PubMed Health⌕ Search

Biomedical subjects

Gang Liu

Publications and source records attributed to Gang Liu.

At least 217 records · Page 12Linked to original sources
PubMed2003

[Molecular cloning and expression in cryptorchid testis of SRG2 from a mouse testis spermatocyte apoptosis-related gene].

It was observed that the spermatogenic cells apoptosis dramatically increased in infertile man. Cloning of novel spermatogenic cell-specific gene related to apoptosis is of momentous physiological and pathological significance to illustrate the apoptosis mechanism and the biology process of spermatogenic cells. A novel mouse gene full-length cDNA sequence-SRG2 was identified (GenBank accession number AF395083), which was significantly changed in cryptorchidism, from a mouse testis cDNA library using a cDNA fragment (GenBank accession number BE644542) as an electronic probe. SRG2 was 1,088 bp in length. The putative protein encoded by this gene was 295 amino acids with a theoretical molecular weight of 33,579 kDa and isoelectric point of 9.64. The sequence shared no significant homology with any known protein in databases except TSARG2, with which its homology was 78%. RT-PCR showed that SRG2 was expressed significantly in testis. Using molecular beacon probe to examine the mRNA expression level of SRG2 gene in cryptorchid testis of various stages, we found that the gene was up-regulated distinctly. Therefore, we conclude that this gene plays an important role in cryptorchid testis.

Amino Acid Sequence↗
PubMed2003

[Molecular cloning of mTSARG3 gene related to apoptosis in mouse spermatogenic cells].

Beginning from a mouse EST (GenBank Accession No: BE644537) which was significantly changed in cryptorchidism and represented a novel gene, GeneScan program was performed and a predicted mouse novel gene full-length cDNA sequence containing the BE644537 sequence was attained. Gene-specific primers were designed for PCR in mouse testis cDNA library. The sequencing result of the PCR product showed that we obtain a new gene mTSARG3 (GenBank Accession No: AF419292) whose full cDNA length is 1328 bp containing 8 exons and 7 introns. The predicted open reading frame encodes a protein of 316 amino acid residues. The protein encoded by the new gene is a new member of HSP40 protein family because the sequence contains the highly conserved J domain which is present in all DnaJ-like proteins and is considered to have a critical role in DnaJ-DnaK protein-protein interactions. mTSARG3 protein displays a 46% identity in a 336-amino-acid overlap with DJB4-MOUSE protein. The result of RT-PCR analysis and Northern blot showed that mTSARG3 is specifically expressed in mouse testis. Southern blot showed that there were no loss and rearrangement in cryptorchid. Based upon all these observations, it is considered that the function of the new gene is related to inhibit mouse testis spermatogenesis apoptosis.

Amino Acid Sequence↗
PubMed2003

[A study on the estimation of the size of male homosexual population].

OBJECTIVE: To study the practical survey method on estimating the size of male homosexual population. METHODS: Nine male homosexual gathering spots were selected and three methods as division method, capture-mark-recapture method and multiplier method were applied in counting the numbers of homosexual men in one city in Sichuan province. RESULTS: Number of counting through division method was 877 and the three numbers through capture-mark-recapture method were 1408, 1207 and 949 respectively. However, appropriate data was not obtained by multiplier method. CONCLUSIONS: Division method was easy to operate with its high credibility, but costly. Capture-mark-recapture method was less costly less both in capital and time, and the results could be testified to each other. Multiplier method should be modified before applied to obtain reliable information.

China↗
PubMed2003

[Human placenta derived adherent cells support in vitro expansion of umbilical cord blood CD34+ cells].

