HISTOCHEMISTRY OF PLACENTA 



903 



blastic cell columns (primary villi) are 

 converted into vascularized secondary and 

 tertiary villi covered by Langhans cells and 

 syncytium. However, the trophoblastic shell 

 persists and, through the expansion and 

 growth of the placental cotyledons, is trans- 

 formed into a basal plate contiguous to the 

 decidua basalis and placental septa forming 

 the boundaries between the cotyledons (Fig. 

 15.43). The septa placentae consist of 

 masses of cells associated with a ground 

 substance termed "fibrinoid" by Grosser 

 (1925a, b), which is distinguishable his- 

 tologically from actual fibrin intermingled 

 with it by the fact that with Mallory's con- 

 nective stain, as well as with azan, it is 

 colored blue, whereas the fibrin stains red. 



Contrary to earlier opinion, the septa 

 placentae are now regarded as being fetal in 

 origin and the component cells as tropho- 

 blasts (Spanner, 1935a; Stieve, 1940; Stieve 

 and von der Heide, 1941). On the other 

 hand, the nature and origin of the elements 

 of the basal plate have not been so well 

 clarified. Grosser (1948) , for example, states 

 that, in the mature placenta, decidua con- 

 stitutes the foundation of the basal plate, 

 but that it contains remnants of the "junc- 

 tional" or "penetration" zone and that "the 

 fetal side is clothed by trophoblastic cell 

 derivatives in various stages of regression." 

 However, more recent work has shown that 

 the basal plate is composed mainly of func- 

 tional trophoblasts (Wislocki, 1951). The 

 so-called cell islands which preponderate in 

 the first half of gestation (Stieve and von 

 der Heide, 1941) also consist of clusters of 

 trophoblasts. The cells in these various sites, 

 from the beginning until the end of gesta- 

 tion, will be referred to in the present chap- 

 ter as peripheral trophoblasts and the sum 

 total of them as the peripheral cytotropho- 

 blast. It has been demonstrated (Wislocki, 

 1951) that the peripheral trophoblasts are 

 chromophilic and differ in several important 

 cytochemical respects from the chromo- 

 phobic Langhans cells of the secondary 

 and tertiary chorionic villi. Furthermore, 

 whereas the Langhans cells become incon- 

 spicuous and diminish by the end of gesta- 

 tion, the peripheral trophoblasts in the pla- 

 cental septa and basal plate persist in large 

 numbers until term (Wislocki, 1951). 



1. Trophoblasts Forming the Cell Columns 

 and Trophoblastic Shell 



At the junction of the primary villi with 

 the stroma-containing secondary villi dur- 

 ing the first 4 weeks of gestation the tropho- 

 blastic cells are large and chromophobic, 

 resembling Langhans cells. The proximal 

 ends of the cell columns constitute a ger- 

 minal bed of cells exhibiting numerous mi- 

 toses. It is from these cells that the periph- 

 eral trophoblasts apparently arise. Moving 

 outward from the germinal region, along the 

 columns into the shell, the trophoblastic 

 cells change their character. In the first 

 months of gestation they are laden with 

 glycogen as revealed by the PAS method 

 (Figs. 15.31 and 15.32). By the end of the 

 first month, however, a type of cell which 

 is characterized by cytoplasmic basophilia 

 and lower glycogen content has arisen and 

 these cells increase in number. When fully 

 developed, they contain clumps of strongly 

 basophilic cytoplasmic material, reminis- 

 cent of the Nissl substance of neurones ( Fig. 

 15.11), and the staining of the basophilic 

 substance is abolished after treatment of 

 the sections with ribonuclease (Fig. 15.12), 

 a result indicating that the basophilic sub- 

 stance contains ribonucleoprotein (Dempsey 

 and Wislocki, 1945). The staining and na- 

 ture of this basophilic substance have been 

 confirmed by Ortmann (1949). The cyto- 

 plasm of these trophoblasts also stains 

 moderately strongly with acid dyes (Figs. 

 15.46 and 15.47). When stained with the 

 PAS reagents following exposure to saliva, 

 many of the trophoblasts exhibit delicate 

 red stippling against a diffuse reddish back- 

 ground (Figs. 15.49 and 15.55) (Wislocki, 

 1950), a staining reaction indicative of the 

 presence of a mucopolysaccharide or glyco- 

 protein. The cytoplasm does not stain meta- 

 chromatically with toluidin blue, a finding 

 which indicates the absence of strongly acid 

 mucopolysaccharides. The cells do not con- 

 tain triglycerides or lipids of the type oc- 

 curring in the syncytium. However, sudan 

 black and Baker's method for phospholipids 

 differentiate minute granules in variable 

 numbers in the cytotrophoblasts (Figs. 

 15.25 and 15.48). These particles correspond 

 in size and number to mitochondria re- 

 vealed by other methods. Succinic dehydro- 



