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J C Lelièvre

Publications and source records attributed to J C Lelièvre.

9 recordsLinked to original sources
PubMed1995

[A study of leukocyte chemotaxis in a glass micropipette].

Chemotaxis, the directional locomotion of a cell toward a source of a chemical gradient, is an important phenomenon occurring for mobilizing immune cells at sites of infection and injury. This phenomenon has been simulated in analyzing the movement in vitro of a chemoattracted cell inside a glass micropipette. A microneedle filled with fMLP, N-formyl-methionyl-leucyl-phenylalanine, at a concentration of 9.10(-7) M in 1% gelatin, is inserted in a glass micropipette containing Hanks buffer solution. After diffusion of fMLP in the glass micropipette until a constant gradient is established, the tip of the glass micropipette is moved near a polymorphonuclear neutrophil. Its spontaneous movement inside the micropipette towards the chemotactic source can be observed and quantified. Without any counter-pressure (positive pressure), the cell spontaneously advances with an average velocity of 0.14 +/- 0.04 micron/s. Corresponding to the maximal strength developed by the cell during its motion, the required strength to stop the chemotactic migration has been estimated to be 39 +/- 4 nN. Giving both qualitative and quantitative information on the dynamics of cell motility, this experiment will be helpful in the understanding of some aspects of cell motility in the tissues.

Chemotaxis, Leukocyte↗
PubMed1994

[Microrheology of marrow promyelocytes from patients suffering from acute myeloblastic leukemia type 3].

Viscosity values of marrow cells from patients suffering from acute promyelocytic leukemia (acute myeloid leukemia of type 3) have been determined before and during a treatment with all-trans retinoïc acid (active metabolite of the vitamin A, inducing cell differentiation and maturation). Evaluated from aspiration tests into a glass micropipette, the marrow cell viscosity has been compared to that of normal neutrophils. Results seem to point out that the induced hyperleucocytosis is favoured by both a low standard deviation of pathological cell viscosity and a cell viscosity value close to that of normal neutrophils. The systematic study of cell viscosity could therefore help the clinicians to individualize the treatment.

Granulocytes↗
PubMed1993

[Presentation of a clinical hemoviscosimeter].

A clinical hemoviscosiSImeter is presented. It is a Couette type viscometer which is automatic and driven by a microcomputer. It was designed and realized in the laboratory. The measurement of blood viscosity requires 1 ml of anticoagulated blood adjusted at 45% of hematocrit. Experiments are performed at a constant temperature (37 degrees C) according to a well-established protocol: gentle mixing of the blood sample followed by a 3 minute rest just before each of the following measurement modes begins. Under steady state flow conditions, 12 viscosity measurements are realized in a range of shear stress rate step of 1 s-1 is applied. The elastothixotropic response of the blood sample is then obtained. Such a hemorheological test, called "hemorheogram", requires 15 minutes. Given to the clinician, the hemorheogram results include the absolute blood viscosities at the shear stress rates of 0.1 s-1, 1 s-1, 10 s-1, 70 s-1, the thixotropy index and the plasma viscosity. Finally, results to be kept in the laboratory files consist of the whole data issued from the patient hemorheogram including the relative blood viscosities (blood viscosity/plasma viscosity) at the same shear strers rate values.

Blood Viscosity↗
PubMed1989

Effects of clinostatism and orthostatism on blood viscosity.

The present study was planned to study the magnitude of the effects of body position upon blood viscosity. We compared blood rheological properties in nine healthy subjects after 1 h in a horizontal position and after 1 h in a vertical position. After orthostatism, blood viscosity was 38%, 41%, and 22% higher at 0.05, 1, and 20 s-1 shear rates, respectively. This result was the consequence of the increase of hematocrit (41.2% +/- 2.3% vs 44.2% +/- 2.7) and plasma viscosity (1.55 +/- 0.09 mPa.s vs 1.67 +/- 0.08 mPa.s) induced by orthostatism in all the subjects. The rise of the different plasma proteins and fibrinogen was the cause of the plasma viscosity increase. Blood viscosity at standard hematocrit (45%) was not significantly altered by orthostatism. Rheological studies at standard hematocrit showed that body position did not modify red cell deformability and aggregability. As suggested by the increase in hematocrit and plasma proteins and by the absence of alteration of blood rheological properties at standard hematocrit, the large effect of body position upon blood viscosity is the consequence of the hemoconcentration without alteration of erythrocyte deformability and aggregability.

