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Biomedical subjects

Hui Liu

Publications and source records attributed to Hui Liu.

At least 91 records · Page 5Linked to original sources
PubMed2005

Glucose-stimulated DNA synthesis through mammalian target of rapamycin (mTOR) is regulated by KATP channels: effects on cell cycle progression in rodent islets.

The aim of this study was to define metabolic signaling pathways that mediate DNA synthesis and cell cycle progression in adult rodent islets to devise strategies to enhance survival, growth, and proliferation. Since previous studies indicated that glucose-stimulated activation of mammalian target of rapamycin (mTOR) leads to [3H]thymidine incorporation and that mTOR activation is mediated, in part, through the K(ATP) channel and changes in cytosolic Ca2+, we determined whether glyburide, an inhibitor of K(ATP) channels that stimulates Ca2+ influx, modulates [3H]thymidine incorporation. Glyburide (10-100 nm) at basal glucose stimulated [3H]thymidine incorporation to the same magnitude as elevated glucose and further enhanced the ability of elevated glucose to increase [3H]thymidine incorporation. Diazoxide (250 microm), an activator of KATP channels, paradoxically potentiated glucose-stimulated [3H]thymidine incorporation 2-4-fold above elevated glucose alone. Cell cycle analysis demonstrated that chronic exposure of islets to basal glucose resulted in a typical cell cycle progression pattern that is consistent with a low level of proliferation. In contrast, chronic exposure to elevated glucose or glyburide resulted in progression from G0/G1 to an accumulation in S phase and a reduction in G2/M phase. Rapamycin (100 nm) resulted in an approximately 62% reduction of S phase accumulation. The enhanced [3H]thymidine incorporation with chronic elevated glucose or glyburide therefore appears to be associated with S phase accumulation. Since diazoxide significantly enhanced [3H]thymidine incorporation without altering S phase accumulation under chronic elevated glucose, this increase in DNA synthesis also appears to be primarily related to an arrest in S phase and not cell proliferation.

Animals↗
PubMed2005

Asymmetric transfer hydrogenation of ketones catalyzed by hydrophobic metal-amido complexes in aqueous micelles and vesicles.

[Reaction: see text]. Asymmetric transfer hydrogenation of ketones, especially alpha-bromomethyl aromatic ketones, catalyzed by unmodified, hydrophobic transition metal-amido complexes (TsDPEN-M), was performed successfully with significant enhancement of activity, chemoselectivity, and enantioselectivity (up to 99% ee) in aqueous media containing micelles and vesicles. The hydrophobic catalyst, embedded in micelles constructed from the surfactant cetyltrimethylammonium bromide (CTAB), could be separated from the organic phase along with the products and was recycled for at least six times.

Journal Article↗
PubMed2005

Low-frequency Fourier spectrum for predicting membrane protein types.

Cell membranes are vitally important to living cells. Although the infrastructure of biological membrane is provided by the lipid bilayer, membrane proteins perform most of the specific functions. Knowledge of membrane protein types often provides crucial hints toward determining the function of an uncharacterized membrane protein. With the avalanche of new protein sequences generated in the post-genomic era, it is highly demanded to develop a high throughput tool in identifying the type of newly found membrane proteins according to their primary sequences, so as to timely annotate them for reference usage in both basic research and drug discovery. To realize this, the key is to establish a powerful identifier that can catch their characteristic sequence patterns for different membrane protein types. However, it is not easy because they are buried in a pile of long and complicated sequences. In this paper, based on the concept of the pseudo-amino acid composition [K.C. Chou, PROTEINS: Struct., Funct., Genet. 43 (2001) 246-255], the low-frequency Fourier spectrum analysis is introduced. The merits by doing so are that the sequence pattern information can be more effectively incorporated into a set of discrete components, and that all the existing prediction algorithms can be straightforwardly used on such a formulation for protein samples. High success rates were observed by the re-substitution test, jackknife test, and independent dataset test, indicating that the low-frequency Fourier spectrum approach may become a very useful tool for membrane protein type prediction. The novel approach also holds a high potential for predicting many other attributes of proteins.

