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R Masseyeff

Publications and source records attributed to R Masseyeff.

At least 19 recordsLinked to original sources
PubMed1990

Criteria for the selection of a solid phase to be used in immunoassays.

Heterogeneous immunoassays are very sensitive and only limited in terms of performance by non specific binding. They require separation of free from bound fractions and concomitant use of a solid phase coated with an immunoreactive component (i.e. immunosorbent). The improvement of these key immunosorbents is crucial and involves a great deal of expertise and capabilities. Specifications differ according to procedure (e.g. capture or competitive assay). Each routinely used solid phase, such as polystyrene wells, porous membrane or dispersible microbeads, presents specific performance characteristics, advantages, and drawbacks. Among the tasks to be implemented are optimization of the spatial orientation of immunological reagents, selection of the surface neutral hydrophilic support, acceleration of reactions by increasing the reactive surface area of the supports, streamlining and simplification of procedural steps. These various aspects are abundantly described and emphasized here.

Acrylamide↗
PubMed1988

[Principles and methods of immunological diagnosis in infectious and parasitic pathology].

Immunological methods have always represented a major contribution to the diagnosis of infectious diseases. Recent technical advances in immunochemistry make this contribution even more essential than in the past. The author reviews the classic principles of immunological diagnosis in infectious pathology. In the best cases, this diagnosis is based on parasite identification (in the broad sense), or identification of specific products from the parasite. It is also possible to consider shortening culture time, when necessary, by performing an early immunological identification. The most recent developments in this field are presented. When the identification of the parasite or its secretion products is not feasible, one must be content to demonstrate the occurrence of a specific immune response, essentially of humoral nature. The author reminds of the basic theoretical difficulties preventing a real analytic antibody titration. The importance of the expression of the results as well as the predictive value of the tests, is stressed. Finally, the author analyzes some of the recent advances such as the development of immuno-enzymatic techniques, rapid testing which can be performed by non-biologists, the contribution of monoclonal antibodies and the possibility of using them in a new detection diagram of antibodies. The author reminds of the difficulty in the standardization of immunological methods, especially the determination of antibodies.

Animals↗
PubMed1986

A novel enzyme immunoassay for total thyroxine using immobilized antibodies and hydrophobic chromatography purified thyroxine-peroxidase conjugate.

A new and simple competitive enzyme immunoassay method for the measurement of total thyroxine in serum is described. Anti-thyroxine antibodies, raised in sheep with a bovine serum albumin-thyroxine conjugate prepared with carbodiimide as coupling initiator, were physically adsorbed onto a large surface area polypropylene support. Competition occurred between thyroxine in the sample and a thyroxine-peroxidase conjugate prepared with a glutaraldehyde spacer and further purified by octyl Sepharose hydrophobic chromatography. The entire assay was performed in 2 h with a useful range of 10-300 micrograms/l. The coefficients of variation ranged from 6.9 to 12% and good agreement (r = 0.93-0.97) was found between this method and 2 radioimmunoassays on 71 serum samples having well distributed thyroxine values.

Animals↗
PubMed1986

Affinity chromatography of rat alpha-fetoprotein on estradiol-agarose columns.

The use of 17 beta-estradiol-17-hemisuccinate coupled to agarose beads is shown to be a rapid and simple procedure for the isolation of alpha-fetoprotein (AFP) from amniotic fluid. The elution profile of the affinity column shows that AFP is sufficiently retarded by the gel to perform the purification of the protein without specific elution with high-affinity AFP ligands. Rat AFP appeared as a single symmetric peak, a profile that is in good agreement with the existence of a single population of AFP molecules having estrogen-binding properties.

Amniotic Fluid↗
PubMed1986

Distribution of Trop 3 and 4 antigens as defined by monoclonal antibodies raised against a human choriocarcinoma cell line.

