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排序方式: 共有897条查询结果,搜索用时 31 毫秒
91.
Suzanne S. Teuber Robert L. Saunders Georges M. Halpern Robert F. Brucker Victor Conte Brian D. Goldman Edward E. Winger W. Graham Wood M. Eric Gershwin 《Biological trace element research》1995,48(2):121-130
The metatolic fate of silicone gel leaked from an intact or ruptured prosthesis is unknown. In this study, serum was blindly
assayed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) for elemental silicon in 72 women with silicone
gel breast implants and 55 control women (mean age 48 yr, both groups). Blood was drawn and processed using silicon-free materials.
The mean silicon level in controls was 0.13±0.07 mg/L (range 0.06–0.35 mg/L), whereas in implant patients, the mean was significantly
higher at 0.28±0.22 mg/L (range 0.06–0.87 mg/L) (P<0.01, Student'st-test with correction for unequal variances). Using the mean of the control group +2 SD as a cutoff for normal range (0.27
mg/L), 25/72 (34.7%) implant patients exceeded this value, compared with 2/55 (3.6%) controls. There was no significant correlation
between past rupture of one or both implants, current rupture at the time of the blood draw, or the number of years with implants
and silicon levels. The results suggest that serum silicon levels are elevated in many women with silicone gel breast implants.
The chemical species involved and kinetics of this elevation remain to be determined. 相似文献
92.
93.
Weimar T Watanabe Y Kazui T Lee US Moon MR Schuessler RB Damiano RJ 《American journal of physiology. Heart and circulatory physiology》2012,302(12):H2583-H2591
Current techniques to describe atrial function are limited by their load dependency and hence do not accurately reflect intrinsic mechanical properties. To assess the impact of atrial fibrillation on atrial function, combined pressure-volume relationships (PVR) measured by conductance catheters were used to evaluate the right (RA) and left (LA) atrium in 12 isoflurane-anesthetized pigs. Biatrial PVR were recorded over a wide range of volumes during transient caval occlusion at baseline sinus rhythm (SR), after onset of rapid atrial pacing (RAP), after 1 h of RAP, after conversion to SR, and after 1 h of recovery. Cardiac output decreased by 16% (P = 0.008) with onset of RAP. Mean LA and RA pressures increased by 21 and 40% (P < 0.001), respectively, and remained elevated during the entire recovery period. RA reservoir function increased from 51 to 58% and significantly dropped to 43% after resumption of SR (P = 0.017). Immediately after RAP, a right shift of LA end-systolic PVR-intercept for end-systolic volume required to generate an atrial end-systolic pressure of 10 mmHg (24.4 ± 4.9 to 28.1 ± 5.2 ml, P = 0.005) indicated impaired contractility compared with baseline. Active LA emptying fraction dropped from 17.6 ± 7.5 to 11.7 ± 3.7% (P < 0.001), LA stroke volume and ΔP/Δt(max)/P declined by 22% (P = 0.038 and 0.026, respectively), while there was only a trend to impaired RA systolic function. Stiffness quantified by the ratio of pressure to volume at end-diastole was increased immediately after RAP only in the RA (P = 0.020), but end-diastolic PVR shifted rightward in both atria (P = 0.011 LA, P = 0.045 RA). These data suggest that even short periods of RAP have a differential impact on RA and LA function, which was sustained for 1 h after conversion to SR. 相似文献
94.
Fabbrini E Magkos F Conte C Mittendorfer B Patterson BW Okunade AL Klein S 《Journal of lipid research》2012,53(2):321-324
Insulin resistance in adipose tissue increases the release of free fatty acids into the circulation, which likely contributes to impaired insulin action in liver and skeletal muscle associated with obesity. However, reliable assessment of adipose tissue insulin resistance requires performing a hyperinsulinemic-euglycemic clamp procedure in conjunction with a fatty acid tracer infusion to determine insulin-mediated suppression of lipolytic rate. We developed a simpler method for evaluating adipose tissue insulin resistance in vivo, determined as the product of palmitate rate of appearance into the bloodstream and plasma insulin concentration during basal conditions. We validated our Adipose Tissue Insulin Resistance Index (ATIRI) by comparison with an assessment of adipose tissue insulin resistance determined by using the hyperinsulinemic-euglycemic clamp procedure in conjunction with a palmitate tracer infusion in 47 obese nondiabetic subjects (body mass index: 40.1 ± 9.3 kg/m(2)). We found the ATIRI correlated closely with adipose tissue insulin resistance assessed during the clamp procedure (r =-0.854, P < 0.001). These results demonstrate that the ATIRI provides a reliable index of adipose tissue insulin resistance in obese subjects. 相似文献
95.
