Phytic acid and the rickets-producing action of cereals / by Douglas Creese Harrison and Edward Mellanby.

  • Harrison, D. C. (Douglas Creese)
Date:
[1939?]
Catalogue details

Licence: In copyright

Credit: Phytic acid and the rickets-producing action of cereals / by Douglas Creese Harrison and Edward Mellanby. Source: Wellcome Collection.

    6/26 (page 1664)
    As regards the degree of calcification of the bones, this is recorded as the ratio A/R, the ratio of the weight of ash of the bone to the weight of dry fat- extracted bone minus ash. It has been previously pointed out that rickets in young animals is a disease associated with growth, so that it is essential in such work, where comparisons have to be made, to adjust the amount of food given so that each animal eats the same quantit}^ of the basal diet, and that the growth (as measured by weight increase) of the animals in a litter is as similar as possible. It is usually not difficult to attain this in experiments of the duration of those in the present enquiry. Growth curves have not been given in this publication but the similarity in rates of growth can be seen in the figures of weight increase recorded. Usually there is little or no discrepancy between the final weight and the maximum weight of each animal but, where there has been loss of weight before the completion of an experiment, this fact is recorded in the experimental results. There has been one special difficulty about the present experiments which needs to be mentioned. In order to test the effect of some substance in increasing the intensity of rickets it is necessary to make the control diets of such a nature that rickets in these animals is either produced only slightly or just prevented by a narrow margin. If, for instance, the control animals get severe rickets, the effect of adding a rickets-producing substance to the diet of other animals of the litter may be lost because all animals may be so severely affected. If, on the other hand, the basal diet is too antirachitic, the effect of the substance to be tested may be so far overcome as to escape detection. For this reason the amounts or proportions of separated milk powder and cabbage in the diets were sometimes altered. This change affected, of course, every member of the litter. Experience in choosing diets compatible with the production of varying degrees of rickets in puppies has, generally speaking, allowed this difficulty to be avoided in the present work. Preparation of sodium phytate from commercial phytin The phytin used in Exps. 1-3 was a commercial preparation (Phytin “Ciba”). The sodium phytate for these three experiments was made by suspending 75 g. of the same phytin in 750 ml. water, stirring with N HC1 till dissolved and adding N NaOH gradually with stirring till a permanent precipitate just formed. A warm solution of sodium oxalate equivalent to the Ca in the phytin was added, and then N NaOH to bring the solution to about pH 5. The solution was allowed to stand and was filtered, the precipitate being washed with water. The combined filtrate and washings were neutralized, allowed to stand overnight and filtered again. The solution was then diluted so that 20 ml. were equivalent to 0-6 g. of the original phytin, and was stored in the refrigerator. In the first three experiments the sodium phytate and phytin were fed in amounts based on the assumption that oatmeal contained 0*6 % phytin. Soon afterwards the method of McCance & Widdowson [1935] for phytin estimation appeared and, on using this to determine the phytate P of our oatmeal, we found that we had been feeding the sodium phytate and the phytin at only about half the oatmeal equivalent of phytate P. But for this, the rachitogenic effect of sodium phytate would no doubt have been even more marked. In all experiments after Exp. 3, we estimated the phytic P in each phytate preparation and in each batch of oatmeal. Exp. 1. Effects on calcification of phytin and sodium phytate The basal diet consisted of separated milk powder 15-26 g., white flour 100-150 g., lean meat 15-22-5 g., orange juice 6 ml., yeast 5-7-5 g., NaCl 2 g.,