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W H Chung

Publications and source records attributed to W H Chung.

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

Evidence for the exclusive decay B(c)+- --> J/psi pi+- and measurement of the mass of the B(c)+- meson.

We report the first evidence for a fully reconstructed decay mode of the B(c)+- meson in the channel B(c)+- --> J/psi pi+-, with J/psi --> mu+ mu-. The analysis is based on an integrated luminosity of 360 pb(-1) in pp collisions at 1.96 TeV center of mass energy collected by the Collider Detector at Fermilab. We observe 14.6 +/- 4.6 signal events with a background of 7.1 +/- 0.9 events, and a fit to the J/psi pi+-mass spectrum yields a B(c)+- mass of 6285.7 +/- 5.3(stat) +/- 1.2(syst) MeV/c2. The probability of a peak of this magnitude occurring by random fluctuation in the search region is estimated as 0.012%.

Journal Article↗
PubMed2006

Search for charged Higgs bosons from top quark decays in pp collisions at square root s=1.96 TeV.

We report the results of a search for a charged Higgs boson in the decays of top quarks produced in pp collisions at a center-of-mass energy of 1.96 TeV. We use a data sample corresponding to an integrated luminosity of 193 pb-1 collected by the upgraded Collider Detector at Fermilab. No evidence for charged Higgs production is found, allowing 95% C.L. upper limits to be placed on BR(t-->H+b) for different charged Higgs decay scenarios. In addition, we present in the minimal supersymmetric standard model (mH+/-, tanbeta) plane the first exclusion regions with radiative and Yukawa coupling corrections.

Journal Article↗
PubMed2006

Precision top-quark mass measurement in the lepton+jets topology in p p collisions at square root s=1.96 TeV.

We report two measurements of the top-quark mass M(top) using the CDF II detector at the Fermilab Tevatron in a 318 pb(-1) data sample of tt events in the lepton+jets final state. One method uses an event-based likelihood technique resulting in M(top) = 173.2(-2.4)(+2.6)(stat) +/- 3.2(syst) GeV/c2 or 173.2(-4.0)(+4.1) GeV/c2. The second method reconstructs a top-quark mass in each event using the measured invariant mass of the hadronically decaying W boson to constrain the jet energy scale to obtain a value for M(top)of 173.5(-3.6)(+3.7)(stat) +/- 1.3(syst) GeV/c2 or 173.5(-3.8)(+3.9) GeV/c2 . We take the latter, which is more precise, as our result.

Journal Article↗
PubMed2006

Search for neutral Higgs bosons of the minimal supersymmetric standard model decaying to tau pairs in pp collisions at square root of s = 1.96 TeV.

We present a search for neutral supersymmetric Higgs bosons decaying to tau pairs produced in pp collisions at square root of s = 1.96 TeV. The data, corresponding to 310 pb(-1) integrated luminosity, were collected with the Collider Detector at Fermilab in run II of the Tevatron. No significant excess above the standard model backgrounds is observed. We set exclusion limits on the production cross section times branching fraction to tau pairs for Higgs boson masses in the range from 90 to 250 GeV/c2.

Journal Article↗
PubMed2005

Search for new high-mass particles decaying to Lepton pairs in pp collisions at square root s = 1.96 TeV.

A search for new particles (X) that decay to electron or muon pairs has been performed using approximately 200 pb(-1) of pp collision data at (square root) s = 1.96 TeV collected by the CDF II experiment at the Fermilab Tevatron. Limits on sigma(pp --> X)BR (X --> ll) are presented as a function of dilepton invariant mass m(ll) > 150 GeV/c2, for different spin hypotheses (0, 1, or 2). The limits are approximately 25 fb for m(ll) > GeV/c2. Lower mass bounds for X from representative models beyond the standard model including heavy neutral gauge bosons are presented.

Journal Article↗
PubMed2005

Search for [corrected] B0(s) --> mu+ mu- and B0(d) [corrected] --> mu + mu- decays in pp collisions with CDF II.

We report on a search for B0(s) --> mu+ mu- and B0(d) --> mu + mu- decays in pp collisions at square root(s) = 1.96 TeV using 364 pb(-1) of data collected by the CDF II detector at the Fermilab Tevatron Collider. After applying all selection requirements, we observe no candidates inside the B0(s) or B0(d) mass windows. The resulting upper limits on the branching fractions are B(B0(s) --> mu+ mu-) < 1.5 x 10(-7) and B(B0(d) --> mu+ mu-) < 3.9 x 10(-8) at 90% confidence level.

