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PubMedDate not supplied

Replicative senescence: a critical review.

Human cells in culture have a limited proliferative capacity. After a period of vigorous proliferation, the rate of cell division declines and a number of changes occur in the cells including increases in size, in secondary lysosomes and residual bodies, nuclear changes and a number of changes in gene expression which provide biomarkers for senescence. Although human cells in culture have been used for over 40 years as models for understanding the cellular basis of aging, the relationship of replicative senescence to aging of the organism is still not clear. In this review, we discuss replicative senescence in the light of current information on signal transduction and mitogenesis, cell stress, apoptosis, telomere changes and finally we discuss replicative senescence as a model of aging in vivo.

Cell Proliferation↗
PubMed2005

Interaction of chlorine concentration and shear stress on chlorine consumption, biofilm growth rate and particle number.

Eleven test runs (including two replicates) were carried out to explore the interaction of shear stress and chlorine concentration on the growth of heterotrophic microorganisms. Experimental results revealed that influent chlorine concentration and shear stress had no interaction on biofilm formation. Biofilm bacterial numbers decreased with the increase of influent chlorine concentration. Increasing the shear stress up to a specific level could significantly reduce the potential of biofilm formation. A strong interaction on bacterial quality or chlorine consumption rate of bulk water existed. With non-chlorinated and lower chlorinated conditions, the specific growth rate of biofilm increased with the increase of shear stress. However, an inverse relation occurred at higher chlorine conditions. No significant interaction of chlorine concentration and shear stress existed for particle numbers with 2-5, 5-15, 50-100 and >100 microm diameters. However, a significant interaction existed on particle numbers of 15-25 and 25-50 microm diameters.

Biofilms↗
PubMed1999

Comparison of short-term aerobic training and high aerobic power on tolerance to uncompensable heat stress.

This study investigated whether, in subjects of moderate aerobic fitness, short-term aerobic training could replicate the improved physiological responses to exercise-heat stress observed in individuals with a high level of aerobic fitness. Males of moderate (MF; <50 ml x kg(-1) min(-1) VO2peak, n = 8) and high (HF; >55 ml x kg(-1) x min(-1) VO2peak, n = 8) aerobic fitness walked at 3.5 km x h(-1) in the heat (40 degrees C, 30% relative humidity) wearing nuclear, biological, and chemical protective clothing. Tests were conducted once on HF subjects and on MF subjects before (MF-Pre) and after (MF-Post) a 2-week program 6 d x week(-1) of daily aerobic training (1 h treadmill exercise at 65% VO2peak for 12 d, 22 degrees C, 40% relative humidity). The training significantly increased VO2peak by 6.5%, while heart rate (fc) and rectal temperature (Tre) rise decreased during exercise in a thermoneutral environment. HF had lower body mass and body fat content than MF, and VO2peak remained lower in MF pre-or post-training. In the heat, MF-Post had a decreased skin temperature (Tsk) and an increased sweat rate compared with MF-Pre, but no changes were observed in fc, Tre, or tolerance time (TT). No significant differences during the first 60 min in Tre and fc were observed between the MF-Post and the HF subjects, though the HF subjects exhibited a lower Tsk. The endpoint Tre, deltaTre, and TT remained significantly higher in HF than in either the MF-Pre or MF-Post subjects. It was concluded that, in preparation for exercise in an uncompensable heat stress environment, short-term aerobic training offers little, if any, benefit and is not an adequate substitute for a high level of aerobic fitness resulting from habitual exercise and training.

Adaptation, Physiological↗
PubMed1990

Effect of the DNA replication velocity on the response of Salmonella typhimurium to mild heating.

Changes in the DNA replication velocity of Salmonella typhimurium following mild heat stress (52 degrees C) were studied independently of the major physiological parameter of growth rate, using thymine-requiring mutant strains derived from Salm. typhimurium LT2. The isolated mutant strains BM1 or BM2, grown either as batch or chemostat cultures, showed a greater sensitivity to 52 degrees C heat stress when grown on a minimal medium containing near-limiting concentrations of thymine, compared with growth in the presence of excess thymine. Radiolabelling experiments provided evidence for alterations in the velocity of DNA replication upon growth on different thymine concentrations, independent of the growth rate. Thus, replicating DNA was implicated as the major site of injury after mild moist heat stress.

Culture Media↗
PubMed2003

Lung proteome alterations in a mouse model for nonallergic asthma.

