Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.13.12.5 (aequorin)
 1,451 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Circular strips from ferret aorta were used to investigate the mechanism of the intrinsic basal tone. 2. Determinations of stiffness using small sinusoidal length changes showed an abolition of both stiffness and force with cooling, but the temperature dependence of the change in active stiffness did not parallel that of force. At temperatures below 22 degrees C there appeared to be a relatively large population of attached, non-force-generating cross-bridges, indicating that separate mechanisms are involved in regulating cross-bridge attachment and the force per cross-bridge. 3. Active intrinsic tone was not affected by removal of extracellular Ca2+ or removal of endothelium. 4. Intracellular ionized Ca2+ concentrations ([Ca2+]i) as measured with the photoprotein aequorin, did not significantly change when intrinsic tone was abolished by cooling. 5. Myosin light chain phosphorylation, as measured by 2-dimensional polyacrylamide gel electrophoresis, significantly decreased on cooling, but the temperature dependence of phosphorylation did not parallel that of force. The change in phosphorylation in the absence of a change in [Ca2+]i suggests the presence of a constitutively active Ca(2+)-independent form of myosin light chain kinase. 6. Maximal concentrations of staurosporine inhibited but did not eliminate intrinsic tone. 7. Changes in myosin light chain kinase and protein kinase C activities may explain part but not all of the intrinsic tone.
 ...
PMID:Mechanisms of intrinsic tone in ferret vascular smooth muscle. 159 66

To investigate the mechanism of impaired myocardial function after long-term pressure overload, we studied cardiac muscle mechanical contraction and intracellular calcium transients using the bioluminescent indicator aequorin. Left ventricular papillary muscle preparations were examined from three groups of rats: 1) aging spontaneously hypertensive rats (SHR) with clinical and pathological evidence suggesting heart failure (SHR-F group), 2) age-matched SHRs with no evidence of heart failure (SHR-NF group), and 3) age-matched normotensive Wistar-Kyoto rats (WKY group). Isometric force development was depressed in both SHR groups relative to the WKY group. Resting [Ca2+]i was lower in the SHR-F group, and the time to peak [Ca2+]i was prolonged in this group. The relative increases in peak [Ca2+]i with the inotropic interventions of increased [Ca2+]o and the addition of isoproterenol were similar among groups. Although inotropy increased in all groups with increased [Ca2+]o, after isoproterenol, inotropy increased only in the WKY group. Thus, in SHR myocardium, [Ca2+]i increased after isoproterenol, but inotropy failed to increase. Myosin isozymes were shifted toward the V3 isoform in both SHR groups; the V3 isoform was virtually 100% in papillary muscles from the SHR-F group. These changes may reflect events directly contributing to the development of heart failure or represent adaptive changes to chronic pressure overload and heart failure.
 ...
PMID:Intracellular calcium transients in myocardium from spontaneously hypertensive rats during the transition to heart failure. 201 97

During muscarinic activation of canine tracheal smooth muscle with carbachol, myosin phosphorylation is significantly more sensitive than stress to the external Ca2+ concentration ([Ca2+]o) [W. T. Gerthoffer. Am. J. Physiol. 250 (Cell Physiol. 19): C597-C604, 1986]. To determine whether the intracellular Ca2+ concentration ([Ca2+]i) correlated more closely with changes in phosphorylation or force, we measured isometric force and light emitted by the luminescent intracellular Ca2+ indicator aequorin as [Ca2+]o was increased in the presence of 1 microM carbachol or 60 mM K+. Myosin phosphorylation was measured using an immunoblot assay in a second set of muscle strips treated identically. Stimulation with carbachol increased aequorin luminescence slightly in strips incubated in Ca2+-free solution. Active stress and aequorin luminescence subsequently increased in parallel as [Ca2+]o was increased. Myosin phosphorylation at 0.05 mM [Ca2+]o (0.30 +/- 0.04 mol Pi/mol light chain) was significantly higher than phosphorylation in Ca2+-free solution with no carbachol (0.12 +/- 0.048 mol Pi/mol light chain) and increased to a maximum of 0.56 +/- 0.03 mol Pi/mol light chain at 1.6 mM [Ca2+]o. In contrast, active stress and aequorin luminescence remained low at low [Ca2+]o and reached a maximum at 2.4 mM [Ca2+]o. Stimulation with carbachol produced greater increases in myosin phosphorylation and active stress for a given change in aequorin luminescence than did K+ depolarization. Stimulation with carbachol also produced a different phosphorylation-stress relationship than did K+ depolarization. These observations are consistent with the possibility that carbachol induces increases in the Ca2+ sensitivity of contractile proteins in tracheal smooth muscle.
 ...
PMID:Aequorin luminescence, myosin phosphorylation, and active stress in tracheal smooth muscle. 261 Feb 46

Defects in platelet cytoplasmic Ca++ mobilization have been postulated but not well demonstrated in patients with inherited platelet secretion defects. We describe studies in a 42-year-old white woman, referred for evaluation of easy bruising, and her 23-year-old son. In both subjects, aggregation and 14C-serotonin secretion responses in platelet-rich plasma (PRP) to adenosine diphosphate (ADP), epinephrine, platelet activating factor (PAF), arachidonic acid (AA), U46619, and ionophore A23187 were markedly impaired. Platelet ADP and adenosine triphosphate (ATP), contents and thromboxane synthesis induced by thrombin and AA were normal. In quin2-loaded platelets, the basal intracellular Ca++ concentration, [Ca++]i, was normal; however, peak [Ca++]i measured in the presence of 1 mmol/L external Ca++ was consistently diminished following activation with ADP (25 mumol/L), PAF (20 mumol/L), collagen (5 micrograms/mL), U46619 (1 mumol/L), and thrombin (0.05 to 0.5 U/mL). In aequorin-loaded platelets, the peak [Ca++]i studied following thrombin (0.05 and 0.5 U/mL) stimulation was diminished. Myosin light chain phosphorylation following thrombin (0.05 to 0.5 U/mL) stimulation was comparable with that in the normal controls, while with ADP (25 mumol/L) it was more strikingly impaired in the propositus. We provide direct evidence that at least in some patients with inherited platelet secretion defects, agonist-induced Ca++ mobilization is impaired. This may be related to defects in phospholipase C activation. These patients provide a unique opportunity to obtain new insights into Ca++ mobilization in platelets.
 ...
PMID:Impaired cytoplasmic ionized calcium mobilization in inherited platelet secretion defects. 275 41