Purchase this article with an account.
Zhao-Bo Li, Gunther H. Rossmanith, Joseph Foon Yoong Hoh; Cross-Bridge Kinetics of Rabbit Single Extraocular and Limb Muscle Fibers. Invest. Ophthalmol. Vis. Sci. 2000;41(12):3770-3774.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
purpose. To gain insights into the functional significance of myosin heavy-chain
(MyHC) heterogeneity by comparing the mechanical kinetic properties of
single rabbit extraocular muscle (EOM) fibers with those of limb
fibers. EOMs are known to contain developmental and EOM-specific MyHCs
in addition to those present in limb muscles, and MyHCs profoundly
influence muscle mechanics.
methods. Isometric cross-bridge kinetics were analyzed in
Ca2+-activated single glycerinated fibers from rabbit EOM
and limb fast and slow muscles at 15°C by means of mechanical
perturbation analysis. The plots of stiffness and phase against
frequency display a characteristic frequency, f min, at which stiffness is minimum, and
phase shift is zero. The value of f min is
independent of Ca2+ or force level but reflects the
kinetics of cross-bridge cycling.
results. Analysis of 121 limb fast fibers gave f min values ranging from 10 to 26 Hz. f min for
the 10 slow soleus fibers was 0.5 Hz. Analysis of 170 EOM fibers gave f min values in the range for fast limb
fibers, but in addition yielded f min values
below (4–9 Hz) and above (27–33 Hz) this range.
conclusions. The wider range of mechanical kinetic characteristics in EOM fibers
compared with limb fibers is likely due to the expression of
developmental (low f min) and EOM-specific
(high f min) MyHCs in addition to isoforms
present in adult limb muscles. The considerable diversity of functional
characteristics in EOM fibers is likely to be important for rotating
the eyeball at various speeds during tracking and for executing
saccades over a wide range of angles.
This PDF is available to Subscribers Only