A mouse model for nonatopic asthma was employed to study the alterations of the lung proteome to gain insight into the underlying molecular mechanisms of disease pathophysiology post-challenge. Lung samples from asthmatic and control mice were used to generate 24 high quality two-dimensional electrophoresis gels wherein 2115 proteins were examined for disease relevance. In total, 23 proteins were significantly up- or down-regulated following hapten-challenge of dinitro-fluorobenzene-hypersensitive mice. Twenty proteins were identified by mass spectrometry, of which 18 could be linked to asthma related symptoms, such as stress and inflammation, lung detoxification, plasma exudation and/or tissue remodeling. As such, proteomics was clearly vindicated as a means of studying this complex disease phenomenon. The proteins found in this study may not necessarily play a role in the immunological mechanisms and/or pathophysiology of asthma development. However, they may prove useful as surrogate biomarkers for quantitatively monitoring disease state progression or response to therapy. The mathematics of achieving statistical confidence from low numbers of gel replicates containing large numbers of independent variables stress the need for high numbers of replicates to better sample the population of proteins revealed by two-dimensional gel electrophoresis.

Actins↗
PubMed1990

Tension headache: disregulation at some levels of stress.

This study evaluated the role of stress disregulation in tension headache. Two headache groups, a low-life stress group (N = 12) and a high-life stress group (N = 12), that represented different probable etiologies within the disregulation model were compared to analogous control groups. Subjects were selected after screening 441 undergraduate students. Measures of frontalis EMG and self-report acute stress were obtained at multiple intervals during a series of four laboratory stress tasks. Data supported the disregulation model as determined by replication of the significantly different correlations between self-report acute stress and EMG for the headache versus control groups reported by Hovanitz and co-workers (1989), and by several new within-group and within-individual analyses. Curiously, disregulation was found for acute and life stress but not for the intermediate level of daily hassle stress. These data are presented as support for a reformulation of Schwartz' disregulation model.

Adaptation, Psychological↗
PubMedDate not supplied

Stress and cytokine effects on learning: what does sex have to do with it?

Many studies have alluded to sexually dimorphic changes in behavior following stress. Although many have suggested that these changes are a function of stress-induced changes in learning and memory, there are questions regarding whether performance in those learning and memory tasks are influenced by stress-induced changes in drive more than in actual learning and memory processes. We used the classically conditioned eyeblink response (CCER) to determine whether slowed learning following stress in females can be explained by changes in unconditional response (UR) amplitude, a sign of a stress-induced shift in sensory reactivity. In addition, we had a second treatment group injected with the pro-inflammatory cytokine IL-1beta to serve as an interoceptive stress condition, a physiological stressor with minimal stimulation to the animal. Replicating the work by Shors and colleagues, we found that stressed female rats had slower acquisition of the conditioned response (CR), but we also found that an IL-1beta injection leads to a slowing of CR acquisition. However, in both cases, UR amplitude was lower in the treatment groups. We followed up these results by testing sensory reactivity through the acoustic startle response (ASR), where the magnitude of the ASR was marginally, but nonsignificantly, reduced by the same dose regimen of IL-1beta. Together, these experiments suggest that tailshock stress and immune signaling (IL-1beta) reduce sensory reactivity and the saliency of the stimuli used in the CCER, leading to slower learning in female rats.

Animals↗
PubMed2024

Nonlethal deleterious mutation-induced stress accelerates bacterial aging.

Random mutagenesis, including when it leads to loss of gene function, is a key mechanism enabling microorganisms' long-term adaptation to new environments. However, loss-of-function mutations are often deleterious, triggering, in turn, cellular stress and complex homeostatic stress responses, called "allostasis," to promote cell survival. Here, we characterize the differential impacts of 65 nonlethal, deleterious single-gene deletions on Escherichia coli growth in three different growth environments. Further assessments of select mutants, namely, those bearing single adenosine triphosphate (ATP) synthase subunit deletions, reveal that mutants display reorganized transcriptome profiles that reflect both the environment and the specific gene deletion. We also find that ATP synthase &#x3b1;-subunit deleted (&#x394;atpA) cells exhibit elevated metabolic rates while having slower growth compared to wild-type (wt) E. coli cells. At the single-cell level, compared to wt cells, individual &#x394;atpA cells display near normal proliferation profiles but enter a postreplicative state earlier and exhibit a distinct senescence phenotype. These results highlight the complex interplay between genomic diversity, adaptation, and stress response and uncover an "aging cost" to individual bacterial cells for maintaining population-level resilience to environmental and genetic stress; they also suggest potential bacteriostatic antibiotic targets and -as select human genetic diseases display highly similar phenotypes, - a bacterial origin of some human diseases.

