Effects of Gamma Ray Bursts in Earth Biosphere

We continue former work on the modeling of potential effects of Gamma Ray Bursts on Phanerozoic Earth. We focus on global biospheric effects of ozone depletion and show a first modeling of the spectral reduction of light by NO2 formed in the stratosphere. We also illustrate the current complexities involved in the prediction of how terrestrial ecosystems would respond to this kind of burst. We conclude that more biological field and laboratory data are needed to reach even moderate accuracy in this modelingComment: Accepted for publication in Astrophysics & Space Scienc

Experimental model of actinic keratosis due to exposure to ultraviolet A radiation

Las queratosis actínicas son lesiones cutáneas preneoplásicas frecuentes causadas por una exposición crónica a las radiaciones solares. La obtención de modelos animales que contribuyan a comprender los mecanismos implicados en esta patología y a evaluar nuevas terapias farmacológicas resulta de gran interés para la comunidad científica. Se desarrolló un biomodelo de queratosis actínica en ratones Balb/c, empleando como inductor la radiación UVA. Se aplicaron dos esquemas de irradiación: Grupo I, expuesto a tres sesiones diarias de radiación de 2 h y Grupo II, dos sesiones diarias de 4 h, con igual tiempo de receso entre sesiones y durante un período de 14 días. Se evaluaron parámetros macroscópicos y microscópicos, y la frecuencia de aparición de micronúcleos en sangre periférica. Los animales correspondientes al Grupo I no mostraron lesiones mascroscópicas y microscópicamente evidenciaron una leve acantosis con ausencia de displasia; mientras que en los animales del Grupo II se observaron lesiones macroscópicas que se correlacionan histopatológicamente con la presencia de una queratosis actínica. La frecuencia de micronúcleos obtenida en el Grupo II fue significativamente superior a la formación de micronúcleos espontáneos en el Grupo Control. El biomodelo experimental de queratosis actínica obtenido reproduce el efecto de las radiaciones ultravioletas sobre la piel.Actinic keratoses are frequent preneoplastic skin lesions caused by chronic exposure to solar radiation. Obtaining animal models that contribute to understanding the mechanisms involved in this pathology and evaluating new pharmacological therapies is of great interest to the scientific community. A biomodel of actinic keratosis was developed in Balb/c mice, using UVA radiation as an inducer. Two irradiation schemes were applied: Group I, exposed to three daily radiation sessions of 2 h and Group II, two daily sessions of 4 h, with the same break time between sessions and for a period of 14 days. Macroscopic and microscopic parameters were evaluated, as well as the frequency of appearance of micronuclei in peripheral blood. The animals corresponding to Group I did not show mascroscopic lesions and microscopically they showed a slight acanthosis with the absence of dysplasia; while in Group II animals macroscopic lesions were observed that histopathologically correlate with the presence of an actinic keratosis. The frequency of micronuclei obtained in Group II was significantly higher than the formation of spontaneous micronuclei in the Control Group. The experimental biomodel of actinic keratosis obtained reproduces the effect of ultraviolet radiation on the skin.Ciencias Experimentale

Evaluación del efecto de tres condiciones de cultivo in vitro en la calidad de plántulas de caña de azúcar propagadas en Biorreactores de Inmersión Temporal