Journal Article↗
PubMed2004

Clinical association of anti-golgi autoantibodies and their autoantigens.

Anti-Golgi autoantibodies (AGAs) and their targets have been reported from several diseases. However, the association of AGAs, selective autoantigens and related clinical diseases is still obscure. In this study, the presence of AGAs in the sera of 5983 patients was screened to explore the association of AGAs and clinical diseases. By means of indirect immunofluorescence using HEp-2 cells, sera of 12 patients bearing AGAs were identified. The location of recognized Golgi autoantigen(s) was confirmed by the treatment of monensin and double immunostaining using beta-COP. Using the immunoelectron microscopy, AGA immunoreactivity was clearly demonstrated at a stack structure, characteristic of the Golgi complex. Furthermore, analysis of the 12 AGA-positive sera by Western blot revealed at least 15 components of Golgi antigens with relative molecular weights ranging from 54 to 350 kDa, and several Golgi autoantigens identified may be novel. Notably, over half of the AGA-positive cases found belong to non-autoimmune diseases, particularly hepatic disorder. This study presents the association of AGAs, components of the Golgi complex and clinical diseases.

Adult↗
PubMed2003

Search for long-lived charged massive particles in pp collisions at square root s = 1.8 TeV.

We report a search for the production of long-lived charged massive particles in a data sample of 90 pb(-1) of square root[s]=1.8 TeV pp collisions recorded by the Collider Detector at Fermilab. The search uses the muonlike penetration and anomalously high ionization energy loss signature expected for such a particle to discriminate it from backgrounds. The data are found to agree with background expectations, and cross section limits of O(1) pb are derived using two reference models, a stable quark and a stable scalar lepton.

Journal Article↗
PubMed2002

Postsynaptic action mechanism of somatostatin on the membrane excitability in spinal substantia gelatinosa neurons of juvenile rats.

We used tight-seal, whole-cell recording in juvenile rat spinal slices to investigate the action of somatostatin on substantia gelatinosa neurons. Bath application of somatostatin caused a robust and repeatable hyperpolarization or outward current in substantia gelatinosa neurons. Somatostatin inhibited spontaneous action potentials in subpopulation of substantia gelatinosa neurons. The amplitude of dorsal root-evoked excitatory postsynaptic currents and the frequency of spontaneous excitatory postsynaptic currents were not affected by somatostatin. The current induced by somatostatin developed almost instantaneously and did not show any time-dependent inactivation. The current-voltage relationship exhibited inward rectification. The conductance of somatostatin-sensitive current increased with the concentration of external K(+). The reversal potentials in different external K(+) concentrations were close to the K(+) equilibrium potentials. The effect of somatostatin was dose-dependent, with an EC(50) of 113 nM. The somatostatin-sensitive current was blocked by low concentration of extracellular Ba(2+) but not by glibenclamide, an inhibitor of ATP-sensitive K(+) channels. Hyperpolarization-activated cation current in a subpopulation of substantia gelatinosa neurons was not affected by somatostatin. In neurons recorded with an internal solution containing GTPgammaS, somatostatin induced outward current and hyperpolarization that did not reverse on washing. When the spontaneous induction of outward current with GTPgammaS was greatest, somatostatin did not induce any outward currents. Furthermore, intracellular dialysis of GDPbetaS, a G-protein antagonist, abolished the effect of somatostatin. In addition, SST-sensitive neurons were fewer in slices incubated with pertussis toxin than in adjacent control slices incubated without pertussis toxin. These results suggest that somatostatin decreases the postsynaptic membrane excitability of substantia gelatinosa neurons by a pertussis toxin-sensitive G-protein-mediated activation of an inwardly rectifying K(+) conductance.

Age Factors↗
PubMed2001

Changes in external ear resonance after ventilation tube (Grommet) insertion in children with otitis media with effusion.

OBJECTIVE: As otitis media with effusion is common in children, the effects of a ventilation tube should be taken into account in the prescription of hearing aids for children. In ears with a ventilation tube, the external auditory canal communicates directly with the middle ear space, and so the impedance of the middle ear may change. Consequently, this will affect external-ear resonance. The aim of this study is to observe the effects of the tympanic membrane perforations caused by the ventilation tube on external-ear resonance. We selected 30 ears with otitis media with effusion to measure external-ear resonance before and after ventilation tube insertion. We compared the external-ear resonance of a control group with that of the otitis media with the effusion group and two types of ventilation-tube groups, respectively. In the subjects who have otitis media with effusion, the average gain of the peak resonance was larger than that in the control group. After ventilation-tube insertion, the amplitude of the gain decreased to the same level as the control group, but a characteristic negative gain appeared around 1000 Hz in about half of all cases. This negative gain was observed more frequently in the ventilation tube with a larger diameter. The raised peak resonance gain in the otitis media with effusion group decreased to a level roughly the same as that of the control group after ventilation-tube insertion. Provision of an additional gain in the low frequencies around 1000 Hz should be considered for patients with a ventilation tube when prescribing hearing aids.

