Methanethiosulfonate derivatives inhibit current through the ryanodine receptor/channel

To identify regions of the ryanodine receptor (RyR) important for ion conduction we modified the channel with sulfhydryl-reacting compounds. After addition of methanethiosulfonate (MTS) compounds channel conductance was decreased while other channel properties, including channel regulation by ATP, caffeine, or Ca, were unaffected. The site of action was accessible to the MTS compounds from the cytoplasmic, but not the luminal, side of the channel. In addition, the hydrophilic MTS compounds were only effective when the channel was open, suggesting that the compounds covalently modify the channel from within the water-filled ion conducting pathway. The decrease in channel current amplitude occurred in a step-wise fashion and was irreversible and cumulative over time, eventually leading to the complete block of channel current. However, the time required for each consecutive modification during continuous exposure to the MTS compounds increased, suggesting that successive modification by the MTS compounds is not independent. These results are consistent with the hypothesis that the channel forms a wide vestibule on the cytoplasmic side and contains a much smaller opening on the luminal side. Furthermore, our results indicate that the MTS compounds can serve as functional markers for specific residues of the RyR to be identified in molecular studies.     

Visualization of C7-T1 on portable lateral cervical spine radiographs using a lead-lined acrylic filter

OBJECTIVE: To determine whether lead-lined acrylic cervical filters can improve the quality of portable lateral cervical spine (c-spine) radiographs for trauma patients. METHODS: Twenty trauma patients who required portable c-spine x-rays had these taken with a lead filter attached to the collimator of the portable x-ray machine to improve penetration and visualization of lower cervical structures without overpenetrating upper cervical structures. The radiographs of these patients were compared with the first portable c-spine radiographs without filters for 20 controls matched for gender and injury severity. The comparison of radiographs was done by an experienced emergency physician and a neuroradiologist blinded to whether the filter was used. RESULTS: The two groups were similar for demographic and clinical characteristics. There was a significant improvement in the ability to visualize the C7-T1 level for the filter group compared with the control group (65% vs 30%, p < 0.05). Agreement between the physicians was excellent (kappa = 0.79, 95% CI = 0.60-0.99). CONCLUSIONS: Lead-lined acrylic filters improve the ability to visualize the lower c-spine in trauma patients.     

Biorobotic approaches to the study of motor systems

Biorobotics is a promising new area of research at the interface between biology and robotics. Robots can either be used as physical models of biological systems or be directly inspired by biological studies. A great deal of progress has recently been made in biorobotic studies of locomotion, orientation, and vertebrate arm control.     

The effects of surface-active materials on the oscillations of a liquid jet

The oscillatory motion and stability of a liquid jet are examined in the context of a theory which accounts for local variations of interfacial tension induced by expansion and contraction of an interface containing adsorbed molecules. The presence of a soluble surfactant alters the oscillation frequency as well as growth and decay rates via damping in a boundary layer. It is found that the frequency alteration is a substantial effect when considered in the context of measurements made with oscillating jets, i.e. the dynamic surface tension. When viscous effects are large the presence of surfactant may introduce oscillatory character in place of the aperiodic temporal behavior of pure liquids.     

Great Lakes Beginning-of-Month Water Levels and Monthly Rates of Change of Storage

Time series of beginning-of-month water levels and rates of change of lake storage were determined for each of the Great Lakes and Lake St. Clair for 1941-1975 period. The Thiessen polygon procedure was used to compute the beginning-of-month levels because it provides more representative over-all lake levels than straight averaging and requires minimum subjectivity. The effect of crustal movement on the rate of change of lake storage was investigated and found to be negligible. A gage density analysis showed good agreement between various size gage networks with the maximum deviation between networks decreasing with increasing gage density. Thiessen polygon weighting factors are presented for the current gage networks to enable future extension of the time series.     

Relative Accuracy of Connecting Channel Discharge Data with Application to Great Lakes Studies

The flows in the Great Lakes connecting channels are a major component in the water balance of the Great Lakes Basin. The increased emphasis on Great Lakes water quality and quantity requires an assessment of the accuracy of both measured and computed connecting channel discharge data. In this study, the standard error of typical discharge measurements was found to be approximately 3 to 5 percent, depending upon the number of panels used in the cross section. Mesurement sets were found to have a practical limit of about 25 measurements. The standard error of a set of measurements was found to be on the order of 1 percent. The procedure used to compute the published flows of the Niagara River was found to have an apparent bias of about 2 percent on the high side. It is recommended that the published Niagara River flows be adjusted prior to use in detailed water balance studies.     

Effects of injurious compression on matrix turnover around individual cells in calf articular cartilage explants

The effects of mechanical injury on the metabolism of cartilage matrix are of interest for understanding the pathogenesis of osteoarthrosis and the development of strategies for cartilage repair. The purpose of the present study was to examine the effects of injury on matrix turnover in a calf articular cartilage explant system for which the effects of mechanical loading on cell activity and the cell-mediated pathways of matrix metabolism are already well characterized. New methods of quantitative autoradiography were used in combination with established biochemical and biomechanical techniques for the analysis of cell and matrix responses to acute mechanical injury, with particular attention to the processes of localized matrix turnover in the cell-associated matrices of individual chondrocytes. Matrix deposition and turnover around cells in control explants was spatially dependent, with the highest rates of proteoglycan deposition and turnover and the lowest rates of collagen deposition (as indicated by [3H]proline autoradiography) occurring in the pericellular matrix. Injurious compression was associated with (a) an abrupt decrease in the tensile load-carrying capacity of the collagen matrix, apparently associated with mechanical failure of the tissue, (b) a considerable but subtotal decrease in cell viability, marked by the emergence of an apparently inactive cell population interspersed within catabolically active but abnormally large cells, and (c) sustained, elevated rates of proteoglycan turnover, particularly in the cell-associated matrices of apparently viable cells, which involved the increased release of aggregating species in addition to a spectrum of degradation fragments that were also in controls. These results may represent an in vitro model for the responses of chondrocytes and the cartilage extracellular matrix to mechanical injury.     

PLUGE method of adjusting picture monitors in television studios

The PLUGE method is described, and its advantages are given. Five sets of reference conditions for setting up picture monitors are presented. Further, it is shown that the required PLUGE black level is dependent upon the value of base luminance.