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  1. Cerebrovascular dysfunction and microcirculation rarefaction precede white matter lesions in a mouse genetic model of cerebral ischemic small vessel disease

    PubMed Central

    Joutel, Anne; Monet-Leprêtre, Marie; Gosele, Claudia; Baron-Menguy, Céline; Hammes, Annette; Schmidt, Sabine; Lemaire-Carrette, Barbara; Domenga, Valérie; Schedl, Andreas; Lacombe, Pierre; Hubner, Norbert

    2010-01-01

    Cerebral ischemic small vessel disease (SVD) is the leading cause of vascular dementia and a major contributor to stroke in humans. Dominant mutations in NOTCH3 cause cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a genetic archetype of cerebral ischemic SVD. Progress toward understanding the pathogenesis of this disease and developing effective therapies has been hampered by the lack of a good animal model. Here, we report the development of a mouse model for CADASIL via the introduction of a CADASIL-causing Notch3 point mutation into a large P1-derived artificial chromosome (PAC). In vivo expression of the mutated PAC transgene in the mouse reproduced the endogenous Notch3 expression pattern and main pathological features of CADASIL, including Notch3 extracellular domain aggregates and granular osmiophilic material (GOM) deposits in brain vessels, progressive white matter damage, and reduced cerebral blood flow. Mutant mice displayed attenuated myogenic responses and reduced caliber of brain arteries as well as impaired cerebrovascular autoregulation and functional hyperemia. Further, we identified a substantial reduction of white matter capillary density. These neuropathological changes occurred in the absence of either histologically detectable alterations in cerebral artery structure or blood-brain barrier breakdown. These studies provide in vivo evidence for cerebrovascular dysfunction and microcirculatory failure as key contributors to hypoperfusion and white matter damage in this genetic model of ischemic SVD. PMID:20071773

  2. Rarefaction wave gun propulsion

    NASA Astrophysics Data System (ADS)

    Kathe, Eric Lee

    A new species of gun propulsion that dramatically reduces recoil momentum imparted to the gun is presented. First conceived by the author on 18 March 1999, the propulsion concept is explained, a methodology for the design of a reasonable apparatus for experimental validation using NATO standard 35mm TP anti-aircraft ammunition is developed, and the experimental results are presented. The firing results are juxtaposed by a simple interior ballistic model to place the experimental findings into a context within which they may better be understood. Rarefaction wave gun (RAVEN) propulsion is an original contribution to the field of armament engineering. No precedent is known, and no experimental results of such a gun have been published until now. Recoil reduction in excess of 50% was experimentally achieved without measured loss in projectile velocity. RAVEN achieves recoil reduction by means of a delayed venting of the breech of the gun chamber that directs the high enthalpy propellant gases through an expansion nozzle to generate forward thrust that abates the rearward momentum applied to the gun prior to venting. The novel feature of RAVEN, relative to prior recoilless rifles, is that sufficiently delayed venting results in a rarefaction wave that follows the projectile though the bore without catching it. Thus, the projectile exits the muzzle without any compromise to its propulsion performance relative to guns that maintain a sealed chamber.

  3. Life and death in the microcirculation: a role for angiotensin II

    NASA Technical Reports Server (NTRS)

    Greene, A. S.; Cowley, A. W. (Principal Investigator)

    1998-01-01

    OBJECTIVE: Angiotensin II (ANGII) plays a critical role in the maintenance of the microcirculation and in the anatomical loss of microvessels (rarefaction) that occurs in low renin forms of hypertension and in animals fed a high-salt diet. Elevations in sodium intake can trigger a series of hemodynamic and hormonal responses culminating in a substantial rarefaction of small arterioles and capillaries in both normal and reduced renal mass hypertensive rats. METHODS: Immunohistochemistry, Northern blot, and reverse transcription-polymerase chain reaction (RT-PCR) analysis of microdissected blood vessels were used to localize ANGII receptors in the microcirculation. Chronic infusion of ANGII and other physiologic and pharmacologic manipulations of the reninangiotensin system in rats was combined with morphologic and mathematical analysis of the network architecture. RESULTS: We have shown that rarefaction of the microcirculation can cause an increase in total peripheral resistance, reduced tissue perfusion, decreased oxygen delivery, and impaired organ function. Although the mechanisms by which this occurs are not well understood, a number of key observations point to a role for the renin-angiotensin system in this effect. First, ANGII infused systemically at subpressor levels, or locally into the skeletal muscle interstitium, can induce significant microvessel growth. Second, localization of ANGII receptor proteins by immunohistochemistry and Western blotting and RNA localization by RT-PCR confirm the presence of AT1 receptors, which are growth-stimulatory, and AT2 receptors, which are growth-inhibitory in the microcirculation. Third, maintenance of ANGII at normal levels during periods of hypertension or high-salt diet completely eliminates rarefaction. CONCLUSIONS: Taken together, these results support the hypothesis that ANGII acting through AT1- and AT2-receptor mechanisms modulate vessel density during high-salt diet and hypertension.

  4. Microcirculatory rarefaction in South Asians - a potential mechanism for increased cardiovascular risk and diabetes.

    PubMed

    Hughes, Alun D; Bathula, Raj; Park, Chloe; Tillin, Therese; Wit, Nicholas; McG Thom, Simon; Chaturvedi, Nish

    2013-01-01

    People of South Asian descent have an increased risk of cardiovascular disease (CVD) and diabetes, but little is known about the microcirculation in South Asian people despite evidence that this plays an important role in the aetiology of CVD. We compared the retinal microcirculation in a population-based sample of 287 middle-aged adults (144 European 143 South Asian) matched for age and sex. Retinal photographs were taken and analysed using a validated semi-automated program and microvascular measures were compared. Blood pressure, anthropometry and fasting bloods were also measured. South Asians had significantly fewer arteriolar and venular vessels and bifurcations. Arterioles and venules were longer and venules were also more tortuous in South Asians. These differences were not explained by adjustment for traditional risk factors including blood pressure, body mass index, diabetes or measures of insulin resistance. People of South Asian descent have rarefaction of the retinal microcirculation compared to age-sex matched individuals of European descent. Reduced microvascular density could contribute to the elevated risk of CVD and impaired glucose tolerance in South Asian people. PMID:24116136

  5. Rarefaction solitons initiated by sheath instability

    SciTech Connect

    Levko, Dmitry

    2015-09-15

    The instability of the cathode sheath initiated by the cold energetic electron beam is studied by the one-dimensional fluid model. Numerical simulations show the generation of travelling rarefaction solitons at the cathode. It is obtained that the parameters of these solitons strongly depend on the parameters of electron beam. The “stretched” variables are derived using the small-amplitude analysis. These variables are used in order to obtain the Korteweg-de Vries equation describing the propagation of the rarefaction solitons through the plasma with cold energetic electron beam.

  6. Microcirculation and Hemorheology

    PubMed Central

    Popel, Aleksander S.; Johnson, Paul C.

    2010-01-01

    Major experimental and theoretical studies on microcirculation and hemorheology are reviewed with the focus on mechanics of blood flow and the vascular wall. Flow of the blood formed elements (red blood cells (RBCs), white blood cells or leukocytes (WBCs) and platelets) in individual arterioles, capillaries and venules, and in microvascular networks is discussed. Mechanical and rheological properties of the formed elements and their interactions with the vascular wall are reviewed. Short-term and long-term regulation of the microvasculature is discussed; the modes of regulation include metabolic, myogenic and shear-stress-dependent mechanisms as well as vascular adaptation such as angiogenesis and vascular remodeling. PMID:21151769

  7. Rarefaction wave in relativistic steady magnetohydrodynamic flows

    SciTech Connect

    Sapountzis, Konstantinos Vlahakis, Nektarios

    2014-07-15

    We construct and analyze a model of the relativistic steady-state magnetohydrodynamic rarefaction that is induced when a planar symmetric flow (with one ignorable Cartesian coordinate) propagates under a steep drop of the external pressure profile. Using the method of self-similarity, we derive a system of ordinary differential equations that describe the flow dynamics. In the specific limit of an initially homogeneous flow, we also provide analytical results and accurate scaling laws. We consider that limit as a generalization of the previous Newtonian and hydrodynamic solutions already present in the literature. The model includes magnetic field and bulk flow speed having all components, whose role is explored with a parametric study.

  8. Physiopathology of the Cochlear Microcirculation

    PubMed Central

    Shi, Xiaorui

    2011-01-01

    Normal blood supply to the cochlea is critically important for establishing the endocochlear potential and sustaining production of endolymph. Abnormal cochlear microcirculation has long been considered an etiologic factor in noise-induced hearing loss, age-related hearing loss (presbycusis), sudden hearing loss or vestibular function, and Meniere's disease. Knowledge of the mechanisms underlying the pathophysiology of cochlear microcirculation is of fundamental clinical importance. A better understanding of cochlear blood flow (CoBF) will enable more effective management of hearing disorders resulting from aberrant blood flow. This review focuses on recent discoveries and findings related to the physiopathology of the cochlear microvasculature. PMID:21875658

  9. Blood microcirculation of ischemic pancreatitis

    NASA Astrophysics Data System (ADS)

    Dmitrieva, Irina V.; Arakelian, Sergei M.; Antonov, Olga V.

    1998-06-01

    Blood Microcirculation includes many of different components, which are joined by unique multiple system. Capillaries are one of the main link in this morpho-functional chain. Changes in any components of blood microcirculation are revealed by many of pathological processes in different organs and systems of the whole organism. We investigated 250 patients from 30 to 77 ages. Men included 149, women -- 101. The main diagnosis of all patients was the ischaemic pancreatitis. For verification of this diagnosis we used the whole spectrum of clinical, laboratorial and instrumental methods. These were the following: the definition of amylase of blood and urine, sonography and computer's tomography of pancreas, angiography of vessels of pancreas and Doppler's sonography of abdominal aorta and her branches: arteria mesenterica superior (AMS), truncus coeliacus (TC), arteria hepatica communis (AHC) and arteria lienalis (AL). We investigated the blood microcirculation of the mucous of the inferior lip, using Laser Dopplerography. The equipment for this research was LACC-01 with modified computer's program. The normal levels of blood microcirculation were from 120 to 180 Units. But patients with ischaemic pancreatitis had more lower level than in normal situation. This method are suggested as express diagnostic in the cases of abdominal ischaemic pathology. It can used as singel method or in combined with ultrasound Dopplerography.

  10. [Methods of studying the microcirculation].

    PubMed

    Shagal, D I; Tsvik, A I; Razygrin, B A

    1980-01-01

    The article shows possibilities of thermography in the study of peripheral blood circulation. Data are presented on examining the patients with diverse pathology forms by means of conjunctival biomicroscopy and television capillaroscopy of the nail bed. Evaluation of these methods and analysis of the data obtained are presented. The authors believe in more extended possibilities of applying microcirculation study methods together with thermography for disclosure of some diseases. PMID:7402036

  11. The mean and variance of phylogenetic diversity under rarefaction.

    PubMed

    Nipperess, David A; Matsen, Frederick A

    2013-06-01

    Phylogenetic diversity (PD) depends on sampling depth, which complicates the comparison of PD between samples of different depth. One approach to dealing with differing sample depth for a given diversity statistic is to rarefy, which means to take a random subset of a given size of the original sample. Exact analytical formulae for the mean and variance of species richness under rarefaction have existed for some time but no such solution exists for PD.We have derived exact formulae for the mean and variance of PD under rarefaction. We confirm that these formulae are correct by comparing exact solution mean and variance to that calculated by repeated random (Monte Carlo) subsampling of a dataset of stem counts of woody shrubs of Toohey Forest, Queensland, Australia. We also demonstrate the application of the method using two examples: identifying hotspots of mammalian diversity in Australasian ecoregions, and characterising the human vaginal microbiome.There is a very high degree of correspondence between the analytical and random subsampling methods for calculating mean and variance of PD under rarefaction, although the Monte Carlo method requires a large number of random draws to converge on the exact solution for the variance.Rarefaction of mammalian PD of ecoregions in Australasia to a common standard of 25 species reveals very different rank orderings of ecoregions, indicating quite different hotspots of diversity than those obtained for unrarefied PD. The application of these methods to the vaginal microbiome shows that a classical score used to quantify bacterial vaginosis is correlated with the shape of the rarefaction curve.The analytical formulae for the mean and variance of PD under rarefaction are both exact and more efficient than repeated subsampling. Rarefaction of PD allows for many applications where comparisons of samples of different depth is required. PMID:23833701

  12. Magnetic instability in a dilute circular rarefaction wave

    SciTech Connect

    Dieckmann, M. E.; Sarri, G.; Borghesi, M.

    2012-12-15

    The growth of magnetic fields in the density gradient of a rarefaction wave has been observed in simulations and in laboratory experiments. The thermal anisotropy of the electrons, which gives rise to the magnetic instability, is maintained by the ambipolar electric field. This simple mechanism could be important for the magnetic field amplification in astrophysical jets or in the interstellar medium ahead of supernova remnant shocks. The acceleration of protons and the generation of a magnetic field by the rarefaction wave, which is fed by an expanding circular plasma cloud, is examined here in form of a 2D particle-in-cell simulation. The core of the plasma cloud is modeled by immobile charges, and the mobile protons form a small ring close to the cloud's surface. The number density of mobile protons is thus less than that of the electrons. The protons of the rarefaction wave are accelerated to 1/10 of the electron thermal speed, and the acceleration results in a thermal anisotropy of the electron distribution in the entire plasma cloud. The instability in the rarefaction wave is outrun by a TM wave, which grows in the dense core distribution, and its magnetic field expands into the rarefaction wave. This expansion drives a secondary TE wave.

  13. Oxygen gradients in the microcirculation.

    PubMed

    Pittman, R N

    2011-07-01

    Early in the last century August Krogh embarked on a series of seminal studies to understand the connection between tissue metabolism and mechanisms by which the cardiovascular system supplied oxygen to meet those needs. Krogh recognized that oxygen was supplied from blood to the tissues by passive diffusion and that the most likely site for oxygen exchange was the capillary network. Studies of tissue oxygen consumption and diffusion coefficient, coupled with anatomical studies of capillarity in various tissues, led him to formulate a model of oxygen diffusion from a single capillary. Fifty years after the publication of this work, new methods were developed which allowed the direct measurement of oxygen in and around microvessels. These direct measurements have confirmed the predictions by Krogh and have led to extensions of his ideas resulting in our current understanding of oxygenation within the microcirculation. Developments during the last 40 years are reviewed, including studies of oxygen gradients in arterioles, capillaries, venules, microvessel wall and surrounding tissue. These measurements were made possible by the development and use of new methods to investigate oxygen in the microcirculation, so mention is made of oxygen microelectrodes, microspectrophotometry of haemoglobin and phosphorescence quenching microscopy. Our understanding of oxygen transport from the perspective of the microcirculation has gone from a consideration of oxygen gradients in capillaries and tissue to the realization that oxygen has the ability to diffuse from any microvessel to another location under the conditions that there exists a large enough PO(2) gradient and that the permeability for oxygen along the intervening pathway is sufficient. PMID:21281453

  14. Microcirculation and the Physiome Projects

    PubMed Central

    Bassingthwaighte, James B.

    2010-01-01

    The Physiome projects comprise a loosely knit worldwide effort to define the Physiome through databases and theoretical models, with the goal of better understanding the integrative functions of cells, organs, and organisms. The projects involve developing and archiving models, providing centralized databases, and linking experimental information and models from many laboratories into self-consistent frameworks. Increasingly accurate and complete models that embody quantitative biological hypotheses, adhere to high standards, and are publicly available and reproducible, together with refined and curated data, will enable biological scientists to advance integrative, analytical, and predictive approaches to the study of medicine and physiology. This review discusses the rationale and history of the Physiome projects, the role of theoretical models in the development of the Physiome, and the current status of efforts in this area addressing the microcirculation. PMID:19051119

  15. Effect of hypokinesia on blood microcirculation

    NASA Technical Reports Server (NTRS)

    Chernukh, A. M.; Gazenko, O. G.; Fedorov, B. M.; Krupina, T. N.; Aleksandrov, P. N.; Shagal, D. I.; Ranferova, N. Y.; Proskurina, T. N.

    1980-01-01

    Blood microcirculation in the region of the scleral bulbar conjunctiva and the nail folds on the fingers and toes was studied in 18 practically healthy men during 182 day antiorthostatic hypokinesia and 30 day rehabilitation period. Marked changes in microcirculation in the sclera and feet and less evident changes on the hands was revealed. A complex of special prophylactic physical exercises had a distinctly favorable effect on circulation in the hands.

  16. Formation of rarefaction waves in origami-based metamaterials.

    PubMed

    Yasuda, H; Chong, C; Charalampidis, E G; Kevrekidis, P G; Yang, J

    2016-04-01

    We investigate the nonlinear wave dynamics of origami-based metamaterials composed of Tachi-Miura polyhedron (TMP) unit cells. These cells exhibit strain softening behavior under compression, which can be tuned by modifying their geometrical configurations or initial folded conditions. We assemble these TMP cells into a cluster of origami-based metamaterials, and we theoretically model and numerically analyze their wave transmission mechanism under external impact. Numerical simulations show that origami-based metamaterials can provide a prototypical platform for the formation of nonlinear coherent structures in the form of rarefaction waves, which feature a tensile wavefront upon the application of compression to the system. We also demonstrate the existence of numerically exact traveling rarefaction waves in an effective lumped-mass model. Origami-based metamaterials can be highly useful for mitigating shock waves, potentially enabling a wide variety of engineering applications. PMID:27176382

  17. Characterization of rarefaction waves in van der Waals fluids

    NASA Astrophysics Data System (ADS)

    Yuen, Albert; Barnard, John J.

    2015-12-01

    We calculate the isentropic evolution of an instantaneously heated foil, assuming a van der Waals equation of state with the Maxwell construction. The analysis by Yuen and Barnard [Phys. Rev. E 92, 033019 (2015), 10.1103/PhysRevE.92.033019] is extended for the particular case of three degrees of freedom. We assume heating to temperatures in the vicinity of the critical point. The self-similar profiles of the rarefaction waves describing the evolution of the foil display plateaus in density and temperature due to a phase transition from the single-phase to the two-phase regime. The hydrodynamic equations are expressed in a dimensionless form and the solutions form a set of universal curves, depending on a single parameter: the dimensionless initial entropy. We characterize the rarefaction waves by calculating how the plateau length, density, pressure, temperature, velocity, internal energy, and sound speed vary with dimensionless initial entropy.

  18. Formation of rarefaction waves in origami-based metamaterials

    NASA Astrophysics Data System (ADS)

    Yasuda, H.; Chong, C.; Charalampidis, E. G.; Kevrekidis, P. G.; Yang, J.

    2016-04-01

    We investigate the nonlinear wave dynamics of origami-based metamaterials composed of Tachi-Miura polyhedron (TMP) unit cells. These cells exhibit strain softening behavior under compression, which can be tuned by modifying their geometrical configurations or initial folded conditions. We assemble these TMP cells into a cluster of origami-based metamaterials, and we theoretically model and numerically analyze their wave transmission mechanism under external impact. Numerical simulations show that origami-based metamaterials can provide a prototypical platform for the formation of nonlinear coherent structures in the form of rarefaction waves, which feature a tensile wavefront upon the application of compression to the system. We also demonstrate the existence of numerically exact traveling rarefaction waves in an effective lumped-mass model. Origami-based metamaterials can be highly useful for mitigating shock waves, potentially enabling a wide variety of engineering applications.

  19. Formation of rarefaction waves in origami-based metamaterials

    DOE PAGESBeta

    Yasuda, H.; Chong, C.; Charalampidis, E. G.; Kevrekidis, P. G.; Yang, J.

    2016-04-15

    Here, we investigate the nonlinear wave dynamics of origami-based metamaterials composed of Tachi-Miura polyhedron (TMP) unit cells. These cells exhibit strain softening behavior under compression, which can be tuned by modifying their geometrical configurations or initial folded conditions. We assemble these TMP cells into a cluster of origami-based metamaterials, and we theoretically model and numerically analyze their wave transmission mechanism under external impact. Numerical simulations show that origami-based metamaterials can provide a prototypical platform for the formation of nonlinear coherent structures in the form of rarefaction waves, which feature a tensile wavefront upon the application of compression to the system.more » We also demonstrate the existence of numerically exact traveling rarefaction waves in an effective lumped-mass model. Origami-based metamaterials can be highly useful for mitigating shock waves, potentially enabling a wide variety of engineering applications.« less

  20. Characterization of rarefaction waves in van der Waals fluids.

    PubMed

    Yuen, Albert; Barnard, John J

    2015-12-01

    We calculate the isentropic evolution of an instantaneously heated foil, assuming a van der Waals equation of state with the Maxwell construction. The analysis by Yuen and Barnard [Phys. Rev. E 92, 033019 (2015)] is extended for the particular case of three degrees of freedom. We assume heating to temperatures in the vicinity of the critical point. The self-similar profiles of the rarefaction waves describing the evolution of the foil display plateaus in density and temperature due to a phase transition from the single-phase to the two-phase regime. The hydrodynamic equations are expressed in a dimensionless form and the solutions form a set of universal curves, depending on a single parameter: the dimensionless initial entropy. We characterize the rarefaction waves by calculating how the plateau length, density, pressure, temperature, velocity, internal energy, and sound speed vary with dimensionless initial entropy. PMID:26764692

  1. Microcirculation in Acute and Chronic Kidney Diseases.

    PubMed

    Zafrani, Lara; Ince, Can

    2015-12-01

    The renal microvasculature is emerging as a key player in acute and chronic kidney diseases. Renal microvascular disease involves alterations in endothelial barrier permeability, exaggerated inflammation, impairment of endothelium-dependent vasorelaxation involving the nitric oxide system, increased oxidative stress, and loss of angiogenic factors. Moreover, evidence suggests that there is a microvascular component to the pathogenesis of renal scarring. New technology is being developed to explore renal microcirculation in vivo in experimental models and humans. This technology will provide a better understanding of the pathogenesis of kidney diseases and will help guide specific therapeutic strategies aimed at restoring the renal microcirculation. This article reviews the cellular and molecular mechanisms of renal microvascular dysfunction in acute and chronic kidney diseases and the potential diagnostic and therapeutic implications of these findings. Recent developments in the monitoring of renal microcirculation are described with respect to their advantages and limitations, and future directions are outlined. PMID:26231789

  2. Nitric Oxide Signaling in the Microcirculation

    PubMed Central

    Buerk, Donald G.; Barbee, Kenneth A.; Jaron, Dov

    2013-01-01

    Several apparent paradoxes are evident when one compares mathematical predictions from models of nitric oxide (NO) diffusion and convection in vasculature structures with experimental measurements of NO (or related metabolites) in animal and human studies. Values for NO predicted from mathematical models are generally much lower than in vivo NO values reported in the literature for experiments, specifically with NO microelectrodes positioned at perivascular locations next to different sizes of blood vessels in the microcirculation and NO electrodes inserted into a wide range of tissues supplied by the microcirculation of each specific organ system under investigation. There continues to be uncertainty about the roles of NO scavenging by hemoglobin versus a storage function that may conserve NO, and other signaling targets for NO need to be considered. This review describes model predictions and relevant experimental data with respect to several signaling pathways in the microcirculation that involve NO. PMID:22196161

  3. Cerebral Microcirculation during Experimental Normovolaemic Anemia

    PubMed Central

    Bellapart, Judith; Cuthbertson, Kylie; Dunster, Kimble; Diab, Sara; Platts, David G.; Raffel, O. Christopher; Gabrielian, Levon; Barnett, Adrian; Paratz, Jenifer; Boots, Rob; Fraser, John F.

    2016-01-01

    Anemia is accepted among critically ill patients as an alternative to elective blood transfusion. This practice has been extrapolated to head injury patients with only one study comparing the effects of mild anemia on neurological outcome. There are no studies quantifying microcirculation during anemia. Experimental studies suggest that anemia leads to cerebral hypoxia and increased rates of infarction, but the lack of clinical equipoise, when testing the cerebral effects of transfusion among critically injured patients, supports the need of experimental studies. The aim of this study was to quantify cerebral microcirculation and the potential presence of axonal damage in an experimental model exposed to normovolaemic anemia, with the intention of describing possible limitations within management practices in critically ill patients. Under non-recovered anesthesia, six Merino sheep were instrumented using an intracardiac transeptal catheter to inject coded microspheres into the left atrium to ensure systemic and non-chaotic distribution. Cytometric analyses quantified cerebral microcirculation at specific regions of the brain. Amyloid precursor protein staining was used as an indicator of axonal damage. Animals were exposed to normovolaemic anemia by blood extractions from the indwelling arterial catheter with simultaneous fluid replacement through a venous central catheter. Simultaneous data recording from cerebral tissue oxygenation, intracranial pressure, and cardiac output was monitored. A regression model was used to examine the effects of anemia on microcirculation with a mixed model to control for repeated measures. Homogeneous and normal cerebral microcirculation with no evidence of axonal damage was present in all cerebral regions, with no temporal variability, concluding that acute normovolaemic anemia does not result in short-term effects on cerebral microcirculation in the ovine brain. PMID:26869986

  4. On the interaction between turbulence and a planar rarefaction

    SciTech Connect

    Johnson, Bryan M.

    2014-04-01

    The modeling of turbulence, whether it be numerical or analytical, is a difficult challenge. Turbulence is amenable to analysis with linear theory if it is subject to rapid distortions, i.e., motions occurring on a timescale that is short compared to the timescale for nonlinear interactions. Such an approach (referred to as rapid distortion theory) could prove useful for understanding aspects of astrophysical turbulence, which is often subject to rapid distortions, such as supernova explosions or the free-fall associated with gravitational instability. As a proof of principle, a particularly simple problem is considered here: the evolution of vorticity due to a planar rarefaction in an ideal gas. Analytical solutions are obtained for incompressive modes having a wave vector perpendicular to the distortion; as in the case of gradient-driven instabilities, these are the modes that couple most strongly to the mean flow. Vorticity can either grow or decay in the wake of a rarefaction front, and there are two competing effects that determine which outcome occurs: entropy fluctuations couple to the mean pressure gradient to produce vorticity via baroclinic effects, whereas vorticity is damped due to the conservation of angular momentum as the fluid expands. Whether vorticity grows or decays depends upon the ratio of entropic to vortical fluctuations at the location of the front; growth occurs if this ratio is of order unity or larger. In the limit of purely entropic fluctuations in the ambient fluid, a strong rarefaction generates vorticity with a turbulent Mach number on the order of the rms of the ambient entropy fluctuations. The analytical results are shown to compare well with results from two- and three-dimensional numerical simulations. Analytical solutions are also derived in the linear regime of Reynolds-averaged turbulence models. This highlights an inconsistency in standard turbulence models that prevents them from accurately capturing the physics of

  5. Asymptotic stability of rarefaction waves for 2 ∗ 2 viscous hyperbolic conservation laws

    NASA Astrophysics Data System (ADS)

    Xin, Zhouping

    This paper concerns the asymptotic behavior toward rarefaction waves of the solution of a general 2 × 2 hyperbolic conservation laws with positive viscosity. We prove that if the initial data is close to a constant state and its values at ±∞ lie on the kth rarefaction curve for the corresponding hyperbolic conservation laws, then the solution tends as t → ∞ to the rarefaction wave determined by these states.

  6. Rarefaction shock waves in shock-compressed diamond <110> crystal

    NASA Astrophysics Data System (ADS)

    Perriot, Romain; Lin, You; Zhakhovsky, Vasily; White, Carter; Oleynik, Ivan

    2013-03-01

    Piston-driven shock compression of diamond <110> crystal was simulated by molecular dynamics using the REBO potential. At piston velocities between 2 and 5 km/s and corresponding pressures 117 GPA < P < 278 GPa, diamond sample undergoes a polymorphic phase transition, characterized by the coexistence of two elastically compressed phases, low-pressure phase A and high-pressure phase B. This phase transition results in the splitting of the shock wave into two elastic shock waves, composed of pure phase A and a mixture of phases A and B. Upon removal of the piston, a release wave is observed at the rear of the sample, turning into a rarefaction shock wave where the material undergoes the reverse phase transition from coexisting phases to the original low-pressure phase. For strong plastic waves induced by larger piston velocities the release wave propagates as a rarefaction wave without any phase transition corresponding to the adiabatic expansion along the plastic branch of the Hugoniot.

  7. Vascular rarefaction mediates whitening of brown fat in obesity

    PubMed Central

    Shimizu, Ippei; Aprahamian, Tamar; Kikuchi, Ryosuke; Shimizu, Ayako; Papanicolaou, Kyriakos N.; MacLauchlan, Susan; Maruyama, Sonomi; Walsh, Kenneth

    2014-01-01

    Brown adipose tissue (BAT) is a highly vascularized organ with abundant mitochondria that produce heat through uncoupled respiration. Obesity is associated with a reduction of BAT function; however, it is unknown how obesity promotes dysfunctional BAT. Here, using a murine model of diet-induced obesity, we determined that obesity causes capillary rarefaction and functional hypoxia in BAT, leading to a BAT “whitening” phenotype that is characterized by mitochondrial dysfunction, lipid droplet accumulation, and decreased expression of Vegfa. Targeted deletion of Vegfa in adipose tissue of nonobese mice resulted in BAT whitening, supporting a role for decreased vascularity in obesity-associated BAT. Conversely, introduction of VEGF-A specifically into BAT of obese mice restored vascularity, ameliorated brown adipocyte dysfunction, and improved insulin sensitivity. The capillary rarefaction in BAT that was brought about by obesity or Vegfa ablation diminished β-adrenergic signaling, increased mitochondrial ROS production, and promoted mitophagy. These data indicate that overnutrition leads to the development of a hypoxic state in BAT, causing it to whiten through mitochondrial dysfunction and loss. Furthermore, these results link obesity-associated BAT whitening to impaired systemic glucose metabolism. PMID:24713652

  8. Rarefaction and blood pressure in systemic and pulmonary arteries.

    PubMed

    Olufsen, Mette S; Hill, N A; Vaughan, Gareth D A; Sainsbury, Christopher; Johnson, Martin

    2012-08-01

    The effects of vascular rarefaction (the loss of small arteries) on the circulation of blood are studied using a multiscale mathematical model that can predict blood flow and pressure in the systemic and pulmonary arteries. We augmented a model originally developed for the systemic arteries (Olufsen et al. 1998, 1999, 2000, 2004) to (a) predict flow and pressure in the pulmonary arteries, and (b) predict pressure propagation along the small arteries in the vascular beds. The systemic and pulmonary arteries are modelled as separate, bifurcating trees of compliant and tapering vessels. Each tree is divided into two parts representing the `large' and `small' arteries. Blood flow and pressure in the large arteries are predicted using a nonlinear cross-sectional area-averaged model for a Newtonian fluid in an elastic tube with inflow obtained from magnetic resonance measurements. Each terminal vessel within the network of the large arteries is coupled to a vascular bed of small `resistance' arteries, which are modelled as asymmetric structured trees with specified area and asymmetry ratios between the parent and daughter arteries. For the systemic circulation, each structured tree represents a specific vascular bed corresponding to major organs and limbs. For the pulmonary circulation, there are four vascular beds supplied by the interlobar arteries. This manuscript presents the first theoretical calculations of the propagation of the pressure and flow waves along systemic and pulmonary large and small arteries. Results for all networks were in agreement with published observations. Two studies were done with this model. First, we showed how rarefaction can be modelled by pruning the tree of arteries in the microvascular system. This was done by modulating parameters used for designing the structured trees. Results showed that rarefaction leads to increased mean and decreased pulse pressure in the large arteries. Second, we investigated the impact of decreasing vessel

  9. Asymptotic Stability of Planar Rarefaction Waves for the Relaxation Approximation of Conservation Laws in Several Dimensions

    NASA Astrophysics Data System (ADS)

    Luo, Tao

    1997-01-01

    This paper concerns the large time behavior toward planar rarefaction waves of solutions for the relaxation approximation of conservation laws in several dimensions. It is shown that a planar rarefaction wave is nonlinear stable in the sense that it is an asymptotic attractor for the relaxation approximation of conservation laws.

  10. The Role of Pericyte Detachment in Vascular Rarefaction

    PubMed Central

    Schrimpf, Claudia; Teebken, Omke E.; Wilhelmi, Mathias; Duffield, Jeremy S.

    2015-01-01

    Background Pericytes surround endothelial cells at the perivascular interface. Signaling between endothelial cells and pericytes is crucial for capillary homeostasis, as pericytes stabilize vessels and regulate many microvascular functions. Recently it has been shown that pericytes are able to detach from the vascular wall and contribute to fibrosis by becoming scar-forming myofibroblasts in many organs including the kidney. At the same time, the loss of pericytes within the perivascular compartment results in vulnerable capillaries which are prone to instability, pathological angiogenesis, and, ultimately, rarefaction. Aims This review will give an overview of pericyte-endothelial cell interactions, summarize the signaling pathways that have been identified to be involved in pericyte detachment from the vascular wall, and present pathological endothelial responses in the context of disease of the kidney. PMID:25195856

  11. Invasive assessment of the coronary microcirculation in the catheter laboratory.

    PubMed

    Layland, Jamie; Nerlekar, Nitesh; Palmer, Sonny; Berry, Colin; Oldroyd, Keith

    2015-11-15

    Historically much of our understanding of the coronary circulation has been centered towards the epicardial vessels. However, recent work has highlighted the importance of the coronary microcirculation across a broad spectrum of clinical conditions in influencing patient outcomes. Therefore an ability to measure microvascular function is most valuable. While evaluation of the epicardial coronary circulation is widely understood, interrogation of the coronary microcirculation is more complex. Many methods are available to assess the integrity of the microcirculation in the catheter laboratory. This review will discuss the physiology of the coronary microcirculation and evaluate the utility of available invasive techniques. PMID:26197399

  12. Distinct temporal phases of microvascular rarefaction in skeletal muscle of obese Zucker rats.

    PubMed

    Frisbee, Jefferson C; Goodwill, Adam G; Frisbee, Stephanie J; Butcher, Joshua T; Brock, Robert W; Olfert, I Mark; DeVallance, Evan R; Chantler, Paul D

    2014-12-15

    Evolution of metabolic syndrome is associated with a progressive reduction in skeletal muscle microvessel density, known as rarefaction. Although contributing to impairments to mass transport and exchange, the temporal development of rarefaction and the contributing mechanisms that lead to microvessel loss are both unclear and critical areas for investigation. Although previous work suggests that rarefaction severity in obese Zucker rats (OZR) is predicted by the chronic loss of vascular nitric oxide (NO) bioavailability, we have determined that this hides a biphasic development of rarefaction, with both early and late components. Although the total extent of rarefaction was well predicted by the loss in NO bioavailability, the early pulse of rarefaction developed before a loss of NO bioavailability and was associated with altered venular function (increased leukocyte adhesion/rolling), and early elevation in oxidant stress, TNF-α levels, and the vascular production of thromboxane A2 (TxA2). Chronic inhibition of TNF-α blunted the severity of rarefaction and also reduced vascular oxidant stress and TxA2 production. Chronic blockade of the actions of TxA2 also blunted rarefaction, but did not impact oxidant stress or inflammation, suggesting that TxA2 is a downstream outcome of elevated reactive oxygen species and inflammation. If chronic blockade of TxA2 is terminated, microvascular rarefaction in OZR skeletal muscle resumes, but at a reduced rate despite low NO bioavailability. These results suggest that therapeutic interventions against inflammation and TxA2 under conditions where metabolic syndrome severity is moderate or mild may prevent the development of a condition of accelerated microvessel loss with metabolic syndrome. PMID:25305181

  13. Rarefaction shock waves and Hugoniot curve in the presence of free and trapped particles

    SciTech Connect

    Niknam, A. R.; Hashemzadeh, M.; Shokri, B.; Rouhani, M. R.

    2009-12-15

    The effects of the relativistic ponderomotive force and trapped particles in the presence of ponderomotive force on the rarefaction shock waves are investigated. The ponderomotive force alters the electron density distribution. This force and relativistic mass affect the plasma frequency. These physical parameters modify the total pressure and the existence condition of the rarefaction shock wave. Furthermore, the trapping of particles by the high frequency electromagnetic field considerably changes the existence condition of the rarefaction shock wave. The total pressure and Hugoniot curve are obtained by considering the relativistic ponderomotive force and trapped particles.

  14. Dis-ease or disease?: ontological rarefaction in the medical-industrial complex.

    PubMed

    Graham, S Scott

    2011-09-01

    Recent scholarship in medical humanities has expressed strong concern over the ability of pharmaceuticals companies to medicalize discomfort and subsequently invent diseases. In this article, I explore the clinical debates over the ontology of the sinus headache as a possible counter-case. Extending Foucault's concept of principles or rarefaction, this paper documents the efforts of clinicians to resist the pharmaceutically-provided understanding of the sinus headache. In so doing, it offers institutions of rarefaction and rarefactive assemblages as useful heuristics for the exploration of disease legitimization discourse. PMID:21484314

  15. Capillary rarefaction, hypoxia, VEGF and angiogenesis in chronic renal disease

    PubMed Central

    Mayer, Gert

    2011-01-01

    Tubulointerstitial hypoxia and peritubular capillary rarefaction are typical features of chronic progressive renal disease. In response to low oxygen supply, hypoxia-inducible factors (HIFs) are activated but until now, it is unclear if this increased expression leads to a stabilization of the disease process and thus is nephroprotective or contributes to interstitial fibrosis and/or tubular atrophy. This duality has also been described as far as vascular endothelial growth factor (VEGF), one of the major target genes of HIFs, is concerned. On the one hand, neoangiogenesis driven by VEGF, if intact, ameliorates hypoxia, on the other, VEGF is a potent pro-inflammatory mediator and neoangiogenesis, if defective because interference by other pathologies exaggerates injury. In summary, experimental data support the idea that dependent on timing and predominant pathology, hypoxia counter-regulatory factors exert beneficial or undesirable effects. Thus, before their therapeutic potential can be fully explored, a better way to characterize the clinical and pathophysiological situation in an individual patient is mandatory. PMID:21330358

  16. Effects of rarefaction in microflows between coaxial cylinders.

    PubMed

    Taheri, Peyman; Struchtrup, Henning

    2009-12-01

    Microscale gas flows between two rotating coaxial circular cylinders of infinite length with different temperatures are investigated. Navier-Stokes-Fourier (NSF) and regularized 13-moment (R13) equations in their linear form are used to independently analyze velocity and temperature fields in shear-driven rotary flows, i.e., cylindrical Couette flows. Knudsen boundary layers, which present non-Newtonian stress and non-Fourier heat flow, are predicted as the dominant rarefaction effects in the linear theory. We show that the R13 system yields more accurate results for this boundary value problem by predicting the Knudsen boundary layers, which are not accessible for NSF equations. Furthermore, a set of second-order boundary conditions for velocity slip and temperature jump are derived for the NSF system. It is shown that the proposed boundary conditions effectively improve the classical hydrodynamics. The accuracy of NSF and R13 equations is discussed based on their comparison with available direct simulation Monte Carlo data. PMID:20365277

  17. Condensation of water vapor in rarefaction waves. I - Homogeneous nucleation

    NASA Technical Reports Server (NTRS)

    Sislian, J. P.; Glass, I. I.

