Numerical simulation and biomechanical analysis of locking screw caps on clavicle locking plates.

BACKGROUND: The risk of displaced and comminuted midshaft clavicle fractures is increased in high-energy traumas such as sport injuries and traffic accidents. Open reduction and plate fixation have been widely used for midshaft clavicle fractures. Among various plates for clavicle shaft fractures, superior locking compression plates (LCPs) have been mostly used. In plate fixation, nonunion caused by implant failure is the most difficult complication. The most common reasons for metal plate failure are excessive stress and stress concentration caused by cantilever bending. These causes were easily addressed using a locking screw cap (LSC). METHODS: The clavicle 3-dimensional image was made from a computed tomography scan, and the clavicle midshaft fracture model was generated with a 10-mm interval. The fracture model was fixed with a superior LCP, and finite element analysis was conducted between the presence (with LSC model) and absence (without LSC model) of an LSC on the site of the fracture. The stresses of screw holes in models with and without LSCs were measured under 3 forces: 100 N cantilever bending force, 100 N axial compression force, and 1 N·m axial torsion force. After the finite element analysis, a validation test was conducted on the cantilever bending force known as the greatest force applied to superior locking plates. RESULTS: The mean greatest stress under the cantilever bending force was significantly greater than other loading forces. The highest stress site was the screw hole edge on the fracture site in both models under the cantilever bending and axial compression forces. Under the axial torsional force, the maximum stress point was the lateral first screw hole edge. The ultimate plate stress of the with LSC model is completely lower than that of the without LSC model. According to the validation test, the stiffness, ultimate load, and yield load of the with LSC model were higher than those of the without LSC model. CONCLUSIONS: Therefore, inserting an LSC into an empty screw hole in the fracture area reduces the maximum stress on an LCP and improves biomechanical stability.

An azobenzene-based photochromic liquid crystalline amphiphile for a remote-controllable light shutter.

By considering intramolecular conformations and intermolecular interactions, an azobenzene-based photochromic liquid crystalline amphiphile is synthesized for demonstrating a remote-controllable light shutter by the photo-induced isothermal phase transition between the highly ordered crystal phase and the isotropic liquid phase.

Thioredoxin-interacting protein regulates protein disulfide isomerases and endoplasmic reticulum stress.

The endoplasmic reticulum (ER) is responsible for protein folding, modification, and trafficking. Accumulation of unfolded or misfolded proteins represents the condition of ER stress and triggers the unfolded protein response (UPR), a key mechanism linking supply of excess nutrients to insulin resistance and type 2 diabetes in obesity. The ER harbors proteins that participate in protein folding including protein disulfide isomerases (PDIs). Changes in PDI activity are associated with protein misfolding and ER stress. Here, we show that thioredoxin-interacting protein (Txnip), a member of the arrestin protein superfamily and one of the most strongly induced proteins in diabetic patients, regulates PDI activity and UPR signaling. We found that Txnip binds to PDIs and increases their enzymatic activity. Genetic deletion of Txnip in cells and mice led to increased protein ubiquitination and splicing of the UPR regulated transcription factor X-box-binding protein 1 (Xbp1s) at baseline as well as under ER stress. Our results reveal Txnip as a novel direct regulator of PDI activity and a feedback mechanism of UPR signaling to decrease ER stress.

Vasculitis livedoide que responde altratamiento con PUVA / Livedoid vasculitis responding to PUVA therapy

Antecedentes: La vasculitis livedoide es un trastorno crónico que se manifiesta en forma de lesiones recurrentes, dolorosas, reticuladas y ulcerativas de las piernas, que origina cicatrices atróficas de color marfil con telangiectasia e hiperpigmentación periférica. Su etiología sigue siendo oscura y el tratamiento es difícil. En este estudio evaluamos la eficacia clínica del tratamiento de psoraleno más UVA (PUVA) y sus efectos secundarios en el tratamiento de la vasculitis livedoide. Métodos: Ocho pacientes surcoreanos con vasculitis livedoide fueran tratados con 8-metoxipsoraleno (8MOP) y UVA. Se comenzó a administrar PUVA sistémico con cuatro julios/cm2 de UVA dos o tres veces en semana y después la dosis se aumentó 0,5 ó 1 julios/cm2 en cada tratamiento posterior según su tolerancia. Los efectos del tratamiento se valoraron usando fotografías de antes del estudio, durante el estudio y después del estudio. Resultados: Todos los pacientes experimentaron un cese rápido de la formación de nuevas lesiones, alivio significativo de los síntomas y cicatrización completa de las lesiones primarias. Los períodos medios de cada uno de estos parámetros fueron 3,6, 5,9 y 10 semanas y las dosis medias acumuladas de UVA fueron 55,9, 96,8 y 197,9 julios/cm2, respectivamente. Los pacientes toleraron bien el tratamiento con PUVA, usando 8-MOP, sin observarse efectos secundarios inaceptables. Conclusiones: Proponemos que el tratamiento sistémico con PUVA, usando 8-MOP, debe investigarse con más profundidad como tratamiento alternativo de los pacientes con vasculitis livedoide (AU)