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21.
Prediction of femoral impact forces in falls on the hip. 总被引:7,自引:0,他引:7
A major determinant of the risk of hip fracture in a fall from standing height is the force applied to the femur at impact. This force is determined by the impact velocity of the hip and the effective mass, stiffness, and damping of the body at the moment of contact. We have developed a simple experiment (the pelvis release experiment) to measure the effective stiffness and damping of the body when a step change in force is applied to the lateral aspect of the hip. Results from pelvis release experiments with 14 human subjects suggest that both increased soft tissue thickness over the hip and impacting the ground in a relaxed state can decrease the effective stiffness of the body, and subsequently reduce peak impact forces. Comparison between our fall impact force predictions and in-vitro measures of femoral fracture strength suggest that any fall from standing height producing direct, lateral impact on the greater trochanter can fracture the elderly hip. 相似文献
22.
Fracture prediction for the proximal femur using finite element models: Part II--Nonlinear analysis. 总被引:2,自引:0,他引:2
In Part I we reported the results of linear finite element models of the proximal femur generated using geometric and constitutive data collected with quantitative computed tomography. These models demonstrated excellent agreement with in vitro studies when used to predict ultimate failure loads. In Part II, we report our extension of those finite element models to include nonlinear behavior of the trabecular and cortical bone. A highly nonlinear material law, originally designed for representing concrete, was used for trabecular bone, while a bilinear material law was used for cortical bone. We found excellent agreement between the model predictions and in vitro fracture data for both the onset of bone yielding and bone fracture. For bone yielding, the model predictions were within 2 percent for a load which simulated one-legged stance and 1 percent for a load which simulated a fall. For bone fracture, the model predictions were within 1 percent and 17 percent, respectively. The models also demonstrated different fracture mechanisms for the two different loading configurations. For one-legged stance, failure within the primary compressive trabeculae at the subcapital region occurred first, leading to load transfer and, ultimately, failure of the surrounding cortical shell. However, for a fall, failure of the cortical and trabecular bone occurred simultaneously within the intertrochanteric region. These results support our previous findings that the strength of the subcapital region is primarily due to trabecular bone whereas the strength of the intertrochanteric region is primarily due to cortical bone. 相似文献
23.
A novel peptide termed locustamyoinhibiting peptide (LOM-MIP) was isolated from brain-corpora cardiaca-corpora allata-suboesophageal ganglion extracts of the locust, Locusta migratoria. The primary structure of this nonapeptide has been determined Ala-Trp-Gln-Asp-Leu-Asn-Ala-Gly-Trp-NH2. LOM-MIP suppresses the spontaneous contractions of the hindgut and oviduct of Locusta migratoria and of the hindgut of Leucophaea maderae. This novel peptide is, however, structurally different from leucomyosuppressin, a hindgut suppressing peptide isolated from Leucophaea maderae heads. LOM-MIP has a Gly-TrpNH2 carboxy-terminal in common with APGWamide, a penis retractor muscle inhibiting peptide isolated from the snail, Lymnea stagnalis. In addition, it shows carboxy-terminal sequence similarities with locust AKH II which ends in AGWamide. No sequence similarities were found with other vertebrate or invertebrate peptides. Synthetic LOM-MIP showed biological as well as chemical characteristics indistinguishable from those of native LOM-MIP. 相似文献
24.
Induction of neurite outgrowth by v-src mimics critical aspects of nerve growth factor-induced differentiation. 总被引:8,自引:4,他引:4
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S M Thomas M Hayes G D''Arcangelo R C Armstrong B E Meyer A Zilberstein J S Brugge S Halegoua 《Molecular and cellular biology》1991,11(9):4739-4750
PC12 cells treated with nerve growth factor (NGF) or infected with Rous sarcoma virus differentiate into sympathetic, neuronlike cells. To compare the differentiation programs induced by NGF and v-src, we have established a PC12 cell line expressing a temperature-sensitive v-src protein. The v-src-expressing PC12 cell line was shown to elaborate neuritic processes in a temperature-inducible manner, indicating that the differentiation process was dependent on the activity of the v-src protein. Further characterization of this cell line, in comparison with NGF-treated PC12 cells, indicated that the events associated with neurite outgrowth induced by these two agents shared features but could be distinguished by others. Both NGF- and v-src-induced neurite outgrowths were reversible. In addition, NGF and v-src could prime PC12 cells for NGF-induced neurite outgrowth, and representative early and late NGF-responsive genes were also induced by v-src. However, unlike NGF-induced neurite growth, v-src-induced neurite outgrowth was not blocked at high cell density. A comparison of phosphotyrosine containing-protein profiles showed that v-src and NGF each increase tyrosine phosphorylation of multiple cellular proteins. There was overlap in substrates; however, both NGF-specific and v-src-specific tyrosine phosphorylations were observed. One protein which was found to be phosphorylated in both the NGF- and v-src-induced PC12 cells was phospholipase C-gamma 1. Taken together, these results suggest that v-src's ability to function as an inducing agent may be a consequence of its ability to mimic critical aspects of the NGF differentiation program and raise the possibility that Src-like tyrosine kinases are involved in mediating some of the events triggered by NGF. 相似文献
25.
