Measurements of blood flow to individual glomeruli in the ophidian kidney

1990 ◽  
Vol 258 (6) ◽  
pp. R1313-R1319 ◽  
Author(s):  
S. D. Yokota ◽  
W. H. Dantzler
Keyword(s):  
Blood Flow ◽  
Plasma Osmolality ◽  
Blood Flow Rate ◽  
Vessel Diameter ◽  
Intermittent Flow ◽  
Thamnophis Sirtalis ◽  
Instantaneous Rate ◽  
Single Nephron ◽  
The Difference

Continuous measurements of the instantaneous rate of blood flow to individual glomeruli in a normal vertebrate kidney were made in the garter snake Thamnophis sirtalis. Epifluorescence video microscopy was used to visualize and record blood flow in the afferent arterioles of superficial nephrons. The dual-slit method was used for the determination of red blood cell (RBC) velocity from the video replay. Simultaneous measurements of the vessel diameter allowed the continuous determination of the instantaneous rate of blood flow. A total of 100 glomeruli was surveyed in 12 animals. These glomeruli displayed both constant and highly variable rates of blood flow, with 21% of all nephrons displaying intermittent glomerular perfusion. The mean single-nephron blood flow rate (SNBFR) for all individuals was 23.9 +/- 10.3 (SD) nl/min (n = 12). The percentage of nephrons with intermittent flow for an individual animal increased significantly with increasing plasma osmolality. Intermittency was associated with low SNBFR values; SNBFR averaged 13.5 +/- 10.2 (SD) nl/min (n = 21) in intermittent nephrons and 29.2 +/- 19.0 (SD) nl/min (n = 79) in continuous flow nephrons, the difference being significant (P less than 0.001). Nephrons with continuous perfusion displayed a much greater range of SNBFR values than intermittent nephrons. This suggests that, although changes in whole kidney glomerular filtration rate (GFR) in reptiles need not involve glomerular intermittency, intermittency may lower GFR.

scholarly journals A Simplified Model for Predicting Friction Factors of Laminar Blood Flow in Small-Caliber Vessels

Fluids ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 75 ◽  
Author(s):  
Aikaterini Mouza ◽  
Olga Skordia ◽  
Ioannis Tzouganatos ◽  
Spiros Paras
Keyword(s):  
Blood Flow ◽  
Pressure Drop ◽  
Friction Factor ◽  
Small Diameter ◽  
Numerical Data ◽  
Blood Flow Rate ◽  
Vessel Diameter ◽  
Simplified Model ◽  
Glycerol Solution ◽  
Fanning Friction Factor

The aim of this study was to provide scientists with a straightforward correlation that can be applied to the prediction of the Fanning friction factor and consequently the pressure drop that arises during blood flow in small-caliber vessels. Due to the small diameter of the conduit, the Reynolds numbers are low and thus the flow is laminar. This study has been conducted using Computational Fluid Dynamics (CFD) simulations validated with relevant experimental data, acquired using an appropriate experimental setup. The experiments relate to the pressure drop measurement during the flow of a blood analogue that follows the Casson model, i.e., an aqueous Glycerol solution that contains a small amount of Xanthan gum and exhibits similar behavior to blood, in a smooth, stainless steel microtube (L = 50 mm and D = 400 μm). The interpretation of the resulting numerical data led to the proposal of a simplified model that incorporates the effect of the blood flow rate, the hematocrit value (35–55%) and the vessel diameter (300–1800 μm) and predicts, with better than ±10% accuracy, the Fanning friction factor and consequently the pressure drop during laminar blood flow in healthy small-caliber vessels.

