Measurement Of Changes In Diameter Research Articles

The Role of NO and H2O2 in Ach-Induced Dilation of Human Arterioles in the Absence and Presence of Coronary Artery Disease

The endothelium regulates vascular tone through the release of various vasodilatory factors such as NO, PGI2, and endothelium-derived hyperpolarizing (EDH) signaling that is more important in resistance arteries and arterioles. Using freshly isolated human arterioles, previous studies indicate that hydrogen peroxide (H2O2), an EDH factor, mediates flow-mediated dilation in patients with coronary artery disease (CAD), whereas NO plays a more prominent role in patients without CAD. However, the mechanisms of receptor agonists (e.g., acetylcholine)-induced dilation remains to be clarified in human arterioles. The objective of this study was to compare the role of NO and H2O2 in acetylcholine (Ach-induced dilation in human adipose arterioles (HAA) from non-CAD and CAD patients. HAA (100-200 μm) dissected from discarded surgical samples of non-CAD and CAD patients, were cannulated onto glass micropipettes and pressurized at 60 mmHg for measurement of diameter changes by using videomicroscopy. Microvessels were incubated with L-NAME (100 μM), an inhibitor of NO synthase, Indomethacin (Indo, 10 μM), an inhibitor of PGI2 synthesis and peg-CAT (500 U/ml), a scavenger of H2O2. To study the dose-dependent response to Ach (log 10-9 – 10-5 M), HAA were preconstricted with endothelin-1 (0.1-0.5 nM). In non-CAD tissues Ach induced potent concentration-dependent dilation (maximal dilation at 10−5 M: 95.6±1.8%). After preincubation with L-NAME, this dilation was partially reduced (maximal dilation at 10−5 M: 77.4±3.1%, P<0.05 vs. control), while the combination of L-NAME and Indo reduced it to the same extent as L-NAME by itself (maximal dilation at 10−5 M: 73.1±7.4%, P<0.05 vs. control). To further determine the role of H2O2 in dilatory response to Ach, we treated HAA with peg-CAT. Incubation of peg-CAT significantly reduced the dilation (maximal dilation at 10−5 M: 74.6±8.1% and 51.3±8.7% in the absence and presence of L-NAME and Indo, P<0.05 vs. control). In HAA obtained from CAD patients, the dilation response to Ach was similar to non-CAD (maximal dilation at 10−5 M: 93.9± 1.8%) and the combination of L-NAME and Indo reduced this dilation to a lesser extent (maximal dilation at 10−5 M: 83.1±3%, P=0.055), compared to non-CAD patients (maximal dilation at 10−5 M: 73.1±7.4%, P<0.05 vs. control). The preincubation with peg-CAT attenuated the dilation only at log -7 M (maximal dilation at 10−7 M: 33.8±9.5%, P<0.05 vs. 54.6±7.5% in control). The large portion of the dilation remaining after the combination of L-NAME and Indo was almost completely abolished in the presence of high K+ concentration (maximal dilation at 10−5 M: 12.9±5.1% P<0.05 vs. control). Together, these results provide new evidence that in non-CAD arterioles both NO and H2O2 play an important role in Ach-induced dilation whereas PGI2 is likely not involved. In CAD arterioles, NO, PGI2 and H2O2 have much less contribution to Ach-induced dilation, while a H2O2-independent EDH signaling plays the major role in the dilatory response. Further studies are required to determine the specific mechanism or factor involved in Ach-induced EDH-dependent dilation in HAA. This work was supported by the National Heart, Lung, and Blood Institute [R01HL096647]. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Embedded Soft Inductive Sensors to Measure Arterial Expansion of Tubular Diameters in Vascular Phantoms

Measuring diameter change in flexible tubular structures embedded in opaque material is challenging. In this article, we present a soft braided coil embedded in an elastomer tube as a method to continuously measure such a change in diameter. By measuring the inductance change in the braided coil, we estimate the instantaneous diameter with a simple inductance model. In applying this method, we demonstrate that diameter waves in a vascular phantom, a model of a radial artery embedded in a viscoelastic wrist structure, can be recorded continuously. Four sensors were made, and their ability to measure physiologically relevant simulated pulse waves was assessed. Several pressure pulse profiles were generated using a precision digital pump. Inductance of the coil was measured simultaneously as the change in diameter was recorded using an optical laser/mirror deflection measurement. One sensor was then embedded in a vascular phantom model of the human wrist. The diameter of the simulated radial artery was recorded via ultrasound and estimated from coil inductance measurements. The diameter estimates from the inductance model corresponded well with the comparator in both experimental setups. We demonstrate that our method is a viable alternative to ultrasound in recording diameter waves in artery models. This opens opportunities in empirical investigations of physiologically interesting fluid-structure interaction. This method can provide new ability to measure diameter changes in tubular systems where access is obstructed.

