Biomedical subjects

Hua Li

Publications and source records attributed to Hua Li.

At least 37 records · Page 2Linked to original sources

PubMed2006

Modeling and simulation of deformation of hydrogels responding to electric stimulus.

A model for simulation of pH-sensitive hydrogels is refined in this paper to extend its application to electric-sensitive hydrogels, termed the refined multi-effect-coupling electric-stimulus (rMECe) model. By reformulation of the fixed-charge density and consideration of finite deformation, the rMECe model is able to predict the responsive deformations of the hydrogels when they are immersed in a bath solution subject to externally applied electric field. The rMECe model consists of nonlinear partial differential governing equations with chemo-electro-mechanical coupling effects and the fixed-charge density with electric-field effect. By comparison between simulation and experiment extracted from literature, the model is verified to be accurate and stable. The rMECe model performs quantitatively for deformation analysis of the electric-sensitive hydrogels. The influences of several physical parameters, including the externally applied electric voltage, initial fixed-charge density, hydrogel strip thickness, ionic strength and valence of surrounding solution, are discussed in detail on the displacement and average curvature of the hydrogels.

Computer Simulation↗

PubMed2006

CD32B, the human inhibitory Fc-gamma receptor IIB, as a target for monoclonal antibody therapy of B-cell lymphoma.

Human CD32B (FcgammaRIIB), the low-affinity inhibitory receptor for IgG, is the predominant Fc receptor (FcR) present on B cells. Immunohistochemical and expression studies have identified CD32B expression in a variety of B-cell malignancies, suggesting that CD32B is a potential immunotherapeutic target for B-cell malignancies. A high-affinity monoclonal antibody (mAb 2B6), from a novel panel of anti-human CD32B-specific mAbs, was chimerized (ch2B6) and humanized (hu2B6-3.5). Both ch2B6 and hu2B6-3.5 were capable of directing cytotoxicity by peripheral blood mononuclear cells and monocyte-derived macrophages against B-lymphoma lines in vitro. In a human B-cell lymphoma mouse xenograft model, administration of ch2B6 or hu2B6-3.5 reduced tumor growth rate and improved tumor-free survival. Both the in vitro and in vivo activities of 2B6 required an intact Fc, suggesting an FcR-mediated mechanism of action. These data support the hypothesis that CD32B is a viable target for mAb treatment of B-cell lymphoproliferative disorders.

Animals↗

PubMed2006

Fluorine-19 NMR studies on the acid state of the intestinal fatty acid binding protein.

The intestinal fatty acid binding protein (IFABP) is composed of two beta-sheets with a large hydrophobic cavity into which ligands bind. After eight 4-(19)F-phenylalanines were incorporated into the protein, the acid state of both apo- and holo-IFABP (at pH 2.8 and 2.3) was characterized by means of (1)H NMR diffusion measurements, circular dichroism, and (19)F NMR. Diffusion measurements show a moderately increased hydrodynamic radius while near- and far-UV CD measurements suggest that the acid state has substantial secondary structure as well as persistent tertiary interactions. At pH 2.8, these tertiary interactions have been further characterized by (19)F NMR and show an NOE cross-peak between residues that are located on different beta-strands. Side chain conformational heterogeneity on the millisecond time scale was captured by phase-sensitive (19)F-(19)F NOESY. At pH 2.3, native NMR peaks are mostly gone, but the protein can still bind fatty acid to form the holoprotein. An exchange cross-peak of one phenylalanine in the holoprotein is attributed to increased motional freedom of the fatty acid backbone caused by the slight opening of the binding pocket at pH 2.8. In the acid environment Phe128 and Phe17 show dramatic line broadening and chemical shift changes, reflecting greater degrees of motion around these residues. We propose that there is a separation of specific regions of the protein that gives rise to the larger radius of hydration. Temperature and urea unfolding studies indicate that persistent hydrophobic clusters are nativelike and may account for the ability of ligand to bind and induce nativelike structure, even at pH 2.3.

Apoproteins↗

PubMed2006

Breast tumor copy number aberration phenotypes and genomic instability.

