scholarly journals The effect of reduction of perfusion rate on lactate and oxygen uptake, glucose output and energy supply in the isolated perfused liver of starved rats

1979 ◽  
Vol 184 (3) ◽  
pp. 635-642 ◽  
Author(s):  
R A Iles ◽  
P G Baron ◽  
R D Cohen
Keyword(s):  
Oxygen Uptake ◽  
Flow Rate ◽  
Mean Value ◽  
Normal Flow ◽  
Perfusion Rate ◽  
Flow Rates ◽  
Perfusate Flow ◽  
Intrinsic Capacity ◽  
Lactate Uptake ◽  
Glucose Output

1. Lactate and O2 uptake and glucose output were studied in isolated livers from starved rats at perfusate flow rates varying from 100 to 7% of “normal” (11.25-0.75 ml/min per 100 g body wt.). 2. With moderate diminution of flow rate, lactate and oxygen uptake fell more slowly than would be expected if uptake purely depended on substrate supply. 3. Use of a mathematical model suggests that the intrinsic capacity of the liver for lactate uptake is unaffected until the flow rate falls below 25% of “normal”. 4. Some lactate uptake was always observed even at 7% of the “normal” flow rate. 5. At flow rates below 33% of the “normal”, lactate was increasingly metabolized by pathways other than gluconeogenesis, which became a progressively less important consumer of available O2. 6. ATP content decreased with diminution of flow rate, but substantially less markedly than did lactate uptake and glucose output. 7. Intracellular pH fell from a mean value of 7.25 at “normal” flow rate to 7.03 at 7% of the “normal” flow rate.

Stimulation of oxygen uptake by prostaglandin E2 is oxygen dependent in perfused rat liver

1998 ◽  
Vol 275 (3) ◽  
pp. G542-G549 ◽  
Author(s):  
Wei Qu ◽  
Zhi Zhong ◽  
Gavin E. Arteel ◽  
Ronald G. Thurman
Keyword(s):  
Oxygen Uptake ◽  
Oxygen Tension ◽  
Rat Liver ◽  
Kupffer Cells ◽  
High Flow ◽  
Perfused Rat Liver ◽  
Normal Flow ◽  
Flow Rates ◽  
Glucose Output ◽  
Parenchymal Cells

The aim of this study was to determine if the effect of prostaglandin E2(PGE2) on hepatic oxygen uptake was affected by oxygen tension. Livers from fed female Sprague-Dawley rats were perfused at normal or high flow rates (4 or 8 ml ⋅ g−1 ⋅ min−1) to vary local oxygen tension within the liver lobule. During perfusion at normal flow rates, PGE2 (5 μM) infusion increased oxygen uptake by about 50 μmol ⋅ g−1 ⋅ h−1; however, when livers were perfused at high flow rates, the increase was nearly twice as large. Simultaneously, glucose output was increased rapidly by about 50%, whereas glycolysis was decreased about 60%. When flow rate was held constant, increases in oxygen uptake due to PGE2 were proportional to oxygen delivery. Infusion of PGE2 into livers perfused at normal flow rates increased state 3 rates of oxygen uptake of subsequently isolated mitochondria by about 25%; however, rates were increased 50–75% in mitochondria isolated from livers perfused at high flow rates. Thus it is concluded that PGE2stimulates oxygen uptake via mechanisms regulated by oxygen tension in perfused rat liver. High flow rates also increased basal rates of oxygen uptake: this increase was prevented by inactivation of Kupffer cells with GdCl3. In addition, conditioned medium from Kupffer cells incubated at high oxygen tension (75% oxygen) stimulated oxygen uptake of isolated parenchymal cells by >30% and elevated PGE2production about twofold compared with Kupffer cells exposed to normal air-saturated buffer (21% oxygen). These effects were blocked completely by both indomethacin and nisoldipine. These data support the hypothesis that oxygen stimulates Kupffer cells to release mediators such as PGE2 which elevate oxygen consumption in parenchymal cells, possibly by mechanisms involving cyclooxygenase and calcium channels.

