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491.
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493.
In the course of a 2-year predictive testing programme for Huntington's disease (HD), six couples from a total of 52 applicants requested prenatal testing. In each case, the pregnancy was in the first or second trimester when the couples were referred for DNA diagnosis. In five cases, exclusion testing was offered; in one case, a person at risk with an increased risk of being a gene carrier requested prenatal diagnosis. In all cases, informative markers for prenatal testing could be determined. Whenever possible, the newer technique of polymerase chain reaction (PCR) for D4S125 was applied to perform rapid prenatal diagnosis. Two couples withdrew before chorionic villus sampling was undertaken; prenatal diagnosis was completed in the remaining four cases. After exclusion testing, two pregnancies were determined to have an increased risk and two fetuses to have a low risk of being HD gene carriers. 相似文献
494.
This paper deals with some endemic diseases related to selenium, iodine and fluoride in eco-environment. Keshan disease and Kaschin-Beck disease are associated with low selenium, they mainly occur in a belt zone across China ranging from North-East to South-West. Selenium contents in food grains and human hair from the disease affected areas are usually below 0.020ppm and 0.20ppm respectively. The endemic goitre caused by iodine deficiency distributes extensively in China, mainly in mountainous and hilly districts, swamp and peat areas, some sand soil and limestone areas. Also there is another kind of endemic goitre which caused by iodine excess in interior and coast areas. Endemic cretinism usually occurs in the endemic goitre seriously affected areas. Endemic fluorosis is also widely distributed in China, but mainly occurs in dry or semi-dry areas of north China. The fluoride sources for causing endemic fluorisis are drinking water and food grains polluted by coal smoke in the backing process of maize 相似文献
495.
Peng An Xu Langqiu Research Center for Eco-Environmental Sciences Academia Sinica Beijing China 《环境科学学报(英文版)》1989,(2)
The relation between EH [Se(VI)/Se(IV)] and pH of soil aqueous extract in Kaschin-Beck disease region and the effects of natural redox agents, namely humic substances, MnO2 and Fe2+, on the redox property of the system were studied. The results indicated that both humic acid and Fe2+ could enhance the reducibility of Se(VI) and MnO2, a limited oxidizability for Se(IV). Fe2+ showed a weak reducibility only at low pH value. The reducibilities of three sulfur-containing compounds for Se(VI) were in following order:thioglycollic acid > L-cysteine > sulfide 相似文献
496.
中国“硒与健康”数据库应用研究 总被引:9,自引:0,他引:9
由“硒与健康”数据库数据研究表明,中国26个省市人发含量量均值与长寿水平间存在着大致线性关系,相关系数达到0.71。135种常用食品含硒量与品种有关,鱼肉禽蛋>油料>豆类>粮食>蔬菜>水果。对克山病、大骨节病病区与非病区环境硒样品数据模式识别处理表明。环境硒水平不足是患病的根本原因之一,而主食大米与否不是本质原因。 相似文献
497.
泥鳅的网箱养殖及常见病害防治技术 总被引:2,自引:0,他引:2
网箱养泥鳅是一种高产高效,极具发展前景的养殖新模式.介绍了网箱养鳅的技术要点以及泥鳅常见疾病的防治方法. 相似文献
498.
Summary. HPLC analysis of secondary metabolites represents an efficient tool for the studying of plant chemical diversity under different
aspects: chemotaxonomy, metabolomics, adaptative responses to ecological factors, etc. Statistical analyses of HPLC databases,
e.g. correlation analysis between HPLC peaks, can reliably provide information on the similarity/dissimilarity degrees between
the chemical compounds. The similarities, corresponding to positive correlations, can be interpreted in terms of analogies
between chemical structures, synchronic metabolisms or co-evolution of two compounds under certain environment conditions,
etc. . In terms of metabolism, positive correlations can translate precursor-product relationships between compounds; negative
correlations can be indicative of competitive processes between two compounds for a common precursor(s), enzyme(s) or substrate(s).
