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Lei Li

Publications and source records attributed to Lei Li.

At least 235 records · Page 13Linked to original sources
PubMed2002

[Transfection of MDR1-mRNA into human mononuclear cells to improve their resistance to anticancer agents, an in vitro study].

OBJECTIVE: To investigate the expression and function of P-glycoprotein (P-gp), an efflux pump encoded by multidrug resistance complementary DNA (MDR1), in human mononuclear cells (MNCs) transfected with MDR1 mRNA. METHOD: Two kinds of human MDR1 mRNA, pT7TS-MDR1 and pGEM5Zf (+)-MDR1 with difference in the 5' and 3' untranslated regions only, were constructed and modified and then were transfected into human MNCs rich in hematopoietic progenitor cells from a patient with small cell lung cancer. The expression efficiency and pump function of P-gp were measured with FACS. Rhodomine 123 efflux test was used to examine the function of P-gp. Un- transfected mononuclear cells from the same person were used as controls. RESULT: The expression of P-gp 12 hours after transfection was 2.16 % in control group, 8.94% in pGEM5Zf (+)-MDR1 group, and 19.14% in pT7TS-MDR1 group. The expression of P-gp 72 hours after transfection was 2.12% in control group, 6.12% in pGEM5Zf(+)-MDR1 group, and 10.71% in pT7TS-MDR1 group, significantly higher in the third group. Rhodamine-123 efflux test showed that the efflux-pump function of P-gp 12 hours after the trransfection was 19.20% in control group, 25.59% in GEM5Zf (+)- MDR1 group, and 35.02% in pT7TS-MDR1 group (all P < 0.01). The expression and presence of P-gp by transfected cells lasted at least 72 hours. CONCLUSION: Transfection of human mononuclear cells with MDR1 mRNA significantly increases their resistance to anticancer agents.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2002

Human XPA and RPA DNA repair proteins participate in specific recognition of triplex-induced helical distortions.

Nucleotide excision repair (NER) plays a central role in maintaining genomic integrity by detecting and repairing a wide variety of DNA lesions. Xeroderma pigmentosum complementation group A protein (XPA) is an essential component of the repair machinery, and it is thought to be involved in the initial step as a DNA damage recognition and/or confirmation factor. Human replication protein A (RPA) and XPA have been reported to interact to form a DNA damage recognition complex with greater specificity for damaged DNA than XPA alone. The mechanism by which these two proteins recognize such a wide array of structures resulting from different types of DNA damage is not known. One possibility is that they recognize a common feature of the lesions, such as distortions of the helical backbone. We have tested this idea by determining whether human XPA and RPA proteins can recognize the helical distortions induced by a DNA triple helix, a noncanonical DNA structure that has been shown to induce DNA repair, mutagenesis, and recombination. We measured binding of XPA and RPA, together or separately, to substrates containing triplexes with three, two, or no strands covalently linked by psoralen conjugation and photoaddition. We found that RPA alone recognizes all covalent triplex structures, but also forms multivalent nonspecific DNA aggregates at higher concentrations. XPA by itself does not recognize the substrates, but it binds them in the presence of RPA. Addition of XPA decreases the nonspecific DNA aggregate formation. These results support the hypothesis that the NER machinery is targeted to helical distortions and demonstrate that RPA can recognize damaged DNA even without XPA.

Base Sequence↗
PubMed2002

Distinct roles for jasmonate synthesis and action in the systemic wound response of tomato.

Plant defense responses to wounding and herbivore attack are regulated by signal transduction pathways that operate both at the site of wounding and in undamaged distal leaves. Genetic analysis in tomato indicates that systemin and its precursor protein, prosystemin, are upstream components of a wound-induced, intercellular signaling pathway that involves both the biosynthesis and action of jasmonic acid (JA). To examine the role of JA in systemic signaling, reciprocal grafting experiments were used to analyze wound-induced expression of the proteinase inhibitor II gene in a JA biosynthetic mutant (spr-2) and a JA response mutant (jai-1). The results showed that spr-2 plants are defective in the production, but not recognition, of a graft-transmissible wound signal. Conversely, jai-1 plants are compromised in the recognition of this signal but not its production. It was also determined that a graft-transmissible signal produced in response to ectopic expression of prosystemin in rootstocks was recognized by spr-2 but not by jai-1 scions. Taken together, the results show that activation of the jasmonate biosynthetic pathway in response to wounding or (pro)systemin is required for the production of a long-distance signal whose recognition in distal leaves depends on jasmonate signaling. These findings suggest that JA, or a related compound derived from the octadecanoid pathway, may act as a transmissible wound signal.

