Osteoprotegerin expressed by osteoclasts: an autoregulator of osteoclastogenesis

Osteoprotegerin (OPG) is secreted by stromal and osteoblastic lineage cells and inhibits osteoclastogenesis by preventing the interaction of receptor activator of nuclear factor-κB ligand (RANKL) with receptor activator of nuclear factor-κB (RANK). In this study, the expression of OPG in osteoclasts themselves and its biological functions during osteoclastogenesis were investigated for the first time. OPG expression in vivo in the developing rat maxilla was examined by immunofluorescence analysis. OPG expression in osteoclasts during in vitro osteoclastogenesis was determined by reverse-transcription polymerase chain-reaction (RT-PCR), Western blot, and immunofluorescence staining. We determined the function of OPG produced by osteoclasts during osteoclastogenesis by silencing the OPG gene. The effects of OPG on bone-resorbing activity and apoptosis of mature osteoclasts were examined by the assay of resorptive pit formation on calcium-phosphate-coated plate and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining, respectively. In the immunofluorescence findings, strong immunoreactivities were unexpectedly seen in multinucleated tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts around the growing and erupting tooth germs in the rat alveolar bone. In vitro, OPG expression was significantly increased during the differentiation of osteoclasts from mouse bone-marrow-derived cells treated with a combination of macrophage colony-stimulating factor (M-CSF) and RANKL. Interestingly, it was found that OPG small interfering (si)RNA treatment during osteoclastogenesis enhanced the sizes of osteoclasts, but attenuated their bone-resorbing activity. Also, the increased chromosomal DNA fragmentation and caspase-3 activity in the late phase of osteoclastogenesis were found to be decreased by treatment with OPG siRNA. Furthermore, effects of OPG siRNA treatment on osteoclastogenesis and bone-resorbing activity were recovered by the treatment of exogenous OPG. These results suggest that OPG, expressed by the osteoclasts themselves, may play an auto-regulatory role in the late phase of osteoclastogenesis through the induction of apoptosis.

PrPc is temporospatially expressed in molar development of rats

Odontogenesis, tooth development, is derived from two tissue components: ectoderm and neural crest-derived mesenchyme. Cyto-differentiation of odontogenic cells during development involves time-dependent and sequential regulation of genetic programs. This study was conducted to detect molecules implicated in cyto-differentiation of developing molar germs of rats. Differential display-PCR revealed that PrP(c) was differentially expressed between cap/early bell-staged germs (maxillary 3rd molar germs) and root formation-staged germs (maxillary 2nd molar germs) at postnatal day 9. Both levels of PrP(c) mRNA and protein expression were higher in the root formation stage than the cap/early bell stage and increased in a time-dependent manner. Immunofluorescence revealed for the first time that PrP(c) was not localized in the enamel organ, but localized in dental follicular cells for the development of the periodontal ligament and cementum as well as odontoblasts, both of which are of neural crest origin. These results suggest that the physiological functions of the PrP(c) in tooth development may be implicated in the differentiation of neural crest-derived mesenchyme including the periodontal tissues for root formation rather than epithelial tissue.

Psychiatric morbidity of second and third grade primary school children in Korea

This study was undertaken to identify psychiatric morbidity among Korean second and third elementary school children using an objective diagnostic interview tool. Data from 5,118 (2,723 boys, 2,395 girls; mean age = 8.41 years (SD = 0.66)) second and third grade schoolchildren were drawn from 28 elementary schools. After initial screening assessments using the 28-item Child Problem-Behavior Screening Test for parents, 672 primary caregivers were subjected to secondary screening using the Korean version of the CBCL. Two hundred and seventy-one high-risk children selected according to the K-CBCL results, 138 (50.9%) children and their primary caregivers were interviewed using the Korean version of K-SADS-PL for objective DSM-IV psychiatric diagnoses. Sixty-four (46.4%) of the hundred and thirty eight children were determined to have at least one psychiatric disorder. More boys were diagnosed as psychiatric patients than girls (46 males, 18 females; OR = 2.21). The most frequently diagnosed disorder was ADHD (46/64; 71.9%), followed by tic disorder, anxiety disorders, mental retardation, oppositional defiant disorder, and separation anxiety disorder. Two or more comorbid psychiatric disorders were found in 22 (34.4%) of the 64 patients. The computed crude percentage of psychiatric patients in this study was 4.12%, which is similar to previously published data.

Effect of hole-trapping on mass/charge transport properties in acceptor-doped BaTiO3

The equilibrium conductivity and chemical diffusivity of Al-doped, single-crystalline BaTiO3 [C. R. Song and H. I. Yoo, J. Am. Ceram. Soc., 2000, 83, 773] have been re-analyzed by taking account of possible hole-trapping by acceptor-dopants (Al) with reference to the data on undoped BaTiO3 [C. R. Song and H. I. Yoo, Phys. Rev. B, 2000, 61, 3975]. The trapping effect is accounted for by the effective mobility of free holes involving the weighted mobility of trapped holes and by the modified thermodynamic factor due to the shift of the stoichiometric composition of the acceptor-doped system. The equilibrium constant of the trapping reaction Al(Ti)x = Al(Ti)' + h* is evaluated as Ka = 1.9 x 10(23) exp(-1.04 eV/kT) cm(-3) and the mobility of trapped holes (Al(Ti)x) as u(x) approximately = 720 exp(-1.04 eV/kT) cm2 V(-1) s(-1) as the upper bound while those of free electrons and holes as un = 0.044 + 0.010 cm2 V(-1) s(-1) and up approximately = 0.024 +/- 0.007 cm2 V(-1) s(-1), respectively, in the temperature range of 800 degrees C to 1100 degres C. The effect of hole-trapping on DC conductivity, chemical diffusivity and oxygen nonstoichiometry is exhaustively analyzed and further experiments are proposed that allow one to determine the trapping energy of acceptor impurities.