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991.
PF Williams Y Iwasaki K Ishihara GL Powell JA Gilbert N Nakabayashi M LaBerge 《Canadian Metallurgical Quarterly》1997,211(5):359-368
Wear particle production in load-bearing orthopaedic implants is one of the major factors currently limiting the service life of the implant. Most of the research carried out to date in attempting to solve this problem has used the approach of finding more wear-resistant biocompatible material pairs. In contrast, other researchers have attempted to reduce wear by encouraging elastohydrodynamic film formation through the use of elastomeric bearing surfaces. Unfortunately, these elastomeric bearing surfaces have poor tribological properties when a fluid film is not present. Boundary lubrication of an elastomeric orthopaedic bearing may alleviate some of these difficulties. The purpose of this research was to fabricate and characterize an elastomeric material that had a surface capable of specifically adsorbing a naturally occurring boundary lubricant. Dipalmitoyl phosphatidylcholine (DPPC) has been previously shown to be able to act as a boundary lubricant at stresses that occur in human load-bearing joints such as the hip and knee; therefore, DPPC was chosen for use in this study. It was expected that in an aqueous liposome suspension the static coefficient of friction microseconds of such a material would be lower, and increase less quickly over time, than a similar material without an ability to adsorb specifically DPPC when articulated against a polished chrome steel ball bearing. The lipid-adsorbing elastomer did not possess the desired tribological properties. This result was attributed to the polymer adsorbing the DPPC in the liposome phase and not in the bilayer phase, and interaction among the polymeric surface, DPPC and water. This approach to lubricating orthopaedic bearings was shown to have some merit, but a great deal of work needs to be done before such an approach can be used on a clinically available material. 相似文献
992.
DF Lynch W Hassen MA Clements PF Schellhammer GL Wright 《Canadian Metallurgical Quarterly》1997,32(3):214-220
The purpose of this study was to describe the longitudinal development of running economy [defined as the oxygen uptake (VO2) at a submaximal running speed] in males and females from teenage to young adult age using data from the Amsterdam Growth and Health Study. Submaximal VO2 (in ml.kg-1.min-1) was measured in 84 males and 98 females while they ran on a treadmill at a constant speed of 8 km.h-1 for 6 min at three different treadmill slopes (0%, 2.5% and 5%). This test was carried out six times, on the same subjects at the ages of 13, 14, 15, 16, 21, and 27 years. The longitudinal development of running economy in males and females was analysed using a two-way analysis of variance for repeated measurements. At all three slopes, a significant decrease in VO2 with increasing age was found for both males and females, implying a significant increase in running economy for both sexes. Males showed significantly higher VO2 values than females at all ages measured and for all three slopes, suggesting that females have a significantly higher running economy than males. In order to make a better comparison of the VO2 of individuals of different sizes, allometric models were used; power function ratios were constructed in which body mass was expressed to an exponential power. Following this analysis the difference in submaximal VO2 and running economy between males and females appeared even larger. 相似文献
993.
994.
LI Horváth PF Knowles P Kovachev JB Findlay D Marsh 《Canadian Metallurgical Quarterly》1997,73(5):2588-2594
Lipid-peptide interactions with the 27-residue peptide of sequence KLEALYILMVLGFFGFFTLGIMLSYIR reconstituted as beta-sheet assemblies in dimyristoylphosphatidylcholine bilayers have been studied by electron spin resonance (ESR) spectroscopy with spin-labeled lipids. The peptide corresponds to residues 42-68 of the IsK voltage-gated K+ channel protein and contains the single putative transmembrane span of this protein. Lipid-peptide interactions give rise to a second component in the ESR spectra of lipids spin-labeled on the 14C atom of the chain that corresponds to restriction of the lipid mobility by direct interaction with the peptide assemblies. From the dependence on the lipid/peptide ratio, the stoichiometry of lipid interaction is found to be about two phospholipids/peptide monomer. The sequence of selectivity for lipid association with the peptide assemblies is in the order phosphatidic acid > stearic acid = phosphatidylserine > phosphatidylglycerol = phosphatidylcholine. Comparison with previous data for a corresponding 26-residue mutant peptide with a single deletion of the apolar residue Leu2 (Horvath et al., 1995. Biochemistry 34:3893-3898), indicates a very similar mode of membrane incorporation for native and mutant peptides, but a strongly modified pattern and degree of specificity for the interaction with negatively charged lipids. The latter is interpreted in terms of the relative orientations of the charged amino acid side chains in the beta-sheet assemblies of the native and deletion-mutant peptides. 相似文献
995.
PF Austin G DeLeary YL Homsy L Persky JL Lockhart 《Canadian Metallurgical Quarterly》1997,158(5):1704-7; discussion 1707-8
PURPOSE: We investigated the long-term metabolic impact of gastrointestinal composite reservoirs. MATERIALS AND METHODS: Nine patients underwent construction of a gastroileal (7) or gastrocolonic (2) reservoir for continent urinary diversion. Four cases of metabolic acidosis were converted from a preexisting conduit and the other 5 patients had diversion for either preexisting metabolic acidosis or the short bowel syndrome. All were reconstructed using a medium sized gastric segment (8 x 4 cm.) from the greater curvature of the stomach. The anti-incontinence segment was constructed from a tapered and reimplanted ileal segment. All patients underwent preoperative and postoperative measurements of serum pH, serum electrolytes, and urinalysis. Serum gastrin was measured in all patients postoperatively. Followup from surgery ranged from 47 to 61 months (mean 54.4). RESULTS: All 9 patients demonstrated electrolyte neutrality in serum on long-term followup. Postoperative serum pH (mean 7.40) was significantly different (p < 0.01) from preoperative serum pH (mean 7.36) and serum bicarbonate was also significantly different (p < 0.01) preoperatively versus postoperatively (mean 22.3 versus 25.14). Urine pH values were not significantly different throughout the study. One patient with mildly acidic urinary pH (6.0 to 6.5) had ulcerative skin changes at the stoma site. Three patients had elevated serum gastrin levels on short-term followup but all patients had normal serum gastrin levels on long-term followup. One patient, with persistent alkaline urine, had urolithiasis and symptomatic urinary tract infections. CONCLUSIONS: Our results demonstrate that a composite urinary reservoir constructed using gastric and intestinal segments achieved serum electrolyte neutrality on long-term followup. These results indicate a long-term metabolic advantage over other intestinal reservoirs associated with hyperchloremic metabolic acidosis and may be beneficial in patients compromised by either preexisting metabolic acidosis or the short bowel syndrome. 相似文献
996.
