Biomedical subjects

J Wu

Publications and source records attributed to J Wu.

At least 235 records · Page 13Linked to original sources

PubMed2001

Simulation of cooling-water discharges from power plants.

Accurate simulation of the temperature distribution in a cooling lake or reservoir is often required for feasibility studies of engineering options that increase the cooling capacity of the waterbody. A three-dimensional hydrodynamic and temperature model has been developed and applied to several cooling lakes in the south-eastern United States. In this paper, the details of the modeling system are presented, along with the application to the Flint Creek Lake.

Arkansas↗

PubMed2001

FAK induction in keratinocytes in an in vitro model of reepithelialization.

During reepithelialization, keratinocytes must become activated in order to migrate over the provisional extracellular matrix of the wound. Previously we have shown that focal adhesion kinase (FAK) is induced in activated keratinocytes. The mechanisms responsible for keratinocyte activation are unknown. Here we use an organ culture system to investigate FAK up-regulation and regulation of keratinocyte activation. Normal human skin was cultured on type I collagen. Keratinocytes migrated out of the explant onto the supporting collagen. Immunostaining for FAK showed induction in the migrating epithelium and also in the center of the explant some distance from the cut edge. Cells from the center of the explant expressed FAK and showed the activated phenotype as defined by their ability to spread on collagen. Since FAK is a tyrosine kinase, the tyrosine kinase inhibitors genistein or herbimycin A were added to the explant medium for 24 h. Inhibition of tyrosine kinase activity delayed epithelial migration, but keratinocytes were able to begin migrating after removal of the inhibitors. We conclude that FAK is up-regulated in keratinocytes in this whole skin explant model. Furthermore FAK up-regulation and keratinocyte activation are not confined to the migrating cells but are found in cells some distance from the skin margin. These data suggest that (1) cell migration, contact with wound matrix molecules, loss of cell-cell contact, or loss of basement membrane contact is not necessary for FAK up-regulation or keratinocyte activation; and (2) tyrosine kinase signaling pathways are important for reepithelialization.

Cell Movement↗

PubMed2001

A novel mechanism for modulating synaptic gene expression: differential localization of alpha-dystrobrevin transcripts in skeletal muscle.

Alpha-dystrobrevin is a dystrophin-related and -associated protein that is involved in synapse maturation and is required for normal muscle function. There are three protein isoforms in skeletal muscle, alpha-dystrobrevin-1, -2, and -3 that are encoded by the single alpha-dystrobrevin gene. To understand the role of these proteins in muscle we have investigated the localisation and transcript distribution of the different alpha-dystrobrevin isoforms. Alpha-dystrobrevin-1 and -2 are concentrated at the neuromuscular junction and are both recruited into agrin-induced acetylcholine receptor clusters in cultured myotubes. We also demonstrate that all alpha-dystrobrevin mRNAs are transcribed from a single promoter in skeletal muscle. However, only transcripts encoding alpha-dystrobrevin-1 are preferentially accumulated at postsynaptic sites. These data suggest that the synaptic accumulation of alpha-dystrobrevin-1 mRNA occurs posttranscriptionally, identifying a novel mechanism for synaptic gene expression. Taken together, these results indicate that different isoforms possess distinct roles in synapse formation and possibly in the pathogenesis of muscular dystrophy.

Agrin↗

PubMed2001

Size effects of realgar particles on apoptosis in a human umbilical vein endothelial cell line: ECV-304.

Regulation of endothelial cell apoptosis is a critical modulator of normal and pathological angiogenesis. Inorganic arsenic, especially arsenic trioxide, has been demonstrated to induce clinical remission in patients with acute promyelocytic leukemia as well as those with several solid cancers. So, in this study, we examined the in vitro effect of realgar(As2S2), used to treat human diseases for centuries in traditional Chinese medicine, on cell survival and apoptosis in a human umbilical vein endothelial cell (HUVEC) line: ECV-304. Four different suspensions of realgar particles with diameters from 100-500 nm containing equivalent doses were investigated to determine their size effects. After 2, 4, 6 and 8 h, realgar particles of diameters 100 nm and 150 nm obviously reduced ECV-304 cell survival, which was evidenced by a reduction of cell viability in the MTT assay, whereas cells exhibited slight viability reduction in response to treatment with realgar particles of diameters 200 nm and 500 nm. Significant apoptosis was identified by morphological observation, flow cytometry assay and DNA gel electrophoresis in the ECV-304 cells by the presence of realgar particles of diameters 100 nm and 150 nm. It is demonstrated that particles of realgar with average diameters from 100 nm to 150 nm can induce ECV-304 cell apoptosis. These results suggest that particles of realgar smaller than 150 nm may provide a less toxic agent for anti-neoplasia by suppressing angiogenesis.

