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Biomedical subjects

Yi Chen

Publications and source records attributed to Yi Chen.

At least 55 records · Page 3Linked to original sources
PubMed2006

Capillary electrophoretic determination of glucosamine in osteoarthritis tablets via microwave-accelerated dansylation.

A robust capillary electrophoretic method has been established to separate aminosaccharides including glucosamine, galactosamine, N-methyl-glucamine, N-acetyl-glucosamine and amino glucuronic acid. All the aminosaccharides were dansylated fast under microwave irradiation at 385 W for 6 min (about 50-fold faster than common methods) and detected via on-line UV adsorption at 214 nm. Baseline separation of the dansylatied products was achieved in 20 min using a running buffer of 320 mM borate at pH 9.50. Quantitation of glucosamine in osteoarthritis tablets was then conducted. A linear working range was found in between 2.00 microg/mL and 1.80 mg/mL with linear regression coefficient of 0.9964. The limit of detection reached 1.00 microg/mL glucosamine (signal-to-noise, S/N=3). Recoveries were determined by spiking a known amount of glucosamine in tablet-extracted solutions, giving a range of 88.0-99.7%. The run-to-run relative standard deviation was 0.24% (n=5) for migration time and 2.72% for peak area.

Buffers↗
PubMed2006

Label-free reading of microarray-based proteins with high throughput surface plasmon resonance imaging.

A simple method is presented discriminating proteins at a gold surface by using an emerging technology, surface plasmon resonance (SPR) imaging. As a high throughput method, the protein array of bovine serum albumin (BSA), poly-l-lysine (PL), casein and lactate dehydrogenase (LDG) was fabricated and SPR imaging enables detection from different kinds of proteins immobilized on the sensor surface. These proteins can be discriminated directly by various reflected intensity or changing the incident angular position of light. Denaturation of these immobilized proteins on SPR sensor by interacting with denaturant 6M GdnHCl solution was also performed and obvious changes in reflected intensity were occurred after denaturation. The observation of denaturation of these proteins further supported the fact that different proteins could be discriminated on protein array before denaturation. On the other hand, the procedure of denaturation provided useful information that any change of molecular structure with the progress of denaturation would result in change of SPR signal. Excellent reproducibility with a chip-to-chip for label-free discriminating various proteins was achieved.

Image Enhancement↗
PubMed2006

Microsphere organization of nanorods directed by PEG linear polymer.

We demonstrate the sphere organization of ZnO, Bi2S3, MnO2, and La(OH)3 nanorods directed by PEG linear polymer. Our study shows that zinc, bismuth, manganese, or lanthanum species added to PEG solutions, in which PEG molecules are well dissolved in a coil state, convert the polymer coils to aggregate structures, which further aggregate into micrometer-sized M(n+)-PEG globules. The concentration of metallic species is higher in the globules than in bulk solutions. The surfaces of the globules act as soft templates for the initial nucleation and thereafter the growth of the nanorods. Finally, echinus-type assemblies of single-crystalline nanorods form by the metallic species hydrolyzing or reacting with deposition agents. This approach opens the possibility of using polymers as soft templates to control the organization of nano building units into designed structures.

Journal Article↗
PubMed2006

Incorporation of flow injection analysis or capillary electrophoresis with resonance Rayleigh scattering detection for inorganic ion analysis.

Resonance Rayleigh scattering (RRS) has been explored as a detection (RRSD) technique for capillary electrophoresis (CE) or flow injection analysis (FIA) of inorganic ions. The detection was achieved through a scattering probe of ion-association complex formed from rhodamine B (Rh B) and iodine. The probe scatters strongly at 630 nm when oxidants such as Cr(2)O(7)(2-), MnO(4)(-) and ClO(-) present in a mixed solution of Rh B and iodide. The scattering disappears once iodine is reduced by reductants. Oxidant or reductant species in a sample can thus be detected by positive or negative RRS signal. To verify the RRSD, FIA-RRSD was first constructed and continuous measurement of testing samples containing Cr(2)O(7)(2-), MnO(4)(-) and/or ClO(-) was performed. The detection limits reached a level of decade nM and a linear range was found between peak height and concentration at the range of 0.255-2.04microM for Cr(2)O(7)(2-), 0.158-3.16microM for MnO(4)(-), and 1.18-9.43microM for ClO(-), with linear regression coefficients of all above 0.99. The run-to-run relative standard deviation of peak height was less than 3% (n=6). CE-RRSD was then set up and studied, using a capillary of 75microm i.d.x33cm filled with a running buffer of 50mM citrate and 25mM Tris (pH 3.32) and worked under -12kV at room temperature. The CE eluent was at-line conducted into a stream of rhodamine B and iodine flowing inner a wide tube by plugging the capillary outlet into the wide tube. Different mixtures prepared from Cr(2)O(7)(2-), MnO(4)(-) and ClO(-) were successfully separated and detected by the CE-RRSD.

