Tribotronic and electrochemical properties of platinum-nanofluid interfaces formed by aqueous suspensions of 5 and 40 nm TiO2 nanoparticles.

Nanoparticles (NPs) can be highly beneficial as additives to lubricating fluids, and the tribotronic response of charged NPs tuned by external fields represents an area of great technological potential. Tribotronic response, however, is expected to be highly size dependent, which represents a significant design challenge. To explore this issue, quartz crystal microbalance and cyclic voltammetry were employed to characterize nanotribological and electrochemical behavior of platinum-nanofluid interfaces formed by aqueous suspensions of different-sized negatively charged titanium dioxide (TiO2) NPs. Suspensions of 5, 40, and 100 nm NPs were all observed to reduced interfacial frictional drag forces upon introduction into pure water in zero field conditions, with reductions for the 40 nm NPs about twice those of 5 nm particles at comparable concentrations. Suspensions of 100 nm NPs produced even greater reductions, but rapidly precipitated from the suspension when left unstirred. NPs were also driven to and from Pt electrode surfaces by applying external electric fields with varying amplitudes and modulation frequencies. For electric fields of sufficient amplitude and duration, the 40 nm TiO2 nanosuspension exhibited tribological properties consistent with a reversible electrophoretic deposition of the NPs, accompanied by changes in the electrochemical attributes and increasing interfacial drag. The 5 nm NP properties were consistent with progressive reductions in interfacial drag forces at the NP-suspension interface linked to field-induced increases in concentration.

TRPV4 and K(Ca) ion channels functionally couple as osmosensors in the paraventricular nucleus.

BACKGROUND AND PURPOSE: Transient receptor potential vanilloid type 4 (TRPV4) and calcium-activated potassium channels (KCa ) mediate osmosensing in many tissues. Both TRPV4 and KCa channels are found in the paraventricular nucleus (PVN) of the hypothalamus, an area critical for sympathetic control of cardiovascular and renal function. Here, we have investigated whether TRPV4 channels functionally couple to KCa channels to mediate osmosensing in PVN parvocellular neurones and have characterized, pharmacologically, the subtype of KCa channel involved. EXPERIMENTAL APPROACH: We investigated osmosensing roles for TRPV4 and KCa channels in parvocellular PVN neurones using cell-attached and whole-cell electrophysiology in mouse brain slices and rat isolated PVN neurons. Intracellular Ca(2+) was recorded using Fura-2AM. The system was modelled in the NEURON simulation environment. KEY RESULTS: Hypotonic saline reduced action current frequency in hypothalamic slices; a response mimicked by TRPV4 channel agonists 4αPDD (1 µM) and GSK1016790A (100 nM), and blocked by inhibitors of either TRPV4 channels (RN1734 (5 µM) and HC067047 (300 nM) or the low-conductance calcium-activated potassium (SK) channel (UCL-1684 30 nM); iberiotoxin and TRAM-34 had no effect. Our model was compatible with coupling between TRPV4 and KCa channels, predicting the presence of positive and negative feedback loops. These predictions were verified using isolated PVN neurons. Both hypotonic challenge and 4αPDD increased intracellular Ca(2+) and UCL-1684 reduced the action of hypotonic challenge. CONCLUSIONS AND IMPLICATIONS: There was functional coupling between TRPV4 and SK channels in parvocellular neurones. This mechanism contributes to osmosensing in the PVN and may provide a novel pharmacological target for the cardiovascular or renal systems.

Repetitive strain injury to the foot in elite women kendoka.

OBJECTIVE: To account for the apparent high incidence of pain in the feet of elite women kendo players. METHODS: A clinical evaluation was done by a chiropractor, the women were interviewed about their kendo experience, and the conditions and frequency of training and ground reaction forces were measured on a Kistler force plate during the kendo attacking action. RESULTS: Four out the five women presented with plantar fasciitis. They had all practised for some time on wooden floors laid on concrete, for between two to four hours a week. They warmed up conscientiously but cool down was more cursory. The force plate results showed that they were hitting the floor with a mean force of four times body weight during a transient impact. CONCLUSIONS: High motivation for practice and training, hard floors, ignoring painful feet, and cursory postpractice cool down probably produced the condition. Postpractice icing and stretching were found to be most effective in the short term. In the longer term reducing the level of impact, either by training on sprung floors or changing the footwork, might reduce the incidence and intensity of the fasciitis.