title: Morphological and physiological properties of non-striated muscle from the tunicate, Ciona intestinalis: parallels with vertebrate skeletal muscle.
abstract: Non-striated muscle from the longitudinal body wall muscle in an adult ascidian (tunicate) is characterized morphologically and physiologically. These muscles are unique among chordate non-striated (i.e. 'smooth') muscles in that they are composed of discrete bundles of several small diameter (4-10 microns) muscle cells (fibers) arranged in parallel functional units. Each bundle is wrapped by a basal lamina, and at least some appear to be directly innervated at a neuromuscular junction similar to an end plate. In these regards, a bundle of Ciona smooth muscle cells is analogous to a skeletal muscle fiber of a vertebrate. This analogy also extends to physiological properties. Ciona muscle generates a rapid all-or-none Ca action potential which gives rise to a brisk twitch with brief latency. These anatomical and physiological adaptations are discussed in terms of the evolution of vertebrate skeletal muscle.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002938:Ciona intestinalis / Q000166:cytology*; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008564:Membrane Potentials; D008854:Microscopy, Electron; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000166:cytology* / Q000502:physiology / Q000648:ultrastructure; D009132:Muscles / Q000166:cytology* / Q000502:physiology / Q000648:ultrastructure; D009928:Organ Specificity; D013045:Species Specificity; D013324:Strontium / Q000494:pharmacology; D014561:Urochordata / Q000166:cytology*
chemical_list: D001464:Barium; D002110:Caffeine; D002118:Calcium; D013324:Strontium