The myoarchitecture of the vertebrate cardiac ventricles: evolution and classification.

The ventricle of the vertebrate heart is the main segment of the cardiac outflow region. Compared with other cardiac components, it shows remarkable histomorphological variation among different animal groups. This variation is especially apparent in the myocardium, which is generally classified into three main types: trabeculated, compact and mixed.

The Medical versus Zoological Concept of Outflow Tract Valves of the Vertebrate Heart.

The anatomical elements that in humans prevent blood backflow from the aorta and pulmonary artery to the left and right ventriclesare the aortic and pulmonary valves, respectively. Each valve regularly consists of three leaflets (cusps), each supported by its valvular sinus. From the medical viewpoint, each set of three leaflets and sinuses is regarded as a morpho-functional unit.

Development of the ventricular myocardial trabeculae in Scyliorhinus canicula (Chondrichthyes): evolutionary implications.

The development of the ventricular myocardial trabeculae occurs in three steps: emergence, trabeculation and remodeling. The whole process has been described in vertebrates with two different myocardial structural types, spongy (zebrafish) and compact (chicken and mouse). In this context, two alternative mechanisms of myocardial trabeculae emergence have been identified: (1) in chicken and mouse, the endocardial cells invade the two-layered myocardium; (2) in zebrafish, cardiomyocytes from the monolayered myocardium invaginate towards the endocardium.

Myosin heavy chain isoforms in the myocardium of the atrioventricular junction of Scyliorhinus canicula (Chondrichthyes, Carcharhiniformes).

The atrioventricular junction of the fish heart, namely the segment interposed between the single atrium and the single ventricle, has been studied anatomically and histologically in several chondrichthyan and teleost species. Nonetheless, knowledge about myosin heavy chain (MyHC) in the atrioventricular myocardium remains scarce. The present report is the first one to provide data on the MyHC isoform distribution in the myocardium of the atrioventricular junction in chondrichthyans, specifically in the lesser spotted dogfish, Scyliorhinus canicula, a shark species whose heart reflects the primitive cardiac anatomical design in gnathostomes.

Pigmentation of the aortic and pulmonary valves in C57BL/6J x Balb/cByJ hybrid mice of different coat colours.

Neural crest-derived melanocytes have been recorded in several parts of the mammalian heart but not in the pulmonary valve. We report here the presence of melanin-containing cells in the leaflets (cusps) of both the aortic and pulmonary valves. A total of 158 C57BL/6J x Balb/cByJ hybrid mice exhibiting four coat colours, namely black, white, agouti and non-agouti brown, were examined.

Differential expression of myosin heavy chain isoforms in cardiac segments of gnathostome vertebrates and its evolutionary implications.

Background: Immunohistochemical studies of hearts from the lesser spotted dogfish, (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.

The valves of the cardiac outflow tract of the starry ray, Raja asterias (Chondrichthyes; Rajiformes): Anatomical, histological and evolutionary aspects.

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 anatomical components of the cardiac outflow tract of chondrichthyans and actinopterygians.

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.

The bulbus arteriosus of the holocephalan heart: gross anatomy, histomorphology, pigmentation, and evolutionary significance.

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.

Anatomical, histochemical and immunohistochemical characterisation of the cardiac outflow tract of the silver arowana, Osteoglossum bicirrhosum (Teleostei: Osteoglossiformes).

The cardiac outflow tract of chondrichthyans and actinopterygians is composed of a myocardial conus arteriosus and a non-myocardial bulbus arteriosus. In teleosts, the conus has been subjected to a reduction in size over the evolution in conjunction with the further development of the bulbus. Most studies on the outflow tract of the teleost heart refer to species of modern groups and are mainly devoted to the bulbus.

Structure and vascularization of the ventricular myocardium in Holocephali: their evolutionary significance.

It was generally assumed that the ventricle of the primitive vertebrate heart was composed of trabeculated, or spongy, myocardium, supplied by oxygen-poor luminal blood. In addition, it was presumed that the mixed ventricular myocardium, consisting of a compacta and a spongiosa, and its supply through coronary arteries appeared several times throughout fish evolution. Recent work has suggested, however, that a fully vascularized, mixed myocardium may be the primitive condition in gnathostomes.

Quadricuspid aortic valves in Syrian hamsters and their formation according to current knowledge on valvulogenesis.

Occurrence of quadricuspid aortic valves has been reported in humans, in nine dogs and in a greater white-toothed shrew. Moreover, two cases of developing aortic valves with four anticipated leaflets have been described in Syrian hamster embryos. Currently, however, no case of quadricuspid aortic valve in adult hamsters has been recorded.

