Die Anwendung der Biegeschwingermethode zur Messung von Blutdichte und Hämatokrit

Zusammenfassung Dichtemessungen der Genauigkeit von 0,01 g/l wurden an menschlichen Blutproben sowie an Plasma und Erythrozytenkonzentrat mit Hilfe eines Dichtemeßgerätes nach der Biegeschwingermethode vorgenommen.Zwischen Blutdichte und Hämatokrit wurde eine hochsignifikante lineare Beziehung gefunden. Bei Kenntnis der Plasma- und Blutzelldichte einer Blutprobe kann der Hämatokrit aus der Blutdichte genauer ermittelt werden als mit der Zentrifugationsmethode, was insbesondere für den Nachweis geringgradiger Änderungen, etwa durch Verschiebung des transkapillären Filtrationsgleichgewichtes, von Interesse ist.Aus der statistischen Verteilung der Plasma- und Erythrozytendichtewerte ergibt sich ferner der Schwankungsbereich der Blutdichte für bestimmte Hämatokritwerte und umgekehrt.Diese Arbeit wurde vom Fonds zur Förderung der Wissenschaftlichen Forschung unterstützt (Projekt-Nr. 3447)     

Adolescent substance-use assessment: methodological issues in the use of the ADAD (Adolescent Drug Abuse Diagnosis)

During the past twenty years, various instruments have been developed for the assessment of substance use in adolescents, mainly in the United States. However, few of them have been adapted to, and validated in, French-speaking populations. Consequently, although increasing alcohol and drug use among teenagers has become a major concern, the various health and social programs developed in response to this specific problem have received little attention with regard to follow-up and outcome assessment. A standardized multidimensional assessment instrument adapted for adolescents is needed to assess the individual needs of adolescents and assign them to the most appropriate treatment setting, to provide a single measurement within and across health and social systems, and to conduct treatment outcome evaluations. Moreover, having an available instrument makes it possible to develop longitudinal and trans-cultural research studies. For this reason, a French version of the Adolescent Drug Abuse Diagnosis (ADAD) was developed and validated at the University Child and Adolescent Psychiatric Clinic in Lausanne, Switzerland. This paper aims to discuss the methodological issues that we faced when using the ADAD instrument in a 4-year longitudinal study including adolescent substance users. Methodological aspects relating to the content and format of the instrument, the assessment administration and the statistical analyses are discussed.     

Dominant negative selection of vaccinia virus using a thymidine kinase/thymidylate kinase fusion gene and the prodrug azidothymidine

The Escherichia coli thymidine kinase/thymidylate kinase (tk/tmk) fusion gene encodes an enzyme that efficiently converts the prodrug 3'-azido-2',3'-dideoxythymidine (AZT) into its toxic triphosphate derivative, a substance which stops DNA chain elongation. Integration of this marker gene into vaccinia virus that normally is not inhibited by AZT allowed the establishment of a powerful selection procedure for recombinant viruses. In contrast to the conventional vaccinia thymidine kinase (tk) selection that is performed in tk-negative cell lines, AZT selection can be performed in normal (tk-positive) cell lines. The technique is especially useful for the generation of replication-deficient vaccinia viruses and may also be used for gene knock-out studies of essential vaccinia genes.     

Automated mass detection in contrast-enhanced CT colonography: an approach based on contrast and volume

The purpose of this feasibility study was to design and test an algorithm for automating mass detection in contrast-enhanced CT colonography (CTC). Five patients with known colorectal masses underwent a pre-surgical contrast-enhanced (120 ml volume 1.6 g iodine/s injection rate, 60 s scan delay) CTC in high spatial resolution (16-slice CT: collimation: 16×0.75 mm, tablefeed: 24 mm/0.5 s, reconstruction increment: 0.5 mm). A CT-density- and volume-based algorithm searched for masses in the colonic wall, which was extracted before by segmenting and dilating the colonic air lumen and subtracting the inner air. A radiologist analyzed the detections and causes of false positives. All masses were detected, and false positives were easy to identify. Combining CT density with volume as a cut-off is a promising approach for automating mass detection that should be further refined and also tested in contrast-enhanced MR colonography. More information under .