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Aalkjær C, Wang T. The cardiovascular challenges in giraffes. J Muscle Res Cell Motil 2023; 44:53-60. [PMID: 35879488 DOI: 10.1007/s10974-022-09626-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 07/10/2022] [Indexed: 11/30/2022]
Abstract
Giraffes are the highest living animals on Earth and therefore are challenged by gravity more than any other species. In particular the cardiovascular system needs to adapt to this challenge. Giraffes have a mean blood pressure around 200 mmHg, which ensures a mean arterial pressure near the head of 100 mmHg when the giraffe is standing with the neck in a near vertical position. This immediately raises several questions. How do giraffes avoid edema in the legs where the arterial pressure is 300 mmHg or higher? How does the heart produce a pressure of 200 mmHg, and what is the energy required for this endeavor? How can the kidney tolerate a pressure of about 200 mmHg and does this mean that giraffes have a high glomerular filtration rate? What is the arterial pressure in the head of giraffes when they drink, and how is perfusion of the brain maintained when they lift their head after drinking? In this short review, we present some answers to these questions.
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Affiliation(s)
- Christian Aalkjær
- Department of Biomedicine, Aarhus University, 8000, Aarhus C, Denmark.
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - Tobias Wang
- Zoophysiology, Department of Biological Sciences, Aarhus University, 8000, Aarhus C, Denmark
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2
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A Preliminary Study on the Siphon Mechanism in Giraffe ( Giraffa camelopardalis). Animals (Basel) 2022; 12:ani12233348. [PMID: 36496868 PMCID: PMC9740075 DOI: 10.3390/ani12233348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Revised: 11/23/2022] [Accepted: 11/26/2022] [Indexed: 12/04/2022] Open
Abstract
Adult giraffes reach heights of 4.5 m with a heart-to-head distance of over 2 m, making cranial blood supply challenging. Ultrasound confirmed that the giraffe jugular vein collapses during head movement from ground level to fully erect, negating the possibility of a siphon mechanism in the neck. We showed that a short-length siphon structure over a simulated head-to-heart distance for a giraffe significantly influences flow in a collapsible tube. The siphon structure is determined according to brain case measurements. The short-length siphon structure in a shorter-necked ostrich showed no significant increase in flow. The shorter head-to-heart distance might be the reason for the lack of effect in ostriches. A siphon mechanism situated in the cranium is certainly possible, with a significant effect exerted on the amount of pressure the heart must generate to allow adequate cranial blood perfusion in a long-necked giraffe. The study validated that a cranial-bound siphon structure can operate and will be of significant value for adequate cranial blood perfusion in long-necked species such as giraffes and might also have existed in extinct species of long-necked dinosaurs.
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3
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Zhao Y, Seluanov A, Gorbunova V. Revelations About Aging and Disease from Unconventional Vertebrate Model Organisms. Annu Rev Genet 2021; 55:135-159. [PMID: 34416119 DOI: 10.1146/annurev-genet-071719-021009] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Aging is a major risk factor for multiple diseases. Understanding the underlying mechanisms of aging would help to delay and prevent age-associated diseases. Short-lived model organisms have been extensively used to study the mechanisms of aging. However, these short-lived species may be missing the longevity mechanisms that are needed to extend the lifespan of an already long-lived species such as humans. Unconventional long-lived animal species are an excellent resource to uncover novel mechanisms of longevity and disease resistance. Here, we review mechanisms that evolved in nonmodel vertebrate species to counteract age-associated diseases. Some antiaging mechanisms are conserved across species; however, various nonmodel species also evolved unique mechanisms to delay aging and prevent disease. This variety of antiaging mechanisms has evolved due to the remarkably diverse habitats and behaviors of these species. We propose that exploring a wider range of unconventional vertebrates will provide important resources to study antiaging mechanisms that are potentially applicable to humans.