Acridine Orange↗

PubMed2001

Enhancement of Taxol production and excretion in Taxus chinensis cell culture by fungal elicitation and medium renewal.

An endophytic fungus, Aspergillus niger, isolated from the inner bark of a Taxus chinensis tree, was used as an elicitor to stimulate the Taxol (paclitaxel) production in a Taxus chinensis cell suspension culture. Different elicitor doses and elicitation times were tested in a batch culture; and the highest volumetric Taxol yield was achieved when 40 mg of the fungal elicitor (carbohydrate equivalent) l(-1) was added to the culture during the late exponential-growth phase. The elicitation resulted in a more than two-fold increase in the Taxol yield and about a six-fold increase in total secretion. The Taxol yield was further improved substantially by applying medium renewal and re-elicitation to the culture. In particular, with repeated medium renewal (in a way similar to medium perfusion) and a second elicitation of the culture, the volumetric Taxol yield was increased to 67.1+/-7.5 mg l(-1), which was about seven times the amount obtained in the non-elicited batch culture. The Taxol productivity of the perfusion-like culture with repeated fungal elicitation was 1.5 mg l(-1) day(-1), which was about 40% higher than that of the elicitor-treated batch culture and three times the productivity of the non-elicited batch culture.

Antineoplastic Agents, Phytogenic↗

PubMed2001

Structured population on two patches: modeling dispersal and delay.

We derive from the age-structured model a system of delay differential equations to describe the interaction of spatial dispersal (over two patches) and time delay (arising from the maturation period). Our model analysis shows that varying the immature death rate can alter the behavior of the homogeneous equilibria, leading to transient oscillations around an intermediate equilibrium and complicated dynamics (in the form of the coexistence of possibly stable synchronized periodic oscillations and unstable phase-locked oscillations) near the largest equilibrium.

Age Factors↗

PubMed2001

The rice retrotransposon Tos17 prefers low-copy-number sequences as integration targets.

The rice retrotransposon Tos17 is highly activated by tissue culture. To evaluate the impact of transposition of Tos17 on the rice genome and examine its utility for insertional mutagenesis, more than 100 sequences flanking newly transposed Tos17 copies were characterised. The 5-bp target-site duplications flanking Tos17 did not show any consensus sequence, and preferred nucleotides, A/T and G/C, were only found at the second and third nucleotides from both ends of the target site duplications, respectively, indicating that Tos17 has relatively low target-site specificity at the nucleotide sequence level. Integration targets were widely distributed over the chromosomes; however, preferential integration into the sucrose synthase 2 gene and into Tos17 itself was demonstrated by PCR screening using pooled DNA prepared from the mutant population. Hybridisation studies indicated that Tos17 preferentially integrates into low-copy-number regions of the genome. In agreement with this result, about 30% of flanking sequences examined showed significant homology to known genes. Taken together, these results show that Tos17 can have a significant impact on the rice genome and can be used as a tool for efficient insertional mutagenesis.

Binding Sites↗

PubMed2001

Beam hardening correction for computed tomography images using a postreconstruction method and equivalent tissue concept.

A postreconstruction method for correcting the beam-hardening artifacts in computed tomography (CT) images is proposed. This method does not require x-ray spectrum measurement. The authors assumed that a pixel in a CT image can be decomposed into equivalent tissue percentages, depending on its CT number. A scout view of the step wedges made of these equivalent tissues was performed to obtain a beam-hardening correction curve for each tissue. Projecting through the CT image from various angles generated simulated projection data and the total thickness of each tissue along the ray. The correction term was estimated using the tissue thickness traveled by the ray, and this term was then added to its corresponding projection data. A second reconstruction using the corrected projection data yielded a beam-hardening corrected image. The preliminary results show that this method reduces beam hardening artifacts by 14% for aluminum and increased the object contrast by 18% near the aluminum-water boundary. The variation in CT numbers at different locations were reduced, and the aluminum CT number also was restored.

Artifacts↗

PubMed2001

Nodal occult metastasis in patients with peripheral lung adenocarcinoma of 2.0 cm or less in diameter.