Fourier Analysis↗
PubMed2005

Effects of copper and its ethylenediaminetetraacetate complex on the antioxidant defenses of the goldfish, Carassius auratus.

Copper bioavailability in the tissues of goldfish and antioxidant defenses in the liver of fish were investigated in vivo following 40 days of exposure to different species of copper solutions at different concentrations. Copper seemed to be more concentrated in the gill than in the liver after Cu(2+) and copper-ethylenediaminetetraacetate (Cu-EDTA) exposure. The addition of EDTA markedly affected copper adsorption in the gill but had no significant effects in the liver. We also found that in the fish exposed to the concentration of Cu(2+) below the Chinese national fishery water quality standard of 0.01 mg/L, superoxide dismutase (SOD) and glutathione S-transferase (GST) activities in liver were stimulated and catalase (CAT) and Se-dependent glutathione peroxidase (Se-GPx) activities were inhibited after 40 days of exposure. Compared to copper exposure, the addition of EDTA did not affect SOD and GST significantly. However, CAT and GPx activity with Cu(2+) exposure were significantly different from those with Cu-EDTA exposure.

Animals↗
PubMed2005

Genome-wide SNP discovery and linkage analysis in barley based on genes responsive to abiotic stress.

More than 2,000 genome-wide barley single nucleotide polymorphisms (SNPs) were developed by resequencing unigene fragments from eight diverse accessions. The average genome-wide SNP frequency observed in 877 unigenes was 1 SNP per 200 bp. However, SNP frequency was highly variable with the least number of SNP and SNP haplotypes observed within European cultivated germplasm reflecting effects of breeding history on genetic diversity. More than 300 SNP loci were mapped genetically in three experimental mapping populations which allowed the construction of an integrated SNP map incorporating a large number of RFLP, AFLP and SSR markers (1,237 loci in total). The genes used for SNP discovery were selected based on their transcriptional response to a variety of abiotic stresses. A set of known barley abiotic stress QTL was positioned on the linkage map, while the available sequence and gene expression information facilitated the identification of genes potentially associated with these traits. Comparison of the sequenced SNP loci to the rice genome sequence identified several regions of highly conserved gene order providing a framework for marker saturation in barley genomic regions of interest. The integration of genome-wide SNP and expression data with available genetic and phenotypic information will facilitate the identification of gene function in barley and other non-model organisms.

Expressed Sequence Tags↗
PubMed2005

Prediction of protein signal sequences and their cleavage sites by statistical rulers.

Functioning as an "address tag" or "zip code" that guides nascent proteins (newly synthesized proteins in the cytosol) to wherever they are needed, signal peptides (also called targeting signals or signal sequences) have become a crucial tool in finding new drugs or reprogramming cells for gene therapy. To effectively and timely use such a tool, however, the first important thing is to develop an automated method for quickly and accurately identifying the signal peptide for a given nascent protein. With the avalanche of new protein sequences generated in the post-genomic era, the challenge has become even more urgent and critical. In this paper, five statistical rulers were derived via performing a mutual information analysis. By combining these statistical rulers, a new prediction algorithm was established and high success prediction rates were observed. The new algorithm may play a complementary role to the existing algorithms in this area. It is anticipated that the mutual information approach introduced here may be very useful for studying many other sequence-coupling problems in molecular biology as well.

Algorithms↗
PubMed2005

Effects of social isolation stress on immune response and survival time of mouse with liver cancer.