scholarly journals Blood Flow in Portal Systems with Special Reference to the Rat Pituitary Gland

1992 ◽  
Vol 12 (1) ◽  
pp. 128-138 ◽  
Author(s):  
P. D. Lees ◽  
D. T. Lynch ◽  
H. K. Richards ◽  
A. H. J. Lovick ◽  
S. Perry ◽  
...  
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Median Eminence ◽  
Venous Drainage ◽  
Mean Value ◽  
Portal System ◽  
Posterior Pituitary ◽  
Flow Rates ◽  
Fischer 344 ◽  
Rat Pituitary

Regional pituitary blood flow has been studied in adult female Fischer 344 rats by [14C]iodoantipyrine autoradiography. A general mathematical solution has been derived to allow the calculation of blood flow in the second compartment of a portal system and the proportion of blood “shunted” through the first compartment without exposure to tissue uptake from a knowledge of (a) the volume ratios of the two compartments, (b) the tissue tracer uptakes of the two compartments, and (c) the arterial tracer concentration with respect to time of a freely diffusible tracer. Significant diffusion limitation and/or arteriovenous shunting has been demonstrated in the neurohypophysis, suggesting that the majority of incoming blood is “shunted” unchanged to the adenohypophysis. The mean value of the shunt is 89% (range of 84–93%) for the median eminence and lies between 72% (range of 52–82%) and 73% (range of 59–81%) for the posterior pituitary. Neurohypophysial flow rates of 1.20 (range of 0.99–1.55) ml g−1 min−1 for the median eminence and 1.68 (range of 0.83–3.53) ml g−1 min−1 for the posterior pituitary were measured. These values represent “tissue-available” (nonshunted) flow; estimated mean total (shunted plus nonshunted) neurohypophysial flow rates were 11.7 (range of 9.5–17.5) ml g−1 min−1 for the median eminence and 6.1 (range of 3.1–8.9) ml g−1 min−1 (minimum) for the posterior pituitary. Adenohypophysial blood flow is heterogeneous. In the long portal territory, the flow rate was 1.18 (range of 0.95–1.75) ml g−1 min−1 but short portal territory flow calculation is complicated by an unquantifiable nonportal venous drainage; using the natural limits of zero and 100% gives a minimum adenohypophysial flow rate of 1.42 (range of 0.76–2.07) ml g−1 min−1 and a maximum value of 1.97 (range of 1.03–2.82) ml g−1 min−1.

Effects of hematocrit on oxygenation of the isolated perfused rat liver

1983 ◽  
Vol 245 (6) ◽  
pp. G769-G774 ◽  
Author(s):  
G. L. Riedel ◽  
J. L. Scholle ◽  
A. P. Shepherd ◽  
W. F. Ward
Keyword(s):  
Blood Flow ◽  
Oxygen Uptake ◽  
Portal Vein ◽  
Rat Liver ◽  
Male Rats ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver ◽  
Flow Rates ◽  
Perfusate Flow ◽  
Hepatic Portal

The isolated perfused rat liver is used ubiquitously for metabolic and endocrine studies of hepatic function, yet few data are available regarding the inadequacy of the oxygenation of such preparations. Moreover, the isolated rat liver is usually deprived of its arterial supply and perfused via the hepatic portal vein with low-hematocrit or cell-free solutions. To investigate the efficacy of the oxygen supply, we determined the effect of hematocrit on the relation between oxygen consumption and perfusate flow. We then attempted to define a hematocrit at which hepatic oxygenation was maximal. Livers of male rats anesthesized with pentobarbital sodium were perfused via the portal vein with fresh canine red blood cells suspended in Krebs-Ringer-bicarbonate buffer. Perfusions were carried out at various flow rates, and the relation between perfusate flow and oxygen uptake was determined. At flow rates above 100 ml X min-1 X 100 g liver-1, oxygen uptake was independent of flow but below that value was flow limited, regardless of whether the hematocrit was 10, 20, or 40%. To determine the optimal hematocrit for hepatic oxygen uptake, hepatic portal venous and hepatic venous pressures were held at 10 and 0 mmHg, respectively. The hematocrit was lowered in steps from 80 to 10%. Blood flow increased exponentially as hematocrit fell while oxygen uptake increased to a maximum at approximately 20%. It is concluded that an hematocrit of approximately 20% provides the optimal combination of blood flow and oxygen-carrying capacity while maintaining physiological perfusion pressures, e.g., 10 mmHg.

