Title: Calcified tissues; proceedings
Identifier: calcifiedtissues00euro (find matches)
Year: 1963 (1960s)
Authors: European Symposium on Calcified Tissues; European Bone and Tooth Symposium
Subjects: Bone; Collagen; Calcification
Publisher: Berlin, New York (etc. ) Springer-Verlag (etc. )
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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The Two Faces of Resorption ^'m^^ amount of calcium (about 15 gm/day/horse) and an excessive amount of phosphorus (about, 3V2 times as much). The animals were killed after periods of 4, 7, 10, 12 and 30 weeks of abnormal feeding. The clinical observations have been similar to those already published by Krook and Lowe (1964). After 4 weeks, very minor signs of osteitis fibrosa were present but the parathyroids were enlarged about 3 times. After 8 weeks, extremely severe osteitis fibrosa was recognized and in the colourful language of the senior veterinary pathologist (K), "the parathyroids were almost as big as the testicles of a dachshund". The bone response was uneven throughout the body. On the other hand, the horses which were the youngest at the onset of the experiment were the most severely affected. Changes in the mandibles and maxillae were observed sooner and progressed at a more rapid rate than those in the metacarpi (Krook and Lowe, 1964) and long bones. Increased radiolucency was particularly evident in the bones of the skull and face. Complete resorption of the lamina dura dentis was evident after 30 weeks. Comparative alpharadiographs of the periodontal portion of the mandible and maxilla examined in the light of histochemical staining and with the knowledge of the mechanism of bone growth pro- vided by radioautography (Belan- GER and MiGicovsKY, 1963 b) have been very instructive. Short term studies have demon- strated that only mesenchymal cells, preosteoblasts or "osteopro- genitors" (Tonna, 1965; Belanger and MiGicovsKY, 1963 b; Young 1963) are originally labeled. The presence of radioactive osteoblasts and osteocytes occurring later is an indication of growth movements and also of tissue replacement in areas where the adult condition has already been achieved. In 3 weeks-old chicks, the re- placement rate of metaphyseal trabeculae of the tibia has been established at 4 days (Belanger and MiGicovsKY, 1963 b). In the lamina dura of the horse jaw, this time is unknown. However, a con- stant cell movement must be simi- larly taking plase from the border of the osteonic canal, towards the areas of lower tissue density where osteolysis occurs and where the cells die. If osteo- lysis and peripheral accretion are balanced, a static histological, histochemical and radiological picture is maintained. On the other hand, if osteolytic stimuli such as hyperparathyroidism are present, resorption Is presumably greater than accretion.
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