88 CYTOCHEMISTRY OF ALDEHYDES 



other hand should enable all the various artefacts to be dis- 

 tinguished clearly. 



Aldehydes in Fat Transport and Metabolism 



Introducton 



Feulgen and Voigt (1924) showed that aldehydes of fatty 

 type were to be found in many biological materials. My interest 

 in these substances was aroused by the fact that the Rous chicken 

 sarcoma virus is said to contain a considerable quantity of acetal 

 aldehyde. Thus there appears to be a possibility that Rous virus 

 could be localized in cells by analysis of the distribution of alde- 

 hyde. A preliminary examination of this possibility was made 

 together with Dr. L. M. J. Rinaldini. We found that the situa- 

 tion was complicated by the fact that the Rous tumour is char- 

 acteristically heavily infiltrated with fat, and that there appeared 

 to be an association between fat droplets and sites of high alde- 

 hyde activity, particularly in the necrotic areas. As will be seen 

 later, there can be no doubt that aldehydes are intimately con- 

 cerned with fat metabolism, so that the occurrence of long-chain 

 aldehydes in the Rous tumour can hardly be taken as diagnostic 

 for the localization of virus. It may be, of course, that sites con- 

 taining the aldehyde are also rich in virus, and that one of the 

 major consequences of infection of cells with the Rous virus is 

 a disturbance of fat metabolism. 



Comparatively little is known of the steps involved in the syn- 

 thesis and degradation of the higher fatty acids, such as palmitic 

 or stearic acid. It is known that the naturally occurring fatty 

 acids almost invariably contain an even number of carbon 

 atoms and that, when the fatty acids are degraded, they usually 

 lose carbon two atoms at a time. A suggestion which has, there- 

 fore, been considered in connection with fat synthesis is that it 

 proceeds by the condensation of aldehydes, with acetaldehyde as 

 the main condensing agent, in an aldol reaction: 



R-CH 2 .CHO + CH 3 -CHO -> R-CH 2 -CHOH-CH 2 -CHO 



The biochemists have not found it possible to find acetalde- 

 hyde performing this function in tissues. However, it is quite 

 certain that some 2-carbon compound, perhaps acetyl phosphate, 



