Nitric oxide (NO) is implicated in apoptosis and has both cytotoxic and cytoprotective effects. Exogenous NO induced the death of PC12 and HeLa cells via a process showing features of both apoptosis and necrosis, with chromatin condensation, nuclear compaction, and mitochondrial swelling. Activation of caspases was not observed during NO-induced cell death. In addition, cell death was not inhibited by peptide caspase inhibitors or by expression of p35, a baculovirus-encoded caspase inhibitor, indicating that NO-induced cell death was independent of caspases. NO-induced cell death was enhanced by Bax expression in a caspase-independent manner and prevented by the anti-cell death protein Bcl-2. Although Bcl-2 has previously been shown to prevent cell death by inhibiting caspase activation, these results indicate that it can also prevent cell death via a caspase-independent mechanism.Nitric oxide (NO) 1 is enzymatically generated from L-arginine by constitutive or inducible NO synthase, and has a number of physiological roles, including smooth muscle relaxation, and neurotransmission (1, 2). NO has also been implicated in a variety of pathological phenomena, such as septic shock, ␤-cell destruction, and transplant rejection (1, 2). Some of these pathological events are closely related to apoptotic cell death (3,4). In many studies, NO has been shown to induce apoptosis, although the precise mechanism involved is still unclear (5-7). In contrast, some investigators have suggested that NO also has the ability to prevent cell death (8 -10), which seems to be mediated by the inhibition of caspases (8), common mediators of apoptosis (11). So far, more than 10 caspases have been identified in mammals. Apoptosis is also regulated by Bcl-2 family proteins, including anti-apoptotic proteins such as Bcl-2 and Bcl-x L , and pro-apoptotic proteins such as Bax and Bak (12). Accumulating evidence suggests that Bcl-2 acts upstream of caspase activation to prevent apoptosis (13,14).In this study, we analyzed NO-induced cell death, particularly focusing on the role of caspases as well as the influence of apoptosis-regulating molecules such as Bcl-2 family proteins. EXPERIMENTAL PROCEDURESReagents-Caspase inhibitors and substrates were purchased from Peptide Inc. (Minoh, Japan). Other chemicals were purchased from Wako Chemical Co. (Tokyo, Japan).Cell Lines and Transfection-HeLa cells, a human cervical carcinoma-derived cell line, and PC12 cells, a rat pheochromocytoma cell line, were maintained in RPMI 1640 culture medium, as described elsewhere (15). A stable transfectant of PC12 cells expressing mouse Bax (designated as PC12-Bax) was obtained by infecting retrovirus that was produced from the packaging cell line ⌿2 transfected with the retroviral vector pBC140 (15) containing mouse bax cDNA. A stable transfectant of PC12 cells expressing human Bcl-2 (designated as PC12-Bcl-2) was obtained by transfecting the pUC-CAGGS vector bearing the human bcl-2 cDNA using electroporation (13). Empty vector-transduced cells were used as the...

Carbon nanotubes have been synthesized by heat treating the polymer at 400 °C in air which was obtained by polyesterification between citric acid and ethylene glycol. Transmission electron micrographs and an electron diffraction pattern showed the formation of carbon nanotubes. The diameter of the tubes ranged from 5 to 20 nm, whereas the lengths were less than 1 μm.

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Characterization of CO species adsorbed on well-degassed surfaces of polycrystalline MgO at low CO pressures (< 1300 Pa) and at and below room temperature was studied by using temperature-programmed desorption (TPD) and infrared (IR) spectroscopies. Mutual transformation between adsorbed species stable at room temperature, and their reactivities with 0 2 were also investigated. Adsorbed species are classified into five groups, KO, K1 (and K1' ), Kz, K3, and &. Among them species KO and K1 (and K1' ) are stable only below room temperature while species KZ to & are stable above this temperature. Species KO is a linear-type CO monomer with the C atom bonded to surface Mg2+ and has five subspecies depending on its circumstance, while all the other species K1 to & are formed on surface 02-to which the C atom is linked. A chained-type CO monomer, K1, is reversibly transformed at ca. 230 K in the presence of gaseous CO into a linear-type CO monomer, K1'. Species KZ is a chained-type tetramer of CO with a carbonyl CO bond and resonanced bonds. There are two subspecies, K~A and Km, which are formed by the addition of one CO molecule to corresponding trimer species, K~A and K~x , respectively, in the presence of gaseous CO. K~A and Kzx are reversibly transformed into K~A (at 400 K) and K~x (in 300-400 K), respectively, by the elimination of the CO added.There are two more subspecies, K~B and K~c , in species K3, but they have no corresponding KZ subspecies, and hence no transformations occur. All the K3 species seem to be a linear-type trimer with a ketenic group, >C=O=O, and are desorbed in 520-580 K. Species &, though detailed information is not obtained, consists of three subspecies &A, &B, and &c, but no transformations between species K3 and & are observed.