AIM: To investigate the effects of isolation stress on mouse with liver cancer and possible associated mechanisms. METHODS: Transplantable murine hepatoma22 (H22) model was used to evaluate the effects of social isolation stress on murine liver cancer. Mice were immunized with sheep red blood cell (SRBC) and intraperitoneally inoculated with H22 cell, then divided into two groups, one reared individually as group (I) and the other reared in groups as group (G). Titer of antibody to SRBC and interleukin 2 (IL-2) in serum was monitored. The survival time of mouse with liver cancer was observed. RESULTS: The titer of antibody to SRBC in group (G) was 1:24.5 and that in group (I) was 1:11.2. There was a significant difference between these two groups (t = 2.60, P = 0.02). A significant difference in IL-2 concentration was observed between group (G) (39.6 ng/L) and group (I) (47.1 ng/L, t = 2.14, P = 0.046). The survival time in group (G) (16.5 d) was markedly longer than that in group (I) (13.2 d, t = 3.46, P = 0.002). CONCLUSION: Our study suggests that survival time of the mouse bearing H22 tumor is affected by the social isolation stress and the associated mechanism may be the immunological changes under the social isolation stress.

Animals↗
PubMed2005

Estrogen receptor inhibits interleukin-6 gene expression by disruption of nuclear factor kappaB transactivation.

The estrogen receptor (ER) suppresses interleukin-6 (IL-6) gene expression through interaction with nuclear factor kappaB (NF-kappaB) in a hormone-dependent manner. Classic ER binding to DNA is not required and the mechanism of repression is unclear. Previously reported studies suggest that the interference of NF-kappaB binding to DNA by ER may play an important role. An alternative model for repression would be the disruption of NF-kappaB transactivation. In the present study, gel shift assays were used to examine the binding of RelA and p50 dimers to the IL-6 promoter in the presence of ER. The effect of ER on NF-kappaB transactivation was studied independent of NF-kappaB binding to DNA using the mammalian one-hybrid system. ER had little effect on the binding of homodimers or heterodimers of RelA and p50 to the IL-6 promoter. In transfection experiments, both ERalpha and ERbeta inhibited NF-kappaB-mediated expression in a hormone dependent manner with repression also dependent upon dimerization of RelA with p50. Mutant ER that is unable to transactivate failed to repress NF-kappaB expression, but deletion of the N-terminal portion of the receptor had no effect. Taken together, these results suggest that the disruption of NF-kappaB-mediated transactivation plays a significant role in ER inhibition of IL-6 gene expression.

Base Sequence↗
PubMed2005

Genomic sequence analysis and organization of BmKalphaTx11 and BmKalphaTx15 from Buthus martensii Karsch: molecular evolution of alpha-toxin genes.

Based on the reported cDNA sequences of BmKalphaTxs , the genes encoding toxin BmKalphaTx11 and BmKalphaTx15 were amplified by PCR from the Chinese scorpion Buthus martensii Karsch genomic DNA employing synthetic oligonucleotides. Sequences analysis of nucleotide showed that an intron about 500 bp length interrupts signal peptide coding regions of BmKalphaTx11 and BmKalphaTx15. Using cDNA sequence of BmKalphaTx11 as probe, southern hybridization of BmK genome total DNA was performed. The result indicates that BmKalphaTx11 is multicopy genes or belongs to multiple gene family with high homology genes. The similarity of BmKalpha-toxin gene sequences and southern hybridization revealed the evolution trace of BmKalpha-toxins: BmKalpha-toxin genes evolve from a common progenitor, and the genes diversity is associated with a process of locus duplication and gene divergence.

Amino Acid Sequence↗
PubMed2005

Genomic organization of four novel nondisulfide-bridged peptides from scorpion Mesobuthus martensii Karsch: gaining insight into evolutionary mechanism.

At least 25 nondisulfide-bridged peptides (NDBPs) have been identified and characterized from scorpions. However, the genomic organization of the genes that encode these peptides have not been reported yet. BmKa1, BmKa2 and BmKb1 are three novel genes that code for NDBPs identified by our group from Mesobuthus martensii Karsch. Based on their cDNA sequences, the genomic DNA sequences encoding these peptides were obtained using the PCR method. Sequence analysis showed that three distinct genomic structural patterns are used to encode these three peptides. The BmKa1 gene is not interrupted by any introns. However, the BmKa2 gene is composed of two exons, interrupted by a 67 bp intron that is located in the DNA region encoding the mature peptide. Two genomic homologues of the BmKb1 cDNA sequence, named BmKb1' and BmKb2, respectively, were obtained. The BmKb1' gene contains one intron of 593 bp, inserted into the DNA region that encodes the signal peptide. Similarly, the BmKb2 gene also contains an intron that interrupts the exon that encodes the NDBP signal peptide. The amino acid sequences deduced for BmKb2 and BmKb1' differ only at one position. The data suggest that the genomic organizational pattern of NDBPs displays more divergence than that exhibited by the genes that encode disulfide-bridged peptides from scorpions.

