Maximal Dilation Research Articles

Resolvent estimates and smoothing for homogeneous partial differential operators on graded Lie groups

ABSTRACTBy using commutator methods, we show uniform resolvent estimates and obtain globally smooth operators for self-adjoint injective homogeneous operators H on graded groups, including Rockland operators, sublaplacians, and many others. Left or right invariance is not required. Typically the globally smooth operator has the form T = V|H|1∕2, where V only depends on the homogeneous structure of the group through Sobolev spaces, the homogeneous dimension and the minimal and maximal dilation weights. For stratified groups improvements are obtained, by using a Hardy-type inequality. Some of the results involve refined estimates in terms of real interpolation spaces and are valid in an abstract setting. Even for the commutative group ℝN some new classes of partial differential operators are treated.

Intrinsic 3D Dynamic Surface Tracking based on Dynamic Ricci Flow and Teichmüller Map.

3D dynamic surface tracking is an important research problem and plays a vital role in many computer vision and medical imaging applications. However, it is still challenging to efficiently register surface sequences which has large deformations and strong noise. In this paper, we propose a novel automatic method for non-rigid 3D dynamic surface tracking with surface Ricci flow and Teichmüller map methods. According to quasi-conformal Teichmüller theory, the Techmüller map minimizes the maximal dilation so that our method is able to automatically register surfaces with large deformations. Besides, the adoption of Delaunay triangulation and quadrilateral meshes makes our method applicable to low quality meshes. In our work, the 3D dynamic surfaces are acquired by a high speed 3D scanner. We first identified sparse surface features using machine learning methods in the texture space. Then we assign landmark features with different curvature settings and the Riemannian metric of the surface is computed by the dynamic Ricci flow method, such that all the curvatures are concentrated on the feature points and the surface is flat everywhere else. The registration among frames is computed by the Teichmüller mappings, which aligns the feature points with least angle distortions. We apply our new method to multiple sequences of 3D facial surfaces with large expression deformations and compare them with two other state-of-the-art tracking methods. The effectiveness of our method is demonstrated by the clearly improved accuracy and efficiency.

Endoscopic Balloon Dilation Size and Avoidance of Surgery in Stricturing Crohn's Disease.

Endoscopic balloon dilation (EBD) is an effective method for treating stricture-related obstruction in Crohn's disease. We aimed to identify factors predictive of successful avoidance of surgery, including endoscopic features, in patients undergoing balloon dilation. We performed a retrospective review of patients with symptomatic Crohn's disease-related intestinal strictures undergoing EBD. Clinical, medication use, laboratory, and dilation data, including the minimum and maximum balloon sizes used, and number of balloons used per endoscopic session were collected. Multivariate analysis by Cox proportional hazard regression was used to model future surgical bowel resection. In a total of 135 subjects undergoing 292 dilations, multivariate modeling demonstrated that failure to achieve a maximum dilation of 14 mm or more increased the risk of surgery (hazard ratio [HR] 2.88, 95% confidence limit [CL], 1.10-7.53). Although there was no difference in the risk of future surgery between maximum EBD sizes of 14 to 15 mm and 16 to 18 mm, those reaching 16 to 18 mm exhibited a longer interval between subsequent dilations (mean 240 ± 136.7 versus 456 ± 357.3 d, respectively, P = 0.023). Endoscope passage at index dilation was not predictive of future surgery (HR 0.63, 95% CL, 0.31-1.26). Adjusting for covariates of EBD size, stricture location and type, a C-reactive protein >1.5 mg/dL (HR 2.60, 95% CL, 1.12-5.94), and anti-tumor necrosis factor initiation after index EBD (HR 2.39, 95% CL, 1.09-5.25) increased the risk of future surgery. Although dilation calibers larger than 14 to 15 mm were not more protective against future surgery, those reaching 16 to 18 mm underwent maintenance dilation less frequently. The risk of surgery associated with post-EBD anti-tumor necrosis factor initiation suggests that effective therapy is often used too late in the disease course.

Pupil Dynamics Induced by Light Reflex After Posterior Chamber Phakic Intraocular Lens Implantation.

