Image analysis of peripheral compression artefacts of ThinPrep(®) liquid-based cytology preparations.

OBJECTIVE: ThinPrep (TP), one of the Food and Drug Administration-approved liquid-based cytology (LBC) preparations, is widely used for gynaecological and non-gynaecological cytology samples. A unique physical artefact caused by the compression at the periphery in TP slides has not been adequately evaluated to date. METHODS: We processed four established tumour cell lines (MKN28, MKN45, KG-1 and NB4) and mononuclear cells isolated from whole blood over Ficoll-Plaque for TP preparations. For this part of the study, we included five normal cervical LBC preparations. We then auto-counted and auto-measured the area, mean grey value and Feret's diameter in both the inner disc and peripheral rim of the preparations by image morphometry. In addition, we compared the distribution of atypical cell groups in the peripheral rim and inner disc of 132 lung aspirates, 80 thyroid aspirates, 212 cerebrospinal fluids (CSFs) and 50 gynaecological samples. RESULTS: The areas and Feret's diameters of the cytoplasm in the peripheral compressed rim area were statistically larger than those of cells in the inner disc. The mean grey values of cells (cytoplasm and nucleus) in the peripheral compression rim were also smaller than those in the inner disc cells, leading to decreases in nuclear and cytoplasmic chromatism. Except for the mean grey values, the differences were not significant in the cervical samples. CONCLUSIONS: Cellular morphology may be markedly distorted in the peripheral rim, regardless of cell malignancy, which may lead to the misinterpretation of cells during the screening. Accordingly, cytological diagnosis based on the findings within the peripheral rim should take this phenomenon into account. Compressed cells found in the peripheral rim should be interpreted with caution when TP slides are used for cytopathological diagnosis.

Interfacial reactions of nano-structured Cu-doped indium oxide/indium tin oxide ohmic contacts to p-GaN.

Interfacial microstructure and elemental diffusion of Cu-doped indium oxide (CIO)/indium tin oxide (ITO) ohmic contacts to p-type GaN for light-emitting diodes (LEDs) were investigated using cross-sectional transmission electron microscopy (XTEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction. The CIO/ITO contacts gave specific contact resistances of approximately 10(-4) omegacm2 and transmittance greater than 95% at a wavelength of 405 nm when annealed at 630 degrees C for 1 min in air. After annealing at 630 degrees C, multi-component oxides composed of Ga2O3-In2O3, Ga2O3-CuO, and In2O3-CuO formed at the interface between p-GaN and ITO. Formation of multi-component oxides reduced the barrier height between p-GaN and ITO due to their higher work functions than that of ITO, and caused Ga in the GaN to diffuse into the CIO/ITO layer, followed by generation of acceptor-like Ga vacancies near the GaN surface, which lowered contact resistivity of the CIO/ITO contacts to p-GaN after the annealing.

The effect of vertebral material description during vertebroplasty.

Vertebroplasty has attracted much attention as a medical treatment for the collapse of the spine by strengthening the vertebral body, correcting deformities, and relieving pain in patients through the injection of bone cement. The finite element method has become popular for analysing vertebroplasty. The numerical modelling of vertebrae under loading, as in many other cases of representing a composite bone with anatomically scattered properties through a simplified material model, entails difficulties in material assignment for analysis. The aim of this study is to compare and contrast material-assignment methods in the course of modelling through a tetrahedral meshing algorithm. In particular, the study seeks to contrast the element-wise material model with a uniform material assignment for trabecular bone and the bone-poly(methyl methacrylate) (PMMA) composite. The geometries of the vertebral body are constructed from computed tomography image data, which are obtained through scanning at intervals of 1 mm. The finite element models are constructed through a tetrahedral meshing algorithm. Various types of material assignment, which encompass the case of normal persons as well as the case of patients following vertebroplastic surgery, are analysed. The results clearly show that the oversimplification of the trabecular bone and the bone-PMMA composite body may lead to significant deviations in the assessment of the effectiveness of vertebroplastic surgery.

Prognostic implications of type and density of tumour-infiltrating lymphocytes in gastric cancer.

