Biomedical subjects

C Vigneron

Publications and source records attributed to C Vigneron.

At least 37 records · Page 2Linked to original sources

PubMed1999

Rheological behaviour of red blood cells suspended in hemoglobin solutions. In vitro study comparing dextran-benzene-tetra-carboxylate hemoglobin, stroma free hemoglobin and plasma expanders.

Circulating volume expansion for intentional hemodilution and/or resuscitation of hemorrhagic shock can be performed with hemoglobin-based oxygen carriers (HBOC) which, in addition to oxygen transport, have vasoactive effects through poorly documented mechanisms. Among these, the effects of HBOC on red blood cell (RBC) rheology are relatively unknown. The aim of the present in vitro study was to measure the rheological effects of human hemoglobin bound to benzene-tetracarboxylate substituted dextran (Dex-BTC-Hb) as an example of chemically modified hemoglobin. The viscosity was assessed with a capillary and a rotational viscometer for shear rates of 0.5-128 s-1. Erythrocyte aggregation was determined by analysis of the red light backscattered in a RBC suspension and with a rheoscope. The deformability was determined by the pressure-flow relationship of the RBC suspensions passed through polycarbonate filters. At hematocrit of 0.35 l/l and at low shear rates, the viscosity of RBC was higher in the presence of Dex-BTC-Hb as compared to free Hb, Dex-BTC, Dextran 40 (Plasmacair), modified fluid gelatin (MFG-Plasmion) or hydroxyethyl starch (HEA-Elohes). The effect on erythrocyte aggregation of Dex-BTC-Hb was greater than that of standard solutions, but close to that of MFG or HEA. There was no apparent change in RBC deformability. Dex-BTC-Hb, unlike free Hb, has a hyperaggregating effect on RBC, similar to that of some clinically used volume expanders. This hyperaggregating effect could influence the in vivo rheological behavior of substituted Hb by increasing shear stress.

Blood Substitutes↗

PubMed1999

Identification of protein C epitopes altered during its nanoencapsulation.

Protein C is a plasmatic inhibitor which regulates the blood coagulation mechanism by modulating the anticoagulant response. The improvement of its bioavailability would be beneficial for the treatment of the disorders caused by its homozygous deficiency or by an other plasmatic inhibitor deficiency. In this context, the protein C encapsulation into biodegradable nanoparticles could be used to approach the problem. However, the method used to prepare the nanoparticles requires the use of ultrasonication and of an organic solvent such as methylene chloride which interferes with protein activity. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that neither ultrasonication nor methylene chloride, singly or in combination, led to protein C aggregation or cleavage. Thus, a binding study using an ELISA assay with four characterized monoclonal antibodies was carried out to identify the epitopes damaged by these experimental constraints. The correlation between the immunological assay and a functional one i.e. by the means of the assay of its anticoagulant activity (activated partial thromboplastin time) made it possible to show that protein C amino acids 166-169 of the activation peptide were probably altered after ultrasonication and methylene chloride treatment. Indeed, it is likely that these residues were no longer surface-exposed but had moved inside the protein core.

Anticoagulants↗

PubMed1999

Presence of hemoglobin inside aortic endothelial cells after cell-free hemoglobin administration in guinea pigs.

The endothelium is the production site of several potent vasoactive factors that contribute to the modulation of the vascular tone. Because hemoglobin-based oxygen carriers (HBOC) have been demonstrated to cause vasoconstriction and thereby increase arterial pressure by interacting with endothelium-derived factors such as nitric oxide and endothelin-1, we hypothesized that hemoglobin could penetrate into the endothelial cells. Therefore, we investigated the presence of hemoglobin into guinea pig aortic endothelial cells by immunohistochemical staining after exchange transfusion with a hemoglobin-based oxygen carrier. Despite the large molecular size of HBOC due to chemical modifications designed to prevent hemoglobin subunit dissociation and extravascular leakage, hemoglobin was detectable by immunohistochemical staining into the endothelial cells. These findings suggest that the vascular endothelial cells could uptake hemoglobin by endocytosis mechanisms or could help hemoglobin to cross the endothelial barrier toward media by transcytosis mechanisms. These findings are very important to lead future investigations to the mechanisms by which HBOC cause vasoconstriction.

