Structural insights into the gating of DNA passage by the topoisomerase II DNA-gate.

Type IIA topoisomerases (Top2s) manipulate the handedness of DNA crossovers by introducing a transient and protein-linked double-strand break in one DNA duplex, termed the DNA-gate, whose opening allows another DNA segment to be transported through to change the DNA topology. Despite the central importance of this gate-opening event to Top2 function, the DNA-gate in all reported structures of Top2-DNA complexes is in the closed state. Here we present the crystal structure of a human Top2 DNA-gate in an open conformation, which not only reveals structural characteristics of its DNA-conducting path, but also uncovers unexpected yet functionally significant conformational changes associated with gate-opening. This structure further implicates Top2's preference for a left-handed DNA braid and allows the construction of a model representing the initial entry of another DNA duplex into the DNA-gate. Steered molecular dynamics calculations suggests the Top2-catalyzed DNA passage may be achieved by a rocker-switch-type movement of the DNA-gate

Monitoring Apnea in the Elderly by an Electromechanical System with a Carbon Nanotube-based Sensor

SummaryBackgroundBreathing, a part of respiration, is one of the vital functions. Breathing disorders are common in the elderly. An effective breathing sensor for real-time detection of apnea is important in clinical critical care. We aimed to construct a real-time warning platform with a combination of carbon nanotubes (CNTs) and related nano-electromechanical system (NEMS) for elderly care.MethodsThrough a specific acid-treated procedure, multiwalled carbon nanotubes (MWCNTs) were immobilized on a thin silicon dioxide (SiO2) film, coated on a heated silicon wafer. Techniques of photolithography and sputtering with chromium and gold were then implemented on the MWCNT film to develop micro-interdigitated electrodes as a base for the breathing sensor. The sensor was equipped with a programmed microchip processor to become a warning detector for abnormal human breathing, namely less than six breaths per minute. Elderly volunteers were enrolled for examining the effective sensitivity of this novel electromechanical device.ResultsThere were 15 elderly volunteers (9 males and 6 females) tested in this experiment. The dynamic analyses of the MWCNT sensor to exhaled breath showed that it had characteristics of rapid response, high aspect ratio, small tip ratio, and high electrical conductivity. Responses of the MWCNT sensor to exhaled breath was recorded according to different performance parameters, i.e., strength, frequency, flow rate, and breath components. In this study, variable pattern-simulated tests showed that a MWCNT sensor combined with a processor could accurately evoke warning signals (100% of sensitivity rate), indicating its effectiveness and usefulness for detecting abnormal breathing rates, especially apnea.ConclusionOur results showed that a new device composed of an NEMS by combining an MWCNT sensor and complementary metal-oxide semiconductor (CMOS) circuits could be integrated to effectively detect apnea in the elderly. This novel device may improve the pattern of safe respiratory care for the elderly in the future

Covalent linking DNA to graphene oxide and its comparison with physisorbed probes for Hg2+ detection

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.bios.2015.12.043 © 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Graphene oxide (GO) has attracted extensive research interest as a platform for DNA adsorption and biosensor development. While most researchers use simple physisorption of fluorescently labeled DNA, covalent sensors are less susceptible to non-specific probe displacement and minimize false positive results. In this work, three thymine-rich DNA probes of different lengths are modified on their 3'-end with an amino group for covalent conjugation to GO. They also each contain an internally labeled fluorophore so that Hg2+ binding can lead to a large distance increase between the fluorophore and the GO surface for fluorescence signaling. Hg2+-dependent fluorescence signaling from the covalent sensors are compared with that from the non-covalent sensors in terms of sensitivity, selectivity, signaling kinetics, and continuous monitoring. The covalent sensors are much more stable and resistant to nonspecific probe displacement, while still retaining high sensitivity and similar selectivity. The detection limits are 16.3 and 20.6 nM Hg2+, respectively, for the covalent and non-covalent sensors, and detection of spiked Hg2+ in Lake Ontario water is demonstrated. (C) 2015 Elsevier B.V. All rights reserved.Natural Sciences and Engineering Research Council of Canada (NSERC) [386326]; Doctoral Fund for Priority Development Project from the Ministry of Education of China [20120101130009

Fascia tissue engineering with human adipose-derived stem cells in a murine model: Implications for pelvic floor reconstruction

Background/PurposeMesh-augmented vaginal surgery for treatment of pelvic organ prolapse (POP) does not meet patients' needs. This study aims to test the hypothesis that fascia tissue engineering using adipose-derived stem cells (ADSCs) might be a potential therapeutic strategy for reconstructing the pelvic floor.MethodsHuman ADSCs were isolated, differentiated, and characterized in vitro. Both ADSCs and fibroblastic-differentiated ADSCs were used to fabricate tissue-engineered fascia equivalents, which were then transplanted under the back skin of experimental nude mice.ResultsADSCs prepared in our laboratory were characterized as a group of mesenchymal stem cells. In vitro fibroblastic differentiation of ADSCs showed significantly increased gene expression of cellular collagen type I and elastin (p < 0.05) concomitantly with morphological changes. By contrast, ADSCs cultured in control medium did not demonstrate these changes. Both of the engrafted fascia equivalents could be traced up to 12 weeks after transplantation in the subsequent animal study. Furthermore, the histological outcomes differed with a thin (111.0 ± 19.8 μm) lamellar connective tissue or a thick (414.3 ± 114.9 μm) adhesive fibrous tissue formation between the transplantation of ADSCs and fibroblastic-differentiated ADSCs, respectively. Nonetheless, the implantation of a scaffold without cell seeding (the control group) resulted in a thin (102.0 ± 17.1 μm) fibrotic band and tissue contracture.ConclusionOur results suggest the ADSC-seeded implant is better than the implant alone in enhancing tissue regeneration after transplantation. ADSCs with or without fibroblastic differentiation might have a potential but different role in fascia tissue engineering to repair POP in the future

Antinociceptive Activities and the Mechanisms of Anti-Inflammation of Asiatic Acid in Mice

Asiatic acid (AA), a pentacyclic triterpene compound in the medicinal plant Centella asiatica, was evaluated for antinociceptive and anti-inflammatory effects. Treatment of male ICR mice with AA significantly inhibited the numbers of acetic acid-induced writhing responses and the formalin-induced pain in the late phase. In the anti-inflammatory test, AA decreased the paw edema at the 4th and 5th h after λ-carrageenan (Carr) administration and increased the activities of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) in the liver tissue. AA decreased the nitric oxide (NO), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) levels on serum level at the 5th h after Carr injection. Western blotting revealed that AA decreased Carr-induced inducible nitric oxide synthase (iNOS), cyclooxygenase (COX-2), and nuclear factor-κB (NF-κB) expressions at the 5th h in the edema paw. An intraperitoneal (i.p.) injection treatment with AA also diminished neutrophil infiltration into sites of inflammation as did indomethacin (Indo). The anti-inflammatory mechanisms of AA might be related to the decrease in the level of MDA, iNOS, COX-2, and NF-κB in the edema paw via increasing the activities of CAT, SOD, and GPx in the liver