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Biomedical subjects

Jing Zhu

Publications and source records attributed to Jing Zhu.

At least 55 records · Page 3Linked to original sources
PubMed2005

[Studies on fluorescent properties of multi-walled carbon nanotubes before and after concentrated nitric acid treatment].

Fluorescent properties of multi-walled carbon nanotubes (MWNTs) before and after concentrated nitric acid treatment were studied. The results show that both multi-walled carbon nanotubes (MWNTs) and treated multi-walled carbon nanotubes (t-MWNTs) could emit fluorescence; compared with MWNTs, fluorescence from t-MWNTs is stronger and fluorescent emission peak from t-MWNTs blue shifts slightly to short-wavelength. Luminescence from MWNTs could be related to the trapping of excitation energy at defect sites and the energy bandgap between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). Treating MWNTs with concentrated nitric acid could introduce more defects on MWNTs and make MWTNs trap more excitation energy, leading to a fluorescence enhancement of t-MWTNs; in addition, the energy bandgap between LUMO and HOMO increases with length decreasing of MWNT, and the shortening of MWNT caused by concentrated nitric acid treatment could make energy bandgap between LUMO and HOMO increase, resulting in a slight blue shift of fluorescent emission peak of t-MWTNs to short wavelength.

Fluorescence↗
PubMed2005

[Role of tissue factor in lung metastasis of colorectal carcinoma cells in vivo].

OBJECTIVE: To investigate the role of tissue factor(TF) in hematogenous metastasis of human colorectal carcinoma cells (LOVO) in vivo. METHODS: The eukaryotic expression vectors pcDNA3.1/Zeo bearing either sense or antisense TFc DNA were transfected into LOVO cells by lipofectamine 2000. TF protein expression in the transfected cells was detected by Western blot. Eighteen nude mice (Babl/c nu/nu) were randomly divided into three groups, and then transfected and untransfected LOVO cells were implanted via tail vein respectively. The nude mice were sacrificed 8 weeks after implantation, and the number of metastatic nodules in the lung was used to assess the metastatic ability of LOVO cells. RESULTS: Compared with the untransfected group, TF expression of LOVO cells and the numbers of metastatic nodules in the lung increased in sense-TF cDNA transfection group (P< 0.05, P< 0.01, respectively), whereas decreased in antisense-TF cDNA transfection group (P< 0.05, P< 0.01, respectively). CONCLUSION: TF can increase the hematogenous metastatic ability of human colorectal carcinoma cells (LOVO) in vivo.

Animals↗
PubMed2004

BOD: a customizable bioinformatics on demand system accommodating multiple steps and parallel tasks.

The integration of bioinformatics resources worldwide is one of the major concerns of the biological community. We herein established the BOD (Bioinformatics on demand) system to use Grid computing technology to set up a virtual workbench via a web-based platform, to assist researchers performing customized comprehensive bioinformatics work. Users will be able to submit entire search queries and computation requests, e.g. from DNA assembly to gene prediction and finally protein folding, from their own office using the BOD end-user web interface. The BOD web portal parses the user's job requests into steps, each of which may contain multiple tasks in parallel. The BOD task scheduler takes an entire task, or splits it into multiple subtasks, and dispatches the task or subtasks proportionally to computation node(s) associated with the BOD portal server. A node may further split and distribute an assigned task to its sub-nodes using a similar strategy. In the end, the BOD portal server receives and collates all results and returns them to the user. BOD uses a pipeline model to describe the user's submitted data and stores the job requests/status/results in a relational database. In addition, an XML criterion is established to capture task computation program details.

Computational Biology↗
PubMed2004

[Germline E-cadherin gene mutation screening in familial gastric cancer kindreds].

OBJECTIVE: To evaluate the frequency and nature of E-cadherin gene (CDH1) germline mutations in familial gastric cancer kindreds of china. METHODS: Five familial gastric cancer kindreds of Chinese origin were screened for germline CDH1 mutations, all of them meeting the clinical criteria for hereditary diffuse gastric cancer (HDGC), by PCR-DHPLC and direct sequencing. RESULTS: A new truncating mutation in exon 10 in B family was identified, producing a stop codon at position 503 (Q503X), resulting in a truncated protein. The proband of this family had metachronous development of lobular breast and diffuse type gastric carcinoma. No protein expression was detected in the lobular breast carcinoma, indicating complete inactivation of the gene. CONCLUSIONS: A Chinese gastric cancer family with CDH1 germline truncating mutation is described for the first time, and our findings suggest that lobular breast carcinoma might be part of the tumor spectrum of HDGC.

