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Swanson DL, McKechnie AE, Vézina F. How low can you go? An adaptive energetic framework for interpreting basal metabolic rate variation in endotherms. J Comp Physiol B 2017; 187:1039-1056. [PMID: 28401293 DOI: 10.1007/s00360-017-1096-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 03/13/2017] [Accepted: 04/06/2017] [Indexed: 11/24/2022]
Abstract
Adaptive explanations for both high and low body mass-independent basal metabolic rate (BMR) in endotherms are pervasive in evolutionary physiology, but arguments implying a direct adaptive benefit of high BMR are troublesome from an energetic standpoint. Here, we argue that conclusions about the adaptive benefit of BMR need to be interpreted, first and foremost, in terms of energetics, with particular attention to physiological traits on which natural selection is directly acting. We further argue from an energetic perspective that selection should always act to reduce BMR (i.e., maintenance costs) to the lowest level possible under prevailing environmental or ecological demands, so that high BMR per se is not directly adaptive. We emphasize the argument that high BMR arises as a correlated response to direct selection on other physiological traits associated with high ecological or environmental costs, such as daily energy expenditure (DEE) or capacities for activity or thermogenesis. High BMR thus represents elevated maintenance costs required to support energetically demanding lifestyles, including living in harsh environments. BMR is generally low under conditions of relaxed selection on energy demands for high metabolic capacities (e.g., thermoregulation, activity) or conditions promoting energy conservation. Under these conditions, we argue that selection can act directly to reduce BMR. We contend that, as a general rule, BMR should always be as low as environmental or ecological conditions permit, allowing energy to be allocated for other functions. Studies addressing relative reaction norms and response times to fluctuating environmental or ecological demands for BMR, DEE, and metabolic capacities and the fitness consequences of variation in BMR and other metabolic traits are needed to better delineate organismal metabolic responses to environmental or ecological selective forces.
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Affiliation(s)
- David L Swanson
- Department of Biology, University of South Dakota, 414 East Clark Street, Vermillion, SD, 57069, USA.
| | - Andrew E McKechnie
- Department of Zoology and Entomology, DST-NRF Centre of Excellence at the Percy FitzPatrick Institute, University of Pretoria, Private Bag X20, Hatfield, 0028, South Africa
| | - François Vézina
- Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, Rimouski, QC, Canada.,Groupe de recherche sur les environnements nordiques BORÉAS, Centre d'Études Nordiques, Centre de la Science de la Biodiversité du Québec, Rimouski, QC, Canada
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2
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Abstract
Structural and functional complexities of the mammalian lung evolved to meet a unique set of challenges, namely, the provision of efficient delivery of inspired air to all lung units within a confined thoracic space, to build a large gas exchange surface associated with minimal barrier thickness and a microvascular network to accommodate the entire right ventricular cardiac output while withstanding cyclic mechanical stresses that increase several folds from rest to exercise. Intricate regulatory mechanisms at every level ensure that the dynamic capacities of ventilation, perfusion, diffusion, and chemical binding to hemoglobin are commensurate with usual metabolic demands and periodic extreme needs for activity and survival. This article reviews the structural design of mammalian and human lung, its functional challenges, limitations, and potential for adaptation. We discuss (i) the evolutionary origin of alveolar lungs and its advantages and compromises, (ii) structural determinants of alveolar gas exchange, including architecture of conducting bronchovascular trees that converge in gas exchange units, (iii) the challenges of matching ventilation, perfusion, and diffusion and tissue-erythrocyte and thoracopulmonary interactions. The notion of erythrocytes as an integral component of the gas exchanger is emphasized. We further discuss the signals, sources, and limits of structural plasticity of the lung in alveolar hypoxia and following a loss of lung units, and the promise and caveats of interventions aimed at augmenting endogenous adaptive responses. Our objective is to understand how individual components are matched at multiple levels to optimize organ function in the face of physiological demands or pathological constraints.
