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L Sachs

Publications and source records attributed to L Sachs.

At least 289 records · Page 16Linked to original sources
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↗
PubMed1974

Different blocks in the differentiation of myeloid leukemic cells.

Some clones of mouse myeloid leukemic cells (D(+)) can be induced to undergo cell differentiation to mature macrophages and granulocytes, and other clones (D(-)) could not be induced to differentiate to mature cells. Normal mature macrophages and granulocytes have surface receptors that form rosettes with erythrocytes coated with specific immunoglobulin or immunoglobulin-complement. The D(+) clones were induced to form receptors by prednisolone, cytosine-arabinoside, 5-iododeoxyuridine, actinomycin D, or serum from mice injected with endotoxin. All these compounds thus induced a common change in the cell surface membrane. The induction of receptors required protein synthesis, and receptors were formed before the appearance of mature cells. There were two types of D(-) clones. One type was induced by these compounds to form receptors, although with a lower inducibility than D(+) clones; in the other type there was no induction of receptors. The results indicate that there are different blocks in the differentiation of myeloid leukemic cells. Some leukemic cells (IR(+)D(+)) can be induced to form receptors and to differentiate to mature cells; others (IR(+)D(-)) can form receptors but not mature cells; and a third type (IR(-)D(-)) could not be induced to form receptors or mature cells.

Animals↗
PubMed1974

Formation of bone tissue in culture from isolated bone cells.

A system is described for the formation of bone tissue in culture from isolated rat bone cells. The isolated bone cells were obtained from embryonic rat calvarium and periosteum or from traumatized, lifted periosteum of young rats. The cells were cultured for a period of up to 8 wk, during which time the morphological, biochemical, and functional properties of the cultures were studied. Formation of bone tissue by these isolated bone cells was shown, in that the cells demonstrated osteoblastic morphology in light and electron microscopy, the collagen formed was similar to bone collagen, there was mineralization specific for bone, and the cells reacted to the hormone calcitonin by increased calcium ion uptake. Calcification of the fine structure of the cells and the matrix is described. Three stages in the calcification process were observed by electron microscopy. It is concluded that these bone cells growing in vitro are able to function in a way similar to such cells in vivo. This tissue culture system starting from isolated bone cells is therefore suitable for studies on the structure and function of bone.

Alkaline Phosphatase↗
PubMed1974

Surface membrane glycopeptides which coincide with virus transformation and tumorigenesis.

Glycopeptides from the surface of clones of hamster embryo cells were examined at various intervals after infection with polyoma virus. Two types of transformed cells were examined: (i) clones that showed delayed transformation or an initially low tumorigenicity, and (ii) clones that were rapidly transformed showing an initially high tumorigenicity. The glycopeptides were removed from the cell surface by trypsin and, after Pronase digestion, were examined by filtration through Sephadex G-50. With delayed transformation, a specific group of glycopeptides was increasingly evident over an 85-day period as the cells showed phenotypic properties of transformation and the ability to form tumors. In the other series, all but one clone of hamster embryo cells showed rapid transformation after infection with polyoma virus. This clone was less tumorigenic and showed little of the specific glycopeptides. In all cases of delayed or rapid transformation examined, the specific group of glycopeptides increased proportionately to the ability of the cells to form tumors. All of the cells derived from progressively growing tumors formed by injection of these transformed hamster cells into adult animals showed an abundance of this group of glycopeptides. These results suggest that specific surface membrane glycopeptides accompany viral transformation and tumorigenesis.

Animals↗
PubMed1974

Papovaviridae.

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Animals↗