CHANGES IN LIPIDS OF CELLULAR MICROSTRUCTURES 143 



following irradiation and subsequently decreased; the phospholipid 

 content of the same celhilar niicrostructures di-opped slightly; at this 

 point the total lipid content of the hyaloplasm is increased. 



With the aim of ])romoting the study of disturbances initiated by 

 radiation injury in the lipid complexes of cellular organelles and in 

 their lipid metabolism in general, we investigated the quantitative 

 ratio between various lipid fractions of the entire cytoplasm and the 

 hyaloplasm of the liver cells in rabbits exposed to the action of y-rays of 

 60Co at a dose of 1,000 r and a dosage rate of 500 r/min (Blokhina and 

 Doemin, 1959). This radiation dose is sufficient to give an acute form 

 of the radiation disease in rabbits. Most of the animals died within 5 to 7 

 days of exposure. 



As a rule in every experiment one of two rabbits (of equal weight) was 

 irradiated ; the other was used as a control ; 16 hr before the experiment 

 both animals were deprived of food and after irradiation both animals 

 were killed with an air embolism. The livers of the rabbits were washed 

 with isotonic saline and homogenized with a ten-fold amount of isotonic 

 sucrose. Cytoplasm and hyaloplasm preparations of the rabbit liver cells 

 were made as described in detail earlier (Ilyina et al., 1957). 



The dry weight of the preparations (5 ml) was established after 

 elimination of sucrose by dialysis for 48 hr against distilled water. The 

 contents of the dialysis bag w^ere transferred to a weighing bottle and 

 dried at 60°C to constant weight. 



The content of three lipid fractions was measured in the cytoplasm 

 and hyaloplasm preparations. These fractions were called "free", 

 "loosely bound" and "firmly bound" lipids. 



The determination of the "free" lipids was made:-10 ml of the cyto- 

 plasm or hyaloplasm preparations was shaken with 25 ml of petroleum 

 ether at room temperature for 3min; after centrifugation at 2,000 

 r.p.m. for 5 min the top ether layer w^as decanted into a separate 

 flask. A similar extraction with new portions of ether was repeated 

 4 times. The combined lipid ether extracts were evaporated at room 

 temperature to minimal volume and the lipid contents determined in 

 an aliquot by a modification of Bloor's technique (1947). 



The total lipid content was estimated by utilizing another 10 ml of 

 sample of the cytoplasm or hyaloplasm preparations. At first the lipids 

 were extracted according to the method of Folch et al. (1951). After 

 numerous extractions with the aid of methanol-chloroform mixtures, 

 the residue was subjected to alkali hydrolysis with a 30-fold quantity 

 of 8 per cent alcoholic alkali solution for 40 hr; the fatty acids were 

 extracted from the hydrolysate by Romantzev's method (1952). The 

 content of total lipids was determined by adding the amount of lipids 