Assessment of Neoadjuvant Treatment Response Using Automated Breast Ultrasound in Breast Cancer

Breast imaging techniques are used to assess the tumor response to neoadjuvant treatment (NAT), which is increasingly one of the preferred therapeutic options and increases the rate of breast conservation for breast cancer. Herein, we report a case in which a woman was diagnosed with invasive ductal carcinoma in the left breast and received NAT before surgery. Automated breast ultrasound (AB US) was regularly performed before and during the NAT to evaluate the tumor response to NAT by measuring diameter changes and volume reductions of the tumor. Images showed that the tumor size was significantly reduced and disappeared after 7 cycles of NAT, except for macrocalcification. Postoperative histopathological examination confirmed that there were no residual tumor cells. We found that AB US overcame the limitations of handheld US, such as operator dependence, poor reproducibility and limited field of view, and can be an alternative modality to assess the tumor response of NAT in the absence of magnetic resonance imaging (MRI) instruments.

The Influence of Silica Nanoparticles on the Thermal and Mechanical Properties of Crosslinked Hybrid Composites.

This paper presents the synthesis and physicochemical characterization of a new hybrid composite. Its main goals are evaluating the structure and studying the thermal and mechanical properties of the crosslinked polymeric materials based on varying chemical properties of the compounds. As an organic crosslinking monomer, bisphenol A glycerolate diacrylate (BPA.GDA) was used. Trimethoxyvinylsilane (TMVS) and N-vinyl-2-pyrrolidone (NVP) were used as comonomers and active diluents. The inorganic fraction was the silica in the form of nanoparticles (NANOSiO2). The hybrid composites were obtained by the bulk polymerization method using the UV initiator Irqacure 651 with a constant weight ratio of the tetrafunctional monomer BPA.GDA to TMVS or NVP (7:3 wt.%) and different wt.% of silica nanoparticles (0, 1, 3%). The proper course of polymerization was confirmed by the ATR/FTIR spectroscopy and SEM EDAX analysis. In the composites spectra the signals correspond to the C=O groups from NVP at 1672–1675 cm−1, and the vibrations of Si–O–C and Si–O–Si groups at 1053–1100 cm−1 from TMVS and NANOSiO2 are visible. Thermal stabilities of the obtained composites were studied by a differential scanning calorimetry DSC. Compared to NVP the samples with TMVS degraded in one stage (422.6–425.3 °C). The NVP-derived materials decomposed in three stages (three endothermic effects on the DSC curves). The addition of NANOSiO2 increases the temperature of composites maximum degradation insignificantly. Additionally, the Shore D hardness test was carried out with original metrological measurements of changes in diameter after indentation in relation to the type of material. The accuracy analysis of the obtained test results was based on a comparative analysis of graphical curves obtained from experimental tests. The values of the changes course of similarity in the examined factors, represented by those of characteristic coefficients were determined based on the Fréchet’s theory.

Evaporation and propagation of liquid drop streams at vacuum pressures: Experiments and modeling.

Evaporation of streams of liquid droplets in environments at vacuum pressures below the vapor pressure has not been widely studied. Here, experiments and simulations are reported that quantify the change in droplet diameter when a steady stream of ≈100 μm diameter drops is injected into a chamber initially evacuated to <10^{-8}bar. In experiments, droplets fall through the center of a 0.8 m long liquid nitrogen cooled shroud, simulating infinity radiation and vapor mass flux boundary conditions. Experimentally measured changes in drop diameters vary from ≈0 to 6 μm when the initial vapor pressure is increased from 10^{-6} to 10^{-3} bar by heating the liquid. Measured diameter changes are predicted by a model based on the Hertz-Knudsen equation. One uncertainty in the calculation is the "sticking coefficient" β. Assuming a constant β for all conditions studied here, predicted diameter changes best match measurements with β≈0.3. This value falls within the range of β reported in the literature for organic liquids. Finally, at the higher vapor pressure conditions considered here, the drop stream disperses transverse to the main flow direction. This spread is attributed to forces imparted by an absolute pressure gradient produced by the evaporating stream.

