RESUMO
Biological images captured by a microscope are characterized by heterogeneous signal-to-noise ratios (SNRs) across the field of view due to spatially varying photon emission and camera noise. State-of-the-art unsupervised structured illumination microscopy (SIM) reconstruction algorithms, commonly implemented in the Fourier domain, do not accurately model this noise and suffer from high-frequency artifacts, user-dependent choices of smoothness constraints making assumptions on biological features, and unphysical negative values in the recovered fluorescence intensity map. On the other hand, supervised methods rely on large datasets for training, and often require retraining for new sample structures. Consequently, achieving high contrast near the maximum theoretical resolution in an unsupervised, physically principled manner remains a challenging task. Here, we propose Bayesian-SIM (B-SIM), an unsupervised Bayesian framework to quantitatively reconstruct SIM data, rectifying these shortcomings by accurately incorporating all noise sources in the spatial domain. To accelerate the reconstruction process for computational feasibility, we devise a parallelized Monte Carlo sampling strategy for inference. We benchmark our framework on both simulated and experimental images, and demonstrate improved contrast permitting feature recovery at up to 25% shorter length scales over state-of-the-art methods at both high- and low-SNR. B-SIM enables unsupervised, quantitative, physically accurate reconstruction without the need for labeled training data, democratizing high-quality SIM reconstruction and expands the capabilities of live-cell SIM to lower SNR, potentially revealing biological features in previously inaccessible regimes.
RESUMO
Internalization of clathrin-coated vesicles from the plasma membrane constitutes the major endocytic route for receptors and their ligands. Dynamic and structural properties of endocytic clathrin coats are regulated by the mechanical properties of the plasma membrane. Here, we used conventional fluorescence imaging and multiple modes of structured illumination microscopy (SIM) to image formation of endocytic clathrin coats within live cells and tissues of developing fruit fly embryos. High resolution in both spatial and temporal domains allowed us to detect and characterize distinct classes of clathrin-coated structures. Aside from the clathrin pits and plaques detected in distinct embryonic tissues, we report, for the first time, formation of giant coated pits (GCPs) that can be up to two orders of magnitude larger than the canonical pits. In cultured cells, we show that GCP formation is induced by increased membrane tension. GCPs take longer to grow but their mechanism of curvature generation is the same as the canonical pits. We also demonstrate that GCPs split into smaller fragments during internalization. Considering the supporting roles played by actin filament dynamics under mechanically stringent conditions that slow down completion of clathrin coats, we suggest that local changes in the coat curvature driven by actin machinery can drive splitting and internalization of GCPs.
RESUMO
BACKGROUND: Obesity has become a worldwide epidemic, and many methods are currently used to reduce obesity. This systematic review shows the effectiveness of the intragastric balloon (IGB) method compared to the sham/diet (s/d) method. OBJECTIVE: To demonstrate the effectiveness of the IGB method compared to the s/d method. SETTING: Hospital das Clinicas da Universidade de São Paulo, Brazil, Public Hospital. METHODS: After searching MEDLINE, Embase, Cochrane, Lilacs, Scopus, and CINAHL, only enrolled randomized control trials comparing IGB/diet with s/d were analyzed. For qualitative analysis, 12 studies were selected, and 9 of these were acceptable for quantitative analysis. RESULTS: The IGB/diet is more effective than s/d when comparing body mass index (BMI) loss with a mean difference of 1.1 kg/m(2) by the Student's t test and 1.41 kg/m(2) by the meta-analysis, with significant differences in both. It is also more effective in weight loss (WL), with a mean difference of 2 kg by the Student's t test and 3.55 kg by the meta-analysis. In the qualitative analysis of % excess WL (%EWL), the mean %EWL is 14.0% in favor of the IGB group compared to the s/d group by the Student's t test; however, no significant difference was found between these groups by quantitative analysis. CONCLUSION: Based on randomized control trial data alone, IGB>400 mL is more effective than sham/diet in achieving BMI loss, WL, and %EWL.
