Mechanisms induced by transition metal contaminants and their effect on the hydrothermal stability of zirconia-containing bioceramics: an XPS study.

Zirconia containing bioceramics suffer from low temperature degradation in biological and hydrothermal environments, and the presence of transition metal contamination has been shown to greatly affect the zirconia stability in different materials. In this paper, X-ray photoelectron spectroscopy was used to investigate the compositional and structural variations of different zirconia containing hip-joint bioceramics with and without transition metal stains in hydrothermal environments. Non-stained and stainless-steel-stained femoral head samples of 3 mol% Y2O3 doped tetragonal zirconia polycrystals (3Y-TZP) and zirconia-toughened alumina (ZTA) subjected to isothermal treatments in water vapor were investigated with quantifying their respective compositional XP lines. The outputs of these spectroscopic experiments revealed a significant difference in the off-stoichiometric reactions taking place at the surface of zirconia-containing ceramics in the presence and absence of transition metal contamination. The complex off-stoichiometric chemistry that occurred in the presence of metal contaminants could be interpreted in terms of defect-related chemical reactions among metal, water vapor, and oxide lattice, with a crucial contribution of the alumina phase in the transformation kinetics of ZTA.

Annealing-Induced Off-Stoichiometric and Structural Alterations in Ca2+- and Y3+-Stabilized Zirconia Ceramics.

In the current study, high-temperature stability was investigated in two types of zirconia ceramics stabilized with two different additives, namely, calcia and yttria. The evolutions of structure and oxygen-vacancy-related defects upon annealing in air were investigated as a function of temperature by combining X-ray diffractometry with Raman, X-ray photoelectron and cathodoluminescence spectroscopies. We systematically characterized variations in the concentration of oxygen vacancies and hydroxyl groups during thermal treatments and linked them to structural alterations and polymorphic transformation. With this approach, we clarified how the combined effects of different dopants and temperature impacted on structural development and on the thermal stability of the oxygen-vacancy-related defect complex.

Mechanical oscillation accelerating nucleation and nuclei growth in hard-sphere colloidal glass.

Crystallization from amorphous solids is generally caused by activating phonons in a wide frequency range during heat treatment. In contrast, the activation of phonons in a narrow frequency range using ultrasonic treatment also causes crystallization below the glass transition temperature. These behaviors indicate that crystallization is related to the atomic motion in the glass state, and it is suggested that the activation of specific atomic motion can cause crystallization without increasing temperature. In this study, we observe nucleation and nuclei growth caused by mechanical oscillation in a hard-sphere colloidal glass and evaluate the effect of mechanical oscillation on the structural evolution in the early stage of the crystallization. Oscillation between 5 and 100 Hz is applied to the colloidal glass, and it is observed that the nucleation rate increases under the 70 Hz oscillation, resulting in formation of stable nuclei in a short amount of time. The nuclei growth is also accelerated by the 70 Hz oscillation, whereas increases in the nucleation rate and nuclei growth were not observed at other frequencies. Finally, activation of the diffusion-based rattling of particles by caging is considered as a possible mechanism of the observations.

Region-specific effects of copulation on dendritic spine morphology and gene expression related to spinogenesis in the medial preoptic nucleus of male rats.

The medial preoptic nucleus (MPN) plays an essential role in the control of male sexual behavior. In rats, the central part of the MPN (MPNc) contains a sexually dimorphic nucleus exhibiting male-biased morphological sex differences. Although it has been suggested that the MPNc of male rats functions to induce sexual arousal, the mechanisms by which male rats are sexually aroused to successfully achieve copulation are poorly understood. We recently showed that increased neuronal activity in the MPNc of male rats during copulation is higher at their first copulation compared with later copulations, indicating that a plastic change in excitatory synaptic transmission occurs with copulatory experience. In this study, we tested the hypothesis that changes to dendritic spines at structural and molecular levels occur following copulatory experience. First, we examined the effects of at least two copulations on the morphology of dendrites and spines in the MPNc and in the lateral and medial parts of the MPN (MPNlm) of male rats. In the MPNc, the total number of dendrites and their branches, and the surface area of dendrites were not significantly affected by copulation. However, the copulatory experience, specifically experience of ejaculation, significantly reduced the density of mushroom spines but not of filopodia, thin or stubby spines in the MPNc. In the MPNlm, the copulatory experience, specifically experience of ejaculation, significantly increased the surface area of dendrites, although there was no significant effect of copulation on spine density. Next, we measured the mRNA levels of genes encoding actin-binding proteins related to spinogenesis after male rats had copulated for their first and second times. Copulatory stimuli, especially stimuli from ejaculation, significantly reduced the mRNA levels of drebrin A and spinophilin in the MPNc but not in the MPNlm. These results indicate that copulatory experiences, especially experience of ejaculation, reduce spine density in the MPNc of male rats, which may result, in part, from downregulation of genes encoding actin-binding proteins.

