Prenatal diagnosis of syndromes associating albinism and immune deficiencies (Chediak-Higashi syndrome and variant)

We have successfully undertaken the prenatal diagnosis of two hereditary syndromes associating albinism and immune defects. Because the genes responsible for these diseases have not yet been mapped and the immune abnormalities are too subtle to be diagnosed in utero, the prenatal diagnosis was made using a morphological approach. In the case of Chediak-Higashi syndrome, it was based on light microscopic examination of the hair shaft and on light and electron microscopic study of polymorphonuclear cells. In the syndrome associating immune deficiency and partial albinism, the Griscelli syndrome, only examination of the hair was feasible. The diagnosis was negative in 12 fetuses at risk and positive in four.     

A comparison of total and free β-HCG assays in Down syndrome screening

Free β-HCG is a new analyte that has been suggested to be superior to total HCG when used in combination with alpha-fetoprotein (AFP) for Down syndrome risk screening in early pregnancy. We have evaluated this claim on 21 samples collected from Down syndrome pregnancies and 180 samples from unaffected pregnancies. The detection rates for the combination of AFP with free β-HCG or the combination of AFP with total HCG were identical (71 per cent) but the initial screen positive rate (equivalent to the false-positive rate) was 7·5 per cent for AFP+free β-HCG screening compared with 3·5 per cent for AFP+ total HCG screening. We conclude that the case for free β-HCG is unproven and suggest that further data be collected before free β-HCG becomes acceptable.     

A rare inherited euchromatic heteromorphism on chromosome 1

Extra genetic material that is euchromatic is generally regarded to be associated with phenotypic abnormalities. However, recent studies suggest that this is not always the case. Chromosome analysis was performed on amniotic fluid cells from a 37-year-old phenotypi-cally normal patient referred for advanced maternal age. All the cells analysed showed a karyotype of 46, XY, 1p-K The 1p+ chromosome had extra genetic material of uncertain origin in chromosome band region 1p21 →31. Chromosome analysis on the father revealed a normal 46, XY male karyotype. The mother's karyotype showed the same 1p+ chromosome. C and Q banding, as well as silver staining studies, in both the mother and the fetus support the interpretation that the extra chromosomal material was euchromatic in nature. This 1p + chromosome may be characterized as a euchromatic heteromorphism. Euchromatic hetero-morphisms not associated with phenotypic abnormalities have been reported for chromosomes 9 and 16. To the best of our knowledge, this is the first report involving this type of cytogenetic anomaly on chromosome number 1 in a phenotypically normal mother and infant.     

Fetal akinesia/hypokinesia sequence: Prenatal diagnosis and intra-familial variability

Intrauterine fetal movement plays a key role in normal embryonic and fetal development (Moessinger, 1983). When movement is absent or decreased, abnormal development takes place which can be appreciated in newborns and/or fetuses with the fetal akinesia/ hypokinesia sequence. This sequence is caused by a number of heterogeneous entities which result in decreased fetal movements by the action of intrinsic or extrinsic factors. Prenatal diagnosis of the akinesia/hypokinesia sequence may be possible during the second trimester through the use of real-time ultrasonographic evaluation of fetal movement. We report a family with three consecutive affected pregnancies in which the prenatal presentation of this sequence varied. Based on the phenotypic findings of the three affected fetuses, we believe that although they superficially resemble those features found in the New–Laxova syndrome, they are probably affected with a distinctly different lethal form of akinesia/ hypokinesia transmitted in an autosomal recessive fashion.     

Fetal aortic root dilation: a prenatal feature of the Loeys-Dietz syndrome

Loeys-Dietz syndrome is a recently described autosomal dominant disorder with cardinal manifestations in cardiovascular, craniofacial and skeletal systems. Although the disease has some phenotypic overlap with Marfan syndrome, the disease, that is caused by mutations in the transforming growth factor beta-receptor 1 (TGFBR1) or transforming growth factor beta-receptor 2 (TGFBR2) genes, presents many distinctive features and a particularly aggressive cardiovascular course. We describe prenatal identification of an aortic root aneurysm in a fetus of 19 week of gestation as an early marker of Loeys-Dietz syndrome. Copyright © 2006 John Wiley & Sons, Ltd.     

可靠性强化试验的机理探析

概括地介绍了可靠性强化试验,分析了可靠性强化试验的理论基础以及两类强化模型——Arrhenius模型和Miner标准模型,研究了可靠性强化试验的机理,并分析了各种试验应力（包括高低温、温度循环、振动、湿度和综合应力）与诱发故障模式之间的关系。     

流动注射-光度法测定环境空气和工业废气中氨含量

针对分析工作量的逐渐增大,为缩短分析时间,提高工作效率,采用流动注射-光度法分析环境空气和工业废气中氨的含量。该方法主要特点是可以不经过前处理,干扰小、准确度高、精密度高,与国标方法比较,相关性较好,各项指标达到分析要求,是一种值得推广运用的分析方法。     

Prenatal diagnosis of hemoglobinopathies in twin pregnancies by double simultaneous fetoscopy

A new technique for sampling fetal blood in twin pregnancies using two fetoscopes simultaneously is described. Two fetoscopes were inserted, one after the other, into both amniotic cavities and fetal blood samples were obtained from either the chorionic plate vessels or the umbilical cord insertion area. The observation of the bright tip of the second fetoscope behind the septum using the first fetoscope assured the successful entry of the two fetoscopes into the two different amniotic sacs. This technique was performed on 15 out of 17 patients. In all patients the fetuses were at risk of β-thalassemia major. Sampling was successful in all cases. Double simultaneous fetoscopy seems to be a safe and accurate technique without technical problems or complications. The simultaneous use of two fetoscopes opens new possibilities in intrauterine fetal surgery and research.     

Prenatal diagnosis,fetal pathology and cytogenetic analysis of A 46,XX/47,XX, + 15 mosaic

Mosaic trisomy 15 was prenatally diagnosed on amniotic fluid cells from two consecutive amniocenteses and was confirmed on cells from five different fetal tissues. The proportion of normal versus trisomic cells was consistently higher in the amniotic cell cultures and-with one exception-in the fetal tissues, while serial subcultures gave different results. The slightly atypical external features and internal malformations of the affected fetus as compared to the only clinical observation from the literature are not unusual enough to allow the delineation of a specific malformation pattern.