Fluoride exposure is associated with altered metabolism of arsenic in an adult Mexican population.

Arsenic (As) and fluoride (F) are two common groundwater toxicants. The toxicity of As is closely related to As metabolism, and several biological and environmental factors have been associated with As modification. However, limited information about the effect of F exposure on the modification of the As metabolism profile has been described. The aim of this study was to assess the interaction effect of AsF coexposure on the As metabolism profile in an adult population environmentally exposed to low-moderate As levels. A cross-sectional study was conducted in 236 adults from three Mexican communities. F and As concentrations were quantified in water samples. The concentrations of urinary F and As species [inorganic arsenic (iAs), monomethylated arsenic (MAs) and dimethylated arsenic (DMAs)] were also determined and used as exposure biomarkers. As species percentages and methylation indices were estimated to evaluate the As methylation profile. Our results showed a relationship between the water and urine concentrations of both contaminants and, a significant correlation between the As and F concentrations in water and urine samples. A statistically significant interaction of F and As exposure on the increase in MAs% (ß = 0.16, p = 0.018) and the decrease in DMAs% (ß = -0.3, p = 0.034), PMI (ß = -0.07, p = 0.052) and SMI (ß = -0.13, p = 0.097) was observed. These findings indicate that drinking water is the main source of AsF coexposure and suggest that F exposure decreases As methylation capacity. However, additional large and prospective studies are required to confirm our findings, and to elucidate the involved mechanisms of interaction and their implications in adverse health effects.

Analytical and numerical comparisons of two methods of estimation of additive × additive interaction of QTL effects

Epistasis (additive × additive interaction) plays an important role in the genetic architecture of complex traits. This study presents analytical and numerical comparisons of two methods of estimation of additive × additive interaction of QTL effects. In the first method, we observed only the plant phenotype, while in the second method we have additional information from the molecular markers observations. In this study, two data sets were analyzed: i) 150 barley (Hordeum vulgare L.) doubled-haploid lines derived from the cross Steptoe × Morex and ii) 145 doubled-haploid lines of barley obtained from the cross Harrington × TR306. In total, 153 sets of observations were analyzed. The additive × additive interaction effect calculated on the basis of the marker observations is smaller than the total additive × additive interaction effect obtained from phenotypic observations only.

Analytical and numerical comparisons of two methods of estimation of additive × additive interaction of QTL effects

Epistasis (additive × additive interaction) plays an important role in the genetic architecture of complex traits. This study presents analytical and numerical comparisons of two methods of estimation of additive × additive interaction of QTL effects. In the first method, we observed only the plant phenotype, while in the second method we have additional information from the molecular markers observations. In this study, two data sets were analyzed: i) 150 barley (Hordeum vulgare L.) doubled-haploid lines derived from the cross Steptoe × Morex and ii) 145 doubled-haploid lines of barley obtained from the cross Harrington × TR306. In total, 153 sets of observations were analyzed. The additive × additive interaction effect calculated on the basis of the marker observations is smaller than the total additive × additive interaction effect obtained from phenotypic observations only.