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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.

The electrochemical phenomena related to the negative charge of blood cells have provided a means of defining the importance of these parameters in vascular thrombosis. In parallel with these works, measurements of transmembrane potential have revealed that the vessel wall also carries negative charges and thus takes part in the repulsion of blood cells and prevents them from being adhesive on the intima. These charges come from various origins (ion or protein adsorption, active transfer through the vascular wall, ionized groups…). Vascular potential can be approached by means of various techniques : transmembrane potential (electro-osmosis), circulation potential (in vitro and in vivo). On the basis of published results and his own personal research, the author compares the different values that have been obtained. Consequently, it has been observed that the transmembrane charge measurements that are accessible using electro-osmosis techniques and streaming potential do reflect some discordances according to the methods used. The importance of these parameters and the part they play in thrombosis phenomena is discussed.

Electrical phenomena of cell membranes may be examined by means of cell electrophoresis. Direct microscopic techniques are tedious, inaccurate and rarely reproducible. Therefore, the authors have developed a new device using Doppler velocimetry. After describing the apparatus, they propose two methods for testing treatment against electroosmosis and present the first biological applications on mixed populations of red cells.

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.

The viscometer described in this paper comprises a vertical cylinder containing the fluid to be tested and an inner, hollow cylinder floating in the fluid and filled with magnetic liquid. The magnetic liquid and inner cylinder are set in motion by applying a rotating magnetic field. Torque is balanced by the stresses in the fluid and the inertia of the rotating cylinder. The main characteristics of this new apparatus are: - possibility of applying various torques to the rotor. Measurements of angular velocity are made on the inner cylinder (in general, conventional viscometers are built on the opposite principle), - study in transient flow. Various measurements on Newtonian fluids (water, plasma, oils, etc.) and on blood suspensions have made it possible to improve the accuracy of the method.

The authors describe the standardization of a new technique for studying, based on the filtration pressure exerted by x aggregates on a given filter. First results concern the study of the filtration pressure of whole blood, platelet-enriched plasma and the effect of ADP on concentrations ranging from 0.1 to 100/ml. The filtration pressure of PRP increases with the dose of ADP used. Biological and clinical applications of the method are considered both for aggregates of cells and for substances preventing aggregation.

Serotonin is a vasoactive substance that acts on blood vessels and platelets but whose primary action lies in its role as an amplifier for other agents. The aim of this work was to study the effects on blood platelets and erythrocytes of the S2-serotonergic receptor antagonist ketanserin. Twenty-seven patients with untreated hypertension and/or intermittent claudication received a bolus intravenous (i.v.) injection of 10 mg ketanserin followed by 2 mg/h during 3 h i.v. infusion. Platelet function and erythrocyte filterability were studied before and 30 min, 3 h, and 24 h after the bolus injection. The results showed decreases of plasma beta-thromboglobulin and platelet factor 4 levels (p less than 0.001) and platelet aggregation induced by epinephrine plus serotonin (p less than 0.001), whereas ADP-induced aggregation remained unchanged 30 min and 3 h after ketanserin administration. Red cell filterability was decreased (p less than 0.01). There was a tendency toward lower mean arterial blood pressure but heart rate remained unchanged. The dual effect of ketanserin on platelet function and erythrocyte filterability might be of great clinical value in hypertension and peripheral vascular disease in which microcirculatory flow is altered.

Blood suspensions have been studied by using an air-bearing viscosimeter which is driven by a rotating magnetic induction. Each transient motion (rise, relaxation with zero or intermittent field) can be considered as a quasi-static motion, from which the curve viscosity-shear gradient can be obtained. Combining several transient motions allows an easier determination of the parameters describing a non newtonian fluid like blood.

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 essential part played by rheological factors in genesis of thrombosis and atherosclerosis has often been mentioned. Thus the authors have carried out a study of rheological and biochemical parameters on a genetic animal model with modifications in plasma lipids (homozygous obese "Fatty" rat) compared to the non obese heterozygous animal. The results obtained for the evolution of biochemical parameters (blood glucose, cholesterol, triglycerides) over a 16 months period confirm those published earlier. Further, a significant increase in fibrinogen level was observed in homozygous animals, and correlated with plasma viscosity. There results are also connected with changes in apparent blood viscosity which is considerably increased in homozygous rats, particularly at low shear rates (gamma less than 20 s-1). These results show the value of this animal model and the authors suggest the application of such a genetic animal model and of its heterozygous control population to both theoretical rheological and pharmacological studies on atherogenesis and hyperlipoproteinaemia.