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Affiliation(s)
- Connie C.W. Hsia
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Dallas M. Hyde
- California National Primate Research Center, University of California at Davis, Davis, California, USA
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3
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Zhang Y, Eyster K, Liu JS, Swanson DL. Cross-training in birds: cold and exercise training produce similar changes in maximal metabolic output, muscle masses and myostatin expression in house sparrows (Passer domesticus). ACTA ACUST UNITED AC 2015; 218:2190-200. [PMID: 25987736 DOI: 10.1242/jeb.121822] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 05/08/2015] [Indexed: 01/18/2023]
Abstract
Maximal metabolic outputs for exercise and thermogenesis in birds presumably influence fitness through effects on flight and shivering performance. Because both summit (Msum, maximum thermoregulatory metabolic rate) and maximum (MMR, maximum exercise metabolic rate) metabolic rates are functions of skeletal muscle activity, correlations between these measurements and their mechanistic underpinnings might occur. To examine whether such correlations occur, we measured the effects of experimental cold and exercise training protocols for 3 weeks on body (Mb) and muscle (Mpec) masses, basal metabolic rate (BMR), Msum, MMR, pectoralis mRNA and protein expression for myostatin, and mRNA expression of TLL-1 and TLL-2 (metalloproteinase activators of myostatin) in house sparrows (Passer domesticus). Both training protocols increased Msum, MMR, Mb and Mpec, but BMR increased with cold training and decreased with exercise training. No significant differences occurred for pectoralis myostatin mRNA expression, but cold and exercise increased the expression of TLL-1 and TLL-2. Pectoralis myostatin protein levels were generally reduced for both training groups. These data clearly demonstrate cross-training effects of cold and exercise in birds, and are consistent with a role for myostatin in increasing pectoralis muscle mass and driving organismal increases in metabolic capacities.
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Affiliation(s)
- Yufeng Zhang
- Department of Biology, University of South Dakota, Vermillion, SD 57069, USA
| | - Kathleen Eyster
- Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57105, USA
| | - Jin-Song Liu
- School of Life and Environmental Sciences, Wenzhou University, Wenzhou 325035, China
| | - David L Swanson
- Department of Biology, University of South Dakota, Vermillion, SD 57069, USA
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Liao J, Wang Y, Zhao L, Liu N. Effects of environmental factors on organ mass of midday gerbil (Meriones meridianus Pallas, 1773). Mamm Biol 2010. [DOI: 10.1016/j.mambio.2009.11.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Rezende EL, Hammond KA, Chappell MA. Cold acclimation in Peromyscus: individual variation and sex effects in maximum and daily metabolism, organ mass and body composition. ACTA ACUST UNITED AC 2009; 212:2795-802. [PMID: 19684213 DOI: 10.1242/jeb.032789] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We studied metabolic and organ mass responses to thermal acclimation (7 weeks at 5 degrees C or 23 degrees C) in deer mice, Peromyscus maniculatus. Cold acclimation resulted in significantly higher maximal oxygen consumption in thermogenesis (V(O(2)max)) and daily mean oxygen consumption (V(O(2)mean)), an increase in the mass of most visceral organs, a lower absolute body fat and a marginally significant increase in hematocrit. The mass of digestive organs and body fat content differed significantly between sexes. Acclimation effects on fat content were more pronounced in females. Variation in heart and lung mass was positively correlated with V(O(2)max) and V(O(2)mean), while body fat content was negatively correlated with both traits. Nonetheless, a large fraction of the metabolic difference between cold- and warm-acclimated groups remained unexplained. Associations between traits at lower levels of biological organization measured here and whole-organism energetics remained consistent across acclimation temperatures, except for the correlation between kidney mass and V(O(2)mean), which was positive and significant in cold acclimation and negligible following warm acclimation. We conclude that: (1) V(O(2)max) and V(O(2)mean) share a common physiological basis that remains overall the same across acclimation regimes; (2) changes in these traits are associated primarily with changes in heart mass; and (3) male and female deer mice respond differently to thermal acclimation, possibly due to differences in reproductive allocation.
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Affiliation(s)
- Enrico L Rezende
- Departament de Genètica i de Microbiologia, Facultat de Biociències, Universitat Autònoma de Barcelona, Bellaterra 08193, Spain.