To assess the light reflex of the pupil after Implantable Collamer Lens (ICL) (KS-aquaPORT; STAAR Surgical, Nidau, Switzerland) implantation to determine whether the ICL implantation might affect the pupil dynamics. This study examined 28 eyes of 28 consecutive patients who underwent implantation of the posterior phakic ICL for the correction of myopia and astigmatism. Patient age at the time of surgery was 31.1 ± 6.8 years (range: 25 to 42 years). Preoperative refraction was -7.38 ± 2.26 diopters (D) (range: -3.25 to -11.80 D). Light reflex was evaluated using the infrared pupillometer Iriscorder C7364 (Hamamatsu Photonics, Hamamatsu, Japan). Measured parameters included pupil diameter (D1), constriction ratio, maximum constriction velocity, maximum dilation velocity, and the time required to recover 63% of the pupil diameter (T5). At 6 months postoperatively, the authors also investigated the relationship with the amount of vault using the Pentacam (Oculus Optikgeräte, Wetzlar, Germany). Evaluations with the instrument were performed before and at 1, 3, and 6 months after surgery. There was no significant association found between any of the parameters (analysis of variance, D1: P = .99, constriction ratio: P = .59, maximum constriction velocity: P = .87, maximum dilation velocity: P = .13, T5: P =.57). The vault of the ICL at 6 months postoperatively was 382.1 ± 176.5 μm. There were no significant associations between the maximum constriction velocity, maximum dilation velocity, and amount of vaulting (Spearman correlation coefficient maximum constriction velocity: r = 0.07, P = .71, maximum dilation velocity: r = 0.26, P = .28). The light reflex of the pupillary dynamics continued to be maintained at 6 months after ICL implantation. Current findings also verified that ICL implantation had little influence on the postoperative function of the iris. [J Refract Surg. 2017;33(10):704-707.].

Changes in vasodilation following myocardial ischemia/reperfusion in rats

BackgroundBlockage of a coronary artery, usually caused by arteriosclerosis, can lead to life threatening acute myocardial infarction. Opening with PCI (percutaneous coronary intervention), may be lifesaving, but reperfusion might exacerbate the cellular damage, and changes in the endothelium are believed to be involved in this worsened outcome. AimThe aim of the present study was to compare endothelial dependent and independent vasodilatory effect after experimental myocardial ischemia/reperfusion (I/R). MethodsA well-established rat model of myocardial ischemia with 24 h of reperfusion was applied, followed by a study in a wire myograph. ResultsEndothelial NO dependent relaxation in response to carbachol, was sensitive to arterial depolarization, and was unaffected by I/R. In contrast, endothelial NO dependent ADPβS signalling, which was not sensitive to arterial depolarization, was significantly reduced after I/R. Following I/R, an H2O2 dependent EDH induced dilation appears in response to both of the above agonists. In addition, calcitonin gene-related peptide (CGRP) induced vasodilation was reduced. ConclusionThese data show that NO dependent ADPβS induced dilation is reduced after I/R. However, there is some compensation by released H2O2 causing an EDH. Combined with a loss of maximal dilation in response to CGRP, the reduced vasodilation could be an important factor in understanding the exacerbated damage after I/R.

Abstract P156: Estrogen Regulation of Endothelin-B Receptor Mediated Vasodilation

