scholarly journals Cardiac contraction velocity has evolved to match heart rate with body size through variation in β-cardiac myosin sequence

2019 ◽  
Author(s):  
Chloe A. Johnson ◽  
Jake E. McGreig ◽  
Carlos D. Vera ◽  
Dan P. Mulvihill ◽  
Martin Ridout ◽  
...  
Keyword(s):  
Heart Rate ◽  
Biochemical Analysis ◽  
Striated Muscle ◽  
Maximum Velocity ◽  
Fold Increase ◽  
Cardiac Contraction ◽  
Contraction Velocity ◽  
Small Set ◽  
Adp Release ◽  
Contracting Heart

AbstractHeart rate and the maximum velocity of contraction of striated muscle are inversely related to species size. As mammals evolve to different sizes, adaptations are required such as slower contracting heart and skeletal muscles. Analysis of the motor domain of β-myosin from 67 mammals from two clades identifies 14 sites, out of 800, strongly associated with body mass (p<0.01) but not with the clade (p>0.05). Nine of these sites were mutated in the human β-myosin to make it resemble the rat sequence. Biochemical analysis revealed that the rat-human β-myosin chimera functioned like the native rat myosin with a two fold increase in both motility and in the rate of ADP release from the actin.myosin cross-bridge (the step that limits contraction velocity). Both clades use the same small set of amino acids to adjust contraction velocity, suggesting a limited number of ways in which velocity can be manipulated.

scholarly journals Identification of sequence changes in myosin II that adjust muscle contraction velocity

PLoS Biology ◽  
2021 ◽  
Vol 19 (6) ◽  
pp. e3001248
Author(s):  
Chloe A. Johnson ◽  
Jake E. McGreig ◽  
Sarah T. Jeanfavre ◽  
Jonathan Walklate ◽  
Carlos D. Vera ◽  
...  
Keyword(s):  
Muscle Contraction ◽  
Body Mass ◽  
Myosin Ii ◽  
Sequence Divergence ◽  
Fold Increase ◽  
Motor Domain ◽  
Type I ◽  
Contraction Velocity ◽  
Contraction Speed ◽  
Adp Release

The speed of muscle contraction is related to body size; muscles in larger species contract at slower rates. Since contraction speed is a property of the myosin isoform expressed in a muscle, we investigated how sequence changes in a range of muscle myosin II isoforms enable this slower rate of muscle contraction. We considered 798 sequences from 13 mammalian myosin II isoforms to identify any adaptation to increasing body mass. We identified a correlation between body mass and sequence divergence for the motor domain of the 4 major adult myosin II isoforms (β/Type I, IIa, IIb, and IIx), suggesting that these isoforms have adapted to increasing body mass. In contrast, the non-muscle and developmental isoforms show no correlation of sequence divergence with body mass. Analysis of the motor domain sequence of β-myosin (predominant myosin in Type I/slow and cardiac muscle) from 67 mammals from 2 distinct clades identifies 16 sites, out of 800, associated with body mass (padj < 0.05) but not with the clade (padj > 0.05). Both clades change the same small set of amino acids, in the same order from small to large mammals, suggesting a limited number of ways in which contraction velocity can be successfully manipulated. To test this relationship, the 9 sites that differ between human and rat were mutated in the human β-myosin to match the rat sequence. Biochemical analysis revealed that the rat–human β-myosin chimera functioned like the native rat myosin with a 2-fold increase in both motility and in the rate of ADP release from the actin–myosin crossbridge (the step that limits contraction velocity). Thus, these sequence changes indicate adaptation of β-myosin as species mass increased to enable a reduced contraction velocity and heart rate.