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Hauton D, Coney AM, Egginton S. Both substrate availability and utilisation contribute to the defence of core temperature in response to acute cold. Comp Biochem Physiol A Mol Integr Physiol 2009; 154:514-22. [PMID: 19712745 DOI: 10.1016/j.cbpa.2009.08.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Revised: 08/18/2009] [Accepted: 08/18/2009] [Indexed: 11/28/2022]
Abstract
Acute cooling significantly increases energy demand in non-hibernators for the defence of core temperature but the contribution of the liver to thermogenesis is poorly understood. A two-tracer method to estimate lipid metabolism in cold-naïve control (CON) and cold-acclimated (CA) rats was employed to quantify hepatic rates of fat metabolism. Both fenofibrate, to increase liver mass and fat oxidation and dichloroacetate (DCA) to inhibit fat oxidation were used to alter lipid metabolism in CON animals. Following acute cooling, CA led to a doubling of the time to reach a core temperature 25 degrees C (P<0.001), whereas DCA treatment decreased time of cooling (P<0.01). DCA-treatment increased the gradient of Arrhenius-transformed rate-pressure product (P<0.01). CA increased both palmitate uptake (P<0.001) and beta-oxidation (P<0.01) whilst DCA treatment decreased uptake (P<0.01) and beta-oxidation (P<0.05). Tissue-specific estimates of metabolism revealed that CA led to a 12-fold increase in beta-oxidation for brown adipose tissue (P<0.001) whilst fenofibrate halved beta-oxidation in the liver (P<0.01) despite doubling the liver mass (P<0.001) and DCA decreased hepatic beta-oxidation to 15% of control levels. Taken together, these results suggest that the liver has minimal contribution to thermogenesis in the rat, with brown adipose tissue significantly increasing both fat uptake and oxidation in response to CA.
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Affiliation(s)
- David Hauton
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom.
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7
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Abstract
SUMMARYNatural or artificial selection that favors higher values of a particular trait within a given population should engender an evolutionary response that increases the mean value of the trait. For this prediction to hold, the phenotypic variance of the trait must be caused in part by additive effects of alleles segregating in the population, and also the trait must not be too strongly genetically correlated with other traits that are under selection. Another prediction, rarely discussed in the literature, is that directional selection should favor alleles that increase phenotypic plasticity in the direction of selection, where phenotypic plasticity is defined as the ability of one genotype to produce more than one phenotype when exposed to different environments. This prediction has received relatively little empirical attention. Nonetheless, many laboratory experiments impose selection regimes that could allow for the evolution of enhanced plasticity (e.g. desiccation trials with Drosophila that last for several hours or days). We review one example that involved culturing of Drosophila on lemon for multiple generations and then tested for enhanced plasticity of detoxifying enzymes. We also review an example with vertebrates that involves selective breeding for high voluntary activity levels in house mice, targeting wheel-running behavior on days 5+6 of a 6-day wheel exposure. This selection regime allows for the possibility of wheel running itself or subordinate traits that support such running to increase in plasticity over days 1–4 of wheel access. Indeed, some traits, such as the concentration of the glucose transporter GLUT4 in gastrocnemius muscle, do show enhanced plasticity in the selected lines over a 5–6 day period. In several experiments we have housed mice from both the Selected (S) and Control (C) lines with or without wheel access for several weeks to test for differences in plasticity (training effects). A variety of patterns were observed, including no training effects in either S or C mice, similar changes in both the S and C lines, greater changes in the S lines but in the same direction in the C lines, and even opposite directions of change in the S and C lines. For some of the traits that show a greater training effect in the S lines, but in the same direction as in C lines, the greater effect can be explained statistically by the greater wheel running exhibited by S lines (`more pain, more gain'). For others, however, the differences seem to reflect inherently greater plasticity in the S lines (i.e. for a given amount of stimulus, such as wheel running/day, individuals in the S lines show a greater response as compared with individuals in the C lines). We suggest that any selection experiment in which the selective event is more than instantaneous should explore whether plasticity in the appropriate (adaptive) direction has increased as a component of the response to selection.
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Affiliation(s)
- Theodore Garland
- Department of Biology, University of California, Riverside, Riverside, CA 92521, USA.
