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Objectives Breast cancers are classified as invasive or noninvasive based on histopathological findings. Although time-intensity curve (TIC) analysis using magnetic resonance imaging (MRI) can differentiate benign from malignant disease, its diagnostic ability to quantitatively distinguish between invasive and noninvasive breast cancers has not been determined. In this study, we evaluated the ability of TIC analysis of dynamic MRI data (MRI-TIC) to distinguish between invasive and noninvasive breast cancers. Material and Methods We collected and analyzed data for 429 cases of epithelial invasive and noninvasive breast carcinomas. TIC features were extracted in washout areas suggestive of malignancy. Results The graph determining the positive diagnosis rate for invasive and noninvasive cases revealed that the cut-off θi/ni value was 21.6° (invasive: θw > 21.6°, noninvasive: θw ≤ 21.6°). Tissues were classified as invasive or noninvasive using this cut-off value, and each result was compared with the histopathological diagnosis. Using this method, the accuracy of tissue classification by MRI-TIC was 88.6% (380/429), which was higher than that using ultrasound (73.4%, 315/429). Conclusion MRI-TIC is effective for the classification of invasive vs. noninvasive breast cancer.

Background Idiopathic pulmonary arterial hypertension (IPAH) is a disease characterized by progressively increased resistance of pulmonary arteries. In this study, we evaluated the mechanical property of single pulmonary artery smooth muscles cells (PASMC) from patients with IPAH and tested whether the PASMC showed abnormal response to a vasodilator by use of an atomic force microscope (AFM). Methods PASMC were isolated and cultured from explanted lungs of 7 patients with IPAH (IPAH-PASMC). Normal vascular specimens from 3 patients with bronchogenic carcinoma were used as normal controls (normal PASMC). The nano/micro-order elasticity of five to ten living PASMC in each sample was measured by parabolic force curves of cantilever deflection/indentation obtained by using an AFM. The elasticity measurements were performed under control conditions and under condition of nitric oxide (NO) treatment (190 and 380 nmol/L). Results There was no significant difference between nano/micro-order elasticity of normal PASMC and that of IPAH-PASMC under the control conditions. In normal PASMC, NO (190 and 380 nmol/L) significantly reduced (i.e., softened) the nano/micro-order elasticity. However, NO did not reduce elasticity in IPAH-PASMC, indicating higher vasodilator-resistive nano/micro-order rigidity in IPAH-PASMC. Conclusion Nano/micro-order elasticity change in PASMC in response to vasodilation induced by NO is reduced in patients with IPAH.

The external work (EW) efficiency of individual arrhythmic beats of the left ventricle (LV) cannot directly be obtained since LV O(2) consumption (VO(2)) of each beat cannot directly be measured under beat-to-beat varying contractile and loading conditions. We, however, have recently reported that VO(2) of each arrhythmic beat can reasonably be estimated by VO(2) = aPVA + bE(max) + c even under varying PVA and E(max). Here, PVA is the LV pressure-volume (P-V) area as a measure of the LV total mechanical energy, E(max) is the LV end-systolic elastance as an index of the LV contractility, a is a constant O(2) cost of PVA, b is a constant O(2) cost of E(max), and c is the basal metabolic VO(2) of the beat, all on a per-beat basis. Using the above formula in this study, we calculated VO(2) of the individual arrhythmic beats from their measured PVA and E(max) during electrically induced atrial fibrillation (AF) in normal canine hearts. We then calculated their LV EW efficiency by dividing their measured EW with the estimated VO(2). We found that the thus calculated EW efficiency of the arrhythmic beats had a rightward skewed distribution with a mode of 15% and a maximum of 18% around a mean of 13% on average in six hearts. This mode remained comparable to the efficiency (15%) at regular tachycardia though 22% lower than mean arrhythmic tachycardia.

The goal of our study was to evaluate the origin of the increased O(2) consumption in electrically stimulated left ventricular slices of isoproterenol-induced hypertrophied rat hearts with normal left ventricular pressure. O(2) consumption per minute (mVO(2)) of mechanically unloaded left ventricular slices was measured in the absence and presence of 1-Hz field stimulation. Basal metabolic mVO(2), i.e., mVO(2) without electrical stimulation, was significantly smaller, but mVO(2) for the total Ca(2+) handling in excitation-contraction coupling (E-C coupling mVO(2)), i.e., delta mVO(2) (=mVO(2) with stimulation - mVO(2) without stimulation), was significantly larger in the hypertrophied heart. Furthermore, the fraction of E-C coupling mVO(2) was markedly altered in the hypertrophied heart. Namely, mVO(2) consumed by sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2) was depressed by 40%; mVO(2) consumed by the Na(+)/K(+)-ATPase (NKA)-Na(+)/Ca(2+) exchange (NCX) coupling was increased by 100%. The depressed mVO(2) consumption by SERCA2 was supported by lower protein expressions of phosphorylated-Ser(16) phospholamban and SERCA2. The increase in NKA-NCX coupling mVO(2) was supported by marked augmentation of NCX current. However, the increase in NCX current was not due to the increase in NCX1 protein expression, but was attributable to attenuation of the intrinsic inactivation mechanisms. The present results demonstrated that the altered origin of the increased E-C coupling mVO(2) in hypertrophy was derived from decreased SERCA2 activity (1ATP: 2Ca(2+)) and increased NCX activity coupled to NKA activity (1ATP: Ca(2+)). Taken together, we conclude that the energetically less efficient Ca(2+) extrusion pathway evenly contributes to Ca(2+) handling in E-C coupling in the present hypertrophy model.

Aims The present study is designed to investigate the role of neuronal nitric oxide synthase (nNOS) in the regulation of vascular mitogen-activated protein kinase (MAPK) activity under basal and angiotensin II (Ang II)-stimulated conditions. Methods and results Incubation with a potent nNOS inhibitor (L-VNIO) significantly increased superoxide (O2−) levels, with increased MAPK phosphorylation, in isolated aorta and vascular smooth muscle cells (VSMCs) from wild-type mice. Both increases were inhibited by the superoxide dismutase mimetic, tempol, but not by the peroxynitrite scavenger, FeTPPS. The levels of O2− and MAPK phosphorylation were higher in aorta from nNOS−/− mice than from wild-type mice. These parameters were suppressed by tempol and oxypurinal (a xanthine oxidase inhibitor). In isolated VSMCs or aorta from wild-type mice, Ang II stimulation markedly increased the levels of O2− and MAPK phosphorylation. L-VNIO significantly reduced Ang II-induced increases of these parameters. Apocynin, an NAD(P)H oxidase inhibitor, further inhibited Ang II-induced increases of these parameters compared with the L-VNIO-treated group. FeTPPS did not suppress the Ang II-induced increase of O2− levels, but markedly inhibited Ang II-induced MAPK phosphorylation. In contrast to the wild-type, in isolated aorta or VSMCs from nNOS−/− mice, Ang II failed to increase O2− levels and MAPK phosphorylation. Conclusion Under basal conditions, nNOS-derived NO acting as antioxidant reduces O2− accumulation and suppresses vascular MAPK phosphorylation. Under Ang II-stimulated conditions, NAD(P)H oxidase-derived O2−, inducing nNOS uncoupling, potentiates the Ang II-induced increase of O2− generation. The generated O2− may react with NO to form peroxynitrite (ONOO−). Both O2− and ONOO− participate in Ang II-induced activation of vascular MAPK.

