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PubMed2006

Polyamine biosynthesis of apple callus under salt stress: importance of the arginine decarboxylase pathway in stress response.

To clarify the involvement of the arginine decarboxylase (ADC) pathway in the salt stress response, the polyamine titre, putrescine biosynthetic gene expression, and enzyme activities were investigated in apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] in vitro callus under salt stress, during recovery after stress, and when ADC was inhibited by D-arginine, an inhibitor of ADC. Salt stress (200 mM NaCl) caused an increase in thiobarbituric acid-reactive substances (TBARS) and electrolyte leakage (EL) of the callus, which was accompanied by an increase in free putrescine content, during 7 d of treatment. Conjugated putrescine was also increased, but this increase was limited to the early stage of salt stress. Accumulation of putrescine was in accordance with induction of ADC activity and expression of the apple ADC gene (MdADC). When callus that had been treated with 200 mM NaCl was transferred to fresh medium with (successive stress) or without (recovery) NaCl, TBARS and EL were significantly reduced in the recovery treatment, indicating promotion of formation of new callus cells, compared with the successive stress treatment. Meanwhile, MdADC expression and ADC activity were also decreased in the callus undergoing recovery, whereas those of the callus under successive stress were increased. Ornithine decarboxylase (ODC) activity showed a pattern opposite to that of ADC in these conditions. D-Arginine treatment led to more serious growth impairment than no treatment under salt stress. In addition, accumulation of putrescine, induction of MdADC, and activation of ADC in D-arginine-treated callus were not comparable with those of the untreated callus. Exogenous addition of putrescine could alleviate salt stress in terms of fresh weight increase and EL. All of these findings indicated that the ADC pathway was tightly involved in the salt stress response. Accumulation of putrescine under salt stress, the possible physiological role of putrescine in alleviating stress damage, and involvement of MdADC and ADC in response to salt stress are discussed.

Arginine↗

PubMed2000

Morphological changes in osteoblastic cells (MC3T3-E1) due to fluid shear stress: cellular damage by prolonged application of fluid shear stress.

We investigated the effect of fluid shear stress on both changes in morphology and in resting level of cytosolic concentrations of Ca2+ ([Ca2+]i) in MC3T3-E1 cells, osteoblast-like cells derived from the neonatal mouse calvaria. The cells were subjected to fluid shear stress at about 1.0 Pa. Morphological characteristics were compared between stressed and control cells by scanning electron microscopic examination, actin filament evaluation using phalloidin fluorescence and [Ca2+]i measurement using fura-2/AM. The stressed cells changed from a polygonal to a spindle shape after 1-hour exposure to fluid shear stress, whereas control cells remained polygonal, and the stressed cells exhibited an increase in the number of microvilli. The diameter in the long axis of the stressed cells was significantly larger than that of controls, and about half of the stressed cells were oriented nearly along the direction of the fluid shear stress. The arrangement of the actin filaments of the stressed cells changed to parallel, and was positioned along the long axis of the cell process. The resting level of [Ca2+]i in the stressed cells showed a peak at 1 hour after the application of the stress. A more prolonged stress period over 1 hour caused cell shrinkage, an irregularity on the cell surface, and a gradual decrease in the resting level of [Ca2+]i, suggesting that prolonged stress time may cause cellular damage.

3T3 Cells↗

PubMed1998

Reactivity of blood pressure to mental arithmetic stress test, stress-test recovery time, and ambulatory blood pressure in hypertensive and normotensive subjects.

