The study of the effects produced by irradiation upon all biological entities has resulted in the accumulation of a large amount of data. Being unsystematized, this information has helped but little to resolve the many physiological and therapeutic problems connected with radiation. New light on these problems can be provided by relating them to the basic concepts we have been discussing.

Other factors also have led us to study the problem of radiation. Its widespread use for the treatment of cancerous lesions with indisputable success in many cases, and the fact that some of radiation's effects appear to be quite similar to those induced by the administration of different lipids, led us to investigate the mechanism through which radiation works and, especially, the possible relationship between radiation and lipids. We will discuss here briefly, some of the results of this investigation.

Irradiation Of Lipids

We began by trying to determine the effects of radiation upon normal lipids in vitro. As always, we tried to guide the research by theoretical considerations. Investigation of in vivo and in vitro effects of radiation upon proteins in general showed that histones, protamines and alkaline amino acids are most sensitive. These constituents of complex protein molecules have positive electrical character. This relationship between sensitivity to radiation and positive electrical character provided a clue as to where to look in fatty acid molecules for changes induced by radiation. Several positive centers are present in the energetic structure of fatty acid molecules. One is represented by the carbon of the carboxyl. Its positive character is due to its bond to two oxygen atoms. This would explain the exaggerated ionization which takes place at the level of this carboxyl group.

Other positive centers also can be recognized. We have mentioned previously that the positive character of carbon propagates through the chain in an induction effect that causes alternate odd carbons to be positively charged, although the strength of the positive character decreases rapidly with distance from the carboxyl. Since a double bond greatly enhances the energetic character of the carbons linked by it, induction will result in a center in which a more intensive positive carbon is present. Study of the reactions that take place at the double bond in a fatty acid molecule confirms this view, since an electrophilic character predominates at this point. When treated with sodamine, carbons forming double bonds combine selectively with it, indicating the positive electrostatic character of this formation. ConsequenUy, we thought that the effect of irradiation would be most likely to occur here. This has been confirmed experimentally. We could demonstrate that radiations cause changes especially in the reciprocal position of the double bonds in the molecule.

Irradiation and conjugation in vitro

Fig. 79. Irradiation and conjugation in vitro. Spectral analyses in ultraviolet of samples of commercially available linoleic acid (with small amounts of linolenic acid present) irradiated with gamma rays from 80 mgr of platinum filtered radium/10 cc, for 6 days at room temperature. For the analyses, dilutions of 0.002% in alcohol, with alcohol as reference, were used. The absorption spectra of the irradiated (--) linoleic acid compared with the nonirradiated (....) shows the appearance of conjugated trienes recognized through the characteristic peaks.

The results of this research were originally presented before the Fifth International Congress of Radiology in London in July 1951. We will limit ourselves here to a short resume of the procedures and findings: