ABSTRACT
AIM: To investigate the mechanisms of megakaryocyte polyploid cell cycle control. METHODS: The expression and phosphorylation of mTOR/p70s6k pathway proteins was detected by western blot. Double-labeling techniques were used to investigate in which of the phase of the polyploid cell cycle S6K1 at Thr421/Ser424 are phosphorylated. RESULTS: Nocodazole induced a relatively synchronized polyploidization in Dami cells. The expression of mTOR and the phosphorylation of mTOR at Ser2448 increased when Dami cells begin to progress from G1 to S-phase in cell cycle. Analysis of flow cytometry showed that phosphorylation of S6K1 at Thr421/Ser424 increased at G2/M-phase. CONCLUSION: mTOR/S6K1 pathway is involved in megakaryocyte polyploid cell cycle control.
Subject(s)
Megakaryocytes/enzymology , Polyploidy , Ribosomal Protein S6 Kinases, 70-kDa/metabolism , Signal Transduction , TOR Serine-Threonine Kinases/metabolism , Cell Cycle/drug effects , Humans , Megakaryocytes/drug effects , Nocodazole/pharmacology , Phosphorylation/drug effects , Signal Transduction/drug effects , Tubulin Modulators/pharmacologyABSTRACT
In this paper, hydroxyapatite (HA) coatings having the crystallinities of 56% and 98% were deposited by the plasma spraying and vapor-flame treatment process. The phase composition and crystallinity of the coatings were investigated by X-ray diffraction and infrared spectra. The dissolution behavior of the coatings in tris-buffer solutions was examined. The results obtained indicated that the coating having the high crystallinity showed the lower dissolution as compared to the low crystallinity coating. The bone bonding ability of HA coatings were observed in vivo by implanted in dog's femur. After 3 months implantation, the high crystallinity coating showed the higher shear strengths and remained integrated, whereas the separation of the coating fragments was clearly observed in the coating having low crystallinity.
Subject(s)
Coated Materials, Biocompatible/chemistry , Durapatite/chemistry , Animals , Biocompatible Materials/chemistry , Bone Substitutes , Buffers , Crystallization , Dogs , Femur/pathology , Materials Testing , Microscopy, Electron, Scanning , Surface Properties , Tensile Strength , Time Factors , X-Ray DiffractionABSTRACT
Dicalcium silicate coatings on titanium alloys substrates were prepared by plasma spraying and immersed in simulated body fluids for a period of time to investigate the nucleation and growth of apatite on the surface of the coatings. Surface structural changes of the specimens were analyzed by XRD and IR technologies. SEM and EDS were used to observe surface morphologies and determine the composition of dicalcium silicate coatings before and after immersion in simulated body fluid. The plasma sprayed dicalcium silicate coating was bonding tightly to the substrate. The coating was mainly composed of beta-Ca2SiO4 and glassy phase. A dense carbonate-containing hydroxyapatite (CHA) layer was formed on the surface of the plasma sprayed dicalcium silicate coating soaked in SBF solution for 2 days. In addition, a silica-rich layer was also observed between CHA layer and coatings. With an increase in the immersion time, the CHA layer gradually became thicker. The results obtained indicated that the plasma sprayed dicalcium silicate coating possesses excellent bioactivity.
