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B Marty

Publications and source records attributed to B Marty.

54 records · Page 3Linked to original sources
PubMed1991

Trypanosoma cruzi: infection of T lymphocytes and their destruction by antibody-dependent cell-mediated cytotoxicity.

We have demonstrated, with optical and transmission electron microscopy, that Trypanosoma cruzi trypomastigotes infect and multiply inside T lymphocytes. The infection rate we have observed in T cells was similar to that seen in the case of macrophage or polymorphonuclear cell infection. Flow cytofluorometric analysis of T lymphocytes purified from mice in the acute phase of the disease, revealed the presence of parasite-derived antigens on their surface. These antigens appear to be specific to T. cruzi and they could be the result of intracellular parasite antigens as well as adsorption of T. cruzi antigens on the surface of noninfected T cells. Antibodies recognizing these surface antigens were present in both T. cruzi-infected mouse and human sera. They were able to induce antibody-dependent cell-mediated cytotoxicity (ADCC) in the presence of nonimmune mononuclear cells both in autologous and in heterologous combinations. Consequently, we provided evidence suggesting that T lymphocytes could be destroyed during the acute phase of Chagas' disease either by cell infection or by an ADCC mechanism against cells bearing parasite antigens on their surface. Thus, the ability of trypomastigotes to invade T cells may play a crucial role in the immunopathogenesis characteristic of Chagas' disease.

Animals↗
PubMed1990

Trypanosoma cruzi: differential expression and distribution of an 85-kDa polypeptide epitope by in vitro developmental stages.

The expression by Trypanosoma cruzi developmental stages of an 85-kDa polypeptide epitope defined by the 155D3 monoclonal antibody (mAb) has been investigated. Immunoprecipitation revealed the presence of an 85-kDa antigen in the NP-40 soluble extract of parasites freshly released from infected fibroblasts; this antigen was not found in epimastigote and Leishmania infantum promastigote. Indirect immunofluorescence revealed that the mAb 155D3 failed to react with trypomastigotes, whereas extracellular amastigotes were heavily stained. Positive organisms displayed either surface or polar fluorescence. Since the same mAb immunoprecipitated the 85-kDa antigen in both radioactive iodine- and methionine-labeled trypomastigote detergent soluble extracts, the reactive epitope is likely to be hidden in a cryptic site in trypomastigotes. An alternative explanation for the negative immunofluorescence on trypomastigotes and the positive immunoprecipitation is the presence, in the extracts, of a small population of parasites already expressing the 155D3 epitope. Immunoelectron microscopy revealed that the target epitope is heterogenously distributed among the populations of differentiating parasites. Two types of immunogold labeling were observed: (a) mAb revealed a high amount of reactive material associated with the periphery of the parasites and (b) a label was observed on the inner surface of peripheral vacuoles that might correspond to cross sections of inflated flagellar pockets and in association with vesicles which were released by the parasites. The surface expression of the epitope recognized by the 155D3 mAb was followed by fluorescence-activated cell-sorting analysis. The results showed that the epitope is increasingly accessible during trypomastigote differentiation in vitro. Taken together, these results suggest that the epitope reacting with the 155D3 mAb is heavily expressed on extracellular amastigotes after the transformation process and, thus, appears to be developmentally regulated.

Animals↗
PubMed1990

Characterization of major surface and excretory-secretory immunogens of Trypanosoma cruzi trypomastigotes and identification of potential protective antigen.

The surface antigens of Trypanosoma cruzi trypomastigotes were identified by immunoprecipitation and were compared with metabolically labelled excretory-secretory products (ES) released by the parasites in vitro. A series of major immunogenic components in the ES antigens were revealed (160 kDa, 130 kDa and 80-110 kDa). The trypomastigote surface also bears the 130 kDa band and the 80-110 kDa complex. Competition experiments demonstrated the common antigenic structure of the ES and the surface antigens. Two-dimensional analysis of ES antigens immunoprecipitated by human Chagasic serum revealed several spots in the 80-110 kDa region with a wide range of isoelectric points (PI between 5.4 and 6.7). This reflects a charge heterogeneity of these polypeptides. The trypomastigote 85 kDa polypeptide was also identified in the ES antigens by using a monoclonal antibody against this antigen. Two-dimensional analysis of the 85 kDa proteins shed from the surface of trypomastigotes and immunoprecipitated by the monoclonal antibody 155D3 showed 2 major spots: a major part of the 85 kDa polypeptide was found at pH 6.5-6.6, whereas a substantial amount of the antigen was found at pH 5.7. An additional component with molecular weight of approximately 58 kDa and isoelectric points of 6.5 and 6.6, was also visualized. Detection of the 85 kDa polypeptide circulating in serum from patients with acute and chronic Chagas' disease was achieved using an enzyme-linked immunosorbent assay. In addition, the data obtained showed that a polyclonal antibody to the 85 kDa polypeptide could be used to passively induce a partial protection of Fischer rats against acute lethal infection. Thus, the antigens recognized by polyclonal antibody appear to play a role in the development of protective immunity against T. cruzi.

