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Biomedical subjects

R Zheng

Publications and source records attributed to R Zheng.

At least 73 records · Page 4Linked to original sources
PubMed1996

Zinc folds the N-terminal domain of HIV-1 integrase, promotes multimerization, and enhances catalytic activity.

The N-terminal domain of HIV-1 integrase contains a pair of His and Cys residues (the HHCC motif) that are conserved among retroviral integrases. Although His and Cys residues are often involved in binding zinc, the HHCC motif does not correspond to any recognized class of zinc binding domain. We have investigated the binding of zinc to HIV-1 integrase protein and find that it binds zinc with a stoichiometry of one zinc per integrase monomer. Analysis of zinc binding to deletion derivatives of integrase locates the binding site to the N-terminal domain. Integrase with a mutation in the HHCC motif does not bind zinc, consistent with coordination of zinc by these residues. The isolated N-terminal domain is disordered in the absence of zinc but, in the presence of zinc, it adopts a secondary structure with a high alpha helical content. Integrase bound by zinc tetramerizes more readily than the apoenzyme and is also more active than the apoenzyme in in vitro integration assays. We conclude that binding of zinc to the HHCC motif stabilizes the folded state of the N-terminal domain of integrase and bound zinc is required for optimal enzymatic activity.

Amino Acid Sequence↗
PubMed1996

Scavenging effects of phenylpropanoid glycosides from Pedicularis on superoxide anion and hydroxyl radical by the spin trapping method(95)02255-4.

The scavenging activities of six phenylpropanoid glycosides, i.e. leucosceptoside A and martynoside, isolated from Pedicularis alashanica Maxim, verbascoside, and pediculariosides A, M and N isolated from Pedicularis striata Pall ssp. arachnoidea Franch Tsoong, on superoxide anion and hydroxyl radicals have been studied by the spin trapping method. The results demonstrated that the number of phenolic hydroxyl groups in the structures of the phenylpropanoid glycosides is related to their scavenging activities. The scavenging effects of the phenylpropanoid glycosides possessing two o-dihydroxyl groups were stronger than the effects of the compounds possessing two o-hydroxy-methoxy groups.

Cyclic N-Oxides↗
PubMed1996

Repair of dGMP hydroxyl radical adducts by verbascoside via electron transfer: a pulse radiolysis study.

The repair activity of verbascoside (VER), isolated from Pedicularis spicata, towards the oxidizing hydroxyl radical adduct of dGMP and its reaction mechanism were studied using pulse radiolysis. Upon pulse radiolysis of nitrous oxide saturated aqueous solution of 2'-deoxyguanosine-5'-monophosphate (dGMP) and VER, it was found that the transient absorption spectrum of the hydroxyl adduct of dGMP decays with the formation of that of the phenoxyl radical of VER, several tens of microseconds after the electron pulse. From the formation kinetics of the phenoxyl radical of VER, the rate constant of the repair reaction was determined to be 1.12 x 10(9) dm(3) mol(-1) s(-1).

Antioxidants↗
PubMed1996

Reaction of hydroxyl radical with phenylpropanoid glycosides from Pedicularis species: a pulse radiolysis study.

Using pulse radiolysis technique, the reaction between hydroxyl radical and 7 phenylpropanoid glycosides: echinacoside, verbascoside, leucosceptoside A, martynoside, pediculariosides A, M and N which were isolated from Pedicularis were examined. The rate constants of these reactions were determined by transient absorption spectra. All 7 phenylpropanoid glycosides react with hydroxyl radical at high rate constants within (0.97-1.91) x 10(10)L.mol-1.s-1, suggesting that they are effective hydroxyl radical scavengers. The results demonstrate that the numbers of phenolic hydroxyl groups of phenylpropanoid glycosides are directly related to their scavenging activities. The scavenging activities are likely related to o-dihydroxy group of phenylpropanoid glycosides as well.

Drugs, Chinese Herbal↗
PubMed1995

Catalytic and potentiometric characterization of E201D and E201Q mutants of Trypanosoma congolense trypanothione reductase.

