The bovine intercaruncular placenta throughout gestation

The attachment of chorion to uterine epithelium which results in a functional placenta began in the middle of the ipsilateral horn near the embryonic disc and spread towards the tip of each uterine horn. The intercaruncular union was fragile but perfusion and careful tissue processing preserved contact between chorion and intercaruncular epithelium from the fourth week until late in gestation. The adhesion-attachment process included binucleate cell migration from the chorion and remodelling of the maternal tissue. In areas where attachment was occurring or maintained, maternal epithelial height was reduced from columnar to cuboidal or squamous. Multinucleated cells and syncytium, which resulted from fusion of migrant binucleate cells with uterine epithelium, were common in the earlier stages of placentation. Extensive syncytium did not persist beyond the second month but some multinucleates were found throughout gestation. Attachment involved substantial areas in the bodies and middle regions of both horns but was not universal. Very limited attachment was found in the tip of the ipsilateral horn and none in the tip of the contralateral horn. In sections where contact could not be preserved the uterine epithelium was composed of tall columnar cells and no binucleate cell migration was detected. Intraepithelial lymphocytes were common in the tall columnar epithelium but almost totally absent where attachment and migration were occurring. Preservation of contact between the chorion and intercaruncular uterine epithelium throughout gestation demonstrated the diffuse nature of bovine placental attachment.     

Effects of three methods of selection for litter size in mice on pre-implantation embryonic development.

Characteristics of preimplantation embryonic development to Day 3.5 of gestation were evaluated in lines of mice after 21 generations of selection for litter size or components of litter size. Selection criteria were direct selection for number born (LS), selection on an index of ovulation rate and the proportion of ova shed that resulted in fully formed pups (IX), selection for number born in unilaterally ovariectomized females as an indication of uterine capacity (UT), and an unselected control (LC). Comparison of the average distributions of embryonic stage of development on the left side of the uterus showed that selection (average effect of LS, IX, and UT vs. LC) tended to advance (p = 0.07) the average stage of embryonic development at Day 3.5 and shift the distribution (p = 0.10) by increasing the frequency of expanded blastocysts and decreasing the frequency of pre-morula embryos. A similar shift in the distribution on the right side of the uterus was not statistically significant. Selection decreased (p = 0.06) variability in developmental stage among embryos within the right uterine horn. These selection criteria evaluated in the mouse appear to have changed the frequencies of genes that affect some determinants of average stage of embryonic development and uniformity of development within a uterine horn at Day 3.5 of gestation.     

A microscopical study of uterine lining modification,binucleate cell numbers and trophoblastic development,at day 14, 20 and 24 of gestation in single and multiple pregnancies in sheep

In order to evaluate possible differences in some key anatomical characteristics of the placental components between single and multiple pregnancies in sheep, mean percentage values of trophoblastic development (TD), binucleate cell numbers (BC) and modification of the uterine lining epithelium (ULM) were obtained in ewes carrying one (natural single pregnancies; Group 1) and two or more embryos (multiple pregnancies obtained by superovulation; Group 2) at 14, 20 and 24 days postmating. Two sheeps per stage were used in Group 1, and three in Group 2 were employed. TD, BC and ULM mean values were higher at all stages in Group 2. Under the conditions of the present study, it appears that in multiple pregnancies, implantation ensues earlier compared to in singles, and the correspondent anatomical changes in the conceptus and endometrium are more advanced in multiple gestations. A possible explanation for the present findings is that each embryo locally influences the development of the above mentioned modifications at day 20 and 24 postmating. In multiple pregnancies at day 14, it appears that the degree of development differs among conceptuses confined to the same uterine environment. The present studies corroborate previous findings that a critical phase during implantation for embryonic survival might be the time period between 14 and 24 days of pregnancy due to the gradual and relatively slow nature of the implantation phenomenon. It can be stated that TD, ULM and BC are important histological features to evaluate embryonic viability in postmortem assessments.     

Prostaglandin E2 secretion by oviductal transport-stage equine embryos.

