Respiratory impedance measured with head generator to minimize upper airway shunt.

A new method for measuring total respiratory input impedance (Zrs), which ensures minimal motion of extrathoracic airway walls, was tested over frequencies of 4-30 Hz in 14 normal subjects and 10 patients with airway obstruction. It consists of applying pressure variations around the head, rather than at the mouth, so that transmural pressure across upper airway walls is equal to the small pressure drop across the pneumotachograph. Compared with reference Zrs values obtained by directly measuring airway wall motion with a head plethysmograph and correcting the data for it, the investigated method provided similar values for respiratory resistance at all frequencies (30 Hz, 3.67 +/- 2.24 cmH2O X 1(-1) X s compared with 3.55 +/- 2.00) but slightly overestimated respiratory reactance at the largest frequencies (30 Hz, 2.82 +/- 1.28 cmH2O X 1(-1) X s compared with 2.52 +/- 1.22, P less than 0.01). In contrast, when the data were not corrected for airway wall motion, resistance was largely underestimated, especially in patients (-48% at 30 Hz, P less than 0.001), and the reactance-frequency curve was shifted to the right. The investigated method is almost as accurate as the reference method, provides equally reproducible data, and is much simpler.

A theoretical approach of the measurement of osmotic fragility of erythrocytes by optical transmission.

The osmotic fragility of the erythrocyte membrane to hypotonic solutions is investigated theoretically. The fragility curves exhibit a strong transmittance rise. This variation is assumed to result from changes in the scattering properties of erythrocytes under dialysis resulting from swelling and hemolysis. The refractive indices of erythrocytes are obtained through the Lorentz-Lorenz relation based on hemoglobin and water contents. The scattering cross sections (needed to calculate the collimated transmittance) and the forward scattered intensity (needed to calculate the incoherent transmittance) are expressed according to the simple algebraic relations of the anomalous diffraction approximation. It is shown that swelling (or shrinking) has no influence on the collimated transmittance. Hemolysis alone causes the abrupt sigmoidal increase of the collimated transmittance with time. The possible transmittance increase (decrease) observed during swelling (shrinking) is due to incoherent transmittance and depends on the detecting solid angle value of the experimental setup.

Investigation of 3-D mechanical properties of blood vessels using a new in vitro tests system: results on sheep common carotid arteries.

In order to investigate the three-dimensional (3-D) mechanical properties of blood vessels, a new experimental device is described allowing in vitro static and dynamic measurements on segments of arteries with high technical performances. Static tests are applied to sheep common carotid arteries. Considering a thick-walled cylindrical model of orthotropic material under large deformations, a classical 3-D approach based on strain energy density is used to calculate the resulting mechanical behavior law in radial and circumferencial directions and stresses distribution throughout the wall thickness. Results are presented with reference to unloaded and zero-stress initial state thanks to simple measurements of inner and outer circumferences. A particular ratio relating the two main stresses (circumferential and longitudinal) is calculated that put into the forth the progressive modifications in the direction of the predominant stress in the wall and the specific radial location where these changes occur. We observe that this point location is a function of the test conditions of the specimen, i.e., stretching length and level of pressure.

Osmotic fragility of the erythrocyte membrane: characterization by modeling of the transmittance curve as a function of the NaCl concentration.

The theoretical extinction of blood suspensions submitted to a slow dialysis is analyzed in terms of their NaCl concentration. The model involves two adjustable parameters, chi and K, related to swelling and hemolysis. During swelling, the erythrocyte volume is supposed to vary linearly with the saline concentration. During hemolysis, an exponential decay of the hemoglobin concentration in the erythrocyte is used. The theoretical transmittance curves are consistent with the measurements carried out at a wavelength of 0.808 microm on native and incubated blood samples. Chi and K are relevant parameters to characterize quantitatively the fragility of the erythrocyte membrane. The effect of a non ideal character of the hemoglobin solutions and of normal distributions of chi and K is also discussed.

Elasto-thixotropic properties of bronchial mucus and polymer analogs. I. Experimental results.

The non-newtonian viscous and elasto-thixotropic properties of native and lyophilized pathological bronchial mucus and of polymer solutions (3% and 6% PIB in decalin) used as mucus analogs were analyzed using a cone-plate Carri-Med rheometer and a Couette viscoelastometer that we have specifically developed for measuring the rheological properties of bronchial mucus in clinical practice. The master curves obtained for apparent viscosity under steady conditions as a function of shear rates (gamma: 2.6 X 10(-3) to 6.9 X 10(1) sec-1) were fairly similar, whatever the apparatus used. Under transient conditions, at low shear rate (gamma less than 1.4 sec-1), PIB and mucus exhibited a typical viscoelastic behavior: the shear stress increased slightly up to a steady-state value. At higher gamma, a transitory overshoot of sigma characteristic of the elastothixotropic systems appeared. Such a behavior can be interpreted as resulting from structural changes such as formation and rupture of the three-dimensional network present in bronchial mucus as in polymer solutions.

