Transforming growth factor beta (TGF-beta), a potent regulator of bone formation, has bifunctional effects on osteoblast replication and biochemical activity that appear differentiation dependent. We now show that cell surface binding sites for TGF-beta vary markedly among fibroblasts, bone-derived cells, and highly differentiated osteosarcoma cultures from fetal rats. Expression of betaglycan and type II receptors decline relative to type I receptor expression in parallel with an increase in osteoblast-like activity, predicting that the ratio among various TGF-beta binding sites could influence how its signals are perceived. Bone morphogenetic protein 2 (BMP-2), which induces osteoblast function, does not alter TGF-beta binding or biochemical activity in fibroblasts and has only small effects in less differentiated bone cells. In contrast, BMP-2 rapidly reduces TGF-beta binding to betaglycan and type II receptors in osteoblast-enriched primary cell cultures and increases its relative binding to type I receptors in these cells and in ROS 17/2.8 cultures. Pretreatment with BMP-2 diminishes TGF-beta-induced DNA synthesis in osteoblast-enriched cultures but synergistically enhances its stimulatory effects on either collagen synthesis or alkaline phosphatase activity, depending on the present state of bone cell differentiation. Therefore, BMP-2 shifts the TGF-beta binding profile on bone cells in ways that are consistent with progressive expression of osteoblast phenotype, and these changes distinguish the biochemical effects mediated by each receptor. Our observations indicate specific stepwise actions by TGF-beta family members during osteoblast differentiation, developing in part from changes imprinted by BMP-2 on TGF-beta receptor stoichiometry.

We present a case of an intracranial adenocystic carcinoma that clinically and radiographically mimicked a primary intracranial tumor. The radiological work-up of this tumor is presented in detail. We suggest that perineural intracranial invasion by the tumor along the trigeminal nerve resulted in its presentation as a primary intracranial tumor.

Purpose: Synthetic polymers have been used to coat the surface of existing low‐energy brachytherapy sources to improve their fixity in tissue in order to minimize seed migration in the patient. The purpose of this study was to evaluate the effects of the polymer‐coating on the photon energy spectra emitted by Pd‐103 seeds and to estimate its impact on the dosimetric characteristics of these seeds. Methods: Two Pd‐103 AnchorSeeds (Biocompatibles, Inc) and two Pd‐103 TheraSeeds (Theragenics Corporation) were used in this study. The AnchorSeed is made from the TheraSeed by coating its surface with bio‐absorbable polymeric anchoring rings and ribs. Photon energy spectra emitted by these seeds were measured using a high‐resolution, high‐purity Germanium (HPGe) photon spectrometer. The effects of polymer coating on the dose rate constant were quantified by comparisons of the coated seed with a non‐coated seed. Results: The relative photon energy spectrum emitted by the AnchorSeed was nearly identical to that emitted by the TheraSeed without polymer coating. The dose‐rate constants determined from the emitted photon energy spectra for the two seed models were identical to the third digit after the decimal point (0.679 ± 0.037 cGyh‐1U‐1). Because the basic dosimetric property of a brachytherapy seed is fundamentally determined by the photon characteristics emitted by the seed, effects of the polymer‐coating on the relative dosimetry data of TheraSeed is also expected to be minimal. Using a preexisting photon spectrometer, these measurements and calculations were completed in about 10 working hours. Conclusion: The polymer coating used in the AnchorSeed has minimal impact on its dosimetric characteristics compared to the non‐coated TheraSeed. We also demonstrate that photon spectroscopy provides a ready tool for the evaluation of impact of various coatings or other material changes in the seed manufacture process.