Search

Purpose This is the first study to examine whether age impacts the response of single muscle fibers to high/low frequency and high/low volume electrical pulse stimulation. We performed in vitro experiments to evaluate the effect of low-frequency high-volume electrical pulse stimulation (EPS) on mechanistic target of rapamycin (mTOR), mitogen-activated protein kinase (MAPK) signaling pathway, and satellite cell activation in singles fibers of young and aged muscles. Methods Isolated single fibers from gastocnemius in 12-wk (n=21) and 72-wk (n=21) old male C57BL/6 mice were divided into four groups: 1) control (Con) received no EPS, 2) low-frequency low-volume EPS (LL), 3) low-frequency high-volume EPS (LH), and 4) high-frequency low-volume EPS (HL) were made to contract using independent EPS protocols. Satellite cell activation and anabolic pathway (mTOR and MAPK signaling) were measured before and after EPS. Results The number of quiescent (Pax7+/Ki67-) and active (Pax7+/Ki67+) satellite cells, myonuclear content and the phosphorylation of 4E-BP1 and ERK were higher in young when compared with old. However, regardless of age, LH and HL EPS significantly increased the number of activate satellite cells (142%, both) and phosphorylation of mTOR (129% and 133%, respectively), p70S6K (133% and 136%, respectively) and 4E-BP1 (140% and 129%, respectively) compared with Con. The protein expression of ERK phosphorylation only increased by LH EPS in both the young and old groups (123% and 125%, respectively). Conclusion Low-frequency high-volume EPS stimulated satellite cell activation and the mTOR signaling pathway in older similar to young muscle.

A novel calix[n]triazolium was synthesized and exhibited excellent selectivity for AMP. The binding between calix[n]triazolium and chromenolate anions forms a non-fluorescent complex and the resulting supramolecular ensemble selectively detects AMP in water and induces "turn-on" fluorescence. The sensing platform is the first macrocyclic system to discriminate AMP from ADP and ATP through fluorescence changes. ispartof: CHEMICAL COMMUNICATIONS vol:57 issue:91 pages:12139-12142 ispartof: location:England status: published

Skeletal muscle plays an indispensable role in metabolic health and physical function. A decrease in muscle mass and function with advancing age exacerbates the likelihood of mobility impairments, disease development, and early mortality. Therefore, the development of non-pharmacological interventions to counteract sarcopenia warrant significant attention. Currently, resistance training provides the most effective, low cost means by which to prevent sarcopenia progression and improve multiple aspects of overall health. Importantly, the impact of resistance training on skeletal muscle mass may be augmented by specific dietary components (i.e., protein), feeding strategies (i.e., timing, per-meal doses of specific macronutrients) and nutritional supplements (e.g., creatine, vitamin-D, omega-3 polyunsaturated fatty acids etc.). The purpose of this review is to provide an up-to-date, evidence-based account of nutritional strategies to enhance resistance training-induced adaptations in an attempt to combat age-related muscle mass loss. In addition, we provide insight on how to incorporate the aforementioned nutritional strategies that may support the growth or maintenance of skeletal muscle and subsequently extend the healthspan of older individuals.

Insulin was precipitated from solution in dimethylsulfoxide using supercritical carbon dioxide as an antisolvent. Solution enhanced dispersion by supercritical fluids (SEDS) process was applied to produce nano‐size insulin particles. We used dimethylsulfoxide to help the supercritical carbon dioxide to extract water from the aqueous protein solution. Various sizes of insulin nano‐particles were successfully prepared with a narrow particle size distribution from aqueous dimethylsulfoxide solution without using any additive. The theoretical particle sizes were deduced from the calculated droplet sizes based on a modified Jasuja's equation. The calculated mean particle sizes and the experimentally obtained ones were compared and the results showed an excellent correlation coefficient (R2) of 0.9738.

Solution-enhanced dispersion by supercritical fluids (SEDS) was applied to produce nano-sized recombinant human growth hormone (hGH) particles. Ethanol was used to help the supercritical carbon dioxide to extract water from the aqueous protein solution. Various sizes of hGH nanoparticles were successfully prepared with a narrow particle size distribution from aqueous ethanol solution without using any additive. The theoretical particle sizes were deduced from the calculated droplet sizes based on a modified Jasuja's equation. The calculated mean particle sizes and the experimentally obtained ones were compared and the results showed an excellent correlation coefficient (R (2)) of 0.995.

The use of supercritical fluids for the analytical extraction of the nonvolatile, higher molecular weight compound, microcystin LR, from cyanobacteria was investigated. The microcystin LR included in this study was sparingly soluble in neat supercritical fluid CO2. However, the microcystin LR was successfully extracted with a ternary mixture (90% CO2, 9.5% acetonitrile, 0.5% water) at 40°C and 250 atm. The polar carbon dioxide‐aqueous acetonitrile fluid system gave a high extraction efficiency for the extraction of the polar microcystin LR from cyanobacteria. In our laboratory, in the past, aqueous acetic acid‐modified CO2 was used for the extraction of microcystins from cyanobacteria and aqueous methanol was also used as a modifier. In this study, we tried a new organic solvent, aqueous acetonitrile as a co‐solvent, so that we could obtain a higher extraction efficiency of the microcystin LR from cyanobacteria than in earlier experiments.

