Effect of catecholamine-induced cardiac hypertrophy on the force–interval relationship

1989 ◽  
Vol 67 (1) ◽  
pp. 40-46 ◽  
Author(s):  
Paul B. Taylor ◽  
Reinhard K. Helbing ◽  
Sean Rourke ◽  
Dennis Churchill
Keyword(s):  
Cardiac Hypertrophy ◽  
Time Constant ◽  
Papillary Muscle ◽  
Tissue Growth ◽  
Least Square ◽  
Maximum Force ◽  
Total Force ◽  
Time Constants ◽  
Atrial Muscle ◽  
The Right

Cardiac hypertrophy was induced in adult female Wistar rats following 12 days of daily subcutaneous injections of isoproterenol (ISO). The left atria responded with a 13–14% increase in tissue growth, while the ventricles achieved a 34–39% increased tissue mass. Maximum force generation and twitch characteristics in 1.0 mM external Ca2+ for the left atria or the right papillary muscle were unchanged in the ISO-treated animals. The force–interval relation was determined at 26 °C between 0.5 and 120 s. The development of maximum force clearly passed through two phases identified as alpha and beta. To characterize these two processes the data were fitted to a two-term linear combination of exponentials (two-compartment model). The time constant and capacity of each process to contribute to the whole force–interval curve was determined by a four-parameter least square fit method. In control atrial muscle the time constants for the alpha and beta processes were 0.47 and 11.23 s, respectively. The contribution of each process to the total force curve in control atrial muscle was approximately 50% alpha and 50% beta. Following ISO-induced growth the time constants were 0.38 and 13.33 s with a shift of contributions towards 60% alpha and 40% beta. Control papillary muscle from the right ventricle had a similar alpha time constant of 0.49 s compared with atrial muscle but possessed a considerably slower beta time constant of 26.17 s. The contribution of each process to interval-dependent force development was 44.5 and 55.5%, respectively. Treatment with ISO to induce ventricular growth resulted in a 20% reduced alpha time constant, with a 45% increased contribution by the alpha process. These results suggest that during the development of catecholamine-induced hypertrophy, there is a significant change in the fundamental alpha process which appears to be mediated by a reduced time constant and an enhanced capacity to contribute to force development.Key words: excitation–contraction, interval-dependent force recovery, post-rest contractions, cardiac muscle, sarcoplasmic reticulum.

Peristaltic Carreau-Yasuda nanofluid flow and mixed heat transfer analysis in an asymmetric vertical and tapered wavy wall channel

2020 ◽  
Vol 1 (1) ◽  
pp. 128-140 ◽  
Author(s):  
Mohammad Hatami ◽  
◽  
D Jing ◽  
Keyword(s):  
Heat Transfer ◽  
Least Square Method ◽  
Weissenberg Number ◽  
Least Square ◽  
Heat Transfer Analysis ◽  
Phase Method ◽  
Nanofluid Flow ◽  
Two Phase ◽  
Nanoparticles Concentration ◽  
The Right

In this study, two-phase asymmetric peristaltic Carreau-Yasuda nanofluid flow in a vertical and tapered wavy channel is demonstrated and the mixed heat transfer analysis is considered for it. For the modeling, two-phase method is considered to be able to study the nanoparticles concentration as a separate phase. Also it is assumed that peristaltic waves travel along X-axis at a constant speed, c. Furthermore, constant temperatures and constant nanoparticle concentrations are considered for both, left and right walls. This study aims at an analytical solution of the problem by means of least square method (LSM) using the Maple 15.0 mathematical software. Numerical outcomes will be compared. Finally, the effects of most important parameters (Weissenberg number, Prandtl number, Brownian motion parameter, thermophoresis parameter, local temperature and nanoparticle Grashof numbers) on the velocities, temperature and nanoparticles concentration functions are presented. As an important outcome, on the left side of the channel, increasing the Grashof numbers leads to a reduction in velocity profiles, while on the right side, it is the other way around.

scholarly journals Individual motion perception parameters and motion sickness frequency sensitivity in fore-aft motion

