Calcified Tissue Research最新文献

The chemical and crystalline composition of the mineral deposited in ossified arterial and lung tissues of cows affected by enteque seco (enteque ossificans) has been investigated. The arterial calcification precedes that of lung. The latter was observed only in animals with a calcification of the aorta above 150 mumoles Ca per gram of wet tissue. The mineral deposited in arterial and lung tissues appeared to be a poorly crystallized apatite; following incineration the diffraction patterns of carbonate apatite and magnesium whitlockite, respectively, were found.

The mean wall thickness (MWT) of packets of trabecular bone was measured in undecalcified iliac crest bone samples of 36 normal subjects (14 female and 22 male) under polarized light. The mean wall thickness was 49.7 +/- 8.7 microns at a mean age of 50.9 years. There existed a significant decrease of MWT with advancing age. With an appositional rate of 0.72 micron/day, the mean formation time of iliac trabecular bone packets is 69 days. The decrease of MWT with age corresponds to a decrease in bone formation at the basic multicellular unit (BMU) level with aging and can partly explain the physiological senile osteopenia.

Mineral particle clusters, corresponding to calcospherites or matrix vesicle-initiated clusters in calcifying cartilage and dentin and to collagen bundle-related mineralization in lamellar bone, have been isolated from NaOCl solutions used to dissolve the organic matrix in preparation of anorganic mineralizing fronts for scanning electron microscopy.

Twenty-four hours after a tetracycline injection, the unimpeded, and more rapidly erupting, mouse mandibular incisor contained 20% to 44% more tetracycline than the contralateral, uncut incisor. It was concluded that the increased tetracycline incorporation reflected a higher rate of mineralization associated with faster tooth formation in the unimpeded tooth. By measuring the amount of tetracycline which became incorporated at different times after an incisor was shortened, it was possible to investigate an early stage of the response of the incisor to cutting. A significant increase in the capacity of the tooth to incorporate tetracycline was detectable 4 h after shortening the tooth, and this was maximal after another 4 h.

Articular cartilage of fetal calves, calves, and steers together with normal and osteoarthrotic human cartilage was analyzed for hyaluronate. The hyaluronate content increased with maturation in healthy tissue, particularly in regions of maximum contact, but was low in diseased cartilage.

The osteoclast number and its relation to parathyroid hormone have been studied in rat alveolar bone by quantitative histology and fluorescent labeling. The osteoclast number decreases 60 h after parathyroidectomy and remains constant for the next 132 h. Parathyroid hormone administration to parathyroidectomized animals 96 h after the operation induces an increase in osteoclast number within 12 h to somewhat above those of control animals. The elevated osteoclast counts remain constant for 60 h then rapidly fall over the next 24 h to the level seen in untreated parathyroidectomized animals. As determined by fluorescent labeling, normal alveolar bone resorption and formation were disturbed by parathyroidectomy, such that significant bone formation occurred for only 6 days after surgery, after which a quiescent state followed.

Ca2+ and Pi uptake induced in vitro by a collagenous matrix derived from bovine tendon is inhibited by 1 X 10(-6) to 2 X 10(-5) M NaF and stimulated by 2 X 10(-5) to 2 X 10(-3) M NaF. Fluoride uptake occurs only over the latter concentration range. The uptake of Ca2+, Pi, and F-1 progresses toward a limiting extent at which the molar Ca/P and Ca/F values are 1.6 to 1.7 and 4.5 to 5.7, respectively. Although the matrix-bound mineral, previously formed in the absence of NaF, readily undergoes dissolution when exposed to a Ca2+- and P-free medium of pH less than 7.4, the bound mineral phase formed in the presence of NaF does not. We conclude that fluoroapatite is the primary matrix-bound mineral. The uptake of fluoride, Ca2+. amd Pi by both uncalcified and previously calcified matrices is inhibited by methylenediphosphonate and by phosphonoacetate as is calcification in the absence of NaF. Kinetic studies indicate that formation of a CaP complex precedes the uptake of F-1 and suggest that F-1 and OH-1 compete for interaction with that CaP complex during the calcification process. We concluded that fluoroapatite formation induced by the collagenous matrix occurs by a multistep pathway comparable to that proposed previously for hydroxyapatite formation.

Measurements of intestinal-calcium-absorption efficiency are fundamental for understanding calcium homeostasis in health and disease. Stable calcium isotopes are attractive tracers for such measurements, to avoid excessive radiation exposure to the subject and permit serial studies at short intervals. To realize this, we found it necessary to improve the sensitivity and precision of existing thermal neutron activation analyses for 48Ca. This report describes the details, sensitivity, precision, and accuracy of the improved method, and gives the results of studies in which intravenous 48Ca was used in conjunction with oral 47Ca to measure intestinal-calcium-absorption efficiency in patients.