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Schaeffer PJ, Villarin JJ, Pierotti DJ, Kelly DP, Lindstedt SL. Cost of transport is increased after cold exposure in Monodelphis domestica: training for inefficiency. ACTA ACUST UNITED AC 2006; 208:3159-67. [PMID: 16081613 DOI: 10.1242/jeb.01703] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Monodelphis domestica (Didelphidae: Marsupialia) lacks brown adipose tissue and thus relies on skeletal muscle as its primary thermogenic organ. Following cold exposure, the aerobic capacity of skeletal muscle in these animals is greatly increased. We investigated the effects of this plastic response to thermogenesis on locomotion and muscle mechanics. In cold-exposed animals, cost of transport was 15% higher than in controls but was unaffected by exercise training. Twitch kinetics in isolated semitendinosus muscles of cold-exposed animals were characteristic of slow-oxidative fiber types. Both time-to-peak tension and half-relaxation time were longer and maximal shortening velocity was slower following cold exposure compared to either thermoneutral controls or exercise-trained animals. Further, muscles from the cold-exposed animals had greater fatigue resistance than either control or exercise-trained animals, indicating greater oxidative capacity. Finally, we identified an uncoupling protein 3 homologue, whose gene expression was upregulated in skeletal muscle of cold-exposed Monodelphis domestica. Cold exposure provided a potent stimulus for muscle plasticity, driving a fast-to-slow transition more effectively than exercise training. However, linked to the dramatic shift in muscle properties is an equally dramatic increase in whole animal muscle energetics during locomotion, suggesting an uncoupled state, or 'training for inefficiency'.
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Affiliation(s)
- Paul J Schaeffer
- Department of Biological Sciences, Physiology and Functional Morphology Group, Northern Arizona University, Flagstaff, AZ 86011, USA.
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Yilmaz C, Johnson RL, Hsia CCW. A rebreathing method for measuring lung volume, diffusing capacity and cardiac output in conscious small animals. Respir Physiol Neurobiol 2005; 146:215-23. [PMID: 15766909 DOI: 10.1016/j.resp.2004.12.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2004] [Revised: 12/07/2004] [Accepted: 12/17/2004] [Indexed: 11/20/2022]
Abstract
We developed a multiple gas rebreathing technique for measuring lung diffusing capacity (DL(CO)), lung volume (V(L)) and cardiac output simultaneously in conscious spontaneously breathing small animals. Lung volume was measured from the dilution of methane (CH4) or sulfur hexafluoride (SF6) and verified independently by a helium washout technique. Cardiac output and DL(CO) were estimated from the uptake of acetylene and carbon monoxide, respectively. We tested guinea pigs at two levels of alveolar oxygen tension in order to estimate membrane diffusing capacity and pulmonary capillary blood volume by the Roughton-Forster technique. Results show that measured DL(CO) are consistent with reported values in anesthetized guinea pigs as well as with allometric comparison across species. Lung volume estimated from SF6 dilution agreed closely with that estimated independently from helium washout; however, lung volume estimated from CH4 dilution was systematically lower due to the addition of endogenously produced CH4 to the rebreathing system. We conclude that this technique can be used to measure resting lung function in conscious unsedated small animals.
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Affiliation(s)
- Cuneyt Yilmaz
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9034, USA
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11
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Weibel ER, Bacigalupe LD, Schmitt B, Hoppeler H. Allometric scaling of maximal metabolic rate in mammals: muscle aerobic capacity as determinant factor. Respir Physiol Neurobiol 2004; 140:115-32. [PMID: 15134660 DOI: 10.1016/j.resp.2004.01.006] [Citation(s) in RCA: 203] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/26/2004] [Indexed: 10/26/2022]
Abstract
Maximal metabolic rate (MMR) of mammals scales differently from basal metabolic rate (BMR). This is first shown by scrutinizing data reported on exercise-induced Vo2 max in 34 eutherian mammalian species covering a body mass range of 7 g-500 kg. Vo2 max was found to scale with the 0.872 (+/-0.029, 95% confidence limits 0.813-0.932) power of body mass which is significantly different from the 3/4 power reported for basal metabolic rate. The aerobic scope is higher in athletic than non-athletic species, and it is also higher in large than in small species. Integrated structure-function studies on a subset of 11 species (body mass 20 g-450 kg) show that the variation of Vo2 max with body size is tightly associated with the aerobic capacity of the locomotor musculature: the scaling exponents for Vo2 max, the total volume of mitochondria, and the volume of capillaries are nearly identical. The higher Vo2 max of athletic species is tightly linked to proportionally larger mitochondrial and capillary volumes in animals of the same size class. As a result Vo2 max is linearly related to both total mitochondrial and capillary erythrocyte volumes. We conclude that the scaling of maximal metabolic rate is explained by features and mechanisms different from those determining basal metabolic rate.
