Concepts on Accumulation of Pesticides and Veterinary Drugs in Fish: A Review with Emphasis in Tilapia.

The quality of the aquatic environment can be compromised by the practice of intensive use of pesticides in agriculture and by the misuse of veterinary drugs. Therefore, organisms that live in aquatic ecosystems may be affected due to the presence of these chemicals, through runoff, leaching and other processes. Exposure of aquatic organisms to these xenobiotics could pose health risks. Consequently, there is a growing interest in predicting the bioaccumulation of these substances in aquatic biota from experiments conducted under laboratory conditions. Studies on fish have been performed due to its importance as human food and their wide distribution in most of the aquatic environment. Thus, this article reviews the concepts on determining the accumulation of pesticides and veterinary drugs in fish. The risk regarding the consumption of fish containing residues of these chemical agents, the acceptable daily intake, the testing protocols and the analytical techniques used to determine the residues of these substances in fish tissues are discussed. An emphasis on studies involving tilapia as the test organism was included because, according to Food and Agricultural Organization (FAO), this species is one of the most cultivated in the world.

Ecotoxicity studies of two atrazine nanoformulations: From the evaluation of stability in media to the effects on aquatic organisms.

In the field of agriculture, nanopesticides have been developed as an alternative to the conventional pesticides, being more efficient for pest control. However, before their widespread application it is essential to evaluate their safe application and no environmental impacts. In this paper, we evaluated the toxicological effects of two kinds of atrazine nanoformulations (ATZ NPs) in different biological models (Raphidocelis subcapitata, Danio rerio, Lemna minor, Artemia salina, Lactuca sativa and Daphnia magna) and compared the results with nanoparticle stability over time and the presence of natural organic matter (NOM). The systems showed different characteristics for Zein (ATZ NPZ) (184 ± 2 nm with a PDI of 0.28 ± 0.04 and zeta potential of (30.4 ± 0.05 mV) and poly(epsilon-caprolactone (ATZ PCL) (192 ± 3 nm, polydispersity (PDI) of 0.28 ± 0.28 and zeta potential of -18.8 ± 1.2 mV) nanoparticles. The results showed that there is a correlation between nanoparticles stability and the presence of NOM in the medium and Environmental Concentrations (EC) values. The stability loss or an increase in nanoparticle size result in low toxicity for R. subcapitata and L. minor. For D. magna and D. rerio, the presence of NOM in the medium reduces the ecotoxic effects for ATZ NPZ nanoparticles, but not for ATZ NPs, showing that the nanoparticles characteristics and their interaction with NOM can modulate toxic effects. Nanoparticle stability throughout the evaluation must be considered and become an integral part of toxicity protocol guidelines for nanopesticides, to ensure test quality and authentic results regarding nanopesticide effects in target and non-target organisms.

Exposure of tilapia (Oreochromis niloticus) to the antibiotic florfenicol in water: determination of the bioconcentration factor and the withdrawal period.

The demand for healthier foods with high nutritional value has resulted in intensive fish farming. In this production system, high-frequency infections occur, and antibiotics are administrated for control. Only two antibiotics are allowed for use in Brazilian aquaculture, one of which is florfenicol. In this work, a bioconcentration assay was performed to assess the accumulation of florfenicol in the muscle of Nile tilapia (Oreochromis niloticus). Tilapia was evaluated as it is the most produced fish species in Brazil. The fish were exposed to florfenicol at a nominal concentration of 10 mg/L, through the water. Muscle and water were collected at 0, 1.5, 3, 6, 24, and 48 h during the exposure phase and at 1.5, 3, 6, 24, 48, and 120 h during the depuration phase. Quantification was performed using an LC-MS/MS. The results showed rapid absorption and elimination of the antibiotic (half-life, t1/2 = 5 h), with low potential for accumulation of florfenicol in tilapia muscles. The study was performed to determine the bioconcentration factor (BCF) and withdrawal period of florfenicol, being 0.05 mL/µg and 1.8 h, respectively. The results contribute to set protocols for the safe use of florfenicol in tilapia transport, avoiding residues in fish that may pose risks to human health.