BACKGROUND: Genomic DNA copy number aberrations are frequent in solid tumors, although the underlying causes of chromosomal instability in tumors remain obscure. Genes likely to have genomic instability phenotypes when mutated (e.g. those involved in mitosis, replication, repair, and telomeres) are rarely mutated in chromosomally unstable sporadic tumors, even though such mutations are associated with some heritable cancer prone syndromes. METHODS: We applied array comparative genomic hybridization (CGH) to the analysis of breast tumors. The variation in the levels of genomic instability amongst tumors prompted us to investigate whether alterations in processes/genes involved in maintenance and/or manipulation of the genome were associated with particular types of genomic instability. RESULTS: We discriminated three breast tumor subtypes based on genomic DNA copy number alterations. The subtypes varied with respect to level of genomic instability. We find that shorter telomeres and altered telomere related gene expression are associated with amplification, implicating telomere attrition as a promoter of this type of aberration in breast cancer. On the other hand, the numbers of chromosomal alterations, particularly low level changes, are associated with altered expression of genes in other functional classes (mitosis, cell cycle, DNA replication and repair). Further, although loss of function instability phenotypes have been demonstrated for many of the genes in model systems, we observed enhanced expression of most genes in tumors, indicating that over expression, rather than deficiency underlies instability. CONCLUSION: Many of the genes associated with higher frequency of copy number aberrations are direct targets of E2F, supporting the hypothesis that deregulation of the Rb pathway is a major contributor to chromosomal instability in breast tumors. These observations are consistent with failure to find mutations in sporadic tumors in genes that have roles in maintenance or manipulation of the genome.

Adult↗

PubMed2006

Cytoglobin overexpression protects against damage-induced fibrosis.

Cytoglobin (Cygb), a member of the hexacoordinate globin superfamily (hxHb), is expressed in fibroblasts from a broad range of tissues. The physiological functions of hxHb are still unclear, but biochemical studies reveal that they can scavenge toxic species, such as nitric oxide, peroxynitrite, and hydrogen peroxide. We demonstrate that the overexpression of Cygb in rat hepatic stellate cells, both in vitro and in vivo, protects against oxidative stress, inhibiting their differentiation into a myofibroblast-like phenotype. Accordingly, the overexpression of Cygb reduces extracellular matrix deposition in both toxic and cholestatic models of liver injury. The overexpression of Cygb also promotes recovery from previously initiated damage-induced fibrogenesis. By inhibiting free radical-induced activation of hepatic stellate cells, Cygb plays an important role in controlling tissue fibrosis. Therefore, the normal upregulation of Cygb during tissue injury has a homeostatic effect, inhibiting free radical-induced fibroblast activation and tissue fibrosis.

Animals↗

PubMed2006

MnO2-embedded-in-mesoporous-carbon-wall structure for use as electrochemical capacitors.

We present an in situ reduction method to synthesize a novel structured MnO(2)/mesoporous carbon (MnC) composite. MnO(2) nanoparticles have been synthesized and embedded into the mesoporous carbon wall of CMK-3 materials by the redox reaction between permanganate ions and carbons. Thermogravimetric analysis (TG), X-ray photoelectron spectrum (XPS), X-ray diffraction (XRD), nitrogen sorption, transmission electron microscopy (TEM), and cyclic voltammetry were employed to characterize these composite materials. The results show that different MnO(2) contents could be introduced into the pores of CMK-3 treated with different concentrations of potassium permanganate aqueous solution, while retaining the ordered mesostructure and larger surface area. Increasing the MnO(2) content did not result in a decrease in pore size from the data of nitrogen sorption isotherms, indicating that MnO(2) nanoparticles are embedded in the pore wall, as evidenced by TEM observation. We obtained a large specific capacitance over 200 F/g for the MnC composite and 600 F/g for the MnO(2), and these materials have high electrochemical stability and high reversibility.

Journal Article↗

PubMed2006

Enhanced pathogenicity of Leptosphaeria maculans Pycnidiospores from paired co-inoculation of Brassica napus cotyledons with ascospores.

BACKGROUND AND AIMS: Blackleg, caused by Leptosphaeria maculans, is a major disease of oilseed rape (Brassica napus) worldwide, including Australia. In most cases, the severity of the disease in the field is related to infections caused by airborne ascospores. In contrast, pycnidiospores originating from leaf and stem lesions and stubble are widely assumed to play only a relatively minor role in the epidemiology of blackleg. It is not clear whether, under certain conditions, pycnidiospores can cause severe disease in the field. The aim of the work reported was to determine if the pathogenicity of pycnidiospores is enhanced by paired co-inoculation of B. napus cotyledons with ascospores. METHODS: Three investigations were carried out under controlled-environment conditions using various L. maculans isolates and B. napus cultivars with different levels of host resistance to blackleg. KEY RESULTS: In all three experiments, co-inoculation with ascospores increased the ability of pycnidiospores to cause more disease on B. napus than when inoculations consisted of pycnidiospores alone. This effect was significantly influenced by the host resistance of the cultivar, but overall was independent of the L. maculans isolate used in the different experiments. This effect was also independent of timing of inoculation with the ascospores, with increased disease from pycnidiospores occurring on the cotyledon of the seedling in situations where inoculations with ascospores were carried out 0, 1 or 2 d after pycnidiospore inoculation. This enhanced pathogenicity of pycnidiospores was evident even when low concentrations of pycnidiospores were applied to the other cotyledon of the same seedling. CONCLUSIONS: These results may explain continuing severe blackleg disease cycles throughout the cropping season even when ascospore fallout was low or constrained only to a brief period or phase of the cropping season, and suggest that disease epidemics may be polycyclic rather than monocyclic.

