Multicolor FISH using tándem probes to detect Chromosome alterations in humans cells and populations exposed to genotoxic agents

12 páginas, 2 figuras y 2 tablas estadísticasFluorescence in situ hybridization (FISH) with chromosome- or region-specific DNA probes is being increasingly used in cytogenetic studies to detect aneuploidy in interphase human cells. This technique utilizes chemically modified DNA sequences (probes) which hybridize to distinct regions, often blocks of repetitive DNA, located on specific chromosomes. Hybridization with these probes in situ results in the staining of a compact chromosomal región which can be easily detected on metaphase chromosomes or within interphase nuclei. The number of chromosomes within a given cell is then determined by counting the number of hybridized regions. Where conventional cytogenetics is limited to actively proliferating cells or those which could be stimulated to divide in vitro such as peripheral blood lymphocytes, FISH studies with centromeric probes can be conducted on interphase cells, significantly increasing the types of cells and tissues available for analysis.Peer reviewe

NB2001, a Novel Antibacterial Agent with Broad-Spectrum Activity and Enhanced Potency against β-Lactamase-Producing Strains

Enzyme-catalyzed therapeutic activation (ECTA) is a novel prodrug strategy to overcome drug resistance resulting from enzyme overexpression. β-Lactamase overexpression is a common mechanism of bacterial resistance to β-lactam antibiotics. We present here the results for one of the β-lactamase ECTA compounds, NB2001, which consists of the antibacterial agent triclosan in a prodrug form with a cephalosporin scaffold. Unlike conventional β-lactam antibiotics, where hydrolysis of the β-lactam ring inactivates the antibiotic, hydrolysis of NB2001 by β-lactamase releases triclosan. Evidence supporting the proposed mechanism is as follows. (i) NB2001 is a substrate for TEM-1 β-lactamase, forming triclosan with a second-order rate constant (k(cat)/K(m)) of greater than 77,000 M(−1) s(−1). (ii) Triclosan is detected in NB2001-treated, β-lactamase-producing Escherichia coli but not in E. coli that does not express β-lactamase. (iii) NB2001 activity against β-lactamase-producing E. coli is decreased in the presence of the β-lactamase inhibitor clavulanic acid. NB2001 was similar to or more potent than reference antibiotics against clinical isolates of Staphylococcus aureus (including MRSA), Staphylococcus epidermidis, Streptococcus pneumoniae, vancomycin-resistant Enterococcus faecalis, Moraxella catarrhalis and Haemophilus influenzae. NB2001 is also active against Klebsiella pneumoniae, Enterobacter aerogenes, and Enterobacter cloacae. The results indicate that NB2001 is a potent, broad-spectrum antibacterial agent and demonstrate the potential of ECTA in overcoming β-lactamase-mediated resistance