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Al-Nuaimi DA, Rütsche D, Abukar A, Hiebert P, Zanetti D, Cesarovic N, Falk V, Werner S, Mazza E, Giampietro C. Hydrostatic pressure drives sprouting angiogenesis via adherens junction remodelling and YAP signalling. Commun Biol 2024; 7:940. [PMID: 39097636 PMCID: PMC11297954 DOI: 10.1038/s42003-024-06604-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Accepted: 07/17/2024] [Indexed: 08/05/2024] Open
Abstract
Endothelial cell physiology is governed by its unique microenvironment at the interface between blood and tissue. A major contributor to the endothelial biophysical environment is blood hydrostatic pressure, which in mechanical terms applies isotropic compressive stress on the cells. While other mechanical factors, such as shear stress and circumferential stretch, have been extensively studied, little is known about the role of hydrostatic pressure in the regulation of endothelial cell behavior. Here we show that hydrostatic pressure triggers partial and transient endothelial-to-mesenchymal transition in endothelial monolayers of different vascular beds. Values mimicking microvascular pressure environments promote proliferative and migratory behavior and impair barrier properties that are characteristic of a mesenchymal transition, resulting in increased sprouting angiogenesis in 3D organotypic model systems ex vivo and in vitro. Mechanistically, this response is linked to differential cadherin expression at the adherens junctions, and to an increased YAP expression, nuclear localization, and transcriptional activity. Inhibition of YAP transcriptional activity prevents pressure-induced sprouting angiogenesis. Together, this work establishes hydrostatic pressure as a key modulator of endothelial homeostasis and as a crucial component of the endothelial mechanical niche.
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Affiliation(s)
| | - Dominic Rütsche
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Experimental Continuum Mechanics, Dübendorf, 8600, Switzerland
| | - Asra Abukar
- ETH Zürich, DMAVT, Experimental Continuum Mechanics, Zürich, 8092, Switzerland
| | - Paul Hiebert
- Department of Biology, ETH Zürich, Institute of Molecular Health Sciences, 8093, Zürich, Switzerland
- Centre for Biomedicine, Hull York Medical School, The University of Hull, Hull, HU6 7RX, UK
| | - Dominik Zanetti
- Department of Biology, ETH Zürich, Institute of Molecular Health Sciences, 8093, Zürich, Switzerland
| | - Nikola Cesarovic
- Department of Cardiothoracic and Vascular Surgery, German Heart Center Berlin, 13353, Berlin, Germany
- Department of Health Sciences and Technology, ETH Zürich, 8093, Zürich, Switzerland
| | - Volkmar Falk
- Department of Cardiothoracic and Vascular Surgery, German Heart Center Berlin, 13353, Berlin, Germany
- Department of Health Sciences and Technology, ETH Zürich, 8093, Zürich, Switzerland
| | - Sabine Werner
- Department of Biology, ETH Zürich, Institute of Molecular Health Sciences, 8093, Zürich, Switzerland
| | - Edoardo Mazza
- ETH Zürich, DMAVT, Experimental Continuum Mechanics, Zürich, 8092, Switzerland.
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Experimental Continuum Mechanics, Dübendorf, 8600, Switzerland.
| | - Costanza Giampietro
- ETH Zürich, DMAVT, Experimental Continuum Mechanics, Zürich, 8092, Switzerland.
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Experimental Continuum Mechanics, Dübendorf, 8600, Switzerland.
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2
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Geng C, Huang L, Li Q, Li G, Li Y, Zhang P, Feng Y. A nomogram prediction model for treatment failure in primary membranous nephropathy. Ren Fail 2023; 45:2265159. [PMID: 37795790 PMCID: PMC10557540 DOI: 10.1080/0886022x.2023.2265159] [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: 05/22/2023] [Accepted: 09/26/2023] [Indexed: 10/06/2023] Open
Abstract
BACKGROUND Primary membranous nephropathy (PMN) has a heterogeneous natural course. Immunosuppressive therapy is recommended for PMN patients at moderate or high risk of renal function deterioration. Prediction models for the treatment failure of PMN have rarely been reported. METHODS This study retrospectively studied patients diagnosed as PMN by renal biopsy at Sichuan Provincial People's Hospital from January 2017 to December 2020. Information on clinical characteristics, laboratory test results, pathological examination, and treatment was collected. The outcome was treatment failure, defined as the lack of complete or partial remission at the end of 12 months. Simple logistic regression was used to identify candidate predictive variables. Forced-entry stepwise multivariable logistic regression was used to develop the prediction model, and performance was evaluated using C-statistic, calibration plot, and decision curve analysis. Internal validation was performed by bootstrapping. RESULTS In total, 310 patients were recruited for this study. 116 patients achieved the outcome. Forced-entry stepwise multivariable logistic regression indicated that PLA2Rab titer (OR = 1.002, 95% CI: 1.001-1.004, p = 0.003), inflammatory cells infiltration (OR = 2.753, 95% CI: 1.468-5.370, p = 0.002) and C3 deposition on immunofluorescence (OR = 0.217, 95% CI: 0.041-0.964, p = 0.049) were the three independent risk factors for treatment failure of PMN. The final prediction model had a C-statistic (95% CI) of 0.653 (0.590-0.717) and a net benefit of 23%-77%. CONCLUSIONS PLA2R antibody, renal interstitial inflammation infiltration, and C3 deposition on immunofluorescence were the three independent risk factors for treatment failure in PMN. Our prediction model might help identify patients at risk of treatment failure; however, the performance awaits improvement.
