考虑声散射的街道交通噪声预报模型

提出一种预报典型的两侧密集分布建筑物的城市街道交通噪声ＬＡ１０和ＬＡｅｑ声级的计算机仿真模型。模型依据一种修正的虚声源原理。它不仅考虑发生于建筑方面的镜象反射和表面吸收，而且考虑了由于墙面的粗糙性所引起的发生于有限尺寸建筑表面声散射的影响。与实测比较表明本模型可得出良好的预报结果。通过对散射强度加以变化可估计表面声散射对预报声级的影响。结果表明，即使在一个相当混响的场合，镜象反射声能对扩散反射声能     

Prenatal diagnosis of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in a family with a previous fatal case of sudden unexpected death in childhood

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a potentially fatal inherited disease with a carrier frequency of approximately 1:100 in most Caucasian populations. The disease is implicated in sudden unexpected death in childhood. A prevalent disease-causing point mutation (A985G) in the MCAD gene has been characterized, thus rendering diagnosis easy in the majority of cases. Since the clinical spectrum of MCAD deficiency ranges from death in the first days of life to an asymptomatic life, there are probably other genetic factors—in addition to MCAD mutations—involved in the expression of the disease. Thus, families who have experienced the death of a child from MCAD deficiency might have an increased risk of a seriously affected subsequent child. In such a family we have therefore performed a prenatal diagnosis on a chorionic villus sample by a highly specific and sensitive polymerase chain reaction (PCR) assay for the G985 mutation. The analysis was positive and resulted in abortion. We verified the diagnosis by direct analysis on blood spots and other tissue material from the aborted fetus and from family members.     

Early amniocentesis at 11–14 weeks' gestation for the diagnosis of fetal chromosomal abnormality—a clinical evaluation

Early arnniocentesis between 11 and 14 weeks' gestation was offered to 110 women at risk of a chromosomally abnormal fetus due to maternal age. Four were found to be unsuitable for the procedure, and 106 early amniocenteses were performed. In 102 cases, clear amniotic fluid was obtained with a single tap. There were two dry taps and two bloodstained tapis; sampling was repeated in three of these cases before 15 weeks. In the fourth case, placental biopsy was performed at 16 weeks. Thus, we were able to obtain a satisfactory sample in all but three cases(2.8 percent). Karyotyping of cells harvested from the early amniotic fluid samples was successful in all the 105 cases. Cell culture from the initial samples revealed a normal karyotype in 99 cases, two balanced translocations, two tetraploid karyotypes, and two cases of pseudomosaicism. Of the 105 pregnancies successfully sampled, there have been two losses to date (1–8 per cent). Two further patients presented with premature rupture of membranes, both pregnancies having successful outcomes. Sixty-two babies have delivered to date, with four congenital anomalies. There were no respiratory problems. Twenty-nine pregnancies are continuing without known complications, and details are not yet available on the remaining 12. The results indicate that early arnniocentesis may replace the traditional test at 15–17 weeks.     

Pallister-Killian syndrome diagnosed by chorionic villus sampling

The first prenatal diagnosis of Pallister-Killian syndrome by chorionic villus sampling is presented. Fetal hydrops was noted on ultrasound in early pregnancy, and the karyotype revealed isochromosome 12p mosaicism.     

Preimplantation diagnosis: A patient perspective

A new dimension in the prevention of birth defects will be achieved when genetic diseases can be routinely diagnosed in embryos prior to implantation. The impressions and attitudes towards preimplantation diagnosis were studied in prospective patients, women at high reproductive risk for a genetic disease. Their perspective highlighted not only the advantages and disadvantages of this new approach, but also those changes necessary in order for preimplantation diagnosis to become a useful and practical technique. The data presented are based on information obtained by a mailed questionnaire answered by 58 women. The main benefit of preimplantation diagnosis for these high-risk women would be the ability to undertake a pregnancy without having to be subjected to the physical and/or emotional trauma of elective termination. Their major concerns related to possible damage to the embryo following biopsy, the cost of the procedure, and the low success rate of completed pregnancies. Other issues to be addressed before preimplantation diagnosis could begin to compare favourably with existing forms of prenatal testing were that the methods of obtaining oocytes or embryos should be simple, well tolerated, highly efficient, and low in maternal risk, and that the genetic analysis of embryonic or extraembryonic cells should be unequivocally accurate.     

A rare case of de novo structural rearrangement of X chromosome diagnosed by amniocentesis

A dicentric X chromosome was found in a female fetus during cytogenetic studies performed on amniotic cells. Blood samples from the parents showed normal karyotypes and the pregnancy was terminated. The mechanism for the formation of this ‘de novo’ rearrangement is discussed.     

Cystic hygroma: Prenatal diagnosis and genetic counselling

Six cases of cystic hygromas detected during second trimester ultrasound examination are reported: 4 fetuses (67 per cent) had a 45, X karyotype, 1 fetus had trisomy 18, 1 fetus had a normal karyotype (46,XX) and at autopsy multiple anomalies were observed. In the latter case the family history suggested an autosomal recessive pattern of inheritance. In order to reach a definite diagnosis and give proper genetic counselling when a fetus is found to have cystic hygroma, a fetal karyotype as well as a family and reproductive history should be obtained.     

Prenatal diagnosis of the hurler syndrome: Report on 40 pregnancies at risk

In 40 pregnancies at risk for the Hurler syndrome 13 affected fetuses were detected by the demonstration of an α-L -iduronidase deficiency and an increased level of ³⁵S-sulphate incorporation. The diagnoses were confirmed by the analysis of fetal tissues and/or cultured fetal skin fibroblasts. Microassays for α-L -iduronidase, using phenyl α-L -iduronide and more recently 4–methyl-umbelliferyl α-L -iduronide, enabled a reliable diagnosis to be made within 15 to 18 days after amniocentesis. ³⁵S-sulphate incorporation has been a valuable adjunct in cases with a low (heterozygote) enzyme activity.