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Hermes-Lima, M., Moreira, D. C., Rivera-Ingraham, G. A., Giraud-Billoud, M., Genaro-Mattos, T. C., & Campos, É. G. (2015). Preparation for oxidative stress under hypoxia and metabolic depression: Revisiting the proposal two decades later. Free Radical Biology and Medicine, 89, 1122–1143.
Résumé: Organisms that tolerate wide variations in oxygen availability, especially to hypoxia, usually face harsh environmental conditions during their lives. Such conditions include, for example, lack of food and/or water, low or high temperatures, and reduced oxygen availability. In contrast to an expected strong suppression of protein synthesis, a great number of these animals present increased levels of antioxidant defenses during oxygen deprivation. These observations have puzzled researchers for more than 20 years. Initially, two predominant ideas seemed to be irreconcilable: on one hand, hypoxia would decrease reactive oxygen species (ROS) production, while on the other the induction of antioxidant enzymes would require the overproduction of ROS. This induction of antioxidant enzymes during hypoxia was viewed as a way to prepare animals for oxidative damage that may happen ultimately during reoxygenation. The term “preparation for oxidative stress” (POS) was coined in 1998 based on such premise. However, there are many cases of increased oxidative damage in several hypoxia-tolerant organisms under hypoxia. In addition, over the years, the idea of an assured decrease in ROS formation under hypoxia was challenged. Instead, several findings indicate that the production of ROS actually increases in response to hypoxia. Recently, it became possible to provide a comprehensive explanation for the induction of antioxidant enzymes under hypoxia. The supporting evidence and the limitations of the POS idea are extensively explored in this review as we discuss results from research on estivation and situations of low oxygen stress, such as hypoxia, freezing exposure, severe dehydration, and air exposure of water-breathing animals. We propose that, under some level of oxygen deprivation, ROS are overproduced and induce changes leading to hypoxic biochemical responses. These responses would occur mainly through the activation of specific transcription factors (FoxO, Nrf2, HIF-1, NF-κB, and p53) and post translational mechanisms, both mechanisms leading to enhanced antioxidant defenses. Moreover, reactive nitrogen species are candidate modulators of ROS generation in this scenario. We conclude by drawing out the future perspectives in this field of research, and how advances in the knowledge of the mechanisms involved in the POS strategy will offer new and innovative study scenarios of biological and physiological cellular responses to environmental stress.
Mots-Clés: Anoxia; Dehydration; Estivation; Freeze tolerance; Hypoxia tolerance; Ischemia
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Paulino, C., Aroni, E., Xu, H., Alburqueque, E., & Demarcq, H. (2017). Use of nighttime visible images in the study of the spatial and temporal variability of fishing areas of jumbo flying squid (Dosidicus gigas) outside Peruvian EEZ 2004-2015. Fish Res., 191, 144–153.
Résumé: We analyzed the temporal variability of the fishing fleet of Dosidicus gigas, located outside the exclusive economic zone of Peru (EEZ), with a spatial luminosity index. The nighttime satellite images were provided by the Operational Linescan System (DMSP-OLS) from 2004 to 2015. 2995 images were processed, selecting pixels in the range of 30-63 Digital Number (DN), to identify the presence of vessels in the image. The time series showed an extensive latitudinal distribution of the fishing fleet from 6 degrees S to 32 degrees S, with years of low (2005-2009) and high (2004, 2010-2015) presence, describing a recurrent seasonal pattern of latitudinal displacement measured from its center of gravity (CG). The CG reaches its southernmost position between February to April and its northernmost position between August to October. Some vessels were also detected within the Peruvian EEZ. The latitudinal inertia presented values of 0.3-1 indicating high fleet concentration between 12 degrees S to 17 degrees S and the longitudinal inertia presented values >2, showing the wide distribution of the resource. Luminous pixels showed high fishing occurrence (>18 times) on a single pixel, in front of Chimbote around 9 degrees 51'S-82 degrees 31'W from 2004 to 2011. From 2012 to 2015 areas of high fishing occurrence increased in front of Huarmey (10 degrees 36'S/82 degrees 41'W) and San Juan de Marcona (15 degrees 53'S/80 degrees 6'W). For both periods, high intensity pixels (DN >60) show extensive areas of fishing operation between 9 degrees S to 20 degrees S along 200 nautical miles from the coast, while values between 30 and 45 DN could be mostly associated with the search for fishing zones. Since 2012, pixels with DN >58 have increased, indicating a greater fishing activity likely related to a higher availability of the resource or a better knowledge of the fishing zones, associated with an increase of the fishing effort and a possible higher pressure on the resource. (C) 2017 Elsevier B.V. All rights reserved.
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