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José M. Icardo - One of the best experts on this subject based on the ideXlab platform.
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Heart Morphology and Anatomy
Fish Physiology, 2017Co-Authors: José M. IcardoAbstract:This chapter covers morphological aspects of the fish heart. It starts with the recognition of the existence of six heart components that are present during embryonic development, and in the adult, and that are anatomically arranged in sequence: sinus venosus, atrium, atrioventricular canal, ventricle, Conus arteriosus, and bulbus arteriosus. The anatomy and structure of all the cardiac components are then described and compared between the different fish groups. Data from the basal Cyclostomata, chondrichthyans, basal Osteichthyes, and more advanced teleosts are included and analyzed. Then, data on blood supply to the heart, nerves, and localization of the heart pacemaker are discussed. A separate section at the end of the chapter is committed to the lungfish heart. Lungfishes share many anatomical and functional characteristics with both freshwater fish and amphibians, and the lungfish heart shows some unique and very peculiar characteristics. The enormous diversification of morphological characteristics of the fish heart is emphasized throughout this chapter.
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Dorsoventral transposition of the heart chambers in sturgeon Acipenser naccarii alevins
Diseases of aquatic organisms, 2007Co-Authors: A Guerrero, Borja Fernández, A. Domezain, José M. Icardo, Ana C Duran, Valentín Sans-comaAbstract:This is the first description of a dorsoventral transposition of the heart chambers in sturgeons Acipenser naccarii. The affected individuals were 2 farmed alevins aged 9 and 10 d posthatching, respectively. One was examined by light microscopy and the other by scanning electron microscopy. In both cases, the atrium and sinus venosus occupied a left ventrolateral position, the ventricle, Conus arteriosus and bulbus arteriosus were located dorsally, and the transverse septum was incomplete. The anomalous heart examined by light microscopy did not differ histologically from normal hearts of similar developmental stages. The abnormal dorsoventral arrangement of the heart chambers was presumably due to a distortion of the morphogenetic movements that bring the ventricle to the ventral and the atrium to the dorsal position. The present findings, together with genetic data reported in the literature, suggest that the defective cardiac phenotype detected in the present specimens might result from a mutation affecting the sturgeon ortholog of the zebrafish overlooped (olp) gene.
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Conus arteriosus of the teleost heart: dismissed, but not missed.
The anatomical record. Part A Discoveries in molecular cellular and evolutionary biology, 2006Co-Authors: José M. IcardoAbstract:The heart outflow tract (OFT) of primitive fish is formed by two portions: a proximal Conus arteriosus and a distal bulbus arteriosus. The OFT of modern teleosts is considered to be formed by a single component, the bulbus, the Conus having been lost through evolution. This article challenges the concept of the disappearance of the Conus arteriosus in the teleost heart. A total of 28 teleost species belonging to 19 families and 10 orders were analyzed. The hearts were divided into two large groups: those having entirely trabeculated ventricles, and those possessing a compacta. In the hearts having entirely trabeculated ventricles, the Conus arteriosus appears as a distinct segment interposed between the ventricle and the bulbus arteriosus, being formed by compact vascularized myocardium. However, the Conus of several species lacks vessels. In these cases, the Conus presents large intercellular spaces bounded by collagen. In the hearts possessing a ventricular compacta, the Conus either appears as a muscular ring of variable length connecting the ventricle and the bulbus or forms a crown or ring of myocardium apposed to the ventricular base. In all the teleosts studied, the Conus can be recognized as an anatomic entity different from the ventricle. Furthermore, the Conus appears as a distinct heart segment in the developing fish. Therefore, the Conus arteriosus has not been lost in evolution and constitutes a fundamental part of the teleost OFT. In all the species studied, the Conus supports the OFT valves, which should properly be named Conus valves.
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differentiation of the cardiac outflow tract components in alevins of the sturgeon acipenser naccarii osteichthyes acipenseriformes implications for heart evolution
Journal of Morphology, 2004Co-Authors: A Guerrero, A. Domezain, José M. Icardo, Ana C Duran, Alejandro Gallego, Elvira Colvee, Valentin SanscomaAbstract:Previous work showed that in the adult sturgeon an intrapericardial, nonmyocardial segment is interposed between the Conus arteriosus of the heart and the ventral aorta. The present report illustrates the ontogeny of this intermediate segment in Acipenser nac- carii. The sample studied consisted of 178 alevins be- tween 1 and 24 days posthatching. They were examined using light and electron microscopy. Our observations indicate that the entire cardiac outflow tract displays a myocardial character during early development. Be- tween the fourth and sixth days posthatching, the distal portion of the cardiac outflow tract undergoes a pheno- typical transition, from a myocardial to a smooth muscle-like phenotype. The length of this region with regard to the whole outflow tract increases only moder- ately during subsequent developmental stages, becom- ing more and more cellularized. The cells soon organize into a pattern that resembles that of the arterial wall. Elastin appears at this site by the seventh day post- hatching. Therefore, two distinct components, proximal and distal, can be recognized from the fourth day post- hatching in the cardiac outflow tract of A. naccarii. The proximal component is the Conus arteriosus, character- ized by its myocardial nature and the presence of endo- cardial cushions. The distal component transforms into the intrapericardial, nonmyocardial segment mentioned above, which is unequivocally of cardiac origin. We pro- pose to designate this segment the "bulbus arteriosus" because it is morphogenetically equivalent to the bulbus arteriosus of teleosts. The present findings, together with data from the literature, point to the possibility that cells from the cardiac neural crest are involved in the phenotypical transition that takes place at the dis- tal portion of the cardiac outflow tract, resulting in the appearance of the bulbus arteriosus. Moreover, they suggest that the cardiac outflow tract came to be formed by a bulbus arteriosus and a Conus arteriosus from an early period of the vertebrate evolutionary story. Fi- nally, we hypothesize that the embryonic truncus of birds and mammals is homologous to the bulbus arteri- osus of fish. J. Morphol. 260:172-183, 2004. © 2004 Wiley-Liss, Inc.
