ガンビアトリパノソーマ原虫(Trypanosoma brucei gambiense)の細胞骨格の電子顕微鏡的研究

Abstract

The cytoskeleton of Trypanosoma brucei gambiense trypomastigote was investigated electron microscopically with emphasis on structural relationships between each component. The parasite has two prominent microtubular systems, namely axonemal complex in the flagellum and pellicular microtubules underneath the plasma membrane. The two systems are physically connected by a linear array of rivet structures that runs from the anterior end of the parasite towards a ring-shaped structure around the flagellar pocket. The rivet structure is composed of a pair of macula-like dots, which are shared by flagellum and cell body membranes. The binding between flagellum and cell body is resistant against saponin treatment but labile to Triton X treatment. The flagellum is equipped with an axonemal complex commonly seen in other organisms. Extraction of the parasite with saponin or Triton X results in clear visualization of the cytoskeleton, preserving the peculiar spacial relationships among the cytoplasmic organelles. A network of filaments with a diameter of about 4 nm is present between kinetoplast and centriole/basal body, where cytoplasmic ribosomes are excluded. And filaments with the same morphology are also found in the vicinity of microtubules, suggesting that the filaments are playing a major role in maintaining cell integrity. Ribosome-like granules are closely associated with pellicular microtubules. Whole mount preparation after parasite-extraction with Triton X discloses a general structural profile of the parasite's cytoskeleton including pellicular microtubules, rivet structures and flagellum. The anterior end of the parasite is tapering and the posterior end terminates abruptly without any particular device. Centriole is always associated with basal body. This investigation seems to be the first comprehensive description of the cytoskeleton of T. b. gambiense which would make a base to understand all aspects of the parasite.