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Affiliation(s)
- Yang Zhao
- Department of Biology, University of Rochester, Rochester, New York 14627, USA; ,
| | - Andrei Seluanov
- Department of Biology, University of Rochester, Rochester, New York 14627, USA; ,
| | - Vera Gorbunova
- Department of Biology, University of Rochester, Rochester, New York 14627, USA; ,
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4
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Natterson-Horowitz B, Baccouche BM, Mary J, Shivkumar T, Bertelsen MF, Aalkjær C, Smerup MH, Ajijola OA, Hadaya J, Wang T. Did giraffe cardiovascular evolution solve the problem of heart failure with preserved ejection fraction? EVOLUTION MEDICINE AND PUBLIC HEALTH 2021; 9:248-255. [PMID: 34447575 PMCID: PMC8385250 DOI: 10.1093/emph/eoab016] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 06/04/2021] [Indexed: 11/18/2022]
Abstract
The evolved adaptations of other species can be a source of insight for novel biomedical innovation. Limitations of traditional animal models for the study of some pathologies are fueling efforts to find new approaches to biomedical investigation. One emerging approach recognizes the evolved adaptations in other species as possible solutions to human pathology. The giraffe heart, for example, appears resistant to pathology related to heart failure with preserved ejection fraction (HFpEF)—a leading form of hypertension-associated cardiovascular disease in humans. Here, we postulate that the physiological pressure-induced left ventricular thickening in giraffes does not result in the pathological cardiovascular changes observed in humans with hypertension. The mechanisms underlying this cardiovascular adaptation to high blood pressure in the giraffe may be a bioinspired roadmap for preventive and therapeutic strategies for human HFpEF.
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Affiliation(s)
- Barbara Natterson-Horowitz
- Department of Medicine, Harvard Medical School, Boston, MA, USA.,Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA.,Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Basil M Baccouche
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA.,Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK
| | - Jennifer Mary
- Zoobiquity Research Initiative at UCLA, Los Angeles, CA 90024, USA
| | | | | | | | - Morten H Smerup
- Department of Cardiothoracic Surgery, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Olujimi A Ajijola
- UCLA Cardiac Arrhythmia Center, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Joseph Hadaya
- UCLA Cardiac Arrhythmia Center, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.,Molecular, Cellular and Integrative Physiology Program, UCLA, Los Angeles, CA, USA
| | - Tobias Wang
- Zoophysiology, Department of Biology, Aarhus University, Aarhus, Denmark
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5
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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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6
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Abstract
Gravity affects the physiology of many animals, and the effect is, for good reason, most pronounced in tall species. The physiology-in particular, cardiovascular function-of giraffes has therefore captivated the interest of physiologists for centuries. Several studies document high mean arterial blood pressure of giraffes of about 200 mm Hg. This appears necessary to establish a cerebral perfusion pressure on the order of 100 mm Hg at the cranial end of the carotid arteries. Here, we discuss the unique characteristics of blood vessels, the heart, and the kidney of giraffes and how these functional and structural adaptations are related to very high blood pressure. We also discuss how the cerebral circulation of giraffes is established and what we know about how the blood flow and arterial and venous pressures in giraffes change when they stop to drink and subsequently lift their heads 5-6 m in one sweeping movement.
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Affiliation(s)
- Christian Aalkjær
- Department of Biomedicine, Aarhus University, Aarhus C 8000, Denmark; .,Department of Biomedical Sciences, University of Copenhagen, Copenhagen 2200, Denmark
| | - Tobias Wang
- Department of Biology, Aarhus University, Aarhus C 8000, Denmark;
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7
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Horowitz BN, Kutinsky IB, Linde A. Species-Spanning Echocardiography: Cardiovascular Insights from Across the Animal Kingdom. Curr Cardiol Rep 2020; 22:165. [PMID: 33037937 DOI: 10.1007/s11886-020-01417-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/03/2020] [Indexed: 10/23/2022]
Abstract
PURPOSE OF REVIEW The objective of this review is to present comparative echocardiography as a source of insights for human cardiovascular medicine. RECENT FINDINGS We present echocardiographic examples of high impact human cardiovascular pathologies, including valvular, vascular, conduction, and myocardial disorders, in a wide range of species in varying environments. Unique features associated with comparative echocardiographic assessments are linked to human cardiology, including natural animal models of resistance and vulnerability. The cardiovascular vulnerabilities and strengths of other species can be a source of invaluable insights for human healthcare professionals. Echocardiography is playing a key role in bridging human and veterinary cardiology. Consequently, species-spanning echocardiography can deliver novel insights for human medicine.
