Vascular peripheral resistance and compliance in the lobster Homarus americanus

1997 ◽  
Vol 200 (3) ◽  
pp. 477-485 ◽  
Author(s):  
J Wilkens ◽  
G Davidson ◽  
M Cavey
Keyword(s):  
Striated Muscle ◽  
Peripheral Resistance ◽  
Systolic Pressure ◽  
Body Part ◽  
Homarus Americanus ◽  
Arterial System ◽  
Flow Rates ◽  
Flow Through ◽  
Lateral Walls

The peripheral resistance to flow through each arterial bed (in actuality, the entire pathway from the heart back to the pericardial sinus) and the mechanical properties of the seven arteries leaving the lobster heart are measured and compared. Resistance is inversely proportional to artery radius and, for each pathway, the resistance falls non-linearly as flow rate increases. The resistance of the hepatic arterial system is lower than that predicted on the basis of its radius. Body-part posture and movement may affect the resistance to perfusion of that region. The total vascular resistance placed on the heart when each artery is perfused at a rate typical of in vivo flow rates is approximately 1.93 kPa s ml-1. All vessels exhibit adluminal layers of fibrils and are relatively compliant at pressures at or below heart systolic pressure. Arteries become stiffer at pressures greater than peak systolic pressure and at radii greater than twice the unpressurized radius. The dorsal abdominal artery possesses striated muscle in the lateral walls. This artery remains compliant over the entire range of hemolymph pressures expected in lobsters. These trends are illustrated when the incremental modulus of elasticity is compared among arteries. All arteries should function as Windkessels to damp the pulsatile pressures and flows generated by the heart. The dorsal abdominal artery may also actively regulate its flow.

A PERFUSED TELEOSTEAN GILL PREPARATION: VASCULAR ACTIONS OF NEUROHYPOPHYSIAL HORMONES AND CATECHOLAMINES

1971 ◽  
Vol 51 (4) ◽  
pp. 621-635 ◽  
Author(s):  
J. C. RANKIN ◽  
J. MAETZ
Keyword(s):  
Adrenergic Receptors ◽  
Ringer Solution ◽  
Arginine Vasotocin ◽  
Millipore Filter ◽  
Flow Rates ◽  
Alternative Pathways ◽  
Neurohypophysial Hormones ◽  
Flow Through ◽  
Β Adrenergic Receptors

SUMMARY When isolated eel gills were perfused under conditions resembling, as closely as possible, those found in vivo and under constant pressure, neurohypophysial hormones decreased and catecholamines increased the rate of flow of perfusate, the latter response being mediated by β-adrenergic receptors. When the Ringer solution was not filtered before use, flow rates rapidly declined and 10−5 m-adrenaline or noradrenaline was required to maintain constant flow. Under these conditions, 10−14 m-isotocin or 10−13 m-arginine vasotocin (AVT) produced vasoconstriction. When the Ringer solution was filtered through a 0·22 μm Millipore filter before use, constant high flow rates could be maintained in the absence of catecholamines. Noradrenaline increased the flow rate at concentrations of down to 10−9 mol/l, adrenaline being slightly less active when filtered Ringer solution was used. However, the sensitivity to neurohypophysial hormones was considerably reduced, 10−11 to 10−10 m-isotocin and 5 × 10−11 to 5 × 10−10 m-AVT being the lowest concentrations producing vasoconstriction. No difference in sensitivity to neurohypophysial hormones or catecholamines was observed between gills from seawater adapted or freshwater adapted gills. The results are discussed in relation to the alternative pathways of blood flow through the gills.

Cardiac contractility modulation by electric currents applied during the refractory period

2002 ◽  
Vol 282 (5) ◽  
pp. H1642-H1647 ◽  
Author(s):  
Satoshi Mohri ◽  
Kun-Lun He ◽  
Marc Dickstein ◽  
Yuval Mika ◽  
Juichiro Shimizu ◽  
...  
Keyword(s):  
Refractory Period ◽  
Cardiac Contractility ◽  
Total Duration ◽  
Peripheral Resistance ◽  
Systolic Pressure ◽  
Segment Length ◽  
Electric Currents ◽  
Inotropic Effects

Inotropic effects of electric currents applied during the refractory period have been reported in cardiac muscle in vitro using voltage-clamp techniques. We investigated how electric currents modulate cardiac contractility in normal canine hearts in vivo. Six dogs were instrumented to measure regional segment length, ventricular volume (sonomicrometry), and ventricular pressure. Cardiac contractility modulating (CCM) electric currents (biphasic square pulses, amplitude ±20 mA, total duration 30 ms) were delivered during the refractory period between pairs of electrodes placed on anterior and posterior walls. CCM significantly increased index of global contractility ( E es) from 5.9 ± 2.9 to 8.3 ± 4.6 mmHg/ml with anterior CCM, from 5.3 ± 1.8 to 8.9 ± 4.0 mmHg/ml with posterior CCM, and from 6.1 ± 2.6 to 11.0 ± 7.0 mmHg/ml with combined CCM ( P < 0.01, no significant change in volume axis intercept). End-systolic pressure-segment length relations showed contractility enhancement near CCM delivery sites, but not remotely. Relaxation was not influenced. CCM increased mean aortic pressure, but did not change peripheral resistance. Locally applied electrical currents enhanced global cardiac contractility via regional changes in myocardial contractility without impairing relaxation in situ.