Escherichia coli↗
PubMed1982

Survival under heat stress of lines selected for fast and slow growth at two temperatures.

Two replicates of four lines of White Leghorn chickens previously selected for fast and slow gain from 5 to 9 weeks of age in a hot (32.2 C) and cold (21.1 C) selection environment were grown from 5 to 9 weeks in the hot and cold temperature environments and then subjected to high temperature stress at 40.6 C. Four different experiments were run. The percent mortality was analyzed when approximately 50% of the birds had died. Birds reared in the cold environment were heavier and consistently had higher mortality than those reared in the hot environment when both were subjected to acute heat stress (40.6 C). The importance of acclimation to mild heat stress on response to acute heat stress was demonstrated by the mortality difference. No significant differences in survival under heat stress were found between lines selected in the hot and the cold selection environments. Lines selected for fast growth had significantly higher mortality rates under high temperature stress than lines selected for slow growth in replicate 1 but not in replicate 2. Estimates of the genetic correlation between weight gain from 5 to 9 weeks of age and percent mortality under heat stress after two generations of selection in replicate 2 was -.004, and after three generations of selection in replicate 1 was +.076.

Animals↗
PubMed2004

Global analyses of sumoylated proteins in Saccharomyces cerevisiae. Induction of protein sumoylation by cellular stresses.

We have undertaken a global analysis of sumoylated proteins in Saccharomyces cerevisiae by tandem mass spectrometry. Exposure of cells to oxidative and ethanol stresses caused large increases in protein sumoylation. A large number of new sumoylated proteins were identified in untreated, hydrogen peroxide-treated, and ethanol-treated cells. These proteins are known to be involved in diverse cellular processes, including gene transcription, protein translation, DNA replication, chromosome segregation, metabolic processes, and stress responses. Additionally, the known enzymes, including E1, E2, and E3 of the sumoylation cascade were found to be auto-sumoylated. Taken together, these results show that protein sumoylation is broadly involved in many cellular functions and this mass spectrometry-based proteomic approach is useful in studying the regulation of protein sumoylation in the cells.

Blotting, Western↗
PubMed2001

Environmental blue light prevents stress in the fish Nile tilapia.

The present study aimed to test the effects of blue, green or white light on the stress response of the Nile tilapia, Oreochromis niloticus (L.). Each color was tested on two groups of isolated adult Nile tilapia (8 replicates each): one being subjected to confinement stress, and the other not (control). A different environmental color was imposed on each compartment by covering the light source with cellophane of the respective color (green or blue; no cellophane was used for white light). The intensity of green, white and blue lights was 250, 590 and 250 lux, respectively. Basal plasma cortisol levels were determined for each fish prior to the experimental procedures. The fish were confined by being displaced toward one side of the aquarium using an opaque partition for 1 h both in the morning and the afternoon of the two consecutive days of the test. At the end of this 48-h period, plasma cortisol levels were measured again. Basal cortisol levels (ng/ml) were similar for each group (ANOVA, F(2;42) = 0.77, P = 0.47). Thus, plasma cortisol levels were analyzed in terms of variation from their respective basal level. After confinement, plasma cortisol levels were not increased in fish submitted to a blue light environment. Thus, blue light prevents the confinement-induced cortisol response, an effect not necessarily related to light intensity.

Analysis of Variance↗
PubMed1989

Food cues and perceptual distortion of the female body: implications for food avoidance in the early dynamics of anorexia nervosa.

The present studies concerned a perceptual mechanism that could partially explain the anorexic's severe eating restraint despite continuing hunger. If a woman values a thin body, unrealistic perception of food's fattening effects should increase the aversiveness of ingesting food and foster restraint in eating. The first study considered the perceived thinness/fatness of women's bodies without and with food cues present. College women who (1) shared the stress-generating personality characteristics of anorexics (AP); and (2) judged models as fatter after food cues were introduced (enhancers) reported more stress than AP non-enhancers; no effect of enhancement upon stress was observed in controls. This moderator effect was replicated in a second study. Thus, women with the personality characteristics and high stress that put them at-risk for anorexia also displayed the perceptual distortion involved in the proposed mechanism. Self-ratings verified the same perceptual mechanism in the high-stress AP woman's perception of her own body.

