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Hong Liu

Publications and source records attributed to Hong Liu.

At least 361 records · Page 20Linked to original sources
PubMed2002

Genome sequence of Shigella flexneri 2a: insights into pathogenicity through comparison with genomes of Escherichia coli K12 and O157.

We have sequenced the genome of Shigella flexneri serotype 2a, the most prevalent species and serotype that causes bacillary dysentery or shigellosis in man. The whole genome is composed of a 4 607 203 bp chromosome and a 221 618 bp virulence plasmid, designated pCP301. While the plasmid shows minor divergence from that sequenced in serotype 5a, striking characteristics of the chromosome have been revealed. The S.flexneri chromosome has, astonishingly, 314 IS elements, more than 7-fold over those possessed by its close relatives, the non-pathogenic K12 strain and enterohemorrhagic O157:H7 strain of Escherichia coli. There are 13 translocations and inversions compared with the E.coli sequences, all involve a segment larger than 5 kb, and most are associated with deletions or acquired DNA sequences, of which several are likely to be bacteriophage-transmitted pathogenicity islands. Furthermore, S.flexneri, resembling another human-restricted enteric pathogen, Salmonella typhi, also has hundreds of pseudogenes compared with the E.coli strains. All of these could be subjected to investigations towards novel preventative and treatment strategies against shigellosis.

Amino Acid Sequence↗
PubMed2002

Induction of specific CTL by MAGE-3/CEA peptide-pulsed dendritic cells from HLA-A2/A24(+) gastrointestinal cancer patients.

PURPOSE: In this study, we aimed to investigate whether MAGE3/CEA peptide-pulsed dendritic cells could induce specific cytotoxic T lymphocytes (CTL). METHODS: In this pilot study, we selected 25 patients expressing MAGE-3-HLA-A2/A24 or CEA-HLA-A24. Patients' dendritic cells (DCs) were expanded in vitro in the presence of recombined-human granular macrophage colony stimulating factor (rhGM-CSF) and recombined-human interleukin 4 (rhIL-4), pulsed with MAGE-3/CEA (HLA-A2/A24) peptide. The cytolytic cells' activity, induced by peptide-pulsed DCs and unpurified T cells as effector cells, and with Mel526, 803, Raji, and K562 as target cells, were measured using LDH-releasing assay. RESULTS: DCs were obtained by in vitro expansion in all cases although DC harvest rates varied among different patients (7.1+/-3.2%). Compared with T-IL-2 (IL-2-induced T cells), T-DC-P - which resulted from T-IL-2 co-cultured with DCs pulsed by MAGE3 or CEA peptides - exhibited an increase in cytolytic activity against Mel526 (expressing MAGE-3-HLA-A2) and 803 (expressing CEA-HLA-A24) cell lines by about 25-30% ( P<0.01). In contrast, there was no significant difference between the activity against Raji and K562 cells, which are negative for both peptides. CONCLUSIONS: This study showed that combined usage of rhGM-CSF and rhIL-4 in vitro could expand DCs, and that the DCs pulsed with specific peptides could induce MAGE- and CEA-specific CTL responses. The DC-based vaccine may provide an important method for the immunological treatment of gastrointestinal cancers.

Adult↗
PubMed2002

Effect of different components of laser immunotherapy in treatment of metastatic tumors in rats.

Induction of a long-term tumor-specific immunity is the ultimate cure of metastatic cancers. Laser immunotherapy is a novel approach that aims at the tumor-directed stimulation of the immune system of the host. It involves an intratumor administration of a laser-absorbing dye and an immunoadjuvant, followed by noninvasive laser irradiation. Previous studies using glycated chitosan (GC) as immunoadjuvant and indocyanine green (ICG) as laser-absorbing dye have shown positive effects of the treatment on metastatic breast tumors in rats. In vivo experiments showed promising results such as: (a) eradication of treated primary tumors; (b) regression of untreated metastases; (c) induced antitumor immune response; and (d) long-term resistance to tumor rechallenge. In this study, rats bearing metastatic breast tumors and metastatic prostate tumors were treated with various combinations of the three components of laser immunotherapy. The rat survival rates and profiles of primary and metastatic tumors, after treatment by individual components and various combinations of the components, were analyzed. In the treatment of breast tumors, all of the experimental groups without immunoadjuvant showed little or no positive effect. The use of GC, either by itself or in combination with other components, had a noticeable impact on the survival rate of tumor-bearing rats. However, it was the combination of all of the three components that resulted in the highest cure rate. Three different concentrations of GC, 0.5, 1, and 2%, were also used to treat the metastatic breast tumors. The results showed that 1% GC was most effective in laser immunotherapy. In the treatment of metastatic prostate tumors, both the laser-ICG and laser-ICG-GC treatments significantly reduced the growth of primary tumors and lung metastases. Long-term survival of the rats bearing the prostate tumors was also observed after the laser immunotherapy treatment in our preliminary studies. These results revealed the important function of the immunoadjuvant in laser immunotherapy.

