The anatomical components of the cardiac outflow tract of the bichir, polypterus senegalus. Evolutionary significance

El resumen aparece en el Program & Abstracts of the 10th International Congress of Vertebrate Morphology, Barcelona 2013.Anatomical Record, Volume 296, Special Feature — 1: P-077.In chondrichthyans and actinopterygians, the outflow tract of the heart, namely, the cardiac portion intercalated between the ventricle and the ventral aorta, consists of two anatomical components: conus arteriosus and bulbus arteriosus. In chondrichthyans and extant representatives of phylogenetically ancient actinopterygian groups, the conus and bulbus are well-developed in size, whereas in most teleosts, the bulbus is markedly larger than the conus. Current knowledge about the cardiac outflow tract of the polypteriformes is scarce and highly contradictory, a fact that contrasts with their crucial phylogenetic position at the source of the actinopterygian lineage. In fact, it remains uncertain whether they have a bulbus at the arterial pole of the heart. The present study aimed to elucidate the anatomical arrangement of the cardiac outflow tract of the bichir in an attempt to improve our understanding of the evolution of the vertebrate heart. We examined the hearts from 12 bichirs using histochemical and immunohistochemical techniques. Our findings showed that the outflow tract of the bichir consists of two components, namely, a long conus arteriosus, largely composed of myocardial tissue and furnished with a variable number of valves at its luminal side, and a very short, elastin rich bulbus arteriosus, devoid of myocardium. The bulbus has an arterial-like histological composition. However, it differs from the aorta because it has a thicker wall, shows a different arrangement of the histological elements, is covered by the epicardium and is crossed by coronary arteries. The present observations are consistent with the notion that the conus arteriosus and the bulbus arteriosus have coexisted from the beginning of the jawed vertebrate radiation. This is of particular interest, because there is evidence that the bulbus arteriosus, which is a second heart field derivative, is homologous with the intrapericardial portions of the aorta and pulmonary artery of birds and mammals.Proyecto CGL2010-16417/BOS; Fondos FEDER

Endocardial-mesenchymal transition underlies fusion of the conotruncal ridges during embryonic cardiac outflow tract septation

The embryonic cardiac outflow tract (conotruncus) is a single tubular chamber that connects the right ventricle with the aortic arch arteries. It contains two opposite, long and helical mesenchymal cushions covered by endocardial cells (conotruncal ridges). Conotruncal division (septation) gives rise to the adult right and left outflows together with the aortic and pulmonary valves. It takes place by fusion of the two opposite ridges and formation of the conotruncal septum. Although the participation of neural crest cells in septation is well established, the mechanism of fusion of the conotruncal ridges remains unknown. Defects in fusion have been shown to produce bicuspid aortic valve, the most prevalent human congenital cardiac malformation, in a hamster model. Three fusion mechanisms have been proposed to operate during embryonic development: epithelial adhesion, epithelial apoptosis and epithelial-mesenchymal transition (EMT). The first mechanism entails the expression of adhesion molecules and the maintenance of the identity of cells in contact, whereas in the other two, epithelial cells covering the fusing structures disappear by apoptosis or by transforming into mesenchymal cells. The objective of this study is to elucidate the mechanism involved in the fusion of the conotruncal ridges. Immunofluorecence techniques were used in ED 11-12 hamster embryos. The results indicate that the mechanism of EMT, but not epithelial adhesion or apoptosis, is involved in the process of fusion of the conotruncal ridges. The EMT mechanism associated with conotruncal septation seems to be uncoupled from the process of formation of the endocardial cushions, which takes place at early stages. With these results, we can raise the hypothesis that defects in the EMT process may lead to different morphological types of bicuspid aortic valve.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. This study was supported by P10-CTS-6068 (Junta de Andalucía), CGL2014-52356-P and CGL2017-85090-P (Ministerio de Economía y Competitividad), contract UMAJI75 (Junta de Andalucía, European Social Fund), and Universidad de Málaga

ICN as Network Infrastructure for Multi-Sensory Devices: Local Domain Service Discovery for ICN-based IoT Environments

