The lysosomal compartment is a major site for intracellular degradation. Lysosomal degradation of the cell’s own constituents, so-called autophagy, not only provides a cell with nutrients, but also removes damaged and potentially dangerous endogenous structures, thus securing intracellular homeostasis. On the other hand, lysosomes have been shown to be involved in the initial stages of apoptosis, and the protective effect of autophagy has been suggested to switch to cell death when excessive. Ageing-related changes of cellular structures result from damage caused by eactive oxygen species (ROS), which are an inevitable by-product of aerobic life. Intracellular turnover of compromised organelles and macromolecules, to which lysosomal degradation is a major contributor, does not function perfectly, even under favourable conditions. This inherent incompleteness of lysosomal degradation is responsible for the accumulation of a variety of nondegraded and functionally inefficient structures, which can be considered biological “garbage”. Biological “garbage” includes damaged non-degraded macromolecules and organelles, as well as intralysosomal non-degradable polymer-like structure called lipofuscin, or age pigment. Although accumulation of biological “garbage” has been suggested harmful, little is known about the mechanisms of its deleterious effects. To gain a better understanding of ageing-related changes of the lysosomal compartment and their influence on cell functions, we focused on studying: (1) the role of macroautophagy in the turnover of organelles and lipofuscin formation; (2) the role of biological “garbage” accumulation in the development of ageing-related changes and eventual death of growth-arrested, postmitotic-like cells; (3) the possible cell-protective effect of mitosis; (4) the influence of lipofuscin on cell survival during complete starvation; and (5) the effects of lipofuscin on lysosomal stability. As a model of induced biological “garbage” accumulation we used confluent human fibroblasts treated with the autophagy inhibitor 3-methyladenine (3MA). Alternatively, lysosomal degradation was suppressed by using the cysteine protease inhibitor leupeptin, or the cathepsin D inhibitor pepstatin A. As a cellular model of aged cells, we used lipofucsin-loaded human fibroblasts. Lipofuscin-loading was achieved by culturing confluent fibroblasts under hyperoxic conditions for 2-4 months. Using these in vitro models, the present study shows that: (1) inhibition of autophagy results in accumulation of lysosome-associated autofluorescent material and mitochondria with low membrane potential; (2) detrimental effect of biological “garbage” accumulation following inhibition of autophagy is prevented by continuous cell division; (3) lipofuscin-loaded cells are more resistant to starvation-induced cell death than control cells; (4) lysosomes of lipofuscinloaded fibroblasts are more resistant to the organelle-targeted stress then lysosomes of control cells. Based on the results of the present study we conclude that properly operating autophagic machinery plays a crucial role in preventing age-related changes associated with accumulation of biological “garbage”. We also suggest that continual proliferation is the natural mechanism by which cells cope with the accumulation of non-degradable material, employing mechanical dilution during the cell division. Finally, we introduce an idea of lipofuscin being a hormetic agent, and possibly possessing some lysosome-stabilising properties. Better understanding of the influence of the age-related accumulation of biological “garbage” on cellular functions may be helpful for future development of anti-ageing therapy and management of age-associated pathologies.

The exposure to high doses of ionizing radiation (>5Gy) is unequivocally associated with increased cancer risk. However, there is substantial experimental evidence showing that in response to low doses of ionizing radiation (LDR: <100mGy), cells and organisms are benefitted with delayed ageing, improved immunity and reduced cancer growth. These intriguing findings have proposed the “Radiation Hormesis” hypothesis. Herein, I studied the senescence effects of LDR exposure to normal human HFL1 cells and examined transcriptional changes. I found that HFL1 cells exposed to 10 mGy of gamma radiation had delayed senescence measured at 12 weeks post-irradiation compared to unirradiated cells. Through qPCR array analysis, I found that genes involved in human cellular senescence functions are differentially regulated in 10 mGy exposed cells at 12 weeks compared to 1-week post-exposure. A nucleolar protein, SIRT7, that belongs to the family of proteins called Sirtuins with known roles in aging, was found to be upregulated transcriptionally in LDR-exposed HFL1 cells. Knocking out SIRT7 protein significantly accelerated senescence in HFL1 cells suggesting a direct role of SIRT7 in the deceleration of senescence and potentially in mediating radiation hormesis. Furthermore, overexpression of the HRAS oncogene strongly accelerated senescence in HFL1 cells through gene expression of cell cycle regulators and checkpoint proteins. Together, my studies revealed that LDR induces unique transcriptional changes resulting in a potentially radio adaptive protective cellular response. I also discuss the HRAS overexpression system as a time-efficient cellular model that could be used to more rapidly study the effect of LDR on senescence using primary cultures.

