942 



SPERM, OVA, AND PREGNANCY 



labyrinth of the rat, it has been ob- 

 served that the alkaline phosphatase reac- 

 tion predominates in the trophoblast, 

 whereas the PAS reaction occurs mainly in 

 the adjacent basement membrane which 

 supports the syncytium and encloses the 

 fetal capillaries. Thus, although the two re- 

 actions are closely associated, they are by 

 no means located in the same tissue ele- 

 ments. Despite this discrepancy, there is no 

 question but that in many tissues the thesis 

 Moog and Wenger have stated holds true. 

 Indeed, numerous examples which bear out 

 their conclusion can be found in the pla- 

 centas of various animals. Thus, in the hu- 

 man placenta, intense reactions for alkaline 

 phosphatase and for PAS-positive sub- 

 stances occur in the outer zone and brush 

 border of the syncytial trophoblast. In the 

 cat's placental labyrinth, both occur to- 

 gether with great intensity in the perivascu- 

 lar sheaths intervening between the mater- 

 nal blood vessels and the trophoblast, as 

 well as in the columnar chorionic epithelium 

 of the paraplacental brown border. In the 

 rat and guinea pig the two reactions are 

 encountered in the epithelium of the vis- 

 ceral layer of the yolk sac placenta. Finally, 

 in the pig's placenta, the two reactions co- 

 incide in the distal ends of the columnar 

 cells lining the chorionic fossae. 



D. RELATIONSHIP OF LIPIDS TO THE 

 PLACENTAL BARRIER 



In reference to the question of lipids 

 demonstrable in the placental barrier, Wis- 

 locki and Bennett (1943) emphasized, and 

 Dempsey and Wislocki (1944) offered fur- 

 ther substantiating evidence to show that, 

 although lipids are demonstrable histologi- 

 cally in great abundance in the human 

 trophoblastic syncytium, they are probably, 

 for the most part, lipids associated with 

 mitochondria and with the production of 

 steroid hormones, rather than lipids in 

 process of transmission across the placenta. 

 Huggett and Hammond (1952) summarized 

 the question of the manner of transmission 

 of fat from mother to the fetus. In their 

 opinion the chemical results do not show 

 how the fat actually traverses the placenta ; 

 ■'they neither prove nor disprove the pos- 

 sibility of hydrolysis at the placental mem- 



brane and subsequent resynthesis in the 

 deep syncytium." All that the results show 

 is "that particular or labeled fatty acids, 

 originally on the maternal side, appear later 

 in the fetal tissues." 



Regarding phospholipids, Popjak and 

 Beeckmans (1950) concluded from a study 

 of rabbits that the placenta does riot trans- 

 mit unhydrolyzed phospholipid molecules 

 to the fetus. Similarly, glycerophosphate 

 which is a phosphorus-containing degrada- 

 tion product of lecithin does not pass un- 

 hydrolyzed. In a previous investigation 

 Popjak (1947) showed that fetal phospho- 

 lipids in rats, rabbits, and guinea pigs are 

 formed by synthesis within the fetal tissues. 

 Popjak and Beeckman's findings offer a 

 situation where phosphatases might serve as 

 the dephosphorylating agents. 



E. FIBRINOID 



Earlier in this review the histologic prop- 

 erties of the ground substance of the human 

 trophoblastic cell columns and shell were 

 described. Grosser (1925a) called this 

 ground substance "fibrinoid," adopting a 

 term which had been introduced previously 

 to describe substances occurring in a vari- 

 ety of pathologic lesions. Fibrinoid was de- 

 fined originally as a somewhat refractile, 

 homogeneous, intercellular substance with 

 an affinity for acid dyes and with histologic 

 resemblances to fibrin (Neumann, 1880). 

 Recently, Altshuler and Angevine (1949, 

 1951) maintained that fibrinoid stains met- 

 achromatically with toluidin blue and re- 

 acts with the PAS reagents. From this, they 

 concluded that fibrinoid consists of an acid 

 mucopolysaccharide containing mucoitin 

 sulfuric acid. On the basis of metachromatic 

 staining, they identified placental fibrinoid 

 in Nitabuch's membrane, the subchorial 

 plate, and degenerating chorionic villi. Wis- 

 locki and Dempsey (1948) described meta- 

 chromatic staining of the stroma of degen- 

 erating villi (Fig. 15.57) and of the ground 

 substance of the decidua (Fig. 15.58), but 

 they did not observe metachromasia of the 

 ground substance of the peripheral tropho- 

 blast. However, it is specifically in the latter 

 that Grosser (1925a) placed the placental 

 fibrinoid, distinguishing it from fibrin and 

 indicating that he did not believe it is re- 