Animals↗
PubMed1988

The major surface protein of Leishmania promastigotes is a fibronectin-like molecule.

The major surface glycoprotein of Leishmania chagasi promastigotes showed crossreactivity with fibronectin (Fn), a large glycoprotein that is a major constituent of the extracellular matrix of most mononuclear cells. Polyclonal and monoclonal antibodies against Fn precipitated two molecules of 63-58 kDa from the lysates of both 125I and [35S]methionine-labeled promastigotes. In addition, a monoclonal antibody against a 15-kDa fragment of Fn containing the Arg-Gly-Asp-Ser (RGDS) sequence and several polyclonal monospecific mouse antibodies against a synthetic RGDS peptide also recognized the above two molecules. The attachment of Leishmania promastigotes to mouse peritoneal macrophages in vitro was partially inhibited when promastigotes were treated with F(ab')2 fragment of an anti-Fn IgG. Identical results were obtained by saturating the Fn receptors on macrophages using different peptides containing the RGDS sequence. Moreover, antigen preparations rich in glycoprotein 63 could efficiently promote the attachment and spreading of 3T3 mouse fibroblasts to surfaces coated with the antigen. These results clearly suggest that the gp63 of L. chagasi promastigotes is an Fn-like molecule that shares certain biological and molecular characteristics with Fn.

Animals↗
PubMed1980

Thermodynamic studies of binding proteins: effects of temperature variations on substrate binding and conformation of the leucine-isoleucine-valine binding protein of Escherichia coli.

The behaviour of the Leucine isoleucine Valine binding protein of Escherichia coli as a function of temperature has been examined. Substrate binding measurements showed a temperature dependence of the leucine-isoleucine-valine binding protein leucine complex formation constants. The protein-substrate complex was completely dissociated beyond 70 degrees C. In the range 5-65 degrees C the protein remained active but Van't Hoff's plots indicated changes of the reaction thermodynamic parameters. Large negative delta Cp values (--2.25 kJ mole-1 K-1 between 5 and 40 degrees C and--9.40 above 40 degrees C) indicate important substrate induced modifications of the protein conformation. Scanning calorimetry of the leucine isoleucine valine binding protein before and after addition of leucine was also performed. Two thermal events were recorded when the protein was substratefree and only one, at a higher temperature and more important, when the substrate was added. The results of these two approaches were in agreement in that both methods suggested a binding dependent conformational change of the protein which resulted in a greater stability of its structure.

Bacterial Proteins↗
PubMed1978

Biphasic saturations of binding proteins can be the result of a competitive inhibition of substrate fixation.

A mathematical model is proposed which explains some biphasic saturations of Binding Proteins by their substrates through an effect of a competitive inhibition. The inhibitor can be the substrate itself especially when the retention phenomenon is occuring. This model has been verified with two periplasmic Binding Proteins of Escherichia coli: the Glutamine Binding Protein and the Leucine-Isoleucine-Valine Binding Protein. A significant connection is found between experimental results and the hypothesis.

Binding, Competitive↗
PubMedDate not supplied

Biomembrane mimicry provides improved thromboresistance for total artificial hearts.