BACKGROUND: Detection of occult micrometastasis in regional lymph nodes is crucial for diagnosis and selection of appropriate therapy for patients with pN0 non-small-cell lung carcinoma. Using immunohistochemical staining, we evaluated the impact of detection of occult micrometastasis on the prevalence and prognosis of patients with lung adenocarcinoma of 2.0 cm or less in diameter. METHODS: A total of 103 pN0 disease patients with peripheral lung adenocarcinomas of 2.0 cm or less in diameter were enrolled in this study. We studied 1,438 regional lymph nodes for occult micrometastasis by immunohistochemical staining for cytokeratins. RESULTS: Micrometastasis was detected in 49 lymph nodes (3.4%) of 21 patients (20.4%) but not in patients with localized bronchioloalveolar carcinoma or localized bronchioloalveolar carcinoma with foci of collapse of alveolar structure. The 5-year survival rate (61.9%) of patients with micrometastasis was significantly (p = 0.0041) lower than that of patients without micrometastasis (86.3%). CONCLUSIONS: There still remains a risk of nodal micrometastasis in patients with primary peripheral lung adenocarcinoma, even if the diameter of the tumor is smaller than 2.0 cm. Selection of patients for limited surgery should be done prudently, taking into consideration the risk of nodal micrometastasis.

Adenocarcinoma↗

PubMed2001

Full-length cloning and 3'-terminal portion expression of human perforin cDNA.

BACKGROUND: Perforin (also known as pore-forming protein, PFP) is one of the main effector molecules which natural killer cells (NK) and cytotoxic T lymphocytes (CTL) utilize to kill their targets both in vivo and in vitro. We report the full length of human perforin cDNA, which was cloned from liver tissue. RESULTS: Sequencing analysis showed that there were discrepancies of four nucleotides and three amino acids compared with previously published sequence of human PFP. The cDNA fragment was then inserted into fusion protein expressive vector pGEX-2T to construct a recombinant expressive plasmid. The C-terminal truncated 125 amino acids polypeptide (410-534aa) of human perforin (hPFP-C) was selectively expressed in a form of fusion protein. Under the induction of IPTG, GST/hPFP-C fusion protein was expressed in E. coli BL21 (DE3). The fusion protein GST/hPFP-C was purified by affinity chromatography with glutathione agarose. The recombinant hPFP-C obtained by thrombin cleavage showed a significant hemolytic activity when tested with rabbit erythrocytes. CONCLUSION: These results suggest that the domain responsible for lytic function lies not only in the N-terminal portion but also in the C-terminal portion of perforin molecule. The recombinant hPFP-C protein will be useful as a highly purified biological factor for immunological, pathological and structural studies.

Amino Acid Sequence↗

PubMed2001

Assessment of a vaccinia virus vectored multi-epitope live vaccine candidate for Plasmodium falciparum.

We constructed a live recombinant vaccinia virus vaccine candidate containing a synthesised hybrid gene termed 'HGFSP' encoding circumsporozoite protein (CSP), major merozoite surface antigen-1(MSA1), major merozoite surface antigen-2 (MSA2), and ring-infected erythrocyte surface antigen (RESA) of Plasmodium falciparum, interleukin-1 (IL-1) and tetanus toxin (TT) epitopes. Anti-recombinant vaccinia virus rabbit sera and IgG were tested in inhibition experiments in vitro. Results showed that the recombinant vaccinia virus had some capability to inhibit the growth of P. falciparum in vitro. The sera of rabbits, rats, and mice immunised with recombinant virus showed obvious IL-2 activity 4-6 weeks after immunisation. The interferon (IFN) level of sera from these animals 6 weeks after immunisation was significantly higher than before immunisation. These results indicate that the recombinant vaccinia virus can stimulate cell mediated responses (Th1 cell response) in immunised animals, and has the capability to inhibit multiplication of in vitro cultured P. falciparum. Thus this recombinant vaccinia virus is an appropriate vaccine candidate for further evaluation in Aotus monkey or human clinical trails.

Animals↗

PubMed2001

An alternative approach to the identification of respiratory central chemoreceptors in the brainstem.