The study aims to determine whether type and density of tumour-infiltrating lymphocytes (TILs) can predict the clinical course in gastric cancer. Gastric carcinomas (n=220) were immunostained for CD3, CD8, CD20, and CD45RO and evaluated for clinicopathologic characteristics. Number of TILs that immunostained positively for each marker were counted using NIH ImageJ software. Tumours were grouped into low- and high-density groups for each marker (CD3, CD8, CD45RO). The densities of CD3(+), CD8(+), and CD45RO(+) TILs were found to be independent predictors of lymph node metastasis by multivariate analysis with odds ratios (95% CI) of 0.425 (0.204-0.885), 0.325 (0.150-0.707), and 0.402 (0.190-0.850), respectively. Kaplan-Meier survival analysis revealed that patients in the high-density groups for CD3, CD8, and C45RO had a significantly longer survival time than the patients in the corresponding low-density groups, respectively. In multivariate survival analysis, the densities of CD3(+), CD8(+), and CD45RO(+) TILs remained independent prognostic factors with hazard ratios (95% CI) of 0.549 (0.317-0.951), 0.574 (0.347-0.949), and 0.507 (0.298-0.862), respectively. In conclusion, density of TILs was found to be independently predictive of regional lymph node metastasis and patient survival in gastric cancer.

Angiopoietin-1 reduces VEGF-stimulated leukocyte adhesion to endothelial cells by reducing ICAM-1, VCAM-1, and E-selectin expression.

Vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang1) are potent vasculogenic and angiogenic factors that hold promise as a means to produce therapeutic vascularization and angiogenesis. However, VEGF also acts as a proinflammatory cytokine by inducing adhesion molecules that bind leukocytes to endothelial cells, an initial and essential step toward inflammation. In the present study, we used human umbilical vascular endothelial cells (HUVECs) to examine the effect of Ang1 on VEGF-induced expression of three adhesion molecules: intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin. Interestingly, Ang1 suppressed VEGF-induced expression of these adhesion molecules. Furthermore, Ang1 reduced VEGF-induced leukocyte adhesion to HUVECs. These results demonstrate that Ang1 counteracts VEGF-induced inflammation by reducing VEGF-induced endothelial adhesiveness.

Angiopoietin-1 induces endothelial cell sprouting through the activation of focal adhesion kinase and plasmin secretion.

Angiopoietin-1 (Ang1) is a strong inducer of endothelial cell sprouting, which is a first step in both angiogenesis and neovascularization. We examined the mechanisms underlying Ang1-induced cell sprouting using porcine pulmonary artery endothelial cells. Ang1 induced the nondirectional and directional migration of endothelial cells mediated through the Tie2 but not the Tie1 receptor. Ang1 induced tyrosine phosphorylation of p125(FAK), and this phosphorylation was dependent on phosphatidylinositol (PI) 3'-kinase activity. Ang1 induced the secretion of plasmin and matrix metalloproteinase-2 (MMP-2), which is inhibited by PI 3'-kinase inhibitors. Ang1 also induced the secretion of small amounts of proMMP-3 and proMMP-9 but not proMMP-1. Ang1 suppressed the secretion of tissue inhibitor of metalloproteinase-2 (TIMP-2), but not of TIMP-1. Addition of alpha(2)-antiplasmin, a combination of TIMP-1 and TIMP-2, or PI 3'-kinase inhibitors inhibited Ang1-induced sprouting activity. Therefore, Ang1-induced sprouting activity in endothelial cells may be accomplished by cytoskeletal changes and secretion of proteinases and may be largely mediated through intracellular PI 3'-kinase activation.

Mechanism of cyclosporine-induced overgrowth in gingiva.

UNLABELLED: Cyclosporine A (CsA) is a widely used immunosuppressant but with significant side-effects, such as gingival overgrowth. This study investigates how CsA induces gingival proliferation and shows the effects of the CsA-associated signaling messengers, IL-6 and TGF-beta1, on gingival proliferation. CsA increased both IL-6 and TGF-beta1 levels. In addition to CsA, an IL-6 or TGF-beta1 treatment also induced gingival fibroblast proliferation. Inhibiting the cytokine resulted in the suppression of CsA-induced proliferation. MAPKs and PI3K are known to be involved in cell proliferation. Therefore, the effect of CsA on the kinase activities was examined. The results showed that both p38 MAPK and PI3K are essential for gingival fibroblast proliferation. TGF-beta1 and IL-6 and their associated signaling transduction may be novel bona fide molecular targets for the prevention of gingival overgrowth in CsA-treated patients. ( ABBREVIATIONS: MAPK, mitogen-activated protein kinase; P13K, phosphatidylinositol 3-kinase.)

