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91.
Tung-Wu Lu Stephen J. G. Taylor John J. O'Connor Peter S. Walker 《Journal of biomechanics》1997,30(11-12)
Experiments were performed on two patients with custom-made instrumented massive proximal femoral prostheses implanted after tumour resection. In vivo axial forces transmitted along the prostheses were telemetered during level walking, single- and double-leg stance, and isometric exercises of the hip muscles. These activities varied the lever arms available to the external loads: minimum for double-leg stance and maximum for hip isometric exercises. Kinematic, force plate, EMG and telemetered force data were recorded simultaneously. The force magnification ration (FMR; the ratio of the telemetered axial force to the external force) was calculated. The FMRs ranged from 1.3 (during double-leg stance) to 29.8 (during abductors test), indicating that a major part of the axial force in the long bones is a response to muscle activity, the strength of which depends on the lever arms available to the external loads. From these results, it was shown that the bulk of the bending moment along limbs is transmitted by a combination of tensile forces in muscles and compressive forces in bones, so moments transmitted by the bones are smaller than the limb moments. It was concluded that appropriate simulation of muscle forces is important in experimental or theoretical studies of load transmission along bones. 相似文献
92.
Energy-dispersive X-ray analysis of the extracellular cadmium sulfide crystallites of Klebsiella aerogenes 总被引:4,自引:0,他引:4
Justin D. Holmes Peter R. Smith Richard Evans-Gowing David J. Richardson David A. Russell John R. Sodeau 《Archives of microbiology》1995,163(2):143-147
Klebsiella aerogenes forms electron-dense partieles on the cell surface in response to the presence of cadmium ions in the growth medium. These particles ranged from 20 to 200 nm in size, and quantitative energy dispersive X-ray analysis established that they comprise cadmium and sulfur in a 1:1 ratio. This observation leads to the conclusion that the particles are cadmium sulfide crystallites. A combination of atomic absorption spectroscopy, inductively coupled plasma mass spectrometry, and acid-labile sulfide analysis revealed that the total intracellular and bound extracellular cadmium:sulfur ratio is also 1:1, which suggests that the bulk of the cadmium is fixed as extracellular cadmium sulfide. The tolerance of K. acrogenes to cadmium ions and the formation of the cadmium sulfide crystallites were dependent on the buffer composition of the growth medium. The addition of cadmium ions to phosphate-buffered media resulted in cadmium phosphate precipitates that remove the potentially toxic cadmium ions from the growth medium. Electrondense particles formed on the surfaces of bacteria grown under these conditions were a combination of cadmium sulfide and cadmium phosphates. The specific bacterial growth rate in the exponential phase of batch cultures was not affected by up to 2mM cadmium in Tricine-buffered medium, but formation of cadmium sulfide crystallites was maximal during the stationary phase of batch culture. Cadmium tolerance was much lower (10 to 150 M) in growth media buffered with Tris, Bistris propane, Bes, Tes, or Hepes. These results illustrate the importance of considering medium composition when comparing levels of bacterial cadmium tolerance.Abbreviations
EDXA
Energy dispersive X-ray analysis
-
AAS
Atomic absorption spectroscopy
-
TEM
Transmission electron microscopy
-
SEM
Scanning electron microscopy
-
ICP-MS
Inductively coupled plasma mass spectrometry
-
ALSA
Acid-labile sulfide analysis 相似文献
93.
M. B. Swindells 《Protein science : a publication of the Protein Society》1995,4(1):103-112
A procedure is described for detecting domains in proteins of known structure. The method is based on the intuitively simple idea that each domain should contain an identifiable hydrophobic core. By applying the algorithm described in the companion paper (Swindells MB, 1995, Protein Sci 4:93-102) to identify distinct cores in multi-domain proteins, one can use this information to determine both the number and the location of the constituent domains. Tests have shown the procedure to be effective on a number of examples, even when the domains are discontinuous along the sequence. However, deficiencies also occur when hydrophobic cores from different domains continue through the interface region and join one another. 相似文献
94.
Ethanol utilization regulatory protein: profile alignments give no evidence of origin through aldehyde and alcohol dehydrogenase gene fusion. 下载免费PDF全文
H. B. Nicholas Jr B. Persson H. Jrnvall J. Hempel 《Protein science : a publication of the Protein Society》1995,4(12):2621-2624
The suggestion that the ethanol regulatory protein from Aspergillus has its evolutionary origin in a gene fusion between aldehyde and alcohol dehydrogenase genes (Hawkins AR, Lamb HK, Radford A, Moore JD, 1994, Gene 146:145-158) has been tested by profile analysis with aldehyde and alcohol dehydrogenase family profiles. We show that the degree and kind of similarity observed between these profiles and the ethanol regulatory protein sequence is that expected from random sequences of the same composition. This level of similarity fails to support the suggested gene fusion. 相似文献
95.
Calcium fluxes at plasmalemma and tonoplast 总被引:4,自引:2,他引:2
A. E. S. MACKLON 《Plant, cell & environment》1984,7(6):407-413
Abstract. An account is given of the characterization of calcium fluxes across plasmalemma and tonoplast membranes of root cortical cells, using compartmental analysis. Some of the assumptions associated with the method are discussed. Recent evidence regarding the concentration of free Ca2+ in plant cells, and the mechanisms driving active calcium transport across cell membranes, is reviewed. It is proposed that the evidence from whole cell studies and work at the molecular level is mutually supportive, and some speculation is ventured about the general pattern of calcium transport in higher plant cells. 相似文献
96.
