Mecanismos de regulação de Na+ nas brânquias de peixes da Amazônia: modulação por fatores ambientais e ajustes espécie-específicos

The mechanisms of Na+ transport in gills of Amazonian fish species remains poorly understood, particularly regarding to the physiological adjustments involved in adaptation to the singular environmental conditions of Amazon waters. The aim of the present study was analyze the physiological mechanisms involved in Na+ transport in gills of different Amazonian fish species, at both natural and laboratory conditions. Therefore, we evaluated the influence of water physical and chemical conditions on Na+ unidirectional fluxes and Na+ uptake kinetic properties of fishes, as well as on Na+/K+-ATPase and H+-ATPase activity, looking for intraespecific and interespecific adjustments in Na+ transport according to environmental conditions. The responses in branchial Na+ transport were strongly related to H+-ATPase activity, suggesting that this enzyme plays a importante role in the maintenance of the ionic and acid-base balance in the studied fish species during the process of acclimatization and acclimation to acidic conditions ion-poor conditions. However, others Na+ transporters seems to be involved in branchial transport of Na+, particularly in Hyphessobrycon copelandi during acute exposure to higher temperatures. There was also seen that differences in controlling gill permeability modulate the tolerance of some cichlid fish species, as Pterophyllum scalare and Symphysodon discus, to ionoregulatory disturbances from the exposure to acidic water and ion-poor conditions. Moreover, intraspecific and interspecific variation in the response of H+-ATPase activity, and in a lower extent to the Na+/K+-ATPase activity, were associated with adaptive adjustments of fish to the natural environmental conditions founded in streams of the Rio Negro basin.Os mecanismos de transporte de Na+ nas brânquias de peixes da Amazônia permanece pouco estudado, particularmente no que se refere aos ajustes fisiológicos relacionados à adaptação às condições ambientais peculiares das águas da região. O presente estudo teve como objetivo analisar os mecanismos fisiológicos relacionados ao transporte de Na+ nas brânquias de diferentes espécies de peixes da Amazônia, em condições naturais e em laboratório. Para tanto, foi avaliada a influencia das condições físicas e químicas da água no fluxo unidirecional e propriedades cinéticas para a absorção de Na+ dos animais, assim com a atividade da Na+/K+-ATPase e H+-ATPase, verificando a presença de ajustes intra e interespecíficos na regulação do transporte de Na+ em função das condições ambientais. As respostas no transporte branquial de Na+ foram fortemente relacionadas a atividade da H+-ATPase, sugerindo que essa enzima exerce um papel na manutenção do equilíbrio iônico e ácido base das espécies estudadas durante os processos de aclimatização e aclimatação a condições ácidas e com baixa disponibilidade iônica. Contudo, outros transportadores parecem estar envolvidos no transporte branquial de Na+, particularmente em Hyphessobrycon copelandi durante a exposição aguda a maiores temperaturas Foi observado também que diferenças no controle da permeabilidade branquial influenciam na tolerância de alguns ciclídeos, como Pterophyllum scalare e Symphysodon discus, a distúrbios ionoregulatórios decorrentes da exposição a águas ácidas e pobre ionicamente. Além disso, variações intraespecíficas e interespecíficas na regulação da atividade da H+-ATPase, e em menor grau da Na+/K+-ATPase, foram associadas a ajustes adaptativos dos peixes às condições ambientais naturais de igarapés da bacia do Rio Negro

Hybrid particle swarm optimization with spiral-shaped mechanism for solving high-dimension problems

Particle swarm optimization (PSO) is a well-known metaheuristic, whose performance for solving global optimization problems has been thoroughly explored. It has been established that without proper manipulation of the inertia weight parameter, the search for a global optima may fail. In order to handle this problem, we investigate the experimental performance of a PSO-based metaheuristic known as HPSO-SSM, which uses a logistic map sequence to control the inertia weight to enhance the diversity in the search process, and a spiral-shaped mechanism as a local search operator, as well as two dynamic correction factors to the position formula. Thus, we present an application of this variant for solving high-dimensional optimization problems, and evaluate its effectiveness against 24 benchmark functions. A comparison between both methods showed that the proposed variant can escape from local optima, and demonstrates faster convergence for almost every evaluated function

Da nutrição à digestão: uma proposta contextualizada para o ensino do sistema digestório

