Effect of Colchicine and Vinblastine on the Agglutination of Polymorphonuclear Leucocytes by Concanavalin A

IT is generally accepted that microtubules serve as supportive elements within cell structures such as the mitotic spindle and a role for microtubules in the mechanical stabilization of cell surfaces was suggested by the microcinematographic experiments of Vasiliev, Gelfand et al.¹. On contact, surfaces lost their ruffled movement and this immobilization could be abolished by colcemid which, like colchicine and vinblastine, binds to and dissolves microtubules. We tested the possibility that microtubular proteins might also determine or maintain the topographical organization of surface elements in several functional systems in which this is believed important.     

Thermotropic Properties of Cellular Membranes in Dormant and Non-Dormant Echinochloa crus-galli(L.) Beauv. Seeds

Steady-state fluorescence polarization measurements with l,6-diphenyl-l,3,5-hexatriene(DPH) were used to monitor thermotropic transitions in microsomalfractions and plasma membrane vesicles isolated from barnyardgrass[Echinochloa crus-galli (L.) Beauv.] seeds during the transititionfrom dormancy to germination. The effect of dormancy-relievingor inactive alcohols on the thermotropic properties of the cellularmembranes was determined both in vivo and in vitro. Membranefractions isolated from dormant seeds showed some discontinuitiesin the Arrhenius plots. In non-dormant or germinating seedscellular membranes showed linear Arrhenius plots over the entirerange of temperature examined. Membrane preparations from imbibedseeds showed a similar pattern in their Arrhenius plots upontreatment with the various alcohols in vitro. The results suggestthat the release from dormancy in seeds is associated with somechanges in their cellular membranes. Key words: Germination, alcohols, thermotropic transition     

Effect of Concanavalin A on Phagocytosis

Concanavalin A has been shown to inhibit phagocytosis by polymorphonuclear leucocytes. The effect is reversed by specific sugars.