Biomedical subjects
Publications and source records attributed to J Barreto.
We present a search for charged Higgs bosons in decays of pair-produced top quarks in pp collisions at sqrt[s] = 1.8 TeV recorded by the D0 detector at the Fermilab Tevatron collider. With no evidence for signal, we exclude most regions of the ( M(H+/-),tan(beta)) parameter space where the decay t--> H(+)b has a branching fraction >0.36 and B(H+/--->tau(nu)(tau)) is large.
The inclusive cross section for production of isolated photons has been measured in pp macro collisions at square root of s = 630 GeV with the D0 detector at the Fermilab Tevatron Collider. The photons span a transverse energy (E(T)) range from 7-49 GeV and have pseudorapidity absolute value of eta < 2.5. This measurement is combined with the previous D0 result at square root of s = 1800 GeV to form a ratio of the cross sections. Comparison of next-to-leading-order QCD with the measured cross section at 630 GeV and the ratio of cross sections show satisfactory agreement in most of the E(T) range.
We describe QUAERO, a method that (i) enables the automatic optimization of searches for physics beyond the standard model, and (ii) provides a mechanism for making high energy collider data generally available. We apply QUAERO to searches for standard model WW, ZZ, and t t macro production, to searches for these objects produced through a new heavy resonance, and to the first direct search for W'-->WZ. Through this interface, we make three data sets collected by the D0 experiment at square root of [s] = 1.8 TeV publicly available.
We present results of searches for technirho (rho(T)), techniomega (omega(T)), and Z' particles, using the decay channels rho(T),omega(T),Z'-->e(+)e(-). The search is based on 124.8 pb(-1) of data collected by the D0 detector at the Fermilab Tevatron during 1992-1996. In the absence of a signal, we set 95% C.L. upper limits on the cross sections for the processes pp-->rho(T),omega(T),Z'-->e(+)e(-) as a function of the mass of the decaying particle. For certain model parameters, we exclude the existence of degenerate rho(T) and omega(T) states with masses below about 200 GeV. We exclude a Z' with mass below 670 GeV, assuming that it has the same couplings to fermions as the Z boson.
Transmission characteristics of malaria were studied in Matola, a coastal suburb of Maputo, the capital City, in southern Mozambique, from November 1994 to April 1996. The local climate alternates between cool dry season (May-October) and hot rainy season (November-April) with mean annual rainfall 650-850 mm. Saltmarsh and freshwater pools provide mosquito breeding sites in Matola. Malaria prevalence reached approximately 60% among people living nearest to the main breeding sites of the vectors. Plasmodium falciparum caused 97% of malaria cases, others being P. malariae and P. ovale. Potential malaria vector mosquitoes (Diptera: Culicidae) collected at Matola during daytime indoor-resting (n = 1021) and on human bait at night (n = 5893) comprised 12% Anopheles coustani Laveran (93% biting outdoors), 46% An. funestus Giles (68% biting indoors) and 42% An. gambiae Giles sensu lato (60% biting outdoors). All 215 specimens of An. gambiae s.l. identified genetically were An. arabiensis Patton. Anopheles funestus populations remained stable throughout the year, whereas densities of the An. gambiae complex fluctuated considerably, with An. arabiensis peaking during the rainy season. No concomitant rise in malaria incidence was observed. Human landing indices of An. funestus and An. arabiensis averaged 1.8 and 3.8 per man-night, respectively. Overall Plasmodium sporozoite rates were 2.42+/-1.24% in 2181 An. funestus and 1.11+/-1.25% in 1689 An. arabiensis dissected and examined microscopically. Mean daily survival rates were 0.79 for both vector species. Estimated infective bites/person/year were 15 An. funestus and 12 An. arabiensis. Biting rates were greatest at 2100-24.00 hours for An. funestus (68% endophagic) and 21.00-03.00 hours for An. arabiensis (40% endophagic). The entomological inoculation rate (EIR) declined sharply over very short distances (50% per 90m) away from breeding-sites of the vectors. Consequently, P. falciparum prevalence among Matola residents was halved 350 m within the town. Implications for the protective effectiveness of a 'cordon sanitaire' by residual house-spraying and/or the use of insecticide-treated bednets are discussed.
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The Brazilian Wilms' Tumour Study Group carried out a hospital-based multicentre case-control study of potential risk factors for the disease between April 1987 and January 1989. The parents of 109 cases of Wilms' tumour (WT) were interviewed when they were admitted to hospital for diagnosis and treatment. Also interviewed were the parents of two controls per case, matched for age, sex and interviewer, who were admitted to the same or nearby hospitals for treatment of non-neoplastic conditions. Odds ratios adjusted for family income and parental education were calculated by conditional logistic regression. Among cases diagnosed before 25 months of age there was a marked gradient of increasing risk of WT with increasing maternal age at the time of the child's birth. There was no increased risk for cases diagnosed after 25 months of age. The effects of paternal age were less marked. Possible explanations for these results are discussed.
