X. EFFECTS OF DEFICIENCY 99 



turnover rate of phosphorii.s-containiiij;- (•()mi)oiiiKls after the administration 

 of P'". Single feedings of choline increased the activity of the choline-contain- 

 ing phosphohpids.^^- Measurements on samples of blood and on liver l)iopsy 

 specimens after the administration of choline and of P^- led to the conclusion 

 that the removal of IWcv fat under the influence of choline does not involve 

 increased transport of fat from li\'er to peripheral tissues via plasma phos- 

 pholipids.^^^ No increase in the calculated turnover rates of plasma lecithin 

 or sphingomyelin was found, contrary to a previous conclusion on this 

 point.'-^^ However, determinations of rates of disappearance of these two 

 phospholipids from plasma showed that the turnover rate of lecithin was 

 t\ye times as great as that of sphingomyelin. ^"^^ It was suggested that choline 

 acts on the utilization of fat within the liver itself and that glycerylphos- 

 phoric acid is a precursor of lecithin. ^''^ The greater activity of liver lecithin 

 phosphorus than that of cephalin rules out the possil)ility of synthesis of 

 lecithin by the methylation of cephalin. 



Liver lipids were unclianged after hypophysectomy even though the dogs 

 were observed as long as 32 months.'^*^'^ Thyroidectomy, however, resulted 

 in fatty livers. The increase in lipids was more rapid and of greater magni- 

 tude in force-fed dogs if both th^a'oid and hypophysis were removed. The 

 hepatic changes were prevented for the most part by choline, but this sub- 

 stance did not prevent an increase in blood lipids. 



Davis has reported a depression of cobalt-induced polycythemia in dogs 

 by choline^*^*^ and has extended his findings to the involvement of choline in 

 an experimental anemia and in pathological changes in the nervous system 

 related to changes observed in pernicious anemia. ^^^ ■ ^^'^ This effect of cho- 

 line, ascribed by Davis to a vasodilator action on bone marrow arterioles 

 wdth a resulting decrease in hematopoiesis,^^^ has not been confirmed.^''" 

 Choline was ineffective in reducing arteriosclerotic lesions in dogs fed a 

 diet containing added cholesterol and thiouracil."^ A limited beneficial ac- 

 tion of choline was observed in dogs with fat emboli produced by bone mar- 

 row curettage. ^^' The latter study was prompted by the finding that the 



362 C. Entenman, I. L. Chaikoff, and H. D. Friedlander, J. Biol. Chem. 162, 111 (1946). 

 3" D. B. Zilversmit, C. P^ntenman, and I. L. Chaikoff, /. Biol. Chem. 176, 193 (1948). 



364 D. B. Zilversmit, C. Entenman, and I. L. Chaikoff, ./. Biol. Chem. 176, 209 (194S). 



365 C. Entenman, I. L. Chaikoff, and F. L. Reichert, Endocrinology 42, 210 (1948); 

 C. Entenman, I. L. Chaikoff, F. L. Reichert, and T. Gillman, ibid. 42, 215 (1948). 



366 J. E. Davis, Am. J. Physiol. 127, 322 (1939); /. Pharmacol. 70, 408 (1940). 



367 J. E. Davis and D. E. Fletcher, ./. Pharmacol. 88, 246 (1946). 



368 J. E. Davis, Science 105, 43 (1947). 



369 J. E. Davis, Am.. J. Physiol. 142, 65 (1944). 



3'» M. F. Clarkson and C. H. Best, Science 105, 622 (1947). 



3" J. D. Davidson, W. Meyer, and F. E. Kendall, Circulation 3, 332 (1951). 



3'2 E. M. Monson and C. Dennis, Proc. Soc. Expil. Biol. Med. 70, 330 (1949). 



