title: Direct measurement of Vorticella contraction force by micropipette deflection.
abstract: The ciliated protozoan Vorticella convallaria is noted for its exceptionally fast adenosine triphosphate-independent cellular contraction, but direct measurements of contractile force have proven difficult given the length scale, speed, and forces involved. We used high-speed video microscopy to image live Vorticella stalled in midcontraction by deflection of an attached micropipette. Stall forces correlate with both distance contracted and the resting stalk length. Estimated isometric forces range from 95 to 177 nanonewtons (nN), or 1.12 nN·μm-1of the stalk. Maximum velocity and work are also proportional to distance contracted. These parameters constrain proposed biochemical/physical models of the contractile mechanism.
authors.affiliation: Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Danielle
authors.initials: D
authors.lastname: France
authors.affiliation: Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Tejada
authors.affiliation: Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Matsudaira
mesh_terms: D000465:Algorithms; D001696:Biomechanical Phenomena; D002118:Calcium / Q000378:metabolism*; D018715:Microscopy, Video / Q000295:instrumentation / Q000379:methods*; D009068:Movement / Q000502:physiology; D016802:Oligohymenophorea / Q000502:physiology*; D015800:Protozoan Proteins / Q000378:metabolism; D013997:Time Factors
chemical_list: D015800:Protozoan Proteins; D002118:Calcium
keywords: 
  Vorticella
  ; biomimicry; ciliate; molecular spring; motility; stall force