Electrophoresis, Capillary↗
PubMed2006

WISP-3 functions as a ligand and promotes superoxide dismutase activity.

WISP-3 (Wnt1 inducible secreted protein-3) mutations have been linked to the connective tissue diseases progressive pseudorheumatoid dysplasia and polyarticular juvenile idiopathic arthritis, both of which are accompanied by disorders in cartilage maintenance/homeostasis. The molecular mechanism of WISP-3 mediated effects in the sustenance of cartilage has not been described in detail. Our previous study illustrates the potential role of WISP-3 in regulating the expression of cartilage-specific molecules that sustain chondrocyte growth and cartilage integrity. The present study was conducted to investigate the mode of action of WISP-3 in greater detail. Experimental results depicted here suggest that WISP-3 can function as a ligand and signal via autocrine and/or paracrine modes upon being secreted by chondrocytes. Furthermore, apart from regulating collagen II and aggrecan expression, WISP-3 may also promote superoxide dismutase expression and activity in chondrocytes.

CCN Intercellular Signaling Proteins↗
PubMed2006

Chiral capillary electrophoretic separation of amino acids derivatized with 9-fluorenylmethylchloroformate using mixed chiral selectors of beta-cyclodextrin and sodium taurodeoxycholate.

Chiral separation of 19 pairs of amino acid (AA) enantiomers derivatized with 9-fluorenylmethylchloroformate (FMOC) was successfully conducted by capillary electrophoresis using the mixture of beta-CD and sodium taurodeoxycholate (STDC) as selectors. Resolution was considerably superior to that obtained by using either beta-CD or STDC alone. After a systematic inspection, a buffer composed of 150 mM borate and 18% v/v isopropanol at pH 8.0, dissolved with 30 mM beta-CD and 30 mM STDC, was adopted and able to generate baseline resolution (>1.50) for 17 pairs of FMOC-AA enantiomers and somewhat lower resolution for arginine (1.36) and alanine (1.18), respectively. Experimental data revealed that the addition of the second selector did not increase the mobility difference between a pair of enantiomers (Delta mu = mu(D) - mu(L) and the number of theoretical plates (N), but decreased the summed apparent mobility of a pair of enantiomers (Sigma mu = mu(D) - mu(L)), which was mainly due to the decrease of the electroosmotic flow. The variation of Sigma mu was thus the major reason responsible for the improvement of chiral resolution in this study. The result demonstrated that not only the intrinsic selectivity of the selectors was the basis of the chiral separation, but also the non-chiral effect of the selectors, the change of the electroosmotic flow, was an important factor in enhancing the enantioseparation resolution. This study could probably help to explain the reasons for resolution improvement in some dual selectors systems, which are not very clear at present.

Amino Acids↗
PubMed2006

Online acid barrage stacking anti-salt injection for capillary electrophoresis of 9-fluorenylmethylchloroformate-derivatized amino acids in high ionic strength solutions by UV detection.

An acid barrage stacking (ABS) method has been shown to be feasible for online anti-salt injection in CE of 9-fluorenylmethyl chloroformate (FMOC)-labeled amino acids (AAs) detected by common UV absorption. The operation was performed on normal polar CE by sucking in an extra plug of acid following a sample zone, serving as a selective acid barrage to block the backward migration of weak anionic analytes due to a sudden mobility reduction via acid-base reaction which does not affect strong co-ions such as Cl(-) to penetrate the barrage freely. By CE-UV of FMOC-AAs in various NaCl solutions, the effectiveness of ABS was firmly validated, able to stand up to 500 mM NaCl and to stack analytes by 10(3)-fold calculated from the UV detection limits, that is 0.01 microM for ABS and 10 microM for non-stacking injection. The method was also validated by determining trace Glu and Asp in real samples of rat brain microdialysate, rat serum and human saliva. The intraday RSDs were 0.33-4.9% for migration time and 1.8-9.6% for peak area. The recoveries measured by spiking technique were 82-115% for Glu and 86-116% for Asp. Working equations were obtained by plotting peak height vs. concentration at 0.1-50 microM, with correlation coefficients of >0.999. The contents of Glu and Asp were thus found at 0.26-0.83 microM and 0.24-0.64 microM respectively, in rat brain microdialyste; 37-40 microM and 8.4-10 microM, respectively, in rat serum; and 3.5-5.8 microM and 1.0-4.1 microM, respectively in human saliva. They were consistent with the data from other methods.

