. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 132 XELSOX T. SPRATT, JR. periments in particular, indicate that there is no qualitative difference between the metabolic basis (at least as regards the fundamental energy-yielding mechanisms) of the differentiation as compared with the maintenance of a structure. The theoretical implications of this concept of the "identity of maintenance and mor- phogenetic energy" have been discussed by Spiegelman (1945) in connection with his physiological competition hypothesis. Finally, analysis of the inhibitor and previous
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 132 XELSOX T. SPRATT, JR. periments in particular, indicate that there is no qualitative difference between the metabolic basis (at least as regards the fundamental energy-yielding mechanisms) of the differentiation as compared with the maintenance of a structure. The theoretical implications of this concept of the "identity of maintenance and mor- phogenetic energy" have been discussed by Spiegelman (1945) in connection with his physiological competition hypothesis. Finally, analysis of the inhibitor and previous experiments on differential nutrient requirements, in so far as they reveal a pattern of both quantitative and qualitative differences in metabolic activity in the early embryo, demonstrates that there is an apparently significant coincidence between the time course and spatial pattern of degeneration produced by inhibitors or starvation and the time course and spatial pattern of differentiation activity (Fig. 2). Regions of the early embryo where differentiation activity is greater (, the node and head-fold, or later, the fore-brain and the segmental plate, etc.) are more sensitive to adverse environmental conditions (presence of metabolic inhibitors, INHIBITION OF METABOLIC ACTIVITY (INHIBITOR POTENTIAL AVo u CONCENTRATION) ^ .fC / *-» (/} ENERGY REQUIREMENT (SUBSTRATE CONCENTRATION) SPATIAL PATTERN OF DEVELOPMENT FIGURE 3. Diagram illustrating the relationship of substrate requirements and inhibitor effects to differentiation activity and to a spatial pattern of development. See text for further description. starvation, oxygen deficiency) than are regions which have already passed through a period of differentiation activity (, hind-brain, spinal cord, somites, pulsating heart, etc.). It is thus not surprising that the energy requirements (in terms of substrate level necessary) for morphogenesis and histogenesis are greater than are those for maintenance. The buildi
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
