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Biology subjects

Calvo, G.

Publications and source records attributed to Calvo, G..

2 recordsLinked to original sources

Self-Supervised Missing Wedge Correction in Soft X-Ray Tomography: Towards Accurate Cellular Morphology and Volume Quantification

Soft X-Ray tomography (SXT) is a non-invasive bio-imaging technique that enables 3D imaging of cellular structures in large volume, with a unique resolution range that bridges the gap between fluorescence and transmission electron microscopy. However, a fundamental limitation, the missing wedge artefact caused by incomplete tilt-series acquisition, introduces systematic structural elongation in the reconstructed tomograms. This artifact compromises accurate quantitative biological analysis by overestimating cellular and organelle volumes. To overcome this persistent issue, we introduce a novel, self-supervised missing wedge correction model that learns key sine-wave patterns from existing SXT sinograms of the tilt series stacks. This model can be applied to recover the missing-angle region of the sinogram, reducing distortions and elongations in the reconstructed tomograms. We demonstrate a significant quantitative improvement in artifact removal, achieving faithful recovery of the spherical morphology of lipid droplets. We further applied this method to Plasmodium falciparum hemozoin crystals, a biomarker in antimalarial drug efficacy studies. Our model successfully reduced volume overestimation, achieving up to a 16% decrease in distorted volume. This level of precision is paramount for correctly interpreting the mode of action of antimalarial drugs.

cell biology↗

Small extracellular vesicles secreted by Candida albicans hyphae have highly diverse protein cargoes that include virulence factors and stimulate macrophages

Extracellular vesicles (EVs) have been described as mediators of microorganism survival and interaction with the host. In Candida albicans, a relevant commensal fungal pathogen, the dimorphic transition is an important virulence trait in candidiasis. We have analyzed EVs secreted by yeast (YEVs) or hyphal cells (HEVs) from C. albicans, finding interesting differences in both size distribution and protein loading. In general, HEVs were smaller and carried a much more diverse protein cargo than YEVs, including most of the proteins identified in YEVs, which were mainly cell surface proteins. Virulence factors such as phospholipases, aspartic proteases (Saps), adhesins and invasins, and the precursor protein of candidalysin toxin Ece1p were also detected. HEVs were also enriched in proteasomal and ribosomal proteins, and in enzymes from amino acid biosynthetic pathways, all involved in protein metabolism, as well as proteins related to intracellular protein transport and components of the ESCRT pathway related to exosome biogenesis. Both types of EV presented immune reactivity with human sera from patients suffering invasive candidiasis. In our conditions, only HEVs could elicit the release of TNF by activated macrophages. This first analysis of C. albicans HEVs shows their relevance to pathogenesis and possible new diagnostics or treatments.

microbiology↗