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Structure of the Conus arteriosus of the sturgeon (Acipenser naccarii) heart. I: The Conus valves and the subendocardium
The Anatomical record, 2002Co-Authors: José M. Icardo, Elvira Colvee, Maria Carmela Cerra, Bruno TotaAbstract:Sturgeons are bony fish that retain structural traits typical of the more primitive Chondrostei. From an evolutionary viewpoint, sturgeons are considered relic fish. However, they show remarkable ecological plasticity and are well adapted to contemporary environmental conditions. Although development of the cardiovascular system is critical for all organs and systems, and is affected by evolutionary changes, the structure of the sturgeon heart has been mostly overlooked. This is also true for the Conus arteriosus, which, as in Chondrostei, is endowed with several rows of valves and a layer of contractile myocardium. This work reports on the structure of the valves, the endocardium, and the subendocardium of the Conus arteriosus of the sturgeon (Acipenser naccarii) heart. It is part of a broader study that aims to cover the entire structure of the sturgeon heart. The Conus arteriosus of 15 A. naccarii hearts, ranging in age from juveniles to sexually-differentiated adults, has been studied by conventional light, transmission (TEM), and scanning electron microscopy (SEM). In addition, maceration of the soft tissues with NaOH, and actin localization by fluorescent phalloidin has been used. The Conus is a tubular chamber that arises from the right ventricular side and presents two constrictions at the Conus-ventricle and Conus-aorta junctions. The Conus is endowed with three rows of valves: one distal and two proximal. The segment of the Conus located between the distal and the two proximal rows is devoid of valvular structures. The distal row has four leaflets, while the two proximal rows show the greatest variation in leaflet number, size, and shape. All leaflets have collagenous chordae tendineae arising from the free border and from the parietal side of the leaflets. The endocardium is a flat endothelium which shows a thick, irregular basement membrane. The leaflet body is formed by a loose connective tissue which blends with the subendocardium. The subendocardium is a connective tissue consisting of myofibroblasts, collagen, and elastin. It is divided into two distinct areas: one proximal, which shows little elastin and poorly organized collagen; and one distal, which is rich in elastin, with cells and extracellular fibers organized into layers that are oriented in alternative circumferential and longitudinal directions. The present report is the first systematic analysis of the structure of the sturgeon Conus. Descriptions of the Conus valves should recognize the existence of three valve rows only. The variability in valve morphology, and the loose structure of the leaflet tissue make it unlikely that the valves play an effective role in preventing blood backflow. In this regard, the ventricle-Conus constriction may act as a sphincter. The subendocardium is an elastic coat capable of actively sustaining the tissue deformation that accompanies the heart contractile cycle. Further comparative studies are needed to provide deeper insight into the structural changes that accompany phyletic diversification. Anat Rec 267:17–27, 2002. © 2002 Wiley-Liss, Inc.
Valentín Sans-coma - One of the best experts on this subject based on the ideXlab platform.
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Differential expression of myosin heavy chain isoforms in cardiac segments of gnathostome vertebrates and its evolutionary implications
Frontiers in Zoology, 2019Co-Authors: Miguel A. López-unzu, Ana Carmen Durán, María Teresa Soto-navarrete, Valentín Sans-coma, Borja FernándezAbstract:Background Immunohistochemical studies of hearts from the lesser spotted dogfish, Scyliorhinus canicula (Chondrichthyes) revealed that the pan-myosin heavy chain (pan-MyHC) antibody MF20 homogeneously labels all the myocardium, while the pan-MyHC antibody A4.1025 labels the myocardium of the inflow (sinus venosus and atrium) but not the outflow (ventricle and Conus arteriosus) cardiac segments, as opposed to other vertebrates. We hypothesized that the conventional pattern of cardiac MyHC isoform distribution present in most vertebrates, i.e. MYH6 in the inflow and MYH7 in the outflow segments, has evolved from a primitive pattern that persists in Chondrichthyes. In order to test this hypothesis, we conducted protein detection techniques to identify the MyHC isoforms expressed in adult dogfish cardiac segments and to assess the pan-MyHC antibodies reactivity against the cardiac segments of representative species from different vertebrate groups. Results Western and slot blot results confirmed the specificity of MF20 and A4.1025 for MyHC in dogfish and their differential reactivity against distinct myocardial segments. HPLC-ESI-MS/MS and ESI-Quadrupole-Orbitrap revealed abundance of MYH6 and MYH2 in the inflow and of MYH7 and MYH7B in the outflow segments. Immunoprecipitation showed higher affinity of A4.1025 for MYH2 and MYH6 than for MYH7 and almost no affinity for MYH7B. Immunohistochemistry showed that A4.1025 signals are restricted to the inflow myocardial segments of elasmobranchs, homogeneous in all myocardial segments of teleosts and acipenseriforms, and low in the ventricle of polypteriforms. Conclusions The cardiac inflow and outflow segments of the dogfish show predominance of fast- and slow-twitch MyHC isoforms respectively, what can be considered a synapomorphy of gnathostomes. The myocardium of the dogfish contains two isomyosins (MYH2 and MYH7B) not expressed in the adult heart of other vertebrates. We propose that these isomyosins lost their function in cardiac contraction during the evolution of gnathostomes, the later acquiring a regulatory role in myogenesis through its intronic miRNA. Loss of MYH2 and MYH7B expression in the heart possibly occurred before the origin of Osteichthyes, being the latter reacquired in polypteriforms. We raise the hypothesis that the slow tonic MYH7B facilitates the peristaltic contraction of the Conus arteriosus of fish with a primitive cardiac anatomical design and of the vertebrate embryo.
