Matching the Heart to Heat-Induced Circulatory Load: Heat-Acclimatory Responses

Physiology ◽  
2003 ◽  
Vol 18 (6) ◽  
pp. 215-221 ◽  
Author(s):  
Michal Horowitz
Keyword(s):  
Heart Rate ◽  
Oxygen Demand ◽  
Heat Acclimation ◽  
Regulatory Proteins ◽  
Contractile Apparatus ◽  
Cardiac Efficiency ◽  
Cross Tolerance ◽  
Altered Expression ◽  
Expression Of Genes ◽  
Cardiac Adaptation

Heat acclimation enhances cardiac efficiency by increasing stroke volume and decreasing heart rate. These adaptations involve biochemical changes in the contractile apparatus, switched on by altered expression of genes coding contractile and calcium-regulatory proteins and partially mediated by persistent low thyroxine. Heat acclimation also produces cross-tolerance to oxygen deprivation, thus reinforcing cardiac adaptation to oxygen demand/supply mismatching via energy-sparing pathways.

Changes in cardiac mechanics with heat acclimation: adrenergic signaling and SR-Ca regulatory proteins

2000 ◽  
Vol 279 (1) ◽  
pp. R77-R85 ◽  
Author(s):  
Eynan Mirit ◽  
Chaya Gross ◽  
Yonathan Hasin ◽  
Aharon Palmon ◽  
Michal Horowitz
Keyword(s):  
Systolic Pressure ◽  
Cardiac Mechanics ◽  
Heat Acclimation ◽  
Regulatory Proteins ◽  
Inotropic Response ◽  
Altered Expression ◽  
Adrenergic Signaling ◽  
Plasmic Reticulum ◽  
Encoded Proteins ◽  
Steady State Levels

The involvement of adrenergic signaling and sarcoplasmic calcium regulatory proteins in the development of heat acclimation-induced adaptations in cardiac mechanics was studied in heat-acclimated (34°C) rats for 2, 5, and 30 days (AC2, AC5, and AC30, respectively). Control (C) rats were held at 24 ± 1°C. Systolic pressure (LVP) and velocities of contraction (dP/d t/P) and relaxation (−dP/d t/P) were measured using a Langendorff system. For adrenergic signaling, β-adrenoreceptor (AR) density and affinity (Scatchard plots) and cardiac inotropic response to norepinephrine (10− 7 mM, ± 10− 6 mM propranolol) were measured. For the regulatory proteins, steady-state levels of Ca2+-ATPase and phospholamban (PLB) mRNAs and the encoded proteins Ca2+-ATPase [sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA)] and PLB were measured using semiquantitative RT-PCR and Western immunoblotting, respectively. Both short (STHA; AC2 and AC5)- and long-term heat acclimation (LTHA; AC30) enhanced LVP. However, dP/d t ⋅ P and −dP/d t ⋅ P in STHA hearts resembled that of the controls, whereas on LTHA, both parameters decreased ( P< 0.05), implying decreased velocity of contraction and relaxation. β-AR density remained unchanged with their affinity markedly decreased ( P < 0.05). AR responsiveness, however, diminished in AC2 but was markedly enhanced on LTHA. During STHA, PLB and sarcoplasmic reticulum Ca2+-ATPase transcripts were upregulated with no change in the encoded proteins except for SERCA downregulation on AC5, leading to an increased PLB/SERCA ratio ( P < 0.05). This mismatched preacclimation lusitropic state on STHA and increased PLB/SERCA ratio was evident ( P < 0.05) due to downregulation of SERCA and upregulation of PLB. Our data fit a biphasic acclimation model in which desensitized adrenergic signaling is dominant during STHA, whereas on LTHA, the contractile machinery is influenced by altered expression of the calcium regulatory proteins leading to both augmented adrenergic inotropic response (via PLB elevation) and decreased velocity of relaxation. The sustained low thyroxin measured on LTHA causally associates with this response.

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.

Herpesvirus-Associated Proliferative Skin Disease in Frogs and Toads: Proposed Pathogenesis

2021 ◽  
pp. 030098582110063
Author(s):  
Francesco C. Origgi ◽  
Patricia Otten ◽  
Petra Lohmann ◽  
Ursula Sattler ◽  
Thomas Wahli ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Rana Temporaria ◽  
Skin Lesions ◽  
Bufo Bufo ◽  
Careful Examination ◽  
Altered Expression ◽  
Expression Of Genes ◽  
Cell Remodeling ◽  
Tissue Changes

