The effect of hypervitaminosis A on embryonic limb-bones cultivated in vitro / by Honor B. Fell and E. Mellanby.

  • Fell, Honor B.
Date:
[1952?]
Catalogue details

Licence: In copyright

Credit: The effect of hypervitaminosis A on embryonic limb-bones cultivated in vitro / by Honor B. Fell and E. Mellanby. Source: Wellcome Collection.

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    normal medium and the other in the same medium to which excess vitamin A had been added. Explants were fixed and sectioned at intervals. The results are summarized in Table 1. Only one experiment (Exp. 48) was done with blastemas at stage 1, a rather low concentration of vitamin A (1475 i.u./lOO in plasma) being used. After 48 hr. growth, in both the control and experimental explants, the individual bone rudiments had become visible and the knee- and elbow-joints had appeared. In the two pairs of wing-buds, however, only the humerus developed well; it enlarged to several times its original length and acquired some semblance of its normal shape. There was little difference between the experimental and control humerus in the pair of wing explants fixed after 5 days; in both the cartilage differentiated into hyper¬ trophic, proliferative and epiphysial zones and a thin layer of periosteal bone was deposited. In the 7-day pair, however, chondrobiastic hypertrophy and ossification were much more advanced in the hypervitaminotic humerus than in the control. The radius and ulna in both pairs of wing blastemas grew much less than the humerus and underwent neither chondrobiastic hypertrophy nor ossification. The femur, tibia, fibula and part of the tarso-metatarsal region developed in the leg blastemas. The bones grown on the AH medium were rather more slender than those on the control medium. The femur, tibia and fibula of all four explants showed chondrobiastic hypertrophy and ossification, but dif¬ ferentiation was more advanced in the hypervitaminotic rudiments than in the controls. Control rudiments explanted at stages 2-4 grew and differentiated extremely well in cultures, sometimes increasing to more than four times their original length and assuming a surprisingly normal shape (Text-figs. 1 and 2). The soft tissue adhering to the cartilage proliferated rapidly and soon formed a capsule of organized connective tissue which often contained many muscle fibres and was permeated by a network of rather dilated endothelial channels. The zone of hypertrophic cartilage cells could be seen gradually spreading towards the ends of the diaphysis; the proliferative zone of flattened cells could be distin¬ guished in life and the demarcation of this region from the epiphysis could also be observed. A yellowish layer of periosteal bone or osteoid was deposited on the surface of the hypertrophic cartilage, the structure of which it soon obscured. This layer became thicker and more opaque but it did not appear to become densely calcified. In the explants the cartilage enclosed by the bone was not excavated by ingrowing tissue as in normal development in ovo. Sections of the control bones fixed after 9-11 days’ cultivation in normal medium confirmed the observations on living cultures (PI. 1, figs. 2, 4 and 6). The diaphysis consisted of hypertrophic cartilage enclosed by a thick sheath of periosteal bone; beyond the hypertrophic region was a broad proliferative zone of flattened cells which ended abruptly at the border of the small-celled
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