Endocytosis of sugars in embryonic skeletal tissues in organ culture: I. general introduction and histological effects

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Abstract
The addition of sucrose to a chemically denned culture medium caused intense cytoplasmic vacuolation of the perichondrial, oesteogenic and articular cartilage cells of limb-bone rudiments from day embryonic chicks grown in organ culture. The rest of the cartilage appeared unaffected by the sugar. The osteocytes were intensely vacuolated; the bone matrix was much less dense than that of the controls and had an abnormal fibrillar structure. When the explants were transferred to medium without sucrose, after 6 days vacuolation had almost disappeared. The effect of the sucrose was dose-dependent; at a concentration of 0·32M the sugar was highly toxic; at 0·16M the explants survived and vacuolation of the chondrocytes extended further into the cartilage than at 0·08M. A similar vacuolation of the cells in response to sucrose was seen in the isolated shafts of the limb-bones and in the mandibular rami from 11- to 13-day embryos; in the sucrose-treated explants osteogenesis was arrested and in places the bone showed osteolytic changes. In the absence of glucose, day limb-bone rudiments failed to grow and rapidly degenerated in medium containing 0·08 M sucrose, indicating that sucrose was very little if at all metabolized. Explants of day rudiments grown for 8 days in the presence of 0·08M glucose showed no vacuolation; dextran had some effect, and both mannitol and sorbitol caused vacuolation.