Purified smooth muscle myosin in the in vitro motility assay propels actin filaments at 1/10 the velocity, yet produces 3-4 times more force than skeletal muscle myosin. At the level of a single myosin molecule, these differences in force and actin filament velocity may be reflected in the size and duration of single motion and force-generating events, or in the kinetics of the cross-bridge cycle. Specifically, an increase in either unitary force or duty cycle may explain the enhanced force-generating capacity of smooth muscle myosin. Similarly, an increase in attached time or decrease in unitary displacement may explain the reduced actin filament velocity of smooth muscle myosin. To discriminate between these possibilities, we used a laser trap to measure unitary forces and displacements from single smooth and skeletal muscle myosin molecules. We analyzed our data using mean-variance analysis, which does not rely on scoring individual events by eye, and emphasizes periods in the data with constant properties. Both myosins demonstrated multiple but similar event populations with discrete peaks at approximately +11 and -11 nm in displacement, and 1.5 and 3.5 pN in force. Mean attached times for smooth muscle myosin were longer than for skeletal-muscle myosin. These results explain much of the difference in actin filament velocity between these myosins, and suggest that an increased duty cycle is responsible for the enhanced force-generating capacity of smooth over skeletal-muscle myosin.

A stable force potential well was generated by two collimated focused ultrasonic (3.5 MHz) beams propagating along opposite directions. Latex particles (270-microns diameter) and clusters of frog eggs were trapped in the potential well. The trapped object can be moved axially or laterally by moving one of the PZT focusing transducers that generate the ultrasonic focused beams. The axial position of the trapped object can also be maneuvered by tuning the frequency of the electrical voltage applied on the transducers.

To improve the gas-sensing performance of metal-oxide-semiconductors, the effect of defects on gas-sensing properties has been widely investigated. Nevertheless, although the metal cation defect is the dominative acceptor defect in p-type semiconductors, its effect on the gas-sensing properties remains blank, which leads to a hindrance for further developing p-type semiconductor-based gas sensors. Accordingly, to eleborate the effect of metal cation defects on the sensing properties, mesoporous NiO nanosheets with different amounts of nickel vacancies were prepared by annealing at different temperatures. It was found that the amount of nickel vacancies increased with increasing the annealing temperature. Gas-sensing studies revealed that the NiO with a higher concentration of nickel vacancies exhibited higher sensitivity to NO2 at room temperature. With further increasing the annealing temperature to 600 °C, although the rapid decrease in the specific surface area of the NiO might limit the physisorption of NO2, the NiO could also present a better sensitivity to NO2 due to the abundant nickel vacancies with high activity. Furthermore, an in situ DRIFTS study demonstrated that the number of adsorbed nitrate and nitrite species on NiO surfaces increased with increasing the amount of nickel vacancies, indicating that the nickel vacancies acted as the dominative active sites participating in the gas–solid reaction and then determined the room-temperature sensing properties. According to the defect ionization equation, a hole conduction model was further proposed to decipher the dependency of sensing properties on the metal cation defects. We hope this work could make us better understand the roles of cation defect in the sensing properties, and it could also benefit the improvement of p-type semiconductor-based gas sensors.

As activated microglia (MG) is an early sign that often precedes and triggers neuronal death, inhibition of microglial activation and reduction of subsequent neurotoxicity may offer therapeutic benefit. The present study demonstrates that rat primary cultured MG expressed Kir6.1 and SUR2 subunits of KATP channel, which was identical to that expressed in BV-2 microglial cell line. The classic KATP channel opener pinacidil and selective mitochondrial KATP (mito-KATP) channel opener diazoxide prevented rotenone-induc microglial activation and production of pro-inflammatory factors (tumour necrosis factor[TNF]-α and prostaglandin E2[PGE2]). And the effects of pinacidil and diazoxide were reversed by mito-KATP blocker 5-hydroxydecanoate (5-HD), indicating that mito-KATP channels participate in the regulation of microglial activation. Moreover, the underlying mechanisms involved the stabilization of mitocho drial membrane potential and inhibition of p38/c-Jun-N-terminal kinase (JNK) activation in microglia. Furthermore, the in vivo study confirmed that diazoxide exhibited neuroprotective effects against rotenone along with the inhibition of microglial activation and neuroinflammation. Thus, microglial mito-KATP channel might be a novel prospective target for the treatment of neuroinflammation-related degenerative disorders such as Parkinson's disease.