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Affiliation(s)
- Chanyu Geng
- Department of Nephrology, Sichuan Provincial People’s Hospital, University of Electronic Science and Technology of China, Chengdu, China
| | - Liming Huang
- Department of Nephrology, Sichuan Provincial People’s Hospital, University of Electronic Science and Technology of China, Chengdu, China
| | - Qiang Li
- Renal and Metabolic Division, The George Institute for Global Health, Sydney, Australia
| | - Guisen Li
- Department of Nephrology, Sichuan Provincial People’s Hospital, University of Electronic Science and Technology of China, Chengdu, China
| | - Yi Li
- Department of Nephrology, Sichuan Provincial People’s Hospital, University of Electronic Science and Technology of China, Chengdu, China
| | - Ping Zhang
- Department of Nephrology, Sichuan Provincial People’s Hospital, University of Electronic Science and Technology of China, Chengdu, China
| | - Yunlin Feng
- Department of Nephrology, Sichuan Provincial People’s Hospital, University of Electronic Science and Technology of China, Chengdu, China
- Renal and Metabolic Division, The George Institute for Global Health, Sydney, Australia
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3
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Birkedal R, Laasmaa M, Branovets J, Vendelin M. Ontogeny of cardiomyocytes: ultrastructure optimization to meet the demand for tight communication in excitation-contraction coupling and energy transfer. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210321. [PMID: 36189816 PMCID: PMC9527910 DOI: 10.1098/rstb.2021.0321] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The ontogeny of the heart describes its development from the fetal to the adult stage. In newborn mammals, blood pressure and thus cardiac performance are relatively low. The cardiomyocytes are thin, and with a central core of mitochondria surrounded by a ring of myofilaments, while the sarcoplasmic reticulum (SR) is sparse. During development, as blood pressure and performance increase, the cardiomyocytes become more packed with structures involved in excitation–contraction (e-c) coupling (SR and myofilaments) and the generation of ATP (mitochondria) to fuel the contraction. In parallel, the e-c coupling relies increasingly on calcium fluxes through the SR, while metabolism relies increasingly on fatty acid oxidation. The development of transverse tubules and SR brings channels and transporters interacting via calcium closer to each other and is crucial for e-c coupling. However, for energy transfer, it may seem counterintuitive that the increased structural density restricts the overall ATP/ADP diffusion. In this review, we discuss how this is because of the organization of all these structures forming modules. Although the overall diffusion across modules is more restricted, the energy transfer within modules is fast. A few studies suggest that in failing hearts this modular design is disrupted, and this may compromise intracellular energy transfer. This article is part of the theme issue ‘The cardiomyocyte: new revelations on the interplay between architecture and function in growth, health, and disease’.
