Virtual Reality-Induced Modification of Vestibulo-Ocular Reflex Gain in Posturography Tests.

Background: The aim of the study was to demonstrate the influence of virtual reality (VR) exposure on postural stability and determine the mechanism of this influence. Methods: Twenty-six male participants aged 21-23 years were included, who underwent postural stability assessment twice before and after a few minute of single VR exposure. The VR projection was a computer-generated simulation of the surrounding scenery. Postural stability was assessed using the Sensory Organization Test (SOT), using Computerized Dynamic Posturography (CDP). Results: The findings indicated that VR exposure affects the visual and vestibular systems. Significant differences (p < 0.05) in results before and after VR exposure were observed in tests on an unstable surface. It was confirmed that VR exposure has a positive influence on postural stability, attributed to an increase in the sensory weight of the vestibular system. Partial evidence suggested that the reduction in vestibulo-ocular reflex (VOR) reinforcement may result in an adaptive shift to the optokinetic reflex (OKR). Conclusions: By modifying the process of environmental perception through artificial sensory simulation, the influence of VR on postural stability has been demonstrated. The validity of this type of research is determined by the effectiveness of VR techniques in the field of vestibular rehabilitation.

Correction: Electrostatics at the nanoscale.

Correction for 'Electrostatics at the nanoscale' by David A. Walker et al., Nanoscale, 2011, 3, 1316-1344.

The remarkable phenotypic variability of the p.Arg269HiS variant in the TRPV4 gene.

INTRODUCTION: Mutations in the TRPV4 gene are associated with neuromuscular disorders and skeletal dysplasias, which present a phenotypic overlap. METHODS: Next-generation sequencing and Sanger sequencing were used to analyze the TRPV4 gene. RESULTS: We present 2 Polish families with TRPV4-related disorder harboring the same p.Arg269His mutation. The disease phenotypic expression was extremely variable (from mild scapular winging to severe hypotonia, global weakness, inability to walk unaided, congenital contractures, scoliosis, and respiratory insufficiency), but did not suggest anticipation. The 2 most severely affected patients showed congenital distal contractures of the upper limbs and involvement of cranial nerves (manifesting as facial asymmetry and strabismus). The disease course seemed to be stable, although in later stages it caused respiratory insufficiency and progression of physical disability. DISCUSSION: The phenotypic variability observed in p.Arg269His carriers suggests that an additional modifier or a more complex pathogenic mechanism exists. Muscle Nerve 59:129-133, 2019.

Treatment of the Lower Extremity Contracture/Deformities.

Lower extremity deformities of patients with arthrogryposis multiplex congenita present a wide spectrum of severity and deformity combinations. Treatment goals range from merely ensuring comfortable seating and shoe wear, to fully independent and active ambulation, but the overarching intention is to help realize the patient's greatest potential for independence and function. Treatment of hip and knee contractures and dislocations has become more interventional, whereas treatment of foot deformities has paradoxically become much less surgical. This article synopsizes the treatment strategies presented in September 2014 in Saint Petersburg, Russia at the second international symposium on arthrogryposis.

Engineering Gram Selectivity of Mixed-Charge Gold Nanoparticles by Tuning the Balance of Surface Charges.

Nanoparticles covered with ligand shells comprising both positively and negatively charged ligands exhibit Gram-selective antibacterial action controlled by a single experimental parameter, namely the proportion of [+] and [-] ligands tethered onto these particles. Gram selectivity is attributed to the interplay between polyvalent electrostatic and non-covalent interactions that work in unison to disrupt the bacterial cell wall. The [+/-] nanoparticles are effective in low doses, are non-toxic to mammalian cells, and are tolerated well in mice. These results constitute the first example of rational engineering of Gram selectivity at the (macro)molecular level.

Arthrogryposis: an update on clinical aspects, etiology, and treatment strategies.

