UNIPROT:P21817 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P21817 (RyR1)
1,154 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The goal was to determine the existence of differential effects of long-term moderate- or low-intensity exercise on selected bio-behavioral variables in 72 community-dwelling persons over 60 years of age. After screening, subjects were randomly assigned to a moderate (n = 39, 60-70% heart rate reserve [HRR]) or low (n = 33, 30-40% HRR) intensity exercise protocol. Both groups exercised three times per week for 9 months and dependent measures were taken at baseline, 4.5 months and after 9 months. Repeated measures ANOVA with Tukey post hoc comparisons constituted the analysis approach. Moderate exercise showed no superiority over low-intensity exercise; both groups improved about equally. Variables that significantly improved included: self-reported sleep (sleep quantity and dream recall), mental status (attention/concentration, short-term memory and higher cognitive functioning), health perceptions (health outlook, health worry, rejection of the sick role), and cardiovascular fitness indicators (submaximum stress test heart rate, maximum oxygen consumption (VO2max), maximum work capacity and maximum exercise time). Similarity of outcomes in both groups may mean that the moderate exercise protocol was too conservative. Conversely, the findings may indicate that lower levels of exercise, which may be safer and more feasible over time, do improve fitness levels, prolong independent functioning, and promote positive perceptions of well-being in older adults.
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PMID:Effects of moderate and low intensity long-term exercise by older adults. 237 29

Seven normotensive untreated patients with obstructive sleep apnea (OSA) and five control subjects without OSA were compared. Patients with cardiac dilation, chronic airflow limitation, liver and kidney disease, or diabetes mellitus were excluded. Change in pressure-heart rate relation to alpha-adrenergic stimulation (P-HRR), extracellular volume (ECV), and plasma volume (Vp) were measured during daytime. Plasma atrial natriuretic peptide (ANP), plasma renin and aldosterone concentrations were obtained at 1 hour intervals during the night. A mean apnea/hypopnea index (AHI) of 52.2 +/- 23.9/h and a mean lowest arterial oxygen saturation (SaO2) of 61.2 +/- 19.3% (mean +/- SD) were determined from polysomnographic monitoring in the patient group. Release of ANP was significantly higher during sleep in OSA patients than in control subjects (P < .01), with a maximum concentration between 4 and 6 AM in the former. Daytime ECV was significantly higher (P < .05) and Vp significantly lower (P < .05) in OSA patients. Night maximum concentration of ANP (max ANP) was negatively related to AHI (P < .05). P-HRR was negatively related to AHI (P < .05) and positively related to max ANP (P < .05). In conclusion, OSA syndrome alters hormonal system control of body fluid compartment regulation. The decreased response in night max ANP secretion in the most severe OSA patients could be explained by the smaller Vp observed in these patients, decreasing atrial and ventricular pressure loading. Furthermore, alteration of P-HRR, correlated to AHI and max ANP, strengthens the hypothesis that patients who develop hypertension are those in whom the protective mechanism of ANP release failed.
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PMID:Pressure-heart rate responses to alpha-adrenergic stimulation and hormonal regulation in normotensive patients with obstructive sleep apnea. 900 45

In agriculture, occupational injuries are common, and several of them lead to permanent physical disability. The objective of this case study was to assess the strain and the ergonomic needs of four farmers (aged 34-49 years) with physical disabilities. A maximal bicycle ergometer test or an arm-crank test was done to assess their maximal heart rate (HR _max) and maximal oxygen consumption (V0_2max). The strain at work was analyzed by measuring heart rate (HR), muscle activity (EMG), and the rating of perceived exertion (RPE). The farmers were interviewed as to possible and impossible work tasks and the ergonomic redesign measures taken to improve the work environment. The work tasks performed were mainly light or moderate work for the cardiorespiratory system according to mean HR (88-102 beats/min), the percentage of HR range (17-31% HRR), and the relative V0₂ (22-46% V0_2max). The mean activity of the trapezius muscles was 0.4-9% of the maximal voluntary contraction (%MVC). All the participants had work tasks they were unable to perform. They had made ergonomie redesign changes mainly to the tractor. This case study showed that some agricultural work tasks were possible for farmers with physical disabilities and that the physical strain associated with these tasks was mainly light or moderate.
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PMID:Physical Strain and Work Ergonomics in Farmers with Disabilities. 1060 97

