Search PubMed⌕ Search

Biomedical subjects

Chun Liang

Publications and source records attributed to Chun Liang.

18 recordsLinked to original sources
PubMed2006

Ecdysone induces transcription and amplification in Sciara coprophila DNA puff II/9A.

DNA replication is normally tightly regulated to ensure the production of only one copy of the genome per cell cycle. However, DNA puffs of the salivary gland giant polytene chromosomes of Sciara coprophila undergo DNA amplification during the normal course of development, overriding this control. This developmental strategy provides more template for the production of large amounts of protein needed for pupation. We have focused on DNA puff II/9A, which amplifies approximately 17-fold over the rest of the genome. Evidence presented here suggests that DNA amplification at this locus is controlled by the steroid hormone ecdysone, the master regulator of insect development. Explanted, pre-amplification stage salivary glands undergo premature amplification when incubated with ecdysone. Injection of ecdysone into pre-amplification stage larvae induces amplification. Ecdysone also induces transcription of the II/9A genes. We report the presence of a putative ecdysone response element directly adjacent to the origin recognition complex (ORC)-binding site in the II/9A origin and demonstrate that it is efficiently bound by the Sciara ecdysone receptor. These results implicate ecdysone in the regulation of DNA amplification in Sciara and suggest the ecdysone receptor may be the elusive amplification factor. This would be a new role for this transcription factor.

Animals↗
PubMed2006

MAGIC-SPP: a database-driven DNA sequence processing package with associated management tools.

BACKGROUND: Processing raw DNA sequence data is an especially challenging task for relatively small laboratories and core facilities that produce as many as 5000 or more DNA sequences per week from multiple projects in widely differing species. To meet this challenge, we have developed the flexible, scalable, and automated sequence processing package described here. RESULTS: MAGIC-SPP is a DNA sequence processing package consisting of an Oracle 9i relational database, a Perl pipeline, and user interfaces implemented either as JavaServer Pages (JSP) or as a Java graphical user interface (GUI). The database not only serves as a data repository, but also controls processing of trace files. MAGIC-SPP includes an administrative interface, a laboratory information management system, and interfaces for exploring sequences, monitoring quality control, and troubleshooting problems related to sequencing activities. In the sequence trimming algorithm it employs new features designed to improve performance with respect to concerns such as concatenated linkers, identification of the expected start position of a vector insert, and extending the useful length of trimmed sequences by bridging short regions of low quality when the following high quality segment is sufficiently long to justify doing so. CONCLUSION: MAGIC-SPP has been designed to minimize human error, while simultaneously being robust, versatile, flexible and automated. It offers a unique combination of features that permit administration by a biologist with little or no informatics background. It is well suited to both individual research programs and core facilities.

Algorithms↗
PubMed2006

Water stress-responsive genes in loblolly pine (Pinus taeda) roots identified by analyses of expressed sequence tag libraries.

Drought stress is the principal cause of seedling mortality in pine forests of the southeastern United States and in many other forested regions around the globe. As part of a larger effort to discover loblolly pine genes, this study subjected rooted cuttings of three unrelated pine genotypes to three watering regimens. Expressed sequence tags (ESTs) were obtained from both the 3' and 5' ends of 12,918 randomly selected cDNAs generated from root tissues. These ESTs were clustered to identify 6,765 unique transcripts (UniScripts) derived from 6,202 putative unique genes (UniGenes-S). Tentative annotations were assigned on the basis of BLASTX comparisons to the Protein Information Resource Nonredundant Reference (PIR-NREF) database. Expression levels of 42 UniScripts varied with high statistical significance with respect to treatment. Many of them resembled gene products shown to be important for drought tolerance in other species, including dehydrins, endochitinases, cytochrome P450 enzymes, pathogenesis-related proteins and various late-embryogenesis abundant (LEA) gene products. Similarly, expression levels of 110 UniScripts varied with high statistical significance among genotypes, indicating that gene expression patterns in this species are much more dependent on genotype than on treatment. Most of the water stress-induced pine UniScripts that appeared to encode products resembling drought tolerance factors in other species were most highly induced in a single genotype, suggesting that particularly useful adaptive alleles for drought tolerance might exist within the collection of cDNAs characterized from this genotype. Mining and visualizing the complete data set, as well as downloading of both EST and UniScript contig sequences, are possible using MAGIC Gene Discovery at http://fungen.org/genediscovery/.

