Search PubMed⌕ Search

Biomedical subjects

Dongmei Xiao

Publications and source records attributed to Dongmei Xiao.

13 recordsLinked to original sources
PubMed2006

Competition between plasmid-bearing and plasmid-free organisms in a chemostat with nutrient recycling and an inhibitor.

The asymptotic behavior of solutions of a model for competition between plasmid-bearing and plasmid-free organisms in the chemostat with two distributed delays and an external inhibitor is considered. The model presents a refinement of the one considered by Lu and Hadeler [Z. Lu, K.P. Hadeler, Model of plasmid-bearing plasmid-free competition in the chemostat with nutrient recycling and an inhibitor, Math. Biosci. 167 (2000) p. 177]. The delays model the fact that the nutrient is partially recycled after the death of the biomass by bacterial decomposition. Furthermore, it is assumed that there is inter-specific competition between the plasmid-bearing and plasmid-free organisms as well as intra-specific competition within each population. Conditions for boundedness of solutions and existence of non-negative equilibrium are given. Analysis of the extinction of the organisms, including plasmid-bearing and plasmid-free organisms, and the uniform persistence of the system are also carried out. By constructing appropriate Liapunov-like functionals, some sufficient conditions of global attractivity to the extinction equilibria are obtained and the combined effects of the delays and the inhibitor are studied.

Bioreactors↗
PubMed2006

Procedures for a dynamical system on {0,1}n with DNA molecules.

In this paper, an improved form of DNA representations of elements in {0,1}n, which was first proposed by Fujiwara et al. [Fujiwara, A., Matsumoto, K., Chen, W., 2004. Procedures for logic and arithmetic operations with DNA molecules. Int. J. Found. Comput. Sci. 15, 461-474], is given. Using this improved representations, a procedure for cycling shift is proposed, and this procedure can be implemented in O(1) lab steps theoretically. Based on the operation for cycling shift, dynamic behavior of an operator on {0,1}n is investigated by DNA molecules.

Algorithms↗
PubMed2005

Bombesin regulates cyclin D1 expression through the early growth response protein Egr-1 in prostate cancer cells.

Our previous studies indicate that the activation of mitogen-activated protein kinase (MAPK) pathway is involved in bombesin-induced cell proliferation in prostate cancer cells. Cyclin D1 is a critical regulator involved in cell cycle progression through the G1 phase into the S phase, thereby contributing to cell proliferation. Mostly, mitogen-stimulated expression of cyclin D1 is attributed to the extracellular signal-regulated kinase (ERK) activation. Here, we found that bombesin induced human cyclin D1 expression on both mRNA and protein levels in DU-145 prostate cancer cells. Mutational analyses showed that bombesin-enhanced cyclin D1 transcription required the binding of nuclear proteins to the -143 to -105 region of the human cyclin D1 promoter, which contains binding sites for transcription factors Sp-1 and early growth response protein (Egr-1). Do novo protein synthesis was requisite for bombesin-induced cyclin D1 expression. Further studies showed Egr-1 was induced upon bombesin stimulation. The induction of Egr-1 expression and its binding to the cyclin D1 promoter were essential for bombesin-enhanced cyclin D1 transcription. Inhibition of MAPK pathway with either the MEK1 inhibitor PD98059 or a dominant-negative Ras mutant, RasN17, abolished bombesin-induced cyclin D1 activation. Taken together, bombesin-induced cyclin D1 expression in prostate cancer cells is mediated by Egr-1 activation and the interaction of Egr-1 with the Egr-1/Sp1 motif of the cyclin D1 promoter through the activation of MAPK pathway. These findings represent a novel mechanism of bombesin-dependent stimulation of mitogenesis by regulating directly the cell cycle in prostate cancer.

Bombesin↗
PubMed2005

[Stem respiration of Pinus koraiensis in Changbai Mountains].

In this paper, soil respiration chamber, a simple and precise method, was used to measure the stem respiration of trees. LI-6400-09 respiration chamber serving as a system is usually used in soil respiration, but we made polyvinyl chloride (PVC) collar and fixed it on the stem surface to measure the stem respiration. From May to October 2003, the stem respiration of Pinus koraiensis, the dominant tree species in Changbai Mountain, was measured in different time and different places using this technique. Meanwhile, the temperatures in the stems and in the forests were measured. The results showed that the stem respiration rate had a remarkably seasonal tendency with a single peak, the maximum was in August and the minimum was in February. The stem respiration rate had an exponential relationship with stem temperature, and the curve exponential regressions for stem respiration rate and temperature factor of trees with big DBH were better than those with small DBH. The stem respiration in different DBH trees was higher in the south stem face than that in the north stem face, and the variance of respiration rate between south and north decreased with a decrease of DBH trees. During the growing season from May to October, the average maintenance respiration accounted for 63.63% in different DBH trees, and the maintenance respiration contribution to total respiratory consumption increased with increasing DBH, which was 66.76, 73.29% and 50.84%, respectively. The stem respiration Q10 values ranged from 2.56-3.32 in different DBH of trees, and the seasonal tendency for stem R, and Rm in different DBH of trees was obtained by using respiration Q10. Therefore, the differences between different parts of stem and different DBH of trees should be considered in estimating the respiration model in ecosystem.

