Areas Of New Bone Formation Research Articles

Drugs in Breast Milk

Drugs in Breast Milk

Distribution of 99mTc-phosphate compounds in osteoarthritic femoral heads.

In a study of the distribution of 99mTc-polyphosphate and 99mTc-methylene diphosphonate in osteoarthritic femoral heads by macroautoradiography of samples obtained during replacement surgery, the bone-seeking agents were seen to accumulate in the weight-bearing, denuded areas, mainly in the cyst walls and at the osteochondral junctions in the osteophytes. The autoradiographic findings were substantiated by findings from impulse-counting of different zones in the femoral heads that were done on frozen sections. Morphological studies of sections adjacent to the cut surface used for autoradiography showed that the accumulations of the radionuclides were located in areas of new-bone formation, particularly enchondral ossification. This finding was confirmed by histochemical staining for alkaline phosphatase, a marker enzyme for bone mineralization. The over-all distribution of alkaline phosphatase activity in cells roughly paralleled the deposition of the bone-seeking agents. Scintigrams of osteoarthritic joints reflect primarily the rate of osteogenesis in subchondral bone and osteophytes. As the scan is positive even in very early stages in the development of the disease, a more detailed knowledge of the mechanism responsible for an increased uptake of 99mTc-phosphate compounds may, among other things, contribute to the elucidation of the pathogenesis.

Tc-99m-polyphosphate bone imaging of orthodontically treated dog teeth

A number of bone lesions are detectable by means of skeletal imaging with injected, short-lived, bone-seeking radiopharmaceuticals. These include osteonecrosis,l> 2 osteoarthritis,3 infectious spondylitis,4 primary5 and metastaticj tumors, fractures,? and osteomyelitis. s High concentrations of radioactivity in surrounding areas of new bone formation *, 5* o facilitate the localization of a lesion with externally placed radiation-measuring devices. Since the method is sensitive to small changes in the rates of local bone formation in the early stages of disease, it can often detect skeletal lesions before they are recognizable on radiographs. This clinical tool, therefore, provides diagnostic information of a metabolic or functional nature. In the present study we have attempted to apply this nondestructive method to a study of metabolic events in alveolar bone supporting orthodontically treated teeth in dogs. The objectives of the study were to determine whether bone-seeking radionuclide methods could (1) provide longitudinal metabolic information through repeated measurements of the same animal, (2) distinguish the effects of orthodontic and orthopedic forces of different magnitudes, and (3) measure separately the metabolic events occurring in areas of pressure and tension. In addition, two different radiation-detection systems were used for the collection of data, and their usefulness as research tools in dentistry was evaluated and compared.

The fine structure of bone in the nasal tubinates of young pigs.

AbstractThe three types of bone cells in the nasal turbinates had characteristic ultrastructural features. Osteoblasts were located in areas of new bone formation and had abundant endoplasmic reticulum, prominent Golgi apparatuses, numerous vesicles, and cytoplasmic processes that penetrated the adjacent osteoid. Osteocytes had variable ultrastructural characteristics. The predominant cell filled the lacuna, had few organelles, smooth plasma membranes, and was interpreted to be a mature resting osteocyte. Some osteocytes appeared to be transitional between osteoblasts and mature osteocytes. Evidence of matrix formation was seen near osteocytes with well developed organelles, whereas osteocytes with swollen mitochondria, dense bodies and irregular plasma membranes appeared to be involved with resorption of bone. Multinucleated osteo‐clasts contained numerous mitochondria and had crystals or unmineralized collagen fibrils between folds and within vacuoles of the cytoplasmic projections forming the brush border.

Comparative Deposition of 45 Ca, 65 Zn, and 91 Y in Bone

Autoradiographic studies of bone were made after intravenous injections of three radioisotopes-45 Ca, ${}^{91}{\rm Y}$, and65 Zn-into rats, dogs, and a monkey. Counting techniques were used to measure the amount of each of these radioisotopes retained in the concentrated areas of new bone formation compared with that retained diffusely in the fully calcified bone. It was found that the ratio of concentrated to diffuse concentrations differed considerably for the three radioisotopes studied. For45 Ca the mean ratio was 8.9; for65 Zn the ratio was 40.1; and for ${}^{91}{\rm Y}$ the ratio was 4.4. Some attempts were made to discover the mechanism of uptake of these radioisotopes in bone tissue. Both calcium and yttrium were taken up in association with the mineral phase of bone but in a different way, while the mechanism of the uptake of65 Zn remains obscure.