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G Potron

Publications and source records attributed to G Potron.

At least 37 records · Page 2Linked to original sources
PubMed1995

Regulatory effects of pentoxifylline on T-helper cell-derived cytokine production in human blood cells.

Pentoxifylline (PTX), a methyl xanthine derivative, was examined for its regulatory effect on Th1-and Th2-cell-derived cytokines in human whole blood and peripheral blood mononuclear cells stimulated with phytohemagglutinin (PHA) and phorbol myristate acetate (PMA). Cytokine production was analyzed by enzyme-linked immunosorbent assay and cytokine mRNA expression was examined by the polymerase chain reaction (PCR) after reverse transcription (RT). The results showed that PTX at 5 x 10(-4) M concentration selectively suppressed Th-1 cytokines [interleukin-2 (IL-2) and interferon-gamma (IFN-gamma)] but not IL-4, as observed by the measurement of protein secretion. Using sensitive RT-PCR assays, data show that at this same PTX concentration (5 x 10(-4) M), these cells also exhibited inhibition in the expression of IL-4 and IL-10 mRNA, together with inhibition of IL-2 and IFN-gamma mRNA expression. At 1 x 10(-4) M, no apparent change in IL-4 and IL-10 mRNA expression was observed, whereas IL-2 mRNA was still inhibited. It was noted that PTX at 1 x 10(-3) M induced a generalized inhibition of all cytokines. Our findings showed that PTX at the appropriate concentrations could induce selective suppression of IL-2 and IFN-gamma, whereas at high concentrations this drug could act as a suppressive agent of both Th1- and Th2-derived cytokines. Moreover, these data provide further evidence that the induction of IL-2 gene transcription is highly sensitive to an elevation of cAMP, whereas IL-4 gene transcription appeared to be less affected.

Adult↗
PubMed1995

In vitro study of THP-doxorubicin retention in human leukemic cells using confocal laser microspectrofluorometry.

Microspectrofluorometry allows the analysis of fluorescent molecules such as anthracyclines in the nucleus of isolated living cells. Using this technique, we confirmed that the amount of doxorubicin or THP-doxorubicin incorporated into the nucleus was related to the resistant or sensitive character of K562 cells. It was then extended to the study of fresh leukemic cells and kinetic studies were performed allowing the calculation of the retention rate (RR) of anthracycline (THP-doxorubicin) into the cell nucleus. A reproducibility study confirmed the accuracy of the method. Blast cells collected in patients with acute myeloid (n = 22) or lymphoid (n = 8) leukemia, at diagnosis (n = 26), or in relapse (n = 4) have been studied. RR varied from 8 to 98% independently of the type of leukemia or the clinical status. RR did not correlate either with P-glycoprotein or with CD34 expression although this latter result should be confirmed on a higher number of subjects. Among 18 patients presenting with AML at diagnosis, 14 have been treated with intensive chemotherapy including anthracyclines; the only one who had resistant disease had the lowest RR value. In conclusion, the results obtained here show that microspectrofluorometry allows the performance of kinetic studies on fresh leukemic cells in order to quantify chemo-resistance phenomena related to drug transport.

Biological Transport↗
PubMed1995

[Respiratory burst of neutrophils and cytokine profile in the non-insulin-dependent diabetic].

Many clinical and experimental data are in favour of a participation of leukocytes in vascular disease. Diabetes, a risk factor, is associated with a dysfunction of neutrophils. If chemotaxis and phagocytosis are deficient, it is not clearly established whether superoxide generation is conserved in these patients. We have measured this function in 35 noninsulin dependent diabetic patients, compared with a control population. We have assessed, in parallel, a profile of the cytokines involved in vascular phenomenons including TNF alpha, IL-1 beta et IL-6. Our results indicate that the generation of free radicals is normal in diabetics, with a significant elevation of TNF alpha. These results suggest a possible participation of this cytokine in the modulation of granulocyte reactivity.