Our laboratory has recently demonstrated that a loss of endothelin-B (ETB) receptor mediated dilation contributes to impaired vasodilatory function in postmenopausal women. It is unclear if these changes are due to aging, or alterations in ovarian hormones that occur after menopause. The purpose of this study was to test the hypothesis that in a low estradiol state, there is a loss of ETB mediated dilation, and that estradiol administration reverses these responses and mediates dilation. Methods: We tested 8 young women (YW: 24±2 years, 23±1 kg/m 2 , mean arterial BP 84±2mHg) and 6 postmenopausal women (PMW: 56±1 years, 24±1 kg/m 2 , mean arterial BP 94±2mHg). In YW, we suppressed endogenous ovarian hormone production with daily gonadotropin-releasing hormone antagonist (GnRHant; Ganirelix) administration for 10 days, adding estradiol (E2, 0.1 mg/day, Vivelle dot patch) on days 4-10. PMW were tested at baseline and after 1-week E2 administration (0.1 mg/day, Vivelle dot patch). We measured nitric-oxide mediated vasodilation in the cutaneous circulation during local heating (42°C) via laser Doppler flowmetry, followed by microdialysis perfusions of sodium nitroprusside (28mM) with local heating to 43°C to elicit maximal dilation. Cutaneous vascular conductance (CVC) was calculated as cutaneous blood flow/mean arterial blood pressure, and expressed as a percent of maximal dilation. Results: ETB receptor blockade increased vasodilation in YW during hormone suppression with GnRHant (control: 88±3 vs. BQ-788: 94±2 CVC %max, P <0.05). However, ETB receptor blockaded tended to reduce vaodilation during E2 administration (control: 88±3 vs. BQ-788: 82±2 CVC %max, P =0.12). In PMW, ETB receptor blockade had no significant effect on vasodilatory responses (control: 90±4 vs. BQ-788: 95±2 CVC %max, P =0.20). Similarly, ETB receptor blockade did not alter vasodilation after E2 administration (control: 88±7 vs. BQ-788: 88±4 CVC %max). Conclusions: These preliminary data suggest that suppression of endogenous ovarian hormone production alters ETB receptor responses in young women, which is partially mediated by E2. Additional data are needed to determine ETB receptor sensitivity to E2 after menopause.

Small Bowel Dilatation Predicts Prolonged Parenteral Nutrition and Decreased Survival in Pediatric Short Bowel Syndrome.

To analyze risk factors and prognostic significance of small bowel (SB) dilatation in children with short bowel syndrome (SBS). In SBS, the remaining SB may dilate as part of intestinal adaptation. The impact of dilatation on parenteral nutrition (PN) dependence and survival has not been studied systematically. SB diameter of SBS children (n = 61) was measured in contrast SB series (n = 169, median age 0.94, range 0.32-2.7 years) during 2002 to 2015, and expressed as millimeters (SB width) and as ratio to L5 vertebra height (SB diameter ratio). Linear regression was used to examine risk factors for dilatation. PN weaning and survival were analyzed with Cox proportional hazards regression. Maximal SB diameter ratio during follow-up was predicted by PN dependence and SB atresia, while maximal absolute SB width by birth weight, age, PN duration, and remaining bowel length. Weaning off PN was 14-fold more likely in patients with maximal SB diameter ratio <2.00 compared with >3.00 (P = 0.005), and 5.4-fold more likely when maximal SB width was <20 mm compared with >30 mm (P = 0.023). After adjustment for age, remaining SB length, and the presence of ileocecal valve, both estimates of maximal SB dilatation remained significant independent predictors for weaning off PN. When all measurements were included, the cumulative survival was worse if SB diameter ratio exceeded 2.00 (P = 0.002-0.042). SB dilatation predicts prolonged PN duration and decreased survival in SBS children. Measurement of maximal SB diameter standardized to L5 vertebra height may be a valuable objective tool for patient follow-up and assessment of prognosis.

Aerobic exercise prevents rarefaction of pial collaterals and increased stroke severity that occur with aging

Variation in extent of the brain’s collateral circulation is an important determinant of variation in the severity of stroke and efficacy of revascularization therapies. However, the number and diameter of pial collateral “arterioles” decrease with aging in associated with reduced eNOS and increased oxidative stress. We tested whether exercise reduces this aging-induced rarefaction. Twelve-month-old mice were randomized to sedentary or voluntary wheel-running. At 26 months’ age, permanent MCA occlusion was followed 72 h later by determination of infarct volume and vascular casting after maximal dilation. The decline in collateral number and diameter and 2.4-fold increase in infarct volume evident in 26-versus 3-month-old sedentary mice were prevented by exercise-training. In contrast, number and diameter of the posterior communicating collateral “arteries” were unaffected by aging or exercise. Interestingly, diameter of the primary intracranial arteries increased with aging. Mechanistically, genetic overexpression of eNOS inhibited age-induced collateral rarefaction, and exercise increased eNOS and SOD2 and decreased the inflammatory marker NFkB assessed in hindlimb arteries. In conclusion, exercise prevented age-induced rarefaction of pial collaterals and reduced infarct volume. Aging also promoted outward remodeling of intracranial arteries. These effects were associated with increased eNOS and reduced markers of inflammation and aging in the vascular wall.

