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Physiology, Biochemistry, and Pathology of Neuromuscular Transmission
Published in Marc H. De Baets, Hans J.G.H. Oosterhuis, Myasthenia Gravis, 2019
AChE can be measured with a simple radiochemical method in homogenates of segments of muscle.130 ACh measurements are difficult because skeletal muscle contains little ACh, 0.2 to 1.0 pmol per mg of wet tissue weight, and gas chromatography/mass spectrometry is one of the few methods that can adequately cope with these small amounts of ACh.231 In this method the ACh extracted from the tissue or incubation medium is first purified with a precipitation method (together with tetramethylammonium ions and iodine/iodide complex) and the mixture is pyrolyzed on glass, which causes a reaction of ACh to its (volatile) tertiary amine analogue. After gas chromatography, the tertiary amine is detected with high sensitivity by mass spectrometry (GC/MS method). The main disadvantage of the GC/MS system is that it is very expensive. Recently, high performance liquid chromatography, combined with an electrochemical detector, has been used with success at much less cost for the determination of ACh in skeletal muscle, based on a method of conversion of ACh to H2O2.232-234
High-Performance Liquid Chromatography
Published in Joseph Chamberlain, The Analysis of Drugs in Biological Fluids, 2018
Another classical method for effecting extraction of charged compounds from aqueous phases is the technique of ion-pairing, which is also used in altering partition coefficients in HPLC. In the classical method, a counter-ion is added to the solution containing the ion to be extracted and association with a reduced charge is formed; this entity is then extractable with an organic solvent. Thus, for organic acids, a suitable counter-ion would be tetramethylammonium, while for organic bases, such ions as heptane sulfonate have been used. Much of the development of the use of paired ion chromatography is due to the work of Schill681 and Tomlinson et al.682 who have written several extensive reviews on the theory and practice of the technique.
Drugs Affecting Autonomic Ganglia (Including the Adrenal Medulla)
Published in Kenneth J. Broadley, Autonomic Pharmacology, 2017
The prototype of the nicotinic receptor stimulants is nicotine, whose pharmacological properties will be described. The best known other members of this group are tetramethylammonium (TMA), lobeline and DMPP, which have similar properties. Their structures are shown, together with that of nicotine, in Table 11.1. A brief indication of any differences in their activity compared with nicotine will be given later.
Organotypic and primary neural cultures as models to assess effects of different gold nanostructures on glia and neurons
Published in Nanotoxicology, 2019
Jeff Ji, Alexandre Moquin, Franck Bertorelle, Philip KY Chang, Rodolphe Antoine, Julia Luo, R. Anne McKinney, Dusica Maysinger
Au25(SG)18 which served as a spherical-like nanocluster control were synthesized as follow: 234mg of glutathione (GSH) was dissolved in 35mL of methanol, 2mL of tributylamine and 2mL of triethylamine. Then 100mg of HAuCl4, 3H2O dissolved in 10mL of water was added and the solution was stirred 3h at 45°C. The solution was cooled to ambient temperature and 50mg of tetramethylammonium borohydride was added under strong stirring. 1h later another 25mg of borohydride was added and the solution was stirred 3h. The solution was left undisturbed overnight before purification. Precipitation of Au-nanoclusters was induced by adding 1mL of NH4OH 10% and diethyl ether. The unwanted products were removed with cycles of dissolution/precipitation/centrifugation. The powder was dissolved in a minimum of H2O/NH4OH then precipitated with methanol. After centrifugation, the powder was dissolved again in 10mL of water. Then 2mL of glacial acetic acid was added and the solution was left undisturbed for 1h before being centrifuged. The supernatant was collected and precipitated with methanol. Another cycle of dissolution/precipitation with H2O/NH4OH and acetic acid/methanol was done before drying the powder under vacuum over P2O5.
N-Acetylcysteine reverses silver nanoparticle intoxication in rats
Published in Nanotoxicology, 2019
Monique Culturato Padilha Mendonça, Luiz Bandeira Ferreira, Cintia Rizoli, Ângela Giovana Batista, Mário Roberto Maróstica Júnior, Emanueli do Nascimento da Silva, Solange Cadore, Nelson Durán, Maria Alice da Cruz-Höfling, Marcelo Bispo de Jesus
For GF-AAS measurements in tissue and feces, 0.05–0.15 g of lyophilized samples (depending on the available tissue amount) were homogenized in 9.5 mL of deionized water (depending on the available tissue amount) and incubated for 5 min. Subsequently, 0.5 mL of 25% tetramethylammonium hydroxide (TMAH) was added to the solution and incubated in an ultrasound cleaning apparatus until complete solubilization of the samples. The absorbance was determined at the 328.1-nm resonance line, and some posterior dilution was made if necessary. Analysis of urine samples was performed without adding TMAH. The analytical calibration curve was generated at 10–60 μg/L using aqueous metallic silver standards and a 3 μg solution of 5 μg/mg Pd (NO3)2 as a chemical modifier. The pyrolysis and atomization temperatures were 800 °C and 1700 °C, respectively. All readings were performed in triplicate.
Synergistic photothermal/photodynamic suppression of prostatic carcinoma by targeted biodegradable MnO2 nanosheets
Published in Drug Delivery, 2019
Dewang Zeng, Lei Wang, Lu Tian, Shili Zhao, Xianfeng Zhang, Hongyan Li
The MnO2 nanosheets were synthesized according to the previous report with some modification (Zhao et al., 2014). In brief, a mixture of tetramethylammonium hydroxide (0.6 M, 15 mL) and 3 wt % H2O2 was added into MnCl2 solution (0.3 M, 10 mL) within 15 s. The resulting dark brown suspension was stirred vigorously for 12 h at room temperature and the bulk manganese dioxide was obtained by centrifugation (2000 rpm, 10 min), washed thoroughly with water and ethanol for three times, and finally dried under vacuum at 55 °C. Then, MnO2 nanosheets were prepared by ultrasonicating exfoliation of the above bulk MnO2. Briefly, 10 mg of bulk manganese dioxide was dispersed in 20 mL water and ultrasonicated for 15 h (500 W). Then, the dispersion was centrifuged at 2000 rpm for 20 min, and the supernatant was collected for further use. For cRGD-PEG2000-NH2 modification, the cRGD-PEG2000-NH2 (0.45 mg/mL, 15 mL) was added into a concentration of 4 mg mL−1 MnO2 nanosheets aqueous solution. After that, the mixture was ultrasonicated for 2 h and then centrifuged at 8000 rpm for 10 min. The precipitate was suspended in water for further use.