Biomedical subjects

C G White

Publications and source records attributed to C G White.

10 recordsLinked to original sources

PubMed2006

Measurement of the asymmetry in the decay Omega+-->LamdaKappa+-->rhopi+Kappa+.

The asymmetry in the rho angular distribution in the sequential decay Omega+-->LamdaKappa+-->rhopi+Kappa+. has been measured to be alphaOmegaalphaLamda=[+1.16+/-0.18(stat)+/-0.17(syst)]x10(-2) using 1.89x10(6) unpolarized Omega+ decays recorded by the HyperCP (E871) experiment at Fermilab. Using the known value of alphaLamda, and assuming that alphaLamda=-alphaLamda, alphaOmega=[-1.81+/-0.28(stat)+/-0.26(syst)]x10(-2). A comparison between this measurement of alphaOmegaalphaLamda and recent measurements of alphaOmegaalphaLamda made by HyperCP shows no evidence of a violation of CP symmetry.

Journal Article↗

PubMed2005

Search for the lepton-number-violating decay Xi(-)-->pmu(-)mu(-).

A sensitive search for the lepton-number-violating decay Xi(-)-->pmu(-)mu(-) has been performed using a sample of approximately 10(9) Xi(-) hyperons produced in 800 GeV/c p-Cu collisions. We obtain B(Xi(-)-->pmu(-)mu(-))<4.0x10(-8) at 90% confidence, improving on the best previous limit by 4 orders of magnitude.

Journal Article↗

PubMed2005

Search for DeltaS = 2 nonleptonic hyperon decays.

A sensitive search for the rare decays Omega(-)--> Lambdapi(-) and Xi(0)--> ppi(-) has been performed using data from the 1997 run of the HyperCP (Fermilab E871) experiment. Limits on other such processes do not exclude the possibility of observable rates for |DeltaS| = 2 nonleptonic hyperon decays, provided the decays occur through parity-odd operators. We obtain the branching-fraction limits B(Omega(-)-->Lambdapi(-)) < 2.9 x 10(-6) and B(Xi(0)--> ppi(-)) < 8.2 x 10(-6), both at 90% confidence level.

Journal Article↗

PubMed2005

Evidence for the decay sigma+ --> pmu+ mu-.

We report the first evidence for the decay Sigma(+)-->pmu(+)mu(-) from data taken by the HyperCP (E871) experiment at Fermilab. Based on three observed events, the branching ratio is B(Sigma(+)-->pmu(+)mu(-))=[8.6(+6.6)(-5.4)(stat)+/-5.5(syst)]x10(-8). The narrow range of dimuon masses may indicate that the decay proceeds via a neutral intermediate state, Sigma(+)-->pP(0),P0-->mu(+)mu(-) with a P0 mass of 214.3+/-0.5 MeV/c(2) and branching ratio B(Sigma(+)-->pP(0),P0-->mu(+)mu(-))=[3.1(+2.4)(-1.9)(stat)+/-1.5(syst)]x10(-8).

Journal Article↗

PubMed2005

Syphilitic scrotal abscess: the great mimic returns.

We present an unusual case of a scrotal abscess. The patient's previous history of syphilis highlights the need for a thorough sexual history especially in light of the current increasing incidence of syphilis in the UK.

Abscess↗

PubMed2004

Search for CP violation in charged-Xi and Lambda hyperon decays.

We have compared the p and p angular distributions in 117 x 10(6) Xi- -->Lambdapi- -->ppi-pi- and 41 x 10(6) Xi+ -->Lambda pi+ -->p pi+pi+ decays using a subset of the data from the HyperCP experiment (E871) at Fermilab. We find no evidence of CP violation, with the direct-CP-violating parameter AXiLambda identical with (alphaXialphaLambda-alpha Xialpha Lambda)/(alphaXialphaLambda+alphaXialphaLambda)=[0.0+/-5.1(stat)+/-4.4(syst)] x 10(-4).

Journal Article↗

PubMed2001

Haem-linked interactions in horseradish peroxidase revealed by spectroscopic analysis of the Phe-221-->Met mutant.

A gene encoding a Phe-221-to-Met substitution in the haem enzyme horseradish peroxidase has been constructed and expressed in Escherichia coli. In the wild-type enzyme the side chain of Phe-221 is tightly stacked against the imidazole ring of His-170, which provides the only axial ligand to the haem iron atom. The Phe-221-->Met enzyme is active, and forms characteristic complexes with typical peroxidase ligands (CO, cyanide, fluoride), and with benzhydroxamic acid. Significant differences between the mutant and wild-type enzymes can be detected spectroscopically. These include a change in the Fe(III) resting state of the enzyme to an unusual quantum mechanically mixed-spin haem species, a marked decrease in the pK(a) of the alkaline transition and a reduction in enzyme stability at alkaline pH for both Fe(III) and Fe(II) forms. The perturbation of the haem pocket in the mutant can be attributed to several factors, including the increased steric freedom and solvent accessibility of the His-170 ligand, as indicated by (1)H-NMR data, and the loss of the pi-pi interaction between His-170 and Phe-221.

