Biomedical subjects

G Luo

Publications and source records attributed to G Luo.

168 records · Page 10Linked to original sources

PubMedDate not supplied

A novel selenocystine-beta-cyclodextrin conjugate that acts as a glutathione peroxidase mimic.

A novel artificial glutathione peroxidase mimic consisting of a selenocystine-di-beta-cyclodextrin conjugate (selenium-bridged-6, 6'-amino-selenocystine-6,6'-deoxy-di-beta-cyclodextrin), in which selenocystine is bound to the primary side of beta-cyclodextrin through the two amino nitrogen groups of selenocystine, was synthesized. The glutathione peroxidase activities of the mimic-catalyzed reduction of H(2)O(2), tert-butylhydroperoxide, and cumene hydroperoxide by glutathione are 4.1, 2.11, and 5.82 units/micromol, respectively. The first activity was 82 and 4.2 times as much as that of selenocysteine and ebselen, respectively. Studies on the effect of substrate binding on the glutathione peroxidase activity suggest that it is important to consider substrate binding in designing glutathione peroxidase mimics. The detailed steady-state kinetic studies showed that the mimic-catalyzed reduction of H(2)O(2) by glutathione followed a ping-pong mechanism, which was similar to that of the native glutathione peroxidase.

Binding Sites↗

PubMedDate not supplied

A case report of frosted branch angiitis and its visual electrophysiology.

We reported a 5-years old boy with frosted branch angiitis in both eyes. The visual acuities of the two eyes were suddenly lost to 5/50. The fluorescein angiography, electroretinograms (ERGs) and pattern evoked potentials (PVEPs) had been tested at the acute and the recovery stage of the disease. At the onset of the disease, fluorescein angiography showed obvious dye leakage from dilated retinal veins. The PVEPs and whole field ERGs including rod, maximum, OPs and cone responses were seriously decreased and prolonged, indicating that the visual pathway's and retinal functions were greatly damaged. The patient had an excellent response to systemic prednisone. One month after the treatment, the visual acuities recovered to 60/50 in both eyes. The fluorescein angiography showed that leakage from blood vessels was diminished, but the lesions at macula and optic disc were persisted a longer time even to the end of treatment. Through 6 months medication, nearly all of the electrophysiological abnormalities had been resolved.

Administration, Oral↗

PubMedDate not supplied

Reverse transcriptase polymerase chain reaction (RT-PCR) detection of HLP gene expression in Candida glabrata and its possible role in in vitro haemolysin production.

Although haemolysins are known to be putative virulence factors contributing to pathogenicity in Candida species, the haemolytic activity of Candida glabrata and its genetic expression is ill understood at present. Thus, we studied a total of 34 Candida glabrata isolates for their in vitro haemolytic activity using a previously described plate assay system. The mRNA expression of HLP, a putative haemolysin gene, of these isolates was also evaluated using a semi-quantitative, non-competitive RT-PCR assay. All 34 C. glabrata isolates exhibited both partial (alpha) and complete (beta) haemolytic activity to varying degrees. In parallel with the haemolytic activity, all isolates were also positive for HLP mRNA expression. The expression levels of HLP mRNA (as relative units) ranged from 1.01 to 1.82, with a mean value of 1.32. On regression analysis of latter values and the haemolytic activity (in terms of the dimension of the haemolytic zone in the plate assay) of the C. glabrata isolates a highly significant positive correlation was noted (r=0.759, p<0.0001). Taken together, our data illustrate not only the phenotypic characteristics of haemolysin(s) and HLP expression of a battery of C. glabrata clinical isolates, but also, for the first time, evidence for a role of HLP in haemolysis.

Base Sequence↗

PubMedDate not supplied

Actinomyces spp. in supragingival plaque of ethnic Chinese preschool children with and without active dental caries.

Very limited molecular epidemiological data are available on the role of Actinomyces spp. in the pathogenesis of caries in the primary dentition. Therefore, we investigated their distribution in supragingival plaque of ethnic Chinese preschool children from Singapore and Hong Kong, either with or without active caries. Plaque samples were taken from intact interproximal enamel areas using dental floss. Bacterial genomic DNA of each sample was extracted and variable regions of 16S ribosomal DNA amplified and labelled with digoxigenin. Oligonucleotide probes specific for Actinomyces bovis, Actinomyces gerencseriae, Actinomyces israelii, Actinomyces meyeri, Actinomyces odontolyticus, catalase-negative Actinomyces naeslundii (genospecies 1 and 2) and catalase-positive Actinomyces naeslundii genospecies 2 (previously Actinomyces viscosus serotype II) were used to detect these species using Southern hybridization with a Minislot and Miniblotter system. A. odontolyticus, A. gerencseriae and A. meyeri were detected with similar frequency in both Singapore and Hong Kong samples or in those with and without active caries. However, the prevalence of A. naeslundii was significantly different in the two locales (p<0.05). A. odontolyticus (88.7%), A. gerencseriae (56.6%) and A. naeslundii (50.9%) were detected in a majority of the samples and the positive hybridization signals of A. gerencseriae in the caries-active group were stronger than from the caries-free group. A. bovis and A. israelii were undetectable in any of the samples. These data imply that A. odontolyticus, A. naeslundii and A. gerencseriae may play an important role in supragingival plaque formation on primary teeth in ethnic Chinese, with others such as A. meyeri contributing.

Actinomyces↗

PubMedDate not supplied

Hydrolysis of the 2',3'-allylic epoxides of allylbenzene, estragole, eugenol, and safrole by both microsomal and cytosolic epoxide hydrolases.

2',3'-Allylic epoxide derivatives of allylbenzene and its analogs estragole, eugenol, and safrole were synthesized, and their enzymatic conversion to dihydrodiols by cytosolic and microsomal epoxide hydrolases was examined. All four epoxides were good substrates for both epoxide hydrolases, with Michaelis constants in the low micromolar range. Two putatively selective inhibitors of cytosolic and microsomal epoxide hydrolases, trichloropropylene oxide and nordihydroguaiaretic acid, were used to inhibit the hydrolysis of these allylic epoxides. Minimal selectivity toward either hydrolase was seen with either inhibitor, suggesting that the "selectivity" of these inhibitors is highly substrate-dependent. The susceptibilities of these epoxides to rapid hydrolysis by both epoxide hydrolases may explain their low genotoxic potencies in vivo.

Allylbenzene Derivatives↗

PubMedDate not supplied

Detoxication of the 2',3'-epoxide metabolites of allylbenzene and estragole. Conjugation with glutathione.

The enzymatic detoxication in vitro of the 2',3'-epoxide derivatives of allylbenzene and estragole was examined, and the relative rates of enzymatic glutathione conjugation and epoxide hydrolysis were compared with those for styrene 1',2'-oxide. HPLC was used to determine the amounts of dihydrodiol and glutathione conjugate metabolites formed by cell extracts from several sources. Although some differences among species were observed, in general, the rates of epoxide inactivation by both pathways are similar. We conclude that one explanation for the apparent lack of genotoxicity of these allylic epoxides in vivo may be their rapid metabolic inactivation by both glutathione S-transferases and epoxide hydrolases, which occur to approximately equal degrees in vitro.

Allylbenzene Derivatives↗