Riboswitches are non-coding RNA structures located in messenger RNAs that bind endogenous ligands, such as a specific metabolite or ion, to regulate gene expression. As such, riboswitches serve as a novel, yet largely unexploited, class of emerging drug targets. Demonstrating this potential, however, has proven difficult and is restricted to structurally similar antimetabolites and semi-synthetic analogues of their cognate ligand, thus greatly restricting the chemical space and selectivity sought for such inhibitors. Here we report the discovery and characterization of ribocil, a highly selective chemical modulator of bacterial riboflavin riboswitches, which was identified in a phenotypic screen and acts as a structurally distinct synthetic mimic of the natural ligand, flavin mononucleotide, to repress riboswitch-mediated ribB gene expression and inhibit bacterial cell growth. Our findings indicate that non-coding RNA structural elements may be more broadly targeted by synthetic small molecules than previously expected.

Spaceflight (SF) has been shown to cause skeletal muscle atrophy; a loss in force and power; and, in the first few weeks, a preferential atrophy of extensors over flexors. The atrophy primarily results from a reduced protein synthesis that is likely triggered by the removal of the antigravity load. Contractile proteins are lost out of proportion to other cellular proteins, and the actin thin filament is lost disproportionately to the myosin thick filament. The decline in contractile protein explains the decrease in force per cross-sectional area, whereas the thin-filament loss may explain the observed postflight increase in the maximal velocity of shortening in the type I and IIa fiber types. Importantly, the microgravity-induced decline in peak power is partially offset by the increased fiber velocity. Muscle velocity is further increased by the microgravity-induced expression of fast-type myosin isozymes in slow fibers (hybrid I/II fibers) and by the increased expression of fast type II fiber types. SF increases the susceptibility of skeletal muscle to damage, with the actual damage elicited during postflight reloading. Evidence in rats indicates that SF increases fatigability and reduces the capacity for fat oxidation in skeletal muscles. Future studies will be required to establish the cellular and molecular mechanisms of the SF-induced muscle atrophy and functional loss and to develop effective exercise countermeasures.

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Restoration of neuronal functions by outgrowths regenerating at ~1mm/d from the proximal stumps of severed peripheral nerves takes many weeks or months, if it occurs at all, especially after ablation of nerve segments. Distal segments of severed axons typically degenerate in 1–3 days. The purpose of this study was to show that Wallerian degeneration could be prevented or retarded and lost behavioral function restored following ablation of 0.5 – 1 cm segments of rat sciatic nerves in host animals. This is achieved using 0.8 – 1.1cm microsutured donor allografts treated with bioengineered solutions varying in ionic and polyethylene glycol (PEG) concentrations (modified PEG-fusion procedure), being careful not to stretch any portion of donor or host sciatic nerves. Our data show that PEG-fusion permanently restores axonal continuity within minutes as initially assessed by action potential conduction and intracellular diffusion of dye. Behavioral functions mediated by the sciatic nerve are largely restored within 2 – 4 wk as measured by the Sciatic Functional Index (SFI). Increased restoration of sciatic behavioral functions after ablating 0.5 – 1 cm segments is associated with greater numbers of viable myelinated axons within, and distal to, PEG-fused allografts. Many such viable myelinated axons are almost-certainly spared from Wallerian degeneration by PEG-fusion. PEG-fusion of donor allografts may produce a paradigm-shift in the treatment of peripheral nerve injuries.

The utility of point-of-care ultrasound is well supported by the medical literature. Consequently, pediatric emergency medicine providers have embraced this technology in everyday practice. Recently, the American Academy of Pediatrics published a policy statement endorsing the use of point-of-care ultrasound by pediatric emergency medicine providers.  To date, there is no standard guideline for the practice of point-of-care ultrasound for this specialty. This document serves as an initial step in the detailed “how to” and description of individual point-of-care ultrasound examinations.  Pediatric emergency medicine providers should refer to this paper as reference for published research, objectives for learners, and standardized reporting guidelines.

Assessment of hemodynamic status in a shock state remains a challenging issue in Emergency Medicine and Critical Care. As the use of invasive hemodynamic monitoring declines, bedside-focused ultrasound has become a valuable tool in the evaluation and management of patients in shock. No longer a means to simply evaluate organ anatomy, ultrasound has expanded to become a rapid and noninvasive method for the assessment of patient physiology. Clinicians caring for critical patients should strongly consider integrating ultrasound into their resuscitation pathways.

Complete crush- or cut- severance of sciatic nerve axons in rats and other mammals produces immediate loss of axonal continuity. Loss of locomotor functions subserved by those axons are not restored for months, if ever, by outgrowths regenerating at ~1 mm/d from the proximal stumps of severed axonal segments. The distal stump of a severed axon typically begins to degenerate in 1–3 days. We have recently developed a PEG-fusion technology consisting of sequential exposure of severed axonal ends to hypotonic Ca2+-free saline, methylene blue (MB), polyethylene glycol (PEG) in distilled water, and finally to Ca2+-containing isotonic saline. We examined factors that affect the PEG-fusion restoration of axonal continuity within minutes as measured by conduction of action potentials and diffusion of an intracellular fluorescent dye across the lesion site of rat sciatic nerves completely cut- or crush-severed in the mid-thigh. We also examined factors that affect the longer-term PEG-fusion restoration of lost behavioral functions within days to weeks as measured by the Sciatic Functional Index. We report that exposure of cut-severed axonal ends to Ca2+-containing saline prior to PEG-fusion and stretch/tension of proximal or distal axonal segments of cut-severed axons decrease PEG-fusion success. Conversely, trimming cut-severed ends in Ca2+-free saline just prior to PEG-fusion increases PEG-fusion success. PEG-fusion prevents or retards the Wallerian degeneration of cut-severed axons as assessed by measures of axon diameter and G ratio. PEG-fusion may produce a paradigm-shift in the treatment of peripheral nerve injuries.