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PubMed1991

The role of stress waves in thoracic visceral injury from blast loading: modification of stress transmission by foams and high-density materials.

Materials have been applied to the thoracic wall of anaesthetised experimental animals exposed to blast overpressure to investigate the coupling of direct stress waves into the thorax and the relative contribution of compressive stress waves and gross thoracic compression to lung injury. The ultimate purpose of the work is to develop effective personal protection from the primary effects of blast overpressure--efficient protection can only be achieved if the injury mechanism is identified and characterized. Foam materials acted as acoustic couplers and resulted in a significant augmentation of the visceral injury; decoupling and elimination of injury were achieved by application of a high acoustic impedance layer on top of the foam. In vitro experiments studying stress wave transmission from air through various layers into an anechoic water chamber showed a significant increase in power transmitted by the foams, principally at high frequencies. Material such as copper or resin bonded Kevlar incorporated as a facing upon the foam achieved substantial decoupling at high frequencies--low frequency transmission was largely unaffected. An acoustic transmission model replicated the coupling of the blast waves into the anechoic water chamber. The studies suggest that direct transmission of stress waves plays a dominant role in lung parenchymal injury from blast loading and that gross thoracic compression is not the primary injury mechanism. Acoustic decoupling principles may therefore be employed to reduce the direct stress coupled into the body and thus reduce the severity of lung injury--the most simple decoupler is a high acoustic impedance material as a facing upon a foam, but decoupling layers may be optimized using acoustic transmission models. Conventional impacts producing high body wall velocities will also lead to stress wave generation and transmission--stress wave effects may dominate the visceral response to the impact with direct compression and shear contributing little to the aetiology of the injury.

Acoustics↗

PubMedDate not supplied

Ethanol-stress interaction: immediate versus delayed effects of ethanol and handling on stress responses of ethanol-consuming rats.

Rats screened for voluntary ethanol intake (high, medium, and low ethanol-preferring rats and non-ethanol-exposed controls) were given acute immobilization stress either immediately following the ethanol screening procedure, or after a 20 day period without access to ethanol. Among animals examined for stress responses immediately after ethanol screening, it was observed that water-only control rats developed significantly less frequent and less severe gastric stress ulcers than rats in all ethanol-exposed groups. This result suggests that ethanol, stress and routine handling may have contributed to ulcer formation in these animals. In contrast, among rats tested for stress responses after 20 days without ethanol, it was observed that the high ethanol-preferring animals showed less severe stress ulcers. These results indicate that among high ethanol-consuming animals, the presence of ethanol enhances ulcer severity, while prior experience with ethanol consumption does not appear to predispose rats to exacerbated stress gastric pathology.

Alcohol Drinking↗

PubMed2004

Latent abnormal fatty acid metabolism in apparently normal perfusion during stress in patients with restenosis after coronary angioplasty: assessment by exercise stress thallium-201 and iodine-123-labeled 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid-dual myocardial single-photon emission computed tomography.

Restenosis is a major problem in patients undergoing coronary angioplasty. Reduced uptake of iodine-123-labeled 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (I-BMIPP-123) relatively to thallium-201 (Tl-201) has been attributed to the metabolic damage in the myocardium in patients with coronary artery disease. Therefore, we performed exercise stress Tl-201 and I-BMIPP-123 dual myocardial single-photon emission computed tomography (SPECT) to detect coronary restenosis in 48 patients (35 men and 13 women, mean age 66 +/- 8 years), followed by coronary angiography at follow-up. Patients were divided into 2 groups: those with (n = 24) and without (n = 24) restenosis. Redistribution of Tl-201 was seen more frequently in the restenosis group than in no-restenosis group (58% [14 of 24] vs 8% [2 of 24], p <0.05). Five of 10 patients (50%) with restenosis but without Tl-201 redistribution had Tl-201/I-BMIPP-123 discrepancy during stress. In patients without restenosis, only 1 patient had this discrepancy during stress. Incorporation of Tl-201/I-BMIPP-123 uptake discrepancy during stress significantly improved the sensitivity (58% [14 of 24] to 79% [19 of 24]) with preserved specificity (92% [22 of 24] to 88% [21 of 24]). Exercise stress Tl-201 and I-BMIPP-123 dual myocardial SPECT revealed that latent abnormal fatty acid metabolism may exist in apparently normal perfusion during stress in patients with restenosis after coronary angioplasty. Use of I-BMIPP-123 together with Tl-201 during stress SPECT substantially improved the diagnostic accuracy of restenosis based on Tl-201 redistribution (from 75% to 83%).

