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PubMed2001

Heat shock protein 70 (HSP70) in gastric adaptation to aspirin in Helicobacter pylori infection.

We have recently shown that adaptation of gastric mucosa to aspirin (ASA) is disturbed in Helicobacter pylori (H. pylori)-infected human stomach, but can be restored by eradication of the bacterium. The aim of this study was 1) to evaluate the influence of H. pylori on expression of heat shock protein 70 (HSP70) during ASA ingestion in these subjects and in mice model and 2) to evaluate, whether altered HSP70 expression might be associated with different adaptation to ASA in H. pylori-positive and eradicated subjects. The gastric mucosal HSP 70 gene expression was determined by quantitative RT-PCR and Western blot and immunohistochemistry during 14 days of ASA ingestion (1 g bid) in the same 8 subjects before and 3 months after successful eradication of H. pylori. In addition, HSP70 mRNA and protein expression were examined in 30 mice without and with H. pylori infection and eradication. During 14 days of ASA treatment, human H. pylori-infected mucosa revealed a decrease of HSP70 expression, while after eradication a higher expression and further increase of HSP70 expression during ASA ingestion were observed. Mice inoculated with H. pylori also exhibited decreased gastric mucosal HSP70 mRNA expression that was restored after eradication therapy. Decreased basal and ASA-induced expression of HSP70 may partly be responsible for impaired gastric adaptation to ASA in H. pylori-positive subjects. We conclude that 1. The HSP70 gene and protein expression is reduced during infection with H. pylori in men and mice and that gastric adaptation to ASA in H. pylori eradicated subjects is accompanied by increased HSP70 expression; 2. It is reasonable to assume that decreased HSP70 expression might contribute to disturbed gastric adaptation in H. pylori infection in humans and 3. The expression of HSP70 plays an important role in the mechanism of gastric adaptation to ASA and that H. pylori infection interferes with this adaptation due to decrease of HSP70 expression in gastric mucosal cells.

Adaptation, Physiological↗
PubMed2001

Adaptive changes in dynamic properties of human disparity-induced vergence.

PURPOSE: Vergence eye movements undergo adaptive recalibration in response to a training stimulus in which the initial disparity is changed just after vergence begins (the double-step paradigm). In the present study the changes in the dynamic properties of convergence, speed and acceleration, were examined by using this double-step paradigm, before and after adaptation. METHODS: Four normal subjects participated. Three-dimensional visual stimuli were provided by a head-mounted display with two liquid crystal diode (LCD) panels. To induce adaptation, a double step of disparity was used: an initial step from distances of 2 to 1 m was followed by a second step to distances of 0.7 m ("increasing paradigm") or 1.4 m ("decreasing paradigm") after a constant period of 0.2 seconds. The dynamic properties of vergence were compared before and after 30 minutes of training with these paradigms. RESULTS: Peak velocity of convergence became significantly greater (increasing paradigm) or smaller (decreasing paradigm) after 30 minutes' training. Changes in the dynamic properties of convergence were also obvious in phase-plane (velocity versus position) and main sequence (peak velocity versus amplitude) plots. Further analysis revealed that adaptive increases in vergence velocity were accomplished by an increase in the duration of the acceleration period, whereas adaptive decreases were induced by a decrease in the maximum value of acceleration. CONCLUSIONS: The pattern of change in the dynamic characteristics of vergence after adaptation was similar to that of saccades and the initiation of pursuit eye movements, suggesting common neural mechanisms for adaptive changes in the open-loop control of eye movements.

Adaptation, Ocular↗
PubMed2001

Ten-day cold exposures develop adaptation-compensatory mechanisms of regulation of heat exchange and breathing.

