Independence of heart rate and circadian period in the golden hamster

1993 ◽  
Vol 264 (2) ◽  
pp. R235-R238
Author(s):  
R. Refinetti ◽  
M. Menaker
Keyword(s):  
Heart Rate ◽  
Cardiac Pacemaker ◽  
Myocardial Cell ◽  
Circadian Oscillation ◽  
Circadian Period ◽  
Isolated Hearts ◽  
Rate Oscillations ◽  
The Mean ◽  
Freely Moving

Cardiac contractions are under the influence of at least two processes of biological timing, one responsible for the mean level of heart rate (oscillations with a frequency of up to several hundred per minute) and another responsible for the circadian rhythm of heart rate (oscillations with a frequency of one per 24 h). To investigate whether the mean level of heart rate is proportional to the frequency of circadian oscillation, we compared the heart rates of normal golden hamsters (circadian period approximately 24 h) and tau-mutant hamsters (circadian period approximately 20 h). Neither in anesthetized preparations nor in freely moving animals was there a difference in heart rate between the two groups despite the 20% difference in circadian period. Thus the mean level of heart rate seems to be independent of the circadian period. It is likely that the tau gene, which affects the frequency of the circadian pacemaker, has no effect on the intrinsic frequency of the cardiac pacemaker. In vitro studies of isolated hearts or myocardial cell cultures are necessary to confirm this inference.

scholarly journals RE-EVALUATION OF THE STRETCH SENSITIVITY HYPOTHESIS OF CRUSTACEAN HEARTS: HYPOXIA, NOT LACK OF STRETCH, CAUSES REDUCTION IN HEART RATE OF ISOLATED HEARTS

1993 ◽  
Vol 176 (1) ◽  
pp. 223-232
Author(s):  
J. L. Wilkens
Keyword(s):  
Heart Rate ◽  
Isolated Heart ◽  
Carcinus Maenas ◽  
Three Dimensional ◽  
Decapod Crustacean ◽  
Diastolic Filling ◽  
Elastic Recoil ◽  
Isolated Hearts

Decapod crustacean hearts are suspended by a three-dimensional array of alary ligaments. These ligaments are stretched during systole; diastolic filling via the ostia occurs as the ventricle is stretched by ligamental elastic recoil. There is no direct venous return to the hearts in these animals. In the present study, an isolated heart preparation with intact ligaments, hereafter called in situ, was used to evaluate the effects of artificially induced stretch on heart rate. Strongly beating in situ neurogenic hearts of the crab Carcinus maenas responded to direct perfusion of the ventricle with oxygenated saline and the attendant augmentation of natural stretch with a small increase in heart rate (fh); however, fh was well maintained for up to 15 min after eliminating stretch by cutting the alary ligaments. In contrast to crabs, high rates of artificial perfusion usually depressed fh in crayfish hearts. Crab heart rate falls during hypoxia and this is readily reversed by even low rates of perfusion with oxygenated saline. It is concluded that the gradual decline in fh of totally isolated in vitro hearts arises from the deepening intraventricular hypoxia experienced by the cardiac ganglion.

scholarly journals 348 Effect of propranolol on heart rate and arrhythmias in freely moving mice and isolated hearts of deltaKPQ-SCN5A LQT3 mice

EP Europace ◽  
2005 ◽  
Vol 7 (Supplement_1) ◽  
pp. 71-71
Author(s):  
L. Fabritz ◽  
P. Kirchhof ◽  
M. Emmerich ◽  
L. Fortm ller ◽  
G. M nnig ◽  
...  
Keyword(s):  
Heart Rate ◽  
Isolated Hearts ◽  
Freely Moving

scholarly journals CikA Modulates the Effect of KaiA on the Period of the Circadian Oscillation in KaiC Phosphorylation

2019 ◽  
Vol 34 (2) ◽  
pp. 218-223 ◽  
Author(s):  
Manpreet Kaur ◽  
Amy Ng ◽  
Pyonghwa Kim ◽  
Casey Diekman ◽  
Yong-Ick Kim
Keyword(s):  
Circadian Clock ◽  
Binding Site ◽  
Competitive Binding ◽  
Circadian Oscillator ◽  
Circadian Oscillation ◽  
Circadian Period ◽  
Phosphorylation State ◽  
Constant Period ◽  
Insight Into

