Cell death of uterine natural killer cells in murine placenta during placentation and preterm periods

In the murine uterus granulated metrial gland (GMG) cells appear only during normal pregnancy. GMG cells belong to a member of natural killer (NK) cells and play an important role in fetus survival and placental growth. Our previous study revealed that mouse GMG/uterine NK (uNK) cells in the late pregnancy rapidly disappear from the uterus, due to the degenerative change classified as necrosis. But there are few reports regarding appearance and morphology of uNK cells during late pregnancy. We examined histologically and histochemically how and when uNK cells undergo cell death. The uNK cells in the metrial gland increased in number and reached maximum until day 12 of pregnancy. Sudden disappearance, however, occurred after day 15 and the granules reduced in both number and size. In situ DNA fragmentation detection revealed that DNA fragmented uNK cells increased in number during days 13 to 15 and reached 70.2% at day 15 of pregnancy. From days 13 to 17, uNK cells were positive against anti-perforin antibody. Ultrastructurally, uNK cells at day 15 showed poor organelles and unusual granules in structure. In uNK cells at day 17, condensation of nucleus chromatin, reduction in size and phagocytosis into other uNK cells were observed. These results suggested that uNK cells undergo at least two types of cell death, classified as necrosis and apoptosis, at the different stages of pregnancy, and that perforin is not a mediator for cell death.     

Insulin-like growth factor-I as a follicular growth promoter during early pregnancy in thoroughbred mares

To elucidate the physiological role of insulin-like growth factor-I (IGF-I) during early pregnancy in mares, number of ovarian follicles was monitored ultrasonically during different stages of the first trimester of pregnancy in 36 thoroughbred mares. From 9 of 36 mares, blood samples were collected weekly from the mating day till the end of the first trimester of pregnancy and plasma IGF-I profiles were examined with other hormones, like follicle stimulating hormone (FSH), luteinizing hormone (LH), ir-inhibin, progesterone and estradiol-17beta. Plasma IGF-I level fluctuated throughout the studied period with four peaks on the 7th, 28th, 49th and 84th days of pregnancy. Plasma IGF-I showed a positive correlation with plasma FSH (P<0.05), whereas no correlation was found with other hormones during the studied period. Plasma IGF-I had no correlation with the foetal size, but positive correlation with the number of large (> 30 mm) and medium (10-30 mm) follicles. These results suggested that IGF-I might produce from the medium and large follicles during early pregnancy and promote to develop their growth via pituitary FSH mediated effects in the mares.     

Uterine NK cells produce epidermal growth factor in the murine pregnant uterus.

Uterine natural killer (uNK) cells belong to the large granular lymphocytes in the murine pregnant uterus and play essential roles in pregnancy success. We defined whether uNK cells can produce epidermal growth factor (EGF) important for implantation and embryo growth. The uNK cells were immunohistochemically positive for anti-EGF antibody especially during days 6 to 9 and at day 15 of pregnancy. Immunoreaction for EGF receptor was observed on the stromal cells in the metrial gland and trophoblasts in the placental labyrinth. EGF secretion (72.1 +/- 2.25 ng/10(40 cells) was noted in cultured uNK cells isolated from the metrial gland at day 15 of pregnancy. Treatment of anti-asialo-GM I antibody raised the level of EGF (129 +/- 21.5 ng/10(4) cells). These results suggest uNK cell can produce and release EGF for placental development.     

Generation and purification of recombinant bovine pregnancy associated glycoprotein

Bovine pregnancy-associated glycoprotein-1 (bPAG-1) is predicted to play an essential role during pregnancy and is labelled as a potential biochemical marker of pregnancy in ungulates. We have compared the generation of the glycosylated form of recombinant bPAG-1 (rbPAG-1) by human embryonic kidney 293 (HEK 293) and Chinese hamster ovary (CHO) cells in attached cultures and evaluated the adaptation of the rbPAG-1 transfected cell line to suspension culture. The PAG cDNA was cloned from placental RNA obtained from a slaughtered cow on day 55 of pregnancy. The PAG-pRcRSV expression vector was transfected into HEK 293 and CHO cells. Western blot analysis showed that clonal HEK 293 cells expressed rbPAG-1 better than CHO cells in attached cultures. Transfected HEK 293 cells were adapted to suspension culture in spinner flasks and the rbPAG-1 purified to homogeneity using ion-exchange, pepstatin-sepharose affinity chromatographies and preparative SDS-PAGE. The expression of rbPAG-1 was immunocharacterised using a polyclonal antibody. Our findings indicated that 293 cells are suitable for production of glycosylated form of rbPAG-1 and that the availability of the recombinant glycoprotein will aid in further studies to elucidate the function and structure of the protein.     