BACKGROUND: Laboratory mental stress testing and 24 h ambulatory blood pressure monitoring may analyse reactivity of blood pressure during provoked stress and stressful situations in daily-life, respectively. OBJECTIVE: To evaluate whether the responses to a mental stress test and during the stress-test recovery time were associated with ambulatory blood pressure parameters. METHODS: Fifty-two untreated male subjects (22 normotensives and 30 hypertensives) were subjected both to mental arithmetic stress testing and ambulatory blood pressure monitoring. RESULTS: We found a positive correlation between baseline and peak-test blood pressures during the stress test and 24 h blood pressures. Maximal values of systolic and diastolic blood pressures measured during the 24 h were also correlated to the maximal systolic and diastolic blood pressures reached during the stress test ( P < 0.001). We observed no relationship between reactivity during the stress test and 24 h parameters. On the contrary, changes in diastolic blood pressure during the time of recovery from the stress test (expressed as percentage-change scores) were correlated to the 24 h diastolic blood pressure parameters, the diastolic load being the most closely associated variable. CONCLUSION: The absence of relationships between variations in blood pressure during the provoked stress and ambulatory monitoring parameters indicates that reactivity of blood pressure to an acute stress does not predict the 24 h profile. However, the correlation between the maximal blood pressure measured by ambulatory monitoring and that observed during stress testing indicates that the maximal 24 h values may show the extreme blood pressure response (like the one provoked acutely by a laboratory stress test) of an individual subject. The correlation between the percentage-change score during the recovery time of diastolic blood pressure and the 24 h diastolic load could account forr a lower than normal capacity for recovery of subjects with persistently high blood pressures.

Journal Article↗

PubMed2003

Mild heat stress at a young age in Drosophila melanogaster leads to increased Hsp70 synthesis after stress exposure later in life.

In a number of animal species it has been shown that exposure to low levels of stress at a young age has a positive effect on stress resistance later in life, and on longevity. The positive effects have been attributed to the activation of defence/cleaning systems (heat shock proteins (Hsps), antioxidases, DNA repair) or to effects of a changed metabolic rate, or both. We investigated the effect of mild stress exposures early in life on Hsp70 synthesis after a harder stress exposure later in life in five isofemale lines of Drosophila melanogaster. Female flies were either exposed to repeated bouts of mild heat stress (3 h at 34 degrees C) at a young age (days 2, 4 and 6 post-eclosion) or held under standard laboratory conditions. At 16 and 32 days of adult age, respectively, flies were exposed to a high-temperature treatment known to induce Hsp70 in the investigated species (1 h at 37 degrees C). Thereafter, the inducible Hsp70 levels were measured. Our data show a tendency towards increased Hsp70 synthesis with increased age for both 'mild stress' and 'no stress' flies. Moreover, the results show that flies exposed to mild stress at a young age synthesized more Hsp70 upon induction, compared to control flies, and that this difference was accentuated at 32 days compared to 16 days of age. Thus, bouts of mild heat stress at a young age impact on the physiological stress response system later in life. This may be caused by an increased ability to react to future stresses. Alternatively, the mild stress exposure at a young age may actually have caused cellular damages increasing the need for Hsp70 levels after stress exposure later in life. The importance of an Hsp70 upregulation (throughout life) in explaining the phenomenon of hormesis is discussed, together with alternative hypotheses, and suggestions for further studies.

Animals↗

PubMed2006

Stress triggered changes in gene expression in adrenal medulla: transcriptional responses to acute and chronic stress.

