Chemical structure and biological activities of lipid A's from various bacterial families

The endotoxic principle of lipopolysaccharides (LPS) is localized in their lipid A component. Biological effects of LPS on, for instance, body temperature, blood pressure, and blood picture, are also induced by free lipid A. In contrast to the great variability of the 0-specific chains, the chemical structure of lipid A is much more constant. It is common for Salmonella and similar for other genera of the Enterobacteriaceae. Recently, a number of lipid A's have been recognized that exhibited distinct structural features compared with Enterobacteriaceae. These lipid A's were found to be also distinct with regard to some of their biological properties.     

北极苔原和森林地区的稳定性及脆弱性与社会和环境变化

北极苔原带和北方森林(北部地区)因其分布广阔并远离农业土地利用变化及工业发展的影响,而一度被认为是地球上最后的净土.但如今这些地区如同地球上任何别的地区一样,也正经受着环境和社会变化的影响.本文总结了北部地区在全球系统中所起的作用,并提出方案以便对导致该地区对社会和环境变化敏感的那些因子进行评价.     

Rapid karyotyping in prenatal diagnosis: A comparative study of the ‘pipette method’ and the ‘in situ’ technique for chromosome harvesting

Rapid karyotyping in the second and third trimesters has important implications for the management of pregnancies at risk. From September 1985 to March 1992, 735 amniotic fluid samples sent to our laboratory for rapid karyotyping from 64 different diagnostic centres of the Federal Republic of Germany were included in a comparative study on harvesting for chromosome analysis using the ‘pipette method’ or the ‘in situ’ technique. The average time between preparation of the amniotic fluid and verbal notification of the analysed karyotype was 5·41 days. The ‘pipette method’ needed on average 4·65 days, and the ‘in situ’ technique 5·97 days. In comparison with other more invasive techniques available for rapid karyotyping such as cordocentesis and placental biopsy, amniocentesis and subsequent chromosome harvesting using the ‘pipette method’ and/or the ‘in situ’ technique proved very useful and efficient. The overall incidence of chromosome aberrations was 15·3 per cent. The high rate of structural chromosome aberrations and uncommon aneuploidies found in our investigation (12 per cent) indicates that for rapid karyotyping in the second and third trimesters, conventional cytogenetic techniques cannot be replaced by faster techniques based on fluorescent in situ hybridization on interphase cells in the near future.