SEARCH · PubMed Health

Results for “ADAPTATION, PHYSIOLOGICAL”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 307 records · Page 17Linked to original sources

PubMed2002

Transmitral and pulmonary venous flow study in elite male runners and young adults.

BACKGROUND: Even if diastolic function has been assessed in athletes by analysis of transmitral Doppler flow, no one has studied pulmonary venous flow in this population. The aim of this study was to establish if the physiological adaptations following a prolonged physical training could influence the diastolic function in a professional Olympic male runner group. METHODS: From February to December 1999 we studied 25 athletes (Group I) during the period of maximal training compared with 18 age- and sex-matched healthy sedentary subjects (Group II). We used mono- and bidimensional Echocardiography to assess left ventricular structure and systolic function. The diastolic function was evaluated by Doppler method assessing transmitral and venous pulmonary flow. RESULTS: From the comparison between the two groups, we found great differences in the interventricular septum and the posterior wall thickness; the analysis of the systolic function demonstrated a significant increase in ejection fraction, stroke volume, left ventricular mass, and end diastolic volume in the athletes' population. Fluximetric study showed that ventricular diastolic function is not influenced by hypertrophy: indeed, Doppler evaluation of the transmitral flow showed a bigger velocity of the E wave, similarly, when we assessed pulmonary venous flow, we found faster retrograde Ar wave in group I. CONCLUSIONS: Our data indicate that diastolic function remains normal or improves in some cases after physical training; left ventricular hypertrophy and concentric remodeling do not involve diastolic changes like hypertrophic and hypertensive heart diseases.

Adaptation, Physiological↗

PubMed2003

Interactions between earthworms and arsenic in the soil environment: a review.

Chemical pollution of the environment has become a major source of concern. In particular, many studies have investigated the impact of pollution on biota in the environment. Studies on metalliferous contaminated mine spoil wastes have shown that some soil organisms have the capability to become resistant to metal/metalloid toxicity. Earthworms are known to inhabit arsenic-rich metalliferous soils and, due to their intimate contact with the soil, in both the solid and aqueous phases, are likely to accumulate contaminants present in mine spoil. Earthworms that inhabit metalliferous contaminated soils must have developed mechanisms of resistance to the toxins found in these soils. The mechanisms of resistance are not fully understood; they may involve physiological adaptation (acclimation) or be genetic. This review discusses the relationships between earthworms and arsenic-rich mine spoil wastes, looking critically at resistance and possible mechanisms of resistance, in relation to soil edaphic factors and possible trophic transfer routes.

Adaptation, Physiological↗

PubMed1997

Transmission of acquired adjustments to salinity in Sorghum bicolor.

Previous studies showed that exposure of eight-day-old Sorghum bicolor for three weeks to sublethal salinity induces an increase in salinity tolerance, called physiological adaptation (A). During A, plants of a same population differ in reaction and tolerance to salinity. Tolerance levels of the reaction types depend on environmental conditions besides salinity. Reactions observed most frequently in an experiment have generally highest tolerance levels. This phenomenon is defined adaptive determinism (AD). In this study, the relationship between a potential source of the information subjacent to AD and AD itself is analysed in plants first exposed to salt-inducing A. When the reaction types are close variations of one reaction mode. AD is highest. This relationship is inversed in progeny of adapted plants. Results suggest that information relevant to AD is transmitted to the progeny of adapted plants, and that adaptive information is created during A in plants first exposed to adaptation inducing treatment.

Adaptation, Physiological↗

PubMed1998

The associations of body size and body composition with left ventricular mass: impacts for indexation in adults.

OBJECTIVES: We investigated the relationship between body size, body composition and left ventricular mass (LVM) in adults, and assessed the impact of different indexations of LVM on its associations with gender, adiposity and blood pressure. BACKGROUND: The best way to normalize LVM for body size to appropriately distinguish physiologic adaptation from morbid heart morphology was discussed. METHODS: We undertook a community survey of 653 men and 718 women, aged 25 to 74 years. Lean body mass (LBM) was determined by bioelectric impedance analyses and LVM was assessed by two-dimensional guided M-mode echocardiography. RESULTS: After traditional indexations to body height, body height2.7, or body surface area, men had higher LVM than women (p < 0.001). These gender differences disappeared (p > 0.05) when LVM was indexed to LBM. The type of indexation also modified the strength of the association between adiposity and LVM. The estimated impact of body fat on LVM indexed to LBM was less than half that obtained with traditional indexations. In contrast, the magnitude of the associations of blood pressure with LVM was entirely independent of the type of indexation. CONCLUSIONS: This study showed the prominent influence of body composition on adult heart size. Indexation for LBM removed gender differences for LVM and reduced the impact of adiposity, but left the effects of blood pressure unchanged. We suggest that this approach be used for clinical and research applications.

