. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 268 J. G. KUNKEL Epidermal cell proliferation Since the beginning of proliferation of the epidermis could not be followed adequately as a quantal event it was decided to follow the increase of cell number quantitatively using the synchronous cultures. The intertergite region was used because of its lack of large numbers of organules. Groups of ten animals were fixed at various times after feeding, stained by the Feulgen reaction, and the density of nuclei per unit area of intertergite measured by camera Inciila. Figure 5 sho
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 268 J. G. KUNKEL Epidermal cell proliferation Since the beginning of proliferation of the epidermis could not be followed adequately as a quantal event it was decided to follow the increase of cell number quantitatively using the synchronous cultures. The intertergite region was used because of its lack of large numbers of organules. Groups of ten animals were fixed at various times after feeding, stained by the Feulgen reaction, and the density of nuclei per unit area of intertergite measured by camera Inciila. Figure 5 shows the densities of generalized epidermal cell nuclei which were found at various times. During the first 44 hours after feeding, the nuclei per unit area declines approximately 10 per cent. This decrease in density could be accom- plished by a combination of cell death, Figure 2E, and differentiation of epidermal cells into organules. Since few organules exist in the intertergite region the ten per cent decline has to he explained in terms of the observed cell death and perhaps differentiation into oenocytes. According to Figure 5, between 48-84 hours after feeding the epidermis doubles its nuclear density. This apparent 36-hour proliferative phase in the intertergite region is most likely an overestimate. The overestimation is an artifact of follow- ing a rapid process in a less than perfectly synchronized (quasi-synchronized) cul- ture of animals. The overestimate is indicated by some results obtained using colchicine in a non-parametric approach to estimating the length of the proliferative phase. ,- LLJ Q 20 40 60 HOURS 80 FIGURE 5. Density of generalized epidermal cell nuclei (nuclei/100 square microns) of the abdominal intertergite region during the fourth instar of Blattclla gennanica. Ecdysis oc- curred at a mean time of 130 hours after feeding. It was impossible to analyze samples after 86 hours of feeding due to shifting of the epidermis under the old
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
