The influence exerted by the sex of the organism upon lipidic balance was brought to our attention by a curious effect seen when cholesterol was administered in an ether oil solution to rats. Only the females showed paraplegia and ulcerations of the hind legs. While castration or administration of sex hormones did not alter this response, it was influenced by the administration of two groups of lipids. The insaponifiable fraction of human placenta, for instance, was seen to induce a high sensitivity to this preparation of cholesterol even for males, while the acid lipidic fraction of placenta prevented paraplegia in females. (Note 21)

Similarly, the fact that in females alone, adipous cells appeared quickly in the skin of the ear after the application of sulfur mustard could be related to the intervention of the insaponifiable fractions. (Note 22)

Starting with these observations, it could be seen that, in general, a higher proportion of positive lipids exists in females than in males. This could be shown by direct analyses and by analyses of manifestations related to such lipids. While many differences are to be seen in various manifestations between females and males, only some could be related to the direct or indirect intervention of sex hormones. In such instances, castration with or without the administration of sex hormones was able to change, and even to reverse, the differences in manifestations seen between sexes. However, in instances in which these measures were without effect, the differences could be related to the intervention of lipids.

Influence Exerted By Age

The changes in lipidic balance related to age have been made the object of an extensive study which also sought to determine the role of lipids in aging processes. A general predominance of positive lipids, more manifest in the cellular and tissue levels than in the blood, was seen in youth. This would be expected in view of the special metabolic influence exerted by this group of lipids. The anoxybiotic character of metabolism induced by sterols results in the intervention of dehydrogenases which lead to an abundance of hydrogen ions. This, in turn, leads to a predominance of the kind of syntheses which favor anabolism. Growth thus could be related to the predominance of lipids with positive polar groups, especially sterols.

Aging processes, on the contrary, could be related to a predominance of lipids with negative polar groups, especially fatty acids. This predominance could be found especially at the cellular level, as seen in cultures of tetrahymena. (Note 23) In complex organisms or in rats (Note 24) in which an increase in the proportion of fatty acids at the cellular level is present, an opposite change occurs at the systemic and even at the organic level. There is an excess of cholesterol, this time limited to the higher levels, as revealed through analyses of the blood, for instance. Changes in the blood vessels are related in part to this excess of sterols at the systemic level. Many manifestations have confirmed such an offbalance with sterol predominance at higher levels. For example, we found the urine surface tension abnormally high in old age. (Note 25) Similarly, skin wheal absorption in old people requires more than 90 minutes for completion as against approximately 20 minutes in middle aged adults. A predominance of fatty acids at lower levels and of sterols at higher levels would thus characterize the changes in lipidic balance related to old age. (Fig. 68)