Surface damages of zirconia by Nd:YAG dental laser irradiation

The purpose of this study was to characterize the surface damages of zirconia by Nd:YAG dental laser irradiation through a systematic evaluation of the associated microstructural changes. Disk specimens of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/Al₂O₃ nanocomposite) were irradiated by Nd:YAG dental laser. The specimens were characterized using scanning electron microscopy, X-ray diffractometry, and wavelength dispersive X-ray spectroscopy. Every single irradiated spot was indicated by a circular black pit surrounded by a circular raised rim with a sunken depression at the center. On surface changes, many cracks were formed inside each irradiated pit. On changes in elemental composition, the concentration of oxygen decreased while that of zirconium increased. After heating in air, the assembly of circular black pits turned white, although the depression and raised rim remained. This study showed that Nd:YAG dental laser irradiation induced cracking and reduced oxygen content on the surface of zirconia. Consequently, these phenomena reduced the mechanical strength of zirconia. Therefore, Nd:YAG dental laser welding should not be performed on tetragonal zirconia.

The Reck tumor suppressor protein alleviates tissue damage and promotes functional recovery after transient cerebral ischemia in mice

The extracellular matrix (ECM) is important for both structural integrity and functions of the brain. Matrix metalloproteinases (MMPs) play major roles in ECM-remodeling under both physiological and pathological conditions. Reversion-inducing cysteine-rich protein with Kazal motifs (Reck) is a membrane-anchored MMP-regulator implicated in coordinated regulation of pericellular proteolysis. Although patho-physiological importance of MMPs and another group of MMP-regulators, tissue inhibitor of metalloproteinases, in brain ischemia has been demonstrated, little is known about the role of Reck in this process. In this study, we found that Reck is up-regulated in hippocampus and penumbra of subventricular zone after transient cerebral ischemia in mice. Most of the Reck-positive cells found at day 2 after ischemia are positive for Nestin as well as Ki67 and localized to the CA2 region of the hippocampus. At day 7 after ischemia, the Reck-positive cells increased in number, extended processes, expressed the reactive astrocyte marker GFAP and the neuronal marker NF200, and were widely distributed in the hippocampus. In the mutant mice carrying single functional Reck allele (Reck+/-), tissue damage and cell death after cerebral ischemia were augmented, the recovery of long-term potentiation in the hippocampus was compromised, NR2C subunit of NMDA receptor was up-regulated, gelatinolytic activity of MMPs were up-regulated and laminin-immunoreactivity was reduced. Our data implicate Reck in protection of ECM/tissue integrity and promotion of functional recovery in the brain after transient cerebral ischemia.

A novel screen using the Reck tumor suppressor gene promoter detects both conventional and metastasis-suppressing anticancer drugs

The membrane-anchored matrix metalloproteinase-regulator RECK is often downregulated in various types of cancers; the levels of residual RECK in resected tumors often correlate with better prognosis. Forced expression of RECK in cancer cells suppresses tumor angiogenesis, invasion, and metastasis in xenograft models. RECK is therefore a promising marker for benignancy and a potential effector in cancer therapy. We established a cell line containing two transgene systems: (1) the secreted alkaline phosphatase (SEAP) gene fused to Reck promoter and (2) the HRAS(12V) oncogene driven by the Tet-off promoter system. This cell line exhibits transformed phenotype in regular medium and flat morphology with increased SEAP activity in the presence of doxycycline, allowing the assessment of RECK-inducing activity of chemicals in the contexts of both transformed and untransformed cells. Our pilot experiments with 880 known bioactive compounds detected 34 compounds that activate RECK promoter; among these, 10 were authentic anticancer drugs. Four selected compounds up-regulated endogenous RECK protein in several human cancer cell lines. The top-ranking compound, disulfiram, strongly suppressed spontaneous lung-metastasis of human fibrosarcoma cells in nude mice. Our data demonstrate the value of this screen in discovering effective cancer therapeutics.