Abstract 062: Regulation of Nephron Afferent Arteriole Resistance in Obesity: Role of Connecting Tubule Glomerular Feedback

Hypertension ◽  
2016 ◽  
Vol 68 (suppl_1) ◽  
Author(s):  
Sumit R Monu ◽  
Mani Maheshwari ◽  
Hong Wang ◽  
Ed Peterson ◽  
Oscar Carretero
Keyword(s):  
Blood Flow ◽  
Renal Blood Flow ◽  
Tubuloglomerular Feedback ◽  
Afferent Arteriole ◽  
Connecting Tubule ◽  
Single Nephron ◽  
Renal Micropuncture ◽  
The Difference

In obesity, renal damage is caused by increase in renal blood flow (RBF), glomerular capillary pressure (P GC ), and single nephron glomerular filtration rate but the mechanism behind this alteration in renal hemodynamics is unclear. P GC is controlled mainly by the afferent arteriole (Af-Art) resistance. Af-Art resistance is regulated by mechanism similar to that in other arterioles and in addition, it is regulated by two intrinsic feedback mechanisms: 1) tubuloglomerular feedback (TGF) that causes Af-Art constriction in response to an increase in sodium chloride (NaCl) in the macula densa, via sodium–potassium-2-chloride cotransporter-2 (NKCC2) and 2) connecting tubule glomerular feedback (CTGF) that causes Af-Art dilatation and is mediated by connecting tubule via epithelial sodium channel (ENaC). CTGF is blocked by the ENaC inhibitor benzamil. Attenuation of TGF reduces Af-Art resistance and allows systemic pressure to get transmitted to the glomerulus that causes glomerular barotrauma/damage. In the current study, we tested the hypothesis that TGF is attenuated in obesity and that CTGF contributes to this effect. We used Zucker obese rats (ZOR) while Zucker lean rats (ZLR) served as controls. We performed in-vivo renal micropuncture of individual rat nephrons while measuring stop-flow pressure (P SF ), an index of P GC. TGF response was measured as a decrease in P SF induced by changing the rate of late proximal perfusion from 0 to 40nl/min in stepwise manner.CTGF was calculated as the difference of P SF value between vehicle and benzamil treatment, at each perfusion rate. Maximal TGF response was significantly less in ZOR (6.16 ± 0.52 mmHg) when compared to the ZLR (8.35 ± 1.00mmHg), p<0.05 , indicating TGF resetting in the ZOR. CTGF was significantly higher in ZOR (6.33±1.95 mmHg) when compared to ZLR (1.38±0.89 mmHg), p<0.05 . When CTGF was inhibited with the ENaC blocker Benzamil (1μM), maximum P SF decrease was 12.30±1.72 mmHg in ZOR and 10.60 ± 1.73 mmHg in ZLR, indicating that blockade of CTGF restored TGF response in ZOR. These observations led us to conclude that TGF is reset in ZOR and that enhanced CTGF contributes to this effect. Increase in CTGF may explain higher renal blood flow, increased P GC and higher glomerular damage in obesity.

scholarly journals Two-compartment model of inner medullary vasculature supports dual modes of vasopressin-regulated inner medullary blood flow

2010 ◽  
Vol 299 (1) ◽  
pp. F273-F279 ◽  
Author(s):  
Julie Kim ◽  
Thomas L. Pannabecker
Keyword(s):  
Blood Flow ◽  
Blood Flow Rate ◽  
Outer Zone ◽  
Compartment Model ◽  
Transverse Dimension ◽  
Vessel Diameter ◽  
Functional Coupling ◽  
Vascular Bundles ◽  
Transport Pathways ◽  
Vasa Recta

