Survival responses in stressed organs

Apoptosis or programmed cell death is a regulated form of cell suicide executed by cysteine proteases, or "caspases", to maintain proper tissue homeostasis in multicellular organisms. Dysregulation of apoptosis leads to pathological complications including cancer, autoimmunity, neurodegenerative, and heart diseases. Beside their known function as the key executioners of apoptotic cell death, caspases were reported to mediate non-apoptotic functions. In this report we study the survival signals conveyed through caspase-3-mediated cleavage of Ras GTPase-activating proteins (RasGAP). Ubiquitously expressed, RasGAP senses caspase activity and controls the cell death/survival switch. RasGAP is cleaved once at low caspase activity and the generated N-terminal fragment (fragment N) induces a survival response by activating Ras/PI3K/Akt pathway. However, high caspase activity associated with increased stress leads to fragment Ν cleavage into fragments that do not mediate any detectable survival signals. In this thesis project we studied the role of fragment Ν in protecting stressed organs as well as in maintenance of their functionality. In response to stress in different organs, we found that mice lacking caspase-3 or unable to cleave RasGAP (Knock-In mice), and therefore unable to generate fragment N, were deficient in Akt activation and experienced increased apoptosis compared to wild-type mice. Augmented tissue damage and organ dysfunction in those mice highlight the importance of fragment Ν in activating Akt-mediated prosurvival pathway and in protection of organs during episodes of stress. In parallel we investigated the role of fragment Ν in regulating the activation of transcription factor NF-kB, a master regulator of inflammation. Sustained NF-kB activation may be detrimental by directly causing apoptosis or leading to a persistent damaging inflammation response. We found that fragment Ν is a potent inhibitor of NF-kB by favoring its nuclear export. Therefore, fragment Ν regulates NF-kB activity and contributes to a controlled response as well as maintenance of homeostasis in stressed cells. Importantly, these findings introduce new insights of how activated caspase-3 acts as a stress intensity sensor that controls cell fate by either initiating a fragment N- dependent cell resistance program or a cell suicide response. This identifies the pivotal role of fragment Ν in protection against patho-physiological damage, and encourages the development of therapies which aim to increase cell resistance to vigorous treatment. - L'apoptose, ou mort cellulaire programmée, est une forme contrôlée de suicide cellulaire exécuté par des protéines appelées caspases, dans le but de maintenir l'homéostasie des tissus sains dans les organismes multicellulaires. Un mauvais contrôle de l'apoptose peut mener à des pathologies comme le cancer, la neurodégénération et les maladies cardiaques et auto-immunes. En dehors de leur rôle connu d'exécutrices de l'apoptose, les caspases ont aussi été identifiées dans d'autres contextes non-apoptotiques. Dans ce projet, nous avons étudié les signaux de survie émis par le résultat du clivage de RasGAP par la caspase-3. Exprimée de façon ubiquitaire, RasGAP est sensible à l'activité de caspase-3 et contrôle la décision de la cellule à entreprendre la mort ou la survie cellulaire. A un taux d'activité faible, la caspase-3 clive RasGAP, ce qui mène à la génération d'un fragment N-terminal, appelé Fragment N, qui induit des signaux de survie via l'activation de la cascade Ras/PI3K/Akt. Cependant, lorsque l'activité de la caspase-3 augmente, le fragment N est clivé, ce qui a pour effet d'éliminer ces signaux de survie. Dans ce travail, nous avons étudié le rôle du Fragment N dans la protection des organes en état de stress et dans le maintien de leur fonctionnalité. En réponse à certains stress, nous avons découvert que les organes de souris n'exprimant pas la caspase-3 ou alors incapables de cliver RasGAP (souris Kl), et de ce fait n'ayant pas la possibilité de générer le Fragment N, perdaient leur faculté d'activer la protéine Akt et démontraient un taux d'apoptose plus élevé que des organes de souris sauvages. Le fait que les organes et tissus de ces souris manifestaient de graves dommages et dysfonctions met en évidence l'importance du Fragment N dans l'activation des signaux de survie via la protéine Akt et dans la neutralisation de l'apoptose induite par la caspase-3. En parallèle, nous avons investigué le rôle du Fragment N dans la régulation de l'activation de NF-kB, un facteur de transcription clé dans l'inflammation. Une activation soutenue de NF-kB peut être délétère par activation directe de l'apoptose ou peut mener à une réponse inflammatoire persistante. Nous avons découvert que le Fragment N, en favorisant l'export de NF-kB depuis le noyau, était capable de l'inhiber très efficacement. Le Fragment N régule donc l'activité de NF-kB et contribue au maintien de l'homéostasie dans des cellules stressées. Ces découvertes aident, de façon importante, à la compréhension de comment l'activation de la caspase-3 agit comme senseur de stress et décide du sort de la cellule soit en initiant une protection par le biais du fragment N, ou en induisant un suicide cellulaire. Cette étude définit le Fragment Ν comme ayant un rôle de pivot dans la protection contre des dommages patho-physiologiques, et ouvre des perspectives de développement de thérapies qui cibleraient à augmenter la résistance à divers traitements.

