PubMed Health⌕ Search

Biomedical subjects

Dan Xu

Publications and source records attributed to Dan Xu.

At least 19 recordsLinked to original sources
PubMed2006

Protective effect of verapamil on multiple hepatotoxic factors-induced liver fibrosis in rats.

The purpose of the present work was to investigate the effect of verapamil on liver fibrosis induced by multiple hepatotoxic factors in rats. Male Wistar rats were divided into a normal control group, a liver fibrosis model control group, and verapamil groups with different dosages. Multiple hepatotoxic factors including carbon tetrachloride (CCl(4)), ethanol and high cholesterol were used to make the animal model of liver fibrosis. The parameters of serum l-alanine aminotransferase (ALT), liver malondialdehyde and hydroxyproline contents were measured. Samples of the liver obtained by biopsy were subjected to histological and immunohistochemical studies for the expressions of alpha-smooth muscle actin (alpha-SMA) and transforming growth factor-beta(1) (TGF-beta(1)). Results showed that verapamil induced a dose-dependent decrease of serum ALT, liver malondialdehyde and hydroxyproline compared with liver fibrosis model control. Verapamil reduced hepatocyte degeneration and necrosis, and delayed the formation of liver fibrosis. The levels of expression of alpha-SMA and TGF-beta(1) in the hepatic tissue of three of the verapamil-treated groups were significantly less than those of the liver fibrosis model control group. The results showed that verapamil acts against the formation of liver fibrosis, the mechanism might be due to a protective effect for hepatocytes and through decreasing TGF-beta(1) to block the activation of hepatic stellate cells (HSCs) and collagen gene expression.

Actins↗
PubMed2006

Truncation effects in SENSE reconstruction.

Finite sampling is an important practical issue in Fourier imaging systems. Although data truncation effects are well understood in conventional Fourier imaging where a single uniform receiver channel is used for data acquisition, this issue is not yet fully addressed in parallel imaging where an array of nonuniform receiver channels is used for sensitivity encoding to enable sub-Nyquist sampling of k-space. This article presents a systematic analysis of the problem by comparing the truncation effects in parallel imaging with those in conventional Fourier imaging. Specifically, it derives a convolution kernel function to characterize the truncation effects, which is shown to be approximately equal to that associated with the conventional Fourier imaging scheme. This article also describes a set of conditions under which significant differences between the truncation effects in parallel imaging and conventional Fourier imaging occur. The results should provide useful insight into interpreting and reducing data truncation effects in parallel imaging.

Fourier Analysis↗
PubMed2006

Limited role for CD4+ T-cell help in the initial priming of Trypanosoma cruzi-specific CD8+ T cells.

Immune control of the protozoan parasite Trypanosoma cruzi requires the activation of both CD4+ and CD8+ T cells. We recently identified two T. cruzi trans-sialidase peptides that are targets of approximately 30% of all CD8+ T cells during acute T. cruzi infection in mice. To determine whether CD4+ T cells are required for generation of these dominant CD8+ T-cell responses, major histocompatibility complex class II (MHC II)-deficient mice were infected with the Brazil strain of T. cruzi and examined for the generation of antigen-specific CD8+ T cells. Strong trans-sialidase TSKB18- and TSKB20-specific CD8+ T-cell responses were generated in both the presence and the absence of CD4+ help. However, the magnitudes of the immunodominant TSKB20-specific CD8+ T-cell responses detectable using class I MHC-peptide tetramers were consistently lower in the blood and spleens of MHC II-deficient mice. Spleen cells from infected MHC II-deficient mice produced gamma interferon after in vitro stimulation with T. cruzi peptides at levels similar to those in wild-type mice, and MHC II-deficient mice displayed strong T. cruzi peptide-specific cytotoxic T-lymphocyte activity in vivo. Thus, primary CD8+ T-cell responses in experimental T. cruzi infection are generated in the absence of CD4+ T cells, providing further evidence that T. cruzi directly activates and licenses antigen-presenting cells. Nevertheless, unhelped CD8+ T cells in T. cruzi-infected mice fail to reach the frequencies achieved in the presence of CD4 T-cell help and are unable to prevent acute-phase death of these mice.