Revision surgeries of total hip arthroplasty are often caused by a deficient structural compatibility of the implant. Two main culprits, among others, are bone-implant interface instability and bone resorption. To address these issues, in this paper we propose a novel type of implant, which, in contrast to current hip replacement implants made of either a fully solid or a foam material, consists of a lattice microstructure with nonhomogeneous distribution of material properties. A methodology based on multiscale mechanics and design optimization is introduced to synthesize a graded cellular implant that can minimize concurrently bone resorption and implant interface failure. The procedure is applied to the design of a 2D left implanted femur with optimized gradients of relative density. To assess the manufacturability of the graded cellular microstructure, a proof-of-concept is fabricated by using rapid prototyping. The results from the analysis are used to compare the optimized cellular implant with a fully dense titanium implant and a homogeneous foam implant with a relative density of 50%. The bone resorption and the maximum value of interface stress of the cellular implant are found to be over 70% and 50% less than the titanium implant while being 53% and 65% less than the foam implant. 相似文献
96.
Isolani ME Conte M Deri P Batistoni R 《The International journal of developmental biology》2012,56(1-3):127-133
Planarians contain a large population of stem cells, named neoblasts, and use these for continuous turnover of all cell types. In addition, thanks to the amazing flexibility of these cells, planarians respond well to the effects of stressful situations, for example activating regeneration after trauma. How neoblasts respond to stress and support continuous proliferation, maintaining long-term stability, is still an open question. Heat shock proteins (HSPs) are a complex protein family with key roles in maintaining protein homeostasis, as well as in apoptosis and growth-related processes. We recently characterized some planarian homologs of hsp genes that are highly expressed in mammalian stem cells, and observed that some of them are critical for neoblast survival/maintenance. The results of these studies support the notion that some HSPs play crucial roles in the modulation of pathways regulating stem cell activity, regeneration and tissue repair. In this review we compare the evidence available for planarian hsp genes and focus on questions emerging from these results. 相似文献
97.
98.
Gina L. Conte Matthew E. Arnegard Catherine L. Peichel Dolph Schluter 《Proceedings. Biological sciences / The Royal Society》2012,279(1749):5039-5047
Genomic and genetic methods allow investigation of how frequently the same genes are used by different populations during adaptive evolution, yielding insights into the predictability of evolution at the genetic level. We estimated the probability of gene reuse in parallel and convergent phenotypic evolution in nature using data from published studies. The estimates are surprisingly high, with mean probabilities of 0.32 for genetic mapping studies and 0.55 for candidate gene studies. The probability declines with increasing age of the common ancestor of compared taxa, from about 0.8 for young nodes to 0.1–0.4 for the oldest nodes in our study. Probability of gene reuse is higher when populations begin from the same ancestor (genetic parallelism) than when they begin from divergent ancestors (genetic convergence). Our estimates are broadly consistent with genomic estimates of gene reuse during repeated adaptation to similar environments, but most genomic studies lack data on phenotypic traits affected. Frequent reuse of the same genes during repeated phenotypic evolution suggests that strong biases and constraints affect adaptive evolution, resulting in changes at a relatively small subset of available genes. Declines in the probability of gene reuse with increasing age suggest that these biases diverge with time. 相似文献
99.
The synthesis of novel star-like heteroarms polymers A(BC)(n) containing m-PEG (block A), methylmethacrylate (MMA), and nonquaternized 2-(dimethylamino)ethyl methacrylate (DMAEMA) (blocks BC) is here reported. We demonstrated that copolymer films with comparable amounts of DMAEMA have antimicrobial properties strongly depending on the topological structure (i.e., the number of arms) of the composing copolymers. We interpret the highest antimicrobial activity of A(BC)(2) with respect to A(BC)(4) and linear copolymers (respectively, A(BC)(2) ≥ A(BC)(4) > A(BC)) as probably due to the formation of strong hydrogen bonds between close amino-ammonium groups in the A(BC)(2) film. Strong hydrogen bonds seem to be somewhat disfavored in the case of the linear species by the difference in both polymer architecture and film morphology compared with the A(BC)(2) and A(BC)(4) architectures. 相似文献
100.
Iaffaldano P Viterbo RG Paolicelli D Lucchese G Portaccio E Goretti B Direnzo V D'Onghia M Zoccolella S Amato MP Trojano M 《PloS one》2012,7(4):e35843