Scanning electron microscopy of stromal cells of human placental villi throughout pregnancy

Morphological changes in fixed stromal cells and Hofbauer cells were studied throughout pregnancy in different types of placental chorionic villi by scanning electron microscopy. In the mesenchymal villus the fixed stromal cells were characterized by thin cytoplasmic processes. Hofbauer cells exhibited blebs on their surface. Large sail-like processes with a crescent profile which surrounded well developed stromal channels and a small cell body typified the small reticulum cells of the immature intermediate villus. The Hofbauer cells here displayed blebs, microplicae and large lamellipodia. Short cytoplasmic expansions and a large cell body characterized the fibroblasts present inside the stem villus. Hofbauer cells were rare, having blebs or a few short lamellipodia. The mature intermediate villus contained small and large reticulum cells. The latter had a much larger cell body than the small ones and displayed a few short cytoplasmic processes partly delimiting narrow incomplete stromal channels. Occasional Hofbauer cells with small microplicae and/or blebs were present. The small reticulum cells and fibroblasts present in the terminal villus showed similar morphological features as above. However, the former exhibited less developed cytoplasmic extensions and therefore no stromal channels were observed. In the terminal villus, the morphology of the rare Hofbauer cells was similar to that found in the mature intermediate villus.

Ultrastructural observations of chorionic villi at term in diabetic women

An electron microscopic study has been performed on placentas from women with maternal diabetes. None of the patients had suffered from any of the hypertensive complications of pregnancy (White's class A). Most villous trophoblasts were morphologically normal and showed features suggestive of normal or increased synthetic transport and excretory activity. These cells appeared to be far more "active" than their counterparts in normal term placentas in that many contained Golgi bodies that were often associated with membrane-bound osmiophilic vesicles. Focal thickening of the trophoblastic basement membrane was seen. The endothelial capillaries contained an excessive number of microfibrillae and micropinocytotic vesicles and appeared unduly immature. Very abundant osmiophilic granules were seen in many villous components, such as syncytiotrophoblasts, stromal fetal endothelial cells, pericytes, Hofbauer cells and fibroblasts. These may have been concerned in the cross-transportation of materials between the maternal intervillous space and the fetal capillaries, rather than the incorporation of substances within them. These morphological changes did not show, however, any specific, constant or uniform pattern of abnormality attributable maternal diabetes.

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.

The stromal architecture of the immature intermediate villus of the human placenta. Functional and clinical implications

Scanning electron microscopy of cryofractured immature intermediate villi showed numerous intercommunicating channels in the central region of the stroma, oriented mostly parallel to the major axis of the villus. In the stromal channels, numerous Hofbauer cells were present and their aspect and position inside the channels highly suggested a motility of these cells. These morphological data strongly support the fundamental role played by the immature intermediate villus in the normal and pathological development of the human placenta.

Some new findings about Hofbauer cells in the chorionic villi of the human placenta

The cytological structure of the Hofbauer cells was investigated in human placentas of the first and second trimesters of gestation. These cells are found in the stromal channel system of the chorionic villi core. Their walls, which are supported by collagen fiber bundles, are produced by reticulum cells and fibroblasts. The cytoplasmic processes of the Hofbauer cells are in contact with the walls of the channels without being associated with them by desmosomal complexes. Some of these cells have features in common with macrophages, such as cytoplasmic processes, larger vacuoles, many pinocytotic vesicles and intracytoplasmic granules. This system of vacuoles and vesicles enables micropinocytotic activity and phagocytosis. This type of Hofbauer cell resembles the typical macrophages. These cells may play a role in the regulation of stromal water content, transportation of ions and the flow of interstitial fluid. The most original finding of this study are long tubes observed in some Hofbauer cells and extending between the nucleus and the extracellular ground substance through the cytoplasm. One of these tubular formations resembles a cilium in structure with three limiting membranes and is filled with a slightly electron-dense substance. This type of Hofbauer cell may transport information between the nucleus and the extracellular ground substance by means of these tubular structures.

Scanning electron microscopic observations on the opossum yolk sac chorion immediately prior to uterine attachment

The 10 day opossum embryo is enclosed by a yolk sac chorion in which distinct vascular and non-vascular regions are established before attachment to the uterine epithelium. The embryo is closely associated with the vascular region which becomes adherent to the uterine lining. Cells of the external layer bear abundant, closely packed, long microvilli, which may serve to absorb nutrients from the uterine secretions. Cells of the inner surface show only scattered microvilli and microplicae on their apical surfaces.