Adult↗
PubMed2004

Local near-field enhancement of random Sb-SiN films.

Local near-field enhancement of random Sb-SiN films has been studied. Specimens consisting of a random Sb-SiN film and an optical recording layer were prepared and exposed to a focused laser beam. Laser-induced ablation occurred on the recording layer adjacent to random Sb-SiN film much faster and at much lower power than on a single recording layer. These results indicate that an optical field can be enhanced by random Sb-SiN films. The enhanced field was subsequently investigated by scanning near-field optical microscopy, and the pictures revealed that the enhanced field was localized.

Journal Article↗
PubMed2004

[The role of tissue factor expression in the invasive and metastatic ability of colorectal carcinoma].

OBJECTIVE: To investigate the role of tissue factor (TF) expression in the invasive and metastatic ability of colorectal carcinoma and explore the influence of TF on the invasive ability of HT-29 cells. METHODS: TF expression of specimens from 85 colorectal carcinomas and 6 colorectal adenomas was observed by immunohistochemistry. The role of TF expression in prognosis and tumor invasion and metastasis was analyzed. The plasmids pcDNA3.1/Zeo bearing either sense or antisense-TFcDNA were transfected into HT-29 cells by the way of Lipofectamine 2000. TF proteins in transfected and untransfected HT-29cells were detected by Western blot. In vitro Matrigel invasion assays were performed to show the invasive ability of those cells. RESULTS: TF expression was positive in 40 (47.1%) of 85 colorectal carcinoma specimens, but negative in normal mucosa and adenoma specimens. TF expression showed significant correlation with tumor invasive depth (r = 0.895, P < 0.01). TF expression showed significant correlation with synchronous and metachronous hepatic metastasis (r = 0.974, P < 0.01 and r = 0.963, P < 0.01 respectively). TF expression was a significant risk factor for hepatic metastasis (P < 0.01) and prognosis (P < 0.01). TF expression in HT-29 cells with sense/antisense-TFcDNA transfection was more/less than that of the cells without transfection. The invasive ability of HT-29 cells with sense-TFcDNA transfection was increased in vitro compared with the untransfected cells, but HT-29 cells with antisense-TFcDNA transfection got the contrary change. CONCLUSIONS: TF may take part in the invasive and metastatic process of primary colorectal carcinoma, and TF expression may be an indicator of hepatic metastasis and prognosis for colorectal carcinoma patients. TF expression may increase the invasive ability of HT-29 cell in vitro.

Blotting, Western↗
PubMed2004

Locating volition.

In this paper, it is examined how neuroscience can help to understand the nature of volition by addressing the question whether volitions can be localized in the brain. Volitions, as acts of the will, are special mental events or activities by which an agent consciously and actively exercises her agency to voluntarily direct her thoughts and actions. If we can pinpoint when and where volitional events or activities occur in the brain and find out their neural underpinnings, this can substantively aid to demystify the concept of volition. After first discussing some methodological issues regarding whether it is possible to locate volition in the brain, various approaches by which neuroscientists and psychologists explore the neural correlates and substrates of volition are examined. Although different psychological conceptualizations of volition shape different perspectives toward understanding the functions of volition, the explorations of the neural basis of volition converge on certain common brain areas and structures. A unifying conception of volition that helps to make better sense of recent empirical findings is then suggested.

Brain↗
PubMed2004

[Optimizing the reaction system of DDRT-PCR by positive-cross test].

The method of mRNA Differential display PCR (DDRT-PCR) is used to identify differentially expressed genes widely. To improve further the efficiency and reproducibility of the method, the positive-cross test were performed to find the optional conditions of DDRT-PCR by analyzing the six critical parameters of dNTPs, MgCl2, arbitrary primer, anchor primer, Taq enzyme, and template systematically. The experimental findings delineated the best possible DDRT-PCR conditions for a more reliable assessment of differential gene expression. Additionally, in this study, nondenaturing polyacrylamide gel electrophoresis (PAGE) and silver straining were adopted to reduce the false-positive ratio, and the reclaimed fragments were detected by reverse Northern analysis. Finally, we obtained the optimal condition for DDRT-PCR.

Animals↗
PubMed2004

[Monitoring of the residue of fosthiazate in water samples using solid-phase extraction coupled with gas chromatography/mass spectrometry].

