Amniotic fluid microvillar enzyme activities in the early detection of fetal abnormalities

Measurement of the microvillar enzymes, γ-glutamyltranspeptidase (GGTP), aminopeptidase M (APM) and alkaline phosphatase (ALP), in amniotic fluid supernatant has been proposed as a method for the early prenatal diagnosis of cystic fibrosis. The activities of these enzymes in a series of other fetal abnormalities have now been examined. GGTP activities were below the 5th percentile in 28 out of 54 cases of trisomy 21 and 9 of 14 cases of trisomy 18, while APM values were below this cut-off in 26 of 54 cases of trisomy 21 and 8 of 14 cases of trisomy 18. Abnormal ALP isoenzyme ratios were found in 6 of 54 cases of trisomy 21 and 4 of 14 cases of trisomy 18. If prenatal cytogenetic studies are routinely carried out on amniotic fluid cells, the occasional confounding effect of abnormal microvillar enzymes associated with fetal trisomies rather than with cystic fibrosis should be avoided.     

中巴车实测排放因子和MOBILE6预测值的对比分析

利用车载尾气检测(OEM)技术对在实际道路上行驶的中巴车辆进行测试，得到该车的实测排放因子；同时应用美国环保局(EPA)开发的MOBILE6模型，在对相关参数进行适当调整后计算相应的排放因子；对得到的排放因子进行比较和分析，并就MOBILE6模型在我国的适用性做出探讨。     

Infantile hypophosphatasia: Successful prenatal assessment by testing for tissue-non-specific alkaline phosphatase isoenzyme gene mutations

We successfully assessed a fetus at risk for lethal infantile hypophosphatasia using amniocyte DNA and allele-specific oligonucleotide (ASO) probes for two missense mutations in the tissue-non-specific alkaline phosphatase isoenzyme (TNSALP) gene. The nucleotide changes had been discovered in a sister who died at 8 months of age from this inborn error of metabolism. The mother was known to carry the 747 (cDNA) G→A transition, whereas her husband and 5-year-old daughter, who were also healthy, carried the 1309 A→T transversion. Amniocytes, obtained at 16 weeks' gestation, provided genomic DNA for polymerase chain reaction (PCR) amplification of the appropriate TNSALP gene exons. ASO hybridization revealed absence of the 747A mutation and presence of the 1309T base change in the fetus, indicating a carrier for hypophosphatasia. At 8 months of age, the offspring was in excellent health and without any radiological evidence of skeletal disease. His serum ALP activity and plasma pyridoxal 5′-phosphate level were decreased and increased, respectively, at levels consistent with the prenatal assessment. The ASO studies were confirmed postnatally using peripheral blood leukocyte DNA. This is the first application of direct mutational analysis to assess a fetus at risk for hypophosphatasia.     

Isolating fetal cells in maternal circulation for prenatal diagnosis

Fetal cells unequivocally exist in and can be isolated from maternal blood. Erythroblasts, trophoblasts, granulocytes and lymphocytes have all been isolated by various density gradient and flow sorting techniques. Chromosomal abnormalities detected on isolated fetal cells include trisomy 21, trisomy 18, Klinefelter syndrome (47,XXY) and 47,XYY. Polymerase chain reaction (PCR) technology has enabled the detection of fetal sex, Mendelian disorders (e.g. β-globin mutations), HLA polymorphisms, and fetal Rhesus (D) blood type. The fetal cell type that has generated the most success is the nucleated erythrocyte; however, trophoblasts, lymphocytes and granulocytes are also considered to be present in maternal blood. Fetal cells circulate in maternal blood during the first and second trimesters, and their detection is probably not affected by Rh or ABO maternal-fetal incompatibilities. Emphasis is now directed toward determining the most practical and efficacious manner for this technique to be applied to prenatal genetic diagnosis. Only upon completion of clinical evaluations could it be considered appropriate to offer this technology as an alternative to conventional invasive and non-invasive methods of prenatal cytogenetic diagnosis.     

