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Starck JM, Wyneken J. Comparative and Functional Anatomy of the Ectothermic Sauropsid Heart. Vet Clin North Am Exot Anim Pract 2022; 25:337-366. [PMID: 35422257 DOI: 10.1016/j.cvex.2022.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The heart development, form, and functional specializations of chelonians, squamates, crocodilians, and birds characterize how diverse structure and specializations arise from similar foundations. This review aims to summarize the morphologic diversity of sauropsid hearts and present it in an integrative functional and phylogenetic context. Besides the detailed morphologic descriptions, the integrative view of function, evolution, and development will aid understanding of the surprising diversity of sauropsid hearts. This integrated perspective is a foundation that strengthens appreciation that the sauropsid hearts are the outcome of biological evolution; disease often is linked to arising mismatch between adaptations and modern environments.
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Affiliation(s)
- J Matthias Starck
- Department of Biology, Ludwig-Maximilians-University Munich, Planegg-Martinsried D82152, Germany.
| | - Jeanette Wyneken
- Florida Atlantic University, FAU Marine Lab at Gumbo Limbo Environmental Complex, Boca Raton, FL 33431-0991, USA
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2
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Mitova E, Wittnich C. Cardiac Structures in Marine Animals Provide Insight on Potential Directions for Interventions for Pediatric Congenital Heart Defects. Am J Physiol Heart Circ Physiol 2021; 322:H1-H7. [PMID: 34652986 DOI: 10.1152/ajpheart.00451.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Despite recent advances in pediatric diagnosis and surgical intervention, mortality and morbidity continue to be a prevalent issue in both Tetralogy of Fallot (ToF) and Hypoplastic Left Heart Syndrome (HLHS). Therefore, novel approaches to studying both of these conditions is warranted. Investigating cardiac anatomical features of different species in the animal kingdom similar to the defects and complications present in ToF and HLHS (as well as others) could serve as a new avenue for improving the management of congenital heart diseases (CHD). This review reveals that although structures found in HLHS and ToF are pathological, similar structures are found in diving mammals and reptiles that are adaptive. Pathologic aortic dilation in CHD resembles the aortic bulb present in diving mammals, but the latter is more elastic and distensible compared to the former. The unrepaired HLHS heart resembles the univentricular heart of non-crocodilian reptiles. Right ventricle hypertrophy is pathological in HLHS and ToF, but adaptive in crocodilians and diving mammals. Lastly, the increased pulmonary resistance due to pulmonary stenosis in ToF is comparable to increased pulmonary resistance in crocodilians due to the presence of an active valve proximal to the pulmonary valve. Some of these anatomical structures could potentially be adapted for palliative surgery in children with HLHS or ToF. Moreover, further investigating the underlying molecular signals responsible for the adaptive tissue responses seen in other species may also be useful for developing novel strategies for preventing some of the complications that occur after surgical repair in both of these CHDs.
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Affiliation(s)
- Emilia Mitova
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Carin Wittnich
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada.,Department of Surgery, University of Toronto, Toronto, Ontario, Canada
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3
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EFFECT OF BODY POSITION ON ECHOCARDIOGRAPHIC PARAMETERS IN PRAIRIE RATTLESNAKES ( CROTALUS VIRIDIS). J Zoo Wildl Med 2021; 52:742-748. [PMID: 34130421 DOI: 10.1638/2020-0167] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/13/2021] [Indexed: 11/21/2022] Open
Abstract
Echocardiography is a noninvasive diagnostic tool that can provide instantaneous information about cardiac function, but it is uncommonly used by veterinarians to assess reptilian patients. Echocardiograms were performed on 14 clinically healthy, adult prairie rattlesnakes (Crotalus viridis), and cardiac measurements were taken in a horizontal and vertical position. Cardiac parameters including ventricular volume in systole and diastole, as well as the diameter of the left atrium, pulmonary artery, and paired left and right aortic arches were obtained. No evidence of cardiac disease was noted in any of the study animals. Males had a greater percentage of ventricular volume change (VVC) than females in the vertical position (P = 0.043). The percentage of ventricular volume change was significantly lower in the horizontal compared with the vertical position (P = 0.032) and was not different by sex. For the short-axis views, the right atrial diameter and short-axis ventricular area in diastole and systole were significantly smaller in snakes in the vertical compared with the horizontal position. This study is the first to obtain echocardiographic measurements in North American vipers and adds to the understanding of techniques used to evaluate the cardiac function of these species.
