Trophoblast antigenicity demonstrated by altered challenge graft survival.

Adult C57BL/6J male mice received either a primary ectopic transplant or a primary and a challenge ectopic transplant of trophoblast tissue obtained from the ectoplacental cones of 7(1/2)-day-old C3H/HeJ x C3H/HeJ embryos. Gross and histologic examinations of these grafts at 5, 7, and 12 days of growth indicated that the challenge grafts were inhibited in growth; there were a smaller percentage of grossly successful grafts, smaller hemorrhagic reactions, fewer viable cells at all stages of growth, and better host containment of the colony. The evidence indicates that exposure to pure trophoblast alters an animal's subsequent reaction to grafts syngeneic with the original trophoblast and can best be explained as evidence of immunologic sensitization of the host.

On the factors which contribute to thinning of the villous membrane in human placentae at high altitude. I. Thinning and regional variation in thickness of trophoblast.

Sections of human term placentae delivered at low and high altitude to indigenous and non-indigenous populations in Bolivia were analysed by stereological methods. Estimates were obtained of the arithmetic and harmonic mean thicknesses of villous membrane and of trophoblast. These values were then used to derive indices of thickness variation. No significant ethnic, sex or interaction effects were found. At high altitude, the villous membrane was significantly more variable in thickness owing to a lower harmonic mean but the same arithmetic mean thickness. Alterations in the arithmetic and harmonic mean thicknesses of the trophoblast contributed to the thinning of the villous membrane. The trophoblast was thinner and more irregular in thickness at high altitude. These findings are discussed in the context of placental diffusing capacity and the possible mechanisms for formation of vasculosyncytial membranes.

On the factors which contribute to thinning of the villous membrane in human placentae at high altitude. II. An increase in the degree of peripheralization of fetal capillaries.

The contribution made by fetal capillary peripheralization to the thinning of the villous membrane seen in human placentae from high-altitude pregnancies is examined by stereological methods. Variables characterizing the shape of the villous core and the spatial relationships between trophoblast and capillaries are quantified. They shed light on the relative importance of dynamic versus mechanistic processes of villous membrane attenuation. Highland villi differ from lowland villi in several ways. On average, they possess a thinner barrier due to closer approximation of capillaries to overlying trophoblast; in consequence, the villous core is more irregular in outline and its surface (that of the inner aspect of the trophoblast) exceeds in area that of the outer aspect of the trophoblast. These results suggest that the dynamic process (protoplasmic streaming within syncytiotrophoblast) cannot alone explain thinning of the villous membrane. A mechanistic process (capillary peripheralization and obtrusion into the trophoblastic epithelium) is sufficient to account for the differences observed, although the possibility that both processes operate concurrently cannot be discounted. This report completes a study into factors contributing to villous membrane thinning at high altitude.

Stereological re-examination of the effects of varying oxygen tensions on human placental villi maintained in organ culture for up to 12 h.

The effects of exposure to various oxygen tensions on villi in organ culture are re-examined. Villi from ten normal mature placentae were cultured under hypoxic (6 per cent oxygen) and hyperoxic (40 per cent oxygen) conditions for 6 or 12 h. Control tissue (zero time in culture) was also taken. Pieces of tissue were fixed by immersion and embedded in resin for semithin sectioning. Systematically sampled microscopical fields were analysed stereologically to estimate harmonic and arithmetic mean thicknesses for the trophoblast and for the villous membrane and to assess the volumetric composition and mean diameter of villi. Trophoblast thicknesses were influenced significantly by oxygen tension, being smaller in hypoxic and greater in hyperoxic media. No significant interaction terms or effects of time in culture were detected. Villous membrane thicknesses altered in a similar fashion to trophoblast thicknesses. No significant differences in the composition of villi were detected but villi tended to be greater in diameter during hyperoxia. Findings are discussed in the context of previously reported adaptations in vivo, in different regions of the placental lobule and during chronic maternal hypoxic stress at high altitude. We conclude that there is insufficient evidence to support the claim that villi can adapt in vitro to varying ambient oxygen tensions.

Early implantation and embryonic development of the baboon: stages 5, 6 and 7.

Implantation stages of the olive baboon, Papio cynocephalus anubis, showing embryonic development equivalent to Carnegie stages 5, 6 and 7 of development, were collected by hysterotomy and examined histologically. The younger specimens (stage 5) consisted of a thick trophoblastic plate composed of cytotrophoblast and syncytiotrophoblast with multiple small clefts, and a bilaminar disk embryo with a small slit-like amniotic cavity. An epithelial plaque response was present in the uterine epithelium immediately peripheral to the implantation site, within an area of pronounced uterine edema. The bilaminar embryonic disk consisted of columnar epiblast cells underlying the amniotic cavity, and thickened visceral endodermal cells that form part of the yolk sac. The slightly further developed placenta (stage 6) consisted predominantly of cytotrophoblast including primary villi and syncytiotrophoblast lining large spaces containing maternal blood. Secondary placental villi were present in the oldest group (stage 7), and there was modest decidualization of the uterine stroma. An epithelial plaque response persisted, but varied in extent. The sequence of events in early development in the baboon is similar to that in the rhesus monkey insofar as blood space formation and endometrial responses are concerned. However, the plaque response is not so great as in the rhesus; there is no secondary placenta, and the decidual response is slightly more extensive.

Morphology and chemical analysis of the sheep conceptus from the 13th to the 19th day of pregnancy.