1. Stress elicits activation of several transcription factors involved in the regulation of catecholamine biosynthetic enzyme gene expression depending on its duration or repetition. However, the dynamic of the conversion of transient transcriptional activation with acute stress to sustained changes in transcription in response to repeated exposure to stress in adrenomedullary catecholaminergic systems is not clear. 2. Here, we analyzed changes in levels of phospho-CREB (P-CREB), phospho-ERK1/2 (P-ERK1/2) and Fra-2 by Western Blot analysis in adrenal medulla of Sprague Dawley male rats exposed to single or repeated immobilization stress (IMO). For single stress, rats were immobilized for 5 min, 30 min, or 2 h and sacrificed immediately afterwards. In the repeated stress conditions, animals were immobilized for 2 h daily on each consecutive day prior to the final day (day 2 for 2x IMO, day 6 for 6x IMO) in which the rats were immobilized for a session lasting 5 min, 30 min or 2 h. There were two control groups, an absolute control (AC) not exposed to stress, and a handled control (HC) gently handled daily for 6 days. 3. Phosphorylation of CREB was rapid and elevated at the earliest time examined, even with single stress. However, with a second daily episode of stress the increase in P-CREB was observed for at least the entire duration of the stress. In contrast, phosphorylation of ERK1/2 was only significant after brief exposure to a single IMO. The elevation of Fra-2 protein level was slower, but was significant after 2 h of a single IMO. With repeated IMO, there were marked elevations of Fra-2 throughout the 2 h IMO, which were especially pronounced at the end of the immobilization. 4. The transient nature of the phosphorylation of CREB may be responsible for the short-lived induction of transcription of catecholamine biosynthetic enzymes after brief exposure to a single immobilization stress. The sustained phosphorylation of CREB throughout the repeated stress coupled with induction of Fra-2 may mediate the longer lasting responses to repeated stress.

Adrenal Medulla↗

PubMed1987

T-lymphocyte polyclonal proliferation: effects of stress and stress response style on medical students taking national board examinations.

This study investigated the effects of stress and stress response style on T-lymphocyte polyclonal proliferation (TLPP). The TLPP levels of 15 medical students taking NBME Part I were compared to those of a matched (on age and sex) sample of students not taking exams and hospital employees. All subjects completed the Impact of Events Scale to measure recent stress levels and style of responding to stress. TLPP data for both experimental and control groups, pre- and post-boards, were analyzed via a 2 X 2 factorial analysis of variance. Results indicated a significant main effect for the NBME stress vs control conditions and a significant interaction between stress response style (avoidance vs intrusion) and NBME stress vs control conditions. TLPP levels were significantly depressed (relative to the controls) for the NBME stress group 1 week after examinations. Furthermore, those students whose stress response style was characterized by intrusion were significantly more immunosuppressed than those characterized by an avoidance stress response style. Four- and six-week follow-up measures of TLPP were taken on 10 and 11 NBME group students, respectively. Follow-up results, analyzed via t tests, indicated that TLPP levels were significantly suppressed for 4 weeks but returned to initial normal levels at 6 weeks. Results are discussed in terms of needed research examining the mechanism of stress intruders' susceptibility to stress-induced immunosuppression and the possible clinical significance of brief periods of stress-induced decrements in TLPP levels.

Adult↗

PubMed1995

Crude saponin extracted from Vietnamese ginseng and its major constituent majonoside-R2 attenuate the psychological stress- and foot-shock stress-induced antinociception in mice.

Effects of Vietnamese ginseng (VG) crude saponin and majonoside-R2, a major saponin constituent, on the psychological stress- and foot shock stress-induced antinociception in the tail pinch test were examined in mice. VG crude saponin (6.2, 12.5, and 25 mg/kg, P.O.) attenuated psychological stress- but not foot shock stress-induced antinociceptive response, whereas majonoside-R2 (3, 6.2, and 12.5 mg/kg, P.O. and i.p.), as well as naloxone (2 mg/kg, i.p.), suppressed both psychological stress- and foot shock stress-induced antinociception. Pretreatment with the crude saponin (12.5 mg/kg, P.O.) or majonoside-R2 (6.2 mg/kg, P.O.) for 5 days followed by the treatment in combination with stress for next 5 days did not affect the development of adaptation to foot shock stress, but they significantly suppressed the antinociceptive action of the stress measured on the first, second, and third day during the stress exposure period. Majonoside-R2 (6.2 mg/kg, P.O.) but not the crude saponin (12.5 mg/kg, P.O.) significantly blocked the development of adaptation to psychological stress. These results suggest that VG crude saponin has the suppressing effect on psychological stress- and foot shock stress-induced antinociception and that majonoside-R2 is important for the action of the saponin.

Adaptation, Psychological↗

PubMed1988

Neuroendocrine correlates of sustained stress: the activity-stress paradigm.