La indemnización de los perjuicios extrapatrimoniales en la jurisdicción de lo contencioso administrativo de Colombia

Al interior del Consejo de Estado se aplican de manera discordante los criterios objetivos y subjetivos al momento de fijar la indemnización de los perjuicios extrapatrimoniales. Lo anterior resulta problemático en tanto que se producen decisiones diferentes en casos fácticamente similares, vulnerando con ello la equidad y la seguridad jurídica. Como consecuencia de lo anterior, esta tesis está encaminada a resolver la siguiente pregunta de investigación: ¿Cuáles son los criterios que permiten que la indemnización de los perjuicios extrapatrimoniales en la jurisdicción de lo contencioso administrativo se haga de manera armónica frente a casos con supuestos fácticos similares?

Leaf gas exchange and fruit yield in sweet orange trees as affected by citrus variegated chlorosis and environmental conditions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Changes in leaf physiology caused by Calacarus heveae (Acari, Eriophyidae) on rubber tree

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Alterações histológicas e bioquímicas e potencial fisiológico de sementes de soja

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Uso de substâncias ergogênicas suplementares nutricionais em praticantes de musculação

Ergogenic substances are all nutritional or pharmacological additional devices which physiologically influence on the individual's performance. Currently, the practice of physical exercises that modern gyms have is growing and embracing a new recreational space for the population. In particular, for the male audience, weight training; and for the female audience, aerobic gymnastics. This study has the objective of explaining the importance of ergogenic resources in the physiological and psychological planes, emphasizing the point that supplementation is really valid and beneficial. To achieve the objective of the study, a literature review will be carried out, searching for scientific articles published in books, magazines and online newspapers that address some issues that cut across the thematic proposed in this work. From the point of view of Sport Psychology, the issues discussed on body image and emotional changes have concerns professionals of this area, but the literature suggests it is unnecessary the use of ergogenic substances to the concreteness of that purpose. Supplements of any kind will not be enough to transform the psychological and physiological aspects, the way the media assume conclusively. Thus, with our documentary research, we started a provocation that feeds new studies in the area. We conclude that supplementation is a resource that should be used in the final occasion, that is, if the bodybuilders (non-athletes) have time to be nourished from the normal diet, the use of supplements like whey and creatine, are not needed. Used appropriately supplements do not result in physiological damage, however, can contribute beneficially to the individual's nutrition, thus the abusing dosages, in addition to financial loss, can cause damage to the body

Short-term Physiological Changes In Roots And Leaves Of Sugarcane Varieties Exposed To H2o2 In Root Medium.

The aim of this study was to evaluate the differential sensitivity of sugarcane genotypes to H2O2 in root medium. As a hypothesis, the drought tolerant genotype would be able to minimize the oxidative damage and maintain the water transport from roots to shoots, reducing the negative effects on photosynthesis. The sugarcane genotypes IACSP94-2094 (drought tolerant) and IACSP94-2101 (drought sensitive) were grown in a growth chamber and exposed to three levels of H2O2 in nutrient solution: control; 3mmolL(-1) and 80mmolL(-1). Leaf gas exchange, photochemical activity, root hydraulic conductance (Lr) and antioxidant metabolism in both roots and leaves were evaluated after 15min of treatment with H2O2. Although, root hydraulic conductance, stomatal aperture, apparent electron transport rate and instantaneous carboxylation efficiency have been reduced by H2O2 in both genotypes, IACSP94-2094 presented higher values of those variables as compared to IACSP94-2101. There was a significant genotypic variation in relation to the physiological responses of sugarcane to increasing H2O2 in root tissues, being root changes associated with modifications in plant shoots. IACSP94-2094 presented a root antioxidant system more effective against H2O2 in root medium, regardless H2O2 concentration. Under low H2O2 concentration, water transport and leaf gas exchange of IACSP94-2094 were less affected as compared to IACSP94-2101. Under high H2O2 concentration, the lower sensitivity of IACSP94-2094 was associated with increases in superoxide dismutase activity in roots and leaves and increases in catalase activity in roots. In conclusion, we propose a general model of sugarcane reaction to H2O2, linking root and shoot physiological responses.

