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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The neuromuscular and skeletal muscle actions of Naja naja kaouthia snake venom were studied in mammalian (rat left hemidiaphragm) and avian (chick biventer cervicis) nerve-muscle preparations. The venom (5 and 10 micro g/ml) produced neuromuscular blockade (85% in 36.8+/-2.0min, mean+/-SEM, n=5, and 18+/-0.6min, n=3, p<0.01, respectively) in the rat preparation. That the phospholipase A(2) (PLA(2)) activity of the venom is involved in this effect was evaluated by inhibiting this enzyme with p-bromophenacyl bromide. This resulted in significantly (p<0.01) increasing the time required for 85% blockade with 5 and 10 micro g/ml to 54+/-4.6min (n=3) and 29+/-0.6min (n=3), respectively. In chick preparations, the venom (5 micro g/ml) produced neuromuscular blockade in 14.0+/-1.8min (n=5). The contractures to exogenous acetylcholine were completely inhibited by the venom, whereas those to 134 micro M KCl were partially blocked in chick preparations (n=4, n=3, respectively). The venom (5 micro g/ml) produced a progressive decrease in the amplitude of miniature end-plate potentials (m.e.p.ps) in the rat hemidiaphragm, but did not alter the resting membrane potential at 5 micro g/ml. Neostigmine (5.8 micro M) immediate and partially reversed the 85% blockade produced by venom (61%, n=3) in rat preparations, as did 4-aminopyridine (53 micro M) ( approximately 59%, n=3). The 4-aminopyridine and neostigmine also restored the m.e.p.ps to pre-venom (control) values. In rat preparations, the venom damaged 47%+/-11% and 62.7+/-3.6% of the muscle fibers at concentrations of 5 and 10 micro g/ml, respectively. For venom in which PLA(2) activity was inhibited, the corresponding values were 38+/-11.8% (5 micro g/ml) and 67+/-9.6% (10 micro g/ml). These findings suggest a post-synaptic neurotoxic action for N. n. kaouthia venom, and that inhibiting phospholipase activity of the venom reduces significantly the neuromuscular block but not the direct myotoxicity.
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PMID:Neurotoxic and myotoxic actions of Naja naja kaouthia venom on skeletal muscle in vitro. 1272 70

It was found that single-walled carbon nanotubes (SWNTs) solubilized into water by complexation with DNA (salmon testes) can be readily deposited on the ITO electrode by electrochemical oxidative polymerization of ethylenedioxythiophene (EDOT). The driving force for this novel deposition is an electrostatic interaction between the anionic charges of wrapping DNA and the cationic charges of poly(EDOT) formed in the oxidative polymerization process. The presence of poly(EDOT), SWNTs and DNA in the composite was confirmed by measurements of UV-Vis, IR, resonance Raman spectra, cyclic voltammetry (CV) and confocal laser scanning microscopy (CLSM). The composite adsorbed a DNA intercalator (ethidium bromide: EB) very efficiently, which is regarded to be further evidence for inclusion of DNA. The surface morphology, characterized by CLSM, SEM and AFM, featured the network structure consisting of 0.5-ca. 10 microm nanorods. Very interestingly, we found that photoexcitation of EB bound to the DNA generates the photocurrent, indicating that the excited energy of EB is injected into SWNTs, which is collected by the electroconductive poly(EDOT) film on the ITO electrode. We believe, therefore, that the present system is a very convenient method to explore new materials related to redox and photochemical functions.
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PMID:Electrochemical fabrication of single-walled carbon nanotubes-DNA complexes by poly(ethylenedioxythiophene) and photocurrent generation by excitation of an intercalated chromophore. 1506 89

A new approach involving the introduction of the common cationic surfactant cetyltrimethylammonium bromide (CTAB) for modifying a rutile TiO2 film during its formation from hydrolyzed TiCl4 solution has been adopted, intending to improve the photoelectrochemical properties of the pertinent dye-sensitized solar cell. CTAB-routed films were found to consist of smaller clusters of near-spherical TiO2 particles, compared with larger clusters of long rod-shaped particles in the absence of CTAB. As a consequence, the photocurrent and photovoltage of the cell fabricated by using CTAB have increased significantly, leading to a conversion efficiency increase, compared with those of the cell prepared without CTAB. On the basis of FE-SEM, BET, and XRD analyses, the increases are attributed to decreased particle size, improved interparticle connectivity, and enhanced crystallinity of the CTAB-promoted TiO2 particles and decreased void volume in the film. Faster growth of the TiO2 film was another beneficial effect of CTAB. A mechanism is proposed for the beneficial role of CTAB during the film formation.
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PMID:Beneficial role of cetyltrimethylammonium bromide in the enhancement of photovoltaic properties of dye-sensitized rutile TiO2 solar cells. 1527 95

