Search PubMed⌕ Search

Biomedical subjects

H Y Liu

Publications and source records attributed to H Y Liu.

At least 37 records · Page 2Linked to original sources
PubMed2000

CD4-Dependent and CD4-independent utilization of coreceptors by human immunodeficiency viruses type 2 and simian immunodeficiency viruses.

More than 10 G protein-coupled receptors (GPCRs) have been reported to act as coreceptors for entry of human and simian immunodeficiency viruses (HIV and SIV). We investigated the utilization of six GPCRs as coreceptors by T-cell-line-adapted HIV-2 strains (CBL-20, CBL-21, CBL-23, GH-1, ROD, and SBL6669) and SIV strains (SIVagmTYO-1, SIVmac251, and SIVmndGB-1). NP-2/CD4 cells were transduced with CCR3, CCR5, CCR8, CXCR4, GPR1, or APJ, and examined for susceptibilities to cell-free HIV/SIV. HIV-2 strains were grouped into two types by their coreceptor usage. The first group, CBL-20 and CBL-21, used CXCR4 exclusively; the other four strains used a few or all of the six coreceptors. These strains could further infect CD4-negative NP-2/CXCR4 or NP-2/CCR5 cells in the presence (all strains) or absence (SBL6669 and ROD strains) of soluble CD4. SIVagm and SIVmnd infected NP-2/CD4/GPR1 cells. The coreceptors CCR3, CCR8, GPR1, and APJ did not mediate the CD4-independent infection. Although HIV-2ROD and SIVmnd infected both NP-2/CD4/CXCR4 and NP-2/CD4/CCR5 cells, only CXCR4 and CCR5, respectively, were used in CD4-independent infection. Binding of virions to CD4-negative cells occurred at 4 degrees C. These findings suggest that there may be a correlation between the promiscuous use of coreceptors by HIV-2/SIV strains and their ability to infect CD4-negative cells.

CD4 Antigens↗
PubMed2000

Enteric infection acts as an adjuvant for the response to a model food antigen.

Oral administration of soluble protein Ags typically induces Ag-specific systemic nonresponsiveness. However, we have found that feeding a model food protein, OVA, to helminth-infected mice primes for a systemic OVA-specific Th2 response. In this report we show that, in addition to creating a Th2-priming cytokine environment, helminth infection up-regulates costimulatory molecule expression on mucosal, but not peripheral, APCs. To examine the consequences of mucosal infection for the T cell response to orally administered Ag, we adoptively transferred transgenic, OVA-specific, T cells into normal mice. We found that helminth infection enhances the expansion and survival of transgenic T cells induced by Ag feeding. Transfer of 5,6-carboxyfluorescein diacetate succinimidyl ester-labeled donor cells showed that T cell proliferation in response to Ag feeding takes place primarily in the mesenteric lymph nodes. Upon subsequent peripheral exposure to Ag in adjuvant, the proliferative capacity of the transferred transgenic T cells was reduced in noninfected mice that had been fed OVA. Helminth infection abrogated this reduction in proliferative capacity. Our data suggests that enteric infection can act as an adjuvant for the response to dietary Ags and has implications for allergic responses to food and the efficacy of oral vaccination.

Adjuvants, Immunologic↗
PubMed2000

Solution structure of the TAZ2 (CH3) domain of the transcriptional adaptor protein CBP.

The TAZ2 (CH3) domain of the transcriptional adapter protein CBP has been implicated in direct functional interactions with numerous cellular transcription factors and viral oncoproteins. The solution structure of the TAZ2 domain of murine CBP has been determined by nuclear magnetic resonance (NMR). The protein adopts a novel helical fold stabilized by three zinc ions, each of which is bound to one histidine and three cysteine ligands in HCCC-type motifs. Each zinc-binding site is formed from the carboxy terminus of an alpha-helix, a short loop, and the amino terminus of the next alpha-helix. A peptide derived from the N-terminal transactivation domain of p53 binds specifically to one face of the TAZ2 domain. The close similarities between the TAZ2 and TAZ1 (CH1 domain of CBP/p300) sequences suggest that both domains will adopt similar three-dimensional structures.

Adenovirus E1A Proteins↗
PubMed2000

Apelin peptides block the entry of human immunodeficiency virus (HIV).

