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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Intact frog, mouse and finch hearts were quick-frozen on a liquid He-cooled copper block. Adjacent frozen samples from the same heart were processed by freeze-substitution (followed by embedding and thin sectioning), freeze-fracture/etch (followed by platinum/carbon replication) and frozen sectioning (followed by freeze-drying), respectively, and examined with the electron microscope for fidelity of reproducing the in vivo state of heart muscle geometry, especially that of the narrow intercellular clefts between frog cardiac muscle cells. It was concluded that quick-freezing followed by the above procedures accomplishes that and that, therefore, narrow intercellular clefts are an invariant feature of the normal anatomy of frog cardiac muscle, which must be considered in physiological experiments. The methodology showed that quick-freezing through the epicardial surface is capable of producing superb cryopreservation for ultrathin cryosections, as well.
J Mol Cell Cardiol 1988 Apr
PMID:Cardiac muscle following quick-freezing: preservation of in vivo ultrastructure and geometry with special emphasis on intercellular clefts in the intact frog heart. 326 68

P19 embryonal carcinoma (EC) cells are multipotential stem cells which can be induced to differentiate in vitro into a variety of cell types, including cardiac muscle cells. A cloned human cardiac actin (CH-actin) gene was transfected into P19 cells, and stable transformants were isolated. Low levels of CH-actin mRNA were present in transformed EC cells, but a marked increase in the level of CH-actin mRNA was found as these cells differentiated into cardiac muscle. The accumulation of CH-actin mRNA paralleled that of the endogenous mouse cardiac actin mRNA. A chimeric gene, which consisted of the CH-actin promoter linked to the herpes simplex virus thymidine kinase coding region, was constructed and transfected into P19 cells. In these transformants, the thymidine kinase protein was located almost exclusively in cardiac muscle cells and was generally not detectable in EC or other nonmuscle cells. These results suggest that the transfected CH-actin promoter functions in the appropriate developmental and tissue-specific manner during the differentiation of multipotential EC cells in culture.
Mol Cell Biol 1988 Jan
PMID:Regulated expression of a transfected human cardiac actin gene during differentiation of multipotential murine embryonal carcinoma cells. 327 77

Ca research in the heart was historically surveyed. First, reference was made to the development of the concept involving Ca2+ in the contraction of skeletal muscle. This was followed by an overview of studies on Ca regulation in cardiac muscle. Emphasis was laid on the fact that the "Ca era" today originated from Ca research in muscle initiated by Ringer and expanded by Heilbrunn.
J Mol Cell Cardiol 1987 May
PMID:Ca2+ in the heart. 330 64

We isolated a cDNA clone from the tumorigenic human fibroblast cell line HuT-14 that contains the entire protein coding region of tropomyosin isoform 3 (Tm3) and 781 base pairs of 5'- and 3'-untranslated sequences. Tm3, despite its apparent smaller molecular weight than Tm1 in two-dimensional gels, has the same peptide length as Tm1 (284 amino acids) and shares 83% homology with Tm1. Tm3 cDNA hybridized to an abundant mRNA of 1.3 kilobases in fetal muscle and cardiac muscle, suggesting that Tm3 is related to an alpha fast-tropomyosin. The first 188 amino acids of Tm3 are identical to those of rat or rabbit skeletal muscle alpha-tropomyosin, and the last 71 amino acids differ from those of rat smooth muscle alpha-tropomyosin by only 1 residue. Tm3 therefore appears to be encoded by the same gene that encodes the fast skeletal muscle alpha-tropomyosin and the smooth muscle alpha-tropomyosin via an alternative RNA-splicing mechanism. In contrast to Tm4 and Tm5, Tm3 has a small gene family, with, at best, only one pseudogene.
Mol Cell Biol 1988 Jan
PMID:Cloning and characterization of a cDNA encoding transformation-sensitive tropomyosin isoform 3 from tumorigenic human fibroblasts. 333 57

