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At least 919 records · Page 51Linked to original sources
PubMed1996

The behaviour of collagen fibres in stress relaxation and stress distribution in the jaw-joint disc of rabbits.

The physical properties of the temporomandibular joint disc are largely attributable to its collagen fibre and proteoglycan composition and organization. Structural and stress relaxation data were obtained from the discs of six rabbits. Two stainless-steel balls, 4.8 mm dia, were used to load the disc surfaces in compression. Stress relaxation tests were performed at loads of 0.8-1.4 kg, and the disc was then placed in fixative while still in the loading apparatus in order to preserve its deformed state at equilibrium stress. After overnight fixation the discs were sectioned and assessed by means of a polarizing microscope with a rotating universal stage. This allowed measurement of three-dimensional changes in collagen fibre waviness and alignment as the result of loading. The data showed that despite significant stress relaxation and strains, only minor changes in fibre waviness and alignment occurred within the disc, reflecting its effectiveness as a tough but compliant structure, well suited to distribute load in the temporomandibular joint.

Animals↗
PubMed2003

Divergence of endocrine and metabolic responses to stress in two rainbow trout lines selected for differing cortisol responsiveness to stress.

Rainbow trout (Oncorhynchus mykiss) of two lines selected for low (LR) and high (HR) cortisol stress-responsiveness were subjected to confinement for a period of 336 h. Endocrine (plasma cortisol, hepatic cortisol binding) and metabolic (plasma glucose, lactate, amino acids; hepatic glycogen and alanine aminotransferase levels) indices of stress were measured at intervals in confined and unconfined fish of both lines. During confinement plasma cortisol concentration reached maximum values earlier in HR fish (2h) than in LR fish (6h) returning to control values within 336 h in both lines. Paradoxically, although both HR and LR lines displayed a characteristic metabolic stress response, these changes were more pronounced in LR fish. Plasma glucose and lactate levels increased during confinement in both lines but to a significantly greater extent in LR fish. Confinement significantly elevated plasma amino acids to a greater extent in LR fish than in HR fish. Liver glycogen concentration was depleted most rapidly in LR fish but was significantly higher in confined fish of both lines than controls at the end of the experiment. No significant changes were observed in hepatic alanine aminotransferase activity during confinement. Confined fish of both lines displayed a decrease in hepatic cortisol receptor abundance within 24h and this was more sustained in HR fish. The more pronounced disturbance of a broad range of indicators of stress in confined LR fish, compared to HR fish, throws doubt on the magnitude of the cortisol response being the primary driver of these differences.

Adaptation, Physiological↗
PubMed2003

Facilitation of hypothalamic-pituitary-adrenal responses to novel stress following repeated social stress using the resident/intruder paradigm.

Our goal in these studies was to characterize some specific aspects of hypothalamic-pituitary-adrenal (HPA) activity in rats exposed to repeated social stress. We used a modification of the resident/intruder paradigm in which male intruder rats were subjected to defeat and then separated from the resident by an enclosure for a total of 30 min on Day 1. On Days 2-7, intruder rats were exposed to different resident rats every day through a wire mesh enclosure for 30 min in order to minimize injurious physical contact between the two rats. The intruder rats gained significantly less weight than controls over the 7-day period of stress though basal corticosterone levels and adrenal and thymus weights were not significantly different between the two groups. On Day 8, repeatedly stressed rats exhibited facilitation of HPA responses to novel restraint compared to controls but no differences in negative feedback sensitivity to dexamethasone (0.05 or 0.2 mg/kg) were observed. Thus, the HPA axis of socially stressed rats remains responsive to a stimulus that has never been encountered. Using this type of repeated presentation to an aggressive resident allows us to examine the neuroendocrine and behavioral consequences, and their underlying neural mechanisms, of exposure to a stressor that is social in nature and naturalistic for rodents.

Adrenocorticotropic Hormone↗
PubMed1997

Assessing illness-related stress in psoriasis: the psychometric properties of the Psoriasis Life Stress Inventory.

