Biomedical subjects

W Rolf

Publications and source records attributed to W Rolf.

3 recordsLinked to original sources

PubMed1999

Automated comet assay analysis.

BACKGROUND: Recently the "comet assay" or "single-cell gel electrophoresis assay" has been established as a sensitive method for the detection of DNA damage and repair. Most of the software now available to quantify various parameters for DNA damage requires the interaction of a human observer. In this report, we describe an automated analysis system that is based on self-developed software and hardware and needs minimal human interaction. METHODS: The image analysis is divided into two parts: 1) automatic cell recognition and comet classification and 2) quantification of desired comet parameters. Image preprocessing, segmentation, and feature classification were developed with algorithms based on mathematical morphology. To enhance evaluation speed, we have introduced parallel processing of data under the Windows NT operating system (Microsoft Corporation, Redmond, WA). Use of an analogue real-time autofocus unit (Böcker et al.: Phys Med Biol 1997;42:1981-1992) allows for faster analysis. RESULTS: Our recognition software shows a sensitivity of 95.2% and a specificity of 92.7% when tested on test samples from routine work with DNA damage by low-dose radiation (0-2 Gy). The parallel hardware and software concept enables us to analyze 100 comets on one slide in less than 15 min. CONCLUSIONS: A comparison of measurements made on the same samples by manual and automated analysis systems revealed that there are no significant differences. The slope of the dose-response curves and the repair kinetics are very similar and demonstrate that automatic comet assay analysis is possible.

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PubMed1999

[The pattern of health behavior and its determinants--results of the Bern-Munich Life Style Panel].

Results from a study on health-related lifestyles of Munich citizens aged between 55 and 65 were compared with an independent data set from Bern. Cluster analysis identified eight health-related behavior patterns in the Munich sample which were also found in the Bern sample. Predictors of health-relevant behavior patterns were analysed via multiple logistic regressions. Most results showed different effects on cluster membership between the two samples. Gender, professional status, social support from friends, and paying attention to regular meals were identified as predictor variables in both samples. Other variables identified as predictors occurred either in only one of the two samples or differed in the direction of their effect.

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PubMed1997

A fast autofocus unit for fluorescence microscopy.

In this paper a fast autofocus unit is introduced for fluorescence microscopy based on image content information. The module, an electronic board with several differentiators and integrators, is designed for high-speed autofocusing and is directly coupled to the output of the video camera. A Leitz MPV II fluorescence microscope with x, y, z stepping motors was used as basic equipment. The microscope images were focused by using an intensified target camera with a following analogue-digital converter and a PC. Thus one obtains a focus value for the current image within one video cycle. Furthermore, it is possible to process three different focus functions (weighted intensity, first derivative and second derivative) simultaneously. The flexibility to select a certain focus function or a combination of these functions allows the use of the analogue detector for various cell types and fluorescent dyes. In order to test the experimental set-up we use three different kinds of biological specimen (lymphocytes, fibroblasts and comet cells) which are distinguished by large differences in their morphological structure. Successful focusing is carried out in more than 95% of cases (investigation of several hundred different cells). The focusing procedure is almost finished after 1-2 s.

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