The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
John S. Terblanche - One of the best experts on this subject based on the ideXlab platform.
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Evolution of the Mechanisms Underlying Insect Respiratory Gas Exchange
Advances in Insect Physiology, 2015Co-Authors: Philip G. D. Matthews, John S. TerblancheAbstract:Abstract Many factors influence Gas Exchange patterns in insects and are generally treated in isolation from one another. Here, we provide a review of the current state of knowledge on the physics of Gas Exchange, insect respiratory chemoreceptors, the diversity and the methods typically used in the characterisation of respiratory pattern types, briefly covering some of the new tools and techniques that are being incorporated into this field. We then discuss the functional significance of insect Gas Exchange pattern variation, and possible evolutionary explanations of discontinuous Gas Exchange as a derived control mechanism for effecting physiological change in the context of (a) adaptive hypotheses, (b) non-adaptive hypotheses and (c) mathematical modelling of Gas Exchange. The lack of consensus in the literature for all proposed adaptive or mechanistic hypotheses suggests that multiple factors influence which Gas Exchange pattern is displayed by any particular insect during a given experiment. Thus, while the primary function of a breathing pattern is to meet an animal's Gas Exchange requirements, it is an interacting hierarchy of constraints that most likely determines how this demand may be met. We conclude the review with a brief discussion of future directions for the field.
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Scaling of Gas Exchange cycle frequency in insects.
Biology letters, 2007Co-Authors: John S. Terblanche, Elrike Marais, Craig R. White, Tim M. Blackburn, Steven L. ChownAbstract:Previously, it has been suggested that insect Gas Exchange cycle frequency (fC) is mass independent, making insects different from most other animals where periods typically scale as mass−0.25. However, the claim for insects is based on studies of only a few closely related taxa encompassing a relatively small size range. Moreover, it is not known whether the type of Gas Exchange pattern (discontinuous versus cyclic) influences the fC–mass scaling relationship. Here, we analyse a large database to examine interspecific fC–mass scaling. In addition, we investigate the effect of mode of Gas Exchange on the fC–scaling relationship using both conventional and phylogenetically independent approaches. Cycle frequency is scaled as mass−0.280 (when accounting for phylogeneticnon-independence and Gas Exchange pattern), which did not differ significantly from mass−0.25. The slope of the fC–mass relationship was shallower with a significantly lower intercept for the species showing discontinuous Gas Exchange than for those showing the cyclic pattern, probably due to lower metabolic rates in the former. Insects therefore appear no different from other animals insofar as the scaling of Gas Exchange fC is concerned, although Gas Exchange fC may scale in distinct ways for different patterns.
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Insect Gas Exchange patterns: a phylogenetic perspective.
Journal of Experimental Biology, 2005Co-Authors: Elrike Marais, C. Jaco Klok, John S. Terblanche, Steven L. ChownAbstract:Most investigations of insect Gas Exchange patterns and the hypotheses proposed to account for their evolution have been based either on small-scale, manipulative experiments, or comparisons of a few closely related species. Despite their potential utility, no explicit, phylogeny-based, broad-scale comparative studies of the evolution of Gas Exchange in insects have been undertaken. This may be due partly to the preponderance of information for the endopterygotes, and its scarcity for the apterygotes and exopterygotes. Here we undertake such a broad-scale study. Information on Gas Exchange patterns for the large majority of insects examined to date (eight orders, 99 species) is compiled, and new information on 19 exemplar species from a further ten orders, not previously represented in the literature (Archaeognatha, Zygentoma, Ephemeroptera, Odonata, Mantodea, Mantophasmatodea, Phasmatodea, Dermaptera, Neuroptera, Trichoptera), is provided. These data are then used in a formal, phylogeny-based parsimony analysis of the evolution of Gas Exchange patterns at the order level. Cyclic Gas Exchange is likely to be the ancestral Gas Exchange pattern at rest (recognizing that active individuals typically show continuous Gas Exchange), and discontinuous Gas Exchange probably originated independently a minimum of five times in the Insecta.
Steven L. Chown - One of the best experts on this subject based on the ideXlab platform.
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Scaling of Gas Exchange cycle frequency in insects.