Idiopathic intrauterine growth retardation: histomorphometry of the human placenta

The morphological changes in the functional structure of the placenta in cases of idiopathic intrauterine growth retardation (IUGR) have been investigated with quantitative analyses. It has shown that the placentae of the small-for-gestational-age (SGA) infants were 45 per cent smaller than the controls, due to an almost equal reduction in parenchymal (48 per cent) and non-parenchymal (42 per cent) tissues. Consequently, in relative values the placentae of the SGA infants were shown to be otherwise very similar to the controls. In contrast, in absolute values, the placentae of the growth-retarded infants were shown to differ from the controls by having significantly less surface area of exchange between mother and fetus, mainly in terms of peripheral capillary (3.85 vs 7.21 m2; P less than 0.02) and villous (4.31 vs 8.74 m2; P less than 0.005) surface areas, and intervillous space volume (53.71 vs 103.26 cm3; P less than 0.001). The total number of cells (53 418 x 10(6) vs 104 820 x 10(6); P less than 0.005) was also shown to be markedly decreased in the placentae of the SGA infants, compared with the controls, and the placental membrane showed a 51 per cent decrease in trophoblast mass or cellular content. On a functional basis, these findings suggest that, in these cases of idiopathic IUGR, the placental morphological changes are bound to produce placental insufficiency and fetal growth retardation.

[Viability of human chorionic villi in organ culture]

The method and technique of organ culture of human chorionic villi was elaborated in our laboratory. In this report, placental specimens obtained at 15 to 18 weeks of gestation were studied in organ culture for 7 days in terms of the maintenance of morphological integrity and the preservation of functions. The morphological aspect of the viability of the various villous elements with special emphasis on the trophoblast cells was described histologically and ultrastructurally. The functional aspect of the viability was discussed by analysis of the suppressive effect of the cultivated villi on plasminogen activator (PA) secretion by OK-432 elicited mouse peritoneal macrophages, by analyses of the activity of delta 5-3 beta-hydroxysteroid dehydrogenase coupled with delta 5-delta 4-isomerase (HSD) and of the radioactivity of [125I]-Iododeoxyuridine ( [125I]-IUdR) retained in the DNA of the trophoblast cells. Specimens of normal placenta were obtained at the time of induced abortion. The gestational ages were 15, 16 and 18 weeks. Specimens for organ culture were prepared under sterile conditions within one hour after expulsion of the placenta. Through gross dissection, the villi were isolated and minced into fragments of approximately 1 to 2 mm3. Incubation was carried out at 37 degrees C in a conventional static chamber with a gas mixture of 95% air, 5% CO2. The culture dishes and culture media were renewed every day. Data are the mean values of the duplicate incubations. In the first series of organ culture, placental fragments were removed at the end of each day of incubation, washed thoroughly and transferred to the new dishes with a culture medium freed from fetal bovine serum, where further incubation was performed for 24 hours. After this, placental fragments were fixed in 4% neutral buffered formalin, processed through paraffin embedding, serially sectioned at 5 micron and stained by periodic-acid Schiff (PAS) procedure. Culture medium obtained in this series at each end of incubation was put into a "macrophage plate" with the addition of plasminogen in the concentration of 2 IU/m1, in which OK-432 elicited mouse peritoneal macrophages with the capacity to secrete PA were cultured. Reaction was terminated at 24 hours unless otherwise indicated. Ten microliters of the medium in the "macrophage plate" was applied to the fibrin plate, and reaction was performed for 18 hours. PA activity was expressed by plasmin activity converted from plasminogen measured by the single radial immuno-diffusion method.(ABSTRACT TRUNCATED AT 400 WORDS)

Efficient direct chromosome analyses and enzyme determinations from chorionic villi samples in the first trimester of pregnancy

Chorionic villi were obtained by an aspiration technique which proved to be the best of four alternative procedures. We report in detail the series of experiments which led to (1) successful, rapidly growing cell cultures practically free of maternal cell contamination (the use of hormone-supplemented Chang medium greatly increased the growth rate); (2) an efficient direct method to obtain high quality metaphases from the Langhans cells of the cytotrophoblast tissue and with which the fetal karyotype is defined within a few hours of chorionic villi sampling; and (3) successful testing for the activity of eight enzymes directly from the villi samples, thus showing that this material is suitable for a rapid, direct diagnosis of the related metabolic diseases.

Morphological study of the fetal vasculature of the human term placenta: scanning electron microscopy of corrosion casts

Microvascular corrosion casts of the fetal vessels of the normal human placenta were studied using the scanning electron microscope. All available evidence suggests that when prepared under standard conditions the resultant casts accurately replicate the original luminal morphology of the vessels, and are comparable between placentae. In conjunction with stereo-pair photography this technique allows for the rapid and unequivocal interpretation of the three-dimensional configuration of villous vasculature. Previously described structures such as dilated capillary loops and perivascular capillary networks can be viewed in new and dramatic perspective. It is hoped the technique may thus be of assistance to physiologists in the interpretation of experimental data concerning placental transport. Further work is in progress to apply the technique to the investigation of possible changes in fetal vasculature occurring in abnormal pregnancies.

