. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CELL DIVISION, CELL MOTILITV. AND DEVELOPMENT 241. Figure 1. Sequential computed images of a compressed Lytechinus variegatus :vgote at S-, 16-. and 32-cell stages. All spindles in side view, regardless of orientation, show up as while areas of/ugh birefringence. The metaphasc plate coincides with the plane of cytokinesis. These images were generated using Oldenbourg's newpol-scope (5). Four images were taken at different compensator angles: from ihese a computed image with a pixel brightness proportional to the sample biref
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CELL DIVISION, CELL MOTILITV. AND DEVELOPMENT 241. Figure 1. Sequential computed images of a compressed Lytechinus variegatus :vgote at S-, 16-. and 32-cell stages. All spindles in side view, regardless of orientation, show up as while areas of/ugh birefringence. The metaphasc plate coincides with the plane of cytokinesis. These images were generated using Oldenbourg's newpol-scope (5). Four images were taken at different compensator angles: from ihese a computed image with a pixel brightness proportional to the sample birefringence regardless oj specimen orientation was rapidly and automatically calculated. compressed between two thin sheets of agarose (3) or between a sheet of agarose and a coverslip. Compression down to 20 ^m was achieved. These compressed embryos were then mounted in a micro-drop chamber for observation with either a polarized light microscope (4) or a novel pol-scope (5). Development was followed by time-lapse video. With the new pol-scope we were able to visualize spindles in any orientation in the plane of focus. This allowed us to predict the cleavage pattern of the embryos more precisely (Fig. 1). In embryos that were compressed between two sheets of aga- rose, we observed that highly flattened embryos continued to cleave as a monolayer. Overnight these embryos reached several thousand cells and after 15 h of development, the cells had spread out over several fields of view. In one such embryo, we did ob- serve the formation of micromeres at the 16- and 32-cell stages. These embryos showed no evidence of differentiated structures (ciliated cells, spicules, etc.). Embryos compressed between coverslip and agarose sheet did not remain highly compressed. These embryos began forming a second layer of cells at the 5th cleavage (32 cell stage). In these embryos, epithelial differentiation, ciliogenesis, and perhaps even primordial spicule formation were observed. These results s
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
