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Biomedical subjects

S Avrameas

Publications and source records attributed to S Avrameas.

At least 145 records · Page 8Linked to original sources
PubMed1979

Comparison between peroxidase-conjugated antigen or antibody and peroxidase-anti-peroxidase complex in a postembedding procedure.

The staining efficiency of peroxidase labeled immunoglobulin conjugate, used either as antigen or as antibody, has been compared with that of peroxidase-anti-peroxidase complex (PAP) on ultrathin sections of araldite embedded material. The conjugate gave positive results in a two layer method as well as in a three layer method when used as antibody. No staining was observed when it was used as antigen. The conjugation seemed to impair the antigenic reactivity of immunoglobulin. The conjugate when used as antibody in the three layer method gave approximately the same staining efficiency as PAP.

Animals↗
PubMed1979

The use of avidin-biotin interaction in immunoenzymatic techniques.

Biotin was covalently attached to antibodies, antigens and enzymes, and the effects of this labeling on the antigen and antibody binding capacity and on enzymatic activity were tested. Based on avidin-biotin interaction, the labeled proteins were used in quantitative enzyme-immunoassay and enzyme-immunohistochemical staining procedures. Two procedures were developed. In the first procedure, named the Bridged Avidin-Biotin (BRAB) technique four steps were used sequentially in order to quantify or detect an immobilized antigen: 1) incubation with biotin-labeled antibody; 2) incubation with avidin; 3) incubation with biotin-labeled enzyme; 4) measurement or histochemical staining of the enzyme. The technique is based on the observation that avidin possesses four active sites. In the second procedure, named the Labeled Avidin-Biotin (LAB) technique, biotin-labeled antibody and enzyme-labeled avidin are used sequentially. Enzyme-associated antigen is then quantified or revealed immunohistochemically. The optimal conditions for enzyme-immunoassay and enzyme-immunohistochemical staining using BRAB and LAB procedures were established.

Animals↗
PubMed1979

Subpopulations of Ig-secreting cells induced by peroxidase immunization: discrimination according to antibody storage and secretion.

Mice were injected in their hind footpads with peroxidase (PO) emulsified in Freund's complete adjuvant. The development of cells secreting anti-peroxidase antibody (Ab) and cells secreting immunoglobulins (Ig) were detected in the draining popliteal lymph nodes in the subsequent 35 days, using local haemolysis plaque assay with sheep red cell blood cells coated with either PO or anti-mouse Ig antibody. Plaque-forming cells (PFC) were isolated from the centre of plaques by micromanipulation and after appropriate treatment, were examined by electron microscopy for their intracellular Ab content and in corporation of [3H]-thymidine. Four subpopulations of Ig secreting cells were distinguished: (1) cells secreting Ig without Ab function and not containing intracellular Ab detectable between days 5 and 20; (2) cells secreting Ig without Ab function but containing Ab appearing on day 6 and present throughout the immune response; (3) cells secreting Ab and containing Ab; (4) cells secreting Ab, but without detectable intracellular Ab. These last subpopulations appeared on day 7 and were found in all subsequent assays. The analysis of the kinetics of these subpopulations suggest that cells secreting Ig without Ab function might be precursors of Ab secreting cells.

Animals↗
PubMed1978

Magnetically responsive polyacrylamide agarose beads for the preparation of immunoabsorbents.

Glutaraldehyde-activated magnetically responsive polyacrylamide agarose beads have been employed to bind bovine serum albumin and human, sheep and rabbit IgG. These were tested for their effectiveness as immunoabsorbents and were found to allow isolation of pure antibodies in high yields. The use of magnetically responsive beads as the solid support in immunoabsorption procedures renders isolation of antibodies easy and rapid.

Animals↗
PubMed1978

Detection of tubulin and actin in various cell lines by an immunoperoxidase technique.

This paper reports on the preparation of immunsera against tubulin and actin, and the purification of anti-tubulin and anti-actin antibodies on immunoadsorbent columns. These purified antibodies were used in an indirect immunoperoxidase assay to visualize microtubules and microfilaments in various cell lines. The specificity of antibodies and the methods of cell fixation required are discussed, as well as some aspects of microtubule and microfilament organization, as visualized by this technique.

Actins↗
PubMed1978

Quantitative ultramicro-scale immunoenzymic method for measuring Ig antigenic determinants in single cells.

The Fluoro Ultra Micro Enzyme Linked Immuno Assay (FUMELIA) allows one routinely and quantitatively to measure a few thousand antigenic determinants on single cells. Highly purified Escherichia coli beta-galactosidase has been coupled to specific antibodies. By use of the Parafilm microcuvette techniuqe, the activity of the antibody-conjugated beta-galactosidase is assayed with a conventional spectrophotofluorometer. Attempts were undertaken to sensitize FUMELIA even further, so as to be able to detect a very few antigenic sites. It seems that even in its present state of development FUMELIA is more sensitive for the quantitation of cell-associated antigens than are techniques in which radiolabeled reagents are used. The potential of FUMELIA is illustrated by the quantitative measurement of membrane-bound immunoglobulins on single lymphocytes. It could be shown that T-cells as well as C-cells can synthesize Ig antigenic determinants. Thus it seems likely that T-cell receptors will, after all, be found to be immunoglobulins.

