scholarly journals AGE-DEPENDENCE OF THE CHRONOTROPIC RESPONSE TO NORADRENALINE, ACETYLCHOLINE AND TRANSMURAL STIMULATION IN ISOLATED RABBIT ATRIA

1976 ◽  
Vol 26 (3) ◽  
pp. 359-366 ◽  
Author(s):  
Noboru TODA ◽  
Wang L.H. FU ◽  
Yoshitsugu OSUMI
Keyword(s):  
Age Dependence ◽  
Transmural Stimulation ◽  
Chronotropic Response ◽  
Rabbit Atria

The effect of pH on rabbit atrial response to histamine

1976 ◽  
Vol 54 (2) ◽  
pp. 118-127 ◽  
Author(s):  
M. J. Hughes ◽  
I. A. Coret
Keyword(s):  
Histamine Receptor ◽  
Maximum Response ◽  
Force Of Contraction ◽  
Histamine Concentration ◽  
Adenyl Cyclase Activity ◽  
Chronotropic Response ◽  
Spontaneous Rate ◽  
Histamine Response ◽  
Ph Range ◽  
Rabbit Atria

The chronotropic response of isolated rabbit atria in normal Tyrode's medium increases monotonically with increasing doses of histamine (9 × 10−7–9 × 10−4 M). Plots of the inverse of response against the inverse of concentration were linear; and from these plots were derived values for the theoretical maximum response at 'infinite' dose and for the histamine concentration required to evoke a half maximum response. Alteration of pH by changing [HCO3−] at constant pCO2, [Na+] and osmolality did not appreciably affect the response to histamine in the range pH 7.0–7.6. However, at pH below 7.0 the magnitude of histamine response was reduced at all concentrations of histamine tested. In the pH range 7.0–7.6, additions of NaHCO3 at constant pCO2 increased the spontaneous rate of rabbit atria (in the absence of histamine); however, there was little effect of changing pH (in this range) by altering [HCO3−] at constant pCO2 when [Na+] and osmolality were kept constant. Immersion in solutions at pH's less than 7.0 led to decline in spontaneous rate and force of contraction. It is probable that depression of adenyl cyclase activity rather than a specific change in ionization of histamine receptor is responsible for a decreased response to histamine at pH 6.9.

Chronotropic response of spontaneously beating rabbit atria to hyperosmotic media

1977 ◽  
Vol 233 (2) ◽  
pp. H228-H233 ◽  
Author(s):  
L. A. Roberts ◽  
M. J. Hughes
Keyword(s):  
Rate Control ◽  
Passive Tension ◽  
Force Of Contraction ◽  
Tyrode Solution ◽  
Chronotropic Response ◽  
Wide Range ◽  
Osmotic Agent ◽  
Hyperosmolar Solutions ◽  
Rabbit Atria ◽  
Plateau Level

Spontaneously beating rabbit atria responded to hyperosmotic Tyrode bathing media with an increase in rate, force of contraction, and passive tension dependent on the level of osmolality and the osmotic agent employed. The positive chronotropic response reached a maximum within a few minutes and then declined to a lower, maintained plateau level. The plateau change in rate was similar whether the osmotic agent added to Tyrode solution was sucrose, mannitol or NaCl. For these agents, the response increased linearly with osmotic pressure of the bathing media from 300 to 500 mosmol/kg H2O, then progressively decreased approaching zero (plateau rate = control) at about 700 mosmol/kg H2O. The chronotropic response to urea in Tyrode solution, though less than for the other three agents, progressively increased over the entire range of osmolalities tested (from 300 to 700 mosmol/kg H2O). The inotropic response was positive for all agents from 300 to 600 mosmol/kg H2O. Passive tension of atria increased with added NaCl, sucrose, or mannitol, but not with urea. Propranolol did not alter the atrial response to hyperosmolality. Thus, we find that the chronotropic response of atria to hyperosmolar solutions is positive over a wide range of agents and osmolalities, in contrast to earlier reports of a direct negative chronotropic effect.

The characterization of cardiac histaminergic chronotropic receptors in the rabbit

1981 ◽  
Vol 59 (1) ◽  
pp. 14-18 ◽  
Author(s):  
Alicia Polanin ◽  
Thomas E. Tenner Jr. ◽  
John H. McNeill
Keyword(s):  
Histamine Receptor ◽  
Receptor Blockade ◽  
Chronotropic Response ◽  
Atrial Rate ◽  
Chronotropic Effects ◽  
Rabbit Atria ◽  
Stimulation Of

The effects of selective histamine receptor analogs were studied in spontaneously beating rabbit atria. Atrial rate was increased by histamine (an H1 and H2 agonist), 4-methylhistamine and impromidine (H2 agonists), and 2-pyridylethylamine (PEA, an H1 agonist). The responses to histamine, 4-methylhistamine, and impromidine were not affected by propranolol (1 × 10−7 M) or reserpine pretreatment. However, the response to PEA was nearly abolished upon pretreatment with propranolol or reserpine.Cimetidine pretreatment (H2 receptor blockade) competitively antagonised the positive chronotropic effects of histamine, 4-methylhistamine, and impromidine. Promethazine pretreatment (H1 receptor blockade) competitively blocked the chronotropic effects of histamine but had no effect on the responses to 4-methylhistamine or impromidine. These results suggest that stimulation of H1 and H2 receptors will cause a positive chronotropic response.