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Affiliation(s)
- B N Horowitz
- Department of Medicine, Harvard Medical School, Boston, MA, USA. .,Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA. .,David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
| | - Ilana B Kutinsky
- William Beaumont School of Medicine, Oakland University, Rochester, MI, USA
| | - Annika Linde
- College of Veterinary Medicine, Western University of Health Sciences, Pomona, CA, USA
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8
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Michel JB. Phylogenic Determinants of Cardiovascular Frailty, Focus on Hemodynamics and Arterial Smooth Muscle Cells. Physiol Rev 2020; 100:1779-1837. [DOI: 10.1152/physrev.00022.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The evolution of the circulatory system from invertebrates to mammals has involved the passage from an open system to a closed in-parallel system via a closed in-series system, accompanying the increasing complexity and efficiency of life’s biological functions. The archaic heart enables pulsatile motion waves of hemolymph in invertebrates, and the in-series circulation in fish occurs with only an endothelium, whereas mural smooth muscle cells appear later. The present review focuses on evolution of the circulatory system. In particular, we address how and why this evolution took place from a closed, flowing, longitudinal conductance at low pressure to a flowing, highly pressurized and bifurcating arterial compartment. However, although arterial pressure was the latest acquired hemodynamic variable, the general teleonomy of the evolution of species is the differentiation of individual organ function, supported by specific fueling allowing and favoring partial metabolic autonomy. This was achieved via the establishment of an active contractile tone in resistance arteries, which permitted the regulation of blood supply to specific organ activities via its localized function-dependent inhibition (active vasodilation). The global resistance to viscous blood flow is the peripheral increase in frictional forces caused by the tonic change in arterial and arteriolar radius, which backscatter as systemic arterial blood pressure. Consequently, the arterial pressure gradient from circulating blood to the adventitial interstitium generates the unidirectional outward radial advective conductance of plasma solutes across the wall of conductance arteries. This hemodynamic evolution was accompanied by important changes in arterial wall structure, supported by smooth muscle cell functional plasticity, including contractility, matrix synthesis and proliferation, endocytosis and phagocytosis, etc. These adaptive phenotypic shifts are due to epigenetic regulation, mainly related to mechanotransduction. These paradigms actively participate in cardio-arterial pathologies such as atheroma, valve disease, heart failure, aneurysms, hypertension, and physiological aging.
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Lauridsen H, Gonzales S, Hedwig D, Perrin KL, Williams CJA, Wrege PH, Bertelsen MF, Pedersen M, Butcher JT. Extracting physiological information in experimental biology via Eulerian video magnification. BMC Biol 2019; 17:103. [PMID: 31831016 PMCID: PMC6907275 DOI: 10.1186/s12915-019-0716-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Accepted: 10/30/2019] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Videographic material of animals can contain inapparent signals, such as color changes or motion that hold information about physiological functions, such as heart and respiration rate, pulse wave velocity, and vocalization. Eulerian video magnification allows the enhancement of such signals to enable their detection. The purpose of this study is to demonstrate how signals relevant to experimental physiology can be extracted from non-contact videographic material of animals. RESULTS We applied Eulerian video magnification to detect physiological signals in a range of experimental models and in captive and free ranging wildlife. Neotenic Mexican axolotls were studied to demonstrate the extraction of heart rate signal of non-embryonic animals from dedicated videographic material. Heart rate could be acquired both in single and multiple animal setups of leucistic and normally colored animals under different physiological conditions (resting, exercised, or anesthetized) using a wide range of video qualities. Pulse wave velocity could also be measured in the low blood pressure system of the axolotl as well as in the high-pressure system of the human being. Heart rate extraction was also possible from videos of conscious, unconstrained zebrafish and from non-dedicated videographic material of sand lizard and giraffe. This technique also allowed for heart rate detection in embryonic chickens in ovo through the eggshell and in embryonic mice in utero and could be used as a gating signal to acquire two-phase volumetric micro-CT data of the beating embryonic chicken heart. Additionally, Eulerian video magnification was used to demonstrate how vocalization-induced vibrations can be detected in infrasound-producing Asian elephants. CONCLUSIONS Eulerian video magnification provides a technique to extract inapparent temporal signals from videographic material of animals. This can be applied in experimental and comparative physiology where contact-based recordings (e.g., heart rate) cannot be acquired.
