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Biomedical subjects

X Shi

Publications and source records attributed to X Shi.

At least 37 records · Page 2Linked to original sources
PubMed2006

Pulsed-field gel electrophoresis patterns of Escherichia coli O157 isolates from Kansas feedlots.

This study investigated the prevalence and distribution of Escherichia coli O157 genetic types within and among feedlots using pulsed-field gel electrophoresis to separate XbaI-digested DNA. The study population consisted of 300 pens of cattle in 30 feedlots in Kansas that were sampled (feces, water, and water sediment) within a month of being shipped for slaughter. The prevalence of E. coli O157 was 8.5% in feces, 3.1% in water, and 4.5% in water sediment samples. A total of 424 E. coli O157 isolates were characterized by pulsed-field gel electrophoresis, and 139 subtypes (100% Dice similarity with no band differences) were identified. The majority of subtypes (70/139) was identified only once, but nine were identified 10 or more times. Identical subtypes were recovered from both feces and water tanks in 10 feedlots. The majority of subtypes were identified in only one feedlot, and the number of subtypes ranged from one to 23 within a feedlot and from one to seven within a pen. There were 10 feedlots with at least 15 positive samples. In these 10 feedlots, the most common subtype accounted for 16.9-78.6% of the isolates. Common subtypes differed among feedlots. In eight of the 10 feedlots, the most common subtype was identified in multiple pens. The results support a complex ecology for E. coli O157 in feedlot operations, with factors associated with exposure and transmission likely acting at a common level for multiple feedlots, within feedlots, and within pens of cattle.

Animals↗
PubMed2006

Study on the potential of farmland soils as non-point sources of nitrogen and phosphorus in Japan.

The amounts of N and P accumulated in farmland soils of 50 cm depth were equivalent to the amount of chemical fertilizer supplied for 50-70 years. The values of N/P of surface soils in farmlands were 1.0-4.3, lower than expected. The median diameter of soil particles in run-off waters was generally less than 10 microm. The mean values of particulate fractions over 1 microm and over 0.22 microm were 19% for N, 27% for P, and 39% for N, 64% for P respectively. Fine particles of soil containing concentrated phosphorus should be carefully monitored as potential sources related to eutrophication.

Agriculture↗
PubMed2005

Observation of a resonance in Chi(1835) in J/psi --> gammapi+ pi- eta-.

The decay channel J/psi --> gamma(pi)(+)pi(-)eta is analyzed using a sample of 5.8 x 10(7) J/psi events collected with the BESII detector. A resonance, the Chi(1835), is observed in the pi(+)pi(-)eta invariant-mass spectrum with a statistical significance of 7.7 sigma. A fit with a Breit-Wigner function yields a mass M = 1833.7 +/- 6.1(stat) +/- 2.7(syst) MeV/c(2), a width Tau = 67.7 +/- 20.3(stat) +/- 7.7(syst) MeV/c(2), and a product branching fraction B(J/psi --> gammaChi) . B(Chi --> pi(+)pi(-)eta) = [2.2 +/- 0.4(stat) +/- 0.4(syst)] x 10(-4). The mass and width of the Chi(1835) are not compatible with any known meson resonance. Its properties are consistent with expectations for the state that produces the strong pp mass threshold enhancement observed in the J/psi --> gammapp process at BESII.

Journal Article↗
PubMed2005

Evidence for Bs* Bs* production at the Gamma(5S) resonance.

We use data collected by the CLEO III detector at the Cornell Electron Storage Ring to measure the inclusive yields of D(s) mesons as B(Y(5S) --> D(s)X) = (44-7 +/- 4.2 +/- 9.9)% and B(Y(4S) --> D(s)X) = (18.1 +/- 0.5 +/- 2.8)%. From these measurements, we make a model dependent estimate of the ratio of B(s)*B(s)* to the total bb quark pair production of (16.0 +/- 2.6 +/- 5.8)% at the Y(5S) energy.

Journal Article↗
PubMed2005

Improved measurement of B(D+ --> mu+nu) and the pseudoscalar decay constant fD+.

