In order to elucidate the ultrastructural changes of human spermatozoa afteradministration of gossypol acetate 40 mg/day for 50 days,freeze-replica techniqueswere employed.In addition to the ordinary changes of spermatozoa,such as swelling,wasting,atrophy,tortuosity,nodulation in the head and/or tail region and fracture betweenhead and tail,the internal structure,biomembrane and intramembranous particles ofsperm also showed relatively more sensitive changes.The changes of biomembranerevealed certain shift in regard to the firmness of reciprocating attachment of inner-and outer-leaflets of the unit membrane.On the other hand,the changes of intra-membranous particles revealed a specialized arrangement,this is,on the plasmamembrane of head and tail they were concentrated into lattice work,whereas,in thehind-head region they accumulated as clusters.In the hind-acrosomal membranetwo types of particles,large and small,may be distinguished,the smaller ones werearranged orderly in lines of all directions.As for the nuclear pores,no changewas found in this study.It is considered that the influences of gossypol upon human spermatozoa,firstof all,were shown in the biomembrane and intramembranous particles,and theordinary changes in appearance were the secondary result.In the discussion,it'ssuggested that a special agent,gossypol receptor,responsible for the gossypol effectsto the sperm,may be present in the plasma membrane of the spermatozoa.

Objective To establish the examination criteria for the prosthodontic clinical practice using Delphi method,to improve the evaluation level of clinical practice of dental students.Method 15 clinical experts in the department of prosthodontics,Peking University School of Stomatology were selected in this study.The evaluation indicators system of prosthodontic clinical practice was established by two rounds of investigations by Delphi method.Initiative ratio and authority coefficient (Cr) of the experts were used to evaluate the reliability of the new examination criteria.Next,the eight-year program students in class of 2007 (38 students) and 2008 (34 students) were examined by old and new examination criteria respectively and the feedback of the students were collected by the method of questionnaire.SPSS 16.0 was used for data processing.Results In this study,the initiative and the authority of the experts was very high,and the initiative ratio and authority coefficient were 100％ and 0.860 respectively.A new examination criterion of prosthodontic clinical practice was established,including 3 first-level indicators,9 second-level indicators and 19 third-level indicators.Questionnaire analysis revealed that only 12％ (n=4) and 9％ (n=3)of the students in class of 2008 considered the new examination criteria was not comprehensive enough or objective enough,which was obviously less than the students in class of 2007 [45％ (n=17) and 36％ (n=14)].Conclusion A new examination criterion of prosthodontic clinical practice was successfully established by Delphi method.The new examination criterion is more comprehensive and objective than the old one and can promote the educational quality of clinical practice of dental students.The method of this study also provides reference for the educational reform of clinical practice in other fields.

The epithelial cells of normal human epididymis were studied by ultrathin section and freeze-etching replica techniques. It was found that the pseudostratified epithelium is composed mainly of dark-columnar, clear-columnar, ciliated, basal and few narrow-columnar cells. The ultrastructure of the epithelia from the head region to the tail of the epdidymis reveals no distinctive segmental demarcation, but transits gradually. The ciliated cells distributed chiefly in the initial segment of epididymis, fibril-like elements were found frequently in the supranuclear region of its cytoplasm, yet their function remains unknown. The dark-columnar cells as well as the clearcolumnar and the cillated cells of the head region of the epididymis exhibit the cytological ultrastructural characteristic features of absorption as is often the case with endocytotic vesicles and lysosomes, etc. These morphologycal findings confirm the view that these cells, particularly the dark-columnar cell, appear to be responsible to the absorption of testicular secretion in the epididymis. The clear-columnar and the dark-columnar cells, especially the former, in the distal portion of the epididymis possesses the secretory cytological characterestics. It is suggested that these cells were concerned with the production of the epididymis semen.In the discussion, the authors pointed out that the scientific basis for the detailed functions of the epididymis remains to be investigated further.

Radio-synthesis of PET tracers in microfluidic chip system for imaging research could fa-cilitate synthesis and screening of radiotracer. Moreover, modular and multi-functional microfluidic chip syn-thesis system could realize the combination of functional modules, synthetic automation, system integration and improvement of radiochemical protection. In this review, research progress in microfluidic chip system for radio-synthesis of PET tracers has been summarized.