scholarly journals Effects of Flow Rate on Mesenchymal Stem Cell Oxygen Consumption Rates in 3D Bone-Tissue-Engineered Constructs Cultured in Perfusion Bioreactor Systems

Fluids ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 30 ◽  
Author(s):  
Michael L. Felder ◽  
Aaron D. Simmons ◽  
Robert L. Shambaugh ◽  
Vassilios I. Sikavitsas
Keyword(s):  
Stem Cells ◽  
Oxygen Consumption ◽  
Oxygen Uptake ◽  
Bone Tissue ◽  
Residence Time ◽  
Flow Rate ◽  
Perfusion Bioreactor ◽  
Flow Rates ◽  
Uptake Rates ◽  
Consumption Rates

Bone grafts represent a multibillion-dollar industry, with over a million grafts occurring each year. Common graft types are associated with issues such as donor site morbidity in autologous grafts and immunological response in allogenic grafts. Bone-tissue-engineered constructs are a logical approach to combat the issues commonly encountered with these bone grafting techniques. When creating bone-tissue-engineered constructs, monitoring systems are required to determine construct characteristics, such as cellularity and cell type. This study aims to expand on the current predictive metrics for these characteristics, specifically analyzing the effects of media flow rate on oxygen uptake rates (OURs) of mesenchymal stem cells seeded on poly(L-lactic acid) (PLLA) scaffolds cultured in a flow perfusion bioreactor. To do this, oxygen consumption rates were measured for cell/scaffold constructs at varying flow rates ranging from 150 to 750 microliters per minute. Residence time analyses were performed for this bioreactor at these flow rates. Average observed oxygen uptake rates of stem cells in perfusion bioreactors were shown to increase with increased oxygen availability at higher flow rates. The residence time analysis helped identify potential pitfalls in current bioreactor designs, such as the presence of channeling. Furthermore, this analysis shows that oxygen uptake rates have a strong linear correlation with residence times of media in the bioreactor setup, where cells were seen to exhibit a maximum oxygen uptake rate of 3 picomoles O2/hr/cell.

Superflow of helium II through narrow slits

1952 ◽  
Vol 213 (1113) ◽  
pp. 158-175 ◽  
Keyword(s):  
Flow Rate ◽  
Critical Flow ◽  
Heat Current ◽  
Normal Flow ◽  
Critical Rate ◽  
Intermediate Point ◽  
Flow Rates ◽  
Critical Flow Rate ◽  
Helium Ii ◽  
Frictional Dissipation

The flow of liquid helium II has been investigated under gradients of pressure and temperature in slits of 1 μ diameter. Besides the flow rate, the heat current and the pressure difference at the ends of the slit, the pressure at an intermediate point within the slit has been determined. It was found that for superflow the entire drop in pressure and temperature occurs at the narrowest place in the slit. In the remainder of the slit mass flow takes place under effectively zero gradient of pressure or temperature. The experiments also indicate the existence of a critical flow rate beyond which frictional dissipation makes its appearance. The critical rate was determined by four different criteria which yielded consistent results. The temperature dependence of the critical rate is similar to that observed in the helium II film. With flow under a temperature gradient and for higher flow rates the hydrostatic pressure within the slit was found to drop below that at the ends and an explanation for this effect has been suggested. Some experiments with wider slits have shown that in these even for small velocities the transport is a mixture of superflow and normal flow which renders the phenomena very complex.