Adolescent↗
PubMed2006

Activation of genes inducing cell-cycle arrest and of increased DNA repair in the hearts of rats with early streptozotocin-induced diabetes mellitus.

BACKGROUND: Oxidative stress was proposed as a critical factor in diabetic complications. The etiology of cell degeneration in diabetes mellitus (DM)-induced cardiomyopathy is unclear. The transition between apoptotic degeneration and cell proliferation under stress conditions is regulated at cell-cycle checkpoints. This study was aimed at elucidating the role of a potent cellular stress-response system of the p53-dependent checkpoint genes, i.e. P21WAF1/CIP1 and 14-3-3 sigma, in the heart in diabetes. MATERIAL/METHODS: Target gene expression levels were analyzed ex vivo in cardiomyocytes of streptozotocin-induced rats by Western blots and two-dimensional immunoblots. The levels of DNA damage/repair in diabetic cardiomyocytes were evaluated by "comet assay" and compared with a control group. RESULTS: Whereas no detectable expression of 14-3-3 sigma and only traces of both p53 and p21WAF1/CIP1 were found in cardiomyocytes of the controls, high expression rates of all three genes were observed in the DM group. Individual levels of DNA breakage were significantly lower in diabetic than in non-diabetic cardiomyocytes. CONCLUSIONS: We propose a dual role for cell-cycle regulation under diabetic conditions: the expressions of both p21WAF1/CIP1 and 14-3-3 sigma genes, activated via p53 function, trigger cell-cycle arrest and DNA repair, preventing replication of mutated DNA and increasing stress resistance of heart tissue at least in early diabetes. However, the double cell-cycle arrest ultimately inhibits the replication of cells, which consequently accumulate in the G1 and G2 phases; this could lead to retarded proliferative activity and tissue degeneration in diabetic myocardium in later diabetes.

Animals↗
PubMed2005

Size versus shape differences: contrasting voxel-based and volumetric analyses of the anterior cingulate cortex in individuals with acute posttraumatic stress disorder.

BACKGROUND: Two studies found morphological differences in the anterior cingulate cortex (ACC) of individuals with chronic posttraumatic stress disorder (PTSD). We sought to replicate and extend these findings in a sample of individuals with acute PTSD. METHODS: The ACCs of individuals with acute PTSD (n = 14) and matched healthy control subjects (n = 14) were compared using voxel-based morphometry (VBM), semi-automated volumetric analyses, and probabilistic maps. Posttraumatic stress disorder diagnosis was ascertained by a psychologist using a structured interview. RESULTS: Voxel-based morphometry analyses revealed significantly less gray-matter density in the right pregenual ACC and in the left insula of the PTSD group. However, volumetric analyses of the ACC revealed no significant differences between groups. Probabilistic maps of the labels of the pregenual ACC indicated that the difference between groups in gray matter density was due to shape differences. CONCLUSIONS: Although there are no volumetric differences in the ACC of acute PTSD individuals compared with normal control subjects, significant shape differences exist, which might indicate volumetric differences in the surrounding structures.

Accidents, Traffic↗
PubMed2002

Replication of a cytopathic strain of bovine viral diarrhea virus activates PERK and induces endoplasmic reticulum stress-mediated apoptosis of MDBK cells.

Endoplasmic reticulum (ER) stress signaling is an adaptive cellular response to the loss of ER Ca(2+) homeostasis and/or the accumulation of misfolded, unassembled, or aggregated proteins in the ER lumen. ER stress-activated signaling pathways regulate protein synthesis initiation and can also trigger apoptosis through the ER-associated caspase 12. Viruses that utilize the host cell ER as an integral part of their life cycle would be predicted to cause some level of ER stress. Bovine viral diarrhea virus (BVDV) is a positive-stranded RNA virus of the Flaviviridae family. BVDV and related flaviviruses use the host ER as the primary site of envelope glycoprotein biogenesis, genomic replication, and particle assembly. We are using a cytopathic strain of BVDV (cpBVDV) that causes cellular apoptosis as a model system to determine how virus-induced ER stress contributes to pathogenesis. We show that, in a natural infection of MDBK cells, cpBVDV activates the ER transmembrane kinase PERK (PKR-like ER kinase) and causes hyperphosphorylation of the translation initiation factor eIF2 alpha, consistent with the induction of an ER stress response. Additionally, we show that initiation of cellular apoptosis correlates with downregulation of the antiapoptotic Bcl-2 protein, induced expression of caspase 12, and a decrease in intracellular glutathione levels. Defining the molecular stress pathways leading to cpBVDV-induced apoptosis provides the basis to study how other ER-tropic viruses, such as hepatitis C and B viruses, modulate the host cell ER stress response during the course of persistent infection.