Learning about the human body is understanding the functioning of the body itself, considering its biological and sociocultural aspects. However, teaching practices prefer a Cartesian approach in which the body is treated in a reductionist way, restricting it to anatomical and physiological aspects often disconnected. That is the case of the digestive system and the approach to food and nutrition education is considered a contemporary cross-cutting topic by the National Common Curriculum Base. With this in mind, this research surveyed previous conceptions on the guiding theme "nutrition" with 6th-grade students of elementary school II in São Vicente, SP. From there, we develop and apply a didactic sequence to promote anatomical and physiological knowledge of the digestive system from nutrition. Results indicate that after applying the sequence, the students acquired concepts about the morphophysiology of the digestive system, and also, understood that nutrition is guided by sociocultural aspects.Aprender sobre el cuerpo humano es comprender el funcionamiento del propio cuerpo, considerando sus aspectos biológicos y socioculturales. Sin embargo, en la docencia prevalece un enfoque cartesiano en el que se trata el cuerpo de forma reduccionista, restringiéndolo a aspectos anatómicos y fisiológicos, que muchas veces están desconectados. Este es el caso del aparato digestivo y el enfoque de la educación alimentaria y nutricional, considerado un tema transversal contemporáneo por la Base Curricular Común Nacional. Con esto en mente, esta investigación llevó a cabo el levantamiento de concepciones previas sobre el tema rector "nutrición" con estudiantes de 6 ° grado de la escuela primaria II en São Vicente / SP. A partir de allí, se elaboró y aplicó una secuencia didáctica, con el objetivo de promover el conocimiento anatómico y fisiológico del sistema digestivo a partir de la nutrición. Los resultados indican que luego de aplicar la secuencia, los estudiantes no solo adquirieron conceptos sobre la morfofisiología del aparato digestivo, sino que también entendieron que la nutrición está guiada por aspectos socioculturales.Aprender sobre o corpo humano é compreender sobre o funcionamento do próprio corpo, contemplando seus aspectos biológicos e socioculturais. Contudo percebe-se no ensino de ciências na educação básica dos anos finais, a prevalência de uma abordagem cartesiana em que o corpo é tratado de forma reducionista, restringindo-o a aspectos anatômicos e fisiológicos, muitas vezes desconexos. Esse é o caso do sistema digestório e da abordagem da educação alimentar e nutricional, considerada um tema contemporâneo transversal pela Base Nacional Comum Curricular. Tendo isso em vista, esta pesquisa realizou o levantamento das concepções prévias a respeito do tema norteador “nutrição” com alunos do 6º ano do ensino fundamental II de uma escola municipal de São Vicente/SP. A partir disso, elaborou-se e aplicou-se uma sequência didática visando promover conhecimentos anatômicos e fisiológicos do sistema digestório a partir da nutrição. Os resultados indicam que após a aplicação da sequência didática os alunos não só adquiriram conceitos a respeito da morfofisiologia do sistema digestório, mas também compreenderam que a nutrição é pautada por aspectos socioculturais

Dissolved organic carbon from the upper Rio Negro protects zebrafish (Danio rerio) against ionoregulatory disturbances caused by low pH exposure

The so-called â œ blackwatersâ of the Amazonian Rio Negro are rich in highly coloured dissolved organic carbon (DOC), but ion-poor and very acidic, conditions that would cause fatal ionoregulatory failure in most fish. However these blackwaters support 8% of the worldâ ™ s ichthyofauna. We tested the hypothesis that native DOC provides protection against ionoregulatory dysfunction in this extreme environment. DOCs were isolated by reverse-osmosis from two Rio Negro sites. Physico-chemical characterization clearly indicated a terrigenous origin, with a high proportion of hydroxyl and phenolic sites, high chemical reactivity to protons, and unusual proteinaceous fluorescence. When tested using zebrafish (a model organism), Rio Negro DOC provided almost perfect protection against ionoregulatory disturbances associated with acute exposure to pH 4.0 in ion-poor water. DOC reduced diffusive losses of Na + and Cl â', and promoted a remarkable stimulation of Na + uptake that otherwise would have been completely inhibited. Additionally, prior acclimation to DOC at neutral pH reduced rates of branchial Na + turnover, and provided similar protection against acid-induced ionoregulatory disturbances, even if the DOC was no longer present. These results reinforce the important roles that DOC molecules can play in the regulation of gill functions in freshwater fish, particularly in ion-poor, acidic blackwaters

Roundup® exposure promotes gills and liver impairments, DNA damage and inhibition of brain cholinergic activity in the Amazon teleost fish Colossoma macropomum

Roundup Original® (RD) is a glyphosate-based herbicide used to control weeds in agriculture. Contamination of Amazon waters has increased as a consequence of anthropogenic pressure, including the use of herbicides as RD. The central goal of this study was to evaluate the toxic effects of RD on juveniles of tambaqui (Colossoma macropomum). Our findings show that biomarkers in tambaqui are organ specific and dependent on RD concentration. Alterations in gills structural and respiratory epithelium were followed by changes in hematological parameters such as concentration of hemoglobin, particularly in fish exposed to the higher concentration tested (75% of RD LC50 96h). In addition, both RD concentrations affected the biotransformation process in gills of tambaqui negatively. Instead, liver responses suggest that a production of reactive oxygen species (ROS) occurred in fish exposed to RD, particularly in the animals exposed to 75% RD, as seen by imbalances in biotransformation and antioxidant systems. The increased DNA damage observed in red blood cells of tambaqui exposed to RD is in agreement with this hypothesis. Finally, both tested sub-lethal concentrations of RD markedly inhibited the cholinesterase activity in fish brain. Thus, we can suggest that RD is potentially toxic to tambaqui and possibly to other tropical fish species. © 2015 Elsevier Ltd

Recovery of fat snook, Centropomus parallelus (Teleostei: Perciformes) after subchronic exposure to copper