Temperature changes influence cardiac diastolic function. The monoexponential time constant (tauE), which is a conventional lusitropic index of the rate of left ventricular (LV) pressure fall, increases with cooling and decreases with warming. We have proposed that a half-logistic time constant (tauL) is a better lusitropic index than tauE at normothermia. In the present study, we investigated whether tauL can remain a superior measure as temperature varies. The isovolumic relaxation LV pressure curves from the minimum of the first time derivative of LV pressure (dP/dtmin) to the LV end-diastolic pressure were analyzed at 30, 33, 36, 38, and 40 °C in excised, cross-circulated canine hearts. tauL and tauE were evaluated by curve-fitting using the least squares method and applying the half-logistic equation, P(t) = PA/[1 + exp(t/tauL)] + PB, and the monoexponential equation, P(t) = P0exp(–t/tauE) + P∞. Both tauL and tauE increased significantly with decreasing temperature and decreased with increasing temperature. The half-logistic correlation coefficient (r) values were significantly higher than the monoexponential r values at the 5 above-mentioned temperatures. This implies that the superiority of the goodness of the half-logistic fit is not temperature dependent. The half-logistic model characterizes the amplitude and time course of LV pressure fall more reliably than the monoexponential model. Hence, we concluded that tauL is a more useful lusitropic index regardless of temperature.

In consideration of clinical implications, it is often complained that short-term experimental diseased heart models do not mimic long-term diseased hearts that are often clinically encountered. The aim of the present study was (i) to compare the left ventricular function between rat cardiac hypertrophy models treated with isoproterenol for 3 days (Iso 3d) and 7 days (Iso 7d) by pressure-volume measurements with a catheter method, and (ii) to follow up the left ventricular function in the same model treated with Iso up to 16 weeks with a less-invasive echocardiography. An infusion of either Iso (1.2 mg x kg(-1) x day(-1) for 3 days-16 weeks) or vehicle (saline 24 microl x day(-1) for 3 days-16 weeks; Sa group) was performed by subcutaneously implanting an osmotic minipump. There were no significant differences in the systolic pressure-volume area at midrange left ventricular volume (PVA(mLVV): a mechanical work capability index) between Iso 3d and 7d groups, though PVA(mLVV) in both groups was significantly reduced from that in the Sa group. From echocardiography, the left ventricular function of the hypertrophy models at 3 days, 1 week, and 2 weeks was unchanged, but the model at a term longer than 4 weeks resulted in prolonged systolic failure. The results indicated that (i) no marked differences in the left ventricular mechanical work capability were found between the Iso 3d and 7d groups, and that (ii) only a 3-day Iso infusion induced the hypertrophy model similar in shape and function to that induced by a 2-week Iso infusion. We concluded that the 3-day model was sufficient.

Pulmonary hypertension (PH) causes right ventricular (RV) hypertrophy and, according to the extent of pressure overload, eventual heart failure. We tested the hypothesis that the mechanical stress in PH-RV impairs the vasoreactivity of the RV coronary microvessels of different sizes with increased superoxide levels. Five-week-old male Sprague-Dawley rats were injected with monocrotaline ( n = 126) to induce PH or with saline as controls ( n = 114). After 3 wk, coronary arterioles (diameter = 30–100 μm) and small arteries (diameter = 100–200 μm) in the RV were visualized using intravital videomicroscopy. We evaluated ACh-induced vasodilation alone, in the presence of Nω-nitro-l-arginine methyl ester (l-NAME), in the presence of tetraethylammonium (TEA) or catalase with or without l-NAME, and in the presence of SOD. The degree of suppression in vasodilation by l-NAME and TEA was used as indexes of the contributions of endothelial nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF), respectively. In PH rats, ACh-induced vasodilation was significantly attenuated in both arterioles and small aretries, especially in arterioles. This decreased vasodilation was largely attributable to reduced NO-mediated vasoreactivity, whereas the EDHF-mediated vasodilation was relatively robust. The suppressive effect on arteriolar vasodilation by catalase was similar to TEA in both groups. Superoxide, as measured by lucigenin chemiluminescence, was significantly elevated in the RV tissues in PH. SOD significantly ameliorated the impairment of ACh-induced vasodilation in PH. Robust EDHF function will play a protective role in preserving coronary microvascular homeostasis in the event of NO dysfunction with increased superoxide levels.

Nuclear magnetic resonance (NMR) spectroscopy of the heart is normally carried out using whole heart preparations under coronary perfusion. In such preparations, either radical changes in ionic composition of the perfusate or applications of numerous drugs would affect coronary microcirculation. This report communicates the first31P NMR spectroscopy study using a heart slice preparation (left ventricular slices) superfused with extracellular medium. The ratio of phosphocreatine concentration to ATP concentration was ∼2.1. Also, intracellular pH and Mg2+concentration ([Mg2+]i), estimated from the chemical shifts of inorganic phosphate and ATP, were comparable with those under retrograde perfusion. [Mg2+]iwas significantly increased by the removal of extracellular Na+, supporting the essential role of Na+-coupled Mg2+transport in Mg2+homeostasis of the heart. Heart slice preparation could also be used to evaluate the potency of cardiac drugs, regardless of their possible effects on coronary microcirculation.

The aim of the present study was performed to determine whether a novel histone deacetylase (HDAC) inhibitor, N-(2-aminophenyl)-4-{[benzyl(2-hydroxyethyl)amino]methyl} benzamide (K-183), prevents a reversible cardiac hypertrophy induced by isoproterenol and improves left ventricular (LV) dysfunction in rats. Either isoproterenol or vehicle was infused for 3 days by osmotic minipump. One hour prior to the implantation of isoproterenol, K-183 or trichostatin A (TSA) was injected twice a day for 3 days. We recorded continuous LV pressure-volume (P-V) loops of in situ hearts one hour after removal of the osmotic minipump. LV work capability (systolic P-V area at midrange LV volume: PVAmLVV) and hemodynamics were evaluated. K-183 per se induced neither cardiac hypertrophy nor collagen production. Although K-183 did not prevent the hypertrophy, where PVAmLVV remained decreased, K-183, differently from TSA, significantly attenuated the decrease of cardiac output and the increase of effective arterial elastance in the hypertrophied heart. These results indicate that the novel HDAC inhibitor K-183 has some beneficial effects on hemodynamics, although K-183 has no effects of antihypertrophic modalities. Keywords:: left ventricular volumetry, conductance catheter, hypertrophy, collagen, histone deacetylase

Objectives Identity of the optimal heart preservation solution remains unknown. Because oxidative stress contributes to contractile failure in the ischaemic/reperfused myocardium and the main characteristic of Celsior is its antioxidant effect, it is important to elucidate the relationship between the inhibitory effect on oxidative stress and cardiac mechano-energetics. We therefore evaluated the efficacy of Celsior from both aspects by comparison with the University of Wisconsin solution (UWS). Methods We used 18 excised cross-circulated canine hearts. Excised hearts were preserved with UWS (n = 6) or Celsior (n = 6) for 3 h at 4 °C; the remaining six served as controls. Hearts were then cross-circulated and rewarmed. The end-systolic pressure-volume ratio (LV Emax) and the ventricular pressure-volume area, which is a measure of total mechanical energy, were assessed after reperfusion. Biopsies were taken from the endocardium after excising the heart, before reperfusion, after reperfusion and 4 h after reperfusion to assess the inhibitory effect of each agent on oxidative stress. Endo-myocardial biopsy samples were studied immunohistochemically for expression of 4-hydroxy-2-nonenal (HNE)-modified protein, which is a major lipid peroxidation product. Results Emax in the UWS group was significantly smaller than in the control group, whereas the Emax in the Celsior group was preserved. Oxygen cost of Emax in the UWS group was significantly higher than in the Celsior group. Myocardial HNE-modified protein levels increased gradually, both under preservation and after reperfusion in the UWS group. Myocardial HNE-modified protein levels in the Celsior group were lower, mainly before and 4 h after reperfusion compared with the UWS group. Conclusions Celsior may maintain cardiac contractility and conserve oxygen cost by inhibiting oxidative stress.