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Affiliation(s)
- Ewald R Weibel
- Department of Anatomy, University of Berne, Bühlstrasse 26, CH 3000, Berne 9, Switzerland.
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12
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Schaeffer PJ, Villarin JJ, Lindstedt SL. Chronic Cold Exposure Increases Skeletal Muscle Oxidative Structure and Function inMonodelphis domestica, a Marsupial Lacking Brown Adipose Tissue. Physiol Biochem Zool 2003; 76:877-87. [PMID: 14988803 DOI: 10.1086/378916] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/05/2003] [Indexed: 11/04/2022]
Abstract
Monodelphis domestica (Marsupialia: Didelphidae) was used as a model animal to investigate and compare muscle adaptation to exercise training and cold exposure. The experimental treatment consisted of four groups of animals: either warm or cold acclimation temperature and with or without endurance exercise training. Maximal aerobic capacity during a running VO2max test in the warm-exercised or cold-exposed (with or without exercise) groups was about 130 mL O(2)/kg/min, significantly higher than the warm-acclimated controls at 113.5 mL O(2)/kg/min. Similarly, during an acute cold challenge (VO2summit), maximal aerobic capacity was higher in these three experimental groups at approximately 95 mL O(2)/kg/min compared with 80.4 mL O(2)/kg/min in warm-acclimated controls. Respiratory exchange ratio was significantly lower (0.89-0.68), whereas relative heart mass (0.52%-0.73%) and whole-body muscle mitochondrial volume density (2.59 to 3.04 cm(3)) were significantly higher following cold exposure. Chronic cold exposure was a stronger stimulus than endurance exercise training for tissue-specific adaptations. Although chronic cold exposure and endurance exercise are distinct challenges, physiological adaptations to each overlap such that the capacities for aerobic performance in response to both cold exposure and running are increased by either or both treatments.
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Affiliation(s)
- P J Schaeffer
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA.
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13
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Abstract
Lung diffusing capacity (DL) for carbon monoxide (DLCO), nitric oxide (DLNO) or oxygen (DLO2) increases from rest to peak exercise without reaching an upper limit; this recruitment results from interactions among alveolar volume (VA), and cardiac output (q), as well as changing physical properties and spatial distribution of capillary erythrocytes, and is critical for maintaining a normal arterial oxygen saturation. DLCO and DLNO can be used to interpret the effectiveness of diffusive oxygen transport and track structural alterations of the alveolar-capillary barrier, providing sensitive noninvasive indicators of microvascular integrity in health and disease. Clinical interpretation of DL should take into account Q in addition to VA and hemoglobin concentration.
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Affiliation(s)
- Connie C W Hsia
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas TX 75390-9034, USA
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14
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Sapoval B, Filoche M, Weibel ER. Smaller is better--but not too small: a physical scale for the design of the mammalian pulmonary acinus. Proc Natl Acad Sci U S A 2002; 99:10411-6. [PMID: 12136124 PMCID: PMC124928 DOI: 10.1073/pnas.122352499] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/12/2002] [Indexed: 11/18/2022] Open
Abstract
The transfer of oxygen from air to blood in the lung involves three processes: ventilation through the airways, diffusion of oxygen in the air phase to the alveolar surface, and finally diffusion through tissue into the capillary blood. The latter two steps occur in the acinus, where the alveolar gas-exchange surface is arranged along the last few generations of airway branching. For the acinus to work efficiently, oxygen must reach the last branches of acinar airways, even though some of it is absorbed along the way. This "screening effect" is governed by the relative values of physical factors like diffusivity and permeability as well as size and design of the acinus. Physics predicts that efficient acini should be space-filling surfaces and should not be too large. It is shown that the mammalian acini fulfill these requirements, small mammals being more efficient than large ones both at rest and in exercise.
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Affiliation(s)
- Bernard Sapoval
- Laboratoire de Physique de la Matière Condensée, Centre National de la Recherche Scientifique, Ecole Polytechnique, 91128 Palaiseau, France.