Microcirculatory Effects of Botulinum Toxin A in the Rat: Acute and Chronic Vasodilation.

Botulinum toxin-A (BTX) has numerous cosmetic and therapeutic applications. Our previous studies have found that BTX augments pedicled flap survival through both vasodilatory effects and attenuation of the inflammatory response to ischemia in the rat. This study examines the effect of chronic BTX on microcirculatory vascular tone and its response to acute topical vasodilators in muscle flaps. The spinotrapezius muscle of Sprague-Dawley rats underwent a single 2-week pretreatment of 0.2 mL saline either with (n = 5) or without (n = 5) 2u BTX. After surgical elevation, an arcade arteriole was observed using a video caliper device. Vessel diameter was measured at 30-second intervals after sequential superfusion of nitroglycerin (100 and 200 μg/mL), multiple concentrations of lidocaine, and a combination of adenosine (10 μM) and nitroprusside (10 μM) to induce maximum dilation. Baseline and dilation diameters were expressed as ratios of pharmacologically induced maximum dilation, whereas percent dilation was defined as the change in diameter over baseline diameter. We found a significant increase in resting diameter with BTX pretreatment (P = 0.0028). Compared with the control group, mean baseline diameter was 15% greater, and percent dilation was 25% less in BTX-pretreated flaps. There was no significant relationship between BTX pretreatment and dilation diameter (P = 0.2895) after adjusting for the effect of acute vasodilators. Pretreatment with BTX may induce the arteriolar resting diameter to be closer to their maximum potential diameter. Additionally, BTX does not display a synergistic effect with topical vasodilators on vasodilation.

Teichmüller's problem in space

Quasiconformal homeomorphisms of the whole space Rn, onto itself normalized at one or two points are studied. In particular, the stability theory, the case when the maximal dilatation tends to 1, is in the focus. Our main result provides a spatial analogue of a classical result due to Teichmüller. Unlike Teichmüller's result, our bounds are explicit. Explicit bounds are based on two sharp well-known distortion results: the quasiconformal Schwarz lemma and the bound for linear dilatation. Moreover, Bernoulli type inequalities and asymptotically sharp bounds for special functions involving complete elliptic integrals are applied to simplify the computations. Finally, we discuss the behavior of the quasihyperbolic metric under quasiconformal maps and prove a sharp result for quasiconformal maps of Rn∖{0} onto itself.

Efficacy of digital pupillometry for diagnosis of Horner syndrome.

ObjectivesTo evaluate the efficacy of digital pupillometry in the diagnosis of anisocoria related to Horner syndrome in adult patients.DesignRetrospective, observational, case control study.MethodsNineteen patients with unilateral Horner syndrome (Horner group) and age-matched controls of 30 healthy individuals with normal vision and neither optic nerve dysfunction nor pupillary abnormalities were included. Pupillary light reflex (PLR) of the Horner group and controls were measured by a dynamic pupillometer (PLR-200; NeurOptics Inc., Irvine, USA). Minimal and maximal (min/max) pupil diameters, latency, constriction ratio, constriction velocity, dilation velocity, and total time taken by the pupil to recover 75% of maximal pupil diameter (T75) were noted. PLR were measured at baseline in both groups and at 30–45 minutes later after 0.5% apraclonidine (Iopidine®; Alcon Laboratories, Fort Worth, TX, USA) instillation in the Horner group.Main outcome measuresThe PLR parameters in the affected eye and inter-eye difference before and after 0.5% apraclonidine instillation.ResultsIn the Horner group, pupil diameters and T75 showed significant difference between the affected eye and unaffected contralateral eye at baseline (all P<0.00625). Compared to controls, inter-eye difference values of pupil diameters and T75 were significantly larger in the Horner group (all P<0.001). After 0.5% apraclonidine instillation, changes in pupil diameter and constriction ratio were significantly larger in the affected eye compared to the unaffected contralateral eye (all P<0.00625). The area under the receiver operating characteristic curves for diagnosing Horner syndrome were largest for baseline inter-eye difference in min/max pupil sizes (AUC = 0.975, 0.994), T75 (AUC = 0.838), and change in min/max pupil sizes after apraclonidine instillation (AUC = 0.923, 0.929, respectively). The diagnostic criteria for Horner syndrome relying on baseline pupillary measurements was defined as one of the two major findings; 1) smaller maximal pupil diameter in the affected eye with an inter-eye difference of > 0.5 mm, or 2) T75 > 2.61 seconds in the affected eye, which showed a sensitivity of 94.7% and specificity of 93.3%. The diagnostic accuracy of apraclonidine testing showed a sensitivity of 84.6% and specificity of 92.3%.ConclusionsDigital pupillometry is an objective method for quantifying PLR. Baseline inter-eye difference in maximal pupil sizes and dilation lag measured by T75 was equally effective in the diagnosis of Horner syndrome compared to the reversal of anisocoria after apraclonidine instillation.