Cyanobacteria contain a circadian oscillator that can be reconstituted in vitro. In the reconstituted circadian oscillator, the phosphorylation state of KaiC oscillates with a circadian period, spending about 12 h in the phosphorylation phase and another 12 h in the dephosphorylation phase. Although some entrainment studies have been performed using the reconstituted oscillator, they were insufficient to fully explain entrainment mechanisms of the cyanobacterial circadian clock due to the lack of input pathway components in the in vitro oscillator reaction mixture. Here, we investigate how an input pathway component, CikA, affects the phosphorylation state of KaiC in vitro. In general, CikA affects the amplitude and period of the circadian oscillation of KaiC phosphorylation by competing with KaiA for the same binding site on KaiB. In the presence of CikA, KaiC switches from its dephosphorylation phase to its phosphorylation phase prematurely, due to an early release of KaiA from KaiB as a result of competitive binding between CikA and KaiA. This causes hyperphosphorylation of KaiC and lowers the amplitude of the circadian oscillation. The period of the KaiC phosphorylation oscillation is shortened by adding increased amounts of CikA. A constant period can be maintained as CikA is increased by proportionally decreasing the amount of KaiA. Our findings give insight into how to reconstitute the cyanobacterial circadian clock in vitro by the addition of an input pathway component, and explain how this affects circadian oscillations by directly interacting with the oscillator components.

A new method for measurement of blood pressure, heart rate, and activity in the mouse by radiotelemetry

2000 ◽  
Vol 88 (5) ◽  
pp. 1537-1544 ◽  
Author(s):  
Perry A. Mills ◽  
Daniel A. Huetteman ◽  
Brian P. Brockway ◽  
Lynn M. Zwiers ◽  
A. J. Mick Gelsema ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Locomotor Activity ◽  
Dynamic Response ◽  
Frequency Response ◽  
Pulse Pressure ◽  
Laboratory Mice ◽  
New Device ◽  
The Mean ◽  
Freely Moving

A simple and reliable means for accurate, chronic measurement of pulsatile blood pressure (BP) from conscious, freely moving laboratory mice was developed and validated. The newly developed device consists of a small (1.9 ml, 3.4 g), fully implantable radiotelemetry transmitter. Initial frequency response tests showed an adequate dynamic response; the average −3-dB point found in five transmitters was 145 ± 14 (SD) Hz. BP, heart rate, and locomotor activity were recorded from 16 chronically (30–150 days) implanted mice. Mean arterial and pulse pressure, checked at regular intervals, ranged from 90–140 mmHg and from 30–50 mmHg, respectively, throughout the study. Transmitter BP measurements were validated against a Millar 1.4-Fr. transducer-tipped catheter. The mean error of the transmitters for diastolic pressures was +1.1 ± 6.9 mmHg ( n = 7). The error for systolic pressures was, on average, 2.7 ± 3.9 mmHg larger. This new device accurately monitors BP, heart rate, and locomotor activity in conscious, untethered, freely moving mice living in their home cages for periods of at least 150 days.

Influence of Platelet Membrane Sialic Acid and Platelet-Associated IgG on Ageing and Sequestration of Blood Platelets in Baboons

1993 ◽  
Vol 70 (04) ◽  
pp. 676-680 ◽  
Author(s):  
H F Kotzé ◽  
V van Wyk ◽  
P N Badenhorst ◽  
A du P Heyns ◽  
J P Roodt ◽  
...  
Keyword(s):  
Sialic Acid ◽  
Life Span ◽  
Blood Platelets ◽  
Senescent Cell ◽  
Platelet Membrane ◽  
Antigen Complex ◽  
The Mean ◽  
Aggregation Of Platelets

SummaryPlatelets were isolated from blood of baboons and treated with neuraminidase to remove platelet membrane sialic acid, a process which artificially ages the platelets. The platelets were then labelled with 111In and their mean life span, in vivo distribution and sites of Sequestration were measured. The effect of removal of sialic acid on the attachment of immunoglobulin to platelets were investigated and related to the Sequestration of the platelets by the spleen, liver, and bone marrow. Removal of sialic acid by neuraminidase did not affect the aggregation of platelets by agonists in vitro, nor their sites of Sequestration. The removal of 0.51 (median, range 0.01 to 2.10) nmol sialic acid/108 platelets shortened their life span by 75 h (median, range 0 to 132) h (n = 19, p <0.001), and there was an exponential correlation between the shortening of the mean platelet life span and the amount of sialic acid removed. The increase in platelet-associated IgG was 0.112 (median, range 0.007 to 0.309) fg/platelet (n = 25, p <0.001) after 0.79 (median, range 0.00 to 6.70) nmol sialic acid/108 platelets was removed (p <0.001). There was an exponential correlation between the shortening of mean platelet life span after the removal of sialic acid and the increase in platelet-associated IgG. The results suggest that platelet membrane sialic acid influences ageing of circulating platelets, and that the loss of sialic acid may have exposed a senescent cell antigen that binds IgG on the platelet membrane. The antibody-antigen complex may then provide a signal to the macrophages that the platelet is old, and can be phagocytosed and destroyed.

