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Biomedical subjects

Ken Onda

Publications and source records attributed to Ken Onda.

7 recordsLinked to original sources
PubMed2006

Ultrafast interfacial proton-coupled electron transfer.

The coupling of electron and nuclear motions in ultrafast charge transfer at molecule-semiconductor interfaces is central to many phenomena, including catalysis, photocatalysis, and molecular electronics. By using femtosecond laser excitation, we transferred electrons from a rutile titanium dioxide (110) surface into a CH3OH overlayer state that is 2.3 +/- 0.2 electron volts above the Fermi level. The redistributed charge was stabilized within 30 femtoseconds by the inertial motion of substrate ions (polaron formation) and, more slowly, by adsorbate molecules (solvation). According to a pronounced deuterium isotope effect (CH3OD), this motion of heavy atoms transforms the reverse charge transfer from a purely electronic process (nonadiabatic) to a correlated response of electrons and protons.

Deuterium↗
PubMed2006

Expression of bovine parathyroid hormone/parathyroid hormone- related protein (PTH/PTHrP) receptor mRNA in the mammary gland of cows.

To examine the PTH/PTHrP receptor in the mammary gland, molecular cloning of bovine PTH/PTHrP receptor and measurement of its mRNA expression were carried out in cows during the periparturient period. The PTH/PTHrP receptor gene was partially cloned, and expression of bovine PTH/PTHrP receptor mRNA was detected in various tissues of the cow. In the mammary gland, PTH/PTHrP receptor mRNA expression was constantly low during the periparturient period, whereas PTHrP mRNA expression dramatically increased after parturition. This suggested that expression of PTH/PTHrP receptor mRNA in the mammary gland is not affected by lactation in cows.

Animals↗
PubMed2006

Parathyroid hormone-related protein (PTHrP) and Ca levels in the milk of lactating cows.

To investigate the roles of mammary PTHrP in calcium uptake and/or release in the mammary gland of cows, plasma PTHrP and Ca levels, and their arterial-venous differences were examined in a Jersey cow during the periparturient period. Levels of Ca in both abdominal aorta and abdominal subcutaneous vein blood slightly decreased around the parturition and at 24 days after the parturition, however, no remarkable arterial-venous differences were observed. Plasma PTHrP levels in both arterial and venous samples were below the detection limit (0.57 pmol/l) during the experimental period. Milk PTHrP and Ca levels were measured in 9 Holstein dairy cows. Although plasma PTHrP levels in all arterial and venous samples were also below the detection limit, milk PTHrP and Ca levels were remarkably high, ranging from 14,900 pmol/l to 41,200 pmol/l and from 772 mg/l to 1,200 mg/l, respectively. In addition, a significant positive correlation (P<0.01) was observed between milk PTHrP and Ca levels. These results suggested that mammary PTHrP is closely related to Ca concentration in the milk.

Animals↗
PubMed2006

Expression of parathyroid hormone-related protein (PTHrP) mRNA in mammary gland of periparturient cows.

The expression of parathyroid hormone-related protein (PTHrP) mRNA was examined in mammary gland with or without lactation, and during periparturient period in a Holstein cow and a Jersey cow. In the lactating mammary gland, PTHrP was detected in alveolar epithelial cells and the lumen by immunohistochemical analysis. The relative expression levels of PTHrP mRNA in mammary gland from lactating cows were significantly higher than those from non-lactating cows (P<0.05). During periparturient period, relative PTHrP mRNA level was remarkably low before the parturition in a Jersey and a Holstein cow, however, both levels were gradually increased and reached a peak level at 5-6 weeks after the parturition. In addition, the peak level in a Jersey cow was approximately 3-fold higher than that in a Holstein cow. From these results, PTHrP was synthesized and secreted in alveolar epithelial cells in mammary gland and increased subsequently with the lactation, suggesting a possible mechanism for the regulation of local calcium homeostasis.

Animals↗
PubMed2005

Wet electrons at the H2O/TiO2(110) surface.

At interfaces of metal oxide and water, partially hydrated or "wet-electron" states represent the lowest energy pathway for electron transfer. We studied the photoinduced electron transfer at the H2O/TiO2(110) interface by means of time-resolved two-photon photoemission spectroscopy and electronic structure theory. At approximately 1-monolayer coverage of water on partially hydroxylated TiO2 surfaces, we found an unoccupied electronic state 2.4 electron volts above the Fermi level. Density functional theory shows this to be a wet-electron state analogous to that reported in water clusters and which is distinct from hydrated electrons observed on water-covered metal surfaces. The decay of electrons from the wet-electron state to the conduction band of TiO2 occurs in </=15 femtoseconds.

Journal Article↗
PubMed2005

Femtosecond imaging of surface plasmon dynamics in a nanostructured silver film.

Light interacting with nanostructured metals excites the collective charge density fluctuations known as surface plasmons (SP). Through excitation of the localized SP eigenmodes incident light is trapped on the nanometer spatial and femtosecond temporal scales and its field is enhanced. Here we demonstrate the imaging and quantum control of SP dynamics in a nanostructured silver film. By inducing and imaging the nonlinear two-photon photoemission from the sample with a pair of identical 10-fs laser pulses while scanning the pulse delay, we record a movie of SP fields at a rate of 330-attoseconds/frame.

Electrons↗