Study of parameters involved in specific immunoadsorption of apolipoprotein B.

A therapeutic immunoadsorption system on immobilized and anti-apolipoprotein B as a plasma cholesterol lowering procedure was optimized. Several antibodies were compared and highest adsorption capacity was obtained with goat polyclonal antibodies. Optimum quantities of antibodies to be immobilized on the gel and quantities of apo-B to be applied to columns were determined. The amount of antibodies released from immunoadsorbents can be minimized by treatment with a 0.005% glutaraldehyde solution with an acceptable reduction rate of adsorption capacity. Each phase, adsorption and desorption respectively, were well-defined and synchronized so two columns could be used in parallel in an automated procedure. In these conditions, the immunoadsorption system can efficiently, specifically and safely remove cholesterol and has to be subjected to clinical trials.

[New automatic test for the study of platelet response to variations in osmotic pressure: application in the evaluation of the viability of platelet concentrates]. / Nouveau test automatique d'étude de la réponse des plaquettes aux variations de pression osmotique: application à l'évaluation de la viabilité des concentrés plaquettaires.

Studying the osmotic resistance or swelling of platelets has often been suggested as a global test to assess the viability of those cells. A number of authors have also analysed the behaviour of platelets in hypotonic media by a variety of complementary methods (cell count, morphology, determinations of substances released, photometric measurement of aggregation induced by aggregating agents, etc). Most studies are currently based on the so-called "osmotic shock response" test, which measures according to time the light transmitted through platelet-rich plasma (PRP) after dilution in distilled water. In this study, the authors describe a new automated and reproducible test using slow dialysis to assess platelet osmotic resistance. The "Fragilimeter", a device initially described by the authors to characterise RBC fragility, has been adapted to the study of platelet osmotic behaviour. The variations in light transmission through a platelet suspension according to NaCl concentration are linked to the change in cellular volume and lysis and characterise the viability of the cells. The results obtained with normal platelets revealed the good reproducibility of the technique. The osmotic resistance is evaluated for two parameters: anticoagulant (citrate, EDTA) and cellular concentration. The test was applied to quality control of stored platelet concentrates for transfusion, prepared with different cell separators.

Validation of a test of the red cell membrane osmotic resistance.

The aim of the present work was to validate a new technique for the measurement of resistance of the red blood cell membrane using an automated apparatus called a Fragilimeter. Its principle lies in the measurement of the extinction of a laser beam projected through a red blood cell suspension subjected, by diffusion, to a variation of salinity from an isotonic equilibrium (154 mM NaCl) to, a hypotonic one, 25 mM NaCl. The variation of osmotic pressure induces on the cells a progressive lysis and a modification of the extinction of the transmitted light. The validation of the method was based on the comparison between results obtained with the Fragilimeter and those obtained using the reference DACIE technique. Analyses were based on blood samples from healthy donors. The determination of the initial, the 50% and the full haemolysis thresholds allowed observation of the fragility of the cell, through its membrane resistance. The physical phenomenon measured in these cells when subjected to various ionic strengths is discussed on the basis of observations realised by means of an optical microscope.

[Effect of cholesterol on the cellular deformability and osmotic fragility of erythrocytes]. / Influence du cholestérol sur la déformabilité cellularire et la fragilité osmotique des hématies.

The effect of cholesterol hemisuccinate incorporation on the rheological properties of the erythrocyte membrane was assessed by measuring deformability (elongation index) and osmotic fragility ("baseline hemolysis"). These two experimental methods have different response sensitivities according to the incubation protocols (12 h 25 degrees C/12 h 25 degrees C then 12 h 37 degrees C) ant to the amount of cholesterol incorporated in the membrane (C/Pt from 0.18 to 0.83). The deformability and osmotic fragility variations observed are inversely related with the cholesterol concentrations incorporated. The experimental differences observed in the deformability and osmotic fragility are discussed in view of the type of membrane deformation and of the signals collected by the two systems.

Development and evaluation of an automatic method for the study of platelet osmotic response.

