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Q Jiang

Publications and source records attributed to Q Jiang.

204 records · Page 12Linked to original sources

Mapping and characterization of the hisD-unlinked nif mutants in Klebsiella pneumoniae.

Two hisD-unlinked genes NifC5 and NifC7 are mapped in the chromosome of K. pneumoniae. The sequence of NifC5 and NifC7 is suggested as NifC5--gltB--NifC7--argG. The P1 infected E. coli lysate can transduce the mutant C-7 to be Nif+ transductant, yet fails to transduce the hisD-linked nif mutants to be Nif+ ones. This indicates that the gene encoding C-7 is not the structural gene of nitrogen fixation and is present in E. coli. It is actually a gene specifying the glutamate synthetase. SDS electrophoresis shows the marked low content of nitrogen reductase and immunoelectrophoretic test reveals the reduced amount of both nitrogenase and nitrogen reductase in the mutant cells.

Chromosome Mapping↗

Chiral separation of naphthalene-2,3-dialdehyde labelled peptides by cyclodextrin-modified electrokinetic chromatography.

The chiral separation of several dipeptide enantiomers, derivatized by naphthalene-2,3-dialdehyde (NDA), was achieved by use of cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC). The dipeptides contained one or two chiral centers. In the case of several dipeptides containing two chiral centers, all four of the optical isomers could be separated and baseline resolved in less than 15 min with 20 mM gamma-CD and 50 mM sodium dodecyl sulphate (SDS) in the background electrolyte. The order of elution of these derivatized dipeptides was explained by considering important chemical equilibria in the SDS, CD and peptide system. Additionally, the influence of geometric location of the chiral center, the structure of the side-chain and the effect of CD concentration on the resolution are discussed.

Chromatography↗

Antibiotic susceptibilities of Helicobacter pylori strains isolated in the Province of Alberta.

The incidence of antibiotic resistance to amoxicillin, clarithromycin, erythromycin, metronidazole and tetracycline in Helicobacter pylori strains isolated from gastric biopsy specimens obtained in Alberta was investigated. Results for all antibiotics were obtained using agar dilution, and in addition to metronidazole, the E test was used. Resistance to amoxicillin and tetracycline was not detected. Metronidazole resistance determined using agar dilution was approximately 12% (95% CI 4% to 26%) when minimal inhibitory concentrations (MICs) were at least 8 micrograms/mL, but fell to 2% (95% CI 0.1% to 13%) when MICs were set at 32 micrograms/mL or greater. The E test for metronidazole resistance (MIC 8 micrograms/mL or greater) yielded a slightly higher percentage of resistant strains compared with agar dilution tests (14%, 95% CI 5% to 29%). One of the 31 strains was resistant to clarithromycin (MIC 8 micrograms/mL) and erythromycin (MIC 16 micrograms/mL). Thus, the incidence of resistance to clarithromycin, part of the currently used triple therapy for eradication of H pylori, was 3% (95% CI 0.1% to 17%).

Alberta↗

Colonization and immune responses in mice to Helicobacter pylori expressing different Lewis antigens.

BACKGROUND AND AIMS: A mouse model was established to compare colonization by the H. pylori Sydney strain SS1 with several clinical isolates expressing different Lewis antigens on their surface. In addition, both humoral and cell mediated immune responses were determined for different H. pylori strains. METHODS: Mice were inoculated intragastrically separately with the Sydney strain as well as with five clinical isolates of H. pylori expressing different Lewis (Le) antigen phenotypes. Colonization of the mouse stomach by the bacteria was monitored from two to fourteen weeks post inoculation by four independent methods namely, urease, PCR (using CagA primers), bacterial culture and histology. Antibody titers and cellular immune responses were monitored by ELISA and antigen stimulation test respectively. RESULTS: Different degrees of colonization were observed in C57, CD1 and Balb/c mice inoculated with H. pylori strain SS1 (Le(x), Le(y)) and clinical isolates UA948 (Le(a), Le(x)), UA861 (alpha-glucosyl polyLacNAc), UA1258 (Le(y)), UA802 (Le(y)) and UA1264 (no Le antigen) starting from week two post inoculation. All three mice strains mounted high immune responses against different H. pylori antigens. Treatment of mice with vancomycin prior to inoculation has no effect either on colonization of the stomach or the immune response of the mice. Histological evaluation established colonization after 10 weeks post inoculation but not gastritis. CONCLUSIONS: Stomach of mice can be colonized consistently, with H. pylori strain SS1, and colonization was also achieved with all clinical isolates that were not mouse adapted. These strains could be detected more consistently by PCR in the early stages, then by culture only after 8 - 10 weeks. In our study, Lewis(x) expressing bacterial strain (UA948) failed to colonize Balb/c mice, whereas the Le(y) expressing strain (UA1258) did not colonize C57/BL6 mice.

Animals↗

Localization of glial fibrillary acidic protein in retinal astrocytoma: an immunohistochemical study.

Glial fibrillary acidic protein (GFA) is found in glial filaments, and is specific for reactive or neoplastic astrocytes and ependyma. Using a commercially available antibody to GFA protein, a retinal neoplasm from a patient with neurofibromatosis is intensely stained with the brown immunoperoxidase reaction product. Rather than the less specific phosphotungstic acid hematoxylin (PTAH) or Holzer's stain, antibody to GFAP protein is a relatively rapid, simple, and reliable immunohistochemical technique for formalin-fixed and paraffin-embedded tissue.

Astrocytoma↗