JoVE Visualize What is visualize?
Stop Reading. Start Watching.
Advanced Search
Stop Reading. Start Watching.
Regular Search
Find video protocols related to scientific articles indexed in Pubmed.
The characterization of the saddle shaped nickel(iii) porphyrin radical cation: an explicative NMR model for a ferromagnetically coupled metallo-porphyrin radical.
Chem. Commun. (Camb.)
PUBLISHED: 10-07-2014
Show Abstract
Hide Abstract
Ni(iii)(OETPP?)(Br)2 is the first Ni(iii) porphyrin radical cation with structural and (1)H and (13)C paramagnetic NMR data for porphyrinate systems. Associating EPR and NMR analyses with DFT calculations as a new model is capable of clearly determining the dominant state from two controversial spin distributions in the ring to be the Ni(iii) LS coupled with an a1u spin-up radical.
Related JoVE Video
Quantitative description of structural effects on the stability of gold(i) carbenes.
Chemistry
PUBLISHED: 09-21-2014
Show Abstract
Hide Abstract
Invited for the cover of this issue is the group of Prof.?Dr. Peter Chen at the Swiss Federal Institute of Technology Zurich, Switzerland. The cover illustrates how the Chen group puts together an idea with elements stretching from physical to computational to preparative chemistry. Read the full text of the article at 10.1002/chem.201403988.
Related JoVE Video
Dual-channel-mediated spin coupling for one-electron-oxidized cobalt(II)-saddled porphyrin.
Inorg Chem
PUBLISHED: 08-14-2014
Show Abstract
Hide Abstract
Saddle-shaped Co(II)[OET(p-R)PP] (R = CF3, H, CH3) can be readily oxidized with Cl2, Br2, and I2 to the corresponding one-electron-oxidation product Co[OET(p-R)PP]X (X = Cl, Br, I) with the clear character of a ring cation radical. With the series of (1)H and (13)C NMR spectra of these related complexes, both the axial ligand and peripheral substituent of the ring macrocycle are proven to act as a dual channel to tune spin coupling between low-spin Co(II) and a porphyrin ?-cation radical. Density functional theory calculations have shown that the antiferromagnetic coupling between spins residing in d(z)(2) and a(2u) are expected to exist as the ground state. The paramagnetic properties are attributed to an a(1u)-type ferromagnetic excited triplet state.
Related JoVE Video
A lithiomethyl trimethylammonium reagent as a methylene donor.
Chem. Commun. (Camb.)
PUBLISHED: 08-06-2014
Show Abstract
Hide Abstract
Straightforward deprotonation of soluble tetramethylammonium salts with alkyllithium reagents gives lithiomethyl trimethylammonium reagents. Coordination of the Li cation is crucial to the stability of these 'N-C ylides'. These reagents were used to prepare epoxides, aziridines and allylic alcohols.
Related JoVE Video
Cyclopropanation of styrenes and stilbenes using lithiomethyl trimethylammonium triflate as methylene donor.
Chem. Commun. (Camb.)
PUBLISHED: 07-30-2014
Show Abstract
Hide Abstract
Lithiomethyl trimethylammonium triflate, prepared from tetramethylammonium triflate, cyclopropanates several styrenes and stilbenes with electron-donating and selected electron-withdrawing substituents efficiently. Kinetic data support a stepwise nucleophilic addition-ring closure mechanism for this methylenation.
Related JoVE Video
Rotational and vibrational pattern interpretation for high-resolution coherent 3D spectroscopy.
J Phys Chem A
PUBLISHED: 07-29-2014
Show Abstract
Hide Abstract
High-resolution coherent multidimensional spectroscopy provides an alternative to conventional methods for generating rotationally resolved electronic spectra of gas phase molecules. In addition to revealing information such as the relationships among peaks, it can provide clearly recognizable patterns for spectra that otherwise appear patternless due to rotational congestion. Despite this improvement, high-resolution coherent 2D spectroscopy can still exhibit congestion problems; expansion to the second dimension is often not sufficient to prevent overlapping of peaks from different patterns. A new 3D version of the technique that provides improved resolution and selectivity to help address cases with severe congestion was recently demonstrated. The experimental design and interpretation of data for the 3D technique are significantly more complicated than that for the 2D version. The purpose of this paper is to provide important information needed to plan, run, and interpret results from high-resolution coherent 3D spectroscopy experiments.
Related JoVE Video
Low-temperature sputtered nickel oxide compact thin film as effective electron blocking layer for mesoscopic NiO/CH3NH3PbI3 perovskite heterojunction solar cells.
ACS Appl Mater Interfaces
PUBLISHED: 07-25-2014
Show Abstract
Hide Abstract
We introduce the use of low temperature sputtered NiOx thin film, which substitutes the PEDOT-PSS and solution-processed NiOx as an effective electron blocking layer for mesoscopic NiO/CH3NH3PbI3 perovskite solar cells. The influences of film thickness and oxygen doping on the photovoltaic performances are scrutinized. The cell efficiency has been improved from 9.51 to 10.7% for devices using NiOx fabricated under pure argon atmosphere. With adequate doping under 10% oxygen flow ratio, we achieved power conversion efficiency of 11.6%. The procedure is large area scalable and has the advantage for cost-effective perovskite-based photovoltaics.
Related JoVE Video
Coinage-metal mediated ring opening of cis-1,2-dimethoxycyclopropane: trends from the gold, copper, and silver Fischer carbene bond strength.
J. Am. Chem. Soc.
PUBLISHED: 06-19-2014
Show Abstract
Hide Abstract
N-heterocyclic carbene (NHC) supported coinage metal cations proved to react in the gas phase with the electron-rich cis-1,2-dimethoxycyclopropane. Upon Collision Induced Dissociation (CID), several spectrometric fragment-ion signals were observed, one corresponding to the recovery of the bare cation IMes-M(+) (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) and the second to the methoxymethylidene metal complex IMes-M-[HCOCH3](+). The gold and copper complexes appear to stabilize the carbene sufficiently enough to promote the latter channel. On the contrary, the silver complex binds weakly to the methoxymethylidene moiety as observed by the predominance of the bare cation IMes-M(+) channel. Density Functional Theory (DFT) investigations of the Potential Energy Surface and Bond Energy Decomposition Analyses provided results that correlate well with the experimental data. In the case of the bare cation channel, two distinct reaction pathways were found: a straightforward decoordination of the cyclopropane and a cationic rearrangement of the three-membered ring into a dimethoxypropylene isomer before dissociation. However, for the abstraction of the methoxymethylidene moiety by the metal cation, only one pathway was found. In analogy to earlier studies by other groups, we found the trend Au > Cu > Ag for the metal-carbene bond strength.
Related JoVE Video
Quantitative description of structural effects on the stability of gold(i) carbenes.
Chemistry
PUBLISHED: 06-16-2014
Show Abstract
Hide Abstract
The gas-phase bond-dissociation energies of a SO2 -imidazolylidene leaving group of three gold(I) benzyl imidazolium sulfone complexes are reported (E0 =46.6±1.7, 49.6±1.7, and 48.9±2.1?kcal?mol(-1) ). Although these energies are similar to each other, they are reproducibly distinguishable. The energy-resolved collision-induced dissociation experiments of the three [L]-gold(I) (L=ligand) carbene precursor complexes were performed by using a modified tandem mass spectrometer. The measurements quantitatively describe the structural and electronic effects a p-methoxy substituent on the benzyl fragment, and trans [NHC] and [P] gold ligands, have towards gold carbene formation. Evidence for the formation of the electrophilic gold carbene in solution was obtained through the stoichiometric and catalytic cyclopropanation of olefins under thermal conditions. The observed cyclopropane yields are dependent on the rate of gold carbene formation, which in turn is influenced by the ligand and substituent. The donation of electron density to the carbene carbon by the p-methoxy benzyl substituent and [NHC] ligand stabilizes the gold carbene intermediate and lowers the dissociation barrier. Through the careful comparison of gas-phase and solution chemistry, the results suggest that even gas-phase leaving-group bond-dissociation energy differences of 2-3?kcal?mol(-1) enormously affect the rate of gold carbene formation in solution, especially when there are competing reactions. The thermal decay of the gold carbene precursor complex was observed to follow first-order kinetics, whereas cyclopropanation was found to follow pseudo-first-order kinetics. Density-functional-theory calculations at the M06-L and BP86-D3 levels of theory were used to confirm the observed gas-phase reactivity and model the measured bond-dissociation energies.
