Microvascular Dysfunction in Peripheral Artery Disease: Is Heat Therapy a Viable Treatment?

Peripheral artery disease (PAD) is characterized by the development of atherosclerotic plaques in the lower-body conduit arteries. PAD is commonly accompanied by microvascular disease, which may result in poor wound healing, plantar ulcer development, and subsequent limb amputation. Understanding the mechanisms underlying the development of plantar ulcers is a critical step in the development of adequate treatment options for patients with PAD. Skin is classified into two major components: glabrous and non-glabrous. These skin types have unique microcirculation characteristics, making it important to differentiate between the two when investigating mechanisms for plantar ulcer development in PAD. There is evidence for a microcirculation compensatory mechanism in PAD. This is evident by the maintenance of basal microcirculation perfusion and capillary filling pressure despite a reduced pressure differential beyond an occlusion in non-critical limb ischemia PAD. The major mechanism for this compensatory system seems to be progressive vasodilation of the arterial network below an occlusion. Recently, heat therapies have emerged as novel treatment options for attenuating the progression of PAD. Heat therapies are capable of stimulating the cardiovascular system, which may lead to beneficial adaptations that may ultimately reduce fatigue during walking in PAD. Early work in this area has shown that full-body heating is capable of generating an acute cardiovascular response, similar to exercise, which has been suggested as the most efficient treatment modality and may generate adaptations with chronic exposure. Heat therapies may emerge as a conservative treatment option capable of attenuating the progression of PAD and ultimately impeding the development of plantar ulcers

IMPACT OF SEX ON MACROVASCULAR ENDOTHELIAL FUNCTION DURING PROLONGED SITTING WITH A MILD HYPERCAPNIC ENVIRONEMNT

IMPACT OF SEX ON MACROVASCULAR ENDOTHELIAL FUNCTION DURING PROLONGED SITTING WITH A MILD HYPERCAPNIC ENVIORNMENT Andres Benitez-Albiter1, Michael F. Allen1, Elizabeth J. Pekas1, Cody P. Anderson1, and Song-Young Park1 1 - School of Health & Kinesiology University of Nebraska Omaha, Omaha, NE Introduction: Prolonged sitting (PS), defined as sitting for 2+ hours at a time[SYP1] , has been identified as an independent risk factor for cardiovascular disease. It has been well-documented that an acute PS bout can impair macro- and microvascular dysfunction in healthy young individuals. Recently, we reported that PS in mild hypercapnic environments (elevated CO2 concentrations equivalent to crowded areas such as offices or auditoriums) can further exacerbate these impairments in healthy young adults, and these impairments can be partially prevented by intermittent bouts of passive and active leg movements. Office workers are one of the largest sectors of the US workforce, and have been reported to be frequently exposed to PS with mild hypercapnic environments. Therefore, there is a need of study to examine if our previous findings can be seen in office workers. Additionally, it is crucial to investigate if there is any differential contribution of biological sex on these findings. The purpose of this study was to examine the impact of active and passive muscular contraction on macrovascular endothelial function during PS with mild-hypercapnic environment in middle-aged office workers, and further compare potential differences between sex. Methods: Healthy office workers (n=13, 6 males and 7 females, 39±4, 41±9, respectively) participated in three experimental visits and consisted of 2.5 h of prolonged sitting in a mild-hypercapnic environment (CO2 = 1500 ppm): control (CON, no movement), passive (PASS, passive limb movement), and active (ACT, active limb movement). Brachial artery and popliteal artery endothelial function were measured pre- and post-sitting for all visits using flow-mediated dilation (FMD). Results: Following 2.5 h of sitting, ACT showed greater popliteal artery FMD compared to CON. Additionally, females exhibited a significant reduction in popliteal artery FMD in the CON but was preserved in males after PS. No changes in Brachial artery FMD after PS, and no sex difference was found. Conclusion: PS significantly reduces leg vascular function in middle-aged office workers. Additionally, females showed greater reduction in leg vascular function compared to males. We conclude that uninterrupted prolonged sitting may induce a greater impairment on leg vascular function in females, indicating that this population may be at a greater risk compared to males. Additionally, intermittent bouts of active movement required to preserve leg vascular function during bouts of PS