We developed a pH/CO 2 sensor system using two ion-sensitive field effect transistors (ISFETs) to evaluate the metabolic activity of cultured cells. One ISFET measures total pH changes and the other ISFET, covered with a gas-permeable silicon tube, measures pH changes due to CO 2 . These ISFETs were placed in a flow-through chamber with a window to be attached to a glass plate on which cells were cultured. Measurements were performed with a baseline solution of low buffer capacity. In the quantitative estimation of cellular products, we assumed that cells secreted CO 2 , lactic acid and sodium bicarbonate ( NaHCO 3 ), and then lactic acid and NaHCO 3 proceeded to the neutralization reaction to form sodium lactate and additional CO 2 . We applied this system to evaluate the metabolic activity of bovine aortic endothelial cells (BAEC) and rabbit aortic smooth muscle cells (RASMC). The production of CO 2 by RASMC was significantly higher than that by BAEC (204 ± 16 and 4.1 ± 0.3 × 10 8 molecules/cell/s, respectively). More NaHCO 3 than lactic acid was produced in RASMC, whereas they were not significantly different in BAEC.

The logistic time constant (tau(L)) has been proposed as a better index of the rate of left ventricular (LV) relaxation or lusitropism than the conventional monoexponential time constant (tau(E)). However, whether and how the Frank-Starling effect influences tau(L) remains to be elucidated. We compared the effect of LV volume (LVV) loading on both logistic and monoexponential fittings. The isovolumic LV relaxation pressure curves from the maximum negative time derivative of pressure (-dP/dt(max)) were analyzed at 3 different end-points at 4 LVVs of 10, 12, 14, and 16 mL in 8 excised, cross-circulated canine hearts. We found that the logistic fitting was superior to the monoexponential fitting at all LVVs and end-points. LVV loading did not affect tau(L) but affected tau(E) slightly. Although the advancing end-point increased both tau(L) and tau(E), the increases were significantly smaller for tau(L) than for tau(E) at all LVVs. Moreover, the changes in both the amplitude constants and nonzero asymptotes with the advancing end-point were significantly smaller for the logistic fitting than for the monoexponential fitting. We conclude that tau(L) served as a more reliable index of lusitropism that is independent of the change in LVV loading or the Frank-Starling effect.

Background Cardiac function of non–heart-beating donors (NHBDs) is uncertain due to severe myocardial damage. We developed an isolated myocardial perfusion system to resuscitate NHBD hearts and attempted to predict functional recovery of 60-minute warm ischemic hearts by analyzing systolic and diastolic functions. Methods Hypoxic cardiac arrest was induced in 8 mongrel dogs without any pre-treatments. After 60-minute ischemia, intracoronary microthrombi were flushed out by retrograde blood cardiopledia with tissue-type plasminogen activator. Coronary arteries were initially perfused from the aortic root with tepid hyperkalemic blood (20 mmol/liter) at low pressure (20 mm Hg) for the first 60 minutes and then with normothermic blood for the next 60 minutes. After 120 minutes of reperfusion, pre-load was increased for ejection against an after-load of 80 mm Hg. Pressure–volume loops were recorded to obtain the end-systolic pressure–volume relationship (ESPVR) and end-diastolic pressure–volume relationship (EDPVR). Stroke volume at a given pre-load was calculated from averaged ESPVR, EDPVR and after-load identical to an averaged baseline value. The Frank–Starling relationship was obtained and cardiac status was classified according to Forrester’s hemodynamic sub-set. Results End-systolic elastance decreased significantly to about 60% of baseline and the time constant of isovolumic relaxation was prolonged significantly by about 20%. Cardiac index was decreased to about 50% and cardiac status was classified in the Forrester III or IV sub-set. Conclusions The extent of functional recovery of NHBD hearts is predictable by cardiac output. Although 120 minutes of recovery time may be short for 60-minute ischemic damage, this system may be feasible to predict post-transplant cardiac function before transplantation.

Background Better protective effects of Celsior on cardiac function than the other conventional solutions have been reported in acute experiments and in clinical trials for at-risk patients. However, no study has yet precisely elucidated how these preservation solutions affect cardiac mechanoenergetics. Therefore, we evaluated the effects of St. Thomas' Hospital solution No. 2, University of Wisconsin solution, and Celsior on left ventricular contractility (E max : end-systolic pressure–volume ratio) and oxygen consumption. Methods We used 32 canine excised cross-circulated hearts. Twenty-three hearts served as donor hearts after hypothermic ischemia with one of the three solutions, and the remaining 9 served as controls. After arrest with each solution, the hearts were preserved for 4 hours at 4°C. Then, we measured left ventricular pressure, volume, and oxygen consumption to obtain E max and the relation between ventricular pressure–volume area (a measure of total mechanical energy) and oxygen consumption. We also evaluated the oxygen cost of E max by changing E max with calcium administration. Results Celsior did not significantly affect E max (6.3 ± 2.4 in control versus 5.3 ± 1.3 mm Hg · mL −1 · 100 g with Celsior) nor the oxygen cost of E max (1.2 ± 0.6 versus 1.6 ± 0.5 mL O 2 · mL · mm Hg −1 · beat −1 · 100 g −2 , respectively). In contrast, St. Thomas' Hospital and University of Wisconsin solutions significantly decreased E max (4.5 ± 1.1 and 3.5 ± 0.9 mm Hg · mL −1 · 100 g, respectively) and increased the oxygen cost of E max (2.5 ± 0.8 and 2.4 ± 0.9 mL O 2 · mL · mm Hg −1 · beat −1 · 100 g −2 , respectively) compared with control and Celsior-preserved hearts. The slope and intercept of the oxygen consumption versus pressure–volume area relation showed no significant difference among the four groups. Conclusions Celsior showed better protective effects on cardiac mechanoenergetics than St. Thomas' Hospital and University of Wisconsin solutions in the acute phase of heart transplantation.

