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At least 253 records · Page 14Linked to original sources
PubMed1997

Relationships between gas exchange adaptation of Sitka x interior spruce genotypes and ribosomal DNA markers.

Adaptive physiological changes were investigated in seven populations of Sitka (Picea sitchensis (Bong.) Carr.) x interior spruce (P. glauca (Moench) Voss x P. engelmannii Parry ex Engelm.) spanning the Nass-Skeena transition zone in British Columbia, Canada. Each population was represented by an Si rDNA index that was calculated from the relative optical densities on a gel autoradiogram of five ribosomal DNA bands characteristic of Sitka spruce and interior spruce. This index estimates the proportion of the genome contributed by interior spruce. Physiological adaptations were assessed by gas exchange parameters measured under both well-watered and drought conditions. Under well-watered conditions, Sitka spruce populations had higher maximal photosynthesis at saturating light and ambient CO(2), higher quantum yield at the light compensation point, and higher dark respiration than interior spruce populations. Sitka spruce populations also reached maximal photosynthesis at lower photosynthetically active radiation and higher CO(2) concentrations, and had higher stomatal densities that resulted in lower stomatal limitations to photosynthesis than interior spruce populations. In contrast, interior spruce populations exhibited greater drought tolerance than Sitka spruce populations. Their gas exchange rates declined at a slower rate in response to drought. They maintained higher gas exchange rates in response to moderate to severe drought (predawn plant water potentials = -1.5 MPa), and their photosynthetic rates recovered faster when they were rewatered after exposure to drought. Comparison of the seven populations indicated that physiological parameters were significantly related to the Si rDNA index. An increase in Si rDNA index was associated with proportional changes in physiological measurements, suggesting that genetic interchange among species with contrasting ecological adaptations can enhance the environmental adaptation of natural populations.

Journal Article↗
PubMedDate not supplied

Human responses to chronic illness: physiologic and psychosocial adaptation.

To identify factors that promote adaptation, physiological and psychosocial responses to chronic illness were studied. The adaptation to chronic illness model (Pollock, 1984a) served as the theoretical framework for integrating the major variables of chronicity, stress, hardiness, and physiological and psychosocial adaptation. The sample (N = 60) consisted of three equal-sized groups of adults who had been diagnosed with diabetes mellitus, essential hypertension, or rheumatoid arthritis for at least one year. Data were collected from all subjects over a 9-month interval to determine their physiological and psychosocial adaptation and if they had the hardiness characteristic. The hypothesis, that presence of the hardiness characteristic was significantly correlated with physiological adaptation, was supported for the diabetic group but not for the hypertensive or rheumatoid arthritic groups. Physiological and psychosocial adaptation were found to be two independent domains in this study.

Adaptation, Physiological↗
PubMed1982

[Is secondary myocardial hypertrophy a physiological or pathological adaptive mechanism?].

Physiological hypertrophy is present when the increase in myocardial mass resulting from chronic mechanical loading is associated with normal or enhanced myocardial function and myosin ATPase activity. Morphological alterations occurring during the formation of hypertrophy are fully reversible in physiological hypertrophy. In pathological hypertrophy myocardial function and myosin ATPase activity are depressed and morphological changes do not or only incompletely regress following the elimination of the stimulus of hypertrophy. In the experimental animal myocardial hypertrophy resulting from exercise conditioning or slight to moderate ventricular pressure overload fulfills the criteria of physiological hypertrophy. More severe sudden pressure overload is accompanied by depression of contractile function. These pressure overload models have however, little analogy to the more progressive development of pressure loading in humans. In young dogs and in cats with a gradually increasing pressure load, in vivo ventricular ejection fraction remained within normal limits 37 to 60 weeks after banding of the ventricular outflow vessel. In vitro myocardial function evaluated in the hypertrophied papillary muscle was, however, at least in part depressed, notably when hydroxyproline concentration was augmented. Following debanding in rats with aortic constriction hydroxyproline content did not regress suggesting that fibrosis once established is not reversible. In man myocardial hypertrophy from exercise conditioning is associated with normal ventricular function except in older athletes, who may show a subtle reduction in ventricular shortening. Patients with chronic pressure overload from aortic stenosis or volume overload from aortic insufficiency in whom the angiographic muscle mass is severely increased (greater than or equal to 180 g/m2) elicit a depressed left ventricular contractile function. Preserved left ventricular ejection performance in aortic valve disease is however not associated with normal myocardial structure because interstitial fibrosis evaluated from endomyocardial biopsies or biopsies obtained at surgery was found to be increased. Patients with depressed left ventricular contractility were characterized by having an abnormally high muscle fibre diameter. Normal function after surgery was not accompanied by normalization of myocardial structure: Interstitial fibrosis increased, fibrous content remained the same and cellular hypertrophy regressed incompletely regardless whether angiographic muscle mass had regressed to normal or remained still increased after surgery. In summary, the bulk of available functional and morphological data suggests that the occurrence of true physiological hypertrophy is probably limited to exercise conditioning and eventually to mild chronic mechanical overload. The more severe secondary hypertrophy such as in patients with aortic valve disease who undergo valve replacement, is not a physiological adaptation, but must be considered as a pathological process.

