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Biomedical subjects

B A Sela

Publications and source records attributed to B A Sela.

At least 19 recordsLinked to original sources
PubMed1992

Microalbuminuria immunoassay based on antibodies covalently conjugated to Eupergit C-coated beads.

OBJECTIVE: To develop a reliable, simple, and sensitive assay for microalbuminuria, based on covalent attachment of anti-HSA to oxirane-bearing polymethylmethacrylate beads (Eupergit CB6200). RESEARCH DESIGN AND METHODS: Anti-HSA antibodies were coupled to CB6200 beads by reaction of their amino groups with the oxirane groups of the matrix. The capability of the beads to bind HSA from standard solutions or urine was evaluated and compared with the state of the art ELISA test. RESULTS: The new bead immunoassay is sensitive and linear in the range of 1-25 mg/L, which is considered the low microalbuminuria range. When HSA levels in urine were tested, the intra- and interassay CV values ranged between 2.7 and 3.9% and between 5.6 and 6.6%, respectively. The long-term storage stability of the antibodies covalently bound on the beads was higher than of the same antibodies adsorbed on ELISA plates. After 16 wk of storage, the CV was about 7.3% with the bead assay, compared with 14% obtained for the ELISA test under the same experimental conditions. CONCLUSIONS: A new procedure for microalbuminuria assay was developed, with Eupergit CB6200 beads as a solid support for covalent binding of the first antibody. Accuracy, sensitivity, reproducibility, and precision of the bead immunoassay were similar to those of commonly used immunoassays, as exemplified by the analysis of HSA in 53 clinical urine samples. The bead assay retains a low degree of variability over long storage periods, and the beads may be reapplied after a simple acid-washing procedure.

Albuminuria↗
PubMed1991

Characterization of tenascin secreted by human melanoma cells.

Tenascin is a large glycoprotein of the extracellular matrix. It shows a site-restricted expression during embryogenesis and can be found in adult tissues during wound healing and tumorigenesis. Because of the potential involvement of tenascin in adhesion and invasion during metastasis, the study of the interactions of tumor cells with tenascin is of considerable interest. Using five anti-melanoma monoclonal antibodies to four different epitopes of human tenascin, we found that most melanoma cells secrete tenascin in vitro constitutively. Transforming growth factor beta 1 in the medium increased secretion in tenascin-producing cells. Tenascin was present in sera of melanoma patients, with significantly elevated levels in patients with advanced melanomas as compared to patients with low tumor burden or to normal donors. Normal and malignant melanocytes did not attach to tenascin as substrate within 1 to 2 h and tenascin could also inhibit fibronectin-dependent adhesion. These results indicate that tenascin may play a critical role in cell-substrate interactions of melanoma cells.

Antibodies, Monoclonal↗
PubMed1990

Monoclonal antibody-dependent, cell-mediated cytotoxicity against human malignant gliomas.

Two monoclonal antibodies (MAbs), IgG2a MAb ASHG4 and IgG2b MAb ASHE2, were produced in mice immunized with cultured human malignant glioma cells. Both MAbs bound strongly to the surfaces of long-term cultured glioma cells, and MAb ASHE2 also bound strongly to short-term cultured glioma cells. Sections of frozen glioma tissues bound both MAbs strongly, whereas normal brain tissues showed weaker reactivities, and tissues derived from carcinomas of various histological types were completely unreactive. Furthermore, the MAbs did not bind to peripheral blood cells or bone marrow cells. Although both MAbs bound to the same Mr 27,000-29,000 protein, they may detect different or overlapping epitopes on this antigen. Because MAbs ASHE2 and ASHG4 lysed cultured glioma cells with human peripheral blood lymphocytes as effector cells, they are promising reagents for approaches to immunotherapy of human malignant gliomas.

Antibodies, Monoclonal↗
PubMed1990

Multiple sclerosis: cell-mediated immunity to human brain gangliosides.

Cell-mediated immunity (CMI) to myelin components has been implicated in Multiple Sclerosis (MS) pathogenesis: two targets were suggested, Myelin Basic Protein with controversial results and, more recently, gangliosides. In order to investigate their possible involvement, we have performed Leukocyte Migration inhibition (LMI) tests in the presence of human brain gangliosides. Thirty nine MS patients (twenty four being "definite", according to McDonald and Halliday's classification), twenty nine patients with Other Neurological Diseases (OND), thirty six patients with Inflammatory diseases (ID) and forty healthy controls were tested. MS patients were divided into two groups, depending on the clinical stage of the disease. The mean migration inhibition percentage of the MS-attack group was found to be significantly different from the four others (p less than 0.01) (24.4 +/- 16.2 versus 10.9 +/- 8.5 in MS without attack, 4.4 +/- 12.9 in OND, 3.9 +/- 13.9 in ID and 11.1 +/- 12.1 in healthy subjects). LMI to gangliosides is therefore significantly increased during the attack stage in MS. These results support the notion of a Delayed Type Hypersensitivity to these glycolipids during the active stage of the disease.

Adult↗
PubMed1990

Magnesium-deficient diet aggravates anaphylactic shock and promotes cardiac myolysis in guinea pigs.

