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Biomedical subjects

Zheng Xu

Publications and source records attributed to Zheng Xu.

At least 37 records · Page 2Linked to original sources
PubMed2006

[Photostimulated luminescence and optical storage of BaLiF3:Eu2+].

BaLiF3:Eu2+ was prepared by high temperature solid state reaction. The peaks of photoluminescence spectrum and photostimulated luminescence (PSL) spectrum are both at 410 nm which are attributed to the 5d-4f emission of Eu2+. The photostimulated luminescence excitation spectrum has its maximum at about 660 nm. Therefore, He-Ne laser is suitable for the reading-out process. The mechanism of PSL was also studied according to the characters of the spectra in the present paper. The PSL decay property of the glass ceramics was investigated, and it was shown that the storage information is easy to be erased. BaLiF3:Eu2+ has good properties of PSL and a promising future.

English Abstract↗
PubMed2006

[Tm3+ concentration dependence of upconversion intensity of YLiF4: Er3+, Tm3+, Yb3+].

A series of YLiF4: Er3+ , Tm3+ , Yb3+ samples were synthesized by hydrothermal method. The concentrations of Er+ and Yb3+ were 1 mol% and 1.5 mol%, respectively. Tm3+ concentration changed from 2 to 8 mol%. The absorption of Er3+, Tm3+ and Yb3+ were observed, and the absorption of Tm3+ increased along with the increase in Tm3+ concentration. The color of upconversion luminescence of YLiF4: Er3+, Tm3+ and Yb3+ excited by 980 nm was white when Tm3+ concentration was low. The blue light resulted from the transition of 1G4-->3H6 of Tm3+, the green light from the transition of 4S(3/2)(2H(11/2))-->4I(15/2) of Er3+, and the red light from the transitions 1G4-->3F4 of Tm3+ and 4F(9/2)-->4I(15/2) of Er3+. All the upconversion intensities decreased when Tm3+ concentration increased, but the relative intensity decrease was different due to the interaction between Er3+ and Tm3+.

English Abstract↗
PubMed2006

[The influence of holes buffer layer doped with different one-dimensional nanomaterials on the performance of polymer light-emitting diodes].

The effect of holes buffer layer PEDOT doped with one-dimensional nanomaterials on the performance of polymer light-emitting diodes was investigated. The photoluminescence efficiency of double layer sample PEDOT/MEH-PPV was enhanced by doping one-dimensional nanomaterials (TiO2 nanotube and ZnO nanorod) into PEDOT layer. Stronger interaction of one-dimensional nanomaterials and PEDOT suppressed the creation of defect states which can quench radiative recombination of excitons. The electroluminescence efficiency of device was improved by 2 and 2.5 folds by doping TiO2 nanotubes and ZnO nanorods into holes buffer layer PEDOT respectively.

English Abstract↗
PubMed2006

[Optical and morphological investigation on the interaction of dual dopants in poly (N-vinylcarzole)].

The effect of optical and electrical properties of poly(N-vinylcarzole) (PVK) doped with two dyes, i. e. 8-tris-hydroxyquinoline (Alq3) and 4-(dicyanomethylene)-2-tert-butyl-6 (1, 1, 7, 7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), on the energy transfer and charge trapping processes was investigated. The phase separation in blends film at different doping concentration was also studied. More homogeneous dispersion of dyes in PVK with increasing doping concentration was showed. The results indicate that there is a certain interaction of Alq3 and DCJTB in this dual-doped system. It is the incorporation of DCJTB that untangled the aggregation of Alq3 owing to the interaction of DCJTB and Alq3. But for higher doping concentration, DCJTB results in an isolated charge transport channel that decreases the electroluminescence (EL) operating voltage.

English Abstract↗
PubMed2006

The methylation status of the TMS1/ASC gene in cholangiocarcinoma and its clinical significance.