New monoclonal antibodies (mAbs) against microcystin (MC), a cyclic peptide toxin of the freshwater cyanobacterium Microcystis aeruginosa, were prepared from cloned hybridoma cell lines. Using these mAbs, an immunochromatographic assay system was designed for the detection of cyanobacterial hepatotoxins, MCs in water. The immunochromatographic assay system is composed of anti‐MCs‐mAb, fluorescence conjugates in detection solution, an immunochromatographic assay strip, and a laser fluorescence scanner. The performance of the immunochromatographic assay system was compared with high performance liquid chromatography (HPLC) detection. As the detection limit of HPLC is several orders of magnitude higher than with immunochromatographic assay systems, attention was also given to preconcentration of samples with solid phase extraction cartridges.

The use of compressed (dense) gases and supercritical fluids as chromatographic mobile phases in conjunction with liquid chromatographic (LC)-type packed columns was first reported by Klesper et al. in 1962. During its relatively short history, supercritical fluid chromatography (SFC) has become an attractive alternative to GC and LC in certain industrially important applications. SFC gives the advantage of high efficiency and allows the analysis of nonvolatile or thermally labile mixtures. The density of the mobile phase in SFC is about 200-500 times that in gas chromatography. The effect of shorter intermolecular distances and the resulting increase in molecular interactions is an enhanced solubilizing capability of the solvent towards various solutes. Compounds with much higher molecular weights than gas chromatography normally allows can therefore be chromatographed. However, the most commonly used mobile phases in SFC are all relatively non-polar fluids. Carbon dioxide, the most widely used fluid, is no more polar than hexane, even at high densities. Solute polarity should be between that of the stationary phase and the mobile phase in order to have a well behaved separation. Few real samples contain only nonpolar solutes, so a major objective of research in SFC has been directed toward increasing the range of solute polarity that can be handled by the technique. To bring the SFC technique into routine use, mobile phases that are more polar than the commonly used carbon dioxide are necessary. The solvent strength of supercritical CO2, even at high density, is not sufficient for the elution of polar solutes. Polar mobile phase such as NH3 exhibit useful properties, but a more practical way to extend the range of compounds separable by SFC is to use a mixed mobile phase. The solubility of the solute in the supercritical phase can be influenced considerably by adding modifiers to the mobile phase. The use of modifiers has been reported by Jentoft and Gouw and by Novotny et al. The latter group showed that adding 0.1% 2-propanol to pentane as the mobile phase decreases the observed partition coefficient (K) values for many polynuclear aromatic hydrocarbons by 20-35%. Thus, the addition of modifiers (generally organic solvents) to a supercritical mobile phase changes the polarity of the mobile phase and also leads to deactivation of the column packing material. In capillary SFC, most separations are made with pure CO2 because of its compatibility with an flame ionization detection (FID); except for formic acid and water, the addition of any common modifier precludes the use of FID. Modifiers are essential in packed-column SFC for the elution of polar compounds and are extensively used. Several workers have reported the influence of modifiers on peak shape, selectivity and retention time in capillary and packed-column SFC. A simple and effective way to add modifiers to a supercritical fluid mobile phase is to use a saturator column, which is usually a silica column saturated with polar alcohols. In this work, water was used as a polar modifier and a μporasil column as a saturator column. The μ-porasil column was inserted between the pump outlet and the injection valve. During the passage of the supercritical fluid mobile phase through the silica column, a polar modifier (water) can be dissolved in the pressurized supercritical fluid. Dimethylpolysiloxane polymer has been known as more polar polymer than polystyrene polymer. Dimethylpolysiloxane polymer has never been separated using water modified mobile phase. In this paper, using a μ-porasil column as a saturator column, excellent supercritical fluid chromatograms of dimethylpolysiloxane oligomers were obtained.

Background Limited data are available examining dietary interventions for optimizing protein and leucine intake to stimulate muscle protein synthesis (MPS) in older humans. Objectives We aimed to investigate the aminoacidemia and appetite responses of older adults after consuming breakfast, a meal frequently consumed with high-carbohydrate and below-par amounts of protein and leucine for stimulating MPS. Methods Five men and 3 women (means ± SD; age: 74 ± 7 y, BMI: 25.7 ± 4.9 kg/m2, fat- and bone-free mass: 63 ± 7 kg) took part in this experiment in which they consumed breakfasts with low-protein (LP = 13 ± 2 g), high-protein (HP = 32 ± 5 g), and LP followed by a protein- and leucine-enriched bar formulation 2 h later (LP + Bar = 29 ± 2 g). The LP, HP, and LP + Bar breakfast conditions contained 519 ± 86 kcal, 535 ± 83 kcal, and 739 ± 86 kcal, respectively. Blood samples were drawn for 6 h and analyzed for amino acid, insulin, and glucose concentrations. Visual analog scales were assessed for hunger, fullness, and desire to eat. Results The net AUC for essential amino acid (EAA) exposure was similar between the LP + Bar and HP conditions but greater in the HP condition compared with the LP condition. Peak leucinemia was higher in the LP + Bar condition compared with the HP, and both were greater than the LP condition. Net leucine exposure was similar between HP and LP + Bar, and both were greater than LP. Hunger was similarly reduced in LP + Bar and HP, and LP + Bar resulted in a greater hunger reduction than LP. Both LP + Bar and HP resulted in greater net fullness scores than LP. Conclusions Consuming our bar formulation increased blood leucine availability and net exposure to EAAs to a similar degree as consuming a high-protein meal. High-protein at breakfast results in a greater net exposure to EAAs and leucine, which could support MPS in older persons. This study was registered at clinicaltrials.gov as NCT03712761., There are practical limitations for older persons to sufficiently increase daily protein intake. Dietary recommendations aimed to prevent or minimize sarcopenia may benefit from inclusion of supplementing with unique formulations containing milk proteins with free leucine.