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Biomedical subjects

Q Xu

Publications and source records attributed to Q Xu.

At least 73 records · Page 4Linked to original sources
PubMed2001

Structural revision of isovalertatins M03, M13, and M23 isolated from the culture of Streptomyces luteogriseus.

Three aminooligosaccharides, isovalertatins M03 (1), M13 (2), and M23 (3) were isolated and purified from the culture filtrate of Streptomyces luteogriseus. Their physicochemical properties, liquid chromatographic behavior, and spectroscopic data were in full accordance with the reported compounds [Xu, Q.; Wang, Q.; Lu, D. CN Patent 1100756, 1995; Chem. Abstr. 1995, 123, 110278n], but their structures were reinvestigated and revised by spectroscopic methods, including ESI multistage mass spectrometry and 2-dimensional NMR techniques.

Amines↗
PubMed2001

Characterization of single-stranded DNA on chitosan-modified electrode and its application to the sequence-specific DNA detection.

Single-strand DNA could bind with chitosan on a platinum electrode via forming a tight DNA-chitosan complex. The salt concentration of the ssDNA solution had an obvious effect on the surface coverage, the immobilization was remarkably reduced at high salt concentration. The sample ssDNA immobilized on the chitosan-modified electrode can hybridize efficiently with the complementary sequences and be successfully used for the sequence-specific DNA detection. The same results could be obtained using a gold or graphite electrode modified with chitosan. The stability of this electrode has been also discussed.

Biopolymers↗
PubMed2001

Chronic infections and the risk of carotid atherosclerosis: prospective results from a large population study.

BACKGROUND: Chronic infections have been implicated in the pathogenesis of atherosclerosis, yet from an epidemiological perspective, this concept remains controversial. METHODS AND RESULTS: The Bruneck Study is a prospective population-based survey on the pathogenesis of atherosclerosis. In 826 men and women 40 to 79 years old (1990 baseline), 5-year changes in carotid atherosclerosis were thoroughly assessed by high-resolution duplex scanning. The presence of chronic respiratory, urinary tract, dental, and other infections was ascertained by standard diagnostic criteria. Chronic infections amplified the risk of atherosclerosis development in the carotid arteries. The association was most pronounced in subjects free of carotid atherosclerosis at baseline (age-/sex-adjusted odds ratio [95% CI] for any chronic infection versus none, 4.08 [2.42 to 6.85]; P:<0.0001) and applied to all types of chronic (bacterial) infections. It remained independently significant after adjustment for classic vascular risk attributes and extended to low-risk individuals free of conventional risk factors. Among subjects with chronic infections, atherosclerosis risk was highest in those with a prominent inflammatory response. Markers of systemic inflammation, such as soluble adhesion molecules and circulating bacterial endotoxin, and levels of soluble human heat-shock protein 60 and antibodies to mycobacterial heat-shock protein 65 were elevated in subjects with chronic infections and predictive of an increased risk of atherosclerosis. CONCLUSIONS: The present study provides solid evidence for a role of common chronic infections in human atherogenesis. Induction of systemic inflammation and autoimmunity may be potential pathophysiological links.

Adult↗
PubMed2001

Stereocontrolled total synthesis of alkaloid G via the oxy-anion Cope rearrangement and improved total synthesis of (+)-ajmaline.

[figure: see text] The oxy-anion Cope rearrangement followed by protonation of the enolate which resulted under conditions of kinetic control has been employed to generate the key asymmetric centers at C(15), C(16), and C(20) in alkaloid G (1) and (+)-ajmaline (2) in a highly stereocontrolled fashion. The aldehyde 7b from this process has been converted into alkaloid G (1) and (+)-ajmaline (2) in 36% and 13% overall yields (11 reaction vessels from 3), respectively.

Ajmaline↗
PubMed2001

Mouse model of myocardial remodelling after ischemia: role of intercellular adhesion molecule-1.

