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71.
72.
Richard W. Bowtell Andrew Peters Jonathan C. Sharp Peter Mansfield Edward W. Hsu Nanci Aiken Anthony Horsman Stephen J. Blackband 《Magnetic resonance in medicine》1995,33(6):790-794
NMR microimages of single neural cells were acquired at 500 MHz using a conventional spin echo pulse sequence and a line-narrowing sequence that eliminates susceptibility effects. The data show that any contribution to the measured T2 relaxation rate arising from diffusion in local field inhomogeneities using spin echo sequences at high fields and high spatial resolution is relatively small. We conclude that the measured T2 difference between the nucleus and cytoplasm in these cells represents primarily a true T2 relaxation effect arising from the interactions of water with macromolecules in the two compartments and does not result from microsusceptibility differences. These observations have implications regarding water compartmentation in single cells and the interpretation of the MR characteristics of tissues in vivo. 相似文献
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Metabolic clearance rate (MCR) and production rate (PR) of calcitriol is decreased in experimental renal failure. In this experiment, we studied uremia and secondary hyperparathyroidism as possible causes of the abnormal calcitriol metabolism. Normal rats were made uremic by infusing phosphorus-free urine for 24 hours. Both the MCR (0.22 +/- 0.01 ml/min/kg, N = 6 P less than 0.001) and the PR (16.6 +/- 1.97 ng/kg/day, P less than 0.01) of calcitriol were significantly suppressed in normal rats following urine infusion when compared to saline infused rats (MCR, 0.30 +/- 0.01; PR, 32.9 +/- 4.1, N = 6). Different levels of protein intake by rats with renal failure produced by subtotal nephrectomy also alter the PR but not the MCR of calcitriol. Thus, the synthesis of calcitriol was significantly lower in rats with renal failure fed a high protein (50% protein) diet (17.6 +/- 0.7 ng/kg/day, N = 8, P less than 0.001) than in rats with renal failure fed a normal protein (20% protein) diet (22.2 +/- 1.4, N = 7). Thyroparathyroidectomy (TPTX) did not alter the MCR of calcitriol in renal failure, even though parathyroid hormone, which may suppress the degradation enzyme, could be elevated in this model of renal failure. The MCR of TPTXed rats with renal failure (0.15 +/- 0.01 ml/min/kg, N = 7) remained lower than that of the TPTXed control rats (0.19 +/- 0.01, N = 7, P less than 0.001), and chronic infusion of PTH to TPTXed rats with renal failure did not change the MCR of calcitriol (0.15 +/- 0.01, vs. control, 0.24 +/- 0.01).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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Bart D. Maes Wim Lemahieu Dirk Kuypers Pieter Evenepoel Willy Coosemans Jacques Pirenne Yves F. CH. Vanrenterghem 《American journal of transplantation》2002,2(10):989-992
Diarrhea is the most frequently reported adverse event in patients treated with mycophenolate mofetil. Twenty-six renal transplant patients on a mycophenolate mofetil-based immunosuppressive regime with persistent afebrile diarrhea were examined. Diarrhea caused a significant rise in FK-506 trough levels despite intake of stable doses, necessitating FK-506 dose reductions of 30% to obtain pre-diarrhea trough levels. In contrast, trough levels of cyclosporine A remained stable without dose adjustments. This suggests that absorption and/or metabolism is differentially altered for FK506 compared with cyclosporine A in patients with diarrhea. In nine patients mycophenolate mofetil was reduced or stopped because of persistent diarrhea without identifiable cause. This resulted in end-stage renal disease because of chronic rejection in two patients, and in acute rejection in two patients, all taking FK506 and steroids. Therefore, dose adjustments of FK506 in patients with diarrhea must be carefully monitored, especially when doses of mycophenolate mofetil are also reduced. 相似文献
78.
Deng-Shan Chen Ging-Ho Hsiue Chain-Shu Hsu 《Macromolecular chemistry and physics.》1992,193(6):1469-1479
Two kinds of side-chain liquid-crystalline (LC) polymers with different side-chain mesogenic end groups were synthesized. The laminated membrane was prepared by sandwiching the side-chain LC polymer between two porous polypropene (Celgard) films. Permeation properties for O2, N2, CO2 and CH4 through the laminated side-chain LC polymer-based membranes were measured using a gas-chromatographic method at several temperatures corresponding to the stability range of the different phases of the side-chain LC polymers. The gas permeation behaviour depends strongly on the state of the side-chain LC polymer. The activation energy for permeation depends on the state, too. The plot of separation factor P/P versus P exhibits an unusual behaviour. P/P increases with P when the temperature rises and the phase of the side-chain LC Polymer changes from the glassy state to the liquid-crystalline state. The magnitude of gas permeability coefficients for the laminated membranes is rather low compared to those of some common polymers. The low gas permeability seems to originate from the low gas solubility rather than from the low gas diffusivity in the laminated side-chain LC polymer membrane. 相似文献
79.
Proteolytic activity for [3H]elastin, pyro-Glu-Pro-Val-pNA(S-2484), and Suc-(Ala)3-pNA(AAApNA) was demonstrated in the bound fraction extracted with 2 M KSCN + 0.1% Triton X-100 from hypersensitivity-type murine lepromas in C57BL/6N mice, while elastase-inhibitor activity was separately observed in the soluble fraction extracted with a Tris-saline buffer. Sephacryl S-200 gel chromatography showed a peak of elastolytic activity with approximately 20,000 in molecular weight. The following DEAE-Sepharose chromatography demonstrated three fractions of elastolytic activity (E-I, II, III). The inhibitory profile showed that E-I is a thiol proteinase, while E-II and E-III belong to serine proteinase-type elastases. Both E-II and E-III showed different properties with neutrophil elastase or elastase secreted from cultured macrophages, but identical characteristics to membrane bound-type elastase of monocytes. A lower level of elastolytic activity was detected in the bound fraction of nonhypersensitivity-type murine lepromas in CBA/N mice, suggesting a more involvement of membrane bound-type elastase from monocytes/macrophages during the tissue remodelings of hypersensitivity-type granulomas. 相似文献
80.
The biomechanical properties and histocompatibility of a glutaraldehyde-treated xenograft were examined after implanting it in 27 rabbits. This xenograft was used as an Achilles tendon substitute placed in vivo for 2 to 48 wk. The specimens were then subjected to mechanical strength testing using a specially constructed tensioning device. The contralateral Achilles tendon was used as the reference baseline. Mechanical testing showed that the strength of the implanted graft increased to 33.5% of the normal side at week 10 and to 79.5% at week 14. The host generated a fibrous cord around the xenograft, linking the two ends of the Achilles tendon. Light and electron microscopic examination showed fibroblastic infiltration of varying magnitude in all specimens but no statistical correlation between degree of infiltration and duration of implantation was found. Also, there was no histological evidence of immunological rejection within the 48 wk of study. 相似文献