Rats sacrificed after 4 days in the activity-stress paradigm or after 4 days of food restriction had significantly elevated levels of plasma corticosterone as compared to control rats. The approximately 5 fold increase in corticosterone in the stressed treatment groups was consistently found in all experiments. ACTH levels were elevated in activity-stress and food-restricted groups in some experiments but these increases were not statistically significant. Prolactin levels were significantly elevated in food-restricted group rats as compared to controls or activity-stress group animals in one experiment but this finding was not repeated in further experiments. In a second series of experiments, rats from activity-stressed and food-restricted treatment groups and controls were exposed to an acute stressor for 15 min prior to sacrifice to assess the effects of prior sustained stress on hormonal responses to an acute stressor. Exposure to 15 min of immobilization or intermittent footshock immediately prior to sacrifice increased plasma levels of corticosterone, ACTH and prolactin in control, food-restricted and activity-stressed rats. Generally, hormonal responses to the acute stress were similar in all treatment groups. However, in two experiments where the resting levels of corticosterone were especially elevated in the activity-stress group, the acute stress-induced rise in corticosterone was less than that seen for the other two treatment groups. In another experiment, administration of dexamethasone suppressed acute stress-evoked levels of ACTH and corticosterone in control, activity-stressed and food-restricted rats. Thus, rats exposed to 4 days of sustained stress were found to have consistently elevated resting levels of corticosterone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed2005

Sex and ovarian steroids modulate brain-derived neurotrophic factor (BDNF) protein levels in rat hippocampus under stressful and non-stressful conditions.

Abnormal levels of brain-derived neurotrophic factor (BDNF) are associated with major depression, a disorder with a higher incidence in women than men. Stress affects BDNF levels in various brain regions and thus, a heightened stress response in females could contribute to the development of depression. As well, ovarian hormones directly affect brain levels of BDNF mRNA and protein. Two experiments were performed to investigate the effects of stress and sex and gonadal hormones on BDNF protein levels in CA1, CA3, and dentate gyrus (DG) subregions of the hippocampus. In the first experiment, male and female Sprague-Dawley rats were subjected to one hour of restraint stress or control handling prior to sacrifice. In the second experiment, fifty-one female rats were ovariectomized and separated into stress and control conditions, as described for the first experiment. Stressed and handled groups received a single injection of estrogen (E; 53h prior to stress), estrogen and progesterone (EP; E given at 53h and P given 5h prior to stress), or vehicle (OVX). In both experiments BDNF protein was quantified using an enzyme-linked immunosorbent enzyme assay (ELISA) in micropunches of hippocampus. Gonadally intact females had significantly higher levels of BDNF in CA3, but significantly lower levels in DG, relative to males. In CA3, stress significantly decreased BDNF in both males and females. In DG of ovariectomized female rats, the effects of stress were significantly different following EP vs. vehicle treatment. Thus, stress increased BDNF levels in EP-treated rats but decreased BDNF levels in vehicle-treated rats. Reduced trophic support in DG in the presence of estrogen and progesterone could jeopardize neurogenesis and under certain conditions could be a contributing factor to the hippocampal atrophy associated with stress-induced affective disorders. These results emphasize the need to consider sex, gonadal steroids, and hippocampal subregion when examining the effects of stress on the brain.

Animals↗

PubMed1995

Shear stress-conditioned, endothelial cell-seeded vascular grafts: improved cell adherence in response to in vitro shear stress.

