Contractile properties of chick embryo muscles in development.

In this paper we report on the observation of two parameters of embryonic muscles which show the functional activity of myofibrillar ATPase activity of embryonic muscles and superprecipitation (SP) of natural actomyosin. Our results indicate that, during the embryonic period, the myofibrillar ATPase activity and the SP of actomyosin significantly increased, the rate of this increase being different for leg and breast muscles.

[ATPase activity and the contractile capacity of the muscle tissue in chick embryos during development].

The value of ATPase activity of the myofibril preparations and the value and duration of actomyosin superprecipitation were estimated for different muscles during the chick embryonic development. The ATPase level increases during embryogenesis 4.5-fold, in the leg muscle this change takes place distinctly earlier than in the leg muscle.

[Myosin isoforms of skeletal muscles in development].

The latest data are reviewed concerning identification of myosin from the skeletal muscle during embryonic and postnatal development in vertebrates. The data are given on the composition of light subunits and specificity of heavy chains of the early isoforms obtained by electrophoresis, peptide mapping, DNA-RNA hybridization, as well as immunological methods with poly-and monoclonals. The substitution of embryonic heavy chains by neonatal and definitive ones is discussed.

Contraction induced by antibodies to paramyosin in glycerinated fibers of Barnacle giant muscle in an ATP-deficient medium: a possible function of paramyosin.

Glycerinated giant muscle fibers of the barnacle Balanus rostratus in an ATP-deficient solution respond to antibodies to paramyosin (aPM) by an isometric tension development followed by an immediate spontaneous relaxation. The aPM presence does not affect the subsequent contraction and relaxation of the fibers in suitable ATP-containing media. The effects of ATP and aPM present together in a contracting medium are additive.

[The paramyosin function in glycerinated muscle fibers during blocking with antibodies of its contacts with structural proteins].

Antibodies to paramyosin (APM) induce a partial decrease of the isometric tension in glycerinated fibres of the Anodonta cygnea catch muscle in the presence of ATP and Ca2+; the myofibrillar Mg2+ ATPase increases concomitantly. Assumedly paramyosin inhibits the cross-bridges unlocking, retaining them mechanically in a locked state. The fibres of barnacle giant muscle in an ATP deficient solution respond to APM by transient isometric tension development.