Metabolic and structural rearrangement during dark-induced autophagy in soybean (Glycine max L.) nodules: An electron microscopy and P-31 and C-13 nuclear magnetic resonance study

The effects of dark-induced stress on the evolution of the soluble metabolites present in senescent soybean (Glycine max L.) nodules were analysed in vitro using C-13- and P-31-NMR spectroscopy. Sucrose and trehalose were the predominant soluble storage carbons. During dark-induced stress, a decline in sugars and some key glycolytic metabolites was observed. Whereas 84% of the sucrose disappeared, only one-half of the trehalose was utilised. This decline coincides with the depletion of Gln, Asn, Ala and with an accumulation of ureides, which reflect a huge reduction of the N-2 fixation. Concomitantly, phosphodiesters and compounds like P-choline, a good marker of membrane phospholipids hydrolysis and cell autophagy, accumulated in the nodules. An autophagic process was confirmed by the decrease in cell fatty acid content. In addition, a slight increase in unsaturated fatty acids (oleic and linoleic acids) was observed, probably as a response to peroxidation reactions. Electron microscopy analysis revealed that, despite membranes dismantling, most of the bacteroids seem to be structurally intact. Taken together, our results show that the carbohydrate starvation induced in soybean by dark stress triggers a profound metabolic and structural rearrangement in the infected cells of soybean nodule which is representative of symbiotic cessation.

Accuracy and Precision of Head Motion Information in Multi-Channel Free Induction Decay Navigators for Magnetic Resonance Imaging.

Free induction decay (FID) navigators were found to qualitatively detect rigid-body head movements, yet it is unknown to what extent they can provide quantitative motion estimates. Here, we acquired FID navigators at different sampling rates and simultaneously measured head movements using a highly accurate optical motion tracking system. This strategy allowed us to estimate the accuracy and precision of FID navigators for quantification of rigid-body head movements. Five subjects were scanned with a 32-channel head coil array on a clinical 3T MR scanner during several resting and guided head movement periods. For each subject we trained a linear regression model based on FID navigator and optical motion tracking signals. FID-based motion model accuracy and precision was evaluated using cross-validation. FID-based prediction of rigid-body head motion was found to be with a mean translational and rotational error of 0.14±0.21 mm and 0.08±0.13(°) , respectively. Robust model training with sub-millimeter and sub-degree accuracy could be achieved using 100 data points with motion magnitudes of ±2 mm and ±1(°) for translation and rotation. The obtained linear models appeared to be subject-specific as inter-subject application of a "universal" FID-based motion model resulted in poor prediction accuracy. The results show that substantial rigid-body motion information is encoded in FID navigator signal time courses. Although, the applied method currently requires the simultaneous acquisition of FID signals and optical tracking data, the findings suggest that multi-channel FID navigators have a potential to complement existing tracking technologies for accurate rigid-body motion detection and correction in MRI.

Studying the non-thermal lobes of IRAS 16547-4247 through a multi-wavelength approach

In recent years, massive protostars have turned out to be a possible population of high-energy emitters. Among the best candidates is IRAS 16547-4247, a protostar that presents a powerful outflow with clear signatures of interaction with its environment. This source has been revealed to be a potential high-energy source because it displays non-thermal radio emission of synchrotron origin, which is evidence of relativistic particles. To improve our understanding of IRAS 16547-4247 as a high-energy source, we analyzed XMM-Newton archival data and found that IRAS 16547-4247 is a hard X-ray source. We discuss these results in the context of a refined one-zone model and previous radio observations. From our study we find that it may be difficult to explain the X-ray emission as non-thermal radiation coming from the interaction region, but it might be produced by thermal Bremsstrahlung (plus photo-electric absorption) by a fast shock at the jet end. In the high-energy range, the source might be detectable by the present generation of Cherenkov telescopes, and may eventually be detected by Fermi in the GeV range.