Biology letters, 2007Co-Authors: John S. Terblanche, Elrike Marais, Craig R. White, Tim M. Blackburn, Steven L. ChownAbstract:Previously, it has been suggested that insect Gas Exchange cycle frequency (fC) is mass independent, making insects different from most other animals where periods typically scale as mass−0.25. However, the claim for insects is based on studies of only a few closely related taxa encompassing a relatively small size range. Moreover, it is not known whether the type of Gas Exchange pattern (discontinuous versus cyclic) influences the fC–mass scaling relationship. Here, we analyse a large database to examine interspecific fC–mass scaling. In addition, we investigate the effect of mode of Gas Exchange on the fC–scaling relationship using both conventional and phylogenetically independent approaches. Cycle frequency is scaled as mass−0.280 (when accounting for phylogeneticnon-independence and Gas Exchange pattern), which did not differ significantly from mass−0.25. The slope of the fC–mass relationship was shallower with a significantly lower intercept for the species showing discontinuous Gas Exchange than for those showing the cyclic pattern, probably due to lower metabolic rates in the former. Insects therefore appear no different from other animals insofar as the scaling of Gas Exchange fC is concerned, although Gas Exchange fC may scale in distinct ways for different patterns.
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Insect Gas Exchange patterns: a phylogenetic perspective.
Journal of Experimental Biology, 2005Co-Authors: Elrike Marais, C. Jaco Klok, John S. Terblanche, Steven L. ChownAbstract:Most investigations of insect Gas Exchange patterns and the hypotheses proposed to account for their evolution have been based either on small-scale, manipulative experiments, or comparisons of a few closely related species. Despite their potential utility, no explicit, phylogeny-based, broad-scale comparative studies of the evolution of Gas Exchange in insects have been undertaken. This may be due partly to the preponderance of information for the endopterygotes, and its scarcity for the apterygotes and exopterygotes. Here we undertake such a broad-scale study. Information on Gas Exchange patterns for the large majority of insects examined to date (eight orders, 99 species) is compiled, and new information on 19 exemplar species from a further ten orders, not previously represented in the literature (Archaeognatha, Zygentoma, Ephemeroptera, Odonata, Mantodea, Mantophasmatodea, Phasmatodea, Dermaptera, Neuroptera, Trichoptera), is provided. These data are then used in a formal, phylogeny-based parsimony analysis of the evolution of Gas Exchange patterns at the order level. Cyclic Gas Exchange is likely to be the ancestral Gas Exchange pattern at rest (recognizing that active individuals typically show continuous Gas Exchange), and discontinuous Gas Exchange probably originated independently a minimum of five times in the Insecta.
Susan R. Hopkins - One of the best experts on this subject based on the ideXlab platform.
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Precapillary pulmonary Gas Exchange is similar for oxygen and inert Gases.
The Journal of physiology, 2019Co-Authors: Michael K. Stickland, Peter D. Wagner, Vincent Tedjasaputra, Desi P. Fuhr, Harrieth Wagner, Sophie É. Collins, Bradley W. Byers, Susan R. HopkinsAbstract:Key points Precapillary Gas Exchange for oxygen has been documented in both humans and animals. It has been suggested that, if precapillary Gas Exchange occurs to a greater extent for inert Gases than for oxygen, shunt and its effects on arterial oxygenation may be underestimated by the multiple inert Gas elimination technique (MIGET). We evaluated fractional precapillary Gas Exchange in canines for O2 and two inert Gases, sulphur hexafluoride and ethane, by measuring these Gases in the proximal pulmonary artery, distal pulmonary artery (1 cm proximal to the wedge position) and systemic artery. Some 12-19% of pulmonary Gas Exchange occurred within small (1.7 mm in diameter or larger) pulmonary arteries and this was quantitatively similar for oxygen, sulphur hexafluoride and ethane. Under these experimental conditions, this suggests only minor effects of precapillary Gas Exchange on the magnitude of calculated shunt and the associated effect on pulmonary Gas Exchange estimated by MIGET. Abstract Some pulmonary Gas Exchange is known to occur proximal to the pulmonary capillary, although the magnitude of this Gas Exchange is uncertain, and it is unclear whether oxygen and inert Gases are similarly affected. This has implications for measuring shunt and associated Gas Exchange consequences. By measuring respiratory and inert Gas levels in the proximal pulmonary artery (P), a distal pulmonary artery 1 cm proximal to the wedge position (using a 5-F catheter) (D) and a systemic artery (A), we evaluated precapillary Gas Exchange in 27 paired samples from seven anaesthetized, ventilated canines. Fractional precapillary Gas Exchange (F) was quantified for each Gas as F = (P - D)/(P - A). The lowest solubility inert Gases, sulphur hexafluoride (SF6 ) and ethane were used because, with higher solubility Gases, the P-A difference is sufficiently small that experimental error prevents accurate assessment of F. Distal samples (n = 12) with oxygen (O2 ) saturation values that were (within experimental error) equal to or above systemic arterial values, suggestive of retrograde capillary blood aspiration, were discarded, leaving 15 for analysis. D was significantly lower than P for SF6 (D/P = 88.6 ± 18.1%; P = 0.03) and ethane (D/P = 90.6 ± 16.0%; P = 0.04), indicating partial excretion of inert Gas across small pulmonary arteries. Distal pulmonary arterial O2 saturation was significantly higher than proximal (74.1 ± 6.8% vs. 69.0 ± 4.9%; P = 0.03). Fractional precapillary Gas Exchange was similar for SF6 , ethane and O2 (0.12 ± 0.19, 0.12 ± 0.20 and 0.19 ± 0.26, respectively; P = 0.54). Under these experimental conditions, 12-19% of pulmonary Gas Exchange occurs within the small pulmonary arteries and the extent is similar between oxygen and inert Gases.