2021 ◽  
Author(s):  
Tugrul Irmak ◽  
Ksander N. de Winkel ◽  
Daan M. Pool ◽  
Heinrich H. Bülthoff ◽  
Riender Happee
Keyword(s):  
Motion Sickness ◽  
Motion Perception ◽  
Time Constant ◽  
Storage Time ◽  
Velocity Storage ◽  
Strong Positive Correlation ◽  
Subjective Vertical ◽  
Time Constants ◽  
Frequency Sensitivity ◽  
Observer Model

AbstractPrevious literature suggests a relationship between individual characteristics of motion perception and the peak frequency of motion sickness sensitivity. Here, we used well-established paradigms to relate motion perception and motion sickness on an individual level. We recruited 23 participants to complete a two-part experiment. In the first part, we determined individual velocity storage time constants from perceived rotation in response to Earth Vertical Axis Rotation (EVAR) and subjective vertical time constants from perceived tilt in response to centrifugation. The cross-over frequency for resolution of the gravito-inertial ambiguity was derived from our data using the Multi Sensory Observer Model (MSOM). In the second part of the experiment, we determined individual motion sickness frequency responses. Participants were exposed to 30-minute sinusoidal fore-aft motions at frequencies of 0.15, 0.2, 0.3, 0.4 and 0.5 Hz, with a peak amplitude of 2 m/s2 in five separate sessions, approximately 1 week apart. Sickness responses were recorded using both the MIsery SCale (MISC) with 30 s intervals, and the Motion Sickness Assessment Questionnaire (MSAQ) at the end of the motion exposure. The average velocity storage and subjective vertical time constants were 17.2 s (STD = 6.8 s) and 9.2 s (STD = 7.17 s). The average cross-over frequency was 0.21 Hz (STD = 0.10 Hz). At the group level, there was no significant effect of frequency on motion sickness. However, considerable individual variability was observed in frequency sensitivities, with some participants being particularly sensitive to the lowest frequencies, whereas others were most sensitive to intermediate or higher frequencies. The frequency of peak sensitivity did not correlate with the velocity storage time constant (r = 0.32, p = 0.26) or the subjective vertical time constant (r = − 0.37, p = 0.29). Our prediction of a significant correlation between cross-over frequency and frequency sensitivity was not confirmed (r = 0.26, p = 0.44). However, we did observe a strong positive correlation between the subjective vertical time constant and general motion sickness sensitivity (r = 0.74, p = 0.0006). We conclude that frequency sensitivity is best considered a property unique to the individual. This has important consequences for existing models of motion sickness, which were fitted to group averaged sensitivities. The correlation between the subjective vertical time constant and motion sickness sensitivity supports the importance of verticality perception during exposure to translational sickness stimuli.

scholarly journals Growth factors in the regulation of reparative response in the presence of peritoneal damage

2020 ◽  
Vol 5 (4) ◽  
Author(s):  
Irina A. Shurygina ◽  
Мichael G. Shurygin ◽  
Lubov V. Rodionova ◽  
Nataliya I. Ayushinova
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Extended Period ◽  
Tissue Growth ◽  
Tissue Response ◽  
Heparin Binding ◽  
Lower Quadrant ◽  
Male Wistar Rats ◽  
The Right ◽  
Endothelial Growth Factor

AbstractObjectivesTo study the expression of growth factors in the regulation of tissue repair after peritoneal damage tissue response to peritoneal damage.MethodsExperimental study in 35 male Wistar rats determining the evolution over time of the tissue response to aseptic peritoneal damage. A standardized bowel and peritoneal lesions were created in the right lower quadrant by laparotomy. Then, tissular expression of growth factors was evaluated by multiplex polymerase chain reaction at seven timepoints between 6 h and 30 days, postoperatively.ResultsTissular responses of granulocyte-stimulating factors (Csf2, Csf3), connective tissue growth factor (Ctgf), epidermal growth factors and receptor (Egf, Egfr), fibroblast growth factors (Fgf2, 7 and 10), heparin binding EGF-like growth factor (Hbegf), hepatocyte growth factor (Hgf), insulin-like growth factor-1 (Igf1), mitogenic transforming growth factors (Tgfa, Tgfb1, Tgfbr3), and vascular endothelial growth factor A (Vegfa) were biphasic with a first expression peak at day 3, followed by a more pronounced peak at day 14.ConclusionsWe observed a long-lasting, widespread response of tissular growth factors for at least two weeks after peritoneal damage. To be clinically effective, the prophylaxis of postoperative adhesions might be needed for an extended period of time.

