Human mini-chromosomes in mouse embryonal stem cells

We have introduced human mini-chromosomes of 4 Mb and approximately 15 Mb in size into mouse embryonal stem cells. Although these human mini- chromosomes are stable in hamster and chicken cells, they re-arrange or segregate aberrantly in the embryonal stem cells and are rapidly lost in the absence of selection. However, one of the mini-chromosomes re- arranged, acquired mouse centromeric sequences and was then stably maintained for at least 60 population doublings in culture. This mini- chromosome, which is 4 Mb in size, is a candidate for a mouse germ line chromosome vector.      

平贝碱乙的分离和鉴定

本文报道了自东北平贝母(Fritillaria ussuriensis Maxim)中分得一种新的甾体生物碱,经光谱(IR,MS,¹HNMR及¹³CNMR)解析和衍生物制备,推定其结构为5α,17β,22α-cevanine-3 β,6α,12α,14α,16β,20β-hexol,定名为平贝碱乙。     

单克隆抗体博来霉素A6偶联物对白血病细胞特异性结合与内化

抗CCT2单克隆抗体博来霉素A6偶联物可吸附胶体金颗粒(McAb-A6-Au)。电镜观察表明,在4℃,1h,表面有McAb-A6-Au颗粒的CEM细胞最高达78%;在37℃,4h,内化McAb-A6-Au颗粒的CEM细胞高达72%。而抗原性无关的U937细胞仅为14%。并且McAb-A6-Au颗粒能直接穿过细胞膜、核膜进入细胞浆和细胞核。37℃,1h已有10～18%的CEM细胞核内有McAb-A 6-Au颗粒。实验结果提示了单抗与博来霉素A6的偶联物与选择性地结合靶细胞,而且进入细胞速度快、穿透力强,有可能成为治疗白血病药物。     

RESEARCH BASIC TO MEDICAL EDUCATION: Pimping: Perspectives of 4th Year Medical Students

Background: A well-known phenomenon among U.S. medical students known as pimping, or the pedagogical device of questioning students in the clinical setting, receives virtually no attention in medical literature. Purpose: Identifying 4th-year medical students' relevant knowledge and attitudes about pimping may help educators understand the range of beliefs about pimping and the role it plays in the socialization process into the medical community. Methods: Over a 2-month period, 11 fourth-year medical students at a Midwest medical school were asked 6 open-ended questions focusing on pimping as understood and experienced in the clinical setting. Investigators individually analyzed the interview data using qualitative methods to characterize students' experiences and recurring ideas and concepts. Results: All students noted the hierarchical nature of pimping, viewing it as a tool for attendings or residents to assess students' levels of knowledge. Although some students experienced malignant pimping, humiliated by incessant questioning or questions inappropriate to their level of training, all the students in the sample were positive about pimping and its effectiveness as a pedagogical tool. Investigators found that location within the clinical setting determines how students define and understand the motives for pimping. Conclusions: Understanding how students define and experience the pimping phenomenon prepares medical educators to scrutinize pimping as a pedagogical tool and to provide the most effective and encouraging environment for students.