Natural images were subjected to patchwise Fourier analysis, and the local amplitude and phase spectra were swapped between different images. When the patches were large relative to the image size, the appearance of the reconstructed image was similar to that of the image from which the phase information had been derived, in agreement with previous reports of phase-dominance in the global Fourier Transform. However, when the patch size was made sufficiently small, the appearance of reconstructed images was dominated by amplitude rather than phase. This was not simply due to the DC component of the amplitude spectrum. Prior low-pass filtering of the images enhanced the dominance of amplitude information in the patchwise transform. We conclude that patchwise-reconstructed images contain two quite distinct kinds of information for the human observer. The first is the positional information (local sign) of the patches themselves; the second is the textural information within patches, which is dominated by amplitude rather than phase. The reason why the global Fourier Transform is dominated by phase is that in the absence of any other information about local sign, phase is necessary to reconstruct localised features such as edges. 相似文献
26.
The murine non-fusing muscle cell line contains distinct receptors for insulin and insulin-like growth factors. Pretreatment of myocytes with insulin for 20 h at 37 degrees C inhibits the binding of [125I]iodoinsulin by 60% without affecting the binding of [125I]iodoinsulin-like growth factor I. The ED50 values for down-regulation of the insulin and insulin-like growth factor receptor by their respective ligands are 1 nM and 3 nM, respectively. Insulin, (Thr-59)-insulin-like growth factor I and multiplication-stimulating activity stimulate 2-[3H]deoxyglucose transport in myocytes with ED50 values of 5 nM, 5.6 nM and 33 nM, respectively. In order to determine whether (Thr-59)-insulin-like growth factor I stimulates 2-[3H]deoxyglucose transport in myocytes via its own receptor or the insulin receptor, we determined the activity of these peptides after down-regulation of the insulin receptor. The rate of 2-[3H]deoxyglucose transport in myocytes pretreated with insulin (5 nM) is elevated but returns to control levels by 1 h after the washout of insulin. The dose-response curve for insulin-stimulated 2-[3H]deoxyglucose transport is shifted to the right (ED50 greater than 100 nM) immediately after insulin washout but is normal by 1 h after insulin washout. In contrast, the dose-response curve for (Thr-59)-insulin-like growth factor I is unchanged in insulin-pretreated cells immediately after insulin washout. These data show that (Thr-59)-insulin-like growth factor I stimulates 2-[3H]deoxyglucose transport in myocytes by acting through an insulin-like growth factor receptor and not through the insulin receptor. Since multiplication-stimulating activity is 6-fold less active than (Thr-59)-insulin-like growth factor, they both may be acting through a type 1 insulin-like growth factor receptor. 相似文献
27.
Paramolybdate anion-exchange resin, an improved catalyst for the C-1-C-2 rearrangement and 2-epimerization of aldoses 总被引:1,自引:0,他引:1
Aqueous solutions of molybdate at 90 degrees bring about the inversion of the C-1-C-2 fragment of aldoses having four or more carbon atoms, generating thermodynamically equilibrated mixtures of the starting aldose and its 2-epimer. In some cases, notably with the aldopentoses, substantial proportions of the 3-epimers are produced, as well as 2-epimers that have not undergone inversion of the C-1-C-2 fragment. These side-reactions can be controlled by using the paramolybdate form of an anion-exchange resin (AG MP-1) together with the formate form of the same resin. The latter acts to scavenge unbound molybdate and paramolybdate anions that appear to be responsible for the side reactions. 相似文献
28.
Mitogenic responses of B and T lymphocytes from spleens of rats infected with Trypanosoma brucei rhodesiense were suppressed. Plasma from infected rats suppressed the mitogenic responses of B and T lymphocytes from spleens of normal uninfected rats. Removal of immune complexes from plasma of infected rats significantly reduced the suppressive effect of the plasma on splenic lymphocytes of normal uninfected rats. Normal thymus cells treated with plasma from infected rats and added to cultures of normal spleen lymphocytes inhibited the mitogenic responses of B and T lymphocytes. We suggest that the interaction of immune complexes and Fc or C3b receptors of T lymphocytes resulted in the in vitro induction or activation of T suppressor lymphocytes. 相似文献
29.
30.
M B Smith R W Briggs E A Shoubridge D J Hayes G K Radda 《Biochimica et biophysica acta》1985,846(1):174-178
The maximum activity of creatine kinase in vitro is similar in the pectoralis major muscle of the chicken and the duck. However, the flux (phosphocreatine to ATP) as measured by 31P saturation transfer NMR in vivo is almost 2-fold higher in the duck. This apparent discrepancy can be accounted for by the differences in the cytosolic free ADP concentrations in resting muscle. 相似文献