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ABSTRACT: The effect of the liposoluble organophosphorus insecticide fenitrothion (FS) on lipid packing and rotation of two crustacean plasma HDL was investigated. These lipoproteins, HDL-1 and HDL-2, differed in their lipid composition, but their lipid/protein ratios were similar. The rotational behavior of the fluorescent probes 1,6-diphenyl-1,3,5-hexatriene (DPH) and 3-(p-(6-phenyl)-1,3,5-hexatrienyl) phenylpropionic acid (DPH-PA) was used to obtain information about the lipid dynamics in the outer and inner regions, respectively, of the lipid phase of the lipoproteins. Fluorescent steady-state anisotropy (r(s)), lifetime (tau), rotational correlation time (tau(r)), and the limiting anisotropy (r(infinity)) of these probes were measured in the lipoproteins exposed to different concentrations of FS in vitro. The results showed the penetration of FS into both plasma lipoproteins, altering the lipid dynamics of the inner as well as the outer regions. The overall effect of the insecticide was to induce an increase in the lipid order in a concentration-dependent fashion. DPH and DPH-PA fluorescence-lifetime shortening indicated that FS increased the polarity of the probe environment, suggesting an enhanced water penetration into the lipoprotein lipid phase, may be due to the induction of failures in the lipid packing. Even in the absence of FS, a higher ordering of the lipid phase was found in HDL-2 compared to HDL-1, a fact that might be attributed to a higher percentage of sphingomyelin in HDL-2.
Lipids 08/2002; 37(7):673-9. · 2.13 Impact Factor
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ABSTRACT: The effects of the organophosphorous insecticide fenitrothion (phosphorothioic acid, O,O-dimethyl O-(3-methyl-4-nitrophenyl) ester; FS) on the physical state of pure dipalmitoyl (DPPC) and 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) membranes were investigated. FS lowers the phase transition temperature of DPPC. It has no large effects on the DPPC gel phase, but it increases the order of the liquid-crystalline state of DPPC and POPC. FS also decreases 1,6-diphenyl-1,3,5-hexatriene (DPH) lifetime (tau) in the DPPC and POPC liquid-crystalline states. Since a direct quenching of DPH emission by FS was ruled out, tau shortening is assigned to an increased water penetration in the bilayer. The effect of FS is different from most perturbing agents for which an increased order is accompanied by a higher tau. Furthermore, quenching of DPH by KI was increased by FS in POPC liposomes indicating an increased accessibility of the quencher to the hydrophobic core where DPH distributes. The effect of FS on dipole relaxation at the hydrophilic-hydrophobic interface of POPC bilayers was studied with 2-dimethylamino-6-lauroylnaphthalene (Laurdan). FS produces a decrease in Laurdan tau and a narrowing of its emission band. FS significantly increases the generalized polarization values at both emission band ends. These results indicate that FS may allow the coexistence of microdomains that have different physical properties.
Biochimica et Biophysica Acta 10/2000; 1468(1-2):304-10. · 4.66 Impact Factor
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ABSTRACT: The activities of the enzymatic systems involved in the activation and degradation of fatty acids, and in the synthesis of triacylglycerols and phospholipids were studied in vitro using total cellular homogenate and subcellular fractions of eggs of the shrimp Macrobrachium borellii at different developing stages. Egg development was divided into seven stages based on morphological features of the embryo. Palmitoyl-CoA ligase activity increased as the embryo developed and showed its maximum at stage V. An increase in the synthesis of triacylglycerols and diacylglycerols was also observed at this stage. Diacylglycerylethers were synthesized more actively during the first stages of development. The higher specific activity observed in total homogenate than in microsomal fraction suggested that their synthesis was not exclusively microsomal. Phospholipid synthesis was very active all along development, reflecting active membrane biosynthesis. The highest activity of the cytosolic triacylglycerol lipase was observed at stage V. Fatty acid degradation, measured as mitochondrial beta-oxidation activity, did not vary significantly during development. We conclude that both the anabolic and catabolic processes concerning lipid metabolism are very active, with values similar to those described for adult hepatopancreas, revealing the major role of lipids during shrimp embryogenesis energetics, and that the highest activities of lipid synthesis-hydrolysis take place at stage V when embryos are under active organogenesis. J. Exp. Zool. 286:231-237, 2000.
Journal of Experimental Zoology 03/2000; 286(3):231-7.
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ABSTRACT: 1.1. The mechanism of cholesterol transport in snail hemolymph was studied in Ampullaria canaliculata. Plasma and hemocytes were obtained 7 hr after injecting labelled cholesterol into the foot muscle.2.2. The radioactive tracer circulated in the free form mainly in plasma (90%) and to a lesser extent, associated with hematic cells.3.3. Labelled plasma was centrifuged in density gradients and fractionated. It was possible to detect a high-density lipoprotein (HDL), with a hydrated density in the range 1.10–1.15 g/ml.4.4. HDL was isolated from non-labelled plasma and partially characterized. It presents a protein-to-lipid ratio of about 1:9. Its lipid moiety is mainly composed of phospholipids, moderate amounts of triacylglycerols, free cholesterol and free fatty acids, and minor concentrations of hydrocarbons.
Comparative Biochemistry and Physiology Part B: Comparative Biochemistry.
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ABSTRACT: The effects of the organophosphorus insecticide fenitrothion [phosphorothioic acid,O,O-dimethylO-(3-methyl-4-nitrophenyl) ester] on the physical state of microsomal membranes from the hepatopancreas of the freshwater shrimpMacrobrachium borelliiwere investigated. Physical properties of native membranes and liposomes obtained from their total lipids were studied by fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH), probing the bilayer core, and by its anionic propionic acid derivative (DPH–PA), probing the outer regions of the bilayer. Fenitrothion was found to increase DPH and DPH–PA polarization of microsomal and liposomal membranes when addedin vitroat concentrations within the order of 10−6M. No significant effects were observed in membranes from animals exposed to the insecticidein vivo.Nevertheless, the effect of fenitrothion on the microsomes of exposed animals is observed in a lesser degree than on those from control animals, suggesting an adaptation of the membranes to fenitrothion. Considering that this effect is lower in the liposomes of control and exposed animals, the adaptation seems to involve the protein moiety of the membranes. Fluorescence anisotropy lifetimes (determined by phase-shift (>P) and demodulation (>M) techniques) of DPH were decreased by 0.72 μM fenitrothion in microsomes. The limiting anisotropy of DPH is increased in native membranes that contain fenitrothion, indicating a further ordering effect.
Pesticide Biochemistry and Physiology.
