Enzyme-histochemical studies of the pig placenta. II. Histotopics of enzymes in the areolar placenta epithelium

In porcine areolar placental epithelia, the following enzymes were demonstrated by histochemical methods after 30, 58, 80, 100, and 110 d of pregnancy, respectively: beta-N-acetyl-hexosaminidase, beta-galactosidase, beta-glucuronidase, alpha-mannosidase, acid phosphatase, alkaline phosphatase, nonspecific esterases, cytochrome oxidase, 5-nucleotidase, leucine aminopeptidase, adenosine triphosphatase, diaphorases (NADH, NADPH), glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, succinate dehydrogenase, isocitrate dehydrogenase (NAD, NADP), beta-hydroxybutyrate dehydrogenase, glycero-3-phosphate dehydrogenase, NAD-glycero-3-phosphate dehydrogenase, glutamate dehydrogenase (NAD, NADP), lactate dehydrogenase. The results show that the enzyme activities remained almost unchanged during the period of investigation. Of the dehydrogenases, the diaphorases as well as succinate and lactate dehydrogenase demonstrated generally an intensive activity within the epithelia. The activity of the other dehydrogenases was only low. The activity of unspecific esterase was very intensive within the uterine epithelia but remarkably low within chorionic epithelia. Contrarily, the reaction of adenosine triphosphatase was more intensive within chorionic than uterine epithelia. All investigated glucosidases reacted distinctly positive within chorionic epithelia, but only beta-N-acetyl-hexosaminidase and beta-galactosidase in uterine epithelia. The high activity of acid phosphatase, especially within the chorionic epithelium, seems to be connected with uteroferrin, an iron-binding protein. The histochemical results are discussed in context with the function of the areolae in histiotrophic nutrition and iron transport.     

Activity and expression of Na+/H+ exchanger isoforms in the syncytiotrophoblast of the human placenta

The purpose of this study was to compare Na⁺/H⁺ exchanger (NHE) activity in the microvillous (MVM) and basal (BM) plasma membrane of the human placental syncytiotrophoblast and to determine the relative contribution of various NHE isoforms to this activity. Uptake of ²²Na into isolated MVM vesicles in the presence of a H⁺ gradient, at initial rate, was four- to fivefold higher than that by BM vesicles (214±28 vs. 49±9 pmol/mg protein per 30 s, respectively, means±SEM, n=8, 6, P<0.001). The ²²Na uptake by MVM, but not by BM, was reduced in the absence of a H⁺ gradient and in the presence of 500 M amiloride. To determine the contribution of NHE1, NHE2 and NHE3 isoforms to NHE activity in MVM, we investigated the effect of amiloride analogues which show isoform selectivity. HOE 694, an analogue selective for NHE1 at low concentrations, inhibited ²²Na uptake with an EC₅₀ of 0.13±0.05 M (n=6), whereas S3226, an analogue selective for NHE3 at low concentrations had an EC₅₀ of 3.01±0.85 M (n=5). To investigate this further, we measured recovery of syncytiotrophoblast intracellular pH (pH_i) from an acid load using a H⁺-selective, fluorescent dye (BCECF) loaded into isolated intact placental fragments. This recovery was blocked in the absence of Na⁺ and the presence of amiloride (500 M) and concentrations of HOE 694 and S3226 were comparable to those used in vesicle experiments. Overall these data show that under the conditions used NHE activity in the term placental syncytiotrophoblast is absent from BM. NHE activity in the MVM is attributable predominantly to NHE1.     

Chosphatases of the human placenta

Summary Acid and alkaline phosphatase activity has been examined in chorionic and placental tissues of 123 women in the 4–5th to the 40th week of pregnancy, by the method of Gomori. Both enzymes could be detected over the whole duration of pregnancy. Most of the villi of preparations from early pregnancy showed trace or low acid phosphatase activity, and the proportion of such villi increased as pregnancy progressed. At the same time, there was a gradual rise in the acid and alkaline phosphatase activity of the structures, to a maximum at term. Alkaline phosphatase was present in the nuclei, but more abundantly in the cytoplasm of the syncytium; it was absent from the Langhans cells. Acid phosphatase was concentrated mainly in the nuclei, and was more widely distributed among the placental tissues than was alkaline phosphatase. The trophoblast showed the highest acid and alkaline phosphatase activities. The results reported are not in agreement with those of Thomsen.(Presented by Member AMN SSSR A. V. Lebedinskii) Translated from Byulleten Éksperimental'noi Biologii i Meditsiny, Vol. 56, No. 8, pp. 64–68, August, 1963     

Localization of glycogen in the human placenta

Summary Glycogen was determined by the Bauer-Feulgen method in the chorion and placenta of 4- to 40-weeks-pregnant women. It could be detected through the whole pregnancy in the ectodermal epithelium of the amnion and mesenchymal cells of the chorion laeve, extraplacental chorion, and amnion. Glycogen was also found throughout the entire cross section of the umbilical cord up to the 16th week inclusive; at the 20th week of pregnancy glycogen was determined only in the wall of the umbilical vessels with an insignificant spread beyond the muscular layer of the umbilical vein. With the progress of pregnancy the amount of glycogen in the cellular nodules increased, but in the last third of pregnancy, with the rise of the fibrinoid content, the amount of glycogen in the cellular nodules began to drop; at the 40th week of pregnancy it could be detected only in small amounts between the cells. The glycogen level in the stroma of the villi was low at first, but rose later; large amounts of glycogen were found in the stroma of the larger and stem villi during the last half of pregnancy; it was almost entirely absent in the stroma of smaller villi. Glycogen was revealed in the Langhans' cells throughout the whole period of pregnancy, whereas in the syncitial layer of the trophoblast it was absent altogether.(Presented by Active Member AMN SSSR N. A. Kraevskii) Translated from Byullenten' Eksperimental'noi Biologii i Meditsiny, Vol. 50, No. 9, pp. 112–116, September, 1960.     