Membrane integrity fluorescent staining is used routinely to evaluate islet viability. Results are used as one of the determining factors in islet product release criteria, and are used to assess the efficacy of different culture conditions. Recently, it has been observed that there is variation in the viability staining of freshly isolated islets based on which viability assay is used. This investigation compares three membrane integrity stains for the viability assessment of isolated human islets. Fluorescein diacetate/propidium iodide (FDA/ PI), the current standard method for assessing islet viability, demonstrates intense extracellular fluorescence, reducing the differential staining of intact islets. We further evaluated SYTO-13/ethidium bromide (SYTO/ EB) and calcein AM/ethidium homodimer (C/EthD) as alternative viability assays, and found considerable variation between FDA/PI and either SYTO/EB or C/EthD staining. Preparations of human islets were obtained from cadaveric pancreata after collagenase digestion, mechanical separation, and purification by continuous Ficoll gradient centrifugation. For each preparation, two replicate samples of 50 islets were counted for each stain, and the percent viability calculated. The results for SYTO/EB and C/EthD were nearly identical [57.6 +/- 7.3% and 57.9 +/- 7.2%, respectively (mean +/- SEM), N = 11]. FDA/PI-stained islets, however, showed consistently elevated values when compared to SYTO/EB. Accurate assessment of islet viability remains a critical determinant of islet product release. The discrepancies found between FDA/PI scoring and visual quality, compared with alternative stains, suggests that the FDA/PI stain may not be the optimal approach to assess islet viability.
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PMID:Variation in human islet viability based on different membrane integrity stains. 1556 60

Twenty patients with expansive pathologic intracranial lesions, who were anesthetized with thiopental, nitrous oxide in oxygen, and fentanyl and mechanically ventilated to ensure normocarbia, received pipecuronium bromide 70 microg/kg i.v. Intracranial pressure (ICP), heart rate, arterial pressure, central venous pressure (CVP), EKG, and end-tidal CO2 were simultaneously recorded for 5 min before and for 15 min after administration of the muscle relaxant. No statistically significant changes in ICP and cerebral perfusion pressure were observed after administration of pipecuronium bromide. Cardiovascular stability was maintained during the study period except for a small, although significant, decrease of the CVP from 5.7 +/- 2.5 (SEM) to 5.0 +/- 2.5 mm Hg. These results, together with the long-lasting muscular effect of pipecuronium bromide, suggest that this new neuromuscular blocking agent may be used for muscle relaxation during neurosurgical operations in patients who have normal intracranial pressure at the time of administration of the drug.
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PMID:The effects of pipecuronium bromide on intracranial pressure and cerebral perfusion pressure. 1581 19

Surfaces of Wyoming SWy-2-Na-montmorillonite were modified using ultrasonic and hydrothermal methods through the intercalation and adsorption of the cationic surfactant octadecyltrimethylammonium bromide (ODTMA). Changes in the surfaces and structure were characterized using X-ray diffraction (XRD), thermal analysis (TG), and electron microscopy. The ultrasonic preparation method results in a higher surfactant concentration within the montmorillonite interlayer when compared with that from the hydrothermal method. Three different molecular environments for surfactants within the surface-modified montmorillonite are proposed upon the basis of their different decomposition temperatures. Both XRD patterns and TEM images demonstrate that SWy-2-Na-montmorillonite contains superlayers. TEM images of organoclays prepared at high surfactant concentrations show alternate basal spacings between neighboring layers. SEM images show that modification with surfactant reduces the clay particle size and aggregation. Organoclays prepared at low surfactant concentration display curved flakes, whereas they become flat with increasing intercalated surfactant. Novel surfactant-modified montmorillonite results in the formation of new nanophases with the potential for the removal of organic impurities from aqueous media.
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PMID:Modification of Wyoming montmorillonite surfaces using a cationic surfactant. 1614 47

Mesoporous SBA-16 and SBA-15 were studied in order to control their possible morphologies. SBA-16 is synthesized using a silicon source (tetraethoxysilane, TEOS) and a ternary system consisting of surfactant F127 (EO106PO70EO106), water, and butanol. The same ternary system, with higher butanol concentration, is used to form SBA-15 material as well. An increase of the TEOS concentration results in a morphology shift of SBA-16 from micron-sized spheres, over randomly shaped aggregated particles, to macrospheres with a size of 15 mm. An identical increase in TEOS concentration also results in the formation of SBA-15 macrospheres, which can be controlled in size. Micron-sized spheres of SBA-15 were formed using a quaternary system of surfactant P123 (EO20PO70EO20), cetyltrimethylammonium bromide (CTAB), ethanol, and water. All mesoporous silica materials were characterized using SEM, XRD, and N2 sorption techniques.
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PMID:Investigation of the morphology of the mesoporous SBA-16 and SBA-15 materials. 1667 32

