Biomedical subjects

Wei Yao

Publications and source records attributed to Wei Yao.

At least 37 records · Page 2Linked to original sources

PubMed2005

[Effects of post diameter on retention of post-core crown system].

OBJECTIVE: To access the effects of post's diameter on the retention of post-core restorations. METHODS: Thirty-three simulant roots with same length,taper and different diameter (1.305 mm, 1.830 mm, 2.175 mm and 2.700 mm respectively) were made of polymethylmethacrylate and were divided into 4 groups. The wax patterns of post-cores were manufactured and cast. The post-cores were cemented. After that, the adhesion, frictional force and restriction of the post-core restorations were measured. RESULTS: When the proportion of length and diameter was smaller than 4.372, the linear regression between the post's diameter and the retention of post-core crown system was F = 107.98 + 72.08D. The linear regression between the post's diameter and the adhesion was P = 9.60 + 2.22D. The linear regression between the post's diameter and the frictional force and restriction was Q = 98.37 + 69.87D. The statistical analysis of the results indicated significant difference (P < 0.05). When the proportion of length and diameter was lager than 4.372, the retention of post-core crown system increased although the post's diameter decreased. CONCLUSION: When the proportion of length and diameter was smaller than 4.372, the retention of post-core crown system increased with the decrease of the post's diameter. While the proportion was lager than a certain value, this rule did not exist.

Crowns↗

PubMed2005

[Role of Fas and FasL expression in apoptosis of pulmonary artery smooth muscle cells in hypoxia induced by inhibition of Na+/H+ exchanger isoform-1 in rat].

OBJECTIVE: To investigate the role of Fas and FasL expression in apoptosis of pulmonary artery smooth muscle cells (PASMCs) in hypoxia induced by inhibition of Na(+)/H(+) exchanger isoform-1 (NHE-1) in rat. METHODS: The cells were cultured in hypoxia (<1% O(2)) for 2, 6, 12, 24 and 48 hours respectively. Then cell apoptosis was observed with terminal deoxynudeotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL). The changes in fas and fasl mRNA expression in PASMCs were detected by semi-quantitative reverse transcription-polymerase chain reaction (sqRT-PCR) in vitro. The expression of Fas and FasL protein in cells was determined immunohistochemically. RESULTS: No significant changes in the expression of fas/fasL mRNA and protein between cells transfected with NHE-1 ribozyme gene and cells transfected with pLXSN, or non-transfected control in hypoxia. CONCLUSION: Apoptosis of PASMCs induced by NHE-1 inhibition may occur independently of Fas/FasL death pathway.

Animals↗

PubMed2005

[Effects of post length on the dislocation of post and core crown].

OBJECTIVE: To evaluate the effects of the length of post on the dislocation of cast post and core crown. METHODS: Forty simulated tooth roots made of polymethyl methacrylate were divided into five groups according to different length of post. These cast post and core were bonded with zinc phosphate cement. Then these specimens were strectched on the INSTRON-4302 by the speed of 10 mm/min. The maximum of load was recorded. RESULTS: The loads of 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm were (203.25 +/- 57.19) N, (213.63 +/- 45.06) N, (234.44 +/- 59.27) N, (317.75 +/- 60.94) N, (334.25 +/- 58.00) N respectively. Linear regression analysis revealed the linear relationship of post length with dislocation, bonding, and mechanical interlocking; the values of r being 0.676, 1.000, 0.949; the regression equations being D = 73.225L - 325.776, B = 0.442L + 9.951, M = 72. 676L-334. 338. CONCLUSION: Mechanical interlocking is the main factor in dislocation of post and core crown. The length of post should be increased from 2/3 to 3/4 of the length of tooth root when prepared in clinic.

Crowns↗

PubMed2005

[Effects of the loss of alveolar bone on the areas of periodontal ligament, mechanical fulcrum and fracture resistance of root and post-core system].

