PubMed Health⌕ Search

Biomedical subjects

R S Wu

Publications and source records attributed to R S Wu.

At least 19 recordsLinked to original sources
PubMed2001

Invasion and metastasis of a mammary tumor involves TGF-beta signaling.

Several studies have correlated escape from TGF-beta-mediated cell cycle arrest with the tumorigenic phenotype. Most often, this escape from growth control has been linked to dysfunctional TGF-beta receptors or defects in the TGF-beta-mediated SMAD signaling pathway. In this report, we found that highly metastatic 4T1 mammary carcinoma cells express functional TGF-beta receptors capable of initiating SMAD-mediated transcription, yet are not growth inhibited by TGF-beta1. We further observed that TGF-beta directly contributes to the metastatic behavior of this cell line. Exposure to TGF-beta caused 4T1 cells to undergo morphological changes associated with the metastatic phenotype and invade more readily through collagen coated matrices. Furthermore, expression of a dominant negative truncated type II receptor diminished TGF-beta signaling and significantly restricted the ability of 4T1 cells to establish distant metastases. Our results suggest that regardless of 4T1 resistance to TGF-beta-mediated growth inhibition, TGF-beta signaling is required for tumor invasion and metastases formation.

Animals↗
PubMed2001

Comparative analysis of IFN-gamma B7.1 and antisense TGF-beta gene transfer on the tumorigenicity of a poorly immunogenic metastatic mammary carcinoma.

Cancer progression is attributed in part to immune evasion strategies that include lack of co-stimulation, down-regulation of cell surface MHC molecules, and secretion of immunosuppressive factors, such as transforming growth factor-beta (TGF-beta). Gene therapy has been employed to counter these mechanisms of immune evasion by transference of B7.1, IFN-gamma or antisense TGF-beta genes into tumor cells, resulting in cell surface expression of B7.1, upregulation of MHC class I and class II molecules, or elimination of tumor-derived TGF-beta, respectively. Although each of these transgenes has been shown to alter tumorigenicity in murine models, a direct comparison of their efficacy has not been performed. In this study, we have employed a very aggressive, poorly immunogenic and highly metastatic mammary model, 4T1, to compare the efficacy of B7.1, IFN-gamma and antisense TGF-beta gene transfer in stimulating an anti-tumor response. We demonstrate that both IFN-gamma and antisense TGF-beta gene expression significantly reduced the tumorigenicity of these cells compared to mock transduced cells, with IFN-gamma having a greater effect. In contrast, B7.1 gene transfer did not affect the tumorigenicity of 4T1 cells. The anti-tumor response directed against antisense TGF-beta-expressing 4T1 tumors was mediated by CD4+ and CD8+ T cells. However, CD8+ T cells, and not CD4+ T cells, appeared to mediate the anti-tumor response against IFN-gamma-expressing tumors. Treatment of tumor-bearing animals with IFN-gamma or antisense TGF-beta gene-modified tumor cell vaccines reduced the number of clonogenic metastases to the lungs and liver compared to treatment with mock-transduced cells. Finally, in a residual disease model in which the primary tumor was excised and mice were vaccinated with irradiated tumor cells, treatment of mice with vaccinations consisting of 4T1 cells expressing both antisense TGF-beta and IFN-gamma genes was the most effective in prolonging survival.

Animals↗
PubMed2001

Bioenergetics and RNA/DNA ratios in the common carp (Cyprinus carpio) under hypoxia.

Hypoxia caused by eutrophication occurs over large areas in aquatic systems worldwide. Common carp (Cyprinus carpio) exposed to hypoxia (1 mg.O2.l(-1) and 2 mg.O2.l(-1)) for 1 week showed a significant reduction in feeding rate, respiration rate, faecal production and nitrogenous excretion compared to those maintained at normoxia (7 mg.O2.l(-1)). Fish exposed to hypoxia showed negative scope for growth (SfG), but no significant difference in the specific growth rate was revealed after 1 week in both hypoxic groups. A significant reduction in RNA/DNA ratio was, however, clearly evident in the white muscle of the 1 mg.O2.l(-1) treatment group, but not in the 2 mg.O2.l(-1) treatment group. Both specific growth rate and RNA/DNA ratio were significantly reduced when fish were exposed to severe hypoxia (0.5 mg.O2.l(-1)) for 4 weeks. At all levels of hypoxia, growth reduction was accompanied by a significant decrease in RNA/DNA ratio in white muscle. Covariance analysis showed no significant difference between the slope of RNA/DNA ratio and growth rate under normoxic conditions and 0.5 mg. O2.l(-1) for 4 weeks (F= 1.036, P > 0.326), as well as 1.0 mg.O2.l(-1) and 2.0 mg.O2.l(-1) for 1 week (F = 0.457, P > 0.5), indicating that the RNA/DNA ratio serves as a biomarker of growth under all oxygen levels, at least under controlled experimental conditions. SfG also appears to be more sensitive than the RNA/DNA ratio in responding to hypoxia in fish.

