A model of nitric oxide tubulovascular cross talk in a renal outer medullary cross section

2007 ◽  
Vol 292 (2) ◽  
pp. F711-F722 ◽  
Author(s):  
Wensheng Zhang ◽  
Aurélie Edwards
Keyword(s):  
Blood Flow ◽  
Cross Section ◽  
Cross Talk ◽  
Vascular Bundle ◽  
Flow Distribution ◽  
Structural Heterogeneity ◽  
No Production ◽  
Vascular Bundles ◽  
Outer Medulla ◽  
Blood Flow Ratio

We developed a two-dimensional model of NO transport in a cross section of the inner stripe (IS) of the rat outer medulla to determine whether tubular and vascular generation of NO result in significant NO concentration (CNO) differences between the periphery and the center of vascular bundles and thereby affect medullary blood flow distribution. Following the approach of Layton and Layton (Layton AT, Layton HE. Am J Physiol Renal Physiol 289: F1346–F1366, 2006), the structural heterogeneity of the IS was incorporated in a representative unit consisting of four concentric regions centered on a vascular bundle. Our model suggests that the diffusion distance of NO in the interstitium is limited to a few micrometers. We predict that, under basal conditions, epithelial NO generation raises the average CNO in pericytes surrounding peripheral descending vasa recta (DVR) by a few nanomoles relative to that in pericytes surrounding central DVR. The short descending limbs and long ascending limbs are found to exert the greatest effect on CNO in pericytes; long descending limbs and short ascending limbs only have a moderate effect, whereas outer medullary collecting ducts, which are situated far from the vascular bundle center, do not affect pericyte CNO. Our results suggest that selective stimulation of epithelial NO production should significantly raise the periphery-to-center DVR diameter ratio, thereby increasing the outer medulla-to-inner medulla blood flow ratio. However, concomitant increases in epithelial superoxide (O2−) production would counteract this effect. This model confirms the importance of NO and O2− interactions in mediating tubulovascular cross talk.

scholarly journals Nitric oxide and superoxide transport in a cross section of the rat outer medulla. I. Effects of low medullary oxygen tension

2010 ◽  
Vol 299 (3) ◽  
pp. F616-F633 ◽  
Author(s):  
Aurélie Edwards ◽  
Anita T. Layton
Keyword(s):  
Nitric Oxide ◽  
Cross Section ◽  
Vascular Bundle ◽  
Fluid Model ◽  
Vascular Bundles ◽  
Concentration Gradients ◽  
Outer Medulla ◽  
Vasa Recta ◽  
The Difference ◽  
The Impact

To examine the impact of the complex radial organization of the rat outer medulla (OM) on the distribution of nitric oxide (NO), superoxide (O2−) and total peroxynitrite (ONOO), we developed a mathematical model that simulates the transport of those species in a cross section of the rat OM. To simulate the preferential interactions among tubules and vessels that arise from their relative radial positions in the OM, we adopted the region-based approach developed by Layton and Layton ( Am J Physiol Renal Physiol 289: F1346–F1366, 2005). In that approach, the structural organization of the OM is represented by means of four concentric regions centered on a vascular bundle. The model predicts the concentrations of NO, O2−, and ONOO in the tubular and vascular lumen, epithelial and endothelial cells, red blood cells (RBCs), and interstitial fluid. Model results suggest that the large gradients in Po2 from the core of the vascular bundle toward its periphery, which stem from the segregation of O2-supplying descending vasa recta (DVR) within the vascular bundles, in turn generate steep radial NO and O2− concentration gradients, since the synthesis of both solutes is O2 dependent. Without the rate-limiting effects of O2, NO concentration would be lowest in the vascular bundle core, that is, the region with the highest density of RBCs, which act as a sink for NO. Our results also suggest that, under basal conditions, the difference in NO concentrations between DVR that reach into the inner medulla and those that turn within the OM should lead to differences in vasodilation and preferentially increase blood flow to the inner medulla.

scholarly journals Morphological and Anatomical Studies of Hippocrepis L. Genus in Turkey