OBJECTIVE: To assess the effects of loss of alveolar bone on the areas of periodontal ligament (PL), mechanical fulcrum and fracture resistance of root and post-core system. METHODS: One hundred and eight simulated roots in the same length, taper and diameter were made of polymethylmethacrylate and were divided into 13 groups. Then the wax patterns of post-cores were casted and cemented. Each specimen was embedded in acrylic resin in accordance with different loss of alveolar bone and different mechanical fulcrum. Base on the anatomic and physiological special features of the periodontal tissues, three mechanical methods were designed. The compress test was run by the speed of 1 mm/min and the fracture resistance was recorded. The areas of periodontal ligament were measured and calculated. RESULTS: When the loss of alveolar bone and the mechanical fulcrum were 0 mm and 12/12 group, 1 mm and 11/12 group, 2 mm and 10/12 group, 3 mm and 9/12 group, 3.5 mm and 8.5/12 group, 4 mm and 8/12 group, 4.5 mm and 7.5/12 group, 5 mm and 7/12 group,5. 5 mm and 6.5/12 group, 6 mm and 6/ 12 group, 7 mm and 5/12 group, 8 mm and 4/12 group, 9 mm and 3/12 group, the means of the areas of PL (mm2) and fracture resistance (N) were 178.95 and 232. 90 +/- 25. 93, 159. 64 and 195.58 +/- 12.46, 141.18 and 173.92 +/- 13.51, 123.27 and 154.00 +/- 11.74, 106.14 and 123.25 +/- 14.29, 89.67 and 96.86 +/- 6. 20, 73.90 and 59.14 +/- 7.28, 58.82 and 52.52 +/- 5. 82, 44.44 and 45.90 +/- 7.40, 30.76 and 58.60 +/- 6.63 (mm, N). The linear correlations were found between the percentage of the loss of alveolar bone and surplus areas of PL, the loss of alveolar bone and the fracture resistance of root and post-core system, the percentage of the areas of PL and the fracture resistance of root and post-core system, the distance of the fulcrum and the percentage of the loss of alveolar bone. CONCLUSION: The loss of alveolar bone caused the decrease in areas of PL, the dessent of mechanical fulcrum, and the diminution of the fracture resistance of root and post-core system.

Alveolar Bone Loss↗

PubMed2004

Protection of pirfenidone against an early phase of oleic acid-induced acute lung injury in rats.

The potential role of PFD [5-methyl-L-phenyl-2-(1H)-pyridone], an antifibrotic compound with anti-inflammatory effects, in several models of acute lung injury (ALI) has gained increasing attention; however, the protective effect of PFD in oleic acid (OA)-induced ALI remains unknown. We hypothesized that PFD protects from OA-induced ALI in rats, and we hoped to obtain the optimum preclinical conditions with PFD in ALI. Sprague-Dawley rats were randomized into five groups (five rats per group): normal control group, OA-treated group (0.15 ml/kg), and three PFD-treated groups (20, 40, and 80 mg/kg p.o., respectively). Arterial blood gases, lung wet/dry weight ratio, and postmortem histological changes were determined 0.5, 1, 2, 6, and 24 h after OA challenge. Electron spin resonance spectroscopy was used for free radical detection and measurement. Experiments were examined based on the orthogonal test L4 (4(2)) setting two factors (PFD dose and PFD valid time) with four different levels. The results of the orthogonal test showed that the sequence of effect of PFD was 0.5 h (oxygen radicals), 1 h (histological changes), 2 h (lung edema), and 6 h (partial pressure of oxygen) after OA challenge, and 40 mg/kg PFD was the most effective dose in this study. We conclude that PFD protects against OA-induced ALI in rats. The mechanism of these protective effects partly involves decrease of oxygen radicals. The data of this study proves that the orthogonal test will be a powerful method to help obtain the optimum experimental conditions with PFD in ALI in the future.

Animals↗

PubMed2004

Capsaicin-sensitive sensory neurons contribute to the maintenance of trabecular bone integrity.

