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PubMed2003

Exercise-trained but not untrained rats maintain free carnitine reserves during acute exercise.

Exercise training is known to induce physiological adaptations that improve exercise performance and alter patterns of energy substrate utilization to favour fatty acid oxidation. L-Carnitine is an essential cofactor for the oxidation of fatty acids under all physiological conditions, including exercise. This study evaluated the effect of acute exercise on carnitine concentrations in tissue and serum, liver carnitine palmitoyltransferase-I activity and expression, and serum lipids in both trained and untrained rats as compared to non-exercised rats. Serum acyl- and total carnitine was significantly higher in the trained animals, whether exercised or not, suggesting an exercise-induced increase in a renal threshold for carnitine. Untrained rats had significantly higher acylcarnitine in skeletal muscle and an acyl/free carnitine ratio of 0.63 +/- 0.06 compared with 0.31 +/- 0.16 in trained animals receiving an identical acute bout of exercise, demonstrating that untrained animals utilized a significantly higher percentage of free carnitine reserves during exercise. This study suggests that free carnitine reserves may be reduced during exercise in untrained rats, an effect that has the potential to impair both carbohydrate and fat metabolism during exercise.

Adaptation, Physiological↗
PubMed1996

Skeletal muscle and cardiovascular adaptations to exercise conditioning in older coronary patients.

BACKGROUND: Older coronary patients suffer from a low functional capacity and high rates of disability. Supervised exercise programs improve aerobic capacity in middle-aged coronary patients by improving both cardiac output and peripheral extraction of oxygen. Physiological adaptations to aerobic conditioning, however, have not been well studied in older coronary patients. METHODS AND RESULTS: The effect of a 3-month and a 1-year program of intense aerobic exercise was studied in 60 older coronary patients (mean age, 68 +/- 5 years) beginning 8 +/- 5 weeks after myocardial infarction or coronary bypass surgery. Outcome measures included peak aerobic capacity, cardiac output, arterio-venous oxygen difference, hyperemic calf blood flow, and skeletal muscle fiber morphometry, oxidative enzyme activity, and capillarity. Training results were compared with a sedentary, age- and diagnosis-matched control group (n = 10). Peak aerobic capacity increased in the intervention group at 3 months and at 1 year by 16% and 20%, respectively (both P < .01). Peak exercise cardiac output, hyperemic calf blood flow, and vascular conductance were unaffected by the conditioning protocol. At 3 and 12 months, arteriovenous oxygen difference at peak exercise was increased in the exercise group but not in control subjects. Histochemical analysis of skeletal muscle documented a 34% increase in capillary density and a 23% increase in succinate dehydrogenase activity after 3 months of conditioning (both P < .02). At 12 months, individual fiber area increased by 29% compared with baseline (P < .01). CONCLUSIONS: Older coronary patients successfully improve peak aerobic capacity after 3 and 12 months of supervised aerobic conditioning compared with control subjects. The mechanism of the increase in peak aerobic capacity is associated almost exclusively with peripheral skeletal muscle adaptations, with no discernible improvements in cardiac output or calf blood flow.

Adaptation, Physiological↗
PubMed1976

Physiological changes associated with long-term increases in acceleration.

The long-term retention of organisms in increased acceleration fields is an experimental approach towards understanding the biological consequences of earth gravity. Such treatment, called chronic acceleration, simulates a change in gravity and requires exposed organisms to adapt physiologically to the new environment. Information from chronic acceleration supplements that from space physiology in understanding gravitational physiology. Many of the responses in long-term exposure to increased acceleration are those which would be anticipated from the imposed symmetrical loading. For example, increased requirements for posture and locomotion induce appropriate changes in musculo-skeletal organs. Displacement of body fluids and increased hydrostatic pressures lead to greater blood volumes and increased tissue hydration. However, there are also specific acceleration effects which cannot be so directly interpreted. Among these are decreases of mature body size and of depot fat, which are proportional in degree to field strength. The role of chronic acceleration research in the development of gravitational biology and its relationship to earth-orbital experiments are considered. The applicability of chronic acceleration studies with human subjects towards planning of deep space exploration is also discussed.

Acceleration↗
PubMed1984

Chronic adaptations to physical conditioning in cardiac patients. Implications regarding exercise trainability.

