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parasites or to the sand fly. On the other hand, concurrent 

 infections with bacteria resulted in rapid degeneration of the 

 leishmanial infection and premature death of the host fly, due to 

 rupturing of the peritrophic sac. The large, peanut-shaped 

 flagellates did not seem to be affected by the presence of the 

 bacteria. 



Ultrastructure Studies 



Leishmania mexicana (strain WR-411) amastigotes from hamsters 

 infected by the bite of J_u. diabol ica were examined with an electron 

 microscope. Up to 17 parasites were observed in cross-sections of a 

 single macrophage (Fig. 4-12). Their shape was elliptical and size 

 was fairly uniform, measuring about 3.5 urn long by 1.5 urn wide. The 

 parasites (Fig. 4-13) were surrounded by a pellicle (P) below which 

 subpel licular microtubules (SM) ran spirally along the longitudinal 

 axis. The number of microtubules counted in transverse sections of 

 amastigotes averaged 89 and ranged from 81 to 97 (n = 43). Other 

 conspicuous organelles included a short flagellum (F), with a typical 

 nine-plus-two microtubule configuration, emerging eccentrically from a 

 flagellar reservoir (FR), a kinetoplast (K), and an electron-dense 

 nucleus (N) (see Gardener, 1974). 



Promastigotes of L mexicana were examined in the midgut and 

 card i a of female Lu. diabol ica that had been fixed six days after the 

 infecting blood meal. As expected, a much greater variation in size 

 and shape was observed in promastigotes than in amastigotes. Figure 

 4-14 shows several promastigotes in transverse section. The pellicle 

 (P) and subpel 1 icul ar microtubules (SM) surrounding the parasites are 