The purpose of the present investigation was to examine the relationship between the percent heart rate reserve (%HRR) in arm exercise and the corresponding percent oxygen uptake (VO2) reserve, and to compare this relationship to that occurring in running. Fourteen male physical education students took part in the study. Each subject performed a maximal running exercise test and a maximal arm cycling test. The subjects also performed three submaximal exercise bouts (in both exercise modes) at 30%, 60% and 80% of their HRR. The subjects were monitored for their heart rate (HR) at rest, maximal HR (HRmax), HR at submaximal work loads. maximal VO2 (VO2max), VO2 at rest and VO2 at submaximal loads. For each subject, load and exercise mode, %HRR and %VO2 reserve were calculated (from HRmax and VO2max as measured during running and arm cycling) and the relationship between the two was evaluated. The main finding of the present investigation is that the prediction of %VO2 reserve in arm cycling from %HRR is grossly overestimated when calculated from HRmax and VO2max measured during running. The prediction is better but still overestimated when calculated from HRmax and VO2max measured during arm cycling. The findings indicate a better prediction of %VO2 reserve from %HRR for running than for arm exercise. These findings should be taken into consideration when prescribing the target HR for arm training.
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PMID:Estimation of %VO2 reserve from heart rate during arm exercise and running. 1119 63

Alteration of skeletal muscle function by reactive oxygen species and nitric oxide (NO) may involve regulation of the activity of the skeletal muscle Ca2+ release channel (also known as RyR1). We have shown that oxidants can activate RyR1 and produce inter-subunit disulfide bonds. Both effects are prevented by pretreatment with either NO donors or N-ethylmaleimide under conditions that modify less than 5% of the total sulfhydryls on RyR1. Oxidation-induced intersubunit crosslinking can also be prevented by the binding of either Ca2+ calmodulin or apocalmodulin to RyR1. Also, both Ca2+ calmodulin and apocalmodulin binding are blocked by oxidation of RyR1. In contrast, alkylation with N-ethylmaleimide or reaction with NO donors preferentially blocks apocalmodulin binding to RyR1, suggesting the existence of a regulatory cysteine within the apocalmodulin binding site. We have demonstrated that Ca2+ calmodulin and apocalmodulin bind to overlapping, but nonidentical, sites on RyR1 and that cysteine 3635 is close to or within the apocalmodulin-binding site on RyR1. This cysteine is also one of the cysteines that form the intersubunit disulfide bonds, suggesting that calmodulin binds at an intersubunit contact site. Our findings are consistent with a model in which oxidants regulate the activity of RyR1 directly by altering subunit-subunit interactions and indirectly by preventing the binding of either Ca2+-bound calmodulin or apocalmodulin. NO also has both a direct and an indirect effect: it blocks the ability of oxidants to generate intersubunit disulfide bonds and prevents apocalmodulin binding.
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PMID:RyR1 modulation by oxidation and calmodulin. 1123 98

The skeletal muscle Ca(2+) release channel/ryanodine receptor (RyR1) is a prototypic redox-responsive ion channel. Nearly half of the 101 cysteines per RyR1 subunit are kept in a reduced (free thiol) state under conditions comparable with resting muscle. Here we assessed the effects of physiological determinants of cellular redox state (oxygen tension, reduced (GSH) or oxidized (GSSG) glutathione, and NO/O(2) (released by 3-morpholinosydnonimine)) on RyR1 redox state and activity. Oxidation of approximately 10 RyR1 thiols (from approximately 48 to approximately 38 thiols/RyR1 subunit) had little effect on channel activity. Channel activity increased reversibly as the number of thiols was further reduced to approximately 23/subunit, whereas more extensive oxidation (to approximately 13 thiols/subunit) inactivated the channel irreversibly. Neither S-nitrosylation nor tyrosine nitration contributed to these effects. The results identify at least three functional classes of RyR1 thiols and suggest that 1) the channel may be protected from oxidation by a large reservoir of functionally inert thiols, 2) the channel may be designed to respond to moderate oxidative stress by a change in activation setpoint, and 3) the channel is susceptible to oxidative injury under more extensive conditions.
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PMID:Classes of thiols that influence the activity of the skeletal muscle calcium release channel. 1127 99

In chronic congestive heart failure (CHF), attenuated heart rate response to exercise, a manifestation of chronotropic incompetence (CI), contributes to limiting exercise capacity. The present study was thus conducted to evaluate the respective role of chronic attenuation of cardiac vagal tone associated with depressed baroreflex sensitivity or affected cardiac sympathetic responsiveness in CHF patients with CI. Spontaneous cardiac baroreflex sensitivity (BRS) assessed by sequence method and spectral- and time-domain analysis of heart rate variability (HRV) were analysed in 21 chronic CHF patients. All patients performed a symptom-limited exercise test with measurement of gas exchange. Chronic incompetence which was defined as failure to achieve > or =80% of the heart rate reserve (%HRR) given by (HRpeak - HRrest)/(predictive maximal heart rate - HRrest) was observed in 14 (66%) patients. There was no significant difference in age, heart rate, peak oxygen uptake or left ventricular ejection fraction between the patients with and without CI. Although there was no significant difference in BRS, low frequency power of HRV in normalized units (LFnu) and SDNN were significantly lower in CI patients. Percentage of HRR correlated significantly with LFnu on 15 min (r=0.64, P<0.005) and, with LFnu on 24 h (r=0.52, P<0.01), SDNN (r=0.48, P=0.03) and SDANN (r=0.48, P=0.03), but not BRS (r=0.04, P=NS). Autonomic nervous system derangement is a complex process in CHF. The role of basal depressed cardiac sympathetic tone seems to contribute more closely than depressed baroreflex sensitivity to the impaired heart rate response to exercise frequently observed in CHF patients.
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PMID:Chronotropic incompetence response to exercise in congestive heart failure, relationship with the cardiac autonomic status. 1138 May 33

