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Biomedical subjects

A Verga

Publications and source records attributed to A Verga.

At least 19 recordsLinked to original sources
PubMed2001

Dynamical approach to the microcanonical ensemble.

An analytical method to compute thermodynamic properties of a given Hamiltonian system is proposed. This method combines ideas of both dynamical systems and ensemble approaches to thermodynamics, providing de facto a possible alternative to traditional ensemble methods. Thermodynamic properties are extracted from effective motion equations. These equations are obtained by introducing a general variational principle applied to an action averaged over a statistical ensemble of paths defined on the constant energy surface. The method is applied first to the one-dimensional beta-Fermi-Pasta-Ulam chain and to the two-dimensional lattice straight phi(4) model. In both cases, the method gives a good insight of some of their statistical and dynamical properties.

Journal Article↗
PubMed2001

Effect of viscosity in the dynamics of two point vortices: exact results.

An exact, unstationary, two-dimensional solution of the Navier-Stokes equations for the flow generated by two point vortices is obtained. The viscosity nu is introduced as a Brownian motion in the Hamiltonian dynamics of point vortices. The point vortices execute a stochastic motion whose probability density can be computed from a Fokker-Planck equation, equivalent to the original Navier-Stokes equation. The derived solution describes, in particular, the merging process of two Lamb vortices, and the development of the characteristic spiral structure in the topology of the vorticity. The viscous effects are thoroughly investigated by an asymptotic analysis of the solution. In particular, the selection mechanism of a specific pattern among the infinity satisfying the nu=0 (Euler) equation is discussed.

Journal Article↗
PubMed2000

ESA payloads and experiments on the Foton-12 mission.

The international Foton-12 mission in September 1999 was a milestone in terms of payload mass, complexity and scientific diversity. ESA's contribution amounted to an unprecedented 240 kg--almost half of Foton's total payload. The Agency's 11 experiments covered fluid physics, biology, radiation dosimetry, materials science and meteoritics. This article describes the mission from an ESA perspective and highlights the initial results.

Equipment Design↗
PubMed1995

Factors related to the development of sensitization to green coffee and castor bean allergens among coffee workers.

BACKGROUND: Occupational allergic respiratory symptoms in coffee workers have been frequently reported, but the ultimate cause of sensitization is still debated, castor bean being considered besides green coffee beans. Atopy and cigarette smoking have been suggested as promoting factors of sensitization for several occupational allergens. OBJECTIVE: This study was carried out to assess the prevalence of allergic respiratory symptoms and of sensitization to both green coffee beans and castor bean in the whole workforce of a coffee manufacturing plant. Furthermore we wanted to ascertain both the presence of castor bean antigens in the settled dust of the green coffee beans warehouse and the possible crossreactivity between the two beans. Meanwhile, the effect of smoking and atopy was considered. METHOD: Two-hundred and eleven workers were examined. A questionnaire on oculorhinitis and asthma was administered and skin-prick tests for green coffee beans, castor bean and 15 common inhalant allergens were carried out. Isoelectric focusing, isoelectric focusing immunoblot and radioallergosorbent assay (RAST) inhibition were performed on samples of settled environmental dust from the green coffee area, as well as on castor bean and green coffee beans. RESULTS: Ten per cent of the workers complained of oculorhinitis alone and 16% of asthma (nearly always associated with oculorhinitis). The overall prevalence of skin-sensitization was: 15% for green coffee beans, 22% for castor bean, 22% for common allergens. Evidence of sensitization to occupational allergens was more common in smokers, with a more than twofold increase in relative risk. The strong association between skin positivity to common and occupational allergens suggests that atopy acts as an enhancing host factor towards occupational sensitization. The analysis of the dust confirmed the presence of castor bean antigens. CONCLUSION: Our findings indicate that castor bean is the major cause of occupational sensitization among coffee workers, whereas smoking and atopy act as enhancing factors.

Adult↗
PubMed1994

Asthma caused by live fish bait.

BACKGROUND: Larvae of insects and worms are commonly used as live fish bait (LFB) by anglers. Asthma, rhinoconjunctivitis, and urticaria related to various kinds of LFB have been reported. METHODS: We studied 14 subjects with respiratory symptoms associated with exposure to LFB. Skin prick tests and RASTs with Lucilia caesar, Galleria mellonella, and Tenebrio molitor extracts were carried out in all subjects. Monitoring of peak expiratory flow rate and evaluation of bronchial responsiveness to methacholine before and after exposure to LFB were performed in seven subjects. RESULTS: Thirteen subjects had asthma, all 14 had rhinoconjunctivitis, and three had contact urticaria. Eleven subjects had respiratory symptoms after fishing with LFB, and the other three subjects had symptoms during their work in a commercial fish bait farm. Positive skin prick test results or significant RAST binding to L. caesar extract were observed in 13 subjects, to G. mellonella extract in four subjects, and to T. molitor extract in three subjects. After exposure to LFB, two subjects had an early asthmatic response, three had a late asthmatic response, and two had no asthmatic response. Late asthmatic response was associated with a long-lasting increase in bronchial responsiveness. CONCLUSIONS: This study demonstrates that emanations from LFB are sensitizers, which have the potential to elicit IgE-mediated asthma. Exposure to LFB is common and LFB should be considered as a possible sensitizing agent for asthma.

Adolescent↗
PubMed1991

Eicosanoid release and mepyramine, LTC4 and LTD4 binding in passively sensitized human lung parenchyma in vitro.

