Protozoa inhibition by different salts: Osmotic stress or ionic stress?

Cell density and morphology changes were tested to examine the effects of salts including NaHCO₃, NaCl, KHCO₃, and KCl at 160 mM on protozoa. It was demonstrated that ionic stress rather than osmotic stress led to protozoa cell death and NaHCO₃ was shown to be the most effective inhibitor. Deformation of cells and cell shrinkage were observed when protozoan cells were exposed to polyethylene glycol (PEG) or any of the salts. However, while PEG treated cells could fully recover in both number and size, only a small portion of the salt‐treated cells survive and cell size was 36–58% smaller than the regular. The disappearance of salt‐treated protozoa cells was hypothetically attributed to disruption of the cytoplasmic membrane of these cells. It is further hypothesized that the PEG‐treated protozoan cells carried out regulatory volume increase (RVI) after the osmotic shock but the RVI of salt‐treated protozoa was hurdled to varied extents. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1418–1424, 2017     

PKCα binds G3BP2 and regulates stress granule formation following cellular stress

Protein kinase C (PKC) isoforms regulate a number of processes crucial for the fate of a cell. In this study we identify previously unrecognized interaction partners of PKCα and a novel role for PKCα in the regulation of stress granule formation during cellular stress. Three RNA-binding proteins, cytoplasmic poly(A)(+) binding protein (PABPC1), IGF-II mRNA binding protein 3 (IGF2BP3), and RasGAP binding protein 2 (G3BP2) all co-precipitate with PKCα. RNase treatment abolished the association with IGF2BP3 and PABPC1 whereas the PKCα-G3BP2 interaction was largely resistant to this. Furthermore, interactions between recombinant PKCα and G3BP2 indicated that the interaction is direct and PKCα can phosphorylate G3BP2 in vitro. The binding is mediated via the regulatory domain of PKCα and the C-terminal RNA-binding domain of G3BP2. Both proteins relocate to and co-localize in stress granules, but not to P-bodies, when cells are subjected to stress. Heat shock-induced stress granule assembly and phosphorylation of eIF2α are suppressed following downregulation of PKCα by siRNA. In conclusion this study identifies novel interaction partners of PKCα and a novel role for PKCα in regulation of stress granules.     

Contributions of individual σB-dependent general stress genes to oxidative stress resistance of Bacillus subtilis

The general stress regulon of Bacillus subtilis comprises approximately 200 genes and is under the control of the alternative sigma factor σ(B). The activation of σ(B) occurs in response to multiple physical stress stimuli as well as energy starvation conditions. The expression of the general stress proteins provides growing and stationary nonsporulating vegetative cells with nonspecific and broad stress resistance. A previous comprehensive phenotype screening analysis of 94 general stress gene mutants in response to severe growth-inhibiting stress stimuli, including ethanol, NaCl, heat, and cold, indicated that secondary oxidative stress may be a common component of severe physical stress. Here we tested the individual contributions of the same set of 94 mutants to the development of resistance against exposure to the superoxide-generating agent paraquat and hydrogen peroxide (H(2)O(2)). In fact, 62 mutants displayed significantly decreased survival rates in response to paraquat and/or H(2)O(2) stress compared to the wild type at a confidence level of an α value of ≤ 0.01. Thus, we were able to assign 47 general stress genes to survival against superoxide, 6 genes to protection from H(2)O(2) stress, and 9 genes to the survival against both. Furthermore, we show that a considerable overlap exists between the phenotype clusters previously assumed to be involved in oxidative stress management and the actual group of oxidative-stress-sensitive mutants. Our data provide information that many general stress proteins with still unknown functions are implicated in oxidative stress resistance and further support the notion that different severe physical stress stimuli elicit a common secondary oxidative stress.     

What drives plant stress genes?

Currently, there is a lot of interest in the plant stress response. Using large-scale genomics approaches, more and more genes are being identified that are involved in or even regulate this complex process. The recent boost in expression profile analyses for several plant stress responses has enabled the identification of new promoter elements as important factors in establishing the expression regulatory network controlling plant stress response.     

