Biomedical subjects

X Wen

Publications and source records attributed to X Wen.

At least 73 records · Page 4Linked to original sources

PubMed1998

Large-scale temporal gene expression mapping of central nervous system development.

We used reverse transcription-coupled PCR to produce a high-resolution temporal map of fluctuations in mRNA expression of 112 genes during rat central nervous system development, focusing on the cervical spinal cord. The data provide a temporal gene expression "fingerprint" of spinal cord development based on major families of inter- and intracellular signaling genes. By using distance matrices for the pair-wise comparison of these 112 temporal gene expression patterns as the basis for a cluster analysis, we found five basic "waves" of expression that characterize distinct phases of development. The results suggest functional relationships among the genes fluctuating in parallel. We found that genes belonging to distinct functional classes and gene families clearly map to particular expression profiles. The concepts and data analysis discussed herein may be useful in objectively identifying coherent patterns and sequences of events in the complex genetic signaling network of development. Functional genomics approaches such as this may have applications in the elucidation of complex developmental and degenerative disorders.

Animals↗

PubMed1998

Effect of baffles and a louvered bypass on the airflow and the convective patterns of contaminant inside a fume hood.

Various numerical predictions are given for the containment testing of fume hoods with internal baffles of different size and at different locations and with a louvered bypass. The numerical predictions were compared with experimental data and a fairly good agreement for the air velocity was found, although there was only qualitative agreement for the concentration of the contaminant. It was found that the level of contaminant leakage at the working aperture depended not only on the size of the recirculating airflow behind the fume hood sash but also on the blockage caused by the baffles inside the fume hood near the exhaust duct. Finally, some new suggestions for the design of the fume hood have been proposed. However, before implementing these suggestions it is essential that either experimental testing be performed, or the cost-effective alternative of using numerical predictions for containment testing, to determine accurately the level of contaminant leakage from the working aperture.

Air Movements↗

PubMed1998

The NH2 terminus of the herpes simplex virus type 1 regulatory protein ICP0 contains a promoter-specific transcription activation domain.

The transcriptional program of herpes simplex virus is regulated by the concerted action of three immediate-early (alpha) proteins, ICP4, ICP27, and ICP0. The experiments described in this study examine the role of the acidic amino terminus (amino acids 1 to 103) of ICP0 in gene activation. When tethered to a DNA binding domain, this sequence activates transcription in the yeast Saccharomyces cerevisiae. Deletion of these amino acids affects the ability of ICP0 to activate alpha-gene promoter reporters in transient expression assays, while it has little or no effect on a beta- and a gamma-gene reporter in the same assay. Viruses that express the deleted form of ICP0 (ICP0-NX) have a small-plaque phenotype on both Vero cells and the complementing cell line L7. Transient expression and immunofluorescence analyses demonstrate that ICP0-NX is a dominant negative form of ICP0. Immunoprecipitation of ICP0 from cells coinfected with viruses expressing ICP0-NX and ICP0 revealed that ICP0 oligomerizes in infected cells. These data, in conjunction with the finding that ICP0-N/X is dominant negative, provide both biochemical and genetic evidence that ICP0 functions as a multimer in infected cells.

Animals↗

PubMed1998

Intestinal inflammation reduces expression of DRA, a transporter responsible for congenital chloride diarrhea.

The pathogenesis of diarrhea in intestinal inflammatory states is a multifactorial process involving the effects of inflammatory mediators on epithelial transport function. The effect of colonic inflammation on the gene expression of DRA (downregulated in adenoma), a chloride-sulfate anion transporter that is mutated in patients with congenital chloridorrhea, was examined in vivo as well as in an intestinal epithelial cell line. DRA mRNA expression was diminished five- to sevenfold in the HLA-B27/beta2m transgenic rat compared with control. In situ hybridization showed that DRA, which is normally expressed in the upper crypt and surface epithelium of the colon, was dramatically reduced in the surface epithelium of the HLA-B27/beta2m transgenic rat, the interleukin-10 (IL-10) knockout mouse with spontaneous colitis, and in patients with ulcerative colitis. Immunohistochemistry demonstrated that mRNA expression of DRA reflected that of protein expression in vivo. IL-1beta reduced DRA mRNA expression in vitro by inhibiting gene transcription. The loss of transport function in the surface epithelium of the colon by attenuation of transporter gene expression, perhaps inhibited at the level of gene transcription by proinflammatory cytokines, may play a role in the pathogenesis of diarrhea in colitis.

