985 resultados para Academic Stress
Resumo:
The purpose of the present study is to break down, in a general and summarised way, the concept of the coherence of the European Foreign Policy, in order to analyse its meaning, its scope and its implications. This focus on coherence will be specifically dealt with upon the analysis of the impact of this phenomenon on single institutional framework, as defined by the Treaty on European Union.
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1. Dietary conditions affect cognitive abilities of many species, but it is unclear to what extent this physiological effect translates into an evolutionary relationship. 2. A reduction of competitive ability under nutritional stress has been reported as a correlated response to selection for learning ability in Drosophila melanogaster. Here we test whether the reverse holds as well, i.e. whether an evolutionary adaptation to poor food conditions leads to a decrease in learning capacities. 3. Populations of D. melanogaster were: (i) not subject to selection (control), (ii) selected for improved learning ability, (iii) selected for survival and fast development on poor food, or (iv) subject to both selection regimes. 4. There was no detectable response to selection for learning ability. 5. Selection on poor food led to higher survival, faster development and smaller adult size as a direct response, and to reduced learning ability as a correlated response. This study supports the hypothesis that adaptation to poor nutrition is likely to trade off with the evolution of improved learning ability.
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Among the various work stress models, one of the most popular has been the job demands-control (JDC) model developed by Karasek (1979), which postulates that work-related strain is highest under work conditions characterized by high demands and low autonomy. The absence of social support at work further increases negative outcomes. This model, however, does not apply equally to all individuals and to all cultures. This review demonstrates how various individual characteristics, especially some personality dimensions, influence the JDC model and could thus be considered buffering or moderator factors. Moreover, we review how the cultural context impacts this model as suggested by results obtained in European, American, and Asian contexts. Yet there are almost no data from Africa or South America. More crosscultural studies including populations from these continents would be valuable for a better understanding of the impact of the cultural context on the JDC model.
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AIMS/HYPOTHESIS: Pro-atherogenic and pro-oxidant, oxidised LDL trigger adverse effects on pancreatic beta cells, possibly contributing to diabetes progression. Because oxidised LDL diminish the expression of genes regulated by the inducible cAMP early repressor (ICER), we investigated the involvement of this transcription factor and of oxidative stress in beta cell failure elicited by oxidised LDL. METHODS: Isolated human and rat islets, and insulin-secreting cells were cultured with human native or oxidised LDL or with hydrogen peroxide. The expression of genes was determined by quantitative real-time PCR and western blotting. Insulin secretion was monitored by EIA kit. Cell apoptosis was determined by scoring cells displaying pycnotic nuclei. RESULTS: Exposure of beta cell lines and islets to oxidised LDL, but not to native LDL raised the abundance of ICER. Induction of this repressor by the modified LDL compromised the expression of important beta cell genes, including insulin and anti-apoptotic islet brain 1, as well as of genes coding for key components of the secretory machinery. This led to hampering of insulin production and secretion, and of cell survival. Silencing of this transcription factor by RNA interference restored the expression of its target genes and alleviated beta cell dysfunction and death triggered by oxidised LDL. Induction of ICER was stimulated by oxidative stress, whereas antioxidant treatment with N-acetylcysteine or HDL prevented the rise of ICER elicited by oxidised LDL and restored beta cell functions. CONCLUSIONS/INTERPRETATION: Induction of ICER links oxidative stress to beta cell failure caused by oxidised LDL and can be effectively abrogated by antioxidant treatment.
Resumo:
The long-term implications of sexual abuse in childhood or adolescence (CSA) have been relatively well documented regarding attachment (disorganized attachment in childhood, unresolved trauma in adulthood), stress reactions (altered patterns of stress reactivity under experimental conditions), and psychopathology. Attachment has been shown to mediate the implications of CSA, namely on psychopathology. The implication of attachment on stress responses of abused persons has not been documented. Twenty-seven 20-46 years old women who had experienced episodes of CSA, and 17 controls have been interviewed using the Adult Attachment Interview. Sixty-three percent of abused women presented an unresolved trauma (12% for the controls). Thirty-six women (14 controls and 22 abused) came again to the laboratory for a session involving an experimental stress challenge (TSST). Subjects provided repeated appreciations of perceived stress on visual analogue scales and saliva samples were collected to assay cortisol levels. Whereas abused women with unresolved trauma showed the highest levels of perceived stress, they simultaneously presented the most suppressed cortisol reactions (there were significant post hoc differences between "unresolved abused" and controls on the increase of perceived stress and on cortisol recovery after the acute stress). It is suggested that important stressful experiences (such as CSA), especially when they have not been psychologically assimilated, may cause a disconnection, during subsequent mildly stressful circumstances, between the perception of stress and natural defensive body reactions.