Biochemical and Protein Profile of Alpaca (Vicugna pacos) Uterine Horn Fluid During Early Pregnancy

South American camelids show high embryo loss rate, during the first 60 days of pregnancy. One of the factors which may be related to this situation is that over 98% of the embryos implant in the left uterine horn (LUH) even though both ovaries contribute similarly to ovulation. There is scarce information about the uterine environment of female camelids at any physiological state that could explain the capability of the LUH to attract the embryo and maintain pregnancy. We describe, for the first time, the biochemical and protein profile of uterine fluid (UF), addressing the right and LUH environment in non‐pregnant and pregnant alpacas. Different substrates, electrolytes and metabolites were assayed in both uterine horn fluids. Small changes were observed in glucose and total protein levels, which were more noticeable during pregnancy. In addition, 10 specific proteins were found in the left horn fluid in 5‐week‐pregnant alpacas, and two protein bands were identified in non‐pregnant alpaca right horn fluid. These results would provide basic information for identification of possible markers for pregnancy diagnosis, reproductive diseases and hormone‐treated animals evaluation and hence contributing to improve the pregnancy rate.     

Ultrasonographic studies on the reproductive tract of mares after parturition: effect of involution and uterine fluid on pregnancy rates in mares with normal and delayed first postpartum ovulatory cycles

During breeding of mares, ultrasonographic detection of uterine fluid accumulations in the first postpartum ovulatory period was associated with significantly decreased pregnancy rates, when compared with rates in control mares (P less than 0.005). The previously gravid uterine horn was recognized as the larger horn, when assessed for size by ultrasonography, for a mean of 21 days (range, 15 to 25 days) after parturition. On the basis of similar measurements obtained during 3 ultrasonographic scans (5-day period), uterine involution was determined to be completed in a mean of 23 days (range, 13 to 29 days). Progestin treatment did not affect uterine size, fluid accumulation, or rate of involution after parturition. However, delaying the first postpartum ovulation with 8 days of progestin treatment significantly improved pregnancy rates (P less than 0.05). More (P less than 0.05) mares became pregnant (23 of 28, 82%) when ovulation occurred after day 15 in the first postpartum ovulatory period, compared with those mares that ovulated before day 15 (6 of 12, 50%). We concluded that ultrasonographic detection of uterine fluid and postpartum progestin treatment can be used to manipulate breeding strategies and to improve pregnancy rates in mares bred during the first postpartum ovulatory period.     

Role of ghrelin in regulating rabbit ovarian function and the response to LH and IGF-I

The aim of these in vivo and in vitro studies was to examine the role of ghrelin in the control of plasma hormone concentrations, the proliferation, apoptosis and secretory activity of ovarian granulosa cells and the response of these cells to hormonal treatments. Female rabbits were injected with ghrelin (10 μg/animal/day for one week before ovulation induced by 25 IU PMSG and 0.25 IU LHRH). On the day of ovulation, blood samples were collected and analyzed for concentrations of progesterone (P₄), testosterone (T), estradiol (E₂), estrone-sulphate (ES), insulin-like growth factor I (IGF-I) and leptin (L) by RIA. Some control and ghrelin-treated animals were killed in the periovulatory period, their ovaries were weighed and granulosa cells were isolated and cultured for 2 d. Cell proliferation (expression of PCNA) and apoptosis (expression of TdT) were evaluated by immunocytochemistry and TUNEL respectively. Secretion of P₄, T, E₂, IGF-I, and prostaglandin F (PGF) by granulosa cells cultured with and without LH or IGF-I (1, 10 or 100 ng/ml medium) was assessed by RIA. The remaining control and treated animals were kept until parturition, while the number, viability and body weight of pups were recorded.     

