多视点学习条件下场景内在参照系的建立

The aim of the present study was to investigate whether people can establish two oblique spatial reference directions to represent objects’ locations in memory. Participants learned a layout of objects from two oblique viewpoints (0º and 225º) and made judgments of relative direction (“Imagine you are standing at X, facing Y, please point to Z”). Experiments 1 to 3 showed that performance in pointing were better at either one of the familiar imagined headings (0º and 225º) in most of the participants even when they were instructed to learn the layout along their actual heading at both learning directions, and when their actual headings at the test were the same as the imagined headings. Experiments 4 to 6 showed performance in pointing could be equivalent at the two familiar imagined headings for significant number of the participants when participants learned two different set of objects occupied at the same locations from the two learning viewpoints, and when participants learned the same layout of objects together with two different layouts from the two learning viewpoints. These results suggest that the orientation dependent performance in Experiments 1 to 3 cannot be attributed to the possibility that participants had formed two oblique spatial reference directions during learning but only used one of them during testing. Experiments 7 and 8 further showed that the performance of pointing at the two familiar viewpoints were significantly different when participants experienced one viewpoint by learning the actual layout and the other viewpoint by learning the map of the same layout, and when participants experienced two viewpoints alternatively over the ten times of learning sessions. All these results strongly suggest that people establish only one spatial reference system to represent locations of objects when they learn the same layout in the same background from two oblique viewpoints.

Development of an in vitro multicellular tumor spheroid model using microencapsulation and its application in anticancer drug screening and testing

In this study, an in vitro multicellular tumor spheroid model was developed using microencapsulation, and the feasibility of using the microencapsulated. multicellular tumor spheroid (MMTS) to test the effect of chemotherapeutic drugs was investigated. Human MCF-7 breast cancer cells were encapsulated in alginate-poly-L-lysine-alginate (APA) microcapsules, and a single multicellular spheroid 150 mu m in diameter was formed in the microcapsule after 5 days of cultivation. The cell morphology, proliferation, and viability of the MMTS were characterized using phase contrast microscopy, BrdU-Iabeling, MTT stain, calcein AM/ED-2 stain, and H&E stain. It demonstrated that the MMTS was viable and that the proliferating cells were mainly localized to the periphery of the cell spheroid and the apoptotic cells were in the core. The MCF-7 MMTS was treated with mitomycin C (MC) at a concentration of 0.1, 1, or 10 times that of peak plasma concentration (ppc) for up to 72 h. The cytotoxicity was demonstrated. clearly by the reduction in cell spheroid size and the decrease in cell viability. The MMTS was further used to screen the anticancer effect of chemotherapeutic drugs, treated with MC, adriamycin (ADM) and 5-fluorouracil (5-FU) at concentrations of 0.1, 1, and 10 ppc for 24, 48, and 72 h. MCF-7 monolayer culture was used as control. Similar to monolayer culture, the cell viability of MMTS was reduced after treatment with anticancer drugs. However, the inhibition rate of cell viability in MMTS was much lower than that in monolayer culture. The MMTS was more resistant to anticancer drugs than monolayer culture. The inhibition rates of cell viability were 68.1%, 45.1%, and 46.8% in MMTS and 95.1%, 86.8%, and 91.6% in monolayer culture treated with MC, ADM, and 5-FU at 10 ppc for 72 h, respectively. MC showed the strongest cytotoxicity in both MMTS and monolayer, followed by 5-FU and ADM. It demonstrated that the MMTS has the potential to be a rapid and valid in vitro model to screen chemotherapeutic drugs with a feature to mimic in vivo three-dimensional (3-D) cell growth pattern.