Adult↗
PubMed1995

Multicenter evaluation of nine commercial kits for the quantitation of anticardiolipin antibodies. The Working Group on Methodologies in Haemostasis from the GEHT (Groupe d'Etudes sur l'Hémostase et la Thrombose).

The performances of nine commercial kits and an in-house method (HM) for the quantitation of anticardiolipin antibodies (ACA) have been evaluated in a multicenter study. Ninety control and patient samples and six standards from Louisville University were run with kits and with the HM. Marked differences in positivity rate between kits were observed, ranging from 31 to 60% for IgG and 6 to 50% for IgM. Concordance between kits occurred in 59 and 51% of samples for IgG and IgM respectively. Concordance coefficients (kappa) ranged from 0.13 to 0.92. Slopes of regression lines between the declared units of Louisville standards and the units measured from the calibrators of the kits showed great diversity and ranged from 0.159 to 0.931 for IgG and from 0.236 to 0.836 for IgM. The beta 2-glycoprotein I (beta 2-GPI) content of the dilution buffers and the wells supplied with the kits revealed noticeable differences. However samples containing anti-beta 2-GPI antibodies were classified similarly by all but one kit. In contrast the ability to measure samples devoid of anti-beta 2-GPI antibodies differed markedly between the kits. This study shows that differences in positivity rates between the commercial kits may contribute to the differences in ACA prevalence rate found in the literature. The choice of cut-off levels may partly explain the moderate concordance between the kits. In addition some samples behave very differently depending on the kits. In spite of the expression of results in PL units, standardization of ACA assays has not been achieved.

Antibodies, Anticardiolipin↗
PubMed1995

[Outpatient treatment of deep venous thromboses].

Deep vein thromboses (DVT), which are serious because of their associated risk of pulmonary embolism and troublesome due to the possible development of a post-phlebitic syndrome, require rigorous management. However, the diagnosis is facilitated by Doppler ultrasound and treatment by low molecular weight heparins (LMWH) is simple to administer and follow. It is therefore logical to propose out patient treatment, provided certain rigorous rules are respected: establishment of an objective diagnosis of DVT, as the clinical signs are relatively nonspecific, admission to hospital of patients with a haemorrhagic risk or presenting a contraindication to anticoagulants, extensive DVT (extending beyond the mid-femoral zone), floating thrombus, patients with moderate signs may suggest pulmonary embolism. The recommended dosage for LMWH is 100 IU/kg twice a day (s.c.) (or 175 IU/kg once a day for the LMWH most recently available in France) which must be followed by oral anticoagulants for 5 months (aspirin is not sufficiently effective). Contention and rigorous clinical follow-up are obviously essential. The management of DVT is fascinating and requires coordination of several competent specialists.

Ambulatory Care↗
PubMed1994

Cuprophane but not synthetic membrane induces increases in serum tumor necrosis factor-alpha levels during hemodialysis.

Cytokine synthesis and secretion by blood mononuclear cells is a well-documented phenomenon in hemodialyzed patients. The present study was conducted in 17 chronically hemodialyzed patients to test the relative effect of uremic toxicity, membrane biocompatibility, dialysate composition, and the risk of endotoxinemia on the serum level of tumor necrosis factor-alpha (TNF-alpha). The only significant parameter that influenced circulating TNF-alpha was the chemical characteristics of the dialyzer membrane. Tumor necrosis factor-alpha levels significantly increased during the session with cuprophane, whereas they decreased with AN69. The TNF-alpha increase was documented whatever the dialysate buffer and the presence or absence (negative Limulus amoebocyte lysate test) of endotoxin in the dialysate. In the subgroup of patients treated with a contaminated dialysate and AN69, none had clinical symptoms and the central body temperature remained constant throughout the session. In these patients, serum TNF-alpha levels did not change after priming the dialyzer with sterile saline. In conclusion, the serum TNF-alpha level during hemodialysis appears to be modulated by biocompatibility, permeability, and binding properties of dialysis membrane rather than dialysate composition. Endotoxin in the dialysate did not result in positive TNF-alpha balance no matter what its possible priming effect on mononucleated blood cells.