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Rocha GC, Castro SA, Taylor EW, Tavares D, Leite CAC. A Decerebrate Preparation of the Rattlesnake, Crotalus durissus, Provides an Experimental Model for Study of Autonomic Modulation of the Cardiovascular System in Reptiles. Physiol Biochem Zool 2021; 94:269-285. [PMID: 34142933 DOI: 10.1086/714973] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AbstractThe South American rattlesnake, Crotalus durissus, has been successfully used as an experimental model to study control of the cardiovascular system in squamate reptiles. Recent technical advances, including equipment miniaturization, have lessened the impact of instrumentation on in vivo recordings, and an increased range of anesthetic drugs has improved recording conditions for in situ preparations. Nevertheless, any animal-based experimental approach has to manage limitations regarding the avoidance of pain and stress the stability of the preparation and duration of experiments and the potentially overriding effects of anesthesia. To address such aspects, we tested a new experimental preparation, the decerebrate rattlesnake, in a study of the autonomic control of cardiovascular responses following the removal of general anesthesia. The preparation exhibited complex cardiovascular adjustments to deal with acute increases in venous return (caused by tail lifting), to compensate for blood flow reduction in the cephalic region (caused by head lifting), for body temperature control (triggered by an external heating source), and in response to stimulation of chemoreceptors (triggered by intravenous injection of NaCN). The decerebrate preparation retained extensive functional integrity of autonomic centers, and it was suitable for monitoring diverse cardiac and vascular variables. Furthermore, reanesthetizing the preparation markedly blunted cardiovascular performance. Isoflurane limited the maintenance of recovered cardiovascular variables in the prepared animal and reduced or abolished the observed cardiovascular reflexes. This preparation enables the recording of multiple concomitant cardiovascular variables for the study of mechanistic questions regarding the central integration of autonomic reflex responses in the absence of anesthesia.
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Sanches PVW, Taylor EW, Duran LM, Cruz AL, Dias DPM, Leite CAC. Respiratory sinus arrhythmia is a major component of heart rate variability in undisturbed, remotely monitored rattlesnakes, Crotalus durissus. ACTA ACUST UNITED AC 2019; 222:jeb.197954. [PMID: 30967516 DOI: 10.1242/jeb.197954] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 04/05/2019] [Indexed: 11/20/2022]
Abstract
ECG recordings were obtained using an implanted telemetry device from the South American rattlesnake, Crotalus durissus, held under stable conditions without restraining cables or interaction with researchers. Mean heart rate (f H) recovered rapidly (<24 h) from anaesthesia and operative procedures. This preceded a more gradual development of heart rate variability (HRV), with instantaneous f H increasing during each lung ventilation cycle. Atropine injection increased mean f H and abolished HRV. Complete autonomic blockade revealed a cholinergic tonus on the heart of 55% and an adrenergic tonus of 37%. Power spectral analysis of HRV identified a peak at the same frequency as ventilation. This correlation was sustained after temperature changes and it was more evident, marked by a more prominent power spectrum peak, when ventilation is less episodic. This HRV component is homologous to that observed in mammals, termed respiratory sinus arrhythmia (RSA). Evidence for instantaneous control of f H indicated rapid conduction of activity in the cardiac efferent nervous supply, as supported by the description of myelinated fibres in the cardiac vagus. Establishment of HRV 10 days after surgical intervention seems a reliable indicator of the re-establishment of control of integrative functions by the autonomic nervous system. We suggest that this criterion could be applied to other animals exposed to natural or imposed trauma, thus improving protocols involving animal handling, including veterinarian procedures.
