Relation of lectin-induced and spontaneous adhesion to tumorigenicity.
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Animals↗
Biomedical subjects
T E Ukena
Publications and source records attributed to T E Ukena.
Diminished spectrin extraction from ATP-depleted human erythrocytes. Evidence relating spectrin to changes in erythrocyte shape and deformability.
We measured spectrin "extractability" in erythrocytes which were metabolically depleted by incubation at 37 degrees C in plasma or glucose-free buffers. Membranes were extracted with 1 mM EDTA (pH 8, 40 h, 4 degrees C) and analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. This procedure solubilized 85--90% of the spectrin, actin, and residual hemoglobin from ghosts of fresh erythrocytes. In incubated erythrocytes, inextractable spectrin rapidly accumulated when ATP concentrations fell below 0--15% of normal. In severely depleted cells, 60--90% of the total ghost spectrin became inextractable. Inextractability was not abolished by physically disrupting the ghost before extraction, but was reversed when erythrocyte ATP was replenished with adenosine. The accumulation of inextractable spectrin correlated temporally with the increase in apparent membrane deformability and the increases in erythrocyte vicosity, calcium content, sodium gain, and potassium loss characteristic of ATP-depleted erythrocytes. No change in integral membrane protein topography (assessed by the distribution of intramembranous particles and concanavalin A surface-binding sites) was detected in depleted cells. Analogous changes were observed in erythrocytes exposed to extremes of pH and temperature. When the pH in the erythrocyte interior fell below 5.5, a pH where spectrin was aggregated and isoelectrically precipitated, erythrocyte and ghost viscosity increased coincident with a marked decrease in spectrin extractability. Similarly above 49 degrees C, a temperature where spectrin was denatured and precipitated, erythrocyte viscosity rose as inextractable spectrin accumulated. These observations provide direct evidence of a change in the physical state of spectrin associated with a change in erythrocyte shape and deformability. They support the concept that erythrocyte shape and deformability are largely determined by the shape and deformability of the spectrin-actin protein meshwork which laminates the inner membrane surface.
Adenosine Triphosphate↗
Asymmetrical distribution of microvilli in cytochalasin B-induced pseudocleavage of mouse oocytes.
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Animals↗
The role of microvilli in the agglutination of cells by concanavalin A.
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Agglutination↗
Effects of db-cAMP and theophylline on Concanavalin A binding site distribution on transformed and protease-treated cell lines.
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Adenosine↗
Rates of aggregation, loss of anchorage dependence, and tumorigenicity of cultured cells.
The net rate of spontaneous aggregation of cells suspended with EDTA was measured for various cell types including spontaneous transformants and cells transformed with DNA and RNA viruses. The anchorage dependence as determined by growth in methyl cellulose and the tumorigenicity in vivo were also determined. All cells that had lost their anchorage dependency and were tumorigenic showed a high net rate of spontaneous adhesion. A31 was the only nontransformed cell line to have a high net rate of adhesion. The net rate of spontaneous aggregation of cells is a quick and reliable index of tumorigenicity and offers a new approach to understanding the mechanisms of cell surface changes associated with transformation.
Cell Adhesion↗
Cytochalasin B-induced pseudo-cleavage of mouse oocytes in vitro. II. Studies of the mechanism and morphological consequences of pseudocleavage.
Mouse oocytes are induced by cytochalasin B to undergo 'pseudocleavage' in vitro into 2 compartments, only one of which possesses microvilli. It has been found that this particular response to cytochalasin B is related to oocyte size and, possibly, to the acquisition of meiotic competence by the oocyte during its growth phase. Certain of the morphological events which characterize pseudocleavage have been determined using transmission and scanning electron microscopy. These events include: (i) an initial withdrawal of microvilli from the surface of the oocyte, together with the concomitant disappearance of microfilaments normally associated with the microvilli; (ii) the subsequent formation of a pseudocleavage furrow and contractile ring; and (iii) the reappearance of microvilli and associated microfilaments in one of the two resulting oocyte compartments. These changes in surface architecture are reflected in the distribution of fluorescein-conjugated lectins bound to the oocyte surface during pseudocleavage.
Animals↗
Lack of correlation between agglutinability, the surface distribution of con A and post-confluence inhibition of cell division in ten cell lines.
Agglutinability by concanavalin A, distribution of surface-bound concanavalin A, and maximal cell density in monolayer culture were examined under similar conditions in parallel cultures of ten established cell lines. The degree of agglutinability of the cell lines did not correlate with the presence or absence of patching of concanavalin A bound to the cell surface, as determined with a hemocyanin marker. Agglutinability was also not always correlated with the loss of post-confluence inhibition of cell division. Two clones of mouse 3T3 fibroblasts that maintained post-confluence inhibition of cell division and low agglutinability differed substantially with respect to the surface distribution of concanavalin A. Patching of concanavalin A binding sites is neither necessary nor sufficient to explain differences in agglutinability between cell lines.
Agglutination↗
Patching, microvilli, and the agglutination of normal and transformed cells.
Transmission and scanning electron microscopy were used to study possible structural correlates in the process of agglutination of several types of normal and transformed cells by Concanavalin A. In parallel studies we found that post-confluence inhibition of cell division and agglutiniability of cells by Concanavalin A were not correlated with patching of surface bound lectin molecules as determined with a hemocyanin marker. Transformed cells growing in monolayer cultures were found to have many more microvilli than the corresponding normal cells. However, when cells were brought into suspension with EDTA, all cells developed numerous microvilli and we were not able to distinguish between agglutinable and nonagglutinable cells on the basis of morphological appearance. Cells agglutinated by Concanavalin A had numerous interdigitated microvilli at points of cell-cell contact. The appearance of spontaneously agglutinated cells and lectin agglutinated cells was very similar with respect to the involvement of microvilli in cell-cell attachments, and labeling studies with hemocyanin indicated that Concanavalin A bound to microvilli is rapidly cleared from these surface specializations in a manner analogous to that observed with patching of surface bound lectin. Several lines of SV-40 transformed fibroblasts were shown to be considerably more spontaneously agglutinable than untransformed cells. These results indicate that Concanavalin A may amplify an intrinsic membrane property common to many transformed cells that is expressed as an increase in the rate of adhesion of suspended cells. It is proposed that the membrane change detected by the agglutination reaction may also be involved in the loss of post-confluence inhibition of cell division and growth of transformed cells in semisolid media, due to a surface interaction that allows transformed cells to use each other as growth substrata.
Agglutination↗