Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ADAPTATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,405 records · Page 78Linked to original sources
PubMed1989

[Prevention of arrhythmogenic and contractile effects of excessive Ca2+ on the heart through adaptation to stress by increasing the activity of sarcoplasmic reticulum].

The experiments with rat isolated hearts and papillary muscles showed that adaptation to short-term stresses increased myocardial resistance to arrhythmogenic and contractile effects of excessive Ca2+. Adaptation caused a three- and fivefold reduction in the contracture and premature beats, respectively, while Ca2+ levels were increased from 1.36 to 10 mM. In the experiments with papillary muscles, the adaptation showed a 6.5-fold decrease in the contracture and significantly limited resting potential depression resulted from lower Na+ concentrations (up to 9 mM) in the perfusion solution. The adaptation to stresses was found to restrict depression of cardiomyocyte electrophysiological parameters that was due to high Ca2+ levels and high heart rate. With the factors, the resting potential in adaptation proved to be significantly higher than in controls and the time of action potential was twice as such as in controls. Biochemical studies demonstrated that Ca2+ transport rates in the sarcoplasmic reticulum, cardiomyocytes of adapted animals were increased by more than 30% whereas the sarcoplasmic reticulum of the heart was more resistant to the effects of endogenous factors of degradation. The authors also discuss a possible mechanism of the cardioprotective effects of adaptation to stress undamaging exposures, which is associated with limited depression of electrophysiological parameters on pathological exposures and with increased Ca2+-transporting capacity of the sarcoplasmic reticulum.

Adaptation, Physiological↗
PubMed1987

Two types of change in sensitivity during light adaptation in cat retina.

The electroretinograms (ERG) were recorded during light adaptation at various levels of background in the urethane-anaesthetized cat. Our previous assumption that for a fixed background all the stimulus strength-response amplitude curves at any moment during light adaptation were similar in slope[1] has been confirmed experimentally. It thus offers a method to deduce the transient sensitivity from b-wave amplitude. Two kinds of change in retinal sensitivity were observed during light adaptation according to the strength of adapting light. When a dim adapting light was used the sensitivity decreased suddenly and then remained at a low level, as soon as the adapting light was over 10(3) scotopic td the initial decrease in sensitivity was followed by a partial recovery within 10 min after the onset of adapting light. It is suggested that the sensitivity recovery is related to the degree in which cones are released from rod suppression and participate in the generation of the b-wave.

Animals↗
PubMed1987

Characterization of the adaptive response to ionizing radiation induced by low doses of X rays to human lymphocytes.

In previous studies we have shown that low doses of radiation from incorporated tritiated thymidine can make human lymphocytes less susceptible to the genetic damage manifested as chromatid breakage induced by a subsequent high dose of X rays. We have also shown that this adaptive response to ionizing radiation can be induced by very low doses of X rays (0.01 Gy; i.e., 1 rad) delivered during S phase of the cell cycle. To see if a low dose of X rays could induce this response in cells at other phases of the cell cycle, human lymphocytes were irradiated with 0.01 or 0.05 Gy before stimulation by phytohemagglutinin (G0) or with 0.01 Gy at various times after stimulation (G1), followed by 1.5 Gy (150 rad) at G2 phase. Although G0 lymphocytes failed to exhibit an adaptive response, G1 cells irradiated as early as 4 h after stimulation did show the response. Experiments were also carried out to determine how long the adaptive response induced by 0.01 Gy could persist. A 0.01-Gy dose was delivered to lymphocytes in the first S phase, followed by 1.5 Gy in the same or subsequent cell cycles. Lymphocytes receiving a 1.5-Gy dose at 40, 48, or 66 h after stimulation exhibited an adaptive response, whereas those receiving a 1.5-Gy dose at 90 or 114 h did not. Duplicate cultures containing bromodeoxyuridine showed that at 40 h all the lymphocytes were in their first cell cycle after stimulation, at 48 h half of the lymphocytes were in their first cell cycle and half in their second, and at 66 h 80% of the lymphocytes were in their third cell cycle. Thus the adaptive response persists for at least three cell cycles after it is induced by 0.01 Gy of X rays. In other experiments, the time necessary for maximal expression of the adaptive response was determined by delivering 0.01 Gy at hourly intervals 1-6 h before the 1.5-Gy dose. While a 4-h interval was enough for expression of the adaptive response, shorter intervals were not.

Adaptation, Physiological↗
PubMed1985

Effects of thermal adaptation at 40 degrees C on membrane viscosity and the sodium-potassium pump in Chinese hamster ovary cells.

