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Biomedical subjects

Yan Chen

Publications and source records attributed to Yan Chen.

At least 199 records · Page 11Linked to original sources
PubMed2004

Cereal alkylresorcinols elevate gamma-tocopherol levels in rats and inhibit gamma-tocopherol metabolism in vitro.

Alkylresorcinols (AR) are a class of amphiphilic phenolic lipids present in high amounts in wheat and rye bran. They have been reported to be both growth retarding and innocuous when fed to rats, and to have a broad range of bioactivities in vitro, suggested to be related to their ability to bind to proteins and modify membranes. This study was designed to test the effects of AR (purified from rye bran) on growth, tocopherol levels, and cholesterol levels in rats. Rats were fed 1 of 4 different levels of AR for 4 wk: 0 (control), 1, 2, and 4 g/kg diet. AR did not affect final body, liver, or lung weights. The AR diets increased the levels of gamma-tocopherol in liver and lungs (P < 0.05). To investigate whether AR could have increased gamma-tocopherol levels via inhibition of tocopherol-omega-hydroxylase, HepG2 cells were incubated with AR and the metabolism of gamma-tocopherol measured. AR significantly inhibited the conversion of gamma-tocopherol to its water-soluble hydroxychroman metabolite in vitro, indicating that AR may increase gamma-tocopherol levels via inhibition of tocopherol metabolism in vivo. The 4 g AR/kg diet decreased liver cholesterol (P < 0.001), but did not affect plasma lipids. AR were detected in the perirenal adipose tissue samples of rats fed AR, indicating that they can accumulate in the fatty tissues of rats. High levels of dietary AR moderately affect gamma-tocopherol, possibly via inhibition of tocopherol metabolism, and decrease liver cholesterol in rats.

Animals↗
PubMed2004

Lung heme oxygenase-1 is elevated in acute respiratory distress syndrome.

OBJECTIVE: We aimed to quantify concentrations of inducible heme oxygenase (HO)-1 in the lungs of patients with acute respiratory distress syndrome (ARDS) and to investigate its role as a source of ferrous iron and as a signaling agent for iron regulation. Control of such processes by heme oxygenase has implications for the onset, progression, and resolution of ARDS. DESIGN: Retrospective analysis of archived samples. SETTING: Adult intensive care unit of a postgraduate teaching hospital. PATIENTS: Patients admitted to the adult intensive care unit who fulfilled the American-European Consensus Conference criteria for ARDS. INTERVENTIONS: Biochemical and immunohistochemical studies using bronchoalveolar lavage fluid or lung tissue were performed in patients with established ARDS and in those undergoing lung resection (controls). MEASUREMENTS AND MAIN RESULTS: Concentrations of heme oxygenase protein were significantly elevated in lung tissue (193.7 +/- 13.27 vs. 81.0 +/- 16.0%, p < .01) and in bronchoalveolar lavage fluid (2.4 x 10(5) vs. 1.4 x 10(5) densitometric units, p = .047) taken from patients with ARDS compared with controls. Concentrations of heme oxygenase protein in bronchoalveolar lavage fluid from patients with ARDS correlated positively and significantly with changes in the concentrations of ferritin (r = .697, p = .02) and the iron saturation of transferrin (r = .8, p = .014) but correlated negatively and significantly with concentrations of bleomycin-detectable (redox-active) iron (r = -.73, p = .031). Significantly elevated (p < .05) concentrations of heme oxygenase staining in cell types expressing this protein were detected in patients with ARDS, compared with concentrations in the same cells taken from controls undergoing lung resection. CONCLUSIONS: Heme oxygenase protein is elevated in the lungs of patients with ARDS and may contribute to the changes in iron mobilization, signaling, and regulation seen in this condition.

Adult↗
PubMed2004

Increased expression of lung resistance-related protein in lower grade urothelial carcinoma of the renal pelvis and ureter.

BACKGROUND: Lung resistance-related protein (LRP), like multidrug resistance gene 1 (MDR1) and multidrug resistance-associated proteins (MRP), has been associated with intrinsic therapeutic resistance in various malignancies. To date, there has been no study on the expression of LRP in urothelial carcinomas of the renal pelvis and ureter. We investigated the protein and mRNA expression levels of LRP, MDR1 and MRP1 in this malignancy and the clinical significance of their expression was evaluated. METHODS: Forty urothelial carcinomas of the renal pelvis and ureter and 31 normal upper urothelial samples were examined by immunohistochemistry and reverse transcription polymerase chain reaction to determine the protein and mRNA levels of the multidrug resistance-related genes, respectively. RESULTS: The positive staining rates and mRNA levels of LRP were the highest among these multidrug resistance-related genes in both normal urothelium and carcinoma examinations. In contrast to the up-regulated expression of MDR1, the expression of LRP tended to be down-regulated in carcinomas. Moreover, the expression of LRP inversely correlated with tumor grades, but this correlation was not found for the other two genes. However, there was no correlation among the expression of the three genes observed. CONCLUSION: Lung resistance-related protein was strongly expressed in urothelial carcinomas of the renal pelvis and ureter, particularly in well-differentiated carcinomas.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2004

TGF-beta induces proangiogenic and antiangiogenic factors via parallel but distinct Smad pathways.