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Differential expression of myosin heavy chain isoforms in cardiac segments of gnathostome vertebrates and its evolutionary implications
Frontiers in zoology, 2019Co-Authors: Miguel A. López-unzu, María Teresa Soto-navarrete, Valentín Sans-coma, Ana C Duran, Borja FernándezAbstract:Immunohistochemical studies of hearts from the lesser spotted dogfish, Scyliorhinus canicula (Chondrichthyes) revealed that the pan-myosin heavy chain (pan-MyHC) antibody MF20 homogeneously labels all the myocardium, while the pan-MyHC antibody A4.1025 labels the myocardium of the inflow (sinus venosus and atrium) but not the outflow (ventricle and Conus arteriosus) cardiac segments, as opposed to other vertebrates. We hypothesized that the conventional pattern of cardiac MyHC isoform distribution present in most vertebrates, i.e. MYH6 in the inflow and MYH7 in the outflow segments, has evolved from a primitive pattern that persists in Chondrichthyes. In order to test this hypothesis, we conducted protein detection techniques to identify the MyHC isoforms expressed in adult dogfish cardiac segments and to assess the pan-MyHC antibodies reactivity against the cardiac segments of representative species from different vertebrate groups. Western and slot blot results confirmed the specificity of MF20 and A4.1025 for MyHC in dogfish and their differential reactivity against distinct myocardial segments. HPLC-ESI-MS/MS and ESI-Quadrupole-Orbitrap revealed abundance of MYH6 and MYH2 in the inflow and of MYH7 and MYH7B in the outflow segments. Immunoprecipitation showed higher affinity of A4.1025 for MYH2 and MYH6 than for MYH7 and almost no affinity for MYH7B. Immunohistochemistry showed that A4.1025 signals are restricted to the inflow myocardial segments of elasmobranchs, homogeneous in all myocardial segments of teleosts and acipenseriforms, and low in the ventricle of polypteriforms. The cardiac inflow and outflow segments of the dogfish show predominance of fast- and slow-twitch MyHC isoforms respectively, what can be considered a synapomorphy of gnathostomes. The myocardium of the dogfish contains two isomyosins (MYH2 and MYH7B) not expressed in the adult heart of other vertebrates. We propose that these isomyosins lost their function in cardiac contraction during the evolution of gnathostomes, the later acquiring a regulatory role in myogenesis through its intronic miRNA. Loss of MYH2 and MYH7B expression in the heart possibly occurred before the origin of Osteichthyes, being the latter reacquired in polypteriforms. We raise the hypothesis that the slow tonic MYH7B facilitates the peristaltic contraction of the Conus arteriosus of fish with a primitive cardiac anatomical design and of the vertebrate embryo.
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The valves of the cardiac outflow tract of the starry ray, Raja asterias (Chondrichthyes; Rajiformes): Anatomical, histological and evolutionary aspects.
Anatomia histologia embryologia, 2018Co-Authors: Miguel Lorenzale, Miguel A. López-unzu, Borja Fernández, Ana C Duran, Valentín Sans-comaAbstract:The cardiac outflow tract of chondrichthyans is composed of the myocardial Conus arteriosus, equipped with valves at its luminal side, and the bulbus arteriosus devoid of myocardium. Knowledge of the histomorphology of the conal valves is scarce despite their importance in preventing blood backflow to the heart. Current information on the subject refers to a single shark species. The present report is the first to describe the structure of the conal valves of a batoid species, namely, Raja asterias. Hearts from seven starry rays were examined using scanning electron microscopy and histochemical techniques for light microscopy. In all hearts, the Conus showed four transverse rows of three pocket-like valves each. Each valve was composed of a leaflet and its supporting sinus. The leaflet had a stout central body, rich in glycosaminoglycans, which contained fibroblasts, collagen and elastin. The central body was surrounded by two thin fibrous layers, outer and inner, formed mainly by collagen. The valves of the anterior row, which were the largest of the valvular system, were attached proximally to the Conus arteriosus and distally to the bulbus arteriosus, and not to the ventral aorta as previously reported for chondrichthyans. The arrangement of the anterior valves in the starry ray is an anatomical pattern that apparently has been preserved throughout the evolution of vertebrates.
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The anatomical components of the cardiac outflow tract of chondrichthyans and actinopterygians.
