scholarly journals Nano-imaging of the beating mouse heart in vivo: Importance of sarcomere dynamics, as opposed to sarcomere length per se, in the regulation of cardiac function

2015 ◽  
Vol 147 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Fuyu Kobirumaki-Shimozawa ◽  
Kotaro Oyama ◽  
Togo Shimozawa ◽  
Akari Mizuno ◽  
Takashi Ohki ◽  
...  
Keyword(s):  
High Speed ◽  
Sarcomere Length ◽  
Imaging System ◽  
Critical Role ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Mouse Heart ◽  
Tight Coupling ◽  
Sarcomere Dynamics

Sarcomeric contraction in cardiomyocytes serves as the basis for the heart’s pump functions in mammals. Although it plays a critical role in the circulatory system, myocardial sarcomere length (SL) change has not been directly measured in vivo under physiological conditions because of technical difficulties. In this study, we developed a high speed (100–frames per second), high resolution (20-nm) imaging system for myocardial sarcomeres in living mice. Using this system, we conducted three-dimensional analysis of sarcomere dynamics in left ventricular myocytes during the cardiac cycle, simultaneously with electrocardiogram and left ventricular pressure measurements. We found that (a) the working range of SL was on the shorter end of the resting distribution, and (b) the left ventricular–developed pressure was positively correlated with the SL change between diastole and systole. The present findings provide the first direct evidence for the tight coupling of sarcomere dynamics and ventricular pump functions in the physiology of the heart.

scholarly journals High-Speed, High-Performance Real-Time Imaging of Physiological Sarcomere Dynamics in the Beating Mouse Heart in Vivo

2016 ◽  
Vol 110 (3) ◽  
pp. 463a
Author(s):  
Fuyu Kobirumaki-Shimozawa ◽  
Kotaro Oyama ◽  
Togo Shimozawa ◽  
Takashi Ohki ◽  
Takako Terui ◽  
...  
Keyword(s):  
Real Time ◽  
High Speed ◽  
High Performance ◽  
Mouse Heart ◽  
Real Time Imaging ◽  
Sarcomere Dynamics

scholarly journals Synchrony of sarcomeric movement regulates left ventricular pump function in the in vivo beating mouse heart

2021 ◽  
Vol 153 (11) ◽  
Author(s):  
Fuyu Kobirumaki-Shimozawa ◽  
Togo Shimozawa ◽  
Kotaro Oyama ◽  
Shunsuke Baba ◽  
Jia Li ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Sarcomere Length ◽  
Left Ventricular ◽  
Mouse Heart ◽  
The Novel ◽  
Passive Force ◽  
Pump Function ◽  
Average Value ◽  
Contribution Index

Sarcomeric contraction in cardiomyocytes serves as the basis for the heart’s pump functions. It has generally been considered that in cardiac muscle as well as in skeletal muscle, sarcomeres equally contribute to myofibrillar dynamics in myocytes at varying loads by producing similar levels of active and passive force. In the present study, we expressed α-actinin–AcGFP in Z-disks to analyze dynamic behaviors of sequentially connected individual sarcomeres along a myofibril in a left ventricular (LV) myocyte of the in vivo beating mouse heart. To quantify the magnitude of the contribution of individual sarcomeres to myofibrillar dynamics, we introduced the novel parameter “contribution index” (CI) to measure the synchrony in movements between a sarcomere and a myofibril (from −1 [complete asynchrony] to 1 [complete synchrony]). First, CI varied markedly between sarcomeres, with an average value of ∼0.3 during normal systole. Second, when the movements between adjacent sarcomeres were asynchronous (CI < 0), a sarcomere and the ones next to the adjacent sarcomeres and farther away moved in synchrony (CI > 0) along a myofibril. Third, when difference in LV pressure in diastole and systole (ΔLVP) was lowered to <10 mm Hg, diastolic sarcomere length increased. Under depressed conditions, the movements between adjacent sarcomeres were in marked asynchrony (CI, −0.3 to −0.4), and, as a result, average CI was linearly decreased in association with a decrease in ΔLVP. These findings suggest that in the left ventricle of the in vivo beating mouse heart, (1) sarcomeres heterogeneously contribute to myofibrillar dynamics due to an imbalance of active and passive force between neighboring sarcomeres, (2) the force imbalance is pronounced under depressed conditions coupled with a marked increase in passive force and the ensuing tug-of-war between sarcomeres, and (3) sarcomere synchrony via the distal intersarcomere interaction regulates the heart's pump function in coordination with myofibrillar contractility.

