Interactions between pH and nutrients on benthic algae in streams and consequences for ecological status assessment and species richness patterns

Eutrophication and acidification are among the major stressors on freshwater ecosystems in northern Europe and North America, but possible consequences of interactions between pH and nutrients on ecological status assessment and species richness patterns have not previously been assessed. Using data from 52 river sites throughout Norway, we investigated the combined effects of pH and nutrients on benthic algae assemblages, specifically 1) taxa-specific couplings between nutrient and acidity traits, 2) the degree of consistency between different biotic indices, separately for nutrients and acid conditions, 3) the impact of pH on nutrient indices and phosphorus on indices of acid conditions, and 4) the impact of pH and phosphorus supply on diatom and non-diatom taxon richness. We found that 1) acid-tolerant taxa are generally associated with nutrient-poor conditions, with only a few exceptions; this is probably more a consequence of habitat availability than reflecting true ecological niches; 2) correlation coefficients between nutrient indices and TP, as well as acid conditions indices and pH were barely affected when the confounding factor was removed; 3) the association of acid-tolerant taxa with nutrient-poor conditions means that the lowest possible nutrient index at a site, as indicated by benthic algae, is lower at acid than at circumneutral sites. Although this may be an artifact of the datasets from which taxa-specific indicator values were derived, it could lead to a drift in nutrient indices with recovery from acidification; 4) the response of non-diatom taxon richness follows a complex pattern with a synergistic interaction between nutrient supply and pH. In contrast, diatom richness follows a simple additive pattern; this suggests structural differences between diatoms and non-diatom benthic algae in their response to nutrient supply and pH; diatom taxon richness tended to increase with nutrient supply, while non-diatom richness decreased. (C) 2012 Elsevier B.V. All rights reserved

Protector mechanisms of the association between gastroesophageal reflux disease and asthma: experimental study in rats Mecanismos protetores: doença do refluxo gastroesofágico e asma. Estudo experimental em ratos

BACKGROUND: It is well known the association between gastroesophageal reflux disease and asthma. The hyperreactivity of the airways is a characteristic of an asthmatic. Many studies associate the increase of the airways reactivity with gastroesophageal reflux disease. AIM: In this study we have evaluated the effect of the intraluminal exposition to gastric juice of trachea on the reactivity to methacholine from rats submitted to a pulmonary allergic inflammation. METHODS: Group of rats were sensitized and challenged with ovalbumin. After 24 hours the animals were sacrificed, and their tracheae were removed to be cultured with gastric juice. The gastric juice was obtained from a donor rat. Subsequently the segments were placed into plastic plates with RPMI-1640 for incubation, under suitable atmosphere and time. After the period of incubation the segments were put into chambers for the analysis of the contractile response to methacholine. RESULTS: We observed reduction in the contractile response of trachea cultured with gastric juice from allergic rats. This result was confirmed by the pharmacological treatments with compound 48/80 and dissodium cromoglicate (mast cells blockade), L-NAME (nitric oxide inhibitor, NO), capsaicin (neuropeptides depletion) and indomethacin (ciclooxigenase inhibitor). CONCLUSIONS: Our results highlight to the existence of a complex interaction between pulmonary allergy and gastric juice in the airways. The involvement of the non-adrenergic non-cholinergic system, NO, prostanoids and mast cells are directly related to this interaction. We suggest that the reduced contractile response observed in vitro may represent a protector mechanism of the airways. Despite its presence in the human body it can not be observed due to the predominant effects of excitatory the non-adrenergic non-cholinergic system.<br>RACIONAL: É bem estabelecida a relação entre a doença do refluxo gastroesofágico e a asma. A hiperreatividade das vias aéreas é uma das características que o indivíduo asmático desenvolve e diversos estudos associam o aumento da reatividade das vias aéreas com o refluxo gastroesofágico. OBJETIVO: Avaliar a reatividade à metacolina de traquéia exposta intraluminalmente ao suco gástrico de ratos submetidos a inflamação alérgica pulmonar. MÉTODOS: Grupos de ratos foram sensibilizados e broncoprovocados com ovoalbumina. Após 24 horas, os animais foram sacrificados e a traquéia removida para preenchimento de seu lúmen com suco gástrico obtido de um animal doador. A seguir, os segmentos foram colocados em placas plásticas com RPMI-1640 e mantidos em estufa por 3 horas em condições ambientais adequadas. Após o tempo de incubação, os fragmentos foram montados em cubas de vidro para órgão isolado para registro isométrico de contração, através da construção de curvas concentração-efeito à metacolina. RESULTADOS: Observou-se redução da resposta contrátil em traquéia exposta ao suco gástrico proveniente de ratos alérgicos. Os tratamentos farmacológicos com composto 48/80 e cromoglicato de sódio (bloqueio de mastócitos), L-NAME (inibidor de óxido nítrico, NO), capsaicina (depleção de neuropeptídios) e indometacina (inibidor da ciclooxigenase) corroboraram esta observação. CONCLUSÕES: Os resultados apontam para a existência de complexa interação entre a alergia pulmonar e o suco gástrico nas vias aéreas, com o envolvimento do sistema não-adrenérgico não-colinérgico, NO, prostanóides e mastócitos. À luz das evidências in vivo sobre a hiperreatividade das vias aéreas na associação asma e refluxo gastroesofágico, sugere-se que a reduzida resposta contrátil detectada in vitro pode representar um mecanismo protetor das vias aéreas. A despeito de sua presença, esta redução pode não ser observada in vivo devido à proeminência dos efeitos do sistema não-adrenérgico não-colinérgico excitatório