A comparative study was carried out on common and agile frogs ( Rana temporaria and R. dalmatina) naturally infected with ranid herpesvirus 3 (RaHV3) and common toads ( Bufo bufo) naturally infected with bufonid herpesvirus 1 (BfHV1) to investigate common pathogenetic pathways and molecular mechanisms based on macroscopic, microscopic, and ultrastructural pathology as well as evaluation of gene expression. Careful examination of the tissue changes, supported by in situ hybridization, at different stages of development in 6 frogs and 14 toads revealed that the skin lesions are likely transient, and part of a tissue cycle necessary for viral replication in the infected hosts. Transcriptomic analysis, carried out on 2 naturally infected and 2 naïve common frogs ( Rana temporaria) and 2 naturally infected and 2 naïve common toads ( Bufo bufo), revealed altered expression of genes involved in signaling and cell remodeling in diseased animals. Finally, virus transcriptomics revealed that both RaHV3 and BfHV1 had relatively high expression of a putative immunomodulating gene predicted to encode a decoy receptor for tumor necrosis factor in the skin of the infected hosts. Thus, the comparable lesions in infected frogs and toads appear to reflect a concerted epidermal and viral cycle, with presumptive involvement of signaling and gene remodeling host and immunomodulatory viral genes.

The effect of diabetes on heart rate and other determinants of myocardial oxygen demand in acute coronary syndromes

2004 ◽  
Vol 21 (9) ◽  
pp. 1025-1031 ◽  
Author(s):  
K. Foo ◽  
N. Sekhri ◽  
C. Knight ◽  
A. Deaner ◽  
J. Cooper ◽  
...  
Keyword(s):  
Heart Rate ◽  
Acute Coronary Syndromes ◽  
Oxygen Demand ◽  
Myocardial Oxygen Demand ◽  
Coronary Syndromes

Physiological Assessment of Bagpipers: A Preliminary Study of Cardiopulmonary Parameters

2000 ◽  
Vol 15 (2) ◽  
pp. 51-54
Author(s):  
Deborah Barr ◽  
Lee Van Dusen ◽  
Steve Ess ◽  
Julie Plezbert
Keyword(s):  
Heart Rate ◽  
Repeated Measures ◽  
Vital Capacity ◽  
A Priori ◽  
Mean Values ◽  
Time Period ◽  
Impedance Cardiograph ◽  
Cardiac Adaptation ◽  
Automatic Blood Pressure ◽  
Predicted Values

This study examined pulmonary function of pipers and cardiac adaptation to the playing of the Great Highland bagpipe. Pipers (n = 13) of varying ages (31-65 years) and playing experiences (2-20+ years) were evaluated for vital capacity (VC), maximal voluntary ventilation (MVV), and forced vital capacity (FVC) using a RIKO AS-600 spirometer. Subjects were monitored by impedance cardiograph for heart rate (HR), stroke volume (SV), and cardiac output (CO) at rest and during 5 minutes of playing. An automatic blood pressure (BP) monitor collected BP values over the same time period. Eleven weeks after initial cardiac data collection, the BP and cardiac measurements were repeated using the same protocols. Mean values for HR, SV, and CO were calculated for rest and each minute (1-5) of playing. A 2 (data session) by 6 (rest, min 1–5) repeated-measures ANOVA was performed. Analysis revealed a significant overall time effect (p < 0.001) on HR. A-priori contrast comparing all playing times with rest showed significant differences at all time points. Analysis of SV and CO failed to find significance. Heart rate values calculated for percent of maximum ranged from 68% to 89% of maximum overall while playing (session 1) and from 55% to 81% of maximum (session 2). Predicted percent of maximum values for VC and MVV found 77% of players above their maximum predicted values.

Heat acclimation, aerobic fitness, and hydration effects on tolerance during uncompensable heat stress

1998 ◽  
Vol 84 (5) ◽  
pp. 1731-1739 ◽  
Author(s):  
Stephen S. Cheung ◽  
Tom M. McLellan
Keyword(s):  
Heart Rate ◽  
Heat Stress ◽  
Aerobic Fitness ◽  
Protective Clothing ◽  
Sweat Rate ◽  
Heat Acclimation ◽  
Short Term ◽  
Chemical Protective Clothing ◽  
Uncompensable Heat Stress ◽  
C 30

—The purpose of the present study was to determine the separate and combined effects of aerobic fitness, short-term heat acclimation, and hypohydration on tolerance during light exercise while wearing nuclear, biological, and chemical protective clothing in the heat (40°C, 30% relative humidity). Men who were moderately fit [(MF); <50 ml ⋅ kg−1 ⋅ min−1maximal O2 consumption; n = 7] and highly fit [(HF); >55 ml ⋅ kg−1 ⋅ min−1maximal O2 consumption; n = 8] were tested while they were euhydrated or hypohydrated by ∼2.5% of body mass through exercise and fluid restriction the day preceding the trials. Tests were conducted before and after 2 wk of daily heat acclimation (1-h treadmill exercise at 40°C, 30% relative humidity, while wearing the nuclear, biological, and chemical protective clothing). Heat acclimation increased sweat rate and decreased skin temperature and rectal temperature (Tre) in HF subjects but had no effect on tolerance time (TT). MF subjects increased sweat rate but did not alter heart rate, Tre, or TT. In both MF and HF groups, hypohydration significantly increased Tre and heart rate and decreased the respiratory exchange ratio and the TT regardless of acclimation state. Overall, the rate of rise of skin temperature was less, while ΔTre, the rate of rise of Tre, and the TT were greater in HF than in MF subjects. It was concluded that exercise-heat tolerance in this uncompensable heat-stress environment is not influenced by short-term heat acclimation but is significantly improved by long-term aerobic fitness.