Solid-phase extraction (SPE) coupled with gas chromatography/mass spectrometry (GC/MS) was used to determine the fosthiazate residue in water samples. The water samples were first filtered through cellulose filters (0.45 microm pore size). A 100 mL volume of filtered water, in which 1 mL of methanol has been added, was then passed through a pre-conditioned 3 cm C18 cartridge at a flow-rate of 1.5 mL/min. Elution was performed by 1 mL of methanol. The eluant was finally dried under reduced pressure for solvent evaporation. The volume was quantitatively adjusted to 0.5 mL with methanol. The analysis was carried out on GC/MS. The mass spectrometer was operated in selected ion monitoring (SIM) mode. According to mass spectrum of fosthiazate, three selected ions at m/z of 126, 195, 283, respectively, were monitored for identification and quantification. High sensitivity and selectivity were achieved by using this method. The limit of detection for fosthiazate in water samples was determined to be 56.4 ng/L. The linearity was demonstrated over a wide range of concentrations covering from 0.282 to 141 microg/L. The recoveries were more than 85.5% and the relative standard deviations for the overall procedure were less than 4.42%. The fosthiazate residue was detected in the water samples from a pool near cropland where fosthiazate was used. The results demonstrate the suitability of the SPE-GC/MS approach for the analysis of fosthiazate in water.

Gas Chromatography-Mass Spectrometry↗
PubMed2003

Glycosylation affects the protein stability and cell surface expression of Kv1.4 but Not Kv1.1 potassium channels. A pore region determinant dictates the effect of glycosylation on trafficking.

Kv1.1 and Kv1.4 potassium channels are plasma membrane glycoproteins involved in action potential repolarization. We have shown previously that glycosylation affects the gating function of Kv1.1 and that a pore region determinant of Kv1.1 and Kv1.4 affects their cell surface trafficking negatively or positively, respectively. Here we investigated the role of N-glycosylation of Kv1.1 and Kv1.4 on their protein stability, cellular localization pattern, and trafficking to the cell surface. We found that preventing N-glycosylation of Kv1.4 decreased its protein stability, induced its high partial intracellular retention, and decreased its cell surface protein levels, whereas it had little or no effect on these parameters for Kv1.1. Exchanging a trafficking pore region determinant between Kv1.1 and Kv1.4 reversed these effects of glycosylation on these chimeric channels. Thus it appeared that the Kv1.4 pore region determinant and the sugar tree attached to the S1-S2 linker showed some type of dependence in promoting proper trafficking of the protein to the cell surface, and this dependence can be transferred to chimeric Kv1.1 proteins that contain the Kv1.4 pore. Understanding the different trafficking programs of Kv1 channels, and whether they are altered by glycosylation, will highlight the different posttranslational mechanisms available to cells to modify their cell surface ion channel levels and possibly their signaling characteristics.

Animals↗
PubMed2003

[Role of tissue factor in the invasive ability of cultured human colon carcinoma cells].

OBJECTIVE: To analyze the role of tissue factor (TF) in the in vitro invasive ability of human colon carcinoma cells (HT-29). METHODS: The eukaryotic expression vectors pcDNA3.1/Zeo bearing either sense or antisense TFcDNA were transfected into HT-29 cells by the way of lipofactamine 2000. TF proteins in transfected cells were detected by Western blot. In vitro Matrigel invasion assays were used to show the invasive ability of HT-29 cells with sense/antisense TFcDNA transfection. RESULTS: HT-29 cells with sense-TFcDNA transfection showed increased TF expression and invasive ability compared with the cells without transfection, but HT-29 cells with antisense-TFcDNA transfection got the contrary change. CONCLUSION: TF can increase the invasive ability of HT-29 cells in vitro.

Colonic Neoplasms↗
PubMed2003

Allowed N-glycosylation sites on the Kv1.2 potassium channel S1-S2 linker: implications for linker secondary structure and the glycosylation effect on channel function.

