Mitochondrial bioenergetics is affected by the herbicide paraquat

AbstractThe potential toxicity of the herbicide paraquat (1,1-dimethyl-4,4′-bipyridylium dichloride) was tested in bioenergetic functions of isolated rat liver mitochondria. Paraquat increases the rate of State 4 respiration, doubling at 10 mM, indicating uncoupling effects. Additionally, State 3 respiration is depressed by about 15%, at 10 mM paraquat, whereas uncoupled respiration in the presence of CCCP is depressed by about 30%. Furthermore, paraquat partially inhibits the ATPase activity through a direct effect on this enzyme complex. However, at high concentrations (5–10 mM), the ATPase activity is stimulated, probably as consequence of the described uncoupling effect. Depression of respiratory activity is mediated through partial inhibitions of mitochondrial complexes III and IV. Paraquat depresses Δψ as a function of herbicide concentration. In addition, the depolarization induced by ADP is decreased and repolarization is biphasic suggesting a double effect. Repolarization resumes at a level consistently higher than the initial level before ADP addition, for paraquat concentrations up to 10 mM. This particular effect is clear at 1 mM paraquat and tends to fade out with increasing concentrations of the herbicide

Changes induced by malathion, methylparathion and parathion on membrane lipid physicochemical properties correlate with their toxicity

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 mainly in the fluid phase. Parathion is more effective than methylparathion. On the other hand, malathion had almost no effect. All the three xenobiotics displaced the phase transition midpoint to lower temperature values and broadened the phase transition profile of DPPC, the effectiveness following the sequence: parathion>methylparathion>>malathion. A shifting and broadening of the phase transition was also observed by DSC. Furthermore, at methylparathion/lipid molar ratio of 1/2 and at parathion/lipid molar ratio of 1/7, the DSC thermograms displayed a shoulder in the main peak, in the low temperature side, suggesting coexistence of phases. For higher ratios, the phase transition profile becomes sharp as the control transition, but the midpoint is shifted to the previous shoulder position. Conversely to methylparathion and parathion, malathion did not promote phase separation. The overall data from fluorescence anisotropy and calorimetry indicate that the degree of effect of the insecticides on the physicochemical membrane properties correlates with toxicity to mammals. Therefore, the in vivo effects of organophosphorus compounds may be in part related with their ability to perturb the phospholipid bilayer structure, whose integrity is essential for normal cell function.http://www.sciencedirect.com/science/article/B6T1T-42NY32W-K/1/9c5c8320a8dff42bbf122281b5056b8

Lipid composition and dynamics of cell membranes of Bacillus stearothermophilus adapted to amiodarone

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. Significant changes are observed at 2 [mu]M and expressed by a decrease of phosphatidylethanolamine (relative decrease of 23.3%) and phosphatidylglycerol (17.9%) and by the increase of phosphoglycolipid (162%). The changes in phospholipid acyl chains are expressed by a decrease of straight-chain saturated fatty acids (relative decrease of 12.2%) and anteiso-acids (22%) with a parallel increase of the iso-acids (9.8%). Consequently, the ratio straight-chain/branched iso-chain fatty acids decreases from 0.38 (control cultures) to 0.30 (cultures adapted to 2 [mu]M amiodarone). The physical consequences of the lipid composition changes induced by the drug were studied by fluorescence polarization of diphenylhexatriene and diphenylhexatriene-propionic acid, and by differential scanning calorimetry. The thermotropic profiles of polar lipid dispersions of amiodarone-adapted cells are more similar to control cultures (without amiodarone) than those resulting from a direct interaction of the drug with lipids, i.e., when amiodarone was added directly to liposome suspensions. It is suggested that lipid composition changes promoted by amiodarone occur as adaptations to drug tolerance, providing the membrane with physico-chemical properties compatible with membrane function, counteracting the effects of the drug.http://www.sciencedirect.com/science/article/B6VNN-419BF60-K/1/8f2d4fae7f9c131d26230cf4123da94

Size dependence of the translational diffusion of large integral membrane proteins in liquid-crystalline phase lipid bilayers. A study using fluorescence recovery after photobleaching

