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71.
Ramaswamy Y Haynes DR Berger G Gildenhaar R Lucas H Holding C Zreiqat H 《Journal of materials science. Materials in medicine》2005,16(12):1199-1205
Biomaterials used in bone regeneration are designed to be gradually resorbed by the osteoclast and replaced by new bone formed
through osteoblastic activity. The aim of the present study is to analyze the role of osteoclasts in the resorption process.
The attachment of human osteoclasts and the appearance of their resorption lacunae, when cultured on either the resorbable
crystalline, calcium orthophosphate materials or on the long-term stable bioceramic material was investigated. The resorbable
materials contain Ca10[K,Na](PO4)7 (AW-Si) and Ca2KNa(PO4)2 (GB14, GB9 & D9/25) as their main crystal phases, however they differ in their total solubility. These differences result
from small variations in the composition. The long-term stable material consist of about 30% fluorapatite beside calcium zirconium
phosphate (Ca5(PO4)3F + CaZr4(PO4)6) and shows a very small solubility. AW-Si has an alkali containing crystalline phase, Ca10[K,Na](PO4). While GB14, GB9 and D9/25 contain the crystalline phase Ca2KNa(PO4)2 with small additions of crystalline and amorphous diphosphates and/or magnesium potassium phosphate (GB14). D9/25 and AW-Si
is less soluble compared to GB14, and GB9 among the resorbable materials. Resorbable and long-term stable materials vary in
their chemical compositions, solubility, and surface morphology. Osteoclasts modified the surface in their attempts to resorb
the materials irrespective of the differences in their physical and chemical properties. The depth and morphology of the resorption
imprints were different depending on the type of material. These changes in the surface structure created by osteoclasts are
likely to affect the way osteoblasts interact with the materials and how bone is subsequently formed. 相似文献
72.
Structural basis of biological nitrogen fixation 总被引:2,自引:0,他引:2
Rees DC Akif Tezcan F Haynes CA Walton MY Andrade S Einsle O Howard JB 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2005,363(1829):971-84; discussion 1035-40
Biological nitrogen fixation is mediated by the nitrogenase enzyme system that catalyses the ATP dependent reduction of atmospheric dinitrogen to ammonia. Nitrogenase consists of two component metalloproteins, the MoFe-protein with the FeMo-cofactor that provides the active site for substrate reduction, and the Fe-protein that couples ATP hydrolysis to electron transfer. An overview of the nitrogenase system is presented that emphasizes the structural organization of the proteins and associated metalloclusters that have the remarkable ability to catalyse nitrogen fixation under ambient conditions. Although the mechanism of ammonia formation by nitrogenase remains enigmatic, mechanistic inferences motivated by recent developments in the areas of nitrogenase biochemistry, spectroscopy, model chemistry and computational studies are discussed within this structural framework. 相似文献
73.
Haynes RK Chan HW Ho WY Ko CK Gerena L Kyle DE Peters W Robinson BL 《Chembiochem : a European journal of chemical biology》2005,6(4):659-667
An economical phase-transfer method is used to prepare 10-arylaminoartemisinins from DHA and arylamines, and artemether, arteether, and artelinate from the corresponding alcohols. In vivo sc screens against Plasmodium berghei and P. yoelii in mice reveal that the p-fluorophenylamino derivative 5 g is some 13 and 70 times, respectively, more active than artesunate; this reflects the very high sc activity of 10-alkylaminoartemisinins. However, through the po route, the compounds are less active than the alkylaminoartemisinins, but still approximately equipotent with artesunate. 相似文献
74.
