Loss of phylogenetic information in chorion gene families of Bombyx mori gene conversion

The silkmoth chorion has provided a stimulating model for the study of evolution and developmental regulation of gene families. Previous attempts at inferring relationships among chorion sequences have been based on pairwise comparisons of overall similarity, a potentially problematic approach. To remedy this, we identified the alignable regions of low sequence variability and then analyzed this restricted database by parsimony and neighbor-joining methods. At the deepest level, the chorion sequence tree is split into two branches, called "alpha" and "beta." Within each branch, early- and late-expressing genes each constitute monophyletic groups, while the situation with middle-expressing genes remains uncertain. The HcB gene family appears to be the most basal beta-branch group, but this conclusion is qualified because the effect of gene conversion on branching order is unknown. Previous studies by Eickbush and colleagues have strongly suggested that ErA, HcA, and HcB families undergo gene conversion within a gene family, whereas the ErB family does not. The occurrence of conversion correlates with a particular tree structure; namely, branch lengths are much greater at the base of the family than at higher internodes and terminal branches. These observations raise the possibility that chorion gene families are defined by gene conversion events (reticulate evolution) rather than by descent with modification (synapomorphy).      

A wearable system to assess risk for anterior cruciate ligament injury during jump landing: measurements of temporal events, jump height, and sagittal plane kinematics

The incidence of anterior cruciate ligament (ACL) injury remains high, and there is a need for simple, cost effective methods to identify athletes at a higher risk for ACL injury. Wearable measurement systems offer potential methods to assess the risk of ACL injury during jumping tasks. The objective of this study was to assess the capacity of a wearable inertial-based system to evaluate ACL injury risk during jumping tasks. The system accuracy for measuring temporal events (initial contact, toe-off), jump height, and sagittal plane angles (knee, trunk) was assessed by comparing results obtained with the wearable system to simultaneous measurements obtained with a marker-based optoelectronic reference system. Thirty-eight healthy participants (20 male and 18 female) performed drop jumps with bilateral and unilateral support landing. The mean differences between the temporal events obtained with both systems were below 5 ms, and the precisions were below 24 ms. The mean jump heights measured with both systems differed by less than 1 mm, and the associations (Pearson correlation coefficients) were above 0.9. For the discrete angle parameters, there was an average association of 0.91 and precision of 3.5° for the knee flexion angle and an association of 0.77 and precision of 5.5° for the trunk lean. The results based on the receiver-operating characteristic (ROC) also demonstrated that the proposed wearable system could identify movements at higher risk for ACL injury. The area under the ROC plots was between 0.89 and 0.99 for the knee flexion angle and between 0.83 and 0.95 for the trunk lean. The wearable system demonstrated good concurrent validity with marker-based measurements and good discriminative performance in terms of the known risk factors for ACL injury. This study suggests that a wearable system could be a simple cost-effective tool for conducting risk screening or for providing focused feedback.     

Plasma proteins present in osteoarthritic synovial fluid can stimulate cytokine production via Toll-like receptor 4

Introduction

Osteoarthritis (OA) is a degenerative disease characterized by cartilage breakdown in the synovial joints. The presence of low-grade inflammation in OA joints is receiving increasing attention, with synovitis shown to be present even in the early stages of the disease. How the synovial inflammation arises is unclear, but proteins in the synovial fluid of affected joints could conceivably contribute. We therefore surveyed the proteins present in OA synovial fluid and assessed their immunostimulatory properties.

Methods

We used mass spectrometry to survey the proteins present in the synovial fluid of patients with knee OA. We used a multiplex bead-based immunoassay to measure levels of inflammatory cytokines in serum and synovial fluid from patients with knee OA and from patients with rheumatoid arthritis (RA), as well as in sera from healthy individuals. Significant differences in cytokine levels between groups were determined by significance analysis of microarrays, and relations were determined by unsupervised hierarchic clustering. To assess the immunostimulatory properties of a subset of the identified proteins, we tested the proteins' ability to induce the production of inflammatory cytokines by macrophages. For proteins found to be stimulatory, the macrophage stimulation assays were repeated by using Toll-like receptor 4 (TLR4)-deficient macrophages.