Oxidative stress in microorganisms—I

Oxidative stress in microbial cells shares many similarities with other cell types but it has its specific features which may differe in prokaryotic and eukaryotic cells. We survey here the properties and actions of primary sources of oxidative stress, the role of transition metals in oxidative stress and cell protective machinery of microbial cells, and compare them with analogous features of other cell types. Other features to be compared are the action of reactive oxygen species (ROS) on cell constituents, secondary lipid-or protein-based radicals and other stress products. Repair of oxidative injury by microorganisms and proteolytic removal of irreparable cell constituents are briefly described. Oxidative damage of aerobically growing microbial cells by endogenously formed ROS mostly does not induce changes similar to the aging of multiplying mammalian cells. Rapid growth of bacteria and yeast prevents accumulation of impaired macromolecules which are repaired, diluted or eliminated. During growth some simple fungi, such as yeast orPodospora spp., exhibit aging whose primary cause seems to be fragmentation of the nucleolus or impairment of mitochondrial DNA integrity. Yeast cell aging seems to be accelerated by endogenous oxidative stress. Unlike most growing microbial cells, stationaryphase cells gradually lose their viability because of a continuous oxidative stress, in spite of an increased synthesis of antioxidant enzymes. Unlike in most microorganisms, in plant and animal cells a severe oxidative stress induces a specific programmed death pathway-apoptosis. The scant data on the microbial death mechanisms induced by oxidative stress indicate that in bacteria cell death can result from activation of autolytic enzymes (similarly to the programmed mother-cell death at the end of bacillar sporulation). Yeast and other simple eukaryotes contain components of a proapoptotic pathway which are silent under normal conditions but can be activated by oxidative stress or by manifestation of mammalian death genes, such asbak orbax. Other aspects, such as regulation of oxidative-stress response, role of defense enzymes and their control, acquisition of stress tolerance, stress signaling and its role in stress response, as well as cross-talk between different stress factors, will be the subject of a subsequent review.     

When does stress end? Evidence of a prolonged stress reaction in shiftworking truck drivers

This study aimed to analyze individual cortisol levels in relation to work conditions, sleep, and health parameters among truck drivers working day shifts (n = 21) compared to those working irregular shifts (n = 21). A total of 42 male truck drivers (39.8 (+/-) 6.2 yrs) completed questionnaires about sociodemographics, job content, work environment, health, and lifestyle. Rest-activity profiles were measured using actigraphy, and cardiovascular blood parameters were collected. Salivary cortisol samples were obtained: (i) at waking time, (ii) 30?min after waking, and (iii) at bedtime, during both one workday and one day off from work. Irregular-shift workers, compared to day-shift workers, showed significantly higher waist-hip ratio, very-low-density lipoprotein (VLDL) cholesterol, tiredness after work, years working as a driver, truck vibration, and less job demand (p < .05). High cortisol levels in irregular-shift workers were correlated with certain stressors, such as short sleep duration and low job satisfaction, and to metabolic parameters, such as total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), VLDL, and triglycerides. Day-shift workers had higher cortisol levels collected 30?min after waking (p = .03) and a higher cortisol awakening response (CAR; p = .02) during workdays compared to off days. Irregular-shift workers had higher cortisol levels on their off days compared to day-shift workers (p = .03). In conclusion, for the day-shift workers, a higher cortisol response was observed on workdays compared to off days. Although no direct comparisons could be made between groups for work days, on off days the irregular-shift workers had higher cortisol levels compared to day-shift workers, suggesting a prolonged stress response in the irregular-shift group. In addition, cortisol levels were correlated with stressors and metabolic parameters. Future studies are warranted to investigate further stress responses in the context of irregular work hours.     

Acacetin antagonized lipotoxicity in pancreatic β-cells via ameliorating oxidative stress and endoplasmic reticulum stress

Molecular Biology Reports - During the pathogenesis and progression of diabetes, lipotoxicity is a major threat to the function and survival of pancreatic β-cells. To battle against the...     