Physical conditioning in patients with coronary heart disease can result in increased functional capacity, symptomatic relief of angina pectoris, favorable reduction of risk factors, enhanced psychological status, and improved quality of life. The mechanisms underlying the adaptations to training are poorly understood, but it is clear that several factors affect exercise trainability. Guidelines are available that suggest the appropriate intensity, frequency, and duration of exercise needed to obtain beneficial physiologic adaptations.

Adaptation, Physiological↗
PubMed1999

Delayed adaptation of the pulmonary hemodynamics in infants with mild to moderate meconium aspiration syndrome.

Early postnatal pulmonary hemodynamic changes were investigated with Doppler echocardiography in 17 infants with mild or moderate meconium aspiration syndrome (MAS) and 16 healthy infants in a control group. The results indicate that the physiologic adaptation of the pulmonary hemodynamics is delayed in mild and moderate forms of MAS. Thus infants with clinical evidence of MAS need careful cardiovascular monitoring during postnatal circulatory transition.

Adaptation, Physiological↗
PubMed2006

Endurance training and detraining in mitochondrial myopathies due to single large-scale mtDNA deletions.

At present there are limited therapeutic interventions for patients with mitochondrial myopathies. Exercise training has been suggested as an approach to improve physical capacity and quality of life but it is uncertain whether it offers a safe and effective treatment for patients with heteroplasmic mitochondrial DNA (mtDNA) mutations. The objectives of this study were to assess the effects of exercise training and detraining in eight patients with single, large-scale mtDNA deletions to determine: (i) the efficacy and safety of endurance training (14 weeks) in this patient population; (ii) to determine the effect of more prolonged (total of 28 weeks) exercise training upon muscle and cardiovascular function and (iii) to evaluate the effect of discontinued training (14 weeks) upon muscle and cardiovascular function. Our results show that: (i) 14 weeks of exercise training significantly improved tolerance of submaximal exercise and peak capacity for work, oxygen utilization and skeletal muscle oxygen extraction with no change in the level of deleted mtDNA; (ii) continued training for an additional 14 weeks maintained these beneficial adaptations; (iii) the cessation of training (detraining) resulted in loss of physiological adaptation to baseline capacity with no overall change in mutation load. Patients' self assessment of quality of life as measured by the SF-36 questionnaire improved with training and declined with detraining. Whilst our findings of beneficial effects of training on physiological outcome and quality of life without increases in the percentage of deleted mtDNA are encouraging, we did not observe changes in mtDNA copy number. Therefore there remains a need for longer term studies to confirm that endurance exercise is a safe and effective treatment for patients with mitochondrial myopathies. The effects of detraining clearly implicate physical inactivity as an important mechanism in reducing exercise capacity and quality of life in patients with mitochondrial myopathy.

Adaptation, Physiological↗
PubMed2002

Computer systems analysis of the cardiovascular mechanisms of reentry orthostasis in astronauts.

Reentry orthostasis secondary to a prolonged exposure to microgravity is a common problem among astronauts. However, the physiologic mechanisms are poorly understood due to the many control systems involved. In this study an advanced computer model of cardiovascular functioning was employed in a systems analysis approach to clarify the relative importance of some of the adaptive physiologic processes engaged when humans return from space. After simulation of the conditions of zero gravity for one month, the model predicted that the change in capacitance of the lower extremity veins resulting from a loss of external fluid forces in the dehydrated extracellular compartment was the dominant mechanism associated with reentry orthostasis. This condition appears accentuated in women due to their inherent lower center of gravity and proportionately larger mass in the lower extremities.

Adaptation, Physiological↗
PubMed1998

Resistance training and elite athletes: adaptations and program considerations.

The skepticism surrounding the potential benefits of resistance exercise training prevalent just decades ago has evolved over the years to an understanding of the integral nature muscular overload plays in the training programs for athletes. The science of training elite athletes is progressing rapidly, as insights into the physiological adaptations resulting from varying program configurations become available. Resistance training impacts several body systems, including muscular, endocrine, skeletal, metabolic, immune, neural, and respiratory. An understanding and appreciation of basic scientific principles related to resistance training is necessary in order to optimize training responses. Careful selection of the acute program variables in a workout to simulate sports-specific movements is required for optimal transfer of gains made in training to competition. Thus, whether athletes require predominantly eccentric, isometric, slow-velocity, or high-velocity strength or power in their athletic event will dictate the time commitment to each component and form the basis for designing individual workouts. Program variation over a training period is essential to maximize gains and prevent overtraining.

