OBSERVATIONS ON SOME HISTOCHEMICAL REACTIONS IN THE HUMAN PLACENTA, WITH SPECIAL REFERENCE TO THE SIGNIFICANCE OF THE LIPOIDS, GLYCOGEN AND IRON

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Abstract
The present study embodies the results obtained by the application of a number of histochemical reactions to human placental tissue. These reactions have centered around the localization of lipids, glycogen and Fe. The lipids of the fetal placenta occur almost entirely as droplets in the syncytial trophoblast. These droplets apparently contain steroidal substances, since they give positive reactions characteristic of steroids. The reactions employed in this investigation consist of birefringence, lipid-soluble auto-fluorescence, the Liebermann-Burchardt or sulfuric acid reaction, and the Schiff or plasmal reaction. The results obtained by these methods indicate that the syncytium is the site of localization of the placental steroid hormones. The cytotrophoblastic cell columns, cell islands, and cyto-trophoblastic shell contain histologically demonstrable glycogen especially during the early parts of pregnancy. Similarly, heavy deposits of glycogen occur in the maternal decidua in the first half of pregnancy. The glycogen-con-taining tissues in these localities are characterized by a relative or complete avascularity and by deficient mechanisms for aerobic oxidation. From consideration of glycogen distribution in various tissues, both fetal and adult, the concept is developed that glycogen deposition is generally associated with anerobic conditions, and that, through anerobic breakdown, it may provide a mechanism for the oxidative reactions of tissues in which the O2 supply is deficient. It was demonstrated by the Turnbull blue reaction, as well as by the study of microincinerated sections, that the syncytium of early placentae contains considerable quantities of Fe, while in later stages of pregnancy the amt. is greatly reduced. A dense Fe conc. exists in the intercellular matrix associated with the cytotrophoblastic cells in the various localities where they occur. These findings are briefly discussed in relation to the topic of Fe transport by the placenta.