Amino Acids↗
PubMed2006

Overexpression of laminin-8 in human dermal microvascular endothelial cells promotes angiogenesis-related functions.

This study examined the effects of endogenous overexpression of laminin-8 on angiogenesis and wound healing in primary human dermal microvascular endothelial cells (HDMECs). HDMECs expressed laminin-8 and laminin-10, but no other laminins, as determined by radioimmunoprecipitation assay using a panel of antibodies to individual laminin chains. To study laminin-8 function, full-length human laminin alpha4 cDNA was retrovirally transferred to HDMEC, and specific overexpression of laminin-8 was verified by Western blot. Laminin-8 overexpression promoted endothelial cell spreading and migration in scratch assays and accelerated angiogenic tubule formation in collagen gel overlay assays. Strong inhibitory effect of beta1 integrin and weak inhibition by alphavbeta3 integrin antibodies were observed in laminin-8-stimulated cell migration, but only beta1 integrin antibodies affected tubule formation. These studies suggest that laminin-8 overexpression may prove to be a useful method to engineer HDMECs to promote angiogenesis and wound repair.

Antibodies↗
PubMed2006

The relationship of retinal VEGF and retinal IGF-1 mRNA with neovascularization in an acidosis-induced model of retinopathy of prematurity.

PURPOSE: Acidosis-induced retinopathy (AIR) in the neonatal rat provides an alternative model for retinopathy of prematurity (ROP). We studied the relationship of vascular endothelial growth factor (VEGF) retinal mRNA and insulin-like growth factor-1 (IGF-1) retinal mRNA expression with the emergence of neovascularization (NV) in AIR. METHODS: Two hundred seventy-five newborn Sprague-Dawley rats were raised in 11 expanded litters of 25. Using our established AIR model, acidosis was induced by twice-daily gavage with NH4Cl from day 2 to day 8 of life (n=175). Rats were sacrificed at days 5, 8, and 10. Nongavaged rats were used as age-matched controls (n=100). Retinae from left eyes were dissected, flatmounts were ADPase-stained, and the presence and severity of NV was scored in a masked manner. Individual right retinae were processed for analysis of retinal VEGF and IGF-1 mRNA using quantitative real-time reverse-transcriptase PCR (qRT-PCR). RESULTS: Retinal VEGF mRNA was increased 1.4-fold at day 10 in AIR, when compared with age-matched controls (p=0.03). This correlated with maximal NV at day 10 in AIR. Retinal IGF-1 mRNA was decreased to 82% of its normal expression on day 8 (p=0.006), prior to maximal NV, before returning to normal expression at day 10, when compared with nonacidotic controls. CONCLUSIONS: In AIR, preretinal neovascularization is associated with decreased retinal IGF-1 mRNA prior to maximal NV and increased retinal VEGF mRNA at the time of maximal NV. These growth factor changes in AIR are similar to those seen with hypercarbic oxygen-induced retinopathy. The retinal IGF-1 pathway may provide an alternative target for therapeutic intervention in abnormal retinal angiogenesis.

Acidosis↗
PubMed2006

Corticospinal tract transection permanently abolishes H-reflex down-conditioning in rats.

Previous studies have shown that corticospinal tract (CST) transection, but not transection of other major spinal cord tracts, prevents down-conditioning of the H-reflex, the electrical analog of the spinal stretch reflex. This study set out to determine whether the loss of the capacity for H-reflex down-conditioning caused by CST transection is permanent. Female Sprague-Dawley rats received CST, lateral column (LC), or dorsal column ascending tract (DA) transection at T8-9; 9-10 months later, they were exposed to the H-reflex down-conditioning protocol for 50 days. In the LC and DA rats, H-reflex size fell to 60 (+/- 9 SEM)% and 60 (+/- 19)%, respectively, of its initial size. This down-conditioning was comparable to that of normal rats. In contrast, H-reflex size in the CST rats rose to 170 (+/- 42)% of its initial size. A similar rise does not occur in rats exposed to down-conditioning shortly after CST transection. These results indicate that CST transection permanently eliminates the capacity for H-reflex down-conditioning and has gradual long-term effects on sensorimotor cortex function. They imply that H-reflex down-conditioning can be a reliable measure of CST function for long-term studies of the effects of spinal cord injury and/or for evaluations of the efficacy of experimental therapeutic procedures, such as those intended to promote CST regeneration. The results also suggest that the role of sensorimotor cortex in down-conditioning extends beyond generation of the essential CST activity.

