Metabolism of and DNA adduct formation by benzo[alpha]pyrene in human skin epithelial cells in vitro pretreated with cytochrome P450 modulators

This study was designed to investigate the effects of four compounds that are shown to influence the cytochrome P450 system, on the metabolism of and DNA adduct formation by benzo[alpha]pyrene (BaP) in human skin epithelial cells in culture. Radiolabeled BaP was used in the metabolism studies, and the levels of metabolites in the ethylacetate extracts of the intracellular and extracellular fractions were determined by HPLC. Among the various metabolites detected BaP-7,8-diol was the only one that was an intermediate on the activation pathway of BaP to the ultimate carcinogen, BPDE I. Both BHA and 7,8-BF pretreatment significantly decreased intracellular production of BaP-7,8-diol compared to cultures treated with only radiolabeled BaP. MeBHA pretreatment greatly increased intracellular BaP-7,8-diol formation compared to BaP treated controls, while disulfiram pretreatment had no effect on the intracellular concentration. Cultures pretreated with BHA, 7,8-BF or disulfiram formed 30-40% less BPDE I-dG adducts than nonpretreated cultures, while cultures pretreated with MeBHA exhibited approximately 200% increase in the BPDE I-dG adduct formation. Thus, BHA and 7,8-BF act similarly in reducing BaP activation and adduct formation. Alternatively, MeBHA increased BaP activation and adduct formation in human keratinocyte cultures in vitro. Disulfiram pretreatment did not reduce BaP-7,8-diol formation, but decreased BPDE I-dG adducts. These studies indicate that modulators of the P450 system act in different fashions at the level of production of an oxygenated procarcinogen metabolite, altering the amount of specific carcinogen-dG adducts that lead to the expression of a transformed phenotype.     

Enhanced cell survival and diminished apoptotic response to simulated ischemia–reperfusion in H9c2 cells by magnetic field preconditioning

The potential for 60?Hz magnetic field (MF) preconditioning to protect heart-derived, H9c2 cultures from damage by simulated ischemia and reperfusion (I–R) was examined. The most effective MF exposure conditions (120?μT, 4–8?h) increased cell survival by 40–50?% over that seen with I–R alone. Potential targets of MF preconditioning were assessed by investigating the apoptosis-related drop in Bcl-2 levels and elevation of the specific activities of caspases 3, 8 and 9 produced by I–R. In response to MF exposure Bcl-2 levels rose 2 to 2.6-fold, and caspase specific activities fell 51–72?% from the values seen after I–R alone. Levels of Hsp’s 25, 32 and 72 were examined in response to the MF, but showed little-to-no elevation beyond that produced by I–R. However, MF preconditioning produced a 77?% decrease in the I–R-induced translocation of phosphorylated Hsp25 (Hsp25-P) from the cytosolic to the nuclear-cytoskeletal cell fraction. This might protect by maintaining active Hsp25-P in the cytosol to function as a chaperone or to bind cytochrome c. Blocking Hsp25 phosphorylation with SB203580, an inhibitor of p38 MAPK, resulted in increases of 64 and 80?% in the respective specific activities of caspases 3 and 9 in cells subjected to I–R, and eliminated the MF-induced reduction in caspase 3 activity.     

Phenazine carboxylic acid production and rhizome protective effect of endophytic Pseudomonas aeruginosa isolated from Zingiber officinale

Ginger (Zingiber officinale) is cultivated commercially in most parts of the world especially in India for its culinary and medicinal applications. One of the major challenges that limit the yield of ginger is rhizome rot disease caused by organisms including Pythium myriotylum. A feasible ecofriendly method is yet to be devised to prevent the plant from this threatening disease. Recent studies on plant microbiome show the possibility of having endophytic organisms with plant protective characteristics associated with the plants. Because of the uniquely evolved underground nature of the ginger rhizome and its peculiar survival in soil for a long time, many interesting endophytic microbes with plant protective characters can be well expected from it. In the current study, previously isolated endophytic Pseudomonas aeruginosa from ginger was investigated in detail for its effect on Pythium myriotylum. The rhizome protective effect of the organism was also studied by co-inoculation studies, which confirmed that Pseudomonas aeruginosa has very potent inhibitory effect on Pythium myriotylum. On further studies, the active antifungal compound was identified as phenazine 1-carboxylic acid.     

Spatiotemporal patterns of macrophage migration inhibitory factor (Mif) expression in the mouse placenta

Background  

Macrophage migration inhibitory factor (MIF) has special pro-inflammatory roles, affecting the functions of macrophages and lymphocytes and counter-regulating the effects of glucocorticoids on the immune response. The conspicuous expression of MIF during human implantation and early embryonic development also suggests this factor acts in reproductive functions. The overall goal of this study was to evaluate Mif expression by trophoblast and embryo placental cells during mouse pregnancy.     

Cooperative problem solving in a cooperatively breeding primate (Saguinus oedipus)

We investigated cooperative problem solving in unrelated pairs of the cooperatively breeding cottontop tamarin, Saguinus oedipus, to assess the cognitive basis of cooperative behaviour in this species and to compare abilities with other apes and monkeys. A transparent apparatus was used that required extension of two handles at opposite ends of the apparatus for access to rewards. Resistance was applied to both handles so that two tamarins had to act simultaneously in order to receive rewards. In contrast to several previous studies of cooperation, both tamarins received rewards as a result of simultaneous pulling. The results from two experiments indicated that the cottontop tamarins (1) had a much higher success rate and efficiency of pulling than many of the other species previously studied, (2) adjusted pulling behaviour to the presence or absence of a partner, and (3) spontaneously developed sustained pulling techniques to solve the task. These findings suggest that cottontop tamarins understand the role of the partner in this cooperative task, a cognitive ability widely ascribed only to great apes. The cooperative social system of tamarins, the intuitive design of the apparatus, and the provision of rewards to both participants may explain the performance of the tamarins.     

Metabolism of benzo[a]pyrene in human skin xenografts.

Although a human neonatal foreskin graft to a nude mouse has been shown to be morphologically intact for several months after establishment, the feasibility of using this system for carcinogenesis studies has not been widely investigated. In this study, we have investigated the metabolism of benzo[a]pyrene (BaP) in human skin xenografts after the topical application of different concentrations of [3H]BaP (0.5 microgram-10.0 micrograms and 20 muCi/graft) for 2 h and 1.0 micrograms [3H]BaP for various intervals of time up to 4 h. Significant amounts of different organic solvent soluble metabolites were observed in all the different samples. The increase in the amounts of the organic solvent soluble metabolites was linear over the 0.5 microgram to 5.0 micrograms/graft range. When 1.0 microgram [3H]BaP was applied to each graft, the maximum production of the organic solvent soluble metabolites was observed 10 minutes after treatment and it then decreased with time. Diols were the major metabolites detected in each of the experiments, followed by phenols, and then tetrols. The levels of water soluble glucuronide and sulfate conjugates were almost equivalent for each treatment over the same range of application of BaP per graft. The combined levels of these conjugates and the non-extractable organic soluble metabolites in the residue, generally ranged between 7-24% of the total metabolites in the various experiments.