Biomedical subjects

Yuan Li

Publications and source records attributed to Yuan Li.

At least 163 records · Page 9Linked to original sources

PubMed2003

CCR5 expression and beta-chemokine production during placental neonatal monocyte differentiation.

The stage of maturation of monocytes affects their susceptibility to HIV infection. The beta-chemokines and their receptor CCR5 play a crucial role in inflammatory reactions and HIV infection. We therefore examined the correlation between the expression of CCR5 and beta-chemokine production and the susceptibility to HIV infection during cord monocyte (CM) differentiation into macrophages. CM and CM-derived macrophages (CMDM) were examined for beta-chemokine and CCR5 expression. The susceptibility of the CM cultured in vitro at different time points to HIV infection was also determined. Although the levels of CCR5 mRNA expression in freshly isolated CM are comparable to those in CMDM, CM had significantly lower levels of CCR5 protein on the cell surface than CMDM did. Steady increase of CCR5 protein expression on the cell surface was observed during CM differentiation into macrophages. The CCR5 expression correlated with the increased susceptibility to HIV infection by CMDM. Although there was no significant difference in endogenous beta-chemokine production between CM and CMDM, HIV infection of CMDM significantly enhanced production of macrophage inflammatory protein-1alpha and -1beta. CCR5 receptor plays a critical role in HIV infection of neonatal blood monocyte/macrophages.

Cell Differentiation↗

PubMed2003

Human neuronal cells (NT2-N) express functional substance P and neurokinin-1 receptor coupled to MIP-1 beta expression.

Substance P (SP), the most extensively studied and potent member of the tachykinin family, is a major modulator of inflammation and immunomodulatory activities within the central and peripheral nervous systems. We have examined the gene expression of SP and its receptor in a human neuronal cell line (NT2-N). Using reverse transcribed polymerase chain reaction (RT-PCR), the four isoforms of preprotachykinin-A gene transcripts (alpha, beta, gamma, and delta) were detected in the NT2-N. We also identified the presence of mRNA for neurokinin-1 receptor (NK-1R), a primary receptor for SP, in the NT2-N cells. Concomitant with NT2 cell differentiation into neurons, SP and NK-1R mRNA expression increased consistently. Intracellular SP and cell membrane NK-1R immunoreactivity were all observed in NT2-N cells. Most importantly, we demonstrated that SP and NK-1R presented in NT2-N cells are functionally involved in the regulation of macrophage inflammatory protein 1 beta (MIP-1beta), an important beta-chemokine participating in the activation and directional migration of immune cells to sites of central nervous systems (CNS) inflammation. Thus, SP and its receptor may play an important role in modulation of neuronal functions related to regulation of immune activities within the CNS. The NT2-N cell line is well suited for in vitro investigations of the SP-NK-1R pathway in immune responses and inflammation in the CNS.

Cells, Cultured↗

PubMed2003

Interleukin-1beta induces macrophage inflammatory protein-1beta expression in human hepatocytes.

The investigation of factors that regulate expression of CC-chemokines, the important mediators in immune responses and inflammation processes, has an important significance in understanding the immunopathogenesis of liver diseases. We examined the role of interleukin-1beta (IL-1beta), a multifunctional cytokine, in regulating the expression of macrophage inflammatory protein (MIP)-1beta in human hepatocytes (Huh7 and HepG2). IL-1beta significantly enhanced MIP-1beta expression in these cells at both the mRNA and protein levels. Cytokine-enriched supernatants from monocyte-derived macrophage (MDM) cultures also induced MIP-1beta expression. IL-1beta is responsible for MDM supernatant-mediated up-regulation of MIP-1beta since the antibody to IL-1beta abolished MDM supernatant action. Investigation of the mechanism involved in MIP-1beta induction by IL-1beta showed that IL-1beta activated the nuclear factor kappa B (NF-kappaB) promoter in Huh7 cells. In addition, caffeic acid phenethyl ester (CAPE), a specific inhibitor of the activation of NF-kappaB, not only abolished IL-1beta-mediated NF-kappaB promoter activation, but also blocked IL-1beta-induced MIP-1beta expression. These observations suggest that IL-1beta-mediated up-regulation of MIP-1beta production in the hepatic cells may contribute a critical mechanism for continuous recruitment of inflammatory cell to liver and maintenance of inflammation.

Caffeic Acids↗

PubMed2003

Morphine enhances hepatitis C virus (HCV) replicon expression.