Animals↗
PubMed2006

Urgent and emergency coronary artery bypass grafting for acute coronary syndromes.

BACKGROUND: Urgent and emergency coronary artery bypass grafting may be associated with significant mortality and morbidity. We report our recent experience with this group of patients. METHODS: A retrospective analysis of 441 patients undergoing urgent and emergency surgery over a 3-year period was carried out. Multivariate analysis was used to identify subgroups of patients who were most at risk of death. RESULTS: The 30-day mortality was 3.3 and 16.3% in the urgent and emergency groups, respectively. Urgent surgery was associated with significantly shorter duration of ventilation (16 h vs 69 h) and stay at the intensive care unit (31 h vs 102 h). The incidence of pneumonia, pulmonary embolism, renal failure and neurological events were also less in the urgent group. The preoperative use of the intra-aortic balloon pump was low (0.8% in the urgent group and 4.8% in the emergency group). Multivariate analysis showed that patients over 70 years of age (odds ratio 3.2, 95% confidence interval 1.1-9.5) with left main stenosis (odds ratio 4.4, 95% confidence interval 1.5-12.4) complicated by cardiogenic shock (odds ratio 17.8, 95% confidence interval 5.2-61.1) were at highest risk of death. Patients transferred directly to theatre from cardiac catheter laboratory following failed percutaneous interventions were found to be most at risk. Mortality in this group was 29%, with 50% patients being in shock and 36% having left main stenosis. CONCLUSION: Satisfactory results have been obtained in urgent coronary artery bypass grafting, but acute coronary syndromes complicated by cardiogenic shock remain a high-risk group. Further studies are needed to define the optimal operative management in this group of patients.

Acute Disease↗
PubMed2006

Experience with unipolar radiofrequency ablation for atrial fibrillation.

BACKGROUND: The cut and sew Cox maze procedure for atrial fibrillation (AF), although effective, is not widely used because of technical complexity, prolonged duration and significant risk of postoperative bleeding. This study reviews our experience with the unipolar radiofrequency ablation (RFA) procedure, which was used to create a modified maze to treat AF. METHODS: A retrospective review of 31 patients undergoing consecutive cardiac surgery who had concomitant RFA for AF over a 16-month period was carried out. A Cobra unipolar RFA probe (EPT; Boston Scientific, San Jose, CA, USA) was used to create a standard set of lesions. RESULTS: There were 20 men and 11 women (mean age, 66 +/- 9 years; range, 48-87 years). AF was continuous in 21 patients and intermittent in 10. The median duration of AF leading up to surgery was 48 months (range, 6 months-20 years). Left atrium was enlarged in 81% of the patients. Operations included mitral valve repair (7 patients), replacement (5), coronary artery bypass (10), aortic valve replacement (1) and combined procedures (8). There were no complications directly attributable to RFA. There were three early deaths. One patient required a permanent pacemaker. Median follow up was 22 months (range, 12-30 months). One patient died 2 years after the operation from a stroke. Cardioversion was attempted in five patients within 3 months of operation and was successful in four. At 2 years following the procedure, the probability of the patient remaining in sinus rhythm was 0.71 +/- 0.15. CONCLUSION: Surgical RFA can be carried out as a useful adjunct to conventional cardiac surgery. Although the results were satisfactory in this series, further studies are needed to refine the indication of the procedure and to assess its longer-term efficacy.

Aged↗
PubMed2006

Pseudomonas aeruginosa pyocyanin inactivates lung epithelial vacuolar ATPase-dependent cystic fibrosis transmembrane conductance regulator expression and localization.