Biological reviews of the Cambridge Philosophical Society, 2018Co-Authors: Miguel Lorenzale, Miguel A. López-unzu, Borja Fernández, Ana C Duran, Cristina Castillo Rodríguez, Valentín Sans-comaAbstract:The outflow tract of the fish heart is the segment interposed between the ventricle and the ventral aorta. It holds the valves that prevent blood backflow from the gill vasculature to the ventricle. The anatomical composition, histological structure and evolutionary changes in the fish cardiac outflow tract have been under discussion for nearly two centuries and are still subject to debate. This paper offers a brief historical review of the main conceptions about the cardiac outflow tract components of chondrichthyans (cartilaginous fish) and actinopterygians (ray-finned fish) which have been put forward since the beginning of the nineteenth century up to the current day. We focus on the evolutionary origin of the outflow tract components and the changes to which they have been subject in the major extant groups of chondrichthyans and actinopterygians. In addition, an attempt is made to infer the primitive anatomical design of the heart of the gnathostomes (jawed vertebrates). Finally, several areas of further investigation are suggested. Recent work on fish heart morphology has shown that the cardiac outflow tract of chondrichthyans does not consist exclusively of the myocardial Conus arteriosus as classically thought. A Conus arteriosus and a bulbus arteriosus, devoid of myocardium and mainly composed of elastin and smooth muscle, are usually present in cartilaginous and ray-finned fish. This is consistent with the suggestion that both components coexisted from the onset of the gnathostome radiation. There is evidence that the Conus arteriosus appeared in the agnathans. By contrast, the evolutionary origin of the bulbus is still unclear. It is almost certain that in all fish, both the Conus and bulbus develop from the embryonic second heart field. We suggest herein that the primitive anatomical heart of the jawed vertebrates consisted of a sinus venosus containing the pacemaker tissue, an atrium possessing trabeculated myocardium, an atrioventricular region with compact myocardium which supported the atrioventricular valves, a ventricle composed of mixed myocardium, and an outflow tract consisting of a Conus arteriosus, with compact myocardium in its wall and valves at its luminal side, and a non-myocardial bulbus arteriosus that connected the Conus with the ventral aorta. Chondrichthyans have retained this basic anatomical design of the heart. In actinopterygians, the heart has been subject to notable changes during evolution. Among them, the following two should be highlighted: (i) a decrease in size of the Conus in combination with a remarkable development of the bulbus, especially in teleosts; and (ii) loss of the myocardial compact layer of the ventricle in many teleost species.
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The bulbus arteriosus of the holocephalan heart: gross anatomy, histomorphology, pigmentation, and evolutionary significance.
Zoology (Jena Germany), 2017Co-Authors: Cristina Castillo Rodríguez, Miguel A. López-unzu, Borja Fernández, Valentín Sans-coma, Miguel Lorenzale, Francisca Salmerón, Ana C DuranAbstract:This study was designed to determine whether the outflow tract of the holocephalan heart is composed of a myocardial Conus arteriosus and a non-myocardial bulbus arteriosus, as is the case in elasmobranchs. This is a key issue to verify the hypothesis that these two anatomical components existed from the onset of the jawed vertebrate radiation. The Holocephali are the sister group of the elasmobranchs, sharing with them a common, still unknown Palaeozoic ancestor. The sample examined herein consisted of hearts from individuals of four species, two of them belonging to the Chimaeridae and the other two to the Rhinochimaeridae. In all specimens, the cardiac outflow tract consisted of a Conus arteriosus, with myocardium in its walls and two rows of valves at its luminal side, and an intrapericardial bulbus arteriosus shorter than the Conus and devoid of valves. The bulbus, mainly composed of elastin and smooth musculature, was covered by the epicardium and crossed longitudinally by coronary artery trunks. These findings give added support to the viewpoint that the outflow tract of the primitive heart of the gnathostomes was not composed of a single component, but two, the Conus and the bulbus. All rabbitfish (Chimaera monstrosa) examined had pigment cells over the surface of the heart. The degree of pigmentation, which varied widely between individuals, was particularly intense in the cardiac outflow tract. Pigment cells also occurred in the bulbus arteriosus of one of the two hearts of the straightnose rabbitfish (Rhinochimaera atlantica) included in the study. The cells containing pigment, presumably derived from the neural crest, were located in the subepicardium.
Ana C Duran - One of the best experts on this subject based on the ideXlab platform.
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Differential expression of myosin heavy chain isoforms in cardiac segments of gnathostome vertebrates and its evolutionary implications
Frontiers in zoology, 2019Co-Authors: Miguel A. López-unzu, María Teresa Soto-navarrete, Valentín Sans-coma, Ana C Duran, Borja FernándezAbstract:Immunohistochemical studies of hearts from the lesser spotted dogfish, Scyliorhinus canicula (Chondrichthyes) revealed that the pan-myosin heavy chain (pan-MyHC) antibody MF20 homogeneously labels all the myocardium, while the pan-MyHC antibody A4.1025 labels the myocardium of the inflow (sinus venosus and atrium) but not the outflow (ventricle and Conus arteriosus) cardiac segments, as opposed to other vertebrates. We hypothesized that the conventional pattern of cardiac MyHC isoform distribution present in most vertebrates, i.e. MYH6 in the inflow and MYH7 in the outflow segments, has evolved from a primitive pattern that persists in Chondrichthyes. In order to test this hypothesis, we conducted protein detection techniques to identify the MyHC isoforms expressed in adult dogfish cardiac segments and to assess the pan-MyHC antibodies reactivity against the cardiac segments of representative species from different vertebrate groups. Western and slot blot results confirmed the specificity of MF20 and A4.1025 for MyHC in dogfish and their differential reactivity against distinct myocardial segments. HPLC-ESI-MS/MS and ESI-Quadrupole-Orbitrap revealed abundance of MYH6 and MYH2 in the inflow and of MYH7 and MYH7B in the outflow segments. Immunoprecipitation showed higher affinity of A4.1025 for MYH2 and MYH6 than for MYH7 and almost no affinity for MYH7B. Immunohistochemistry showed that A4.1025 signals are restricted to the inflow myocardial segments of elasmobranchs, homogeneous in all myocardial segments of teleosts and acipenseriforms, and low in the ventricle of polypteriforms. The cardiac inflow and outflow segments of the dogfish show predominance of fast- and slow-twitch MyHC isoforms respectively, what can be considered a synapomorphy of gnathostomes. The myocardium of the dogfish contains two isomyosins (MYH2 and MYH7B) not expressed in the adult heart of other vertebrates. We propose that these isomyosins lost their function in cardiac contraction during the evolution of gnathostomes, the later acquiring a regulatory role in myogenesis through its intronic miRNA. Loss of MYH2 and MYH7B expression in the heart possibly occurred before the origin of Osteichthyes, being the latter reacquired in polypteriforms. We raise the hypothesis that the slow tonic MYH7B facilitates the peristaltic contraction of the Conus arteriosus of fish with a primitive cardiac anatomical design and of the vertebrate embryo.