    1976-01-01

    A detailed theoretical investigation has been made of the condensation of water vapor/carrier gas mixtures in the nonstationary rarefaction wave generated in a shock tube. It is assumed that condensation takes place by homogeneous nucleation. The equations of motion together with the nucleation rate and the droplet growth equations were solved numerically by the method of characteristics and Lax's method of implicit artificial viscosity. It is found that, for the case considered, the condensation wave formed by the collapse of the metastable nonequilibrium state is followed by a shock wave generated by the intersection of characteristics of the same family. The expansion is practically isentropic up to the onset of condensation. The condensation front accelerates in the x,t plane. The results of the computations for a chosen case of water vapor/nitrogen mixture are presented by plotting variations of pressure, nucleation rate, number density of critical clusters, and condensate mass-fraction along three particle paths. Some consideration is given to homogeneous condensation experiments conducted in a shock tube. Although a direct comparison of the present theoretical work and these experiments is not possible, several worthwhile interpretative features have resulted nevertheless.

  18. Propagation of rarefaction pulses in particulate materials with strain-softening behavior

    SciTech Connect

    Herbold, E B; Nesterenko, V F

    2011-07-29

    We investigate rarefaction waves in nonlinear periodic systems with a 'softening' power-law relationship between force and displacement to understand the dynamic behavior of this class of materials. A closed form expression describing the shape of the strongly nonlinear rarefaction wave is exact for n = 1/2 and agrees well with the shape and width of the pulses resulting from discrete simulations. A chain of particles under impact was shown to propagate a rarefaction pulse as the leading pulse in initially compressive impulsive loading in the absence of dissipation. Compression pulses generated by impact quickly disintegrated into a leading rarefaction solitary wave followed by an oscillatory train. Such behavior is favorable for metamaterials design of shock absorption layers as well as tunable information transmission lines for scrambling of acoustic information.

  19. Evaluating microcirculation by pulsatile laser Doppler signal

    NASA Astrophysics Data System (ADS)

    Chao, P. T.; Jan, M. Y.; Hsiu, H.; Hsu, T. L.; Wang, W. K.; Wang, Y. Y. Lin

    2006-02-01

    Laser Doppler flowmetry (LDF) is a popular method for monitoring the microcirculation, but it does not provide absolute measurements. Instead, the mean flux response or energy distribution in the frequency domain is generally compared before and after stimulus. Using the heartbeat as a trigger, we investigated whether the relation between pressure and flux can be used to discriminate different microcirculatory conditions. We propose the following three pulsatile indices for evaluating the microcirculation condition from the normalized pressure and flux segment with a synchronized-averaging method: peak delay time (PDT), pressure rise time and flux rise time (FRT). The abdominal aortic blood pressure and renal cortex flux (RCF) signals were measured in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). The mean value of the RCF did not differ between SHR and WKY. However, the PDT was longer in SHR (87.14 ± 5.54 ms, mean ± SD) than in WKY (76.92 ± 2.62 ms; p < 0.001). The FRT was also longer in SHR (66.56 ± 1.98 ms) than in WKY (58.02 ± 1.77 ms; p < 0.001). We propose that a new dimension for comparing the LDF signals, which the results from the present study show, can be used to discriminate RCF signals that cannot be discriminated using traditional methods.

  20. Non-invasive imaging of microcirculation: a technology review

    PubMed Central

    Eriksson, Sam; Nilsson, Jan; Sturesson, Christian

    2014-01-01

    Microcirculation plays a crucial role in physiological processes of tissue oxygenation and nutritional exchange. Measurement of microcirculation can be applied on many organs in various pathologies. In this paper we aim to review the technique of non-invasive methods for imaging of the microcirculation. Methods covered are: videomicroscopy techniques, laser Doppler perfusion imaging, and laser speckle contrast imaging. Videomicroscopy techniques, such as orthogonal polarization spectral imaging and sidestream dark-field imaging, provide a plentitude of information and offer direct visualization of the microcirculation but have the major drawback that they may give pressure artifacts. Both laser Doppler perfusion imaging and laser speckle contrast imaging allow non-contact measurements but have the disadvantage of their sensitivity to motion artifacts and that they are confined to relative measurement comparisons. Ideal would be a non-contact videomicroscopy method with fully automatic analysis software. PMID:25525397

  1. Compressive and rarefactive solitary waves in nonthermal two-component plasmas

    SciTech Connect

    Verheest, Frank; Hellberg, Manfred A.

    2010-10-15

    Using a Sagdeev pseudopotential formalism where nonlinear structures are stationary in a comoving frame, large ion-acoustic solitary waves and double layers have been studied in plasmas with positive ions and nonthermal electrons. The velocity range of positive, compressive solitary waves is limited by the ion density reaching infinite compression, whereas negative, rarefactive solitary waves and double layers can exist when the electron nonthermality exceeds a certain minimum. There are even regions of coexistence, the limits of which can be elucidated by considering the properties of the special Sagdeev pseudopotential at the acoustic speed. In particular, when the compositional parameters and Mach numbers admit only compressive or rarefactive solitary structures, these have to be superacoustic, their amplitude vanishing at the acoustic speed. When both compressive and rarefactive modes can occur, one of them is Korteweg-de Vries (KdV)-like, the other having a non-KdV character, with a finite amplitude at the acoustic speed.

  2. Monitoring the microcirculation in critically ill patients.

    PubMed

    De Backer, Daniel; Durand, Arthur

    2014-12-01

    Alterations in microvascular perfusion have been identified in critically ill patients, especially in sepsis but also in cardiogenic shock, after cardiac arrest, and in high-risk surgery patients. These alterations seem to be implicated in the development of organ dysfunction and are associated with outcome. Even though microvascular perfusion can sometimes be homogenously decreased as in acute hemorrhage or in non-resuscitated cardiogenic shock, heterogeneity of perfusion is observed in sepsis and in resuscitated hemorrhagic/cardiogenic shock. Heterogeneity of perfusion has major implications for monitoring, as many techniques cannot detect microcirculatory alterations when heterogeneity of flow is present in significant amount. Indeed, devices such as laser Doppler or O2 electrodes and near-infrared spectroscopy have a relatively large sampling volume and measurements are affected by the highest values in the field. Using these techniques during a vascular occlusion test may help to characterize microvascular reactivity; however, microvascular reactivity sometimes fails to represent actual microvascular perfusion. Videomicroscopic techniques can nowadays be applied at bedside but are still restricted to some selected patients (quiet or sedated patients). Tissue PCO2 is an elegant alternative but is not yet broadly used. In this manuscript, we discuss the main advantages and limitations of the techniques available for bedside evaluation of the microcirculation in critically ill patients. PMID:25480773

  3. Microcirculation abnormalities provoked by Loxosceles spiders' envenomation.

    PubMed

    Cristina de Oliveira-Lima, Kátia; Farsky, Sandra Helena P; Lopes, Priscila Hess; de Andrade, Rute Maria Gonçalves; van den Berg, Carmen W; Tambourgi, Denise V

    2016-06-15

    Loxoscelism is caused by envenomation by spiders from Loxosceles genus. Clinical symptoms only appear a few hours after envenomation and can evolve in local reactions, such as dermonecrosis, and systemic reactions, including intravascular haemolysis, intravascular coagulation and renal failure. Considering that alterations in the microcirculatory network are involved in the pathogenesis of different diseases, including the inflammatory process, the aim of this study was to investigate the action of venoms of males and females of Loxosceles intermedia and Loxosceles laeta on the microcirculatory network and examine the systemic production of inflammatory mediators in a murine model of loxoscelism. We observed that during systemic envenomation, the alterations in the microcirculation include increase in the number of rolling cells, which was more intense in animals injected with female Loxosceles spider venoms. This positively correlated with increase in TNF-α and NO serum levels, induction of which was higher by female venoms when compared with male venoms. The increase of leukocytes rolling was not accompanied by increase of cell adhesion. The absence of leukocyte extravasation may explain why in mice, in contrast to humans, no cutaneous loxoscelism occurs. Thus, targeting the neutrophil adhesion and extravasation in Loxosceles envenomed patients may prevent cutaneous pathology. PMID:26256792

  4. Tumor growth in a defined microcirculation.

    PubMed

    Christofferson, R H; Sköldenberg, E G; Nilsson, B O

    1997-06-01

    The fate of human tumor cells deposited in rat uteri was investigated by light microscopy of histological sections, immunohistochemistry, and scanning electron microscopy of microvascular corrosion casts. The human colonic tumor cell line LS 174 T was used as graft since it can be detected by CEA immunohistochemistry, and spayed nude rats (PVG rnu/rnu) were used as hosts, subjected to different hormonal regimens (no exogenous hormones, medroxyprogesterone acetate, 17-beta-estradiol, or the last two regimens in combination). Intrauterine deposition of a suspension of 2 x 10(6) tumor cells resulted in tumor take in 72% (21/29) of the nude rats. Endometrial growth was verified in only three animals (14%, 3/21). Extraendometrial growth, however, was found in all animals with tumor take. These observations suggest that the endometrium is comparatively resistant to growth of xenografted human colonic tumor cells. The tumor microcirculation consisted of new vessels, giving morphological evidence that tumor growth is dependent on angiogenesis and not on invasion of preexisting vessels. PMID:9236867

  5. Asymptotic stability of rarefaction waves for 2 × 2 viscous hyperbolic conservation laws—The two-modes case

    NASA Astrophysics Data System (ADS)

    Xin, Zhouping

    In this paper, we continue our study on the asymptotic behavior toward rare-faction waves of a general 2 × 2 system of hyperbolic conservation laws with positive viscosity matrix. It is shown that when the initial data is a small perturbation of a weak rarefaction wave (a linear superposition of a 1-rarefaction wave and a 2-rarefaction wave) for the corresponding inviscid hyperbolic conservation laws, then the solution of the Cauchy problem for the viscous system globally exists and tends to the rarefaction wave. The result is proved by using an energy method, combining the technique in [Z. P. Xin, J. Differential Equations73 (1988), 45-77], and using the characteristic-energy method of T. P. Liu [ Mem. Amer. Math. Soc.328 (1975), 1-108].

  6. Comprehensive computer model for magnetron sputtering. I. Gas heating and rarefaction

    SciTech Connect

    Jimenez, Francisco J.; Dew, Steven K.

    2012-07-15

    The complex interaction between several variables in magnetron sputtering discharges is a challenge in developing engineering design tools for industrial applications. For instance, at high pressures, rarefaction and gas heating should no longer be neglected for determining several parameters of the process. In this article, we use a comprehensive 3D reactor-scale simulator that incorporates most phenomena of interest in a self-consistent manner to simulate the transport of sputtered particles over a wide range of pressures and powers. Calculations of aluminum deposition rates and metal vapor densities are in reasonable agreement with experiments over a wide range of pressures and powers. Of the elements investigated (Al, Ti, and Cu), copper showed the greatest rarefaction (30%) due to its higher sputtering yield. Titanium, despite a slightly lower sputtering yield than Al, shows a greater rarefaction than aluminum as more particles are reflected from the target as high energy neutrals. In this case, a more efficient energy transfer process is responsible for the higher rarefaction observed in Ti sputtering when compared to Al. The authors also observed that by sputtering at a higher pressure, the probability of electron impact ionization of sputtered particles is increased and speculate about the role of this process in contrast to penning ionization, which is believed to be the dominant ionization mechanism in magnetron sputtering.

  7. Addenda to the Preceding Paper

    NASA Astrophysics Data System (ADS)

    Bhatnagar, Rajat; Finn, Robert

    2016-05-01

    This work contains largely afterthoughts, relating to the paper immediately preceding it. We correlate and interpret our contributions in that paper, relative to those of an earlier publication by Aspley, He and McCuan. We propose specific laboratory experiments, suggested by formal predictions of those two papers.

  8. Design of sensors for microcirculation investigation in pharyngeal mucosa

    NASA Astrophysics Data System (ADS)

    Mareew, Gleb O.; Mareew, Oleg V.; Fedosov, Ivan V.; Tuchin, Valery V.

    2004-08-01

    Sensors designed for research of blood microcirculation in pharyngeal mucosa by a laser Doppler flowmetry, are described and considered in view of anatomic and physiological features of objects of research. Two designs of sensors for laser Doppler flowmetry are described - non-contact and contact. The results of and clinical testing at norm and different pathologies of pharynx of on calibration of sensors, and also their comparative technical characteristics and materials of clinical researches of microcirculation are resulted at norm and at a various pathology.

  9. 47 CFR 213.5 - Precedence designators.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Precedence designators. 213.5 Section 213.5 Telecommunication OFFICE OF SCIENCE AND TECHNOLOGY POLICY AND NATIONAL SECURITY COUNCIL GOVERNMENT AND PUBLIC CORRESPONDENCE TELECOMMUNICATIONS PRECEDENCE SYSTEM § 213.5 Precedence designators. (a) The following precedence designators are available...

  10. In vivo label-free quantification of liver microcirculation using dual-modality microscopy

    NASA Astrophysics Data System (ADS)

    Yan, Jie; Kang, Yuzhan; Xu, Shuoyu; Ong, Lee-Ling S.; Zhuo, Shuangmu; Bunte, Ralph M.; Chen, Nanguang; Asada, H. Harry; So, Peter T. C.; Wanless, Ian R.; Yu, Hanry

    2014-11-01

    Microcirculation lesion is a common symptom of chronic liver diseases in the form of vasculature deformation and circulation alteration. In acute to chronic liver diseases such as biliary atresia, microcirculation lesion can have an early onset. Detection of microcirculation lesion is meaningful for studying the progression of liver disease. We have combined wide-field fluorescence microscopy and a laser speckle contrast technique to characterize hepatic microcirculation in vivo without labeling in a bile-duct ligation rat fibrosis model of biliary atresia. Through quantitative image analysis of four microcirculation parameters, we observed significant microcirculation lesion in the early to middle stages of fibrosis. This bimodal imaging method is useful to assess hepatic microcirculation lesion for the study of liver diseases.

  11. Compression and strong rarefaction in high power impulse magnetron sputtering discharges

    SciTech Connect

    Horwat, David; Anders, Andre

    2010-11-11

    Gas compression and strong rarefaction have been observed for high power impulse magnetron sputtering (HIPIMS) discharges using a copper target in argon. Time-resolved ion saturation currents of 35 probes were simultaneously recorded for HIPIMS discharges operating far above the self-sputtering runaway threshold. The argon background pressure was a parameter for the evaluation of the spatial and temporal development of the plasma density distribution. The data can be interpreted by a massive onset of the sputtering flux (sputter wind) that causes a transient densification of the gas, followed by rarefaction and the replacement of gas plasma by the metal plasma of sustained self-sputtering. The plasma density pulse follows closely the power pulse at low pressure. At high pressure, the relatively remote probes recorded a density peak only after the discharge pulse, indicative for slow, diffusive ion transport.

  12. PIC simulation of compressive and rarefactive dust ion-acoustic solitary waves

    NASA Astrophysics Data System (ADS)

    Li, Zhong-Zheng; Zhang, Heng; Hong, Xue-Ren; Gao, Dong-Ning; Zhang, Jie; Duan, Wen-Shan; Yang, Lei

    2016-08-01

    The nonlinear propagations of dust ion-acoustic solitary waves in a collisionless four-component unmagnetized dusty plasma system containing nonextensive electrons, inertial negative ions, Maxwellian positive ions, and negatively charged static dust grains have been investigated by the particle-in-cell method. By comparing the simulation results with those obtained from the traditional reductive perturbation method, it is observed that the rarefactive KdV solitons propagate stably at a low amplitude, and when the amplitude is increased, the prime wave form evolves and then gradually breaks into several small amplitude solitary waves near the tail of soliton structure. The compressive KdV solitons propagate unstably and oscillation arises near the tail of soliton structure. The finite amplitude rarefactive and compressive Gardner solitons seem to propagate stably.

  13. Shock waves, rarefaction waves, and nonequilibrium steady states in quantum critical systems

    NASA Astrophysics Data System (ADS)

    Lucas, Andrew; Schalm, Koenraad; Doyon, Benjamin; Bhaseen, M. J.

    2016-07-01

    We reexamine the emergence of a universal nonequilibrium steady state following a local quench between quantum critical heat baths in spatial dimensions greater than one. We show that energy transport proceeds by the formation of an instantaneous shock wave and a broadening rarefaction wave on either side of the interface, and not by two shock waves as previously proposed. For small temperature differences the universal steady state energy currents of the two-shock and rarefaction-shock solutions coincide. Over a broad range of parameters, the difference in the energy flow across the interface between these two solutions is at the level of 2%. The properties of the energy flow remain fully universal and independent of the microscopic theory. We briefly discuss the width of the shock wave in a viscous fluid, the effects of momentum relaxation, and the generalization to charged fluids.

  14. Ion-acoustic compressive and rarefactive solitons in an electron-beam plasma system

    SciTech Connect

    Yadav, L.L.; Tiwari, R.S.; Sharma, S.R. )

    1994-03-01

    Using the general formulation of reductive perturbation method, the Korteweg--de Vries (KdV) equation is derived for an electron-beam plasma with hot isothermal beam and plasma electrons and warm ions. The soliton solution of the KdV equation is discussed in detail. It is found that above a critical velocity of electron-beam two additional ion-acoustic soliton branches appear. It is found that corresponding to two linear modes, the system supports the existence of compressive as well as rarefactive solitons depending upon the plasma parameters, while corresponding to other two wave modes, the system supports only rarefactive solitons. The effect of different parameters on the characteristics of solitons have been investigated in detail.

  15. Rarefaction effects in microchannel gas flow driven by rhythmic wall contractions

    NASA Astrophysics Data System (ADS)

    Chatterjee, Krishnashis; Staples, Anne; Department of Biomedical Engineering; Mechanics, Virginia Tech Collaboration

    2015-11-01

    Current state of the art microfluidic devices employ precise and timely operation of a complex arrangement of micropumps and valves for fluid transport. A much more novel flow transport mechanism is found in entomological respiratory systems, which involve rhythmic wall contractions for driving the fluid flow. The practical viability of using this technique in future microfluidic devices has been studied earlier. The present study investigates the incorporation of rarefaction effects in the above model of microscale gas flow by including slip boundary conditions. The Navier Stokes equations for gas flow in rectangular microchannel are solved analytically with microscale and lubrication theory assumptions. First order slip boundary conditions are incorporated to account for the rarefaction effects. The dependence of fluid velocities and pressure gradient on the slip boundary conditions is studied. Time averaged unidirectional fluid flow rates are plotted for different phase lags between the contractions, with and without slip in order to obtain an optimum range under different conditions.

  16. Observational and Modeling Study of Pickup Ion Cooling Behavior in Solar Wind Compression and Rarefaction Regions

    NASA Astrophysics Data System (ADS)

    Chen, J.; Moebius, E.; Schwadron, N.; Klecker, B.; Bzowski, M.; Galvin, A. B.; Isenberg, P. A.; Sokol, J. M.; Gorby, M.; Bochsler, P. A.

    2013-12-01

    In many previous studies, the velocity distribution function of interstellar pickup ions (PUIs), which are produced by ionization of interstellar neutral atoms in the solar wind, were described as evolving through fast pitch angle scattering followed by adiabatic cooling during radial transport with in the reference frame of the solar wind [e.g., Vasyliunas & Siscoe, 1976 VS76 hereafter]. In the VS76 model, the slope of the velocity distributions is controlled by the combination of the ionization rate and the cooling process. Recently, Chen et al. [2013] have shown that the related adiabatic cooling index varies with solar activity between ~1 and 2, compared with 1.5 predicted by the VS76 model. Contributors to the observed variations include solar wind compression and rarefaction regions. Here, we performed a statistical study of the PUI cooling behavior in solar wind compression and rarefaction regions based on STEREO-A PLASTIC data sets using a set of events from the co-rotating interaction region (CIR) list (http://www-scc.igpp.ucla.edu/forms/stereo/stereo_level_3.html). We found that PUIs undergo stronger cooling in rarefaction regions and weaker cooling in compression regions. In order to analyze the PUI cooling behavior under these conditions, we modeled the PUI velocity distributions in CIRs using the Energetic Particle Radiation Environment Module (EPREM) [Schwadron et al., 2010]. For this analysis, we adopted a magneto-hydrodynamic CIR model proposed by [Giacalone et al., 2002]. The resulting PUI distributions exhibit a flatter slope in the compression region and are steeper in the rarefaction region compared with those in the undisturbed solar wind, in accordance with STEREO observations. These results indicate that gradients in the solar wind speed, as observed in CIRs, have substantial effects on the PUI cooling process.

  17. Tissue microcirculation measured by vascular occlusion test during anesthesia induction.

    PubMed

    Kim, Tae Kyong; Cho, Youn Joung; Min, Jeong Jin; Murkin, John M; Bahk, Jae-Hyon; Hong, Deok Man; Jeon, Yunseok

    2016-02-01

    Tissue microcirculation measured by vascular occlusion test is impaired during septic shock. However, it has not been investigated extensively during anesthesia induction. The aim of the study is to evaluate tissue microcirculation during anesthesia induction. We hypothesized that during anesthesia induction, tissue microcirculation measured by vascular occlusion test might be enhanced with peripheral vasodilation during anesthesia induction. We conducted a prospective observational study of 50 adult patients undergoing cardiac surgery. During anesthesia induction, we measured and analyzed tissue oxygen saturation, vascular occlusion test, cerebral oximetry, forearm-minus-fingertip skin temperature gradients and hemodynamic data in order to evaluate microcirculation as related to alterations in peripheral vasodilation as reflected by increased Tforearm-finger thermal gradients. During anesthesia induction, recovery slope during vascular occlusion test and cerebral oxygen saturation increased from 4.0 (1.5) to 4.7 (1.3) % s(-1) (p = 0.02) and 64.0 (10.2) to 74.2 (9.2) % (p < 0.001), respectively. Forearm-minus-fingertip skin temperature gradients decreased from 1.9 (2.9) to -1.4 (2.2) °C (p < 0.001). There was an inverse correlation between changes in the skin temperature gradients and changes in cerebral oximetry (r = 0.33; p = 0.02). During anesthesia induction, blood pressure and forearm-minus-fingertip skin temperature gradients decrease while cerebral oximetry and vascular occlusion test recovery slope increase. These findings suggest that anesthesia induction increases tissue microcirculation with peripheral vasodilation. PMID:25750016

  18. EphrinB2 Reverse Signaling Protects against Capillary Rarefaction and Fibrosis after Kidney Injury

    PubMed Central

    Kida, Yujiro; Ieronimakis, Nicholas; Schrimpf, Claudia; Reyes, Morayma

    2013-01-01

    Microvascular disease, a characteristic of acute and chronic kidney diseases, leads to rarefaction of peritubular capillaries (PTCs), promoting secondary ischemic injury, which may be central to disease progression. Bidirectional signaling by EphB4 receptor and ephrinB2 ligand is critical for angiogenesis during murine development, suggesting that ephrinB2 reverse signaling may have a role in renal angiogenesis induced by injury or fibrosis. Here, we found that ephrinB2 reverse signaling is activated in the kidney only after injury. In mice lacking the PDZ intracellular signaling domain of ephrinB2 (ephrinB2 ΔV), angiogenesis was impaired and kidney injury led to increased PTC rarefaction and fibrosis. EphrinB2 ΔV primary kidney pericytes migrated more than wild-type pericytes and were less able to stabilize capillary tubes in three-dimensional culture and less able to stimulate synthesis of capillary basement membrane. EphrinB2 ΔV primary kidney microvascular endothelial cells migrated and proliferated less than wild-type microvascular endothelial cells in response to vascular endothelial growth factor A and showed less internalization and activation of vascular endothelial growth factor receptor-2. Taken together, these results suggest that PDZ domain-dependent ephrinB2 reverse signaling protects against PTC rarefaction by regulating angiogenesis and vascular stability during kidney injury. Furthermore, this signaling in kidney pericytes protects against pericyte-to-myofibroblast transition and myofibroblast activation, thereby limiting fibrogenesis. PMID:23492730

  19. Aging exacerbates obesity-induced cerebromicrovascular rarefaction, neurovascular uncoupling, and cognitive decline in mice.

    PubMed

    Tucsek, Zsuzsanna; Toth, Peter; Tarantini, Stefano; Sosnowska, Danuta; Gautam, Tripti; Warrington, Junie P; Giles, Cory B; Wren, Jonathan D; Koller, Akos; Ballabh, Praveen; Sonntag, William E; Ungvari, Zoltan; Csiszar, Anna

    2014-11-01

    Epidemiological studies show that obesity has deleterious effects on the brain and cognitive function in the elderly population. However, the specific mechanisms through which aging and obesity interact to promote cognitive decline remain unclear. To test the hypothesis that aging exacerbates obesity-induced cerebromicrovascular impairment, we compared young (7 months) and aged (24 months) high-fat diet-fed obese C57BL/6 mice. We found that aging exacerbates the obesity-induced decline in microvascular density both in the hippocampus and in the cortex. The extent of hippocampal microvascular rarefaction and the extent of impairment of hippocampal-dependent cognitive function positively correlate. Aging exacerbates obesity-induced loss of pericyte coverage on cerebral microvessels and alters hippocampal angiogenic gene expression signature, which likely contributes to microvascular rarefaction. Aging also exacerbates obesity-induced oxidative stress and induction of NADPH oxidase and impairs cerebral blood flow responses to whisker stimulation. Collectively, obesity exerts deleterious cerebrovascular effects in aged mice, promoting cerebromicrovascular rarefaction and neurovascular uncoupling. The morphological and functional impairment of the cerebral microvasculature in association with increased blood-brain barrier disruption and neuroinflammation (Tucsek Z, Toth P, Sosnowsk D, et al. Obesity in aging exacerbates blood-brain barrier disruption, neuroinflammation and oxidative stress in the mouse hippocampus: effects on expression of genes involved in beta-amyloid generation and Alzheimer's disease. J Gerontol Biol Med Sci. 2013. In press, PMID: 24269929) likely contribute to obesity-induced cognitive decline in aging. PMID:24895269

  20. Rarefaction and compressional standing slow mode structures in Mercury's magnetosheath: 3D MHD simulations

    NASA Astrophysics Data System (ADS)

    Pantellini, Filippo; Griton, Léa; Varela, Jacobo

    2015-07-01

    We show that slow mode compressional fronts form upstream of the day side magnetopause in MHD simulations of Mercury's magnetosphere. The strongest compressional fronts are located upstream of the magnetopause with strong magnetic shear. Compressional fronts are crossed by magnetic field lines connecting the interplanetary magnetic field and the planet's intrinsic field, their role is to bend the magnetic field in the magnetosheath towards the magnetopause. Besides these compressional fronts, already observed in space and theoretically discussed by various authors for the case of the Earth, we observe the formation of a slow mode standing rarefaction wave spatially growing over a substantial fraction of the distance between the bow shock and the magnetopause. The slow mode source region for the rarefaction waves is located in the magnetosheath, near the bow shock's nose. The generated standing rarefaction waves, however, form even at large distances from the source region along the magnetospheric flanks. They fine-tune the magnetic field line draping and plasma flow around the magnetopause. In ideal MHD the magnetospheres of Mercury, the Earth and the giant planets do closely resemble each other, we therefore expect the mentioned slow mode structures not to be specific to Mercury.

  1. Aging causes collateral rarefaction and increased severity of ischemic injury in multiple tissues

    PubMed Central

    Faber, James E.; Zhang, Hua; Lassance-Soares, Roberta M.; Prabhakar, Pranay; Najafi, Amir H.; Burnett, Mary Susan; Epstein, Stephen E.

    2011-01-01

    Objective Aging is a major risk factor for increased ischemic tissue injury. Whether collateral rarefaction and impaired remodeling contribute to this is unknown. We quantified the number and diameter of native collaterals, and their remodeling in 3-, 16-, 24-, and 31-months-old mice. Methods and Results Aging caused an “age-dose-dependent” greater drop in perfusion immediately after femoral artery ligation, followed by a diminished recovery of flow and increase in tissue injury. These effects were associated with a decline in collateral number, diameter and remodeling. Angiogenesis was also impaired. Mechanistically, these changes were not accompanied by reduced recruitment of T-cells or macrophages to remodeling collaterals. However, eNOS signaling was dysfunctional, as indicated by increased protein nitrosylation and less phosphorylated eNOS and VASP in collateral wall cells. The cerebral circulation exhibited a similar age-dose-dependent loss of collateral number and diameter and increased tortuosity, resulting in an increase in collateral resistance and infarct volume (e.g., 6- and 3-fold, respectively, in 24-months-old mice) after artery occlusion. This was not associated with rarefaction of similarly-sized arterioles. Collateral remodeling was also reduced. Conclusions Our findings demonstrate that aging causes rarefaction and insufficiency of the collateral circulation in multiple tissues, resulting in more severe ischemic tissue injury. PMID:21617137

  2. A case study of global stability of strong rarefaction waves for 2×2 hyperbolic conservation laws with artificial viscosity

    NASA Astrophysics Data System (ADS)

    Duan, Ran; Ma, Xuan; Zhao, Huijiang

    This paper is concerned with the global stability of strong rarefaction waves for a class of 2×2 hyperbolic conservation laws with artificial viscosity, i.e., the p-system with artificial viscosity {

  3. 47 CFR 213.5 - Precedence designators.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Precedence designators. 213.5 Section 213.5 Telecommunication OFFICE OF SCIENCE AND TECHNOLOGY POLICY AND NATIONAL SECURITY COUNCIL GOVERNMENT AND PUBLIC CORRESPONDENCE TELECOMMUNICATIONS PRECEDENCE SYSTEM § 213.5 Precedence designators. (a) The following...

  4. Precedence relationship representations of mechanical assembly sequences

    NASA Technical Reports Server (NTRS)

    Homendemello, L. S.; Sanderson, A. C.

    1989-01-01

    Two types of precedence relationship representations for mechanical assembly sequences are presented: precedence relationships between the establishment of one connection between two parts and the establishment of another connection, and precedence relationships between the establishment of one connection and states of the assembly process. Precedence relationship representations have the advantage of being very compact. The problem with these representations was how to guarantee their correctness and completeness. Two theorems are presented each of which leads to the generation of one type of precedence relationship representation guaranteeing its correctness and completeness for a class of assemblies.

  5. Myocardial Microcirculation and Mitochondrial Energetics in the Isolated Rat Heart.

    PubMed

    Ashruf, J F; Ince, C

    2016-01-01

    Normal functioning of myocardium requires adequate oxygenation, which in turn is dependent on an adequate microcirculation. NADH-fluorimetry enables a direct evaluation of the adequacy of tissue oxygenation while the measurement of quenching of Pd-porphyrine (PpIX) phosphorescence enables quantitative measurement of microvascular pO2. Combination of these two techniques provides information about the relation between microvascular oxygen content and parenchymal oxygen availability in Langendorff hearts. In normal myocardium there is heterogeneity at the microcirculatory level resulting in the existence of microcirculatory weak units, originating at the capillary level, which reoxygenate the slowest upon reoxygenation after an episode of ischemia. Sepsis and myocardial hypertrophia alter the pattern of oxygen transport whereby the microcirculation is disturbed at the arteriolar/arterial level. NADH fluorimetry also reveals a disturbance of mitochondrial oxygen availability in sepsis. Furthermore it is shown that these techniques can also be applied to various organs and tissues in vivo. PMID:26782208

  6. Influence of Receptor Antagonists, Local Anesthetics, and Denervation on Microcirculation

    PubMed Central

    Homann, Heinz H.; Hirsch, Tobias; Steinau, H.U.; Muehlberger, Thomas; Moll, Wibke; Lehnhardt, Marcus; Goertz, Ole

    2011-01-01

    Objective: Impaired microcirculation is one of the most important factors in delayed wound healing. The aim of the study was to investigate the influence of chemical and surgical interruption of sympathetic nerve fibers and α- and β-receptors blockers on muscular microcirculation. Methods: The experiment was performed on a standardized cremaster muscle model of male Wistar rats (n=51). Microcirculation was recorded via transillumination microscopy on each of the 4 test groups and in a control group before and after their respective treatments with one of the following: topical application of bupivacaine, metoprolol, phentolamine, or surgical denervation. The arteriolar diameter and functional capillary density (FCD) as parameter for tissue perfusion were assessed. Results: The α-blocker phentolamine was the only agent that caused a significant dilation of the arteriolar diameter (76.6 ± 6.9 vs 100.0 ± 12.0 µm). However, like bupivacaine, metoprolol, and the surgical sympathectomy, it did not improve FCD as a parameter for tissue perfusion. The strongest vasoconstriction (35.9 ± 4.3 vs 28.6 ± 4.0) and impairment of the FCD (10.0 ± 0.7 vs 4.1 ± 0.9) was induced by the β-blocker metoprolol. Conclusions: This study shows that phentolamine could be an agent for dilating arteriolar diameter, but it did not improve FCD. Whereas the other agents, including sympathectomy, did not alter arteriolar diameter, the β-blocker worsened both investigated parameters. Our results raise the question whether β-blockers negatively influence microcirculation. Therefore, further studies are needed to investigate the potential adverse effects of β-blockers on wound healing. PMID:21283734

  7. [Nailfold capillaroscopy in the study of microcirculation in childhood].

    PubMed

    Baserga, M; Bonacci, E; Cammarota, M G; D'Amico, N

    1996-01-01

    The nailfold capillaroscopy allows to study the microcirculation: for its simple and rapid execution it can be used also in children. We examined the nailfold capillaroscopy features in childhood and valued the maturation of microcirculation in connection to age and presented some pathologic patterns. We studied nailfold capillaroscopy patterns in sixty-six children without chronic cutaneous diseases. Our results showed that development of microcirculation during childhood is incomplete. In connection to age we observed the capillaries are arranged as arches in children younger than six months, there are disposed as saddles between 12 and 24 months and they became similar to those of the adult at about 10-11 years. We observed immature capillaries in one child with hypothyroidism and one's delay growth. The cutaneous hemorrhages were rarely found in children who bit the in nails. The capillaroscopy is helpful to value the maturation of the capillaries from the birth to the adolescence. Moreover we would like to underline how our children took part to this exam almost like as if it were a game. PMID:8965760

  8. [Relation between microcirculation parameters and Pc3 geomagnetic pulsations].

    PubMed

    Zenchehko, T A; Poskotinova, L V; Rekhtina, A G; Zaslavskaia, R M

    2010-01-01

    An individual analysis of long-term monitoring of microcirculation parameters of nine healthy volunteers showed that an increase in the geomagnetic activity led to an increase in tissue perfusion, variability of blood flow and growth of the amplitude of neurogenic and myogenic oscillations in four volunteers. It was found that the degree of microcirculation sensitivity to the level of geomagnetic activity values with time and is proportional to its average level in the period of measurement. A comparison of frequency ranges of oscillations of blood flow and variations of the geomagnetic activity shows that neurogenic and myogenic oscillations showing the highest sensitivity to the geomagnetic activity have the same frequency as geomagnetic Pc3 pulsations. The pulsations of this frequency range are excited mainly during geomagnetic disturbances, which may explain the correlation between the microcirculation parameters and the Kp index. The relation of the amplitude-frequency characteristics of Pc3-pulsations can explain the results obtained using the alternating magnetic fields. PMID:20968090

  9. Mechanobiology and the microcirculation: cellular, nuclear and fluid mechanics

    PubMed Central

    Dahl, Kris Noel; Kalinowski, Agnieszka; Pekkan, Kerem

    2010-01-01

    Endothelial cells are stimulated by shear stress throughout the vasculature and respond with changes in gene expression and by morphological reorganization. Mechanical sensors of the cell are varied and include cell surface sensors that activate intracellular chemical signaling pathways. Here, possible mechanical sensors of the cell including reorganization of the cytoskeleton and the nucleus are discussed in relation to shear flow. A mutation in the nuclear structural protein lamin A, related to Hutchinson Gilford progeria syndrome, is reviewed specifically since the mutation results in altered nuclear structure and stiffer nuclei; animal models also suggest significantly altered vascular structure. Nuclear and cellular deformation of endothelial cells in response to shear stress provides partial understanding of possible mechanical regulation in the microcirculation. Increasing sophistication of fluid flow simulations inside the vessel is also an emerging area relevant to the microcirculation since visualization in situ is difficult. This integrated approach to study – including medicine, molecular and cell biology, biophysics and engineering – provides a unique understanding of multi-scale interactions in the microcirculation. PMID:20374482

  10. Prototype of an in vitro model of the microcirculation.

    PubMed

    Shevkoplyas, Sergey S; Gifford, Sean C; Yoshida, Tatsuro; Bitensky, Mark W

    2003-03-01

    We have used microfabrication technology to construct a network of microchannels, patterned after the dimensions and architecture of the mammalian microcirculation. The network is cast in transparent silicone elastomer and the channels are coated with silanated mPEG to provide lubrication. Flow of red and white blood cells through the network is readily visualized by the use of high-speed digital image acquisition. The acquired sequences of high-quality images are used to calculate hematocrits and rates of red cell movement in the microchannels. Our prototype system has significant advantages over scaled-up room-size experimental systems in that it permits experimentation with actual human blood cells. Experiments can be carried out under well-controlled conditions in a network of microchannels with precisely known dimensions using cell suspensions of defined composition. Moreover, there is no need to counteract or anticipate the host's adaptive responses that may confound live animal experiments. Notwithstanding its limitations, the current prototype demonstrates certain features characteristic of the microcirculation, such as parachute and bullet shapes of red cells deformed in capillary channels, rouleaux formation, plasma skimming, and the utilization of collateral flow pathways due to flow obstruction caused by a white cell blocking a microchannel. We present this device as a prototype scale-to-scale model of the mammalian microcirculation. Limitations of the system as well as a variety of possible applications are described. PMID:12686171

  11. [Microcirculation impairment in periodontal tissues in patients with chronic generalized periodontitis combined with metabolic syndrome].