OBJECTIVE: We studied the effects of temporary myocardial ischemia and reperfusion on myocyte injury and ventricular remodelling in wildtype and intercellular adhesion molecule-1- (ICAM-1) deficient mice. METHODS: ICAM-1-/- and ICAM-1+/+ mice were subjected to 30 min of myocardial ischemia and subsequent reperfusion for 2 h, 1 week and 3 weeks, respectively. The evaluation of tissue damage and scar size was performed with histological sections stained with hematoxilin and eosin. Serum levels of troponin T, creatine kinase and lactate dehydrogenase isoenzyme 1 were evaluated as an index of cardiac cellular damage. Immunohistological analysis was employed to determine cell compositions in ischemic regions. RESULTS: After myocardial ischemia (30 min) and 2 h reperfusion, elevation in serum troponin T, creatine kinase and lactate dehydrogenase isoenzyme 1 were found in both groups, but significantly reduced in ICAM-1-/- mice compared with wildtype mice (P<0.05). Absence of a functional ICAM-1 gene in ICAM-1-/- mice resulted in a marked reduction of ischemia-reperfusion injury at the early stage. The damage score and size of the infarct area were lower in ICAM-1 -/- mice by 30 min of ischemia and 2 h of reperfusion (1.4+/-0.54 vs. 2.4+/-0.47, P<0.05). The percentage of MAC-1-positive cells in the ischemic region and the border zone was also significantly diminished in groups of ICAM-1-/- mice. Surprisingly, the scar size in ventricles in animals 1 or 3 weeks after ischemia was similar between ICAM-1-/- and ICAM-1+/+ mice, although the number of infiltrated MAC-1 positive cells in the scar in wildtype mice was higher. CONCLUSION: Our results demonstrate that the absence of ICAM-1 expression results in less myocardial damage induced by ischemia-reperfusion at the early stage, but does not influence the size of myocardial infarction and scar formation.

Animals↗
PubMed2001

Solubilization of cyclosporin A.

This study investigated the solubilization of cyclosporin A (CsA), a neutral undecapeptide, by cosolvency, micellization, and complexation. Cosolvents (ethanol, propylene glycol, polyethylene glycol, tetrahydrofurfuryl alcohol polyethyleneglycol ether, and glycerin), surfactants (polyoxyethylene sorbitan monooleate [(Tween 80)], polyoxyethylene sorbitan monolaurate [(Tween 20)], and Cremophor EL), and cyclodextrins (alpha-cyclodextrin [(alphaCD)] and hydroxypropyl-beta-cyclodextrin[(HPbetaCD)] were used as solubilizing agents in this study. Surfactants had a noticeable effect in increasing CsA solubility. Twenty percent solutions of Tween 20, Tween 80, and Cremophor EL increased the solubility by 60 to 160 fold. Cyclodextrins can increase the CsA solubility, but alphaCD was more effective than HPbetaCD. Cosolvents on the other hand did not increase the solubility of CsA as much as expected from the LOGP (logarithm of water-octanol partition coefficient) value of CsA.

Chemistry, Pharmaceutical↗
PubMed2001

Selective roles of retinoic acid receptor and retinoid x receptor in the suppression of apoptosis by all-trans-retinoic acid.

Retinoic acids exert profound effects on many biological processes including cell proliferation, differentiation, and morphogenesis. We previously reported that all-trans-retinoic acid (t-RA) protected mesangial cells from H(2)O(2)-triggered apoptosis by suppressing the activator protein 1 (AP-1) pathway. It was via inhibition of c-fos and c-jun expression and suppression of c-Jun N-terminal kinase (JNK) activation. In this report, we investigated the involvement of retinoic acid receptor (RAR) and retinoid X receptor (RXR) in the antiapoptotic effect of t-RA in H(2)O(2)-exposed cells. We found that pretreatment with RAR pan-antagonist (AGN193109) or RXR pan-antagonist (HX531) attenuated the antiapoptotic effect of t-RA. Similarly, transient transfection with a dominant-negative mutant of RAR or a dominant-negative RXR diminished the antiapoptotic effect of t-RA. Both RAR and RXR antagonists reversed the suppressive effect of t-RA on AP-1 activity. However, the roles of RAR and RXR in the suppression of AP-1 components by t-RA were found to be different. RAR antagonist reversed the suppressive effect of t-RA on both c-fos and c-jun, whereas RXR antagonist reversed the effect of t-RA on c-fos but not c-jun. Furthermore, suppression of JNK activation by t-RA was observed even in the presence of RAR and RXR antagonists. Consistently, suppression of JNK by t-RA was not affected by overexpression of either the dominant-negative RAR or the dominant-negative RXR. These data elucidated that the antiapoptotic effect of t-RA is mediated by both nuclear receptor-dependent and -independent mechanisms.