2019 ◽  
Vol 37 ◽  
Author(s):  
K. YETISEN ◽  
C. ÖZDEMIR
Keyword(s):  
Cross Section ◽  
Vascular Bundle ◽  
The Other ◽  
Vascular Bundles ◽  
Stem Anatomy ◽  
Anatomical Studies ◽  
Anatomical Features

ABSTRACT: In this study, the morphological and anatomical features were investigated of three taxon of Hippocrepis L. species which spreading naturally in Turkey. In the morphological part of the study, H. unisiliquosa subsp. unisiliquosa’s stem is erect or decumbent. The species H. ciliata’s Willd. stem is erect. H. multisiliquosa’s L. stem is decumbent. The fruit of H. multisiliquosa is much more convoluted than the other two taxa. There are cilia on the fruit of H. ciliata, but there are not found any cilia the other two taxa. The stem anatomy of all the studied taxa is hexagonal. In the stem cross section of H. ciliata 12-14 vascular bundle are found, H. unisiliquosa subsp. unisiliquosa 12-15 and H. multisiliquosa 12-13. Leaf vascular bundles are arranged regularly, H. unisiliquosa subsp. unisiliquosa have 18-20, H. ciliata have 6-8, H. multisiliquosa have 9-13 vascular bundles.

scholarly journals Efficiently, accurately, intelligently dissecting bamboo: characteristic of vascular bundle in Phyllostachys

2021 ◽  
Author(s):  
Haocheng Xu ◽  
Ying Zhang ◽  
Jiajun Wang ◽  
Tuhua Zhong ◽  
Xinxin Ma ◽  
...  
Keyword(s):  
Cross Section ◽  
Radial Distribution ◽  
Vascular Bundle ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Width Ratio ◽  
Vascular Bundles ◽  
Fiber Volume ◽  
Detection Model ◽  
Gradient Change

AbstractA comprehensive understanding of vascular bundles is the key to elucidate the excellent intrinsic mechanical properties of bamboo. This research aims to investigate the gradient distribution of fiber volume fraction and the gradient changes in the shape of vascular bundles along the radial axis in Phyllostachys. We constructed a universal transfer-learning-based vascular bundle detection model with high precision of up to 96.97%, which can help to acquire the characteristics of vascular bundles quickly and accurately. The total number of vascular bundles, total fiber sheath area, the length, width and area of fiber sheath of individual vascular bundles within the entire cross-section were counted, and the results showed that these parameters had a strongly positive linear correlation with the outer circumference and wall thickness of bamboo culms, but the fiber volume fraction (around 25.5 %) and the length-to-width ratio of the vascular bundles (around 1.226) were relatively constant. Furthermore, we layered the cross section of bamboo according to the wall thickness finely and counted the characteristics of vascular bundle in each layer. The results showed that the radial distribution of fiber volume fraction decreased exponentially, the radial distribution of the length-to-width ratio of vascular bundle decreased quadratically, the radial distribution of the width of vascular bundle increased linearly. The trends of the gradient change in vascular bundle’s characteristics were found highly consistent among 29 bamboo species in Phyllostachys.One sentence summaryA universal vascular bundle detection model can efficiently dissect vascular bundles in Phyllostachys, and the radial gradient change of vascular bundles in cross-section are found highly consistent.

Freeze-dissection analysis of 133Xe distribution to measure regional renal blood flow

1983 ◽  
Vol 244 (5) ◽  
pp. F574-F578
Author(s):  
J. C. Passmore ◽  
R. L. Allen ◽  
C. E. Hock ◽  
R. E. Neiberger
Keyword(s):  
Blood Flow ◽  
Renal Blood Flow ◽  
Flow Distribution ◽  
Kidney Weight ◽  
Outer Medulla ◽  
Anesthetized Dogs ◽  
Measured Flow ◽  
Regional Renal Blood Flow ◽  
Dissection Technique ◽  
133Xe Washout