    PubMed

    Krechina, E K; Zorina, O A; Molchanov, A M; Shilov, A M

    2016-01-01

    Using the method of laser Doppler flowmetry the study of microcirculation in periodontal tissues in patients with moderate chronic generalized periodontitis and metabolic syndrome was carried out. The analysis of microcirculation values proved not only the reduction of blood flow intensity but also the decreased vasoactivity of microvessels essential to maintain normal microcirculation in periodontal tissues, as it provides active modulation of tissue blood flow and its adaptation to local metabolic needs. PMID:26925562

  12. Effect of copper IUD on microcirculation of blood flow in rabbit uterus

    SciTech Connect

    Zhang, M.; Wang, H.F.; Meng, Z.; Huang, H.Y.

    1987-12-01

    A survey of the rabbit's normal microcirculation of blood flow volume in the endometrium and myometrium with or without a copper intrauterine device (IUD) was made. It was found through statistical analyses that the IUD stimulated the endometrium so that microcirculation of blood flow volume in the endometrium increased significantly, but it did not change the microcirculation of blood flow volume in the myometrium and in the opposite uterus.

  13. Compressive and rarefactive dressed solitons in plasma with nonthermal electrons and positrons

    NASA Astrophysics Data System (ADS)

    Abdelwahed, H. G.; El-Shewy, E. K.; Zahran, M. A.; Elwakil, S. A.

    2016-02-01

    The study of dressed solitary ion waves in a collisionless unmagnetized plasma composed warm fluid of ion, nonthermal distributed positrons and electrons are discussed. Concerning nonlinear ion acoustic waves, a reductive perturbation method is applied to obtain the KdV equation in terms of first order potential. Our results exemplify that, if soliton amplitude enlarged, the shape of the wave sidetrack from KdV equation. In order to improve the soliton shape, the perturbed KdV equation is suggest. In particular, the effects of nonthermal positrons and ionic temperature on the electrostatic dressed rarefactive and compressive soliton structures are discussed.

  14. Asymptotic Stability of Rarefaction Wave for the Navier-Stokes Equations for a Compressible Fluid in the Half Space

    NASA Astrophysics Data System (ADS)

    Kawashima, Shuichi; Zhu, Peicheng

    2009-10-01

    This paper is concerned with the asymptotic stability towards a rarefaction wave of the solution to an outflow problem for the Navier-Stokes equations in a compressible fluid in the Eulerian coordinate in the half space. This is the second one of our series of papers on this subject. In this paper, firstly we classify completely the time-asymptotic states, according to some parameters, that is the spatial-asymptotic states and boundary conditions, for this initial boundary value problem, and some pictures for the classification of time-asymptotic states are drawn in the state space. In order to prove the stability of the rarefaction wave, we use the solution to Burgers’ equation to construct a suitably smooth approximation of the rarefaction wave and establish some time-decay estimates in L p -norm for the smoothed rarefaction wave. We then employ the L 2-energy method to prove that the rarefaction wave is non-linearly stable under a small perturbation, as time goes to infinity.

  15. Excitation of ion rarefaction waves in a low pressure plasma by applying a short high negative voltage pulse

    SciTech Connect

    Kar, S.; Mukherjee, S.; Saxena, Y. C.

    2011-05-15

    The ion rarefaction response to a high negative voltage pulse (U{sub 0} >> kT{sub e}/e) applied to a metal plate immersed in a low pressure argon plasma, for time duration lower than ion plasma period, is experimentally examined. In the present experiment the pulse duration is kept intermediate between the ion and electron plasma response times. Such a pulse duration is chosen so that ions are collectively undisturbed and, according to general understanding, no force is given to ions. Hence no ion rarefaction wave should be excited. But contrary to the general understanding, excitation of a rarefaction wave is observed. The results indicate that the speed of the rarefaction waves for various conditions (like plasma density, applied pulse magnitude, and pulse duration) is supersonic. After a distance from the exciter (biased plate), typically three-fourth of the exciter diameter, the rarefaction waves are turned into ion acoustic waves. The experimental results indicate that even though the bias durations are shorter than the ion plasma period, if the bias magnitude is large enough, some collective plasma behavior can still be excited.

  16. Rarefaction windows in a high-power impulse magnetron sputtering plasma

    SciTech Connect

    Palmucci, Maria; Britun, Nikolay; Konstantinidis, Stephanos; Snyders, Rony

    2013-09-21

    The velocity distribution function of the sputtered particles in the direction parallel to the planar magnetron cathode is studied by spatially- and time-resolved laser-induced fluorescence spectroscopy in a short-duration (20 μs) high-power impulse magnetron sputtering discharge. The experimental evidence for the neutral and ionized sputtered particles to have a constant (saturated) velocity at the end of the plasma on-time is demonstrated. The velocity component parallel to the target surface reaches the values of about 5 km/s for Ti atoms and ions, which is higher that the values typically measured in the direct current sputtering discharges before. The results point out on the presence of a strong gas rarefaction significantly reducing the sputtered particles energy dissipation during a certain time interval at the end of the plasma pulse, referred to as “rarefaction window” in this work. The obtained results agree with and essentially clarify the dynamics of HiPIMS discharge studied during the plasma off-time previously in the work: N. Britun, Appl. Phys. Lett. 99, 131504 (2011)

  17. Compressive and rarefactive DIA solitons beyond the KdV limit

    SciTech Connect

    Mamun, A. A.; Deeba, F.

    2012-04-15

    The modified Gardner equation (MGE), showing the existence of compressive and rarefactive dust-ion-acoustic (DIA) solitons in a nonplanar dusty plasma (containing inertial ions, Boltzmann electrons, and negatively charged stationary dust) beyond the KdV Korteweg-de Vries (KdV) limit, is derived and numerically solved. The basic features of the compressive and rarefactive cylindrical and spherical DIA solitons, which are found to exist beyond the KdV limit, i.e., exist for {mu} {approx} 2/3 (where {mu} = Z{sub n}n{sub d0}/n{sub i0}, z{sub d} is the number of electrons residing onto the dust grain surface, n{sub d0}(n{sub i0}) is the dust (ion) number density at equilibrium, and {mu} {approx} 2/3 means that {mu} is not equal to 2/3, but it is around 2/3) are identified. These solitons (which can be referred to as DIA Gardner solitons (DIA-GSs)) are completely different from the KdV solitons because {mu} = 2/3 corresponds to the vanishing of the nonlinear coefficient of the KdV equation, and {mu} {approx} 2/3 corresponds to extremely large amplitude KdV solitons for which the validity of the reductive perturbation method breaks down. It is also shown that the properties of the nonplanar (cylindrical and spherical) DIA-GSs are significantly different from those of the one dimensional planar ones.

  18. CHANGES IN SUBLINGUAL MICROCIRCULATION IS CLOSELY RELATED WITH THAT OF BULBAR CONJUNCTIVAL MICROCIRCULATION IN A RAT MODEL OF CARDIAC ARREST.

    PubMed

    Yin, Lu; Yang, Zhengfei; Yu, Haifang; Qian, Jie; Zhao, Shen; Wang, Jiangang; Wu, Xiaobo; Cahoon, Jena; Tang, Wanchun

    2016-04-01

    Following successful resuscitation, a significantly impaired microcirculation has been identified. The severity of the impairment of microcirculation is closely related to that of vital organ dysfunction. Sublingual microcirculation is a traditional site for the measurement of tissue perfusion. In the present study, we investigated the bulbar conjunctival microcirculatory alterations following CPR and its relationship with the changes of sublingual microcirculation in a rat model of cardiac arrest.Male Sprague-Dawley rats (450-550 g) were utilized. Ventricular fibrillation was induced and untreated for 8 min followed by 8 min of CPR. Sublingual and bulbar conjunctival microcirculatory blood flow was visualized by a sidestream dark-field imaging device at baseline, 30 min, 1, 2, 4, and 8 h post-resuscitation. Both perfused vessel density (PVD) and microcirculatory flow index (MFI) were recorded.The post-resuscitation PVD and MFI were significantly decreased in both sublingual and bulbar conjunctival sites. Sublingual PVD decreased from baseline of 5.9 ± 0.3 to 3.1 ± 0.4 n/mm at 30 min post-resuscitation and MFI from 3.0 ± 0.0 to 1.5 ± 0.3 (both P < 0.05 vs. baseline). Bulbar conjunctival PVD was significantly reduced from baseline of 6.5 ± 0.6 to 3.9 ± 0.5 n/mm at 30 min post-resuscitation and MFI from 3.0 ± 0.0 to 1.2 ± 0.4 (both P < 0.05 vs. baseline). PVD, MFI, and cardiac function did not change significantly from the 30-min measurements in the surviving rats throughout the remainder of the study (both P > 0.05 vs. 30-min post-resuscitation). The decreases in sublingual microcirculatory blood flow were closely correlated with the reductions of bulbar conjunctival microcirculatory blood flow (PVD: r = 0.87, P < 0.05; MFI: r = 0.92, P < 0.05). Myocardial function was significantly impaired in all animals after resuscitation when compared with baseline values (P < 0.05). The impairments of both sublingual and bulbar conjunctival microcirculation were

  19. Nonlinear Stability of Strong Planar Rarefaction Waves for the Relaxation Approximation of Conservation Laws in Several Space Dimensions

    NASA Astrophysics Data System (ADS)

    Zhao, Huijiang

    2000-04-01

    In this paper, we show that a strong planar rarefaction wave is nonlinear stable, namely it is an attractor for the relaxation approximation of the scalar conservation laws in several space dimensions. Compared with former results obtained by T. P. Liu (1987, Comm. Math. Phys.108, 153-175) and T. Luo (1997, J. Differential Equations133, 255-279), our main novelty lies in the fact that the planar rarefaction waves do not need to be small, and in the one-dimensional case, the initial disturbance can also be chosen arbitrarily large.

  20. Syndecan-1 in the Mouse Parietal Peritoneum Microcirculation in Inflammation

    PubMed Central

    Kowalewska, Paulina M.; Patrick, Amanda L.; Fox-Robichaud, Alison E.

    2014-01-01

    Background The heparan sulfate proteoglycan syndecan-1 (CD138) was shown to regulate inflammatory responses by binding chemokines and cytokines and interacting with adhesion molecules, thereby modulating leukocyte trafficking to tissues. The objectives of this study were to examine the expression of syndecan-1 and its role in leukocyte recruitment and chemokine presentation in the microcirculation underlying the parietal peritoneum. Methods Wild-type BALB/c and syndecan-1 null mice were stimulated with an intraperitoneal injection of Staphylococcus aureus LTA, Escherichia coli LPS or TNFα and the microcirculation of the parietal peritoneum was examined by intravital microscopy after 4 hours. Fluorescence confocal microscopy was used to examine syndecan-1 expression in the peritoneal microcirculation using fluorescent antibodies. Blocking antibodies to adhesion molecules were used to examine the role of these molecules in leukocyte-endothelial cell interactions in response to LTA. To determine whether syndecan-1 co-localizes with chemokines in vivo, fluorescent antibodies to syndecan-1 were co-injected intravenously with anti-MIP-2 (CXCL2), anti-KC (CXCL1) or anti-MCP-1 (CCL2). Results and Conclusion Syndecan-1 was localized to the subendothelial region of peritoneal venules and the mesothelial layer. Leukocyte rolling was significantly decreased with LPS treatment while LTA and TNFα significantly increased leukocyte adhesion compared with saline control. Leukocyte-endothelial cell interactions were not different in syndecan-1 null mice. Antibody blockade of β2 integrin (CD18), ICAM-1 (CD54) and VCAM-1 (CD106) did not decrease leukocyte adhesion in response to LTA challenge while blockade of P-selectin (CD62P) abrogated leukocyte rolling. Lastly, MIP-2 expression in the peritoneal venules was not dependent on syndecan-1 in vivo. Our data suggest that syndecan-1 is expressed in the parietal peritoneum microvasculature but does not regulate leukocyte recruitment

  1. Effect of zero magnetic field on cardiovascular system and microcirculation

    NASA Astrophysics Data System (ADS)

    Gurfinkel, Yu. I.; At'kov, O. Yu.; Vasin, A. L.; Breus, T. K.; Sasonko, M. L.; Pishchalnikov, R. Yu.

    2016-02-01

    The effects of zero magnetic field conditions on cardiovascular system of healthy adults have been studied. In order to generate zero magnetic field, the facility for magnetic fields modeling "ARFA" has been used. Parameters of the capillary blood flow, blood pressure, and the electrocardiogram (ECG) monitoring were measured during the study. All subjects were tested twice: in zero magnetic field and, for comparison, in sham condition. The obtained results during 60 minutes of zero magnetic field exposure demonstrate a clear effect on cardiovascular system and microcirculation. The results of our experiments can be used in studies of long-term stay in hypo-magnetic conditions during interplanetary missions.

  2. Acute effects of cigarette smoking on microcirculation of the thumb.

    PubMed

    van Adrichem, L N; Hovius, S E; van Strik, R; van der Meulen, J C

    1992-01-01

    The acute effect of smoking on the microcirculation of the skin of the thumb was investigated in healthy volunteers. Twenty-two were smokers and 10 were non-smokers. The flow was assessed by means of laser Doppler flowmetry. The smokers inhaled 2 cigarettes. During smoking of their first and second cigarette respectively, a mean decrease in laser Doppler flow of 23.8% and 29.0% was seen (p = 0.03; p = 0.01). Ten minutes after smoking this decrease was recovered by half. This experiment confirms that one should prohibit smoking of cigarettes pre- and postoperatively for optimal wound healing conditions. PMID:1737221

  3. Effect of zero magnetic field on cardiovascular system and microcirculation.

    PubMed

    Gurfinkel, Yu I; At'kov, O Yu; Vasin, A L; Breus, T K; Sasonko, M L; Pishchalnikov, R Yu

    2016-02-01

    The effects of zero magnetic field conditions on cardiovascular system of healthy adults have been studied. In order to generate zero magnetic field, the facility for magnetic fields modeling "ARFA" has been used. Parameters of the capillary blood flow, blood pressure, and the electrocardiogram (ECG) monitoring were measured during the study. All subjects were tested twice: in zero magnetic field and, for comparison, in sham condition. The obtained results during 60 minutes of zero magnetic field exposure demonstrate a clear effect on cardiovascular system and microcirculation. The results of our experiments can be used in studies of long-term stay in hypo-magnetic conditions during interplanetary missions. PMID:26948007

  4. Compressive and rarefactive dust ion-acoustic solitary waves with degenerate electron-positron-ion plasma

    NASA Astrophysics Data System (ADS)

    Mukta, K. N.; Zobaer, M. S.; Roy, N.; Mamun, A. A.

    2015-06-01

    The nonlinear propagation of dust ion-acoustic (DIA) waves in a unmagnetized collisionless degenerate dense plasma (containing degenerate electron and positron, and classical ion fluids) has been theoretically investigated. The K-dV equation has been derived by employing the reductive perturbation method and by taking into account the effect of different plasma parameters in plasma fluid. The stationary solitary wave solution of K-dV equation is obtained, and numerically analyzed to identify the basic properties of DIA solitary structures. It has been shown that depending on plasma parametric values, the degenerate plasma under consideration supports compressive or rarefactive solitary structures. It has been also found that the effect of pressures on electrons, ions, and positrons significantly modify the basic features of solitary waves that are found to exist in such a plasma system. The relevance of our results in astrophysical objects such as white dwarfs and neutron stars, which are of scientific interest, is discussed briefly.

  5. Rarefaction shock in plasma with a bi-Maxwellian electron distribution function

    SciTech Connect

    Diaw, A.; Mora, P.

    2011-09-15

    The one-dimensional collisionless expansion into a vacuum of a plasma with a bi-Maxwellian electron distribution function and a single ion species is studied both theoretically and numerically. A shock wave occurs when the ratio of the temperatures between the hot and the cold electrons is larger than 5+{radical}(24)[B. Bezzerides, D. W. Forslund, and E. L. Lindman, Phys. Fluids 21, 2179 (1978)]. The theoretical model presented here gives a coherent and complete description of the rarefaction shock and its effects on the ion acceleration process. Analytical expressions of the characteristics of the shock are given. The analytical findings are compared to the results of a hybrid code describing the plasma expansion, and an excellent agreement is obtained.

  6. Rarefaction shock in plasma with a bi-Maxwellian electron distribution function.

    PubMed

    Diaw, A; Mora, P

    2011-09-01

    The one-dimensional collisionless expansion into a vacuum of a plasma with a bi-Maxwellian electron distribution function and a single ion species is studied both theoretically and numerically. A shock wave occurs when the ratio of the temperatures between the hot and the cold electrons is larger than 5+√24 [B. Bezzerides, D. W. Forslund, and E. L. Lindman, Phys. Fluids 21, 2179 (1978)]. The theoretical model presented here gives a coherent and complete description of the rarefaction shock and its effects on the ion acceleration process. Analytical expressions of the characteristics of the shock are given. The analytical findings are compared to the results of a hybrid code describing the plasma expansion, and an excellent agreement is obtained. PMID:22060508

  7. Slip and accommodation coefficients from rarefaction and roughness in rotating microscale disk flows

    NASA Astrophysics Data System (ADS)

    Blanchard, Danny; Ligrani, Phil

    2007-06-01

    Accommodation coefficients are determined from experimental results and analysis based on the Navier-Stokes equations for rotation-induced flows in C-shaped fluid chamber passages formed between a rotating disk and a stationary surface. A first-order boundary condition is used to model the slip flow. The fluid chamber passage height ranges from 6.85to29.2μm to give Knudsen numbers from 0.0025 to 0.031 for air and helium. In all cases, roughness size is large compared to molecular mean free path. The unique method presented for deducing tangential momentum accommodation coefficients gives values with less uncertainty compared to procedures that rely on flows in stationary tubes and channels. When channel height is defined at the tops of the roughness elements, slip velocity magnitudes and associated accommodation coefficients are a result of rarefaction at solid-gas interfaces and shear at the gas-gas interfaces. With this arrangement, tangential accommodation coefficients obtained with this approach decrease, and slip velocity magnitudes increase, at a particular value of Knudsen number, as the level of surface roughness increases. At values of the mean roughness height greater than 500nm, accommodation coefficients then appear to be lower in air flows than in helium flows, when compared for a particular roughness configuration. When channel height is defined midway between the crests and troughs of the roughness elements, nondimensional pressure rise data show little or no dependence on the level of disk surface roughness and working fluid. With this arrangement, slip is largely independent of surface roughness magnitude and mostly due to rarefaction, provided the appropriate channel height is chosen to define the roughness height.

  8. Systemic influences contribute to prolonged microvascular rarefaction after brain irradiation: a role for endothelial progenitor cells

    PubMed Central

    Ashpole, Nicole M.; Warrington, Junie P.; Mitschelen, Matthew C.; Yan, Han; Sosnowska, Danuta; Gautam, Tripti; Farley, Julie A.; Csiszar, Anna; Ungvari, Zoltan

    2014-01-01

    Whole brain radiation therapy (WBRT) induces profound cerebral microvascular rarefaction throughout the hippocampus. Despite the vascular loss and localized cerebral hypoxia, angiogenesis fails to occur, which subsequently induces long-term deficits in learning and memory. The mechanisms underlying the absence of vessel recovery after WBRT are unknown. We tested the hypotheses that vascular recovery fails to occur under control conditions as a result of loss of angiogenic drive in the circulation, chronic tissue inflammation, and/or impaired endothelial cell production/recruitment. We also tested whether systemic hypoxia, which is known to promote vascular recovery, reverses these chronic changes in inflammation and endothelial cell production/recruitment. Ten-week-old C57BL/6 mice were subjected to a clinical series of fractionated WBRT: 4.5-Gy fractions 2 times/wk for 4 wk. Plasma from radiated mice increased in vitro endothelial cell proliferation and adhesion compared with plasma from control mice, indicating that WBRT did not suppress the proangiogenic drive. Analysis of cytokine levels within the hippocampus revealed that IL-10 and IL-12(p40) were significantly increased 1 mo after WBRT; however, systemic hypoxia did not reduce these inflammatory markers. Enumeration of endothelial progenitor cells (EPCs) in the bone marrow and circulation indicated that WBRT reduced EPC production, which was restored with systemic hypoxia. Furthermore, using a bone marrow transplantation model, we determined that bone marrow-derived endothelial-like cells home to the hippocampus after systemic hypoxia. Thus, the loss of production and homing of EPCs have an important role in the prolonged vascular rarefaction after WBRT. PMID:25038144

  9. Coronary Microvascular Rarefaction and Myocardial Fibrosis in Heart Failure with Preserved Ejection Fraction

    PubMed Central

    Mohammed, Selma F.; Hussain, Saad; Mirzoyev, Sultan A.; Edwards, William D.; Maleszewski, Joseph J.; Redfield, Margaret M.

    2014-01-01

    Background Characterization of myocardial structural changes in heart failure (HF) with preserved ejection fraction (HFpEF) has been hindered by limited availability of human cardiac tissue. Cardiac hypertrophy, coronary artery disease (CAD), coronary microvascular rarefaction and myocardial fibrosis may contribute to HFpEF pathophysiology. Methods and Results We identified HFpEF patients (n=124) and age-appropriate control patients (non-cardiac death, no HF diagnosis; n=104) who underwent autopsy. Heart weight and CAD severity were obtained from the autopsy reports. Using whole field digital microscopy and automated analysis algorithms in full thickness left ventricular (LV) sections, microvascular density (MVD), myocardial fibrosis and their relationship were quantified. Subjects with HFpEF had heavier hearts (median 538 g; 169% of age/sex/body size expected heart weight vs. 335 g; 112% in controls), more severe CAD (65% with ≥ one vessel with >50% diameter stenosis in HFpEF vs 13% in controls), more LV fibrosis (median % area fibrosis, 9.6 vs. 7.1) and lower MVD (median 961 vs. 1316 vessels per mm2) than control (p <0.0001 for all). Myocardial fibrosis increased with decreasing MVD in controls (r = − 0.28, p=0.004) and HFpEF (r = − 0.26, p=0.004). Adjusting for MVD attenuated the group differences in fibrosis. Heart weight, fibrosis and MVD were similar in HFpEF patients with vs without CAD. Conclusions In this study, patients with HFpEF had more cardiac hypertrophy, epicardial CAD, coronary microvascular rarefaction and myocardial fibrosis than controls. Each of these findings may contribute to the LV diastolic dysfunction and cardiac reserve function impairment characteristic of HFpEF. PMID:25552356

  10. Simulations of the Microcirculation in the Human Conjunctiva

    NASA Astrophysics Data System (ADS)

    Dow, William; Jacobitz, Frank; Chen, Peter

    2012-11-01

    The microcirculation in the conjunctiva of a healthy human subject is analyzed using a simulation approach. A comparison between healthy and diseased states may lead to early diagnosis for a variety of vascular related disorders. Previous work suggests that hypertension, arteriosclerosis, and diabetes mellitus have noticeable very early changes in the microvasculature (Davis and Landau, 1957; Ditzel, 1968; Kunitomo, 1974) and the vessels of the conjunctiva are specifically useful for this research because they can be studied non-invasively. The microcirculation in the conjunctiva has been documented over the course of disease treatments, providing both still images and video footage for information on vessel length, diameter, and connectivity as well as the direction of blood flow. The numerical method is based on a Hagen-Poiseuille balance in the microvessels and a sparse matrix solver is used to obtain the solution. The simulations use realistic vessel topology for the microvasculature, reconstructed from microscope images of tissue samples, and consider blood rheology as well as passive and active vessel properties.

  11. 2-D Model for Normal and Sickle Cell Blood Microcirculation

    NASA Astrophysics Data System (ADS)

    Tekleab, Yonatan; Harris, Wesley

    2011-11-01

    Sickle cell disease (SCD) is a genetic disorder that alters the red blood cell (RBC) structure and function such that hemoglobin (Hb) cannot effectively bind and release oxygen. Previous computational models have been designed to study the microcirculation for insight into blood disorders such as SCD. Our novel 2-D computational model represents a fast, time efficient method developed to analyze flow dynamics, O2 diffusion, and cell deformation in the microcirculation. The model uses a finite difference, Crank-Nicholson scheme to compute the flow and O2 concentration, and the level set computational method to advect the RBC membrane on a staggered grid. Several sets of initial and boundary conditions were tested. Simulation data indicate a few parameters to be significant in the perturbation of the blood flow and O2 concentration profiles. Specifically, the Hill coefficient, arterial O2 partial pressure, O2 partial pressure at 50% Hb saturation, and cell membrane stiffness are significant factors. Results were found to be consistent with those of Le Floch [2010] and Secomb [2006].

  12. Cerebral Microcirculation and Oxygen Tension in the Human Secondary Cortex

    PubMed Central

    Linninger, A. A.; Gould, I. G.; Marinnan, T.; Hsu, C.-Y.; Chojecki, M.; Alaraj, A.

    2013-01-01

    The three-dimensional spatial arrangement of the cortical microcirculatory system is critical for understanding oxygen exchange between blood vessels and brain cells. A three-dimensional computer model of a 3 × 3 × 3 mm3 subsection of the human secondary cortex was constructed to quantify oxygen advection in the microcirculation, tissue oxygen perfusion, and consumption in the human cortex. This computer model accounts for all arterial, capillary and venous blood vessels of the cerebral microvascular bed as well as brain tissue occupying the extravascular space. Microvessels were assembled with optimization algorithms emulating angiogenic growth; a realistic capillary bed was built with space filling procedures. The extravascular tissue was modeled as a porous medium supplied with oxygen by advection–diffusion to match normal metabolic oxygen demand. The resulting synthetic computer generated network matches prior measured morphometrics and fractal patterns of the cortical microvasculature. This morphologically accurate, physiologically consistent, multi-scale computer network of the cerebral microcirculation predicts the oxygen exchange of cortical blood vessels with the surrounding gray matter. Oxygen tension subject to blood pressure and flow conditions were computed and validated for the blood as well as brain tissue. Oxygen gradients along arterioles, capillaries and veins agreed with in vivo trends observed recently in imaging studies within experimental tolerances and uncertainty. PMID:23842693

  13. Effects of low-dose extracorporeal shock waves on microcirculation

    NASA Astrophysics Data System (ADS)

    Khaled, Walaa; Goertz, Ole; Lauer, Henrik; Lehnhardt, Marcus; Hauser, Jörg

    2012-11-01

    The extended wounds of burn patients remain a challenge due to wound infection and following septicemia. The aim of this study was to analyze microcirculation, angiogenesis and leukocyte endothelium interaction after burn injury with and without extracorporeal shock wave application (ESWA). A novel shockwave system was developed based on a commercially available device for orthopedics (Dornier Aries®) that was equipped with a newly developed applicator. This system is based on the electromagnetic shock wave emitter (EMSE) technology and was introduced to accomplish a localized treatment for wound healing. The system includes a novel field of focus for new applications, with high precision and ease of use. In the animal study, full-thickness burns were inflicted on to the ears of hairless mice (n=51). Intravital fluorescent microscopy was used to assess microcirculatory parameters, angiogenesis and leukocyte behavior. ESWA was performed on day 1, 3 and 7. Values were obtained immediately after burn, as well as at days 1, 3, 7, and 12 post burn. All shockwave treated groups showed an accelerated angiogenesis with a less non-perfused area and an improved blood flow after burn injury compared to the placebo control group. After three treatments, the shock waves increased the number of rolling leukocytes significantly compared to the non-treated animals. Shock waves seem to have a positive effect on several parameters of wound healing after burn injury. However, further investigations are necessary to detect positive influence of shock waves on microcirculation after burn injuries.

  14. Splanchnic microcirculation-evaluation with whole body computed tomography

    NASA Astrophysics Data System (ADS)

    Ritman, Erik L.; Pagel, Denise A.; Beighley, Patricia E.

    1995-05-01

    A fast, volume scanning, CT method is used to explore the feasibility of quantitating functional aspects of the in situ splanchnic microcirculation. Anesthetized pigs were scanned during and following the injection of contrast agent into the aorta. The indicator dilution curves generated by the passage of contrast medium through an imaged region of interest in the gut wall or through the liver parenchyma, were used to compute regional tissue perfusion and intravascular blood content of the tissue. Splanchnic perfusion was modulated by intra-arterial injection of Bradykinin and by the intragastric infusion of alcohol or hydrochloric acid. The results are consistent with values obtained with more invasive traditional methods for estimating these parameters under similar experimental conditions. We conclude that the resolution of the CT imaging method permits quantitative evaluation of changes in those splanchnic microcirculation following physiologic stimuli. The importance of bowel motion is apparent in these analyses. Indeed, the poorly periodic motion of the gut, even though it is slower than that of the heart wall, presents a greater problem than does the rapid motion of the heart wall, which is gateable because of its cycle-to-cycle reproducibility.

  15. 8 CFR 103.10 - Precedent decisions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... General are governed by part 1003 of 8 CFR chapter V. (b) Decisions as precedents. Except as Board... provided in paragraph (c) of this section or 8 CFR 1003.1(h)(2). (d) Publication of Secretary's...

  16. Note: Flow mediated skin fluorescence—A novel technique for evaluation of cutaneous microcirculation

    NASA Astrophysics Data System (ADS)

    Piotrowski, L.; Urbaniak, M.; Jedrzejczak, B.; Marcinek, A.; Gebicki, J.

    2016-03-01

    This note describes a newly developed technique for evaluation of cutaneous microcirculation. The technique called Flow Mediated Skin Fluorescence (FMSF) is based on monitoring of NADH fluorescence intensity emitted from the skin tissue cells of a forearm. The changes in fluorescence intensity as a function of time in response to blocking and releasing of blood flow in a forearm are used as a measure of oxygen transport with blood to the tissue, which directly correlates with the skin microcirculation status. Preliminary results collected for healthy volunteers and patients experiencing serious cardiovascular problems indicated a usefulness of FMSF technique for evaluation of health related perturbations in cutaneous microcirculation.

  17. Alpha adrenoceptors in the rabbit ear thermoregulatory microcirculation.

    PubMed

    Li, Z; Koman, L A; Smith, B P; Gordon, E S; Smith, T L

    1998-03-01

    The rabbit ear microcirculation was analyzed in a chronic unanesthetized model to evaluate alpha adrenergic microvascular control in a thermoregulatory end organ. This model allowed direct measurement of microcirculatory responses without the effects of anesthetics or inflammatory responses induced by acute surgical intervention. The ipsilateral facial artery was catheterized for drug injections into the experimental ear. Microvascular diameter changes following stimulation or blockade of adrenoceptor (AR) subtypes were observed directly through a chronic microvascular chamber implanted in the rabbit ear. Vascular alpha1- and alpha2-ARs appear to be distributed differently across the arterioles and AVAs of the rabbit ear. Both alpha1- and alpha2-ARs appear to contribute to vasoconstriction of AVAs in the conscious rabbit ear. In contrast, alpha1-AR's (vs alpha2-ARs) appear to predominate in adrenergically mediated sympathetic vasoconstriction of arterioles. PMID:9521886

  18. Effect of Convection in Microcirculation on Diffusion to Tissue

    NASA Astrophysics Data System (ADS)

    Thamire, Chandrasekhar

    2000-11-01

    Flow and transport of Oxygen in a capillary are studied numerically. Governing equations for flow and mass transport in the lumen are solved using a finite-differencing method. Creeping flow situation is studied because of the small Reynolds numbers existing in the microcirculation, with a zero-drag condition imposed on the erythrocyte. Relative sizes of the erythrocyte and the plasma-gap are varied for different physiologically relevant Peclet numbers, Pe. Mass-transfer ratios at the capillary and erythrocyte walls are calculated for no-flow and flow situations. Results indicate that the effect of recirculation in the plasma gap on diffusion of species decreases with increasing radial clearance between the erythrocyte and the capillary for all values of hematocrit and Pe studied.

  19. Integrating in vitro organ-specific function with the microcirculation

    PubMed Central

    Moya, Monica L.; George, Steven C.

    2014-01-01

    There is significant interest within the tissue engineering and pharmaceutical industries to create 3D microphysiological systems of human organ function. The interest stems from a growing concern that animal models and simple 2D culture systems cannot replicate essential features of human physiology that are critical to predict drug response, or simply to develop new therapeutic strategies to repair or replace damaged organs. Central to human organ function is a microcirculation that not only enhances the rate of nutrient and waste transport by convection, but also provides essential additional physiological functions that can be specific to each organ. This review highlights progress in the creation of in vitro functional microvessel networks, and emphasizes organ-specific functional and structural characteristics that should be considered in the future mimicry of four organ systems that are of primary interest: lung, brain, liver, and muscle (skeletal and cardiac). PMID:24729953

  20. Influence of topically applied antimicrobial agents on muscular microcirculation.

    PubMed

    Goertz, Ole; Hirsch, Tobias; Ring, Andrej; Steinau, Hans U; Daigeler, Adrien; Lehnhardt, Marcus; Homann, Heinz H

    2011-10-01

    Bacterial infections cause major complications in wound healing. Local antiseptics are used for daily wound care; however, their potential toxic effects on the vasculature have not yet been thoroughly investigated. The aim of this study was to assess the effects of antiseptics on microcirculation. Investigations were performed on a standardized cremaster muscle model on rats (n = 60). The arteriolar diameter and functional capillary density (FCD) were investigated using transillumination microscopy before and 60 and 120 minutes after application of each of the following antimicrobial agents: alcohol, hydrogen peroxide, imipenem, octenidine dihydrochloride, polyhexanide, and ethacridine lactate. Although polyhexanide caused a significant arteriolar dilatation (106.25 ± 3.23 vs. 88.54 ± 6.74 μm [baseline value]) and increase of FCD compared with baseline value (12.65 ± 0.82 vs. 9.10 ± 0.50 n/0.22 mm), alcohol led to a significant decrease of both parameters (90.63 ± 10.80 vs. 52.09 ± 7.69 and 5.35 ± 0.54 vs. 1.68 ± 0.48) and was the only agent that caused arteriolar thrombosis. The FCD also increased significantly after treatment with hydrogen peroxide (10.55 ± 0.33 vs. 12.30 ± 0.48) and octenidine (6.82 ± 0.63 vs. 12.32 ± 0.63). However, no positive effect on arteriolar diameter could be found. Ethacridine lactate and imipenem did not impact either parameter. In addition to reducing bacteria, an antiseptic should be nontoxic, especially to the microcirculation. Polyhexanide seems to have a positive influence on vessel diameter and capillary density, whereas alcohol reduces both parameters. If the antimicrobial efficacy is comparable, the antiseptic with less toxic effects should be chosen, especially in critically perfused wounds. PMID:21407057

  1. Normal velocity freeze-out of the Richtmyer-Meshkov instability when a rarefaction is reflected.

    PubMed

    Wouchuk, J G; Sano, T

    2015-02-01

    The Richtmyer-Meshkov instability (RMI) develops when a shock front hits a rippled contact surface separating two different fluids. After the incident shock refraction, a transmitted shock is always formed and another shock or a rarefaction is reflected back. The pressure-entropy-vorticity fields generated by the rippled wave fronts are responsible for the generation of hydrodynamic perturbations in both fluids. In linear theory, the contact surface ripple reaches an asymptotic normal velocity which is dependent on the incident shock Mach number, fluids density ratio, and compressibilities. It was speculated in the past about the possibility of getting a zero value for the asymptotic normal velocity, a phenomenon that was called "freeze-out" [G. Fraley, Phys. Fluids 29, 376 (1986); K. Mikaelian, Phys. Fluids 6, 356 (1994), A. L. Velikovich et al., Phys. Plasmas 8, 592 (2001)]. In a previous paper, freeze-out was studied for the case when a shock is reflected at the contact surface [J. G. Wouchuk and K. Nishihara, Phys. Rev. E 70, 026305 (2004)]. In this work the freeze-out of the RMI is studied for the case in which a rarefaction is reflected back. Two different regimes are found: nearly equal preshock densities at the interface at any shock intensity, and very large density difference for strong shocks. The contour curves that relate shock Mach number and preshock density ratio are obtained in both regimes for fluids with equal and different compressibilities. An analysis of the temporal evolution of different cases of freeze-out is shown. It is seen that the freeze-out is the result of the interaction between the unstable interface and the rippled wave fronts. As a general and qualitative criterion to look for freeze-out situations, it is seen that a necessary condition for freeze-out is the same orientation for the tangential velocities generated at each side of the contact surface at t=0+. A comparison with the results of previous works is also shown. PMID

  2. Microcirculation of liver cancer, microenvironment of liver regeneration, and the strategy of Chinese medicine.

    PubMed

    Li, Han-min

    2016-03-01

    Microcirculation of liver cancer is the micro-vascular system which comes from the tissue of liver cancer. It can offer the nutritional requirement for accelerating the cancer cell proliferation and metastasis. The intrinsic mechanism of angiogenesis is the key link in the formation of liver cancer microcirculation system. Liver regeneration microenvironment also plays an important role in the construction of liver cancer microcirculation, through the improvement of liver regeneration microenvironment affecting tumor microcirculation is the new strategy of prevention and treatment of liver cancer. In recent years, it is found that many kinds of Chinese medicine can inhibit angiogenesis, decrease the microvessel density, and delay or prevent the development of liver cancer. PMID:26919996

  3. Effect of electroconvulsive stimulation on morphological and physiological aspects of post-cardiac arrest cerebral microcirculation.

