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Biomedical subjects

Wei Li

Publications and source records attributed to Wei Li.

At least 343 records · Page 19Linked to original sources
PubMed2005

Determination of lafutidine in human plasma by high-performance liquid chromatography-electrospray ionization mass spectrometry: application to a bioequivalence study.

A rapid, sensitive and specific high-performance liquid chromatography-electrospray ionization mass spectrometry (LC/ESI-MS) method was developed and validated for the first time to determine the concentration of lafutidine in human plasma. After the addition of diazepam (the internal standard, IS) and 1 M sodium hydroxide solution to 0.5-ml plasma sample, lafutidine was extracted from plasma with n-hexane : isopropanol (95 : 5, v/v). The organic layer was evaporated and the residue was redissolved in 200-microl mobile phase. The analyte was chromatographically separated on a prepacked Shimadzu Shim-pack VP-ODS C(18) column (250 x 2.0 mm i.d.) using a mixture of methanol-water (20 mM CH(3)COONH(4)) = 80 : 20 (v/v) as mobile phase. Detection was performed on a single quadrupole mass spectrometer using an electrospray ionization interface and the selected-ion monitoring (SIM) mode. The method showed excellent linearity (r = 0.9993) over the concentration range of 5-400 ng/ml and had good accuracy and precision. The within- and between-batch precisions were within 10% relative standard deviation. The limit of detection was 1 ng/ml. The validated LC/ESI-MS method has been successfully applied to the bioequivalence study of lafutidine in 24 healthy male Chinese volunteers.

Acetamides↗
PubMed2005

Prokaryotic expression and biological activity analysis of human arresten gene.

To express recombinant arresten in Escherichia coli (E. Coli) and investigate its biological activity, prokaryotic expression vector of human arresten gene was constructed by gene engineering. Human arresten gene was amplified from recombinant plasmid pGEMArr by polymerase chain reaction (PCR), and inserted into prokaryotic expression vector pRSET containing T7 promoter. Restriction analysis and DNA sequencing verified that the arresten gene was correctly cloned into the expression vector. The recombinant plasmid pRSETAt was subsequently transformed into E. coli BL21 (DE3), and the target gene was expressed under induction of IPTG. SDS-PAGE analysis revealed that the recombinant protein with a molecular weight of 29 kD (1 kD = 0.992 1 ku) amounted to 29% of the total bacterial proteins. After purification and renaturation, the recombinant protein could significantly suppress the proliferation of human umbilical vein endothelial cells (HUVECs). These results suggested that the expression of a biologically active form of human arresten in the pRSET expression system laid a foundation for further study on the mechanistic insight into arresten action on angiogenesis and the development of powerful anti-cancer drugs.

Angiogenesis Inhibitors↗
PubMed2005

Comparative analysis of the pig BAC sequence involved in the regulation of myostatin gene.

Myostatin (GDF8, MSTN) is a member of the transforming growth factor beta superfamily that is essential for proper regulation of skeletal muscle mass. In order to study its expression and regulatory mechanism deeply, we have presented a comparative analysis of about 170-kb pig BAC sequence containing the myostatin gene among pig, human and mouse. The genomic region is characterized by high interspersed repeats and low G+C content. As for the myostatin gene, a higher sequence similarity is found between human and pig than between these species and the mouse. One striking feature is that the structure of two TATA-boxes in the nearby downstream of CCAAT-box is identified in the promoter. Further analysis reveals that the TATA-box1 is responsible for the transcription in pig and human, but the TATA-box2 acts on the transcription in mouse. The other interesting feature is that two polyadenylation signal sequences (AATAAA) exist in 3'UTR of the pig myostatin gene. Moreover, a large number of potential transcription factor-binding sites are also identified in evolutionary conserved regions (ECRs), which may be associated with the regulation of myostatin. Many putative transcription factors play an important role in the muscle development, and the complex interaction between myostatin and these factors may be required for proper muscle development.

3' Flanking Region↗
PubMed2005

Inhibition of neuropathy target esterase expressing by antisense RNA does not affect neural differentiation in human neuroblastoma (SK-N-SH) cell line.