We proposed a mathematical model for the microdynamics of cultured cells measured with ECIS (Electrical Cell-substrate Impedance Sensing) system that can separately evaluate cell-to-cell and cell-to-substrate gaps. Our mathematical model is composed of culture medium impedance between cells (Zsol), cell impedance (Zc), and polarization impedance of the electrode (Zp). Zsol consists of the resistance between cells (Rsol) and the capacitance between cells (Csol) of the culture medium. In particular, Rsol is the resistance component related to the cell-to-cell distance (A). Zc consists of capacitance of the cell membrane (Cc) and resistance of the cell membrane (Rc). Zp depends on the cell-to-substrate distance (h) because of the shielding effect of cells to the electrode. The shielding effect is defined as shielding coefficient (Sk). We examined the changes in the impedance of the electrode without or with cells in various conditions. The electrical characteristics of the electrode with or without cells agreed well with those measured in ECIS system. It was found that whether A or h caused the changes in the impedance could be determined based on the changes in the total resistance and reactance (capacitance); A mainly affects the total resistance value, and h mainly affects total capacitance value. Therefore, we can simply estimate the changes in cell-to-cell and cell-to-substrate gaps with measured total resistance and reactance (capacitance). Based on these results, when the cultured endothelial cells (HUVEC) were stimulated with estrogen for 40 hours, it was proved that the cell-to-cell distances decreased, even though the cell-to-electrode distances slightly increased. This result suggests that the barrier function of endothelium is fortified by estrogen.

We previously found the frequency distribution of the left ventricular (LV) effective afterload elastance (Ea) of arrhythmic beats to be nonnormal or non-Gaussian in contrast to the normal distribution of the LV end-systolic elastance (Emax) in canine in situ LVs during electrically induced atrial fibrillation (AF). These two mechanical variables determine the total mechanical energy [systolic pressure-volume area (PVA)] generated by LV contraction when the LV end-diastolic volume is given on a per-beat basis. PVA and Emax are the two key determinants of the LV O2 consumption per beat. In the present study, we analyzed the frequency distribution of PVA during AF by its χ2, significance level, skewness, and kurtosis and compared them with those of other major cardiodynamic variables including Ea and Emax. We assumed the volume intercept (V0) of the end-systolic pressure-volume relation needed for Emax determination to be stable during arrhythmia. We found that PVA distributed much more normally than Ea and slightly more so than Emax during AF. We compared the χ2, significance level, skewness, and kurtosis of all the complex terms of the PVA formula. We found that the complexity of the PVA formula attenuated the effect of the considerably nonnormal distribution of Ea on the distribution of PVA along the central limit theorem. We conclude that mean (SD) of PVA can reliably characterize the distribution of PVA of arrhythmic beats during AF, at least in canine hearts.

The recently proposed Physiome is considered as a powerful successor to the Genome. The definition of Physiome is the quantitative description of the physiological dynamics or functions of the intact organism. The physiome includes integration of knowledge through functional modules of hierarchical system elements of biological systems, and modeling. Biomechanics will offer potent tools to promote the Physiome. By using modern microvisualization technology with physiomic model, this manuscript introduces our physiomic approach to coronary microcirculation which supplies oxygen and nutrients to heart muscles; 1. Mechanical interaction between coronary blood flow and cardiac contraction, and 2. Capillary network and its function.

Using high-resolution intravital charge-coupled device video microscopy, we visualized the epicardial capillary network of the beating canine heart in vivo to elucidate its functional role under control conditions, during reactive hyperemia (RH), and during intracoronary adenosine administration. The pencil-lens video-microscope probe was placed over capillaries fed by the left anterior descending artery in atrioventricular-blocked hearts of open-chest, anesthetized dogs paced at 60–90 beats/min ( n = 17). In individual capillaries under control conditions, red blood cell flow was predominant during systole or diastole, indicating that the watershed between diastolic arterial and systolic venous flows is located within the capillaries. Capillary flow increased during RH and reached a peak flow velocity (2.1 ± 0.6 mm/s), twice as high as control (1.2 ± 0.5 mm/s), with enhancement of intercapillary cross-connection flow and enlargement of diameter (by 17%). With adenosine, capillary flow velocity significantly increased (1.8 ± 0.7 mm/s). However, the increase in volumetric capillary flow with adenosine estimated from red blood cell velocity and diameter was less than the increase in arterial flow, whereas that during RH was nearly equivalent to the increase in arterial flow. There was a time lag of ∼1.5 s for refilling of capillaries during RH, indicating their function as capacitance vessels. In conclusion, the coronary capillary network functions as 1) the major watershed between diastolic-dominant arterial and systolic-dominant venous flows, 2) a capacitor, and 3) a significant local flow amplifier and homogenizer of blood supply during RH, but with adenosine the increase in capillary flow velocity was less than the increase in arterial flow.

We have reported that the contractility index (E(max)) and the total mechanical energy (PVA) of arrhythmic beats of the left ventricle (LV) distribute normally in canine hearts under electrically induced atrial fibrillation (AF). Here, E(max) is the ventricular elastance as the slope of the end-systolic (ES) pressure-volume (P-V) relation (ESPVR), and PVA is the systolic P-V area as the sum of the external mechanical work within the P-V loop and the elastic potential energy under the ESPVR. To obtain E(max) and PVA, we had to assume the systolic unstressed volume (V(o)) as the V-axis intercept of the ESPVR to be constant despite the varying E(max), since there was no method to obtain V(o) directly in each arrhythmic beat. However, we know that in regular stable beats V(o) decreases by approximately 7 ml/100 g LV with approximately 100 times the increases in E(max) from ~0.2 mmHg/(ml/100 g LV) of almost arresting weak beats to approximately 20 mmHg/(ml/100 g LV) of strong beats with a highly enhanced contractility. In the present study, we investigated whether E(max) and PVA under AF could still distribute normally, despite such E(max)-dependent V(o) changes. The present analyses showed that the E(max) changes were only approximately 3 times at most from the weakest to the strongest arrhythmic beat under AF. These changes were not large enough to affect V(o) enough to distort the frequency distributions of E(max) and PVA from normality. We conclude that one could practically ignore the slight E(max) and PVA changes with the Emax-dependent V(o) changes under AF.

We examined the sarcomere length-dependence of the spacing of the hexagonal lattice of the myofilaments and the mass transfer of myosin cross-bridges during contraction of right ventricular papillary muscle of the rat. The lattice spacing and mass transfer were measured by using X-ray diffraction, and the sarcomere length was monitored by laser diffraction at the same time. Although the lattice spacing and the sarcomere length were inversely related, their relationship was not exactly isovolumic. The cell volume decreased by about 15% when the sarcomere length was shortened from 2.3 micro m to 1.8 micro m. Twitch tension increased with sarcomere length (the Frank-Starling law). At the peak tension, the ratio of the intensity of the (1,0) equatorial reflection to that of the (1,1) reflection was smaller when the tension was greater, showing that the larger tension at a longer sarcomere length accompanies a larger amount of mass transfer of cross-bridges from the thick to the thin filament. The result suggests that the Frank-Starling law is due to an increase in the number of myosin heads attached to actin, not in the average force produced by each head.