BACKGROUND: Angiogenesis has a key role in numerous disease processes. One of the most important angiogenic factors is vascular endothelial growth factor (VEGF-A), whereas thrombospondin-1 (TSP-1) is a major antiangiogenic factor. Recent studies have shown that VEGF-A as well as TSP-1 is regulated by transforming growth factor-beta1 (TGF-beta1), but the mechanism remains unclear. METHODS: We examined the role of TGF-beta1 and its signaling pathways in mediating expression of these two molecules. Rat proximal tubular cells (NRK52E) were stimulated with TGF-beta1 to induce VEGF-A and TSP-1 synthesis. To clarify roles of receptor-activated Smads (R-Smads), we blocked Smad signaling using overexpression of the inhibitory Smad, Smad7, and by using fibroblasts from wild-type or knockout mice. To confirm the antiantigenic role of Smads, soluble Flt-1 regulation in response to TGF-beta1 was also examined. In addition, the effect of conditioned media from NRK52E and Smad knockout cells was examined on endothelial cell proliferation. RESULTS: Induction of VEGF-A and TSP-1 by TGF-beta1 in NRK52E cells was associated with activation of pathway-restricted R-Smads (Smad2 and 3) and blocking these Smads by overexpression of Smad7 blocked their induction. By using of Smad knockout cells, Smad3 was shown to have a key role in the stimulation of VEGF-A expression whereas Smad2 was critical for TSP-1 expression. Consistent with the hypothesis that Smad2 has an antiangiogenic function, we also demonstrated that Smad2, but not Smad3, mediated the expression of VEGF-A antagonist, soluble VEGF-A receptor sFlt-1, in response to TGF-beta1. Conditioned media from NRK52E, which was stimulated by TGF-beta1 for 24 hours, did not induce endothelial cell proliferation. However, conditioned media from Smad2 knockout induced endothelial cell proliferation, whereas endothelial cell proliferation was inhibited by Smad3 knockout-derived conditioned media. CONCLUSION: R-Smads have distinct roles in mediating the expression of pro- and antiangiogenic growth factors in response to TGF-beta1.

Animals↗
PubMed2004

A graph-searching method for MLC leaf sequencing under constraints.

A new leaf-sequencing algorithm for step-and-shoot IMRT that is based on a graph-searching technique is described. An iterative process guided by a quantitative measure for the complexity of the initial or residual intensity pattern is used to identify the field segments shaped by a multileaf collimator (MLC). Given a user selected number of intensity levels, the algorithm searches deliverable segment candidates considering all intensity levels and two collimator positions separated by 90 degrees. The candidates for each intensity level are obtained as the least number of segments to cover the areas with equal or higher intensity. The shape of a deliverable segment is adjusted by leaving out certain beam elements for later delivery if this results in a simpler residual intensity pattern and the segment is still deliverable. For a MLC design that does not allow leaf interdigitation, it is initially assumed that a single segment cannot cover two disjoined areas. Among all candidates the segment with the greatest reduction of the complexity of the residual intensity distribution is chosen for the current step of iteration. The iterative process generates a set of deliverable segments of simply connected areas. These segments are combined later under specific MLC constraints. Different orders of segment combination are considered for minimizing the beam-on time. The final segments are sequenced to minimize the leaf travel. This algorithm has been tested using randomly generated intensity distributions and clinical cases for the Varian, Siemens, and Elekta MLC systems. The results show that as the number of intensity levels is increased, the numbers of segments and MUs increase only modestly. Using two collimator angles results in decreases in the required number of segments and the number of monitor units that can be as much as 20%.

Algorithms↗
PubMed2004

A method to improve spatial resolution and smoothness of intensity profiles in IMRT treatment planning.

