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Filogonio R, Dubansky BD, Dubansky BH, Wang T, Elsey RM, Leite CAC, Crossley DA. Arterial wall thickening normalizes arterial wall tension with growth in American alligators, Alligator mississippiensis. J Comp Physiol B 2021; 191:553-562. [PMID: 33629153 DOI: 10.1007/s00360-021-01353-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 01/21/2021] [Accepted: 01/28/2021] [Indexed: 01/21/2023]
Abstract
Arterial wall tension increases with luminal radius and arterial pressure. Hence, as body mass (Mb) increases, associated increases in radius induces larger tension. Thus, it could be predicted that high tension would increase the potential for rupture of the arterial wall. Studies on mammals have focused on systemic arteries and have shown that arterial wall thickness increases with Mb and normalizes tension. Reptiles are good models to study scaling because some species exhibit large body size range associated with growth, thus, allowing for ontogenetic comparisons. We used post hatch American alligators, Alligator mississippiensis, ranging from 0.12 to 6.80 kg (~ 60-fold) to investigate how both the right aortic arch (RAo) and the left pulmonary artery (LPA) change with Mb. We tested two possibilities: (i) wall thickness increases with Mb and normalizes wall tension, such that stress (stress = tension/thickness) remains unchanged; (ii) collagen content scales with Mb and increases arterial strength. We measured heart rate and systolic and mean pressures from both systemic and pulmonary circulations in anesthetized animals. Once stabilized alligators were injected with adrenaline to induce a physiologically relevant increase in pressure. Heart rate decreased and systemic pressures increased with Mb; pulmonary pressures remained unchanged. Both the RAo and LPA were fixed under physiological hydrostatic pressures and displayed larger radius, wall tension and thickness as Mb increased, thus, stress was independent from Mb; relative collagen content was unchanged. We conclude that increased wall thickness normalizes tension and reduces the chances of arterial walls rupturing in large alligators.
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Affiliation(s)
- Renato Filogonio
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, SP, 13565-905, Brazil.
| | - Benjamin D Dubansky
- Department of Biological Sciences, Developmental Integrative Biology Cluster, University of North Texas, Denton, TX, 76203-5220, USA
| | - Brooke H Dubansky
- Department of Medical Laboratory Sciences and Public Health, Tarleton State University, Fort Worth, TX, USA
| | - Tobias Wang
- Section for Zoophysiology, Department of Biosciences, Aarhus University, 8000, Aarhus C, Denmark
| | - Ruth M Elsey
- Louisiana Department of Wildlife and Fisheries, Rockefeller Wildlife Refuge, Grand Chenier, LA, 70643, USA
| | - Cléo A C Leite
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, SP, 13565-905, Brazil
| | - Dane A Crossley
- Department of Biological Sciences, Developmental Integrative Biology Cluster, University of North Texas, Denton, TX, 76203-5220, USA
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Armelin VA, da Silva Braga VH, Guagnoni IN, Crestani AM, Abe AS, Florindo LH. Autonomic control of cardiovascular adjustments associated with orthostasis in the scansorial snake Boa constrictor. ACTA ACUST UNITED AC 2019; 222:jeb.197848. [PMID: 30760553 DOI: 10.1242/jeb.197848] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 02/04/2019] [Indexed: 11/20/2022]
Abstract
Orthostatic hypotension is a phenomenon triggered by a change in the position or posture of an animal, from a horizontal to a vertical head-up orientation, characterised by a blood pooling in the lower body and a reduction in central and cranial arterial blood pressure (P A). This hypotension elicits systemic vasoconstriction and tachycardia, which generally reduce blood pooling and increase P A Little is known about the mediation and importance of such cardiovascular adjustments that counteract the haemodynamic effects of orthostasis in ectothermic vertebrates, and some discrepancies exist in the information available on this subject. Thus, we sought to expand our knowledge on this issue by investigating it in a more elaborate way, through an in vivo pharmacological approach considering temporal circulatory changes during head-up body inclinations in unanaesthetised Boa constrictor To do so, we analysed temporal changes in P A, heart rate (f H) and cardiac autonomic tone associated with 30 and 60 deg inclinations, before and after muscarinic blockade with atropine, double blockade with atropine and propranolol, and α1-adrenergic receptor blockade with prazosin. Additionally, the animals' f H variability was analysed. The results revealed that, in B. constrictor: (1) the orthostatic tachycardia is initially mediated by a decrease in cholinergic tone followed by an increase in adrenergic tone, a pattern that may be evolutionarily conserved in vertebrates; (2) the orthostatic tachycardia is important for avoiding an intense decrease in P A at the beginning of body inclinations; and (3) α1-adrenergic orthostatic vasomotor responses are important for the maintenance of P A at satisfactory values during long-term inclinations.