Abstract 5402: Two Photon Microscopy Measurements Of Sub-epicardial Sarcomere Length In Perfused Rat Hearts

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Patrizia Camelliti ◽  
Gil Bub ◽  
Daniel J Stuckey ◽  
Christian Bollensdorff ◽  
Damian J Tyler ◽  
...  
Keyword(s):  
Sarcomere Length ◽  
Left Ventricular ◽  
Model Systems ◽  
Future Research ◽  
Fundamental Parameter ◽  
Rat Hearts ◽  
Perfused Hearts ◽  
Over Time

Sarcomere length (SL) is a fundamental parameter underlying the Frank Starling relation in the heart, as it offers an absolute representation of myocardial stretch. Previous studies addressed the Frank Starling relation by measuring SL in isolated myocytes or muscle strips. Here, we report first data obtained using a novel technique to measure sub-epicardial SL in perfused hearts. Rat hearts were Langendorff perfused (normal Tyrode solution) at a constant pressure of 90mmHg, labeled with the fluorescent membrane marker di-4-ANEPPS, and then arrested with high-K + Tyrode for either 2-photon microscopy (n=4) or MRI (n=4). Image analysis software was developed to extract SL at the cell level from >1,400 2-photon images (Fig 1 ) and correct for cell angle. SL increased by 10±2 % between 30 and 80 min of perfusion (1.98±0.04 to 2.17±0.03 μm; p<0.05; Fig 1 ). Measurements of left ventricular myocardial volume (LVMV) were made in vivo and in perfused hearts using 3D MRI. LVMV increased by 24±7% from in vivo to 30 min of perfusion, and by 11±3 % between 30 and 90 min (539±35; 664±44; 737±49 mm 3 , respectively; p<0.05; Fig 1 ). We show that SL can be measured in isolated perfused hearts. The method allowed monitoring of changes in SL over time, and showed that SL and LVMV increase to a similar extent during 30–80 min perfusion with crystalloid solution, probably due to tissue oedema. This result, together with the increase in LVMV during the first 30 min, highlights the pronounced differences between in vivo , in situ , and in vitro model systems for studies of cardiac physiology and mechanics. Future research will compare changes in SL in healthy hearts and disease models involving contractile dysfunction. Figure 1: Left: 2-photon microscopy image of di-4-ANEPPS labeled myocardium. Right: SL and LVMV changes over time.

In vivo safety and accuracy of a clinically applicable telemetered left ventricular pressure module: intermediate-term results

2004 ◽  
Vol 10 (4) ◽  
pp. S67 ◽  
Author(s):  
Patrick I. McConnell ◽  
Daise de Cunha ◽  
Tanya Shipkowitz ◽  
Justin Van Hee ◽  
Phillip H. Long ◽  
...  
Keyword(s):  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Ventricular Pressure

Abstract 1008: A Protective Role for Cardiac Specific Muscle Ring Finger-1 (MuRF1) in Ischemia/Reperfusion Injury In Vivo

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Monte S Willis ◽  
Mauricio Rojas ◽  
Pamela Lockyer ◽  
Thomas G Hampton ◽  
Luge Li ◽  
...  
Keyword(s):  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Critical Role ◽  
Ring Finger ◽  
Left Ventricular ◽  
Ex Situ ◽  
Histological Evaluation ◽  
Area At Risk ◽  
Fractional Shortening