UNLABELLED: This investigation used capsaicin to selectively lesion unmyelinated sensory neurons in rats. Neuronal lesioning induced a loss of trabecular integrity, reduced bone mass and strength, and depleted neuropeptides in nerve and bone. These data suggest that capsaicin-sensitive sensory nerves contribute to trabecular bone integrity. INTRODUCTION: Familial dysautomia is an autosomal recessive disease in which patients suffer from unmyelinated sensory neuron loss, reduced BMD, and frequent fractures. It has been proposed that the loss of neurotransmitters synthesized by unmyelinated neurons adversely affects bone integrity in this hereditary syndrome. The purpose of this study was to determine whether small sensory neurons are required for the maintenance of bone integrity in rats. MATERIALS AND METHODS: Ten-month-old male Sprague-Dawley rats were treated with either capsaicin or vehicle. In vivo DXA scanning and micro CT scanning, and histomorphometry were used to evaluate BMD, structure, and cellular activity. Bone strength was measured in distal femoral sections. Body weight and gastrocnemius/soleus weights were measured and spontaneous locomotor activity was monitored. Peroneal nerve morphometry was evaluated using light and electron microscopy. Substance P and calcitonin gene-related peptide (CGRP) content in the sciatic nerve and proximal tibia were determined by enzyme immunoassay (EIA). Substance P signaling was measured using a sciatic nerve stimulation extravasation assay. RESULTS: Four weeks after capsaicin treatment, there was a loss of BMD in the metaphyses of the tibia and femur. In the proximal tibia, the osteoclast number and surface increased, osteoblast activity and bone formation were impaired, and trabecular bone volume and connectivity were diminished. There was also a loss of bone strength in the distal femur. No changes occurred in body weight, 24-h grid-crossing activity, weight bearing, or muscle mass after capsaicin treatment, indicating that skeletal unloading did not contribute to the loss of bone integrity. Capsaicin treatment destroyed 57% of the unmyelinated sensory axons, reduced the substance P and CGRP content in the sciatic nerve and proximal tibia, and inhibited neurogenic extravasation. CONCLUSION: These results support the hypothesis that capsaicin-sensitive sensory neurons contribute to the maintenance of trabecular bone integrity. Capsaicin-sensitive neurons have efferent functions in the tissues they innervate, effects mediated by transmitters released from the peripheral nerve terminals. We postulate that the deleterious effects of capsaicin treatment on trabecular bone are mediated by reductions in local neurotransmitter content and release.

Absorptiometry, Photon↗

PubMed2004

Mice lacking the integrin beta5 subunit have accelerated osteoclast maturation and increased activity in the estrogen-deficient state.

UNLABELLED: Integrin alphavbeta5 is expressed on osteoclast precursors and is capable of recognizing the same amino acid motif as alphavbeta3. Three-month-old beta5(-/-) female OVX mice had increased osteoclastogenesis ex vivo, and microCT assessment of trabecular bone volume was 53% lower than WT-OVX animals. These preliminary data suggest alphavbeta5 integrin's presence on osteoclast precursors may inhibit of osteoclast formation. INTRODUCTION: Osteoclasts are unique resorptive skeletal cells, capable of degrading bone on contact to the juxtaposed matrix. Integrin alphavbeta5 is expressed on osteoclast precursors, structurally similar to alphavbeta3, and capable of recognizing the same amino acid motif. Given the structural relationship and reciprocal regulation of alphavbeta3 and alphavbeta5, the purpose of this study was to evaluate how alphavbeta5 might contribute to osteoclast maturation and activity. MATERIALS AND METHODS: Three-month-old wildtype (WT) and beta5(-/-) female mice had ovariectomy (OVX) or sham operations. The osteoclastogenic capacity of marrow-derived precursors, the kinetic, the circulating, and structural parameters of bone remodeling, was determined after 6 weeks of paired feeding. RESULTS AND CONCLUSIONS: OVX increased osteoclastogenesis ex vivo and in vivo. Osteoclast formation and prolonged pre-osteoclast survival were substantially enhanced in cultures containing beta5(-/-) cells whether obtained from sham-operated or OVX mice. Expression of cathepsin K, beta3 integrin subunit, and calcitonin receptor were accelerated in cultured beta5(-/-)osteoclasts. beta5(-/-) osteoclasts from OVX animals showed a 3-fold enhancement of net resorptive activity, with quantitative muCT showing trabecular bone volume loss after OVX 53% greater in beta5(-/-) OVX compared with similarly treated WT OVX mice (p < 0.05). alpha5beta3 seems to be an inhibitor of osteoclast formation, in contrast to alphavbeta3. In addition, loss of alphavbeta5 seems to accelerate osteoclast formation in the OVX model. Further examination of alphavbeta5 signaling pathways may enhance our understanding of the activation of bone resorption.

Animals↗

PubMed2004

N-aroyloxylthioxo-naphthalimides as DNA photocleavers of aroyloxyl oxygen radicals: synthesis, evaluation, and substituents' effect.