We extract a relatively precise value for the decay constant of the meson by measuring B(D+ --> mu+nu) = (4.40 +/-0.66(+0.09)(-0.12) x 10(-4) using 281 pb(-1) of data taken on phi(3770) the resonance with the CLEO-c detector. We find fD+ = (222.6 +/- 16.7(+2.8)(-3.4)) MeV, and compare with current theoretical calculations. We also set a 90% confidence upper limit on B(D+e+nu)< 2.4 x 10(-5) which constrains new physics models.

Journal Article↗
PubMed2005

Search for rare and forbidden decays D+ --> h+/- e+/- e+.

Using 0.8 x 10(6) D+ D- pairs collected with the CLEO-c detector at the psi(3770) resonance, we have searched for flavor-changing neutral current and lepton-number-violating decays of D+ mesons to final states with dielectrons. We find no indication of either, obtaining 90% confidence level upper limits of B(D+ --> pi+ e+ e-) < 7.4 x 10(-6), B(D+ --> pi- e+ d+) < 3.6 x 10(-6), B(D+ --> K+ e+ e-) < 6.2 x 10(-6), and B(D+ --> K- e+ e+) < 4.5 x 10(-6).

Journal Article↗
PubMed2005

Filling fraction limit for intrinsic voids in crystals: doping in skutterudites.

The doping limit or the filling fraction limit (FFL) of various impurities for the intrinsic voids in the lattice of is studied by the density functional method. The FFL is shown to be determined not only by the interaction between the impurity and host atoms but also by the formation of secondary phases between the impurity atoms and one of the host atoms. The predicted FFLs for Ca, Sr, Ba, La, Ce, and Yb in are in excellent agreement with reported experimental data. A correlation between the FFL of an impurity atom and its valence state and electronegativity is discovered.

Journal Article↗
PubMed2005

Absolute branching fraction measurements of exclusive D+ semileptonic decays.

Using data collected at the psi(3770) resonance with the CLEO-c detector at the Cornell e+e- storage ring, we present improved measurements of the absolute branching fractions of D+decays to K0e+ve, pi0e+ve, K*0e+ve, and p0e+ve, and the first observation and absolute branching fraction measurement of D+ --> omega e+ve. We also report the most precise tests to date of isospin invariance in semileptonic D0 and D+ decays.

Journal Article↗
PubMed2005

Measurement of absolute hadronic branching fractions of D mesons and e+e- -->DD cross sections at Ec.m.=3773 MeV.

Using 55.8 pb(-1) of e+e- collisions recorded at the psi(3770) resonance with the CLEO-c detector at CESR, we determine absolute hadronic branching fractions of charged and neutral D mesons using a double tag technique. Among measurements for three D0 and six D+ modes, we obtain reference branching fractions B(D0-->K-pi+)=(3.91+/-0.08+/-0.09)% and B(D+-->K-pi+pi+)=(9.5+/-0.2+/-0.3)%, where the uncertainties are statistical and systematic, respectively. Final state radiation is included in these branching fractions by allowing for additional, unobserved, photons in the final state. Using a determination of the integrated luminosity, we also extract the cross sections sigma(e+e- -->D0D0)=(3.60+/-0.07(+0.07)(-0.05)) nb and sigma(e+e- -->D+D-)=(2.79+/-0.07(+0.10)(-0.04)) nb.

Journal Article↗
PubMed2005

Observation of the hc(1P1) state of charmonium.

The h(c)((1)P(1)) state of charmonium has been observed in the reaction psi(2S) --> pi(0)h(c) --> (gammagamma)(gammaeta(c)) using 3.08 x10(6) psi(2S) decays recorded in the CLEO detector. Data have been analyzed both for the inclusive reaction, where the decay products of the eta(c) are not identified, and for exclusive reactions, in which eta(c) decays are reconstructed in seven hadronic decay channels. We find M(h(c)) = 3524.4 +/- 0.6 +/- 0.4 MeV which corresponds to a hyperfine splitting DeltaM(hf)(1P) triple-bond pi(0)h(c)) x B(h(c) --> gammaeta(c)) = (4.0 +/- 0.8 +/- 0.7) x 10(-4).

