Biomedical subjects

Dan Wu

Publications and source records attributed to Dan Wu.

At least 37 records · Page 2Linked to original sources

PubMed2005

Liquid-core capsules via interfacial polymerization: a free-radical analogy of the nylon rope trick.

Liquid-core capsules have wide-ranging applications in the high-efficiency encapsulation and controlled release of drugs, dyes, enzymes, and other substrates. Their great utility has driven the rapid development of various preparation techniques. However, there remains no convenient technique for the preparation of submicrometer liquid-core capsules with shell thicknesses less than 100 nm. Here, we demonstrate a new interfacial free-radical polymerization approach for the straightforward preparation of liquid-core polymer capsules. Conceptually, this interfacial free-radical polymerization is analogous to the classical "nylon rope trick" wherein hydrophobic and hydrophilic monomers alternately copolymerize to constrain the polymerization at interfaces, but its free-radical mechanism allows precise control of initiation, which makes it possible to finely disperse the immiscible phases prior to polymerization.

Journal Article↗

PubMed2005

Fabrication of superhydrophobic surfaces from microstructured ZnO-based surfaces via a wet-chemical route.

The fabrication of a superhydrophobic surface is demonstrated via a wet chemical route, and this method offers advantages of being cleanroom free, cost efficiency, and wide applicability. The preferable growth of ZnO crystalline forms a microstructured surface, and a variety of alkanoic acids were adopted to tune the surface wettability. Although all surfaces show an advancing contact angle greater than 150 degrees , they substantially differ in the wetting mechanisms. It is found that only when the length of alkanoic acid is greater than 16, the microstructured surface shows a stable superhydrophobicity, in which the Cassie state dominates. While for those moderate-length alkanoic acids (C8-C14), their corresponding surfaces have a tendency to fall into the Wenzel state and display a great contact angle hysteresis.

Hydrophobic and Hydrophilic Interactions↗

PubMed2005

[The application of RNAi to the medical genetics].

Experimental RNA interference (RNAi) leading to the selective knockdown of gene function is induced by introducing into cells either double stranded RNA (dsRNA), or short interfering RNA (siRNA) fragments into which dsRNA is cut. The siRNA triggers degradation of homologous messenger RNA (mRNA). Widely used as a research tool in the genetic model organisms Caenorhabditis elegans, Drosophila melanogaster and mouse to investigate the function of individual genes, RNAi has also been deployed in genome-wide, specific gene-knockdown screens. Recent rapid progress in the application of RNAi to mammalian cells, including neurons and muscle cells, offers new approaches to drug target identification and validation. Advances in targeted delivery of RNAi-inducing molecules have raised the possibility of using RNAi directly as a therapy for a variety of human genetic and other neural and neuromuscular disorders. Here, we review examples of the application of RNAi to worm, fly and mouse models of such diseases aimed at understanding their pathophysiology.

Gene Silencing↗

PubMed2005

Metastasis of primary gallbladder carcinoma in lymph node and liver.

AIM: To evaluate the patterns with metastasis of gallbladder carcinoma in lymph nodes and liver. METHODS: A total of 45 patients who had radical surgery were selected. The patterns with metastasis of primary gallbladder carcinoma in lymph nodes and liver were examined histopathologically and classified as TNM staging of the American Joint Committee on Cancer. RESULTS: Of the 45 patients, 29 (64.4%) had a lymph node positive disease and 20 (44.4%) had a direct invasion of the liver. The frequency of involvement of lymph nodes was strongly influenced by the depth of the primary tumor (P = 0.0001). The postoperative survival rate of patients with negative lymph node metastasis was significantly higher than that of patients with positive lymph node metastasis (P = 0.004), but the postoperative survival rate of patients with N1 lymph node metastasis was not significantly different from that of patients with N2 lymph node metastasis (P = 0.3874). The postoperative survival rate of patients without hepatic invasion was significantly better than that of patients with hepatic invasion (P = 0.0177). CONCLUSION: Complete resection of the regional lymph nodes is important in advanced primary gallbladder carcinoma (PGC). The initial sites of liver spread are located mostly in segments IV and V. It is necessary to achieve negative surgical margins 2 cm from the tumor. In patients with hepatic hilum invasion, extended right hepatectomy with or without bile duct resection or portal vein resection is necessary for curative resection.

Adult↗

PubMed2005

Effects of gap junction to Ca(2+) and to IP(3) on the synchronization of intercellular calcium oscillations in hepatocytes.

