HISTOCHEMISTRY OF PLACENTA 



927 



of this material by the 21st day. Concerning 

 tliese fluctuations, it may be said that the 

 glycogen content of the fetal placenta is 

 highest immediately preceding the great 

 terminal growth spurt of the embryo and 

 fetal placenta. It should also be noted that, 

 as in the human, placental glycogen content 

 is decreasing during the period when the 

 fetal liver is beginning to store glycogen 

 (Padykula and Leduc, 1955). 



The distribution of glycogen in the rab- 

 l)it placenta is drastically different from 

 that of the human and the rat. In this spe- 

 cies glycogen is localized exclusively in the 

 decidua of the maternal placenta ; the fetal 

 placental tissue, including the yolk sac, is 

 devoid of glycogen (Bernard, 1859; Chip- 

 man, 1902; Lochhead and Cramer, 1908; 

 Loveland, Maurer and Snyder, 1931 ; Tuch- 

 mann-Duplessis and Bortolami, 1954; 

 Davies, 1956). Glycogen content reaches a 

 peak near the 17th day of gestation, and 

 decreases until term. Several investigators 

 (Lochhead and Cramer, 1908; Tuchmann- 

 Duplessis and Bortolami, 1954) have fur- 

 ther substantiated Claude Bernard's obser- 

 vation that the decline in placental glycogen 

 correlates in time with the onset of the 

 hepatic glycogenic function in the fetus. In 

 the guinea pig a similar temporal correla- 

 tion has been made for glycogen storage in 

 the placenta and fetal liver (DuBois and 

 Ducommun, 1955). 



Saliva-insoluble carbohydrates, such as 

 glycoproteins and mucopolysaccharides, re- 

 vealed by the PAS reaction are demonstra- 

 ble in the placentas of all animals which 

 have been examined (Wislocki, 1951). In 

 the pig's placenta a positive reaction is 

 given by minute droplets in the apical ends 

 of the uterine gland cells, in the glandular 

 secretion (Fig. 15.66), and in the uterine 

 surface epithelium. An intense reaction is 

 given by the secretion (uterine milk) in the 

 lumens of the chorionic areolae. Numerous 

 ]iositively stained, delicate droplets are 

 present in the distal cytoplasm of the colum- 

 nar epithelium lining the chorionic fossae 

 and areolae (Fig. 15.65). In the basal part 

 of the tall columnar cells lining the chori- 

 onic fossae there are, in addition, large ''col- 

 loid" droplets (Fig. 15.65) which are 

 stained intenselv red (Wislocki and Demp- 

 sev, 1946b). 



In the numerous trophoblastic binucleate 

 giant cells of the sheep and cow, Wimsatt 

 (1951) reported the presence of many PAS- 

 positive cytoplasmic granules. The tropho- 

 blastic giant cells of the Virginia deer react 

 similarly (Wislocki, unpublished observa- 

 tion) . 



In the chorionic lamellae of the cat's pla- 

 centa, deeply stained PAS-reactive mate- 

 rial is present between the fetal trophoblast 

 and the maternal vessels (Figs. 15.56 and 

 15.61). In addition, large, deeply stained 

 colloid droplets are located irregularly in 

 the trophoblastic syncytium (Fig. 15.56). 

 In the placental "brown" border of the cat, 

 a reaction is present in the chorionic epithe- 

 lium, as well as in the secretion in the uter- 

 ine lumen and in the surface and glandular 

 uterine epithelium (Fig. 15.62) . 



In the rat's placenta, the apical cyto- 

 plasm of the uterine epithelium, amorphous 

 material in the uterine and vitelline cavi- 

 ties, the substance of Reichert's membrane 

 and the apical cytoplasm of the vitelline epi- 

 thelial cells (Fig. 15.72) all react strongly 

 (Wislocki, and Padykula, 1953) . The tropho- 

 blast of the chorio-allantoic placenta gives 

 a relatively faint reaction (Fig. 15.72). 



C. METACHROMASIA 



None of the structures in the placentas of 

 the various animals cited above, which are 

 strongly PAS positive, exhibits any meta- 

 chromasia (Wislocki, 1953) , except that the 

 binucleate cells of the sheep react faintly 

 under some conditions of staining (Wim- 

 satt, 1951). Also the ground substance of 

 the stroma of the chorionic rugae of the 

 pig's placenta is moderately metachromatic. 



D. PHOSPHATASES 



Because the methods for alkaline and 

 acid phosphatase were among the first his- 

 tochemical procedures for localizing en- 

 zymes, many observations have been made 

 on this type of hydrolytic activity. The ab- 

 sorptive surfaces of the small intestine, kid- 

 ney, and placenta, which are characterized 

 by brush borders, contain strong alkaline 

 phosphatase activity. In many forms the 

 syncytial trophoblast is rich in alkaline 

 phosphatase activity. In the human syncy- 

 tium, alkaline phosphatase activity which 

 is low early in gestation increases greatly 