Impact of flow rate on lactate uptake and gluconeogenesis in glucagon-stimulated perfused livers

2006 ◽  
Vol 290 (1) ◽  
pp. E185-E191 ◽  
Author(s):  
Ken D. Sumida ◽  
Jerry H. Urdiales ◽  
Casey M. Donovan
Keyword(s):  
Flow Rate ◽  
Dominant Role ◽  
Bicarbonate Buffer ◽  
Flow Rates ◽  
Exponential Decline ◽  
Actual Flow Rate ◽  
Actual Flow ◽  
Lactate Uptake ◽  
The Impact ◽  
Bovine Erythrocytes

The impact of reduced hepatic flow on lactate uptake and gluconeogenesis was examined in isolated glucagon-stimulated perfused livers from 24-h-fasted rats. After surgical isolation, livers were perfused (single pass) for 30 min with Krebs-Henseleit (KH) bicarbonate buffer, fresh bovine erythrocytes (hematocrit ∼20%), and no added substrate. After this “washout” period, steady-state perfusions were initiated with a second reservoir containing the KH buffer, bovine erythrocytes, [U-14C]lactate (10,000 dpm/ml), lactate (2.5 mM), and glucagon (250 μg/ml). Perfusion flow rate was adjusted to one of five rates (i.e., 1.8, 2.7, 3.9, 7.4, and 11.0 ml·min−1·100 g body wt−1). After the perfusion, the liver was dissected out and weighed so as to establish the actual flow rate per gram of liver. The resulting flow rates ranged from 0.52 to 4.03 ml·min−1·g liver−1. As a function of flow rate, lactate uptake rose in a hyperbolic fashion to an apparent plateau of 2.34 μmol·min−1·g liver−1. Fractional extraction (FX) of lactate from the perfusate demonstrated an exponential decline with increased flow rates ( r = 0.97). At flow rates above 1.0 ml·min−1·g liver−1, adjustments in FX compensated for changes in lactate delivery, resulting in steady rates of lactate uptake and gluconeogenesis. Below 1.0·min−1·g liver−1 the increased FX was unable to compensate for the decline in lactate delivery and lactate uptake declined rapidly. Gluconeogenesis demonstrated similar kinetics to lactate uptake, reflecting its dominant role among pathways for lactate removal under the current conditions.

Nutritive blood flow affects microdialysis O/I ratio for [14C]ethanol and3H2O in perfused rat hindlimb

2001 ◽  
Vol 281 (6) ◽  
pp. H2731-H2737 ◽  
Author(s):  
John M. B. Newman ◽  
Carla A. Di Maria ◽  
Stephen Rattigan ◽  
Michael G. Clark
Keyword(s):  
Blood Flow ◽  
Oxygen Uptake ◽  
Flow Rate ◽  
Perfusion Pressure ◽  
Total Flow ◽  
Flow Rates ◽  
Perfusion Flow ◽  
Pressure Oxygen ◽  
Saline Vehicle ◽  
Perfusion Flow Rate

Changes in the microdialysis outflow-to-inflow (O/I) ratio for [14C]ethanol and3H2O were determined in the perfused rat hindlimb after increases and decreases in nutritive flow mediated by the vasoconstrictors norepinephrine (NE) and serotonin (5-HT), respectively. Microdialysis probes (containing 10 mM [14C]ethanol and 3H2O pumped at 1 or 2 μl/min) were inserted through the calf of the rat. Hindlimb perfusion flow rate was varied from 6 to 56 ml · min−1 · 100 g−1 in the presence of NE, 5-HT, or saline vehicle. The O/I ratios for both tracers were determined at each perfusion flow rate, as was perfusion pressure, oxygen uptake (a surrogate indicator of nutritive flow), and lactate release. Both tracers showed a decreased O/I ratio as hindlimb perfusion flow was increased, with [14C]ethanol being higher than 3H2O. NE decreased the O/I ratio compared with vehicle, and 5-HT increased it for both tracers and both microdialysis flow rates. We conclude that the microdialysis O/I ratio, while able to detect changes in total flow, is also sensitive to changes in nutritive and nonnutritive flow, where the latter still extracts tracer, but less than the former.

