Biomedical subjects

D Fanelli

Publications and source records attributed to D Fanelli.

8 recordsLinked to original sources

PubMed2005

Dynamics and stabilization of the Elettra storage-ring free-electron laser.

The ultimate performance of a storage-ring free-electron laser in terms of light stability and extracted power depends on the possibility of simultaneously controlling the electron-beam and laser dynamics. As a preliminary requirement, the level of longitudinal and transverse electron-beam stability must be high enough to guarantee the laser start-up and growth. This is usually obtained by means of dedicated feedback systems. Once such a requirement is satisfied, the possibility of establishing and maintaining a continuous-wave operation mode finally resides in a deep understanding of the strongly coupled laser-electrons dynamics. For this purpose, we have developed a simple theoretical model which has been proved to be able to provide insight into the evolution of the laser intensity. In this framework, we have also proposed the possibility of utilizing a derivative closed-loop feedback to create or enlarge the region of stable signal. A feedback of this type has been implemented on the Elettra storage-ring free-electron laser. The obtained results, which fully confirm our predictions, are discussed in this paper.

Journal Article↗

PubMed2005

Anti-cooperativity in diffusion-controlled reactions with pairs of anisotropic domains: a model for the antigen-antibody encounter.

The encounter between anisotropic agents in diffusion-controlled reactions is a topic of very general relevance in chemistry and biology. Here we introduce a simplified model of encounter of an isotropic molecule with a pair of partially reacting agents and apply it to the encounter reaction between an antibody and its antigen. We reduce the problem to the solution of dual series relations, which can be solved iteratively, yielding the exact solution for the encounter rate constant at any desired order of accuracy. We quantify the encounter effectiveness by means of a simple indicator and show that the two binding centers systematically behave in an anti-cooperative fashion. However, we demonstrate that a reduction of the binding active sites allows the composite molecule to recover binding effectiveness, in spite of the overall reduction of the rate constant. In addition, we provide a simple formula that enables one to calculate the anti-cooperativity as a function of the size of the binding site for any values of the separation between the two active lobes and of the antigen size. Finally, some biological implications of our results are discussed.

Animals↗

PubMed2005

Dynamics of antibodies from cryo-electron tomography.

The issue of protein dynamics and its implications in the biological function of proteins are arousing greater and greater interest in molecular biology. In cryo-electron tomography experiments one takes several snapshots of a given biological macromolecule. In principle, a large enough collection of snapshots may then be used to calculate its equilibrium configuration in terms of the experimentally accessible degrees of freedom, and hence estimate its potential energy. Consequently, one could analyze the biological functions of biomolecules by directly accessing their dynamics. In this work, we analyze the results of cryo-electron tomography experiments on monoclonal murine IgG2a antibodies. With the aid of a novel software for image processing, we measure the equilibrium distribution of the angles which describe the configuration of the molecule. This helps us shed some critical light on recent results from X-ray crystallography. We then build a model of the antibody dynamics, which enables us to use the measured angular distribution in order to derive an explicit expression of the IgG potential energy. Finally, as a preliminary application of our results, we investigate the dynamical effects in the rate of formation of the antigen-antibody encounter complex. In particular, we suggest that the dynamics of antibodies operates in the direction of decreasing anticooperativity of the two antigen binding arms.

Animals↗

PubMed2005

The social parasite wasp Polistes atrimandibularis does not form host races.

Parasites that exploit the parental behaviour of several host species may be selected to form distinct host-specific genetic lineages. This process is well documented in bird brood parasites, but not in insect social parasites. Polistes atrimandibularis is the only paper-wasp social parasite known to exploit four host species. It does not form genetically distinct host races according to analyses based on microsatellite loci. Also, there were no size-matching between parasites and host species. Instead, P. atrimandibularis queens seemed to be successful as parasites in this population only when they originated from nests of P. dominulus, the largest species. The other host species are a sink for P. atrimandibularis since adult females emerging from those nests appear too small to usurp colonies themselves. Traits that may help P. atrimandibularis infiltrate multiple species may include its nonaggressive usurpation tactics and its ability to acquire host cuticular hydrocarbon recognition labels.

Analysis of Variance↗

PubMed2004

Freezing immunoglobulins to see them move.

The issue of protein dynamics and its implications in the biological function of proteins are arousing greater and greater interest in different fields of molecular biology. In cryo-electron tomography experiments one may take several snapshots of a given biological macromolecule. In principle, a large enough collection of snapshots of the molecule may then be used to calculate its equilibrium configuration in terms of the experimentally accessible degrees of freedom and, hence, to estimate its potential energy. This information would be crucial in order to analyze the biological functions of biomolecules by directly accessing the relevant dynamical indicators. In this article, we analyze the results of cryo-electron tomography experiments performed on monoclonal murine IgG2a antibodies. We measure the equilibrium distribution of the molecule in terms of the relevant angular coordinates and build a mechanical model of the antibody dynamics. This approach enables us to derive an explicit expression of the IgG potential energy. Furthermore, we discuss the configuration space at equilibrium in relation to results from other techniques, and we set our discussion in the context of the current debate regarding conformation and flexibility of antibodies.

Cryoelectron Microscopy↗

PubMed2001

One-dimensional toy model of globular clusters.

We introduce a one-dimensional toy model of globular clusters. The model is a version of the well-known gravitational sheets system, where we also take into account mass and energy loss by evaporation of stars at the boundaries. Numerical integration by the "exact" event-driven dynamics is performed, for initial uniform density and Gaussian random velocities. Two distinct quasistationary asymptotic regimes are attained, depending on the initial energy of the system. We guess the forms of the density and velocity profiles that fit numerical data extremely well and allow us to perform an independent calculation of the self-consistent gravitational potential. Some power laws for the asymptotic number of stars and for the collision times are suggested.

Journal Article↗

PubMed2001

Nestmate recognition in Parischnogaster striatula (Hymenoptera Stenogastrinae), visual and olfactory recognition cues.

The recognition of nestmates from alien individuals is a well known phenomenon in social insects. In the stenogastrine wasp Parischnogaster striatula, we investigated the ability of females to recognize nestmates and the cues on which such recognition is based. Recognition of nestmates was observed in naturally occurring interactions between wasps approaching a nest and the resident females on that nest. This recognition was confirmed in experiments in which nestmates or alien conspecifics were presented to resident females. In naturally occurring interactions, nestmates generally approach their nest with a direct flight, while aliens usually hover in front of the nest before landing. In experiments in which the presented wasps were placed close to the nest in a direct manner, antennation of the presented wasp generally occurred, indicating that chemical cues are involved. Experiments in which dead alien individuals, previously washed in hexane, and then reapplied with extracts were recognized by colonies giving further evidence that chemical cues mediate nestmate recognition. Epicuticular lipids, known to be nestmate recognition cues in social insects, were chemically analysed by GC-MS for 44 P. striatula females from two different populations (13 different colonies). Discriminant analysis was performed on the data for the lipid mixture composition. The discriminant model showed that, in the samples from these two populations, 68.2% and 81.9% of the specimens could be correctly assigned to their colony.

Journal Article↗

PubMedDate not supplied

Documenting for patient-focused care.

Hospitals across the country are rethinking the way health care is delivered. With a shift from inpatient to outpatient care, there is an effort to deliver quality, "patient-focused care" in the hospital setting. Multidisciplines have embarked in cross-training to provide immediate services at the bedside. The premise of "nursing" documentation is no longer feasible in multicaregiver environments. One hospital's adaptation to documentation methods to meet the needs of a patient-focused system is described.

Forms and Records Control↗