Is stress really all that important?

There is growing concern in many parts of the world that fertility of dairy cattle is reducing as milk yields increase. Stress could be one important cause. As an example, fertility is lower after caesarian operations. Delayed uterine involution after dystocia is associated with abnormal ovarian cyclicity and prolonged intervals to the next pregnancy. There is a greater reduction in fertility as the clinical conditions of lameness, milk fever or mastitis worsen. Changes in social groupings greatly increase the number of inseminations required per pregnancy. Transport reduces the number of CL after superovulation, and can interfere with pregnancy rates after estrous synchronization. Embryos collected from heat-stressed donors are less viable and have delayed trophoblast function. Human-animal interactions influence stress-responses in cattle--the behavior of stockman and embryo transfer personnel could affect success. Putting aside financial aspects, exposure of an animal to avoidable stress compromises welfare, whether application of biotechnology is involved or not. The fact that stressors can be deleterious to such an important function as reproduction, emphasizes that stress is very important and should be minimized whenever possible.     

How cells protect themselves against stress?

The current evidence on the mechanisms underlying cell response to heat shock is reviewed. The response dynamics, induction, and attenuation as well as heat shock proteins and the mechanisms through which they protect cells from stress are considered. The role of these proteins in regulating the signaling cascades, including apoptosis suppression, is shown.     

Enteric bacteria and osmotic stress: intracellular potassium glutamate as a secondary signal of osmotic stress?

Enteric bacteria have evolved an impressive array of mechanisms that allow the cell to grow at widely different external osmotic pressures. These serve two linked functions; firstly, they allow the cell to maintain a relatively constant turgor pressure which is essential for cell growth; and secondly they permit changes in cytoplasmic composition such that the accumulation of intracellular osmolytes required to restore turgor pressure does not impair enzyme function. The primary event in turgor regulation is the controlled accumulation of potassium and its counterion glutamate. At high external osmolarities the cytoplasmic levels of potassium glutamate can impair enzyme function. Rapid growth is therefore dependent upon secondary responses, principally the accumulation of compatible solutes, betaine (N-trimethylglycine), proline and trehalose. The accumulation of these solutes is achieved by the controlled activity of transport systems and enzymes in response to changes in external osmotic pressure. It has been proposed that the accumulation of potassium glutamate during turgor regulation acts as a signal for the activation of these systems [1,2]. This brief review will examine the evidence that control over the balance of cytoplasmic osmolytes is achieved by sensing of the intracellular potassium (and glutamate) concentration.     

Does Trypanosoma cruzi stress its vectors?

Trypanosoma cruzi seems to compete with its vector, Triatoma infestans, for nutrients. When starved the resistance of infected Triatoma is reduced but it is rarely affected i f it is given an adequate food supply. Infected individuals also might be more sensitive than uninfected bugs to other environmental stress factors. Günter Schaub believes that the theory, that T. cruzi does not affect its vectors, should be re-examined.     

Secretin—a new stress hormone?

The plasma concentration of secretin was measured during a 5-day military training course comprising prolonged physical exercise (35% of max O₂ uptake), severe caloric deficiency (approx. 35700 kJ/24 h) and sleep deprivation (only 2 h of sleep as a total during 5 days). 24 subjects were divided into 3 groups, one group was compensated for the caloric deficiency and another group was partly compensated for the sleep deprivation. The results showed that the fasting plasma secretin increased 3–6-fold (from 1.8–3.7 to 13.3–19.1 pmol/l) during the course with small differences in increase between the groups. Ingestion of a mixed meal reduced the fasting plasma secretin by about 40% during the course, while oral glucose reduced the plasma secretin to the concentrations found in the control experiment.The study shows that plasma secretin is increased when man is exposed to prolonged multifactorial stress. Additional food or sleep appears to have small influence on the fasting plasma secretin, but after giving a meal or oral glucose solution the plasma secretin decreases rapidly.     