The translational diffusion of bovine rhodopsin, the Caz+-activated adenosinetriphosphatase of rabbit muscle sarcoplasmic reticulum, and the acetylcholine receptor monomer of Torpedo marmorata has been examined at a high dilution (molar ratios of lipid/protein 1 3000/1) in liquidcrystalline phase phospholipid bilayer membranes by using the fluorescence recovery after photobleaching technique. These integral membrane proteins having molecular weights of about 37 000 for rhodopsin, about 100000 for the adenosinetriphosphatase, and about 250 000 for the acetylcholine receptor were reconstituted into membranes of dimyristoylphosphatidylcholine (rhodopsin and acetylcholine receptor), soybean lipids (acetylcholine receptor), and a total lipid extract of rabbit muscle sarcoplasmic reticulum (adenosinetriphosphatase). The translational diffusion coefficients of all the proteins at 310 K were found to be in the range (1-3) X cm2/s. In consideration of the sizes of the membranebound portions of these proteins, this result is in agreement with the weak dependence of the translational diffusion coefficient upon diffusing particle size predicted by continuum fluid hydrodynamic models for the diffusion in membranes [Saffman, P. G., & Delbriick, M. (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 3 1 1 1-3 1 131. Lipid diffusion was also examined in the same lipid bilayers with the fluorescent lipid derivative N-(7-nitro-2,1,3-benzoxadiazol-4-yl)dimyristoylphosphatidylethanolamine. The translational diffusion coefficient for this lipid derivative was found to be in the range (9-14) X cm2/s at 310 K. In consideration of the dimensions of the lipid molecule, this value for the lipid diffusion coefficient is in agreement with the continuum fluid hydrodynamic model only if a near-complete slip boundary condition is assumed at the bilayer midplane. Alternatively, kinetic diffusion models [Trauble, H., & Sackmann, E. (1972) J. Am. Chem. SOC9. 4,4499-45101 may have to be invoked to explain the lipid diffusion behavior

Catálogo Taxonômico da Fauna do Brasil: setting the baseline knowledge on the animal diversity in Brazil

The limited temporal completeness and taxonomic accuracy of species lists, made available in a traditional manner in scientific publications, has always represented a problem. These lists are invariably limited to a few taxonomic groups and do not represent up-to-date knowledge of all species and classifications. In this context, the Brazilian megadiverse fauna is no exception, and the Catálogo Taxonômico da Fauna do Brasil (CTFB) (http://fauna.jbrj.gov.br/), made public in 2015, represents a database on biodiversity anchored on a list of valid and expertly recognized scientific names of animals in Brazil. The CTFB is updated in near real time by a team of more than 800 specialists. By January 1, 2024, the CTFB compiled 133,691 nominal species, with 125,138 that were considered valid. Most of the valid species were arthropods (82.3%, with more than 102,000 species) and chordates (7.69%, with over 11,000 species). These taxa were followed by a cluster composed of Mollusca (3,567 species), Platyhelminthes (2,292 species), Annelida (1,833 species), and Nematoda (1,447 species). All remaining groups had less than 1,000 species reported in Brazil, with Cnidaria (831 species), Porifera (628 species), Rotifera (606 species), and Bryozoa (520 species) representing those with more than 500 species. Analysis of the CTFB database can facilitate and direct efforts towards the discovery of new species in Brazil, but it is also fundamental in providing the best available list of valid nominal species to users, including those in science, health, conservation efforts, and any initiative involving animals. The importance of the CTFB is evidenced by the elevated number of citations in the scientific literature in diverse areas of biology, law, anthropology, education, forensic science, and veterinary science, among others

Toxicity of MCPA on non-green potato tuber calli

Abstract Growth of potato tuber calli cells (non-green) is inhibited by 4-chloro-2-methylphenoxyacetic acid (MCPA) as a consequence of perturbation of membrane integrity. MCPA also depresses ATP content with simultaneous increase of ADP and AMP, i.e., the energy charge is severely compromised. Cell redox state is also affected by MCPA, as a function of concentration. Up to 60 µM, MCPA stimulates glutathione reductase and glutathione transferase, whereas superoxide dismutase and catalase activities are not affected. However, 120 µM MCPA inhibits all these activities. Cell death challenged by MCPA is putatively related to disturbance of membrane integrity responsible for mitochondrial uncoupling with decrease of the energy charge and subsequent loss of ions and metabolites

Degradability and Sediment Sorption of an Alcohol Polyglycol Ether Surfactant Putatively Useful for the Control of Red Swamp Crayfish in Rice Fields

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 experimental conditions: type of inocula and temperature. Thedistribution of this chemical in aquatic systems was also examined. Genapol OXD-080 was removed into the sedimentsreadily after application, and sorption was considered the majorpath of removal from the water phase. Data suggest that furtherstudies are required regarding the effects of Genapol OXD-080 in aquatic organisms resident in rice fields, in parallelwith the development of technologies related with the use ofsurfactants to control P. clarkii populations