Avaliação de risco ecológico do óleo essencial de Piper aduncum em organismos não alvo / Ecological risk assessment of Piper aduncum essential oil in non-target organisms

Uma possível alternativa ao uso de fármacos veterinários no tratamento e prevenção de doenças na piscicultura é o uso do óleo essencial de Piper aduncum. No entanto, são necessários dados ecotoxicológicos para garantir seu uso apropriado sem causar efeitos adversos a organismos não alvo. Esta informação é relevante, pois esse óleo essencial é descrito como tendo atividades inseticidas, moluscicidas e citotóxicas, possivelmente associadas à sua composição química. Assim, o objetivo deste estudo foi avaliar a ecotoxicidade do óleo essencial de P. aduncum para cinco organismos-teste, usando o método estatístico da Distribuição da Sensibilidade das Espécies (SSD). A composição química do óleo essencial foi caracterizada por cromatografia gasosa acoplada a espectrometria de massa (GC-MS) e cromatografia gasosa com detector de ionização de chama (GC-FID), para fins de identificação e quantificação, respectivamente. O principal componente (75,5%) do óleo essencial foi o dilapiol. A concentração perigosa para 5% de espécies biológicas (HC5) foi calculada com um nível de proteção de 95%, resultando em um valor de 0,47 mg L-1 (com intervalo de confiança de 50% = 0,028 - 1,19 mg L-1). A faixa de concentração relacionada aos níveis de proteção para comunidades aquáticas (concentração sem efeito previsto - PNEC) foi calculada através da aplicação de fatores de segurança ao valor de HC5. Os parâmetros de ecotoxicidade indicaram que o óleo essencial de P. aduncum pode ser usado com segurança em corpos d'água se a concentração for igual ou inferior a 0,09 mg L-1.(AU)

Risk assessment and acute toxicological effects of atrazine on Nile tilapia larvae after stress.

The present study aimed to evaluate the risk assessment, median lethal concentration LC50-96h, development, and mortality of Nile tilapia Oreochromis niloticus larvae exposed to atrazine after stress management. An LC50-96h trial was carried out using fish (n = 147; 8.5 ± 1.0 mg; seven larvae/aquarium), which were allocated randomly in 21 aquaria (1 L) and exposed to five concentrations of atrazine: 2, 4, 8, 16, and 32 mg L-1 plus one control (without herbicide) and a control with a solubility adjuvant (acetone). Temperature, pH, dissolved oxygen, conductivity, and total ammonia were measured daily. In addition, a stress test was performed with fish (n = 150; 17.9 ± 1.7 mg; 10 larvae/aquarium) submitted to air exposition (five minutes) and posteriorly distributed randomly in 15 aquaria (1 L), and exposed to atrazine at 0.18, 6, 12, and 18 mg L-1. The LC50-96h of atrazine for Nile tilapia larvae was 17.87 mg L-1. Significant differences (P < 0.05) were found for weight and final length, pH, and dissolved oxygen that was responsive to the increased levels of herbicide. Larvae mortality post-stress was registered to 6, 12, and 18 mg L-1 of atrazine, and was more critical at 24 h. The increased doses of atrazine used in LC50-96h test depressed the development of Nile tilapia larvae. Fish submitted to stress (air exposition) and exposed to sub-lethal doses of atrazine showed significant mortality, indicating that stressors may increase the toxic effect of atrazine for Nile tilapia larvae. On the other hand, based on risk assessment atrazine can be classified as herbicide with low toxicity for Nile tilapia larvae and low toxicological risk.

Evaluation of health and environmental risks for juvenile tilapia (Oreochromis niloticus) exposed to florfenicol.

