Selective recognition of Ni2+ ion based on fluorescence enhancement chemosensor.

A new enhancing fluorescent chemosensor was introduced for selective and sensitive determination of nickel ions based on 2-(1-H-benzo[d]imidazol-2yl)-N-phenyl hydrazine carbothioamide (L). L has an intrinsic fluorescent emission which enhances in presence of nickel ions in CH3CN/H2O (70:30, v/v) solution. The fluorescence enhancement of L is attributed to a 1:1 complex formation between L and Ni2+ ion which has been used for selective detection of Ni2+ ion. At the optimum conditions, the fluorescence intensity of L at 352 nm enhances linearly by the concentration of nickel ion from 1.6×10(-5) to 1.6×10(-7) M and detection limit of 7.9×10(-8) M. The new fluorescent probe exhibited high selectivity to Ni2+ ion over the other common mono, di-and trivalent cations.

Evaluation of ganciclovir resistance in cytomegalovirus infection of renal transplant recipients in Tehran.

BACKGROUND: Human cytomegalovirus (CMV) infection is a major issue in solid organ transplant recipients. Although development of prophylaxis and preemptive procedures have presented significantly improved consequences in CMV infection, increasing incidence of antiviral resistance has raised virologists' concern. METHODS: The present study focused on kidney transplant recipients with high quantities of CMV load after antiviral therapy. We collected 5 mL blood from each of 58 patients. DNA extraction was performed with the use of the QIAamp DNA Mini kit (Qiagen), in accordance with the manufacturer's instructions. RESULTS: Our population study was 38% female and 62% male. CMV DNA was observed in 50 specimens (86%) with the range of 1.9 × 10(3) to 11 × 10(7) copies/mL serum. All of these patients had received ganciclovir for >3 months. Sequencing showed 18 mutations in 10 patients. Among these, 16 mutations were associated with Ul97 and the rest with Ul54 gene. Forty CMV-positive patients did not show any mutations. CONCLUSIONS: The consequences of long-term ganciclovir resistance could not be determined.

Plasmid association and nucleotide sequence relationships of two genes encoding heat-stable enterotoxin production in Escherichia coli H-10407.

Plasmid DNA from enterotoxigenic Escherichia coli strains H-10407 and H-10407-P was examined for nucleotide sequence homology to two E. coli genes encoding infant mouse-active heat-stable enterotoxins (ST). A 62-megadalton plasmid of strain H-10407 contained sequences homologous to the gene encoding a toxin designated STIb, previously isolated from a human isolate of E. coli. A 42-megadalton plasmid of strains H-10407 and H-10407-P contained sequences homologous to the gene encoding a toxin designated STIa, previously isolated from bovine and porcine isolates of E. coli.

Detection of enterotoxigenic Escherichia coli by DNA colony hybridization.

A method fo detecting large numbers of isolates of enterotoxigenic Escherichia coli is described in which the genes encoding th enterotoxins are detected, rather than the toxins themselves. Radiolabeled fragments of DNA encoding the heat-labile (LT) or heat-stable (ST) toxins were used as hybridization probes for homologous DNA sequences in E. coli colonies grown and lysed in situ on nitrocellulose filters. The LT probe detected all of 31 E. coli strains producing ST and LT or only LT, while the ST probe detected 12 of 17 strains producing only ST and three of 26 strains producing ST and LT. These results suggest that the LTs produced by different isolates of E. coli are homologous and that human isolates of E. coli produce at least two heterologous STs detectable in the infant mouse assay. The hybridization method also detected the presence of enterotoxigenic E. coli in bacterial growth in directly spotted stools from patients with acute diarrhea.