Biomedical subjects
Publications and source records attributed to N Yagi.
Highly stretched muscles in which thick and thin filaments no longer overlap produce little or no tension on activation. In preparations producing no tension, the 42.9-nanometer myosin layer line shown in x-ray diffraction patterns does not become weaker. This suggests that myosin heads do not move from their resting positions in the absence of actin.
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The metabolic detoxication of thymol was investigated in rabbit and man. Thymol glucuronide which the aglycone is intact, was isolated from thymol medicated rabbit urine and identified as a acetyl derivative of methyl glucuronate. The hydroxylated product of thymol, thymohydroquinone, was recognized in a small amount in thymol medicated human urine. It was presumed that thymohydroquinone is excreted as ethereal sulfuric acid conjugate in man.
We have clarified that thiamine is cleaved by residual chlorine in proportion to the rise in temperature, pH and concentration of residual chlorine. When rice was boiled in an electric rice cooker, the thiamine in the rice was cleaved by residual chlorine. It is assumed that thiamine is cleaved into hydroxymethylpyrimidine and the thiazole moiety.
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1. A position sensitive X-ray counter was connected to a data-collection system which registered the outputs of the counter as a function of time. This enabled us to study time-dependent changes in the intensities of the equatorial reflexions from frog sartorius muscle during an isometric twitch. 2. The intensity ratio of the 1.0 and 1.1 equatorial reflexions (I1,0/I1,1) decreased during a twitch. The time at which the intensity ratio started to decrease coinsided approximately with the onset of tension development. No detectable change in the intensity ratio occurred during the latency relaxation. 3. The intensity ratio reached a minimum level approximately 90 msec before the peak of tension, and stayed at that level until the peak tension. 4. The intensity ratio returned to the 'resting' value 0.7--1.1 sec after the twitch tension had fallen to zero. 5. The observed decrease in the intensity ratio was interpreted as being caused by radial movements of the myosin projections from the vicinity of thick filaments to that of thin filaments. This leads us to conclude that, early in the rising phase of twitch tension, the number of myosin projections in the vicinity of thin filaments reaches the value obtained during a maximum isometric tetanus.
The effect of different vasodilating drugs on the perilymphatic oxygen content in the cat has been examined by means of the polarographic method. The drugs used such as Papaverin, Rheomacrodex, Ronicol, Praxilen and Lasix have had no significant effect on the oxygen concentration in the perilymph. Histamin, 7% Na2CO3 and 50% glycerol have produced a diminution of the perilymphatic oxygen tension. Only angiotensin has produced a 20% rise of the oxygen pressure in the perilymph. This effect is, however, five times smaller than that reached by inhalation of 5% CO2 and 95% O2.
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The equatorial X-ray reflections were recorded from contracting muscle after a slow stretch. The intensity ratio of the 1,0 to the 1,1 reflections (I10/I11) after the stretch was not significantly different from that during an isometric tetanus at the same sarcomere length, although the tension after the stretch was considerably greater than isometric. This suggests that an almost identical number of cross-bridges produce a greater tension after a slow stretch than during an isometric tetanus.
The heads of myosin molecules, which move to the vicinity of the thin filaments to react with actin during muscle contraction, return to the thick filaments after contraction. The return occurs in two stages; a rapid return of the majority of the myosin heads is followed by a slow return of the rest.
1. The equatorial X-ray diffraction pattern was recorded from a papillary muscle of a cross-circulated canine heart at different phases of the cardiac cycle. The intensity ratio of the 1, 0 and the 1, 1 reflexions (I1, o/I1,1) was 0-79 in the systolic phase and 1-19 in the diastolic phase. 2. Using the intensity ratio obtained, the approximate proportion of the myosin projections present in the vicinity of the thin filaments was calculated. This was 70-71% in the systolic phase and 51-52% in the diastolic phase of the total myosin projections. 3. The peak systolic tension was roughly proportional to the proportion of the projections present in the vicinity of the thin filaments during systole. 4. The projections which stayed in the vicinity of the thin filaments during diastole did not produce significant contractile force.