Concentration of IGF-I and estradiol-17beta in the blood plasma of pregnant cattle

Blood samples were collected from pregnant cows, heifers and also from non pregnant cows serving as controls. The determination of insulin-like-growth-factor-I (IGF-I) and estradiol-17 beta (E2) were performed immunologically. In the non pregnant cows E2 remained unchanged. IGF-I decreased around parturition and increased again commencing the 6th week of lactation. Compared to nonpregnant animals E2 but not IGF-I was slightly elevated during the first 10 weeks of pregnancy. During the 10th up to 20th week of pregnancy the mean values of IGF-I were increased as well as the ones of E2. During the late pregnancy the values of IGF-I in heifers are obviously more elevated as in lactating pregnant or non-pregnant cows; analogous high values were determined in pregnant cows only during the dry period. Before parturition even a negative correlation exists between IGF-I and E2. It is concluded that IGF-I is predominantly regulated by other factors.     

Apoptosis in the porcine uterine endometrium during the estrous cycle, early pregnancy and post partum

The mammalian uterus changes dramatically during the estrous cycle, pregnancy, and involution post partum. Dynamic changes in the uterine endometrium are a type of homeostasis and proceed with proliferation and exclusion of cells. Homeostasis of the uterus is closely related to apoptosis involving various hormones and cytokines. The objective of the present study was to determine the morphological features and occurrence of apoptosis in the porcine endometrium during the estrous cycle, early pregnancy, and post partum. Cyclic changes in the morphology of the surface epithelium were observed during the estrous cycle. The heights of surface epithelia were significantly high on day 4 of the estrous cycle and the early pregnancy. The heights of the surface epithelium remained low from days 1 to 31 post partum. We then used terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphate nick end-labeling (TUNEL) of the 3'-terminal of fragmented DNA, which is effective for detection of apoptosis in various tissues. We found that apoptosis in the porcine endometrium contributed to homeostasis of the endometrium during the estrous cycle through control of cell proliferation and exclusion. Conversely, apoptosis on days 4 and 8 of gestation before the implantation window depended on the plasma estrogen and progesterone levels; however, suppressive homeostasis of apoptosis occurred at the time of implantation on days 15, 18 and 21 of gestation. Our study is the first to demonstrate apoptotic cell death in the porcine endometrium directly by TUNEL method. The results strongly suggest that uterine homeostasis is mainly controlled by apoptosis during the estrous cycle and early pregnancy.     

A field study of patterns of unobserved foetal loss as determined by rectal palpation in foaling, barren and maiden thoroughbred mares.

Records of 1,009 pregnancies in 574 foaling, barren and maiden Thoroughbred mares on a single stud farm, over a period of 12 years were examined. The farm is situated in the eastern Cape Province of South Africa, at an elevation of 1,800 m, and in an area of climatic extremes. Records of 604 pregnancies in 249 foaling Thoroughbred mares were examined. For these purposes, those pregnancies in which a mare conceived in the same breeding season during which she had foaled were considered as pregnancies in foaling mares. Pregnancy was confirmed by rectal palpation by a single experienced practitioner. Of the 604 pregnancies examined, conceptus attachment occurred in the horn opposite the previously gravid horn in 345 cases (57%), and in the previously gravid horn in 259 cases (43%; P less than 0.005). Unobserved foetal loss after pregnancy diagnosis amounted to 30 (9%) in the former group, while in the latter group (pregnancy established in the postgravid horn) 46 pregnancies were lost (18%; P less than 0.005). This study confirmed that conceptus attachment tends to occur in the uterine horn opposite the previously gravid horn in foaling Thoroughbred mares conceiving during the same season. A significantly higher incidence of foetal loss accompanied conceptus attachment in the postgravid horn. Of 242 pregnancies in 162 previously barren mares, 95 (39%) occurred in the left uterine horn and 147 (61%) in the right horn (P less than 0.005). The incidence of pregnancy failure in this group was 7%. The side of attachment did not affect the rate of loss. Evaluation of the records of 163 maiden mares revealed that conceptus attachment occurred in the left uterine horn in 58 (36%) pregnancies and in the right horn in 105 (64%) pregnancies (P less than 0.005), which is consistent with previously reported observations. Pregnancy failure was recorded in 4% of maiden mares. Side of attachment did not influence rate of loss in this group.     

