Biomedical subjects

J A Benitez

Publications and source records attributed to J A Benitez.

15 recordsLinked to original sources

PubMed2006

Search for pair production of scalar bottom quarks in pp collisions at square root of s = 1.96 TeV.

A search for direct production of scalar bottom quarks (b) is performed with 310 pb(-1) of data collected by the D0 experiment in pp collisions at square root s = 1.96 TeV at the Fermilab Tevatron Collider. The topology analyzed consists of two b jets and an imbalance in transverse momentum due to undetected neutralinos (chi(1)0), with chi(1)0 assumed to be the lightest supersymmetric particle. We find the data consistent with standard model expectations, and set a 95% C.L. exclusion domain in the (m(b), m(chi(1)0)) mass plane, improving significantly upon the results from run I of the Tevatron.

Journal Article↗

PubMed2006

Search for neutral, long-lived particles decaying into two muons in pp[over] collisions at sqrt[s]=1.96 TeV.

We present a search for a neutral particle, pair produced in pp[over] collisions at sqrt[s]=1.96 TeV, which decays into two muons and lives long enough to travel at least 5 cm before decaying. The analysis uses approximately 380 pb(-1) of data recorded with the D0 detector. The background is estimated to be about one event. No candidates are observed, and limits are set on the pair-production cross section times branching fraction into dimuons + X for such particles. For a mass of 10 GeV and lifetime of 4x10(-11) s, we exclude values greater than 0.14 pb (95% C.L.). These results are used to limit the interpretation of NuTeV's excess of dimuon events.

Journal Article↗

PubMed2006

Search for the standard model Higgs Boson in the pp[over]-->ZH-->nunu[over]bb[over] channel.

We report a search for the standard model (SM) Higgs boson based on data collected by the D0 experiment at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of 260 pb(-1). We study events with missing transverse energy and two acoplanar b jets, which provide sensitivity to the ZH production cross section in the nunu[over]bb[over] channel, and to WH production when the lepton from the W-->lnu decay is undetected. The data are consistent with the SM background expectation, and we set 95% C.L. upper limits on sigma(pp[over]-->ZH/WH)xB(H-->bb[over]) from 3.4/8.3 to 2.5/6.3 pb, for Higgs-boson masses between 105 and 135 GeV.

Journal Article↗

PubMed2006

Search for associated higgs boson production WH-->WWW*-->l+/-nul'+/-nu'+X in pp collisions at square root s=1.96 Te V.

We present a search for associated Higgs boson production in the process pp-->WH-->WWW*-->l;+/-nul'+/-nu'+X in final states containing two like-sign isolated electrons or muons (e+/-e;+/-, e+/-micro+/-, or micro+/-micro+/-). The search is based on D0 run II data samples corresponding to integrated luminosities of 360-380 pb-1. No excess is observed over the predicted standard model background. We set 95% C.L. upper limits on sigma(pp-->WH)xBr(H-->WW*) between 3.2 and 2.8 pb for Higgs boson masses from 115 to 175 GeV.

Journal Article↗

PubMed2006

Search for neutral Higgs bosons decaying to tau pairs in pp[over ] collisions at sqrt[s]=1.96 TeV.

A search for the production of neutral Higgs bosons Phi decaying into tau(+)tau(-) final states in pp[over ] collisions at a center-of-mass energy of 1.96 TeV is presented. The data, corresponding to an integrated luminosity of approximately 325 pb(-1), were collected by the D0 experiment at the Fermilab Tevatron Collider. Since no excess compared to the expectation from standard model processes is found, limits on the production cross section times branching ratio are set. The results are combined with those obtained from the D0 search for Phib(b[over ])-->bb[over ]b(b[over ]) and are interpreted in the minimal supersymmetric standard model.

Journal Article↗

PubMed2006

Search for resonant second generation slepton production at the Fermilab Tevatron.

We present a search for supersymmetry in the R-parity violating resonant production and decay of smuons and muon sneutrinos in the channels mu-->chi(1)(0)mu, mu-->chi(2,3,4)(0)mu, and nu(mu)-->chi(1,2)(+/-)mu. We analyzed 0.38 fb(-1) of integrated luminosity collected between April 2002 and August 2004 with the D0 detector at the Fermilab Tevatron Collider. The observed number of events is in agreement with the standard model expectation, and we calculate 95% C.L. limits on the slepton production cross section times branching fraction to gaugino plus muon, as a function of slepton and gaugino masses. In the framework of minimal supergravity, we set limits on the coupling parameter lambda(211)('), extending significantly previous results obtained in Run I of the Tevatron and at the CERN LEP collider.