Cyclopentanes↗
PubMed2002

KCNQ1 and KCNH2 mutations associated with long QT syndrome in a Chinese population.

The long QT syndrome (LQTS) is a cardiac disorder characterized by prolongation of the QT interval on electrocardiograms (ECGs), syncope and sudden death caused by a specific ventricular tachyarrhythmia known as torsade de pointes. LQTS is caused by mutations in ion channel genes including the cardiac sodium channel gene SCN5A, and potassium channel subunit genes KCNQ1, KCNH2, KCNE1, and KCNE2. Little information is available about LQTS mutations in the Chinese population. In this study, we characterized 42 Chinese LQTS families for mutations in the two most common LQTS genes, KCNQ1 and KCNH2. We report here the identification of four novel KCNQ1 mutations and three novel KCNH2 mutations. The KCNQ1 mutations include L191P in the S2-S3 cytoplasmic loop, F275S and S277L in the S5 transmembrane domain, and G306V in the channel pore. The KCNH2 mutations include L413P in transmembrane domain S1, E444D in the extracellular loop between S1 and S2, and L559H in domain S5. The location and character of these mutations expand the spectrum of KCNQ1 and KCNH2 mutations causing LQTS. Excitement, exercises, and stress appear to be the triggers for developing cardiac events (syncope, sudden death) for LQTS patients with KCNQ1 mutations F275S, S277L, and G306V, and all three KCNH2 mutations L413P, E444D and L559H. In contrast, cardiac events for an LQTS patient with KCNQ1 mutation L191P occurred during sleep or awakening from sleep. KCNH2 mutations L413P and L559H are associated with the bifid T waves on ECGs. Inderal or propanolol (a beta blocker) appears to be effective in preventing arrhythmias and syncope for an LQTS patient with the KCNQ1 L191P mutation.

Cation Transport Proteins↗
PubMed2002

Behavioral visual responses of wild-type and hypopigmented zebrafish.

Zebrafish possess three classes of chromatophores that include iridophores, melanophores, and xanthophores. Mutations that lack one or two classes of chromatophores have been isolated or genetically constructed. Using a behavioral assay based on visually mediated escape responses, we measured the visual response of fully and partially pigmented zebrafish. In zebrafish that lack iridophores (roy mutants), the behavioral visual responses were similar to those of wild-type animals except at low contrast stimulation. In the absence of melanophores (albino mutants) or both melanophores and iridophores (ruby mutants), the behavioral visual responses were normal under moderate illumination but reduced when tested under dim or bright conditions or under low contrast stimulation. Together, the data suggest that screening pigments in the retina play a role in the regulation of behavioral visual responses and are necessary for avoiding "scatter" under bright light conditions.

Albinism, Ocular↗
PubMed2002

Rapid vascular cell responses to estrogen and membrane receptors.

There is a growing interest in the effects of estrogen on the vascular wall, due to the marked gender difference in the incidence of clinically apparent coronary heart disease, when comparing premenopausal women with age-matched males. Estrogen has numerous effects on vascular endothelial and smooth muscle cells, both of which express estrogen receptors (ERs). Although ERs are classically defined as ligand-activated transcription factors, it has become increasingly clear that estrogen-stimulated, ER-dependent cellular responses can be rapid consequences of signal transduction cascades. The cellular localization and molecular form of the ER(s) which mediates rapid signaling are poorly defined. In this review, we describe the mounting evidence for membrane-localized ERs that vary in structure from classical forms. We also discuss ER-catalyzed molecular complex formations and a variety of estrogen-triggered signal transduction cascades, including those involving phosphatidylinositol 3-kinase/Akt, MAP kinase and G-protein-coupled receptors, all of which may induce "protective" profiles in vascular cells.

Animals↗
PubMed2002

XPD/ERCC2 EXON 8 Polymorphisms: rarity and lack of significance in risk of squamous cell carcinoma of the head and neck.