Blood Viscosity↗
PubMed1988

Blood viscosity after a 1-h submaximal exercise with and without drinking.

Ten healthy subjects performed two exercise sessions similar to an endurance training session for average athletes (1 cycling exercise at 85% of the maximal heart rate on a Monark cycle ergometer). In the first session, the subjects were not allowed to drink during exercise. During the second session, the same subjects performed the same exercise as during the first session but they drank a beverage volume equal to the weight loss induced by the first exercise session to verify the hypothesis that the compensation of sweat loss by drinking could attenuate the exercise-induced blood viscosity increase. Both protocols (with and without drinking) induced a significant increase of hematocrit and plasma viscosity. The whole blood viscosity increased at all shear rates but this increase was significant only for the exercise protocol without drinking. Blood thixotropic property, erythrocyte deformability, and erythrocyte aggregability remained unchanged after both exercise protocols. Hemoconcentration explained the increase of hematocrit and plasma viscosity. Hemoconcentration was probably the consequence of a filtration process through capillary leakage in addition to sweat loss, which could explain the partial effect of drinking in our study.

Adult↗
PubMed1988

Theoretical and experimental study of the time dependent flow of red blood cell suspension through narrow pores.

The Hemorheometer has been adapted to allow the recording of the flow rate during the filtration process. For newtonian fluids, the flow rate variation versus time through the pores is well approximated by Poiseuille's law. For dilute red blood cell suspensions, the same analysis can be applied by introducing the concept of "apparent filtration viscosity" which is higher than the usual viscosity measured by Couette viscometry. The apparent filtration viscosity parameter is related to the deformations undergone by red blood cells as they pass through the narrow pores. Apparent filtration viscosity can be used to obtain a precise determination of the erythrocyte deformability. Measurements performed, for a given blood sample, with pores of different diameters (5 microns, 8 microns and 12 microns) show that the error on the value of apparent filtration viscosity is less than 3%. As a result, the sensitivity of the filtration method allows to discriminate among normal blood samples. High concentrations of erythrocytes or leucocytes are found to modify the apparent filtration viscosity. These factors are apparent in the recorded filtration curves. Their effects on filtration measurements can be easily estimated.

Erythrocytes↗
PubMed1988

The RBC morphological dependence of the RBC disaggregability.

The aim of this study was to determine the red blood cell (RBC) disaggregability dependence upon the RBC shape. The study concentrated on stored blood during bank storage and on suspensions of artificially induced echinocytes. Measurements was performed in autologous plasma of hematocrit 0.45 and at constant plasmatic content. Rheological studies using stationary viscometry, nonstationary viscometry and rheoscopy were made in order to assess different stages of the disaggregability process. Whatever the method of measurement used, the morphological interpretation of the results reveal that beyond 75% of echinocytes within the sample, the disaggregation process is altered. The shear stresses required to dissociate the echinocyte aggregates are significantly higher than those required to disaggregate normal RBC rouleaux.

Erythrocyte Aggregation↗
PubMedDate not supplied

Relevance of measuring red blood cell disaggregability in insulin-dependent diabetic patients.

A viscometric study of blood from insulin-treated diabetic patients is carried out. Patients are divided into three major groups--group I: without or with minimal retinopathy and recent diabetes (n = 37), group II: without or with minimal retinopathy and at least 20 years of diabetes duration (n = 35), group III: with severe retinopathy (n = 27). Each group is also subdivided according to the glycosylated hemoglobin (HbA1c) level, used to assess long-term glycemic control. Finally, the rheological parameters of six groups are compared: three of which have a HbA1c level less than 7.5% [I1 (n = 15), II1 (n = 9), III1 (n = 9)] and three others have a HbA1c level more than 7.5% [I2 (n = 22), II2 (n = 26), III2 (n = 18)]. The most important result concerns the thixotropy index xi t, which reflects the dynamic property of red blood cell (RBC) disaggregability under shear. Strong correlations between this parameter and HbA1c level are found for groups I (r = -0.53, p < 0.001) and III (r = -0.68, p < 0.001), providing evidence of a RBC disaggregability disorder for a poor glycemic control of diabetes. In contrast, such a correlation is not pointed out for the group II. As the value for xi t is not statistically different for groups II1 and II2 and is close to the normal value in both groups, the existence of a rheological protection against the retinopathy could be involved.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