Altered expression of genes regulating angiogenesis in experimental androgen-independent prostate cancer

The Prostate ◽  
2007 ◽  
Vol 68 (2) ◽  
pp. 161-170 ◽  
Author(s):  
Heléne Gustavsson ◽  
Karin Jennbacken ◽  
Karin Welén ◽  
Jan-Erik Damber
Keyword(s):  
Prostate Cancer ◽  
Altered Expression ◽  
Expression Of Genes ◽  
Androgen Independent

scholarly journals Depletion of KNL2 Results in Altered Expression of Genes Involved in Regulation of the Cell Cycle, Transcription, and Development in Arabidopsis

2019 ◽  
Vol 20 (22) ◽  
pp. 5726 ◽  
Author(s):  
Anastassia Boudichevskaia ◽  
Andreas Houben ◽  
Anne Fiebig ◽  
Klara Prochazkova ◽  
Ales Pecinka ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Critical Role ◽  
Histone H3 ◽  
Global Gene Expression ◽  
Proper Function ◽  
Knockout Mutant ◽  
Flower Bud ◽  
Altered Expression ◽  
Expression Of Genes ◽  
Histone H3 Variant

Centromeres contain specialized nucleosomes at which histone H3 is partially replaced by the centromeric histone H3 variant cenH3 that is required for the assembly, maintenance, and proper function of kinetochores during mitotic and meiotic divisions. Previously, we identified a KINETOCHORE NULL 2 (KNL2) of Arabidopsis thaliana that is involved in the licensing of centromeres for the cenH3 recruitment. We also demonstrated that a knockout mutant for KNL2 shows mitotic and meiotic defects, slower development, reduced growth rate, and fertility. To analyze an effect of KNL2 mutation on global gene transcription of Arabidopsis, we performed RNA-sequencing experiments using seedling and flower bud tissues of knl2 and wild-type plants. The transcriptome data analysis revealed a high number of differentially expressed genes (DEGs) in knl2 plants. The set was enriched in genes involved in the regulation of the cell cycle, transcription, development, and DNA damage repair. In addition to comprehensive information regarding the effects of KNL2 mutation on the global gene expression, physiological changes in plants are also presented, which provides an integrated understanding of the critical role played by KNL2 in plant growth and development.

scholarly journals Age-dependent changes in electrophysiology and calcium handling – implications for pediatric cardiac research

2019 ◽  
Author(s):  
Luther M. Swift ◽  
Morgan Burke ◽  
Devon Guerrelli ◽  
Manelle Ramadan ◽  
Marissa Reilly ◽  
...  
Keyword(s):  
Postnatal Development ◽  
Cardiac Electrophysiology ◽  
Calcium Handling ◽  
Cell Coupling ◽  
Altered Expression ◽  
Expression Of Genes ◽  
Age Dependent ◽  
Genes Encoding ◽  
Cardiac Maturation

ABSTRACTRationaleThe heart continues to develop and mature after birth and into adolescence. Accordingly, cardiac maturation is likely to include a progressive refinement in both organ morphology and function during the postnatal period. Yet, age-dependent changes in cardiac electrophysiology and calcium handling have not yet been fully characterized.ObjectiveThe objective of this study, was to examine the relationship between cardiac maturation, electrophysiology, and calcium handling throughout postnatal development in a rat model.MethodsPostnatal rat cardiac maturation was determined by measuring the expression of genes involved in cell-cell coupling, electrophysiology, and calcium handling. In vivo electrocardiograms were recorded from neonatal, juvenile, and adult animals. Simultaneous dual optical mapping of transmembrane voltage and calcium transients was performed on isolated, Langendorff-perfused rat hearts (postnatal day 0–3, 4-7, 8-14, adult).ResultsYounger, immature hearts displayed slowed electrical conduction, prolonged action potential duration and increased ventricular refractoriness. Slowed calcium handling in the immature heart increased the propensity for calcium transient alternans which corresponded to alterations in the expression of genes encoding calcium handling proteins. Developmental changes in cardiac electrophysiology were associated with the altered expression of genes encoding potassium channels and intercalated disc proteins.ConclusionUsing an intact whole heart model, this study highlights chronological changes in cardiac electrophysiology and calcium handling throughout postnatal development. Results of this study can serve as a comprehensive baseline for future studies focused on pediatric cardiac research, safety assessment and/or preclinical testing using rodent models.

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