What we learn from transformation suppressor genes: lessons from RECK

Expression cloning is a powerful approach to finding genes that induce appreciable changes in cultured cells. One way to use this technique in cancer research is to isolate cDNAs that induce flat reversion in transformed cells. Such screening, however, is inherently artificial, and therefore requires independent validation of the clinical relevance of isolated genes. Studies of the mechanisms of actions, physiological functions and mechanisms of regulation of these genes at various levels may enrich our knowledge of cancer biology and supplement our toolbox in developing new cancer diagnoses and therapies. In this article we discuss the promise, limitations and recent innovations in this approach, taking one transformation suppressor gene, RECK, as an example.

Radio-opacity of core materials for all-ceramic restorations

The aim of this study was to investigate and compare the radio-opacity of core materials for all-ceramic restorations, such as zirconia (NANOZR and Y-TZP) and alumina, against commercially pure titanium (cpTi) and aluminum. X-ray images were taken under general settings using an X-ray film. The X-ray film images were scanned using a digital scanner, and the darkness at the central area of each specimen image was quantitatively analyzed using an image analysis software. Amongst the materials investigated, alumina showed the most transparency against X-rays. Conversely, both types of zirconia showed the highest radio-opacity, whereby that of NANOZR was slightly lower than that of Y-TZP. This was because NANOZR contained 30 vol% of alumina and its density was also slightly lower than that of Y-TZP.

RECK is up-regulated and involved in chondrocyte cloning in human osteoarthritic cartilage

Reversion-inducing cysteine-rich protein with Kazal motifs (RECK) is a membrane-anchored matrix metalloproteinase regulator, but its functions in cartilage are not fully understood. The aim of the present study was to examine the expression and functions of RECK in human osteoarthritic (OA) cartilage. Quantitative RT-PCR indicated that the expression level of RECK is significantly higher in OA cartilage than in normal cartilage. By immunohistochemical analysis, RECK was localized to chondrocytes in OA cartilage, and the immunoreactivity directly correlated with the Mankin score and degree of chondrocyte cloning and proliferation. In cultured OA chondrocytes, RECK was expressed on the cell surface by glycosylphosphatidylinositol anchoring. The expression was stimulated by insulin-like growth factor-1 and suppressed by interleukin-1 and tumor necrosis factor-alpha. Down-regulation of RECK by small interfering RNA showed reduced spreading and smaller focal adhesions in the chondrocytes. Chondrocyte migration in a monolayer wounding assay was increased by down-regulation of RECK and inhibited by RECK overexpression in an matrix metalloproteinase activity-dependent manner. On the other hand, chondrocyte proliferation was suppressed by RECK silencing, and this was associated with reduced phosphorylation of focal adhesion kinase and extracellular signal-regulated kinase, whereas the proliferation was enhanced by RECK overexpression. These data are the first to demonstrate that RECK is up-regulated in human OA cartilage and suggest that RECK plays a role in chondrocyte cloning probably through suppression and promotion of chondrocyte migration and proliferation, respectively.

[Surgical approaches for superior sulcus tumor]

Surgical approach is one of the most crucial aspects in the treatment of superior sulcus tumor (SST). Posterior approach as described by Paulson and coworkers is appropriate for the resection of SST invading posterior part of the 1st rib and the vertebrae, whereas anterior approaches as described by Masaoka, Dartevelle, Grunenwald, or Rusca are suitable for resection of SST involving subclavian vessels. We present 2 cases of SST who underwent complete resection through the posterior approach and a modified hemi-clamshell approach, respectively. We also discuss the surgical approaches for SST with referring to literatures.

Calcium, vitamin D and dairy intake in relation to type 2 diabetes risk in a Japanese cohort

AIMS/HYPOTHESIS

Calcium and vitamin D have been implicated in the development of type 2 diabetes, but epidemiological evidence is limited. We examined prospectively the relation of calcium and vitamin D intake to type 2 diabetes risk in a Japanese cohort.

METHODS

Participants were 59,796 middle-aged and older men and women, who participated in the Japan Public Health Center-based Prospective Study and had no history of type 2 diabetes or other serious diseases. Dietary intake of calcium and vitamin D were estimated using a validated food frequency questionnaire. Logistic regression was used to assess the association between intake of these nutrients and self-reported newly diagnosed type 2 diabetes.