Adaptation, Physiological↗
PubMed1994

Starvation and survival: some military considerations.

The combination of calorie deprivation and forced evasion is a unique and severe stress. The physiologic adaptations which occur under these conditions are complex. Performance decrements and psychological changes are evident within 24 hours of cessation of nutritional intake. Although marked losses of both lean tissue and total body mass are unavoidable, ultimate survival duration depends on many things. This article reviews some of the physiologic and pathologic changes which occur during total calorie deprivation and some of the factors which impact on the ability to survive.

Adaptation, Physiological↗
PubMed2006

Mechanisms of neuroprotection during ischemic preconditioning: lessons from anoxic tolerance.

Different physiological adaptations for anoxia resistance have been described in the animal kingdom. These adaptations are particularly important in organs that are highly susceptible to energy deprivation such as the heart and brain. Among vertebrates, turtles are one of the species that are highly tolerant to anoxia. In mammals however, insults such as anoxia, ischemia and hypoglycemia, all cause major histopathological events to the brain. However, in mammals even ischemic or anoxic tolerance is found when a sublethal ischemic/anoxic insult is induced sometime before a lethal ischemic/anoxic insult is induced. This phenomenon is defined as ischemic preconditioning. Better understanding of the mechanisms inducing both anoxic tolerance in turtles or ischemic preconditioning in mammals may provide novel therapeutic interventions that may aide mammalian brain to resist the ravages of cerebral ischemia. In this review, we will summarize some of the mechanisms implemented in both models of tolerance, emphasizing physiological and biochemical similarities.

Adaptation, Physiological↗
PubMed1994

Exercise performance of birds.

Birds are excellent endurance athletes. Not only do many birds undertake long migratory flights, but many do so under extreme environmental conditions: excessive heat, extreme cold, and the hypoxic conditions of high altitude. We are just now starting to understand the physiological adaptations these animals possess for surviving and thriving in these environments. Still, relatively few studies have actually been performed on exercising birds, particularly on birds flying under the conditions mentioned here. Furthermore, not all birds are capable of sustained exercise in hypoxia, heat, and cold. More work is needed to increase our understanding of the differences in the physiological systems that allow some birds to be better able to exercise under such conditions.

Adaptation, Physiological↗
PubMed2005

Linking biogeography to physiology: Evolutionary and acclimatory adjustments of thermal limits.

Temperature-adaptive physiological variation plays important roles in latitudinal biogeographic patterning and in setting vertical distributions along subtidal-to-intertidal gradients in coastal marine ecosystems. Comparisons of congeneric marine invertebrates reveal that the most warm-adapted species may live closer to their thermal tolerance limits and have lower abilities to increase heat tolerance through acclimation than more cold-adapted species. In crabs and snails, heart function may be of critical importance in establishing thermal tolerance limits. Temperature-mediated shifts in gene expression may be critical in thermal acclimation. Transcriptional changes, monitored using cDNA microarrays, have been shown to differ between steady-state thermal acclimation and diurnal temperature cycling in a eurythermal teleost fish (Austrofundulus limnaeus). In stenothermal Antarctic notothenioid fish, losses in capacity for temperature-mediated gene expression, including the absence of a heat-shock response, may reduce the abilities of these species to acclimate to increased temperatures. Differences among species in thermal tolerance limits and in the capacities to adjust these limits may determine how organisms are affected by climate change.

Journal Article↗
PubMed2026

T2T Genome Assembly and Multi-Omics Data Reveal Terrestrial Adaptation and Mucus Biosynthesis in Tropical Leatherleaf Slug (Laevicaulis alte).

Laevichaulis alte is a slug in the order Systellommatophora that evolved from aquatic ancestors and now faces strong challenges from desiccation, respiration on land, and novel pathogens. Its mucus is essential for water retention, locomotion, and defense. To link terrestrial adaptation with mucus biosynthesis, we generated a gap-free genome assembly of L. alte using PacBio HiFi reads, Oxford Nanopore ultra-long reads, and Hi-C data. The genome shows low heterozygosity and holocentromeric chromosomes. Functional metabolomics revealed marked metabolic shifts between L. alte and the closely related aquatic species Peronia verruculata. In L. alte, differential metabolites were enriched in lipid metabolism, immune regulation, and stress response pathways, consistent with life in a dry and microbe-rich terrestrial environment. Comparative genomics and transcriptomics identified candidate genes linked to mucus secretion and physiological adaptation, including VEGF, ASGR2, and COL6A6. Further analyses highlighted the vascular endothelial growth factor (VEGF) gene family as a key regulator connecting angiogenesis, tissue remodeling, and mucus production pathways in L. alte. Together, this gap-free genome and multi-omics dataset establish a molecular framework that links genomic innovation, mucus biology, and terrestrial adaptation in Systellommatophora, and they offer a basis for understanding ecological niche specialization in land molluscs.

