Diffuse reflectance spectroscopy accurately discriminates early and advanced grades of fatty liver in mice.

Nonalcoholic fatty liver disease (NAFLD) ranges from steatosis to nonalcoholic steatohepatitis and cirrhosis. Liver biopsy, considered the gold standard to diagnose NAFLD, shows significantly high rates of interobserver variability. Thus there is a need to develop tools that accurately categorize mild and advanced grades of steatosis in order to identify patients at higher risk of developing chronic liver disease. Diffuse reflectance spectroscopy (DRS) has proved to be useful in grading liver fibrosis and cirrhosis, without having been implemented for steatosis. We aim to categorize early and advanced stages of liver steatosis in a methionine-choline deficient (MCD) mouse model. C57bl/6 mice are fed either methionine-choline control or MCD diet during 2 or 8 weeks to induce mild and advanced steatosis. Liver samples are obtained and steatosis is evaluated by oil red O staining. Diffuse reflectance spectra are directly measured on ex vivo liver specimens, in a wavelength range of 400 to 800 nm. DRS is able to discriminate between early or advanced steatosis and healthy hepatic tissue with negligible error while showing high average sensitivity and specificity (0.94 and 0.95, respectively). Our results suggest that liver steatosis can be accurately evaluated by DRS, highlighting the importance of applied spectroscopic methods in assessing NAFLD.

Development of a passive doas system to retrieve atmospheric pollution columns in the 200 to 355 nm region.

In recent years several techniques have been developed to measure and monitor the pollution of the air. Among these techniques, remote sensing using optical methods stands out due to several advantages for air quality control applications. A Passive Differential Optical Absorption Spectroscopy system that uses the ultraviolet region from 200 to 355 nm of the solar radiation is presented. The developed system is portable; therefore it is practical for real time and in situ measurements. The enhanced wavelength range of the system is intended to detect the ultraviolet light penetration in the Mexican Valley considering the solar zenith angle and the altitude. The system was applied to retrieve atmospheric SO2 columns emitted either by anthropogenic (power plant) or natural sources (volcano), reaching a detection limit of about 1 ppm. The measurement of the penetrating solar radiation on the earth surface at the UVC range is presented and the possibility to measure pollution traces of some contaminants as O3, NO2 and aromatic compounds in real time and in situ in the ultraviolet region is discussed.