Is hypoxia a stressor to American bullfrog tadpoles?

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

Efeito do stressor moderado sobre o desafio social e o crescimento na tilália-do-nilo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Molecular crosstalk between a chemical and a biological stressor and consequences on disease manifestation in rainbow trout.

The aim of the present study was to examine the molecular and organism reaction of rainbow trout, Oncorhynchus mykiss, to the combined impact of two environmental stressors. The two stressors were the myxozoan parasite, Tetracapsuloides bryosalmonae, which is the etiological agent of proliferative kidney disease (PKD) and a natural stressor to salmonid populations, and 17β-estradiol (E2) as prototype of estrogen-active chemical stressors in the aquatic environment. Both stressors, the parasite and estrogenic contaminants, co-exist in Swiss rivers and are discussed as factors contributing to the decline of Swiss brown trout populations over the last decades. Using a microarray approach contrasting parasite-infected and non-infected rainbow trout at low or high estrogen levels, it was observed that molecular response patterns under joint exposure differed from those to the single stressors. More specifically, three major response patterns were present: (i) expression responses of gene transcripts to one stressor are weakened by the presence of the second stressor; (ii) expression responses of gene transcripts to one stressor are enhanced by the presence of the second stressor; (iii) expression responses of gene transcripts at joint treatment are dominated by one of the two stressors. Organism-level responses to concurrent E2 and parasite treatment - assessed through measuring parasite loads in the fish host and cumulative mortalities of trout - were dominated by the pathogen, with no modulating influence of E2. The findings reveal function- and level-specific responses of rainbow trout to stressor combinations, which are only partly predictable from the response to the single stressors.

I shouldn't have to do this: Illegitimate tasks as a stressor in relation to organizational control and resource deficits

The performance of tasks that are perceived as unnecessary or unreasonable, illegitimate tasks, represents a new stressor concept that refers to assignments that violate the norms associated with the role requirements of professional work. Research has shown that illegitimate tasks are associated with stress and counterproductive work behaviour. The purpose of this study was to provide insight into the contribution of characteristics of the organization on the prevalence of illegitimate tasks in the work of frontline and middle managers. Using the Bern Illegitimate Task Scale (BITS) in a sample of 440 local government operations managers in 28 different organizations in Sweden, this study supports the theoretical assumptions that illegitimate tasks are positively related to stress and negatively related to satisfaction with work performance. Results further show that 10% of the variance in illegitimate tasks can be attributed to the organization where the managers work. Multilevel referential analysis showed that the more the organization was characterized by competition for resources between units, unfair and arbitrary resource allocation and obscure decisional structure, the more illegitimate tasks managers reported. These results should be valuable for strategic-level management since they indicate that illegitimate tasks can be counteracted by means of the organization of work.