Quantification of suprarenal aortic neck dilation after fenestrated endovascular aneurysm repair

ObjectiveSuprarenal aortic neck dilation (AND) after fenestrated endovascular aneurysm repair (FEVAR) with commercially available devices has not yet been well characterized. The aim of this study was to measure diameter changes in the supravisceral aorta after FEVAR. MethodsThis is a single-center retrospective review involving patients with juxtarenal aneurysms treated with Cook ZFEN devices (Cook Medical, Bloomington, Ind). Patients with at least 1 year of cross-sectional radiologic follow-up were included. AND was defined as ≥3 mm at any measured location. Aortic diameter, defined as the average outer to outer diameter on three-dimensional centerline imaging, was measured at seven locations along the length of the ZFEN device from the proximal fixation struts to the bottom of the second seal stent. The first postoperative CT scan (≤1 month) served as a baseline from which subsequent measurements at annual intervals were compared. ResultsA total of 43 patients who underwent FEVAR from 2012 to 2018 met inclusion criteria, with a total of 119 target vessels (83 renal stents, 41 superior mesenteric artery scallops or large fenestrations). Mean follow-up time was 30.3 months. Any AND was found to occur in 32 (74.4%) patients. Aortic diameter dilation at latest follow-up was found to occur at all measured locations from the top of the fixation struts (1.9 ± 2.4 mm; P < .0001) to the middle of the second seal stent (1.3 ± 3.8 mm; P < .01). Diameter growth was most pronounced in the middle of the first seal stent, with mean AND of 3.6 ± 3.2 mm. At this location, the aorta experienced nearly linear annual growth of 0.99 mm (95% confidence interval, 0.7-1.28 mm) per year. Increasing device oversizing relative to the native visceral aorta was the strongest predictor of postoperative neck diameter growth (1.34 mm per 10% increase in oversizing; P = .02), whereas increasing proximal seal length was protective of growth (−1.82 mm per 10-mm increase in seal length; P = .016). Proximal seal lengths ≥3 cm were associated with less neck dilation compared with <3 cm (2.6 mm vs 4.9 mm; P = .022). Type IA endoleak in this cohort was rare (n = 1) and not associated with AND (P = .256). ConclusionsDilation of the suprarenal aorta is a common finding in midterm follow-up after FEVAR and not associated with proximal endoleak. Aggressive device oversizing is predictive of dilation, whereas longer seal lengths are associated with less dilation along the suprarenal seal zone. These results support the continued use of FEVAR for juxtarenal aneurysms, particularly in patients in whom ≥3 cm of healthy seal length can be obtained.

FJVIS 17. Quantification of Suprarenal Aortic Neck Dilation After Fenestrated Endovascular Aneurysm Repair

Suprarenal aortic neck dilation (AND) after fenestrated endovascular aneurysm repair (FEVAR) has not yet been characterized. The aim of this study was to measure diameter changes in the juxtavisceral aorta after FEVAR. This is a single-center retrospective review involving patients with pararenal or juxtarenal aneurysms treated with Cook ZFEN devices (Cook, Bloomington, Ind). Patients with at least 1 year of radiologic follow-up were included. Aortic diameter, defined as the average outer-to-outer diameter on three-dimensional centerline imaging, was measured at seven locations along the length of the ZFEN device from the proximal fixation struts to the bottom of the second seal stent (Fig, left). The first postoperative computed tomography scan (≤1 month) served as a baseline with which subsequent measurements at annual intervals were compared. A total of 43 patients who underwent FEVAR met inclusion criteria, with a total of 119 target vessels (83 renal stents, 41 superior mesenteric artery scallops or large fenestrations). Median follow-up time was 30.3 months. AND at latest follow-up was found to occur at all measured locations from the top of the fixation struts (1.9 ± 2.4 mm; P < .001) to the bottom of the first seal stent (3.4 ± 3.3 mm; P < .001). AND was most pronounced in the middle of the first seal stent, with mean AND of 3.6 ± 3.2 mm (Fig). At this location, aortic diameter was found to increase at each interval compared with the baseline scan (mean, 1.4 mm/y). Aortic diameter did not significantly change along the second seal stent (−1.8 to +1.3 mm; P = .08-.1). AND ≥3 mm at any location was found to occur in 32 (74.4%) patients. Increasing device oversizing relative to the native visceral aorta was the strongest predictor of AND (0.34 mm per 10% increase in oversizing; P = .007), whereas increasing length of the seal zone was protective of AND (−1.97 mm per 10-mm increase in seal length; P = .023). Seal lengths ≥3 cm were associated with less AND compared with <3 cm (2.6 vs 4.9 mm; P = .022). However, type IA endoleak in this cohort was rare (n = 1). Dilation of the suprarenal aorta is a common and benign finding in midterm follow-up after FEVAR. Aggressive device oversizing is predictive of dilation, whereas longer seal lengths are associated with less dilation along the suprarenal seal zone.