The outer zone of the renal inner medulla (IM) is spatially partitioned into two distinct interstitial compartments in the transverse dimension. In one compartment (the intercluster region), collecting ducts (CDs) are absent and vascular bundles are present. Ascending vasa recta (AVR) that lie within and ascend through the intercluster region (intercluster AVR are designated AVR2) participate with descending vasa recta (DVR) in classic countercurrent exchange. Direct evidence from former studies suggests that vasopressin binds to V1 receptors on smooth muscle-like pericytes that regulate vessel diameter and blood flow rate in DVR in this compartment. In a second transverse compartment (the intracluster region), DVR are absent and CDs and AVR are present. Many AVR of the intracluster compartment exhibit multiple branching, with formation of many short interconnecting segments (intracluster AVR are designated AVR1). AVR1 are linked together and connect intercluster DVR to AVR2 by way of sparse networks. Vasopressin V2 receptors regulate multiple fluid and solute transport pathways in CDs in the intracluster compartment. Reabsorbate from IMCDs, ascending thin limbs, and prebend segments passes into AVR1 and is conveyed either upward toward DVR and AVR2 of the intercluster region, or is retained within the intracluster region and is conveyed toward higher levels of the intracluster region. Thus variable rates of fluid reabsorption by CDs potentially lead to variable blood flow rates in either compartment. Net flow between the two transverse compartments would be dependent on the degree of structural and functional coupling between intracluster vessels and intercluster vessels. In the outermost IM, AVR1 pass directly from the IM to the outer medulla, bypassing vascular bundles, the primary blood outflow route. Therefore, two defined vascular pathways exist for fluid outflow from the IM. Compartmental partitioning of V1 and V2 receptors may underlie vasopressin-regulated functional compartmentation of IM blood flow.

Metabolic CO2 Removal by Dialysis: THAM vs NaOH Infusion

1989 ◽  
Vol 12 (11) ◽  
pp. 720-727 ◽  
Author(s):  
J.P. Gille ◽  
C. Saunier ◽  
F. Schrijen ◽  
D. Hartemann ◽  
B. Tousseul
Keyword(s):  
Blood Flow ◽  
Blood Flow Rate ◽  
Co2 Removal ◽  
Control Value ◽  
New Methods ◽  
Lower Blood ◽  
Acid Base Equilibrium ◽  
Marked Weight ◽  
The Difference ◽  
The Right

New methods of respiratory support are needed to reduce the high mortality rate of acute respiratory failure. To simplify the procedures of extracorporeal CO2 elimination under apneic oxygenation, one approach is to replace the membrane lung by a hemodialyzer and to administer an alkali, since hemodialysis requires a lower blood flow rate than blood-gas exchange. This study compared the effectiveness of trishydroxymethyl aminomethane (THAM) and NaOH in this procedure. Twelve male Anglo-Poitevin dogs (25 to 33 kg) were anesthetized, curarized and mechanically hypoventilated (&Vdot;E = 41% of the control value). After not less than 15 min, a venovenous shunt was used for dialysis with blood flow of 7-10 ml. min.-1kg-1 for at least 8 hours. The dialysate contained no acetate, bicarbonate or lactate, but was alkalinized to a pH of 8-9 by the addition of NaOH. A solution of THAM (0.5 N) was infused into the right heart at the rate of 0.30 ml.min.-1kg-1 in six animals, and NaOH (0.15 N) was infused in the other six at the rate of 0.80 ml.min.-1 kg-1. The injected volumes were compensated for by an equivalent amount of ultrafiltration. Elimination of CO2 (mean †CO2 = 2.3 ml.min.-1kg-1) was the same with both methods and the difference for the electrolytes and acid-base equilibrium was only very small. However, hemolysis was six times greater with NaOH than with THAM. Despite ultrafiltration, a similar marked weight gain was observed from the second hour of the experiment in the NaOH series, but only after 7 hours with THAM. It thus appears that hemodialysis combined with alkalinisation is still too complex a procedure to be safely applied in acute or chronic pulmonary failure

scholarly journals Noninvasive transcutaneous determination of access blood flow rate

2001 ◽  
Vol 60 (1) ◽  
pp. 284-291 ◽  
Author(s):  
Robert R. Steuer ◽  
David R. Miller ◽  
Songbiao Zhang ◽  
David A. Bell ◽  
John K. Leypoldt
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Blood Flow Rate

scholarly journals The Natural-Mineral-Based Novel Nanomaterial IFMC Increases Intravascular Nitric Oxide without Its Intake: Implications for COVID-19 and beyond

