90 CYTOCHEMISTRY OF ALDEHYDES 



also large areas of the liver sections which appeared to be free 

 from aldehyde. These areas were also lacking in fat droplets. 



When the animals were placed on a diet rich in fat, there was 

 an increase in the number of fat droplets to be seen in the 

 hepatic cells, and a concomitant increase in the amount of alde- 

 hyde found in the liver. All the droplets were surrounded by a 

 spherical shell of aldehyde (e.g., Plate XII, Fig. A). 



Some animals were also starved up to 6 days, although allowed 

 free access to water. It is known that under such conditions fat 

 passes from the fat depots of the body to the liver, where it is 

 broken down into carbohydrates. It was found that under these 

 circumstances the liver becomes heavily infiltrated with fat, and 

 gives an intense aldehyde reaction, with a high concentration of 

 aldehyde as a spherical shell surrounding the fat droplets. This 

 result and the result recorded in the preceding paragraph make 

 it clear that long-chain aldehyde is closely connected with the 

 conversion of fat to carbohydrate. 



Another group of animals was fed on a diet containing protein 

 and a high concentration of carbohydrate, but no fat. It is 

 known from isotope experiments that under these conditions no 

 fat is lost from the fat depots, and that fat is synthesized in the 

 liver from carbohydrate. When animals were killed at various 

 times after being placed on this carbohydrate-rich diet, it was 

 found that the initial response was a sharp decline in the amount 

 of aldehyde in the liver, together with the loss of fat drops from 

 the liver. After 2 or 3 days on this diet, a considerable amount 

 of aldehyde appeared diffusely distributed in the cytoplasm. Fat 

 droplets reappeared and were closely associated as a general rule 

 with a spherical shell of aldehyde. Some fat droplets, however, 

 did not contain aldehyde. On this diet aldehyde was also fre- 

 quently found in the bile canaliculi. It was concluded that it 

 was probable that there is also a close connection between long- 

 chain aldehydes and fat synthesis, although the evidence for this 

 is not quite so strong as is the case for the relationship between 

 fat degradation and long-chain aldehydes. 



All the experiments reported above, both those on the liver and 

 those on the intestine, were performed on material which had 

 been fixed for little more than 2 hours. The intensity of the alde- 

 hyde reaction was not influenced by conducting fixation, etc., 

 under anaerobic conditions. 



