ABSTRACT
BACKGROUND: The vast majority of pediatric distal-third tibial shaft fractures can be treated with closed reduction and casting. If conservative measures fail, then these fractures are usually treated with 2 antegrade flexible intramedullary nails. A postoperative cast is usually applied because of the tenuous fixation of the 2 nails. Recent studies have described the use of 4 nails to increase the stability of the fixation, a technique that may preclude the need for postoperative casting. The purpose of this biomechanical study is to quantify the relative increase in stiffness and load to failure when using 4 versus 2 nails to surgically stabilize these fractures. METHODS: Short, oblique osteotomies were created in the distal third of small fourth-generation tibial sawbones and stabilized with 2 (double) or 4 (quadruple) flexible intramedullary nails. After pilot testing, 5 models per fixation method were tested cyclically in axial compression, torsion, and 4-point bending in valgus and recurvatum. At the end of the study, each model was loaded to failure in valgus. Stiffness values were calculated, and yield points were recorded. The data were compared using Student's t tests. Results are presented as mean±SD. The level of significance was set at P≤0.05. RESULTS: Stiffness in valgus 4-point bending was 624±231 and 336±162 N/mm in the quadruple-nail and double-nail groups, respectively (P=0.04). There were no statistically significant differences in any other mode of testing. CONCLUSIONS: The quadruple-nail construct was almost 2 times as stiff as the double-nail construct in resisting valgus deformation. This provides biomechanical support for a previously published study describing the clinical success of this fixation construct.
Subject(s)
Bone Nails , Fracture Fixation, Intramedullary/instrumentation , Tibia/injuries , Tibial Fractures/surgery , Biomechanical Phenomena , Child , Diaphyses/injuries , Diaphyses/surgery , Fracture Fixation, Intramedullary/methods , Humans , Male , Prosthesis Design , Tibia/surgery , Tibial Fractures/physiopathologyABSTRACT
There is great interest in point-of-care antibody testing for the diagnosis of infectious and autoimmune diseases. As a first step in the development of self-contained and miniaturized devices for highly quantitative antibody detection, we demonstrate the application of Luciferase Immunoprecipitation Systems (LIPS) technology in a microfluidic format. Protein A/G was immobilized on the walls of PDMS-glass microchannels of 500 nL volume. The assay proceeds with the simultaneous introduction of plasma and Renilla luciferase-tagged antigens. Following washing, coelenterazine substrate was added and bound antigen-luciferase measured by chemiluminescence. Total assay time, including rinsing and detection, is under 10 min. Using these stable microfluidic devices, high diagnostic performance (100% sensitivity and 100% specificity) was achieved for the diagnosis of HSV-2 infection. Based on these findings, the LIPS microfluidic format should readily lend itself to automation and the transfer to portable instrumentation.
Subject(s)
Antibodies, Viral/blood , Antibodies, Viral/isolation & purification , Herpes Genitalis/diagnosis , Microfluidic Analytical Techniques/instrumentation , Equipment Design , Herpesvirus 2, Human/isolation & purification , Humans , Immunoprecipitation/methods , Luciferases/metabolism , Microfluidic Analytical Techniques/methods , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Lentiviruses have recently attracted considerable interest for their potential as a genetic modification tool for dendritic cells (DCs). In this study, we explore the ability of lentiviruses enveloped with alphaviral envelope glycoproteins derived from Semliki Forest virus (SFV) to mediate transduction of DCs. We found that SFV glycoprotein (SFV-G)-pseudotyped lentiviruses use C-type lectins (DC-SIGN and L-SIGN) as attachment factors for transduction of DCs. Importantly, SFV-G pseudotypes appear to have enhanced transduction towards C-type lectin-expressing cells when produced under conditions limiting glycosylation to simple high-mannose, N-linked glycans. These results, in addition to the natural DC tropism of SFV-G, offer evidence to support the use of SFV-G-bearing lentiviruses to genetically modify DCs for the study of DC biology and DC-based immunotherapy.
Subject(s)
Dendritic Cells/virology , Glycoproteins/metabolism , Lentivirus/genetics , Receptors, Virus/metabolism , Semliki forest virus/metabolism , Transduction, Genetic/methods , Viral Envelope Proteins/metabolism , Cell Line , Cells, Cultured , Glycoproteins/genetics , Humans , Plasmids , Receptors, Virus/genetics , Semliki forest virus/genetics , Viral Envelope Proteins/geneticsABSTRACT
Lentiviral vectors (LVs) pseudotyped with envelope proteins of alphaviruses have recently attracted considerable interest for their potential as gene delivery tools. We report the production of human immunodeficiency virus type 1 (HIV-1)-derived LVs pseudotyped with envelope glycoproteins derived from the Aura virus (AURA). We found that the AURA-glycoprotein-pseudotyped LVs use C-type lectins (DC-SIGN and L-SIGN) as attachment factors. These interactions with DC-SIGN are specific as determined by inhibition assays and appear to facilitate transduction through a pH-dependent pathway. AURA-pseudotyped LVs were used to transduce monocyte-derived dendritic cells (DCs) and the transduction was shown to be DC-SIGN mediated, as illustrated by competitive inhibition with DC-SIGN and L-SIGN antibodies and yeast mannan. Comparisons with LVs enveloped with glycoproteins derived from vesicular stomatitis virus and Sindbis virus suggest that AURA-glycoprotein-bearing LVs might be useful to genetically modify DCs for the study of DC biology and DC-based immunotherapy.