Pitfalls in the prenatal diagnosis of peroxisomal β-oxidation defects by chorionic villus sampling

Variability in the level of expression of very long chain fatty acids (VLCFAs) is documented in cultured chorionic villus (CV) cells derived from two fetuses, one at risk for an unusual peroxisomal fatty acid β-oxidation defect, and the other at risk for the X-linked form of adrenoleucodystrophy (ALD). Cells from early subcultures of chorionic cells from both cases gave normal values for VLCFA ratios. The results for the fetus at risk for the β-oxidation defect were interpreted to indicate that the fetus was not affected; however, at birth, the infant was clinically and biochemically affected. In the case of the fetus at risk for X-linked ALD, although VLCFAs were normal in subculture 1, the levels of these fatty acids increased dramatically in subculture 3, suggesting an abnormal fetus. Termination of the pregnancy and subsequent biochemical and morphological follow-up confirmed that the fetus was indeed affected by ALD.     

MSAFP levels and oesophageal atresia

This study was undertaken to evaluate the relationship between maternal serum alpha-fetoprotein (MSAFP) levels and oesophageal atresia (OA). OA occurred in 16 fetuses of mothers who had an MSAFP test in the study interval. The multiple of the median (MOM) value for MSAFP averaged 1·54 ± 0·65 (range 0·5–2·9 MOM), which was significantly higher than the value seen in controls. The median MOM was 1·35. Using a cut-off of 2·5 MOM, the sensitivity of MSAFP for detecting OA was 19 per cent. Although OA should be considered in the differential diagnosis of an elevated MSAFP level, MSAFP cannot be considered an appropriate screening test for OA given the low sensitivity.     

Chromosome preparations of both direct and long-term cultures from the same fragment of chorionic villi

A simplified method is described for processing both direct preparations and long-term cultures from the same fragment of chorionic villi. Enzyme separation of the outer trophoblast layers (used for direct preparations) from the inner mesenchymal core (used to initiate long-term cultures) facilitates the utilization of the same fragments for the two procedures, without jeopardizing the success of either method. This has proved useful in cases where the sample was so small that only one method of chromosome preparation may have been possible using other techniques.     

Carrier screening for cystic fibrosis

A number of different models of CF carrier screening have now been tested in pilot trials. Apart from opportunistic and cascade testing (which are strictly speaking not true forms of screening), the major programmes have been directed either to young adults in primary care or to pregnant women in antenatal clinics. Only in the latter form of screening has sufficient data been collected to allow conclusions to be reached on the optimum mode of delivery. It seems very probable that when CF carrier screening passes into routine service, it will be the antenatal couple model that is used.     

海水入侵污水放流系统及其清除研究

研究海水入侵污水放流系统及其清除特性有助于系统优化设计和运行保护。运用水力学一般原理推导了清除流量和入侵临界流量的估算公式,并根据数学模型模拟结果讨论了部分系统参数对清除和入侵的影响,指出系统沿程阻力的增加及扩散器主管截面逐渐减小对减小清除流量作用不大,而立管在主管底部与主管联结与在顶部联结相比一般可减小清除流量10％以上。系统清除流量和人侵临界流量与立管个数成正比。还介绍了鸭嘴阀,文丘里喉管等几种限制入侵和帮助清除的技术措施。介绍的方法与结果可供工程实际应用。