Acoustic Stimulation↗
PubMed2001

Allergic contact dermatitis to temporary tattoos with positive para-phenylenediamine reactions: report of four cases.

BACKGROUND: In recent years, temporary tattoos instead of permanent tattoos have become popular worldwide. Although contact allergy to temporary henna tattoos appears to be rare in the past, it is progressively more commonly reported. PATIENTS: Four Taiwanese patients of allergic contact dermatitis following application of temporary tattoos were patch tested and they were followed up for 1 year after treatment. RESULTS: All four of the tested patients were positive to paraphenylenediamine. At 1-year follow-up, all four patients still showed various degrees of remnant hyperpigmentation on their previous tattooed areas. CONCLUSION: Temporary tattoos may pose similar risks of allergic reactions associated with permanent tattoos. A high risk of prolonged post-inflammatory hyperpigmentation after allergic contact dermatitis from temporary tattoos should also be alerted, especially in Asian skin type.

Adult↗
PubMed2001

Changes in external ear resonance after 3 types of surgery in the patients with chronic otitis media.

OBJECTIVE: This study was designed to identify the external ear resonance characteristics of patients with tympanic membrane perforation and to investigate subsequent changes in external ear resonance, depending on the length of the postoperative period and which of 3 different types of operation was performed: tympanoplasty with canal wall-up mastoidectomy, epitympanoplasty, and canal wall-down mastoidectomy. STUDY DESIGN AND SETTING: A total of 227 ears of 188 patients and 96 control ears comprised the study. We measured the gain and frequency of the first peak of external ear resonance with a real ear analyzer. RESULTS: Gain and frequency of the first peak recorded in the preoperative group did not differ from those of the control group. However, negative peaks appeared around 1 to 1.5 kHz in half of these ears. The gain increased markedly in all 3 postoperative groups. The canal wall-down mastoidectomy and epitympanoplasty groups showed significantly lower frequencies compared with the tympanoplasty with canal wall-up mastoidectomy and control groups, but there was no difference between them. The increased gain diminished over time, but the peak gain did not equalize with that of the controls, even after 15 months. CONCLUSIONS: Additional gain should be considered of around 1 to 1.5 kHz for hearing aid users with tympanic membrane perforation. Postoperative changes in external ear resonance should be expected in patients with chronic otitis media, suggesting that fine readjustments of the hearing aid may be necessary.

Adolescent↗
PubMed2001

Induction of c-jun and TGF-beta 1 in Fischer 344 rats during amiodarone-induced pulmonary fibrosis.

Amiodarone (AM) is an antidysrhythmic agent with a propensity to cause pulmonary toxicity, including potentially fatal fibrosis. In the present study, the potential roles of c-Jun and transforming growth factor (TGF)-beta 1 in AM-induced inflammation and fibrogenesis were examined after intratracheal administration of AM (1.83 micromol/day on days 0 and 2) or an equivalent volume (0.4 ml) of distilled water to male Fischer 344 rats. Northern and immunoblot analyses demonstrated that lung TGF-beta 1 (mRNA and protein) expression was increased 1.5- to 1.8-fold relative to control during the early inflammation period and 1 day, 1 wk, and 2 wk post-AM treatment. Lung c-Jun protein expression was increased concomitantly with evidence of AM-induced fibrosis; at 5 wk post-AM treatment, c-Jun protein was increased 3.3-fold relative to control. The results indicate a role for induction of c-jun and TGF-beta 1 expression in the development of AM-induced pulmonary fibrosis in the Fischer 344 rat and provide potential targets for therapeutic intervention.

Amiodarone↗
PubMed2001

Inflammatory pseudotumour involving the skull base and cervical spine.