Weed management options in agronomic crop production have been severely limited by widespread populations of weeds resistant to herbicides, including waterhemp [Amaranthus tuberculatus (Moq.) Sauer (syn. rudis)] resistant to foliar applications of herbicides that inhibit protoporphyrinogen oxidase (PPO; EC 1.3.3.4) activity (PPO-R). Herbicides within this site of action (WSSA site of action #14) remain efficacious when soil-applied to PPO-R waterhemp populations. Therefore, the continued use of these herbicides for soil-residual control of PPO-R waterhemp, especially in soybean production, is paramount with limited postemergence herbicides that remain effective. An improved understanding of the selection for PPO-R waterhemp would provide information to help minimize future loss of residual PPO-inhibiting herbicide activity. Five studies, consisting of 14 experiments, were conducted to improve our understanding of the selection for herbicide-resistant individuals. Soil-residual herbicides have been suspected to select for herbicide-resistant individuals; however, this phenomenon has never been observed experimentally in field conditions. This dissertation provides direct evidence from greenhouse and field experiments that significant selection pressure can occur from soil-residual herbicides; however, this selection for resistance could be delayed when using full commercial herbicide rates and effective herbicides from multiple sites of action. Also, the frequency of heterozygous individuals (RS) and PPO-inhibiting herbicide efficacy on RS individuals is a factor in the selection for herbicide resistance; however, current information on the these topics is limited. To provide additional information on RS individuals, a large-scale genotypic and phenotypic screen of multiple PPO-R waterhemp populations was conducted. It was determined that RS individuals were less frequent than expected and PPO-inhibiting herbicide efficacy on RS individuals was population-dependent. Finally, the hormetic effects of soil-residual herbicides have been paradoxically implicated as a means of both mitigating and exacerbating the selection for herbicide resistant biotypes; however, limited information was available on the hormetic effects of soil-residual PPO inhibitors. Greenhouse and growth chamber experiments were conducted to improve understanding of hormesis and soil-residual PPO-inhibiting herbicides. Experiments indicated that PPO-inhibiting herbicides may exert a limited hormetic effect on waterhemp germination below doses that cause a phytotoxic effect of the emerging seedling, indicating this effect may exacerbate the issue of selection for PPO-R waterhemp. Overall, data presented in this dissertation provides important information on the under-studied interaction between PPO-inhibiting herbicides and PPO-R waterhemp to safeguard the sustained efficacy of herbicides within this site of action.

Oxidative stress from high-dose ionizing radiation can contribute to accumulating cellular damage, affecting various fitness related traits. However, studies on low-dose ionizing radiation (LDIR) have shown hormetic effects on growth, longevity, and immunity. Comprehensive lifetime studies assessing LDIR effects and studies investigating LDIR immune stimulation in insects are limited. We utilized 137Cs gamma radiation with a dose rate of 0.25 Gy/min. We examined the impacts of early-life exposure (doses: 0, 0.2, 0.5, 1, 2, 4, 7, and 10 Gy) on life history and immunity in Acheta domesticus. Moderate doses (above 4 Gy) increased mean longevity but decreased growth rate, adult body mass and innate immunity. We also performed a time course study in male A. domesticus to assess the acute effects of radiation (doses: 0, 0.2, 0.5, 0.75, 1, 5, and 15 Gy) on innate immunity and redox status. LDIR (below 1 Gy) generally achieved immune stimulation and improved the encapsulation response but effects were time dependent. Benefits could extend to improved immune responses and protection against infection. Our results provide evidence of immune stimulation with LDIR in insects but with potential trade- offs with life history traits when assessing early-life exposure. With increasing concern of radiation exposure in the environment, more comprehensive studies utilizing a multi- discipline approach will help to elucidate the full mechanism of hormesis. / Thesis / Master of Science (MSc) / High-dose ionizing radiation can have inhibitory effects on cellular systems while low doses can have lasting stimulatory effects. The latter phenomenon, known as hormesis, can act on growth, longevity, and immunity. We investigated the effects of early life gamma radiation exposure on life history traits and measures of innate immunity in the cricket (Acheta domesticus). We observed trade-offs between survival, growth, and immunity. We also tested late life radiation exposure to assess potential hormetic effects on innate immunity and redox status. Our results show immune stimulation with low doses but effects are complex and dependent on dose, type of immunity measured, and time of assessment.

