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Biomedical subjects

L Feng

Publications and source records attributed to L Feng.

At least 127 records · Page 7Linked to original sources
PubMed1999

RelB modulation of IkappaBalpha stability as a mechanism of transcription suppression of interleukin-1alpha (IL-1alpha), IL-1beta, and tumor necrosis factor alpha in fibroblasts.

Members of the NF-kappaB/RelB family of transcription factors play important roles in the regulation of inflammatory and immune responses. RelB, a member of this family, has been characterized as a transcription activator and is involved in the constitutive NF-kappaB activity in lymphoid tissues. However, in a previous study we observed an overexpression of chemokines in RelB-deficient fibroblasts. Here we show that RelB is an important transcription suppressor in fibroblasts which limits the expression of proinflammatory mediators and may exert its function by modulating the stability of IkappaBalpha protein. Fibroblasts from relb(-/-) mice overexpress interleukin-1alpha (IL-1alpha), IL-1beta, and tumor necrosis factor alpha in response to lipopolysaccharide (LPS) stimulation. These cells have an augmented and prolonged LPS-inducible IKK activity and an accelerated degradation which results in a diminished level of IkappaBalpha protein, despite an upregulated IkappaBalpha mRNA expression. Consequently, NF-kappaB activity was augmented and postinduction repression of NF-kappaB activity was impaired in these cells. The increased kappaB-binding activity and cytokine overexpression was suppressed by introducing RelB cDNA or a dominant negative IkappaBalpha into relb(-/-) fibroblasts. Our findings suggest a novel transcription suppression function of RelB in fibroblasts.

Animals↗
PubMed1999

Human endothelium: endovascular biopsy and molecular analysis.

PURPOSE: To develop a safe and reproducible method for harvesting viable vascular endothelium to analyze gene expression at sites of vascular lesions. MATERIALS AND METHODS: Coaxial curved stainless-steel guide wires were used to obtain samples of endothelial cells from large arteries and veins in 29 patients undergoing routine endovascular procedures. Three immunocytochemical markers were used to identify cells as endothelial. Cellular viability was evaluated in terms of cell membrane integrity, energy-dependent uptake of acetylated low-density lipoprotein, and cellular response to lipopolysaccharide. Single-cell reverse transcription polymerase chain reaction (PCR) and immunocytochemistry were used to study endothelial gene expression. RESULTS: Cells with endothelial morphology and immunoreactivity for von Willebrand factor, thrombomodulin, and angiotensin-converting enzyme were consistently obtained from iliac and carotid arteries and large veins (average yield [+/- standard error] from 26 iliac arteries, 262 endothelial cells +/- 45, 20%-30% of which were viable). These cells displayed induction of E-selection messenger RNA at PCR after exposure to lipopolysaccharide. Expression of vascular cell adhesion molecule 1 transcripts in endothelial cells increased with patient age (P < .01), whereas expression of intercellular adhesion molecule 1 did not. CONCLUSION: Viable endothelium can be obtained during routine angiography. Immunocytochemical and reverse transcription PCR analyses of these cells allowed determination of transcripts and proteins expressed by endothelium at sites of vascular lesions. Such information could aid in understanding mechanisms of vascular diseases and in clinical decision making.

Adolescent↗
PubMed1999

Pervanadate-mediated tyrosine phosphorylation of keratins 8 and 19 via a p38 mitogen-activated protein kinase-dependent pathway.