KM Heaton JJ Sussman JE Gershenwald JE Lee DS Reintgen PF Mansfield MI Ross 《Canadian Metallurgical Quarterly》1998,5(4):322-328
PURPOSE: The aim of this project was to analyze and validate the diagnostic applications of Volumetric High Resolution CT in the study of focal or diffuse infiltrative lung disease compared with High Resolution CT. To date HRCT is the gold standard in the assessment of infiltrative lung diseases, but it shows some limitations such as artifacts due to both respiratory and cardiac motions, as well as the need for multiple breath-holds. MATERIAL AND METHODS: September, 1996, to September, 1997, anthropomorphic test phantoms and a group of 34 subjects (8 without lung disease and 26 with aspecific lung disease: TBC, BPCO, micronodular conditions, cardiogenic interstitial pulmonary edema) were submitted to both HRCT and VHRCT. VHRCT was carried out with a 3-mm slab thickness and the images were reconstructed with a 1-mm interval and processed with MIP and MinIP reconstructions. With both techniques we compared some physical parameters (slice sensitivity profile, noise, longitudinal resolution) and some radiographic findings (central and peripheral airways lumen, peripheral vessels, nodular and interstitial abnormalities, emphysema foci, focal areas of ground glass pattern and bronchiectasis). We calculated the radiation exposure dose of both HRCT and VHRCT, also testing a low-dose protocol. RESULTS: The analysis of physical parameters showed no major differences between HRCT and VHRCT regarding longitudinal resolution, while minimal advantages were found with HRCT for slice sensitivity profile and image noise. Radiographic analysis showed additional findings in 27% of patients with nodular disease using VHRCT-MIP in 8% of patients with emphysema and 25% of cases with focal areas of ground glass opacities, using VHRCT-MinIP. Relative to HRCT findings, VHRCT better depicted all patterns but subpleural nodules. The surface radiation dose was 2.8 times higher with VHRCT than HRCT. It is possible to halve radiation exposure using a low dose protocol (120 kV, 110-150 mA). CONCLUSIONS: Our study provides conclusive results concerning the use of VHRCT with standard technical parameters because this technique showed some advantages in the study of a wide range of diffuse or focal lung diseases. We suggest that this protocol be applied only in patients with mild forms of lung disease or in the cases of difficult interpretation, such as suspicious abnormal areas at HRCT, because its doses are higher. Out low-dose protocol is currently on trial but we expect promising results. 相似文献
997.
PF Meeus 《Canadian Metallurgical Quarterly》1998,143(16):451-452
998.
RA Karron PF Wright JE Crowe ML Clements-Mann J Thompson M Makhene R Casey BR Murphy 《Canadian Metallurgical Quarterly》1997,176(6):1428-1436
Two live-attenuated, cold-passaged (cp), temperature-sensitive (ts) candidate vaccines, designated cpts530/1009 and cpts248/955, were attenuated, genetically stable, and immunogenic in chimpanzees and were highly attenuated for human adults. In respiratory syncytial virus (RSV)-seropositive children, cpts530/1009 was more restricted in replication than cpts248/955. In seronegative children, 10(4) pfu of cpts248/955 was insufficiently attenuated, and a high titer of vaccine virus was shed (mean peak titer, 10(4.4) pfu/mL), whereas 10(4) pfu of cpts530/1009 was relatively attenuated and restricted in replication (mean peak titer, 10(2.0) pfu/mL). At a dose of 10(5) pfu, cpts530/1009 was immunogenic in seronegative children (geometric mean titer of RSV neutralizing antibodies, 1:724). Transmission of either vaccine to seronegative placebo recipients occurred at a frequency of 20%-25%. Of importance, vaccine viruses recovered from chimpanzees and humans were ts. In contrast to previous studies, this study indicates that live attenuated RSV vaccines that are immunogenic and phenotypically stable can be developed. Additional studies are being conducted to identify a live RSV vaccine that is slightly more attenuated and less transmissible than cpts530/1009. 相似文献
999.
A Lydon J McGinley T Cooke PF Duggan GD Shorten 《Canadian Metallurgical Quarterly》1998,81(4):522-525
We studied the morphology and distribution of nerve endings in the human triangular fibrocartilage complex using both silver staining and immunohistochemical staining using a protein specific to nerve fibres. Free nerve endings were found in the ulnar side of the triangular fibrocartilage complex, especially in the ulnar collateral ligament, meniscus homologue and the adjacent collagen fibre area of the peripheral part of the ulnar side of the articular disc. Meissner's and Krause's corpuscles were observed in the ulnar collateral ligament and meniscus homologue. The fact that free nerve endings were observed in the meniscus homologue and adjacent collagen fibre area of the peripheral part of the ulnar side of the articular disc suggests that this disc may be a source of wrist pain. The presence of nerve end bulbs in the triangular fibrocartilage complex also suggests a possible role for corpuscles as mechanoreceptors. 相似文献
1000.