Os lipídios microbianos apresentam composição similar aos óleos vegetais, e tem despertado o interesse de muitos pesquisadores, uma vez que podem suprir a demanda por óleos e gorduras. Além disso, estudos demonstram que ao submeter um microrganismo a baixas doses de radiação gama, estímulos são promovidos, podendo aumentar a função, a resistência celular, e o crescimento. Objetivou-se com esse estudo: avaliar os efeitos de baixas doses de radiação gama no crescimento e na síntese lipídica de Yarrowia lipolytica. A levedura foi submetida às doses de: (controle) 0,3; 0,5; 0,75; 1,0; 1,25 e 2,5 kGy de radiação gama, sob taxa de dose de 0,259 kGy/h. Foi utilizada câmara de Neubauer para determinação da viabilidade celular da levedura. Uma curva de crescimento e outra de sobrevivência foi determinada por densidade óptica em um espectrofotômetro. Posteriormente, a levedura foi inoculada em meio composto por xarope de cana-de-açúcar e vinhaça, e incubada por 7, 14 e 21 dias para a obtenção da biomassa seca, por liofilização, e da síntese lipídica, por metodologia de extração. A irradiação não interferiu na produção de biomassa seca, no crescimento e na sobrevivência da levedura Y. lipolytica. O período de incubação afetou a produção final de biomassa, sendo a maior produção obtida no 14° dia (13,46 g/L). Para os resultados de síntese lipídica, observou-se interferência na produção final, durante 21 dias de incubação e dose de 0,5 kGy, com produção de 4,17 g/L (34,94%). Conclui-se que não foi observado o efeito hormético durante as análises de crescimento, sobrevivência e produção de biomassa, quando submetidas às doses de radiação. Este efeito foi observado apenas durante a síntese lipídica, quando avaliadas as junções entre dose de radiação e período de incubação / Microbial lipids present similar composition to vegetable oils and has aroused great interest among researchers. In addition, studies show that by submitting a microorganism to low doses of gamma radiation, stimuli are promoted, which could increase the function, cell resistance, and the growth. Therefore, this study aimed to evaluate the effects of low doses of gamma radiation on the growth and lipid synthesis of Yarrowia lipolytica. The yeast received irradiation doses of: (control); 0.3; 0.5; 0.75; 1.0; 1.25 and 2.5 kGy gamma radiation dose rate in 0.259 kGy/h. Neubauer Chamber was used to analyze cell viability of the yeast. A growth curve and survival curve was determined by spectrophotometry. Then, the yeast was inoculated in the medium composed of syrup sugarcane and vinasse and incubated for 7, 14 and 21 days for the obtaining of dry biomass, by lyophilization, and lipid synthesis, by extraction methodology. The low doses of irradiation had no effect on the growth, survival, and production of dry biomass of Y. lipolytica. For the incubation periods, there was interference in the final production; the highest production was obtained on day 14 (13.46 g/L). The results for lipid synthesis revealed interference with the final production of lipids, being better at a dose of 0.5 kGy to 21 days incubation with yield of 4.17 g/L (34.94%). In conclusion, the low doses of irradiation had no effect on the growth, survival and biomass production of Y. lipolytica. Hormetic effect was observed only in the lipid synthesis, when the radiation dose was associated with the incubation time