The orphan G protein-coupled receptor APJ has been shown to be a coreceptor for human and simian immunodeficiency virus (HIV and SIV) strains. We have determined that some HIV and SIV strains use APJ as a coreceptor to infect the brain-derived NP-2/CD4 cells. Because apelin is an endogenous ligand for the APJ receptor, we examined the inhibitory effects of apelin peptides on HIV infection, and found that the apelin peptides inhibit the entry of some HIV-1 and HIV-2 into the NP-2/CD4 cells expressing APJ. The inhibitory efficiency has been found to be in the order of apelin-36>apelin-17>apelin-13>apelin-12.

Amino Acid Sequence↗
PubMed2000

A putative G protein-coupled receptor, RDC1, is a novel coreceptor for human and simian immunodeficiency viruses.

More than 10 G protein-coupled receptors (GPCRs) have been shown to act as coreceptors for infection of human immunodeficiency virus type 1 (HIV-1), HIV-2, and simian immunodeficiency virus (SIV). We have isolated HIV-1 variants infectious to primary brain-derived CD4-positive cells (BT-3 and BT-20/N) and U87/CD4 glioma cells that are resistant to T-cell line-tropic (T-tropic), macrophage-tropic (M-tropic), and T- and M-tropic (dualtropic) (X4, R5, and R5X4) HIV-1 strains. These primary brain-derived cells were also highly susceptible to HIV-2(ROD), HIV-2(SBL6669), and SIV(mndGB-1). A factor or coreceptor that determines the susceptibility of these brain-derived cells to these HIV and SIV strains has not been fully identified. To identify this coreceptor, we examined amino acid sequences of all known HIV and SIV coreceptors and noticed that tyrosine residues are well conserved in their extracellular amino-terminal domains. By this criterion, we selected 18 GPCRs as candidates of coreceptors for HIV and SIV strains infectious to these brain-derived cells. mRNA expression of an orphan GPCR, RDC1, was detected in the brain-derived cells, the C8166 T-cell line, and peripheral blood lymphocytes, all of which are susceptible to HIV-1 variants, but not in macrophages, which are resistant to them. When a CD4-expressing cell line, NP-2/CD4, which shows strict resistance to infection not only with HIV-1 but also with HIV-2 or SIV, was transduced with the RDC1 gene, the cells became highly susceptible to HIV-2 and SIV(mnd) strains but to neither M- nor T-tropic HIV-1 strains. The cells also acquired a low susceptibility to the HIV-1 variants. These findings indicate that RDC1 is a novel coreceptor for several HIV-1, HIV-2, and SIV strains which infect brain-derived cells.

Animals↗
PubMed2000

Molecular mechanism of apoptosis induced by ricin in HeLa cells.

AIM: To study the morphological changes and molecular mechanism of HeLa cell apoptosis induced by ricin. METHODS: HeLa cells were coincubated with ricin 0.05 mumol.L-1 for 1, 2, 3, 6, 12, 18, and 24 h, then scanning electron microscopy (SEM), transmission electron microscopy (TEM), Western blot cell cycle, cell cytotoxicity, and cell viability were assayed. RESULTS: The typical apoptosis was induced by ricin 0.05 mumol.L-1 and necrotic cells increased after being cultured with ricin 0.05 mumol.L-1 for more than 12 h. The apoptotic cells mainly showed cytoplasmic membrane blebbing, chromatin condensation and fragmentation, and crescentic nuclear and membrane bound apoptotic bodies formation. No detectable levels of p53, Bax, Bcl-2 and the subunit p20 of interleukin-1 beta-converting enzyme (ICE) were found by Western blot, but the active subunit p17 of 32-kDa putative cysteine protease (CPP32) was detected at 3, 6, and 9 h after ricin treatment. The activity of CPP32 in HeLa cells increased 4 to 5 folds after being treated with ricin 0.05 mumol.L-1 and reached the peak at 6 h of treatment. There was no significant difference of ICE activity between the ricin treated cells and control cells. The percentage of G2/M cells increased from 13.9% +/- 0.5% to 33.2% +/- 0.5% after 24 h of ricin 0.05 mumol.L-1 treatment. CONCLUSION: CPP32 but not ICE was involved in the ricin-induced apoptosis in HeLa cells. Ricin 0.05 mumol.L-1 had no effect on the G0/G1 phase of cell cycle, but induced G2/M arrest.

Apoptosis↗
PubMed2000

[Establishment of a TLC identification method for xuanshen(radix scrophulariae)].

OBJECTIVE: To establish a TLC identification method for Xuanshen(Radix Scrophulariae). METHOD: Using TLC with harpagoside and harpagide as reference substances. RESULT: A TLC identification method of Xuanshen has been established. The specificity of the method has been proved by a comparative detection of Xuanshen from different habitats and several crude drugs which are easily confused with Xuanshen. CONCLUSION: The method is simple, accurate and reliable.