Strength–dilatancy relation of sand containing non-plastic fines

Bolton's stress–dilatancy equation is mainly used for clean sands. It needs to be investigated whether this equation could be used for sand with non-plastic fines or not. A series of drained triaxial compress tests were conducted for the sand with non-plastic fines. It was observed from these tests that the peak-state and critical-state friction angles increased with increasing the fines content. The peak-state friction angle and maximum dilatancy angle increased with decreasing the confining pressure. It was also found that the relationship between the excess friction angle (i.e. the difference between the peak-state and critical-state friction angles) and maximum dilatancy angle was unchanged with the non-plastic fines content. This has illustrated that the Bolton's stress–dilatancy equation proposed for clean sands could still be applied to sands with non-plastic fines.

Percutaneous pulmonary Melody® valve implantation in small conduits

The Melody® pulmonary valve has received approval for the treatment of dysfunctional right ventricular (RV) outflow tract conduits ≥16mm. To investigate technical and clinical outcomes in patients who underwent percutaneous pulmonary valve implantation (PPVI) in conduits ≤16mm. Eleven patients were enrolled retrospectively between 2000 and 2015 in a cardiac referral centre. The PPVI indications were obstruction (n=5); regurgitation (n=1); and mixed lesions (n=5). Pre-stenting was performed during the procedure in seven cases. Three of the remaining four patients had previous stent implantation. The mean maximal dilatation balloon diameter/surgical initial diameter ratio was 1.3. Procedural haemodynamics showed a decrease in peak RV to pulmonary artery gradient (mmHg) from 50 (14-86) to 11 (5-23) (P<0.001), in RV systolic pressure (mmHg) from 69 (35-110) to 40 (25-50) (P=0.006) and in RV/aortic systolic pressure ratio from 0.8 (0.4-1.0) to 0.4 (0.3-0.6) (P=0.004). Acute device-related complications occurred in four patients (36.4%): two confined conduit tears managed with placement of a covered stent; and two vascular access complications. Mean follow-up after PPVI was 3.9 years (41 days to 6.7 years). At last follow-up, one patient had undergone surgical conduit replacement for recurrent conduit stenosis, one had percutaneous pulmonary valve dilatation and two had developed bacterial endocarditis and undergone surgical conduit replacement. Freedom from valve dysfunction at 1, 2 and 3 years was 91%, 91% and 82%, respectively. PPVI is feasible in small conduits ≤ 16mm with good procedural and early haemodynamic results, postponing the need for surgery. These results are not sustainable over time. Larger studies are needed to determine if bare-metal stent implantation as a bridge to surgical replacement provides the same results in this specific population.

Ten days of repeated local forearm heating does not affect cutaneous vascular function.