Intensive fish cultivation has a high incidence of infection, which is often controlled by administering antibiotics. Florfenicol (FF) is one of the two antimicrobial drugs permitted for aquaculture in Brazil. Due to their intensive use, potentially harmful effects on aquatic organisms are of great concern. In this sense, we investigated whether the presence of FF in cultivation water could change the health parameters of Nile tilapia. For this, we evaluated hemoglobin, hematocrit, mean corpuscular hemoglobin (MCHC) concentration, mean corpuscular volume (MCV), total plasma protein (TPP), number of circulating red blood cells and leukocytes, as lipid peroxidation levels, catalase activity and glutathione S-transferase activity of fish exposed to 11.72 mg L-1 of FF in water for 48 h. The fish were divided into two groups: Nile tilapia in water with FF or without FF (control). Exposure to FF in cultivation water for a short period didn't change the hematological variables analyzed, but caused changes in liver ROS (Reactive oxygen species) markers of the Nile tilapia, which was revealed by lipid peroxidation levels, catalase activity, and glutathione S-transferase. The 48h exposure period was enough to induce oxidative stress in hepatocytes, causing cellular oxidative damage. Therefore, the antibiotic florfenicol may cause toxicity to organisms and aquatic ecosystems, even at a sublethal concentrations near 1/100 LC50-48h for fish species.

Acute Toxicity and Risk Assessment of Florfenicol for Nile Tilapia Larvae.

The aim of this study was to determine the median lethal concentration (LC50-96h), effective concentration (EC50-96h), risk assessment, and development of Nile tilapia Oreochromis niloticus larvae submitted to florfenicol (FF) exposure. Fish (n = 147; 8.6 ± 0.6 mg; 7 fish/aquarium) were randomly distributed in 21 aquaria (1 L) and exposed to five concentrations of FF 58.73; 131.31; 198.96; 241.88 and 381.81 mg L-1 plus one control and a control with solvent, totalizing seven treatments and three replicates. The estimated median LC50-96h of FF for Nile tilapia larvae was 349.94 mg L-1. The EC50-96h of FF was 500 mg L-1 for weight reduction and was 1040 mg L-1 for length reduction. After the exposure period, final weight and length differed (p < 0.05) among treatments, showing the lowest biometric values ​​with the highest concentrations of FF. The pH and dissolved oxygen were altered (p < 0.05) during the experimental period. The FF high doses used to determine the LC 50 after 96 h negatively affected the development of the larvae. On the other hand, through risk assessment analysis this antibiotic can be classified as low toxicity to Nile tilapia larvae and show low environmental risk.

Effects of Artemisia annua alcohol extract on physiological and innate immunity of Nile tilapia (Oreochromis niloticus) to improve health status.

Plants are a potential source of active molecules and are environmentally safer and cheaper than synthetic antibiotics. Bioactive compounds of Artemisia annua have shown pharmacological activities and are used globally as a supplement. The present study tested whether dietary supplementation with alcohol extract of the plant A. annua (ae-Aa; patent BR10201902707) improves the health status of juvenile Nile tilapia and increases resistance to diseases when fish are challenged with the bacteria Aeromonas hydrophila. The experimental design was completely randomized with four experimental groups (0.0, 0.1, 0.25, and 0.5% ae-Aa in the diets) with five repetitions (12 fish per repetition/experimental unit). We assessed serum glucose and cortisol levels in plasma, leukocyte respiratory activity, total plasma protein, serum lysozyme levels, as well as the number of circulating red blood cells and fish leukocytes at the end of the 30 days of feeding (phase I) and 24h after exposure to bacteria (phase II). The levels of lipid peroxidation, catalase activity and glutathione S-transferase of fish were also analyzed. The supplementation of 0.5% of ae-Aa was sufficient to increase the respiratory burst of leukocyte and lysozyme activity, total plasma protein, blood thrombocytes, neutrophils and monocytes after bacterial challenge (P < 0.05), and minimized stress response with decreases in plasmatic glucose and cortisol, and reduction in lipid peroxidation levels (P < 0.05). Results of the present study suggest that ae-Aa as a dietary supplement has benefits, including supplementation with 0.5% A. annua extract for 30 days to minimize the stress response and modulate innate immunity in Nile tilapia, providing fish with greater resistance and disease protection.

