Role of myosin phosphorylation in contractility of a platelet aggregate

1985 ◽  
Vol 249 (3) ◽  
pp. C297-C303 ◽  
Author(s):  
M. E. Bromberg ◽  
R. W. Sevy ◽  
J. L. Daniel ◽  
L. Salganicoff
Keyword(s):  
Steady State ◽  
Light Chain ◽  
Myosin Phosphorylation ◽  
Nonmuscle Cells ◽  
Platelet Aggregate ◽  
Steady State Levels ◽  
State Contraction ◽  
The Relationship ◽  
Dose Dependent

The relationship between tension and myosin 20,000-Da light chain phosphorylation in intact nonmuscle cells was investigated using a preparation of thrombin-activated, irreversibly aggregated platelets known as the platelet strip. Steady-state levels of tension generated by the platelet strip were found to be linearly related to the level of myosin phosphorylation. This relationship was observed during dose-dependent relaxation induced by the adenylate cyclase activators prostaglandin (PG) E1 and PGI2, and during contraction induced by ADP, epinephrine, and the prostaglandin endoperoxide analogue U-46619, which did not appreciably alter the basal level of adenosine 3',5'-cyclic monophosphate in the preparation. The fully relaxed platelet strip, in the absence of external Ca2+, was associated with a level of 12% light chain phosphorylation, which increased to 72% on maximal contraction. During both relaxation and contraction, changes in myosin phosphorylation were also found to precede or coincide with tension changes. Furthermore, steady-state contraction induced by ADP was associated with a maintained elevation in the level of myosin phosphorylation. These results support the concept that myosin phosphorylation is an important regulatory mechanism for contractility in platelets.

scholarly journals The critical role of T cells in glucocorticoid-induced osteoporosis

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Lin Song ◽  
Lijuan Cao ◽  
Rui Liu ◽  
Hui Ma ◽  
Yanan Li ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
Steady State ◽  
Side Effects ◽  
Critical Role ◽  
Wild Type ◽  
Receptor Activator ◽  
Steady State Levels ◽  
Induced Apoptosis

AbstractGlucocorticoids (GC) are widely used clinically, despite the presence of significant side effects, including glucocorticoid-induced osteoporosis (GIOP). While GC are believed to act directly on osteoblasts and osteoclasts to promote osteoporosis, the detailed underlying molecular mechanism of GC-induced osteoporosis is still not fully elucidated. Here, we show that lymphocytes play a pivotal role in regulating GC-induced osteoporosis. We show that GIOP could not be induced in SCID mice that lack T cells, but it could be re-established by adoptive transfer of splenic T cells from wild-type mice. As expected, T cells in the periphery are greatly reduced by GC; instead, they accumulate in the bone marrow where they are protected from GC-induced apoptosis. These bone marrow T cells in GC-treated mice express high steady-state levels of NF-κB receptor activator ligand (RANKL), which promotes the formation and maturation of osteoclasts and induces osteoporosis. Taken together, these findings reveal a critical role for T cells in GIOP.

The Regulatory Role Of Camp In Induction Of Human Platelet Receptor For Fibrinogen

1981 ◽  
Author(s):  
S E Graber ◽  
J Hawiger
Keyword(s):  
Human Platelets ◽  
Membrane Receptor ◽  
Fibrinogen Receptor ◽  
Fibrinogen Binding ◽  
Platelet Receptor ◽  
The Relationship ◽  
Camp Levels ◽  
Dose Dependent ◽  
Stimulation Of