The purpose of the study was to determine types of general cold adaptation and to reveal adaptation-compensatory regulation mechanisms of heat exchange and breathing. 24 healthy subjects were tested. Thermoregulation and gas exchange was measured before, during and after a 10-day cold exposure (13 degrees C, 2 h). Before and after cold exposures the ventilatory CO2 and O2 sensitivity was measured by the rebreathing method. The gas-analyser Eos Sprint ("Erich Jaeger", Germany) was used. The whole group exhibited the hypothermic isoinsulative adaptation type: during cold exposure Tre decreased (P < 0.01), Tsk did not change, the delay for the onset of shivering increased (P < 0.001), Tre of the onset of shivering decreased (P < 0.01). According to Tre measured at 120 min of the 10th day the group was divided in two. In the first group the adaptive response was based on thermoregulation changes only. In the second group adaptive response was based on both thermoregulation changes and breathing regulation changes: ventilatory CO2 and O2 sensitivity increased (P < 0.01), the oxyhaemoglobin dissociation curve moved to the right (P < 0.01). Thus we can propose that subjects of the first group will be more successful in cold adaptation, whereas the second group will be unsuccessful in cold adaptation and at risk for respiratory diseases.

Adaptation, Physiological↗
PubMed2001

[Free radical oxidation as a link of early and prolonged adaptation to environmental factors].

Analyzing his own findings and the data available in the literature, the author has found that free radicals are a connecting link in the development of early and prolonged adaptation. With rapid adaptation, they make a weighty contribution to the body's bactericidal protection and antimicrobial constitutional immunity. This role is mainly played by the oxygen-dependent phagocytic bactericidal system that generates active oxygen forms and by the inducible arginine-dependent connective tissue cell system that synthesizes nitrogen oxide. While performing, the above enzymatic systems spend their cell energy resources on two concurrent processes: the formation of free radical products and the work of ionic pumps that restore an intracellular ionic and osmotic balance. This causes the accelerated expenditure of the body's energy "currency" ATP and the development of energy deficiency in the cells and tissues. Energy shortage serves as a signal for triggering the cellular genetic apparatus to primarily induce the increased development of the cell energy system, namely that of mitochondria, and the activation of the key systems responsible for steady-state long-term individual adaptation of the immune system, antioxidative protection, etc. It has been now ascertained that there is a common pathogenetic link (excessive production of free radicals) in the mechanism responsible for the influence of not only infections on the body, but other environmental factors (fibrogenic dust, ionizing or ultraviolet radiation, cooling, toxic agents oxidized on cytochrome P-450, hypoxia, hyperoxia, etc.) and vital functions (physical overstrain, emotional stress, informational overload, etc.). The above factors all cause the same metabolic change in different ways: the production of higher quantities of active oxygen forms, nitrogen oxide, and other radical products. So the generation of free radicals is an universal connecting link of early and prolonged adaptation. The fact that there is a common link (the excessive production of radicals) in the mechanism of influence of environmental factors and vital activities makes the most important biological reserve (cross adaptation that lies in higher resistance to the whole complex of active influences at adaptation to one of them) serve as a preventive means. The most rapid increase in the production of free radicals and the development of energy-rich products are achieved by hypoxia. So the adaptive and preventive effect of dosage hypoxia are the most pronounced.

Adaptation, Physiological↗
PubMed2001

Repressive adaptation in children with cancer: a replication and extension.

Prior research has shown a higher incidence of a repressive adaptive style in children with cancer. To explore whether repressive adaptation in this population is premorbid or reactive, adaptive style was assessed longitudinally in children with cancer at the time of diagnosis and at 6 months and 1 year after diagnosis. Comparison groups included healthy children and children with other serious but nonmalignant chronic illnesses. At diagnosis, children with cancer showed a higher incidence of a repressive adaptive style than healthy children, and the incidence of repressive adaptation remained stable over time. Children with other chronic illnesses also showed levels of repressive adaptive style comparable to the cancer group. These findings suggest a shift toward repressiveness in response to the diagnosis of cancer that is then maintained over time and necessitate further examination of the health consequences of adaptive style in this population.

Adaptation, Psychological↗
PubMedDate not supplied

Marginal and internal adaptation of stratified compomer-composite Class II restorations.

