The vacuolated morphology of chordoma cells is dependent on cytokeratin intermediate filaments.

Notochordal cells (NCs), characterized by their vacuolated morphology and coexpression of cytokeratin and vimentin intermediate filaments (IFs), form the immature nucleus pulposus (NP) of the intervertebral disc. As humans age, NCs give way to mature NP cells, which do not possess a vacuolated morphology and typically only express vimentin IFs. In light of their concomitant loss, we investigated the relationship between cytosolic vacuoles and cytokeratin IFs, specifically those containing cytokeratin-8 proteins, using a human chordoma cell line as a model for NCs.

Correction to: Deformability of Human Mesenchymal Stem Cells Is Dependent on Vimentin Intermediate Filaments.

This erratum is to correct the following: (1) in the Western Blotting subsection under the Materials and Methods section, the concentration of protein from each sample loaded into Criterion Tris-HCl gels was incorrectly stated as 155 µg of protein. The correct value is 9.7 µg; (2) in Fig.

A Biomechanical Comparison of Allograft Tendons for Ligament Reconstruction.

Background: Allograft tendons are frequently used for ligament reconstruction about the knee, but they entail availability and cost challenges. The identification of other tissues that demonstrate equivalent performance to preferred tendons would improve limitations. Hypothesis/Purpose: We compared the biomechanical properties of 4 soft tissue allograft tendons: tibialis anterior (TA), tibialis posterior (TP), peroneus longus (PL), and semitendinosus (ST).

When Should We Change Drill Bits? A Mechanical Comparison of New, Reprocessed, and Damaged Bits.

Objectives: We assessed how reprocessed and damaged drill bits perform relative-to-new drill bits in terms of drilling force required, heat generated at near and far cortices, and number of usable passes.

Methods: Nine pairs of nonosteoporotic human cadaveric femora were tested using 3 types of 3.2-mm drill bits (new, reprocessed, and damaged) in 3 investigations (force, temperature, and multiple usable passes).

Deformability of Human Mesenchymal Stem Cells Is Dependent on Vimentin Intermediate Filaments.

Mesenchymal stem cells (MSCs) are being studied extensively due to their potential as a therapeutic cell source for many load-bearing tissues. Compression of tissues and the subsequent deformation of cells are just one type physical strain MSCs will need to withstand in vivo. Mechanotransduction by MSCs and their mechanical properties are partially controlled by the cytoskeleton, including vimentin intermediate filaments (IFs).

Biomechanical Comparison of Cadaveric and Commercially Available Synthetic Osteoporotic Bone Analogues in a Locked Plate Fracture Model Under Torsional Loading.

Objectives: Biomechanical studies of osteoporotic bone have used synthetic models rather than cadaveric samples because of decreased variability, increased availability, and overall ease of the use of synthetic models. We compared the torsional mechanical properties of cadaveric osteoporotic bone with those of currently available synthetic osteoporotic bone analogues.

Methods: We tested 12 osteoporotic cadaveric humeri and 6 specimens each of 6 types of synthetic analogues.

Ultrasonic Structural Health Monitoring to Assess the Integrity of Spinal Growing Rods In Vitro.

Background: Rod fracture is a common complication of growing rods and can result in loss of correction, patient discomfort, and unplanned revision surgery. The ability to quantitate rod integrity at each lengthening would be advantageous to avoid this complication. We investigate the feasibility of applying structural health monitoring to evaluate the integrity of growing rods in vitro.

Biomechanical and Cost Comparisons of Near-Far and Pin-Bar Constructs.

Orthopedic dogma states that external fixator stiffness is improved by placing 1 pin close to the fracture and 1 as distant as possible ("near-far"). This fixator construct is thought to be less expensive than placing pins a shorter distance apart and using "pin-bar" clamps that attach pins to outriggers. The authors therefore hypothesized that the near-far construct is stiffer and less expensive.

Layered Alginate Constructs: A Platform for Co-culture of Heterogeneous Cell Populations.

Many load bearing tissues possess structurally and functionally distinct regions, typically accompanied by different cell phenotypes with differential mechanosensing characteristics. Engineering and analysis of these tissue types remain a challenge. Layered hydrogel constructs provide an opportunity for investigating the interactions among multiple cell populations within single constructs.