Membrane receptor for fibrinogen plays an essential role in adhesion and aggregation of human platelets by allowing fibrinogen to bridge two or more platelets together. Whereas in normal, unstimulated platelets fibrinogen receptor is not available, it becomes mobilized upon stimulation of platelets with thrombin, ADP, and other stimuli. The mechanism(s) regulating availability of membrane receptor for fibrinogen remains unknown. Following our recent demonstration that prostacyclin (PGI2) prevents mobilization of fibrinogen receptor by thrombin and ADP (Nature 1980, 283,195), we investigated the relationship between cAMP levels and fibrinogen receptor availability. Platelets separated from plasma proteins were briefly exposed to a low thrombin concentration (0.05 U/ml) followed by hirudin to inactivate free thrombin. Binding of 125I-fi- brinogen and cAMP levels were determined in parallel samples. A dose-dependent rise in platelet cAMP levels from 3.3 pM to 10.3 pM/108 platelets in response to PGI2 (3×10-9M - 3×108M) was accompanied by a corresponding inhibition of 125I-fibrinogen binding. The degree of the cAMP increment correlated with binding inhibition (r=0.96). The inhibition of 125I-fibrinogen binding by PGI2 was sustained up to 120 min and was paralleled by a persistent rise in cAMP level. Stimulation of platelet cAMP synthesis “from within” by a ribosylation of the nucleotide regulatory component with subunit A1 of cholera toxin also increased cAMP levels and inhibited fibrinogen receptor mobilization.These results provide evidence that “up and down” regulation of fibrinogen receptor in platelets is linked to changes in cAMP levels induced by different types of adenyl cyclase antagonists and agonists.

cAMP, myosin dephosphorylation, and isometric relaxation of airway smooth muscle

1988 ◽  
Vol 64 (2) ◽  
pp. 705-709 ◽  
Author(s):  
P. de Lanerolle
Keyword(s):  
Smooth Muscle ◽  
Steady State ◽  
Muscle Relaxation ◽  
Fold Increase ◽  
Treatment Results ◽  
Myosin Phosphorylation ◽  
Temporal Relationships ◽  
Steady State Levels ◽  
Two Parameters ◽  
Camp Levels

The temporal relationships among increases in adenosine 3',5'-cyclic monophosphate (cAMP) levels, myosin dephosphorylation, and relaxation were investigated to clarify the mechanisms of airway muscle relaxation. Canine tracheal muscles isometrically contracted (82% of maximum force) with 10(-6) M methacholine were relaxed by adding either 4 x 10(-7) M atropine or 4 x 10(-5) M forskolin. Atropine had no effect on cAMP levels; myosin phosphorylation and force, however, decayed at the same rates and these two parameters returned to their basal pre-methacholine levels within 5 min. Forskolin treatment results in about a 10-fold increase in cAMP levels; myosin phosphorylation and force decayed simultaneously to their respective steady-state levels by 10 min but neither parameter returned to its pre-methacholine level. The addition of forskolin to muscles maximally contracted with 10(-4) M methacholine leads to about a 30-fold increase in cAMP levels. However, there are minimal decreases in myosin phosphorylation and force in these muscles. Thus myosin dephosphorylation appears to be essential for airway muscle relaxation, whereas an increase in cAMP in the absence of myosin dephosphorylation is insufficient to cause relaxation. Moreover, myosin dephosphorylation appears to be a common step in the cAMP-independent and cAMP-dependent mechanisms for airway muscle relaxation.

scholarly journals Role of Human Sec63 in Modulating the Steady-State Levels of Multi-Spanning Membrane Proteins

PLoS ONE ◽  
2012 ◽  
Vol 7 (11) ◽  
pp. e49243 ◽  
Author(s):  
Andreas Mades ◽  
Katherina Gotthardt ◽  
Karin Awe ◽  
Jens Stieler ◽  
Tatjana Döring ◽  
...  
Keyword(s):  
Steady State ◽  
Membrane Proteins ◽  
Steady State Levels

The relationship between the serum free light chain assay and serum immunofixation electrophoresis, and the definition of concordant and discordant free light chain ratios

