Operative contractility: A functional concept of the inotropic state

2005 ◽  
Vol 32 (10) ◽  
pp. 871-881
Author(s):  
Roberto Curiel ◽  
Juan Perez-Gonzalez ◽  
Edwar Torres ◽  
Ruben Landaeta ◽  
Miguel Cerrolaza
Keyword(s):  
Inotropic State ◽  
Functional Concept

What does the concept of affordances afford?

2021 ◽  
pp. 105971232098268
Author(s):  
Rob Withagen ◽  
Alan Costall
Keyword(s):  
Lived Experience ◽  
Theoretical Basis ◽  
Scientific Work ◽  
Ecological Approach ◽  
Design Practices ◽  
The Many ◽  
Architecture And Design ◽  
Functional Concept

Gibson once suggested that his ecological approach could provide architecture and design with a new theoretical basis. Erik Rietveld takes up this suggestion—the concept of affordances figures prominently not only in his philosophical and scientific work but also in the design practices he is engaged in. However, as Gibson introduced affordances as a functional concept, it seems ill-suited to capture the many dimensions of our lived experience of the (manufactured) environment. Can the concept of affordances also take on the expressive and aesthetic qualities of artifacts and buildings?

Cholinergic stimulation modulates negative inotropic effect of cocaine on ferret ventricular myocardium

1996 ◽  
Vol 270 (2) ◽  
pp. H678-H684
Author(s):  
L. Miao ◽  
Z. Qiu ◽  
J. P. Morgan
Keyword(s):  
Response Curve ◽  
Negative Inotropic Effect ◽  
Ventricular Myocardium ◽  
Inotropic Effect ◽  
Dependent Manner ◽  
Cholinergic Stimulation ◽  
Concentration Dependent Manner ◽  
Cell Shortening ◽  
Inotropic State ◽  
Concentration Response Curve

We tested the hypothesis that the negative inotropic effect (NIE) of cocaine is mediated, at least in part, by cholinergic stimulation and can be correlated with the degree of adenosine 3',5'-cyclic monophosphate (cAMP) dependency of the inotropic state. Cardiac myocytes were isolated from left ventricles of ferrets and loaded with the fluorescent Ca2+ indicator indo 1. Cells were placed in physiological solution containing 2.0 mM Ca2+ and stimulated at 0.5 Hz and 30 degrees C. Cocaine decreased peak cell shortening and peak intracellular Ca2+ in a concentration-dependent manner (10(-8)-10(-4) M). The concentration-response curve of cocaine was shifted significantly downward compared with those of lidocaine and procaine in the same range of concentrations. Atropine (10(-6) M) shifted the concentration-response curve of cocaine, but not those of lidocaine and procaine, rightward, with a pA2 value (7.66) similar to that obtained with carbachol (7.99). With prior addition of isoproterenol (ISO, 10(-8) M) or increased Ca2+ (4.0 mM) to increase cell shortening to the same degree (approximately 60%), cocaine and carbachol decreased contractility to a significantly greater extent in ISO-stimulated myocytes. To clarify whether these treatments changed responsiveness of the contractile elements to Ca2+, the effect of 2,3-butanedione monoxime, an agent that interferes with the interaction of myosin and actin, was tested with previous addition of ISO or increased Ca2+, and no differential effect occurred. Therefore, we postulate that 1) the NIE of cocaine on myocytes is caused by decreased Ca2+ availability; 2) this effect is due to specific stimulation of cholinergic receptors in addition to other direct myocardial (probably local anesthetic) effects; and 3) the NIE correlates with the level of cAMP dependence of the inotropic state.

scholarly journals Many-Body Perturbation Theory Using the Density-Functional Concept: Beyond theGWApproximation

2005 ◽  
Vol 94 (18) ◽  
Author(s):  
Fabien Bruneval ◽  
Francesco Sottile ◽  
Valerio Olevano ◽  
Rodolfo Del Sole ◽  
Lucia Reining
Keyword(s):  
Perturbation Theory ◽  
Density Functional ◽  
Many Body ◽  
Many Body Perturbation Theory ◽  
Functional Concept

Light Design of Small Towns’ Coastal Areas

2021 ◽  
pp. 51-54
Author(s):  
Oleg G. Maksimov ◽  
Olga Yu. Zaripova
Keyword(s):  
Cultural Heritage ◽  
Water Storage ◽  
Small Towns ◽  
Coastal Areas ◽  
Town Development ◽  
Experimental Project ◽  
Storage Basin ◽  
Effective Use ◽  
The Town ◽  
Functional Concept

This paper touches upon the problems of development and illumination of small Russian towns located on the banks of rivers and water storage basins (as exemplified by master’s theses). These problems lie on the plane of preservation and effective use of architectural, historical, and cultural heritage of towns, their unusual aura and colour. In the experimental project of town development based on the town of Yurievets situated on the bank of Volga water storage basin, the authors propose an architectural-spatial functional concept of filling up the town territory with the ideas on original colour and light design in the evening and at night.