Animals↗
PubMed2001

Alkyne-based, highly stereo- and regioselective synthesis of stereodefined functionalized vinyl tellurides.

(Z)-beta-Aryltellurovinylphosphonates and (Z)-beta-aryltellurovinyl sulfones were synthesized via the highly stereoselective anti-hydrotelluration of 1-alkynylphosphonates and 1-alkynyl sulfones. The configurations of these compounds were characterized via 1H NMR spectra or NOESY experiments and by X-ray diffraction analysis; (E)-beta-aryltellurovinyl sulfones were obtained with the reaction of sodium aryltellurate with (E)-2-iodovinyl sulfones to confirm the stereochemistry of the above anti-hydrotelluration. When the tandem reaction of alkynes with diaryl ditellurides and sodium arylsulfinates was carried out in AcOH/H2O (4/1), the corresponding (E)-beta-aryltellurovinyl sulfones were obtained in one step in good yields. This reaction is highly regio- and stereoselective and proceeds by using arylsulfinate as the sulfonyl radical precursor and diaryl ditellurides as free radical acceptors. (E)-1-Iodo-2-aryltelluroalkenes can be obtained by the anti-addition of ArTeI with terminal alkynes in THF. The stereochemistry of compound 17b was also determined by X-ray diffraction analysis.

Journal Article↗
PubMed2001

Stability Characteristics of Dispersed Oil Droplets Prepared by the Microchannel Emulsification Method.

A novel emulsification method, microchannel (MC) emulsification, was developed for making monodispersed regular-sized droplets in our laboratory. An oil-in-water dispersed system, in which phosphate buffer was used as the continuous phase, sodium dodecyl sulfate (SDS) as the surfactant, and clove oil as the dispersed phase, was prepared by this technique. The average diameter of oil droplets was about 20 µm, with a narrow size distribution. The stability characteristics of the dispersed oil droplets were investigated by an optical microscope and kinetic light scattering method. The stability of the dispersed oil droplets depended on the SDS concentration. When the SDS concentration was above the critical micelle concentration (CMC), the turbidity of the dispersed solution sharply increased at the initial stage. Optical microscopic observation has confirmed that a part of the oil droplets broke up with time, and submicrometer droplets appeared. On the other hand, when the SDS concentration was below the CMC, the turbidity of the dispersed solution had little change in the initial stage, showing that the oil droplets were very stable. The effect of ion concentration was also examined. The results showed that the stability of the oil droplets depended on the balance of the Van der Waals attraction and electrical repulsion between the oil droplets in low ion concentration. Copyright 2001 Academic Press.

Journal Article↗
PubMed2001

Adenovirus-based overexpression of tissue inhibitor of metalloproteinases 1 reduces tissue damage in the joints of tumor necrosis factor alpha transgenic mice.

OBJECTIVE: Rheumatoid arthritis is a prototype of a destructive inflammatory disease. Inflammation triggered by the overexpression of tumor necrosis factor alpha (TNFalpha) is a driving force of this disorder and mediates tissue destruction. Since matrix metalloproteinases (MMPs) are among the molecules activated by TNFalpha, we hypothesized that overexpression of their natural inhibitor, tissue inhibitor of metalloproteinases 1 (TIMP-1), in TNFalpha transgenic mice could inhibit the development of destructive arthritis. METHODS: Systemic treatment was carried out by replication-defective adenoviral vectors for TIMP-1, beta-galactosidase, or phosphate buffered saline (PBS), which were applied once at the onset of arthritis. Clinical, serologic, radiologic, and histologic outcomes were assessed 18 days after the treatment. RESULTS: The AdTIMP-1 group showed significantly reduced paw swelling and increased grip strength compared with the 2 control groups, whereas total body weight, TNFalpha, and interleukin-6 levels were similar in all 3 groups. Radiographic assessment revealed a significant reduction of joint destruction in the AdTIMP-1 group; this was confirmed by histologic analyses showing reduced formation of pannus and erosions in the AdTIMP-1 group compared with the AdLacZ and PBS control groups. The formation of arthritis-specific autoantibodies to heterogeneous nuclear RNP A2 was not observed in the AdTIMP-1 group but was present in the 2 control groups. CONCLUSION: These results indicate a central role of MMPs in TNFalpha-mediated tissue damage in vivo and a promising therapeutic role for TIMP-1.

