A chemical inhibitor of p53 that protects mice from the side effects of cancer therapy.
(17/1074)
Chemotherapy and radiation therapy for cancer often have severe side effects that limit their efficacy. Because these effects are in part determined by p53-mediated apoptosis, temporary suppression of p53 has been suggested as a therapeutic strategy to prevent damage of normal tissues during treatment of p53-deficient tumors. To test this possibility, a small molecule was isolated for its ability to reversibly block p53-dependent transcriptional activation and apoptosis. This compound, pifithrin-alpha, protected mice from the lethal genotoxic stress associated with anticancer treatment without promoting the formation of tumors. Thus, inhibitors of p53 may be useful drugs for reducing the side effects of cancer therapy and other types of stress associated with p53 induction. (+info)
Involvement of the cis/trans isomerase Cti in solvent resistance of Pseudomonas putida DOT-T1E.
(18/1074)
Pseudomonas putida DOT-T1E is a solvent-resistant strain that is able to grow in the presence of high concentrations of toluene. We have cloned and sequenced the cti gene of this strain, which encodes the cis/trans isomerase, termed Cti, that catalyzes the cis-trans isomerization of esterified fatty acids in phospholipids, mainly cis-oleic acid (C(16:1,9)) and cis-vaccenic acid (C(18:1,11)), in response to solvents. To determine the importance of this cis/trans isomerase for solvent resistance a Cti-null mutant was generated and characterized. This mutant showed a longer lag phase when grown with toluene in the vapor phase; however, after the lag phase the growth rate of the mutant strain was similar to that of the wild type. The mutant also showed a significantly lower survival rate when shocked with 0.08% (vol/vol) toluene. In contrast to the wild-type strain, which grew in liquid culture medium at temperatures up to 38.5 degrees C, the Cti-null mutant strain grew significantly slower at temperatures above 37 degrees C. An in-frame fusion of the Cti protein with the periplasmic alkaline phosphatase suggests that this constitutively expressed enzyme is located in the periplasm. Primer extension studies confirmed the constitutive expression of Cti. Southern blot analysis of total DNA from various pseudomonads showed that the cti gene is present in all the tested P. putida strains, including non-solvent-resistant ones, and in some other Pseudomonas species. (+info)
Initial reactions in anaerobic oxidation of m-xylene by the denitrifying bacterium Azoarcus sp. strain T.
(19/1074)
The initial enzymatic steps in anaerobic m-xylene oxidation were studied in Azoarcus sp. strain T, a denitrifying bacterium capable of mineralizing m-xylene via 3-methylbenzoate. Permeabilized cells of m-xylene-grown Azoarcus sp. strain T catalyzed the addition of m-xylene to fumarate to form (3-methylbenzyl)succinate. In the presence of succinyl coenzyme A (CoA) and nitrate, (3-methylbenzyl)succinate was oxidized to E-(3-methylphenyl)itaconate (or a closely related isomer) and 3-methylbenzoate. Kinetic studies conducted with permeabilized cells and whole-cell suspensions of m-xylene-grown Azoarcus sp. strain T demonstrated that the specific rate of in vitro (3-methylbenzyl)succinate formation accounts for at least 15% of the specific rate of in vivo m-xylene consumption. Based on these findings, we propose that Azoarcus sp. strain T anaerobically oxidizes m-xylene to 3-methylbenzoate (or its CoA thioester) via (3-methylbenzyl)succinate and E-(3-methylphenyl)itaconate (or its CoA thioester) in a series of reactions that are analogous to those recently proposed for anaerobic toluene oxidation to benzoyl-CoA. A deuterium kinetic isotope effect was observed in the (3-methylbenzyl)succinate synthase reaction (and the benzylsuccinate synthase reaction), suggesting that a rate-determining step in this novel fumarate addition reaction involves breaking a C-H bond. (+info)
Assessment of workers' exposure to aromatic hydrocarbons in a paint industry.
(20/1074)
A factory survey was conducted in a paint industry in Tehran-Iran. The time-weighted average of toluene and xylene concentration in breathing zone and environmental air were monitored by charcoal tube samplers and GC-FID. The results showed that the tank cleaners had the highest exposure to toluene and xylene (1.5-5.4 times of TLV), while the workers in packaging workshops had the lowest. However, environmental concentration did not show significant differences in workshops and their levels were all lower than the TLV. (+info)
Linking toluene degradation with specific microbial populations in soil.