RESULTS

During a 5 year follow-up, 1,114 cases of type 2 diabetes were documented. Overall, calcium intake was not associated with a significantly lower risk of type 2 diabetes; the multivariable odds ratio for the highest vs lowest quartiles was 0.93 (95% CI 0.71-1.22) in men and 0.76 (95% CI 0.56-1.03) in women. However, among participants with a higher vitamin D intake, calcium intake was inversely associated with diabetes risk; the odds ratio for the highest vs lowest intake categories was 0.62 (95% CI 0.41-0.94) in men and 0.59 (95% CI 0.38-0.91) in women. Dairy food intake was significantly associated with a lower risk of type 2 diabetes in women only.

CONCLUSIONS/INTERPRETATION

Calcium and vitamin D may not be independently associated with type 2 diabetes risk. Our finding suggesting a joint action of these nutrients against type 2 diabetes warrants further investigation.

The role of immune cells in brain metastasis of lung cancer cells and neuron-tumor cell interaction

Following any type of brain injury such as lesion, stroke, and tumor/cancer invasion, microglia are rapidly activated and recruited to the site of injury. Microglia is the main immune effector cell population of the central nervous system and control immune cell recruitment. However, the molecular mechanism of brain metastasis and interaction between neuron-glia-tumor cells are poorly understood. Therefore, we established an animal model for brain metastasis using human lung cancer-derived cells (HARA-B) in nude mice. Accumulation of activated microglia was observed around tumor cells depending on the size of metastatic foci and the area of the brain. In vitro study, conditioned medium from primary cultured mouse microglia inhibited the proliferation of tumor cells, while tumor cell-conditioned medium inhibited the proliferation of primary cultured neurons from mouse cortex. Though the responsible factors released from microglia and tumor cells are still under investigation, these studies will contribute to understand the mechanism of cell-cell interaction in the brain and possible therapeutic target for brain metastasis.

Combinatory effects of androgen receptor deficiency and hind limb unloading on bone

Male sex hormones play a critical role in regulation of bone metabolism. In male mice lacking androgen receptor (AR), osteopenia and high turnover state in bone remodeling have been reported. However, androgen receptor's role in disuse-induced osteopenia is not known. Therefore, we examined the effects of AR deficiency on unloading-induced bone loss. Wild type or androgen receptor deficient mice (ARKO) were subjected to hind limb unloading (HU) or normal housing (Control). The groups of mice were as follows; wild type control mice (Group WT-Cont), ARKO control mice (Group ARKO-Cont), wild type HU mice (Group WT-HU), and ARKO-HU mice (Group ARKO-HU). HU reduced cancellous bone mass in ARKO (ARKO-HU) by about 70% compared to ARKO-Cont and this reduction rate was over two-fold more than that of wild type (WT-HU) (reduction by less than 30% compared to WT-Cont). Combination of ARKO and HU (ARKO-HU) resulted in the least levels of cortical bone mass and bone mineral density among the four groups. ARKO-HU group indicated the highest levels of systemic bone resorption marker, deoxypyridinoline. Osteoclast development levels in the cultures in ARKO-HU derived bone marrow cells were the highest among the four groups. These data suggest that combination of androgen receptor deficiency and hind limb unloading results in exacerbation of disuse-induced osteopenia due to the enhanced levels of bone resorption.

Transplantation of cultured choroid plexus epithelial cells via cerebrospinal fluid shows prominent neuroprotective effects against acute ischemic brain injury in the rat

Choroid plexus (CP) epithelial cells (CPECs) produce cerebrospinal fluid (CSF) to provide the CNS with a specialized microenvironment. Our previous study showed that the conditioned medium of cultured CPECs enhanced the survival and neurite extension of hippocampal neurons. The present study examined the ability of cultured CPECs to protect against ischemic brain injury when transplanted into the CSF. Rats were subjected to a transient occlusion of the middle cerebral artery, followed by an injection of cultured CPECs into the fourth ventricle. The injection markedly reduced neurological deficits and infarction volume within 24h. Other beneficial effects were (1) a reduction in number of apoptotic and inflammatory cells, (2) an up-regulation of the mRNA expression of an anti-apoptotic effecter, cAMP-response element binding protein, and (3) a down-regulation of the production of pro-inflammatory factors such as interleukin-1 beta and inducible nitric oxide synthase. The injected CPECs were located within the ventricles and on the brain's surface, not in the ischemic foci, suggesting that they exert their effects by releasing diffusible neuroprotective factors into the CSF. The transplantation of CPECs via CSF is a potential new strategy for protecting against ischemic brain injury.