Amino Acid Sequence↗
PubMed2005

Two residues in the hemagglutinin of A/Fujian/411/02-like influenza viruses are responsible for antigenic drift from A/Panama/2007/99.

The H3N2 vaccine strain (A/Panama/2007/99) for the 2003-2004 influenza season did not antigenically match the circulating A/Fujian/411/02-like H3N2 viruses and had reduced effectiveness against influenza outbreaks. A/Wyoming/03/2003, an A/Fujian-like virus, was recommended as the vaccine strain for the 2004-2005 season. A/Wyoming differed from A/Panama by 16 amino acids in the HA1 molecule. Reverse genetics was used to determine the minimal amino acid changes that were responsible for the antigenic drift from A/Panama to A/Wyoming. After substitutions of 2 of the 16 amino acids in the HA (H155T, Q156H), the A/Panama HA variant was antigenically equivalent to A/Wyoming as determined by hemagglutination inhibition and microneutralization assays using ferret postinfection antisera. Conversely, A/Wyoming containing the His-155 and Gln-156 residues from A/Panama was antigenically equivalent to A/Panama. These results indicated that only these two HA residues specified the antigenic drift from A/Panama to A/Wyoming; other amino acid differences between these two H3N2 viruses had minimal impact on virus antigenicity but impacted virus replication efficiency in eggs.

Amino Acid Substitution↗
PubMed2005

[Comparison of therapeutic effects of low-dose versus high-dose interferon alpha-2b treatment on chronic myelocytic leukemia: a prospective randomized study].

OBJECTIVE: To compare the therapeutic effects of low-dose and high-dose interferon alpha-2b (IFN) treatment on chronic myelocytic leukemia (CML). METHODS: A real-time quantitative reverse transcriptase PCR (RQ-PCR) method was established to detect the fusion gene bcr-abl expression, thereby studying the reduction of leukemic cells. Thirty newly diagnosed CML patients, 21 males and 9 females, aged 14 - 69, were treated with hydroxyurea to keep the white blood cell count less than 20 x 10(9)/L, and then randomized into 2 groups: high-dose IFN group receiving IFN alpha-2b 5MIU 6 times per week for 3 - 6 months and low-dose IFN group receiving IFN alpha-2b 3MIU every other day for 3 - 6 months. Bone marrow was collected every month to Real-time PCR was used to detect the expression of bcr-abl mRNA. Mononuclear cells were isolated and RNA was extracted to detect the expression of fusion gene bcr-abl and a control gene GAPDH. The results were reported as the number of bcr-abl copies/GAPDH copy. RESULTS: The established real-time quantitative PCR method could detect the bcr-abl molecules as low as 50 copies. The intra-assay coefficient of variation (CV) was less than 5% and the inter-assay CV was 5.13%. The median bcr-abl fusion gene expression level of 30 CML patients before IFN therapy was 0.098 (range: 0.010 - 5.799). The bcr-abl expression level decreased by 19.37% and 24.86% in the low-dose and high-dose IFN groups respectively after 3 months' therapy. No significant difference was observed between the two groups (P = 0.398). Relatively more side effects were observed in the high-dose IFN group than in low-dose group. CONCLUSION: RQ-PCR is a reliable method to monitor CML therapy by analyzing fusion gene bcr-abl expression. There is a difference in bcr-abl fusion gene expression levels among the newly diagnosed patients, and low-dose IFN is as effective as high-dose IFN in reducing bcr-abl expression but with less side effects.

Adolescent↗
PubMed2005

Targeted deletion of the chicken beta-globin regulatory elements reveals a cooperative gene silencing activity.