Acrylic Resins↗
PubMed1994

[Hemorheologic changes in preoperative hemodilution during total hip replacement. Randomized study comparing hydroxyethyl starch 200,000/0.62 (HES) and a dextran 60,000].

Hemodilution can be used to save blood transfusion during total hip replacement. We have carried out a randomized study to compare the hemorheological effects of two plasma substitutes: a hydroxyethylstarch 200,000/0.62 versus a dextran 60,000. Twenty-two patients were hemodiluted with 20 mk/kg of either substitute, just after the spinal anesthesia. Whereas the hematocrit have fallen by 30% in the two groups, significant differences are observed about hemorheological parameters. The plasma viscosity express a greater increase at hour 4 in the dextran group. The whole blood viscosities are more increased in the dextran group at hour 4 and 24. The erythrocyte aggregation is decreased in the HES group at hour 4 and 24, but is increased in the dextran group. The fibrinogen is more increased in the dextran group at day 7. In spite of similar hemodilutions, the two substitutes express different hemorheological effects with a favourable role of HES on erythrocyte aggregation and blood viscosities. This can improve the microcirculation and decrease the activation of the endothelial cells, reducing the inflammatory reaction.

Adult↗
PubMed1994

Erythrocyte aggregation--determination of normal values. Influence of age, sex, hormonal state, oestroprogestative treatment, haematological parameters and cigarette smoking.

Erythrocyte aggregation is a physiological phenomenon and constitutes one of the most important factors accounting for the non-Newtonian properties of normal human blood. Pathological aspects have also been described and therapy aimed at reducing hyperaggregability has been proposed. The object of this study was to establish normal values of erythrocyte aggregation parameters as measured by laser light backscattering and to study the influence of various physiological factors. Normal values were determined from a reference population. Sex and age induce variations in erythrocyte aggregation which are neither fibrinogen nor haematocrit dependent and there is a general trend towards stronger aggregation in women, although neither hormonal state nor oestroprogestative treatment appear to influence the female aggregation parameters. In elderly people stronger aggregation is also observed but this effect is of lower magnitude. In vivo, the plasma fibrinogen level is the most important factor influencing erythrocyte aggregation, while variations in haematocrit play a lesser role and mean corpuscular volume, red cell distribution width and white blood cell and platelet counts have no effect. Finally, no difference is noted in cigarette smokers.

Adolescent↗
PubMed1994

Approach to erythrocyte aggregation through erythrocyte sedimentation rate: application of a statistical model in pathology.

Erythrocyte sedimentation rate (ESR) is mainly used in clinical practice as a screening test for inflammatory diseases and sometimes in the follow-up of patients. However, ESR is highly dependent on erythrocyte aggregation. In this study, using a Sediscan (Becton) automatic device measuring the kinetics of ESR, these results are compared with the measurement of erythrocyte aggregation as determined by laser light backscattering (Erythroaggregometer Affibio). A series of 188 samples from in-patients were tested. Statistical analysis of 13 parameters indicates that 82% of ESR variance may be explained by fibrinogen level, haematocrit and a parameter characterizing erythrocyte aggregation: the aggregation index at 10 s. This correlation was then validated prospectively in 128 other patients and seems to be independent of the underlying disease. Thus ESR in combination with fibrinogen assay and haematocrit may be considered as a simple and economic method to assess erythrocyte aggregation.

Blood Sedimentation↗
PubMed1994

[Study of blood sedimentation by photo-thermal radiometry with random excitation].