We have shown previously that at physiologically relevant oxygen tension (pO(2) approximately 10 mmHg), NO S-nitrosylates 1 of approximately 50 free cysteines per ryanodine receptor 1 (RyR1) subunit and transduces a calcium-sensitizing effect on the channel by means of calmodulin (CaM). It has been suggested that cysteine-3635 is part of a CaM-binding domain, and its reactivity is attenuated by CaM [Porter Moore, C., Zhang, J. Z., Hamilton, S. L. (1999) J. Biol. Chem. 274, 36831-36834]. Therefore, we tested the hypothesis that the effect of NO was mediated by C3635. The full-length RyR1 single-site C3635A mutant was generated and expressed in HEK293 cells. The mutation resulted in the loss of CaM-dependent NO modulation of channel activity and reduced S-nitrosylation by NO to background levels but did not affect NO-independent channel modulation by CaM or the redox sensitivity of the channel to O(2) and glutathione. Our results reveal that different cysteines within the channel have been adapted to serve in nitrosative and oxidative responses, and that S-nitrosylation of the cysteine-containing CaM-binding domain underlies the mechanism of CaM-dependent regulation of RyR1 by NO.
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PMID:Cysteine-3635 is responsible for skeletal muscle ryanodine receptor modulation by NO. 1156 75

This study evaluated the ability to use the relationship between heart rate (HR) and oxygen uptake (VO2 ) to estimate energy expenditure (EE) from low to high physical activity with different HR-based prediction equations. General prediction equations were established based on the individual relations between HR and EE. Possibilities to improve the EE estimation with using alternatives for respective HR were also assessed. The alternatives were % of HR reserve: 100 x [(activity HR - resting HR)/(maximal HR - resting HR)], (HRR), and the difference between activity HR and resting HR (activity HR - resting HR), (HRnet). Forty-two men (age mean 36.5 [sd 7.6] y, BMI 24.5 [2.4] kg x m(-2), VO2 max 45.2 [6.5]) kg x ml x min(-1) and 47 women (mean age 37.5 [9.5], BMI 23.3 [3.4], VO2 max 36.3 [5.4]) performed an exercise test consisting of physically low-activity tasks and a maximal treadmill uphill walking test. Respiratory gases were obtained from indirect calorimetry. HR was registered by electrocardiography and EE was calculated from (VO2 ) and carbon dioxide (VCO2 ) production. Generalised linear models with random effects were used for the prediction of EE. EE values of the tests (one value at each intensity level) were predicted in separate models by the respective HR, HRR or HRnet values. The other predictors used in all models were body weight, sex and the intensity of exercise. The standard error of estimate (SEE) was 1.41 kcal x min(-1) (5.89 kJ) in the model with HR variable as a predictor, 1.01 kcal x min(-1) (4.22 kJ) with HRR variable, and 1.08 (4.51 kJ) with HRnet variable. The results show that the prediction of EE is more accurate if HRR or HRnet are used in prediction equation instead of HR.
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PMID:Use of heart rate to predict energy expenditure from low to high activity levels. 1286 43

Hepatocytes were isolated from eight species of birds ranging from 13 g zebra finches to 35 kg emus. This represents a 2800-fold range of body mass (Mb). Liver mass (g) was allometrically related to species body mass by the equation: liver mass=19.6 x Mb(0.91). There was a significant allometric decline in hepatocyte respiration rate (HRR; nmol O2 mg(-1) dry mass min(-1)) with species body mass (kg) described by the relationship: HRR=5.27 x Mb(-0.10). The proportions of hepatocyte oxygen consumption devoted to (i) mitochondrial ATP production, (ii) mitochondrial proton leak and (iii) non-mitochondrial processes were estimated by using excess amounts of appropriate inhibitors. It was found that although hepatocyte respiration rate varied with body mass in birds, these processes constitute a relatively constant proportion of hepatocyte metabolic rate irrespective of the size of the bird species. The respective percentages were 54%, 21% and 25%. The portion of hepatocyte respiration devoted to ATP production for use by the sodium pump was estimated and found to be a relatively constant 24% of hepatocyte respiration and 45% of mitochondrial ATP production in different-sized bird species. These results are discussed in the context of competing theories to explain the metabolism-body size allometry, and are found to support the 'allometric cascade' model.
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PMID:Respiration rate of hepatocytes varies with body mass in birds. 1515 35

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