Os lipídios microbianos apresentam composição similar aos óleos vegetais, e tem despertado o interesse de muitos pesquisadores, uma vez que podem suprir a demanda por óleos e gorduras. Além disso, estudos demonstram que ao submeter um microrganismo a baixas doses de radiação gama, estímulos são promovidos, podendo aumentar a função, a resistência celular, e o crescimento. Objetivou-se com esse estudo: avaliar os efeitos de baixas doses de radiação gama no crescimento e na síntese lipídica de Yarrowia lipolytica. A levedura foi submetida às doses de: (controle) 0,3; 0,5; 0,75; 1,0; 1,25 e 2,5 kGy de radiação gama, sob taxa de dose de 0,259 kGy/h. Foi utilizada câmara de Neubauer para determinação da viabilidade celular da levedura. Uma curva de crescimento e outra de sobrevivência foi determinada por densidade óptica em um espectrofotômetro. Posteriormente, a levedura foi inoculada em meio composto por xarope de cana-de-açúcar e vinhaça, e incubada por 7, 14 e 21 dias para a obtenção da biomassa seca, por liofilização, e da síntese lipídica, por metodologia de extração. A irradiação não interferiu na produção de biomassa seca, no crescimento e na sobrevivência da levedura Y. lipolytica. O período de incubação afetou a produção final de biomassa, sendo a maior produção obtida no 14° dia (13,46 g/L). Para os resultados de síntese lipídica, observou-se interferência na produção final, durante 21 dias de incubação e dose de 0,5 kGy, com produção de 4,17 g/L (34,94%). Conclui-se que não foi observado o efeito hormético durante as análises de crescimento, sobrevivência e produção de biomassa, quando submetidas às doses de radiação. Este efeito foi observado apenas durante a síntese lipídica, quando avaliadas as junções entre dose de radiação e período de incubação / Microbial lipids present similar composition to vegetable oils and has aroused great interest among researchers. In addition, studies show that by submitting a microorganism to low doses of gamma radiation, stimuli are promoted, which could increase the function, cell resistance, and the growth. Therefore, this study aimed to evaluate the effects of low doses of gamma radiation on the growth and lipid synthesis of Yarrowia lipolytica. The yeast received irradiation doses of: (control); 0.3; 0.5; 0.75; 1.0; 1.25 and 2.5 kGy gamma radiation dose rate in 0.259 kGy/h. Neubauer Chamber was used to analyze cell viability of the yeast. A growth curve and survival curve was determined by spectrophotometry. Then, the yeast was inoculated in the medium composed of syrup sugarcane and vinasse and incubated for 7, 14 and 21 days for the obtaining of dry biomass, by lyophilization, and lipid synthesis, by extraction methodology. The low doses of irradiation had no effect on the growth, survival, and production of dry biomass of Y. lipolytica. For the incubation periods, there was interference in the final production; the highest production was obtained on day 14 (13.46 g/L). The results for lipid synthesis revealed interference with the final production of lipids, being better at a dose of 0.5 kGy to 21 days incubation with yield of 4.17 g/L (34.94%). In conclusion, the low doses of irradiation had no effect on the growth, survival and biomass production of Y. lipolytica. Hormetic effect was observed only in the lipid synthesis, when the radiation dose was associated with the incubation time

Os corantes são amplamente utilizados nas indústrias têxteis, farmacêuticas, alimentícias, cosméticas, fotográficas, entre outras. Contudo, essas substâncias podem ser tóxicas, mutagênicas e resistentes a muitos processos de degradação utilizados em estações de tratamento. Estima-se que cerca de 15% dos corantes utilizados no mundo sejam perdidos durante o processo de tingimento e lançados no ambiente, atingindo principalmente os corpos d\'água. No entanto, apesar da grande quantidade de corantes comerciais disponíveis e da alta quantidade lançada no ecossistema aquático, os estudos sobre a toxicidade dessas substâncias são escassos e