Lymphocyte division has been the subject of many studies from the point of view of cellular immunology and antibody synthesis. Blast cell transformation and mitosis occur both in vitro and in vivo under stimulus from a number of agents which act on the cell surface, particularly in experimental situations by lectins (1).Although the sequence of events which connect the mitogenic stimulus to DNA synthesis is still incompletely known and several different cell types may be involved, a nmnber of preliminary changes have been recognized. Thus, for example, the cyclic AMP level in lymphocyte cultures rises within 2 rain of stimulation (2), membrane biosynthesis increases within 1/4 h of stimulation (3), nuclear template activity increases within 2 h (4). I t is of considerable importance to an understanding of the neoplastic change in lymphoid cells to know the extent to which such processes and factors controlling them are retained in replicating lymphoma cells, and the extent to which they are altered.We here report a comparison, between the effects of certain thiols and disulfides which we have found to be necessary for the growth of mouse lymphoma cells in vitro, and their effects in enhancing the action of mitogens on splenic lymphocytes.Our observations stem from the finding that mouse lymphoma cells of the line L1210 (V) which had previously been established in culture only with great difficulty (5), proliferate in a medium formulated by Balk (6). The specific growth promoting component of this medium was found to be its high concentration of added L-cysteine (1.5 mM) (7). As will be described, a number of thiols and disulfides can substitute for L-cysteine, some at very low concentration (to < 1 #M). Precise structure activity relationships exist. Furthermore, 13 of 23 other mouse leukemic and neoplastic lymphoid cell lines were also thiol-disulfide dependent in vitro.
Immunization with irradiated sporozoites produces a considerable degree of protection against rodent, simian, and human malaria. This protection is in part antibody mediated. Antibodies neutralize sporozoites (SNA), i.e., abolish their infectivity, and cause, in vitro, the formation of a thread-like precipitate on the parasites (CSP reaction). The present study was undertaken to characterize the ultrastructural aspects of antibody-sporozoite interaction. Gradient concentrated sporozoites of Plasmodium berghei and Plasmodium cynomolgi were incubated with immune and normal sera. Transmission electron microscopy revealed the presence of a prominent, thick coat surrounding the outer membrane of the sporozoites incubated in immune serum. The inner structure of these parasites appeared to be relatively unaltered. The coat was absent or minimal on parasites incubated in normal serum. Incubation of immune serum-pretreated sporozoites with rabbit anti-mouse γ-globulin conjugated with hemocyanin demonstrated the participation of immunglobulin in the formation of this surface deposition. Coat formation occurred also on the surface of metabolically inactive, non-secreting parasites such as formalin-treated sporozoites and parasites kept on ice. Metabolically inactive sporozoites failed, however, to produce a positive CSP reaction. Scanning electron microscopy and negative staining indicated that the anterior end of the parasites was free of coat deposition and that the thread-like precipitate (CSP) was located at the posterior end of the sporozoites.
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