Frequency and antigenicity of type C retrovirus-like particles in human placentas

Seventeen placentas from normal Japanese women, obtained from 15 full term gestations and at 2 earlier gestational periods, were observed by electron microscopy for the presence of type C retrovirus-like particles. Immature free and budding particles were found in 16 placentas including those obtained pre-term. Free virus-like particles were seen in the intercellular spaces and within the lysosomes of syncytiotrophoblasts of the chorionic villi. Forms budding from syncytiotrophoblasts were found in 3 cases. Coincident data with the electron microscopic observations were obtained by immunohistological methods. Specific positive staining with antisera against heterogeneic whole murine leukaemia virus were seen within the cytoplasm of trophoblastic cells both in and along the basal lamina.

The human placenta in idiopathic intrauterine growth retardation: a light and electron microscopic study

Six placentae from small for gestational age infants were examined by both light and electron microscopy. These were from pregnancies in which all maternal or fetal factors known to be associated with intrauterine growth retardation, including maternal cigarette smoking, were excluded. At the light microscopic level the only significant finding was an excess of villous cytotrophoblastic cells whilst electron microscopy showed these placentae to be characterized by villous cytotrophoblastic hyperplasia, focal syncytial necrosis, microvillous abnormalities, reduced syncytial secretory activity, irregular thickening of the trophoblastic basement membrane and the presence of small fetal villous vessels with multilayered basement membranes. It is thought that most of the observed abnormalities are due to uteroplacental ischaemia and it is possible that the fetal vascular abnormalities are a reflection of the fetal growth retardation. There is little evidence that the functional efficiency of the placenta is impaired in these cases and it is suggested that the principal factor in the pathogenesis of fetal growth retardation is a restriction of nutrient supply to the fetus because of an inadequate degree of physiological change within the maternal spiral vessels.

Surface ultrastructure of the human placental villi and sites of contact with maternal red blood cells

With the aid of the scanning electron microscope the possible sites of materno-foetal oxygen transfer were investigated. Fresh small tissue pieces were obtained and processed from at least six regions of central and peripheral parts of the maternal surface of human full-term placentas. The surface ultrastructural features of the syncytiotrophoblast lining the stem and floating villi were surveyed. The microvilli projecting from the apical portion of the syncytiotrophoblast appeared to be highly pleomorphic and showed regional variation in their distribution. On the other hand, our results confirmed the occurrence of non-microvillous areas on the apices of some floating villi. When present, these areas were always free from contact with maternal red blood cells. Maternal red blood cells, however, were seen in close contact only with areas covered with microvilli. Occasionally, impressions ("footmarks") were apparent on some surfaces and detached microvilli were seen adherent to the surface of other maternal red cells which had separated from the villous surface. Our results indicate, therefore, that the microvillous areas of the chorionic villi are the most likely sites for oxygen transfer and that one of the functions of the microvilli is gas transfer across the placenta.

Developmental changes in rhesus monkey placental villi and cell columns. Scanning electron microscopy

Developing rhesus monkey placentas were analyzed by scanning electron microscopy with special attention directed toward defining stages in the development of the villus branches. The initial phase in formation of villi was the conversion of reticulated trabeculae of syncytial trophoblast into chorionic villi by growth and proliferation of cell columns of cytotrophoblast. These villi were stout and unbranched. The second phase of development appeared to be the longitudinal splitting of the villi and cell columns to form groups of parallel branches but there was a common insertion of these into the basal plate. The third phase in formation of villi, which appeared to begin at about the same time as the longitudinal splitting occurred, was the outgrowth of large-diameter side branches in a zone nearer the chorionic plate. At about 38-40 days of gestation the next stage in villus formation occurred, characterized by the emergence of numerous, small syncytial sprouts. Continued proliferation of villi at later stages of gestation resulted in a decreased diameter of the terminal villi and an increasing complexity in the course of fetal capillaries.