We have demonstrated increased heat resistance in Chinese hamster ovary cells grown to confluence at 37 degrees C and thermally adapted at the nonlethal temperature of 40 degrees C for 24 h. Membrane viscosity, estimated by fluorescence anisotropy, was inversely related to temperature, from 5 degrees C to 45 degrees C. For a given temperature viscosity was consistently higher in thermally adapted cells than in native cells. Having demonstrated a change in membrane structure associated with thermal adaptation, we carried out a study of the Na+-K+ pump in native and thermally adapted cells as an example of a vital active transport process known to be sensitive to membrane viscosity. 86Rb uptake measured from 31 degrees C to 50 degrees C increased steadily to 46 degrees C and then decreased rapidly in both native and thermally adapted cells. Detailed measurement of ouabain-sensitive 86Rb influx demonstrated an increase in both Km and Vmax between 37 degrees C and 45 degrees C, but there was no difference between native and thermally adapted cells. We have thus demonstrated an adaptive structural change in the cell membrane of mammalian cells which may be related to the induction of thermal resistance at 40 degrees C but which is not associated with any change in this active transport system.

Adaptation, Physiological↗
PubMed1978

Retinal mechanisms of visual adaptation and afterimages.

Recent results obtained from recordings of isolated photoreceptor activity and from correlations of this activity with time-dependent changes in the responses of other retinal cells in several vertebrates have made a thorough revision of former theories of visual adaptation necessary. The present paper reviews the current state of research and relates the new discoveries with psychophysical findings in an attempt to explain human light and dark adaptation from the novel starting point. The former conceptions of adaptation have to be replaced with a three-level process consisting of photochemical receptor neural and network adaptation. Several adaptive mechanisms can be discerned at each level. Depending on adaptation conditions, any level of the three can play a dominating role and can also produce afterimages that display the behaviour of the mechanisms working at each level. The total achievement of visual adaptation is an optimized end product of the actions of all the various mechanisms.

Adaptation, Ocular↗
PubMed1984

Spatial adaptation of the cortical visual evoked potential of the cat.

Adaptation that is spatially specific for the adapting pattern has been seen psychophysically in humans. This is indirect evidence for independent analyzers (putatively single units) that are specific for orientation and spatial frequency in the human visual system, but it is unclear how global adaptation characteristics may be related to single unit performance. Spatially specific adaptation was sought in the cat visual evoked potential (VEP), with a view towards relating this phenomenon with what we know of cat single units. Adaptation to sine-wave gratings results in a temporary loss of cat VEP amplitude, with induction and recovery similar to that seen in human psychophysical experiments. The amplitude loss was specific for both the spatial frequency and orientation of the adapting pattern. The bandwidth of adaptation was not unlike the average selectivity of a population of cat single units.

Adaptation, Ocular↗
PubMed1983

The construct and predictive validity of adaptive behavior.

The construct and predictive validity of adaptive behavior of mentally retarded persons was investigated using a multitrait multimethod analysis. The validity issues of concern were (a) how generalizable the adaptive behavior dimension is over a variety of measurement methods, (b) how adaptive behavior relates to mental age (MA), and (c) how well adaptive behavior assessment references placement in programs and situations. Adaptive behavior and MA were assessed by program participation, psychometric ratings, and overall staff ratings. Adaptive behavior had high convergent validity and low discriminant validity and predicted MA program placement better than did MA. We concluded that adaptive behavior scores could replace MA.

Adaptation, Psychological↗
PubMed1981

Abnormal dark adaptation in sickle cell anemia.

Patients with sickle cell anemia may be zinc-deficient. Zinc deficiency has been reported to cause delayed dark adaptation. We have studied dark adaptation in 13 patients with homozygous sickle cell anemia. Six patients had delayed dark adaptation. Their mean plasma and neutrophil zinc levels were 93.83 +/- 8.26 micrograms/100 microliters and 37.33 +/- 11.88 micrograms/10(10) cells, respectively, compared to the corresponding mean values for seven patients with normal dark adaptation of 105.86 +/- 13.31 and 86.71 +/- 19.53. For the six patients with delayed dark adaptation, the lower neutrophil zinc value, but not the plasma value, was significant (p less than 0.01). Three of the six were treated with oral zinc, with improvement in their dark adaptation. Neutrophil zinc levels correlated inversely (r = -0.77, p less than 0.01) with log relative threshold at 30 min. We conclude that patients with sickle cell anemia may show decreased ability to dark-adapt that is related to zinc deficiency.