Why is the perceptual octave stretched? An account based on mismatched time constants within the auditory brainstem

2021 ◽  
Author(s):  
Alain de Cheveigné
Keyword(s):  
Time Constant ◽  
Auditory Brainstem ◽  
The Other ◽  
Inhibitory Synapses ◽  
Coincidence Counting ◽  
Time Constants ◽  
Direct Pathway ◽  
Lower Tone ◽  
Excitatory And Inhibitory Synapses

This paper suggests an explanation for listener’s greater tolerance to positive than negative mistuning of the higher tone within an octave pair. It hypothesizes a neu- ral circuit tuned to cancel the lower tone, that also cancels the higher tone if that tone is in tune. Imperfect cancellation is the cue to mistuning of the octave. The circuit involves two pathways, one delayed with respect to the other, that feed a coincidence-counting neuron via excitatory and inhibitory synapses. A mismatch between the time constants of these two synapses results in an asymmetry in sen- sitivity to mismatch. Specifically, if the time constant of the delayed pathway is greater than that of the direct pathway, there is a greater tolerance to positive than to negative mistuning, which can lead to a perceptual“stretch” of the octave. The model is applicable to both harmonic and – with qualification – melodic oc- taves. The paper describes the model and reviews the evidence from auditory psychophysics and physiology in favor – or against – it.

scholarly journals Voltage-gated transient currents in bovine adrenal fasciculata cells. I. T-type Ca2+ current.

1993 ◽  
Vol 102 (2) ◽  
pp. 217-237 ◽  
Author(s):  
B Mlinar ◽  
B A Biagi ◽  
J J Enyeart
Keyword(s):  
Time Constant ◽  
Low Voltage ◽  
Zona Fasciculata ◽  
Patch Clamp Technique ◽  
Time Constants ◽  
Voltage Gated ◽  
Wide Range ◽  
Boltzmann Function ◽  
Voltage Dependent ◽  
Ca2 Channels

The whole cell version of the patch clamp technique was used to identify and characterize voltage-gated Ca2+ channels in enzymatically dissociated bovine adrenal zona fasciculata (AZF) cells. The great majority of cells (84 of 86) expressed only low voltage-activated, rapidly inactivating Ca2+ current with properties of T-type Ca2+ current described in other cells. Voltage-dependent activation of this current was fit by a Boltzmann function raised to an integer power of 4 with a midpoint at -17 mV. Independent estimates of the single channel gating charge obtained from the activation curve and using the "limiting logarithmic potential sensitivity" were 8.1 and 6.8 elementary charges, respectively. Inactivation was a steep function of voltage with a v1/2 of -49.9 mV and a slope factor K of 3.73 mV. The expression of a single Ca2+ channel subtype by AZF cells allowed the voltage-dependent gating and kinetic properties of T current to be studied over a wide range of potentials. Analysis of the gating kinetics of this Ca2+ current indicate that T channel activation, inactivation, deactivation (closing), and reactivation (recovery from inactivation) each include voltage-independent transitions that become rate limiting at extreme voltages. Ca2+ current activated with voltage-dependent sigmoidal kinetics that were described by an m4 model. The activation time constant varied exponentially at test potentials between -30 and +10 mV, approaching a voltage-independent minimum of 1.6 ms. The inactivation time constant (tau i) also decreased exponentially to a minimum of 18.3 ms at potentials positive to 0 mV. T channel closing (deactivation) was faster at more negative voltages; the deactivation time constant (tau d) decreased from 8.14 +/- 0.7 to 0.48 +/- 0.1 ms at potentials between -40 and -150 mV. T channels inactivated by depolarization returned to the closed state along pathways that included two voltage-dependent time constants. tau rec-s ranged from 8.11 to 4.80 s when the recovery potential was varied from -50 to -90 mV, while tau rec-f decreased from 1.01 to 0.372 s. At potentials negative to -70 mV, both time constants approached minimum values. The low voltage-activated Ca2+ current in AZF cells was blocked by the T channel selective antagonist Ni2+ with an IC50 of 20 microM. At similar concentrations, Ni2+ also blocked cortisol secretion stimulated by adrenocorticotropic hormone. Our results indicate that bovine AZF cells are distinctive among secretory cells in expressing primarily or exclusively T-type Ca2+ channels.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification of Time-Varying Time Constants of Thermocouple Sensors and Its Application to Temperature Measurement