BACKGROUND: TMS1/ASC is a bipartite protein comprising two protein-protein interactive domains: pyrin (PYD) and caspase recruitment domain (CARD). Proteins containing these domains play pivotal roles in regulating apoptosis and immune response pathways. The absence of TMS1/ASC expression in some tumors is because methylation of the TMS1/ASC gene contributes to carcinogenesis and cancer development. We studied the methylation status of the TMS1/ASC gene and its clinical significance in cholangiocarcinoma. METHODS: Target DNA was modified by sodium bisulfite, coverting all unmethylated, but not methylated, cytosines to uracil, and subsequently by a nested amplification with primers specific for methylated versus unmethylated DNA. The PCR product was detected by gel electrophoresis and combined with the clinical records of patients. RESULTS: Aberrant methylation of the TMS1/ASC gene was detected in specimens of colorectal cancer tissues from 13 (36.1%) of 36 patients, and specimens of adjacent normal tissues from 3 patients (8.3%). No statistical differences were seen in the extent of differentiation and invasion, lymph node metastasis, and pathologic type between the methylated and unmethylated tissues (P>0.05). CONCLUSIONS: The frequency of TMS1/ASC gene methylation in cholangiocarcinoma is high, but it is not related to pathologic changes. The TMS1/ASC gene is probably suppressed by methylation, and is resistant to apoptosis and immunological surveillance. The gene epigenetically affected in methylated tissues could be associated with carcinogenesis of cholangiocarcinoma.

Base Sequence↗
PubMed2006

[The influence of frequency on solid state cathodoluminescence].

Solid state cathodoluminescence (SSCL) is a new mechanism of light emission in organic-inorganic system. In the present article, we get SSCL under sinusoidal alternating-current voltage with a structure of ITO/SiO2/MEH-PPV/SiO2/Al. The spectra have two peaks: 410 and 580 nm, which obey molecular theory and band model, respectively. The temporal behaviors of both peaks in SSCL are studied with a new method of estimating lifetime in frequency domain. The intensity of the peak at 410 nm decreases as the frequency of the driving voltage increases, and the intensity of the peak at 580 nm increases as the frequency of the driving voltage increases. The difference in the dependence of light intensity on the frequency of excitation comes from the difference in the lifetime of the two peaks. The lifetime of short wavelength emission is found to be less than 5 ms while that of long wavelength emission is more than 0.05 ms.

English Abstract↗
PubMed2006

[The change in optical spectra from solid and liquid solution of copper phthalocyanines derivatives].

In the present work, the change in electronic absorption spectra from three copper phthalocyanines (CuPc, tb-CuPc, oo-CuPc) in different environments was investigated. The mechanism of red shift Q-band absorption from the three species in an organic solvent before and after protonation was discussed. This was used to compare with those dispersed in solid films. The relation between the molecular interactions and the spectra change was studied. In a combination of POM, DSC and XRD techniques, the structure and morphology of the thin films were characterised. It was found that the molecules in the doped matrices of PC were associated or aggregated. This association and hence the corresponding change in absorption spectra cannot be altered by the modification of dopant concentration.

English Abstract↗
PubMed2006

[The electroluminescence of a novel complex Eu(o-BBA)3(phen)].

A novel rare earth complex of Eu ion with 2-benzoylbenzoic acid and 1,10-phenathrolinephen (Eu(o-BBA)3 (phen)) was synthesized and used as a dopant to fabricate efficient electroluminescence(EL) devices. It was doped into poly(N-vinylcarbazole) (PVK) and spin coated into films. Devices using organic layer Alq3 (or inserted hole blocking layer BCP) and inorganic layer ZnS as electron transporting layer respectively were fabricated. The luminescence properties of the single-layer decvice A (ITO/PVK : Eu/Al) and the organic-inorganic heterostructure device were analyzed. It was found that the device using ZnS as the electron transporting layer has higher brightness and lower threshold voltage while maintains pure emission.

English Abstract↗
PubMed2006

[Luminescence of rare earth complex in organic-inorganic heterostructure].

Luminescence of rare earth complex based on organic-inorganic heterostructure is reported. The structure of the device is ITO/PVK:Tb/inorganic material/Al, where inorganic material includes ZnS, ZnO or ZnSe. For this structure, the authors obtained the characteristic emission of Tb ion. A large part of driving voltage was dropped on the PVK layer because the dielectric constant of ZnS is 3 times bigger than that of PVK. The electric field strength in PVK layer was improved, so the velocity of hole in PVK was increased. The balance of injected charge was enhanced.

English Abstract↗
PubMed2005

Antifungal activities and action mechanisms of compounds from Tribulus terrestris L.

