Cytoskeletal structure of myoblasts with the mitochondrial DNA 3243A-->G mutation and of osteosarcoma cells with respiratory chain deficiency.

The cytoskeleton, mainly composed of actin filaments, microtubules, and intermediate filaments, is involved in cell proliferation, the maintenance of cell shape, and the formation of cellular junctions. The organization of the intermediate filaments is regulated by phosphorylation and dephosphorylation. We examined cell population growth, apoptotic cell death, and the morphology of cytoskeletal components in myoblast cultures derived from patients with the 3243A-->G mutation in mitochondrial DNA (mtDNA) and from control subjects by means of assays detecting cellular nucleic acids, histone-associated DNA fragments and by immunolabeling of cytoskeletal components. Population growth was slower in the 3243A-->G myoblast cultures, with no difference in the amount of apoptotic cell death. The organization of vimentin filaments in myoblasts with 3243A-->G was disturbed by randomization of filament direction and length, whereas no disturbances were observed in the other cytoskeletal proteins. Vimentin filaments formed large bundles surrounding the nucleus in mtDNA-less (rho(0)) osteosarcoma cells and in osteosarcoma cells after incubation with sodium azide and nocodazole. We conclude that defects in oxidative phosphorylation lead to selective disruption of the vimentin network, which may have a role in the pathophysiology of mitochondrial diseases.

Experimental Chlamydia pneumoniae infection in NIH/S mice: effect of reinoculation with chlamydial or cell preparation on culture, PCR and histological findings of lung tissue.

The cellular components present in chlamydial preparations may contribute to the course of the experimental infection. NIH/S mice were inoculated and reinoculated intranasally with Chlamydia pneumoniae or a cellular preparation. The mock inoculation induced only mild histological changes in the lungs, which possibly induced partial protection against subsequent C. pneumoniae infection and, when given as reinoculation, possibly reactivated the culture-negative infection as culture-positive. In addition, serum antibodies against mouse heat shock protein 60 (Hsp60) were found in a few mice. In conclusion, the main immunopathogenic factors in a C. pneumoniae mouse model are chlamydial components. However, a cellular preparation may participate in an inflammatory reaction. Autoimmunity against Hsp60 may also play a role in the pathogenesis of C. pneumoniae infection.