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Rob Rubin Group

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Dj Maeli Oxygen

In the current study, we showed that the morphological injury severity induced by ischaemia of 4 h increased progressively according to perfusion duration. A slow twitch muscle with aerobic metabolism, soleus, was selected (Bigard et al. 1998) because it is considered a muscle more sensitive to ischaemia when compared with the fast twitch muscle, such as gastrocnemius (Karpatti et al. 1974; Jennische et al. 1979). In fact, gastrocnemius has both oxidative and glycolytic metabolism and it is composed by a heterogeneous mixture of type 1 and type 2 muscle fibres. On the other hand, soleus predominantly has type 1 muscle fibres (slow twitch) with an oxidative metabolism and therefore more sensitive to changes of oxygen providing, when compared with gastrocnemius.

Dj Maeli Oxygen

Reports have shown a relationship among insults of IR, alterations in tissue oxygen metabolism and cellular changes (Santavirta et al. 1979; Carvalho et al. 1997; Troitzsch et al. 2005; Zimiani et al. 2005). Impairment between free radicals and antioxidant production lead to oxidative stress. This mechanism is often related to the cell degeneration process. In the current study, we did identify a pronounced inflammatory infiltrate (IR-1 h, IR-24 h), which could stimulate free radical production and therefore the oxidative stress. In addition, it was observed a progressive morphological and histochemical degeneration from IR-1 h until IR-24 h. The severity degree was accompanied by decrease of oxidative metabolism (NADH-TR/SDH), showing moderate (I, IR-1 h, IR-24 h) to weak (IR-72 h) reactivity. The change of oxidative metabolism was specially observed between IR-24 h and IR-72 h, indicating an oxidative stress reduction. This statement is supported by fibres in regeneration process identified morphologically at 72nd hour of reperfusion. Besides the less pronounced inflammatory infiltrate, we also observed weak reactivity by histochemical analyses at IR-72 h. These conditions may represent an environment of low oxidative stress. Previous studies have shown that oxidative stress leads to progressive cell changes, but the antioxidant supplementation can attenuate this process (Marchetti et al. 1999; McCord et al. 2000). Metabolism and IR injury also have been studied in skeletal muscles by biochemical analysis and no alterations were observed when the evaluation occurs immediately after 4 h of ischaemia period (Korthuis et al. 1985), but changes appear after 2 h of reperfusion (Troitzsch et al. 2005), suggesting a progressive metabolism alteration.

Muscle growth reflects the balance between protein synthesis and degradation. These two processes are influenced by numerous biotic and abiotic factors including food availability, growth factors, age, sex, diet composition, swimming activity, oxygen saturation, light and temperature [8,9]. The Insulin-like growth factor (Igf) network, composed of Igfs, binding proteins (Igfbp) and receptors (Igf1r and Igf2r), plays a pivotal role in integrating internal and external inputs to regulate muscle mass [8]. Igf1 regulates several signalling pathways including the Pi3k/Akt/mTor network that controls protein synthesis [8,9]. Typically, fibre production continues until 45% of the maximum body length of the fish, and subsequent growth is entirely by fibre elongation and hypertrophy [10-12]. Myogenesis involves the activation, proliferation and fusion of a resident myoblast population involving hundreds of structural and regulatory genes [10,11].

Food intake, composition and availability represent important factors leading to muscle growth6. In general, fish exhibit mammal-like nutritional requirements for growth, reproduction and other physiological functions, and in confinement, fish require a nutritionally complete and balanced diet13. Several studies have shown that ascorbic acid (vitamin C) plays an important role in the diet of fish. Ascorbic acid-deficient diets, especially fed to larvae fish14, promote reduced growth, impaired feed conversion, skeletal deformities in the operculum and cartilage of the gills, anemia, delay or decrease in wound healing, reduction in reproductive performance and decrease in hatchability13,15,16. Ascorbic acid plays several important cellular and biochemical roles as an antioxidant because of its high reducing potential17. Ascorbic acid neutralizes reactive oxygen species (ROS) produced during cellular metabolism or functional activities, which have deleterious effects on several molecules in excessive amounts (oxidative stress)18. Oxidative stress can be induced chemically using stressing agents, such as menadione (2-methyl-1,4-naphtoquinone)19. Menadione is a polycyclic aromatic ketone that has been widely used as an oxidant and has demonstrated cytotoxic activity via the elevation of superoxide anions and hydrogen peroxide19,20,21. As a cellular reducing agent, ascorbic acid also plays a role in collagen biosynthesis, acting as a cofactor in the hydroxylation of lysine and proline present in procollagen17. The formation of a stable collagen matrix is crucial for the structure and maintenance of connective tissue, stimulation of osteogenesis and bone growth22,23. Therefore, ascorbic acid directly influences the growth of animals, including fish species, and is necessary for the normal development of their bodies13. However, whether ascorbic acid influences fish growth exclusively due to its action on connective and bone tissues or whether it can directly influence the mechanisms of skeletal muscle growth remain unclear.