Information Centric Networking (ICN) is an emerging research topic aiming at shifting the Internet from its current host-centric paradigm towards an approach centred around content, which enables the direct retrieval of information objects in a secure, reliable, scalable, and efficient way. The exposure of ICN to scenarios other than static content distribution is a growing research topic, promising to extend the impact of ICN to a broader scale. In this context, particular attention has been given to the application of ICN in Internet of Things (IoT) environments. The current paper, by focusing on local domain IoT scenarios, such as multi-sensory Machine to Machine environments, discusses the challenges that ICN, particularly Interest-based solutions, impose to service discovery. This work proposes a service discovery mechanism for such scenarios, relying on an alternative forwarding pipeline for supporting its core operations. The proposed mechanism is validated through a proof-of-concept prototype, developed on top of the Named Data Networking ICN architecture, with results showcasing the benefits of our solution for discovering services within a collision domain. © 2017 Springer Science+Business Media New Yor

Ventricular myocardial trabeculation in chondrichthyans. Evolutionary implications

The formation of trabeculae (trabeculation) in vertebrates occurs during cardiac development in the three structural types of ventricular myocardium, namely, compact, spongy and mixed. The compact type is mainly composed of compacted muscular fibers and the spongy type of muscular trabeculae. The mixed type, with an inner trabecular and an outer compact layer, has been proposed as the primitive condition in gnathostomes. In vertebrate models, trabeculation initiates following two alternative mechanisms: (1) in chicken and mouse, the endocardial cells evaginate towards the two-layered myocardium; (2) in zebrafish, cardiomyocytes from the mono-layered myocardium invaginate towards the endocardium. Trabeculation in the mixed myocardium has not been described yet. We have studied the mixed myocardium formation in the dogfish (Scyliorhinus canicula, Elasmobranchii) using light, scanning and transmission electron microscopy. At stage 27, the ventricle consists of a two-layered myocardium internally lined by endocardium, both separated by cardiac jelly. Trabeculation starts at stage 28, when small spaces between cardiomyocytes appear, the cardiac jelly become thinner and the endocardium focally contacts the myocardium. At stage 29 the spaces between cardiomyocytes increase in size and get lined by the endocardium, shaping the presumptive trabeculae. At later stages, the trabeculae increase in complexity and the outer cardiomyocytes proliferate and get compacted, delineating the definitive trabeculated and compact myocardia. We conclude that early trabeculation in elasmobranchs matches that described in tetrapods. Thus, the mechanism of trabeculation of the mixed ventricular myocardium has been conserved in the formation of the compact myocardium of tetrapods. Additional studies in actinopterygians with different myocardial types may uncover how trabeculation has evolved during the evolution of gnathostomes.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. CGL2017-85090-P, FPU15/03209, UMAJI75 and FEDER

Coronary artery high take-off in rodents and the possible involvement of Smad2

The coronary arteries (CAs) supply the mammalian heart with oxygenated blood. They arise from the right and left aortic valve sinuses at the aortic root. In humans, the occurrence of a CA arising ectopically from the tubular aorta, a condition called high take-off (HTO), is rare (A (Smad2C>A) allele is associated with HTO in this species. In order to test whether HTO occurs in association with Smad2C>A in other rodents, we examined the anatomical origin of the CAs, by means of stereomicroscopy and a corrosion cast technique, in 3,388 specimens belonging to 17 rodent species. In addition, Smad2 DNA sequence from M. musculus was compared by Blastn analyses with that from six of the species examined in which this sequence is known (Mus spretus, Rattus norvegicus, Apodemus sylvaticus, Myodes glareolus, Mesocricetus auratus, Microtus agrestis). HTO occurred in nine out of 17 species studied. The incidence of HTO ranged from 0.4% to 6.5% (low) in three species and from 15.9% to 25% (high) in six species. The Smad2 sequence showed similarities higher than 75% for the whole gene, and higher than 71% for the intron sequence that includes the rs29725537:C>A Single Nucleotide Polymorphism. The Smad2C>A allele was identified only in M. spretus and A. sylvaticus, with high incidences of HTO, whereas R. norvegicus, M. glareolus, M. auratus and M. agrestis showed low or null incidences. We conclude that HTO is a common trait in rodents, which does not lead to cardiac pathology probably due to the intramyocardial condition of their CAs, as opposed to the human subepicardial CAs. The Smad2C>A allele may be involved in the development of HTO and probably other phenotypes in different rodent species.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Funding: CGL2017-85090-P, FPU15/03209, UMAJI75 and FEDER