Age-Dependence in Alterations in Nitric Oxide Synthesis in Cardiovascular System during Adaptation to Physical Training

2010 ◽  
Vol 1 (4) ◽  
pp. 345-356 ◽  
Author(s):  
O. V. Bazilyuk ◽  
Anatolii V. Kotsuruba ◽  
Lyubov. G. Stepanenko ◽  
Sergey A. Talanov ◽  
Yu. P. Korchak ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Cardiovascular System ◽  
Physical Training ◽  
Nitric Oxide Synthesis ◽  
Age Dependence

scholarly journals Age-dependent and radial sectional differences in the dynamic viscoelastic properties of bamboo culms and their possible relationship with the lignin structures

2020 ◽  
Vol 66 (1) ◽  
Author(s):  
Yoko Okahisa ◽  
Keisuke Kojiro ◽  
Hatsuki Ashiya ◽  
Takeru Tomita ◽  
Yuzo Furuta ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Viscoelastic Properties ◽  
Structural Variation ◽  
Thermal Softening ◽  
Peak Temperature ◽  
Outer Side ◽  
Phyllostachys Pubescens ◽  
Age Dependence ◽  
Age Dependent ◽  
S Peak

Abstract Age is an important factor that dictates bamboo’s mechanical properties. In Japan, bamboo plants aged 3–5 years are selected for use as materials because of their robustness and decorative or craft-friendly characteristics. In this study, the age-dependent and radial sectional differences in bamboo’s dynamic viscoelastic properties in relation to lignin structural variation, were evaluated. We used Phyllostachys pubescens samples at the current year and at 1.5, 3.5, 6.5, 9.5, 12.5, and 15.5 years of age. There was a clear age dependence in the peak temperature of tan δ and in the yield of thioacidolysis products derived from β-O-4 lignin structures. The highest peak temperature tan δ value was detected in 3.5-year-old bamboo, which contained the highest amount of the thioacidolysis products. Moreover, tan δ’s peak temperature was always higher on the outer side, and the ratio of S/G thioacidolysis products was always higher on the inner side of bamboo plants of all ages. These results suggest that changes in bamboo’s thermal softening properties from aging are caused by the maturation and degradation of lignin in bamboo.

scholarly journals POS0486 FACTORS ASSOCIATED WITH CHRONOTROPIC RESPONSE IN PEOPLE WITH RHEUMATOID ARTHRITIS

2021 ◽  
Vol 80 (Suppl 1) ◽  
pp. 475.2-476
Author(s):  
A. Osailan
Keyword(s):  
Rheumatoid Arthritis ◽  
Risk Factors ◽  
Cardiorespiratory Fitness ◽  
Inflammatory Markers ◽  
Exercise Intolerance ◽  
Cvd Risk Factors ◽  
Cvd Risk ◽  
Chronotropic Response ◽  
Factors Associated ◽  
The University

Background:People with rheumatoid arthritis (RA) are at high risk for cardiovascular diseases (CVD) and CVD mortality. Reduced Chronotropic response (CR), which produces exercise intolerance, is known as a contributing factor to CVD and mortality. Studies have shown that people with RA have reduced CR. However, knowledge about the factors associated with CR in people with RA is limited.Objectives:To explore the factors associated with CR including CVD risk factors, inflammatory markers and cardiorespiratory fitness (VO2 peak).Methods:106 people with RA completed a treadmill exercise tolerance test while heart rate (HR) was monitored via 12 leads ECG. CR was defined as the percentage of [(achieved peak HR minus resting HR) divided by (age-predicted maximum HR minus resting HR)]. Serological CVD risk factors and inflammatory markers including lipids profile, markers of insulin resistance and sensitivity (HOMA, QUICKi), high sensitivity C-reactive protein (hsCRP), erythrocyte sedimentation rate (ESR), fibrinogen and white blood cells (WBC) were examined via a fasted blood sample. VO2 peak was assessed via breath-by-breath gas analysis.Results:34% had reduced CR based on the cut-off value (≤ 80%) and the average CR was 86.2 ± 21%. Body mass index (r=-0.33, p=.001), HOMA (r=-0.26, p=.009), hsCRP (r=-0.23, p=.02), ESR (r=-0.21, p=.04), fibrinogen (r=-0.2, p=.05), WBC (r=-0.21, p=.04) were inversely associated with CR, whereas, high density lipoprotein (HDL) (r=0.43, p<.001), QUICKi (r=0.31, p=.002), and VO2 peak (r=0.4, p<.001) were positively associated with CR. When all the variables were entered into a stepwise linear regression, HDL (p<.001) and VO2 peak (p=.009) were independently associated with CR.Conclusion:The current findings suggest that CR in RA was associated with many CVD risk factors, inflammatory markers, and cardiorespiratory fitness. Among all the varibales, HDL and cardiorespiratory fitness were moderately and independently associated with CR. Future studies should investigate the effect of improving these associated variables on CR in people with RA via exercise training programes.Acknowledgements:Thanks to physical activity in Rheumatoid arthritis research team and Research department in Dudley Hospital. Sincere appreciation and gratitude to Dr Jet Veldhuizen van Zanten, Prof. Joan Duda, and Prof. George Kitas from the University of Birmingham and Prof. George Metsios from the University of Wolverhampton.Disclosure of Interests:None declared

