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Notes: Protein synthesis and secretion in mouse uterine glands during the peri-implantation period were studied, by both light and electron microscopic autoradiography, after the in vivo administration of tritiated leucine (3H-leucine) and proline (3H-proline). Light microscopic autoradiography revealed that the time course of synthesis and secretion of labeled proteins was constant during days four, five, and six of pregnancy. Labeled material could be detected in the glandular lumen by 45 minutes after administration and in higher concentrations by 90 minutes after administration.Analysis of electron microscopic autoradiographs from days five and six of pregnancy showed that high levels of activity were initially present over the rough endoplasmic reticulum and Golgi complexes and subsequently declined at the longer time intervals (45 and 90 minutes), while activity over the glandular lumen increased with time. The pathway of intracellular transport to the glandular lumen appeared to be via small cytoplasmic vesicles on both days five and six of pregnancy. Additional pathways for transport of the labeled protein to the glandular lumen appeared to be present in the form of the large vesicles on day five and granules on day six of pregnancy.Throughout the peri-implantation period, mouse uterine glands were active secretory structures in which the mode of secretion was similar to other exocrine cells. Thus, the uterine glands of the mouse must be considered a source of uterine fluid proteins at the time of implantation that may contribute to quantitative changes in these proteins.

Notes: The luminal and glandular epithelia of the rat uterus during delayed implantation have been studied with the electron microscope. The tall columnar cells of the luminal epithelium are characterized by a distinct zonation of organelles. On the free surface there are short microvilli and occasional cytoplasmic extrusions, with terminal bars joining adjacent cells at their apical margins. Beneath the free surface are numerous pinocytotic vesicles and mitochondria. Above the nucleus are a prominent Golgi apparatus with large dilated vacuoles, and numerous dense inclusion bodies. Large clusters of lipid droplets and aggregations of mitochondria occupy the basal zone of the cell.The apical portion of the gland cell has fewer pinocytotic vesicles and the Golgi is smaller than in the luminal epithelial cells. Dense bodies are numerous above the nucleus. The basal portion of the gland cell is devoid of lipid, but there are often one or more enlarged mitochondria. Although a dense PAS+ substance fills the lumina of the glands, there is no obvious evidence of secretory activity in the glands during delay.The relationships of the epithelia to the environment of the blastocysts during delay is discussed.

Notes: The structure and development of the female reproductive tract, fetal membranes and placenta have not previously been recorded for any member of the family Thyropteridae. Recently implanted embryos were obtained in late January, limb-bud stages in March, and full-term fetuses in late May, suggesting a possible gestation length of approximately five months. It is likely, however, that Thyroptera experiences at least two breeding cycles per year. The uterus was narrowly bicornuate; the corpus uteri was unusually large and lacked the glandular density observed in the cornua. The cervix was long, pleated, and relatively aglandular. The oviducts opened at the apices of the cornua; oviductal papillae were absent. A bursa ovarii surrounded the ovary, but there was a small pore opening to the peritoneal cavity adjacent to the fimbriated end of the oviduct. Never more than a single embyro or fetus was present, and only a single corpus luteum was observed; thus Thyroptera, like most bats, is monovular. Ovoimplantation was interstitial; a decidua capsularis was present early but disappeared by the late limb-bud stage. The decidual reaction involved both glandular epithelium and stromal cells, but most of the decidua was destroyed by term. Amniogenesis was initiated after implantation, by cavitation. Primitive entoderm was formed precociously above, as well as below, the presumptive embryonic disc, and a thin extension of Reichert's membrane passed over the cell mass, separating it from the cytotrophoblast of the chorionic placenta. During the amniogenic period, the yolk-sac entoderm fused to the parietal trophoblast via an intervening Reichert's membrane, forming an extensive bilaminar omphalopleure; this was rapidly converted to a trilaminar structure in early post-implantation stages. An avascular chorio-vitelline relationship involved most of the chorionic wall in early post-implantation stages and persisted to term in the abembryonic hemisphere after the partial inversion of the yolk-sac roof in late presomite embryos. The invaginated yolk-sac roof (splanchnopleure) also persisted to term as a viable paraplacental component. A small sac-like allantois was formed between late pre-somite and early limb-bud stages but disappeared by the late limb-bud stage. Development of the definitive chorioallantoic placenta resembled that in other bats, but the maternal endothelium disappeared relatively early, and trophoblastic differentiation was precocious. The ultrastructural organization of the interhemal membrane was hemodichorial, and otherwise generally resembled the organization previously described in vespertilionid bats. Similarities and differences in the structure of the uterus, placenta, and paraplacental organs of Thyropteridae, in comparison with other families of bats, are discussed. On the basis of fetal membrane characteristics, the Thyropteridae show closer affinities with the Phyllostomatoidea than with the Vespertilionoidea, to which they are presently assigned.

Notes: Implantation sites were obtained from rats at various stages of pregnancy and were studied by light microscopy and scanning electron microscopy. Early in pregnancy the uterine luminal epithelium and the decidual cells in the implantation site formed an implantation chamber containing the conceptus. The epithelial cells lining the chamber and the mouth of the chamber degenerated, and the uterine lumen that was mesometrial to the conceptus was obliterated such that the uterine lumen became discontinuous, and the luminal epithelia of intersite areas were isolated. As the conceptus continued to grow, the decidua-conceptus unit bulged into the intersite areas and was partially covered by an epithelium that eventually became discontinuous and degenerated. Once this had occurred, the luminal epithelium of the intersite areas reestablished contact antimesometrial to the decidua-conceptus unit, and the uterine lumen was again continuous. However, the epithelium lining the lumen was not complete in the mesometrial region because of the vascular connections between the uterine stroma and the placenta. Factors influencing the restructuring of the uterine luminal epithelium were discussed.