Experimental chronic low-frequency resistance training produces skeletal muscle hypertrophy in the absence of muscle damage and metabolic stress markers

Volitional animal resistance training constitutes an important approach to modeling human resistance training. However, the lack of standardization protocol poses a frequent impediment to the production of skeletal muscle hypertrophy and the study of related physiological variables (i.e., cellular damage/inflammation or metabolic stress). Therefore, the purposes of the present study were: (1) to test whether a long-term and low frequency experimental resistance training program is capable of producing absolute increases in muscle mass; (2) to examine whether cellular damage/inflammation or metabolic stress is involved in the process of hypertrophy. In order to test this hypothesis, animals were assigned to a sedentary control (C, n = 8) or a resistance trained group (RT, n = 7). Trained rats performed 2 exercise sessions per week (16 repetitions per day) during 12 weeks. Our results demonstrated that the resistance training strategy employed was capable of producing absolute mass gain in both soleus and plantaris muscles (12%, p<0.05). Furthermore, muscle tumor necrosis factor (TNF-alpha) protein expression (soleus muscle) was reduced by 24% (p<0.01) in trained group when compared to sedentary one. Finally, serum creatine kinase (CK) activity and serum lactate concentrations were not affected in either group. Such information may have practical applications if reproduced in situations where skeletal muscle hypertrophy is desired but high mechanical stimuli of skeletal muscle and inflammation are not. Copyright (C) 2010 John Wiley & Sons, Ltd.

Photochemical damage and comparative performance of superoxide dismutase and ascorbate peroxidase in sugarcane leaves exposed to paraquat-induced oxidative stress

The physiological responses of sugarcane (Succharion officinarum L.) to oxidative stress induced by methyl viologen (paraquat) were examined with respect to photochemical activity, chlorophyll content, lipid peroxidation and superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities. Thirty-day-old sugarcane plants were sprayed with 0, 2, 4, 6 and 8 mM methyl viologen (MV). Chlorophyll fluorescence was measured after 18 It and biochemical analyses were performed after 24 and 48 h. Concentrations of MV above 2 mM caused significant damage to photosystem II (PSII) activity. Potential and effective quantum efficiency of PSII and apparent electron transport rate were greatly reduced or practically abolished. Both chlorophyll and soluble protein contents steadily decreased with MV concentrations above 2 mM after 24 It of exposure, which became more pronounced after 48 It, achieving a 3-fold decrease. Insoluble protein contents were little affected by MV. Oxidative stress induced by MV was evidenced by increases in lipid peroxidation. Specific activity of SOD increased, even after 48 h of exposure to the highest concentrations of MV, but total activity on a fresh weight basis did not change significantly. Nondenaturing YAGE assayed with H2O2 and KCN showed that treatment with MV did not change Cu/Zn-SOD and MnSOD isoform activities. In contrast, APX specific activity increased at 2 mM MV but then dropped at higher doses. Oxidative damage induced by MV was inversely related to APX activity. It is suggested that the major MV-induced oxidative damages in sugarcane leaves were related to excess H2O2, probably in chloroplasts, caused by an imbalance between SOD and APX activities, in which APX was a limiting step. Reduced photochemical activity allowed the early detection of the ensuing oxidative stress. (c) 2007 Elsevier Inc. All rights reserved.

Changes in hemodynamic and neurohumoral control cause cardiac damage in one-kidney, one-clip hypertensive mice