Study of the osmotic resistance to hypotonic medium of platelets has often been suggested as a global test to assess the viability of these cells in transfusion or to study modification during haematological pathologies. A number of authors have analysed the behaviour of platelets in hypotonic media by a variety of methods (cell count, determinations of substances released, morphology, etc.), but most studies are currently based on the so-called "Hypotonic Shock Response" test (HSR). In this study, the authors describe a new automated and reproducible apparatus, called fragilimeter, using slow dialysis to assess platelet osmotic resistance. The variations in light transmission through a platelet suspension according to ionic strength are linked to the change in cellular volume and lysis and characterise the osmotic behaviour of the cells. The results revealed the good reproducibility and sensibility of the technique. This apparatus allows also the realisation of the "HSR" test.

[Reoperations for early thromboses of femoropopliteal and tibial artery bypass. Apropos of 50 cases]. / Les réinterventions pour thromboses précoces des pontages artériels fémoro-poplités et jambiers. A propose de 50 cas.

The mechanism of thrombosis early after subinguinal bypass and outcome after revision surgery have been rarely analyzed. Results are reported of revision surgery for early thrombosis in 50 cases (10% of subinguinal bypass operations during the same period). Initial indication in the 40 men and 9 women (mean age 66.9 +/- 1.74 (SEM) years), was severe chronic or acute ischemia in 82%. The 50 thrombosed bypasses included 40 femoropopliteal, 8 femorotibial and 2 short bypasses. The bypass was by saphenous in situ (21 times), an inversed saphenous (9 times), a mixed bypass (12 times) and a prosthesis (8 times). The distal arterial bed was evaluated as good in 50% of cases. Analysis of cause of thrombosis, of the operative procedure and of the time before surgery enabled a technical cause to be determined in 31 of the 50 cases. Corrective surgery produced 16 permeable bypasses and 34 definitive thromboses complicated by 21 amputations and a 10% mortality. Improved results were related to a venous bypass (p less than 0.05), to a time before operation of less than 24 hours (p less than 0.02) and to a good distal bed. The 1 year actuarial permeability for the 50 bypass operations was 35%. Mixed bypass procedures and technical problems during surgery appear to be the principal predisposing factors of early thrombosis. In this series, the preoperative distal pressure index and intraoperative flowmetric recordings were not reliable predictive elements.

[Conditions for functioning of an effective peritoneo-jugular shunt. Doppler infrared thermographic study]. / Conditions de fonctionnement d'un shunt péritonéo-jugulaire efficace. Etude par Doppler et thermovision infrarouge.

A peritoneo-jugular shunt clinically effective in a 48 years old male patient with cirrhosis, is explored concomitantly with Doppler and infrared thermography. In this patient, without clinical signs of ascites, these two non invasive methods associated to sensitization techniques (decubitus, deep breathing, abdominal binding) specify the functioning conditions of the valve and permit to consider a close monitoring of these patients for screening and prevention of the frequent, asymptomatic obstruction of their shunt.

Spinability of respiratory mucous. Validation of a new apparatus: the Filancemeter.

Spinability is the ability of various biological fluids to be drawn into threads when stretched. This rheological parameter is of particular importance in the mucous transport process and can be easily measured using a newly commercialized apparatus: the Filancemeter. The measurement limits and the volumes of the samples used are presented. By studying the effect of sample volume on spinability, the importance of using well-calibrated samples is demonstrated. For the small volumes of sample (less than 5 microliters), the reproducibility of the measurement is low (coefficient of variation: 63% with 1 microliter sample), whereas it is significantly improved with larger volumes (coefficient of variation: 16% with 5 microliters sample). The measurements on respiratory mucous are in good agreement with the results obtained with a previous apparatus using a clip as a prehension system of the sample. With fluids exhibiting low viscosity like saliva, the higher values obtained with the Filancemeter can be attributed to a better prehension of the sample. This apparatus appears to be suitable for measuring the spinability of various biological fluids such as mucous.

Kinetics, biodistribution and therapeutic efficacy of hexylester 5-aminolevulinate induced photodynamic therapy in an orthotopic rat bladder tumor model.

