Does the right muscular atrioventricular valve in the avian heart perform two functions?

Prosheva, V. I.; Dernovoj, Bronislav; Kharin, S. N.; Kaseva, Natalya; Shklyar, T. F.; Blyakhman, F. A.

doi:10.1016/j.cbpa.2015.02.001

Cited by 12 publications

(14 citation statements)

References 15 publications

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“…This is called the secondary or subsidiary pacemaker. Our recent study has shown that the sinus rhythm in the normal chicken heart is 218 ± 13 beats per minute (Prosheva et al, ). In the present study, after detaching the sinoatrial area (where the primary pacemaker is located), the spontaneous rate in the isolated AV‐muscular valve was 121 ± 7 beats per minute, approximately twice lower than the sinoatrial rate in intact animal.…”

Section: Discussionmentioning

confidence: 96%

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Location and functional characterization of the right atrioventricular pacemaker ring in the adult avian heart

Prosheva

Kaseva

2015

Journal of Morphology

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Previous histological studies showed that in addition to a sinus node, an atrioventricular (AV) node, an AV bundle, left and right bundle branches, birds also possess a right AV-Purkinje ring that is located in the atrial sheet of the right muscular AV-valve along all its base length. The functionality of the AV-Purkinje ring is unknown. In this work, we studied the topology of pacemaker myocytes in the atrial side of the isolated chicken spontaneously contracting right muscular AV-valve using the method of microelectrode mapping of action potentials. We show that AV-cells having the ability to show pacemaking reside in the right muscular AV-valve. Pacemaker action potentials were exclusively recorded close to the base of the valve along its whole length from dorsal to the ventral attachment to the interventricular septum. These action potentials have much slower rate of depolarization, lower amplitude, and higher diastolic depolarization than action potentials of Purkinje (conducting) cells. We conclude the right AV-valve has a ring bundle of pacemaker cells (but not Purkinje cells) in the adult chicken heart.

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Section: Discussionmentioning

confidence: 96%

“…It should be noted that the avian right AV-valve is not a fibrous, cusped valve as in mammals (except the monotremes), but it is a large, single, crescent-shaped muscular flap guarding long, slitlike AV-orifice (Davies, 1930;Vassall-Adams, 1982;Alsafy et al, 2009;Prosheva et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Location and functional characterization of the right atrioventricular pacemaker ring in the adult avian heart

Prosheva

Kaseva

2015

Journal of Morphology

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“…CRUs in the form of PCs have been identified in the hearts of all vertebrates studied, except in the frog ventricle, and are most often associated with the Z-lines (Shiels and Galli, 2014). The mean distance between nearest neighbour PCs in the white leghorn chicken ranged from 334 nm in the LV to 462 nm in the RV, which is comparable to previous values measured using 2D TEM in the LV [472 nm (Franzini-Armstrong et al, 1999) and 567 nm (Perni et al, 2012)].…”

Section: Pc Distancesmentioning

confidence: 99%

“…The functional significance of this pattern is unclear. Size and frequency of peripheral CRUs vary between vertebrate species and between cardiac chambers within a species, and in some studies this variability has been related to the efficacy of excitation-contraction coupling (Perni et al, 2012;Shiels and Galli, 2014). Indeed, animals with high heart rates (i.e.…”

Section: Pc Distancesmentioning

confidence: 99%

“…T-tubules are found in all mammalian ventricular myocytes and in atrial myocytes of large mammals, and are important for synchronised depolarisation in these larger cells (Dibb et al, 2009). The lack of T-tubules, characteristic of ectothermic vertebrates (fish, amphibians and non-avian reptiles), has been associated with slower heart rates and less robust contractile function (Shiels and Galli, 2014). We hypothesise that the subcellular organisation of calcium (Ca 2+ ) release units (CRUs) within the avian myocyte may reconcile this apparent enigma.…”

Section: Introductionmentioning

confidence: 99%

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3D ultrastructural organisation of calcium release units in the avian sarcoplasmic reticulum

Sheard

Kharche

Pinali

et al. 2019

Journal of Experimental Biology

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Excitation-contraction coupling in vertebrate hearts is underpinned by calcium (Ca 2+) release from Ca 2+ release units (CRUs). CRUs are formed by clusters of channels called ryanodine receptors on the sarcoplasmic reticulum (SR) within the cardiomyocyte. Distances between CRUs influence the diffusion of Ca 2+ , thus influencing the rate and strength of excitation-contraction coupling. Avian myocytes lack T-tubules, so Ca 2+ from surface CRUs (peripheral couplings, PCs) must diffuse to internal CRU sites of the corbular SR (cSR) during centripetal propagation. Despite this, avian hearts achieve higher contractile rates and develop greater contractile strength than many mammalian hearts, which have T-tubules to provide simultaneous activation of the Ca 2+ signal through the myocyte. We used 3D electron tomography to test the hypothesis that the intracellular distribution of CRUs in the avian heart permits faster and stronger contractions despite the absence of T-tubules. Nearest edge-edge distances between PCs and cSR, and geometric information including surface area and volume of individual cSR, were obtained for each cardiac chamber of the white leghorn chicken. Computational modelling was then used to establish a relationship between CRU distance and cell activation time in the avian heart. Our data suggest that cSR clustered close together along the Z-line is vital for rapid propagation of the Ca 2+ signal from the cell periphery to the cell centre, which would aid in the strong and fast contractions of the avian heart.

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Comparative analysis of avian hearts provides little evidence for variation among species with acquired endothermy

Kroneman

Faber

Schouten

et al. 2019

Journal of Morphology

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Mammals and birds acquired high performance hearts and endothermy during their independent evolution from amniotes with many sauropsid features. A literature review shows that the variation in atrial morphology is greater in mammals than in ectothermic sauropsids. We therefore hypothesized that the transition from ectothermy to endothermy was associated with greater variation in cardiac structure. We tested the hypothesis in 14 orders of birds by assessing the variation in 15 cardiac structures by macroscopic inspection and histology, with an emphasis on the atria as they have multiple features that lend themselves to quantification. We found bird hearts to have multiple features in common with ectothermic sauropsids (synapomorphies), such as the presence of three sinus horns. Convergent features were shared with crocodylians and mammals, such as the cranial offset of the left atrioventricular junction. Other convergent features, like the compact organization of the atrial walls, were shared with mammals only. Pacemaker myocardium, identified by Isl1 expression, was anatomically node‐like (Mallard), thickened (Chicken), or indistinct (Lesser redpoll, Jackdaw). Some features were distinctly avian, (autapomorphies) including the presence of a left atrial antechamber and the ventral merger of the left and right atrial auricles, which was found in some species of parrots and passerines. Most features, however, exhibited little variation. For instance, there were always three systemic veins and two pulmonary veins, whereas among mammals there are 2–3 and 1–7, respectively. Our findings suggest that the transition to high cardiac performance does not necessarily lead to a greater variation in cardiac structure.

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Does the right muscular atrioventricular valve in the avian heart perform two functions?

Cited by 12 publications

References 15 publications

Location and functional characterization of the right atrioventricular pacemaker ring in the adult avian heart

Location and functional characterization of the right atrioventricular pacemaker ring in the adult avian heart

3D ultrastructural organisation of calcium release units in the avian sarcoplasmic reticulum

Comparative analysis of avian hearts provides little evidence for variation among species with acquired endothermy

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