Contribution of Ryanodine Receptors in Forming Presynaptic Ca²⁺ Level and Cholinergic Modulation in Response to Single Potential in Frog Neuromuscular Junction

© 2016, Springer Science+Business Media New York.Ca2+ entering through voltage-gated Ca2+ channels plays a key role in the initiation of neurotransmitter secretion. However, intracellular Ca2+ storages such as endoplasmic reticulum (ER) can also contribute in the presynaptic Ca2+ level forming. Also ryanodine-dependent Ca2+-induced Ca2+ channels of endoplasmic reticulum may contribute in secretion inhibiting action of cholinomimetics. In this work, we use a photometric method for estimating the relative change in the level of presynaptic Ca2+ ions (Ca2+ transient). We have shown that during low-frequency stimulation Ca2+ release from the ER is involved in forming of presynaptic Ca2+ level. And more likely those effects of the cholinomimetics on Ca2+ transient are not related to Ca2+ release from the endoplasmic reticulum

Virtual reality and reproduction of sociality: Experience of social and philosophical analysis

© 2014, Mediterranean Center of Social and Educational Research. All rights reserved. The article considers the situation in the community determined by the philosophers as a "social death." What does it mean? Is there a way out of this situation? If so, what is it? These are the questions the authors look answers for. According to the authors, the metaphor "social death" is the acknowledgement of the extreme exhaustion of the modern society's humanistic potential. Addressing the issue, by the authors, is in virtualization, i.e. the process of creation of the virtual worlds, where the man "gets" himself/herself and the society to the absolute completeness. The man returns to the world of physical reality, willing to improve it and to live in it as he/she would do in his/her dreams. And so goes permanently

Calcium Transient and Quantal Release in Mouse Neuromuscular Junction Under Extracellular Calcium Concentration Change

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. In mouse neuromuscular junction, the amplitude of the presynaptic calcium (Ca2+) transient was measured and correlated with mediator release at different extracellular Ca2+ concentrations. Fluorescent calcium-sensitive dye Oregon Green 488 BAPTA 1 hexapotassium salt was used for Ca2+ transient registration. The quantal content of release was assessed by the amplitude of the endplate potentials (EPPs) and was measured using intracellular microelectrodes. The amplitude of the EPPs changed more significantly than the amplitude of the Ca2+ transient when the extracellular calcium concentration was changed. Linear approximation of the dependence of the quantal content on the amplitude of the Ca2+ transient on double logarithmic scale gave a slope showing that the biochemical cooperativity was 2.86. The obtained value is comparable with the data calculated earlier in the neuromuscular junction of the rat and other synapses using electrophysiological measurements. Our data suggest that the change of the Ca2+ transients recorded from the whole volume of the nerve terminal properly reflects the variation of calcium concentration responsible for the neurotransmitter release in active zone. Thus, analysis of the bulk Ca2+ transient can be used to evaluate the calcium entry into the nerve endings and compare it with the number of quanta released under different conditions

Action of ATP on Ca²⁺-Transient in Different Parts of the Frog Motor Nerve Ending

© 2016, Springer Science+Business Media New York.Electrophysiological evidence indicates a difference in neurotransmitter secretion along the motor nerve terminals of the frog neuromuscular junction. This includes a decrease of the minimal synaptic delay value and a reduction in the quantal content of the evoked endplate currents from the proximal to distal portion of the motor nerve ending. Besides, various physiologically active compounds may have different effects on the acetylcholine secretion in the proximal and distal parts of the nerve terminal. Here, we explored the effects of ATP on Ca2+-transient using optical detection methods with high-speed camera in different parts of the frog nerve terminal. There was shown a significant inhibitory effect of ATP on Ca2+-transient in both the proximal and distal regions of nerve terminals. However, in different parts of nerve endings, any significant differences in ATP effects were not found. Thus, ATP decreases the Ca2+-transient along the entire presynaptic terminal

Loading a calcium dye into frog nerve endings through the nerve stump: Calcium transient registration in the frog neuromuscular junction

© 2017 Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. One of the most feasible methods of measuring presynaptic calcium levels in presynaptic nerve terminals is optical recording. It is based on using calcium-sensitive fluorescent dyes that change their emission intensity or wavelength depending on the concentration of free calcium in the cell. There are several methods used to stain cells with calcium dyes. Most common are the processes of loading the dyes through a micropipette or pre-incubating with the acetoxymethyl ester forms of the dyes. However, these methods are not quite applicable to neuromuscular junctions (NMJs) due to methodological issues that arise. In this article, we present a method for loading a calcium-sensitive dye through the frog nerve stump of the frog nerve into the nerve endings. Since entry of external calcium into nerve terminals and the subsequent binding to the calcium dye occur within the millisecond time-scale, it is necessary to use a fast imaging system to record these interactions. Here, we describe a protocol for recording the calcium transient with a fast CCD camera

Calcium Transient Registration in Response to Single Stimulation and During Train of Pulses in Mouse Neuromuscular Junction