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Kenneth Kar ◽  
Akshya K. Swain ◽  
Robert Raine
Keyword(s):  
Kalman Filter ◽  
Least Squares ◽  
Time Constant ◽  
Identification Problem ◽  
Basis Functions ◽  
New Technique ◽  
Ratio Test ◽  
Time Varying ◽  
Time Constants ◽  
Orthogonal Least Squares

The present study addresses the problem of estimating time-varying time constants associated with thermocouple sensors by a set of basis functions. By expanding each time-varying time constant onto a finite set of basis sequences, the time-varying identification problem reduces to a parameter estimation problem of a time-invariant system. The proposed algorithm, to be called as orthogonal least-squares with basis function expansion algorithm, combines the orthogonal least-squares algorithm with an error reduction ratio test to include significant basis functions into the model, which results in a parsimonious model structure. The performance of the method was compared with a linear Kalman filter. Simulations on engine data have demonstrated that the proposed method performs satisfactorily and is better than the Kalman filter. The new technique has been applied in a Stirling cycle compressor. The sinusoidal variations in time constant are tracked properly using the new technique, but the linear Kalman filter fails to do so. Both model validation and thermodynamic laws confirm that the new technique gives unbiased estimates and that the assumed thermocouple model is adequate.

Voltage Dependence of the Glycine Receptor–Channel Kinetics in the Zebrafish Hindbrain

1999 ◽  
Vol 82 (5) ◽  
pp. 2120-2129 ◽  
Author(s):  
Pascal Legendre
Keyword(s):  
Time Constant ◽  
Rise Time ◽  
Time Course ◽  
Voltage Dependence ◽  
Good Description ◽  
Glycine Receptor ◽  
Relative Amplitude ◽  
Time Constants ◽  
Low Concentration ◽  
Voltage Dependent

Electrophysiological recordings of outside-out patches to fast-flow applications of glycine were made on patches derived from the Mauthner cells of the 50-h-old zebrafish larva. As for glycinergic miniature inhibitory postsynaptic currents (mIPSCs), depolarizing the patch produced a broadening of the transient outside-out current evoked by short applications (1 ms) of a saturating concentration of glycine (3 mM). When the outside-out patch was depolarized from −50 to +20 mV, the peak current varied linearly with voltage. A 1-ms application of 3 mM glycine evoked currents that activated rapidly and deactivated biexponentially with time constants of ≈5 and ≈30 ms (holding potential of −50 mV). These two decay time constants were increased by depolarization. The fast deactivation time constant increased e-fold per 95 mV. The relative amplitude of the two decay components did not significantly vary with voltage. The fast component represented 64.2 ± 2.8% of the total current at −50 mV and 54.1 ± 10% at +20 mV. The 20–80% rise time of these responses did not show any voltage dependence, suggesting that the opening rate constant is insensitive to voltage. The 20–80% rise time was 0.2 ms at −70 mV and 0.22 ms at +20 mV. Responses evoked by 100–200 ms application of a low concentration of glycine (0.1 mM) had a biphasic rising phase reflecting the complex gating behavior of the glycine receptor. The time constant of these two components and their relative amplitude did not change with voltage, suggesting that modal shifts in the glycine-activated channel gating mode are not sensitive to the membrane potential. Using a Markov model to simulate glycine receptor gating behavior, we were able to mimic the voltage-dependent change in the deactivation time course of the responses evoked by 1-ms application of 3 mM glycine. This kinetics model incorporates voltage-dependent closing rate constants. It provides a good description of the time course of the onset of responses evoked by the application of a low concentration of glycine at all membrane potentials tested.

scholarly journals Logistic Time Constant of Isometric Relaxation Force Curve of Ferret Ventricular Papillary Muscle. Reliable Index of Lusitropism.

