186,722 research outputs found
3D alignment and averaging of quasi equivalent volumes extracted from tomograms
No full textElectron tomographic studies more and more require the averaging of volumes extracted from one or more reconstructions. In case of cryo-tomography, the structures extracted are generally equivalent from both topological and geometrical point of view. In case of room-temperature tomography of native specimen, however, shrinkage and stain in-homogeneities make so that a perfect superimposition is often not possible, even for topologically equivalent complexes. These latter are difficult to align and even more to correctly averaging, often also because of their size.
We have recently developed a method to reconstruct portions of tomograms rotated with respect to the original orientation, starting from patches of the original micrographs and proper orientation parameters. Using this approach and after a coarse alignment of the volumes, the average coming from all the patches of all reconstructions is performed like in “single particle” strategy. The preliminary model is then refined by use of correlation techniques. If the model is obtained by averaging the volumes in direct space, the missing wedges often combine in such a way that a missing volume in Fourier space still remains. When the reconstruction is performed via Radon transform, however, the Fourier space may be almost filled even if only a few volumes are considered.
We applied our strategy to study Intra-Fagellar Transport (IFT) particles in axonemes of Chlamydomonas. Many tomograms were reconstructed in dual-axes geometry, from which 20 quasi-equivalent “short trains” of IFT particles were extracted. They were aligned by use of different strategy: 1) use of gross features, like mass center and inertia axes; 2) 3D correlation; 3) alignment of doublets by means of their coordinates extracted by segmentation. Often a combination of these approaches was used. After a few cycles of refinement, the average of the trains appeared more and more defined and some periodicities ascribable to the trains were identified. Furthermore, some differences between the trains showed a possible subdivision in two families, not previously observed
Integrazione del counseling dietetico nutrizionale nell’approccio cognitivo-comportamentale al paziente con disordini temporomandibolari
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Factors affecting the infant antibody response to measles immunisation in Entebbe-Uganda.
No full textBACKGROUND: Vaccine failure is an important concern in the tropics with many contributing elements. Among them, it has been suggested that exposure to natural infections might contribute to vaccine failure and recurrent disease outbreaks. We tested this hypothesis by examining the influence of co-infections on maternal and infant measles-specific IgG levels. METHODS: We conducted an observational analysis using samples and data that had been collected during a larger randomised controlled trial, the Entebbe Mother and Baby Study (ISRCTN32849447). For the present study, 711 pregnant women and their offspring were considered. Helminth infections including hookworm, Schistosoma mansoni and Mansonella perstans, along with HIV, malaria, and other potential confounding factors were determined in mothers during pregnancy and in their infants at age one year. Infants received their measles immunisation at age nine months. Levels of total IgG against measles were measured in mothers during pregnancy and at delivery, as well as in cord blood and from infants at age one year. RESULTS: Among the 711 pregnant women studied, 66% had at least one helminth infection at enrolment, 41% had hookworm, 20% M. perstans and 19% S. mansoni. Asymptomatic malaria and HIV prevalence was 8% and 10% respectively. At enrolment, 96% of the women had measles-specific IgG levels considered protective (median 4274 mIU/ml (IQR 1784, 7767)). IgG levels in cord blood were positively correlated to maternal measles-specific IgG levels at delivery (r = 0.81, p < 0.0001). Among the infants at one year of age, median measles-specific IgG levels were markedly lower than in maternal and cord blood (median 370 mIU/ml (IQR 198, 656) p < 0.0001). In addition, only 75% of the infants had measles-specific IgG levels considered to be protective. In a multivariate regression analysis, factors associated with reduced measles-specific antibody levels in infancy were maternal malaria infection, infant malaria parasitaemia, infant HIV and infant wasting. There was no association with maternal helminth infection. CONCLUSION: Malaria and HIV infection in mothers during pregnancy, and in their infants, along with infant malnutrition, may result in reduction of the antibody response to measles immunisation in infancy. This re-emphasises the importance of malaria and HIV control, and support for infant nutrition, as these interventions may have benefits for vaccine efficacy in tropical settings
Simultaneous alignment of dual-axis tilt series
No full textWe present a strategy for the alignment of dual-axis tomographic series, based on reference points and
simultaneous alignment of both series. Each series is first aligned individually, an affine transformation is
determined to bring the two series in a unique reference system, and all experimental coordinates are
combined in a single system of equations. In case of severe shrinkage, a global and a local refinement
of the orientation parameters are performed to correct all minors misalignments.
The strategy is illustrated on tomographic experiments performed on sections from plastic-embedded
biological samples. The efficiency in correcting the misalignment of gold particles and in improving the
quality of the reconstruction is documented both visually and quantitatively.
In our approach every region of the tomogram is associated with its own orientation parameters and
can be eventually reconstructed with the preferred algorithm. This is convenient in the computation of
3D averages of equivalent structures. A simulation experiment is presented to show that the performances
of this approach are superior to those of the method of rotation in direct space
Ruolo dell’igienista dentale nella gestione del paziente con disordini temporomandibolari mediante counseling dietetico nutrizionale
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