The erythrocyte sedimentation rate is a complex phenomena involving a large number of parameters. The rate of sedimentation is highly dependent on the haematocrit, the internal viscosity of the red cells and the viscosity of the suspending medium and its composition. The experimental conditions also have a non-negligible effect (geometry and nature of the test tube, temperature, foreign substances in the medium...). In order to respond to the need for more precise and more rapid methods of analyzing the erythrocyte sedimentation rate, we developed new physical methods allowing a real time evaluation of the phenomena involved. Several of these new photothermal methods have already been applied for non-destructive evaluation of thin or layered material (such as composite material or glued structures) both in laboratory situations and in the industry. When a material is placed in a modulated laser beam, the incident rays absorbed heat the sample. The heat then diffuses throughout the material and the surface temperature of the sample increases locally with a periodicity. The surface thus emits a modulated flow of infrared radiation. The amplitude and phase shift of the photothermal signal generated is characteristically dependent of the optic and thermal properties of the material for a given modulation frequency. The early photothermal modelling based on a two-layer model and a physico-mathematical theory of red cell sedimentation proposed by S. Oka made it possible to simulate the phenomena as they occur over time. We hypothesize that the temperature gradients created within the sample are too small to create a convection current and that the all heat transfer occurs by conduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Sedimentation↗
PubMed1993

Variations of protein C in uremic hemodialysed patients.

Protein C has been measured by three different assays (antigenic, amidolytic and chronometric) in 27 end-stage renal insufficient patients before and after hemodialysis. Protein C levels have been compared with other coagulation inhibitors (antithrombin III, protein S) and fibrinolytic parameters. Baseline anticoagulant activity of protein C has been found impaired in eight cases whereas other inhibitors were normal. In four cases, both anticoagulant and antigenic levels were low. In one case, amidolytic method could also found a low activity. Hemodialysis leads to an increase of protein C activity and antigen level. Heparinemia after hemodialysis does not interfere with the chronometric measurement of protein C anticoagulant activity. Total protein level, hematocrit, protein S and antithrombin III are also elevated after hemodialysis. Baseline fibrinolytic parameters are normal and remain unchanged after hemodialysis. The clinical relevance of such modifications is discussed.

Adult↗
PubMed1993

Interlaboratory evaluation of methods for the assay of Protein C in purified concentrates.

Determination of the quantity and activity of the Protein C molecule is of the utmost importance in highly purified concentrates prepared for replacement therapy. A multicenter study was undertaken to evaluate the comparability and accuracy of Protein C assays from commercial sources. Significant between-assay and interlaboratory differences were found for both functional and immunological assays. The interlaboratory variability is explained in part by the use of different control plasmas. The results also indicate the importance of the diluent used. This study emphasizes the need for standardized methods for determining the characteristics of Protein C concentrates.

Enzyme-Linked Immunosorbent Assay↗
PubMed1991

[Alterations in erythrocyte membrane. Effect of neutrophil activation].

White blood cells, especially polymorphonuclear neutrophils (PMN), are known to alter some hemorheological parameters. Most of in vitro results have been obtained with passive PMN. Stimulated PMN also lead to other hemorheological changes. In our study, we have firstly activated PMN with opsonized zymosan and collected a PMN-free supernatant after 30 minutes activation. This supernatant was secondarily incubated with erythrocytes either in whole blood or in suspension. After 10 minutes incubation, hemorheological parameters were evaluated: 1) red blood deformability (RBC) (Ektacytometer* Technicon), 2) RBC filtration (Hemorheometer MK 1), 3) RBC aggregation (Erythroaggregometer* Sefam), 4) Plasmatic and whole blood viscosities (Low Shear 30* Contraves). Our results show that activated PMN-supernatant increases rigidity index (IR) of RBC in suspensions (IR of RBC control = 14.59 +/- 3.30 towards RI of incubated RBC = 22.91 +/- 7.06 p less than 0.001). Other rheological parameters remain unchanged. Activated PMN suspenatant influence on RBC is slight but could suggest of an alteration of RBC membrane. With an in vitro model of washed platelets aggregation, we have previously demonstrated that proaggregant activity of PMN supernatant was inhibited by specific Platelet-Activating Factor (PAF-acether) antagonists: BN 52021, BN 50723, Web 2086. We have so compared both effects of activated PMN-supernatant and synthetic PAF-acether on RBC membrane fluidity. Membrane fluidity was studied by fluorescence polarization of 4 probes embedded at different deep in the membrane of intact RBC. Similar modifications of RBC membrane fluidity are observed with either synthetic PAF-acether or PMN supernatant.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythrocyte Membrane↗
PubMed1991

[Effects of contrast media products on erythrocyte aggregation. An ex vivo study].