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Affiliation(s)
- Vinicius Araújo Armelin
- Department of Zoology and Botany, São Paulo State University (UNESP), Rua Cristóvão Colombo, 2265, São José do Rio Preto, SP 15054-000, Brazil .,National Institute of Science and Technology in Comparative Physiology (INCT - FISC - FAPESP/CNPq), Rio Claro, SP 13506-900, Brazil
| | - Victor Hugo da Silva Braga
- Department of Zoology and Botany, São Paulo State University (UNESP), Rua Cristóvão Colombo, 2265, São José do Rio Preto, SP 15054-000, Brazil.,National Institute of Science and Technology in Comparative Physiology (INCT - FISC - FAPESP/CNPq), Rio Claro, SP 13506-900, Brazil
| | - Igor Noll Guagnoni
- Department of Zoology and Botany, São Paulo State University (UNESP), Rua Cristóvão Colombo, 2265, São José do Rio Preto, SP 15054-000, Brazil.,National Institute of Science and Technology in Comparative Physiology (INCT - FISC - FAPESP/CNPq), Rio Claro, SP 13506-900, Brazil
| | - Ariela Maltarolo Crestani
- Department of Zoology and Botany, São Paulo State University (UNESP), Rua Cristóvão Colombo, 2265, São José do Rio Preto, SP 15054-000, Brazil.,National Institute of Science and Technology in Comparative Physiology (INCT - FISC - FAPESP/CNPq), Rio Claro, SP 13506-900, Brazil
| | - Augusto Shinya Abe
- National Institute of Science and Technology in Comparative Physiology (INCT - FISC - FAPESP/CNPq), Rio Claro, SP 13506-900, Brazil.,Department of Zoology, São Paulo State University (UNESP), Avenida 24A, 1515, Rio Claro, SP 13506-900, Brazil.,Aquaculture Centre (CAUNESP), São Paulo State University (UNESP), Rodovia Prof. Paulo Donato Castellane, n/n, Jaboticabal, SP 14884-900, Brazil
| | - Luiz Henrique Florindo
- Department of Zoology and Botany, São Paulo State University (UNESP), Rua Cristóvão Colombo, 2265, São José do Rio Preto, SP 15054-000, Brazil .,National Institute of Science and Technology in Comparative Physiology (INCT - FISC - FAPESP/CNPq), Rio Claro, SP 13506-900, Brazil.,Aquaculture Centre (CAUNESP), São Paulo State University (UNESP), Rodovia Prof. Paulo Donato Castellane, n/n, Jaboticabal, SP 14884-900, Brazil
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Jensen B, H Smit T. Examples of Weak, If Not Absent, Form-Function Relations in the Vertebrate Heart. J Cardiovasc Dev Dis 2018; 5:E46. [PMID: 30205545 PMCID: PMC6162483 DOI: 10.3390/jcdd5030046] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 08/31/2018] [Accepted: 09/05/2018] [Indexed: 12/12/2022] Open
Abstract
That form and function are related is a maxim of anatomy and physiology. Yet, form-function relations can be difficult to prove. Human subjects with excessive trabeculated myocardium in the left ventricle, for example, are diagnosed with non-compaction cardiomyopathy, but the extent of trabeculations may be without relation to ejection fraction. Rather than rejecting a relation between form and function, we may ask whether the salient function is assessed. Is there a relation to electrical propagation, mean arterial blood pressure, or propensity to form blood clots? In addition, how should the extent of trabeculated muscle be assessed? While reviewing literature on trabeculated muscle, we applied Tinbergen's four types of causation-how does it work, why does it work, how is it made, and why did it evolve-to better parse what is meant by form and function. The paper is structured around cases that highlight advantages and pitfalls of applying Tinbergen's questions. It further uses the evolution of lunglessness in amphibians to argue that lung reduction impacts on chamber septation and it considers the evolution of an arterial outflow in fishes to argue that reductions in energy consumption may drive structural changes with little consequences to function. Concerning trabeculations, we argue they relate to pumping function in the embryo in the few weeks before the onset of coronary circulation. In human fetal and postnatal stages, a spectrum of trabeculated-to-compact myocardium makes no difference to cardiac function and in this period, form and function may appear unrelated.