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Affiliation(s)
- Henrik Lauridsen
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, 304 Weill Hall, Ithaca, NY 14853-7202 USA
- Department of Clinical Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
| | - Selina Gonzales
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, 304 Weill Hall, Ithaca, NY 14853-7202 USA
- California State University, 333 S Twin Oaks Valley Rd, San Marcos, CA 92096 USA
| | - Daniela Hedwig
- Cornell Lab of Ornithology, Cornell University, 159 Sapsucker Woods Road, Ithaca, NY 14850 USA
| | - Kathryn L. Perrin
- Center for Zoo and Wild Animal Health, Copenhagen Zoo, Roskildevej 32, 2000 Frederiksberg, Denmark
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Dyrlægevej 6, 1870 Frederiksberg C, Denmark
| | - Catherine J. A. Williams
- Center for Zoo and Wild Animal Health, Copenhagen Zoo, Roskildevej 32, 2000 Frederiksberg, Denmark
- Department of Bioscience, Aarhus University, C.F. Møllers Allé 3, 8000 Aarhus C, Denmark
| | - Peter H. Wrege
- Cornell Lab of Ornithology, Cornell University, 159 Sapsucker Woods Road, Ithaca, NY 14850 USA
| | - Mads F. Bertelsen
- Center for Zoo and Wild Animal Health, Copenhagen Zoo, Roskildevej 32, 2000 Frederiksberg, Denmark
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Dyrlægevej 6, 1870 Frederiksberg C, Denmark
| | - Michael Pedersen
- Department of Clinical Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
| | - Jonathan T. Butcher
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, 304 Weill Hall, Ithaca, NY 14853-7202 USA
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10
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Nielles-Vallespin S, Scott A, Ferreira P, Khalique Z, Pennell D, Firmin D. Cardiac Diffusion: Technique and Practical Applications. J Magn Reson Imaging 2019; 52:348-368. [PMID: 31482620 DOI: 10.1002/jmri.26912] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 08/13/2019] [Accepted: 08/14/2019] [Indexed: 12/12/2022] Open
Abstract
The 3D microarchitecture of the cardiac muscle underlies the mechanical and electrical properties of the heart. Cardiomyocytes are arranged helically through the depth of the wall, and their shortening leads to macroscopic torsion, twist, and shortening during cardiac contraction. Furthermore, cardiomyocytes are organized in sheetlets separated by shear layers, which reorientate, slip, and shear during macroscopic left ventricle (LV) wall thickening. Cardiac diffusion provides a means for noninvasive interrogation of the 3D microarchitecture of the myocardium. The fundamental principle of MR diffusion is that an MRI signal is attenuated by the self-diffusion of water in the presence of large diffusion-encoding gradients. Since water molecules are constrained by the boundaries in biological tissue (cell membranes, collagen layers, etc.), depicting their diffusion behavior elucidates the shape of the myocardial microarchitecture they are embedded in. Cardiac diffusion therefore provides a noninvasive means to understand not only the dynamic changes in cardiac microstructure of healthy myocardium during cardiac contraction but also the pathophysiological changes in the presence of disease. This unique and innovative technology offers tremendous potential to enable improved clinical diagnosis through novel microstructural and functional assessment. in vivo cardiac diffusion methods are immediately translatable to patients, opening new avenues for diagnostic investigation and treatment evaluation in a range of clinically important cardiac pathologies. This review article describes the 3D microstructure of the LV, explains in vivo and ex vivo cardiac MR diffusion acquisition and postprocessing techniques, as well as clinical applications to date. Level of Evidence: 1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019. J. Magn. Reson. Imaging 2020;52:348-368.
