Biomedical subjects

Hui Li

Publications and source records attributed to Hui Li.

At least 235 records · Page 13Linked to original sources

PubMed2004

Association of -238G/A polymorphism of tumor necrosis factor-alpha gene promoter region with outcomes of hepatitis B virus infection in Chinese Han population.

AIM: To clarify whether -238G/A polymorphism of tumor necrosis factor-alpha (TNF-alpha) gene promoter region was associated with outcomes of hepatitis B virus (HBV) infection in Han population of northern China, and to analyze the gene-environment interaction between -238G/A polymorphism and cigarette smoking or alcohol consumption. METHODS: A case-control study was conducted to analyze the association of TNF-alpha gene promoter polymorphism with HBV infection outcomes. A total of 207 patients with chronic hepatitis B (HB) and 148 cases of self-limited HBV infection from Ditan Hospital and Shunyi District Hospital in Beijing, respectively were recruited. History of smoking and alcohol drinking was inquired by a questionnaire. The -238G/A polymorphism of TNF-alpha gene promoter was genotyped by polymerase chain reaction-restricted fragment length polymorphism (PCR-RFLP). RESULTS: The frequencies of GG and GA genotypes were 98.07% and 1.93% in chronic HB patients and 93.24% and 6.76% in self-limited HBV infection individuals, respectively (chi(2)=5.30, P=0.02). The frequency of G allele was significantly higher in patients with chronic HB that in individuals with self-limited HBV infection (99.03% vs 96.62%, chi(2)=5.20, P=0.02). Only modestly increased risk of onset of chronic HB was found in smokers (OR=1.40, 95% CI: 0.87-2.28, P=0.14) and drinkers (OR=1.26, 95%CI: 0.78-2.05, P=0.32). There was a positive interaction between genotype GG and cigarette smoking with an interaction index (II) of 2.95, or alcohol consumption with an II of 1.64. CONCLUSION: The -238G/A polymorphism of TNF-alpha gene promoter region is independently associated with different outcomes of HBV infection.

Asian People↗

PubMed2004

Identification of a novel family of ankyrin repeats containing cofactors for p160 nuclear receptor coactivators.

Members of the p160 nuclear receptor coactivators interact with liganded nuclear receptors to enhance transcription of target genes. Here we identify a novel family of ankyrin repeats containing cofactors (ANCOs) that interact with the p160 coactivators. ANCO-1 binds to the conserved Per-Arnt-Sim (PAS) region of the p160 coactivators. It encodes a large nuclear protein with five ankyrin repeats, and parts of its sequences have been reported as nasopharyngeal carcinoma susceptibility protein and medulloblastoma antigen. Immunofluorescence staining reveals discrete nuclear foci of ANCO-1 that are distinct from known nuclear structures. Intriguingly, ANCO-1 also colocalizes and interacts with histone deacetylases. Transient reporter gene assay shows that ANCO-1 expression inhibits ligand-dependent transactivation by both steroid and nonsteroid nuclear receptors. Taken together, we have identified a novel family of ankyrin repeats containing cofactors that may recruit histone deacetylases to the p160 coactivators/nuclear receptor complex to inhibit ligand-dependent transactivation.

Amino Acid Sequence↗

PubMed2004

Unexpected reductions of glycosyl spacer-armed phthalimides.

An unusual reductive ring-opening reaction in the title compounds, of the phthalimide group with sodium hydride in anhydrous DMF is observed for the first time and the presumed mechanism is described in detail. An unexpected hydrogenation of the phthalimide group was also observed.

Anhydrides↗

PubMed2004

The determinants of carboxyl pKa values in turkey ovomucoid third domain.