Carbon monoxide and nitric oxide protect against tumor necrosis factor-alpha-induced apoptosis in osteoblasts: HO-1 is necessary to mediate the protection.

BACKGROUND: Carbon monoxide (CO) and nitric oxide (NO) each have unique roles for various inflammatory states, including inflammatory bone resorption. Although it is known that NO can induce the expression of the cytoprotective enzyme HO-1, there is no information as to whether the protective effect of CO requires NO production or whether CO must induce the expression of HO-1 to exert its functional effects. METHODS: Murine osteoblast cells, MC3T3E1 osteoblasts, were cultured for CO and NO-associated HO-1 experiments and were transfected with pcDNA 3, pcDNA 3-HO-1, control siRNA or HO-1 siRNA using Nucleofector. For cell death measurement, MTT and annexin V assays were used. We performed Western blotting to check the expressions of HO-1 and iNOs and measured the HO-1 enzyme activity. We also measured the amounts of nitrite and nitrate using Griess reagents. RESULTS: The increased expression of HO-1 is required for the protective effect of NO and a single treatment of CO can increase the expression of HO-1, and this is also important for the protective effect of CO in MC3T3E1 osteoblasts. CO as well as NO attenuates the TNF-alpha-induced apoptosis in osteoblasts. The anti-apoptotic effect of CO or NO is not mediated by cGMP, and CO has no effect on the release of NO. The inhibition of HO-1 with using the HO-1 inhibitor ZnPP or HO-1 siRNA resulted in a striking increase of apoptosis in the CO/TNF-alpha-treated cells. Furthermore, HO-1 overexpression showed resistance against the TNF-alpha-induced cytotoxicity in the MC3T3E1 osteoblasts. CONCLUSIONS: There is a need for HO-1 expression to mediate the protection provided by exogenous CO or NO in osteoblasts.

An immunohistochemical study of the expression of cell-cycle-regulated proteins p53, cyclin D1, RB, p27, Ki67 and MSH2 in gallbladder carcinoma and its precursor lesions.

Gallbladder carcinomas are rare but highly lethal neoplasms. We examined the expression of five cell-cycle-related molecules (p53, RB, cyclin D1, p27, Ki-67), and MSH2, in 46 carcinomas, 14 adenomas, 15 low-grade dysplasias, 9 intestinal metaplasias and 20 normal gallbladder epithelia. The expression of these molecules was altered in gallbladder carcinomas and adenomas. In gallbladder carcinomas we observed increased expression of p53, cyclin D1, Ki-67, and MSH2 together with decreased expression of RB and p27 protein. Aberrant expression of cyclin D1 and reduced expression of RB were noted in adenomas, and expression of cyclin D1 was elevated in low-grade dysplasias. However, there was no change in the levels of these cell-cycle molecules in metaplasia. Expression of p53, p27, Ki-67, and MSH2 was correlated with clinical stage (P<0.05) and there was also a correlation between the expression of Ki-67 and MSH-2 and patient age (P<0.05). These results suggest that altered expression of cell-cycle molecules p53, cyclin D1, RB, p27, and of MSH-2 is involved in the progression of gallbladder carcinomas.

Inferior tilt fixation of the glenoid component in reverse total shoulder arthroplasty: A biomechanical study.

BACKGROUND: Glenoid component fixation with an inferior tilt has been suggested to decrease scapular notching, but this remains controversial. We aimed here to evaluate the effect of glenoid component inferior tilt in reverse total shoulder arthroplasty (RSA) on micromotion and loss of fixation of the glenoid component by biomechanical testing. HYPOTHESIS: Increased inferior reaming of the glenoid for inferiorly tilted implantation of the glenoid component will decrease glenoid bone stock and compromise the fixation of RSA. MATERIALS AND METHODS: The micromotions of the glenoid components attached to 14 scapulae from fresh frozen cadavers were measured and compared between neutral and 10° inferior tilts in 0.7- and 1-body weight cyclic loading tests using digital-image analysis. The incidence of bone breakage or loss of fixation was assessed in the 1-body weight fatigue-loading test. RESULTS: Micromotion was higher with a 10° inferior tilt than with a neutral tilt during both the 0.7-body weight (36 ± 11 µm vs. 22 ± 5 µm; P = 0.028) and 1-body weight (44 ± 16 µm vs. 28 ± 9 µm; P = 0.045) cyclic loading. The incidence of bone breakage or loss of fixation was 17% and 60% with a neutral and 10° inferior tilt, respectively. DISCUSSION: Glenoid component inferior tilt fixation in RSA may reduce primary stability and increase mechanical failure of the glenoid component, thereby reducing longevity of the prosthesis. Accordingly, we recommend careful placement of the glenoid component when an inferior tilt is used.