Related JoVE Video
5-hydroxymethyl-2-furfural and derivatives formed during acid hydrolysis of conjugated and bound phenolics in plant foods and the effects on phenolic content and antioxidant capacity.
J. Agric. Food Chem.
PUBLISHED: 05-12-2014
Show Abstract
Hide Abstract
A common protocol for the extraction of phenolic aglycons or bound phenolics in plants generally involves hydrothermal hydrolysis in an aqueous methanol or ethanol solution containing 2-4 N HCl. However, as shown in the present study, this process also forms 5-(hydroxymethyl)furan-2-carbaldehyde (HMF) and its derivative products 5-(methoxymethyl)furan-2-carbaldehyde (MMF) and 5-(ethoxymethyl)furan-2-carbaldehyde (EMF), as identified by HPLC-DAD-ESI-MS/MS and NMR. These compounds are commonly misidentified as phenolics due to similar UV absorption at 280 nm. In this study, production of HMF, MMF, and EMF was shown to be dependent on the solvent condition and duration and temperature of hydrolysis. Fruits and vegetables produced HMF more readily than grains. HMF and its derivatives were subjected to various spectrophotometric antioxidant assays [2-diphenyl-1-picryhydrazyl radical scavenging activity (DPPH), ferric-reducing antioxidant power (FRAP), and oxygen radical absorbing capacity (ORAC)] and displayed antioxidant activity mainly in the ORAC assay. Results of this study help avoid overestimation of phenolic content and antioxidant activities of plant foods.
Related JoVE Video
Femtosecond excitonic relaxation dynamics of perovskite on mesoporous films of Al?O? and NiO nanoparticles.
Angew. Chem. Int. Ed. Engl.
PUBLISHED: 04-21-2014
Show Abstract
Hide Abstract
The excitonic relaxation dynamics of perovskite adsorbed on mesoporous thin films of Al2O3 and NiO upon excitation at 450?nm were investigated with femtosecond optical gating of photoluminescence (PL) via up-conversion. The temporal profiles of emission observed in spectral region 670-810?nm were described satisfactorily with a composite consecutive kinetic model and three transient components representing one hot and two cold excitonic relaxations. All observed relaxation dynamics depend on the emission wavelength, showing a systematic time-amplitude correlation for all three components. When the NiO film was employed, we observed an extent of relaxation proceeding through the non-emissive surface state larger than through the direct electronic relaxation channel, which quenches the PL intensity more effectively than on the Al2O3 film. We conclude that perovskite is an effective hole carrier in a p-type electrode for NiO-based perovskite solar cells showing great performance.
Related JoVE Video
The role of betel-quid chewing in smoking cessation among workers in Taiwan.
BMC Public Health
PUBLISHED: 03-26-2014
Show Abstract
Hide Abstract
Current smokers exhibit a higher rate of betel-quid chewing than non-smokers. However, little is known regarding the extent to which betel-quid chewing may affect attempts to quit smoking and smoking cessation. The aim of the present study is to examine the association between betel-quid chewing and patterns of quitting smoking. Specifically, we explore whether betel-quid chewing is associated with (1) current smokers who have never attempted to quit versus those who have attempted to quit and have failed, those who are in the process of quitting, and successful cessation smokers, and (2) current smokers who have attempted to quit and have failed versus those who have successfully quit smoking.
Related JoVE Video
Characterisation of phenolics, betanins and antioxidant activities in seeds of three Chenopodium quinoa Willd. genotypes.
Food Chem
PUBLISHED: 03-17-2014
Show Abstract
Hide Abstract
Quinoa (Chenopodium quinoa Willd.) is known for its exceptional nutritional value and potential health benefits. The present study identified the composition of different forms of extractable phenolics and betacyanins of quinoa cultivars in white, red and black, and how they contribute to antioxidant activities. Results showed that at least 23 phenolic compounds were found in either free or conjugated forms (liberated by alkaline and/or acid hydrolysis); the majority of which were phenolic acids, mainly vanillic acid, ferulic acid and their derivatives as well as main flavonoids quercetin, kaempferol and their glycosides. Betacyanins, mainly betanin and isobetanin, were confirmed for the first time to be the pigments of the red and black quinoa seeds, instead of anthocyanins. Darker quinoa seeds had higher phenolic concentration and antioxidant activity. Findings of these phenolics, along with betacyanins in this study add new knowledge to the functional components of quinoa seeds of different cultivar background.
Related JoVE Video
Creep of trabecular bone from the human proximal tibia.
Mater Sci Eng C Mater Biol Appl
PUBLISHED: 03-05-2014
Show Abstract
Hide Abstract
Creep is the deformation that occurs under a prolonged, sustained load and can lead to permanent damage in bone. Creep in bone is a complex phenomenon and varies with type of loading and local mechanical properties. Human trabecular bone samples from proximal tibia were harvested from a 71-year old female cadaver with osteoporosis. The samples were initially subjected to one cycle load up to 1% strain to determine the creep load. Samples were then loaded in compression under a constant stress for 2h and immediately unloaded. All tests were conducted with the specimens soaked in phosphate buffered saline with proteinase inhibitors at 37 °C. Steady state creep rate and final creep strain were estimated from mechanical testing and compared with published data. The steady state creep rate correlated well with values obtained from bovine tibial and human vertebral trabecular bone, and was higher for lower density samples. Tissue architecture was analyzed by micro-computed tomography (?CT) both before and after creep testing to assess creep deformation and damage accumulated. Quantitative morphometric analysis indicated that creep induced changes in trabecular separation and the structural model index. A main mode of deformation was bending of trabeculae.
Related JoVE Video
Sangye Gyatso (1653-1705) and the medical paintings of Tibet.
J Med Biogr
PUBLISHED: 03-04-2014
Show Abstract
Hide Abstract
Sangye Gyatso played a major role in the politics of 17th century Tibet, and was the originator of the medical paintings that encompassed the full scope of Tibetan medicine.The depictions became an important aid in medical education, and was heavily influenced by Buddhist thinking. The paintings arose in a visual culture dominated by religious art.
Related JoVE Video
Leukocyte infiltration and activation of the NLRP3 inflammasome in white adipose tissue following thermal injury.
Crit. Care Med.
PUBLISHED: 03-04-2014
Show Abstract
Hide Abstract
Severe thermal injury is associated with extreme and prolonged inflammatory and hypermetabolic responses, resulting in significant catabolism that delays recovery or even leads to multiple organ failure and death. Burned patients exhibit many symptoms of stress-induced diabetes, including hyperglycemia, hyperinsulinemia, and hyperlipidemia. Recently, the nucleotide-binding domain, leucine-rich family (NLR), pyrin-containing 3 (NLRP3) inflammasome has received much attention as the sensor of endogenous "danger signals" and mediator of "sterile inflammation" in type II diabetes. Therefore, we investigated whether the NLRP3 inflammasome is activated in the adipose tissue of burned patients, as we hypothesize that, similar to the scenario observed in chronic diabetes, the cytokines produced by the inflammasome mediate insulin resistance and metabolic dysfunction.
Related JoVE Video
Feasibility of a Web-based Gatekeeper Training: Implications for Suicide Prevention.
