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We present a method for learning spectrally descriptive edge weights for graphs. We generalize a previously known distance measure on graphs (graph diffusion distance [GDD]), thereby allowing it to be tuned to minimize an arbitrary loss function. Because all steps involved in calculating this modified GDD are differentiable, we demonstrate that it is possible for a small neural network model to learn edge weights which minimize loss. We apply this method to discriminate between graphs constructed from shoot apical meristem images of two genotypes of Arabidopsis thaliana specimens: wild-type and trm678 triple mutants with cell division phenotype. Training edge weights and kernel parameters with contrastive loss produce a learned distance metric with large margins between these graph categories. We demonstrate this by showing improved performance of a simple k -nearest-neighbour classifier on the learned distance matrix. We also demonstrate a further application of this method to biological image analysis. Once trained, we use our model to compute the distance between the biological graphs and a set of graphs output by a cell division simulator. Comparing simulated cell division graphs to biological ones allows us to identify simulation parameter regimes which characterize mutant versus wild-type Arabidopsis cells. We find that trm678 mutant cells are characterized by increased randomness of division planes and decreased ability to avoid previous vertices between cell walls.

Mechanical signals play many roles in cell and developmental biology. Several mechanotransduction pathways have been uncovered, but the mechanisms identified so far only address the perception of stress intensity. Mechanical stresses are tensorial in nature, and thus provide dual mechanical information: stress magnitude and direction. Here we propose a parsimonious mechanism for the perception of the principal stress direction. In vitro experiments show that microtubules are stabilized under tension. Based on these results, we explore the possibility that such microtubule stabilization operates in vivo, most notably in plant cells where turgor-driven tensile stresses exceed greatly those observed in animal cells.

Although the formation of new walls during plant cell division tends to follow maximal tensile stress direction, analyses of individual cells over time reveal a much more variable behavior. The origin of such variability as well as the exact role of interphasic microtubule behavior before cell division have remained mysterious so far. To approach this question, we took advantage of the Arabidopsis stem, where the tensile stress pattern is both highly anisotropic and stable. Although cortical microtubules (CMTs) generally align with maximal tensile stress, we detected a specific time window, ca. 3 h before cell division, where cells form a radial pattern of CMTs. This microtubule array organization preceded preprophase band (PPB) formation, a transient CMT array predicting the position of the future division plane. It was observed under different growth conditions and was not related to cell geometry or polar auxin transport. Interestingly, this cortical radial pattern correlated with the well-documented increase of cytoplasmic microtubule accumulation before cell division. This radial organization was prolonged in cells of the trm678 mutant, where CMTs are unable to form a PPB. Whereas division plane orientation in trm678 is noisier, we found that cell division symmetry was in contrast less variable between daughter cells. We propose that this "radial step" reflects a trade-off in robustness for two essential cell division attributes: symmetry and orientation. This involves a "reset" stage in G2, where an increased cytoplasmic microtubule accumulation transiently disrupts CMT alignment with tissue stress. [ABSTRACT FROM AUTHOR]

We report the case of obstructive sleep apnea in a 19-year-old, otherwise healthy male presenting with persistent daytime sleepiness and nonrestorative sleep after velo- and uvuloplasty. An individually tailored prototype of an orally inserted pharyngeal stenting device was proposed in the framework of a first clinical feasibility trial. The noninvasive, easily self-administered device is mounted on a simple inferior dental guard. Baseline total apnea-hypopnea index (AHI) was 15.5 and 24.4 per hour of rapid eye movement (REM) sleep. With the device, total AHI dropped to 6.7 per hour (56.8% reduction) and 1.4 per hour of REM (94.3% reduction). Recorded sleep efficiency during treatment was excellent at 96.5%. Laryngoscope, 129:1945-1948, 2019. [ABSTRACT FROM AUTHOR]

Based on the latest knowledge and technological advancements, it is still debatable whether a modern revascularisation approach in the setting of acute myocardial infarction (AMI), including complete revascularisation (in patients with significant non-culprit lesions) with newer-generation highly biocompatible drug-eluting stents, requires prolonged dual antiplatelet therapy (DAPT). TARGET-FIRST (ClinicalTrials.gov: NCT04753749) is a prospective, open-label, multicentre, randomised controlled study comparing short (one month) DAPT versus standard (12 months) DAPT in a population of patients with non-ST/ST-segment elevation myocardial infarction, completely revascularised at index or staged procedure (within 7 days), using Firehawk, an abluminal in-groove biodegradable polymer rapamycin-eluting stent. The study will be conducted at approximately 50 sites in Europe. After a mandatory 30-40 days of DAPT with aspirin and P2Y 12 inhibitors (preferably potent P2Y 12 inhibitors), patients are randomised (1:1) to 1) immediate discontinuation of DAPT followed by P2Y 12 inhibitor monotherapy (experimental arm), or 2) continued DAPT with the same regimen (control arm), up until 12 months. With a final sample size of 2,246 patients, the study is powered to evaluate the primary endpoint (non-inferiority of short antiplatelet therapy in completely revascularised patients) for net adverse clinical and cerebral events. If the primary endpoint is met, the study is powered to assess the main secondary endpoint (superiority of short DAPT in terms of major or clinically relevant non-major bleeding). TARGET-FIRST is the first randomised clinical trial to investigate the optimisation of antiplatelet therapy in patients with AMI after achieving complete revascularisation with an abluminal in-groove biodegradable polymer rapamycin-eluting stent implantation.