In vitro passive sensitization of human lung parenchyma with hyper-immune serum did not affect the release of prostaglandin D2 (PGD2) or leukotriene (LT)-like activity upon challenge with anti-IgE antibody with respect to control lung, despite a marked difference in IgE levels between control (C) and sensitized (S) tissue. Binding studies with [3H]LTC4, [3H]LTD4 and [3H]mepyramine (a histamine H1 antagonist) showed a statistically significant increase in the amount bound in sensitized vs control lung for [3H]mepyramine only. Contractile response to 5 x 10(-5) M histamine (H) in C and S lung parenchymal strips did not correlate with binding data. It is concluded that in vitro elevated IgE levels do not affect the interaction of sulfidopeptide leukotrienes with their putative receptors. As for the observed increase in [3H]mepyramine binding, this might not represent a true increase in histamine receptors on lung smooth muscle cells.

Animals↗
PubMed1991

Antigenic activity of nonpollen parts (leaves and stems) of allergenic plants (Parietaria judaica and Dactylis glomerata).

In patients with respiratory allergy to pollen it is common to correlate the onset, duration and intensity of clinical symptoms with the count of atmospheric allergenic pollen grains. Pollen counts, however, may not reflect the total airborne allergen exposure since previous data suggest that pollen allergens may also be carried in microaerosol suspensions. These microdroplets may penetrate deeply into the airways, where pollen grains are too large to penetrate, eventually inducing asthma. The origin of these allergenic aerosols is still uncertain. We investigated whether antigenic activity is present in vegetative parts of allergenic plants. We have used extracts from leaves and stems of Parietaria judaica and Dactylis glomerata to evaluate patients with allergic sensitization to pollen allergens of these plants (19 grass-sensitive patients and 23 Parietaria sensitive). By using skin prick testing and RAST to stem and leaf extracts other than pollen extracts we observed that most patients sensitive to grass or Parietaria pollen had small responses to extracts of stem or leaf. We conclude that allergenic components are present throughout most of Parietaria judaica and Dactylis glomerata plants, most highly concentrated in the pollen but present in the leaves with a trace in the stems.

Adolescent↗
PubMed1991

Relationships between skin prick test, radioallergosorbent test, and chemiluminescent assays in allergic children.

The results of skin prick tests (SPT), radioallergosorbent tests (RAST), and multiple chemiluminescent tests (DHS-CLA) to grass mix, parietaria, D. farinae, and D. pteronyssinus were evaluated in 43 allergic children. All CLA tests had valid positive and negative control threads. Chemiluminescent assays class 4 matched with RAST class 3 and/or 4 and CLA class 3 with RAST class 2. The D. farinae, D. pteronyssinus, and grass results obtained with CLA, RAST, and SPT were investigated by principal components analysis that showed a good association between different methods of measuring allergenicity. The results of the present study confirm that DHS-CLA is an effective "in vitro" method for the detection of IgE-allergen specific antibody.

Allergens↗
PubMed1989

Skin and serum reactivity to some storage mites in children sensitive to Dermatophagoides pteronyssinus.

The incidence of skin test and RAST positivity for Dermatophagoides farinae and storage mites (Glycyphagus privatus, Lepidoglyphus destructor, Tyrophagus putrescentiae, Acarus siro, and Gohieria fusca) have been evaluated in children with bronchial asthma and positive prick test to Dermatophagoides pteronyssinus. The storage mite with highest incidence of skin and RAST positivity was Gohieria fusca, which caused a positive response in more than 50% of the children evaluated. This antigen appears to possess allergenic determinants not present in Dermatophagoides pteronyssinus. The sensitivity to this antigen might be considered in house dust mite-allergic children who do not improve after specific immunotherapy with Dermatophagoides pteronyssinus extracts.

Adolescent↗
PubMed1986

Late bronchial response and increase in methacholine hyperresponsiveness after exercise and distilled water challenge in atopic subjects with asthma with dual asthmatic response to allergen inhalation.

We investigated the occurrence of late asthmatic response and increased methacholine responsiveness after exercise and ultrasonically nebulized distilled water (UNDW) inhalation in 12 subjects with asthma with dual asthmatic response and increased responsiveness after allergen challenge. On 3 separate days, allergen, exercise, and UNDW challenges were performed 2 hours after methacholine. FEV1 was measured for 8 hours to detect any delayed change in airway caliber. If there were a further significant reduction in FEV1 after the recovery from the immediate bronchoconstriction, methacholine challenge was performed again when FEV1 had returned to baseline. Reproducibility of any observed late response to exercise and UNDW was also investigated by repeating these challenges on 2 subsequent days. After allergen inhalation only nine subjects had an early asthmatic response, whereas all the tested subjects demonstrated a late reaction and increased methacholine responsiveness. Ten subjects had an immediate response to exercise, and this was followed by a late response in only four patients. Nine subjects demonstrated early response to UNDW inhalation, and five subjects also had a late reaction. These late responses were associated with an increase in methacholine responsiveness in a subset of the tested subjects. Late-phase reactions to exercise and UNDW were not reproducible.

Administration, Inhalation↗
PubMed1985

The stopping of deuterons in lithium.

The interaction of 52 MeV deuterons with lithium was investigated, in view of the optimization of a lithium target for an intense neutron source based on the d-Li stripping reaction. The experimental results are compared with theoretical calculations obtained from an updated version of the Bragg code. This code describes in detail the interaction of charged particles with matter. Within the experimental uncertainties the theoretical results are well reproduced by the experiments.

Cyclotrons↗