Skeletal changes affecting the nervous system produced in young dogs by diets deficient in vitamin A / by Edward Mellanby.

  • Mellanby, Edward, Sir, 1884-1955.
Date:
[1941?]
Catalogue details

Licence: In copyright

Credit: Skeletal changes affecting the nervous system produced in young dogs by diets deficient in vitamin A / by Edward Mellanby. Source: Wellcome Collection.

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    cancer cells, change their function or act in a way different from the normal cells of tlie same type. Summary 1. A function of vitamin A is to influence the structure of growing bones, probably by limiting the number and the degree of activity of osteoblasts and osteoclasts. In its absence from the growing dog osteo¬ blastic and osteoclastic activity is increased, thus resulting in proliferation of cancellous at the expense of compact bone and causing many bones to lose their normally fine moulding and outline and to become thickened and enlarged. 2. Some of the main positions of bone overgrowth in the skull and vertebral column produced by the vitamin A deficient diets used in these experiments are described. These overgrowths are related to degenerative changes in the brain and in cranial and peripheral nerves, of which accounts have been given in earlier publications. 3. Overgrowth of the cranial bones may press on and produce deformity of parts of the brain. The greatest hypertrophy is found in the bones forming the posterior fossa of the skull, so that the medulla oblongata, pons, cerebellum and nerves in close association with these parts of the brain are more particularly affected. Most of the cranial nerves of young dogs are liable to be compressed and to suffer destructive changes if the A deficient diets are continued over long enough periods (about 4 to 8 months). 4. The posterior root ganglia and the anterior root nerves of the spinal cord may also be squeezed and the nerve fibres destroyed by over¬ growth of the vertebral bones. The bone overgrowth and nerve de¬ generative changes are greatest in the cervical region of the cord. 5. In advanced cases on these vitamin A deficient diets there is evidence of a substantial increase in intracranial pressure. The pressure of the cerebrospinal fluid in the cisterna magna may be double that of animals receiving similar diets containing vitamin A. Associated with these changes the cisterna magna and the 4th ventricle are diminished in capacity, while a degree of internal hydrocephalus (expansion of the 3rd and lateral ventricles) indicates increased pressure, probably trans¬ mitted from the posterior fossa. Note. Since this paper went to press, the author has seen a publica¬ tion by L. A. Moore and J. F. Sykes (Amer. J. Physiol. [1940], 130, 684) in which are described experiments showing increased cerebrospinal fluid pressure in calves on a ration deficient in vitamin A.