Glandular epithelia express the keratin intermediate filament (IF) polypeptides 8, 18 and 19 (K8/18/19). These proteins undergo significant serine phosphorylation upon stimulation with growth factors and during mitosis, with subsequent modulation of their organization and interaction with associated proteins. Here we demonstrate reversible and dynamic tyrosine phosphorylation of K8 and K19, but not K18, upon exposure of intact mouse colon or cultured human cells to pervanadate. K8/19 tyrosine phosphorylation was confirmed by metabolic 32PO4-labeling followed by phosphoamino acid analysis, and by immunoblotting with anti-phosphotyrosine antibodies. Pervanadate treatment increases keratin solubility and also indirectly increases K8/18 serine phosphorylation at several known sites, some of which were previously shown to be associated with EGF stimulation, extracellular signal-regulated kinase (ERK), or p38 kinase activation. However, K8/19 tyrosine phosphorylation is independent of EGF signaling or ERK activation while inhibition of p38 kinase activity blocks pervanadate-induced K8/19 tyrosine phosphorylation. Our results demonstrate tyrosine phosphatase inhibitor-mediated in vivo tyrosine phosphorylation of K8/19, but not K18, and suggest that tyrosine phosphorylation may be a general modification of other IF proteins. K8/19 tyrosine phosphorylation involves a pathway that utilizes the p38 mitogen-activated protein kinase, but appears independent of EGF signaling or ERK kinase activation.

Animals↗
PubMed1999

[Epidemiological analysis on the risk factors of intrauterine transmission of hepatitis virus C].

OBJECTIVE: To investigate the possibility and risk factors of intrauterine transmission of hepatitis virus C (HCV) in Taiyuan City. METHODS: Anti-HCV and HCV RNA were detected by enzyme linked immunosorbent assay(ELISA) and reverse transcriptase Polymerase Chain Reaction(RT-PCR), in 64 mothers with HCV or HCV RNA positive and their newborns cord blood samples. Case-control study was used for the risk factors analysis. RESULTS: The infection rate of HCV was 66.15% in newborns from anti-HCV or HCV RNA positive mothers. The intrauterine transmission rate was 100% in newborns from HCV RNA positive mothers. There was a significant correlation between HCV intrauterine transmission and maternal history of blood transfusion and abnormal serum alanine aminotransferase(ALT), and the relative risk was 317.15 and 2.60, respectively. CONCLUSIONS: The higher incidence of intrauterine transmission was found in newborns from HCV RNA or anti-HCV positive mothers. The high risk factors of intrauterine transmission are maternal blood transfusion history and abnormal ALT.

Antibodies, Viral↗
PubMed1999

The effect of the pulse-delay cure technique on residual strain in composites.

Polymerization-induced shrinkage of composites leads to residual stress in the final restoration. For composites with a high modulus of elasticity, the level of stress can have significant clinical consequences, including crack formation in the enamel or microscopic separations at the preparation/restoration interface. The pulse-delay cure technique cures composites by providing low-energy pulse initially (e.g., 200 mW/cm2 for 3 seconds), followed by a waiting period of 3 to 5 minutes for strain relief, during which the composite can be finished and polished. The final cure is obtained by exposure to a high-intensity light source of 500 mW/cm2 for the recommended time. In vitro data obtained by strain gauges show that the pulse-delay cure technique can reduce residual strain in the composite by as much as 34%.

Composite Resins↗
PubMed1999

[Experimental study on ultrashort wave therapy on the healing of fracture].

The models of fracture in the rabbit radii were made. The rabbits in the experimental group were treated--with ultrashort wave at the fracture sites. The changes in the x-ray, histology, and biomechanics were observed dynamically. The results were that the speed and quality of the fracture healing in the experimental group were much better than in the control group.

Animals↗
PubMed1999

[Study on thermodynamic interactions between polyoctene-1 and solvents using gas chromatography].

Polymer of long chain alpha-olefins is a kind of comb-like polymer with special properties. In this paper, the thermodynamic interactions of polyoctene-1 with eight solvents have been studied by using gas chromatography. The eight Flory-Huggins interaction parameters chi 1 were calculated. The results indicated that chi 1 decreases with increase of the carbon number of linear alkane, but when the carbon number is larger than 8, chi 1 tends to increase with the carbon number. It was also shown that the interaction of polyoctene-1 with cyclohexane is the strongest among all the studied solvents, and that with n-octane is the strongest among the linear alkanes. The relation of interaction parameter (polyoctene-1/n-octane) with temperature T was also determined: chi 1 = 1.697-523.1/T. It was shown that the dissolution of polyoctene-1 in n-octane is an exothermic process with an enthalpy change of -4.84 kJ/mol. The solubility parameter delta 2 of polyoctene-1 is 27.42 (J/mL)1/2, determined from the interaction parameters chi 1.