Experiments have been performed to determine whether the antisecretory (antidiarrhoeal) actions of difenoxin and loperamide are mediated by enteric neurones. An iso-osmotic perfusion solution was circulated around the lumen of the jejunum of anaesthetised rats. Vasoactive intestinal peptide was infused intra-arterially to induce net fluid secretion which was inhibited by difenoxin (ED50, 0.23 mg/kg) and loperamide (ED50, 0.5 mg/kg). However, neither were able to restore the fluid transport rate to the control level of absorption. The antisecretory effects of difenoxin (0.77 mg/kg) and loperamide (0.6 mg/kg) were blocked by the opiate receptor antagonist naloxone (2 mg/kg). Their effects were also abolished by pretreatment with the 5-HT synthesis inhibitor p-chlorophenylalanine (PCPA; 200 mg/kg; with desmethylimipramine given beforehand to protect noradrenergic nerves and enhance 5-HT depletion). The effect of difenoxin was blocked with methiothepin (1 mg/kg) and methysergide (30 micrograms/kg) but not ketanserin (30 micrograms/kg), ritanserin (30 mg/kg), ondansetron (10 micrograms/kg) or ICS 205-930 (3 mg/kg). None of the above 5-HT receptor antagonists modified the antisecretory effect of loperamide. The antisecretory effect of difenoxin but not loperamide was prevented by phentolamine (2 mg/kg) and by pretreatment with 6-hydroxy-dopamine (150 mg/kg total). It is concluded that both difenoxin and loperamide inhibit net fluid secretion by indirect mechanisms. It is proposed that the initial action is on enteric mu-opiate receptors and that this results in the release of 5-HT. In the case of difenoxin, the 5-HT may act on 5-HT1-like receptors to release noradrenaline.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
75.
Fabio Lorenzini Eoghain OHara Shimeng Qian Fabio Marchetti James M. Birbeck Anthony Haynes Alexander J. Blake Graham C. Saunders Andrew C. Marr 《Inorganic chemistry communications》2009,12(10):1071-1073
Rh2(cod)2(μ2-dppm)(μ2-Cl)]BF4 (1) rearranges under carbon monoxide to give [Rh3(μ2-dppm)2(μ2-CO)3(K1-CO)3]BF4 (2). Complex 2 has been structurally characterized by single crystal X-ray crystallography. The hydroformylation activities of 1 and 2 were compared for substrates styrene and 1-hexene and the activity of 2 found to be unexpectedly high. 相似文献
76.
77.
A differential capacitance sensor has been used in the servosystem of a magnetic suspension densimeter to detect the position of a magnetic buoy. This type of sensor has not previously been used in this application. Its design, performance, and advantages are described. 相似文献
78.
Svetlana M. Zemskova Camille Y. Jones Kevin M. Cooley J. Allen Haynes 《Journal of the American Ceramic Society》2004,87(12):2201-2207
Fabrication of mullite (3Al2 O3 ·2SiO2 ) coatings by chemical vapor deposition (CVD) using AlCl3 –SiCl4 –H2 –CO2 gas mixtures was studied. The resultant CVD mullite coating microstructures were sensitive to gas-phase composition and deposition temperature. Chemical thermodynamic calculations performed on the AlCl3 –SiCl4 –H2 –CO2 system were used to predict an equilibrium CVD phase diagram. Results from the thermodynamic analysis, process optimization, and effects of various process parameters on coating morphology are discussed. Dense, adherent crystalline CVD mullite coatings ∼2 μm thick were successfully grown on Si3 N4 substrates at 1000°C and 10.7 kPa total pressure. The resultant coatings were 001 textured and contained well-faceted grains ∼0.3–0.5 μm in size. 相似文献
79.
Philip J. Bourque Dominique Gambier Raymond J. Burby III Jack E. Adams Jeffrey B. Nugent D. van der Werf William J. Serow Edward L. Prill Willard Tim Chow R. J. Johnston Craig Zumbrunnen Kingsley E. Haynes Nolin Masih Robert Hines Wilson Philip S. Morrison Debnath Mookherjee Robin Flowerdew Noel D. Uri Panayotis H. Mavrakis Leo E. Zonn Joseph A. Ziegler J. S. L. McCombie Ronald A. Oliveira Jacob J. van Duijn Douglas M. Brown Robert G. Fletcher Lawrence Hugg W. T. Trulove Alene Anderson Bruce Domazllcky 《The Annals of Regional Science》1978,12(1):105-164
80.
Elisabeth Lichtenberger A. Subbakrishniah Milton H. Grannatt rd Antoine S. Bailly Charles G. Schmidt Dougald A. MacFarlane Rudolf Andorka Ernesto Quintanilla L. B. Wallerstein Stan Openshaw Herman G. Berkman Kingsley E. Haynes W. W. Hall Jr. Richard B. Le Heron John E. Stapleford Alan Pearman Paul Soyke Thomas R. Beard Howard F. Newell Michael Dear Kenneth D. Lawrence Peter Mastenbroek Rolf B. Schmitt Sung Woong Hong A. A. Horner James M. Murray Donald W. Jones W. E. Mullendore 《The Annals of Regional Science》1977,11(3):129-183