(21/1074)
Phospholipid fatty acid (PLFA) analysis of a soil microbial community was coupled with (13)C isotope tracer analysis to measure the community's response to addition of 35 microg of [(13)C]toluene ml of soil solution(-1). After 119 h of incubation with toluene, 96% of the incorporated (13)C was detected in only 16 of the total 59 PLFAs (27%) extracted from the soil. Of the total (13)C-enriched PLFAs, 85% were identical to the PLFAs contained in a toluene-metabolizing bacterium isolated from the same soil. In contrast, the majority of the soil PLFAs (91%) became labeled when the same soil was incubated with [(13)C]glucose. Our study showed that coupling (13)C tracer analysis with PLFA analysis is an effective technique for distinguishing a specific microbial population involved in metabolism of a labeled substrate in complex environments such as soil. (+info)
Molecular characterization of a toluene-degrading methanogenic consortium.
(22/1074)
A toluene-degrading methanogenic consortium enriched from creosote-contaminated aquifer material was maintained on toluene as the sole carbon and energy source for 10 years. The species in the consortium were characterized by using a molecular approach. Total genomic DNA was isolated, and 16S rRNA genes were amplified by using PCR performed with kingdom-specific primers that were specific for 16S rRNA genes from either members of the kingdom Bacteria or members of the kingdom Archaea. A total of 90 eubacterial clones and 75 archaeal clones were grouped by performing a restriction fragment length polymorphism (RFLP) analysis. Six eubacterial sequences and two archaeal sequences were found in the greatest abundance (in six or more clones) based on the RFLP analysis. The relative abundance of each putative species was estimated by using fluorescent in situ hybridization (FISH), and the presence of putative species was determined qualitatively by performing slot blot hybridization with consortium DNA. Both archaeal species and two of the six eubacterial species were detected in the DNA and FISH hybridization experiments. A phylogenetic analysis of these four dominant organisms suggested that the two archaeal species are related to the genera Methanosaeta and Methanospirillum. One of the eubacterial species is related to the genus Desulfotomaculum, while the other is not related to any previously described genus. By elimination, we propose that the last organism probably initiates the attack on toluene. (+info)
Anaerobic toluene-catabolic pathway in denitrifying Thauera aromatica: activation and beta-oxidation of the first intermediate, (R)-(+)-benzylsuccinate.
(23/1074)
Anaerobic catabolism of toluene is initiated by addition of the methyl group of toluene to the double bond of a fumarate cosubstrate to yield the first intermediate, benzylsuccinate. This reaction is catalysed by the glycyl-radical enzyme benzylsuccinate synthase, as shown for the denitrifying bacterium Thauera aromatica. Benzylsuccinate is further oxidized to benzoyl-CoA, the central intermediate of anaerobic degradation of aromatic compounds. The authors show here by experiments with cell extracts of toluene-grown T. aromatica that the pathway of benzylsuccinate oxidation requires activation of the free acid to a CoA-thioester, catalysed by a toluene-induced, reversible succinyl-CoA-dependent CoA-transferase. The product of the CoA-transferase reaction, benzylsuccinyl-CoA, is oxidized to benzoyl-CoA and succinyl-CoA in extracts of toluene-grown cells, adding proof to the proposed anaerobic toluene-catabolic pathway. The stereochemical preferences of the enzymes catalysing formation and activation of benzylsuccinate have been analysed. Benzylsuccinate synthase was found to produce exclusively (R)-(+)-benzylsuccinate, although the proposed reaction mechanism of this enzyme proceeds via radical intermediates. In accordance, the reaction of succinyl-CoA:benzylsuccinate CoA-transferase is also specific for (R)-(+)-benzylsuccinate and does not proceed with the (S)-(-)-enantiomer. (+info)
Effects of toluene on regulation of adenylyl cyclase by stimulation of G-protein-coupled receptors expressed in CHO cells.
(24/1074)
We determined the effects of toluene exposure on activation or inhibition of adenylyl cyclase by stimulating human beta2-adrenergic receptors (beta2-AR) and muscarinic acetylcholine receptor (mAChR) m2 subtypes, respectively, expressed in CHO cells. The formation of cAMP via beta2-AR stimulation was slightly but not significantly facilitated in the presence of 3.7 microM toluene. On the other hand, the inhibition of adenylyl cyclase by 10 microM of carbamylcholine stimulation of mAChR m2 subtypes was attenuated in the presence of toluene. These results strongly suggest that toluene affects activation of Gi rather than Gs. (+info)