Changes In Stress Resistance Research Articles

Correlated changes in stress resistance and biochemical parameters in response to long-term protein restriction in Drosophila melanogaster.

Studies in fruit flies, Drosophila melanogaster, have observed considerable variation in the effect of dietary protein restriction (PR) on various fitness traits. In addition, not only are there inconsistent results relating lifespan to stress resistance, but also the long-term effects of PR are unexplored. We study PR implementation across generations (long term) hypothesizing that it will be beneficial for fitness traits, stress resistance and storage reserves due to nutritional plasticity transferred by parents to offspring in earlier Drosophila studies. By imposing two concentrations of PR diets (50% and 70% of control protein) from the pre-adult and adult (age 1 day) stages of the flies, we assessed the stage-specific and long-term effect of the imposed PR. All long-term PR flies showed increased resistance against the tested stressors (starvation, desiccation, H2O2-induced oxidative stress). In addition, we also found long-term PR-induced increased stress resistance across generations. The PR flies also possessed higher protein and triglyceride (TG) content, reduced glucose and unaffected glycogen levels. We also assayed the effect of returning the PR flies to control (AL) food for a single generation and assessed their biochemical parameters to witness the transient PR effect. It was seen that TG content upon reversal was similar to AL flies except for PRI70 males; however, the glucose levels of PR males increased, while they were consistently lower in females. Taken altogether, our study suggests that long-term PR implementation contributes to increased stress resistance and was found to influence storage reserves in D. melanogaster.

Влияние стажа службы на стрессоустойчивость, стратегии копинг поведения и карьерные ориентации руководителей ОВД

The relevance of the research topic is determined by the high stress level of the work activities of employees of internal affairs bodies and especially heads of departments, who bear a large burden of responsibility both for their subordinates and for the success and efficiency of the department as a whole. The main goal of this study is to study changes in stress resistance, coping behavior strategies and career orientations of heads of internal affairs bodies with different length of service in a leadership position in conditions of highly stressful work activities. To achieve the goal of the study, 276 heads of internal affairs bodies were examined, divided into three groups according to length of service in a leadership position. The main psychodiagnostic tools were the “Prognoz-2” method for studying neuropsychic stability, the SRRSYu scale for assessing stress resistance and social adaptation, the SACS method for studying leading coping behavior strategies, and the “Career Anchors” questionnaire. According to the results of the study, a decrease in the stress resistance of heads of internal affairs bodies was established when they reach more than 10 years of service in a leadership position; there is also an increase in professionalism, independence and confidence in their actions, while at the same time a decrease in reliance on the social environment and the desire to maintain the current situation. Managers with a high intensity of professional stress have a predominant focus on work activity and the stability of their official position to the detriment of other areas of life, with a decrease in reliance on the social environment, which causes a decrease in stress resistance and an increase in the level of professional stress and neuropsychic tension. The results obtained indicate the need for targeted psychological work with heads of internal affairs bodies with more than 10 years of service, aimed at improving social adaptation and correcting career orientations in order to reduce the level of professional stress and neuropsychic tension.

Changes in the Content of Carotenoids in Moss Shoots Hylocomium splendens Hedw. under Conditions of Temperature Stress

The ability of plants to adapt to unfavorable living conditions is a necessary condition for the survival of plants, the preservation of the genotype, and the maintenance of flora diversity. A promising approach to solving the problem of increasing plant resistance is to study the mechanisms of stress resistance of “extremophiles”, including mosses, higher nonvascular plants. The relative simplicity of their anatomical structure and ability to survive in unfavorable environmental conditions make these evolutionarily ancient plants ideal models for studying adaptation mechanisms. It is known that the functional activity of the photosynthetic apparatus can change dynamically under the influence of stress factors. In this work, we conducted a study of stress-induced changes in the content of carotenoids in the forest moss Hylocomium splendens Hedw. under temperature stress conditions. We have identified the main carotenoids of H. splendens moss. It has been established that the relative content of lutein, β-carotene, and zeaxanthin increased under the influence of negative and elevated temperatures, while the total content of carotenoids decreased under temperature stress. It was shown that 1 h of exposure to unfavorable temperatures led to a significant decrease in nonphotochemical quenching of chlorophyll fluorescence a, with stronger changes observed when exposed to negative temperatures. Transcript level analysis of HsLUT1, one of the key genes for lutein biosynthesis, showed a significant increase of four to five times under temperature stress. Thus, our data revealed that changes in the expression of the carotenoid biosynthesis gene are accompanied by changes in their content under temperature stress. The data obtained expand our knowledge of resistance mechanisms in bryophytes and will contribute to the understanding of evolutionary changes in stress resistance in higher plants.