Journal Article↗
PubMed2005

Observation of thirteen new exclusive multibody hadronic decays of the psi(2S).

Using data accumulated with the CLEO detector corresponding to an integrated luminosity of [symbol: see text] = 5.63 pb(-1) on the peak of the psi(2S) [3.08 x 10(6) psi(2S) decays] and 20.70 pb(-1) at square root of[s] = 3.67 GeV, we report first measurements of the branching fractions for the following 13 decay modes of the psi(2S): eta3pi, &eta'3pi, rhoK+K-, K+K-pi+pi-pi0, 2(K+K-), 2(K+K-)pi0, rhopp, pppi+pi-pi0, etapp, ppK+K-, lambdalambdapi+pi-, lambdapK+, and lambdapK+pi+pi-, and more precise measurements of 8 previously measured modes: 2(pi+pi-), rhopi+pi-, 2(pi+pi-)pi0, omegapi+pi-, K+K-pi+pi-, omegaK+K-, phiK+K-, and pppi+pi-. We also report new branching fraction measurements of phipi+pi- and omegapp and upper limits for etapi+pi-, etaK+K-, and phivpp. Results are compared, where possible, with the corresponding J/psi branching ratios to provide new tests of the 12% rule.

Journal Article↗
PubMed2005

Three laboratory assessments of a new triple-head toothbrush and the Oral-B 40 toothbrush.

OBJECTIVE: The objective of this series of laboratory studies was to assess a new triple-head toothbrush, the DR BEST FreiKopf, compared to the Oral-B 40 toothbrush, for interproximal access efficacy (IAE), gingival margin cleaning (GMC), and subgingival access (SA) as measures of toothbrush efficacy. METHODOLOGY: In each procedure, six toothbrushes of each product were tested four times for a total of twenty-four tests on each toothbrush design. In the IAE assay, the tooth brushing technique involved independent evaluations of each toothbrush in a vertical or horizontal brushing motion, tooth shapes simulating anterior and posterior teeth, and a brushing weight of 250 g. The brushing apparatus was set to brush 15 seconds at two strokes per second with a 50 mm stroke. In the GMC assay, the tooth brushing technique involved independent evaluations of each toothbrush in a horizontal brushing motion, tooth shapes simulating posterior teeth, and a brushing weight of 500 g. Simulated gingivae were prepared from self-curing dental acrylic. The brushing apparatus was set to brush for 60 seconds at two strokes per second with a 15 mm stroke. In the SA evaluations, the tooth shapes simulating posterior teeth were used, as well as a brushing weight of 500 g for 60 seconds at two strokes per second with a 15 mm stroke. All readings were measured with 3x magnification by one investigator. RESULTS: The mean IAE value on anterior and posterior tooth shapes, with vertical and horizontal brushing, and overall, was significantly (p < 0.001) higher for the triple-head toothbrush than for the Oral-B 40 toothbrush. In the GMC assay, the triple-head toothbrush had a significantly (p < 0.001) superior mean value compared to the Oral-B 40 product tested. In the SA study, the triple-head toothbrush was significantly (p < 0.001) superior compared to the Oral-B 40 toothbrush product tested. CONCLUSIONS: The triple-head toothbrush has demonstrated superiority to a traditional flat-head toothbrush for access into interproximal areas, and for removing deposits from the gingival margin, as well as below the gumline, in these laboratory assays.

Analysis of Variance↗
PubMed2003

Mamestra configurata serpin-1 homologues: cloning, localization and developmental regulation.