The aim of the present study was to determine whether 10 days of repeated local heating could induce peripheral adaptations in the cutaneous vasculature and to investigate potential mechanisms of adaptation. We also assessed maximal forearm blood flow to determine whether repeated local heating affects maximal dilator capacity. Before and after 10 days of heat training consisting of 1-h exposures of the forearm to 42°C water or 32°C water (control) in the contralateral arm (randomized and counterbalanced), we assessed hyperemia to rapid local heating of the skin (n = 14 recreationally active young subjects). In addition, sequential doses of acetylcholine (ACh, 1 and 10 mM) were infused in a subset of subjects (n = 7) via microdialysis to study potential nonthermal microvascular adaptations following 10 days of repeated forearm heat training. Skin blood flow was assessed using laser-Doppler flowmetry, and cutaneous vascular conductance (CVC) was calculated as laser-Doppler red blood cell flux divided by mean arterial pressure. Maximal cutaneous vasodilation was achieved by heating the arm in a water-spray device for 45 min and assessed using venous occlusion plethysmography. Forearm vascular conductance (FVC) was calculated as forearm blood flow divided by mean arterial pressure. Repeated forearm heating did not increase plateau percent maximal CVC (CVCmax) responses to local heating (89 ± 3 vs. 89 ± 2% CVCmax, P = 0.19), 1 mM ACh (43 ± 9 vs. 53 ± 7% CVCmax, P = 0.76), or 10 mM ACh (61 ± 9 vs. 85 ± 7% CVCmax, P = 0.37, by 2-way repeated-measures ANOVA). There was a main effect of time at 10 mM ACh (P = 0.03). Maximal FVC remained unchanged (0.12 ± 0.02 vs. 0.14 ± 0.02 FVC, P = 0.30). No differences were observed in the control arm. Ten days of repeated forearm heating in recreationally active young adults did not improve the microvascular responsiveness to ACh or local heating.NEW & NOTEWORTHY We show for the first time that 10 days of repeated forearm heating is not sufficient to improve cutaneous vascular responsiveness in recreationally active young adults. In addition, this is the first study to investigate cutaneous cholinergic sensitivity and forearm blood flow following repeated local heat exposure. Our data add to the limited studies regarding repeated local heating of the cutaneous vasculature.

Effect of granulated rubber on shear strength of fine-grained sand

Review of the literature related to the mixture of shredded tire and sand shows that, despite of the increase in shear strength due to addition of tire chips, granulated rubber causes reduction in shear strength of sand. In this study, the shear behavior of mixtures of fine-grained sand and 1–5 mm granulated rubber is investigated. Sixty direct shear tests were conducted on sand–granulated rubber mixtures with various rubber contents (0%, 5%, 10%, 20% and 30%) at different relative densities (50%, 70% and 90%) and different normal stresses (34.5 kPa, 54.5 kPa, 74.5 kPa and 104.5 kPa). The obtained results show that the granulated rubber improves the shear strength of fine-grained sand at medium relative density and low normal stress. The degree of improvement in shear strength is a function of rubber content, relative density and normal stress. The results show that at relative density of 50%, by adding 5% granulated rubber, the internal friction angle of sand increases from 35.1° to 39.2°. However, at relative densities of 70% and 90%, addition of granulated rubber to sand decreases its internal friction angle. The results also indicate that the behavior of sand becomes more ductile with increasing granulated rubber content. Adding granulated rubber leads to greater yielding strain and less tangent stiffness of sand. The maximum dilation angle decreases with the decrease in granulated rubber content. The stress ratio of sample at critical state (ψ = 0°) decreases with increasing granulated rubber content.

Abstract 438: Macrophages in a BAPN/AT2 Induced Model of Murine Aneurysm are Predominantly Lyve-1 and Tim-4 Negative