Intramyocardial Ca(2+) recirculation fraction (RF) critically determines the economy of excitation-contraction coupling. RF is obtainable from the exponential decay of the postextrasystolic potentiation of left ventricular (LV) contractility. We have shown that RF remains unchanged despite increasing LV volume (LVV) at normothermia, but decreases with increasing temperature at a constant LVV. However, it remains unknown whether the temperature-dependent RF was not due to the simultaneously changed peak LV pressure (LVP) at a constant LVV. We hypothesized that this temperature-dependent RF would be independent of the simultaneous change in LVP. We used nine excised, cross-circulated canine hearts and allowed their LVs to contract isovolumically. During stable regular beats at 500 msec intervals, we inserted an extrasystolic beat at 360 msec interval followed by the postextrasystolic beats (PESs) at 500 msec intervals. We equalized the temperature-dependent peak LVPs of the regular beats at 36 degrees C and 38 degrees C to the peak LVP level of the stable regular beat at 33 degrees C by adjusting LVV. We fitted the same equation: nEmax = a.exp[-(i - 1)/tau(e)] + b.exp[-(i - 1)/tau(s)]cos[pi(i - 1)] + 1, used before to the normalized Emax (maximum elastance) values of PESi (i = 1-6) relative to the regular beat Emax. RF given by exp(-1/tau(e)) decreased by 19% to 38 degrees C from 33 degrees C. The temperature coefficient (Q(10)) of 1/RF was significantly greater than 1.3. The present results indicated a similar temperature dependence of RF and its Q(10) to those we observed previously without equalizing peak LVP. Thus, the temperature-dependent RF is independent of ventricular loading conditions.

We have previously found that the postextrasystolic (PES) potentiation (PESP) of the left ventricular (LV) contractility (Emax) decays typically in transient alternans even in the normally ejecting canine heart. This contradicted the general expectation that arterial pressure (AP) and LV pressure (LVP) usually decay exponentially during PESP. We hypothesized this contradiction to be due to the different cardiodynamic behaviors of AP and LVP from LV Emax during PESP. We tested this hypothesis by measuring AP, LVP, LV volume, Emax, effective arterial elastance (Ea) as an index of afterload, and pulse pressure (PP) during PESP in eight anesthetized open-chest dogs by using the conductance catheter system. We changed Ea by changing the total peripheral resistance (TPR) with methoxamine hydrochloride (iv) and repeated the measurements. Although the Emax alternans patterns during PESP were comparable between the normal and high afterloads, LVP and PP were slightly potentiated and alternated under the normal afterload, whereas LVP and PP were obviously potentiated and alternated under the high afterload. We also simulated the effects of Ea/Emax on the transient alternans of AP and LVP on a computer. Despite the same alternans pattern of Emax, a higher Ea/Emax, which is typical in heart failure, caused a larger PP alternans, whereas a lower Ea/Emax, which is typical in normal hearts, almost eliminated it. These results suggest that a transient alternans of LV contractility during PESP could be overlooked when AP and LVP are monitored in in situ normal hearts.

Objective If the geometric distortion during dilated heart failure could be corrected, the tension on the myocytes would be decreased, thereby leading to an improvement in left ventricular systolic function. We tested the effects of the CardioClasp (CardioClasp Inc, Pine Brook, NJ), a left ventricular reshaping device, on the failing heart, and our empirical data were compared with computationally derived data. Methods Heart failure was induced by 4-week rapid cardiac pacing. At the terminal experiment, an isolated failing heart preparation (isovolumic contraction, n=5) or an intact failing heart in vivo (n = 7) was used. The effects of the reshaping device on left ventricular performance were assessed by the slopes (Ees) of the left ventricular end-systolic pressure-volume relations, hemodynamics, and echocardiograph before and after placing the CardioClasp on the heart. The change in Ees as the result of left ventricular reshaping was also estimated from computed theoretical analysis and compared with empirical data. Results There was a significant change in left ventricular dimension after placing the CardioClasp on the heart. In isolated heart preparation, Ees significantly increased from 1.40 ± 0.44 mm Hg/mL to 2.42 ± 0.63 mm Hg/mL after placing the device on the heart but returned to the baseline level (1.46 ± 0.27 mm Hg) after removing it. Left ventricular developed pressure and left ventricular fractional area shortening were significantly increased as the result of left ventricular reshaping. Ees derived from computed theoretical analysis was highly correlated with confirming empirical data. Conclusions The CardioClasp can reshape the left ventricle and improve left ventricular systolic performance in failing hearts. 17,22

We investigated the mechanism of positive inotropism of electric currents applied during the absolute refractory period. Ten Langendorff-perfused ferret hearts were instrumented to measure isovolumic left ventricular pressure (LVP) and the aequorin luminescence. Biphasic square-wave electric currents (±20 mA, total duration 30 ms) were delivered between pairs of electrodes. Six hearts were perfused at different extracellular Ca2+ concentrations ([Ca2+]o; 1, 2, 4, and 8 mM). These signals increased LVP from 50.0 ± 9.4 to 70.1 ± 14.7, from 67.5 ± 11.0 to 79.0 ± 15.6, from 79.3 ± 21.0 to 87.1 ± 22.8, and from 84.6 ± 24.0 to 91.8 ± 28.5 mmHg at the respective [Ca2+]o ( P< 0.05). Peak free intracellular [Ca2+] ([Ca2+]i) increased from 0.52 ± 0.13 to 1.37 ± 0.23, from 0.76 ± 0.23 to 1.73 ± 0.14, from 1.10 ± 0.24 to 2.05 ± 0.33, and from 1.41 ± 0.36 to 2.24 ± 0.36 μM/ml, respectively ( P < 0.001). With the use of 1 mg/l propranolol with 1 mM [Ca2+]o, LVP and [Ca2+]i were increased significantly from 48.7 ± 8.18 to 56.3 ± 6.11 mmHg and from 0.61 ± 0.11 to 1.17 ± 0.20 μM, respectively ( P < 0.05). In conclusion, positive inotropism of such electrical currents was due to increased peak [Ca2+]i and Ca2+responsiveness of the myofilaments did not change significantly.

We have found that cardiac temperature proportionally changes O2 cost of contractility, defined as O2 consumption for myocardial total Ca2+handling normalized to contractility in terms of the end-systolic pressure-volume ratio (maximal elastance, E max), in the canine left ventricle (temperature sensitivity, Q10 = 2). We have separately found that a decrease in the recirculation fraction (RF) of Ca2+ within myocardial cells underlies an increased O2 cost of E max in stunned hearts. We therefore hypothesized that a similar change in RF would underlie the Q10 of O2 cost of E max. We tested this hypothesis by analyzing RF calculated from an exponential decay component of the transiently alternating postextrasystolic potentiation in the canine left ventricle. RF decreased from 0.7 to 0.5 as cardiac temperature increased from 33 to 38°C with Q10 of 0.5, reciprocal to that of O2 cost of E max. We conclude that Q10 of ATP-consuming reactions involved in Ca2+handling and E max response to it could reasonably account for the reciprocal Q10 of RF and O2 cost of E max.

Mean levels of left ventricular rhythm and contractility averaged over arrhythmic beats would characterize the average cardiac performance during atrial fibrillation (AF). However, no consensus exists on the minimal number of beats for their reliable mean values. We analyzed their basic statistics to find out such a minimal beat number in canine hearts. We produced AF by electrically stimulating the atrium and measured left ventricular arrhythmic beat interval (RR) and peak isovolumic pressure (LVP). From these, we calculated instantaneous heart rate (HR = 60,000/RR), contractility (E(max) = LVP/isovolumic volume above unstressed volume), and beat interval ratio (RR1/RR2). We found that all their frequency distributions during AF were variably nonnormal with skewness and kurtosis. Their means +/- standard deviations alone cannot represent their nonnormal distributions. A 90% reduction of variances of E(max) and RR1/RR2 required a moving average of 15 and 24, respectively, arrhythmic beats on the average, whereas that of RR and HR required 60 beats on the average. These results indicate that a statistical characterization of arrhythmic cardiodynamic variables facilitates better understanding of cardiac performance during AF.

