Resumen: En los últimos años, el estudio de la vitamina D ha aumentado debido al incremento en la incidencia de personas que presentan niveles deficientes de esta vitamina. Pocos alimentos contienen vitamina D3 de manera natural, siendo la principal fuente de obtención la radiación solar ultravioleta (UV), la cual desencadena la síntesis en la superficie de la piel. En este estudio se determinó la irradiancia solar UV efectiva para la síntesis de pre-vitamina D3 en la ciudad de Rosario, Argentina, utilizando tres métodos: a) Coeficiente de proporcionalidad, b) Ecuación de Herman y c) Modelo TUV. Los valores se compararon para condiciones de cielo despejado al mediodía solar. Se calcularon los Tiempos de Exposición Solar (TES) que alcanzan las dosis mínimas de radiación solar UV para la síntesis de la pre-vitamina D3 y para producir eritema, en el periodo junio 2019 - mayo 2020. Se discute la variación de los TES para acumular una dosis mínima para la síntesis de pre-vitamina D3 y aparición de eritema con una fotoexposición del 25% de la superficie corporal (la cara, el cuello y los brazos).

Abstract: In the last years, the study of vitamin D has raised due to the increase in the incidence of people who have deficient levels of this vitamin. Few foods contain vitamina D3 naturally, the main source of obtaining the ultraviolet (UV) solar radiation, which triggers the synthesis on the skin’s surface. In this study, the effective UV solar irradiance for the synthesis of pre-vitamin D3 was determined in Rosario city, Argentina, using three methods: a) Proportionality Coefficient, b) Herman’s equation and c) TUV model. The values were compared in clear sky conditions at solar noon. The Solar Exposure Times (TES) that reach the minimum doses of solar UV radiation for the synthesis of pre-vitamin D3 and erythema were calculated, along the period june 2019 - may 2020. The variation of the TES to accumulate the minimum dose of pre-vitamin D3 and erythema with a photoexposure of 25% of the body (face, neck and arms) is discussed.

The presence of virulence genes (VG) and bacteriocins from different clinical samples was studied in Enterococcus faecalis isolated from urinary tract infections (UTI), bacteremia and endodontitis and was correlated with haemolysin and gelatinase activity. We evaluated the presence of VG by PCR in 150 strains of E. faecalis including cylA, aggA, efaA, eep, gelE, esp, as-48, bac31, entL50A/B, entA, entP, entB, enlA andentl071. Haemolysin and gelatinase activity was studied. gelE and cylA genes expressed hemolysin and gelatinase, respectively. This activity was observed in some strains of bacteremia, UTI and endodontitis. The highest number of VG was detected in bacteremic strains, being aggA and entA genes the most frequent. efaA, esp, entA, entL50A/B were associated with their clinical origin (p < 0.05). The most common genetic profile was aggA-eep-enlA-entL50A/B. E. faecalis from UTI, bacteremia and endodontitis presented different gene combinations. Some of the genes studied were related to their clinical origin. The results obtained in this study are similar to those reported in other countries.

Desde diferentes muestras clínicas se determinó la presencia de genes codificantes de factores de virulencia (FV) y bacteriocinas en Enterococcus faecalis aislados desde infecciones del tracto urinario (ITU), bacteriemias y endodontitis, correlacionándose con la actividad hemolisina y gelatinasa. En 150 cepas de E. faecalis fue evaluada mediante RPC la presencia de cylA, aggA, efaA, eep, gelE, esp, as-48, bac31, entL50A/B, entA, entP, entB, enlA, y ent1071 determinándose actividad hemolisina y gelatinasa. Los genes cylA y gelE expresaron hemolisina y gelatinasa, respectivamente. Esta actividad fue observada en algunas de las cepas causantes de bacteriemia, ITU y endodontitis. El mayor número de genes estudiados se detectó en cepas bacteriémicas. Los genes aggA y entA, fueron los más frecuentes. Los genes efaA, esp, entL50/AB y entA se asociaron a su origen clínico (p < 0,05). El perfil genético más recurrente fue aggA-eep-enlA-entL50A/B. Enterococcusfaecalis de ITU, bacteriemias y endodontitis presentaron distintas combinaciones génicas. AAlgunos de los genes estudiados se relacionaron con su origen clínico. Los resultados obtenidos son similares a los reportados en otros países.