Arabidopsis↗

PubMed2001

Reduction of illness absenteeism in elementary schools using an alcohol-free instant hand sanitizer.

Hand washing is the most effective way to prevent the spread of communicable disease. The purpose of this double-blind, placebo-controlled study was to assess whether an alcohol-free, instant hand sanitizer containing surfactants, allantoin, and benzalkonium chloride could reduce illness absenteeism in a population of 769 elementary school children and serve as an effective alternative when regular soap and water hand washing was not readily available. Prior to the study, students were educated about proper hand washing technique, the importance of hand washing to prevent transmission of germs, and the relationship between germs and illnesses. Children in kindergarten through the 6th grade (ages 5-12) were assigned to the active or placebo hand-sanitizer product and instructed to use the product at scheduled times during the day and as needed after coughing or sneezing. Data on illness absenteeism were tracked. After 5 weeks, students using the active product were 33% less likely to have been absent because of illness when compared with the placebo group.

Absenteeism↗

PubMed1997

Identification of a critical phenylalanine residue in horseradish peroxidase, Phe179, by site-directed mutagenesis and 1H-NMR: implications for complex formation with aromatic donor molecules.

The functional and structural significance of Phe179 of horseradish peroxidase isoenzyme C (HRP C) has been investigated by site-directed mutagenesis. This residue is located in a structurally variable insertion between helices F and G, a motif unique to peroxidases of higher plants. Results obtained for three recombinant enzymes, with Phe179 substituted by Ala, His, or Ser, provide the first demonstration of the importance of this side chain for the binding of aromatic donor molecules. Experimental parameters for direct comparison with the wild-type enzyme were obtained by extensive solution state characterization using both optical and 1H-NMR spectroscopy. Significant chemical shift variations for resonances associated with the exposed heme edge, notably heme methyl C18H3 and heme propionate C17(1)H2, were recorded in NMR spectra of both the resting and cyanide-ligated states of the three Phe179 mutants. Furthermore, comparison of NOE connectivities in NOESY spectra of cyanide-ligated wild-type and mutant enzymes enabled the elusive assignment of the aromatic side chain in close proximity to heme methyl C18H3 to be made to Phe179. Replacement of Phe179 by Ala resulted in an 80-fold decrease in the binding affinity of the cyanide-ligated enzyme for benzhydroxamic acid, with a Kd value similar to that determined for cyanide-ligated HRP A2 (an acidic isoenzyme with valine at position 179). The binding affinity of Phe179-->Ser was similarly decreased, while that of Phe179-->His was partially restored relative to wild-type HRP C. Cyanide-ligated Phe179-->His HRP C exhibited a unique pH-dependent spectral transition associated with a pKa value of 6.5 +/- 0.2, assigned to the His179 side chain. Two closely related enzyme forms exhibiting different affinities for benzhydroxamic acid were observed at neutral pH and above, indicating that the protonation state of His179 gave rise to microheterogeneity in the aromatic donor molecule binding site.

Benzoates↗

PubMed1984

Blood flow changes and conceptal development in pregnant rats in response to caffeine.

Alterations in blood flow to the uterus and its contents during pregnancy have been suggested to account for the teratogenicity and/or embryotoxicity of several agents, including caffeine. Using a radioactive microsphere technique, blood flow to several maternal organs, including ovary, uterus, decidua, and chorioallantoic placenta (CAP), was measured following a single dose of 0 or 120 mg/kg caffeine by gavage to pregnant CD rats on Day 12 of gestation. At 1 or 4 hr after treatment, animals were anesthetized and strontium 85-labeled microspheres (25 micrometers diam) were infused into the left ventricle. Whole body and tissue radioactivity were determined. Maternal cardiac output (CO) and absolute flow (f1; ml/min), relative flow (f2; ml/min/g tissue), and flow as %CO (f3) to each tissue were calculated. Maternal CO was not altered. All blood flow parameters for ovaries, uterus, and bladder were reduced in treated animals at both time points except for absolute flow (f1) to the ovaries at 1 hr. Decidual changes included reduced weight at 1 hr, reduced f2 at 4 hr, and reduced f1 and f3 at both times. However, CAP weight and blood flow wre not significantly altered by caffeine treatment. Examination of conceptuses from thse litters, and from other animals at 24 hr after treatment or at term did not reveal any significant effect of this dose of caffeine on viability, growth, or physical development. The ratio of embryo to maternal blood caffeine concentrations was approximately 1, indicating free transfer of caffeine to the embryos.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