Surface functionalization for tailoring the aggregation and magnetic behaviour of silica-coated iron oxide nanostructures.

We report here a detailed structural and magnetic study of different silica nanocapsules containing uniform and highly crystalline maghemite nanoparticles. The magnetic phase consists of 5 nm triethylene glycol (TREG)- or dimercaptosuccinic acid (DMSA)-coated maghemite particles. TREG-coated nanoparticles were synthesized by thermal decomposition. In a second step, TREG ligands were exchanged by DMSA. After the ligand exchange, the ζ potential of the particles changed from -10 to -40 mV, whereas the hydrodynamic size remained constant at around 15 nm. Particles coated by TREG and DMSA were encapsulated in silica following a sol-gel procedure. The encapsulation of TREG-coated nanoparticles led to large magnetic aggregates, which were embedded in coalesced silica structures. However, DMSA-coated nanoparticles led to small magnetic clusters inserted in silica spheres of around 100 nm. The final nanostructures can be described as the result of several competing factors at play. Magnetic measurements indicate that in the TREG-coated nanoparticles the interparticle magnetic interaction scenario has not dramatically changed after the silica encapsulation, whereas in the DMSA-coated nanoparticles, the magnetic interactions were screened due to the function of the silica template. Moreover, the analysis of the AC susceptibility suggests that our systems essentially behave as cluster spin glass systems.

[Ribavirin in the treatment of bronchiolitis caused by syncytial respiratory virus]. / Ribavirina como tratamiento de la bronquiolitis por virus respiratorio sincitial.

OBJECTIVE: The aim of this study was to evaluate ribavirin therapy for acute bronchiolitis caused by viral syncytial respiratory infection. PATIENTS AND METHODS: Ninety-seven patients with acute bronchiolitis in which respiratory syncytial virus was identified by direct immunofluorescence and admitted to the hospital between October 1990 and May 1995 were studied. Data pertaining to age, sex, weight, respiratory frequency at admission, respiratory frequency on the fourth day, day in which respiratory ausculation was normal, day in which there were no thoracic retractions, number of days that the infants needed oxygen, duration of hospital stay, and whether or not they were treated with ribavirin were collected retrospectively. RESULTS: At admission there were no statistically significant differences in patients treated or not with ribavirin or in age, sex or weight, but the respiratory frequency was higher in those patients treated with ribavirin than in those who were not. The number of days of oxygen therapy was statistically different between these groups, with infants treated with ribavirin requiring oxygen for 2.7 days and the nontreated group requiring 1.7 days. However, we think that this difference is not clinically relevant. CONCLUSIONS: We did not find any difference of clinical relevance between patients treated or not with ribavirin.

Prevalence of asthma-related symptoms and bronchial responsiveness to exercise in children aged 13-14 yrs in Barcelona, Spain.

It is not clear whether asymptomatic bronchial responsiveness is a risk factor for development of asthma. A cross-sectional study was conducted to determine the prevalence of asthma among schoolchildren from Barcelona (Spain). The association between respiratory symptoms and bronchial responsiveness to exercise was examined. For this study 3,033 schoolchildren aged 13-14 yrs were studied from the general population. Participants answered a respiratory questionnaire and a self-reporting video-questionnaire. A total of 2,842 children underwent bronchial responsiveness testing by exercise challenge. The study was part of the International Study of Asthma and Allergies in Childhood (ISAAC) project. The prevalence of "current asthma" (recent wheezing and bronchial responsiveness to exercise) was 4% and the prevalence of "wheezing only" 10%. A fall in peak expiratory flow rate (PEFR) > or = 15% after exercise testing was found in 324 (11%) children, 29 (9%) of whom presented clinical symptoms of asthma. Bronchial responsiveness to exercise was significantly associated with all items of the asthma questionnaire. The prevalence of asthma-related symptoms in this inner-city area was lower than frequently reported rates in other countries, although the prevalence of exercise-induced bronchoconstriction was relatively high, and threefold greater than in a geographical area in the vicinity of Barcelona. These findings are consistent with the current view that asthma-related symptoms and bronchial responsiveness to exercise have different meanings in a community survey, and that local environmental factors could influence the prevalence of bronchial responsiveness.

[Study of biliary tract atresia with HIDA Tc 99]. / Estudio de la atresia de vías biliares con HIDA Tc 99.

This report has been motivated to assess the permeability of portoenterostomy with isotopic methods (HIDA Tc 99) in two cases of biliary tract atresia. Both cases have followed a good evolution during 1 1/2 and 8 years respectively, with vanishing of the icterus and achieving an acceptable biliary flow. We used the hepatic gammagraphy with HIDA Tc 99 to evaluate biliary drainage and functional status of biliary tract. Also we used other classical biochemical parameters. This isotope is useful to evaluate the effectiveness of portoenterostomy by the amount and quality of biliary flow, and specially drainage ducts. Actually this method is the safest as compared to all the others, specially transparietohepatic cholangiography. The special characteristics os this isotope and the quality of the records allow the study of both function and structure of hepatic parenchyma through the curves activity/time. This curve measures between the periphery of hepatogram and porta hepatis follows a parallel course to bilirubin clearance. By all that we think that this method, with serial determinations, can be a precise parameter of surgical intervention, and it is useful as a early indicator of bad course, allowing an evaluation of cholangitis and the indication to reintervention.