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Biomedical subjects

X C Wu

Publications and source records attributed to X C Wu.

At least 19 recordsLinked to original sources
PubMed2006

Periodic ZnO nanorod arrays defined by polystyrene microsphere self-assembled monolayers.

We demonstrate a low-cost and effective method to fabricate hexagonally patterned, vertically aligned ZnO nanorod arrays. Selective wet-etching is used to develop the catalyzing gold particle hexagonal pattern with the aid of a polystyrene microsphere self-assembled monolayer. The gold particles have tunable sizes independent of the polystyrene microsphere's diameter and are inherently round in shape. Each ZnO rod is grown individually from a catalyzing site via catalyst-initiated epitaxy, and the original hexagonal periodicity is well-preserved. The rods have flat ends, and the diameters of the rods can be controlled well by the amount of source materials. This method provides a promising way to create ZnO one-dimensional nanostructures for applications as two-dimensional photonic crystal, sensor arrays, nanolaser arrays, and optoelectronic devices.

Crystallization↗
PubMed2006

Using carbon nanotubes to absorb low-concentration hydrogen sulfide in fluid.

Hydrogen sulfide is a colorless and flammable gas under room temperature. Usually hydrogen sulfide is considered to be toxic; however, the recent research revealed that hydrogen sulfide in the cardiovascular system plays the role of a vascular dilator. The physiological role of hydrogen sulfide depends on its in vivo level. As such, the measurement of hydrogen sulfide with nano-quantity resolution becomes an important subject. Existing methods generally require bulky samples and are invasive and offline. It will be significantly helpful to measure hydrogen sulfide with a small amount of tissue in a noninvasive method The first attempt was to take a blood or serum sample with a trace amount to examine the interaction between hydrogen sulfide and carbon nanotube. The carbon nanotube is chosen because of a known fact that hydrogen sulfide can be adsorbed by activated carbon. The carbon nanotube is an excellent activated carbon in this regard. Fluorescence intensity of the carbon nanotube with and without immersion of it in a hydrogen sulfide medium was examined in the study. It was found that the intensities increase as the concentrations of hydrogen sulfide increase. Furthermore, the concentration of 10 microM hydrogen sulfide in water was successfully measured.

Absorption↗
PubMed2005

Synthesis, photoluminescence, and adsorption of CdS/dendrimer nanocomposites.

CdS/dendrimer nanocomposites can be synthesized from methanolic Cd(2+) and S(2-) with amine-terminated polyamidoamine dendrimers of generation 8 (G8NH(2)) as stabilizers. By controlling the preparation conditions, nanoparticles with diameters < or = 2 nm can be obtained with a narrow size distribution. They show blue photoluminescence at approximately 450 nm. We studied the effects of various additives on the photoluminescence and elucidated its mechanism. Stable aggregates of two to three G8NH(2) molecules with several CdS nanoparticles form; the particles are located at the surface of the G8NH(2) molecules. The adsorption of the CdS/G8NH(2) nanocomposites on flat substrate surfaces is determined by the substrate chemistry. The hydrophilic nature of G8NH(2) results in weak affinity to graphite but strong affinity to hydroxy-terminated substrates such as mica, oxidized silicon wafers, and carboxylate-terminated monolayers. Patterning of nanocomposites on these hydrophilic substrates is achieved by the microcontact printing method. We propose to use only one molecule, a large dendrimer, to control the nanoparticle formation and also the immobilization of the synthesized nanoparticle/dendrimer composites.

Adsorption↗
PubMed2003

Wear performance of ultrahigh molecular weight polyethylene/quartz composites.

Ultrahigh molecular weight polyethylene (UHMWPE)/quartz composites were compression molded in the presence of organosiloxane, and then hydrolyzed. The used organosiloxane is vinyl tri-ethyloxyl silane. The gelation, the melting behavior, the crystallinity, the mechanical properties and the wear resistance of UHMWPE/quartz composites were investigated. The results showed that organosiloxane can act as a cross-linking agent for UHMWPE matrix and serve as a coupling agent for improving the bonding between the quartz particles and the UHMWPE matrix. The correlation between the various properties and the morphology of the composites has been discussed. At about 0.5phr organsiloxane while the degree of crystallinity of the composite is at the peak value of 57%, the mechanical properties and the wear resistance of UHMWPE/quartz composites reaches their maximum.

Biocompatible Materials↗
PubMed2002

Enhanced wear performance of ultra high molecular weight polyethylene crosslinked by organosilane.