HEART COMPLICATIONS IN HYPERTHYROIDISM

2011 ◽  
pp. 7-17
Author(s):  
Hai Thuy Nguyen ◽  
Anh Vu Nguyen
Keyword(s):  
Atrial Fibrillation ◽  
Blood Pressure ◽  
Heart Rate ◽  
Heart Diseases ◽  
Systolic Dysfunction ◽  
Oxygen Demand ◽  
Left Ventricular ◽  
Cardiac Contraction ◽  
Cardiac Complications ◽  
Cardiac Symptoms

Thyroid hormone increases the force of the contraction and the amount of the heart muscle oxygen demand. It also increases the heart rate. Due to these reasons, the work of the heart is greatly increased in hyperthyroidism. Hyperthyroidism increases the amount of nitric oxide in the intima, lead them to be dilated and become less stiff. Cardiac symptoms can be seen in anybody with hyperthyroidism, but can be particularly dangerous in whom have underlying heart diseases. Common symptoms include: tachycardia and palpitations. Occult hyperthyroidism is a common cause of an increased heart rate at rest and with mild exertion. Hyperthyroidism can also produce a host of other arrhythmias such as PVCs, ventricular tachycardia and especially atrial fibrillation. Left ventricular diastolic dysfunction and systolic dysfunction, Mitral regurgitation and mitral valve prolapsed are heart complications of hyperthyroism could be detected by echocardiography. The forceful cardiac contraction increases the systolic blood pressure despite the increased relaxation in the blood vessels reduces the diastolic blood pressure. Atrial fibrillation, atrial enlargement and congestive heart failure are important cardiac complications of hyperthyroidism. An increased risks of stroke is common in patients with atrial fibrillation. Graves disease is linked to autoimmune complications, such as cardiac valve involvement, pulmonary arterial hypertension and specific cardiomyopathy. Worsening angina: Patients with coronary artery disease often experience a marked worsening in symptoms with hyperthyroidism. These can include an increase in chest pain (angina) or even a heart attack.

Cardiovascular changes in the exercising emu

1983 ◽  
Vol 104 (1) ◽  
pp. 193-201 ◽  
Author(s):  
B. Grubb ◽  
D. D. Jorgensen ◽  
M. Conner
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Oxygen Consumption ◽  
Stroke Volume ◽  
Oxygen Content ◽  
Body Mass ◽  
Fold Increase ◽  
Exercise Heart Rate ◽  
Rate Of Oxygen Consumption ◽  
Cardiovascular Variables

Cardiovascular variables were studied as a function of oxygen consumption in the emu, a large, flightless ratite bird well suited to treadmill exercise. At the highest level of exercise, the birds' rate of oxygen consumption (VO2) was approximately 11.4 times the resting level (4.2 ml kg-1 min-1). Cardiac output was linearly related to VO2, increasing 9.5 ml for each 1 ml increase in oxygen consumption. The increase in cardiac output is similar to that in other birds, but appears to be larger than in mammals. The venous oxygen content dropped during exercise, thus increasing the arteriovenous oxygen content difference. At the highest levels of exercise, heart rate showed a 3.9-fold increase over the resting rate (45.8 beats min-1). The mean resting specific stroke volume was 1.5 ml per kg body mass, which is larger than shown by most mammals. However, birds have larger hearts relative to body mass than do mammals, and stroke volume expressed per gram of heart (0.18 ml g-1) is similar to that for mammals. Stroke volume showed a 1.8-fold increase as a result of exercise in the emus, but a change in heart rate plays a greater role in increasing cardiac output during exercise.

scholarly journals Extreme bradycardia and tachycardia in the world’s largest animal

2019 ◽  
Vol 116 (50) ◽  
pp. 25329-25332 ◽  
Author(s):  
J. A. Goldbogen ◽  
D. E. Cade ◽  
J. Calambokidis ◽  
M. F. Czapanskiy ◽  
J. Fahlbusch ◽  
...  
Keyword(s):  
Heart Rate ◽  
Large Diameter ◽  
Large Body ◽  
Fold Increase ◽  
Oxygen Depletion ◽  
Blue Whale ◽  
Heart Rates ◽  
Physiological Limits ◽  
Low Mass ◽  
Lunge Feeding