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The valves of the cardiac outflow tract of the starry ray, Raja asterias (Chondrichthyes; Rajiformes): Anatomical, histological and evolutionary aspects.
Anatomia histologia embryologia, 2018Co-Authors: Miguel Lorenzale, Miguel A. López-unzu, Borja Fernández, Ana C Duran, Valentín Sans-comaAbstract:The cardiac outflow tract of chondrichthyans is composed of the myocardial Conus arteriosus, equipped with valves at its luminal side, and the bulbus arteriosus devoid of myocardium. Knowledge of the histomorphology of the conal valves is scarce despite their importance in preventing blood backflow to the heart. Current information on the subject refers to a single shark species. The present report is the first to describe the structure of the conal valves of a batoid species, namely, Raja asterias. Hearts from seven starry rays were examined using scanning electron microscopy and histochemical techniques for light microscopy. In all hearts, the Conus showed four transverse rows of three pocket-like valves each. Each valve was composed of a leaflet and its supporting sinus. The leaflet had a stout central body, rich in glycosaminoglycans, which contained fibroblasts, collagen and elastin. The central body was surrounded by two thin fibrous layers, outer and inner, formed mainly by collagen. The valves of the anterior row, which were the largest of the valvular system, were attached proximally to the Conus arteriosus and distally to the bulbus arteriosus, and not to the ventral aorta as previously reported for chondrichthyans. The arrangement of the anterior valves in the starry ray is an anatomical pattern that apparently has been preserved throughout the evolution of vertebrates.
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The anatomical components of the cardiac outflow tract of chondrichthyans and actinopterygians.
Biological reviews of the Cambridge Philosophical Society, 2018Co-Authors: Miguel Lorenzale, Miguel A. López-unzu, Borja Fernández, Ana C Duran, Cristina Castillo Rodríguez, Valentín Sans-comaAbstract:The outflow tract of the fish heart is the segment interposed between the ventricle and the ventral aorta. It holds the valves that prevent blood backflow from the gill vasculature to the ventricle. The anatomical composition, histological structure and evolutionary changes in the fish cardiac outflow tract have been under discussion for nearly two centuries and are still subject to debate. This paper offers a brief historical review of the main conceptions about the cardiac outflow tract components of chondrichthyans (cartilaginous fish) and actinopterygians (ray-finned fish) which have been put forward since the beginning of the nineteenth century up to the current day. We focus on the evolutionary origin of the outflow tract components and the changes to which they have been subject in the major extant groups of chondrichthyans and actinopterygians. In addition, an attempt is made to infer the primitive anatomical design of the heart of the gnathostomes (jawed vertebrates). Finally, several areas of further investigation are suggested. Recent work on fish heart morphology has shown that the cardiac outflow tract of chondrichthyans does not consist exclusively of the myocardial Conus arteriosus as classically thought. A Conus arteriosus and a bulbus arteriosus, devoid of myocardium and mainly composed of elastin and smooth muscle, are usually present in cartilaginous and ray-finned fish. This is consistent with the suggestion that both components coexisted from the onset of the gnathostome radiation. There is evidence that the Conus arteriosus appeared in the agnathans. By contrast, the evolutionary origin of the bulbus is still unclear. It is almost certain that in all fish, both the Conus and bulbus develop from the embryonic second heart field. We suggest herein that the primitive anatomical heart of the jawed vertebrates consisted of a sinus venosus containing the pacemaker tissue, an atrium possessing trabeculated myocardium, an atrioventricular region with compact myocardium which supported the atrioventricular valves, a ventricle composed of mixed myocardium, and an outflow tract consisting of a Conus arteriosus, with compact myocardium in its wall and valves at its luminal side, and a non-myocardial bulbus arteriosus that connected the Conus with the ventral aorta. Chondrichthyans have retained this basic anatomical design of the heart. In actinopterygians, the heart has been subject to notable changes during evolution. Among them, the following two should be highlighted: (i) a decrease in size of the Conus in combination with a remarkable development of the bulbus, especially in teleosts; and (ii) loss of the myocardial compact layer of the ventricle in many teleost species.
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The bulbus arteriosus of the holocephalan heart: gross anatomy, histomorphology, pigmentation, and evolutionary significance.