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15
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Deveci D, Egginton S. Differing mechanisms of cold-induced changes in capillary supply in m. tibialis anterior of rats and hamsters. J Exp Biol 2002; 205:829-40. [PMID: 11914391 DOI: 10.1242/jeb.205.6.829] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
The physiological, metabolic and anatomical adaptations of skeletal muscle to chronic cold exposure were investigated in Wistar rats (Rattus norvegicus), a species that defends core temperature, and Syrian hamsters (Mesocricetus auratus), which may adopt a lower set point under unfavourable conditions. Animals were exposed to a simulated onset of winter in an environmental chamber, progressively shortening photoperiod and reducing temperature from 12 h:12 h L:D and 22°C to 1 h:23 h L:D and 5°C over 4 weeks. The animals were left at 4°C for a further 4 weeks to complete the process of cold-acclimation. M. tibialis anterior from control (euthermic) and cold-acclimated animals of similar mass showed a significant hyperactivity-induced hypertrophy in the rat, but a small disuse atrophy in the hamster. Little evidence was found for interconversion among fibre types in skeletal muscle on cold-acclimation, and only modest differences were seen in activity of oxidative or glycolytic enzymes in either species. However, adjustments in Type II fibre size paralleled the muscle hypertrophy in rat and atrophy in hamster. Cold-induced angiogenesis was present in the rat, averaging a 28 % increase in capillary-to-fibre ratio (C:F) but, as this was balanced by fibre hypertrophy across the whole muscle, there was no change in capillary density (CD). In contrast, the C:F was similar in both groups of hamsters, whereas CD rose by 33 % in line with fibre atrophy. Within distinct regions of the m. tibialis anterior, there was a correlation between angiogenesis and fibre size in rats, in which oxygen diffusion distance increased, but not in hamsters, in which there was a reduced oxygen diffusion distance. Consequently, the change in C:F was greatest (39 %) in the glycolytic cortex region of the m. tibialis anterior in rats. We conclude that non-hibernator and hibernator rodents improve peripheral oxygen transport following cold-acclimation by different mechanisms. In rats, an increase in fibre girth was accompanied by a true angiogenesis, while the improved apparent capillary supply in hamsters was due to smaller fibre diameters. These responses are consistent with the strategies of resisting and accommodating, respectively, an annual fall in environmental temperature.
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Affiliation(s)
- Durmus Deveci
- Department of Physiology, Cumhuriyet University, 58140 Sivas, Turkey
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16
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Schaeffer PJ, Hokanson JF, Wells DJ, Lindstedt SL. Cold exposure increases running VO(2max) and cost of transport in goats. Am J Physiol Regul Integr Comp Physiol 2001; 280:R42-7. [PMID: 11124132 DOI: 10.1152/ajpregu.2001.280.1.r42] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We inadvertently subjected a group of goats to 5 mo of cold exposure (mean minimum temperature less than -13 degrees C) during an experiment designed to examine the effects of training by daily running on one member of each sibling pair. During the three coldest months, the sedentary but cold-exposed goats experienced a 34% increase in maximal oxygen uptake (VO(2 max), P < 0.01) and a 29% increase in running speed at maximal (P < 0.05). When temperatures increased in the spring, both oxygen uptake and running speed decreased. We interpret these findings as evidence that cold is a sufficient stimulus to invoke the development of aerobic structures in muscle and that these structures subsequently can be utilized for the novel task of running. When the experiment was subsequently repeated without the cold exposure, running speed and VO(2 max) of trained animals increased less than in either group of cold-exposed animals. However, the cost of transport of these warm runners was lower than either group of cold-exposed animals (from 13-19%, P < 0. 0001). Thus, although aerobic capacity was increased with acclimation to severe winter weather, cold-acclimated goats operated with lower efficiency during locomotion.
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Affiliation(s)
- P J Schaeffer
- Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona 86011-5640, USA
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17
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Terblanche SE, Masondo TC, Nel W. Effects of chronic cold exposure on the activities of cytochrome c oxidase, glutathione peroxidase and glutathione reductase in rat tissues (Rattus norvegicus). Comp Biochem Physiol B Biochem Mol Biol 2000; 127:319-24. [PMID: 11126762 DOI: 10.1016/s0305-0491(00)00269-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The effects of cold acclimation on the activity levels of cytochrome c oxidase, glutathione peroxidase and glutathione reductase in various tissues of the rat (Rattus norvegicus) were investigated. One group was individually housed at 4 +/- 1 degrees C and the other at 24 +/- 1 degrees C for 6 months. Chronic cold acclimation resulted in significantly (P < 0.05) increased cytochrome c oxidase activity levels in liver, kidney, heart, interscapular brown adipose tissue and gastrocnemius muscle. The activity of glutathione peroxidase was significantly (P < 0.05) elevated in liver, interscapular brown adipose tissue, lung and muscle, whereas glutathione reductase was only significantly (P < 0.05) elevated in interscapular brown adipose tissue as a result of chronic cold exposure. The results obtained are possibly indicative of a positive compensatory response against the increased production of oxygen derived radicals as a result of chronic cold exposure.
