Ultrastructure of Trypanosoma lewisi, localization and alterations in rat liver.

Fine structure of Trypanosoma lewisi in rat liver has been studied by electron microscopy 14 days after infection. Various sections examined showed the parasites to be located in liver’s sinusoids or space of Disse.Electron micrographs demonstrate that the contact between the flagellum and the pellicle at the attachment zone is maintained through a desmosome-like substance, while a peculiar section illustrates a fusion of two cells which tangentially depict lattice-like surface and cross-striation of flagellar bundle.Parasites found in sinusoids showed double-membranes, double coiled, DNA-rich kinetoplast with cristae present in basal portion and a prokinetosome parallel in position to the kinetosomal plate which is completely separated from the kinetosome that fastens the flagellum to it like a zipping hook. The positions of these flagellar organelles to the kinetoplast indicate that the kinetosome replication is initiated beyond the kinetoplast division. It is not certain whether the four vacuole-like tubules located in the cytoplasm parallel to kinetosome complex are functionally related to impulse coordination. However, they appear to be involved in pinocytotic activity.Striking features of the parasite in the sinusoid and space of Disse include dense cytoplasmic granules, free ribosomes, nucleus with double membranes and nuclear pores, variable size vacuoles, dense bodies, and rough surface endoplasmic reticulum stretching from the anterior region and bypassing the golgi area all the way to the posterior end of the kinetoplast. The existence of a continuous highly organised relationship between the external nuclear membrane, endoplasmic reticulum and other cytoplasmic contents is demonstrated in the micrographs of the ’ liver parasites The complexity observed and reported here is further documented by (a ) that external mitochondrial membrane is shown to be in contact with sub-pellicular microtubules, (b ) unity and continuity of the mitochondria with an agranular secretory reticulum exist, and (c ) that the elongated mitochondrial extension from the kinetoplast deep into the cytoplasm confirms a previous report that it originates from the kinetoplast. The presence of abundant free ribosomes in the parasite convincingly indicates that the organism is progressively synthesizing more protein when trapped in the tissue.The investigation also demonstrates that when Trypanosoma lewisi where found enclosed in hepatic sinusoid and space of Disse, pathological alterations in the parasite occurred. Inflammation of flagellum at the base and the entire cytoplasmic content of the mid-posterior portion of the organism also occurred.Liver cells parasitized by the trypanosomes showed dilated cisternae of endoplasmic reticulum, swollen mitochondria, fatty infiltrations, dense bodies, vacuoles of different sizes and numerous clusters of ferritin granules. The parasite increased rhythmic activity of locommotion might have enhanced these alterations. Hydrolytic effect of numerous lysosomes of the liver cells might have accelerated the alterations. On the other hand the accumulation of excessive metabolic products of the parasites themselves could also have exerted alterable effect on the liver cells and the sinusoids. Lysosomes or microbodies found in the various liver trypanosomes were possibly spontaneously released by rupture due to injured or dying cells.