A computational methodology for protein pK(a) predictions, based on ab initio quantum mechanical treatment of part of the protein and linear Poisson-Boltzmann equation treatment of the bulk solvent, is presented. The method is used to predict and interpret the pK(a) values of the five carboxyl residues (Asp7, Glu10, Glu19, Asp27, and Glu43) in the serine protease inhibitor turkey ovomucoid third domain. All the predicted pK(a) values are within 0.5 pH units of experiment, with a root-mean-square deviation of 0.31 pH units. We show that the decreased pK(a) values observed for some of the residues are primarily due to hydrogen bonds to the carboxyl oxygens. Hydrogen bonds involving amide protons are shown to be particularly important, and the effect of hydrogen bonding is shown to be nonadditive. Hydrophobic effects are also shown to be important in raising the pK(a). Interactions with charged residues are shown to have relatively little effect on the carboxyl pK(a) values in this protein, in general agreement with experiment.

Animals↗

PubMed2004

Adenosine suppresses GABAA receptor-mediated responses in rat sacral dorsal commissural neurons.

The modulatory effect of adenosine on gamma-aminobutyric acid (GABA)-activated whole-cell currents were investigated in the neurons acutely dissociated from the rat sacral dorsal commissural nucleus (SDCN) using the nystatin perforated patch recording configuration under the voltage-clamp conditions. The results showed that: (1) GABA acted on GABAA receptor and elicited inward Cl- currents (IGABA) at a holding potential (VH) of -40 mV; (2) adenosine suppressed GABA-induced Cl- current without affecting the reversal potential of IGABA and the apparent affinity of GABA to its receptor; (3) N6-cyclohexyladenosine mimicked the suppression effect of adenosine on IGABA, whereas 8-cyclopentyl-1,3-dipropylxanthine blocked the suppression effect of adenosine; (4) adenosine fails to suppress IGABA on the neurons that were pretreated with bisindolylmaleimide I (BIM), while after pretreatment with H-89, the inhibitory effect of adenosine on IGABA were not affected; (5) the suppression effect of adenosine on IGABA remained in the presence of BAPTA-AM. The present results indicate that the suppression of adenosine on IGABA is mediated by adenosine A1 receptor and through a Ca2+-independent protein kinase C transduction pathway, and that the interactions between adenosine and GABA might participate in the modulation of nociceptive information transmission at the SDCN.

Adenosine↗

PubMed2004

Wwp2, an E3 ubiquitin ligase that targets transcription factor Oct-4 for ubiquitination.

The POU transcription factor Oct-4 is a master regulator affecting the fate of pluripotent embryonic stem cells. However, the precise mechanisms by which the activation and expression of Oct-4 are regulated still remain to be elucidated. We describe here a novel murine ubiquitin ligase, Wwp2, that specifically interacts with Oct-4 and promotes its ubiquitination both in vivo and in vitro. Remarkably, the expression of a catalytically inactive point mutant of Wwp2 abolishes Oct-4 ubiquitination. Moreover, Wwp2 promotes Oct-4 degradation in the presence of overexpressed ubiquitin. The degradation is blocked by treatment with proteasome inhibitor. Fusion of a single ubiquitin to Oct-4 inactivates its transcriptional activity in a heterologous Oct-4-driven reporter system. Furthermore, overexpression of Wwp2 in embryonic stem cells significantly reduces the Oct-4-transcriptional activities. Collectively, we demonstrate for the first time that Oct-4 can be post-translationally modified by ubiquitination and that this modification dramatically suppresses its transcriptional activity. These results reveal that the functional status of Oct-4, in addition to its expression level, dictates its transcriptional activity, and the results open up a new avenue to understand how Oct-4 defines the fate of embryonic stem cells.

Animals↗

PubMed2004

Quantitation of acrolein-protein adducts: potential biomarker of acrolein exposure.