The purpose of the present study was to undertake a clinical and psychometric reappraisal of the Psoriasis Life Stress Inventory (PLSI). Total PLSI score was inversely related to age of onset of psoriasis, but bore no significant relationship to duration or to clinical severity. Similarly, patients' stress score did not differ with regards to the nature of their current treatment, to their beliefs as to what was responsible for exacerbation or improvement of their condition, or to the patients' gender. Factor analysis extracted two factors which suggested that the psychosocial impact of psoriasis results from stress associated with: (i) engaging in anticipatory/avoidance coping behavior that is effected to limit the sociocognitive intrusiveness of psoriasis; and (ii) stress resulting from patients' beliefs or actual experiences of being evaluated by others solely on the basis of their skin. The internal reliability of the scale can be improved by the deletion of three items. Revision of the PLSI is recommended to render it psychometrically and clinically acceptable for use in the UK.

Adaptation, Psychological↗
PubMed2002

Effects of prenatal stress on stress-induced changes in behavior and macrophage activity of mice.

The present study analyzed the effects of maternal stress on behavior and macrophage activity of mice. Pregnant mice received a daily footshock (0.2 mA) from gestational days 15 (GD15) to 19. Experiments were performed on male offspring, challenged or not with another footshock (0.2 mA) on postnatal day 30 (PND30) or 60. The following results were obtained for maternal stress: (1) increment in locomotor activity of juvenile but not of adult mice observed in both open-field and plus-maze; (2) increment in rearing frequency of juvenile but not of adult mice observed in the open-field; (3) decrement in macrophage spreading of adult but not of juvenile mice; (4) abolishment of postnatal footshock effects in both macrophage spreading on PND30 and macrophage nitric oxide (NO) production on PND60; (5) reversion of postnatal footshock effects on H(2)O(2) spontaneous and PMA-induced release by macrophage on PND30; (6) modification of postnatal stress effects on macrophage phagocytosis on PND60. These changes were unrelated to differences in gestational parameters and did not reflect altered maternal-pup interactions or nutritional factors. The observed data provide experimental evidence that maternal stress alters behavior, and macrophage activity at the same time and in the same litter. These data were discussed in the light of possible neuroimmune interactions that involve catecholaminergic pathways.

Animals↗
PubMed2002

Stress-induced social avoidance: a new model of stress-induced anxiety?

We have studied the long-term behavioral effects of a single stressor in male rats by using an approach/avoidance situation as the behavioral endpoint. A single exposure to social defeat or electric shocks was used as stressors. Behavioral testing was performed in a two-compartment cage divided by an opaque wall and connected by a short tunnel. The larger compartment contained an unfamiliar male rat that was separated from the rest of the compartment by a transparent, perforated Plexiglas wall. The subject was placed in the small compartment and allowed to explore the cage for 5 min. The test was performed on Days 1, 5, or 10 after stress application. Unstressed rats spent 90% of time in the large compartment that contained the unfamiliar male. Social defeat dramatically reduced the exploration of the large compartment, without time-related changes in this response. A mild electric shock had a similar effect that lasted more than 5 days but less than 10 days. The exploration of an empty cage was significantly less inhibited by stress than the exploration of a cage that contained the stimulus rat. The test could be applied repeatedly in the same rat, without major changes in the response. Chlordiazepoxide applied 1 h before behavioral testing abolished completely the stress-induced behavioral deficit. We suggest that the model can be used for studying the effects of various compounds on stress-induced anxiety.

Animals↗
PubMedDate not supplied

Sex differences in the effects of prenatal stress on stress-induced analgesia.

Prenatal stress (PS) is known to cause demasculinizing and feminizing effects on sexually dimorphic behavior in laboratory animals. In three separate experiments performed on the same subjects at 10 week intervals, nociceptive sensitivity and the analgesic response to a cold-water swim stress were assessed in adult male and female Swiss-Webster mice that were either stressed prenatally or nonstressed (NS) control subjects. Experiment 1 showed analgesic magnitude to increase in female mice as a result of PS compared to nonstressed controls, whereas no changes were noted in male subjects. The increase in analgesia in female mice is maintained by estrogen. as gonadectomy eliminated the increase in Experiment 2, and estrogen replacement restored it in Experiment 3. Withdrawal latency to a noxious heat stimulus (hot-plate test) was also influenced by the PS manipulation; a decrease in hot-plate latency (indicating greater nociceptive sensitivity) was noted in PS subjects of both sexes in Experiment 1. Repeated testing (and/or age) may influence the effect of PS on nociceptive responses in a sex-dependent manner. The reduction in hot-plate latency was only present in males in Experiment 2, and was not present in either sex by Experiment 3. Thus, PS influences both baseline pain sensitivity and stress-induced analgesia responses in a sex and hormone-dependent fashion.