We report herein the template-directed synthesis, characterization, and electric properties of single-walled carbon nanotube- (SWNT-) based coaxial nanowires, that is, core (SWNT)-shell (conducting polypyrrole and polyaniline) nanowires. The SWNTs were first dispersed in aqueous solutions containing cationic surfactant cetyltrimethylammonium bromide (CTAB) or nonionic surfactant poly(ethylene glycol) mono-p-nonyl phenyl ether (O pi-10). Each individual nanotube (or small bundle) was then encased in its own micellelike envelope with hydrophobic surfactant groups orientated toward the nanotube and hydrophilic groups orientated toward the solution. And thus a hydrophobic region within the micelle/SWNT (called a micelle/SWNT hybrid template) was formed. Insertion and growth of pyrrole or aniline monomers in this hybrid template, upon removal of the surfactant, produce coaxial structures with a SWNT center and conducting polypyrrole or polyaniline coating. Raman and Fourier transform infrared (FTIR) spectroscopy and scanning (SEM) and transmission (TEM) electron microscopy were used to characterize the composition and the structures of these coaxial nanowires. The results revealed that the micellar molecules used could affect the surface morphologies of the resulting coaxial nanowires but not the molecular structures of the corresponding conducting polymers. Electric properties testing indicated that the SWNTs played the key roles in the conducting polymer/SWNT composites during electron transfer in the temperature range 77 K to room temperature. Compared with the SWNT network embedded in the conducting polymers, the composites within which SWNTs were coated perfectly by the identical conducting polymers exhibited higher barrier heights during electron transfer.
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PMID:Single-walled carbon nanotube-based coaxial nanowires: synthesis, characterization, and electrical properties. 1685 Oct 66

We report a simple and efficient single-step synthesis of tungsten carbide nanorods and nanoplatelets by direct pyrolysis of a hybrid composite material of 12-tungstophosphoric acid and hexadecyltrimethylammonium bromide in a closed Swagelok cell at 1000 degrees C. The product was characterized by XRD, TGA, SEM, TEM, XPS, and CV. The diameter of the nanorods is 30-50 nm, and the length varies from 200 to 500 nm. The size of the platelets is around 55 nm. The WC exhibits an interesting structural surface with kinks, steps, and terraces which is evidenced by HRTEM studies.
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PMID:Solid state synthesis of tungsten carbide nanorods and nanoplatelets by a single-step pyrolysis. 1685 56

A hydroxyl-containing antimony oxide bromide (AOB) nanorods was synthesized by a hydrothermal method. TEM and SEM images showed that the as-prepared AOB nanorods were very copious with diameters of about 50 nm. The AOB nanorods could be easily combined with biopolymer chitosan (Chi) to form an organic-inorganic hybrid material, and a biocompatible, crack-free and porous Chi-AOB composite film could be readily obtained. Horseradish peroxidase (HRP) was chosen as a model protein to construct a reagentless mediator-free third-generation HRP biosensor. UV-visible and FTIR spectroscopy revealed that HRP entrapped in the composite film could retain its native secondary structure. A pair of stable and well-defined redox peaks of HRP with a formal potential of about -0.24 V (vs. Ag/AgCl) in a pH 7.0 phosphate-buffered solution (PBS) were obtained at the HRP-Chi-AOB composite film modified glassy carbon (GC) electrode. With advantages of organic-inorganic hybrid materials, dramatically facilitated direct electron transfer of HRP and excellent bioelectrocatalytic activity towards H(2)O(2) were demonstrated. The apparent Michaelis-Menten constant K(M)(app) was calculated to be 7.5mum, indicating that HRP entrapped in the composite film possessed high affinity to H(2)O(2) and exhibited high enzymatic activity. The prepared biosensor displayed good sensitivity and reproducibility, wide linear range, low detection limit, fast response and excellent long-term stability. The Chi-AOB composite film could be used efficiently for the entrapment of other redox-active proteins and may find wide potential applications in biosensors, biocatalysis, biomedical devices and bioelectronics.
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PMID:Hydroxyl-containing antimony oxide bromide nanorods combined with chitosan for biosensors. 1690 39


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