Notes: Mouse uterine glands, obtained during the peri-implantation period of pregnancy, were investigated using light and electron microscopy. From day 4 to day 6 of pregnancy, there was a progressive luminal dilation and an accumulation of dense homogeneous material in the gland lumina. Although numerous large electron-lucent vesicles were present in the apical portion of the glandular cells on day 4, their number decreased by days 5 and 6 of pregnancy. Dense granules were present along the apical border of many glandular cells on day 6. In addition, there was an increase in the number and more orderly arrangement of RER cisternae by day 6 of pregnancy. Cytochemical studies on days 4, 5, and 6 of pregnancy, using the periodic acid-thiocarbohydrazide-silver proteinate method for the ultrastructural localization of carbohydrate material, showed specific staining of the multivesicular bodies and the saccules of the concave surface of the Golgi complex, but not the dilated saccules of the convex surface. Specific staining was also observed over both the luminal material and apical granules present on day 6 of pregnancy.The cytochemical evidence suggests that the secretory product of the uterine glands has carbohydrate components and that carbohydrate material accumulates in the Golgi complex. In addition, the morphological changes observed imply increased secretory activity of the uterine glands during the peri-implantation period. Thus, the uterine glands must be considered an important source of uterine fluid components during the peri-implantation period.

Notes: A series of peri-implantation stages of the rhesus monkey has been collected; these range from preimplantation blastocysts through initial implantation to early villus formation. The three earliest postimplantation specimens encompass the stages of penetration into and through the uterine luminal epithelium and into endometrial blood vessels. The day of pregnancy was established by radioimmunoassay of estrogen (E) levels to determine the prevulatory E peak, and in each instance the embryo was examined to determine the extent of development. The conceptus collected on day 9.5 of pregnancy was the earliest implantation stage; it ballooned above a depression in the endometrium to which it was firmly attached. A column of syncytial trophoblast penetrated into the uterine epithelium to the basal lamina of the latter. The syncytial trophoblast shared junctional complexes with the uterine epithelial cells to which it was apposed at the margin of the site of epithelial penetration. Basal to the apical junction complexes, processes of syncytium indented uterine epithelial cells. Several epithelial cells had been partially isolated and surrounded by flanges of syncytial trophoblast. In the next specimen, at 10.0 days after ovulation, the uterine epithelium had initiated the epithelial plaque reaction. The trophoblast had extended along the residual basal lamina of the uterine epithelium and into the neck of an adjacent uterine gland. Cytotrophoblast was abundant in the central region of the implantation site, and was intermixed with syncytium which formed the majority of the peripheral trophoblast. In several places clefts had formed in the syncytial trophoblast; these clefts were lined with microvilli, had intermicrovillous caveolae, and consequently more closely resemble the trophoblast that eventually lines the intervillous spaces than the trophoblast involved in initial invasion. In the day-10.5 specimen, in addition to prelacunar clefts, lacunae containing maternal blood were present for the first time. The basal lamina was penetrated in many places, and syncytial trophoblast was interposed between maternal endothelial cells of the underlying vessels.It was concluded that syncytial trophoblast is the first tissue to penetrate the uterine luminal epithelium; that the basal lamina of the uterine luminal epithelium, but not the basal lamina of endothelium, constitutes a temporary barrier to trophoblast penetration; that invasion is accomplished with less destruction of maternal tissue than previously suggested; and that the rapid superficial growth of the placenta is made possible by the early tapping of the endometrial vessels.

Notes: Fixed uteri from rats on the afternoon of day 6 of pregnancy were split to expose the implantation chambers, their enclosed blastocysts, and the imprints of the blastocysts on the adjacent epithelium of the chamber. Some ofthe implantation chambers were prepared for scanning electron microscopy; other chambers were treated with colloidal iron hydroxide, with cationized ferritin, or with the tannic acid method, and subsequently were prepared for transmission electron microscopy. In this manner, the disposition of the surfacecoat markers on the surface of the blastocyst, surface of the uterus within the chamber, and the surface of the uterus that had been apposed to a blastocyst were compared. Despite the pronounced morphological differences between the microvilli of the uterine luminal epithelium in the imprint and those in the rest of the chamber, the binding of the markers was remarkably similar. No evidence of removal of surface coat could be found in that area of the uterus in contact with the blastocyst. In addition, in two instances in the cationized ferritintreated material, and in another instance in tannic acid-stained material, regions of the apparently adhering trophoblastic cell membranes and uterine cell membranes had abundant coat materials and, possibly, even secretory materials interposed. When blastocyst-sized glass beads were introduced into uteri from animals made pseudopregnant or unilaterally pregnant, the beads failed to elicit a decidual response and made an imprint that did not resemble the imprint of a blastocyst in an implantation chamber. It was concluded that, at least in the initial stages of adhesion, the blastocyst does not bring about a physical removal of the demonstrable aspects of the surface coat of the uterus. It was concluded further, that glass beads are not a suitable object for mimicking a blastocyst in the rat uterus.