Animals↗

PubMed1999

Cardiovascular and hemorheological effects of three modified human hemoglobin solutions in hemodiluted rabbits.

The cardiovascular effects of human albumin (Alb) and three human hemoglobin (Hb) solutions, dextran-benzene-tetracarboxylate Hb, alphaalpha-crosslinked Hb, and o-raffinose-polymerized Hb were compared in anesthetized rabbits undergoing acute isovolemic hemodilution with Hct reduction from 41.4 +/- 2.7 to 28.8 +/- 1.6%. The impact of the vasoconstricting properties of Hb was examined by measuring heart rate (HR), mean arterial pressure (MAP), abdominal aortic, and femoral arterial blood flow, vascular resistance (VR), and aortic distension during the first 3 h after hemodilution. The impact of the hemorheological parameters was assessed by measurements of hemodiluted blood viscosity. In contrast to Alb, the Hb solutions elicited an immediate increase in MAP (20-38%). The effects of Alb and Hb solutions on HR, as well as on aortic and femoral arterial blood flow, were similar. VR decreased with Alb (20-28%) and increased with all three Hb solutions (30-90%), but the MAP and VR rising trends were different with each Hb solution. Aortic distension decreased in Hb groups compared with the Alb group for the first 60 min. The viscosity of hemodiluted blood was similar for all groups at high shear rates but was dependent on the viscosity of the solutions at low shear rates. We conclude that the vasoconstriction elicited by the Hb solutions overrides the vasodilation associated with viscosity changes due to hemodilution and would be the major factor responsible to the cardiovascular changes.

Albumins↗

PubMed1999

The effects of stroma-free and dextran-conjugated hemoglobin on hemodynamics and carotid blood flow in hemorrhaged guinea pigs.

Hemoglobin solutions are potential resuscitative fluids with volume expanding and oxygen delivery abilities developed to reduce the use of blood transfusion. Most hemoglobin solutions in clinical trials increase transiently arterial pressure by inhibiting nitric oxide-dependent vasodilation. Our objective was to compare the effects on central hemodynamics and carotid blood flow of two hemoglobin solutions after resuscitation from hemorrhage in anesthetized guinea pigs. After anesthesia and instrumentation, severe hemorrhage was induced by withdrawing 50% of the blood volume. Resuscitation was performed after 15 min of hypovolemia with 5% albumin, stroma-free hemoglobin, or hemoglobin conjugated to dextran-benzenetetracarboxylate (Dex-BTC-Hb). The mean arterial pressure (MAP), carotid blood flow (CBF), vascular resistance index and heart rate (HR) were monitored for 3 hours after resuscitation. After hemorrhage, MAP and CBF dropped to 57.6 +/- 4.4% and 58.9 +/- 3.7% of control values respectively. Albumin failed to maintain hemodynamics in the decompensatory phase of shock. Both hemoglobin solutions gave rise to a transient increase in MAP (35%); stroma-free hemoglobin increased the CBF (150%) and resistance index (24%) whereas Dex-BTC-Hb had no effect on CBF and vascular resistances. None of the solutions affected the HR. Modified hemoglobin has attenuated effects on CBF and resistance index compared to stroma-free hemoglobin. This may be due to a balance between the stimulation of nitric oxide synthesis by shear-stress and the inhibition of vasodilation by nitric oxide trapping.

Animals↗

PubMed1999

Induction of superficial bladder tumors in the female Fischer 344 rats with AY-27 tumor cells for the study of diffusion and localization of hemoglobin derived components (hematoporphyrin derivative) in view of photochemotherapy.