    PubMed

    Sheleg, Sergey; Hixon, Hugh; Aizberg, Oleg R; Korotkevich, Alexander E; Nedzved, Mikhail K

    2008-09-01

    We investigated the effect of electroconvulsive stimulation (ECS) on cerebral circulation in vivo using the method for measuring microcirculation in real time with the photosensitizer dye Photosense and the fiber optic spectrofluorometer LESA-01-BIOSPEC. We have found that electroconvulsive stimulation significantly improved cerebral microcirculation (fourfold higher comparing to the control cerebral perfusion) after 30 min of room-temperature cardiac arrest. Morphologic study of the brain tissue showed the absence of rouleaux formation of erythrocytes ("sludged blood") in the cerebral cortex microcirculation after the application of electrical stimulus. Electroconvulsive stimulation may be useful for improving cerebral microcirculation (blood flow) in cases of long-term brain hypoxia/anoxia after prolonged cardiac arrest. PMID:18586374

  4. Compressive and rarefactive ion acoustic solitons in a magnetized two-ion component plasma

    NASA Astrophysics Data System (ADS)

    Ur-Rehman, Hafeez; Mahmood, S.; Aman-ur-Rehman

    2014-10-01

    The formation of compressive (hump) and rarefactive (dip) ion acoustic solitons is studied in magnetized O+- H+- e and O+- H-- e plasmas. The hydrodynamics equations are described for cold heavy (oxygen) ions, warm light (hydrogen) ions and isothermal Boltzmann distributed electrons along with Poisson equations in the presence of a magnetic field. The reductive perturbation method is used to derive the nonlinear Zakharov-Kuznetsov (ZK) equation for an ion acoustic wave in magnetized two-ion component plasma. It is found that two modes of ion acoustic waves with fast and slow speeds can propagate in the linear limit in such a plasma. It is noticed that, in the case of positively charged light hydrogen ions O+- H+- e plasmas, the slow ion acoustic wave solitons formed both potential hump as well as dip structures, while fast ion acoustic wave solitons give only hump structures. However in the case of negatively charged light hydrogen ions O+- H-- e plasmas, the slow ion acoustic wave solitons formed potential hump structures while fast ion acoustic wave solitons produce dip structures. The variations in the amplitude and width of the nonlinear slow and fast ion acoustic wave structures with density, temperature of light ions and magnetic field intensity are obtained in magnetized two-ion component plasmas. The magnetic field has its effect only on the width of the nonlinear ion acoustic wave structures in two-ion component plasmas.

  5. Muscle-specific vascular endothelial growth factor deletion induces muscle capillary rarefaction creating muscle insulin resistance.

    PubMed

    Bonner, Jeffrey S; Lantier, Louise; Hasenour, Clinton M; James, Freyja D; Bracy, Deanna P; Wasserman, David H

    2013-02-01

    Muscle insulin resistance is associated with a reduction in vascular endothelial growth factor (VEGF) action and muscle capillary density. We tested the hypothesis that muscle capillary rarefaction critically contributes to the etiology of muscle insulin resistance in chow-fed mice with skeletal and cardiac muscle VEGF deletion (mVEGF(-/-)) and wild-type littermates (mVEGF(+/+)) on a C57BL/6 background. The mVEGF(-/-) mice had an ~60% and ~50% decrease in capillaries in skeletal and cardiac muscle, respectively. The mVEGF(-/-) mice had augmented fasting glucose turnover. Insulin-stimulated whole-body glucose disappearance was blunted in mVEGF(-/-) mice. The reduced peripheral glucose utilization during insulin stimulation was due to diminished in vivo cardiac and skeletal muscle insulin action and signaling. The decreased insulin-stimulated muscle glucose uptake was independent of defects in insulin action at the myocyte, suggesting that the impairment in insulin-stimulated muscle glucose uptake was due to poor muscle perfusion. The deletion of VEGF in cardiac muscle did not affect cardiac output. These studies emphasize the importance for novel therapeutic approaches that target the vasculature in the treatment of insulin-resistant muscle. PMID:23002035

  6. ADZE: a rarefaction approach for counting alleles private to combinations of populations

    PubMed Central

    Szpiech, Zachary A.; Jakobsson, Mattias; Rosenberg, Noah A.

    2008-01-01

    Motivation: Analysis of the distribution of alleles across populations is a useful tool for examining population diversity and relationships. However, sample sizes often differ across populations, sometimes making it difficult to assess allelic distributions across groups. Results: We introduce a generalized rarefaction approach for counting alleles private to combinations of populations. Our method evaluates the number of alleles found in each of a set of populations but absent in all remaining populations, considering equal-sized subsamples from each population. Applying this method to a worldwide human microsatellite dataset, we observe a high number of alleles private to the combination of African and Oceanian populations. This result supports the possibility of a migration out of Africa into Oceania separate from the migrations responsible for the majority of the ancestry of the modern populations of Asia, and it highlights the utility of our approach to sample size correction in evaluating hypotheses about population history. Availability: We have implemented our method in the computer pro-gram ADZE, which is available for download at http://rosenberglab.bioinformatics.med.umich.edu/adze.html. Contact: szpiechz@umich.edu PMID:18779233

  7. Rarefaction-singular shock dynamics for conserved volume gravity driven particle-laden thin film

    NASA Astrophysics Data System (ADS)

    Wang, L.; Mavromoustaki, A.; Bertozzi, A. L.; Urdaneta, G.; Huang, K.

    2015-03-01

    We employ a recently proposed model [Murisic et al., "Dynamics of particle settling and resuspension in viscous liquids," J. Fluid. Mech. 717, 203-231 (2013)] to study a finite-volume, particle-laden thin film flowing under gravity on an incline. For negatively buoyant particles with concentration above a critical value and buoyant particles, the particles accumulate at the front of the flow forming a particle-rich ridge, whose similarity solution is of the rarefaction-singular shock type. We investigate the structure in detail and find that the particle/fluid front advances linearly to the leading order with time to the one-third power as predicted by the Huppert solution [H. E. Huppert, "Flow and instability of a viscous current down a slope," Nature 300, 427-419 (1982)] for clear fluid (i.e., in the absence of particles). We also explore a deviation from this law when the particle concentration is high. Several experiments are carried out with both buoyant and negatively buoyant particles whose results qualitatively agree with the theoretics.

  8. Intermittent pressure overload triggers hypertrophy-independent cardiac dysfunction and vascular rarefaction

    PubMed Central

    Perrino, Cinzia; Prasad, Sathyamangla V. Naga; Mao, Lan; Noma, Takahisa; Yan, Zhen; Kim, Hyung-Suk; Smithies, Oliver; Rockman, Howard A.

    2006-01-01

    For over a century, there has been intense debate as to the reason why some cardiac stresses are pathological and others are physiological. One long-standing theory is that physiological overloads such as exercise are intermittent, while pathological overloads such as hypertension are chronic. In this study, we hypothesized that the nature of the stress on the heart, rather than its duration, is the key determinant of the maladaptive phenotype. To test this, we applied intermittent pressure overload on the hearts of mice and tested the roles of duration and nature of the stress on the development of cardiac failure. Despite a mild hypertrophic response, preserved systolic function, and a favorable fetal gene expression profile, hearts exposed to intermittent pressure overload displayed pathological features. Importantly, intermittent pressure overload caused diastolic dysfunction, altered β-adrenergic receptor (βAR) function, and vascular rarefaction before the development of cardiac hypertrophy, which were largely normalized by preventing the recruitment of PI3K by βAR kinase 1 to ligand-activated receptors. Thus stress-induced activation of pathogenic signaling pathways, not the duration of stress or the hypertrophic growth per se, is the molecular trigger of cardiac dysfunction. PMID:16741575

  9. One-dimensional rarefactive solitons in electron-hole semiconductor plasmas

    NASA Astrophysics Data System (ADS)

    Wang, Yunliang; Eliasson, Bengt

    2014-05-01

    We present a theory for linear and nonlinear excitations in semiconductor quantum plasmas consisting of electrons and holes. The system is governed by two coupled nonlinear Schrödinger equations for the collective wave functions of the electrons and holes and Poisson's equation for the electrostatic potential. This gives a closed system including the effects of charge separation between the electrons and holes, quantum tunneling, quantum statistics, and exchange correlation due to electron spin. Three typical semiconductors, GaAs, GaSb, and GaN, are studied. For small-amplitude excitations, the dispersion relation reveals the existence of one high-frequency branch due to charge-separation effects and one low-frequency branch due to the balance between pressure and inertia of the electrons and holes. For the fully nonlinear excitations, the profiles of quasistationary soliton solutions are obtained numerically and show depleted electron and hole densities correlated with a localized potential. The simulation results show that the rarefactive solitons are stable and can withstand perturbations and turbulence for a considerable time.

  10. DSMC-LBM hybrid scheme for flows with variable rarefaction conditions

    NASA Astrophysics Data System (ADS)

    di Staso, Gianluca; Succi, Sauro; Toschi, Federico; Clercx, Herman

    2015-11-01

    The kinetic description of gases, based on the Boltzmann equation, allows to cover flow regimes ranging from the rarefied to the continuum limit. The two limits are traditionally studied by numerically approximating the Boltzmann equation via Direct Simulation Monte Carlo (DSMC) method or the Lattice Boltzmann Equation method (LBM). While DSMC is suitable for rarefied flows, its computational cost makes it unpractical to study hydrodynamic flows. The LBM has instead proved itself to be an efficient and accurate method in the hydrodynamic limit even though simulation of rarefied flows requires additional modeling. Here, results on the development of a hybrid scheme capable of coupling the LBM and the DSMC methods and able to efficiently simulate flows with variable rarefaction conditions are presented. The coupling scheme is based on Grad's moment method approach and the local single particle distribution function at a given order of truncation is built by using the Hermite polynomials expansion approach and Gauss-Hermite quadratures. The capabilities of the hybrid approach for simulating flows in the transition regime are illustrated in the case of planar Couette and Poiseuille flows.

  11. Low Intensity Laser Therapy (LILT) Versus Transcutaneous Electrical Nerve Stimulation On Microcirculation In Diabetic Neuropathy

    NASA Astrophysics Data System (ADS)

    Battecha, Kadria H.; Atya, Azza M.

    2011-09-01

    Reduced microcirculation is a morbid element of neuropathy and one of the most common complications of uncontrolled diabetes. Many physical modalities have gained a considerable attention for enhancing cutaneous microcirculation in diabetic patients and prevent its serious complications. Accordingly, the present study was conducted to compare between the effect of low intensity laser therapy (LILT) and transcutaneous electrical nerve stimulation (TENS) on microcirculation in diabetic neuropathy. Thirty diabetic polyneuropathic patients ranged in age from 45-60 years participated in this study. They were randomly divided into two groups of equal number; patients in group (A) received LILT on plantar surface of foot with a dose of 3 J/cm2 and wavelength (904 nm), while those in group (B) received TENS on lower leg for 30 minutes with frequency (2 HZ). Treatment was conducted 3 times/week for 6 weeks. The cutaneous microcirculation was evaluated by Laser Doppler flowmetry at the baseline and at the end of treatment. Results revealed that group (A) showed statistically significant increase in the cutaneous microcirculation compared with group (B). So, it was concluded that LILT has to be more efficient than TENS in increasing cutaneous microcirculation in patients with diabetic neuropathy.

  12. Generation of precedence relations for mechanical assemblies

    NASA Technical Reports Server (NTRS)

    Zhang, Hui; Sanderson, A. C.

    1989-01-01

    Planning of assembly sequences is essential to the manufacturing system design process. Several methodologies have been proposed to represent all the feasible assembly sequences. In this thesis, three algorithms are presented to generate three sets of precedence relations based on all the infeasible assembly tasks, all the infeasible assembly states, and all the feasible assembly sequences, respectively. The equivalence of the resulting sets of precedence relations to the AND/OR graph is established. A new property, the real time property, of a representation of assembly sequences is defined and discussed. A representation of assembly sequences is said to have the real time property, if it is possible to generate the next assembly task by testing locally in the representation, and it will guarantee that the generated assembly task will not lead the assembly sequence to a dead end situation, in which no feasible assembly task can be performed any more. It is shown that the correctness and completeness of one representation can not guarantee the real time property of the representation. It is proven that the directed graph representation and the set of precedence relations based on all the infeasible assembly states have the real time property, while the AND/OR graph representation and the set of precedence relations based on all the infeasible assembly tasks do not have the real time property. Finally in the thesis, the PLEIDEAS system, a PLanning Environment for Integrated DEsign of Assembly Systems, is described and illustrated by an example.

  13. On the Rhetoric and Precedents of Racism.

    ERIC Educational Resources Information Center

    Villanueva, Victor

    1999-01-01

    Considers contribution of rhetorical training of the Aztecs prior to the European conquest as well as other early philosophers from the Americas. Encourages breaking precedent in order to battle racism by looking to rhetorical training developed in the Americas and Puerto Rico in addition to the European thinkers. (SC)

  14. More Than the Rules of Precedence

    ERIC Educational Resources Information Center

    Liang, Yawei

    2005-01-01

    In a fundamental computer-programming course, such as CSE101, questions about how to evaluate an arithmetic expression are frequently used to check if our students know the rules of precedence. The author uses two of our final examination questions to show that more knowledge of computer science is needed to answer them correctly. Furthermore,…

  15. Sleep Disturbance Preceding Completed Suicide in Adolescents

    ERIC Educational Resources Information Center

    Goldstein, Tina R.; Bridge, Jeffrey A.; Brent, David A.

    2008-01-01

    We examined sleep difficulties preceding death in a sample of adolescent suicide completers as compared with a matched sample of community control adolescents. Sleep disturbances were assessed in 140 adolescent suicide victims with a psychological autopsy protocol and in 131 controls with a similar semistructured psychiatric interview. Rates of…

  16. Thrombotic thrombocytopenic purpura preceding systemic lupus erythematosus.

    PubMed Central

    Simeon-Aznar, C P; Cuenca-Luque, R; Fonollosa-Pla, V; Bosch-Gil, J A

    1992-01-01

    The case of a patient admitted with thrombotic thrombocytopenic purpura nine years after developing systemic lupus erythematosus (SLE) is reported. Thrombotic thrombocytopenic purpura associated with SLE has been described on other occasions, but in most patients the diagnosis of SLE precedes that of thrombotic thrombocytopenic purpura. The unusual sequence and the chronological separation of the two diseases is emphasised. PMID:1575591

  17. Targeting of the tumor microcirculation with a new photosensitizer

    NASA Astrophysics Data System (ADS)

    Abels, Christoph; Dellian, Marc; Szeimies, Rolf-Markus; Steinbach, Pia; Richert, C.; Goetz, Alwin E.

    1996-01-01

    Tumors are characterized by an insufficient neoangiogenesis. Therefore targeting of the fragile tumor microcirculation by photodynamic therapy (PDT) may induce easily tumor ischemia leading to tumor necrosis. Nine-acetoxy-2,7,12,17-tetrakis-((beta) -methoxyethyl)- prophycene (ATMPn) is a chemically pure, lipophilic substance and revealed superior photodynamic characteristics in vitro as compared to PhotofrinR. In this study pharmacokinetics, photodynamic effects and localization of ATMPn incorporated in small unilamellar liposomes in tumor and surrounding normal tissue were evaluated. Amelanotic melanomas (A-Mel-3) were implanted in dorsal skin fold chambers fitted to Syrian Golden hamsters (70 - 80 g b.w.). Fluorescence kinetics of ATMPn administered intravenously (1.4 micrometers ol/kg b.w.; n equals 8) were monitored by intravital microscopy. Quantitative measurements of fluorescence intensity were carried out by digital image analysis. For tumor growth studies 1.4 micrometers ol/kg was injected 24 h (n equals 3), 3 h (n equals 3), 1 min (n equals 6) and 2.8 micrometers ol/kg 1 min (n equals 6) before PDT (630 nm, 100 mW/cm2, 100 J/cm2). Tumor growth was measured over 28 days. Solid tumors (n equals 3) were excised 1 min after injection of ATMPn (1.4 micrometers ol/kg) and cryostat sections (10 micrometers) were analyzed by confocal laser scanning microscopy (CSLM) to determine tissue localization of dye. Maximal fluorescence (mean plus or minus S.E.) arose in tumor (94 plus or minus 7%) and surrounding host tissue (67 plus or minus 5%) 30 s post injection followed by a rapid decrease. Hardly any fluorescence was detectable after 12 h. Only PDT 1 min after injection of ATMPn was effective yielding 1/6 complete remission (1.4 micrometers ol/kg) and 3/6 complete remissions (2.8 mmol/kg), respectively. At that time dye is primarily localized in vessels and vessel walls as shown by CSLM. ATMPn in liposomes reveals very rapid kinetics thus suitable for intraoperative

  18. Microvascular Transport and Tumor Cell Adhesion in the Microcirculation

    PubMed Central

    Fu, Bingmei M.; Liu, Yang

    2016-01-01

    One critical step in tumor metastasis is tumor cell adhesion to the endothelium forming the microvessel wall. Understanding this step may lead to new therapeutic concepts for tumor metastasis. Vascular endothelium forming the microvessel wall and the glycocalyx layer at its surface are the principal barriers to, and regulators of the material exchange between circulating blood and body tissues. The cleft between adjacent ECs (interendothelial cleft) is the principal pathway for water and solutes transport through the microvessel wall in health. It is also suggested to be the pathway for high molecular weight plasma proteins, leukocytes and tumor cells across microvessel walls in disease. Thus the first part of the review introduced the mathematical models for water and solutes transport through the interendothelial cleft. These models, combined with the experimental results from in vivo animal studies and electron microscopic observations, are used to evaluate the role of the endothelial surface glycocalyx, the junction strand geometry in the interendothelial cleft, and the surrounding extracellular matrix and tissue cells, as the determinants of microvascular transport. The second part of the review demonstrated how the microvascular permeability, hydrodynamic factors, microvascular geometry and cell adhesion molecules affect tumor cell adhesion in the microcirculation. PMID:22476895

  19. Numerical Simulation of Sickle Cell Blood Flow in the Microcirculation

    NASA Astrophysics Data System (ADS)

    Berger, Stanley A.; Carlson, Brian E.

    2001-11-01

    A numerical simulation of normal and sickle cell blood flow through the transverse arteriole-capillary microcirculation is carried out to model the dominant mechanisms involved in the onset of vascular stasis in sickle cell disease. The transverse arteriole-capillary network is described by Strahler's network branching method, and the oxygen and blood transport in the capillaries is modeled by a Krogh cylinder analysis utilizing Lighthill's lubrication theory, as developed by Berger and King. Poiseuille's law is used to represent blood flow in the arterioles. Applying this flow and transport model and utilizing volumetric flow continuity at each network bifurcation, a nonlinear system of equations is obtained, which is solved iteratively using a steepest descent algorithm coupled with a Newton solver. Ten different networks are generated and flow results are calculated for normal blood and sickle cell blood without and with precapillary oxygen loss. We find that total volumetric blood flow through the network is greater in the two sickle cell blood simulations than for normal blood owing to the anemia associated with sickle cell disease. The percentage of capillary blockage in the network increases dramatically with decreasing pressure drop across the network in the sickle cell cases while there is no blockage when normal blood flows through simulated networks. It is concluded that, in sickle cell disease, without any vasomotor dilation response to decreasing oxygen concentrations in the blood, capillary blockage will occur in the microvasculature even at average pressure drops across the transverse arteriole-capillary networks.

  20. Patterns of seismic activity preceding large earthquakes

    NASA Technical Reports Server (NTRS)

    Shaw, Bruce E.; Carlson, J. M.; Langer, J. S.

    1992-01-01

    A mechanical model of seismic faults is employed to investigate the seismic activities that occur prior to major events. The block-and-spring model dynamically generates a statistical distribution of smaller slipping events that precede large events, and the results satisfy the Gutenberg-Richter law. The scaling behavior during a loading cycle suggests small but systematic variations in space and time with maximum activity acceleration near the future epicenter. Activity patterns inferred from data on seismicity in California demonstrate a regional aspect; increased activity in certain areas are found to precede major earthquake events. One example is given regarding the Loma Prieta earthquake of 1989 which is located near a fault section associated with increased activity levels.

  1. Dysfunctional Microcirculation of the Lumbar Vertebral Marrow Prior to the Bone Loss and Intervertebral Discal Degeneration

    PubMed Central

    Lu, Guang-ming

    2015-01-01

    Study Design. Descriptive study, stratified sampling. Objective. Using dynamic computed tomographic perfusion (CTP) to explore the age-related distribution patterns of the microcirculation perfusion in the vertebral marrow, the vertebral bone mineral density (BMD), and the intervertebral discal degeneration (IDD) further to discuss the possible causation between them. Summary of Background Data. A latest viewpoint deemed that reduced blood supply of the vertebral marrow was correlated with an increased incidence of IDD and loss of BMD. However, the causative relationship between them needs more investigation. Methods. One hundred eighty-six general people were randomly enrolled by stratified sampling and grouped by age: 15 years or less, 16 to 25 years, 26 to 35 years, 36 to 45 years, 46 to 55 years, 56 to 65 years, 66 to 75 years, and 76 years or more. Both CTP and BMD of the third and fourth lumbar vertebral marrow were measured, and the IDD incidence of the third-fourth vertebrae was assessed. The temporal-spatial distribution patterns of the age-related changes of CTP, BMD, and IDD were described, and the correlations between them were calculated. Results. Microcirculatory perfusion of the vertebral marrow developed to maturate by 25 years, maintained stable at 35 years, and then declined by age after 35 years. BMD grew to a peak phase in 26 to 45 years and then dropped by years. However, IDD presented a sudden increase after 45 years of age. CTP (blood flow [r = 0.806], blood volume [r = 0.685], and permeability [r = 0.619]) showed strong positive correlations and CTP (time to peak [r = −0.211], mean transit time [r = −0.598]) showed negative correlations with BMD. Meanwhile, CTP (blood flow [r = −0.815], blood volume [r = −0.753], and permeability [r = −0.690]) had strong negative correlations and CTP (time to peak [r = 0.323] and mean transit time [r = 0.628]) had positive correlations with the incidence of IDD. Conclusion. Aging-related decrease

  2. Threshold of the precedence effect in noise

    PubMed Central

    Freyman, Richard L.; Griffin, Amanda M.; Zurek, Patrick M.

    2014-01-01

    Three effects that show a temporal asymmetry in the influence of interaural cues were studied through the addition of masking noise: (1) The transient precedence effect—the perceptual dominance of a leading transient over a similar lagging transient; (2) the ongoing precedence effect—lead dominance with lead and lag components that extend in time; and (3) the onset capture effect—determination by an onset transient of the lateral position of an otherwise ambiguous extended trailing sound. These three effects were evoked with noise-burst stimuli and were compared in the presence of masking noise. Using a diotic noise masker, detection thresholds for stimuli with lead/lag interaural delays of 0/500 μs were compared to those with 500/0 μs delays. None of the three effects showed a masking difference between those conditions, suggesting that none of the effects is operative at masked threshold. A task requiring the discrimination between stimuli with 500/0 and 0/500 μs interaural delays was used to determine the threshold for each effect in noise. The results showed similar thresholds in noise (10–13 dB SL) for the transient and ongoing precedence effects, but a much higher threshold (33 dB SL) for onset capture of an ambiguous trailing sound. PMID:24815272

  3. Correlation mapping: rapid method for retrieving microcirculation morphology from optical coherence tomography intensity images

    NASA Astrophysics Data System (ADS)

    Jonathan, E.; Enfield, J.; Leahy, M. J.

    2011-03-01

    The microcirculation plays a critical role is maintaining organ health and function by serving as a vascular are where trophic metabolism exchanges between blood and tissue takes place. To facilitate regular assessment in vivo, noninvasive microcirculation imagers are required in clinics. Among this group of clinical devices, are those that render microcirculation morphology such as nailfold capillaroscopy, a common device for early diagnosis and monitoring of microangiopathies. However, depth ambiguity disqualify this and other similar techniques in medical tomography where due to the 3-D nature of biological organs, imagers that support depth-resolved 2-D imaging and 3-D image reconstruction are required. Here, we introduce correlation map OCT (cmOCT), a promising technique for microcirculation morphology imaging that combines standard optical coherence tomography and an agile imaging analysis software based on correlation statistic. Promising results are presented of the microcirculation morphology images of the brain region of a small animal model as well as measurements of vessel geometry at bifurcations, such as vessel diameters, branch angles. These data will be useful for obtaining cardiovascular related characteristics such as volumetric flow, velocity profile and vessel-wall shear stress for circulatory and respiratory system.

  4. The diagnosis of lymph microcirculation in experimental studies on rat mesentery in vivo

    NASA Astrophysics Data System (ADS)

    Galanzha, Ekateryna I.; Tuchin, Valery V.; Zharov, Vladimir P.; Solovieva, Anastasia V.; Stepanova, Tatyana V.; Brill, Gregory E.

    2003-07-01

    The many biological and medical problems associated with microlymphatic functioning and its disturbances at different diseases, include primary and secondary lymphedema, inflammation, lymphatic malformations, and so on. It is important both to establish an adequate animal model for study lymph microcirculation in vivo and to match it with corresponding diagnostic techniques. The rat mesentery has been successfully used in experiments focusing on the microcirculation, including small lymphatics. Among optical methods the transmittance microscopy is most widely employed to study microcirculation. We have undertaken following investigations: development and evaluation of capability of transmission microscopy for in vivo studies of microcirculation; obtaining of single cell images; estimation of lymph microcirculation parameters, including the relation of forward to backward flow in intact lymphatics; regulation of microlymphatic function by nitric oxide and study of microlymphatic disturbances at the experimental lymphedema. Although interesting data has been obtained, the transmission microscopy has the relatively low absorption sensitivity and prevents obtaining good absorption contrast. To obtain more comprehensive physiological data, the further development and improvement imaging of rat mesentery is discussed with focus on new combined optical imaging systems which integrate recent advances in video-transmission and photothermal (PT) microscopy, PT fluid velocimetry, and laser spectroscopy.

  5. Characterization of skin dermis microcirculation in flow-mediated dilation using optical sensor with pressurization mechanism.

    PubMed

    Yamakoshi, Yoshiki; Kotani, Kazuhiko; Taniguchi, Nobuyuki; Miwa, Takashi

    2013-05-01

    Blood flows out of microvessels in the dermis when pressure higher than arterial blood pressure is applied to the fingertip, and subsequently re-flows into the microcirculation when pressure is released. Both the blood outflow and the reflow characteristics of microcirculation under pressurization are associated with microvasculature, blood and blood pressure. This study describes a novel method of measuring blood inflow and outflow characteristics of dermis microcirculation. An optical sensor, which is furnished with a 571 nm wavelength light source and a photodetector, is pressed to the skin surface using a pressure higher than the human subject's systolic arterial pressure. Hemoglobin concentration by change of the blood flow amount is estimated by the Beer-Lambert law. This method is applied to the measurement of blood inflow and outflow characteristics of microcirculation caused by reactive hyperemia after ischemia with duration of 5 min. Among three parameters evaluated, the one relating to the amplitude of pulsation shows a close correlation with conventional plethysmography, while the other two show varying time responses. Our method provides a new and useful insight into pathophysiology in health and disease conditions and may help researchers better understand the underlying mechanisms of numerous microcirculation-influenced diseases and medical conditions. PMID:23274949

  6. In vivo assessment of the structure of skin microcirculation by reflectance confocal-laser-scanning microscopy

    NASA Astrophysics Data System (ADS)

    Sugata, Keiichi; Osanai, Osamu; Kawada, Hiromitsu

    2012-02-01

    One of the major roles of the skin microcirculation is to supply oxygen and nutrition to the surrounding tissue. Regardless of the close relationship between the microcirculation and the surrounding tissue, there are few non-invasive methods that can evaluate both the microcirculation and its surrounding tissue at the same site. We visualized microcapillary plexus structures in human skin using in vivo reflectance confocal-laser-scanning microscopy (CLSM), Vivascope 3000® (Lucid Inc., USA) and Image J software (National Institutes of Health, USA) for video image processing. CLSM is a non-invasive technique that can visualize the internal structure of the skin at the cellular level. In addition to internal morphological information such as the extracellular matrix, our method reveals capillary structures up to the depth of the subpapillary plexus at the same site without the need for additional optical systems. Video images at specific depths of the inner forearm skin were recorded. By creating frame-to-frame difference images from the video images using off-line video image processing, we obtained images that emphasize the brightness depending on changes of intensity coming from the movement of blood cells. Merging images from different depths of the skin elucidates the 3-dimensional fine line-structure of the microcirculation. Overall our results show the feasibility of a non-invasive, high-resolution imaging technique to characterize the skin microcirculation and the surrounding tissue.

  7. IMPACT OF CHRONIC ANTI-CHOLESTEROL THERAPY ON DEVELOPMENT OF MICROVASCULAR RAREFACTION IN THE METABOLIC SYNDROME

    PubMed Central

    Goodwill, Adam G.; Frisbee, Stephanie J.; Stapleton, Phoebe A.; James, Milinda E.; Frisbee, Jefferson C.

    2011-01-01

    Object The obese Zucker rat (OZR) model of the metabolic syndrome is partly characterized by moderate hypercholesterolemia in addition to other contributing co-morbidities. Previous results suggest that vascular dysfunction in OZR is associated with chronic reduction in vascular nitric oxide (NO) bioavailability and chronic inflammation, both frequently associated with hypercholesterolemia. As such, we evaluated the impact of chronic cholesterol reducing therapy on the development of impaired skeletal muscle arteriolar reactivity and microvessel density in OZR and its impact on chronic inflammation and NO bioavailability. Materials and Methods Beginning at 7 weeks of age, male OZR were treated with gemfibrozil, probucol, atorvastatin or simvastatin (in chow) for 10 weeks. Subsequently, plasma and vascular samples were collected for biochemical/molecular analyses, while arteriolar reactivity and microvessel network structure were assessed using established methodologies after 3, 6 and 10 weeks of drug therapy Results All interventions were equally effective at reducing total cholesterol, although only the statins also blunted the progressive reductions to vascular NO bioavailability, evidenced by greater maintenance of acetylcholine-induced dilator responses, an attenuation of adrenergic constrictor reactivity, and an improvement in agonist-induced NO production. Comparably, while minimal improvements to arteriolar wall mechanics were identified with any of the interventions, chronic statin treatment reduced the rate of microvessel rarefaction in OZR. Associated with these improvements was a striking statin-induced reduction in inflammation in OZR, such that numerous markers of inflammation were correlated with improved microvascular reactivity and density. However, using multivariate discriminant analyses, plasma RANTES, IL-10, MCP-1 and TNF-α were determined to be the strongest contributors to differences between groups, although their relative importance varied

  8. Effects of pegylated hamster red blood cells on microcirculation.

    PubMed

    Chen, Peter C Y; Huang, Wei; Stassinopoulos, Adonis; Cheung, Anthony T W

    2008-01-01

    The objective of this study was to examine the effects of polyethylene glycol (PEG) treated red blood cells (RBCs) on the microcirculation in a hamster back skin window chamber model. Donor hamster RBCs were PEGylated through an incubation with an activated PEG solution, washed, resuspended, and infused through a 10% volume top loading procedure into the carotid artery in an awake Syrian Golden hamster. Eight hamster groups were treated with activated PEG different sizes and concentrations: 0.05 mM-5 kDa PEG, 0.5 mM-5 kDa PEG, 1.1 mM-5 kDa PEG, 2.2 mM-5 kDa PEG, 22 mM-5 kDa PEG, 0.05 mM-20 kDa PEG, 0.5 mM-20 kDa PEG, and 5 mM-20 kDa PEG. Non-treated RBCs were used as control. The microvascular bed under observation was videotaped 30 min before the infusion and followed for 30 min post infusion. The diameter of individual blood vessels and blood flow velocities in selected vessels was measured. Hematocrit and hemoglobin concentration were recorded before infusion and at the end of experiment. Tissue pO(2) was also monitored. Results showed the hamsters tolerated the PEGylated RBCs without apparent ill effects. No significant changes were recorded for the hematocrit, the hemoglobin concentration, the blood vessel diameters, blood flow velocities, and the interstitial partial oxygen pressure (pO(2)) before, during, and after the injections of PEG-RBCs (P > 0.05). Unlike most hemoglobin-based oxygen carrying compounds, which can cause vasoconstriction, the PEGylated RBCs did not produce any measurable vasoactivity. Together with the absence of rouleaux formation and the fact that PEG molecules can mask the surface antigens on RBCs, PEGylation appeared promising as a circulation enhancement treatment. PMID:18649167

  9. Rarefactive and compressive soliton waves in unmagnetized dusty plasma with non-thermal electron and ion distribution

    SciTech Connect

    Eslami, Esmaeil Baraz, Rasoul

    2014-02-15

    Sagdeev's pseudo potential method is employed to study dust acoustic solitary waves in an unmagnetized plasma containing negatively charged dusts with non-thermal electron and ion. The range of parameters for the existence of solitary waves using the analytical expression of the Sagdeev potential has been found. It is observed that, depending on the values of the plasma parameters like ion to electron temperature ratio σ, non-thermal parameters β and γ, electron to ion density ratio μ, and the value of the Mach number M, both rarefactive and compressive solitary waves may exist.

  10. Comment on "Electrostatic compressive and rarefactive shocks and solitons in relativistic plasmas occurring in polar regions of pulsar"

    NASA Astrophysics Data System (ADS)

    Hafez, M. G.; Talukder, M. R.; Hossain Ali, M.

    2016-05-01

    The aim of this comment is to show the solution of the KdVB equation used by Shah et al. (Astrophys. Space Sci. 335:529-537, 2011, doi: 10.1007/s10509-011-0766-y) is not correct. So, the numerical results that are predicted in this manuscript should not be helpful for further investigations in a plasma laboratory. For this reason, we have employed the Bernoulli's equation method to obtain the correct form of analytical solution to this equation, which is appropriate for the study of electrostatic compressive and rarefactive shocks and solitons in relativistic plasmas occurring in polar regions of pulsar.

  11. INTERVALS OF RADIAL INTERPLANETARY MAGNETIC FIELDS AT 1 AU, THEIR ASSOCIATION WITH RAREFACTION REGIONS, AND THEIR APPARENT MAGNETIC FOOT POINTS AT THE SUN

    SciTech Connect

    Orlove, Steven T.; Smith, Charles W.; Vasquez, Bernard J.; Schwadron, Nathan A.; Skoug, Ruth M.; Zurbuchen, Thomas H.; Zhao Liang E-mail: Charles.Smith@unh.edu E-mail: N.Schwadron@unh.edu E-mail: thomasz@umich.edu

    2013-09-01

    We have examined 226 intervals of nearly radial interplanetary magnetic field orientations at 1 AU lasting in excess of 6 hr. They are found within rarefaction regions as are the previously reported high-latitude observations. We show that these rarefactions typically do not involve high-speed wind such as that seen by Ulysses at high latitudes during solar minimum. We have examined both the wind speeds and the thermal ion composition before, during and after the rarefaction in an effort to establish the source of the flow that leads to the formation of the rarefaction. We find that the bulk of the measurements, both fast- and slow-wind intervals, possess both wind speeds and thermal ion compositions that suggest they come from typical low-latitude sources that are nominally considered slow-wind sources. In other words, we find relatively little evidence of polar coronal hole sources even when we examine the faster wind ahead of the rarefaction regions. While this is in contrast to high-latitude observations, we argue that this is to be expected of low-latitude observations where polar coronal hole sources are less prevalent. As with the previous high-latitude observations, we contend that the best explanation for these periods of radial magnetic field is interchange reconnection between two sources of different wind speed.

  12. Oral lichen planus preceding concomitant lichen planopilaris.

    PubMed

    Stoopler, Eric T; Alfaris, Sausan; Alomar, Dalal; Alawi, Faizan

    2016-09-01

    Lichen planus (LP) is an immune-mediated mucocutaneous disorder with a wide array of clinical presentations. Oral lichen planus (OLP) is characterized clinically by striae, desquamation, and/or ulceration. Lichen planopilaris (LPP), a variant of LP, affects the scalp, resulting in perifollicular erythema and scarring of cutaneous surfaces accompanied by hair loss. The association between OLP and LPP has been reported previously with scant information on concomitant or sequential disease presentation. We describe a patient with concomitant OLP and LPP, and to the best of our knowledge, this is the first report on OLP preceding the onset of LPP. PMID:27544399

  13. [Wide QRS tachycardia preceded by pacemaker spikes].

    PubMed

    Romero, M; Aranda, A; Gómez, F J; Jurado, A

    2014-04-01

    The differential diagnosis and therapeutic management of wide QRS tachycardia preceded by pacemaker spike is presented. The pacemaker-mediated tachycardia, tachycardia fibrillo-flutter in patients with pacemakers, and runaway pacemakers, have a similar surface electrocardiogram, but respond to different therapeutic measures. The tachycardia response to the application of a magnet over the pacemaker could help in the differential diagnosis, and in some cases will be therapeutic, as in the case of a tachycardia-mediated pacemaker. Although these conditions are diagnosed and treated in hospitals with catheterization laboratories using the application programmer over the pacemaker, patients presenting in primary care clinic and emergency forced us to make a diagnosis and treat the haemodynamically unstable patient prior to referral. PMID:23768570

  14. Precedence effects and the evolution of chorusing

    PubMed Central

    Greenfield, M. D.; Tourtellot, M. K.; Snedden, W. A.

    1997-01-01

    The structured choruses produced by rhythmically signalling males in many species of acoustic animals have long-captured the imagination of evolutionary biologists. Though various hypotheses have been forwarded to explain the adaptive significance of such chorusing, none have withstood empirical scrutiny. We suggest instead that alternating and synchronous choruses represent collective epiphenomena resulting from individual males competing to jam each other's signals. These competitions originate in psychoacoustic precedence effects wherein females only orient toward the first call of a sequence, thus selectively favouring males who produce leading calls. Given this perceptual bias, our modelling confirms that a resetting of signal rhythm by neighbours' signals, which generates either alternation or synchrony, is evolutionarily stable provided that resetting includes a relativity adjustment for the velocity of signal transmission and selective attention toward only a subset of signalling neighbours. Signalling strategies in chorusing insects and anurans are consistent with these predicted features.

  15. Cerebral Hypoperfusion Precedes Nausea During Centrifugation

    NASA Technical Reports Server (NTRS)

    Serrador, Jorge M.; Schlegel, Todd T.; Black, F. Owen; Wood, Scott J.