Cardiac muscle cell injury may be related to metabolic changes associated with a rise in intracellular calcium. The mechanisms by which an elevated Ca2+ can cause injury are uncertain, but injury could occur by activation of any one or several calcium-dependent processes. To examine whether the process is mediated by prostaglandins (PG) or leukotriens (LT), we measured the successive release of creatine kinase (CK), PGE2 and LTC4 that have been reported to induce the cell injury via the arachidonic acid cascade, to the culture medium from myocardial cells under hypoxic or aerobic conditions. CK release, a biochemical marker of muscle cell necrosis, was first detected in the medium of hypoxic cultures at 9 h. Both PGE2 and LTC4 production and release were delayed, being first detected at 12 h after initiating hypoxia treatment. Addition of exogenous PGE2 or LTC4 to the culture medium (1.0 or 10 ng/ml) did not cause any effect on the CK release under aerobic condition. Cyclooxygenase inhibitor, indomethacin (1 X 10(-5) M) or lipoxygenase inhibitor, AA861 (1 X 10(-5) M), reduced the synthesis of PGE2 by 80% or LTC4 by 68% under hypoxia, respectively, but caused no beneficial effect on the CK release. These findings suggest that cardiac muscle cells themselves produce PGE2 and LTC4 after hypoxia and that the production of these compounds merely occurs as a result, but not as a cause of cell injury.
J Mol Cell Cardiol 1987 Jun
PMID:Stimulated synthesis of prostaglandin E2 or leukotrien C4 from myocardial cells is not a cause but a result of their injury under hypoxia. 347 55

The recently described adherens junction-specific 135-kD protein (Volk, T., and B. Geiger, 1984, EMBO (Eur. Mol. Biol. Organ.) J., 3:2249-2260) was localized along cardiac muscle intercalated discs by immunogold labeling of ultrathin frozen sections. Analysis of this labeling indicated that the 135-kD protein, adherens junction-specific cell adhesion molecule (A-CAM), is tightly associated with the plasma membrane unlike vinculin labeling, which was present along the membrane-bound plaques of the fascia adherens. In cultured chick lens cells, A-CAM was associated with Ca2+-dependent junctions that were cleaved upon a decrease of extracellular Ca2+ concentrations to less than or equal to 0.5 mM. In the chelator-separated junction, A-CAM became exposed to exogenously added antibodies or to proteolytic enzymes. Upon addition of trypsin to EGTA-treated cells, A-CAM was cleaved into three major cell-bound antigenic peptides with apparent molecular masses of 78, 60, and 46 kD, suggesting that the extracellular domain of A-CAM has a size greater than or equal to kD. Incubation of electrophoretic gels with 125I-concanavalin A (Con A) indicated that one of the major Con A-binding proteins in chicken lens membranes is a integral of 135-kD glycoprotein that was partially purified on Con A-Sepharose column and identified as A-CAM by immunoblotting. Detergent partitioning assay using Triton X-114 biphasic system was carried out to determine whether A-CAM displays properties of an integral membrane protein. This assay indicated that the intact A-CAM molecule was recovered in the buffer phase but its cell-associated tryptic peptides, which presumably lost a great part of the A-CAM extracellular extension, readily partitioned into the detergent phase. The results obtained in this and in the following paper (Volk, T., and B. Geiger, 1986, J. Cell Biol., 103:1451-1464) strongly suggest that A-CAM is a Ca2+-dependent adherens junction-specific membrane glycoprotein that is involved in intercellular adhesion in these sites.
 ...
PMID:A-CAM: a 135-kD receptor of intercellular adherens junctions. I. Immunoelectron microscopic localization and biochemical studies. 353 54