Results

We identified 108 proteins in OA synovial fluid, including plasma proteins, serine protease inhibitors, proteins indicative of cartilage turnover, and proteins involved in inflammation and immunity. Multiplex cytokine analysis revealed that levels of several inflammatory cytokines were significantly higher in OA sera than in normal sera, and levels of inflammatory cytokines in synovial fluid and serum were, as expected, higher in RA samples than in OA samples. As much as 36% of the proteins identified in OA synovial fluid were plasma proteins. Testing a subset of these plasma proteins in macrophage stimulation assays, we found that Gc-globulin, α₁-microglobulin, and α₂-macroglobulin can signal via TLR4 to induce macrophage production of inflammatory cytokines implicated in OA.

Conclusions

Our findings suggest that plasma proteins present in OA synovial fluid, whether through exudation from plasma or production by synovial tissues, could contribute to low-grade inflammation in OA by functioning as so-called damage-associated molecular patterns in the synovial joint.     

Study on effect of graded facetectomy on change in lumbar motion segment torsional flexibility using three-dimensional continuum contact representation for facet joints

Facet joints provide rigidity to the lumbar motion segment and thus protect the disk, particularly against torsional injury. A surgical procedure that fully or partially removes the facet joints (facetectomy) will decrease the mechanical stiffness of the motion segment, and potentially place the disk at risk of injury. Analytical models can be used to understand the effect of facet joints on motion segment stability. Using a facet joint model that represents the contact area as contact between two surfaces rather than as point contact, it was concluded that a substantial sudden change in rotational motion, due to applied torsion moment, was observed after 75 percent of any one of the facet joints was removed. Applied torsional moment loading produced coupled extension motion in the intact motion segment. This coupled motion also experienced a large change following complete unilateral facetectomy. Clinically, the present study showed that surgical intervention in the form of unilateral or bilateral total facetectomy might require fusion to reduce the primary torsion motion.     

Salivary alpha amylase and salivary cortisol response to fluid consumption in exercising athletes

The objective of the study was to examine salivary biomarker response to fluid consumption in exercising athletes. Exercise induces stress on the body and salivary alpha amylase (sAA) and salivary cortisol are useful biomarkers for activity in the sympathoadrenal medullary system and the hypothalamic pituitary adrenal axis which are involved in the stress response. Fifteen college students were given 150 ml and 500 ml of water on different days and blinded to fluid condition. The exercise protocol was identical for both fluid conditions using absolute exercise intensities ranging from moderate to high. Saliva was collected prior to exercise, post moderate and post high intensities and analyzed by Salimetrics assays. Exercise was significant for sAA with values different between pre-exercise (85 ± 10 U · ml⁻¹) and high intensity (284 ± 30 U · ml⁻¹) as well as between moderate intensity (204 ± 32 U · ml⁻¹) and high intensity. There was no difference in sAA values between fluid conditions at either intensity. Exercise intensity and fluid condition were each significant for cortisol. Cortisol values were different between pre-exercise (0.30 ± 0.03 ug · dL⁻¹) and high intensity (0.45 ± 0.05 ug · dL⁻¹) as well as between moderate intensity (0.33 ± 0.04 ug · dL⁻¹) and high intensity. Moderate exercise intensity cortisol was lower in the 500 ml condition (0.33 ± 0.03 ug · dL⁻¹) compared with the 150 ml condition (0.38 ± 0.03 ug · dL⁻¹). This altered physiological response due to fluid consumption could influence sport performance and should be considered. In addition, future sport and exercise studies should control for fluid consumption.     

Posturographic analysis through markerless motion capture without ground reaction forces measurement

The ability of the central nervous system to control posture and balance has been used with increasing frequency for the diagnosis and/or treatment evaluation of various neuromuscular diseases. Typically this analysis (Posturographic Analysis) is based on tracking the motion of the center of mass (COM) during quiet standing, however direct measurement of the COM has been commonly approximated using the movement of the center of pressure (COP). The purpose of this study was to apply and validate a new method to track the COM (center of mass) and COP (center of pressure) from a visual hull measured using a markerless motion capture (MMC) method. The method was tested by comparing the calculation of the COP from direct measurements of the COP. The deviations between the methods, below 2 mm, were small relative to the average range of movement guaranteeing a satisfactory signal to noise ratio. This new method requires only kinematic data through MMC method and without the need of a force plate can identify the influence of individual body segments to motion of the COM.     

