RESUMO
This study investigates the impact of water quality, specifically elevated phosphate and zinc content, on the diversity and functional properties of mangrove fungal endophytes in two distinct mangrove forests. Mangrove plant performance is directly related to the presence of fungal leaf endophytes as these fungi could enhance plant health, resilience, and adaptability under stressed environmental conditions. Two distinct mangrove forest sites, one non-disturbed (ND) and one disturbed by aquaculture practices (D), were assessed for differences in water quality parameters. We further analyzed the fungal endophyte diversity associated with the leaves of a target host mangrove, Rhizophora mucronata Lamk., with the aim to elucidate whether fungal diversity and functional traits are linked to disturbances brought about by aquaculture practices and to characterize functional traits of selected fungal isolates with respect to phosphate (PO4) and zinc (Zn) solubilization. Contrary to expectations, the disturbed site exhibited a higher fungal diversity, challenging assumptions about the relationship between contamination and fungal community dynamics. Water quality, as determined by nutrient and mineral levels, emerged as a crucial factor in shaping both microbial community compositions in the phyllosphere of mangroves. From both sites, we isolated 188 fungal endophytes, with the ND site hosting a higher number of isolates and a greater colonization rate. While taxonomic diversity marginally differed (ND: 28 species, D: 29 species), the Shannon (H' = 3.19) and FAI (FA = 20.86) indices revealed a statistically significant increase in species diversity for fungal endophytes in the disturbed mangrove site as compared to the non-disturbed area (H' = 3.10, FAI = 13.08). Our chosen mangrove fungal endophytes exhibited remarkable phosphate solubilization capabilities even at elevated concentrations, particularly those derived from the disturbed site. Despite their proficiency in solubilizing zinc across a wide range of concentrations, a significant impact on their mycelial growth was noted, underscoring a crucial aspect of their functional dynamics. Our findings revealed a nuanced trade-off between mycelial growth and enzymatic production in fungal endophytes from ostensibly less contaminated sites, highlighting the relationship between nutrient availability and microbial activities. These insights provide a foundation for understanding the impact of anthropogenic pressures, specifically nutrient pollution, on mangrove-associated fungal endophytes.
RESUMO
Clinical experience with hydralazine has led to conflicting data concerning its effect on the pulmonary vasculature. We studied the effects of hydralazine on the hypoxic pulmonary vasoconstrictor response in 9 dogs challenged with inhalation of 10% oxygen in the presence and absence of hydralazine. Prior to administration of the drug, hypoxia increased cardiac output from 174 +/- 13 to 209 +/- 21 ml/kg/min (p less than 0.05) and pulmonary artery pressure from 9 +/- 1 to 19 +/- 1 mmHg (p less than 0.05). After hydralazine, cardiac output rose during normoxia to 275 +/- 30 and during hypoxia to 305 +/- 34 ml/kg/min (p less than 0.05). Pulmonary artery pressure continued to respond to hypoxia, rising from 11 +/- 1 to 21 +/- 1 mmHg (p less than 0.05) in the presence of hydralazine. Hydralazine reduced pulmonary vascular resistance during normoxia from 173 +/- 14 to 136 +/- 13 dynes X s X cm-5 (p less than 0.05) but even after the drug, pulmonary vascular resistance rose sharply during hypoxia. There was no significant difference in the response to hypoxia of pulmonary artery pressure or pulmonary vascular resistance after hydralazine when compared with that before hydralazine. In a second set of 6 dogs, we repeated these experiments but volume-depleted the dogs after the administration of hydralazine to prevent the passive pulmonary vasodilation that occurs because of the rise in cardiac output with the drug. We again found no inhibition of hypoxic pulmonary vasoconstriction by hydralazine. Finally, we administered sodium nitroprusside to 4 dogs using the same model and found a significant inhibition of hypoxic pulmonary vasoconstriction. Hydralazine, unlike nitroprusside, does not inhibit the pulmonary vascular response to hypoxia.