Ascomycota↗

PubMed2006

Conformational fluctuations of proteins revealed by variable pressure NMR.

With the high-resolution variable-pressure NMR spectroscopy, one can study conformational fluctuations of proteins in a much wider conformational space than hitherto explored by NMR and other spectroscopic techniques. This is because a protein in solution generally exists as a dynamic mixture of conformers mutually differing in partial molar volume, and pressure can select the population of a conformer according to its relative volume. In this review, we describe how variable-pressure NMR can be used to probe conformational fluctuations of proteins in a wide conformational space from the folded to the fully unfolded structures, with actual examples. Furthermore, the newly emerging technique "NMR snapshots" expresses amply fluctuating protein structures as changes in atomic coordinates. Finally, the concept of conformational fluctuation is extended to include intermolecular association leading to amyloidosis.

Nuclear Magnetic Resonance, Biomolecular↗

PubMed2006

Study on the drug release property of cholesteryl end-functionalized poly(epsilon-caprolactone) microspheres.

End-functionalized poly/oligo(epsilon-caprolactone)s were synthesized through the ring-opening polymerization of epsilon-caprolactone initiated by cholesterol with a hydroxyl group. Using the end-functionalized poly/oligo(epsilon-caprolactone)s with different molecular weights, the microsphere drug delivery systems were fabricated using a convenient melting-emulsion method. The drug release properties of microspheres were investigated with the presence of an enzyme, Pseudomonas cepacia lipase, as well as in the absence of the enzyme. The release profiles can be fitted nicely by the classical empirical exponential expression. Under the hydrolytic condition, the drug release is mainly controlled by Fickian diffusion, and the high molecular weight of the matrix results in a slower drug release rate. Under the enzymatic condition, the drug release is dominated by combined degradation and diffusion mechanism, and the high molecular weight sample exhibits a faster release rate that is mainly caused by the higher degradation rate of the sample with lower cholesteryl moiety content.

Biocompatible Materials↗

PubMed2006

Equilibrium yields of mono- and di-lauroyl mannoses through lipase-catalyzed condensation in acetone in the presence of molecular sieves.

Modification was made to our previously reported method to predict the equilibrium yields for the synthesis of mono- and di-lauroyl mannoses through the lipase-catalyzed condensation of lauric acid and mannose in acetone in the presence of molecular sieves. HPLC and mass spectra (MS) analyses indicated that two types of dilauroyl mannoses, which would be positional isomers of each other and are designated dilauroyl mannose I and II, were produced as well as monolauroyl mannose. The predicted yields of total mannose esters and dilauroyl mannose I agreed well with the experimental ones on the whole. The equilibrium yields of dilauroyl mannose II were higher than the predicted values, while the experimental values of monolauroyl mannose were lower than the predicted values.

Acetone↗

PubMed2006

A transient simulation to predict the kinetic behavior of hydrogels responsive to electric stimulus.

A kinetic analysis of the response of electric-sensitive hydrogels to an externally applied electric field is conducted for the first time through modeling and transient simulation. This model, called the multieffect coupling electric stimulus (MECe), considers the effects of multiphases and multiphysics. Its extended application to transient simulation is validated against available experimental data, and good agreement is achieved. The concentration kinetics of ionic species is simulated. The simulation predicts the kinetic behavior of the hydrogels with consideration of the influences of important parameters such as the electric potential, fixed-charge density, bath solution concentration, and hydrogel average curvature.

Computer Simulation↗

PubMed2006

Inhibitive effect of genistein on hypoxia-induced basic fibroblast growth factor expression in human retinal pigment epithelium cells.

