[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

The last decade has provided a virtual explosion of data on the molecular biology and function of osteocytes. Far from being the “passive placeholder in bone,” this cell has been found to have numerous functions, such as acting as an orchestrator of bone remodeling through regulation of both osteoclast and osteoblast activity and also functioning as an endocrine cell. The osteocyte is a source of soluble factors not only to target cells on the bone surface but also to target distant organs, such as kidney, muscle, and other tissues. This cell plays a role in both phosphate metabolism and calcium availability and can remodel its perilacunar matrix. Osteocytes compose 90% to 95% of all bone cells in adult bone and are the longest lived bone cell, up to decades within their mineralized environment. As we age, these cells die, leaving behind empty lacunae that frequently micropetrose. In aged bone such as osteonecrotic bone, empty lacunae are associated with reduced remodeling. Inflammatory factors such as tumor necrosis factor and glucocorticoids used to treat inflammatory disease induce osteocyte cell death, but by different mechanisms with potentially different outcomes. Therefore, healthy, viable osteocytes are necessary for proper functionality of bone and other organs. © 2011 American Society for Bone and Mineral Research.

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The Amazing Osteocyte

BACKGROUND Fibroblast growth factor 23 (FGF-23) is a hormone that increases the rate of urinary excretion of phosphate and inhibits renal production of 1,25-dihydroxyvitamin D, thus helping to mitigate hyperphosphatemia in patients with kidney disease. Hyperphosphatemia and low 1,25-dihydroxyvitamin D levels are associated with mortality among patients with chronic kidney disease, but the effect of the level of FGF-23 on mortality is unknown. METHODS We examined mortality according to serum phosphate levels in a prospective cohort of 10,044 patients who were beginning hemodialysis treatment and then analyzed FGF-23 levels and mortality in a nested case-control sample of 200 subjects who died and 200 who survived during the first year of hemodialysis treatment. We hypothesized that increased FGF-23 levels at the initiation of hemodialysis would be associated with increased mortality. RESULTS Serum phosphate levels in the highest quartile (>5.5 mg per deciliter [1.8 mmol per liter]) were associated with a 20% increase in the multivariable adjusted risk of death, as compared with normal levels (3.5 to 4.5 mg per deciliter [1.1 to 1.4 mmol per liter]) (hazard ratio, 1.2; 95% confidence interval [CI], 1.1 to 1.4). Median C-terminal FGF-23 (cFGF-23) levels were significantly higher in case subjects than in controls (2260 vs. 1406 reference units per milliliter, P<0.001). Multivariable adjusted analyses showed that increasing FGF-23 levels were associated with a monotonically increasing risk of death when examined either on a continuous scale (odds ratio per unit increase in log-transformed cFGF-23 values, 1.8; 95% CI, 1.4 to 2.4) or in quartiles, with quartile 1 as the reference category (odds ratio for quartile 2, 1.6 [95% CI, 0.8 to 3.3]; for quartile 3, 4.5 [95% CI, 2.2 to 9.4]; and for quartile 4, 5.7 [95% CI, 2.6 to 12.6]). CONCLUSIONS Increased FGF-23 levels appear to be independently associated with mortality among patients who are beginning hemodialysis treatment. Future studies might investigate whether FGF-23 is a potential biomarker that can be used to guide strategies for the management of phosphorus balance in patients with chronic kidney disease.

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Fibroblast growth factor 23 and mortality among patients undergoing hemodialysis.

Systematic review of the chemical composition of contemporary dental adhesives

Dental adhesion review: Aging and stability of the bonded interface

Effects of water content and initiator composition on photopolymerization of a model BisGMA/HEMA resin.

Smear layers are generally present on any dentin surface prepared with cutting instruments and are often the only available substrate for bonding. It is commonly reported that acid removes these layers, but to date there has been no chemical evidence to support this observation. Confocal Raman microspectroscopy was used to investigate changes in the composition and molecular structure of acid-treated smear debris and in situ dentin smear layers. The exposed dentin in human molars was abraded with 600-grit silicon carbide sandpaper. Raman spectra were acquired on the smear debris and collected from the sandpaper before and after treatment with 10% citric acid, 35% H3PO4, or 0.5M ethylenediaminetetraacetic acid (EDTA). The resultant smeared dentin samples were treated with one of the aforementioned reagents, and spectra were acquired at 1.0-μm intervals across the interfaces of the smear layers/demineralized dentin/mineralized dentin. Corresponding specimens were morphologically analyzed with scanning electron microscopy (SEM). The results showed that the composition of the smear debris and the in situ smear layers was a mixture of disorganized collagen and mineral. Spectral changes in the smear debris suggested that the disorganized collagen was denatured by acid treatment. The denatured collagen formed a gelatinous matrix around the mineral in the smear layer, thereby shielding it from the acid. The smear layers were not apparent in the SEM micrographs of acid-etched dentin prepared and processed with conventional techniques. The micro-Raman spectroscopic results presented in this study provide the first direct evidence that partially denatured collagen within smear layers is not removed and that the mineral is only partially removed with acids that represent conventional dentin adhesive etchants. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 60: 300–308, 2002; DOI 10.1002/jbm.10108

Analysis of acid-treated dentin smear debris and smear layers using confocal Raman microspectroscopy.

It is commonly reported that acid etchants remove the smear layer, but to date, there has been no chemical evidence to support these observations. The purpose of this study was to determine the molecular structure of acid-etched carbide- and diamond-bur-created smear layers. This project tested the null hypothesis that such smear layers are totally removed with current etchants. Smear layer/demineralized/mineralized dentin interfaces were analyzed at 1- m intervals by micro-Raman spectroscopy. Features associated with the organic component were substantially broadened with loss of fine structure, and mineral peaks were clearly evident in the spectra of acid-etched smear layers. The organic features in the spectra of the EDTAtreated smear layer showed relative intensity ratios similar to demineralized dentin without contribution from the mineral phase. The disorganized collagen within the smear layer was not removed but was denatured by the acid treatment; the mineral was trapped in this gelatinous matrix ...

Yong Wang

Papers

Effects of water content and initiator composition on photopolymerization of a model BisGMA/HEMA resin.

Analysis of acid-treated dentin smear debris and smear layers using confocal Raman microspectroscopy.

Molecular Structure of Acid-etched Dentin Smear Layers-in situ Study

Morphological and chemical characterization of bonding hydrophobic adhesive to dentin using ethanol wet bonding technique

Physicochemical interactions at the interfaces between self-etch adhesive systems and dentine