The reactivities of Trop 3 and 4 monoclonal antibodies (MAbs) were studied on human term and 7-week extraembryonic membranes, adult tissues, and cell lines. Trop 3 MAb reacted with cells of chorionic villi, decidua, amniotic epithelium, and basal plate trophoblast. Trop 4 MAb reacted only with syncytiotrophoblast. On epithelium, Trop 3 MAb bound to stratified and glandular epithelium, but Trop 4 MAb reactivity was limited to basal keratinocytes. On peripheral blood mononuclear cells, Trop 3 MAb reacted with the majority of cells and Trop 4 MAb with the totality. Most cell lines were positive with both MAbs. However, one chemically induced MHC mutant was negative and another decreased its expression of Trop 3 antigen. Our results suggest Trop 3 MAb might recognize a monomorphic determinant of TLX antigens and Trop 4 is involved in cell proliferation or in cell-to-cell interaction.

Antibodies, Monoclonal↗
PubMed1985

Effect of pH on the recovery of human alpha-fetoprotein from immunosorbent columns. An improved elution procedure.

A slow decrease in pH was shown to be more efficient in eluting human alpha-fetoprotein bound to Sepharose-immobilized antibodies than a pH shock. With this method, nearly 50% of the antigen absorbed onto the column was recovered in a single peak whereas the yield was 3 times lower in the case of a single elution at pH 2.6. Our result suggests that dissociation of the antigen-antibody complex occurred only within a narrow pH range.

Antigen-Antibody Reactions↗
PubMed1985

Alpha-fetoprotein favours accumulation of estrone but not arachidonic acid into the fetal and new-born rat brain.

Tritriated estrone or arachidonic acid, two high affinity ligands for rat alpha-fetoprotein (AFP), were injected into adult, pregnant or newborn Sprague Dawley rats in order to evaluate their possible transfer into the brain. This study shows that the developing brain accumulates the estrogen but not the fatty acid, suggesting that the uptake of AFP by the developing brain is a mechanism for transporting estrogens, but not fatty acids.

Animals↗
PubMed1985

Immunoassay of melatonin with enzyme-labeled antibodies.

This paper reports a non equilibrium competitive enzyme immunoassay method using enzyme-labeled antibodies, for the quantitation of melatonin in chloroform-extracted samples. Its principle is as follows: methoxytryptamine hemisuccinate-human serum albumin conjugate physically absorbed onto a polystyrene sphere and melatonin to be measured, compete for a limited and fixed amount of peroxidase-labeled anti melatonin IgG. After incubation and washings the enzymatic activity bound to the sphere was measured with a chromogenic substrate. This simple method can detect as low as 22 fm of melatonin and is fairly precise. We also present its application to the determination of melatonin in serum and pineal gland.

Animals↗
PubMed1984

Interaction of retinoids and bilirubin with the binding of arachidonic acid to human alpha-fetoprotein.

Human alpha-fetoprotein (HAFP) has three binding sites for polyunsaturated fatty acids with association constant Ka = 1.8 X 10(7) M-1. One of these binding sites overlaps with a retinoid binding site with Ka = 2.6 X 10(6)M-1. Competition experiments with bilirubin showed that this compound does not compete neither with fatty acids nor with retinoids. Thus, the two bilirubin binding sites previously demonstrated appear as two additional binding sites on HAFP. Nevertheless, the close proximity of two fatty acid binding sites and two bilirubin binding sites resulted in a modification of the binding constants for fatty acids. It is hypothesised that the binding properties of HAFP reflect the three domain structures of the protein recently deduced from the study of the nucleotide sequence of HAFP mRNA and AFPcDNA segments.

Arachidonic Acid↗
PubMed1983

Human alpha-fetoprotein-fatty acid interaction.

Human alpha-fetoprotein (AFP) is able to bind arachidonic acid with high affinity Ka = 10(7)M-1 and a limited number of binding sites NS = 3. Thirty different fatty acids were tested by competition using labelled arachidonic acid as tracer. This experiment demonstrated a great specificity for the fatty acid-AFP interaction. Only polyunsaturated long chain fatty acids were able to bind to AFP with high affinity. The metabolic products of arachidonic acid i.e. prostaglandins presented no affinity for the AFP molecule.

Arachidonic Acids↗
PubMed1983

On rat alpha-fetoprotein as a fatty acid carrier. Influence of the structure of fatty acids.