The frequency of free cytosolic calcium concentration ([Ca(2+)]) oscillations elicited by a given agonist concentration differs between individual hepatocytes. However, in multicellular systems of rat hepatocytes and even in the intact liver, [Ca(2+)] oscillations are synchronized and highly coordinated. In this paper, we have investigated theoretically the gap junction permeable to calcium and to IP(3) on intercellular synchronization by means of a mathematical model, respectively. It is shown that gap junction permeable to calcium and to IP(3) are effective on synchronizing calcium oscillations in coupled hepatocytes. Our theoretical results are similar either for the case of Ca(2+) acting as coordinating messenger or for the case of IP(3) as coordinating messenger. There exists an optimal coupling strength for a pair of connected hepatocytes. Appropriate coupling strength and IP(3) level can induce various harmonic locking of intercellular [Ca(2+)] oscillations. Furthermore, a phase diagram in two-dimensional parameter space of the coupling strength and IP(3) level (or the velocity of IP(3) synthesis) has been predicted, in which the synchronization region is similar to Arnol'd tongue.

Animals↗

PubMed2005

Phase synchronization and coherence resonance of stochastic calcium oscillations in coupled hepatocytes.

The frequency of free cytosolic calcium concentration ([Ca(2+)]) oscillations elicited by a given agonist concentration differs between individual hepatocytes. However, in multicellular systems of rat hepatocytes and even in the intact liver, [Ca(2+)] oscillations are synchronized and highly coordinated. In this paper, we have investigated theoretically the effects of gap junction permeable to calcium and of the total Ca(2+) channel number located on endoplasmic reticulum on intercellular synchronization. Figures of ratio between mean oscillating frequency of coupled cells describe visually the process of phase-locking. By virtue of a set of phase analysis, we can observe a gradual transition from synchronous behavior to nonsynchronous behavior. Furthermore, a signal-to-noise ratio in two dimensional parameter space (coupling strength-total Ca(2+) channel number) has suggested that, coherence resonance will occur for appropriate noise and coupling.

Animals↗

PubMed2005

The EMBL Nucleotide Sequence Database.

The EMBL Nucleotide Sequence Database (http://www.ebi.ac.uk/embl), maintained at the European Bioinformatics Institute (EBI) near Cambridge, UK, is a comprehensive collection of nucleotide sequences and annotation from available public sources. The database is part of an international collaboration with DDBJ (Japan) and GenBank (USA). Data are exchanged daily between the collaborating institutes to achieve swift synchrony. Webin is the preferred tool for individual submissions of nucleotide sequences, including Third Party Annotation (TPA) and alignments. Automated procedures are provided for submissions from large-scale sequencing projects and data from the European Patent Office. New and updated data records are distributed daily and the whole EMBL Nucleotide Sequence Database is released four times a year. Access to the sequence data is provided via ftp and several WWW interfaces. With the web-based Sequence Retrieval System (SRS) it is also possible to link nucleotide data to other specialist molecular biology databases maintained at the EBI. Other tools are available for sequence similarity searching (e.g. FASTA and BLAST). Changes over the past year include the removal of the sequence length limit, the launch of the EMBLCDSs dataset, extension of the Sequence Version Archive functionality and the revision of quality rules for TPA data.

Base Sequence↗

PubMed2005

Spatio-temporal expression of the pathway-specific regulatory gene redD in S. coelicolor.

Confocal laser scanning microscopy was used to observe the spatio-temporal expression of the pathway-specific gene redD during S. coelicolor cell cultivation. The corresponding mutant S. coelicolor lyqRY1522 carrying redD::eyfp in the chromosome was constructed. The temporal expression results of the fusion protein during submerged cultivation demonstrated that expression of redD began in the transition phase, continuing through the exponential growth phase to the stationary phase, and reached maximum in the stationary phase. On the other hand, redD was expressed only in substrate mycelia during solid-state culture, while aerial mycelia remained essentially non-fluorescent throughout culture. Results demonstrated that the expression pattern of redD coincides with that of the biosynthesis of the antibiotics during culture, revealing a direct correlation between the spatio-temporal distribution of regulatory gene expression and second metabolism.

Anti-Bacterial Agents↗

PubMed2005

[Spectrophotometric determination of trace amount of copper with trimethoxyphenylfluorone in microemulsion after preconcentration and separation by sulphydryl dextran gel].

In this paper, the color reaction of copper with trimethoxyphenylfluorone (TM-PF) in microemulsion has been studied. Copper (II) reacts with TM-PF to form a stable 1:2 complex at pH 10.40. Its apparent molar absorptivity is 1.46 x 10(5) L x mol(-1) x cm(-1) at 552 nm. Beer's law is obeyed in the range of 0-0.6 microg x mL(-1). Sulphydryl dextran gel (SDG), in which sulphydryl group has a big share, is a new type of metallic ion adsorbent. It presents the advantage of higher adsorption capacity, better reuse ability and higher mechanical stability. So the coexistent metal ions can be separated effectively and copper can be enriched by SDG, greatly improving the selectivity and sensibility of the system. The method was used to determine trace amount of copper in blood, urine, iron ore and water samples with satisfactory results, the relative standard deviation is less than 4.8%, and the recovery is 94.2%-106%.

