scholarly journals Load Independence of Temperature-Dependent Ca2+ Recirculation Fraction in Canine Heart

2004 ◽  
Vol 54 (4) ◽  
pp. 319-329 ◽  
Author(s):  
J. Mizuno ◽  
S. Mohri ◽  
J. Shimizu ◽  
S. Suzuki ◽  
T. Mikane ◽  
...  
Keyword(s):  
Canine Heart ◽  
Temperature Dependent ◽  
Recirculation Fraction

Energy-wasteful total Ca2+ handling underlies increased O2 cost of contractility in canine stunned heart

2000 ◽  
Vol 278 (5) ◽  
pp. H1464-H1472 ◽  
Author(s):  
Shinyu Lee ◽  
Junichi Araki ◽  
Takeshi Imaoka ◽  
Masaki Maesako ◽  
Gentaro Iribe ◽  
...  
Keyword(s):  
Exponential Decay ◽  
Myocardial Stunning ◽  
Left Ventricular ◽  
Canine Heart ◽  
Ventricular Contractility ◽  
Left Ventricular Contractility ◽  
Postextrasystolic Potentiation ◽  
Decay Component ◽  
Recirculation Fraction ◽  
Integrative Method

Postischemic myocardial stunning halved left ventricular contractility [end-systolic maximum elastance ( E max)] and doubled the O2 cost of E max in excised cross-circulated canine heart. We hypothesized that this increased O2 cost derived from energy-wasteful myocardial Ca2+ handling consisting of a decreased internal Ca2+ recirculation, some futile Ca2+ cycling, and a depressed Ca2+ reactivity of E max. We first calculated the internal Ca2+ recirculation fraction (RF) from the exponential decay component of postextrasystolic potentiation. Stunning significantly accelerated the decay and decreased RF from 0.63 to 0.43 on average. We then combined the decreased RF with the halved E maxand its doubled O2 cost and analyzed total Ca2+handling using our recently developed integrative method. We found a decreased total Ca2+ transport and a considerable shift of the relation between futile Ca2+ cycling and Ca2+ reactivity in an energy-wasteful direction in the stunned heart. These changes in total Ca2+ handling reasonably account for the doubled O2 cost of E max in stunning, supporting the hypothesis.

A new integrative method to quantify total Ca2+ handling and futile Ca2+ cycling in failing hearts

1998 ◽  
Vol 275 (6) ◽  
pp. H2325-H2333 ◽  
Author(s):  
Juichiro Shimizu ◽  
Junichi Araki ◽  
Ju Mizuno ◽  
Shinyu Lee ◽  
Yi Syuu ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Left Ventricle ◽  
Present Method ◽  
Direct Application ◽  
Cardiac Contraction ◽  
Canine Heart ◽  
Contraction Coupling ◽  
Before And After ◽  
Recirculation Fraction ◽  
Integrative Method

Ca2+ handling in excitation-contraction coupling requires considerable O2 consumption (Vo 2) in cardiac contraction. We have developed an integrative method to quantify total Ca2+ handling in normal hearts. However, its direct application to failing hearts, where futile Ca2+ cycling via the Ca2+-leaky sarcoplasmic reticulum (SR) required an increased Ca2+handling Vo 2, was not legitimate. To quantify total Ca2+ handling even in such failing hearts, we combined futile Ca2+ cycling with Ca2+ handling Vo 2 and the internal Ca2+ recirculation fraction via the SR. We applied this method to the canine heart mechanoenergetics before and after intracoronary ryanodine at nanomolar concentrations. We found that total Ca2+ handling per beat was halved after the ryanodine treatment from ∼60 μmol/kg left ventricle before ryanodine. We also found that futile Ca2+ cycling via the SR increased to >1 cycle/beat after ryanodine from presumably zero before ryanodine. These results support the applicability of the present method to the failing hearts with futile Ca2+ cycling via the SR.

Postextrasystolic contractile decay always contains exponential and alternans components in canine heart

2000 ◽  
Vol 279 (1) ◽  
pp. H225-H233 ◽  
Author(s):  
Juichiro Shimizu ◽  
Junichi Araki ◽  
Gentaro Iribe ◽  
Takeshi Imaoka ◽  
Satoshi Mohri ◽  
...  
Keyword(s):  
Heart Rate ◽  
Left Ventricle ◽  
Experimental Evidence ◽  
Canine Heart ◽  
Determination Method ◽  
Decay Constants ◽  
Decay Component ◽  
Alternative Method ◽  
Coupling Interval ◽  
Recirculation Fraction

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.

scholarly journals Ryanodine Decreases Internal Ca2+ Recirculation Fraction of the Canine Heart as Studied by Postextrasystolic Transient Alternans.