Neuropathy target esterase (NTE) is phosphorylated and aged by oraganophosphorus compounds (OP) that induce delayed neuropathy in human and some animals. NTE has been proposed to play a role in neurite outgrowth and process elongation during neural differentiation. However, to date, there is no direct evidence of the relevance of NTE in neural differentiation under physiological conditions. In this study we have investigated a possible role for NTE in the all-trans retinoic acid (ATRA)-induced differentiation of neuroblastoma cells by antisense RNA. A NTE antisense RNA construct was generated and then transfected into human neuroblastoma SK-N-SH cells. A positive cell clone that can stably express NTE antisense RNA was obtained by G418 selection and then identified by western blotting. NTE activity was depressed in the transfected cells with only about 50% activity of the enzyme in the control cells. ATRA-induced differentiation of the neuroblastoma cells with lowered NTE activity revealed that inhibition of NTE expression does not affect neural differentiation in SK-N-SH cells. The result suggested that organophosphates may inhibit neural differentiation by initially acting on other targets other than NTE.

Carboxylic Ester Hydrolases↗
PubMed2005

Constitutive expression of CIITA directs CD4 T cells to produce Th2 cytokines in the thymus.

We generated mice expressing a human type III CIITA transgene (CIITA Tg) under control of the CD4 promoter to study the role of CIITA in CD4 T cell biology. The transgene is expressed in peripheral CD4 and CD8 T cells, as well as in thymocytes. When CD4 T cells were differentiated towards the Th2 lineage, both control and CIITA Tg Th2 cells expressed similar levels of Th2 cytokines. Th1 cells from control and CIITA Tg mice cells produced comparable levels of IFN-gamma. CIITA Tg Th1 cells also expressed IL-4, IL-5, and IL-13 in the absence of Stat6. There was an approximate 10-fold increase in the number of peripheral naïve CD4 T cells and NK1.1- thymocytes producing IL-4 from CIITA Tg mice compared to control mice. Finally, Th1 cells from irradiated control mice reconstituted with CIITA Tg bone marrow displayed the same cytokine production profiles as Th1 cells from CIITA Tg mice. Together, our data demonstrate that CIITA expression pre-disposes CD4 T cells to produce Th2 type cytokines. Moreover, phenotypic similarities between Th1 cells expressing the CIITA transgene and CIITA deficient Th1 cells suggest that the role of CIITA in cytokine regulation is complex and may reflect both direct and indirect mechanisms of T cell development and differentiation.

Adoptive Transfer↗
PubMed2005

Enzymatic metabolism of ergosterol by cytochrome p450scc to biologically active 17alpha,24-dihydroxyergosterol.

We demonstrate the metabolism of ergosterol by cytochrome P450scc in either a reconstituted system or isolated adrenal mitochondria. The major reaction product was identified as 17alpha,24-dihydroxyergosterol. Purified P450scc also generated hydroxyergosterol as a minor product, which is probably an intermediate in the synthesis of 17alpha,24-dihydroxyergosterol. In contrast to cholesterol and 7-dehydrocholesterol, cleavage of the ergosterol side chain was not observed. NMR analysis clearly located one hydroxyl group to C24, with evidence that the second hydroxyl group is at C17. 17alpha,24-Dihydroxyergosterol inhibited cell proliferation of HaCaT keratinocytes and melanoma cells. Thus, in comparison with cholesterol and 7-dehydrocholesterol, the 24-methyl group and the C22-C23 double bond of ergosterol prevent side chain cleavage by P450scc and change the enzyme's hydroxylase activity from C22 and C20, to C24 and C17, generating bioactive product.

Adrenal Glands↗
PubMed2005

Solubilization and biodegradation of phenanthrene in mixed anionic-nonionic surfactant solutions.

The effects of mixed anionic-nonionic surfactants, sodium dodecyl sulfate (SDS) mixed with Tween80 (TW80), Triton X-100 (TX100) and Brij35 respectively on the solubility enhancement and biodegradation of phenanthrene in the aqueous phase were investigated. The efficiency of solubilization and biodegradation of phenanthrene in single-, and mixed-surfactant solutions were also compared. The critical micellar concentrations (CMCs) of mixed surfactants were sharply lower than that of sole SDS. The degree of solubility enhancements by the mixed surfactants followed the order of SDS-TW80>SDS-Brij35>SDS-TX100. Synergistic solubilization was observed in the mixed surfactant solutions, in which the molar ratios of SDS to nonionic surfactant were 1:0, 9:1, 7:3, 5:5, 3:7, 1:9 and 0:1 while the total concentration of surfactants was kept at 5.0 and 10.0 mM, respectively. SDS-Brij35 exhibited more significant degree of synergistic solubility enhancement for phenanthrene. The mixed surfactants exhibited no inhibitory effect on biodegradation of phenanthrene. Substantial amounts of the solubilized phenanthrene by mixed surfactants were completely degraded by phenanthrene-degrading microorganisms within 96 h. The results suggested that anionic-nonionic surfactants would improve the performance of remediation of PAH-contaminated soils.