Animals↗
PubMed1978

Comparison of the developmental kinetics of antibody- and immunoglobulin-forming cells in normal and tolerant mice.

The developmental kinetics of antibody-forming cells (AFC) and of cells synthesizing immunoglobulins without detectable antibody function against the antigen injected (IFC) were compared in lymph nodes of normal mice and tolerant mice receiving an immunogenic challenge. Tolerant states to bovine serum albumin (BSA), induced in adult mice, and to human gamma-globulin (HGG), induced in newborn mice, were studied. Whatever the tolerant state induced, the following main results were obtained: 1) both AFC and IFC were suppressed in tolerant mice, and this to approximately the same extent for the two populations; 2) both the suppression of the AFC and of the antigen-induced IFC were specific to the tolerogen used.

Animals↗
PubMed1977

[An hypothesis for the process of selection at the subcellular level leading to the appearance of new clones].

According to the hypothesis we propose, the stimulation of one lymphocyte by an antigen induces the simultaneous expression of a great diversity of immunoglobulins of different specificities. Each molecular species is associated with the corresponding mRNA within a subcellular structure: the ergastoplasmic cisterna. It has been shown that in some responding lymphocytes at an early stage of the immune response a few such cisternae are loaded with antibodies while most of the cisternae are synthesizing non specific immunoglobulins. The main point of our proposal is that the selective action of antigen bears on these cisternae and that the mRNA corresponding to the immunoglobulins fitting best to the antigen is transcribed to DNA which is then inserted into the genome. This cell and its progeny become thereafter a monospecific clone submitted to regulation as an element of the network.

Animals↗
PubMed1977

Control of density and microredistribution of concanavalin-A receptors in rat thymocytes at 4 degrees C.

In a previous paper, we reported that at 4 degrees C, a cooperative binding of concanavalin A to rat thymocytes is observed which corresponds to a modification of the membrane leading to the recruitment of receptors and their immobilization. In this paper, we report that both phenomena are modulated at 4 degrees C by drugs such as colchicine and cytochalasin B; cooperative binding of concanavalin A, which reflects receptor recruitment is only slightly modified by each drug alone. when the two drugs are used simultaneously, the binding of concanavalin A to rat thymocytes at low concentrations of the lectin is decreased, while at high concentrations it remains unchanged. The binding of succinyl-concanavalin A to drug-treated cells is lowered at all concentrations of lectin. Also, we have studied the effects of colchicine and cytochalacine B on the binding of horseradish peroxidase to cell-bound concanavalin A, or succinyl-concanavalin A. We have found a decreased amount of horseradish peroxidase binding to concanavalin A bound to cells treated with colchicine or cytochalasine B. In the presence of the two drugs the decrease of peroxidase binding suggested a synergistic action of colchicine and cytochalasin B.

Animals↗
PubMed1977

Antibodies to tubulin in normal nonimmunized animals.

Sera of normal nonimmunized rabbits, pigs, calves, and humans contain tubulin-reactive antibodies. Usually, low amounts of antibodies against tubulin of the IgG class (2.5-4 mg/100 ml of serum from nonimmunized animals) were isolated. Anti-tubulin antibodies were also produced by injecting pig tubulin in complete Freund's adjuvant into rabbits. Slightly higher amounts of anti-tubulin antibody were isolated from sera of immunized rabbits (7 mg/100 ml of serum). The cytoplasmic network of microtubules of Tcc 36 mouse cells in culture was not clearly stained by natural anti-tubulin antibodies, but dense staining of the centrosphere was observed. In contrast, induced anti-tubulin antibodies densely stained cytoplasmic microtubular networks. Vinblastine-induced tubulin paracrystals were equally stained by natural and induced anti-tubulin antibodies.

Animals↗
PubMed1977

Internalization of lectins in neuronal GERL.

Conjugates of ricin agglutinin and phytohemagglutinin with horseradish peroxidase (HRP) were used for a cytochemical study of internalization of their plasma membrane "receptors" in cultured isolated mouse dorsal root ganglion neurons. Labeling of cells with lectin-HRP was done at 4 degrees C, and internalization was performed at 37 degrees C in a culture medium free of lectin-HRP. 15-20 min after incubation at 37 degrees C, lectin-HRP receptor complexes were seen in vesicles or tubules located near the plasma membrane. After 1-3 h at 37 degrees C, lectin-HRP-receptor complexes accumulated in vesicles and tubules corresponding to acid phosphatase-rich vesicles and tubules (GERL) at the trans aspect of the Golgi apparatus. A few coated vesicles and probably some dense bodies contained HRP after 3-6 h of incubation at 37 degrees C. Soluble HRP was not endocytosed under the conditions of this experiment or when it was present in the incubation medium at 37 degrees C. Internalization of lectin-HRP-receptor conjugates was decreased or inhibited by mitochondrial respiration inhibitors but not by cytochalasin B or colchicine. These studies indicate that lectin-labeled plasma membrane moieties of neurons are endocytosed primarily in elements of GERL.

Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone↗