The objective of this study was to obtain landscape fragility indexes (LFI) as a way of acquiring trustworthy data for a sustainable use of soils in the Coatepec- La Antigua basin, in Veracruz, Mexico. For collecting landscape data, an altitude transect was done from 3200 m on the east side of the Cofre de Perote mountain, up to the sea level, close to the city of Veracruz. National forestry inventory data and soil use charts were used along with GIS techniques to generate images showing landscape fragility resulting from soil use. Geographical data were contrasted with socioeconomic characteristics in the region and with the social value of landscapes for the inhabitants. Results show that high LFI (grade 5) correspond to only 2.8% of the landscape; a 22.5% were classified as medium-high (grade 4), and are related to high and medium forest in the mountain range. The most fragile areas are located in the upper parts of the basin, which is coincidental with the highest marginality indexes, the highest population density, and factors of socioeconomic fragility such as international migration fluxes and lower income.

El objetivo del trabajo fue obtener índices de fragilidad del paisaje (IFP) como una forma de proporcionar datos confiables para el uso sostenible del suelo en la Cuenca Coatepec- La Antigua, Veracruz, México. Se incorporó un transecto altitudinal de colecta de datos de paisaje, desde los 3200 m en la cara oriental del cofre de Perote, hasta el nivel de mar, cerca de la ciudad de Veracruz. Se utilizaron datos del inventario nacional forestal y cartas de uso del suelo para, con sistemas de información geográficos para generar imágenes que muestran la fragilidad de los paisajes por uso del suelo. Los datos geográficos fueron contrastados con las características socioeconómicas de la región y el valor social de los paisajes para la población que los habita. Los resultados muestran que los IFP altos (5), se localizan en el 2.8 % del paisaje, el 22.5 % se clasificaron como medio-alto (4), e inciden en zonas de bosque, selva mediana y selva alta, en la zona de montaña. Las áreas más frágiles se localizan en las partes altas de la Cuenca, lo cual coincide con los mayores índices de marginalidad, mayor densidad de población y factores de fragilidad socioeconómica como flujo migratorio internacional y menor ingreso.

Environmental and genetic factors affecting the in vitro spontaneous mutation frequencies to aminoglycoside resistance in Escherichia coli K12 were investigated. Spontaneous mutation frequencies to kanamycin resistance were at least 100 fold higher on modified Luria agar (L2) plates, when compared to results obtained in experiments carried out with Nutrient agar (NA) plates. In contrast to rifampincin, the increased mutability to kanamycin resistance could not be attributed to a mutator phenotype expressed by DNA repair defective strains. Kanamycin mutant selection windows and mutant preventive concentrations on L2 plates were at least fourfold higher than on NA plates, further demonstrating the role of growth medium composition on the mutability to aminoglycosides. Mutability to kanamycin resistance was increased following addition of sorbitol, suggesting that osmolarity is involved on the spontaneous mutability of E. coli K12 strains to aminoglycosides. The spontaneous mutation rates to kanamycin resistance on both L2 and NA plates were strictly associated with the selective antibiotic concentrations. Moreover, mutants selected at different antibiotic concentrations expressed heterogeneous resistance levels to kanamycin and most of them expressing multiple resistance to all tested aminoglycoside antibiotics (gentamicin, neomycin, amykacin and tobramycin). These results will contribute to a better understanding of the complex nature of aminoglycoside resistance and the emergence of spontaneous resistant mutants among E. coli K12 strains.