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.     

Estimating the risk of a fetal autosomal trisomy at mid-trimester using maternal serum alpha fetoprotein and age: A retrospective study of 142 pregnancies

Risks appropriate for mid-trimester prenatal screening for autosomal trisomies have been estimated from a combination of maternal age and maternal serum (MS) alpha-fetoprotein (AFP) levels at 16–20 weeks gestation. Published data on the frequency of Down's syndrome births relative to maternal age were modified to include the additional age-related frequency of trisomy 18 and trisomy 13 cases to provide an overall risk for an autosomal trisomy at midtrimester. MSAFP results from a retrospective study of 142 affected (114 trisomy 21, 19 trisomy 18, and 9 trisomy 13)and 113 000 unaffected pregnancies were converted to multiples of the appropriate gestational median (MOM). The AFP levels in the autosomal trisomy pregnancies were found to be significantly reduced at 0.72 MOM of the unaffected pregnancies. Risks (likelihood ratios) were derived from the overlapping log Gaussian distributions for affected and unaffected pregnancies and combined with maternal age risks to give the overall odds of an affected pregnancy. A mid-trimester cut-off risk of 1:280 gave an estimated 37 per cent detection rate for autosomal trisomies in the west of Scotland population for a follow-up (false-positive) rate of 6.6 per cent. These figures compare with a 30 per cent detection and 6.7 per cent false-positive rate if age 35 years and over is used as the sole criterion for selection of at-risk pregnancies.     

A study on Se application for improving the soil in the environment at lower Se level

A result that application of sodium selenite or fly ash to some of soilin loess plateau can increase Se content in wheat grain has been demonstrated by the pot and field experiments, and added Se in soil can last its availability for 3 years. So this is a good measure for improving the low Se soils and preventing the Kaschin-Beck disease.     

可变电荷表面对磷的吸附与解吸动力学

研究了可变电荷表面为主的土壤对磷的吸附与解吸动力学。结果麦明,磷吸附和解吸动力学均可用修正的Elovich方程、双常数速率方程和分段拟合的抛物线扩散公式来表征。吸附和解吸过程均可分为快、慢两个反应阶段。磷吸附过程是一个扩散控制的不可逆过程.     

Prenatal diagnosis of a mosaic 46,XY/47,X,i (Xq)Y

A case of mosaic 46,XY/47,X,i(Xq)Y is diagnosed at 18 gestational weeks in amniotic fluid cells and confirmed at birth in the lymphocytes of the child. The literature on Klinefelter's syndromes with structural chromosome X rearrangements is reviewed. This is the first case reported of a mosaic isochromosome Xq in a boy.     

Mosaicism of 46,XX/47,XX,+9/47,XX,+?mar in the same amniotic fluid with apparent loss of one cell line after delivery

A 46,XX; 47,XX,+9; 47,XX, + ?mar karyotype was detected in an amniotic fluid cell culture and confirmed in a subsequent fetal blood sample from a 40-year-old woman. After termination of the pregnancy, none of the 186 mitoses obtained from a second blood sample was trisomic for chromosome 9 (p<0.001). Selection against cells containing trisomy 9 is postulated to explain the disappearance of the lymphocyte clone.     

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.     

Prenatal diagnosis using deletion studies in Duchenne muscular dystrophy

Accurate carrier testing and prenatal diagnosis in Duchenne muscular dystrophy (DMD) families is facilitated when an Xp21 deletion is found to be segregating within a family. We discuss the results of the DNA testing in two families, one in which DNA from affected males was available for study and the other in which no DNA from an affected male was available. Factors complicating the counselling of DMD deletion families are outlined.     

Prenatal diagnosis of a rare heteropagus

The prenatal diagnosis by ultrasound of an unusual case of supernumerary head is reported. The problems of differential diagnosis, the pathological findings after voluntary interruption of the pregnancy, and the problems of obstetric management are presented.