It has been suggested (Fisher and al., Rainiko and al.) that contrast media could interfere with a red blood cell aggregation, low-osmolarity and non ionic contrast media leading to red blood cell aggregates in vitro. Clinical significance of this phenomenon is not known. We have studied 21 consecutive patients admitted in X ray department for pyelography. Sodium and meglumine ioxitalamate (Telebrix 38 R; Guerbet) osmolarity 2 100 mOsm kg--viscosity 8.5 cp at 37 degrees C is used for contrast. Red blood cell aggregation is studied by erythraggregometer Sefam. Samples are collected before (T0), 10 and 30 minutes (T10, T30) after contrast infusion. Hemogram and coagulation parameters are measured in parallel. Results show a significant increase of aggregation times at T10, with a trend towards baseline at T30. Dissociation shear rates follow the same fluctuations. We note a concomitant diminution of both fibrinogen and hematocrit levels, well-correlated with red blood cell aggregation. These results suggest a process of hemodilution which could explain the diminution of red blood cell aggregation with this type of contrast medium.

Adult↗
PubMed1990

[Effect of contrast media products on the erythrocyte aggregation and deformability in vitro].

It has been suggested that contrast media could interfere with red blood cell aggregation, hyperosmolar media leading to an inhibition of red blood cell aggregation whereas non ionic products might induce a sludge phenomenon. We present an in vitro study accompanying two contrast media: 1) Ioxitalamate of sodium and meglumin (ionic, hyperosmolar). 2) Iopaminol (non ionic). In their effect on hemorheological parameters of red blood cell aggregation. Blood samples have been obtained from 7 healthy donors. Contrast media have been tested at increased contrast media (O.1, 1, 2, 10, 100 mg/ml of Iodine in final concentration). The following parameters have been studied: hematocrit, fibrinogen level, erythrocyte aggregation using the Erythro-aggregometer*, whole blood viscosity at 3 different shear rates (0.87, 18.74, 118 sec.-1) using Low Shear 30*. Deformability of red blood cell was assessed by ektacytometry. Osmolarity was controlled in each sample. Results show an inhibition effect of both contrasts media on red blood cell aggregation. There is a concomitant decrease of blood viscosity at low shear rates. On the contrary, apparent viscosity increases at high shear rates in parallel with the contrast media concentration. This effect is more pronounced with ioxitalamate above a concentration of 10 mg/ml. Ektacytometric parameters are not modified by contrast media and this could indicate a complete reversibility of the media-induced alteration on red blood cell. In order to precise the prothrombotic effect on contrast media, hemorheological studies have to be completed by the assessment of their effect on hemostatic parameters.

Adult↗
PubMed1987

Measurement of low molecular weight heparin ex vivo activities in clinical laboratories using various anti-Xa assays: interlaboratory variability and requirement for an agreed low molecular weight heparin standard.

The only sensitive and convenient assay to assess the biological activity of low molecular weight heparins (LMWHs) is based on the potentiation of activated factor Xa inhibition. Several procedures for measuring the socalled anti Xa activity have been proposed. In this collaborative study including eight laboratories, we have used four different assays (three amidolytic and one clotting based methods) for measuring the anti Xa activity of ex vivo samples obtained after injecting three different LMWHs. The dispersion of the results obtained by calibration against standard heparin could be reduced by using any of the three LMWHs for calibration. A coefficient of variation less than 0.20 between values obtained in different laboratories using a variety of methods seems acceptable. However it is necessary to refer to a common international standard for expressing the results in units and to define, for each of the three products, the therapeutic range.

Factor Xa↗