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Quarterly Report for Contract Number N68171-94-C-9101 (Norweigan Radium Hospital, Oslo, Norway).
NORWEGIAN RADIUM HOSPITAL OSLO INST FOR CANCER RESEARCH
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The general purpose of the present project is to evaluate flow cytometry as a means of detecting, enumerate and characterise bacteria harvested from air and water samples as part of a system for continuous monitoring of the environment with regard to potentially harmful organisms. In this initial phase of the project we have, in accordance with the project proposal, concentrated on the aspect of detection and enumeration of bacteria, using as a model a variety of species grown in culture. When bacteria are measured for monitoring purposes it is preferable to work with vital unfixed cells, partly to save time and partly because fixation of cells may cause aggregation, and also mask phenomena associated with vital functions, including the very aspect of vital versus dead. Thus, much of our effort has been directed towards development of staining procedures for unfixed samples. In order to establish such procedures, screening experiments with different fluorescent dyes were necessary. The emphasis has been primarily on the effects of different buffers and temperature as means of permeabilising the cell wall sufficiently to admit the dyes used, but not enough to facilitate efflux of macromolecules. Flow cytometry FCM is a technique for measuring the fluorescence and the light scattering of individual cells in large numbers. The cells are measured as they flow in a fluid stream one by one through the focus of an intense light source. The fluorescence intensity FL is usually proportional to the cellular content of the fluorescent substances. Most FCMs can measure two or more fluorescence wavelength components simultaneously, thus facilitating the staining of cells with two or more different dyes.
APPROVED FOR PUBLIC RELEASE