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Affiliation(s)
- Pollyana V W Sanches
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, 13565-905 São Paulo, Brazil.,National Institute of Science and Technology in Comparative Physiology (INCT - FISC - FAPESP/CNPq), Rio Claro, SP 13506-900, Brazil
| | - Edwin W Taylor
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, 13565-905 São Paulo, Brazil.,School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Livia M Duran
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, 13565-905 São Paulo, Brazil.,National Institute of Science and Technology in Comparative Physiology (INCT - FISC - FAPESP/CNPq), Rio Claro, SP 13506-900, Brazil
| | - André L Cruz
- National Institute of Science and Technology in Comparative Physiology (INCT - FISC - FAPESP/CNPq), Rio Claro, SP 13506-900, Brazil.,Institute of Biology, Federal University of Bahia (UFBA), Salvador, 40140-310 Bahia, Brazil
| | - Daniel P M Dias
- Barão de Mauá University Center, Ribeirão Preto, 14090-180 São Paulo, Brazil
| | - Cleo A C Leite
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, 13565-905 São Paulo, Brazil .,National Institute of Science and Technology in Comparative Physiology (INCT - FISC - FAPESP/CNPq), Rio Claro, SP 13506-900, Brazil
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Jensen B. Commemoration of Comparative Cardiac Anatomy of the Reptilia I-IV. J Morphol 2019; 280:623-626. [PMID: 30741427 PMCID: PMC6594047 DOI: 10.1002/jmor.20964] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 01/28/2019] [Accepted: 02/01/2019] [Indexed: 12/13/2022]
Abstract
Our understanding of the anatomy of hearts of ectothermic saurosids, or colloquially “reptiles”, was much advanced by the publication of the series of four papers under the heading of Comparative Cardiac Anatomy of the Reptilia in Journal of Morphology between 1971 and 1981. Here, I commemorate the papers, show how they moved our understanding forwards, and briefly describe the state‐of‐the‐art.
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Affiliation(s)
- Bjarke Jensen
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, University of Amsterdam, Amsterdam UMC, Amsterdam, The Netherlands
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MacIver DH, Stephenson RS, Jensen B, Agger P, Sánchez-Quintana D, Jarvis JC, Partridge JB, Anderson RH. The end of the unique myocardial band: Part I. Anatomical considerations. Eur J Cardiothorac Surg 2018; 53:112-119. [PMID: 28958005 DOI: 10.1093/ejcts/ezx290] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2017] [Accepted: 07/18/2017] [Indexed: 01/04/2023] Open
Abstract
The concept of the 'unique myocardial band', which proposes that the ventricular myocardial cone is arranged like skeletal muscle, provides an attractive framework for understanding haemodynamics. The original idea was developed by Francisco Torrent-Guasp. Using boiled hearts and blunt dissection, Torrent-Guasp created a single band of ventricular myocardium extending from the pulmonary trunk to the aortic root, with the band thus constructed encircling both ventricular cavities. Cooked hearts can, however, be dissected in many ways. In this review, we show that the band does not exist as an anatomical entity with defined borders. On the contrary, the ventricular cardiomyocytes are aggregated end to end and by their branching produce an intricate meshwork. Across the thickness of the left ventricular wall, the chains of cardiomyocytes exhibit a gradually changing helical angle, with a circumferential zone formed in the middle. There is no abrupt change in helical angle, as could be expected if the wall was constructed of opposing limbs of a single wrapped band, nor does the long axis of the cardiomyocytes consistently match with the long axis of the unique myocardial band. There are, furthermore, no connective tissue structures that could be considered to demarcate its purported boundaries. The unique myocardial band should be consistent with evolution, and although the ventricular wall of fish and reptiles has one or several distinct layers, a single band is not found. In 1965, Lev and Simpkins cautioned that the ventricular muscle mass of a cooked heart can be dissected almost at the whim of the anatomist. We suggest that the unique myocardial band should have ended there.