Furthermore, the correlation analysis under a metabolic aspect can help to understand the biochemical origins of an observed
polymorphism in a plant species. With the aim of showing this, we present a new approach based on a simplex mixture design,
Scheffé matrix, which provides a correlation network making it possible to graphically visualise and to numerically model
the metabolic trends between HPLC peaks. The principle of the approach consisted in mixing individual HPLC profiles representative
of different phenotypes, then from a complete mixture set, a series of average profiles were calculated to provide a new database
with a small variability. Several iterations of the mixture design provided a smoothed final database from which the relationships
between the secondary metabolites were graphically and numerically analysed. These relationships were scale-dependent, namely
either deterministic or systematic: the first consisted of a monotonic global trend covering the whole variation field of
each metabolites’ pair; the second consisted of repetitive monotonic variations which gradually attenuated or intensified
along a global trend. This new metabolomic approach was illustrated from 404 individual plants of Astragalus caprinus (Leguminoseae), belonging to four chemical phenotypes (chemotypes) on the basis of flavonoids analysed in their leaves. After
smoothing, the relationships between flavonoids were numerically fitted using linear or polynomial models; therefore the co-response
coefficients were easily interpreted in terms of metabolic affinities or competitions between flavonoids which would be responsible
of the observed chemical polymorphism (the four chemotypes). The statistical validation of the approach was carried out by
comparing Pearson correlations to Spearman correlations calculated from the smoothed and the crude HPLC database, respectively.
Moreover, the signs of the smoothed relationships were finely supported by analogies and differences between the chemical
structures of flavonoids, leading to fluent interpretation in relation to the pathway architecture. 相似文献
499.
鼎湖山主要植被类型土壤微生物生物量研究 总被引:26,自引:2,他引:26
对鼎湖山国家级自然保护区3种主要植被类型:季风常绿阔叶林,针阔叶混交林和马尾松林土壤微生物生物量进行了研究。结果表明,土壤微生物生物量(mg.kg^-1)在季风常绿阔叶林、针阔叶混交林和马尾松林中分别为:822,588,530,季风常绿阔叶林显著高于针阔叶混交林和马尾松林(P〈0.01),而针阔叶混交林和马尾松林无显著差异(P〉0.05);土壤中微生物量高的土壤中,有机碳含量也相应高,两者的比值可反应土壤碳的积累或损失,研究表明,鼎湖山3种主要植被类型土壤均处于碳积累过程;季风常绿阔叶林、针阔叶混交林和马尾松林土壤微生物碳周转量(t.hm^-2.a^-1)依次为:14.07,11.45,9,60,碳素的周转带动了其他营养元素的循环和能量的流动;土壤微生物代谢熵(mg.g^-1.h^-1)由低到高依次是季风常绿阔叶林(0.59)、针阔叶混交林(0.96)和马尾松林(1.33),表明土壤微生物对土壤碳的利用效率季风常绿阔叶林较高,马尾松林较低。 相似文献
500.
Geochemical Environment and Health Problems in China 总被引:3,自引:0,他引:3
China is a very large developing country covering vast territories and having a complex natural environment. It has an enormous population and numerous endemic diseases. The total population of China is 14 x 10(8) of which 3 x 10(3) live in endemic disease-affected areas and 0.48 x 10(3) suffer from these diseases. The distribution of the endemic diseases has obvious geographical characteristics. Among the most harmful and widely distributed of the endemic diseases are Kaschin-Beck disease, Keshan disease, iodine deficiency, endemic fluorosis and hepatic carcinoma. The geographical environments have a close relationship to endemic diseases and are influenced by climate, geology, landform, soil, food and drinking water. Drinking water is the key issue, since polluted water, or water lacking in or having an excess of certain minerals and elements, as well as water containing certain organic components, has been shown to be harmful to human health. Research has shown that some diseases can be reduced or eliminated by paying attention to the way drinking water is obtained, as well as by improving the nutritional values of the food by eliminating negative components. Fifty years of research has already gone into this subject and there is still much research to be done. This paper puts forth a model of health problems related to geographical environment and the importance of continued research in this field. 相似文献