Animals↗

PubMed1998

[The effect of brain-derived neurotrophic factor on the rat electroretinography after pressure-induced ischemic injury].

Brain-derived neurotrophic factor (BDNF) or normal goat serum (NGS) was injected intravitreously in each 11 wistar albino rats two days before the induction of ischemia. Retinal ischemia was induced in 22 rats by increasing intraocular pressure to the threshold level which extinguished the electroretinography (ERG) b-wave individually, and maintaining for 90 minutes. The ERG b-wave of the BDNF-treated rats recovered to 80.5 +/- 24.4% of their normal amplitude three days after ischemia, while that of the NGS-treated rats recovered only to 11.1 +/- 5.3%. Statistic analysis showed that the recovery level of ERG b-wave after ischemia in the BDNF and NGS treated rats was significantly different (P < 0.01). The results suggest that BDNF could promote the recovery of the retinal electrophysiologic function from ischemia induced by high intraocular pressure.

Animals↗

PubMed1998

[Effect of -6 degrees bed-rest on T-lymphocyte proliferation and cytokines production in human].

In this study, the effect of -6 degrees head-down bed-rest on proliferation of T lymphocyte stimulated by phytohemagglutinin, a kind of polyclone T cell activators and cytokines production were observed. The results showed: after 2 d bed-rest, proliferation of T lymphocyte stimulated by phytohemagglutinin decreased significantly; the activity of interleukin-2 trended to decrease; the expression of interleukin-2 receptor tended to increase; the production of interleukin-6 decreased significantly. After 6 d bed-rest, T lymphocyte proliferation restored to normal; the activity of interleukin-2 and expression of interleukin-2 receptor had no change; the production of interleukin-6 decreased significantly. This result demonstrated that -6 degrees bed-rest can decrease T lymphocyte proliferation function, and this decrease may be caused by the reduction of cytokines secretion.

Adult↗

PubMed1998

[An observation on antiviral effect of IFN--alpha N1 (Wellferon) in patients with chronic hepatitis B].

In order to observe the antiviral effect of IFN-alpha N1(Wellferon, British Glaxowellcome Company) on CHB, each 50 cases of CHB were selected as the therapy group and the control group. The patients in the therapy group were administrated with 3MU of IFN-alpha N1 once a day for one week, and then 3MU of IFN-alpha N1 three times weekly for 11-23 weeks, whereas the patients in the control group did not receive any antiviral treatment. At 3 months, the serum alanine transaminsae(ALT) was decreased to normal level in 84%(42/50) cases of the therapy group, while only in 46% (23/50) cases of the control group (P < 0.01). The negative seroconversion rate of HBeAg was 56.7% (17/30) and 10.8% (4/37), of HBV DNA was 36.4%(12/33) and 5.9% (1/17) in therapy and control groups respectively. There was obvious difference in two groups. The results suggest that IFN-alpha N1 is satisfying antiviral drug for CHB patients or patients non-responsive to other IFNs.

Adult↗

PubMed1998

[Investigation of HGV infection in various populations in Guangxi].

