We studied enzymatic activity and measured strain-gauge contraction properties of the frog rana temporaria m. tibialis anterior muscle fascicles during the action of aluminum chloride solution. It was shown that Alcl 3 solutions did not affect the dynamic properties of skeletal muscle preparation in concentrations less than 10-4 M. Increasing the concentration of Alcl 3 to 10-2 M induce complete inhibition of muscle contraction. A linear correlation between decrease in ca 2+ ,Mg 2+-ATPase activity of sarcoplasmic reticulum and the investigated concentrations range of aluminum chloride was observed. The reduction in the dynamic contraction performance and the decrease ca 2+ ,Mg 2+-ATPase activity of the sarcoplasmic reticulum under the effect of the investigated Alcl 3 solution were minimal in pre-tetanus period of contraction. k e y w o r d s: aluminum chloride, muscle contraction, ca 2+ ,Mg 2+-ATPase activity, muscle contractile force, length of muscle fibers.

The backbone of the myosin filament is an aggregate of alpha-helical coiled coil myosin rods. Its surface forms a three-stranded helix composed of myosin heads. Currently there is no adequate model to describe the organization of the myosin filament. It is proposed here that, in cross-section the light meromyosin (LMM) of 18 myosin molecules form an outer tube, with nine S2 forming the interior core. At the surface of the thick filament, myosin heads are arranged in three rows, giving the filament a periodicity of 14.3 nm per three myosin molecules. Two of these molecules are organized at an angle of 120 degrees to each other on the same level, while the third is shifted 7.2 nm along the filament axis. This packing gives a striation pattern of 7.2 nm by electron microscopy. An alternative model is also possible, in which the heads of the myosin molecules are uniformly spaced at an interval of 14.3 nm along the filament axis. The packing of individual molecules within the myosin filament is based on a regular pattern of charge on the 28 amino-acid repeat in the rod domain.

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UDC 547. and Together with various chromone derivatives, their structural isomers --coumarins --are widely distributed in the plant world. Great interest in the study of coumarin compounds appeared with the detection of an anticoagulant action of 4-hydroxycoumarin and it increased in the following decades in connection with the discovery of many coumarin derivatives having hypothermal, anthelmintic, hypotensive, antimicrobial, diuretic, insecticidal, and vasodilatory actions and the possibility of their use as effective drugs (dicoumarol, novobiocin, nafarin, etilendikumarin, propenan, nitrofarin, ksilokumarol, and many others) in various diseases.Coumarin compounds with aryl substituents in position 3 are rarely encountered among substances of plant origin. Coumarins containing heterocyclic residues in this position are not found in nature. They can be obtained synthetically.Recently, intensive investigations on the synthesis and study of the chemical and biological properties of heterocyclic coumarin derivatives have been pursued in many laboratories [1], and compounds with interesting biological activities have already been found among them.In order to study their chemical and biological properties and to find new highly effective drugs among heterocyclic coumarin derivatives, we have synthesized derivatives of 4-hydroxycoumarin by the scheme given below. The synthesis was achieved under the conditions of the Claisen condensation with sodium tert-butanolate as catalyst. The 3-furyl-4-hydroxycoumarins obtained consisted of yellow crystalline substances readily soluble in the majority of organic solvents. They possessed a powerful characteristic fluorescence both in solutions and in the crystalline state.

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