Animals↗
PubMed2006

Mechanical strain-induced c-fos expression in pulmonary epithelial cell line A549.

Pulmonary epithelial cells are exposed to mechanical strain during physiological breathing and mechanical ventilation. It was not clear which style was more related with cell mechanotransduction. c-fos is known to be a component of a transcription factor, activator protein-1, which is induced by oxidative stress. The regulatory pathways involved in the rapid response of the AP-1 transcription factor, c-fos, to mechanical load in the human pulmonary epithelial cell line A549 were investigated using a four-point bending model. In an effort to better understand what processes are involved in mechanotransduction, we have examined whether and how soon c-fos induction occurs in human A549 shortly after the application of the different mechanical strains stimuli.

Cell Line↗
PubMed2006

[Non-infectious pulmonary complications after allogeneic hematopoietic stem cell transplantation: analysis of 17 cases].

OBJECTIVE: To analyze the clinical feature, cause, treatment and outcome of late onset non-infectious pulmonary complications (LONIPC) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). METHODS: The clinical data of 17 patients with malignant hematological diseases who survived for at least 3 months and suffered from LONIPC after allo-HSCT were retrospectively analyzed. RESULTS: The incidence of LONIPC was 17.7% in allo-HSCT recipients. The median of onset of respiratory symptoms was 6.5 months (3-13.5 months). Seven patients came down with LONIPC during fast tapering of cyclosporine A prophylaxis and 15 patients had already chronic graft versus host disease (cGVHD) before the occurrence of respiratory symptoms. The initial symptoms were non-productive cough and dyspnoea in all patients; five of them had low grade or moderate fever. CT scans revealed patchy ground-glass opacities, irregular patchy consolidation, band-like opacities, and micronodular densities. Histological examination of transbronchial biopsy showed infiltration of lymphocyte and monocytes in interstitium, peribronchiolar fibrosis and alveoli pulmonis obliteration. The response rate of corticosteroids in addition to cyclosporine therapy was 70.6%. Treatment beginning at the early stage was more effective than that beginning late. The mortality rate of LONIPC was 35.3%. Chest CT scanning showed lung fibrosis in the patients with protracted LONIPC. CONCLUSION: The clinical manifestations and radiological changes of LONIPC are non-specific. The diagnosis is made by combination of functional and histological examinations and exclusion of pathogen infection. Examination of transbronchial biopsy is of significance for the diagnosis. LONIPC may be considered as pathognomonic of cGVHD in the lung of patients after allo-HSCT; and cGVHD should be regarded as a useful diagnostic proof for LONIPC. Earlier treatment with corticosteroids and maintenance treatment may result in improved survival and decrease of the fibrotic residue.

Adolescent↗
PubMed2006

The correlation of reproduction-related gene expression with germ cell number in DM and PLL gilts.

In this study, the ovarian germ cell number was counted in 3-week-old Duroc x Meishan (DM, n=30) and PIC x (Landrace x Large White) (PLL, n=53) gilts, and the mRNA expression levels of four reproduction-related genes were investigated by quantitative RT-PCR. Correlation of germ cell number with the expression level of these genes was analyzed. Results showed that the germ cell number of DM was significantly higher than that of PLL gilts (P<0.01), although there was no significant difference between the ovarian weight of DM and PLL gilts (P=0.269). No significant correlation existed between germ cell number and ovarian weight in the two gilt groups (R=0.335, P=0.07; R=0.119, P=0.398, respectively). A significant correlation was found between the germ cell number and expression level of ESR and IGF1R mRNA in DM gilts (R=0.648, P<0.05; R=0.757, P<0.01, respectively), but the correlation between the germ cell number and expression level of FSHR and INHBA mRNA did not reach statistical significance. Significant correlation was found between the germ cell number and the expression level of ESR, FSHR, and IGF1R mRNA in PLL gilts (R=0.435, P<0.01; R=0.438, P<0.01; R=0.292, P<0.05, respectively), but not with INHBA mRNA in PLL gilts.

Animals↗
PubMed2006

On the number of rectangular tilings.