The biology of the blue whale has long fascinated physiologists because of the animal’s extreme size. Despite high energetic demands from a large body, low mass-specific metabolic rates are likely powered by low heart rates. Diving bradycardia should slow blood oxygen depletion and enhance dive time available for foraging at depth. However, blue whales exhibit a high-cost feeding mechanism, lunge feeding, whereby large volumes of prey-laden water are intermittently engulfed and filtered during dives. This paradox of such a large, slowly beating heart and the high cost of lunge feeding represents a unique test of our understanding of cardiac function, hemodynamics, and physiological limits to body size. Here, we used an electrocardiogram (ECG)-depth recorder tag to measure blue whale heart rates during foraging dives as deep as 184 m and as long as 16.5 min. Heart rates during dives were typically 4 to 8 beats min−1 (bpm) and as low as 2 bpm, while after-dive surface heart rates were 25 to 37 bpm, near the estimated maximum heart rate possible. Despite extreme bradycardia, we recorded a 2.5-fold increase above diving heart rate minima during the powered ascent phase of feeding lunges followed by a gradual decrease of heart rate during the prolonged glide as engulfed water is filtered. These heart rate dynamics explain the unique hemodynamic design in rorqual whales consisting of a large-diameter, highly compliant, elastic aortic arch that allows the aorta to accommodate blood ejected by the heart and maintain blood flow during the long and variable pauses between heartbeats.

Hemodynamic effects of vasopressin compared with angiotensin II in conscious rats

1987 ◽  
Vol 252 (3) ◽  
pp. H628-H637 ◽  
Author(s):  
J. W. Osborn ◽  
M. M. Skelton ◽  
A. W. Cowley
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Angiotensin Ii ◽  
Arterial Pressure ◽  
Peripheral Resistance ◽  
Fold Increase ◽  
Adrenergic Blockade ◽  
Ganglionic Blockade ◽  
Conscious Rats ◽  
Potent Vasoconstrictor

The mechanisms whereby arginine vasopressin influences hemodynamic and autonomic function were investigated in conscious rats. In normal rats, 60-min intravenous infusions produced dose-related increases of arterial pressure and total peripheral resistance with marked decreases of both heart rate and cardiac output. Cholinergic blockade with methscopolamine attenuated the bradycardia at higher doses of vasopressin, whereby the fall of cardiac output was not affected. beta-Adrenergic blockade with atenolol attenuated the fall of heart rate seen with lower doses of vasopressin but did not prevent the fall of cardiac output. Ganglionic blockade with methscopolamine and hexamethonium resulted in nearly a 60-fold enhancement of vasopressin pressor sensitivity. This was related to a greater rise of peripheral resistance, since the fall of cardiac output was not altered compared with normal rats. Hemodynamic responses to angiotensin II were determined in other groups of conscious, normal rats and rats with ganglionic blockade. Peripheral resistance increased in the normal rats, whereas the related decreases in cardiac output and heart rate were only 30% of the responses seen with equipressor doses of vasopressin. Ganglionic blockade increased pressor activity only two- to eightfold compared with the 60-fold increase observed with vasopressin. We conclude that vasopressin is a more potent vasoconstrictor than angiotensin II, decreases cardiac output independent of neural mechanisms, and results in withdrawal of sympathetic vascular tone to buffer rises of arterial pressure.

scholarly journals The panniculus carnosus muscle: A novel model of striated muscle regeneration that exhibits sex differences in the mdx mouse

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ola A. Bahri ◽  
Neia Naldaiz-Gastesi ◽  
Donna C. Kennedy ◽  
Antony M. Wheatley ◽  
Ander Izeta ◽  
...  
Keyword(s):  
Muscle Regeneration ◽  
Striated Muscle ◽  
Fold Increase ◽  
Wide Distribution ◽  
Calcium Handling ◽  
Mdx Mouse ◽  
Wild Type ◽  
Health And Disease ◽  
Fast Twitch ◽  
Shivering Thermogenesis