N-glycosylation is a post-translational modification that plays a role in the trafficking and/or function of some membrane proteins. We have shown previously that N-glycosylation affected the function of some Kv1 voltage-gated potassium (K+) channels [Watanabe, Wang, Sutachan, Zhu, Recio-Pinto and Thornhill (2003) J. Physiol. (Cambridge, U.K.) 550, 51-66]. Kv1 channel S1-S2 linkers vary in length but their N-glycosylation sites are at similar relative positions from the S1 or S2 membrane domains. In the present study, by a scanning mutagenesis approach, we determined the allowed N-glycosylation sites on the Kv1.2 S1-S2 linker, which has 39 amino acids, by engineering N-glycosylation sites and assaying for glycosylation, using their sensitivity to glycosidases. The middle section of the linker (54% of linker) was glycosylated at every position, whereas both end sections (46% of linker) near the S1 or S2 membrane domains were not. These findings suggested that the middle section of the S1-S2 linker was accessible to the endoplasmic reticulum glycotransferase at every position and was in the extracellular aqueous phase, and presumably in a flexible conformation. We speculate that the S1-S2 linker is mostly a coiled-loop structure and that the strict relative position of native glycosylation sites on these linkers may be involved in the mechanism underlying the functional effects of glycosylation on some Kv1 K+ channels. The S3-S4 linker, with 16 amino acids and no N-glycosylation site, was not glycosylated when an N-glycosylation site was added. However, an extended linker, with an added N-linked site, was glycosylated, which suggested that the native linker was not glycosylated due to its short length. Thus other ion channels or membrane proteins may also have a high glycosylation potential on a linker but yet have similarly positioned native N-glycosylation sites among isoforms. This may imply that the native position of the N-glycosylation site may be important if the carbohydrate tree plays a role in the folding, stability, trafficking and/or function of the protein.

Amino Acid Sequence↗
PubMed2003

Trafficking of Kv1.4 potassium channels: interdependence of a pore region determinant and a cytoplasmic C-terminal VXXSL determinant in regulating cell-surface trafficking.

Kv1.4 and Kv1.1 potassium channel homomers have been shown to exhibit different intracellular trafficking programmes and cell-surface expression levels in cell lines: a determinant in the pore region of Kv1.4 and Kv1.1 [Zhu, Watanabe, Gomez and Thornhill (2001) J. Biol. Chem. 276, 39419-39427] and a cytoplasmic C-terminal VXXSL determinant on Kv1.4 [Li, Takimoto and Levitan (2000) J. Biol. Chem. 275, 11597-11602] have been described, which affected trafficking and cell-surface expression levels. In the present study, we examined whether trafficking pore determinants influenced any cytoplasmic C-terminal trafficking determinant. We found that removal of VXXSL from a Kv1.4 chimaera that contained the pore of Kv1.1 did not affect cell-surface trafficking. Therefore removal of the C-terminal VXXSL of Kv1.4 inhibited protein surface levels only in the presence of the Kv1.4 pore. In contrast, truncating the cytoplasmic C-terminus of Kv1.1 or truncating a Kv1.1 chimaera with the pore of Kv1.4, had little effect on surface protein levels. Furthermore, the subregion of the Kv1.4 pore trafficking determinant that was required for the inhibitory effect of VXXSL removal was mapped to a threonine residue in the deep pore region. Therefore the Kv1.4 pore determinant affected the trafficking and cell-surface levels directed by the C-terminal VXXSL determinant. Different Kv1 trafficking programmes would affect cell-surface expression levels either positively or negatively and also cell signalling. Cells may use differential trafficking programmes of membrane proteins as a post-translational mechanism to regulate surface protein levels and cell function.

Amino Acid Motifs↗
PubMed2003

The permeation and activation properties of brain sodium channels change during development.

BTX-modified sodium channels from 15-day embryonic (E15) rat forebrains were studied in planar lipid bilayers. Compared to postnatal sodium channels, E15 channels had a lower maximal single channel conductance, whereas their permeation pathway sensed a comparable surface charge density and had a similar apparent binding affinity for sodium ions. The steady-state activation curve of E15 channels was significantly more hyperpolarized and had a shallower slope than postnatal channels. The apparent BTX binding affinity was significantly lower for E15 channels than for postnatal channels. Finally, E15 channel alpha-subunits displayed a lower apparent molecular weight, and a lower sialylation level than postnatal sodium channel alpha-subunits. Together with previous studies, our data suggested that the observed functional differences between E15 and postnatal voltage-dependent sodium channels cannot be explained solely by the observed differences in channel sialylation, and hence they also appeared to reflect the presence of other channel structural differences.

Animals↗
PubMed2003

Glycosylation affects rat Kv1.1 potassium channel gating by a combined surface potential and cooperative subunit interaction mechanism.