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lung function and Gas Exchange
2014Co-Authors: Andrew M. Luks, Susan R. HopkinsAbstract:As the first step in the path for oxygen transport to the body, the response of the respiratory system is critical to maintaining an adequate level of function at high altitude. Environmental hypoxia, combined with cold and heavy exercise all contribute to considerable stress to the lung. Acute altitude exposure results in hypoxia, and a rapid and sustained increase in alveolar ventilation, with an associated fall in alveolar and arterial partial pressure of carbon dioxide. In addition cardiac output and pulmonary vascular pressures also increase. These changes along with any occurring as a result of altitude illness have the potential to alter pulmonary function and Gas Exchange. In addition, acclimatization to hypoxia of hours to days duration results in additional physiological changes overlying the acute changes. This review explores the changes in pulmonary function, as well as changes in pulmonary Gas Exchange at rest or during exercise that occur within the first hours to weeks of hypoxic exposure following ascent to high altitude.
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Pulmonary Gas Exchange
2013Co-Authors: G. Kim Prisk, Susan R. HopkinsAbstract:Abstract Download Free Sample The lung receives the entire cardiac output from the right heart and must load oxygen onto and unload carbon dioxide from perfusing blood in the correct amounts to meet the metabolic needs of the body. It does so through the process of passive diffusion. Effective diffusion is accomplished by intricate parallel structures of airways and blood vessels designed to bring ventilation and perfusion together in an appropriate ratio in the same place and at the same time. Gas Exchange is determined by the ventilation-perfusion ratio in each of the Gas Exchange units of the lung. In the normal lung ventilation and perfusion are well matched, and the ventilation-perfusion ratio is remarkably uniform among lung units, such that the partial pressure of oxygen in the blood leaving the pulmonary capillaries is less than 10 Torr lower than that in the alveolar space. In disease, the disruption to ventilation-perfusion matching and to diffusional transport may result in inefficient Gas exch...
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comparative physiology of lung complexity implications for Gas Exchange
Physiology, 2004Co-Authors: Frank L Powell, Susan R. HopkinsAbstract:Lungs evolved to increase diffusing capacity by compartmentalizing and reducing the size of individual Gas Exchange units. This increased the potential for Gas Exchange limitations from ventilation-perfusion heterogeneity. However, comparative studies on reptiles, birds, and mammals show that heterogeneity is independent of lung complexity.
Steen Andreassen - One of the best experts on this subject based on the ideXlab platform.
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A stratified model of pulmonary Gas Exchange
IFAC Proceedings Volumes, 2012Co-Authors: Mads Lause Mogensen, Dan Stieper Karbing, Stephen Edward Rees, Kristoffer Lindegaard Steimle, Steen AndreassenAbstract:Abstract This paper describes a model of pulmonary Gas Exchange including CO2 and O2 storage and transport in the anatomical dead space, alveoli, capillaries, arterial and mixed venous blood. Model simulations of Gas Exchange, ventilation and perfusion for an average healthy adult were in general in good agreement with previously reported values. However, the model overestimates the heterogeneity of ventilation/perfusion ratios down the lungs. Results indicate that the model is able to simulate the pulmonary Gas Exchange in healthy human lungs but that modifications are required to counter the large degree of ventilation/perfusion heterogeneity currently simulated by the model.