To verify the freeze-dissection technique for measuring renal blood flow (RBF) distribution in anesthetized dogs we compared the sum of all compartment flow rates with total RBF, compared compartment flow distribution with intercepts, and determined recirculated 133Xe. By dissection, we found that the cortex, delineated by its granular brownish red appearance, comprised 69%, whereas the outer medulla (the reddish portion) was 18% of the total kidney weight. Average cortical flow was 3.77 ml X g-1 X min-1 and the y-intercept for 133Xe washout was 85% of the initial radioactivity distribution. Outer medullary flow was 2.01 ml X g-1 X min-1 with a y-intercept of 13%. In a 100-g kidney, total cortical flow would be 259.8 ml/min (3.77 ml X g-1 X min-1 X 68.9 g) and total outer medullary flow would be 36.0 ml/min. These calculations indicate that 86% of the total flow is distributed to the cortex and 13% to the outer medulla, as the intercept-calculated percentages indicated. Summing whole cortical and medullary flows results in a flow that agrees with the electromagnetically measured flow of 292 ml/min for a 100-g kidney.

scholarly journals Effects of pH and medullary blood flow on oxygen transport and sodium reabsorption in the rat outer medulla

2010 ◽  
Vol 298 (6) ◽  
pp. F1369-F1383 ◽  
Author(s):  
Jing Chen ◽  
Aurélie Edwards ◽  
Anita T. Layton
Keyword(s):  
Blood Flow ◽  
Rat Kidney ◽  
Sodium Reabsorption ◽  
Vascular Bundles ◽  
Outer Medulla ◽  
Medullary Blood Flow ◽  
Blood Ph ◽  
Effects Of Ph ◽  
Tubular Flow

We used a mathematical model of O2 transport and the urine concentrating mechanism of the outer medulla of the rat kidney to study the effects of blood pH and medullary blood flow on O2 availability and Na+ reabsorption. The model predicts that in vivo paracellular Na+ fluxes across medullary thick ascending limbs (mTALs) are small relative to transcellular Na+ fluxes and that paracellular fluxes favor Na+ reabsorption from the lumen along most of the mTAL segments. In addition, model results suggest that blood pH has a significant impact on O2 transport and Na+ reabsorption owing to the Bohr effect, according to which a lower pH reduces the binding affinity of hemoglobin for O2. Thus our model predicts that the presumed greater acidity of blood in the interbundle regions, where mTALs are located, relative to that in the vascular bundles, facilitates the delivery of O2 to support the high metabolic requirements of the mTALs and raises the concentrating capability of the outer medulla. Model results also suggest that increases in vascular and tubular flow rates result in disproportional, smaller increases in active O2 consumption and mTAL active Na+ transport, despite the higher delivery of O2 and Na+. That is, at a sufficiently high medullary O2 supply, O2 demand in the outer medulla does not adjust precisely to changes in O2 delivery.

NO supports right ventricular flow dominance and whole body O2 utilization in midgestation fetal lambs

2001 ◽  
Vol 280 (4) ◽  
pp. R1016-R1022 ◽  
Author(s):  
Joseph J. Smolich
Keyword(s):  
Blood Flow ◽  
Flow Distribution ◽  
The Body ◽  
Whole Body ◽  
Blood Flow Distribution ◽  
Blood Flows ◽  
Blood Flow Ratio ◽  
Placental Blood ◽  
Flow Changes ◽  
Placental Blood Flow

It is unknown if nitric oxide (NO) modulates the relative levels of left (LV) and right (RV) ventricular output, fetal O2 consumption, or blood flow distribution between the body and placenta at midgestation. To address these questions, six fetal lambs were instrumented at 89–96 days gestation (term 147 days), and blood flows were measured with radioactive microspheres 3–4 days later at baseline and after inhibition of NO synthesis with 10 mg/kg (l-NNA10) and 25 mg/kg (l-NNA25) N ω-nitro-l-arginine. LV output fell by 74 ± 15 ml · min−1 · kg−1 atl-NNA10 ( P < 0.005), whereas RV output decreased by 90 ± 18 ml · min−1 · kg−1 atl-NNA10 ( P < 0.02) and by a further 80 ± 22 ml · min−1 · kg−1 atl-NNA25 ( P < 0.05). As a result, RV output exceeded LV output at baseline ( P = 0.03) and l-NNA10 ( P < 0.02) but not at l-NNA25. Fetal body blood flow fell by 95 ± 25 ml · min−1 · kg−1 atl-NNA10 ( P < 0.01), but because placental blood flow decreased by 70 ± 22 ml · min−1 · kg−1 atl-NNA10 ( P < 0.01) and a further 71 ± 21 ml · min−1 · kg−1 atl-NNA25 ( P < 0.01), the fetal body-to-placental blood flow ratio was near unity at baseline andl-NNA10 but rose to 1.5 ± 0.3 atl-NNA25 ( P < 0.05). In association with these flow changes, fetal O2 consumption declined by 1.4 ± 0.3 ml · min−1 · kg−1 atl-NNA10 ( P < 0.05) and by a further 1.5 ± 0.6 ml · min−1 · kg−1 atl-NNA25 ( P < 0.02). These findings suggest that, in midgestation fetal lambs, NO supports an RV flow dominance, whole body O2 utilization, and the maintenance of a near-equal fetoplacental blood flow distribution.