Chromatography, Thin Layer↗
PubMed1999

Quantitative analysis of formyl peptide receptor coupling to g(i)alpha(1), g(i)alpha(2), and g(i)alpha(3).

The human formyl peptide receptor (FPR) is a prototypical G(i) protein-coupled receptor, but little is known about quantitative aspects of FPR-G(i) protein coupling. To address this issue, we fused the FPR to G(i)alpha(1), G(i)alpha(2), and G(i)alpha(3) and expressed the fusion proteins in Sf9 insect cells. Fusion of a receptor to Galpha ensures a defined 1:1 stoichiometry of the signaling partners. By analyzing high affinity agonist binding, the kinetics of agonist- and inverse agonist-regulated guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) binding and GTP hydrolysis and photolabeling of Galpha, we demonstrate highly efficient coupling of the FPR to fused G(i)alpha(1), G(i)alpha(2), and G(i)alpha(3) without cross-talk of the receptor to insect cell G proteins. The FPR displayed high constitutive activity when coupled to all three G(i)alpha isoforms. The K(d) values of high affinity agonist binding were approximately 100-fold lower than the EC(50) (concentration that gives half-maximal stimulation) values of agonist for GTPase activation. Based on the B(max) values of agonist saturation binding and ligand-regulated GTPgammaS binding, it was previously proposed that the FPR activates G proteins catalytically, i.e. one FPR activates several G(i) proteins. Analysis of agonist saturation binding, ligand-regulated GTPgammaS saturation binding and quantitative immunoblotting with membranes expressing FPR-G(i)alpha fusion proteins and nonfused FPR now reveals that FPR agonist binding greatly underestimates the actual FPR expression level. Our data show the following: (i) the FPR couples to G(i)alpha(1), G(i)alpha(2), and G(i)alpha(3) with similar efficiency; (ii) the FPR can exist in a state of low agonist affinity that couples efficiently to G proteins; and (iii) in contrast to the previously held view, the FPR appears to activate G(i) proteins linearly and not catalytically.

Animals↗
PubMed1999

Establishment of a new system for determination of coreceptor usages of HIV based on the human glioma NP-2 cell line.

CD4 and one of the G-protein-coupled receptors (GPCRs) on the cell surface function as a receptor and a coreceptor, respectively, in infection of cells with human and simian immunodeficiency viruses (HIV/SIV). To determine which GPCRs can be coreceptors for HIV (HIV-1 and HIV-2) or SIV infection, several cell lines, including human osteosarcoma HOS-T4 cells and human glioma U87/CD4 cells, have been used. However, these cells often show susceptibilities to some HIV or SIV strains before transduction of GPCRs. The results of this study showed that a CD4-transduced human glioma cell line, NP-2/CD4, a human erythroleukemia cell line, K562/CD4, and a human ovarian cancer cell line, TYK/CD4, were completely resistant to the HIV-1 and HIV-2 strains tested. After transduction of several GPCRs into NP-2/CD4, K562/CD4, or TYK/CD4 cells, NP-2/CD4 cells but not K562/CD4 or TYK/CD4 cells mostly showed expected susceptibilities to several HIV strains. Therefore, an NP-2 cell system would be useful to determine the coreceptor usage of HIV isolates, to find a new coreceptor for HIV/SIV, and to analyze the early stages of HIV/SIV infection.

Base Sequence↗
PubMed1999

Catatonic features: differential diagnosis and treatments at an emergency unit.

During a 2-year period, 34 patients of catatonic features in Chinese ethnic background Taiwanese were brought to the emergency unit of Chang Gung Memorial Hospital at Linkou. The ratios of the causes of catatonic features by schizophrenic disorders, mood disorders, neuroleptic-induced disorders, and general medical conditions were 26, 9, 24 and 41%, respectively. After the treatments of antipsychotics, benzodiazepam, or electroconvulsive therapy (ECT), 24 patients (70.6%) showed complete remission, seven patients (20.6%) showed partial remission, and three patients (8.8%) showed no response (two died). Additionally, a suggestive period is proposed in order to distinguish acute and insidious onset catatonic conditions to help clinicians in deciding on probability immediately. The patients were grouped into four diagnostic categories; namely, schizophrenic disorders, mood disorders, neuroleptic-induced disorders, and general medical conditions for comparison. One-way ANOVA and Duncan's multiple-range test were used for continuous variables, and the Chi-squared test was used for categorical variables. The mean duration of 'insidious onset catatonic condition' (including schizophrenic disorders and general medical conditions) before seeking medical help was longer than 3.33 weeks, while the mean duration of 'acute catatonic condition' (including mood disorders and neuroleptic-induced disorders) was shorter than 1.83 weeks. These findings suggest that 2-3 weeks would be a cut-off point for acute or insidious onsets of catatonic conditions.

