Experimental rickets : the effect of cereals and their interaction with other factors of diet and environment in producing rickets / by Edward Mellanby.

  • Edward Mellanby
Date:
1925
Catalogue details

Licence: In copyright

Credit: Experimental rickets : the effect of cereals and their interaction with other factors of diet and environment in producing rickets / by Edward Mellanby. Source: Wellcome Collection.

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    preparation of nucleic acid made from yeast was used. No doubt it would have been more appropriate had the nucleic acid used in the experiments been prepared either from oatmeal or wheat germ. The evidence, however, shows that yeast nucleic acid is identical with triticonucleic acid obtained from wheat embryo. Tritico- nucleic acid, first prepared from wheat germ by Osborne and Harris [38], was also found by them to give the same end-products of hydrolysis as yeast nucleic acid. These observations were con¬ firmed by Levene and La Forge [39], when they found that acid- hydrolysis of wheat germ nucleic acid at 175° C., under pressure with ammonia, yielded three of the nucleosides of yeast nucleic acid, viz. guanosine, adenosine, and cytidine, and also that the pentose of the germ product was cZ-ribose as in the case of yeast nucleic acid. Seven experiments were made to test the action of nucleic acid on rickets. To diets made up of separated milk, bread, meat, olive oil, and orange juice, the commercial preparation of nucleic acid (1 to 2 gms. daily) was added, but no evidence was obtained to show that this substance had a definite rickets-producing effect. In other experiments yeast itself as a source of nucleic acid was added in fairly large quantities to the diets. In an earlier publication I pointed out that yeast eaten by puppies in quantities of 5 to 10 gms. daily did not have any special action on rickets. In these later experiments it was found that even 40 gms. of yeast daily had no obvious effect in hastening rickets. In exper ments using yeast it is, of course, essential to kill the cells by heat before giving it to the animals. I have obtained no evidence up to the present time that nucleic acid is the substance in cereals responsible for the rickets-producing effect of these foodstuffs. (ii) Fatty Substances. Another chemical constituent of a distinctive nature present in appreciable quantities in oatmeal and wheat germ is fat. It will be seen from the figures on p. 45 how large is the fat content of oatmeal (7-2 per cent.) as compared with the amount in white flour (1-4 per cent.) and rice (0-3 per cent.). Although it is usual to ascribe many of the supposed advantages of oatmeal over other -cereals to its relatively high fat content, it seemed desirable, especially in view of the failure of investigations along other lines, to see whether this constituent had any detrimental action so far as bones are concerned. In the case of wheat germ there was already evidence from the experimental work of McCollum, Simmonds, and Pitz [40] that something in the germ that could be partially extracted by ether was capable of exerting a toxic action. They pointed out that, although wheat germ contained protein of good biological value, some vitamin A and abundant vitamin B, yet it interfered with the growth of their rats on synthetic diets when it formed too large a portion of their diets. Its action could be overcome in some degree by an addition to the diet of 5 per cent, casein and also by in¬ creasing the butter from 2 per cent, to 5 per cent, of the food eaten. They could not decide whether the toxic product of germ was the D 3