Blood ◽  
2009 ◽  
Vol 114 (1) ◽  
pp. 38-39 ◽  
Author(s):  
Seema Singhal ◽  
Eric Vickrey ◽  
Jairam Krishnamurthy ◽  
Veerpal Singh ◽  
Sharon Allen ◽  
...  
Keyword(s):  
Light Chain ◽  
Normal Serum ◽  
Free Light Chain ◽  
Serum Free ◽  
Serum Free Light Chain ◽  
Immunofixation Electrophoresis ◽  
Serial Samples ◽  
Definition Of ◽  
The Relationship

Abstract“Stringent” complete remission in myeloma has been defined by a normal serum free light chain ratio (SFLCR) in addition to the standard criteria for CR. 2648 serial samples from 122 IgG or IgA myeloma patients were studied to explore the relationship between SFLCR and serum immunofixation electrophoresis (SIFE). SFLCR was normal in 34% of cases with positive SIFE and abnormal in 66%. SFLCR was normal in 69% of cases with negative SIFE and abnormal in 31%. When evaluated with SIFE as the benchmark, the sensitivity of SFLCR was 66% and specificity was 69%. These findings were unchanged when abnormal SFLCR values were classified as concordant (< 0.26 for λ disease and > 1.65 for κ) or discordant (< 0.26 for κ disease and > 1.65 for λ). Additional studies are required to determine the temporal relationship between SFLCR normalization and paraprotein clearance. Until then, the role of SFLCR in defining response remains controversial.

scholarly journals Cytochrome redox states and respiratory control in mouse and beef heart mitochondria at steady-state levels of hypoxia

2015 ◽  
Vol 119 (10) ◽  
pp. 1210-1218 ◽  
Author(s):  
David K. Harrison ◽  
Mario Fasching ◽  
Mona Fontana-Ayoub ◽  
Erich Gnaiger
Keyword(s):  
Oxygen Consumption ◽  
Steady State ◽  
Cytochrome C ◽  
Respiratory Control ◽  
Low Noise ◽  
Mouse Heart ◽  
Redox States ◽  
Steady State Levels ◽  
Cytochrome Oxidation ◽  
The Relationship

Mitochondrial control of cellular redox states is a fundamental component of cell signaling in the coordination of core energy metabolism and homeostasis during normoxia and hypoxia. We investigated the relationship between cytochrome redox states and mitochondrial oxygen consumption at steady-state levels of hypoxia in mitochondria isolated from beef and mouse heart (BHImt, MHImt), comparing two species with different cardiac dynamics and local oxygen demands. A low-noise, rapid spectrophotometric system using visible light for the measurement of cytochrome redox states was combined with high-resolution respirometry. Monophasic hyperbolic relationships were observed between oxygen consumption, JO2, and oxygen partial pressure, Po2, within the range <1.1 kPa (8.3 mmHg; 13 μM). P50 j (Po2 at 0.5· Jmax) was 0.015 ± 0.0004 and 0.021 ± 0.003 kPa (0.11 and 0.16 mmHg) for BHImt and MHImt, respectively. Maximum oxygen consumption, Jmax, was measured at saturating ADP levels (OXPHOS capacity) with Complex I-linked substrate supply. Redox states of cytochromes aa3 and c were biphasic hyperbolic functions of Po2. The relationship between cytochrome oxidation state and oxygen consumption revealed a separation of distinct phases from mild to severe and deep hypoxia. When cytochrome c oxidation increased from fully reduced to 45% oxidized at 0.1 Jmax, Po2 was as low as 0.002 kPa (0.02 μM), and trace amounts of oxygen are sufficient to partially oxidize the cytochromes. At higher Po2 under severe hypoxia, respiration increases steeply, whereas redox changes are small. Under mild hypoxia, the steep slope of oxidation of cytochrome c when flux remains more stable represents a cushioning mechanism that helps to maintain respiration high at the onset of hypoxia.

