The morphological identification of cells by flow cytometry is difficult. Usually cell sorting and microscopical analysis have to be used in addition. Morphological analysis is simplified by taking cell pictures from a range of particular interest immediately during flow cytometric analysis. Instruments using the video scanning technique for fluorescence imaging are slow and expensive (8, 10). Morphological information can also be obtained by transmission imaging of cells in flow, which requires shorter exposure times. Therefore a cell volume activated flow imaging device has been developed which operates at flow speeds up to 5 m/sec and which depicts transmission images of selected cells on a 16-mm film by a nsec flashlamp illumination. An electronic unit detects the particles in the optically accessible orifice, performs the pulse height analysis, triggers the flashlamp if particles are in the preselcted range of interest and feeds the film. The instrument is capable of delivering up to 150 pictures per second and works either as a flow microscope in which the cells in the preselected volume range are directly observed, or as a picture system in which the cell pictures are stored on the 16-mm film for documentation or for image analysis.

A new flow through instrument that simultaneously measures cell volume (resistance pulse technique) and cell fluorescence in the same orifice will be described. The fluorescence pulses of the hydrodynamically focussed cells are picked up by the optics via the axial direction (principle of Dittrich and Goehde, Z Naturforsch 24b:360, 1969).

Recently, it was shown that the lateral orientation of sperm cells disturbs the deoxynibonucleic acid distribution measured by fluorescence in a laterally laser-illuminated flow system. The present results show how flat particles may be influenced to assume a uniform lateral orientation. This was achieved by choosing the geometrical dimensions of the hydrodynamic focusing flow path. High speed photographs of fixed chicken erythrocytes oriented in experimental chambers are presented.

In state of the art flow cytometric transducers, the cells are supplied through tubes. Passage through the tube and washing between different samples is time consuming and limits the number of samples that can be processed in a given time. This is a drawback particularly with automatic routine instruments. For kinetic studies in the time range of seconds, it is necessary to perform the cell reactions directly in the transducer in order to have a short delay between the suspension vessel where the cell reaction is in progress and the point of measurement. A new one parameter electrical sizing transducer without a particle supplying tube is described and compared with a conventional Metricell transducer. The cells are directly supplied from an exchangeable vessel to the measuring point in the transducer. The vessel which is an inexpensive mass produced product, serves as the injection tip for passing the cell suspension into the focusing flow path. There is no interconnected tube to delay or intermix the cells in the stage between the reaction in progress in the vessel and flow analysis. Delay times of only 1 second are achieved with the new transducer, and by supplying each sample with its own vessel subsequent samples are analyzed without the necessity of cleaning a cell supplying tube. In this way a high throughput of samples per time unit is achieved and time kinetic experiments in the time range of seconds can be performed. The design of a tubeless multiparameter Fluvo Metricell transducer is explained.

A newly developed macro flow planktometer is described for measuring plankton organisms with a size of 100-2,000 pm by the flow principle in timesaving and noncontact fashion. Based on the method of changes in electric resistance (Coulter principle), the device allows determination of the body volume of living organisms in their natural medium (fresh or seawater) at a measuring rate of up to 50 organisms per second. Simultaneous, laser-excited fluorescence measurement permits quantitative detection of fluorescent substances within the organisms. Controlled by the multiparametric measurement, video images of organisms of particular interest can be taken in the flow chamber using a stroboscopic imaging system. Valuable morphological information on the material under test is thus available in addition to the analytical measurement. Data acquisition and imaging, the total system control, and the fast data evaluation are performed with an IBM-AT compatible computer using an extensive software package. The easy-to-handle desktop unit can be used both in land laboratories and on ships. The modular structure of the system permits any desired combination of individual components to adapt it to various requirements. The operability of this new measuring system is demonstrated by several applications.