pouco se conhece sobre seus efeitos mutagênicos e principalmente ecotoxicológicos. Dentro deste contexto, o objetivo do trabalho foi avaliar a ecotoxicidade, bem como a capacidade dos corantes têxteis Reactive Blue 4 (RB 4) e Reactive Blue 15 (RB 15) de lesar o material genético, empregando ensaios de toxicidade aguda com Daphnia similis e Vibrio fischeri, toxicidade crônica com Ceriodaphnia dubia, genotoxicidade (Teste do Cometa) com fibroblastos de derme humana e mutagenicidade com Salmonella typhimurium. Adicionalmente, avaliou-se a concentração de cobre em Ceriodaphnia dubia expostas ao corante Reactive Blue 15, que possui esse metal na sua estrutura química. O corante RB 4 foi moderadamente tóxico e o corante RB 15 foi relativamente não tóxico para Daphnia similis. Ambos corantes reduziram a luminescência de Vibrio fischeri em elevadas concentrações, sendo o corante RB 4 mais tóxico para a bactéria quando comparado ao corante RB 15. O corante RB 4 induziu efeito hormesis nos ensaios com C. dubia, ou seja, houve um estímulo na reprodução nas menores concentrações, seguido por um decréscimo em concentrações mais elevadas, ao passo que, o corante RB 15 reduziu a fecundidade de C. dubia. Não houve acúmulo de cobre nos organismos expostos ao corante RB 15. Nenhum dos corantes foram genotóxicos para fibroblastos de derme humana e apenas o corante RB 4 induziu mutagenicidade, por substituição de pares de base. Os resultados obtidos mostram que os corantes podem causar efeitos adversos nos organismos mesmo em baixas concentrações e que o lançamento contínuo dessas substâncias nos corpos d\'água é preocupante. / Dyes are widely used in different types of industries, such as textile, pharmaceutical, food, cosmetics, photographic, among others. However, these substances can be toxic, mutagenic and resistant to many degradation processes used in wastewater treatment. It is estimated that about 15% of the dyes used in the world is lost during the dyeing process and released into the environment, affecting mainly water bodies. However, despite the large amount of commercial dyes available and high quantity released in the aquatic ecosystem, studies on the toxicity of these substances are scarce and little is known about their mutagenic and ecotoxicological effects. Considering that, the aim of this study was to evaluate the ecotoxicity, and the ability of the Reactive Blue 4 (RB 4) and Reactive Blue 15 (RB 15) textile dyes to damage the genetic material, using acute toxicity tests with Daphnia similis and Vibrio fischeri, Ceriodaphnia dubia chronic toxicity, genotoxicity (Comet assay) in human dermal fibroblasts and mutagenicity with Salmonella typhimurium. Additionally, we assessed the concentration of copper in Ceriodaphnia dubia exposed to the Reactive Blue 15 dye, which has this metal in its chemical structure. The RB 4 dye was moderately toxic and RB 15 dye was relatively non-toxic to Daphnia similis. Both dyes reduced the Vibrio fischeri luminescence in high concentrations, and the RB 4 was more toxic to bacteria when compared to dye RB 15. The RB 4 dye induced hormesis effect in the C. dubia tests. We observed that the reproduction was stimulated at lower concentrations followed by a decrease at higher concentrations. While the RB 15 dye reduced fecundity of Ceriodaphnia dubia. There was no accumulation of copper in organisms exposed to the RB 15 dye. None of the dyes were genotoxic to human dermal fibroblasts, and only the RB 4 dye induced mutagenicity, by base-pair substitution. The results show that the dyes can cause adverse effects on organisms even at low concentrations and that the continuous release of these substances in water bodies is worrying.