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BACKGROUND: A hallmark of the pathophysiology of schizophrenia is a dysfunction of parvalbumin-expressing fast-spiking interneurons, which are essential for the coordination of neuronal synchrony during sensory and cognitive processing. Oxidative stress as observed in schizophrenia affects parvalbumin interneurons. However, it is unknown whether the deleterious effect of oxidative stress is particularly prevalent during specific developmental time windows. METHODS: We used mice with impaired synthesis of glutathione (Gclm knockout [KO] mice) to investigate the effect of redox dysregulation and additional insults applied at various periods of postnatal development on maturation and long-term integrity of parvalbumin interneurons in the anterior cingulate cortex. RESULTS: A redox dysregulation, as in Gclm KO mice, renders parvalbumin interneurons but not calbindin or calretinin interneurons vulnerable and prone to exhibit oxidative stress. A glutathione deficit delays maturation of parvalbumin interneurons, including their perineuronal net. Moreover, an additional oxidative challenge in preweaning or pubertal but not in young adult Gclm KO mice reduces the number of parvalbumin-immunoreactive interneurons. This effect persists into adulthood and can be prevented with the antioxidant N-acetylcysteine. CONCLUSIONS: In Gclm KO mice, early-life insults inducing oxidative stress are detrimental to immature parvalbumin interneurons and have long-term consequences. In analogy, individuals carrying genetic risks to redox dysregulation would be potentially vulnerable to early-life environmental insults, during the maturation of parvalbumin interneurons. Our data support the need to develop novel therapeutic approaches based on antioxidant and redox regulator compounds such as N-acetylcysteine, which could be used preventively in young at-risk subjects.
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In this article we compare regression models obtained to predict PhD students’ academic performance in the universities of Girona (Spain) and Slovenia. Explanatory variables are characteristics of PhD student’s research group understood as an egocentered social network, background and attitudinal characteristics of the PhD students and some characteristics of the supervisors. Academic performance was measured by the weighted number of publications. Two web questionnaires were designed, one for PhD students and one for their supervisors and other research group members. Most of the variables were easily comparable across universities due to the careful translation procedure and pre-tests. When direct comparison was notpossible we created comparable indicators. We used a regression model in which the country was introduced as a dummy coded variable including all possible interaction effects. The optimal transformations of the main and interaction variables are discussed. Some differences between Slovenian and Girona universities emerge. Some variables like supervisor’s performance and motivation for autonomy prior to starting the PhD have the same positive effect on the PhD student’s performance in both countries. On the other hand, variables like too close supervision by the supervisor and having children have a negative influence in both countries. However, we find differences between countries when we observe the motivation for research prior to starting the PhD which increases performance in Slovenia but not in Girona. As regards network variables, frequency of supervisor advice increases performance in Slovenia and decreases it in Girona. The negative effect in Girona could be explained by the fact that additional contacts of the PhD student with his/her supervisor might indicate a higher workload in addition to or instead of a better advice about the dissertation. The number of external student’s advice relationships and social support mean contact intensity are not significant in Girona, but they have a negative effect in Slovenia. We might explain the negative effect of external advice relationships in Slovenia by saying that a lot of external advice may actually result from a lack of the more relevant internal advice
Resumo:
BACKGROUND: In our hands, in vivo segmental vessel length changes up to 5% because of blood pressure: increasing in arterial pressure is associated to decrease in segmental vessel length. METHODS AND MATERIAL: Using two piezoelectric crystals sutured on vessel wall and a high fidelity pressure probe, we recorded artery length variations as function of blood pressure, before and after an end-to-end anastomosis on four pigs carotid arteries. RESULTS: Mean arterial pressure before anastomosis = 73 mmHg (+/- 12); mean arterial pressure after anastomosis = 91 mmHg (+/- 14); mean crystals displacement before anastomosis during systole = -0.21 mm; mean crystals displacement after anastomosis during systole = +0.24 mm; mean distance between crystals before anastomosis = 12.3 mm (+/- 0.8) and after anastomosis = 11.2 mm (+/- 0.5). CONCLUSIONS: In the acute phase following an end-to-end anastomosis, an increase in blood pressure causes increasing in vessel length, with an exponential correlation. The anastomosis is constantly subjected to a longitudinal traction whose magnitude depends on blood pressure.
