THE EFFECT OF TEMPERATURE ON THE CIRCULATION OF THE ISOLATED PERFUSED RABBIT EAR

1952 ◽  
Vol 30 (4) ◽  
pp. 340-352
Author(s):  
James T. Nichol
Keyword(s):  
Temperature Effects ◽  
Ringer Solution ◽  
Effect Of Temperature ◽  
Perfusion Solution ◽  
Viscosity Effects ◽  
Rabbit Ear ◽  
Critical Closing Pressure ◽  
Micro Flow ◽  
Rabbit Ears ◽  
Closing Pressure

Isolated rabbit ears were perfused with Ringer solution, and the rates of flow were measured by a micro flow-gauge. It was found that changes in flow produced by changes in temperature of the ear (amounting to two and a half times between 40° and 0° C), could be quantitatively explained by changes in the viscosity of the perfusion solution with temperature. No evidence of a “hunting reaction” to cold could be demonstrated either with or without a temperature gradient in the ear. The residual “critical closing pressure” of the isolated rabbit ear was shown to be independent of temperature. It is concluded that in the isolated perfused rabbit ear the temperature effects on circulation are entirely explicable in terms of viscosity changes, and that in the intact innervated ear, viscosity effects also underlie, but do not completely explain the observed changes with temperature.

A square-pulse flow method for measuring characteristics of the arterial bed

1976 ◽  
Vol 40 (3) ◽  
pp. 425-433 ◽  
Author(s):  
M. G. Bottomley ◽  
G. W. Mainwood
Keyword(s):  
Arterial Compliance ◽  
Peripheral Resistance ◽  
Mean Value ◽  
Pressure Response ◽  
Arterial System ◽  
Response Curves ◽  
Arterial Tree ◽  
Pulse Flow ◽  
Critical Closing Pressure ◽  
Closing Pressure

A device was designed to provide a “square” pulse of blood flow into the arterial system. Pulses were injected into the carotid artery of the rabbit during transient cardiac arrest. Analysis of pressure response curves generated by the flow provides information as to the state of the arterial tree. With certain assumptions it is possible to estimate from these curves lumped values of peripheral resistance, critical closing pressure, and arterial compliance. In a series of 12 rabbits the mean value of peripheral resistance was found to be 0.21 +/- 0.7 mmHg-ml-1-min and critical closing pressure was estimated to be 23.6 +/- 3.8 mmHg. This method gives two possible values for arterial compliance 0.036 +/- 0.010 and 0.055 +/- 0.010 ml-mm-1 based, respectively, on the rise and decay curves of the pressure response. The theory and limitations of the method are discussed. The use of the method is illustrated in following the response to increased PCO2 and hemorrhage.

Critical Closing Pressure During a Controlled Increase in Intracranial Pressure

2018 ◽  
pp. 133-137
Author(s):  
Katarzyna Kaczmarska ◽  
Magdalena Kasprowicz ◽  
Antoni Grzanka ◽  
Wojciech Zabołotny ◽  
Peter Smielewski ◽  
...  
Keyword(s):  
Intracranial Pressure ◽  
Critical Closing Pressure ◽  
Closing Pressure

scholarly journals Effect of Temperature on Stiffness of Sandstones from the Deep North Sea Basin

2020 ◽  
Author(s):  
Tobias Orlander ◽  
Katrine Alling Andreassen ◽  
Ida Lykke Fabricius
Keyword(s):  
North Sea ◽  
Temperature Effects ◽  
Mass Density ◽  
Thermal Strain ◽  
High Stress ◽  
Testing Temperature ◽  
Effect Of Temperature ◽  
Stress Regime ◽  
The North