Air↗
PubMed2005

[Effects of simulated water stress on photosynthesis rate and WUE of Fraxinus mandshurica].

This paper studied the photosynthesis characteristics and water use efficiency (WUE) of Fraxinus mandshurica under three years simulated water stresses 85%-100% (CK), 65%-85% (MW) and 45%-65% (LW) of field water-holding capacity. The results showed that in comparing with CK, the photosynthesis rate and WUE were higher in treatment MW, but decreased by 7.26% and 1.13%, respectively in treatment LW, indicating that Fraxinus mandshurica could fully exert its photosynthesis potentiality under long-term medium water stress, and was more resistant to moderate than to critical water stress. In treatment CK, the diurnal change of Pn and WUE was a single and a double peak curve, respectively, while in treatments MW and LW, the diurnal change of Pn was a double peak curve, but that of WUE had no significant peak, which correlated not only to the physiological characteristics of Fraxinus mandshurica under different water stress, but also to the diurnal change of environmental factors.

Ecosystem↗
PubMed2005

[Effects of exogenous nitric oxide on drought-resistance of poplar].

This paper studied the effects of NO donor sodium nitroprusside (SNP) on the photosynthesis and active oxygen-scavenging enzyme activities of poplar leaves under drought stress. The results showed that SNP had a remarkable positive effect on leaf water content. When the SNP level was > 500 micromol.L(-1), no significant difference in leaf water content was found between SNP treatments. SNP could increase photosynthesis rate, photochemical efficiency of PSII (F(v)/F(m)), and ratios of F(m)/F(o) and F(v)/F(o), but the effects decreased with the prolongation of drought stress. The SOD and POD activities of poplar leaves were higher in short time (1 h) drought stress than in longer time (3 h) one. The activity of POD was increased by SNP, while that of SOD was changed little. With increasing SNP level, the POD and SOD activities first increased and then decreased. The NO donor could retard the accumulation of active oxygen through inducing POD and SOD activities, alleviate the effects of drought stress on photosynthesis, and increase the drought-resistance of poplar.

Disasters↗
PubMed2004

Transcriptional activation of the human gastrin-releasing peptide receptor gene in gastrointestinal and prostatic epithelial cancer cells.

The mammalian gastrin-releasing peptide receptor (GRP-R) belongs to the superfamily of G protein-coupled receptors and mediates actions of the regulatory GRP and bombesin, the amphibian homolog of GRP. Owing to its frequent ectopic expression in some epithelial human malignancies, such as cancers of the colon, lung, and prostate, ligand-specific receptor activation may initiate intracellular signals of cell proliferation, differentiation and migration in this context. Because the underlying molecular mechanisms of aberrant human GRP-R (hGRP-R) expression in tumorigenesis remain unknown, we examined in this study the transcriptional activation of hGRP-R in gastrointestinal and prostate cancer cells, which natively express functional hGRP-R. Using various hGRP-R promoter mutants cloned into a luciferase reporter plasmid, transient transfection studies demonstrated robust transcriptional activation in gastrointestinal and prostate cancer cells. Although our study revealed distinct patterns of transcriptional hGRP-R activation in gastrointestinal and prostate cancer cells, genomic sequences between 97 and 247 bp upstream of the major RNA initiation site appear to be of particular significance for basal transcriptional hGRP-R activation. Based on this study, future examination of transcription factor interaction with the hGRP-R promoter will be important to identify molecular mechanisms of hGRP-R regulation relevant in human cancers that express functional receptor sites

Carcinoma↗
PubMed2004

[Nitric oxide, a signaling component of ABA-induced stomatal closure].

The present study provided the evidence that exogenous NO and ABA regulated the stomatal movement in poplar leaves. It showed that different levels of SNP and ABA induced the stomatal closure in detached leaves. NO enhanced stomatal closure that induced by ABA. The effect of NO and ABA on stomatal closure was suppressed by c-PTIO, a specific NO scavenger. It was confirmed that NO involved in ABA-mediated stomatal movement. The activities of POD were dramatically inhibited, but those of SOD hardly decreased in different levels of SNP and ABA treatment. However, in vitro experiments indicated that the activities of POD were dramatically inhibited by NO, but not ABA. The results demonstrated that NO mediated ABA-induced stomatal closure of trees, and was a signaling component of ABA-induced stomatal closure.