The chicken beta-globin locus represents a well characterized system to study the role of both proximal and distal regulatory elements in a eukaryotic multigene domain. The function of the chicken beta(A)/epsilon-intergenic enhancer and upstream regulatory elements 5'-HS1 and 5'-HS2 were studied using a gene targeting approach in chicken DT40 cells followed by microcell-mediated chromosome transfer into human erythroleukemia cells (K562). These regulatory elements all repressed expression of the rho- and beta(H)-chicken globin genes in the chromosome transfer assay. No rho- or beta(H)-globin gene expression was detected in K562 cells containing the chicken chromosome without deletions, whereas rho- and beta(H)-mRNA was activated in K562 cells containing chicken chromosomes with deletions of the intergenic enhancers, 5'-HS1 and 5'-HS2. Transcriptional activation of the rho- and beta(H)-globin genes correlated with hyperacetylation of histones H3 and H4, loss of histone H3 lysine 9 methylation, and binding of RNA polymerase II to the gene promoters. Surprisingly, the status of CpG dinucleotide methylation at the promoters did not correlate with the transcriptional status of the genes. Our results using a chromosomal transfer assay demonstrate an identical silencing function for these regulatory elements, which suggests they function as part of a common silencing pathway or complex.

Animals↗
PubMed2005

Developmental incompetency of denuded mouse oocytes undergoing maturation in vitro is ooplasmic in nature and is associated with aberrant Oct-4 expression.

BACKGROUND: Germinal vesicle (GV) oocytes constitute a potential resource but their developmental competence is questionable especially when surrounding cumulus cells are removed. The intercellular factors/mechanisms underlying such poor embryonic competence may originate at a nuclear and/or ooplasmic level. METHODS: Immature or mature oocytes were obtained from three mouse strains following pregnant mare serum gonadotropin (PMSG) or PMSG+ human chorionic gonadotropin (hCG) treatment. Immature oocytes were denuded of cumulus cells prior to in vitro maturation. Pronuclear (PN) transfer was used to examine nuclear-ooplasmic interplay on resultant embryonic development and Oct-4 immuno-staining patterns. RESULTS: Embryos arising from ooplasts of in vivo matured oocytes displayed significant increases in blastocyst formation rates and total blastomere numbers when compared to those created from ooplasts of denuded oocytes. Oct-4 staining was more pronounced and restricted to the inner cell mass (ICM) in blastocysts arising from the ooplasm of in vivo matured zygotes than in those created from denuded oocytes. CONCLUSIONS: Developmental defect(s) appear to develop primarily in the ooplasm of oocytes that are denuded of their cumulus cells prior to in vitro maturation. Such oocytes result in embryos with poor developmental competence. These defects result in anomalies in cell number and Oct-4 expression during the morula-blastocyst developmental transition.

Animals↗
PubMed2005

Effect of hydrodynamics-based gene delivery of plasmid DNA encoding interleukin-1 receptor antagonist-Ig for treatment of rat autoimmune myocarditis: possible mechanism for lymphocytes and noncardiac cells.