IMPACT OF PASSIVE LEG MOVEMENT ON LOWER LIMB VASCULAR FUNCTION IN PATIENTS WITH A SPINAL CORD INJURY

Background: Individuals with spinal cord injuries (SCI) are at a greater risk for developing cardiovascular diseases. Of note, post injury mediated increases in physical inactivity leads to muscle atrophy, which also results in vascular dysfunction in this population. Although a growing body of evidence suggests that passive leg movement (PLM) may be a useful exercise modality to improve peripheral blood flow and skeletal muscle activation in individuals with limited mobility, few studies have examined the impact of PLM on local skeletal muscle blood flow. Therefore, there is a need to examine the impact of PLM on lower limb vascular function and skeletal muscle oxygen utilization capacity in patients with SCI. Methods: Individuals with SCI (n=2) and healthy age-matched controls (CON, n=5) were recruited for this study. Participants were fitted with a standard knee brace and were instructed to rest in the seated position for 20 minutes with their legs bent at 90. PLM was performed by flexion and extension of the lower leg (90-180) at a rate of 1 Hz (60 bpm) for 5 minutes. A Doppler ultrasound was located on the superficial femoral artery, and blood flow and diameter were measured for 5 minutes at rest and during the PLM protocol. Following the PLM protocol, the leg was held in the extended position (180) for 5 minutes of recovery. Results: We found that the SCI group had a significantly lower blood flow response to PLM compared to the CON group (p=0.004). Furthermore, post-PLM femoral artery blood velocity and shear rate significantly increased in both SCI and CON compared to pre-PLM (p=0.014, and p=0.016, respectively) but no differences were found between groups. Finally, the SCI group had significantly smaller vessel diameters compared with CON (pConclusion: We found that PLM could efficiently increase blood flow and blood velocity in SCI. Although the magnitude of this increase was significantly lower in SCI compared to healthy age-matched control, PLM produced shear rates in the leg arteries that were similar between SCI and CON, which indicates that PLM may potentially be an efficient exercise modality to improve leg vascular function in individuals with SCI

Optimal search strategies for hidden targets

What is the fastest way of finding a randomly hidden target? This question of general relevance is of vital importance for foraging animals. Experimental observations reveal that the search behaviour of foragers is generally intermittent: active search phases randomly alternate with phases of fast ballistic motion. In this letter, we study the efficiency of this type of two states search strategies, by calculating analytically the mean first passage time at the target. We model the perception mecanism involved in the active search phase by a diffusive process. In this framework, we show that the search strategy is optimal when the average duration of "motion phases" varies like the power either 3/5 or 2/3 of the average duration of "search phases", depending on the regime. This scaling accounts for experimental data over a wide range of species, which suggests that the kinetics of search trajectories is a determining factor optimized by foragers and that the perception activity is adequately described by a diffusion process.Comment: 4 pages, 5 figures. to appear in Phys. Rev. Let

Endothelial cell Nrf2-KO attenuates endothelial function and skeletal muscle antioxidant capacity

INTRODUCTION: Endothelial cells line the inner surface of blood vessels and play a major role in modulating blood flow and gas exchange. Endothelial dysfunction is thought to be a contributor to cardiovascular disease development, and it is well-accepted that excessive reactive oxygen species (harmful molecules) likely contribute to endothelial dysfunction. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) is considered the master regulator of cellular protection in response to elevated reactive oxygen species. Therefore, Nrf2 may be a potential therapeutic target to protect against endothelial dysfunction. However, the roles of endothelial cell-specific Nrf2 on endothelial function are not known. The purpose of this study was to investigate the impacts of endothelial cell-specific Nrf2 deletion on vascular function (endothelium-dependent and endothelium-independent vasodilation) and skeletal muscle antioxidant status. METHODS: Leg arteries were harvested from 6-mo old C57BL/6 mice (WT, n = 6) and endothelial cell-specific Nrf2-knockout mice (Tie2-Cre-Nrf2 floxed-KO, n = 6). Endothelium-dependent vasodilation was assessed in response to flow (30 uL·min-1) and acetylcholine (ACh, 10-7-10-3 M) with and without Nω-Nitro-L-arginine methyl ester (L-NAME), and endothelium-independent vasodilation was assessed with sodium nitroprusside (SNP, 10-9-10-4 M) using videomicroscopy. Skeletal muscle antioxidant protein expression for glutathione peroxidase-1 (GPX-1) and catalase (CAT) was assessed by immunoblotting. RESULTS: Endothelium-dependent vasodilation was lower in Nrf2-KO compared to WT induced by flow (WT: 34.8±2.9%, Nrf2-KO: 20.7±3.7%, P-3M, WT: 68.3±8.2%, Nrf2-KO: 44.5±7.1%, PP-3 M, 19.1±4.4%, PP=0.28) or ACh (10-3 M, 37.7±7.0%, P = 0.16). Endothelium-independent vasodilation was not different (SNP 10-4 M, WT: 92.7±3.6%, Nrf2-KO: 81.9± 0.2%, P=0.157). In addition, GPX-1 was lower in Nrf2-KO mice (WT: 0.47±0.06, Nrf2-KO: 0.001±0.003, PP=0.08). CONCLUSIONS: Endothelial cell Nrf2 may play a key role in endothelial-mediated vasodilatory function. The nitric oxide synthase inhibitor L-NAME attenuated endothelial-mediated vasodilation in WT but not in endothelial cell Nrf2-KO. Furthermore, endothelial cell Nrf2 may play a role in skeletal muscle antioxidant homeostasis, which suggests potential systemic implications of endothelial cell Nrf2 deletion. These results collectively suggest that the endothelial cell Nrf2 system is linked to endothelial dysfunction and changes in the skeletal muscle redox environment, likely through nitric oxide- and oxidative stress-related mechanisms

