scholarly journals Contractile System

2020 ◽  
Author(s):  
Keyword(s):  
Contractile System

scholarly journals Calcium sensitivity of the contractile system and phosphorylation of troponin in hyperpermeable cardiac cells.

1980 ◽  
Vol 75 (3) ◽  
pp. 271-282 ◽  
Author(s):  
L Mope ◽  
G B McClellan ◽  
S Winegrad
Keyword(s):  
Cyclic Nucleotides ◽  
Polyacrylamide Gel Electrophoresis ◽  
Calcium Sensitivity ◽  
Ventricular Myocardium ◽  
Cardiac Cells ◽  
Contractile System ◽  
Maximum Activation ◽  
Nonionic Detergent ◽  
Inhibitory Subunit Of Troponin ◽  
Ca Sensitivity

Bundles of cells from rat right ventricular myocardium were made "hyperpermeable" by an overnight soak in 10 mM EGTA (McClellan and Winegrad. 1978. J. Gen. Physiol. 72:737-764). In this preparation the cytoplasmic concentration of Ca++ and ATP could be controlled while sarcolemmal receptors and enzymes were retained. The Ca sensitivity of the tissues (as indicated by the pCa for 50% maximum activation) was altered to different extents in the presence of [32Pgamma]ATP by treatment with cyclic nucleotides, catecholamines, or a low concentration of nonionic detergent. The proteins of the tissue were then isolated by SDS-polyacrylamide gel electrophoresis, and the identity of 32P-labeled proteins was determined. The Ca sensitivity is inversely related to the relative amount of 32P incorporated into the inhibitory subunit of troponin (TNI). Extrapolation of the relation to the lowest Ca sensitivity observed gives a stoichiometry of about 0.8 mol PO4 per mol TNI. These results support the hypothesis that Ca sensitivity of cardiac myofibrils is regulated by a phosphrylation of TNI that is stimulated by cyclic AMP (cAMP) and inhibited by cGMP.

CONTROL OF CELLULAR CONTRACTION BY CALCIUM IN VORTICELLA

1994 ◽  
Vol 189 (1) ◽  
pp. 163-177 ◽  
Author(s):  
K Katoh ◽  
Y Naitoh
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Body ◽  
Ruthenium Red ◽  
Measurable Effect ◽  
External Application ◽  
Sustained Contraction ◽  
Intracellular Injection ◽  
Contractile System ◽  
Triton X

1. Vorticella extracted with Triton X-100 contracted (i.e. the cell body shrank and the stalk coiled) when the external Ca2+ concentration was raised. The degree of contraction increased with increasing Ca2+ concentration. 2. The threshold Ca2+ concentration for shrinkage of the cell body was identical with that for coiling of the stalk in Vorticella extracted with Triton X-100. 3. Living Vorticella showed a graded shrinkage of the cell body when Ca2+ buffer was injected into the cell body, while the stalk showed coiling of an all-or-nothing type. The degree of shrinkage of the cell body increased with increasing free Ca2+ concentration of the buffer. 4. Living Vorticella showed a sustained contraction in response to external application or intracellular injection of caffeine. The effect of caffeine was inhibited by intracellular injection of procaine or Ruthenium Red. 5. Vorticella injected with Ruthenium Red showed graded shrinkage of the cell body as well as graded coiling of the stalk when Ca2+ buffer was injected into the cell body. 6. Caffeine, procaine and Ruthenium Red had no measurable effect on Ca2+-activated contraction in Vorticella extracted with Triton X-100. 7. It is assumed that regenerative liberation of Ca2+ from the endoplasmic reticulum and/or membranous tubules in the contractile system (Ca2+-induced Ca2+ release) is responsible for evoking contraction of an all-or-nothing type following stimulation in living Vorticella.

The effects of Acute and Chronic β-Adrenoceptor Blockade on the Myofibrillar Contractile System in the Dog Heart

1984 ◽  
Vol 67 (2) ◽  
pp. 259-267 ◽  
Author(s):  
M. K. Davies ◽  
P. Cummins ◽  
W. A. Littler
Keyword(s):  
Calcium Sensitivity ◽  
Maximal Activity ◽  
Biopsy Specimens ◽  
Contractile System ◽  
Chronic Therapy ◽  
Before And After ◽  
Adaptive Effect ◽  
Electrophoretic Techniques ◽  
Myocardial Contractile ◽  
And Function

1. Electrophoretic and enzyme techniques have been used to study the structure and function of the contractile protein system in the myocardium of dogs before and after β-adrenoceptor blockade. Animals were examined after acute β-adrenoceptor blockade by using intravenous atenolol (0.2 mg/kg) and following chronic therapy with oral atenolol (100 mg twice daily) for a mean period of 106 days. 2. Two-dimensional polyacrylamide-gel electrophoretic techniques were used to examine the myocardial contractile and regulatory proteins present in endomyocardial biopsy specimens obtained after acute and chronic β-adrenoceptor blockade. No differences in charge, molecular weight or the relative proportions of actin, myosin light chains, tropomyosin or troponin-C were seen after either acute or chronic β-adrenoceptor blockade. 3. The maximal activity and calcium sensitivity of the myofibrillar adenosine triphosphatase (ATPase) was also unchanged after acute and chronic atenolol therapy. 4. It is concluded that β-adrenoceptor blockade has no significant adaptive effect on the structural or functional properties of the myofibril.