Acute Disease↗
PubMed1999

Lipophilicity determination of some potential photosystem II inhibitors on reversed-phase high-performance thin-layer chromatography.

The retention characteristics of 25 2-cyano-3-methylthio-3-substituted amine-acrylates are determined using reversed-phase thin-layer chromatography (RP-TLC) with methanol-water mixtures as eluents. The relationship between Rm values and partition coefficients (C log P) are established. The Rm values decrease linearly with increasing methanol concentration in the eluent. The Rm values extrapolated to zero organic modifier concentration (Rm0) in the eluent are highly related to C log P. The Rm0 value can be used to evaluate the lipophilicity of this kind of compound.

Acrylates↗
PubMed1999

An orphan G protein-coupled receptor, GPR1, acts as a coreceptor to allow replication of human immunodeficiency virus types 1 and 2 in brain-derived cells.

Twelve G protein-coupled receptors, including chemokine receptors, act as coreceptors and determinants for the cell tropisms of human immunodeficiency virus type 1 (HIV-1), HIV-2, and simian immunodeficiency virus (SIV). We isolated HIV-1 variants from T-cell-line (T)- and macrophage (M)-tropic (i.e., dualtropic) (R5-R3-X4) HIV-1 strains and also produced six HIV-1 mutants carrying single-point amino acid substitutions at the tip of the V3 region of the Env protein of HIV-1. These variants and three mutants infected brain-derived CD4-positive cells that are resistant to M-, T-, or dualtropic (R5, X4, or R5-X4) HIV-1 strains. However, a factor that determines this cell tropism has not been identified. This study shows that primary brain-derived fibroblast-like cell strains, BT-3 and BT-20/N, as well as a CD4-transduced glioma cell line, U87/CD4, which were susceptible to these HIV-1 variants and mutants and the HIV-2ROD strain, expressed mRNA of an orphan G protein-coupled receptor (GPCR), GPR1. When a CD4-positive cell line which was strictly resistant to infection with diverse HIV-1 and HIV-2 strains was transduced with GPR1, the cell line became susceptible to these HIV-1 variants and mutants and to an HIV-2 strain but not to T- or dualtropic HIV-1 strains, and numerous syncytia formed after infection. These results indicate that GPR1 functions as a coreceptor for the HIV-1 variants and mutants and for the HIV-2ROD strain in vitro.

Brain↗
PubMed1999

The CCR4 and CAF1 proteins of the CCR4-NOT complex are physically and functionally separated from NOT2, NOT4, and NOT5.

The CCR4-NOT complex (1 mDa in size), consisting of the proteins CCR4, CAF1, and NOT1 to NOT5, regulates gene expression both positively and negatively and is distinct from other large transcriptional complexes in Saccharomyces cerevisiae such as SNF/SWI, TFIID, SAGA, and RNA polymerase II holoenzyme. The physical and genetic interactions between the components of the CCR4-NOT complex were investigated in order to gain insight into how this complex affects the expression of diverse genes and processes. The CAF1 protein was found to be absolutely required for CCR4 association with the NOT proteins, and CCR4 and CAF1, in turn, physically interacted with NOT1 through its central amino acid region from positions 667 to 1152. The NOT3, NOT4, and NOT5 proteins had no significant effect on the association of CCR4, CAF1, and NOT1 with each other. In contrast, the NOT2, NOT4, and NOT5 interacted with the C-terminal region (residues 1490 to 2108) of NOT1 in which NOT2 and NOT5 physically associated in the absence of CAF1, NOT3, and NOT4. These and other data indicate that the physical ordering of these proteins in the complex is CCR4-CAF1-NOT1-(NOT2, NOT5), with NOT4 and NOT3 more peripheral to NOT2 and NOT5. The physical separation of CCR4 and CAF1 from other components of the CCR4-NOT complex correlated with genetic analysis indicating partially separate functions for these two groups of proteins. ccr4 or caf1 deletion suppressed the increased 3-aminotriazole resistance phenotype conferred by not mutations, resulted in opposite effects on gene expression as compared to several not mutations, and resulted in a number of synthetic phenotypes in combination with not mutations. These results define the CCR4-NOT complex as consisting of at least two physically and functionally separated groups of proteins.