The objective of this study was to elucidate the effect of human placenta adherent cells (hPDAC) on expansion of human umbilical cord blood CD34(+) cells in vitro. hPDAC was isolated and characterized in human placenta tissue by using enzyme-digesting method and flow cytometry. A co-culture system was established with hPDAC and cord blood CD34(+) cells. The CD34(+) cells were cultured in different culture systems with different combinations of hPDAC and SCF, IL-3, IL-6 and FL. The number of total nucleated cells, CFC and CD34(+) cells were repeatedly counted in culture for 4 weeks. The results showed that the hPDAC displayed fibroblast-like morphology, and were positive for CD29, CD44, CD166, HLA-ABC and UEA-1, and negative for CD34, CD45 and HLA-DR. Functionally, ex vivo expansion of CD34(+) cells on feeder layer of placental adherent cells was significantly higher than that no feeder layer group. SCF + IL-3 + IL-6 + FL + hPDAC manifested the most potent combination, with the number of total nucleated cells increasing by (126.0 +/- 6.7)-fold, progenitor cells (CFC) (49.8 +/- 1.7)-fold and CD34(+) cells (8.3 +/- 1.65)-fold. It is concluded that placental adherent cells could support hematopoiesis in vitro and work as a suitable feeder layer for cord blood stem/progenitor cell expansion.

Antigens, CD34↗
PubMed2003

[Isolation and characterization of human placenta derived adherent cells and their hematopoietic growth factor expression].

OBJECTIVE: To isolate and culture human placenta derived adherent cells (hPDAC) and assay their hematopoietic growth factor expression. METHODS: By enzyme digestion, hPDAC were isolated from human placenta tissue and cultured, and their biological characteristics were studied. The hematopoietic growth factor (HGF) mRNA expression of hPDAC was assayed by RT-PCR. RESULTS: hPDAC was successfully isolated from human placenta tissue, which was further confirmed as mesenchymal stem cell-like cells. HGF including SCF, FL, G-CSF, GM-CSF, M-CSF and IL-6 were expressed in hPDAC. CONCLUSION: hPDAC could be used as feeder layer for umbilical cord blood CD(34)(+) cells ex vivo expansion.

Cells, Cultured↗
PubMed2003

[Identification and functional characterization of sawE--a gene involved in differentiation of Streptomyces ansochromogenes 7100].

A 2.8kb DNA fragment including whiB-like gene was cloned from the partial DNA library of Streptomyces ansochromogenes 7100 by using whiB of Streptomyces coelicolor J1501 as a probe. The nucleotide sequence of 1.4kb DNA fragment was determined and analyzed. The result showed that the fragment contains one complete open reading frame-designated sawE. sawE shows strong identity to whiB, an essential gene for early stage of sporulation. The deduced product of sawE gene is a regulatory protein. sawE disruptant was blocked at aerial hyphae stage of Streptomyces ansochromogenes 7100, no sporulation septation, no formation of grey mature spore. Disruptants maintained white phenotype on prolonged incubation. The result indicated that sawE is essential for the morphological differentiation of S. ansochromogenes.

Amino Acid Sequence↗
PubMed2002

[Expression and significance of B-cell-specific activator protein of H/RS cell in classical Hodgkin's Lymphoma].

OBJECTIVE: To explore the expression of B-cell-specific activator protein (BSAP) of H/RS cell in classical Hodgkin's lymphoma (cHL). METHODS: Immunohistochemical method was used to detect the expression of BSAP in 33 samples of formalin-fixed, paraffin-embedded tissues of cHL. Nine samples of lymph node of reactive hyperplasia, 10 samples of B-cell lymphoma, and 10 samples of T-cell lymphoma were also detected as BSAP controls. Mouse-anti-human monoclonal antibodies CD20, CD30 and CD15 were detected among the cHL cases as routine comparison. RESULTS: 30 of 33 (90.91%) cases of cHL were BSAP expression positive in H/RS cells, while all of the 33 (100%) cases of background B-lymphocytes were BSAP positive. Almost all B cells of lymph node reactive hyperplasia were BSAP positive. All malignant cells in B-cell lymphoma were BSAP positive, while all malignant cells in T-cell lymphoma were BSAP negative. Among the 33 cases of cHL there was a significant difference between the expression of BSAP and the expression of CD20 (30.30%) in H/RS cells (P = 0.000), and no significant difference between the expression of CD30 (93.94%) and CD15 (75.75%, P = 0.082). CONCLUSION: The frequent expression of BSAP in H/RS cells of classical Hodgkin's disease provides further evidence for its B-cell origin and helps to identify H/RS cells. The expression of BSAP in H/RS cells can be used to distinguish HL from anaplastic large cell lymphoma (ALCL).