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Affiliation(s)
- David H MacIver
- Department of Cardiology, Taunton and Somerset Hospital, Musgrove Park, Taunton, UK.,Medical Education, University of Bristol, Senate House, Tyndall Avenue, Bristol, UK.,Biological Physics Group, School of Physics and Astronomy, University of Manchester, Manchester, UK
| | - Robert S Stephenson
- Comparative Medicine Lab, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Bjarke Jensen
- Department of Medical Biology, Academic Medical Center, Amsterdam University, Netherlands
| | - Peter Agger
- Department of Paediatrics, Aarhus University Hospital, Denmark
| | - Damián Sánchez-Quintana
- Department of Anatomy and Cell Biology, Faculty of Medicine, University of Extremadura, Badajoz, Spain
| | - Jonathan C Jarvis
- Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - John B Partridge
- Eurobodalla Unit, Rural Clinical School of the ANU College of Medicine, Biology and Environment, Batemans Bay, NSW, Australia
| | - Robert H Anderson
- Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne, UK
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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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9
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Vagal tone regulates cardiac shunts during activity and at low temperatures in the South American rattlesnake, Crotalus durissus. J Comp Physiol B 2016; 186:1059-1066. [DOI: 10.1007/s00360-016-1008-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 05/18/2016] [Accepted: 06/03/2016] [Indexed: 11/26/2022]
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Jensen B, Elfwing M, Elsey RM, Wang T, Crossley DA. Coronary blood flow in the anesthetized American alligator ( Alligator mississippiensis ). Comp Biochem Physiol A Mol Integr Physiol 2016; 191:44-52. [DOI: 10.1016/j.cbpa.2015.09.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 09/06/2015] [Accepted: 09/24/2015] [Indexed: 12/13/2022]
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11
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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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12
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Leite CAC, Wang T, Taylor EW, Abe AS, Leite GSPC, de Andrade DOV. Loss of the Ability to Control Right-to-Left Shunt Does Not Influence the Metabolic Responses to Temperature Change or Long-Term Fasting in the South American Rattlesnake Crotalus durissus. Physiol Biochem Zool 2014; 87:568-75. [DOI: 10.1086/675863] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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13
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Burggren WW, Christoffels VM, Crossley DA, Enok S, Farrell AP, Hedrick MS, Hicks JW, Jensen B, Moorman AFM, Mueller CA, Skovgaard N, Taylor EW, Wang T. Comparative cardiovascular physiology: future trends, opportunities and challenges. Acta Physiol (Oxf) 2014; 210:257-76. [PMID: 24119052 DOI: 10.1111/apha.12170] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 07/16/2013] [Accepted: 09/12/2013] [Indexed: 12/23/2022]
Abstract
The inaugural Kjell Johansen Lecture in the Zoophysiology Department of Aarhus University (Aarhus, Denmark) afforded the opportunity for a focused workshop comprising comparative cardiovascular physiologists to ponder some of the key unanswered questions in the field. Discussions were centred around three themes. The first considered function of the vertebrate heart in its various forms in extant vertebrates, with particular focus on the role of intracardiac shunts, the trabecular ('spongy') nature of the ventricle in many vertebrates, coronary blood supply and the building plan of the heart as revealed by molecular approaches. The second theme involved the key unanswered questions in the control of the cardiovascular system, emphasizing autonomic control, hypoxic vasoconstriction and developmental plasticity in cardiovascular control. The final theme involved poorly understood aspects of the interaction of the cardiovascular system with the lymphatic, renal and digestive systems. Having posed key questions around these three themes, it is increasingly clear that an abundance of new analytical tools and approaches will allow us to learn much about vertebrate cardiovascular systems in the coming years.
