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Biomedical subjects

J F Stoltz

Publications and source records attributed to J F Stoltz.

At least 163 records · Page 9Linked to original sources
PubMed1984

Use of a laser-Doppler electrophoresis method in bacteriology (preliminary results).

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.

Anti-Bacterial Agents↗
PubMed1984

Interests and limits of continuous excitation photo-physical methods applied to cellular rheology.

It is possible to characterize the cohesion of the lipidic zones in cells or in membranes by using molecular emission spectroscopy techniques such as : fluorescence polarization, quenching reactions, intramolecular reactions. However, applying these techniques in biology can be improved by the use of pulsed excitations leading to the time-resolved evolutions of some properties of the probe, which can themselves be a function of their environment. The first and the last techniques, based on the use of diphenylhexatriene and dipyrenylpropane respectively are used in practice by steady state excitation. In the case of fluorescence polarization, it can be shown that the method can be applied, within certain limits, which have to be precised when studying the modifications in the membranes. This is also partly true for methods based on the use of intramolecular reactions. However these continuous excitation techniques usually only lead to a global result which is a function of several spectroscopic parameters and of the "cohesion" of the membrane. Then it can be shown that to go beyond this step of semi-quantitative analysis, it is necessary to use pulsed or modulated excitation methods. Moreover this more sophisticated technical approach implies a new theoretical effort to understand the molecular dynamics of the membranes.

Animals↗
PubMed1984

Investigation of human blood platelets with fluorescence spectroscopy.

Intramolecular excimer formation of dipyrenylpropane was investigated in human blood platelets. The ratio of the emission intensities of excimer to monomer (IE/IM) is sensitive to changes in lipidic membrane structure, induced by external perturbations, such as cholesteryl hemisuccinate introduction and temperature. Lack of reliable "microviscosities" determinations could be due to poor solubility of the probe in aqueous cells suspensions. Results were compared to those obtained with the fluorescence polarization technique.

Blood Platelets↗
PubMed1984

A technique for continuously measuring filtration resistance at constant pressure.

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.

Electronics↗
PubMed1984

[Blood rheology in Raynaud's disease].

The part played by blood rheological factors in any vasomotor phenomenon is still difficult to define, in relation to its onset, maintenance and possible worsening. A high viscosity may contribute towards a difficulty in flow and viscosity is known to vary in an inverse manner with temperature. Many studies have been published reporting results of rheological investigations in Raynaud's syndromes, but whereas the majority describe both blood and plasma hyperviscosity, others report negative results or those that are interpretable with difficulty. A recent study in 49 patients with Raynaud's syndromes confirmed the presence of elevated blood and plasma viscosity values, particularly in Raynaud's syndromes secondary to other disorders and in digital arteritis. Elevated viscosity levels in "essential" Raynaud's syndromes were significant at low speeds only, suggesting the association of a disorder of erythrocyte aggregation with the properly termed vasomotor disturbance.

Blood Viscosity↗
PubMed1983

Beta-thromboglobulin levels in diabetes mellitus: influence of degenerative lesions and glycemic regulation using an artificial pancreas.

Plasma beta-Thromboglobulin levels (beta-TG) were measured by radioimmunoassay in two groups of diabetic patients: first group of 152 diabetics classified according to their vascular complications and anti-diabetic therapy, a second group of 21 poorly controlled insulin-dependent diabetics before and after 24 and 48 hours of strict blood glucose control using an artificial pancreas. beta-TG levels were on average higher in diabetic patients than in 47 healthy subjects. There was no difference between beta-TG levels in non-insulin-dependent patients with one or two microangiopathic lesions were not different from patients without complications. Only diabetics with severe degenerative lesions reveal plasma beta-TG levels significantly increased. Blood Glucose control during 48 hours is accompanied by a significant reduction of beta-TG levels, although the values remained higher than those of the control group. These results suggest that platelet hyperfunction shown in diabetes by beta-TG can precede the appearance of clinically detectable lesions, but the influence of lesions on platelet behaviour is still obscure. It appears however that strict metabolic control of diabetes could have some part in platelet hyperactivity.

Adolescent↗
PubMed1983

[Rheologic activation of blood platelets. Preliminary study].