Age dependence of brachial cuff-based ambulatory PWV in end-stage kidney disease patients undergoing long-term peritoneal dialysis

2021 ◽  
pp. 089686082199692
Author(s):  
Vasilios Vaios ◽  
Panagiotis I Georgianos ◽  
Georgia Vareta ◽  
Dimitrios Divanis ◽  
Evangelia Dounousi ◽  
...  
Keyword(s):  
Risk Factors ◽  
Blood Pressure ◽  
Heart Rate ◽  
Peritoneal Dialysis ◽  
Kidney Disease ◽  
Pulse Wave ◽  
Age Dependence ◽  
End Stage Kidney Disease ◽  
End Stage

Background: The newly introduced device Mobil-O-Graph (IEM, Stolberg, Germany) combines brachial cuff oscillometry and pulse wave analysis, enabling the determination of pulse wave velocity (PWV) via complex mathematic algorithms during 24-h ambulatory blood pressure monitoring (ABPM). However, the determinants of oscillometric PWV in the end-stage kidney disease (ESKD) population remain poorly understood. Methods: In this study, 81 ESKD patients undergoing long-term peritoneal dialysis underwent 24-h ABPM with the Mobil-O-Graph device. The association of 24-h oscillometric PWV with several demographic, clinical and haemodynamic parameters was explored using linear regression analysis. Results: In univariate analysis, among 21 risk factors, 24-h PWV exhibited a positive relationship with age, body mass index, overhydration assessed via bioimpedance spectroscopy, diabetic status, history of dyslipidaemia and coronary heart disease, and it had a negative relationship with female sex and 24-h heart rate. In stepwise multivariate analysis, age ( β: 0.883), 24-h systolic blood pressure (BP) ( β: 0.217) and 24-h heart rate ( β: −0.083) were the only three factors that remained as independent determinants of 24-h PWV (adjusted R 2 = 0.929). These associations were not modified when all 21 risk factors were analysed conjointly or when the model included only variables shown to be significant in univariate comparisons. Conclusion: The present study shows that age together with simultaneously assessed oscillometric BP and heart rate are the major determinants of Mobil-O-Graph-derived PWV, explaining >90% of the total variation of this marker. This age dependence of oscillometric PWV limits the validity of this marker to detect the premature vascular ageing, a unique characteristic of vascular remodelling in ESKD.

Evaluation of β-Adrenerglc Blocking Agents in Presence of Adrenergic Tone

1972 ◽  
Vol 50 (5) ◽  
pp. 381-388
Author(s):  
Victor Elharrar ◽  
Reginald A. Nadeau
Keyword(s):  
Dose Response ◽  
Sinus Node ◽  
Stellate Ganglion ◽  
Sodium Pentobarbital ◽  
Response Curves ◽  
Chronotropic Response ◽  
Blocking Agents ◽  
Sinus Node Artery ◽  
Anesthetized Dogs ◽  
The Right

The importance of the level of adrenergic tone in the determination of the dose–response curve to noradrenaline (NA) and in the evaluation of β-adrenergic blocking agents was studied in open-chest sodium pentobarbital anesthetized dogs by injecting drugs directly into the sinus node artery. Changes in the level of adrenergic tone by stimulating the right stellate ganglion resulted in variation of the observed chronotropic response to NA and of its ED50. The chronotropic responses were corrected by taking into account the underlying adrenergic tone. The negative chronotropic effect of dl-propranolol (1 and 10 μg) appeared to be related to its β-blocking properties and not to its quinidine-like effects as shown by the lack of effect of d-propranolol injected at the same doses. The magnitude of the negative chronotropic effects of 10 μg of propranolol and 100 μg of practolol, oxprenolol, and sotalol was shown to be related to the initial heart rate and consequently to the level of adrenergic tone. The comparison of these four β-blocking agents was carried out on corrected dose-response curves to NA. Their relative potencies were found to be: propranolol > oxprenolol > practolol > sotalol, corresponding to ratios of 1, [Formula: see text], [Formula: see text], and [Formula: see text]

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