Acrolein, an alpha,beta-unsaturated aldehyde, is a ubiquitous environmental toxic pollutant. Because of potential human exposure, there is a need for a sensitive, reliable, and specific method to monitor acrolein exposure. Acrolein is a potent electrophile and reacts with proteins mainly through Michael addition reaction, leading to acrolein-protein adducts (APA). The present study aimed to develop a competitive enzyme-linked immunosorbent assay (ELISA) method for the quantitation of APA in biological samples. Antibody to acrolein-keyhole limpet hemocyanin adduct was raised in rabbits, and the specificity of the antibody was determined by ELISA using acrolein-albumin adduct (AAA) or native albumin. A dose-dependent response was observed with AAA, but no immunoreactivity with native albumin. Further, lack of cross-reactivity of anti-acrolein antibody with formaldehyde-, malondialdehyde-, or 4-hydroxynonenal-albumin adducts indicates its specificity for acrolein. For the competitive ELISA, 1:16,000 diluted antisera was used with varying concentrations of AAA, which provided a linear detection range between 250 and 10,000 pg. To test the efficacy of the method for possible use as a biomarker of acrolein exposure, SD rats were orally administered 1 or 7 doses of 9.2 mg/kg/d acrolein. APA levels, quantitated in the serum, showed significantly greater formation (32% and 58% after 1 and 7 doses, respectively) in acrolein-treated rats as compared to the controls. Western blot analyses of APA in the sera from acrolein-treated rats showed APA bands (especially 29, 31, and 100 kD) with greater intensity in comparison to controls, further supporting our ELISA results. These results suggest that quantitation of APA has potential to be used as biomarker of acrolein exposure and eventually for molecular dosimetry and risk assessment.

Acrolein↗

PubMed2004

Analyses of genetic structure of Tibeto-Burman populations reveals sex-biased admixture in southern Tibeto-Burmans.

An unequal contribution of male and female lineages from parental populations to admixed ones is not uncommon in the American continents, as a consequence of directional gene flow from European men into African and Hispanic Americans in the past several centuries. However, little is known about sex-biased admixture in East Asia, where substantial migrations are recorded. Tibeto-Burman (TB) populations were historically derived from ancient tribes of northwestern China and subsequently moved to the south, where they admixed with the southern natives during the past 2600 years. They are currently extensively distributed in China and Southeast Asia. In this study, we analyze the variations of 965 Y chromosomes and 754 mtDNAs in >20 TB populations from China. By examining the haplotype group distributions of Y-chromosome and mtDNA markers and their principal components, we show that the genetic structure of the extant southern Tibeto-Burman (STB) populations were primarily formed by two parental groups: northern immigrants and native southerners. Furthermore, the admixture has a bias between male and female lineages, with a stronger influence of northern immigrants on the male lineages (approximately 62%) and with the southern natives contributing more extensively to the female lineages (approximately 56%) in the extant STBs. This is the first genetic evidence revealing sex-biased admixture in STB populations, which has genetic, historical, and anthropological implications.

Chromosomes, Human, Y↗

PubMed2004

An ab initio potential energy surface and predissociative resonances of HArF.

A three-dimensional potential energy surface of the ground electronic state HArF is constructed from more than 2000 ab initio points at the multireference averaged quadratic coupled-cluster level employing an augmented large basis set. The calculations indicate that the linear HArF molecule is metastable with a barrier of 0.643 eV in the atomization (HArF --> H + Ar + F) channel and a barrier of 1.017 eV in the dissociation (HArF --> Ar + HF) channel. Variational calculations of low-lying predissociative resonances of both HArF and DArF are performed on the three-dimensional potential energy surface using a complex-symmetric Lanczos propagation method, which yields both positions and widths of the resonance states. The resonance lifetime generally decreases with energy, but strong mode selectivity exists. Reasonably good agreement with experiment confirms the accuracy of our potential. These calculations provide valuable information on the stability and dynamics of HArF/DArF in its ground electronic state.

Journal Article↗

PubMed2004

Evaluation of free hydroxyl radical scavenging activities of some Chinese herbs by capillary zone electrophoresis with amperometric detection.