Differential inhibition of inflammatory cytokine release from cultured alveolar macrophages from smokers and non smokers by No2

1997 ◽  
Vol 16 (10) ◽  
pp. 577-588 ◽  
Author(s):  
Tiziana Dandrea ◽  
Ba Tu ◽  
Anders Blomberg ◽  
Thomas Sandström ◽  
Magnus Sköld ◽  
...  
Keyword(s):  
Steady State ◽  
Alveolar Macrophages ◽  
Exposure Model ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Tnf Α ◽  
Dependent Inhibition ◽  
Steady State Levels ◽  
Dose Dependent

Human alveolar macrophages (AMs) obtained from smokers and non-smokers by bronchoalveolar lavage (BAL) were subjected to various concentrations of NO2 in an inverted monolayer exposure model. Culture super natants were collected 4 h after the exposure and assayed for secreted TNF-α, IL-1β, IL-8 and MIP-1α. The steady state levels of the mRNAs for these cytokines were also analysed in the cells. The adherence of BAL cells to plastic prior to exposure to the gas elevated the steady state mRNA levels of all four cytokines tested in smoker's cells and that of TNF-α and IL-1β, but not IL-8 (MIP-1α not tested), in non-smoker's cells. Interestingly, adherent cells from non-smokers released circa 15-, 3-,1.5- and 3-fold the amounts of IL-1β, IL-8, TNF-α and MIP-1α, respectively, than smoker's cells during control incubation or exposure to air. A 20 min exposure to NO2 (5 or 20 p.p.m.) did not increase the secretion of any of the cytokines from either cell type. In contrast, NO2 caused a concentration- dependent inhibition of the secretion of all cytokines except IL-1β from smoker's cells. Additionally, NO2 greatly diminished the release of all cytokines in response to further treatment with lipopolysaccharide (LPS). In contrast, only the secretion of TNF-α from non-smoker's cells was inhibited by the gas in a concentration- dependent manner, whilst LPS-induced secretion of the cytokines was not affected by the gas. The steady state levels of the respective mRNAs for each of the cytokines were not significantly affected in smoker's cells by exposure to NO2, except for a negative, dose-dependent trend in the case of TNF-α. Nitrogen dioxide also failed to elevate the levels of the mRNAs in non-smoker's cells but, again, tended to diminish the levels, particularly of IL-1β mRNA. However, exposure to the gas inhibited LPS- induced accumulation of cytokine mRNAs in smoker's cells only. The data suggest that macrophage-derived cytokine mediators of the sepsis response may not play a role in the generation of NO2-induced inflammation in the human lung. Conversely, the gas seems to non-specifically inhibit the release and/or production of cytokines, particularly from smoker's cells, at the post-transcrip tional level, and impairs the ability of the cells to increase the transcription and release of the cytokines in response to bacterial LPS. The fact that NO2 seriously impaired the already diminished capacity of smoker's cells to release several important pro-inflammatory cytokines, both under control conditions and in response to LPS, strongly suggest that the inhalation of NO2 in cigarette smoke may contribute to impairing host defence against infection in the lung.

scholarly journals The Role of Autophagy in Osteoarthritis

2020 ◽  
Vol 8 ◽  
Author(s):  
Ran Duan ◽  
Hui Xie ◽  
Zheng-Zhao Liu
Keyword(s):  
Steady State ◽  
Energy Metabolism ◽  
Pathological Changes ◽  
Cell Type ◽  
Normal Cartilage ◽  
Intracellular Degradation ◽  
New Ideas ◽  
Autophagy Pathway ◽  
The Relationship

Chondrocytes are the only cell type in normal cartilage. The pathological changes of osteoarthritis (OA) mostly revolve around the apoptosis and dysfunction of chondrocytes. Autophagy, as an intracellular degradation system that maintains the steady state of energy metabolism in cells, has been shown to restore the function of damaged chondrocytes, alleviating the occurrence and progression of OA. In this review, we explored the relationship between autophagy and OA and the key molecules of autophagy pathway that regulate the progression of OA, providing new ideas for OA treatment by targeting autophagy.

scholarly journals Role of STE genes in the mating factor signaling pathway mediated by GPA1 in Saccharomyces cerevisiae.

