Maternal serum hyperglycosylated human chorionic gonadotrophin (HhCG) in the first trimester of pregnancies affected by Down syndrome,using a sialic acid-specific lectin immunoassay

In a series of 54 cases of pregnancies complicated by Down syndrome and 224 unaffected pregnancies we examined maternal serum levels of hyperglycosylated human chorionic gonadotrophin (HhCG) in samples collected in the first trimester (11–13 weeks) using a sialic acid-specific lectin immunoassay. We compared these levels with those of other potential first trimester serum markers [free β-hCG, pregnancy-associated plasma protein A (PAPP-A) and total hCG (ThCG)] and modeled detection rates and false-positive rates of various biochemical markers in conjunction with fetal nuchal translucency (NT) and maternal age using an maternal age standardized population. Maternal serum HhCG in cases of Down syndrome were significantly elevated (median MoM 1.97) with 24/54 (44%) of cases above the 95th centile for unaffected pregnancies. Free β-hCG was also elevated (median MoM 2.09) with 33% of cases above the 95th centile. PAPP-A levels were reduced (median MoM 0.47) with 38% below the 5th centile. ThCG levels, whilst elevated (median MoM 1.34), had only 20% of cases above the 95th centile. Maternal serum HhCG levels were not correlated with fetal NT but showed significant correlation with ThCG and free β-hCG and with PAPP-A in the Down syndrome group (r=0.536). Maternal serum HhCG levels in cases with Down syndrome had a significant correlation with gestational age, increasing as the gestation increased. When HhCG was combined together with fetal NT, PAPP-A and maternal age, at a 5% false-positive rate the modeled detection rate was 83%, some 6% lower than when free β-hCG was used and some 4% better than when ThCG was used. Maternal serum HhCG is unlikely to be of additional value when screening for Down syndrome in the first trimester. Copyright © 2002 John Wiley & Sons, Ltd.     

Human impacts on the terrestrial ecosystem of Fildes Peninsula of King George Island, Antarctica

Ｓｉｎｃｅｔｈｅｉｎｔｅｒｎａｔｉｏｎａｌｇｅｏｐｈｙｓｉｃａｌｙｅａｒ(ＩＧＹ,1957—1958),Ａｎｔａｒｃｔｉｃａｈａｓｂｅｅｎｔｈｅｏｂｊｅｃｔｏｆｉｎｔｅｎｓｉｖｅｓｃｉｅｎｔｉｆｉｃｉｎｖｅｓｔｉｇａｔｉｏｎｂｙｔｅａｍｓｏｆｓｃｉｅｎｔｉｓｔｓ...     

基于环境自净能力的龙凤湿地水质改善优化调控模型

为解决城市湿地生态系统存在的严重污染问题,找到合理的排污削减方案,选择大庆市龙凤湿地作为研究对象,以主要的污染物NH_3-N、TP、COD_(Cr)和石油类污染物为指标,应用MIKE21建立试验湿地二维水动力和水质耦合模型,采用数值模拟的方法,研究提出湿地水质改善的优化调控模型.进而,采用模拟试验研究了清淤、曝气、补水及上述措施两两组合下的调控方案对改善龙凤湿地水质效果的影响.结果表明:单一工程措施下无法使染物削减到控制目标浓度,各类措施的削减效果为补水清淤曝气;在各组合情况下,补水+清淤方案的削减作用更佳;在工程措施相同情况下,提高排污标准也能起到削减作用.最后,在考虑不同排污方式下既能使污染物排放达标、又能充分利用湿地纳污能力的前提下,优选出了最佳方案.