We previously identified a critical role for MuRF1 in suppressing pathologic cardiac hypertrophy. To extend these observations to other pathologic processes, we tested the role of MuRF1 in cardiac ischemia reperfusion (I/R) injury. We challenged MuRF1 transgenic (Tg) mice to I/R injury both ex situ and in vivo. First, we examined isolated MuRF1 Tg and age-matched sibling wild-type (WT) hearts after global ischemia (15 min) followed by reperfusion (20 min) in a Langendorff apparatus. Baseline function of MuRF1 Tg hearts did not significantly differ from WT hearts (mean left ventricular developed pressure (LVDP) 88.5 +/− 18 vs. 82.5 +/− 6.7, respectively; n = 4/group). Mean LVDP of hearts from MuRF1 Tg mice after reperfusion was 76.0 +/− 22.9% of baseline function compared to 27.2 +/− 13.3% in WT hearts (N = 5/group, P< 0.05)). To confirm that MuRF1 is cardioprotective in vivo, we subjected MuRF1 Tg and WT mice to a 30 minute ligation of the left anterior descending coronary artery, followed by 24 hours reperfusion. Mice underwent conscious echocardiography at baseline and after 24 hours; cardiac function was further interrogated by Millar pressure volume catheterization at 24 hours. Additionally, hearts underwent a histological evaluation of area at risk and infarct size. By echocardiography, a ~7% decrease in fractional shortening was identified in MuRF1 Tg mice after 24 hours reperfusion compared to baseline. This was in striking contrast to WT mice, which exhibited ~48% decrease in fractional shortening. Steady state catheterization measurements showed a significantly higher ejection fraction in MuRF1 Tg compared to WT mice after I/R injury (81.6 ± 2.3% vs. 49.0 +/− 4.0%, P < 0.05). Contractility reflected by +dP/dt max was better preserved in MuRF1 Tg compared to WT mice after I/R injury (12,614 +/− 776 vs. 7,448 +/−752, N = 3–12/group, P < 0.05). Histologically, the area of infarct in MuRF1 Tg mice was significantly smaller (10.0 +/− 0.8%) than in WT mice (25.5 +/− 2.5%, N = 4/group, P < 0.05). We demonstrate here for the first time that cardiac MuRF1 expression preserves function after I/R injury in vivo. Since MuRF1 is known to interact with metabolic and structural targets, this model will allow us to identify mechanisms by which MuRF1 modifies cardiac pathophysiology.

Abstract 96: Inactivation of Neddylation Causes Left Ventricular Noncompaction Cardiomyopathy Through Suppressing YAP Signaling

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Jianqiu Zou ◽  
Wenxia Ma ◽  
Jie Li ◽  
Rodney Littlejohn ◽  
Il-man Kim ◽  
...  
Keyword(s):  
Cardiac Development ◽  
Heart Diseases ◽  
Left Ventricular ◽  
Late Gestation ◽  
Mouse Heart ◽  
Cardiomyocyte Proliferation ◽  
Transcription Cofactor ◽  
Wild Type Counterpart

Rationale: Cardiac development is orchestrated by a number of growth factors, transcription factors and epigenetic regulators, perturbation of which can lead to congenital heart diseases and cardiomyopathies. However, the role of novel ubiquitin-like protein modifiers, such as NEDD8 (neural precursor cells expressed developmentally downregulated 8), in cardiac development is unknown. Objectives: The objective of this study was to determine the significance of NEDD8 modification (neddylation) during perinatal cardiac development. Methods and Results: Neddylated proteins and NEDD8 enzymes were highly abundant in fetal and neonatal hearts but downregulated in adult hearts. We employed an αMHC Cre transgene to delete NAE1, a subunit of the NEDD8 E1 enzyme, in the perinatal mouse heart. Cardiac-specific deletion of NAE1 (NAE1 CKO ) significantly decreased neddylated proteins in the heart. The NAE1 CKO mice displayed cardiac hypoplasia, ventricular non-compaction and heart failure during late gestation, which became more pronounced by postnatal day 1 and led to perinatal lethality. Mechanistically, genetic deletion or pharmacological inhibition of NAE1 resulted in accumulation of Hippo kinases Mst1 and LATS1/2, which in turn phosphorylated and inactivated YAP, a transcription cofactor necessary for cardiomyocyte proliferation, leading to dysregulation of a number of cell cycle-regulatory genes and blockade of cardiomyocyte proliferation in vivo and in vitro . Reactivation of YAP signaling by overexpression of a constitutively-active YAP mutant (YAP 5SA ), but not its wild-type counterpart, overcame the blockade of cardiomyocyte proliferation induced by inhibition of NAE1. Conclusions: Our findings establish the importance of neddylation in the heart, more specifically, in ventricular chamber maturation, and identify neddylation as a novel regulator of Hippo-YAP signaling to promote cardiomyocyte proliferation.

