灰化-火焰原子吸收法测定人发中的金属元素

讨论了人发中元素测定的前处理条件，并采用灰化－火焰原子吸收法测定了人发中锌，铜，铁，钙和镁５种金属元素的含量。     

The time of appearance and disappearance of fetal DNA from the maternal circulation

A single copy Y-chromosome DNA sequence was amplified using the polymerase chain reaction (PCR) from the peripheral blood of 30 women who had achieved a pregnancy through an in vitro fertilization (IVF) programme. The time of conception was known precisely and was confirmed by serial ultrasound scans. Conceptions were dated as the number of weeks after fertilization plus 2, to give a time equivalent to the obstetric menstrual dating of the pregnancy (LMP). Y-chromosome-specific DNA was detected in all pregnancies with a male fetus (18/30). The earliest detection was at 4 weeks and 5 days, and the latest at 7 weeks and 1 day. Y-chromosome-specific sequences were no longer detected in any of the male pregnancies 8 weeks after delivery. No Y-chromosome sequences were detected in any of the pregnancies where only female babies were delivered. This demonstrates that fetal DNA appears in the maternal circulation early in the first trimester, that it can be identified in all pregnancies tested by 7 weeks, that it continues to be present throughout pregnancy, and that it has been cleared from the maternal circulation 2 months after parturition. Early non-invasive prenatal diagnosis for aneuploidies and inherited disorders will be possible in all pregnancies if fetal cells can be isolated free from maternal contamination (or identified accurately in the presence of maternal cells) without problems of contamination from previous pregnancies.     

Chromosome analysis of multipronuclear human oocytes after in vitro fertilization

Multipronuclear human eggs are frequent after in vitro fertilization. Their chromosome analysis can provide useful information. Before cleavage it can confirm the suspected poly-ploidy. Among the cleaved multipronuclear eggs it provides an estimation of the incidence of the possible return to diploidy. Ninety-four multipronuclear eggs were fixed at the first, second, or third cleavage according to the air-drying method of Tarkowski with or without colchicine exposure: 60 were successfully analysed. Twelve were stopped before cleavage (six without colchicine treatment and six with colchicine treatment). They were polyploid, confirming the cytological observation. Forty-eight eggs cleaved and were stopped by colchicine treatment and karyotyped. Seventeen eggs (35 per cent) had produced diploid embryos. Mosaicism was frequent (15 cases, 31 per cent). Triploidy was not frequent (8 eggs, 17 per cent). Haploidy constituted the remaining cases (8 eggs, 17 per cent). Our data indicate that the initial count of pronuclei is a reliable test. Multipronuclear one-cell oocytes were confirmed to be polyploid. Furthermore, the developmental capacity of the multipronuclear oocytes is variable. Most of them cleaved. However, many multipronuclear oocytes led to diploid cleaving eggs.     

Fetal curarization for prenatal magnetic resonance imaging

Fetal magnetic resonance (MR) imaging was performed at 33 weeks of gestation for investigation of a posterior fossa abnormality found at ultrasound screening. Fetal movements were abolished by vecuronium injected under ultrasound guidance into the umbilical vein. MR images showed atrophy of the left cerebellar lobe with cisternal dilatation. These were confirmed postnatally by CT scan.     

Longitudinal assessment of blood flow velocity waveforms in the healthy human fetus

A longitudinal study was carried out on 30 healthy fetuses in order to assess the modifications of fetal blood flow throughout pregnancy. The pulsatility index was evaluated at two-week intervals by means of pulsed Doppler equipment. In the umbilical artery measurements were performed from 20 weeks onwards, whereas in the descending aorta and internal carotid artery analysis started from 26 weeks onwards. A decrease of the pulsatility index in umbilical artery and in the ratio between the pulsatility indexes in umbilical artery and internal carotid artery was found over the second half of pregnancy.     

Abnormal immunological development in fetuses with trisomy 18

Flow cytometry was used to enumerate the lymphocyte subpopulations in fetal blood obtained by cordocentesis from eight trisomy 18 fetuses at 20–36 weeks' gestation. Compared with values in chromosomally normal fetuses, in trisomy 18 the mean T- and natural killer (NK) cell counts were significantly lower (t= − 7·63, P<0·001 and t= − 3·58, P<0·01, respectively); the mean B-cell count was not significantly different (t= − 1·32). These findings demonstrate that in trisomy 18 there is abnormal intrauterine development of the immune system.     

Antenatal thrombocytopenia in three patients with TAR (thrombocytopenia with absent radii) syndrome

Three fetuses with TAR (thrombocytopenia with absent radii) or TAR variant syndrome were found to be thrombocytopenic during the third trimester of the pregnancy. These findings indicate that fetal blood sampling, besides ultrasonography, skeletal radiographs, or even fetoscopy, may indeed contribute to the prenatal diagnosis of TAR syndrome, and thus may help in differentiating TAR syndrome from other syndromes with malformations of the upper limbs.     

46,XY/47,XY,+ 17p+ mosaicism in amniocytes associated with fetal abnormalities despite normal fetal blood karyotype

46,XY/47,XY, + 17p + mosaicism was found in two primary amniotic fluid cultures (AFCs). Fetal blood karyotype was normal, but ultrasonography revealed Dandy-Walker malformation and bilateral choroid plexus cysts. Following termination of pregnancy, fetal examination revealed post-axial polydactyly and neuroblastoma-in-situ affecting both adrenals in addition to the cerebellar abnormalities. Mosaicism for the aberrant cell line was confirmed in all fetal tissues sampled and in the placenta.     

Maternal serum human chorionic gonadotropin levels in twin pregnancies

Introduction of combined screening with maternal serum alpha-fetoprotein and human chorionic gonadotropin (MShCG) assays for fetal chromosome defects requires establishment of the normal range for twins. This report documents that the normal range for MShCG between 15 and 19 weeks in twin gestations was 1.84–2.41 multiples of the singleton median. Of the 192 twin pregnancies studied, 31.7 and 47.9 per cent had MShCG values ≥2.5 and ≥ 2.0 multiples of the singleton median, respectively.     

Prenatal exclusion of late infantile metachromatic leucodystrophy in a late-presenting pregnancy by assay of fetal leucocytes

Metachromatic leucodystrophy was excluded in a fetus at risk, by assay of fetal blood collected at fetoscopy. Isolated fetal leucocytes were shown to have activities of arylsulphatase A and cerebroside sulphatase in the heterozygous range. The prediction was confirmed in the newborn.