Animals↗
PubMed1996

The 5-HT1A receptor is not involved in emotional stress-induced rises in stress hormones.

To determine whether emotional stress-induced rises in stress hormone levels are mediated by activation of 5-HT1A receptors, we studied the effects of the selective 5-HT1A receptor antagonist, N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexanecarboxamide trihydrochloride (WAY-100635) on plasma ACTH, corticosterone, prolactin, and glucose levels in the conditioned ultrasonic vocalisation (USV) model in adult rats. The effects of WAY-100635 on USVs were also investigated in this paradigm. WAY-100635 (0.3, 1, and 3 mg/kg SC) had no clear effects on basal plasma ACTH, corticosterone, and glucose levels, but the 3 mg/kg dose significantly increased the plasma prolactin levels. The increases in plasma ACTH, corticosterone, and prolactin levels induced by the USV procedure were not affected by WAY-100635. This indicates that the 5-HT1A receptor does not play a major role in the distress-induced activation of the hypothalamic-pituitary-adrenal axis and prolactin secretion. The USVs were significantly enhanced by low doses of WAY-100635 (0.03 and 0.3 mg/kg SC), whereas higher doses (1.0 and 3.0 mg/kg SC) had no effect. These findings suggest that blockade of 5-HT1A receptors during stress may enhance the behavioural stress-response.

Adrenocorticotropic Hormone↗
PubMed1998

A family of stress-inducible GADD45-like proteins mediate activation of the stress-responsive MTK1/MEKK4 MAPKKK.

The stress-responsive p38 and JNK MAPK pathways regulate cell cycle and apoptosis. A human MAPKKK, MTK1 (= MEKK4), mediates activation of both p38 and JNK in response to environmental stresses. Using a yeast two-hybrid method, three related proteins, GADD45alpha (= GADD45), GADD45, (= MyD118), and GADD45gamma, were identified that bound to an N-terminal domain of MTK1. These proteins activated MTK1 kinase activity, both in vivo and in vitro. The GADD45-like genes are induced by environmental stresses, including MMS, UV, and gamma irradiation. Expression of the GADD45-like genes induces p38/JNK activation and apoptosis, which can be partially suppressed by coexpression of a dominant inhibitory MTK1 mutant protein. We propose that the GADD45-like proteins mediate activation of the p38/JNK pathway, via MTK1/ MEKK4, in response to environmental stresses.

Amino Acid Sequence↗
PubMed2003

Persistent behavioral and autonomic supersensitivity to stress following prenatal stress exposure in rats.

Prenatal restraint stress (PS) has been suggested as an attractive chronic model of anxiety. Here, we characterized the behavioral and autonomic responsivity to acute stress exposure in adult PS subjects. In Wistar rats, locomotor activity, as well as spontaneous behavior in an established animal model of anxiety, the elevated plus-maze, was unaffected by PS. However, the anxiogenic-like response normally seen on the plus-maze following a restraint stress was markedly potentiated in adult PS subjects, despite indistinguishable corticosterone responses. In addition, we assessed the tail skin temperature response to a mild social stressor, transient social mixing. The diazepam-sensitive, late phase of the temperature response was markedly potentiated in adult PS subjects. In summary, PS induces a persistent phenotype of increased behavioral and autonomic sensitivity to stress. This paradigm might serve as an attractive screening model for anti-anxiety compounds.

Animals↗
PubMedDate not supplied

Psychoneuroendocrinological contributions to the etiology of depression, posttraumatic stress disorder, and stress-related bodily disorders: the role of the hypothalamus-pituitary-adrenal axis.

