The Sensitivity of Developing Cardiac Myofibrils to Cytochalasin-B

  1. Francis J. Manasek*,
  2. Beth Burnside†,‡, and
  3. John Stroman*
  1. *Department of Anatomy, Harvard Medical School, Boston, Massachusetts 02115
  2. Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02115
  3. Department of Cardiology and Pathology, The Children's Hospital Medical Center, Boston, Mass. 02115
  4. †Department of Anatomy, Harvard Medical School, Boston, Mass. 02115

Abstract

Developing cardiac muscle cells of 11- to 13-somite chick embryos are sensitive to cytochalasin-B. In cultured chick embryos, ranging in development from 11 to 13 somites, hearts stop beating in the presence of this agent. Both polarized light and electron microscopic examination show that cytochalasin-B disrupts existing myofibrils and inhibits the formation of new ones. Discrete Z-bands are not present in treated heart cells and thick, presumably myosin, filaments are found in disarray. These effects are reversible; after cytochalasin-B is removed from the medium, heartbeat recovers and myofibrils with discrete Z-bands reappear. Fibrillar sensitivity appears to be a function of age since fibrils in hearts of embryos having from 22 to 28 pairs of somites are more resistant.

Footnotes

  • ↵ ‡ Address reprint requests to: Dr. M. B. Burnside, Department of Anatomy, Harvard Medical School, Boston, Mass. 02115

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  1. PNAS 1972-02 vol. 69 no. 2 308-312
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