932 



SPERM, OVA, AND PREGNANCY 



man placenta, demonstrable by a trichrome 

 stain devised by Severinghaus (1932). Ac- 

 cording to them, these granules enlarge to- 

 ward the surface of the syncytium and then 

 seem to liquefy, forming vacuoles which 

 liberate their contents through the brush 

 border into the maternal blood stream. In 

 late pregnancy, as the syncytium becomes 

 thinner, these granules and vacuoles dis- 

 appear. The investigators interpreted these 

 findings as signifying that the trophoblast 

 of early pregnancy performs a significant 

 secretory function, and they emphasized 

 that the period of activity was roughly con- 

 temporaneous with the time of greatest ex- 

 cretion of gonadrotrophin. 



Bruner and Witschi (1947) and Bruner 

 (1951), investigating tlie distribution of 

 chorionic gonadotrophin in the human pla- 

 centa by biochemical means, reported that 

 it is found at all stages of pregnancy, the 

 concentration being highest in the fetal por- 

 tion of the placenta. It is evident, they 

 stated, that the major part of the hormone 

 is "released from the plasmotrophoblast into 

 the maternal blood, whereas only a small 

 fraction passes the inner placental barrier, 

 the cytotrophoblast, to enter the fetal blood 

 stream." They apparently believed that the 

 hormone is formed by the synctium. 



Similarities between the peripheral tro- 

 phoblasts and the cells of the anterior lobe 



of the hypophysis believed to produce the 

 hypophyseal gonadotrophic hormones, sug- 

 gested to Dempsey and Wislocki (1945) 

 that the peripheral trophoblasts produce 

 chorionic gonadotrophin. They demon- 

 strated that the cytoplasm of the syncytium 

 and peripheral trophoblasts of the human 

 placenta contains a basophilic substance 

 similar to that in the true basophilic cells of 

 the anterior lobe of the hypophysis, which 

 in both instances is abolished by digestion 

 with crystalline ribonuclease. That the hy- 

 pophyseal basophilic cells contain ribonu- 

 cleoprotein was first demonstrated by 

 Desclin (1940). Since ribonucleoprotein is 

 generally concentrated in cells in which pro- 

 tein synthesis is actively taking place, Wis- 

 locki, Dempsey and Fawcett (1948) sug- 

 gested that its presence in the peripheral 

 trophoblast might be related to the forma- 

 tion tlierc of chorionic gonadotrophin. On 

 the other hand, they thought that the ri- 

 bonucleoprotein in the syncytium which is 

 particularly abundant in the first months of 

 gestation might represent the primary site 

 of synthesis of fetal plasma proteins, a 

 function taken over by the hepatic cells 

 when the fetal liver becomes sufficiently dif- 

 ferentiated. Wislocki (1951) observed that 

 the basophilia of the peripheral trophoblasts 

 persists until full term, coinciding with the 



Plate 15.XV 



Fig. 15.64. Cliorionic fold.s of a pig's placenta (fetal crown to rump length, 130 mm.), show- 

 ing many intraepithelial blood capillaries (blood cells not visible), resulting in the formation 

 of many extremely thin epithelial plates some of which appear to be quite as thin as the 

 human "epithehal plates" seen at full term {cj. with Figure 15.50). Compare with Figures 

 15.23 and 15.28 which are also of pig's placenta. Zenker-formol fixative. Eosin and nifthylene 

 blue stain. X 400. (Wislocki and Dempsey, 1946b.) 



Fig. 15. 65. A chorionic fossa of a pig's placenta (fetal crown to rump length, 120 mm.), 

 illustrating the presence of finely dispersed periodic acid-Schiff (PAS) positive material in 

 the distal ends of the columnar cells and coarse PAS stained droplets in their proximal ends. 

 Orth's fixative. X 150. 



Fig. 15.66. Uterine glands in the maternal placenta of a pig (fetal crown to rump lengtli. 

 120 mm.), showing the strongly PAS-reactive secretion in the lumens. Orth's fixative. X 165. 



Fig. 15.67. The chorion of a pig's placenta (fetal crown to rump length, 120 mm.) to il- 

 lustrate the intense reaction of alkaline phosphatase in the columnar cells of the chorionic 

 fossae located between the chorionic rugae. Gomori's method, using nuclei acid at pH 9.6. X 

 200. 



Fig. 15.68. The endometrium of a pig's placenta (fetal crown to rump length, 120 mm.), to 

 illustrate the intense alkaline phosphatase reaction in the endometrial stroma and blood 

 vessel walls. The enzyme is essentially negative in the epithelium (ep) covering the endo- 

 metrial folds as well as in the epithelium lining the uterine glands (g). Gomori's method, 

 using fructose diphosphate at pH 9.4. X 200. 



Fig. 15.69. Uterine glands in a pig's placenta (fetal crown to rump length, 125 mm.), il- 

 lustrating the intense acid phosphata.se activity of the glandular cells. Gomori's method, 

 using glycerophosphatase at pH 4.7. X 170. (Wislocki and Dempsey, 1946b.) 