Macrophages are key effector cells in aneurysm progression. Aneurysm macrophages may derive from monocyte recruitment and turnover of resident cells. We tested the hypothesis that aneurysm macrophages have a non-resident (lyve-1/tim-4 negative) phenotype. C57/Bl6 mice were administered beta-aminopropriononitrile (BAPN) and angiotensin-2 (AT2). At four weeks, whole aortas were excised, photomicrographed, and single cell suspensions created for immunophenotyping with flow cytometry. Results were compared to wild-type controls. BAPN/AT2 causes aortic dilatation (p&lt;0.01) with maximal aneurysmal degeneration at the suprarenal aorta (wild-type control aortic diameter 0.93±0.03mm, n=8; BAPN/AT2 2.00±0.10mm, n=23; p&lt;0.0001). BAPN/AT2 significantly increased aortic cd45+ myeloid-lymphoid cells and cd11b+ f4/80+ macrophages (p&lt;0.02). Maximal aneurysm diameter correlated positively with aortic cell numbers of cd45+ myeloid-lymphoid cells (R=0.8168, p&lt;0.001) and macrophages (R=0.5977, p=0.02). In wild-type, aortic macrophages are predominantly lyve-1 positive (67±3%, n=10). Whilst overall macrophage numbers are increased in aneurysm, the percentage of lyve-1 positive macrophages is significantly reduced (40±3%, n=18; p&lt;0.001). The number of lyve-1 negative macrophages (R=0.6875, p=0.02), correlated with maximal suprarenal aortic diameter. In controls and aneurysm, lyve-1 positive, but not lyve-1 negative, macrophages are also tim-4 positive. In a BAPN/AT2 murine aneurysm model, aortic cd45+ myeloid-lymphoid cells and macrophages are increased and cell counts correlate with maximal aortic dilatation. Wild-type murine aortic macrophages are predominantly lyve-1/tim4 positive, with a significant relative increase in lyve-1/tim4 negative macrophages in aneurysm, suggesting lyve-1/tim-4 may indicate a resident macrophage phenotype.

Abstract 460: Intra- and Inter-Day Reproducibility of Low-Flow Mediated Constriction Response in Young Adults

Purpose: When assessing vasomotor endothelial function of the brachial artery by reactive hyperemia, blood flow is stopped and creates a period of low-flow mediated constriction (L-FMC). Little is known about how this parameter influences flow-mediated vasodilation (FMD). The purpose of this study was to better understand this relationship and to determine the intra- and inter-day reproducibility of brachial L-FMC in healthy adults. Methods: Brachial L-FMC and FMD were measured on 26 healthy, young adults (13 males, 13 females; 24.6 ± 2.7 years). Each subject had two assessments conducted on two separate visits, separated by a minimum of seven days. Brachial artery pre-occlusion baseline diameter was imaged during rest and prior to cuff-occlusion. Continuous imaging of the artery was captured during the last 20 seconds of cuff-occlusion to 180 seconds post-cuff release. An L-FMC was considered present if the relative change from pre-occlusion baseline to L-FMC artery diameter was less than -0.1%. Peak FMD was measured as the greatest 10-second average in brachial artery diameter following occlusion compared to pre-occlusion baseline. Results: Overall, there was a strong, positive correlation between increased brachial L-FMC and blunted FMD (visit 1 test 1: r=0.758, p &lt;0.001; visit 1 test 2: r=0.706, p &lt;0.001; visit 2 test 1: r=0.836, p &lt;0.001; visit 2 test 2: 0.857, p &lt;0.001). The reproducibility of intra- and inter-day L-FMC diameter were ICC = 0.627, CV = 54.4% and ICC = 0.734, CV = 43.5%, respectively. Conclusion: The results of the present study suggest that the degree of vasoconstriction to low-flow conditions influences the subsequent maximal dilation during reactive hyperemia. However, L-FMC in young adults is variable as evidenced by the weak inter- and intra-day reproducibility of the measure. Further research is needed to study brachial L-FMC reproducibility among varying subject populations and the implications L-FMC has on the interpretation of FMD results.