scholarly journals Nitric oxide and superoxide transport in a cross section of the rat outer medulla. II. Reciprocal interactions and tubulovascular cross talk

2010 ◽  
Vol 299 (3) ◽  
pp. F634-F647 ◽  
Author(s):  
Aurélie Edwards ◽  
Anita T. Layton
Keyword(s):  
Nitric Oxide ◽  
Cross Sections ◽  
Cross Talk ◽  
Three Dimensional ◽  
No Production ◽  
Outer Medulla ◽  
Nacl Transport ◽  
Hypoxic Conditions ◽  
Outer Stripe ◽  
Main Determinants

In a companion study (Edwards A and Layton AT. Am J Physiol Renal Physiol. doi:10.1152/ajprenal.00680.2009), we developed a mathematical model of nitric oxide (NO), superoxide (O2−), and total peroxynitrite (ONOO) transport in mid-outer stripe and mid-inner stripe cross sections of the rat outer medulla (OM). We examined how the three-dimensional architecture of the rat OM, together with low medullary oxygen tension (Po2), affects the distribution of NO, O2−, and ONOO in the rat OM. In the current study, we sought to determine generation rate and permeability values that are compatible with measurements of medullary NO concentrations and to assess the importance of tubulovascular cross talk and NO-O2− interactions under physiological conditions. Our results suggest that the main determinants of NO concentrations in the rat OM are the rate of vascular and tubular NO synthesis under hypoxic conditions, and the red blood cell (RBC) permeability to NO ( PNORBC). The lower the PNORBC, the lower the amount of NO that is scavenged by hemoglobin species, and the higher the extra-erythrocyte NO concentrations. In addition, our results indicate that basal endothelial NO production acts to significantly limit NaCl reabsorption across medullary thick ascending limbs and to sustain medullary perfusion, whereas basal epithelial NO production has a smaller impact on NaCl transport and a negligible effect on vascular tone. Our model also predicts that O2− consumption by NO significantly reduces medullary O2− concentrations, but that O2− , when present at subnanomolar concentrations, has a small impact on medullary NO bioavailability.

scholarly journals Impact of nitric oxide-mediated vasodilation on outer medullary NaCl transport and oxygenation

2012 ◽  
Vol 303 (7) ◽  
pp. F907-F917 ◽  
Author(s):  
Aurélie Edwards ◽  
Anita T. Layton
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Supply And Demand ◽  
Vascular Bundles ◽  
Concentration Gradients ◽  
Outer Medulla ◽  
Nacl Transport ◽  
Reciprocal Interactions ◽  
Medullary Blood Flow ◽  
Vasa Recta

The present study aimed to elucidate the reciprocal interactions between oxygen (O2), nitric oxide (NO), and superoxide (O2−) and their effects on vascular and tubular function in the outer medulla. We expanded our region-based model of transport in the rat outer medulla (Edwards A, Layton AT. Am J Physiol Renal Physiol 301: F979–F996, 2011) to incorporate the effects of NO on descending vasa recta (DVR) diameter and blood flow. Our model predicts that the segregation of long DVR in the center of vascular bundles, away from tubular segments, gives rise to large radial NO concentration gradients that in turn result in differential regulation of vasoactivity in short and long DVR. The relative isolation of long DVR shields them from changes in the rate of NaCl reabsorption, and hence from changes in O2 requirements, by medullary thick ascending limbs (mTALs), thereby preserving O2 delivery to the inner medulla. The model also predicts that O2− can sufficiently decrease the bioavailability of NO in the interbundle region to affect the diameter of short DVR, suggesting that the experimentally observed effects of O2− on medullary blood flow may be at least partly mediated by NO. In addition, our results indicate that the tubulovascular cross talk of NO, that is, the diffusion of NO produced by mTAL epithelia toward adjacent DVR, helps to maintain blood flow and O2 supply to the interbundle region even under basal conditions. NO also acts to preserve local O2 availability by inhibiting the rate of active Na+ transport, thereby reducing the O2 requirements of mTALs. The dual regulation by NO of oxygen supply and demand is predicted to significantly attenuate the hypoxic effects of angiotensin II.

