Vitamin A and bone growth : the reversibility of vitamin A-deficiency changes / by E. Mellanby.

  • Edward Mellanby
Date:
[1947?]
Catalogue details

Licence: In copyright

Credit: Vitamin A and bone growth : the reversibility of vitamin A-deficiency changes / by E. Mellanby. Source: Wellcome Collection.

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    injury or even destruction of the nervous tissue and ultimately to the death of the animal. The restoration of vitamin A to the diet of the deficient anima quickly brings about a response in the bone cells directed to correct the dysplasia resulting from the absence of the vitamin. EXPEKIMENTAL METHODS A full account has been previously given (MeUanby, 1931) of the symptoms which develop in puppies on diets similar to the one used in the experiments now to be described, which is as fonows. wheatmeal bread 30-280 g., salt 1-2 g., baker’s yeast 5 % of cereal, separated mdk powder g., lean meat 15 g., peanut oil 10 c.c., ascorbic acid 5 mg., vitamin 200-2000 i.u. The wheatmeal flour from which the bread was made varied between 80 and 8o% extraction at difl-erent times during the period of the investigation and contained a trace of carotene. Similarly, the meat part of the ration no doubt included a small quantity of vitamin A. The diet was theretore not totally devoid of the vitamin or its precursor. j ^ i f For the sake of brevity the term + A dog is used to denote one having an abundant supp y o vitamin A, and - A dog for one receiving only the basal diet, and recovery dog or - A + A dog tor one having at first the basal diet only, and later the same diet supplemented by abundant vitamm A. The bones of - A dogs become thickened and cancellous as compared with those o + ^ i er mates. To produce compact bones more calcium is needed. For instance, if extra calcium as calcium carbonate (1 g. daily) is added to the above basal diet, the bones of both A and - A animals are less cancellous than without such addition, but the - A bone is still much the + A. Calcium is not, therefore, the controlling factor as regards bone hypertrophy (MeUanby, 1944). In the case of + A diets, it has been usual to add to the basal diet vitamin A (2000-5000 i.u. daily) in the form of a proprietary preparation of mammalian liver oil or as pure vitamin A acetate. This apphes both to the control + A dogs and to the recovery animals. i j The histological side of this investigation, involving serial sections of large blocks of decalcike bone cut at carefully chosen angles in relation to the nervous tissue, was long and tedious, ihe blocks were usually embedded in celloidin, one in every ten sections being stained and mounted. One of the difficulties in this work was that bone overgrowth, especially in complicated structures, often made histological examination of identical positions in + A and - A dogs impossible. The difficulty was partly overcome by examining serial sections; for instance, PI. 6, Fig. 1 a ( + A) s ows the internal auditory meatus and the helix of the cochlea, but although PL 6, Fig. 16 ( - A) s rows a similar portion of the hehx, it is necessary to examine other sections to trace the tortuous course of the internal auditory meatus of this animal. Most of the results described in this paper refer to three fitter-mate puppies, the experimental feeding of which started at the age of 7 weeks and continued in the case of the -f A and - A dogs for 26 weeks. In the case of the third dog (referred to as the recovery or - A + A dog) the feeding of the -A diet lasted for 24 weeks and of the +A recovery diet lasted for 23 days, making the experimental feeding period 27 weeks in all. Less complete examinations were made on another three animals. The feeding period of the + A and - A dogs lasted from the age of 6 to 20 weeks, i.e. for 14 weeks, and the third (reeovery) animal then had vitamin A added to the diet for 13 days. At the end of the experiment these animals were only 20-22 weeks old, as compared with the first set of three, which were about 33 weeks old at For special points, bone tissues were examined from a number of other experimentally fed dogs, usually in order to see what happened to the bones of dogs of different ages, and m such cases time was saved by embedding decalcified bones in paraffin wax instead of celloidin. Serial sections were not prepared. ... j Although bone changes in both the recovery animals ( - A + A) give similar pictures as regar s the reaction of osteoclasts and osteoblasts, the age of the animals greatly affects the cell activity
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