Animals↗
PubMed2004

The biology and life history of arctic populations of the littoral mite Ameronothrus lineatus (Acari, Oribatida).

The present study attempts to elucidate possible microevolutionary adaptations of life-history traits of high-latitude populations of the holarctic, littoral oribatid mite Ameronothrus lineatus by comparing arctic and temperate populations. Additionally, the paper provides an overview of the limited research on general ecology and population biology of arctic populations. In the Arctic the larviparous A. lineatus has a 5-year life cycle (larva-to-larva), and adults survive a further 2-3 years. High survival to maturity is consistent with a low lifetime reproductive output of ca. 20 larvae. The life history can be regarded as an extreme version of the typical oribatid life history. However, several life-history features suggest specific adaptations of arctic populations. In particular, the pre-moult resting stage is synchronized with the warmest part of the arctic summer, which shortens this vulnerable part of development. High reproductive investment by females at relatively low temperatures may represent a physiological adaptation to the cool arctic summer. Finally, prolonged cold exposure positively affects reproduction and survival the following summer, suggesting adaptation of the species to the highly seasonal arctic environment. On the other hand, the ability of all life-cycle stages to overwinter, and a flexible life history with the species being able to take advantage of favourable climatic conditions to accelerate development and larviposition, seem to be ancestral features. Thus, the success of A. lineatus in arctic habitats is probably attributable to a combination of derived and ancestral life-history traits. Studies of conspecific temperate populations are required to elucidate further local adaptations of arctic populations.

Adaptation, Physiological↗
PubMed2004

Respiratory adaptations to the deep-sea hydrothermal vent environment: the case of Segonzacia mesatlantica, a crab from the Mid-Atlantic Ridge.

Segonzacia mesatlantica (Crustacea; Decapoda; Brachyura) is the only endemic crab species known from the Mid-Atlantic Ridge (MAR) hydrothermal vents. Known from all explored sites in the Atlantic, its wide distribution makes this species a model to study physiological adaptation, and specifically respiratory strategies. Native haemocyanin (Hc) comprises four non-covalent associations in equilibrium formed by monomers, hexamers, dodecamers and octadecamers made up of approximately 75 kDa polypeptide chains. Four different amino acid chains are observed with a molecular mass ranging from 75,234 to 75,972 Da. Experiments carried-out under pressure suggested that the percentage of monomer increased in the haemolymph under hypoxic condition. We have also observed a shift of the proportion of the two dodecamer series, suggesting a rapid modification of the Hc phenotype between hypoxic and hyperoxic conditions. Native Hc possesses a high oxygen affinity ( P50 = 2.2 Torr at 15 degrees C and pH 7.5), a large Bohr effect (Deltalog P50 / DeltapH approximately -2.7) and a slightly reverse temperature effect (DeltaH = +17.19 kJ mol(-1). The composition of Segonzacia haemolymph is similar to that of other littoral species except for the large enrichment in free copper and zinc. As for other species from hydrothermal vent sites, Segonzacia haemolymph possesses a higher buffer capacity than littoral species. Moreover, species from the hydrothermal vent decapods from Pacific hydrothermal vent that encounter higher CO2 content in their environment have a higher buffer capacity than Atlantic vent species. The results presented are discussed in relation with the physico-chemical characteristics of the hydrothermal vent environment.

Adaptation, Physiological↗
PubMedDate not supplied

[Chronic low doze ionizing irradiation and polyfactors of adaptation].