Ultra high molecular weight polyethylene (UHMWPE) crosslinked by organosilane was thermal compression molded. The organosilane used was the tri-ethyloxyl vinyl silane. Its gelation, melting behavior, crystallinity, mechanical and wear-resisting properties were systematically investigated. The results showed that the gel ratio of UHMWPE increases with the incorporation of organosilane. At a low content of organosilane, the melting point and crystallinity of the crosslinked UHMWPE increase, and hence the mechanical and wear-resisting properties are improved. However, at a high content of organosilane, these performances of the crosslinked UHMWPE become worse. At 0.4 phr silane, the wear resistance of crosslinked UHMWPE reaches its optimum value.

Journal Article↗
PubMed2001

Gene transfer and metabolic modulators as new therapies for pulmonary hypertension. Increasing expression and activity of potassium channels in rat and human models.

UNLABELLED: Chronic Hypoxic Pulmonary Hypertension (CH-PHT) is characterized by pulmonary artery (PA) vasoconstriction and cell proliferation/hypertrophy. PA smooth muscle cell (PASMC) contractility and proliferation are controlled by cytosolic Ca++ levels, which are largely determined by membrane potential (E(M)). E(M) is depolarized in CH-PHT due to decreased expression and functional inhibition of several redox-regulated, 4-aminopyridine (4-AP) sensitive, voltage-gated K+ channels (Kv1.5 and Kv2.1). Humans with Pulmonary Arterial Hypertension (PAH) also have decreased PASMC expression of Kv1.5 and Kv2.1. We speculate this "K+-channelopathy" contributes to PASMC depolarization and Ca++ overload thus promoting vasoconstriction and PASMC proliferation. We hypothesized that restoration of Kv channel expression in PHT and might eventually be beneficial. METHODS: Two strategies were used to increase Kv channel expression in PASMCs: oral administration of a metabolic modulator drug (Dichloroacetate, DCA) and direct Kv gene transfer using an adenovirus (Ad5-Kv2.1). DCA a pyruvate dehydrogenase kinase inhibitor, promotes a more oxidized redox state mimicking normoxia and previously has been noted to increase K+ current in myocytes. Rats were given DCA in the drinking water after the development of CH-PHT and hemodynamics were measured approximately 5 days later. We also tested the ability of Ad5-Kv2.1 to increase Kv2.1 channel expression and function in human PAs ex vivo. RESULTS: The DCA-treated rats had decreased PVR, RVH and PA remodeling compared to the control CH-PHT rats (n=5/group, p<0.05). DCA restored Kv2.1 expression and PASMC Kv current density to near normoxic levels. Adenoviral gene transfer increased expression of Kv2.1 channels and enhanced 4-AP constriction in human PAs. CONCLUSION: Increasing Kv channel function in PAs is feasible and might be beneficial.

Animals↗
PubMed2001

Expression of lipopolysaccharide binding protein and its receptor CD14 in experimental alcoholic liver disease.

AIM: To evaluate the relationship between the expression of lipopolysaccharides (LPS) binding protein (LBP) and CD14 mRNA and the severity of liver injury in alcohol-fed rats. METHODS: Twenty Wistar rats were divided into two groups:ethanol-fed group (group E) and control group (group C). Group E was fed with ethanol(5-12 g x kg(-1) x d(-1)) and group C received dextrose instead of ethanol. Rats of the two groups were sacrificed at 4 weeks and 8 weeks. Levels of endotoxin and alanine transaminase (ALT) in blood were measured, and liver pathology was observed under light and electronic microscopy. Expressions of LBP and CD14 mRNA in liver tissues were determined by RT-PCR analysis. RESULTS: Plasma endotoxin levels were increased more significantly in group E(129+/-21) ng x L(-1) and (187+/-35) ng x L(-1) at 4 and 8 wk than in control rats(48+/-9) ng x L(-1) and (53+/-11) ng x L(-1), respectively (P<0.05). Mean values of plasma ALT levels were (1867+/-250) nkat x L(-1) and (2450+/-367) nkat x L(-1) in Group E. The values were increased more dramatically in ethanol-fed rats than in Group C after 4 and 8 weeks. In liver section from ethanol-fed rats, there were marked pathological changes (steatosis, cell infiltration and necrosis). In ethanol-fed rats, ethanol administration led to a significant increase in LBP and CD14 mRNA levels compared with the control group (P<0.05). CONCLUSION: Ethanol administration led to a significant increase in endotoxin levels in serum and LBP and CD14 mRNA expressions in liver tissues. The increase of LBP and CD14 mRNA expression might wake the liver more sensitive to endotoxin and liver injury.

Acute-Phase Proteins↗
PubMed2001

Calcium channel blockade in vascular smooth muscle cells: major hypotensive mechanism of S-petasin, a hypotensive sesquiterpene from Petasites formosanus.