Expression of HLA-G in the human placenta

The unique structure of the human placenta provides a separation between maternal and fetal tissues and circulations. Although the maternal–fetal proximity is very close, the placenta and the fetus are not rejected by the maternal immune system. Among the various factors implicated in the mother's tolerance of the fetus, a key factor has been attributed to HLA-G molecules, which are expressed by specialized trophoblast cells. By the alternative splicing of its primary mRNA, HLA-G, belonging to Class I MHC molecules, results in four membrane bound (HLA-G1, -G2, -G3, -G4) and three soluble proteins (HLA-G5, -G6, -G7). Which of these HLA-G isoforms are expressed on the cell surface and which are secreted was the aim of our study.
Whereas the generally agreed upon opinion is that the full length HLA-G1 isoform is expressed by extravillous cytotrophoblast cells, the source of soluble HLA-G5 isoform and the expression of all other isoforms in the human placenta is still under debate. However, soluble HLA-G products, which might be present in body fluids, could also come from membrane bound HLA-G1 by shedding; a process, that has been described for classical HLA molecules. HLA-G expression in organs, other than placenta and certain tumors, has not yet been explained convincingly.
Since immunological detection methods crucially depend on the antibodies and preparation techniques used, we investigated HLA-G specific antibodies for their specificity and binding properties. We compared the binding ability of some antibodies on HLA-G1, G2, -G5 transfected cell lines with naturally expressed placental HLA-G molecules. A broad range of methods, from immunolocalization to protein-biochemical and Elisa techniques, were used to clarify which HLA-G isoform is actually expressed in the normal placenta.     

Functional morphology of the human placenta

An account is given of latest knowledge on the structure of the human placenta. Reference is made to the early stages of development as well as to maturation under both normal and pathological conditions. The paper is intended to contribute to better understanding of the pathogenesis of chronic placental insufficiency.     

Immunohistochemical demonstration of fibronectin in the human placenta

The distribution pattern of fibronectin in the human placenta has been studied using the indirect immunoperoxidase (PAP) technique on formalin fixed paraffin embedded tissue samples. Fibronectin was demonstrated as intensely stained fibrillar or strand-like structures on the endothelial cells of blood vessels and on the amniotic epithelium. The most interesting fibronectin staining result, however, was found in the cytotrophoblast cells and in the bud-like structures of the syncytiotrophoblast. The results were discussed with regard to differentiation and proliferation in course of placental development.     

Activity of glutathione-metabolizing and antioxidant enzymes in malignant and benign tumors of human lungs

We measured the content of glutathione and activity of glutathione-metabolizing and antioxidant enzymes superoxide dismutase and catalase in samples obtained from 52 patients with malignant lung tumors and 20 patients with benign lung tumors. The content of glutathione and activity of glutathione-metabolizing enzymes underwent similar changes, but these changes were most pronounced in malignant tumors. Antioxidant enzyme activity changed insignificantly in benign tumors, but significantly decreased in malignant tumors (squamous cell carcinoma and adenocarcinoma). The severity of changes in malignant tumors depended on the degree of malignancy. Most pronounced changes were observed in adenocarcinoma, which often metastasizes and is resistant to chemotherapy. These changes were least pronounced in bronchoalveolar carcinoma sensitive to chemotherapy.     

Expression of galanin in human placenta

The neuropeptide galanin was originally implicated in the regulation of feeding behaviour. Today, galanin is implicated in several physiological functions including reproduction and feeding. Many hypothalamic neurohormones of the hypothalamo--pituitary axis (HPA) are also expressed in the placenta where the specialized topological compartments of the HPA are missing and where paracrine and autocrine regulatory mechanisms consequently prevail. Since galanin influences gonadotrophin-releasing hormone secretion in the HPA, we argued that a similar regulatory role for galanin might exist in human placenta. Since the presence of galanin in human placenta had not been previously reported, we analysed galanin expression in the human placenta by immunohistochemistry and quantitative polymerase chain reaction (PCR) throughout gestation. We found that the peptide hormone localizes to the syncytio- and cytotrophoblast layers; its RNA could be detected. By quantitative PCR we observed that throughout gestation, there is a loss of galanin mRNA which parallels the fall in signal intensity from immunohistochemical detection of the galanin oligopeptide. Furthermore, we detected secretion of galanin from isolated trophoblastic cells. We conclude that galanin may be an important and novel regulator of placental function.     

Macrophage populations in the human placenta and amniochorion

Fetal and maternal macrophage populations in human utero-placental tissues at different stages of gestation have been studied using immunohistological and histochemical techniques. A large population of macrophages has been identified within maternal decidualized endometrium in both term and first trimester tissues, although lymphoid cells also constitute a major component of the bone marrow derived cells in the decidua of early pregnancy. In contrast, fetal macrophages have been shown to contribute nearly all of the substantial bone marrow derived cell population within placental chorionic villous mesenchyme and within the mesenchyme of the term amniochorion. Apart from a small population of stellate intensely HLA-DR positive cells in term placental villous stroma, these extra-embryonic fetal macrophages could be shown consistently to express both the leu-M3 tissue macrophage antigen and lysosomal enzyme activities. It is suggested that the major HLA-DR positive cell population of fetal amniochorion comprises 'classical' macrophages rather than dendritic type cells. These various macrophage populations may perform vital phagocytic and degradative functions within utero-placental tissues and amniochorion.