Novel N-Aroyloxylthioxo-naphthalimides as highly efficient 'time-resolved' DNA photocleavers of aroyloxyl radicals type were designed and synthesized. The substituents at the aroyloxyl moiety have an important and unusual influence on the DNA photocleavage, and DNA photodamages of the compounds were unusually not depended on the electronic effects of substituents on the corresponding oxygen-centered radicals. With AM1 semi-empirical quantum calculation, it was found that their photocleaving activities were correlated with the densities of electron clouds on the N-O bonds in the triplet state. N-(m-Dichloro-benzoyloxy)-thioxo-naphthalimide could photodamage DNA effectively at less than the concentration of 2 microM.

DNA↗

PubMed2004

Star algorithm: detecting the ultrasonic endocardial boundary automatically.

In clinical practice, interuser variability, high computational cost and low image quality are always big problems that puzzle the clinical application of computer-aided echocardiographic boundary detection. Star algorithm (StaA) is a new endocardial boundary detector that has been designed to overcome these problems. The purpose of the paper is to present the detection details of the algorithm and evaluate its clinical value. The main elements of StaA are radial search technique, cost function-driven system and self-designed edge detector. The algorithm has four main steps: image preprocessing, initial left ventricular chamber detection, left ventricular chamber center detection and left ventricular endocardial boundary detection. StaA was performed on 50 pairs of end-diastolic (ED) and end-systolic (ES) echocardiographic images, which were divided into high image-quality group (HImQ) and low image-quality group (LImQ). The results of the test were analyzed in two ways: 1. Compared with the manually-traced boundary, the mean relative radial error (MRRerr) of the computer-detected boundary was 12.07% and there is no significant difference of MRRerr between HImQ and LImQ. 2. The two-dimensional (2-D) ejection fraction calculated by the computer detected boundary (EFa) can be used interchangeably with that calculated by the manually-traced boundary (EFm). The test proves that simple and effective methods can also make the echocardiographic boundary detector automatic, quick and robust.

Algorithms↗

PubMed2004

Changes in serum receptor activator of nuclear factor-kappaB ligand, osteoprotegerin, and interleukin-6 levels in patients with glucocorticoid-induced osteoporosis treated with human parathyroid hormone (1-34).

Changes in biochemical markers of bone turnover following intermittent injections of human (h)PTH (1-34) suggest that bone formation is initially favored over bone resorption. hPTH (1-34) is also known to influence osteoclast maturation and activity through modulation of osteoblast-derived cytokines, such as receptor activator of nuclear factor-kappaB ligand (RANKL), osteoprotegerin (OPG), IL-6, and IL-6 soluble receptor (IL-6sR). In this experiment, we investigated the changes in serum levels of soluble RANKL (sRANKL), OPG, IL-6, and IL-6sR in patients with glucocorticoid-induced osteoporosis treated with hPTH (1-34). Fifty-one postmenopausal women with glucocorticoid-induced osteoporosis were randomized to receive 12 months of 400 U hPTH (1-34) ( approximately 40 microg) daily and standard hormone replacement therapy, or hormone replacement therapy alone. Serum levels of sRANKL, OPG, IL-6, and IL-6sR were measured at baseline, 1 month, and every 3 months thereafter for a total of 24 months. hPTH (1-34) caused a rapid and significant increase in sRANKL within 1 month, and the levels remained elevated throughout the duration of therapy. IL-6 and IL-6sR increased significantly within 1 month, but returned to baseline levels more rapidly. In contrast, OPG was mildly suppressed beginning 6 months after hPTH therapy. These data support the hypothesis that hPTH (1-34) initially stimulates osteoblast maturation and function, which in turn leads to osteoclast activation and a gradual rebalancing of bone formation and resorption.

Aged↗

PubMed2004

[Clinical significance of soluble selectins and matrix metalloproteinases-9 in patients after successful cardiopulmonary resuscitation].