This study was conducted to identify embryonic products whose secretion was temporally associated with the oviductal transport period of the mare. Chemicals secreted by oviductal-transport-stage equine embryos were identified by incubating Day 6 or Day 7 early uterine embryos with 35S-methionine/cysteine, 3H-progesterone, or 3H-arachidonic acid for 24 h, and subsequently identifying radioactively labeled proteins (SDS-PAGE; n = 3 embryos), steroids (HPLC; n = 3 embryos), or prostaglandins (HPLC; n = 3 embryos) in the culture medium. Early uterine embryos secreted 116.1 +/- 45.5 pg of prostaglandin (PG) E2/embryo, 1.0 +/- 0.2 pg of 17 alpha-hydroxy progesterone/embryo, 4.8 +/- 0.6 pg of androstenedione/embryo, and 11.5 +/- 4.5 pg of PGF2 alpha/embryo. They did not secrete detectable quantities of protein, testosterone, or estradiol-17 beta. A second experiment was conducted to measure temporal changes in embryonic PGE2 secretion during the oviductal and early uterine period. Day 3, Day 4, Day 5, and Day 6 embryos (n = 8 embryos/day) were incubated with 3H-arachidonic acid for 24 h, and the concentration of 3H-PGE2 in the culture medium was subsequently measured by HPLC. Embryos did not secrete detectable amounts of PGE2 prior to the expected time of oviductal transport (Day 3 and Day 4). They secreted 5.7 +/- 1.0 pg of PGE2/embryo immediately before and during the expected time of oviductal transport (Day 5), and they secreted significantly of PGE2/embryo immediately before and during the expected time of oviductal transport (Day 5), and they secreted significantly (p less than 0.01) higher amounts (42.0 +/- 11.5 pg) of PGE2/embryo immediately after uterine entry (Day 6).(ABSTRACT TRUNCATED AT 250 WORDS)     

Embryonic survival at day 9, 21 and 35 of pregnancy in intact and unilaterally oviduct ligated multiparous sows

To investigate the effect of uterine space on timing of embryonic mortality, multiparous sows were left intact (CTR; n=42) or subjected to unilateral oviduct ligation (LIG; n=23), after their first post wean oestrus. Intact sows were killed at day 9 (n=10), day 21 (n=15), or day 35 (n=17), and LIG sows were killed at day 21 (n=11) or day 35 (n=12) of gestation. At day 9, 92% of ovulations were represented by an embryo. At day 21, embryonic mortality was 24% and was not altered by increasing uterine space. At day 35, space per embryo was twice as large in LIG sows (30±3 v. 16±0.8 cm), and implantation length tended to be larger (19.0±1.2 v. 15.5±1.3 cm). Between day 21 and day 35, CTR sows lost another 8% to 14% of their embryos, whereas LIG sows lost none. Embryos tended to be heavier (4.9±0.2 v. 4.3±0.3 g) in LIG sows. In conclusion, embryonic loss in multiparous sows is 24% by day 21 and is not related to space, whereas after day 21 limited space causes additional 8% to 14% embryonic mortality in intact sows only.     

Factors affecting pregnancy rate following nonsurgical embryo transfer in buffalo (Bubalus bubalis): a retrospective study

The objectives of this study were to determine the pregnancy rate and factors affecting it following nonsurgical embryo transfer in buffalo. Donor buffalo were superovulated with FSH, and embryos collected nonsurgically were evaluated for stage of development and quality. They were transferred nonsurgically to 91 recipients on Days 5 to 7 of the natural (n = 52) or induced (n = 39) estrus (estrus = Day 0). The overall pregnancy rate of 24/91(26.4%) was higher than in earlier reports for buffalo but was much lower than in cattle. Pregnancy rates were not affected by season (autumn vs winter), side of transfer (right vs left uterine horn), or type of estrus (spontaneous vs induced). The pregnancy rate was high 11/27(40.7%) when donors and recipients were closely synchronized, while it was compromised when recipients were in estrus at +12 h (1/7, 14.3%) and at -12 h (5/27, 18.5%). Asynchrony beyond 12 h on either side resulted into conception failure. The pregnancy rate tended to increase with the increase in CL size of recipients, while stage of embryonic development had no effect. The transfer of an 8-cell embryo with a 16-cell embryo led to the birth of heterosexual twins, indicating that the uterine milieu of Day 5 to 6 recipients may be tolerated by the out-of-phase 8-cell embryo, at least in the presence of a more mature embryo. Embryo quality had the greatest effect on pregnancy rate as it was higher (P < 0.005) after the transfer of Grade I than Grade III embryos (6/10, 60.0% vs 3/36, 13.9%). Assessment of returns to estrus indicated that among nonpregnant recipients, 17/67 (25.4%) embryos never matured sufficiently to prevent luteolysis through maternal recognition of pregnancy (MRP), while 14/67 (20.8%) embryos probably died following MRP. These results indicate that efforts to increase pregnancy rate following embryo transfer in buffalo should include prevention of luteolysis during the first week of transfer and a reduction in the incidence of embryonic mortality.     

