| Budget Amount *help |
¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2001: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2000: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
In order to clarify the role of myosin in the proliferation and differentiation of placenta! tissues, the isoform compositions of myosin and actin as well as their cellular distributions were determined for human placentas at the term and at various developmental stages. The term placenta was found to contain four heavy-chain isoforms of myosin, Le. smooth muscle-type-1 myosin (SMl), smooth muscle-type-2 myosin (SM2), non-muscle-type myosin OVUIA) and brain/fetus-type myosin (MHB2). The relative contents in the term placenta of SMl, SM2, MEA and MHB2 were approximately 15, 15, 65, and 5 %, respectively. The SMl was localized primarily in the vascular smooth muscle tissues and occasionally in the extra-vascular tissues as dots. MHA was distributed in both vascular and extra-vascular tissues, being concentrated in the former tissue. The term placenta was found to contain three actin isoforms, i.e. a-smooth muscle actin, (3-nonmuscle actin, and y'smooth muscle/nonmuscle actin. The relativ
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e contents of the orsmooth muscle actin and p-nonmuscle actin were about 70 and 30 %, respectively, and the content of ysmooth muscle/nonmuscle actin was very small. The a-smooth muscle actin and (3-nonmuscle actin were distributed primarily in the vascular and extra-vascular tissues, respectively. In 10- to 20-week-old, ie. early to middle stages of placentas, MEA and MHB2 comprised about 70 and 20 %, respectively, of the total myosin, and the contents of SMl and SM2 were very low. The isoform composition ofmyosin in the placenta at this stage resembled that offetal liver at the same period. MHB2 thus appear to be actively working in both placenta and liver at this period. The level ofMHB2 in the placenta decreased afterward, while that of the liver did not change. MDB2 thus appears to participate in the fundamental organization and differentiation of the placental tissues, but not directly in the proliferation of the tissues. It is of interest to examine the cellular as well as intracellular distribution ofMIIB2. These findings obtained in this study may serve as the basis for understandings of the mechanisms underlying the proliferation, differentiation and diseases of the placenta. Less
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