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At least 505 records · Page 28Linked to original sources
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↗
PubMed2000

Meal-feeding scheme: twenty years of research in Brazil.

Naomi Shinomiya Hell was the first researcher to investigate the physiological adaptations to a meal-feeding scheme (MFS) in Brazil. Over a period of 20 years, from 1979 to 1999, Naomi's group determined the physiological and metabolic adaptations induced by this feeding scheme in rats. The group showed the persistence of such adaptations even when MFS is associated with moderate exercise training and the performance to a session of intense physical effort. The metabolic changes induced by the feeding training were discriminated from those caused by the effective fasting period. Naomi made an important contribution to the understanding of the MFS but a lot still has to be done. One crucial question still remains to be satisfactorily answered: what is the ideal control for the MFS?

Adaptation, Physiological↗
PubMed2003

Repeated episodes of ozone inhalation attenuates airway injury/repair and release of substance P, but not adaptation.

To determine the impact of repeated episodes of ozone exposure on physiologic adaptation, epithelial injury/repair, and tracheal substance P levels, adult rats were subjected to episodes of ozone (5 days, 1 ppm, 8 h/day) followed by 9 days of filtered air for four cycles. Rats were sampled on days 1 and 5 of each episode and 9 days after day 5 of episodes 1, 2, and 4. One hour before being euthanized each rat was injected with 5-bromo-2'-deoxyuridine to label proliferating cells. Each 5-day episode showed a characteristic pattern of rapid shallow breathing (days 1 and 2), epithelial injury, and interstitial and intraluminal inflammation. In contrast, the neutrophil component of inflammation, tracheal substance P release, and cell proliferation became attenuated with each consecutive episode of exposure. Concurrent with this cyclic and attenuated response there was progressive hypercellularity and hyperplasia in all airways studied and a progressive remodeling present in the terminal bronchioles. Our findings are consistent with the notion that the cumulative distal airway lesion is at least in part the result of a depressed cell proliferative response to injury in these airways. This depressed cell proliferative response may be in part the result of diminished neutrophil inflammation and/or release of mitogenic neuropeptides in response to ozone-induced injury.

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 (π), 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↗
PubMed1991

Remodeling of the heart in chronic pressure overload.

Cardiac hypertrophy resulting from a chronic mechanical overload is the physiological adaptation of the heart to a disease. From a physiological point of view it is characterized by a slowing of the maximum unloaded shortening velocity and an increased duration of the action potential. This slowing allows the heart to maintain a normal maximum tension at a slower rate. In addition, the heart produced per gram of tension is normalized and the efficiency returns to normal. From a biological point of view the expression of two protooncogenes and of two heat-shock proteins genes is enhanced at the beginning of the overload. The biological determinants of the changed shortening velocity are species-specific. An isomyosin shift plays a major role in some species, e.g., rat, while in others, e.g., man, changes in membrane proteins are determinant. The density in Ca2+ channels remains unmodified, with a significant drop in the density of Ca2+ ATPase of SR, adrenergic and muscarinic receptors, and a slowing of the Na+/Ca2+ exchange. More complex changes occur at the level of the Na+, K+ ATPase. One of the principal consequences of these findings is that most of the usual targets of inotropes are modified and that new drugs have to be conceptualized accordingly.

Adaptation, Physiological↗
PubMed1982

Avian flight energetics.

Flight energy is an important factor in the lives of birds. Many strategies and adaptations serve to minimize energy cost and to allow a range of performance consistent with a bird's ecological needs. Theoretical methods can produce good estimates of flight energy that suggest why flight adaptations occur; but remarkably little is known of the physiological adaptations required by flight, or of how these change, a I believe they must, in relation to ecology and flight behavior. More data on the metabolic power consumption of birds in natural flight would be valuable, but it is more important to determine the changes in internal metabolic processes associated with different levels of flight activity. Muscle efficiency in flight, in particular, may have substantial implications for our understanding of the energetic performance of birds. This is but one of a variety of unknown quantities, and only when the mechanisms that determine these are more deeply investigated can flight adaptations be completely understood.

Adaptation, Physiological↗
PubMed2001

Body building and concurrent mass loss: flight adaptations in tree sparrows.

