ac tive ions through the skin of fish in 

 storage. The radioactivity of the tissues 

 of tuna contaminated with radioactive fall- 

 out material or in fish from water contain- 

 ing this material has been measured, 

 including autoradiography of the various 

 tissues (Tsujii, personal communication), 

 but published accounts are not available. 



Accordingly the following experiments 

 were undertaken. Miss Maureen Downey 

 assisted in the preparation of samples and in 

 measurement of their radioactivity. 



MATERIALS AND METHODS 



The tuna were obtained by offshore troll - 

 •ng. After capture they were "iced down" 



and brought to the laboratory where they were 

 cepi iced and refrigerated until they were 



used for the experiments 8 to 20 hours after 



being caught 



89 90 

 The isotopes employed were Sr ' 



added to the sea water as strontium chloride; 



-Ba' J/ , added as cesium chloride; and 



p u; lvJC-i{j 1 106 > added as ruthenium trichloride 



in acid solution. The radioactive materials 



were obtained from the Oak Ridge National 



Laboratory under allocation by the Atomic 



Energy Commission. 



The presence of the radioactive daughters, 

 Ba 137 and RhlOo did not affect the measure- 

 ments since they are both of very short half- 

 life and secular equilibrium is reached in a 

 very short time . 



I here was a small amount of Sr90 present 

 th the Sr 89 . This was taken into considera- 

 i on in the experiments with due allowance 

 lade for the return to secular equilibrium 



.90 



90 



Ii 



between the Sr™ and its daughter, Y 

 is recognized that both radioisotopes of 

 strontium were present, although reference 

 nade throughout the paper only to Sr 89 



In the first series of experiments, cut 

 pieces of skin of the little tur.ny were placed 

 across the mouths of large plastic test tubes 

 of which the bottom portion had been cut off, 

 and the skin tightly held in place by winding 

 thread around the lip of the tubes . Sea water 

 containing strontium -89, cesium- 137, or 

 ruthenium -i 06 was placed in the tubes and 

 the mounted skin immersed in a beaicer of 

 the same sea water, to which no isotopes 

 had been added The beakers with their 

 tubes were kept in a domestic -type refriger- 

 ator at about 38° F . It was not convenient 

 to arrange for continuous stirring. The 

 outer surface of the skin faced the inside of 

 the lube containing the radioactive sea water. 

 The volumes were 30 ml. inside the tube and 

 100 ml. outside. Samples of the water were 

 removed periodically, dried in a stainless - 

 steel planchet under a heat lamp, and their 

 radioactivity measured at a fixed distance 

 below a glass Geiger-Mtiller tube of 30 

 mg./cm . thickness in a hoiizontal lead 

 shiel ,i 



The percentage of equilibrium reached 

 after intervals of time was calculated using 

 the radioactivity expected from dilution of the 

 one liquid with the other if there were no 

 membrane separating the two 



In the second series of experiments, 

 circular absorbent cellulose pads, 47 mm . 

 in diameter, were soaked in sea water to 

 which were added various concentrations of 

 strontium -89, cesium-137, or ruthenium-106 

 These pads were then placed in contact with 

 the skin of the iced fish. They were usually 

 placed just above the lateral line with two 

 pads on each side of the fish and covered with 

 the concave side of a watch glass held in place 

 by a heavy rubber band. The fish were again 

 iced, and the container of crushed ice and 

 fish was placed in a refrigerator Care was 

 taken to prevent the fish from becoming im- 

 mersed in ice water. Periodically a fish was 

 taker, and the area under the pads dissected, 