OBJECTIVE: To investigate whether patients after successful cardiopulmonary resuscitation (CPR) exist elevated levels of soluble P-and E-selectin (sP-selectin, sE-selectin), matrix metalloproteinases-9 (MMP-9) and to evaluate the clinical significance of changes in these cytokine levels. METHODS: Plasma levels of sP-and sE-selectin, MMP-9 of 82 patients who survived >or=48 hours after CPR were determined on the second day after successful CPR. They were classified into different groups according to whether causing systemic inflammatory response syndrome (SIRS) and developing sepsis. Sixty-five non-critically ill patients were served as control group. RESULTS: Incidence of SIRS was 68.3% (56/82 cases) after successful CPR. Plasma levels of sP-selectin were higher in patients with SIRS compared with those in patients without SIRS or control group (all P<0.01). Plasma levels of sE-selectin and MMP-9 were not significantly different between patients with SIRS and without SIRS (all P>0.05), but were higher in both patient groups than those in the control group (all P<0.01) 43.9% of the patients developed sepsis within 1 week after CPR. Plasma levels of sP-selectin were higher in patients developing sepsis than those in patients without sepsis (P<0.05), but plasma levels of sE-selectin and MMP-9 were not significantly different between two groups (all P>0.05). Plasma levels of sE-selectin and MMP-9 were higher in nonsurvivors than those in survivors (both P<0.01), but plasma levels of sP-selectin were not significantly different between two groups (all P>0.05). CONCLUSION: SIRS is a frequent but unspecific finding after CPR with only minor impact on outcome. Determination of sP-and sE-selectin, MMP-9 early after CPR might help to identify patients at a high risk for sepsis or an adverse, respectively.

Adult↗

PubMed2004

[The effect of Na(+)/H(+) exchanger-1 (NHE-1) antisense expression vector on NHE-1 gene expression in human lung adenocarcinoma cells and its biological significance].

OBJECTIVE: To explore the inhibitory effect of Na(+)/H(+) exchanger-1 (NHE-1) antisense expression vector on NHE-1 gene in human lung neoplasm cells and to observe its biological effect. METHODS: NHE-1 antisense vector (pNHE-1) was introduced into human lung adenocarcinoma cell line A549 cells with cationic liposome transfection methods. Semi-quantification RT-PCR was performed to analyze the expression level of NHE-1 mRNA in A549 cells and transfected A549 cells. Intracellular pH (pHi) values were measured with fluorescence spectrophotometer. The growth characteristics of the cells was observed. Tumor cell apoptosis was observed with in situ apoptosis assessment. RESULTS: PCR verified the integration of antisense vector with the genomic DNA of transfected cells in positive clones. Semi-quantification RT-PCR showed that the NHE-1 gene expression level was significantly lower in transfected A549 cells (0.42 +/- 0.06) than in those untransfected (0.71 +/- 0.08, P < 0.01) and those transfected with pLXSN (0.69 +/- 0.16, P < 0.01). Compared with A549 cells, pHi values decreased significantly in transfected A549 cells at 12 h, 24 h and 48 h (6.990 +/- 0.005, 6.840 +/- 0.005 and 6.750 +/- 0.005 respectively vs 7.150 +/- 0.004, 7.140 +/- 0.007 and 7.120 +/- 0.008 respectively, P < 0.001). The growth of transfected A549 cells was significantly slower (P < 0.01), the double time was longer (3.20 vs 4.97) and the apoptosis rate was markedly higher [(24.50 +/- 3.62)% vs (1.50 +/- 0.55)%, P < 0.01]. CONCLUSION: The antisense vector was successfully transfected to A549 cells with liposome and integrated with transfected cell genome, and the expression of NHE-1 mRNA of A549 cells was inhibited, thereby resulted in a decrease of the pHi value by means of reduction of Na(+)/H(+) exchanging activity, with the inhibition of proliferation and growth of A549 cells and increased of A549 cell apoptosis.

Adenocarcinoma↗

PubMed2004

[Role of bcl-2 and bax expression in apoptosis of hypoxic pulmonary artery smooth muscle cells of rats induced by Na+/H+ exchanger isoform-1 inhibition in vitro].