English Abstract↗
PubMed1999

[Applications of porous polymeric materials and its biocompatibility].

With the barrier materials, guided tissue regeneration materials and hybrid artificial organs as the representafive materials, the applications of polymer skeletal materials in biomedical fields are introduced in this paper. Based on the results of the induced carcinoma, collagenous encapsulation and chronic inflammation around implanted polymers, the effects of polymers topography on biocompatibility are discussed, and the importance of topographical compatibility of materials is emphasized.

Biocompatible Materials↗
PubMed1999

[Determination of anions in recycle sodium formate from sodium hydrosulfite industry with single column ion chromatography].

The analysis of recycle materials from industrial waste water of sodium hydrosulfite production was made by single-column anion exchange chromatography. The recycle material was sodium formate (HCOONa) in which various anions, such as SO(3)2-, Cl-, thiosulfate, hydroxyethyl sulfonate (HOC2H4SO3-), hydroxyethyl thiosulfate (HOC2H4S2O3-), SO(4)2- and NO3- as impurities were existed simultaneously. Except hydroxyethyl sulfonate anion, all other ions can be separated by using anion exchange column Shim-pack IC-Al (4.6 mm i.d. x 100 mm) with the mixture of 1.8 mmol/L of phthalic acid and 1.35 mmol/L of Tri(hydroxymethyl) aminomethane as eluent. The flow rate of mobile phase is 1.0 mL/min. The injection volume was 20 microL. The column oven temperature was controlled at 40 degrees C. Hydroxyethyl sulfonate anion and SO(3)2- could not be separated at the above conditions, but they did not interfere the determination of HCOO-. The detection limits for HCOO-, SO(3)2-, NO3-, S2O(3)2-, HOC2H4S2O3-, Cl- and SO(4)2- were 1.0, 0.7, 1.4, 5.0, 0.7, 0.2 and 2.0 mg/L, respectively. The recoveries were between 96%-102%, and the relative standard deviations (RSD) were lower than 6.0% (n = 5) for all seven ions. This method is characterized by rapidity, sensitivity and simultaneous determination of several kinds of ions.

English Abstract↗
PubMed1998

[The use of microsatellite DNA markers for distinguishing metastatic tumor cells].

OBJECTIVE: To study the genetic stability and to establish a method for detection of micrometastasis using microsatellite DNA in human breast cancer xenograft in nude mice. METHODS: Fresh tissue of human breast cancer was xenotransplanted in nude mice or thotopically. Genomic DNA extracted from tissues of human breast cancer, xenotransplanted tumors and metastatic foci in nude mice were PCR amplified at three microsatellite loci (D14S68, D18S69, D20S199) and were analysed by electrophoresis and silver stain on PAGE. RESULTS Microsatellite DNA in genome of the xenotransplanted tumors and metastatic foci in nude mice were identical with that of the human breast cancer. CONCLUSION: This study has demonstrated in nude mice the xenotransplanted tumors and metastatic foci that originated from human breast cancer. The genetic stability in human breast cancer is evident in the processes of xenotransplantation, serial passages in nude mice, metastasis and in vitro culture. This method is sensitive and specific for the discrimination of metastatic tumor cells.

Animals↗
PubMed1998

Identification of a serine protease with nerve growth promoting activity from snake venom.

A new protein with nerve growth promoting activity was purified from the crude venom of the Agkistrodon halys Pallas, a Chinese snake. Its amino-terminal sequence unexpectedly showed high homology with serine proteases, suggesting that it is a new member of the serine protease family. It also cross-reacted with antibodies against thrombin-like enzyme and possessed weak arginine esterase activity, amounting to about 3% of the activity of trypsin. However, its nerve growth promoting activity was comparable to that of nerve growth factor (NGF). It was named NGF-like protease (NLP). Northern blot analysis further demonstrated different patterns of induction of c-myc, vgf and trkA mRNA transcription in PC12 pheochromocytoma cells treated with NGF and NLP, respectively. These data suggested that NLP represents a novel potent neurotrophic factor.

