In addition, aspirin increased the susceptibility of H. pylori to antimicrlbials including metronidazole, clarithromycin and amoxicillin. However, the mechanisms remained unknown.
A research team led by Prof. Wang from Peking University First Hospital of China addressed this issue and their results will be published on February 28, 2009 in the World Journal of Gastroenterology .
H. pylori reference strain 26695 and two metronidazole-resistant isolates of H. pylori were included in this study. The effect of aspirin on the permeability of the outer membrane of H. pylori was determined using [7-3H] tetracycline. The effects of aspirin on the expression of OMPs of H. pylori were also determined. Taqman-based real-time quantitative PCR was used to analyze the influence of aspirin on the expression of the related OMPs genes.
They found that the mutations in rdxA gene did not change in metronidazole resistant isolates treated with aspirin. The radioactivity of H. pylori increased when treated with aspirin, indicating that aspirin improved the permeability of the outer membrane of H. pylori . However, the expression of two OMP bands between 55 kDa and 72 kDa altered in the presence of aspirin. The expression of the mRNA of hopA, hopB, hopC, hopD, hopE and hefA, hefB, hefC of H. pylori did not change when treated with aspirin.
Their results indicated that although aspirin increases the susceptibility of H. pylori to metronidazole, it has no effect on the mutations of rdxA gene of H. pylori . Aspirin increases endocellular concentrations of antimicrobials and probably by altering the expression of the outer membrane proteins (OMP) of H. pylori . Their study will help understand the mechanisms of the resistance of H. pylori to antibiotics more intensively and discover a more effective eradication regimen in clinical practice.
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Based on earlier human work, Peterson hypothesized that the well separated blocks of conserved DNA in tephritids were regulatory sequences. Since there was no method available for testing these sequences in tephritids, Peterson inserted them into the laboratory mainstay Drosophila melanogaster. More than 150 million years of evolution separate tephritids from Drosophila melanogaster, but six of the nine pieces of conserved tephritid DNA functioned as regulatory sequences in the fruit fly. Furthermore, Peterson found matches for each of the tephritid sequences in the Drosophila melanogaster genome, and showed that the matched tephritid and Drosophila sequences drive the same patterns of gene expression.
Thus, it may be easier to identify regulatory sequences in the widely studied Drosophila melanogaster genome by sequencing and comparing tephritid genomes than sequencing more Drosophila genomes, Eisen says.
The findings have broader implications, too, Eisen says. Many biologists have been left with the impression that gene regulation is simpler in invertebrates than in vertebrates, since virtually all sequenced invertebrate genomes are small, with compact regulatory regions, and most sequenced vertebrate genomes are big. But Eisen points out that the sequenced invertebrate genomes are not representative. With limited funds available to study species not closely related to humans, and with the cost of genome sequencing scaling directly to genome size, the myriad invertebrate species with large genomes have been shunned.
"While the idea that there is a fundamental difference in the complexity of vertebrate and invertebrate genomes fits with our anthropocentrism," says Eisen, "it does not appear to be true. It's an illusion created by a bias towards sequencing small genomes whenever possible."
Eisen is optimistic that observations from studies like this, together with the rapidly dropping cost of sequencing, will reverse this bias, allowing researchers to generate a clearer picture of the structure and evolution of animal genomes. To aid in that goal, he is working with scientists from the Department of Agriculture and Baylor College of Medicine to sequence complete tephritid genomes.
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