Early Pregnancy Diagnosis by Serum Progesterone and Ultrasound in Sheep Carrying Somatic Cell Nuclear Transfer-Derived Pregnancies

Early pregnancy diagnosis and monitoring play an important role following embryo transfer in sheep. The aims of the current study were to investigate (i) the pattern of serum progesterone profiles in sheep carrying somatic cell nuclear transfer (SCNT)‐derived (clone) pregnancies, and (ii) the frequency of pregnancy loss during development following SCNT embryo transfer. Sheep SCNT embryos were made using standard nuclear transfer techniques. Day 7 embryos were surgically transferred to oestrus‐synchronized recipients (n = 27). As a control, normal fertile ewes (n = 12) were bred by natural breeding. Serum was collected from all the ewes on the day of estrus (day 0 sample), 7 days post‐estrus (day 7 sample) and 19 days post‐estrus (day 19 sample) and every 10 days thereafter until lambing or pregnancy loss occurred. Serum progesterone (P4) was assessed using enzyme immunoassay. Pregnancy was confirmed by ultrasound scanning on day 35 of pregnancy followed by subsequent scanning every 10 days. In control ewes, pregnancy rate on day 35 was 83.3% (10/12), whereas in the ewes that received SCNT embryos, it was 22.2% (6/27; p < 0.05). The day 45 pregnancy rate in the control ewes was 83.3%, whereas in the SCNT embryo recipients it was 11.0% (p < 0.05). Hormone analysis revealed that SCNT embryo recipients exhibited a significantly lower P4 profiles at different time points in pregnancy compared to controls (p < 0.05). This study highlights the use of serum progesterone in combination with ultrasound for the investigation of embryo loss and crucial times during development of normal and SCNT embryos in sheep. Further, the serum P4 levels directly reflect the degree of placental development in these two groups.     

Morphometric and histochemical study of involution in the rat uterus after parturition

Morphological changes to and collagen loss from the rat uterus during postpartum involution were investigated. The expression patterns of collagen type III and myeloperoxidase (MPO) were also determined. Morphological changes were studied on days 1, 3, 5, 10, 15, 20, 22 and 25 postpartum. As a control, diestrus rats’ uterine were used. Specimens from the uterine horn were embedded in paraffin, cut into 8 µm coronal sections, and stained with hematoxylin‐eosin. The thickness of the longitudinal and circular smooth muscle layers and of the endometrium were measured. The collagen content was determined using hydroxyproline analysis. Immunostaining was used to examine the expression of collagen type III on days 1, 3, 5, 10, 15 and 20 postpartum; and MPO on days 1, 3, 5, 10 and 22 postpartum. The thickness of the smooth muscle layers was found to decrease rapidly postpartum: the circular smooth muscle layer returned to that of a non‐pregnant, control uterus by day 5 postpartum and the longitudinal smooth muscle layer by day 15 postpartum. Eosinophilic cells were observed in the endometrial stroma adjacent to the myometrium on days 10, 15 and 20 postpartum, and were confirmed as collagenous cells. Immunostaining identified collagen type III positive cells in the vessel‐rich layer adjacent to the placental site on days 1, 3, 5 and 10 postpartum, and these cells were confirmed to be phagocytic. Postpartum reduction in the weight of the uterus was accompanied by decreases in both the collagen content and the thickness of the longitudinal and circular smooth muscle layers. Furthermore, the phagocytic cells were shown to express MPO during postpartum involution of the uterus.     