AIM: The time course changes of basic fibroblast growth factor (bFGF) expression induced by hypoxia and the effects of genistein on hypoxia-induced bFGF expression in the human retinal pigment epithelium (RPE) cells were studied. METHODS: The bFGF mRNA expression was examined by reverse transcription polymerase chain reaction. The bFGF protein expression was detected by Western blot. RESULTS: Hypoxia significantly increased bFGF mRNA expression. The maximal level detected at 24 h was approximately two times that at the start of treatment. With pretreatment of genistein (10, 20, 50, 100, and 200 microM) for 30 min, the elevated expression of bFGF mRNA was suppressed in a concentration-dependent manner. bFGF mRNA expression was reduced to 30.4% by 200 microM of genistein when compared with that untreated with genistein. Hypoxia treatment also remarkably increased the expression of bFGF protein. At 24 h after hypoxia, when the highest expression of bFGF protein was observed, it was approximately two times as much as that at the start of treatment. Genistein (10, 20, 50, 100, and 200 microM) could also suppress bFGF protein expression in a concentration-dependent manner. The highest suppression was observed when exposed to 200 microM of genistein, which was 43% of control. CONCLUSIONS: These results suggested that suppression of bFGF expression in RPE cells might partly account for the inhibitive effect of genistein on retinal neovascularization in vivo.

Angiogenesis Inhibitors↗

PubMed2006

Establishment and application of a TaqMan real-time quantitative reverse transcription-polymerase chain reaction assay for rubella virus RNA.

The aim of this study was to establish and apply a real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) for rubella virus (RV) RNA. First, the primer and TaqMan probe concentrations, as well as reaction temperatures were optimized to establish an efficient real-time quantitative RT-PCR assay for RV RNA. Next, an RV-specific PCR amplicon was made as an external standard to estimate the linearity, amplification efficiency, analytical sensitivity and reproducibility of the real time quantitative assay. Finally, the assay was applied to quantify RV RNA in clinical samples for rubella diagnosis. The RV-specific PCR amplicon was prepared for evaluation of the assay at 503 bp, and its original concentration was 2.75x109 copies/mul. The real time quantitative assay was shown to have good linearity (R2=0.9920), high amplification efficiency (E=1.91), high sensitivity (275 copies/ml), and high reproducibility (variation coefficient range, from 1.25% to 3.58%). Compared with the gold standard, the specificity and sensitivity of the assay in clinical samples was 96.4% and 86.4%, respectively. Therefore, the established quantitative RT-PCR method is a simple, rapid, less-labored, quantitative, highly specific and sensitive assay for RV RNA.

Humans↗

PubMed2006

Inhibition of IL-8 production by green tea polyphenols in human nasal fibroblasts and A549 epithelial cells.

The attraction of leukocytes to tissues is essential in order for inflammation and the host response to infection to occur. Airway inflammation is a very common cause illness with a substantial impact on health care. Neutrophils play an essential role in the host defense and in inflammation, but the latter may trigger and sustain the pathogenesis of a range of acute and chronic diseases. Infiltration of neutrophils occurs as a response to chemoattractant molecules by resident tissue cells. The recruitment of neutrophils in airway inflammation may account for the generation of IL-8. To evaluate the effectiveness of green tea polyphenols in the modulation of airway inflammation through the blocking of neutrophil chemokine production, nasal mucosal fibroblasts and A549 bronchial epithelial cells were analyzed for the production of IL-8. Both nasal mucosal fibroblasts and bronchial epithelial cells produced significant amounts of IL-8 through stimulation of IL-1beta. Tea polyphenols were very effective in the inhibition of IL-8 production. Among the polyphenols tested, EGCG and ECG showed strong inhibitory activity in dose-dependent manners. EGC and EC showed moderate inhibition at 48 h culture, whereas (-)catechin was not effective. Production of IL-8 after stimulation by proinflammatory cytokines in both nasal fibroblasts and bronchial epithelial cells was significantly blocked by pretreatment with green tea polyphenols.

Blotting, Western↗

PubMed2006

Improved efficiency of bovine cloning by autologous somatic cell nuclear transfer.

Somatic cell nuclear transfer (SCNT) has been used for the cloning of various mammals. However, the rates of successful, healthy birth are generally poor. To improve cloning efficiency, we report the utilization of an 'autologous SCNT' cloning technique in which the somatic nucleus of a female bovine donor is transferred to its own enucleated oocyte recovered by ovum pick up, in contrast to the routine 'allogeneic SCNT' procedure using oocytes from unrelated females. Our results showed that embryos derived from autologous SCNThave significantly higher developmental competence than those derived from allogeneic SCNT, especiallyat the eight-cell (60 vs 44%), morula (45 vs 36%), and blastocyst (38 vs 23%) stages. The pregnancy and birth rates were also higher for the autologous (39 and 23%), compared to the allogeneic (22 and 6%) SCNT groups. Genome-wide histone3-lysine9 methylation profiles reveal that autologous SCNTembryos have less epigenetic defects than the allogeneic SCNTembryos. This study indicates that autologous SCNT can improve the efficiency of bovine cloning with less reprogramming deficiency.