Different approaches have been proposed to improve the adaptation of Class II restorations, including applying low-elasticity modulus base liners. This in vitro fatigue test (or study) evaluated the influence of the compomer base-lining configuration on restoration adaptation. Direct Class II MOD box-shaped composite restorations with or without base and lining (n=3x8) were placed on intact human third molars with proximal margins 1 mm above or under the CEJ. The compomer (Dyract) was applied as a 1 mm-thick lining or as a base, closing proximo-gingival margins. Marginal adaptation was assessed before and after each phase of mechanical loading (250,000 cycles at 50N, 250,000 cycles at 75N and 500,000 cycles at 100N); internal adaptation was evaluated after test completion. Gold-sputtered resin replicas were observed in the SEM and restoration quality evaluated in percentages of continuity (C) at the margins and within the internal interface after sample section. Mechanical loading did not influence adaptation to enamel, while it adversely affected restoration adaptation to dentin for the full composite and compomer-base restorations (C varied, respectively, from 95.2 to 75.3% and from 98.0 to 10.6%). The internal adaptation quality showed the same general trend, however, with reduced scores of continuity. In this experimental condition, application of a low elasticity modulus layer under the restorative material proved advantageous but the compomer should not contact the gingival margins.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1992

[Survival and the repair of single-stranded DNA breaks in gamma-irradiated Escherichia coli cells adapted to methylmethane sulfonate].

The survival and repair of single-strand breaks of DNA in gamma-ray-irradiated E. coli adapted to MMS (20 mkg/ml during 3 hours) have been investigated. It is shown that the survival of adapted bacteria of radioresistant strains B/r, H/r30, AB1157 and W3110 pol+ increases with DMF (dose modification factor) ranging within 1.4-1.8 and in radiosensitive strains Bs-1, AB1157 recA13 and AB1157 lexA3 with DMF ranging within 1.3-1.4, and does not change in strains with mutation in polA gene P3478 polA1 and 016 res-3. There is no increase in radioresistance during the adaptation to MMS under the action of the protein synthesis inhibitor chloramphenicol. The increase in radioresistance during the adaptation to MMS correlates with the acceleration of repair of gamma-ray-induced single-strand breaks in the radioresistant strains B/r and W3110 pol+ and with the appearance of the ability to repair some part of DNA single-strand breaks in the mutant Bs-1, which beyond the adaptation to MMS does not repair these damages. The incomplete reparability of DNA single-strand breaks in P3478 polA1 strain cells, both adapted and non-adapted to MMS, is equal.

Adaptation, Physiological↗
PubMed2003

Orientation-specific adaptation in human visual cortex.

Nearly all methods for analyzing and interpreting functional magnetic resonance imaging (fMRI) data assume that the fMRI signal behaves in an approximately linear manner. However, it has been shown that the mean fMRI response to a pair of briefly presented visual stimuli is significantly smaller than would be expected from the response to a single stimulus. This smaller response could be the result of either a nonlinearity in the fMRI signal or neuronal adaptation. We tested the neuronal adaptation hypothesis by measuring the fMRI response to sequential pairs of sinusoidal gratings that had either the same or orthogonal orientation. The adaptation hypothesis predicts that brain areas with orientation-selective neurons should show a more linear response when the stimulus pair is orthogonal than when the pair is identical. Our results show no orientation-specific adaptation effects in primary visual cortex (V1) but increasing effects along the hierarchy of visual areas (V2, V3, and V4V). A psychophysical contrast detection experiment, using similar oriented gratings as adapters, shows evidence of orientation-specific adaptation in the visual system. These results have implications for the interpretation of rapid event-related fMRI experiments, as well as for recently developed methods that use adaptation as a tool to measure the response properties of underlying neuronal subpopulations.

Adaptation, Physiological↗
PubMed2003

Quantifying generalization from trial-by-trial behavior of adaptive systems that learn with basis functions: theory and experiments in human motor control.