Arthrogryposes - multiple joint contractures - are a clinically and etiologically heterogeneous class of diseases, where accurate diagnosis, recognition of the underlying pathology and classification are of key importance for the prognosis as well as for selection of appropriate management. This treatment remains challenging and optimally in arthrogrypotic patients should be carried out by a team of specialists familiar with all aspects of arthrogryposis pathology and treatment modalities: rehabilitation, orthotics and surgery. In this comprehensive review article, based on literature and clinical experience, the authors present an update on current knowledge on etiology, classifications and treatment options for skeletal deformations possible in arthrogryposis.

Self-assembly of like-charged nanoparticles into microscopic crystals.

Like-charged nanoparticles, NPs, can assemble in water into large, faceted crystals, each made of several million particles. These NPs are functionalized with mixed monolayers comprising ligands terminating in carboxylic acid group ligands as well as positively charged quaternary ammonium ligands. The latter groups give rise to electrostatic interparticle repulsions which partly offset the hydrogen bonding between the carboxylic acids. It is the balance between these two interactions that ultimately enables self-assembly. Depending on the pH, the particles can crystallize, form aggregates, remain unaggregated or even - in mixtures of two particle types - can "choose" whether to crystallize with like-charged or oppositely charged particles.

Label-free in situ optical monitoring of the adsorption of oppositely charged metal nanoparticles.

The mechanism of alternating deposition of oppositely charged gold nanoparticles (AuNPs) was investigated by optical waveguide lightmode spectroscopy (OWLS). OWLS allows monitoring of the kinetics of layer-by-layer (LbL) adsorption of positively and negatively charged nanoparticles in real time without using any labels so that the dynamics of layer formation can be revealed. Positively charged NPs that are already deposited on a negatively charged glass substrate strongly facilitate the adsorption of the negatively charged particles. The morphology of the adsorbed layer was also investigated with atomic force microscopy (AFM). AFM revealed that the interaction between oppositely charged particles results in the formation of NP clusters with sizes varying between 100 and 6000 NPs. The cluster size distribution is found to be an exponentially decaying function, and we propose a simple theory to explain this finding.

Temperature driven assembly of like-charged nanoparticles at non-planar liquid-liquid or gel-air interfaces.

Gold nanoparticles (NPs) functionalized with 2-fluoro-4-mercaptophenol (FMP) ligands form densely packed NP films at liquid-liquid interfaces, including surfaces of liquid droplets. The process is driven by a gradual lowering of temperature that changes the solution's pH, altering both the energy of interfacial adsorption for NPs traveling from solution to the interface as well as the balance between electrostatic and vdW interactions between these particles. Remarkably, the system shows hysteresis in the sense that the films remain stable when the temperature is increased back to the initial value. The same phenomena apply to gel-air interfaces, enabling patterning of these wet materials with durable NP films.

Biomechanical parameters of the BP-enriched bone cement.

Bisphosphonates (BPs) are well-known substances with very efficient antiresorptive properties. Their beneficial actions are useful not only in achieving better bone mineral density but also in improving bone microarchitecture, strength and, consequently, its quality. Surgical cement, being a polymer composite, is required to be highly biocompatible and biotolerant. The goal of the presented study was to assess whether the enrichment of cement with pamidronate has changed its biomechanical properties. We compared the biomechanical parameters of clean bone cement and BP-enriched bone cement, which were both used formerly in our rat models. Biomechanical properties of BP-enriched bone cement are defined by two basic terms: stress and strain, which are caused by the influence of external force. In the investigatory process of the bone's biomechanical parameters, the compressive test and the three-point flexural tests were used. During the three-point flexural investigation, the sample was supported at both ends and loaded in the middle, resulting in a flexure. After a specific range of flexure, the sample was fractured. In obtained results, there were no significant differences in the values of the stress determined at the point of maximal load and the energy stored in the samples for proportional stress-strain limit (elastic region). There were also no significant differences in the density of the samples. The study shows that the enrichment of bisphosphonates causes yielding of the bone cement material. In the presented data, we conclude that use of pamidronate implanted in bone cement did not have a detrimental effect on its biomechanical properties. Therefore, the obtained results encouraged us to perform further in vivo experiments which assess the biomechanical properties of bones implanted with BP-enriched bone cement.