Astrocytes Do Not Forfeit Their Neuroprotective Roles After Surviving Intense Oxidative Stress.

In order to fulfill their evolutionary role as support cells, astrocytes have to tolerate intense oxidative stress under conditions of brain injury and disease. It is well known that astrocytes exposed to mild oxidative stress are preconditioned against subsequent stress exposure in dual hit models. However, it is unclear whether severe oxidative stress leads to stress tolerance, stress exacerbation, or no change in stress resistance in astrocytes. Furthermore, it is not known whether reactive astrocytes surviving intense oxidative stress can still support nearby neurons. The data in this Brief Report suggest that primary cortical astrocytes surviving high concentrations of the oxidative toxicant paraquat are completely resistant against subsequent oxidative challenges of the same intensity. Inhibitors of multiple endogenous defenses (e.g., glutathione, heme oxygenase 1, ERK1/2, Akt) failed to abolish or even reduce their stress resistance. Stress-reactive cortical astrocytes surviving intense oxidative stress still managed to protect primary cortical neurons against subsequent oxidative injuries in neuron/astrocyte co-cultures, even at concentrations of paraquat that otherwise led to more than 80% neuron loss. Although our previous work demonstrated a lack of stress tolerance in primary neurons exposed to dual paraquat hits, here we show that intensely stressed primary neurons can resist a second hit of hydrogen peroxide. These collective findings suggest that stress-reactive astroglia are not necessarily neurotoxic, and that severe oxidative stress does not invariably lead to stress exacerbation in either glia or neurons. Therefore, interference with the natural functions of stress-reactive astrocytes might have the unintended consequence of accelerating neurodegeneration.

Resistance to Stress Can Be Experimentally Dissociated From Longevity

On the basis of multiple experiments demonstrating that high resistance to stress is associated with long lifespan, it has been proposed that stress resistance is a key determinant of longevity. However, the extent to which high resistance to stress is necessary or sufficient for long life is currently unclear. In this work, we use a genetic approach to disrupt different stress response pathways and examine the resulting effect on the longevity of the long-lived insulin-like growth factor 1 (IGF1) receptor mutant daf-2. Although mutation of the heat shock factor gene hsf-1, deletion of sod genes, deletion of the p38 MAPK kinase gene pmk-1, or deletion of the transcription factor gene egl-27 all resulted in decreased resistance to at least one form of stress and decreased lifespan, the magnitude of change in stress resistance did not correspond to the magnitude of change in lifespan. In addition, we found that deletion of the glycerol-3-phosphate dehydrogenase genes gpdh-1 and gpdh-2 or deletion of the DAF-16 cofactor gene nhl-1 also results in decreased resistance to at least one form of stress but increases lifespan. Overall, our results suggest that while increased stress resistance is associated with longevity, stress resistance, and lifespan can be experimentally dissociated.

Morphological Characterization and Gene Expression Profiling during Bud Development in a Tropical Perennial, Litchi chinensis Sonn.

Tropical evergreen perennials undergo recurrent flush growth, and their terminal buds alternate between growth and dormancy. In sharp contrast to the intensive studies on bud development in temperate deciduous trees, there is little information about bud development regulation in tropical trees. In this study, litchi (Litchi chinensis Sonn.) was used as a model tropical perennial for morphological characterization and transcriptomic analysis of bud development. Litchi buds are naked with apical meristem embraced by rudimentary leaves, which are brown at dormant stage (Stage I). They swell and turn greenish as buds break (Stage II), and as growth accelerates, the rudimentary leaves elongate and open exposing the inner leaf primodia. With the outgrowth of the needle-like leaflets, bud growth reaches a maximum (Stage III). When leaflets expand, bud growth cease with the abortion of the rudimentary leaves at upper positions (Stage IV). Then buds turn brown and reenter dormant status. Budbreak occurs again when new leaves become hard green. Buds at four stages (Stage I to IV) were collected for respiration measurements and in-depth RNA sequencing. Respiration rate was the lowest at Stage I and highest at Stage II, decreasing toward growth cessation. RNA sequencing obtained over 5 Gb data from each of the bud samples and de novo assembly generated a total of 59,999 unigenes, 40,119 of which were annotated. Pair-wise comparison of gene expression between stages, gene profiling across stages, GO/KEGG enrichment analysis, and the expression patterns of 17 major genes highlighted by principal component (PC) analysis displayed significant changes in stress resistance, hormone signal pathways, circadian rhythm, photosynthesis, cell division, carbohydrate metabolism, programmed cell death during bud development, which might be under epigenetic control involving chromatin methylation. The qPCR results of 8 selected unigenes with high PC scores agreed with the RPKM values obtained from RNA-seq. Three Short Vegetative Phase (SVP) genes, namely LcSVP1, LcSVP2, and LcSVP3 displayed different expression patterns, suggesting their differential roles in bud development regulation. The study brought an understanding about biological processes associated with the phase transitions, molecular regulation of bud development, as well as cyclic bud growth as a strategy to survive tropical conditions.