Hormesis is a dose response phenomenon where low doses of a stress bring about a positive response in the organism undergoing treatment. UV-C hormesis has been known for over three decades and has a broad range of benefits on postharvest produce. Benefits include increased nutritional content, delayed chlorophyll degradation and disease resistance. The beneficial effects have been observed on many varieties of fresh produce including climacteric and non-climacteric fruit, tubers, salads and brassicas. The majority of previous studies have used low-intensity (LIUV) UV-C sources. LIUV sources require lengthy treatment times, which are in the region of 6 minutes for tomato fruit. This has, in part, prevented the commercial application of this technique. High-intensity, pulsed polychromatic light (HIPPL) sources, however, have recently been developed. HIPPL sources may have the potential to drastically reduce treatment times and increase their commercial viability. It was shown, here, that the use of HIPPL can control disease (reduce disease progression) caused by Botrytis cinerea and Penicillium expansum and also delay ripening on tomato fruit. Both disease control and delayed ripening were at similar levels for LIUV and HIPPL treatments on mature green fruit. The HIPPL treatments used in these studies can reduce treatment times for tomato fruit by 97.3%. Both HIPPL and LIUV treatments elicit local responses irrespective of the treatment orientation and tomato fruit, therefore, require full surface irradiation. Furthermore, UV-C in the HIPPL source is not required for disease control or delayed ripening. It does, however, contribute approximately 50% towards the total observed effects. Investigations into the mechanisms underpinning postharvest HIPPL and LIUV hormesis, on tomato fruit, identified that the expression of genes involved in plant hormone biosynthesis, defence, secondary metabolism and ripening were affected. This indicates that disease control is achieved through induced resistance. Changes to expression, following treatment, were highly similar for both HIPPL and LIUV treatments and were mediated by salicylic acid, jasmonic acid and ethylene. This may lead to broad range resistance against necrotrophic and biotrophic pathogens as well as abiotic stresses and herbivorous pests. Recently, the exposure of foliage to UV-C has been shown to induce resistance against B. cinerea on Arabidopsis thaliana. The horticultural applications of such treatments, however, have not been explored. Pre-harvest treatments of lettuce in the glasshouse showed variation in damage threshold and optimal treatment to control disease following LIUV and HIPPL treatment. Further sources of variation included the cultivar, pathogen of interest and the point that treatment was applied during the year. Using a controlled environment allowed seasonal variation to be mitigated and both HIPPL and LIUV treatments controlled disease against B. cinerea. For pre-harvest treatments to be a success in the glasshouse, further studies into how both biotic and abiotic factors influence treatment is required. To circumvent the problems associated with pre-harvest treatments and environmental variation in the glasshouse, LIUV seed treatments were performed on tomato. Control of B. cinerea was established with an approximately 10% reduction in incidence and disease progression with a 4 kJ/m2 treatment. When monitoring the effect of treatment on germination and early seedling development it was also identified that an 8 kJ/m2 treatment led to biostimulation of germination and root and shoot growth.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Metals environment aquatic contamination has been a growing problem with serious consequences to life of different species over time, even after interrupted their emission into the environment. Among relevance metals, manganese (Mn) has shown importance to be related to several activities such as oil exploration, coal deposits extraction, fertilizer use in agriculture, among others. In living organisms, Mn is an essential trace element for a number of vital functions, and involves energy regulation by blood clotting. On the other hand, high concentrations of Mn can cause irreversible damage to living organisms primarily affecting central nervous system (CNS). Thus, waterborne Mn toxicity can switch from aquatic species, while metal bioaccumulation in marine fish or freshwater has been found around 0.2 to 19.0 mg/kg dry weight. In this study, silver catfish (Rhamdia quelen) were exposed to different Mn concentrations (4.2; 8.4 e 16.2 mg/L), under two different dissolved