Adaptation, Physiological↗

PubMed2006

Exercise capacity and impact of exercise training in patients after a Fontan procedure: a review.

After a successful Fontan procedure, children and adolescents should improve their exercise capacity. However, several studies have shown that these children have a reduced maximal oxygen consumption compared with healthy children. The lower exercise performance in these patients was mainly explained by a reduced cardiorespiratory functional capacity. However, it has recently been reported that the lower exercise performance may also be related to altered skeletal muscle function. Moreover, exercise training had a beneficial impact on several parameters related to exercise tolerance in these patients. The main studies supporting these observations are reviewed, with a focus on the physiological adaptation and limitation of the exercise performance as well as the benefits of exercise training in patients after a Fontan procedure.

Adaptation, Physiological↗

PubMed2002

Red blood cell and iron metabolism during space flight.

Space flight anemia is a widely recognized phenomenon in astronauts. Reduction in circulating red blood cells and plasma volume results in a 10% to 15% decrement in circulatory volume. This effect appears to be a normal physiologic adaptation to weightlessness and results from the removal of newly released blood cells from the circulation. Iron availability increases, and (in the few subjects studied) iron stores increase during long-duration space flight. The consequences of these changes are not fully understood.

Adaptation, Physiological↗

PubMed2001

An evaluation of the concept of living at moderate altitude and training at sea level.

Despite equivocal findings about the benefit of altitude training, current theory dictates that the best approach is to spend several weeks living at > or =2500 m but training near sea level. This paper summarizes six studies in which we used simulated altitude (normobaric hypoxia) to examine: (i) the assumption that moderate hypoxia compromises training intensity (two studies); and (ii) the nature of physiological adaptations to sleeping in moderate hypoxia (four studies). When submaximal exercise was >55% of sea level maximum oxygen uptake (VO2max), 1800 m simulated altitude significantly increased heart rate, blood lactate and perceived exertion of skiers. In addition, cyclists self-selected lower workloads during high-intensity exercise in hypoxia (2100 m) than in normoxia. Consequently, our findings partially confirm the rationale for 'living high, training low'. In the remaining four studies, serum erythropoietin increased 80% in the early stages of hypoxic exposure, but the reticulocyte response did not significantly exceed that of control subjects. There was no significant increase in haemoglobin mass (Hb(mass)) and VO2max tended to decrease. Performance in exercise tasks lasting approximately 4 min showed a non-significant trend toward improvement (1.0+/-0.4% vs. 0.1+/-0.4% for a control group; P=0.13 for group x time interaction). We conclude that sleeping in moderate hypoxia (2650-3000 m) for up to 23 days may offer practical benefit to elite athletes, but that any effect is not likely due to increased Hb(mass) or VO2max.

Adaptation, Physiological↗

PubMed1999

Hydrodynamic modelling of stress.

This work is a qualitative study of an organism's physiological adaptative response to stress. The experimental data were selected from a previous study leading to the conclusion that stress may be considered as a topological retraction within a vital space that must be more precisely defined. The experimental methodology uses rat poisoning by neurotoxins. The control parameter is the intensity of the toxic doses. Measured parameters are the animals' survival rate and the kinetics of cerebral acetylcholinesterase activity. The results, when expressed as a function of the inverted doses, show a characteristic evolution. The pattern of the curve closely resembles a vortex profile. This analogy is studied more extensively in both the physical and biological domains. These findings help to clarify the concept of biological stress which presents the same vectorial properties as hydrodynamic vorticity. In particular, the dissipation of stress and the dissipation of vorticity seem to obey the same laws. This observation is valid for both diffusion and convection processes. The decompensation phase of stress could be compared with the instability and turbulence in flows. Our approach in this paper is mainly to establish a general and phenomenological description of the stress response fitting experimental observations.