Following the assumption that stressors play an important part in the etiology and maintenance of psychiatric disorders, it is necessary to evaluate parameters reflecting stress-related physiological reactions. Results from these examinations may help to deepen the insight into the etiology of psychiatric disorders and to elucidate diagnostic uncertainties. One of the best-known stress-related endocrine reactions is the hormonal release of the hypothalamic-pituitary-adrenal (HPA) axis. Dysregulations of this axis are associated with several psychiatric disorders. Profound hyperactivity of the HPA-axis has been found in melancholic depression, alcoholism, and eating disorders. In contrast, posttraumatic stress disorder, stress-related bodily disorders like idiopathic pain syndromes, and chronic fatigue syndrome seem to be associated with diminished HPA activity (lowered activity of the adrenal gland). Hypotheses referring to (a) the psychophysiological meaning and (b) the development of these alterations are discussed.

Arousal↗
PubMed2002

Immobilization stress induces the expression of alphaB-crystallin in rat hippocampus: implications of glial activation in stress-mediated hippocampal degeneration.

Overexpression and abnormal aggregation of a small heat shock protein, B-crystallin, in reactive astrocytes has been implicated in various neurodegenerative diseases and brain tumors. To investigate the potential involvement of glial activation in stress-induced hippocampal damage, we analyzed B-crystallin gene expression in the hippocampus of immobilized rats. Male Sprague-Dawley rats were subjected to single or repeated immobilization stress. Both single and repeated immobilization markedly increased the level of B-crystallin mRNA in the hippocampus. Repeated immobilization notably accumulated B-crystallin protein, with a substantial portion in the insoluble fraction. Treatment of primary cortical astrocytes with stress-related glucocorticoid resulted in considerable elevation of B-crystallin expression. The accumulation of B-crystallin may serve as one of the important pathogenic mechanisms involved in hippocampal degeneration associated with stress.

Animals↗
PubMed2003

Are laboratory animals stressed by their housing environment and are investigators aware that this stress can affect physiological data?

Although stress can affect the behavior and physiology of laboratory animals, there has been little investigation into how the quality of animal research is affected if the animals are stressed. Even minor perturbations (i.e., environmental noise) can produce a stress response. A pilot survey was designed (29/49 responded) to determine the prevalence of noise in animal facilities and whether researchers are aware that noise can affect animal physiology. Most respondents agreed that environmental factors are stressful to laboratory animals (97%) and minor pain/stress causes physiological changes (62%). Of 19/29 respondents who believed their facility was quiet, 8 identified at least 3-5 pronounced noise sources. We hypothesize that the level of extraneous noise considered acceptable by an investigator depends on their degree of awareness that environment can affect an animal's physiology, and their perception of the existence of 'mind-body' interactions in an animal.

Animals↗
PubMedDate not supplied

Developmental factors modify stress ulcer incidence in a stress-susceptible rat strain.

Our multifactor theory of stress ulcer assumes that environmental factors that operate during early growth stages influence the elaboration of stress ulcer in adult rats. The theory would predict that rats exposed to either neonatal handling, or raised in a stimulus enriched environment, would reveal differences in stress ulcer susceptibility. In study 1, some Wistar rats and ulcer-susceptible Wistar Kyoto (WKY) rats were handled daily from birth to day 21, whereas other rats from each strain were not disturbed. In study 2, Wistar and WKY rats were raised (3 months) in a large stimulus-dense enriched environment, whereas other rats from each strain were raised in standard rat cages where visual and auditory stimuli were minimized. At 3 months all rats were observed in the open field test (OFT), a test of emotionality, as well as the Porsolt forced swim test (FST), a test of behavioral depression, and subsequently exposed to the ulcerogenic water restraint procedure. Neonatal handling produced results suggesting increased wall climbing activity in the FST, reduced response latency in the OFT, increased body weight and reduced ulcer severity, but these differences were not significant. Rearing in an enriched environment produced similar results but these difference were more pronounced and significant in the Wistar rats as compared to the WKY rats. Thus early environmental manipulations can influence adult behavior and the elaboration of stress ulcer disease, but the impact of these manipulations is less salient in an organism with an endogenous susceptibility to the disease.