Thromboembolic events remain a significant issue in mechanical circulatory support. The aim of this study was to evaluate the potential benefit of surface modification in total artificial hearts (TAHs) using polymeric phospholipids (biomembrane mimicry). For this purpose, pneumatic TAHs (vacuum formed pellethane housing, hard double flap hinged inflow valves, soft trileaflet polyurethane outflow valves) had their blood-exposed surfaces either modified with polymeric phospholipids or unmodified before evaluation in bovine experiments. Orthotopic implantation of the TAHs was performed with cardiopulmonary bypass (CPB) using tip-to-tip heparin surface coated perfusion equipment and very low systemic heparinization (50 IU/kg bodyweight). After weaning from CPB and stabilizing hemodynamics, circulating heparin was neutralized with protamine (1:1). All animals were totally supported for 24 hours before elective sacrifice. No heparin was added at any time during support. Mean activated coagulation time (ACT) was 167+/-24 s at baseline before heparinization for CPB, 330+/-45 s at the end of CPB, 181+/-25 s after 1 hour of support, 180+/-31 s after 6 hours, and 185+/-28 s after 18 hours. After explantation, the TAHs perfused without anticoagulation were carefully analyzed. Atrial cuff coverage with red clot was 30+/-21% for artificial surfaces modified by biomembrane mimicry versus 100+/-0% for standard control surfaces (p<0.01). The number of macroscopic deposits found on the inflow valves was 1.33+/-0.47 for surfaces modified by biomembrane mimicry versus 3.83+/-1.86 for standard control surfaces (p<0.05). Likewise, on the outflow valves the number of macroscopic deposits was 0.00+/-0.00 for surfaces modified by biomembrane mimicry versus 1.00+/-0.81 for standard control surfaces (p<0.05). We conclude that presence and distribution of red clots and other macroscopic deposits are significantly different for artificial surfaces with biomembrane mimicry versus standard control surfaces. Application of the biomembrane mimicry concept has the potential to provide improved TAHs.

Animals↗
PubMedDate not supplied

A siliconized hollow fiber membrane oxygenator.

Most membrane oxygenators are built with microporous fibers known for plasma leakage in long-term use such as extracorporeal life support or extracorporeal membrane oxygenation. The current study was designed to evaluate the Quadrox oxygenator in which the fibers have been coated with silicone (Jostra). Six calves (mean weight, 62 +/- 4 kg) were connected to cardiopulmonary bypass (CPB) by jugular venous and carotid arterial cannulation, with a mean flow rate of 3 L/min for 6 hours. They were randomly assigned to a standard Quadrox oxygenator (standard group, n = 3) or a siliconized Quadrox oxygenator (silicone group, n = 3). After 7 days, the animals were sacrificed. A standard battery of blood samples was taken before bypass, after mixing for 10 minutes, and after 1, 2, 5, and 6 hours of perfusion. Analysis of variance was used for repeated measurements. Total oxygen transfer and carbon dioxide transfer did not differ between groups (p = 0.5 for comparison). Blood trauma, evaluated by plasma hemoglobin (Hb), did not detect any significant hemolysis in either group. Thrombocyte and white blood cell count profiles in both groups were parallel and without significant differences (p = 0.1 and 0.6, respectively). At the end of testing no clot deposition was found in the oxygenator. At postmortem, there were no signs of peripheral emboli. The results of this study suggest that this silicone coating of hollow fibers allows for good gas transfer, while preserving all the mechanical advantages of a conventional hollow fiber oxygenator.

Animals↗
PubMedDate not supplied

Intravascular oxygenation. Influence of the host vessel diameter on oxygen transfer.

An extra corporeal venovenous bypass circuit (right atrium to pulmonary artery), including an intravascular gas exchanger in a blood chamber with a variable inner diameter, was developed for ex vivo evaluation of the host vessel diameter/intravascular oxygen transfer relationship. Three host vessel diameters mimicking different configurations of the caval axis were studied in three bovine experiments (body weight 82 +/- 3 kg). Blood flow was 3,000 ml/min and device oxygen inflow was 2,300 ml/min. Serial blood samples were taken for 26 mm, 23 mm, and 20 mm inner blood chamber diameters after hemodynamic stabilization before and after exposure of the circulating blood to the intravascular gas exchanger (sampling ports at blood chamber inlet and outlet). Measured oxygen saturation at the blood chamber inlet was 25.0 +/- 11.7% for the 26 mm diameter as compared to 31.7 +/- 12.6% for 23 mm, and 28.7 +/- 9.2% for 20 mm. At the outlet, the corresponding O2 saturations were 34.5 +/- 11.5% for 26 mm, 42.9 +/- 8.8% for 23 mm, and 43.2 +/- 6.2 for 20 mm. Total O2 transfer was 24.9 +/- 11.5 ml/min for 26 mm, 31.9 +/- 7.4 ml/min for 23 mm, and 35.9 +/- 12.2 ml/min for 20 mm (p < 0.05). Likewise, O2 transfer rate was 8.3 +/- 3.8 ml/L, 10.6 +/- 2.4 ml/L, and 12.0 +/- 4.0 ml/L (p < 0.05). Parallel analyses of total CO2 transfer and CO2 transfer rates provided less consistent findings. At 3 L/min, the pressure drop between the inlet and outlet of the blood chamber was 12 +/- 3 mmHg for 26 mm, 26 +/- 1 mmHg for 23 mm, and 38 +/- 2 mmHg for 20 mm diameters (p < 0.001). The authors conclude that oxygen transfer of a given intravascular gas exchanger appears to be indirectly proportional to the host vessel diameter. Increasing blood pressure gradient as a function of decreasing diameter has to be considered in clinical application.