Due to the severe damage caused by free hydroxyl radicals (OH.) to cells and tissues, there is much interest in finding and studying effective and non-toxic OH. scavengers, including traditional Chinese herbs. In this paper, the simple and highly-sensitive technique of capillary zone electrophoresis with amperometric detection (CZE-AD) was used to study the OH. scavenging activities of aqueous extracts from some traditional Chinese herbs. Salicylic acid (SAL) was used as an OH. trap, and the content of OH. could be determined by assaying their products, 2,3-dihydroxybenzoic acid (2,3-DHBA) and 2,5-dihydroxybenzoic acid (2,5-DHBA). The optimum conditions for CZE-AD for the determination of 2,3-DHBA and 2,5-DHBA were explored. The linearity ranges of 2,3-DHBA and 2,5-DHBA were 1.0 x10(-7) approximately 1.0 x10(-4) mol L(-1), and their detection limits were as low as 2 x 10(-8) mol L(-1), which were much better than the CE-UV method often used. The traditional Chinese herbs studied included Radix angelicae sinensis, Rhizoma coptidis, Ligustrum lucidum, Ligusticum wallichii, Radices glycyrrhizae and Semen plantaginis. The experiments showed that the aqueous extracts from all of the above traditional Chinese herds had free OH. scavenging activities, although to different degrees.

Electrochemistry↗

PubMed2004

The mouse FKBP23 binds to BiP in ER and the binding of C-terminal domain is interrelated with Ca2+ concentration.

FK506 binding protein 23 from mouse (mFKBP23) is a peptidyl-prolyl cis-trans isomerase (PPIase) from the endoplasmic reticulum (ER), which consists of an N-terminal PPIase domain and a C-terminal domain with Ca(2+) binding sites. The assay of adsorption from ER extract with glutathione S-transferase-mFKBP23 attached to glutathione-Sepharose 4B shows that mFKBP23 binds to mouse immunoglobulin binding protein (mBiP). The same assay with the recombinant proteins of the N- and C-termini of mFKBP23 shows that the binding of the C-terminus is Ca(2+)-dependent and the switch point is between 2 and 3 mM. By high concentration of Ca(2+) this binding cannot be detected. Furthermore, the Ca(2+)-regulated binding of mFKBP23 and mBiP in ER can be detected by means of co-immunoprecipitation.

Animals↗

PubMed2004

Localization of dopamine D1-receptor to A-type horizontal cells in the rabbit retina by single cell RT-PCR.

Dopamine is an important neurotransmitter regulating light-dark adaptation in the retina. The effect of dopamine is widespread and dependent on the localization of its receptors. We performed single cell RT-PCR on A-type horizontal cells visually selected from dissociated rabbit retinal neurons. Dopamine D1-receptor mRNA was positively identified. Subsequent sequencing of the fragment showed 82% homology with rat D1 receptor and 87% homology with human D1 receptor. This study supported previous observations that dopamine regulated A-type horizontal cell coupling via D1 receptors at the level of transcription.

Adaptation, Ocular↗

PubMed2004

Innervation-dependent and fiber type-specific transcriptional regulation of the slow myosin heavy chain 2 promoter in avian skeletal muscle fibers.

Skeletal muscle fiber type is regulated, in part, by innervation leading to transcriptional regulation of fiber type-specific genes. Here, we report the initial characterization of the transcriptional regulation of the slow myosin heavy chain 2 (MyHC2) promoter in innervated and noninnervated slow medial adductor (MA) and fast pectoralis major (PM) muscle fibers in cell culture. The proximal 1358 bp of slow MyHC2 upstream DNA contains a functional E-box and binding sites for myocyte enhancer factor 2 (MEF2) and nuclear factor of activated T cells (NFAT). Mutagenesis studies indicated that both MEF2 and NFAT binding sites are required for innervation-induced slow MyHC2 promoter activity in MA muscle fibers. However, MEF2 transcription factor activity was unaffected by innervation and did not demonstrate fiber type-specific interactions with the slow MyHC2 MEF2 binding site. NFAT transcription factor activity did increase in innervated MA muscle fibers and not in PM muscle fibers, indicating innervation and muscle fiber type-specific regulation. However, transfection of constitutively active NFAT indicated that NFAT is insufficient to induce slow MyHC2 gene expression in either fast PM or slow MA muscle fibers without innervation. These results indicate the requirement for MEF2 and NFAT in innervation-induced slow MyHC2 gene expression and suggest that additional innervation-dependent and fiber type-specific control of slow MyHC2 gene expression resides in MA and PM muscle fibers, respectively.