Pseudomonas aeruginosa (PA) is a major pathogen causing morbidity and ultimately mortality in patients afflicted with cystic fibrosis (CF) lung disease. One important virulence factor, pyocyanin (PCN), is a blue, redox-active compound that is secreted in such copious amounts by PA in the CF lungs that it determines the colour of expectorated sputum. In this study, we discovered that physiological concentrations of PCN inactivate the airway epithelial vacuolar ATPase, resulting in reduced expression and trafficking of the cystic fibrosis transmembrane conductance regulator in cultured lung and primary nasal epithelial cells. Our study supports the notion that PCN contributes significantly to the pathogenesis of CF and other bronchiectasis patients infected by PA.

Calcium Channels, L-Type↗
PubMed2006

Influence of generation 2-5 of PAMAM dendrimer on the inhibition of Tat peptide/ TAR RNA binding in HIV-1 transcription.

The special binding of Tat protein to TAR RNA leads to the transcription of HIV-1 virus. In this study, the influence of 2-5 generation of PAMAM dendrimers on the inhibition of Tat protein/TAR RNA binding has been investigated. The absorption of PAMAM dendrimers on TAR RNA, fixed on a gold substrate through an avidin-biotion connection, was carried out by using a quartz crystal microbalance. Experimental result shows a Langmuir-type isotherm could be used to describe this kind of binding, implying a specific and monolayer adsorption existed. The combination coefficient (K(D)(-1))s can be calculated according to Langmuir Equation, having the order of G3 > G4 > G5 >Tat > G2, indicating that PAMAM G3, G4 and G5 having the possibility to be the inhibitors of HIV-1 transcription. The migration time (T(migra)) of capillary electrophoretic technique has the same sequence as (K(D)(-1))s. These two parameters could be used as simple and quantitative criteria for the selection of possible drugs from numerous candidates for HIV therapy in vitro.

Amino Acid Sequence↗
PubMed2006

The NKG2D-activating receptor mediates pulmonary clearance of Pseudomonas aeruginosa.

The NKG2D-activating receptor is expressed on cytotoxic lymphocytes and interacts with ligands expressed on the surface of cells stressed by pathogenic and nonpathogenic stimuli. In this study, we investigated the physiologic importance of NKG2D receptor-ligand interactions in response to acute pulmonary Pseudomonas aeruginosa infection. P. aeruginosa infection increased the expression of mouse NKG2D ligands (Rae1) in airway epithelial cells and alveolar macrophages in vivo and also increased the cell surface expression of human NKG2D ligands (ULBP2) on airway epithelial cells in vitro. NKG2D receptor blockade with a specific monoclonal antibody inhibited the pulmonary clearance of P. aeruginosa. NKG2D receptor blockade also resulted in decreased production of Th1 cytokines and nitric oxide in the lungs of P. aeruginosa-infected mice. Additionally, NKG2D receptor blockade reduced the epithelial cell sloughing that accompanies P. aeruginosa infection. Macrophage phagocytosis and bronchoalveolar lavage cellularity were not different in P. aeruginosa-infected mice with and without NKG2D receptor blockade. These results demonstrate the importance of NKG2D-mediated immune activation in the clearance of acute bacterial infection and suggest that epithelial cell-lymphocyte interactions mediate pulmonary cytokine production, epithelial cell integrity, and bacterial clearance.

Animals↗
PubMed2006

Anti-IL-23 therapy inhibits multiple inflammatory pathways and ameliorates autoimmune encephalomyelitis.

IL-23 is a member of the IL-12 cytokine family that drives a highly pathogenic T cell population involved in the initiation of autoimmune diseases. We have shown that IL-23-dependent, pathogenic T cells produced IL-17 A, IL-17 F, IL-6, and TNF but not IFN-gamma or IL-4. We now show that T-bet and STAT1 transcription factors are not required for the initial production of IL-17. However, optimal IL-17 production in response to IL-23 stimulation appears to require the presence of T-bet. To explore the clinical efficacy of targeting the IL-23 immune pathway, we generated anti-IL-23p19-specific antibodies and tested to determine whether blocking IL-23 function can inhibit EAE, a preclinical animal model of human multiple sclerosis. Anti-IL-23p19 treatment reduced the serum level of IL-17 as well as CNS expression of IFN-gamma, IP-10, IL-17, IL-6, and TNF mRNA. In addition, therapeutic treatment with anti-IL-23p19 during active disease inhibited proteolipid protein (PLP) epitope spreading and prevented subsequent disease relapse. Thus, therapeutic targeting of IL-23 effectively inhibited multiple inflammatory pathways that are critical for driving CNS autoimmune inflammation.

Animals↗