Zoology (Jena Germany), 2017Co-Authors: Cristina Castillo Rodríguez, Miguel A. López-unzu, Borja Fernández, Valentín Sans-coma, Miguel Lorenzale, Francisca Salmerón, Ana C DuranAbstract:This study was designed to determine whether the outflow tract of the holocephalan heart is composed of a myocardial Conus arteriosus and a non-myocardial bulbus arteriosus, as is the case in elasmobranchs. This is a key issue to verify the hypothesis that these two anatomical components existed from the onset of the jawed vertebrate radiation. The Holocephali are the sister group of the elasmobranchs, sharing with them a common, still unknown Palaeozoic ancestor. The sample examined herein consisted of hearts from individuals of four species, two of them belonging to the Chimaeridae and the other two to the Rhinochimaeridae. In all specimens, the cardiac outflow tract consisted of a Conus arteriosus, with myocardium in its walls and two rows of valves at its luminal side, and an intrapericardial bulbus arteriosus shorter than the Conus and devoid of valves. The bulbus, mainly composed of elastin and smooth musculature, was covered by the epicardium and crossed longitudinally by coronary artery trunks. These findings give added support to the viewpoint that the outflow tract of the primitive heart of the gnathostomes was not composed of a single component, but two, the Conus and the bulbus. All rabbitfish (Chimaera monstrosa) examined had pigment cells over the surface of the heart. The degree of pigmentation, which varied widely between individuals, was particularly intense in the cardiac outflow tract. Pigment cells also occurred in the bulbus arteriosus of one of the two hearts of the straightnose rabbitfish (Rhinochimaera atlantica) included in the study. The cells containing pigment, presumably derived from the neural crest, were located in the subepicardium.
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The anatomical components of the cardiac outflow tract of the gray bichir, Polypterus senegalus: their evolutionary significance.
Zoology (Jena Germany), 2014Co-Authors: Ana C Duran, Borja Fernández, Valentín Sans-coma, Cristina Castillo Rodríguez, Ismael Reyes-moya, Adrian C GrimesAbstract:It has been reported that in chondrichthyans the cardiac outflow tract is composed of the myocardial Conus arteriosus, while in most teleosteans it consists of the nonmyocardial bulbus arteriosus. Classical studies already indicated that a Conus and a bulbus coexist in several ancient actinopterygian and teleost groups. Recent work has shown that a cardiac outflow tract consisting of a Conus and a bulbus is common to both cartilaginous and bony fishes. Nonetheless and despite their position at the base of the actinopterygian phylogenetic lineage, the anatomical arrangement of the cardiac outflow tract of the Polypteriformes remained uncertain. The present study of hearts from gray bichirs was intended to fill this gap. The cardiac outflow tract of the bichir consists of two main components, namely a very long Conus arteriosus, furnished with valves, and a short, intrapericardial, arterial-like bulbus arteriosus, which differs from the ventral aorta because it is covered by epicardium, shows a slightly different spatial arrangement of the histological elements and is crossed by coronary arteries. Histomorphologically, the outflow tract consists of three longitudinal regions, distal, middle and proximal, an arrangement which has been suggested to be common to all vertebrates. The distal region corresponds to the bulbus, while the Conus comprises the middle and proximal regions. The present findings reinforce the notion that the bulbus arteriosus of fish has played an essential role in vertebrate heart evolution as it is the precursor of the intrapericardial trunks of the aorta and pulmonary artery of birds and mammals.
Borja Fernández - One of the best experts on this subject based on the ideXlab platform.
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Differential expression of myosin heavy chain isoforms in cardiac segments of gnathostome vertebrates and its evolutionary implications
Frontiers in zoology, 2019Co-Authors: Miguel A. López-unzu, María Teresa Soto-navarrete, Valentín Sans-coma, Ana C Duran, Borja FernándezAbstract:Immunohistochemical studies of hearts from the lesser spotted dogfish, Scyliorhinus canicula (Chondrichthyes) revealed that the pan-myosin heavy chain (pan-MyHC) antibody MF20 homogeneously labels all the myocardium, while the pan-MyHC antibody A4.1025 labels the myocardium of the inflow (sinus venosus and atrium) but not the outflow (ventricle and Conus arteriosus) cardiac segments, as opposed to other vertebrates. We hypothesized that the conventional pattern of cardiac MyHC isoform distribution present in most vertebrates, i.e. MYH6 in the inflow and MYH7 in the outflow segments, has evolved from a primitive pattern that persists in Chondrichthyes. In order to test this hypothesis, we conducted protein detection techniques to identify the MyHC isoforms expressed in adult dogfish cardiac segments and to assess the pan-MyHC antibodies reactivity against the cardiac segments of representative species from different vertebrate groups. Western and slot blot results confirmed the specificity of MF20 and A4.1025 for MyHC in dogfish and their differential reactivity against distinct myocardial segments. HPLC-ESI-MS/MS and ESI-Quadrupole-Orbitrap revealed abundance of MYH6 and MYH2 in the inflow and of MYH7 and MYH7B in the outflow segments. Immunoprecipitation showed higher affinity of A4.1025 for MYH2 and MYH6 than for MYH7 and almost no affinity for MYH7B. Immunohistochemistry showed that A4.1025 signals are restricted to the inflow myocardial segments of elasmobranchs, homogeneous in all myocardial segments of teleosts and acipenseriforms, and low in the ventricle of polypteriforms. The cardiac inflow and outflow segments of the dogfish show predominance of fast- and slow-twitch MyHC isoforms respectively, what can be considered a synapomorphy of gnathostomes. The myocardium of the dogfish contains two isomyosins (MYH2 and MYH7B) not expressed in the adult heart of other vertebrates. We propose that these isomyosins lost their function in cardiac contraction during the evolution of gnathostomes, the later acquiring a regulatory role in myogenesis through its intronic miRNA. Loss of MYH2 and MYH7B expression in the heart possibly occurred before the origin of Osteichthyes, being the latter reacquired in polypteriforms. We raise the hypothesis that the slow tonic MYH7B facilitates the peristaltic contraction of the Conus arteriosus of fish with a primitive cardiac anatomical design and of the vertebrate embryo.
