An implantable transducer for measuring tension in an anterior cruciate ligament graft.

The goal of this study was to develop a new implantable transducer for measuring anterior cruciate ligament (ACL) graft tension postoperatively in patients who have undergone ACL reconstructive surgery. A unique approach was taken of integrating the transducer into a femoral fixation device. To devise a practical in vivo calibration protocol for the fixation device transducer (FDT), several hypotheses were investigated: (1) The use of a cable versus the actual graft as the means for applying load to the FDT during calibration has no significant effect on the accuracy of the FDT tension measurements; (2) the number of flexion angles at which the device is calibrated has no significant effect on the accuracy of the FDT measurements; (3) the friction between the graft and femoral tunnel has no significant effect on measurement accuracy. To provide data for testing these hypotheses, the FDT was first calibrated with both a cable and a graft over the full range of flexion. Then graft tension was measured simultaneously with both the FDT on the femoral side and load cells, which were connected to the graft on the tibial side, as five cadaver knees were loaded externally. Measurements were made with both standard and overdrilled tunnels. The error in the FDT tension measurements was the difference between the graft tension measured by the FDT and the load cells. Results of the statistical analyses showed that neither the means of applying the calibration load, the number of flexion angles used for calibration, nor the tunnel size had a significant effect on the accuracy of the FDT. Thus a cable may be used instead of the graft to transmit loads to the FDT during calibration, thus simplifying the procedure. Accurate calibration requires data from just three flexion angles of 0, 45, and 90 deg and a curve fit to obtain a calibration curve over a continuous range of flexion within the limits of this angle group. Since friction did not adversely affect the measurement accuracy of the FDT, the femoral tunnel can be drilled to match the diameter of the graft and does not need to be overdrilled. Following these procedures, the error in measuring graft tension with the FDT averages less than 10 percent relative to a full-scale load of 257 N.     

A Study in Neo‐conservative Populism: Richard Trudgen's Why Warriors Lie Down and Die

First appearing in 2000, and with 20,000 copies sold as it entered its sixth printing in 2004, Richard Trudgen's Why Warriors Lie down and Die is a minor publishing phenomenon. Although scholarly forums have generally ignored the book, Christian media outlets, the popular press and neo‐conservative political activists have enthusiastically received and promoted it. An examination of the merits of Why Warriors Lie down and Die suggests that its popularity is only partly explained by original observations or insights on the part of the author. The most important explanation, and implication, of the book's remarkable take‐up lies in the opportune way in which it corresponds with now ascendant neo‐conservative political perspectives on indigenous policy.     

Latitudinal variation in population structure of wintering Pacific Black Brant

ABSTRACT.   Latitudinal variation in population structure during the winter has been reported in many migratory birds, but has been documented in few species of waterfowl. Variation in environmental and social conditions at wintering sites can potentially influence the population dynamics of differential migrants. We examined latitudinal variation in sex and age classes of wintering Pacific Black Brant ( Branta bernicla nigricans ). Brant are distributed along a wide latitudinal gradient from Alaska to Mexico during the winter. Accordingly, migration distances for brant using different wintering locations are highly variable and winter settlement patterns are likely associated with a spatially variable food resource. We used resightings of brant banded in southwestern Alaska to examine sex and age ratios of birds wintering at Boundary Bay in British Columbia, and at San Quintin Bay, Ojo de Liebre Lagoon, and San Ignacio Lagoon in Baja California from 1998 to 2000. Sex ratios were similar among wintering locations for adults and were consistent with the mating strategy of geese. The distribution of juveniles varied among wintering areas, with greater proportions of juveniles observed at northern (San Quintin Bay and Ojo de Liebre Lagoon) than at southern (San Ignacio Lagoon) locations in Baja California. We suggest that age-related variation in the winter distribution of Pacific Black Brant is mediated by variation in productivity among individuals at different wintering locations and by social interactions among wintering family groups.     

Activity of crystalline turkey egg white lysozyme.

Hexagonal crystals of turkey egg white lysozyme have been examined for activity in order to evaluate their potential for use in time-resolved X-ray crystallographic experiments. Substrates used in this study were hexa-N-acetylglucosamine (hexa-GlcNAc) and a modified analogue of hexa-GlcNAc where the terminal sugar ring was opened by reduction with tritiated sodium borohydride. This gave a labeled beta-N-acetylglucosaminitol unit at the sixth position of the sugar chain and allowed easy quantitation of enzymatic cleavage on TLC plates. Using these substrates, it has been shown that turkey egg white lysozyme is enzymatically active in the crystal. Enzyme dispersed in the buffer surrounding the crystal does not show detectable activity under conditions relevant to an X-ray experiment. Unmodified hexa-GlcNAc is hydrolyzed into di-, tri-, and tetrasaccharides in the crystal. This cleavage pattern is different from that obtained with hen egg white lysozyme in solution and likely causes of the differences are discussed. The reduced radiolabeled oligosaccharide has a unique cleavage pattern with trisaccharides as the products. The specific activity of the enzyme with the radiolabelled analogue was 9.8 (+/- 1.0) x 10(-7) mmol/min/mg protein at 22 degrees C in the crystal.     

Targeting and fusion in vesicular transport

Vesicular transport of proteins and lipids between distinct subcellular compartments is directly responsible for generating and maintaining the structure of the organelles of the secretory and endocytic pathways in eukaryotic cells. Rapid advances in a variety of experimental systems have resulted in the identification of molecules involved in late steps of the transport process. This article presents a general paradigm for vesicular fusion and reviews the available experimental evidence.     

Hemodynamic effects of anti-G suit inflation in a 1-G environment

This study evaluated effects of various anti-G inflation pressures on cardiac volumes and the relationship of these volume changes to mean arterial pressure changes. Ventricular volumes were calculated using two-dimensional echocardiography. An anti-G suit was inflated to 2, 4, and 6 psi in the standing and supine positions for 10 male subjects. In the supine position, mean arterial pressure increased from base line for all three inflation pressures (P = 0.05). The end-diastolic volume increased after 2-psi inflation (P = 0.03). Cardiac output or stroke volume did not change. After standing, mean arterial pressure (P = 0.002), end-diastolic volume (P = 0.002), and stroke volume (P = 0.05) fell after suit deflation. Peripheral vascular resistance fell in the 2- and 4-psi inflation profiles. In the standing protocol, mean arterial pressure, end-diastolic volume, stroke volume, and cardiac output rose with all three inflation pressures (P less than 0.05). After reclining, heart rate increased (P = 0.02) and mean arterial pressure fell (P less than 0.05) in the 4- and 6-psi inflation profiles after suit deflation. Increases in mean arterial pressure are caused by increases in cardiac preload and cardiac output after inflation of the anti-G suit while subjects were standing. Increased cardiac preload was not consistently seen after inflation while subjects were supine. Changes in end-diastolic volume and mean arterial pressure were dependent on the pressure used to inflate the anti-G suit.