A Couette type coaxial cylinder viscosimeter was used to evaluate the influence of deformation rates up to 20,000/s on blood platelets, in the presence or absence of red cells. Plasma lactate dehydrogenase and haemoglobin levels were determined in order to assess cell lysis and the estimation of beta-thromboglobulin (beta-TG) was considered to be an index of platelet activation. Results for whole blood revealed a change in red cells from 10,000/s upwards, which increased as the rate rose. At the same time, beta-TG rose slowly from the lowest deformation rates then considerably, in relation with the liberation of erythrocytic substances. The rise in LDH and beta-TG levels in platelet rich plasma (PRP) remained small up to 7,000/s approximately, then increased very rapidly, suggesting earlier mechanical and biochemical activation than in whole blood.

Beta-Globulins↗
PubMed1983

Vascular potential and thrombosis.

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.

Adsorption↗
PubMed1983

[Blood hyperviscosity syndromes. Classification and physiopathological understanding. Therapeutic deductions].

Blood has a number of rheological properties which partially determine flow, especially at capillary level, and its capacity to deliver oxygen. It is non-Newtonian, pseudoplastic, thixotropic and viscoelastic. Viscosity can be studied with different types of viscosimeters (coaxial cylinder or capillary viscosimeters). It can be defined by the ratio of stress of deformation to rate of deformation. Viscosity depends on macrorheological parameters: hematocrit, serum proteins, especially fibrinogen and globulins, and also on microrheological parameters: degree of aggregation and red blood cell deformability. Viscosity rises when the temperature falls and decreases with the radius of the tube through which the blood flows (Fahraeus-Linqvist effects). Blood viscosity is studied clinically at different temperatures, and, above all, at different rates of deformation by carefully recording the hematocrit. Plasma viscosity, fibrinogen, albumia and immunoglobulin levels, the viscosity of blood cell suspensions in normal saline must also be taken into consideration. Special investigations (rheoscopy, filtrability) provide information about red cell aggregation and deformability. Hyperviscosity syndromes are observed with: --raised hematocrit (polycythemia and pseudopolycythemia), --conditions with raised serum proteins or changes in their composition (especially hyperfibrinogenemia, raised immunoglobulins, low albumin levels); inflammatory syndromes, dysglobulinemias (Fahey's syndrome of plasma hyperviscosity), --low temperature (hypothermia), --increased red cell aggregability (shock, fat embolism), --reduced red cell deformability due to various congenital and acquired conditions (sickle cell anemia, renal failure, hyperlipoproteinemia, thrombosis, diabetes). Conversely, hypoviscosity may occur with a low hematocrit, hypoproteinemia, hypofibrinogenemia, and hyperthermia. Increased viscosity results in a slowing of blood flow, stagnation of its constituents and in ischemia. Therapeutic interventions may be considered on the different components of the hyperviscosity syndrome: hemodilation, plasmapheresis, dispersion of aggregants, agents acting on red cell deformability.

Blood Viscosity↗
PubMed1983

Red blood cell microrheology (clinical and pharmacological applications).

In order to understand blood circulation, knowledge of the rheological properties of blood is required. However, the characteristic parameters which must be considered differ according to the circulatory region investigated. A distinction must therefore be made between the macrorheological parameters (viscosity, viscoelasticity) and the microrheological parameters (aggregation, cell deformability). As far as the microrheological parameters are concerned, red blood cell deformability is quite definitely the most important parameter in any physiopathological study of capillary circulation and the resulting exchanges. The main intrinsic parameters of red blood cell deformability are: inner viscosity of the cell, surface/volume ratio and membrane properties related to the lipid bilayer or to the cytoskeleton. Abnormal erythrocyte microrheology may result form alterations any one of these three parameters and would affect the ability of the cell to transit in the capillaries. Disturbances of red blood cell deformability are encountered in many clinical cases, mainly during anomalies relating to hemoglobin structure or its oxygen affinity, in constitutional deficiency of the membrane and during degenerative cardiovascular diseases or diseases which are considered to be atherosclerosis risk factors.

Animals↗
PubMed1983

Vascular potential and thrombosis.

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.

Animals↗