Concentrations Of Concanavalin Research Articles

Surface morphology and agglutination of lectin-treated human lymphocytes and lymphoblasts.

Two human lymphoblasts (Raji and EB3) and normal human peripheral lymphocytes were exposed to different concentrations of Concanavalin A and wheat germ agglutinin. The lectin-induced agglutination was determined and correlated with lectin-induced changes in the surface morphology of these cells as studied in a scanning electron microscope. Whenever the lectin induced high agglutinability in a cell type, it also invariably had a smoothing effect on the cell surface. In contrast, when cells did not agglutinate well with a certain lectin, their cell surface remained essentially rough (villous) after addition of the lectin. The correlation found between increased agglutinability and altered cell surface morphology upon treatment with certain lectins suggests that both phenomena result from one and the same process. Additional evidence for this postulate is presented.

Receptor Mobility and its Cooperative Restriction by Ligands

The functional significance of membrane fluidity and receptor mobility in lymphoid cells has been studied in the recent literature. Although far from clarified, the role of membrane fluidity in achieving control over cell activity is probably important; it allows cooperative interactions over long distances. Here, the emphasis is put on the phenomenon of restriction of receptor mobility by ligands such as Concanavalin A, a phenomenon discovered in recent years using morphological techniques. We discuss in some detail our own approach for studying this phenomenon. This consists of quantitatively measuring the active sites on cell-bound lectin molecules by subsequent fixation of horse-radish peroxidase. This study has shown a cooperative binding of Concanavalin A to cells which corresponds to a modification of the membrane, leading to the recruitment of new receptors. The existence of a post-binding event, that we have called micro-redistribution, has been shown at 4 degrees C, through the use of peroxidase binding to cell-bound lectin. A cooperative restriction of receptor microredistribution is observed when the cooperative recruitment of receptors induced by increasing concentrations of Concanavalin A occurs. Both phenomena were shown to be modulated by drugs such as colchicine and cytochalasin B. The characteristics of this modulation suggest that density and distribution of receptors are dependent upon the state of a multimeric submembrane structure which is still functional at 4 degrees C.

Kinetics of Insulin-Stimulated Accumulation of Glucose by Heart Cells from Newborn Rats

Cells isolated from the hearts of newborn (1-day-old) rat accumulate <sup>14</sup>C-glucose. Insulin stimulates glucose accumulation by the heart cells. Values for net accumulation of glucose by heart cells agree well with those values obtained earlier using whole hearts. Lineweaver-Burk plots of initial rates of glucose accumulation at different concentrations of glucose show that the effect of insulin is to increase the V<sub>max</sub>. It is concluded that the effect of insulin is to increase the rate of glucose accumulation rather than to alter the concentration of glucose required to half-saturate the system. Glucose accumulation is also stimulated by mild trypsin digestion of the cells. Increasing concentrations of concanavalin A inhibit glucose accumulation.

Suppression of the in vitro secondary antibody response of rabbit lymphoid cells by Concanavalin A.

The effect of various concentrations of concanavalin A (Con A) on the in vitro secondary antibody response of rabbit lymph node and spleen cells to sheep red blood cells (SRBC) was studied. Complete suppression of the IgM plaque-forming cell (PFC) response of both lymph node and spleen cultures was observed when 10 mug/ml of Con A was added at the time of initiation of the cultures whereas only partial suppression was observed when 1 mug/ml of Con A was added. Moreover, marked suppression of the immune responses of both spleen and lymph node cultures was observed when 10 mug/ml of Con A was added at 24 hr after antigenic challenge and to a lesser extent when added at 48 hr. Suppression of the IgM PFC response was also detected when spleen cultures were exposed to 10 mug/ml of Con A for as little as 2 hr after antigenic challenge. However, substantial increases in DNA synthesis were observed only in those cultures which were in contact with Con A for at least 24 hr. Finally evidence is presented that the Con A-induced suppression is mediated by a soluble substance(s).

Study of the growth regulation of preimplantation mouse embryos using concanavalin A.

SummaryUnfertilized eggs and preimplantation mouse embryos had the same binding capacity for Concanavalin A. Concanavalin A in doses of 10 μg/ml agglutinated preimplantation embryos and the embryos derived from parthenogenetically stimulated eggs, but did not agglutinate unfertilized eggs. Unfertilized eggs became agglutinable with Concanavalin A in doses of 10 μg/ml after prolonged pretreatment with pronase or if the concentration of Concanavalin A was raised to 2000 μg/ml. The presence of 50 μg/ml of Concanavalin A in the medium inhibited development of preimplantation mouse embryos. Inhibition of growth was partially reversible after treatment of Concanavalin A-treated embryos with methyl-α-D-mannopyranose.We are grateful to Dr. Max M. Burger for helpful consultation, Dr. Christopher Graham for providing parthenogenetically stimulated eggs, and Mrs. Marguerite Solomon for excellent technical assistance.

A Quantitative Assay for Concanavalin A-mediated Cell Agglutination

SUMMARY A quantitative method was developed for measuring cell agglutination by the plant lectin, concanavalin A. The method, based on an assay for intercellular adhesion, determines the concanavalin A-stimulated rate of attachment of single cells to a cell layer. The rate depended on the number of single cells and the concentration of concanavalin A. Experiments on concanavalin A agglutinability of mouse BALB/c 3T3 cells agreed qualitatively with observations obtained with a visual method presently in use. For example, the concanavalin A-stimulated rate was low when EDTA was used to prepare the single cells, high when trypsin-dispersed cells were employed, and highest when the latter cells were assayed with trypsin-treated cell layers. The latter result was not explicable in terms of concanavalin A binding to the cell layer, since the same quantities of labeled lectin attached to untreated and to trypsin-treated cell layers. Concanavalin A attached to an untreated cell layer in such a manner that it retained high binding activity toward surface receptors on trypsin-treated single cells. Above a threshold density of concanavalin A bound to the cell layer, the stimulation of single cell attachment to the layer was directly proportional to the amount of concanavalin A bound to the layer. The concanavalin A-stimulated rate of attachment was specifically inhibited by methyl a-D-mannopyranoside. However, once single cells were attached to the cell layer in the presence of concanavalin A, they were not released by methyl a-mannoside. Agglutination is considered to be more complex than the simple binding of cells together through lectin bridges.

Changes in the binding of concanavalin A and wheat germ agglutinin to human lymphocytes during [formula omitted] transformation

Concanavalin A binds to human circulating lymphocytes in a complex manner suggesting the presence of multiple binding sites. Saturation of one or more of these binding sites is observed at concentrations of concanavalin A which induce blast transformation in lymphocytes. In contrast, only one saturable binding site is observed for wheat germ agglutinin. During in vitro transformation, the amount of concanavalin A which can be bound by lymphocytes increases, whereas the amount of wheat germ agglutinin which can be bound remains unchanged. Since the size increases during transformation, there must be a fall in the density of surface receptors for wheat germ agglutinin whereas the density of concanavalin A receptors remains unchanged.

Syngeneic immune serum specifically inhibits the motility of tumour cells.

TUMOUR cells, both animal and human, are actively motile in tissue culture1,2. Simple techniques have recently become available for the quantitation of this motility3,4 and Friberg et al.3 have shown that the motility of mouse lymphoma cells can be inhibited by a concentration of concanavalin A below that which causes agglutination.