A screen of a Mamestra configurata (bertha armyworm) midgut cDNA library identified three types of cDNA clones that resemble the Manduca sexta serpin-1 gene family. Two serpins, 1b and 1c, possess a common conserved serpin amino terminal scaffold domain but bear no similarity to any members of the M. sexta gene family within the reactive centre loop. These serpins differ from one another by only two amino acids in the reactive centre loop (S(363)-->P) and serpin signature (M(369)-->T) regions. The other member, denoted serpin-1a, is closely related to the M. sexta serpin-1Z. M. configurata serpins as a group were expressed in all insect developmental stages including eggs, larvae and adult moths. Within larvae, serpin gene expression was restricted to the early to middle instar developmental phase and mainly in the fat body and hemocytes. Stress imposed by starvation strongly induced expression in fat body and to a lesser degree in alimentary organs, nervous system and Malphigian tubules. Conversely, starvation decreased expression in hemocytes. Wounding or inoculation with bacteria did not induce serpin gene transcription but did lead to the formation of higher and lower molecular weight forms, presumably serpin-protease complexes and resultant truncated serpin, respectively. Two dimensional PAGE and western blotting analysis revealed at least 12 distinct serpins consisting primarily of neutral, but also highly acidic and basic isoforms, as well as additional high and low molecular weight immuno-reactive species. Serpins-1b/1c are the more prominent serpin isoforms and are expressed predominantly in the fat body and subsequently exported to the hemolymph as revealed by western blotting and immunolocalization. The serpin-1b/1c isoform was found only as the fully glycosylated species within the hemolymph. Hemolymph protease activity was comprised mostly of serine proteases whose overall activity increased dramatically at the onset of the molt concomitant with a sharp decline in serpin gene expression.

Amino Acid Sequence↗
PubMed2002

Determination of toxicokinetic parameters for bioconcentration of water-soluble fraction of petroleum hydrocarbon associated with no. 0 diesel in Changjiang estuary and Jiaozhou bay: model versus mesocosm experiments.

A method is proposed for determination of toxicokinetic parameters for bioconcentration by phytoplankton of the water-soluble fraction (WSF) of petroleum hydrocarbon (PH) associated with No. 0 diesel, in which WSF-PH concentration in phytoplankton cells, C(A(d)), is estimated by subtracting concentration in water (S-bottle) containing a phytoplankton sample from that in a C-bottle without phytoplankton. It was demonstrated that C(A(d)) agrees well with the concentration found by direct ultrasonication extraction of collected cells, C(A(ind)) ( r = 0.88, p < 0.0001), and its uncertainty was about 17.6%. Mesocosms in 25-m3 ethylene vinyl acetate or 4-m3 polyethylene bags were performed at two sites in China: Changjiang Estuary in spring/summer 1998 and Jiaozhou Bay in autumn 1999 and spring/summer 2000. The experiments were designed to determine toxicokinetic parameters, including specific rates of uptake and elimination, and bioconcentration factor (BCF), for bioconcentration of WSF-PH by phytoplankton. A modified kinetic two-compartment model for bioconcentration of WSF-PH by phytoplankton was developed to estimate the toxicokinetic parameters. In the model, the influence of phytoplankton growth on bioconcentration and WSF-PH decline due to biotic and abiotic processes other than bioconcentration, such as volatilization, microbial degradation, phytolysis, and sorption expressed as an exponential-decay equation, are taken into account. Size-dependent BCF was observed in the laboratory experiment. BCFs were 1.0 x 10(4) in summer in Changjiang Estuary, 1.6 x 10(4) in summer, and 1.1 x 10(4) in autumn in Jiaozhou Bay. The difference in BCF may be interpreted by its size dependence.

Biological Availability↗
PubMed2002

The inherent cellular level of reactive oxygen species: one of the mechanisms determining apoptotic susceptibility of leukemic cells to arsenic trioxide.

Though reactive oxygen species (ROS) has been noticed to be involved in arsenic trioxide (As(2)O(3))-induced apoptosis of tumor cells, its role in apoptosis signaling remained to be elucidated. The objective of this work was to explore the association of the inherent cellular ROS level with the susceptibility of the tumor cells to apoptosis induction by As(2)O(3). Low concentration of As(2)O(3) was administered to cultured leukemic cell lines NB4, U937, HL60 and K562. The difference in apoptotic sensitivity was displayed among four cell types. ROS probes were incubated with the cells in the absence of As(2)O(3), and ROS was thus quantified relatively by flow cytometry. We manifested, in four cell types, the inherently existed difference in whole ROS quantity, and a positive correlation between the inherent ROS level and their apoptotic sensitivity to As(2)O(3). Furthermore, by interference using a ROS producer, we demonstrated that an elevation of ROS level would sensitize the cells to As(2)O(3)-induced apoptosis. The results of the present work suggested that the inherent ROS level might be determinative in tumor cells for their apoptotic susceptibility to As(2)O(3).