Photochemotherapy (PCT) consists in administration of a photosensitizer and subsequent irradiation of the tumor with visible light. Routinely, the photosensitizer is given intravenously (i.v.), but the major drawback of this procedure is the resulting skin photosensitivity. The goal of our study is to examine whether intravesical (i.b.) instillation of the photosensitizer for PDT of bladder cancer might be feasible in order to target the tumors and to avoid the photosensitization phenomenon. After first studying the biodistribution of hematoporphyrin derivative (HpD) in vivo in the rat bladder, two and four hours after intravesical administration, by fluorescence microscopy, we compared two different methods for the induction of superficial bladder tumors in rats with AY-27 tumor cell line in order to perform the same study on bladder tumors. The best results for the penetration depth of HpD in the normal bladder wall were obtained two hours after the bladder instillation where the photosensitizer was detected only in the bladder surface (urothelium and small part of the chorion). That's why we must choose the most appropriate bladder tumor model in order to obtain superficial bladder tumors that mimic the clinical behavior of superficial bladder cancer in man. Both techniques used in this study gave a high tumor take rate in a short time (> 90%). But we really obtained superficial bladder tumors directly attached to the bladder surface with one of the two methods of tumor induction consisting in the abrasion of the bladder surface prior to the administration of the tumoral cells in the bladder cavity.

Animals↗

PubMed1999

Determination of endogenous porphyrins and the maximal HpD tumor/normal skin ratio in SKH-1 hairless mice by light induced fluorescence spectroscopy.

The treatment of skin tumors is an application of photochemotherapy (PCT) which involves an initial administration of a photosensitizer (PS) followed by irradiation with a light beam that causes the PS to produce cytotoxic oxygen species within the tumors. As the PS is also present in normal skin, it is necessary to know how it is distributed between the two tissues. In this study, we have used SKH-1 hairless mice bearing papillomas or carcinomas chemically induced. The biodistribution of hematoporphyrin derivative (HpD) and the tissue autofluorescence measurements were studied by light induced fluorescence spectroscopy. The tumor and normal autofluorescence spectra measured on control mice with papillomas or carcinomas had a very similar shape. However, the principal endogenous porphyrin peak at about 630 nm showed a fluorescence signal amplitude 2 (for papilloma) and 1.5 (for carcinoma)-fold higher than the one found for the normal skin. Moreover, the fluorescence intensity of carcinoma spectrum is 1.4-fold lower than the one of papilloma spectrum at 630 nm. The tissue autofluorescence can be used to distinguish tumor from normal skin and benign from malignant tumor. This difference in fluorescence intensity at 630 nm was directly related to the concentration of endogenous porphyrins in the tumor. Fluorescence intensity ratios between tumor and normal skin were measured 4, 8, 24, 48, 72 and 96 hours after intraperitoneal injection of HpD (5 mg/kg body weight). The best tumor/normal skin ratio was 6.2 for HpD and the time required to reach this ratio was 48 h. HpD showed a moderate selectivity since the ratio was higher than 1 during the four first days. Photodynamic therapy with the same dose of HpD used in this biodistribution study must also be carried out to verify that the maximal tumor/skin ratio corresponds to the maximal efficiency of HpD.

Animals↗

PubMed1998

Microporous microparticles designed as stable immunoadsorbents.

We have developed a solid-phase immunoadsorbent based on encapsulated goat anti-apolipoprotein B polyclonal antibodies previously crosslinked with a 0.25% glutaraldehyde solution, and designed to remove by immunoaffinity the excess of apolipoproteins B from the plasma of patients affected by familial hypercholesterolemia. Compared to a classical immunoadsorbent prepared by activation of Sepharose CL-4B with cyanogen bromide, the resulting immunoadsorbent exhibits both optimal adsorption capacity and stability over the entire range of chemical and biochemical conditions during its practical handling. This approach will serve as a model system to demonstrate the applicability of microparticles as immunoadsorbents, which can be achieved for other encapsulated crosslinked proteins.

Adsorption↗

PubMed1998

Influence of experimental parameters on the characteristics of poly(lactic acid) nanoparticles prepared by a double emulsion method.