In IMRT optimization, the size of beamlets used for optimizing the beam intensity distributions is a planner-selected parameter. The appropriate setting for the beamlet size is critical to the outcome of IMRT planning. With too small beamlets the dose calculation can be inaccurate, and the resulting intensity profiles can be unnecessarily complex and difficult to generate. Relatively simple intensity profiles can be obtained using large beamlets. However, this may compromise the conformity of the dose distribution. In this paper we present a method, in which multiple beamlet matrices displaced from each other by a shift in MLC leaf travel direction are used instead of the single beamlet matrix per beam in a conventional method, to achieve finer spatial resolution for the intensity distribution than the given beamlet size. Two test cases were used to assess the method by the resultant DVHs and dose distributions and characteristic indices of the intensity profiles. The results show that this method can produce optimized dose distributions that are similar to those produced by the conventional inverse planning method with the benefit of smoother intensity profiles that are easier to deliver with a computer controlled MLC.

Biophysical Phenomena↗
PubMed2004

Gianotti-Crosti syndrome caused by acute hepatitis B virus genotype D infection.

A 12-year-old girl with Gianotti-Crosti syndrome caused by hepatitis B virus (HBV) infection was admitted due to eruption on her extremities. Laboratory findings revealed elevation of transaminase, positivity for HB surface antigen (HBsAg), and an IgM type anti-HB core. The eruption and level of transaminase improved, and HBsAg became negative within 2 months of onset. Analysis of the virus revealed it to be genotype D with a genomic length of 3,182 bases and the HBsAg serotype was ayw3, which is very rare in Japan. The possible relationship between Gianotti-Crosti syndrome and HBV genotype D infection is discussed.

Acrodermatitis↗
PubMed2004

[Investigation of microcystin pollution on Dong Lake, Wuhan City].

OBJECTIVE: To investigate the level of pollution of microcystin and its changing in freshwater lake and fish. METHODS: Samples of freshwater and fish were collected from Dong Lake in Wuhan City. Samples were tested using ELISA. RESULTS: All freshwater samples collected in July and October contained blue-green algae and it had become the dominant species. For the same waterblooming lake, MC content was significantly lower in July than that in October (P < 0.05). MC content in fish muscle was significantly lower than that in liver (P < 0.05).

Animals↗
PubMed2004

[Effect of curcumin on STAT5 signaling molecule in K562 cells].

OBJECTIVE: To investigate the effect of curcumin on STAT 5 signaling molecule in K562 cells and its molecular mechanism of antileukemia. METHODS: Cell proliferation was studied by tetrazolium dye assay. The expressions of STAT5 mRNA and protein were assayed by in situ hybridization, and Western blotting respectively. RESULTS: Curcumin could inhibit K562 cell proliferation in a time- and dose-dependent manner. The percentage of STAT5-positive cells was 19% in curcunin group, significantly less than 31% of that in K562 cell group (P < 0.01). The A value of the expression level of STAT5 protein in curcumin group was 15 266 +/- 769, significantly less than 25 781 +/- 1240 of that in K562 cell group (P < 0.01). CONCLUSION: The expressions of STAT5 mRNA and protein in K562 cells were inhibited by curcumin and curcumin could inhibit K562 cell proliferation.

Cell Proliferation↗
PubMed2004

[Effect of trichostatin A on histone acetylation level and apoptosis in HL-60 cells].

In order to explore the underlying mechanism of high effects and low toxicity of trichostatin A (TSA), the effect of TSA on growth inhibition, histone acetylation level and apoptosis in HL-60 cells and normal human peripheral blood mononuclear cells (NPBMNC) were examined using MTT method, immunocytochemistry technology, and Annexin-V-FITC/PI double staining flow cytometry. The results showed that TSA inhibited growth of HL-60 in time- and dose-dependent manners, and the IC(50) of 36 hours was 100 ng/ml. The apoptosis induction effect of TSA in HL-60 cells was also time- and dose-dependent. Besides, the dose of TSA showing significant apoptotic cytotoxicity in HL-60 cells did not demonstrate apparent apoptosis induction in NPBMNC within definite dose and time range. The histone acetylation level in HL-60 cells and NPBMNC both showed remarkable increase (P < 0.05) after incubated with 100 ng/ml TSA for 4 hours without statistical difference between them is detected (P > 0.05). It is concluded that TSA shows effects of definite and significant growth inhibition and apoptosis induction on HL-60 cells in time- and dose-dependent manners. TSA is able to selectively induce apoptosis in HL-60 cells with low toxicity in NPBMNC at the same time. The mechanism of this selectivity can not be ascribed to the differential regulation of histone acetylation level between HL-60 cells and NPBMNC.

Acetylation↗
PubMed2004

Gene expression of collagen types IX and X in the lumbar disc.