In vitro and in vivo development of mouse morulae encapsulated in 2% sodium alginate or 0.1% poly-l-lysine

In Experiment 1, development of zona pellucida-intact (ZPI) morulae was measured every 24 hours for 120 hours after encapsulation in 2% sodium alginate (ALG) or 0.1% poly-L-lysine (PLL). Encapsulation significantly reduced development to hatched blastocysts at 48 and 72 hours. Developmental stages and diameters of ZPI and zona pellucida-free (ZPF) unencapsulated and encapsulated morulae were measured every 24 hours for 72 hours in Exeriment 2. At 72 hours, the percentage of ZPI embryos developing to expanded blastocysts, their diameters and their nuclear counts were not different from each other or from ZPF embryos. In Experiment 3, ZPI morulae encapsulated in ALG or PLL were transferred into recipients. Five of six recipients that received unencapsulated embryos (n=71) delivered 16 live pups. None of the recipients of encapsulated embryos delivered offspring; therefore, a final experiment was performed to examine fetal development on Day 10 of gestation. The percentage of pregnant recipients was similar for all 3 treatments: unencapsulated (71.4%), ALG (87.5%) and PLL (87.5%). However, the presence of viable fetuses was higher for unencapsulated embryos (42.1%) than for ALG (17%) and PLL (14.6%) embryos. These results suggest that encapsulation did not detrimentally affect embryonic size or cellular development in vitro; however, mortality occurred in vivo due to an asynchronous condition between the uterine environment and the embryos.     

Biodegradable estradiol microspheres do not affect uterine involution or characteristics of postpartum estrus in mares

Quarterhorse mares were used to investigate effects of estradiol-17beta on uterine involution, duration of estrus, interval to ovulation, and fertility achieved by breeding on the first postpartum estrus. On the day of foaling, mares were injected with biodegradable poly (DL-lactide) microspheres containing either 100 mg estradiol-17beta (25 mares) or no drug (27 mares). The treatment period was considered to last for 12 to 15 d. Estrus was determined by teasing mares (n=16) with a stallion. Ovulation was detected by transrectal ultrasonographic examination of ovaries (n=48). On Days 6, 11 and 16 post partum, transrectal ultrasonography was used to measure cross-sectional diameters of the uterine body, uterine horns, and fluid within the uterine lumen (n=28). Uteri were swabbed for bacteriologic culture, and uterine biopsies were obtained from the previously gravid uterine horn on Days 11 and 16 post partum, for assessment of endometritis and morphometric analysis of endometrial histioarchitecture (n=19). Twenty-two mares were bred on foal-heat, and pregnancy was determined by transrectal ultrasonography on 14 to 16 and 30 to 35 d after breeding. With only one exception (diameter of previously gravid uterine horn on Day 11), mean values for all measures of uterine involution did not differ between treatment groups (P > 0.05). No differences were detected between treatment group means for length of estrus or interval to ovulation (P > 0.05). No differences were detected between treatment group liklihoods for recovery of potential bacterial pathogens, presence of endometritis, or presence of intrauterine fluid at 11 or 16 d post partum (P > 0.05). Pregnancy rate of mares treated with estradiol (5 11 ; 45%) was not different from that of control mares (9 11 ; 82%; P > 0.05). Estradiol treatment did not hasten uterine involution, increase duration of estrus, delay ovulation, or increase fertility in these postpartum mares.     

Developing embryo and cyclic changes in the uterus of Peripatus (Macroperipatus) acacioi (Onychophora,Peripatidae)