Antifungal activity of natural products is being studied widely. Saponins are known to be antifungal and antibacterial. We used bioassay-guided fractionation to have isolated eight steroid saponins from Tribulus terrestris L., which were identified as hecogenin-3-O-beta-D-glucopyranosyl (1-->4)-beta-D-galactopyranoside (TTS-8), tigogenin-3-O-beta-D-glucopyranosyl (1-->4)-beta-D-galactopyranoside (TTS-9), hecogenin-3-O-beta-D-glucopyranosyl (1-->2)-beta-D-glucopyranosyl (1-->4)-beta-D-galactopyranoside (TTS-10), hecogenin-3-O-beta-D-xylopyranosyl (1-->3)-beta-D-glucopyranosyl (1-->4)-beta-D-galactopyranoside (TTS-11), tigogenin-3-O-beta-D-xylopyranosyl (1-->2)-[beta-D-xylopyranosyl (1-->3)]-beta-D-glucopyranosyl (1-->4)-[alpha-L-rhamnopyranosyl (1-->2)]-beta-D-galactopyranoside (TTS-12), 3-O-[beta-D-xylopyranosyl (1-->2)-[beta-D-xylopyranosyl (1-->3)]-beta-D-glucopyranosyl (1-->4)-[alpha-L-rhamnopyranosyl (1-->2)]-beta-D-galactopyranosyl]-26-O-beta-D-glucopyranosyl-22-methoxy-(3beta,5alpha,25R)-furostan-3,26-diol (TTS-13), hecogenin-3-O-beta-D-glucopyranosyl (1-->2)-[beta-D-xylopyranosyl (1-->3)]-beta-D-glucopyranosyl (1-->4)-beta-D-galactopyranoside (TTS-14), tigogenin-3-O-beta-D-glucopyranosyl (1-->2)-[beta-D-xylopyranosyl (1-->3)]-beta-D-glucopyranosyl (1-->4)-beta-D-galactopyranoside (TTS-15). The in vitro antifungal activities of the eight saponins against five yeasts, Candida albicans, Candida glabrata, Candida parapsilosis, Candida tropicalis and Cryptococcus neoformans were studied using microbroth dilution assay. In vivo activity of TTS-12 in a Candida albicans vaginal infection model was studied in particular. The results showed that TTS-12 and TTS-15 were very effective against several pathogenic candidal species and Cryptococcus neoformans in vitro. It is noteworthy that TTS-12 and TTS-15 were very active against Candida albicans (MIC(80) = 10 and 2.3 microg/mL) and Cryptococcus neoformans (MIC(80) = 1.7 and 6.7 microg/mL). Phase contrast microscopy showed that TTS-12 inhibited hyphal formation, an important virulence factor of Candida albicans, and transmission electron microscopy showed that TTS-12 destroyed the cell membrane of Candida albicans. In conclusion, TTS-12 has significant in vitro and in vivo antifungal activity, weakening the virulence of Candida albicans and killing fungi through destroying the cell membrane.

Animals↗
PubMed2005

Effects of Changtai granules, a traditional compound Chinese medicine, on chronic trinitrobenzene sulfonic acid-induced colitis in rats.

AIM: To study the effects of Changtai granules (CTG), a traditional compound Chinese medicine, on chronic trinitrobenzene sulfonic acid-induced colitis in rats. METHODS: Healthy adult Sprague-Dawley (SD) rats of both sexes, weighing 250-300 g, were employed in the present study. The rat colitis models were induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS) enemas at a concentration of 100 mg/kg in 50% ethanol. The experimental animals were randomly divided into dexamethasone (DX) treatment, CTG treatment, and model control groups, which were intracolicly treated daily with DX (0.2 mg/kg), CTG at doses of 2.9, 5.7 and 11.4 g crude drug/kg, and the equal amount of saline respectively from 6 h following induction of the colitis in rats inflicted with TNBS to the end of study. A normal control group of rats treated without TNBS but saline enema was also included in the study. After 3 wk of treatment, the animals were assessed for colonal inflammatory and ulcerative responses with respect to mortality, frequency of diarrhea, histology and myeloperoxidase activity (MPO). RESULTS: The therapeutic effect of CTG on ulcerative colitis (UC) was better than DX. CTG effectively inhibited the activity of granulocytes, macrophages and monocytes in a dose-dependent manner. Also it reduced MPO and formation of inflammation in colonic mucosal tissue. Furthermore, administration of CTG significantly prevented body mass loss and death, and decreased frequency of diarrhea in UC rats, when compared with the model control group rats. CONCLUSION: CTG would prove to be an ideal drug for chronic UC, and is warranted to be studied further.

