Abolition of the presynaptic action of carbachol by tubocurarine

The presynaptic action of carbachol (C) was studied in experiments on a neuromuscular preparation of the sartorius muscle ofRana ridibunda. C was shown to significantly reduce the quantum composition of the endplate potentials (mEPP) as a result of the direct action of C on motor nerve endings. D-Tubocurarine caused a marked decrease in the sensitivity of motor nerve endings to C. Relations between C and tubocurarine as regards their action on the quantum composition of mEPP were of the competitive antagonism type. Atropine, in low concentrations, had no effect on the presynaptic action of C. The results of these experiments indicate that the decrease in mEPP under the influence of C is mediated through specific nicotinic cholinergic structures of motor nerve endings.Department of Physiology, Medical Institute, Kazan'. (Presented by Academician of the Academy of Medical Sciences of the USSR V. V. Zakusov). Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 87, No. 2, pp. 171–174, February, 1979.     

The Effects of Glutamate on Spontaneous Acetylcholine Secretion Processes in the Rat Neuromuscular Synapse

Experiments on rat diaphragm muscles showed that glutamate (10 M – 1 mM) had no effect on the mean frequency, interspike intervals, and amplitude-time characteristics of miniature endplate potentials, but had a suppressive action on non-quantum secretion (the intensity of which was assessed in terms of the H effect). The effect of glutamate was markedly concentration-dependent and was completely overcome by blockade of NMDA receptors, inhibition of NO synthase, and by binding of NO molecules in the extracellular space by hemoglobin. It is suggested that glutamate can modulate the non-quantum release of acetylcholine, initiating the synthesis of NO molecules in muscle fibers via activation of NMDA receptors followed by the retrograde action of NO on nerve terminals.     

Stimulation of the DNA replication and murine bone marrow cell proliferation with exogenous zinc-metallothionein

It is shown that zinc-metallothionein from rat liver increases 1.5-fold thein vitro incorporation of³H-thymidine in murine bone marrow cells. The same concentrations of zinc chloride and a mixture imitating zinc-metallothionein (zinc, cysteine, and albumin) inhibit DNA synthesis. In mice receiving an intraperitoneal injection of zinc-metallothionein 10–15 min before γ-irradiation, the incorporation of³H-thymidine and the content of nucleated cells in the bone marrow is 1.5- to 2-fold higher than those in unprotected animals, the number of endogenous splenic colonies in pretreated mice being 2.7-fold higher. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 122, No. 11, pp. 505–508, November, 1996     

Calcium mechanism of norepinephrine activation of ionic pump in somatic cells of lumbricus terrestris earthworm muscle wall

Blockade of norepinephrine-induced hyperpolarization in earthworm muscle cells was observed in a calcium-free medium, after substitution of Ca²⁺ with Mn²⁺, and in the presence of verapamil or chlorpromazine to the incubation saline. Changes in Ca²⁺ concentration in the saline and addition of caffeine had no effect on the resting potential of muscle cells. It was hypothesized that signal transduction from norepinephrine-activated membrane adrenoceptors to the ionic pump in earthworm muscle cells depends on influx of extracellular Ca²⁺ and subsequent involvement of Ca²⁺-accepting proteins similar to calmodulin in vertebrates.     

Effect of thymus extract and of late thymectomy on interferon production

Mice aged 10 days do not produce interferon in response to injection of Newcastle disease virus (NDV). A single injection of a fraction of calf thymus extract, obtained by the method of Gyulling et al., into newborn mice conferred the ability to produce interferon on mice at the age of 10 days. In response to injection of NDV, adult rats produce interferon in high titers. The intensity of interferon synthesis was unchanged 2–3 months after thymectomy.Laboratory of Physiology and Pathophysiology and Laboratory of Virology, Kiev Research Institute of Otolaryngology. (Presented by Academician of the Academy of Medical Sciences of the USSR N. N. Gorev.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 10, pp. 439–440, October, 1977.     

Modulation by Nitric Oxide (NO) of the Intensity of Non-Quantum Mediator Secretion in Neuromuscular Junctions in Rats

Experiments on rat diaphragm muscle showed that the nitric oxide (NO) donors sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP), as well as L-arginine, a substrate for NO synthesis, decreased the level of muscle fiber hyperpolarization (the H effect) after blockade of cholinoceptors on the postsynaptic membrane by d-tubocurarine in conditions of irreversible inhibition of acetylcholinesterase with armine. Conversely, disruptions to NO synthesis in muscle fibers by the NO synthase blocker N^G-nitro-L-arginine methyl ester (L-NAME) led to increases in the H effect both in vitro and in vivo. Inactivated solutions of sodium nitroprusside and inactive forms of arginine and NAME (D-arginine, D-NAME) had no effect on the magnitude of the H effect, while hemoglobin, which efficiently binds NO molecules, blocked the inhibitory effects of sodium nitroprusside, SNAP, and L-arginine on the magnitude of the H effect. All these points provide evidence that NO can function as a modulator of non-quantum mediator release in the neuromuscular junctions of warm-blooded animals.     

Effect of tetraalkylammonium derivative of 6-methyluracil on amplitude and temporal parameters of miniature endplate potentials in frog neuromuscular junction

The effect of C-547, a tetraalkylammonium derivative of 6-methyluracil, a novel highly selective acetylcholinesterase inhibitor, on frog neuromuscular junction was studied. In concentrations 10^-9-10^-7 M the preparation increased the amplitude and temporal parameters of miniature endplate potentials. In contrast to the effect of C-574 on purified acetylcholinesterase from mammals, the effect of this agent on frog neuromuscular junction was reversible. In a concentration of 10^-6 M the preparation apart from anticholinesterase activity produced a parasympatholytic effect manifested in a decrease in amplitude and decay time constant of miniature endplate potentials accompanied by a decrease in spontaneous transmitter secretion. After washout, the parasympatholytic effect recovered more slowly, but disappeared more rapidly compared to anticholinesterase activity. These findings suggest that parasympatholytic effect of C-547 results from direct action on receptor-channel complexes in the endplate membrane.     

Effect of endothelium-dependent stabilization of the pressure drop in small arteries

Laboratory of Biomechanics and Regulation of the Circulation, All-Union Cardiologic Scientific Center, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR, V. N. Smirnov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 107 No. 6, pp. 649–651, June, 1989.     

Effect of exogenous acetylcholine on ionic currents of the frog and mouse motor nerve ending

Department of Normal Physiology, Kazan' Medical Institute. (Presented by Academician of the Russian Academy of Medical Sciences A. D. Ado.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 114, No. 8, pp. 124–126, August, 1992.