Little information is available regarding whether substance abuse enhances hepatitis C virus (HCV) replication and promotes HCV disease progression. We investigated whether morphine alters HCV mRNA expression in HCV replicon-containing liver cells. Morphine significantly increased HCV mRNA expression, an effect which could be abolished by either of the opioid receptor antagonists, naltrexone or beta-funaltrexamine. Investigation of the mechanism responsible for this enhancement of HCV replicon expression demonstrated that morphine activated NF-kappaB promoter and that caffeic acid phenethyl ester, a specific inhibitor of the activation of NF-kappaB, blocked morphine-activated HCV RNA expression. In addition, morphine compromised the anti-HCV effect of interferon alpha (IFN-alpha). Our in vitro data indicate that morphine may play an important role as a positive regulator of HCV replication in human hepatic cells and may compromise IFN-alpha therapy.

Antiviral Agents↗

PubMed2003

Resonance energy transfer from dibucaine to acriflavine in polystyrene latex dispersions.

Resonance energy transfer from dibucaine (DC) to acriflavine (AF) has been investigated both in homogeneous aqueous solutions and in polystyrene latex dispersions. The energy transfer reaction is observed by monitoring fluorescence quenching of DC as well as sensitized emission of AF. It is found that the energy transfer from DC to AF is remarkably enhanced on going from the aqueous homogeneous solution to the latex dispersion. This is mainly attributed to the fact that both the donor and acceptor are effectively adsorbed onto the latex particles, as evidenced by the measurement of adsorption isotherms. From the adsorption experiments, it is also elucidated that electrostatic interaction is significant at low DC concentration, while hydrophobic interaction dominates at the higher concentration especially at higher pH.

Acriflavine↗

PubMed2003

Interleukin-1beta stimulates macrophage inflammatory protein-1alpha and -1beta expression in human neuronal cells (NT2-N).

Chemokines are important mediators in immune responses and inflammatory processes of neuroimmunologic and infectious diseases. Although chemokines are expressed predominantly by cells of the immune system, neurons also express chemokines and chemokine receptors. We report herein that human neuronal cells (NT2-N) produce macrophage inflammatory protein-1alpha and -1beta (MIP-1alpha and MIP-1beta), which could be enhanced by interleukin (IL)-1beta at both mRNA and protein levels. The addition of supernatants from human peripheral blood monocyte-derived macrophage (MDM) cultures induced MIP-1beta mRNA expression in NT2-N cells. Anti-IL-1beta antibody removed most, but not all, of the MDM culture supernatant-induced MIP-1beta mRNA expression in NT2-N cells, suggesting that IL-1beta in the MDM culture supernatants is a major factor in the induction of MIP-1beta expression. Investigation of the mechanism(s) responsible for IL-1beta-induced MIP-1alpha and -1beta expression demonstrated that IL-1beta activated nuclear factor kappa B (NF-kappaB) promoter-directed luciferase activity in NT2-N cells. Caffeic acid phenethyl ester, a potent and specific inhibitor of activation of NF-kappaB, not only blocked IL-1beta-induced activation of the NF-kappaB promoter but also decreased IL-1beta-induced MIP-1alpha and -1beta expression in NT2-N cells. These data suggest that NF-kappaB is at least partially involved in the IL-1beta-mediated action on MIP-1alpha and -1beta in NT2-N cells. IL-1beta-mediated up-regulation of beta-chemokine expression may have important implications in the immunopathogenesis of inflammatory diseases in the CNS.

Cell Line↗

PubMed2003

Alcohol potentiates hepatitis C virus replicon expression.

Alcohol consumption accelerates liver damage and diminishes the anti-hepatitis C virus (HCV) effect of interferon alfa (IFN-alpha) in patients with HCV infection. It is unknown, however, whether alcohol enhances HCV replication and promotes HCV disease progression. The availability of the HCV replicon containing hepatic cells has provided a unique opportunity to investigate the interaction between alcohol and HCV replicon expression. We determined whether alcohol enhances HCV RNA expression in the replicon containing hepatic cells. Alcohol, in a concentration-dependent fashion, significantly increased HCV replicon expression. Alcohol also compromised the anti-HCV effect of IFN-alpha. Investigation of the mechanism(s) responsible for the alcohol action on HCV replicon indicated that alcohol activated nuclear factor kappaB (NF-kappaB) promoter. Caffeic acid phenethyl ester (CAPE), a specific inhibitor of the activation of NF-kappaB, abolished alcohol-induced HCV RNA expression. In addition, naltrexone, an opiate receptor antagonist, abrogated the enhancing effect of alcohol on HCV replicon expression. In conclusion, alcohol, probably through the activation of NF-kappaB and the endogenous opioid system, enhances HCV replicon expression and compromises the anti-HCV effect of IFN-alpha. Thus, alcohol may play an important role in vivo as a cofactor in HCV disease progression and compromise IFN-alpha-based therapy against HCV infection.