Borges GR, Salgado HC, Silva CA, Rossi MA, Prado CM, Fazan R Jr. Changes in hemodynamic and neurohumoral control cause cardiac damage in one-kidney, one-clip hypertensive mice. Am J Physiol Regul Integr Comp Physiol 295: R1904-R1913, 2008. First published October 1, 2008; doi:10.1152/ajpregu.00107.2008.-Sympathovagal balance and baroreflex control of heart rate (HR) were evaluated during the development (1 and 4 wk) of one-kidney, one-clip (1K1C) hypertension in conscious mice. The development of cardiac hypertrophy and fibrosis was also examined. Overall variability of systolic arterial pressure (AP) and HR in the time domain and baroreflex sensitivity were calculated from basal recordings. Methyl atropine and propranolol allowed the evaluation of the sympathovagal balance to the heart and the intrinsic HR. Staining of renal ANG II in the kidney and plasma renin activity (PRA) were also evaluated. One and four weeks after clipping, the mice were hypertensive and tachycardic, and they exhibited elevated sympathetic and reduced vagal tone. The intrinsic HR was elevated only 1 wk after clipping. Systolic AP variability was elevated, while HR variability and baroreflex sensitivity were reduced 1 and 4 wk after clipping. Renal ANG II staining and PRA were elevated only 1 wk after clipping. Concentric cardiac hypertrophy was observed at 1 and 4 wk, while cardiac fibrosis was observed only at 4 wk after clipping. In conclusion, these data further support previous findings in the literature and provide new features of neurohumoral changes during the development of 1K1C hypertension in mice. In addition, the 1K1C hypertensive model in mice can be an important tool for studies evaluating the role of specific genes relating to dependent and nondependent ANG II hypertension in transgenic mice.

Chk1 regulates the S phase checkpoint by coupling the physiological turnover and ionizing radiation-induced accelerated proteolysis of Cdc25A

Chk1 kinase coordinates cell cycle progression and preserves genome integrity. Here, we show that chemical or genetic ablation of human Chk1 triggered supraphysiological accumulation of the S phase-promoting Cdc25A phosphatase, prevented ionizing radiation (IR)-induced degradation of Cdc25A, and caused radioresistant DNA synthesis (RDS). The basal turnover of Cdc25A operating in unperturbed S phase required Chk1-dependent phosphorylation of serines 123, 178, 278, and 292. IR-induced acceleration of Cdc25A proteolysis correlated with increased phosphate incorporation into these residues generated by a combined action of Chk1 and Chk2 kinases. Finally, phosphorylation of Chk1 by ATM was required to fully accelerate the IR-induced degradation of Cdc25A. Our results provide evidence that the mammalian S phase checkpoint functions via amplification of physiologically operating, Chk1-dependent mechanisms.

Effects of physical exercise training in DNA damage and repair - could the difference be in hOGG1 Ser326Cys polymorphism?

Acute physical exercise is associated with increased oxygen consumption, which could result in an increased formation of reactive oxygen species (ROS). ROS can react with several organic structures, namely DNA, causing strand breaks and a variety of modified bases in DNA. Physical exercise training seems to decrease the incidence of oxidative stress-associated diseases, and is considered as a key component of a healthy lifestyle. This is a result of exercise-induced adaptation, which has been associated with the possible increase in antioxidant activity and in oxidative damage repair enzymes, leading to an improved physiological function and enhanced resistance to oxidative stress (Radak et al. 2008). Human 8-oxoguanine DNA glycosylase 1 (hOGG1) is involved in the base excision repair (BER) pathway and encodes an enzyme responsible for removing the most common product of oxidative damage in DNA, 8-hydroxyguanine (8-OH-G). The genetic polymorphism of hOGG1 at codon 326 results in a serine (Ser) to cysteine (Cys) amino acid substitution (Ser326Cys). It has been suggested that the carriers of at least one hOGG1Cys variant allele exhibit lower 8-OH-G excision activity than the wild-type (Wilson et al. 2011). The aim of this study was to investigate the possible influence of hOGG1 Ser326Cys polymorphism on DNA damage and repair activity in response to 16 weeks of combined physical exercise training, in thirty healthy Caucasian men. Comet assay was carried out using peripheral blood lymphocytes and enabled the evaluation of DNA damage, both strand breaks and FPG-sensitive sites, and DNA repair activity. Genotypes were determined by PCR-RFLP analysis. The subjects with Ser/Ser genotype were considered as wild-type group (n=20), Ser/Cys and Cys/Cys genotype were analyzed together as mutant group (n=10). Regarding differences between pre and post-training in the wild-type group, the results showed a significant decrease in DNA strand breaks (DNA SBs) (p=0.002) and also in FPG-sensitive sites (p=0.017). No significant differences were observed in weight (p=0.389) and in lipid peroxidation (MDA) (p=0.102). A significant increase in total antioxidant capacity (evaluated by ABTS) was observed (p=0.010). Regarding mutant group, the results showed a significant decrease in DNA SBs (p=0.008) and in weight (p=0.028). No significant differences were observed in FPG-sensitive sites (p=0.916), in ABTS (p=0.074) and in MDA (p=0.086). No significant changes in DNA repair activity were observed in both genotype groups. This preliminary study suggests the possibility of different responses in DNA damage to physical exercise training, considering the hOGG1 Ser326Cys polymorphism.

