Influence of oxidative and nitrosative stress on accumulation of diphosphate intermediates of the non-mevalonate pathway of isoprenoid biosynthesis in corynebacteria and mycobacteria.

Artificial generation of oxygen superoxide radicals in actively growing cultures of Mycobacterium tuberculosis, Myc. smegmatis, and Corynebacterium ammoniagenes is followed by accumulation in the bacterial cells of substantial amounts of 2-C-methyl-D-erythritol-2,4-cyclodiphosphate (MEcDP) - an intermediate of the non-mevalonate pathway of isoprenoid biosynthesis (MEP) - most possibly due to the interaction of the oxygen radicals with the 4Fe-4S group in the active center and inhibition of the enzyme (E)-4-oxy-3-methylbut-2-enyl diphosphate synthase (IspG). Cadmium ions known to inhibit IspG enzyme in chloroplasts (Rivasseau, C., Seemann, M., Boisson, A. M., Streb, P., Gout, E., Douce, R., Rohmer, M., and Bligny, R. (2009) Plant Cell Environ., 32, 82-92), when added to culture of Myc. smegmatis, substantially increase accumulation of MEcDP induced by oxidative stress with no accumulation of other organic phosphate intermediates in the cell. Corynebacterium ammoniagenes'', well-known for its ability to synthesize large amounts of MEcDP, was also shown to accumulate this unique cyclodiphosphate in actively growing culture when NO at low concentration is artificially generated in the medium. A possible role of the MEP-pathway of isoprenoid biosynthesis and a role of its central intermediate MEcDP in bacterial response to nitrosative and oxidative stress is discussed.

[Ultrastructure of hepatocytes after local cooling of the liver]. / Ul'trastruktura gepatotsitov posle dozirovannogo lokal'nogo okhlazhdeniia pecheni.

Electron-microscopic and stereometric study of hepatocyte ultrastructure with local liver cooling to -30 degrees C have been performed using the method of vital fixation by rat liver perfusion. Quantitative and qualitative data obtained testify to the presence of destructive changes in hepatocytes immediately after thawing expressed in hyaloplasm lightening, formation of cavities in cytoplasm and injury of mitochondria membrane and endoplasmic reticulum integrity. Changes in nuclear structure of hepatocytes and Kupffer cells (widening of nuclear pores and channels in condensed chromatine, as well as the presence of ribosomal complexes in the nucleus and edge position of the nucleolus) may be connected with the beginning of the reparation process.