Expression and actions of corticotropin-releasing factor/diuretic hormone-like peptide (CDLP) and teneurin C-terminal associated peptide (TCAP) in the vase tunicate, Ciona intestinalis: Antagonism of the feeding response.

Teneurin C-terminal associated peptide (TCAP) is a neuropeptide that bears some structural similarity to the corticotropin-releasing factor (CRF) family of peptides. TCAP and CRF are both implicated in the regulation of stress-related behaviors, as established in rodent models. However, in vertebrates, both TCAP and CRF possess three additional paralogous forms making vertebrate models difficult to assess with respect to TCAP-CRF interaction.

Optical Coherence Tomographic Elastography Reveals Mesoscale Shear Strain Inhomogeneities in the Annulus Fibrosus.

Study Design: Basic science study using in vitro tissue testing and imaging to characterize local strains in annulus fibrosus (AF) tissue.

Objective: To characterize mesoscale strain inhomogeneities between lamellar and inter-/translamellar (ITL) matrix compartments during tissue shear loading.

Summary Of Background Data: The intervertebral disc is characterized by significant heterogeneities in tissue structure and plays a critical role in load distribution and force transmission in the spine.

Rib Fracture Fixation Restores Inspiratory Volume and Peak Flow in a Full Thorax Human Cadaveric Breathing Model.

Background: Multiple rib fractures cause significant pain and potential for chest wall instability. Despite an emerging trend of surgical management of flail chest injuries, there are no studies examining the effect of rib fracture fixation on respiratory function.

Objectives: Using a novel full thorax human cadaveric breathing model, we sought to explore the effect of flail chest injury and subsequent rib fracture fixation on respiratory outcomes.

Effect of Dynamic Culture and Periodic Compression on Human Mesenchymal Stem Cell Proliferation and Chondrogenesis.

We have recently developed a bioreactor that can apply both shear and compressive forces to engineered tissues in dynamic culture. In our system, alginate hydrogel beads with encapsulated human mesenchymal stem cells (hMSCs) were cultured under different dynamic conditions while subjected to periodic, compressive force. A customized pressure sensor was developed to track the pressure fluctuations when shear forces and compressive forces were applied.

Axial strain enhances osteotomy repair with a concomitant increase in connexin43 expression.

The mechanical environment is known to influence fracture healing. We speculated that connexin43 (Cx43) gap junctions, which impact skeletal homeostasis, fracture healing and the osteogenic response to mechanical load, may play a role in mediating the response of the healing bone to mechanical strain. Here, we used an established rat fracture model, which uses a 2 mm osteotomy gap stabilized by an external fixator, to examine the impact of various cyclical axial loading protocols (2%, 10%, and 30% strain) on osteotomy healing.

Effects of angular frequency during clinorotation on mesenchymal stem cell morphology and migration.

Aims: To determine the short-term effects of simulated microgravity on mesenchymal stem cell behaviors-as a function of clinorotation speed-using time-lapse microscopy.

Background: Ground-based microgravity simulation can reproduce the apparent effects of weightlessness in spaceflight using clinostats that continuously reorient the gravity vector on a specimen, creating a time-averaged nullification of gravity. In this work, we investigated the effects of clinorotation speed on the morphology, cytoarchitecture, and migration behavior of human mesenchymal stem cells (hMSCs).

Transient solid-fluid interactions in rat brain tissue under combined translational shear and fixed compression.

An external mechanical insult to the brain may create internal deformation waves, which have shear and longitudinal components that induce combined shear and compression of the brain tissue. To isolate such interactions and to investigate the role of the extracellular fluid (ECF) in the transient mechanical response, translational shear stretch up to 1.25 under either 0 or 33% fixed normal compression is applied without preconditioning to heterogeneous sagittal slices which are nearly the full length of the rat brain cerebrum.

Effects of proinflammatory cytokines on axonal outgrowth from adult rat lumbar dorsal root ganglia using a novel three-dimensional culture system.