PURPOSE: To optimize photodynamic therapy (PDT) we investigated the kinetics and biodistribution of hexylester 5-aminolevulinate (hALA) induced protoporphyrin IX (PpIX) and the therapeutic efficacy of PDT at different drug and light doses in an orthotopic rat bladder tumor model. MATERIALS AND METHODS: Healthy and tumor bearing rats were instilled intravesically with hALA (4, 8 and 16 mM) for 1 hour. Fluorescence was recorded spectroscopically in situ. PpIX fluorescence distribution and quantification across the bladders was visualized with fluorescence microscopy. PDT efficacy at different fluences (15 to 80 J/cm2) was histologically assessed 48 hours and 1 week after treatment. RESULTS: Spectroscopic analysis in normal or tumor bearing rats showed the highest tumor-to-normal ratios 2 or 3 hours after the end of the 8 or 16 mM hALA instillation (5.4 and 5.7, respectively). Within the same tumor bearing animal the same fluorescence levels were observed in normal epithelium and transitional cell carcinoma, whereas the tumor-to-muscle ratio was 3. Tumor necrosis with an intact normal bladder wall was observed with a fluence of 20 J/cm2 for 8 mM hALA, while 15 J/cm2 was ineffective and 25 J/cm2 induced total wall necrosis. Although it induced comparable PpIX fluorescence, 16 mM hALA did not result in tumor eradication at any fluence. CONCLUSIONS: An optimal PDT effect was obtained with 8 mM hALA and a fluence of 20 J/cm2. While different hALA concentrations ind uce identical PpIX fluorescence intensities, the PDT outcome was considerably different. Thus, fluorescence does not necessarily predict the therapeutic efficacy of PDT.

Increase of hybridoma productivity using an original dialysis culture system.

Hybridoma cell growth and monoclonal antibody production were investigated with a laboratory-made system in which cells were grown in dialysis tubing (MW cut-off 25 kD). The dialysis system contained 10 ml of cell suspension and was immersed in 200 ml of culture medium which when replaced or was at 4-day intervals. With this system, monoclonal antibody concentrations similar to those observed in ascites (concentrations in the order of one gram per liter) were obtained. With no medium replacement, the antibody production was 3.3 g/l and the cell productivity 3.2 x 10(-8) micrograms of IgM produced per cell in one minute. With medium replacement the antibody production was higher, 4.4 g/l but the cell productivity was lower, 1.49 x 10(-8) micrograms per cell in one minute. Cells cultivated in non-optimized conditions were better producers than cells growing in a good environment.

[Peripheral arterial catheterization in neonates and infants. Remote study of the arterial permeability by the Doppler effect]. / Cathétérisme artériel périphérique chez le nouveau-né et le petit nourrisson. Etude à distance de la perméabilité artérielle par effet Doppler.

Nineteen peripheral arteries were examined by Doppler US 1 month to 2 years after their catheterization. Two of them were completely obstructed and 4 showed signs of arterial stenosis. No functional repercussion was observed. This minor risk seems low as compared to the advantages of the technique.

A new viscoelastometer for studying the rheological properties of bronchial mucus in clinical practice.

In clinical practice, a wide variety of drugs are given to modify the rheological properties of bronchial mucus but they are frequently not correctly chosen because there is not a simple apparatus available for the routine measurement of the mucus viscoelasticity. We designed a new viscoelastometer which is easy to operate and permit accurate measurement of the viscoelastic properties of mucus. The system has a Couette geometry and requires a sample of 1 ml. The outer cylinder is thermostated and rotates at a constant rate. The resulting torque is measured on the inner cylinder using a microdisplacement transducer. The inner cylinder is suspended by a special wire system which maintains a constant 0.75 mm gap between the two cylinders. The apparent viscosity is calculated up to 100 Pa.s. at a low shear rate (0.4 s-1) and the elasticity is analyzed by a stress relaxation method. The characteristics of the apparatus and the typical viscoelasticity behaviour of several sputum samples are reported.

[Development of a technique of immunoadsorption of LDL-cholesterol]. / Mise au point d'une technique d'immuno-adsorption du LDL-cholestérol.

An immunoadsorption system for lowering plasma cholesterol was optimized. Several polyclonal and monoclonal antibodies were compared and the best results were obtained with goat polyclonal antibodies. The optimum quantity of antibodies to be immobilized on the gel was 5 mg/ml. Taking into account two variables, i.e., 1) that the regeneration must be as complete as possible and, 2) that immunoadsorbents must be used several times without a loss of adsorption capacity, desorption was achieved with 0.3 M glycine adjusted to pH 2.8. Antibody release from the immunoadsorbent was determined and can be minimized by glutaraldehyde treatment of the immunoadsorbent. Each phase, adsorption and desorption, respectively, was well-defined and synchronized, so that two columns could be used in parallel in an automated procedure. The kinetics of plasma protein removal demonstrated the efficiency and the specificity of the procedure.