Biodegradation, Environmental↗
PubMed2005

A resampling approach for adjustment in prediction models for covariate measurement error.

Recent works on covariate measurement errors focus on the possible biases in model coefficient estimates. Usually, measurement error in a covariate tends to attenuate the coefficient estimate for the covariate, i.e., a bias toward the null occurs. Measurement error in another confounding or interacting variable typically results in incomplete adjustment for that variable. Hence, the coefficient for the covariate of interest may be biased either toward or away from the null. This paper presents a new method based on a resampling technique to deal with covariate measurement errors in the context of prediction modeling. Prediction accuracy is our primary parameter of interest. Prediction accuracy of a model is defined as the success rate of prediction when the model predicts new response. We call our method bootstrap regression calibration (BRC). We study logistic regression with interacting covariates as our prediction model. We measure the prediction accuracy of a model by receiver operating characteristic (ROC) method. Results from simulations show that bootstrap regression calibration offers consistent enhancement over the commonly used regression calibration (RC) method in terms of improving prediction accuracy of the model and reducing bias in the estimated coefficients.

Calibration↗
PubMed2005

Wound-healing perspectives.

Wound-healing in the skin is a complex orchestration of cellular processes, which has been perfected throughout the eons of phylogeny. It has so many coordinated biologic processes invoked both simultaneously and in a regulated orderly fashion that it has been likened to a recapitulation of gestation. Part of the problem with studying wound healing is in analyzing the processes independently and then seeing how they fit together and influence each other. This article discusses selected and recent scientific observations that have given insight into the biology of human skin wound healing. The article then discusses selected clinical advances that are based less on evidence-based observation and more on what works in practice and promotes wound healing.

Bandages↗
PubMed2005

Safety and tolerability of bosentan in adults with Eisenmenger physiology.

BACKGROUND: Bosentan, a dual-endothelin receptor antagonist, is an established treatment for pulmonary arterial hypertension. We hypothesized that bosentan is safe and well tolerated in patients with Eisenmenger physiology. METHODS: In this pilot open-label study, we primarily examined safety and tolerability of oral bosentan. Patients were recruited from our adult congenital heart clinic following informed consent. Baseline and 3-month assessment included WHO functional class, resting oxygen saturations, 6-min walk test, transthoracic echocardiography and respiratory mass spectrometry. Patient clinical status and liver enzymes were closely monitored throughout. RESULTS: All 10 study patients (42+/-4 years; eight female) tolerated bosentan well. No major adverse events or significant liver enzyme elevations were observed. All but one patient felt better; none felt worse. Four patients experienced transient leg oedema. Resting oxygen saturations (83+/-5 versus 80+/-5%; P=0.011) and the distance travelled in the 6-min walk test (348+/-112 versus 249+/-117 m; P=0.004) increased relative to baseline. Changes in echocardiographic parameters (maximum aortic forward flow velocity 1.3+/-0.1 versus 1.1+/-0.2 ms, P=0.013; pulmonary arterial acceleration time 66+/-10 versus 58+/-12 m/s, P=0.02) and pulmonary blood flow (3.45+/-1.2 versus 2.58+/-1.0 L/min, P=0.008) suggested improved pulmonary haemodynamics by study end. Other echocardiographic changes suggested improved right ventricular systolic function (septal amplitude 1.0 versus 1.1 cm, P=0.048; systolic tissue Doppler velocity 4.8 versus 2.3 cm s(-1), P=0.002) by study end. CONCLUSIONS: Bosentan was safe and well tolerated in adults with Eisenmenger physiology both at initiation and after 3 months of oral therapy. Clinical status of patients and pulmonary haemodynamics appeared to improve, and this warrants further investigation.

Adult↗
PubMed2005

An alternate pathway for CD4 T cell development: thymocyte-expressed MHC class II selects a distinct T cell population.

Conventional understanding of CD4 T cell development is that the MHC class II molecules on cortical thymic epithelial cell are necessary for positive selection, as demonstrated in mouse models. Clinical data, however, show that hematopoietic stem cells reconstitute CD4 T cells in patients devoid of MHC class II. Additionally, CD4 T cells generated from human stem cells in immunocompromised mice were restricted to human, but not mouse, MHC class II. These studies suggest an alternative pathway for CD4 T cell development that does not normally exist in mice. MHC class II is expressed on developing human thymocytes, indicating a possible role of MHC II on thymocytes for CD4 T cell generation. Therefore, we created mice in which MHC class II is expressed only on T lineage cells. Remarkably, the CD4 compartment in such mice is efficiently reconstituted with unique specificity, demonstrating a novel thymocyte-driven pathway of CD4 T cell selection.

