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.

    12/28 page 392
    Notes on other bones Of the bones examined, most appear to react in the same way as the basi- occipital, but there are several special regions m which strong osteoclastic activity in the + A becomes reduced osteoclastic activity in the - , ® ® cessation of absorption and deposition of bone being uncommon positions is part of the surface of the vertebral column adjacent to the lateral Le of the posterior root ganglion. It was shown in the Croonian Lecture that osteoclasts may remain in this position in the - A animal, and further exami nations have confirmed that these cells persist here in a comparatively mact state when they have completely disappeared from the rest of the surface adjacent to the spinal cord. Eeversal from osteoclastic to osteoblastic activity does, however, occur in very severe A deficiency. Recovery animals show strong osteoclastic activity over the whole of the surface of tne vertebrae adjacent to the nervous system, including this special region, irrespec ive o whether the deficiency has been severe or only of a degree to produce reduced ^'^Bones in which efforts are made by bone cells to correct the abnormal shape, when vitamin A is added to the diet of an animal showing signs of A deficiency, include the long bones (femur and radius), the pelvis, the petrous ri ge an e walls of the V nerve foramen. Osteoclastic action to reduce the enlarged petrous ridge and to widen the V nerve foramen is particularly intense. DISCUSSION The foregoing account of the effect on bone of vitamin A, its absence and its replacement in the diet of an A-deficient animal, shows clearly that it plays an important part in controlling bone growth and shape, its special function being to model bones. In the case of bones adjacent to the growing nervous system, even the finer degrees of moulding have to be specially adjusted. Thus, the precise chemical control of bone development in this position is of the utmost importance to the animal’s well-being. As the nervous system and its branches grow, the brain and cord cavities and the foramina which allow the passage o nerves to and from the central nervous system must enlarge to accommodate these tissues. If vitamin A is deficient in the growing puppy, bone growth is so changed that the skull cavity and the spinal canal enlarge inadequately an irregularly, and the foramina may even become smaller, with disastrous results, which may include destruction of the olfactory, optic, trigeminal and auditory nerves and the posterior roots of the spinal cord. If, after a period of some weeks, the vitamin is restored to the defective diet, there is a vigorous attempt to correct the wrong growth of the deficient period. This fact strengthens the evidence that vitamin A exerts a powerful controlling infiuence on the elements responsible for co-ordinated bone growth and thereby brings about the necessary adjustment between the growth of bone and nervous
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