Colloidal assembly directed by virtual magnetic moulds.

Interest in assemblies of colloidal particles has long been motivated by their applications in photonics, electronics, sensors and microlenses. Existing assembly schemes can position colloids of one type relatively flexibly into a range of desired structures, but it remains challenging to produce multicomponent lattices, clusters with precisely controlled symmetries and three-dimensional assemblies. A few schemes can efficiently produce complex colloidal structures, but they require system-specific procedures. Here we show that magnetic field microgradients established in a paramagnetic fluid can serve as 'virtual moulds' to act as templates for the assembly of large numbers (∼10(8)) of both non-magnetic and magnetic colloidal particles with micrometre precision and typical yields of 80 to 90 per cent. We illustrate the versatility of this approach by producing single-component and multicomponent colloidal arrays, complex three-dimensional structures and a variety of colloidal molecules from polymeric particles, silica particles and live bacteria and by showing that all of these structures can be made permanent. In addition, although our magnetic moulds currently resemble optical traps in that they are limited to the manipulation of micrometre-sized objects, they are massively parallel and can manipulate non-magnetic and magnetic objects simultaneously in two and three dimensions.

Control of surface charges by radicals as a principle of antistatic polymers protecting electronic circuitry.

Even minute quantities of electric charge accumulating on polymer surfaces can cause shocks, explosions, and multibillion-dollar losses to electronic circuitry. This paper demonstrates that to remove static electricity, it is not at all necessary to "target" the charges themselves. Instead, the way to discharge a polymer is to remove radicals from its surface. These radicals colocalize with and stabilize the charges; when they are scavenged, the surfaces discharge rapidly. This radical-charge interplay allows for controlling static electricity by doping common polymers with small amounts of radical-scavenging molecules, including the familiar vitamin E. The effectiveness of this approach is demonstrated by rendering common polymers dust-mitigating and also by using them as coatings that prevent the failure of electronic circuitry.

Controlled pH stability and adjustable cellular uptake of mixed-charge nanoparticles.

Nanoparticles functionalized with mixed self-assembled monolayers (m-SAMs) comprising positively and negatively charged thiols are stable at both low and high pH but precipitate sharply at the pH where the charges on the particle are balanced (pH(prec)). By adjusting the proportion of the positively and negatively charged ligands in the m-SAM or changing particle size, pH(prec) can be varied flexibly between ~4 and ~7. In addition, changes in the SAMs' composition and particles' net charge translate into different degrees of cellular uptake. Remarkably, the presence of the positively charged thiols allows for the uptake of particles having net negative charge.

Age-related differences in medial patellofemoral ligament injury patterns in traumatic patellar dislocation: case series of 50 surgically treated children and adolescents.

BACKGROUND: Complete rupture of the medial patellofemoral ligament (MPFL) during traumatic patellar dislocation may contribute to further patellar instability. As there is still no consensus regarding indications for treatment of such injuries, data on exact localization and extent of tear may influence the treatment decisions. PURPOSE: Analysis of the patterns and the age-related differences in the distribution of medial patellofemoral ligament injury during traumatic patellar dislocation in children and adolescents. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Fifty consecutive patients aged 10.5 to 17.5 years were operated on for injuries after a first episode of traumatic patellar dislocation. The indications for surgery were osteochondral fracture and/or complete MPFL tear. Medial patellofemoral ligament injuries were assessed preoperatively by sonography and then verified at surgery. To assess the influence of skeletal maturity on the injury pattern, the cohort was subdivided into 2 subgroups: skeletally immature and skeletally mature. Distribution of MPFL injuries in both groups was compared. RESULTS: Medial patellofemoral ligament injury was present at surgery in 94% of cases, most commonly at the patellar attachment (66%), followed by mid-fibers (50%) and femoral attachment (32%). In 46%, it occurred in more than 1 localization. Based on functional status of the ligament during dynamic ultrasound examination, 2 types of injury were distinguished: complete and partial rupture. Eighteen of 21 complete ruptures were localized at the patellar attachment, and all but 1 case had a form of the avulsion fracture. Age-related analysis revealed these differences in the incidence of MPFL injury in all 3 localizations comparing skeletally immature with skeletally mature patients: 79% vs 54% at the patellar attachment, 46% vs 54% at the mid-fiber region, and 33% vs 31% at the femoral attachment. Nevertheless, the only statistically significant difference was the higher incidence of patellar attachment injury in the skeletally immature group (P = .029). Sonography demonstrated more than 90% accuracy and predictive value in assessing pathoanatomy as well as the functional status of the medial patellofemoral ligament. CONCLUSION: Medial patellofemoral ligament injury patterns vary in skeletally immature patients compared with skeletally mature patients. Sonography proved high reliability as a diagnostic tool in traumatic patellar dislocation.