Animals↗
PubMed1997

Follow-up study of young stress-affected and stress-resilient urban children.

Reports follow-up study of 181 young highly stressed urban children, classified as stress-resilient (SR) and stress-affected (SA) 1 1/2-2 years earlier. At follow-up (T2), children were retested on five initial (T1) test measures: self-rated adjustment, perceived competence, social problem solving, realistic control attributions, and empathy; parents and teachers did new child adjustment ratings, and parents participated in a phone interview focusing on the T1-T2 interval. Child test and adjustment measures and parent interview responses at T2 sensitively differentiated children classified as SR and SA at T1. Test and interview variables used at T1 and T2 correlated moderately across time periods. At T2, four child test indicators (i.e., rule conformity, global self-worth, social problem solving, and realistic control attributions) and four parent interview variables (positive future expectations for the child, absence of predelinquency indicators, good parent mental health in the past year, and adaptive parent coping strategies) sensitively differentiated children classified as SR and SA at T1. No relationship was found between family stress experienced in the T1-T2 interval and changes in children's adjustment during that period.

Adaptation, Psychological↗
PubMed2000

Psychometric properties of the Stanford Acute Stress Reaction Questionnaire (SASRQ): a valid and reliable measure of acute stress.

A reliable and valid measure is needed for assessing the psychological symptoms experienced in the aftermath of a traumatic event. Previous research suggests that trauma victims typically experience dissociative, anxiety and other symptoms, during or shortly after a traumatic event. Although some of these symptoms may protect the trauma victim from pain, they may also lead to acute stress, posttraumatic stress, or other disorders. The Stanford Acute Stress Reaction Questionnaire (SASRQ) was developed to evaluate anxiety and dissociation symptoms in the aftermath of traumatic events, following DSM-IV criteria for acute stress disorder. We present data from multiple datasets and analyses supporting the reliability and construct, convergent, discriminant, and predictive validity of the SASRQ.

Acute Disease↗
PubMed1997

Success in mating: a coordinated approach to fitness through genotypes incorporating genes for stress resistance and heterozygous advantage under stress.

Natural populations are normally exposed to substantial environmental stress. In these circumstances, an association occurs between success in mating and extremes of sexual ornaments, rapid development, long life span, and low fluctuating morphological asymmetry. This association between important fitness traits depends on high metabolic efficiency underlain by genes for stress resistance and heterozygous advantage. In particular, the high energy demands from the development and maintenance of sexual ornaments imply that the "good genes" favored in the sexual selection process should be stress resistant. However, the generalized heterozygous advantage under stress suggests that many interacting genes are involved in promoting metabolic efficiency, so that the "good genes" approach should be replaced by a "good genotypes" approach. This "good genotype" approach has predictive power for incorporating additional fitness traits, especially where metabolic consequences can be perceived.

Animals↗
PubMed2001

Effects of academic stress on oral hygiene--a potential link between stress and plaque-associated disease?

BACKGROUND: While there seems to be a common belief that psychosocial stress affects oral hygiene behavior, this assumption has rarely been proved. The present study thus aims to analyse stress effects on oral hygiene. MATERIAL AND METHODS: 16 matched pairs of medical students each consisting of 1 student participating in a major academic exam and 1 control without current academic stress, were formed on the basis of baseline plaque levels. At baseline, a professional tooth cleaning was performed. On the last day of exams, students answered questionnaires about oral hygiene during the exams and were afterwards asked to attend for a 2nd dental examination, of which they had no prior knowledge. RESULTS: On the last day of exams, approximately 6 weeks after professional tooth cleaning, 20.9+/-18.3% of control students' sites but only 10.5+/-9.3% of exam students' sites were found to be free of any plaque (p=0.022). Differences were most obvious at oral, as compared to vestibular, sites. Exam students reported a reduction in thoroughness (p=0.019) but not of frequency of oral hygiene behavior. CONCLUSION: The study strongly supports the assumption that psychosocial stress may induce neglect of oral hygiene and increase of plaque accumulation.

Attitude to Health↗