Adjuvants, Immunologic↗
PubMed2002

New p-methylsulfonamido phenylethylamine analogues as class III antiarrhythmic agents: design, synthesis, biological assay, and 3D-QSAR analysis.

Class III antiarrhythmic agents selectively delay the effective refractory period (ERP) and increase the transmembrane action potential duration (APD). Using dofetilide (2) as a template of class III antiarrhythmic agents, we designed and synthesized 16 methylsulfonamido phenylethylamine analogues (4a-d and 5a-l). Pharmacological assay indicated that all of these compounds showed activity for increasing the ERP in isolated animal atrium; among them, the effective concentration of compound 4a is 1.6 x 10(-8) mol/L in increasing ERP by 10 ms, slightly less potent than that of 2, 1.1 x 10(-8) mol/L. Compound 4a also produced a slightly lower change in ERP at 10(-5) M, DeltaERP% = 17.5% (DeltaERP% = 24.0% for dofetilide). On the basis of this bioassay result, these 16 compounds together with dofetilide were investigated by the three-dimensional quantitative structure-activity relationship (3D-QSAR) techniques of comparative molecular field analysis (CoMFA), comparative molecular similarity index analysis (CoMSIA), and the hologram QSAR (HQSAR). The 3D-QSAR models were tested with another 11 compounds (4e-h and 5m-s) that we synthesized later. Results revealed that the CoMFA, CoMSIA, and HQSAR predicted activities for the 11 newly synthesized compounds that have a good correlation with their experimental value, r(2) = 0.943, 0.891, and 0.809 for the three QSAR models, respectively. This indicates that the 3D-QSAR models proved a good predictive ability and could describe the steric, electrostatic, and hydrophobic requirements for recognition forces of the receptor site. On the basis of these results, we designed and synthesized another eight new analogues of methanesulfonamido phenylethyamine (6a-h) according to the clues provided by the 3D-QSAR analyses. Pharmacological assay indicated that the effective concentrations of delaying the ERP by 10 ms of these newly designed compounds correlated well with the 3D-QSAR predicted values. It is remarkable that the percent change of delaying ERP at 10(-5) M compound 6c is much higher than that of dofetilide; the effective concentration of compound 6c is 5.0 x 10(-8)mol/L in increasing the ERP by 10 ms, which is slightly lower than that of 2. The results showed that the 3D-QSAR models are reliable and can be extended to design new antiarrhythmic agents.

Animals↗
PubMed2002

[Adenovirus-mediated NT3 gene transfer protects spiral ganglion neurons from degeneration after noise trauma].

Numerous studies have shown that the health of spiral ganglion neurons is highly important for hearing. As a trophic factor of spiral ganglion neurons, neurotrophin 3 (NT3) is a potential candidate for prevention of spiral ganglion neuron degeneration in human. In our experiments, efficient transduction and long term expression of foreign gene of cochlea cells has been found with adenovirus carried lacZ gene (Ad-lacZ). A model of guinea pig deafness was made by intense noise exposure, which destroyed the entire organ of Corti in the middle part of the cochlea. Seven days after noise exposure, the animals were anesthetized and 1 10(8) recombinant adenoviral particles were injected into the scala tympani through the round window membrane. Animals inoculated with neurotrophin 3 adenovirus(Ad-NT3) were designated as the experimental group, animals inoculated with Ad-lacZ vector served as the control group. Four weeks after the inoculation of the virus, NT3 immunoreactivity was observed in the Ad-NT3 inoculated group. HE histochemical staining results showed that in the Ad-lacZ injected group, the neuronal degeneration was severer and the density of spiral ganglion neurons was significantly lower than those in the Ad-NT3 injected group. Our results demonstrate that with adenovirus-mediated overexpression NT3 may be developed into a new treatment to prevent secondary spiral ganglion degeneration following the damage to Corti organ.

Adenoviridae↗
PubMed2002

Distinct proteins encoded by alternative transcripts of the PURG gene, located contrapodal to WRN on chromosome 8, determined by differential termination/polyadenylation.