The chorioallantoic placenta of the spotted hyena (Crocuta crocuta Erxleben): an electron microscopic study

The histology and ultrastructure of the chorioallantoic placenta of the spotted hyena have been studied in three specimens obtained in the field and fixed promptly with glutaraldehyde. Observations revealed that the interhemal membrane at its minimal thickness is hemomonochorial, consisting of a continuous layer of syncytial trophoblast, a basal lamina, and fetal capillary endothelium. Cytotrophoblastic cells form a discontinuous layer beneath the syncytial trophoblast and are distinguished by the presence of numerous extracted lipid droplets in their cytoplasm. A network of extracellular spaces, incorrectly identified as cisternae of endoplasmic reticulum by earlier investigators, occurs beneath the maternal surface of the syncytial trophoblast. These spaces contain moderately dense, nonfibrillar material resembling the intrasyncytial lamina previously described only in the hemochorial placenta of certain bats. Hence, these spaces may contain remnants of maternal capillary basal lamina following displacement of the endothelium by extensions of syncytial trophoblast at an early stage of placental development.

A three-dimensional study of the normal human placental villous core: II. Stromal architecture

The three-dimensional architecture of the villous core of the chorionic villi has been studied in the human placenta throughout pregnancy by scanning electron microscopy, and compared with light microscopic and transmission electron microscopic, findings. Five different types of villi are recognizable: the mesenchymal villi are characterized by a network of tiny bundles of collagen fibrils, enmeshing mesenchymal cells, Hofbauer cells and vessels. The immature intermediate villi display a system of intercommunicating channels, parallel to the major axis of the villi. Within the channels, Hofbauer cells are present. The mature intermediate villi show narrow and short stromal channels, surrounded by a rather tight network of collagen fibrils. Large vessels and a highly compact network of collagen are typical of the stem villi. The terminal villi contain sinusoidally dilated capillaries and a small amount of connective tissue. These findings have numerous functional implications. They are particularly related both to the presence of the stromal channels which could facilitate the macrophagic and immunological task of the Hofbauer cells, and to the different types of villi, playing different roles in placental and fetal life, under normal and pathological conditions.

[Negative surface charge of human trophoblast and its biological role (author's transl)]

The negative charges on the various trophoblast was investigated, in order to cast light on the biological roles, by electron microscopy using cationized ferritin as an ultrastructural marker, in comparison with surface glycoprotein. The following results were obtained: 1. The surface glycoprotein distributed on the trophoblastic plasma membrane forming regularly situated aggregates, 15 to 20 millimicron in diameter separated by 50 to 100 millimicron from neighboring ones. 2. The negative charge on the cell surface was distributed in two different configurations: A strongly negative part and weakly negative one. 3. The placental villi were revealed to carry an extremely high level of negative surface charge. 4. One maternal lymphocyte in a first trimester pregnancy was calculated to carry a 5.9 x 10(-11) Coulomb negative surface charge. 5. In a simplified model, the electronic repulsive force between the lymphocyte and placental villus was calculated as 5.7 x 10(-4) Newton, showing that the electronegative charge on human trophoblast was strong enough to repel the negatively charged lymphocyte against the lymphocyte gradient. 6. For villi from spontaneous abortion with mild degeneration, the surface glycoprotein was observed to make prominent aggregates on the trophoblastic surface in concomitance with the reduced negative surface charge. 7. With the observation by electron microscopy, The complete mole differed essentially from the partial mole in that former resembled normal villi while the later spontaneous abortion.

Ultrastructure of the villi and fetal capillaries of the placentas delivered by non-smoking diabetic women (White group D)

The ultrastructure of the placentas from nine non-smoking. White group D diabetic women were studied. The terminal villi showed changes in maturation, increased vascularization mainly due to very small vessels located at the periphery of the villus, and glycogen accumulation within the stroma cells and pericytes, corresponding to the known higher glycogen content of diabetic placentas. Multilaminal basement membrane surrounded the capillaries, but great variation appeared possibly due to variation in capillary age. It is suggested that diabetic metabolism induces a proliferative small vessel disease in combination with accelerated aging.

The placental lesions in congenital syphilis. A study of six cases

Placentas from six mothers with serological tests suggestive of recent syphilitic infection and whose babies were suspected of being or proven to be infected by Treponema pallidum are described. One placenta from this series was large, bulky and pale, while the other 5 were without remarkable gross features. In all cases, the associated histological lesions were 1) hypercellular areas in the terminal and stem villi and 2) a focal peri- and/or intravillous polymorphonuclear concentration with or without necrosis. The former change which was the most frequent was characterized by an apparent increase of villous stromal cells, ultrastructurally identified as mesenchymal cells and Hofbauer cells. In addition, numerous fetal monocytes were found in the villous vascular lumina. The findings described here and in the literature suggest that congenital syphilis is associated with a spectrum of placental changes. We believe that these changes depend on the immunological reaction of the fetus. According to the sequence of events described in untreated patients, we distinguish two morphological phases: 1) an inductive phase without placental changes and 2) a reactive phase characterized by a predominantly lymphocytic inflammatory infiltration of the villi, followed by a reaction of mononuclear phagocytes.