Animals↗
PubMed2003

Photo-elastic stress analysis of initial alignment archwires.

Photo-elastic models replicating a lower arch with a moderate degree of lower incisor crowding and a palatally displaced maxillary canine were used to evaluate the stresses transmitted to the roots of the teeth by initial alignment archwires. Six initial alignment archwires were compared, two multi-strand stainless steel wires, two non-super-elastic (stabilized martensitic form) nickel titanium wires, and two stress-induced super-elastic (austenitic active) nickel titanium wires. Three specimens of each archwire type were tested. Analysis of the photo-elastic fringe patterns, in the medium supporting the teeth, revealed that the non-super-elastic nickel titanium archwires produced the highest shear stresses (P = 0.001). However, the shear stresses generated by the super-elastic alignment archwires and the multi-strand stainless steel archwires were very similar (P = 1.00). These results show that even in situations where large deflections of initial alignment archwires are required, super-elastic archwires do not appear to have any marked advantage over multi-strand stainless steel alignment archwires in terms of the stresses transferred to the roots of the teeth.

Analysis of Variance↗
PubMed2000

Unresponsiveness to psychosocial stress in a subgroup of autistic-like children, multiple complex developmental disorder.

In this study, we tried to replicate the finding of a diminished cortisol response to stress in autistic-like patients in a more homogenous Multiple Complex Developmental Disorder (MCDD) group. MCDD forms a distinct group within the autistic-like disorders, characterized by impaired regulation of anxiety and affective state, impaired social behavior/sensitivity, and thought disorder. A number of MCDD children develop schizophrenia in adult life. Responses to a psychosocial stressor, consisting of speaking in public while recorded on video, were measured in 10 MCDD children and 12 healthy control children. The public speaking test was imbedded in a two-hour test session, and compared to a control test session. Hypothalamic-pituitary-adrenal (HPA) responses were measured on salivary cortisol at about 20-minute intervals. Heart rate was measured continuously. Delta AUC's were computed for both heart rate (dAUCHR) and salivary cortisol (dAUCCORT), as a measure of response to the test.The public speaking task resulted in significant responses in heart rate and salivary cortisol in healthy control children, but not in MCDD children. dAUCHR was 3.28+/-2.37 in healthy control children, but -0.09+/-1.73 in MCDD children (t=3.31, P<0.01). dAUCCORT was 3.22+/-3.16 in healthy control children, but 0. 17+/-1.74 in MCDD children (t=2.72, P<0.05).The impaired responses to psychosocial stress found in MCDD children may be the result of their limited abilities to react adequately to their (social) environment. The same impairment in stress processing has been found in schizophrenia, and might be a factor in the vulnerability of these MCDD children to develop schizophrenia.

Adrenal Glands↗
PubMed2007

Shifts from competition to facilitation between a foundation tree and a pioneer shrub across spatial and temporal scales in a semiarid woodland.

* Theoretical and empirical research has supported the hypothesis that plant-plant interactions change from competition to facilitation with increasing abiotic stress. However, the consistency of such changes has been questioned in arid and semiarid ecosystems. * During a drought in the semiarid south-western USA, we used observations and a field experiment to examine the interactions between juveniles of a foundation tree (Pinyon pine, Pinus edulis) and a common shrub (Apache plume, Fallugia paradoxa) in replicated areas of high and low stress. * The presence of F. paradoxa reduced P. edulis performance at low-stress sites, but had the opposite effect at high-stress sites. However, the intensity of the interactions depended on temporal variation in climate and age of P. edulis. Both above- and below-ground factors contributed to competition, while only above-ground factors contributed to facilitation. * These results support the hypothesis that interactions can change from competition to facilitation as abiotic stress increases in semiarid environments. A shift from competition to facilitation may be important for the recovery of P. edulis and other foundation species that have experienced large-scale mortality during recent droughts.

Adaptation, Physiological↗