A mechanistic model of winter stem diameter dynamics reveals the time constant of diameter changes and the elastic modulus across tissues and species

When freezing occurs in trees in the autumn living cells are able to withstand the rapid dehydration that they experience due to the chemical properties of ice that fills apoplastic spaces. Elasticity and hydraulic permeability of living tissue are important properties influencing the frost tolerance of trees, because of their effects on how rapidly the dehydration occurs. Stem diameter change measurements have been used to quantify these tissue properties during the summer, but no such attempt has yet been made during winter when the apoplast is frozen. Here the dynamics of xylem, phloem and whole stem diameter changes for three tree species were simulated by formulating a mechanistic model using temperature of ice as a driver for water exchange between symplast and apoplast in accordance with theory of extracellular freezing. Hence in our model formulation, a decrease in the temperature of the apoplastic ice leads to a decrease in the apoplastic water potential drawing water from the living cells, which could be also observed in diameter change measurements in the field. The model was successful in explaining diameter changes in the case of all tree species when modelled diameter changes were fitted against measured diameter changes. Estimates for the elastic modulus, the time constant of diameter changes and the hydraulic permeability at tissue level were obtained by the fitting of three model parameters. The elastic modulus of the living tissue was found to exhibit a negative temperature dependency, while the time constant of diameter changes was found to exhibit a positive temperature dependency. Overall, this modelling approach offers an easy and non-destructive way of gaining valuable information about physiological properties of trees and their tissues in the winter. However, a complete understanding of the parameters estimated by the model requires further investigation into the physical processes that result in winter diameter changes.

Role of NADPH oxidases in TRPV4‐mediated vasodilation of human arterioles

NADPH oxidases (NOXs) are a major source of reactive oxygen species (ROS) in the vascular system and play diverse roles in cardiovascular health and disease. We recently reported that H2O2, a diffusible ROS, regulates protein phosphorylation of endothelial transient receptor potential vanilloid 4 (TRPV4) channels and TRPV4‐mediated vasodilation in human coronary arterioles (HCA) from subjects with coronary artery disease (CAD). The endogenous source of H2O2 involved in TRPV4 regulation remains unclear. In this study, we investigated the expression of different NOX isoforms in human arterioles and their potential role in the regulation of TRPV4‐mediated arteriolar dilation.Human adipose arterioles (HAA) and HCA were dissected from fresh adipose and heart tissues obtained as discarded surgical specimens. The mRNA and protein expression of NOXs were detected by RT‐PCR and Western blotting. TRPV4 agonist‐induced vasodilation was examined in cannulated arterioles (100–200 μm internal diameter at 60 mmHg) by measuring diameter changes using video microscopy.RT‐PCR analysis revealed consistent expression of NOX2 and 4 but low expression of other isoforms (NOX1, 3, and 5) in HAA and HCA. Using endothelium‐intact and denuded arterioles (n=3 tissues/each) as well as freshly isolated endothelial cells and smooth muscle cells (n=2 tissues/each), we further found that NOX2 and 4 are more abundantly expressed in endothelial cells and at a significantly higher level than other NOX isoforms. Consistent with mRNA expression, NOX2 and 4 proteins were detected in HAA and HCA using Western blot analysis. In cannulated arterioles, TRPV4 agonist GSK1016790A (10−9–10−7 M) induced potent and concentration‐dependent dilation in HAA (maximal dilation at 10−7 M, 76±6%, logEC50 −8.0±0.1, n=6) and HCA (maximal dilation, 69±8%, logEC50 −7.9±0.1, n=5). This dilation was significantly reduced by the small molecule NOX2 inhibitor GSK2795039 (1 μM) in both HAA (22±8%, n=6, p&lt; 0.05 vs control) and HCA (22±10%, n=5, p&lt;0.05 vs control). Interestingly, NOX4 inhibitor GKT137831 (1 μM) also significantly reduced the dilation in HAA (maximal dilation at 10−7 M, 18±8% vs. 72±8% in control, n=6, p&lt;0.05). Both NOX2 and 4 inhibitors did not affect sodium nitroprusside (10−10–10−4 M, an endothelium‐independent vasodilator)‐induced dilation in HAA (maximal dilation at 10−4 M, 94±2% with GSK2795039 vs. 94±2% of control, and 96±3% with GKT137831 vs. 97±3% of control, n=4 and 3, respectively).These results indicate that NOX2 and NOX4 represent two main isoforms of NOXs expressed in endothelial cells of human arterioles and play a potentially important role in TRPV4‐mediated endothelium‐dependent vasodilation. Future studies will explore whether the mechanisms of TRPV4 regulation involves NOX2/4‐derived and H2O2‐mediated channel protein phosphorylation or other signaling pathways in endothelial cells.Support or Funding InformationNational Heart, Lung and Blood Institute Grant RO1‐HL 096647This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Optogenetic interrogation of neurovascular coupling in the cerebral cortex of transgenic mice