Acetylcholinesterase↗

PubMed1986

Metabolic responses of women to exercise attributable to long term use of a manual wheelchair.

The purpose of this study was to determine the effects of long term use of a manual wheelchair by wheelchair-confined women (means = 14.6 years) on physiological responses to wheelchair ergometry. Six experimental subjects were compared to six able bodied women during maximal exercise as well as submaximal wheelchair ergometry at 50 and 80% of peak VO2. The wheelchair dependent women achieved higher power outputs, greater efficiency at the higher submaximal workload, less metabolic acidosis during submaximal exercise as well as less ventilatory stress. There was no significant difference in peak VO2 between the two groups of women. Because these were not athletically trained women, it was concluded that the long term use of a manual wheelchair leads to physiological adaptations favourable to the daily requirements of wheelchair locomotion.

Acid-Base Equilibrium↗

PubMed2001

Reptilian echocardiography: insights into ontogeny and phylogeny?

We describe the echocardiographic findings in a large reptile-the carpet python. If ontogeny recapitulates phylogeny, the study of reptilian hearts may provide insights into human cardiac development. In addition, the reptilian heart has unique structural and physiological adaptations that may broaden our perspective on evolutionary cardiac adaptation.

Adaptation, Physiological↗

PubMed2003

Heredity and pituitary response to exercise-related stress in trained men.

To evaluate the role of heredity in the pituitary responses to exercise-related stress, serum ACTH, beta-endorphin, cortisol, GH, and PRL responses to a thirty-minute treadmill exercise at individual anaerobic threshold were evaluated in nine pairs of male monozygotic twin athletes. Hormone evaluations were performed before (-30, -15, 0 pre) and after exercise (0 post, + 15, + 30, + 45, + 60, and + 90 min). The intraclass correlation coefficient (expression of within-pair resemblance) was computed for each hormone before and after exercise as area under curves (AUC), absolute values, and percentage of variation, respectively. The exercise-related stress condition induced a significant increase for all evaluated hormones before (anticipatory response) and/or after exercise. As new data, we observed: 1) A significant within-pair resemblance for exercise-related GH and PRL increase (AUCs and/or absolute values), and for the percentage of variation of cortisol, and 2) the lack of significant resemblance for the observed increase of ACTH, cortisol and absolute beta-endorphin serum concentration. This first co-twin control study supports the hypothesis that, in trained men, there are probably different relative roles for the influence of genetic factors on the pituitary hormones involved in physiological adaptation to exercise-related stress. Furthermore, our findings justify further investigations into this topic.

Adaptation, Physiological↗

PubMed2005

Aerobic and functional capacities in a selected active population of European octogenarians.

Master athletes are often considered to represent the ideal rate of decline of aerobic function; however, most of the studies interested in active elderly people are often limited to people younger than 75. We aimed to determine the physiological adaptations and aerobic fitness in a selected European population of active octogenarians during maximal and submaximal exercise tests. Aerobic capacity was measured during maximal incremental tests on treadmill (TR) and cycle-ergometer (CE) and functional capacity during a 6-minute walk test (6-MWT) in 17 subjects aged 81.2 +/- 0.8 years. Pulmonary gas exchange and heart rate (HR) were continuously measured during the different exercise tests. Maximal oxygen consumption (V.O (2max)) on TR and CE was significantly higher than predicted values (TR: 28.7 +/- 1.2 vs. 17 +/- 0.5 ml . kg (-1) . min (-1); CE: 23 +/- 1.2 vs. 16 +/- 0.6 ml . kg (-1) . min (-1) for measured and predicted values respectively). V.O (2max) and HR (max), as well as V.O (2) and HR at the ventilatory threshold (V.O (2)T (V.E) and HR T (V.E)) were significantly higher on TR than on CE (HR (max): 144 +/- 4 vs. 138 +/- 4 bpm; V.O (2)T (V.E): 22.5 +/- 0.8 vs. 17.7 +/- 0.9 ml . kg (-1) . min (-1) for TR and CE respectively). V.O (2)T (V.E) and HR T (V.E) on TR were equivalent to V.O (2) and HR measured during the 6-MWT. HR T (V.E) on TR and mean HR during the 6-MWT were strongly correlated (R = 0.82, p < 0.01). Maintenance of regular physical activity provides high aerobic fitness, in octogenarians, as was shown by the higher values of our subjects in comparison to predicted values. Moreover, the close relation between the intensity developed at T (V.E) on TR and 6-MWT could support the idea that a walk test is a submaximal test performed at high intensity that could provide a basis for exercise prescription in an individualized manner in active elderly people.