The Unfolded Protein Response in a Pair of Sensory Neurons Promotes Entry of C. elegans into Dauer Diapause

In response to unfavorable environmental conditions such as starvation, crowding, and elevated temperature, Caenorhabditis elegans larvae enter an alternative developmental stage known as dauer, which is characterized by adaptive changes in stress resistance and metabolism. The genetic dissection of the molecular mechanisms of the C. elegans dauer developmental decision has defined evolutionarily conserved signaling pathways of organismal neuroendocrine physiology. Here, we have identified a mechanism by which a dominant mutation in a neuronal insulin gene, daf-28(sa191), causes constitutive entry into dauer diapause. We demonstrate that expression of the mutant DAF-28 insulin peptide results in endoplasmic reticulum (ER) stress in the ASI pair of chemosensory neurons. The neuronal ER stress does not compromise cellular survival but activates PEK-1, the C. elegans ortholog of the mammalian eIF2α kinase PERK, which in turn phosphorylates Ser49 of eIF2α, specifically in the ASI neuron pair, to promote entry into dauer diapause. Our data establish a novel role for ER stress and the unfolded protein response (UPR) in promoting entry into dauer diapause and suggest that, in addition to cell-autonomous activities in the maintenance of ER homeostasis, the UPR may act in a non-cell-autonomous manner to promote organismal adaptation to stress during larval development.

Spread and change in stress resistance of Shiga toxin‐producing Escherichia coli O157 on fungal colonies

To elucidate the effect of fungal hyphae on the behaviour of Shiga toxin-producing Escherichia coli (STEC) O157, the spread and change in stress resistance of the bacterium were evaluated after coculture with 11 species of food-related fungi including fermentation starters. Spread distances of STEC O157 varied depending on the co-cultured fungal species, and the motile bacterial strain spread for longer distances than the non-motile strain. The population of STEC O157 increased when co-cultured on colonies of nine fungal species but decreased on colonies of Emericella nidulans and Aspergillus ochraceus. Confocal scanning microscopy visualization of green fluorescent protein-tagged STEC O157 on fungal hyphae revealed that the bacterium colonized in the water film that existed on and between hyphae. To investigate the physiological changes in STEC O157 caused by co-culturing with fungi, the bacterium was harvested after 7 days of co-culturing and tested for acid resistance. After co-culture with eight fungal species, STEC O157 showed greater acid resistance compared to those cultured without fungi. Our results indicate that fungal hyphae can spread the contamination of STEC O157 and can also enhance the stress resistance of the bacteria.

Sirtuins, aging and diseases

SIR2 and related genes (sirtuins) are NAD-dependent deacetylases that link metabolism, protein acetylation and aging in a variety of species. Sirtuins are also involved in the longevity conferred by dietary or calorie restriction (CR). The mammalian sirtuins SIRT1-7 are involved in changes in stress resistance and metabolism that are triggered by CR, which not only extends life span, but also protects against many diseases of aging. In this talk, I will describe how mamamlian SIRT1 impacts tissue metabolism and diseases by deacetylating nuclear transcription factors that govern key physiological pathways. I will also describe new data from several labs showing that the mitochondrial sirtuin SIRT3 suppresses reactive oxygen species (ROS) in mitochondria and thus links sirtuins, calorie restriction, ROS, mitochondria and aging. The effect of SIRT3 on mitochondrial generated ROS further regulates the key nuclear transcription factor HIF-1α, and may thus govern the metabolic reprogramming (Warburg effect) in cancer. Finally, I will touch upon recent progress in trying to understand the mechanism of action of SIRT1-activating compounds, which are currently in numerous human clinical trials. Supported by NIA & Glenn Foundation for Medical Research. LG consults for Sirtris/GSK.

