The effect of sterilization and storage on the viscoelastic properties of human tendon allografts - Continued: Storage for 0 to 4 months.

The role of donor-derived tendons, also known as allografts, in anterior cruciate ligament replacement surgeries is steadily increasing. Before surgery, temporary storage and, in most cases, sterilization are essential. It is, thus, crucial to determine how these procedures alter the grafts' biomechanical properties.

Reliable Methods for Classification, Characterization, and Design of Cellular Structures for Patient-Specific Implants.

In our research, our goal was to develop a characterization method that can be universally applied to periodic cell structures. Our work involved the accurate tuning of the stiffness properties of cellular structure components that can significantly reduce the number of revision surgeries. Up to date porous, cellular structures provide the best possible osseointegration, while stress shielding and micromovements at the bone-implant interface can be reduced by implants with elastic properties equivalent to bone tissue.

Nonlinear fiber-bundle-cells-based phenomenological modeling of human tissue samples.

Certain assemblies of fibers, called fiber bundles, play a crucial role in the statistical macroscale properties of fibrous structures like natural or artificial materials. Based on the concept of using idealized statistical fiber bundle cells (FBCs) as model elements, the software named FiberSpace was developed by us earlier for the phenomenological modeling of the tensile test process of real fibrous structures. The model fibers of these FBCs had been considered linear elastic, which was suitable for modeling certain textiles and composites.

The effect of sterilization and storage on the viscoelastic properties of human tendon allografts.

Allografts have become increasingly preferred for anterior cruciate ligament replacement purposes. The risk of infections necessitates thorough sterilization procedures, and the allografts usually need to be stored prior to surgery. Classical mechanical tests have been performed with various types of tendons, however, tibialis anterior and peroneus longus tend to suffer the least biomechanical changes after irradiation.

Processing Analysis of Nanoparticle Filled PTFE: Restrictions and Limitations of High Temperature Production.

In this research work, unfilled and monofilled polytetrafluoroethylene (PTFE) were investigated. The applied fillers were graphene, alumina (AlO), boehmite alumina (BA80) and hydrotalcite (MG70). Graphene and AlO are already known in the literature as potential fillers of PTFE, while BA80 and MG70 are novel fillers in PTFE.

Thermal, Viscoelastic, Mechanical and Wear Behaviour of Nanoparticle Filled Polytetrafluoroethylene: A Comparison.

In this research work, unfilled and mono-filled polytetrafluoroethylene (PTFE) materials were developed and characterised by physical, thermal, viscoelastic, mechanical, and wear analysis. The applied fillers were graphene, alumina (AlO), boehmite alumina (BA80), and hydrotalcite (MG70) in 0.25/1/4/8 and 16 wt % filler content.

Detection of Delamination in Polymer Composites by Digital Image Correlation-Experimental Test.

Fiber-reinforced polymer composite structures are frequently used in industries where personal safety is critical; therefore, it is important to periodically estimate or monitor the condition of high value, load bearing structures. The digital image correlation (DIC) is well known as an effective method to obtain full field surface strains; in this paper, it was used to detect artificial damage inside the structures. Carbon or glass fabric reinforced epoxy specimens were produced and tested.

The Effect of Multilevel Carbon Reinforcements on the Fire Performance, Conductivity, and Mechanical Properties of Epoxy Composites.

We studied the effect of a multilevel presence of carbon-based reinforcements-a combination of conventional load-bearing unidirectional carbon fiber (CF) with multiwalled carbon nanotubes (CNT) and conductive CNT-containing nonwoven carbon nanofabric (CNF(CNT))-on the fire performance, thermal conductivity, and mechanical properties of reference and flame-retarded epoxy resin (EP) composites. The inclusion of carbon fibers and flame retardant reduced the peak heat release rate (pHRR) of the epoxy resins. The extent to which the nanoreinforcements reduced the pHRR depended on their influence on thermal conductivity.

Does a different dose of gamma irradiation have the same effect on five different types of tendon allografts? - a biomechanical study.

Introduction: The goals of our study were to evaluate the biomechanical differences between five tendons and the changes in biomechanical properties caused by irradiation.

Methods: Achilles, quadriceps, semitendinosus + gracilis (STG), tibialis anterior (TA) and the peroneus longus (PL) were harvested from 30 donors. Group A contained 50 tendons without gamma irradiation.

Pitfalls during biomechanical testing - Evaluation of different fixation methods for measuring tendons endurance properties.

The goal of the study was to find a proper technique to fix tendon grafts into an INSTRON loading machine. From 8 human cadavers, 40 grafts were collected. We removed the bone-patella tendon-bone grafts, the semitendinosus and gracilis tendons, the quadriceps tendon-bone grafts, the Achilles tendons, and the peroneus longus tendons from each lower extremity.

Hook2 contributes to aggresome formation.

Background: Aggresomes are pericentrosomal accumulations of misfolded proteins, chaperones and proteasomes. Their positioning near the centrosome, like that of other organelles, requires active, microtubule-dependent transport. Linker proteins that can associate with the motor protein dynein, organelles, and microtubules are thought to contribute to the active maintenance of the juxtanuclear localization of many membrane bound organelles and aggresomes.

Hook2 localizes to the centrosome, binds directly to centriolin/CEP110 and contributes to centrosomal function.