    2004-01-01

    Nausea and motion sickness are important operational concerns for aviators and astronauts. Understanding underlying mechanisms associated with motion sickness may lead to new treatments. The goal of this work was to determine if cerebral blood flow changes precede the development of nausea in motion sick susceptible subjects. Cerebral flow velocity in the middle cerebral artery (transcranial Doppler), blood pressure (Finapres) and end-tidal CO2 were measured while subjects were rotated on a centrifuge (250 degrees/sec). Following 5 min of rotation, subjects were translated 0.504 m off-center, creating a +lGx centripetal acceleration in the nasal-occipital plane. Ten subjects completed the protocol without symptoms while 5 developed nausea (4 while 6ff-center and 1 while rotating on-center). Prior to nausea, subjects had significant increases in blood pressure (+13plus or minus 3 mmHg, P less than 0.05) and cerebrovascular resistance (+46 plus or minus 17%, P less than 0.05) and decreases in cerebral flow velocity both in the second (-13 plus or minus 4%) and last minute (-22 plus or minus 5%) before symptoms (P less than 0.05). In comparison, controls demonstrated no change in blood pressure or cerebrovascular resistance in the last minute of off-center rotation and only a 7 plus or minus 2% decrease in cerebral flow velocity. All subjects had significant hypocapnia (-3.8 plus or minus 0.4 mmHg, P less than 0.05), however this hypocapnia could not fully explain the cerebral hypoperfusion associated with the development of nausea. These data indicate that reductions in cerebral blood flow precede the development of nausea. Further work is necessary to determine what role cerebral hypoperfusion plays in motion sickness and whether cerebral hypoperfusion can be used to predict the development of nausea in susceptible individuals.

  16. Removing noises caused by motion artefacts in microcirculation maps of human skin in vivo.

    PubMed

    Chen, C; Shi, W; Gao, W

    2015-12-01

    This paper presents a zero-padding and cross-correlation technique-based correlation mapping optical coherence tomography (ZPCC-cmOCT) to reconstruct microcirculation maps of human skin in vivo, which can remove the background decorrelation noise caused by motion artefacts. In conventional correlation mapping optical coherence tomography method, the correlation degree of static tissue may be lowered by the motion artefacts due to cardiac and respiratory motion, resulting in background decorrelation noise in microcirculation maps. In zero-padding and cross-correlation technique-based correlation mapping optical coherence tomography method, structural images are first obtained by performing Fourier transform on zero-padded interference fringes, and then cross-correlation-based image registration is utilized to align local areas in two adjacent structural images. Finally, correlation mapping optical coherence tomography method is performed to generate microcirculation maps. Both phantom experiments and in vivo experiments were implemented and the results demonstrate that the proposed method is capable of providing microcirculation maps with the background decorrelation noise removed. PMID:26356237

  17. Localization of the ANG II type 2 receptor in the microcirculation of skeletal muscle

    NASA Technical Reports Server (NTRS)

    Nora, E. H.; Munzenmaier, D. H.; Hansen-Smith, F. M.; Lombard, J. H.; Greene, A. S.; Cowley, A. W. (Principal Investigator)

    1998-01-01

    Only functional studies have suggested the presence of the ANG II type 2 (AT2) receptor in the microcirculation. To determine the distribution of this receptor in the rat skeletal muscle microcirculation, a polyclonal rabbit anti-rat antiserum was developed and used for immunohistochemistry and Western blot analysis. The antiserum was prepared against a highly specific and antigenic AT2-receptor synthetic peptide and was validated by competition and sensitivity assays. Western blot analysis demonstrated a prominent, single band at approximately 40 kDa in cremaster and soleus muscle. Immunohistochemical analysis revealed a wide distribution of AT2 receptors throughout the skeletal muscle microcirculation in large and small microvessels. Microanatomic studies displayed an endothelial localization of the AT2 receptor, whereas dual labeling with smooth muscle alpha-actin also showed colocalization of the AT2 receptor with vascular smooth muscle cells. Other cells associated with the microvessels also stained positive for AT2 receptors. Briefly, this study confirms previous functional data and localizes the AT2 receptor to the microcirculation. These studies demonstrate that the AT2 receptor is present on a variety of vascular cell types and that it is situated in a fashion that would allow it to directly oppose ANG II type 1 receptor actions.

  18. Critical Oxygen Delivery: The Crux of Bypass with a Special Look at the Microcirculation

    PubMed Central

    Spiess, Bruce D.

    2011-01-01

    Abstract: The microcirculation can be defined as those vascular structures where respiratory gas flux occurs. These are generally the arterioles, venules, and capillaries. Larger vascular conduits tend to have thicker walls, are at considerable distance from cellular sites of oxygen utilization, and therefore contribute little to oxygen flux. The microcirculation is complex, not a simple straight line of parallel groups of pipes with unidirectional flow. Rather, the complex network has most vascular structures not open (held in reserve) and often has bidirectional flow. Understanding the movement of O2, CO2, and other gases within this network has only recently been the center of focused research. The cardiopulmonary bypass machine is meant to keep the microcirculation normal, but research is demonstrating major changes within. This review looks at what is known today in spontaneously perfusing animals as well as early findings noting differences in cardiopulmonary bypass. We, as yet, do not understand all the mechanisms involved in the changes of the micro-circulation so thoughts regarding future areas for research are discussed. PMID:21449234

  19. Impaired metabolic profile is a predictor of capillary rarefaction in a population of hypertensive and normotensive individuals.

    PubMed

    Triantafyllou, Areti; Anyfanti, Panagiota; Triantafyllou, Georgios; Zabulis, Xenophon; Aslanidis, Spyros; Douma, Stella

    2016-08-01

    Capillary rarefaction is typically encountered in essential hypertension, yet identification of factors interfering with this phenomenon remains substantially underinvestigated. We examined whether components of metabolic profile (dyslipidemia, insulin resistance), inflammatory (high-sensitivity C-reactive protein, high-sensitivity C-reactive protein), and angiogenic (vascular endothelial growth factor) factors are implicated in this phenomenon in a population of newly diagnosed, never-treated hypertensive patients and normotensive controls. Nailfold capillary density was estimated with nailfold capillaroscopy using specifically designed software. A total of 159 individuals, 93 hypertensives, and 66 normotensives were included. Nailfold capillary density was lower among hypertensives compared to normotensives (146.4 ± 31.0 vs. 155.4 ± 26.9, respectively; P = .047). In the total population, capillary density significantly correlated with high-density lipoprotein (HDL) (r = 0.232; P = .003), HDL/low-density lipoprotein ratio (r = 0.175; P = .025), age (r = 0.236; P = .003), but neither with vascular endothelial growth factor or high-sensitivity C-reactive protein. An inverse association was found with body mass index (r = -0.174; P = .029), insulin levels (r = -0.200; P = .018), and homeostasis model assessment-insulin resistance (r = -0.223; P = .009). In the separate analysis for the hypertensive population, sex (P = .014) and homeostasis model assessment-insulin resistance (P = .011) were identified as significant predictors of capillary rarefaction after adjustment for other factors. On the contrary, only HDL levels (P = .036) predicted capillary density in the multiple regression model for the normotensive population. Different aspects of impaired metabolic profile, that is, insulin resistance and low HDL levels, but not angiogenic or inflammatory markers, appear to be independently associated with capillary rarefaction in

  20. Healing of apical rarefaction of three nonvital open apex anterior teeth using a white portland cement apical plug

    PubMed Central

    Chakraborty, Amitabha; Dey, Bibhas; Dhar, Reema; Sardar, Prabir

    2012-01-01

    The major challenge of performing root canal treatment in an open apex pulp-less tooth is to obtain a good apical seal. MTA has been successfully used to achieve a good apical seal, wherein the root canal obturation can be done immediately. MTA and White Portland Cement has been shown similarity in their physical, chemical and biological properties and has also shown similar outcome when used in animal studies and human trials. In our study, open apex of three non vital upper central incisors has been plugged using modified white Portland cement. 3 to 6 months follow up revealed absence of clinical symptoms and disappearance of peri-apical rarefactions. The positive clinical outcome may encourage the future use of white Portland cement as an apical plug material in case of non vital open apex tooth as much cheaper substitute of MTA. PMID:23230357

  1. The NRF2 knockout rat: a new animal model to study endothelial dysfunction, oxidant stress, and microvascular rarefaction.

    PubMed

    Priestley, Jessica R C; Kautenburg, Katie E; Casati, Marc C; Endres, Bradley T; Geurts, Aron M; Lombard, Julian H

    2016-02-15

    Nuclear factor (erythroid-derived 2)-like-2 (NRF2) is a master antioxidant and cell protective transcription factor that upregulates antioxidant defenses. In this study we developed a strain of Nrf2 null mutant rats to evaluate the role of reduced NRF2-regulated antioxidant defenses in contributing to endothelial dysfunction and impaired angiogenic responses during salt-induced ANG II suppression. Nrf2(-/-) mutant rats were developed using transcription activator-like effector nuclease technology in the Sprague-Dawley genetic background, and exhibited a 41-bp deletion that included the start codon for Nrf2 and an absence of immunohistochemically detectable NRF2 protein. Expression of mRNA for the NRF2-regulated indicator enzymes heme oxygenase-1, catalase, superoxide dismutase 1, superoxide dismutase 2, and glutathione reductase was significantly lower in livers of Nrf2(-/-) mutant rats fed high salt (HS; 4% NaCl) for 2 wk compared with wild-type controls. Endothelium-dependent dilation to acetylcholine was similar in isolated middle cerebral arteries (MCA) of Nrf2(-/-) mutant rats and wild-type littermates fed low-salt (0.4% NaCl) diet, and was eliminated by short-term (3 days) HS diet in both strains. Low-dose ANG II infusion (100 ng/kg sc) reversed salt-induced endothelial dysfunction in MCA and prevented microvessel rarefaction in wild-type rats fed HS diet, but not in Nrf2(-/-) mutant rats. The results of this study indicate that suppression of NRF2 antioxidant defenses plays an essential role in the development of salt-induced oxidant stress, endothelial dysfunction, and microvessel rarefaction in normotensive rats and emphasize the potential therapeutic benefits of directly upregulating NRF2-mediated antioxidant defenses to ameliorate vascular oxidant stress in humans. PMID:26637559

  2. Life events and difficulties preceding stroke.

    PubMed Central

    House, A; Dennis, M; Mogridge, L; Hawton, K; Warlow, C

    1990-01-01

    Life events and difficulties were recorded for the year before stroke, using a standardised semi-structured interview, in 113 surviving patients seen after their first ever in a lifetime stroke. An age and sex-matched control group (n = 109) was also interviewed about the preceding year. The stroke patients reported fewer non-threatening events and events with only a short-term threat, while difficulties were reported with equal frequency by the two groups. However, events which were severely threatening in the long-term were significantly more common in the stroke patients (in the 52 weeks before stroke 26% versus 13%, odds ratio 2.3, 95% confidence interval 1.1-4.9). The increased rate was apparent throughout the year and not just in the weeks immediately before stroke onset. The number of stroke patients experiencing severe events in the follow up year fell to the level found in the control group. Recognised risk factors for stroke were found equally in those patients with and without severe events before onset, except that hypertension was rather less common in the patients who had experienced a severe event. It therefore appears that severe life events may be one of the determinants of stroke onset. PMID:2292691

  3. White Dwarf Convection Preceding Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Zingale, Michael; Almgren, A. S.; Bell, J. B.; Malone, C. M.; Nonaka, A.; Woosley, S. E.

    2010-01-01

    In the single degenerate scenario for Type Ia supernovae, a Chandrasekhar mass white dwarf `simmers' for centuries preceding the ultimate explosion. During this period, reactions near the center drive convection throughout most of the interior of the white dwarf. The details of this convective flow determine how the first flames in the white dwarf ignite. Simulating this phase is difficult because the flows are highly subsonic. Using the low Mach number hydrodynamics code, MAESTRO, we present 3-d, full star models of the final hours of this convective phase, up to the point of ignition of a Type Ia supernova. We discuss the details of the convective velocity field and the locations of the initial hot spots. Finally, we show some preliminary results with rotation. Support for this work came from the DOE/Office of Nuclear Physics, grant No. DE-FG02-06ER41448 (Stony Brook), the SciDAC Program of the DOE Office of Mathematics, Information, and Computational Sciences under the DOE under contract No. DE-AC02-05CH11231 (LBNL), and the DOE SciDAC program, under grant No. DE-FC02-06ER41438 (UCSC). We made use of the jaguar machine via a DOE INCITE allocation at the Oak Ridge Leadership Computational Facility.

  4. Animal Detection Precedes Access to Scene Category

    PubMed Central

    Crouzet, Sébastien M.; Joubert, Olivier R.; Thorpe, Simon J.; Fabre-Thorpe, Michèle

    2012-01-01

    The processes underlying object recognition are fundamental for the understanding of visual perception. Humans can recognize many objects rapidly even in complex scenes, a task that still presents major challenges for computer vision systems. A common experimental demonstration of this ability is the rapid animal detection protocol, where human participants earliest responses to report the presence/absence of animals in natural scenes are observed at 250–270 ms latencies. One of the hypotheses to account for such speed is that people would not actually recognize an animal per se, but rather base their decision on global scene statistics. These global statistics (also referred to as spatial envelope or gist) have been shown to be computationally easy to process and could thus be used as a proxy for coarse object recognition. Here, using a saccadic choice task, which allows us to investigate a previously inaccessible temporal window of visual processing, we showed that animal – but not vehicle – detection clearly precedes scene categorization. This asynchrony is in addition validated by a late contextual modulation of animal detection, starting simultaneously with the availability of scene category. Interestingly, the advantage for animal over scene categorization is in opposition to the results of simulations using standard computational models. Taken together, these results challenge the idea that rapid animal detection might be based on early access of global scene statistics, and rather suggests a process based on the extraction of specific local complex features that might be hardwired in the visual system. PMID:23251545

  5. Segmentation precedes face categorization under suboptimal conditions

    PubMed Central

    Van Den Boomen, Carlijn; Fahrenfort, Johannes J.; Snijders, Tineke M.; Kemner, Chantal

    2015-01-01

    Both categorization and segmentation processes play a crucial role in face perception. However, the functional relation between these subprocesses is currently unclear. The present study investigates the temporal relation between segmentation-related and category-selective responses in the brain, using electroencephalography (EEG). Surface segmentation and category content were both manipulated using texture-defined objects, including faces. This allowed us to study brain activity related to segmentation and to categorization. In the main experiment, participants viewed texture-defined objects for a duration of 800 ms. EEG results revealed that segmentation-related responses precede category-selective responses. Three additional experiments revealed that the presence and timing of categorization depends on stimulus properties and presentation duration. Photographic objects were presented for a long and short (92 ms) duration and evoked fast category-selective responses in both cases. On the other hand, presentation of texture-defined objects for a short duration only evoked segmentation-related but no category-selective responses. Category-selective responses were much slower when evoked by texture-defined than by photographic objects. We suggest that in case of categorization of objects under suboptimal conditions, such as when low-level stimulus properties are not sufficient for fast object categorization, segmentation facilitates the slower categorization process. PMID:26074838

  6. An automated method for analysis of microcirculation videos for accurate assessment of tissue perfusion

    PubMed Central

    2012-01-01

    Background Imaging of the human microcirculation in real-time has the potential to detect injuries and illnesses that disturb the microcirculation at earlier stages and may improve the efficacy of resuscitation. Despite advanced imaging techniques to monitor the microcirculation, there are currently no tools for the near real-time analysis of the videos produced by these imaging systems. An automated system tool that can extract microvasculature information and monitor changes in tissue perfusion quantitatively might be invaluable as a diagnostic and therapeutic endpoint for resuscitation. Methods The experimental algorithm automatically extracts microvascular network and quantitatively measures changes in the microcirculation. There are two main parts in the algorithm: video processing and vessel segmentation. Microcirculatory videos are first stabilized in a video processing step to remove motion artifacts. In the vessel segmentation process, the microvascular network is extracted using multiple level thresholding and pixel verification techniques. Threshold levels are selected using histogram information of a set of training video recordings. Pixel-by-pixel differences are calculated throughout the frames to identify active blood vessels and capillaries with flow. Results Sublingual microcirculatory videos are recorded from anesthetized swine at baseline and during hemorrhage using a hand-held Side-stream Dark Field (SDF) imaging device to track changes in the microvasculature during hemorrhage. Automatically segmented vessels in the recordings are analyzed visually and the functional capillary density (FCD) values calculated by the algorithm are compared for both health baseline and hemorrhagic conditions. These results were compared to independently made FCD measurements using a well-known semi-automated method. Results of the fully automated algorithm demonstrated a significant decrease of FCD values. Similar, but more variable FCD values were calculated

  7. Laser speckle-imaging of blood microcirculation in the brain cortex of laboratory rats in stress

    SciTech Connect

    Vilensky, M A; Semyachkina-Glushkovskaya, Oxana V; Timoshina, P A; Kuznetsova, Jana V; Semyachkin-Glushkovskii, I A; Agafonov, Dmitry N; Tuchin, Valerii V

    2012-06-30

    The results of experimental approbation of the method of laser full-field speckle-imaging for monitoring the changes in blood microcirculation state of the brain cortex of laboratory rats under the conditions of developing stroke and administration of vasodilating and vasoconstrictive agents are presented. The studies aimed at the choice of the optimal conditions of speckle-image formation and recording were performed and the software implementing an adaptive algorithm for processing the data of measurements was created. The transfer of laser radiation to the probed region of the biotissue was implemented by means of a silica-polymer optical fibre. The problems and prospects of speckle-imaging of cerebral microcirculation of blood in laboratory and clinical conditions are discussed.

  8. Laser speckle contrast imaging of cerebral autoregulation in rats at a macro- and microcirculation level

    NASA Astrophysics Data System (ADS)

    Semyachkina-Glushkovskaya, O. V.; Abdurashitov, A. S.; Sindeev, S. S.; Tuchin, V. V.

    2016-06-01

    Using the method of laser speckle imaging for the simultaneous study of macro- and microcirculation in cerebral vessels of healthy rats, we show that the mechanisms underlying cerebral autoregulation depend on the initial condition of the organism and the sex of individual animals. The pharmacological dose-dependent stimulation of the peripheral arterial pressure increase is not accompanied by the cerebral circulation responses of analogous intensity, but manifests itself as 'compensating' reactions, namely, the redistribution of the blood flow at the level of macro- (in females) and microcirculation (in females and males). The obtained results extend our understanding of the capabilities of laser speckle imaging technique in neurophysiological studies of reserve abilities of cerebral circulation autoregulation under the conditions of hypertensive status formation.

  9. Application of colour magnification technique for revealing skin microcirculation changes under regional anaesthetic input

    NASA Astrophysics Data System (ADS)

    Rubins, Uldis; Spigulis, Janis; Miscuks, Aleksejs

    2013-11-01

    In this work the colour magnification technique was applied for monitoring of palm skin microcirculation changes under peripheral (Plexus Brachialis with axiliary access) Regional Anaesthesia (RA). During the RA procedure 20 minute video of patient's forearm was taken at steady light conditions. Video content was processed offline by custom developed Matlab software with build-in colour magnification algorithm that performs temporal filtering of video sequence near-heartbeat frequency, spatial decomposition of video and amplification of pulsatile signal in every pixel of skin image. Using this method, we are able to visualize the subcutaneous microcirculation changes in high spatial resolution. The results showed different blood pulse amplitude dynamics over the skin regions of palm and forearm during the RA. The colour magnification technique could be used for real-time monitoring of RA effect.

  10. In situ testing of CO2 laser on dental pulp function: Effects on microcirculation

    SciTech Connect

    Friedman, S.; Liu, M.; Doerscher-Kim, J.K.; Kim, S. )

    1991-01-01

    The effect of CO2 laser irradiation on pulpal microcirculation was studied in cat canines. The enamel surfaces of 4 teeth were exposed with energy densities of 304-1440J/cm2, using either a handpiece or a microslad, with a focal spot of 0.21mm and 0.33mm respectively. Pulpal blood flow (PBF) before and following lasing was recorded through the intact tooth surface by a laser Doppler flowmeter. CO2 laser irradiation caused an increase in PBF, which was immediate and transient. The PBF increase was higher in a large pulp than in a small pulp, and it was inversely related to the focal spot size. These findings confirm that the dental pulp is thermally affected by CO2 lasing of the tooth surface, however, without extensive pulp coagulation. It is concluded that the effects of laser irradiation on the pulpal microcirculation may be studied in situ by means of the presented methodology.

  11. MR imaging of hand microcirculation as a potential tool for space glove testing and design

    NASA Technical Reports Server (NTRS)

    Peterson, Steven W.; Strauss, Alvin M.; Niemann, Trista A.; Lorenz, Christine H.

    1991-01-01

    The task of evaluating and designing space gloves requires accurate biomechanical characterization of the hand. The availability of magnetic resonance (MR) imaging has created new opportunities for in vivo analysis of physiological phenomena such as the relationship between circulation and fatigue. An MR imaging technique originally proposed to quantitatively evaluate cerebral perfusion has been modified to evaluate the capillary microcirculation in hand muscles. An experimental protocol was developed to acquire perfusion-weighted images in the hand before and after various levels of exercise. Preliminary results on the feasibility of applying the MR imaging technique to the study of microcirculation and fatigue in the hand are presented. The potential of this method for space glove testing and design is also discussed.

  12. Laser speckle-imaging of blood microcirculation in the brain cortex of laboratory rats in stress

    NASA Astrophysics Data System (ADS)

    Vilensky, M. A.; Semyachkina-Glushkovskaya, Oxana V.; Timoshina, P. A.; Kuznetsova, Jana V.; Semyachkin-Glushkovskii, I. A.; Agafonov, Dmitry N.; Tuchin, Valerii V.

    2012-06-01

    The results of experimental approbation of the method of laser full-field speckle-imaging for monitoring the changes in blood microcirculation state of the brain cortex of laboratory rats under the conditions of developing stroke and administration of vasodilating and vasoconstrictive agents are presented. The studies aimed at the choice of the optimal conditions of speckle-image formation and recording were performed and the software implementing an adaptive algorithm for processing the data of measurements was created. The transfer of laser radiation to the probed region of the biotissue was implemented by means of a silica-polymer optical fibre. The problems and prospects of speckle-imaging of cerebral microcirculation of blood in laboratory and clinical conditions are discussed.

  13. Activated protein C improves intestinal microcirculation in experimental endotoxaemia in the rat

    PubMed Central

    Lehmann, Christian; Meissner, Konrad; Knöck, Andreas; Diedrich, Stephan; Pavlovic, Dragan; Gründling, Matthias; Usichenko, Taras; Wendt, Michael; Birnbaum, Jürgen

    2006-01-01

    Introduction Successful treatment of severe sepsis and septic shock remains a major challenge in critical care medicine. The recently introduced recombinant human activated protein C (APC) remarkably improved the outcome of septic patients. The influence of APC on intestinal circulation is still poorly understood. Therefore, the present study aimed to investigate the effects of APC on intestinal microcirculation during experimental endotoxaemia in rats by using intravital microscopy. Methods A total of 44 male Lewis rats were randomly assigned to receive intravenous injections of 15 mg/kg lipopolysaccharide alone (LPS) (n = 11) or LPS followed by subsequent injection of 2 mg/kg recombinant human APC (LPS + APC) (n = 11), whereas control animals received either APC (n = 11) or saline (n = 11). Animals underwent observations of functional capillary density and leucocyte adherence on venular endothelium in the microcirculation of the intestinal wall by means of intravital fluorescence microscopy. Indicators of macrocirculation as well as plasma levels of tumour necrosis factor-α, interleukin (IL)-1β, IL-6, and IL-10 were measured. Results Although APC administration of both LPS-treated and control rats did not change macrocirculation or release of inflammatory cytokines, it increased mucosal and muscular functional capillary density (p < 0.001 and p < 0.05, respectively) and reduced the number of firmly adhering leucocytes in intestinal submucosal V1 and V3 venules (p < 0.01) in LPS + APC-treated compared with LPS-treated animals, which did not receive APC. No remarkable differences that could be attributed to APC treatment were observed between the two control groups. Conclusion APC administration during experimental endotoxaemia improved intestinal microcirculation by protecting functional capillary density as a measure of microvascular perfusion and exerted anti-inflammatory effects by reducing leucocyte adherence to the endothelium in submucosal venules

  14. Wavelet-based analysis of gastric microcirculation in rats with ulcer bleedings

    NASA Astrophysics Data System (ADS)

    Pavlov, A. N.; Rodionov, M. A.; Pavlova, O. N.; Semyachkina-Glushkovskaya, O. V.; Berdnikova, V. A.; Kuznetsova, Ya. V.; Semyachkin-Glushkovskij, I. A.

    2012-03-01

    Studying of nitric oxide (NO) dependent mechanisms of regulation of microcirculation in a stomach can provide important diagnostic markers of the development of stress-induced ulcer bleedings. In this work we use a multiscale analysis based on the discrete wavelet-transform to characterize a latent stage of illness formation in rats. A higher sensitivity of stomach vessels to the NO-level in ill rats is discussed.

  15. Microcirculation-on-a-Chip: A Microfluidic Platform for Assaying Blood- and Lymphatic-Vessel Permeability

    PubMed Central

    Sato, Miwa; Sasaki, Naoki; Ato, Manabu; Hirakawa, Satoshi; Sato, Kiichi; Sato, Kae

    2015-01-01

    We developed a microfluidic model of microcirculation containing both blood and lymphatic vessels for examining vascular permeability. The designed microfluidic device harbors upper and lower channels that are partly aligned and are separated by a porous membrane, and on this membrane, blood vascular endothelial cells (BECs) and lymphatic endothelial cells (LECs) were cocultured back-to-back. At cell-cell junctions of both BECs and LECs, claudin-5 and VE-cadherin were detected. The permeability coefficient measured here was lower than the value reported for isolated mammalian venules. Moreover, our results showed that the flow culture established in the device promoted the formation of endothelial cell-cell junctions, and that treatment with histamine, an inflammation-promoting substance, induced changes in the localization of tight and adherens junction-associated proteins and an increase in vascular permeability in the microdevice. These findings indicated that both BECs and LECs appeared to retain their functions in the microfluidic coculture platform. Using this microcirculation device, the vascular damage induced by habu snake venom was successfully assayed, and the assay time was reduced from 24 h to 30 min. This is the first report of a microcirculation model in which BECs and LECs were cocultured. Because the micromodel includes lymphatic vessels in addition to blood vessels, the model can be used to evaluate both vascular permeability and lymphatic return rate. PMID:26332321

  16. Assesment of gingival microcirculation in anterior teeth using laser Doppler flowmetry

    NASA Astrophysics Data System (ADS)

    Canjau, Silvana; Miron, Mariana I.; Todea, Carmen D.

    2016-03-01

    Introduction: Evaluating the health status of the gingival tissue represents an important objective in the daily practice. Inflammation changes the microcirculatory and micromorphological dynamics of human gingiva. Aim: The purpose of this study was to evaluate the microcirculation in subjects with moderate gingivitis and healthy gingiva by using laser Doppler flowmetry (LDF). Material and Methods: Recordings of the gingival microcirculation (GM) were taken from 20 healthy gingival sites and from 20 sites with moderate gingivitis. The gingival blood flows in the gingivitis group before treatment was significantly different from those in the healthy gingiva group. Signals were recorded with the aid of a laser Doppler MoorLab instrument VMS-LDF2 probe VP3 10 mm S/N 2482. Three consecutive determinations of the GM were registered for each site, as follows: before the initial therapy, at 24 hours after the initial therapy and then, 7 days after the initial therapy. The data were processed using the statistical analysis software SPSS v16.0.1. Results: The results of this preliminary study showed statistically significant differences among the GM values recorded before and after the initial therapy. Conclusions: LDF could be a useful, noninvasive, sensitive, reproducible, and harmless method for measuring gingival blood flow (gingival microcirculation) in humans.

  17. Impact of methylene blue in addition to norepinephrine on the intestinal microcirculation in experimental septic shock.

    PubMed

    Nantais, Jordan; Dumbarton, Tristan C; Farah, Nizam; Maxan, Alexander; Zhou, Juan; Minor, Samuel; Lehmann, Christian

    2014-01-01

    Methylene blue (MB) has been used with some success as a treatment for the vasoplegia of vasopressor-refractory septic shock. The putative mechanism of action of MB is the inhibition of endothelial nitric oxide within the microvasculature and improved responsiveness to endogenous catecholamines (norepinephrine (NE)). However, to date, no study has demonstrated the microcirculatory effect of methylene blue in septic shock. The objective of this randomized, controlled, animal study was to show, in an experimentally-induced, septic shock model in rats, the effects of MB and NE on global hemodynamics and the microcirculation. Mean arterial pressure (MAP) was drastically reduced following bacterial endotoxin (lipopolysaccharide, LPS) administration in animals not receiving vasopressors. Only the combination of NE + MB restored MAP to control levels by the end of the three hour experiment. Intravital microscopy of the microcirculation was performed in the terminal ileum in order to examine functional capillary density in intestinal muscle layers and the mucosa, as well as leukocyte activation in venules (rolling, adhesion to the endothelium). Untreated LPS animals showed a significant increase in leukocyte adhesion and a decrease in capillary perfusion in the intestinal microcirculation. In groups receiving NE or NE+MB, we observed a significant decrease in leukocyte adhesion and improved functional capillary density, indicating that microvasculature function was improved. This study suggests that methylene blue may be able to improve hemodynamics while preserving microvascular function in septic shock. PMID:25227191

  18. The effect of wound ointments on tissue microcirculation and leucocyte behaviour.

    PubMed

    Peter, F W; Li-Peuser, H; Vogt, P M; Muehlberger, T; Homann, H H; Steinau, H U

    2002-01-01

    An intact microcirculation is essential for normal healing to occur. Wound repair may be impaired by various endogenous and exogenous factors, such as reduced microvascular perfusion, infection and debris. In the nonhealing wound, radical surgical debridement is critical. To supplement healing, various ointments are used in clinical practice. Little is known about their effects on tissue perfusion. We have therefore selected two substances widely used, the antiseptic Betadine and the enzyme combination Elase and investigated their impact on the microcirculation and on leucocyte activity, using the cremaster muscle as a model. We found that functional capillary density and arteriolar diameters were significantly reduced by Betadine, whereas leucocyte activity was not affected. In the Elase group, capillary flow and arteriolar diameters were significantly increased, and again leucocyte activity was not changed. The mechanism by which Betadine reduces microvascular flow is believed to be the same as in reperfusion injury. The positive effect of Elase on the microcirculation might be attributed to plasmin, which has been shown to dilate blood vessels. PMID:11952671

  19. Effects of some anesthetic agents on skin microcirculation evaluated by laser Doppler perfusion imaging in mice

    PubMed Central

    2013-01-01

    Background Anesthetic agents alter microcirculation, influencing tissue oxygenation and delivery of vital substrates. Laser Doppler perfusion imaging is a widespread technique in the field of microvascular research that can evaluate noninvasively and in real time the effects of environmental conditions, physical manipulations, diseases and treatments on peripheral perfusion. This study aims to evaluate laser Doppler perfusion imaging as a means to detect changes in skin microcirculation induced by some popular anesthetic agents in a murine model. Twenty-four age- and gender-matched healthy CD1 mice were examined by laser Doppler perfusion imaging. The skin microcirculatory response was measured at the level of plantar surfaces during isoflurane anesthesia with or without subsequent dexmedetomidine or acepromazine. At the end of the procedure, dexmedetomidine was reversed by atipamezole administration. Results In all mice, skin blood flow under isoflurane anesthesia did not show significant differences over time (P = 0.1). The serial perfusion pattern and values following acepromazine or dexmedetomidine administration differed significantly (P < 0.05). Conclusions We standardized a reliable laser Doppler perfusion imaging protocol to non-invasively assess changes in skin microcirculation induced by anesthesia in mice, considering the advantages and drawbacks of this technique and its translational value. PMID:24341447

  20. Renovascular disease, microcirculation, and the progression of renal injury: role of angiogenesis.

    PubMed

    Chade, Alejandro R

    2011-04-01

    Emerging evidence supports the pivotal role of renal microvascular disease as a determinant of tubulo-interstitial and glomerular fibrosis in chronic kidney disease. An intact microcirculation is vital to restore blood flow to the injured tissues, which is a crucial step to achieve a successful repair response. The purpose of this review is to discuss the impact and mechanisms of the functional and structural changes of the renal microvascular network, as well as the role of these changes in the progression and irreversibility of renal injury. Damage of the renal microcirculation and deterioration of the angiogenic response may constitute early steps in the complex pathways involved in progressive renal injury. There is limited but provocative evidence that stimulation of vascular proliferation and repair may stabilize renal function and slow the progression of renal disease. The feasibility of novel potential therapeutic interventions for stabilizing the renal microvasculature is also discussed. Targeted interventions to enhance endogenous renoprotective mechanisms focused on the microcirculation, such as cell-based therapy or the use of angiogenic cytokines have shown promising results in some experimental and clinical settings. PMID:21307362

  1. Influences of high-voltage electrical burns on the pulmonary microcirculation in rabbits.

    PubMed

    Zhou, H M; Xu, S J; Wang, L; Shao, H B; Xie, B; Feng, J K; Wang, C J; Bai, Y Q; Zhang, Q F

    2016-04-01

    This study was performed to investigate the effects of high-voltage electrical burns (HEB) on the pulmonary microcirculation in rabbits. Total of 120 rabbits were randomly divided into control and HEB group using a random number table. HEB model was developed with a voltage regulator and experimental transformer. Laser Doppler perfusion imager was utilized to monitor and quantify the blood perfusion in pulmonary microcirculation. The microvascular morphologic changes of the lung were observed using light microscopy and transmission electron microscope (TEM). The lung wet/dry weight ratio and the PaO2 were determined. The values of blood perfusion in rabbit pulmonary microcirculation in the HEB group were decreased at 5 min, but increased at 1 h after burn (P <  0.01) and then decreased gradually. Light microscopy reveals microthrombus formation in pulmonary venules and bleeding in venous capillaries in HEB group. We found the number of microvilli in the capillary endothelial cells decreased, the rough endoplasmic reticulum expanded and severe degranulation occurred, the mitochondrial cristae fused or disappeared, and severe edema surrounded the capillary endothelial cells by TEM. The values of lung wet/dry weight ratio were higher and the PaO2 were lower than that of before burn group (P <  0.01). These results demonstrated that microcirculatory disorders play a major role in the development of progressive lung damage after high-voltage electrical burns. PMID:25547412

  2. Comparison of cerebral microcirculation of alloxan diabetes and healthy mice using laser speckle contrast imaging

    NASA Astrophysics Data System (ADS)

    Timoshina, Polina A.; Shi, Rui; Zhang, Yang; Zhu, Dan; Semyachkina-Glushkovskaya, Oxana V.; Tuchin, Valery V.; Luo, Qingming

    2015-03-01

    The study of blood microcirculation is one of the most important problems of the medicine. This paper presents results of experimental study of cerebral blood flow microcirculation in mice with alloxan-induced diabetes using Temporal Laser Speckle Imaging (TLSI). Additionally, a direct effect of glucose water solution (concentration 20% and 45%) on blood flow microcirculation was studied. In the research, 20 white laboratory mice weighing 20-30 g were used. The TLSI method allows one to investigate time dependent scattering from the objects with complex dynamics, since it possesses greater temporal resolution. Results show that in brain of animal diabetic group diameter of sagittal vein is increased and the speed of blood flow reduced relative to the control group. Topical application of 20%- or 45%-glucose solutions also causes increase of diameter of blood vessels and slows down blood circulation. The results obtained show that diabetes development causes changes in the cerebral microcirculatory system and TLSI techniques can be effectively used to quantify these alterations.

  3. Simulation of flow in the microcirculation using a hybrid Lattice-Boltzman and Finite Element algorithm

    NASA Astrophysics Data System (ADS)

    Gonzalez-Mancera, Andres; Gonzalez Cardenas, Diego

    2014-11-01

    Flow in the microcirculation is highly dependent on the mechanical properties of the cells suspended in the plasma. Red blood cells have to deform in order to pass through the smaller sections in the microcirculation. Certain deceases change the mechanical properties of red blood cells affecting its ability to deform and the rheological behaviour of blood. We developed a hybrid algorithm based on the Lattice-Boltzmann and Finite Element methods to simulate blood flow in small capillaries. Plasma was modeled as a Newtonian fluid and the red blood cells' membrane as a hyperelastic solid. The fluid-structure interaction was handled using the immersed boundary method. We simulated the flow of plasma with suspended red blood cells through cylindrical capillaries and measured the pressure drop as a function of the membrane's rigidity. We also simulated the flow through capillaries with a restriction and identify critical properties for which the suspended particles are unable to flow. The algorithm output was verified by reproducing certain common features of flow int he microcirculation such as the Fahraeus-Lindqvist effect.

  4. Local microcirculation disorders in uterus under laser tissue welding and their influence in the healing process

    NASA Astrophysics Data System (ADS)

    Kozlov, Valentine I.; Skobelkin, Oleg K.; Fatkullin, Ildar; Terman, Oleg A.; Chizhov, Gennadii; Gabidullina, Rushania

    1994-12-01

    To study the possibility of using Nd:YAG laser to weld the tissues of the uterus experiments in rats and dogs have been conducted. With the biomicroscopy and the laser Doppler flowmetry we have evaluated the microcirculation in the uterus wall under traditional suture and laser welding suture. As a model of the wound, the dissection of serosa and muscles of the organ wall have been used. In laser welding suture we have welded the zone of tissue about 1 mm3 with the laser (power density 270 W/cm2). Histological control has been fulfilled on various phases of the healing process. The investigation of the uterus wall demonstrates that there are zones of microcirculation disorders in tissues: (1) the zone of coagulation of microvessels and adjacent tissues (about 100 micrometers ); (2) the zone of stasis (150 - 200 micrometers ); (3) the zone of reactive-destructive changes of microvessels (300 micrometers ), (4) the zone of malfunctional microcirculatory changes (600 micrometers ). The coagulation of microvessels changes the character of inflammation and the healing process, decreases the exudation phase and the leucocyte infiltration of tissues, and accelerates the capillary growth. In contrast with traditional suture, in the case of laser welding suture the edema and hemorrhagic signs are less expressed. The complete restoration of microcirculation under laser welding suture has been observed by the fourteenth day of the healing process. Under the traditional suture method normalization of tissue nutritious blood flow has been achieved by 21 days.

