Expression of chimeric antibody in mammalian cells using dicistronic expression vector.

A dicistronic expression vector was constructed for Chinese hamster ovary (CHO) cells that produce both selectable marker-DHFR (dihydrofolate reductase) gene and recombinant antibody cDNA from a single primary transcript via differential splicing. The vector was derived from a pDHL vector and contained the human constant region cDNA so that any human-mouse chimeric antibodies could be expressed. The expression vector produced stable CHO cell clones that secreted nearly double the amount of chimeric antibodies than produced by conventional expression approaches, where the DHFR gene and relevant cDNA are controlled by separate transcription cassettes. Clones with increased expression of interested genes can be efficiently generated by selection in medium containing a gradually increasing amount of methotrexate. The dicistronic expression system using incomplete splicing DHFR gene strategy thus provides a convenient, high-level, and rapid expression of chimeric antibodies.

[Applied anatomy study related to implants in the temporal bone region].

OBJECTIVE: To study the bone anatomic structure of the temporal bone region and provide reference in implant surgery in this region. METHODS: Manual quantitative measurements of the bone structure were performed in 73 skull specimens (38 from male and 35 from female). RESULTS: In the area of 8:00-11:00 (right ear) and 16-22 mm from center of the external auditory canal in the temporal bone region, the minimum bone thickness is as follows: 11:00: 6.77 mm in male, 5.18 mm in female; 10:00: 8.60 mm in male, 6.77 mm in female; 9:00: 9.85 mm in male, 7.30 mm in female; 8:00: 14.50 mm in male, 10.80 mm in female. CONCLUSION: (1) In the temporal bone region, the area of 8:00-11:00 (right ear) and 16-22 mm from center of the external auditory canal offers sufficient bone for implants. The length of implants should be as follows: 11:00: 4-5 mm in male, 3-4 mm in female; 10:00: 4-7 mm in male, 4-5 mm in female; 9:00: 4-8 mm in male, 4-6 mm in female; 8:00: 4-12 mm in male, 4-8 mm in female. (2) Towards the external auditory canal and from 12:00 to 11:00, 10:00 to 8:00, the bone became thicker, so, if no ample bone is available in the initial site, the location should be shifted anti-clockwise in right side (clockwise in left side) and closer to the external auditory canal. (3) The differences between male and female are statistically significant in the temporal bone region, so they should be treated distinguishingly during the clinical practices.