scholarly journals Developmental Changes in the Contractile System of the Mesenteric Small Artery of Rabbit

1997 ◽  
Vol 41 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Toshio Nakanishi ◽  
Hong Gu ◽  
Kazuhiko Abe ◽  
Kazuo Momma
Keyword(s):  
Developmental Changes ◽  
Small Artery ◽  
Contractile System

Localization of actin in the Tetrahymena basal body-cage complex

1992 ◽  
Vol 103 (3) ◽  
pp. 629-641 ◽  
Author(s):  
J.G. Hoey ◽  
R.H. Gavin
Keyword(s):  
Basal Body ◽  
Specific Binding ◽  
Ultrastructural Level ◽  
Basal Bodies ◽  
Muscle Actin ◽  
Cage Complex ◽  
Contractile System ◽  
Chicken Muscle ◽  
Filament Bundles

In the ciliate cytoskeleton, basal bodies are contained within separate, filamentous cages which are closely associated with basal body microtubules. We have used two polyclonal anti-actin antibodies to localize actin within the basal body-cage complex of Tetrahymena. An antiserum against a Tetrahymena oral apparatus fraction enriched for basal body proteins was produced in rabbits. Agarose-linked chicken muscle actin was used to affinity-purify anti-Tetrahymena actin antibodies from the anti-oral apparatus antiserum. Agarose-linked chicken muscle actin was used to affinity-purify anti-chicken muscle actin antibodies from a commercially available antiserum against chicken muscle actin. Both affinity-purified antibodies were monospecific for Tetrahymena actin on immunoblots containing total oral apparatus protein. The anti-actin antibodies were localized to both somatic and oral basal bodies in Tetrahymena by immunofluorescence microscopy. At the ultrastructural level with the immunogold technique, these antibodies labeled actin epitopes in four distinct regions of the basal body-cage complex: (a) basal body walls, (b) basal plate filaments, (c) proximal-end filaments and (d) cage wall filaments. In addition, the antibody labeled filament bundles that interconnect groups of basal bodies (membranelles) within the oral apparatus. Identical labeling patterns were observed with basal bodies in the isolated oral apparatus, basal bodies in the in situ oral apparatus and somatic basal bodies in situ. Quantitative analysis of gold particle distribution was used to demonstrate the specificity of the antibodies for the basal body-cage complex and to show that non-specific binding of the antibodies was negligible. Preadsorption of the antibody with muscle actin effectively eliminated the capacity of the antibody to bind to proteins on immunoblots and to basal body structures with the immunogold labeling technique. These results provide evidence for actin in the basal body-cage complex and raise the possibility of a contractile system associated with basal bodies.

Effects of ischemia on sarcoplasmic reticulum and contractile myofilament activity in human myocardium

1993 ◽  
Vol 265 (4) ◽  
pp. H1334-H1341 ◽  
Author(s):  
G. B. Luciani ◽  
A. D'Agnolo ◽  
A. Mazzucco ◽  
V. Gallucci ◽  
G. Salviati
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Heart Surgery ◽  
Open Heart Surgery ◽  
Isometric Tension ◽  
Hill Coefficient ◽  
Calmodulin Antagonist ◽  
Contractile System ◽  
Cardiac Fiber ◽  
And Control

The effects of global ischemia on the contractile system and on sarcoplasmic reticulum (SR) function were studied by measuring the isometric tension and the SR Ca2+ release activity of chemically skinned cardiac fiber preparations from seven patients undergoing open-heart surgery. Ten minutes of ischemia caused 1) a decrease in the myofilament sensitivity to Ca2+ (expected Ca2+ concentration giving half-maximal tension; from 0.69 +/- 0.04 to 1.38 +/- 0.06 microM, n = 7) and in the cooperativity index (Hill coefficient; from 2.61 +/- 0.45 to 0.92 +/- 0.15, n = 7), 2) a decrease in myosin light chain phosphorylation, and 3) a 300% increase in the threshold caffeine concentration for SR Ca2+ efflux channel activation, with a 30% reduction in the rate of Ca2+ release by caffeine at threshold concentrations and a 23% reduction in the rate of release by 20 mM caffeine. After preincubation with 5 microM trifluoperazine, a calmodulin antagonist, the caffeine threshold of ischemic and control cardiac muscle became comparable. Most changes were reversed by reperfusion, while the caffeine threshold was still two times greater than control. These results indicate that ischemia caused alterations of the cardiac muscle contractile apparatus and the SR that were reversed only after reperfusion.

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