A gene encoding a new member of the Pur protein family, Purgamma, has been detected upstream of, and contrapodal to, the gene encoding the Werner syndrome helicase, Wrn, at human chromosome band 8p11-12. Both the PURG and WRN genes initiate transcription at multiple sites, the major clusters of which are approximately 90 bp apart. A segment containing this region strongly promotes transcription of a reporter gene in both directions. Both promoters are TATA-less and CAAT-less and both are positively regulated by Sp1 elements. While promoter elements for the two genes are interleaved, in the contrapodal direction, certain elements critical for each gene are distinct. Sequencing of cDNAs for Purgamma mRNA reveals that two alternative coding sequences are generated from a single gene, resulting in different Purgamma C-termini. PURG-A mRNA consists of a single intronless transcript of approximately 3 kb. PURG-B mRNA results from transcription through the PURG-A polyadenylation site and splicing out of an intron of >30 kb. In this unique example of a switch, splicing of a single intron either occurs or does not occur depending upon differential termination/polyadenylation. PURG-B is the primary PURG transcript detected in testis, but it is undetectable in all members of a normal adult tissue cDNA panel. PURG-A levels are low or undetectable in the normal tissue panel, but they are greatly elevated in all members of a tumor tissue panel. PURG-B is detected in several tumor panel members.

5' Untranslated Regions↗
PubMed2002

Extraction of extracellular polymeric substances (EPS) of sludges.

The efficacies of extracting extracellular polymeric substances (EPS) from aerobic, acidogenic and methanogenic sludges using EDTA, cation exchange resin and formaldehyde under various conditions were compared. Results show that formaldehye plus NaOH was most effective in extracting EPS for all sludges; only 1.1-1.2% of DNA in the sludge samples were detected, suggesting the EPS extracted were not contaminated by intracellular substances. For each gram of volatile solids, formaldehyde-NaOH extracted 165, 179 and 102 mg of EPS from aerobic, acidogenic and methanogenic sludges, respectively. All EPS were mainly composed of carbohydrate, protein and humic substance, plus small quantities of uronic acid and DNA. Carbohydrate was predominant in the acidogenic sludge (62% in the EPS extracted by formaldehyde-NaOH), whereas protein was predominant in the methanogenic sludge (41%). Humic substance, which has often been overlooked, accounted for 30.6, 8.4 and 22.8% of the extracted EPS from aerobic, acidogenic and methanogenic sludges, respectively. However, judging from EPS quantities estimated from confocal laser scanning microscopic observations, formaldehyde-NaOH extracted only a limited portion of EPS. Optimization of extraction procedures and/or development of a more effective extraction method are warranted.

Biopolymers↗
PubMed2002

Sphingosine-1-phosphate and lipid phosphohydrolases.

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid that acts as both an extracellular ligand for the endothelial differentiation gene-1 (EDG-1) G-protein coupled receptor (GPCR) family and as an intracellular messenger. Cellular levels of S1P are low and tightly regulated in a spatial-temporal manner not only by sphingosine kinase (SPHK) but also by degradation catalyzed by S1P lyase, specific S1P phosphohydrolases, and by general lipid phosphate phosphohydrolases (LPPs). LPPs are characterized as magnesium-independent, insensitive to inhibition by N-ethylmaleimide (NEM) and possessing broad substrate specificity with a variety of phosphorylated lipids, including S1P, phosphatidic acid (PA), and lysophosphatidic acid (LPA). LPPs contain three highly conserved domains that define a phosphohydrolase superfamily. Recently, several specific S1P phosphohydrolases have been identified in yeast and mammalian cells. Phylogenetic and biochemical analyses indicate that these enzymes constitute a new subset of the LPP family. As further evidence, S1P phosphohydrolases exhibit high specificity for phosphorylated sphingoid bases. Enforced expression of S1P phosphohydrolase alters the cellular levels of sphingolipid metabolites in yeast and mammalian cells, increasing sphingosine and ceramide, bioactive sphingolipids that often have opposing biological actions to S1P. By regulating the cellular ratio between ceramide/sphingosine and S1P, S1P phosphohydrolase is poised to be a critical factor in cell survival/cell death decisions. Indeed, expression of S1P phosphohydrolase in mammalian cells increases apoptosis, whereas deletion of S1P phosphohydrolases in yeast correlates with resistance to heat stress. In this review, we discuss the role of phosphohydrolases in the metabolism of S1P and how turnover of S1P can regulate sphingolipid metabolites signaling.

Animals↗
PubMed2002

Characterization of a CCD-based digital x-ray imaging system for small-animal studies: properties of spatial resolution.

