Low-level chemiluminescence of isolated hepatocytes.

1. Oxygenation of isolated hepatocytes leads to an increased emission of low level chemiluminescence and to an accumulation of malondialdehyde, both occurring after a lag phase of about 20--40 min. 2.

Oxygen- or organic hydroperoxide-induced chemiluminescence of brain and liver homogenates.

Oxygenation of anaerobically isolated brain and liver homogenates is associated with chemiluminescence and formation of lipid hydroperoxides, the latter determined by the thiobarbituric acid assay. Light emission and formation of malonaldehyde are 20-fold higher in the brain than in liver; chemiluminescence of both decays when accumulation of malonaldehyde ceases. Exogenous organic peroxides, such as t-butyl hydroperoxide, inhibit the light-emission response to oxygenation by brain homogenate, whereas they enhance that of liver homogenate.

Ultraweak chemiluminescence: a sensitive assay for oxidative radical reactions.

Application of chemiluminescence to the study of lipid peroxidation reactions is based on the occurence of short-lived free radicals and excited states derived from side reactions of the lipid peroxidation process. Thus, the light emission yield is extremely low: 10(-9)-10(15). Chemiluminescence is induced or enhanced by conditions that normally increase lipid peroxidation or that create a peroxidative stress, i.

Hydroperoxide-induced chemiluminescence of the perfused lung.

Light-emission of the perfused lung is induced by t-butyl hydroperoxide, giving chemiluminescence yields that oscillate between 800 and 1500 counts/s depending on the site and position of the lung. The response of the perfused lung to infusion with different hydroperoxides gives a pattern similar to that observed with the liver microsomal fraction; ethyl hydroperoxide shows a much higher chemiluminescence yield than the tertiary (t-butyl and cumene)hydroperoxides. Alveolar oedema affected the light-emission of the perfused lung depending on the time at which oedema developed, decreasing light emission on infusion of hydroperoxide in the oedematous lung and increasing it when oedema appeared after the maximal chemiluminescence yield was already achieved.

Chemiluminescence of lipid vesicles supplemented with cytochrome c and hydroperoxide.

The increase in light emission of hydroperoxide-supplemented cytochrome c observed on addition of lipid vesicles was related to the degree of unsaturation of the fatty acids of the phospholipids: dipalmitoyl phosphatidylcholine was without effect, whereas dioleoyl phosphatidylcholine and soya-bean phosphatidylcholine enhanced chemiluminescence 2- and 3-fold respectively. Effects on light-emission were similar to those on O2 uptake. The chemiluminescence of the present system was sensitive to cyanide and to the radical trap 2,5-di-t-butylquinol, indicating a catlytic activity of cytochrome c and the presence of free-radical species respectively.

Enhancement of hydrogen peroxide formation by protophores and ionophores in antimycin-supplemented mitochondria.

Rat and pigeon heart mitochondria supplemented with antimycin produce 0.3-1.0nmol of H(2)O(2)/min per mg of protein.

Low-level chemiluminescence of hydroperoxide-supplemented cytochrome c.

Ferricytochrome c showed low-level chemiluminescence, with a light-emission measured of about 1x10(3)-3x10(3) counts/s, when supplemented with organic hydroperoxides. Tertiary hydroperoxides (cumene hydroperoxide and t-butyl hydroperoxide) showed a saturation behaviour at about 5mm-hydroperoxide, whereas primary hydroperoxides showed a quadratic dependence on the hydroperoxide concentration. Chemiluminescence depended linearly on cytochrome c concentration, and optimal light-emission was observed at [t-butyl hydroperoxide]/[ferricytochrome c] ratios of 160-500.

Low-level chemiluminescence of bovine heart submitochondrial particles.

Submitochondrial particles from bovine heart mitochondria showed low-level chemiluminescence when supplemented with organic hydroperoxides. Chemiluminescence seems to measure integratively radical reactions involved in lipid peroxidation and related processes. Maximal light-emission was about 1500 counts/s and was reached 2-10min after addition of hydroperoxides.

Organ chemiluminescence: noninvasive assay for oxidative radical reactions.

In situ and perfused rat livers showed a spontaneous chemiluminescence of 7-12 counts/sec . cm2 (corresponding to 7-12 x 10(3) photons/sec . cm2); chemiluminescence was increased up to 30 times by infusion of exogenous hydroperoxides.

Synthesis of cytoplasmic membrane during growth and division of Escherichia coli. Dispersive behaviour of respiratory nitrate reductase.

We have used the penicillin selection method of Autissier & Kepes [(1972) Biochimie 54, 93--101] to study the segregation of membrane-bound respiratory nitrate reductase (EC 1.9.6.

Nitrate Utilization by the Diatom Skeletonema costatum: II. Regulation of Nitrate Uptake.

Nitrate utilization has been characterized in nitrogen-deficient cells of the marine diatom Skeletonema costatum. In order to separate nitrate uptake from nitrate reduction, nitrate reductase activity was suppressed with tungstate. Neither nitrite nor the presence of amino acids in the external medium or darkness affects nitrate uptake kinetics.

Nitrate Utilization by the Diatom Skeletonema costatum: I. Kinetics of Nitrate Uptake.

Nitrate uptake has been studied in nitrogen-deficient cells of the marine diatom Skeletonema costatum. When these cells are incubated in the presence of nitrate, this ion is quickly taken up from the medium, and nitrite is excreted by the cells. Nitrite is excreted following classical saturation kinetics, its rate being independent of nitrate concentration in the incubation medium for nitrate concentration values higher than 3 micromolar.

Role of ubiquinone in the mitochondrial generation of hydrogen peroxide.

Antimycin-inhibited bovine heart submitochondrial particles generate O2- and H2O2 with succinate as electron donor. H2O2 generation involves the action of the mitochondrial superoxide dismutase, in accordance with the McCord & Fridovich [(1969) j. biol.

Enzymatic basis of mannose toxicity in honey bees.

Honey bees have a negligible amount of phosphomannoseisomerase, together with a high content of a hexokinase which phosphorylates mannose more efficiently than fructose or glucose. Competition at the phosphorylation level plus accumulation of mannose-6-phosphate can fully account for the toxicity of mannose in honey bees.