OBJECTIVE:To determine the concentration of dehydroisoandrosterone sulfate (DHEAS) in human plasma by LC-MS.METHODS:With estrogen sulfate (ES) served as an internal standard,the plasma samples were deproteinized with acetonitrile,extracted by solid phase,hydrolyzed and derivatized.Then the concentration of DHEAS was determined by HPLC-MSD on Agilent SB C18 with column temperature kept at 40℃.The mobile phase consisted of acetonitrile-water (in gradient elution).Atmosphere pressure chemical ion source in negative ion detection model was employed.The ions selected for SIM (selected ion monitoring) quantitative analysis included m/z 490.0 (DHEAS ) and m/z 472.1(ES)[M-H]-.RESULTS:The linear range of DHEAS was 250.0～320.0 ng?mL-1(r=0.999 4).The extraction recovery of the simulated human albumin samples ranged from 71.1%～78.9% and its relative recovery ranged from 98.3%～101.4%.Both the intra-day RSD and inter-day RSD were less than 10%.The mean concentration of DHEAS in 15 health aged male volunteers was (981.6?353.4) ng?mL-1.CONCLUSION:The method is simple,practical,accurate and sensitive,and it is applicable for the determination of plasma concentration of DHEAS.

OBJECTIVE: To observe the clinical effect on site preservation with self platelet-rich fibrin (PRF) in posterior dental areas after extraction.
 METHODS: Thirty patients who asked to extract posterior teeth and were ready for dental implantation were enrolled. PRF was implanted immediately in alveolar fossa after extraction. Cone beam computer tomography (CBCT) images were taken after 4-6 months and the changes in height and width of alveolar bone were observed.
 RESULTS: There was no statistical difference in the height and width between the alveolar bone treated with PRF after the extraction of tooth and the bone condition before the extraction of tooth.
 CONCLUSION The site preservative technology with PRF could maintain the mass of alveolar bone in posterior dental areas, which provide a better bone condition for later dental implantation.
Alveolar Process ; Blood Platelets ; Cone-Beam Computed Tomography ; Dental Implantation ; Fibrin ; therapeutic use ; Humans ; Tooth Extraction