[Changes in the content of glutathion and ascorbic acid in bovine lenses in dependence on age (author's transl)]

Effects of age and dietary vitamin C on the contents of ascorbic acid and acid-soluble thiol in lens and aqueous humour of guinea-pigs

Variations in ascorbate and thiol concentration in lens and aqueous humour, with age and vitamin C nutrition, are of potential biological importance. To study these relationships, Dunkin-Hartley guinea-pigs were maintained for periods of up to 1.3 yr on diets containing either high or low (marginal) vitamin C. Ascorbate contents of liver, spleen, adrenals, lens and aqueous humour, and acid-soluble thiol of lens and aqueous humour were measured. High vitamin C intake maintained ascorbate levels in the internal organs between five and 30 times the level attained by the low vitamin C intake and aqueous humour vitamin C was 10-20 times higher at high vitamin C intake. Lens ascorbate, however, was only about twice as high at high vitamin C intake than at low intake, and at both intake levels it declined steadily to about half its initial value, after 1.3 yr. Thus an animal aged 1.3 yr on the low intake had about one-quarter to one-fifth of the lens ascorbate level of a young animal receiving a generous intake. Acid-soluble thiol in the lens, in contrast to ascorbic acid, increased significantly with age but was not significantly affected by dietary vitamin C intake. Acid-soluble thiol in the aqueous humour was only 0.5-2% of the concentration found in lens, and unlike the lens thiol level, it declined with age. No sex differences were observed for ascorbate or thiol levels either in lens or in aqueous humour.

Comparative investigations of catalase activity in different ocular tissues of cattle and man

As previously published, ocular catalase activity was measured by Warburg's respirometer, the examined material being taken from the local slaughterhouse and keratoplasty-donor eyes. The results were given in microliter O2 per mg soluble protein (Biuret's solution) and showed an extensive parallelism between human and bovine eyes: They were in a decreasing order of catalase activity, i.e., conjunctiva > retina > vitreous > sclera > iris > choroid > cornea > aqueous humor > serum > lens. In the latter, catalase activity was a sensitive indicator of aerobic metabolism. Oxidative processes in the vitreous merit more consideration.

Carbohydrate metabolism of the lens depending on age. V. Problems of mathematical approach and graphical presentation

For investigations on age-dependent changes of lens metabolism, longitudinal studies are requisite. Graphic representation of such findings should be based on a proper arithmetic age scale. Using the lens weight for representing the age leads to distortion of the curves, whereby certain periods of life are liable to be overemphasized. In longitudinal studies, data on concentrations should never be given per unit weight, but rather for the whole lens. Absolute values of the whole, intact lens may be referred to a reference value, a percental representation of the curves is possible. With regard to the expectancy of life of test animals one may already state that longitudinal studies including the senile phase will only be feasible with rats.