The interaction of the catalytic subunit of bovine cardiac muscle cAMP-dependent protein kinase with N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide (H-8), the most potent and selective inhibitor toward cyclic nucleotide-dependent protein kinases in the series of isoquinolinesulfonamide derivatives, was studied. The addition of H-8 protected the catalytic subunit of the enzyme in a dose-dependent manner from irreversible inactivation by the ATP analogue p-fluorosulfonylbenzoyl-5'-adenosine (FSBA). The inactivation followed pseudo-first order kinetics and H-8 reduced the steady state constant of inactivation (Ki) without any effect on the first order rate constant (K3). The quantitative binding of H-8 to the enzyme was measured under conditions of thermodynamic equilibrium using a gel filtration method. The catalytic subunit bound approximately 1 mol of drug/mol of protein with apparent half-maximal binding at 1.0 microM drug, whereas the enzyme irreversibly modified by FSBA did not bind the drug, confirming that the enzyme has no site for H-8 in the catalytic subunit other than the active site. The binding studies also showed that H-8 does not require divalent cations such as Mg2+ to bind to the catalytic subunit of the protein kinase. The binding of H-8 to the active site was characterized using FSBA and other affinity labeling reagents which have been postulated to modify residues at or near the active site of the catalytic subunit. H-8 protected the enzyme against inactivation by FSBA and Cibacron Blue F3GA but did not afford any protection against the covalent modification of 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) and 7-chloro-4-nitro-2,1,3-benzoxadiazole (NBD-Cl), suggesting that the binding site of H-8 does not involve the gamma-subsite of the ATP binding site in the catalytic subunit, since DTNB and NBD-Cl are thought to modify the residues complementary to gamma-phosphate of the ATP molecules.
Mol Pharmacol 1987 May
PMID:Specific binding of a novel compound, N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide (H-8) to the active site of cAMP-dependent protein kinase. 357 96

We believe that the weight of present evidence suggests that acute contractile failure in hypoxic or ischaemic cardiac muscle is accompanied by a fall in A but this fall is not the direct cause of the reduced force production. The main established causes of acute contractile failure are the effects of intracellular pH and of Pi accumulation on the contractile proteins and, at a later stage, failure of calcium release. It is worth stressing the role of Pi accumulation both because the effects of Pi have only been recognised relatively recently and because it has a large depressant effect. Pi accumulation is the best candidate to explain the rapid fall of force which occurs during hypoxia and ischaemia when ATP levels are unchanged and before pH changes are substantial.
J Mol Cell Cardiol 1986 Sep
PMID:Is force production in the myocardium directly dependent upon the free energy change of ATP hydrolysis? 378 27

Human cardiac muscle has been studied to determine whether the ratio of cardiac alpha-actin to skeletal alpha-actin varies between the different chambers of the human heart taken from a single individual. Using mRNA dot-blots, and DNA probes specific for the cardiac and skeletal alpha-actin isotypes, we have found that both cardiac and skeletal alpha-actin mRNAs are present and co-expressed throughout the human heart. The pattern of alpha-actin co-expression in the left and right ventricles and in the interventricular septum is approximately the same, with cardiac alpha-actin being the dominant isotype (approx. 80% of total). However, the left atrium has a different relative composition of the two actins, with an even higher level of cardiac alpha-actin expression (95% of total).
J Mol Cell Cardiol 1986 Sep
PMID:Differential co-expression of alpha-actin genes within the human heart. 378 33

Rates of loss of mitochondrial respiratory function were monitored during autolyses of canine myocardial samples pretreated so as to affect tissue pH and/or tissue ATP content prevailing during tissue autolysis. When autolyses occurred under conditions of differing tissue pH, but at nearly identical tissue ATP levels, the rate of loss of mitochondrial function was virtually unchanged suggesting that tissue acidosis in the absence of a concomitant tissue ATP differential had little or no effect upon the rate of progression of mitochondrial damage. In a second comparison, autolyses were carried out at constant tissue pH, but where tissue ATP content differed dramatically. Here, the rate of loss of mitochondrial function was increased markedly suggesting that tissue ATP depletion in the absence of a concomitant tissue pH differential had a major effect upon the rate of loss of mitochondrial function. Thus, of the two parameters studied, tissue ATP content alone was far more important than tissue pH alone in determining the rate of cell membrane damage during ischemia. Finally, autolyses were carried out where both tissue pH and ATP content differed. Here, an even more dramatic increase in the rate of progression of mitochondrial damage occurred suggesting the operation of synergism between tissue ATP depletion and acidosis in promoting cell injury in ischemic cardiac muscle.
J Mol Cell Cardiol 1986 Nov
PMID:Factors affecting the loss of mitochondrial function in autolyzing cardiac muscle. 379 79


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