Central chemoreceptors (CCRs) play a crucial role in autonomic respiration. Although a variety of brainstem neurons are CO(2) sensitive, it remains to know which of them are the CCRs. In this article, we discuss a potential alternative approach that may allow an access to the CCRs. This approach is based on identification of specific molecules that are CO(2) or pH sensitive, exist in brainstem neurons, and regulate cellular excitability. Their molecular identity may provide another measure in addition to the electrophysiologic criteria to indicate the CCRs. The inward rectifier K(+) channels (Kir) seem to be some of the CO(2) sensing molecules, as they regulate membrane potential and cell excitability and are pH sensitive. Among homomeric Kirs, we have found that even the most sensitive Kir1.1 and Kir2.3 have pK approximately 6.8, suggesting that they may not be capable of detecting hypocapnia. We have studied their biophysical properties, and identified a number of amino acid residues and molecular motifs critical for the CO(2) sensing. By comparing all Kirs using the motifs, we found the same amino acid sequence in Kir5.1, and demonstrated the pH sensitivity in heteromeric Kir4.1 and Kir5.1 channels to be pK approximately 7.4. In current clamp, we show evidence that the Kir4.1-Kir5.1 can detect P(CO(2)) changes in either hypercapnic or hypocapnic direction. Our in-situ hybridization studies have indicated that they are coexpressed in brainstem cardio-respiratory nuclei. Thus, it is likely that the heteromeric Kir4.1-Kir5.1 contributes to the CO(2)/pH sensitivity in these neurons. We believe that this line of research intended to identify CO(2) sensing molecules is an important addition to current studies on the CCRs.

Animals↗

PubMed2001

Ozonation of aqueous azo dye in a semi-batch reactor.

The ozonation of wastewater containing azo dye in a semi-batch reactor has been studied. Results revealed that the rate of ozone transfer increased with increases in the initial dye concentration, the applied ozone dose and temperature. A model was developed to predict the enhancement factor of ozone mass transfer. This model enables the prediction of mass transfer coefficient of ozone from the following parameters: initial dye concentration, applied ozone dose, temperature and concentration of dissolved ozone in the organic-free water. This model was also valid for reactors of larger sizes. Result of kinetic studies showed that ozonation of the azo dye was a pseudo-first-order reaction with respect to dye. The apparent rate constant increased with the applied ozone dose and temperature. However, the apparent rate constant declined logarithmically with increasing initial dye concentration. In addition, ozonation reduced chemical oxygen demand and enhanced the biodegradability of the wastewater.

Azo Compounds↗

PubMed2001

Biological perchlorate reduction in high-salinity solutions.

Perchlorate (ClO4-) has been detected in numerous ground and surface waters, and has recently been added to the drinking water Candidate Contaminant List in the United States. Perchlorate can be removed from drinking water using ion exchange, but this results in the production of highly saline (7-12%) perchlorate-contaminated brines. Perchlorate-degrading microbial enrichments capable of growth in highly saline water were obtained by screening six salt water environments including marine and lake surface waters, salt marshes, subtidal sediments, and a biofilm/sludge from a seawater filter. Perchlorate reduction was obtained in three of these samples (seawater, saline lake water, and biofilm/sludge) at a salinity of 3%. The salinity range of two of these cultures was extended through serial transfers into media having higher salt concentrations (3-7%). Growth rates were measured over a salinity range of 1-15%. The maximum growth rate measured for the saline lake-water enrichment was 0.060+/-0.003 d(-1) (doubling time of 11.6+/-0.8 d) at a salinity of 5%. Growth rates decreased to 0.037+/-0.002 d(-1) at a salinity of 11%, and no growth was observed at salinities of 13 or 15%. These results demonstrate for the first time that biological perchlorate reduction is possible in solutions having a salinity typical of ion exchange brines.

Biodegradation, Environmental↗

PubMed2001

Positioning errors and prostate motion during conformal prostate radiotherapy using on-line isocentre set-up verification and implanted prostate markers.

PURPOSE: To evaluate treatment errors from set-up and inter-fraction prostatic motion with port films and implanted prostate fiducial markers during conformal radiotherapy for localized prostate cancer. METHODS: Errors from isocentre positioning and inter-fraction prostate motion were investigated in 13 men treated with escalated dose conformal radiotherapy for localized prostate cancer. To limit the effect of inter-fraction prostate motion, patients were planned and treated with an empty rectum and a comfortably full bladder, and were instructed regarding dietary management, fluid intake and laxative use. Field placement was determined and corrected with daily on-line portal imaging. A lateral portal film was taken three times weekly over the course of therapy. From these films, random and systematic placement errors were measured by matching corresponding bony landmarks to the simulator film. Superior-inferior and anterior-posterior prostate motion was measured from the displacement of three gold pins implanted into the prostate before planning. A planning target volume (PTV) was derived to account for the measured prostate motion and field placement errors. RESULTS: From 272 port films the random and systematic isocentre positioning error was 2.2 mm (range 0.2-7.3 mm) and 1.4 mm (range 0.2-3.3 mm), respectively. Prostate motion was largest at the base compared to the apex. Base: anterior, standard deviation (SD) 2.9 mm; superior, SD 2.1 mm. Apex: anterior, SD 2.1 mm; superior, SD 2.1 mm. The margin of PTV required to give a 99% probability of the gland remaining within the 95% isodose line during the course of therapy is superior 5.8 mm, and inferior 5.6 mm. In the anterior and posterior direction, this margin is 7.2 mm at the base, 6.5 mm at the mid-gland and 6.0 mm at the apex. CONCLUSIONS: Systematic set-up errors were small using real-time isocentre placement corrections. Patient instruction to help control variation in bladder and rectal distension during therapy may explain the observed small SD for prostate motion in this group of patients. Inter-fraction prostate motion remained the largest source of treatment error, and observed motion was greatest at the gland base. In the absence of real-time pre-treatment imaging of prostate position, sequential portal films of implanted prostatic markers should improve quality assurance by confirming organ position within the treatment field over the course of therapy.