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Affiliation(s)
- Rikke Birkedal
- Laboratory of Systems Biology, Department of Cybernetics, Tallinn University of Technology, Akadeemia 15, room SCI-218, 12618 Tallinn, Estonia
| | - Martin Laasmaa
- Laboratory of Systems Biology, Department of Cybernetics, Tallinn University of Technology, Akadeemia 15, room SCI-218, 12618 Tallinn, Estonia
| | - Jelena Branovets
- Laboratory of Systems Biology, Department of Cybernetics, Tallinn University of Technology, Akadeemia 15, room SCI-218, 12618 Tallinn, Estonia
| | - Marko Vendelin
- Laboratory of Systems Biology, Department of Cybernetics, Tallinn University of Technology, Akadeemia 15, room SCI-218, 12618 Tallinn, Estonia
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4
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Nishiyama A, Kitada K, Suzuki M. Blood pressure adaptation in vertebrates: Comparative biology. Kidney Int 2022; 102:242-247. [PMID: 35671910 DOI: 10.1016/j.kint.2022.03.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 03/18/2022] [Accepted: 03/30/2022] [Indexed: 11/26/2022]
Abstract
With evolution from water to land, the osmotic regulation of body fluids and cardiovascular systems of vertebrates evolved to cope with dryness and gravity. While aquatic vertebrates can use buoyancy to compensate for the effects of gravity, terrestrial vertebrates cannot, and must circulate blood throughout their body - a necessity that likely led to the development of strong hearts and high blood pressure. These changes may be supported by anatomical evolution of the cardiovascular system and by functional evolution, with alterations in hormonal systems. Thus, during the evolution of terrestrial animals, increased performance of body functions to endure harsher environments was required, necessitating increased blood pressure. In an age of overeating and insufficient exercise, modern man does not fully utilize the high levels of physical functions acquired through evolution. Drastic changes in our living environment cause hypertension, the pathogenesis of which remains unknown. To survive in new environments, as might be expected in outer space or underwater, an understanding is required of how changes in blood pressure have occurred that enabled adaptation through evolution in vertebrates.
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Affiliation(s)
- Akira Nishiyama
- Department of Pharmacology, Faculty of Medicine, Kagawa University, Kagawa, Japan.
| | - Kento Kitada
- Department of Pharmacology, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Miwa Suzuki
- Department of Marine Science and Resources, College of Bioresource Sciences, Nihon University, Fujisawa, Japan
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5
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Yano S. Does body height affect vascular function? Hypertens Res 2022; 45:369-371. [PMID: 34876696 DOI: 10.1038/s41440-021-00812-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 10/21/2021] [Indexed: 02/03/2023]
Affiliation(s)
- Shozo Yano
- Department of Laboratory Medicine, Shimane University Faculty of Medicine, Izumo, Japan.
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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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7
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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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8
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Jensen B, Christoffels VM. Reptiles as a Model System to Study Heart Development. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a037226. [PMID: 31712265 DOI: 10.1101/cshperspect.a037226] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A chambered heart is common to all vertebrates, but reptiles show unparalleled variation in ventricular septation, ranging from almost absent in tuataras to full in crocodilians. Because mammals and birds evolved independently from reptile lineages, studies on reptile development may yield insight into the evolution and development of the full ventricular septum. Compared with reptiles, mammals and birds have evolved several other adaptations, including compact chamber walls and a specialized conduction system. These adaptations appear to have evolved from precursor structures that can be studied in present-day reptiles. The increase in the number of studies on reptile heart development has been greatly facilitated by sequencing of several genomes and the availability of good staging systems. Here, we place reptiles in their phylogenetic context with a focus on features that are primitive when compared with the homologous features of mammals. Further, an outline of major developmental events is given, and variation between reptile species is discussed.
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Affiliation(s)
- Bjarke Jensen
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, University of Amsterdam, Amsterdam UMC 1105AZ, Amsterdam, The Netherlands
| | - Vincent M Christoffels
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, University of Amsterdam, Amsterdam UMC 1105AZ, Amsterdam, The Netherlands
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9
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Damkjær M, Poulsen CB, Wang T. Douglas Adams and the question of arterial blood pressure in mammals. Acta Physiol (Oxf) 2020; 228:e13452. [PMID: 32017416 DOI: 10.1111/apha.13452] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 01/30/2020] [Indexed: 11/30/2022]
Affiliation(s)
- Mads Damkjær
- Department of Paediatrics Kolding Hospital Kolding Denmark
| | | | - Tobias Wang
- Department of Zoophysiology Aarhus University Aarhus Denmark
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10
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11
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Sandal PH, Damgaard M, Secher NH. Comments on the Review 'Does mean arterial blood pressure scale with body mass in mammals? Effect of measurement of blood pressure' Acta Physiol (Oxf). Acta Physiol (Oxf) 2020; 228:e13407. [PMID: 31633305 DOI: 10.1111/apha.13407] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 10/15/2019] [Accepted: 10/17/2019] [Indexed: 11/28/2022]
Affiliation(s)
- Peter H. Sandal