Adenosine Triphosphatases↗
PubMed1991

[Physiology and physiopathology of postnatal pulmonary adaptation. 1: Physiology].

The aim of the review consists of the help to understand the complex physiological mechanisms of the onset of breathing and the regulation of the respiration during the early newborn period. The lungs of the newborn contain nearly no alveoli. Postnatal formation of alveoli enlarges the gas exchange surface until the 20th year of life, the lung volume increases by a factor of 27. Immediately postnatal the aeration of the lungs is performed by several deep inspirations with breath hold and following crying. The fetal lung liquid is resorbed via both, lymph and blood vessels. Stability of the functional residual capacity is reached very rapidly. The inflation augmenting reflex and sighing support effectively this process. The significant importance of the surfactant for the successful begin of air breathing is described. Onset of respiration is combined with the decrease of the pulmonary arterial resistance and the remarkable increase of the pulmonary blood flow. The hypoxic response in the newborn is biphasic. An initial short hyperventilation is regularly followed by ventilatory depression. Neurophysiological causes are evident. Hyperventilation by inhalation of gas mixtures with higher CO2 concentrations is low, at least in preterm infants. The causes are believed to ly in the limitation of the efficiency of the respiratory muscles. Peripheral chemoreceptors in the glomus caroticum and in the bronchial mucosa, stretch receptors in the bronchial muscles, and muscle spindles in the intercostal muscles are functioning in newborns as well as in preterm infants.

Adaptation, Physiological↗
PubMed1985

A review of physiological prestress adaptation: effects of duration and context.

This review focuses on 3 aspects of experimental designs for prestress, physiological adaptation periods: (1) effects of duration on stabilization of various physiological parameters:(2) effect of type of activity and instruction on prestress physiological adaptation: and (3) definitions of physiological baselines. Analyses of the literature revealed that for many physiological parameters it remains unclear how much time is required for stabilization and that for the remaining variables the necessary duration of prestress adaptation varies greatly, with blood pressure potentially being the slowest variable to stabilize. Effects of type of activity are essentially unknown. Instructions which create certainly about experimental procedures in subjects tend to facilitate adaptation to the laboratory environment. Baseline definitions were remarkably variable with no less than 15 different definitions being used across the 50 studies reviewed. Suggestions for future research and recommendations for prestress experimental designs are put forward in the discussion.

Adaptation, Physiological↗
PubMed1993

Force-time characteristics of the rowing stroke and corresponding physiological muscle adaptations.

The force-time characteristics of the rowing stroke was examined in a coxless pair. Sixteen highly trained rowers were evaluated in their usual training positions (stroke or bow). Stroke rowers had higher stroke speed and stroke force in the first part of the stroke than bow rowers. This finding was more prominent during competition speed rowing than during endurance training. Higher blood lactate levels and lower base excess were found at both speeds in stroke rowers. During and incremental ergometer rowing test, lactate performance curves were shifted to the left in the stroke rowers. Analysis of morphometric data in the left deltoid muscle demonstrated higher FT fiber content and lower oxidative fiber capacity and fiber areas in the stroke rowers. The results demonstrate adaptation to years of training in a specific boat position.

Adaptation, Physiological↗
PubMed2005

Promoting physiologic-physical adaptation in chronic obstructive pulmonary disease: pharmacotherapeutic evidence-based research and guidelines.