Antidotes↗

PubMed2003

Isolation and sequencing of glycosyltransferase gene and UDP-glucose dehydrogenase gene that are located on a gene cluster involved in a new exopolysaccharide biosynthesis in Streptomyces.

Streptomyces sp. 139 produces a new exopolysaccharide (EPS) that shows anti-rheumatic arthritis activity in vivo. To investigate the gene cluster involved in EPS biosynthesis, degenerate primers were designed to amplify an internal fragment of the priming glycosyltransferase gene that catalyzes the first step in EPS biosynthesis. Using this PCR product as probe, positive cosmid clones were selected from a genomic library of Streptomyces sp. 139, which led to the localization of ste (Streptomyces eps) gene cluster on the approximately 65-kb chromosomal region. A 4.0-kb Bam HI fragment from all positive cosmids that hybridized to this probe was sequenced, which revealed two genes encoding the priming glycosyltransferase and UDP-glucose dehydrogenase. The putative priming glycosyltransferase is suggested to catalyze the first step in the biosynthesis of EPS repeating unit and UDP-glucose dehydrogenase is suggested to convert UDP-glucose into UDP-glucuronic acid involved in nucleotide sugar precursor synthesis of EPS biosynthesis.

Amino Acid Sequence↗

PubMed2003

Production of C-terminal amidated recombinant salmon calcitonin in Streptomyces lividans.

Salmon calcitonin (sCT) is one of the many bioactive peptides that require C-terminal amidation for full biologic activity. To produce fully bioactive sCT in large scale, we constructed Streptomyces lividans [pMSA], an engineering Streptomyces strain. In the expression vector, glycine-extended sCT, the substrate for amidation, and rat alpha-amidating enzyme cDNA were cloned under the control of the strong constitutive promoter from the Streptomyces fradiae aph gene in pIJ680. Both were expressed in a secretory manner by the recombinant strain using the expression and secretion signals of melC1. Extracellularly expressed recombinant sCT was purified to near homogeneity and characterized by enzyme immunoassay, followed by direct amino-terminal sequencing. High-performance liquid chromatography, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry, and bioassay in vivo demonstrated purified product to be equivalent to synthetic standard. Thus, the engineered Streptomyces strain can produce bioactive, C-terminal amidated recombinant sCT in the culture supernatant directly. The ease of the recombinant process, as well as its potential for scale-up, makes it adaptable to production demands for sCT, and it may be applied to other bioactive peptides that need C-terminal amidation.

Animals↗

PubMed2003

[Different gene expression during hepatocarcinogenesis in tree shrew induced by aflatoxin B1].

OBJECTIVE: To understand the molecular mechanism and find out the responsible genes for liver cancer by exploring the regulation of gene expression during hepatocarcinogenesis in tree shrew induced by aflatoxin B1 (AFB1). METHODS: The tissues from tree shrew of different stages during the pathogenesis and development of hepatocellular carcinoma (HCC), liver cancer tissue, para-cancerous tissues, pre-cancerous liver tissues, liver tissues of the same stage from normal controls and the liver tissues taken before AFB1-treatment were analyzed for gene expression by cDNA array. RESULTS: Four patterns of gene expression were observed during AFB1-induced hepatocarcinogenesis. They were: genes up-regulated in HCC tissue and para-cancerous tissue, especially in HCC tissues; genes with similar expressing level in both HCC tissue and para-cancerous tissue, but higher than that in pre-cancerous tissue; genes down-regulated in HCC tissue; genes up-regulated before HCC appeared but down-regulated after HCC appeared. CONCLUSION: Dynamic observation of gene expression will be beneficial to elucidate the mechanisms of AFB1- induced hepatocarcinogenesis and locate the responsible genes.

Aflatoxin B1↗

PubMed2003

[Alteration of p53 gene during tree shrews' hepatocarcinogenesis].