© 2016, Springer Science+Business Media New York.Calcium (Ca2+) is a key ion involved in transmitter release in chemical synapses. Optical recording of fluorescence changes of Ca2+ indicators is one of the most frequently used methods to measure intracellular Ca2+ dynamics. This technique is based on use of Ca2+-binding fluorescent dyes which change their emission intensity after binding to Ca2+. The most crucial step in this type of experiments is loading of Ca2+ dye. In this paper, we present the method of Ca2+-sensitive dye loading to mammalian nerve endings through the stump of the nerve. We represent Ca2+ transient registered parameters in response to a single motor nerve stimulus. The study of Ca2+ dynamics during high frequency stimulation close to real pattern of synaptic transmission allows us to understand such fundamental process as synaptic plasticity. We describe the results obtained during the registration of Ca2+ transient caused by the rhythmic motor nerve stimulation. Intracellular level of Ca2+ estimated by the amplitude of Ca2+ transient rises with the increase of stimulation frequency. The amplitude of Ca2+ transient decreases after blocking of voltage dependent Ca2+ channels by cadmium. The obtained data showed that detected increase of fluorescence intensity is induced by Ca2+ influx through the voltage-gated Ca2+ channels to the nerve ending during an action potential. This dye-loading method is suitable for registration of presynaptic Ca2+ dynamics under both single nerve stimulus and rhythmic activity

Acetylcholine-induced inhibition of presynaptic calcium signals and transmitter release in the frog neuromuscular junction

© 2016 Khaziev, Samigullin, Zhilyakov, Fatikhov, Bukharaeva, Verkhratsky and Nikolsky.Acetylcholine (ACh), released from axonal terminals of motor neurons in neuromuscular junctions regulates the efficacy of neurotransmission through activation of presynaptic nicotinic and muscarinic autoreceptors. Receptor-mediated presynaptic regulation could reflect either direct action on exocytotic machinery or modulation of Ca2+ entry and resulting intra-terminal Ca2+ dynamics. We have measured free intra-terminal cytosolic Ca2+ ([Ca2+]i) using Oregon-Green 488 microfluorimetry, in parallel with voltage-clamp recordings of spontaneous (mEPC) and evoked (EPC) postsynaptic currents in post-junctional skeletal muscle fiber. Activation of presynaptic muscarinic and nicotinic receptors with exogenous acetylcholine and its non-hydrolized analog carbachol reduced amplitude of the intra-terminal [Ca2+]i transients and decreased quantal content (calculated by dividing the area under EPC curve by the area under mEPC curve). Pharmacological analysis revealed the role of muscarinic receptors of M2 subtype as well as d-tubocurarine-sensitive nicotinic receptor in presynaptic modulation of [Ca2+]i transients. Modulation of synaptic transmission efficacy by ACh receptors was completely eliminated by pharmacological inhibition of N-type Ca2+ channels. We conclude that ACh receptor-mediated reduction of Ca2+ entry into the nerve terminal through N-type Ca2+ channels represents one of possible mechanism of presynaptic modulation in frog neuromuscular junction

Synthesis and biological activity of quaternary phosphonium salts based on 3-hydroxypyridine and 4-deoxypyridoxine

© 2016, Springer Science+Business Media New York.Methods for the synthesis of quaternary phosphonium salts based on 3-hydroxypyridine and 4-deoxypyridoxine were developed. Some of obtained compounds possess high antibacterial and antitumor activity in vitro

Synthesis and Antimycobacterial Activity of Hydrazides Based on Pyridoxine Derivatives

© 2018, Pleiades Publishing, Ltd. Pyridoxine derivatives, 3-hydroxy-2-methylpyridine-4- and -5-carbohydrazides, were synthesized according to optimized known procedures, and a method for the synthesis of 5-(hydroxymethyl)-2,2,8-trimethyl-4H-[1,3]dioxino[4,5-c]pyridine-6-carbohydrazide was developed. The hydroxymethyl groups in positions 5 and 6 of 2,2,8-trimethyl-4H-[1,3]dioxino[4,5-c]pyridine showed different reactivities, and only the 6-hydroxymethyl group was selectively oxidized to aldehyde under mild conditions. The lactone ring in 5,6-dihydrofuro[3,4-b]pyridin-7(5H)-one was found to be stable to nucleophiles. The synthesized hydrazides showed no antimycobacterial activity

Intelligent diagnostic system for hydraulic actuator

© 2019 IEEE. The proposed technical solution allows optimizing the process of hydraulic drive control, which leads to increased energy efficiency, as well as diagnosing the state of the hydraulic system of the industrial machine. To ensure the speed of the process of diagnosing the state of the hydraulic drive in addition to the hardware of the system, an analytical software expert system is required. The subsystem allows one not only to speed up the existing diagnostic process, but to perform it faster and more accurately, in addition, it allows you to implement the prediction of diagnostic parameters in real time and planning the optimal timing of maintenance and repair to prevent failure in the process of equipment operation. In addition, the establishment of the causes of failure increases the likelihood of elimination of violations committed during the operation or detection of factory and other defects in the details of the equipment