Abstract SY09-02: Can sitruin activation treat cancer

Abstract SIR2 and related genes are NAD-dependent deacetylases that slow aging in yeast, C. elegans, and Drosophila. In yeast and flies, SIR2 genes are also involved in the longevity conferred by dietary or calorie restriction (CR). The mammalian SIR2 homologs termed SIRT genes, or sirtuins, are involved in changes in stress resistance and metabolism and are known to be associated with CR. Critically, the CR diet in rodents not only extends life span, but also protects against many diseases of aging. In this talk, I will describe recent findings in the field regarding SIRT1 function in specific mammalian tissues in relation to murine disease models, with an emphasis on cancer. Our findings indicate that SIRT1 can influence many of the major diseases of aging, including metabolic diseases like diabetes, neurodegenerative diseases (Alzheimer's and Huntington's), cancer and osteoporosis. Therefore small molecules that alter the activity of SIRT1 (i.e. CR mimetic drugs) offer a new approach to prevent and possibly treat the major diseases of aging. Supported by NIA, The Glenn Foundation, and The AAF. Guarente consults for Sirtris/GSK Guarente, L. (2007). Sirtuins in aging and disease. CSH Symp. Quant. Biol. 72, 483-488. Guarente, L. (2008). Mitochondria - a nexus for aging, calorie restriction and sirtuins?. Cell 132, 171-175. Citation Format: Leonard P. Guarente. Can sitruin activation treat cancer [abstract]. In: Proceedings of the AACR 101st Annual Meeting 2010; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr SY09-02

SIRTUINS, AGING AND DISEASE

SIR2 and related genes are NAD‐dependent deacetylases that slow aging in yeast, C. elegans, and Drosophila. In yeast and flies, SIR2 genes are also involved in the longevity conferred by dietary or calorie restriction (CR). The mammalian SIR2 homologs termed SIRT genes, or sirtuins, are involved in changes in stress resistance and metabolism and are known to be associated with CR. Critically, the CR diet in rodents not only extends life span, but also protects against many diseases of aging. In this talk, I will describe recent findings in the lab regarding SIRT1 function in specific mammalian tissues in relation to murine disease models. Our findings indicate that SIRT1 can influence many of the major diseases of aging, includingmetabolic diseases like diabetes, neurodegenerative diseases (Alzheimer's and Huntington's), cancer and osteoporosis. Therefore small molecules that alter the activity of SIRT1 (i.e. CR mimetic drugs) offer a new approach to prevent and possibly treat the major diseases of aging.Supported by NIA, Glenn Foundation, Hi‐Q, HDF, Estee Lauder. Guarente consults for Sirtris/GSKGuarente, L. (2007). Sirtuins in aging and disease. CSH Symp. Quant. Biol. 72, 483–488.Guarente, L. (2008). Mitochondria – a nexus for aging, calorie restriction and sirtuins?. Cell 132, 171–175.

Studies of Caenorhabditis elegans DAF‐2/insulin signaling reveal targets for pharmacological manipulation of lifespan

SummaryMuch excitement has arisen from the observation that decrements in insulin-like signaling can dramatically extend lifespan in the nematode, Caenorhabditis elegans, and fruitfly, Drosophila melanogaster. In addition, there are tantalizing hints that the IGF-I pathway in mice may have similar effects. In addition to dramatic effects on lifespan, invertebrate insulin-like signaling also promotes changes in stress resistance, metabolism and development. Which, if any, of the various phenotypes of insulin pathway mutants are relevant to longevity? What are the genes that function in collaboration with insulin to prolong lifespan? These questions are at the heart of current research in C. elegans longevity. Two main theories exist as to the mechanism behind insulin's effects on invertebrate longevity. One theory is that insulin programs metabolic parameters that prolong or reduce lifespan. The other theory is that insulin determines the cell's ability to endure oxidative stress from respiration, thereby determining the rate of aging. However, these mechanisms are not mutually exclusive and several studies seem to support a role for both. Here, we review recently published reports investigating the mechanisms behind insulin's dramatic effect on longevity. We also spotlight several C. elegans genes that are now known to interact with insulin signaling to determine lifespan. These insights into pathways affecting invertebrate lifespan may provide a basis for developing strategies for pharmacological manipulation of human lifespan.