Between the 13th and 19th day of pregnancy the sheep conceptus developed into a structure showing considerable differentiation and all the extraembryonic membranes were established. Both length and dried weight of the embryo increased exponentially during this period. A highly significant regression of dried weight on length of embryos was found but measurement of the additional variable, width, did not improve the accuracy of estimating weight from the embryo's dimensions. The mass of the extraembryonic membranes also increased greatly. The dried weight of the trophoblast increased 90-fold over this period; that of the yolk sac increased 17-fold from day 15 to day 19. The protein content of each of the structures making up the sheep conceptus approached 50% of dried weight, which is similar to the proportion in adult soft tissues. The contribution of glycogen to dried weight was low in the sheep embryo and embryonic membranes when compared with estimates in the mouse blastocyst. However, at about the time of implantation the level of this polymer in the embryo was high compared with that in adult soft tissues and approached the level found in adult muscle. Concentrations of DNA and RNA in the sheep conceptus are much higher than the levels in most adult soft tissues and probably reflect higher synthetic rates and a smaller cytoplasmic volume in the embryonic cells.

Fetal membrane morphology and circulation of the liquor amnii.

Morphological study of the human fetal membranes (at the term of pregnancy) shows that under the amniochorion lies the chorionic cytophoblast, which completely surrounds the amniotic cavity. Chorionic cytotrophoblast as well as parietal decidua persist until full term and remain well-developed. Within trophoblastic cells there are numerous canalicular formations bordered by microvilli resembling those observed between amniotic cells. The authors therefore believe that the circulation of amniotic fluid, after traversing the amnion, will continue through the intercellular canaliculi of the chorionic cytotrophoblast to reach the decidua parietalis. All the components of this complex membrane must play a part in the amniotic fluid circulation.

[The human placenta and its normal role and in pathology]. / Platsenta cheloveka i ee rol' v norme i pri patologii.

The information on placenta formation, development and structure in health and disease, as well as the role of the placenta as a unique organ which ensures the fetal growth and development during pregnancy is given on the basis of the literature and author's data. Attention is drawn to the formation of the compensatory-adaptive reactions as a complex dynamic process whose manifestations are considered on the subcellular, cellular and tissue levels. Connection between the morphological equivalents of the compensatory mechanisms and the process of maturation of placental barrier structural elements is shown. Determining the character of maturation disorders in combination with the placenta damage allows one to suggest, by means of clinico-anatomical analysis, a particular maternal pathology as the most probable cause of the unfavourable intrauterine conditions of the fetal development. A working classification of placental insufficiency resulting mainly from the disturbance of the compensatory-adaptive reactions is proposed.

[Morphological characteristics of normal trophoblast and choriocarcinoma]. / Morfologicheskaia kharakteristika normal'nogo trofoblasta i khoriokartsinomy.

A certain ratio of cyto- and syntrophoblast cells in the chorion is known to exist during a certain third of pregnancy. It was shown that cell differentiation taking place in the placental epithelium can occur in the same order during malignant transformation of the trophoblast, too. The histological type of tumor was found to be in correlation with the pattern of pregnancy (normal or pathologic) preceding the disease as well as with the stage of pregnancy termination. A significant difference in syncytial choriocarcinoma incidence after normal pregnancy (88.7 +/- 8.8%) and pathological one (41.2 +/- 11.2%) (t = 3.2) was registered. These findings can be interpreted on the basis of morphological characteristics of the disease, which should be considered in planning therapy. The results should also be taken into account when making prognosis.

[Trophoblast in villi of the early human chorion according to the data of optico-structural analysis and electron microscopy]. / Trofoblast vorsin rannego khoriona cheloveka po dannym optiko-strukturnogo mashinnogo analiza i élektronnoi mikroskopii.

Presence of nuclei with tetraploid content of DNA in syncytiotrophoblast of the early chorion has been demonstrated. Before 8 weeks of pregnancy their content makes 31% and then it drops up to 26%. At this age certain severe changes are revealed in texture characteristics of the nucleus--asymmetry and kurtosis of chromatin distribution. Possible pathways of ultrastructural rearrangements in epithelium of the early chorion are discussed.

A stereologic study on the thickness of the trophoblastic layer and its regional variation in the human term placenta.

A new stereological method was applied to estimate the average thickness of the trophoblastic layer in chorial villi from different regions of the human term placenta. Statistically significant differences were demonstrated among the 5 regions considered. The results suggest that the thickness of the trophoblastic layer is related to the pO2 gradient in the intervillous space blood.

Histology of the chorioallantoic placenta of the golden-rumped elephant shrew (Rhynchocyon chrysopygus Gunther, 1881).

The chorioallantoic placenta of the golden-rumped elephant shrew, Rhynchocyon chrysopygus has been studied. The implantation is eccentric and mesometrial. The placenta is haemochorial and is divisible into 4 zones namely columnar, proliferative, spongy and basal trophoblastic zones. The proliferative zone, which is peculiar to the Macroscelididae, is present in the early and mid pregnancy but disappears in later stages. The presence of the basal trophoblastic zone, the absence of a true zone of degeneration, the absence of the "mesoplacentarium" (of Starck 1949) and the structure of the wall of the allantoic vessels differentiate Rhynchocyon from other elephant shrews that have been studied. The presence of large cells in the maternal blood spaces and in the lumen of decidual vessels is also reported but the fate of such cells is not yet known.