  5. IVIM-based MRI method to study the microcirculation in the heart: preliminary results in dogs

    NASA Astrophysics Data System (ADS)

    Callot, Virginie; Bennett, Eric; Wen, Han

    2003-05-01

    In living organs, microcirculation in the capillaries and high order branches can be seen as a macroscopically random process. The Intra Voxel Incoherent Motion (IVIM) method uses a diffusion-weighted magnetic resonance imaging sequence to register this pseudo-random motion. It is able to observe perfusion in addition to the brownian diffusion by its relatively large distance of movement. The dependence of the MR signal (S) on the diffusion weighting b can be approximated as a bi-exponential relation: (S/S0)=(1-f).exp(-bD)+f.exp[-b(D+D*)], where S0 is the signal intensity for b=0, f the vascular volume fraction, D the molecular diffusion coefficient and D* a flow index. This effect, largely investigated in the brain, has never been applied in the heart, where the diffusion-weighted sequence is highly sensitive to bulk motion. We have studied microcirculation in the canine heart in vivo, with a well-controlled cardiac and respiratory gating protocol that overcomes the bulk motion effects. We demonstrated that the IVIM effect could be applied in the myocardium. The IVIM parameters were found equal to D=1.26*10-3 mm2/s, f=11.98%, D*=12.87*10-3 mm2/s. Moreover, the microcirculation is directionally anisotropic. The preferred direction of capillaries/small vessels is aligned with the myofibers in mid-myocardium in the left ventricle.

  6. 10 CFR 205.11 - Order of precedence.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Order of precedence. 205.11 Section 205.11 Energy DEPARTMENT OF ENERGY OIL ADMINISTRATIVE PROCEDURES AND SANCTIONS General Provisions § 205.11 Order of precedence. (a) If there is any conflict or inconsistency between the provisions of this part and any...

  7. 48 CFR 3452.215-33 - Order of precedence.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 7 2010-10-01 2010-10-01 false Order of precedence. 3452.215-33 Section 3452.215-33 Federal Acquisition Regulations System DEPARTMENT OF EDUCATION ACQUISITION REGULATION CLAUSES AND FORMS SOLICITATION PROVISIONS AND CONTRACT CLAUSES Texts of Provisions and Clauses 3452.215-33 Order of precedence....

  8. 26 CFR 1.665(e)-1 - Preceding taxable year.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 8 2010-04-01 2010-04-01 false Preceding taxable year. 1.665(e)-1 Section 1.665... (CONTINUED) INCOME TAXES Treatment of Excess Distributions of Trusts Applicable to Taxable Years Beginning Before January 1, 1969 § 1.665(e)-1 Preceding taxable year. (a) Definition. For purposes of subpart...

  9. 26 CFR 1.665(e)-1 - Preceding taxable year.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 8 2011-04-01 2011-04-01 false Preceding taxable year. 1.665(e)-1 Section 1.665... (CONTINUED) INCOME TAXES (CONTINUED) Treatment of Excess Distributions of Trusts Applicable to Taxable Years Beginning Before January 1, 1969 § 1.665(e)-1 Preceding taxable year. (a) Definition. For purposes...

  10. 26 CFR 1.665(e)-1 - Preceding taxable year.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 8 2012-04-01 2012-04-01 false Preceding taxable year. 1.665(e)-1 Section 1.665... (CONTINUED) INCOME TAXES (CONTINUED) Treatment of Excess Distributions of Trusts Applicable to Taxable Years Beginning Before January 1, 1969 § 1.665(e)-1 Preceding taxable year. (a) Definition. For purposes...

  11. 26 CFR 1.665(e)-1 - Preceding taxable year.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 8 2014-04-01 2014-04-01 false Preceding taxable year. 1.665(e)-1 Section 1.665... (CONTINUED) INCOME TAXES (CONTINUED) Treatment of Excess Distributions of Trusts Applicable to Taxable Years Beginning Before January 1, 1969 § 1.665(e)-1 Preceding taxable year. (a) Definition. For purposes...

  12. MgO melting curve constraints from shock temperature and rarefaction overtake measurements in samples preheated to 2300 K

    NASA Astrophysics Data System (ADS)

    Fat'yanov, O. V.; Asimow, P. D.

    2014-05-01

    Continuing our effort to obtain experimental constraints on the melting curve of MgO at 100-200 GPa, we extended our target preheating capability to 2300 K. Our new Mo capsule design holds a long MgO crystal in a controlled thermal gradient until impact by a Ta flyer launched at up to 7.5 km/s on the Caltech two-stage light-gas gun. Radiative shock temperatures and rarefaction overtake times were measured simultaneously by a 6-channel VIS/NIR pyrometer with 3 ns time resolution. The majority of our experiments showed smooth monotonic increases in MgO sound speed and shock temperature with pressure from 197 to 243 GPa. The measured temperatures as well as the slopes of the pressure dependences for both temperature and sound speed were in good agreement with those calculated numerically for the solid phase at our peak shock compression conditions. Most observed sound speeds, however, were ~800 m/s higher than those predicted by the model. A single unconfirmed data point at 239 GPa showed anomalously low temperature and sound speed, which could both be explained by partial melting in this experiment and could suggest that the Hugoniot of MgO preheated to 2300 K crosses its melting line just slightly above 240 GPa.

  13. Vanishing viscosity and Debye-length limit to rarefaction wave with vacuum for the 1D bipolar Navier-Stokes-Poisson equation

    NASA Astrophysics Data System (ADS)

    Li, Yeping

    2016-06-01

    In this paper, we consider the one-dimensional (1D) compressible bipolar Navier-Stokes-Poisson equations. We know that when the viscosity coefficient and Debye length are zero in the compressible bipolar Navier-Stokes-Poisson equations, we have the compressible Euler equations. Under the case that the compressible Euler equations have a rarefaction wave with one-side vacuum state, we can construct a sequence of the approximation solution to the one-dimensional bipolar Navier-Stokes-Poisson equations with well-prepared initial data, which converges to the above rarefaction wave with vacuum as the viscosity and the Debye length tend to zero. Moreover, we also obtain the uniform convergence rate. The results are proved by a scaling argument and elaborate energy estimate.

  14. Systemic increase in blood flow in conditions of disturbed microcirculation after low-power laser irradiation

    NASA Astrophysics Data System (ADS)

    Schindl, Andreas; Schindl, Liesbeth

    1996-11-01

    As described earlier by our group, topical application of low power laser irradiation seems to have a systemic effect in terms of improving microcirculation in patients suffering from microangiopathic disorders. The aim of the presented study was to prove these clinical findings by measuring the skin temperature as a parameter of microcirculation suing an infrared-thermography-camera system. Patients who attended the Institute for Laser medicine between January and July 1996 and suffered from angiopathy of different origin were examined. The laser system used was a combined IR/HeNe- laser, power output 30mW, irradiation time was varied to keep the IED at a value of 20J/cm2. Irradiation was performed proximally to the affected area, the contralateral side being left untreated, IR-thermography was started after reaching adaption to the room temperature, with pictures of both extremities taken in 10 minute intervals during the irradiation and up to 45 minutes after stopping the irradiation. Results show a rise in temperature over the affected region as well as over the contralateral extremity, with maximal changes of up to + 3.0 degrees C. The improvement of blood flow started 15 min. after the onset of laser irradiation and persisted up to 45 min. after stopping the irradiation. The results obtained are in good accordance with findings of previously performed studies, undertaken with patients with autoimmune-angiopathies such as Buerger's disease. Therefore, we conclude that topical application of low power lasers is able to induce a systemic improvement of blood flow in conditions of disturbed microcirculation.

  15. Static magnetic field effect on microcirculation, direct versus baroreflex-mediated approach.

    PubMed

    Gmitrov, Juraj

    2013-12-01

    We compared in conscious rabbits, sedated using pentobarbital intravenous (i.v.) infusion (5 mg kg(- 1) h(- 1)), the effect of a static magnetic field (SMF), generated by Nd2-Fe14-B magnets, on microcirculation during its 40 min local exposure to the microvascular network in cutaneous tissue [20 sham exposure and 20 SMF (0.25 T) exposure runs] or to sinocarotid baroreceptors [14 sham exposure and 14 SMF (0.35 T) exposure runs]. Mean femoral artery blood pressure (BP), heart rate (HR), arterial baroreflex sensitivity (BRS), assessed from HR and BP responses to i.v. bolus of nitroprusside and phenylephrine, and microcirculatory blood flow, using microphotoelectric plethysmography (MPPG), were simultaneously monitored. SMF significantly increased microcirculation on a 17.8% in microvascular and on a 23.3% in baroreceptor exposure series. In baroreceptor exposure series, SMF significantly decreased BP, increased heart rate variability, BRS and sodium nitroprusside (NO-donor) i.v. bolus microcirculatory vasodilatory effect. These suggest augmentation of the arterial baroreflex capacity support NO-dependent vasodilation, by increased sensitivity of vessels to NO, to be a new physiological mechanism of BP buffering and microcirculatory control. A significant positive correlation was also found between increase in BRS and in MPPG (r = 0.66, p < 0.009), indicating baroreflex participation in the regulation of the microcirculation and its enhancement after SMF exposure. Both direct and baroreflex-mediated approaches demonstrate SMF significant vasodilatory effect with potential clinical implication in macro- and microcirculatory disorders. PMID:23323761

  16. A preparation for in vivo study of the diaphragmatic microcirculation in the rat.

    PubMed

    Boczkowski, J; Vicaut, E; Aubier, M

    1990-07-01

    A new preparation is described for the study of the microcirculation of the rat diaphragm by in vivo microscopy. After midline laparotomy, the abdominal site of the diaphragm muscle was exposed. The rat was mechanically ventilated and placed in the Trendelenburg position, thus allowing a microscope placed on a three-dimensional articulated system to be set up perpendicular to the diaphragm. The diaphragm was then transilluminated by inserting fiberoptic microprobes into the thorax cavity by thoracotomy in the fifth intercostal space. This preparation allowed us to describe the morphological characteristics of the arteriolar network in vivo. As regards the venular network, two parts were distinguished: one part collects the blood of the external half of the diaphragm, runs roughly parallel to the arterioles, and converges toward the internal mammary and intercostal veins; the other part collects the blood of the central half of the diaphragm and converges on the central venous arcade along its central tendon. Anastomotic channels between these two parts were observed, as well as spontaneous inversion of the direction of the blood flow, indicating the presence of unsteady pressure gradients in some branches of the venular network. Capillary density was also studied by measuring intercapillary distance, whose mean value was 21.43 +/- 0.67 microns. No differences in intercapillary distance were found between the external and central parts of the diaphragm. In conclusion, we describe a preparation which allowed us to study the diaphragmatic microcirculation for at least 2 hr under good hemodynamic conditions. The study of this specific microcirculation is important because the diaphragm's metabolism and functions are specific and because it is essential to life that its perfusion should be adapted to its specific metabolic requirements. PMID:2398828

  17. Is there a stimulation of blood microcirculation at low level laser irradiation

    NASA Astrophysics Data System (ADS)

    Rogatkin, Dmitry; Dunaev, Andrey

    2014-05-01

    In 1980-2000 besides the laser surgery an intensive evolution of Low Level Laser Therapy (LLLT) had started in medicine, especially in Russia as well as in several other East-European countries. At the same time the biophysical mechanisms of LLLT are still the subject of disputes. One of the most popular clinical effects at Low Level Laser Irradiation (LLLI) being mentioned in medical publications for justification of the LLLT healing outcome is a stimulation of blood microcirculation in irradiated area. It was declared a priori at a dawn of LLLT and is now a basis of medical interpretation of healing mechanisms of LLLT at least in Russia. But in past 20 years a lot of investigation was carried out on optical registration of microhaemodynamic parameters in vivo as well as a number of noninvasive diagnostic tools was created for that. So, today it is possible to experimentally check the blood microcirculation stimulation hypothesis. Our study was aimed on that during the past 10 years. The most precision and accurate experiments we have carried out recently using simultaneously three different noninvasive diagnostic techniques: Laser Doppler Flowmetry, Tissue Reflectance Oximetry and Infrared Thermography. All these methods didn't confirm the effect on the blood microcirculation stimulation in skin or mucosa at irradiation with the power density below 50 mW/cm2 and irradiation time up to 5-6 minutes. Above this threshold the heating on 0,8…1 °C of tissue in the field of irradiation and the corresponding synchronous increase of all parameters of microhemodynamics were observed.

  18. Influence of low-intensity laser radiation on human blood microcirculation

    NASA Astrophysics Data System (ADS)

    Korolevich, Alexander N.; Dubina, Natali S.; Vecherinski, Sergei I.

    2000-05-01

    The paper investigated in vivo the influence of low- intensity laser radiation (He-Ne laser with wavelength 0.63 nm) on the relative value of perfusion (the product of the number of particles moving in the volume being investigated into the mean velocity of their movement) of human blood erythrocytes and the mean velocity of their movement. It is known that characteristic of cardiovascular diseases are microcirculation disturbances and disorder in rheological properties of blood. Therefore these investigations were carried out on cardiac ischemia patients.

  19. Intestinal and sublingual microcirculation are more severely compromised in hemodilution than in hemorrhage.

    PubMed

    Ferrara, Gonzalo; Kanoore Edul, Vanina Siham; Martins, Enrique; Canales, Héctor Saúl; Canullán, Carlos; Murias, Gastón; Pozo, Mario Omar; Estenssoro, Elisa; Ince, Can; Dubin, Arnaldo

    2016-05-15

    The alterations in O2 extraction in hemodilution have been linked to fast red blood cell (RBC) velocity, which might affect the complete release of O2 from Hb. Fast RBC velocity might also explain the normal mucosal-arterial Pco2 (ΔPco2). Yet sublingual and intestinal microcirculation have not been completely characterized in extreme hemodilution. Our hypothesis was that the unchanged ΔPco2 in hemodilution depends on the preservation of villi microcirculation. For this purpose, pentobarbital-anesthetized and mechanically ventilated sheep were submitted to stepwise hemodilution (n = 8), hemorrhage (n = 8), or no intervention (sham, n = 8). In both hypoxic groups, equivalent reductions in O2 consumption (V̇o2) were targeted. Microcirculation was assessed by videomicroscopy, intestinal ΔPco2 by air tonometry, and V̇o2 by expired gases analysis. Although cardiac output and superior mesenteric flow increased in hemodilution, from the very first step (Hb = 5.0 g/dl), villi functional vascular density and RBC velocity decreased (21.7 ± 0.9 vs. 15.9 ± 1.0 mm/mm(2) and 1,033 ± 75 vs. 850 ± 79 μm/s, P < 0.01). In the last stage (Hb = 1.2 g/dl), these variables were lower in hemodiution than in hemorrhage (11.1 ± 0.5 vs. 15.4 ± 0.9 mm/mm(2) and 544 ± 26 vs. 686 ± 70 μm/s, P < 0.01), and were associated with lower intestinal fractional O2 extraction (0.61 ± 0.04 vs. 0.79 ± 0.02, P < 0.01) but preserved ΔPco2 (5 ± 2 vs. 25 ± 4 mmHg, P < 0.01). Therefore, alterations in O2 extraction in hemodilution seemed related to microvascular shunting, not to fast RBC velocity. The severe microvascular abnormalities suggest that normal ΔPco2 was not dependent on CO2 washout by the villi microcirculation. Increased perfusion in deeper intestinal layers might be an alternative explanation. PMID:26989219

  20. Retinal microcirculation in patients with diabetes mellitus: dynamic and morphological analysis of perifoveal capillary network.

    PubMed Central

    Arend, O; Wolf, S; Jung, F; Bertram, B; Pöstgens, H; Toonen, H; Reim, M

    1991-01-01

    The new scanning laser technique allows one to quantify the retinal microcirculation. A digital image analysing system was used to study capillary blood flow velocities and morphological parameters of perifoveal intercapillary areas and foveal avascular zones in normal and diabetic subjects. Diabetic patients showed a significant reduction in capillary blood cell velocities in comparison with normal subjects. Perifoveal intercapillary areas and foveal avascular zones were significantly increased in all stages of diabetic retinopathy, and both parameters increased with progressing diabetic retinopathy. Significant changes in the perifoveal intercapillary areas were observed between normal subjects and patients with no retinopathy. Images PMID:1911651

  1. EFFECTS OF LOW-FREQUENCY ULTRASOUND ON MICROCIRCULATION IN VENOUS LEG ULCERS

    PubMed Central

    Wollina, Uwe; Heinig, Birgit; Naumann, Gunther; Scheibe, Armin; Schmidt, Wolf-Dieter; Neugebauer, Reimund

    2011-01-01

    Background: Therapeutic low-frequency ultrasound (US) has been used for many years to improve wound healing in chronic wounds like venous leg ulcers. No human data are available for the possible effects of single US applications on microcirculation and their frequency-dependency. Aims: To investigated the role of therapeutic low-frequency US on microcirculation of venous leg ulcers in vivo. Patients and Methods: This is a pilot study on an inpatient basis. We use a newly developed low-frequency continuous-wave US-equipment composed of a US transducer based on piezo-fiber composites that allow the change of frequency. In this study, we apply US of 34 kHz, 53.5 kHz, and 75 kHz respectively. Twelve patients with chronic venous leg ulcers are analyzed. As an adjunct to good ulcer care, therapeutic US is applied, non-contacting, once a day, in a subaqual position for 10 minutes. Microcirculation is assessed in the ulcers adjacent to skin before US-therapy, immediately after the treatment and 30 minutes later. We use a micro-light guide spectrophotometer (O2C, LEA Medizintechnik GmbH, Gieίen, Germany) for calculation of blood flow velocity, hemoglobin oxygen saturation (SCO2) and relative hemoglobin concentration (rHb) in 2 and 8 mm depth. Contact-free remission spectroscopy (SkinREM3, Color Control Chemnitz GmbH, Chemnitz, Germany) allows contact free measurements in the VIS-NIR range of the spectrum (400 ± 1600 nm). Results: It is seen that therapeutic US is well tolerated. One patient dropped out from a treatment series since he developed erysipelas responding to standard antibiotic. Effects were seen at 34 kHz only. The SO2 values increased after single US application. The values for rHb were higher in the superficial layer of the wound bed (depth 2 mm) compared to deeper parts (8 mm depth). US treatment did not result in significant changes of rHb and blood cell velocity. The data obtained by remission spectroscopy disclose an increase of oxygenized hemoglobin

  2. The synchronizing research on structure of microcirculation and dynamic changes of monoamine neurotransmitter in the rat endbrain after exhaustive swimming

    NASA Astrophysics Data System (ADS)

    Yuan, Qiongjia; Li, He; Xiong, Ruo-Hong; Su, Quan-Sheng; Tan, Jin; Dai, Yi; Xu, Ming

    2003-12-01

    The changes of microconfiguration and dynamic changes of monoamines, 5-hydroxytryptamine (5-HT), norepinephrine (NE) and dopamine(DA), in the rat endbrain after exhaustive swimming were observed in order to provide objective reference for evaluation of exercise central fatigue. Thirty-six male SD rates were divided randomly into 4 groups: group control (G1); group immediate after exhaustive swimming (G2); group 24 hours after exhaustive swimming (G3) and group 48 hours after exhaustive swimming (G4), 9 in each group. After adaptive swimming for 4 days, rats in G2, G3 and G4 took loaded swimming in ratio of 5 g for every 100g body weight (5%) till exhaustion. After decapitation, the endbrains of the rats in each group were taken for ordinary electron microscopic observation of change of microcofiguration and measurement of contents of 5-HT, NE and DA by fluorometric photometer. The ultrastructure of the endbrain cortex in G2 had apparent changes. In G3, improvement of ultrastructure of microcirculation in endbrain were observed; In G4, structure of microcirculation almost recovered to normal level. The level of 5-HT and NE in the endbrain of exhaustive swimming rat increased significantly, up to the highest in G3 (24h). It was therefore demonstrated that the configuration change of microcirculation and change of 5-HT and NE contents in rat endbrain after exhaustive exercise were synchronous and that the recovery of the configuration change of microcirculation was faster than change of 5-HT and NE contents, the ultrastructure change of microcirculation being reversible. These results indicate that the improvement of microcirculation in endbrain can help promote recovery of sporting central fatigue.

  3. Robust optimal design of diffusion-weighted magnetic resonance experiments for skin microcirculation

    NASA Astrophysics Data System (ADS)

    Choi, J.; Raguin, L. G.

    2010-10-01

    Skin microcirculation plays an important role in several diseases including chronic venous insufficiency and diabetes. Magnetic resonance (MR) has the potential to provide quantitative information and a better penetration depth compared with other non-invasive methods such as laser Doppler flowmetry or optical coherence tomography. The continuous progress in hardware resulting in higher sensitivity must be coupled with advances in data acquisition schemes. In this article, we first introduce a physical model for quantifying skin microcirculation using diffusion-weighted MR (DWMR) based on an effective dispersion model for skin leading to a q-space model of the DWMR complex signal, and then design the corresponding robust optimal experiments. The resulting robust optimal DWMR protocols improve the worst-case quality of parameter estimates using nonlinear least squares optimization by exploiting available a priori knowledge of model parameters. Hence, our approach optimizes the gradient strengths and directions used in DWMR experiments to robustly minimize the size of the parameter estimation error with respect to model parameter uncertainty. Numerical evaluations are presented to demonstrate the effectiveness of our approach as compared to conventional DWMR protocols.

  4. Evaluation of three inverse problem models to quantify skin microcirculation using diffusion-weighted MRI

    NASA Astrophysics Data System (ADS)

    Cordier, G.; Choi, J.; Raguin, L. G.

    2008-11-01

    Skin microcirculation plays an important role in diseases such as chronic venous insufficiency and diabetes. Magnetic resonance imaging (MRI) can provide quantitative information with a better penetration depth than other noninvasive methods, such as laser Doppler flowmetry or optical coherence tomography. Moreover, successful MRI skin studies have recently been reported. In this article, we investigate three potential inverse models to quantify skin microcirculation using diffusion-weighted MRI (DWI), also known as q-space MRI. The model parameters are estimated based on nonlinear least-squares (NLS). For each of the three models, an optimal DWI sampling scheme is proposed based on D-optimality in order to minimize the size of the confidence region of the NLS estimates and thus the effect of the experimental noise inherent to DWI. The resulting covariance matrices of the NLS estimates are predicted by asymptotic normality and compared to the ones computed by Monte-Carlo simulations. Our numerical results demonstrate the effectiveness of the proposed models and corresponding DWI sampling schemes as compared to conventional approaches.

  5. Impact of 10 Sessions of Whole Body Cryostimulation on Cutaneous Microcirculation Measured by Laser Doppler Flowmetry

    PubMed Central

    Renata, Szyguła; Tomasz, Dybek; Andrzej, Klimek; Sławomir, Tubek

    2011-01-01

    The aim of the present study was to evaluate the basic and evoked blood flow in the skin microcirculation of the hand, one day and ten days after a series of 10 whole body cryostimulation sessions, in healthy individuals. The study group included 32 volunteers – 16 women and 16 men. The volunteers underwent 10 sessions of cryotherapy in a cryogenic chamber. The variables were recorded before the series of 10 whole body cryostimulation sessions (first measurement), one day after the last session (second measurement) and ten days later (third measurement). Rest flow, post-occlusive hyperaemic reaction, reaction to temperature and arterio–venous reflex index were evaluated by laser Doppler flowmetry. The values recorded for rest flow, a post-occlusive hyperaemic reaction, a reaction to temperature and arterio – venous reflex index were significantly higher both in the second and third measurement compared to the initial one. Differences were recorded both in men and women. The values of frequency in the range of 0,01 Hz to 2 Hz (heart frequency dependent) were significantly lower after whole-body cryostimulation in both men and women. In the range of myogenic frequency significantly higher values were recorded in the second and third measurement compared to the first one. Recorded data suggest improved response of the cutaneous microcirculation to applied stimuli in both women and men. Positive effects of cryostimulation persist in the tested group for 10 consecutive days. PMID:23487007

  6. Gene expression profile and synovial microcirculation at early stages of collagen-induced arthritis

    PubMed Central

    Gierer, Philip; Ibrahim, Saleh; Mittlmeier, Thomas; Koczan, Dirk; Moeller, Steffen; Landes, Jürgen; Gradl, Georg; Vollmar, Brigitte

    2005-01-01

    A better understanding of the initial mechanisms that lead to arthritic disease could facilitate development of improved therapeutic strategies. We characterized the synovial microcirculation of knee joints in susceptible mouse strains undergoing intradermal immunization with bovine collagen II in complete Freund's adjuvant to induce arthritis (i.e. collagen-induced arthritis [CIA]). Susceptible DBA1/J and collagen II T-cell receptor transgenic mice were compared with CIA-resistant FVB/NJ mice. Before onset of clinical symptoms of arthritis, in vivo fluorescence microscopy of knee joints revealed marked leucocyte activation and interaction with the endothelial lining of synovial microvessels. This initial inflammatory cell response correlated with the gene expression profile at this disease stage. The majority of the 655 differentially expressed genes belonged to classes of genes that are involved in cell movement and structure, cell cycle and signal transduction, as well as transcription, protein synthesis and metabolism. However, 24 adhesion molecules and chemokine/cytokine genes were identified, some of which are known to contribute to arthritis (e.g. CD44 and neutrophil cytosolic factor 1) and some of which are novel in this respect (e.g. CC chemokine ligand-27 and IL-13 receptor α1). Online in vivo data on synovial tissue microcirculation, together with gene expression profiling, emphasize the potential role played by early inflammatory events in the development of arthritis. PMID:15987489

  7. Cerebral microcirculation shear stress levels determine Neisseria meningitidis attachment sites along the blood–brain barrier

    PubMed Central

    Mairey, Emilie; Genovesio, Auguste; Donnadieu, Emmanuel; Bernard, Christine; Jaubert, Francis; Pinard, Elisabeth; Seylaz, Jacques; Olivo-Marin, Jean-Christophe; Nassif, Xavier; Duménil, Guillaume

    2006-01-01

    Neisseria meningitidis is a commensal bacterium of the human nasopharynx. Occasionally, this bacterium reaches the bloodstream and causes meningitis after crossing the blood–brain barrier by an unknown mechanism. An immunohistological study of a meningococcal sepsis case revealed that neisserial adhesion was restricted to capillaries located in low blood flow regions in the infected organs. This study led to the hypothesis that drag forces encountered by the meningococcus in the bloodstream determine its attachment site in vessels. We therefore investigated the ability of N. meningitidis to bind to endothelial cells in the presence of liquid flow mimicking the bloodstream with a laminar flow chamber. Strikingly, average blood flows reported for various organs strongly inhibited initial adhesion. As cerebral microcirculation is known to be highly heterogeneous, cerebral blood velocity was investigated at the level of individual vessels using intravital imaging of rat brain. In agreement with the histological study, shear stress levels compatible with meningococcal adhesion were only observed in capillaries, which exhibited transient reductions in flow. The flow chamber assay revealed that, after initial attachment, bacteria resisted high blood velocities and even multiplied, forming microcolonies resembling those observed in the septicemia case. These results argue that the combined mechanical properties of neisserial adhesion and blood microcirculation target meningococci to transiently underperfused cerebral capillaries and thus determine disease development. PMID:16864659

  8. Improvement of Impaired Cerebral Microcirculation Using Rheological Modulation by Drag-Reducing Polymers.

    PubMed

    Bragin, D E; Peng, Z; Bragina, O A; Statom, G L; Kameneva, M V; Nemoto, E M

    2016-01-01

    Nanomolar intravascular concentrations of drag-reducing polymers (DRP) have been shown to improve hemodynamics and survival in animal models of ischemic myocardium and limb, but the effects of DRP on the cerebral microcirculation have not yet been studied. We recently demonstrated that DRP enhance microvascular flow in normal rat brain and hypothesized that it would restore impaired microvascular perfusion and improve outcomes after focal ischemia and traumatic brain injury (TBI). We studied the effects of DRP (high molecular weight polyethylene oxide, 4000 kDa, i.v. at 2 μg/mL of blood) on microcirculation of the rat brain: (1) after permanent middle cerebral artery occlusion (pMCAO); and (2) after TBI induced by fluid percussion. Using in vivo two-photon laser scanning microscopy (2PLSM) over the parietal cortex of anesthetized rats we showed that both pMCAO and TBI resulted in progressive decrease in microvascular circulation, leading to tissue hypoxia (NADH increase) and increased blood brain barrier (BBB) degradation. DRP, injected post insult, increased blood volume flow in arterioles and red blood cell (RBC) flow velocity in capillaries mitigating capillary stasis, tissue hypoxia and BBB degradation, which improved neuronal survival (Fluoro-Jade B, 24 h) and neurologic outcome (Rotarod, 1 week). Improved microvascular perfusion by DRP may be effective in the treatment of ischemic stroke and TBI. PMID:27526149

  9. Intravenous contrast medium aggravates the impairment of pancreatic microcirculation in necrotizing pancreatitis in the rat.

    PubMed Central

    Schmidt, J; Hotz, H G; Foitzik, T; Ryschich, E; Buhr, H J; Warshaw, A L; Herfarth, C; Klar, E

    1995-01-01

    BACKGROUND: Previous reports demonstrated that radiographic contrast medium, as used in contrast-enhanced computed tomography, increases acinar necrosis and mortality in experimental pancreatitis. The authors studied the possibility that these changes may be related to an additional impairment of pancreatic microcirculation. METHODS: Fifty Wistar rats had acute pancreatitis induced by intraductal glycodeoxycholic acid (10 mmol/L for 10 min) and intravenous cerulein (5 micrograms/kg/hr for 6 hrs). After rehydration (16 mL/kg), pancreatic capillary perfusion was quantified by means of intravital microscopy at baseline before intravenous infusion of contrast medium (n = 25) or saline (n = 25), and 30 and 60 minutes thereafter. In addition to total capillary flow, capillaries were categorized as high- or low-flow (> or < 1.6 nL/min). RESULTS: Pancreatic capillary flow did not change in either high- or low-flow capillaries after saline infusion. However, contrast medium infusion induced a significant decrease of total capillary flow (p < 0.001). Analysis according to the relative flow rate revealed that this was primarily because of a significant additional reduction of perfusion in low-flow capillaries (p < 0.0001). Furthermore, complete capillary stasis was observed in 15.9 +/- 3.4% after contrast medium as compared with 3.2 +/- 1.2% after saline infusion (p < 0.006). CONCLUSION: Radiographic contrast medium aggravates the impairment of pancreatic microcirculation in experimental necrotizing pancreatitis. PMID:7717779

  10. Pilot Study of Laser Doppler Measurement of Flow Variability in the Microcirculation of the Palatal Mucosa

    PubMed Central

    Le Bars, Pierre; Niagha, Gaston; Kouadio, Ayepa Alain; Demoersman, Julien; Roy, Elisabeth; Armengol, Valérie; Soueidan, Assem

    2016-01-01

    Background. Histopathological alterations can arise when the denture-supporting mucosa experiences microbial and mechanical stress through the denture base and diagnosis of these diseases usually follows microvascular changes. Microcirculation measurement could allow for detection of such dysfunction and aid in the early diagnosis of palatal mucosa pathologies. Materials and Methods. We tested the sensitivity of laser Doppler for measuring the microcirculation of the palatal mucosa, assessing the median raphe (MR), Schroeder area (SA), and retroincisive papilla (RP). A Doppler PeriFlux 5000 System, containing a laser diode, was used. 54 healthy participants were recruited. We compare the measurements of PU (perfusion unit) using ANOVA test. Results. The numerical values for palatal mucosa blood flow differed significantly among the anatomical areas (p = 0.0167). The mean value of Schroeder area was 92.6 (SD: 38.4) and was significantly higher than the retroincisive papilla (51.9) (SD: 20.2) (p < 0.05), which in turn was higher than that of median raphe (31.9) (SD: 24.2) (p < 0.0001). Conclusion. Schroeder area appeared to have the greatest sensitivity, and vascular flow variability among individuals was also greatest in this region. We suggest that analysis of blood stream modification with laser Doppler of the palatal mucosa can help to detect onset signs of pathological alterations. PMID:27340663

  11. Imaging photoplethysmography for clinical assessment of cutaneous microcirculation at two different depths

    NASA Astrophysics Data System (ADS)

    Marcinkevics, Zbignevs; Rubins, Uldis; Zaharans, Janis; Miscuks, Aleksejs; Urtane, Evelina; Ozolina-Moll, Liga

    2016-03-01

    The feasibility of bispectral imaging photoplethysmography (iPPG) system for clinical assessment of cutaneous microcirculation at two different depths is proposed. The iPPG system has been developed and evaluated for in vivo conditions during various tests: (1) topical application of vasodilatory liniment on the skin, (2) skin local heating, (3) arterial occlusion, and (4) regional anesthesia. The device has been validated by the measurements of a laser Doppler imager (LDI) as a reference. The hardware comprises four bispectral light sources (530 and 810 nm) for uniform illumination of skin, video camera, and the control unit for triggering of the system. The PPG signals were calculated and the changes of perfusion index (PI) were obtained during the tests. The results showed convincing correlations for PI obtained by iPPG and LDI at (1) topical liniment (r=0.98) and (2) heating (r=0.98) tests. The topical liniment and local heating tests revealed good selectivity of the system for superficial microcirculation monitoring. It is confirmed that the iPPG system could be used for assessment of cutaneous perfusion at two different depths, morphologically and functionally different vascular networks, and thus utilized in clinics as a cost-effective alternative to the LDI.

  12. Wavelet-analysis of gastric microcirculation in rats with ulcer bleedings

    NASA Astrophysics Data System (ADS)

    Pavlov, A. N.; Semyachkina-Glushkovskaya, O. V.; Pavlova, O. N.; Bibikova, O. A.; Kurths, J.

    2013-10-01

    Nitric oxide (NO) plays an important role in regulation of central and peripheral circulation in normal state and during hemorrhagic stress. Because the impaired gastric mucosal blood flow is the major cause of gastroduodenal lesions including ulcer bleeding (UB), we study in this work the NO-ergic mechanism responsible for regulation of this blood flow. Our study is performed in rats with a model of stress-induced UB using laser Doppler flowmetry (LDF) that characterizes the rate of blood flow by measuring a Doppler shift of the laser beam scattered by the moving red blood cells. Numerical analysis of LDF-data is based on the discrete wavelet-transform (DWT) using Daubechies wavelets aiming to quantify influences of NO on the gastric microcirculation. We show that the stress-induced UB is associated with an increased level of NO in the gastric tissue and a stronger vascular sensitivity to pharmacological modulation of NO-production by L-NAME. We demonstrate that wavelet-based analyses of NO-dependent regulation of gastric microcirculation can provide an effective endoscopic diagnostics of a risk of UB.

  13. Insights Into Microcirculation Underlying Critical Limb Ischemia by Single-Photon Emission Computed Tomography

    PubMed Central

    Liu, Jung-Tung; Chang, Cheng-Siu; Su, Chen-Hsing; Li, Cho-Shun

    2015-01-01

    Abstract Perfusion difference is used as a parameter to evaluate microcirculation. This study aims to differentiate lower-limb perfusion insufficiency from neuropathy to prevent possible occurrence of failed back surgery syndrome (FBSS). Patients were retrospectively gathered from 134 FBSS cases diagnosed in the past 7 years. Up to 82 cases that were excluded from neuralgia by radiologic imaging, electrodiagnostic electromyography, and nerve conduction velocity were enrolled in this study. Perfusion difference was evaluated by single-photon emission computed tomography, and pain intensities were recorded via visual analog scale (VAS) score. Lower perfusion at the left leg comprises 51.2% (42 of 82) of the patients. The mean perfusion difference of the 82 patients was 0.86 ± 0.05 (range: 0.75–0.93). Patients with systemic vascular diseases exhibited significantly higher perfusion difference than that of patients without these related diseases (P < 0.05), except for renal insufficiency (P = 0.134). Significant correlation was observed between perfusion difference and VAS score (r = −0.78; P < 0.0001; n = 82). In this study, we presented perfusion difference as a parameter for evaluating microcirculation, which cannot be detected by ultrasonography or angiography. PMID:26166084

  14. Diffusing wave spectroscopy and its application for monitoring of skin blood microcirculation

    NASA Astrophysics Data System (ADS)

    Meglinski, Igor V.

    2003-10-01

    Diffusing Wave Spectroscopy (DWS) is a novel modern technique uniquely suited for the non-invasive measurements of the particles size and their motion within the randomly inhomogeneous highly scattering and absorbing media, including biological tissues as a human skin. The technique is based on the illuminating the media (tissues) with a coherent laser light, and analyzing the loss of coherence of the scattered field arises from motion of the scattering particles with respect to each other. Both theoretical and experimental results has shown the potentialities and viability of DWS application for the express non-invasive quantitative monitoring and functional diagnostics of skin blood microcirculation, with down to 1 μm/sec resolution. This is likely lead to quantitative monitoring in general diagnostics, diabetes studies, pharmacological intervention for the failing surgical skin flaps or replants, blood microcirculation monitoring during sepsis, assess burn depth, diagnose atherosclerotic disease, and investigate mechanisms of photodynamic therapy for cancer treatment. In frame of current report we describe the recent developments of DWS further to the point that skin blood micro-flow can be routinely and accurately obtained in a separate skin vascular bed on normal skin tissues.

  15. In Vivo Monitoring of Microcirculation in Burn Healing Process with Optical Microangiography

    PubMed Central

    Qin, Wan; Li, Yuandong; Wang, Jingang; Qi, Xiaoli; Wang, Ruikang K.

