PubMed · 11540294
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K Ostrowski, A Dziedzic-Goclawska. 1996. Optical diffractometry in bone research.. https://pubmed.ncbi.nlm.nih.gov/11540294/
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A synchrotron infrared (IR) beamline, U2B, dedicated to the biomedical and biological sciences has been constructed and is in operation at the National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory. The facility is operated by the Center for Synchrotron Biosciences of the Albert Einstein College of Medicine in cooperation with the NSLS. Owing to the broadband nature of the synchrotron beam with brightness 1000 times that of conventional sources, Fourier transform IR spectroscopy experiments are feasible on diffraction-limited sample areas at high signal-to-noise ratios and with relatively short data-acquisition times. A number of synchrotron IR microscopy experiments that have been performed in the mid-IR spectral range (500-5000 cm(-1)) are summarized, including time-resolved protein-folding studies in the microsecond time regime, IR imaging of neurons, bone and other biological tissues, as well as imaging of samples of interest in the chemical and environmental sciences. Owing to the high flux output of this beamline in the far-IR region (50-500 cm(-1)), investigations of hydrogen bonding and dynamic molecular motions of biomolecules have been carried out from 10 to 300 K using a custom-made cryostat and an evacuated box. This facility is intended as an international resource for biological IR spectroscopy fully available to outside users based on competitive proposal.
STUDY DESIGN: The outcome of two patients with Larsen's syndrome after spinal surgery was evaluated after follow-up for 9 and 16 years. OBJECTIVE: To report on a new phenomenon of anteroposterior dissociation of the vertebrae in Larsen's syndrome. To demonstrate that it can be visualized before surgery with imaging and also seen intraoperatively. To show that the neurologic recovery after surgery is sustained and to review the technical reasons for the difficulties in achieving a surgical fusion. The critical role of CT scanning will be illustrated. SUMMARY OF BACKGROUND DATA: The results of preoperative and postoperative radiologic investigations and intraoperative findings are presented to support this new phenomenon. METHODS: Two patients underwent multiple spinal surgeries because of a deteriorating myelopathic clinical status. Intraoperatively, anteroposterior dissociation was documented in both patients. There was great difficulty in obtaining a surgical fusion, and an unusually long circumferential fusion was eventually necessary to obtain stability. Prolonged halo-vest immobilization was essential. RESULTS: Neurologic recovery was sustained over time, and the spinal deformity did not deteriorate. CONCLUSION: Awareness of this phenomenon is essential to the management of spinal deformities in Larsen's syndrome when presenting with myelopathy. Special features in the radiologic workup should be sought after so as to plan staged surgical procedures. Conventional principles of planning of fusion levels are inadequate. Early treatment is advocated, as the neurologic compromise is reversible.
Bone resorption in balance with bone formation is vital for the maintenance of the skeleton and is mediated by osteoclasts. Cathepsin K is the predominant protease in osteoclasts that degrades the bulk of the major bone forming organic component, type I collagen. Although the potent collagenase activity of cathepsin K is well known, its mechanism of action remains elusive. Here, we report a cathepsin K-specific complex with chondroitin sulfate, which is essential for the collagenolytic activity of the enzyme. The complex is an oligomer consisting of five cathepsin K and five chondroitin sulfate molecules. Only the complex exhibits potent triple helical collagen-degrading activity, whereas monomeric cathepsin K has no collagenase activity. The primary substrate specificity of cathepsin K is not altered by complex formation, suggesting that the protease-chondroitin sulfate complex primarily facilitates the destabilization and/or the specific binding of the triple helical collagen structure. Inhibition of complex formation leads to the loss of collagenolytic activity but does not impair the proteolytic activity of cathepsin K toward noncollagenous substrates. The physiological relevance of cathepsin K complexes is supported by the findings that (i) the content of chondroitin sulfate present in bone and accessible to cathepsin K activity is sufficient for complex formation and (ii) Y212C, a cathepsin K mutant that causes pycnodysostosis (a bone sclerosing disorder) and that has no collagenase activity but remains potent as a gelatinase, is unable to form complexes. These findings reveal a novel mechanism of bone collagen degradation and suggest that targeting cathepsin K complex formation would be an effective and specific treatment for diseases with excessive bone resorption such as osteoporosis.