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Figure 9 Alterations in serum urea and protein in 

 captive Squalus acanthias. 



Histological alterations in interrenal tissue accompanying an increase in 

 secretory activity have been described for a number of osteichthyean fishes 

 (Weatherley 1963; Leloup-Hatey 1964; Rasquin and Rosenbloom 1954; 

 Olivereau 1962; Fontaine and Olivereau 1957; Fagerlund, McBride, and 

 Donaldson 1968; Hill and Fromm 1968; Wedemeyer 1969). The sequence 

 described above— (a) increase in vascularity and nuclear hypertrophy, (b) 

 decrease in cell height, lipid content, and cholesterol, (c) increase in baso- 

 philic cells with low lipid contents, and (d) disorganization of the gland— is 

 consistent with their descriptions. The basic observations of Dittus (1941) 

 on stimulated interrenals of Torpedo are paralleled in this report. However, 

 mitoses of parenchymal cells were not found in Squalus interrenals. 



Fraser (1929) described lipid secretion in the interrenal of Scy Ilium as a 

 complex process involving a cycle of (a) lobular hypertrophy, (b) rupture, 

 (c) acinus formation, (d) acinus disintegration, and (e) reformation of lobule. 

 Aboim (1946) saw no comparable stages in his specimens but did report 

 hypertrophy of cells followed by rupture and regeneration. No similarity 

 exists with the secretory cycle of Squalus interrenals reported here, and 

 further observations should be made on interrenal secretion in Scy Ilium. 