Binding Sites↗
PubMed1999

[Effect of OFQ injection into intracerebroventricular and preoptic area on blood pressure and heart rate in rats].

Orphanin FQ (OFQ) is a novel peptide comprised of an amino acid sequence very similar to that of dynorphin A. In the present investigation the effect of OFQ on cardiovascular activities was studied. Introcerebroventricular (icv) injection of OFQ at doses of 1 and 10 micrograms produced significant decrease in heart rate (HR) and mean arterial pressure (MAP). Icv pretreatment with naloxone could not prevent the hypotensive and bradycardial response produced by 1 microgram OFQ. Injection of 1 microgram OFQ preoptic area (POA) also caused a profound decrease of MAP and HR. These results indicate that OFQ can inhibit cardiovascular activities which are not mediated by mu, delta and kappa receptors. POA may be one of the target areas of these inhibitory effects.

Animals↗
PubMed1998

Selection at a P-glycoprotein gene in ivermectin- and moxidectin-selected strains of Haemonchus contortus.

Resistance to anthelmintics that are used to control parasite populations in domestic animals has become a serious problem worldwide. The development of resistance is an evolutionary process that leads to genetic changes in parasite populations in response to drug exposure. The anthelmintic ivermectin is known to bind to the human membrane transport protein, P-glycoprotein, and P-glycoprotein-deficient mice treated with ivermectin have shown signs of neurotoxicity. P-glycoprotein is believed to be involved in the multidrug resistance phenotype seen in some human cancers and for drug resistance in some protists. We have examined the genetic variation of a P-glycoprotein homologue from the nematode Haemonchus contortus to see if an association exists between specific alleles of this gene and survival to exposure to ivermectin or moxidectin. Two parasite strains passaged without drug treatment and three strains, subjected to anthelmintic selection and derived from the unselected strains, were examined. Allelic variation in the unselected strains showed this locus to be highly polymorphic. chi 2 analyses of allele frequencies showed significant differences between the unselected and the drug-selected derived strains. In all three drug-selected strains, an apparent selection for the same allele was observed. These findings suggest that P-glycoprotein may be involved in resistance to both ivermectin and moxidectin in H. contortus.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

The NOT proteins are part of the CCR4 transcriptional complex and affect gene expression both positively and negatively.

The CCR4 transcriptional regulatory complex consisting of CCR4, CAF1, DBF2 and other unidentified factors is one of several groups of proteins that affect gene expression. Using mass spectrometry, we have identified the 195, 185 and 116 kDa species which are part of the CCR4 complex. The 195 and 185 kDa proteins were found to be NOT1 and the 116 kDa species was identical to NOT3. NOT1, 2, 3 and 4 proteins are part of a regulatory complex that negatively affects transcription. All four NOT proteins were found to co-immunoprecipitate with CCR4 and CAF1, and NOT1 co-purified with CCR4 and CAF1 through three chromatographic steps in a complex estimated to be 1.2x10(6) Da in size. Mutations in the NOT genes affected many of the same genes and processes that are affected by defects in the CCR4 complex components, including reduction in ADH2 derepression, defective cell wall integrity and increased sensitivity to monoand divalent ions. Similarly, ccr4, caf1 and dbf2 alleles negatively regulated FUS1-lacZ expression, as do defects in the NOT genes. These results indicate that the NOT proteins are physically and functionally part of the CCR4 complex which forms a unique and novel complex that affects transcription both positively and negatively.

Alleles↗
PubMed1998

NMR spectroscopic studies of the hydrogenosomal [2Fe-2S] ferredoxin from Trichomonas vaginalis: hyperfine-shifted 1H resonances.

The hyperfine-shifted 1H NMR resonances of oxidized and reduced Trichomonas vaginalis ferredoxin, a functionally unique [2Fe-2S] ferredoxin, have been studied. The oxidized protein spectrum displayed a pattern of six broad upfield-shifted resonances between 13 and 40 ppm with chemical shifts distinct from those of other [2Fe-2S] ferredoxins. All hyperfine 1H resonances of the oxidized ferredoxin displayed anti-Curie temperature dependences. Reduced T. vaginalis ferredoxin displayed hyperfine resonances both upfield and downfield of the diamagnetic region. These resonances showed Curie temperature dependences. Overall the hyperfine-shifted NMR spectrum of T. vaginalis ferredoxin, along with other spectroscopic properties, suggested different structural properties for the active center of oxidized hydrogenosomal ferredoxins from those of other [2Fe-2S] ferredoxins.

Animals↗