Ralph M. Wynn

Fetomaternal cellular relations in the human basal plate: An ultrastructural study of the placenta

Abstract Deciduotrophoblastic cellular relations in the basal plate were studied by correlative histology and electron microscopy. The floor of the human placenta consists of varying proportions of maternal and fetal cells, both viable and degenerating, and fibrinoid. Ultrastructurally well-preserved trophoblast and decidua, however, are never in direct contact, but remain separated by regressing tissues of dual origin, by fibrinoid, or by both. The fibrinoid may arise from degeneration of decidual or trophoblastic cytoplasm or through transformation of the ground substance. Although fibrinoid may serve the ancillary function of providing an antigenic barrier in many hemochorial placentas, its absence from areas of fetomaternal contact in histologically less intimate placentas precludes its playing a principal immunologic role in placentation in general. The apparently viable giant cells of the basal plate are essentially syncytiotrophoblastic, representing either derivatives of the peripheral syncytium or results of differentiation in situ of cytotrophoblast. Transitional elements, similar to those described in villous trophobtast, are commonly observed. These giant cells very likely sustain placental endocrine function throughout gestation. Although there is not yet proof of hormonal activity in the maternal component of the human placenta, the ultrastructure of the basal decidua provides the basis for suggesting that possibility. The basal plate, with its intimate juxtaposition of genetically dissimilar cells, represents a unique region for study of placental endocrinoloey and immunology. Ultrastructurat histogenetic identification of the components is thus a preliminary requisite toward that goal.

Derivation and ultrastructure of the so-called Hofbauer cell

Abstract The derivation and significance of the so-called Hofbauer cells were studied by analysis of sex chromatin, histochemistry, and electron microscopy, in an attempt to ascertain their immunologic and metabolic significance, if any, in human placentation. Ultrastructurally, the Hofbauer cell is characterized by vacuolar cytoplasm and scant ergastoplasmic fragments, but well-developed endoplasmic reticulum and Golgi complexes are absent. Various stages of degeneration are normally found. Although the ordinary Hofbauer cell may be distinguished by histochemistry and electron microscopy from the typical fibroblast and plasma cell, transitional and poorly differentiated forms are commonly found, exemplifying the variety and interconversion of villous mesenchymal elements. The Hofbauer cell is not a specific entity with regard to either origin or function, but rather a villous stromal component arising by differentiation or degeneration of other mesenchymal elements; since, furthermore, it may differentiate in situ from the villous mesenchyme throughout pregnancy, it provides little aid in diagnosis of placental abnormalities.

Renal Effects of Angiotensin II Infusions in Normotensive Pregnant and Nonpregnant Women

Normotensive pregnant women are relatively resistant to angiotensin II in that they give smaller pressor responses and show smaller reductions in urine flow and sodium and chloride excretions than do normotensive nonpregnant women. Women early in the third trimester of pregnancy are more resistant to angiotensin II than are women at term, with respect to the effect upon sodium and chloride excretions. The less pronounced renal effects of angiotensin II in pregnant women cannot be attributed merely to error caused by increase in the dead space of the urinary tract.

Intrauterine Devices: Effects on Ulrastructure of Human Endometrium

The human endometrium, studied with the electron microscope, undergoes asynchronous and premature cyclic development in response to inin uterine contraceptive devices. Typical nucleolar channel systems and other cellular characteristics of the normal secretory phase appear before ovulation, and decidualization occurs several days prematurely. Disturbance of the synchrony of ovular and endometrial development may be a mechanism of contraceptive action of these devices.

ELECTRON MICROSCOPIC CONTRIBUTIONS TO PLACENTAL PHYSIOLOGY

IN the decade since the publication of the classic papers by Wislocki and Dempsey (1953, 1955) in the United States, and by Boyd and Hughes (1954) in England, on the electron microscopy of the human placenta, numerous corroborative studies have been performed in both countries, as well as in France (Panigel and Nguyen Anh, 1963, 1964a), Germany (Bargmann and Knoop, 1959; Arnold, Geller and Sasse, 1961), Japan (Hashimoto et a/ . , 1960a, b; Sawasaki et al., 1957; Ikawa, 1959), and Italy (Sermann and Rigano, 1962). In general, the observations of the mid-fifties have been confirmed and refined by the newer techniques, but with respect to pure descriptive morphology few, if any, new significant data have been provided. Electron microscopy of the placenta nevertheless remains a rewarding application of electronics to histology because it permits an exquisite correlation of ultrastructure with physiological activity at the cellular level. Inasmuch as details of human placental fine structure are readily available in the recent papers of Rhodin and Terzakis (1962), Terzakis (1963) and Lister (1963a, b, 1964), for example, and in the comparative studies of Wynn and Davies (1965) and Enders (1 969, this report will deal with a few selected examples of the aid provided by the electron microscope in the elucidation of placental function. These problems were chosen for study in our laboratory in the belief that they respresent topics of clinical significance in obstetrics and gynaecology.

Ultrastructure of trophoblast and endometrium in invasive hydatidiform mole (chorioadenoma destruens)

Abstract Trophoblast of invasive mole maintains the ultrastructural features of its counterparts in normal placenta, benign hydatidiform mole, and choriocarcinoma. Syncytium, poorly differentiated cytotrophoblast, and prominent clumps of transitional trophoblast are distinguished. The endometrial stroma in closest relation to the invasive trophoblast, however, is ultrastructurally less complex than normal decidua basalis, bearing greater resemblance to parietal decidua. There is relatively little necrosis of trophoblast and adjacent decidua and less deposition of fibrinoid than in normal placentation. The decreased reaction of decidua to trophoblast may permit the more extensive invasion characteristic of malignant chorionic neoplasms. Endometrial epithelial cells exhibit the Arias-Stella phenomenon. The affected cells are more highly differentiated ultrastructurally than those of normal proliferative or secretory endometria. This reaction appears to reflect cellular hyperactivity rather than involution.

Morphologic studies of the ruptured amnion

An operative technique of experimental rupture of the fetal membranes in the guinea pig was devised to permit continuation of the pregnancy and subsequent histologic examination for evidence of regeneration. The definitive amnion after premature rupture may regenerate morphologically normal tissue. Although the origin and disposition of the fetal membranes differ among mammalian species, comparative histologic and electron microscopic studies indicate basic structural characteristics common to all mammalian amnions. Earlier concepts of the fate of the ruptured human amnion are reviewed. Direct application to man of these experimental findings may not be valid, but comparative anatomical evidence suggests that one explanation for cessation of leakage and continuation of pregnancy following premature rupture of the human membranes may be healing of the defect by regenerated amnion.