Determination of acute median lethal concentration and sublethal effects on AChE activity of Gymnotus carapo (Teleostei: Gymnotidae) exposed to trichlorfon / Determinação da concentração letal média e efeitos subletais da atividade AchE de Gymnotus carapo (Teleostei: Gymnotidae) exposto ao triclorfon

Trichlorfon (TRF) is a pesticide widely used in aquaculture to control fish ectoparasites. This pesticide is an inhibitor of acetylcholinesterase, an essential enzyme for termination of nerve impulses. High rates of TRF use generate risks to the environment and human health. In the environment, pesticides can affect the local fauna and generate an ecological breakdown. There are several studies performed with fish production; however, gaps are created for native fish with other commercial values. The tuvira (Gymnotus carapo) is a fish native to Brazilian fauna and has great commercial importance in sport fishing. The present study aimed to determine the lethal concentration of trichlorfon (Masoten) in Gymnotus carapo and its sublethal effects on the enzyme AChE. In this study, the acute toxicity (the concentrations to kill 50% of the fish LC50) of TRF in tuviras (Gymnotus carapo) and acetylcholinesterase inhibition in liver and muscle tissue of tuviras submitted to sublethal concentrations were evaluated. For the acute assay, concentrations of 0.0, 5.0, 7.5, 15, 22.5, 30, 37.5 and 45 mg L-1 were used for a period of 96 h. After the acute exposure period, a LC50 of 6.38 mg L-1 was determined. In the sublethal assay, concentrations of 0.0, 0.238, 0.438 and 0.638 mg L-1 were used, based on 10% of the LC50, over a period of 14 days. Two collections were performed: one at seven days and the other at the end (day 14). Inhibition of acetylcholinesterase in the liver was only shown (p < 0.05) for the treatment with 0.638 mg L-1 after 14 days of exposure. At seven days, muscle activity showed a significant difference only for the treatments 0.438 and 0.638 mg L-1, compared with the treatment 0.238 mg L-1 and control. At 14 days of exposure, only the treatment 0.638 mg L-1 showed significant differences in relation to the other groups, thus showing that enzyme recovery had occurred. The value found in the acute test allowed the conclusion that TRF presents moderately toxic characteristics to Gymnotus carapo. The toxicity parameter values calculated in the present study assisted in estimation of maximum allowable limits in bodies of water when combined with test data from other non-target organisms.(AU)

O triclorfon (TRC) é um pesticida muito utilizado na aquicultura para o controle de ectoparasitos de peixes. Este pesticida é um inibidor da acetilcolinesterase, uma enzima essencial para a finalização de impulsos nervosos. As altas concentrações utilizadas de TRC geram riscos ao meio ambiente e à saúde humana. No ambiente, os pesticidas podem afetar a fauna local e gerar um colapso ecológico. Existem vários estudos com peixes de produção, no entanto, há lacunas para peixes nativos com outros valores comerciais. A tuvira (Gymnotus carapo) é um peixe nativo da fauna brasileira e possui grande importância comercial na pesca esportiva. O presente trabalho, delineado para determinar a concentração letal de triclorfon (Masoten) em Gymnotus carapo e seus efeitos subletais na enzima AChE, avaliou a toxicidade aguda (concentrações para matar 50% dos peixes CL50) do TRC em tuviras (Gymnotus carapo) e a inibição da acetilcolinesterase no fígado e tecido muscular de tuviras. Para o ensaio agudo, foram utilizadas concentrações de 0,0, 5,0, 7,5, 15, 22,5, 30, 37,5 e 45 mg L-1por um período de 96 horas. Após o período de exposição aguda, foi determinado uma CL50 de 6,38 mg L-1. No ensaio subletal, foram utilizadas concentrações de 0,0, 0,238, 0,438 e 0,638 mg L-1, com base em 10% do CL50, durante um período de catorze dias. Foram realizadas duas colheitas: uma aos sete dias e a outra ao final (décimo quarto dia). A inibição da acetilcolinesterase no fígado foi demonstrada apenas (p <0,05) para o tratamento com 0,638 mg L-1 após catorze dias de exposição. Aos sete dias, a atividade muscular mostrou diferença significativa apenas para os tratamentos 0,438 e 0,638 mg L-1, em comparação com o tratamento 0,238 mg L-1 e controle. Aos catorze dias de exposição, apenas o tratamento 0,638 mg L-1 apresentou diferenças significativas em relação aos demais grupos, demonstrando a recuperação enzimática. O valor encontrado no teste agudo permitiu concluir que o TRC apresenta características moderadamente tóxicas para Gymnotus carapo. Os valores dos parâmetros de toxicidade calculados no presente estudo permitiram o estabelecimento da estimativa dos limites máximos permitidos em corpos d'água quando combinados com dados de testes de outros organismos não-alvo.(AU)

