Regulating the thin-filament length in muscle is crucial for controlling the number of myosin motors that generate power. The giant protein nebulin forms a long slender filament that associates along the length of the thin filament in skeletal muscle with functions that remain largely obscure. Here nebulin’s role in thin-filament length regulation was investigated by targeting entire super-repeats in the Neb gene; nebulin was either shortened or lengthened by 115 nm. Its effect on thin-filament length was studied using high-resolution structural and functional techniques. Results revealed that thin-filament length is strictly regulated by the length of nebulin in fast muscles. Nebulin’s control is less tight in slow muscle types where a distal nebulin-free thin-filament segment exists, the length of which was found to be regulated by leiomodin-2 (Lmod2). We propose that strict length control by nebulin promotes high-speed shortening and that dual-regulation by nebulin/Lmod2 enhances contraction efficiency.

Key pointsr The zebrafish is emerging as an attractive cost-effective model for the study of structurefunction relationships. However, cardiac contractile function in the zebrafish remains to be investigated.r We applied novel approaches used to study contractile function at the cellular level in mammalian models to zebrafish. We found that contractile force regulation in the adult zebrafish shares many similarities with that in the mammalian myocardium as previously determined by others and ourselves, indicating that the zebrafish is an appropriate model system for the study of cardiac contractile biology.Abstract The zebrafish (Danio rerio) has been used extensively in cardiovascular biology, but mainly in the study of heart development. The relative ease of its genetic manipulation may indicate the suitability of this species as a cost-effective model system for the study of cardiac contractile biology. However, whether the zebrafish heart is an appropriate model system for investigations pertaining to mammalian cardiac contractile structure-function relationships remains to be resolved. Myocytes were isolated from adult zebrafish hearts by enzymatic digestion, attached to carbon rods, and twitch force and intracellular Ca 2+ were measured. We observed the modulation of twitch force, but not of intracellular Ca 2+ , by both extracellular [Ca 2+ ] and sarcomere length. In permeabilized cells/myofibrils, we found robust myofilament length-dependent activation. Moreover, modulation of myofilament activation-relaxation and force redevelopment kinetics by varied Ca 2+ activation levels resembled that found previously in mammalian myofilaments. We conclude that the zebrafish is a valid model system for the study of cardiac contractile structure-function relationships.

The effect of thiourea (0.5-10 mM) on the kinetics of the hydrogen evolution reaction (HER) at iron and the hydrogen transport through a steel membrane out of ethylene glycol (containing 2 and 10 wt % H 2 O) and aqueous solutions containing HCl (0.1-0.99 M) with a constant ionic strength equal to unity is studied in parallel experiments. The presence of 0.5 mM of thiourea in the solutions raises the overvoltage of hydrogen evolution, while a subsequent increase in its concentration does not effect the HER kinetics. The dependence of the flux of hydrogen diffusion through the membrane on the thiourea content passes through a maximum.

Аннотация: Показано как протекает процесс в безводной серной кислоте поликонденсации гексаметилентетрамина. Предложен механизм протекающих превращений и структура образующихся продуктов. Для образующегося продукта предложено техническое название «аминокумулен». Найдены условия получения растворимого и нерастворимого продуктов поликонденсации гексаметилентетрамина. Исследованы спектральные свойства полученных продуктов. Показано, что растворимый аминокумулен является эффективным диспергатором и стабилизатором дисперсий углеродных нанотрубок и графеновых материалов.

As a rule, carbon materials with developed energy are produced by physical or active activation of carbon-containing precursor materials. Physical activation is usually carried out at a temperature of 800-900 °C. For chemical activation, many reagents have been proposed-phosphoric acid, zinc chloride, potassium sulfide, sodium hydroxide, potassium hydroxide, potassium carbonate, and others. All these techniques are aimed at increasing the specific surface and porosity of the original carbon nanomaterials. The presented paper describes the synthesis technology for substances, presumably of a cumulene structure, based on the polycondensation of hexamethyltetramine in anhydrous sulfuric acid. A change in the heat treatment modes makes it possible to intensify the polymerization process, which results in synthesis products that are insoluble in an aqueous medium. Optionally, carbon nanotubes were added to the reaction system. The substances obtained were activated with potassium hydroxide. The analysis of the specific surface area of the synthesized materials showed extremely high values (4288-5346 m 2 /g). Increasing the ratio of potassium hydroxide to the initial carbon substance leads to increasing the pore width. The addition of carbon nanotubes to the initial substance dramatically increasesthe pore width. The activated materials can be used as effective adsorbents and electrode materials for chemical current sources.