OBJECTIVE: To detect the expression and variation of p53 gene during tree shrews' hepatocarcinogenesis induced by hepatitis B virus (HBV) and aflatoxin B1 (AFB1). METHODS: Tree shrews were divided into four groups: the tree shrews were infected with HBV and fed with AFB1 in group A, only infected with HBV in group B, fed with AFB1 alone in group C, and normal control in group D. All the tree shrews were performed liver biopsy every 15 weeks. The tissues of liver and tumor were detected by immunohistochemistry and molecular biotechnologies. RESULTS: (1) The incidence of hepatocellular carcinoma (HCC) in group A (66.7%) was higher than that in Group B and C (30%). HCC appearance in group A was earlier than that in group C (120.0 weeks +/-16.6 weeks vs 153.3 weeks +/-5.8 weeks, t = 3.336, P<0.01). (2) Mutated p53 protein was not found before the 75th week of the experiment in each group. (3) At the 105th week, the expression rates of mutated p53 protein were 78.6%, 60% and 71.4% in group A, B and C respectively, which were much higher than that (10%) in group D (x2 > or = 5.03, P<0.05). An abnormal band of p53 gene was detected in both group A and C. (4) The mutation points of p53 gene in liver cancer of tree shrew were at codon 275, 78 and 13. The nucleotide sequence and amino acids sequence of tree shrew's wild-type p53 showed 91.7% and 93.4% homology with those of human p53 respectively. CONCLUSIONS: There is a remarkable synergistic effect between HBV and AFB1 on HCC. Mutated p53 protein is expressed before HCC occurrence, which promotes the development and progress of HCC. HBV and AFB1 may synergistically induce p53 gene mutation.

Aflatoxin B1↗

PubMed2003

[The value of autofluorescence spectrum analysis of gastric juice in diagnosing gastric carcinoma: a preliminary result].

OBJECTIVE: To reveal the difference of autofluorescence spectrums of gastric juice derived from malignancy and benignancy for screening and diagnosis of gastric carcinoma. METHOD: Gastric juice from 202 patients with different gastric diseases were collected, then detected their autofluorescence spectrums (the excitation wavelength is 288 nm, whereas the range of emission wavelength is 300 - 800 nm) after diluted by 1:10. The diagnostic model for gastric cancer was made by Classification and Regression Trees V2.0 software. RESULTS: There were three peaks (the emission wavelength were 320 - 360 nm, 576 nm and 670 - 690 nm respectively) in the autofluorescence spectrums of all patients, though the intensity of the first peak (with the emission wavelength of 320 - 360 nm) were enhanced distinctively in malignance than those in benignancy. The diagnostic model's sensitivity and specificity of prior probability were 91.4% and 83.2% respectively, whereas the sensitivity and specificity of posterior probability were 85.7% and 82.6%. CONCLUSION: Detection of autofluorescence spectrum of gastric juice has great prospect in the diagnosis and screening gastric carcinoma.

Adult↗

PubMed2003

[Treatment of endonasal-encephalomeningocele by transnasal endoscopic surgery].

OBJECTIVE: To inquire into the feasibility of transnasal endoscopic surgery for endonasal encephalomeningocele, and to put forward the basic management guidelines. METHOD: Five cases of endonasal encephalomeningocele were managed by transnasal endoscopic surgery. Different surgical techniques were applied according to the size and shape of skull base defect. At the same time, one-stage repair of skull base defect was achieved by applying muscle, fascia, cartilage and bone. RESULTS: All 5 patients were successfully treated without complication and relapse during 1-5 year follow-up. CONCLUSION: Endonasal type encephalomeningocele can be managed by transnasal endoscopic surgery. If the skull base defect is less than 0.5 cm, it can be repaired by packing muscle and fascia. If the defect is larger than 0.5 cm, the cartilage or bone should be used to repair the skull base.

Adolescent↗

PubMed2003

[Expression of the human extracellular domain of high density lipoprotein receptor in methylotropic yeast].

HDL receptor plays a very important role in reverse cholesterol transport, and it represents a novel therapeutic target for atherosclerosis. For construction of an in vitro high-throughput drug screening model based on competitive receptor--ligand binding, the extracellular domain of HDL receptor was expressed in the methylotropic yeast Pichia pastoris. The DNA fragment encoding for extracellular domain of HDL receptor was cloned by RT-PCR from Hepatoma Bel-7402 total RNA and the nucleotide sequence of the cloned cDNA was verified by inserting it into pGEM-T vector. Then the cDNA was subcloned into pPIC9K, the integrative secretory expression plasmid of Pichia pastoris was constructed, with the methanol-inducible alcohol oxidase promoter and alpha-signal peptide. The recombinant plasmid was transformed into Pichia pastoris GS115 (His- strain) by electroporation. PCR was used to confirm the insertion of HDLR gene into the genome of Mut+ transformants. During cultivation the recombinant strain was induced by 1% methanol and supernatant was analyzed by SDS-PAGE and Western blot. The result showed a specific protein band at approximately 64.5 kDa after 5 days of induction. Then the ligand binding activity was confirmed using the DiI-AcLDL as ligand.