The effect of glycosylation on Kv1.l potassium channel function was investigated in mammalian cells stably transfected with Kv1.l or Kv1.1N207Q. Macroscopic current analysis showed that both channels were expressed but Kv1.1N207Q, which was not glycosylated, displayed functional differences compared with wild-type, including slowed activation kinetics, a positively shifted V 1/2, a shallower slope for the conductance versus voltage relationship, slowed C-type inactivation kinetics, and a reduced extent of and recovery from C-type inactivation. Kv1. 1N207Q activation properties were also less sensitive to divalent cations compared with those of Kv1.l. These effects were largely due to the lack of trans-Golgi added sugars, such as galactose and sialic acid, to the N207 carbohydrate tree. No apparent change in ionic current deactivation kinetics was detected inKv1.1N207Q compared with wild-type. Our data, coupled with modelling, suggested that removal of the N207 carbohydrate tree had two major effects. The first effect slowed the concerted channel transition from the last dosed state to the open state without changing the voltage dependence of its kinetics. This effect contributed to the G-V curve depolarization shift and together with the lower sensitivity to divalent cations suggested that the carbohydrate tree and its negatively charged sialic acids affected the negative surface charge density on the channel's extracellular face that was sensed by the activation gating machinery. The second effect reduced a cooperativity factor that slowed the transition from the open state to the dosed state without changing its voltage dependence. This effect accounted for the shallower G-V slope, and contributed to the depolarized G-V shift, and together with the inactivation changes it suggested that the carbohydrate tree also affected channel conformations. Thus N-glycosylation, and particularly terminal sialylation, affected Kv1.l gating properties both by altering the surface potential sensed by the channel's activation gating machinery and by modifying conformational changes regulating cooperative subunit interactions during activation and inactivation. Differences in glycosylation pattern among closely related channels may contribute to their functional differences and affect their physiological roles.

Amino Acid Sequence↗
PubMed2003

Heteromeric Kv1 potassium channel expression: amino acid determinants involved in processing and trafficking to the cell surface.

Kv1.4 and Kv1.1 potassium channels are expressed in brain as mature glycoproteins that are trans-Golgi glycosylated. When expressed in cell lines these homomers had very different trans-Golgi glycosylation efficiencies and cell surface expression levels with Kv1.4 > Kv1.1 for both parameters (Zhu, J., Watanabe, I., Gomez, B., and Thornhill, W. B. (2001) J. Biol. Chem. 276, 39419-39427). This previous study identified determinants in the outer pore region of Kv1.4 and Kv1.1 that positively and negatively, respectively, affected these events when expressed as homomers. Here we investigated which subunit exhibited positive or negative effects on these processes when expressed as heteromers. Kv1.4/Kv1.1 heteromers, by coexpression or expression as tandem-linked heteromers, were expressed on the cell surface at approximately 20-fold lower levels versus Kv1.4 homomers but they were trans-Golgi glycosylated. The lower Kv1.4/Kv1.1 expression level was not rescued by Kvbeta 2.1 subunits. Thus Kv1.1 inhibited high cell surface expression and partially retained the heteromer in the endoplasmic reticulum, whereas Kv1.4 stimulated trans-Golgi glycosylation. The subunit determinants and cellular events responsible for these differences were investigated. In a Kv1.4/Kv1.1 heteromer, the Kv1.1 pore was a major negative determinant, and it inhibited high cell surface expression because it induced high partial endoplasmic reticulum retention and it decreased protein stability. Other Kv1.1 regions also inhibited high surface expression of heteromers. The Kv1.1 C terminus induced partial Golgi retention and contributed to a decreased protein stability, whereas the Kv1.1 N terminus contributed to only a decreased protein stability. Thus a neuron may regulate its cell surface K+ channel protein levels by different Kv1 subfamily homomeric and heteromeric combinations that affect intracellular retention characteristics and protein stability.

Amino Acid Sequence↗
PubMed2002

Conversion of proepithelin to epithelins: roles of SLPI and elastase in host defense and wound repair.

Increased leukocyte elastase activity in mice lacking secretory leukocyte protease inhibitor (SLPI) leads to impaired wound healing due to enhanced activity of TGFbeta and perhaps additional mechanisms. Proepithelin (PEPI), an epithelial growth factor, can be converted to epithelins (EPIs) in vivo by unknown mechanisms with unknown consequences. We found that PEPI and EPIs exert opposing activities. EPIs inhibit the growth of epithelial cells but induce them to secrete the neutrophil attractant IL-8, while PEPI blocks neutrophil activation by tumor necrosis factor, preventing release of oxidants and proteases. SLPI and PEPI form complexes, preventing elastase from converting PEPI to EPIs. Supplying PEPI corrects the wound-healing defect in SLPI null mice. Thus, SLPI/elastase act via PEPI/EPIs to operate a switch at the interface between innate immunity and wound healing.

Amino Acid Sequence↗