OBJECTIVE: To investigate the role of bcl-2 and bax expression in apoptosis of hypoxic pulmonary artery smooth muscle cells (PASMCs) of rats induced by Na+/H+ exchanger isoform-1 (NHE-1) inhibition in vitro. METHODS: Cultured rat PASMCs transfected with NHE-1 ribozyme gene (PRZ cell), cultured rat PASMCs transfected only with pLXSN vector (PX cell) and non-transfected rat PASMCs (PA cell) were obtained in our previous studies. The cells were cultured under low oxygen tension (<1% O2) for 0, 2, 6, 12, 24 and 48 hours respectively. Then cell apoptosis was examined with terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). Intracellular Ca2+([Ca2+]i) of cells was measured using fluorescence dye Fura-2/AM. The changes in mRNA expression of bcl-2 and bax in cells were assessed by semi quantitative reverse transcription-polymerase chain reaction (sqRT-PCR). The expression of Bcl-2 protein and Bax protein of cells was detected immunohistochemically. RESULTS: In contrast to normal PASMCs and cells transfected with pLXSN, the apoptosis rates in recombinant vectors transfected cells increased significantly and continuously. [Ca2+]i values were also increased in these cells, but the increase extent was remarkably lower than in the normal PASMCs (all P<0.01). The expression of bax mRNA and protein of cells transfected with recombinant vectors was increased significantly compared with cells of other two groups. Meanwhile, the expression of bcl-2 mRNA and protein of these cells were decreased significantly. CONCLUSION: The NHE-1 specific hammerhead ribozymes induce apoptosis of PASMCs under low oxygen tension by inhibiting the increase in intracellular Ca2+ concentration, increasing bax expression and decreasing bcl-2 expression.

Animals↗

PubMed2004

[Inhibition of human lung fibroblast proliferation and the mitogen activated protein kinase pathway by dexamethasone].

OBJECTIVE: To investigate the effects of dexamethasone on human lung fibroblast cell proliferation, cell cycles, and cell mitogen-activated protein kinases (MAPKs) passway. METHODS: Dexamethasone was used at various concentration in culture medium. Cell number was counted using a hemacytometer. Whole cell propidium iodide staining and flow cytometric analysis were performed to determine cellular DNA content. MAPK proteins and activation were tested by Western blot analysis with antibodies to c-Jun N-terminal kinase (JNK), phospho-JNK, extracellular signal-regulated kinase (ERK), phospho-ERK, p38 and phospho-p38. RESULTS: 1x10(-7) mol/L and 1x10(-6) mol/L dexamethasone suppressed the proliferation of lung fibroblast cells by 34% and 72%, respectively, than that of control. This suppression was dose-dependant. Dexamethasone suppressed cell cycle with accumulation of cells in G1/G0 stage. It increased from 81.9% to 90.1% compared with that of control. We did not find any apoptosis induced by dexamethasone for lung fibroblast cells. Using Western blot analysis, we found that dexamethasone resulted in decreased activity of ERK, but had no effects on JNK and p38. CONCLUSIONS: Dexamethasone may suppresses the proliferation of lung fibroblast cells, which is partly resulted from the facts that it can inhibit ERK activation in MAPK-signaling pathway but has little effect on JNK and p38 pathway. Dexamethasone may not induce lung fibroblast cell apoptosis directly.

Cell Cycle↗

PubMed2004

[Detection of RNA of SARS coronavirus in hospital sewage].

OBJECTIVE: In order to explore the existence of SARS coronavirus (Co-V) and/or its RNA in sewage of hospitals administered SARS patients. METHODS: A novel electropositive filter was used to concentrate the SARS-CoV from the sewage of two hospitals administered SARS patients in Beijing, including twelve 2,500 ml sewage samples from the hospitals before disinfection, and ten 25,000 ml samples after disinfection; as well as cell culture, RT-PCR and sequencing of gene to detect and identify the viruses from sewage. RESULTS: There was no live SARS-CoV detected in the sewage in this study. The nucleic acid of SARS-CoV had been found in the 12 sewage samples before disinfection from both hospitals by semi-nested PCR. After disinfection, SARS-CoV RNA could only be detected from the samples from the 309th Hospital, and the others were negative. CONCLUSION: It provides evidence that there is no live SARS-Cov in the sewage from hospitals with SARS patients though SARS-CoV RNA can be detected.

Hospitals↗

PubMed2004

[A comparative study on experimental and mathematical analysis of mechanical properties of PFM].