Journal Article↗

PubMed2006

Direct limits on the oscillation frequency.

We report results of a study of the B(s)(0) oscillation frequency using a large sample of B(s)(0) semileptonic decays corresponding to approximately 1 fb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider in 2002-2006. The amplitude method gives a lower limit on the B(s)(0) oscillation frequency at 14.8 ps(-1) at the 95% C.L. At delta m(s) = 19 ps(-1), the amplitude deviates from the hypothesis A= 0(1) by 2.5 (1.6) standard deviations, corresponding to a two-sided C.L. of 1% (10%). A likelihood scan over the oscillation frequency, delta m(s), gives a most probable value of 19 ps(-1) and a range of 17 < delta m(s) < 21 ps(-1)at the 90% C.L., assuming Gaussian uncertainties. This is the first direct two-sided bound measured by a single experiment. If delta m(s) lies above 22 ps(-1), then the probability that it would produce a likelihood minimum similar to the one observed in the interval 16-22 ps(-1) is (5.0 +/- 0.3)%.

Journal Article↗

PubMed2001

Environmental signals controlling production of hemagglutinin/protease in Vibrio cholerae.

Vibrio cholerae hemagglutinin/protease (Hap) was induced upon nutrient limitation and strongly repressed by glucose. Hap was not produced in a mutant defective in the cyclic AMP (cAMP) receptor protein, suggesting that intracellular cAMP levels mediate Hap expression. No difference was found in Hap production between an rpoS deletion mutant and its isogenic wild-type precursor, indicating that the alternate sigma(s) factor is not essential for Hap expression. Based on these and previous results, we discuss the role of Hap in the pathogenesis of cholera.

Bacterial Proteins↗

PubMed1999

Diarrheagenicity evaluation of attenuated Vibrio cholerae O1 and O139 strains in the human intestine ex vivo.

The recent spread of El Tor cholera in Latin America highlights the need for a safe and economical vaccine. The main approach for developing live recombinant vaccines has been to disarm known pathogenic strains of cholera toxin leaving intact antigens involved in protection. These recombinant vaccine candidates do not cause severe diarrhea, but they are too reactogenic for wide scale usage. We describe here a test capable of determining the diarrheagenic potential of attenuated V. cholerae strains. The functional test consists in the simultaneous recording of net water movement, electrical potential difference and short-circuit current across the human intestine ex vivo. We found that human tissues incubated with supernatants from the attenuated 638, 413 and 251a V. cholerae strains caused no changes in the ion conductances and water absorption in ileal and colon tissues allowing them to be assayed in volunteers.

Animals↗

PubMed1999

The use of high oil corn in broiler diets.

We examined the effect of substituting conventional corn (CC; 3.5% crude fat) with high oil corn (HOC; 8.81 and 6.75% crude fat) on broiler performance. In Experiment 1, 100 chicks were assigned to 16 experimental pens consisting of two treatments. Treatment 1, the control group used CC, whereas in Treatment 2, CC was totally replaced with HOC containing 8.81% crude fat. In Experiment 2, 52 chicks were assigned to each of 16 experimental pens divided also into two treatments. Treatment 1 was the control group using CC and in Treatment 2 CC was totally replaced by HOC (6.75% crude fat). Body weight, cumulative feed intake, and feed efficiency were determined weekly for each pen from 7 to 42 d of age. Carcass weight and percentage yield were determined prechill. Results in Experiment 1 showed no significant differences for any parameter measured. In Experiment 2, body weight was significantly higher (P < 0.05) for birds fed HOC at 42 d of age. There were no significant differences among treatments for the remaining parameters. These results indicate that comparable performance of broilers can be obtained when CC is substituted with HOC.

Animal Feed↗

PubMed1998

Replicating function of the RS1 element associated with Vibrio cholerae CTX phi prophage.