Effect of afterload resistance on end-systolic pressure-thickness relationship

1988 ◽  
Vol 254 (4) ◽  
pp. H658-H663
Author(s):  
T. Aversano ◽  
W. L. Maughan ◽  
K. Sunagawa ◽  
L. C. Becker
Keyword(s):  
Peripheral Resistance ◽  
Systolic Pressure ◽  
Arterial System ◽  
Wall Thickening ◽  
Significant Shift ◽  
Systolic Performance ◽  
Shortening Deactivation ◽  
The Right ◽  
Systolic Wall Thickening ◽  
Contractile Performance

The influence of afterload resistance on the end-systolic pressure-thickness relationship (ESPTR) was assessed in six isolated canine left ventricles made to eject into a simulated arterial system. An increase of simulated peripheral resistance from 1.5 to 6.0 mmHg.s.ml-1 resulted in a modest but significant shift of the ESPTR upward and to the right, indicating augmented contractile performance. A relationship between the extent of systolic wall thickening and end-systolic performance was also observed: increased wall thickening impairing and decreased wall thickening enhancing end-systolic performance. The dependence of end-systolic performance on wall thickening history in this setting is consistent with shortening deactivation. This phenomenon appears to account at least in part for the observed shift in the ESPTR with altered afterload resistance.

Epicardial Coronary Blood Flow Including the Presence of Stenoses and Aorto-Coronary Bypasses—II: Experimental Comparison and Parametric Investigations

1988 ◽  
Vol 110 (2) ◽  
pp. 144-149 ◽  
Author(s):  
T. F. Wiesner ◽  
M. J. Levesque ◽  
E. Rooz ◽  
R. M. Nerem
Keyword(s):  
Coronary Circulation ◽  
Peripheral Resistance ◽  
Critical Value ◽  
Systematic Investigation ◽  
Experimental Comparison ◽  
Dramatic Reduction ◽  
Governing Equations ◽  
Flow Through ◽  
Selection Of

This article is the second in a series which presents a computer model of the left coronary arteries. The first article discussed the geometry, the governing equations, and the numerical method employed. This paper details an acute canine experiment used to validate the approach as well as the systematic investigation of several important parameters governing the left coronary circulation. These parameters include peripheral resistance, wall properties, and altered geometric properties through various stenosis/bypass configurations. With appropriate selection of parameters, the model reproduces an in vivo waveform very closely. The model also predicts many clinical phenomena, such as the “critical” value of stenosis, the dramatic reduction in flow through a stenosis when bypassed, and the restorative effect of the bypass upon flow to the distal bed. The model also is used to show that the autonomic state of the animal profoundly affects the influence of various factors, e.g., the critical value of a stenosis is much higher under resting conditions than under hyperemic conditions.

Relation of effective arterial elastance to arterial system properties

2002 ◽  
Vol 282 (3) ◽  
pp. H1041-H1046 ◽  
Author(s):  
Patrick Segers ◽  
Nikos Stergiopulos ◽  
Nico Westerhof
Keyword(s):  
Arterial Compliance ◽  
Linear Regression Analysis ◽  
Peripheral Resistance ◽  
Systolic Pressure ◽  
Interaction Model ◽  
Left Ventricular ◽  
Arterial System ◽  
Stroke Work ◽  
Arterial Elastance ◽  
Effective Arterial Elastance

Effective arterial elastance ( E a), defined as the ratio of left ventricular (LV) end-systolic pressure and stroke volume, lumps the steady and pulsatile components of the arterial load in a concise way. Combined with E max, the slope of the LV end-systolic pressure-volume relation, E a/ E max has been used to assess heart-arterial coupling. A mathematical heart-arterial interaction model was used to study the effects of changes in peripheral resistance ( R; 0.6–1.8 mmHg · ml−1 · s) and total arterial compliance (C; 0.5–2.0 ml/mmHg) covering the human pathophysiological range. E a, E a/ E max, LV stroke work, and hydraulic power were calculated for all conditions. Multiple-linear regression analysis revealed a linear relation between E a, R/ T (where T is cycle length), and 1/C: E a= −0.13 + 1.02 R/ T + 0.31/C, indicating that R/ T contributes about three times more to E a than arterial stiffness (1/C). It is demonstrated that different pathophysiological combinations of R and C may lead to the same E a and E a/ E max but can result in differences of 10% in stroke work and 50% in maximal power.