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Using serum or infected blood from Danish volunteers and Plasmodium falciparum-infected Mozambican patients, respectively, the impact of curative doses of chloroquine and pyrimethamine/sulfadoxine upon infectivity of P. falciparum to Anopheles arabiensis and An. gambiae or of P. berghei to An. stephensi was studied. Both treatments cleared circulating P. falciparum gametocytes within 28 days. Before this clearance, chloroquine enhanced infectivity to An. arabiensis, whereas pyrimethamine/sulfadoxine decreased infectivity. Patients harboring chloroquine-resistant parasites as opposed to -sensitive ones were 4.4 times more likely to have gametocytes following treatment. In contrast, pyrimethamine/sulfadoxine-resistant parasites were 1.9 times less likely to produce gametocytes. In laboratory infections using replicated P. berghei or P. falciparum preparations, serum from chloroquine-treated, uninfected, nonimmune volunteers enhanced gametocyte infectivity with increasing efficiency for 21 days following treatment, whereas pyrimethamine/sulfadoxine significantly suppressed infectivity. The observed enhancement in infectivity induced by the use of chloroquine combined with increased gametocytemias in chloroquine-resistant strains may in part explain the rapid spread of chloroquine resistance in endemic populations.
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A temporal and spatial study of malaria transmission in a suburban area of Maputo, Mozambique with a mean population density of 2,737/km2 was made from December 1992 to June 1995. A steep but continuous gradient was observed in the Plasmodium falciparum prevalence from 59.0% adjacent to the breeding sites to 5.4% only a few hundred meters distant. The entomologic inoculation rate ranged from a number too low to be determined in some districts to 20 infectious bites per person per year in the others. The risk of malaria was 6.2 times higher for individuals living less than 200 meters from the breeding sites than for individuals living 500 meters or more away from the breeding sites. In areas of high human density, mosquito and parasite dispersion is very limited, and therefore malaria control strategies could be more specifically targeted.
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OBJECTIVE: To develop a method of functional classification of the elderly (FCE) in Primary Health Care and to define the age limit for considering someone "a frail elderly person." DESIGN: A descriptive study in two phases: a) the method's design by means of "brainwriting" and b) the evaluation of the method in a descriptive crossover study. SETTING: A rural medical consulting-room. PATIENTS AND OTHER PARTICIPANTS: The research team, in the design of the method; and the elderly population attending for health care (n = 131), in the method's evaluation. MEASUREMENTS AND MAIN RESULTS: The FCE method was based on the Katz (IK) and Lawton-Brodie (IL-B) indices and classified the patients as independent and at different levels of disability. Urinary incontinence (UI) was excluded from the IK. 85.4% of the patients were independent, which bore relation to age (p < 0.001), but not to gender. When UI was included in the IK, the number of people classified as disabled increased by 32% (CI 95%, 23-41%) over when it was not included. Yet 80% of patients with UI were independent. No differences in the percentage of disabled patients were observed when the cut-off age for detecting disabled patients varied from 75 to 80. CONCLUSIONS: The inclusion of UI as a negative factor in the IK gives rise to overestimates of the number of disabled people. In our study the data suggested that the age for considering an elderly person as 'frail' should be 80.
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We have observed specific and nonspecific reactivities to the asexual states and gametocytes of Plasmodium falciparum and examined the effect of chloroquine and Fansidar (pyrimethamine/sulfadoxine) on the dynamics of gametocytemia. Schoolchildren peripheral blood films positive for P. falciparum gametocytes were identified in a malaria-endemic area of Mozambique. The children were randomly allocated into two groups to receive chloroquine or pyrimethamine/sulfadoxine, and were followed for 28 days after treatment. In patients harboring drug-sensitive parasites, asexual parasitemias were cleared by day 4, but gametocytes persisted for an additional 17 days. The prevalence of the asexual parasites was 67.6% in the chloroquine-treated group at day 0 and 61.1% at day 28, whereas in the pyrimethamine/sulfadoxine treated group, the initial parasite prevalence of 70.7% was reduced to 2.4% at day 28, suggesting a high prevalence of chloroquine-resistant parasites. On day 0, gametocyte prevalence was 59.5% in the chloroquine-treated group and in 68.3% in the pyrimethamine/sulfadoxine-treated group; these values were reduced to 5.6% and 2.4%, respectively, at day 28. Our results suggest strongly that there is no induction of gametocytogenesis by either course of chemotherapy.