Adenoviridae↗
PubMed2001

Determination of the disulfide bond pattern of a novel C-type lectin from snake venom by mass spectrometry.

The disulfide bond pattern of Trimeresurus stejnegeri lectin (TSL), a new member of the C-type lectin family, was determined by mass spectrometry. Four intrachain disulfide bonds of TSL, Cys(3)-Cys(14), Cys(31)-Cys(131), Cys(38)-Cys(133) and Cys(106)-Cys(123), and two interchain linkages, Cys(2)-Cys(2) and Cys(86)-Cys(86), were determined. Three strategies were used in this work. One intrachain (Cys(106)-Cys(123)) and one interchain (Cys(86)-Cys(86)) disulfide linkages were detected by standard MS methods. The disulfide bonds Cys(2)-Cys(2) and Cys(3)-Cys(14) were analyzed using a modified partial reduction procedure and MS/MS. The last two disulfide bonds were characterized by a MS/MS/MS technique. The strategies developed in this work could be applied more generally to detection of disulfide bond patterns.

Amino Acid Sequence↗
PubMed2001

Site formation processes at Zhoukoudian, China.

Zhoukoudian is often cited for its human remains and the early evidence of fire. Yet, since its first excavations over 70 years ago, detailed studies of processes responsible for the accumulation of anthropogenic and geogenic sediments in the site have been sparse. This paper provides some details of site formation processes mainly through field observations of the extant section at Locality 1, and the use of soil micromorphology and Fourier Transform Infrared Spectrometry (FTIR) analyses of the sediments. Samples from Layers 10 through 3 show extensive water deposition of fine silt-sized material (reworked loess), including fine-grained organic matter. The dark organic-rich unit in Layer 10--often cited as one of the earliest evidence of fire--is a water-laid accumulation. Much of the fine-grained sediment was derived from outside Locality 1, implying that the site was open to varying extents throughout most of its depositional history. The 4-6 m accumulation of "ashes" in Layer 4 represents subaerial water-laid silt deposits derived from the loess-covered hillslopes surrounding the site. They presumably accumulated in an open depression that formed after the collapse of the brecciated roof deposits represented by Layer 6. Diagenesis is present in many of the Layers, and is exemplified by calcite precipitation and dissolution, and localized apatite (dahllite) replacement of calcite. In Layer 4 diagenesis is more advanced, including calcite/dahllite precipitation, subaerial weathering of the loess and associated precipitation of hematite, alteration of clay and the neoformation of quartz. Many of our conclusions concur with those of Teilhard de Chardin & Young published over 70 years ago.

Animals↗
PubMed2001

Astilbin selectively facilitates the apoptosis of interleukin-2-dependent phytohemagglutinin-activated Jurkat cells.

The present study examined the relationship between the activation of T cells and the apoptosis-facilitating effect of astilbin on them. By the stimulation of PHA, a remarkable IL-2 production was detected in the supernatant of Jurkat cells after 120 h among 72--144 h incubation. This kinetics was quite in accordance with that of astilbin-induced apoptosis of Jurkat cells, where 1 h-exposure of the PHA-activated cells to astilbin caused a significantly increased apoptosis in a dose-dependent manner. To the Jurkat cells that had been cultivated for 72--144 h without PHA, however, astilbin did not show any facilitation of the cell apoptosis. Pre-treatment by cyclosporine A simultaneously with PHA dose-dependently lowered the IL-2 production and susceptibility of the cells to astilbin, while the treatment after 120 h of PHA-activation did not. The exogenous IL-2 treatment after 72 h of PHA-activation significantly and dose-dependently raised the susceptibility of the Jurkat cells to astilbin. These results indicated the dependency of the apoptosis-facilitating effect of astilbin on appropriate status of activated T lymphocytes with a relation to IL-2 production. This characteristic of astilbin may be of great significance for the treatment of a variety of immunologically related diseases.

Antioxidants↗
PubMed2001

Smooth muscle cell apoptosis in arteriosclerosis.