Ligand-independent activation of steroid receptors

In several transformed cell lines, the growth factors IGF-I and epidermal growth factor (EGF) activate second messenger systems that cause the phosphorylation of the estrogen receptor (ER). One kinase catalysing receptor phosphorylation is mitogen activated protein (MAP) kinase, and the result of phosphorylation is an increase in receptor transactivation function. EGF and IGF-I, secreted locally and systemically, are involved in uterine-conceptus interactions in early pregnancy, and therefore it is of interest to determine whether these growth factors affect ER function in the uterus. An estrogen response element, chloramphenicol acetyl transferase reporter gene construct (CATERE) was transfected into bovine endometrial epithelial and stromal cells in vitro, and CAT measured during transient expression. Growth factors were added at various times following transfection, and MAP kinase phosphorylation was monitored by western blotting of p42 and p44. The MEK inhibitor U 0126 was used to determine whether the effect of IGF-I on CATERE expression was mediated through MAP kinase, and the anti-estrogen ICI 182780 was used to identify effects involving the ER. In stromal cells, reporter gene activity was increased in a dose dependent manner by IGF-I or hEGF in the presence or absence of estradiol-17beta. In the absence of estradiol the effect of IGF-I was not inhibited by ICI 182780. The effect of IGF-I occurred within an hour, before any detectable increase in cell proliferation, and the activation of CAT expression in response to IGF-I or EGF was blocked by U 0126. In contrast to their effects in stromal cells, neither IGF-I nor EGF affected CAT expression in bovine endometrial epithelial cells. Measurement of phosphorylated MAP kinases p42/p44 by western blotting showed that EGF but not IGF-I activated MAP kinase phosphorylation in both epithelial and stromal cells. In stromal cells, the fact that U 0126 blocked the CAT responses to IGF-I and EGF indicates the involvement of a MAP kinase. But since IGF-I did not activate p42/p44, a different MAP kinase, not detected by the antibody used here, is implicated. As the response was not blocked by ICI 182780, we conclude this effect is independent of ER activation. Therefore in bovine uterine cells in culture effects on MAP kinases p42/p44 can be dissociated from those on ERE-dependent gene expression, and reporter gene expression may be independent of ER activation.     

Pregnancy and lactation affect the microvasculature of the mammary gland in mice.

Microvascular changes in the mammary gland in mice during pregnancy and lactation were investigated by scanning electron microscopy (SEM) with a corrosion cast method, transmission electron microscopy (TEM) and morphometry. By SEM, duct-associated capillary plexuses were sparsely distributed to branch into adipocytes during virgin period. With advance in pregnancy, both branches from the capillary plexuses and branches from the vessels surrounding adipocytes extended further to form capillary networks. The basket-like architecture was completed by day 18 of pregnancy. These findings may indicate that angiogenesis occurs frequently during this period. During lactation, the basket-like architecture still remained and the capillaries surrounding alveoli meandered. After weaning, the regression of microvasculature followed the degeneration of alveoli. By TEM and morphometry, the density of pinocytotic vesicles (PVs) (number of PVs per microns 2 of endothelium cytoplasm) increased twofold from day 18 of pregnancy to day 5 of lactation, furthermore increased threefold from days 10 to 20 of lactation, and subsequently decreased after weaning. Marginal folds and microvillous processes gradually increased in length with advance in pregnancy, reached the maximum from days 5 to 15 of lactation, and thereafter decreased. In addition, the capillaries with thinner walls were in close contact with alveoli during the late stage of pregnancy and during lactation. Furthermore, the alveolar epithelial cells had well-developed basal infoldings during lactation. These findings suggest that the capillaries play an important role in transporting materials necessary for milk production.     

Anomalous Pregnancies during Late Embryonic/Early Foetal Period in High Producing Dairy Cows