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Affiliation(s)
- Sonia Nielles-Vallespin
- Cardiovascular MR Unit, Royal Brompton And Harefield NHS Foundation Trust, London, UK.,NHLI, Imperial College of Science, Technology and Medicine, London, UK
| | - Andrew Scott
- Cardiovascular MR Unit, Royal Brompton And Harefield NHS Foundation Trust, London, UK.,NHLI, Imperial College of Science, Technology and Medicine, London, UK
| | - Pedro Ferreira
- Cardiovascular MR Unit, Royal Brompton And Harefield NHS Foundation Trust, London, UK.,NHLI, Imperial College of Science, Technology and Medicine, London, UK
| | - Zohya Khalique
- Cardiovascular MR Unit, Royal Brompton And Harefield NHS Foundation Trust, London, UK.,NHLI, Imperial College of Science, Technology and Medicine, London, UK
| | - Dudley Pennell
- Cardiovascular MR Unit, Royal Brompton And Harefield NHS Foundation Trust, London, UK.,NHLI, Imperial College of Science, Technology and Medicine, London, UK
| | - David Firmin
- Cardiovascular MR Unit, Royal Brompton And Harefield NHS Foundation Trust, London, UK.,NHLI, Imperial College of Science, Technology and Medicine, London, UK
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11
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Snelling EP, Seymour RS, Giussani DA, Fuller A, Maloney SK, Farrell AP, Mitchell D, George KP, Dzialowski EM, Jonker SS, Wube T. Scaling of cardiac morphology is interrupted by birth in the developing sheep Ovis aries. J Anat 2019; 235:96-105. [PMID: 30993709 DOI: 10.1111/joa.12990] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/05/2019] [Indexed: 11/28/2022] Open
Abstract
Scaling of the heart across development can reveal the degree to which variation in cardiac morphology depends on body mass. In this study, we assessed the scaling of heart mass, left and right ventricular masses, and ventricular mass ratio, as a function of eviscerated body mass across fetal and postnatal development in Horro sheep Ovis aries (~50-fold body mass range; N = 21). Whole hearts were extracted from carcasses, cleaned, dissected into chambers and weighed. We found a biphasic relationship when heart mass was scaled against body mass, with a conspicuous 'breakpoint' around the time of birth, manifest not by a change in the scaling exponent (slope), but rather a jump in the elevation. Fetal heart mass (g) increased with eviscerated body mass (Mb , kg) according to the power equation 4.90 Mb 0.88 ± 0.26 (± 95% CI ) , whereas postnatal heart mass increased according to 10.0 Mb 0.88 ± 0.10 . While the fetal and postnatal scaling exponents are identical (0.88) and reveal a clear dependence of heart mass on body mass, only the postnatal exponent is significantly less than 1.0, indicating the postnatal heart becomes a smaller component of body mass as the body grows, which is a pattern found frequently with postnatal cardiac development among mammals. The rapid doubling in heart mass around the time of birth is independent of any increase in body mass and is consistent with the normalization of wall stress in response to abrupt changes in volume loading and pressure loading at parturition. We discuss variation in scaling patterns of heart mass across development among mammals, and suggest that the variation results from a complex interplay between hard-wired genetics and epigenetic influences.
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Affiliation(s)
- Edward P Snelling
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
| | - Roger S Seymour
- School of Biological Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Dino A Giussani
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - Andrea Fuller
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
| | - Shane K Maloney
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, Gauteng, South Africa.,School of Human Sciences, University of Western Australia, Crawley, WA, Australia
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada.,Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, Canada
| | - Duncan Mitchell
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, Gauteng, South Africa.,School of Human Sciences, University of Western Australia, Crawley, WA, Australia
| | - Keith P George
- Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - Edward M Dzialowski
- Developmental Integrative Biology Research Group, Department of Biological Sciences, University of North Texas, Denton, TX, USA
| | - Sonnet S Jonker
- Knight Cardiovascular Institute, Oregon Health and Science University, Portland, OR, USA
| | - Tilaye Wube
- Department of Zoological Sciences, College of Natural and Computational Sciences, Addis Ababa University, Addis Ababa, Ethiopia
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12
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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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13
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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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14
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Sauer C, Clauss M, Bertelsen MF, Weisbjerg MR, Lund P. Rumen content stratification in the giraffe (Giraffa camelopardalis). Comp Biochem Physiol A Mol Integr Physiol 2017; 203:69-76. [DOI: 10.1016/j.cbpa.2016.08.033] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 08/30/2016] [Accepted: 08/30/2016] [Indexed: 11/16/2022]
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15
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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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16
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Williams EM. Giraffe Stature and Neck Elongation: Vigilance as an Evolutionary Mechanism. BIOLOGY 2016; 5:biology5030035. [PMID: 27626454 PMCID: PMC5037354 DOI: 10.3390/biology5030035] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/02/2016] [Accepted: 09/07/2016] [Indexed: 11/16/2022]
Abstract
Giraffe (Giraffa camelopardalis), with their long neck and legs, are unique amongst mammals. How these features evolved is a matter of conjecture. The two leading ideas are the high browse and the sexual-selection hypotheses. While both explain many of the characteristics and the behaviour of giraffe, neither is fully supported by the available evidence. The extended viewing horizon afforded by increased height and a need to maintain horizon vigilance, as a mechanism favouring the evolution of increased height is reviewed. In giraffe, vigilance of predators whilst feeding and drinking are important survival factors, as is the ability to interact with immediate herd members, young and male suitors. The evidence regarding giraffe vigilance behaviour is sparse and suggests that over-vigilance has a negative cost, serving as a distraction to feeding. In woodland savannah, increased height allows giraffe to see further, allowing each giraffe to increase the distance between its neighbours while browsing. Increased height allows the giraffe to see the early approach of predators, as well as bull males. It is postulated that the wider panorama afforded by an increase in height and longer neck has improved survival via allowing giraffe to browse safely over wider areas, decreasing competition within groups and with other herbivores.