BACKGROUND: Prosthetic vascular grafts with adherent endothelial cell monolayers may prove useful for small-caliber vessel bypass. However, endothelial cells adhere poorly to prosthetic graft material, and they are stripped when exposed to in vivo shear stress. This study sought to determine whether in vitro shear stress conditioning improves endothelial cell adhesion and decreases thrombogenicity of endothelial cell-seeded grafts. METHODS: The lumens of 1.5 mm (inside diameter) spun polyurethane polymer vascular grafts were seeded with bovine aortic endothelial cells and cultured in vitro for 6 days with or without continuous laminar shear stress, first at 1 to 2 dynes/cm2 for 3 days, then at approximately 25 dynes/cm2 for 3 days. Grafts preconditioned by shear stress and the static control grafts were then exposed to arterial shear stress at 25 dynes/cm2 for 25 seconds. The number of dislodged cells was counted, and the grafts were examined by light and scanning electron microscopy. Whole blood clotting time in the grafts was also determined. RESULTS: Exposure of grafts to acute shear stress dislodged 1.35 x 10(6) +/- 0.44 x 10(6) cells from static grafts compared with 1.05 x 10(4) +/- 0.16 x 10(4) cells from grafts preconditioned by shear stress. By light and electron microscopy an intact endothelial monolayer was observed to cover the lumen of shear stress-conditioned grafts, whereas few cells remained on the luminal surface of grafts not previously exposed to shear stress. The clotting time in shear stress-conditioned grafts was significantly prolonged in relation to grafts not exposed to shear stress. CONCLUSIONS: These findings show that endothelial cell adhesion and retention on vascular grafts in vitro is markedly enhanced by preconditioning the seeded endothelial cell monolayer with long-term shear stress. Consequently, vascular grafts containing shear stress-conditioned endothelial monolayers are less thrombogenic in vitro than small-caliber vascular grafts without intact endothelial cell monolayers.

Animals↗

PubMed2001

Stress and symptoms in patients with interstitial cystitis: a life stress model.

Objectives. Stress-related exacerbation of interstitial cystitis (IC) symptoms has frequently been reported. Previous research has found stress-related IC symptom exacerbation in an experimental model. However, this relationship has not been objectively examined with daily life stressors. We used a prospective daily symptom diary method to investigate the relationships among stress and bladder symptoms in patients with IC and age-matched healthy controls.Methods. Forty-five previously diagnosed female patients with IC completed a bladder symptom and stress diary nightly for 1 month; 31 female age-matched healthy controls completed a similar diary for 7 days. The symptom questions were modified from the Interstitial Cystitis Data Base study.Results. Patients reported greater mean daily stress, bladder pain, urgency, and daytime and nocturnal frequency than controls (all P values less than 0.001). Among all patients, a significant relationship between stress and urgency was observed. In addition, a significant relationship between stress and pain was observed among patients with moderate and severe disease. As the disease severity increased, more pronounced relationships between stress and the symptoms of urgency and pain were evidenced. Greater stress was associated with greater nocturnal frequency among patients with more severe disease. These stress-symptom relationships were not observed among the controls.Conclusions. Higher levels of stress were related to greater pain and urgency in patients with IC but not in the controls. In addition, the relationship of stress and these IC symptoms was stronger among patients with more severe disease. The results indicate that life stress is associated with greater IC symptoms, particularly among patients whose disease is not well controlled.

Activities of Daily Living↗

PubMed2002

Ligament creep recruits fibres at low stresses and can lead to modulus-reducing fibre damage at higher creep stresses: a study in rabbit medial collateral ligament model.