Animals↗
PubMed2001

The sleeper Bostrichthys sinensis (family Eleotridae) stores glutamine and reduces ammonia production during aerial exposure.

Bostrichthys sinensis inhabits brackish water, living in the crevices of the river mouths of Shang Xi and Guangdong, China. In its natural habitat, it may encounter aerial exposure frequently during low tides, and it usually remains quiescent in the absence of water. Upon aerial exposure in the laboratory, the ammonia excretion rate decreased to one-fourth that of the submerged control. Although all the enzymes of the ornithine-urea cycle were detected in the liver of this fish, the activity of hepatic carbamoyl phosphate synthetase was too low for the cycle to be functioning. Indeed, ammonia accumulated in the tissues and was not converted to urea. Results indicate that ammonia produced through amino acid catabolism was detoxified to glutamine during the first 24 h of aerial exposure. The excess amount of glutamine stored in the muscle during this period couldaccount approximately for the reduction in ammonia equivalent excreted. There was indeed a significant increase in the activity of glutamine synthetase from the liver of specimens exposed to terrestrial conditions. In contrast to the production of alanine, formation of glutamine is energetically expensive. Since B. sinensis remained relatively inactive on land, the reduction in energy demand for muscular activity might provide it with the opportunity to exploit glutamine formation as a means to detoxify ammonia. After 72 h of aerial exposure, B. sinensis reduced internal ammonia production, possibly through reductions in proteolysis and amino acid catabolism, to avoid excessive accumulation of ammonia.

Adaptation, Physiological↗
PubMed2001

DNA adduct formation and DNA strand breaks in green-lipped mussels (Perna viridis) exposed to benzo[a]pyrene: dose- and time-dependent relationships.

Green-lipped mussels, Perna viridis, were exposed to 0, 0.3, 3 and 30 micrograms l-1 (nominal concentrations) B[a]P under laboratory conditions over a period of 24 days. Mussels were collected on day 0, 1, 3, 6, 12, 18 and 24, and the levels of DNA adducts and DNA strand breaks in their hepatopancreas tissues monitored. Mussels exposed to 0.3 and 3 micrograms l-1 B[a]P showed marked increases in strand breaks after 1 day of exposure. DNA strand break levels in these mussels remained high and significantly different from the control values until day 3 for the 0.3 microgram l-1 treatment group, and day 6 for the 3 micrograms l-1 treatment group. This was followed by a gradual reduction in strand breaks. After 12 days, the levels of both groups had returned to the same level as that of the control. No increase in DNA strand breaks was observable in mussels exposed to 30 micrograms l-1 B[a]P in the first 12 days of exposure, but a significant increase was observed from day 12 to day 24. Increasing B[a]P concentrations resulted in elevated DNA adduct levels after 3-6 days of exposure, but this pattern of dose-related increase disappeared after 12 days. These results indicate that a better understanding of the complex interactions between exposure levels and durations is crucially important before DNA adduct levels and DNA strand breaks in P. viridis can be used as effective biomarkers for monitoring genotoxicants in marine waters.

Animals↗
PubMed2001

The use of microangiography in detecting aberrant vasculature in zebrafish embryos exposed to cadmium.

