Sei-ichi Tanuma

Change in electrophoretic mobility of HL-60RG cells by apoptosis

We measured the electrophoretic mobilities of HL-60RG cells and their apoptotic cells triggered by Actinomycin D as a function of the ionic strength of the suspending medium at pH 7.4. Both types of cells showed negative mobilities. The apoptotic HL-60RG cells exhibited larger mobility values in magnitude than intact HL-60RG cells in the whole range of the electrolyte concentration measured. The obtained data were analyzed via a mobility expression for “soft particles’, that is, colloidal particles with ionpenetrable surface layers. The observed mobility difference between the intact and apoptotic HL-60RG cells was found to be due mainly to the difference in friction exerted by the cell surface layers on the liquid flow around the cells between these two types of cells rather than the difference in charge density in their surface layers. A possible explanation for this mobility change by apoptosis is given.

Induction of autoantibodies in normal mice by injection of nucleobindin and natural occurrence of antibodies against nucleobindin in autoimmune MRL/lpr/lpr mice

Our previous works have shown that nucleobindin (Nuc) or recombinant (r) Nuc not only augments anti-DNA antibody production in vitro but also accelerates autoimmune response in vivo in MRL/+/+ (MRL/n) mice which are the substrain of autoimmune MRL/lpr/lpr (MRL/l) mice. To investigate whether rNuc can induce autoimmune response similarly in naive mice, we carried out intraperitoneal (i.p.) injection of rNuc (5 micrograms) without adjuvant into 8-week-old female BALB/c mice and continued injection twice a week for 12 weeks. About 5 weeks after the first injection, all the mice began to show IgG hypergammaglobulinemia (HG) followed by elevation of a number of autoantibodies of the IgG class such as anti-double-stranded (ds) DNA, anti-U1 ribonuclear protein (RNP), anti-ssB(La) and anti-Fc antibodies (RF), but not by anti-Sm antibodies. However, the IgG anti-dsDNA antibody response and histopathological changes in the kidney of these BALB/c mice were not so noticeable as those in MRL/n mice induced by rNuc in our previous experiment. In contrast, the IgG anti-rNuc antibody response of normal BALB/c mice induced by rNuc was stronger than that of MRL/n mice induced by rNuc. Since the titers of each autoantibody of BALB/c mice induced by rNuc were not always associated with the level of IgG HG, and either IgG HG or IgG autoantibodies could not be induced by control administration of extracts (5 micrograms) of Escherichia coli with or without harboring plasmid alone, polyclonal B cell activation (PBA) appeared not to be the mechanism of this autoimmunity.(ABSTRACT TRUNCATED AT 250 WORDS)

An Endonuclease Responsible for Apoptosis

Apoptosis is a form of cell death that plays important roles in physiological and pathological phenomena as diverse as embryogenesis, metamorphosis, hemopoiesis, and carcinogenesis (Kerr et al. 1972; Wyllie 1980; Berger 1985; Carson et al. 1986; Ucker 1987; Smith et al. 1989; Dive and Hickman 1991; Groux et al. 1992; Cohen et al. 1992; Tanuma et al. 1993). Although apoptosis is thought to be a gene-directed cell death, how this suicide is regulated is still unknown. Apoptosis is characterized morphologically by cell shrinkage, nuclear collapse, and cell fragmentation, known as apoptotic bodies, which is accompanied by internucleosomal DNA fragmentation (Kerr et al. 1972; Wyllie 1980). The signal transduction and determination processes in apoptosis initiated by apoptotic signals are complex and dependent on cell types and states. However, the DNA fragmentation, which is suggested to be catalyzed by a constitutive endonuclease, is a crucial process common in apoptosis, irrespective of the initial stimulus.