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Teaching about citric acid cycle using plant mitochondrial preparations: Some a...
Vicente, Joaquim A. F.; Gomes-Santos, Carina S. S.; Sousa, Ana Paula M.; Madeira, Vítor M. C.Potato tubers and turnip roots were used to prepare purified mitochondria for laboratory practical work in the teaching of the citric acid cycle (TCA cycle). Plant mitochondria are particularly advantageous over the animal fractions to demonstrate the TCA cycle enzymatic steps, by using simple techniques to measure O2 consumption and transmembrane potential (ΔΨ). The several TCA cycle intermediates induce speci...
A comparative study of plant and animal mitochondria exposed to paraquat reveal...
Peixoto, Francisco; Vicente, Joaquim; Madeira, Vítor M. C.Rat liver mitochondria are much more susceptible to protein oxidation induced by paraquat than plant mitochondria. The unsaturated index and the peroxidizability index are higher in rat than in potato tuber. The levels of superoxide dismutase and glutathione reductase are concurrent with the different sensitivities to paraquat, with higher activities in plant mitochondria. However, glutathione peroxidase and ca...
Regulation by Magnesium of Potato Tuber Mitochondrial Respiratory Activities
Vicente, Joaquim A. F.; Madeira, Vítor M. C.; Vercesi, Anibal E.Dehydrogenase activities of potato tuber mitochondria and corresponding phosphorylation rates were measured for the dependence on external and mitochondrial matrix Mg2+. Magnesium stimulated state 3 and state 4 respiration, with significantly different concentrations of matrix Mg2+ required for optimal activities of the several substrates. Maximal stimulation of respiration with all substrates was obtained at 2...
Comparative effects of herbicide dicamba and related compound on plant mitochon...
Peixoto, Francisco; Vicente, Joaquim A. F.; Madeira, Vítor M. C.The herbicide dicamba (3,6-dichloro-2-methoxybenzoic acid) was evaluated for its effects on bioenergetic activities of potato tuber mitochondria to elucidate putative mechanisms of action and to compare its toxicity with 2-chlorobenzoic acid. Dicamba (4 mumol/mg mitochondrial protein) induces a limited stimulation of state 4 respiration of ca. 10%, and the above concentrations significantly inhibit respiration,...
Tamoxifen induces ultrastructural alterations in membranes of Bacillus Stearoth...
Luxo, C.; Jurado, A. S.; Madeira, Vítor M. C.; Silva, M. T.Tamoxifen (TAM), a non-steroid antiestrogen, is the mostly used drug for chemotherapy and chemoprevention of breast cancer. However, the mechanisms by which TAM inhibits cell proliferation in breast cancer are not fully understood. TAM strongly incorporates in biomembranes and a variety of effects have been assigned to biophysical and biochemical interactions with membranes. Therefore, a better understanding of...
Degradability and Sediment Sorption of an Alcohol Polyglycol Ether Surfactant P...
Fonseca, Júlio C.; Marques, João C.; Madeira, Vítor M. C.This work reports studies of the degradation rates of a fattyalcohol polyglycol ether non-ionic surfactant, Genapol OXD-080, putatively useful for the control of red swamp crayfish (Procambarus clarkii Girard) in rice fields under laboratory and field conditions. The influence of temperature,sediment site specificity and sorption were taken into account.The degradation kinetics of the surfactant depends on the ...
Ethylazinphos Interaction with Membrane Lipid Organization Induces Increase of ...
Videira, Romeu A.; Antunes-Madeira, Maria C.; Madeira, Vítor M. C.Ethylazinphos increases the passive proton permeability of lipid bilayers reconstituted with dipalmitoylphosphatidylcholine (DPPC) and mitochondrial lipids. A sharp increase of proton permeability is detected at insecticide/lipid molar ratios identical to those inducing phase separation in the plane of DPPC bilayers, as revealed by differential scanning calorimetry (DSC). Ethylazinphos progressively depresses t...
Changes induced by malathion, methylparathion and parathion on membrane lipid p...
Videira, Romeu A.; Antunes-Madeira, Maria C.; Lopes, Virgínia I. C. F.; Madeira, Vítor M. C.Perturbations induced by malathion, methylparathion and parathion on the physicochemical properties of dipalmitoylphosphatidylcholine (DPPC) were studied by fluorescence anisotropy of DPH and DPH-PA and by differential scanning calorimetry (DSC). Methylparathion and parathion (50 [mu]M) increased the fluorescence anisotropy evaluated by DPH-PA and DPH, either in gel or in the fluid phase of DPPC bilayers, but m...
Differential sensitivities of plant and animal mitochondria to the herbicide pa...
Vicente, Joaquim A. F.; Peixoto, Francisco; Lopes, M. Ludovina; Madeira, Vítor M. C.Paraquat herbicide is toxic to animals, including humans, via putative toxicity mechanisms associated to microsomal and mitochondrial redox systems. It is also believed to act in plants by generating highly reactive oxygen free radicals from electrons of photosystem I on exposure to light. Paraquat also acts on non-chlorophyllous plant tissues, where mitochondria are candidate targets, as in animal tissues. The...
Lipid composition and dynamics of cell membranes of Bacillus stearothermophilus...
Rosa, Sónia M. L. J.; Antunes-Madeira, Maria do Carmo; Matos, Manuel J.; Jurado, Amália S.; Madeira, Vítor M. C.Bacillus stearothermophilus, a useful model to evaluate membrane interactions of lipophilic drugs, adapts to the presence of amiodarone in the growth medium. Drug concentrations in the range of 1-2 [mu]M depress growth and 3 [mu]M completely suppresses growth. Adaptation to the presence of amiodarone is reflected in lipid composition changes either in the phospholipid classes or in the acyl chain moieties. Sign...
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