first is the genetic-nuclear body shown in 

 Scheme I. Within this decision-making body, 

 namely the nucleus, there are many interlock- 

 ing, interlinking, rate-dependent and rate 

 limiting-processes. These processes are con- 

 nected together in clockwise fashion as pictured 

 in the scheme. The second "decision-making 

 body" is the cytoplasm. In this "decision-making 

 body", as well, there are many interlinking, 

 rate-limiting processes which are shown con- 

 nected in counter clockwise fashion in the 

 scheme to indicate that they may be different 

 from those in the nucleus. We now must set up 

 a communication system between these two 

 decision making bodies (Scheme I). Let us 

 imagine a sensory system for the nuclear body 

 which receives the cytoplasmic signals. We will 

 similarly imagine a sensory system for the 

 cytoplasmic body to receive the signals from 

 the nucleus. These sensory systems can have 

 varying degrees of sensitivities to various 

 signals at a given time so as to allow certain 

 information to be transmitted with great effi- 

 ciency while other information is not trans- 

 mitted at all. Thus, the communication system 

 between these two decision-making bodies is 

 controlled by the selectivity in transmission 

 as well as by the regulation in generation of 

 these signals. We do not have much information 

 about the biochemical nature of these signals 

 or about the sensory systems. This is certainly 

 one of the most important problems of cell 

 biology as related to developmental biology, i.e., 

 "What is the biochemical nature of the com- 

 munication network between the nucleus and the 

 cytoplasm?". Recent research in molecular 

 biology has indicated that one kind of signal 

 which goes from nucleus to cytoplasm is the 



Schemel 



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Decision - making Bodies Inside a Cell 



messenger RNA. The production or the trans- 

 mission of this signal can be blocked by inhibi- 

 tors such as actinomycin-D. The use of this 

 inhibitor has provided us with much needed 

 information about communication via m-RNAas 

 evidenced in many of the talks given here. As 

 to the biochemical nature of the cytoplasmic 

 signals to the nucleus, the following experi- 

 mental systems may be useful: hormonal con- 

 trol of protein synthesis in higher organisms; 

 inductive enzymes formation in bacteria; and 

 perhaps antibody formation in response to 

 antigens. Research in these areas is of the 

 utmost importance. 



Because of problems of presentation, 

 Scheme I is drawn in an awkward manner as a 

 reminder that the cell has spherical rather 

 than bilateral symmetry. This has an impor- 

 tant consequence. An external stimulus can 

 not enter the nuclear region without passing 

 through the cytoplasm. Nucleus and cytoplasm 

 undoubtedly differ in sensitivity to external 

 stimuli. Some stimuli may be more harmful 

 to the nucleus than to the cytoplasm even though 

 the stimulus has first passed through the 

 cytoplasm. Nevertheless, we should remember 

 that external effects on the cell always pass 

 through the cytoplasm and therefore are sub- 

 ject to possible control from the cytoplasm. 



The elegant experiments of Dr. James 

 Gregg presented in the workshop and the dis- 

 cussion thereafter, enables us to assume for 

 the moment that in order for this kind of deci- 

 sion making process (Scheme I) to take place 

 no cell division is necessary. Thus, the barrier 

 and the sensory systems between the nuclear 

 and the cytoplasmic bodies need not be torn 

 down in order for the decision to be made. 

 This, of course, may not be true in all cases 

 but the assumption will at least simplify dis- 

 cussion of our scheme. We have a cell which 

 is going along in a dynamic state. Suddenly, it 

 receives a new challenge or it reaches a cer- 

 tain state. It then makes a decision to embark 

 on a course different from its original one. 

 Where is the location of the decision making 

 process and what is its pathway? 



I shall try to describe three different 

 pathways by which the decision making process 

 might take place. The first I shall call the 

 genetic-nuclear-determinant path. In this case, 

 there is only one dominating influence in the 

 cell. The decision is made in the nucleus in 

 accordance with preinscribed genetic program 

 and all the cytoplasm can do is to listen to the 

 command of the nucleus. The best biological 



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