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Affiliation(s)
- W. W. Burggren
- Developmental Integrative Biology Cluster; Department of Biological Sciences; University of North Texas; Denton TX USA
| | - V. M. Christoffels
- Department of Anatomy, Embryology & Physiology; Academic Medical Centre; Amsterdam The Netherlands
| | - D. A. Crossley
- Developmental Integrative Biology Cluster; Department of Biological Sciences; University of North Texas; Denton TX USA
| | - S. Enok
- Zoophysiology; Department of Bioscience; Aarhus University; Aarhus Denmark
| | - A. P. Farrell
- Department of Zoology and Faculty of Land and Food Systems; University of British Columbia; Vancouver BC Canada
| | - M. S. Hedrick
- Developmental Integrative Biology Cluster; Department of Biological Sciences; University of North Texas; Denton TX USA
| | - J. W. Hicks
- Department of Ecology and Evolutionary Biology; University of California; Irvine CA USA
| | - B. Jensen
- Department of Anatomy, Embryology & Physiology; Academic Medical Centre; Amsterdam The Netherlands
- Zoophysiology; Department of Bioscience; Aarhus University; Aarhus Denmark
| | - A. F. M. Moorman
- Department of Anatomy, Embryology & Physiology; Academic Medical Centre; Amsterdam The Netherlands
| | - C. A. Mueller
- Developmental Integrative Biology Cluster; Department of Biological Sciences; University of North Texas; Denton TX USA
| | - N. Skovgaard
- Zoophysiology; Department of Bioscience; Aarhus University; Aarhus Denmark
| | - E. W. Taylor
- School of Biosciences; University of Birmingham; Birmingham UK
| | - T. Wang
- Zoophysiology; Department of Bioscience; Aarhus University; Aarhus Denmark
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Jensen B, Moorman AFM, Wang T. Structure and function of the hearts of lizards and snakes. Biol Rev Camb Philos Soc 2013; 89:302-36. [DOI: 10.1111/brv.12056] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 06/26/2013] [Accepted: 07/30/2013] [Indexed: 12/20/2022]
Affiliation(s)
- Bjarke Jensen
- Department of Bioscience, Zoophysiology; Aarhus University; Aarhus C 8000 Denmark
- Department of Anatomy, Embryology & Physiology, Academic Medical Center; University of Amsterdam; Amsterdam 1105 The Netherlands
| | - Antoon F. M. Moorman
- Department of Anatomy, Embryology & Physiology, Academic Medical Center; University of Amsterdam; Amsterdam 1105 The Netherlands
| | - Tobias Wang
- Department of Bioscience, Zoophysiology; Aarhus University; Aarhus C 8000 Denmark
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Jensen B, van den Berg G, van den Doel R, Oostra RJ, Wang T, Moorman AFM. Development of the hearts of lizards and snakes and perspectives to cardiac evolution. PLoS One 2013; 8:e63651. [PMID: 23755108 PMCID: PMC3673951 DOI: 10.1371/journal.pone.0063651] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 04/04/2013] [Indexed: 12/16/2022] Open
Abstract
Birds and mammals both developed high performance hearts from a heart that must have been reptile-like and the hearts of extant reptiles have an unmatched variability in design. Yet, studies on cardiac development in reptiles are largely old and further studies are much needed as reptiles are starting to become used in molecular studies. We studied the growth of cardiac compartments and changes in morphology principally in the model organism corn snake (Pantherophis guttatus), but also in the genotyped anole (Anolis carolinenis and A. sagrei) and the Philippine sailfin lizard (Hydrosaurus pustulatus). Structures and chambers of the formed heart were traced back in development and annotated in interactive 3D pdfs. In the corn snake, we found that the ventricle and atria grow exponentially, whereas the myocardial volumes of the atrioventricular canal and the muscular outflow tract are stable. Ventricular development occurs, as in other amniotes, by an early growth at the outer curvature and later, and in parallel, by incorporation of the muscular outflow tract. With the exception of the late completion of the atrial septum, the adult design of the squamate heart is essentially reached halfway through development. This design strongly resembles the developing hearts of human, mouse and chicken around the time of initial ventricular septation. Subsequent to this stage, and in contrast to the squamates, hearts of endothermic vertebrates completely septate their ventricles, develop an insulating atrioventricular plane, shift and expand their atrioventricular canal toward the right and incorporate the systemic and pulmonary venous myocardium into the atria.
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Affiliation(s)
- Bjarke Jensen
- Department of Bioscience-Zoophysiology, Aarhus University, Aarhus, Denmark.
