Biomedical subjects

J F Stoltz

Publications and source records attributed to J F Stoltz.

At least 109 records · Page 6Linked to original sources

PubMed1992

Single-step method for purification of human transferrin from a by-product of chromatographic fractionation of plasma.

A rapid, simple and convenient method is described for the isolation, on a pilot scale, of pure and functional human transferrin from an unexploited by-product of chromatographic fractionation of plasma. In a single chromatographic step on DEAE-Spherodex, 97% pure transferrin was obtained in 75% yield. A virus inactivation treatment was included in the preparative process in order to guarantee the safety of the final product, which could be used in culture media.

Chromatography, Ion Exchange↗

PubMed1992

Dye-affinity purification of transthyretin from an unexploited by-product of human plasma chromatographic fractionation.

Dye-affinity chromatography of human plasma transthyretin on Remazol Yellow GGL-Sepharose from an unexploited by-product of chromatographic fractionation of plasma was optimized for large-scale preparation of a therapeutic product. With this system, transthyretin is only weakly bound to the gel. The residence time on gel and the transthyretin level in the by-product were observed to have no influence on the binding capacity of gel, and the optimum amount of transthyretin to be applied to the gel was found to be 1 g/l of gel. The adsorbent can be used more than ten times. The procedure resulted in the isolation, with a 30% yield with respect to plasma, of an 80% pure protein, which retained its thyroxine-binding capacity. Although the purity is acceptable for substitutive therapy, it can be improved further with a second chromatography on Cibacron Blue-Sepharose.

Adsorption↗

PubMed1992

Use of fluorescence anisotropy determinations for indicating the physiological status of hybridoma cell cultures.

The evolution of lipid compartment fluidity during culture of hybridoma cells was studied by fluorescence polarization measurements. The probe partition between the plasma membrane and intracytoplasmic compartments was determined by a quenching fluorescence method. A progressive decrease of the plasma membrane fluidity was observed during the growth phase with an increase during stationary and degeneration phases of the culture. These data suggest that fluidity parameters could be used to follow the behaviour of hybridoma cell cultures.

Cell Membrane↗

PubMed1992

[In vivo rheologic studies of plasma substitutes].

The aim of this study was to compare in 60 ASA1 patients, the rheological effects of a 500 ml plasma substitute infusion at induction of general anaesthesia. The 60 patients were allocated into 6 groups of 10. Each group received either albumin 4%, or dextran 40 3.5%, or dextran 60 6%, or hydroxyethylstarch (HES) 200 6%, or modified fluid gelatin or Ringer lactate. The infusion extended over 30 minutes. In blood samples obtained before infusion, immediately after the end, three and 24 hours after the end of infusion, osmotic pressure, oncotic pressure, proteins and fibrinogen concentration were measured. Following rheological parameters were also assessed: plasma viscosity, blood viscosity at two shear rates (0.5 and 128 s-1), erythrocyte aggregation by primary and final aggregation times as well as total and partial dissociation thresholds. The determinations were carried out at haematocrit corrected to 40%. At intergroup analysis of the different substitutes compared to albumin 4%, with the exception of Ringer lactate, there was no significant modification of osmotic and oncotic pressures or fibrinogen concentrations. Only gelatin and dextran 60 modified the rheological parameters. The intragroup comparison did not demonstrate significant variations of osmotic and oncotic pressures. Fibrinogen concentrations remained unchanged up to the 24th hours, where they increased as a reaction to surgery. Similar changes of rheological parameters occurred for Ringer lactate, albumin 4% and dextran 40: decrease of plasma viscosity (< 10%) and blood viscosity (< 20% at shear rate of 0.5 s-1), increase of primary aggregation time (30-50%) with decrease of total dissociation threshold (10-20%). These changes ended 24 hours after infusion. Dextran 60 and gelatin elicited a modification of blood rheology until the 24th hour after the end of infusion. Such modifications did not occur with HES. It is concluded that when a rheological effect is required albumin 4% or dextran 40 3.5% should be used.

Albumins↗

PubMed1992

A sensitive enzyme immunoassay for the detection of a synthetic affinity ligand, the reactive yellow 13 dye.