Female reproductive tracts of the viviparous neo-tropical onychophoran Peripatus acacioi have been examined at different times throughout the year, and the altering relationship between the developing embryo and the uterus is described. Depending on her age and time of year, the female may have one or two generations of embryos within her uterus. The uterine wall consists of a thin outer epithelium and basal lamina, three layers of muscles, and a thick basal lamina beneath an inner epithelium lining the uterus lumen. These layers are consistent along the length of the uterus apart from the inner epithelial lining, which varies according to position in the uterus and the developmental stage of embryos contained in the uterus. Early embryos are positioned along the length of the uterus and therefore have space in which to grow. During cleavage and segment formation, each embryo is contained within a fluid-filled embryo cavity that increases in size as the embryo grows. Morulae and blastulae are separated by lengths of empty uterus in which the epithelial lining appears vacuolated. Until the process of segment formation is complete, the embryos are attached to a placenta by a stalk and remain in the same part of the upper region of the uterus. As these embryos grow, the lengths of vacuolated cell-lined uterus between them decrease. Each embryo cavity is surrounded by the epithelial sac, the maternal uterine epithelium, which becomes overlaid by a thin layer of cells, the embryo sac, which is believed to be of embryonic origin. The placenta is a syncytial modification of the epithelial sac located at the ovarian end of each embryo cavity covered by the embryo sac and is analogous to the mammalian noninvasive epitheliochorial placenta. Segment-forming embryos have their heads directed toward the ovary. As the embryo gets longer during segment formation, its posture changes from coiled to flexed. Once segment formation is complete, the embryo loses contact with its stalk, an embryonic cuticle forms, and the embryo turns around so that its head is directed toward the vagina. The embryo escapes from its embryo sac and moves to the lower part of the uterus. In the lower part of the uterus, the straightened fetuses are first unpigmented but subsequently become pigmented as the secondary papillae on the body surface form and an adult-type cuticle forms beneath the embryonic cuticle. While the embryos are contained within their embryo cavities, nutrients are supplied by the placenta. Throughout development the mouth is open and in the mature fetus the gut is lined by peritrophic membrane and material is present in the gut lumen. Trachea have been observed only in fetuses that were ready for birth. Insemination, cyclical changes in the uterine epithelium, and the nature of the cuticle shed at parturition are discussed. © 1995 Wiley-Liss, Inc.     

Unilateral uteroovarian relationship in pregnant cattle and role of uterine vein

The hypothesis of a unilateral uteroovarian relationship between location of embryos and maintenance of corpora lutea (CL) was tested in superovulated cattle. Ovulations were induced in both ovaries and a uterine horn was isolated subsequent to insemination to produce unilateral pregnancy. The mean weight of CL on day 24 was greater (P<.05) on the gravid side (2580 mg) than on the nongravid side (1200 mg; n=5), supporting the hypothesis. Involvement of the main uterine vein in the unilateral pathway between a gravid horn and the adjacent ovary was demonstrated in an experiment which utilized separation of uterine horns, anastomosis of uterine veins between sides, and insertion of embryos into one side by embryo transfer. Mean weight of CL on day 24 was less (P<.05) when the gravid horn was contralateral to the CL (950 mg; n=3), than when the gravid horn was ipsilateral to the CL (4760 mg) or when the gravid horn was contralateral to the CL and the uterine vein from the contralateral side was anastomosed to the vein on the ipsilateral side (3580 mg; n=3).     

Fertilization rates and embryonic development in superovulated cattle inseminated in different sites within the reproductive tract

Superovulated Jersey and Holstein heifers and cows were bred 9.7 ± 2.7 h after the first observation of estrus with a single dose of frozen semen. Animals were grouped by site of insemination: 1) right uterine horn (n = 5), 2) left uterine horn (n = 4), 3) mid- uterine body (n = 5), and 4) mid-cervix (n = 6). The number of unfertilized ova, normal and abnormal embryos were recorded for each horn at slaughter 115.8 ± 18.6 h after insemination. All viable embryos were cultured in vitro and assessed for development. The overall fertilization rate was 76.8%, with the ipsilateral horn being higher than that of the contralateral horn (P < 0.05). Similar fertilization rates resulted among all treatments except those inseminated in the contralateral horn (P < 0.05). In vivo development of embryos was higher for the ipsilateral horn inseminations than those of the body of the uterus or cervical inseminations (P < 0.05), but it was not higher than the contralateral horn inseminations (P > 0.05). Under the conditions of this study with superovulated cows, these results suggest than 1) spermatozoa migrate from one horn to the other and 2) inseminating too deep into one horn may reduce the chances for concention when ovulation occurs contralaterally.     

