Localization of human cardiac beta-myosin heavy chain gene (MYH7) to chromosome 14q12 by in situ hybridization.

The genes coding for each human cardiac myosin heavy chain (alpha-MHC and beta-MHC, MYH6 and MYH7, respectively) are tightly linked and the alpha-MHC gene has been assigned to chromosome 14. In order to provide a more precise regional localization, in situ hybridization experiments were carried out using a 3H-labeled probe derived from a beta-MHC genomic clone. The results demonstrated that the human cardiac MHC genes are located within the q12 band of chromosome 14.

Regeneration of cat posterior temporalis muscle in culture.

Cat posterior temporalis muscle has a rapid speed of contraction associated with a unique superfast myosin isoform. Superfast myosin expression appears to be an intrinsic property of the muscle fibres and satellite cells, though in culture they failed to express superfast myosin. We have, therefore, cultured this muscle in a system which had previously been shown to encourage the expression of an adult phenotype.

Immunocytochemical analysis of the perinatal development of cat masseter muscle using anti-myosin antibodies.

The developmental changes in myosin gene expression in the masseter muscle of embryonic and juvenile kittens were examined immunocytochemically using anti-myosin heavy chain antibodies of various specificities. In the mature cat, this muscle contains only two phenotypes, the majority of fibres are superfast, the rest being slow fibres. In foetal tissues, the histological appearance of bundles of myotubes, comprising a large central myotube surrounded by a rosette of smaller myotubes, strongly suggest the existence in the jaw muscle of primary and secondary fibres during development.

Adrenaline increases the rate of cycling of crossbridges in rat cardiac muscle as measured by pseudo-random binary noise-modulated perturbation analysis.

The mechanism of action of adrenaline on cardiac contractility in rat papillary muscles containing V1 and V3 isomyosins was analyzed during barium-activated contractures at 25 degrees C by frequency domain analysis using pseudo-random binary noise-modulated perturbations. The analysis characterizes a frequency (fmin) at which dynamic stiffness of a muscle is a minimum, a parameter that reflects the rate of cycling of crossbridges. We have previously shown that fmin for V1- and V3-containing papillary muscles were 2.

Immunocytochemical and electrophoretic analyses of changes in myosin gene expression in cat posterior temporalis muscle during postnatal development.

Changes in myosin gene expression during the postnatal development of the homogeneously superfast kitten posterior temporalis muscle were examined using immunocytochemical techniques supplemented by pyrophosphate gel electrophoresis and gel electrophoresis-derived enzyme linked immunosorbent assay (GEDELISA) of myosin isoforms. The antibodies used were polyclonals directed against the heavy chains of superfast and foetal myosins and monoclonals against the heavy chains of slow and fast myosins. The fibres of the posterior temporalis in the newborn kitten stained almost uniformly with the anti-foetal myosin antibody and the largest of these fibres stained strongly for superfast myosin.

Immunocytochemical and electrophoretic analyses of changes in myosin gene expression in cat limb fast and slow muscles during postnatal development.

Changes in myosin synthesis during the postnatal development of the fast extensor digitorum longus (EDL) and the slow soleus muscles of the kitten were examined using immunocytochemical techniques supplemented by pyrophosphate gel electrophoresis and gel electrophoresis-derived enzyme linked immunosorbent assay (GEDELISA) of myosin isoforms. The antibodies used were monoclonals against heavy chains of slow and fast myosins and a polyclonal against foetal/embryonic myosin. In both muscles in the newborn kitten, there was a population of more mature fibres which stained strongly for slow but weakly for foetal/embryonic myosin.

Myogenic and neurogenic regulation of myosin gene expression in cat jaw-closing muscles regenerating in fast and slow limb muscle beds.

Immunocytochemical techniques were used to study changes in myosin gene expression during the regeneration of the cat posterior temporalis muscle transplanted into the bed of either the fast extensor digitorum longus (EDL) or the slow soleus muscle. Strips of the posterior temporalis, a homogeneously superfast muscle, were treated with Marcaine and then transplanted into limb muscle beds which had been completely cleared of host muscle fibres. The regenerates were examined 6 to 224 days after surgery.

Sequence diversity of gap junction proteins.

This paper summarizes our understanding of the molecular organization of gap junction proteins. There appear to be overall similarities in the organization of heart and liver junctions in terms of general domains, even though the molecular sizes of the two proteins are quite different. Sequence data on the amino-terminal regions of these two proteins show 43% of the residues to be identical and 25% more to be homologous.