Muscle contraction is powered by the interaction of the molecular motor myosin with actin. With new techniques for single molecule manipulation and f luorescence detection, it is now possible to correlate, within the same molecule and in real time, conformational states and mechanical function of myosin. A spot-confocal microscope, capable of detecting single f luorophore polarization, was developed to measure orientational states in the smooth muscle myosin light chain domain during the process of motion generation. Fluorescently labeled turkey gizzard smooth muscle myosin was prepared by removal of endogenous regulatory light chain and re-addition of the light chain labeled at cysteine-108 with the 6-isomer of iodoacetamidotetramethylrhodamine (6-IATR). Single myosin molecule f luorescence polarization data, obtained in a motility assay, provide direct evidence that the myosin light chain domain adopts at least two orientational states during the cyclic interaction of myosin with actin, a randomly disordered state, most likely associated with myosin whereas weakly bound to actin, and an ordered state in which the light chain domain adopts a finite angular orientation whereas strongly bound after the powerstroke.At the molecular level, muscular force and motion generation are the result of a cyclic interaction between myosin and actin.

No abstract

Inhibition of microglia-mediated neuroinflammation has been regarded as a prospective strategy for treating neurodegenerative disorders, such as Parkinson's disease (PD). In the present study, we demonstrated that systematic administration with iptakalim (IPT), an adenosine triphosphate (ATP)-sensitive potassium channel (K ATP ) opener, could alleviate rotenone-induced degeneration of dopaminergic neurons in rat substantia nigra along with the downregulation of microglial activation and mRNA levels of tumor necrosis factor-a (TNF-a) and cyclooxygenase-2 (COX-2). In rat primary cultured microglia, pretreatment with IPT suppressed rotenone-induced microglial activation evidenced by inhibition of microglial amoeboid morphological alteration, declined expression of ED1 (a marker for activated microglia), and decreased production of TNF-a and prostaglandin E2 (PGE 2 ). These inhibitory effects of IPT could be reversed by selective mitochondrial K ATP (mitoK ATP ) channel blocker 5-hydroxydecanoate (5-HD). Furthermore, pretreatment with IPT prevented rotenone-induced mitochondrial membrane potential loss and p38/c-jun N-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) activation in microglia, which might in turn regulate microglial activation and subsequent production of TNF-a and PGE 2 . These data strongly suggest that the K ATP opener IPT may be a novel and promising neuroprotective drug via inhibiting microgliamediated neuroinflammation.

Although photodynamic therapy (PDT) has been an attractive strategy for several cancer treatments in the clinical setting, PDT efficacy is attenuated by consumption of oxygen. To address this photodynamic issue, we adopted a phototherapy–chemotherapy combination strategy based on targeted delivery of the near-infrared photosensitizer indocyanine green (ICG), photothermal conversion agent polydopamine (PDA), and tirapazamine (TPZ), a hypoxia-activated prodrug. Under laser irradiation, ICG consumption of oxygen and aggravated hypoxia in tumor sites can activate TPZ to damage DNA. In parallel, ICG produces reactive oxygen species which work in synergy with PDA to enhance phototherapeutic efficiency. Herein, hybrid CaCO3/TPGS nanoparticles delivering ICG, PDA, and TPZ (ICG-PDA-TPZ NPs) were designed for effective and safe cancer therapy. ICG-PDA-TPZ NPs showed significantly improved cellular uptake and accumulation in tumors. Furthermore, we demonstrated that ICG-PDA-TPZ NPs showed intensive photodynamic and photothermal effects in vitro and in vivo, which synergized with TPZ in subcutaneous U87 malignant glioma growth and orthotopic B16F10 tumor inhibition, with negligible side effects. Thus, ICG-PDA-TPZ NPs could be an effective strategy for improvement of PDT.