Adaptive multiscale representations via quadtree splitting and two-dimensional (2-D) wavelet packets, which amount to space and frequency decompositions, respectively, are powerful concepts that have been widely used in applications. These schemes are direct extensions of their one-dimensional counterparts, in particular, by coupling of the two dimensions and restricting to only one possible further partition of each block into four subblocks. In this paper, we consider more flexible schemes that exploit more variations of multidimensional data structure. In the meantime, we restrict to tree-based decompositions that are amenable to fast algorithms and have low indexing cost. Examples of these decomposition schemes are anisotropic wavelet packets, dyadic rectangular tilings, separate dimension decompositions, and general rectangular tilings. We compute the numbers of possible decompositions for each of these schemes. We also give bounds for some of these numbers. These results show that the new rectangular tiling schemes lead to much larger sets of 2-D space and frequency decompositions than the commonly-used quadtree-based schemes, therefore bearing the potential to obtain better representation for a given image.

Algorithms↗
PubMed2006

Identification and characterization of Trichoplusia ni furin truncated mutant.

We report a new prohormone convertase gene of insect origin, Trichoplusia ni furin, which was cloned from BTI-Tn-5B-4 (Tn5) insect cells. We constructed a truncated mutant that lacked Cys-rich repeated segments. Using baculovirus expression system and standard enzymatic assay, we obtained recombinant Tn furin and evaluated aspects of its function.

Animals↗
PubMed2006

[The prognostic value of hyponatremia in patients with acute myocardial infarction].

OBJECTIVE: To evaluate the prognostic significance of hyponatremia in patients with AMI. METHODS: The study population consisted of 670 patients with AMI in coronary care unit in our hospital from January 2003 to December 2004. The patients were designed into three groups according to serum sodium concentration within twenty four to forty eight hours following the onset of AMI: Group A. Na(+) > or = 135 mmol/L; Group B. Na(+) 120-135 mmol/L; Group C. Na(+) < or = 120 mmol/L. The data of myocardial enzymes, myocardial infarction size, heart function and inhospital mortality were analyzed retrospectively. RESULTS: 1. The inhospital mortality of each group: group A was 7.6% (17/225), group B was 8.1% (34/421), group C was 33.3% (8/24). The difference between group C and group B or group A was significant. The P value was little than 0.05. 2. Activities of serum creatine phosphatase kinase and serum creatine phosphatase kinase isoenzymes and myocardial infarction sizes in each group were different (P < 0.05). 3. 59 cases of all died and 611 cases of all recovered in duration of hospital stay. Serum sodium concentrations of the recovered group were (133.00 +/- 5.25) mmol/L, and that of the died group were (122.00 +/- 7.25) mmol/L (P < 0.01). 4. In a multivariate logistic regression analysis, hyponatremia was associated with 30-day mortality in patients with AMI. In analysis of the association between the degree of hyponatremia and outcome, we observed that the risk of 30-day mortality increased with the severity of hyponatremia. CONCLUSION: Hyponatremia may be one of the important markers that predict a worse prognosis in patients with AMI.

Adult↗
PubMed2006

[A comparative study of unrelated donor bone marrow transplantation and peripheral blood stem cell transplantation for their therapeutic effects on leukemia].