BACKGROUND: Interleukin-1 (IL-1) is a powerful and important cytokine in myocarditis. The purpose of this study was to evaluate the effect and possible mechanism of hydrodynamics-based delivery of the IL-1 receptor antagonist (IL-1RA)-immunoglobulin (Ig) gene for treatment of rat experimental autoimmune myocarditis (EAM). METHODS AND RESULTS: On the day after immunization, rats were transfected with either pCAGGS encoding IL-1RA-Ig or pCAGGS encoding Ig alone. On day 17, IL-1RA-Ig gene therapy was effective in controlling EAM, as monitored by a decreased ratio of heart weight to body weight, reduced myocarditis areas, reduced gene expression of atrial natriuretic peptide in hearts, and improved cardiac function in echocardiographic and hemodynamic parameters. Examination of the expression of IL-1-related genes in purified cells from EAM hearts suggested that ectopic IL-1RA-Ig-acting target cells were alphabetaT cells and noncardiomyocytic noninflammatory cells such as fibroblasts, smooth muscle cells, and endothelial cells. Therefore, we examined the effect of serum containing IL-1RA-Ig on the expression of immune-relevant genes within noncardiomyocytic cells cultured from EAM hearts or concanavalin A-stimulated lymphocytes derived from lymph nodes in EAM-affected rats. The expression of immunologic molecules (prostaglandin E synthase, cyclooxygenase-2, and IL-1beta) in cultivated noncardiomyocytic cells and Th1 cytokines (IL-2 and IFN-gamma) in lymphocytes was significantly decreased by the serum containing IL-1RA-Ig. CONCLUSIONS: EAM was suppressed by hydrodynamics-based delivery of plasmid DNA encoding IL-1RA-Ig. In addition, IL-1RA-Ig suppressed gene expression of prostaglandin synthases and IL-1 in noncardiomyocytic cells and Th1 cytokines in lymphocytes.

Animals↗
PubMed2005

A host-range restricted parainfluenza virus type 3 (PIV3) expressing the human metapneumovirus (hMPV) fusion protein elicits protective immunity in African green monkeys.

Human metapneumovirus (hMPV) infection causes respiratory tract disease similar to that observed during human respiratory syncytial virus infection (hRSV). hMPV infections have been reported across the entire age spectrum although the most severe disease occurs in young children. No vaccines, chemotherapeutics or antibodies are presently available for preventing or treating hMPV infections. In this study, a bovine/human chimeric parainfluenza virus type 3 (b/h PIV3) expressing the human parainfluenza type 3 (hPIV3) fusion (F) and hemagglutinin-neuraminidase (HN) proteins was engineered to express hMPV fusion (F) protein from the second genome position (b/h PIV3/hMPV F2) with the goal of generating a novel hMPV vaccine. b/h PIV3/hMPV F2 was previously shown to protect hamsters from challenge with wt hMPV (Tang RS, Schickli JH, Macphail M, Fernandes F, Bicha L, Spaete J, et al. Effects of human metapneumovirus and respiratory syncytial virus antigen insertion in two 3' proximal genome positions of bovine/human parainfluenza virus type 3 on virus replication and immunogenicity. J Virol 2003;77:10819-28) and is here further evaluated for efficacy and immunogenicity in African green monkeys (AGMs). AGMs immunized intranasally and intratracheally with b/h PIV3/hMPV F2 generated hMPV- and hPIV3-specific humoral and cellular immune responses and were protected from wt hMPV infection. In a separate study, the host-range restriction of b/h PIV3/hMPV F2 replication relative to wt hPIV3 was performed in rhesus monkeys to demonstrate attenuation. These studies showed that b/h PIV3/hMPV F2 was immunogenic, protective and attenuated in non-human primates and warrants further evaluation in humans as a vaccine candidate for prevention of hMPV-associated respiratory tract diseases.

Animals↗
PubMed2005

Characterisation and functional analysis of two barley caleosins expressed during barley caryopsis development.

Two full-length cDNA sequences homologous to caleosin, a seed-storage oil-body protein from sesame, were identified from a series of barley grain development cDNA libraries and further characterised. The cDNAs, subsequently termed HvClo1 and HvClo2, encode proteins of 34 kDa and 28 kDa, respectively. Real-time RT-PCR indicated that HvClo1 is expressed abundantly during the later stages of embryogenesis and is seed-specific, accumulating in the scutellum of mature embryos. HvClo2 is expressed mainly in the endosperm tissues of the developing grain. We show that HvClo1 and HvClo2 are paralogs that co-segregate on barley chromosome 2HL. Transient expression of HvClo1 in lipid storage and non-storage cells of barley using biolistic particle bombardment indicates that caleosins have different subcellular locations from the structural oil-body protein oleosin, and by inference participate in different sorting pathways. We observe that caleosin sorts via small vesicles, suggesting a likely association with lipid trafficking, membrane expansion and oil-body biogenesis.

Calcium-Binding Proteins↗