Adult and juvenile common marmosets were introduced to unfamiliar conspecifics individually and in whole groups. In introductions
using animals of the same sex, adults were mutually hostile unless they were related or socially familiar; juveniles behaved
submissively to adults and little aggression was observed between juveniles. In introductions using animals of the opposite
sex, males of all ages solicited females but females did not reciprocate. When whole groups were introduced, in two experiments
most of the elder group members behaved aggressively and younger animals did not interact frequently; but in a third experiment,
in which the adult males were related, little aggression was observed and younger animals behaved amicably. It is argued that
the behavioral reactions shown by individual marmosets are related to territorial hostility and that the behavior of juveniles
to adults may aid assimilation of younger animals into new groups. 相似文献
97.
R. van den Driessche 《Plant and Soil》1984,80(2):155-169
Summary Effects of P fertilizers on growth of Douglas fir (Pseudotsuga menziesii var.menziesii (Mirb.) Franco.) seedlings were examined in pots and nursery beds. In pot experiments levels of P equivalent to 300 kg/ha were adequate for maximum growth over 14–18 weeks and resulted in available soil P levels of 80 ppm after 15 weeks' growth. Maximum growth in pots was obtained with shoot P concentrations of 0.18%–0.20%, with higher values at lower temperatures, but the optimum concentration for one-year old (1-0) nursery seedlings was 0.16% P. Growth of seedlings was greatly restricted at a soil temperature of 5°C and an air temperature of 12°C. At a soil temperature of 10°C and an air temperature of 14°C seedling P requirement was greater than at soil and air temperatures of 20°C.Comparison showed that monammonium phosphate was more effective than calcium superphosphate in stimulating growth in pots and nursery. Triple superphosphate was also effective in the nursery. Diammonium phosphate, potassium dihydrogen phosphate and phosphoric acid had no advantages as P sources in the nursery. Available P levels of 100–130 ppm, in the loamy sand and sandy loam nurseries studied, and needle P concentrations of 0.18%, when sampled in October, were associated with maximum growth of two-year old (2-0) seedlings.P fertilization decreased root/shoot ratio, but did not alter the allometric relationship of shoot to root. Improving P status from a low level increased root growth capacity in 2-0 seedlings and P fertilization of potted seedlings increased dry weight/height ratio. Uptakes per seed bed ha of 236 kg N, 31 kg P, 81 kg K and 73 kg Ca by 2-0 seedlings were comparable with, or greater than, uptake rates of agricultural crops. Recoveries of 6–11% of P from fertilizer were recorded in the nursery. 相似文献
98.
M Vokac 《Chronobiology international》1984,1(1):87-92
A comprehensive set of cosinor treatment programs has been written for an Apple II microcomputer. The system includes Single Cosinor, Mean (population) Cosinor and Serial Sections analyses as well as extensive graphics and file management. The package is integrated and used through a hierarchically ordered system of menus and choices. 48k memory and two disk drives are required, and both EPSON and SILENTYPE printers are supported. 相似文献
99.
G. V. S. Rao Prof. Dr. R. S. Paroda 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1982,62(3):273-276
Summary The pattern of diversity in forty genotypes of clusterbean (Cyamopsis tetragonoloba (L.) Taub) was analysed using the centroid method of factor analysis based on nine characters. Three factors were found to adequately account for most of the intercorrelations in the four environments. Branches, clusters, pods and seed yield/plant could be grouped as productivity factors; days to flowering, maturity and plant height as growth factors; seeds/pod and gum content as economic factor. Interestingly, the constitution of the factors were the same in all the environments. The loadings on the economic factors were relatively unstable, whereas the loadings on productivity and growth factors were stable. It is concluded that productivity and growth factors play a pivotal role towards diversity in clusterbean. The results of factor analysis provides confirmatory evidence of diversity in clusterbean, which was earlier studied by using generalized distance, and thus proves the adequacy of the centroid method in biological investigations. 相似文献
100.
M J Schoeninger 《American journal of physical anthropology》1979,51(3):295-310
Determination of the levels of particular trace elements preserved in bone provides a potential pathway for reconstructing the diet of extinct primate species and archaic human groups. Strontium is one of the most useful trace elements for dietary reconstruction but several empirical properties of strontium must be considered during the interpretation of results. (1) Strontium is distributed unevenly throughout the physical environment. (2) Plants, in general, do not discriminate against strontium. (3) During ionic transfer across biological membranes, strontium is discriminated against by terrestrial vertebrates. (4) It is unlikely that strontium would be selectively removed from bone mineral during diagenesis. A particular difficulty in trace element analysis is caused by interaction between analytical technique and sample matrix. To assess this problem the skeletal population from Chalcatzingo was analyzed by two techniques: atomic absorption spectrometry and neutron activation analysis. The results from the two techniques compared favorably indicating that the pattern of bone strontium levels could be accepted as an accurate reflection of the distribution of bone strontium within the population. After demonstrating the internal accuracy of the results, the bone strontium level and position of social rank within Chalcatzingo were compared. Ethnographic and archaeological evidence on chiefdoms and states indicate that dietary differences in the amount of meat consumed occur between social ranks. The relative social ranks were reconstructed by using a "pattern analysis" of the burial goods accompanying each individual. The individuals accompanied by jade had the lowest mean bone strontium level (X = 532). Those individuals buried with a shallow dish had a slightly higher level (X = 635). A third group, which had no grave goods, had the highest mean bone strontium level (X = 700) which suggests that their diet contained less meat than was available to the rest of the community. 相似文献