A digital x-ray imaging system was designed for small-animal studies. This system is a fiber-optics taper-coupled imaging system with two CCD arrays uniquely jointed. The x-ray source of the system has a small focal spot of 20 microm. This digital imaging system contains specially designed shelves to provide magnification levels, ranging from 1.5x to 5x. The system is characterized in terms of its properties of spatial resolution. An observer-based spatial resolution measurement was conducted with a line-pair target and a sector test pattern. The modulation transfer function of the system, with different magnifications, was studied by use of a 10-microm lead slit. The average resolutions at 50% and 5% modulations at 1x magnification were measured as 3.9 and 8.4 lp/mm, respectively, where lp indicates line pairs. With 5x magnification, the 50% and the 5% modulations provided 13.2- and 29.9-lp/mm, respectively, average spatial resolutions. The measurements showed consistency between the two individual CCD arrays; the difference in resolution between the two CCDs is less than 1%, even at high magnifications.

Animals↗
PubMed2002

Ceramide kinase, a novel lipid kinase. Molecular cloning and functional characterization.

Ceramide-1-phosphate is a sphingolipid metabolite that has been implicated in membrane fusion of brain synaptic vesicles and neutrophil phagolysosome formation. Ceramide-1-phosphate can be produced by ATP-dependent ceramide kinase activity, although little is known of this enzyme because it has not yet been highly purified or cloned. Based on sequence homology to sphingosine kinase type 1, we have now cloned a related lipid kinase, human ceramide kinase (hCERK). hCERK encodes a protein of 537 amino acids that has a catalytic region with a high degree of similarity to the diacylglycerol kinase catalytic domain. hCERK also has a putative N-myristoylation site on its NH(2) terminus followed by a pleckstrin homology domain. Membrane but not cytosolic fractions from HEK293 cells transiently transfected with a hCERK expression vector readily phosphorylated ceramide but not sphingosine or other sphingoid bases, diacylglycerol or phosphatidylinositol. This activity was clearly distinguished from those of bacterial or human diacylglycerol kinases. With natural ceramide as a substrate, the enzyme had a pH optimum of 6.0-7.5 and showed Michaelis-Menten kinetics, with K(m) values of 187 and 32 microm for ceramide and ATP, respectively. Northern blot analysis revealed that hCERK mRNA expression was high in the brain, heart, skeletal muscle, kidney, and liver. A BLAST search analysis using the hCERK sequence revealed that putative ceramide kinases (CERKs) exist widely in diverse multicellular organisms including plants, nematodes, insects, and vertebrates. Phylogenetic analysis revealed that CERKs are a new class of lipid kinases that are clearly distinct from sphingosine and diacylglycerol kinases. Cloning of CERK should provide new molecular tools to investigate the physiological functions of ceramide-1-phosphate.

Amino Acid Sequence↗
PubMed2002

Characterization of a hydrogen-producing granular sludge.

This study demonstrated that hydrogen-producing acidogenic sludge could agglutinate into granules in a well-mixed reactor treating a synthetic sucrose-containing wastewater at 26 degrees C, pH 5.5, with 6 h of hydraulic retention. A typical matured granule is 1.6 mm in diameter, 1.038 g/mL in density, 11% in ash content, and over 50 m/h in settling velocity. Treating a solution containing 12.15 g/L of sucrose at a volumetric loading rate of 48.6 g/(L x d), the reactor containing 20 g/L of granular sludge degraded 97% of sucrose. Effluent comprised 46% acetate and 49% butyrate and the methane-free biogas comprised 63% hydrogen, 35% carbon dioxide, and 2% nitrogen. Hydrogen production rate was 13.0 L/(L x d), and the yield was 0.28 L/g-sucrose. The granule had multiple cracks on the surface and comprised two morphological types of bacteria: fusiform bacilli and a spore-forming bacterium. Phylogenetic analysis showed that 69.1% of the clones were affiliated with four Clostridium species in the family Clostridiaceae, and 13.5% with Sporolactobacillus racemicus in the Bacillus/Staphylococcus group.

Alcohols↗
PubMed2002

Sphingosine kinases: a novel family of lipid kinases.

Sphingosine kinase (SPHK) catalyzes the formation of sphingosine-1-phosphate (S11). S1P plays an important role in regulation of a variety of biological processes through intracellular and extracellular actions. S1P has recently been shown to be the ligand for the EDG-1 family of G-protein-coupled receptors. To date, seven cloned SPHKs have been reported with confirmed SPHK activity, including human, mouse, yeast, and plant. A computer search of various databases suggests that a new SPHK family is emerging. The cloning and manipulation of SPHK genes will no doubt provide us with important information about the functions of S1P in a wide range of organisms.

