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Biomedical subjects

U Rutishauser

Publications and source records attributed to U Rutishauser.

At least 127 records · Page 7Linked to original sources
PubMed1975

Cell-to-cell binding induced by different lectins.

The cell-to-cell binding induced by concanavalin A (Con A) and the lectins from wheatgerm, soybean, and waxbean has been analyzed by measuring the ability of single cells to bind to lectin-coated cells immobilized on nylon fibers. The cells used were lymphoma, myeloid leukemia, and normal fibroblast cells. With all lectins, cell-to-cell binding was inhibited if both cells were prefixed with glutaraldehyde. However, in most cases cell-to-cell binding was enhanced when only the lectin-coated cell was prefixed. With normal fibroblasts, treatment of either one or both cells with trypsin enhanced the cell-to-cell binding induced by Con A and the wheatgerm lectin. Neuraminidase, which increases the number of receptors for soybean agglutinin, increased cell-to-cell binding only if both cells were treated. Although cell-to-cell binding induced by the lectins from soybean and wheatgerm could be partially reversed by the appropriate competitive saccharide inhibitor, binding induced by Con A could not be reversed. The experiments indicate that cell-to-cell binding induced by a lectin can be prevented by an insufficient density of receptors for the lectin, insufficient receptor mobility, or induced clustering of receptors. These effects can explain the differences in cell-to-cell binding and agglutination observed with different cell types and lectins. They also suggest that cell-to-cell binding induced by different lectins with a variety of cell types is initiated by a mechanism involving the alignment of complementary receptors on the colliding cells for the formation of multiple cell-to-lectin-to-cell bridges.

Agglutination↗
PubMed1975

Receptor mobility and the binding of cells to lectin-coated fibers.

The ability of cells to bind to nylon fibers coated with lectin molecules interspaced with varying numbers of albumin molecules has been analyzed. The cells used were lymphoma cells, normal lymphocytes, myeloid leukemia cells, and normal and transformed fibroblasts, and the fibers were coated with different densities of concanavalin A or the lectins from soybean or wheat germ. Cells fixed with glutaraldehyde did not bind to lectin-coated fibers. The number of cells bound to fibers could be increased by increasing the density of lectin molecules on the fiber, the density of specific receptors on the cell, or the mobility of the receptors. It is suggested that binding of cells to fibers involves alignment and binding of specific cell surface receptors with lectin molecules immobilized on the fibers, and that this alignment requires short-range rapid lateral mobility (RLM) of the receptors. The titration of cell binding to fibers coated with different densities of lectin and albumin has been used to measure the relative RLM of unoccupied cell surface receptors for the lectin. The results indicate a relationship of RLM to lectin-induced cell-to-cell binding. The RLM or receptors for concanavalin A (Con A) was generally found to be higher than that of receptors for the lectins from wheat germ or soybean. Receptor RLM could be decreased by use of metabolic inhibitors or by lowering the temperature. Receptors for Con A had a lower RLM on normal fibroblasts than on SV40-transformed fibroblasts, and trypsinization of normal fibroblasts increased Con A receptor RLM. Normal lymphocytes, lymphoma cells, and lines of myeloid leukemia cells that can be induced to differentiate had a high receptor RLM, whereas lines of myeloid leukemia cells that could not be induced to differentiate had a low receptor RLM. These results suggest that the RLM of Con A receptors is related to the transformation of fibroblasts and the ability of myeloid leukemia cells to undergo differentiation

Animals↗
PubMed1974

Morphology, motility, and surface behavior of lymphocytes bound to nylon fibers.

Mouse B lymphocytes that were specifically bound to dinitrophenylated bovine serum albumin on nylon fibers exhibited continuous morphological changes, whereas bound T lymphocytes remained more or less spherical. Cinematomicrographic studies showed that the shape changes were associated with local and global movements, although the attached cells did not translocate along the fiber. Cap formation induced by anti-immunoglobulin was always found to be opposite to the point of attachment. The movements and the shape changes were prevented by cytochalasin B and colchicine. Treatment with these agents did not prevent cap formation but led to randomization of the position of the caps with respect to the fiber. Exposure to concanavalin A or attachment of cells to concanavalin A fibers prevented both movement and patch and cap formation, suggesting that cellular structures regulating the mobility of various receptors are altered by binding to concanavalin A fibers. These observations also indicate that interactions of local areas of the lymphocyte surface with certain ligands and substrates can strongly affect the movement and morphology of the entire cell.

Animals↗
PubMed1974

Receptor mobility and the mechanism of cell-cell binding induced by concanavalin A.