Animals↗
PubMed2005

Mapping residues of SUMO precursors essential in differential maturation by SUMO-specific protease, SENP1.

SUMO (small ubiquitin-related modifier) is a member of the ubiquitin-like protein family that regulates cellular function of a variety of target proteins. SUMO proteins are expressed as their precursor forms. Cleavage of the residues after the 'GG' region of these precursors by SUMO-specific proteases in maturation is a prerequisite for subsequent sumoylation. To understand further this proteolytic processing, we expressed and purified SENP1 (sentrin-specific protease 1), one of the SUMO-specific proteases, using an Escherichia coli expression system. We show that SENP1 is capable of processing all SUMO-1, -2 and -3 in vitro; however, the proteolytic efficiency of SUMO-1 is the highest followed by SUMO-2 and -3. We demonstrate further that the catalytic domain of SENP1 (SENP1C) alone can determine the substrate specificity towards SUMO-1, -2 and -3. Replacement of the C-terminal fragments after the 'GG' region of SUMO-1 and -2 precursors with that of the SUMO-3, indicates that the C-terminal fragment is essential for efficient maturation. In mutagenesis analysis, we further map two residues immediately after the 'GG' region, which determine the differential maturation. Distinct patterns of tissue distribution of SENP1, SUMO-1, -2 and -3 are characterized. Taken together, we suggest that the observed differential maturation process has its physiological significance in the regulation of the sumoylation pathway.

Amino Acid Sequence↗
PubMed2005

The effect on anterior column loading due to different vertebral augmentation techniques.

BACKGROUND: Vertebral compression fractures are a significant cause of morbidity amongst the elderly, resulting in pain, kyphosis, decreased mobility, and often depression. The two most popular operative treatments of compression wedge fractures are vertebroplasty and kyphoplasty, however, which method leads to restoration of normal spinal loading is unknown. METHODS: A cadaveric thoracolumbar spine model was fractured and then treated using one of two techniques: vertebroplasty or kyphoplasty. Three non-destructive loading regimes were applied to the intact, fractured and treated cases. Sub-adjacent nuclear pressure, used as a measure of anterior column loading, was determined for each experimental variant and loading case. FINDINGS: The data indicate that nuclear pressure was substantially reduced after the spine was fractured. These pressures were minimally increased after treatment, however, not to the level of the pre-fractured condition. In all loading cases, there were no significant differences between the two treatment types. INTERPRETATION: While our data show that both vertebroplasty and kyphoplasty allow the disc to generate higher nuclear pressures, neither treatment increased nucleus pulposus pressure above the level of the intact state. This directly relates to the clinical condition in that adjacent segment fractures sustained subsequent to either treatment is likely the result of overall disease progression, and not a direct result of the intervention.

Adult↗
PubMed2005

cDNA array analysis of the differential expression change in virulence-related genes during the development of resistance in Candida albicans.

Candida albicans is the most frequently isolated fungus in immunocompromised patients associated with mucosal and deep-tissue infections. To investigate the correlation between virulence and resistance on a gene expression profile in C. albicans, we examined the changes in virulence-related genes during the development of resistance in C. albicans from bone marrow transplant patients using a constructed cDNA array representing 3096 unigenes. In addition to the genes known to be associated with azole resistance, 16 virulence-related genes were identified, whose differential expressions were newly found to be associated with the resistant phenotype. Differential expressions for these genes were confirmed by RT-PCR independently. Furthermore, the up-regulation of EFG1, CPH2, TEC1, CDC24, SAP10, ALS9, SNF1, SPO72 and BDF1, and the down-regulation of RAD32, IPF3636 and UBI4 resulted in stronger virulence and invasiveness in the resistant isolates compared with susceptible ones. These findings provide a link between the expression of virulence genes and development of resistance during C. albicans infection in bone marrow transplant (BMT) patients, where C. albicans induces hyphal formation and expression change in multiple virulence factors.

Candida albicans↗
PubMed2005

cDNA microarray analysis of differential gene expression in Candida albicans biofilm exposed to farnesol.