Adolescent↗
PubMed2002

The ferredoxin reductase gene is regulated by the p53 family and sensitizes cells to oxidative stress-induced apoptosis.

The p53 tumor suppressor protein, a transcription factor, induces cell cycle arrest and apoptosis via the upregulation of downstream target genes. Ferredoxin Reductase (protein, FR; gene, FDXR) transfers electron from NADPH to cytochrome P450 via ferredoxin in mitochondria. Here, we identified FDXR as a target gene of the p53 family, that is, p53, p63, and p73. We found that FDXR can be induced by DNA damage in cells in a p53-dependent manner and by a mutated form of p53 that is competent in inducing apoptosis. In addition, we identified a p53 response element located within the FDXR promoter that is responsive to wild-type p53, p63alpha, p63gamma, p73alpha, and p73beta. Furthermore, we showed that p53, p63alpha and p73alpha directly bind to the p53 response element in vivo and promote the accessibility of the FDXR promoter by increasing the acetylation of histones H3 and H4. To determine the role of FR in p53 tumor suppression, we generated cell lines that express FR using a tetracycline-regulated promoter. We found that over-expression of FR in lung H1299, breast MCF7, and colorectal HCT116 carcinoma cells have no effect on cell proliferation. However, we showed that FR increases the sensibility of H1299 and HCT116 cells to 5-fluorouracil-, doxorubicin- and H(2)O(2)- mediated apoptosis. Our data support a model of feed-forward loop for p53 activity, that is, various cellular stresses, including reactive oxygen species (ROS), activate p53, which induces the expression of FDXR; and the FDXR gene product, FR, in turn sensitizes cells to ROS-mediated apoptosis.

Apoptosis↗
PubMed2002

Activation of gold on titania: adsorption and reaction of SO(2) on Au/TiO(2)(110).

Synchrotron-based high-resolution photoemission and first-principles density-functional slab calculations were used to study the interaction of gold with titania and the chemistry of SO(2) on Au/TiO(2)(110) surfaces. The deposition of Au nanoparticles on TiO(2)(110) produces a system with an extraordinary ability to adsorb and dissociate SO(2). In this respect, Au/TiO(2) is much more chemically active than metallic gold or stoichiometric titania. On Au(111) and rough polycrystalline surfaces of gold, SO(2) bonds weakly and desorbs intact at temperatures below 200 K. For the adsorption of SO(2) on TiO(2)(110) at 300 K, SO(4) is the only product (SO(2) + O(oxide) --> SO(4,ads)). In contrast, Au/TiO(2)(110) surfaces (theta;(Au) < or = 0.5 ML) fully dissociate the SO(2) molecule under identical reaction conditions. Interactions with titania electronically perturb gold, making it more chemically active. Furthermore, our experimental and theoretical results show quite clearly that not only gold is perturbed when gold and titania interact. The adsorbed gold, on its part, enhances the reactivity of titania by facilitating the migration of O vacancies from the bulk to the surface of the oxide. In general, the complex coupling of these phenomena must be taken into consideration when trying to explain the unusual chemical and catalytic activity of Au/TiO(2). In many situations, the oxide support can be much more than a simple spectator.

Journal Article↗
PubMed2002

Synthesis and biological evaluation of 2-indolyloxazolines as a new class of tubulin polymerization inhibitors. Discovery of A-289099 as an orally active antitumor agent.