The junctional pattern of the human villous trophoblast. A freeze-fracture study

This investigation of the junctional pattern of the human trophoblastic epithelium was carried out on the fractured faces of (a) the syncytial plasma membrane bathed by the maternal blood (S-PMm); (b) by syncytial plasma membrane in contact with either the cytotrophoblast or the trophoblastic basement membrane (S-PMf), and (c) the cytotrophoblastic plasma membrane (C-PM). The most relevant findings were tight junctions on the SPMm, and the intertrophoblastic junctional pattern, not realizing a tight subcompartmentalization between syncytium and cytotrophoblast. The following aspects were discussed: the SPMf represents the last membrane barrier before the fetal capillary, and the function of the cytotrophoblast seems to be limited to the modulation of syncytial activity.

Electron microscopic study of intercellular canalicular systems in the parietal fetal membranes

An electron microscopic study of the amnion and the chorionic cytotrophoblast has demonstrated the existence of intercellular channels running between the lateral sides of the cells with typical junctional complexes sealing their proximal ends. In the amnion these channels open through the basal lamina into the connective tissue, and in the chorionic cytotrophoblast they open in the direction of the decidua. This situation seems to indicate that fluid emerges from the open mouth of the amniotic intercellular channels and then continues to flow into the channels of the cytotrophoblast, across its podocytic processes, to be discharged into the decidua, and finally drained by maternal decidual vessels. This morphological study suggests that parietal fetal membranes might be an important route for transport of solute and fluid from the amniotic fluid to the maternal circulation.

[Ultrastructural study of chorionic villi in maternal-fetal isoimmunity]

The Authors studied the Human normal full term placenta and in the feto-maternal Rh and ABO incompatibilities. In the Human normal full term placenta the sincitium trophoblastum coat shows the usual microvillosity and the normal cytoplasmatic organules; in the placenta of ABO isoimmunized subjects the sincitium trophoblastum coat is intensely vacuolyzated; in the placenta of Rh isoimmunized subjects the lamina sincitiale vacuolyzation is more evident in the basal side. Discussion on the morphology related to the placenta barrier function.

Morphogenesis of human placental chorionic villi: cytoskeletal, syncytioskeletal and extracellular matrix proteins

Immunocytochemical and ultrastructural methods were used to investigate the distribution of a family of structural proteins in the human placenta near term. These reveal the distribution of cytoskeletal and 'syncytioskeletal' components that may account for some of the more obvious micromorphological features of placental structure. In the syncytiotrophoblast a potentially supporting structure 'the syncytioskeletal layer' is described. It is an apparently continuous and complex polymeric network covering the villous tree, a surface of the order of 10 m2 in area in the full term placenta (Aherne & Dunnill 1966). It is suggested that this layer plays a part in morphogenesis of the villous tree.

[Morphometric studies in placental villi of mature human placentas (author's transl)]

In 56 placentas from uncomplicated pregnancies and normal spontaneous deliveries at term were investigated. Mature placental villi situated in the periphery of placentones (fetomaternal circulation units) were measured. The contents of intervillous fibrinoid was determined as well as the number of syncytial knots. Automatic ("TAS" Leitz, West Germany and Videmat "Zeiss", West Germany) and semiautomatic ("MOP AM 01" Kontron, West Germany) planimeters were used. Some of the results could be compared with earlier results published in the literature so far. The "normal values" revealed in normal term placentas will be compared with placentas of pathologic pregnancies in consecutive studies.

Developmental changes in the fine structure of the chorion laeve (smooth chorion) of the rhesus monkey placenta

Developmental changes in the fine structure of the chorion laeve (smooth chorion) of the rhesus monkey were studied at two time periods during gestation: 1) Early (19-60 days of gestation), before the chorionic epithelium fuses with the parietal decidua, and 2) near term, when the fused chorioamnion has also fused with the parietal decidua. Early in gestation the chorionic epithelium consisted of columnar and cuboidal cells one or two layers thick. The apical border of the cells had microvilli and coated pits, and adjacent cells were joined by tight junctions and desmosomes. The chorionic epithelial cells during this early period contained numerous large vesicles and vacuoles of varying electron-density. The apical cytoplasm contained various small coated vesicles and tubules. Taken together these observations were interpreted as indicating a possible role for these cells in endocytosis or phagocytosis of substances from the uterine lumen; i.e., a potential role in histiotrophic nutrition during this early period. Late in gestation the trophoblastic cells were more irregular in shape. The cells contained abundant granular endoplasmic reticulum (ER) and mitochondria, and a well-developed Golgi complex, suggesting the cells were actively synthetic late in gestation. The numerous cytoplasmic vacuoles characteristic of the trophoblastic cells of early gestation were absent near term. Glycogen deposits and lipid droplets were moderately well-developed near term. Most of the cells were joined by desmosomes but wide intercellular spaces, unobstructed by any cell junctions, were frequently observed. This observation provides at least one explanation for the increase in permeability of the chorion laeve later in gestation. Cells of the parietal decidua associated with the chorion laeve were also examined. These cells generally had a well-developed granular ER and Golgi apparatus, and numerous mitochondria. Limited numbers of membrane-bounded secretory bodies, similar to those in human decidual cells, were also present.

