estrogen receptor content in progesterone-dominated animals can be attributed to a reduction in the number of Type I and Type II cells, and to a significant (P less than 0.05) reduction in their estrogen receptor concentrations.

Decidual changes in the endometrium and morphological adaptation of the associated supplying arteries in the normal and diabetic pseudopregnant rat

After an electrically induced pseudopregnancy in rats in which deciduomas were produced by an intraluminal oil injection, the decidual tissue was studied morphologically on days 7, 10 and 13. A constant and dynamic wave of mitotic figures was found, which started on day 7 in the antimesometrial decidua, moving to the mesometrial decidua on day 10 and finally to the mesometrial triangle area on day 13 of pseudopregnancy. This and other morphological changes were compared with those found in pseudopregnant rats with streptozotocin-induced diabetes. On days 7 and 10 the incidence and distribution of mitotic figures were practically identical in both groups and statistically no significant difference was found in the uterine weight between the two groups on these two days. On day 13, two statistically significant differences were observed in the diabetic group: a fall in the uterine weight and a fall in the incidence of mitotic figures in the mesometrial triangle decidual cells. Associated with decidualization, a series of histological changes were studied in the arteries of the mesometrial triangle. Although the difference was not statistically significant, changes seemed to occur to a lesser degree in the diabetic group. It is concluded that the diabetic state has no influence in the early decidualization period, but it does have influence late in pseudopregnancy: a fall in the mitotic activity in the decidual tissue, a fall in the uterine weight and a less marked change in the spiral arteries which during pregnancy would supply the developing placenta with maternal blood.

Ultrastructure of decidualization in the pseudopregnant rat

The ultrastructure of the endometrial stroma in rats bearing deciduomata was examined in detail on day 9 (day of vaginal cornification = day 0) of pseudopregnancy, together with the development of deciduomata from day 4 to day 8. Five major regions were recognizable on day 9. 1) In the basal zone, which contributes to endometrial regeneration following decidualization, stromal cells remained fibrocyte-like and were separated by wide bands of collagen fibrils. Capillaries were fenestrated and large. 2) The capsule surrounding the antimesometrial (region of the) deciduoma was composed of flattened cells, showing mitosis, which appeared to provide a source of appositional growth of the deciduoma. 3) The large, tightly packed, polyploid cells of the antimesometrial deciduoma showed morphological evidence of protein synthesis activity, an absence of smooth endoplasmic reticulum, and surface specializations suggestive of adhesion (adherens junctions), communication (gap junctions), and maintenance of an extensive surface area (lamellar processes). These cells came into very close apposition with capillary endothelial cells, which were seldom fenestrated, lacked any continuous basal lamina, and showed evidence of high metabolic activity. 4) The loosely packed mesometrial deciduoma contained a structurally supportive, "fixed" population of spiny cells and a "free" population of granulated cells and their putative precursors, together with a meshwork of large, sinusoidal capillaries whose endothelium was generally supported by a basal lamina. 5) The peripheral parts of the glycogenic area, which was structurally similar to the mesometrial deciduoma, contained many grossly enlarged intercellular spaces of undetermined function. The stromal cells at day 4, which give rise to all non-vascular elements except the granulated cells mentioned above, were structurally simple and fibrocyte-like. Only two distinct regions, subepithelial and deep, were recognizable. Capillaries at day 4 generally possessed a continuous endothelium, with a complete basal lamina and many pericytes. Between days 5 and 8, the stromal cells showed divergent forms of differentiation according to their position in the endometrium. Ultrastructural differentiation of the vasculature also showed divergence according to position, leading to the various types of capillaries seen at day 9. Regional variation, and high levels of structural organization, characterize the "programmed" decidual response in the pseudopregnant rat.

Effects of prostaglandin F2 alpha and its synthesis inhibitor indomethacin on corporaluteal functions in pseudopregnant rats

The effects of PGF2 alpha and its synthesis inhibitor indomethacin on corporaluteal (CL) functions were studied in adult pseudopregnant rats. The CL functions were assessed by studying the duration of pseudopregnancy and histological changes in the ovary. Administration of PGF2 alpha (4 mg/kg BW) significantly (P less than 0.001) shortened the duration of pseudopregnancy. Histological examination of ovaries revealed regressed CL. Administration of indomethacin, on the other hand, significantly (P less than 0.001) prolonged the duration of pseudopregnancy. Histological examination of ovaries revealed large and well formed CL, the diameters of which were significantly (P less than 0.05) increased. Administration of indomethacin and PGF2 alpha simultaneously, however, keeps the duration of pseudopregnancy within normal limit. Further, the shortening in the duration of pseudopregnancy by PGF2 alpha alone was completely reversed by exogenous administration of progesterone. Since PGF2 alpha shortens and indomethacin (an inhibitor of PGF2 alpha synthesis) prolongs the duration of pseudopregnancy, it is concluded that PGF2 alpha acts as a luteolytic agent in rats. The mechanism of luteolysis is most likely to be due to decrease plasma progesterone level. An estimation of blood progesterone level after administration of PGF2 alpha to pseudopregnant rats is therefore, suggested.