The anatomical components of the cardiac outflow tract of the gray bichir, Polypterus senegalus: their evolutionary significance.

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.

Factors other than genotype account largely for the phenotypic variation of the pulmonary valve in Syrian hamsters.

Understanding of the aetiology of congenitally anomalous pulmonary valves remains incomplete. The aim of our study, therefore, was to elucidate the degree to which the phenotypic variation known to exist for the pulmonary valve relies on genotypic variation. Initially, we tested the hypothesis that genetically alike individuals would display similar valvar phenotypes if the phenotypic arrangement depended entirely, or almost entirely, on the genotype.

Genetically alike Syrian hamsters display both bifoliate and trifoliate aortic valves.

The bifoliate, or bicuspid, aortic valve (BAV) is the most frequent congenital cardiac anomaly in man. It is a heritable defect, but its mode of inheritance remains unclear. Previous studies in Syrian hamsters showed that BAVs with fusion of the right and left coronary leaflets are expressions of a trait, the variation of which takes the form of a phenotypic continuum.

Phylogeny informs ontogeny: a proposed common theme in the arterial pole of the vertebrate heart.

In chick and mouse embryogenesis, a population of cells described as the secondary heart field (SHF) adds both myocardium and smooth muscle to the developing cardiac outflow tract (OFT). Following this addition, at approximately HH stage 22 in chick embryos, for example, the SHF can be identified architecturally by an overlapping seam at the arterial pole, where beating myocardium forms a junction with the smooth muscle of the arterial system. Previously, using either immunohistochemistry or nitric oxide indicators such as diaminofluorescein 2-diacetate, we have shown that a similar overlapping architecture also exists in the arterial pole of zebrafish and some shark species.

Bicuspid aortic valves with different spatial orientations of the leaflets are distinct etiological entities.

Objectives: The aim of this study was to decide whether bicuspid aortic valves (BAVs) with fused right and noncoronary leaflets (R-N) and BAVs with fused right and left leaflets (R-L) have different etiologies or are the product of a single diathesis.

Background: The BAV is the most common congenital cardiac malformation. The R-N and R-L BAVs are the most frequent BAV subtypes.

The development of the epicardium in the sturgeon Acipenser naccarii.

This article reports on the development of the epicardium in alevins of the sturgeon Acipenser naccarii, aged 4-25 days post-hatching (dph). Epicardial development starts at 4 dph with formation of the proepicardium (PE) that arises as a bilateral structure at the boundary between the sinus venosus and the duct of Cuvier. The PE later becomes a midline organ arising from the wall of the sinus venosus and ending at the junction between the liver, the sinus venosus and the transverse septum.

Chondrichthyans have a bulbus arteriosus at the arterial pole of the heart: morphological and evolutionary implications.

It has been generally assumed that the outflow tract of the chondrichthyan heart consists of the conus arteriosus, characterized by cardiac muscle in its walls. However, classical observations, neglected for many years, indicated that the distal component of the cardiac outflow tract of several elasmobranch species was composed of tissue resembling that of the ventral aorta. The present study was outlined to test the hypothesis that this intrapericardial, non-myocardial component might be homologous to the actinopterygian bulbus arteriosus.

Dorsoventral transposition of the heart chambers in sturgeon Acipenser naccarii alevins.

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.

Solitary coronary ostium in the aorta in Syrian hamsters. A morphological study of 130 cases.

Background: Solitary coronary ostium in the aorta (SCOA) is a rare anomaly, the pathogenesis of which remains uncertain. The lack of an animal model is one of the reasons why little understanding of this question has been gained. The aim was to examine the coronary distribution patterns associated with SCOA in laboratory inbred Syrian hamsters.

The development of the sturgeon heart.

This paper presents a sequential analysis of the development of the sturgeon (Acipenser naccarii) heart from the end of gastrulation to the early juvenile stages. At late neurulation, the heart appears as a straight, short tube located over the endoderm that forms the wall of the yolk sac, in front of the developing head. The heart axis is aligned with the axis of the developing head.

Differentiation of the cardiac outflow tract components in alevins of the sturgeon Acipenser naccarii (Osteichthyes, Acipenseriformes): implications for heart evolution.

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 naccarii. The sample studied consisted of 178 alevins between 1 and 24 days posthatching.

Formation of cartilage in the heart of the Spanish terrapin, Mauremys leprosa (Reptilia, Chelonia).

Cartilaginous deposits are regularly present in the heart of several reptilian, avian, and mammalian species. The formation of these extraskeletal cartilages has been studied in birds and mammals, but not in reptiles. The aim here was to elucidate this question in the Spanish terrapin.