Dexamethasone suppresses tumor necrosis factor-alpha-induced apoptosis in osteoblasts: possible role for ceramide.

Ceramide has been proposed as a second messenger molecule implicated in a variety of biological processes, including apoptosis. Recently, it has been reported that tumor necrosis factor-alpha (TNF-alpha) activates the release of ceramide and that ceramide acts as a mediator for the TNF-alpha-induced stimulation of the binding affinity of nuclear factor-KB (NF-KB), a ubiquitous transcription factor of particular importance in immune and inflammatory responses. In this study we demonstrate that dexamethasone, which reduces the production of ceramide, significantly inhibits TNF-alpha-induced activation of NF-KB, c-Jun N-terminal kinase, also known as stress-activating protein kinase, caspase-3-like cysteine protease, redistribution of cytochrome c, and apoptosis in MC3T3E1 osteoblasts. Compared with TNF-alpha-induced JNK activation, ceramide elicits a more rapid activation of JNK within 30 min. C2-ceramide activates NF-KB and caspase-3 like protease to the same degree and with kinetics similar to those of TNF-alpha. This study provides evidence that the release of ceramide may be required as a second messenger in TNF-alpha-induced apoptosis. These results also suggest a regulatory role for dexamethasone in TNF-alpha-induced apoptosis via inhibition of ceramide release. Therefore, our in vitro results suggest that therapies targeted at the inhibition of ceramide release may abrogate inflammatory processes in TNF-alpha-related diseases, including rheumatoid arthritis and periodontitis.

Selectivity of phospholipase C isozymes in growth factor signaling.

Xenopus laevis oocytes were injected with mRNA extracted from growth factor-responsive CCL39, Chinese hamster lung fibroblasts. The expression of functional growth factor receptors on the oocytes was demonstrated by growth factor-induced 45Ca2+ efflux. To determine the isozyme(s) of phospholipase C (PLC) coupled to growth factor receptors, growth factor-induced 45Ca2+ efflux were measured following coinjection of mRNA from CCL39 cells with PLC antibodies. PLC-gamma 1 antibody did not lead to loss of 45Ca2+ efflux induced by thrombin but resulted in loss of that induced by platelet-derived growth factor (PDGF). In contrast, PLC-delta 1 antibody did not block PDGF-induced 45Ca2+ efflux but led to inhibition of thrombin-induced 45Ca2+ efflux. PLC-beta 1 antibody did not affect Ca2+ efflux by the treatment of either thrombin or PDGF. These results suggest that these growth factor receptors are coupled to specific effectors, i.e. thrombin receptor to PLC-delta 1 and PDGF receptor to PLC-gamma 1.

Signal transduction of thapsigargin-induced apoptosis in osteoblast.

The toxicity of thapsigargin, a selective inhibitor of endoplasmic reticular Ca2+-ATPase, was investigated in osteoblasts. We induced apoptosis in murine osteoblastic MC3T3E1 cells by exposure to the thapsigargin. Thapsigargin transiently increased the phosphotransferase activity of c-Jun N-terminal kinases1 (JNK1), which might in turn activate transcriptional activity of activation protein-1 (AP-1). We then prepared extracts from thapsigargin-treated MC3T3E1 cells and monitored cleavage of acetyl-YVAD-AMC and acetyl-DEVD-AMC, fluorogenic substrates for caspase 1-like and caspase 3-like proteases, respectively. Thapsigargin significantly increased the proteolytic activity of caspase 3-like proteases, but not the activity of caspase 1-like proteases. Furthermore, thapsigargin increased the transcriptional activity of nuclear factor-kappaB (NF-kappaB). These data suggest that thapsigargin-induced apoptosis in osteoblasts may be via activation of JNK1, caspase 3-like family proteases, and transcriptional factors including AP-1 and NF-kappaB.

The p38 mitogen-activated protein kinase pathway regulates interleukin-6 synthesis in response to tumor necrosis factor in osteoblasts.

