Heart and the peritoneal cover of the gut sinus in the polychaete Arenicola marina: an ultrastructural and autoradiographic study.
To elucidate the cellular mechanism underlying the growth of the peritoneal cover of the gut sinus and the heart in the polychaete Arenicola marina, cellular organization of these structures and proliferative potential of their cells were investigated using electron microscopy and electron microscopic autoradiography. Arenicola has a pair of dorsolaterally situated hearts connected to the gut sinus via a short duct and composed of two muscular layers separated by a layer of the extracellular matrix (ECM). The peritoneal cover of the gut sinus and the outer muscular layer of the heart present a myoepithelial layer resting on the ECM. The inner muscular layer of the heart is composed of myofibril-containing cells lacking well-defined polarity in arrangement of organelles. However, their persistent connection to branches of the ECM and the adherens-like intercellular junctions allow for considering the inner layer a modified myoepithelium. In the peritoneal cover of the gut sinus and in both myoepithelial layers of the heart, noncontractile epithelial cells have been observed. As determined by thymidine labeling, these epithelial cells are capable of DNA synthesis, while myoepithelial cells are not. Some suggestions are made about the myogenic nature of the epithelial cells in the investigated structures of A. marina.
Martynova
Marina G
MG
Institute of Cytology, Russian Academy of Sciences, 194064 St Petersburg, Russia. heartdev@mail.cytspb.rssi.ru
Chaga
Oleg Y
OY
D000818:Animals; D019521:Body Patterning / Q000502:physiology; D004064:Digestive System / Q000196:embryology / Q000648:ultrastructure; D004068:Digestive System Physiological Phenomena; D004847:Epithelial Cells / Q000502:physiology / Q000648:ultrastructure; D006321:Heart / Q000196:embryology* / Q000254:growth & development*; D008854:Microscopy, Electron; D009206:Myocardium / Q000648:ultrastructure*; D032389:Myocytes, Smooth Muscle / Q000502:physiology / Q000648:ultrastructure; D010537:Peritoneum / Q000196:embryology / Q000502:physiology / Q000648:ultrastructure; D011077:Polychaeta / Q000254:growth & development* / Q000502:physiology / Q000648:ultrastructure*