Nanoparticles were prepared by the double emulsion method (w/o/w), using methylene chloride as an organic solvent and polyvinyl alcohol (PVA) or human serum albumin (HSA) as a surfactant. Experimental parameters such as the preparation temperature, the solvent evaporation methods, the internal aqueous phase volume, the surfactant concentration and the polymer molecular weight were investigated for particle size, the zeta potential, the residual surfactant percentage and the polydispersity index. Preparation parameters leading to particles with well-defined characteristics such as an average size around 200 nm and a polydispersity index lower than 0.1 were identified. The conditions were optimized to ensure protein encapsulation: a cool temperature, a short processing time, a sufficient internal aqueous phase and careful washing. It appeared that the higher the surfactant concentration in the external aqueous phase was, the smaller the particles, the lower the polydispersity index and the higher the residual amount of surfactant were. For PVA or HSA, the agreement between the convenient surfactant concentration and its critical aggregation concentration could be emphasized. Otherwise, an increased polymer molecular weight led both to a slightly decreased particle size and to a lower polydispersity index. Moreover, multilayer absorption of PVA which does not depend on Poly(lactic-acid) molecular weight was exhibited. Finally, the zeta potential resulted from the polymer molecular weight and the residual PVA.

Drug Delivery Systems↗

PubMed1998

Hb Nancy and Hb Osler: two distinct genetic variants with identical clinical and hemoglobin phenotype.

Three hemoglobin variants (Hb Nancy, Osler and Fort Gordon), carrying the same Tyr-->Asp substitution at position beta 145 (HC2), have been independently described in 1975 in patients with marked polycythemia. The first one was found in a French caucasian family from Lorraine, and the two others in African Americans. Two unrelated individuals with Hb Osler have been recently reinvestigated at the DNA level and surprisingly, in their beta gene, codon 145 was found to be AAT which encodes for asparagine and not for aspartic acid, the aspartate at the protein level resulting, thus, from a very efficient posttranslational event. We reinvestigated a patient from the family of Hb Nancy and found that codon 145 was GAT, encoding for aspartate. This demonstrates that Hb Nancy is genetically distinct from Hb Osler despite an almost identical phenotype.

Asparagine↗

PubMed1998

Proposition of a technique to assess the vasoactive effects of hemoglobin-based oxygen carrying solutions in vivo: preliminary results in the rabbit aorta.

Most of hemoglobin-based oxygen carriers (HBOCs) increase the blood pressure after injection in the blood stream by a mechanism involving one or more factors that contribute to the regulation of the vascular tone. Many techniques make it possible to study the vascular effects of HBOCs both in vivo and in vitro. The in vivo methods assess the blood pressure and some estimated regional blood flows (use of radioactive or colored microspheres). Measurements of the real vessel diameter and blood flow would be useful to understand hemoglobin-mediated vasoconstriction mechanism. Our purpose was to elaborate an experimental model in anesthetized rabbits to monitor the diameter and the blood flow velocity in the same vessel in order to calculate the absolute blood flow. The blood flow velocity (in cm/s) was assessed by pulsed Doppler velocimetry and the diameter (in mm) was assessed by a technique of Wall Tracking. The first results indicate that the method is well adapted to study the effects of resuscitative fluids (plasma and blood substitutes) on the aorta vascular tone after hemodilution or resuscitation from severe hemorrhage.

Animals↗

PubMed1998

Hemoglobin autooxidation/oxidation mechanisms and methemoglobin prevention or reduction processes in the bloodstream. Literature review and outline of autooxidation reaction.

The amount of circulating methemoglobin in healthy humans is the result of a balance between methemoglobin production (from autooxidation and oxidation) and hemoglobin reduction. Hemoglobin autooxidation and oxidation are very complex and are not well understood. This article analyses the literature on hemoglobin autooxidation, oxidation and reduction and sets out a sequence of reactions for the oxidation of hemoglobin and the ways in which the percentage of methemoglobin is regulated or methemoglobin production prevented. Most of the information concerns erythrocyte hemoglobin, but plasma extracellular hemoglobin (from hemolysis or hemoglobin-based blood substitutes) is also considered where possible.