The cell-cell binding induced by concanavalin A between single cells has been analyzed by use of cells attached to nylon fibers. Binding of a concanavalin A-coated cell to an untreated cell was found to a high degree between two lymphoma tumor cells, less frequently between a lymphoma cell and a normal lymphocyte, and only rarely between two normal lymphocytes. The binding was inhibited by the presence of a saccharide inhibitor of concanavalin A, but could not be reversed by addition of the inhibitor after the cells had bound to each other. Although no binding was obtained when both cells were coated with lectin or fixed with glutaraldehyde, fixation of a cell before coating with concanavalin A enhanced its ability to bind an untreated cell. The results indicate that cell-cell binding induced by concanavalin A requires short-range lateral movement of cell receptors for the lectin, that only one cell has to have mobile receptors, and that some receptors must be unoccupied by lectin molecules before cell-cell contact. Clustering of the receptors is not necessary and seems to hinder cell-cell binding. It is suggested that the short-range movement is required for alignment of individual receptors so as to form multi-point bridges between two cells by lectin molecules. The bridging is then followed by the formation of irreversible bonds between the cells. The receptors on tumor cells appear to have a greater ability than receptors on normal cells to align themselves for cell-cell binding.

Agglutination↗
PubMed1973

Characterization of splenic lymphoid cells in fetal and newborn mice.

In order to clarify the cellular events that precede the onset of immunological competence in the mouse, we have characterized and quantitated the lymphoid cells of the spleen as a function of age. Our results show that T cells and B cells both appeared in the spleens of Swiss-L mice as early as the 15th-16th day of gestation. Antigen-binding cells specific for each of three different antigens were also first detected during this same 24 h interval. The B cells and three varieties of antigen-binding cells increased in number rapidly and in parallel until about 1 wk after birth. The T cells, which were more numerous than B cells at first, increased in number somewhat more slowly. Coincident with the onset of response to antigen, there was a further increase in B cell numbers and a decrease in the T cell to B cell ratio. The capacity to respond to antigen by cellular proliferation and synthesis of antibody did not arise until about 2 wk after birth although there were no quantitative changes in the total numbers of T cells, B cells, and antigen-binding cells between 1 and 2 wk of age. Some qualitative change, such as the functional maturation of an antigen-reactive cell, may be required during this interval for the onset of this immunological response. Although the numbers of antigen-binding cells present in fetuses and young animals were smaller than in adults, we have as yet been unable to detect any restriction in the variety of specificities that can be expressed in fetuses, either in the kinds of antigens bound or in the range of avidities with which a single antigen is bound.

Age Factors↗
PubMed1973

Immunological functions of lymphocytes fractionated with antigen-derivatized fibers.

Specific antigen-binding cells from spleens of immune and nonimmune mice were isolated by the method of fiber fractionation. After removal from the fibers, these cells were assayed for their viability, their ability to rebind to fibers of the same specificity, and their in vivo response to the antigen after transfer to syngeneic irradiated recipients. These experiments indicate that the fiber method yields highly enriched populations of specific antigen-binding cells that are viable and include antigen-sensitive bone marrow-derived cells capable of undergoing mitosis and differentiating into antibody-secreting cells.

Animals↗
PubMed1972

Binding of thymus- and bone marrow-derived lymphoid cells to antigen-derivatized fibers.

Thymus-derived lymphocytes (T cells) and bone marrow-derived lymphocytes (B cells) from mouse spleens bind specifically to antigen-derivatized nylon fibers. The fiber-bound population consisted of about 60%-70% B cells and 30% T cells as determined by cytotoxicity, fluorescence, and antibody-complement binding assays. Essentially all fiber-bound cells were viable and could be accounted for as T or B cells. Enriched populations of T or B cells could be isolated on the fibers by destruction of one or the other cell type with the appropriate antiserum plus complement. T or B cells could also be fractionated according to their relative affinity (or avidity) for a given antigen.

Animals↗
PubMed1972

Specific fractionation of immune cell populations.

Antigen-binding cells from spleens of immune and nonimmune mice were isolated by the method of fiber fractionation. Binding of the lymphoid cells to derivatives of nylon fibers made with various antigens was prevented by the presence of the respective free antigen, as well as by antibodies to mouse immunoglobulins. Antigen-binding cells specific for dinitrophenyl groups were separated from direct and indirect plaque-forming cells of the same specificity. Spleen cells from immune and nonimmune animals were fractionated according to their relative affinities for antigen, and the percentage of antigen-binding cells in the spleens of nonimmune animals was estimated. A comparison of the numbers and relative affinities of immunoglobulin receptors of immune and nonimmune populations indicated that after immunization only those antigen-binding cells of higher affinities were increased in number. This finding suggests that the specificity of clonal selection depends not only upon the binding of antigen to a lymphoid cell but also upon the capacity of that cell to be triggered to mature and replicate.