Influence of V1 and V3 isomyosins on the mechanical behaviour of rat papillary muscle as studied by pseudo-random binary noise modulated length perturbations.

Experiments were done on four-week-old rats, containing biochemically verified V1 only, and thyroidectomized adult rats, treated with propylthiouracil, verified to contain V3 only. Contracture tension was induced in isolated papillary muscles either by high potassium solution or 0.5 mmol l-1 Ba2+.

Myosin isoenzymes in single muscle fibres of Xenopus laevis: analysis of five different functional types.

An analysis has been performed of the native myosin isoenzyme composition of isolated skeletal muscle fibres from Xenopus laevis with well-defined isotonic contraction properties. Fast twitch 'white' (type 1) fibres contained three isomyosins; fast twitch 'red' (type 2) fibres showed two major myosin bands with migration velocities very similar to those of the two slower bands in type 1. Slow twitch (type 3) fibres yielded a single, slowly migrating band as did slow tonic (type 5) fibres, whereas the myosin from type 4 (very slow twitch, 'intermediate') fibres migrated with a somewhat higher mobility.

Sexual dimorphism in the Harderian gland proteins of the golden hamster.

SDS polyacrylamide gel electrophoresis of male and female hamster Harderian gland homogenates has shown a clear-cut sexual dimorphism. At least three major proteins present in the male gland are missing from the female gland. Two of the above are associated with the tubular clusters of the male gland while the third seems to be a structural component.

Myosin isoenzymes in fast-twitch and slow-twitch muscles of normal and dystrophic mice.

An analysis of the native myosin isoenzyme composition, myosin light-chain distribution and histochemical profile of fast-twitch and slow-twitch muscles of normal and dystrophic (129 REJ dy/dy) mice has been performed, and the results correlated with the known contractile abnormalities of murine dystrophic muscles. Normal mouse slow-twitch soleus contained two isomyosins (slow myosin, SM and intermediate myosin, IM) which were electrophoretically distinct from the three major isomyosins (FM1, FM2, FM3) of fast-twitch extensor digitorum longus (e.d.

Energetic consequences of thyroid-modulated shifts in ventricular isomyosin distribution in the rat.

Heat production (measured myothermically), force development and isomyosin distribution were measured in left ventricular papillary muscles from adult male rats in three thyroid states: hyperthyroid (T3), euthyroid (C) and hypothyroid (Tx). Rats were rendered hyperthyroid by daily injections of tri-iodothyronine and hypothyroid by radioisotopic thyroidectomy. Papillary muscle performance was measured both for trains of isometric twitches and for brief (2 s) tetani achieved by increasing the Ca2+ concentration and adding caffeine to the bathing solution.

Embryonic and foetal myosins in human skeletal muscle. The presence of foetal myosins in duchenne muscular dystrophy and infantile spinal muscular atrophy.

Recently described techniques for separating myosin isoenzymes have been adapted for analysis of myosins from diseased and developing human skeletal muscle. The method is highly suitable for analysis of human myosins because only 2 - 3 mg of muscle are required for routine analyses. Human embryonic/foetal myosins are electrophoretically distinct from mature skeletal myosins, and are not normally detected beyond the first month of post-natal life, except in premature infants.

Contractile properties and ultrastructure of extensor digitorum longus and soleus muscles in spinal cord transected rats.

The spinal cord of rats 25 days of age was transected at the thoracic level, and the contractile properties as well as the ultrastructure of their extensor digitorum longus (EDL) and soleus muscles was examined. In the normally slow-twitch soleus muscle, the operation produces a marked reduction of contraction time as well as the appearance of other contractile characteristics of a fast-twitch muscle, namely, post-tetanic potentiation and cooling potentiation of the isometric twitch. This operation has little effect on the fast-twitch EDL.

Isomyosins in human type 1 and type 2 skeletal muscle fibres.

Human myosin from different skeletal muscles was analysed in a non-denaturing gel system, and the isoenzyme composition correlated with the histochemical composition of the muscle. Two components (SM1 and SM2) were associated with type 1 (slow-twitch) fibres, and three (FM1, FM2 and FM3) with type 2 (fast-twitch) fibres. Light-chain analysis was performed in sodium dodecyl sulphate/polyacrylamide gels.