During reaching movements, the brain's internal models map desired limb motion into predicted forces. When the forces in the task change, these models adapt. Adaptation is guided by generalization: errors in one movement influence prediction in other types of movement. If the mapping is accomplished with population coding, combining basis elements that encode different regions of movement space, then generalization can reveal the encoding of the basis elements. We present a theory that relates encoding to generalization using trial-by-trial changes in behavior during adaptation. We consider adaptation during reaching movements in various velocity-dependent force fields and quantify how errors generalize across direction. We find that the measurement of error is critical to the theory. A typical assumption in motor control is that error is the difference between a current trajectory and a desired trajectory (DJ) that does not change during adaptation. Under this assumption, in all force fields that we examined, including one in which force randomly changes from trial to trial, we found a bimodal generalization pattern, perhaps reflecting basis elements that encode direction bimodally. If the DJ was allowed to vary, bimodality was reduced or eliminated, but the generalization function accounted for nearly twice as much variance. We suggest, therefore, that basis elements representing the internal model of dynamics are sensitive to limb velocity with bimodal tuning; however, it is also possible that during adaptation the error metric itself adapts, which affects the implied shape of the basis elements.

Adaptation, Physiological↗
PubMed2003

Adaptive changes in the angular VOR: duration of gain changes and lack of effect of nodulo-uvulectomy.

Alterations in the gain of the vertical angular vestibulo-ocular reflex (VOR) are dependent on the head position in which the gain changes were produced. We determined how long gravity-dependent gain changes last in monkeys after four hours of adaptation, and whether the adaptation is mediated through the nodulus and uvula of the vestibulocerebellum. Vertical VOR gains were adaptively modified by rotation about an interaural axis, in phase or out of phase with the visual surround. Vertical VOR gains were modified with the animals in one of three orientations: upright, left-side down, or right-side down. Monkeys were tested in darkness for up to four days after adaptation using sinusoidal rotation about an interaural axis that was incrementally tilted in 10 degrees steps from vertical to side down positions. Animals were unrestrained in their cages in normal light conditions between tests. Gravity-dependent gain changes lasted for a day or less after adaptation while upright, but persisted for two days or more after on-side adaptation. These data show that gravity-dependent gain changes can last for prolonged periods after only four hours of adaptation in monkeys, as in humans. They also demonstrate that natural head movements made while upright do not provide an adequate stimulus for rapid recovery of vertical VOR gains that were induced on side. In two animals, the nodulus and uvula were surgically ablated. Vertical gravity-dependent gain changes were not significantly different before and after surgery, indicating that the nodulus and uvula do not have a critical role in producing them.

Adaptation, Physiological↗
PubMedDate not supplied

[Endogenic opioid peptides and antiarrhythmic effect of adaptation to stress].

Adaptation of rats to repeated short-term immobilization increases cardiac resistance to an arrhythmogenic action of coronary artery occlusion (10 min) and reperfusion (10 min) in rats anesthetized with ketamine and artificially ventilated. We examined the role of opioid receptors and endogenous opioid peptides in the development of this antiarrhythmic effect produced in response to repeated periods of immobilization stress. We found that repeated daily stress during a 15-day period resulted in an increase of leu-enkephalin in blood plasma, in the suprarenal gland and myocardium. Adaptation to stress also resulted in an increase in beta-endorphinl-31 in blood plasma, the hypophysis, hypothalamus and midbrain. Pretreatment with selective mu, delta and cappa opioid receptor (OR) antagonists had no effect on the incidence of occlusion and reperfusion-induced arrhythmias in non-adapted control rats. However, pretreatment with the selective muOR antagonist CTAP (0.5 mg/kg) intravenously completely abrogated the antiarrhythmic effect of adaptation. Selective delta and cappa receptor antagonists did not affect the antiarrhythmic effect of adaptation. Prior administration of the selective muOR agonist DALDA (0.1 mg/kg) decreased the incidence of occlusion and reperfusion-evoked arrhythmias in non-adapted rats. This effect was abolished by pretreatment with the selective muOR antagonist CTAP (0.5 mg/kg). These data suggest that mu opioid receptors and endogenous opioid peptides play an important role in the antiarrhythmic effect of adaptation to stress in rats.

Adaptation, Psychological↗
PubMedDate not supplied

[On the mechanism of adaptive response in human cells].