- Department of Clinical Physiology and Nuclear Medicine Centre for Functional and Diagnostic Imaging and Research Hvidovre Hospital University of Copenhagen Copenhagen Denmark
- Department of Anaesthesiology, Rigshospitalet University of Copenhagen Copenhagen Denmark
| | - Morten Damgaard
- Department of Clinical Physiology and Nuclear Medicine Centre for Functional and Diagnostic Imaging and Research Hvidovre Hospital University of Copenhagen Copenhagen Denmark
| | - Niels H. Secher
- Department of Anaesthesiology, Rigshospitalet University of Copenhagen Copenhagen Denmark
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12
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Mrowka R. Recent advances in hypertension research. Acta Physiol (Oxf) 2019; 226:e13295. [PMID: 31067363 DOI: 10.1111/apha.13295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 04/30/2019] [Accepted: 05/02/2019] [Indexed: 11/29/2022]
Affiliation(s)
- Ralf Mrowka
- Klinik für Innere Medizin III, AG Experimentelle Nephrologie Universitätsklinikum Jena Jena Germany
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13
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Joyce W, White DW, Raven PB, Wang T. Weighing the evidence for using vascular conductance, not resistance, in comparative cardiovascular physiology. J Exp Biol 2019; 222:222/6/jeb197426. [DOI: 10.1242/jeb.197426] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
ABSTRACT
Vascular resistance and conductance are reciprocal indices of vascular tone that are often assumed to be interchangeable. However, in most animals in vivo, blood flow (i.e. cardiac output) typically varies much more than arterial blood pressure. When blood flow changes at a constant pressure, the relationship between conductance and blood flow is linear, whereas the relationship between resistance and blood flow is non-linear. Thus, for a given change in blood flow, the change in resistance depends on the starting point, whereas the attendant change in conductance is proportional to the change in blood flow regardless of the starting conditions. By comparing the effects of physical activity at different temperatures or between species – concepts at the heart of comparative cardiovascular physiology – we demonstrate that the difference between choosing resistance or conductance can be marked. We also explain here how the ratio of conductance in the pulmonary and systemic circulations provides a more intuitive description of cardiac shunt patterns in the reptilian cardiovascular system than the more commonly used ratio of resistance. Finally, we posit that, although the decision to use conductance or resistance should be made on a case-by-case basis, in most circumstances, conductance is a more faithful portrayal of cardiovascular regulation in vertebrates.
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Affiliation(s)
- William Joyce
- Department of Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark
| | - Daniel W. White
- School of Arts & Sciences, University of Houston-Victoria, Victoria, TX 77901, USA
| | - Peter B. Raven
- Department of Physiology and Anatomy, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - Tobias Wang
- Department of Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark
- Aarhus Institute of Advanced Sciences (AIAS), Aarhus University, 8000 Aarhus C, Denmark
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14
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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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15
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Lillie MA, Vogl AW, Raverty S, Haulena M, McLellan WA, Stenson GB, Shadwick RE. The caval sphincter in cetaceans and its predicted role in controlling venous flow during a dive. ACTA ACUST UNITED AC 2018; 221:jeb.177212. [PMID: 29674378 DOI: 10.1242/jeb.177212] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 04/10/2018] [Indexed: 11/20/2022]
Abstract
A sphincter on the inferior vena cava can protect the heart of a diving mammal from overload when elevated abdominal pressures increase venous return, yet sphincters are reported incompetent or absent in some cetacean species. We previously hypothesized that abdominal pressures are elevated and pulsatile in fluking cetaceans, and that collagen is deposited on the diaphragm according to pressure levels to resist deformation. Here, we tested the hypothesis that cetaceans generating high abdominal pressures need a more robust sphincter than those generating low pressures. We examined diaphragm morphology in seven cetacean and five pinniped species. All odontocetes had morphologically similar sphincters despite large differences in collagen content, and mysticetes had muscle that could modulate caval flow. These findings do not support the hypothesis that sphincter structure correlates with abdominal pressures. To understand why a sphincter is needed, we simulated the impact of oscillating abdominal pressures on caval flow. Under low abdominal pressures, simulated flow oscillated with each downstroke. Under elevated pressures, a vascular waterfall formed, greatly smoothing flow. We hypothesize that cetaceans maintain high abdominal pressures to moderate venous return and protect the heart while fluking, and use their sphincters only during low-fluking periods when abdominal pressures are low. We suggest that pinnipeds, which do not fluke, maintain low abdominal pressures. Simulations also showed that retrograde oscillations could be transmitted upstream from the cetacean abdomen and into the extradural veins, with potentially adverse repercussions for the cerebral circulation. We propose that locomotion-generated pressures have influenced multiple aspects of the cetacean vascular system.
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Affiliation(s)
- Margo A Lillie
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - A Wayne Vogl
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Stephen Raverty
- Animal Health Centre, 1767 Angus Campbell Road, Abbotsford, BC V3G 2M3, Canada
| | - Martin Haulena
- Vancouver Aquarium Marine Science Centre, PO Box 3232, Vancouver, BC V6G 3E2, Canada
| | - William A McLellan
- Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC 28403, USA
| | | | - Robert E Shadwick
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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