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Although microplastics’ (MPs) toxicity has been reported in several aquatic and terrestrial organisms, the knowledge about how these pollutants can affect insects at the early developmental stage remains incipient. Thus, the aim of this study was to use Culex quinquefasciatus larvae as a model system to test the hypothesis that, besides accumulating in animals, polyethylene microplastics (PE MPs) lead to biochemical changes predictive of nutritional impacts, as well as induce oxidative stress, redox state imbalance, and neurotoxicity in them. Our results have indicated that short exposure to PE MPs (5 days) at the environmental concentration of 4.24 x 106 particles m-3 induced changes suggesting damage to energy metabolism such as reduced total proteins, total soluble carbohydrates, and triglycerides levels. In addition, increased hiobarbituric acid reactive species, in association with reduced total glutathione and DPPH radical scavenging activity (%) have suggested an imbalance between oxide-reducing agents and antioxidant defense system, induced by pollutant. On the other hand, increased acetylcholinesterase activity has suggested the neurotoxic effect of PE MPs. Finally, PE MPs have accumulated in the larvae, and it may have been a triggering factor for the observed changes. Thus, our study has confirmed the potential of C. quinquefasciatus larvae to act as vector of MPs in different ecosystems and helped improving the knowledge about how PE MPs can affect their development and lead to losses in different ecological functions of this species.

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Obesity and chronic stress have been considered important public health problems that affect millions of people worldwide. Our aim was to analyze the effect of obesity associated with chronic stress on neurobehavioral parameters in female rats, considering that the association of these syndromes can enhance the negative effects on homeostasis. The animals were distributed into standard diet (Std), standard diet+stress (Std+stress), cafeteria diet (Cafe), and cafeteria diet+stress (Cafe+stress) groups. The animals of groups Std and Std+stress were fed with rodent standard feed. Groups Cafe and Cafe+stress, additionally to the standard feed, were offered palatable and calorie-rich processed food and cola-type soft drink ad libitum. From the eighth experimental week, groups Std+stress and Cafe+stress were subjected to restraint chronic stress model (50 days). After the stress protocol, predictive anxiety (open-field and elevated plus-maze tests) and depression (forced swim) were applied. The cafeteria diet was effective in inducing obesity. The ratio locomotion in the central quadrants/total locomotion evaluated during the open field test was not indicative of anxiogenic or anxiolytic effect in the animal's behavior. However, the elevated plus maze test showed that obese and stressed animals were prone to higher anxiety levels. In addition, the obese and stressed animals display less climbing behavior than all the other groups, which can be considered an indicator of depression-like behavior. Nevertheless, it is suggested that the mechanisms involved in effects of obesity associated with chronic stress be better investigated in female rats, considering the organic complexity related to these modern illnesses.