Role of Diastole in Left Ventricular Function, I: Biochemical and Biomechanical Events

2004 ◽  
Vol 13 (5) ◽  
pp. 394-403 ◽  
Author(s):  
Penelope S. Villars ◽  
Shannan K. Hamlin ◽  
Andrew D. Shaw ◽  
Joseph T. Kanusky
Keyword(s):  
Left Ventricle ◽  
Calcium Release ◽  
Troponin I ◽  
Regulatory Protein ◽  
Systolic Pressure ◽  
Left Ventricular Diastolic Function ◽  
Left Ventricular ◽  
Release Mechanism ◽  
Adrenergic Stimulation ◽  
Inotropic State

Left ventricular diastolic function plays an important role in cardiac physiology. Lusitropy, the ability of the cardiac myocytes to relax, is affected by both biochemical events within the myocyte and biomechanical events in the left ventricle. β-Adrenergic stimulation alters diastole by enhancing the phosphorylation of phospholamban, a substrate within the myocyte that increases the uptake of calcium ions into the sarcoplasmic reticulum, increasing the rate of relaxation. Troponin I, a regulatory protein involved in the coupling of excitation to contraction, is vital to maintaining the diastolic state; depletion of troponin I can produce diastolic dysfunction. Other biochemical events, such as defects in the voltage-sensitive release mechanism or in inositol triphosphate calcium release channels, have also been implicated in altering diastolic tone. Extracellular collagen determines myocardial stiffness; impaired glucose tolerance can induce an increase in collagen cross-linking and lead to higher end-diastolic pressures. The passive properties of the left ventricle are most accurately measured during the diastasis and atrial contraction phases of diastole. These phases of the cardiac cycle are the least affected by volume status, afterload, inherent viscoelasticity, and the inotropic state of the myocardium. Diastolic abnormalities can be conceptualized by using pressure-volume loops that illustrate myocardial work and both diastolic and systolic pressure-volume relationships. The pressure-volume model is an educational tool that can be used to demonstrate isolated changes in preload, afterload, inotropy, and lusitropy and their interaction.

Ventricular function in the newborn lamb

1965 ◽  
Vol 208 (5) ◽  
pp. 931-937 ◽  
Author(s):  
S. Evans Downing ◽  
Norman S. Talner ◽  
Thomas H. Gardner
Keyword(s):  
Ventricular Function ◽  
Diastolic Pressure ◽  
Systemic Arterial Pressure ◽  
Left Ventricular ◽  
Stroke Work ◽  
Ventricular Mechanics ◽  
Inotropic State ◽  
Ejection Rate ◽  
Norepinephrine Infusion

The present study was initiated with the objective of evaluating in the newborn those aspects of ventricular mechanics which form the basis of the Frank-Starling relation, and which permit a determination of changes in the inotropic state of the heart. Left ventricular function was studied in lambs, 12 hr to 5 days old, utilizing a preparation designed to permit control and measurement of systemic arterial pressure (AP), cardiac output, heart rate (HR), and temperature. Continuous measurements of arterial Po2 and pH were made. These data permitted the construction of ventricular function curves relating stroke volume, mean ejection rate, and stroke work and power to left ventricular end-diastolic pressure, at constant AP and HR. In all preparations the Frank-Starling relation was found to be operative. Norepinephrine infusion, 1–2 µg/kg per min, resulted in a substantial increment of both force and speed parameters, thereby demonstrating the ability of the newborn heart to alter its inotropic state. Severe metabolic acidosis did not inhibit the response of the myocardium to norepinephrine.

Left ventricular-arterial coupling in conscious dogs

1991 ◽  
Vol 261 (1) ◽  
pp. H70-H76 ◽  
Author(s):  
W. C. Little ◽  
C. P. Cheng
Keyword(s):  
Stroke Volume ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Arterial System ◽  
Conscious Dogs ◽  
Stroke Work ◽  
Arterial Elastance ◽  
Inotropic State ◽  
End Diastolic Volume ◽  
Wide Range

We investigated the criteria for the coupling of the left ventricle (LV) and the arterial system to maximize LV stroke work (SW) and the transformation of LV pressure-volume area (PVA) to SW. We studied eight conscious dogs that were instrumented to measure LV pressure and determine LV volume from three ultrasonically determined dimensions. The LV end-systolic pressure (PES)-volume (VES) relation was determined by caval occlusion. Its slope (EES) was compared with the arterial elastance (EA) and determined as PES per stroke volume. At rest, with intact reflexes, EES/EA was 0.96 +/- 0.20 EES/EA was varied over a wide range (0.18-2.59) by the infusion of graded doses of phenylephrine and nitroprusside before and during administration of dobutamine. Maximum LV SW, at constant inotropic state and end-diastolic volume (VED), occurred when EES/EA equaled 0.99 +/- 0.15. At constant VED and contractile state, SW was within 20% of its maximum value when EES/EA was between 0.56 and 2.29. The conversion of LV PVA to SW increased as EES/EA increased. The shape of the observed relations of the SW to EES/EA and SW/PVA to EES/EA was similar to that predicted by the theoretical consideration of LV PES-VES and arterial PES-stroke volume relations. We conclude that the LV and arterial system produce maximum SW at constant VED when EES and EA are equal; however, the relation of SW to EES/EA has a broad plateau. Only when EA greatly exceeds EES does the SW fall substantially. However, the conversion of PVA to SW increases as EES/EA increases. These observations support the utility of analyzing LV-arterial coupling in the pressure-volume plane.

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