    2016-01-01

    Objective: Optical microangiography (OMAG)-based optical coherence tomography is a noninvasive technique capable of imaging functional microvasculature innervating scanned tissue volume. In this study, we utilize OMAG to investigate dynamic changes of microcirculation during the healing process of a burn. Approach: A soft-contact superficial burn injury was induced on a mouse ear with 1 μL 70°C hot water. Microangiograms were generated by using OMAG before and after the burn. Results: Vessel recruitment and remodeling were observed in the healing process. Burn injury reached to the worst extent within the first 24 h and had no expansion thereafter. The interrupted microcirculation in the mouse ear was progressively recovered in the consequent postburn days and completely healed on postburn day 7. Innovation: OMAG provides a novel way for noninvasive visualization and quantification of vasculature changes over time after burn injuries. The high resolution achieved by the imaging system reveals microvascular details down to capillary level. Conclusion: Our results demonstrated that OMAG has great potential to improve the understanding of microcirculatory responses to burns and thus benefit the development of effective therapeutics. PMID:27602252

  16. A new contrast-assisted method in microcirculation volumetric flow assessment

    NASA Astrophysics Data System (ADS)

    Lu, Sheng-Yi; Chen, Yung-Sheng; Yeh, Chih-Kuang

    2007-03-01

    Microcirculation volumetric flow rate is a significant index in diseases diagnosis and treatment such as diabetes and cancer. In this study, we propose an integrated algorithm to assess microcirculation volumetric flow rate including estimation of blood perfused area and corresponding flow velocity maps based on high frequency destruction/contrast replenishment imaging technique. The perfused area indicates the blood flow regions including capillaries, arterioles and venules. Due to the echo variance changes between ultrasonic contrast agents (UCAs) pre- and post-destruction two images, the perfused area can be estimated by the correlation-based approach. The flow velocity distribution within the perfused area can be estimated by refilling time-intensity curves (TICs) after UCAs destruction. Most studies introduced the rising exponential model proposed by Wei (1998) to fit the TICs. Nevertheless, we found the TICs profile has a great resemblance to sigmoid function in simulations and in vitro experiments results. Good fitting correlation reveals that sigmoid model was more close to actual fact in describing destruction/contrast replenishment phenomenon. We derived that the saddle point of sigmoid model is proportional to blood flow velocity. A strong linear relationship (R = 0.97) between the actual flow velocities (0.4-2.1 mm/s) and the estimated saddle constants was found in M-mode and B-mode flow phantom experiments. Potential applications of this technique include high-resolution volumetric flow rate assessment in small animal tumor and the evaluation of superficial vasculature in clinical studies.

  17. Pilot Study of Laser Doppler Measurement of Flow Variability in the Microcirculation of the Palatal Mucosa.

    PubMed

    Le Bars, Pierre; Niagha, Gaston; Kouadio, Ayepa Alain; Demoersman, Julien; Roy, Elisabeth; Armengol, Valérie; Soueidan, Assem

    2016-01-01

    Background. Histopathological alterations can arise when the denture-supporting mucosa experiences microbial and mechanical stress through the denture base and diagnosis of these diseases usually follows microvascular changes. Microcirculation measurement could allow for detection of such dysfunction and aid in the early diagnosis of palatal mucosa pathologies. Materials and Methods. We tested the sensitivity of laser Doppler for measuring the microcirculation of the palatal mucosa, assessing the median raphe (MR), Schroeder area (SA), and retroincisive papilla (RP). A Doppler PeriFlux 5000 System, containing a laser diode, was used. 54 healthy participants were recruited. We compare the measurements of PU (perfusion unit) using ANOVA test. Results. The numerical values for palatal mucosa blood flow differed significantly among the anatomical areas (p = 0.0167). The mean value of Schroeder area was 92.6 (SD: 38.4) and was significantly higher than the retroincisive papilla (51.9) (SD: 20.2) (p < 0.05), which in turn was higher than that of median raphe (31.9) (SD: 24.2) (p < 0.0001). Conclusion. Schroeder area appeared to have the greatest sensitivity, and vascular flow variability among individuals was also greatest in this region. We suggest that analysis of blood stream modification with laser Doppler of the palatal mucosa can help to detect onset signs of pathological alterations. PMID:27340663

  18. High sensitive volumetric imaging of renal microcirculation in vivo using ultrahigh sensitive optical microangiography

    NASA Astrophysics Data System (ADS)

    Zhi, Zhongwei; Jung, Yeongri; Jia, Yali; An, Lin; Wang, Ruikang K.

    2011-03-01

    We present a non-invasive, label-free imaging technique called Ultrahigh Sensitive Optical Microangiography (UHSOMAG) for high sensitive volumetric imaging of renal microcirculation. The UHS-OMAG imaging system is based on spectral domain optical coherence tomography (SD-OCT), which uses a 47000 A-line scan rate CCD camera to perform an imaging speed of 150 frames per second that takes only ~7 seconds to acquire a 3D image. The technique, capable of measuring slow blood flow down to 4 um/s, is sensitive enough to image capillary networks, such as peritubular capillaries and glomerulus within renal cortex. We show superior performance of UHS-OMAG in providing depthresolved volumetric images of rich renal microcirculation. We monitored the dynamics of renal microvasculature during renal ischemia and reperfusion. Obvious reduction of renal microvascular density due to renal ischemia was visualized and quantitatively analyzed. This technique can be helpful for the assessment of chronic kidney disease (CKD) which relates to abnormal microvasculature.

  19. A laser Doppler system for monitoring cerebral microcirculation: implementation and evaluation during neurosurgery.

    PubMed

    Rejmstad, Peter; Åkesson, Gustav; Åneman, Oscar; Wårdell, Karin

    2016-01-01

    The aim of this study was to adapt and evaluate laser Doppler perfusion monitoring (LDPM) together with custom-designed brain probes and software for continuous recording of cerebral microcirculation in patients undergoing neurosurgery. The LDPM system was used to record perfusion and backscattered light (TLI). These parameters were displayed together with the extracted heart rate (HR), pulsatility index (PI) and signal trends from adjustable time intervals. Technical evaluation was done on skin during thermal provocation. Clinical measurements were performed on ten patients undergoing brain tumour surgery. Data from 76 tissue sites were captured with a length varying between 10 s to 15 min. Statistical comparisons were done using Mann-Whitney tests. Grey and tumour tissue could be separated from white matter using the TLI signal (p < 0.05). The perfusion was significantly higher in grey and tumour tissue compared to white matter (p < 0.005). LDPM was successfully used as an intraoperative tool for monitoring local blood flow and additional parameters linked to cerebral microcirculation (perfusion, TLI, HR and PI) during tumour resection. The systems stability opens up for studies in the postoperative care of patients with, for example, traumatic brain injury or subarachnoid haemorrhage. PMID:26105147

  20. Using a laser-Doppler flowmetry to measure pulsatile microcirculation on the kidney in rats

    NASA Astrophysics Data System (ADS)

    Jan, Ming-Yie; Chao, Pin-Tsun; Hsu, Tse-Lin; Wang, Yuh-Yin L.; Wang, Wei-Kung

    2001-10-01

    Although Laser Doppler flowmetery (LDF) been extensively used in measurement of microvascular blood flow of different tissues. However, due to some physiological vibrations, fast oscillations of the renal cortical flux (RCF) are hard to be measured. In the study, a commercial 3mW 780nm Laser Doppler flowmetery, with a single fiber and a de-vibration holder, was used to measure the pulsatile RCF in rats. Considering the fast response due to the heart rate of rats, the time constant (TC) was set to 0.05 second and thus the frequency response is up to 20Hz. Furthermore, a calibration standard and a static blood sample were also measured as the references without the pulsatile driving force. In order not to perturb the RCF with tiny momentum, the applying force that the fiber exerted on the renal surface was controlled below 100 dyne. To enhance the signal to noise ratio (SNR), an averaged periodogram was used to estimate the frequency components of the pulsatile microcirculation. It is found that the dominating fast oscillation of RCF is pulsatile and its harmonic components are directly correlated with those of the heartbeat (correlation coefficient =0.999, P<0.001, n=17). The result shows that, in the kidney, the pulsatile RCF is the dominating component of microcirculation oscillation and driven by the fast propagating blood pressure. This technique could be further utilized to analyze the pharmacological effect and hemodynamic parameters on renal function.

  1. Polysomnographic findings in nights preceding a migraine attack.

    PubMed

    Göder, R; Fritzer, G; Kapsokalyvas, A; Kropp, P; Niederberger, U; Strenge, H; Gerber, W D; Aldenhoff, J B

    2001-02-01

    Sleep recordings were performed in eight patients to analyse sleep alterations preceding migraine attacks. Polysomnographic recordings from nights before an attack were compared with nights without following migraine. We analysed standard sleep parameters and electroencephalogram (EEG) power spectra. The main findings preceding migraine attacks were a significant decrease in the number of arousals, a decrease in rapid eye movement (REM) density, a significant decrease of beta power in the slow wave sleep, and a decrease of alpha power during the first REM period. The results suggest a decrease in cortical activation during sleep preceding migraine attacks. According to the models of sleep regulation, alterations in the function of aminergic or cholinergic brainstem nuclei have to be discussed. PMID:11298661

  2. Next-generation pyrosequencing of gonad transcriptomes in the polyploid lake sturgeon (Acipenser fulvescens): the relative merits of normalization and rarefaction in gene discovery

    PubMed Central

    Hale, Matthew C; McCormick, Cory R; Jackson, James R; DeWoody, J Andrew

    2009-01-01

    Background Next-generation sequencing technologies have been applied most often to model organisms or species closely related to a model. However, these methods have the potential to be valuable in many wild organisms, including those of conservation concern. We used Roche 454 pyrosequencing to characterize gene expression in polyploid lake sturgeon (Acipenser fulvescens) gonads. Results Titration runs on a Roche 454 GS-FLX produced more than 47,000 sequencing reads. These reads represented 20,741 unique sequences that passed quality control (mean length = 186 bp). These were assembled into 1,831 contigs (mean contig depth = 4.1 sequences). Over 4,000 sequencing reads (~19%) were assigned gene ontologies, mostly to protein, RNA, and ion binding. A total of 877 candidate SNPs were identified from > 50 different genes. We employed an analytical approach from theoretical ecology (rarefaction) to evaluate depth of sequencing coverage relative to gene discovery. We also considered the relative merits of normalized versus native cDNA libraries when using next-generation sequencing platforms. Not surprisingly, fewer genes from the normalized libraries were rRNA subunits. Rarefaction suggests that normalization has little influence on the efficiency of gene discovery, at least when working with thousands of reads from a single tissue type. Conclusion Our data indicate that titration runs on 454 sequencers can characterize thousands of expressed sequence tags which can be used to identify SNPs, gene ontologies, and levels of gene expression in species of conservation concern. We anticipate that rarefaction will be useful in evaluations of gene discovery and that next-generation sequencing technologies hold great potential for the study of other non-model organisms. PMID:19402907

  3. Intravascular disorders of microcirculation in patients with chronic obstructive pulmonary disease: the results of clinical and morphological examination

    NASA Astrophysics Data System (ADS)

    Fiodorova, Tatiana A.

    1999-05-01

    We have evaluated the results of clinical and morphological study of microcirculation and its intravascular factors in 120 patients with chronic obstructive pulmonary diseases (COPD). Conjunctival biomicroscopy with quantitative evaluation of microcirculatory changes we performed. This data were compared with the results of laboratory study of erythrocytes and thrombocytes aggregation, some plasma hemostasis indices and morphological examination of microcirculation. The results of conjunctival biomicroscopy showed the close correlation between the clinical severity of the disease, the degree of respiratory failure and the degree of microcirculatory disorders. Progress of the disease with the development of respiratory failure and cor pulmonale was characterized by the expansion of the process of erythrocytes aggregation to the whole parts of the microcirculatory bad and was associated with perivascular hemorrhages. In some patients with severe COPD laboratory data showed chronic disseminated intravascular microcoagulation (DVS-syndrome). Intravascular platelets, erythrocytes and mixed aggregates which completely cork the vessels and compressed endothelium were uncovered by electron microscopy. Platelets membrane injuring with its degranulation was seen. This discovered correlation between microcirculatory abnormalities in lungs and in conjunctiva in patients with COPD demonstrate that this abnormalities of microcirculation are prevalent. This allows to use in clinical accessible and informative method of conjunctival biomicroscopy to estimate the condition of microcirculation in this pathology.

  4. In vivo microcirculation imaging of the sub surface fingertip using correlation mapping optical coherence tomography (cmOCT)

    NASA Astrophysics Data System (ADS)

    Dsouza, Roshan I.; Zam, Azhar; Subhash, Hrebesh M.; Larin, Kirill V.; Leahy, Martin

    2013-02-01

    We describe a novel application of correlation mapping optical coherence tomography (cmOCT) for sub-surface fingerprint biometric identification. Fingerprint biometrics including automated fingerprint identification systems, are commonly used to recognise the fingerprint, since they constitute simple, effective and valuable physical evidence. Spoofing of biometric fingerprint devices can be easily done because of the limited information obtained from the surface topography. In order to overcome this limitation a potentially more secure source of information is required for biometric identification applications. In this study, we retrieve the microcirculation map of the subsurface fingertip by use of the cmOCT technique. To increase probing depth of the sub surface microcirculation, an optical clearing agent composed of 75% glycerol in aqueous solution was applied topically and kept in contact for 15 min. OCT intensity images were acquired from commercial research grade swept source OCT system (model OCT1300SS, Thorlabs Inc. USA). A 3D OCT scan of the fingertip was acquired over an area of 5x5 mm using 1024x1024 A-scans in approximately 70 s. The resulting volume was then processed using the cmOCT technique with a 7x7 kernel to provide a microcirculation map. We believe these results will demonstrate an enhanced security level over artificial fingertips. To the best of our knowledge, this is the first demonstration of imaging microcirculation map of the subsurface fingertip.

  5. Blood microcirculation monitoring by use of spatial filtering of time-integrated speckle patterns: potentialities to improve the depth resolution

    NASA Astrophysics Data System (ADS)

    Zimnyakov, Dmitry A.; Misnin, Alexander B.

    2001-06-01

    Statistical analysis of images of time-integrated dynamic speckle patterns is considered as the tool for diagnostics and imaging of in vivo tissue dynamics such as blood microcirculation in superficial layers of human tissues and organs. Basic approach for blood microcirculation monitoring using the contrast analysis of time-averaged speckle images is known as LASCA (Laser Speckle Contrast Analysis) technique. This paper presents the modified version of LASCA, which is based on application of the localized probe light source and the spatial filtration of analyzed speckle pattern in the object plane. Being compared with classical LASCA technique, this method has the certain disadvantage as the necessity of scanning procedure to provide the reconstruction of maps of blood microcirculation parameters, but it gives the additional possibilities for the analysis of depth distributions of these parameters. Theoretical background for the depth-resolved analysis of blood microcirculation parameters on the basis of the concept of effective optical path distributions for multiply scattered probe light is considered. The effect of non-zero residual contrast even in the case of large integration times is also discussed.

  6. In situ assessment of the renal microcirculation in mechanically ventilated rats using sidestream dark-field imaging.

    PubMed

    Astapenko, D; Jor, O; Lehmann, C; Cerny, V

    2015-02-01

    For microcirculation research there is a need for baseline data and feasibility protocols describing microcirculation of various organs. The aim of our study was to examine the reliability and reproducibility of sidestream dark-field (SDF) imaging within the renal cortical microcirculation in rats. Renal microcirculation was observed using SDF probe placed on the exposed renal surface via the upper midline laparotomy. Video sequences recorded intermittently in short apneic pauses were analyzed off-line by using AVA 3.0 software (MicroVision Medical, Amsterdam, the Netherlands). Results are expressed as mean (SD) or median (25-75% percentiles). We obtained 60 clear sequences from all recorded analyzable videos from all the animals. The total small vessel and all vessel density (in mm.mm(-2) ) were (28.79 ± 0.40) and (28.95 ± 0.40), respectively. The perfused small and all vessel density were (28.79 ± 0.40) and (28.95 ± 0.40), respectively. The DeBacker Score was (19.14 ± 0.43), the proportion of perfused vessels was 100% (100-100%) and the microvascular flow index was 3.49 (3-3.75). We conclude SDF imaging provides a reliable method to examine the renal microvascular bed in vivo and thus can be used for the study of the renal cortical vascular network in various experimental diseases models and clinical settings. PMID:25545609

  7. High-sensitivity detection and monitoring of microcirculation using cutaneous and catheter probes for Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Yang, Victor X.; Gordon, M. L.; Qi, B.; Yue, E. Seng; Tang, S.; Bisland, Stuart K.; Pekar, J.; Lo, S.; Marcon, Norman E.; Wilson, B.; Vitkin, Alex

    2003-07-01

    Background: Currently clinical Doppler ultrasound cannot detect microvascular blood flow and it is difficult to provide depth discrimination using laser Doppler flowmetry. Doppler optical coherence tomography (DOCT) is a novel technique for noninvasive subsurface imaging of microcirculation and tissue structure. Aims: To design handheld and catheter-based DOCT probes for clinical cutaneous and endoscopic imaging. To develop signal processing techniques for real-time detection and quantification of microvascular blood flow. Methods: A DOCT system, with interchangeable cutaneous and catheter probes, was developed. The axial spatial resolution was 10 μm, and the velocity resolution was 20 μm/s, using a 1300 nm broadband infrared light. The system achieved real-time imaging with frame rates up to 32 Hz at 512 x 256 pixels per frame. We used the system to detect microcirculation in human skin and rat esophagus, and to monitor microvascular responses to photodynamic therapy (PDT) in a rat tumor model. Results: We present experimental results from in vivo DOCT imaging of microcirculation in human skin arterio-venous malformations (AVM), normal rat esophagus, and a rat gliosarcoma PDT model. In the PDT model, we followed microvascular responses to PDT and observed differences in the microcirculation during and after therapy, which can have important implications for PDT dosimetry and treatment optimization. Conclusions: To our knowledge, this is the first demonstration of endoscopic catheter-based DOCT detection of microcirculation in vivo. In addition, AVM can be detected using handheld cutaneous DOCT probes under clinical settings. DOCT may serve as a real-time monitoring tool for PDT dosimetry, especially for vascular targeting photosensitizers.

  8. The mouse cremaster muscle preparation for intravital imaging of the microcirculation.

    PubMed

    Bagher, Pooneh; Segal, Steven S

    2011-01-01

    Throughout the body, the maintenance of homeostasis requires the constant supply of oxygen and nutrients concomitant with removal of metabolic by-products. This balance is achieved by the movement of blood through the microcirculation, which encompasses the smallest branches of the vascular supply throughout all tissues and organs. Arterioles branch from arteries to form networks that control the distribution and magnitude of oxygenated blood flowing into the multitude of capillaries intimately associated with parenchymal cells. Capillaries provide a large surface area for diffusional exchange between tissue cells and the blood supply. Venules collect capillary effluent and converge as they return deoxygenated blood towards the heart. To observe these processes in real time requires an experimental approach for visualizing and manipulating the living microcirculation. The cremaster muscle of rats was first used as a model for studying inflammation using histology and electron microscopy post mortem. The first in vivo report of the exposed intact rat cremaster muscle investigated microvascular responses to vasoactive drugs using reflected light. However curvature of the muscle and lack of focused illumination limited the usefulness of this preparation. The major breakthrough entailed opening the muscle, detaching it from the testicle and spreading it radially as a flat sheet for transillumination under a compound microscope. While shown to be a valuable preparation to study the physiology of the microcirculation in rats and hamsters, the cremaster muscle in mice has proven particularly useful in dissecting cellular pathways involved in regulating microvascular function and real-time imaging of intercellular signaling. The cremaster muscle is derived from the internal oblique and transverse abdominus muscles as the testes descend through the inguinal canal. It serves to support (Greek: cremaster = suspender) and maintain temperature of the testes. As described here

  9. The Role of Sexual Precedence in Verbal Sexual Coercion

    ERIC Educational Resources Information Center

    Livingston, Jennifer A.; Buddie, Amy M.; Testa, Maria; VanZile-Tamsen, Carol

    2004-01-01

    Experiences of verbal sexual coercion are common and have potential for negative consequences, yet are not well understood. This study used qualitative and descriptive statistics to examine verbal sexual coercion experiences among a community sample of 114 women and explored the role of sexual precedence in these experiences. Analyses revealed…

  10. Episodic Mood Changes Preceding an Exacerbation of Multiple Sclerosis

    PubMed Central

    Sharma, Priya; Morrow, Sarah A.; Owen, Richard J.

    2015-01-01

    Multiple sclerosis is a neurologic inflammatory disease that can manifest with psychiatric symptoms. Although depression is the most common psychiatric diagnosis in patients with multiple sclerosis, how depression develops is not fully understood. We present the case of an individual who displayed episodic mood changes preceding an exacerbation of multiple sclerosis symptoms. The clinical and research implications of this association are discussed. PMID:26835163

  11. Metrical expectations from preceding prosody influence perception of lexical stress.

    PubMed

    Brown, Meredith; Salverda, Anne Pier; Dilley, Laura C; Tanenhaus, Michael K

    2015-04-01

    Two visual-world experiments tested the hypothesis that expectations based on preceding prosody influence the perception of suprasegmental cues to lexical stress. The results demonstrate that listeners' consideration of competing alternatives with different stress patterns (e.g., 'jury/gi'raffe) can be influenced by the fundamental frequency and syllable timing patterns across material preceding a target word. When preceding stressed syllables distal to the target word shared pitch and timing characteristics with the first syllable of the target word, pictures of alternatives with primary lexical stress on the first syllable (e.g., jury) initially attracted more looks than alternatives with unstressed initial syllables (e.g., giraffe). This effect was modulated when preceding unstressed syllables had pitch and timing characteristics similar to the initial syllable of the target word, with more looks to alternatives with unstressed initial syllables (e.g., giraffe) than to those with stressed initial syllables (e.g., jury). These findings suggest that expectations about the acoustic realization of upcoming speech include information about metrical organization and lexical stress and that these expectations constrain the initial interpretation of suprasegmental stress cues. These distal prosody effects implicate online probabilistic inferences about the sources of acoustic-phonetic variation during spoken-word recognition. PMID:25621583

  12. 48 CFR 819.202-72 - Order of precedence. [Reserved

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 5 2014-10-01 2014-10-01 false Order of precedence. 819.202-72 Section 819.202-72 Federal Acquisition Regulations System DEPARTMENT OF VETERANS AFFAIRS SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS Policies 819.202-72 Order of...

  13. Metrical expectations from preceding prosody influence perception of lexical stress

    PubMed Central

    Brown, Meredith; Salverda, Anne Pier; Dilley, Laura C.; Tanenhaus, Michael K.

    2015-01-01

    Two visual-world experiments tested the hypothesis that expectations based on preceding prosody influence the perception of suprasegmental cues to lexical stress. The results demonstrate that listeners’ consideration of competing alternatives with different stress patterns (e.g., ‘jury/gi’raffe) can be influenced by the fundamental frequency and syllable timing patterns across material preceding a target word. When preceding stressed syllables distal to the target word shared pitch and timing characteristics with the first syllable of the target word, pictures of alternatives with primary lexical stress on the first syllable (e.g., jury) initially attracted more looks than alternatives with unstressed initial syllables (e.g., giraffe). This effect was modulated when preceding unstressed syllables had pitch and timing characteristics similar to the initial syllable of the target word, with more looks to alternatives with unstressed initial syllables (e.g., giraffe) than to those with stressed initial syllables (e.g., jury). These findings suggest that expectations about the acoustic realization of upcoming speech include information about metrical organization and lexical stress, and that these expectations constrain the initial interpretation of suprasegmental stress cues. These distal prosody effects implicate on-line probabilistic inferences about the sources of acoustic-phonetic variation during spoken-word recognition. PMID:25621583

  14. Counselor Interventions Preceding Client Laughter in Brief Therapy.

    ERIC Educational Resources Information Center

    Falk, Dana R.; Hill, Clara E.

    1992-01-01

    Examined whether 6 categories of counselor humor and 4 categories of risk interventions preceded client laughter in 236 events from 8 cases of brief psychotherapy. Found most client laughter was mild and moderate, with only eight instances of strong laughter. Humorous interventions led to more client laughter than did interventions that encouraged…

  15. The open microcirculation in human spleens: a three-dimensional approach.

    PubMed

    Steiniger, Birte; Bette, Michael; Schwarzbach, Hans

    2011-06-01

    It has long been debated whether the red pulp of human spleens harbors an open or a closed microcirculation or both. To solve this issue, the authors differentially stained the endothelium in red pulp arterial microvessels and in venous sinuses using brightfield and fluorescence immunohistology with reagents against CD34 and CD141. Three-dimensional models of red pulp arterial microvessels and sinuses were derived from serial double-stained paraffin sections with the help of license-free open-access software. In each model, arterial microvascular ends were traced and verified by reference to the original serial sections. In total, 142 ends were analyzed in the specimens of three individuals. None of these ends was connected to a sinus, suggesting that the human splenic red pulp harbors an entirely open circulatory system. Thus, the spleen is the only human organ where blood passes through spaces not lined by endothelia or other barrier-forming cells. PMID:21525186

  16. Influence of low-intensity laser radiation on degree of oxygenation and speed microcirculation of blood

    NASA Astrophysics Data System (ADS)

    Korolevich, Alexander N.; Dubina, Natali S.; Vecherinski, Sergei I.

    2000-11-01

    The paper investigated in vivo the influence of low-intensity laser radiation (he-Ne laser with wavelength 0,63 nm) on the mean velocity of their movement. It is known that characteristic of cardiovascular diseases (CVD) are microcirculation disturbances and disorder in rheological properties of blood. Therefore these investigations were carried out on cardiac ischemia patients. The blood perfusion valve and the mean velocity were measured by the method of photon correlation spectroscopy with the use of fiber optic cables. As the radiation source, a semiconductor laser with wavelength 780 nm (0,8 mW) was used. It has been found that, between the erythrocytes and the mean velocity of their movement there is an inverse dependence on the time of irradiation of patients.

  17. Laser reflectance oximetry and Doppler flowmetry in assessment of complex physiological parameters of cutaneous blood microcirculation

    NASA Astrophysics Data System (ADS)

    Dunaev, Andrey V.; Sidorov, Victor V.; Stewart, Neil A.; Sokolovski, Sergei G.; Rafailov, Edik U.

    2013-03-01

    The integration of multiple optical techniques within a single diagnostic device is used to address the difficulties in standardising measurement of cutaneous blood micro-dynamics caused by high variability. We demonstrate the benefits of simultaneous assessment of blood relative volume (Vb), microcirculation index (Im) and tissue oxygen saturation (StO2), during long-term examination of healthy volunteers. Consequently, five rhythmic components: endothelial, neurogenic, myogenic, breath and heart pulses were established showing high variability up to 30 - 50% as well as in initial parameters around 16%. All rhythmic components were synchronous with some latency between Im and StO2 in the myogenic component supports the hypothesis of strong correlation between peripheral hemodynamics and oxygen utilisation in tissues.

  18. Development of a 3D finite element model of lens microcirculation

    PubMed Central

    2012-01-01

    Background It has been proposed that in the absence of a blood supply, the ocular lens operates an internal microcirculation system. This system delivers nutrients, removes waste products and maintains ionic homeostasis in the lens. The microcirculation is generated by spatial differences in membrane transport properties; and previously has been modelled by an equivalent electrical circuit and solved analytically. While effective, this approach did not fully account for all the anatomical and functional complexities of the lens. To encapsulate these complexities we have created a 3D finite element computer model of the lens. Methods Initially, we created an anatomically-correct representative mesh of the lens. We then implemented the Stokes and advective Nernst-Plank equations, in order to model the water and ion fluxes respectively. Next we complemented the model with experimentally-measured surface ionic concentrations as boundary conditions and solved it. Results Our model calculated the standing ionic concentrations and electrical potential gradients in the lens. Furthermore, it generated vector maps of intra- and extracellular space ion and water fluxes that are proposed to circulate throughout the lens. These fields have only been measured on the surface of the lens and our calculations are the first 3D representation of their direction and magnitude in the lens. Conclusion Values for steady state standing fields for concentration and electrical potential plus ionic and fluid fluxes calculated by our model exhibited broad agreement with observed experimental values. Our model of lens function represents a platform to integrate new experimental data as they emerge and assist us to understand how the integrated structure and function of the lens contributes to the maintenance of its transparency. PMID:22992294

  19. Geomagnetic field modulates artificial static magnetic field effect on arterial baroreflex and on microcirculation

    NASA Astrophysics Data System (ADS)

    Gmitrov, Juraj

    2007-03-01

    Spreading evidence suggests that geomagnetic field (GMF) modulates artificial magnetic fields biological effect and associated with increased cardiovascular morbidity. To explore the underlying physiological mechanism we studied 350 mT static magnetic field (SMF) effect on arterial baroreflex-mediated skin microcirculatory response in conjunction with actual geomagnetic activity, reflected by K and K p indices. Fourteen experiments were performed in rabbits sedated by pentobarbital infusion (5 mg/kg/h). Mean femoral artery blood pressure, heart rate, and the ear lobe skin microcirculatory blood flow, measured by microphotoelectric plethysmogram (MPPG), were simultaneously recorded before and after 40 min of NdFeB magnets local exposure to sinocarotid baroreceptors. Arterial baroreflex sensitivity (BRS) was estimated from heart rate/blood pressure response to intravenous bolus injections of nitroprusside and phenylephrine. We found a significant positive correlation between SMF-induced increase in BRS and increment in microvascular blood flow (ΔBRS with ΔMPPG, r=0.7, p<0.009) indicated the participation of the arterial baroreflex in the regulation of the microcirculation and its enhancement after SMF exposure. Geomagnetic disturbance, as opposed to SMF, decreased both microcirculation and BRS, and counteracted SMF-induced increment in microcirculatory blood flow ( K-index with ΔMPPG; r s=-0.55, p<0.041). GMF probably affected central baroreflex pathways, diminishing SMF direct stimulatory effect on sinocarotid baroreceptors and on baroreflex-mediated vasodilatatory response. The results herein may thus point to arterial baroreflex as a possible physiological mechanism for magnetic-field cardiovascular effect. It seems that geomagnetic disturbance modifies artificial magnetic fields biological effect and should be taken into consideration in the assessment of the final effect.

  20. Geomagnetic field modulates artificial static magnetic field effect on arterial baroreflex and on microcirculation.

    PubMed

    Gmitrov, Juraj

    2007-03-01

    Spreading evidence suggests that geomagnetic field (GMF) modulates artificial magnetic fields biological effect and associated with increased cardiovascular morbidity. To explore the underlying physiological mechanism we studied 350 mT static magnetic field (SMF) effect on arterial baroreflex-mediated skin microcirculatory response in conjunction with actual geomagnetic activity, reflected by K and K ( p ) indices. Fourteen experiments were performed in rabbits sedated by pentobarbital infusion (5 mg/kg/h). Mean femoral artery blood pressure, heart rate, and the ear lobe skin microcirculatory blood flow, measured by microphotoelectric plethysmogram (MPPG), were simultaneously recorded before and after 40 min of NdFeB magnets local exposure to sinocarotid baroreceptors. Arterial baroreflex sensitivity (BRS) was estimated from heart rate/blood pressure response to intravenous bolus injections of nitroprusside and phenylephrine. We found a significant positive correlation between SMF-induced increase in BRS and increment in microvascular blood flow (DeltaBRS with DeltaMPPG, r=0.7, p<0.009) indicated the participation of the arterial baroreflex in the regulation of the microcirculation and its enhancement after SMF exposure. Geomagnetic disturbance, as opposed to SMF, decreased both microcirculation and BRS, and counteracted SMF-induced increment in microcirculatory blood flow (K-index with DeltaMPPG; r (s)=-0.55, p<0.041). GMF probably affected central baroreflex pathways, diminishing SMF direct stimulatory effect on sinocarotid baroreceptors and on baroreflex-mediated vasodilatatory response. The results herein may thus point to arterial baroreflex as a possible physiological mechanism for magnetic-field cardiovascular effect. It seems that geomagnetic disturbance modifies artificial magnetic fields biological effect and should be taken into consideration in the assessment of the final effect. PMID:16983578

  1. Manipulation of magnetic nanoparticle retention and hemodynamic consequences in microcirculation: assessment by laser speckle imaging

    PubMed Central

    Ma, Yunn-Hwa; Chen, Si-Yi; Tu, Shu-Ju; Yang, Hung-Wei; Liu, Hao-Li

    2012-01-01

    Magnetic nanoparticles (MNPs) have been proposed for targeted or embolization therapeutics. How MNP retention occurs in circulation may critically determine local hemodynamics, tissue distribution of MNPs, and the therapeutic effects. We attempted to establish a microcirculation model to study the magnetic capture of MNPs in small vessels and to determine the factors affecting MNP retention. Two-dimensional hemodynamic changes in response to magnet-induced MNP retention in the microvessels of the cremaster muscle in vivo were observed in a real-time manner using a laser speckle imaging technique. Changes in tissue perfusion of the cremaster muscle appeared to be closely correlated with the location of the magnet placement underneath the muscle in response to intra-arterial administration of dextran-coated MNPs. Magnet-related retention was observed along the edge of the magnet, as corroborated by the results of histology analysis and microcomputed tomography. In these preparations, tissue iron content almost doubled, as revealed by inductively coupled plasma optical emission spectroscopy. In addition, MNP retention was associated with reduced downstream flow in a dose-dependent manner. Dissipation of MNPs (5 mg/kg) occurred shortly after removal of the magnet, which was associated with significant recovery of tissue flow. However, MNP dissipation did not easily occur after administration of a higher MNP dose (10 mg/kg) or prolonged exposure to the magnetic field. An ultrasound after removal of the magnet may induce the partial dispersion of MNPs and thus partially improve hemodynamics. In conclusion, our results revealed the important correlation of local MNP retention and hemodynamic changes in microcirculation, which can be crucial in the application of MNPs for effective targeted therapeutics. PMID:22745544

  2. Improved instrumentation for blood flow velocity measurements in the microcirculation of small animals

    NASA Astrophysics Data System (ADS)

    de Mesquita, Jayme Alves; Bouskela, Eliete; Wajnberg, Eliane; de Melo, Pedro Lopes

    2007-02-01

    Microcirculation is the generic name of vessels with internal diameter less than 100μm of the circulatory system, whose main functions are tissue nutrition and oxygen supply. In microcirculatory studies, it is important to know the amount of oxyhemoglobin present in the blood and how fast it is moving. The present work describes improvements introduced in a classical hardware-based instrument that has usually been used to monitor blood flow velocity in the microcirculation of small animals. It consists of a virtual instrument that can be easily incorporated into existing hardware-based systems, contributing to reduce operator related biases and allowing digital processing and storage. The design and calibration of the modified instrument are described as well as in vitro and in vivo results obtained with electrical models and small animals, respectively. Results obtained in in vivo studies showed that this new system is able to detect a small reduction in blood flow velocity comparing arteries and arterioles (p<0.002) and a further reduction in capillaries (p<0.0001). A significant increase in velocity comparing capillaries and venules (p<0.001) and venules and veins (p<0.001) was also observed. These results are in close agreement with biophysical principles. Moreover, the improvements introduced in the device allowed us to clearly observe changes in blood flow introduced by a pharmacological intervention, suggesting that the system has enough temporal resolution to track these microcirculatory events. These results were also in close conformity to physiology, confirming the high scientific potential of the modified system and indicating that this instrument can also be useful for pharmacological evaluations.

  3. ggstThe role of tendon microcirculation in Achilles and patellar tendinopathy

    PubMed Central

    Knobloch, Karsten

    2008-01-01

    Tendinopathy is of distinct interest as it describes a painful tendon disease with local tenderness, swelling and pain associated with sonographic features such as hypoechogenic texture and diameter enlargement. Recent research elucidated microcirculatory changes in tendinopathy using laser Doppler flowmetry and spectrophotometry such as at the Achilles tendon, the patellar tendon as well as at the elbow and the wrist level. Tendon capillary blood flow is increased at the point of pain. Tendon oxygen saturation as well as tendon postcapillary venous filling pressures, determined non-invasively using combined Laser Doppler flowmetry and spectrophotometry, can quantify, in real-time, how tendon microcirculation changes over with pathology or in response to a given therapy. Tendon oxygen saturation can be increased by repetitive, intermittent short-term ice applications in Achilles tendons; this corresponds to 'ischemic preconditioning', a method used to train tissue to sustain ischemic damage. On the other hand, decreasing tendon oxygenation may reflect local acidosis and deteriorating tendon metabolism. Painful eccentric training, a common therapy for Achilles, patellar, supraspinatus and wrist tendinopathy decreases abnormal capillary tendon flow without compromising local tendon oxygenation. Combining an Achilles pneumatic wrap with eccentric training changes tendon microcirculation in a different way than does eccentric training alone; both approaches reduce pain in Achilles tendinopathy. The microcirculatory effects of measures such as extracorporeal shock wave therapy as well as topical nitroglycerine application are to be studied in tendinopathy as well as the critical question of dosage and maintenance. Interestingly it seems that injection therapy using color Doppler for targeting the area of neovascularisation yields to good clinical results with polidocanol sclerosing therapy, but also with a combination of epinephrine and lidocaine. PMID:18447938

  4. Improved instrumentation for blood flow velocity measurements in the microcirculation of small animals

    SciTech Connect

    Mesquita, Jayme Alves Jr. de; Bouskela, Eliete; Wajnberg, Eliane; Lopes de Melo, Pedro

    2007-02-15

    Microcirculation is the generic name of vessels with internal diameter less than 100 {mu}m of the circulatory system, whose main functions are tissue nutrition and oxygen supply. In microcirculatory studies, it is important to know the amount of oxyhemoglobin present in the blood and how fast it is moving. The present work describes improvements introduced in a classical hardware-based instrument that has usually been used to monitor blood flow velocity in the microcirculation of small animals. It consists of a virtual instrument that can be easily incorporated into existing hardware-based systems, contributing to reduce operator related biases and allowing digital processing and storage. The design and calibration of the modified instrument are described as well as in vitro and in vivo results obtained with electrical models and small animals, respectively. Results obtained in in vivo studies showed that this new system is able to detect a small reduction in blood flow velocity comparing arteries and arterioles (p<0.002) and a further reduction in capillaries (p<0.0001). A significant increase in velocity comparing capillaries and venules (p<0.001) and venules and veins (p<0.001) was also observed. These results are in close agreement with biophysical principles. Moreover, the improvements introduced in the device allowed us to clearly observe changes in blood flow introduced by a pharmacological intervention, suggesting that the system has enough temporal resolution to track these microcirculatory events. These results were also in close conformity to physiology, confirming the high scientific potential of the modified system and indicating that this instrument can also be useful for pharmacological evaluations.

  5. Effects of cadmium on the renal and skeletal muscle microcirculation in rats

    SciTech Connect

    Zhang Chong.