Myocardial substrate metabolism influences left ventricular energetics in vivo

2000 ◽  
Vol 278 (4) ◽  
pp. H1345-H1351 ◽  
Author(s):  
Christian Korvald ◽  
Odd Petter Elvenes ◽  
Truls Myrmel
Keyword(s):  
Fatty Acid ◽  
Coronary Flow ◽  
Left Ventricular Pressure ◽  
Random Order ◽  
Left Ventricular ◽  
Acid Oxidation ◽  
Left Ventricular Volumes ◽  
Acid Consumption ◽  
Myocardial Substrate

The myocardial oxygen consumption (MV˙o 2) to left ventricular pressure-volume area (PVA) relationship is assumed unaltered by substrates, despite varying phosphate-to-oxygen ratios and possible excess MV˙o 2 associated with fatty acid consumption. The validity of this assumption was tested in vivo. Left ventricular volumes and pressures were assessed with a combined conductance-pressure catheter in eight anesthetized pigs. MV˙o 2 was calculated from coronary flow and arterial-coronary sinus O2 differences. Metabolism was altered by glucose-insulin-potassium (GIK) or Intralipid-heparin (IH) infusions in random order and monitored with [14C]glucose and [3H]oleate tracers. Profound shifts in glucose and fatty acid oxidation were observed. Contractility, coronary flow, and slope of the MV˙o 2-PVA relationship were unchanged during GIK and IH infusions. MV˙o 2 at zero PVA (unloaded MV˙o 2) was 0.16 ± 0.13 J ⋅ beat− 1 ⋅ 100 g− 1 higher during IH compared with GIK infusion ( P = 0.001), a 48% increase. The study demonstrates a marked energetic advantage of glucose oxidation in the myocardium, profoundly affecting the MV˙o 2-PVA relationship. This may in part explain the “oxygen-wasting” effect of lipid-enhancing interventions such as adrenergic drugs and ischemia.

Altered sensitivity of chronic diabetic rat heart to calcium

1983 ◽  
Vol 245 (6) ◽  
pp. E560-E567 ◽  
Author(s):  
D. R. Bielefeld ◽  
C. S. Pace ◽  
B. R. Boshell
Keyword(s):  
Rat Heart ◽  
Calcium Metabolism ◽  
Left Ventricular Pressure ◽  
Calcium Sensitivity ◽  
Diabetic Rats ◽  
Left Ventricular ◽  
Diabetic Rat ◽  
Isolated Hearts ◽  
Pressure Development

An alteration in calcium metabolism in cardiac muscle was observed in diabetic rats 3 mo after streptozotocin treatment. Depression of cardiac output and left ventricular pressure development were more sensitive to decreased extra-cellular calcium in hearts from diabetic than from control animals and occurred within the normal physiological range of freely ionized serum calcium. This decrease in calcium sensitivity was not present after 2 wk of diabetes. In vivo treatment with insulin for 1 mo completely reversed the effect. Addition of octanoate (0.3 mM) to the perfusate of isolated hearts completely reversed the defect, whereas epinephrine (25 nM) only partially reversed it. When the glucose concentration of the perfusate was decreased, the function of diabetic hearts declined and was further diminished at decreasing calcium levels. Hearts from normal rats were unaffected. These results suggest that there is a defect in calcium metabolism or flux in the chronic diabetic rat heart.

scholarly journals Insulin-like stimulation of cardiac fuel metabolism by physiological levels of glucagon: involvement of PI3K but not cAMP

2008 ◽  
Vol 295 (1) ◽  
pp. E155-E161 ◽  
Author(s):  
Julie A. Harney ◽  
Robert L. Rodgers
Keyword(s):  
Left Ventricular Pressure ◽  
Adenosine Monophosphate ◽  
Left Ventricular ◽  
Glycolytic Flux ◽  
Blood Levels ◽  
Response Curves ◽  
Fuel Metabolism ◽  
Camp Levels ◽  
Stimulation Of