In order to understand the situation of HGV infection in various populations in Liuzhou prefecture of Guangxi, Zhuangzu Autonomous Region, and also to compare the HGV, HBV, HCV infections between intravenous drug abusers and healthy persons (those for physical examination, the same below), the anti-HGV, -HCV and HBVM (HBsAg, HBsAb, HBeAg, HBeAb, HBcAb) were detected by ELA and, besides, tested further the 20 anti-HGV seropositive cases for HGV-RNA by RT-nPCR. The results showed that in the populations tested, the HGV seropositive rate was 9.8% (106/1079), separately they were 23.8% (5/21), 21.1% (23/109), 12.5% (6/48), 12.0% (6/50), 12.0% (20/166), 9.3% (3/32), 8.2% (34/413), 4.3% (6/140), and 3.0% (3/100) in liver cirrhosis, intravenous drug abusers, repeated blood and blood products transfused patients, hepatocellularcarcinoma patients, viral hepatitis, haemodialysis patients, healthy persons, paid blood donors and healthy pregnant women respectively. In intravenous drug abusers, the HGV, HBV, HCV infection rate were 21.2% (23/109), 75.3% (82/109) and 7.3% (8/109) respectively, while they were 8.2% (9/109), 20.1% (22/109), and 1.8% (2/109) in healthy persons respectively. These data showed that Liuzhou prefecture of Guangxi was HGV high epidemic area, HGV infection rate was higher in populations of intravenous drug abusers, viral hepatitis, liver cirrhosis and repeatedly blood and blood products transfused patients, even in pregnant women the HGV infection also occurred. There was a significant difference of HGV, HBV, HCV infection rates between intravenous drug abusers and healthy persons (P < 0.005).

Adult↗

PubMed1998

[Application of simple OMA system for rapid spectrochemical quantitative analysis to steel sample composition].

In this paper, the experimental method and characteristic of a simple optical multichannel analyzer (OMA) system used for rapid spectrochemical quantitative analysis was introduced. Mangangese and chromium contents in different steel samples were measured. The reliability of experimental results was discussed according to the mathematical statistics theory. Analytical results were compared with those of chemical and ICP analysis.

English Abstract↗

PubMed1998

[Research of eximer laser-excited fast speed spectrochemical analysis].

Experimental method including XeCl eximer Laser-excited, optical multichannel analyzer (OMA) combined with the simultaneous spectrum widen technique was introduced in this paper. We programed data acquisition software and tested alloy-steel sample. The acquisition result of 150nm simultaneous spectrum was showed. The charaterics and significances of our research were discussed.

English Abstract↗

PubMed1998

[A kind of method for measuring absorbance spectrum with dual beam light and one detector].

A kind of method of measuring spectral transmittivity with source compensated is introduced in this paper. It detects simultaneously intensity of source and transmission light with dual light road and one detector by means of the characters of selective frequence amplifing and coherent detection of a lock-in amplifier. The experimental result shows that the method is excellent on overcoming shake of a source and improving signal-to-noise ratio.

English Abstract↗

PubMed1998

Cluster analysis and data visualization of large-scale gene expression data.

The discovery of any new gene requires an analysis of the expression context for that gene. Now that the cDNA and genomic sequencing projects are progressing at such a rapid rate, high throughput gene expression screening approaches are beginning to appear to take advantage of that data. We present a strategy for the analysis for large-scale quantitative gene expression measurement data from time course experiments. Our approach takes advantage of cluster analysis and graphical visualization methods to reveal correlated patterns of gene expression from time series data. The coherence of these patterns suggests an order that conforms to a notion of shared pathways and control processes that can be experimentally verified.

Base Sequence↗

PubMed1998

Corrosion resistance and ion dissolution of titanium with different surface microroughness.

In vitro corrosion resistance and ion dissolution of commercial pure titanium with different surface microroughness are studied adopting constant potential meter and atomic absorption spectroscopy. In terms of the surface roughness, titanium samples are divided into 5 groups: smooth surface, machining surface, 2 different microroughness surfaces and macrorough surface. Each group contains three category samples under different treatments: natural oxidation (24 h exposure to air), oxidation under 400 degrees C (400 degrees C, 45 min thermal oxidation), oxidation under 700 degrees C (700 degrees C, 45 min thermal oxidation). In Hanks corrosion media, comparative studies through constant potential anode polarization curves and titanium release rates of the 5 groups of Ti samples demonstrates that oxidation under 400 degrees C best increase corrosion resistance and decrease ion release sharply, oxidation under 700 degrees C is better than natural oxidation. Ti samples with a different surface roughness all have good corrosion resistance and their corrosion resistance drop with the raising of surface roughness. Comparing with macrorough surface and machining surface, microrough surfaces have better corrosion resistance and a lower ion release rate which are similar to those of smooth surfaces. Moreover, the corrosion resistance of machining surface Ti is the lowest. It is hypothesized that surface treatment methods such as surface thermal oxidation, surface aging and so on will improve the corrosion resistance and decrease the ion release rate of rough surface effectively by increasing the thickness of surface protection film, improving its structural uniformity and facilitating the formation of ordered, compact surface protection film.