Dye-affinity chromatography is widely and increasingly used for the isolation of various proteins. In particular, the purification of transthyretin can be efficiently achieved by affinity chromatography on immobilized Reactive Yellow 13. Measurement of trace-amounts of dye leaching from affinity columns is important because of possible toxicity or side effects linked with the presence of dye in therapeutic transthyretin preparations. A competitive enzyme immunoassay was developed to monitor yellow-dye column leaching. Biotinylated rabbit anti-Reactive Yellow 13 antibodies (immunoglobulin G fraction) were used as principal reagent. The assay is specific sensitive to 1 ng/ml of Reactive Yellow 13, has a good reproducibility and allows the accurate detection of the dye in the presence of transthyretin.

Affinity Labels↗

PubMed1992

[Affinity chromatography for extracorporeal purification or for separation of molecules for biological use: technical and legal restraints].

Affinity and/or immunoaffinity chromatography is one of the less commonly method used for large scale separation purposes. As this technic is greatly selective and gives high yields, it allows in vivo removal, in an extracorporeal circulation, of harmful substances in patient plasma as well as purification of molecules for biological and therapeutic uses. Large development with increased safety of such a method is dependent on some economic, technical and legal requirements. Particular attention must be drawn to the following points. Possibility of multiple uses of affinity supports contributes to lowering the cost of the method. Desorption agents should be chosen according to the best compromise between total desorption and preservation of adsorption capacity over runs. It is likewise essential to store affinity supports in conditions allowing prevention from contamination without loss of adsorption capacity. In developing and optimizing an affinity chromatography procedure, it is important to minimize the amount of ligand released from the affinity support. Besides economic and technical aspects, it is necessary to take into account legal requirements, particularly those related to the preparation of the ligand especially if it is monoclonal or polyclonal antibodies. An important consideration for the therapeutic use of antibodies (either in the preparation of biological products or in an extracorporeal circulation procedure) is the possible presence of viruses and/or potentially oncogenic macromolecules. Source material should be shown to be free of viruses, the cell banks (for monoclonal antibodies) and the production of antibodies must be closely controlled, viral inactivation of antibodies should be performed and the inactivation process should be shown to be effective.

Chromatography, Affinity↗

PubMed1992

Specific removal of transthyretin from plasma of patients with familial amyloidotic polyneuropathy: optimization of an immunoadsorption procedure.

Familial amyloidotic polyneuropathy is characterized by the presence in patients plasma of a genetic variant of transthyretin. No specific treatment has been found and extracorporeal immunoadsorption on immobilized anti-transthyretin antibodies appears as a potentially attractive procedure. Parameters involved in specific immunoadsorption of transthyretin were studied and optimized. Several monoclonal anti-TTR antibodies were compared as affinity ligands and one of them was found to be suitable for such purposes. Optimum quantities of antibodies to be immobilized on the gel were determined. Three desorption agents were tested for regenerating immunoadsorbents and best results were obtained with basic variation of pH, allowing total desorption of TTR and possibility of multiple use without loss of adsorption capacity. Simulation of an immunoadsorption procedure in well-defined conditions showed efficiency and specificity of adsorption to remove TTR and the system thus should be subjected to clinical trials.

Amyloidosis↗

PubMed1992

Blood rheology in arterial hypertension.