The induction of interleukin-6 (IL-6), using a proinflammatory cytokine (tumor necrosis factor-alpha), was studied in a human osteoblast cell line (MG-63) in relation to p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-kappaB transcription factor. When added to MG-63 cells, tumor necrosis factor-alpha (TNF-alpha) had a stimulatory effect on the production of IL-6, and this elevation was significantly reduced by SB203580, a specific p38 MAPK inhibitor. In addition, the stimulation of IL-6 release was also reduced by pyrrolidine dithiocarbamate (PDTC) or NF-kappaB SN50, which has been reported to be a potent NF-kappaB inhibitor. Both the NF-kappaB inhibitors in the presence of SB203580 had a more inhibitory effect on IL-6 release. In this study, TNF-alpha stimulated NF-kappaB binding affinity as well as p38 MAP kinase activation, leading to the release of IL-6. However, the specific inhibitor of p38 MAPK, SB203580, had no effect on TNF-alpha-induced NF-kappaB activation and both NF-kappaB inhibitors failed to reduce the p38 MAPK activation in the TNF-alpha-stimulated osteoblasts. In addition, inhibition of p38 MAPK partially, but significantly, impaired TNF-alpha-regulated release of osteocalcin, an important differentiation marker in osteoblasts. These results strongly suggest that both p38 MAPK and NF-kappaB are required in TNF-alpha-induced IL-6 synthesis and that these two TNF-alpha-activated pathways can be primarily dissociated. Furthermore, p38 MAPK may play a significant role in differentiation in MG-63 cells.

Mutation and expression of the p27KIP1 and p57KIP2 genes in human gastric cancer.

Cyclin-dependent kinase inhibitors (CDKI) are negative regulators of cell cycle progression by binding the cyclin-CDK complex and inhibiting the CDK activity. Genetic alteration in the CDKI genes has been implicated for carcinogenesis. To test the genetic alteration in the p27 and p57 genes, KIP family CDKI genes, 30 gastric tumor-normal pairs and 8 gastric cancer cell lines were analyzed for mutations by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP). No mutation was detected in these genes although length polymorphisms in the proline-alanine repeat of the p57 gene were detected. When the p27 and p57 mRNAs were analyzed in gastric cancer cell lines by RT-PCR, the p27 mRNA was expressed considerably high in tumor cells but expression of the p57 mRNA was much low in gastric cancer cell lines compared to that of normal cells. The result suggests that inactivation of gene expression rather than mutations in the p57 gene accounts possibly for the involvement of this gene in tumorigenesis of gastric cancer. However, expression of the p27 gene seems to be essential for cell survival.

Cyclins and cyclin dependent kinases during cardiac development.

The molecular mechanisms that regulate the cardiomyocyte cell cycle and its terminal differentiation remain largely unknown. To determine which cyclins or cyclin dependent kinases (CDKs) are important for cardiomyocyte proliferation, we examined the expression of cyclins and CDKs during normal cardiac development. All cyclins and CDKs were highly expressed during embryonic cardiac development, then they decreased at different rates after birth. The mRNAs and proteins of cyclins A and B (G2 and M phase cyclins) were found in embryonic and neonatal hearts, but were not detected in young or adult hearts. In contrast, while the mRNAs of cyclins D1, D2, D3, and E (G1 and S phase cyclins) were observed during all stages of development, the proteins of cyclins D1, D3, and E were observed in hearts at the young growth stage, although the levels decreased differently. Reverse transcriptase-polymerase chain reaction (RT-PCR) using specific cyclin B and D3 primers revealed that cyclins B and D3 originated from cardiomyocytes and noncardiomyocytes. The CDKs (cdc2, CDK2, and CDK4) were highly expressed during embryonic cardiac development and maintained almost constant levels during neonatal periods. However, they were expressed at very low levels at the young and adult stages. The pattern of proliferating cell nuclear antigen (PCNA) expression during cardiac development was similar to the expression of CDKs. These findings suggest that all cyclins and CDKs are involved in the cardiac cell cycle, and that marked and rapid reduction of mitotic cyclins may be associated with the withdrawal of the cardiac cell cycle after birth.

Sodium nitroprusside induces apoptosis of H9C2 cardiac muscle cells in a c-Jun N-terminal kinase-dependent manner.