Anemia, Sickle Cell↗
PubMed1995

Mild hyperthermia can induce adaptation to cytogenetic damage caused by subsequent X irradiation.

Many low-level environmental agents are able to induce an increased resistance to subsequent mutagenic effects induced by ionizing radiation. In this paper, an induced cytogenetic adaptation to radiation in human lymphocytes was studied with mild hyperthermia as the adaptive treatment and compared with that induced by low-dose radiation. We found that this adaptation could be induced not only in PHA-stimulated human lymphocytes (at 14, 38 and 42 h after addition of PHA), but also in unstimulated G0-phase cells (before addition of PHA) by mild hyperthermia (41 degrees C for 1 h) as well as 50 mGy X rays. When the two adaptive treatments were combined, no additive effects on the magnitude of the adaptation induced were observed, suggesting that low-dose radiation and hyperthermia may share one mechanism of induction of adaptation to cytogenetic damage. Some mechanisms which may be involved in the induction of adaptation to cytogenetic damage by low-dose radiation are discussed and compared with the effects of mild hyperthermia in inducing thermotolerance and radioresistance.

Adaptation, Physiological↗
PubMed1995

[The effect of virginiamycin on rumen fermentation in vitro after adaptation of donors to the inoculum].

Virginiamycin is an antibiotic active against grampositive bacteria in the alimentary tract, which is also suitable for supplementation of diets of growing and finishing ruminants. The aim of this work was to specify the effect of virginiamycin on some parameters of rumen fermentation in vitro with inoculi taken from wethers adapted or non-adapted to the virginiamycin intake. Incubations were performed anaerobically at 39 degrees C in serum bottles closed with Bunsen valves. Virginiamycin was added at 0 or 10 mg/l to the rumen fluid diluted with McDougall buffer. Virginiamycin significantly decreased production and utilization of lactic acid, production of methane and decomposition of casein when rumen fluid was taken from non-adapted wethers. Most of its effects disappeared when rumen fluid was sampled from wethers adapted to the virginiamycin intake (100 mg per head daily for 2 months). Adaptation of wethers to virginiamycin was further confirmed by analyses of the rumen fluid which was used for inoculation of in vitro cultures. Molar percentages of acetate, propionate, butyrate and valerate were the same before and after the adaptation. Therefore it can be concluded that the effects of virginiamycin on rumen parameters are not stable and its addition to ruminant diets cannot be recommended, with exception of the milk nutrition period. In the last experiment the stability of virginiamycin in the rumen fluid of adapted wethers was investigated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1994

Modification of oxygen tolerance in rats by adaptation to combined hypoxia and hypercapnia.

Tolerance to 100% O2 or to O2 with 60 torr PICO2 (O2-CO2) was determined at pressures of 1.0-4.0 atm abs in normal rats and in rats adapted to combined hypoxia and hypercapnia (HHA) before O2 or O2-CO2 exposure. Results were compared with previous studies of tolerance to O2 or O2-CO2 after adaptation to hypoxia or hypercapnia alone. Both the positive effect on pulmonary O2 tolerance and the negative effect on CNS O2 tolerance found in hypoxia-adapted rats were reduced or eliminated in HHA rats. The increased CNS tolerance to O2-CO2 found in hypercapnia-adapted rats was also reduced in HHA rats. The observation that some of the O2 tolerance modifications associated with adaptation to hypoxia or hypercapnia were reduced or eliminated by adaptation to both stresses concurrently may be because physiologic responses to chronic hypoxia and chronic hypercapnia are opposite in some ways. Results of the present and previous related studies indicate that physiologic adaptations to chronic alterations in the oxygen and acid-base environments have prominent influences on O2 tolerance over a range of useful pressures.

Adaptation, Physiological↗
PubMed1993

Adaptive modeling in a mammalian skeletal model system.