Suicide Life Threat Behav
PUBLISHED: 02-27-2014
Show Abstract
Hide Abstract
Web-based training programs have advantages such as increased scheduling flexibility and decreased training costs. Yet the feasibility of applying them to injury prevention programs such as suicide prevention gatekeeper training has not been empirically verified. Two studies were conducted to assess the feasibility and effectiveness of a web-based version of the Question, Persuade, and Refer (QPR) gatekeeper training program. Results of Study 1 revealed that participants in a web-based training demonstrated significant gains in knowledge of suicide prevention, self-efficacy for suicide prevention, and behavioral intentions to engage in suicide prevention, as compared to those in a control group. Results of Study 2 further showed that the web-based training may be as effective as the face-to-face QPR training across pre- (T1) and post training (T2); however, knowledge, self-efficacy, and behavioral intentions in both groups generally declined from T2 to 6-months after the training. Overall, these results provide initial evidence to support the feasibility of adopting web-based media to deliver gatekeeper training. Moreover, the present findings suggest the need to understand how to maintain gatekeepers' knowledge, confidence, motivation, and skills after training.
Related JoVE Video
High voltage and efficient bilayer heterojunction solar cells based on an organic-inorganic hybrid perovskite absorber with a low-cost flexible substrate.
Phys Chem Chem Phys
PUBLISHED: 02-21-2014
Show Abstract
Hide Abstract
A low temperature (<100 °C), flexible solar cell based on an organic-inorganic hybrid CH3NH3PbI3 perovskite-fullerene planar heterojunction (PHJ) is successfully demonstrated. In this manuscript, we study the effects of energy level offset between a solar absorber (organic-inorganic hybrid CH3NH3PbI3 perovskite) and the selective contact materials on the photovoltaic behaviors of the planar organometallic perovskite-fullerene heterojunction solar cells. We find that the difference between the highest occupied molecular orbital (HOMO) level of CH3NH3PbI3 perovskite and the Fermi level of indium-tin-oxide (ITO) dominates the voltage output of the device. ITO films on glass or on the polyethylene terephthalate (PET) flexible substrate with different work functions are investigated to illustrate this phenomenon. The higher work function of the PET/ITO substrate decreases the energy loss of hole transfer from the HOMO of perovskite to ITO and minimizes the energy redundancy of the photovoltage output. The devices using the high work function ITO substrate as contact material show significant open-circuit voltage enhancement (920 mV), with the power conversion efficiency of 4.54%, and these types of extra-thin planar bilayer heterojunction solar cells have the potential advantages of low-cost and lightweight.
Related JoVE Video
c-Met expression is a marker of poor prognosis in patients with locally advanced head and neck squamous cell carcinoma treated with chemoradiation.
Int. J. Radiat. Oncol. Biol. Phys.
PUBLISHED: 02-14-2014
Show Abstract
Hide Abstract
To examine the prognostic significance of c-Met expression in relation to p16 and epidermal growth factor receptor (EGFR) in patients with locally advanced head and neck squamous cell carcinoma (HNSCC) treated with definitive concurrent chemoradiation.
Related JoVE Video
A palladium-catalyzed methylenation of olefins using halomethylboronate reagents.
Org. Lett.
PUBLISHED: 02-03-2014
Show Abstract
Hide Abstract
Methylenation of electron-rich olefins is a highly challenging reaction, for which we have developed a new methodology exploiting Pd-catalysis and halomethylboronate reagents, the latter replacing diazomethane and zinc carbenoids as methylene donors. Optimization of the reaction for norbornene and extension to several other olefins are reported, with reasonable-to-excellent yields of cyclopropanes in combination with ?-H elimination products. Several mechanisms are plausible for this methylenation reaction.
Related JoVE Video
p-type Mesoscopic nickel oxide/organometallic perovskite heterojunction solar cells.
Sci Rep
PUBLISHED: 01-28-2014
Show Abstract
Hide Abstract
In this article, we present a new paradigm for organometallic hybrid perovskite solar cell using NiO inorganic metal oxide nanocrystalline as p-type electrode material and realized the first mesoscopic NiO/perovskite/[6,6]-phenyl C61-butyric acid methyl ester (PC61BM) heterojunction photovoltaic device. The photo-induced transient absorption spectroscopy results verified that the architecture is an effective p-type sensitized junction, which is the first inorganic p-type, metal oxide contact material for perovskite-based solar cell. Power conversion efficiency of 9.51% was achieved under AM 1.5 G illumination, which significantly surpassed the reported conventional p-type dye-sensitized solar cells. The replacement of the organic hole transport materials by a p-type metal oxide has the advantages to provide robust device architecture for further development of all-inorganic perovskite-based thin-film solar cells and tandem photovoltaics.
Related JoVE Video
Nickel oxide electrode interlayer in CH3 NH3 PbI3 perovskite/PCBM planar-heterojunction hybrid solar cells.
Adv. Mater. Weinheim
PUBLISHED: 01-25-2014
Show Abstract
Hide Abstract
This study successfully demonstrates the application of inorganic p-type nickel oxide (NiOx ) as electrode interlayer for the fabrication of NiOx /CH3 NH3 PbI3 perovskite/PCBM PHJ hybrid solar cells with a respectable solar-to-electrical PCE of 7.8%. The better energy level alignment and improved wetting of the NiOx electrode interlayer significantly enhance the overall photovoltaic performance.
Related JoVE Video
Fatty acid, carotenoid and tocopherol compositions of 20 Canadian lentil cultivars and synergistic contribution to antioxidant activities.
Food Chem
PUBLISHED: 01-24-2014
Show Abstract
Hide Abstract
Understanding the profile of lipophilic phytochemicals in lentils is necessary to better understand the health benefits of lentils. The fatty acid, carotenoid and tocopherol compositions and antioxidant activities of the lipophilic extracts of 20 lentil cultivars (10 red and 10 green) were therefore examined. Lentils contained 1.52-2.95% lipids, of which 77.5-81.7% were unsaturated essential fatty acids. Total tocopherols ranged from 37 to 64?g/g DW, predominantly ?-tocopherol (96-98% of the tocopherol content), followed by ?- and ?-tocopherol. trans-Lutein was the primary and major carotenoid (64-78%) followed by trans-zeaxanthin (5-13%). Carotenoids and tocopherols showed weak correlation with 2,2-diphenyl-1-picrylhydrazyl (DPPH) activity (r=0.4893 and 0.3259, respectively), but good correlation when combined (r=0.6688), suggesting they may act synergistically. Carotenoids were found to contribute the most to the strong antioxidant activity measured by photochemiluminescence (PCL) assay. Results from this study contribute to the development of lentil cultivars and related functional foods with increased health benefits.
Related JoVE Video
Trigeminal neuralgia pain relief after gamma knife stereotactic radiosurgery.
Clin Neurol Neurosurg
PUBLISHED: 01-21-2014
Show Abstract
Hide Abstract
To report outcomes of patients with medical and/or surgical refractory trigeminal neuralgia (TN) treated with gamma knife stereotactic radiosurgery (GK SRS).
Related JoVE Video
Effect of microseparation and third-body particles on dual-mobility crosslinked hip liner wear.
J Arthroplasty
PUBLISHED: 01-15-2014
Show Abstract
Hide Abstract
Large heads have been recommended to reduce the risk of dislocation after total hip arthroplasty. One of the issues with larger heads is the risk of increased wear and damage in thin polyethylene liners. Dual-mobility liners have been proposed as an alternative to large heads. We tested the wear performance of highly crosslinked dual-mobility liners under adverse conditions simulating microseparation and third-body wear. No measurable increase in polyethylene wear rate was found in the presence of third-body particles. Microseparation induced a small increase in wear rate (2.9mm(3)/million cycles). A finite element model simulating microseparation in dual-mobility liners was validated using these experimental results. The results of our study indicate that highly crosslinked dual-mobility liners have high tolerance for third-body particles and microseparation.
Related JoVE Video
Exfoliation and performance properties of non-oxidized graphene in water.