This study analyses anomalous cases of gestation ending in pregnancy loss during the early foetal period and their effect on progesterone and plasma pregnancy-associated glycoprotein-1 (PAG-1) concentrations. Data derived from a large-scale ultrasound pregnancy diagnosis programme in high producing dairy cows. Over a 3-year period (2004–2007), a very low incidence (0.5%: 15 of 3094) of anomalous pregnancies was recorded. The results revealed that the following anomalies were detected on days 35–41 of gestation in cows carrying singletons with one single corpus luteum: embryo death in eight cows (0.3%); and embryo in the uterine horn contralateral to the corpus luteum in seven cows (0.2%). All these animals suffered pregnancy loss during the early foetal period. In cows carrying dead embryos, no signs of conceptus degeneration were observed on pregnancy diagnosis. Amnion size (approximately 25 mm diameter) and uterine horn fluid contents were estimated to be similar to those of the normal pregnant cows in this period. In the contralateral gestations, live embryos were observed in all ultrasound checks before pregnancy loss. Uterine fluid contents increased in the two cows in which gestation continued for more than a week. In the cases of embryo death but not in those of contralateral gestation, a drop in PAG-1 levels was noted prior to pregnancy loss. Two cows carrying dead embryos increased with time allantoic fluid contents. The PAG-1 values increased with time in one cow bearing a dead embryo (from 2.31 to 6.79 ng/ml) and in two of the contralateral gestations (from 1.66 to 2.33 ng/ml and from 0.39 to 6.79 ng/ml, respectively). Results of this study indicate that the foetal membranes continue to undergo some activity following embryo death, and that contralateral pregnancy may determine failure of the gestation process.     

Effect of Conceptus on Transforming Growth Factor (TGF) β1 mRNA Expression and Protein Concentration in the Porcine Endometrium—In Vivo and In Vitro Studies

Transforming growth factor (TGF) β and its receptors are expressed at the conceptus-maternal interface during early pregnancy in the pig. The present studies were conducted to examine: (1) the effect of conceptus products on TGFβ1 mRNA expression and protein concentration in the porcine endometrium using in vivo and in vitro models, and (2) the effect of TGFβ1 on proliferation of porcine trophoblast cells in vitro. During in vivo experiments, gilts with one surgically detached uterine horn were slaughtered on days 11 or 14 of the estrous cycle and pregnancy. For in vitro studies, endometrial explants and luminal epithelial (LE) cells co-cultured with stromal (ST) cells were treated with conceptus-exposed medium (CEM). Moreover, porcine trophoblast cells were treated with TGFβ1, and the number of viable cells was measured. On day 11, the presence of conceptuses had no effect on TGFβ1 mRNA expression, but decreased the TGFβ1 protein concentration in the connected uterine horn compared with the detached uterine horn. In contrast to day 11, on day 14 after estrus, TGFβ1 mRNA expression and protein content in the endometrium collected from the gravid uterine horn were greater when compared with the contralateral uterine horn. The treatment of endometrial slices with CEM resulted in greater TGFβ1 mRNA expression and protein secretion. LE cells responded to CEM with an increased TGFβ1 mRNA level. Moreover, TGFβ1 stimulated the proliferation of day 14 trophoblast cells. In summary, porcine conceptuses may regulate TGFβ1 synthesis in the endometrium at the time of implantation. TGFβ1, in turn, may promote conceptus development by increasing the proliferation of trophoblast cells.     

Expression Pattern of CD34 at the Maternal–Foetal Interface During Pregnancy in Pigs

The pig exhibits a non‐invasive, epitheliochorial placentation. Adhesion molecules are indispensable for successful implantation and establishment of placentation. CD34 is an adhesion molecule belonging to the immunoglobulin superfamily (IgSF). To take the first step to investigate the role of CD34 in placentation, we examined the expression pattern of CD34 at the maternal–foetal interface in Yorkshire gilts on days 15, 26, 50 or 95 and in Meishan gilts on days 26, 50 or 95 of pregnancy (n = 3 gilts/breed/day of pregnancy) by immunohistochemical technique. The CD34‐positive signals were detected in uterine luminal epithelium and trophectoderm in Yorkshire pigs; the staining for CD34 was located in trophectoderm but barely detectable at the uterine luminal epithelium on day 15 of pregnancy. Then, the expression of CD34 increased dramatically in both the uterine luminal epithelium and trophectoderm by day 26, and weak staining intensity was observed at the maternal–foetal interface on days 50 and 95 of pregnancy. The expression pattern of CD34 in Meishan pigs is similar to that in Yorkshire pigs except that only a few positive signals were observed at the luminal epithelium on day 26 of pregnancy. These results suggest that CD34 may be involved in mediating the cell‐to‐cell adhesion between trophectoderm and the luminal epithelial cells during early pregnancy in pigs.     