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This paper investigates the factors in_uencing grade performance in two different high school tracks (academic and vocational), including the effect of the amount of work achieved while studying. The empirical strategy analyzes grade progression through the outcomes, passing, repeating and dropping out, conditioning on previous outcomes, and dealing with the endogeneity introduced by the working variable. The analysis is based on a unique Spanish data with information on schooling and labor histories. Findings show that working reduces performance in both tracks, mainly during the first year, although the ffects are less detri- mental in the vocational path. Additionally, good performance in compulsory education, at- tending a private high school, or having high-educated parents improve outcomes, particularly in academic high school.
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Mothers' general anxiety, anxiety about the well-being of the child and psychological stress before prenatal testing was studied by comparing women who conceived through in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) with women who conceived naturally. Before the first trimester screening test for Down's syndrome, a group of 51 women who conceived through IVF/ICSI and a group of 54 women who conceived spontaneously completed the State Scale of the State-Trait Anxiety Inventory (S-Anxiety; Spielberger, 1983), the Fear of Bearing a Physically or Mentally Handicapped Child Subscale of the Pregnancy-related Anxiety Questionnaire (PRAQ-R; Huizink et al., 2004), the Psychological Stress Measure (PSM; Lemyre & Tessier, 1988), and the Prenatal Psychosocial Profile (PPP; Curry, Campbell, & Christian, 1994). Women who conceived through IVF/ICSI had more elevated levels of general anxiety and psychological stress than the women who conceived naturally; however, no difference was observed between the two groups for anxiety specifically related to the health of the child. These results underline the need to monitor women's emotional state after conception via IVF/ICSI-when counseling usually ends-and around the time of the first trimester screening. Counseling might thus be extended.
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Objective: Converging evidence speak in favor of an abnormal susceptibility to oxidative stress in schizophrenia. A decreased level of glutathione (GSH), the principal non-protein antioxidant and redox regulator, was observed both in cerebrospinal-fluid and prefrontal cortex of schizophrenia patients (Do et al., 2000). Results: Schizophrenia patients have an abnormal GSH synthesis most likely of genetic origin: Two independent case-control studies showed a significant association between schizophrenia and a GAG trinucleotide repeat (TNR) polymorphism in the GSH key synthesizing enzyme glutamate-cysteine-ligase (GCL) catalytic subunit (GCLC) gene. The most common TNR genotype 7/7 was more frequent in controls, whereas the rarest TNR genotype 8/8 was three times more frequent in patients. The disease-associated genotypes correlated with a decrease in GCLC protein expression, GCL activity and GSH content. Such a redox dysregulation during development could underlie the structural and functional anomalies in connectivity: In experimental models, GSH deficit induced anomalies similar to those observed in patients. (a) morphology: In animal models with GSH deficit during the development we observed in prefrontal cortex a decreased dendritic spines density in pyramidal cells and an abnormal development of parvalbumine (but not of calretinine) immunoreactive GABA interneurones in anterior cingulate cortex. (b) physiology: GSH depletion in hippocampal slices induces NMDA receptors hypofunction and an impairment of long term potentiation. In addition, GSH deficit affected the modulation of dopamine on NMDA-induced Ca 2+ response in cultured cortical neurons. While dopamine enhanced NMDA responses in control neurons, it depressed NMDA responses in GSH-depleted neurons. Antagonist of D2-, but not D1-receptors, prevented this depression, a mechanism contributing to the efficacy of antipsychotics. The redox sensitive ryanodine receptors and L-type calcium channels underlie these observations. (c) cognition: Developing rats with low [GSH] and high dopamine lead deficit in olfactory integration and in object recognition which appears earlier in males that females, in analogy to the delay of the psychosis onset between man and woman. Conclusion: These clinical and experimental evidence, combined with the favorable outcome of a clinical trial with N-Acetyl Cysteine, a GSH precursor, on both the negative symptoms (Berk et al., submitted) and the mismatch negativity in an auditory oddball paradigm supported the proposal that a GSH synthesis impairment of genetic origin represent, among other factors, one major risk factor in schizophrenia.
Time of injection determines the effect of alpha-MSH antiserum on DA neurons in psychological stress
Resumo:
Male rats were subjected to "psychological stress" which consisted in 10 sec footshock on the first day followed 24 hr later by a 10 sec stay in the experimental chamber without shock. Intravenous antiserum against alpha-MSH markedly changed the functional state of mesencephalic and hypothalamic DA neurons (assessed by histochemical microfluorimetry) when administered before the second session but not when given before the first session. These observations reveal an interesting parallelism in the temporal characteristics of the effects of alpha-MSH on avoidance behavior and central DA systems.