Interaction of a non-linear gravity wave with shear flows containing a vortex layer

The interaction of a large amplitude progressing wave with a piecewise linear shear flow is described

A simulating analysis of the effects of increased joint stiffness on muscle loading in a thumb

<p>Abstract</p> <p>Background</p> <p>The development of osteoarthritis (OA) in the hand results in increased joint stiffness, which in turn affects the grip strength. The goal of the present study is to theoretically analyze the muscle forces in a thumb in response to the increased joint stiffness.</p> <p>Methods</p> <p>The thumb was modeled as a linkage system consisting of a trapezium, a metacarpal bone, a proximal and a distal phalanx. Nine muscles were included in the model: flexor pollicis longus (FPL), extensor pollicis longus (EPL), extensor pollicis brevis (EPB), abductor pollicis longus (APL), flexor pollicis brevis (FPB), abductor pollicis brevis (APB), the transverse head of the adductor pollicis (ADPt), the oblique head of the adductor pollicis (ADPo), and opponens pollicis (OPP). Numerical tests were performed using an inverse dynamic approach. The joints were prescribed to an angular motion at one degree-of-freedom (DOF) each time with all other DOFs of the joints being mechanically constrained, while the muscle forces in response to the joint motions were predicted. The normal joint stiffness was assumed to be 0.05, 0.10, and 0.15 <it>N m/rad </it>for interphalangeal (IP), metacarpophalangeal (MCP), and carpometacarpal (CMC) joint, respectively. The joint stiffness was assumed to increase by 50% and 100%, simulating the biomechanical consequences of OA.</p> <p>Results</p> <p>Our simulations indicated that the increase in joint stiffness induced substantial increases in muscle forces, especially in the EPL and FPL muscles in response to IP, MCP, or CMC extension/flexion motions.</p> <p>Conclusions</p> <p>Because the strength of the muscles in the fingers is limited, the muscles will not be able to overcome joint resistance if joint stiffness is increased to its limit due to OA. This may contribute to the reduced range of motion typically seen in OA.</p

QUANTIFICATION OF THE DYNAMIC GLENOHUMERAL STABILITY PROVIDED BY THE ROTATOR CUFF MUSCLES IN THE LATE COCKING PHASE OF THROWING

The purpose of this study was to investigate quantitatively the dynamic glenohumeral stability provided by the rotator cuff muscles in the late-cocking phase of throwing. Using ten cadaveric shoulders, a new biomechanical parameter (dynamic stability index) was calculated considering compressive and shear forces to the glenoid provided by each cuff muscle. The rotator cuff muscles provided the joint with significant dynamic stability in the late cocking. However, the dynamic stability provided by the cuff muscles with the arm in coronal plane significantly decreased when compared with that in the scapular plane. Rehabilitation of the throwing athletes should emphasize strengthening of the external and internal rotators. Moving the arm into the coronal plane in the late cocking phase should be avoided by a specific strengthening program to prevent further anatomic damage to the static stabilizers

Increasing CD44+/CD24- tumor stem cells, and upregulation of COX-2 and HDAC6, as major functions of HER2 in breast tumorigenesis

<p>Abstract</p> <p>Background</p> <p>Cancer cells are believed to arise primarily from stem cells. CD44⁺/CD24^-have been identified as markers for human breast cancer stem cells. Although, HER2 is a well known breast cancer oncogene, the mechanisms of action of this gene are not completely understood. Previously, we have derived immortal (M13SV1), weakly tumorigenic (M13SV1R2) and highly tumorigenic (M13SV1R2N1) cell lines from a breast epithelial cell type with stem cell phenotypes after successive SV40 large T-antigen transfection, X-ray irradiation and ectopic expression of HER2/C-erbB2/neu. Recently, we found that M13SV1R2 cells became non-tumorigenic after growing in a growth factor/hormone-deprived medium (R2d cells).</p> <p>Results</p> <p>In this study, we developed M13SV1R2N1 under the same growth factor/hormone-deprived condition (R2N1d cells). This provides an opportunity to analyze HER2 effect on gene expression associated with tumorigenesis by comparative study of R2d and R2N1d cells with homogeneous genetic background except HER2 expression. The results reveal distinct characters of R2N1d cells that can be ascribed to HER2: 1) development of fast-growing tumors; 2) high frequency of CD44⁺/CD24^-cells (~50% for R2N1d vs. ~10% for R2d); 3) enhanced expression of COX-2, HDAC6 mediated, respectively, by MAPK and PI3K/Akt pathways, and many genes associated with inflammation, metastasis, and angiogenesis. Furthermore, HER2 expression can be down regulated in non-adhering R2N1d cells. These cells showed longer latent period and lower rate of tumor development compared with adhering cells.</p> <p>Conclusions</p> <p>HER2 may induce breast cancer by increasing the frequency of tumor stem cells and upregulating the expression of COX-2 and HDAC6 that play pivotal roles in tumor progression.</p

