Inter-subject variability effects on the primary stability of a short cementless femoral stem.

This paper is concerned with the primary stability of the Furlong Evolution(®) cementless short stem across a spectrum of patient morphology. A computational tool is developed that automatically selects and positions the most suitable stem from an implant system made of a total of 48 collarless stems to best match a 3D model based on a library of CT femur scans (75 males and 34 females). Finite Element contact models of reconstructed hips, subjected to physiologically-based boundary constraints and peak loads of walking mode, were simulated using a coefficient of friction of 0.

Template-assisted electrohydrodynamic atomization of polycaprolactone for orthopedic patterning applications.

This paper presents the development of the novel deposition of biodegradable polycaprolactone (PCL) polymer patterns on a metallic substrate using a jet spraying technique, template-assisted electrohydrodynamic atomization (TAEA), at ambient temperature. The structure of patterns was controlled by systematically varying the polymer concentration (2-15 wt.%) and the flow rate (1-25 μl min(-1)).

In vitro comparison of mechanical and degradation properties of equivalent absorbable suture materials from two different manufacturers.

Objective: To compare the mechanical, knotting, and absorption properties of 3 synthetic absorbable suture materials (polyglactin 910, polydioxanone, poliglecaprone 25) from 2 different manufacturers (Huaiyin Medical Instruments Co. Ltd. and Ethicon Inc.

Polarization of the yeast pheromone receptor requires its internalization but not actin-dependent secretion.

In the best understood models of eukaryotic directional sensing, chemotactic cells maintain a uniform distribution of surface receptors even when responding to chemical gradients. The yeast pheromone receptor is also uniformly distributed on the plasma membrane of vegetative cells, but pheromone induces its polarization into "crescents" that cap the future mating projection. Here, we find that in pheromone-treated cells, receptor crescents are visible before detectable polarization of actin cables and that the receptor can polarize in the absence of actin-dependent directed secretion.

Dse1 may control cross talk between the pheromone and filamentation pathways in yeast.

The filamentous/invasive growth pathway is activated by nutrient limitation in the haploid form of the yeast Saccharomyces cerevisiae, whereas exposure to mating-pheromone causes cells to differentiate into gametes. Although these two pathways respond to very different stimuli and generate very different responses, they utilize many of the same signaling components. This implies the need for robust mechanisms to maintain signal fidelity.

The mating-specific Galpha interacts with a kinesin-14 and regulates pheromone-induced nuclear migration in budding yeast.

As a budding yeast cell elongates toward its mating partner, cytoplasmic microtubules connect the nucleus to the cell cortex at the growth tip. The Kar3 kinesin-like motor protein is then thought to stimulate plus-end depolymerization of these microtubules, thus drawing the nucleus closer to the site where cell fusion and karyogamy will occur. Here, we show that pheromone stimulates a microtubule-independent interaction between Kar3 and the mating-specific Galpha protein Gpa1 and that Gpa1 affects both microtubule orientation and cortical contact.

Regional load bearing of the canine acetabulum.

Objective: To determine the load bearing areas of the canine acetabulum.

Materials And Methods: A kinematic study of four healthy dogs was used to determine the orientation of the femur to the pelvis at mid-stance. Femora and pelves from 10 canine cadavers were loaded with the physiological canine hip reaction force and angle being replicated.

Aging enhances a mechanically-induced reduction in tendon strength by an active process involving matrix metalloproteinase activity.

Age-associated and degenerative loss of functional integrity in soft tissues develops from effects of cumulative and subtle changes in their extracellular matrix (ECM). The highly ordered tendon ECM provides the tissue with its tensile strength during loading. As age and exercise collide in the high incidence of tendinopathies, we hypothesized that aged tendons fail due to cumulative damage resulting from a combination of diminished matrix repair and fragmentation of ECM proteins induced by prolonged cyclical loading, and that this is an active cell-mediated process.

Noninvasive Raman spectroscopy of human tissue in vivo.

We report the first transcutaneous Raman spectrum of human bone in vivo obtained at skin-safe laser illumination levels. The spectrum of thumb distal phalanx was obtained using spatially offset Raman spectroscopy (SORS), which provides chemically specific information on deep layers of human tissue, well beyond the reach of existing comparative approaches. The spectroscopy is based on collecting Raman spectra away from the point of laser illumination using concentric rings of optical fibers.

Mechanical testing of human cardiac tissue: some implications for MRI safety.

Purpose: The effects of aging on tissue strength and its ability to withstand forces associated with MRI have not been investigated. This study aimed to determine the forces required to cause partial or total detachment of a heart valve prosthesis in patients with age-related degenerative diseases exposed to MRI.

Methods: Eighteen tissue samples excised during routine heart valve replacement surgery were subjected to a suture pull-out test using a tensile materials testing machine.

Novel assessment of bone using time-resolved transcutaneous Raman spectroscopy.

Unlabelled: With fragility fractures increasing as the population ages, there is a need for improved means to estimate risk of fracture. We recorded Raman spectra of both the mineral and organic phases of bone transcutaneously, a technology with potential to enhance bone quality and fracture risk assessment.

Introduction: The current "gold standard" assessment of bone quality is BMD determined by DXA.

Kerr-gated time-resolved Raman spectroscopy of equine cortical bone tissue.

Picosecond time-resolved Raman spectroscopy in equine cortical bone tissue is demonstrated. Using 400-nm pulsed laser excitation (1 ps at 1 kHz) it is shown that Kerr cell gating with a 4-ps window provides simultaneously time-resolved rejection of fluorescence and time-resolved Raman scatter enabling depth profiling through tissue. The Raman shifts are the same as those observed by conventional cw Raman spectroscopy using deep-red or near-infrared lasers.

Regional load bearing of the feline acetabulum.

Objective: To test if the caudal acetabulum of the cat is unloaded at mid-stance as has been asserted.

Materials And Methods: A kinematic study of five healthy cats was performed to ascertain the mid-stance angle of the hip joint, and the orientation of the pelvis and femur. Femora and pelves from 10 feline cadavers were loaded at physiological load at the mid-stance angle.

A novel technique for four-point bending of small bone samples with semi-automatic analysis.

The design of this system takes into account the following parameters: the effects of excessive strain; specimen depth and width; span-depth ratio; overhang; rate of loading; measuring displacement from the crosshead position; radius of contact points; and the distance between the contacts. The contacts are radius edges rather than cylinders, although this is not to be recommended for multiple cycles because of wear problems, it does make the system as stiff as possible (allowance is made for this compliance). Equations are presented that allow the surface stress and strain to be calculated for each time point semi-automatically.

Early experience with a new technique and technology designed for the study of pulsatile cardiopulmonary bypass in the rat.

The benefits of pulsatile flow during the period of cardiopulmonary bypass (CPB) applied during open-heart surgery remains controversial. We have developed a rodent (rat) model of CBP that has been designed to functionally mimic the clinical setting, principally, but not solely, for the study of pulsatile CPB. The successful development of this model centres on the design of the bypass circuitry and the surgical approach employed.