Light and X‐ray diffraction studies on chick skeletal muscle under controlled physiological conditions

Abstract

SUMMARY1. The sarcomere length (s) of chick slow and fast muscles (anterior and posterior latissimus dorsi (ant. lat. dorsi and post. lat. dorsi)) was measured by the method of light diffraction. In resting ant. lat. dorsi, s changed from 1-76 to 2-30 ,um during stretch from minimum to maximum muscle lengths in situ, and in resting post. lat. dorsi from 2-18 to 2-63 Itm.2. Resting tension started to rise in ant. lat. dorsi when s exceeded 1-7-1-8 gim, but in post. lat. dorsi not until s exceeded 2-6-2-7 4am.3. X-ray diffraction patterns showed that ant. lat. dorsi contains collagen filaments; collagen reflexions were not seen in patterns obtained from post. lat. dorsi with the same exposure time.4. The relation between active tension and sarcomere length was similar for ant. and post. lat. dorsi. The maximum active tension was observed when s = 2-05-2-15 #m in ant. lat. dorsi, and when s = 2-10-2-25 ,m in post. lat. dorsi.5. X-ray diffraction patterns from both muscles showed that the periodic structures of the thick and thin filaments are similar to those in frog and rabbit skeletal muscles.6. The volume of the myofilament lattice in resting ant. lat. dorsi was 3-06 (± 0*14) x 109 A , in resting post. lat. dorsi 2-98 (± 0.09) x 109 A .These values are close to that of frog skeletal muscle. The lattice volume remained constant in ant. lat. dorsi and post. lat. dorsi over the range of sarcomere lengths found in situ. 7. The equatorial diffraction patterns from the ant. lat. dorsi in rigor (glycerol extracted) were different from that of the resting muscle, and suggested that a large number of cross-bridges were attached to the thin

Cross‐bridge movement in fast and slow skeletal muscles of the chick.

“…1, X-ray equatorial diffraction patterns from both ALD and PLD ( Fig. 1) showed two equatorial intensity peaks indexed as (1,0) and (1,1) reflections from the hexagonal myofilament lattice (Matsubara, 1974). The diffraction pattern from ALD had a higher background than that from PLD, suggesting the presence of larger amounts of non-contractile materials.…”

“…The (1, 0) spacings were 34 and 36 nm respectively. From these spacings and the constant volume relationship between sarcomere length and the (1,0) spacing in ALD and PLD (Matsubara, 1974), it is deduced that the sarcomere length was approximately 2-6 and 2-3 ,tm, respectively.…”

Myosin

“…Part of the problem may be the time domain in which motions occur, since various methods used to study this problem are sensitive to motions on vastly different time scales. X-ray patterns fr om resting vertebrate striated muscle (fast and slow skeletal and cardiac) show a series of layer lines that are believed to arise from the myosin cross-bridges (97,122,123). Another possible source of variations lies in the effect of solvent since the proteolytic susceptibility of myosin rod is highly sensitive to the presence and concentration of Hofmeister series anions (121).…”

Difference in Stretching of Sarcomeres between Medial Gastrocnemius and Tibialis Anterior by Tibial Lengthening: An Experiment in Rabbits

“…Sarcomere length was calculated as the distance between the zeroth and first order diffraction lines using the grating equation: nλ = d⋅sin θ n where n is the order of the diffraction line assuming the zeroth order bisected the orders on either side, λ is the wavelength of the light, d is the sarcomere length, and θ n is the n-th order diffraction angle. 12,13 Measurements were obtained from 10 different sites in the middle two thirds on each muscle fibre bundle and averaged to one value per muscle fibre bundle. The mean sarcomeric length of a given muscle was calculated by averaging the sarcomeric lengths of 5 muscle fibre bundles.…”