Ligaments are subjected to a range of loads during different activities in vivo, suggesting that they must resist creep at various stresses. Cyclic and static creep tests of rabbit medial collateral ligament were used as a model to examine creep over a range of stresses in the toe- and linear-regions of the stress-strain curve: 4.1 MPa (n = 7), 7.1 MPa (n = 6), 14 MPa (n = 9) and 28 MPa (n = 6). We quantified ligament creep behaviour to determine if, at low stresses, modulus would increase in a cyclic creep test and collagen fibres would be recruited in a static creep test. At higher creep stresses, a decrease in measured modulus was expected to be a potential marker of damage. The increase in modulus during cyclic creep and the increase in strain during static creep were similar between the three toe-region stresses (4.1, 7.1, 14 MPa). However, at the linear-region stress (28 MPa), both these parameters increased significantly compared to the increases at the three toe-region stresses. A concurrent crimp analysis revealed that collagen fibres were recruited during creep, evidenced by decreased area of crimped fibres at the end of the static creep test. Interestingly, a predominance of straightened fibres was observed at the end of the 28 MPa creep test, suggesting a limited potential for fibre recruitment at higher, linear-region stresses. An additional 28 MPa (n = 6) group had mechanically detectable discontinuities in their stress-strain curves during creep that were related to reductions in modulus and suggested fibre damage. These data support the concept that collagen fibre recruitment is a mechanism by which ligaments resist creep at low stresses. At a higher creep stress, which was still only about a third of the failure capacity, damage to some ligaments occurred and was marked by a sudden reduction in modulus. In the cyclic tests, with continued cycling, the modulus increased back to original values obtained before the discontinuity suggesting that other fibres were being recruited to bear load. These results have important implications for our understanding of how fibre recruitment and stress redistribution act in normal ligament to minimize creep and restore modulus after fibre damage.

Animals↗

PubMedDate not supplied

How does stress affect you? An overview of stress, immunity, depression and disease.

OBJECTIVE: Stress is a term that has become synonymous with modern life. This review aims to appraise the evidence linking stress with disease with particular reference to the major causes of morbidity and mortality in the Western World, cardiovascular disease, cancer, and depression. Changes in immune parameters in stressful situations were reviewed as a possible pathophysiological mechanism for such effects. METHOD: A Medline search was carried out for the period 1996-2000 to identify recent findings in this field using the terms "stress", "disease", "immune system". Relevant references that were found in all identified publications were also followed up. RESULTS: There is evidence to link stress with the onset of major depression and with a poorer prognosis in cardiovascular disease and cancer. Few small studies suggest that stress management strategies may help to improve survival. Chronic stress appears to result in suppression of the immune response, whereas immune activation and suppression have been associated with acute stress. Inflammatory cytokines, soluble mediators of the immune response, can result in symptoms of depression. CONCLUSION: Further prospective epidemiologically based studies are needed to clarify the role of stress on disease onset, course, and prognosis. Stress management strategies, aimed at prolonging survival in patients with cardiovascular disease, cancer, and possibly other chronic illnesses, are an exciting area of further research. Immune system changes may account for the relationship between stress and disease. We propose the "stress, cytokine, depression" model as a biological pathway to explain the link between stressful life events and depression.

Coronary Disease↗

PubMed2004

Exposure to juvenile stress exacerbates the behavioural consequences of exposure to stress in the adult rat.

To examine the effects of exposure to post-weaning pre-puberty (juvenile) stress on the emotional and cognitive abilities in response to exposure to stress in adulthood, we first exposed rats to a platform stress at the age of 28 d. Two months later the rats were exposed to acute swim stress. Rats exposed to both stressors showed a higher level of anxiety (as measured both in open-field and startle response tests) than controls or rats exposed to either the juvenile or the adulthood stressor. In the Morris water-maze, rats that were exposed to both juvenile and adulthood stress performed better than the other groups. In a second experiment we verified that the effect of the juvenile stress was indeed age-dependent. One group was exposed at the age of 26-28 d and again at the age of 60 d (juvenile + adulthood stress); the other group was exposed to the first stressor at the age of 60-62 d and to the second at the age of 90 d [adulthood (60) + adulthood (90) stress]. Juvenile + adulthood stress had a significantly greater effect than exposure to stress twice in adulthood, on anxiety level and on the performance in the water-maze. Finally, in a third experiment we found that the juvenile+adulthood stress group swam faster and tended to explore the central area more than the other groups--a finding that could explain their better performance on the first trial of the spatial task. These results indicate that an exposure to a relatively brief juvenile stressful experience has profound and long-lasting effects on the ability to cope with stress in adulthood.

Aging↗

PubMed2005

Modulation of motor function by stress: a novel concept of the effects of stress and corticosterone on behavior.

