One of the most used ecotoxicity bioassays is based on the luminescence of Vibrio fischeri, for which commercial kits such as Microtox® and several others are available. However, this assay might not always be suitable for several reasons: Its protocol cannot be easily adapted for particular purposes, and it requires the continuous purchases of the kit and the availability of specialized equipment or at least, a luminometer. As a versatile alternative, this paper describes an optimized and kit-free protocol, referred to as “Macrotox”, which allows a wide range of treatment periods (for example, 1, 3, 7, 12, 24, 30 and 36 h) to follow the effects on the luminescence and proliferation of V. fischeri. While the optimized protocol involves 1-mL treatments, it could be easily adapted to use other volumes and times. Importantly, to evaluate the effects on luminescence, only a digital came...

En este trabajo se determinaron los niveles de secreción conferidos por dos diferentes mecanismos en la levadura Saccharomyces cerevisiae, aplicados a la enzima glutatión S-transferasa (GST) y mediante ensayos de electroforesis y Western blot (o transferencia Western). Se construyeron previamente plásmidos que permiten la producción de dos tipos de GST fusionadas con sendas secuencias que facilitan su secreción (péptidos de señal, PS): el PS-Alfa (derivado del factor de apareamiento alfa) y un PS-sintético (diseñado a partir de secuencias de consenso derivadas de proteínas que son eficientemente secretadas en la levadura). Después de la separación electroforética de las muestras de proteínas intracelulares y extracelulares, se realizó un ensayo de Western blot que permitió la detección específica de GST mediante un anticuerpo monoclonal. Los ensayos permitieron la ident...

An assay based on the survival rates of UV-irradiated yeast Saccharomyces cerevisiae cells was used to compare the photoprotectant capabilities of several commercial sunscreens with different sun protection factors (SPFs). Ten lotions with SPF values from 15 to 100 were tested using UVB and UVC irradiations. The results showed that all lotions with SPFs ≥50 exhibited similar photoprotectant capabilities. However, the lotions with SPF 15 and SPF 30 exhibited proportionally lower photoprotection levels. Likewise, the prices per gram of the analyzed lotions were compared, finding them widespread. Since the photoprotection levels of the lotions with SPF values above 50 were equivalent, it could be inferred that other factors are responsible for the variations in the prices, such as the recognition of the brand name, product presentation, marketing strategies, and others. This work shows th...

This work focuses on simple methods that allow comparison of the photoprotective effects of sunscreens. One such method described by Mansur and colleagues relies on the spectrophotometric measurements of the organic filters extracted with ethanol. The extracts are subjected to absorbance measurements in the of 290 to 320 nm range, with 5 nm intervals. The sunscreen sun protection factor (SPF) is estimated with an equation that relates each absorbance value with their respective erythemal effect, at the wavelength used for each measurement. In the current work, three commercial sunscreens were assayed using this method, which produced SPF values that were markedly lower than those declared by the manufacturers. These results prompted a more thorough analysis, which concluded that the Mansur method is not suitable for assaying sunscreens with SPFs above 15. The analysis included a survey o...