In this study we compare the experimental and mathematical analyses of mechanical properties of PFM and analyze their correlation levels and inner links. Fifteen PFM specimens with different thickness ratio of metal to porcelain are made , with the shape of 26mm x 4mm x 1.5mm, and are divided into 5 groups, the metal thickness increases with 0.05mm change each among every group from 0.25mm to 0.45mm, the porcelain thickness decreases accordingly. The three-point-fracture test is used to measure their bending strength and elastic modulus, exhibit their changing laws, and disclose their inner relationships. When the whole thickness of the specimen is determined, the fracture load, bending strength and elastic modulus increase according to the increase of the metal thickness. The experimental mechanical properties of PFM are significantly influenced by the thickness ratio of metal to porcelain, and are the same as the theoretical ones calculated by the mixed law formula of compound material. There is significant correlation between the experimental analysis and mathematical analysis of mechanical properties of PFM. The regression coefficients can be obtained to describe this relationship. Further more, they can be used as the corrected parameters of the theoretical formula. The corrected mathematical formula is helpful to predicting and improving the mechanical properties of PFM.

Compressive Strength↗

PubMed2003

The signaling adapter protein DAP12 regulates multinucleation during osteoclast development.

UNLABELLED: Deficiency of the signaling adapter protein DAP12 is associated with bony abnormalities in both mice and humans. We identify specific DAP12-associated receptors expressed by osteoclasts and examine function of DAP12 in murine osteoclasts in vivo and in vitro. These data show a new role for DAP12 signaling in regulating formation of multinucleated osteoclasts. INTRODUCTION: Osteoclasts are bone-resorbing cells derived from hematopoietic precursors in the myeloid lineage. In other myeloid cell types, the signaling adapter protein DAP12 transmits activating signals on ligation of a DAP12-associated receptor (DAR). The aim of this study was to clarify the role of DAP12 signaling during osteoclast development. MATERIALS AND METHODS: Osteoclasts from DAP12 -/- or control mice were analyzed in vitro for morphology, function, and for osteoclast markers. DARs were identified in osteoclast cultures through reverse transcriptase-polymerase chain reaction (RT-PCR). Bone density of DAP12 -/- and control mice were analyzed by microcomputed tomography. DAP12 -/- osteoclasts were retrovirally reconstituted with DAP12. RAW264.7 cells were transfected with FLAG-tagged DAP12 or TREM2 and stimulated by anti-FLAG antibody during in vitro osteoclastogenesis. RESULTS: C57BL/6 DAP12-deficient mice have higher bone mass than C57BL/6 wildtype controls. We verified the presence of DAP12 in pre-osteoclasts and osteoclasts derived from C57BL/6 or the pre-osteoclast line RAW 264.7 and identified the DARs expressed. DAP12 -/- osteoclasts developed in vitro with macrophage colony-stimulating factor (M-CSF) and RANKL formed only intensely TRACP+ mononuclear cells and failed to generate multinuclear osteoclasts. These mononuclear cells are functional osteoclast-like cells because, by RT-PCR, they express other osteoclast markers and generate resorption pits on dentine slices, although quantitative assessment of bone resorption shows decreased resorption by DAP12 -/- osteoclasts compared with C57BL/6 osteoclasts. Restoration of DAP12 expression by retroviral transduction of DAP12 -/- osteoclast precursors rescued in vitro osteoclast multinucleation. Direct stimulation of DAP12 expressed in RAW264.7 during in vitro osteoclastogenesis led to a marked increase in the number of TRACP+ multinucleated osteoclast-like cells formed. CONCLUSION: Our studies indicate that stimulation of the DAP12 adapter protein plays a significant role in formation of multinuclear osteoclasts and that DAP12 and DARs likely participate in the regulation of bony remodeling.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Novel naphthalimide hydroperoxide photonucleases: the role of thiocyclic-fused area and the difference in spectra, photochemistry and photobiological activity.

Novel five- and six-membered thiocyclic-fused naphthalimide hydroperoxides (7, 8) as photonucleases were designed, synthesized via unusual isomerization in Pschorr cyclization and photooxygenation. The five-membered 7 was able to induce single-strand nicks in duplex DNA pH independently (7.0-8.5) at 0.5 microM under 366 nm, while the six-membered 8 could photonick the duplex DNA pH dependently (7.0-8.5) at 5 microM under 450 nm and showed 'time-controlled' photo-bioactivity. Their thiocycles and the angular conjugated plane have contributions to their binding affinity with DNA and photocleaving efficiency.

Cyclization↗