Humans↗

PubMed2001

The H1 double-stranded RNA genome of Ustilago maydis virus-H1 encodes a polyprotein that contains structural motifs for capsid polypeptide, papain-like protease, and RNA-dependent RNA polymerase.

The Ustilago maydis viral (UmV) genome consists of three distinct size groups of double-stranded RNA (dsRNA) segments: H (heavy), M (medium), and L (light). The H segments have been suggested to encode all essential viral proteins, but without any molecular evidences. As a preliminary step to understand viral genomic organization and the molecular mechanism governing gene expression in UmV, we determined the complete nucleotide sequence of the H1 dsRNA genome in P1 viral killer subtype. The H1 dsRNA genome (designated UmV-H1) contained a single open reading frame that encodes a polyprotein of 1820 residues, which is predicted to be autocatalytically processed by a viral papain-like protease to generate viral proteins. The amino-terminal region is the capsid polypeptide with a predicted molecular mass of 79.9 kDa. The carboxy-terminal region is the RNA-dependent RNA polymerase (RDRP) that has a high sequence homology to those of the totiviruses. The H2 dsRNA also encodes a distinct RDRP, suggesting that UmV is a complex virus system like the Saccharomyces cerevisiae viruses ScV-L1 and -La.

Amino Acid Sequence↗

PubMed2001

Purification of an osmotin-like protein from the seeds of Benincasa hispida and cloning of the gene encoding this protein.

A pathogenesis-related (PR) protein was purified from the seeds of Benincasa hispida, which is a medicinal plant and a member of the Cucurbitaceae family. Purification was achieved by using a procedure consisting of an acid treatment step followed by two chromatography steps. The protein is a basic protein with molecular mass of approximately 28 kDa. The sequences of the N-terminal 30 amino acids and four peptides generated from protease digestion were determined. These sequences indicated that the protein is an osmotin-like protein (OLP). Osmotin and OLPs are members of the thaumatin-like, PR-5 family of the PR proteins. A genomic clone of the gene encoding the protein was isolated and sequenced. The predicted protein has a signal peptide of 18 amino acids, and the mature protein has a molecular mass of 24.8 kDa with an isoelectric point of 7.67. The protein has 17 cysteine residues, of which 16 appear in the same positions as those appear in the sweet-tasting protein thaumatin and several other thaumatin-like proteins. Southern hybridization analysis indicated that the gene encoding the protein is a single copy gene. A computer-generated, three-dimensional model of the protein is presented.

Journal Article↗

PubMed2001

Ultrasound-induced physiological effects and secondary metabolite (saponin) production in Panax ginseng cell cultures.

This work was aimed at the effects of ultrasound (US) on the growth and secondary metabolite biosynthesis of cultured plant cells. Suspension cultures of Panax ginseng cells were exposed to US at power density below 82 mW/cm3 for short periods of time (1-4 min) in a US bath (38.5-kHz fixed frequency and 810 W maximum peak power). Under most exposure conditions, US stimulated the biosynthesis of secondary metabolites, the ginsenoside saponins of ginseng cells, increasing the total saponin content of the cell by up to 75%. The growth and viability of ginseng cells were usually depressed immediately after the exposure to US, but recovered gradually to levels similar to those of a normal culture in a few days, with virtually no net loss of biomass yield at the end of the culture period. At some lower US doses, sonicated cultures could even reach slightly higher biomass yields than that of normal cultures. The effects of US on cell growth and secondary metabolite yield showed a significant correlation with the total US energy emitted (i.e., the product of US power and exposure time). Mechanical stress and microstreaming induced by acoustic cavitation were considered as the most possible causes of the various physiological effects of US on ginseng cells. In particular, the stimulation of secondary metabolite production by US may be a result of US-induced plant cell defense response.

Cells, Cultured↗