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A new electrophoresis system using Laser Doppler velocimetry has been developed. This technic allows fast measurements, (1 minute) over a large number of particles (several thousand or more). Furthermore, the small size of the particles is no longer a limitation of the measurement. These qualities made it possible to study the electrokinetic properties of cells. In this paper the authors present the first application obtained on different types of bacteria (Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli, Proteus vulgaris) submitted to five antibiotics (gentamycin, minocyclin, cephalotin, spiramycin, sobramycin). After four hours of incubation at 37 degrees C, important decreases of electrophoretic mobility were observed on bacteria treated with antibiotics to which they were sensitive. On the other hand, no significant modification appeared on bacteria treated with antibiotics to which they were not sensitive. In conclusion, the electrophoretic mobility test seems to be useful to study the response of bacteria to antibiotics and perhaps could be used to set antibiograms.

A device for continuously measuring, at constant pressure, the filtration resistance of different liquid suspensions is described. It is made up of two main parts: flowmeter system and electronic circuit. The flowmeter consists of a capillary tube and a sensitive pressure transducer, and has a time response of 100 ms and a linearity of +/- 1% from 1 uls-1. The electronic part allows the calculation and recording of flow versus time and filtration resistance versus the volume which passes through the filter. Principle, technical characteristics of the system and examples of recording with several Red Blood Cell populations are reported.

The Erythrometer is a new device capable of determining both red blood cell filterability and plasma viscosity. In the case of filterability measurements, a suspension of washed red blood cells is filtered at a steady flow rate through a 3 or 5 microns pore-diameter membrane. Pressure drop across the membrane is recorded and a red blood cell filterability index can be calculated according to the change in pressure. The authors describe the instrument's operating principle and performance and present some of the results obtained.