An Ovariectomy-Induced Rabbit Osteoporotic Model: A New Perspective

Study DesignExperimental Animal Model.PurposeThe aim of our study was to validate a pure bilateral ovariectomy (OVX) female New Zealand white rabbit model of postmenopausal osteoporosis utilizing animal-sparing in vivo techniques for evaluating bone mineral density (BMD). We also sought to demonstrate that bilateral OVX in female New Zealand white rabbits can produce diminished BMD in the spinal column and simulate osteoporosis, without the need for adjuvant chemotherapeutic agents (i.e., no additional glucocorticosteroids or other drugs were used for stimulating accelerated BMD loss), which can be assessed by in vivo BMD testing.Overview of LiteratureMultiple animal models of postmenopausal osteoporosis have been described. Rat ovariectomy models have been successful, but are limited by rats' inability to achieve true skeletal maturity and a slight morphology that limits surgical instrumentation. Rabbit models have been described which do not have these limitations, but previous models have relied on adjunctive steroid therapy to achieve osteoporosis and have required animal sacrifice for bone mineral density assessment.MethodsThirty-six skeletally mature female rabbits underwent bilateral OVX. BMD was measured using dual-energy X-ray absorptiometry on the metaphysis of the proximal tibia and distal femur, at baseline and 17 weeks postoperatively.ResultsMean BMD values were significantly reduced by 21.9% (p<0.05) in the proximal tibia and 11.9% (p<0.001) in the distal femur at 17 weeks.ConclusionsThis study is the first to demonstrate a significant bone loss within four months of pure OVX in rabbits using animal-sparing validation techniques. We believe that this OVX model is safe, reproducible, and can be employed to longitudinally evaluate the effect of anti-osteoporosis therapeutics and surgical interventions

Lubricin Surface Modification Improves Tendon Gliding After Tendon Repair in a Canine Model In Vitro

Introduction: The role of friction as a source of adhesions has been recently investigated, with data suggesting that many strong repairs also have higher friction [1], and that this higher friction is associated with poorer results, at least in animal models [2]. Lubricin is a mucinous glycoprotein responsible for the boundary lubrication of articular cartilage [3,4]. Recent studies have identified lubricin on the surface of FDP tendon [5,6] suggesting that it may play a role in tendon lubrication. Tendon surface modification with gelatin and hyaluronic acid reduces the gliding resistance of both tendon graft and repaired tendon [7][8][9]. The purpose of this study was to investigate the effects of lubricin with or without hyaluronic acid (HA) on the gliding of repaired FDP tendon in a canine model in vitro. Materials and Methods: 32 flexor digitorum profundus (FDP) tendons from the 2nd -5th digits of forepaws from 4 adult mongrel dogs were used. The dogs were sacrificed for other IACUC approved projects. In each digit the proximal and middle phalanges, FDP tendon, flexor digitorum superficialis (FDS) tendon and FDS insertion, and proximal pulley were then harvested as a unit. The proximal interphalangeal joint was fixed in full extension. A complete laceration to the FDP tendon was made 6mm distal to the proximal pulley (analogous to the A2 pulley in humans) and repaired with a modified Pennington technique. After the gliding resistance of the repaired tendon was measured in vitro, the tendons were treated with one of four solutions (n=8 per group): Saline; 10% gelatin/1% HA/1% EDC (1-ethyl-3-(3-dimethylaminopropyl) carbdiimide hydrochloride) /1% NHS (Nhydroxysuccinimde) (cd-HA-gelatin); 10% gelatin/1% EDC/1% NHS + lubricin (cd-gelatin + lubricin); 10% gelatin/1% HA/1% EDC/1% NHS+ lubricin (cd-HA-gelatin + lubricin). Lubricin was purified from bovine synovial fluid [10]. After treatment, tendon gliding resistance was measured for 1000 cycles of simulated flexion/extension tendon motion. The average and peak gliding resistance over the flexion/extension cycle were calculated and compared to baseline. Treatment groups were compared using ANOVA. Following testing, the surface of the repaired tendon and its proximal pulley was also assessed qualitatively for surface smoothness by scanning electron microscopy. Results: The increase in average and peak gliding resistance in cd-HA-gelatin, cd-gelatin+lubricin, and cd-HA-gelatin+ lubricin tendons was significantly less than that of the saline control tendons after 1000 cycles (p&lt;0.05) Discussion: In this study, the cd-HA-gelatin, cd-gelatin+lubricin and cd-HAgelatin+lubricin all improved the gliding resistance of the repaired flexor tendon compared to the saline controls. The two lubricin treated groups had the lowest gliding resistance throughout testing. The cd-HA-gelatin+lubricin tendons were significantly lower than the tendons treated with cd-HA-gelatin alone. While not significant, there was clearly a trend for improved results with cd-gelatin+lubricin, as well. The addition of lubricin to a tendon surface pre-treated with cd-gelatin and HA significantly reduces gliding resistance and maintains a qualitatively smooth tendon and pulley surface after 1000 cycles of simulated flexion/extension tendon motion compared to the carbodiimide derivatized hyaluronic acid (cd-HA-gelatin) preparation alone. These findings may have important implications for the development of tissue engineered tendon surfaces to improve the results after tendon repair