Actively sensitized guinea pigs were rendered Mg(2+)-deficient for 2-3 weeks and then subjected to immune stress. No differences could be seen between treated and control groups prior to immune challenge. 1-2 h after antigen challenge, 95% of the Mg(2+)-deficient animals were observed to be anaphylactic, i.e. apathetic, dyspneic, and they had a rapid pulse rate. Only 4% of the control animals showed signs of anaphylaxis. Serum magnesium concentration, [Mg2+], fell from 1.32 +/- 0.07 mM in control guinea pigs to 0.56 +/- 0.04 mM in those fed an Mg(2+)-deficient diet. Cardiomyolysis (CM) developed in 19% of the anaphylactic animals and in 3% of the controls. We conclude that Mg(2+)-deficient animals continue to function, provided conditions are normal, but they are unable to withstand stress. The heart, however, appears to be better equipped to defend itself against Mg2+ deficiency and low serum [Mg2+], a supposition supported by the fact that heart [Mg2+] is not significantly reduced in hypomagnesemic guinea pigs (0.864 +/- 0.021 microgram/mg dry weight in control, and 0.834 +/- 0.062 microgram/mg dry weight in magnesium-deficient animals). The data indicate that hypomagnesemia heightens the intensity of the immune response, thereby exacerbating both anaphylactic shock (AS) and CM. A normal serum [Mg2+] would thus seem essential for protection against immune stress.

Anaphylaxis↗
PubMed1989

Transformation of normal human melanocytes and non-malignant nevus cells by adenovirus 12-SV40 hybrid virus.

Infection of normal human melanocyte and nevus cultures with an adenovirus 12-Simian Virus 40 hybrid virus (Ad12-SV40) produced transformed cells that expressed SV40-T antigen. The Ad12-SV40 cells exhibited rapid cell proliferation to high cell densities and efficient growth in soft agar, but none of 15 transformed melanocyte and nevus cultures formed tumors when injected s.c. or under the renal capsule into athymic nude mice. While the Ad12-SV40-transformed cells lost certain properties associated with the melanocytic phenotype, i.e., pigmentation, tyrosinase activity and melanosome content, the expression of melanoma-associated antigens, including nerve growth factor receptor, p97 melano-transferrin, and chondroitin sulfate proteoglycan, remained stable. The transformed melanocytes acquired the ability to express HLA-DR antigen, which is found on nevus and melanoma cells. Total ganglioside patterns in Ad12-SV40-transformed cells changed to reflect more advanced stages of tumor progression. Transformed melanocytes, like nevus and melanoma cells, showed increased GD3 content and transformed nevus cells increased GD2 which is a feature of malignant melanoma cells. Ad12-SV40-transformed human melanocytes and nevus cells are useful tools for studying tumor progression under experimental conditions.

Adenoviruses, Human↗
PubMed1989

Levels of disialogangliosides in sera of melanoma patients monitored by sensitive thin-layer chromatography and immunostaining.

Levels of GD2, GD3, and 9-O-acetyl GD3 were monitored in sera of patients with melanoma and healthy adults with two monoclonal antibodies that specifically detect these gangliosides. By direct measurement of radioactivity in the immunolabeled chromatogram, GD2 could be detected in normal sera at 2 ng/mL. Serum levels of GD2 and GD3 were increased approximately sixfold and fivefold, respectively, in patients with disseminated melanoma, compared with those of healthy adults. The acetylated derivative of GD3, which is highly specific for melanoma cells, was not detected in serum. This sensitive assay allows the quantitation of tumor-associated gangliosides that are circulating in sera of melanoma patients.

Adult↗
PubMed1989

Colon carcinoma-associated glycoproteins recognized by monoclonal antibodies CO-029 and GA22-2.

Two murine monoclonal antibodies (MAb) CO-029 and GA22-2 are described which reacted specifically with the human gastrointestinal tumor cell lines LS180 and SW1222, respectively. CO-029 specific antigen was found by immunoprecipitation and Western blotting to be a highly expressed protein consisting of a single polypeptide chain of 32kDa. The gastric tumor associated antigen GA22-2 was a 185kDa polypeptide which did not comigrate with the 180 kDa carcinoembryonic antigen (CEA), neither was it immunologically crossreactive with the latter. Both CO-029 and GA22-2 antigens were shown to be glycosylated by their retention on Sepharose-lectin columns. CO-029 was highly bound by wheat germ agglutinin indicating the accessibility of N-acetylglucosamine or N-acetyl-neuraminic acid residues. GA22-2 showed higher specificity to soybean agglutinin inferring the preferential accessibility of galactose or N-acetylgalactosamine-like residues on its saccharide moiety.

Animals↗
PubMed1989

Monoclonal antibodies with cytotoxic reactivities against human gliomas.

