PubMed Health⌕ Search

Biomedical subjects

M Ia Mikhel'son

Publications and source records attributed to M Ia Mikhel'son.

17 recordsLinked to original sources
PubMedDate not supplied

[Enzymatic hydrolysis and reversible binding of suberyldicholine by cholinesterases].

A hydrolysis of suberyldicholine and monocholic ester of suberic acid by butyrylcholinesterase was studied. In the region of Sopt the rates of suberyldicholine hydrolysis were slightly below and under S less than Sopt they were far in excess of the rates of acetylcholine hydrolysis. The following kinetic constants of hydrolysis were obtained: for suberyldicholine--Km=2.3-10(-5)M, V=2.4 mcM/mg. min, Kss=7.2-10(-2)M; for monocholic ester of suberic acid--Km=7.5-10(-4)M, V=1.5 mcM/mg, min, Kss=1.2-10(-2)M (25 degrees, pH 7.5, 0.1 M KCl). Suberyldicholine was shown to be highly active reversible inhibitor of competitive--non-competitive type (Ki=2.3-10(-6)M, alpha=0.5) of acetylcholinesterase from human erythrocytes; the inhibitory effect of monocholic ester of suberic acid was distinctly lower. By biological and indirect biochemical methods it was found that low concentrations of suberyldicholine 10(-5)=10(-6)M (similar to concentrations that were in an organism upon myorelaxation) were hydrolyzed by acetlycholinesterase with the rate, approximately equal to the rate of acetylcholine hydrolysis. The reversible binding and the enzymatic hydrolysis of suberyldicholine by acetylcholinesterase of tissues were likely to be the main factors that determined the effectiveness and prolonged blocking action of suberyldicholine on the nerve-muscle conductivity.

Acetylcholine↗
PubMedDate not supplied

[Effect of cholinesterase inhibitors and reactivators on the blocking action of dicarboxylic acid amino esters on neuromuscular conduction].

Inhibition of active cholinesterases in cats with armine or the GT-165 compound (0,0-diethyl-S-/beta-arylmethylamino) ethyl/thiophosphate methylsulphomethylate) potentiases ten- and hundred-fold the blocking action of subecholine and its derivatives on the neuro-muscular condution. The cholinesterase reactivator dipyroxime (2-5 mg/kg) quickly lifts the conduction block, provoked by muscle relaxants of the subecholine type under the cholinesterase inhibition. The subecholine analogue with a single propyl radical at each atom of nitrogen does not display any pressor action and, upon inhibition of cholinesterases, it blocks the neuro-muscular conduction when used in a dose of 0.1-0.2 gamma/kg. The maximal potentiation of the blocking action exerted by subecholine and its analogues is achieved in inhibiting not only pseudocholinesterase but acetylcholinesterase as well.

Amino Acids, Dicarboxylic↗
PubMedDate not supplied

[Action of polymethylene-bis-quaternary compounds on the muscarinic and nicotinic cholinoreceptors].

The action of compounds with general formula (formula: see text) on the frog heart ventricle, cat blood pressure, guinea pig ileum and frog rectus abdominis was studied. With dioxolane radicals (type F-2268) a strong muscarinomimetic action on the cat arterial blood pressure and guinea pig ileum was observed, with maximum marked action at n = 10, which was more pronounced at an even than at odd number of methylene groups. On the frog heart the compounds with an odd number of "n" elicited an atropine-like action. The compounds with pentyl radicals produced no effect on blood pressure and a weak cholinolytic effect on the frog heart. On the ileum they exhibited a cholinomimetic effect. All compounds studied acted as noncompetitive cholinolytics on the frog rectus.

Abdominal Muscles↗
PubMedDate not supplied

[Study of skeletal muscle cholinoreceptors using alkylating agents].

The ability of decamethonium containing beta-clorethylamino groups to alkylate the nicotinic cholinoreceptors of the frog tonic muscles was studied. D-tubocurarine prevented the action of the alkylating decamethonium (AD). The latter equally inhibited the effects of carbacholine and tetramethylammonium. The degree of alkylation did not change with pH varying from 6 to 11. AD did not produce any parallel shifts, but inhibited at once the maximal response to carbacholine both of the frog intact muscle and of a single tonic fibre. It is suggested that decamethonium blocks the cholinoreceptors anionic sites, which are represented by the carboxylate, or phosphate anions. The frog tonic muscle probably fails to posses any spare receptors.

Alkylation↗
PubMedDate not supplied

[A comparative study of the stereoselectivity of cholinoreceptors].

Muscarine-sensitive cholinoreceptors (M-ChR) of higher vertebrates exhibit high stereoselectivity which is also revealed with respect to enantiomers of a very potent muscarinomimetic methyldilvasen (F-2268), the stereospecific index (SSI) being about 100. M-ChRs in the neuronal membrane of the gastropod mollusc Planorbarius corneus and in the hearts of the bivalve molluscs Mercenaria stimpsoni and Anadara broughtoni are highly sensitive to methyldilvasen (10(-9)-10(-10) M), but their sensitivity to its enantiomers is identical. In heart atria of the tortoise Testudo horsfieldi, frog Rana temporaria, and fishes Siluris glanis, Cyprinus carpio, as well as in ventricles of tadpoles, high SSI was revealed. These data are consistent with a hypothesis that during evolution of vertebrates no significant changes took place in the active center of M-ChR. Possibly, the lack of stereoselectivity in the investigated molluscan M-ChRs, together with their other peculiarities (they are not blocked by atropine), indicate "immaturity" of these receptors.

Animals↗
PubMedDate not supplied

[Comparative findings on the stereoselectivity of cholinoreceptors].

The potency of the optical isomers of the muscarinomimetic agent 2-methyl-4-dimethylaminomethyl-1.3-dioxolane methiodide (F-2268) was compared on cholinoreceptors, (ChR) of different animals. The greatest difference between optical isomers was observed on the muscarinic ChR of guinea pig ileum smooth muscle cis-L(+)isomer being more than hundred times as potent as cis-D(-)isomer. On the ChR of muscarinic type in the holothuria Cucumaria japonica retractor muscle, cis-L(+)isomer was 25 times as efficient as cis-D(-)isomer. On the ChR of sea urchin and sipunculid locomotor muscles, optical isomers differ only 3 to 5 times. There was no difference between the effect of optical isomers on the ChR of muscarinic type which mediate hyperpolarization in the neurones of the gastropod mollusc Planorbarius corneus. This suggest that some changes in ChR stereoselectivity may occur in the course of evolution.

Animals↗