Recruitment Pattern in a Complete Cerebral Arterial Circle

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Christine L. de Lancea ◽  
Tim David ◽  
Jordi Alastruey ◽  
Richard G. Brown
Keyword(s):  
Blood Flow ◽  
Cerebral Arteries ◽  
Peripheral Resistance ◽  
Maximum Flow ◽  
Pressure Waves ◽  
Recruitment Pattern ◽  
Middle Cerebral Arteries ◽  
Flow Through ◽  
The Brain

Blood flow through a vessel depends upon compliance and resistance. Resistance changes dynamically due to vasoconstriction and vasodilation as a result of metabolic activity, thus allowing for more or less flow to a particular area. The structure responsible for directing blood to the different areas of the brain and supplying the increase flow is the cerebral arterial circle (CAC). A series of 1D equations were utilized to model propagating flow and pressure waves from the left ventricle of the heart to the CAC. The focus of the current research was to understand the collateral capability of the circle. This was done by decreasing the peripheral resistance in each of the efferent arteries, up to 10% both unilaterally and bilaterally. The collateral patterns were then analyzed. After the initial 60 simulations, it became apparent that flow could increase beyond the scope of a 10% reduction and still be within in vivo conditions. Simulations with higher percentage decreases were performed such that the same amount of flow increase would be induced through each of the efferent arteries separately, same flow tests (SFTs), as well as those that were found to allow for the maximum flow increase through the stimulated artery, maximum flow tests (MFTs). The collateral pattern depended upon which efferent artery was stimulation and if the stimulation was unilaterally or bilaterally induced. With the same amount of flow increase through each of the efferent arteries, the MCAs (middle cerebral arteries) had the largest impact on the collateral capability of the circle, both unilaterally and bilaterally.

scholarly journals A Region of the Myosin Rod Important for Interaction With Paramyosin in Caenorhabditis elegans Striated Muscle

Genetics ◽  
2000 ◽  
Vol 156 (2) ◽  
pp. 631-643
Author(s):  
Pamela E Hoppe ◽  
Robert H Waterston
Keyword(s):  
Caenorhabditis Elegans ◽  
Heavy Chain ◽  
Molecular Interaction ◽  
Striated Muscle ◽  
Genetic Interaction ◽  
Specific Interaction ◽  
Thick Filament ◽  
Parallel Arrangement ◽  
Myosin Rod

Abstract The precise arrangement of molecules within the thick filament, as well as the mechanisms by which this arrangement is specified, remains unclear. In this article, we have exploited a unique genetic interaction between one isoform of myosin heavy chain (MHC) and paramyosin in Caenorhabditis elegans to probe the molecular interaction between MHC and paramyosin in vivo. Using chimeric myosin constructs, we have defined a 322-residue region of the MHC A rod critical for suppression of the structural and motility defects associated with the unc-15(e73) allele. Chimeric constructs lacking this region of MHC A either fail to suppress, or act as dominant enhancers of, the e73 phenotype. Although the 322-residue region is required for suppression activity, our data suggest that sequences along the length of the rod also play a role in the isoform-specific interaction between MHC A and paramyosin. Our genetic and cell biological analyses of construct behavior suggest that the 322-residue region of MHC A is important for thick filament stability. We present a model in which this region mediates an avid interaction between MHC A and paramyosin in parallel arrangement in formation of the filament arms.

scholarly journals Analysis of Performance of the Wind-Driven Pulverizing Aerator Based on Average Wind Speeds in the Conditions of Góreckie Lake

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2796
Author(s):  
Andrzej Osuch ◽  
Ewa Osuch ◽  
Stanisław Podsiadłowski ◽  
Piotr Rybacki
Keyword(s):  
Mathematical Model ◽  
Wind Speed ◽  
Water Pump ◽  
Average Wind Speed ◽  
Flow Rates ◽  
Wind Speeds ◽  
Average Wind ◽  
Flow Through ◽  
Analysis Of Performance ◽  
Research Period

In the introduction to this paper, the characteristics of Góreckie lake and the construction and operation of the wind-driven pulverizing aerator are presented. The purpose of this manuscript is to determine the efficiency of the pulverizing aerator unit in the windy conditions of Góreckie Lake. The efficiency of the pulverization aerator depends on the wind conditions at the lake. It was necessary to conduct thorough research to determine the efficiency of water flow through the pulverization segment (water pump). It was necessary to determine the rotational speed of the paddle wheel, which depended on the average wind speed. Throughout the research period, measurements of hourly average wind speed were carried out. It was possible to determine the efficiency of the machine by developing a dedicated mathematical model. The latest method was used in the research, consisting of determining the theoretical volumetric flow rates of water in the pulverizing aerator unit, based on average hourly wind speeds. Pulverization efficiency under the conditions of Góreckie Lake was determined based on 6600 average wind speeds for spring, summer and autumn, 2018. Based on the model, the theoretical efficiency of the machine was calculated, which, under the conditions of Góreckie Lake, amounted to 75,000 m3 per year.

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