Animals↗
PubMedDate not supplied

Intravascular gas transfer. Membrane surface area and sweeping gas flows are of prime importance.

Single and double hollow fiber intravascular gas exchangers were evaluated in an extracorporeal veno-venous bypass circuit (right atrium to pulmonary artery) including a tubular blood chamber (mimicking caval veins with an inner diameter of 26 mm) for evaluation of the membrane surface area/host vessel diameter gas transfer relationships. Six bovine experiments (body wt: 68 +/- 4 kg) with staged ex vivo blood flows of 1, 2, 3, and 4 L/min and a device oxygen inflow of 0, 3, and 6 L/min (0 or 3 L/min/device) were performed. Total oxygen transfer at a blood flow of 1 L/min was 33 +/- 4 ml/ min for a gas flow of 3 L/min (one device) vs 60 +/- 25 ml/ min for a gas flow of 6 L/min (two devices); at a blood flow of 2 L/min, the corresponding oxygen transfer was 46 +/- 16 ml/min for a gas flow of 3 L/min vs 95 +/- 44 ml/min for a gas flow of 6 L/min; at a blood flow of 3 L/min, the corresponding oxygen transfer was 48 +/- 24 ml/min for a gas flow of 3 L/ min vs 92 +/- 37 ml/min for a gas flow of 6 L/min (p < 0.01 for comparison of areas under the curves). Total carbon dioxide transfer at a blood flow of 1 L/min was 47 +/- 18 ml/min for a gas flow of 3 L/min vs 104 +/- 26 ml/min for a gas flow of 6 L/min; at a blood flow of 2 L/min, the corresponding carbon dioxide transfer was 59 +/- 19 ml/min for a gas flow of 3 L/ min vs 129 +/- 39 ml/min for a gas flow of 6 L/min; at a blood flow of 3 L/min, the corresponding carbon dioxide transfer was 60 +/- 22 ml/min for a gas flow of 3 L/min vs 116 +/- 49 ml/min for a gas flow of 6 L/min (p < 0.01). For the given setup, the blood flow/gas transfer relationship is non linear, and a plateau is achieved at a blood flow of 2.5 L/min for O2 and CO2. Doubling membrane surface area and consecutively sweeping gas flows result in doubling of gas transfers at all tested blood flows. However, increased membrane surface area and blood flow produce a higher pressure drop that in turn limits the fiber density that can be used clinically.

Animals↗
PubMedDate not supplied

Flow rate dependent ex vivo deheparinization with immobilized cationic ligand.

The Heparin Removal Device is a deheparinization system that provides a good alternative when adverse reaction to protamine is suspected or when a heparin coated device is employed for cardiopulmonary bypass. In a bovine model, after systemic heparinization with 300 IU/kg body wt, the authors investigated the rate of deheparinization using this plasmapheresis system that allows exposition of heparinized plasma to an immobilized cationic ligand. Blood was shunted through a heparin coated veno-venous circuit to the plasma separator at a flow rate of 500 ml/min (n = 3, body wt 68 +/- 4 kg) or 1,000 ml/min (n = 3, body wt 57 +/- 4 kg). All plasma separators remained patent without any failure of the devices. Blood samples were drawn at regular intervals for coagulation parameters. The evolution of the activated coagulation time (ACT) was measured during the first 60 min of the deheparinization procedure, and results were compared with spontaneous evolution in a control group (n = 3, body wt 73 +/- 5 kg) without reversal of heparinization. After heparin administration, mean ACT was longer than 1,000 sec in the three groups. Fifteen minutes later it was still > 1,000 sec in the control group, whereas it was 427 +/- 8 sec in the slow flow group (500 ml/min) and 340 +/- 26 sec in the high flow group (1,000 ml/min). At 30 min it was 1,000, 367 +/- 26, and 200 +/- 24 sec, respectively, in the three groups. A regression curve was calculated for each group, and areas under the curves were compared. Ex vivo deheparinization was efficient in normalization of ACT, but removal of heparin appeared to be flow rate dependent. Increased blood flow from 500 to 1,000 ml/min across the deheparinization system resulted in significant acceleration of ACT normalization (p < 0.05).

Animals↗