Proliferation-driven mechanical compression induces signalling centre formation during mammalian organ development.

Localized sources of morphogens, called signalling centres, play a fundamental role in coordinating tissue growth and cell fate specification during organogenesis. However, how these signalling centres are established in tissues during embryonic development is still unclear. Here we show that the main signalling centre orchestrating development of rodent incisors, the enamel knot (EK), is specified by a cell proliferation-driven buildup in compressive stresses (mechanical pressure) in the tissue. Direct mechanical measurements indicate that the stresses generated by cell proliferation are resisted by the surrounding tissue, creating a circular pattern of mechanical anisotropy with a region of high compressive stress at its centre that becomes the EK. Pharmacological inhibition of proliferation reduces stresses and suppresses EK formation, and application of external pressure in proliferation-inhibited conditions rescues the formation of the EK. Mechanical information is relayed intracellularly through YAP protein localization, which is cytoplasmic in the region of compressive stress that establishes the EK and nuclear in the stretched anisotropic cells that resist the pressure buildup around the EK. Together, our data identify a new role for proliferation-driven mechanical compression in the specification of a model signalling centre during mammalian organ development.

Enhancing Whole-Brain Magnetic Field Homogeneity for 3D-Magnetic Resonance Spectroscopic Imaging with a Novel Unified Coil: A Preliminary Study.

The spectral quality of magnetic resonance spectroscopic imaging (MRSI) can be affected by strong magnetic field inhomogeneities, posing a challenge for 3D-MRSI's widespread clinical use with standard scanner-equipped 2nd-order shim coils. To overcome this, we designed an empirical unified shim-RF head coil (32-ch RF receive and 51-ch shim) for 3D-MRSI improvement. We compared its shimming performance and 3D-MRSI brain coverages against the standard scanner shim (2nd-order spherical harmonic (SH) shim coils) and integrated parallel reception, excitation, and shimming (iPRES) 32-ch AC/DC head coil. We also simulated a theoretical 3rd-, 4th-, and 5th-order SH shim as a benchmark to assess the UNIfied shim-RF coil (UNIC) improvements. In this preliminary study, the whole-brain coverage was simulated by using B0 field maps of twenty-four healthy human subjects (n = 24). Our results demonstrated that UNIC substantially improves brain field homogeneity, reducing whole-brain frequency standard deviations by 27% compared to the standard 2nd-order scanner shim and 17% compared to the iPRES shim. Moreover, UNIC enhances whole-brain coverage of 3D-MRSI by up to 34% compared to the standard 2nd-order scanner shim and up to 13% compared to the iPRES shim. UNIC markedly increases coverage in the prefrontal cortex by 147% and 47% and in the medial temporal lobe and temporal pole by 29% and 13%, respectively, at voxel resolutions of 1.4 cc and 0.09 cc for 3D-MRSI. Furthermore, UNIC effectively reduces variations in shim quality and brain coverage among different subjects compared to scanner shim and iPRES shim. Anticipated advancements in higher-order shimming (beyond 6th order) are expected via optimized designs using dimensionality reduction methods.

In situ quantification of osmotic pressure within living embryonic tissues.

Mechanics is known to play a fundamental role in many cellular and developmental processes. Beyond active forces and material properties, osmotic pressure is believed to control essential cell and tissue characteristics. However, it remains very challenging to perform in situ and in vivo measurements of osmotic pressure. Here we introduce double emulsion droplet sensors that enable local measurements of osmotic pressure intra- and extra-cellularly within 3D multicellular systems, including living tissues. After generating and calibrating the sensors, we measure the osmotic pressure in blastomeres of early zebrafish embryos as well as in the interstitial fluid between the cells of the blastula by monitoring the size of droplets previously inserted in the embryo. Our results show a balance between intracellular and interstitial osmotic pressures, with values of approximately 0.7 MPa, but a large pressure imbalance between the inside and outside of the embryo. The ability to measure osmotic pressure in 3D multicellular systems, including developing embryos and organoids, will help improve our understanding of its role in fundamental biological processes.

Peripherally inserted central catheter related pericardial effusion/cardiac tamponade in neonates: Analysis of two cases and literature review.