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Leite CAC, Taylor EW, Wang T, Abe AS, de Andrade DOV. Ablation of the ability to control the right-to-left cardiac shunt does not affect oxygen consumption, specific dynamic action or growth in rattlesnakes, Crotalus durissus. J Exp Biol 2013; 216:1881-9. [DOI: 10.1242/jeb.083840] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Summary
The morphologically undivided ventricle of the heart in non-crocodilian reptiles permits the mixing of oxygen-rich blood returning from the lungs and oxygen-poor blood from the systemic circulation. A possible functional significance for this intra-cardiac shunt has been debated for almost a century. Unilateral left vagotomy rendered the single effective pulmonary artery of the South American rattlesnake, Crotalus durissus, unable to adjust the magnitude of blood flow to the lung. The higher constant perfusion of the lung circulation and the incapability of adjusting R-L shunt in left-denervated snakes persisted over time, providing a unique model for investigation of the long-term consequences of cardiac shunting in a squamate. Oxygen uptake recorded at rest, during spontaneous and forced activity, was not affected by removing control of the cardiac shunt. Furthermore, metabolic rate and energetic balance during the post-prandial metabolic increment, plus the food conversion efficiency and growth rate were all similarly unaffected. These results show that control of cardiac shunting is not associated with a clear functional advantage in adjusting metabolic rate, effectiveness of digestion or growth rates.
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Evolution and development of the building plan of the vertebrate heart. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:783-94. [PMID: 23063530 DOI: 10.1016/j.bbamcr.2012.10.004] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Revised: 10/01/2012] [Accepted: 10/03/2012] [Indexed: 12/11/2022]
Abstract
Early cardiac development involves the formation of a heart tube, looping of the tube and formation of chambers. These processes are highly similar among all vertebrates, which suggest the existence of evolutionary conservation of the building plan of the heart. From the jawless lampreys to man, T-box transcription factors like Tbx5 and Tbx20 are fundamental for heart formation, whereas Tbx2 and Tbx3 repress chamber formation on the sinu-atrial and atrioventricular borders. Also, electrocardiograms from different vertebrates are alike, even though the fish heart only has two chambers whereas the mammalian heart has four chambers divided by septa and in addition has much higher heart rates. We conclude that most features of the high-performance hearts of mammals and birds can be traced back to less developed traits in the hearts of ectothermic vertebrates. This article is part of a Special Issue entitled: Cardiomyocyte biology: Cardiac pathways of differentiation, metabolism and contraction.
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Jensen B, Larsen CK, Nielsen JM, Simonsen LS, Wang T. Change of cardiac function, but not form, in postprandial pythons. Comp Biochem Physiol A Mol Integr Physiol 2011; 160:35-42. [PMID: 21605694 DOI: 10.1016/j.cbpa.2011.04.018] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 04/27/2011] [Accepted: 04/27/2011] [Indexed: 11/28/2022]
Abstract
Pythons are renowned for a rapid and pronounced postprandial growth of the heart that coincides with a several-fold elevation of cardiac output that lasts for several days. Here we investigate whether ventricular morphology is affected by digestive state in two species of pythons (Python regius and Python molurus) and we determine the cardiac right-to-left shunt during the postprandial period in P. regius. Both species experienced several-fold increases in metabolism and mass of the digestive organs by 24 and 48 h after ingestion of meals equivalent to 25% of body mass. Surprisingly there were no changes in ventricular mass or dimensions as we used a meal size and husbandry conditions similar to studies finding rapid and significant growth. Based on these data and literature we therefore suggest that postprandial cardiac growth should be regarded as a facultative rather than obligatory component of the renowned postprandial response. The cardiac right-to-left shunt, calculated on the basis of oxygen concentrations in the left and right atria and the dorsal aorta, was negligible in fasting P. regius, but increased to 10-15% during digestion. Such shunt levels are very low compared to other reptiles and does not support a recent proposal that shunts may facilitate digestion in reptiles.
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Affiliation(s)
- Bjarke Jensen
- Department of Biological Sciences, Zoophysiology, Aarhus University, Denmark.
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