Bone cell responses of titanium blasted with bioactive glass particles.

Surface modification of Ti-based metals is an important issue in improving the bone cell responses and bone-implant integration. Blasting Ti with granules (mostly alumina) is commonly used to prepare a clean surface and provide a level of roughness. In this study, glass granules with a bioactive composition were used as the blasting source to improve the surface bioactivity and biocompatibility of a Ti substrate. Bioactive glass particles with a composition of 70SiO(2) * 25CaO * 5P(2)O(5) were prepared using a sol-gel method. A Ti disc was blasted with glass particles using a dental blasting unit (BG-Ti). A Ti disc blasted with commercial spherical-shaped glass (G-Ti) and a disc without blasting (Ti) were also prepared for comparison. The blasted Ti contained a large number of glass particles after the blasting process. The surface roughness of the samples in ascending order was G-Ti>BG-Ti>Ti. Murine-derived preosteoblasts (MC3T3-E1) were seeded on the samples, and the cell growth, differentiation, and mineralization behaviors were observed. The osteoblastic cells attached well and spread actively over all the sample groups with extensive cytoskeletal processes. The level of cell growth on the BG-Ti showed a continual increase with culturing up to 7 days, showing good cell viability. However, there was no significant difference (ANOVA, p<0.05) with respect to the G-Ti and Ti groups. In particular, the alkaline phosphatase (AP) activity of the cells was significantly higher on the BG-Ti than on the other groups after culturing for 14 days. Moreover, the mineralization behavior of the cells, as assessed by Alizarin S Red, was superior on the BG-Ti to that observed on the other groups after culturing for 14 and 28 days. Overall, the blasting of Ti with a bioactive glass composition is considered beneficial for producing substrates with enhanced osteogenic potential.

Merlin, a tumor suppressor, interacts with transactivation-responsive RNA-binding protein and inhibits its oncogenic activity.

The neurofibromatosis type 2 gene-encoded protein, merlin, is related to the ERM (ezrin, radixin, and moesin) family of membrane-cytoskeleton-associated proteins. Recent studies suggest that the loss of neurofibromatosis type 2 function contributes to tumor development and metastasis. Although the cellular functions of merlin as a tumor suppressor are relatively well characterized, the cellular mechanism whereby merlin controls cell proliferation from membrane locations is still poorly understood. During our efforts to find potential merlin modulators through protein-protein interactions, we identified transactivation-responsive RNA-binding protein (TRBP) as a merlin-binding protein in a yeast two-hybrid screen. The interaction between TRBP and merlin was confirmed by glutathione S-transferase pull-down assays, co-immunoprecipitation, and co-localization experiments. The carboxyl-terminal regions of each protein were responsible for their interaction. Cells overexpressing TRBP showed enhanced cell growth in cell proliferation assays and also exhibited transformed phenotypes, such as anchorage-independent cell growth and tumor development in mouse xenografts. Merlin efficiently inhibited these oncogenic activities of TRBP in our experiments. These results provide the first clue to the functional interaction between TRBP and merlin and suggest a novel mechanism for the tumor suppressor function of merlin both in vitro and in vivo.

Review of long-term results of stereotactic psychosurgery.

Stereotactic psychosurgery is an effective method for treating some medically intractable psychiatric illnesses. However, it is unfamiliar and the long-term clinical results have not been reported in Asia. The long-term results of psychosurgery are evaluated and the neuroanatomical basis is discussed. Twenty-one patients underwent stereotactic psychosurgery for medically intractable psychiatric illnesses since 1993. All were referred from psychiatrists for these disorders. Two patients showed aggressive behavior, 12 had obsessive-compulsive disorder (OCD), and seven had depression with anxiety disorders. Bilateral amygdalotomy and subcaudate tractotomy were performed for aggressive behavior, limbic leucotomy was performed for OCD, and subcaudate tractotomy with or without cingulotomy was performed for depression with anxiety. OCD was evaluated with the Yale-Brown Obsessive Compulsive Scale (YBOCS), the visual analogue scale, the Clinical Global Impression Scale, and the Overt Aggression Scale (OAS). The Mini-Mental State Examination and the Wechsler Adult Intelligence Scale-Revised were used for the evaluation of aggressive behavior. The 17-item Hamilton Depression Rating Scale (HAMD) was used for evaluation of depression. Ventriculography was used in the first seven patients and magnetic resonance imaging-guided stereotaxy was used in the recent 14 cases for localization of the target. The lesions were made with a radiofrequency lesion generator. OAS scores in the two patients with aggressive behavior during follow up declined from 8 to 2 with clinical improvement. All 12 patients with OCD returned to their previous life and showed the mean YBOCS scores decreased from 34 to 3. Ten patients with OCD could be followed up (mean 45 months). All patients returned to their previous social life. In seven patients with depression with anxiety, HAMD scores declined from 28.5 to 16.5. There was no operative mortality and no significant morbidity except for one case of mild transient urinary incontinence. These long-term results indicate that stereotactic psychosurgery is a safe and effective method of treating some medically intractable psychiatric illnesses.