Effective fisheries management instrumental in improving fish stock status

Marine fish stocks are an important part of the world food system and are particularly important for many of the poorest people of the world. Most existing analyses suggest overfishing is increasing, and there is widespread concern that fish stocks are decreasing throughout most of the world. We assembled trends in abundance and harvest rate of stocks that are scientifically assessed, constituting half of the reported globalmarine fish catch. For these stocks, on average, abundance is increasing and is at proposed target levels. Compared with regions that are intensively managed, regions with less-developed fisheries management have, on average, 3-fold greater harvest rates and half the abundance as assessed stocks. Available evidence suggests that the regions without assessments of abundance have little fisheries management, and stocks are in poor shape. Increased application of area-appropriate fisheries science recommendations and management tools are still needed for sustaining fisheries in places where they are lacking.Fil: Hilborn, Ray. University of Washington; Estados UnidosFil: Amoroso, Ricardo Oscar. University of Washington; Estados UnidosFil: Anderson, Christopher M.. University of Washington; Estados UnidosFil: Baum, Julia K.. University of Victoria; CanadáFil: Branch, Trevor A.. University of Washington; Estados UnidosFil: Costello, Christopher. University of California at Santa Barbara; Estados UnidosFil: de Moor, Carryn L.. University of Cape Town; SudáfricaFil: Faraj, Abdelmalek. Einstitut National de Recherche Halieutique; MarruecosFil: Hively, Daniel. University of Washington; Estados UnidosFil: Jensen, Olaf P.. Rutgers University; Estados UnidosFil: Kurota, Hiroyuki. Japan Fisheries Research and Education Agency; JapónFil: Little, L. Richard. Csiro Oceans and Atmosphere; AustraliaFil: Mace, Pamela. Ministry for Primary Industries; Nueva ZelandaFil: McClanahan, Tim. Wildlife Conservation Society; Estados UnidosFil: Melnychuk, Michael C.. University of Washington; Estados UnidosFil: Minto, Cóilín. Galway-Mayo Institute of Technology; IrlandaFil: Osio, Giacomo Chato. Joint Research Centre (JRC); Italia. DG Maritime Affairs and Fisheries, European Commission; BélgicaFil: Pons, Maite. University of Washington; Estados UnidosFil: Parma, Ana María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Segurado, Susana. Sustainable Fisheries Partnership; Estados UnidosFil: Szuwalski, Cody S.. University of California at Santa Barbara; Estados UnidosFil: Wilson, Jono R.. University of California at Santa Barbara; Estados Unidos. The Nature Conservancy; Estados UnidosFil: Ye, Yimin. Food and Agriculture Organization of the United Nations; Itali

Black liquor and the hangover effect: fish assemblage recovery dynamics following a pulse disturbance