Charged nanoparticles as supramolecular surfactants for controlling the growth and stability of microcrystals.

Microcrystals of desired sizes are important in a range of processes and materials, including controlled drug release, production of pharmaceutics and food, bio- and photocatalysis, thin-film solar cells and antibacterial fabrics. The growth of microcrystals can be controlled by a variety of agents, such as multivalent ions, charged small molecules, mixed cationic-anionic surfactants, polyelectrolytes and other polymers, micropatterned self-assembled monolayers, proteins and also biological organisms during biomineralization. However, the chief limitation of current approaches is that the growth-modifying agents are typically specific to the crystalizing material. Here, we show that oppositely charged nanoparticles can function as universal surfactants that control the growth and stability of microcrystals of monovalent or multivalent inorganic salts, and of charged organic molecules. We also show that the solubility of the microcrystals can be further tuned by varying the thickness of the nanoparticle surfactant layers and by reinforcing these layers with dithiol crosslinks.

Electrostatics at the nanoscale.

Electrostatic forces are amongst the most versatile interactions to mediate the assembly of nanostructured materials. Depending on experimental conditions, these forces can be long- or short-ranged, can be either attractive or repulsive, and their directionality can be controlled by the shapes of the charged nano-objects. This Review is intended to serve as a primer for experimentalists curious about the fundamentals of nanoscale electrostatics and for theorists wishing to learn about recent experimental advances in the field. Accordingly, the first portion introduces the theoretical models of electrostatic double layers and derives electrostatic interaction potentials applicable to particles of different sizes and/or shapes and under different experimental conditions. This discussion is followed by the review of the key experimental systems in which electrostatic interactions are operative. Examples include electroactive and "switchable" nanoparticles, mixtures of charged nanoparticles, nanoparticle chains, sheets, coatings, crystals, and crystals-within-crystals. Applications of these and other structures in chemical sensing and amplification are also illustrated.

How and why nanoparticle's curvature regulates the apparent pKa of the coating ligands.

Dissociation of ionizable ligands immobilized on nanopaticles (NPs) depends on and can be regulated by the curvature of these particles as well as the size and the concentration of counterions. The apparent acid dissociation constant (pK(a)) of the NP-immobilized ligands lies between that of free ligands and ligands self-assembled on a flat surface. This phenomenon is explicitly rationalized by a theoretical model that accounts fully for the molecular details (size, shape, conformation, and charge distribution) of both the NPs and the counterions.

Bridging interactions and selective nanoparticle aggregation mediated by monovalent cations.

Selective aggregation and precipitation of like-charged nanoparticles (NPs) covered with carboxylate ligands can be induced by different monovalent cations. The ordering of critical concentrations required for NP precipitation is Cs(+) ≫ K(+) > Li(+) > Na(+) > Rb(+) and does not correlate with the size of hydrated cations M(+), nor can it be predicted by the Hofmeister series. On the other hand, different anions have no effect on the precipitation trends. These observations are rationalized by a theoretical model combining the elements of the DLVO theory with molecular-level calculations. The key component of the model is the cation-specific binding of various metal cations to the carboxylate ligands.