Transverse Plane Tendon and Median Nerve Motion in the Carpal Tunnel: Ultrasound Comparison of Carpal Tunnel Syndrome Patients and Healthy Volunteers

The median nerve and flexor tendons are known to translate transversely in the carpal tunnel. The purpose of this study was to investigate these motions in differential finger motion using ultrasound, and to compare them in healthy people and carpal tunnel syndrome patients.Transverse ultrasounds clips were taken during fist, index finger, middle finger and thumb flexion in 29 healthy normal subjects and 29 CTS patients. Displacement in palmar-dorsal and radial-ulnar direction was calculated using Analyze software. Additionally, the distance between the median nerve and the tendons was calculated.We found a changed motion pattern of the median nerve in middle finger, index finger and thumb motion between normal subjects and CTS patients (p<0.05). Also, we found a changed motion direction in CTS patients of the FDS III tendon in fist and middle finger motion, and of the FDS II and flexor pollicis longus tendon in index finger and thumb motion, respectively (p<0.05). The distance between the median nerve and the FDS II or FPL tendon is significantly greater in patients than in healthy volunteers for index finger and thumb motion, respectively (p<0.05).Our results suggest a changed motion pattern of the median nerve and several tendons in carpal tunnel syndrome patients compared to normal subjects. Such motion patterns may be useful in distinguishing affected from unaffected individuals, and in studies of the pathomechanics of carpal tunnel syndrome

A Modified Sagittal Spine Postural Classification and Its Relationship to Deformities and Spinal Mobility in a Chinese Osteoporotic Population

BACKGROUND: Abnormal posture and spinal mobility have been demonstrated to cause functional impairment in the quality of life, especially in the postmenopausal osteoporotic population. Most of the literature studies focus on either thoracic kyphosis or lumbar lordosis, but not on the change of the entire spinal alignment. Very few articles reported the spinal alignment of Chinese people. The purpose of this study was threefold: to classify the spinal curvature based on the classification system defined by Satoh consisting of the entire spine alignment; to identify the change of trunk mobility; and to relate spinal curvature to balance disorder in a Chinese population. METHODOLOGY/PRINCIPAL FINDINGS: 450 osteoporotic volunteers were recruited for this study. Spinal range of motion and global curvature were evaluated noninvasively using the Spinal-Mouse® system and sagittal postural deformities were characterized. RESULTS: We found a new spine postural alignment consisting of an increased thoracic kyphosis and decreased lumbar lordosis which we classified as our modified round back. We did not find any of Satoh's type 5 classification in our population. Type 2 sagittal alignment was the most common spinal deformity (38.44%). In standing, thoracic kyphosis angles in types 2 (58.34°) and 3 (58.03°) were the largest and lumbar lordosis angles in types 4 (13.95°) and 5 (-8.61°) were the smallest. The range of flexion (ROF) and range of flexion-extension (ROFE) of types 2 and 3 were usually greater than types 4 and 5, with type 1 being the largest. CONCLUSIONS/SIGNIFICANCE: The present study classified and compared for the first time the mobility, curvature and balance in a Chinese population based on the entire spine alignment and found types 4 and 5 to present the worst balance and mobility. This study included a new spine postural alignment classification that should be considered in future population studies