Objective. We introduce an engineering approach to study spatiotemporal correlations between vasodynamics and the nearby neural activity in open-loop and closed-loop paradigms. Approach. We integrated optogenetic technology with optical coherence tomography to apply spatiotemporal patterns of optical neurostimulation to the cortex of transgenic optogenetic mice and measure blood flow-rate, velocity, and diameter changes of selected middle cerebral artery branches. Main results. The spatiotemporal characteristics of blood flow-rate, velocity, and vessel diameter responses to localized neurostimulation light pulses were measured. It was observed that the location of stimulation relative to the surrounding vascular topology had notable effects on temporal patterns of vasodynamic responses. This effect was studied by creating velocity, flow-rate, and diameter sensitivity maps for selected arteries. Generally, neural stimulation in the vicinity of downstream capillaries of an artery evoked a fast transient increase in the blood flow-rate, velocity, and vessel diameter which was followed by a long-lasting secondary peak-response. The temporal span of the flow-rate response was quasi-linearly proportional to the length of stimulation. When neural stimulation was delivered to the area in the vicinity of one daughter branch of an artery, in other branches, we observed some drop in blood velocity and/or flow-rate and concurring increase of the vessel diameter. To examine the reliability of the coupling between neural activity and regional blood flow, a closed-loop feedback controller was implemented which is capable of maintaining blood flow-rate at any desired level for relatively longer periods by continuously adjusting the width of stimulation pulses. Significance. The proposed approach opens new lines of research with potential applications in understanding the role of different cell types in the cerebrovascular regulatory mechanisms and the study of the adaptive process of angiogenesis in the cerebral cortex. The observation of incoherent responses of vessel diameter, blood flow-rate, and velocity suggests that such detailed information is necessary to obtain an accurate interpretation of the data acquired via hemodynamic based functional imaging techniques.

Relationships between motor patterns and intraluminal pressure in the 3-taeniated proximal colon of the rabbit

Manometry is used worldwide to assess motor function of the gastrointestinal tract, and the measured intraluminal pressure patterns are usually equated with contraction patterns. In the colon, simultaneous pressure increases throughout the entire colon are most often called simultaneous contractions, although this inference has never been verified. To evaluate the relationship between pressure and contraction in the colon we performed high-resolution manometry and measured diameter changes reflecting circular muscle contractions in the rabbit colon. We show that within a certain range of contraction amplitudes and frequencies, the intraluminal pressure pattern faithfully resembles the contraction pattern. However, when the frequency is very high (as in fast propagating contractions in a cluster) the consequent intraluminal pressures merge. When the contraction speed of propagation is very fast (above ~5 cm/s), the resulting pressure occurs simultaneous throughout the colon; hence simultaneous pressure is measured as are caused by fast propagating contractions. The very slow propagating, low amplitude haustral boundary contractions show a very characteristic pattern in spatiotemporal contraction maps that is not faithfully reproduced in the pressure maps. Correct interpretation of pressure events in high-resolution manometry is essential to make it a reliable tool for diagnosis and management of patients with colon motor dysfunction.