Aged↗

PubMed2005

Stress-induced eating in restrained eaters may not be caused by stress or restraint.

Restrained eaters tend to increase and unrestrained eaters to decrease their food intake when stressed. This relationship, though robust, does not appear to be caused by restrained eating or by stress per se. For restraint, evidence indicates that none of the common operationalizations of restraint can account for restraint-related effects that have been examined to date. It is therefore unlikely that restraint is responsible for stress-induced eating in restrained eaters. Rather, behavioral and physiological data suggest that restrained eating may be a proxy risk factor for vulnerability to weight gain. For stress, a variety of minimally stressful perturbations (e.g. non-threatening cognitive loads) have been shown to elicit increased intake in restrained eaters. Thus, the negative affect created by manipulations used to create stress (e.g. scary movies, failure at a task) does not appear to be necessary to provoke overeating. An adequate explanation for stress-induced eating in restrained eaters remains elusive.

Eating↗

PubMed2004

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.

Animals↗

PubMed2005

Effects of polymerization shrinkage on the interfacial stress at resin-metal joint in denture-base: a non-linear FE stress analysis.

OBJECTIVES: The purpose of this study was to investigate the effects of polymerization shrinkage on stress at the interface between resin and metal in removable dentures. METHODS: Three-dimensional finite element models of a denture-base were studied, which consisted of acrylic occlusal rims with different heights and metal frameworks. A relaxation modulus of 1.5 GPa for the resin and a Young's modulus of 220 GPa for the metal were used as the material properties. Each model was constrained at the edge of the framework on the palatal vault. Surface-to-surface contact elements were used to calculate the interfacial stress in a direction perpendicular to the bond surface under a linear shrinkage ranging from 0.41 to 0.65%. The principal stress within the resin was also calculated. RESULTS: The maximum interfacial and principal stresses within the denture-base increased with resin shrinkage. Under the lowest linear shrinkage, the mean area percentages in the resin-metal joint that showed interfacial tensile stresses over 10 and 20 MPa were 63.4 and 0%, respectively. While under the highest linear shrinkage, these mean area percentages were 98.8 and 38.1%, respectively. Negligible differences in the stresses were shown by occlusal heights. SIGNIFICANCE: The polymerization shrinkage level has a significant influence on the residual stress at the resin-metal interface. Enhancement of the bond strength on the interface can reduce the failure probability at a resin-metal joint.

Acrylic Resins↗

PubMed2006

Impact of post-traumatic stress disorder and job-related stress on burnout: a study of fire service workers.

Burnout and stress are common, related problems in service professionals, and post-traumatic stress disorder (PTSD) is a major concern among fire service workers. The purpose of this study was to evaluate the impact of PTSD and job-related stressors on burnout. A total of 243 fire service workers completed questionnaires, including the Impact of Event Scale-Revised (IES-R), Maslach Burnout Inventory (MBI), and Japan Brief Job Stress Questionnaire. Relationships were found between PTSD and burnout, and between job stressors and burnout. Social support reduced the impact on burnout. Stressors that impacted on burnout in fire service personnel were PTSD-related acute stress and general job-related chronic stress. Countermeasures, not only against job stress, but also against PTSD-related stress, are essential to prevent burnout. Social support and the development of human relationships in the work place are crucial in mitigating burnout.

Adult↗

PubMed2006

The relationship of attachment insecurity to subjective stress and autonomic function during standardized acute stress in healthy adults.

OBJECTIVE: The purpose of this study was to test predicted relationships between adult attachment and stress using subjective and physiological measures. METHODS: Sixty-seven healthy adults completed measures of adult attachment and perceived chronic stress. Subjective stress and the high-frequency (HF) and low-frequency (LF) spectral bandwidths of heart rate variability (HRV) were measured during a standardized stress protocol. RESULTS: Attachment anxiety is associated with between-subject differences in chronic perceived stress (P=.001) and subjective acute stress (P=.01). There is a main effect of attachment avoidance on between-subject differences in HF HRV (P=.004). Attachment avoidance is inversely associated with HF HRV, independent of age and variability in respiration. CONCLUSION: Attachment anxiety is associated with self-reported distress. Attachment avoidance is inversely associated with HF HRV, a marker of vagal influence on cardiac activity, but is not associated with subjective stress.

Acute Disease↗

PubMed2004

The role of osteogenic index, octahedral shear stress and dilatational stress in the ossification of a fracture callus.