Animals↗

PubMed2006

[Effects of traditional Chinese medicine for invigorating spleen to resolve dampness and dredging collaterals on patients with rheumatoid arthritis and anemia].

OBJECTIVE: To observe the clinical effects of Xinfeng Capsules (XFC), a traditional Chinese medicine for invigorating the spleen to resolve dampness and dredging collaterals, on patients with rheumatoid arthritis (RA) and anemia, and to investigate its mechanism. METHODS: Forty patients with RA and anemia were divided into three groups: XFC-treated group (n=20), Tripterygium glycosides Tablets (TGT)-treated group (n=10) and methotrexate (MTX)-treated group (n=10). The patients in each group took corresponding medicine for three months. The response rates of the three groups were evaluated after treatment. The general symptoms and specific signs and symptoms of RA were observed before and after the treatment. The indexes of blood routine examination and some other laboratory indexes such as erythrocyte sedimentation rate (ESR), and blood levels of rheumatoid factor (RF), iron, C-reaction protein (CRP), immunoglobins (Ig), complements 3 and 4, tumor necrosis factor-alpha (TNF-alpha), interleukin-10 (IL-10) and erythropoietin (EPO) were all examined and compared before and after treatment. RESULTS: The total response rate in the XFC-treated group was similar to those both in the TGT-treated and MTX-treated groups. The effects on relieving specific symptoms of RA in the three groups were also similar. The ESR and serum levels of RF, CRP, IgG, IgA and IgM were all decreased after treatment as compared with those before treatment in the three groups, and there were no significant differences among those laboratory indexes in the three groups after treatment. The XFC displayed more obvious effects on improving the general symptoms of patients with RA and anemia, increasing the blood levels of hemoglobin, iron and IL-10, while decreasing the serum level of TNF-alpha and regulating the serum EPO level, as compared with those in the TGT-treated and MTX-treated groups. CONCLUSION: The XFC for invigorating the spleen to resolve dampness and dredging collaterals was developed on the basic principle of regulating spleen. It can obviously improve the symptoms and laboratory indicators of RA. Such effects may be related to maintaining the balance of cytokines, regulating the serum level of EPO and increasing the serum iron level in patients with RA and anemia.

Anemia↗

PubMed2006

[Screening and identification of therapeutic effect evaluation antigens of angiostrongyliasis].

OBJECTIVE: To identify antigens which may help evaluate the therapeutic effect of angiostrongyliasis from adult worm antigen of Angiostrongylus cantonensis. METHODS: The adult worm antigens of A. cantonensis were analyzed by Western blotting with the sera of rats infected with A. cantonensis before and after treatment. The sera of rats were tested by enzyme-linked immunosorbent assay (ELISA). RESULTS: The antigens with relative molecular mass between 38,000 and 78,000 reacted not only with the sera of rats before treatment, but also with that after treatment. The antigens with M(r) between 190,000 and 17,000 reacted with the sera of rats before treatment but not with that after treatment; those with M(r) between 32,000 and 24,000 antigens strongly reacted with the former, but the reaction became much weakened with the latter. The AC32-IgG antibody appeared earlier than the AC-IgG, and disappeared rapidly after treatment. Six of the 10 treated rats became negative for AC-IgG as found by ELISA. CONCLUSION: The antigens of adult worm antigen of A. cantonensis with M(r) of 190,000, 32,000, 24,000, 17,000 and 16,000 may serve as candidate antigens for therapeutic effect evaluation of angiostrongyliasis.

Angiostrongylus cantonensis↗

PubMed2006

[Determination of epicatechin in Rhizoma Fagopyri dibotoryis by HPLC-ECD].

OBJECTIVE: To establish a quantitative method of determination of epicatechin in Rhizoma fagopyri dibotoryis by HPLC-electrochemical detection. METHOD: The sample was separated on a column of Diamonsil C18 (4.6 mm x 250 mm, 5 microm) which was eluted with methanol-0.1 mol x L(-1) phosphate buffer (1:3, pH 2.5), the flow rate was 1.0 mL x min(-1), the column temperature was 35 degrees C, the reference electrode was ISAAC (in-situ silver/silver chloride), the work electrode was glassy carbon, the applied potential was + 600 mV. RESULT: The linear range of epicatechin was 0.004 875-1.56 microg, r = 0.999 9. The average recovery was 100.7% with RSD 1.9% (n = 5). The content of epicatechin was different in nine samples purchased. CONCLUSION: The method is good reproducible and can be used to determine epicatechin in Rhizoma fagopyri dibotoryis.

Catechin↗