Illegitimate Tasks: Accumulating Evidence for a New Stressor Concept

INTRODUCTION: Task stressors typically refer to characteristics such as not having enough time or resources, ambiguous demands, or the like. We suggest the perceived lack of legitimacy as an additional feature of tasks as a source of stress. Tasks are “illegitimate” to the extent that it is perceived as improper to expect employees to execute them – not because of difficulties in executing them, but because of their content for a given person, time, and situation; they are illegitimate because a) they are not conforming to a specific occupational role, as in “non-nursing activities” (called unreasonable) or b) there is no legitimate need for them to exist (called unnecessary; Semmer et al., 2007). These features make illegitimate tasks a unique task-related stressor. The concept of illegitimate tasks grew from the “Stress-as-Offense-to-Self” theory (SOS; Semmer et al, 2007); it is conceptually related to role stress (Kahn et al., 1964; Beehr & Glazer, 2005) and the organizational justice tradition (Cropanzano et al., 2001; Greenberg, 2010). SOS argues that a threat to one’s self-image is at the core of many stressful experiences. Violating role expectations, illegitimate tasks can be regarded as a special case of role conflict. As roles shape identities, this violation is postulated to constitute a threat to one’s professional identity. Being assigned a task considered illegitimate is likely to be considered unfair. Lack of fairness, in turn, contains a message about one’s social standing, and thus, the self. However, the aspects discussed have not received much attention in the role stress or the justice/fairness tradition. OBJECTIVE: Illegitimate tasks are a rather recent concept that has to be established as a construct in its own right by showing that it is associated with well-being/strain while controlling for other stressors, most notably role conflict and lack of justice. The aim of the presentation is to present the evidence accumulated so far. METHODS AND RESULTS: We present several studies employing different designs, using different control variables, and testing associations with different criteria. Study 1 demonstrates associations of illegitimate tasks with self-esteem, feelings of resentment against one’s organization, and burnout, controlling for distributive justice, role conflict, and social stressors (i.e. tensions). Study 2 yielded comparable results, using the same outcome variables but controlling for distributive as well as procedural / interactional justice. Study 3 demonstrated associations between illegitimate tasks and feelings of stress, sleeping problems, and emotional exhaustion, controlling for demands, control, and social support among medical doctors. Study 4 showed that feeling appreciated by one’s superior acted as a mediator between illegitimate tasks and job satisfaction and resentments towards the military in Swiss military officers. Study 5 demonstrated an association of illegitimate tasks with counterproductive work behavior (Semmer et al. 2010). Studies 1 to 5 were cross-sectional. In Study 6, illegitimate demands predicted irritability and resentments towards one’s organization longitudinally. Study 7 also was longitudinal, focusing on intra-individual variation in multilevel modeling; occasion-specific illegitimate tasks predicted cortisol among those who judged their health as comparatively poor. Studies 1-3 and 6 used SEM, and measurement models that used unreasonable and unnecessary tasks as indicators (isolated parceling) yielded a good fit. IMPLICATIONS & CONCLUSIONS: These studies demonstrate that illegitimate tasks are a stressor in its own right that is worth studying. It illuminates the social meaning of job design, emphasizing the implications of tasks for the (professional) self, and thus combining aspects that are traditionally treated as separate, that is, social aspects and task characteristics. Practical implications are that supervisors and managers should be alerted to the social messages that may be contained in task assignments (cf. Semmer & Beehr, in press).

Temperature Dependent Effects of Elevated CO2 on Shell Composition and Mechanical Properties of Hydroides elegans: Insights from a Multiple Stressor Experiment

The majority of marine benthic invertebrates protect themselves from predators by producing calcareous tubes or shells that have remarkable mechanical strength. An elevation of CO2 or a decrease in pH in the environment can reduce intracellular pH at the site of calcification and thus interfere with animal's ability to accrete CaCO3. In nature, decreased pH in combination with stressors associated with climate change may result in the animal producing severely damaged and mechanically weak tubes. This study investigated how the interaction of environmental drivers affects production of calcareous tubes by the serpulid tubeworm, Hydroides elegans. In a factorial manipulative experiment, we analyzed the effects of pH (8.1 and 7.8), salinity (34 and 27), and temperature (23°C and 29°C) on the biomineral composition, ultrastructure and mechanical properties of the tubes. At an elevated temperature of 29°C, the tube calcite/aragonite ratio and Mg/Ca ratio were both increased, the Sr/Ca ratio was decreased, and the amorphous CaCO3 content was reduced. Notably, at elevated temperature with decreased pH and reduced salinity, the constructed tubes had a more compact ultrastructure with enhanced hardness and elasticity compared to decreased pH at ambient temperature. Thus, elevated temperature rescued the decreased pH-induced tube impairments. This indicates that tubeworms are likely to thrive in early subtropical summer climate. In the context of climate change, tubeworms could be resilient to the projected near-future decreased pH or salinity as long as surface seawater temperature rise at least by 4°C.