Although tachycardia is well known to increase cardiac oxygen consumption (Vo2) per min, the relationship between Vo2 for excitation-contraction (E-C) coupling per beat and heart rate change over its full working range still remains controversial.To elucidate this relationship, we varied heart rate over a reasonably wide range (60-180 beat/min) and studied the relationship between left ventricular (LV) Emax (load-independent contractility index), PVA (pressure-volume area)-independent Vo2, and basal metabolic Vo2 in nine excised, cross-circulated canine hearts.PVA-independent Vo2 per min significantly increased linearly with increasing heart rate while Emax remained unchanged. Basal metabolic Vo2 per min was measured under KCl arrest. E-C coupling Vo2 per min obtained by subtracting the constant basal metabolic Vo2 from the PVA-independent Vo2 also significantly increased linearly with increasing heart rate. However, PVA-independent Vo2 per beat significantly decreased with increasing heart rate. In contrast, E-C coupling Vo2 per beat, as well as that normalized to Emax, slightly but significantly increased with increasing heart rate.The E-C coupling energy for myocardial Ca2+ handling increases with heart rate despite constant contractility in the left ventricle of the excised cross-circulated canine heart.

We have aimed to assess total Ca 2+ handling in excitation-contraction coupling in a beating left ventricle (LV). Our newly developed integrative analysis method utilizes the internal Ca 2+ recirculation fraction (RF), O2 consumption ( Vo 2) for Ca2+ handling, and O 2 cost of Emax (contractility index) of the LV. We have obtained the O 2 cost of Emax from Vo 2 measured at different contractility levels, and have combined the cost with RF calculated from the beat-constant of the exponential decay component of the postextrasystolic potentiation. Our method calculates the unknown total Ca2+ handling from the RF and the " Ca 2+ handling Vo 2". The calculated total Ca 2+ handling fell between 30 and 110 μmol/kg, depending on contractility and pathological conditions. The present method also enable's reasonable assessment of futile Ca 2+ cycling and of the Ca 2+ reactivity of Emax. Our method seems useful to better understanding of the pathophysiology of total Ca 2+ handling in a beating heart.

Murine models of cardiac disease are becoming an important tool for studying pathophysiological processes. Development of methods to accurately assess ventricular function are therefore important. The purpose of this study was to evaluate the feasibility of echocardiographic assessment of segmental wall motion abnormalities in a murine model of myocardial infarction. Two-dimensional contrast (C+) and noncontrast (C−) echocardiography were performed in 76 awake mice 2 days before and 2 days after left coronary ligation. The short-axis images obtained with two-dimensional echocardiography and corresponding postmortem cross-sectional histological samples stained with Evans blue dye were each divided into 16 segments, and all matched segments were examined for correlation between wall motion abnormalities and myocardial hypoperfusion. With the use of contrast enhancement, the number of visualized segments was significantly increased (base: C− 86%, C+ 98%; midpapillary: C− 57%, C+ 89%; apex: C− 30%, C+ 74%). Agreement between echocardiographically assessed regional wall motion abnormalities and pathologically determined hypoperfusion in basal, midpapillary, and apical levels were 90%, 93%, and 93%, respectively. Agreement between echocardiographically normal wall motion and pathologically normal findings in basal, midpapillary, and apical levels were 99%, 88%, and 71%, respectively. Thus echocardiographic assessment of segmental wall motion in awake mice was feasible and the accuracy was improved with the use of a contrast agent.

The estimation of global left ventricular function using M-mode echocardiography has technical limitations in the murine model of myocardial infarction (MI), but the recent improvements in 2-dimensional (2-D) echocardiography using a high-frequency transducer provide more accessible images. Furthermore, intravenous injection of contrast agent has the additional benefit of enhancing the endocardial border in the murine heart. The present study was designed to evaluate the value of 2-D echocardiography with intravenous injection of contrast agent in the assessment of global systolic function of the murine heart with MI. Two-dimensional and M-mode echocardiography without and with intravenous injection of contrast agent (Optison, 0.1-0.15 ml) were performed in 76 awake mice 2 days before and 2 days after left coronary artery ligation. Fractional shortening (FS) was calculated from the end-diastolic and end-systolic diameters on M-mode echocardiography, and fractional area change (FAC) from the end-diastolic and end-systolic areas on 2-D echocardiography. Both FS and FAC were compared with the areas of hypoperfusion observed in the pathological samples. The use of contrast agent improved the number of hearts that could be evaluated by both the M-mode and 2-D method (M-mode: non-contrast 87% vs contrast 99%, p

The purpose of this study was to evaluate the feasibility of the conductance catheter (CC) method in measuring cross-sectional area (CSA) of small vessels like human coronary arteries. Lumen CSA (A) of phantom tubes (2–10 mm in diameter) and excised canine arteries (n = 10, 2.3–4.5 mm in diameter) were measured with 3-F CC (A cc) and intravascular ultrasound (A us). To investigate the influence of parallel conductance in accuracy of A cc, solution with various resistivities was applied to the surrounding of the arteries (n = 4). A cc showed an excellent agreement with phantom model CSA. In the excised arteries, A cc and A us highly correlated (R 2 = 0.906) with each other. When the resistivities of the solution surrounding the vessels was changed, A cc–Aus regression lines were similar regardless of different resistivities. The conductance method is feasible to measure CSA of small vessels like human coronary arteries.

Daniel Burkhoff MD PhD , Itzik Shemer , Bella Felzen , Juichiro Shimizu , Yuval Mika , Marc Dickstein , David Prutchi , Nissim Darvish 3 and Shlomo A. Ben-Haim 2,5 Divisions of Circulatory Physiology and Cardiology, Cardiac Physiology Laboratory, Department of Medicine, Columbia University, N.Y., Impulse Dynamics, Tirat HaCarmel 39120, Israel, Department of Physiology and Biophysics, The Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, P.O.B. 9649, Haifa 31096, Israel, Department of Anesthesiology, Columbia University, N.Y., Harvard-Thorndike Arrhythmia Institute, Beth-Israel Hospital, 330 Brookline Ave, Boston, Massachusetts 02215, USA

We assessed total Ca2+ handling (transport, flux) in excitation-contraction (E-C) coupling in a beating left ventricle (LV). We developed a new integrative analysis method that utilizes the internal Ca2+ recirculation fraction (RF), O2 consumption ([Formula: see text]o2) for Ca2+ handling, and O2 cost of Emax (contractility index) of the LV. We obtained the RF from the beat constant of the exponential decay component of the postextrasystolic potentiation, and the O2 cost of Emax from [Formula: see text]o2measured at different Emax. Our equation calculated the unknown total Ca2+ handling, futile Ca2+ cycling, and Ca2+ reactivity of Emax from the RF and Ca2+ handling [Formula: see text]o2. The calculated total Ca2+ handling fell between 30 and 110 µmol/kg, depending on Emax and pathological conditions. Our method also allowed an assessment of futile Ca2+ cycling and Ca2+ reactivity of Emax in a beating LV. These data are not available using conventional methods. Our method can be used to better understand the pathophysiology of total Ca2+ handling in a beating heart.Key words: excitation-contraction coupling, myocardial Ca2+, contractility, cardiac O2 consumption.

