Shinsuke Yamashita

Mechanism of bone destructiondue to middle ear cholesteatoma as revealed by laser-Raman spectrometry

In an investigation of the mechanism of bone destruction caused by chronic otitis media complicated with cholesteatoma, both the processes of demineralization and remineralization were studied in an animal model and clinically at the molecular level, using a laser-Raman spectrometer. From this investigation, it is proposed that the mechanism of bone destruction associated with cholesteatoma is a form of demineralization.

Increase in the Magnetic Ordering Temperature (Tc) as a Function of the Applied Pressure for A2Mn[Mn(CN)6] (A = K, Rb, Cs) Prussian Blue Analogues

Magnetization measurements under pressure reveal that the external hydrostatic pressure significantly increases in the ferrimagnetic transition temperature, Tc, for A2Mn[Mn(CN)6] (A = K, Rb, Cs). In the case of monoclinic A = K and Rb, dTc/dp values are 21.2 and 14.6 K GPa-1, respectively, and Tc increases by 53 and 39%, respectively, from ambient pressure to 1.0 GPa. The cubic A = Cs compound also shows a monotonous increase with an initial rate of 4.22 K GPa-1 and about 11.4 K GPa-1 above 0.6 GPa, and an overall Tc increase by 26% at 1.0 GPa. The increase in Tc is attributed to deformation of the structure such that the MnII-N≡C angle decreases with increasing pressure. The smaller the alkali cation, the greater the decrease in the MnII-N≡C angle induced by pressure and the larger the increase of dTc/dp. This is in accordance with the ambient-pressure structures for A2Mn[Mn(CN)6] (A = K, Rb, Cs), which have decreasing MnII-N≡C angles that correlate to the observed increasing Tcs as K > Rb > Cs. The large increase in Tc for the A = K compound is the highest class among several cyano-bridged metal complexes. The tuning of the transition temperature by such a weak pressure may lead to additional applications such as switching devices.

Long-term observation of surface structure of synthetic auditory ossicle (Apaceram)*

Methods: A study was made to obtain information about the surface structure of thin Apaceram disks of dense hydroxyapatite (HA) implanted in the soft tissue of rats for 6, 14, and 20 months. Thin Apaceram disks were implanted subcutaneously into the interscapular regions of 12 rats. Apaceram surfaces were analyzed by laser-Raman spectrometry at the molecular level and observed by scanning electron microscope. Surfaces of Apaceram specimens were compared with untreated Apaceram used as a control. Results: Apaceram surfaces were observed by scanning electron microscopy at magnifications of • • and • Many small crater-like cavities observed in the smooth surface area at 6-month implantation decreased prominently after 20 months, whereas the untreated surface was smooth. Numerous crystal grains were observed on original particle surfaces of Apaceram after implantation for 20 months. The study monitored a Raman spectral signal of v 1 (wave number = 960 cm-l: the strongest peak) on the basis of vibration due to PO43of HA as an indicator of the Apaceram component. Half-peak breadths (HPBs) of v I signal, as an indicator of demineralization and renfineralization, were compared. (1) Mean HPB (4.148 _+ 0.065, n = 12) of Apaceram surface after 14 months was significantly narrower than (4.310 + 0.173, n = 10) after 6 months (P < 0.05). (2) Mean HPB (4.225 _+ 0.028, n = 13) after 20 months was significantly wider than (4.148 _+ 0.065, n = 12) after 14 months of implantation (P < 0.01). (3) Comparison of mean HPB between untreated Apaceram surface and 20 months of implantation showed no significant difference. Using scanning electron microscopy, although untreated particle surfaces appeared to differ from implanted particle surfaces at 20 months, both had basically the same composition because there was no significant difference in mean HPBs. Conclusions: Ions such as Ca 2+ and PO43were released from the Apaceram surface implanted in the subcutaneous tissue of rats. Remineralization might have progressed gradually on the surface of Apaceram when released ions were saturated in the interfacial region (body fluid phase) between the Apaceram disk and the tissue. (Supported by grant no. 10671594 from the Ministry of Education, Science, Sports and Culture of the Japanese Government.)