Juvenile BALB/c mice were used as a model system to test the effects of various loading and exercise regimens on the growth and development of femora. Six treatments and three controls were used to document changes in geometric, mechanical, and material properties of the femora associated with strength. In each age-matched experiment, body weight and the strength, length, anterior and posterior diameters, cross-sectional area, moments of inertia in the anteroposterior and lateromedial directions, cortical wall thickness, and mineral content of the femora were assessed and found to vary significantly among treatment groups. An adaptive interpretation of these data was provided by calculating Pearson correlation coefficients between moment at failure (one measure of strength) and each geometric, mechanical and material property of the femora that contributes to strength. We make the assumption that at the termination of the experiment the greater the coordination between changes in strength and changes in the parameters that contribute to strength (the greater the number of correlations), the more adaptively modeled the femora are. Adaptive modeling here refers to the manner in which the femora grow and develop (adapt) under a given treatment regimen. Absolute strength of whole femora was reflected by our measure of adaptive modeling in all groups with one exception. In each experiment, the voluntary exercise controls were the most adaptively modeled. The least adaptively modeled groups also showed a general retardation of growth. It appears that juvenile mouse femora demonstrate a wide range of responses to different conditions of loading and exercise and that some of these changes are likely permanent. Moreover, at least two major variables--1) mechanical loading and 2) glucocorticoid mediated psychological stress--appear to contribute to the differences seen between the treatment groups.

Adaptation, Physiological↗
PubMed1977

[Effects of dimethylsulfoxide and salicine on the delayed adaption on sorbose and dulcitol of Salmonellae (author's transl)].

Among the majority of Salmonella strains splitting sorbose or dulcitol with delay dimethylsulfoxide shortens the latent period preceding acid formation and abolishes the deceleration of sorbose adaption caused by salicine. In other strains, especially S. paratyphi B cultures, DMSO doesn't touch sorbose adaption directly but amplifies the restraing effect of salicine. From the whole of our findings it can be concluded that in the first group of strains sorbose adaption starts with segregation of adaptive sorbose permease positive mutants, followed by the - salicin-sensitive - induction of this permease, the appearance of mutants aditionally metabolizing sorbose constitutively, and, finally, the substrate-promoted particular growth of adapted cells. The latter category of strains, however, apparently possesses a wild type (constitutive or adaptive?) sorbose permease but splits off mutants with adaptive metabolizing enzymes the induction of which is salicine-sensitive. The amplification of the salicine effect by DMSO found in these strains might be refered to an enhancement of salicine uptake caused by DMSO.

Adaptation, Physiological↗
PubMed1997

How to measure human adaptation in extreme environments: the case of Antarctic wintering-over.

BACKGROUND: Whether wintering-over causes cognitive and sensory impairment and associated adaptation problems is still a subject of debate. Conflicting results reported in the literature may be due to the difference in the experimental tasks. Moreover, interpersonal variability can hide the effects. HYPOTHESIS: Performance on cognitive and psychomotor tasks can be an indicator of adaptation problems. METHODS: Subjects were 10 scientists and 6 technicians (both clinically normal) who wintered-over for a year in the Antarctic. A subset of tasks of the AGARD battery of Standardized Tests for Research with Environmental Stressors (SB) was completed eight times during the isolation. To assess adaptation, the adaptability questionnaire (AQ) was completed by the physician before every performance test. RESULTS: SB showed a sensitive period of adaptation at mid-winter and at the end of the isolation, but the performance in the different tasks did not deteriorate exactly at the same time. No systematic relationship between AQ notations and SB performances was noted. However, three subjects showed significant positive correlations: r > 0.8, p < 0.05 (i.e., low adaptation = low performance). CONCLUSION: Some clinically normal individuals can experience adaptation problems, and SB tasks can be an indicator of these problems when comparisons are done at an individual level.

Adaptation, Physiological↗
PubMed1998

Impact of family demands and family strengths and capabilities on family well-being and adaptation after critical injury.

BACKGROUND: Increases in demands on patients' family members that are not reduced by family strengths may contribute to decreases in family adaptation and complicate patients' recovery after trauma. The purpose of this study was to examine family demands (prior stressors and severity of patients' injuries) and family strengths and capabilities (hardiness, resources, coping, and problem-solving communication) associated with outcomes of family well-being and adaptation. METHODS: A multivariate, descriptive design based on the Resiliency Model of Family Stress was used. A convenience sample of family members (N = 51) of adult patients participated within the first 2 days of critical injury. Family demands were measured with the Family Inventory of Life Events and Changes and the Acute Physiology, Age, and Chronic Health Evaluation III. Family strengths were measured with the Family Hardiness Index, Family Inventory of Resources for Management, Family Crisis Oriented Personal Evaluation Scale, and Family Problem Solving Communication Index. Family adaptation outcomes were measured with the Family Well Being Index and Family Adaptation Scale. RESULTS: Increases in family demands were significantly related to decreases in family strengths and family adaptation. Family demands scores accounted for 40% of the variance in family well-being scores. The only significant family strength variable influencing family adaptation was problem-solving communication. CONCLUSIONS: Increases in family demands seem to be an important indicator of the amount of assistance a family may need. Interventions that help mobilize family strengths, such as problem-solving communication, may be effective in promoting the adaptation of families of critically injured patients.

