| Project/Area Number |
05670688
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Pediatrics
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| Research Institution | Yokohama City University |
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Principal Investigator |
SHIBATA Toshimitsu Yokohama City Univ.School of Med., Assist.Prof, 医学部, 講師 (80106319)
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| Co-Investigator(Kenkyū-buntansha) |
SAGAWA Koichi Yokohama City Univ.School of Med., Instructor, 医学部, 助手 (20244428)
SEKI Kazuo Yokohama City Univ.School of Med., Instructor, 医学部, 助手 (50236072)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1994: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1993: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | Ductus arteriosus / Spectral analysis / Rabbit / Fetus / Frequency response / Stiffness |
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| Research Abstract |
We studied mechanical property of the contracted smooth muscle of rabbit ductus arteriosus (DA).
Rings of DA (diameter : 1.2mm, length : 1.5mm, n=14) of fetal rabbits at 28 days of gestational age were quickly excised and slipped over 2 tungsten pins in a tissue bath which was perfused by hypoxic Tyrode' solution (35_ﾟC) bubbled by a gas mixture of 98% N_2 and 2% CO_2. A pin was connected to a force transducer and the other to a vibrator. After 2 hours' equilibration, the ductus ring was stretched to the length where the DA produced force of 0.1 gm, and the gas mixture was changed to 98% O_2 and 2% CO_2 or the perfusate was changed to high potassium solution (K=65mEq/1). Under high potassium condition, small sinusoidal length perturbations (25mum, range : 0.005-20Hz) were given to the DA and dynamic stiffness (k=DELTAF/DELTAL) was calculated. The dynamic stiffness curve of potassiumactivated DA did not demonstrate marked dependence on the frequency like as a cardiac muscle in rigor.
The trace of the force of DA with intact and damaged endothelium showed irregular, small oscillations in oxygen-induced contracture, but not in high potassium contracture. Marked sunusoidal oscillation in force after step length perturbation (20mum) was observed in the DA with intact or damaged endothelium. The frequency calculated by Maximum Entropy Method was 8.78x10<@D2-4@>D2 (]SY.+-。[) 1.55x10<@D2-4@>D2 Hz (n=6). High potassium contracture, however, did not show any oscillation.
We concluded that oxygen-induced contracture force appeared to be developed by cyclic movements of cross-bridges whereas the potassium-induced contracture was not the case. Endothelial function might not affect the oscillatory movement of force.
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