Sci Rep
PUBLISHED: 01-14-2014
Show Abstract
Hide Abstract
Single-layered graphene has unique electronic, chemical, and electromechanical properties. Recently, graphite exfoliation in N-methylpyrrolidone and molten salt has been demonstrated to generate monolayer exfoliated graphene sheets (EGS). However, these solvents are either high-priced or require special care and have high boiling points and viscosities, making it difficult to deposit the dispersed graphene onto substrates. Here we show a universal principle for the exfoliation of graphite in water to single-layered and several-layered graphene sheets via the direct exfoliation of highly oriented pyrolytic graphite (HOPG) using pyridinium tribromide (Py(+)Br3(-)). Electrical conductivity >5100?S/cm was observed for filtered graphene paper, and the EGS exhibited superior performance as a hole transport layer compared to the conventional material N,N-di(naphthalene-1-yl)-N,N-diphenylbenzidine at low voltage. The overall results demonstrate that this method is a scalable process for the preparation of highly conductive graphene for use in the commercial manufacture of high-performance electronic devices.
Related JoVE Video
Quantification of magnetically induced changes in ECM local apparent stiffness.
Biophys. J.
PUBLISHED: 01-14-2014
Show Abstract
Hide Abstract
The stiffness of the extracellular matrix (ECM) is known to influence cell behavior. The ability to manipulate the stiffness of ECM has important implications in understanding how cells interact mechanically with their microenvironment. This article describes an approach to manipulating the stiffness ECM, whereby magnetic beads are embedded in the ECM through bioconjugation between the streptavidin-coated beads and the collagen fibers and then manipulated by an external magnetic field. It also reports both analytical results (obtained by formal modeling and numerical simulation) and statistically meaningful experimental results (obtained by atomic force microscopy) that demonstrate the effectiveness of this approach. These results clearly suggest the possibility of creating desired stiffness gradients in ECM in vitro to influence cell behavior.
Related JoVE Video
Electron transfer and binding affinities in an electrochemically controlled ligand transfer system containing zinc porphyrin and a meso-phenylenediamine substituent.
Dalton Trans
PUBLISHED: 11-08-2013
Show Abstract
Hide Abstract
Investigations on the transfer of the ligand, imidazole (HIm), between two covalently linked redox centres - zinc porphyrin and phenylenediamine (PD) - and the influence of the length of the linker are reported. Since the binding affinity of the ligand with zinc porphyrin is different from that of the ligand with the phenylenediamine moiety, the transfer of the ligand could be electrochemically controlled by adjusting the oxidation potentials. Changes in cyclic voltammograms and absorption spectra of the complexes revealed the site of ligand binding in the various oxidation states of the modified zinc porphyrins. Binding constants of the modified zinc porphyrins in various oxidation states were also determined by photometric titration with the ligand and digital simulations. Evidence for the delocalization of the electron from the zinc porphyrin to the phenylenediamine moiety and the influence of the delocalization on them were obtained from EPR studies.
Related JoVE Video
Role of IGF-1 pathway in lung fibroblast activation.
Respir. Res.
PUBLISHED: 10-04-2013
Show Abstract
Hide Abstract
IGF-1 is elevated in pulmonary fibrosis and acute lung injury, where fibroblast activation is a prominent feature. We previously demonstrated that blockade of IGF pathway in murine model of lung fibrosis improved outcome and decreased fibrosis. We now expand that study to examine effects of IGF pathway on lung fibroblast behaviors that could contribute to fibrosis.
Related JoVE Video
[Experimental study on CD105+/CD166+ cells and its chondrogenic potential in early osteoarthritis cartilage].
Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi
PUBLISHED: 09-26-2013
Show Abstract
Hide Abstract
To study the variation of CD105+/CD166+ cells and its multilineage potential in early osteoarthritis (OA) cartilage so as to lay a foundation for cartilage repair and pathologic cartilage remodeling in arthritis.
Related JoVE Video
Co-C bond energies in adenosylcobinamide and methylcobinamide in the gas phase and in silico.
J. Am. Chem. Soc.
PUBLISHED: 09-10-2013
Show Abstract
Hide Abstract
Essential to biological activity of adenosylcobalamin (AdoCbl) and methylcobalamin (MeCbl) is the Co-C bond cleavage step. Hence, we report an accurate determination of the homolytic gas-phase Co-C bond dissociation energies in the related adenosyl- and methylcobinamides (41.5 ± 1.2 and 44.6 ± 0.8 kcal/mol, respectively) utilizing an energy-resolved threshold collision-induced dissociation technique. This approach allows for benchmarking of electronic structure methods separate from (often ill-defined) solvent effects. Adequacy of various density functional theory methods has been tested with respect to the experimentally obtained values.
Related JoVE Video
Tumor volume as a predictor of survival and local control in patients with brain metastases treated with Gamma Knife surgery.
J. Neurosurg.
PUBLISHED: 08-23-2013
Show Abstract
Hide Abstract
The aim of this study was to examine tumor volume as a prognostic factor for patients with brain metastases treated with Gamma Knife surgery (GKS).
Related JoVE Video
Long-term impact of young age at diagnosis on treatment outcome and patterns of failure in patients with ductal carcinoma in situ treated with breast-conserving therapy.
Breast J
PUBLISHED: 07-03-2013
Show Abstract
Hide Abstract
We reviewed our institutions long-term experience treating patients diagnosed with ductal carcinoma in situ (DCIS) of the breast with breast-conserving therapy (BCT) to determine the impact of patient age on outcome over time. All DCIS cases receiving BCT between 1980 and 1993 were reviewed. Patient demographics (including age <45) and pathologic factors were analyzed for effect on outcomes including ipsilateral breast tumor recurrence (IBTR) and survival. BCT included limited surgery (excisional biopsy or lumpectomy) followed by radiotherapy to the whole breast (median whole-breast dose: 50 Gy, median tumor bed dose: 60.4 Gy). One hundred and forty-five cases were evaluated; the median follow-up was 19.3 years. Twenty-five patients developed an IBTR, for 5-, 10-, 15-, and 20-year actuarial rates of 9.9%, 12.2%, 13.7%, and 17.5%, respectively. The 10-year ipsilateral rate of recurrence was 23.3% (<45 years) versus 9.1% (? 45 years) (p = 0.05). Younger patients more frequently developed invasive recurrences (20-year actuarial rates: 20.4% versus 12.8%, p = 0.22) and true recurrences/marginal misses of the index lesion (23.3% versus 9.7%, p = 0.04) with lower rates of contralateral breast cancer (0.0% and 0.0% versus 12.0% and 20.5%, p = < 0.01, at 10 and 20 years, respectively). Young women under the age of 45 diagnosed with DCIS have a greater risk of local recurrence with different patterns of failure following BCT, which is most notable within 10 years of diagnosis.
Related JoVE Video
Characterization of uniaxial stiffness of extracellular matrix embedded with magnetic beads via bio-conjugation and under the influence of an external magnetic field.
J Mech Behav Biomed Mater
PUBLISHED: 06-14-2013
Show Abstract
Hide Abstract
In this paper, we study the deformation, and experimentally quantify the change in stiffness, of an extracellular matrix (ECM) embedded with magnetic beads that are bio-conjugated with the collagen fibers and under the influence of an external magnetic field. We develop an analytical model of the viscoelastic behavior of this modified ECM, and design and implement a stretch test to quantify (based on statistically meaningful experiment data) the resulting changes in its stiffness induced by the external magnetic field. The analytical results are in close agreement with that obtained from the experiments. We discuss the implication of these results that point to the possibility of creating desired stiffness gradients in an ECM in vitro to influence cell behavior.
Related JoVE Video
Comparative evaluation of miRNA expression between in vitro and in vivo airway epithelium demonstrates widespread differences.
Am. J. Pathol.
PUBLISHED: 05-20-2013
Show Abstract
Hide Abstract
Airway epithelial cells cultured at an air-liquid interface bear many hallmarks of in vivo cells and are used extensively to study the biology of the lung epithelium. Because miRNAs regulate many cellular functions, we postulated that miRNA profiling would provide an unbiased assessment of the effects of in vitro culturing. RNA was extracted from primary airway epithelial cells either immediately after cell procurement (in vivo condition) or after air-liquid interface culture was established (in vitro condition). We assessed 742 miRNAs and determined differential expression between in vivo and in vitro conditions. Air-liquid interface culturing of airway epithelial cells caused widespread changes in miRNA expression. A similarly extensive alteration in gene expression was observed in an independent set of publicly available microarray data. We integrated miRNA and gene expression results to identify culture-induced differences in transcriptional programs (including several involved in epithelial injury and repair). Air-liquid interface cultures are useful models for studying airway biology, but the present findings indicate that, despite phenotypic similarities with primary cells, these culture systems profoundly perturb miRNA and gene expression. Studies of lung epithelium based on in vitro culture should therefore be designed and interpreted with an appreciation of the limitations of air-liquid interface culture systems.
