Biomedical subjects

Hong-Bo Wang

Publications and source records attributed to Hong-Bo Wang.

9 recordsLinked to original sources

PubMed2006

Formation of supramolecular permethrin/beta-cyclodextrin nanorods.

Molecular dynamics simulations along with scanning tunneling microscopy (STM) imaging demonstrate the formation of a novel type of nanorods, with a stable [permethrin(beta-CD)(2)](n) structure in which the host:guest ratio is 2:1 and n=21-27 giving a length of approximately 30.0-38.5 nm and an average diameter of approximately 1.5 nm, self-assembled from an inclusion complex composed of permethrin and biocompatible beta-cyclodextrin.

Computer Simulation↗

PubMed2006

Efficient photosensitized splitting of the thymine dimer/oxetane unit on its modifying beta-cyclodextrin by a binding electron donor.

Two modified beta-cyclodextrins (beta-CDs) with a thymine dimer and a thymine oxetane adduct respectively, TD-CD and Ox-CD, have been prepared, and utilized to bind an electron-rich chromophore, indole or N,N-dimethylaniline (DMA), to form a supramolecular complex. We have examined the photosensitized splitting of the dimer/oxetane unit in TD-CD/Ox-CD by indole or DMA via an electron-transfer pathway, and observed high splitting efficiencies of the dimer/oxetane unit. On the basis of measurements of fluorescence spectra and splitting quantum yields, it is suggested that the splitting reaction occurs in a supramolecular complex by an inclusion interaction between the modified beta-CDs and DMA or indole. The back electron transfer, which leads low splitting efficiencies for the covalently-linked chromophore-dimer/oxetane compounds, is suppressed in the non-covalently-bound complex, and the mechanism has been discussed.

Electrons↗

PubMed2006

Bioactive permethrin/beta-cyclodextrin inclusion complex.

Permethrin is popularly used in a variety of therapeutic areas. However, the poor water solubility of permethrin seriously limits its wider clinical applications. The present study demonstrates that solubility of permethrin in aqueous solution can considerably increase in the presence of beta-cyclodextrin (beta-CD). Extensive experimental data along with computational modeling reveal the formation of stable permethrin/beta-CD inclusion complexes, including permethrin(beta-CD) and permethrin(beta-CD)2, through hydrophobic binding. Both permethrin(beta-CD) and permethrin(beta-CD)2 complexes coexisted in aqueous solution, and the ratio of the concentration of permethrin(beta-CD) complex to that of permethrin(beta-CD)2 complex was dependent on the concentration of beta-CD. The complexation of permethrin with beta-CD significantly improved the bioavailability of permethrin and, therefore, increased the bioactivity. The significant increase of the bioactivity of permethrin in the presence of beta-CD provides an effective approach to improve the practical use of permethrin in public health and agriculture.

Calorimetry, Differential Scanning↗

PubMed2005

Model studies of the (6-4) photoproduct photoreactivation: efficient photosensitized splitting of thymine oxetane units by covalently linked tryptophan in high polarity solvents.

Three covalently linked tryptophan-thymine oxetane compounds used as a model of the (6-4) photolyase-substrate complex have been prepared. Under 290 nm light, efficient splitting of the thymine oxetane with aromatic carbonyl compounds gives the thymine monomer and the corresponding carbonyl compounds by the covalently linked tryptophan via an intramolecular electron transfer, and exhibits a strong solvent dependence: the quantum yield (Phi) is ca. 0.1 in dioxane, and near 0.3 in water. Electron transfer from the excited tryptophan residue to the oxetane unit is the origin of fluorescence quenching of the tryptophan residue, and is more efficient in strong polar solvents. The splitting efficiency of the oxetane radical anion within the tryptophan.+-oxetane.- species is also solvent-dependent, ranging from ca. 0.2 in dioxane to near 0.35 in water. Thus, the back electron transfer reaction in the charge-separated species would be suppressed in water, but is still a main factor causing low splitting efficiencies in the tryptophan-oxetane systems. In contrast to the tryptophan-oxetane system, fast nonradiation processes are the main causes of low efficiency in the flavin-oxetane system. Hence, nonradiative processes of the excited FADH-, rather than electron transfer to oxetane, may be an important factor for the low repair efficiency of (6-4) photolyase.

Electrons↗

PubMed2005

Mechanism of counterattack of colorectal cancer cell by Fas/Fas ligand system.