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Affiliation(s)
- S E Terblanche
- Department of Biochemistry and Microbiology, University of Zululand, KwaDlangezwa, South Africa.
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18
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Thomas RG, LaStayo PC, Hoppeler H, Favier R, Ferretti G, Kayser B, Desplanches D, Spielvogel H, Lindstedt SL. Exercise training in chronic hypoxia has no effect on ventilatory muscle function in humans. RESPIRATION PHYSIOLOGY 1998; 112:195-202. [PMID: 9716303 DOI: 10.1016/s0034-5687(98)00017-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
At the highest altitude, aerobic work is limited by environmental oxygen availability. We therefore reasoned that the hyperpnea associated with endurance training at altitude should provide a strong stimulus for adaptation of the ventilatory muscles. We measured peak inspiratory muscle pressure-flow characteristics (inspiring through graded resistors) and maximum sustainable ventilation capacity in ten permanent residents of La Paz, Bolivia (3600 m) prior to and immediately following 6 weeks of incremental endurance training. Additionally, eight local residents did no training and functioned as controls for the capacity test. While V(O2)max measured in hypoxia increased by 19% (Favier et al., 1995b. J. Appl Physiol. 78, 2286-2293.), none of the tested ventilatory variables showed significant changes. The values for the group mean slopes of maximum inspiratory pressure-flow pairs (- 10.5 vs. - 9.8 cm H2O x sec x L(-1), P=0.301; before versus after training, respectively), maximum inspiratory pressure (112.1+/-8.9 vs. 106.9+/-8.6 cmH2O, P=0.163), peak inspiratory flow (9.8+/-0.41 vs. 10.2+/-0.55 L x sec(-1) P=0.172) and the maximum volitional volume in 12 sec (43.9+/-2.4 vs. 45.6+/-2.4 L in 12 sec, P=0.133) were unchanged with exercise training. Likewise, maximal sustainable minute volume was not different between post-training and control subjects (177.4+/-7.9 vs. 165.4+/-8.4 L x min(-1), P=0.141). These data support the concept that endurance training fails to elicit functional adaptations in ventilatory muscles in humans, even when exercise is done in hypoxia.
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Affiliation(s)
- R G Thomas
- Department of Biological Sciences, Northern Arizona University, Flagstaff 86011-5640, USA
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Turner DL, Hoppeler H, Hokanson J, Weibel ER. Cold acclimation and endurance training in guinea pigs: changes in daily and maximal metabolism. RESPIRATION PHYSIOLOGY 1995; 101:183-8. [PMID: 8570920 DOI: 10.1016/0034-5687(95)00022-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The physiological effects of training or cold acclimation on maximal oxygen uptake (VO2,max) and average daily metabolic rate (VO2,dav) of a small mammal, the guinea pig, are described. Young male guinea pigs were assigned to three experimental groups; control, endurance trained (70% VO2,max) or cold acclimated (5-7 degrees C) for six weeks. Measurements of VO2,max and VO2,dav were made before and after the treatments. VO2,max increased significantly in cold acclimated (+29%) and endurance trained (+23%) animals and was achieved at a higher maximal running speed compared to post-treatment controls. Maximal blood lactate concentration was significantly higher in cold acclimated compared to endurance trained animals. Endurance trained animals had a reduced VO2,dav compared to control animals, whereas cold acclimation raised VO2,dav in the cold as expected, but also at room temperature. All three groups showed a daily pattern in metabolic rate (night > day). In conclusion, both endurance training and cold acclimation lead to enhanced VO2,max and changes in resting oxygen consumption throughout the day.
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Affiliation(s)
- D L Turner
- Department of Anatomy, University of Bern, Switzerland
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