Related JoVE Video
Cdc42 Inhibits ERK-Mediated Collagenase-1 (MMP-1) Expression in Collagen-Activated Human Keratinocytes.
J. Invest. Dermatol.
PUBLISHED: 05-10-2013
Show Abstract
Hide Abstract
Following injury, keratinocytes switch gene expression programs from the one that promotes differentiation to the one that supports migration. A common feature of human wounds and ulcerations of any form is the expression of matrix metalloproteinase 1 (MMP-1; collagenase-1) by leading-edge basal keratinocytes migrating across the dermal or provisional matrix. Induction of MMP-1 occurs by signaling from the ?2?1 integrin in contact with dermal fibrillar type I collagen, and the activity of MMP-1 is required for human keratinocytes to migrate on collagen. Thus, MMP-1 serves a critical role in the repair of damaged human skin. Here, we evaluated the mechanisms controlling MMP-1 expression in primary human keratinocytes from neonatal foreskin and adult female skin. Our results demonstrate that shortly following contact with type I collagen extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase were markedly activated, whereas c-Jun N-terminal kinase (JNK) phosphorylation remained at basal levels. ERK inhibition markedly blocked collagen-stimulated MMP-1 expression in keratinocytes. In contrast, inhibiting p38 or JNK pathways had no effect on MMP-1 production. Moreover, investigating the role of Rho GTPases revealed that Cdc42 attenuates MMP-1 expression by suppressing ERK activity. Thus, our data indicate that injured keratinocytes induce MMP-1 expression through ERK activation, and this process is negatively regulated by Cdc42 activity.Journal of Investigative Dermatology advance online publication, 19 December 2013; doi:10.1038/jid.2013.499.
Related JoVE Video
The Potential Role of Meaning in Life in the Relationship Between Bullying Victimization and Suicidal Ideation.
J Youth Adolesc
PUBLISHED: 05-03-2013
Show Abstract
Hide Abstract
Adolescent bullying is a common problem in schools across America. The consequences of bullying are significant, and can include severe psychological trauma and suicide. A better understanding of the mechanisms that link bullying and suicidal ideation is needed in order to develop effective prevention and intervention initiatives. Meaning in life is a potential mechanism that has not been studied in this context. It was hypothesized that meaning in life could serve as both a mediator and a moderator of the relationship between bullying victimization and suicidal ideation. As a mediator, meaning in life is considered to explain why bullying victimization leads to suicidal ideation. As a moderator, meaning in life is considered to buffer the ill effect of bullying victimization on suicidal ideation. Data collected from an ethnically diverse sample of 2,936 (50 % female), 6th-12th grade students from one urban school district in the Northeastern US were used to examine the hypotheses. The model for girls was consistent with mediation (i.e., meaning in life may explain how victimization leads to suicidal ideation). The model for boys was consistent with moderation (i.e., the ill effect of victimization on suicidal ideation was attenuated as meaning in life increased). Implications for prevention are discussed.
Related JoVE Video
Postmortem imaging of antemortem myocardial ischaemia.
Eur Radiol
PUBLISHED: 04-03-2013
Show Abstract
Hide Abstract
To determine the minimum survival time for detection of antemortem myocardial ischaemia with postmortem imaging (PMI) techniques.
Related JoVE Video
CH3NH3PbI3 perovskite/fullerene planar-heterojunction hybrid solar cells.
Adv. Mater. Weinheim
PUBLISHED: 03-25-2013
Show Abstract
Hide Abstract
All-solid-state donor/acceptor planar-heterojunction (PHJ) hybrid solar cells are constructed and their excellent performance measured. The deposition of a thin C60 fullerene or fullerene-derivative (acceptor) layer in vacuum on a CH3 NH3 PbI3 perovskite (donor) layer creates a hybrid PHJ that displays the photovoltaic effect. Such heterojunctions are shown to be suitable for the development of newly structured, hybrid, efficient solar cells.
Related JoVE Video
Construction workers reasons for not reporting work-related injuries: an exploratory study.
Int J Occup Saf Ergon
PUBLISHED: 03-19-2013
Show Abstract
Hide Abstract
Although under-reporting of work-related injuries by workers is recognized as a significant problem in construction and other industries, little is known about the specific reasons for such occurrences. Qualitative and quantitative methods were used in this study to (a) identify reasons why construction workers may choose not to report work-related injuries, and (b) to investigate the frequency of the identified reasons. Twenty-seven percent of a sample of construction workers (N = 135) indicated that they had failed to report a work-related injury. The most frequent reasons given were related to perceptions of injuries as "small" and "part of the job" as well as fear of negative consequences, which may follow injury reporting. These findings are discussed in terms of practical implications. Strategies to overcome these reasons are suggested to decrease the under-reporting of injuries in the construction industry.
Related JoVE Video
Epigenetic regulation of CXCR4 expression by the ocular microenvironment.
Invest. Ophthalmol. Vis. Sci.
PUBLISHED: 03-13-2013
Show Abstract
Hide Abstract
Expression of the chemokine receptor CXCR4 by tumors is associated with metastatic migration and invasion of tumor cells. The importance of CXCR4 expression by uveal melanomas in metastasis to the liver was recently demonstrated when injection of CXCR4-negative uveal melanoma cells into mice resulted in reduced liver metastasis compared with CXCR4-positive uveal melanoma cells. Factors in the eye can induce downregulation of genes by epigenetic mechanisms. This study examined whether epigenetic regulation by the ocular environment induced downregulation of CXCR4 expression.
Related JoVE Video
TNF-? induced down-regulation of lysyl oxidase family in anterior cruciate ligament and medial collateral ligament fibroblasts.
Knee
PUBLISHED: 03-11-2013
Show Abstract
Hide Abstract
BACKGROUND: The lysyl oxidase (LOX) family has the capacity to catalyze the cross-linking of collagen and elastin, implicating its important fundamental role in injury healing. Tumor necrosis factor alpha (TNF-?) is considered to be an important chemical mediator in the acute inflammatory phase of the ligament injury. The role of the lysyl oxidase family induced by TNF-? in the knee ligaments wound healing process is poorly understood. Our purpose was to determine the different expressions of the LOXs in poorly self-healing anterior cruciate ligament (ACL) and well functionally self-healing medial collateral ligament (MCL) induced by TNF-?. METHODS: Semi-quantitative PCR, quantitative real-time PCR and western blot were performed for original research. RESULTS: The results showed that all LOX family members were expressed at higher levels in MCL than those in ACL fibroblasts; the significant differences existed in the down-regulations of the LOXs induced by TNF-?; and the TNF-?-mediated down-regulations of the LOXs were more prominent in ACL than those in MCL fibroblasts. 1-20ng/ml TNF-? down-regulated mRNA levels in ACL and MCL fibroblasts by up to 76% and 58% in LOX; 90% and 45% in LOXL-1; 97.5% and 90% in LOXL-2; 89% and 68% in LOXL-3; 52% and 25% in LOXL-4, respectively. Protein assay also showed LOXs had lower expressions in ACL than those in MCL. CONCLUSIONS: Based on these results, the differential expressions of the LOXs might help to explain the intrinsic differences between the poorly self-healing ACL and well functionally self-healing MCL. CLINICAL RELEVANCE: .
Related JoVE Video
Digital micromirror device projection printing system for meniscus tissue engineering.