Regulation by Magnesium of Potato Tuber Mitochondrial Respiratory Activities

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-mM external Mg2+. However, respiration of malate, citrate, and a-ketoglutarate requires at least 4-mM Mg2+ inside mitochondria for maximization of dehydrogenase activities. The phosphorylation system, requires a low level of internal Mg2+ (0.25 mM) to reach high activity, as judged by succinate-dependent respiration. However, mitochondria respiring on citrate or a-ketoglutarate only sustain high levels of phosphorylation with at least 4-mM matrix Mg2+. Respiration of succinate is active without external and matrix Mg2+, although stimulated by the cation. Respiration of a-ketoglutarate was strictly dependent on external Mg2+ required for substrate transport into mitochondria, and internal Mg2+ is required for dehydrogenase activity. Respiration of citrate and malate also depend on internal Mg2+ but, unlike a-ketoglutarate, some activity still remains without external Mg2+. All the substrates revealed insensitive to external and internal mitochondrial Ca2+, except the exogenous NADH dehydrogenase, which requires either external Ca2+ or Mg2+ for detectable activity. Calcium is more efficient than Mg2+, both having cumulative stimulation. Unlike Ca2+, Mn2+ could substitute for Mg2+, before and after addition of A23, showing its ability to regulate phosphorylation and succinate dehydrogenase activities, with almost the same efficiency as Mg2+

Rapid isolation of low density lipoproteins in a concentrated fraction free from water-soluble plasma antioxidants

A rapid method is described for isolation and concentration of plasma low density lipoproteins (LDL) using a Beckman L80 ultracentrifuge equipped with a 70.1 Ti fixed angle rotor. The isolation of LDL achieved by a discontinuous gradient density step (180 min) was followed by a simultaneous purification and concentration step (45 min) using ultrafiltration through a collodium bag under nitrogen. This dialysis/concentration step, in contrast to the standard dialysis techniques in batch or by filtration through short gel columns, prevents oxidation and dilution of the sample. Electrophoresis in agarose and sodium dodecylsulfate-polyacrylamide (SDS-PAGE) gels were used to monitor LDL surface charge, purity, and contamination with plasma proteins. The artifactual oxidation of LDL during isolation and subsequent handling, and thus the ability of LDL preparation for oxidation/antioxidation studies, was assessed by the determination of endogenous hydroperoxides and thiobarbituric acid reactive substances. The dialysis/concentration step by ultrafiltration that allows the obtention of a concentrated and purified LDL preparation was validated by the absence of ascorbate and urate, as measured by HPLC. This method led to LDL preparations free of water-soluble plasma antioxidants that were minimally oxidized and suitable for reliable in vitro LDL oxidation and inhibition studies. The applicability of this methodology was tested by studying the alpha-tocopherol content of LDL in a Portuguese population of university student

Ethylazinphos Interaction with Membrane Lipid Organization Induces Increase of Proton Permeability and Impairment of Mitochondrial Bioenergetic Functions

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 the transmembrane potential ([Delta][Psi]) of mitochondria supported by piruvate/malate, succinate, or ascorbate/TMPD. Additionally, a decreased depolarization induced by ADP depends on ethylazinphos concentration, reflecting a phosphorylation depression. This loss of phosphorylation is a consequence of a decreased [Delta][Psi]. A decreased respiratory control ratio is also observed, since ethylazinphos stimulates state 4 respiration and inhibits ADP-stimulated respiration (state 3). Ethylazinphos concentrations up to 100 nmol/mg mitochondrial protein increase the rate of state 4 together with a decrease in [Delta][Psi], without significant perturbation of state 3 and carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP)-uncoupled respiration. For increased insecticide concentrations, the state 3 and FCCP-uncoupled respiration are inhibited to approximately the same extent. The perturbations are more pronounced when the energization is supported by pyruvate/malate and less effective when succinate is used as substrate. The present data, in association with previous DSC studies, indicate that ethylazinphos, at concentrations up to 100 nmol/mg mitochondrial protein, interacts with the lipid bilayer of mitochondrial membrane, changing the lipid organization and increasing the proton permeability of the inner membrane. The increased proton permeability explains the decreased oxidative phosphorylation coupling. Resulting disturbed ATP synthesis may significantly underlie the mechanisms of ethylazinphos toxicity, since most of cell energy in eukaryotes is provided by mitochondria.http://www.sciencedirect.com/science/article/B6WXH-45BBYFP-25/1/8df8835c5305825c596440b25248b30