Alteration in lysosome supravital staining as a marker of hydroxyurea-induced cytotoxicity and its modification by radical scavengers in L5178Y cells in culture.

Supravital staining of lysosomal membranes with euchrysine was employed to study hydroxyurea (HU)-induced side toxic effects in L5178Y lymphoblasts in culture. Exposure of cells to 0.1-1.0-10.0 mM HU-induced progressive increase in the proportion of cells without detectable lysosomal fluorescence. This effect preceded the occurrence of non-viable cells, determined by trypan-blue exclusion test. Addition of alpha-tocopherol, acetylsalicylic acid, sodium benzoate or ascorbic acid to the culture medium afforded a concentration-dependent modification of lysosomal response to HU treatment. It is suggested that the fluorescence technique of supravital lysosome staining can be a useful test in studies on the side toxic effects of free radical-forming drugs and their amelioration by radical scavengers.

Antigenic variation in cancer metastasis: immune escape versus immune control.

Antigenic variation in cancer metastasis was observed in a syngeneic murine tumor system consisting of a low metastatic parental tumor line (derived from a methylcholanthrene-induced DBA/2 T lymphoma, Eb), a high metastatic spontaneous variant thereof (ESb), and a low metastatic 'revertant' from ESb (ESb-M). All three lines expressed tumor-associated transplantation antigens (TATA) which elicited specific T cell-mediated antitumor immune reactions in the host. The strongest host response was elicited upon intradermal inoculation. It could be followed by (a) the infiltration of the locally growing tumor by host cells, such as lymphocytes and macrophages, (b) the establishment of specific systemic antitumor immunity, (c) the generation of immune cells capable of transferring protective antitumor immunity into a normal syngeneic recipient, and (d) the generation of tumor specific cytotoxic T lymphocytes (CTL). Anti-TATA CTL were used as typing reagents to investigate the stability or variability in the TATA expression by cloned tumor cell lines. Antigenic variability in the TATA expression was seen under various conditions: (a) clone-dependent variation in the sensitivity to anti-TATA CTL lysis upon prolonged growth in tissue culture, (b) qualitative change in the TATA (TATA1 leads to TATA2) upon successive i.p. transplantation of the parental Eb tumor line and, (c) generation of TATA negative immune escape variants (TATA2 leads to TATA-) during metastasis formation from a s.c. site. The relative inefficiency of specific immunization procedures against ESb was found to be due to the effective generation of TATA negative variants by this highly metastatic tumor. The balance between immune control and immune escape could be influenced to the advantage of the host by some means, for instance optimizing the route of antitumor-immune sensitization or by infusion of allogeneic but H-2 identical antitumor-immune T cells. Such immune cells recognized the tumor via minor histocompatibility antigens and thus circumvented the need of TATA recognition. Finally, manipulations at the cell surface of the highly malignant ESb tumor such as those introduced in the ESb-M variant were found to dramatically effect its metastatic potential.

Chromatin changes in apoptosis.

Murine lymphoid cell lines and rat thymocytes treated in vitro with glucocorticoid hormones provide a convenient system for studying the nuclear changes in apoptosis. Morphologically the nucleolus disintegrates and chromatin undergoes an unusual generalized condensation. This is associated with excision of most of the nuclear DNA to short but well-organized chains of nucleosomes, apparently by an endogenous non-lysosomal nuclease. The process is dependent upon macromolecular synthesis and probably is mediated, at least remotely, by the classical steroid-receptor-gene activation pathway. A similar process of chromatin condensation and excision can be produced by the calcium-magnesium ionophore A23187. In other circumstances of 'programmed cell death', analogous chromatin condensation, excision and requirements for macromolecular synthesis have been documented.

Alterations in the structure and function of the mammalian cell membrane after exposure to ionizing radiation.

Although the nucleus appears to represent the primary target for the killing of cells by ionizing radiation, the cell membrane may be another important site for radiation injury and modification of the radiation response. In this paper, the effects of radiation on various membrane-associated parameters which are expected to affect cellular viability or function are reviewed. These include the effect of radiation on membrane transport, lectin or hormone receptor sites, cell surface electrokinetics, cell membrane fluidity, cell surface topography, etc. Alternative biochemical mechanisms that may account for the effects of radiation on cell membrane in general will also be discussed.

Location of tumoral antigens in L5178Y murine lymphoma cells.

Location of neoplasia specific tumoral antigens (ANE) were investigated in L5178Y murine cells. Cells were treated by means of concanavalin A (CoA), Vibrio cholerae neuraminidase (NVC) or a combination of both (Coa-NVC) and were inactivated by 6,000 rad irradiation. With 5 x 10(6) treated cells four groups, 15 mice in each group of the BALB/c strain were immunized weekly and 10 days latter immunity to L5178Y lymphoma cells was tested by means of intraperitoneal inoculation of 5 x 10(7) intact, viable L5178Y cells. None of the mice immunized with concanavalin A treated and irradiated cells developed the inoculated lymphoma. However all mice immunized with cells treated with CoA or CoA-NVC developed a lymphoma. Electron microscopy studies of normal L5178Y cells, irradiated or treated with NVC showed the exterior cell coating or glycocalix that was absent in those treated with CoA or CoA-CoA-NVC. These results allowed us to conclude that ANE of L5178Y cells susceptible to modification by NVC as if to induce an immunologic rejection response are located in the glycocalix of these cells.