Structural evidence for contractile units in the giant smooth muscle cell ofBeröe

✍ Scribed by Hernandez-Nicaise, M. L. ;Nicaise, G.

• Book ID: 102806042
• Publisher: John Wiley and Sons
• Year: 1986
• Tongue: English
• Weight: 680 KB
• Volume: 6
• Category: Article
• ISSN: 0886-1544
• DOI: 10.1002/cm.970060213

✦ Synopsis

Bundles of giant smooth muscle fibers of the ctenophore Beroe have been stretched up to four times their initial length and then examined by transmission electron microscopy. Stretching induces the segregation of actin and thick (myosinlike) filaments into separate domains. The thick filaments domains are made of 20-30 filaments, with a regular spacing identical to that of nonstretched fibers. A moderate stretching permits the visualization of microtendons associating actin filament bundles to hyaluronidase-resistant condensations of the extracellular matrix. It is deduced from these observations that Beroe giant smooth muscle fibers possess myofibrils which attach at both ends upon the sarcolemmal membrane. Each myofibril is probably made of two long actin filament bundles (of approximately 150 filaments) and short (2-3 pm) myosinlike bundles (of approximately 30 filaments).