The analysis of cytogenetic anomaly dynamics in conditions of chronic low doze effect of ionizing irradiation in generations of genetically homogeneous laboratory line of mice CC57W/Mv and genetically heterogeneous populations of vole's species, trapped in alienation zone of Chernobyl's NPP in places with different levels of radio nuclide contamination in 1994-2001 was carried out. The data about the physiological adaptation to ionizing irradiation effects under age of linear mice and non-linearity of frequency changes of separate cytogenetic anomalies in generations as laboratory line of mice, and genetically heterogeneous populations of vole's species were obtained. Was supposed, that the number of non-linear effects of the ionizing irradiation in low doze range could be stipulated by comparability between the intensity of it's damage effects and the activation by it the polyfactor systems of anti oxidant ones, reparation events, and also elimination of defective cells.

Adaptation, Physiological↗
PubMed1993

Biology, ecology, and biotechnological applications of anaerobic bacteria adapted to environmental stresses in temperature, pH, salinity, or substrates.

Anaerobic bacteria include diverse species that can grow at environmental extremes of temperature, pH, salinity, substrate toxicity, or available free energy. The first evolved archaebacterial and eubacterial species appear to have been anaerobes adapted to high temperatures. Thermoanaerobes and their stable enzymes have served as model systems for basic and applied studies of microbial cellulose and starch degradation, methanogenesis, ethanologenesis, acetogenesis, autotrophic CO2 fixation, saccharidases, hydrogenases, and alcohol dehydrogenases. Anaerobes, unlike aerobes, appear to have evolved more energy-conserving mechanisms for physiological adaptation to environmental stresses such as novel enzyme activities and stabilities and novel membrane lipid compositions and functions. Anaerobic syntrophs do not have similar aerobic bacterial counterparts. The metabolic end products of syntrophs are potent thermodynamic inhibitors of energy conservation mechanisms, and they require coordinated consumption by a second partner organism for species growth. Anaerobes adapted to environmental stresses and their enzymes have biotechnological applications in organic waste treatment systems and chemical and fuel production systems based on biomass-derived substrates or syngas. These kinds of anaerobes have only recently been examined by biologists, and considerably more study is required before they are fully appreciated by science and technology.

Adaptation, Physiological↗
PubMed1980

Adaptations of alpha2- and beta-cells of rat and mouse pancreatic islets to starvation, to refeeding after starvation, and to obesity.

The effects of starvation and refeeding and of obesity on pancreatic alpha2- and beta-cell responses to glucose or tolbutamide were studied with the isolated rat or mouse pancreas perfused with an amino acid mixture in the presence and absence of glucose. It was observed that the physiological adaptation to a regimen of fasting and realimentation and to obesity differed greatly in the two types of endocrine cells. Whereas beta-cells of rats showed a dramatic reduction of glucose- and tolbutamide-stimulated insulin release during starvation that was reversed by refeeding, alpha2-cells preserved their response to stimulators and inhibitors during this experimental manipulation. Amino acid stimulation of glucagon release occurred equally well with the pancreas from fed and starved rats and was suppressed efficiently by glucose and tolbutamide in both nutritional states. Surprisingly, the rate of onset of glucose suppression of alpha2-cells was significantly higher in the fasted than in the fed state. This glucose hypersensitivity was apparent 2 d after after food deprivation and had disappeared again on the 2nd d of refeeding. In the pancreas from animals starved for 3 d, glucose and tolbutamide suppression of alpha2-cells took place in the absence of demonstrable changes of insulin release. In the isolated perfused pancreas taken from the hyperphagic obese hyperglycemic mouse (C57 Black/6J; ob/ob), the observed rate of insulin secretion as a result of a combined stimulus of amino acids and glucose and of glucagon release stimulated by amino acids was about four times higher than achieved by the pancreas of lean controls. However, glucose was unable to suppress the alpha2-cells in the pancreas of obese animals, in spite of the hypersection of the beta-cells, again in contrast to the alpha2-cells of controls that were readily inhibited by glucose. These data imply that the acute suppression of alpha2-cells by glucose is largely independent of a concomitant surge of extracellular insulin levels and that the adaptation of the islet organ to starvation leads to decreased glucose sensitivity of beta-cells, which contrasts with an improved glucose responsiveness of alpha2-cells. However, hyperphagia, which is assumed to be the primary abnormality in the ob/ob mouse, leads to overproduction of insulin and glucagon by the pancreas while greatly reducing the alpha2-cell sensitivity to glucose. An attempt is made to incorporate these data on starvation, refeeding, and obesity, as well as previous results with experimental diabetes, in a comprehensive picture describing a regulative principle underlying the glucose responsivness of alpha2-cells.

Adaptation, Physiological↗