Retinal vessel diameters and reactivity in diabetes mellitus and/or cardiovascular disease

BackgroundRetinal vessel calibre and vascular dilation/constriction in response to flicker light provocation may provide a measure distinguishing patients suffering from diabetes mellitus and/or cardiovascular disease.MethodsOne hundred and sixteen age and sex matched patients with diabetes mellitus (DM), cardiovascular disease (CVD) and both DM and CVD (DM + CVD) underwent systemic and intraocular pressure measurements. Retinal vessel calibres were assessed using a validated computer-based program to compute central retinal artery and vein equivalents (CRVE) from monochromatic retinal images. Vessel dilation and constriction responses to flicker light provocation were assessed by continuous retinal vessel diameter recordings. Plasma endothelial markers von Willebrand factor (vWf) and soluble E selectin (sEsel) were measured by ELISA.ResultsRetinal vessel calibres were comparable across groups but CRVE correlated significantly with disease duration in DM patients (r = 0.57, p < 0.001). Patients suffering DM only exhibited reduced arterial vasomotion at rest and reduced arterial constriction following flicker light induced vessel dilation compared to patients with CVD and those suffering both CVD + DM (p = 0.030). Patients suffering from CVD + DM exhibited significant differences between each flicker cycle in regards to arterial maximum constriction (p = 0.006) and time needed to reach arterial maximum dilation (p = 0.004), whereas the other two groups did not show such inconsistencies between individual flicker cycles. vWf was raised in CVD + DM compared to the other two groups (p ≤ 0.02), whilst sEsel was raised in CVD + DM compared to DM alone (p = 0.044).ConclusionsDynamic retinal vascular calibres as obtained by continuous diameter measurements using flicker light provocation can reveal subtle differences between groups suffering from CVD with and without DM. This difference in reaction pattern and lack of arterial constriction in DM may provide a suitable marker to monitor progression.

ETB receptor contribution to vascular dysfunction in postmenopausal women.

Endothelin-1 (ET-1) contributes to age-related endothelial dysfunction in men via the ETA receptor. However, there are sex differences in the ET-1 system, and ETB receptors are modulated by sex hormones. The purpose of this study was to test the hypothesis that ETB receptors contribute to impaired vasodilatory function in postmenopausal women (PMW). We measured flow-mediated dilation (FMD) using ultrasound, and cutaneous nitric oxide-mediated vasodilation during local heating (42°C) via laser Doppler flowmetry in 18 young women (YW; 22 ± 1 yr) and 16 PMW (56 ± 1 yr). Cutaneous microdialysis perfusions of lactated Ringer (control), an ETB receptor antagonist (BQ-788, 300 nM), and an ETA receptor antagonist (BQ-123, 500 nM), were done through separate fibers, followed by perfusions of sodium nitroprusside (28 mM) and local heating to 43°C (max). Cutaneous vascular conductance (CVC) was calculated as cutaneous blood flow/mean arterial pressure and expressed as a percent of maximal dilation. FMD (YW: 7.5 ± 0.5 vs. PMW: 5.6 ± 0.6%) and cutaneous vasodilation (YW: 93 ± 2 vs. PMW: 83 ± 4%CVCmax) were lower in PMW (both P < 0.05). Blockade of ETB receptors decreased cutaneous vasodilation in YW (87 ± 2%CVCmax; P < 0.05 vs. control) but increased vasodilation in PMW (93 ± 1%CVCmax; P < 0.05 vs. control). ETA receptor blockade had minimal effect in YW (92 ± 1%CVCmax) but increased cutaneous vasodilation in PMW (91 ± 2%CVCmax; P < 0.05 vs. control). In conclusion, ETB receptors mediate vasodilation in YW, but this effect is lost after menopause. Impaired vasodilatory function in PMW is due in part to a loss of ETB-mediated dilation.

An exact algorithm for the minimum dilation triangulation problem

Given a triangulation of a point set on the plane, dilation of any pair of the points is the ratio of their shortest path length to their Euclidean distance. The maximum dilation over all pairs of points is called the dilation of this triangulation. Minimum dilation triangulation problem seeks a triangulation with the least possible dilation of an input point set. For this problem no polynomial time algorithm is known. We present an exact algorithm based on a branch and bound method for finding minimum dilation triangulations. This deterministic algorithm after generating an initial solution, iteratively computes a lower bound for the answer and then applies a branch and bound method to find a better solution. It also uses a local search method to improve the initial solution and the obtained solution of the branch and bound method. We implemented our algorithm and conducted computational experiments on some benchmark instances. The efficacy of the approach is demonstrated by comparing its results with two other published methods.