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1699
Author(s):  
Tomohiro Akiyama ◽  
Takamichi Hirata ◽  
Takahiro Fujimoto ◽  
Shinnosuke Hatakeyama ◽  
Ryuhei Yamazaki ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Flow Rate ◽  
Vascular System ◽  
Vascular Complications ◽  
Blood Flow Rate ◽  
Vessel Diameter ◽  
Human Hand ◽  
Natural Mineral ◽  
Living Body

There are currently no promising therapy strategies for either the treatment or prevention of novel coronavirus disease 2019 (COVID-19), despite the urgent need. In addition to respiratory diseases, vascular complications are rapidly emerging as a key threat of COVID-19. Existing nitric oxide (NO) therapies have been shown to improve the vascular system; however, they have different limitations in terms of safety, usability and availability. In light of this, we hypothesise that a natural-mineral-based novel nanomaterial, which was developed based on NO therapy, might be a viable strategy for the treatment and prevention of COVID-19. The present study examined if it could induce an increase of intravascular NO, vasodilation and the consequent increase of blood flow rate and temperature in a living body. The intravascular NO concentration in the hepatic portal of rats was increased by 0.17 nM over 35.2 s on average after its application. An ultrasonic Doppler flow meter showed significant increases in the blood flow rate and vessel diameter, but no difference in the blood flow velocity. These were corroborated by measurements of human hand surface temperature. To our knowledge, this result is the first evidence where an increase of intravascular NO and vasodilation were induced by bringing a natural-mineral-based nanomaterial into contact with or close to a living body. The precise mechanisms remain a matter for further investigation; however, we may assume that endothelial NO synthase, haemoglobin and endothelium-derived hyperpolarising factor are deeply involved in the increase of intravascular NO.

scholarly journals Blood Flow Velocity in the Pial Arteries of Cats, with Particular Reference to the Vessel Diameter

1984 ◽  
Vol 4 (1) ◽  
pp. 110-114 ◽  
Author(s):  
Masahiro Kobari ◽  
Fumio Gotoh ◽  
Yasuo Fukuuchi ◽  
Kortaro Tanaka ◽  
Norihiro Suzuki ◽  
...  
Keyword(s):  
Blood Flow ◽  
Flow Velocity ◽  
Flow Rate ◽  
Blood Flow Velocity ◽  
Blood Flow Rate ◽  
Video Camera ◽  
Vessel Diameter ◽  
Pial Arteries ◽  
Cross Sectional ◽  
Pial Artery

The blood flow velocity and diameter of feline pial arteries, ranging in diameter from 20 to 200 μm, were measured simultaneously using a newly developed video camera method under steady-state conditions for all other parameters. There was a linear relationship between blood flow velocity and pial artery diameter ( y = 0.340 x + 0.309), the correlation coefficient being 0.785 (p < 0.001). The average values for blood flow velocity in pial arteries <50 μm, ≧50 but <100 μm, ≧100 but <150 μm, and ≧150 μm in diameter were 12.9 ± 1.3, 24.6 ± 3.4, 42.1 ± 4.7, and 59.9 ± 5.3 mm/s, respectively. Blood flow rate was calculated as a product of the cross-sectional area and the flow velocity. The blood flow rate increased exponentially as the pial artery diameter increased ( y = 2.71 × 10−4 x2.98). The average values for blood flow rate in pial arteries <50 μm, ≧50 but <100 μm, ≧100 but <150 μm, and ≧150 μm in diameter were 12.8 ± 1.5, 122.1 ± 24.8, 510.2 ± 74.8, and 1524.2 ± 174.4 10−3 mm3/s, respectively. Hemorheological parameters such as the wall shear rate and Reynolds' number were also calculated. The data obtained provide a useful basis for further investigations in the field of cerebral circulation.

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