BACKGROUND: Inherited polymorphisms of DNA repair genes may contribute to genetic susceptibility to squamous cell carcinoma of the head and neck (SCCHN). The objective was to assess whether two polymorphisms in the nucleotide excision repair gene XPD (ERCC2) are markers of SCCHN risk. METHODS: We performed a hospital-based case-control study of 180 SCCHN patients and 400 cancer-free controls frequency matched on age, sex, smoking, and alcohol use. All subjects were non-Hispanic whites. XPD alleles 23047 and 23051 were assessed by digestion with the restriction enzymes XhoII and SphI after PCR amplification. RESULTS: The XPD 23047 G and XPD 23051 T alleles were extremely rare among both the cases and controls (allele frequencies<1.0%), and not statistically different between groups (P>0.6). CONCLUSIONS: The 23047 and 23051 variants of the DNA repair gene XPD are extremely rare and do not contribute significantly to the risk of SCCHN in the non-Hispanic white population.

Adult↗
PubMed2002

Regulation of syndecan-4 expression with mechanical stress during the development of angioplasty-induced intimal thickening.

In this study, we postulated that acute mechanical strain of the arterial wall induces changes in syndecan-4 expression that in turn may modulate cellular events, which promote neointima formation. Correlative in vivo and in vitro studies were performed to determine whether: (1) balloon injury of the rat carotid artery induces spatially and temporally regulated changes in syndecan-4 messenger RNA (mRNA) and protein expression; (2) the application of biaxial mechanical strain to cultured vascular wall cells regulates the expression of syndecan-4 mRNA and protein and its cell surface distribution and surface shedding; and (3) shed syndecan-4 directly effects cell motility behavior. We observed that syndecan-4 mRNA and protein expression were regulated in a temporally and spatially specific manner, such that initial expression of syndecan-4 was localized to adventitial cells followed by later expression in the neointima. Notably, in vitro stimulation of isolated adventitial fibroblasts with a mechanical stretch protocol that was designed to mimic in vivo balloon injury produced a rapid increase in syndecan-4 (4.3-fold increase; P <.001) that was accompanied both by enhanced protein shedding and by the disassembly of focal adhesions. Also significant was that shed syndecan-4, induced with mechanically conditioned media, appeared to be responsible for a chemotactic response of adventitial fibroblasts (P =.005). These results indicate that mechanical strain tightly regulates syndecan-4 expression, which may, in part, provide a mechanism for the activation of myofibroblast migration from the tunica adventitia into the neointima.

Angioplasty, Balloon↗
PubMed2002

Neuronal differentiation and protection from nitric oxide-induced apoptosis require c-Jun-dependent expression of NCAM140.

c-Jun, a crucial component of the dimeric transcription factor activating protein 1 (AP-1), can regulate apoptosis induced by oxidative stress and has been implicated in neuronal differentiation, but the mechanisms are largely unknown. We found that specific inhibition of transcription or stable transfection with cDNA encoding dominant-negative c-Jun sensitized SH-SY5Y neuroblastoma cells (TAM-67 cells) to apoptosis induced by the nitric oxide (NO) donor sodium nitroprusside or SIN-1. TAM-67 cells also became refractory to nerve growth factor (NGF)-induced neuronal differentiation. Dominant-negative c-Jun abolished expression of a 140-kDa neural cell adhesion molecule (NCAM140) and dramatically enhanced the expression of NCAM180 in TAM-67 cells. Inhibition of c-Jun in TAM-67 cells also resulted in a corresponding decrease in the amount of NCAM140 mRNA and an increase in the amount of NCAM180 mRNA. Reexpression of NCAM140 in TAM-67 cells restored NGF-induced neuronal differentiation and resistance to NO-induced apoptosis. Our results show that c-Jun/AP-1, through up-regulation of NCAM140, plays an important role in both NGF-induced neuronal differentiation and resistance to apoptosis induced by NO in neuroblastoma cells. As NCAM140 and NCAM180 are translated from differentially spliced mRNAs transcribed from the same gene, alternative splicing of NCAM pre-mRNA (and consequently the synthesis of the smaller NCAM140 species) appears to be regulated by c-Jun/AP-1.

Apoptosis↗
PubMed2002

High-mobility group protein 2 may be involved in the locus control region regulation of the beta-globin gene cluster.