In vivo and in vitro studies were carried out to examine the putative hypotensive actions of S-petasin, a sesquiterpene extracted from the medicinal plant Petasites formosanus. Intravenous S-petasin (0.1-1.5 mg/kg) in anesthetized rats produced a dose-dependent hypotensive effect. In isolated aortic ring, isometric contraction elicited by KCl or the L-type Ca2+ channel agonist Bay K 8644 was reduced by S-petasin (0.1-100 microM), an action not affected by the cyclooxygenase inhibitor indomethacin, nitric-oxide synthase inhibitor N(omega)-nitro-L-arginine, guanylyl cyclase inhibitor methylene blue, or removal of vascular endothelium. Pretreatment with S-petasin for 10 min shifted the concentration-response curve for KCl (15-90 mM)-induced contraction to the right and reduced the maximal response. In Ca2+-depleted and high K+-depolarized aortic rings preincubation with S-petasin attenuated the Ca2+-induced contraction in a concentration-dependent manner, suggesting that S-petasin reduced Ca2+ influx into vascular smooth muscle cells (VSMCs). Moreover, in cultured VSMCs, whole-cell patch-clamp recording indicated that S-petasin (1-50 microM) inhibited the L-type voltage-dependent Ca2+ channel (VDCC) activities. Intracellular Ca2+ concentration ([Ca2+[(i)) estimation using the fluorescent probe 1-[2-(5-carboxyoxazol-2-yl)-6-aminobenzofuran-5-oxy]-2-(2'-amino-5'-methylphenoxy)-ethane-N,N,N,N-tetraacetic acid pentaacetoxymethyl ester indicated that S-petasin (10, 100 microM) suppressed the KCl-stimulated increase in ([Ca2+[(i)). Taken together, the results suggested that a direct Ca2+ antagonism of L-type VDCC in vascular smooth muscle may account, at least in part, for the hypotensive action of S-petasin.

Animals↗
PubMed2001

Breast cancer: incidence, mortality, and early detection in Louisiana, 1988-1997.

Breast cancer is the most commonly diagnosed cancer and the second leading cause of cancer death among Louisiana women. The incidence data from Louisiana Tumor Registry were used to calculate breast cancer incidence rates, which were compared with the combined rates from the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) program. Breast cancer mortality rates for Louisiana were compared with the US death rates from the National Center for Health Statistics (NCHS). Our data revealed that Louisiana women were not at a higher risk for developing breast cancer than women in the SEER areas, but that mortality rates in Louisiana were not correspondingly low. Although the percentage of cases diagnosed at an early stage (in situ and localized) increased in Louisiana from 1988 through 1997, the average in Louisiana was still below the level for the SEER areas (65.9% and 71.6%) in 1993-1997. The rates of in situ breast cancer significantly increased (on average 5.3% for whites per year and 7.1% for blacks), and localized breast cancer also significantly increased (2.6% for whites and 2.5% for blacks), while the incidence of distant stage breast cancer significantly decreased (3.4% for whites and 2.0% for blacks). Compared with white women, black women still were less likely to be diagnosed with early stage breast cancer in 1993-1997 (56.4% and 68.9%). Women residing in the parishes with high percentages of persons in poverty were less likely to be diagnosed with early stage of disease.

Black People↗
PubMed2001

[The RAPD analysis of haploid strain of thermotolearnt yeast].

The haploid strains HZ line from the thermololeant strain HU-TY-1 of Saccharomyces cerevisiae have been obtained by sporulation, and the analysis of growth and fermentation test was performed. The strains HZ-21 and HZ-84 were used as the analysis of random amplified polymerphic DNA (RAPD). The result showed that there were some polymorphic DNA fragments of genomic DNA among haploid, the diploid parent strain HU-TY-1 and the original strain LK, some of them may be correlation with thermotolerant property.

DNA, Fungal↗
PubMed2000

[A quantitative analysis of renal pathology in the children with anaphylactoid purpura nephritis (APN)].

