Aortic collagen and elastin were quantitated in three groups of castrated and two groups of noncastrated male rats treated by intramuscular injection for 3 wk with oil, testosterone, or estradiol. The greatest differences were found between the castrated rats receiving testosterone and those receiving estradiol, the estradiol-treated rats having significantly lower total collagen, percent collagen, total elastin, and collagen/elastin (C/E), and higher percent elastin than those rats receiving testosterone. In noncastrated rats, administration of estradiol resulted in significantly lower total collagen, percent collagen, total elastin, and C/E. Systolic blood pressure was highest in rats receiving testerone and lowest in rats receiving estradiol. It is concluded that 1) estradiol in the presence or absence of testosterone decreases total accumulation of vascular connective tissue and alters the proportions of collagen and elastin so that the vessel is more distensible, 2) testosterone has an opposite but less marked effect than estradiol on vascular connective tissue, and 3) estradiol and testosterone alter blood pressure in opposite directions in the male rat.

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Summary Existing ultraviolet spectrophotometric methods have been modified for application primarily to the detection and estimation of low proportions of conjugated and nonconjugated unsaturated constituents in fats, oils, and soaps. The method is applicable also to fatty materials having high proportions of these constituents. Modifications include corrections for absorption by interfering substances, use of alkaline glycerol as an isomerization medium in the analytical procedure, and correction of absorption data on the isomerized product for absorption by conjugated constituents in the material before isomerization. The presence of small proportions of highly unsaturated conjugated and nonconjugated compounds is established in lards, tallows, tallow soaps, and highly purified esters and acids. Tall oil fatty acids are shown to contain approximately 10% of conjugated diene acids and a small amount of linolenic acid.

Summary Spectrophotometric methods of analysis for the polyunsaturated constituents of oils and fats have been carefully restandardized for several conditions of alkali‐isomerization, using purified methyl esters of linoleic, linolenic, and arachidonic acids prepared by physical rather than by chemical means. A number of vegetable oil and animal fat samples were subjected to spectrophotometric analysis, and the results based on natural and on bromination‐debromination fatty acid standards were compared. The natural fatty acid standards lead to significantly higher accuracy and their use in the spectrophotometric analysis of natural fatty materials is strongly recommended. Results obtained under different conditions of isomerization were in satisfactory agreement. An isomerization time of 45 minutes is recommended rather than 25 or 30 minutes. The glycerol‐air technique is preferred for general use because of its simplicity and high precision. The ethylene‐glycol‐nitrogen technique is a close second choice because of the greater transparency of reagent blanks.

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