A morphometric study of placenta in fetal congenital nephrotic syndrome of Finnish type

A qualitative light microscopic study was performed on 9 fetal congenital nephrotic (CNF) and 13 control placentas obtained from legal pregnancy terminations or spontaneous abortions at 16-20 weeks of gestation. From this material 6 CNF cases and 6 age matched controls were selected for morphometric analysis. The total villous volume and the ramification pattern of the villi were similar in CNF and controls. A significant decrease in the villous vascularization was found in CNF. It is suggested that disturbed oxygen exchange due to poor development of the villous vessels causes a compensatory hyperplasia of the placenta at birth in CNF. Electron microscopic investigation was performed on three CNF and two control placentas. No changes typical of fetal CNF were found in the villous ultrastructure. The syncytial microvillous projections seemed to be more numerous and longer in CNF, otherwise the structure of the trophoblastic layer of the villi and the lining of the subtrophoblastic vessels were identical in CNF and controls.

Ultrastructure of the nidatory site in tubal pregnancy

Nidatory site of pre-abortive tubal pregnancy, obtained from 41 years old women was studied in both scanning and transmission electron microścopes. The nidatory site was basically composed of anchoring villi, trophoblastic column and shell, fibrinoid layer and marked round cell infiltration. In spite of the histologically normal appearance of the chorionic villi, villous syncytiotrophoblast ultrastructurally showed slight tendency of degeneration, being concurrent with blighted ovum. The trophoblast at the trophoblastic column and shell contained a great amount of glycogen which decreased at the distal part near and in the fibrinoid layer. The degenerating trophoblast were surrounded by massive fibrin bundles and fibrin bundles and fibrin-like deposits. The more the degeneration of the trophoblast proceeded, the more the fibrin deposits accumulated around the trophoblast. The trophoblast which ran over the fibrinoid layer was scarcely observed and if there, it showed marked degenerative appearance. These findings suggest the possible role of fibrinoid layer: protection of maternal tissue from trophoblastic invasion, not the protection of fetus from maternal immunological attack. No direct contact such as tight junction, desmosome and so on between trophoblast and maternal cell was observed in the present study, suggesting the formation of special connection with the allogeneic cell, one of the unique characters of the trophoblast, is expressed only when it is primitive in the early stage of development.

An electron microscopic study of histiotrophe in the interareolar part of the porcine placenta

Placentae from nine sows covering gestational stages from 33 to 112 days were examined by light and electron microscopy. Deeply stainable electron-dense histiotrophe was demonstrated in the interareolar placenta. Focal accumulations of cell debris with profiles of organelles were demonstrated in the intermicrovillous space between uterine epithelium and trophoblast. In addition, small expansions of amorphous histiotrophe were found between the microvilli. Furthermore, histiotrophe with profiles of cytomembranes was shown in intercellular spaces in columnar trophoblast between the microvillar border and tight junctions. Dense bodies were demonstrated in the uterine epithelium, and endocytic vesicles and branched tubular structures with dense contents were found in the columnar trophoblast. It is concluded that focal accumulations of cell debris are derived from degenerating epithelial cells in the endometrium and chorion, and that amorphous histiotrophe arises by secretory activity of uterine epithelium. It is further concluded that the histiotrophe is absorbed by columnar trophoblast of the chorionic fossae.

[Syncytial sprouts and intervillous bridges in human placenta (author's transl)]

In general syncytial sprouts and intervillous bridges are artifacts. Complete series of histological sections reveal that sprouts and bridges are caused by tangential sections through the syncytiotrophoblast. These observations are supported by scanning electron microscopy, graphical reconstructions and model experiments. However, it cannot be decided unequivocally whether short syncytial sprouts are artifacts or true differentiations of the syncytiotrophoblast.