Acclimatization↗
PubMed2006

[Increased lectin-like oxidized low density lipoprotein receptor-1 expression in the autologous vein grafts and vein graft atherosclerosis].

OBJECTIVE: To study the changes of lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) expression in the autologous vein grafts and vein graft atherosclerotic lesions. METHODS: Thirty New Zealand white rabbits were randomly assigned to normal control group (rabbits fed with normal diet, n = 10), vein graft group (autologous external jugular vein grafting to common carotid artery and fed with normal diet, n = 10) or vein graft plus high-lipid diet group (autologous vein graft and fed with high-lipid diet, n = 10) for 12 weeks. LOX-1 expressions in the grafts were examined by immunohistochemistry and semi-quantitative reverse transcription-PCR. The relationships between serum total cholesterol level, intimal thickness and LOX-1 expression were also investigated. RESULTS: LOX-1 expression was low in the endothelium of external jugular veins in the normal control group and significantly increased in the endothelium and neointima of vein grafts in the vein graft group (0.31 +/- 0.14 vs. 0.09 +/- 0.04, P < 0.01) and which was further increased in the endothelium and atherosclerotic lesions in the vein graft plus high-lipid diet group (0.93 +/- 0.34 vs. 0.31 +/- 0.14, P < 0.01). LOX-1 expression in the atherosclerotic lesions was located both in endothelial cells and foam cells and the expression was most prominent in endothelial cells. LOX-1 expression and intimal thickness were positively related to serum total cholesterol level (P = 0.00 and 0.02) and the partial correlation coefficient was 0.78 and 0.42, respectively. CONCLUSIONS: LOX-1 expression is increased in endothelium and neointima of autologous vein grafts of rabbits. Hypercholesterolemia upregulates LOX-1 expression in vein graft atherosclerosis. Thus, LOX-1 might play an important role in the pathogenesis of vein graft atherosclerosis.

Animals↗
PubMed2005

Elevated matrix metalloproteinase expression after stent implantation is associated with restenosis.

OBJECTIVE: Matrix metalloproteinases (MMPs) play a key role in intimal growth and is responsible for ventricular remodeling after stent implantation. However, little is known about the relationship between early MMPs expression post-stent implantation and follow-up restenosis. METHODS: We investigated the serial changes of serum MMP-9, MMP-2 and tissue inhibitor of metalloproteinase-1 (TIMP-1) in 16 control subjects with normal coronary angiography (control) and 40 patients before and on the 1st, 3rd and 7th day after uncomplicated stent implantation. Follow-up angiography was performed at 6 months after stent implantation. RESULTS: Serum MMP-2 level was higher in patients with restenosis on the 1st day post-stent implantation and returned to pre-operation level thereafter. Serum MMP-9 levels consistently increased in patients with restenosis up to 7th day post-stent implantation; MMP-9 levels in the 1st, 3rd and 7th day after stent implantation were positively correlated to the late loss index 6 months after stent implantation. CONCLUSIONS: Increased serum MMP-9 level is associated with increased risk of restenosis post-stent implantation.

Adult↗
PubMed2005

Sorghum expressed sequence tags identify signature genes for drought, pathogenesis, and skotomorphogenesis from a milestone set of 16,801 unique transcripts.

