SPERM, OVA, AND PREGNANCY 



also merits discussion with reference to 

 the basement membrane. With connective 

 tissue stains, such as Mallory's, each of 

 the clear, chromophobic Langhans cells 

 seems to be enclosed by a deeply stained 

 surface film or membrane which seems to 

 be continuous with the subjacent reticular 

 basement membrane (Fig. 15.9). However, 

 unlike the latter, these encapsulating mem- 

 branes of the Langhans cells are neither 

 argyrophilic nor stained by the PAS rea- 

 gents (Fig. 15.54). Grosser (1925a, b) con- 

 cluded that the "capsules" represent a se- 

 cretion liberated by the Langhans cells, 

 which he designated as "fibrinoid" (Wis- 

 locki and Bennett, 1943). Electron micro- 

 graphs of early and late human placentas 

 demonstrate that these cells are not sepa- 

 rated from the syncytium or encapsulated 

 by a collagenous material (Wislocki and 

 Dempsey, 1955). However, narrow clefts 

 often occur between the plasma membranes 

 of the .syncytial and Langhans cells and also 

 between two contiguous Langhans cells. 



The mesenchymal cells or fibroblasts of 

 the chorionic villi contain a moderate quan- 

 tity of glycogen in the first 2 months of 

 gestation, but this substance declines there- 

 after. They possess numerous mitochondria 

 (Fig. 15.26) and also give faint cytoi)la.smic 

 reactions for sulfhydryl groups (Figs. 15.33 

 and 15.35), esterase (Fig. 15.36), and suc- 

 cinic dehydrogenase (Fig. 15.38). Gersh and 

 Catchpole (1949) described glycoprotein 

 granules in the mesenchymal cells, which in- 

 crease in number up to 4 months of gesta- 

 tion, after which they decline. To these cells 

 they ascribed the role of producing the 

 ground substance of the villi. The endoplas- 

 mic reticulum is conspicuous in these cells, 

 being highly branched and irregular in 

 shape, and its matrix has unusually high 

 density (Wislocki and Dempsey, 1955) . 



Besides mesenchymal cells, the stroma 

 contains peculiar, large, predominantly 

 round, vacuolated cells designated as Hof- 

 bauer cells (Fig. 15.13). They are numerous 

 in human villi in the first months of gesta- 

 tion but diminish in number afterwards. In 

 the first 6 weeks of gestation these cells con- 

 tain some glycogen which is located be- 

 tween the cytoplasmic vacuoles. On removal 

 of the glycogen they exhibit a residual PAS 



reaction in the cytoplasm surrounding the 

 nucleus and vacuoles (Fig. 15.57). They 

 contain a moderate number of mitochondria 

 (Fig. 15.26), and succinic dehydrogenase 

 activity has been demonstrated in these 

 cells. They do not exhibit alkaline phos- 

 I)hatase activity, but give a moderately 

 strong cytoplasmic reaction for acid phos- 

 phatase. Hofbauer (1905) described osmi- 

 cated droplets in some of them. Lipids occur 

 in finely granular form, when demonstrated 

 by Sudan black. Ashbel and Hertig (1952), 

 utilizing the Ashbel-Seligman reaction, re- 

 ported that a carbonyl reaction occurs in 

 some of the Hofbauer cells. Wislocki and 

 Bennett (1943, Fig. 16) observed them to be 

 filled occasionally with vacuoles or droplets 

 deeply stained with iron hematoxylin. 



The nature of the Hofbauer cells is un- 

 certain. Some investigators have regarded 

 them as degenerating cells (Mall and 

 Meyer, 1921), whereas Lewis (1924) con- 

 sidered them to be macrophages because of 

 the affinity of their cytoplasm for neutral 

 red. The latter opinion also receives support 

 from their observed increase in numbers 

 in syphilitic infections (Hofbauer, 1925). 

 Their histochemical properties enumerated 

 above, particularly the presence of a posi- 

 tive PAS reaction after removal of glycogen, 

 of finely dispersed lipids, and of acid phos- 

 l)hatase activity, are also compatible with 

 similar reactions encountered in macro- 

 phages (Leblond, 1950; Doyle, 1950; Weiss 

 and Fawcett, 1953j. The Hofbauer cells dif- 

 ferentiate presumably from the mesenchy- 

 mal cells of the villi, altiiough an origin 

 from the Langhans cells has also been sug- 

 gested; the latter, although unproven, is a 

 distinct possibility. It seems quite unlikely, 

 as some have thought, that they originate 

 from either erythroblasts or endothelial 

 cells (Mall and Meyer, 1921). 



4- Age Changes in the Chorionic Villi 



The chorionic y\\\\ undei-go changes as 

 the placenta ages. They become more 

 branched, numerous, and slender. The Lang- 

 hans cells diminish in number and assume 

 a flattened shape, while the syncytium be- 

 comes thinned out over the distended si- 

 nusoidal capillaries. The stroma becomes 

 less cellular, denser, and more fibrous. The 