Biochemical changes in the developing rat central nervous system due to hyperthermia

Rat embryos at 10 days of gestation were exposed to 43 degrees C for 8 minutes by submerging the exteriorized right uterine horn in heated saline solution and then reinserting the uterine horn into the abdominal cavity. At 15 days, the fetuses were removed, and cells from the cerebral hemispheres were dissociated and grown as primary cultures. Embryos from the left uterine horn served as controls. No morphological changes were observed between the cultures of cells from control and heat-exposed embryos at different days in culture. However, exposure of embryos to hyperthermia at 10 days significantly affected the developmental pattern of activities of acetylcholine esterase associated with cholinergic neurons and of 2',3'-cyclic nucleotide phosphohydrolase associated with oligodendrocytes and myelin membrane formation. These results suggest that hyperthermia at 10 days of gestation in the rat may lead to an impairment in the development of neurons and oligodendrocytes in the central nervous system.     

Distribution and development of embryos in the pig.

The distribution and development of pig embryos were determined in relation to the number of embryos and their positions within the uterine horn between Days 14 and 34 after mating. The observed distribution of 1-11 embryos within a uterine horn was highly correlated (r = 0-96) with the theoretical expected distribution. Embryo spacing was uniform regardless of the number of embryos within the horn. Nitrogen content of the embryo in relation to its position within the uterine horn indicated that development was similar for embryos located at the utero-tubal end or cervical end and comparable to those located in the middle portion of the horm. Placental development, as indicated by nitrogen content, was similar regardless of location within the horn.     

Effect of transfer of one or two in vitro-produced embryos and post-transfer administration of gonadotropin releasing hormone on pregnancy rates of heat-stressed dairy cattle

Pregnancy rates following transfer of an in vitro-produced (IVP) embryo are often lower than those obtained following transfer of an embryo produced by superovulation. The purpose of the current pair of experiments was to examine two strategies for increasing pregnancy rates in heat stressed, dairy recipients receiving an IVP embryo. One method was to transfer two embryos into the uterine horn ipsilateral to the CL, whereas the other method involved injection of GnRH at Day 11 after the anticipated day of ovulation. In Experiment 1, 32 virgin crossbred heifers and 26 lactating crossbred cows were prepared for timed embryo transfer by being subjected to a timed ovulation protocol. Those having a palpable CL were randomly selected to receive one (n = 31 recipients) or two (n = 27 recipients) embryos on Day 7 after anticipated ovulation. At Day 64 of gestation, the pregnancy rate tended to be higher (P = 0.07) for cows than for heifers. Heifers that received one embryo tended to have a higher pregnancy rate than those that received two embryos (41% versus 20%, respectively) while there was no difference in pregnancy rate for cows that received one or two embryos (57% versus 50%, respectively). Pregnancy loss between Day 64 and 127 only occurred for cows that received two embryos (pregnancy rate at Day 127=17%). Between Day 127 and term, one animal (a cow with a single embryo) lost its pregnancy. There was no difference in pregnancy rates at Day 127 or calving rates between cows and heifers, but females that received two embryos had lower Day-127 pregnancy rates and calving rates than females that received one embryo (P < 0.03). Of the females receiving two embryos that calved, 2 of 5 gave birth to twins. For Experiment 2, 87 multiparous, late lactation, nonpregnant Holstein cows were synchronized for timed embryo transfer as in Experiment 1. Cows received a single embryo in the uterine horn ipsilateral to the ovary containing the CL and received either 100 microg GnRH or vehicle at Day 11 after anticipated ovulation (i.e. 4 days after embryo transfer). There was no difference in pregnancy rate for cows that received the GnRH or vehicle treatment (18% versus 17%, respectively). In conclusion, neither unilateral transfer of two embryos nor administration of GnRH at Day 11 after anticipated ovulation improved pregnancy rates of dairy cattle exposed to heat stress.     

A model for implantation: coculture of blastocysts and uterine endometrium in mice

One of the limitations in embryo implantation research is the lack of an available in vitro model that faithfully replicates embryo-uterine interactions. In previous studies, embryos were cultured on a monolayer of either uterine epithelial cells or extracellular matrix substratum on which embryos could adhere and outgrow. However, these models failed to display embryonic invasion, primarily because of the shortage of critical structural and molecular supports that are available in vivo. In the present study, we used intact mouse uterine endometrium collected on Day 4 of pregnancy and placed in contact with blastocysts to initiate coculture experiments in a defined medium at the air-liquid interface. The culture medium was composed of Ham F-12/Dulbecco modified Eagle medium (1:1), 30% fetal calf serum, 63.5 nmol/L of progesterone, 7.14 nmol/L of estradiol-17beta, 100 mug/ml of insulin, and 20 ng/ml of epidermal growth factor, whereas the incubation condition was mixed air of 50% oxygen, 5% carbon dioxide, and 45% nitrogen with a humidity of greater than 90% at 37 degrees C. Our observations from 24 h of culture clearly demonstrated that embryos were capable of attachment to the uterine endometrium and displayed partial invasion into the endometrial stroma. Interestingly, no outgrowth of trophoblasts on the surface of uterine endometrium was seen, but embryos exhibited a pole-specific attachment. Overall, this model is capable of demonstrating a true invasion of embryo within the endometrial stroma and may be suitable in studies related to early embryo implantation.     