Hemoglobin A↗

PubMed1998

A stable reagent system for screening and identifying red blood cell irregular antibodies: application to commercial antibodies.

OBJECTIVE: Development of a new solid-phase system for screening and identifying irregular red cell antibodies. MATERIALS AND METHODS: Red blood cell membranes were prepared by a semi-automated procedure in which the hemolysate solution was passed through a hollow-fiber system. The membranes were fixed to the solid phase (microtiter plates) by centrifugation and incubated with 8% fat-free milk. Antibodies added to the microtiter plate were detected by anti-human antibodies adsorbed onto yellow latex particles. RESULTS: The system had good sensitivity (titer <1); 97% of anti-D samples were detected. The detection system was stable for 6 months at 4 degrees C. CONCLUSION: This stable-antigen solid-phase system readily detects and identifies red cell antibodies that are important in transfusion.

Commerce↗

PubMed1997

Selective in vitro removal of anti-A antibodies by adsorption on encapsulated erythrocyte-ghosts.

Large volume plasma exchanges are used for the removal of anti-A or anti-B antibodies from the plasma of patients undergoing transplantation from donors with major ABO incompatibility. Previous works suggest that solid-phase immunoadsorption can be substituted for plasma exchange in situations where antigens can be purified and immobilized on columns through which plasma is percolated. However, the preparation of purified antigens of the ABO system is large quantities is laborious and requires the use of considerable blood volumes. Studies were therefore undertaken to determine the feasibility of an original immunoadsorbent based on porous microparticles prepared by a water/oil/water emulsification-solvent evaporation method, within which erythrocytes-ghosts carrying blood group antigens were entrapped. The decrease of the antibody hemagglutinating titre after adsorption onto encapsulated ghosts suggests that antibodies can cross the polymeric membrane and bind to the antigens. This original approach of using encapsulated antigens for the batchwise removal of antibodies could be extended to affinity chromatography, and immunoadsorption therapy with a chromatographic column linked to an extracorporeal circulation could be considered.

ABO Blood-Group System↗

PubMed1997

In vitro study of the protective effect of trehalose and dextran during freezing of human red blood cells in liquid nitrogen.

Two nonpermeant cryoprotectants, the disaccharide trehalose and the polymeric carbohydrate (dextran, 40 kDa), were assessed as substitutes for glycerol in the cryopreservation of human red blood cells (RBC). The agents were evaluated by measuring the percentage of RBC recovery (total of free hemoglobin after freezing) and by evaluating the erythrocyte state after freezing. Ninety percent of the red cells were recovered after freezing in 30% (w/v) dextran in liquid nitrogen, which is very close to the recovery obtained in 35. 5% (w/v) glycerol (92%). The activities of pyruvate kinase and glucose-6-phosphate dehydrogenase of RBCs frozen and thawed with dextran were not modified, and the 2,3-diphosphoglycerate was reduced by 26%, but remained within normal values. ATP was reduced by 56%. The erythrocyte membrane integrity, evaluated by its osmotic fragility, was not altered, and the RBCs protected by dextran retained their normal discoid shape without the formation of microvesicles. The 24-h hemolysis of the washed red cells after storage at 4 degrees C was 7%. These results suggest that dextran protects red blood cells during freezing in liquid nitrogen, but that some effort is still needed to limit the drop of ATP concentration. One of the main advantages of dextran is that it does not penetrate the RBCs and requires less washing than glycerol.

Adenosine Triphosphate↗

PubMed1997

Determination of the maximal tumor/normal skin ratio after HpD or m-THPC administration in hairless mouse (SKh-1) by fluorescence spectroscopy--a non-invasive method.

