178 



Embryogenesis: Preparatory Phases 



Entenman et al. ('38), Chargaff ('42) and 

 Lorenz et al. ('43) (see also Hevesy, '47). 

 It is known, in the first place (see Needham, 

 '31), that these compounds are formed by 

 hens when the diet contains phosphorus in 

 inorganic form. The organic phosphorus 

 compovmds are evidently synthesized by the 

 hen. It is also known that the serum of lay- 

 ing birds, as well as of reptiles and fish, con- 

 tains larger amounts of phosphatides and 

 phosphoproteins than are present in the 

 serum of the males or nonlaying females 

 (Roepke and Bushnell, '36; Laskowski, '38; 

 Landauer et al., '39; Zondek and Marx, '39; 

 Riddle, '42; Chaikoff and Entenman, '46). 



in the albumin and shell. Other experiments 

 show that active phosphatides are only found 

 in laid eggs that had been in the ovary at 

 the time of injection, and tests up to 6^ 

 days after injection show a progressive in- 

 crease in the activity of this fraction. 

 Another control, soaking eggs for one day 

 in a solution of labelled inorganic phosphate, 

 showed no incorporation of P^^ in the 

 phosphatides extracted from the yolk, al- 

 though active inorganic phosphate had pene- 

 trated it. 



In the experiments of Entenman et al. 

 ('38) determinations were also made of the 

 relative amounts of P^^ incorporated in the 



Table 10. Relative Radiophospholipid of Tissues of Laying and Nonlaying Birds at 6 and 12 

 Hours after Injection of 50 mg. of Phosphorus as Na2HP0i Containing 10^ Ra- 

 dioactive Units [1 Radioactive Unit = 2xl0~^~ curie) (from Entenman et al., 

 '38) 



6 HRS. 



12 HRS. 



NONLAYING 



6 HRS. 



12 HRS. 



Total radiophospholipid of bird as per cent 



administered P'^ 3 . 62 



Per cent of total radiophospholipid found in: 



gastrointestinal tract 10 



muscle + bone + blood 32 



reproductive system (ovary, oviducts, and yolks) 11 



liver 44 



4.55 



3.25 



4.57 



This suggests that these substances might be 

 synthesized in some other organ than the 

 ovary. Hevesy and Hahn ('38) determined 

 the content of radioactive phosphorus in 

 inorganic and organic form in the plasma, 

 liver, intestinal mucosa, ovary, yolks and 

 eggs of hens at various times after the sub- 

 cutaneous injection of labelled sodium phos- 

 phate. Table 9 gives the results of a set of 

 analyses performed 5 hours after the injec- 

 tion. The labelled phosphorvis content of 

 the phosphatide-phosporus is found to be 

 relatively low in the ovary and the yolk 

 of an ovarian egg at this time. It is much 

 higher in the plasma and highest in the liver. 

 Since the oocytes are growing rather rapidly, 

 in contrast to the liver, the experiment 

 gives strong indication that the phosphatides 

 are synthesized in the liver and transported 

 through the plasma to the ovary. Various 

 controls were run in these experiments. No 

 labelled phosphorus was found in the phos- 

 phatides of the yolk of an egg laid at 5 

 hours after the injection, although active in- 

 organic phosphate is found in it as well as 



phosphatides of variovxs parts of the laying 

 and nonlaying hen. The results of one of 

 their experiments, given in Table 10, show 

 that about half of the P^--containing phos- 

 phatide of the bird is present in the liver 

 although this organ contains only about 5 

 per cent of the total phosphatides of the 

 bird. In other experiments from Chaikoff's 

 laboratory the incorporation of P'^^ in phos- 

 phatides and other compounds of the yolk 

 was shown to be expressable as a function 

 of the rate of growth of the yolk and the 

 amount of P^^-phosphatide present in the 

 plasma at the time (Lorenz et al., '43). 

 These workers and others have also shown 

 a high rate of labelled phosphatide forma- 

 tion by liver slices of male birds, which 

 could be increased significantly by injec- 

 tion of estrogenic hormone (diethylstil- 

 bestrol) (see Taurog et al., '44). 



The incorporation of P^^ i^^Q i]jq vitellin 

 as well as in the free phosphatide and lipo- 

 vitellin (a complex containing about half 

 of the total phosphatide of the yolk) of the 

 growing oocyte has been investigated by 