Animals↗

PubMed2004

Improving the efficiency and convergence of geometry optimization with the polarizable continuum model: new energy gradients and molecular surface tessellation.

New equations are derived and implemented for efficient and accurate computation of solvation energy derivatives for the conductor-like polarizable continuum model (C-PCM) and the isotropic integral equation formalism polarizable continuum model (IEF-PCM). Two new molecular surface tessellation procedures GEPOL-RT and GEPOL-AS that generate near continuous potential energy surfaces are proposed for PCM geometry optimization. The combined use of these new techniques leads to efficient and convergent geometry optimizations with the PCMs.

Journal Article↗

PubMed2004

Carbocyanine labeled LDL for optical imaging of tumors.

RATIONALE AND OBJECTIVES: The purpose of this study was to define and characterize carbocyanine labeled low-density lipoprotein (LDL) to be used in the optical imaging of LDL receptor (LDLr)-overexpressing tumor models. MATERIALS AND METHODS: 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) was used to label LDL (DiI-LDL). Scatchard plots were generated to determine the maximum binding capacity B(max) and dissociation constants K(D) of DiI-LDL in B16 melanoma (B16) and hepatoblastoma G(2) (HepG(2)) cell lines. Selective uptake of DiI-LDL into both tumor cells and corresponding subcutaneous tumors in mice were demonstrated by confocal microscopy and three-dimensional Cryo-imaging, respectively. RESULTS: The labeling efficiency of DiI-LDL was 61 ng DiI/microg LDL protein (34 mol DiI/mol LDL protein). B(max) and K(D) for B16 cells were 6.311 ng LDL/mg cell protein and 60.38 microg protein/mL (117 nM), respectively. B(max) and K(D) were 7.573 ng LDL/mg cell protein and 26.79 microg protein/mL (52 nM) for HepG(2) cells, respectively. Confocal microscopic images showed specific uptake of DiI-LDL throughout the cytoplasm in the B16/HepG(2) cells. Cryo-imaging demonstrated preferential accumulations of DiI-LDL in the viable tumor regions of both B16 and HepG(2) tumors compared with their adjacent normal tissues and corresponding necrotic tumor regions. In addition, uptake of DiI-LDL by the HepG(2) tumor was much higher than that of the B16 tumor, consistent with the fact that the probe binding affinity for LDLrs of HepG(2) cells is 2.3 times that of B16 cells. CONCLUSION: This study suggested that carbocyanine labeled LDL could be used for optical imaging of tumors overexpressing LDLr.

Animals↗

PubMed2004

A mouse optical simulation environment (MOSE) to investigate bioluminescent phenomena in the living mouse with the Monte Carlo method.

RATIONALE AND OBJECTIVES: As an important part of bioluminescence tomography, which is a newly developed optical imaging modality, mouse optical simulation environment (MOSE) is developed to simulate bioluminescent phenomena in the living mouse and to predict bioluminescent signals detectable outside the mouse. This simulator is dedicated to small animal optical imaging based on bioluminescence. MATERIALS AND METHODS: With the parameters of biological tissues, bioluminescent sources, and charge coupled device (CCD) detectors, the 2-dimensional/3-dimensional MOSE simulates the whole process of the light propagation in 2-dimensional/3-dimensional biological tissues using the Monte Carlo method. Both the implementation details and the software architecture are described in this article. RESULTS: The software system is implemented in the Visual C++ programming language with the OpenGL techniques and has a user-friendly interface facilitating interactions relevant to bioluminescent imaging. The accuracy of the system is verified by comparing the MOSE results with independent data from analytic solutions and commercial software. CONCLUSION: As shown in our simulation and analysis, the MOSE is accurate, flexible, and efficient to simulate the photon propagation for bioluminescence tomography. With graduate refinements and enhancements, it is hoped that the MOSE will become a standard tool for bioluminescence tomography.