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Affiliation(s)
- Edgar M Williams
- Faculty of Life Sciences and Education, University of South Wales, Wales CF37 1DL, UK; ; Tel.: +44-1443-483-893.
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17
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Hughes S, Barry J, Russell J, Bell R, Gurung S. Can giraffes be supersized? Response to ‘Why vascular siphons with sub-atmospheric pressures are physiologically impossible in sauropod dinosaurs’. J Exp Biol 2016; 219:2079-80. [DOI: 10.1242/jeb.141879] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 05/22/2016] [Indexed: 11/20/2022]
Affiliation(s)
- S. Hughes
- Queensland University of Technology, Gardens Point Campus, 2 George Street, Brisbane, QLD 4000, Australia
| | - J. Barry
- Queensland University of Technology, Gardens Point Campus, 2 George Street, Brisbane, QLD 4000, Australia
| | - J. Russell
- Royal Brisbane and Women's Hospital, Herston, Brisbane, QLD 4029, Australia
| | - R. Bell
- CSIRO Education, EcoSciences Precinct, 41 Boggo Road, Dutton Park, QLD 4102, Australia
| | - S. Gurung
- Paro College of Education, Royal University of Bhutan, Paro, Bhutan
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18
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Hughes S, Barry J, Russell J, Bell R, Gurung S. Neck length and mean arterial pressure in the sauropod dinosaurs. J Exp Biol 2016; 219:1154-61. [DOI: 10.1242/jeb.137448] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 02/07/2016] [Indexed: 11/20/2022]
Abstract
How blood was able to reach the heads of the long-necked sauropod dinosaurs has long been a matter of debate and several hypotheses have been presented. For example, it has been proposed that sauropods either had exceptionally large hearts, multiple ‘normal’ sized hearts spaced at regular intervals up the neck, held their necks horizontal, or the siphon effect was in operation. By means of an experimental model, we demonstrate that the siphon principle is able to explain how blood was able to adequately perfuse the sauropod brain. The return venous circulation may have been protected from complete collapse by a structure akin to the vertebral venous plexus. We derive an equation relating neck height and mean arterial pressure, which indicates that with a mean arterial pressure similar to the giraffe, the maximum safe vertical distance between heart and head would have been about 12 m. A hypothesis is presented that the maximum neck length in the fossil record is due to the siphon height limit. The equation indicates that to migrate over high ground, sauropods would either have had to significantly increase their mean arterial pressure or keep their necks below a certain height dependent on altitude.
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Affiliation(s)
- S. Hughes
- Biomedical Engineering and Medical Physics, School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology (QUT), 2 George St, Brisbane, Queensland 4000, Australia
| | - J. Barry
- School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology (QUT), 2 George St,Brisbane, Queensland 4000, Australia
| | - J. Russell
- Department of Neurosurgery, Royal Brisbane & Women's Hospital, Herston, Brisbane, Queensland 4029, Australia
| | - R. Bell
- CSIRO Education, EcoSciences Precinct, 41 Boggo Road, Dutton Park, Queensland 4102, Australia
| | - S. Gurung
- School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology (QUT), 2 George St, Brisbane, Queensland 4000, Australia and Paro College of Education, Royal University of Bhutan, Bhutan
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