Prenatal diagnosis of a true mosaic trisomy 20 substantiated by demonstration of a gene dosage effect for adenosine deaminase (ADA)

Fibroblasts from a fetus with the prenatal diagnosis of mosaic trisomy 20 were cloned by dilution plating. Adenosine deaminase (ADA), a biochemical marker for chromosome 20, was assayed in trisomic clones and normal clones as control. The cytogenetic diagnosis was substantiated by demonstration of a triplex gene dosage effect for ADA in the trisomic cells.     

Microphthalmia–prenatal ultrasonic diagnosis: A case report

Prenatal real-time ultrasonographic diagnosis of microphthalmia is presented. Diagnosis was made at 18 weeks' gestation in a fetus of a patient with a previous infant affected with the syndrome of cryptophthalmia with absence of septum nasi and ambiguous genitalia (Fraser syndrome). Recognition of microphthalmia as a part of Fraser syndrome and the easy visualization of fetal facial bones and orbits in the second trimester made the diagnosis possible.     

Evidence of a second gamete fusion after the first cleavage of the zygote in a 47,XX, + 18/70,XXX, + 18 mosaic. A remarkable diploid-triploid discrepancy after CVS

A 70,XXX, +18 karyotype was found by chorionic villus sampling, while the fetal fibroblast culture of the affected fetus revealed a 47,XX,+ 18 karyotype. From several possible mechanisms, we assume that a second gamete fusion occurred after the first cell division of the zygote. According to this interpretation, the mosaicism arose in very early pregnancy (at the two-cell stage). This discrepancy can therefore be explained by selection pressure, due to the differentiation processes in the embryonic tissues.     

Successful DNA-based prenatal exclusion of juvenile neuronal ceroid lipofuscinosis

A family with two siblings, 10 and 8 years old, both with clinical and ultrastructural evidence of juvenile neuronal ceroid lipofuscinosis is described. The family was found to be informative for the restriction fragment length polymorphisms (RFLPs) detected by the probes pCJ52–95Ml (locus D16S148) and pCJ52-94Tl (locus D16S159) flanking the juvenile neuronal ceroid lipofuscinosis locus, CLN3. The parents were both heterozygous using these probes, while their two children with juvenile neuronal ceroid lipofuscinosis were both homozygous. Chorionic villi analysis showed that the fetus was heterozygous and had inherited the one allele of the mother which was not found in the two siblings. This suggested that the fetus had derived one healthy allele from the mother, the risk for a double crossing-over being less than 1 per cent. Electron microscopy showed no fingerprint inclusions in chorionic villi. The child was investigated at 6 months of age and found to be healthy, as new fingerprint inclusions were found at electron microscopy and no vacuolated lymphocytes were found in the blood smear. Due to the risk of heterogeneity, both DNA-based analysis and electron microscopy on chorionic villi are recommended for prenatal examination for juvenile neuronal ceroid lipofuscinosis.     

Prenatal investigation of a 45,X/46,X,r(?) karyotype in amniocytes using fluorescence in situ hybridization with an X-centromeric probe

The karyotype of cultured amniotic fluid cells obtained on the indication of advanced maternal age was shown to be a mosaic 45,X/46,X,r(?). The small size and banding pattern made it difficult to determine whether the ring was derived from and X or a Y chromosome, or even from an autosome. By using an X-centromeric probe and fluorescence in situ hybridization (FISH), we demonstrated the ring to have an X centromere. Thus, a more complete genetic counselling was possible. This confirms the usefulness of FISH in identifying and characterizing this and other chromosome rearrangements in prenatal diagnosis.     

Introduction of early amniocentesis to routine prenatal diagnosis

With growing awareness of the problems associated with prenatal cytogenetic diagnoses after CVS, attempts have been made to provide early amniocentesis as an alternative to CVS. Since 1990, at our clinic the gestational age limit for routine diagnostic amniocentesis has been successively lowered, first to 14 and then to 13 weeks of gestation. Thus, 811 prenatal diagnoses were performed after early amniocentesis at 13 weeks (n = 217) and at 14 weeks of gestation (n = 594). No problems were encountered. Culture failure was never observed in the early samples. Using the criteria ‘number of colonies’ and ‘culture duration until harvest’, early samples taken at 14 weeks did not differ significantly from the controls after standard amniocentesis performed at 15 and 16 weeks, respectively, whereas a minority of samples taken at 13 weeks experienced some delay in culturing. However, in each group at least 85 per cent of samples led to a diagnosis fulfilling our standard criteria of a safe diagnosis (at least 20 metaphases of at least five colonies from at least one primary culture after trypsinization) within 15 days. Some differences between the different groups can be recognized: culture duration of less than 11 days tends to be increasing after standard amniocentesis, whereas long culture duration (more than 20 days) is more often associated with early amniocentesis. However, this trend is only minimal and did not result in an increased risk of missing a diagnosis.     

Nature and frequency of chromosomal abnormalities in pregnancies with abnormal ultrasound findings: An analysis of 117 cases with review of the literature

During a 7-year period, 117 fetal karyotypes were available from 131 genetic amniocenteses. These procedures were performed between 14 and 37 weeks' gestation for the following abnormal ultrasound findings: (1) intrauterine growth retardation (IUGR)—61 cases; (2) fetal malformation—71 cases; and (3) amniotic fluid volume (AFV) abnormality—60 cases. Chromosomal abnormalities were identified in 19 cases (16.2 per cent). Aneuploidy was 2.5 times as frequent in the presence of malformations than in their absence. No correlation was demonstrated between specific fetal malformations and specific chromosomal abnormalities. Aneuploidy was also twice as frequent in the presence of symmetrical IUGR than in its absence. No chromosomal abnormalities were found among eight cases of asymmetrical IUGR. Four cases of aneuploidy presented with isolated IUGR, three of these involving the X chromosome. The frequency of aneuploidy was the same with or without abnormalities of AFV (14.3 versus 16.4 per cent). No chromosomal abnormality was found associated with isolated AFV abnormalities.     

浙东南早白垩世火山—沉积岩系地层划分

浙东南下白垩统火山岩极为发育,岩石组合与浙江中部永康群差异甚大,称之为馆头组和朝川组似不合适。文成县峃口镇龙潭山(又称龙井山)剖面具代表性,拟以此部面为基础建立梅坪组和龙潭山组,合称文成群。与永康群对比,梅坪组大体相当馆头组,龙潭山组与朝川组和方岩组对比。     

Fetal cystic hygromata: Insights gained from fetal blood sampling

Twelve second-trimester fetuses with cystic hygroma underwent fetal blood sampling for rapid karyotyping, haematologic evaluation, and blood gas analysis. An abnormal karyotype was found in seven cases: monosomy X in five, trisomy 21 in one, and trisomy 13 in the other. Eight often fetuses undergoing blood gas analysis showed hypoxaemia, five of which were growth-retarded. Nine pregnancies were terminated. Of the remaining three, only one fetus survived the perinatal period.     

Activities of alkaline phosphatase in first trimester chorion biopsy tissue

We have determined the activity of alkaline phosphatase in chorionic villous tissue obtained in the first trimester of pregnancy, in order to obtain the normal range of values as a prerequisite for application to the prenatal diagnosis of the rare bone disease hypophosphatasia. The activities found were a combination of intestinal and liver/bone/kidney types; traces of placental type were present in only one sample.