Media highlights in the Dec. 15 issue of Biophysic...( Bethesda MD - The December 15th issu...)

Bethesda, MD - The December 15th issue of Biophysical Journal, published by the Biophysical Society, is now available online. Topics of interest include cardiac contraction, x-ray diffraction, DNA elasticity, optical trapping; single-molecule, ADP-bound cross-bridges; cooperativity, and sarcomere.

Volume 93, Issue 12, December 15, 2007

Effects of Sustained Length-Dependent Activation on In Situ Cross-Bridge Dynamics in Rat Hearts

James T Pearson, Monash University
Mikiyasu Shirai, Hiroshima International University
Hirotsugu Tsuchimochi, National Cardiovascular Center
Daryl O Schwenke, University of Otago
Takayuki Ishida, Hiroshima International University
Kenji Kangawa, National Cardiovascular Center
Hiroyuki Suga, National Cardiovascular Center
Naoto Yagi, JASRI, SPring-8

Keywords: cardiac contraction; interfilament spacing; myosin cross-bridges; x-ray diffraction

The intrinsic ability of the heart to adjust the strength of its contractions to the amount of blood filling the heart has been the subject of much interest, and even more speculation. This fundamental mechanism that regulates heart work with every single beat is vital to our existence. Breakdown of this cellular mechanism of control leads to lung congestion and heart failure. The force of contraction is essentially determined by the interactions of two large proteins, actin and myosin. Our group now demonstrates that the cellular mechanism involves sensing the spacing between the filaments of myosin and actin as the heart fills with blood. The strength of contraction is then adjusted according to the stretch of the proteins within the muscle fibres. We have been able to do this by rapidly analyzing the scatter of pulses of synchrotron x-ray radiation off the muscle fibres of the intact heart as it contracts spontaneously. Many other proteins are known to be associated with actin and my
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