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[The conduction system secretes unique isoforms of cardiac myosin].Il tessuto di conduzione esprime isoforme uniche di miosina cardiaca.
No full textAbstract in Inglese, non disponibil
A NOVEL TYPE OF CARDIAC MYOSIN IS EXCLUSIVELY EXPRESSED IN NODAL CONDUCTION TISSUE OF THE MAMMALIAN HEART
No full textCARDIAC MYOSINS - DISTRIBUTION OF MYOSIN HEAVY-CHAIN ISOFORMS IN ORDINARY MYOCARDIUM AND CONDUCTION TISSUE
No full textMyosin changes in hypertrophied human atrial and ventricular myocardium. A correlated immunofluorescence and quantitative immunochemical study on serial cryosections.
No full textTwo antigenically distinct types of myosin heavy chain, referred to as alpha and beta, have been identified in autoptic and bioptic specimens of human heart using specific antimyosin antibodies. By immunofluorescence heavy chain alpha was present in all atrial myocytes and in a variable number of ventricular myocytes. Heavy chain beta was present in all ventricular myocytes and in a number of atrial myocytes. Ventricular hypertrophy in patients with aortic stenosis, systemic hypertension or tetralogy of Fallot was characterized by an almost complete absence of fibres reactive with anti-alpha. A striking decrease in alpha chain reactivity and a parallel increase in beta chain reactivity was apparent in the hypertrophied left atria of patients with mitral stenosis. To quantify these myosin changes a novel procedure was developed whereby myosin was extracted from single cryosections serial to those processed for immunofluorescence and the relative amount of alpha and beta heavy chain was determined by enzyme immunoassay. Heavy chain alpha was less than 5% in most normal ventricular specimens and disappeared completely under the effect of pressure overload. On the other hand heavy chain beta was generally undetectable in the left atrial myocardium but increased up to 90% in biopsies of hypertrophied atria
Cardiac troponin T in developing, regenerating and denervated rat skeletal muscle.
No full textFetal rat skeletal muscles express a troponin T (TnT) isoform similar to the TnT
isoform expressed in the embryonic heart with respect to electrophoretic mobility
and immunoreactivity with cardiac TnT-specific monoclonal antibodies.
Immunoblotting analyses reveal that both the embryonic and the adult isoforms of
cardiac TnT are transiently expressed during the neonatal stages. In addition,
other TnT species, different from both cardiac TnTs and from the TnT isoforms
expressed in adult muscles, are present in skeletal muscles during the first two
postnatal weeks. By immunocytochemistry, cardiac TnT is detectable at the somitic
stage and throughout embryonic and fetal development, and disappears during the
first weeks after birth, persisting exclusively in the bag fibers of the muscle
spindles. Cardiac TnT is re-expressed in regenerating muscle fibers following a
cold injury and in mature muscle fibers after denervation. Developmental
regulation of this TnT variant is not coordinated with that of the embryonic
myosin heavy chain with respect to timing of disappearance and cellular
distribution. No obligatory correlation between the two proteins is likewise
found in regenerating and denervated muscles
Troponin I switching in the developing heart.