Fatty acids interfere with rat alpha-fetoprotein-estrogen interaction. We present here a quantitative study of the association constants for the binding to alpha-fetoprotein of different fatty acids. It can be concluded that fatty acids bind more strongly if the number of carbon atoms increases with the number of double bonds. The maximum binding ability occurred with the C20 fatty acids having three or four double bonds. As these fatty acids are the precursors in the synthesis of prostaglandins, we tested some compounds in this series and showed that prostaglandins presented no particular affinity for rat alpha-fetoprotein.

Animals↗
PubMed1983

An enzyme immunoassay design using labelled antibodies for the determination of haptens. Application to methotrexate assay.

A competitive enzyme immunoassay with labelled antibodies has been developed for methotrexate (MTX). Methotrexate in the sample and a constant quantity of this hapten physically absorbed to polystyrene spheres through a methylated bovine albumin carrier were allowed to compete for a limiting amount of peroxidase labelled antibody. After washing, the residual enzyme activity bound to the solid phase was measured. This test was able to detect 10 fm of MTX per sample. A comparative study of this test with a commercial radioimmunoassay kit using the same antiserum and a high pressure liquid chromatography method showed that the sensitivity, specificity and precision of this test were as good as of the radioimmunoassay. The high pressure liquid chromatography method was 500 times less sensitive. Good agreement was found among the 3 methods on 83 serum samples from patients receiving methotrexate therapy.

Animals↗
PubMed1983

Inhibition of rat alpha-fetoprotein-estrogen interaction by adult rat ovarian extracts--role of unsaturated fatty acids.

Thin layer chromatography with four different solvent systems enabled us to show that ovarian extracts contained nonesterified unsaturated fatty acids able to compete with estradiol on the alpha-fetoprotein binding site. Gas chromatography demonstrated a high level of oleic and linoleic acids and the presence of arachidonic acid, a strong competitor of the rat alpha-fetoprotein-estrogen interaction. Arachidonic acid is a precursor of prostaglandins thus we suggest that its binding to AFP might play a role in the AFP-mediated ovarian regulation previously demonstrated.

Animals↗
PubMed1983

Comparative binding properties of rat and human alpha-fetoproteins for arachidonic acid and estradiol.

Rat and human alpha-fetoproteins, (AFP) were able to bind arachidonic acid with high affinity (Ka = 10(7) to 10(8) M-1). Nevertheless, a great difference was found in the binding capacity of these two proteins. Rat AFP was shown to possess one high affinity binding site and several (12-13) low affinity sites while human AFP presented three equivalent binding sites for polyunsaturated fatty acids. Estrogenic hormones compete with fatty acids bound to the high affinity binding site of rat AFP but remained unable to displace arachidonic acid bound to the human one.

Animals↗
PubMed1982

[Blood group ABO (H) cell surface antigens in bladder tumours invading the chorion. Prognostic value of their determination by immunofluorescence. Retrospective study of one hundred and twenty-five cases].

The authors have studied 125 stage A bladder tumours with a follow-up period of at least 5 years. The ABH cell surface antigens were collected by a double-layer immunofluorescence technique which has already been described. All the cross sections were read by the same pathologist who knew nothing about the clinical developments. The results were divided into 3 groups : (I) all the tumour cells had retained their surface antigens. (II) Only some cells had retained surface antigens. (III) All cells were negative. Study of the development of the 3 groups shows that : in group I, all the patients (11) are alive 5 years later, and only one has presented with a lesion evolving towards infiltration. In group II (32 patients), only 38 p. cent of the patients are still living 5 years later, and 65 p. cent developed towards muscular infiltration. In group III (77 patients), 27 p. cent are alive after 5 years and 80 p. cent have developed towards muscular infiltration. Homogeneous retention of the surface antigens would therefore seem to be a favourable factor in the prognosis, even in the case of a tumour which has already infiltrated the chorion. The significance of the loss of surface antigens is less clear-cut, but is on the whole adverse. The significance would, however, probably be enhanced by study of the mucosa distal from the lesion, and by marking the substances which determine the blood groups.

ABO Blood-Group System↗