[Correlation between the placental surface and the maturity of the newborn]

Morphometrical method of determination of the surface of the vili of placenta is described. The average of the surface of placental vili in normal pregnancy appeared to be - 12,14 +/- 2,27 m2. This valued in toxaemia of pregnancy - 9,25 +/- 1,52 m2, and in cases of dismaturation 7,62 +/- 0,98 m2. It was established that the morphometrical method was sensitive and suitable for the study of the relationship between the surface of the placenta and intrauterine development of the foetus. This was evidenced by the fact that surface of the placenta of low weight newborns (10-25%) and that of the newborns with overweight (75%) had shown a significant difference. These findings are not in accordance with the data reported in the literature.

Lamella-particle complexes in the human placenta

Lamella-particle complexes, similar in appearance to those found most abundantly in human hematopoietic malignancies, were seen within the cytoplasm of pericytes within the villus cores of 2 our ot 10 human placentas, 1 from a normal pregnancy and 1 from a pregnancy complicated by postpartum toxemia. Nine placentas were from term pregnancies, 6 normal and 3 complicated by toxemia, and 1 from a pregnancy complicated by premature delivery. The lamellae measured from 62-88 A in thickness and the particles from 175-220 A in diameter. The lamellae and particles were arranged in 3-6 apparently concentric layers around 0.08-0.24 micrometer diameter central cores to form complexes measuring from 0.37-0.75 micrometer in diameter. The complexes were infrequent, in pericytes and their presence did not appear to be correlated with either parity or any specific drug treatment. The reason for their presence in some human placentas is not known.

Regional ultrastructural differences in placental villi in cotyledons of a mature human placenta

Earlier histological, histochemical, biochemical and autoradiographic studies revealed a marked difference in the morphology and biology of placental villi dependence upon their localization within the materno-fetal circulation units (placentones). The quantitative differences demonstrated characterize the villi in the centres of the circulation units as morphologically and functionally less differentiated than the villi in the periphery. In the present study it should be scrutinized whether these differences can also be proven on the ultramicroscopic level. Small and large villi from both regions (centre and periphery) were studied. Two well-defined syncytial areas, namely syncytium directly overlying a fetal vessel and syncytium over a Langhans cell were studied separately. The following structures were chosen for study and counted by the "grid" method. Microvilli, rough endoplasmic reticulum with parallel channels, vesicular rough endoplasmic reticulum, and the number mitochondria. The ultrastructural studies support the earlier histological, enzyme-histochemical, biochemical and autoradiographic findings, which suggested that the villi in the periphery of the placentones have a higher degree of differentiation (maturation) than those in the centre. There are no qualitative differences between the two regions of the placentone but only quantitative differences which reflect the maturity of the villi.

A three-dimensional study of the normal human placental villous core. I. The Hofbauer cells

In order to study the three-dimensional ultrastructure of the Hofbauer cells, human placentae from the 6th to the 21st week of gestation and also from the end of pregnancy were cryofractured and observed by scanning electron microscopy. Hofbauer cells were found in the villous core at all the gestation stages examined. Their surface morphology was characterized by lamellipodia, funnel-like structures, blebs and microplicae. This pleomorphic aspect was probably related to functional or environmental conditions. In addition, thin cytoplasmic processes connected the Hofbauer cells with each other and with the components of the villous stroma. Fractured Hofbauer cells revealed large vacuoles in the cytoplasm; the vacuoles were smaller in size both at the beginning and at the end of pregnancy. This study further attests to the macrophagic nature of these cells.

Junctions on the maternal blood surface of the human placental syncytium

Terminant chorionic villi of the human placenta at 8, 9, 12, 14 weeks' gestation and at full term have been studied in freeze-fracture replicas and in thin sections. In replicas, maculae occludentes of different size have been detected in all placental samples on the cleaved plasma membrane of the free (maternal) surface of the syncytiotrophoblast. In thin sections they are located in narrow invaginations of the syncytium luminal plasma membrane. These invaginations are in turn similar to flattened vesicles (also associated with junctions) located in the underlying syncytioplasm. Possible origin and function of the junctions on the syncytium free surface are discussed.

Inflammatory lesions of the human placenta. III. The histopathology of villitis of unknown aetiology

All placentae delivered in a large obstetrics hospital in a two-year period were examined macroscopically and histologically. Of 7505 consecutive singleton placentae, chronic focal placental villitis of unknown aetiology (VUE) was found in 575 (7.6 per cent). The clinical correlates of these cases have been published previously (Russell, 1979). The present report details histological spectra of severity and distribution of the lesions, cell types within the inflammatory foci and secondary changes consequent upon local reduction in both maternal and fetal blood flow through the placenta. Histological findings tend to support direct extension of the infection from uterine sources rather than haematogenous inoculation of the placenta. The clinical sequelae for the infant appear to correlate positively with the severity of the villitis process.