Inhibition of neurite outgrowth and alteration of cytoskeletal gene expression by sodium arsenite.

Arsenic compounds that are often found in drinking water increase the risk of developmental brain disorders. In this study, we performed live imaging analyses of Neuro-2a cells expressing SCAT3, a caspase-3 cleavage peptide sequence linking two fluorescent proteins; enhanced cyan fluorescence protein (ECFP) and Venus, to determine whether sodium arsenite (NaAsO(2); 0, 1, 5, or 10 µM) affects both neurite outgrowth and/or induces apoptosis with the same doses and in the same cell cultures. We observed that the area ratio of neurite to cell body in SCAT3-expressing cells was significantly reduced by 5 and 10 µM NaAsO(2), but not by 1 µM, although the emission ratio of ECFP to Venus, an endpoint of caspase-3 activity, was not changed. However, cytological assay using apoptotic and necrotic markers resulted in that apoptosis, but not necrosis, was significantly induced in Neuro-2a cells when NaAsO(2) exposure continued after the significant effects of NaAsO(2) on neurite outgrowth were found by live imaging. These results suggested that neurite outgrowth was suppressed by NaAsO(2) prior to NaAsO(2)-induced apoptosis. Next, we examined the effects of NaAsO(2) on cytoskeletal gene expression in Neuro-2a cells. NaAsO(2) increased the mRNA levels of the light and medium subunits of neurofilament and decreased the mRNA levels of tau and tubulin in a dose-dependent manner; no significant effect was found in the mRNA levels of the heavy subunit of neurofilament, microtubule-associated protein 2, or actin. The changes in cytoskeletal gene expression are likely responsible for the inhibitory effects of NaAsO(2) on neurite outgrowth.

Rapid and sustained increase of large granular lymphocytes and rare cytomegalovirus reactivation during dasatinib treatment in chronic myelogenous leukemia patients.

We retrospectively investigated increases in large granular lymphocytes (LGL) in peripheral blood during dasatinib treatment in 25 chronic myelogenous leukemia patients. Fifteen of 25 patients (60 %) showed an increase in LGL. All 15 of these patients also showed an increase in NK cells, and 11 showed an increase in CD8(+) T cells. High frequencies of clonal rearrangements of TCR-ß, -γ, and -δ genes were observed in LGL (+) patients, and at lower frequencies in LGL (-) patients as well. Clinical responses were favorable for all. With respect to their newly obtained complete molecular response after dasatinib treatment, LGL (+) patients showed higher response rates than did LGL (-) patients. In contrast, pleural effusions were more commonly observed in LGL (+) patients (60 %) than in LGL (-) patients (20 %). LGL counts significantly increased at 2 h after oral intake of dasatinib in all 25 patients. This was not observed in treatment with imatinib or nilotinib. Cytomegalovirus (CMV) C7-HRP tests were negative in all patients. Serum CMV-IgM antibodies were positive in only 2 of 25 patients without symptom of infection. Thus, LGL lymphocytosis during dasatinib treatment may be correlated with favorable molecular response, and with increased incidence of pleural effusions. In the clinical setting, CMV reactivation appears uncommon.

Involvement of postnatal apoptosis on sex difference in number of cells generated during late fetal period in the sexually dimorphic nucleus of the preoptic area in rats.

Postnatal apoptosis is involved in formation of the sex difference in neuron number of the sexually dimorphic nucleus of the preoptic area (SDN-POA) in rats. In this study, we examined the origin of neurons that die with apoptosis on the postnatal period to exhibit the sex difference in neuron number of the SDN-POA. First, we measured the number of cells that were labeled with 5-bromo-2'-deoxyuridine (BrdU) on embryonic day (ED) 17, ED18, and ED19 in the SDN-POA of rats on postnatal day (PD) 4 and PD8. The SDN-POA had many more cells labeled with BrdU on ED17 and ED18 than those on ED19. Significantly fewer cells labeled with BrdU on ED18 in the female SDN-POA from PD4 to PD8 resulted in a significant sex difference in the number at PD8. Next, combination analyses of BrdU-labeling and immunohistochemistry for single-stranded DNA (ssDNA), an apoptotic marker, were succeeded to investigate whether SDN-POA neurons generated during ED17-18 were removed by apoptosis. Many more ssDNA-immunoreactive cells that had been labeled with BrdU during ED17-18 were found in the SDN-POA of PD8 females, but few in the SDN-POA of PD8 males and PD4 females and males. These results suggest that the sex difference in the number of SDN-POA neurons generated during the late fetal period was caused by postnatal apoptosis.