Chronic restraint stress impairs T-cell immunity and promotes tumor progression in mice

Long-term exposure to stressful situations can affect the immune system. The T-cell response is an important component of anti-tumoral immunity. Hence, impairment of the immune function induced by a chronic stressor has been postulated to alter the immunosurveillance of tumors, thus leading to a worse neoplastic prognosis. Here, we show that chronic restraint stress affects T-cell mediated immunity in mice. This was evidenced by a decrease of mitogen-induced T-cell proliferation, a reduction in CD4(+)T lymphocyte number and a decrease of tumor necrosis factor-alpha (TNF-alpha) and Interferon-gamma (IFN-gamma) production in stressed mice. Additionally, mice subjected to chronic restraint stress displayed an enhancement of tumor growth in a syngeneic lymphoma model, i.e. an increase of tumor proliferation and a reduction of animal survival. Finally, stressed mice had a reduced specific cytotoxic response against these tumor cells. These results suggest that chronic exposure to stress promotes cancer establishment and subsequent progression, probably by depressing T-cell mediated immunity. The T-cell immunity impairment as well as the tumor progression enhancement emphasize the importance of the therapeutic management of stress to improve the prognosis of cancer patients.     

Application of regression and neural models to predict competitive swimming performance

This research problem was indirectly but closely connected with the optimization of an athlete-selection process, based on predictions viewed as determinants of future successes. The research project involved a group of 249 competitive swimmers (age 12 yr., SD = 0.5) who trained and competed for four years. Measures involving fitness (e.g., lung capacity), strength (e.g., standing long jump), swimming technique (turn, glide, distance per stroke cycle), anthropometric variables (e.g., hand and foot size), as well as specific swimming measures (speeds in particular distances), were used. The participants (n = 189) trained from May 2008 to May 2009, which involved five days of swimming workouts per week, and three additional 45-min. sessions devoted to measurements necessary for this study. In June 2009, data from two groups of 30 swimmers each (n = 60) were used to identify predictor variables. Models were then constructed from these variables to predict final swimming performance in the 50 meter and 800 meter crawl events. Nonlinear regression models and neural models were built for the dependent variable of sport results (performance at 50m and 800m). In May 2010, the swimmers' actual race times for these events were compared to the predictions created a year prior to the beginning of the experiment. Results for the nonlinear regression models and perceptron networks structured as 8-4-1 and 4-3-1 indicated that the neural models overall more accurately predicted final swimming performance from initial training, strength, fitness, and body measurements. Differences in the sum of absolute error values were 4:11.96 (n = 30 for 800m) and 20.39 (n = 30 for 50m), for models structured as 8-4-1 and 4-3-1, respectively, with the neural models being more accurate. It seems possible that such models can be used to predict future performance, as well as in the process of recruiting athletes for specific styles and distances in swimming.     

Recent exposure to a dangerous context impairs extinction and reinstates lost fear reactions

Rats were shocked in a context and then exposed to that context in the absence of shock. Shorter intervals between these extinction trials produced more long-term freezing than did longer ones, and shorter intervals between the final extinction trial and test produced more freezing than did longer ones. A short interval between a context extinction trial and test with an extinguished conditioned stimulus (CS) produced more freezing than did a longer one, and a short interval between a nonreinforced context exposure and an extinguished CS reinstated freezing when the CS was tested 24 hr later. The results suggest that recent fear acts to favor subsequent retrieval of the memory formed at conditioning rather than extinction and to render the retrieved memory more salient.     

Working-memory and auditory localization: Demand for central resources impairs performance

Four experiments explored possible roles for working memory in sound localization. In each experiment, the angular error of localization was assessed when performed alone, or concurrently with a working-memory task. The role of the phonological slave systems in auditory localization was ruled out by Experiments 1 and 2, while an engagement of central resources was suggested by the results of Experiment 3. Experiment 4 examined the involvement of visuo-spatial systems in auditory localization and revealed impairment of localization by the concurrent spatial working-memory task. A comparison of dual-task decrement across all four studies suggests that localization places greater demand on central than on spatial resources.     