Abstract Development of high-pressure, high-temperature (HPHT) petroleum reservoirs situated at depths exceeding 5 km and in situ temperature of 170 °C increases the demand for theories and supporting experimental data capable of describing temperature effects on rock stiffness. With the intention of experimentally investigating temperature effects on stiffness properties, we investigated three sandstones from the deep North Sea Basin. As the North Sea Basin is presently undergoing substantial subsidence, we assumed that studied reservoir sandstones have never experienced higher temperature than in situ. We measured ultrasonic velocities in a low- and high-stress regime, and used mass density and stress–strain curves to derive, respectively, dynamic and static elastic moduli. We found that in both regimes, the dry sandstones stiffens with increasing testing temperature and assign expansion of minerals as a controlling mechanism. In the low-stress regime with only partial microcrack closure, we propose closure of microcracks as the stiffening mechanism. In the high-stress regime, we propose that thermal expansion of constituting minerals increases stress in grain contacts when the applied stress is high enough for conversion of thermal strain to thermal stress, thus leading to higher stiffness at in situ temperature. We then applied an extension of Biot’s effective stress equation including a non-isothermal term from thermoelastic theory and explain test results by adding boundary conditions to the equations.

Cerebral Critical Closing Pressure During Infusion Tests

2016 ◽  
pp. 215-220 ◽  
Author(s):  
Georgios V. Varsos ◽  
Marek Czosnyka ◽  
Peter Smielewski ◽  
Matthew R. Garnett ◽  
Xiuyun Liu ◽  
...  
Keyword(s):  
Critical Closing Pressure ◽  
Closing Pressure

Abolition of autoregulation of renal blood flow by acetylcholine

1964 ◽  
Vol 207 (1) ◽  
pp. 123-127 ◽  
Author(s):  
Victor E. Nahmod ◽  
Alfredo Lanari
Keyword(s):  
Blood Flow ◽  
Renal Blood Flow ◽  
Run Off ◽  
Critical Closing Pressure ◽  
Flow Pressure ◽  
Renal Blood Flow Autoregulation ◽  
Autoregulatory Mechanism ◽  
Closing Pressure

In order to study the mechanism of autoregulation of renal blood flow, 36 mongrel dogs were connected in parabiosis according to the Brull method. The following determinations were made: a) flow/pressure curves in innervated and denervated kidneys and b) acetylcholine and arterenol infusion in innervated kidneys. The critical closing pressure and the "run-off" index were also determined in all cases. The results of these experiments show the existence of renal blood flow autoregulation in innervated, denervated, and arterenol-infused kidneys, and the abolition of the autoregulatory mechanism in the acetylcholine-infused kidneys. The run-off index showed a better correlation with renal resistance than with critical closing pressure.

scholarly journals The critical closing pressure contribution to dynamic cerebral autoregulation in humans: influence of arterial partial pressure of CO 2

2020 ◽  
Vol 598 (24) ◽  
pp. 5673-5685
Author(s):  
Ronney B. Panerai ◽  
Jatinder S. Minhas ◽  
Osian Llwyd ◽  
Angela S. M. Salinet ◽  
Emmanuel Katsogridakis ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Cerebral Autoregulation ◽  
Arterial Partial Pressure ◽  
Critical Closing Pressure ◽  
Closing Pressure ◽  
Dynamic Cerebral Autoregulation

Immediate responses of collateral vessels to abrupt arterial occlusion

1964 ◽  
Vol 206 (6) ◽  
pp. 1299-1303 ◽  
Author(s):  
Albert J. Roy ◽  
Peter B. Lambert ◽  
Howard A. Frank
Keyword(s):  
Arterial Occlusion ◽  
Cheek Pouch ◽  
Large Artery ◽  
Opening Pressure ◽  
Hamster Cheek Pouch ◽  
Arterial Ligation ◽  
Critical Closing Pressure ◽  
Collateral Vessels ◽  
Closing Pressure

The vascular bed of the hamster cheek pouch was observed in vivo under the microscope as a major artery within the field was occluded. Two changes were noted: 1) an alteration in pattern of blood flow and 2) the opening of previously unseen branches on each side of the ligature. Both responses were immediate and persisting. Besides providing for new flow patterns, the newly opened arterial branches preserve additional length of the ligated artery which becomes obliterated on each side of the ligature to the nearest open branch. Comparison of in vivo with postmortem observations indicated that latent and open branches of the artery under observation were about equal in number, and that about half of the latent branches opened in response to the ligation. Induced vasoconstriction delayed the opening of latent branches, cold prevented it. Priscoline opened all latent vessels, with or without arterial ligation. In connection with Burton's data on "critical closing pressure" of fine vessels, the ligation of a large artery appears to establish a "critical opening pressure" within latent branches.

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