OBJECTIVE: To provide the theoretical value for the treatment and prognostic judgement of APN. METHODS: All cases were scored on the pathologic change of glomeruli and tubules. RESULTS: The pathologic scores of glomeruli in 30 cases were as follows: no one on Grade 0; 6(20%) on Grade 1; 17(56.7%) on Grade 2 and 7 (23.3%) on Grade 3. The pathologic scores of tubule were: Grade 0 was 2(6.7%); Grade 1 was 6(20%); Grade 2 was 14(46.7%); Grade 3 was 8(26.7%). There was positive correlation between glomerulus and tubule pathologic degree(r = 0.783, P < 0.01). The pathologic score of nephrotic syndrome in clinical manifestation was higher than that of non-nephrotic syndrome(P < 0.01). There was no significant difference in glomerular pathologic score between the simple urinary protein group and acute glomerulonephritis(AGN) group(P > 0.05), but tubular pathologic score in simple urinary proteins group was higher than that of AGN and essential hematuria group (P < 0.01, P < 0.05). The pathologic score of kidney(including glomerulus and tubule) was positively correlated with the disease course(r = 0.563, P < 0.01), but not with serum urea nitrogen and creatinine(r = 0.281, r = 0.236, P > 0.05). CONCLUSION: Serious tubular pathologic changes(not only glomerular pathologic change, but also tubular pathologic change in the APN children) were found in the patients with nephrotic syndrome and simple urinary proteins. Long-term urinary protein and the recurrence of the disease may be the important risk factor in kidney pathologic of APN.

Adolescent↗
PubMed2000

Mutations induced by some DNA minor groove binding alkylators in AS52 Chinese hamster cells.

Nitrogen mustards are commonly used in cancer chemotherapy. They interact with DNA at electronegative sites, primarily forming N7 guanine mono-adducts and interstrand cross-links. Targeting nitrogen mustards to DNA by attachment of a DNA minor groove binding carrier such as the bisbenzimidazoles Hoechst 33258 (pibenzimol) or Hoechst 33342 (HOE) makes it possible to direct DNA alkylation to more specific stretches of DNA. We have performed a detailed molecular analysis of 6-thioguanine resistant clones arising in Chinese hamster AS52 cells after treatment with HOE, in comparison with a mono- and bifunctional pair of bisbenzimidazole-targeted nitrogen mustards (MGBs). HOE showed no significant ability to induce 6-thioguanine resistant mutants, possibly because drug-treated cells are highly susceptible to apoptosis within very short times. Neither of the MGBs caused the rapid cell death seen with the bisbenzimidazole. However, both MGBs were weaker mutagens than previously found for undirected mustards in the same system, an effect that we suggest could relate to greater structure-directed binding to less mutable DNA sites in the minor groove. Additionally, the nature of some of the mutants suggested there may be a small component of topo I and/or II-mediated events in the mutagenicity of the MGBs. Both MGBs showed high activity in causing deletion mutations, which may be due to errors in attempted repair of the complex lesions formed by minor groove targeted alkylators.

Alkylating Agents↗
PubMed2000

Incidence of lymphohaematopoietic malignancies in a petrochemical industry cohort: 1983-94 follow up.

OBJECTIVES: In response to a previous finding of increased mortality from lymphohaematopoietic (LH) malignancies, this study examines incidence of LH malignancy in a petrochemical industry cohort. Emphasis is on chronic lymphocytic leukaemia (CLL) and on comparisons by period of first employment. METHOD: The study cohort consists of 8942 employees who were active in the period 1970-92 and alive on 31 December 1982. Record linkage with the Louisiana tumour registry (LTR) provided information on cancer for cases occurring between 1983 and 1994. Standardised incidence ratios (SIR), with the south Louisiana population as a comparison, were computed for all cancers, all LH malignancies and specific LH subtypes. Analyses were conducted for sex and race categories, and by period of first employment, job type, duration of employment, and latency. RESULTS: 672 Cases of cancer were identified, including 59 LH malignancies. Women (n=1169) had an overall cancer SIR below unity and four LH malignancies versus 2.28 expected. Among the 7773 men, those first employed before 1950 had no overall cancer excess, a significant 1.4-fold increase in overall LH malignancies (43 observed versus 30.78 expected), and four CLL cases versus 3.27 expected. Findings for men first employed after 1950 are based on fewer cases, but there was no indication of excesses of overall cancer or LH malignancy. Numbers were too small in the group first employed after 1950 for meaningful analysis of LH malignancy subtypes such as CLL (one case). CONCLUSION: These findings do not suggest a continuing excess of CLL but do suggest a small increase in incidence of overall LH malignancy for workers first employed before 1950. This may reflect associations with earlier workplace conditions, although work related patterns are mixed. Interpretation is limited by the diverse group of diseases within LH malignancies, and the lack of control for non-work factors other than sex, age, race, and period of diagnosis. This study has a major advantage of more complete and reliable cancer ascertainment compared with the mortality investigation, and shows the feasibility and benefits of using cancer registry incidence data in an occupational cohort study.

Adult↗
PubMed1999

Nitric oxide and renal nerve-mediated proximal tubular reabsorption in normotensive and hypertensive rats.

