554 Protozoa of the Digestive and Urogenital Tracts 



served occasionally (173). A fibril, similar to the paradesmose of tricho- 

 monad flagellates, sometimes joins two nuclei in D. fragilis (49). 



The ability of D. fragilis to encyst remains unproven, although sphe- 

 roid to ovoid bodies (4-9 x 4-6[x) containing two supposed nuclei have 

 been identified tentatively as cysts of this amoeba (130). 



Entamoeba coli 



Losch emend. Schaudinn 



This species occurs in monkeys (46, 48) as well as man. The amoe- 

 boid stages (Fig. 1 1. 6, A) vary from 15 to 40^;. in diameter, with a common 

 range of 20-30[ji. Locomotion is sluggish, with blunt and often granular 

 pseudopodia. Food vacuoles contain bacteria and other material from the 

 intestine but ordinarily no tissue cells. The stained interphase nucleus 

 shows a rather small and normally eccentric endosome, as well as a 

 fairly coarse layer of peripheral granules. In addition, finely granular 

 periendosomal material is stained in the Feulgen technique. The rest of 

 the nucleus is Feulgen-negative (169a). As would be expected, the typical 

 nuclear structure is much modified in mitosis (158). 



Spheroid precystic forms usually measure 15-18[i., with a range of 12 to 

 35[j(,. There are no food vacuoles and it is sometimes difficult to distin- 

 guish precystic E. coli from E. histolytica. 



The cysts (Fig. 11. 6, B-E) range from 10 to 38[ji, in diameter, although 

 the majority measure 15-20[x. Young cysts contain one or two nuclei and 

 relatively large masses of glycogen. Mature cysts contain eight nuclei, or 

 sometimes 16 or more (48). Chromatoid bodies, visible in the unstained 

 cyst as refractile inclusions, are common in young cysts but have usually 

 disappeared, along with the glycogen, in mature cysts. Chromatoid ma- 

 terial may appear as splinters, filaments, irregular clumps of splinter-like 

 bodies, small irregular fragments, or as one or more lobulated masses. 



Effects on the host 



Pathogenicity of Endolimax nana and lodamoeba biltschlii is 

 doubtful and perhaps improbable, although Smithies (150) observed 

 digestive disturbances in all of his patients infected with amoebae. The 

 report of a fatal infection, apparently with /. biltschlii, seems to be the 

 only case of its kind on record (43). 



Dientamoeba fragilis also is often considered a commensal. However, 

 heavy infection has been associated with definite illness involving diges- 

 tive disturbances, chronic fatigue, and loss of weight, and both the infec- 

 tion and the symptoms were eliminated by chemotherapy (66). Wenrich 

 also has suggested possible pathogenicity for this species (168), and has 

 reviewed other reports of this nature (173). 



Entamoeba coli is another supposedly harmless species, but various 

 gastro-intestinal complaints have been noted in infected patients (150). 