OBJECTIVE: To study gene expression of collagen types IX and X in human lumbar intervertebral discs during aging and degeneration and to explore the role of collagen types IX and X in disc degeneration. METHODS: Fetal, adult and pathologic specimens were subjected to in situ hybridization with cDNA probes to investigate mRNA-expressions of types IX and X collagen gene. RESULTS: In fetal intervertebral discs, positive mRNA hybridization signals of type IX collagen were concentrated in the nucleus pulposus and the inner layer of anulus fibrosus. Interstitial matrix of the nucleus pulposus also showed positive type X collagen staining. Positive mRNA hybridization signals of types IX and X were not detected in the middle and outer layers of anulus fibrosus. In adult specimens, expression of type IX collagen mRNA was markedly decreased. No hybridization signals of type X collagen was observed. As for pathological specimens, there was no gene expression of type IX collagen. In severe degenerated discs from adults, there were focal positive expressions of type X collagen. CONCLUSIONS: Obvious changes of collagen gene expression occur with aging. Expression of type IX collagen decreases in adult and pathological discs. Results of type X collagen expression suggest that type X collagen is expressed only in older adult and senile discs (i.e., when disc degeneration has already reached a terminal stage), indicating the terminal stage of degeneration.

Adolescent↗
PubMed2004

[The relationship between Chlamydia pneumoniae infection and primary biliary cirrhosis].

OBJECTIVE: The aim of this study was to evaluate the association between Chlamydia pneumoniae (CP) infection and primary biliary cirrhosis (PBC). METHODS: Chlamydia pneumoniae IgG and IgM were determined by enzyme-linked immunosorbent assay (ELISA) in 41 well-established PBC patients and two race-matched control groups, PHC, n = 70; healthy controls, HC, n =57). RESULTS: The mean levels and seroprevalence of CP IgG in PBC group and PHC group were significantly higher than in the HC [(46.8 +/- 43.4) RU/ml, (49.5 +/- 45.2) RU/ml vs (28.3 +/- 32.7) RU/ml, P = 0.042 and P < 0.001 respectively; 68.3%, 71.4% vs 42.1%, chi2 values were 5.389 and 11.110 respectively]. There was a markedly elevated seroprevalence of CP IgM in patients with PBC (22.0%) compared with the PHC and HC groups. The odds ratios (ORs) for the presence of CP IgG and IgM for the PBC patients versus the HC were 2.7 (95% CI 0.9 to 6.1) and 5.1 (95% CI 1.4 to 18.5). Though there was no correlation in the level of CP IgG with total IgG in sera of patients with PBC (r=-0.857, p=0.344), CP IgM was related with the abnormally high concentrations of total IgM in the PBC group. CONCLUSIONS: The results of this study do not support the hypothesis that infection with Chlamydia pneumoniae may be a triggering agent for PBC, but suggest that Chlamydia pneumoniae infection probably contributes to the high level of IgM presented in most of the patients with PBC

Adult↗
PubMed2004

[Effect of curcumin on STAT5 signaling pathway in primary CML cells].

To study the effect of curcumin on signaling pathway of signal transducers and activators of transcription (STAT5) in primary newly-diagnosed chronic myelocytic leukemia (CML) cells, and to explore the clinical significance of curcumin in the treatment of primary CML cells, the cells were randomly divided into 3 groups: normal control group, CML cells group, and curcumin group; the cellular proliferation was assayed by MTT test; the expression of cellular STAT5 mRNA in CML cells was detected by RT-PCR; the activation of STAT5 in CML cell was detected by electrophoretic mobility shift assay (EMSA). The results showed that the cellular proliferation of curcumin group (OD value 0.640 +/- 0.073) was decreased, as compared with that of the CML cells group (OD value 0.856 +/- 0.083, P <0.01). The expression levels of STAT5 mRNA in CML cells group (integral ratio of OD 1.782 +/- 0.156) were significantly greater than that in the normal control group (integral ratio of OD 0.289 +/- 0.025, P <0.01). The expression of STAT5 mRNA in curcumin group (integral ratio of OD 1.398 +/- 0.126) was significantly decreased as compared with that in the CML cells group (P <0.01). The activation of STAT5 was significantly increased in CML cells group (gray value 5323.375 +/- 515.640) as compared with that in the normal control group (gray value 2943.000 +/- 273.377, P <0.01). The activation of STAT5 of curcumin group (gray value 4331.750 +/- 398.035) was significantly decreased as compared with that of CML cells group (P <0.01). It is concluded that the cellular proliferation and the expression of STAT5 mRNA are increased in the primary CML cells. The activation of STAT5 in primary CML cells is markedly enhanced. STAT5 signaling pathway may be involved in the proliferation of primary CML cells. Curcumin can inhibit the cellular proliferation and the expression of STAT5 mRNA, and down-regulate the activation of STAT5 in primary CML cells. Curcumin may be used in treatment of leukemia.