Background Context: Degeneration of the intervertebral disc is often associated with low back pain and increased infiltration of nerve fibers originating from dorsal root ganglia (DRG). The degenerated disc is also characterized by the presence of proinflammatory cytokines, which may influence axonal outgrowth. Toward an improved understanding of the growth of DRG neurons into compliant extracellular matrices, we developed a novel experimental system to measure axonal outgrowth of adult rat lumbar DRG neurons within three-dimensional (3D) collagen hydrogels and used this system to examine the effects of interleukin 1β (IL-1β) and tumor necrosis factor (TNF)-α treatment.

Internal anterior fixators for pelvic ring injuries: Do monaxial pedicle screws provide more stiffness than polyaxial pedicle screws?

Objectives: Little is known about the mechanical properties of internal anterior fixators (known as INFIX), which have been proposed as subcutaneous alternatives to traditional anterior external fixators for pelvic ring disruptions. We hypothesised that INFIX has superior biomechanical performance compared with traditional external fixators because the distance from the bar to the bone is reduced.

Methods: Using a commercially available synthetic bone model, 15 unstable pelvic ring injuries were simulated by excising the pubic bone through the bilateral superior and inferior rami anteriorly and the sacrum through the bilateral sacral foramen posteriorly.

Three dimensional mesoscale analysis of translamellar cross-bridge morphologies in the annulus fibrosus using optical coherence tomography.

The defining characteristic of the annulus fibrosus (AF) of the intervertebral disc (IVD) has long been the lamellar structures that consist of highly ordered collagen fibers arranged in alternating oblique angles from one layer to the next. However, a series of recent histologic studies have demonstrated that AF lamellae contain elastin- and type VI collagen-rich secondary "cross-bridge" structures across lamellae. In this study, we use optical coherence tomography (OCT) to elucidate the three-dimensional (3-D) morphologies of these translamellar cross-bridges in AF tissues.

Bar diameter is an important component of knee-spanning external fixator stiffness and cost.

The authors' objective was to determine the effects of bar diameter on the stiffness and cost of a knee-spanning external fixator. The authors studied 2 versions of an external fixator with a difference in bar diameter (small bars, 8-mm diameter; large bars, 11-mm diameter). Fixators were tested using frame dimensions and a synthetic fracture model appropriate for a tibial plateau fracture.

A computational model to describe the regional interlamellar shear of the annulus fibrosus.

Interlamellar shear may play an important role in the homeostasis and degeneration of the intervertebral disk. Accurately modeling the shear behavior of the interlamellar compartment would enhance the study of its mechanobiology. In this study, physical experiments were utilized to describe interlamellar shear and define a constitutive model, which was implemented into a finite element analysis.

WITHDRAWN: Corrigendum to "Ring chromosome 21 presenting with sacrococcygeal teratoma: Prenatal diagnosis, molecular cytogenetic characterization and literature review" [Gene 522 (2013) 111-116].

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.

Analysis of strategies to increase external fixator stiffness: is double stacking worth the cost?

We compared the mechanical benefits and costs of 3 strategies that are commonly used to increase knee-spanning external fixator stiffness (resistance to deformation): double stacking, cross-linking, and use of an oblique pin. At our academic trauma centre and biomechanical testing laboratory, we used ultra-high-molecular-weight polyethylene bone models and commercially available external fixator components to simulate knee-spanning external fixation. The models were tested in anterior-posterior bending, medial-lateral bending, axial compression, and torsion.

Solid-extracellular fluid interaction and damage in the mechanical response of rat brain tissue under confined compression.

The mechanical processes that underlie mild traumatic brain injury from physical insults are not well understood. One aspect in particular that has not been examined is the tissue fluid, which is known to be critical in the mechanical function of other organs. To investigate the contributions of solid-fluid interactions to brain tissue mechanics, we performed confined compression tests, that force the extracellular fluid (ECF) to flow in the direction of the deformation, on 6.

Does a trochanteric lag screw improve fixation of vertically oriented femoral neck fractures? A biomechanical analysis in cadaveric bone.

Background: We assessed the biomechanical performances of a trochanteric lag screw construct and a traditional inverted triangle construct in the treatment of simulated Pauwels type 3 femoral neck fractures.

Methods: An inverted triangle construct (three 7.3-mm cannulated screws placed in inverted triangle orientation) and a trochanteric lag screw construct (two 7.