Multiple stressor effects of near-future elevated seawater temperature and decreased pH on righting and escape behaviors of two common Antarctic gastropods

Warming seawater temperatures and ocean acidification on the coastal western Antarctic Peninsula pose unique challenges to stenothermal marine invertebrates. The present study examines prospective sub-lethal effects of elevated temperature, pCO2, and resultant decrease in seawater pH, on righting behavior and maximal escape speeds for two common gastropods, the limpet Nacella concinna (Strebel) and mesogastropod snail Margarella antarctica (Lamy). Replicate individuals held in individual containers were exposed to four combinations of seawater temperature (1.5 °C-current average, 3.5 °C-projected average by 2100) and pH (pH 8.0-current average, pH 7.8-projected average by 2100 as a result of elevated pCO2 levels) for a period of 6 weeks. Following this chronic exposure, righting behavior, determined for the limpets as proportion to right over 24 h and for snails as time to right, as well as maximum escape speed following contact with a sea star predator were measured. We found no significant differences in proportions of limpets displaying the capacity to right among the four temperature-pH treatments. However, there was a significant temperature-pH interaction effect for mean righting times in snails, indicating that the effect of pH on the time to right is dependent on temperature. We found no significant effects of temperature or pH on mean maximal escape speed in limpets. Additionally, we observed a significant temperature-pH interaction effect for mean maximal escape speed in snails. These interactive effects make it difficult to make clear predictions about how these environmental factors may impact behavioral responses.

Medial prefrontal cortex suppression of the hypothalamic–pituitary–adrenal axis response to a physical stressor, systemic delivery of interleukin-1β

Previous studies have shown that the medial prefrontal cortex can suppress the hypothalamic-pituitary-adrenal axis response to stress. However, this effect appears to vary with the type of stressor. Furthermore, the absence of direct projections between the medial prefrontal cortex and corticotropin-releasing factor cells at the apex of the hypothalamic-pituitary-adrenal axis suggest that other brain regions must act as a relay when this inhibitory mechanism is activated. In the present study, we first established that electrolytic lesions involving the prelimbic and infralimbic medial prefrontal cortex increased plasma adrenocorticotropic hormone levels seen in response to a physical stressor, the systemic delivery of interleukin-1beta. However, medial prefrontal cortex lesions did not alter plasma adrenocorticotropic hormone levels seen in response to a psychological stressor, noise. To identify brain regions that might mediate the effect of medial prefrontal cortex lesions on hypothalamic-pituitary-adrenal axis responses to systemic interleukin-1beta, we next mapped the effects of similar lesions on interleukin-1beta-induced Fos expression in regions previously shown to regulate the hypothalamic-pituitary-adrenal axis response to this stressor. It was found that medial prefrontal cortex lesions reduced the number of Fos-positive cells in the ventral aspect of the bed nucleus of the stria terminalis. However, the final experiment, which involved combining retrograde tracing with Fos immunolabelling, revealed that bed nucleus of the stria terminalis-projecting medial prefrontal cortex neurons were largely separate from medial prefrontal cortex neurons recruited by systemic interleukin-1beta, an outcome that is difficult to reconcile with a simple medial prefrontal cortex-bed nucleus of the stria terminalis-corticotropin-releasing factor cell control circuit.

Selective processing of masked and unmasked verbal threat material in anxiety: Influence of an immediate acute stressor

Attentional biases for threat were investigated using a computerised version of the emotional Stroop task. The study examined the influence of state and trait anxiety by employing a student sample assigned to high trait anxious (HTA; n = 32) or low trait anxious (LTA; n = 32) groups on the basis of questionnaire scores, and state anxiety was manipulated within participants through the threat of electric shock. Threatening words that were either unrelated (e.g., cancer, danger) or related to the threat of shock (e.g., electrocute, shock) were presented to participants both within and outside of awareness. In the latter condition a backward masking procedure was used to prevent awareness and exposure thresholds between the target and mask were individually set for each participant. For unmasked trials the HTA group showed significant interference in colour naming for all threat words relative to control words when performing under the threat of shock, but not in the shock safe condition. For the masked trials, despite chance performance in being able to identify the lexical status of the items, HTA participants showed facilitated colour naming for all threat words relative to control items when performing under threat of shock, but this effect was not evident in the shock safe condition. Neither valence of the items nor the threat of shock influenced colour naming latencies in either exposure mode for the LTA group.