Monoclonal antibodies (MAb's) reactive with human malignant glioma cells were derived from mice inoculated with cells from fresh glioma tissue. Seven MAb's were selected for study based on their high-level binding in immunoperoxidase and immunofluorescence assay to most of the glioma tissues derived from various patients and based on the absence of binding to normal bone marrow cells. Four of the seven MAb's did not bind to any of the four normal brain tissues tested, whereas three MAb's bound to one or two of these tissues. Two MAb's bound to the surfaces of cultured glioma cells in radioimmunoassay. One of these MAb's (AS-AY1, immunoglobulin (Ig)(G1) lysed cultured glioma cells with human lymphocytes or murine macrophages as effector cells; the other MAb (AS-AY2, IgM) was reactive in complement-dependent cytotoxicity assay. These two MAb's therefore seem especially promising reagents in approaches to immunotherapy of human malignant glioma.

Antibodies, Monoclonal↗
PubMed1978

Antibodies to ganglioside GM1 induce mitogenic stimulation and cap formation in rat thymocytes.

Antibodies towards the ganglioside GM1 [galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosyglucosyl ceramide] stimulated DNA synthesis in rat thymocytes. No mitogenic stimulation was observed with the monomeric Fab fragment of anti-GM1, suggesting that cross-linking of the gangliosides or associated components was required for activation by these antibodies. Incubation of thymocytes with anti-GM1 and fluorescein-labeled anti-rabbit IgG at 0 degree C resulted in uniform ring-like or patchy staining that developed into a pronounced cap upon elevation of temperature. The cap had a characteristic uropod form, enriched with intracellular organelles. Sodium azide and cytochalasin B completely inhibited cap formation, while colchicine was without effect. These results imply a possible direct or indirect association between surface gangliosides and submembraneous cytoskeletal assemblies that control modulation of these surface components and may transmit stimuli to the interior of the cell.

Animals↗
PubMed1977

Isolation by cell-column chromatography of immunoglobulins specific for cell surface carbohydrates.

A new method of affinity chromatography using glutaraldehyde-fixed cells immobilized on Sephadex beads has been used to isolate immunoglobulins (Ig's) specific for cell surface glycoproteins. Ig's that specifically bound and agglutinated the same cells as those originally fixed on the columns were isolated from nonimmune sera of various species. Periodate treatment of the cell-columns and the free cells destroyed their ability to bind the Ig's, and the binding of the Ig's to untreated cells was inhibited by monosaccharides such as D-galactose and sialic acid. The binding of antibodies directed against cell surfaces obtained by immunizing animals with the same mouse tumor cell lines used on the columns (P388 and EL4) was not inhibited by various saccharides. Surface glycoproteins obtained from the mouse tumor cells by immunoprecipitation with the column-isolated Ig's yielded specific electrophoretic patterns that differed from those obtained using Ig's from the sera of rabbits immunized with the tumor cells. The data suggest that the Ig's isolated by cell-column chromatography were directed against carbohydrates, probably those in terminal positions of the polysaccharide portions of the tumor cell surface glycoproteins. Column-isolated Ig's specific for carbohydrates were also useful in studies of cell interactions in nonmammalian systems including Dictyostelium discoideum and Saccharomyces cerevisiae. The cell-column method appears to be adaptable to the isolation of a variety of molecules in addition to antibodies.

Agglutinins↗
PubMed1976

Lymphocyte activation by monovalent fragments of antibodies reactive with cell surface carbohydrates.

Antibodies reactive with cell surface carbohydrates were isolated from normal chicken serum and were found to be mitogenic for mouse splenic lymphocytes as assayed by both blast transformation and [3H]thymidine incorporation. The Fab' fragments of these carbohydrate-binding immunoglobulins were just as mitogenic as the divalent native antibody. Moreover, succinylated Fab' fragments, which probably would not form self-associating aggregates, showed similar mitogenic properties. All of these results indicate that, at least for saccharide-specific ligands, multipoint attachment and receptor cross-linkage on the cell to which the ligand is attached may not be a stringent requirement for activation.

Animals↗
PubMed1976

Mechanisms of adhesion among cells from neural tissues of the chick embryo.

In order to analyze the molecular mechanisms of cell adhesion during development, proteins on the surface of chick embryonic neural cells were compared with proteins released after placing these cells in culture. One of the components released into culture, F1 (molecular weight, Mr 140,000), was derived by proteolytic cleavage of a cell surface precursor with a molecular weight of at least 240,000. Another protein, F2, recovered from culture as a dimer (Mr 1110,000), appeared to be a product of limited proteolytic cleavage of F1. Cells in retinal tissue possessed a surface protein of Mr 150,000 that also appeared to be derived by limited proteolytic cleavage of the cell surface precursor. Antibodies to F2 interacted with determinants on the cell surface protein of Mr 150,000, and specifically prevented homologous and heterologous binding among dissociated retinal and brain cells. In contrast, antibodies to F1 failed to prevent cell-cell adhesion and did not crossreact with F2. These data suggest that the cell surface protein of Mr 150,000 generated by limited proteolysis is involved in adhesion of both retinal and brain cells. Cell-cell binding of both retinal and brain cells varied as a function of developmental age and brain cells acquired their binding properties at an earlier time than retinal cells. Similar results were obtained in experiments on the binding of retinal and brain cells of different ages to nylon fibres coated with antibodies to F2. The results of the molecular and cellular experiments are incorporated in a model for cell adhesion invoking both proteolytic activation and modulation of cell surface ligands.

Age Factors↗