Partition Coefficient Ratios and Tumour Perfusion Studied with 85mKr and 133Xe

1987 ◽  
Vol 26 (06) ◽  
pp. 253-257
Author(s):  
M. Mäntylä ◽  
J. Perkkiö ◽  
J. Heikkonen
Keyword(s):  
Partition Coefficient ◽  
Partition Coefficients ◽  
Regional Blood Flow ◽  
Blood Perfusion ◽  
Compartmental Analysis ◽  
Malignant Tumour ◽  
Mean Value ◽  
Perfusion Rate ◽  
Biological Variables ◽  
The Mean

The relative partition coefficients of krypton and xenon, and the regional blood flow in 27 superficial malignant tumour nodules in 22 patients with diagnosed tumours were measured using the 85mKr- and 133Xe-clearance method. In order to minimize the effect of biological variables on the measurements the radionuclides were injected simultaneously into the tumour. The distribution of the radiotracers was assumed to be in equilibrium at the beginning of the experiment. The blood perfusion was calculated by fitting a two-exponential function to the measuring points. The mean value of the perfusion rate calculated from the xenon results was 13 ± 10 ml/(100 g-min) [range 3 to 38 ml/(100 g-min)] and from the krypton results 19 ± 11 ml/(100 g-min) [range 5 to 45 ml/(100 g-min)]. These values were obtained, if the partition coefficients are equal to one. The equations obtained by using compartmental analysis were used for the calculation of the relative partition coefficient of krypton and xenon. The partition coefficient of krypton was found to be slightly smaller than that of xenon, which may be due to its smaller molecular weight.

Hydraulic model of a water cooling system in a chemical plant

1988 ◽  
Vol 53 (4) ◽  
pp. 788-806
Author(s):  
Miloslav Hošťálek ◽  
Jiří Výborný ◽  
František Madron
Keyword(s):  
Flow Rate ◽  
Cooling System ◽  
Cooling Water ◽  
Graph Algorithm ◽  
Automatic Generation ◽  
Hydraulic Calculation ◽  
Return Flow ◽  
Flow Rates ◽  
Pressure Losses ◽  
Controlled Flow

Steady state hydraulic calculation has been described of an extensive pipeline network based on a new graph algorithm for setting up and decomposition of balance equations of the model. The parameters of the model are characteristics of individual sections of the network (pumps, pipes, and heat exchangers with armatures). In case of sections with controlled flow rate (variable characteristic), or sections with measured flow rate, the flow rates are direct inputs. The interactions of the network with the surroundings are accounted for by appropriate sources and sinks of individual nodes. The result of the calculation is the knowledge of all flow rates and pressure losses in the network. Automatic generation of the model equations utilizes an efficient (vector) fixing of the network topology and predominantly logical, not numerical operations based on the graph theory. The calculation proper utilizes a modification of the model by the method of linearization of characteristics, while the properties of the modified set of equations permit further decrease of the requirements on the computer. The described approach is suitable for the solution of practical problems even on lower category personal computers. The calculations are illustrated on an example of a simple network with uncontrolled and controlled flow rates of cooling water while one of the sections of the network is also a gravitational return flow of the cooling water.

scholarly journals Geometrical Optimization of a Venturi-Type Microbubble Generator Using CFD Simulation and Experimental Measurements

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 4
Author(s):  
Dillon Alexander Wilson ◽  
Kul Pun ◽  
Poo Balan Ganesan ◽  
Faik Hamad
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Bubble Diameter ◽  
Diameter Ratio ◽  
Experimental Measurements ◽  
Cfd Model ◽  
Flow Rates ◽  
Throat Diameter

Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture and engineering to medical applications. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and computational Fluid Dynamics (CFD) simulation are performed for three water flow rates and three with three different air flow rates. The experimental data presented in the paper are used to validate the CFD model. Then, the CFD model is used to study the effect of diverging angle and throat length/throat diameter ratio on the size of the microbubble produced by the Venturi-type microbubble generator. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubbles. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.

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