Skin vascular bed is a potential blood reservoir during heat stress

1990 ◽  
Vol 259 (6) ◽  
pp. H1796-H1802 ◽  
Author(s):  
A. Deschamps ◽  
S. Magder
Keyword(s):  
Heat Stress ◽  
Potential Role ◽  
Static Pressure ◽  
Venous Drainage ◽  
Force Transducer ◽  
Skin Flaps ◽  
Venous Compliance ◽  
Occlusion Technique ◽  
Blood Reservoir

To determine the potential role of the skin vasculature as a blood reservoir, we measured venous compliance (Cv), resistance (Rv), and their product, the time constant of venous drainage (tau sk = RvCv), in skin flaps from the hindlimbs of 15 dogs anesthetized with pentobarbital sodium at different core temperatures (Tc, 37-42 degrees C), skin temperature (Ts, 25.3-50.0 degrees C), and during an infusion of papaverine (5%). The vasculature of the flap was isolated, and a double-occlusion technique was used to measure the static pressure in the venous compartment. The blood volume of the flap was altered by changing either flow or outflow pressure (Pv). The change in volume was estimated from the change in weight of the flap with a force transducer. At Tc = 37 degrees C, Rv was 2.27 +/- 0.81 mmHg.min.ml-1.100 g-1 (means +/- SD), Cv was 0.17 +/- 0.06 ml.mmHg-1.100 g-1, and tau sk was 28.0 +/- 8.8 s. Rv decreased with elevated Tc, Ts, and with papaverine. Cv increased with a rise in Tc and Ts. Increasing Tc and Ts did not change tau sk, but the papaverine infusion shortened it. The lowest tau sk (20 s) occurred during maximal vasodilatation. This long tau sk indicates that the skin could serve as a blood reservoir during heat stress.

Venous mechanics of contracting gastrocnemius muscle and the muscle pump theory

1995 ◽  
Vol 79 (6) ◽  
pp. 1930-1935 ◽  
Author(s):  
S. Magder
Keyword(s):  
Time Constant ◽  
Gastrocnemius Muscle ◽  
Venous Drainage ◽  
Force Transducer ◽  
Venous Compliance ◽  
Optimal Length ◽  
Mechanically Ventilated ◽  
Anesthetized Dogs ◽  
Venous Resistance ◽  
The Difference

The time constant of venous drainage (tau v) is an important determinant of the return of blood to the heart. The lower the tau v, the higher the flow for a given volume. To determine whether the tau v of muscle decreases during muscle contraction, we anesthetized dogs with pentobarbital sodium and mechanically ventilated them. We isolated the vasculature of the gastrocnemius muscle and attached the muscle to a force transducer. The muscle was pump perfused, and flows were measured with electromagnetic flow probes on the artery and vein. Pressure in the venous compliant region (Pel) was obtained by simultaneously occluding the artery and vein. Changes in volume (delta V) were produced by changing inflow and obtaining the integral of the difference between inflow and outflow. The tau v was obtained from delta V divided by change in flow. Compliance was calculated from delta V divided by change in Pel from before to after a change in flow. The venous resistance was calculated from tau v divided by venous compliance. The muscle was set at the optimal length, and contractions were produced by stimulating the nerve to the muscle with supramaximal voltage at either 1- or 5-Hz trains with stimulations at 20 Hz, 0.2-ms duration, and duty cycle of 0.25. The tau v at rest was 4.06 +/- 2.16 s and decreased to 2.44 +/- 1.07 s (P < 0.05) at 1 Hz and to 1.81 +/- 0.4 s at 5 Hz. There were no significant changes in venous compliance or venous resistance. In conclusion, muscle contractions can reduce the time constant of venous drainage of muscle and could thereby contribute to the increased venous return and cardiac output during exercise.

Hepatic venous compliance and role of liver as a blood reservoir

1976 ◽  
Vol 231 (2) ◽  
pp. 292-295 ◽  
Author(s):  
WW Lautt ◽  
CV Greenway
Keyword(s):  
Central Venous Pressure ◽  
Blood Volume ◽  
Venous Pressure ◽  
Significant Proportion ◽  
Central Venous ◽  
Venous Compliance ◽  
Rapid Changes ◽  
Capacitance Vessels ◽  
Blood Reservoir

Changes in hepatic blood volume in response to rapid elevations in hepatic venous pressure were examined in cats using hepatic plethysmography. The liver was intact and received blood from an intact portal vein and hepatic artery. The hepatic blood volume increased in response to elevated venous pressure. Compliance of the hepatic capacitance vessels became greater as the distending venous pressure was increased over the range of venous pressures studied (0-9.4 mmHg). When hepatic venous pressure was elevated to 9.4 MMHg, the hepatic blood volume more than doubled. The liver serves as an important buffer for rapid changes in blood volume, the importance increasing with greater infused volumes of fluid. While overall venous compliance decreased at distending pressures in excess of 5-6 mmHg, the compliance of the hepatic capacitance vessels shows marked increases at pressures above this level. Expansions of the blood volume results in elevations of central venous pressure. Within a few minutes the hepatic capacitance vessels sequester a significant proportion of the added volume. As long as central venous pressure is raised, the liver demonstrates a secondary fluid buffering role by filtering large volumes of fluid across the vascular bed into the peritoneum.