Radiation induced apoptosis and initial DNA damage are inversely related in locally advanced breast cancer patients.

Background. DNA-damage assays, quantifying the initial number of DNA double-strand breaks induced by radiation, have been proposed as a predictive test for radiation-induced toxicity. Determination of radiation-induced apoptosis in peripheral blood lymphocytes by flow cytometry analysis has also been proposed as an approach for predicting normal tissue responses following radiotherapy. The aim of the present study was to explore the association between initial DNA damage, estimated by the number of double-strand breaks induced by a given radiation dose, and the radio-induced apoptosis rates observed. Methods. Peripheral blood lymphocytes were taken from 26 consecutive patients with locally advanced breast carcinoma. Radiosensitivity of lymphocytes was quantified as the initial number of DNA double-strand breaks induced per Gy and per DNA unit (200 Mbp). Radio-induced apoptosis at 1, 2 and 8 Gy was measured by flow cytometry using annexin V/propidium iodide. Results. Radiation-induced apoptosis increased in order to radiation dose and data fitted to a semi logarithmic mathematical model. A positive correlation was found among radio-induced apoptosis values at different radiation doses: 1, 2 and 8 Gy (p < 0.0001 in all cases). Mean DSB/Gy/DNA unit obtained was 1.70 ± 0.83 (range 0.63-4.08; median, 1.46). A statistically significant inverse correlation was found between initial damage to DNA and radio-induced apoptosis at 1 Gy (p = 0.034). A trend toward 2 Gy (p = 0.057) and 8 Gy (p = 0.067) was observed after 24 hours of incubation. Conclusions. An inverse association was observed for the first time between these variables, both considered as predictive factors to radiation toxicity.

Combined low initial DNA damage and high radiation-induced apoptosis confers clinical resistance to long-term toxicity in breast cancer patients treated with high-dose radiotherapy

BACKGROUND. Either higher levels of initial DNA damage or lower levels of radiation-induced apoptosis in peripheral blood lymphocytes have been associated to increased risk for develop late radiation-induced toxicity. It has been recently published that these two predictive tests are inversely related. The aim of the present study was to investigate the combined role of both tests in relation to clinical radiation-induced toxicity in a set of breast cancer patients treated with high dose hyperfractionated radical radiotherapy. METHODS. Peripheral blood lymphocytes were taken from 26 consecutive patients with locally advanced breast carcinoma treated with high-dose hyperfractioned radical radiotherapy. Acute and late cutaneous and subcutaneous toxicity was evaluated using the Radiation Therapy Oncology Group morbidity scoring schema. The mean follow-up of survivors (n = 13) was 197.23 months. Radiosensitivity of lymphocytes was quantified as the initial number of DNA double-strand breaks induced per Gy and per DNA unit (200 Mbp). Radiation-induced apoptosis (RIA) at 1, 2 and 8 Gy was measured by flow cytometry using annexin V/propidium iodide. RESULTS. Mean DSB/Gy/DNA unit obtained was 1.70 ± 0.83 (range 0.63-4.08; median, 1.46). Radiation-induced apoptosis increased with radiation dose (median 12.36, 17.79 and 24.83 for 1, 2, and 8 Gy respectively). We observed that those "expected resistant patients" (DSB values lower than 1.78 DSB/Gy per 200 Mbp and RIA values over 9.58, 14.40 or 24.83 for 1, 2 and 8 Gy respectively) were at low risk of suffer severe subcutaneous late toxicity (HR 0.223, 95%CI 0.073-0.678, P = 0.008; HR 0.206, 95%CI 0.063-0.677, P = 0.009; HR 0.239, 95%CI 0.062-0.929, P = 0.039, for RIA at 1, 2 and 8 Gy respectively) in multivariate analysis. CONCLUSIONS. A radiation-resistant profile is proposed, where those patients who presented lower levels of initial DNA damage and higher levels of radiation induced apoptosis were at low risk of suffer severe subcutaneous late toxicity after clinical treatment at high radiation doses in our series. However, due to the small sample size, other prospective studies with higher number of patients are needed to validate these results.