Characterization of intrauterine mobility of the early equine conceptus

Intrauterine mobility patterns of the embryonic vesicle were characterized on Days 9 to 17 after ovulation in pony mares using real-time ultrasonography (n=5 or 7 mares per day). The location of the vesicle was determined by dividing the uterus into right horn, left horn, and body. Each uterine horn was further divided into three approximately equal portions (cranial third, middle third, caudal third), yielding seven segments (body plus three portions of each horn). Location of the vesicle within the uterus was recorded every five minutes for two consecutive hours (25 location determinations per trial). The number of times the vesicle was found in the uterine body versus one of the uterine horns was greater for the body on Day 9 (15.2 vs 9.8; not significant) and Day 10 (17.3 vs 7.7 P<0.05) and greater (P<0.05) for the horns on Days 12 (7.3 vs 17.7) through 17 (0.0 vs 25.0). Averaged over all days, when the vesicle was in one of the uterine horns it was present 56% of the time in the caudal third, 30% of the time in the middle third, and 14% of the time in the cranial third. Mobility was determined by the number of times the vesicle changed locations during successive examinations. On Day 9, the mean number of location changes per trial was minimal (horn to horn, 0.2; body to horn or vice versa, 1.8; between two segments, 4.2). The extent of mobility increased on Day 10 and reached an apparent plateau from Day 11 to Day 14. The mean number of location changes per trial during the plateau was as follows: horn to horn, 1.6; body to horn or vice versa, 5.6; between two segments, 10.7. Fixation (cessation of mobility) occurred in one of the horns in 5 7 mares on Day 15 and in 7 7 mares by Day 16. Mobility was present on the earliest day the embryonic vesicle was detected (Day 9), but Days 11 to 14 were characterized as the days of maximum mobility.     

Endometrial surface and secretory alterations associated with embryonic mortality in gilts administered estradiol valerate on days 9 and 10 of gestation

Administration of estrogen to gilts on Days 9 and 10 of pregnancy results in total embryonic loss by Day 18. The present study examined changes in the uterine endometrial surface and secretion during conceptus attachment in control and estrogen-treated (Days 9 and 10) pregnant gilts. Gilts were unilaterally hysterectomized on either Days 12 and 14 or Days 16 and 18 of gestation. Uterine horns were flushed with saline and conceptuses were evaluated. Intact conceptuses were recovered from all control gilts, whereas estrogen-treated gilts contained normal intact conceptuses only on Day 12 of gestation. Antiviral activity, which reflects conceptus viability, was reduced (p less than 0.01) in uterine flushings after Day 14 in estrogen-treated gilts. Culture of endometrial explants with [3H]glucosamine revealed several glycoproteins that are synthesized during the period of conceptus attachment; however, no difference in glycoprotein synthesis between treatment groups was detected by analysis with two-dimensional PAGE and fluorography. Analyses of the uterine epithelium by scanning and transmission electron microscopy demonstrated that estrogen administration caused an alteration in the uterine surface, a thinning of the uterine epithelial glycocalyx, and a reduction of cationic ferritin binding to the microvilli of the uterine epithelium. Results indicate that conceptus mortality after early administration of estrogen is associated with alterations in the uterine endometrial surface during the period of conceptus attachment in the pig.     

The trophotaenial placenta of a viviparous goodeid fish. I. Ultrastructure of the internal ovarian epithelium, the maternal component