Oral administration of guanosine impairs inhibitory avoidance performance in rats and mice

Extracellular guanine-based purines, mainly the nucleoside guanosine, have recently been shown to exert neuroprotective effects, which seem to be related to antagonism of the glutamatergic system. In this study, we investigated the effects of acute oral administration of guanosine on inhibitory avoidance task in rats and mice. We also studied its effects on locomotor activity, anxiety-related behaviors and mechanisms of action involving the purinergic system. Guanosine (2.0 and 7.5mg/kg, per os), administered 75min pretraining, dose-dependently impaired retention of the inhibitory avoidance task in rats and mice, an effect not prevented by the adenosine receptor antagonist caffeine. Guanosine presented no effects on locomotor activity and anxiety-related behaviors. This amnesic effect of guanosine may be compatible with inhibition of glutamatergic system and seems to be not mediated by adenosine.     

Impulsivity,sensation seeking and reproductive behaviour: A life history perspective

Impulsivity has often been invoked as a proximate driver of different life-history strategies. However, conceptualisations of “impulsivity” are inconsistent and ambiguities exist regarding which facets of impulsivity are actually involved in the canalisation of reproductive strategies. Two variables commonly used to represent impulsivity were examined in relation to reproductive behaviour. Results demonstrated that sensation seeking was significantly related to strategy-based behaviour, but impulsivity (defined as a failure to deliberate) was only weakly correlated. The effect of impulsivity disappeared when sensation seeking was controlled. Sex differences emerged for sensation seeking but not impulsivity. We conclude that “impulsivity” is not a unitary trait and that clearer distinctions should be made between facets of this construct.     

The performance and observation of action shape future behaviour

The observation of other people’s actions plays an important role in shaping the perceptual, cognitive, and motor processes of the observer. It has been suggested that these social influences occur because the observation of action evokes a representation of that response in the observer and that these codes are subsequently accessed by other cognitive systems to modify future behaviour. In the case of social search and movement tasks, the observation-evoked response code is thought to activate the same mechanisms that are activated following internally-generated response codes. In support of this hypothesis, the present study revealed that the magnitudes of the between-person inhibition of return (IOR) effects were correlated with within-person IOR effects. These findings provide substantial support for the link between observation-evoked response codes and social cognitive effects.     

Effects of body size and body mass on the swimming performance of preschool children

This research examined the relationship between body size and mass and the performance of 3- to 6-year-old children (n=117) on two categories of swimming tasks: Locomotion: Front and Locomotion: Back. The major hypothesis was that body size and mass measurements would be good predictors of children's swimming performance. The function of age/gender also was examined. Stepwise multiple regression was used to select the best predictors of swimming performance after controlling for amount of aquatic training and child's apprehensiveness about water. Body weight was the best predictor of children's swimming performance on each category of tasks (p<0.01). It accounted for at least 16% of performance variation when entered alone, and it accounted for 5% given age. Age was of little importance after body size and mass were taken into account. The major conclusion was that future research should incorporate more complex research designs to account for the network of influencing factors.     

Behavioural variability and motor performance: Effect of practice specialization in front crawl swimming

The aim was to examine behavioural variability within and between individuals, especially in a swimming task, to explore how swimmers with various specialty (competitive short distance swimming vs. triathlon) adapt to repetitive events of sub-maximal intensity, controlled in speed but of various distances. Five swimmers and five triathletes randomly performed three variants (with steps of 200, 300 and 400 m distances) of a front crawl incremental step test until exhaustion. Multi-camera system was used to collect and analyse eight kinematical and swimming efficiency parameters. Analysis of variance showed significant differences between swimmers and triathletes, with significant individual effect. Cluster analysis put these parameters together to investigate whether each individual used the same pattern(s) and one or several patterns to achieve the task goal. Results exhibited ten patterns for the whole population, with only two behavioural patterns shared between swimmers and triathletes. Swimmers tended to use higher hand velocity and index of coordination than triathletes. Mono-stability occurred in swimmers whatever the task constraint showing high stability, while triathletes revealed bi-stability because they switched to another pattern at mid-distance of the task. Finally, our analysis helped to explain and understand effect of specialty and more broadly individual adaptation to task constraint.     