Acta Biomater
PUBLISHED: 03-07-2013
Show Abstract
Hide Abstract
Meniscus degeneration due to age or injury can lead to osteoarthritis. Although promising, current cell-based approaches show limited success. Here we present three-dimensional methacrylated gelatin (GelMA) scaffolds patterned via projection stereolithography to emulate the circumferential alignment of cells in native meniscus tissue. Cultured human avascular zone meniscus cells from normal meniscus were seeded on the scaffolds. Cell viability was monitored, and new tissue formation was assessed by gene expression analysis and histology after 2weeks in serum-free culture with transforming growth factor ?1 (10ngml(-1)). Light, confocal and scanning electron microscopy were used to observe cell-GelMA interactions. Tensile mechanical testing was performed on unseeded, fresh scaffolds and 2-week-old cell-seeded and unseeded scaffolds. 2-week-old cell-GelMA constructs were implanted into surgically created meniscus defects in an explant organ culture model. No cytotoxic effects were observed 3weeks after implantation, and cells grew and aligned to the patterned GelMA strands. Gene expression profiles and histology indicated promotion of a fibrocartilage-like meniscus phenotype, and scaffold integration with repair tissue was observed in the explant model. We show that micropatterned GelMA scaffolds are non-toxic, produce organized cellular alignment, and promote meniscus-like tissue formation. Prefabrication of GelMA scaffolds with architectures mimicking the meniscus collagen bundle organization shows promise for meniscal repair. Furthermore, the technique presented may be scaled up to repair larger defects.
Related JoVE Video
High-resolution coherent three-dimensional spectroscopy of Br2.
J Phys Chem A
PUBLISHED: 03-06-2013
Show Abstract
Hide Abstract
In the past, high-resolution spectroscopy has been limited to small, simple molecules that yield relatively uncongested spectra. Larger and more complex molecules have a higher density of peaks and are susceptible to complications (e.g., effects from conical intersections) that can obscure the patterns needed to resolve and assign peaks. Recently, high-resolution coherent two-dimensional (2D) spectroscopy has been used to resolve and sort peaks into easily identifiable patterns for molecules where pattern-recognition has been difficult. For very highly congested spectra, however, the ability to resolve peaks using coherent 2D spectroscopy is limited by the bandwidth of instrumentation. In this article, we introduce and investigate high-resolution coherent three-dimensional spectroscopy (HRC3D) as a method for dealing with heavily congested systems. The resulting patterns are unlike those in high-resolution coherent 2D spectra. Analysis of HRC3D spectra could provide a means for exploring the spectroscopy of large and complex molecules that have previously been considered too difficult to study.
Related JoVE Video
Toxicities and costs of placing prophylactic and reactive percutaneous gastrostomy tubes in patients with locally advanced head and neck cancers treated with chemoradiotherapy.
Head Neck
PUBLISHED: 03-01-2013
Show Abstract
Hide Abstract
We compared dependence rates, complications, toxicities, and costs associated with prophylactic versus reactive percutaneous endoscopic gastrostomy (PEG) tube placement.
Related JoVE Video
Spiral microchannel with rectangular and trapezoidal cross-sections for size based particle separation.
Sci Rep
PUBLISHED: 02-28-2013
Show Abstract
Hide Abstract
The paper reports a new method for three-dimensional observation of the location of focused particle streams along both the depth and width of the channel cross-section in spiral inertial microfluidic systems. The results confirm that particles are focused near the top and bottom walls of the microchannel cross-section, revealing clear insights on the focusing and separation mechanism. Based on this detailed understanding of the force balance, we introduce a novel spiral microchannel with a trapezoidal cross-section that generates stronger Dean vortices at the outer half of the channel. Experiments show that particles focusing in such device are sensitive to particle size and flow rate, and exhibits a sharp transition from the inner half to the outer half equilibrium positions at a size-dependent critical flow rate. As particle equilibration positions are well segregated based on different focusing mechanisms, a higher separation resolution is achieved over conventional spiral microchannels with rectangular cross-section.
Related JoVE Video
Comparison of dose-escalated, image-guided radiotherapy vs. dose-escalated, high-dose-rate brachytherapy boost in a modern cohort of intermediate-risk prostate cancer patients.
Brachytherapy
PUBLISHED: 02-12-2013
Show Abstract
Hide Abstract
We compared outcomes in intermediate-risk prostate cancer patients treated with dose-escalated adaptive image-guided radiation therapy (IGRT) or dose-escalated high-dose-rate brachytherapy boost (HDR-B).
Related JoVE Video
A matched-pair comparison of intensity-modulated radiation therapy with cetuximab versus intensity-modulated radiation therapy with platinum-based chemotherapy for locally advanced head neck cancer.
Int. J. Clin. Oncol.
PUBLISHED: 02-12-2013
Show Abstract
Hide Abstract
PURPOSE: We retrospectively compared the efficacy of intensity-modulated radiotherapy (IMRT) and cetuximab (IMRT/cetuximab) versus IMRT and platinum-based chemotherapy (IMRT/platinum) for locally advanced head neck squamous cell carcinoma (LAHNSCC). METHODS: Thirty-one IMRT/cetuximab patients were matched 1:2 with 62 IMRT/platinum patients according to primary site and clinical stage. The primary endpoint was locoregional recurrence (LRR), and secondary endpoints included distant metastasis (DM), cause-specific survival (CSS), and overall survival (OS). RESULTS: Because of inherent selection bias, the IMRT/cetuximab cohort was significantly older and with a higher Charlson Comorbidity Index. IMRT/cetuximab and IMRT/platinum did not have significantly different LRR and DM (33 vs. 23 % at 2 years, P = 0.22; 17 vs. 11 % at 2 years, P = 0.40; respectively). IMRT/cetuximab had significantly worse CSS and OS (67 vs. 84 %, P = 0.04; 58 vs. 83 %, P = 0.001; respectively). However, for the subset of elderly patients ?65 years old, there is no difference between the two cohorts for all endpoints (all P = NS). CONCLUSION: IMRT/platinum should remain the preferred choice of chemoradiotherapy for LAHNSCC, but IMRT/cetuximab may be a reasonable alternative for elderly patients.
Related JoVE Video
Noncovalently functionalized highly conducting carbon nanotube films with enhanced doping stability via an amide linkage.
Chem. Commun. (Camb.)
PUBLISHED: 02-07-2013
Show Abstract
Hide Abstract
Creating superior electrical properties from macroscopic assembly of carbon nanotubes (CNTs) to replace metal is still an unaccomplished goal. Here we report a noncovalent functionalization method to connect individual CNTs with an electrical conductivity reaching 9150 S cm(-1) and the mechanical properties can be increased by an order of 1-2.
Related JoVE Video
Impact of age and duration of banding on left ventricular preparation before anatomic repair for congenitally corrected transposition of the great arteries.
Ann. Thorac. Surg.
PUBLISHED: 01-30-2013
Show Abstract
Hide Abstract
The optimal age and duration of left ventricular (LV) training in congenitally corrected transposition (ccTGA) with an unprepared LV is unknown. The objective of this study was to review the effect of age at pulmonary artery banding (PAB) and duration of ventricular training on LV function and aortic regurgitation (AR) after anatomic repair.
Related JoVE Video
Predictors of reintervention after repair of interrupted aortic arch with ventricular septal defect.
Ann. Thorac. Surg.
PUBLISHED: 01-30-2013
Show Abstract
Hide Abstract
Left ventricular outflow tract obstruction after neonatal repair of interrupted aortic arch with ventricular septal defect may warrant reintervention. We sought to identify clinical and preoperative echocardiographic predictors of reintervention for postoperative left ventricular outflow tract obstruction.
Related JoVE Video
Salvage HDR brachytherapy for recurrent prostate cancer after previous definitive radiation therapy: 5-year outcomes.
Int. J. Radiat. Oncol. Biol. Phys.
PUBLISHED: 01-22-2013
Show Abstract
Hide Abstract
Evaluate efficacy and toxicity of salvage high-dose-rate brachytherapy (HDRB) for locally recurrent prostate cancer after definitive radiation therapy (RT).
Related JoVE Video
Tactile-feedback stabilized molecular junctions for the measurement of molecular conductance.
