Specific inhibition of cell contact formation in Dictyostelium by univalent antibodies.
TL;DR: It is concluded that F ab must be bound to specific sites on the cell surface in order to inhibit cell contact formation, and species specificity and increased activity during cell transformation from growth to aggregation competence are in accord with a function as aggregation-mediating factors.
About: This article is published in Experimental Cell Research.The article was published on 1970-11-01. It has received 203 citations till now. The article focuses on the topics: Dictyostelium discoideum.
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TL;DR: Fab fragments of rabbit anti-embryonal carcinoma cells IgG dramatically perturb cell-cell interactions between embryonal carcinomas cells and between early mouse embryo blastomeres to prevent compaction of preimplantation embryos.
397 citations
TL;DR: Using a quantitative technique for measuring cell association, two classes of target sites for blocking antibodies were distinguished and their developmental dynamics studied, indicating that in one cell, two independent classes of contact sites can be simultaneously active.
Abstract: Membrane interaction in aggregating cells of Dictyostelium discoideum can be blocked by univalent antibodies directed against specific membrane sites. Using a quantitative technique for measuring cell association, two classes of target sites for blocking antibodies were distinguished and their developmental dynamics studied. One class of these sites is specific for aggregation-competent cells, their quantity rising from virtually 0-level during growth, with a steep increase shortly before cell aggregation. The serological activity of these structures is species specific; they are not detectable in a nonaggregating mutant, but present in a revertant undergoing normal morphogenesis. Patterns of cell assembly in the presence of antibodies show that selective blockage of these membrane sites abolishes the preference for end-to-end association which is typical for aggregating cells. A second class of target sites is present in comparable quantities in particle fractions from both growth-phase and aggregation-competent cells. Blockage of these sites leads to aggregation patterns in which the side-by-side contacts of aggregating cells are abolished. The target sites of aggregation-inhibiting antibodies are suggested to be identical or associated with the molecular units of the cell membrane that mediate cell-to-cell contacts during aggregation. The results indicate that in one cell, two independent classes of contact sites can be simultaneously active.
366 citations
TL;DR: During the acquisition of aggregation competence a new antigen appears on the surface of Dictyostelium cells andivalent antibody fragments against this antigen render the cells unable to form the specific type of cell adhesion which is characteristic of aggregating cells.
Abstract: During the acquisition of aggregation competence a new antigen appears on the surface of Dictyostelium cells. Univalent antibody fragments (Fab) against this antigen render the cells unable to form the specific type of cell adhesion which is characteristic of aggregating cells. This membrane constituent has been purified and identified as a concanavalin A-binding glycoprotein present at about 2 X 10(5) copies per cell.
289 citations
TL;DR: A carbohydrate-binding protein assayed by its ability to agglutinate formalinized sheep erythrocytes is synthesized between 3 and 9 hours after Dictyostelium discoideum cells are deprived of food, as the cells become cohesive as discussed by the authors.
Abstract: A carbohydrate-binding protein assayed by its ability to agglutinate formalinized sheep erythrocytes is synthesized between 3 and 9 hr after Dictyostelium discoideum cells are deprived of food, as the cells become cohesive. Agglutination of erythrocytes by this protein was inhibited by N-acetyl-D-galactosamine, D-galactose, and L-fucose, but other monosaccharides had little or no effect. The protein bound completely to Sepharose 4B, and was isolated in highly purified form by elution with D-galactose. It appears to be present on the surface of cohesive but not vegetative slime-mold cells. The possibility that this protein may mediate intercellular adhesion in Dictyostelium is considered.
225 citations
TL;DR: Aggregating cells of the cellular slime mold, Dictyostelium discoideum, are guided by an intercellular signal system comprising chemotaxis, cell contact formation and transmission of periodic stimuli from cell to cell.
Abstract: Aggregating cells of the cellular slime mold, Dictyostelium discoideum, are guided by an intercellular signal system comprising chemotaxis, cell contact formation and transmission of periodic stimuli from cell to cell. This has been studied as a model system for morphogenetic cell interactions in which spatial patterns are formed by self-organization, starting from a homogeneous layer of essentially identical cells.
140 citations
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2,201 citations
TL;DR: A closer look is taken at relations and activities in growth and development which are commonly described as "specific," and to what extent their specific character might be explicable in terms of better known and better understood specificities at other biological, or preferably simpler physical and chemical, levels.
Abstract: The frequency with which such terms as specificity, selectivity, conformity, correspondence, etc., appear in biological literature is ample proof that they denote a universal and fundamental trait, running like -a common theme through all manifestations of life. Yet, they are used with so many different shades of meaning and degrees of precision that it is impossible to tell whether the various phenomena to which they are applied bear a purely formal resemblance to each other or whether there is essentially a single principle in back of them all. A random list of examples will illustrate the case. We describe as \"specific\" the absorption by certain compounds of certain wave lengths of light; the relation between enzymes and their substrata; the matching between egg and sperm; the action of a hormone on its end organ; the effect of genes on characters of development; the association between a parasite and its host; the immunological response to a foreign protein; the adequate response of our nervous system to a given stimulus; the acts of recognition and evaluation, which characterize our highest mental functions. What do these various \"specificities\" have in common? Are they merely superficial parallels, or does one or the other of them perhaps contain the key to the rest so that specificity in all manifestations of life could be resolved to a single operative principle? It may be too early to attempt an answer to this question, but it does not seem too early to ask it. Therefore, let us take a closer look at relations and activities in growth and development which we commonly describe as \"specific,\" and examine to what extent their specific character might be explicable in terms of better known and better understood specificities at other biological, or preferably simpler physical and chemical, levels. In particular, let us explore the
348 citations
TL;DR: In this paper, the role of cyclic-AMP in normal development of an acrasin (cyclicAMP) and the sensitivity to acrasins in the cellular slime mold Dictyostelium discoideum was examined.
269 citations
TL;DR: Evidence is presented for the existence of specific factors associated with the cell surface and intercellular spaces which function as cell ligands and mediate histogenetic attachment and aggregation of sponge cells and in relation to the ECM hypothesis.
251 citations