A series of indole containing oxazolines has been discovered as a result of structural modifications of the lead compound A-105972. The compounds exert their anticancer activity through inhibition of tubulin polymerization by binding at the colchicine site. A-289099 was identified as an orally active antimitotic agent active against various cancer cell lines including those that express the MDR phenotype. The anticancer activity, pharmacokinetics, and an efficient and enantioselective synthesis of A-289099 are described.

Animals↗
PubMed2002

Identification of novel Ah receptor agonists using a high-throughput green fluorescent protein-based recombinant cell bioassay.

The Ah receptor is a ligand-dependent transcription factor that mediates the biological and toxic effects of polycyclic aromatic hydrocarbons and halogenated aromatic hydrocarbons such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin). Recent evidence also suggests a role for the AhR in normal physiology and development. Although a variety of structurally diverse chemicals are reported to bind to and activate the AhR, the full spectrum of structural chemical classes that can interact with the AhR remains to be elucidated. Large-scale analysis of the ligand binding specificity of the AhR requires the use of a high-throughput AhR bioassay system for chemical screening. We have utilized a recombinant mouse hepatoma cell line (H1G1.1c3) containing a stably integrated TCDD- and AhR-responsive enhanced green fluorescent protein (EGFP) reporter gene to screen a 1,5-dialkylamino-2,4-dinitrobenzene combinatorial chemical library consisting of 155 parental amines and up to 12 090 combinatorial products in less than 7 days for novel AhR agonists. These analyses have identified numerous parental amines as relatively potent inducers of EGFP (with EC(50)s between 8 and 1000 microM) and also have revealed several novel products of the combinatorial chemical library synthesis with EC(50)s between 10 and 100 microM. Overall, these results have not only allowed the identification of novel activators of the AhR but also demonstrate the utility of the recombinant H1G1.1c3 cell bioassay for high-throughput chemical screening.

Animals↗
PubMed2002

A novel Streptomyces gene, samR, with different effects on differentiation of Streptomyces ansochromogenes and Streptomyces coelicolor.

A 1.4-kb DNA fragment from Streptomyces ansochromogenes accelerated mycelium formation of S. ansochromogenes when present on a multicopy plasmid. The DNA fragment contains one complete open reading frame, designated samR, encoding a protein with 213 amino acids that contains a likely DNA-binding helix-turn-helix motif close to its N-terminus. The deduced SamR protein resembles the product of the hppR gene, which is involved in the regulation of catabolism of 3-(3-hydroxyphenyl) propionate in Rhodococcus globerulus. A samR disruption mutant was constructed that presented a bald phenotype and failed to form aerial hyphae and spores. We suggest that samR plays an important role in the emergence of aerial hyphae from substrate mycelium. An almost identical gene of Streptomyces coelicolor was also subjected to gene disruption. Surprisingly, the mutant was able to develop an aerial mycelium, but it remained white and deficient in sporulation instead of forming gray spores.

Amino Acid Sequence↗
PubMed2002

Assessment of the gene expression profile of differentiated and dedifferentiated human fetal chondrocytes by microarray analysis.