Inflammatory pseudotumour (IPT) is an idiopathic condition characterized by sclerosing inflammation, which mimics a neoplastic process. IPT involving the skull base and cervical spine is distinctly rare and usually indistinguishable from aggressive neoplasms or infection. We report a case of IPT involving the skull base and cervical spine. Initially the patient complained of headache and hearing loss without other neurological dysfunction. Two cycles of oral systemic steroid therapy resulted in only partial responses. Low dose radiotherapy was followed by quadriparesis as the lesion infiltrated into the cervical vertebral bodies. Subsequently a second course of radiation was administered to the whole cervical spine. Marked improvement was observed clinically and radiologically; however, the patient gradually deteriorated and died of sepsis. Given the aggressive nature of disease and the complications related to the long-term treatment, we suggest that a more aggressive therapeutic approach is suitable in extensive IPT of the skull base.

Cervical Vertebrae↗
PubMed2001

Circling mouse: possible animal model for deafness.

Mutant mice with abnormalities are potentially useful as models for studying human defects. Here we report a group of mice with abnormal behavioral patterns. A new spontaneous mutant mouse exhibited hyperactive behavior at about seven days of age, followed by tight circling behavior. Breeding studies suggest that this mutation is caused by a single gene defect inherited in an autosomal recessive manner. Consequently, this mutation is referred to as a circling (cir) mouse mutation with the gene symbol cir. Auditory test results identified clearly the hearing loss of the cir, compared with wild-type mice. Pathologic studies confirmed developmental defects in cochlea and spiral ganglions that were correlated to the abnormal behavior observed in the cir mice. Thus, cir mice may be useful as a model for studying inner ear abnormalities and deafness in humans.

Animals↗
PubMed1999

The reversed SoxS-binding site upstream of the ribA promoter in Escherichia coli.

The ribA gene, encoding GTP cyclohydrolase II in Escherichia coli, is a member of the soxRS regulon, which is induced by superoxide-generating agents. By evaluating lacZ expression driven by the ribA promoter carrying different lengths of upstream region in a monolysogen, we found that the superoxide-responsive element resides between 56 and 94 nucleotides upstream of the transcriptional start site. Purified SoxS protein bound to this region and protected nucleotides between positions -80 and -58 from degradation by DNase I. This region contains a putative SoxS-binding sequence (soxbox) in reverse orientation. The SoxS protein interacted specifically with four guanine residues within the soxbox sequence, as demonstrated by methylation interference analysis. These results clearly indicate that SoxS binds to the reversed soxbox sequence in the ribA gene, while in other known genes of the soxRS regulon it binds to the normally oriented soxbox. Possible modes of interaction between SoxS and RNA polymerase are discussed.

Bacterial Proteins↗
PubMed1999

The protective effect of brain-derived neurotrophic factor after gentamicin ototoxicity.

HYPOTHESIS: Brain-derived neurotrophic factor (BDNF) influences the process of hair cell recovery in the vestibular sensory epithelium of the chinchilla after local application of gentamicin (GM). BACKGROUND: Hair cell regeneration in the inner ear after GM ototoxicity has been demonstrated. However, the mechanisms responsible for this recovery have yet to be completely elucidated. This report examines the protective and proliferative effects that BDNF exerts on vestibular hair cells in experiments designed to further elucidate the mechanisms of hair cell regeneration. METHODS: The inner ears of three separate groups of chinchillas were treated with GM only, GM and BDNF simultaneously, and GM followed by BDNF 1 week later. The numbers of hair and supporting cells in the horizontal cristae of each group were then estimated at 1, 2, 4, and 8 weeks, and the data were compared. RESULTS: Type I hair cells after GM treatment completely disappeared. After simultaneous BDNF and GM treatment, their numbers decreased to 23% at 1 week and progressively disappeared by week 8. When BDNF was applied 1 week after GM administration, type I hair cells recovered to 12% at week 4 and 28% at week 8. Type II hair cells after GM treatment decreased to 15%, but recovered to 83% 4 weeks later. Simultaneous administration of BDNF and GM prevented the ototoxic effects of GM alone. When BDNF was administered 1 week after GM, type II hair cell recovery was accelerated and was greater than after GM alone (81% versus 18%). Supporting cells after GM treatment decreased to 74% at 1 week after treatment, recovered to 91% at 2 weeks, and remained at 86% at 4 weeks and 85% at 8 weeks. With the simultaneous administration of BDNF and GM, supporting cells significantly decreased at 2 weeks after treatment (63%), but recovered to normal by week 8. CONCLUSIONS: These results suggest that BDNF provided simultaneously with GM minimizes the ototoxic effect of GM on type II hair cells. The increase in the number of new hair cells when BDNF is provided after ototoxic damage is evidence of the proliferative capacity of this neurotrophic factor.

Animals↗