Structural and functional deficiencies that affect survival during acclimatization are present in micropropagated plants. The current study was carried out to determine the effect of three in vitro culture conditions (autotrophic, mixotrophic and moderate mixotrophic) on the morph-physiological and biochemical behavior of plantlets of sugar cane propagated in Temporary Immersion Bioreactors (BIT). Morphological and physiological indicators and key enzymes of carbon metabolism were evaluated. Plantlets that were subjected to autotrophic conditions did not survive due to the stress caused by the absence of sucrose in the culture medium. For this reason it could not be evaluated. The best results were obtained for the condition of moderate mixotrofical. In this case, the morphological variables, height of the plants, fresh weight and dry weight, responded positively. It was minimum the answer of the net photosynthesis in vitro and increased it notably from the second week of acclimatization. Plants with a mixotrophic growth showed very high values of transpiration and estomatic conductance at the beginning of the elongation and during the first week of acclimatization. This group of plants took a longer time than the rest in achieving the control of the loss of water and in reaching a functional stability. Plants that showed a bigger activity of pyruvate kinase were those coming from mixotrophic conditions. An inverse behavior was observed in the phosphoenolpyruvate carboxylase. The activities of syntase sucruse and the neutral invertase were superior for the mixotrofic conditions.Key words: autotrofic, enzymes, mixotrofic, photosynthesisLas plantas micropropagadas poseen deficiencias estructurales y funcionales que comprometen su supervivencia durante la aclimatización. El objetivo de este trabajo fue determinar el efecto de tres condiciones de cultivo in vitro (autotrófica, mixotrófica y de mixotrofismo moderado) en el comportamiento morfo-fisiológico y bioquímico de plántulas de caña de azúcar propagadas en Biorreactores de Inmersión Temporal (BIT). Se evaluaron indicadores morfológicos, fisiológicos y enzimas clave del metabolismo del carbono. Las plántulas que se sometieron a condiciones autotróficas no lograron sobrevivir debido al estrés propiciado por la ausencia de sacarosa en el medio de cultivo. Por esta razón no pudieron ser evaluadas. Los mejores resultados se obtuvieron para la condición de mixotrofismo moderado. En este caso, las variables morfológicas altura de las plantas, masas fresca y seca respondieron positivamente. La respuesta de la fotosíntesis neta fue muy baja in vitro y aumentó notablemente a partir de la segunda semana de aclimatización. Para las plántulas con un desarrollo mixotrófico se observaron valores de transpiración y conductancia estomática muy elevados al inicio de la elongación y durante la primera semana de aclimatización. Este grupo de plántulas se tardó más que el resto en lograr el control de la pérdida de agua y en alcanzar una estabilidad funcional. Las plantas que mostraron una mayor actividad de la Piruvato Quinasa fueron provenientes de condiciones mixotróficas. La Fosfoenol Piruvato Carboxilasa tuvo un comportamiento totalmente inverso. Las actividades de la Sacarosa Sintasa y la Invertasa Neutra, al igual que la Piruvato Quinasa, fueron superiores para las condiciones mixotróficas.Palabras clave: autotrofismo, enzimas, fotosíntesis, mixotrofism

Short-term effects of gamma ray bursts on oceanic photosynthesis

We continue our previous work on the potential short-term influence of a gamma ray bursts on Earth’s biosphere, focusing on the only important short-term effect on life: the ultraviolet flash which occurs as a result of the retransmission of the γ radiation through the atmosphere. Thus, in this work we calculate the ultraviolet irradiances penetrating the first hundred meters of the water column, for Jerlov’s ocean water types I, II and III. Then we estimate the UV flash potential for photosynthesis inhibition in the whole photic zone, showing that it can be important in the first tens of meters of the water column.Peer reviewe

The photobiological regime and oceanic primary production

Peer Reviewe

Influence of solar and geomagnetic storms on terrestrial photosynthesis

It is reviewed the potential influence of solar and geomagnetic storms on terrestrial photosynthesis. Then it is presented a modification of a physical-mathematical model of photosynthesis published by some of us, which allows quantifying the influence of particulate ionizing radiation on this biological process. Some guidelines to obtain this new model from first principles are mentioned and it is applied to some case studies including atmospheric and geomagnetic perturbation due to solar storms

Influence of solar and geomagnetic storms on terrestrial photosynthesis

It is reviewed the potential influence of solar and geomagnetic storms on terrestrial photosynthesis. Then it is presented a modification of a physical-mathematical model of photosynthesis published by some of us, which allows quantifying the influence of particulate ionizing radiation on this biological process. Some guidelines to obtain this new model from first principles are mentioned and it is applied to some case studies including atmospheric and geomagnetic perturbation due to solar storms