The exact mechanism by which mechanical stimulus regulates the healing process of a bone fracture is not understood. This has led to the development of several hypotheses that predict the pattern of differentiation of tissue during healing that may arise from characteristic fields of stress or strain at the fracture. These have so far remained unproved because data on stress fields in actual fracture tissue have been unavailable until recently. Thus the present study examines the predictive performance of the hypothesis proposed in J Orthop Res 6 (1988) 736, against measured and calculated data reported in J Biomech 33 (2000) 415, using a 2D FEM of a clinical fracture. The hypothesis was used to predict the influence of stress fields present in the Gardner et al. tissues at four temporal stages during healing. These predictions were then correlated with callus-size, rate of endochondral ossification and ossification pattern subsequently observed by Gardner et al. in the clinical fracture. Results corroborate the hypothesis that high octahedral shear stresses may increase the size of the callus during the initial phase of healing, and they also suggest that this may be true during the later stages of the fracture fixation period. However, compressive dilatational stresses were not found to inhibit endochondral ossification, as suggested by the hypothesis. Although high shear stresses were found in regions indicative of fibrous tissue as postulated by the hypothesis, this was not found to be the case for high tensile dilatational stresses. Also, contour diagrams of Osteogenic index (I) indicated only limited correlation with callus maturation and the pattern of healing. Therefore, the hypothesis was not wholly successful in predicting healing pattern.

Adult↗

PubMed1988

Dynamic urethral pressure/profilometry pressure transmission ratio determinations in stress-incontinent and stress-continent subjects.

Bladder-to-urethra pressure transmission ratios were calculated in each quarter (designated Q1 through Q4) of the dynamic urethral pressure profile in 110 subjects. Thirty-seven subjects had genuine stress urinary incontinence, whereas 73 were stress continent. Subjects with genuine stress incontinence had significantly lower mean (+/- SD) pressure transmission ratios in all four urethral quarters compared with stress-continent subjects: 71% +/- 14% versus 94% +/- 38% for Q1 (p = 0.004), 69% +/- 16% versus 101% +/- 42% for Q2 (p = 0.00001), 79% +/- 19% versus 113% +/- 46% for Q3 (p = 0.0001), and 90% +/- 22% versus 117% +/- 36% for Q4 (p = 0.001). A pressure transmission ratio value less than 90% in the proximal half of the dynamic profile had a sensitivity of 97%, a specificity of 56%, an abnormal predictive value of 53%, and a normal predictive value of 97%. Calculation of pressure transmission ratios, as opposed to declaring the stress profile positive or negative based on whole urethra/bladder pressure equalization with stress, enhances the utility of the dynamic urethral pressure profile and allows quantification of one of the several variable in the equation of stress urinary incontinence.

Adult↗

PubMed2001

Growth kinetics rather than stress accelerate telomere shortening in cultures of human diploid fibroblasts in oxidative stress-induced premature senescence.

WI-38 human diploid fibroblasts underwent accelerated telomere shortening (490 bp/stress) and growth arrest after exposure to four subcytotoxic 100 microM tert-butylhydroperoxide (t-BHP) stresses, with a stress at every two population doublings (PD). After subcytotoxic 160 microM H2O2 stress or five repeated 30 microM t-BHP stresses along the same PD, respectively a 322 +/- 55 and 380 +/- 129 bp telomere shortening was observed only during the first PD after stress. The percentage of cells resuming proliferation after stress suggests this telomere shortening is due to the number of cell divisions accomplished to reach confluence during the first PD after stress.

Cell Division↗

PubMed2002

Dissociation of stress behaviors in the chick social-separation-stress procedure.

Separation from conspecifics in chicks produces an increase in distress vocalizations and a decrease in response to a noxious stimulus (stress-induced analgesia). This study questioned the relative contributions of novelty to the test chamber and social separation in mediating these stress responses. Eight-day-old chicks were tested either in isolation or in the presence of two social companions for a 3-min observation period in which distress vocalizations were recorded as well as the frequency of footlifts in response to a 50-microl injection of 0.10% formalin into the plantar surface of the footpad. In Expt. 1, chicks received six, 3-min test chamber habituation trials (vs. no habituation) one per day before testing; in Expt. 2, chicks were tested with mirrors placed in the chambers (vs. no mirrors). In both studies, isolated chicks in control groups (i.e., no habituation or no mirror) exhibited increased distress vocalizations and decreased nociceptive responses. In Expt. 1, habituation to the test chamber attenuated stress-induced analgesia but did not affect distress vocalizations. In Expt. 2, placement of mirrors in the test chamber attenuated distress vocalizations but did not affect stress-induced analgesia. These findings demonstrate a dissociation of stress behaviors in the chick social-separation-stress procedure: the stress-induced analgesia response is primarily mediated by novelty to the test apparatus while the distress vocalizations response is mediated by separation from conspecifics.