At concentrations around 10−9 M or higher, glucagon increases cardiac contractility by activating adenylate cyclase/cyclic adenosine monophosphate (AC/cAMP). However, blood levels in vivo, in rats or humans, rarely exceed 10−10 M. We investigated whether physiological concentrations of glucagon, not sufficient to increase contractility or ventricular cAMP levels, can influence fuel metabolism in perfused working rat hearts. Two distinct glucagon dose-response curves emerged. One was an expected increase in left ventricular pressure (LVP) occurring between 10−9.5 and 10−8 M. The elevations in both LVP and ventricular cAMP levels produced by the maximal concentration (10−8 M) were blocked by the AC inhibitor NKY80 (20 μM). The other curve, generated at much lower glucagon concentrations and overlapping normal blood levels (10−11 to 10−10 M), consisted of a dose-dependent and marked stimulation of glycolysis with no change in LVP. In addition to stimulating glycolysis, glucagon (10−10 M) also increased glucose oxidation and suppressed palmitate oxidation, mimicking known effects of insulin, without altering ventricular cAMP levels. Elevations in glycolytic flux produced by either glucagon (10−10 M) or insulin (4 × 10−10 M) were abolished by the phosphoinositide 3-kinase (PI3K) inhibitor LY-294002 (10 μM) but not significantly affected by NKY80. Glucagon also, like insulin, enhanced the phosphorylation of Akt/PKB, a downstream target of PI3K, and these effects were also abolished by LY-294002. The results are consistent with the hypothesis that physiological levels of glucagon produce insulin-like increases in cardiac glucose utilization in vivo through activation of PI3K and not AC/cAMP.

Hypotensive mechanism of [Leu13]motilin in dogs in vivo and in vitro

1998 ◽  
Vol 76 (12) ◽  
pp. 1103-1109 ◽  
Author(s):  
Takeshi Iwai ◽  
Hiroyuki Nakamura ◽  
Hisanori Takanashi ◽  
Kenji Yogo ◽  
Ken-Ichi Ozaki ◽  
...  
Keyword(s):  
Mesenteric Artery ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Gastric Antrum ◽  
Ventricular Pressure ◽  
High Dose ◽  
Aortic Blood Flow ◽  
Arterial Blood

The effects of [Leu13]motilin were examined in vivo after its intravenous administration into anesthetized dogs and in vitro with isolated preparations of canine mesenteric artery. [Leu13]Motilin (0.1-10 nmol·kg-1, i.v.) induced both strong and clustered phasic contractions in the gastric antrum and duodenum. At doses of over 1 nmol·kg-1, [Leu13]motilin also produced transient decreases in arterial blood pressure, left ventricular pressure, maximum rate of rise of left ventricular pressure, and total peripheral resistance, and an increase in aortic blood flow and heart rate. A selective motilin antagonist, GM-109 (Phe-cyclo[Lys-Tyr(3-tBu)-betaAla]betatrifluoroacetate), completely abolished the gastric antrum and duodenal motor responses induced by [Leu13]motilin. In contrast, hypotension induced by [Leu13]motilin (1 nmol·kg-1) was unchanged in the presence of GM-109. In isolated mesenteric artery preparations precontracted with U-46619 (10-7 M), [Leu13]motilin (10-8-10-5 M) induced an endothelium-dependent relaxation, and this was inhibited by a pretreatment with Nomega-nitro-L-arginine, a competitive inhibitor of NO synthase (10-4 M). A high dose (10-4 M) of GM-109 slightly decreased [Leu13]motilin-induced relaxation, and shifted the concentration-response curve of [Leu13]motilin to the right. However, the pA2 value (4.09) of GM-109 for [Leu13]motilin in the present study was conspicuously lower than that previously demonstrated in the rabbit duodenum (7.37). These results suggest that [Leu13]motilin induces hypotension via the endothelial NO-dependent relaxation mechanism and not through the receptor type that causes upper gastrointestinal contractions.Key words: motilin, gastrointestinal motility, hypotension, hemodynamics, anesthetized dog, mesenteric artery, endothelium, nitric oxide.

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