The RS1 element associated with Vibrio cholerae CTX phi prophage was cloned from an E1 Tor biotype Vibrio cholerae strain. We used the recA- vaccine strain Peru-15, that lacks the target for RS-mediated site-specific integration, to show that RS1 promotes autonomous replication of a suicide vector. A linker insertion in the rstR open reading frame abolished autonomous replication in Peru-15 but not in a strain containing an RS1 in the chromosome. An AT-rich region containing cis-acting elements involved in autonomous replication was identified by deletion. This region was sufficient to support autonomous replication in a strain containing an RS1 in the chromosome. DNA sequence analysis of a region present in RS1 and not RS2 revealed the presence of putative binding sites for host proteins involved in plasmid replication. These results indicate that RS1 contains a replicon distinct from RS2 which could be involved in replicative recombination events associated with tandem amplification of the CTX element.

Bacteriophages↗

PubMed1998

Overexpression of a mutant B subunit in toxigenic Vibrio cholerae diminishes production of active cholera toxin in vivo.

A mutant cholera toxin B subunit containing a G33E substitution was constructed and expressed in V. cholerae. The G33E amino acid substitution did not affect the amount of recombinant CTB secreted to the culture medium. The overexpression of the mutant B subunits in wild-type toxigenic cholera vibrios led to an 80% decrease in production of active cholera toxin in vitro and in vivo. Overexpression of BG33E subunits could be instrumental in the increase of the biosafety of live attenuated cholera candidate vaccine strains.

Amino Acid Substitution↗

PubMed1997

Promoter activities in Vibrio cholerae ctx phi prophage.

Comparison of cholera toxin (CT) production directed by different gene constructs and S1 nuclease mapping revealed the presence of a ctxB-specific promoter within the ctxA coding sequence. Initiation of transcription in this region occurred in wild-type El Tor and classical biotype choleragenic vibrios. We propose that transcription from the ctxB-specific promoter and a stronger ribosomal binding site on the ctxB mRNA synergistically contribute to achieve the correct (5B:1A) subunit stoichiometry. Plasmid pB, a CT promoterless vector expressing only CTB, was used to detect promoter activity by restoration of A-subunit synthesis. Promoter activity expressed in vitro and in vivo was detected upstream of the zonula occludens toxin gene, suggesting that this factor could be produced in vivo to contribute to fluid accumulation. No promoter activity was detected in vitro and in vivo upstream from the accessory cholera enterotoxin gene.

Base Sequence↗

PubMed1996

Tagging a Vibrio cholerae El Tor candidate vaccine strain by disruption of its hemagglutinin/protease gene using a novel reporter enzyme: Clostridium thermocellum endoglucanase A.

The celA gene encoding Clostridium thermocellum endoglucanase A was expressed in Vibrio cholerae on its own promoter and used to tag a candidate El Tor biotype cholera vaccine strain. Colonies of the tagged strain could be unequivocally distinguished by overlaying them with CM-cellulose indicator agar and Congo Red staining. Expression of celA did not affect growth of V. cholerae in vitro and in vivo. The celA gene was inserted in the chromosomal hap locus encoding V. cholerae hemagglutinin/protease, a putative "detachase", to create a hap- mutant that could be identified and scored by its halo of cellulolytic activity. The inactivation of hap had a positive effect on colonization in the infant mice model. The above results indicate that celA is a suitable marker gene for V. cholerae and hap is an appropriate locus for insertion of foreign DNA in vaccine development. Inactivation of hap, by increasing the duration of adherence, might decrease excretion of the resulting vaccine vector strain and thus increase its immunogenicity.

Animals↗

PubMed1980

Methods of management of flail chest.

We have treated 30 patients with flail chest, with priority given to associated factors (pain, secretions retention, hemo-/pneumothorax and underlying pulmonary contusion). When this treatment was insufficient IMV + PEEP was instituted; in this group there was a 58.8% incidence of pneumonia, 47.5% of sepsis and 11.7 days average stay in the ICU. These were significantly different when compared to the patients controlled without mechanical ventilatory support 7.7% pneumonia, 0% sepsis, 3.2 days). Surgical fixation was limnited to 4 patients who presented with multiple and greatly displace rib fractures, which made fixation by mechanical ventilation unpredictable.

Abdominal Injuries↗