AIM: To determine the role of Fas/Fas ligand (FasL) in the immune escape of colon cancer cells. METHODS: Immunohistochemistry was used to observe the expression of Fas and FasL in the tissues of colon cancer patients. In situ hybridization was used to detect the localization of FasL mRNA expression in cancer tissues. Terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL) assay and CD45 staining were performed to detect the apoptosis of tumor-infiltrating lymphocytes (TILs). Co-culture assays of colon cancer cells (SW480) and Jurkat cells (Fas-sensitive cells) were performed to observe the counterattack of colon cancer cells to lymphocytes. RESULTS: Of 53 cases of colon carcinomas, 23 cases (43.4%) expressed Fas which was significantly lower as compared to the normal colonic mucosa (73.3%, P<0.01), and 45 cases (84.9%) of colon carcinomas expressed FasL, whereas only two cases (3.75%) in normal mucosa expressed FasL. FasL expression in the colon cancer cells was found to be associated with increased cell death of TILs. The apoptotic rate of TIL in the FasL-positive staining regions of tumor cells was significantly higher than that in the FasL-negative staining region (54.84+/-2.79% vs 25.73+/-1.98%, P<0.01). The co-culture of SW480 cells and Jurkat cells confirmed the function of FasL on the SW480 cells. The apoptotic rates of Jurkat cells were found to be related with the amount of SW480 cells. CONCLUSION: Colon cancer cells can escape the immune surveillance and killing via decreasing Fas expression, and can counterattack the immune system via increasing FasL expression. Fas/FasL can serve as potential targets for effective antitumor therapy.

Apoptosis↗

PubMed2005

Origin of a large temperature dependence of regioselectivity observed for [2 + 2] photocycloaddition (Paternò-Büchi reaction) of 1,3-dimethylthymine with benzophenone and its derivatives: conformational property of the intermediary triplet 1,4-diradicals.

[reaction: see text] The [2 + 2] photochemical additions of 1,3-dimethylthymine (DMT) with benzophenone and its 4,4'-substituted derivatives (BPs), difluoro, di-tert-butyl, and dimethoxy benzophenones, have been investigated at a temperature range from -40 to 70 degrees C. The photochemical reactions, which are cycloaddition of the 5-6 double bond of DMT with the carbonyl group of BPs, the so-called the Paternò-Büchi (PB) reaction, reveal largely temperature-dependent regioselectivity. The chemical yields of one series of regioisomers, 2, decrease with the increase of the reaction temperature, but those of another regioisomer series, 3, increase, and thus the ratio of 2/3 is strongly dependent on the temperature (2/3 = ca. 70:30 to 30:70). The temperature dependence of the regioselectivity yields two linear functions in the corresponding Eyring diagrams. The Eyring plot with changed slopes is clearly indicative of the change for the selectivity-determining step in the PB reaction, in which the triplet 1,4-diradicals play a crucial role. Computational studies reveal the conformational equilibrium structures of the triplet 1,4-diradicals, energy barriers between the conformers, and the conjectural equilibrium constants from relative potential energies of the stable conformers. A proposed mechanism can reasonably explain the temperature-dependent regioselectivity and chemical yields of two regioisomers varying with the reaction temperature.

Journal Article↗

PubMed2005

Early enteral and parenteral nutritional support in patients with cirrhotic portal hypertension after pericardial devascularization.

BACKGROUND: The abnormal metabolism caused by cirrhosis always results in a complex problem about nutritional support, which will be more intricate while patients with portal hypertension are treated with pericardial devascularization. Comparing the effects of early enteral and parenteral nutritional support in patients with cirrhotic portal hypertension after pericardial devascularization, we try to realize the advantages and disadvantages of the two nutritional therapies and to guide our clinical practice. METHODS: After pericardial devascularization, 40 patients with cirrhotic portal hypertension were divided randomly into 2 groups: enteral and parenteral nutritional support, respectively. The general nutritional condition, capability of producing protein, liver function, blood velocity of the portal vein, gut function, bowel bacterial translocation, mortality, complication rate, stay in ICU, duration of hospitalization and costs of treatment were determined in all the patients and compared between the 2 groups. RESULTS: Both enteral and parenteral nutritional supports could improve the general nutrition condition of the patients; but patients receiving enteral nutritional support had fewer complications. Enteral nutrition was more effective than parenteral nutrition in increasing the blood velocity of the portal vein, stimulating gut motion, preventing bowel bacterial translocation, shortening the stay in ICU and the duration of hospitalization, and saving costs of treatment. CONCLUSION: After pericardial devascularization, patients with cirrhotic portal hypertension should be treated with enteral nutritional support as early as possible.