Embryos of goodeid fishes develop to term within the ovarian lumen, where they undergo considerable increase in weight due to transfer of maternal nutrients across a trophotaenial placenta. The placenta consists of an embryonic component, the trophotaeniae, and a maternal component, the ovarian lining. The latter was examined by transmission electron microscopy, scanning electron microscopy, and light microscopy in both gravid and nongravid ovaries of the viviparous goodeid fish, Ameca splendens. The single median ovary of A. splendens is a hollow structure whose lumen is divided into lateral chambers by a highly folded longitudinal ovarian septum. Germinal tissue occurs within folds of the ovarian lining that extend into each of the two lateral chambers. Matrotrophic embryonic development takes place within ovarian chambers. During gestation, the lining of the ovarian lumen is in direct apposition to body surfaces and trophotaenial epithelia of developing embryos. The ovarian lining consists of a simple cuboidal epithelium, termed the internal ovarian epithelium (IOE), overlying a well-vascularized bed of connective tissue. Cells of the IOE are apically convex. Well-developed granular and agranular endoplasmic reticula and numerous large membrane-bound vesicles with electron-dense content occupy the apical cytoplasm of IOE cells. Two functional states of the same cell type are distinguished within the IOE. Phase I cells contain few, if any, large apically situated vesicles; Phase II cells contain many. Secretory products of the IOE are presumed to be an important source of nutrients for embryonic development. Structural and functional relationships of the IOE to the trophotaenial epithelium of developing embryos are discussed in relation to maternal-embryonic nutrient transfer processes.     

Uterine epithelial-sperm interaction, endometrial cycle and sperm storage in the terminal zone of the oviducal gland in the placental smoothhound, Mustelus canis.

The fate of spermatozoa deposited within the female reproductive tract has been described in the smoothhound, Mustelus canis. Evidence of uterine epithelial-sperm interaction is presented, as well as documentation of sperm storage specifically in the terminal zone of the oviducal gland. Sperm fate is correlated with morphology of the endometrial cycle and specificity of storage in the oviducal gland. The endometrium of M. canis undergoes dramatic tissue remodeling associated with gestation. In females harboring fertilized ova or preimplantation yolk-reliant embryos, the uterine epithelium is simple cuboidal with mucous droplets for lubrication. The presence of the embryo elicits a response from the uterus, which becomes modified for nutrient and respiratory exchange into vascular uterine attachment sites that abut the distal aspect of the yolk sac. Areas of the uterus adjacent to the uterine attachment sites are termed paraplacental sites. Uterine attachment sites are simple squamous while the paraplacental epithelium is simple columnar. Paraplacental cells have basal metachromatic vesicles and a dense array of apical cytoplasmic filaments. Immediately postpartum the uterine attachment sites, now termed uterine or placental scars, begin to remodel to a mucous epithelium for the next gestational cycle. Paraplacental cells slough off the apical filamentous portion, and sperm become embedded in the epithelium. Bundled sperm occur throughout gestation in the terminal zone of the oviducal gland. Sperm are not embedded in the terminal zone epithelium as in the uterus. Following sperm release from the uterus, the paraplacental epithelium reverts to a mucous epithelium for the next reproductive cycle. Fertilization is presumed to occur in the anterior oviduct above the oviducal gland. The physiological mechanisms that mediate sperm-uterus attachment, release, and storage in the terminal zone of the oviducal gland are currently under investigation.     

Mobility of twin embryonic vesicles in mares

The patterns of intrauterine mobility and fixation of multiple embryos were studied by ultrasonography in 33 mares with twins, six mares with more than two embryos, and 18 mares with singletons. For both single and multiple embryos, the embryonic vesicles showed a preference for the uterine body on days 11 (57% in body) and 12 (58%) and for the uterine horns on days 13 (40% in body), 14 (20%), 15 (15%), and 16 (1%). The preference for the uterine body was characteristic of vesicles that were 3 to 9 mm in diameter. Based on the number of individual embryos which were in different locations between two successive daily examinations, fixation (cessation of mobility) occurred for 97% of the embryos by day 16 and for all embryos by day 18. For 33 mares with twins, fixation involved one uterine horn in 23 mares and both horns in 10 mares (significantly different from equality). Location determinations were made every five minutes during two-hour trials on days 12, 13, or 14 in nine mares with singletons and ten mares with twins. Individual embryos of twin sets had mobility patterns similar to those of singletons. Summed over singletons and twins, the vesicles moved from one horn to another a mean of 0.9 times per two-hour trial (equivalent to 11 times per day). The smaller embryo of twin sets on the average spent more time in the uterine body, but this finding was attributed to their smaller diameter. The observed frequency with which both embryos of twin sets were simultaneously in a given segment of the uterus (28%) was greater (P<0.01) than the expected frequency if each embryo moved independently of the other (18%). Results indicated that 64% of the location changes of twin embryos occurred independently of one another, supporting the hypothesis that the embryonic vesicle plays an active role in its mobility.