Effects of Dietary Exposure to Sulfamethazine on the Hematological Parameters and Hepatic Oxidative Stress Biomarkers in Nile Tilapia (Oreochromis niloticus).

Sulfamethazine (SMZ) is one of the most commonly used sulfonamide compounds in fish farming, and its physiological effects on fish are unknown. SMZ was administered to juvenile Nile tilapia (Oreochromis niloticus) at a dose level of 422 mg kg(-1) body weight, for a period of 11 days, via medicated feed. Fish were divided into two groups, the control group (CG) and the group fed with SMZ in feed. The administration of SMZ did not alter the erythrograms and leukograms of the Nile tilapia. The SMZ-fed group showed the same hepatic lipid peroxidation (LPO) concentration as the CG. Nonetheless, the oral administration of SMZ raised the hepatic catalase (CAT) and glutathione S-transferase (GST) activities, the increase probably being sufficient to prevent hepatic LPO production. The oral administration of SMZ affects the hepatic GST and CAT activities of Nile tilapia.

Avaliação da toxicidade de herbicidas usados emcana-de-açúcar para o Paulistinha (Danio rerio) / Toxicity evaluation of herbicides used in sugarcane crops toZebrafish (Danio rerio)

Na natureza, os organismos são constantemente expostos a mais de um agente tóxico e, apesar do fenômeno de interaçõesquímicas ser conhecido há tempos, são poucos os estudos realizados que privilegiam a observação dos efeitosdecorrentes da exposição a duas ou mais substâncias. O objetivo deste trabalho foi avaliar o efeito combinado damistura dos herbicidas Gesapax 500® (ametrina 500 g/L) e Velpar K® (diuron 468 g/kg + hexazinone 132 g/kg) sobreo paulistinha (Danio rerio). O ensaio foi baseado no teste FET da OECD, com duração de 96 horas. As concentraçõestestadas foram 0, 21,22, 29,52, 41,08, 57,17 e 79,56 mg/L de Gesapax 500 vs. 0, 15,21, 21,17, 29,46, 40,99 e 57,04mg/L de Velpar K. Os testes foram conduzidos em triplicata e avaliados diariamente. As CL50-96h determinadas foram41,705 ± 8,373 mg/L para o Gesapax 500 e 55,460 ± 20,826 mg/L para o Velpar K. O modelo da mistura que melhordescreve a relação entre os dois componentes é a ação independente, sendo a toxicidade dose-dependente, ou seja,em baixas doses ocorre antagonismo e, em altas doses, sinergismo. Os endpoints edemas, atraso no desenvolvimentoembrionário (delay) e na absorção do saco vitelínico e diminuição na frequência de cardíaca foram observados apartir das concentrações mais baixas da mistura. Pelos dados obtidos, concluiu-se que a mistura de Gesapax 500 eVelpar K é medianamente tóxica para o paulistinha e que os endpoints avaliados foram úteis na determinação de suatoxicidade.