Alcohol Oxidoreductases↗

PubMed2003

Expression of biologically active human tumor necrosis factor beta by Streptomyces lividans.

The production of human tumor necrosis factor beta (hTNF beta) in Streptomyces lividans was studied. The expression of hTNF beta uses the transcription, translation and secretion signals of subtilisin inhibitor VSI which is naturally produced by Streptomyces venezuelae CBS762.70. In direct secretory expression cassette, hTNF beta cDNA was fused 2 amino acids after the signal peptidase cleavage site. In fusion expression cassette, hTNF beta cDNA was fused after the total vsi gene. In intracellular expression cassette, hTNF beta cDNA was fused after initiation codon ATG. The expression cassettes were subcloned into Streptomyces multi-copy plasmid pIJ486 respectively and transformed into S. lividans TK24. The recombinant strains were designated as S. lividans (pIJ486-hTNF beta), S. lividans (pIJ486-vsi-hTNF beta) and S. lividans (pIVPA-hTNF beta). The analysis of expressed proteins by Western blotting and biological activity measurements revealed hTNF beta was expressed by the recombinant strains with bioactivity. The molecular weight of directly secreted product is around 16 kDa, and the expression level at 48 hours in NB medium was 0.7 mg/L. Intact product could be obtained when hTNF beta was expressed intracellularly, although it may be degraded to lower molecular weight product when cultivation was prolonged. The intracellular expression level at 48 hours in NB medium was 25.1 mg/L.

Bacterial Proteins↗

PubMed2003

[Human hepatitis B virus infection of tree shrews and Macaca assamensis in vivo].

OBJECTIVE: To examine sensitivity of the tree shrews and Macaca assamensis to human hepatitis B virus (HHBV) by serologic methods. METHODS: Totally 233 tree shrews and 28 Macaca assamensis were inoculated with human sera containing HBV. After inoculation, the sera were collected weekly from them and HBV markers were detected with HBV ditecting ELISA kits. RESULTS: Ninety percent of the tree shrews developed acute infection, among them, 44.4 % persisted for over one year, 33.3% of them developed chronic infection persisted for 2 years and one month; the persistence of HBV in Macaca assamensis was much shorter. CONCLUSION: These data clearly indicated that tree shrew may be used as an animal model for study of chronic HBV infection, whereas, Macaca assamensis, showed only a transient sensitivity to HHBV.

Animals↗

PubMed2003

[Clinical evaluation of local application of Merogel after endoscopic sinus surgery].

OBJECTIVE: To study the auxo-action of Merogel (hyaluronic acid) for operative cavity epithelialization after endoscopic sinus surgery (ESS). METHOD: Sixteen patients (32 sides) were observed, in which all sinuses(maxillary, frontal, ethmoid and sphenoid) were operated on by ESS. For the purpose of control study, the left nasal side was used as Merogel group, and right side contrast group. The patients were followed-up for 12 weeks. RESULTS: In Merogel group, the curative rate was 93.75%, improvement rate 6.25%, and average time of epithelialization was 3.4 weeks. In contrast group, the curative rate was 87.50%, improvement rate 12.50%, and average time of epithelialization was 8.3 weeks. It was distinct that in Merogel group, the epithelialization time was shorter than that in contrast group. CONCLUSION: Merogel has auxo-action for operative cavity epithelialization after ESS.

Administration, Topical↗

PubMed2003

[Sectional anatomy and computer-assisted three-dimensional reconstruction of lateral skull base in normal].

OBJECTIVE: To investigate the sectional anatomy of lateral skull base in normal and provide data for diagnosis and selecting surgical approach of lesions of lateral skull base. METHOD: Three sets of coronal sections with plastination technique was made and investigated for the location, direction and mutual relationship in different section. Signals of some structures were extracted to reconstructed three-dimensional image. RESULT: The section with plastination displayed distinct nerve, muscle, vessel, bone in lateral skull base. The structures of lateral skull base were described in five typical section: the maxillary sinus, pharyngeal orifice of pharyngotympanic duct, foramen ovale, tympanie orifice of pharyngotympanic duet, inner auditory meatus. The three-dimensional images of sphenoid sinus, ethmoid sinus, trigeminal nerve, pharyngotympanic duet and inner carotid artery after extracted the signals in serial sections. CONCLUSION: Sectional anatomy with plastination contributed to understanding complicated anatomic structure including the location and mutual relationship, three dimensional image can vividly display the structure underlying lateral skull base surgery.

Humans↗