Animals↗
PubMed1971

Cell fractionation and arrangement on fibers, beads, and surfaces.

A new method, fiber fractionation, has been used to isolate and separate cells. The cells are adsorbed to fibers covalently coupled to molecules such as antigens, antibodies, and lectins which can bind specifically to cell-surface components. The cells are then removed mechanically by plucking the taut fibers. Alternatively, competitive inhibitors of binding may be used to remove the cells at a lesser rate. Successful fractionations have been achieved by varying the degree of derivatization of the fibers by the lectin concanavalin A. Lymphoid cells have been separated by the use of different antigens coupled to the fibers. The method may also be used for specific fixation and manipulation of viable cell populations in culture. In addition to fibers, beads and surfaces have been specifically derivatized and used to achieve different geometrical arrangements of the cells.

Animals↗
PubMed1969

The covalent structure of an entire gammaG immunoglobulin molecule.

The complete amino acid sequence of a human gammaG1 immunoglobulin (Eu) has been determined and the arrangement of all of the disulfide bonds has been established. Comparison of the sequence with that of another myeloma protein (He) suggests that the variable regions of heavy and light chains are homologous and similar in length. The constant portion of the heavy chain contains three homology regions each of which is similar in size and homologous to the constant region of the light chain. Each variable region and each constant homology region contains one intrachain disulfide bond. The half-cystines participating in the interchain bonds are all clustered within a stretch of ten residues at the middle of the heavy chains.These data support the hypothesis that immunoglobulins evolved by gene duplication after early divergence of V genes, which specified antigen-binding functions, and C genes, which specified other functions of antibody molecules. Each polypeptide chain may therefore be specified by two genes, V and C, which are fused to form a single gene (translocation hypothesis). The internal homologies and symmetry of the molecule suggest that homology regions may have similar three-dimensional structures each consisting of a compact domain which contributes to at least one active site (domain hypothesis). Both hypotheses are in accord with the linear regional differential of function in antibody molecules.

Amino Acid Sequence↗
PubMed1969

Subgroups of amino acid sequences in the variable regions of immunoglobulin heavy chains.

The amino acid sequence of the first 133 residues of the heavy (gamma) chain from a human gammaG immunoglobulin (He) has been determined. This gamma-chain is identical in Gm type to that of protein Eu, the complete sequence of which has been reported. Comparison of the two sequences substantiates the previous suggestion that there are subgroups of variable regions of heavy chains. The variable region of Eu has been assigned to subgroup I and that of He to subgroup II; on the other hand, the constant regions of the two proteins appear to be identical. Comparison of the sequence of the heavy chain of He with the heavy chain sequences determined in other laboratories suggests that the variable region of subgroup II is at least 118 residues long. The nature and distribution of amino acid variations in this heavy chain subgroup resemble those observed in light chain subgroups. These studies provide evidence that the translocation hypothesis applies to heavy as well as to light chains, viz., genes for variable regions (V) are somatically translocated to genes for constant regions (C) to form complete VC structural genes.

Amino Acid Sequence↗
PubMedDate not supplied

Topological distribution of different forms of neural cell adhesion molecule in the developing chick visual system.

The cell adhesion molecule isolated from neural tissue (N-CAM) is a membrane glycoprotein which is directly involved in calcium-independent adhesion among nerve cells and their processes (for review see refs 1,2). N-CAM has an unusual carbohydrate moiety containing a large and variable amount of sialic acid, the variation reflecting both the type of tissue and its developmental age. N-CAM is believed to be a ligand in the formation of cell-cell bonds and a decrease in sialic acid content from 30% to 10% is associated with a marked enhancement of the molecule's binding activity. Antibodies to N-CAM block its function and inhibit or alter bundling of nerve fibres, retinal cell development and nerve-muscle interaction. Here we use micro-gel electrophoresis to compare N-CAM from several parts of the developing chick visual system. The results indicate that N-CAM from the retina of 5-10-day-old embryos already exists in a relatively sialic acid-poor form, whereas the tectum and optic nerve beyond the eye contain sialic acid-rich N-CAM until much later in development. These studies suggest that the perikaryon and proximal axon shaft of retinoganglion cells have N-CAM with a lower sialic acid content than the distal portion of the axons, and that resulting differences in neurite adhesivity may be an important factor in the formation of the optic system.

Animals↗