DETERMINANTS OF BLOOD RHEOLOGY: Blood flow depends on driving pressure and a resistance factor, the latter being related to geometrical hindrance and to the intrinsic viscosity of the blood. Since whole blood is non-Newtonian in nature, blood viscosity is strongly dependent on shear conditions. Low-shear areas occur in cardiovascular disease, and therefore the interaction between blood viscosity and flow conditions may affect vascular disorders. Increased shear stress secondary to increased viscosity may produce endothelial activation and release of endothelium-derived relaxing factors, leading to flow-dependent vasodilation. All the determinants of blood rheology, including plasma protein and erythrocyte factors may be altered in patients with arterial hypertension. BLOOD RHEOLOGY IN HYPERTENSION: A hyperviscosity state is created which is associated with an unfavourable prognosis, since it is correlated with blood pressure levels and the severity and complications of the disease including left ventricular hypertrophy. The mechanisms of haemorheological abnormalities in hypertension are still unclear. It is not known whether blood rheology is an independent variable in patients with hypertension or whether it is a covariable with other established indices of heterogeneity. However, many aetiopathological changes identified in hypertensive disease may contribute to the observed changes in blood rheology. Haemorheological changes in hypertension, through complex interactions with platelet activation and endothelial function, may contribute to the development of thrombosis and atherosclerosis. Moreover, in acute and chronic ischaemia and other conditions where compensatory mechanisms such as collateral formation and vasodilation are limited, rheological factors may become important determinants of blood flow and tissue oxygenation. TREATMENT EFFECTS: Many antihypertensive agents have direct or indirect potential effects on haemorheological variables. However, to date, most studies that have investigated the effects of therapy on rheological variables have not been performed in clinically relevant situations. Controlled studies that monitor both the acute and longterm effects of antihypertensive drugs on relevant haemorheological variables are required to show whether specific therapeutic approaches can correct abnormalities in blood rheology.

Antihypertensive Agents↗

PubMed1991

Monoclonal antibodies against human plasma protein C and their uses for immunoaffinity chromatography.

Human protein C, isolated by conventional multistep methods, was used for immunization of mice. Monoclonal antibodies were prepared and screening of antibodies to human protein C was achieved using an immunoblotting technique. Five monoclonal anti-protein C antibodies were compared as affinity ligands. Different parameters were studied (adsorption capacity, specificity of adsorption, possibility of desorption under mild conditions) and two antibodies were selected. One antibody allows preparation of highly purified protein C in a single-step procedure from a fraction of plasma containing high levels of coagulation factors whereas the other can be used for preparation of protein C deficient plasma.

Antibodies, Monoclonal↗

PubMed1991

[Hemorrheology in clinical practice. Applications in an in vitro study of troxerutin].

It is now well established that blood behaves like a non Newtonian fluid varying with the shear rate. Blood viscosity pattern relative to various shear rates shows a high viscosity at low shear rate (due to rouleau formation or erythrocyte aggregation) with a decrease at high shear rate. This high blood viscosity will be of a great importance only while pathological blood flowing with low output or stasis. Pathological variations of one factor determining blood viscosity and clinical signs define hyperviscosity syndrome. From an hemodynamical point of view, the appearance of an hyperviscosity syndrome, may, as a result of feedback mechanism, aggravate the disorders leading to a slowing down and even to a stop in local blood flow, subsequently encouraging ischemia. Moreover hyperviscosity also leads to a theoretical lowering capacity of oxygen transport by blood approximatively in proportion with the haematocrit/blood viscosity ratio. With regard to therapeutic aspect, the pharmacology of rheological influence drugs must be displaced into the wider outline proposed by Virchow. So we could distinguish between therapeutic action of drugs upon haematocrit, plasmatic proteins level, red blood cell deformability and erythrocyte aggregation. Among this last category disaggregating effect of rutosides has been first pointed out by Schmid-Schöenbein and Col. Our results of an in vitro study of troxerutine effect with ranging concentrations from 10(-5) to 10(-2) M upon blood viscosity and erythrocyte aggregation are reported.

Anticoagulants↗

PubMed1991

Effective postexposure treatment of rabies-infected sheep with rabies immune globulin and vaccine.

An experiment to assess the efficiency of the treatment recommended for humans after exposure to rabies was conducted in 68 sheep experimentally infected with a fox rabies virus. The infected sheep were divided into three groups and were given either a cell-culture vaccine (on the day of infection, then at day 3, 7, 14), human rabies immunoglobulin (26 IU kg-1 on the day of infection) or a combination of the vaccine immunoglobulin. The latter combination was the only treatment found to be effective in 100% of the animals, as 71% of the controls died. This model appears to be useful in assessing new regimens of postexposure treatment for humans as well as in the reconsideration of its feasibility, or validity, in animals.

Animals↗

PubMed1991

New trends in clinical hemorheology: an introduction to the concept of the hemorheological profile.