Amino Acid Sequence↗
PubMed2002

Anticoagulation for patients with heparin-induced thrombocytopenia using recombinant hirudin during cardiopulmonary bypass.

Heparin-induced thrombocytopenia (HIT) is a common complication of heparin therapy. There are three types of HIT. In the majority of patients, thrombocytopenia is modest and resolves without sequelae (HIT I). In a smaller number of patients, the thrombocytopenia is severe (HIT II), and in still others, the thrombocytopenia is also associated with thrombosis (HITT). Administration of heparin to this latter group of patients causes platelet aggregation, thromboembolism, and thrombocytopenia. It is advisable that heparin not be administered in any form to patients with documented or suspected HIT II or HITT. This situation, of course, poses a problem for those patients requiring cardiopulmonary bypass (CPB) surgery. In this report, we summarize our experience with Lepirudin (Hoechst, Frankfurt Ammain, Germany), which is a recombinant hirudin (r-hirudin), as an alternative to heparin for systemic anticoagulation, as well as the use of the ecarine clotting time (ECT) for monitoring anticoagulation status during CPB.

Aged↗
PubMed2002

Effect of pH on hydrogen production from glucose by a mixed culture.

The effect of pH on the conversion of glucose to hydrogen by a mixed culture of fermentative bacteria was evaluated. At 36 degrees C, six hours hydraulic retention, over 90% of glucose was degraded at pH ranging 4.0-7.0, producing biogas and an effluent comprising mostly fatty acids. At the optimal pH of 5.5, the biogas comprised 64 +/- 2% of hydrogen with a yield of 2.1 +/- 0.1 mol-H2/mol-glucose and a specific production rate of 4.6 +/- 0.4 l-H2/(g-VSS day). The effluent was composed of acetate (15.3-34.1%) and butyrate (31.2-45.6%), plus smaller quantities of other volatile fatty acids and alcohols. The diversity of microbial communities increased with pH, based on 16S rDNA analysis by denaturing gradient gel electrophoresis (DGGE).

Alcohols↗
PubMed2002

Lack of mannose-binding lectin-A enhances survival in a mouse model of acute septic peritonitis.

The mannose-binding lectin (MBL) (also known as the mannose-binding protein) is a serum protein that plays a role as an "ante-antibody" in innate immunity. In man, MBL is encoded by a single gene, whereas in mice there are two homologous proteins, MBL-A and MBL-C. In order to evaluate the relative roles of these two forms of MBL, we created MBL-A null mice that were MBL-C sufficient. We found MBL-A null mice had enhanced survival in a septic peritonitis model compared to wild-type mice and complement 3 null mice at 24 h, 48 h and 10 d (P < 0.05). Reconstitution of these mice with human MBL reversed the phenotype. Surviving mice had significantly decreased TNF-alpha and IL-6 levels in the blood and peritoneal cavity (P < 0.01). In vitro studies indicate that bacteria opsonized with MBL-A-deficient serum induced significantly less cytokine by peritoneal macrophages compared to those with wild-type serum. Our results indicate that MBL-A is a modulator of inflammation in vivo and in vitro in the mouse and that the role of MBL may extend beyond its role as an opsonin.

Animals↗
PubMed2002

RNA interference in the pathogenic fungus Cryptococcus neoformans.

Cryptococcus neoformans is a pathogenic fungus responsible for serious disease in immunocompromised individuals. This organism has recently been developed as an experimental system, with initiation of a genome project among other molecular advances. However, investigations of Cryptococcus are hampered by the technical difficulty of specific gene replacements. RNA interference, a process in which the presence of double-stranded RNA homologous to a gene of interest results in specific degradation of the corresponding message, may help solve this problem. We have shown that expression of double-stranded RNA corresponding to portions of the cryptococcal CAP59 and ADE2 genes results in reduced mRNA levels for those genes, with phenotypic consequences similar to that of gene disruption. The two genes could also be subjected to simultaneous interference through expression of chimeric double-stranded RNA. Specific modulation of protein expression through introduction of double-stranded RNA thus operates in C. neoformans, which is the first demonstration of this technique in a fungal organism. Use of RNA interference in Cryptococcus should allow manipulation of mRNA levels for functional analysis of genes of interest and enable efficient exploration of genes discovered by genome sequencing.

Carboxy-Lyases↗