Embryonic vascular patterns in zebrafish (Danio rerio) could be visualised by confocal microscopy coupled with microinjected fluorescent microbeads. This microangiographic technique was adopted here, for the first time, to study the effects of cadmium on cardiovascular development in zebrafish embryos. Zebrafish embryos were incubated in culture medium containing 100 microM cadmium from 5 h post fertilisation (hpf) to 48 hpf. At 48 hpf, embryos were examined for viability and occurrence of malformations. The 100 microM cadmium caused 32.21 +/- 3.65% mortality and 20.33 +/- 4.04% visible malformations in surviving embryos. In the remaining embryos with no visible signs of malformations, further assessments for less obvious abnormalities were performed. Assessments on craniofacial development were made by digital measurements on areas of brains and eyes. Cardiac development was assessed by immunostaining the heart with the antibody MF20 specific for myosin heavy chain. Body lengths of the embryos were also measured. Embryonic development of brains, eyes, hearts and body lengths of visibly healthy embryos in the cadmium treatment group showed no significant difference from the controls. Embryonic vasculature of these visibly healthy embryos was then studied by microinjecting fluorescent microbeads of diameter 0.02 microm into the circulation. All the cadmium treated embryos showed localised vascular defects in the dorsal aortae, segmental and cranial vessels while none of the control embryos showed any aberrant patterns in the networking of the vasculature. Improved image analyses on the anterior regions revealed that cadmium treated embryos had markedly less complex networks of cranial vessels with fewer vessels perfusing the craniofacial regions. The number of branch points in the vascular network was counted. In untreated embryos, there were 135.6 +/- 51 branches in the vasculature in entire body. In the cadmium treated embryos, there were 64.5+/-31 branches. The difference was significant when assessed with Student's t-test. It appeared that although cadmium did not cause any signs of external malformations in these visibly healthy embryos, nonetheless induced impaired branching and anastomsis of the cranial vessels. This study revealed, for the first time, that vital vascular structures in fish embryos could be affected by exposure to cadmium. This technique allowed visualisation of vascular anomalies in embryos showing no external signs of malformations. The impairment of anatomical features during embryonic development might serve as meaningful health endpoints in ecotoxicological studies and in risk assessment.

Angiography↗
PubMed2001

Reproductive impairment of sea urchins upon chronic exposure to cadmium. Part I: Effects on gamete quality.

Successful reproduction is a determining factor for species survival. Pollution may impair reproductive success of adults through effects on gamete quality. Reproductive impairment of the sea urchin Anthocidaris crassispina upon chronic (4 weeks) exposure to 0.01 and 0.1 mg l-1 Cd2+ was investigated. Criteria used for assessing gamete quality included sperm motility, egg morphology, fertilization rate and dynamics of first cleavage. A dose-response relationship was found between Cd2+ levels and changes in sperm motility, and percentage fertilization. Sperm motility, measured by computer-assisted sperm analysis, indicated that percent motile sperm, velocities, and percent sperm with normal trajectory were significantly affected by chronic exposure to > or = 0.1 mg l-1 Cd2+. A decline in sperm motility was also accompanied by a decrease in fertilization success of sea urchin sperm. Width/height ratio of sea urchin eggs was not affected by cadmium, but larger egg sizes were found when sea urchins were exposed to 0.1 mg l-1 Cd2+. Male sea urchins exposed to Cd2+ produced poorer quality sperm, as indicated by a lower percent fertilization and lower cleavage rate, implying that male sea urchins were more sensitive than females to chronic Cd2+ exposure. Results of the present study provide an explanation of reproductive impairment in marine invertebrates upon chronic exposure to Cd2+.

Animals↗
PubMed2001

Reproductive impairment of sea urchin upon chronic exposure to cadmium. Part II: Effects on sperm development.

Chronic pollution may impair the reproductive success of adult organisms through a decrease in the quality of gametes. Our parallel study on gamete quality, showed that male sea urchins were more sensitive than the females towards cadmium pollution. The effects of chronic exposure to 0.01 and 1 ppm Cd2+ on sperm development of the sea urchin Anthocidaris crassispina were studied. Despite the fact that no significant change in gonad index was observed when sea urchins were exposed to both levels of Cd2+ for 4 weeks, deposition of electron-dense materials was conspicuous at the wall and intracellular space of male gonads. Apparent cytological alterations were observed in sperm cells, including changes in morphology of nuage in spermatogonia. The discrete, granular bodies of nuage were replaced by a large electron-dense body. Spermatozoa with short, incomplete 'broken' tails (scanning electron microscope observation) or tails of spermatids/spermatozoa with extraordinary electron-density (transmission electron microscope observation) were more abundant in gonads exposed to both levels of Cd2+. Mitochondrial cristae deformation was observed for sperm cells at all stages of development. Sperm plasma membrane also became more convoluted but acrosome remained intact. The observed cytological distortion of sperm tails and mitochondria/midpiece could help to explain the decline in motility as well as poor perseverance in sperm produced by sea urchins exposed to cadmium observed in our earlier study.

Animals↗
PubMed2001

A field study on EROD activity and quantitative hepatocytological changes in an immature demersal fish.