Abstract The dermal striated muscle panniculus carnosus (PC), prevalent in lower mammals with remnants in humans, is highly regenerative, and whose function is purported to be linked to defence and shivering thermogenesis. Given the heterogeneity of responses of different muscles to disease, we set out to characterize the PC in wild-type and muscular dystrophic mdx mice. The mouse PC contained mainly fast-twitch type IIB myofibers showing body wide distribution. The PC exemplified heterogeneity in myofiber sizes and a prevalence of central nucleated fibres (CNFs), hallmarks of regeneration, in wild-type and mdx muscles, which increased with age. PC myofibers were hypertrophic in mdx compared to wild-type mice. Sexual dimorphism was apparent with a two-fold increase in CNFs in PC from male versus female mdx mice. To evaluate myogenic potential, PC muscle progenitors were isolated from 8-week old wild-type and mdx mice, grown and differentiated for 7-days. Myogenic profiling of PC-derived myocytes suggested that male mdx satellite cells (SCs) were more myogenic than female counterparts, independent of SC density in PC muscles. Muscle regenerative differences in the PC were associated with alterations in expression of calcium handling regulatory proteins. These studies highlight unique aspects of the PC muscle and its potential as a model to study mechanisms of striated muscle regeneration in health and disease.

Propranolol induces acute natriuresis by β blockade and dopaminergic stimulation

1976 ◽  
Vol 54 (5) ◽  
pp. 683-691 ◽  
Author(s):  
M. C. Carrara ◽  
A. D. Baines
Keyword(s):  
Heart Rate ◽  
Sodium Excretion ◽  
Fold Increase ◽  
Nerve Function ◽  
Distal Nephron ◽  
Salt Diet ◽  
Blocking Effects ◽  
Low Salt ◽  
Dopaminergic Stimulation ◽  
Postganglionic Nerve

dl-Propranolol (0.8–1.6 mg/kg∙h for 1 h) produced a transient two- to three-fold increase in sodium excretion in nondiuretic rats infused with Pitressin and aldosterone and in water diuretic rats. Sodium excretion increased more in rats depleted of renin by chronic Doca and salt administration than in rats maintained on a low salt diet. An angiotensin inhibitor (1,sarcosine-8,valine angiotensin II) decreased sodium excretion. Therefore the natriuresis was not mediated by antidiuretic hormone, aldosterone, or renin–angiotensin. d-Propranolol did not produce a natriuresis. Prior treatment with phenoxybenzamine did not prevent the natriuretic response but chlorisondamine pretreatment did. The natriuresis is produced by β blockade and requires postganglionic nerve function but is independent of α receptors. dl-Propranolol decreased heart rate and cardiac output but systemic pressure did not fall and renal blood flow increased. This suggests a dopamine-mediated renal vasodilation and natriuresis. Haloperidol and pimozide, both dopamine blocking agents with minimal β blocking effects, prevented the natriuretic response. We conclude that propranolol may increase sodium excretion directly by blocking β receptors in the distal nephron and indirectly by dopamine-mediated renal vasodilation.

Contractile parameters and occurrence of alternans in isolated rat myocardium at supra-physiological stimulation frequency

2012 ◽  
Vol 302 (11) ◽  
pp. H2267-H2275 ◽  
Author(s):  
Jessica L. Slabaugh ◽  
Lucia Brunello ◽  
Sandor Gyorke ◽  
Paul M. L. Janssen
Keyword(s):  
Heart Rate ◽  
Steady State ◽  
Refractory Period ◽  
Striated Muscle ◽  
Stable Steady State ◽  
Maximal Heart Rate ◽  
Force Frequency ◽  
Mechanical Instability ◽  
Continuous Increase

The cardiac refractory period prevents the heart from tetanic activation that is typically used in noncardiac striated muscle tissue. To what extent the refractory period prevents successive action potentials to activate the excitation-contraction coupling process and contractile machinery at supra-physiological rates, such as those present during ventricular fibrillation, is unknown. Using multicellular trabeculae isolated from rat hearts, we studied amplitude and kinetics of contraction at rates well above the normal in vivo rat heart range. We show that even at twice the maximal heart rate of the rat, little or no mechanical instability is observed; twitch contractions are at steady state, albeit with an elevated active diastolic force. Although the amplitude of contraction increased within in vivo heart rates (positive force-frequency response), at frequencies beyond the maximal heart rate (10–30 Hz) a steady decline of contractile amplitude is observed. Not until 30 Hz do the majority of the isolated muscle preparations show mechanical alternans, where strong and weak beats alternate. Interestingly, unlike striated limb skeletal muscle, fusing of twitch contractions did not cause a continuous increase in peak force: at frequencies of 10 Hz and above, systolic force declines with relatively little elevation in diastolic force. Contractile kinetics continued to accelerate, from 1 Hz up to 30 Hz, whereas the relative speed of contraction and relaxation remained closely coupled, reflected by a singular linear relationship between the maximal and minimal derivative of force (dF/d t). We conclude that cardiac muscle can produce mechanically stable steady-state contractions at supra-physiological pacing rates, while these contractions continue to decline in amplitude and increase in diastolic force past maximal heart rate.