Cambial Variant in the Stem of Serjania Corrugata (Sapindaceae)

IAWA Journal ◽  
2006 ◽  
Vol 27 (3) ◽  
pp. 269-280 ◽  
Author(s):  
Gabriel U.C. Araújo ◽  
Cecilia G. Costa
Keyword(s):  
Cross Section ◽  
Vascular Bundle ◽  
Vascular Ring ◽  
Cambial Activity ◽  
Vascular Bundles ◽  
Stages Of Development ◽  
Early Stages ◽  
Meristematic Activity ◽  
Cambial Variant

The establishment of the cambial variant and the development of the stem of Serjania corrugata Radlk. (Sapindaceae) was analyzed. In the early stages of development, the stem is lobed, with five lobes and five furrows in cross section. Around the fourth internode, each lobe has a vascular arc with one or two more developed central vascular bundles, two lateral bundles and phloem in the interfascicular regions. Procambial strands are also found in perimedullary position, producing only phloem elements. At this stage, the beginning of the cambial activity can be seen in the central vascular bundle in each lobe. This activity then extends to the lateral vascular bundles and to the perimedullary phloem. Parenchymatic cells, located between the vascular ring of the lobe and the perimedullary phloem, dedifferentiate and initiate meristematic activity, uniting these two regions. The development of xylem masses (one in each lobe) that characterizes the adult stem results from this cambial activity. The development of the cambial variant in S. corrugata is quite similar to that previously described in S. elegans Cambess.

Neonatal changes in renal blood flow distribution in puppies

1975 ◽  
Vol 228 (5) ◽  
pp. 1453-1461 ◽  
Author(s):  
LC Aschinberg ◽  
DI Goldsmith ◽  
H Olbing ◽  
A Spitzer ◽  
Edelmann CM ◽  
...  
Keyword(s):  
Blood Flow ◽  
Renal Blood Flow ◽  
Renal Cortex ◽  
Flow Distribution ◽  
Blood Flow Distribution ◽  
Outer Cortex ◽  
Outer Medulla ◽  
Inner Cortex ◽  
Renal Blood Flow Distribution ◽  
Intrarenal Distribution

The intrarenal distribution of blood flow was studied in 31 newborn mongrel puppies from 18 h to 70 days using xenon washout and krypton autoradiography. Mean renal blood flow increased from 0.39 plus or minus 0.05 ml/g per min (SE) the 1st wk to 2.06 plus or minus 0.12 ml/g per min at 6 wk. During the 1st wk of life renal cortex was perfused homo-geneously at 0.88 plus or minus 0.19 ml/g per min (SE) and accounted for 35 plus or minus 4% of the renal blood flow. During the 2nd wk a narrow, rapidly perfused zone of outer cortex was identified which was perfused at 3.35 plus or minus 0.26 ml/g per min, received 19.53 plus or minus 5.05% of the total renal blood flow, and represented 15 plus or minus 4% of the mass of the total cortex. The inner cortex and outer medulla at this time received 53.40 plus or minus 4.12% of the flow at 1.07 plus or minus 0.08 ml/g per min. Outer cortical flow increased with age reaching adult values by about 6-10 wk when the rapidly perfused area represented 40 plus or minus 8% of the cortex. These changes are parallel to the results of previously reported studies with microspheres in newborn puppies and are compatible with the well established maturational changes noted in neonates of several species. They represent the first gas-washout studies in animals during the first 6 wk of life.

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