Exclusion of chromosomal mosaicism in amniotic fluid cultures: Efficacy of in situ versus flask techniques

Accurate diagnosis of mosaicism in amniotic fluid cell cultures represents a major problem. If insufficient cells are analysed, true fetal mosaicism may go undetected. False-positive diagnosis is also possible since a second cell line may arise in vitro and not reflect the true fetal genetic constitution. These difficulties apply to both flask and in situ culture techniques, to varying degrees. The relative accuracy of flask versus in situ culture techniques in excluding mosaicism was determined by statistical analysis of experimental data from ten pairs of mixed male-female amniotic fluid specimens. The data support the idea that the majority of in situ colonies are independent of one another. The following conclusions are drawn: (1) analysis of a single metaphase from a number of different colonies enhances the confidence for excluding mosaicism; (2) analysis of more than one cell per colony offers little advantage; (3) exclusion of a given level of mosaicism requires analysis of fewer metaphases using the in situ method; (4) the confidence for excluding mosaicism is high with both in situ and flask techniques, using the provided guidelines; and (5) it is shown that the two-stage approach used by many laboratories is currently the most efficient way to exclude mosaicism.     

Zur Freisetzung gentechnisch veränderter Mikroorganismen

Microorganisms have been being released into the environment for a long time, e.g., in agriculture or for biotechnological processes. Amongst these microorganisms were some that had been labeled genetically, or improved by selection. In recent years, efforts have been directed towards alteration or optimization of appropriate bacteria and viruses by methods of recombinant DNA technology. In some cases, first releases of such organisms have been undertaken in experimental plots. There is public concern about the environmental risks of such releases, and about possible adverse effects. The present status of research in this controversial field, the regulations available in Germany and the United States, as well as the prospects of such work for the future are presented.     

Thermisches Verhalten und hochauflösende Durchstrahlungselektronenmikroskopie von YBa2Cu3O7−x

Dr. Mertin haben wir für seine Hilfe bei der Interpretation der elektronenmikroskopischen Aufnahmen, der Deutschen Forschungsgemeinschaft und dem Fonds der Chemischen Industrie für ihre finanzielle Unterstützung zu danken.     

Direct measurement of negative pressure in artificial-biological systems

We are very grateful to A. Gessner for his great help in the construction of the apparatus and A. Meyer for performance of some pressure bomb experiments. This work was supported by grants of the Deutsche Forschungsgemeinschaft (Forschergruppe Ökophysiologie) to U.Z. and O.L.L.     

Nachholbedarf in multidisziplin?rer Forschung

Naturwissenschaften Aktuell

Nachholbedarf in multidisziplinärer Forschung     

Symmetrieüberlegungen zur Supraleitung

Prof. Dr. Max Anwärter, Balzers, zum 80. Geburtstag gewidmet