In isolated, blood-perfused canine hearts, postextrasystolic potentiation (PESP) decays monotonically after a noncompensatory pause following a spontaneous extrasystole (ES). The monotonic PESP decay yields myocardial internal Ca2+ recirculation fraction (RF). We have found that after a compensatory pause (CP), PESP decays in alternans, consisting of an exponential and a sinusoidal decay component. We have proposed that this exponential component also yields RF. In the present study, we examined the reliability of this alternative method by widely changing the ES coupling interval (ESI), CP, and heart rate in the canine excised, cross-circulated left ventricle. We found that all PESP decays consisted of the sum of an exponential and a sinusoidal decay component of variable magnitudes whether a CP existed or not. Their decay constants as well as the calculated RF were independent of the ESI and CP. This confirmed the utility of our alternative RF determination method regardless of the ESI, CP, and heart rate. Direct experimental evidence of Ca2+ dynamics supportive of this alternative method, however, remains to be obtained.

Caffeine causes a considerable O(2) waste for positive inotropism in myocardium by complex pharmacological mechanisms. However, no quantitative study has yet characterized the mechanoenergetics of caffeine, particularly its O(2) cost of contractility in the E(max)-PVA-VO(2) framework. Here, E(max) is an index of ventricular contractility, PVA is a measure of total mechanical energy generated by ventricular contraction, and VO(2) is O(2) consumption of ventricular contraction. The E(max)-PVA-VO(2) framework proved to be powerful in cardiac mechanoenergetics. We therefore studied the effects of intracoronary caffeine at concentrations lower than 1 mmol/l on left ventricular (LV) E(max) and VO(2) for excitation-contraction (E-C) coupling in the excised cross-circulated canine heart. We enhanced LV E(max) by intracoronary infusion of caffeine after beta-blockade with propranolol and compared this effect with that of calcium. We obtained the relation between LV VO(2) and PVA with E(max) as a parameter. We then calculated the VO(2) for the E-C coupling by subtracting VO(2) under KCl arrest from the PVA-independent (or zero-PVA) VO(2) and the O(2) cost of E(max) as the slope of the E-C coupling VO(2)-E(max) relation. We found that this cost was 40% greater on average for caffeine than for calcium. This result, for the first time, characterized integratively cardiac mechanoenergetics of the O(2) wasting effect of the complex inotropic mechanisms of intracoronary caffeine at concentrations lower than 1 mmol/l in a beating whole heart.

Background and Objective: Transmyocardial revascularization (TMR) relieves angina and improves exercise tolerance in patients. Angiogenesis and myocardial denervation have been proposed as factors contributing to these benefits. To test whether radio frequency transmyocardial revascularization (RF-TMR) enhances angiogenesis and causes myocardial denervation. Study Design/Materials and Methods: RF-TMR channels were created in 12 dogs which survived up to 4 weeks. Bromodeoxyuridine was administered subcutaneously to mark proliferating cells as an assay of angiogenesis. Western blot analysis of tyrosine hydroxylase and blood pressure response to topical bradykinin were used as indices of myocardial denervation. Results: RF-TMR increased local vascularity by an average of 50%, whereas the rate of vascular cell proliferation was tripled over that of the untreated region. Changes in mean arterial pressure with bradykinin and tyrosine hydroxylase content were significantly decreased in RF-TMR regions as compared with normal myocardium in the same hearts. Conclusion: RF-TMR enhances angiogenesis and causes myocardial denervation in canine myocardium as with laser TMR.

The Weibull distribution is widely used to analyze the cumulative loss of performance, i.e., breakdown, of a complex system in systems engineering. We found for the first time that the difference curve of two Weibull distribution functions almost identically fitted the isovolumically contracting left ventricular (LV) pressure-time curve [P( t)] in all 345 beats (3 beats at each of 5 volumes in 23 canine hearts; r = 0.999953 ± 0.000027; mean ± SD). The first derivative of the difference curve also closely fitted the first derivative of the P( t) curve. These results suggest the possibility that the LV isovolumic P( t) curve may be characterized by two counteracting cumulative breakdown systems. Of these, the first breakdown system causes a gradual pressure rise and the second breakdown system causes a gradual pressure fall. This Weibull-function model of the heart seems to give a new systems engineering or integrative physiological view of the logic underlying LV isovolumic pressure generation.

We have reported that the postextrasystolic potentiation (PESP) decays in alternans or monotonically, respectively, depending on whether the first postextrasystolic beat interval has a compensatory pause or not, in the canine left ventricle. To get better mechanistic insight into the alternans PESP decay, we hypothesized that the myocardial mechanical restitution and potentiation could partly account for both types of PESP decay. To test this hypothesis, we simulated PESP decay on a computer using a documented equation combining myocardial mechanical restitution and potentiation. We changed the first postextrasystolic beat interval after a fixed extrasystolic beat interval without changing regular and other postextrasystolic beat intervals. The simulated PESP decayed in alternans or monotonically as a function only of the first postextrasystolic beat interval. Thus, the myocardial mechanical restitution and potentiation could partly account for both alternans and monotonic decay of PESP. We conclude that myocardial mechanical restitution and potentiation may partly underlie the initial two alternating beats, the first beat being the most potentiated and the second beat being the most depressed, of alternans PESP decay in the canine heart.

We have reported that, in canine hearts, cardiac cooling to 29°C enhanced left ventricular contractility but changed neither the contractile efficiency of cross-bridge (CB) cycling nor the excitation-contraction coupling energy. The mechanism of this intriguing energetics remained unknown. To get insights into this mechanism, we simulated myocardial cooling mechanoenergetics using basic Ca2+and CB kinetics. We assumed that both adenosinetriphosphatase (ATPase)-dependent sarcoplasmic reticulum (SR) Ca2+uptake and CB detachment decelerated with cooling. We also assumed that all the ATPase-independent SR Ca2+release, Ca2+binding to and dissociation from troponin, and CB attachment remained unchanged. The simulated cooling shifted the CB force-free Ca2+concentration curve to a lower Ca2+concentration, increasing the Ca2+responsiveness of CB force generation, and increased the maximum Ca2+-activated force. The simulation most importantly showed that these cooling effects combined led to a constant contractile efficiency when Ca2+uptake and CB detachment rate constants changed appropriately. This result seems to account for our experimentally observed constant contractile efficiency under cooling inotropy.

Background: Left ventricular (LV) hypertrophy is often present in patients with diastolic heart failure. However, stiffness of hypertrophied cardiomyocytes in the transverse direction has not been fully elucidated. The aim of this study was to assess passive cardiomyocyte stiffness of hypertrophied hearts in the transverse direction and the influence of actin-myosin cross-bridge formation on the stiffness. Methods and Results: Wistar rats received a vehicle (control) or isoproterenol (ISO) subcutaneously. After 7 days, compared with the controls, ISO administration had significantly increased heart weight and LV wall thickness and had decreased peak early annular relaxation velocity (e’) assessed by echocardiography. Elastic modulus of living cardiomyocytes in the transverse direction assessed by an atomic force microscope was significantly higher in the ISO group than in controls. We added butanedione monoxime (BDM), an inhibitor of actin-myosin interaction, and blebbistatin, a specific myosin II inhibitor, to the medium. BDM and blebbistatin significantly reduced the elastic modulus of cardiomyocytes in the ISO group. X-ray diffraction analysis showed that the reflection intensity ratio (I(1,0)/I(1,1)) at diastole was not different before and after treatment with BDM, which induces complete relaxation, in control hearts, but that I(1,0)/I(1,1) was significantly increased after BDM treatment in the ISO group, indicating residual cross-bridge formation in hypertrophied hearts. Conclusions: Passive cardiomyocyte stiffness in the transverse direction is increased in hearts with ISO-induced hypertrophy and this is caused by residual actin-myosin cross-bridge formation. (Circ J 2013; 77: 741–748)

