Wrist pressure and angulation during keyboarding: Comparison between two common wrist supports.

BACKGROUND: Wrist pressure and angulation while working at a computer workstation have been associated with cumulative trauma disorders (CTDs) like carpal tunnel syndrome (CTS). OBJECTIVE: This quantitative, comparative study analyzed wrist pressure and angulation between two common wrist supports while typing at a standardized computer workstation. METHODS: A convenience sample of healthy young adults completed a five-minute typing task at a standardized workstation with no wrist support, with the ErgoBeads™ wrist support, and with an Elzo™ (memory foam) wrist support. Pressure mapping (Tekscan™)) and goniometry were used as quantitative measures to examine wrist pressure and wrist angulation during the typing task; descriptive and inferential statistics were performed to compare wrist angulation and wrist pressure between two supports. RESULTS: For the sample (n = 54), both wrist supports demonstrated a significant (p < 0.001) reduction in wrist extension as well as pressure compared to typing at the workstation with no support. There was no statistically significant difference in peak or mean pressure between the ErgoBeads™ and Elzo™ wrist supports (p = 0.99). Significant difference was identified ((p < 0.001) for wrist angle as participants exhibited less wrist extension using the ErgoBeads™ (x¯=12.56∘; SD = 3.32°) support as compared to the Elzo™ (x¯=19.25∘; SD = 3.77°) support. CONCLUSIONS: The results suggest that the ErgoBeads™ and Elzo™ memory foam wrist supports are effective for reducing pressure between the wrist and work surface while the ErgoBeads™ support may promote a more neutral angle of the wrist while typing.

Effects of actin-myosin kinetics on the calcium sensitivity of regulated thin filaments.

Activation of thin filaments in striated muscle occurs when tropomyosin exposes myosin binding sites on actin either through calcium-troponin (Ca-Tn) binding or by actin-myosin (A-M) strong binding. However, the extent to which these binding events contributes to thin filament activation remains unclear. Here we propose a simple analytical model in which strong A-M binding and Ca-Tn binding independently activates the rate of A-M weak-to-strong binding. The model predicts how the level of activation varies with pCa as well as A-M attachment, N·k(att), and detachment, k(det), kinetics. To test the model, we use an in vitro motility assay to measure the myosin-based sliding velocities of thin filaments at different pCa, N·k(att), and k(det) values. We observe that the combined effects of varying pCa, N·k(att), and k(det) are accurately fit by the analytical model. The model and supporting data imply that changes in attachment and detachment kinetics predictably affect the calcium sensitivity of striated muscle mechanics, providing a novel A-M kinetic-based interpretation for perturbations (e.g. disease-related mutations) that alter calcium sensitivity.

Characterization of tightly associated smooth muscle myosin-myosin light-chain kinase-calmodulin complexes.

A current popular model to explain phosphorylation of smooth muscle myosin (SMM) by myosin light-chain kinase (MLCK) proposes that MLCK is bound tightly to actin but weakly to SMM. We found that MLCK and calmodulin (CaM) co-purify with unphosphorylated SMM from chicken gizzard, suggesting that they are tightly bound. Although the MLCK:SMM molar ratio in SMM preparations was well below stoichiometric (1:73+/-9), the ratio was approximately 23-37% of that in gizzard tissue. Fifteen to 30% of MLCK was associated with CaM at approximately 1 nM free [Ca(2+)]. There were two MLCK pools that bound unphosphorylated SMM with K(d) approximately 10 and 0.2 microM and phosphorylated SMM with K(d) approximately 20 and 0.2 microM. Using an in vitro motility assay to measure actin sliding velocities, we showed that the co-purifying MLCK-CaM was activated by Ca(2+) and phosphorylation of SMM occurred at a pCa(50) of 6.1 and at a Hill coefficient of 0.9. Similar properties were observed from reconstituted MLCK-CaM-SMM. Using motility assays, co-sedimentation assays, and on-coverslip enzyme-linked immunosorbent assays to quantify proteins on the motility assay coverslip, we provide strong evidence that most of the MLCK is bound directly to SMM through the telokin domain and some may also be bound to both SMM and to co-purifying actin through the N-terminal actin-binding domain. These results suggest that this MLCK may play a role in the initiation of contraction.

In vitro study of bacterial adherence to processed dura mater, processed pericardium, pericardium in saline, and human sclera.

PURPOSE: To study bacterial adherence to processed dura mater, processed pericardium, pericardium in saline, and human sclera and the difference in bacterial adherence to these tissues. SETTING: Research Laboratory, Loyola University Medical Center, Maywood, Illinois, USA. METHODS: Specimens of processed dura mater, processed human pericardium, pericardium in saline, and human sclera (N = 32) were exposed to Staphylococcus epidermidis (concentration 3 x 10(8)) for 10, 20, 40, and 60 minutes, washed for 5 seconds, fixed, and processed for scanning electron microscopy (SEM). Each bacterial count represents an average of 50 random SEM fields at x5,000 magnification. After SEM, selected specimens were processed for transmission electron microscopy. RESULTS: The mean number of bacteria/mm(2) +/- SD adhering to the tissues at 10, 20, 40, and 60 minutes, respectively, were dura mater, 107,833 +/- 65,410, 104,500 +/- 13,471, 96,067 +/- 113,884, and 204,267 +/- 153,697; processed pericardium, 131,550 +/- 86,194, 100,900 +/- 20,031, 144,683 +/- 51,730, and 176,933 +/- 111,818; pericardium in saline, 7,925 +/- 1,520, 33,933 +/- 32,085, 1,217 +/- 1,287, and 21,550 +/- 16,436; and human sclera, 4,850 +/- 2,121, 23,700 +/- 17,961, 5,150 +/- 1,273, and 8,175 +/- 8,450. A 2-way analysis of variance showed significant differences among groups (P =.001) and no significant difference in sample time (P =.929). CONCLUSIONS: Bacterial adherence to processed dura mater, processed pericardium, pericardium in saline, and human sclera should be considered when these materials are used clinically during ophthalmic surgery and other surgical specialties. Adequate broad-spectrum antibiotic coverage is needed to prevent infection and subsequent complications in patients.