Full text linkMonoclonal antibodies identify two distinct isoforms of troponin I in rat cardiac muscle, one predominant in the embryonic and fetal heart and one predominant in the adult heart. The two isoforms can be resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with apparent molecular weights of 27,000 and 31,500, respectively. The adult isoform is specifically recognized by a monoclonal antibody that is unreactive with the embryonic variant, while two other monoclonal antibodies recognize both isoforms. A monoclonal antibody to cardiac troponin T was used to isolate by affinity chromatography the troponin complex from adult and neonatal rat heart. Affinity purified troponin from neonatal heart was found to contain both the embryonic and adult isoforms of troponin I. Comparative immunoblotting analysis with different muscle tissues shows that embryonic troponin I is identical with respect to electrophoretic mobility and pattern of immunoreactivity to the major troponin I isoform found in adult slow skeletal muscle. Troponin I switching may be implicated in developmental changes involving Ca2+ and pH sensitivity of the contractile system and response to beta-adrenergic stimulation
IDENTIFICATION OF TRIADIN AND OF HISTIDINE-RICH CA2+-BINDING PROTEIN AS SUBSTRATES OF 60-KDA CALMODULIN-DEPENDENT PROTEIN- KINASE IN JUNCTIONAL TERMINAL CISTERNAE OF SARCOPLASMIC- RETICULUM OF RABBIT FAST MUSCLE
No full textThe endogenous calmodulin-protein kinase system of sarcoplasmic reticulum terminal cisternae of rabbit fast-twitch muscle was studied. Investigation of a single Ca2+-channel in terminal cisternae fused to planar lipid bilayers demonstrated that the endogenous kinase inhibits the channel, although it remained unclear whether the phosphorylation sites are on the channel protein or on other junctional sarcoplasmic reticulum specific proteins [Hain et al., (1994) Biophys. J. 67, 1823-1833]. Our results, which show that two junctional sarcoplasmic reticulum specific proteins,i.e., triadin and histidine-rich, Ca2+-binding protein, but not the ryanodine receptor/Ca2+-channel protein, are phosphorylated by membrane-bound 60 kDa protein kinase, seem to be able to resolve this ambiguity. Furthermore,such aprobably specific protein isoform of calmodulin-protein kinase, by its substrate specificity and exposure to the cytoplasmic side of terminal cisternae at the junctional membrane domain and based on protease sensitivity, also seems to possess some of the potential requirements for a regulatory role in the functional state of the Ca2+-channel
DIFFERENTIATION OF FIBER TYPES IN RAT SKELETAL-MUSCLE VISUALIZED WITH MONOCLONAL ANTIMYOSIN ANTIBODIES
No full textAn embryonic-like myosin heavy chain is transiently expressed in nodal conduction tissue of the rat heart.
No full textIn the bovine nodal conduction tissue we have described the existence of a novel
cardiac myosin isoform, immunologically related to the myosin types expressed
during skeletal muscle development. Using different monoclonal antibodies
specific for the embryonic and the neonatal skeletal myosin heavy chain types we
investigated the myosin composition of the rat sino-atrial and atrio-ventricular
nodes. We find that nodal conduction tissue fibers of the rat heart contain a
distinct cardiac myosin isoform antigenically similar to the skeletal embryonic
myosin heavy chain. The expression of this myosin isoform in nodal tissue appears
to be developmentally regulated and partially controlled by thyroid hormone.
Reactive cardiac fibers were detected in the nodal regions only during fetal
development and a few days after birth, whereas very rare labelled fibers could
be observed in the adult nodes. This myosin type does not represent a primordial
cardiac myosin isoform since it was not detected in the embryonic heart before
13.5 days of gestation. When congenital hypothyroidism was induced in rats, the
post-natal disappearance of reactive fibers in the nodal regions was delayed. On
the other hand, hypothyroidism induced in the adult rats did not change the
number of the reactive nodal fibers with respect to the euthyroid hearts
Embryonic myosin heavy chain as a differentiation marker of developing human skeletal muscle and rhabdomyosarcoma. A monoclonal antibody study.
No full textHybridoma cell lines were obtained from the fusion of NS-O myeloma cells with
spleen cells of mice immunized with bovine fetal skeletal myosin. A stable
hybridoma clone, BF-G6, produced immunoglobulin G1 k antibodies reacting
specifically with embryonic-type myosin heavy chains present in fetal but not in
neonatal or adult human skeletal muscle, as determined by enzyme immunoassay and
immunoblot analysis. Fetal but not adult skeletal muscle fibers were stained by
this monoclonal antibody in indirect immunofluorescence assays; smooth muscle
cells and cardiac muscle cells, as well as non-muscle cells were also unreactive.
Solid tumors of infants and children were tested for reactivity with BF-G6 by
immunofluorescence and immunoperoxidase staining. Embryonic myosin heavy chain
was expressed in rhabdomyosarcomas but not in other types of tumor, except for
Wilms' tumor. Rhabdomyosarcoma cells isolated from a bone marrow metastasis and
grown in vitro for several months were also labelled by BF-G6. Embryonic myosin
heavy chain can thus be used as a specific differentiation marker of normal and
neoplastic skeletal muscle tissue
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