Biocompatible Materials↗

PubMed1997

Oct-1 and CCAAT/enhancer-binding protein (C/EBP) bind to overlapping elements within the interleukin-8 promoter. The role of Oct-1 as a transcriptional repressor.

Interleukin-8 (IL-8), a potent neutrophil chemoattractant, can be expressed at high levels by many different cell types after immune stimulation. In contrast, expression of IL-8 in these same cells is virtually absent in the unstimulated state, demonstrating the tight regulation of the IL-8 gene. Although much is known about how this gene is transcriptionally activated after immune stimulation, little is known about the regulation of the IL-8 promoter in the absence of immune activation. In this study we examine how the IL-8 promoter is transcriptionally regulated in the uninduced state and how these mechanisms are altered in response to immune stimulation by IL-1beta. Electrophoretic mobility shift assay and transfection studies show that the IL-8 promoter is transcriptionally regulated by both positive and negative elements. Although the nuclear factor-kappaB (NFkappaB) element regulates only inducible activity of the IL-8 promoter in response to stimulation with IL-1beta, the AP-1 and CCAAT/Enhancer-binding Protein (C/EBP) elements influence both basal and inducible activities. In contrast to these three positive regulatory elements, the binding of the ubiquitously expressed POU-homeodomain transcription factor, Oct-1, strongly represses transcriptional activity of the IL-8 promoter by binding independently to an element overlapping that of C/EBP.

Base Sequence↗

PubMed1997

Anatomical gradients in proliferation and differentiation of embryonic rat CNS accessed by buoyant density fractionation: alpha 3, beta 3 and gamma 2 GABAA receptor subunit co-expression by post-mitotic neocortical neurons correlates directly with cell buoyancy.

Development of the CNS occurs as a complex cascade of pre-programmed events involving distinct phases of cell proliferation and differentiation. Here we show these phases correlate with cells of specific buoyant densities which can be readily accessed by density gradient fractionation. Sprague-Dawley dams were pulse-labelled with bromodeoxyuridine (BrdU) and selected regions of embryonic (E) CNS tissues at E11-22 dissociated with papain into single-cell suspensions. Proliferative cell populations were assessed by anti-BrdU and propidium iodide staining using flow cytometry. Cell differentiation was evaluated using molecular and immunocytochemical probes against mRNAs and antigens differentiating the neuroepithelial, neuronal and glial cell lineages. The results show the emergence of distinctive spatiotemporal changes in BrdU+ populations throughout the CNS during embryonic development, which were followed by corresponding changes in the cellular distributions of antigens distinguishing specific cell types. Fractionation of neocortical cells using discontinuous Percoll gradients revealed that an increasing number of cells increase their buoyancy during corticogenesis. Immunocytochemical and molecular characterization showed that the proliferative and progenitor cell populations are for the most part associated with lower buoyancy or higher specific buoyant densities (> 1.056 g/ml) whereas the post-mitotic, differentiated neurons generally separated into fractions of higher buoyancy or lower specific buoyant densities (< 1.043 g/ml). Immunostaining with antibodies against several GABAA receptor subunits (alpha 3, beta 3, gamma 2) revealed that the highest percent (70-90%) of immunopositive cells could be identified in the most buoyant, differentiating neurons found in the cortical plate/subplate regions, with the lowest percent of the immunopositive cells found in the least buoyant, proliferative and progenitor cell populations originating from the ventricular/subventricular zones. Taken together, these results indicate that buoyant density is a distinguishing characteristic of embryonic CNS cells transforming from primarily proliferative to mainly differentiating, and that fractionation of these cells according to their buoyant densities provides rapid access to the properties of specific cell lineages during the prenatal period of CNS development.