1997 ◽  
Vol 47 (6) ◽  
pp. 521-530 ◽  
Author(s):  
Yoshiki HATA ◽  
Juichiro SHIMIZU ◽  
Shingo HOSOGI ◽  
Hiromi MATSUBARA ◽  
Junichi ARAKI ◽  
...  
Keyword(s):  
Canine Heart ◽  
Recirculation Fraction

Temperature-dependent postextrasystolic potentiation and Ca2+ recirculation fraction in canine hearts

2002 ◽  
Vol 282 (2) ◽  
pp. H403-H413 ◽  
Author(s):  
Ju Mizuno ◽  
Junichi Araki ◽  
Shunsuke Suzuki ◽  
Satoshi Mohri ◽  
Takeshi Mikane ◽  
...  
Keyword(s):  
Left Ventricle ◽  
Exponential Decay ◽  
Temperature Sensitivity ◽  
Systolic Pressure ◽  
Volume Ratio ◽  
Myocardial Cells ◽  
Temperature Dependent ◽  
Postextrasystolic Potentiation ◽  
Decay Component ◽  
Recirculation Fraction

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.

scholarly journals Temperature-dependent inotropic and lusitropic indices based on half-logistic time constants for four segmental phases in isovolumic left ventricular pressure–time curve in excised, cross-circulated canine heart

2017 ◽  
Vol 95 (2) ◽  
pp. 190-198 ◽  
Author(s):  
Ju Mizuno ◽  
Satoshi Mohri ◽  
Takeshi Yokoyama ◽  
Mikiya Otsuji ◽  
Hideko Arita ◽  
...  
Keyword(s):  
Least Squares Method ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Canine Heart ◽  
Temperature Dependent ◽  
Time Curve ◽  
Time Constants ◽  
Pressure Time ◽  
Systolic And Diastolic Function ◽  
Increasing Temperature

Varying temperature affects cardiac systolic and diastolic function and the left ventricular (LV) pressure–time curve (PTC) waveform that includes information about LV inotropism and lusitropism. Our proposed half-logistic (h-L) time constants obtained by fitting using h-L functions for four segmental phases (Phases I–IV) in the isovolumic LV PTC are more useful indices for estimating LV inotropism and lusitropism during contraction and relaxation periods than the mono-exponential (m-E) time constants at normal temperature. In this study, we investigated whether the superiority of the goodness of h-L fits remained even at hypothermia and hyperthermia. Phases I–IV in the isovolumic LV PTCs in eight excised, cross-circulated canine hearts at 33, 36, and 38 °C were analyzed using h-L and m-E functions and the least-squares method. The h-L and m-E time constants for Phases I–IV significantly shortened with increasing temperature. Curve fitting using h-L functions was significantly better than that using m-E functions for Phases I–IV at all temperatures. Therefore, the superiority of the goodness of h-L fit vs. m-E fit remained at all temperatures. As LV inotropic and lusitropic indices, temperature-dependent h-L time constants could be more useful than m-E time constants for Phases I–IV.

O2cost of contractility but not of mechanical energy increases with temperature in canine left ventricle

1999 ◽  
Vol 277 (1) ◽  
pp. H65-H73 ◽  
Author(s):  
Takeshi Mikane ◽  
Junichi Araki ◽  
Shunsuke Suzuki ◽  
Ju Mizuno ◽  
Juichiro Shimizu ◽  
...  
Keyword(s):  
Mechanical Energy ◽  
Left Ventricular ◽  
Beating Heart ◽  
Canine Heart ◽  
Oxygen Cost ◽  
Temperature Dependent ◽  
Total Mechanical Energy ◽  
Myocardial Temperature ◽  
Linear Manner ◽  
Dependent Processes

We investigated the effects of myocardial temperature on left ventricular (LV) mechanoenergetics in the excised, cross-circulated canine heart. We used the framework of the LV contractility ( Emax)-pressure-volume area (PVA; a measure of total mechanical energy)-myocardial oxygen consumption (Vo2) relationship. We have shown this framework to be useful to integrative analysis of the mechanoenergetics of a beating heart. In isovolumic contractions at a constant pacing rate, increasing myocardial temperature from 30 to 40°C depressed Emaxand increased the oxygen cost of Emax, which was enhanced by dobutamine, in a linear manner. However, the slope of the Vo2-PVA relation (reciprocal of contractile efficiency) and its Vo2intercept remained constant. Q10values of Emax, the oxygen cost of Emax, and the oxygen cost of PVA were 0.4, 2.1 and 1.0, respectively, around normothermia. We conclude that the temperature-dependent processes of cross-bridge cycling and Ca2+handling integratively depress Emaxand augment its oxygen cost without affecting the oxygen cost of PVA as myocardial temperature increases by 10°C around normothermia.

(111) Monocrystalline Nickel Films

1972 ◽  
Vol 30 ◽  
pp. 512-513
Author(s):  
T.E. Pratt ◽  
R.W. Vook
Keyword(s):  
Film Thickness ◽  
Deposition Rate ◽  
Room Temperature ◽  
Narrow Range ◽  
High Vacuum ◽  
Residual Pressure ◽  
Temperature Dependent ◽  
Deposition Parameters ◽  
Transmission Electron ◽  
Substrate Temperatures

(111) oriented thin monocrystalline Ni films have been prepared by vacuum evaporation and examined by transmission electron microscopy and electron diffraction. In high vacuum, at room temperature, a layer of NaCl was first evaporated onto a freshly air-cleaved muscovite substrate clamped to a copper block with attached heater and thermocouple. Then, at various substrate temperatures, with other parameters held within a narrow range, Ni was evaporated from a tungsten filament. It had been shown previously that similar procedures would yield monocrystalline films of CU, Ag, and Au.For the films examined with respect to temperature dependent effects, typical deposition parameters were: Ni film thickness, 500-800 A; Ni deposition rate, 10 A/sec.; residual pressure, 10-6 torr; NaCl film thickness, 250 A; and NaCl deposition rate, 10 A/sec. Some additional evaporations involved higher deposition rates and lower film thicknesses.Monocrystalline films were obtained with substrate temperatures above 500° C. Below 450° C, the films were polycrystalline with a strong (111) preferred orientation.

Sign in / Sign up

Export Citation Format

Share Document