Heart rate is one of the determinant factors of cardiac performance. However, there is no direct evidence for the effect of heart rate on the actin-myosin interaction. Purpose: To test the effect of heart rates on actin-myosin interaction in hearts with X-ray diffraction analysis using SPring-8. Methods: Seven isolated isovolumically contracting rat hearts were mounted so that the X-ray beam (15.0 keV) passed the subepicardial region. We recorded X-ray diffraction images and LV pressure at heart rates of 120 and 300bpm under 0 mmHg end-diastolic pressure. Between two different heart rates, we compared 1) the amount and the duration of actin-myosin interaction from the intensity ratio reduction of inner (1,0) and outer (1,1) X-ray diffraction, and 2) myofilament lattice spacing from the position of inner X-ray diffraction. Results: In all hearts, we did not detect incomplete relaxation at both heart rates. Increasing heart rate from 120 to 300bpm significantly decreased the intensity ratio reduction at the end-systole (0.92 ± 0.15 vs. 1.58 ± 0.17unitless, p

The aim of the present study was to examine the effects of formaldehyde solution on rat left ventricular function and compare it with those in hypertrophic hearts treated with isoproterenol by pressure-volume measurements with the catheter method. After 20-30 min. of intravenous infusion of 3.7% formaldehyde solution (FA) at 10 μl (3.7 mg)/kg/min, normal and hypertrophic hearts showed significant decreases in left ventricle end-systolic pressure (ESP), heart rate and cardiac out-put per minute, indicating an acute pumping failure. Hypertrophic hearts showed significantly smaller ESP, stroke volumes and cardiac output than those in normal hearts. Systolic pressure-volume area at midrange left ventricular volume (PVA mLVV : a mechanical work capability index) was significantly smaller than that in normal hearts and per cent of mean PVA mLVV versus pre-infusion mean value in hypertrophic hearts was significantly decreased compared to normal hearts 30 min. after FA infusion. The marked decrease in pH, base excess and no changes in PaO 2 and PaCO 2 suggest metabolic acidosis. The correction of metabolic acidosis with 9% NaHCO 3 did not influence on the acute pumping failure, indicating that metabolic acidosis did not cause it. Ultrastructural observations revealed marked dilation of the sarcoplasmic reticulum with intact sarcolemmal membranes and no disintegration of muscle myofibrils. Ryanodine receptors and calcium (Ca 2+ ) pumps (SERCA2A) located in the sarcoplasmic reticulum have major roles in the cytosolic Ca 2+ handling. Taken together, acute pumping failure by FA may derive from the impairment of Ca 2+ handling in the cardiac excitation-contraction coupling.

The role of neuronal nitric oxide synthase (nNOS) in cardiac ischemia-reperfusion (IR) and ischemia preconditioning (IP) is still controversial. Here, we focused on the possible roles of nNOS in cardiac IR and IP. Wild type C57BL/6 (WT) mice were subjected to coronary artery occlusion for 30 min followed by 24-h reperfusion (IR). Cardiac injury (infarct size and apoptotic cell number) was increased, associated with elevation of oxidative stress (lipid peroxidation) and nitrative stress (nitrotyrosine formation). A potent nNOS inhibitor, L-VNIO, and a superoxide dismutase mimetic and peroxynitrite scavenger, MnTBAP, significantly reduced IR-induced increases of oxidative/nitrative stress and cardiac injury. IR-induced cardiac injury in nNOS(-/-) (KO) mice was significantly lower than that in WT mice. MnTBAP markedly reduced IR-induced cardiac injury by suppression of oxidative/nitrative stress in KO mice. Cardiac IP was performed by three cycles of 5-min IR before 30-min ischemia followed by 24-h reperfusion. IP attenuated IR-induced cardiac injury in WT mice associated with reductions of oxidative/nitrative stress. IP-induced reduction of cardiac injury and oxidative/nitrative stress were eliminated by pretreatment with L-VNIO. In contrast with WT mice, IP had no protective effects in nNOS KO mice. In conclusion, nNOS played a dual role during cardiac IR and IP; nNOS exacerbated IR-induced injury by increasing oxidative/nitrative stress and contributed to IP-induced protection by inhibition of oxidative/nitrative stress.

Moderate rectal distension elicits recto-rectal reflex contractions and simultaneous recto-internal anal sphincter reflex relaxations that together comprise the defecation reflex. Both reflexes are controlled by 1) pelvic nerves, 2) lumbar colonic nerves, and 3) enteric nervous system. The aim of the present study was to explore a novel approach to repairing the defecation reflex dysfunction by using the plasticity of enteric nervous pathways. Experiments were performed in anesthetized guinea pigs with ethyl carbamate. The rectum 30 mm oral from the anal verge was transected without damage to extrinsic nerves, and subsequent end-to-end one-layer anastomosis was performed. Recovery of the defecation reflex and associated reflex pathways were evaluated. Eight weeks after sectioning of intrinsic reflex nerve pathways in the rectum, the defecation reflex recovered to the control level, accompanied with regeneration of reflex pathways. The 5-HT4-receptor agonist mosapride (0.5 and 1.0 mg/kg) significantly ( P < 0.01) enhanced the recovered defecation reflex 8 wk after surgery. Two weeks after local treatment with brain-derived neurotrophic factor (BDNF: 10−6 g/ml) at the rectal anastomotic site, the recto-internal anal sphincter reflex relaxations recovered and some bundles of fine nerve fibers were shown to interconnect the oral and anal ends of the myenteric plexus. These results suggested a possibility for repairing the anal dysfunction by promoting regeneration of the reflex pathways in the enteric nervous system with local application of BDNF.

Hypovolemia results in hypotension due to a decrease in left ventricular (LV) stroke volume. We have showed a logistic relaxation time constant (tauL) that is a superior lusitropic index during the LV pressure (LVP) falling phase independent of LV preload compared with the conventional monoexponential relaxation time constant (tauE). In the present study, we investigated the effect of decreasing LV preload on tauL and tauE during the LV contraction and other relaxation phases. The isovolumic LVP curve was analyzed at LV Volumes (LVVs) of 18, 14, and 10 mL during 2-Hz pacing in seven excised, cross-circulated canine hearts. TauL and tauE were evaluated using logistic and monoexponential analyses of the four phases of the cardiac cycle: the period from the onset to the maximum time derivative of LVP (LV dP/dtmax), from LV dP/dtmax to peak LVP, from peak LVP to the minimum time derivative of LVP (LV dP/dtmin), and from LV dP/dtmin to LV end-diastolic pressure. TauL and tauE during the four phases did not change significantly with the decrease in LVV. During the change in LVV, the logistic function always fit significantly better compared with the monoexponential function. In conclusion, hypovolemia does not affect the speed of isovolumic LV contraction and relaxation. Each phase of the LVP curve is of a logistic nature. TauL is as a useful index for estimation of the speed of alteration during each phase of cardiac systole and diastole.