Copper↗

PubMed2005

[Effect of branch chain amino acid enriched formula on postoperative fatigue and nutritional status after digestive surgery].

OBJECTIVE: To evaluate the effect of branch chain amino acid (BCAA) enriched formula on nutritional status and postoperative fatigue for digestive surgery patients. METHODS: Forty patients who underwent digestive surgery were randomly received parenteral nutrition with either BCAA enriched (study group, n=20) or routine amino acid (control group, n=20) for seven consecutive days. Nitrogen balance,serum total protein, albumin, prealbumin, transferrin, retinol binding protein and postoperative fatigue score were monitored during the postoperative period. RESULTS: The cumulative postoperative fatigue scores were lower in BCAA group than that in the control group at the 4th, 5th and 7th day after operation (P< 0.05). Patients achieved positive nitrogen balance 2 days earlier in the study group than that in the control group, but there was no significant difference in cumulative nitrogen balance between the two groups. There was no significant difference in elevation of serum total protein, albumin, prealbumin, transferrin at the 7th day after operation between the two groups (P > 0.05), compared with those at the first day after operation. The serum level of retinol binding protein was higher in BCAA-enriched group than that in the control group (P=0.004). CONCLUSION: TPN with BCAA enriched formula can reduce postoperative fatigue score and improve the nutritional status for digestive surgery patients.

Adult↗

PubMed2005

[Studies on the determination of protein with spectroscopic probe of o-chlorophenylfluorone-molybdenum (VI) complex in microemulsion medium].

The interaction and absorption spectral behavior of o-chlorophenylfluorone (o-CPF)-Mo(VI) and protein are studied in OP microemulsion medium. Under the optimum condition, the molar absorptivity of o-CPF-Mo(VI)-BSA system at 532 nm is 6.12 x 10(6) L x mol(-1) x cm(-1), and Beer's law is obeyed in the range of 0-14 microg x mL(-1) of BSA. Moreover, the binding number between the complex and BSA determined by molar ratio and slope ratio methods is 91. The mechanism of interaction of BSA and o-CPF-Mo (VI) is also discussed. OP microemulsion media introduced into the protein determination increased markedly the sensitivity of the system. The result of experiment indicates that the method possesses a high sensitivity as well as a high selectivity. It can be used to determine protein in human urine with satisfactory results.

Emulsions↗

PubMed2005

[The effect of antisense survivin-liposome complex on cell growth, apoptosis and cell cycle in hepatocellular carcinoma cells].

OBJECTIVE: To investigate the effects and the mechanisms of cell growth inhibition in hepatocellular carcinoma cells after induction with antisense survivin-liposome (LIP) complex, and to provide evidence in treatment for hepatocellular carcinoma and tumors expressing survivin. METHODS: Survivin ODNs was transfected into HepG2 cells mediated by LiP reagent. The expression of survivin mRNA and protein was detected by RT-PCR and Western blot. MTT assay was applied to determine cell proliferation in HepG2 cells. Active caspase-3 and apoptosis rate were evaluated by flow cytometric analysis. The morphological changes were assessed by electron microscopy. Cell cycle was analyzed by flow cytometry in the cell cycle-synchronized hepatocellular carcinoma cells treated with the antisense compound. RESULTS: Antisense compound efficiently down-regulated survivin expression (mRNA and protein) in a dose-dependent manner with an IC(50) of 250 nmol/L. Its maximal effect was achieved at a concentration of 600 nmol/L, when expression levels were down-regulated by 80%, as revealed by gradually increase of caspase-3-like protease activity and apoptosis rate in a time-dependent manner. Morphological apoptotic changes such as membrane blebbing, loss of microvilli, cytoplasmic vasculization, condensation of cytoplasm and nucleus, chromatin fragmentation, and apoptosis and cell growth inhibition were observed. In the cell cycle-synchronized hepatocellular carcinoma cells, antisense compound induced cell cycle arrest followed by apoptosis. After treated with low concentration of compound, the cell cycle was arrested at S phase or G2/M phase; while at high concentration, the cell cycle was mainly arrested at S phase. Apoptosis was obviously observed and the rate of apoptosis was increased in a time and concentration-dependent manner. CONCLUSION: Antisense survivin has significant inhibitory effect on growth of hepatocellular carcinoma cells in vitro. This is associated with cell cycle arrest and apoptosis.