Environmental changes are responsible for the evolution of flexible physiology and the extent of phenotypic plasticity in the regulation of birds' organ size has not been appreciated until recently. Rapid reversible physiological changes during different life-history stages are virtually only known from long-distance migrants, and few studies have focused on less extreme aspects of organ flexibility. During moult, birds suffer from increased wing loading due to wing-area reductions, which may impair flight ability. A previous study found that tree sparrows' escape flight (Passer montanus) is unaffected during moult, suggesting compensatory aptness. We used non-invasive techniques to study physiological adaptations to increased wing loading in tree sparrows. As wing area was reduced during natural moult the ratio of pectoral-muscle size to body mass increased. When moult was completed this ratio decreased. We show experimentally a novel, strategic, organ-flexibility pattern. Unlike the general pattern, where body mass is positively coupled to pectoral-muscle size, tree sparrows responded within 7 days to reductions in wing area by reducing body mass concurrently with an increase in pectoral-muscle size. This rapid flexibility in a non-migratory species probably reflects the paramount importance and long history of flight in birds.

Adaptation, Physiological↗
PubMed2007

Space flight rehabilitation.

The weightless environment of space imposes specific physiologic adaptations on healthy astronauts. On return to Earth, these adaptations manifest as physical impairments that necessitate a period of rehabilitation. Physiologic changes result from unloading in microgravity and highly correlate with those seen in relatively immobile terrestrial patient populations such as spinal cord, geriatric, or deconditioned bed-rest patients. Major postflight impairments requiring rehabilitation intervention include orthostatic intolerance, bone demineralization, muscular atrophy, and neurovestibular symptoms. Space agencies are preparing for extended-duration missions, including colonization of the moon and interplanetary exploration of Mars. These longer-duration flights will result in more severe and more prolonged disability, potentially beyond the point of safe return to Earth. This paper will review and discuss existing space rehabilitation plans for major postflight impairments. Evidence-based rehabilitation interventions are imperative not only to facilitate return to Earth but also to extend the safe duration of exposure to a physiologically hostile microgravity environment.

Adaptation, Physiological↗
PubMed1993

[Physiology of the pregnant woman and risk factors].

Physiological adaptations of the pregnant woman involve the circulatory, respiratory, digestive, renal, endocrine and metabolic systems. Their precise knowledge allows the clinician to verify the quality of the adaptation of the pregnant woman and to avoid unnecessary treatment of physiological changes misconsidered as pathological changes in reference to prepregnancy standards.

Adaptation, Physiological↗
PubMed1975

NaCl adaptation in Rana ridibunda and a comparison with the euryhaline toad Bufo viridis.

The physiological adaptation of the frog Rana ridibunda to saline environment was studied. It was found that blood was always hypertonic to the external solution, but at the highest salinity tolerated (i.e. 300 mOsM) the osmotic gradient across the skin was nearly abolished. Water uptake by the living frog remained unchanged, whereas sodium transport across the skin decreased markedly. Neurohypophyseal hormone increased water uptake and sodium transport to levels similar to those in tap water frogs. Water content of the tissues was not affected by saline adaptation, although it varied appreciably under acute conditions. Oxygen consumption increased in dehydrated frogs, but not in adapted ones. The results are discussed and compared to the euryhaline toad Bufo viridis; the importance of high urea levels for high salt adaptation is stressed.

Adaptation, Physiological↗
PubMed1982

Development and regression of increased ventricular mass.

This report deals with increased cardiac mass in the light of the following variables: normal ventricular growth (embryo, fetus, neonate and child), the response to work loads (hemodynamic stress) and hypoxia, the cell responses of hyperplasia (increase in cell number), hypertrophy (increase in cell size) and the type of cell (muscle or connective tissue), the age or maturity of the myocardium at the time the hemodynamic or hypoxic stress is imposed, and the biochemistry, ultrastructure and functional morphology (modeling) of the ventricles in response to volume or pressure overload. The desirable physiologic adaptations to work loads are characterized, and the transition from physiologic to pathologic states is examined, comparing and contrasting increased ventricular mass in patients and in trained athletes. Regression of increased ventricular mass is then discussed, first at the cell level (hypertrophy/hyperplasia; muscle cell/connective tissue cell), then at the organ level. The requirements for maintaining or establishing normal ventricular function after removal of overload are reviewed, together with such variables as the type and duration of preoperative hemodynamic stress, the right versus the left ventricle and the relative rates of contractile protein synthesis and degradation.

Adaptation, Physiological↗