Expression regulation of the beta-globin gene cluster is a result of synergistic interactions between cis-elements and trans-acting factors. Previous studies usually concentrated on the core sequence of each hypersensitive site in the locus control region of the beta-globin gene cluster. But more and more evidence illustrates that the flanking regions are indispensable also. Using electrophoretic mobility shift assay and solid-phase DNase I footprinting methods, we identified a small nuclear protein from K562 cells that binds specifically to the first AT-rich region flanking the hypersensitive site 2 core sequence of the human beta-globin gene locus control region. N-terminal sequencing of the enriched protein proved that it is a member of the high-mobility group protein 2 family. This indicates that the AT-rich region in human hypersensitive site 2 may take part in the regulation of the beta-globin gene cluster by facilitating DNA bending, which is a prerequisite for the looping mechanism in this region.

Base Sequence↗
PubMed2002

Mechanical stress regulates syndecan-4 expression and redistribution in vascular smooth muscle cells.

Syndecan-4 is a unique membrane-associated heparan sulfate proteoglycan that colocalizes with integrin heterodimers in focal adhesion complexes. Because focal adhesions serve as a putative mechanotransduction system, we postulated that physical forces that are sensed by focal adhesions may regulate the expression and intracellular distribution of syndecan-4 and thereby modulate cell movement and orientation. In this report, syndecan-4 was identified as a transcriptionally regulated, immediate-early gene in response to the application of oscillatory stress. This fluctuation was associated with coordinate changes in the concentration and compartmentalization of syndecan-4 proteins. Specifically, syndecan-4 was lost from the dorsal aspect of the cell membrane and translocated from its intracellular pool to the ventral cell surface. Dissociation of syndecan-4 and vinculin from focal adhesions may contribute to promoting cell motility, because overexpression of syndecan-4, in part, blocked this dissociation and also retarded mechanical stretch-induced cell migration. These studies suggest that mechanical stress induces cell locomotion, in part, by the dynamic regulation of syndecan-4 expression and relocation.

Animals↗
PubMed2002

[Experimental study on growth factor in promotion of chondrocytes proliferation].

OBJECTIVE: To study the effect of two cytokines, basic fibrolast growth factor(bFGF) and insulin-like growth factor-I(IGF-I), on cell proliferation in chondrocytes of adult rabbits. METHODS: The primary chondrocytes of adult rabbits were harvested and cultured with bFGF and IGF-I at different concentrations, respectively, as well as with the mixture of the two cytokines; the quantity of cultured chondrocytes was detected by MTT assay at the 24th, 48th and 72nd hours; and the final fold increase of different groups was measured by cell count for the 3rd passage; and the proliferation index of the groups was recorded by flowing cytometer on the 14th day. RESULTS: 1. The cultured chondrocytes with either bFGF, IGF-I or their mixture were significantly more than that of control group at the 24th, 48th and 72th hours (P < 0.01). 2. After the 3rd passage, the final folds of proliferation were significantly higher in the groups with cytokines than in the control group (P < 0.01); and the final fold with the mixture of cytokines was significantly higher than that of both IGF-I and bFGF (P < 0.01). 3. The proliferation index was significantly higher in the groups with cytokines than in the control group (P < 0.01); the proliferation index with the mixture of cytokines was significantly higher than that of both IGF-I and bFGF (P < 0.05); besides, proliferation index was higher when cytokine was applied twice than once (P < 0.05); besides, proliferation index was higher when cytokine was applied twice than once (P < 0.05). CONCLUSION: bFGF and IGF-I could promote chondrocytes proliferation of adult rabbits obviously and they are synergistic in cell proliferation.

Animals↗
PubMed2002

[The role of progesterone in the regulation of gene expression of insulin-like growth factor-I receptor in human decidual stromal cells of early pregnancy in vitro].

OBJECTIVE: To assess the effect of progesterone on the gene expression of insulin-like growth factor-I receptor (IGF-I R) in human decidual stromal cells of early pregnancy in vitro. METHODS: Semiquantitative reverse transcriptase polymerase chain reaction, using beta-ACTIN as internal standard, was applied to determine the levels of IGF-I R mRNA in human decidual stromal cells of early pregnancy in vitro after cultured with different concentrations of progesterone for 72 hours or cultured with 0.1 mumol/L of progesterone for different periods of time. RESULTS: The expression of IGF-I R mRNA was significantly positive in human decidual stromal cells of early pregnancy in vitro. The levels of IGF-I R mRNA were down-regulated by progesterone, and showed significant negative-correlation with the concentration of progesterone (r = -0.680, P < 0.001). The levels of IGF-I R mRNA showed no significant correlation with time when the final concentration of progesterone was 0.1 mumol/L (r = 0.005, P > 0.05). CONCLUSION: Progesterone may play an important role in the regulation of proliferation and decidualization of stromal cells by down-regulating the expression of IGF-I R mRNA in human decidual stromal cells of early pregnancy, which is important for the maintenance of early pregnancy.

