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21.
N Rizzo MC Pittalis G Pilu A Perolo C Banzi A Visentin L Bovicelli 《Canadian Metallurgical Quarterly》1996,16(2):159-163
The participation of sarcoplasmic reticulum Ca2+ release channels in the activation of Ca(2+)-sensitive K+ currents (IK(Ca)) by cyclic dibutyryl GMP was investigated in smooth muscle cells from the circular layer of guinea-pig gastric fundus. All experiments were performed in the presence of 3 microM nicardipine into the bath and low Ca2+ buffering capacity of the pipette-filling solution (pCa 7.4). Ruthenium red (10 microM) as well as its combination with 10 microM heparin abolished the cyclic GMP-induced activation of IK(Ca), while 10 microM heparin remained ineffective. Ryanodine (10 microM) and the subsequently added 1 microM thapsigargin induced a relatively small increase in IK(Ca) amplitudes. The addition of 10 microM ryanodine to 1 microM thapsigargin-containing bath solution caused a vast increase in IK(Ca). It is hypothesyzed that protein kinase G-induced vectorial Ca2+ flux from the cell bulk and sarcoplasmic reticulum Ca2+ stores toward the plasma membrane is realized by a spontaneous Ca(2+)-induced Ca2+ release from a superficially situated Ca2+ store. 相似文献
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JS Anant L Desnoyers M Machius B Demeler JC Hansen KD Westover J Deisenhofer MC Seabra 《Canadian Metallurgical Quarterly》1998,37(36):12559-12568
Rab proteins are geranylgeranylated on one or two C-terminal cysteines by Rab geranylgeranyl transferase (RabGGTase). The reaction is dependent on a Rab-binding protein, termed Rab escort protein (REP). Here, we studied the role of REP in the geranylgeranylation reaction. We first characterized the interaction between REP and ungeranylgeranylated Rab using analytical ultracentrifugation and a fluorescence-based assay. We measured an equilibrium dissociation constant of 0.2 microM for the formation of a 1:1 REP-Rab complex and showed that this interaction relies mostly on ionic bonds and does not involve the two C-terminal cysteine residues. Second, we show that REP is required for recognition of Rab by RabGGTase and therefore that the REP-Rab complex is the true substrate for RabGGTase. Third, we show that free REP inhibits the geranylgeranylation reaction, suggesting that the complex is recognized by RabGGTase primarily via a REP-binding site. Our data suggest a model whereby REP behaves kinetically as an essential activator of the reaction. 相似文献
25.
G Peiró E Lerma MA Climent MA Seguí MC Alonso J Prat 《Canadian Metallurgical Quarterly》1997,10(3):216-222
A two-year multicentre prospective study was performed from 1992 to 1995 in order to evaluate the real value of various kinds of coral blocks as bone substitute in maxillofacial surgery. This study was supported by the French National Agency for Research Valorization (GBM/TEP procedure). Ten Maxillofacial Surgery Units were included. During this time, 28 coral blocks (23 patients) of two different shapes were used as malar implants for correction of congenital or acquired zygomatic hypoplasia. The mean follow-up was 1.8 year (min: 1.5; max: 2). The tolerance was perfect for 89% of cases. The radiologic opacity never decreased more than 30% and the volume augmentation was always stable at the end of the follow-up period. Three implants were removed because of septic complications. Rigid fixation between the implant and the zygomatic bone appears to be the most important factor of success. On the other hand, the surgical approach (endo- or exo-buccal) does not seem to influence the success rate. The aesthetic improvement was always evaluated as satisfactory and stable by the patients and the surgeons. The authors discuss the real value of the various kinds of biomaterials and especially coral, comparing their personal data with those of the literature. Coral blocks clearly constitute a safe and reliable bone substitute, but further investigations are required to determine its long-term behavior. 相似文献
26.