Adaptation, Physiological↗

PubMed1975

South American mammal zoogeography: evidence from convergent evolution in desert rodents.

Current theories regarding colonization of South America by mammals are divided between those supported by fossil evidence, which suggest the original mammal fauna of the isolated continent was augmented by early immigrants (primates, caviomorph rodents, and later, procyonids) with a final large influx of northern mammals occurring with the formation of the Panama land bridge, and an opposing view which states that the purported "recent invaders" are too taxonomically and ecologically differentiated to have colonized since the land bridge arose. The second theory suggests that most extant mammals entered before the Plio-Pleistocene land connection. An analysis of degree of physiological adaptation, natural history, distribution patterns, and a multivariate assessment of convergent evolution of Monte Desert rodents indicate that South American cricetine rodents are not highly specialized for desert life. Their degree of adaptation could be accounted for, in large part, by adaptations for arid or semiarid Andean habitats. No Monte Desert rodent has developed the specialized desert traits that have evolved in most desert rodent faunas of the world, although extinct marsupials similar to living bipedal desert rodents were present in the Monte as recently as late Pliocene. Evidence suggests that Monte caviomorphs have been associated with the desert for a longer period than cricetines, and that the latter represent a fairly recent invasion of the Monte Desert. The data thus support the first hypothesis of South American mammal colonization.

Adaptation, Physiological↗

PubMed2002

Effects of multicycle-run training on triathlete performance.

The purpose of this study was to determine the effect of triathlon training using multiple, short cycle-run sequences (multicycle-run training) on cycle-run performance. Twelve competitive triathletes, randomized into two groups, underwent multicycle-run training or normal training for 6 weeks. During this period, baseline training remained the same for both groups, and only the high-intensity component differed. The differentiated exercises were performed at or above 100% maximal aerobic velocity. The improvements in overall cycle-run performance were similar (3.3 +/- 1.4 % and 6.1 +/- 1.7% rise in Performance in multicycle-run and normal training, respectively). However, the improvement in performance was significantly greater for the multicycle-run training (-11.2 +/- 6.8 s versus -1.2 +/- 7. 7 s for multicycle-run training and normal training, respectively) during both the cycle-run change and the first 333-m lap, which together are termed the cycle-run transition. We concluded that 6 weeks of multicycle-run training did not induce greater improvement in cycle-run performance than did normal training in competitive triathletes. However, it did induce significant improvement in the cycle-run transition. This finding indicates that multicycle-run training may help competitive triathletes to develop greater skill and better physiological adaptations during this critical transition period of the triathlon race.

Adaptation, Physiological↗

PubMedDate not supplied

Age, sex, and reproductive state influence free amino acid concentrations in the fasting elephant seal.

Long-term fasting is a component of northern elephant seal (Mirounga angustirostris) life history requiring physiological adaptations to nitrogen conservation. Plasma free amino acids (FAAs) were determined for five elephant seal pups during the second and eighth weeks of the postweaning fast, six lactating female seals at 4-6 and 25 d postpartum, and seven sexually competitive adult male seals taken midway through the breeding season. Total FAAs declined in lactating females (11%) and pups (30%) with time fasting, but cystine concentration more than doubled in pups while decreasing by approximately 43% in lactating females. Methionine concentration significantly increased (approximately 68%) across lactation in adult females but was low for all classes of seal. Alanine was the most abundant FAA in adult males, and glycine became the dominant FAA in adult females late in lactation. Glutamine dominated the FAAs of weaned pups across the fast. Reductions in total FAAs of weanlings mirrored reductions in protein catabolism, but reductions in total FAAs also occurred in lactating females concomitant with an increase in protein catabolism. Observed variation in FAA concentrations may reflect ontogenetic requirements for certain amino acids in fasting weanlings. Similarly, increases in specific FAA concentrations across lactation may reflect variations in FAA flux resulting from the nutrient demands of lactogenesis.