There was investigated one of the mechanisms of adaptive response, related to chromosome aberrations induced by gamma-rays, in lymphocytes of healthy donors and donors with hereditary diseases (Marfan's syndrome and homocystinurea) whose cells are repair-deficient. 3H-thymidine treatment was used as an adaptive dose in G1-period of cell cycle and 8-methoxypsoralen (8-MOP), activated with UV-light, was used as a challenge agents. Cells of healthy donors and cells of patients with Marfan's syndrome had normal adaptive response in relation to gamma-irradiation and photomutagenic action of 8-MOP. There was no induction of adaptive response in realation to gamma-irradiation and 8-MOP photomutagenic action in cells of patients with homocystinurea. The cells from donors characterised with normal repair system and lack of adaptive response 8-MOP photomutagenic action wasn't modified by 3H-thymidine. We have found parallelism of adaptive response protective effect against chromosome aberrations, induced by UV activated 8-MOP and gamma-rays in repair proficient cells of healthy donors and repair deficient cells of patients with Marfan's syndrome. These data lead us to conclusion that mechanism of adaption, at least in some cases has no connection with repair process modification.

Adaptation, Physiological↗
PubMed2006

Local adaptation, patterns of selection, and gene flow in the Californian serpentine sunflower (Helianthus exilis).

The traditional view of the species as the fundamental unit of evolution has been challenged by observations that in heterogeneous environments, gene flow may be too restricted to overcome the effects of local selection. Whether a species evolves as a cohesive unit depends critically on the dynamic balance between homogenizing gene flow among populations and potentially disruptive local adaptation. To examine this evolutionary balance between "global" gene flow and local selection, we studied northern Californian populations of Helianthus exilis, the serpentine sunflower, within a mosaic of contrasting serpentine and nonserpentine areas that differ considerably in soil chemistry and water availability. Local adaptation to riparian and serpentine habitats was studied in Helianthus exilis along with an analysis of gene flow patterns among populations within these habitats. Local adaptation was assessed in H. exilis during 2002 and 2003 using reciprocal transplant experiments at multiple locations within serpentine and riparian habitats. Effects of competition and germination date on the expression of local adaptation were also examined within the reciprocal transplant experiments. Local adaptation was detected in both years at the local site level and at the level of habitat. The analysis of the transplanted populations indicated that the patterns of selection differed considerably between riparian and serpentine sites. Differential survivorship occurred in serpentine habitats, whereas selection on reproductive output predominated in riparian habitats. Local adaptation was expressed only in the absence of competition. Local adaptation in terms of survivorship was most strongly expressed in treatments with delayed seed germination. Microsatellite markers were used to quantify population genetic parameters and examine the patterns of gene flow among sampled populations. Analysis of molecular markers revealed a system of population patches that freely exchange genes with each other. Strong selection seems to maintain ecotypic variation within this endemic sunflower species, while extensive gene flow among populations prevents local speciation between serpentine and riparian ecotypes.

Adaptation, Physiological↗
PubMed2006

The population genetics of adaptation on correlated fitness landscapes: the block model.

Several recent theoretical studies of the genetics of adaptation have focused on the mutational landscape model, which considers evolution on rugged fitness landscapes (i.e., ones having many local optima). Adaptation in this model is characterized by several simple results. Here I ask whether these results also hold on correlated fitness landscapes, which are smoother than those considered in the mutational landscape model. In particular, I study the genetics of adaptation in the block model, a tunably rugged model of fitness landscapes. Considering the scenario in which adaptation begins from a high fitness wild-type DNA sequence, I use extreme value theory and computer simulations to study both single adaptive steps and entire adaptive walks. I show that all previous results characterizing single steps in adaptation in the mutational landscape model hold at least approximately on correlated landscapes in the block model; many entire-walk results, however, do not.

Adaptation, Physiological↗
PubMed2006

[Risk factors of nurses' occupational adaptability].

