Comet assay protocol for Bombus atratus fat body and pericardial cells (Hymenoptera, bombini) at a safe concentration of mercury.

The decline of the Bombus population is closely related to the presence of environmental pollutants. Among these pollutants, trace metals represent a major concern, which includes mercury, a known genotoxic substance. The induction of genotoxicity may be demonstrated by the comet assay (a.k.a. single-cell gel electrophoresis), a simple and sensitive method for DNA damage estimating. The current work provided, for the first time, a protocol of comet assay for Bombus atratus using mercury as a standard chemical at safe concentrations according to the Environment National Council of Brazil, and the World Health Organization. Bees were collected and divided into three groups (n = 11 each), in which the exposed groups received a 0.2 ppb or a 1 ppb of mercury solution, and the control group received water. The bioassay was performed for 48 h at controlled temperature and humidity conditions, according to the OECD guideline toxicological test method for B. terrestris. The samples were stained with different dyes to observe the efficacy of each one. Variations of parameters in methodology, such as concentration and time of exposure to lysis solution as well as the electrophoretic process, allowed the observation of comets at different levels. DAPI and acridine orange presented an unstable fluorescence, and silver nitrate dye was more effective. Therefore, the comet assay was shown to be an effective method to evaluate genotoxic effects in bees. The obtained results may be helpful for the establishment of a suitable protocol for future genotoxicity assessment in neotropical bees using different doses of xenobiotics.

Cardiac biomarkers as sensitive tools to evaluate the impact of xenobiotics on amphibians: the effects of anionic surfactant linear alkylbenzene sulfonate (LAS).

Amphibian populations have been experiencing a drastic decline worldwide. Aquatic contaminants are among the main factors responsible for this decline, especially in the aquatic environment. The linear alkylbenzene sulfonate (LAS) is of particular concern, since it represents 84% of the anionic surfactants' trade. In Brazil, the maximal LAS concentration allowed in fresh waters is 0.5mgL-1, but its potential harmful effects in amphibians remain unknown. Therefore, this study aimed to analyze the effects of a sublethal concentration of LAS (0.5mgL-1) for 96h on sensitive cardiac biomarkers of bullfrog tadpoles, Lithobates catesbeianus (Shaw, 1802). For this, we measured the activity level (AL - % of animals), in situ heart rate (fH - bpm), relative ventricular mass (RVM - % of body mass), in vitro myocardial contractility and cardiac histology of the ventricles. Tadpoles' AL and fH decreased in LAS group. In contrast, the RVM increased, as a result of a hypertrophy of the myocardium, which was corroborated by the enlargement of the nuclear measures and the increase of myocytes' diameters. These cellular effects resulted in an elevation of the in vitro contractile force of ventricle strips. Acceleration in the contraction (TPT - ms) also occurred, although no alterations in the time to relaxation (THR -ms) were observed. Therefore, it can be concluded that even when exposed to an environmentally safe concentration, this surfactant promotes several alterations in the cardiac function of bullfrog tadpoles that can impair their development, making them more susceptible to predators and less competitive in terms of reproduction success. Thus, LAS concentrations that are considered safe by Brazilian by regulatory agencies must be revised in order to minimize a drastic impact over amphibian populations. This study demonstrates the relevance of employing cardiac biomarkers at different levels (e.g., morphological, physiological and cellular) to evaluate effects of xenobiotics in tadpoles.

Transdução de sinais: uma revisão sobre proteína G / Signal transduction: a review about G protein

Objetivos: revisar o assunto proteína G e seus mecanismos de transdução celular, de forma abrangente e didática.Fonte de dados: foram revisados artigos específicos sobre o tema, disponíveis em periódicos eletrônicos e encontrados através das bases de dados LILACS, PubMed e SciELO.Síntese dos dados: a transdução de sinais é uma função fisiológica que intermedeia o estímulo externo e a resposta celular, sendo o passo de conversão intracelular do agonismo de várias substâncias. Os compostos proteicos envolvidos nessa atividade estão presentes em todos os sistemas do organismo; consequentemente, disfunções na sua estrutura culminam em estados patológicos diversos. A descrição da dinâmica da transdução, da estrutura e funções da proteína G e do seu papel em algumas doenças foram abordados nesta revisão.Conclusões: a revisão da literatura mostra que o tema proteína G não tem gerado muitos trabalhos experimentais.Entretanto, o estudo desse composto protéico evidencia sua grande importância na fisiologia, indicando que disfunções na sua estrutura resultam em vários estados patológicos.

Aims: To review, in a comprehensive and didactic way, the issue G protein and its mechanisms of cellular transduction.Source of data: Articles that address the specific issue, available online, and found through the databases LILACS, PubMed and SciELO, were reviewed.Summary of findings: Signal transduction is a physiological function that mediates the external stimulus and cellular response; it is the conversion step of agonism of several intracellular substances. The protein compounds involved in this activity are present in all body systems, thus dysfunction in its structure results in several pathological states.The description of the dynamics of transduction, structure and functions of G protein and its role in some diseases were addressed in this review.Conclusions: The literature review shows that the subject protein G has not generated many experimental studies.However, the study of this protein compound makes evident its great importance in physiology and indicates that dysfunctions in its structure result in various pathological conditions.