Trypanothione reductase is a member of the structurally and functionally well-characterized family of flavoprotein reductases, which catalyze the reduced pyridine nucleotide dependent reduction of their disulfide, peroxide, or metal ion substrates. Trypanothione reductase is found in a wide variety of Trypanosoma species, where the enzyme serves physiologically to protect the organism from oxidative stress and assists in maintaining low intracellular levels of hydrogen peroxide. The redox potential of the flavin and the hydride ion transfer reaction of the pro-S hydrogen of NADPH to N5 of FAD have been proposed to be influenced by the presence of a conserved Lys-Glu (K60-E201) ion pair at the bottom of the nicotinamide binding pocket. We have evaluated this hypothesis by making modest substitutions for both the Lys and Glu residues using site-directed mutagenesis. Replacement of the K60 residue with an arginine led to a poorly expressed, and completely inactive, enzyme. Replacement of the Glu201 residue with either a glutamine (E201Q) or an aspartate (E201D) residue led to expressed enzymes which could be readily purified in > 20 mg amounts using protocols developed for the WT enzyme, and which had significant residual trypanothione-reducing activity. These enzymes have now been characterized to determine their redox potentials, catalytic activities, and nucleotide specificities. Relative to the WT enzyme, both E201D and E201Q exhibit ca. 5% of WT trypanothione-reducing activity using NADPH as reductant, but significantly enhanced quinone reductase activity. The oxidase activity of both mutants is enhanced by over 50-fold compared to that of the WT. The redox potential of the WT enzyme has been determined to be -273 mV, while both the E201D and E201Q exhibit more positive redox potentials (-259 and -251 mV, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Evidence for a superantigen mediated process in Kawasaki disease.

The clinical, pathological, and immunological similarities between Kawasaki disease and the staphylococcal and streptococcal toxic shock syndromes suggest that a superantigen toxin may be involved in the pathogenesis of the disease. The V beta repertoire of peripheral blood mononuclear cells from 21 children with Kawasaki disease, 28 children with other illnesses, and 22 healthy controls were examined using monoclonal antibodies to V beta 2, 5, 8, 12, and 19. The mean percentage of V beta 2 expressing T cells in the patients with Kawasaki disease was increased when compared with healthy controls or children with other illnesses. The mean percentages of V beta 5, 8, 12, and 19 expressing T cells were also increased in the patients with Kawasaki disease compared with healthy controls, but were not increased when compared with children with other illnesses. The selective use of V beta 2 supports the hypothesis that a superantigen is involved in the pathogenesis of Kawasaki disease.

Acute Disease↗
PubMed1995

[Hepatitis virus infection and bone marrow transplantation].

Hepatitis virus infection is a special problem in China and the role of Hepatitis virus infection in allogeneic bone marrow transplantation (BMT) is not well-defined. In this study, 106 BMT patients were included for analysis of the role of virus infection in allo-BMT. Seven and 65 of 106 patients were found to have HBV infection and HCV infection, respectively. Neither HBV infection and HCV infection interfered with the engraftment of bone marrow cells nor increased the rate of AGVHD, CGVHD, VOID. Neither HBV infection nor HCV infection prohibited allo-BMT. But Hepatitis virus infection can cause mild to moderate liver dysfunction, even death because of acute liver function failure, active prevention and treatment of hepatitis virus infection remains necessary. In this respect, rh-interferon is useful.

Adolescent↗
PubMed1995

[Investigation of blood supply of bronchogenic carcinoma deriving from pulmonary artery].

Microfil perfusion technique was used to investigate the blood supply of bronchogenic carcinoma deriving from pulmonary artery on 20 fresh specimens of lung cancer, including 11 squamous carcinoma, 6 adenocarcinoma, 1 alveolar cell carcinoma and 2 undifferentiated carcinoma cases. The results showed that the appearance and quantity of pulmonary blood supply of bronchogenic carcinoma depended on and changed with the site, activity, growth mode as well as the local condition of tumor nodules; pulmonary artery supplied blood to the periphery of the tumor and its innermost part as well; vessels from pulmonary artery in tumor nodules were generally less in number than those in the surrouding normal lung tissues around. The results suggested that the tumor blood supply from pulmonary artery should be evaluated comprehensively and dynamically; during interventional chemotherapy via pulmonary artery, patients should be selected carefully and the catheter for infusion placed in suitable position so as to gain the best therapeutic effect.

Adenocarcinoma↗
PubMed1995

[Differential diagnosis of delayed encephalopathy induced by anthelmintic imidazoles].

Anthelmintic imidazoles induced delayed encephalopathy (AIIDE) is frequently encountered and has usually been misdiagnosed as sporadic encephalitis of unknown cause (SEU). This study was carried out to facilitate differentiation of the two diseases. The records of 202 cases of AIIDE were reviewed and the clinical features analyzed. As a results, 7 diagnostic criteria for AIIDE were proposed as follows: (1) history of exposure to anthelmintic before the onset; (2) presence of a latent period of of 2 to 5 weeks; (3) onset of the disease acute or subacute; (4) presence of neuropsychiatric symptoms and signs resulted from multifocal cerebral damage; (5) Fulfillment of two of the following conditions; (a) subinflammatory change in CSF with elevation of IgG; (b) diffuse slow waves in EEG during early stage; (c) characteristics of acute demyelinating encephalopathy in brain biopsy; (6) good therapeutic effect of adrenal corticosteroids; (7) exclusion of other neuropsychiatric disorders in a fallow-up period of one year. AIIDE is a new disease entity and its diagnosis is mainly based on the clinical features. EEG, CT or MRI are important diagnostic measures, but history of exposure to anthelmintic is the most important criterion. Multifocal hemorrhagic leukoencephalopathy is its main pathologic feature.