Agkistrodon↗
PubMed1998

Evidence of a direct role for Bcl-2 in the regulation of articular chondrocyte apoptosis under the conditions of serum withdrawal and retinoic acid treatment.

The regulation of chondrocyte apoptosis in articular cartilage may underlay age-associated changes in cartilage and the development of osteoarthritis. Here we demonstrate the importance of Bcl-2 in regulating articular chondrocyte apoptosis in response to both serum withdrawal and retinoic acid treatment. Both stimuli induced apoptosis of primary human articular chondrocytes and a rat chondrocyte cell line as evidenced by the formation of DNA ladders. Apoptosis was accompanied by decreased expression of aggrecan, a chondrocyte specific matrix protein. The expression of Bcl-2 was downregulated by both agents based on Northern and Western analysis, while the level of Bax expression remained unchanged compared to control cells. The importance of Bcl-2 in regulating chondrocyte apoptosis was confirmed by creating cell lines overexpressing sense and antisense Bcl-2 mRNA. Multiple cell lines expressing antisense Bcl-2 displayed increased apoptosis even in the presence of 10% serum as compared to wild-type cells. In contrast, chondrocytes overexpressing Bcl-2 were resistant to apoptosis induced by both serum withdrawal and retinoic acid treatment. Finally, the expression of Bcl-2 did not block the decreased aggrecan expression in IRC cells treated with retinoic acid. We conclude that Bcl-2 plays an important role in the maintenance of articular chondrocyte survival and that retinoic acid inhibits aggrecan expression independent of the apoptotic process.

Aged↗
PubMed1998

Th2-induced eotaxin expression and eosinophilia coexist with Th1 responses at the effector stage of lung inflammation.

The T cell-mediated lung inflammation that is associated with allergic asthma is characterized mainly by massive eosinophil infiltration, which induces airway injury and the subsequent late-phase reactivity. Because Th2 cells are often isolated from asthmatic subjects, these cells are postulated to play a role in asthma pathogenesis. We report that adoptively transferred, influenza hemagglutinin-specific Th1 and Th2 cells induced different patterns of chemokines leading to different types of cellular infiltration. Th2 cells were sufficient to induce dramatic Ag-dependent lung eosinophilia and eotaxin expression; by contrast, Th1 transfer primarily induced neutrophil recruitment with little eotaxin production. To determine whether Th1 cells show inhibitory effects on Th2 cell-mediated responses, Th1 and Th2 cells were cotransferred. Hemagglutinin-specific Th1 cells did not inhibit Ag-induced lung eosinophilia, nor did they inhibit eotaxin expression. Furthermore, influenza virus infection of the lung in mice receiving hemagglutinin-specific Th2 cells also induced eotaxin expression and eosinophilia that could not be inhibited by the cotransfer of Th1 cells. Our results show that Th2-mediated allergic lung inflammation coexists with the Th1-mediated responses that are stimulated by diverse forms of Ags.

Adoptive Transfer↗
PubMed1998

Role for neuronally derived fractalkine in mediating interactions between neurons and CX3CR1-expressing microglia.

A recently identified chemokine, fractalkine, is a member of the chemokine gene family, which consists principally of secreted, proinflammatory molecules. Fractalkine is distinguished structurally by the presence of a CX3C motif as well as transmembrane spanning and mucin-like domains and shows atypical constitutive expression in a number of nonhematopoietic tissues, including brain. We undertook an extensive characterization of this chemokine and its receptor CX3CR1 in the brain to gain insights into use of chemokine-dependent systems in the central nervous system. Expression of fractalkine in rat brain was found to be widespread and localized principally to neurons. Recombinant rat CX3CR1, as expressed in Chinese hamster ovary cells, specifically bound fractalkine and signaled in the presence of either membrane-anchored or soluble forms of fractalkine protein. Fractalkine stimulated chemotaxis and elevated intracellular calcium levels of microglia; these responses were blocked by anti-CX3CR1 antibodies. After facial motor nerve axotomy, dramatic changes in the levels of CX3CR1 and fractalkine in the facial nucleus were evident. These included increases in the number and perineuronal location of CX3CR1-expressing microglia, decreased levels of motor neuron-expressed fractalkine mRNA, and an alteration in the forms of fractalkine protein expressed. These data describe mechanisms of cellular communication between neurons and microglia, involving fractalkine and CX3CR1, which occur in both normal and pathological states of the central nervous system.