Eye movements drive steering: reduced eye movement distribution impairs steering and driving performance

On a winding open road, a driver consistently looks to the inside of each bend before turning the steering wheel. When researchers disrupt this coordination by instructing drivers not to move their eyes, drivers' performance is impaired and their completion time during racing increases. The present authors examined whether changing internal states in a way that also restricts eye movements reduces coordination and affects performance. Participants (N = 24) completed a simulated rally stage under manipulation of their anxiety state through ego threat. Performance decreased under pressure, and the decrement was associated with a narrowing of the range of eye movements and a reduced correlation of eye movements with steering. The authors discuss the possibility that the deterioration in performance is a cost of maintaining steering when eye-movement driving input to the steering controller is reduced.     

Lifelong estrogen exposure and cognitive performance in elderly women

Fluctuating endogenous and exogenous estrogens influence cognition in women. In this study, cognitive functioning in elderly women was examined by applying methodology used in understanding the effects of chronic estrogen exposure on hormone-sensitive tissue other than the brain. An index, combining menstrual, reproductive, and physical markers associated with estrogen levels, was developed for elderly, nondemented, predominantly Caucasian women (n = 87). This index related to better performance on two verbal factors, one attentional and one global in nature. Findings suggest that estrogen exposure across the life span plays a role in brain aging. Possible physiological mechanisms for this effect are discussed.     

Early tutoring and adult reproductive behaviour in female domestic canary (Serinus canaria)

We studied the effect of early tutoring on the subsequent sexual preferences and reproductive activity of female domestic canaries (Serinus canaria). Young female canaries were exposed during the first 4 months of life to songs of either domestic or wild canaries. When adult, these females were again exposed to domestic or wild songs. In the first experiment, the sexual responses of the females to unfamiliar domestic and wild songs were quantified with the copulation solicitation display (CSD) assay. In the second experiment, the same females were tested again with modified tutoring songs. In the third experiment, song stimulation of nest-building and egg-laying was studied. Domestic-strain-tutored females gave more CSDs to domestic than to wild songs. In contrast, wild-strain-tutored females showed no sexual preference. We propose that the sexual preference of adult domestic-strain-tutored female canaries for domestic songs is the consequence of learning and categorisation processes. The discrepancy between the results of the domestic-strain-tutored females and those of the wild-strain-tutored females suggests that female canaries have a predisposition to learn songs of their own strain rather than songs of an alien strain. In the third experiment nest-building and egg-laying activities appeared to be unaffected by early tutoring conditions: there was no significant differential effect of the different tutoring and exposure conditions on nest-building and egg-laying scores. Mate attraction and stimulation of females’ reproductive activity appear to be two separate functions of male song, which may have been shaped by different evolutionary constraints. Received: 24 July 1999 / Accepted after revision: 22 February 2000     

Chronic self-perceived stress and set-shifting performance in undergraduate students

Given recent findings on the potential for detrimental effects of chronic stress on the prefrontal cortex, additional research on the relationship between chronic stress and performance on executive functioning tasks (dependent on prefrontal functioning) is needed. Eighty-one undergraduate students completed a self-report measure of stress over the previous month (perceived stress scale--PSS) and the comprehensive trail-making test (CTMT, Trials 3 and 5). Results revealed a statistically significant positive correlation between PSS score and time needed to complete Trial 5 of the CTMT, which places demands on the set-shifting component of executive functioning. This finding adds to a growing body of work that suggests a relationship between chronic stress and executive functioning, and extends these findings to include set-shifting performance.     

