Esteban R.,University of the Basque Country |
Fernandez-Marin B.,University of the Basque Country |
Hernandez A.,University of the Basque Country |
Jimenez E.T.,University of Seville |
And 10 more authors.
Trees - Structure and Function | Year: 2013
Mangrove forests are ecosystems made up of several woody plants living in saline coastal sedimentary habitats. In order to deal with the high salinity of the substrate, mangrove trees possess a number of different mechanisms to exclude, sequestrate or excrete the excess of salt. The black mangrove (Avicennia germinans L.), one of the dominant species in Central America, is characterized by high levels of salt excretion through epidermal glands. In this study, our aim was to examine whether, apart from its obvious role in salt tolerance, the formation of salt crystals on the upper leaf surface of black mangrove might represent an unusual and dynamic photoprotection mechanism. For this purpose, the reflection of light and a number of physiological parameters were studied during the dry and rainy seasons in black mangroves growing in the Juan Venado Island Nature Reserve (Nicaragua). Excreted salt increased the reflectance of the leaf surface mainly in the blue and red regions of the spectrum. By removing salt crust from the leaf surface, we demonstrated that during the most stressful periods (dry season at noon), this feature allowed leaves to maintain a higher photochemical efficiency and a lower leaf temperature as compared to uncovered leaves. Furthermore, this mechanism is fully reversible when conditions become more favorable, as salt crystals dissolve, forming drops. Thus, while being a detoxification mechanism developed mainly to avoid osmotic imbalance in the tissues, the excretion of salt through the leaves in black mangroves is an example of "exaptation", as it has positive collateral effects on the photosynthetic performance of the plant, protecting A. germinans from overheating and photodamage during the harsher periods. © 2012 Springer-Verlag Berlin Heidelberg.
Raines N.,Mount Sinai School of Medicine |
Gonzalez M.,National Autonomous University of Nicaragua, León |
Wyatt C.,Mount Sinai School of Medicine |
Kurzrok M.,Mount Sinai School of Medicine |
And 10 more authors.
MEDICC Review | Year: 2014
INTRODUCTION: Mesoamerican nephropathy, also known as chronic kidney disease of unknown etiology, is widespread in Pacific coastal Central America. The cause of the epidemic is unknown, but the disease may be linked to multiple factors, including diet as well as environmental and occupational exposures. As many as 50% of men in some communities have Mesoamerican nephropathy. OBJECTIVE: Describe prevalence of reduced glomerular filtration rate in a region of Nicaragua suspected to harbor high rates of Mesoamerican nephropathy; and investigate potential risk factors for such reduction associated with agricultural work (such as pesticide exposure and specific agricultural tasks associated with increased heat stress); sugar consumption; and traditional factors such as age, sex, diabetes, hypertension and nephrotoxic medication use. METHODS: This study uses a cross-sectional design with nested case-control analysis. Cases were individuals with estimated glomerular filtration rates of <60mL/min/1.73m2 and controls were individuals with those >90mL/min/1.73m2, estimated using serum creatinine. Data on nutrition, past medical history, medication and substance use, and agricultural behaviors and exposures were collected using medical questionnaires from June through August, 2012. Venous blood and urine samples were collected to assess hemoglobin A1c, and dipstick proteinuria, respectively; anthropometry and blood pressure measurements were made using standard techniques. Analyses were conducted using chi square, and univariate and multiple logistic regression. RESULTS: Of 424 individuals in the study, 151 had an occupational history in agriculture. Prevalence of glomerular filtration rate <60mL/min/1.73m 2 was 9.8% among women and 41.9% among men (male to female ratio = 4.3, p<0.0001). Proteinuria ≥300 mg/dL was observed in <10% of participants with decreased glomerular filtration rate. Hemoglobin A1c and use of NSAIDs were not associated with decreased glomerular filtration rate. Although systolic and diastolic blood pressure was higher among participants with decreased glomerular filtration rate (p <0.001), hypertension was uncommon. Significant agricultural risk factors for reduced glomerular filtration rate included increased lifetime days cutting sugarcane during the dry season (OR 5.86, 95% CI 2.45-14.01), nondeliberate pesticide inhalation (OR 3.31, 95% CI 1.32-8.31), and sugarcane chewing (OR 3.24, 95% CI 1.39-7.58). CONCLUSIONS: Our findings demonstrate a high prevalence of chronic kidney disease not linked to traditional risk factors, and suggest it may be associated instead with occupational exposure to heat stress in conjunction with pesticide inhalation, sugarcane chewing and sugar intake during the workday.