Demersal fish, Solea ovata, were sampled from a reference site and a site where highly contaminated sediment is dumped. Sexually immature fish from the contaminated site exhibited significantly higher EROD activity compared with counterparts sampled from the reference site. No significant difference in EROD activity could be found for sexually mature males and females between sites. The relationship between EROD activity and quantitative changes in hepatic lipofuscin/ceroid, as well as peroxisome, was investigated for immature S. ovata. A significant correlation was found between EROD activity and volume density of lipofuscin/ceroid in fish hepatocyte (r = 0.750; P < 0.05), but no significant correlation was discernible between EROD activity and peroxisomes. Results from this field study corroborate our earlier laboratory findings, in which induction of EROD activity by intraperitoneal injection of benzo[a]pyrene was associated with increase in absolute volume and absolute number of lipofuscin/ceroid in hepatocytes. The present study provides further evidence that induction of EROD activity is associated with an increase in hepatic lipofuscin/ceroid and possibly cytological damages in immature S. ovata. This cytological change may serve as a potential marker for exposure to PAHs and PCBs.

Animals↗
PubMed2001

Preparation of pentachlorophenol derivatives and development of a microparticle-based on-site immunoassay for the detection of PCP in soil samples.

Pentachlorophenol (PCP) is used as a herbicide in agriculture and as an insecticide for termite control. Because of the apparent hazard associated with its usage, there is a need for an efficient and economic on-site screening method. A 5-min on-site test has been developed for the detection of PCP based on the OnTrak format, a successful Roche on-site test format for drugs of abuse, utilizing the principle of latex agglutination immunoassay. The test detects 1 ppm of PCP in soil samples.

Agglutination Tests↗
PubMed2001

Modeling elastic wave forward propagation and reflection using the complex screen method.

Formulation for calculating forward propagation and reflection in a 3D elastic structure based on the complex-screen method is given in this paper. The calculation of reflections is formulated based on the local Born approximation. When using a small angle approximation, the backscattering operator reduces to a screen operator which is similar to the forward screen propagator. Combining the forward propagator and backscattering operator together, the new method can properly handle the multiple forward scattering and single backscattering in a 3D heterogeneous model. Using a dual-domain technique, the new method is highly efficient in CPU time and memory savings. For models where reverberation and resonance scattering can be neglected, this method provides a fast and accurate algorithm. Synthetic seismograms for two-dimensional elastic models are calculated with this method and compared with those generated by the finite-difference method. The results show that the method works well for small to medium scattering angles and medium velocity contrasts.

Journal Article↗
PubMed2000

Low-level doxorubicin resistance in benzo[a]pyrene-treated KB-3-1 cells is associated with increased LRP expression and altered subcellular drug distribution.

The P-glycoprotein (P-gp)-negative epidermoid pharyngeal carcinoma cells KB-3-1 were grown in 0.25 mM benzo[a]pyrene (BaP) for 3 months and increased resistance to doxorubicin, but not to vinblastine, colchicine, or cisplatin, was found. Doxorubicin resistance was not altered by cyclosporin, the P-gp inhibitor. Intracellular accumulation of BaP or calcein, a substrate for P-gp and multidrug resistance protein (MRP), was not altered by inhibitors of the P-gp and MRP. The expression of cytochrome P450 (CYP) 1A1, lung-resistance-related protein (LRP), P-gp, and MRP was investigated. Overexpression of CYP1A and LRP, on the mRNA and protein levels, was found. BaP-treated KB-3-1 cells remained P-gp negative while the level of MRP was not altered. Subcellular accumulation of BaP was found to be localized in the cytoplasm and minimal in the nuclei in BaP treated cells. In contrast, even penetration of BaP to the nuclei and cytoplasm was found in untreated cells. Subcellular distribution of doxorubicin was altered following BaP treatment with localized accumulation of the cancer drug in cytoplasmic organelles but not in the nuclei. Our data suggested that LRP might play a protective role against toxic compounds. The correlation of increased expression of LRP, but not P-gp nor MRP, with decreased doxorubicin accumulation in the nuclear target suggests a pivotal role of this perinuclear transporter in the MDR phenotype of P-gp-negative cancer cells. These results also propose an alternative mechanism of cancer drug resistance emergence, namely, induction of LRP activity following treatment with BaP, an environmental toxicant and a carcinogen.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Effects of cadmium and phenol on motility and ultrastructure of sea urchin and mussel spermatozoa.

Computer-assisted sperm analysis (CASA) was used to study the effects of Cd(II) and phenol on sperm motility of sea urchin and mussel. In parallel, ultrastructural changes of sperm induced by these two toxicants were also investigated and related to motility impairment. Spermatozoa of sea urchin were more sensitive than mussel spermatozoa to both toxicants. Sea urchin sperm motility showed a good dose-response relationship to Cd(II) levels as well as exposure time. Exposure to the two toxicants changed the size and shape of the midpiece, which might affect the balance of spermatozoa in their swimming. The plasma membrane became more convoluted, and such a change might affect the streamlining and integrity of spermatozoa and hinder their normal movement patterns. Most important, disorganization of mitochondrial membranes and cristae was observed, suggesting disruption of ATP supply for sperm movement. Cadmium also induced greater ultrastructural damages in sea urchin spermatozoa.