Improved knowledge of the sorghum transcriptome will enhance basic understanding of how plants respond to stresses and serve as a source of genes of value to agriculture. Toward this goal, Sorghum bicolor L. Moench cDNA libraries were prepared from light- and dark-grown seedlings, drought-stressed plants, Colletotrichum-infected seedlings and plants, ovaries, embryos, and immature panicles. Other libraries were prepared with meristems from Sorghum propinquum (Kunth) Hitchc. that had been photoperiodically induced to flower, and with rhizomes from S. propinquum and johnsongrass (Sorghum halepense L. Pers.). A total of 117,682 expressed sequence tags (ESTs) were obtained representing both 3' and 5' sequences from about half that number of cDNA clones. A total of 16,801 unique transcripts, representing tentative UniScripts (TUs), were identified from 55,783 3' ESTs. Of these TUs, 9,032 are represented by two or more ESTs. Collectively, these libraries were predicted to contain a total of approximately 31,000 TUs. Individual libraries, however, were predicted to contain no more than about 6,000 to 9,000, with the exception of light-grown seedlings, which yielded an estimate of close to 13,000. In addition, each library exhibits about the same level of complexity with respect to both the number of TUs preferentially expressed in that library and the frequency with which two or more ESTs is found in only that library. These results indicate that the sorghum genome is expressed in highly selective fashion in the individual organs and in response to the environmental conditions surveyed here. Close to 2,000 differentially expressed TUs were identified among the cDNA libraries examined, of which 775 were differentially expressed at a confidence level of 98%. From these 775 TUs, signature genes were identified defining drought, Colletotrichum infection, skotomorphogenesis (etiolation), ovary, immature panicle, and embryo.

DNA, Complementary↗
PubMed2005

Advanced glycosylation end products might promote atherosclerosis through inducing the immune maturation of dendritic cells.

OBJECTIVE: Both advanced glycosylation end products (AGEs) and dendritic cells (DCs) have been shown to play a causative role in atherosclerosis. However, whether they function interactively in the process remains uncertain. We therefore studied the effects of AGE-bovine serum albumin (AGE-BSA) on the maturation of DCs and the expressions of scavenger receptor-A (SR-A) and receptor for AGEs (RAGE) on DCs. METHODS AND RESULTS: AGE-BSA induced DCs maturation accompanied with increased expressions of CD1a, CD40, CD80, CD83, CD86, and MHC class II. The capacity of DCs to stimulate T-cell proliferation and secretion of cytokines (interferon [IFN], IFN-gamma, interleukin [IL]-10 and IL-12) was also enhanced by AGE-BSA. AGE-BSA significantly upregulated SR-A and RAGE expression on DCs and the upregulation was abolished by inhibition of mitogen-activated protein (MAP) kinase Jnk, but not by that of Erk and p38 MAP kinase. AGE-BSA-induced expression of CD83 and secretion of IL-12 were partly inhibited by either an anti-RAGE neutralizing antibody or a Jnk inhibitor. CONCLUSIONS: AGE-BSA induces maturation of DCs and augmented their capacity to stimulate T-cell proliferation and cytokine secretions possibly through upregulation of RAGE and SR-A, which at least in part through Jnk. These findings might explain in part the interactive roles of AGEs and DCs in the processes of atherosclerosis.

Anthracenes↗
PubMed2004

Pairwise interactions of the six human MCM protein subunits.

The eukaryotic minichromosome maintenance (MCM) proteins have six subunits, Mcm2 to 7p. Together they play essential roles in the initiation and elongation of DNA replication, and the human MCM proteins present attractive targets for potential anticancer drugs. The six MCM subunits interact and form a ring-shaped heterohexameric complex containing one of each subunit in a variety of eukaryotes, and subcomplexes have also been observed. However, the architecture of the human MCM heterohexameric complex is still unknown. We systematically studied pairwise interactions of individual human MCM subunits by using the yeast two-hybrid system and in vivo protein-protein crosslinking with a non-cleavable crosslinker in human cells followed by co-immunoprecipitation. In the yeast two-hybrid assays, we revealed multiple binary interactions among the six human MCM proteins, and a subset of these interactions was also detected as direct interactions in human cells. Based on our results, we propose a model for the architecture of the human MCM protein heterohexameric complex. We also propose models for the structures of subcomplexes. Thus, this study may serve as a foundation for understanding the overall architecture and function of eukaryotic MCM protein complexes and as clues for developing anticancer drugs targeted to the human MCM proteins.