Amino Acid Sequence↗
PubMed1998

In vivo inhibition of CC and CX3C chemokine-induced leukocyte infiltration and attenuation of glomerulonephritis in Wistar-Kyoto (WKY) rats by vMIP-II.

Chemokines play a central role in immune and inflammatory responses. It has been observed recently that certain viruses have evolved molecular piracy and mimicry mechanisms by encoding and synthesizing proteins that interfere with the normal host defense response. One such viral protein, vMIP-II, encoded by human herpesvirus 8, has been identified with in vitro antagonistic activities against CC and CXC chemokine receptors. We report here that vMIP-II has additional antagonistic activity against CX3CR1, the receptor for fractalkine. To investigate the potential therapeutic effect of this broad-spectrum chemokine antagonist, we studied the antiinflammatory activity of vMIP-II in a rat model of experimental glomerulonephritis induced by an antiglomerular basement membrane antibody. vMIP-II potently inhibited monocyte chemoattractant protein 1-, macrophage inflammatory protein 1beta-, RANTES (regulated on activation, normal T cell expressed and secreted)-, and fractalkine-induced chemotaxis of activated leukocytes isolated from nephritic glomeruli, significantly reduced leukocyte infiltration to the glomeruli, and markedly attenuated proteinuria. These results suggest that molecules encoded by some viruses may serve as useful templates for the development of antiinflammatory compounds.

Animals↗
PubMed1998

Use of a medium-term liver focus bioassay to assess the hepatocarcinogenicity of 1,2,4,5-tetrachlorobenzene and 1,4-dichlorobenzene.

1,2,4,5-Tetrachlorobenzene (TeCB) and 1,4-dichlorobenzene (DCB) are important environmental contaminants that have been used extensively for a variety of industrial applications. Limited data are available in the literature regarding the carcinogenicity of TeCB. DCB has been shown to cause renal adenocarcinomas in rats and hepatic adenomas and carcinomas in mice at high doses in a 2-year study. In the studies presented here, we report that TeCB can promote the formation of preneoplastic foci and DCB cannot in a medium-term initiation/promotion assay. These results suggest that TeCB is a liver tumor promoter and that DCB is not at fairly low doses (0.1 and 0.4 mmol/kg per day).

Animals↗
PubMed1998

[Studies of microsatellite instability in Chinese gastric cancer tissues].

OBJECTIVE: To identify the microsatellite instability(MSI) rates in Chinese gastric cancer samples. METHODS: 29 microsatellite markers were selected to examine 42 paired gastric cancer tissues for MSI on all chromosomes except Y. RESULTS: The total frequency of MSI in all 42 gastric cancers was 33.9% with higher rates at loci of D3S1577, D3S1067,D8S279,D9S257, D1S248, D7S520 and D2S147,and the highest rate at D3S1577 and D3S1067(51.35%). MSI varied with different pathological types. The frequencies of MSI were signi- ficantly higher in poorly differentiated tumors and signet cell types, compared with well differentiated tumors(P=0.0026 and 0.0013 by chi-square test),and no difference was noted between poorly differentiated and signet cell types. CONCLUSION: MSI may play an important role in Chinese gastric cancer, particularly the poorly differentiated adenocarcinomas. The data presented here further support the previous hypothesis that pathologically distinct subtypes of gastric cancer undergo different genetic pathways during tumorigenesis.

Adult↗