Xylem, phloem, and transpiration flows in developing sweet cherry fruit

Flow in the phloem increased in developing sweet cherry, whereas xylem flow continuously decreased resulting in a fruit water potential that was independent from the tree at fruit maturity. Rain cracking of sweet cherry fruit is associated with water uptake through the skin, but probably also through the vasculature of the pedicel. The aim of this study was to quantify the xylem, phloem, and transpiration contributions to the overall water balance of developing sweet cherry fruit. Using linear variable displacement transducers, changes in fruit diameter were monitored in untreated control fruit, fruit whose pedicels had been steam-girdled, and fruit whose pedicels had been cut through (these fruits were detached, but remained in situ in the canopy). Fruit volume changes with time were inferred from the measured diameter changes. Pedicel xylem and phloem sap-flow rates, and fruit transpiration rates, were inferred from fruit volume changes. Daily phloem flows were low during stage II (phase of pit development), but markedly increased in stage III (phase of cell enlargement in flesh). Xylem flows exceeded phloem flows in stage II, but decreased continuously in stage III to nearly zero at harvest. Transpiration flow essentially mirrored xylem flow in stage II, but exceeded xylem flow in stage III. Transpiration flow was closely related to the water vapour pressure deficit. Phloem flow was linearly related to the increase in fruit dry mass per-unit time. The data reveal a decrease in xylem sap flow throughout stage III resulting in a water-potential isolation of the mature fruit from the tree. Such isolation would prevent uncontrolled osmotic uptake of xylem water by the sugary flesh and a putative backflow in the xylem from fruit to tree.

1A24 浸透圧溶血過程における赤血球径変化の光学計測と血球損傷度評価への応用

Hemolysis test of medical devices is a test to investigate the blood compatibility of the devices. This test has a potential problem that the test results depend on the initial quality of the blood used for the test. We have proposed a simple and rapid optical method to assess the fragility of the blood cells contained in the test blood. When the blood cells are exposed to low osmotic pressure, damaged cells collapse faster than normal cells. Therefore the fragility of cells can be estimated from the change speed of the optical properties of the cells. The proposed method has enabled fast screening. In this study, we focused on the very early stage of the osmotic hemolysis to provide a faster screening method. The new method enables the measurement of diameter change of the cells in swelling process with no calibration.

Induced nanoscale changes with low temperature annealing inside composite optical fibres probed by strain-insensitive long period gratings

Nanoscale glass milling with mild thermal annealing is proposed and shown to occur within a tri-material composite optical fibre. Evidence of glass relaxation with annealing is inferred directly through measured diameter changes in the core and inner cladding of the long period gratings (LPGs) (Δϕcore = (0.13 ± 0.05) μm; Δϕinner cladding = -(0.5 ± 0.2) μm) using scanning electron microscopy (SEM) before and after annealing at T ~300 °C for 1 hour. Large reductions in the magnitudes of both the temperature and strain coefficients are observed after annealing. The temperature sensitivity drops from dλ/dT = -(111.2 ± 2.4) pm/K to dλ/dT = (1.3 ± 0.3) pm/K and the strain sensitivity decreases from dλ/de = -(0.11 ± 0.13) pm/μe to dλ/de = (0.02 ± 0.11) pm/μe. The fabrication of LPGs using 193 nm radiation is shown to produce measurable increases in the core dimensions within tri-material composite fibres whereas no changes are observed under similar conditions for commercial bi-material single mode fibre.

Effects of dynamic shear and transmural pressure on wall shear stress sensitivity in collecting lymphatic vessels.