Animals↗
PubMed2005

Interleukin-6 protects hepatocytes from CCl4-mediated necrosis and apoptosis in mice by reducing MMP-2 expression.

BACKGROUND/AIMS: Interleukin-6 stimulates liver regeneration and promotes hepatoprotection following experimental liver injury, but underlying mechanisms have not been fully characterized. Because studies suggest matrix metalloproteinase-2 (MMP-2) may promote liver injury, we examined whether IL-6 exerted its protective effects via regulation of MMP-2. METHODS: MMP-2 was analyzed in livers of IL-6-/- and IL-6+/+ mice following CCl(4) administration. IL-6-/- mice were pretreated with IL-6 and liver histology and MMP-2 expression were examined after liver injury. IL-6-/- mice were treated with an MMP-2 inhibitor and assessment of injury (histology and serum ALT levels), apoptosis by TUNEL assay, and hepatocyte proliferation by BRDU-labeling was performed. These studies were complemented by analysis of cultured stellate cells. RESULTS: MMP-2 mRNA, protein, and activity was increased in IL-6-/- livers. Restoration of IL-6 signaling in IL-6-/- mice rescued injury and restored MMP-2 expression to wild-type levels. Furthermore, pharmacologic inhibition of MMP-2 decreased hepatocellular injury and apoptosis in IL-6-/- mice. In cultured stellate cells, recombinant IL-6 suppressed endogenous MMP-2 mRNA and protein expression. CONCLUSIONS: IL-6 may be hepatoprotective in acute injury through down-regulation of MMP-2. These findings suggest a role for MMP-2 in amplifying liver injury in vivo.

Acute Disease↗
PubMed2005

Comparison of the four mouse fasciclin-containing genes expression patterns during valvuloseptal morphogenesis.

All four mammalian fasciclin-containing genes are expressed in the adult valves and are localized in partially overlapping and reciprocal patterns during cardiovascular development. Spatiotemporal comparison of the fasciclin-containing secreted adhesion genes, TGFbeta induced clone H3 (betaigH3) and periostin, revealed that they are co-localized within the outflow tract endocardial cushions, but that betaigH3 expression is restricted to the septal cushions within the atrioventricular canal. Conversely, the fasciclin-containing transmembrane gene, stabilin-1, is predominately expressed in the endocardial layer overlaying the cushions and lining the developing heart. However, expression of the fasciclin-containing transmembrane gene, stabilin-2 is only present in the post-natal mature valve endothelial cells. These data illustrate for the first time that the primitive endocardial cushions dynamically express multiple fasciclin-containing adhesion molecules as they undergo the key steps of seeding, proliferation, differentiation, fusion, mesenchymal condensation and remodeling during mouse heart development.

Animals↗
PubMed2005

Correlation of corneal complications with eyelid cicatricial pathologies in patients with Stevens-Johnson syndrome and toxic epidermal necrolysis syndrome.

PURPOSE: To look at the correlation between many factors (time of hospitalization, floppy eyelid syndrome, trichiasis, open lacrimal puncta, symblepharon, and aqueous tear deficiency) and corneal complications in Stevens-Johnson syndrome (SJS). DESIGN: Observational cases series. PATIENTS: Clinical data were retrospectively reviewed from 38 patients (32.7+/-20.1 years old) with SJS (n = 11) and with toxic epidermal necrolysis (TENS) (n = 27) from January 2002 to August 2004. One case report with SJS was included to verify the presence of tarsal/lid margin ulceration at the acute stage. METHODS: The medical history was retrieved regarding presumed causative medications used within 15 days and the duration of hospitalization. Data of the latest photographic documentation and eye examination were compared and correlated in a masked fashion. MAIN OUTCOME MEASURES: Floppy eyelid, trichiasis, lid margin keratinization, meibomian gland orifice metaplasia, symblepharon, tarsal scar, and corneal complications. RESULTS: Acute SJS/TENS was characterized by tarsal conjunctival ulceration. Keratinization of the eyelid margin with variable degrees of meibomian gland dysfunction was observed in all cases. Floppy eyelid, trichiasis, partially or totally opened lacrimal punctum, symblepharon, and aqueous tear deficiency were not significantly correlated with corneal complications. In contrast, there was a strong correlation between the severity of eyelid margin and tarsal pathology and the extent of corneal complications (Spearman r, 0.54; P = 0.0005). A multivariable regression analysis also showed that the extent of eyelid and tarsal pathology had a significant effect on corneal complications (coefficient, 0.84; P = 0.006). CONCLUSIONS: Patients with acute SJS/TENS are characterized by severe inflammation and ulceration of the tarsal conjunctiva and lid margins. If left unattended, lid margin keratinization and tarsal scar, together with lipid tear deficiency, contribute to corneal complications because of blink-related microtrauma. Attempts to suppress inflammation and scarring by amniotic membrane transplantation at the acute stage and to prevent microtrauma at the chronic stage are vital to avoid sight-threatening complications.