Guidelines from the Global Initiative for Chronic Obstructive Lung Disease (GOLD) and evidence-based research include advanced pharmacologic care for patients with chronic obstructive pulmonary disease (COPD). Although clinical trials of medications have not supported evidence that long-term decline in pulmonary function can be prevented, pharmacologic agents can reduce symptoms and prevent complications. High-quality home care services may improve quality of life and prevent hospital admissions because of acute exacerbations.

Adaptation, Physiological↗
PubMed2001

[Physiological cardiovascular adaptation in pregnancy--its significance for cardiac diseases].

Stroke volume and heart rate rise at the very beginning of a pregnancy and decline after birth, over the course of months. Arterial blood pressure is lowered, plasma volume is increased while central venous pressure stays constant during pregnancy. The rise in cardiac output in early pregnancy can be induced quantitatively by oestrogen. The pregnancy-induced rise in cardiac output is based on the fairly general remodelling of the cardiovascular system. In a process of development, many portions of the cardiovascular system undergo programmed dilation (expansion): There is a programmed dilation of the heart, of the aorta, of the resistance vessels of the kidney and the resistance vessels of the placenta, and a programmed dilation of the venous system. All the changes favour the perfusion of the pregnant body. Cardiac dilation increases directly stroke volume, aortic dilation increases the susceptance (Windkessel function) of the aorta, the peripheral dilation increases the vascular conductance, and the venous dilation raises blood volume. Since the vascular conductance increase by peripheral dilation is higher than the increase in stroke volume, arterial pressure drops and evokes, via the baroreceptor reflex, an increase in heart rate; the increase in cardiac output occurs to an equal extent by an increase in stroke volume and an increase in heart rate. Compression of the caval vein by the pregnant uterus increases peripheral venous pressure and possibly slows down blood flow in the limbs. Increase in cardiac output means a burden for the heart, especially when associated with increase in heart rate. In this condition, cardiac energy expenditure is increased while oxygen supply is decreased. The rise in energy expenditure by an increase in flow rate is especially high for turbulent flow conditions at stenotic valves. In addition, there is an increased risk of arterial rupture by arterial remodelling and an increased risk of thrombosis by deceleration of venous blood flow velocity. Thus, the cardiovascular adaptation to pregnancy means an increased cardiovascular risk which may, on the basis of a basic cardiac disease, lead to cardiac failure.

Adaptation, Physiological↗
PubMed1977

Transverse diameter of the chest and of the heart of infants in the course of physiological cardiorespiratory adaptation.

The morphology of the lungs and heart was analysed in 824 newborn infants with normal cardiorespiratory adaptation. Under normal conditions, the air content of the lungs became satisfactory in the first 6--12 hours and normal in all cases after 24 hours. The values for the transverse diameter of the chest and heart were brought into correlation with birth weight, body length and gestational age. The transverse diameter of the chest and heart did not change during the early postnatal period (between 6--12 hours and 5 days). Both diameters were correlated with birth weight. The closest correlation was found in newborns under 1500 g, a varying one in those between 1500 and 2000 g and a close correlation in the category over 2000 g. The correlation of the two diameters with both length was linear and close, without any difference between the values obtained at different times of examination. A rather loose correlation was found between the transverse diameter of the chest and heart, and gestational age.

Adaptation, Physiological↗
PubMed1995

Environmental and physical stress and nutrient requirements.

When faced with hot, cold, or high-altitude environments, humans can either modify the microenvironment to fit human physiology, adapt their physiology to fit the environment, or use a combination of these two tactics. Metabolic adaptations to heat, cold, and high-altitude exposure may, in some instances, be accompanied by changes in nutrient requirements. Energy expenditure is increased in all three environments. B-vitamin cofactor requirements increase in proportion to energy expenditure (oxidation of fat and carbohydrate). Increased B-vitamin nutrient requirements are usually adequately met by an increased consumption of the diet to meet energy requirements. Other nutrients such as iron may be required in greater amounts to meet the altitude-induced hematopoietic response in females. Additional quantities of vitamins and minerals with antioxidant properties may be beneficial to reduce the increased oxidative stress associated with work in heat, cold, or high-altitude outdoor environments.

Adaptation, Physiological↗
PubMed1980

Reactions to hand cooling in workers occupationally exposed to cold.