It has now been clearly established that blood behaves like a non-Newtonian fluid exhibiting specific features with the probable existence of a plasticity threshold, a viscosity that varies as a function of shear rate and a non-homogeneous nature of the medium during flow. When apparent blood viscosity is represented as a function of shear rate, a high viscosity is observed at low shear rates, mainly due to rouleaux formation or red cell aggregates. At high shear rates, viscosity decreases. Apparent blood viscosity is mainly dependent on the following parameters: cell volume concentration (hematocrit); plasma viscosity (which is itself dependent on the type and concentration of the proteins); mechanical properties of the red cells, the main determinants being the cell membrane and internal viscosity; red blood cell aggregation; shear stress applied. Pathological changes in one of the factors controlling blood viscosity and the resulting clinical symptoms constitute the hyperviscosity syndromes. The field of hyperviscosity syndromes concern the situations where the increased blood viscosity and the accompanying modifications in flow resistance must be considered as being the result of the overall rheological behaviour of blood. In this general context, hyperviscosity syndromes can be divided into 4 main groups: 1. Increase in the number of blood cells (mainly red cells) 2. Increase in the plasma protein concentrations or the appearance of high amounts of a monoclonal protein 3. Increase in internal red cell viscosity or a change in the mechanical properties of the erythrocyte membrane 4. Increase in erythrocyte aggregation (formation of barely or in no way dissociable aggregates). Considered from a hemodynamic viewpoint, the appearance of a hyperviscosity syndrome could (by 'feed back' mechanisms) enhance the phenomenon and slow down blood flow or even stop flow completely, thus making ischemia and thrombosis easier. Further, the appearance of the syndrome also results in a decrease in the blood's overall oxygen transport capacity, which, at a primary approach, is proportional to the ratio hematocrit/blood viscosity.

Animals↗

PubMed1991

[Immunohistochemical localization of transforming growth factor-beta (TGF-beta) in smooth muscle tissue].

Anti-TGF-beta antibodies were raised in rabbits against a C-terminal synthetic peptide whose amino acid sequence was chosen after human TGF-beta 1 primary sequence antigenic study by continuous epitope prediction. Immunopurified antibodies were used for an immunohistochemical localization in normal and pathological human tissues. Smooth muscular type tissue seems to be an elective target.

Animals↗

PubMed1991

[Hemorheology in clinical practice. Introduction to the notion of hemorheologic profile].

Although the non-Newtonian characteristics of blood have now been accurately defined, the influence and effect of a hyperviscosity syndrome at the onset of ischemia and in oxygen transport to the tissues remains within the realm of assumptions. Using a simple theoretical approach it can be shown that oxygen transport capacity to the tissues is proportional to the radio H/eta s (where H = hematocrit, eta s = blood viscosity), as long as vascular bed geometry remains constant (with no sign of compensatory vasodilation). With the help of examples, the authors show the changes in oxygen transport as a function of various rheological parameters (red cell aggregation ans deformability). Further, the authors introduce the concept of a hemorheological profile for taking all the hemorheological parameters into consideration and for standardising the presentation of the results for hyperviscosity syndromes.

Blood Viscosity↗

PubMed1991

[Erythrocyte aggregation in patients with monoclonal gammopathies: effect of plasma exchange treatment].

Analyses of erythrocyte aggregation have been carried out in 15 patients with multiple myeloma or Waldenström's macroglobulinemia before and after plasma exchange. The volume of exchanged plasma was about 1.2-1.5 plasmatic mass. It was replaced by the same volume of a 4% solution of human albumin. Each treatment included at least 3 plasma exchanges at 48 hours intervals. The kinetic (aggregation times) and rheological (dissociation threshold) parameters of erythrocyte aggregation were determined before and immediately after each plasma exchange using a device based on the analysis of the backscattered light by a blood suspension. Before the first plasma exchange, erythrocyte aggregation measurements revealed a pronounced reduction in time aggregation and high values of dissociation thresholds indicating an hyperaggregation of red cells. The successive plasma exchanges produced very different changes in erythrocyte aggregation. For some patients, the aggregation parameters presented normal values from the first plasma exchange when similar changes were only noted after the second plasma exchange in other patients. Finally, in some cases, an hyperaggregation state was maintained after a series of three plasma exchanges. The influence of the nature and the concentration of monoclonal immunoglobulin as well as plasmatic fibrinogen are discussed.