Analysis of Variance↗

PubMed2002

Platelet adhesion to commercial and modified polymer materials in animals under psychological stress and in a no-stress condition.

It is well known that stressful stimuli change blood functions and that protein and platelet parameters are altered in humans and animals subjected to stress. We have examined the influence of psychological stress on the morphological responses of platelets on commercially available materials [polyester (VP), fluoropassivated polyester (VPF), non-woven benzylic ester of hyaluronic acid (Hyaff11)] and on materials synthesised (PUPA) and/or surface modified by sulphation (Hyaff11S) or by immobilisation of the anticoagulant molecules heparin and sulphated hyaluronic acid (PUPA-Heparin, PUPA-HyalS, HyalS-PET). Moreover, the anticoagulant activity (i.e. thrombin inactivation) of the materials was analysed. In the no-stress condition, the surfaces with a low degree of platelet adhesion were Hyaff11S, HyalS-PET, PUPA-Heparin and PUPA-HyalS. Hyaff11, PET and PUPA had the highest number of adherent platelets within the series. VP and VPF exhibited an intermediate behaviour. The exposure of animals to stress induced a dramatic change in platelet number and morphology on PET, HyalS-PET, PUPA, PUPA-HyalS and Hyaff11: there was a higher degree of platelet adhesion, increased platelet spreading and the appearance of pseudopodia. In VP, VPF, Hyaff11S and PUPA-Heparin, there were no changes in platelet adhesion in stress conditions with respect to the no-stress condition; the latter two materials, the only ones able to prolong thrombin time, had a very low number of adherent platelets.

Animals↗

PubMed1991

Stress ulceration in rats: impact of prior stress experience.

The role of prior stress experience on the response of the organism to a later stressor has been studied in terms of the extent of gastric ulceration induced by the second stressor. These studies have focused largely on effects of prior stress (shock, restraint, activity) on the ulceration developing under later restraint and activity stress. The studies indicate that prior exposure to restraint stress provides some protection against later restraint ulcer development. Using shock as the prior stressor, the effects on later restraint stress are determined by the particular characteristics of the shock (controllability and predictability), and by contextual factors. Studies are lacking on the significance of these characteristics of shock for later activity stress ulcers. Further studies are required therefore on the significance of psychological characteristics of the prestress, and on the effects of these prestressors at different stages of the life cycle. The identification of these factors, and a clearer picture of the protective and exacerbating effect of prior stress will allow us to explore the physiological (central and peripheral) mechanisms underlying ulcer development and ulcer susceptibility.

Animals↗

PubMed2000

A 6-day intracerebroventricular infusion of the growth hormone-releasing peptide KP-102 stimulates food intake in both non-stressed and intermittently-stressed rats.

The effects of a 6-day intracerebroventricular (i.c.v.) infusion of KP-102, a growth hormone-releasing peptide (GHRP), on food intake and body weight gain were observed in free-feeding rats that were or were not subjected to intermittent electric footshock stress during the 6 days. Food intake and body weight were significantly lower in rats exposed to a 60-min period of footshock twice a day for 6 days compared to non-stressed rats. A 6-day, i.c.v. infusion of KP-102 significantly and steadily increased food intake and body weight in free-feeding non-stressed rats compared to control rats receiving saline i.c.v. In rats exposed to intermittent footshock stress during the 6-day infusion, KP-102 treatment stimulated feeding behavior and resulted in significantly higher body weight compared to stressed rats that received i.c.v. infusion of saline. These results indicate that during a 6-day continuous i.c.v. infusion of GHRP, KP-102, food intake and body weight steadily increased without attenuation of the GHRP effect in both non-stressed rats and those subjected to intermittent stress.

Animals↗

PubMed2004

Mindfulness-based stress reduction in relation to quality of life, mood, symptoms of stress and levels of cortisol, dehydroepiandrosterone sulfate (DHEAS) and melatonin in breast and prostate cancer outpatients.