In nature, organisms are constantly exposed to more than one toxic agent, and although the phenomenon of chemical interactionsare known for some time, there are few previous studies that emphasize observation of the effects resulting fromexposure to two or more substances. The aim of this study was to evaluate the combined effect of the mixture of herbicideGesapax 500® (ametrina 500 g/L) and Velpar K® (diuron 468 g/kg + hexazinone 132 g/kg) on zebrafish (Danio rerio). The testwas based on the Fish Embryo Toxicity (FET) from OECD, lasting 96 hours. The concentrations tested were: 0, 21.22, 29.52,41.08, 57.17 and 79.56 mg/L Gesapax 500 vs. 0, 15.21, 21.17, 29.46, 40.99 and 57.04 mg/L Velpar K. Tests were conductedin triplicate and evaluated daily. LC50-96h was determined to 41.705 ± 8.373 mg/L to Gesapax 500 and 55.460 ± 20.826 mg/Lto Velpar K. The mixture model that best describes the relationship between the two components is independent action andtoxicity of the mixture is dose-dependent, occurring antagonism at low doses and synergism at high doses. The endpointsedema, delay in general development and in yolk sac absorption and decrease in frequency of heart-beat rate were observedfrom the lower concentrations of the mixture. From the data obtained, it is concluded that the mixture of Velpar K and Gesapax500 is moderately toxic to zebrafish and that the endpoints evaluated were useful in determining its toxicity.

Avaliação da toxicidade aguda depiraclostrobin, epoxiconazol e suamistura em Daphnia similis / Toxicity of formulations based on piraclostrobin, epoxiconazole and its combination to Daphnia similis

No presente trabalho avaliou-se o efeito toxicológico (inibição damobilidade) de formulações fungicidas à base de piraclostrobin eepoxiconazol, isoladamente e em formulação conjugada sobreDaphnia similis, mediante determinação da Concentração EfetivaMédia (CE50-48h) de cada uma das formulações. Também foideterminado o possível efeito sinérgico ou antagônico que ouso conjugado dos dois fungicidas poderia exercer em relaçãoà sua toxicidade. Foram encontrados valores de CE50-48h de18,36 μg.L-1 para a formulação à base de piraclostrobin, de89,98 μg.L-1 para a formulação à base de epoxiconazol e de23,50 μg.L-1 para a formulação conjugada. Das três formulaçõesestudadas, o piraclostrobin mostrou-se o mais tóxico para osorganismos em estudo. A análise isobolográfi ca e a determinação doÍndice de Aditividade (IA) sugerem que a mistura dos princípios ativosexerce apenas efeito toxicológico aditivo sobre o organismo-alvo.

Avaliação da toxicidade de Piraclostrobin, epoxiconazol e sua mistura em alga Pseudokirchneriella subcapitata / Toxicity of formulations basedof Piraclostrobin, epoxiconazole and its combination on algae Pseudokirchneriella subcapitata

Estudou-se o efeito toxicológico (inibição de crescimento) deformulações fungicidas à base de piraclostrobin e epoxiconazol,isoladamente e em formulação conjugada, sobre a algaPseudokirchneriella subcapitata mediante determinação daConcentração Efetiva Média (CE50-72 h) dos princípios ativos decada uma das formulações. Foram encontrados valores de CE50-72 h de 5,57 mg.L-1 para a formulação à base de piraclostrobin,de 1,14 mg.L-1 para a formulação à base de epoxiconazol e de0,20 mg.L-1 para a formulação conjugada. O piraclostrobin apresentoumenor toxicidade às algas em relação aos dados encontrados naliteratura, o epoxiconazol resultados semelhantes e a mistura maiortoxicidade. A análise isobolográfi ca e a determinação do Índice deAditividade (IA) sugerem forte sinergismo da mistura quanto à suaação tóxica sobre o organismo-teste. Esse fato realça a necessidadede revisão dos padrões limitantes desses fungicidas em corpos deágua, os quais tendem a subestimar os efeitos adversos resultantesda combinação dos agentes tóxicos.

Susceptibility of non-target invertebrates to Brazilian microbial pest control agents.

