Reductive metabolism of N-nitrosodiphenylamine to the corresponding hydrazine derivative

The first evidence for the reductive metabolism of a noncyclic nitrosamine to the corresponding hydrazine derivative in vivo and in vitro is provided. Under anaerobic conditions, N-nitrosodiphenylamine was reduced by guinea pig liver 9000g supernatant to 1,1-diphenylhydrazine in the presence of 2-hydroxypyrimidine or to acetaldehyde diphenylhydrazone in the presence of acetaldehyde. These metabolites were identified unequivocally by comparative study with authentic samples. In addition, the study shows that such reductive reactions of the nitrosamine can be catalyzed by guinea pig and rabbit liver aldehyde oxidase in the presence of its electron donors. When the nitrosamine was given orally to acetaldehyde-treated guinea pigs, a metabolite was detected from plasma and identified as acetaldehyde diphenylhydrazone by comparison with the authentic sample.     

Distribution of manganese superoxide dismutase in rat stomach: application of Triton X-100 and suppression of endogenous streptavidin binding activity.

The distribution of rat manganese superoxide dismutase (Mn-SOD) was immunohistochemically investigated in the rat stomach with a specific polyclonal antibody and a labeled streptavidin-biotin immunoglobulin detection system in cryosections. Parietal cells in the stomach were intensely stained, whereas the other epithelial cells in the gastric gland and pit exhibited only slight staining. Rapid-freezing and freeze-substitution immunoelectron microscopy revealed that Mn-SOD in parietal cells was mainly localized in mitochondria. Therefore, the large amount of Mn-SOD in parietal cells is due to the abundant mitochondria, in which Mn-SOD is considered to play important roles in protecting the ion pump and the cell itself from superoxide insult. Application of Triton X-100, cryosectioning, and the streptavidin-biotin system are needed to distinctly visualize Mn-SOD with our antibody. Treatment of the cryosections with Triton X-100 enhanced not only the immunoreactivity but also the false-positive staining, which showed a similar distribution pattern to that of Mn-SOD and thus made it difficult to determine the localization. The most plausible cause of the false-positive staining is thought to be endogenous biotin in the stomach, which survives paraformaldehyde fixation and is revealed by Triton X-100 treatment. Suppression of the endogenous streptavidin binding activity is important when cryosections, the streptavidin-biotin system, and Triton X-100 are employed.     

Structure-activity Study of Bacteriostatic Kojic Acid Analogs

The bacteriostatic activity of kojic acid derivatives, where various substituents are introduced into the 2- and/or 7-positions was analyzed in terms of the physicochemical characteristics of the substituents using the method developed by Hansch and his co-workers. Analyses show that 1) activity is attributable to the neutral form of the molecule in the medium, 2) the site of action seems to be in a region close to the bacterial cell surface, and 3) the higher the hydrophobicity of the substituents at the 7-position and the greater the electron withdrawal from the 3-hydroxyl group, the stronger the activity.     

Interleukin-2 induces motility of human lymphocytes, but not their mobility

Interleukin-2 induces cytotoxic and antitumor activities of human lymphocytes. For the expression of these activities, the cytoskeletal system is probably activated. This study was do;ne to find if interleukin-2 causes cell movement. Lymphocytes were incubated with interleukin-2, and their morphology and motile activities were studied. After 72 hr of incubation, some 29% of lymphocytes were larger than before; nucleoli had formed and the microvilli were well-developed. The membrane potential of the lymphocytes increased during incubation. Motility under agar after 3 days of incubation with interleukin-2 was examined. Cells aggregated in clumps in the incubation well, and migration was not observed. When mobility was examined with Boyden's method, fewer cells incubated with interleukin-2 migrated than in control preparations. Cells incubated with interleukin-2 were extracted with Triton X-100. The extract obtained had three more bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis than the controls. The band were at the positions for the molecular weights of 270,000-300,000. We concluded that interleukin-2 activated the motility of lymphocytes, but not their mobility.