We studied the recovery of juvenile fat snook (Centropomus parallelus) after subchronic exposure to different concentrations of copper. Healthy juveniles (1.98 g) were exposed to 25 or 50 μg Cu/L for 30 days (12 replicates with 5 fish in each one), and recovery was observed at 0, 4, 10, and 30 days after exposure (3 replicates with 5 fish in each one). Copper genotoxicity in exposed individuals was observed using a micronucleus assay, and recovery was not observed even 30 days post-exposure. Copper accumulation was observed in fish exposed to 25 or 50 μg/L of copper in the gills (14.4 and 34.4 μg/g, respectively) and muscle (5.7 and 5.5 μg/g, respectively), and a return to normal copper levels (6.0 μg/g for gills and 2.5 μg/g for muscle) was observed 4 and 30 days post-exposure in the gills and muscle tissues, respectively. Glutathione S-transferase (GST) was 80% inhibited in individuals exposed to copper and returned to normal levels for fish exposed to basal concentrations within 10 days. Although copper accumulation in tissues dispersed 30 days post-exposure, no recovery from genotoxicity was observed during this time. Thirty days was not enough to recover juvenile fat snook following subchronic exposure to copper. © 2013 Elsevier Inc

CONSERVAÇÃO DE Genipa americana: TÉCNICAS DE ENCAPSULAMENTO E CRESCIMENTO LENTO

Segmentos nodais de Genipa americana foram armazenados utilizando técnicas de encapsulamento e crescimento lento. Para o armazenamento de unidades encapsuláveis foram avaliados a influência da matriz de alginato de sódio a 3% e 4%, o efeito de um pré-tratamento com soluções de sacarose a 0, 0,25 e 0,50 M, bem como o efeito da temperatura de 8ºC e 15ºC durante 30 dias de armazenamento, sendo avaliada a porcentagem de ruptura dessas cápsulas após 50 dias de inoculação. Para o crescimento lento foram avaliadas diferentes concentrações de sacarose (30, 45 e 60 g L-1) e temperatura 8ºC e 15ºC após 90 e 180 dias de armazenamento. Sendo avaliada a porcentagem de sobrevivência e regeneração, comprimento da parte área, número de brotos e folhas. Apenas as unidades encapsuláveis armazenadas à 15ºC sobreviveram.  Nesta temperatura, a ruptura da cápsula foi melhor no pré-tratamento com 0 M de sacarose. Para o crescimento lento, a temperatura de 8º também não permitiu sobrevivência dos explantes. Assim, após 180 dias os melhores resultados ocorreram na temperatura de 15°C com acréscimo de 60 g L-1 de sacarose ao meio de cultura. Dessa forma, pode-se concluir que é possível fazer o armazenamento da espécie utilizando essas técnica

Regulation of gill transcellular permeability and renal function during acute hypoxia in the Amazonian oscar (Astronotus ocellatus): New angles to the osmorespiratory compromise

Earlier studies demonstrated that oscars, endemic to ion-poor Amazonian waters, are extremely hypoxia tolerant, and exhibit a marked reduction in active unidirectional Na+ uptake rate (measured directly) but unchanged net Na+ balance during acute exposure to low Po2, indicating a comparable reduction in whole body Na+ efflux rate. However, branchial O2 transfer factor does not fall. The present study focused on the nature of the efflux reduction in the face of maintained gill O 2 permeability. Direct measurements of 22Na appearance in the water from bladder-catheterized fish confirmed a rapid 55% fall in unidirectional Na+ efflux rate across the gills upon acute exposure to hypoxia (PO2=10-20torr; 1 torr=133.3 Pa), which was quickly reversed upon return to normoxia. An exchange diffusion mechanism for Na + is not present, so the reduction in efflux was not directly linked to the reduction in Na+ influx. A quickly developing bradycardia occurred during hypoxia. Transepithelial potential, which was sensitive to water [Ca2+], became markedly less negative during hypoxia and was restored upon return to normoxia. Ammonia excretion, net K+ loss rates, and 3H2O exchange rates (diffusive water efflux rates) across the gills fell by 55-75% during hypoxia, with recovery during normoxia. Osmotic permeability to water also declined, but the fall (30%) was less than that in diffusive water permeability (70%). In total, these observations indicate a reduction in gill transcellular permeability during hypoxia, a conclusion supported by unchanged branchial efflux rates of the paracellular marker [3H]PEG-4000 during hypoxia and normoxic recovery. At the kidney, glomerular filtration rate, urine flow rate, and tubular Na+ reabsorption rate fell in parallel by 70% during hypoxia, facilitating additional reductions in costs and in urinary Na+, K+ and ammonia excretion rates. Scanning electron microscopy of the gill epithelium revealed no remodelling at a macro-level, but pronounced changes in surface morphology. Under normoxia, mitochondria-rich cells were exposed only through small apical crypts, and these decreased in number by 47% and in individual area by 65% during 3 h hypoxia. We suggest that a rapid closure of transcellular channels, perhaps effected by pavement cell coverage of the crypts, allows conservation of ions and reduction of ionoregulatory costs without compromise of O2 exchange capacity during acute hypoxia, a response very different from the traditional osmorespiratory compromise