    1990-01-01

    The effects of cadmium on the arteriolar diameters of the kidney and skeletal muscle were quantified, because of the hypertensive effect of cacmium. The effect of cacmium on the constrictor response of the renal arterioles to angiotensin II (Ang II) were also assessed. In vivo preparations of the rat hydronephrotic kidney and cremaster muscle were used for direct visualization of the microvessels with intravital television microscopy. Hydronephrosis was induced in twenty-seven male Wistar-Kyoto rats (150-180 g) by unilateral ureter ligation. The hydronephrotic kidney, with intact cortical circulation and innervation, was exteriorized in a specially designed bath for microcirculation observation 6-8 weeks following the ureter ligation. The cremaster muscle experiments were conducted in another thirty-seven male WKY rats (120-180 g). Disparate effects of cadmium were observed in these two microcirculation beds. Topical cadmium (1.35 [mu]M-0.45 mM) increased the diameters of the pre- and postglomerular vessels in the hydronephrotic kidney maximally by 15-26%. Cadmium (0.27 mM) inhibited the Ang II response of the arterioles non-competitively. However, intraperitoneally injected cadmium (2 mg/kg), which significantly increased the mean arterial pressure, did not dilate the arterioles nor alter the Ang II response. On the other hand, cadmium (13.5 [mu]M-0.72 mM) constricted the larger arterioles in the cremaster muscle (60-160 [mu]m) concentration-dependently, but not small arterioles (15-30 [mu]m). In summary, topical cadmium dilates renal arterioles and decreases their reactivity to Ang II, but constricts the larger cremaster arterioles. The disparate effects of cadmium suggest different Ca[sup 2+] utilization mechanisms in different vascular beds. The construction of the cremaster arterioles may contribute to cadmium-induced hypertension by increasing peripheral resistance.

  6. Coronary microcirculation changes in non-ischemic dilated cardiomyopathy identified by novel perfusion CT

    PubMed Central

    Miller, Wayne L.; Behrenbeck, Thomas R.; McCollough, Cynthia H.; Williamson, Eric E.; Leng, Shuai; Kline, Timothy L.

    2015-01-01

    Intramyocardial microvessels demonstrate functional changes in cardiomyopathies. However, clinical computed tomography (CT) does not have adequate spatial resolution to assess the microvessels. Our hypothesis is that these functional changes manifest as altered heterogeneity of the spatial distribution of arteriolar perfusion territories. Our goal was to determine whether the spatial analysis of perfusion CT could clinically detect changes in the function and structure of the intramyocardial microcirculation in a non-ischemic dilated cardiomyopathy (DCM). Two groups were studied: (1) a Control group (12 male plus 12 female) with no risk factors nor evidence of coronary artery disease, and (2) a DCM group (12 male plus 12 female)with left ventricular ejection fraction ≤40 %and no evidence of coronary artery disease. Using the CT scan, the LV free wall thickness and its radius of curvature were measured. The DCM group was sub divided into those with LV free wall thickness <11.5 mm and those with thickness≥11.5 mm. In themyocardial opacification phase of the CT scan sequence, myocardial perfusion (F) and intramyocardial blood volume (Bv) for multiple intramyocardial regions were computed. No significant differences between the groups were demonstrable in overall myocardial F or Bv. However, the myocardial regional data showed significantly increased spatial heterogeneity in the DCM group when compared to the Control group. The findings demonstrate that altered function of the subresolution intramyocardial microcirculation can be quantified with myocardial perfusion CT and that significant changes in these parameters occur in the DCM subjects with LV wall thickness greater than 11.5 mm. PMID:25712168

  7. Ubiquinol decreases hemorrhagic shock/resuscitation-induced microvascular inflammation in rat mesenteric microcirculation.

    PubMed

    Shen, Qiuhua; Holloway, Naomi; Thimmesch, Amanda; Wood, John G; Clancy, Richard L; Pierce, Janet D

    2014-11-01

    Hemorrhagic shock (HS) is a leading cause of death in traumatic injury. Ischemia and hypoxia in HS and fluid resuscitation (FR) creates a condition that facilitates excessive generation of reactive oxygen species (ROS). This is a major factor causing increased leukocyte-endothelial cell adhesive interactions and inflammation in the microcirculation resulting in reperfusion tissue injury. The aim of this study was to determine if ubiquinol (coenzyme Q10) decreases microvascular inflammation following HS and FR. Intravital microscopy was used to measure leukocyte-endothelial cell adhesive interactions in the rat mesentery following 1-h of HS and 2-h post FR with or without ubiquinol. Hemorrhagic shock was induced by removing ~ 40% of anesthetized Sprague Dawley rats' blood volume to maintain a mean arterial blood pressure <50 mmHg for 1 h. Ubiquinol (1 mg/100 g body weight) was infused intravascularly in the ubiquinol group immediately after 1-h HS. The FR protocol included replacement of the shed blood and Lactate Ringer's in both the control and ubiquinol groups. We found that leukocyte adherence (2.3 ± 2.0), mast cell degranulation (1.02 ± 0.01), and ROS levels (159 ± 35%) in the ubiquinol group were significantly reduced compared to the control group (10.8 ± 2.3, 1.36 ± 0.03, and 343 ± 47%, respectively). In addition, vascular permeability in the control group (0.54 ± 0.11) was significantly greater than the ubiquinol group (0.34 ± 0.04). In conclusion, ubiquinol attenuates HS and FR-induced microvascular inflammation. These results suggest that ubiquinol provides protection to mesenteric microcirculation through its antioxidant properties. PMID:25413319

  8. Vasomotor Regulation of Coronary Microcirculation by Oxidative Stress: Role of Arginase

    PubMed Central

    Kuo, Lih; Hein, Travis W.

    2013-01-01

    Overproduction of reactive oxygen species, i.e., oxidative stress, is associated with the activation of redox signaling pathways linking to inflammatory insults and cardiovascular diseases by impairing endothelial function and consequently blood flow dysregulation due to microvascular dysfunction. This review focuses on the regulation of vasomotor function in the coronary microcirculation by endothelial nitric oxide (NO) during oxidative stress and inflammation related to the activation of L-arginine consuming enzyme arginase. Superoxide produced in the vascular wall compromises vasomotor function by not only scavenging endothelium-derived NO but also inhibiting prostacyclin synthesis due to formation of peroxynitrite. The upregulation of arginase contributes to the deficiency of endothelial NO and microvascular dysfunction in various vascular diseases by initiating or following oxidative stress and inflammation. Hydrogen peroxide, a diffusible and stable oxidizing agent, exerts vasodilator function and plays important roles in the physiological regulation of coronary blood flow. In occlusive coronary ischemia, the release of hydrogen peroxide from the microvasculature helps to restore vasomotor function of coronary collateral microvessels with exercise training. However, excessive production and prolonged exposure of microvessels to hydrogen peroxide impairs NO-mediated endothelial function by reducing L-arginine availability through hydroxyl radical-dependent upregulation of arginase. The redox signaling can be a double-edged sword in the microcirculation, which helps tissue survival in one way by improving vasomotor regulation and elicits oxidative stress and tissue injury in the other way by causing vascular dysfunction. The impact of vascular arginase on the development of vasomotor dysfunction associated with angiotensin II receptor activation, hypertension, ischemia-reperfusion, hypercholesterolemia, and inflammatory insults is discussed. PMID:23966996

  9. Extended precedence preservative crossover for job shop scheduling problems

    NASA Astrophysics Data System (ADS)

    Ong, Chung Sin; Moin, Noor Hasnah; Omar, Mohd

    2013-04-01

    Job shop scheduling problems (JSSP) is one of difficult combinatorial scheduling problems. A wide range of genetic algorithms based on the two parents crossover have been applied to solve the problem but multi parents (more than two parents) crossover in solving the JSSP is still lacking. This paper proposes the extended precedence preservative crossover (EPPX) which uses multi parents for recombination in the genetic algorithms. EPPX is a variation of the precedence preservative crossover (PPX) which is one of the crossovers that perform well to find the solutions for the JSSP. EPPX is based on a vector to determine the gene selected in recombination for the next generation. Legalization of children (offspring) can be eliminated due to the JSSP representation encoded by using permutation with repetition that guarantees the feasibility of chromosomes. The simulations are performed on a set of benchmarks from the literatures and the results are compared to ensure the sustainability of multi parents recombination in solving the JSSP.

  10. Endogenous lipoid pneumonia preceding diagnosis of pulmonary alveolar proteinosis.

    PubMed

    Antoon, James W; Hernandez, Michelle L; Roehrs, Phillip A; Noah, Terry L; Leigh, Margaret W; Byerley, Julie S

    2016-03-01

    Pulmonary alveolar proteinosis (PAP) is an under-reported and under-diagnosed condition, with a high percentage of cases found on autopsy or late stage disease. The etiology of PAP includes genetic, primary (anti-granulocyte-macrophage colony-stimulating factor antibodies) and secondary (oncologic, rheumatologic, infectious, chemical and immunologic) causes. Here, we present the first reported pediatric case of endogenous lipoid pneumonia and non-specific interstitial pneumonitis preceding the development of PAP. PMID:25103284

  11. Influence of complementary Viscum album (Iscador) administration on microcirculation and immune system of ear, nose and throat carcinoma patients treated with radiation and chemotherapy.

    PubMed

    Klopp, R; Schmidt, W; Werner, E; Werner, M; Niemer, W; Beuth, J

    2005-01-01

    With the techniques of vital microscopic and reflection spectrometric imaging, representative characteristics of microcirculation and immunology of white blood cells were evaluated before, during and after radiotherapy and chemotherapy of patients suffering from ear, nose and throat carcinomas. Adverse effects of radiotherapy and chemotherapy on the microcirculation and the immune system were decreased and reconstitution processes were accelerated by complementary administration of a standardized mistletoe extract (Iscador). PMID:15816634

  12. Ultra-high-sensitive optical micro-angiography provides depth resolved visualization of microcirculations within human skin under psoriatic conditions

    NASA Astrophysics Data System (ADS)

    Qin, Jia; An, Lin; Wang, Ruikang

    2011-03-01

    Adequate functioning of the peripheral micro vascular in human skin is necessary to maintain optimal tissue perfusion and preserve normal hemodynamic function. There is a growing body of evidence suggests that vascular abnormalities may directly related to several dermatologic diseases, such as psoriasis, port-wine stain, skin cancer, etc. New in vivo imaging modalities to aid volumetric microvascular blood perfusion imaging are there for highly desirable. To address this need, we demonstrate the capability of ultra-high sensitive optical micro angiography to allow blood flow visualization and quantification of vascular densities of lesional psoriasis area in human subject in vivo. The microcirculation networks of lesion and non-lesion skin were obtained after post processing the data sets captured by the system. With our image resolution (~20 μm), we could compare these two types of microcirculation networks both qualitatively and quantitatively. The B-scan (lateral or x direction) cross section images, en-face (x-y plane) images and the volumetric in vivo perfusion map of lesion and non-lesion skin areas were obtained using UHS-OMAG. Characteristic perfusion map features were identified between lesional and non-lesional skin area. A statistically significant difference between vascular densities of lesion and non-lesion skin area was also found using a histogram based analysis. UHS-OMAG has the potential to differentiate the normal skin microcirculation from abnormal human skin microcirculation non-invasively with high speed and sensitivity. The presented data demonstrates the great potential of UHS-OMAG for detecting and diagnosing skin disease such as psoriasis in human subjects.

  13. Hemoglobin induced NO/cGMP suppression Deteriorate Microcirculation via Pericyte Phenotype Transformation after Subarachnoid Hemorrhage in Rats

    PubMed Central

    Li, Qiang; Chen, Yujie; Li, Bo; Luo, Chunxia; Zuo, Shilun; Liu, Xin; Zhang, John H.; Ruan, Huaizhen; Feng, Hua

    2016-01-01

    Subarachnoid hemorrhage (SAH) usually results from ruptured aneurysm, but how leaked hemoglobin regulates the microcirculation in the pathophysiology of early brain injury after SAH is still unclear. In the present study, we sought to investigate the role and possible mechanism of hemoglobin induced pericyte phenotype transformation in the regulation of microcirculation after SAH. Endovascular perforation SAH rat model, brain slices and cultured pericytes were used, and intervened with endothelial nitric oxide synthase (eNOS) antagonist L-NNA and its agonist scutellarin, hemoglobin, DETA/NO (nitric oxide(NO) donor), PITO (NO scavenger), 8-Br-cGMP (cGMP analog). We found modulating eNOS regulated pericyte α-SMA phenotype transformation, microcirculation, and neurological function in SAH rats. Modulating eNOS also affected eNOS expression, eNOS activity and NO availability after SAH. In addition, we showed hemoglobins penetrated into brain parenchyma after SAH. And hemoglobins significantly reduced the microvessel diameters at pericyte sites, due to the effects of hemoglobin inducing α-SMA expressions in cultured pericytes and brain slices via inhibiting NO/cGMP pathway. In conclusion, pericyte α-SMA phenotype mediates acute microvessel constriction after SAH possibly by hemoglobin suppressing NO/cGMP signaling pathway. Therefore, by targeting the eNOS and pericyte α-SMA phenotype, our present data may shed new light on the management of SAH patients. PMID:26911739

  14. Persistent effects after trigeminal nerve proprioceptive stimulation by mandibular extension on rat blood pressure, heart rate and pial microcirculation.

    PubMed

    Lapi, D; Colantuoni, A; Del Seppia, C; Ghione, S; Tonlorenzi, D; Brunelli, M; Scuri, R

    2013-03-01

    The trigemino-cardiac reflex is a brainstem reflex known to lead to a decrement in heart rate and blood pressure, whereas few data have been collected about its effects on the cerebral hemodynamic. In this study we assess the in vivo effects of trigeminal nerve peripheral stimulation by mandibular extension on pial microcirculation and systemic arterial blood pressure in rats. Experiments were performed in male Wistar rats subjected to mandibular extension obtained inserting an ad hoc developed retractor between the dental arches. Mean arterial blood pressure and heart rate were recorded and the pial arterioles were visualized by fluorescence microscopy to measure the vessel diameters before (15 minutes) during (5-15 minutes) and after (80 minutes) mandibular extension. While in control rats (sham-operated rats) and in rats subjected to the dissection of the trigeminal peripheral branches mean arterial blood pressure, heart rate and pial microcirculation did not change during the whole observation period (110 minutes), in rats submitted to mandibular extension, mean arterial blood pressure, heart rate and arteriolar diameter significantly decreased during stimulation. Afterward mean arterial blood pressure remained reduced as well as heart rate, while arteriolar diameter significantly increased evidencing a vasodilatation persisting for the whole remaining observation time. Therefore, trigeminal nerve proprioceptive stimulation appears to trigger specific mechanisms regulating systemic arterial blood pressure and pial microcirculation. PMID:23807620

  15. Estradiol receptors agonists induced effects in rat intestinal microcirculation during sepsis.

    PubMed

    Sharawy, Nivin; Ribback, Silvia; Al-Banna, Nadia; Lehmann, Christian; Kern, Hartmut; Wendt, Michael; Cerny, Vladimir; Dombrowski, Frank; Pavlovic, Dragan

    2013-01-01

    The steroid hormone estradiol is suggested to play a protective role in intestinal injury during systemic inflammation (sepsis). Our aim was to determine the effects of specific estradiol receptor (ER-α and ER-ß) agonists on the intestinal microcirculation during experimental sepsis. Male and sham ovariectomized female rats were subjected to sham colon ascendens stent peritonitis (CASP), and they were compared to male and ovariectomized female rats underwent CASP and either estradiol receptor α (ER-α) agonist propyl pyrazole triol (PPT), estradiol receptor ß (ER-ß) agonist diarylpropiolnitrile (DPN), or vehicle treatment. Intravital microscopy was performed, which is sufficiently sensitive to measure changes in the functional capillary density (FCD) as well as the major steps in leukocyte recruitment (rolling and adhesion). The leukocyte extravasations were also quantified by using histological paraffin sections of formalin fixed intestine. We found that either DPN (ER-β) or PPT (ER-α) significantly reduced (P<0.05) sepsis-induced leukocyte-endothelial interaction (rolling, adherent leukocytes and neutrophil extravasations) and improved the intestinal muscular FCD. [PPT: Female; Leukocyte rolling (n/min): V(3) 3.7±0.7 vs 0.8±0.2, Leukocyte adhesion(n/mm(2)): V(3) 131.3±22.6 vs 57.2±13.5, Neutrophil extravasations (n/10000 μm(2)): 3.1±0.7 vs 6 ±1. Male; Leukocyte adhesion (n/mm(2)): V(1) 154.8±19.2 vs 81.3±11.2, V(3) 115.5±23.1 vs 37.8±12]. [DPN: Female; neutrophil extravasations (n/10000 μm(2)) 3.8±0.6 vs 6 ±1. Male; Leukocyte adhesion (n/mm(2)) V(1) 154.8±19.2 vs 70±10.5, V(3) 115.5±23.1 vs 52.8±9.6].Those results suggest that the observed effects of estradiol receptors on different phases of leukocytes recruitment with the improvement of the functional capillary density could partially explain the previous demonstrated salutary effects of estradiol on the intestinal microcirculation during sepsis. The observed activity of this class of

  16. The Effects of Vaccinium myrtillus Extract on Hamster Pial Microcirculation during Hypoperfusion-Reperfusion Injury

    PubMed Central

    Mastantuono, Teresa; Starita, Noemy; Sapio, Daniela; D’Avanzo, Sabato Andrea; Di Maro, Martina; Muscariello, Espedita; Paterni, Marco; Colantuoni, Antonio; Lapi, Dominga

    2016-01-01

    Introduction The present study was aimed to assess the in vivo hamster pial microvessel alterations due to 30 min transient bilateral common carotid artery occlusion (BCCAO) and reperfusion (60 min); moreover, the neuroprotective effects of Vaccinium myrtillus extract, containing 34.7% of anthocyanins, were investigated. Materials and Methods Two groups of male hamsters were used: the first fed with control diet and the other with Vaccinium myrtillus supplemented diet. Hamster pial microcirculation was visualized by fluorescence microscopy through an open cranial window. Pial arterioles were classified according to Strahler’s method. Results In age-matched control diet-fed hamsters, BCCAO caused a decrease in diameter of all arterioles. At the end of reperfusion, the reduction of diameter in order 3 arterioles was by 8.4 ± 3.1%, 10.8 ± 2.3% and 12.1 ± 1.1% of baseline in the 2, 4 and 6 month control diet-fed hamsters, respectively. Microvascular permeability and leukocyte adhesion were markedly enhanced, while perfused capillary length (PCL) decreased. The response to acetylcholine and papaverine topical application was impaired; 2’-7’-dichlorofluoresceine-diacetate assay demonstrated a significant ROS production. At the end of BCCAO, in age-matched Vaccinium myrtillussupplemented diet-fed hamsters, the arteriolar diameter did not significantly change compared to baseline. After 60 min reperfusion, order 3 arterioles dilated by 9.3 ± 2.4%, 10.6 ± 3.1% and 11.8 ± 2.7% of baseline in the 2, 4 and 6 month Vaccinium myrtillus supplemented diet-fed hamsters, respectively. Microvascular leakage and leukocyte adhesion were significantly reduced in all groups according to the time-dependent treatment, when compared with the age-matched control diet-fed hamsters. Similarly, the reduction in PCL was progressively prevented. Finally, the response to acetylcholine and papaverine topical application was preserved and there was no significant increase in ROS

  17. APOE polymorphisms influence longitudinal lipid trends preceding intracerebral hemorrhage

    PubMed Central

    Phuah, Chia-Ling; Raffeld, Miriam R.; Ayres, Alison M.; Gurol, M. Edip; Viswanathan, Anand; Greenberg, Steven M.; Biffi, Alessandro; Rosand, Jonathan

    2016-01-01

    Objective: We sought to determine whether APOE genotype influences a previously observed decline in serum total cholesterol (TC) and low-density lipoprotein (LDL) levels preceding primary intracerebral hemorrhage (ICH), as a potential demonstration of nonamyloid mechanisms of APOE in ICH risk. Methods: We performed a single-center retrospective longitudinal analysis using patients with known APOE genotype drawn from an ongoing cohort study of ICH. Serum lipid measurements for TC, triglycerides (TGs), LDL, and high-density lipoprotein (HDL) collected within 2 years before and after index ICH were extracted from electronic medical records. Piecewise linear mixed-effects models were used to compare APOE allele–specific effects on temporal serum lipid trends in ICH. Demographics, medical history, medications, and health maintenance data were included as fixed effects. Inter- and intraindividual variations in lipid levels were modeled as random effects. Results: A total of 124 ICH cases were analyzed. APOE ε4 carriers had greater rates of decline in serum TC and LDL within 6 months preceding ICH (TC: −7.30 mg/dL/mo, p = 0.0035; LDL: −8.44 mg/dL/mo, p = 0.0001). Conversely, serum TC and LDL levels in APOE ε2 carriers were unchanged within the same time period. APOE genotype had no associations with serum HDL or TG trends. Conclusions: APOE allele status predicts serum TC and LDL changes preceding acute ICH. Our results have implications for ongoing efforts in dissecting the role of dyslipidemia in cerebrovascular disease risk. APOE genotype–specific influence on lipid trends provides a clue for one mechanism by which APOE may influence risk of ICH. Further characterization of the metabolic roles of APOE is needed to improve the understanding of APOE biology in cerebrovascular disease risk. PMID:27433544

  18. Precedence based speech segregation in bilateral cochlear implant users

    PubMed Central

    Hossain, Shaikat; Montazeri, Vahid; Assmann, Peter F.; Litovsky, Ruth Y.

    2015-01-01

    The precedence effect (PE) enables the perceptual dominance by a source (lead) over an echo (lag) in reverberant environments. In addition to facilitating sound localization, the PE can play an important role in spatial unmasking of speech. Listeners attending to binaural vocoder simulations with identical channel center frequencies and phase demonstrated PE-based benefits in a closed-set speech segregation task. When presented with the same stimuli, bilateral cochlear implant users did not derive such benefits. These findings suggest that envelope extraction in itself may not lead to a breakdown of the PE benefits, and that other factors may play a role. PMID:26723365

  19. Precedence based speech segregation in bilateral cochlear implant users.

    PubMed

    Hossain, Shaikat; Montazeri, Vahid; Assmann, Peter F; Litovsky, Ruth Y

    2015-12-01

    The precedence effect (PE) enables the perceptual dominance by a source (lead) over an echo (lag) in reverberant environments. In addition to facilitating sound localization, the PE can play an important role in spatial unmasking of speech. Listeners attending to binaural vocoder simulations with identical channel center frequencies and phase demonstrated PE-based benefits in a closed-set speech segregation task. When presented with the same stimuli, bilateral cochlear implant users did not derive such benefits. These findings suggest that envelope extraction in itself may not lead to a breakdown of the PE benefits, and that other factors may play a role. PMID:26723365

  20. Dissociation between sublingual and gut microcirculation in the response to a fluid challenge in postoperative patients with abdominal sepsis

    PubMed Central

    2014-01-01

    Background This study was performed to compare intestinal and sublingual microcirculation and their response to a fluid challenge. Methods Twenty-two septic patients in the first postoperative day of an intestinal surgery, in which an ostomy had been constructed, were evaluated both before and 20 min after a challenge of 10 mL/kg of 6% hydroxyethylstarch 130/0.4. We measured systemic hemodynamics and sublingual and intestinal microcirculation. Correlations between variables were determined through the Pearson test. Results Fluid administration increased the cardiac index (2.6 ± 0.5 vs. 3.3 ± 1.0 L/min/m2, P < 0.01) and mean arterial blood pressure (68 ± 11 vs. 82 ± 12 mm Hg, P < 0.0001). The sublingual but not the intestinal red blood cell (RBC) velocity increased (912 ± 270 vs. 1,064 ± 200 μm/s, P < 0.002 and 679 ± 379 vs. 747 ± 419 μm/s, P = 0.12, respectively). The sublingual and intestinal perfused vascular density (PVD) did not change significantly (15.2 ± 2.9 vs. 16.1 ± 1.2 mm/mm2 and 12.3 ± 6.7 vs. 13.0 ± 6.7 mm/mm2). We found no correlation between the basal sublingual and intestinal RBC velocities or between their changes in response to the fluid challenge. The individual changes in sublingual RBC velocity correlated with those in cardiac index and basal RBC velocity. Individual changes in intestinal RBC velocity did not correlate with either the cardiac index modifications or the basal RBC velocity. The same pattern was observed with the sublingual and the intestinal PVDs. The sublingual RBC velocities and PVDs were similar between survivors and nonsurvivors. But the intestinal RBC velocities and PVDs were lower in nonsurvivors. Conclusions In this series of postoperative septic patients, we found a dissociation between sublingual and intestinal microcirculation. The improvement in the sublingual microcirculation after fluid challenge was dependent on the basal state and the

  1. Assessment of microcirculation dynamics during cutaneous wound healing phases in vivo using optical microangiography.

    PubMed

    Yousefi, Siavash; Qin, Jia; Dziennis, Suzan; Wang, Ruikang K

    2014-01-01

    Cutaneous wound healing consists of multiple overlapping phases starting with blood coagulation following incision of blood vessels. We utilized label-free optical coherence tomography and optical microangiography (OMAG) to noninvasively monitor healing process and dynamics of microcirculation system in a mouse ear pinna wound model. Mouse ear pinna is composed of two layers of skin separated by a layer of cartilage and because its total thickness is around 500 μm, it can be utilized as an ideal model for optical imaging techniques. These skin layers are identical to human skin structure except for sweat ducts and glands. Microcirculatory system responds to the wound injury by recruiting collateral vessels to supply blood flow to hypoxic region. During the inflammatory phase, lymphatic vessels play an important role in the immune response of the tissue and clearing waste from interstitial fluid. In the final phase of wound healing, tissue maturation, and remodeling, the wound area is fully closed while blood vessels mature to support the tissue cells. We show that using OMAG technology allows noninvasive and label-free monitoring and imaging each phase of wound healing that can be used to replace invasive tissue sample histology and immunochemistry technologies. PMID:25036212

  2. Properties of the microcirculation in capillary bundles of rat spinotrapezius muscle fascia

    NASA Astrophysics Data System (ADS)

    Jacobitz, Frank; Engebrecht, Cheryn; Metzger, Ian; Porterfield, Colin

    2006-11-01

    Properties of the microcirculation in capillary bundles of rat spinotrapezius muscle fascia are investigated using microscope observations, empirical modeling, and numerical simulations. Capillary bundles consist of a network of feeding arterioles, draining venules, and capillary vessels. A dozen samples of muscle fascia tissue were prepared for microscope observation. The chosen method of preparation allows for the long-term preservation of the tissue samples for future studies. Capillary bundles are photographed under a microscope with 40x magnification. From the images, the microvasculature of the tissue samples is reconstructed. It was found, for example, that the distribution of vessel length in a capillary bundle follows a log-normal law. In addition to a statistical analysis of the vessel data, the network topology is used for numerical simulations of the flow in the capillary bundles. The numerical approach uses a sparse-matrix solver and it considers vessel elasticity and blood rheology. The numerical simulations show, for example, a strong pressure drop across the capillary vessels of the bundle.

  3. Effects of chronic normovolemic anemia on gastric microcirculation and ethanol-induced gastric damage in rats.

    PubMed

    Marroni, N; Casadevall, M; Panés, J; Piera, C; Jou, J M; Pique, J M

    1994-04-01

    The effects of chronic normovolemic anemia on gastric microcirculation and gastric mucosal susceptibility to ethanol-induced gastric damage were investigated in anesthetized rats. Blood exchange by a plasma expander during four consecutive days rendered the animals anemic with a 34% decrease in the baseline hematocrit but without affecting blood volume. Chronic anemia induced a decrease in whole blood viscosity, an increase in gastric mucosal blood flow measured by hydrogen gas clearance, a decrease in gastric vascular resistance, and a decrease in gastric hemoglobin content without changes in the gastric oxygen content, the latter two parameters being measured by reflectance spectrophotometry. Gastric mucosal blood flow was lowered by intragastric administration of 100% ethanol in both anemic and control rats, but the final blood flow was significantly higher in anemic than in control animals. Macroscopic gastric damage induced by ethanol administration was significantly lower in anemic than in control rats. We conclude that chronic normovolemic anemia increases gastric mucosal blood flow and leads a protecting mechanism against gastric mucosal damage induced by absolute ethanol. PMID:8149840

  4. Accessing the biocompatibility of layered double hydroxide by intramuscular implantation: histological and microcirculation evaluation.

    PubMed

    Cunha, Vanessa Roberta Rodrigues; de Souza, Rodrigo Barbosa; da Fonseca Martins, Ana Maria Cristina Rebello Pinto; Koh, Ivan Hong Jun; Constantino, Vera Regina Leopoldo

    2016-01-01

    Biocompatibility of layered double hydroxides (LDHs), also known as hydrotalcite-like materials or double metal hydroxides, was investigated by in vivo assays via intramuscular tablets implantation in rat abdominal wall. The tablets were composed by chloride ions intercalated into LDH of magnesium/aluminum (Mg2Al-Cl) and zinc/aluminum (Zn2Al-Cl). The antigenicity and tissue integration capacity of LDHs were assessed histologically after 7 and 28 days post-implantation. No fibrous capsule nearby the LDH was noticed for both materials as well any sign of inflammatory reactions. Sidestream Dark Field imaging, used to monitor in real time the microcirculation in tissues, revealed overall integrity of the microcirculatory network neighboring the tablets, with no blood flow obstruction, bleeding and/or increasing of leukocyte endothelial adhesion. After 28 days Mg2Al-Cl promoted multiple collagen invaginations (mostly collagen type-I) among its fragments while Zn2Al-Cl induced predominantly collagen type-III. This work supports previous results in the literature about LDHs compatibility with living matter, endorsing them as functional materials for biomedical applications. PMID:27480483

  5. Effects of dextran 70 versus crystalloids in the microcirculation of porcine hemorrhagic pancreatitis

    SciTech Connect

    Lehtola, A.; Kivilaakso, E.; Puolakkainen, P.; Karonen, S.L.; Lempinen, M.; Schroeder, T.

    1986-06-01

    The cause of hemodynamic changes occurring during acute pancreatitis remains obscure. Using a pig model of acute hemorrhagic pancreatitis and the reference sample method with 113Tin and 46 Scandium labelled microspheres, blood flow to organs was determined before and five hours after the induction of pancreatitis. Blood pressure, pulse rate and cardiac output were measured hourly. There were two treatment groups. The first group received dextran 70 (5.7 milliliters per kilogram per hour) and saline solution (7.5 milliliters per kilogram per hour) in sufficient amounts to maintain cardiac output at the initial (prepancreatic) level. The second group received saline solution (26 milliliters per kilogram per hour) only and during the experiment the cardiac output was allowed to decrease to approximately one-half of the initial level. In the dextran 70 group, blood flow in various organs stayed at the initial level or was slightly increased. However, in the saline solution group there was a marked and significant decrease in the blood flow in all organs except the antral mucosa, gallbladder and adrenal glands. The changes in the pancreatic fraction of the cardiac output during the experiment were similar to those of other organs in respective treatment groups. In conclusion, adequate infusion of dextran maintains cardiac output and organ microcirculation at the initial level during the early phase of acute hemorrhagic pancreatitis. It is suggested that the hemodynamic changes which develop during acute pancreatitis are mainly secondary to the ensuing hypovolemia and not direct consequences of the pancreatic inflammatory process.

  6. Leukotrienes as mediators in ischemia-reperfusion injury in a microcirculation model in the hamster.

    PubMed Central

    Lehr, H A; Guhlmann, A; Nolte, D; Keppler, D; Messmer, K

    1991-01-01

    Leukotriene (LT)B4 promotes leukocyte chemotaxis and adhesion to the endothelium of postcapillary venules. The cysteinyl leukotrienes, LTC4, LTD4, and LTE4, elicit macromolecular leakage from this vessel segment. Both leukocyte adhesion to the endothelium and macromolecular leakage from postcapillary venules hallmark the microcirculatory failure after ischemia-reperfusion, suggesting a role of leukotrienes as mediators of ischemia-reperfusion injury. Using the dorsal skinfold chamber model for intravital fluorescence microscopy of the microcirculation in striated muscle in awake hamsters and sequential RP-HPLC and RIA for leukotrienes, we demonstrate in this study that (a) the leukotrienes (LT)B4 and LTD4 elicit leukocyte/endothelium interaction and macromolecular leakage from postcapillary venules, respectively, that (b) leukotrienes accumulate in the tissue after ischemia and reperfusion, and that (c) selective inhibition of leukotriene biosynthesis (by MK-886) prevents both postischemic leukotriene accumulation and the microcirculatory changes after ischemia-reperfusion, while blocking of LTD4/E4 receptors (by MK-571) inhibits postischemic macromolecular leakage. These results demonstrate a key role of leukotrienes in ischemia-reperfusion injury in striated muscle in vivo. Images PMID:1645749

  7. Correlation of Optic Nerve Microcirculation with Papillomacular Bundle Structure in Treatment Naive Normal Tension Glaucoma

    PubMed Central

    Omodaka, Kazuko; Togashi, Kyousuke; Akiba, Masahiro; Yuasa, Tetsuya; Nakazawa, Toru

    2014-01-01

    Purpose. To assess the association between optic nerve head (ONH) microcirculation, central papillomacular bundle (CPB) structure, and visual function in eyes with treatment naive normal tension glaucoma (NTG). Methods. This study included 40 eyes of 40 patients with NTG and 20 eyes of 20 normal patients. We used laser speckle flowgraphy (LSFG) to measure mean blur rate (MBR) in all eyes and calculated the ratio of MBR in the horizontal quadrants of tissue area ONH (temporal/nasal ratio of MBR in the tissue area: T/N MT). Clinical findings also included retinal nerve fiber layer thickness (RNFLT) and ganglion cell complex thickness (GCCT) in the CPB and macular areas, best-corrected visual acuity (BCVA), mean deviation (MD), and refractive error. Results. T/N MT was correlated with both BCVA and MD. The OCT parameters most highly correlated with T/N MT were macular RNFLT and mid-CPB RNFLT. Furthermore, T/N MT, mid-CPB RNFLT, and macular RNFLT were higher in NTG than in normal eyes. A discrimination analysis revealed that T/N MT and refractive error were independent factors indicating NTG. Conclusions. Our results suggest that T/N MT is a candidate biomarker of NTG. Furthermore, T/N MT reflects visual function, including acuity and sensitivity, and CPB structure. PMID:25574382

  8. Assessment of microcirculation dynamics during cutaneous wound healing phases in vivo using optical microangiography

    NASA Astrophysics Data System (ADS)

    Yousefi, Siavash; Qin, Jia; Dziennis, Suzan; Wang, Ruikang K.

    2014-07-01

    Cutaneous wound healing consists of multiple overlapping phases starting with blood coagulation following incision of blood vessels. We utilized label-free optical coherence tomography and optical microangiography (OMAG) to noninvasively monitor healing process and dynamics of microcirculation system in a mouse ear pinna wound model. Mouse ear pinna is composed of two layers of skin separated by a layer of cartilage and because its total thickness is around 500 μm, it can be utilized as an ideal model for optical imaging techniques. These skin layers are identical to human skin structure except for sweat ducts and glands. Microcirculatory system responds to the wound injury by recruiting collateral vessels to supply blood flow to hypoxic region. During the inflammatory phase, lymphatic vessels play an important role in the immune response of the tissue and clearing waste from interstitial fluid. In the final phase of wound healing, tissue maturation, and remodeling, the wound area is fully closed while blood vessels mature to support the tissue cells. We show that using OMAG technology allows noninvasive and label-free monitoring and imaging each phase of wound healing that can be used to replace invasive tissue sample histology and immunochemistry technologies.

  9. Effect of hypoxia and hypercapnia on ACE activity in the cerebral microcirculation of anesthetized dogs

    SciTech Connect

    Pitt, B.R.; Lister, G.; Dawson, C.A.; Linehan, J.H.

    1986-05-01

    Angiotensin-converting enzyme (ACE) activity of the cerebral microcirculation of anesthetized dogs was measured from cerebral venous outflow curves after bolus injection of a synthetic ACE substrate, (/sup 3/H)benzoyl-phenylalanyl-alanylproline ((/sup 3/H)BPAP), into a common carotid artery. Cerebral BPAP metabolism was quantified by measuring the concentration of (/sup 3/H)benzoyl-phenylalanine (the product of BPAP hydrolysis by ACE) in blood samples from the sagittal sinus after occlusion of the lateral sinuses with bone wax. Instantaneous BPAP metabolism in each sample increased as a function of time after injection, suggestive of perfusion heterogeneity, and averaged 59 +/- 4% (n = 8) over a single pass during normoxia and normocapnia. The ratio of Vmax (the maximal rate of cerebral BPAP metabolism) to Km (the concentration at Vmax/2), was calculated from instantaneous outflow curves using a model based on first-order kinetics. Increases in cerebral blood flow during either hypoxia or hypercapnia significantly reduced BPAP metabolism to 33 +/- 3 (n = 7) and 24 +/- 3% (n = 5), respectively; however, Vmax/Km of ACE activity (0.19 +/- 0.03 ml/s) was not affected by either condition. The lack of change in apparent kinetics of ACE activity (i.e., in Vmax/Km) during hypoxia or hypercapnia suggests that recruitment of cerebral capillaries was not a quantitatively significant factor in controlling BPAP metabolism with this degree of either hypoxia or hypercapnia.

  10. Accessing the biocompatibility of layered double hydroxide by intramuscular implantation: histological and microcirculation evaluation

    PubMed Central

    Cunha, Vanessa Roberta Rodrigues; de Souza, Rodrigo Barbosa; da Fonseca Martins, Ana Maria Cristina Rebello Pinto; Koh, Ivan Hong Jun; Constantino, Vera Regina Leopoldo

    2016-01-01

    Biocompatibility of layered double hydroxides (LDHs), also known as hydrotalcite-like materials or double metal hydroxides, was investigated by in vivo assays via intramuscular tablets implantation in rat abdominal wall. The tablets were composed by chloride ions intercalated into LDH of magnesium/aluminum (Mg2Al-Cl) and zinc/aluminum (Zn2Al-Cl). The antigenicity and tissue integration capacity of LDHs were assessed histologically after 7 and 28 days post-implantation. No fibrous capsule nearby the LDH was noticed for both materials as well any sign of inflammatory reactions. Sidestream Dark Field imaging, used to monitor in real time the microcirculation in tissues, revealed overall integrity of the microcirculatory network neighboring the tablets, with no blood flow obstruction, bleeding and/or increasing of leukocyte endothelial adhesion. After 28 days Mg2Al-Cl promoted multiple collagen invaginations (mostly collagen type-I) among its fragments while Zn2Al-Cl induced predominantly collagen type–III. This work supports previous results in the literature about LDHs compatibility with living matter, endorsing them as functional materials for biomedical applications. PMID:27480483