|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1998 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1997 : ¥1,600,000 (Direct Cost : ¥1,600,000)
(1) Experimental setup...We have made an experimental setup for measurements of diaphragm muscle contractility with an organ bath and an thermal oscilloscope, which we requested for an equipment. Using this setup, we performed the experiment of a theme what effects of continuous hypoxia on diaphragm muscle.
(2) Changes of diaphragm contractility and fibers.. .The force-frequency curves at 1 and 2 weeks under continuous hypoxia decreased significantly from control, and the contractions changed slower and fatigue resistant However, the contractility returned nearly to control level at 3 weeks. The muscle fibers changed to type I (slow-twitch) muscle fiber dominantat 1 and 2 weeks, but gradually returned to control levels.
(3) Changes of Hemo oxygenase (HO) and NO synthase (NOS) expressions...HO-lexpression increased significantly at 1 day, then decreased later. The HO-1 has aprotective action to superoxide, which induced deteriorate effects on diaphragm muscle. The induced NOS (iNOS) expression decreased at 1 day, then increased later, and eNOS increased through 3 weeks of hypoxia. The NOS contributes to produce NO, which is one of free radicals. The eNOS increased throughout 3 weeks of continuous hypoxia.
(4) From these results, it is suggested that there is a protective mechanism to scavenge superoxide at early phase of continuous hypoxia, and is an increment of eNOS at late phase of hypoxia. Although the decrement of diaphragm muscle is strongly related to respiratory muscle failure, the present study suggests that the changes of muscle contractility and fibers may be closely related with expressions of HO-1, iNOS and eNOS.