Photon Factory Activity Report 2004 #22 Part B (2005)
Biological Science

15A/2003G318

The effect of muscle length changes on the X-ray diffraction pattern fromtetanized frog skeletal muscle II
Hidehiro TANAKA1, Takakazu, KOBAYASHI2, Yasunori TAKEZAWA3,Yasunobu SUGIMOTO3, Kanji OSHIMA3, Katsuzo WAKABAYASHI3
1
School of Nursing, Teikyo Heisei Junior College, Ichihara, Chiba 290-0192
2
Dept of Electronic Engineering, Shibaura Institute of Technology, Minato-ku, Tokyo l08-8548
3

Dept of Biophysical Engineering, Graduate School of Engineering Science, Osaka University,Toyonaka, Osaka 560-8531

M3 ac ross th e meridianCount (x 1000)

1.6

re stte tanus
strretched

1.2
0.8
0.4
0-24-16-80816
Chnannel from t he meridian

24Fig.1. Intensity profiles of M3 reflection across the meridian.
The ordinate, total x-ray counts. The abscissa, channel
numbers from the meridian. Half width of M3 increased whenthe muscle contracted, but appreciable effect of the stretch on
the half width was not seen.
245248.psd
1.2
relative cha nges

Introduction
When the skeletal muscle is stretched slowly at theplateau of the isometric tetanus, the tension increases
during the stretch. The tension starts to return to a newtension level, which is higher than the initial isometriclevel when the length change terminates. In a release, thetension behaves in a similar but opposite way. The
intensity of the 3rd meridional reflection (M3), whicharises from the 14.3 nm repeat of the myosin heads,
decreases during both stretch and release [1-3]. Thechange of M3 by the length change is explained asfollows: if myosin heads attach to the thin filament in aconfiguration perpendicular to the filament axis, bothstretch and release tilt the myosin heads. This tilting of
the myosin heads results in the broadening of axial
projection of the mass of the myosin heads [2,3]. In theprevious report it was showed that M3 increases during
stretch and decreases during release if the applied lengthchange is smaller than 1% of the muscle length. [4,5]Methods
The sartorius muscle from a bullfrog was tetanized for 2.2
sec by applying supra-maximal current pulses (20Hz at120C). The contraction was repeated 10 times at aninterval of 3 min. The length change of the muscle wasapplied at the plateau of the isometric tetanus. The X-ray
patterns were recorded by an X-ray CCD detector with atime resolution of 15 msec.
Results
Fig.1 shows the intensity distribution across themeridian in the region of the M3 reflection. Peakbroadening of M3 was observed when the musclecontracted. But the width of M3 after the contraction
remained unchanged during and after stretch. The absenceof peak broadening rules out some types of disorder as
possible origins of the intensity change, and suggests it isdue to either (i) a change in conformation of the myosin
heads so that their mass projection is more sharpened(increased) or spread out (decreased) along the filamentaxis, or (ii) a change in the dispersion of the axial
positions of the heads from the ideal 14.3 nm periodicity.
Fig.2 shows an increase in M3 when the muscle isstretched by 1 % Lo with a steady velocity, which is 10
times faster velocity than the previous case [4],suggesting an intensity increase by stretch is caused by
the amount of stretch rather than the speed of the stretch.

10.8
0.6
0.4

M3tens ion
length0.2000.6s

1.2s

1.8s

2.4s

3.0s

time

Fig.2 At the plateau of contraction, the muscle was stretchedby 1 % Lo with a steady velocity of 0.15Lo/sec, which is 10times faster velocity than the previous case[4].
References[1] N.Yagi & I.Matsubara, Biophys.J. 45 611 (1984)[2] N.Yagi & K.Wakabayashi, J.J.Physio1. 45 583 (1995)[3 K.Wakabayashi et al, Biophys.J. 49 581 (1986)[4] H.Tanaka et al PF activity report 2004
[5] H.Tanaka et al J.J.Physiol. 55, Supplement (2005)
kobataka@sic. shibaura-it.ac.jp

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