Piezoelectric properties have been studied for the composite systems of PZT ceramics and polymers including polyvinylidene fluoride (PVDF), polyethylene (PE), and polyvinyl alcohol (PVA). The values of the piezoelectric constants and their temperature and frequency dependences were discussed on the basis of the theoretical expressions of the piezoelectric constants for a two-phase system with piezoelectric spherical dispersions. The piezoelectric activity of all the composite systems studied was mainly ascribed to the piezoelectricity of PZT ceramics. For the PVDF-PZT system, the piezoelectricity of PVDF was shown to make minor contribution compared to that of PZT ceramics. For the PE-PZT system, the temperature dependence of the d constant due only to elastic relaxation in the PE phase was investigated. For the PVA-PZT system, the retardational and relaxational frequency dependence of the d constant observed above 80 °C were successfully accounted for in terms of the interfacial and electrode polarizations due to the dc conduction in the PVA phase.

Periodontitis is a localized infectious disease caused by periodontopathic bacteria, such as Porphyromonas gingivalis. Recently, it has been suggested that bacterial infections may contribute to the onset and the progression of Alzheimer’s disease (AD). However, we do not have any evidence about a causative relationship between periodontitis and AD. In this study, we investigated by using a transgenic mouse model of AD whether periodontitis evoked by P. gingivalis modulates the pathological features of AD. Cognitive function was significantly impaired in periodontitis-induced APP-Tg mice, compared to that in control APP-Tg mice. Levels of Amiloid β (Aβ) deposition, Aβ40, and Aβ42 in both the hippocampus and cortex were higher in inoculated APP-Tg mice than in control APP-Tg mice. Furthermore, levels of IL-1β and TNF-α in the brain were higher in inoculated mice than in control mice. The levels of LPS were increased in the serum and brain of P. gingivalis-inoculated mice. P. gingivalis LPS-induced production of Aβ40 and Aβ42 in neural cell cultures and strongly enhanced TNF-α and IL-1β production in a culture of microglial cells primed with Aβ. Periodontitis evoked by P. gingivalis may exacerbate brain Aβ deposition, leading to enhanced cognitive impairments, by a mechanism that involves triggering brain inflammation.

Sperm-activating and -attracting factor (SAAF) released from the ascidian, Ciona savignyi, was partially purified from egg seawater with ethanol extraction and separation with the two-phase system of chloroform and water. SAAF did not activate sperm motility and cAMP synthesis in calcium-free seawater (CaFSW), but activated the both in the presence of Ca2+. Sperm activation by SAAF in Ca2+-containing medium was inhibited by flunarizine, a T-type Ca2+ channel antagonist, but L-type Ca2+ channel specific antagonists had no effect. Theophylline, a phosphodiesterase inhibitor, induced the increase of cAMP level and sperm activation in CaFSW without SAAF. On the other hand, the theophylline-activated sperm in CaFSW did not exhibit chemotaxis toward the tip of glass capillary containing SAAF, but upon the addition of Ca2+ they were attracted toward SAAF in the same manner as chemotaxis in normal artificial seawater. These results suggest that sperm activation is induced by the increased cAMP level caused by Ca2+ influx through T-type Ca2+ channel, and that Ca2+ alone mediates the sperm chemotaxis in Ciona.

No abstract

A remanent polarization of 130Ϯ3 mC/m 2 , large among the values reported for organic materials, and rectangular D -E hysteresis curves were realized in synthesized vinylidene fluoride ͑VDF͒ oligomer ͓CF 3 (CH 2 CF 2 ) 17 I͔ film evaporated onto a platinum surface around liquid nitrogen temperature. The results suggested that the VDF oligomer film has an extremely high crystallinity, and the electric dipoles arrange almost perfectly perpendicular to the film surface, and that a Lorentz local field factor of ferroelectric VDF oligomer crystals is nearly zero. Moreover, the obtained value of the coercive field, which was larger than those of ferroelectric polymers, might be attributed to the steric hindrance arising from the existence of iodine atoms at the VDF oligomer chains.