Centrosomes serve as microtubule-organizing centers. However, centrosome function depends on microtubule organization and protein transport because the formation, positioning and maintenance of centrosomes require microtubule-dependent retrograde transport. Linker proteins that associate with the motor protein dynein, organelles and microtubules facilitate loading of cargos for retrograde transport and thus contribute to the composition and placement of the centrosome and other juxtanuclear protein complexes.

JNK mediates pathogenic effects of polyglutamine-expanded androgen receptor on fast axonal transport.

Expansion of the polyglutamine (polyQ) stretch in the androgen receptor (AR) protein leads to spinal and bulbar muscular atrophy (SBMA), a neurodegenerative disease characterized by lower motor neuron degeneration. The pathogenic mechanisms underlying SBMA remain unknown, but recent experiments show that inhibition of fast axonal transport (FAT) by polyQ-expanded proteins, including polyQ-AR, represents a new cytoplasmic pathogenic lesion. Using pharmacological, biochemical and cell biological experiments, we found a new pathogenic pathway that is affected in SBMA and results in compromised FAT.

Activity-driven dendritic remodeling requires microtubule-associated protein 1A.

Activity-prompted dendritic remodeling leads to calcium-influx-dependent activation of signaling pathways within minutes and gene transcription within hours. However, dendrite growth continues for days and requires extension and stabilization of the cytoskeleton in nascent processes. In addition to binding microtubules, microtubule-associated proteins (MAPs) associate with the actin cytoskeleton, anchor ion channels and signaling complexes, and modulate synaptic growth.

A novel CDK5-dependent pathway for regulating GSK3 activity and kinesin-driven motility in neurons.

Neuronal transmission of information requires polarized distribution of membrane proteins within axonal compartments. Membrane proteins are synthesized and packaged in membrane-bounded organelles (MBOs) in neuronal cell bodies and later transported to axons by microtubule-dependent motor proteins. Molecular mechanisms underlying targeted delivery of MBOs to discrete axonal subdomains (i.

Neuropathogenic forms of huntingtin and androgen receptor inhibit fast axonal transport.

Huntington's and Kennedy's disease are autosomal dominant neurodegenerative diseases caused by pathogenic expansion of polyglutamine tracts. Expansion of glutamine repeats must in some way confer a gain of pathological function that disrupts an essential cellular process and leads to loss of affected neurons. Association of huntingtin with vesicular structures raised the possibility that axonal transport might be altered.

Fibroblast growth factor (FGF)-4 can induce proliferation of cardiac cushion mesenchymal cells during early valve leaflet formation.

While much has been learned about how endothelial cells transform to mesenchyme during cardiac cushion formation, there remain fundamental questions about the developmental fate of cushions. In the present work, we focus on the growth and development of cushion mesenchyme. We hypothesize that proliferative expansion and distal elongation of cushion mesenchyme mediated by growth factors are the basis of early valve leaflet formation.

Overexpression of neurofilament H disrupts normal cell structure and function.

Studying exogenously expressed tagged proteins in live cells has become a standard technique for evaluating protein distribution and function. Typically, expression levels of experimentally introduced proteins are not regulated, and high levels are often preferred to facilitate detection. However, overexpression of many proteins leads to mislocalization and pathologies.

Glycogen synthase kinase 3 phosphorylates kinesin light chains and negatively regulates kinesin-based motility.

Membrane-bounded organelles (MBOs) are delivered to different domains in neurons by fast axonal transport. The importance of kinesin for fast antero grade transport is well established, but mechanisms for regulating kinesin-based motility are largely unknown. In this report, we provide biochemical and in vivo evidence that kinesin light chains (KLCs) interact with and are in vivo substrates for glycogen synthase kinase 3 (GSK3).

Regulation of kinesin: implications for neuronal development.

Rapid organelle transport is required for process growth and establishment of specialized structures during neuronal development. Furthermore, maintenance of mature neuronal architecture and function depends on the proper delivery of materials to specialized domains within axons, such as nodes of Ranvier and synaptic terminals. Kinesin is the most abundant member of the kinesin superfamily of microtubule-based motors.

Fibroblast growth factor-2 promotes axon branching of cortical neurons by influencing morphology and behavior of the primary growth cone.

Interstitial branching is an important mechanism for target innervation in the developing CNS. A previous study of cortical neurons in vitro showed that the terminal growth cone pauses and enlarges in regions from which interstitial axon branches later develop (Szebenyi et al., 1998).

Common mechanisms underlying growth cone guidance and axon branching.

During development, growth cones direct growing axons into appropriate targets. However, in some cortical pathways target innervation occurs through the development of collateral branches that extend interstitially from the axon shaft. How do such branches form? Direct observations of living cortical brain slices revealed that growth cones of callosal axons pause for many hours beneath their cortical targets prior to the development of interstitial branches.

Release of kinesin from vesicles by hsc70 and regulation of fast axonal transport.

The nature of kinesin interactions with membrane-bound organelles and mechanisms for regulation of kinesin-based motility have both been surprisingly difficult to define. Most kinesin is recovered in supernatants with standard protocols for purification of motor proteins, but kinesin recovered on membrane-bound organelles is tightly bound. Partitioning of kinesin between vesicle and cytosolic fractions is highly sensitive to buffer composition.