Abscisic Acid↗
PubMed2004

[Soil N2O and CH4 fluxes in broad-leaved Korean pine forest of Changbai Mountains].

The soil N2O and CH4 fluxes in the broad-leaved Korean pine forest of Changbai Mountains under two treatments were measured by static chamber-gas chromatograph. The results showed that litter significantly influenced N2O emission and CH4 uptake, and the effect efficiency was 36.9% and 23.4%, respectively. The N2O emission fluxes of the two treatments showed similar seasonal variations, with the highest in spring, higher in summer, and lower in autumn and winter. Furthermore, their diurnal variations were the same, the maxima both occurred at 18 o'clock, and the minima appeared at 12 o'clock and 14 o'clock. As for CH4 uptake fluxes, their seasonal variations were similar. The CH4 uptake fluxes were significantly higher in summer and autumn than in spring and autumn, and their diurnal variations were also the same, both went up from 14 o'clock to 18 o'clock and then started to go down until 6 o'clock. The results also indicated that soil N2O emission fluxes were negatively linear-correlated to CH4 uptake fluxes in the broad-leaved Korean pine forest.

China↗
PubMed2003

Activation of extracellular signal-regulated kinase mediates bombesin-induced mitogenic responses in prostate cancer cells.

Bombesin and its mammalian homologue gastrin-releasing peptide have been shown to be highly expressed and secreted by neuroendocrine cells in prostate cancer, and are thought to be related to the carcinogenesis and progression of this disease. We found, in this study, bombesin specifically induced mitogen-activated protein (MAP) kinase activation as shown by increased extracellular regulated kinase (ERK) phosphorylation and epidermal growth factor (EGF) receptor transactivation in prostate cancer cells, which express functional gastrin-releasing peptide receptor. The transactivation of EGF receptor was required for bombesin-induced ERK phosphorylation. Furthermore, non-receptor tyrosine kinase Src and cellular Ca2+ were shown to be involved in bombesin-induced EGF receptor transactivation and ERK phosphorylation. Inhibition of either EGF receptor transactivation or ERK activation blocked bombesin-induced DNA synthesis in these cells. Taken together, these data suggest bombesin may act as a mitogen in prostate cancer by activating MAP kinase pathway via EGFR transactivation.

Animals↗
PubMed2002

GRP receptor-mediated immediate early gene expression and transcription factor Elk-1 activation in prostate cancer cells.

Bombesin (BN) and its mammalian homologue gastrin-releasing peptide (GRP) have been shown to play an important role in human cancer as autocrine and paracrine growth factors. Prostatic neuroendocrine cells are thought to secrete these regulatory peptides and they may therefore interact with their specific, aberrantly expressed GRP receptor (GRP-R) in prostate cancer. In this study, we investigated the effect of BN on immediate early gene expression in two androgen-independent prostate cancer cell lines DU-145 and PC-3 with functional GRP receptor. We found that BN induced c-fos mRNA expression in both cell lines in a time-dependent manner. In contrast, c-jun mRNA was only modestly induced in DU-145 cells but not at all in PC-3 cells. On the protein level, we detected BN-induced stimulation of the c-fos gene product but not of c-jun protein. Sustained increase of the c-myc gene product was detectable in PC-3 but not in DU-145 cells. Concurrently, we demonstrated BN-dependent activation of the transcription factor Elk-1 and significant increase of cell proliferation in both prostate cancer cell lines. Taken together, these data suggest that BN acts as a mitogen in prostate cancer and this might be associated with the activation of the transcription factor Elk-1 and the immediate early gene c-fos.

Bombesin↗
PubMed2002

Human gastrin-releasing peptide receptor mediates sustained CREB phosphorylation and transactivation in HuTu 80 duodenal cancer cells.

The G protein-coupled human gastrin-releasing peptide receptor (hGRP-R) is frequently found aberrantly expressed in human cancers of the colon, stomach, and lung, and its ligand-specific activation has been implicated in cell proliferation and differentiation. Here, we demonstrated hGRP-R activation stimulated sustained cyclic AMP response element binding protein (CREB) phosphorylation and transactivation in duodenal cancer cells through a protein kinase C and partially p38 mitogen-activated protein kinase-dependent pathway. In contrast, intracellular calcium, ERK1/2, protein kinase A, and PI3 kinase were not involved. This novel signaling mechanism might be of importance for regulation of CREB-dependent gene expression in human cancer expressing functional hGRP-R.

Bombesin↗