MiRNA398 was the first miRNA described as oxidative stress responsive in plants [16]. In the oxidative stress condition, generated by biotic and abiotic stresses, production of reactive oxygen species (ROS) is increased; some of these are highly toxic and must be rapidly detoxified by various cellular enzymatic and non-enzymatic mechanisms. Oxidative stress generated upon exposure to toxic concentrations of metals like copper (Cu), suppresses Arabidopsis miR398 expression that is essential for the accumulation of CSD1 and CSD2 required for ROS detoxification [16]. In addition, Arabidopsis miR398 is decreased in salt stress [17], in high light and in methyl viologen treatments [16], [18]. Down-regulation of miR398 has also been observed in Medicago sativa and M. truncatula under toxic mercury, cadmium or aluminum concentrations [19], [20]. Contrastingly, miR398 is up-regulated in nitrogen-deficient [21] and in heat-stressed Arabidopsis [22] as well as in drought-stressed M. truncatula [23]. In addition, miR398 responds to phosphate deficiency in different plant species such as Arabidopsis, common bean, soybean and tomato [5], [24], [25]. MiR398 is a central regulator for Cu homeostasis: its down-regulation in Cu toxicity results in high CSDs for ROS detoxification whereas in Cu deficiency increased levels of miR398 are observed together with increased Fe (iron) Superoxide Dismutase (FSD) that takes over ROS detoxification and limited Cu is delivered to Plastocyanin (PC), a Cu-containing protein that is essential for photosynthesis [15], [26]. The GTAC sequence present in the Arabidopsis miR398 promoter is an important feature in Cu responsiveness. This motif is recognized by the SPL7 transcription factor that binds to the promoter and regulates the expression of miR398. In addition SPL7 regulates the expression of other Cu-deficiency responsive miRNAs: miR397, miR408 and miR857 [27]. Moreover, Arabidopsis miR398 expression is regulated by sucrose [28]. Furthermore, the levels of miR398 decrease in Arabidopsis leaves infiltrated with avirulent strains of Pseudomonas syringae pv. tomato while CSD1 was up-regulated [29].

A total of 267 differentially expressed genes (P

Plant hormones play key roles in controlling cell division, plant growth and stress responses, and as such it was expected to find genes involved in their metabolism in this study. Genes related to the metabolism of abscisic acid (ABA), ethylene (ET), gibberellin (GA), auxin (IAA), and jasmonic acid (JA) were all up-regulated in L. xyli subsp. xyli-inoculated plants, mostly at 60 DAI. By contrast, no genes related to the synthesis of salicylic acid (SA) were detected. Our results are in general agreement with a previous study on hormonal changes in sugarcane conducted in a similar experimental design (Zhang et al. 2016b). The concentrations of ABA, IAA, and GA were evaluated in plants regenerated from L. xyli subsp. xyli-inoculated setts at 90, 120, 150, and 180 days after shoot emergence. Although the levels of L. xyli subsp. xyli were not evaluated as in our study, the concentration of ABA increased and of IAA decreased at all evaluation times in inoculated plants compared with noninoculated, whereas the concentration of GA decreased in the inoculated plants only at 180 days. In our study, the up-regulation of the regulatory gene in the biosynthesis of ABA (9-cis-epoxycarotenoid dioxygenase) at 60 DAI was accompanied by the up-regulation of an ABA 8-hydroxylase-1 gene involved in its degradation at the same time, possibly to cope with the increased levels of this hormone in response to higher bacterial titers. The reported reduced levels of IAA could result from the up-regulation of a gene (indole-3-acetic acid-amido synthetase GH3.8) that prevents the accumulation of free IAA (Ding et al. 2008). In addition, it is worth mentioning that the over expression of GH3.8 in rice also hinders plant growth and development (Ding et al. 2008). The up-regulation at 30 DAI of a gene coding for an oxidase (cytochrome P450 ent-kaurenoic acid oxidase) involved in the final three steps of the biosynthetic pathway of GA (Helliwell et al. 2001) suggests an expected increase rather than a decrease in the concentration of this hormone, but this could result from the differences in plant genotypes and times of analysis between our study and that of Zhang et al. (2016b). The up-regulation of three genes involved in the last two steps of the synthesis of ET (one ACC synthase and two ACC oxidases) and of two involved in the metabolism of JA (lipoxygenase [LOX] and a jasmonate ZIM motif protein) extends the range of hormonal responses of sugarcane to L. xyli subsp. xyli reported by Zhang et al. (2016b), but additional experiments are needed to confirm their predicted increased levels in planta in response to increased L. xyli subsp. xyli titers. 041b061a72


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