Sodium nitroprusside (SNP) induces apoptosis in H9C2 cardiac muscle cells. Treatment with an exogenous NO donor SNP (2 mM) to H9C2 cells resulted in apoptotic morphological changes; a bright blue-fluorescent condensed nuclei and chromatin fragmentation by fluorescence microscope of Hoechst 33258-staining. The activity of caspase-3 like protease was increased during SNP-induced cell death. However, the activity of caspase-1 like protease was not affected by SNP. Pretreatment with Z-VAD-FMK (a pan-caspase inhibitor) or Ac-DEVD-CHO (a specific caspase-3 inhibitor) abrogated the SNP-induced cell death. SNP markedly activated three MAP kinases (JNK/SAPK, ERK and p38 MAP kinase) in the cardiac muscle cells. In this study, selective inhibition of the ERK or p38 MAPK pathway (by PD98059 or SB203580, respectively) had no effect on the extent of SNP-induced apoptosis in cardiac muscle cells. In contrast, inhibition of the JNK pathway by transfection of a dominant negative mutant of JNK markedly reduced the extent of SNP-induced cell death. Taken together, we suggest that JNK/SAPK will be related to SNP-induced apoptosis of H9C2 cardiac muscle cells.

Reciprocal modulation of ATP-sensitive K+ channel activity in rat ventricular myocytes by phosphorylation of tyrosine and serine/threonine residues.

The modulation of ATP-sensitive K+ channel (KATP) activity by specific phosphorylation or dephosphorylation of tyrosine and serine/threonine residues was examined in rat ventricular myocytes using the inside-out patch configuration of the patch clamp technique. The run-down process was suppressed by okadaic acid but accelerated by sodium orthovanadate. After run-down of the channels, the ATP-induced reactivation was blocked by H-7, but enhanced by genistein. The channel activity was decreased by protein phosphatase 2A. However, the activity of partially run-down channels was increased by protein tyrosine phosphatase 1B. Our results suggest that KATP channel activity can be inhibited by phosphorylation of tyrosine residues and stimulated by phosphorylation of serine/threonine residues.

Expression patterns of p27Kip1 and Ki-67 in cholesteatoma epithelium.

OBJECTIVES: The cell cycle must be involved in cell proliferation of the epithelium of middle ear cholesteatoma Cyclins and cyclin-dependent kinase (CDK) complexes have important regulatory roles during cell cycle progression. Cyclin-CDK complexes are in turn regulated by the cyclin-dependent kinase inhibitors (CDKIs), which generally inhibit cell cycle progression. One of the important CDKI members is p27(Kip1). The goal of this study is to evaluate the expression of p27(Kip1) and Ki-67, a proliferation marker, in cholesteatoma and in the skin of the external ear canal. METHODS: The expressions of p27(Kip1) and Ki-67 in cholesteatoma epithelium (n = 20) and ear canal epithelium (n = 7) were investigated by an immunohistochemical technique. RESULTS: In cholesteatoma epithelium specimens, the expression of p27(Kip1) was observed from the parabasal layer to the granular layer, but not in the basal layer. Ki-67 was expressed dominantly in the basal and parabasal cell layers. Their expressions tend to be increased compared with their expressions in the normal ear canal skin. The expression pattern of the proliferation marker Ki-67 in the epithelial layers of two groups was inversely related to the expression of p27(Kip1). CONCLUSIONS: In cholesteatoma, the expressions of CDKI and Ki-67 were both increased in this study. The ability to inhibit proliferative activity was also increased in the cholesteatoma epithelium. The expression pattern of the proliferation marker Ki-67 in the epithelial layers was inversely related to the expression of p27(Kip1). Not only is the proliferation activity increased, but also the ability to inhibit hyperproliferation is increased in the cholesteatoma epidermis. Despite increased proliferative activity in the cholesteatoma epidermis, epithelial cells still retain the capability to prevent cell cycle arrest by means of p27(Kip1).

Effect of ionizing radiation on the differentiation of ROS 17/2.8 osteoblasts through free radicals.

Although the acceleration of bone regeneration by radiation has been reported, the mechanisms of action of radiation on bone are unclear. The present results indicate that ionizing radiation-stimulated differentiation could result from the generation of reactive oxygen species during radiation exposure. The free radical release is considered as the most important mechanism of bone effect by radiation treatment. In addition, we report that radiation induced transient activation of c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) activation and the transcription factor, AP-1. The JNK and AP-1 activation is mediated with radiation-released free radicals in ROS 17/2.8 osteoblasts. These results indicate that ionizing radiation at a single dose of up to 5 Gray stimulates differentiation of ROS 17/2.8 osteoblasts via free radial release which may affect JNK/SAPK and AP-1 activities.