The preclinical screening tests used to research tumor chemoprevention agents by overseas research groups were described. These tests composed a screening system for evaluating tumor chemopreventive agents and should be used to screen tumor prevention agents from traditional Chinese herbs.

Objective To investigate the filtration roles of microporous membranes with different pore sizes in the tumor cells with different diameters,and effects on the filtered cells.Methods Three kinds of tumor cells with different cell diameters and same concentrations,including Jurkat,K562 and A549,were filtered by the polycarbonate microporous membranes with different pore sizes such as 1,3,5,8 and 10 μm,respectively,and their filtration rates were determined.The diameters of three kinds of tumor cells before and after filtration,and the fixed K562 cells with formaldehyde,were measured by an optical microscope.The activity of the filtered K562 cells were detected by the trypan blue staining.After the filtered K562 cells were re-cultured,their proliferation activity was analyzed by the growth curve.Results Jurkat,K562 and A549 cells couldn't pass the filter membrane with 1 μm of pore size.The filtration rates of three kinds of tumor cells passing the fliter membranes with 3 μm,5 μm,8 μm and 10 μm of pore sizes increased in turn.The survival rate of K562 cells filtered by 3 μm of pore size of membrane was 92.0％,and the proliferation acticity of re-cultured K562 cells was still strong.The filtration rate of the fixed K562 cells with formaldehyde was significantly decreased,and the average diameter of the filtered cells had no obvious change.Conclusion The living cells are able to pass the membranes with the pore sizes less than their diameters.The living cells passed the filter membranes may still maintain their growth and proliferation activity.However,the fixation of formaldehyde may significantly reduce the number of cells passed the membrane.

Bioseperation, cell cultivation and cell electrofusion are three main biological processes in space laboratories. Microgravity is free from the influences of convection and sedimentation. Therefore, it is an ideal realm for cell electrofusion and hence it can be used in the research of monoclonal antibody, cross breeding and microgravity biology. This paper reviews the research of cell electrofusion under microgravity, including the changes of cytoskeleton and the mechanism of cell electrofusion.
Animals ; Cell Culture Techniques ; Cell Fusion ; methods ; Electric Stimulation ; Electroporation ; methods ; Mice ; Microelectrodes ; Weightlessness ; Weightlessness Simulation

The molecular mechanism underlying muscular atrophy and gravisensing during spaceflight is still unknown. The major effects of spaceflight on body-wall muscles of Caenorhabditis elegans (C. elegans) in the structures and functions wore examined, and five important muscle-related genes and three proteins were studied after nearly 15-day spaceflight. The changes for the wall-muscles were observed in situ. Decreased muscle fiber size was observed with myosin immunofluorescence and duller dense-body staining in flight samples, which suggested that muscular atrophy had happened during spaceflight. However, F-actin staining showed no differences between the spaceflight group and ground control group. Otherwise, after returning to the earth the C eleganu displayed reduced rate of movement with a lower ratio (height/width) in crawl trace wave, which indicated a functional defect. These results demonstrated that C. elegans muscular development was changed in response to microgravity, and changes also occurred at the level of gene transcription and protein translation. Expression of dys-I increased significantly in body-wall muscles, while hlh-1, myo-3, uric-54 and eg1-19 RNA levels decreased after spaceflight. Dystrophin (encoded by dys-1) is one of important components in dystrophin-glycoprotein complex (DGC). Increased dys-I expression after flight implied that the muscular cell would accept more gravity signals by DGC in mierogravity in order to keep mechanical balance within the cells. It is concluded that DGC was involved into the mechanical transduction in body-wall muscles of C. elegans when gravity varied, which potentially played a vital role in gravisensing. The changes ofhlh-l, myo-3, tmc-54 and egl-19 suggested that they had the effects of promoting microgravity-induced muscular atrophy in strcture and function aspects. Result of Western blotting showed that the level of myosin A in spaceflight group decreased, further confirmed that atrophy happened during flight.