OBJECTIVE: To explore factors affecting occupational adaptability in nurses for offering basis to increase their occupational adaptability. METHODS: Five hundred and forty-five nurses were investigated with work ability index questionnaire and occupational stress instruments. RESULTS: There were many risk factors affecting occupational adaptability in nurses. The main variables that influenced occupational adaptability included work-overtime, mental load, social support, physical environment, and job hazards. The social support was the factor increasing the occupational adaptability of the nurses (P < 0.01, OR = 0.912). Five factors including work overtime, mental load, social support, physical environment and job hazards were introduced in the Logistic equation. The established functions were: Logit (P) = -11.357 + 1.011x(1) + 0.335x(2) - 0.076x(3) + 0.260x(4) + 0.129x(5). CONCLUSION: There are many risk factors affecting occupational adaptability in nurses. Relevant measures should be taken to promote the occupational adaptability in nurses to reduce the risk factors.

Adaptation, Psychological↗
PubMed1991

Physiologic adaptations to prolonged high-intensity exercise training in patients with coronary artery disease.

Exercise training elicits numerous beneficial adaptations in patients with coronary artery disease (CAD), but until 10 yr ago these adaptations were generally believed to be peripheral adaptations rather than improvements in myocardial blood supply. However, animal models of CAD have been shown to elicit improvements in myocardial blood flow and left ventricular performance with prolonged, intense exercise training. More recently we have provided electrocardiographic, echocardiographic hemodynamic, and radionuclide evidence of central cardiovascular adaptations in patients with CAD after a year-long program of 1 h of exercise at 70-90% of VO2max 5 d.wk(-1). These training-induced adaptations are consistent with an improvement in myocardial oxygenation and concomitantly an enhanced left ventricular function in these patients. This program also resulted in improvements in glucose tolerance, insulin sensitivity, and plasma lipoprotein-lipid profile. We have also shown that these beneficial cardiovascular and metabolic adaptations are maintained during six additional years of training in patients with CAD. These results do not imply that all patients with CAD should initiate such an intense training program, but rather that, in selected patients undergoing a training stimulus well in excess of that conventionally prescribed for coronary patients, the training-induced adaptations may be substantially greater than previously believed.

Adaptation, Physiological↗
PubMedDate not supplied

[The phenomenon of the adaptive stabilization of cardiac structure and the protection of the heart].

It is known that adaptation to short-term repeated stress-effects may significantly increase human resistance to many factors; it may particularly prevent lethal cardiac fibrillation in the case of acute ischemia and reperfusion of the heart and limit the area of necrotized myocardium in the case of ischemia. The present investigations have shown that the mechanism responsible for this resistance improvement is related not only to neurohormonal factors but also to heart structures as such. Isolated hearts of adapted animals display substantially increased resistance to contractural and arrhythmogenic effects of ischemia and reperfusion, cardio-toxic doses of catecholamines and toxic concentrations of calcium. In all these situations, CPK loss, which is a quantitative characterization of the damage, diminishes as a result of adaptation. Analysis of this phenomenon shows that the structures isolated from hearts of adapted animals, i.e. Ca-pump of the sarcoplasmic reticulum and mitochondria, display a markedly greater resistance to autolysis during prolonged storage. Thus during adaptation to short-term repeated stress-effects the phenomenon of adaptation stabilization of cardiac structures develops at the organ level. This phenomenon is accompanied by an increase in the thermal stability of the heart. From this point of view the role of thermal stress proteins in the phenomenon of adaptation stabilization is discussed and the genetic mechanism underlying the phenomenon is described.

Adaptation, Physiological↗
PubMed1990

Prism adaptation and viewing distance.

Previous studies have shown that subjects with normal binocular vision adapt to prism-induced phorias. However, there are conflicting reports as to the amount of adaptation shown to horizontal prisms. Some investigations found a greater amount of adaptation to base out prisms compared with base in, whilst others found the reverse and one study found no adaptation to base out prism at all. This study investigated the adaptation response to horizontal prisms at distance and near in a larger number of subjects (n = 40). The results confirmed our previous findings and showed that at distance the adaptation responses are asymmetrical, there being a significantly greater amount of adaptation to base out prism compared with base in, whilst at near the responses are virtually symmetrical. Possible reasons for these findings are discussed.

Adaptation, Ocular↗