Density- and serum-dependent regulation of the Reck tumor suppressor in mouse embryo fibroblasts

Reck is a membrane-anchored glycoprotein identified as a transformation suppressor. Accumulating evidence indicates that Reck negatively regulates a wide spectrum of matrix metalloproteinases and is commonly down-regulated in a variety of malignant solid tumors. Physiological cues that regulate Reck expression, however, remained unknown. In this study, we found that Reck expression was up-regulated at high cell density, low serum, or after treatment with some kinase inhibitors, such as PP2 (Src inhibitor), LY294002 (PI3-kinase inhibitor), and PF573228 (FAK inhibitor), in mouse embryo fibroblasts. Curve fitting indicated that the levels of Reck protein and Reck mRNA are quadratic in the cell density. Other factors, including serum, extracellular matrix components (type I collagen and fibronectin), the kinase inhibitors, and some of their oncogenic targets (v-Src and PIK3CA mutants), modify the shape of the quadratic curve. Comparison of these modifications implicated Src in Reck down-regulation under sparse conditions, PI3-kinase in serum-induced Reck down-regulation, and FAK in Reck down-regulation at high cell density. Fibronectin and type I collagen down-regulated Reck, supporting the role of integrin-FAK signaling in Reck down-regulation at high cell density. Our study has revealed multiple signaling pathways impinging on Reck in cultured mouse embryo fibroblasts and sets a foundation for future studies to find effective Reck inducers of potential value in cancer therapy.

Follow-up of a self-resolving renal pseudoaneurysm using contrast-enhanced power Doppler ultrasonography

It has been standard practice to embolise a pseudoaneurysm caused by penetrating trauma whenever it is found, even in the absence of overt symptoms. This is a case report of a renal pseudoaneurysm (RPA) caused by a stab wound, which was safely monitored and followed using colour Doppler ultrasonography. On day 1, angiography showed a pseudoaneurysm of the renal artery in the parenchyma and ultrasonography showed blood flow into the pseudoaneurysm. Although abnormal blood flow into the kidney was seen, there appeared to be no leakage of blood from the pseudoaneurysm. The abnormal flow disappeared on day 12 and the area of the pseudoaneurysm became unclear from day 13. This report suggests the possibility that RPA caused by a stab wound could be an indication for conservative therapy under the following conditions: the RPA is detected initially; close monitoring using a colour Doppler ultrasound is possible; there is no leakage of blood from the right subclavian artery and there is a 2-week period of observation.

Rb Regulates DNA damage response and cellular senescence through E2F-dependent suppression of N-ras isoprenylation

Oncogene-induced cellular senescence is well documented, but little is known about how infinite cell proliferation induced by loss of tumor suppressor genes is antagonized by cellular functions. Rb heterozygous mice generate Rb-deficient C cell adenomas that progress to adenocarcinomas following biallelic loss of N-ras. Here, we demonstrate that pRb inactivation induces aberrant expression of farnesyl diphosphate synthase, many prenyltransferases, and their upstream regulators sterol regulatory element-binding proteins (SREBPs) in an E2F-dependent manner, leading to enhanced isoprenylation and activation of N-Ras. Consequently, elevated N-Ras activity induces DNA damage response and p130-dependent cellular senescence in Rb-deficient cells. Furthermore, Rb heterozygous mice additionally lacking any of Ink4a, Arf, or Suv39h1 generated C cell adenocarcinomas, suggesting that cellular senescence antagonizes Rb-deficient carcinogenesis.