oxygen levels, normoxia (7.48 ± 0.28) and hypoxia (3.88 ± 0.41) for 15 days. At the end of protocol, Mn bioaccumulation as well parameters of oxidative stress and mitochondrial viability were evaluated in different tissues. In hypoxic conditions, the highest Mn concentration (16.2 mg/L) showed the lowest silver catfish kidney and brain lipoperoxidation (LPO) levels, while brain reduced glutathione (GSH) levels were increased in lower Mn concentration (4.2 mg/L) and kidney catalase activity was reduced in the same metal concentration, in relation to normoxia. Lowest Mn concentration (4.2 mg/L) in hypoxia showed higher gills mitochondrial viability, compared to normoxia. Hematocrit of silver catfish exposed to two highest Mn concentration (8.4 and 16.2 mg/L) was reduced in normoxia conditions while under hypoxia, these values were similar to control. Plasma except, Mn bioaccumulation in liver, kidney and gills were higher in normoxia than hypoxia. From these results is possible to suggest that hypoxia stimulates the development of adaptive mechanisms and/or hormesis in silver catfish exposed to Mn, mainly because the lower metal bioaccumulation occurred in this oxygen level. Contributing with this, under hypoxia, oxidative damage indicators were lower than those observed in normoxia, which were accompanied by changes in antioxidant system represented by GSH and catalase. In conclusion, our results show in the first time that silver catfish exposed to Mn contamination is able to show a better survival under hypoxia. These findings indicate need for continuing studies in search of molecular mechanisms involved in the adaptation and or hormesis processes, which were suggested here. / A contaminação do meio aquático por metais tem sido um problema crescente para à vida de diferentes espécies, mesmo depois de interrompida sua emissão no ambiente. Entre os metais de relevância, o manganês (Mn) apresenta importância por estar relacionado a uma série de atividades tais como exploração de petróleo, extrativismo em jazidas de carvão mineral, utilização de fertilizantes na agricultura, entre outros. Nos organismos vivos, o Mn constitui um oligoelemento essencial para uma série de funções vitais, e envolve desde a regulação da energia até coagulação sangüínea. Por outro lado, quando em concentrações elevadas, o Mn pode causar danos irreversíveis aos organismos afetando principalmente o sistema nervoso central (SNC). A toxicidade do Mn dissolvido na água pode variar entre as espécies aquáticas, a bioacumulação do metal em peixes marinhos ou de água doce tem sido encontrada em torno de 0,2 até 19,0 mg/kg de peso seco. No presente estudo, jundiás (Rhamdia quelen) foram expostos a diferentes concentrações de Mn (4,2; 8,4 e 16,2 mg/L), sob dois diferentes níveis de oxigênio dissolvido: normóxia (7,48±0,28 mg/L) e hipóxia (3,88±0,41 mg/L), durante 15 dias. Ao final do protocolo, a bioacumulação de Mn bem como, parâmetros de estresse oxidativo e a viabilidade mitocondrial foram avaliados em diferentes tecidos vitais. Em condições de hipóxia, a maior concentração de Mn (16,2 mg/L) mostrou os menores níveis de lipoperoxidação (LPO) em rim e encéfalo dos jundiás, enquanto os níveis de glutationa reduzida (GSH) encefálico foram aumentados na menor concentração de Mn (4,2 mg/L) e a atividade da catalase renal foi reduzida nesta mesma concentração de metal, em relação à normoxia. A menor concentração de Mn (4,2 m/L) em hipóxia proporcionou maior viabilidade mitocondrial das brânquias, em relação à normóxia. O hematócrito dos jundiás expostos às duas maiores concentrações de Mn (8,4 e 16,2 mg/L) foi reduzido em condições de normóxia, enquanto sob hipóxia, estes valores foram semelhantes ao grupo sem a presença do metal. Sob normóxia, a bioacumulação de Mn em fígado, rim e brânquias foi maior que sob hipóxia, excetuando o plasma. A partir desses resultados é possível sugerir que a hipóxia pode ter estimulado o desenvolvimento de mecanismos adaptativos ou de hormesis nos jundiás, em presença de Mn na água, principalmente porque neste nível de oxigênio, a bioacumulação do metal ocorreu em menor grau. Contribuindo com este resultado, sob hipóxia, os indicadores de danos oxidativos foram mais baixos que os observados sob normóxia, os quais foram acompanhados de alterações do sistema antioxidante representado pela GSH e catalase. Neste sentido, nossos resultados apontam para uma melhor sobrevivência da espécie em estudo, sob hipóxia, quando exposta ao Mn. Estes achados indicam a necessidade da continuidade dos estudos, em busca dos mecanismos moleculares envolvidos no processo de adaptação aqui sugeridos.