Do the serum oxidative stress biomarkers provide a reasonable index of the general oxidative stress status?

The oxidant status of an individual is assessed by determining a group of markers in noninvasive samples. One limitation when measuring these biomarkers is that they do not give information about tissue localization of oxidative stress. The present study was undertaken to establish whether the serum oxidative stress biomarkers are indicative of oxidative stress in tissues of an individual. To accomplish this, we determined a few generic markers of oxidation in serum and tissues of six groups of rats treated experimentally, to modulate their oxidative stress status. The correlation between serum and tissue levels was calculated for each marker. Also, for each tissue, the correlation between the values of these oxidative stress biomarkers was analysed. Our results show that only lipid peroxides in serum could be useful to predict the oxidative stress in tissues. No correlation was found between any of the oxidative stress markers in serum.     

Does competition stress decrease allelopathic potential?

In natural communities, plants compete in different ways, among them chemical interactions in the form of allelopathy. Whereas the effects of abiotic stresses (temperature, light, nutrients, etc.) on the production of allelochemicals are well known, only few studies deal with the impact of the stress induced by competition. When they do so, these studies are done under experimental conditions. The aim of this study is to evaluate the effect of intra-specific competition on the production of allelochemicals and biomass of Pinus halepensis Mill. in a natural forest using three levels of density. Phenolics and aliphatic acids were extracted from pine needles, analysed and quantified by GC-MS. Trunks, branches, needles and necromass were measured. We observed an increase in allelochemical content at low or medium level of competition and a decrease at high competition level. Moreover trees in competition allocate proportionally more biomass to the trunk and less to foliage and branches. This study provides evidence of substantial changes in allocation between the primary and the secondary metabolism.     

When can we measure stress noninvasively? Postdeposition effects on a fecal stress metric confound a multiregional assessment

Measurement of stress hormone metabolites in fecal samples has become a common method to assess physiological stress in wildlife populations. Glucocorticoid metabolite (GCM) measurements can be collected noninvasively, and studies relating this stress metric to anthropogenic disturbance are increasing. However, environmental characteristics (e.g., temperature) can alter measured GCM concentration when fecal samples cannot be collected immediately after defecation. This effect can confound efforts to separate environmental factors causing predeposition physiological stress in an individual from those acting on a fecal sample postdeposition. We used fecal samples from American pikas (Ochotona princeps) to examine the influence of environmental conditions on GCM concentration by (1) comparing GCM concentration measured in freshly collected control samples to those placed in natural habitats for timed exposure, and (2) relating GCM concentration in samples collected noninvasively throughout the western United States to local environmental characteristics measured before and after deposition. Our timed‐exposure trials clarified the spatial scale at which exposure to environmental factors postdeposition influences GCM concentration in pika feces. Also, fecal samples collected from occupied pika habitats throughout the species' range revealed significant relationships between GCM and metrics of climate during the postdeposition period (maximum temperature, minimum temperature, and precipitation during the month of sample collection). Conversely, we found no such relationships between GCM and metrics of climate during the predeposition period (prior to the month of sample collection). Together, these results indicate that noninvasive measurement of physiological stress in pikas across the western US may be confounded by climatic conditions in the postdeposition environment when samples cannot be collected immediately after defecation. Our results reiterate the importance of considering postdeposition environmental influences on this stress metric, especially in multiregional comparisons. However, measurements of fecal GCM concentration should prove useful for population monitoring within an eco‐region or when postdeposition exposure can be minimized.     

Can shear stress direct stem cell fate?

Mechanical forces are important signals in the development and function of the heart and lung, growth of skin and muscle, and maintenance of cartilage and bone. The specific mechanical force “shear stress” has been implicated as playing a critical role in the physiological responses of blood vessels through endothelial cell signaling. More recently, studies have shown that shear stress can induce differentiation of stem cells toward both endothelial and bone‐producing cell phenotypes. This review will highlight current data supporting the role of shear stress in stem cell fate and will propose potential mechanisms and signaling cascades for transducing shear stress into a biological signal. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009