2000 ◽  
Vol 50 (5) ◽  
pp. 479-487 ◽  
Author(s):  
Ju Mizuno ◽  
Junichi Araki ◽  
Takeshi Mikane ◽  
Satoshi Mohri ◽  
Takeshi Imaoka ◽  
...  
Keyword(s):  
Time Constant ◽  
Papillary Muscle ◽  
Reliable Index ◽  
Force Curve ◽  
Relaxation Force

scholarly journals PENGARUH VARIABEL MAKROEKONOMI TERHADAP DANA PIHAK KETIGA BANK UMUM SYARIAH DI INDONESIA

2020 ◽  
Vol 4 (1) ◽  
pp. 164
Author(s):  
Muhammad Dzulfaqori Jatnika
Keyword(s):  
Interest Rates ◽  
Commercial Banks ◽  
Random Effect ◽  
Random Effect Model ◽  
Least Square ◽  
Third Party ◽  
Ordinary Least Square ◽  
Effect Model ◽  
Per Capita ◽  
The Right

Tujuan penelitian ini  adalah menganalisis pengaruh faktor makroekonomi yaitu nilai tukar, inflasi, suku bunga, dan GDP per kapita terhadap dana pihak ketiga di bank umum Syariah. Penelitian ini merupakan penelitian kuantitatif dengan data sekunder yang berupa data panel. Teknik analisis yang digunakan adalah metode analisis linier berganda Ordinary Least Square (OLS). Hasil uji Hausman menunjukan model yang tepat dalam penelitian ini adalah random effect model. Semua variabel signifikan, variabel inflasi dan nilai tukar memiliki pengaruh positif sedangkan variabel suku bunga dan GDP per kapita memiliki pengaruh yang negatif terhadap dana pihak ketiga di bank umum Syariah. Hasil penelitian ini memiliki implikasi bagi para pelaku usaha perbankan untuk menentukan waktu yang tepat dalam menarik dan menyalurkan dana pihak ketiga dari masyarakat. Dan dapat menjadi acuan untuk mengeluarkan kebijakan terkait bisnisnya. Dan bagi peneliti selanjutnya dapat menjadi acuan untuk mengembangkan kembali penelitian berikutnya. Pada penelitian selanjutnya diharapkan dapat menambah variabel-variabel terkait lainnya selain variabel yang telah diteliti dalam penelitian ini. Kebaruan dalam penelitian ini adalah tambahan variabel yang mempengaruhi dana pihak ketiga dan juga tambahan sampel bank umum Syariah sehingga diharapkan penelitian ini lebih mendalam daripada penelitian sebelumnya.  The purpose of this study is to analyze the influence of macroeconomic factors, namely the exchange rate, inflation, interest rates, and GDP per capita on third party funds in Islamic commercial banks. This research is a quantitative study with secondary data in the form of panel data. The analysis technique used is the Ordinary Least Square (OLS) multiple linear analysis method. The Hausman test results showed the right model in this study was the random effect model. All variables are significant, inflation and exchange rates have a positive effect while interest rates and GDP per capita have a negative effect on third-party funds in Islamic commercial banks. The results of this study have implications for banking businesses to determine the right time in attracting and channelling third party funds from the public. And can be a reference for issuing policies related to business. And for further researchers can be a reference to develop further research. In the next research, it is expected to be able to add other related variables besides the variables that have been examined in this study. The novelty in this study is the addition of variables that affect third party funds and also additional samples of Islamic commercial banks so that this research is expected to be more in-depth than previous research.

Traumatic tricuspid insufficiency in a kitten

1999 ◽  
Vol 35 (1) ◽  
pp. 21-24 ◽  
Author(s):  
JM Closa ◽  
A Font
Keyword(s):  
Pleural Effusion ◽  
Right Ventricle ◽  
Papillary Muscle ◽  
Atrioventricular Valve ◽  
Chordae Tendineae ◽  
Color Flow ◽  
Tricuspid Insufficiency ◽  
Muscle Insertion ◽  
Valve Insufficiency ◽  
The Right

A four-month-old, male, common European kitten developed pleural effusion and ascites after falling from a fourth-floor flat. Radiographic, bidimensional echocardiography and color-flow Doppler findings were compatible with right-sided atrioventricular valve insufficiency. Necropsy confirmed the diagnosis that tricuspid insufficiency resulted from the rupture of the chordae tendineae of the nonseptal cusp of the valve at the level of the cranial papillary muscle insertion in the right ventricle.

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