Microbial pest control agents or entomopathogens have been considered an interesting alternative to use instead of chemical insecticides. Knowledge of ecotoxicity data is very important to predict the hazard of any product released in the environment and subsidize the regulation of these products by governmental agencies. In the present study four new Brazilian strains of Bacillus and one fungus were tested to evaluate their acute toxicity to the microcrustacean Daphnia similis, the snail Biomphalaria glabrata and the dung beetle Digitonthophagus gazella. The microcrustaceans and the snails were exposed to entomopathogens in synthetic softwater and the beetles were exposed directly in cattle dung. Obtained data reveal low susceptibility of the non-target species to tested microorganisms, with lethal concentrations being observed only at much higher concentrations than that effective against target insects. These results show that the tested strains are selective in their action mode and seem to be non-hazardous to non-target species.

Assessing the safety of Pseudomonas putida introduction in the environment: an overview of ecotoxicological tests.

Risk assessment guidelines for the environmental release of microbial agents are performed in a tiered sequence which includes evaluation of exposure effects on non-target organisms. However, it becomes important to verify whether environmental risk assessment from temperate studies is applicable to tropical countries, as Brazil. Pseudomonas putida is a bacteria showing potential to be used for environmental applications as bioremediation and plant disease control. This study investigates the effects of this bacteria exposure on rodents and aquatic organisms (Daphnia similis) that are recommended to be used as non-target organism in environmental risk assessments. Also, the microbial activity in three different soils under P. putida exposure was evaluated. Rats did not show clinical alterations, although the agent was recovered 16h after the exposure in lung homogenates. The bacteria did not reduce significantly the reproduction and survival of D. similis. The soil enzymatic activities presented fluctuating values after inoculation with bacteria. The measurement of perturbations in soil biochemical characteristics is presented as an alternative way of monitoring the overall effects of the microbial agent to be introduced even in first stage (Tier I) of the risk assessment in tropical ecosystems.

Effect of copper on the activation of the acid phosphatase from the green algae Pseudokirchneriella subcapitata.

The presence of copper in water environment may have detrimental effects on aquatic organisms, including algae, where different enzymatic systems can be affected. Algae acid phosphatase plays important roles in metabolic processes such as decomposition of organic phosphate, autophagic digestive process, recycling cellular materials and zygote formation during reproduction. This work describes an in vitro activation effect of copper on the acid phosphatase of the green algae Pseudokirchneriella subcapitata (formely Selenastrum capricornutum) under preincubation condition. Apparent Michaelis constant values of 1.21 and 0.37 mM, and activation energy values of 26.8 and 13.6 kJ mol(-1) were determined in the absence and in the presence of 0.2 mM Cu(2+), respectively. The dissociation constant value for Cu(2+) binding to the enzyme was determined to be 22.04 microM. The decrease of the apparent Michaelis constant (Km) and activation energy values in the presence of Cu(2+) correlates well with its activating effect on the acid phosphatase activity. This propriety could be used as a sensitive bioindicator for copper in environmental samples.

Algae acid phosphatase affected by ten metals and enzymatic parameters determination in presence of mercury and copper

Acid phosphatases play important roles in algae metabolism such availability/recycling of inorganic phosphate and autophagic digestive processes. Chemicals released into the environment from agricultural activities and through industrial and urban wastes, may impair algae enzyme activity. The aim of this work was to evaluate the in vitro activation/inhibition effect of ten metals, commonly present as contaminants in soil and water, on the acid phospahatase extracted from the green algae Pseudokirchneriella subcapitata. Results demonstrated that Hg, Al, Mo, Pb, Se, and Cd inhibited the enzyme activity in 56.3, 54.5, 30.6, 25.5, 23.1 and 11.5 per cent respectively. This corresponds to the maximum percentage of effect attained at the metal concentration tested (0.02-2.0 mM). On the other hand, Cu, Zn, Ni and Cr exhibited an increment on phosphatase activity equal to 95.5, 87.6, 87.6, 77.6 and 42.8 per cent, respectively. Kinetic parameters values were calculated for the metals that showed hisghest effects. Thus, Ki ( inhibition constant) and Kd (dissociation constant) values equal to 0.0400 and 0.0016 mM were determined for Hg and Cu, respectively. A non-competitive inhibition mechanism was attributed to the former. Results improved the understanding of the basic events of the impact of metals at biochemical lebels in primary producers organisms.