Ultrastructural study of uterine natural killer cells found in pregnant, interleukin-2 receptor beta-chain overexpressed transgenic mice

We previously reported that all fetuses died or were resorbed on day 12 of pregnancy (Day 1= the day of plug) in interleukin-2 (IL-2) receptor beta-chain overexpressed transgenic (Tg2Rbeta) mice. In this study, to clarify the role of uterine natural killer (uNK) cells in pregnancy, the ultrastructure of Tg2Rbeta mouse uNK cells was analyzed using a transmission electron microscope. uNK cells and their granules on day 10 of pregnancy were larger in Tg2Rbeta mice than control mice, indicating that differentiation of uNK cells in Tg2Rbeta mice progressed rapidly. Additionally, the granules of uNK cells in Tg2Rbeta mice on day 10 of pregnancy had an irregular morphology. The multivesicular regions were present in the cap structure of these granules, suggesting that the uNK cells of the Tg2Rbeta mice had cytotoxic activity.     

Uterine morphology and function in postpartum mares

Ultrasonically detectable characteristics of the uterus and embryo and palpable uterine tone were assessed in 10 postpartum mares. A bright fern-like pattern of ultrasonic uterine echogenicity, outlining the endometrial folds, was observed for an average of 2.1 ±0.2 days following parturition (range, 1 to 3 days). Unexpectedly, the uterus was quiescent throughout the postpartum interval, based on daily one-minute contractility scans. Contractility was maximal on Days 12 to 15 of pregnancy in both postpartum (n=7) and nonparturient (n=7) mares. The mean diameter of ultrasonically detectable intrauterine fluid collections increased (P<0.05) abruptly between days 1 and 2 postpartum and gradually decreased (P<0.05) between days 4 and 7; no collections were detected after day 16. There was no effect of day on echogenicity of the intrauterine fluid collections; on all days, fluid was relatively black or nonechogenic, suggesting that puerperal endometritis was not a problem in this group. Because the increase in intraluminal fluid occurred after parturition and in temporal association with a decrease in diameter and tone of the uterus, the fluid collections apparently represented a physiologic influx from the involuting uterus rather than residual placental fluid. Involution of the horns was completed by day 27 (formerly nongravid horn) and day 31 postpartum (formerly gravid horn), based on failure to detect further significant decreases in diameter. However, the formerly gravid horn was larger (P<0.05) in diameter than the formerly nongravid horn on each of Days 1 to 35 postpartum (end of experiment), indicating residual effects on uterine size. When averaged over both horns, uterine diameters were larger on Days 0 to 24 (Day 0=day of ovulation) of pregnancy in postpartum mares than in nonparturient mares; by Day 25, diameters were similar between statuses. By approximately Day 6 of pregnancy, uterine contractility and ultrasonic endometrial exhotexture were similar between postpartum mares and nonparturient mares. Uterine tone was greater (P<0.05) in postpartum mares than in nonparturient mares on all days between Day 0 and 25. An unexpected, transient increase in uterine tone was detected on Day 5 of pregnancy in both postpartum mares and nonparturient mares. No differences were found between reproductive statuses in patterns of embryo mobility, the day of fixation of the embryonic vesicle (postpartum, Day 15.3 ±0.4; nonparturient, Day 15.0 ±0.3), and diameter of the embryonic vesicle on the day of fixation (postpartum, 22.1 ±1.4 mm; nonparturient, 19.4 ±l.6mm). However, mean uterine tone and mean horn diameters on the side of fixation were greater (cranial and middle cornual segments; P<0.05) or tended to be greater (caudal segment; P<0.1 ) on the day of fixation in postpartum mares than in nonparturient mares. In all postpartum mares, fixation occurred in the formerly nongravid horn. Enhanced uterine tone in postpartum mares may account for the occurrence of fixation on the same day for the two reproductive statuses, despite the larger uterus in postpartum mares.