Animals↗

PubMed1997

Neurotrophins stimulate chemotaxis of embryonic cortical neurons.

During mammalian cortical development, neuronal precursors proliferate within ventricular regions then migrate to their target destinations in the cortical plate, where they organize into layers. In the rat, most cortical neuronal migration occurs during the final week of gestation (Bayer et al, 1991; Jacobson, 1991). At this time (E15-E21), reverse transcriptase-polymerase chain reaction demonstrated that cortical homogenates contain mRNA encoding brain derived neurotrophic factor (BDNF) and the catalytic form of its high-affinity receptor, TrkB. Immunocytochemistry and in situ hybridization of sections revealed that the catalytic TrkB receptors predominantly localize to regions containing migratory cells. Many TrkB+ cells exhibited the classic morphology of migrating neurons, suggesting that TrkB ligands play a role in cortical neuronal migration. We analysed whether TrkB ligands influence the motility of embryonic cortical cells (from E15-E21) using a quantitative in vitro chemotaxis assay. High-affinity TrkB ligands (BDNF and NT4/5) stimulated chemotaxis (directed migration) of embryonic neurons at concentrations ranging from 1 to 100 ng/ml. NT-3, a low-affinity TrkB ligand, only stimulated significant migration at high concentrations (> or =100 ng/ml). Peak migration to BDNF was observed at gestational day 18 (E18). BDNF-induced chemotaxis was blocked by either tyrosine kinase inhibitor, K252a, or the Ca2+-chelator, BAPTA-AM, suggesting that BDNF-induces motility via autophosphorylation of TrkB receptor proteins and involves Ca2+-dependent mechanisms. BDNF-stimulation of increased cytosolic Ca2+ was confirmed with optical recordings of E18 cortical cells loaded with Ca2+ indicator dye. Thus, signal transduction through the TrkB receptor complex directs neuronal migration, suggesting that, in vivo, BDNF exerts chemotropic effects that are critical to morphogenesis of the cortex.

Animals↗

PubMed1997

[Biocompatibility evaluation of Ti50Ni50-xCux shape memory alloys (I)--corrosion resistance].

By means of electrochemical methods, the corrosion resistance of Ti50Ni50 and Ti50Ni50-xCux (x = 1,2, 4,6,8) was investigated. It is discovered that repassivation potential of Ti50Ni50-xCux (x = 2,4,6,8) alloys is about 200 mV higher than that of Ti50Ni50 alloy. This means that the added Cu raises the repassivation of TiNi shape memory alloys and improves corrosion resistance. Pitting potentials of Ti50Ni50 and Ti50Ni50-xCux (x = 1,2,4,6,8) alloys increase with the rising solution pH value, but the repassivation potentials keep constant. The added Cu has no obvious influence on pitting potential (Epit) of TiNi alloys, meanwhile, the corrosion potential and corrosion rate of Ti50Ni50-xCux (x = 1,2,4,6,8) alloys are irrelevant to its Cu content and the values are almost the same as that of TiNi alloys.

Alloys↗

PubMed1997

Effect of simulated weightlessness on TNF-alpha production and the response of bone marrow cells to GM-CSF in rats.

The purpose of this experiment was to investigate the effect of 15 and 30 d simulated weightlessness (SWL) on tumor necrosis factor-alpha(TNF-alpha) production secreted by macrophage stimulated with lipopolysaccharide(LPS) and the ability of bone marrow cells to respond to granulocyte/monocyte colony-stimulating factor(GM-CSF) in tail-suspension rats. The TNF-alpha production was assessed by radioimmunoassay. The ability of bone marrow cells to respond to GM-CSF was measured by 3H-TdR incorporation method. The results showed that after 15 d SWL, TNF-alpha production showed a tendency to decrease; and that after 30 d SWL, the decrease became significant (P < 0.05). The results also demonstrated that the ability of bone marrow cells to respond to GM-CSF decreased significantly after 15 d SWL (P < 0.01); and there was no significant change after 30 d SWL. It suggested that SWL could depress immune function, and that reduction of TNF-alpha production might be related to bone marrow cell proliferation function.

Animals↗