Toxicological and histopathological effects of hydramethylnon on Atta sexdens rubropilosa (Hymenoptera: Formicidae) workers.

The leaf-cut ants are important agricultural pest, because they can cause intense defoliation in plants and destroy large areas cultivated. Although there are several works for the control of these insects by examining the toxicity of natural chemical compounds on various species of ants, few are focused on analyses of morphological changes caused in the affected organs. The aim of this study was to evaluate the effects of hydramethylnon on Atta sexdens rubropilosa workers through toxicological bioassays and morphological analysis of the post-pharyngeal glands, midgut, and Malpighian tubules of these ants. Hydramethylnon dissolved either in acetone (HA) or in a mixture of acetone and soy oil (HAO) was added to the artificial diet at a concentration of 200µg/mL. The workers fed daily with the diet containing hydramethylnon showed higher mortality than the controls, especially when HAO was used. Moreover, light and electron microscopy revealed morphological alterations in the midgut and Malpighian tubules of workers treated with HA, whereas alterations of the post-pharyngeal glands were observed in the HAO-treated group. These results indicated that the presence of soy oil provided an alternate route for the ingestion of the formicide's active ingredient and corroborated previous studies that suggested a role for the post-pharyngeal glands in lipid metabolism. Our findings suggest that the oil may carry hydramethylnon to the gland lumen, resulting in lower quantity of the active ingredient in the intestinal lumen and Malpighian tubules that explains the lower degree of morphological alterations in these structures in the workers treated with HAO. These results may provide insight into the toxicological effects of hydramethylnon on leaf-cutting ants and the use of vegetable oil as an adjuvant in baits to control ants.

Effects of lopinavir-ritonavir combined therapy during the rat pregnancy. Morphological and biochemical aspects.

OBJECTIVE: To evaluate the biochemical and morphological effects in rats subjected to three different dose associations of the protease inhibitors lopinavir and ritonavir administered throughout the entire period of pregnancy. STUDY DESIGN: The animals were treated throughout pregnancy with daily oral doses of lopinavir+ritonavir starting at the day one of pregnancy, and were divided into four groups: E1, 13.3+3.3 mg/kg; E2, 39.9+9.9 mg/kg; E3, 119.7+29.9 mg/kg and C, control (drug vehicle, propyleneglycol). The animals were then sacrificed and maternal blood and fetal and maternal organ samples were taken for morphological and biochemical analysis. RESULTS: No major changes were identified in the group treated with the lowest dose as compared with the control. In the group E2, we found hepatocytes with signs of atrophy, eosinophilic cytoplasm, picnotic nuclei and vasodilatation. The proximal convoluted tubules of maternal kidneys showed eosinophilic areas and hyperchromatic nuclei, as well as signs of vasodilation. In the group treated with the highest dose (group E3), in the maternal kidneys and livers, the morphological changes were similar to those found in E2, although more prominent. Regarding the fetal organs, the single abnormality observed was some liver vasodilation in the group E3 (highest dose). The treatment with lopinavir+ritonavir caused discrete, yet significant, alterations of aspartate aminotransferase activity, blood urea nitrogen and creatinine plasma levels. CONCLUSIONS: Our results showed that the administration of a combination of lopinavir plus ritonavir to pregnant rats can cause morphological as well as functional changes in maternal and fetal liver and kidneys and, in higher than therapeutic doses, might be toxic to those animals.

An oral bioassay for the toxicity of hydramethylnon to individual workers and queens of Argentine ants, Linepithema humile.

We have developed an oral bioassay to determine the toxicity of hydramethylnon to individual workers and queens of the Argentine ant, Linepithema humile. We fed seven concentrations of hydramethylnon in suspension to individual workers or queens, determined the amount of hydramethylnon ingested and evaluated the individual ants for mortality 14 days later. At concentrations > or = 0.37 g liter-1, the amount of liquid the queens ingested decreased dramatically, indicating that Argentine ant queens may detect hydramethylnon. Significantly larger volumes of the two highest concentrations of the hydramethylnon suspension were ingested by the workers, compared to the lower concentrations, suggesting that hydramethylnon may act as a feeding stimulant for the workers. Worker mortality was higher than queen mortality at the highest concentrations tested. The highest worker mortality resulted when the ants ingested 1.03 micrograms of hydramethylnon per mg of ant tissue. At the highest concentration (1.0 g liter-1) tested, workers ingested almost 12 times as much active ingredient per mg of body weight as did queens, suggesting that, in order to increase mortality of queens, multiple feedings must occur.