Computer Simulation↗

PubMed2004

In vivo imaging of MLC2v-luciferase, a cardiac-specific reporter gene expression in mice.

RATIONALE AND OBJECTIVES: A reporter or marker gene that is detectable by in vivo imaging permits longitudinal monitoring of certain fundamental biological processes (eg, differentiation) within the context of physiologically authentic environments. Tissue-specific expression of a reporter gene can be achieved when it is under the transcriptional control of a tissue-specific promoter. The objective of this study was to construct a plasmid vector containing firefly luciferase (Fluc) marker gene downstream of the promoter sequence of rat ventricular myosin light chain 2 (MLC2v); to detect the in vivo expression of this cardiac-specific reporter (MLC2v-Fluc) in the mouse heart by bioluminescent imaging; and to correlate the bioluminescent signal with postmortem luminometer assay. MATERIALS AND METHODS: MLC2v-Fluc plasmid was generated by molecular cloning of 3 kb promoter sequence into a pGL3-Basic vector containing the Fluc reporter. Twenty microg of MLC2v-Fluc plasmid DNA in phosphate-buffered saline was directly injected into mouse myocardium through a midline sternotomy. RESULTS: At 1 week after injection, MLC2v-Fluc expression was detected by in vivo bioluminescent imaging in 60% of injected animals; the average in vivo signal intensity was (1.5 +/- 0.6) x 10(4) radiance (p/sec/cm2/sr); in vivo signal was well above the detection threshold over 3 weeks after injection. In vivo bioluminescent signal is correlated (r2 = 0.8) with the luminometer assay results from homogenized heart samples. CONCLUSION: The capability of noninvasive imaging of the MLC2v-Fluc in the heart will encourage applications that aim at monitoring and tracking the marker gene expression over time in cells undergoing cardiac differentiation.

Animals↗

PubMed2004

MR and fluorescent imaging of low-density lipoprotein receptors.

RATIONALE AND OBJECTIVES: Over-expression of low-density lipoprotein receptors (LDLRs) occurs in many types of malignancies and is related to the requirement for lipids for rapid proliferation of the tumors. On the other hand, LDLRs that are unable to bind LDL are found on hepatocytes of patients with familial hypercholesterolemia (FH), a genetic disease that leads to premature atherosclerosis and death. The highly selective binding of LDL to LDLR makes these particles ideal carriers of therapeutic and diagnostic contrast agents into the targeted cells. The objectives of this paper are to examine whether a prototype contrast agent (PTIR267) with dual detection properties is suitable for labeling of LDL particles for in vivo detection of LDLR by magnetic resonance imaging (MRI) and for in vitro monitoring of cellular localization by confocal fluorescence microscopy. MATERIALS AND METHODS: PTIR267 is a lipophilic GdDTPA derivative conjugated to a fluorescent dye. The conjugated dye molecule makes the probe sufficiently water soluble to allow labeling of LDL by a brief incubation of LDL with PTIR267 dissolved in PBS at 37 degrees C (mole ratio LDL: PTIR267 = 0.09:1). The molar relaxivity of PTIR267 in saline is 26 mM(-1)s(-1). Specific LDLR-mediated uptake of PTIR267-labeled LDL was demonstrated in vitro by confocal fluorescence imaging of B16 melanoma cells using confocal fluorescence imaging. In vivo uptake of PTIR267-labeled LDL by a subcutaneously implanted B16 melanoma in mice leads to 30% decrease in longitudinal relaxation time (T(1)) in the tumor. In vivo uptake of PTIR267-labeled LDL leads to 70% decrease in T(1) in a normal C57BL/6 mouse liver; however, in the liver of LDL receptor gene knockout (LDLr-/-) mice with C57BL/6 background, only 12% decrease in T(1) is observed. CONCLUSIONS: The dual fluorescence and MR imaging properties of PTIR267, combined with the ease of LDL labeling, suggest that it will be a useful tool for optimization of LDLR-targeted cancer diagnosis or therapy and for monitoring the efficacy of gene therapy of FH.

Animals↗