OBJECTIVE: To compare the effect of unrelated donor bone marrow (BM) transplantation and peripheral blood stem cell (PBSC) transplantation in light of hemopoietic reconstitution, immune reconstitution, infection, incidence of graft-versus-host disease (GVHD) and other complications in patients with leukemia. METHODS: The clinical outcomes of 16 patients receiving unrelated PBSC graft mobilized by granulocyte colony-stimulating factor (G-CSF) were compared with 30 patients receiving unrelated BM transplantation. RESULTS: Engraftment was achieved in 97.83% of the total patients. Compared with BM transplantation group, PBSC graft contained significantly more nucleated cells (P=0.000), resulting in a significantly shorter time-to-neutrophil (16.21-/+3.09 vs 12.81-/+4.15 days, P=0.003) and platelet engraftment (20.31-/+7.19 vs 15.50-/+6.91 days, P=0.035). T cell reconstitution differed little between the two groups at different time points after transplantation. The incidences of early-stage infection were 37.50% and 50.00% (P=0.644) in the PBSC and BM groups, respectively. In PBSC and BM groups, the incidences of grades I to IV acute GVHD (aGVHD) were 56.25% and 70.00% (P=0.456), 18.75% and 13.79% (P=0.661) for grades III to IV aGVHD, and 30.77% and 36.36% (P=0.413) for chronic GVHD (cGVHD), respectively. The nonrelapse transplant-related mortality (TRM) rates were 18.75% in PBSC group and 33.33% in BM group (P=0.295). The relapse occurred in 18.75% and 6.90% (P=0.226) of the patients in the two groups, respectively, and the 2-year disease-free survival (DFS) rates were 62.19% and 56.23% (P=0.615), respectively. CONCLUSION: G-CSF-mobilized PBSCs allow more rapid engraftment in unrelated donor recipients in comparison with conventional BM, but T cell reconstitution and the incidence of infection between the two groups differ little, nor are there significant differences in the incidence or severity of aGVHD and cGVHD, nonrelapse TRM or 2-year DFS rates between the two groups.

Adolescent↗
PubMed2006

[Patterns and prognostic value of resection margin involvement and lateral pelvic metastases for patients with rectal cancer].

OBJECTIVE: To study the patterns and prognostic value of resection margin involvement and lateral pelvic metastases, providing surgeons with pathologic proofs of tumor spread within the studied areas. METHODS: Large tissue slices of 62 specimens from patients with rectal cancer were used in the pathologic study and the outcomes were followed. RESULTS: Compared with patients without margin involvement, patients with circumferential margin involvement (CMI), seen in 8 cases (12.9%), had poorer postoperative survival (P=0.003). The 12 patients (19.4%) with lateral pelvic metastases suffered poorer survival, compared with those without lateral pelvic metastases (P=0.026). Eight patients (66.7%) were diagnosed to have single lateral pelvic region involved, while the other 4 had multiple regions involved. The incidence of lateral metastases differed among regions, with higher occurrence in the root of middle rectal artery (6/12, 50.0%), area of the internal iliac artery (4/12, 33.3%) and the obturator region (3/12, 25.0%). CONCLUSION: Occurrence of CMI or lateral metastases in rectal cancer patients predispose poor survival, thus a more radical clearance and postoperative adjuvant therapy are recommended.

Adult↗
PubMed2006

[Comparison of clinical outcomes between unrelated donor peripheral blood stem cell transplantation and bone marrow transplantation for leukemia].

OBJECTIVE: To compare the hemopoietic reconstitution, immune reconstitution, infection, incidence of graft-versus-host disease (GVHD) and clinical outcome between unrelated donor peripheral blood stem cell (PBSC) transplantation and bone marrow (BM) transplantation for leukemias. METHODS: The clinical results of 21 leukemia patients receiving G-CSF mobilized PBSC graft from unrelated donors were compared with that of 32 patients receiving unrelated BM transplants. RESULTS: Compared with BM grafts, the PBSC graft contained significantly more nucleated cells (P = 0.000), and resulted in a significantly shorter time-to-neutrophil (12.43 +/- 3.67 vs 16.16 + 2.99 days) and platelet engraftment (14.67 +/- 6.19 vs 21.23 +/- 8.25 days), (P = 0.000 and 0.003, respectively). T cell reconstitution between the two groups differed little after transplantation. The incidences of early-stage infection (42.86% vs 53.13%), the probabilities of acute graft-versus-host disease (aGVHD) (61.90% vs 71.88%), the grades III to IV aGVHD (23.81% vs 15.63%), the chronic GVHD (47.06% vs 43.48%) and the probabilities of relapse (6.90% vs 12.50%) between PBSC and BM groups all has no statistical significance (NS). The 2-year disease free survival (DFS) rates of the two groups were (50.14 +/- 12.00) % and (59.81 +/- 8.99)%, respectively also have no NS. CONCLUSION: G-CSF-mobilized unrelated donor PBSCs engraft more rapidly in the recipients as compared with conventional BM grafts. The T cell reconstitution, the incidence of infection, the incidence and severity of aGVHD and cGVHD, and the 2-year DFS rates between the two groups all have no significant differences.