Potential role of vitexin in alleviating heat stress-induced cytotoxicity: Regulatory effect of Hsp90 on ER stress-mediated autophagy

Life Sciences ◽  
2015 ◽  
Vol 142 ◽  
pp. 36-48 ◽  
Author(s):  
Monika Bhardwaj ◽  
Souren Paul ◽  
Rekha Jakhar ◽  
Sun Chul Kang
Keyword(s):  
Heat Stress ◽  
Er Stress ◽  
Potential Role ◽  
Regulatory Effect

scholarly journals Jugular Vein Insufficiency and Choroidal Neovascularization in Moderate Myopia: A New Unknown Factor of Additional Risk?

2015 ◽  
Vol 2015 ◽  
pp. 1-4
Author(s):  
Massimiliano Farina ◽  
Cristiano Ratti ◽  
Eugenio Novelli
Keyword(s):  
Choroidal Neovascularization ◽  
Potential Role ◽  
Color Doppler ◽  
Venous Drainage ◽  
Choroidal Blood Flow ◽  
Additional Risk ◽  
Doppler Study ◽  
Blood Flow Reduction ◽  
Local Reduction

To date, choroidal blood flow reduction in highly myopic eyes appears to be related to the development of choroidal neovascularization secondary to local reduction of arterial flow. Instead, no evidence of choroidal neovascularization was found in subjects with low or moderate myopia. The authors’ aim has been to encourage new studies regarding the potential role of chronic retinal venous congestion in the pathogenesis of choroidal neovascularization. In December 2011, a 54-year-old woman with moderate bilateral myopia had a sudden block upon swallowing while she was eating. Subsequently (January 2013) metamorphopsia in the left eye revealed macular degeneration with choroidal neovascularization. The related echo-color Doppler study of the neck veins, performed in November 2014, showed an atypical left jugular insufficiency associated with homolateral hypertension of the superior ophthalmic veins. This singular case highlights the necessity to further investigate the potential role of chronic alterations of intra- and extracranial venous drainage in the disruption of choroidal flow in myopic patients.

scholarly journals Mitochondrial efficiency and exercise economy following heat stress: a potential role of uncoupling protein 3

2017 ◽  
Vol 5 (3) ◽  
pp. e13054 ◽  
Author(s):  
Roy M. Salgado ◽  
Ailish C. Sheard ◽  
Roger A. Vaughan ◽  
Daryl L. Parker ◽  
Suzanne M. Schneider ◽  
...  
Keyword(s):  
Heat Stress ◽  
Potential Role ◽  
Uncoupling Protein ◽  
Exercise Economy ◽  
Uncoupling Protein 3 ◽  
Mitochondrial Efficiency

POPDC proteins and cardiac function

2019 ◽  
Vol 47 (5) ◽  
pp. 1393-1404 ◽  
Author(s):  
Thomas Brand
Keyword(s):  
Potential Role ◽  
Striated Muscle ◽  
Short Review ◽  
Effector Proteins ◽  
Muscle Disease ◽  
Disease Genes ◽  
Protein Protein Interaction ◽  
Interaction Partners ◽  
And Function

Abstract The Popeye domain-containing gene family encodes a novel class of cAMP effector proteins in striated muscle tissue. In this short review, we first introduce the protein family and discuss their structure and function with an emphasis on their role in cyclic AMP signalling. Another focus of this review is the recently discovered role of POPDC genes as striated muscle disease genes, which have been associated with cardiac arrhythmia and muscular dystrophy. The pathological phenotypes observed in patients will be compared with phenotypes present in null and knockin mutations in zebrafish and mouse. A number of protein–protein interaction partners have been discovered and the potential role of POPDC proteins to control the subcellular localization and function of these interacting proteins will be discussed. Finally, we outline several areas, where research is urgently needed.

The Effect of Path Length and Display Size on Memory for Spatial Information

2012 ◽  
Vol 59 (3) ◽  
pp. 147-152 ◽  
Author(s):  
Katherine Guérard ◽  
Sébastien Tremblay
Keyword(s):  
Path Length ◽  
Potential Role ◽  
Spatial Information ◽  
Recall Performance ◽  
Minor Role ◽  
Length Effect ◽  
Serial Memory ◽  
Fixed Reference ◽  
A Minor

In serial memory for spatial information, some studies showed that recall performance suffers when the distance between successive locations increases relatively to the size of the display in which they are presented (the path length effect; e.g., Parmentier et al., 2005) but not when distance is increased by enlarging the size of the display (e.g., Smyth & Scholey, 1994). In the present study, we examined the effect of varying the absolute and relative distance between to-be-remembered items on memory for spatial information. We manipulated path length using small (15″) and large (64″) screens within the same design. In two experiments, we showed that distance was disruptive mainly when it is varied relatively to a fixed reference frame, though increasing the size of the display also had a small deleterious effect on recall. The insertion of a retention interval did not influence these effects, suggesting that rehearsal plays a minor role in mediating the effects of distance on serial spatial memory. We discuss the potential role of perceptual organization in light of the pattern of results.

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