Given the known mechanosensitivity of the lymphatic vasculature, we sought to investigate the effects of dynamic wall shear stress (WSS) on collecting lymphatic vessels while controlling for transmural pressure. Using a previously developed ex vivo lymphatic perfusion system (ELPS) capable of independently controlling both transaxial pressure gradient and average transmural pressure on an isolated lymphatic vessel, we imposed a multitude of flow conditions on rat thoracic ducts, while controlling for transmural pressure and measuring diameter changes. By gradually increasing the imposed flow through a vessel, we determined the WSS at which the vessel first shows sign of contraction inhibition, defining this point as the shear stress sensitivity of the vessel. The shear stress threshold that triggered a contractile response was significantly greater at a transmural pressure of 5 cmH2O (0.97 dyne/cm(2)) than at 3 cmH2O (0.64 dyne/cm(2)). While contraction frequency was reduced when a steady WSS was applied, this inhibition was reversed when the applied WSS oscillated, even though the mean wall shear stresses between the conditions were not significantly different. When the applied oscillatory WSS was large enough, flow itself synchronized the lymphatic contractions to the exact frequency of the applied waveform. Both transmural pressure and the rate of change of WSS have significant impacts on the contractile response of lymphatic vessels to flow. Specifically, time-varying shear stress can alter the inhibition of phasic contraction frequency and even coordinate contractions, providing evidence that dynamic shear could play an important role in the contractile function of collecting lymphatic vessels.

Prolonged Low Flow Reduces Reactive Hyperemia and Augments Low Flow Mediated Constriction in the Brachial Artery Independent of the Menstrual Cycle

Non-invasive forearm ischemia-reperfusion injury and low flow induced vascular dysfunction models provide methods to evaluate vascular function. The role of oestrogen, an endogenous anti-oxidant on recovery from ischemia-reperfusion injury has not been evaluated nor has the impact of prolonged low flow on vascular function been established. Eight healthy women (33±10 yr) attended the lab during the follicular, ovulatory and mid-luteal phases of their menstrual cycles. After 30 minutes of rest, brachial artery vascular function was assessed by ultrasound measurements of diameter changes during 5 minutes of forearm ischemia and 3 minutes after. Subsequently, a 20-minute forearm ischemia period was completed. Further, vascular function assessments were completed 15, 30 and 45 minutes into recovery. Flow-mediated dilation, low-flow-mediated constriction, and reactive hyperaemia proximal to the area of ischemia were determined. Flow-mediated dilation was reduced at 15 minutes of recovery but recovered at 30 and 45 minutes (PRE: 7.1±1.0%, POST15∶4.5±0.6%, POST30∶5. 5±0.7% POST45∶5.9±0.4%, p<0.01). Conversely, low-flow mediated constriction increased (PRE: −1.3±0.4%, POST15: −3.3±0.6%, POST30: −2.5±0.5% POST45: −1.5±0.12%, p<0.01). Reactive hyperaemia was reduced throughout recovery (p<0.05). Data were unaffected by menstrual phase. Prolonged low flow altered vascular function and may relate as much to increased vasoconstriction as with decreased vasodilation. Reductions in anterograde shear and greater retrograde shear likely modulate the brachial artery response, but the reduced total shear also plays an important role. The data suggest substantial alterations in vascular function proximal to areas of ischemia with potential clinical implications following reperfusion.

Distensibility in human veins as affected by 5 weeks of repeated elevations of local transmural pressure

The objectives were to investigate the effects of repeated increments in local intravascular pressure (pressure training; PT) on (1) distensibility in two arm veins, and (2) pain in the arm induced by markedly increased intravascular pressure. Elevation of venous distending pressure (DP) in an arm was induced by placing the subject (n = 8) in a pressure chamber with one arm protruding to the outside via a port in the chamber door, and increasing chamber pressure. During 5 weeks, venous DP in one arm was repeatedly (3 × 40 min/week) increased (65-105 mmHg). Pressure-distension relationships were determined in the brachial and cephalic veins by measuring diameter changes by ultrasonography during stepwise increments in DP to 180 mmHg. In the brachial vein, the diameter change in response to an increase in DP from 30 to 180 mmHg (distensibility) was reduced (P < 0.05) in the pressure-trained arm (11%) compared to that in the control arm before (23%) and after (21%) PT. The cephalic vein showed a similar response with a reduced (P < 0.05) distensibility in the pressure-trained arm (20%) compared to that in the control arm before (29%) and after (25%) PT. At any given DP, arm pain was less (P < 0.05) in the pressure-trained arm than in the control arm before and after PT, presumably reflecting the reduced venous distensibility in the pressure-trained arm. The results support the concept that the distensibility of venous walls adapts to meet the demands imposed by the prevailing local transmural pressures.

