Assessment of facial form modifications in orthodontics: proposal of a modified computerized mesh diagram analysis.

A modified computerized mesh diagram analysis enables rapid, easy, and independent quantifications of facial size, shape, and head position. A lateral cephalometric radiograph is traced, positioned in natural head position (NHP) according to the NHP registered on a lateral photograph, and superimposed by the standard grid of rectangles determined by the patient's upper face height and face depth. The patient's tracing is compared with a reference tracing of a norm. The two tracings are registered at nasion in NHP, and the size difference of the patient's mesh rectangles from the norm is quantified by a size normalization. The shape discrepancies are evaluated by calculating relevant displacement vectors for each cephalometric landmark, and a global difference factor. This computerized method provides a rapid graphic evaluation of the patient's sagittal and vertical discrepancies and can also be applied to determine the effects of orthodontic therapy and/or growth on the skeletal and dental relationships in a single patient.

Differential effects of glucocorticoid on recruitment and activity of osteoclasts induced by normal and osteocalcin-deficient bone implanted in rats.

Prolonged glucocorticoid excess is associated with bone loss. Among the contributory factors are glucocorticoids' suppression of bone formation and stimulation of bone resorption. In this study, the effects of glucocorticoids on bone resorption were evaluated in a rodent model. Subcutaneous implants of devitalized mineralized bone particles (BPs) elicit the recruitment of progenitor cells and their differentiation to osteoclasts which resorb the BPs. The effects of glucocorticoids on both the recruitment and the activity of cells induced by normal BPs were distinguished based upon when treatment was initiated. When treatment with hydrocortisone or dexamethasone was initiated at the time of BP implantation, the recruitment of bone-resorbing cells was impaired and a subsequent decrease in BP resorption was found. On the other hand, when treatment was initiated on day 7, glucocorticoids increased osteoclastic resorption and tartrate-resistant acid phosphatase activity. We also tested hydrocortisone's effect to stimulate the activity of cells associated with osteocalcin-deficient BPs. As previously reported, BPs deficient in osteocalcin were poorly resorbed as a result of decreased formation and activity of osteoclasts. Hydrocortisone had an even more pronounced effect in stimulating the low level resorption of the osteocalcin-deficient BP implants than of the normal BP implants. These findings show differential effects of glucocorticoids on two aspects of bone resorption: they inhibit the recruitment and/or differentiation of bone-resorbing cells, but they stimulate the activity of existing osteoclastic cells. The ability of glucocorticoids to increase resorption of normal bone and to overcome resistance to resorption of osteocalcin-deficient bone suggests an important regulatory effect of glucocorticoids in the activation of osteoclasts to increase bone resorption.

Normal bone particles are preferentially resorbed in the presence of osteocalcin-deficient bone particles in vivo.

In an in vivo model of osteoclastic bone resorption, we previously showed that osteocalcin-deficient bone particles (BPs), derived from warfarin-treated rats, were resorbed 50% as well as normal BPs and that they recruited fewer osteoclastic cells with decreased tartrate-resistant acid phosphatase (TRAP) activity. In order to determine the specificity of the resorption response, we evaluated the fate of implanted mixtures of normal and osteocalcin-deficient BPs. Normal and warfarin-treated donor rats were prelabeled in vivo with oxytetracycline to permit identification of BPs from either source. Normal, osteocalcin-deficient, and 50:50 mixtures of BPs (either labeled or unlabeled) were implanted into normal rats and recovered 12 days later for enzymatic (TRAP) and nondecalcified histomorphometric analyses. The incorporated oxytetracycline had no significant effect on resorption of bone particles. The recovered osteocalcin-deficient BPs were surrounded by fewer osteoclastic cells, were resorbed less, and contained less extractable TRAP activity than normal BPs. In mixed BP implants with normal and osteocalcin-deficient BPs, each type of bone particle elicited the same tissue response as when implanted separately. Remarkably, the different particles evoked dissimilar osteoclastic responses and were resorbed to different extents, even when adjacent within the same implant. These data suggest that osteocalcin may act as a substrate signal for resorption and that osteocalcin in the normal BPs does not influence the cellular response to adjacent osteocalcin-deficient BPs.

Pancreastatin, a presumed product of chromogranin-A (secretory protein-I) processing, inhibits secretion from porcine parathyroid cells in culture.

Chromogranin-A, also referred to as secretory protein-I, is a 50K protein found in and secreted by endocrine cells, in which it is costored with the native hormone. Porcine chromogranin-A contains a sequence identical to pancreastatin, a 49-amino acid, C-terminally amidated peptide that has been isolated from porcine pancreas, suggesting that chromogranin-A is the precursor of pancreastatin. Pancreastatin has been found to be a potent inhibitor of glucose-stimulated insulin release. As it is possible that pancreastatin inhibits secretion from other chromogranin-A-containing tissues in which it may be formed, we tested its action on dispersed porcine parathyroid cells in culture. Secretion of chromogranin-A and PTH was up to 6-fold greater at 0.5 mM Ca2+ than at 3.0 mM Ca2+. Pancreastatin (1 nM) reduced the secretion of both chromogranin-A and PTH at 0.5 mM Ca2+ to approximately the levels found at 3.0 mM Ca2+, but did not affect secretion at 3.0 mM Ca2+. Pancreastatin (0.01-1.0 nM) inhibited secretion of chromogranin-A in a dose-dependent fashion. Preincubation of the cells with pancreastatin was not required for inhibition. Transfer of inhibited cells to medium without pancreastatin led to restoration of secretion within 90 min. Phorbol myristate acetate (1.6 microM) stimulated secretion of PTH and chromogranin-A at 3.0 mM Ca2+, but not at 0.5 mM Ca2+. Pancreastatin reversed this stimulation, demonstrating that its inhibition was independent of Ca2+ concentration. These results are consonant with pancreastatin playing a physiological role in modulation of secretion by the parathyroid and, by extension, other endocrine tissues.