TAK1 mediates lipopolysaccharide-induced RANTES promoter activation in BV-2 microglial cells.

Lipopolysaccharide (LPS), a part of the outer membrane of gram-negative bacteria activates the expression of the regulated upon activation, normal T cell expressed and secreted (RANTES), which plays an important role in the chemo-attraction of leukocytes during the inflammatory response. Recently, we found that LPS-induced RANTES production is mediated by the activation of NF-kappaB, but, the upstream regulatory mechanism involved in mediating this NF-kappaB activation was unclear. In this study, we investigated signal transducing molecules that mediate LPS-induced RANTES promoter activation and found the followings. First, LPS activates the RANTES gene promoter through NF-kappaB binding sites. Second, the expression of dominant negative mutants of TGF-beta-activated kinasel (TAK1) and NF-kappaB-inducing kinase (NIK), blocked the LPS-induced transcriptional activation of RANTES promoter. Moreover, the overexpression of TAK1 along with TAK1-binding protein 1 (TAB1), or NIK stimulated the transcriptional activation of RANTES in the absence of external stimuli. Third, we showed that endogenous TAK1 is phosphorylated by LPS stimulation, and that the association between TAK1 and tumour necrosis factor receptor-associated factor 6 (TRAF6) is constitutive and not induced by LPS treatment. These results indicate that NF-kappaB mediates LPS-triggered RANTES induction and that TAK1 as well as NIK, as NF-kappaB activators participates in LPS-triggered RANTES induction.

Adenosine and purine nucleosides protect rat primary astrocytes from peroxynitrite-potentiated, glucose deprivation-induced death: preservation of intracellular ATP level.

Previously we have reported that immunostimulated astrocytes became highly vulnerable to glucose deprivation. In the present study we examined the effect of various kinds of nucleosides on the augmented death of glucose-deprived immunostimulated astrocytes. Preincubation with interferon-gamma (100 U/ml) and lipopolysaccharide (1 microg/ml) for 48 h and continuous exposure to glucose deprivation (4 h) significantly induced the lactate dehydrogenase (LDH) release, as a marker of cell injury or death, from astrocytes. The glucose deprivation-induced augmented cell death in immunostimulated astrocytes was mimicked by exogenous peroxynitrite generator 3-morpholinosydnonimine (SIN-1). The increased death in immunostimulated or SIN-1-treated astrocytes deprived of glucose was blocked by adenosine and ATP. Other purine nucleos(t)ides, not pyrimidine nucleotides, also showed similar protective effects. Adenosine receptor agonist R(-)-N-(2-phenylisopropyl)-adenosine or N-cyclohexyladenosine did not alter the augmented cell death. Adenosine receptor antagonists 8-cyclopentyl-1,3-dipropylxanthine, xanthine amine congener or 3,7-dimethyl-1-propargylxanthine also did not reverse the protective effect of adenosine. Intracellular ATP levels rapidly decreased prior to the LDH release in glucose-deprived immunostimulated astrocytes. The loss of intracellular ATP was prevented by adenosine and other purine nucleotides. The present results suggest that adenosine and their metabolites may protect astrocytes from peroxynitrite-potentiated, glucose deprivation-induced death by serving as substrates for intracellular ATP generation.

Depletion of intracellular glutathione mediates zinc-induced cell death in rat primary astrocytes.

In the present study, we investigated the possible mechanisms of cellular injury induced by zinc in rat primary astrocytes and C6 glioma cells. Reactive oxygen species (ROS) production, cellular glutathione (GSH) level and mitochondrial transmembrane potential were examined. Exposure to 200-300 microM Zn2+ for 24 h resulted in significant lactate dehydrogenase (LDH) release in rat primary astrocytes and C6 glioma cells. An exposure of 200 microM Zn2+ resulted in profound morphological changes, for example, shrunken and fragmented nuclei. Pretreatment of a protein synthesis inhibitor, cycloheximide, did not attenuate cellular toxicity induced by Zn2+. Zn2+ exposure increased intracellular ROS levels by about 250%, and depleted cellular GSH within 2 h, which preceded observable LDH release from the cell. Addition of GSH, N-acetylcysteine (NAC) and ascorbic acid substantially attenuated cellular death induced by Zn+ in a concentration dependent manner. ROS production and morphological changes induced by zinc were also inhibited by co-treatment of GSH or NAC with Zn2+. Zn2+ significantly depolarized mitochondrial transmembrane potential, which was reversed by co-treatment of GSH or NAC with zinc. In summary, ROS generation, GSH depletion and mitochondrial dysfunction may be key factors in Zn2+-induced glial toxicity.