Physiological changes in Campylobacter jejuni on entry into stationary phase

Campylobacter jejuni NCTC 11168 does not exhibit the general increase in cellular stress resistance on entry into stationary phase that is seen in most other bacteria. This is consistent with the lack of global stationary phase regulatory elements in this organism, deduced from an analysis of its genome sequence. We now show that C. jejuni NCTC 11168 does undergo certain changes in stationary phase, of a pattern not previously described. As cells entered stationary phase there was a change in membrane fatty acid composition, principally a decrease in the proportion of unsaturated fatty acids and an increase in the content of cyclopropane and short-chain fatty acids. These changes in membrane composition were accompanied by an increase in the resilience of the cell membrane towards loss of integrity caused by pressure and an increase in cellular pressure resistance. By contrast, there were no major changes in resistance to acid or heat treatment. A similar pattern of changes in stress resistance on entry into stationary phase was seen in C. jejuni NCTC 11351, the type strain. These changes appear to represent a restricted physiological response to the conditions existing in stationary phase cultures, in an organism having limited capacity for genetic regulation and adaptation to environment.

Stress resistance levels change little during dormancy in ash, sessile oak and sycamore seedlings

The physiological status of ash (Fraxinus excelsior L.), sessile oak (Quercus petraea (Matt.)) and sycamore (Acer pseudoplatanus L.) seedlings sampled from nurseries in Ireland between October and May, 1995/1996 and 1996/1997 was investigated. The results of heat treatments applied to taproots in vitro and evaluated using root electrolyte leakage (REL) indicated that sycamore was more easily damaged than the other species but lift date effects were small in all species. Dormancy release began later each year in ash (mid-November) than in oak or sycamore (late October to early November). The results of the REL and other data indicated that there was little change in stress resistance from November to about March (and April for some parameters). Sycamore was most active (highest shoot xylem pressure potential, REL, and root growth potential) during the winter, suggesting that adverse handling during this period is likely to reduce plant quality than in ash or oak. Field performance was good regardless of lifting/planting date.

Stress resistance declines with age: analysis of data from a survival experiment with Drosophila melanogaster.

An approach towards analyzing survivorship data is proposed for the study of changes in stress resistance with age in the population of Drosophila melanogaster. This is based on the model of heterogeneous mortality (frailty model). Results of the data analysis show that observed populations of flies are heterogeneous and the accelerated selection, debilitative effect and changes in individual frailties are the aftermath of stress. These results also reveal that debilitative effect and accelerated selection are much better pronounced in survivals of flies that are stressed at an older age. Mild stress, when applied at both ages, produced a reduction in frailty variance. Stress of greater magnitude produced higher frailty variance in the young-treated flies. Among the old-treated insects, stress of longer duration led to a reduction of both the mean and the variance of frailty distribution. Population of young-treated flies became more heterogeneous, population of old-treated flies became less heterogeneous, and both populations became more robust in average after stress.

Geographical Variation in the Acclimation Responses of Drosophila to Temperature Extremes

Populations may adapt to climatic stresses by nonplastic or plastic changes in stress resistance. Plastic changes include a range of different acclimation mechanisms. A few previous studies with Drosophila suggest interspecific variation in plastic responses to climatic stresses, but there is not much evidence for variation within species. Tropical and temperate populations of Drosophila melanogaster and Drosophila sirnulans were compared for plastic responses to cold and heat stress. Tropical populations tended to be less resistant to cold stress than temper- ate populations.-In contrast, D. melanogaster populations showed similar acclimation responses to cold stress following different acclimation treatments, which included keeping adults at low temperatures for a few hours or several days and culturing larvae at a low temperature. Popula- tions of D. simulans also showed similar plastic responses to cold stress after adults were acclimated at a low temperature for several days. In the heat resistance experiments, there was no evidence for population differences in acclimation response in either D. melanogaster or D. sitnulans when adults were exposed to high and low temperatures for a few days. Genetic variation for acclimation response may therefore be mainly restricted to the interspecific level, although larger experiments are required to detect small quantitative differences between popu- lations.