scholarly journals Modified uroporphyrinogen decarboxylase activity in a yeast mutant which mimics porphyria cutanea tarda

1984 ◽  
Vol 218 (2) ◽  
pp. 405-413 ◽  
Author(s):  
J Rytka ◽  
T Bilinski ◽  
R Labbe-Bois
Keyword(s):  
Biochemical Analysis ◽  
Porphyria Cutanea Tarda ◽  
Fold Increase ◽  
Recessive Mutation ◽  
Decarboxylase Activity ◽  
Cell Free Extract ◽  
Yeast Mutant ◽  
Uroporphyrinogen Decarboxylase ◽  
Yeast Saccharomyces Cerevisiae ◽  
Biochemical Characteristics

The isolation of a new mutant Sm1 strain of yeast, Saccharomyces cerevisiae, is described: this strain was partially defective in haem formation and accumulated large amounts of Zn-porphyrins. Genetic analysis showed that the porphyrin accumulation was under the control of a single nuclear recessive mutation. Biochemical analysis showed that the main porphyrins accumulated in the cells were uroporphyrin and heptacarboxyporphyrin, mostly of the isomer-III type. The excreted porphyrins comprised mainly dehydroisocoproporphyrin. Analysis of uroporphyrinogen decarboxylase activity in the cell-free extract revealed a 70-80% decrease of activity in the mutant and showed that the relative rates of the different decarboxylation steps were modified with the mutant enzyme. A 2-3-fold increase in 5-aminolaevulinate synthase activity was measured in the mutant. The biochemical characteristics of the Sm1 mutant are very similar to those described for porphyria cutanea tarda.

DIFFERENCES IN PUTTER TRAJECTORY AND PSYCHOPHYSIOLOGICAL VARIABLES BETWEEN PROFESSIONAL AND AMATEUR GOLFERS UNDER STRESS CONDITION

2018 ◽  
Vol 18 (07) ◽  
pp. 1840008
Author(s):  
JIN SEUNG CHOI ◽  
JEONG WOO SEO ◽  
GYE RAE TACK
Keyword(s):  
Heart Rate ◽  
State Anxiety ◽  
Stress Condition ◽  
Maximum Velocity ◽  
Professional Group ◽  
Maximum Speed ◽  
Psychological Variables ◽  
Self Confidence ◽  
Professional Golfers ◽  
Knockout Tournament

This study compared the differences in the putter trajectory and psychophysiological variables of winners and losers in a competitive putting game that targeted professional and amateur golfers under stress. Eight professional golfers (handicap: [Formula: see text]) and eight amateur golfers (handicap: [Formula: see text]) participated. To maximize the tension of the competition, the putting game was held in a single-elimination one-on-one knockout tournament with a single 2.1[Formula: see text]m putting competition for each group. In the case of a hole-in or a failure by both golfers, the game resumed until the winner was determined. To compare the golfers during the game, the maximum speed, moving length, and amplitude of the putter head during the back-swing and the follow-through were set as the motion variables; and psychological variables (heart rate, heart rate variability (HRV), and Competitive State Anxiety Inventory-2 (CSAI-2)) were analyzed. The results showed significant differences between the putter trajectory variables (maximum velocity and amplitude of the putter head during follow-through) of the groups, but no differences in the psychophysiological variables. In comparing winners and losers within each group, however, the professional group showed a difference in only the psychophysiological variables (HRV and self-confidence of CSAI-2), whereas the amateur group showed a difference in only one putter trajectory variable (follow-through length). It was quantitatively confirmed that factors that determine the outcome of the game differed at a technical level.

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