Comparison of ventilatory and circulatory flow rates between animals in various physiological conditions.
TL;DR: Air-, water- and blood-convection requirements in different classes of warm- and cold-blooded vertebrates and in certain Crustacea and mollusks are compared as functions of the O2 concentration of the inspired medium (water or air) or of the post-pulmonary or post-branchial blood or hemolymph.
About: This article is published in Respiration Physiology.The article was published on 1970-05-01. It has received 82 citations till now.
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TL;DR: The general structure of the gills of different fishes is compared and it is concluded that, though essentially the same, there are certain differences by which they can be recognized.
Abstract: Summary
1. The general structure of the gills of different fishes is compared and it is concluded that, though essentially the same, there are certain differences by which they can be recognized. Possible ways in which they may have evolved from one another are considered.
2. A detailed account is given of the structure of the secondary lamellae, where gaseous exchange takes place, and it is shown that two epithelial sheets are separated by a vascular axis mainly composed of pillar cells overlain by a basement membrane on each side. Blood pathways through the gills are discussed in relation to their respiratory function.
3. The embryonic development of gills is described and evidence regarding homo-logies of different structures, particularly the pillar cells, is reviewed.
4. The gills of fish having different modes of life show variations in (a) the number of arches, (b) the number and length of the gill filaments, and (c) the size and frequency of the secondary lamellae. Ways in which measurements of gill area may be carried out and some of the complications involved are reviewed and a summary given of measurements made for a wide variety of species. Measurements of the thickness of the water-blood barrier are also discussed; the more active fish generally have thinner water-blood barriers and larger gill areas.
5. The different mechanisms of gill ventilation are summarized and characteristics of gill resistance in elasmobranchs and teleosts are compared. Gas exchange is discussed in relation to available techniques and the current terminology and symbols, and to indicate the value of analogies between gill exchangers and systems studied by engineers.
6. It is outlined how studies of the functioning of gills during coughing, parasitic infection, and in polluted waters add to knowledge of their role in respiration.
383 citations
TL;DR: Insights into the acclimatization response of lowland animals to high-altitude hypoxia can provide a basis for predicting how altitudinal range limits might shift in response to climate change.
Abstract: High-altitude environments provide ideal testing grounds for investigations of mechanism and process in physiological adaptation. In vertebrates, much of our understanding of the acclimatization response to high-altitude hypoxia derives from studies of animal species that are native to lowland environments. Such studies can indicate whether phenotypic plasticity will generally facilitate or impede adaptation to high altitude. Here, we review general mechanisms of physiological acclimatization and genetic adaptation to high-altitude hypoxia in birds and mammals. We evaluate whether the acclimatization response to environmental hypoxia can be regarded generally as a mechanism of adaptive phenotypic plasticity, or whether it might sometimes represent a misdirected response that acts as a hindrance to genetic adaptation. In cases in which the acclimatization response to hypoxia is maladaptive, selection will favor an attenuation of the induced phenotypic change. This can result in a form of cryptic adaptive evolution in which phenotypic similarity between high- and low-altitude populations is attributable to directional selection on genetically based trait variation that offsets environmentally induced changes. The blunted erythropoietic and pulmonary vasoconstriction responses to hypoxia in Tibetan humans and numerous high-altitude birds and mammals provide possible examples of this phenomenon. When lowland animals colonize high-altitude environments, adaptive phenotypic plasticity can mitigate the costs of selection, thereby enhancing prospects for population establishment and persistence. By contrast, maladaptive plasticity has the opposite effect. Thus, insights into the acclimatization response of lowland animals to high-altitude hypoxia can provide a basis for predicting how altitudinal range limits might shift in response to climate change.
336 citations
Cites background from "Comparison of ventilatory and circu..."
...…mentioned above, the lower critical PO2 at the vascular supply source for tissue oxygenation can be expressed as PvO2PaO2–[bO2 (Q/VO2)]–1, where VO2 is the rate of O2 consumption by the tissues and the product bO2 (Q/VO2) is the specific blood O2 conductance (Dejours et al., 1970; Bouverot, 1985)....
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TL;DR: The transfer rate of a gas species, with dimension (quantity of substance)·(time)−1, may thereby be clearly distinguished from the volume flow rate, which has the dimension (volume).
232 citations
01 Jan 1982
203 citations
TL;DR: Under conditions of progressive hypoxia, oxygen transport was compared in bar-headed geese and Pekin ducks; the goose had a high oxygen affinity hemoglobin, compared with the duck; the oxyhemoglobin curves of both shifted slightly to the right as a result of acclimation to 5640 m; but only the duck developed erythrocytosis as a consequence of Acclimation.
200 citations
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403 citations
TL;DR: Oxygen intake, ventilation and heart rate were measured in six subjects performing ergometer exercise at various altitudes from sea level to 7,440 m (24,400 ft) (Bar. 300 mm Hg) during a Himalayan study.
Abstract: Oxygen intake, ventilation and heart rate were measured in six subjects performing ergometer exercise at various altitudes from sea level to 7,440 m (24,400 ft) (Bar. 300 mm Hg) during a Himalayan ...
237 citations
TL;DR: Before it can be determined whether a given patient with anemia has an adequate circulation, it is necessary to know how anemia per se affects the cardiovascular system and what level of cardiac output should be expected for a given hemoglobin concentration.
Abstract: Many patients with circulatory failure either from hemorrhage or heart failure have anemia. In these patients, the cardiac output may be within normal limits and yet the circulation may be inadequate. The question immediately arises as to what is the effect of anemia on the requirements of the tissues of the body for blood. Before it can be determined whether a given patient with anemia has an adequate circulation, it is necessary to know how anemia per se affects the cardiovascular system and what level of cardiac output should be expected for a given hemoglobin concentration. Studies on the circulation were, therefore, carried out on patients with chronic anemia in whom the picture was not complicated by shock and by the marked decrease in total blood volume which are so often present in the acute anemia produced by hemorrhage.
197 citations
131 citations
TL;DR: During activity increases in oxygen consumption at a given temperature were accompanied by increases in heart rate and AV difference, but stroke volume did not change consistently, and an hypothesis is presented concerning the function of the double systemic arches and incompletely divided ventricles of lizards.
Abstract: 1. Oxygen consumption, stroke volume, heart rate and the difference in oxygen contents of arterial and venous blood ( AV difference) were measured in the resting iguana at body temperatures of 20, 30 and 38° C. Oxygen consumption increased by a factor of 4.4 as temperature changed from 20 to 38° C. This increase was accomplished by a decrease in stroke volume by a factor of 0.5, and increases in heart rate and AV difference by factors of 4.1 and 2.2, respectively. 2. During activity increases in oxygen consumption at a given temperature were accompanied by increases in heart rate and AV difference, but stroke volume did not change consistently. 3. The percentage saturation of arterial blood with oxygen in the iguana may differ in the right and left systemic arches. In some lizards, both arches carried equally saturated blood, but in others the left arch carried blood containing less oxygen than the right arch. 4. An hypothesis is presented concerning the function of the double systemic arches and incompletely divided ventricles of lizards. These structures may be a device for permitting increased cardiac output associated with thermoregulation to bypass the lungs while maintaining a supply of well-oxygenated blood to the head. 5. Data on oxygen capacity, percentage saturation of blood with oxygen, haematocrit and pH of iguana blood are included in this study.
114 citations