Cell Cycle Proteins↗
PubMed2004

Upregulation of lectinlike oxidized low-density lipoprotein receptor-1 expression contributes to the vein graft atherosclerosis: modulation by losartan.

Vein grafts interposed to arteries are susceptible to the development of accelerated atherosclerosis. The role of lectinlike oxidized LDL (ox-LDL) receptor-1 (LOX-1) expression in the atherosclerotic lesions of vein grafts has not been clarified. The current study was designed to examine the expression of LOX-1 in vein grafts atherosclerosis and the modulating effect of losartan on it. Autologous external jugular veins were grafted to common carotid arteries in 30 male New Zealand White rabbits. After surgery, rabbits were fed with high cholesterol diet (HC), high cholesterol diet plus losartan (10 mg/kg/day, LHC) or regular chow (control, n = 10 in each group) for 12 weeks. LOX-1 expressions in the grafts were examined by immunohistochemistry, semi-quantitative RT-PCR and Western blot. Neointimal hyperplasia was observed in all vein grafts characterized by extensive intimal thickening. Atherosclerotic lesions were found in vein grafts of HC group, which were attenuated by losartan. Losartan also reduced the vein grafts atherosclerotic plaque vulnerability. LOX-1 expression was low in the endothelium and neointima of vein grafts in control group and was significantly increased in the endothelium and atherosclerotic lesions in HC group but not in LHC group. In conclusion, LOX-1 was expressed in endothelium and neointima of autologous vein grafts of rabbits. Increased LOX-1 expression was associated with vein grafts atherosclerosis development. Downregulation of LOX-1 by losartan might contribute to its attenuating effect on vein grafts atherosclerosis.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2004

Comparison of the time to onset of action on myocardial ischaemia following intravenous administration of isosorbide dinitrate and 5-isosorbide mononitrate in Chinese patients.

OBJECTIVE: The onset of action of intravenous isosorbide dinitrate (CAS 87-33-2, ISDN) and intravenous 5-isosorbide mononitrate (CAS 16051-77-7, 5-ISMN) were compared by measurement of the indicators of perfusion to ischaemic myocardium. METHODS: Twenty-five patients with coronary heart disease were randomly allocated to receive intravenous ISDN or 5-ISMN. The extent of myocardial ischaemia before infusion and at 3, 15 and 45 min after commencement of infusion was evaluated using 99mTc-MIBI myocardium tomography imaging and electrocardiograms. RESULTS: The perfusion defects were significantly reduced or resolved in 11 patients (84.1%) receiving ISDN and 2 patients (15.38%) receiving 5-ISMN at 3 min. At 15 min the improvement was significantly greater in the ISDN group than in the 5-ISMN group. The improvements of 99mTc-MIBI myocardial uptake ratio and electrocardiograms were statistically significant in the ISDN group at 3 min and 15 min compared to pre-infusion. Although a significant improvement appeared at 15 min in the 5-ISMN group, it was significantly less than that observed in the ISDN group (p < 0.05). After 45 min, there were improvements in ischaemia in both groups with the difference compared to pre-infusion being significant, and there was no statistically significant difference between the ISDN and 5-ISMN group. CONCLUSION: In patients with coronary heart disease with ischaemic episodes the onset of therapeutic activity was more rapid with intravenous ISDN compared to 5-ISMN. ISDN should be the preferred intravenous nitrate for acute ischaemic episodes where a rapid onset of therapeutic action is desired.

Acute Disease↗
PubMed2004

New camptothecin and ellagic acid analogues from the root bark of Camptotheca acuminata.

As part of a study on chemical constituents of Camptotheca species, one new natural camptothecin analogue (2), two new alkaloids (3, 4), one new ellagic acid analogue (5), and 19 known compounds (1, 6-23) have been isolated from the root bark, stem bark, fruits, and leaves of Camptotheca acuminata Decaisne. The structures of 2-5 were determined from spectral data to be 10-methoxy-20-O-acetylcamptothecin (2), 20-O-beta-glucopyranosyl 18-hydroxycamptothecin (3), 20-formylbenz indolizino [1,2-b]quino-line-11(13H)-one (4), and 3,4-methylenedioxy-3'-O-methyl-5'-hydroxyellagic acid (5).