Arteriosclerosis, a paradigmatic age-related disease, encompasses (spontaneous) atherosclerosis, restenosis after percutaneous transluminal coronary angioplasty, autologous arterial or vein graft arteriosclerosis and transplant arteriosclerosis. In all types of arteriosclerosis, vascular smooth muscle cell (SMC) accumulation in the intima is a key event, but abundant evidence also indicates the importance of SMC apoptosis in the development of arteriosclerosis. Because SMC proliferation and apoptosis coincide in arteriosclerotic lesions, the balance between these two processes could be a determinant during vessel remodeling and disease development. Various stimuli, including oxidized lipoproteins, altered hemodynamic stress and free radicals, can induce SMC apoptosis in vitro. As risk factors for arteriosclerosis, these stimuli may also lead to vascular cell apoptosis in vivo. The presence of apoptotic cells in atherosclerotic and restenotic lesions could have potential clinical implications for atherogenesis and contributes to the instability of the lesion. Based on the progress in this field, this review focuses on the mechanism and impact of SMC apoptosis in the pathogenesis of arteriosclerosis and highlights the role of biomechanical stress in SMC apoptosis.

Animals↗
PubMed2001

Strong-light photoinhibition treatment accelerates the changes of protein secondary structures in triton-treated photosystem I and photosystem II complexes.

Changes in the protein secondary structure and electron transport activity of the Triton X-100-treated photosystem I (PSI) and photosystem II (PSII) complexes after strong illumination treatment were studied using Fourier transform-infrared (FT-IR) spectroscopy and an oxygen electrode. Short periods of photoinhibitory treatment led to obvious decreases in the rates of PSI-mediated electron transport activity and PSII-mediated oxygen evolution in the native or Triton-treated PSI and PSII complexes. In the native PSI and PSII complexes, the protein secondary structures had little changes after the photoinhibitory treatment. However, in both Triton-treated PSI and PSII complexes, short photoinhibition times caused significant loss of alpha-helical content and increase of beta-sheet structure, similar to the conformational changes in samples of Triton-treated PSI and PSII complexes after long periods of dark incubation. Our results demonstrate that strong-light treatment to the Triton-treated PSI and PSII complexes accelerates destruction of the transmembrane structure of proteins in the two photosynthetic membranes.

Electron Transport↗
PubMed2001

Expression, regulation, and function of inhibitor of apoptosis family genes in rat mesangial cells.

BACKGROUND: The inhibitor of apoptosis (IAP) family of proteins regulates programmed cell death triggered by various stimuli. The purpose of this investigation was to examine the expression, regulation, and function of IAP genes in cultured rat mesangial cells. METHODS: Basal and inducible expression of c-IAP1, c-IAP2, XIAP, and TIAP mRNAs was examined in mesangial cells, isolated glomeruli, and other cell lines under unstimulated and tumor necrosis factor-alpha (TNF-alpha)-stimulated conditions. To examine a role of nuclear factor-kappa B (NF-kappa B) in the regulation of IAPs, expression of IAPs in NF-kappa B-inactive mesangial cells was compared with that in wild-type cells. To investigate roles of IAPs in mesangial cell apoptosis, NF-kappa B--inactive cells were stably supertransfected with c-IAP1 or c-IAP2, and the susceptibility of these cells to TNF-alpha--induced apoptosis was evaluated quantitatively. RESULTS: Substantial, constitutive expression of c-IAP2, XIAP, and TIAP was observed in serum-deprived rat mesangial cells and c-IAP2 and XIAP in isolated normal rat glomeruli. In response to TNF-alpha, expression of c-IAP1 and c-IAP2 was induced in HeLa cells and ECV304 endothelial cells, but not in mesangial cells. In contrast to previous reports on other cell types, the expression of IAPs in rat mesangial cells was independent of NF-kappa B; that is, expression levels of IAPs in NF-kappa B--inactive cells were same as those in NF-kappa B--active cells under both unstimulated and TNF-alpha--stimulated conditions. Even without the induction of IAPs, NF-kappa B--active mesangial cells were more resistant to TNF-alpha--induced apoptosis than NF-kappa B--inactive cells. Interestingly, overexpression of either c-IAP1 or c-IAP2 completely compensated for the lack of resistance to apoptosis in NF-kappa B--inactive cells. CONCLUSIONS: IAPs are constitutively expressed in cultured rat mesangial cells and isolated normal rat glomeruli. IAPs can contribute to the survival of rat mesangial cells, but unexpectedly, these molecules are not involved in the TNF-alpha--induced, NF-kappa B--dependent cytoprotection in this cell type.

Animals↗