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研究称胎儿出生时机由肺部发育是否成熟决定
他们对老鼠进行的研究暗示，对于哺乳动物来说，是否已经准备好在母体外呼吸，或许是决定胎儿出生时间的主要因素。
德州大学西南医学中心的生物化学、产科学与妇科学教授门德尔松（Carole Mendelson）博士表示：“我们发现肺表面活性剂中的一种蛋白质扮演着分娩激素的角色，当胎儿肺部足够成熟，能够承受向直接呼吸空气的关键过渡期时，就会向母亲子宫发出分娩信号。”
门德尔松及其同事的研究论文刊登在《全国科学院学报》（Proceedings of the National Academy of Sciences）。他们研究了对在母体外正常呼吸起关键作用的肺表面活性物质蛋白A（SP-A）。
对于人类来说，肺表面活性物质蛋白A还能帮助一种名为巨噬细胞的免疫细胞攻击侵入肺部的细菌、病毒和真菌。
“经常早产的女性，其子宫内的胎膜有感染现象；而随着早产的来临，其子宫壁上的巨噬细胞数量会增加，”门德尔松说。
因此，感染和早产之间必定存在某种联系。门德尔松表示，对这个过程了解较多，或许有助研究出预防早产的疗法。
Lungs of Developing Fetus Tell Mom When to Deliver
WASHINGTON - A developing fetus may signal when it is ready to be born by releasing a chemical produced by the lungs, U.S. researchers said on Monday. The study, done in mice, suggests that in mammals, readiness to breathe outside the mother's womb might be the main factor in determining when it is time to be born. "We found that a protein within lung surfactant serves as a hormone of labor that signals to the mother's uterus when the fetal lungs are sufficiently mature to withstand the critical transition to air breathing," said Dr. Carole Mendelson, a professor of biochemistry and obstetrics and gynecology at the University of Texas Southwestern Medical Center at Dallas. "No one really understands what causes normal or preterm labor. There may be several chemical pathways that lead to labor, but we think that this surfactant protein, which is also produced by the fetal lung in humans, may be the first hormonal signal for labor," added Mendelson, who led the study. Writing in the Proceedings of the National Academy of Sciences, Mendelson and colleagues said they looked at surfactant protein A, which is essential for normal breathing outside the womb. In humans surfactant protein A, or SP-A, also helps immune cells called macrophages attack invaders such as bacteria, viruses and fungi in the lungs. "Women who go into preterm labor frequently have an infection of the membranes that surround the fetus, and the number of macrophages in the wall of the uterus increases with the initiation of preterm labor," Mendelson said. So there must be a connection between infection and preterm labor. Mendelson said understanding more about this process may help lead to the development of therapies that could prevent preterm labor. In mice, the developing fetal lung starts producing SP-A at 17 days gestation and mice pups are born at 19 days. The developing human fetus starts producing more SP-A at 30 to 32 weeks in a 40-week normal gestation. As the fetus "breathes" amniotic fluid in the womb, SP-A is released into the fluid. Macrophages activated by the protein make their way through the amniotic fluid to the wall of the uterus. Once embedded there, they produce a chemical that stimulates an inflammatory response in the uterus, ultimately leading to labor. The researchers found that injecting a pregnant mouse with SP-A before day 17 of the pregnancy caused the mouse to deliver early, and blocking it delayed delivery. [标签:content1][标签:content2]
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作者:admin@医学,生命科学 2011-06-16 17:14
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