Camptotheca↗
PubMed2004

Ciglitazone inhibits oxidized-low density lipoprotein induced immune maturation of dendritic cells.

BACKGROUND: The peroxisome proliferator-activated receptor (PPAR) activation has generally been shown to have anti-inflammatory effects and dendritic cells (DCs) are the most efficient antigen presenting cells that play an active role in the development of atherosclerosis. The effects of PPARgamma on DCs maturation and immune function remain unknown now and we, therefore, studied the influence of PPARgamma agonist ciglitazone on the maturation and immune function of DCs. METHODS: Human monocytes were purified and immature DCs derived; ciglitazone (25 micromol/L) was added to the medium for 24 hours; ox-LDL (50 microg/ml) was then added to the medium for another 24 hours. The immunophenotypic expressions (CD1a, CD40, CD86, and HLA-DR) were analyzed by FACS and endocytosis function by FITC-dextran and the cytokines secretions of culture supernatants (IL-12,IL-10,TNFalpha, and IL-2) were measured with ELISA. RESULTS: Ciglitazone reduced ox-LDL induced immunophenotypic expressions of DCs (CD40, CD1a, and HLA-DR). Ox-LDL inhibited the endocytosis of DCs, which was prevented by ciglitazone; ciglitazone attenuated ox-LDL induced cytokine secretions of DCs (IL-12, 116 +/- 29 versus 34 +/- 3 pg/ml*; IL-10, 49 +/- 1 versus 28 +/- 9 pg/ml*; TNFalpha, 46 +/- 16 versus 24 +/- 8 pg/ml*, *P < 0.05 compared with ox-LDL, respectively). CONCLUSION: Our study suggested that one of the anti-inflammatory mechanisms of PPAR-gamma agonist ciglitazone was mediated by inhibiting the ox-LDL induced maturation and immune function of DCs.

Antigens, CD↗
PubMed2004

Losartan inhibited expression of matrix metalloproteinases in rat atherosclerotic lesions and angiotensin II-stimulated macrophages.

AIM: To explore whether the angiotensin II (Ang II) receptor 1 (AT1) antagonist, losartan could reduce activity and expression of matrix metalloproteinases (MMPs) in rat atherosclerotic plaques. METHODS: Male Wistar-Kyoto rats were ip injected a single dose of vitamin D3 600 kU x kg(-1) x month(-1) and fed an atherogenic diet for 4 months to induce experimental atheroma. Then either placebo or losartan 50 mg x kg(-1) x d(-1) was administered in rats for another 2 months. In vitro, the effect of losartan 0.1-10 micromol/L on the expression of MMP-2 and MMP-9 was investigated in Ang II-stimulated rat peritoneal macrophages. The expression and activity of MMP-2 and MMP-9 were monitored by Western blot, RT-PCR, and SDS-PAGE zymography analysis. RESULTS: High levels of MMP-2 and MMP-9 were expressed in rat atherosclerotic lesions. Losartan significantly reduced the activity and expression of MMP-2 and MMP-9 compared with the placebo group (MMP-2, 5861+/-539 vs 8991+/-965, P<0.05; MMP-9,10527+/-1002 vs 14623+/-2462, P<0.01). In cultured rat peritoneal macrophages, Ang II 0.1 micromol/L elicited an increase in MMP-2 and MMP-9 activity and expression that were prevented by losartan in a dose-dependent manner (P<0.01). But the AT2 receptor antagonist PD123319 had no effect. CONCLUSION: Losartan reduced the expression and activity of MMP-2 and MMP-9 in rat atherosclerotic lesions. The anti-atherogenic effects of losartan were due to the direct inhibition of Ang II bioactivity.

