a) Radiation of polyunsaturated fatty acids in vitro induces a conjugation of their double bonds, which increases quantitatively with the intensity of the radiation. This has been shown by spectral analysis and by the oxidative fission method. (Note 1) Samples of commercially available linoleic acid which, through analysis, have been found to contain variable amounts of linolenic acid, or cottonseed oil were treated with radiations of different sources, such as radium in platinum needles for gamma radiation, in monel metal for beta radiation, thorium X for alpha radiation and X rays. Table XIV shows the results of analysis of the oxalic index. Figs. 79 and 80 show the direct spectral analysis of the samples before and after irradiation as well as the result of their chemical conjugation.

Comparison of direct spectral analyses shows the appearance of an important amount of conjugated trienes in the irradiated samples. Analysis after chemical conjugation of irradiated and control samples shows a greater amount of trienes in the irradiated sample indicating that a process of desaturation also has taken place through irradiation.

A direct relationship was observed between conjugation and amount of radiation. (Table XV) The quantity of conjugated isomers, determined by spectral analyses and measured by the oxalic index was seen to increase as radiation was increased either by prolonging exposure time or increasing the amount of radium used.

b) Irradiation of fatty acids appears to induce the appearance of conjugated trienes. When a mixture of polyunsaturated fatty acids, such as those found in cod liver oil, was exposed to a radiation source consisting of platinum filtered radium, the changes were limited to the appearance of conjugated trienes. Conjugated dienes were seen in only some experiments and then only in small amounts. The presence of conjugated members was recognized through their characteristic absorption peaks in ultra violet analysis. When the same mixture of fatty acids was treated by the usual chemical methods employed to produce conjugation, i.e., with potassium hydroxide in ethylene glycol or glycerol (41), the spectral analysis showed that the preparation contained fatty acids having between 2 and 6 double bonds. Figure 81 shows the curves of spectral analysis for such an experiment in which 3 cc. of a cod liver oil fatty acid preparation were treated for six days with 100 milligrams of radium filtered through platinum. In curve "a," of the untreated sample, it can be seen that there is no absorption due to the presence of conjugated members. Curve "b," for the irradiated fraction, shows the typical conjugated trienes, while Fig. 82 shows the result of the chemical conjugation of the nonirradiated preparation with members having from 2 to 6 double bonds.

Irradiation and desaturation

Fig. 80. Irradiation and desaturation. Spectral analyses in ultraviolet (0.002% in ethyl alcohol with alcohol as reference) of untreated sample (-) and of the radiated sample (----) both after alkaline isomerization. They show that the irradiation has induced also an increase in the amount of trienes present, which indicates that a desaturation also occurred.

Table XIV

Fatty Acid

Type of Radiation

Source of Radiation

Exposure Time (Days)

Oxalic Acid mg/g Fatty Acid

Linoleic acid

--

-

-

0

"

gamma

50 mg Radium

6

8.3

"

gamma

120 mg Radium

8

9.9

"

gamma

120 mg Radium

15

13.3

"

beta

25 mg Radium in Monel metal

4

9.85

"

alpha

150 uc Thorium X

7

4.3

"

x ray

5000r daily—deep

27

6.8

therapy machine

"

x ray

5000r daily—deep

53

12.4

therapy machine

Cottonseed oil

-

-

_-

0

"

gamma

80 mg Radium

5

5.2

"

gamma

80 mg Radium

8

8.0

Table XV. Effects Of Irradiation Upon The Quantity Of Oxalic Acid Present After Oxidative Fission

Fatty Acid

Source of Radiation

Exposure time: Days

Oxalic Acid mg/g Fatty Acids

0

0

0

Linoleic Acid

120 mg Ra

4

4.5

10 cc.

"

6

6.2

"

8

9.9

"

15

13.3

"

20

14.4

10 cc.

150 mg Ra

6

8.2

15

16.3

Spectral analysis

Fig. 81. Spectral analysis (0.002% in alcohol) of a mixture of fatty acids from cod liver oil, untreated (----) (a) and irradiated (b) (--) with 100 mg platinum filtered radium/3 cc, at room temperature for 6 days. The analysis shows that the conjugation which takes place leads to the appearance only of conjugated trienes, in spite of the presence of di-, tri-, tetra-, penta- and hexaenic unsaturated fatty acids as shown by the absorption spectrum of the same mixture after chemical conjugation with potassium hydroxide in ethylene glycol, (c) as seen in Fig. 82.

c) The changes induced in fatty acids are essentially the same regardless of radioactive source. Thus the effect upon a linoleic acid preparation containing some linolenic acid was the same with alpha particles of Thorium X, beta rays from radium in monel metal, gamma radiation from platinum filtered radium, and X rays generated by a 400 kw. therapy unit. Figures 83 and 84 and Table XIV show these results.