Adult↗
PubMed2004

[CML cell line K562 cell apoptosis induced by mangiferin].

This study was aimed to investigate the effects and the mechanism of mangiferin on chronic myeloid leukemia cell lines K562 cells in vitro. The antiproliferation effects of mangiferin on K562 leukemia cells were tested by tetrazolium salt (MTT) method; the apoptosis induced by mangiferin on K562 cell line was explored by means of cell morphology, DNA gel electrophoresis and flow cytometry. The changes in bcr/abl gene expression was detected by using reverse transcriptase (RT)-PCR. The results showed that five different concentrations of mangiferin (25 - 200 micromol/L) dose-dependently and time-dependently inhibited the proliferation of K562 cells, and induced apoptosis in K562 cell line. RT-PCR revealed that bcr/abl gene expression was down-regulated when K562 cells had been treated with different concentrations of mangiferin. In conclusion, mangiferin remarkably inhibits the proliferation of K562 leukemia cells in vitro, and induces apoptosis in K562 cell line probably through down-regulation of bcr/abl gene expression.

Apoptosis↗
PubMed2004

[Prediction and identification of autoepitopes of PDC-E2 specific CD8+ CTL in primary biliary cirrhosis patients].

OBJECTIVE: To identify autoepitopes of E2 subunit of pyruvate dehydrogenase complex (PDC-E2) specific CD8+ CTL in primary biliary cirrhosis (PBC) patients. METHODS: An online database SYFPEITHI was applied to predict HLA-A*0201 restricted epitopes which located in PDC-E2 30-50 aa and 150-190 aa where B-cell epitopes clustered with CD4+ T-cell epitopes. T2 cell line reconstitution and stabilization assay, induction of specific CTL lines from peripheral blood mononuclear cells (PBMCs) of patients with PBC and cytotoxicity of peptides-induced CTL were performed to screen the epitopes from those candidates. RESULTS: Five potential epitopes were predicted by database. Of the 5 candidates, two peptides 159-167 aa and 165-174 aa, with highly binding activity to HLA-A*0201 molecules, could stimulate PBMCs from most HLA-A*0201 positive PBC patients to proliferate and peptide-induced CTL lines showed specific cytotoxicity. CONCLUSION: Peptides of KLSEGDLLA (159-167 aa) and LLAEIETDKA (165-174 aa) in the inner lipoyl domain of PDC-E2 are HLA-A*0201 restricted CD8+ CTL immunodominant epitopes in PBC.

Antibody-Producing Cells↗
PubMed2004

[Nutritional depletion in chronic obstructive pulmonary disease].

Chronic obstructive pulmonary disease (COPD) is one of the major diseases worldwide. Nutritional depletion is a common problem in COPD patients and also an independant predictor of survival in these patients. Many data are helpful for determining nutritional depletion, including anthropometric measurement, laboratory markers, body composition analysis (fat-free mass and lean mass), and body weight. The mechanism of nutritional depletion in patients with COPD is still uncertain. It may be associated with energy/metabolism imbalance, tissue hypoxia, systemic inflammation, and leptin/orexin disorders. In patients with nutritional depletion, growth hormone and testosterone can be used for nutritional therapy in addition to nutrition supplementation.

Body Composition↗
PubMed2004

[Experimental study on anticancer effect of curcumin on Raji cells in vitro].

OBJECTIVE: To study the anticancer effect and mechanism of curcumin on Raji cells in vitro and compared the cytotoxicities of curcumin on Raji cells and normal human peripheral blood mononuclear cell (PBMC). METHODS: The effects of curcumin on proliferation of Raji cells and human PBMC were tested by MTT assay, its effects on apoptosis of them were determined by Annexin-V/PI double-labeled cytometry and TUNEL, and its effects on DNA distribution in Raji cells was studied by PI single labeled cytometry. RESULTS: Curcumin showed marked inhibition on proliferation of Raji cell, could induce Raji cell apoptosis in time- and dose-dependent manner. After curcumin treatment, the cell cycle of Raji cells was blocked in G0/G1 and G2/M phase and those in the S phase decreased proportionally. But curcumin showed no significant effect on inhibiting proliferation or inducing apoptosis on human PBMC. CONCLUSION: Curcumin could regulate the cell cycle of Raji cells and induce its apoptosis, so as to inhibit its proliferation, but with no significant cytotoxicity on human PBMC. It selectively affects the tumor cell.

Antineoplastic Agents, Phytogenic↗