Extraction of DNA from amniotic fluid cells for the early prenatal diagnosis of genetic disease

Ten-ml samples of amniotic fluid were taken from pregnancies being terminated at 8–14 weeks' gestation. DNA was extracted from the amniotic cells by sequential centrifugation and analysed using the polymerase chain reaction (PCR). Fifteen samples were analysed for evidence of maternal contamination using Mfd5 oligo-nucleotide primers for repeat polymorphisms. Ten amniotic fluid samples were tested for the Delta-F₅₀₈ deletion characteristic of cystic fibrosis to demonstrate a diagnostic application for the technique. In each case, DNA extracted from fetal tissue from the same pregnancy was included in the controls. In 14 of the 15 cases tested with the Mfd5 primers, both the amniotic fluid DNA and the fetal DNA showed no evidence of contaminating DNA. In one case, neither the amniotic fluid cells nor the fetal cells yielded results. In nine of the ten cases tested with the Delta-F₅₀₈ primers, the amniotic fluid cell DNA provided accurate information about the genetic status of the fetus; in the tenth, the fetal DNA failed to amplify. The results indicate that adequate DNA can be extracted from amniotic fluid from 8 weeks' gestation onward and these samples are suitable for prenatal diagnosis using PCR.     

一个特大城市:墨西哥城大都市区的水资源管理

引言 墨西哥城大都市区(MCMA)位于被称作"墨西哥谷(Valle deMexico)"的天然围合的盆地里,海拔2240m.它下辖联邦区和墨西哥州的34个自治市.墨西哥城是墨西哥的首都,位于联邦区(DistritoFederal,DF),四面环山,海拔高度超过5000m.墨西哥州是墨西哥人口最稠密的地区(据报道有1300万居民),人口仅次于它的是墨西哥城,大约有860万人[1].     

半干法喷射烟气脱硫试验研究

介绍了半干法喷射烟气脱硫试验 ,研究了钙硫比、雾化水量、进口SO2 浓度、湿度等主要因素对脱硫率的影响规律 ,对布袋除尘器的辅助脱硫也进行了研究。结果将有助于改进半干法脱硫技术 ,并为进一步的工业应用提供了参考数据。     

Transient division of labor and behavioral specialization in the ant Formica schaufussi

Cooperative prey retrieval in the monomorphic ant Formica schaufussi is carried out by workers that perform functionally distinct roles which persist only for the duration of a single retrieval event. A forager (scout) that locates prey too large to retrieve individually organizes cooperative prey transport by recruiting nestmates (recruits) to assist in retrieval. The scout and recruit roles appear to be determined by whether a worker activates recruitment or is recruited from the nest. Scouts organize recruitment and play a key role in maintaining the cohesion of the retrieval group. If a scout that has initiated group transport is experimentally removed, the recruited workers composing the retrieval group typically abandon the prey and cooperative foraging is terminated. In this context, recruits are unable to function as scouts and reorganize group transport. Individuals marked as recruits in one prey retrieval, however, can switch and act as scouts in subsequent retrievals. Because the roles of individuals persist within but not between retrieval events, the specialization involved in cooperative prey retrieval cannot easily be explained as a response associated with age-related or genetic predispositions. This transient division-of-labor, in which individual roles may persist only for the duration of a single group action, represents a novel type of short-term individual specialization.     

Occurrence,functions and biosynthesis of polyamides in microorganisms and biotechnological production

Microorganisms are able to synthesize three different polyamides by enzymatic processes independently from ribosomal protein biosynthesis: poly(gamma-D-glutamic acid), poly(epsilon-L-lysine) and multi-L-arginyl-poly(L-aspartic acid) which is also referred to as cyanophycin. These polyamides, which occur mainly in Bacillus spp. (and only a few other eubacteria and the nematocysts of Cnidaria, in Streptomyces albulus or in cyanobacteria, respectively), have recently attracted considerable interest of the chemical industry and may be suitable for various applications. This review summarizes our current knowledge on the occurrence, biosynthesis, physiological functions, and biodegradation as well as on the properties and putative applications of these polyamides. Emphasis is placed on the enzymology of the polymerization and on the genes encoding the polymerizing enzymes, which have only recently become available for cyanophycin synthetases. Prospects for novel production processes. in particular for cyanophycin, are also presented.     

Foreword

Mitigation and Adaptation Strategies for Global Change -     

Utilisation of bubble resonance phenomena to improve gas–liquid contact

 In several branches of science and technology a gaseous phase is dispersed into a liquid in the form of bubbles, a gaseous component then dissolves into the liquid and subsequently undergoes chemical reaction. The overall process performance can be improved substantially when the area of gas–liquid contact is increased. By subjecting the liquid phase to low frequency vibrations, the bubbles are shown to suffer significant breakage, induced by resonance. When the vibration is properly tuned, the interfacial area is found to increase by a factor of 1.8–2.4, depending on the properties of the liquid. Resonance-induced bubble breakage phenomena have a great potential for improving the rates of chemical processes involving fast reactions, with minimal energy input. Received: 7 July 2000 / Accepted in revised form: 28 August 2000