In Inactin-anesthetized Wistar rats with an intact renal innervation, intratubular nitro-L-arginine methyl ester (L-NAME, 10(-4) M) increased proximal fluid uptake (J(va), at 2.47 +/- 0.61 x 10(-4) mm(3). mm(-2). s(-1)) by 17% (P < 0.05), whereas coadministration with sodium nitroprusside (SNP, 10(-4) M) decreased J(va) by 18% (P < 0.01). Similar manipulation of NO generation was without effect in groups of Wistar rats subjected to acute renal denervation. Intratubular aminoguanidine (10(-4) M), a selective inducible nitric oxide synthase (NOS) blocker, had no effect on J(va) in intact kidneys of Wistar rats, but the neuronal NOS (nNOS) blocker, 7-nitroindazole (10(-4) M and 10(-6) M) increased J(va) by 19-23% (both P < 0.001). In stroke-prone spontaneously hypertensive rats (SHRSP), J(va) values in the innervated kidneys were lower (P < 0.05) than in the corresponding Wistar groups and were unchanged by intratubular L-NAME or L-NAME plus SNP. The tonic attenuation of proximal epithelial transport by NO was dependent on the renal sympathetic nerves and appeared to be generated by the nNOS isoform of the enzyme. This role of NO was not evident in the SHRSP.

Absorption↗
PubMed1999

Cancer of the colon and rectum in Louisiana.

Cancer of the colon and rectum ranks fourth for incidence and second for mortality among Louisiana residents. Incidence rates calculated from Louisiana Tumor Registry data for 1991-95 show that whites in Louisiana were diagnosed with colon cancer at approximately the same rates as those in the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program, but rates for African Americans were significantly lower in Louisiana than nationally. For rectal cancer, Louisiana incidence rates approximate the national rates for all but African-American males, whose rate was significantly lower. Mortality rates for colon and rectal cancer in Louisiana were comparable to the SEER rates, suggesting Louisiana blacks, once diagnosed, have a poorer survival than their national counterparts. Risk factors for colorectal cancer and guidelines for screening are discussed, as is an upcoming study of patient care for colon cancer.

Adult↗
PubMed1999

Louisiana Tumor Registry: new developments and activities.

New developments in the Louisiana Tumor Registry (LTR) over the past 3 years have enhanced the operation of the LTR and broadened its functions. Recent funding for numerous special studies and research collaborations have expanded the registry activities from data collection and special etiologic studies to more completely address the mandates of registry law, which require the LTR to participate in studies of cancer causes, treatment, and survival in order to reduce cancer morbidity and mortality in Louisiana.

Humans↗
PubMed1999

Vasorelaxing action of rutaecarpine: effects of rutaecarpine on calcium channel activities in vascular endothelial and smooth muscle cells.

Rutaecarpine (Rut) has been shown to induce hypotension and vasorelaxation. In vitro studies indicated that the vasorelaxant effect of Rut was largely endothelium-dependent. We previously reported that Rut increased intracellular Ca2+ concentrations ([Ca2+]i) in cultured rat endothelial cells (ECs) and decreased [Ca2+]i in cultured rat vascular smooth muscle (VSMCs) cells. The present results showed that the hypotensive effect of Rut (10-100 microgram/kg i.v.) was significantly blocked by the nitric oxide synthase inhibitor Nomega-nitro-L-arginine. In aortic rings, Rut (0. 1-3.0 microM)-induced vasorelaxation was inhibited by Nomega-nitro-L-arginine and hydroquinone but not by antagonists of the various K+ channels, 4-aminopyridine, apamin, charybdotoxin, or glibenclamide. Rut (0.1 and 1.0 microM) inhibited the norepinephrine-induced contraction generated by Ca2+ influx and at 1.0 microM increased cyclic GMP (cGMP) production in endothelium-intact rings and to a lesser extent in endothelium-denuded rings. In whole-cell patch-clamp recording, nonvoltage-dependent Ca2+ channels were recorded in ECs and Rut (0.1, 1.0 microM) elicited an opening of such channels. However, in VSMCs, Rut (10.0 microM) inhibited significantly the L-type voltage-dependent Ca2+ channels. In ECs cells, Rut (1.0, 10.0 microM) increased nitric oxide release in a Ca2+-dependent manner. Taken together, the results suggested that Rut lowered blood pressure by mainly activating the endothelial Ca2+-nitric oxide-cGMP pathway to reduce smooth muscle tone. Although the contribution seemed to be minor in nature, inhibition of contractile response in VSMCs, as evidenced by inhibition of Ca2+ currents, was also involved. Potassium channels, on the other hand, had no apparent roles.

4-Aminopyridine↗