Ultrastructural abnormalities of placental villi in placentae from pregnancies complicated by intrauterine fetal growth retardation: their relationship to decidual spiral arterial lesions

An ultrastructural study has been made of villi adjacent to decidual spiral arteries exhibiting varying degrees of luminal occlusion in placentae from cases of intrauterine growth retardation. Partially occluded spiral arteries are associated with placental villous syncytiotrophoblast exhibiting extensive budding of surface microvilli, vacuolation of the cytoplasm, clumping of nuclear chromatin and a thickening of the underlying basement membrane. Marked degeneration of the syncytium is present in association with severely occluded spiral arteries. In contrast, the capillary endothelium of the villus retains a normal structure despite degenerative changes in villous Langhan's and stromal cells. The most extensive pathological changes in the placental villi are found distal to completely occluded spiral arteries and consist of complete necrosis of the syncytium and underlying fetal blood vessels, These findings suggest that the occlusive lesions in the maternal uterine vasculature may be the major cause of the infarction and impairment of placental function found in pregnancies complicated by fetal growth retardation.

Ultrastructure of the villi and fetal capillaries in placentas from smoking and nonsmoking mothers

The ultrastructure of placental villi from 10 heavy smokers (10 greater than or equal to cigarettes per day) was compared with that of 16 nonsmokers (never smoked). Thickening of the basement membrane and increase in collagen content of the villous stroma was found. The fetal capillaries were fewer in number and with decreased lumen either due to oedema or contraction of the endothelial cells. All cells, both in the fetal capillaries as well as syncytiotrophoblast and cytotrophoblast contained large amounts of filaments and fibrillae possibly capable of cell contraction. Thus a result of these findings might be a decreased placental flow in smokers.

[An immunohistochemical study of HCG and HPL on functional differentiation of human chorionic villi (author's transl)]

The enzyme-labeled antibody method was used to examine the localized distribution and variation by gestation week of HCG and HPL in placenta of 44 cases. 1) HCG: Electron microscopy revealed HRP reaction products in cisterna and membrane of perinuclear spaces and endoplasmic reticulum of syncytial cell (S-cell), but not in surface of S-cell microvilli or in Langhans' cell (L-cell). HRP reaction products in S-cell were more appreciable during 5th-12th weeks of gestation in syncytial sprouts, junction of villi with decidua, and rami or ramuli chorii, and fewer after 12th weeks. 2) HPL: Electron microscopy revealed reaction products in nuclear membrane and membrane of endoplasmic reticulum and Golgi complex, but not in surface of S-cell microvilli or L-cell. Reaction products in S-cell were noted from 8th gestation week, and most appreciably in 16th-18th gestation weeks preceding peak HPL concentration in serum. This indicates HPL exists in S-cell in the from of Pre. Pro-HPL.

Resistance of human syncytiotrophoblast to hypotonic and thermal stress

Human placental syncytiotrophoblast was not lysed when exposed to acutely hypotonic environments (distilled water) or during repeated freeze-thawing. The ability of the syncytiotrophoblast to synthesize and secrete hCG was not blocked after exposure to hypotonic stress (0.055 osmol) and elevated temperature (47 degrees C), treatments which caused lysis of erythrocytes and lymphocytes. The stress-resistant property of the syncytiotrophoblast may be an important element in enabling its survival as a barrier between the maternal environment and the conceptus.

Ultrastructure of the epithelium of the chorionic villi of the human placenta

Human placenta samples obtained at 4, 6, 8 and 10 weeks of gestation and at full term were studied by transmission electron microscopy (TEM). The chorionic villi at early stages of gestation exhibited abundant microvilli on the free surface of the syncytium. The chorionic villi at full term were covered by syncytium which bore short microvilli on its free surface. The syncytial cells were remarkably higher in density than Langhans' cells. In the earlier period of gestation, a dividing membrane was noticed in the inside of the syncytial cells. The cytoplasm of the syncytial cell contained comparatively small mitochondria, well-developed endoplasmic reticulum cells, ill-developed Golgi systems, electron-dense lipoid droplets and plenty of ribosomes. A great number of Langhans' cells were noticed in early gestation; only very few were noticed the later part. Mitochondria of Langhans' cells were comparatively large and the Golgi system was well-developed in the first trimester. Endoplasmic reticulum was less well developed and there were few ribosomes. The basement tended to become thicker a pregnancy proceeded and lamellar structures appeared on its inner face.

A Markham rotation enhancement of two polygon types from isolated negatively stained human placental coated vesicles

A simple image enhancement method has been used to reinforce the rotational symmetries of two types of polygon which form the facets of the clathrin lattice of human placental coated vesicles. Hexagons and pentagons were found but no evidence of other polygons (up to enneagon) was obtained.