OBJECTIVES: This study investigated the relationships between a mindfulness-based stress reduction meditation program for early stage breast and prostate cancer patients and quality of life, mood states, stress symptoms, and levels of cortisol, dehydroepiandrosterone-sulfate (DHEAS) and melatonin. METHODS: Fifty-nine patients with breast cancer and 10 with prostate cancer enrolled in an eight-week Mindfulness-Based Stress Reduction (MBSR) program that incorporated relaxation, meditation, gentle yoga, and daily home practice. Demographic and health behavior variables, quality of life, mood, stress, and the hormone measures of salivary cortisol (assessed three times/day), plasma DHEAS, and salivary melatonin were assessed pre- and post-intervention. RESULTS: Fifty-eight and 42 patients were assessed pre- and post-intervention, respectively. Significant improvements were seen in overall quality of life, symptoms of stress, and sleep quality, but these improvements were not significantly correlated with the degree of program attendance or minutes of home practice. No significant improvements were seen in mood disturbance. Improvements in quality of life were associated with decreases in afternoon cortisol levels, but not with morning or evening levels. Changes in stress symptoms or mood were not related to changes in hormone levels. Approximately 40% of the sample demonstrated abnormal cortisol secretion patterns both pre- and post-intervention, but within that group patterns shifted from "inverted-V-shaped" patterns towards more "V-shaped" patterns of secretion. No overall changes in DHEAS or melatonin were found, but nonsignificant shifts in DHEAS patterns were consistent with healthier profiles for both men and women. CONCLUSIONS: MBSR program enrollment was associated with enhanced quality of life and decreased stress symptoms in breast and prostate cancer patients, and resulted in possibly beneficial changes in hypothalamic-pituitary-adrenal (HPA) axis functioning. These pilot data represent a preliminary investigation of the relationships between MBSR program participation and hormone levels, highlighting the need for better-controlled studies in this area.

Affect↗

PubMed2001

Effects of mental stress on coronary epicardial vasomotion and flow velocity in coronary artery disease: relationship with hemodynamic stress responses.

OBJECTIVES: This study examines the prevalence and hemodynamic determinants of mental stress-induced coronary vasoconstriction in patients undergoing diagnostic coronary angiography. BACKGROUND: Decreased myocardial supply is involved in myocardial ischemia triggered by mental stress, but the determinants of stress-induced coronary constriction and flow velocity responses are not well understood. METHODS: Coronary vasomotion was assessed in 76 patients (average age 59.9 +/- 10.4 years; eight women). Coronary flow velocity responses were assessed in 20 of the 76 patients using intracoronary Doppler flow. Repeated angiograms were obtained after a baseline control period, a 3-min mental arithmetic task and administration of 200 microg intracoronary nitroglycerin. Arterial blood pressure (BP) and heart rate assessments were made throughout the procedure. RESULTS: Mental stress resulted in significant BP and heart rate increases (p < 0.001). Coronary constriction (>0.15 mm) was observed in 11 of 59 patients with coronary artery disease (CAD) (18.6%). Higher mental stress pressor responses were associated with more constriction in diseased segments (rdeltaSBP = -0.26, rdeltaDBP = -0.30, rdeltaMAP = -0.29; p's < 0.05) but not with responses in nonstenotic segments. The overall constriction of diseased segments was not significant (p > 0.10), whereas a small but significant constriction occurred in nonstenotic segments (p = 0.04). Coronary flow velocity increased in patients without CAD (32.2%; p = 0.008), but not in patients with CAD (6.4%; p = ns). Cardiovascular risk factors were not predictive of stress-induced vasomotion in patients with CAD. CONCLUSIONS: Coronary vasoconstriction in angiographically diseased arteries varies with hemodynamic responses to mental arousal. Coronary flow responses are attenuated in CAD patients. Thus, combined increases in cardiac demand and concomitant reduced myocardial blood supply may contribute to myocardial ischemia with mental stress.

Aged↗

PubMed2002

Adaptation to stress improves resistance to gastric damage during acute stress in Wistar rats and decreases resistance in August rats: role of serotonin.

In August rats more resistant to acute stress-induced gastric damage than Wistar rats, preadaptation to nondamaging stress exposure did not prevent damage and even potentiated these damages. By contrast, in Wistar rats such adaptation decreased gastric damage caused by acute stress. Higher initial resistance of August rats to stress damage was associated with higher serotonin level and lower norepinephrine/serotonin ratio in the gastric mucosa than in Wistar rats. The negative effect of adaptation in August rats was associated with decreased serotonin level and increased norepinephrine/serotonin ratio in the stomach during stress. In Wistar rats exposed to stress the protective effect of adaptation was associated with an increase of serotonin content and a decrease of the norepinephrine/serotonin ratio in the stomach. Hence, the degree of resistance to stress-induced gastric damage can be due to genetically determined serotonin level and norepinephrine/serotonin ratio in the stomach.

Adaptation, Physiological↗