A Method for Arterial Diameter Change Measurements Using Ultrasonic B-Mode Data

Arterial diameter change is related to distending blood pressure and is used in estimation of arterial stiffness parameters. A common technique to track the arterial walls is by integration of wall velocities estimated by different methods using cross correlation or tissue Doppler. However, because of the high pulse repetition frequency and the need for separate pulsing sequences, the B-mode image quality is affected. We have previously developed a fast algorithm for direct measurement of lumen diameter using B-mode images. In this study we have improved the technique to be more robust and also implemented measurements of diameter change, maximum differential wall velocity and relative diameter change of the common carotid artery noninvasively in vivo. The influence of the lateral width of the region of interest (ROI; 1 pixel, 0.1 mm, 0.5 mm, 1 mm, 2.5 mm and 5 mm) was evaluated. Using the optimal lateral width (2.5 mm), the systematic and random differences between two consecutive measurements were 21 μm and 105 μm, respectively, for lumen diameter measurement; –7 μm and 39 μm, respectively, for lumen diameter change measurements; –0.2 mm/s and 0.9 mm/s, respectively, for maximum relative wall velocity; and –0.2 % and 0.8 %, respectively, for measurements of the relative diameter change. The coefficient of variation (CV) was 1.9%, 5.2%, 7.9% and 6.0%, respectively. The study indicates that the reproducibility is sufficient for in vivo studies when the width of the ROI is 1.0 mm or wider. (E-mail: magnus.cinthio@elmat.lth.se)

High Salt Diet –Induced Afferent Arteriolar Autoregulatory Dysfunction is Improved by Acute Antioxidant Treatment

High salt (HS) diet reduces myogenic reactivity in resistance arteries and autoregulatory responses of afferent arterioles. Oxidative stress is increased in HS rats. We tested the hypothesis that HS blunts autoregulatory behavior by stimulating accumulation of reactive oxygen species. Rats were fed a normal (NS, 0.4% NaCl) or HS (8% NaCl) diet for a period of 14 days. Baseline arteriolar diameter was similar between the NS and HS groups. Autoregulatory behavior was assessed by measuring diameter changes during step‐wise 15 mmHg increases in perfusion pressure from 65 to 170 mmHg. In NS kidneys, afferent arteriolar diameter decreased by 34 ± 2% (n=6) as perfusion pressure increased from 65 to 170 mmHg. In HS kidneys arteriolar diameter decreased by 6 ± 4% (P &lt; 0.05; n = 8) indicating markedly attenuated pressure induced vasoconstriction. Acute exposure to Tempol (1.0 mM) in the superfusate had no effect on the autoregulatory response in NS rats but markedly improved autoregulation in the HS group. Increasing perfusion pressure from 65 to 170 mmHg in NS kidneys decreased afferent diameter by 32 ± 3% (n=3), whereas diameter decreased by 28 ± 3% (n=6) in kidneys from HS rats exposed to Tempol. These data indicate that reactive oxygen species blunt autoregulatory efficiency in kidneys from HS rats facilitating enhanced excretion of salt by buffering autoregulatory control of glomerular hemodynamics.

Incorporation of Hydroxyapatite Sol Into Collagen Gel to Regulate the Contraction Mediated by Human Bone Marrow-Derived Stromal Cells

In this paper, hydroxyapatite (HA) sol composed of nanosized HA particles was incorporated into collagen gel to regulate cell-mediated collagen contraction. Human bone marrow derived stromal cells (hMSCs) were cultured for 37 days in gels with HA to collagen ratios of 0:1, 0.5:1, 1:1, 1.5:1, and 2:1, respectively. The contraction of gels was evaluated by measuring diameter change with incubation time, and the microstructure of gels at the end of culture was visualized by SEM. The cytotoxicity of HA sol was evaluated according to the percentage of maximum lactate dehydrogenase (LDH) release from hMSCs. A combination of Hoechst 33342, propidium iodide, and calcein esters was used for imaging the live/dead cells and the distribution of loaded cells within the constructs. By incorporating HA sol into the collagen gel, the hMSCs medicated contraction was delayed and the extent of contraction was reduced as the proportion of HA relative to the collagen increased. Depending on the ratio of HA sol incorporated within the collagen gel, hMSC cells revealed different morphology and a change in the distribution of loaded cells within the gels. No significant cytotoxicity was noticed as a consequence of incorporating HA sol into the collagen lattice.