Adult↗

PubMed2004

[Killing effect of adenovirus mediated fusion gene cytosine and deaminase uracil phosphoribosyl transferase directed by glutathione S-transferase P1 promoter on cisplatin-resistant ovarian cancer cells in vitro].

OBJECTIVE: To construct an adenoviral vector in which the fusion gene cytosine and uracil phosphoribosyl (UPP) transferase was directed by glutathione S-transferase P1 (GSTP1) promoter, and to investigate specific killing effect of the suicide gene system on cisplatin-resistant ovarian cancer cells. METHODS: Recombinant adenovirus was generated through homologous recombination in bacteria. A2780 and A2780/DDP cells were infected with Ad and then received flucytosine (5-FC) administration. The relative survival of these cells was tested. And a bystander effect was observed by mixing gene-transferred and gene-untransferred A2780/DDP cells with 5-FC. RESULTS: In vitro, when MOI was 100 and 5-FC was 250 micro g/ml, relative survival rate of A2780/DDP cells was only (3.6 +/- 1.0)%; that of A2780 cells was (76.5 +/- 2.8)%. Significant bystander effect was caused by CD-UPP gene and 20% gene-transferred A2780/DDP cells induced 80.3% of total cells to death. CONCLUSION: Recombinant adenovirus carrying CD-UPP gene driven by GSTP1 promoter has a specific killing effect on cisplatin-resistant ovarian cancer cells.

Adenoviruses, Human↗

PubMed2003

[Susceptibility of 570 Pseudomonas aeruginosa strains to 11 antimicrobial agents and the mechanism of its resistance to fluoroquinolones].

OBJECTIVE: To investigate the resistance of Pseudomonas aeruginosa (P. aeruginosa) to 11 antimicrobial agents and the mechanism of its resistance to fluoroquinolones (FQs). METHODS: The susceptibility of 570 strains of P. aeruginosa isolated clinically to 11 antimicrobial agents were detected by Kirby-Bauer disc diffusion method. The minimal inhibitory concentration (MIC) of 111 strains thereof to two FQs was determined by agar dilution method. 80 strains resistant to ciprofloxacin (MIC >or= 4 mg/L) were studied for the presence of point mutations in the gyrA and parC gene by direct sequencing and polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) method. RESULTS: The resistance rates of P. aeruginosa to cefepine, imipenem, amikacin, and ceftazidine, and aztreonam were 10.9%, 11.1%, 11.8%, 12.5%, and 16.6% respectively. The resistance rates to ciprofloxacin, levofloxacin, cefoperazone/sulbactam, and piperacillin were 29.2%, 32.9%, 23.5% and 33.7% respectively. The resistance rates to gentamycin and cefotaxime were 35.7% and 41.1% respectively. More than 60% of the ciprofloxacin resistant strains and the intensive care units (ICU) isolates were multidrug resistant. Among the 80 ciprofloxacin resistant strains, 66 (75%) had a mutation in gyrA codon: Thr83 (ACC)-->Ile (ATC), 52 strains (65%) had a mutation at parC codon: Ser87 (TCG)-->Leu (TTG), and 52 strains (65%) had both the above mentioned gyrA and parC mutations; while gyrA or parC mutation was not observed in the 31 ciprofloxacin susceptible strains. The MIC of ciprofloxacin for the 52 strains with mutations in both gyrA and parC genes was 19.80 mg/L +/- 2.11 mg/L, significantly higher than those for the 14 strains with mutation only in gyrA gene (11.88 mg/L +/- 2.73 mg/L, P < 0.05) and the 143 strains without gyrA and parC gene mutants (11.89 mg/L +/- 2.12 mg/L, P < 0.05). CONCLUSION: Resistance to antimicrobial agents of P. aeruginosa strains remains a problem. In particular, those ciprofloxacin resistant strains and ICU isolates are resistant to most of the antimicrobial agents. The resistance to fluoroquinolones of the clinical isolates of P. aeruginosa is mainly due to the mutations in gyrA and parC genes encoding the target enzyme of fluoroquinolones.

Anti-Bacterial Agents↗