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We have succeeded in observing the size dependent photoluminescence ͑PL͒ from Ge nanocrystals ͑nc-Ge͒ with 0.9-5.3 nm in average diameter (d ave) in the near-infrared region. The nc-Ge were fabricated by rf cosputtering of Ge and SiO 2 and post annealing at 800°C. It was found that the sample with d ave ϭ5.3 nm shows a PL peak at about 0.88 eV. With decreasing the size, the PL peak shifted to higher energies and reached 1.54 eV for the sample with d ave ϭ0.9 nm. It was also found that the PL intensity increases drastically with decreasing the size. The observed strong size dependence of the PL spectra indicates that the observed PL originates from the recombination of electron-hole pairs confined in nc-Ge. ͓S0163-1829͑98͒09535-6͔

A free-standing biodegradable nanosheet composed of poly(L-lactic acid) (PLLA) was shown to have excellent sealing efficacy for a gastric incision as a novel wound dressing material that did not require adhesive agents, and the PLLA nanosheet-induced wound repair showed neither scars nor tissue adhesion. This material may, therefore, be an ideal alternative to conventional tissue repairing procedures using suture/ligation in surgery.

The homeostasis of body temperature and energy balance is one of the major principles in biology. Nanoscale thermometry of aqueous solutions is a challenging but crucial technique to understand the molecular basis of this essential process. Here, we developed a ratiometric nanothermometer (RNT) for intracellular temperature measurement in real time. Both the thermosensitive fluorophore, β-diketonate chelate europium(III) thenoyltrifluoroacetonate, and the thermoinsensitive fluorophore, rhodamine 101, which was used as a selfreference, are embedded in a polymeric particle that protects the fluorophores from intracellular conditions. The ratiometric measurement of single RNT spots is independent of the displacement of the RNT along the z-axis. The temperature is therefore determined at the location of each RNT under an optical microscope regardless of the dynamic movement of living cells. As a demonstration of the spot-by-spot intracellular thermometry, we successfully followed the temperature change in individual RNT spots in a single cell together with the Ca 2þ burst induced by the Ca 2þ ionophore ionomycin. The temperature increases differently among different spots, implying heterogeneous heat production in the cell. We then show that, in some spots, the temperature gradually decreases, while in others it remains high. The average temperature elevation within a cell is positively correlated to the increase in Ca 2þ , suggesting that the activity and/or number of heat sources are dependent on the Ca 2þ concentration.

Carbon monoxide (CO) derived from heme oxygenase has recently been shown to play a role in controlling hepatobiliary function, but intrahepatic distribution of the enzyme is unknown. We examined distribution of two kinds of the heme oxygenase isoforms (HO-1 and HO-2) in rat liver immunohistochemically using monoclonal antibodies. The results showed that distribution of the two isoforms had distinct topographic patterns: HO-1, an inducible isoform, was observed only in Kupffer cells, while HO-2, a constitutive form, distributed to parenchymal cells, but not to Kupffer cells. Both isoforms were undetectable in hepatic stellate cells and sinusoidal endothelial cells. Of the two isoforms, HO-2 in the parenchymal cell rather than HO-1 in the Kupffer cell, appears to play a major role in regulation of microvascular tone. In the perfused liver, administration of HbO2, a CO-trapping reagent that can diffuse across the fenestrated endothelium into the space of Disse, elicited a marked sinusoidal constriction, while administration of a liposome-encapsulated Hb that cannot enter the space had no effect on the microvascular tone. These results suggest that CO evolved by HO-2 in the parenchymal cells, and, released to the extrasinusoidal space, served as the physiological relaxant for hepatic sinusoids.