Unusual anatomical origins of the coronary arteries in C57BL/6 mice. Are they strain-specific?

A previous manuscript [Fernández B, et al. (2008) J Anat 212, 12] reported on the unusual coronary artery patterns in mice belonging to the C57BL/6 strain. The aim here was to elucidate whether this pattern is unique to C57BL/6 mice or appears in other laboratory mouse strains and in wild-living mice. Stereomicroscopy, scanning electron microscopy, light microscopy and a corrosion cast technique were used to examine 597 adult mice belonging to three inbred strains (C57BL/6, Balb/c, DBA/2), three outbred stocks (CD1, OF1, NMRI) two hybrid lines (129sv × BL/6, CD2F1) and wild mice. It was shown that lock-like ostium is an exclusive trait of C57BL/6 mice, whereas left septal artery, accessory ostium, high take-off, intramural course and solitary ostium in aorta are all present in the different laboratory strains and wild mice included in the present study. However, each mouse population shows a specific incidence of these coronary conditions. Several clinically relevant human coronary artery anomalies are present in healthy mice from different strains that may serve as animal models for humans. These results should be taken into consideration in research concerning the murine coronary system, especially in coronary artery occlusion experiments and in studies on cardiovascular developmental biology using murine mutant lines.

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. Knowledge on the outflow tract of species belonging to early teleost groups is scarce. The aim here was to characterise the structure of the cardiac outflow tract of the silver arowana, a representative of the ancient teleost clade of the Osteoglossomorpha. The material consisted of hearts from six juvenile animals. The cardiac outflow tract of the silver arowana is composed of a conus, which supports two conal valves, and a bulbus. Both components are lined externally by the epicardium and internally by the endocardium. The conus is immunoreactive to antibodies against myosin heavy chains and is composed of compact myocardium, thus contrasting with the ventricle, which has exclusively trabeculated myocardium. The bulbus is immunoreactive to antibodies against smooth muscle α-actin and mainly consists of elastic fibres and smooth muscle cells, both arranged in three layers, outer, middle and inner. The most remarkable feature of the bulbus is the presence of two prominent longitudinal ridges, dorsal and ventral, at the luminal side, which serve to anchor the commissures of the conal valves. This arrangement has not been described so far in any fish species. Pigment cells, presumably of neural crest origin, are present in the subepicardium of the bulbus and anterior part of the ventricle.