Animals↗
PubMed2000

Use of protein phosphatase inhibition assay to detect microcystins in Donghu Lake and a fish pond in China.

Seasonal variations in the level of total microcystins in water samples collected from Donghu Lake and a fish pond in Wuhan, China, were studied between March 1995 and February 1996 using a protein phosphatase inhibition assay involving a radioactive 32P-labelled substrate. The assay is highly reliable and repeatable, and is probably the most sensitive assay for microcystin detection to date. Results of the survey indicated the presence of microcystins in the water samples, and the concentration of microcystins appeared to be related to the degree of eutrophication and water temperature. There is also a correlative relationship between the quantity of microcystins and the abundance of microcystin-producing cyanobacteria (Anabaena and Oscillatoria) in the water bodies over a year cycle. In the present study, the positive detection of microcystins in water bodies having no signs of algal bloom warns of considerable potential threat of these waters to public health.

Animals↗
PubMed2000

Effects of fenoterol and ipratropium on respiratory resistance of asthmatics after tracheal intubation.

We have studied the effects of a beta-agonist, fenoterol, and a cholinergic antagonist, ipratropium, on post-intubation total respiratory system resistance (Rrs) in asthmatics who developed increased Rrs after tracheal intubation. Sixteen stable asthmatics in whom Rrs increased after intubation were allocated randomly to receive either 10 puffs of fenoterol (group F) or 10 puffs of ipratropium (group IB) via a metered dose inhaler 5 min after intubation. Anaesthesia was induced and maintained with propofol i.v. Rrs was recorded before treatment and again 5, 15 and 30 min after treatment. Rrs decreased significantly from pretreatment values by mean 53 (SD 8)%, 53 (7)% and 58 (6)% at 5, 15 and 30 min, respectively, in group F, but declined by only 12 (6)%, 15 (4)% and 17 (5)% in group IB. At all times after treatment, patients in the fenoterol group had significantly lower Rrs values than those in the ipratropium group. We conclude that increased Rrs after tracheal intubation in asthmatics can be reduced effectively by treatment with fenoterol. A secondary finding of our study was that even after induction of anaesthesia with propofol, patients with a history of asthma may develop high Rrs.

Adrenergic beta-Agonists↗
PubMed2000

Construction of new amplifier expression vectors for high levels of IL-2 gene expression.

The success of IL-2 gene therapy in cancer is in part dependent on the development of high level IL-2 gene expression vectors. Currently, expression vectors based on the human cytomegalovirus (CMV) promoter give the highest levels of expression. We have attempted to construct new IL-2 expression vectors to test whether gene expression can be further increased. The first approach was to use the new SR-alpha promoter to control IL-2 gene expression. The second approach was to combine the Tat transcription activator gene and the HIV 1 and 2 promoters in the same construct so that the levels of gene expression can be amplified. Transient transfection results using the human colon cancer cell line SW480 showed that the SR-alpha promoter yields similar levels of activity as the CMV promoter. However, the HIV 1 and 2 promoter-based amplifier constructs produced 11 and 28 times more secreted IL-2 than the CMV promoter control. The augmented activity of the amplifier constructs was dependent on the presence of the Tat gene and the transcriptional units must be placed in the same orientation. Reducing the size of the vectors by elimination of the neomycin selectable marker did not increase the activity of the constructs.

Gene Amplification↗
PubMed2000

Propofol-sodium thiopental admixture reduces pain on injection.

BACKGROUND: Propofol injection associated with a high incidence of pain is well known. Propofol and sodium thiopental mixture has recently been reported to be used for cost saving and able to reduce pain on injection. METHODS: This prospective, randomized, double blind trial was designed to compare the efficacy of different percentages of propofol and sodium thiopental mixture in minimizing propofol injection pain. 146 ASA class 1 patients were assigned to seven groups (pure propofol, pure sodium thiopental, and propofol premixed with 10%, 20%, 30%, 40%, and 50% of sodium thiopental). The intensity of pain was graded and recorded as severe, moderate, mild and no pain according to the response of the patients to the injection. RESULTS: The intensity of injection pain was significantly greater for pure propofol than the others while it was not significantly different among the other groups in comparison. CONCLUSIONS: Sodium thiopental, when added to propofol, can significantly reduce propofol injection pain. This attenuation effect was noted even with as low as 10 volume % of sodium thiopental.

Adult↗