Ten men occupationally exposed to cold and ten office workers participated in the study. Reactions to immersion of the hands in cold water (+ 10 degrees C) for 2 min were studied during the following 30 min at two different ambient temperatures, 10 and 20 degrees C. Hand skin temperature was recorded in thermograms, and the subjects rated cold sensation and pain. Considerable interindividual differences in hand skin temperature reaction were found in both groups. On the average the occupationally exposed workers had a somewhat higher hand skin temperature than the office workers during the recovery period in the 10 degrees C ambient temperature, although the difference did not reach significance. The office workers rated significantly greater cold sensation as a result of the cold immersion, especially during an ambient temperature of 10 degrees C, and the frequency of pain ratings was higher for this group. The results suggest that cooling among the occupationally exposed workers at work was not severe enough to produce physiological adaptations, although some psychological adaptation was indicated.

Adaptation, Physiological↗
PubMed2003

Aerobic biological treatment of synthetic municipal wastewater in membrane-coupled bioreactors.

Membrane-coupled bioreactors (MBRs) offer many benefits compared to conventional biological wastewater treatment systems; however, their performance characteristics are poorly understood. Laboratory-scale MBRs were used to study bacterial adaptations in physiology and community structure. MBRs were fed a mixture of starch, gelatin, and polyoxyethylene-sorbitan monooleate to simulate the polysaccharide, protein, and lipid components of municipal wastewater. Physiological adaptations were detected by measuring ectoenzyme activity while structural dynamics were studied by denaturing gradient gel electrophoresis of PCR-amplified 16S rRNA gene fragments. As cell biomass accumulated in the MBRs, pollutant removal efficiency initially improved and then stabilized with respect to effluent concentrations of chemical oxygen demand, protein, and carbohydrate. Comparison of the MBR effluent to filtered reactor fluid indicated that a portion of the observed pollutant removal was due to filtration by the membrane rather than microbial activity. The rates of ectoenzyme-mediated polysaccharide (alpha-glucosidase) and protein (leucine aminopeptidase) hydrolysis became relatively constant once pollutant removal efficiency stabilized. However, the maximum rate of lipid hydrolysis (heptanoate esterase) concomitantly increased more than 10-fold. Similarly, alpha-glucosidase and leucine aminopeptidase ectoenzyme affinities were relatively constant, while the heptanoate esterase affinity increased more than 30-fold. Community analysis revealed that a substantial community shift occurred within the first 7 days of operation. A Flavobacterium-like bacterial population dominated the community (>50% of total band intensity) and continued to do so for the remainder of the experiment.

Adaptation, Physiological↗
PubMed2001

Issues in life support and human factors in crew rescue from the ISS.

The design and development of crew emergency response systems, particularly to provide an unplanned emergency return to Earth, requires an understanding of crew performance challenges in space. The combined effects of psychological and physiological adaptation during long-duration missions will have a significant effect on crew performance in the unpredictable and potentially life-threatening conditions of an emergency return to Earth. It is therefore important that the systems to be developed for emergency egress address these challenges through an integrated program to produce optimum productivity and safety in times of utmost stress. Fundamental to the success of the CRV is the Environmental Control and Life Support System (ECLSS), which provides the necessary conditions for the crew to survive their return mission in a shirtsleeve environment. This article will discuss the many issues in the design of an ECLSS system for CRV and place it in the context of the human performance challenges of the mission.

Adaptation, Physiological↗
PubMed2001

Human factors and life support issues in crew rescue from the International Space Station (ISS).

The design and development of crew emergency response systems, particularly to provide an unplanned emergency return to earth, requires an understanding of crew performance challenges in space. The combined effects of psychological and physiological adaptation during long duration missions will have a significant effect on crew performance in the unpredictable and potentially life threatening conditions of an emergency return to earth. It is therefore important that the systems to be developed for emergency egress address these challenges through an integrated program to produce optimum productivity and safety in times of utmost stress. Fundamental to the success of the CRV is the Environmental Control and Life Support System (ECLSS), which provides the necessary conditions for the crew to survive their return mission in a shirt-sleeve environment. This paper will discuss the many issues in the design of an ECLSS system for CRV and place it in the context of the human performance challenges of the mission.

Adaptation, Physiological↗