Stress and stress hormones affect a variety of behaviors and cognitive abilities. The influences of stress and glucocorticoids on motor function, however, have not been characterized although the presence of glucocorticoid receptors in the motor system has been documented. Here we demonstrate that stress and the stress hormone corticosterone influence motor system function in rats. Groups of adult female Long-Evans rats underwent either a daily stress-inducing procedure (immobilization or swimming in cold water) or oral corticosterone treatment. While these treatments continued, animals were tested in skilled reaching and skilled walking tasks for a period of 2 weeks. Both acute (day 1) and chronic (day 14) stress and corticosterone treatment reduced skilled movement accuracy in reaching and walking and increased performance speed. Furthermore, both chronic stress and chronic corticosterone treatment altered skilled movement patterns in the reaching task. These findings indicate that stress modulates motor system function and that these effects are partially mediated by glucocorticoids. To examine whether stress-induced changes might also derive from enhanced emotionality, rats were treated with the benzodiazepine diazepam. Based on an inverted U-shaped dose-response relationship, a moderate dose of diazepam significantly improved reaching success while at the same time reducing corticosterone levels. Thus, stress-associated emotional responses such as anxiety might account for diminished movement accuracy. These results suggest that stress affects the motor system both directly via hormonal changes and indirectly via changes in emotionality. These findings are discussed with respect to the role of stress in motor system function and movement disorders.

Analysis of Variance↗

PubMed2003

Contraction stress of flowable composite materials and their efficacy as stress-relieving layers.

BACKGROUND: The authors compared the polymerization contraction stress produced by flowable resin-based composites with stress values produced by nonflowable composites. They also measured the stress reduction produced by placing a precured layer of flowable composite under a nonflowable composite. METHODS: The authors first tested four flowable and six nonflowable composite materials for contraction stress in a tensiometer. In the second part of the study, they applied a 1.4-millimeter-thick layer of flowable composite or unfilled resin and precured it in the test apparatus to assess the stress relief produced by a low-modulus material during light curing of a subsequent layer of highly filled composite. Flexural moduli of the precured materials were determined via a three-point bending test. RESULTS: The stress values ranged between 6.04 and 9.10 megapascals. The authors found no significant differences in stress between flowable and nonflowable composites. Microfilled composites produced lower contraction stress than did hybrids. The flexural modulus of the flowable composites varied between 4.1 and 8.2 GPa. Regarding the effect of a precured layer of composite on contraction stress, the authors observed significant reductions with only one of the flowable materials and with the unfilled resin. CONCLUSIONS: The flowable composites produced stress levels similar to those of nonflowable materials. Most of the flowable materials tested did not produce significant stress reductions when used under a nonflowable composite. CLINICAL IMPLICATIONS: Using a flowable resin-based composite as a restorative material is not likely to reduce the effects of polymerization stress. When used in a thin layer under a nonflowable composite, the stress reduction depended on the elastic modulus of the lining material.

Composite Resins↗

PubMed2004

[The impact of the type of anesthesia on stress-realizing and stress-limiting mechanisms of the immune system in gerontological patients at abdominal surgeries].

Surgical stress resulting from the operative morbidity and narcosis aggravates the associated age-related and secondary immunodeficiency of gerontological patients at surgeries. Stress hormones have a strong depressing effect on the immunity by forming stress immunodeficiency. Not only high blood level determines the damaging effect of stress hormones but also the activity of stress-limiting mechanisms of the immune system protect it from the damaging effect of stress hormones. In this connection, the impact of operative morbidity and anesthetic aggression on the activity of stress-realizing and, in particular, stress-limiting mechanisms plays an important role because of the frequency of postoperative complications in gerontological patients namely. We observed patients operated on the abdominal cavity by urgent indications with a delay or based on a schedule under conditions of epidural anesthesia (45 patients), spinal anesthesia (43 patients) and general anesthesia (41 patients). The analysis of data obtained shows that different types of anesthesia have different effect on the plasmic cortisol level and activity of stress-realizing and stress-limiting systems. Thus, in case of epidural anesthesia of gerontological patients it was possible to observe the reduction of the high plasmic cortisol level and activation of stress-limiting reception of immunocompetent cells contributing to the preservation of the immune function. The increased plasmic cortisol level accompanied spinal anesthesia applied to such patients. However, it did not suppress the stress-limiting reception protecting the immunity against the damaging action of cortisol. In case of general anesthesia of gerontological patients it was possible to observe the increased blood cortisol level and decreased activity of protective stress-limiting receptors contributing to the formation of glucocorticoid immunosuppression.

