Prenatal diagnosis of alpha-1-antitrypsin deficiency by PCR of linked polymorphisms: A study of 17 cases

We describe our experiences of prenatal diagnosis of alpha-1-antitrypsin deficiency using closely linked polymorphisms detected by Southern blotting and the polymerase chain reaction. Prenatal diagnosis was carried out for 17 pregnancies from 15 couples.     

Randomized trial comparing first-trimester transcervical chorionic villus sampling and second-trimester amniocentesis

A total of 800 patients were randomized at the 9th to 11th week of pregnancy either for transcervical chorionic villus sampling (CVS) on the day of trial entry or for amniocentesis (AC) at the 16th week. The indication for fetal karyotyping was maternal age in 94 per cent of the cases; the mean maternal age was 39.2 years. An adequate sample was obtained in 98.3 per cent of the cases in the CVS group and in all cases in the AC group. Retesting was indicated in 3.3 per cent of the CVS cases. An abnormal karyotype was found in 6.1 per cent of the CV samples and in 4.5 per cent of the amniotic fluid samples. There was one false-positive chromosome result in both groups. Twelve (3.1 per cent) miscarriages occurred by the 22nd week of pregnancy in the CVS group in pregnancies intended to continue. No difference was seen between the groups for total fetal loss rates. The number of surviving infants in the CVS group was 92.2 per cent and in the AC group 91.7 per cent (rate difference 0.5 per cent (95 per cent confidence interval − 3.3 to 4.3)). In our study, both the diagnostic accuracy and the risk of fetal loss were equal in the CVS and AC groups.     

First-trimester genetic diagnosis in multiple pregnancy: Principles and potential pitfalls

Both the principles of first-trimester genetic diagnosis in multiple pregnancy and the special considerations required to avoid potential diagnostic pitfalls are presented. The experience consisted of 65 cases of twins and one case of quadruplets. Dichorionic twins were recognized by sonography in 54 cases. Transabdominal aspiration was generally preferred to trans-cervical for obtaining chorionic tissue, although in two cases both approaches were used. Diagnostic error following erroneous sampling was reported in 3 out of 54 sets of dichorionic twins (5.5 per cent). When like-sex dichorionic twins cannot be differentiated by cytogenetic or DNA polymorphism studies, amniocentesis should be recommended to confirm the reliability of the result on chorionic tissue.     

First-trimester prenatal diagnosis of osteogenesis imperfecta type II by DNA analysis and sonography

Osteogenesis imperfecta type II was diagnosed prenatally by analysis of DNA obtained from chorionic villus sampling (CVS) performed at 12 weeks of gestation in a woman who previously had had an affected child. The father had been shown to be mosaic for a mutation in the gene (COL1A2) which encodes the α2(I) chain of type I collagen. An affected fetus was predicted by detection of the mutation in amplified chorionic villus genomic DNA. Ultrasound examination at 13 weeks 4 days demonstrated femoral deformity and virtual absence of calvarial mineralization. In pregnancies at risk for osteogenesis imperfecta type II, sonographic evidence of skeletal abnormalities may be evident by 13 weeks' gestation.     

A rare case of a false-negative finding in both direct and culture of a chorionic villus sample

A discrepancy is reported between the karyotype of both direct and cultured chorionic villus cells (46,XX) and a fetal skin biopsy (47,XX,+18). The significance of this result is discussed and compared with similar discordant findings reported in the literature.     

The significance of trisomy 7 mosaicism in chorionic villus cultures

Two cases of mosaic trisomy 7 confined to the cultured cells and not found in direct preparation were detected from 200 consecutive first-trimester chorionic villus samples (CVS) analysed. The mosaicism was similar in the two cases, but the pregnancy outcome was different. In both cases, the direct metaphases from the CVS were 46, XY. Culture metaphases were mos46,XY/47,XY, + 7; the trisomy 7 was seen in 34 per cent of cells from case 1 and 53 per cent from case 2. A sonogram at 15¹/₂ weeks revealed fetal death in utero in case 1, and the patient declined amniocentesis. The fetal tissue failed to grow in culture, but the placental cultured cells were 47,XY, + 7 in 28 (100 per cent) cells analysed. In the second case, all the amniotic fluid cells were 46,XY and the pregnancy resulted in a normal male with a 46,XY karyotype in the cord blood and foreskin fibroblast cultures. The term placenta was mosaic with 13/163 (8 per cent) trisomy 7 cells. Extensive cytogenetic studies on the placenta for the first time confirmed trisomy 7 mosaicism confined to the villus cultures.     

An improved method of direct chromosome preparation from chorionic villus and high resolution banding technique

The trophoblast was dissociated from the underlying mesenchymal layer either with acetic acid after short-term prefixation or with mechanical power after fixation twice. The colcemid treatment time was shorted to 16 min and trypsin solution of low pH (6.2) was used for banding. By these steps, the quality of chromosome banding was greatly improved and complete standard chromosome diagnoses were made in 24 of 24 cases. With the modified technique, high resolution banding chromosomes were consistently obtained after short-term incubation.     

澳大利亚职业眼睛健康管理

在由于从事具有眼睛伤害风险工作而导致的职业眼睛健康问题之外,随着新兴技术的发展,工作场所电子设备的长时间使用也会导致电脑视觉综合症（CVS）等职业眼睛健康问题。本文主要介绍了澳大利亚职业眼睛健康管理的方法,包括职业眼睛健康风险、单位与职工的职责、预防措施等．以对我国职业眼睛健康风险进行有效管理提供帮助。