Blood Viscosity↗

PubMed1990

Rheological properties and membrane fluidity of red blood cells and platelets in primary hyperlipoproteinemia.

Lipid fluidity of the erythrocyte membrane and intact platelets was examined in 32 male patients affected by types IIA, IIB and IV primary hyperlipoproteinemia and 15 control subjects. Lipid fluidity was determined by fluorescence polarization using two probes: DPH and TMA-DPH which are localized in different lipid areas of the cell membrane. Classical haemorheological tests were also performed including plasma viscosity, whole blood viscosity and erythrocyte aggregation. As compared to a control group, plasma viscosity and whole blood viscosity at low shear rate was significantly increased in types IIB and IV, but not in type IIA patients. In contrast, the increase in erythrocyte aggregation was significant in all HLP types. Concerning lipid fluidity, the results recorded with red cells and platelets were not significantly different for type IIA HLP compared to the control group. In contrast, erythrocyte membranes from patients with types IIB and IV HLP had a significantly higher level of fluidity in lipid regions characterized by TMA-DPH. Using DPH as a fluorescent probe, identical results were only noted in type IIB patients. Regarding intact platelets of IIB and IV patients, an increase in lipid fluidity was noted for two fluorescent probes. These findings suggest that HLP associated erythrocyte and platelet fluidity alterations are not related to hypercholesterolemia but to the triglyceride level.

Adult↗

PubMed1990

[Human plasma fibronectin. Comparison of methods for preparation of a concentrate for therapeutic use from different sources].

Three methods, successive precipitations, affinity chromatography on immobilized gelatin and immunoaffinity chromatography with monoclonal anti-fibronectin antibodies were optimized and compared in order to be used for large scale preparation of human plasma fibronectin (Fn). The functional properties of the various Fn preparations were investigated by means of two assays: quantitation of the gelatin-binding activity by ELISA and quantitation of the Fn-mediated attachment of fibroblasts on plastic. Functional alterations of the purified Fn were observed when it was isolated by successive precipitations. Both chromatographic methods provide a rapid and convenient way for isolation of pure and functional Fn. Mass production of monoclonal antibodies is too expensive and legislative requirements for the therapeutic use of monoclonal antibodies are limiting factors for the choice of immunopurification as large scale isolation procedure. Plasma Fn can be isolated from different sources: fresh frozen plasma, cryoprecipitate supernatant or by-products from factor VIII preparation. When gelatin-Sepharose chromatography is performed under optimized conditions, fibronectins isolated from these sources show similar properties. Large scale purifications of Fn from a by-product of factor VIII preparation were performed either by gelatin affinity chromatography or by successive precipitations. These two purification methods can be easily scaled-up since the data obtained closely correlate with analytical results. The chromatographic method supplies a higher purified (98 vs 75%) and functional (95 vs 50%) material when compared with successive precipitations. Yield is also higher (50 vs 26%). The starting material undergoes viral inactivation and the affinity purified Fn, sterile, atoxic, apyrogen, which can be freeze-dried without additives fulfils all requirements for an injectable product.

Antibodies, Monoclonal↗

PubMed1990

Fluorescence depolarization method in the study of dynamic properties of blood cells.

Fluorescence polarization is the most commonly used method to approach a property of cell membrane, the so-called "fluidity". Whether time resolved determinations may be of potential interest to get precise information on the behaviour of fluorescent probes incorporated into biological membranes, steady state measurements are still the most accessible for biologists. Steady-state anisotropy value may be considered as a semi-quantitative indication of the cohesion of the lipid chains. However, meaningful interpretation of the anisotropy values requires a careful sample preparation and a suitable use of fluorescent probes. This paper reviews the properties and uses of several hydrophobic membrane fluidity probes. In the case of intact cells, the potential interest of the association of fluorescence polarization with quenching fluorescence method in giving information on the "actual" membrane fluidity is outlined.

Diphenylhexatriene↗