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Differential expression of myosin heavy chain isoforms in cardiac segments of gnathostome vertebrates and its evolutionary implications
Frontiers in Zoology, 2019Co-Authors: Miguel A. López-unzu, Ana Carmen Durán, María Teresa Soto-navarrete, Valentín Sans-coma, Borja FernándezAbstract:Background Immunohistochemical studies of hearts from the lesser spotted dogfish, Scyliorhinus canicula (Chondrichthyes) revealed that the pan-myosin heavy chain (pan-MyHC) antibody MF20 homogeneously labels all the myocardium, while the pan-MyHC antibody A4.1025 labels the myocardium of the inflow (sinus venosus and atrium) but not the outflow (ventricle and Conus arteriosus) cardiac segments, as opposed to other vertebrates. We hypothesized that the conventional pattern of cardiac MyHC isoform distribution present in most vertebrates, i.e. MYH6 in the inflow and MYH7 in the outflow segments, has evolved from a primitive pattern that persists in Chondrichthyes. In order to test this hypothesis, we conducted protein detection techniques to identify the MyHC isoforms expressed in adult dogfish cardiac segments and to assess the pan-MyHC antibodies reactivity against the cardiac segments of representative species from different vertebrate groups. Results Western and slot blot results confirmed the specificity of MF20 and A4.1025 for MyHC in dogfish and their differential reactivity against distinct myocardial segments. HPLC-ESI-MS/MS and ESI-Quadrupole-Orbitrap revealed abundance of MYH6 and MYH2 in the inflow and of MYH7 and MYH7B in the outflow segments. Immunoprecipitation showed higher affinity of A4.1025 for MYH2 and MYH6 than for MYH7 and almost no affinity for MYH7B. Immunohistochemistry showed that A4.1025 signals are restricted to the inflow myocardial segments of elasmobranchs, homogeneous in all myocardial segments of teleosts and acipenseriforms, and low in the ventricle of polypteriforms. Conclusions The cardiac inflow and outflow segments of the dogfish show predominance of fast- and slow-twitch MyHC isoforms respectively, what can be considered a synapomorphy of gnathostomes. The myocardium of the dogfish contains two isomyosins (MYH2 and MYH7B) not expressed in the adult heart of other vertebrates. We propose that these isomyosins lost their function in cardiac contraction during the evolution of gnathostomes, the later acquiring a regulatory role in myogenesis through its intronic miRNA. Loss of MYH2 and MYH7B expression in the heart possibly occurred before the origin of Osteichthyes, being the latter reacquired in polypteriforms. We raise the hypothesis that the slow tonic MYH7B facilitates the peristaltic contraction of the Conus arteriosus of fish with a primitive cardiac anatomical design and of the vertebrate embryo.
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The valves of the cardiac outflow tract of the starry ray, Raja asterias (Chondrichthyes; Rajiformes): Anatomical, histological and evolutionary aspects.
Anatomia histologia embryologia, 2018Co-Authors: Miguel Lorenzale, Miguel A. López-unzu, Borja Fernández, Ana C Duran, Valentín Sans-comaAbstract:The cardiac outflow tract of chondrichthyans is composed of the myocardial Conus arteriosus, equipped with valves at its luminal side, and the bulbus arteriosus devoid of myocardium. Knowledge of the histomorphology of the conal valves is scarce despite their importance in preventing blood backflow to the heart. Current information on the subject refers to a single shark species. The present report is the first to describe the structure of the conal valves of a batoid species, namely, Raja asterias. Hearts from seven starry rays were examined using scanning electron microscopy and histochemical techniques for light microscopy. In all hearts, the Conus showed four transverse rows of three pocket-like valves each. Each valve was composed of a leaflet and its supporting sinus. The leaflet had a stout central body, rich in glycosaminoglycans, which contained fibroblasts, collagen and elastin. The central body was surrounded by two thin fibrous layers, outer and inner, formed mainly by collagen. The valves of the anterior row, which were the largest of the valvular system, were attached proximally to the Conus arteriosus and distally to the bulbus arteriosus, and not to the ventral aorta as previously reported for chondrichthyans. The arrangement of the anterior valves in the starry ray is an anatomical pattern that apparently has been preserved throughout the evolution of vertebrates.
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The anatomical components of the cardiac outflow tract of chondrichthyans and actinopterygians.
Biological reviews of the Cambridge Philosophical Society, 2018Co-Authors: Miguel Lorenzale, Miguel A. López-unzu, Borja Fernández, Ana C Duran, Cristina Castillo Rodríguez, Valentín Sans-comaAbstract:The outflow tract of the fish heart is the segment interposed between the ventricle and the ventral aorta. It holds the valves that prevent blood backflow from the gill vasculature to the ventricle. The anatomical composition, histological structure and evolutionary changes in the fish cardiac outflow tract have been under discussion for nearly two centuries and are still subject to debate. This paper offers a brief historical review of the main conceptions about the cardiac outflow tract components of chondrichthyans (cartilaginous fish) and actinopterygians (ray-finned fish) which have been put forward since the beginning of the nineteenth century up to the current day. We focus on the evolutionary origin of the outflow tract components and the changes to which they have been subject in the major extant groups of chondrichthyans and actinopterygians. In addition, an attempt is made to infer the primitive anatomical design of the heart of the gnathostomes (jawed vertebrates). Finally, several areas of further investigation are suggested. Recent work on fish heart morphology has shown that the cardiac outflow tract of chondrichthyans does not consist exclusively of the myocardial Conus arteriosus as classically thought. A Conus arteriosus and a bulbus arteriosus, devoid of myocardium and mainly composed of elastin and smooth muscle, are usually present in cartilaginous and ray-finned fish. This is consistent with the suggestion that both components coexisted from the onset of the gnathostome radiation. There is evidence that the Conus arteriosus appeared in the agnathans. By contrast, the evolutionary origin of the bulbus is still unclear. It is almost certain that in all fish, both the Conus and bulbus develop from the embryonic second heart field. We suggest herein that the primitive anatomical heart of the jawed vertebrates consisted of a sinus venosus containing the pacemaker tissue, an atrium possessing trabeculated myocardium, an atrioventricular region with compact myocardium which supported the atrioventricular valves, a ventricle composed of mixed myocardium, and an outflow tract consisting of a Conus arteriosus, with compact myocardium in its wall and valves at its luminal side, and a non-myocardial bulbus arteriosus that connected the Conus with the ventral aorta. Chondrichthyans have retained this basic anatomical design of the heart. In actinopterygians, the heart has been subject to notable changes during evolution. Among them, the following two should be highlighted: (i) a decrease in size of the Conus in combination with a remarkable development of the bulbus, especially in teleosts; and (ii) loss of the myocardial compact layer of the ventricle in many teleost species.
