Motokawa Tatsuo
Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo, Japan.
Biol Bull. 2011 Dec;221(3):280-9. doi: 10.1086/BBLv221n3p280.
Stiffness changes in response to mechanical and chemical stimulation were studied in muscle-free dermal samples from the body wall of the starfish Linckia laevigata. The ultrastructural study showed that the dermis was packed with collagen fibrils between which only a small number of cells were observed. Muscles were found only in the walls of coelomic extensions leading to papulae. Stress-strain tests were performed on isolated dermis containing no muscles. The tangent modulus was 27.5 MPa at 0.04% strain rate in the stress-strain tests. It was increased to 40.7 MPa by mechanical stimulation, which also increased the tensile strength and breaking-strain energy density. Dynamic mechanical tests showed that the increase in stiffness in response to mechanical stimulation was transient. Acetylcholine (10(-6)-10(-3) mol l(-1)) and artificial seawater with an elevated potassium concentration (KASW) stiffened the dermis. Mechanical stimulation caused a 12% mass loss. KASW also caused mass loss, which was inhibited by anesthesia. These results clearly showed that the stiffness changes in the starfish dermis were based on a non-muscular mechanism that was similar to that of other echinoderm connective tissues with mechanical mutability.
对光滑多棘海盘车体壁无肌肉的真皮样本，研究了其在机械和化学刺激下的刚度变化。超微结构研究表明，真皮中充满胶原纤维，其间仅观察到少量细胞。仅在通向皮鳃的体腔延伸壁中发现有肌肉。对不含肌肉的分离真皮进行了应力-应变测试。在应力-应变测试中，应变率为0.04%时，切线模量为27.5兆帕。通过机械刺激，其增加到40.7兆帕，这也增加了拉伸强度和断裂应变能密度。动态力学测试表明，响应机械刺激的刚度增加是短暂的。乙酰胆碱（10⁻⁶ - 10⁻³摩尔/升）和钾浓度升高的人工海水（KASW）使真皮变硬。机械刺激导致质量损失12%。KASW也导致质量损失，麻醉可抑制这种损失。这些结果清楚地表明，海星真皮的刚度变化基于一种非肌肉机制，该机制与其他具有机械可变性的棘皮动物结缔组织的机制相似。