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Affiliation(s)
- Bjarke Jensen
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, University of Amsterdam, Amsterdam UMC, Meibergdreef 15, 1105AZ Amsterdam, The Netherlands.
| | - Theodoor H Smit
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, University of Amsterdam, Amsterdam UMC, Meibergdreef 15, 1105AZ Amsterdam, The Netherlands.
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Troiano NM, Armelin VA, Braga VHDS, Abe AS, Rantin FT, Florindo LH. The autonomic control of upright posture tachycardia in the arboreal lizard Iguana iguana. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2018; 329:130-139. [PMID: 29992754 DOI: 10.1002/jez.2213] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 06/19/2018] [Accepted: 06/21/2018] [Indexed: 11/11/2022]
Abstract
In terrestrial environments, upright spatial orientation can dramatically influence animals' hemodynamics. Generally, large and elongated species are particularly sensitive to such influence due to the greater extent of their vascular beds being verticalized, favoring the establishment of blood columns in their bodies along with caudal blood pooling, and thus jeopardizing blood circulation through a cascade effect of reductions in venous return, cardiac filling, stroke volume, cardiac output, and arterial blood pressure. This hypotension triggers an orthostatic-(baroreflex)-tachycardia to normalize arterial pressure, and despite the extensive observation of this heart rate (fH ) adjustment in experiments on orthostasis, little is known about its mediation and importance in ectothermic vertebrates. In addition, most of the knowledge on this subject comes from studies on snakes. Thus, our objective was to expand the knowledge on this issue by investigating it in an arboreal lizard (Iguana iguana). To do so, we analyzed fH , cardiac autonomic tones, and fH variability in horizontalized and tilted iguanas (0°, 30°. and 60°) before and after muscarinic blockade with atropine and double autonomic blockade with atropine and propranolol. The results revealed that I. Iguana exhibits significant orthostatic-tachycardia only at 60o inclinations-a condition that is primarily elicited by a withdrawal of vagal drive. Also, as in humans, increases in low-frequency fH oscillations and decreases in high-frequency fH oscillations were observed along with orthostatic-tachycardia, suggesting that the mediation of this fH adjustment may be evolutionarily conserved in vertebrates.
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Affiliation(s)
- Natalia Miriã Troiano
- Department of Zoology and Botany, São Paulo State University (UNESP), São José do Rio Preto, Brazil
- National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq), Rio Claro, Brazil
| | - Vinicius Araújo Armelin
- Department of Zoology and Botany, São Paulo State University (UNESP), São José do Rio Preto, Brazil
- National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq), Rio Claro, Brazil
| | - Victor Hugo da Silva Braga
- Department of Zoology and Botany, São Paulo State University (UNESP), São José do Rio Preto, Brazil
- National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq), Rio Claro, Brazil
| | - Augusto Shinya Abe
- National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq), Rio Claro, Brazil
- Department of Zoology, São Paulo State University (UNESP), Rio Claro, Brazil
- Aquaculture Center (CAUNESP), São Paulo State University (UNESP), Jaboticabal, Brazil
| | - Francisco Tadeu Rantin
- National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq), Rio Claro, Brazil
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, Brazil
| | - Luiz Henrique Florindo
- Department of Zoology and Botany, São Paulo State University (UNESP), São José do Rio Preto, Brazil
- National Institute of Science and Technology in Comparative Physiology (INCT-FAPESP/CNPq), Rio Claro, Brazil
- Aquaculture Center (CAUNESP), São Paulo State University (UNESP), Jaboticabal, Brazil
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Poulsen CB, Wang T, Assersen K, Iversen NK, Damkjaer M. Does mean arterial blood pressure scale with body mass in mammals? Effects of measurement of blood pressure. Acta Physiol (Oxf) 2018; 222:e13010. [PMID: 29210189 DOI: 10.1111/apha.13010] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2017] [Revised: 11/28/2017] [Accepted: 11/28/2017] [Indexed: 01/21/2023]
Abstract
For at least the last 30 years, it has been discussed whether mean arterial blood pressure (MAP) is independent of body mass or whether it increases in accordance with the vertical height between the heart and the brain. The debate has centred on the most appropriate mathematical models for analysing allometric scaling and phylogenetic relationships; there has been previously little focus on evaluating the validity of underlying physiological data. Currently, the 2 most comprehensive scaling analyses are based on data from 47 species of mammals, based on 114 references. We reviewed all available references to determine under which physiological conditions MAP had been recorded. In 44 (38.6%) of the cited references, MAP was measured in anaesthetized animals. Data from conscious animals were reported in 59 (51.8%) of references; of these, 3 (2.6%) were radiotelemetric studies. In 5 species, data were reported from both anaesthetized and conscious animals, and the mean difference in the MAP between these settings was 20 ± 29 mm Hg. From a literature search, we identified MAP measurements performed by radiotelemetry in 11 of the 47 species included in the meta-analyses. A Bland-Altman analysis showed a bias of 1 mm Hg with 95% confidence interval (from -35 to 36 mm Hg); that is, the limits of agreement between radiotelemetric studies and studies in restrained animals were double the supposed difference in the MAP between the mouse and elephant. In conclusion, the existing literature does not provide evidence for either a positive or neutral scaling of arterial pressure to body mass across taxa.