Apoptosis↗

PubMed2004

Prognostic significance of dysadherin expression in cervical squamous cell carcinoma.

The protein and mRNA expression of dysadherin was studied in a series of squamous cell cervical carcinomas, and their clinicopathological associations and prognostic value were explored. Immunohistochemistry was used to assess protein expression of dysadherin in 206 patients with squamous cell cervical carcinoma, FIGO stage Ia-IVb. Frozen tissues from 20 cases in which the tumors showed variable dysadherin protein expression were used for laser capture microdissection (LCM) and processed for RTPCR detection of dysadherin mRNA. Immunohistochemically, all the dysadherin-positive staining was membranous. Positive cell membranous dysadherinpositive staining was often observed at the edge of tumor nests, although strong immunoreactivity throughout whole tumor nests was also seen in some tumors. Basal cells of the normal cervical epithelia were positive for dysadherin while its expression in the squamous cell cervical carcinomas was variable. Among the 206 tumors, 23 (11.2%) were negative, 53 (25.7%) were scored 1+, 54 (26.2%) were scored 2+ and 76 (36.9%) were scored 3+. In the 20 tumors analyzed, mRNA expression of dysadherin basically corresponded to its protein expression. No significant correlation between expression of dysadherin and age, FIGO stage or lymph node status was observed. Higher level of dysadherin expression, however, was significantly associated with shorter overall survival (p=0.04). We conclude that there is dysadherin protein expression in basal and parabasal cells of normal cervical epithelia, and higher level of dysadherin protein expression in squamous cell cervical carcinoma is predictive of a shorter overall survival, indicating that dysadherin may be a valuable prognostic marker in cervical carcinoma.

Adult↗

PubMed2004

Refolding and purification of interferon-gamma in industry by hydrophobic interaction chromatography.

A new technology for renaturation with simultaneous purification of the recombinant human interferon-gamma (rhIFN-gamma) in downstream of biotechnology is presented. The strategies to develop the new technology in industry scale were suggested. Based on chemical equilibrium and molecular interactions, the principle of rhIFN-gamma refolding by HPHIC was described. The kind of stationary and mobile phases were evaluated and found the former to contribute to the rhIFN-gamma refolding more than the latter. The extract containing the rhIFN-gamma in gram scale in 7.0 mol L(-1) guanidine hydrochloride solution of 700 mL was directly pumped into a unit of simultaneous renaturation and purification of proteins (USRPP, 10 x 300 mm i.d.) packed by small particle packings of hydrophobic interaction chromatography and a satisfactory recovery of bioactivity and mass of the rhIFN-gamma was obtained. With flow rate 100 mL min(-1) and a gradient elution by only one step in 4h, the purity and specific bioactivity approach to 95% and 8.7 x 10(7) IU(-1) mg, respectively. To evaluate the goodness of the presented new technology in this study, a usual method with the renaturation by dilution method firstly and then purification with a series of LC in literature was employed to compare with each other. The obtained result in terms of purity, recoveries of mass and bioactivity, cost time as well as expenses, the former is much better than the latter. Comparing the total bioactivity of rhIFN-gamma in the extract before to that after the renaturation by the USRPP, the total bioactivity of rhIFN-gamma increased 62-fold.

Biotechnology↗

PubMed2004

Protection of pigs against Taenia solium cysticercosis using recombinant antigen or in combination with DNA vaccine.

In the present study, we investigated the duration of protection afforded to pigs immunized in two different prime-boost regimens: one is homologus priming and boosting with a protein vaccine, and the other is priming with a DNA vaccine and boosting with the protein vaccine. Groups of pigs that received the same vaccination regimen were then challenged with Taenia solium eggs at 6, 12 or 20 weeks post-immunization (wpi), respectively. The results showed that all vaccinated pigs challenged at 6 or 12 wpi showed significant (P < 0.05) reduction in the development of cysts. When challenged at 20 wpi, pigs primed with the DNA vaccine (pcDNA3-cC1) followed by two boosters of the protein vaccine (GST-cC1) showed significant (P < 0.05) protection against the challenge of T. solium eggs, whereas pigs receiving three injections of the protein vaccine showed no significant protection compared to non-vaccinated controls (P > 0.05). Antibody isotype assays showed that DNA prime-protein boost regimen induced a predominantly IgG2 response, compared to an IgG1 biased response for the protein prime-protein boost regimen. In addition, peripheral blood mononuclear cells (PBMC) obtained from the DNA prime-protein boost group proliferated strongly in response to GST-cC1 protein, and this responsiveness persisted until 20 wpi. Taken together, our data suggest that the use of a prime-boost strategy combining DNA and protein vaccines may be better than protein alone for the longevity of protection against the challenge of T. solium eggs.