Angiotensin II↗
PubMed2003

Inhibiting the expression of DNA replication-initiation proteins induces apoptosis in human cancer cells.

DNA replication-initiation proteins are expressed in cancer cells, whereas some of these proteins are not expressed in nonproliferating normal cells. Therefore, replication-initiation proteins may present attractive targets for anticancer therapy. Using selected antisense oligodeoxynucleotides and small interfering RNA molecules targeted to the mRNA encoding the DNA replication-initiation proteins hCdc6p, hMcm2p, and hCdc45p, we show that the target genes could be effectively and specifically silenced and that, consequently, DNA replication and cell proliferation were inhibited in cultured human cells. In addition, silencing of these genes resulted in apoptosis in both p53-positive and -negative cancer cells but not in normal cells: cancer cells entered an abortive S-phase, whereas normal cells arrested mainly in G(1) phase. Our studies are the first to suggest that inhibiting the expression of selective replication-initiation proteins is a novel and effective anticancer strategy.

Animals↗
PubMed2003

Cdc48p is required for the cell cycle commitment point at Start via degradation of the G1-CDK inhibitor Far1p.

The budding yeast Cdc48p and its mammalian homologue p97 are involved in many important cellular activities. Because previous cdc48 mutants have exclusive G2/M arrest, Cdc48p was thought to play an essential role only during mitosis. We found that Cdc48p is required for the execution of Start (a yeast cell cycle commitment point equivalent to the restriction point in mammalian cells) in both a normal mitotic cell cycle and cell cycle reentry after mating pheromone withdrawal through degradation of the G1-cyclin-dependent kinase inhibitor Far1p. Our work is the first to uncover novel roles of Cdc48p as a critical cell cycle regulator in G1, and to shed new light on cell cycle regulation of Far1p, which is the first cyclin-dependent kinase inhibitor shown to be a substrate of an essential proteolysis event mediated by Cdc48p.

Adenosine Triphosphatases↗
PubMed2002

Noc3p, a bHLH protein, plays an integral role in the initiation of DNA replication in budding yeast.

Initiation of eukaryotic DNA replication requires many proteins that interact with one another and with replicators. Using a yeast genetic screen, we have identified Noc3p (nucleolar complex-associated protein) as a novel replication-initiation protein. Noc3p interacts with MCM proteins and ORC and binds to chromatin and replicators throughout the cell cycle. It functions as a critical link between ORC and other initiation proteins to effect chromatin association of Cdc6p and MCM proteins for the establishment and maintenance of prereplication complexes. Noc3p is highly conserved in eukaryotes and is the first identified bHLH (basic helix-loop-helix) protein required for replication initiation. As Noc3p is also required for pre-rRNA processing, Noc3p is a multifunctional protein that plays essential roles in two vital cellular processes.

Blotting, Western↗
PubMed2002

A DNase I hypersensitive site flanks an origin of DNA replication and amplification in Sciara.

In chromosomes of metazoa, the assembly of the genome into chromatin makes an important but poorly understood contribution to determining where DNA replication will initiate. We addressed this issue by studying the developmental progression of the location of the DNA replication origin (ORI) and alterations in chromatin structure in one of the best-mapped ORIs in metazoa, that found in DNA puff II/9A of the fly Sciara coprophila. We found that DNA synthesis for both normal chromosomal endoduplication and DNA amplification initiates within the same 5.5 kb EcoRI fragment. We showed that irrespective of the mode of ORI function--replication or amplification--chromatin over the 1 kb major ORI is never remodeled into a conventional DNase I hypersensitive site (DH site). Instead, we found that the major site of alterations to chromatin structure at this locus is a large (approximately 400 bp) DH site located 600 bp away from the major ORI, at a position where the frequency of replication initiation events falls dramatically. We describe a tight positive correlation between ORI activity, strength of this DH site, and the intranuclear titer of protein factor(s) that bind the DH site in a sequence-specific manner. We propose that the Sciara replicator in locus II/9A is composed of sequences that reside within the ORI per se as well as sequences encompassed by the DH site.

Animals↗