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.

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.