Two major steps in our study on the treatment of skin tumors by photochemotherapy (PCT) were the development of a skin tumor model in hairless mice by chemical carcinogenesis and by the use fluorescence spectroscopy, a semi-quantitative and non-invasive method, to determine the time after i.p. injection of photosensitizer when the tumor/normal skin ratio is the highest. Carcinogenesis provided mice bearing many benign papillomas and these were used to determine the tumor/normal skin ratios of two photosensitizers by fluorescence spectroscopy. Hematoporphyrin derivative (HpD) (5 mg/kg body weight) and m-tetra(hydroxyphenyl)-chlorin (m-THPC) (0.3 mg/kg body weight) were injected, and fluorescence measured at 4, 8, 24, 48, 72 and 96 h after injection. The tumor/normal skin ratio was 6.2 for HpD and 5.1 for m-THPC. The times required to reach these ratios were 48 h for HpD and 72 h for m-THPC. Published reports indicate that m-THPC gives a much higher tumor/normal skin ratio than HpD. These results must be confirmed by organic extraction. Photodynamic therapy with the same doses of HpD and m-THPC used in this pharmacokinetic study must also be carried out to compare the toxicities of the two photosensitizers and to determine which is best for this type of tumor.

Animals↗

PubMed1996

Hemoglobin-dialdehyde dextran conjugates: improvement of their oxygen-binding properties with anionic groups.

We studied the conjugates formed between hemoglobin and sulfated or unsulfated oxidized dextran. It appears that the presence of sulfated groups favors imino bond formation between the protein and the polymer, as the average molecular size of the conjugates is larger in this case. Under neutral conditions, the oxygen-binding properties of the conjugates depend on the presence or absence of oxygen during the coupling reaction. With unsulfated dextran, oxyhemoglobin leads to conjugates with increased oxygen affinity (P50/P50 native hemoglobin approximately 0.5) compared to that of free hemoglobin (P50 = 4 mm Hg), whereas deoxyhemoglobin leads to conjugates with decreased oxygen affinity (P50/P50 native hemoglobin approximately 3). The use of sulfated dextran reinforces this lowering in oxygen affinity, which indicates that sulfated dextran acts as a permanent macromolecular effector of hemoglobin (P50/P50 native hemoglobin approximately 4). Moreover, it can be assumed that some of the linkages involve the 2,3-diphosphoglycerate binding site, as the strong effector inositol hexaphosphate has only a slight effect on the oxygen-binding properties of the conjugate prepared in the deoxy state (P50/P50 native hemoglobin close to 4.4 and 6, respectively, for unsulfated and sulfated conjugates). Although dextran substituted with benzenehexacarboxylic acid (BHC) leads to a low-oxygen-affinity conjugate when linked to oxyhemoglobin through amide bonds (P50/P50 native hemoglobin approximately 5), oxidized dextran modified with BHC leads, with oxyhemoglobin, to a conjugate whose oxygen affinity is close to that of free hemoglobin (P50/P50 native hemoglobin approximately 1.2).

Aldehydes↗

PubMed1995

[Pulsed Doppler ultrasonography to measure the vasoactive effects of hemoglobin-dextran 10-benzene-tetracarboxylate, a potential erythrocyte substitute].

The effects of Dextran-Benzene-Tetracarboxylate-Hemoglobin (Dex-BTC-Hb), a chemically-modified hemoglobin-based oxygen carrier, on the vascular tone were compared to those of standard solutions, i.e. the animal's own blood and a 50 milligrams albumin solution, by measuring the carotid blood flow velocity, the mean arterial pressure, the heart rate and respiratory frequency, in anesthetized Hartley guinea pigs after a hemorragic shock. Stroma-free hemoglobin induced 40% hypertension and a 110% rise in blood flow velocity immediately after injection. The velocity was still increased 38%, 3 hours after injection. The calculations of the vascular resistances showed an increase in carotid vascular tone. Dex-BTC-Hb brought about 35% hypertension for two hours with no significant modifications of the vascular tone. These effects are similar to those of the albumin solution. These results indicate that, unlike stroma-free hemoglobin, Dex-BTC-Hb does not significantly affect the vascular tone, probably because of its slight interaction with the factors that regulate vascular tone.

Animals↗