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Mathematical modelling of pulmonary Gas Exchange
2007Co-Authors: Dan Stieper Karbing, Steen Andreassen, Søren Kjærgaard, Stephen Edward ReesAbstract:This chapter describes mathematical models used to quantify abnormalities of pulmonary Gas Exchange (i.e., abnormalities of diffusion, ventilation, and perfusion). It begins by deriving the standard equations of pulmonary Gas Exchange, then showing how these equations can be used to obtain more complex models of ventilation–diffusion and ventilation–perfusion mismatch in the lungs. The application of these models is then reviewed in both experimental and clinical environments.
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Modelling the relationship between Gas Exchange and lung mechanics
Journal of Clinical Monitoring and Computing, 2007Co-Authors: Dan Stieper Karbing, Bram Wallace Smith, Stephen Edward Rees, Steen AndreassenAbstract:Introduction Setting ventilator pressures in critically ill patients requires consideration of the effects on both lung mechanics and Gas Exchange. Increasing positive end-expiratory pressure (PEEP) recruits collapsed lung compartments improving Gas Exchange, however, high pressures can also cause ventilator associated lung injury (VALI). Many studies have analysed these effects independently, using blood Gas measurements, dynamic compliance and static pressure volume curves to discuss optimal PEEP settings. However, recent studies have highlighted the need to consider the combined effects of PEEP changes on lung mechanics and Gas Exchange. This study investigates the effects of changes in PEEP on both Gas Exchange, using a model of oxygen transport in the lungs, and lung mechanics, using methods of measuring the static pressure-volume (PV) curve and the dynamic compliance (Cdyn).
Elrike Marais - One of the best experts on this subject based on the ideXlab platform.
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Scaling of Gas Exchange cycle frequency in insects.
Biology letters, 2007Co-Authors: John S. Terblanche, Elrike Marais, Craig R. White, Tim M. Blackburn, Steven L. ChownAbstract:Previously, it has been suggested that insect Gas Exchange cycle frequency (fC) is mass independent, making insects different from most other animals where periods typically scale as mass−0.25. However, the claim for insects is based on studies of only a few closely related taxa encompassing a relatively small size range. Moreover, it is not known whether the type of Gas Exchange pattern (discontinuous versus cyclic) influences the fC–mass scaling relationship. Here, we analyse a large database to examine interspecific fC–mass scaling. In addition, we investigate the effect of mode of Gas Exchange on the fC–scaling relationship using both conventional and phylogenetically independent approaches. Cycle frequency is scaled as mass−0.280 (when accounting for phylogeneticnon-independence and Gas Exchange pattern), which did not differ significantly from mass−0.25. The slope of the fC–mass relationship was shallower with a significantly lower intercept for the species showing discontinuous Gas Exchange than for those showing the cyclic pattern, probably due to lower metabolic rates in the former. Insects therefore appear no different from other animals insofar as the scaling of Gas Exchange fC is concerned, although Gas Exchange fC may scale in distinct ways for different patterns.
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Insect Gas Exchange patterns: a phylogenetic perspective.
Journal of Experimental Biology, 2005Co-Authors: Elrike Marais, C. Jaco Klok, John S. Terblanche, Steven L. ChownAbstract:Most investigations of insect Gas Exchange patterns and the hypotheses proposed to account for their evolution have been based either on small-scale, manipulative experiments, or comparisons of a few closely related species. Despite their potential utility, no explicit, phylogeny-based, broad-scale comparative studies of the evolution of Gas Exchange in insects have been undertaken. This may be due partly to the preponderance of information for the endopterygotes, and its scarcity for the apterygotes and exopterygotes. Here we undertake such a broad-scale study. Information on Gas Exchange patterns for the large majority of insects examined to date (eight orders, 99 species) is compiled, and new information on 19 exemplar species from a further ten orders, not previously represented in the literature (Archaeognatha, Zygentoma, Ephemeroptera, Odonata, Mantodea, Mantophasmatodea, Phasmatodea, Dermaptera, Neuroptera, Trichoptera), is provided. These data are then used in a formal, phylogeny-based parsimony analysis of the evolution of Gas Exchange patterns at the order level. Cyclic Gas Exchange is likely to be the ancestral Gas Exchange pattern at rest (recognizing that active individuals typically show continuous Gas Exchange), and discontinuous Gas Exchange probably originated independently a minimum of five times in the Insecta.
