HISTOLOGICAL CHANGES 



accumulation of ribonucleotide absorption and often a definite decrease, presumably 

 due to interference with less radio-sensitive processes in the disturbance of cellular 

 nucleic acid metabolism (see also work to be published by L. D. Hamilton). Subse- 

 quent experiments have detected increased cytoplasmic absorption in a biopsy of a 

 human basal-celled carcinoma of the skin taken immediately after delivery of 40 r 

 of gamma radiation in 43 minutes. 



Since 1940 I have been carrying out experiments on the irradiation of tissue cultures 

 mainly of chick fibroblasts in situ on the stage of the ultraviolet microscope. Very 

 little of this work has yet been published because of the difficulties of precise quanti- 

 tative interpretation. It is of interest to include the result of an experiment {Figure 2) 

 in which chick fibi^oblasts in culture (provided by Mrs. I. Simon-Reuss) received a 

 dose of 435 r of X-radiation delivered in 6 minutes. There appears to be an increase 

 in cytoplasmic absorption at 2,537 A and also an increase in diffusible absorbing 

 material in the photograph taken at between 2-6 minutes after the end of the X-ray 

 exposure. At about 87 minutes after the irradiation the characteristic absorption 

 is lost, the cells are breaking down and there appears to be gross damage to the 

 chromosomes visible. A great many control experiments were carried out which 



Figure 2. Serial ultraviolet photomicrographs of living cluck Jibroblasts before and after roentgen 

 irradiation in situ on the microscope stage at the times given. 6mm quartz monochromat, N.A. 0-70, 

 wavelength 2,537 A. Roentgen ray dose was 435 r delivered in 6 minutes {87kvp, no added filter ; 



irradiation through quartz coverslip). 



showed that the ultraviolet radiation used for these exposures did not produce 

 comparable effects. 



Recently G. H. Hjort, working with me in Cambridge, has used the methods of 

 ultraviolet photomicrography to study the effects of total body irradiation with doses 

 between 100 and 600 r on the lymphocytes of lymphoid tissue in adult rats. The 

 sections were prepared from frozen dehydrated tissue. It has been found that an 

 increase in nucleotide type of absorption mainly in the cytoplasm can be detected 

 as early as 15 minutes after irradiation and this biochemical change appears before 

 any morphological changes can be detected. There is, however, wide variability 

 in the behaviour of different cells in respect of these changes and much further 

 quantitative examination of the experimental material is necessary. There is 

 definite evidence that these early metabolic changes can be prevented by the adminis- 

 tration of [3-mercaptoethylamine before irradiation. Details of this investigation 

 will be published later. 



REFERENCES 



^ Bacq, Z. M. and Alexander, P. Fundamentals of Radiobiology. London, Butterworths, 



1955. Liege, Thone ; Paris, Masson. 

 2 BAC(i, Z. M., Herve, a. et Scherber, F. Arch. Mem. Pharmac. Therap. 1953, 94 93. 



314 