APACHE↗
PubMed1998

Adaptation after small bowel resection is attenuated by sialoadenectomy: the role for endogenous epidermal growth factor.

BACKGROUND: Epidermal growth factor (EGF) is likely involved during adaptation after small bowel resection (SBR) because some studies have shown enhanced adaptation by EGF administration. Because the major source of endogenous EGF in mice is the submandibular glands, we sought to determine the effect of submandibular gland excision (SAL) and luminal or systemic EGF replacement on adaptation after SBR. METHODS: A 50% proximal SBR or Sham-SBR (bowel transection and reanastomosis) was performed on male C57BL/6 mice after either SAL or gland mobilization only. Additional mice underwent both SBR and SAL and then received daily EGF or saline solution by intraperitoneal or orogastric administration. At 1 week, adaptation was characterized in the ileum as changes in villus height, DNA, and protein content. RESULTS: SAL significantly attenuated the increase in ileal villus height, total protein, and DNA content after SBR. Both systemic and oral EGF reversed these findings equally and significantly augmented all parameters of intestinal adaptation after SAL. CONCLUSIONS: Submandibular EGF is important for the adaptive response to massive SBR. As both luminal and systemic EGF equally reversed the findings following SAL and SBR, the specific site of action for endogenous EGF during adaptation is either the luminal or basolateral surface of the enterocyte.

Adaptation, Physiological↗
PubMed2025

Whole-genome sequencing identifies genetic diversity and adaptive signatures of hypoxia and ultraviolet radiation in Chinese chickens.

INTRODUCTION: Domestic chickens primarily descended from the wild red junglefowl, play a crucial role in global egg and meat production. China hosts diverse indigenous chicken populations that have adapted to various environmental conditions, including high-altitude with hypoxic and ultraviolet radiation stress. METHOD: We analyzed whole-genome sequences of 118 birds from five Indigenous Chinese chicken populations and 295 chicken genomes from publicly available databases to identify genomic diversity, admixture, and selection signatures of chickens adapted to high-altitude environments. Selection signatures were identified using nucleotide diversity (&#x3c0;), Tajima's D, XPEHH, and XP-CLR, selection scan methods. RESULTS: We observed a reduction in genetic diversity and historical declines in effective population size in high-altitude chicken, suggesting ongoing selection pressures shaping these populations. Selection scans identified nine genomic regions under strong positive selection, enriched for genes associated with hypoxia and ultraviolet radiation. Notably, five genes (TPK1, BAZ2B, MARCHF7, LLGL2, and RCAN3) were repeatedly detected across multiple selection signature analyses. RNA-seq analysis further confirmed the differential expression of these genes in the lung and heart tissues of chickens adapted to high and low altitudes, reinforcing their role in physiological adaptation to hypoxic environments. Altitude adaptation is driven by the selection of genes involved in oxygen metabolism, cellular stress response, and energy regulation. CONCLUSION: Our study provides compelling genetic evidence for differentiation between high and low and high-altitude Chinese chicken populations. These findings also ensure our understanding of local adaptation in poultry and establish a genomic framework for breeding strategies to improve environmental resilience to altitude-related stressors.

Animals↗
PubMed2026

No evidence of fine-scale local adaptation of winter moths to variable tree phenology.

Spatial variation in plant phenology can impose strong selective pressures on herbivorous insects whose fitness relies on synchrony with host plants, promoting local adaptation to host timing. Winter moths (Operophtera brumata) have been shown to synchronize egg hatching with host budburst, but whether this reflects local adaptation remains unclear. We used three complementary approaches to assess small-scale local adaptation of winter moths to oak phenology in Wytham Woods, UK, a 385-hectare woodland with repeatable variation in individual oak budburst phenology. We experimentally investigated whether host tree phenology predicts hatch timing using common gardens across multiple temperatures, evaluated fitness benefits of synchrony using translocations, and assessed population structure and gene-environment associations using whole-genome sequencing. We found no support for local adaptation to individual trees. Common garden experiments revealed systematic differences in hatch timing which were unrelated to host budburst, while translocations indicated no fitness consequences of asynchrony. Genetic analyses showed no detectable population structure or association with budburst timing. Local adaptation to host phenology therefore appears not to arise on individual trees but may instead occur at broader spatial scales. Understanding the scale of local adaptation is essential for predicting how insect-plant synchrony will respond to environmental change across heterogeneous landscapes.

Animals↗