Antineoplastic Agents↗
PubMed2002

Clearance of quinupristin-dalfopristin (Synercid) and their main metabolites during continuous veno-venous hemofiltration (CVVH) with or without dialysis.

BACKGROUND: Quinupristin-dalfopristin (Q/D) is often utilized in critically ill patients, some of whom require CVVH. This study was undertaken to determine the clearance of O/D and their main active metabolites (RPR 100391, RP 69012, RP 12536) via CVVH in the swine model. METHODS: Q/D 7.5 mg/kg was intravenously administered over 0.5 h to 12 swine after induction of acute renal failure by ligation of the renal arteries. At 0.5 h post injection, the CVVH procedure was initiated and continued for 8 hours at the following pump rates: (1)100 mL/min, (2)180 rnL/min, and (3)100 mL/min with dialysis (flow rate: 1 L/h). Blood and ultrafiltrate samples were collected at 1 h intervals and assessed by a validated HPLC method. RESULTS: Plasma analysis suggests rapid metabolism to the main active metabolites which are appreciably cleared as demonstrated by high clearance and sieving coefficient estimates. Mean clearance estimates for RP 69012, RP 100391, and RP 12536 are 729, 777, and 578 mL/h in the 100 mL/min CVVH group, 772, 785, 685 mL/min in the 180 mL/min CVVH group, and 753, 791, 616 mL/min in the 100 mL/min CVVH group with 1 L/h dialysis, respectively. CONCLUSION: These data reveal that Q/D is rapidly metabolized and the metabolites are cleared to a large extent via CVVH. Due to the considerable contribution of the metabolites to overall in vivo activities, additional studies are required to fully quantify their removal before final dosage modifications for patients undergoing CVVH can be recommended.

Animals↗
PubMed2002

Laboratory evaluations of elmex inter X toothbrushes for interproximal access efficacy and posterior tooth surface cleaning.

Laboratory methods have been developed to evaluate the ability of toothbrush bristles to remove artificial plaque deposits at interproximal sites (Interproximal Access Efficacy; IAE) and on distal tooth surfaces (Posterior Tooth Surface Cleaning; PTSC). In the testing performed for this study, six toothbrushes were evaluated. These were: elmex inter X Sensitive; elmex inter X Sensitive Short Head; elmex inter X medium; elmex inter X Medium Short Head; Oral-B Cross Action 40 medium; and the ADA reference standard toothbrush. Six toothbrushes of each design were tested four times under wet brushing conditions in all assays. In the IAE studies, toothbrushing was conducted using a vertical or horizontal brushing motion, simulated anterior or posterior teeth, and a brushing weight of 250 g. The bristles were placed at a 90 degree angle to the tooth surface, and brushing was performed for 15 seconds at two strokes per second with 50 mm strokes. IAE was recorded as the maximum width of simulated plaque deposit removed. For the PTSC evaluations, a horizontal brushing motion was used on posterior tooth shapes, with a 250 g brushing pressure for ten seconds. PTSC was determined as the maximum measurement of artificial plaque deposit removed from the mid-facial area to the maximum post-distal area of the most posterior simulated tooth shape. All data were assessed with ANOVA and the post hoc Tukey test. In the individual IAE tests, with vertical or horizontal brushing on anterior and posterior simulated teeth, and on overall IAE mean values, the four elmex inter X toothbrushes were significantly higher (p < 0.01-0.001) than the ADA reference standard and the Oral-B Cross Action 40 toothbrushes. The mean PTSC values for all toothbrushes were significantly higher (p < 0.01-0.001) compared to the ADA Reference Standard toothbrush mean PTSC. All elmex inter X brushes were statistically significantly higher (p < 0.01-0.001) compared to the Oral-B Cross Action 40 product. The elmex inter X Medium had a significantly higher (p < 0.05-0.001) PTSC compared to the PTSC mean values of the other elmex inter X products tested.

Analysis of Variance↗