The Involvement of Platelets and the Coronary Vasculature in Collagen-Induced Sudden Death in Rabbits

1985 ◽  
Vol 53 (01) ◽  
pp. 070-074 ◽  
Author(s):  
G Mallarkey ◽  
G M Smith
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Platelet Count ◽  
Sudden Death ◽  
Myocardial Ischaemia ◽  
Plasma Levels ◽  
Sodium Citrate ◽  
Plasma Samples ◽  
Calcium Entry Blockers

SummaryThe mechanism of collagen-induced sudden death in rabbits was studied by measuring blood pressure (BP), heart rate, ECG, the continuous platelet count and the plasma levels of thromboxane B2 (TxB2) and 6-keto prostaglandin Fia (6-keto PGF1α). Death was preceded by myocardial ischaemia and a sharp fall in BP which occurred before any fall in platelet count was observed. The calcium entry blockers (CEBs), verapamil, nifedipine and PY 108-068 protected the rabbits from sudden death without any significant effect on the decrease in the platelet count or increase in plasma TxB2 levels. 6-keto PGF1α could not be detected in any plasma samples. Indomethacin and tri-sodium citrate also protected the rabbits but significantly reduced the fall in platelet count and plasma TxB2. In vitro studies on isolated aortae indicated that verapamil non-specifically inhibited vasoconstriction induced by KC1, adrenaline and U46619 (a thromboxane agonist). It is concluded that CEBs physiologically antagonize the vasoconstricting actions of platelet-derived substances and that it is coronary vasoconstriction that is primarily the cause of death.

Psychophysiological Responses of Pilots in Hypoxia Training at 7000 and 7500 m

2020 ◽  
Vol 91 (10) ◽  
pp. 785-789
Author(s):  
Dongqing Wen ◽  
Lei Tu ◽  
Guiyou Wang ◽  
Zhao Gu ◽  
Weiru Shi ◽  
...  
Keyword(s):  
Heart Rate ◽  
Psychomotor Performance ◽  
Physiological Responses ◽  
Arterial Oxygen Saturation ◽  
Arterial Oxygen ◽  
Awareness Training ◽  
Similar Frequency ◽  
Psychophysiological Responses ◽  
The Mean ◽  
Training Protocol

INTRODUCTION: We compared the physiological responses, psychomotor performances, and hypoxia symptoms between 7000 m and 7500 m (23,000 and 24,600 ft) exposure to develop a safer hypoxia training protocol.METHODS: In altitude chamber, 66 male pilots were exposed to 7000 and 7500 m. Heart rate and arterial oxygen saturation were continuously monitored. Psychomotor performance was assessed using the computational task. The hypoxic symptoms were investigated by a questionnaire.RESULTS: The mean duration time of hypoxia was 323.0 56.5 s at 7000 m and 218.2 63.3 s at 7500 m. The 6-min hypoxia training was completed by 57.6% of the pilots and 6.1% of the pilots at 7000 m and at 7500 m, respectively. There were no significant differences in pilots heart rates and psychomotor performance between the two exposures. The Spo2 response at 7500 m was slightly severer than that at 7000 m. During the 7000 m exposure, pilots experienced almost the same symptoms and similar frequency order as those during the 7500 m exposure.CONCLUSIONS: There were concordant symptoms, psychomotor performance, and very similar physiological responses between 7000 m and 7500 m during hypoxia training. The results indicated that 7000-m hypoxia awareness training might be an alternative to 7500-m hypoxia training with lower DCS risk and longer experience time.Wen D, Tu L, Wang G, Gu Z, Shi W, Liu X. Psychophysiological responses of pilots in hypoxia training at 7000 and 7500 m. Aerosp Med Hum Perform. 2020; 91(10):785789.

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