Adult↗
PubMed2002

[Gene expression of insulin-like growth factors in human villous trophoblast cells of early pregnancy in vitro].

OBJECTIVE: To investigate the gene expression of insulin-like growth factors(IGFs) in human villous trophoblast cells of early pregnancy in vitro and their action. METHODS: Semiquantitative reverse transcriptase polymerase chain reaction(RT-PCR), with beta-ACTIN as internal standard, was applied to determine the expression of IGFs messenger RNA in human villous trophoblast cells of early pregnancy in vitro. RESULTS: The expression of IGF-II mRNA, IGF-I R mRNA and IGFBP-3 mRNA was detectable in human villous trophoblast cells of early pregnancy in vitro. CONCLUSION: IGFs appear to play important regulation roles in early invasion, proliferation and differentiation of cytotrophoblast, and in the formation of placenta and the development of embryo via autocrine and/or paracrine way.

Adult↗
PubMed2002

[Effect of para-aminobenzoic acid on the growth of Actinomyces viscosus].

OBJECTIVE: To examine the effects of para-aminobenzoic acid (PABA) on the growth of Actinomyces viscosus. METHODS: Different concentrations of PABA (10(-10)-10(-3) g/L) were each transferred to modified Carlsson medium. Actinomyces viscosus ATCC19246 grew in them. And the cultures were incubated at 37 degrees C anaerobically in the atmosphere of 80%N2, 10%H2, 10%CO2 for 48 h. Actinomyces viscosus OD values (lambda = 540 nm) were obtained with UV-1601. Colony forming unit (CFU) was established by growth of Actinomyces viscosus in culture when different concentrations of PABA (10(-10)-10(-3) g/L) were present. RESULTS: Different concentrations of PABA (10(-10)-10(-4) g/L) had different stimulating effects on the growth of Actinomyces viscosus (P < 0.05). But this kind of stimulating effect declined when PABA concentration was 10(-5) g/L, and as PABA (10(-3) g/L) was present, this kind of effect was missing. CONCLUSION: The phenomena indicated that PABA has stimulating effect on the growth of Actinomyces viscosus, particularly when PABA is at the concentration of 10(-6) g/L.

Actinomyces viscosus↗
PubMed2002

[Study on reducing blood sugar of polysaccharide from Cyclocarya paliurus (Batal.) Iljinsk].

OBJECTIVE: To try to find Cyclocarya paliurus (Batal.) Iljinsk contains the polysaccharide complex with reducing blood-sugar activity or not. METHOD: The Polysaccharide was extracted by ultrasonic wave. The diabetes model was induced by alloxan to verify the activity of the polysaccharide. RESULTS: The content of the polgsccharide is 9.6% in Cyclocarya paliurus. The blood-sugar level of the polysaccharide group is lower by 41.3% than that of the diabetes model group. After ig glucose, the blood-sugar level of the pollysaccharide group was obviously lower than that of the diabetes model group. CONCLUSION: Cyclocarya paliurus (Batal.) Iljinsk is rich in polysaccharide complex, which have obvious reducing blood-sugar activity and can improve the capability of glucose tolerance in diabetes mice.

Animals↗
PubMed2002

[The use of gene expression differential display analysis technics in trauma research].

Gene is the regulation core of cell proliferation, differentiation and maturation. It is also the decisive factor of occurrence, progression and prognosis of many diseases. The changes in gene expression will inevitably lead to many kinds of abnormal in cells, tissue, organs even in whole biological organism. Trauma, as well as other stimulators, may bring a series complications through the abnormal expression of genes following injury. With the development of bioinformatics and molecular biology, a series of assays (so called gene expression differential display analysis technics, such as DNA microarray) have been established, which have been used to analyze differentially expressed genes effectively. These methods have been widely used in the research of tumor and other disease. This review will focus to some usage of the ways in traumatology.

Animals↗