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The bulbus arteriosus of the holocephalan heart: gross anatomy, histomorphology, pigmentation, and evolutionary significance.
Zoology (Jena Germany), 2017Co-Authors: Cristina Castillo Rodríguez, Miguel A. López-unzu, Borja Fernández, Valentín Sans-coma, Miguel Lorenzale, Francisca Salmerón, Ana C DuranAbstract:This study was designed to determine whether the outflow tract of the holocephalan heart is composed of a myocardial Conus arteriosus and a non-myocardial bulbus arteriosus, as is the case in elasmobranchs. This is a key issue to verify the hypothesis that these two anatomical components existed from the onset of the jawed vertebrate radiation. The Holocephali are the sister group of the elasmobranchs, sharing with them a common, still unknown Palaeozoic ancestor. The sample examined herein consisted of hearts from individuals of four species, two of them belonging to the Chimaeridae and the other two to the Rhinochimaeridae. In all specimens, the cardiac outflow tract consisted of a Conus arteriosus, with myocardium in its walls and two rows of valves at its luminal side, and an intrapericardial bulbus arteriosus shorter than the Conus and devoid of valves. The bulbus, mainly composed of elastin and smooth musculature, was covered by the epicardium and crossed longitudinally by coronary artery trunks. These findings give added support to the viewpoint that the outflow tract of the primitive heart of the gnathostomes was not composed of a single component, but two, the Conus and the bulbus. All rabbitfish (Chimaera monstrosa) examined had pigment cells over the surface of the heart. The degree of pigmentation, which varied widely between individuals, was particularly intense in the cardiac outflow tract. Pigment cells also occurred in the bulbus arteriosus of one of the two hearts of the straightnose rabbitfish (Rhinochimaera atlantica) included in the study. The cells containing pigment, presumably derived from the neural crest, were located in the subepicardium.
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Structure of the Conus arteriosus of the sturgeon (Acipenser naccarii) heart. I: The Conus valves and the subendocardium
The Anatomical record, 2002Co-Authors: José M. Icardo, Elvira Colvee, Maria Carmela Cerra, Bruno TotaAbstract:Sturgeons are bony fish that retain structural traits typical of the more primitive Chondrostei. From an evolutionary viewpoint, sturgeons are considered relic fish. However, they show remarkable ecological plasticity and are well adapted to contemporary environmental conditions. Although development of the cardiovascular system is critical for all organs and systems, and is affected by evolutionary changes, the structure of the sturgeon heart has been mostly overlooked. This is also true for the Conus arteriosus, which, as in Chondrostei, is endowed with several rows of valves and a layer of contractile myocardium. This work reports on the structure of the valves, the endocardium, and the subendocardium of the Conus arteriosus of the sturgeon (Acipenser naccarii) heart. It is part of a broader study that aims to cover the entire structure of the sturgeon heart. The Conus arteriosus of 15 A. naccarii hearts, ranging in age from juveniles to sexually-differentiated adults, has been studied by conventional light, transmission (TEM), and scanning electron microscopy (SEM). In addition, maceration of the soft tissues with NaOH, and actin localization by fluorescent phalloidin has been used. The Conus is a tubular chamber that arises from the right ventricular side and presents two constrictions at the Conus-ventricle and Conus-aorta junctions. The Conus is endowed with three rows of valves: one distal and two proximal. The segment of the Conus located between the distal and the two proximal rows is devoid of valvular structures. The distal row has four leaflets, while the two proximal rows show the greatest variation in leaflet number, size, and shape. All leaflets have collagenous chordae tendineae arising from the free border and from the parietal side of the leaflets. The endocardium is a flat endothelium which shows a thick, irregular basement membrane. The leaflet body is formed by a loose connective tissue which blends with the subendocardium. The subendocardium is a connective tissue consisting of myofibroblasts, collagen, and elastin. It is divided into two distinct areas: one proximal, which shows little elastin and poorly organized collagen; and one distal, which is rich in elastin, with cells and extracellular fibers organized into layers that are oriented in alternative circumferential and longitudinal directions. The present report is the first systematic analysis of the structure of the sturgeon Conus. Descriptions of the Conus valves should recognize the existence of three valve rows only. The variability in valve morphology, and the loose structure of the leaflet tissue make it unlikely that the valves play an effective role in preventing blood backflow. In this regard, the ventricle-Conus constriction may act as a sphincter. The subendocardium is an elastic coat capable of actively sustaining the tissue deformation that accompanies the heart contractile cycle. Further comparative studies are needed to provide deeper insight into the structural changes that accompany phyletic diversification. Anat Rec 267:17–27, 2002. © 2002 Wiley-Liss, Inc.