Metals and linear alkylbenzene sulphonate as inhibitors of the algae Pseudokirchneriella subcapitata acid phosphatase activity.

Sewage sludge applied to soils as a fertilizer often contains metals and linear alkylbenzene sulphonate (LAS) as contaminants. These pollutants can be transported to the aquatic environment where they can alter the phosphatase activity in living organisms. The acid phosphatase of algae plays important roles in metabolism such as decomposing organic phosphate into free phosphate and autophagic digestive processes. The order of in vitro inhibition of Pseudokirchneriella subcapitata acid phosphatase at the highest concentration tested was LAS > Hg2+ = Al3+ > Se4+ = Pb2+ > Cd2+. A non-competitive inhibition mechanism was obtained for Hg2+ (Ki = 0.040 mM) and a competitive inhibition for LAS (Ki = 0.007 mM). In vivo studies with treated algae cultures showed that the inhibition of specific activity was observed in algae exposed during 7 days, in contrast to short term (24 h) treatments with both these chemicals. Our results suggest that the inhibition parameters in vitro did not markedly differ between the two chemicals. On the other hand, in vivo evaluations showed strong differences between both pollutants regarding the concentration values and the degree of response.

In vitro effect of agriculture pollutants and their joint action on Pseudokirchneriella subcapitata acid phosphatase.

Acid phosphatase plays important roles in algae metabolism such as availability and recycling of inorganic phosphate, autophagic digestive processes and fertilization. Chemicals released into the environment from agriculture activities may impair algae phosphatase activity. The aim of this work was to evaluate the in vitro effect of twenty-four organic compounds and six metals used as pesticides, or present as contaminants in sewage sludge, on the acid phosphatase activity extracted from Pseudokirchneriella subcapitata. Results demonstrated that only the linear surfactant alkyl benzenesulphonate (LAS) and the heavy metals Hg(2+), Al(3+) and Cu(2+) markedly altered (50%) the enzyme activity. Join action inhibition studies indicated that Hg(2+) was more potent inhibitor than Al(3+) or LAS, and that the Hg(2+)+Al(3+) and Hg(2+)+LAS mixtures have, respectively, additive and slight antagonism effects. Copper, which demonstrated an activator effect when preincubated with the enzyme, behaved as a slight antagonist for the inhibitor effect of Hg(2+).

Fator de bioconcentração de poluentes orgânicos de lodos em frutos de laranjeiras / Bioconcentration factor of organic pollutants of the sewage sludge in orange fruits

Estimou-se o fator de bioconcetração de dezenove poluentes orgânicos para verificar quais devem ser monitorados em frutos de laranjeiras, cultivadas em solos tratados com lodo proveniente de estações de tratamento de esgotos. O modelo Fruit Tree Model (FTM) foi aplicado em cultivo hipotético de laranjeiras, utilizando-se a massa molar,a pressão de vapor, a solubilidade em água e o coeficiente de partição pctanol-água de poluentes (compostos orgânicos não-iônicos) que podem ser encontrados em lodos. Os coeficientes de sorção no carbono orgânico do solo, de partição caule-águas e o fator de concentração no fluxo de transpiração foram calculados por meio de expressões que correlacionam cada um desses parâmetros com o coeficiente de partição octanol-água. Obtendo-se o fator de bioconcentração e a concentração do poluente no solo é possível estimar a quantidade desses agentes químicos ingeridos diariamente pelo consumo de frutas frescas. Valores limites de poluentes em lodos podem ser calculados a partir do fator de bioconcentração do poluente em frutas. Os poluentes indicados pela estimativa para monitoramento em frutos de laranjeiras cultivadas com lodo foram: 1,2-diclorobenzeno, 2,4-dinitrofenol, 3,3-diclorobenzidina e nitrobenzeno