Reactive oxygen species (ROS) have been implicated as an important causative factor in cell damage, including apoptosis and necrosis. Their proposed actions comprise lipid peroxidation, DNA damage, destruction of the mitochondrial respiratory chain and protein modifications. Recent experiments underline the importance of peroxynitrite, the reaction product of the two potent reactive species nitric oxide and Superoxide. Several fluorogenic compounds have been used in order to determine ROS formation in living cells. Besides dihydrorhodamine-123 (DHR-123), at present mostly applied to monitor peroxynitrite, 2,7-dihydrodichlorofluorescein (DCF-H) is used for detection of hydrogen peroxide and nitric oxide. We employed a cell free approach to evaluate the specificity and sensitivity of DCF-H to various oxidizing compounds. Our studies imply that DCF-H is much more sensitive to peroxynitrite oxidation than any other compound tested. In order to study peroxynitrite generation within individual cells, primary glial cultures loaded with DCF-H were monitored with a laser scanning microscope. Microglia, stimulated to simultaneously produce the peroxynitrite precursors nitric oxide and Superoxide, displayed the greatest increase in DCF fluorescence, whereas microglia producing either nitric oxide or Superoxide alone showed a relatively small increase in DCF fluorescence. In conclusion, DCF-H was demonstrated to be an excellent peroxynitrite marker with the potential to detect peroxynitrite formation in living cells. © 1997 Federation of European Biochemical Societies.

Microstructured devices are widely used for manufacturing products that benefit from process intensification, with pharmaceutical products or specialties of the chemical industry being prime examples. These devices are ideally used for processing pure fluids. Where particulate or non-pure flows are involved, processes are treated with utmost caution since related fouling and blocking issues present the greatest barrier to operating microstructured devices effectively. Micro process engineering is a relatively new research field and there is limited understanding of fouling in these dimensions and its underlying processes and phenomena. A comprehensive review on fouling in microstructured devices would be helpful in this regard, but is currently lacking. This paper attempts to review recent developments of fouling in micro dimensions for all fouling categories (crystallization, particulate, chemical reaction, corrosion and biological growth fouling) and the sequential events involved (initiation, transport, attachment, removal and aging). Compared to fouling in macro dimensions, an additional sixth category is suggested: clogging by gas bubbles. Most of the reviewed papers present very specific fouling investigations making it difficult to derive general rules and parameter dependencies, and comparative or critical considerations of the studies were difficult. We therefore used a statistical approach to evaluate the research in the field of fouling in microchannels.

Carotenoids are widely used as important micronutrients in food. Furthermore, carotenoid supplementation has been used in the treatment of diseases associated with oxidative stress. However, in some clinical studies harmful effects have been observed, for example, a higher incidence of lung cancer in individuals exposed to extraordinary oxidative stress. The causal mechanisms are still unclear. Carotenoid cleavage products (CCPs), including highly reactive aldehydes and epoxides, are formed during oxidative attacks in the course of antioxidative action. Here, we tested the hypothesis that CCPs may increase oxidative stress by impairing mitochondrial function. We found that CCPs strongly inhibit state 3 respiration of isolated rat liver mitochondria even at concentrations between 0.5 and 20 microM. This was true for retinal, beta-ionone, and mixtures of cleavage products, which were generated in the presence of hypochlorite to mimic their formation in inflammatory regions. The inhibition of mitochondrial respiration was accompanied by a reduction in protein sulfhydryl content, decreasing glutathione levels and redox state, and elevated accumulation of malondialdehyde. Changes in mitochondrial membrane potential favor functional deterioration of the adenine nucleotide translocator. The findings may reflect a basic mechanism of increasing the risk of cancer induced by CCPs.

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