We developed new nonradioactive microspheres and used more sensitive X-ray fluorescence spectrometers than used previously to measure regional blood flow in the heart and other organs. We demonstrated the chemical stability of eight kinds of heavy element-loaded microspheres and validated their use for regional blood flow measurement by comparing duplicate flows measured with radioactive and/or nonradioactive microspheres in both acute and chronic dog experiments. The wavelength-dispersive spectrometer (Philips PW 1480) has a higher sensitivity than the previously described X-ray fluorescent system and reduced the number of microspheres required for accurate measurement. The fine energy resolution of this system makes it possible to increase the numbers of different kinds of microspheres to be quantitated, but at present only eight kinds are available. We also used a synchrotron radiation-excited energy dispersive spectrometer. The monochromatic synchrotron radiation allowed us to obtain much higher signal-to-background ratios of X-ray fluorescence spectra than with the wavelength-dispersive system (50 dB more for Zr-loaded microspheres) and will enable analysis of fluorescent activity in smaller regions (< 20 mg) than the radioactive method does.

Self-assembly of amyloid-β (Aβ) peptides in nonequilibrium, flowing conditions is associated with pathogenesis of Alzheimer’s disease. We examined the role of biologically relevant, nonequilibrium, flowing conditions in the desorption, diffusion, and integration of Aβ-lipid assemblies at the membrane surface using a microchannel connected with microsyringes. A 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayer was formed on a glass substrate and incubated in Aβ solution under either a quiescent condition (no flow) or flowing condition for 24 h. Although dot-like aggregates (<1 μm) comprising Aβ fibrils formed on the DMPC membrane under the quiescent condition, larger plaque-like aggregates formed under the flowing condition, suggesting that nonequilibrium continuous flow governs the cytotoxicity of Aβ species. We propose that Aβ adsorption on the membrane surface involves spontaneous desorption of Aβ-lipid to form self-assembling aggregates, with this accelerated by surface shear forces. These findings suggest that nonequilibrium, flowing conditions influence inter/intra-molecular Aβ-fibril formation to trigger formation of amyloid plaques.

The exumbrellar surfaces of six pelagic cnidarians from three classes were ultra-structurally compared to reveal their structural diversity in relation to their gelatinous, transparent bodies. We examined two hydrozoans (Diphyes chamissonis and Colobonema sericeum), a cubozoan (Chironex yamaguchii), and three scyphozoans (Atolla vanhöffeni, Aurelia coerulea, and Mastigias papua). The exumbrellar surfaces of the mesoglea in D. chamissonis, Ch. yamaguchii, Au. coerulea, and M. papua were covered with a simple epidermis; the shapes of the epidermal cells were remarkably different among the species. The epidermal cells of Ch. yamaguchii and M. papua possessed an array of microvilli on the apical side. The array possibly reduced light reflectance and provided some other surface properties, as seen for the cuticular nipple array in tunicates, considering the length, width, and pitch of the microvilli. The reduction of light reflectance on the array of microvilli was supported by the simulation with rigorous coupled wave analysis (RCWA). Microvilli were sparse and did not form an array in metephyrae of Au. coerulea. The mesoglea matrix beneath the basal side of the epidermis was loose in all of the species. The exumbrellar side of the mesoglea was exposed only in the mesopelagic species, At. vanhöffeni and Co. sericeum, and electrondense layer(s) covered the surface of the mesoglea. It is uncertain whether the exumbrellar epidermis is absent in these species or the epidermal cells are completely exfoliated during the sampling and handling processes. In the latter case, the electron-dense layer(s) on the mesoglea surface might originally underlie the epidermis.

Mastigias papua, known as the golden (or spotted) jellyfish, is an epipelagic jellyfish widely distributed in the warm waters of the West Pacific. This jellyfish has a brownish body, owing to zooxanthellae, and white spots. We measured the maximum force to pierce the umbrella, which averaged 94-144 mm in diameter, to evaluate the hardness of M. papua, and returned a range of 0.14-0.45 N. Correlation analyses indicate that when the M. papua medusa grows (i.e., becomes heavier), the umbrella becomes larger in diameter, as well as thicker and harder within the size range we examined. However, a significant relationship between the hardness of the umbrellar apex and the thickness of the umbrella was not obtained. White spots are comprised of loose aggregates of mesogleal cells containing reflective granules. Since the white spots and the transparent parts were not significantly different in hardness, the spots were unlikely to strengthen the umbrella. The primary function of the spots may be the shading of solar radiation. Most of the zooxanthellae are located in mesogleal cells, and often beneath the exumbrellar epidermis. Therefore, light shading by white spots may be unnecessary for the zooxanthellae in mesogleal cells.