1988 ◽  
Vol 8 (9) ◽  
pp. 3777-3783 ◽  
Author(s):  
N Nakayama ◽  
Y Kaziro ◽  
K Arai ◽  
K Matsumoto
Keyword(s):  
Steady State ◽  
Signaling Pathway ◽  
State Level ◽  
G1 Arrest ◽  
Gene Products ◽  
Mating Efficiency ◽  
Protein Functions ◽  
Steady State Levels ◽  
Mating Factor

The ste mutants (ste2, ste4, ste5, ste7, ste11, and ste12) are insensitive to mating factors and are, therefore, sterile. Roles of the STE gene products in the GPA1-mediated mating factor signaling pathway were studied by using ste gpa1 double mutants. Mating efficiency of a ste2 mutant defective in the alpha-factor receptor increased 1,000-fold in a gpa1 background, while G1 arrest and aberrant morphology (shmoo) caused by gpa1 were not suppressed by ste2. Furthermore, the steady-state level of the FUS1 transcript, which normally increases in response to mating factors, was also elevated when the GPA1 function was impaired. These results suggest that the GPA1 protein functions downstream of the STE2 receptor. Conversely, the sterility of ste4, ste5, ste7, ste11, and ste12 mutants was not suppressed by gpa1, but the lethal phenotype of gpa1 was suppressed by these ste mutations. Northern (RNA) blotting analysis revealed that the ste7, ste11, and ste12 mutations caused reductions of 50 to 70% in the steady-state levels of the GPA1 transcript, while ste4 had a slight effect and ste5 had no effect. This implies that the suppression by ste7, ste11, and ste12 could be due to reduced syntheses of additional components, including an effector, and that suppression by ste4 and ste5 may result from direct effects on the signaling pathway. The STE4, STE5, STE7, STE11, and STE12 products, therefore, appear to specify components of the signal transduction machinery, directly or indirectly, which function together with or downstream of GPA1.

Cyclic nucleotide dependent relaxation in vascular smooth muscle

1994 ◽  
Vol 72 (11) ◽  
pp. 1380-1385 ◽  
Author(s):  
Nancy L. McDaniel ◽  
Christopher M. Rembold ◽  
Richard A. Murphy
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Light Chain ◽  
Cyclic Nucleotide ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Regulatory Light Chain ◽  
Myosin Phosphorylation ◽  
Cross Bridge ◽  
The Relationship

Although not without controversy, the mechanisms inducing contraction of vascular smooth muscle are relatively well defined. There is a stimulus-induced increase in myoplasmic [Ca2+] with activation of myosin light chain kinase by the Ca2+–calmodulin complex, phosphorylation of the 20-kDa regulatory light chain of myosin, with subsequent cross-bridge cycling and force development. Ca2+-dependent phosphorylation of the myosin regulatory light chain appears to be the primary mechanism responsible for regulating stress in vascular smooth muscle. The relationship between myoplasmic [Ca2+] and myosin phosphorylation (i.e., the calcium sensitivity of phosphorylation) is regulated. It is higher with agonist stimulation than in tissues depolarized with high potassium solutions or after skinning procedures. The relationship between myosin phosphorylation and stress appears to be invariant with physiologic stimulation. This suggests that cross-bridge phosphorylation normally determines contraction. The mechanisms of relaxation are less well defined. In the most simple scheme, reduction of myoplasmic [Ca2+] with a fall in myosin light chain kinase activity would suffice to account for dephosphorylation of the regulatory light chain and relaxation. However, other mechanisms have been implicated in cyclic nucleotide dependent relaxation in vascular and other smooth muscle tissues. The current hypotheses of the mechanism of cyclic nucleotide dependent relaxation in vascular smooth muscle are reviewed.Key words: calcium, cyclic adenosine 3′,5′-monophosphate, cyclic guanosine 3′,5′-monophosphate, myosin light chain phosphorylation, vasodilation.

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