Angew. Chem. Int. Ed. Engl.
PUBLISHED: 01-22-2013
Show Abstract
Hide Abstract
Handling the (AFM) tip: The duration of stable molecular junctions was prolonged using a tactile feedback method in which the operator can sense the force of the AFM tip on the sample surface. The movement of the tip is adjusted accordingly, maintaining a more consistent current (i) and voltage (V), instead of having the tip move at a constant preset speed, as in the conventional setup.
Related JoVE Video
Influence of TNF-? and biomechanical stress on matrix metalloproteinases and lysyl oxidases expressions in human knee synovial fibroblasts.
Knee Surg Sports Traumatol Arthrosc
PUBLISHED: 01-21-2013
Show Abstract
Hide Abstract
PURPOSE: It was reported that not only ACL but also the synovium may be the major regulator of matrix metalloproteinases (MMPs) in synovial fluids after ACL injury. In order to further confirm whether synovium is capable of regulating the microenvironment in the process of ACL injury, the complicated microenvironment of joint cavity after ACL injury was mimicked and the combined effects of mechanical injury and inflammatory factor [tumour necrosis factor-? (TNF-?)] on expressions of lysyl oxidases (LOXs) and MMPs in synovial fibroblasts derived from normal human synovium were studied. METHODS: Human normal knee joint synovial fibroblasts were stimulated for 1-6 h with mechanical stretch and inflammatory factor (TNF-?). Total RNA was harvested, reverse transcribed and assessed by real-time polymerase chain reaction for the expression of LOXs and MMP-1, 2, 3 messenger RNAs. MMP-2 activity was assayed from the collected culture media samples using zymography. RESULTS: Compared to control group, our results showed that 6 % physiological stretch increased MMP-2 and LOXs (except LOXL-3), decreased MMP-1 and MMP-3; injurious stretch (12 %) decreased LOXs (except LOXL-2)and increased MMP-1, 2 and 3; the combination of injurious stretch and TNF-? decreased LOXs and increased MMP-1, 2 and 3 in synovial fibroblasts in a synergistical manner. CONCLUSION: This study demonstrated that combination of mechanical injury and inflammatory factors up-regulated the expressions of MMPs and down-regulated the expressions of LOXs in synovial fibroblasts, eventually alter the balance of tissue healing. Thus, synovium may be involved in regulating the microenvironment of joint cavity. Based on the mechanism, early interventions to inhibit the production of MMPs or promote the production of LOXs in the synovial fibroblasts should be performed to facilitate the healing of tissue.
Related JoVE Video
Rational design of a gold carbene precursor complex for a catalytic cyclopropanation reaction.
Angew. Chem. Int. Ed. Engl.
PUBLISHED: 01-18-2013
Show Abstract
Hide Abstract
Bridging gas- and solution-phase chemistry: A gold(I) carbene precursor complex has been developed and investigated for catalytic cyclopropanation. Formation of the carbene intermediate was first probed by mass spectrometry, followed by cyclopropanation of p-methoxystyrene in solution. The imidazolylidene leaving group serves as a base generated in situ that is necessary in the putative catalytic cycle.
Related JoVE Video
External beam pulsed low dose radiotherapy using volumetric modulated arc therapy: planning and delivery.
Med Phys
PUBLISHED: 01-10-2013
Show Abstract
Hide Abstract
To evaluate the feasibility of planning and delivering pulsed low dose radiotherapy (PLRT) using volumetric modulated arc therapy (VMAT) on Elektalinacs.
Related JoVE Video
Optimal elastomeric scaffold leaflet shape for pulmonary heart valve leaflet replacement.
J Biomech
PUBLISHED: 01-05-2013
Show Abstract
Hide Abstract
Surgical replacement of the pulmonary valve (PV) is a common treatment option for congenital pulmonary valve defects. Engineered tissue approaches to develop novel PV replacements are intrinsically complex, and will require methodical approaches for their development. Single leaflet replacement utilizing an ovine model is an attractive approach in that candidate materials can be evaluated under valve level stresses in blood contact without the confounding effects of a particular valve design. In the present study an approach for optimal leaflet shape design based on finite element (FE) simulation of a mechanically anisotropic, elastomeric scaffold for PV replacement is presented. The scaffold was modeled as an orthotropic hyperelastic material using a generalized Fung-type constitutive model. The optimal shape of the fully loaded PV replacement leaflet was systematically determined by minimizing the difference between the deformed shape obtained from FE simulation and an ex-vivo microCT scan of a native ovine PV leaflet. Effects of material anisotropy, dimensional changes of PV root, and fiber orientation on the resulting leaflet deformation were investigated. In-situ validation demonstrated that the approach could guide the design of the leaflet shape for PV replacement surgery.
Related JoVE Video
Impact of the number of cautionary and/or unsuitable risk factors on outcomes after accelerated partial breast irradiation.
Int. J. Radiat. Oncol. Biol. Phys.
PUBLISHED: 01-03-2013
Show Abstract
Hide Abstract
To examine clinical outcomes of accelerated partial-breast irradiation (APBI) stratified by the number of American Society for Radiation Oncology consensus statement cautionary/unsuitable risk factors (RFs) present.
Related JoVE Video
Risks of Breast and Endometrial Cancer in Women with Diabetes: A Population-Based Cohort Study.
PLoS ONE
PUBLISHED: 01-01-2013
Show Abstract
Hide Abstract
We investigated the overall and age-specific risks of developing breast and endometrial cancer among women with diabetes in a population-based cohort study.
Related JoVE Video
Role of IFN-? in the establishment of anterior chamber-associated immune deviation (ACAID)-induced CD8+ T regulatory cells.
J. Leukoc. Biol.
PUBLISHED: 12-16-2011
Show Abstract
Hide Abstract
Introduction of alloantigens into the AC induces a form of immune tolerance known as ACAID, which induces antigen-specific CD8+ Tregs, contributing to ocular immune privilege by down-regulating immune responses. Recent evidence suggests IFN-? is needed for the suppressive function of CD8+ ACAID Tregs. This study tested the hypothesis that IFN-? is needed for alloantigen-specific ACAID CD8+ Tregs to execute their suppressive function but is not required for the establishment of ACAID CD8+ Tregs. To address this hypothesis, ACAID was induced by injecting BALB/c spleen cells into the AC of WT C57BL/6 mice, IFN-?(-/-) C57BL/6 mice, or anti-IFN-?-treated WT C57BL/6 mice. LAT assays using C57BL/6 APCs as stimulators, CD4+ T cells from C57BL/6 mice previously immunized toward BALB/c alloantigens as effector cells, and IFN-?-competent, IFN-?(-/-), or IFN-?R(-/-) CD8+ Tregs were used to evaluate the suppressive function of CD8+ ACAID Tregs in response to IFN-?. IFN-?(-/-) mice or mice treated with anti-IFN-? antibody prior to AC injection of alloantigen failed to develop ACAID. The suppressive function of IFN-?(-/-) ACAID CD8+ Tregs was restored through the administration of exogenous IFN-?. This suppressive responsiveness toward IFN-? was CD8+ Treg-intrinsic, as CD8+ Tregs from IFN-?R(-/-) mice, which were primed in the AC with alloantigens, were not able to suppress alloantigen-specific DTH responses. These results indicate that IFN-? is not needed for the induction of CD8+ ACAID Tregs but is required for ACAID Tregs to exert the suppression of allospecific DTH responses.
Related JoVE Video
Natural killer cell activation enhances immune pathology and promotes chronic infection by limiting CD8+ T-cell immunity.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 12-13-2011
Show Abstract
Hide Abstract
Infections with HIV, hepatitis B virus, and hepatitis C virus can turn into chronic infections, which currently affect more than 500 million patients worldwide. It is generally thought that virus-mediated T-cell exhaustion limits T-cell function, thus promoting chronic disease. Here we demonstrate that natural killer (NK) cells have a negative impact on the development of T-cell immunity by using the murine lymphocytic choriomeningitis virus. NK cell-deficient (Nfil3(-/-), E4BP4(-/-)) mice exhibited a higher virus-specific T-cell response. In addition, NK cell depletion caused enhanced T-cell immunity in WT mice, which led to rapid virus control and prevented chronic infection in lymphocytic choriomeningitis virus clone 13- and reduced viral load in DOCILE-infected animals. Further experiments showed that NKG2D triggered regulatory NK cell functions, which were mediated by perforin, and limited T-cell responses. Therefore, we identified an important role of regulatory NK cells in limiting T-cell immunity during virus infection.
