Sulfur and nitrogen compounds in wet atmospheric deposition on the coast of the Gulf of Mexico from 2003 to 2015.

The Gulf of Mexico region has important sources of acid rain precursors, located in all of the countries; U.S., Mexico and Cuba, and so it is very important to study the chemical composition of the wet atmospheric deposition in all coastal areas. For many years along the U.S. Gulf Coast, acidic precipitation has been measured. Measurements along the Mexican Gulf Coast were begun in 2003. The aim of this study was to evaluate pH, sulfate, nitrate and ammonium concentrations in wet atmospheric deposition, collected daily from 2003 to 2015 at La Mancha (LM), Veracruz and compare the values with the National Atmospheric Deposition Program (NADP) sampling sites located along the U.S. coast of the Gulf of Mexico. The annual Volume Weighted Mean (VWM) pH in wet deposition at La Mancha site ranged from 4.81 to 5.40, which is similar to the U.S. Gulf sites. Additionally, the annual VWM SO42- concentration was from 15 to 31 µeq/L, which is higher than the U.S. sites. Annual VWM NO3- concentrations were from of 3.5 to 15 µeq/L, which is lower than all the U.S. sites. At the Mexican site, the SO42-/NO3- ratio was 4.90 and higher than all of the U.S. sites, which were between 1.03 and 2.38. For LM, the median NH4+/NO3- ratio was 0.77, similar to the Florida sites (0.53-0.91), and below the values measured for Louisiana and Texas (1.07-1.5). The Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) was applied in order to identify the emission sources for the pollutants seen at LM. Trajectories showed an important transport to LM from the East (open water) during the rainy season. The region located East of La Mancha shows offshore petroleum operations as sources of acid rain precursors and deposition of acidifying and nitrogen containing compounds. It is important to consider the sulfur dioxide emission sources in the Mexico Gulf region, and to extend the atmospheric deposition sampling to other sites along the Mexican Gulf coast and Cuba.

Study of the Chemotactic Response of Multicellular Spheroids in a Microfluidic Device.

We report the first application of a microfluidic device to observe chemotactic migration in multicellular spheroids. A microfluidic device was designed comprising a central microchamber and two lateral channels through which reagents can be introduced. Multicellular spheroids were embedded in collagen and introduced to the microchamber. A gradient of fetal bovine serum (FBS) was established across the central chamber by addition of growth media containing serum into one of the lateral channels. We observe that spheroids of oral squamous carcinoma cells OSC-19 invade collectively in the direction of the gradient of FBS. This invasion is more directional and aggressive than that observed for individual cells in the same experimental setup. In contrast to spheroids of OSC-19, U87-MG multicellular spheroids migrate as individual cells. A study of the exposure of spheroids to the chemoattractant shows that the rate of diffusion into the spheroid is slow and thus, the chemoattractant wave engulfs the spheroid before diffusing through it.

Niveles de carboxihemoglobina en donadores de sangre y de monóxido de carbono atmosférico en un área de la ciudad de México / Levels of carboxyhemoglobin in blood donors and of atmospheric carbon monoxide in a Mexico City area

La ciudad de México, con una altura sobre el nivel del mar de 2,240 m, ha alcanzado un elevado nivel de contaminación ambiental. El monóxido de carbono (CO) es uno de los principales contaminantes con capacidad de producir enfermedad cardiovascular de tipo isquémico o de agravar las existentes. El objetivo de este estudio fue conocer qué niveles de carboxihemoglobina (COHb), tiene los donadores de sangre que acuden al Instituto Nacional de Cardiología "Ignacio Chávez" de la ciudad de México, y qué niveles de monóxido de carbono se respiran en la atmósfera que hay en dicho Instituto. De mayo a junio de 1994, se analizaron los niveles venosos de COHb en 186 voluntarios donadores de sangre, y se midió el monóxido de carbono atmosférico en forma cotidiana durante el mismo periodo de tiempo, dentro de la Unidad Coronaria (UC) y en la azotea del 5º piso del Instituto a una distancia aproximada de 300 m de una vía con alto flujo vehicular (periférico sur). Los niveles de COHb en los fumadores fueron de 2.4 ñ 1.4 por ciento, y en los no fumadores de 1.5 ñ 0.6 por ciento, p= 0.002, cifra mucho más alta a la que se tiene de la producción endógena de este gas (0.5 por ciento), pero similar a la informada en otras ciudades del planeta. Los niveles de CO atmosférico nunca sobrepasaron las 4 partes por millón (ppm) (máximo pemitido por la Secretaría de Salud: 11 ppm), Los niveles de COHb no correlacionan con los parámetros estudiados: ocupación laboral, zona de la ciudad en que se habita o trabaja, medio de transporte usado para llegar al Instituto y número de kilómetros recorridos el día antes de la toma de la muestra, pero sí con el tabaquismo. Niveles de CO como los que se respiran en el aire de la UC y en la azotea del Instituto Nacional de Cardiología, no constituyen un peligro para la salud.