Adaptation, Physiological↗

PubMedDate not supplied

The effects of chronic hypoxia on the acute adrenergic stress response in the rainbow trout (Oncorhynchus mykiss).

We have investigated the effects of chronic hypoxia on the acute adrenergic stress response of adult rainbow trout (Oncorhynchus mykiss). The goal of this study was to determine whether a prior 5-d exposure of fish to lowered environmental oxygen levels (60 or 80 Torr) would influence the nature of catecholamine secretion from chromaffin tissue in situ. Using a saline-perfused posterior cardinal vein preparation, it was demonstrated that the basal (unstimulated) secretion of noradrenaline and adrenaline was increased at 60-Torr hypoxia. In response to cholinergic (carbachol-elicited) stimulation, noradrenaline and adrenaline secretion were significantly affected by prior exposure to hypoxia. The construction of dose response curves revealed that noradrenaline secretion was enhanced at the lowest doses of carbachol (1 - 5 x 10(-7) mol kg(-1)) and that this was reflected by an approximate 10-fold reduction in the ED50 (the dose of carbachol eliciting half-maximal noradrenaline secretion). The effect of chronic hypoxia on in situ carbachol-evoked adrenaline secretion was similar but less pronounced. The results of this study suggest that during chronic moderate hypoxia, increased basal catecholamine secretion and enhanced responsiveness of chromaffin cells to cholinergic stimulation, as well aiding the ongoing stress, may assist the physiological adaptations to subsequent bouts of more severe acute stress.

Adaptation, Physiological↗

PubMed1993

Head posture in obstructive sleep apnoea.

In growing subjects, obstruction of the upper airway may lead to excessive vertical facial development. According to the soft-tissue stretching hypothesis (Solow and Kreiborg, 1977) this could be due to an increased cranio-cervical angulation triggered by the airway obstruction. The present study aimed to examine the effect of airway obstruction on cranio-cervical posture in a sample of adult patients with severe obstructive sleep apnoea (OSA). Lateral cephalometric radiographs taken in the natural head position (mirror position) were obtained from 50 male patients aged 28-70 with polysomnographic diagnosis of obstructive sleep apnoea. The Apnoea Index ranged from 21 to 98 episodes per hour with a mean of 54.6. Control samples were available from previous cephalometric studies of head posture in five samples of healthy subjects and one sample of congenitally blind subjects. The average cranio-cervical angle, NSL/OPT, was found to be extremely large (mean 104.1, SD 9.1) exceeding the average values in the control samples by 1-2 standard deviations (P < 0.001). It is suggested that the large cranio-cervical angle in OSA patients is a physiological adaptation aiming to maintain airway adequacy while the head, and thus the visual axis, is kept in its natural relationship to the true vertical. The findings thus provide evidence for the hypothesis that upper airway obstruction may trigger an increase in the cranio-cervical angulation.

Adaptation, Physiological↗

PubMed2000

Aspects of natural cold tolerance in ectothermic animals.

Polar, alpine and temperate ectothermic (cold-blooded) animals encounter temperatures below the melting point of their body fluids either diurnally or seasonally. These animals have developed a number of biochemical and physiological adaptations to survive the low temperatures. The problems posed to the animals during cold periods include changes in membrane and protein structure due to phase changes in these molecules, changes in electrolyte concentrations and other solutes in the body fluids as well as changes in metabolism. Cold-tolerant ectothermic animals can be divided into two groups depending which of two 'strategies' they employ to survive the low temperatures: freeze-tolerant animals which survive ice formation in the tissues and freeze-avoiding animals which tolerate the low temperatures but not crystallization of the body fluids. The adaptations are mainly directed towards the control or avoidance of ice formation and include the synthesis of low mol. wt cryoprotectants, ice-nucleating agents and antifreeze proteins. However, some of the adaptations such as the synthesis of low mol. wt cryoprotectants are also more specific in their mechanism, e.g. direct stabilizing interaction with membranes and proteins. The mechanisms employed by such animals may offer ideas and information on alternative approaches which might be usefully employed in the cryopreservation of cells and tissues frequently required in assisted reproductive technology.

Adaptation, Physiological↗