OBJECTIVE: To study the changes in patterns of gene expression exhibited by human chondrocytes as they dedifferentiate into fibroblastic cells in culture in order to better understand the mechanisms that control this process and its relationship to the phenotypic changes that occur in chondrocytes during the development of osteoarthritis (OA). METHODS: Human fetal epiphyseal chondrocytes (HFCs) were cultured either on poly-(2-hydroxyethyl methacrylate)-coated plates (differentiated HFC cultures) or in plastic tissue culture flasks as monolayers (dedifferentiated HFC cultures). Following 11 days of culture under either condition, poly(A+) RNA was isolated from the two cell populations and subjected to a gene expression analysis using a microarray containing approximately 5,000 known human genes and approximately 3,000 expressed sequence tags (ESTs). RESULTS: A > or =2-fold difference in the expression of 62 known genes and 6 ESTs was observed between the two cell types. The differences in expression of several of the genes detected by the microarray hybridization were confirmed by Northern analyses. Two transcription factor genes, TWIST and HIF-1alpha, and a cellular adhesion protein gene, cadherin 11, were markedly regulated in response to differentiation and dedifferentiation. Expression of these genes was also detected in adult normal and OA cartilage and chondrocytes. Analysis of the gene expression profile of HFCs revealed a complex pattern of gene expression, including many genes not yet reported to be expressed by chondrocytes. CONCLUSION: Chondrocytes in monolayer become dedifferentiated, acquiring a fibroblast-like appearance and changing their pattern of gene expression from one of expression of chondrocyte-specific genes to one that resembles a fibroblastic or chondroprogenitor-like pattern. Changes in gene expression associated with the process of dedifferentiation of HFCs in vitro were observed in a wide variety of genes, including genes encoding extracellular matrix proteins, transcription factors, and growth factors. At least 3 of the genes that were regulated in response to dedifferentiation were also found to be expressed in adult normal and OA articular cartilage and chondrocytes.

Adult↗
PubMed2002

An azurocidin-like protein is induced in Trichoplusia ni larval gut cells after bacterial challenge.

Trichoplusia ni immune genes up-regulated in response to bacterial infection have been isolated using differential display polymerase chain reaction. Here we report the cloning and characterisation of a gut-specific immune gene encoding an azurocidin-like protein. The deduced protein is 317 amino acid residues long with a hydrophobic C-terminus and a predicted 17-residue signal peptide. The mature T. ni protein shows 30% identity to human azurocidin, an antibacterial protein. Like azurocidin, the T. ni protein contains two amino acid substitutions in the active site triad normally present in serine proteases. The T. ni protein was synthesised with a six-histidine C-terminal extension using the baculovirus expression system. Sequencing of the recombinant azurocidin-like protein confirmed the predicted cleavage of the signal peptide. Northern blots show that T. ni azurocidin-like protein is expressed solely in the larval gut and that expression is up-regulated by injecting or feeding bacteria. Expression reaches its highest level at 10 h after bacteria injection.

Amino Acid Sequence↗
PubMed2002

Trichoplusia ni gloverin, an inducible immune gene encoding an antibacterial insect protein.

By using differential display PCR, we obtained a cDNA clone encoding a gloverin homologue from the cabbage looper, Trichoplusia ni. The expression of the gene was induced by bacterial infections. The gene codes for a 174 amino acid residue protein, including a signal sequence and a prosegment. The deduced mature protein is 14 kDa and shows 58% and 49% identity to P2 from Helicoverpa armigera and to Hyalophora gloveri gloverin, respectively. The protein was detected in hemolymph and hemocytes from bacteria-immunized animals. We expressed gloverin using the baculovirus expression system. N-terminal amino acid sequence analysis showed that the purified protein contained a propart. This progloverin inhibited the growth of E. coli and the activity is comparable to that of H. gloveri mature gloverin. Processing of progloverin was possible in vitro, using human furin.

Amino Acid Sequence↗
PubMed2002

Pharmacology of endothelin receptor antagonists ABT-627, ABT-546, A-182086 and A-192621: in vitro studies.

Endothelins (ETs), 21-amino-acid peptides involved in the pathogenesis of various diseases, bind to ET(A) and ET(B) receptors to initiate their effects. Based on the same core structure, we have developed four small-molecule ET receptor antagonists, ABT-627, ABT-546, A-182086 and A-192621, which exhibit difference in selectivity for ET(A) and ET(B) receptors. In this report, we compare the potency and selectivity of these four antagonists in inhibiting (125)I-labelled ET-1 binding to cloned human ET(A) and ET(B) receptors, and in blocking ET-1-induced functional responses (arachidonic acid release and phosphatidylinositol hydrolysis).

Animals↗