Animals↗

PubMed2004

K(+) channel activity and redox status are differentially required for JNK activation by UV and reactive oxygen species.

Upon exposure to ultraviolet (UV) radiation, osmotic changes or the presence of reactive oxygen species (ROS) c-Jun N-terminal kinases (JNKs) are rapidly activated. Extensive studies have elucidated molecular components that mediate the activation of JNKs. However, it remains unclear whether activation of JNKs by various stress signals involves different pathways. Here we show that K(+) channel activity is involved in mediating apoptosis induced by UV but not by H(2)O(2) in myelocytic leukemic ML-1 cells. Specifically, JNKs were rapidly phosphorylated upon treatment of ML-1 cells with UV and H(2)O(2). UV-induced, but not H(2)O(2)-induced, JNK-1 phosphorylation was inhibited by pretreatment with 4-aminopyridine (4-AP), a K(+) channel blocker. 4-AP also blocked UV-induced increase in JNK activity as well as p38 phosphorylation. Immunofluorescent microscopy revealed that phosphorylated JNKs were concentrated at centrosomes in ML-1 cells and that these proteins underwent rapid subcellular translocation upon UV treatment. Consistently, the subcellular translocation of JNKs induced by UV was largely blocked by 4-AP. Furthermore, UV-induced JNK activation was blocked by NEM, a sulfhydryl alkylating agent also affecting K(+) current. Both UV- and H(2)O(2)-induced JNK activities were inhibited by glutathione, suggesting that the redox status does play an important role in the activation of JNKs. Taken together, our findings suggest that JNK activation by UV and H(2)O(2) is mediated by distinct yet overlapping pathways and that K(+) channel activity and redox status are differentially required for UV- and H(2)O(2)-induced activation of JNKs.

4-Aminopyridine↗

PubMed2004

Effects of inositol 1,4,5-trisphosphate receptor-mediated intracellular stochastic calcium oscillations on activation of glycogen phosphorylase.

In various cell types cytosolic calcium (Ca(2+)) is an important regulator. The possible role of Ca(2+) release from the inositol 1,4,5-trisphosphate (IP(3)) receptor channel in the regulation of the phosphorylation-dephosphorylation cycle process involved in glycogen degradation by glycogen phosphorylase have theoretically investigated by using the Li-Rinzel model for cytosolic Ca(2+) oscillations. For the case of deterministic cytosolic Ca(2+) oscillations, there exists an optimal frequency of cytosolic Ca(2+) oscillations at which the average fraction of active glycogen phosphorylase reaches a maximum value, and a mutation for the average fraction of active glycogen phosphorylase occurs at the higher bifurcation point of Ca(2+) oscillations. For the case of stochastic cytosolic Ca(2+) oscillations, the fraction of active phosphorylase is strongly affected by the number of IP(3) receptor channels and the level of IP(3) concentration. Small number of IP(3) receptor channels can potentiate the sensitivity of the activity of glycogen phosphorylase. The average frequency and amplitude of active phosphorylase stochastic oscillations are increased with the level of increasing IP(3) stimuli. The various distributions for the amplitude of active glycogen phosphorylase oscillations in parameters plane are discussed.

Calcium↗

PubMed2004

The EMBL Nucleotide Sequence Database.

The EMBL Nucleotide Sequence Database (http://www.ebi.ac.uk/embl/), maintained at the European Bioinformatics Institute (EBI), incorporates, organizes and distributes nucleotide sequences from public sources. The database is a part of an international collaboration with DDBJ (Japan) and GenBank (USA). Data are exchanged between the collaborating databases on a daily basis to achieve optimal synchrony. The web-based tool, Webin, is the preferred system for individual submission of nucleotide sequences, including Third Party Annotation (TPA) and alignment data. Automatic submission procedures are used for submission of data from large-scale genome sequencing centres and from the European Patent Office. Database releases are produced quarterly. The latest data collection can be accessed via FTP, email and WWW interfaces. The EBI's Sequence Retrieval System (SRS) integrates and links the main nucleotide and protein databases as well as many other specialist molecular biology databases. For sequence similarity searching, a variety of tools (e.g. FASTA and BLAST) are available that allow external users to compare their own sequences against the data in the EMBL Nucleotide Sequence Database, the complete genomic component subsection of the database, the WGS data sets and other databases. All available resources can be accessed via the EBI home page at http://www.ebi.ac.uk.

Animals↗