Impact of post-anoxia stress on membrane lipids of anoxia-pretreated potato cells. A re-appraisal.

The importance of lipid peroxidation and its contributing pathways (via reactive oxygen species and lipoxygenase) during post-anoxia was evaluated with respect to the biphasic behavior of membrane lipids under anoxia (A. Rawyler, D. Pavelic, C. Gianinazzi, J. Oberson, R. Brändle [1999] Plant Physiol 120: 293-300), using potato (Solanum tuberosum cv Bintje) cell cultures. When anoxic cells in the pre-lytic phase were re-oxygenated for 2 h, superoxide anion was not detectable, the hydrogen peroxide (H(2)O(2)) level remained small and similar to that of controls, and cell viability was preserved. Lipids were intact and no lipid hydroperoxides were detected. However, small amounts of lipid hydroperoxides accumulated upon feeding anoxic cells with H(2)O(2) and incubation for an additional 2 h under anoxia. When cells that entered the lytic phase of anoxia were re-oxygenated for 2 h, the H(2)O(2) and superoxide anion levels were essentially unchanged. However, cell respiration decreased, reflecting the extensive lipid hydrolysis that had already started under anoxia and continued during post-anoxia. Simultaneous with the massive release of free polyunsaturated fatty acids, small amounts of lipid hydroperoxides were formed, reaching 1% to 2% of total fatty acids. Catalase and superoxide dismutase activities were not greatly affected, whereas the amount and activity of lipoxygenase tended to increase during anoxia. Lipid peroxidation in potato cells is therefore low during post-anoxia. It is mainly due to lipoxygenase, whereas the contribution of reactive oxygen species is negligible. But above all, it is a late event that occurs only when irreversible damage is already caused by the anoxia-triggered lipid hydrolysis.

Membrane lipid integrity relies on a threshold of ATP production rate in potato cell cultures submitted to anoxia

In this paper we report on our study of the changes in biomass, lipid composition, and fermentation end products, as well as in the ATP level and synthesis rate in cultivated potato (Solanum tuberosum) cells submitted to anoxia stress. During the first phase of about 12 h, cells coped with the reduced energy supply brought about by fermentation and their membrane lipids remained intact. The second phase (12-24 h), during which the energy supply dropped down to 1% to 2% of its maximal theoretical normoxic value, was characterized by an extensive hydrolysis of membrane lipids to free fatty acids. This autolytic process was ascribed to the activation of a lipolytic acyl hydrolase. Cells were also treated under normoxia with inhibitors known to interfere with energy metabolism. Carbonyl-cyanide-4-trifluoromethoxyphenylhydrazone did not induce lipid hydrolysis, which was also the case when sodium azide or salicylhydroxamic acid were fed separately. However, the simultaneous use of sodium azide plus salicylhydroxamic acid or 2-deoxy-D-glucose plus iodoacetate with normoxic cells promoted a lipid hydrolysis pattern similar to that seen in anoxic cells. Therefore, a threshold exists in the rate of ATP synthesis (approximately 10 &mgr;mol g-1 fresh weight h-1), below which the integrity of the membranes in anoxic potato cells cannot be preserved.

Psychological understanding of anthropomorphism in theatre architecture.

Traces of collective projective mechanisms in architecture in general are sedimenting for millenniums. Such case is also with theatre, an old institution of a great social importance. This paper discovers anthropomorphic elements of theatrical architecture. They have been transformed through history into patterns outlined and explained by the author.