Chronic illness and aggressive behaviour: A population-based study of 4-year-olds

The objective of this study was to examine the hypothesis that aggressive behaviour is explained by various medical conditions. The current study investigated this hypothesis in a population-based study of families with a 4-year-old child (n?=?1915). Maternal reports of child health and development were assessed and a paediatrician examined a subsample (n?=?263) with a chronic illness. Twice as many toddlers with a chronic physical disorder displayed aggressive behaviour when compared with toddlers without such disorders. All seven medical diagnostic categories included children with aggressive behaviour, but the highly prevalent condition of asthma contributed to more than a third of the cases with co-occurrence of chronic illness and aggressive behaviour. Neurological, sensory and skin/joint disorders accounted for another third. Subsequent analyses showed that poor language was an additional risk factor while attending day-care centres in groups with 5?–?15 children was a protective factor against aggressive behaviour.     

Feedback during exposure to inescapable shocks and subsequent shock-escape performance

In two experiments, we assessed the ability of a feedback stimulus during helplessness training to reduce the performance deficits common to inescapable shock. In each experiment, four groups of rats were exposed to either escapable shock (E), inescapable shock with a feedback stimulus following shock termination (Y-FS), inescapable shock with no feedback stimulus (Y-NFS), or no shock (N). The feedback stimulus eliminated the interference effects of inescapable shock when tested with an FR-3 lever press escape task (Experiment 1) or on an FR-1 task with a 3-s delay between the response and shock termination (Experiment 2). These results suggest that stress-induced biochemical changes may mediate the interference effects seen in inescapably shocked rats.     

Problem-solving performance and reproductive success of great tits in urban and forest habitats

Success in problem solving, a form of innovativeness, can help animals exploit their environments, and recent research suggests that it may correlate with reproductive success. Innovativeness has been proposed to be especially beneficial in urbanized habitats, as suggested by superior problem-solving performance of urban individuals in some species. If there is stronger selection for innovativeness in cities than in natural habitats, we expect problem-solving performance to have a greater positive effect on fitness in more urbanized habitats. We tested this idea in great tits (Parus major) breeding at two urban sites and two forests by measuring their problem-solving performance in an obstacle-removal task and a food-acquisition task. Urban pairs were significantly faster problem-solvers in both tasks. Solving speed in the obstacle-removal task was positively correlated with hatching success and the number of fledglings, whereas performance in the food-acquisition task did not correlate with reproductive success. These relationships did not differ between urban and forest habitats. Neophobia, sensitivity to human disturbance, and risk taking in the presence of a predator did not explain the relationships of problem-solving performance either with habitat type or with reproductive success. Our results suggest that the benefit of innovativeness in terms of reproductive success is similar in urban and natural habitats, implying that problem-solving skills may be enhanced in urban populations by some other benefits (e.g. increased survival) or reduced costs (e.g. more opportunities to gain practice with challenging tasks).     

The effect of state core self-evaluations on task performance,organizational citizenship behaviour,and counterproductive work behaviour

Although the personality–performance relationship has been studied extensively, most studies focused on the relationship between between-person differences in the Big Five personality dimensions and between-person differences in job performance. The current paper extends this research in two ways. First, we build on core self-evaluations (CSEs): an alternative, broad personality dimension that has proven to be a good predictor of job performance. Second, we tested concurrent and lagged within-person relationships between CSEs and task performance, organizational citizenship behaviour (OCB), and counterproductive work behaviour (CWB). To this end, we conducted two experience sampling studies; the first one assessing the relationship between state CSEs and levels of momentary task performance and OCB, and a second study in which employees reported on their level of state CSEs and momentary CWB. Results showed that there is substantial within-person variability in CSEs and that these within-person fluctuations relate to within-person variation in task performance, OCB, and CWB towards the organization, and CWB towards the individual. Moreover, CSEs prospectively predicted within-person differences in task performance and CWB towards the organization, whereas the reversed effect did not hold. These findings tentatively suggest that state CSEs predict performance, rather than the other way around.