906 



SPERM, OVA, AND PREGNANCY 



stages of normal gestation in primates, 

 hemorrhage in the decidua coincides with 

 the erosion of the uterine mucosa by the 

 advancing trophoblast. However, the tro- 

 phoblast elaborates a substance which ini- 

 tiates changes in the decidual tissue even 

 before the ovum has become attached. In 

 the rhesus monkey, evidence of such a 

 chemical factor is seen in the fact that the 

 epithelium at the secondary implantation 

 site begins to proliferate before actual ero- 

 sion of the uterine surface has taken place 

 (Wislocki and Streeter, 1938) . Similarly, in 

 a previllous human ovum of 11 days' ovula- 

 tion age, an area of congestion and hemor- 

 rhage was found on the opposite endo- 

 metrial wall which had merely been in close 

 proximity to the implantation site (Hertig 

 and Rock, 1941). 



The histologic appearances at the margin 

 of the growing trophoblastic shell of the 

 human placenta in the early months of ges- 

 tation suggest that the cells and matrix of 

 the decidua are attacked and slowly de- 

 stroyed by the action of the advancing, 

 growing cytotrophoblast. In sections which 

 have been impregnated by silver, the disso- 

 lution of the fibers of the reticulum can be 

 observed. Immediately adjacent to the bor- 

 der of the trophoblast, the fibers become 

 broken up and the individual bits dissolve 

 apparently in the outermost part of the ma- 

 trix of the trophoblastic shell (Wislocki and 

 Bennett, 1943, Plate 9). Similar fragmenta- 

 tion of collagen fibers in the vicinity of the 



trophoblast has been noted in the placenta 

 of rodents (Wislocki, Deane and Dempsey, 

 1946, Plate 10) and cat (Wislocki and 

 Dempsey, 1946a, Fig. 5). The metachro- 

 matic ground substance between the decid- 

 ual cells, close to the cytotrophoblast, is also 

 destroyed. 



Similar proteolytic activity has been dem- 

 onstrated experimentally in the presence of 

 fertilized mouse ova transplanted to vari- 

 ous extra-uterine sites including the anterior 

 chamber of the eye (Runner, 1947; Fawcett, 

 Wislocki and Waldo, 1947). In the eye of 

 a mouse containing proliferating ova, leak- 

 age of blood from engorged vessels in the 

 iris and cornea took place before a blasto- 

 cyst had actually become attached to the 

 wall of the anterior chamber. It is note- 

 worthy also that blood began to accumulate 

 behind the iris at the same time that it ap- 

 peared in the anterior chamber. Inasmuch 

 as the vessels on the back of the iris and 

 ciliary body were not in contact with the 

 blastocyst and hence had not presumably 

 been disrupted by actual invasion, the most 

 satisfactory way to account for the bleeding 

 in the posterior chamber was to attribute it 

 to some chemical released by the tropho- 

 blast. Although the trophoblast invades 

 maternal vessels in later stages of implan- 

 tation, direct observation and study of his- 

 tologic sections of ova transplanted to the 

 eye suggested that the interstitial hemor- 

 hage and edema in the early hours of nida- 

 tion were the result of diffuse damage to 



Plate 15.VII 



Fig. 15.29. Human placental villi at 2I/2 months of gestation, stained by the periodic acid- 

 SchilT (PAS) procedure. Section exposed to saliva before staining. Zenker's acetic acid fixa- 

 tive. Observe the positive PAS reaction in the outer zone of the syncytium as well as the 

 variable reaction of the ba.sement membrane on which the trophoblast rests. Note also the 

 reaction in the cells of the stroma. Compare with Figure 15.33. X 150. 



Fig. 15.30. Human placental villi at 31/2 months of gestation stained by Baker's acid hema- 

 tein method for phospholipids. Formalin-calcium-chloride fixative. Observe the intense reac- 

 tion of the syncytial trophoblast clothing the villi, as well as the staining of the stromal cells, 

 particularly of large, vacuolated Langhans cells. Compare with Figure 15.26, which shows 

 more details. X 240. 



Figs. 15.31 and 15.32. Sections illustrating the tip of a secondary chorionic villus attached 

 to the trophoblastic shell (or basal plate) of a human placenta at 2 months of gestation. 

 PAS stain after Rossman's fixative. In Figure 15.31, glycogen is abundantly revealed in the 

 cytotrophoblasts of the basal plate (left side of figure). In Figure 15.32, the section was im- 

 mersed in saliva before staining it, to remove glycogen; as a result the trophoblasts (left side 

 of figure) are now only very faintly stained, the outer zone of the syncytial trophoblast is 

 moderately stained and there is an intense reaction visible in the basement membrane be- 

 tween the stroma of the secondary villus and the cytotrophoblastic cell column. These re- 

 sidual reactions are attributable to carbohydrates (glycoproteins, mucopolysaccharides) other 

 than glycogen. X 300. 



