408 V. BLOOD LIPIDS 



It has also been claimed that fat-soluble dyes, when fed' to pregnant ani- 

 mals, appear in the fetus. 317 However, this conclusion has been denied by 

 at least three groups of workers, 320-322 who were unable to demonstrate the 

 appearance of dye in the fetal fat after it had been fed to the mother. 

 However, these negative results do not necessarily prove that fat cannot 

 be transmitted across the placenta, but only that a non-physiological dye is 

 unable to penetrate this barrier. 



A number of recent studies have given strong positive evidence that the 

 lipid in the maternal blood is transferred to the fetus. Bickenbach and 

 Rupp 323,324 demonstrated that the composition of the maternal and that of 

 the fetal fat of rabbits were identical after the amyl or methyl ester of oleic 

 or palmitic acid had been injected into pregnant rabbits. Miura 326 also 

 found that the iodine number of fetal fat, as well as that of the maternal 

 fat, was increased when linseed oil was given to the mother, while this 

 index was lowered in the fat of both mother and fetus when coconut oil 

 was fed. Moreover, Chaikoff and Robinson 326 showed a correspondence 

 between the iodine numbers and the saturation of the fat fed; however, 

 the maternal fat was far more sensitive to the dietary lipid than was the 

 fetal fat. Sinclair 327 confirmed these observations, while McConnell and 

 Sinclair 328 demonstrated the passage of the unnatural fat, elaidic acid, into 

 the fetuses of rats. Popjak 329 reported that a marked increase in the fat 

 content in the decidual cells of the maternal portion of the placenta occurs 

 in rabbits fed diets high in cholesterol during the last three weeks of preg- 

 nancy. This lipid storage in the placenta apparently interfered with the 

 nutrition of the fetuses, as they were one-third lighter than usual. Neutral 

 fat was actually lower in these fetuses than in the controls. It is suggested 

 that this may have resulted from a partial blockage of the placenta to the 

 transfer of fat precursors. The consensus of the experimental evidence is 

 that, under certain conditions, fetal fat may be derived from that of the 

 mother, although part may be synthesized within the fetus. 



According to Boyd and Wilson, 330 phospholipids and cholesterol (both 



320 S. H. Gage and S. P. Gage, Anat. Record, 3, 203-204 (1909). 



321 L. B. Mendel and A. L. Daniels, J. Biol. Chem., 13, 71-95 (1912-1913). 



322 E. J. Baumann and O. M. Holly, Am. J. Physiol, 75, 618-632 (1926). 



323 W. Bickenbach and H. Rupp, Klin. Wochschr., 10, 63-64 (1931). 



324 W. Bickenbach and H. Rupp, Z. Geburtshiilfe u. Gyndkol, 100, 1-16 (1931). 



325 K. Miura, J. Biochem. (Japan), 25, 579-593 (1937). 



326 1. L. Chaikoff and A. Robinson, /. Biol. Chem., 100, 13-26 (1933). 



327 R. G. Sinclair, Am. J. Physiol., 103, 73-74 (1933). 



32 * K. P. McConnell and R. G. Sinclair, /. Biol. Chem., 118, 123-129 (1937). 



329 G. Popjak, J. Physiol, 105, 236-254 (1946). 



33 ° E. M. Boyd and K. M. Wilson, J. Clin. Invest, 14, 7-15 (1935). 