A novel porous composite of hydroxyapatite/poly[ethylene‐co‐vinyl acetate)] (HAP/EVA) having better osteointegration was fabricated by gas foaming technique using a non toxic gas blowing agent intended for bone replacement applications. Combined techniques of scanning electronic microscopy (SEM) and X‐ray microcomputed tomography (µCT) analysis showed that the pore size and pore volume of the porous composite decrease with the increase of HAP content. The gravimetric analysis evidenced for good pore interconnectivity within the porous composites. Energy dispersive X‐ray analysis (EDX) studies inveterated the even scattering of Ca ions which in turn indicate the uniform dispersion of HAP particles in the composites. The significant gradation in Ca ion concentration seen in EDX studies is well accordance with the amount of HAP loading in the sample. Mechanical properties of the porous composite having different HAP content were measured to have the compressive strength varying from 1.06 to 2.2 MPa. Non‐cytotoxic character of the material was observed by the cytocompatibility studies. The metabolic activity of L929 cells seeded on the material assessed by [3‐(4,5‐dimethylthiazol)‐2‐yl]‐2,5‐diphenyltertrazolium bromide (MTT) assay was found to be 91.8%. The adhesion and migration of the cells inside the pore walls were visualized by confocal microscopy. Copyright © 2010 Society of Chemical Industry 相似文献
27.
Hydrologic Response of Streams Restored with Check Dams in the Chiricahua Mountains,Arizona 总被引:1,自引:0,他引:1 下载免费PDF全文
L. M. Norman F. Brinkerhoff E. Gwilliam D. P. Guertin J. Callegary D. C. Goodrich P. L. Nagler F. Gray 《河流研究与利用》2016,32(4):519-527
In this study, hydrological processes are evaluated to determine impacts of stream restoration in the West Turkey Creek, Chiricahua Mountains, southeast Arizona, during a summer‐monsoon season (June–October of 2013). A paired‐watershed approach was used to analyze the effectiveness of check dams to mitigate high flows and impact long‐term maintenance of hydrologic function. One watershed had been extensively altered by the installation of numerous small check dams over the past 30 years, and the other was untreated (control). We modified and installed a new stream‐gauging mechanism developed for remote areas, to compare the water balance and calculate rainfall–runoff ratios. Results show that even 30 years after installation, most of the check dams were still functional. The watershed treated with check dams has a lower runoff response to precipitation compared with the untreated, most notably in measurements of peak flow. Concerns that downstream flows would be reduced in the treated watershed, due to storage of water behind upstream check dams, were not realized; instead, flow volumes were actually higher overall in the treated stream, even though peak flows were dampened. We surmise that check dams are a useful management tool for reducing flow velocities associated with erosion and degradation and posit they can increase baseflow in aridlands. © 2015 The Authors. River Research and Applications published by John Wiley & Sons, Ltd. 相似文献
28.
The purpose of this study was to calculate the critical difference between two analytical measurements of serum fructosamine concentration in dogs. The critical difference can be used to judge whether the difference between two consecutive analytical results from the same animal is due to natural variation. Blood samples from 15 apparently clinically healthy beagle dogs were collected once a week for six consecutive weeks. The serum fructosamine concentration was measured by the reduction test with nitroblue tetrazolium and the critical difference was calculated from the component of variance for weeks within dogs (sigma2s) and the residual variance (sigma2e). The critical difference between two consecutive analytical results was 33.5 micromol/litre. 相似文献
29.
A Bhandari DG Jones JR Schullek K Vo CA Schunk LL Tamanaha D Chen Z Yuan MC Needels MA Gallop 《Canadian Metallurgical Quarterly》1998,8(17):2303-2308
Phosphomannose Isomerase (PMI) has been shown by genetic methods to be an essential enzyme in fungal cell wall biosynthesis. The PMI inhibitor AF14049 was discovered as an unanticipated side product from high-throughput library screening against the enzyme from C, albicans. Solid-phase synthetic methods were developed and a series of libraries and discrete analogs synthesized to explore SAR around AF14049. 相似文献
30.
1. The cardiac anticholinergic effects of procainamide (1 mg kg(-1) min(-1)) and its N-acetylated metabolite (NAPA) at equimolar dose (1.16 mg kg(-1) min(-1)) were studied using in vivo experimental pharmacological and in vitro radioligand binding studies. 2. Procainamide and NAPA progressively reduced vagal stimulation-induced bradycardia in chloralose-anaesthetized dogs. As indicated by the ED50, the vagolytic activity of NAPA is 1.5-2.0 times weaker than that of procainamide. Both drugs increased heart rate, with lowering of mean blood pressure during the second part of procainamide infusion, but not during NAPA infusion. 3. Binding studies on rat heart membranes yielded Ki values that were 1.5 times higher for NAPA than for procainamide. 4. These results show that NAPA exerts a weaker cardiac vagolytic action than procainamide, which is probably linked to a lower ability to bind to cardiac muscarinic receptors. 相似文献