Peripheral hyaline blebs (podosomes) of macrophages

The plasmalemma and hyaline ectoplasm together constitute the sensory and motor organ of macrophages. The purpose of this study was to isolate this cell fraction in order to analyze it biochemically and functionally. Brief sonification of warmed rabbit lung macrophages caused release of heterodisperse hyaline blebs and filopodia, which were easily collected by differential centrifugation. Viewed in the electron microscope, these structures consisted of membrane-bounded sacs principally containing actin filaments. Some contained secondary lysosomes. They were enriched threefold over whole cell homogenates in specific adenylate cyclase activity and in trichloroacetic-acid-precipitable (125)I when derived from cells labeled with 125(I) by means of a lactoperoxidase-catalyzed reaction. These markers were found to have identical isopycnic densitites when macrophage homogenates were subjected to sedimentation in a focusing sucrose density gradient system, and these markers had densities distinct from those of other cytoplasmic organelles. These markers were therefore assumed to be associated with macrophage plasma membranes. The specific β- glucuronidase activity of the bleb fraction was similar to that of homogenates, but the blebs had considerably lower specific succinic dehydrogenase activity and RNA content, and DNA was undetectable. Electrophoresis of blebs solubilized in sodium dodecyl sulfate on polyacrylamide gels revealed polypeptides co-migrating with macrophage actin-binding protein, myosin, and actin; blebs also had EDTA-activated adenosine triphosphatase activity characteristic of myosin. The concentrations of actin-binding protein and myosin were higher in blebs than in cells or cytoplasmic extracts, whereas actin concentrations were similar (relative to extracts) or only slightly greater (than in cells). Blebs and intact cells had high lactate dehydrogenase activities in the presence but not the absence of Triton X-100. Blebs and cells oxidased 1-[(14)C]glucose, and the rate of glucose oxidation was increased substantially in the presence of latex beads. We conclude that intact sacs of plasmalemma encasing contractile proteins and cytoplasmic enzymes can be isolated from macrophages. They are enriched in myosin and actin-binding protein, indicating that the contractile apparatus is regulated in the cell periphery. These structures have the capacity to respond to environmental signals. We suggest the name "podosomes" for them because of their resemblance to macrophage pseudopodia. We propose that podosome formation results from rapid dissolution of the cortical gel when the membrane is in an actively extended configuration.     

Relationship between moments at the L5/S1 level, hip and knee joint when lifting

A study was performed to determine the influence of load magnitude on the self selected technique of lifting. Specifically, it was hypothesized that with heavier weights a tendency would occur to lift more with the back and less with the legs. Flexion-extension moments at the L5/S1 level, hip and knee joints were calculated for subjects when lifting boxes weighing from 50 to 250 N. Lifts were performed using a freestyle technique at normal speed. The moment profiles (moment plotted vs time) were analyzed kinematically and as a function of the weight lifted. The kinematics of the lift changed as the weight increased. The moment at the L5/S1 level increased with increasing weight, however, the corresponding knee moment decreased. Thus, an inverse relationship was found between the moment at the L5/S1 level and the knee joint moment. An increase in weight lifted was also associated with an increase in the angular velocity at the knee while lifting. Apparently with heavier weights there is a tendency to extend the knees earlier during the lift than with lighter weights, confirming our hypothesis. This explains the reduced knee moment. Our findings lead to the hypothesis that quadriceps muscle strength limits the subjects' ability to lift with their knees flexed.     

The influence of deceleration forces on ACL strain during single-leg landing: a simulation study

Anterior cruciate ligament (ACL) injury commonly occurs during single limb landing or stopping from a run, yet the conditions that influence ACL strain are not well understood. The purpose of this study was to develop, test and apply a 3D specimen-specific dynamic simulation model of the knee designed to evaluate the influence of deceleration forces during running to a stop (single-leg landing) on ACL strain. This work tested the conceptual development of the model by simulating a physical experiment that provided direct measurements of ACL strain during vertical impact loading (peak value 1294N) with the leg near full extension. The properties of the soft tissue structures were estimated by simulating previous experiments described in the literature. A key element of the model was obtaining precise anatomy from segmented MR images of the soft tissue structures and articular geometry for the tibiofemoral and patellofemoral joints of the knee used in the cadaver experiment. The model predictions were correlated (Pearson correlation coefficient 0.889) to the temporal and amplitude characteristic of the experimental strains. The simulation model was then used to test the balance between ACL strain produced by quadriceps contraction and the reductions in ACL strain associated with the posterior braking force. When posterior forces that replicated in vivo conditions were applied, the peak ACL strain was reduced. These results suggest that the typical deceleration force that occurs during running to a single limb landing can substantially reduce the strain in the ACL relative to conditions associated with an isolated single limb landing from a vertical jump.