RATIONALE: Peripherally inserted central catheter (PICC)-related pericardial effusion/cardiac tamponade is a rare but fatal complication which cause a high mortality if not timely diagnosed and treated. However, the atypical manifestations and the rapid deterioration present challenges for neonatologists, and there has been limited investigation reported globally to date. Furthermore, a systematic review and comprehensive summary of clinical management are lacking. The significance of this article lies in emphasizing the importance of maintaining vigilance in high-risk neonates and implementing effective management strategies for PICC-related pericardial effusion/cardiac tamponade, thereby contributing to saving more lives. PATIENT CONCERNS: In the current report, we discuss 2 cases of neonatal pericardial effusion/cardiac tamponade following PICC catheterization. DIAGNOSIS: The first case was diagnosed based on forensic autopsy and the second case was diagnosed by bedside echocardiography. INTERVENTIONS AND OUTCOMES: The first case was treated conservatively and the second case underwent pericardiocentesis, unfortunately both were died. LESSONS: Once sudden hemodynamic or respiratory abnormalities are detected in neonates with PICC placement, particularly in the preterm infants, prompt diagnosis by cardiac ultrasound is required to verify pericardial effusion/cardiac tamponade and immediate pericardiocentesis or pericardiotomy is necessary to improve survival.

Oxide Materials for Thermoelectric Conversion.

Thermoelectric technology has emerged as a prominent area of research in the past few decades for harnessing waste heat and improving the efficiency of next-generation renewable energy technologies. There has been rapid progress in the development of high-performance thermoelectric materials, as measured by the dimensionless figure of merit (ZT = S2 · σ · κ-1). Several heavy-metal-based thermoelectric materials with commercial-level performance (ZT = 1) have so far been proposed. However, the extensive application of these materials still faces challenges due to their low thermal/chemical stability, high toxicity, and limited abundance in the Earth's crust. In contrast, oxide-based thermoelectric materials, such as ZnO, SrTiO3, layered cobalt oxides, etc., have attracted growing interest as they can overcome the limitations of their heavy-metal-based counterparts. In this review, we summarize the recent research progress and introduce improvement strategies in oxide-based thermoelectric materials. This will provide an overview of their development history and design schemes, ultimately aiding in enhancing the overall performance of oxide-based thermoelectric materials.

Mechanical feedback defines organizing centers to drive digit emergence.

During embryonic development, digits gradually emerge in a periodic pattern. Although genetic evidence indicates that digit formation results from a self-organizing process, the underlying mechanisms are still unclear. Here, we find that convergent-extension tissue flows driven by active stresses underlie digit formation. These active stresses simultaneously shape cartilage condensations and lead to the emergence of a compressive stress region that promotes high activin/p-SMAD/SOX9 expression, thereby defining digit-organizing centers via a mechanical feedback. In Wnt5a mutants, such mechanical feedback is disrupted due to the loss of active stresses, organizing centers do not emerge, and digit formation is precluded. Thus, digit emergence does not result solely from molecular interactions, as was previously thought, but requires a mechanical feedback that ensures continuous coupling between phalanx specification and elongation. Our work, which links mechanical and molecular signals, provides a mechanistic context for the emergence of organizing centers that may underlie various developmental processes.

Fluorous Soluble Cyanine Dyes for Visualizing Perfluorocarbons in Living Systems.

The bioorthogonal nature of perfluorocarbons provides a unique platform for introducing dynamic nano- and microdroplets into cells and organisms. To monitor the localization and deformation of the droplets, fluorous soluble fluorophores that are compatible with standard fluorescent protein markers and applicable to cells, tissues, and small organisms are necessary. Here, we introduce fluorous cyanine dyes that represent the most red-shifted fluorous soluble fluorophores to date. We study the effect of covalently appended fluorous tags on the cyanine scaffold and evaluate the changes in photophysical properties imparted by the fluorous phase. Ultimately, we showcase the utility of the fluorous soluble pentamethine cyanine dye for tracking the localization of perfluorocarbon nanoemulsions in macrophage cells and for measurements of mechanical forces in multicellular spheroids and zebrafish embryonic tissues. These studies demonstrate that the red-shifted cyanine dyes offer spectral flexibility in multiplexed imaging experiments and enhanced precision in force measurements.