Adolescent↗
PubMed2005

Application of perceptual difference model on regularization techniques of parallel MR imaging.

Parallel magnetic resonance imaging through sensitivity encoding using multiple receiver coils has emerged as an effective tool to reduce imaging time or to improve image SNR. The quality of reconstructed images is limited by the inaccurate estimation of the sensitivity map, noise in the acquired k-space data and the ill-conditioned nature of the coefficient matrix. Tikhonov regularization is a popular method to reduce or eliminate the ill-conditioned nature of the problem. In this approach, selection of the regularization map and the regularization parameter is very important. Perceptual difference model (PDM) is a quantitative image quality evaluation tool that has been successfully applied to varieties of MR applications. High correlation between the human rating and PDM score shows that PDM should be suitable to evaluate image quality in parallel MR imaging. By applying PDM, we compared four methods of selecting the regularization map and four methods of selecting the regularization parameter. We found that a regularization map obtained using generalized series (GS) together with a spatially adaptive regularization parameter gave the best reconstructions. PDM was also used as an objective function for optimizing two important parameters in the spatially adaptive method. We conclude that PDM enables one to do comprehensive experiments and that it is an effective tool for designing and optimizing reconstruction methods in parallel MR imaging.

Brain Mapping↗
PubMed2005

Solvothermal synthesis of CdS nanowires in a mixed solvent of ethylenediamine and dodecanethiol.

CdS nanowires with an average diameter of 25 nm and lengths of 20-40 mum have been solvothermally synthesized in a mixed solvent of ethylenediamine and dodecanethiol at 180 degrees C. The time-dependent examinations reveal that the formation process of CdS nanowires involves two sequential processes: a short-period solid-solid transformation process in the initial stage and a long-period Ostwald ripening process. The effect of both the volume ratios between the two components of the solvent and the reaction temperatures on the nanowire growth has also been investigated in detail. The results of the photoluminescence and UV-vis spectroscopy measurements reveal that the as-prepared CdS nanowires show a quantum confinement effect.

Journal Article↗
PubMed2005

Growth of Cu2S ultrathin nanowires in a binary surfactant solvent.

We demonstrate a facile solution-phase method for the synthesis of single-crystal, high aspect ratio, and ultrathin nanowires of hexagonal-phase Cu2S by thermal decomposition of CuS2CNEt2 in a mixed surfactant solvent of dodecanethiol and oleic acid at 160 degrees C. Cu2S nanowires can be controllably synthesized with a diameter as thin as 1.7 nm and length up to tens of micrometers; they are usually aligned in the form of bundles with a thickness of hundreds of nanometers. Based on the experimental results, the formation mechanism of the ultrathin nanowires has been properly proposed. Some key synthetic parameters, which have a significant effect on the sizes and shapes of the products, have also been investigated in detail. UV-vis spectroscopy measurement reveals that the resultant ultrathin nanowires show a strong quantum size effect.

Journal Article↗
PubMed2005

Drosophila neuropeptide F and its receptor, NPFR1, define a signaling pathway that acutely modulates alcohol sensitivity.

Alcohol is likely to affect neurons nonselectively, and the understanding of its action in the CNS requires elucidation of underlying neuronal circuits and associated cellular processes. We have identified a Drosophila signaling system, comprising neurons expressing neuropeptide F (NPF, a homolog of mammalian neuropeptide Y) and its receptor, NPFR1, that acutely mediates sensitivity to ethanol sedation. Flies deficient in NPF/NPFR1 signaling showed decreased alcohol sensitivity, whereas those overexpressing NPF exhibited the opposite phenotype. Furthermore, controlled functional disruption of NPF or NPFR1 neurons in adults rapidly confers resistance to ethanol sedation. Finally, the NPF/NPFR1 system selectively mediates sedation by ethanol vapor but not diethyl ether, indicating that the observed NPF/NPFR1 activity reflects a specialized response to alcohol sedation rather than a general response to intoxication by sedative agents. Together, our results provide the molecular and neural basis for the strikingly similar alcohol-responsive behaviors between flies and mammals.

Anesthetics, Inhalation↗