Anthropogenic perturbations impact aquatic systems causing wide-ranging responses, from assemblage restructuring to assemblage recovery. Previous studies indicate the duration and intensity of disturbances play a role in the dynamics of assemblage recovery. In August 2011, the Pearl River, United States, was subjected to a weak black liquor spill from a paper mill which resulted in substantial loss of fish in a large stretch of the main channel. We quantified resilience and recovery of fish assemblage structure in the impacted area following the event. We compared downstream (impacted) assemblages to upstream (unimpacted) assemblages to determine initial impacts on structure. Additionally, we incorporated historic fish collections (1988–2011) to examine impacts on assemblage structure across broad temporal scales. Based on NMDS, upstream and downstream sites generally showed similar assemblage structure across sample periods with the exception of the 2 months postdischarge, where upstream and downstream sites visually differed. Multivariate analysis of variance (PERMANOVA) indicated significant seasonal variation among samples, but found no significant interaction between impacted and unimpacted assemblages following the discharge event. However, multivariate dispersion (MVDISP) showed greater variance among assemblage structure following the discharge event. These results suggest that 2 months following the disturbance represent a time period of stochasticity in regard to assemblage structure dynamics, and this was followed by rapid recovery. We term this dynamic the “hangover effect” as it represents the time frame from the cessation of the perturbation to the assemblage's return to predisturbance conditions. The availability and proximity of tributaries and upstream refugia, which were not affected by the disturbance, as well as the rapid recovery of abiotic parameters likely played a substantial role in assemblage recovery. This study not only demonstrates rapid recovery in an aquatic system, but further demonstrates the value of continuous, long-term, data collections which enhance our understanding of assemblage dynamics.Ye

Variability and associated uncertainty in image analysis for soiling characterization in solar energy systems

The accumulation of soiling on photovoltaic modules and on the mirrors of concentrating solar power systems causes non-negligible energy losses with economic consequences. These challenges can be mitigated, or even prevented, through appropriate actions if the magnitude of soiling is known. Particle counting analysis is a common procedure to characterize soiling, as it can be easily performed on micrographs of glass coupons or solar devices that have been exposed to the environment. Particle counting does not, however, yield invariant results across institutions. The particle size distribution analysis is affected by the operator of the image analysis software and the methodology utilized. The results of a round-robin study are presented in this work to explore and elucidate the uncertainty related to particle counting and its effect on the characterization of the soiling of glass surfaces used in solar energy conversion systems. An international group of soiling experts analysed the same 8 micrographs using the same open-source ImageJ software package. The variation in the particle analyses results were investigated to identify specimen characteristics with the lowest coefficient of variation (CV) and the least uncertainty among the various operators. The mean particle diameter showed the lowest CV among the investigated characteristics, whereas the number of particles exhibited the largest CV. Additional parameters, such as the fractional area coverage by particles and parameters related to the distribution's shape yielded intermediate CV values. These results can provide insights on the magnitude inter-lab variability and uncertainty for optical and microscope-based soiling monitoring and characterization

µChemLab: twenty years of developing CBRNE detection systems with low false alarm rates

Gas Chromatography (GC) is routinely used in the laboratory to temporally separate chemical mixtures into their constituent components for improved chemical identification. This paper will provide a overview of more than twenty years of development of one-dimensional field-portable micro GC systems, highlighting key experimental results that illustrate how a reduction in false alarm rate (FAR) is achieved in real-world environments. Significantly, we will also present recent results on a micro two-dimensional GC (micro GCxGC) technology. This ultra-small system consists of microfabricated columns, NanoElectroMechanical System (NEMS) cantilever resonators for detection, and a valve-based stop-flow modulator. The separation of a 29-component polar mixture in less than 7 seconds is demonstrated along with peak widths in the second dimension ranging from 10-60 ms. For this system, a peak capacity of just over 300 was calculated for separation in about 6 s. This work has important implications for field detection, to drastically reduce FAR and significantly improve chemical selectivity and identification. This separation performance was demonstrated with the NEMS resonator and bench scale FID. But other detectors, suitably fast and sensitive can work as well. Recent research has shown that the identification power of GCxGC-FID can match that of GC-MS. This result indicates a path to improved size, weight, power, and performance in micro GCxGC systems outfitted with relatively non-specific, lightweight detectors. We will briefly discuss the performance of possible options, such as the pulsed discharge helium ionization detector (PDHID) and miniature correlation ion mobility spectrometer (mini-CIMS)