o) In spite of the importance of fatty acids and anti fatty acids, they represent only one part of the mechanism through which radiation acts. The direct and indirect action of radiation on other constituents also must be considered. The influence exercised upon these constituents can be largely related to various changes. There is a quantitative relationship, for instance, between induction of mutations and the direct impact of radiation on proteins. Changes in fatty acids also are the result of such a direct impact. It appeared interesting to ascertain how much and which of the pathological changes that follow irradiation are due to the direct impact upon lipids and how much to the impact on the other constituents.

The three kinds of biological activity of radiationóthrough other constituents, through changed fatty acids, and reactional through anti fatty acidsócould be studied at different levels of the organization. We note here a few of the results of these studies.

Below the cellular level, the influence of lipids seems to decrease, causing the direct effect of the radiation on other constituents to appear predominant. For nucleo proteins and below them, only this last effect seems to occur, the changes induced apparendy affecting histones and alkaline amino acids. The close mathematical relationship between the amount of radiation and mutation would seem to indicate that, even at the gene level, only the effect upon constituents has to be considered.

The introduction of anti fatty acids into the medium in which tetra hymena or suspended cells (as from ascites tumors) were irradiated, served to distinguish the direct effects from those induced through fatty acids. In the presence of anti fatty acids, vacuolization and even changes in the nuclei seen in the irradiated controls are prevented. The fact that these changes, which characterize the radiomimetic effects, were reduced by ami fatty acids, indicates the role of fatty acid changes in the pathogenesis of these effects. Among other agents tested, the insaponifiable fraction of organs, and especially of placenta, appeared to be most effective in preventing radiomimetic effects. The high alcohols or glycerol also showed such influence, but to a lesser extent. In complex organisms, the difference of the effect of radiation on fatty acids and on other constituents is increased at the higher levels. At the systemic level, this effect is almost limited to the fatty acids.

The introduction of polyunsaturated fatty acids to the medium greatly increase the toxic effects of radiation, as compared to controls exposed to radiation or fatty acids alone. The proportion of mutations was not changed, however.

The ultimate effect of radiation at different levels depends upon the relationship between three factors: changed fatty acids, other changed constituents, and the intervention of adrenals. The effect of the adrenals is progressively more manifest at the higher levels of the organization. At lower levels, the direct intervention of the abnormal lipids becomes more important than the adrenal response, the latter being less able to act at these levels. At the cellular level, the influence of lipids is still predominant. At the tissular level, the direct lipid effect is still striking, while the influence of the adrenal response is limited to the connective tissue. Although the effect upon the lymphatic constituents (as part of the adrenal response) is important at the organic level, the steroid response becomes more important at the systemic level.

p) On the other hand, it appears possible to vary the amount of the lipidic effect by changing the nature of the radiation. The use of more penetrating rays or of different corpuscles has to be investigated in terms of the relationship between influence upon fatty acids and the effect on other constituents. It could be seen that, in corresponding dosages, the less penetrating radiations had a greater influence upon fatty acids than the more penetrating. The fact explains the reduction of radiation burns directly related to the intervention of fatty acids. Similarly, in a systemic procedure, such as teleradiotherapy, the effect on other constituents is reduced as compared with the direct influence exerted upon the fatty acids.

It is possible that radiations using neutrons would induce an increased direct impact on other constituents without a correspondingly increased effect upon the systemic fatty acids. The skin effect, which is minimal with these radiations, would indicate little intervention of fatty acids.

The unequal part played by lipids at the different levels can be utilized to obtain variations in radiation effects. If effects upon the lowest levels of the hierarchic organization, such as upon histones and basic amino acids, are desired, radiation could very well be the tool to be chosen, because of the small amounts of lipids present at these levels. If the influence could be limited to such action, radiation could be considered ideal for such therapeutic effects. Unfortunately, this is not possible even when very penetrating radiation is used, and the effect of radiation upon lipids still constitutes one of the principal factors which must be considered when radiation is used as a therapeutic weapon.

Thus radiation is not the ideal means for affecting the subchromosomal level, in spite of the fact that it may, through its effect upon proteins, have a profound influence below this level. Its ability to cause a conjugation of fatty acids represents the serious obstacle to its use. In view of this, the effect of radiation upon lipids actually can be considered as an undesirable epiphenomenon whenever the purpose of the therapy is to achieve a local effect at the lower levels. Frequently, the changes which require discontinuation of radiation therapy can be recognized to correspond to abnormal local or systemic metabolism produced by the abnormal fatty acids.

It must, however, be recognized that the appearance of abnormal fatty acids has some advantages even upon protein effects, since indirectly they can make local tissues more sensitive to radiation. We have previously noted that abnormal fatty acids cause changes in the tissue and cellular metabolism which lead to local alkalosis. This local pH change may have favorable results by acting upon the amphoteric proteins and by increasing the positively charged members which apparently are the only ones sensitive to radiation. Indirectly, the intervention of the abnormal fatty acids will thus increase the sensitivity of tissues to radiation.

Before going further, we wanted to emphasize an aspect of the off balance D for which the study of shock and radiation brought an important contribution. A separation can be made between two phases of offbalance D, one in which oxygen is principally fixed and another in which chlorine is fixed. The first phase, "oxygen," has as characteristic the appearance of peroxides in the urine, and clinically has little noxious manifestation. The other phase, "chlorides," with fixation of this ion leads the serious manifestations as seen, for instance, in shock. For this reason, in radiation the disappearance of urinary peroxides with persisting offbalance D, as seen in the other patterns, will indicate a passage from phase "oxygen" into phase "chlorides," which corresponds to the appearance of a serious condition. (See also Note 4, Chapter 10)