Adolescent↗
PubMed2005

Intrastromal invasion by limbal epithelial cells is mediated by epithelial-mesenchymal transition activated by air exposure.

Corneal epithelial stem cells are located in the basal layer of the limbus between the cornea and the conjunctiva. Regulation of these limbal epithelial progenitor cells by the stromal niche dictates corneal surface health. To further characterize this process, limbal explants were cultured at the air-fluid interface, termed air-lifting, to stimulate the niche. As compared to submerged cultures, air-lifting significantly promoted epithelial stratification, migration, proliferation, and intrastromal invasion by limbal epithelial cells. Epithelial intrastromal invasion was noted when the limbal, but not corneal, epithelium was recombined with the limbal stroma containing live, but not dead, cells. Invading limbal basal cells displayed up-regulated nuclear expression of p63 and Ki67, down-regulated E-cadherin and cornea-specific keratin 3, and switched expression of beta-catenin from intercellular junctions to the nucleus and cytoplasm, indicating the activation of the Wnt/beta-catenin pathway. Invaded cells isolated by collagenase from the stroma of air-lifted, but not submerged, explants showed vivid clonal growth on 3T3 fibroblast feeder layers and complete epithelial-mesenchymal transition by expressing nuclear p63 and cytoplasmic S100A4. These findings collectively suggest that epithelial-mesenchymal transition via the Wnt/beta-catenin pathway influences the fate of limbal epithelial cells, likely to be progenitor cells, between regeneration and fibrosis when the stromal niche is activated.

Air↗
PubMed2005

Methods for the functional genomic analysis of ubiquitin ligases.

Ubiquitin ligases (E3s) are critical components of the ubiquitin-proteasome system as they are the major determinants of specificity in ubiquitin conjugation. The number of predicted E3s in the mammalian genome is exceeding 400 and is represented by two major subfamilies: HECT domain-containing E3s and RING finger-type E3s. Given the size of this protein family and lack of knowledge on the functions of most of these 400 proteins, their functional annotation should benefit from modern genomic tools. This article presents a methodology consisting of the use of a cDNA expression library to identify suppressors of polyglutamine (polyQ)-mediated protein aggregate formation in cells, as an example of a genomic approach to assign functions to E3s. In this screen, we identified novel RING finger-type E3s exhibiting suppressor activity among >50% of all the potential E3s in the mouse and human genomes. This method could be adapted easily to identify E3s that function in other processes and signaling pathways.

Algorithms↗
PubMed2005

Application of inverted J-shaped partial sternotomy in intracardiac operations.

OBJECTIVE: To report our experience of intracardiac surgery with an inverted J-shaped partial sternotomy (IJPS) and describe the technical details of this approach. METHODS: From January to December 2002, 31 patients underwent intracardiac operations using the IJPS instead of a standard conventional full-length median sternotomy (FLMS). Twenty-one patients had mitral valve replacements (MVR), with combined tricuspid valvuloplasty in three, six had closure of secundum atrial septal defects, three had closure of ventricular septal defects and one had repair of cor triatriatum. Data from 26 randomly selected patients who had undergone MVR through a conventional FLMS were included for comparison. RESULTS: There were no perioperative or in-hospital deaths in either group. There was a significant difference between the two MVR groups in incision length, mediastinal drainage and blood transfusion volume, but not in cardiopulmonary bypass time, aortic cross-clamp time, duration of operation and duration of ventilatory support. There were no conversions from IJPS to FLMS, indicating that access was satisfactory for all the procedures. All patients were discharged without any significant postoperative complications. CONCLUSION: The IJPS is aesthetically pleasing with regard to cosmesis and does not affect safety and exposure. Furthermore, the smaller incision resulted in a significant reduction in blood loss and blood requirements.

Cardiac Surgical Procedures↗