Adult↗
PubMed1995

[Intelligence study on 1758 deaf children in China].

In order to determine the character of mental development and the influencing factors of childhood deafness in China the revised H-NTLA was applied to 1758 deaf children within the age range of 3 to 17 years. Compared with 1788 normal hearing children, the results showed that (1) the deaf children were about 20 points lower in IQ than those with normal hearing; (2) the average retardation was found to be about 6 months in 3-5 years old age, the difference became significant from 6 years old, the average retardation was found to be 36 months during 13 years old; (3) the scores were the same as those of the normal hearing children for block patterns, paper folding and puzzle blocks in 3-9 age groups; for visual attention span and spatial reasoning in 16-17 age groups. The scores were retarded significantly on picture association, picture analogies, memory for color and digits; (4) the influencing factors were found with stepwise regression model to be audiphone wearing, education fee and the beginning age of education.

Adolescent↗
PubMed1994

[Fang Chengpei and Zheng's laryngology].

The relationship between Fang Chengpei, a famous physician of the Xin'an school of traditional Chinese medicine and a master of traditional Chinese folk arts of the Qing Dynasty, and successors of Zheng's laryngology of Xin'an was even closer than that between his close relatives and friends. Zheng Meijian imparted laryngological medical skills to Fang, made a preface to Shou Yi Mi Lu (Secret Records of Medical Skills)--a secret document handed down in Fang-family, gave directions to and held discussions with Fang on the doctrine on five elements' motion and six kinds of natural factors. Fang participated in naming, prefacing, and revising Chong Lou Yu Yue (A Jade Key to Laryngeal Diseases) in which three secret recipes for laryngeal diseases that had been handed down in Fang's family were included. Together with Zheng Shufu, he wrote Chong Lou Yu Yue Xu Pian (Continuation of A Jade Key to Laryngeal Diseases). After Fang had passed away, many of his belongings were left in Zhengs' house, including medical documents, calligraphy, music scores, medical instruments, etc. Fang made a great contribution to the academic development of Zheng's Laryngology.

China↗
PubMed1993

An observation on flash evoked cortical potentials and Qigong meditation.

The purpose of this study was to investigate the functional state of the cerebral cortex during Qigong meditation with flash visual evoked potentials (F-VEPs) recorded from the occipital scalp in four groups of adults. The first group included 14 subjects who had exercised in Neiyang Gong for 0.5-5.5 years. The second group was composed of 12 subjects who had practiced Neiyang Gong for only 0.5-3 months. Eleven subjects who had never practiced Qigong before made up the third group and served as control. Eleven Qigong practitioners constituted the fourth group. It was found that F-VEP amplitudes were increased in the first group and decreased in the fourth group with the exception of one subject during Qigong meditation. No significant changes were found in the second group and controls. The results were discussed and it is shown that Qigong mediation may have either facilitative or inhibitory effects on the visual cortex depending on the Qigong methods practiced by different individuals.

Adult↗
PubMed1993

Protection of phenylpropanoid glycosides from Pedicularis against oxidative hemolysis in vitro.

Five phenylpropanoid glycosides from Pedicularis, isoacteoside (1), acteoside (2), echinacoside (3), pedicularioside A (4), cistanoside D (5), and a chemically synthesised compound, permethylacteoside (6), as phenolic compounds can protect against oxidative hemolysis. The inhibitory activity is related to the number of phenolic hydroxy groups. Compounds 1, 2, 3, and 4, possessing four phenolic hydroxy groups, have stronger inhibitory activities than 5 possessing only two phenolic hydroxy groups, and compound 6 with no phenolic hydroxy group inhibited oxidative hemolysis weakly.

Animals↗
PubMed1992

[Mechanism of the photosensitive effects of methylene blue in the inhibition of DNA synthesis in cancer cells].

In the present study, we found that various concentrations of methylene blue (38, 3.8, 0.38, 0.038, 0.0038 mumol/L) significantly inhibited DNA synthesis in ascites hepatoma (AH) cells. The inhibition increased with the concentration of methylene blue as well as with irradiation time. Photosensitization of methylene blue was not due to 1O2, OH., or O2.-, but was closely related to H2O2. The mechanism of inhibition of DNA synthesis may be attributed to the damage of DNA replication template.

Animals↗