Prenatal diagnosis of spinal muscular atrophy in Russia

Ninety-two families with spinal muscular atrophy (SMA) applied for genetic counselling and further prenatal diagnosis. To minimize expenses, only one tightly linked informative marker was determined in the course of preliminary examination, and non-radioactive allele detection was preferably used. Four prenatal diagnoses of SMA type I, four of SMA type II, and one of SMA type III were made. This trial programme shows the considerable requirements, importance, and potential effectiveness of prenatal prediction of SMA in Russia.     

The 48,XXYY syndrome: A case detected by maternal serum alpha-fetoprotein screening

A 17-year-old woman was referred for amniocentesis due to a low maternal serum alpha-fetoprotein (AFP) concentration in a voluntary screening test. The fetal karyotype was 48,XXYY, and the pregnancy was terminated. Autopsy of the fetus disclosed agenesis of the corpus callosum and unusual facial features.     

First-trimester prenatal diagnosis of aspartylglucosaminuria

Fetal aspartylglucosaminuria (AGU) was studied during the first trimester of pregnancy in six at-risk pregnancies using chorionic villus samples. The activity of aspartylglucosaminidase (AGA) was high in five cases, indicating an unaffected fetus. This was confirmed through delivery of healthy newborns with a normal pattern of urinary oligosaccharides. Low enzyme activity in an uncultured biopsy specimen and in cultured amniotic fluid cells in one case demonstrated that the fetus was affected. The pregnancy was terminated and the prenatal diagnosis was confirmed by showing reduced AGA activity in cultured fibroblasts of the fetus.     

The influence of source and timing of nitrogen fertilizers on yield and nitrogen use efficiency of four sweet potato cultivars

Nitrogen (N) availability is a very important determinant of crop yield. It is also one of the most expensive inputs in crop production. Thus, the efficient management of N by farmers with limited resource is a very important part of successful soil and crop management system. A field study was conducted on a Norfolk sandy loam soil at the George Washington Carver Agricultural Experiment Station, Tuskegee, AL, to evaluate the influence of fertilizer source and timing on the yield of four sweet potato [Ipomoea batatas (L.)] cultivars. Two N sources (urea, CO(NH₂)₂ and ammonium nitrate, NH₄NO₃), four sweet potato cultivars (‘Georgia Jet’, GA-Jet; ‘TU-82-155’, TU-155; ‘TU-1892’; and ‘Rojo Blanco’, Rojo-Bl) and three times (zero, single, and split applications) were used in a factorial designed experiment. Plants were harvested after 80 and 120 days and total and marketable yields determined. Nitrogen recovery efficiency, yield efficiency and physiological efficiency were also determined. Total and marketable yields of early maturing cultivars were significantly higher than of late maturing cultivars (P<0.05). The single application of N resulted in significantly higher yield in storage roots than split application (P<0.05). Physiological efficiency values were highly correlated with total marketable yields. Recovery rates increased with time. Late maturing cultivars tended to have higher N recovery and physiological efficiency than early maturing cultivars. These results suggest that cultivar maturity group should play an important part in N fertilization recommendations for sweet potato.     

1998年厄尔尼诺后珊瑚礁的侵蚀与恢复:印度洋查戈斯礁群

在印度洋中部查戈斯礁群的大多数珊瑚死亡之后3年,对30m水深以浅珊瑚的侵蚀和恢复情况进行了研究.北部环礁15m水深以浅、中部和南部环礁＞35m处的珊瑚差不多全部死亡.由于密集珊瑚丛的损失,一些礁体"表面"下降了1 5m.珊瑚的生物侵蚀情况严重,减少了三维礁体"结构"并形成松散的碎石.幼年珊瑚数量众多,尽管大部分是在侵蚀的或不稳定的基底上,并且稳定种较少.在15m的深度,礁体间鱼类丰度和多样性仍旧较高;依赖于珊瑚生存的物种减少,而一些食草动物和食碎屑动物则增加.一个新的海面温度(SST)数据集表明,平均SST自1950年以来升高了0.65℃.造成查戈斯珊瑚礁死亡的临界SST是29.9℃.