Candida albicans biofilms are structured microbial communities with high levels of drug resistance. Farnesol, a quorum-sensing molecule that inhibits hyphal formation in C. albicans, has been found to prevent biofilm formation by C. albicans. There is limited information, however, about the molecular mechanism of farnesol against biofilm formation. We used cDNA microarray analysis to identify the changes in the gene expression profile of a C. albicans biofilm inhibited by farnesol. Confocal scanning laser microscopy was used to visualize and confirm normal and farnesol-inhibited biofilms. A total of 274 genes were identified as responsive, with 104 genes up-regulated and 170 genes down-regulated. Independent reverse transcription-PCR analysis was used to confirm the important changes detected by microarray analysis. In addition to hyphal formation-associated genes (e.g., TUP1, CRK1, and PDE2), a number of other genes with roles related to drug resistance (e.g., FCR1 and PDR16), cell wall maintenance (e.g., CHT2 and CHT3), and iron transport (e.g., FTR2) were responsive, as were several genes encoding heat shock proteins (e.g., HSP70, HSP90, HSP104, CaMSI3, and SSA2). Further study of these differentially regulated genes is warranted to evaluate how they may be involved in C. albicans biofilm formation. Consistent with the down-regulation of the cell surface hydrophobicity-associated gene (CSH1), the water-hydrocarbon two-phase assay showed a decrease in cell surface hydrophobicity in the farnesol-treated group compared to that in the control group. Our data provide new insight into the molecular mechanism of farnesol against C. albicans biofilm formation.

Biofilms↗
PubMed2005

In vitro antifungal activity of ZJ-522, a new triazole restructured from fluconazole and butenafine, against clinically important fungi in comparison with fluconazole and butenafine.

The antifungal activity of ZJ-522, a new triazole antifungal agent restructured from fluconazole and butenafine, was compared to that of fluconazole and butenafine against 43 strains of fungi representing 13 fungal species. MICs were determined by using the National Committee for Clinical Laboratory Standards (NCCLS)-recommended broth microdilution method for yeasts, which was modified for filamentous fungi. ZJ-522 was about 50-fold and 2 to 16-fold more potent than fluconazole against yeasts and filamentous fungi respectively, but it was less active than butenafine against filamentous fungi, although butenafine was inactive against most yeasts. Thus, the fashion of ZJ-522 antifungal activity more similar to that of fluconazole than that of butenafine indicates that ZJ-522 should be an inhibitor of lanosterol 14alpha-demethylase but not of squalene epoxidase, and should be a candidate for clinical development.

Antifungal Agents↗
PubMed2005

In vitro and in vivo antifungal activities of the eight steroid saponins from Tribulus terrestris L. with potent activity against fluconazole-resistant fungal pathogens.

Antifungal activity of natural products is being studied widely. Saponins are known to be antifungal and antibacterial. We have isolated eight steroid saponins from Tribulus terrestris L., namely TTS-8, TTS-9, TTS-10, TTS-11, TTS-12, TTS-13, TTS-14 and TTS-15. TTS-12 and TTS-15 were identified as tigogenin-3-O-beta-D-xylopyranosyl(1-->2)-[beta-D-xylopyranosyl(1-->3)]-beta-D-glucopyranosyl(1-->4)-[alpha-L-rhamnopyranosyl(1-->2)]-beta-D-galactopyranoside and tigogenin-3-O-beta-D-glucopyranosyl(1-->2)-[beta-D-xylopyranosyl(1-->3)]-beta-D-glucopyranosyl(1-->4)-beta-D-galactopyranoside, respectively. The in vitro antifungal activities of the eight saponins against six fluconazole-resistant yeasts, Candida albicans, Candida glabrata, Candida parapsilosis, Candida tropicalis, Candida krusei, and Cryptococcus neoformans were studied using microbroth dilution assay. The results showed that TTS-12 and TTS-15 were very effective against several pathogenic candidal species and C. neoformans in vitro. It is noteworthy that TTS-12 and TTS-15 were very active against fluconazole-resistant C. albicans (MIC(80)=4.4, 9.4 microg/ml), C. neoformans (MIC(80)=10.7, 18.7 microg/ml) and inherently resistant C. krusei (MIC(80)=8.8, 18.4 microg/ml). So in vivo activity of TTS-12 in a vaginal infection model with fluconazole-resistant C. albicans was studied in particular. Our studies revealed TTS-12 also showed in vivo activities against fluconazole-resistant yeasts. In conclusion, steroid saponins TTS-12 and TTS-15 from Tribulus terrestris L. have significant in vitro antifungal activity against fluconazole-resistant fungi, especially TTS-12 also showed in vivo activity against fluconazole-resistant C. albicans.

Animals↗