Os corantes são amplamente utilizados nas indústrias têxteis, farmacêuticas, alimentícias, cosméticas, fotográficas, entre outras. Contudo, essas substâncias podem ser tóxicas, mutagênicas e resistentes a muitos processos de degradação utilizados em estações de tratamento. Estima-se que cerca de 15% dos corantes utilizados no mundo sejam perdidos durante o processo de tingimento e lançados no ambiente, atingindo principalmente os corpos d\'água. No entanto, apesar da grande quantidade de corantes comerciais disponíveis e da alta quantidade lançada no ecossistema aquático, os estudos sobre a toxicidade dessas substâncias são escassos e pouco se conhece sobre seus efeitos mutagênicos e principalmente ecotoxicológicos. Dentro deste contexto, o objetivo do trabalho foi avaliar a ecotoxicidade, bem como a capacidade dos corantes têxteis Reactive Blue 4 (RB 4) e Reactive Blue 15 (RB 15) de lesar o material genético, empregando ensaios de toxicidade aguda com Daphnia similis e Vibrio fischeri, toxicidade crônica com Ceriodaphnia dubia, genotoxicidade (Teste do Cometa) com fibroblastos de derme humana e mutagenicidade com Salmonella typhimurium. Adicionalmente, avaliou-se a concentração de cobre em Ceriodaphnia dubia expostas ao corante Reactive Blue 15, que possui esse metal na sua estrutura química. O corante RB 4 foi moderadamente tóxico e o corante RB 15 foi relativamente não tóxico para Daphnia similis. Ambos corantes reduziram a luminescência de Vibrio fischeri em elevadas concentrações, sendo o corante RB 4 mais tóxico para a bactéria quando comparado ao corante RB 15. O corante RB 4 induziu efeito hormesis nos ensaios com C. dubia, ou seja, houve um estímulo na reprodução nas menores concentrações, seguido por um decréscimo em concentrações mais elevadas, ao passo que, o corante RB 15 reduziu a fecundidade de C. dubia. Não houve acúmulo de cobre nos organismos expostos ao corante RB 15. Nenhum dos corantes foram genotóxicos para fibroblastos de derme humana e apenas o corante RB 4 induziu mutagenicidade, por substituição de pares de base. Os resultados obtidos mostram que os corantes podem causar efeitos adversos nos organismos mesmo em baixas concentrações e que o lançamento contínuo dessas substâncias nos corpos d\'água é preocupante. / Dyes are widely used in different types of industries, such as textile, pharmaceutical, food, cosmetics, photographic, among others. However, these substances can be toxic, mutagenic and resistant to many degradation processes used in wastewater treatment. It is estimated that about 15% of the dyes used in the world is lost during the dyeing process and released into the environment, affecting mainly water bodies. However, despite the large amount of commercial dyes available and high quantity released in the aquatic ecosystem, studies on the toxicity of these substances are scarce and little is known about their mutagenic and ecotoxicological effects. Considering that, the aim of this study was to evaluate the ecotoxicity, and the ability of the Reactive Blue 4 (RB 4) and Reactive Blue 15 (RB 15) textile dyes to damage the genetic material, using acute toxicity tests with Daphnia similis and Vibrio fischeri, Ceriodaphnia dubia chronic toxicity, genotoxicity (Comet assay) in human dermal fibroblasts and mutagenicity with Salmonella typhimurium. Additionally, we assessed the concentration of copper in Ceriodaphnia dubia exposed to the Reactive Blue 15 dye, which has this metal in its chemical structure. The RB 4 dye was moderately toxic and RB 15 dye was relatively non-toxic to Daphnia similis. Both dyes reduced the Vibrio fischeri luminescence in high concentrations, and the RB 4 was more toxic to bacteria when compared to dye RB 15. The RB 4 dye induced hormesis effect in the C. dubia tests. We observed that the reproduction was stimulated at lower concentrations followed by a decrease at higher concentrations. While the RB 15 dye reduced fecundity of Ceriodaphnia dubia. There was no accumulation of copper in organisms exposed to the RB 15 dye. None of the dyes were genotoxic to human dermal fibroblasts, and only the RB 4 dye induced mutagenicity, by base-pair substitution. The results show that the dyes can cause adverse effects on organisms even at low concentrations and that the continuous release of these substances in water bodies is worrying.