Trisomy 8 mosaicism in chorionic villus sampling: Case report and counselling issues

We report an unusual case involving chorionic villus sampling (CVS) and trisomy 8 mosaicism. CVS showed a normal direct preparation while the culture showed mosaicism for trisomy 8. Subsequent amniocentesis revealed only normal chromosomes. A peripheral blood culture after birth revealed low-level trisomy 8 mosaicism. The patient appeared phenotypically and developmentally normal at 30 months of age. We conclude that prenatal counselling for similar cases needs to include the rare but real possibility that chromosome mosaicism detected prenatally may be found postnatally with largely unknown consequences. Secondly, low-level chromosomal mosaicism may be more common than previously recognized. Thirdly, very low-level trisomy 8 mosaicism may be compatible with a normal phenotype but long-term follow-up is required. And lastly, the use of fetal blood sampling is questionable in these cases because the phenotype may not be accurately predicted. Further studies of such cases are needed to address these important and unanswered issues, including the potential implication of mosaicism on academic performance and cognitive functioning.     

[HgI4-(R6G)2]n体系的共振散射光谱法测定微量汞(Ⅱ)的研究

在pH值=4.0的条件下,Hg2 ,I-与罗丹明6G(R6G)形成三元离子缔合物.由于HgI4(R6G)2分子间存在较强的分子间作用力和疏水作用力而生成[HgI4-(R6G)2]n纳米微粒.在320 nm处产生一灵敏共振散射(即共振瑞利散射)光谱峰.Hg质量浓度在0.004～0.36 mg·L-1范围内与共振散射光强度呈现出良好线性关系.实验结果表明,本法具有灵敏度较高、选择性较好等特点.用于水样中微量Hg的测定,效果良好.     

Fetal ear measurements in the prenatal detection of trisomy 21

Although prominent fetal nuchal folds, short long bones, echogenic bowel, and renal pelviectasis have been shown to be associated with trisomy 21, none has acceptable diagnostic efficacy. Diminished fetal ear lengths measured by ultrasound have recently been reported as yet another potential morphological marker for the prenatal detection of trisomy 21. To investigate this further, we measured ear lengths and widths of normal (n = 107) and trisomy 21 (n = 25) second-trimester formalin-preserved fetuses. The normal ear growth characteristics are described and compared with those of trisomy 21 fetuses. The normal fetal ear shape, not unlike that of the neonates, manifested a marked variation. When the ear lengths and widths were regressed against gestational age, the slopes of the regression lines for the two groups were found to be different (P < 0·001). However, despite the statistically significant difference between the ear sizes of normal and trisomy 21 fetuses, the wide range of normal variation seen at each gestational age means that the fetal ear measurements are not diagnostically helpful.     

Use of 4-methylumbelliferyl-6-sulpho-2-acetamido-2-deoxy-β-D-glucopyranoside for prenatal diagnosis of tay-sachs disease using chorionic villi

Prenatal diagnosis of Tay-Sachs disease was performed using the sulphated substrate 4- methylumbelliferyl-6-sulpho-2-acetamido-2-deoxy-β-D-glucopyranoside to detect hexosaminidase A in chorionic villi. The presence or absence of hexosaminidase A in villi was detected by both a quantitative enzyme assay, and by a rapid, novel procedure which permitted visual discrimination between normal and affected villi.     

Trisomy 16 fetus surviving into the second trimester

A 27-year-old gravida 4, para 3 was found to have anhydramnios at 14 weeks' gestation following a size/date discrepancy noted at her routine prenatal visit. A detailed ultrasound revealed multiple fetal anomalies including congenital heart defect, chest hypoplasia, and bilateral dysplastic kidneys. Karyotype revealed trisomy 16 in 15/15 cells from a tissue specimen obtained from the fetal cord insertion site following elective pregnancy termination.     

Research of green cement clinker calcinated from ferrochrome slag

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