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Affiliation(s)
- C. B. Poulsen
- Department of Cardiology; Regional Hospital West Jutland; Herning Denmark
| | - T. Wang
- Department of Zoophysiology; Aarhus University; Aarhus Denmark
| | - K. Assersen
- Department of Cardiovascular and Renal Research; University of Southern Denmark; Odense Denmark
| | - N. K. Iversen
- Department of Zoophysiology; Aarhus University; Aarhus Denmark
- Center for Functionally Integrative Neuroscience; Institute of Clinical Medicine; Aarhus University; Aarhus C Denmark
| | - M. Damkjaer
- Department of Cardiovascular and Renal Research; University of Southern Denmark; Odense Denmark
- Department of Paediatrics; Kolding Hospital; Kolding Denmark
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The influence of midazolam on heart rate arises from cardiac autonomic tones alterations in Burmese pythons, Python molurus. Auton Neurosci 2017; 208:103-112. [PMID: 29104018 DOI: 10.1016/j.autneu.2017.10.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 10/25/2017] [Accepted: 10/25/2017] [Indexed: 11/22/2022]
Abstract
The GABAA receptor agonist midazolam is a compound widely used as a tranquilizer and sedative in mammals and reptiles. It is already known that this benzodiazepine produces small to intermediate heart rate (HR) alterations in mammals, however, its influence on reptiles' HR remains unexplored. Thus, the present study sought to verify the effects of midazolam on HR and cardiac modulation in the snake Python molurus. To do so, the snakes' HR, cardiac autonomic tones, and HR variability were evaluated during four different experimental stages. The first stage consisted on the data acquisition of animals under untreated conditions, in which were then administered atropine (2.5mgkg-1; intraperitoneal), followed later by propranolol (3.5mgkg-1; intraperitoneal) (cardiac double autonomic blockade). The second stage focused on the data acquisition of animals under midazolam effect (1.0mgkg-1; intramuscular), which passed through the same autonomic blockade protocol of the first stage. The third and fourth stages consisted of the same protocol of stages one and two, respectively, with the exception that atropine and propranolol injections were reversed. By comparing the HR of animals that received midazolam (second and fourth stages) with those that did not (first and third stages), it could be observed that this benzodiazepine reduced the snakes' HR by ~60%. The calculated autonomic tones showed that such cardiac depression was elicited by an ~80% decrease in cardiac adrenergic tone and an ~620% increase in cardiac cholinergic tone - a finding that was further supported by the results of HR variability analysis.