Abdominal Cavity↗

PubMed2026

Validation of a Turkish Translation of the Stress in Emergency Healthcare Professionals: The Stress Factors and Manifestations Scale.

AIM: The primary duties of emergency healthcare professionals (EHPs) are to provide emergency patient care to acutely ill and injured individuals. Due to the nature of their work, EHPs operate under constant stress, often requiring rapid decision-making, swift action, and the delivery of necessary medical care in life-or-death situations, sometimes under inadequately safe conditions. Therefore, the aim of this study is to determine the validity and reliability of the Emergency Healthcare Professional Stress Factors and Symptoms (SEHP:SFMS) Scale in Turkish for identifying stress factors and symptoms in emergency medical care professionals providing emergency patient care services. DESIGN: A methodological study design was used in this study. METHODS: The study was conducted with the participation of 211 EHPs from employees working in emergency care institutions affiliated with the Muğla Provincial Health Directorate between November 2023 and June 2024. Data were collected via a face-to-face survey. Data were analysed using Lawshe content validity ratio, Kaiser-Meyer-Olkin coefficient, Bartlett test, exploratory factor analysis, principal component analysis, Varimax factor rotation method, confirmatory factor analysis, Cronbach's α internal consistency coefficient, convergent validity, discriminant validity, test-retest, and Spearman correlation coefficient tests. RESULTS: The linguistic translation and cultural adaptation of the SEHP:SFMS showed strong performance. The scope validity index of the scale is 0.83. The item-total correlation values of the scale were found to be between 0.486 and 0.794, and the factor loadings were between 0.474 and 0.816. Confirmatory factor analysis fit indices: χ2 = 248.727; df = 101; n = 211; p = 0.000; χ2/df = 2.463; RMSEA = 0.083; CFI = 0.914, SRMR = 0.052, which was found to be compatible and acceptable with the proposed 3-factor model. The Cronbach's α reliability coefficient of the scale was 0.931, and the total variance was 61.97%. CONCLUSIONS: SEHP:SFMS is a valid and reliable tool to assess stress factors and symptoms of Turkish emergency healthcare professionals. Its use improves the quality of emergency care. PATIENT OR PUBLIC CONTRIBUTION: These study findings have been used to create a tool with Turkish validity and reliability that allows for the examination of stress factors among healthcare professionals working in emergency and critical services. Identifying and reducing stress factors among healthcare professionals is crucial for the delivery of quality healthcare services. It can also be used to develop targeted interventions and ongoing strategies to facilitate improved clinical supervision and mentoring. IMPLICATION FOR NURSING PRACTICE: Nurses in emergency departments, which are among the most stressful, dynamic, intense, life-saving, and critical environments in healthcare institutions, and where life-saving treatment is administered, are at high risk of experiencing psychological trauma. Trauma experienced in the work environment is a significant problem for nursing. The consequences of trauma negatively affect nurses and institutions. Studies show that post-traumatic stress, anxiety, depression, and burnout are commonly observed in emergency department nurses. In this sense, understanding the stress and stress factors experienced by nurses can guide future interventions. The results of this study are considered important in making visible the stress and stress factors experienced by nurses in the emergency department, and also in guiding managers and nurses working in this field in terms of preventive and protective measures.

Humans↗