Related JoVE Video
Thoracic spinal cord stimulation improves cardiac contractile function and myocardial oxygen consumption in a porcine model of ischemic heart failure.
J. Cardiovasc. Electrophysiol.
PUBLISHED: 12-08-2011
Show Abstract
Hide Abstract
Prior experimental studies show that thoracic spinal cord stimulation (SCS) improves left ventricular (LV) ejection fraction (LVEF). The mechanism of this improvement in the LV contractile function after SCS and its effects on the myocardial oxygen consumption remains unknown.
Related JoVE Video
Highly conductive carbon nanotube buckypapers with improved doping stability via conjugational cross-linking.
Nanotechnology
PUBLISHED: 11-09-2011
Show Abstract
Hide Abstract
Carbon nanotube (CNT) sheets or buckypapers have demonstrated promising electrical conductivity and mechanical performance. However, their electrical conductivity is still far below the requirements for engineering applications, such as using as a substitute for copper mesh, which is currently used in composite aircraft structures for lightning strike protection. In this study, different CNT buckypapers were stretched to increase their alignment, and then subjected to conjugational cross-linking via chemical functionalization. The conjugationally cross-linked buckypapers (CCL-BPs) demonstrated higher electrical conductivity of up to 6200 S cm( - 1), which is more than one order increase compared to the pristine buckypapers. The CCL-BPs also showed excellent doping stability in over 300 h in atmosphere and were resistant to degradation at elevated temperatures. The tensile strength of the stretched CCL-BPs reached 220 MPa, which is about three times that of pristine buckypapers. We attribute these property improvements to the effective and stable conjugational cross-links of CNTs, which can simultaneously improve the electrical conductivity, doping stability and mechanical properties. Specifically, the electrical conductivity increase resulted from improving the CNT alignment and inter-tube electron transport capability. The conjugational cross-links provide effective 3D conductive paths to increase the mobility of electrons among individual nanotubes. The stable covalent bonding also enhances the thermal stability and load transfer. The significant electrical and mechanical property improvement renders buckypaper a multifunctional material for various applications, such as conducting composites, battery electrodes, capacitors, etc.
Related JoVE Video
The effects of situational obstacles and social support on suicide- prevention gatekeeper behaviors.
Crisis
PUBLISHED: 09-24-2011
Show Abstract
Hide Abstract
Although the effectiveness of suicide-prevention gatekeeper-training programs in improving knowledge, attitudes, and referral practices has been documented, their effects do not seem to be lasting.
Related JoVE Video
Initial clinical experience with multilumen brachytherapy catheters for accelerated partial breast irradiation.
Brachytherapy
PUBLISHED: 09-15-2011
Show Abstract
Hide Abstract
To review the initial experience of three institutions using multilumen catheters to deliver accelerated partial breast irradiation (APBI) and evaluate dosimetric improvements.
Related JoVE Video
IL-17-dependent, IFN-gamma-independent tumor rejection is mediated by cytotoxic T lymphocytes and occurs at extraocular sites, but is excluded from the eye.
J. Immunol.
PUBLISHED: 09-14-2011
Show Abstract
Hide Abstract
Although intraocular tumors reside in an immune-privileged site where immune responses are suppressed, some tumors are rejected. An example of this is the rejection of intraocular adenovirus-induced (adenovirus type 5 early region 1 [Ad5E1]) tumors in C57BL/6 mice. We previously identified an Ad5E1 tumor clone in which the rejection is IFN-? dependent and culminates in the destruction of both the tumor and the eye. Although Ad5E1 tumors are not rejected when transplanted into the eyes of IFN-? KO mice, they are rejected after s.c. transplantation. Thus, outside of the eye Ad5E1 tumors elicit a form of tumor immunity that is IFN-? independent. In this article, we demonstrate that IFN-?-independent s.c. rejection requires both CD4(+) and CD8(+) T cells. Furthermore, s.c. tumor rejection requires IL-17, which is produced by IFN-?-deficient CD4(+) T cells in response to tumor Ags (TAs). Splenocytes from CD4-depleted IFN-? KO mice produce significantly less IL-17 compared with splenocytes from isotype-treated IFN-? KO animals in response to TAs. Furthermore, depletion of IL-17 decreases CTL activity against Ad5E1 tumor cells. In this model we propose that, in the absence of IFN-?, CD4(+) T cells produce IL-17 in response to TAs, which increases CTL activity that mediates tumor rejection; however, this does not occur in the eye. IL-6 production within the eye is severely reduced, which is consistent with the failure to induce Th17 cells within the intraocular tumors. In contrast, the s.c. environment is replete with IL-6 and supports the induction of Th17 cells. Therefore, IFN-?-independent tumor rejection is excluded from the eye and may represent a newly recognized form of ocular immune privilege.
Related JoVE Video
Safety performance: the mediating role of safety control.
Work
PUBLISHED: 08-19-2011
Show Abstract
Hide Abstract
Occupational stress models suggest that the ability to understand, predict, and control stressful events minimizes their impact. This study examines the applicability of the stress antidote theory to the safety environment. Newly developed measures assess understanding why and how unsafe events occur, predicting the occurrence of unsafe events, and controlling unsafe events, and how these constructs relate to safety performance at work. In addition, the role of supervisor safety support is explored.
Related JoVE Video
Genetic variation and linkage disequilibrium in Bacillus anthracis.
Sci Rep
PUBLISHED: 08-11-2011
Show Abstract
Hide Abstract
We performed whole-genome amplification followed by hybridization of custom-designed resequencing arrays to resequence 303 kb of genomic sequence from a worldwide panel of 39 Bacillus anthracis strains. We used an efficient algorithm contained within a custom software program, UniqueMER, to identify and mask repetitive sequences on the resequencing array to reduce false-positive identification of genetic variation, which can arise from cross-hybridization. We discovered a total of 240 single nucleotide variants (SNVs) and showed that B. anthracis strains have an average of 2.25 differences per 10,000 bases in the region we resequenced. Common SNVs in this region are found to be in complete linkage disequilibrium. These patterns of variation suggest there has been little if any historical recombination among B. anthracis strains since the origin of the pathogen. This pattern of common genetic variation suggests a framework for recognizing new or genetically engineered strains.
Related JoVE Video
The feasibility of using thermal strain imaging to regulate energy delivery during intracardiac radio-frequency ablation.
IEEE Trans Ultrason Ferroelectr Freq Control
PUBLISHED: 07-20-2011
Show Abstract
Hide Abstract
A method is introduced to monitor cardiac ablative therapy by examining slope changes in the thermal strain curve caused by speed of sound variations with temperature. The sound speed of water-bearing tissue such as cardiac muscle increases with temperature. However, at temperatures above about 50°C, there is no further increase in the sound speed and the temperature coefficient may become slightly negative. For ablation therapy, an irreversible injury to tissue and a complete heart block occurs in the range of 48 to 50°C for a short period in accordance with the well-known Arrhenius equation. Using these two properties, we propose a potential tool to detect the moment when tissue damage occurs by using the reduced slope in the thermal strain curve as a function of heating time. We have illustrated the feasibility of this method initially using porcine myocardium in vitro. The method was further demonstrated in vivo, using a specially equipped ablation tip and an 11-MHz microlinear intracardiac echocardiography (ICE) array mounted on the tip of a catheter. The thermal strain curves showed a plateau, strongly suggesting that the temperature reached at least 50°C.
Related JoVE Video

What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

How does it work?

We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.

Video X seems to be unrelated to Abstract Y...

In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.