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Lillywhite HB, Lillywhite SM. Ontogenetic shifts of heart position in snakes. J Morphol 2017; 278:1105-1113. [PMID: 28470824 DOI: 10.1002/jmor.20697] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 04/10/2017] [Accepted: 04/16/2017] [Indexed: 11/07/2022]
Abstract
Heart position relative to total body length (TL) varies among snakes, with anterior hearts in arboreal species and more centrally located hearts in aquatic or ground-dwelling species. Anterior hearts decrease the cardiac work associated with cranial blood flow and minimize drops in cranial pressure and flow during head-up climbing. Here, we investigate whether heart position shifts intraspecifically during ontogenetic increases in TL. Insular Florida cottonmouth snakes, Agkistrodon conanti, are entirely ground-dwelling and have a mean heart position that is 33.32% TL from the head. In contrast, arboreal rat snakes, Pantherophis obsoleta, of similar lengths have a mean heart position that is 17.35% TL from the head. In both species, relative heart position shifts craniad during ontogeny, with negative slopes = -.035 and -.021% TL/cm TL in Agkistrodon and Pantherophis, respectively. Using a large morphometric data set available for Agkistrodon (N = 192 individuals, 23-140 cm TL), we demonstrate there is an anterior ontogenetic shift of the heart position within the trunk (= 4.56% trunk length from base of head to cloacal vent), independent of head and tail allometry which are both negative. However, in longer snakes > 100 cm, the heart position reverses and shifts caudally in longer Agkistrodon but continues toward the head in longer individuals of Pantherophis. Examination of data sets for two independent lineages of fully marine snakes (Acrochordus granulatus and Hydrophis platurus), which do not naturally experience postural gravity stress, demonstrate both ontogenetic patterns for heart position that are seen in the terrestrial snakes. The anterior migration of the heart is greater in the terrestrial species, even if TL is standardized to that of the longer P. obsoleta, and compensates for about 5 mmHg gravitational pressure head if they are fully upright.
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Affiliation(s)
- Harvey B Lillywhite
- Department of Biology, University of Florida, Gainesville, Florida, 32611-8525
| | - Steven M Lillywhite
- IMPA (Instituto de Matemática Pura e Aplicada), Estrada Dona Castorina, 110, Rio de Janeiro, RJ, 22460-320, Brazil
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Affiliation(s)
- James E. Bogan
- The Critter Fixer of Central Florida, LLC, 83 Geneva Drive, 621679, Oviedo, FL 32765, USA
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Abstract
Cardiovascular function in dinosaurs can be inferred from fossil evidence with knowledge of how metabolic rate, blood flow rate, blood pressure, and heart size are related to body size in living animals. Skeletal stature and nutrient foramen size in fossil femora provide direct evidence of a high arterial blood pressure, a large four-chambered heart, a high aerobic metabolic rate, and intense locomotion. But was the heart of a huge, long-necked sauropod dinosaur able to pump blood up 9 m to its head?
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Affiliation(s)
- Roger S. Seymour
- School of Biological Sciences, University of Adelaide, Adelaide, Australia
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Poulsen CB, Damkjær M, Hald BO, Wang T, Holstein-Rathlou NH, Jacobsen JCB. Vascular flow reserve as a link between long-term blood pressure level and physical performance capacity in mammals. Physiol Rep 2016; 4:4/11/e12813. [PMID: 27255360 PMCID: PMC4908491 DOI: 10.14814/phy2.12813] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 04/18/2016] [Indexed: 11/24/2022] Open
Abstract
Mean arterial pressure (MAP) is surprisingly similar across different species of mammals, and it is, in general, not known which factors determine the arterial pressure level. Mammals often have a pronounced capacity for sustained physical performance. This capacity depends on the vasculature having a flow reserve that comes into play as tissue metabolism increases. We hypothesize that microvascular properties allowing for a large vascular flow reserve is linked to the level of the arterial pressure.To study the interaction between network properties and network inlet pressure, we developed a generic and parsimonious computational model of a bifurcating microvascular network where diameter and growth of each vessel evolves in response to changes in biomechanical stresses. During a simulation, the network develops well-defined arterial and venous vessel characteristics. A change in endothelial function producing a high precapillary resistance and thus a high vascular flow reserve is associated with an increase in network inlet pressure. Assuming that network properties are independent of body mass, and that inlet pressure of the microvascular network is a proxy for arterial pressure, the study provides a conceptual explanation of why high performing animals tend to have a high MAP.
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Affiliation(s)
- Christian B Poulsen
- Department of Cardiology, Aarhus University Hospital, Aarhus N, Denmark Department of Clinical Medicine, Aarhus University, Aarhus N, Denmark
| | - Mads Damkjær
- Hans Christian Andersen Children's Hospital, Odense University Hospital, Odense C, Denmark
| | - Bjørn O Hald
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Tobias Wang
- Department of Zoophysiology, Aarhus University, Aarhus, Denmark
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Autonomic control of heart rate during orthostasis and the importance of orthostatic-tachycardia in the snake Python molurus. J Comp Physiol B 2014; 184:903-12. [DOI: 10.1007/s00360-014-0841-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 06/10/2014] [Accepted: 06/20/2014] [Indexed: 10/25/2022]
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