106 



S. S. COHEN 



by indole acetic acid also appears to be mediated through effects on nucleo- 

 tide metabohsm, since benzimidazole, an analog of adenine, inhibits the 

 lAA-induced elongation. Since benzimidazole also stimulates water intake, 

 the cells swell in the transverse direction and become barrel-shaped (Galston 

 et al., 1953). The structures of these compounds are presented in formula 

 (III). 



CH^COOH 



N^>^ \ C C 



CH 



Indole Gcetic ocid 



(III) 



In addition to these effects of plant hormones, some hormones in differ- 

 entiated animal systems have also been imphcated in the control of polymer 

 synthesis. For example, some steroid hormones, such as estradiol, induce a 

 marked synthesis of RNA and protein in the uterus, followed only somewhat 

 later by an mcrease in DNA synthesis (Mueller, 1957). The first 6 hours are 

 characterized by an imbibition of water. As presented in Fig. 17, there is a 



200 



150 



100 



50 



-50 



mg protein/yLiM thymine 



/iM thymlne/uterus 



6 12 18 24 



Hours after estradiol 



Fig. 17. Alteration in uterine composition following single dose of estradiol. Ten /xg. 

 estradiol injected intravenously at zero time; DNA measured as /^imoles thymine. RNA 

 measured as /Limoles uridine and expressed as ratio, /xmoles uridine per /xmoles thymine 

 during the first 24 hours following hormonal treatment. (Mueller, 1957.) 



rapid synthesis and accumulation of RNA in the mterval from 6 to 24 hours 

 after administration of the hormone; thus RNA synthesis is then followed 



