Installation Restoration Program. Remedial Investigation Report. Minnesota Air National Guard Base Duluth International Airport, Duluth, Minnesota. Volume 3

DTIC Science & Technology

1990-01-01

Migration 5-7 5.2.3 Contaminant Persistence 5-8 5.2.4 Contaminant Mobility and Migration 5-9 5.2.4.1 Contaminant Migration in Surface Water 5-9...of Contaminant 5-11 5.3.2 Potential Routes of Migration 5-11 5.3.3 Contaminant Persistence 5-12 5.3.4 Contaminant Mobility and Migration 5-13 5.3.4.1...Contaminant Mobility and Migration in Soil 5-18 5.6 CONTAMINANT FATE AND TRANSPORT 5-18 AT SITE 10 5.6.1 Summary of Contaminants 5-18 5.6.2 Potential Routes

Tales told by tails: watching DNA driven through a random medium

NASA Astrophysics Data System (ADS)

Guan, Juan; Wang, Bo; Bae, Sung Chul; Granick, Steve

2013-03-01

DNA ligation is used to label separately the ends and centers of monodisperse DNA 16 μm in contour length, and 2-color fluorescence microscopy is used to follow with nm resolution how chains migrate through agarose networks driven by electric fields, at both whole chain and segment level. We observe that the leading segment is always a physical chain end which stretches and pulls out slack in the still-quiescent remainder of the chain until the other end is taken up. Heads and tails behave strikingly differently: the leading end of migrating chains migrates more smoothly, whereas motion of the trailing end shows intermittent pauses and jerky recoil. None of the mechanisms imagined classically for this situation - chain reptation, hooking or entropic trapping, appears to fully describe these data obtained from single-molecule visualization.

Dynamics of Cancer Cell near Collagen Fiber Chain

NASA Astrophysics Data System (ADS)

Kim, Jihan; Sun, Bo

Cell migration is an integrated process that is important in life. Migration is essential for embryonic development as well as homeostatic processes such as wound healing and immune responses. When cell migrates through connective extracellular matrix (ECM), it applies cellular traction force to ECM and senses the rigidity of their local environment. We used human breast cancer cell (MDA-MB-231) which is highly invasive and applies strong traction force to ECM. As cancer cell applies traction force to type I collage-based ECM, it deforms collagen fibers near the surface. Patterns of deforming collagen fibers are significantly different with pairs of cancer cells compared to a single cancer cell. While a pair of cancer cells within 60 um creates aligned collagen fiber chains between them permanently, a single cancer cell does not form any fiber chains. In this experiment we measured a cellular response and an interaction between a pair of cells through the chain. Finally, we analyzed correlation of directions between cancer cell migration and the collagen chain alignment.

An insight on acyl migration in solvent-free ethanolysis of model triglycerides using Novozym 435.

PubMed

Sánchez, Daniel Alberto; Tonetto, Gabriela Marta; Ferreira, María Luján

2016-02-20

In this work, the ethanolysis of triglycerides catalyzed by immobilized lipase was studied, focusing on the secondary reaction of acyl migration. The catalytic tests were performed in a solvent-free reaction medium using Novozym 435 as biocatalyst. The selected experimental variables were biocatalyst loading (5-20mg), reaction time (30-90min), and chain length of the fatty acids in triglycerides with and without unsaturation (short (triacetin), medium (tricaprylin) and long (tripalmitin/triolein)). The formation of 2-monoglyceride by ethanolysis of triglycerides was favored by long reaction times and large biocatalyst loading with saturated short- to medium-chain triglycerides. In the case of long-chain triglycerides, the formation of this monoglyceride was widely limited by acyl migration. In turn, acyl migration increased the yield of ethyl esters and minimized the content of monoglycerides and diglycerides. Thus, the enzymatic synthesis of biodiesel was favored by long-chain triglycerides (which favor the acyl migration), long reaction times and large biocatalyst loading. The conversion of acylglycerides made from long-chain fatty acids with unsaturation was relatively low due to limitations in their access to the active site of the lipase. Copyright © 2016 Elsevier B.V. All rights reserved.

Vinculin is required for cell polarization, migration, and extracellular matrix remodeling in 3D collagen

PubMed Central

Thievessen, Ingo; Fakhri, Nikta; Steinwachs, Julian; Kraus, Viola; McIsaac, R. Scott; Gao, Liang; Chen, Bi-Chang; Baird, Michelle A.; Davidson, Michael W.; Betzig, Eric; Oldenbourg, Rudolf; Waterman, Clare M.; Fabry, Ben

2015-01-01

Vinculin is filamentous (F)-actin-binding protein enriched in integrin-based adhesions to the extracellular matrix (ECM). Whereas studies in 2-dimensional (2D) tissue culture models have suggested that vinculin negatively regulates cell migration by promoting cytoskeleton–ECM coupling to strengthen and stabilize adhesions, its role in regulating cell migration in more physiologic, 3-dimensional (3D) environments is unclear. To address the role of vinculin in 3D cell migration, we analyzed the morphodynamics, migration, and ECM remodeling of primary murine embryonic fibroblasts (MEFs) with cre/loxP-mediated vinculin gene disruption in 3D collagen I cultures. We found that vinculin promoted 3D cell migration by increasing directional persistence. Vinculin was necessary for persistent cell protrusion, cell elongation, and stable cell orientation in 3D collagen, but was dispensable for lamellipodia formation, suggesting that vinculin-mediated cell adhesion to the ECM is needed to convert actin-based cell protrusion into persistent cell shape change and migration. Consistent with this finding, vinculin was necessary for efficient traction force generation in 3D collagen without affecting myosin II activity and promoted 3D collagen fiber alignment and macroscopical gel contraction. Our results suggest that vinculin promotes directionally persistent cell migration and tension-dependent ECM remodeling in complex 3D environments by increasing cell–ECM adhesion and traction force generation.—Thievessen, I., Fakhri, N., Steinwachs, J., Kraus, V., McIsaac, R. S., Gao, L., Chen, B.-C., Baird, M. A., Davidson, M. W., Betzig, E., Oldenbourg, R., Waterman, C., M., Fabry, B. Vinculin is required for cell polarization, migration, and extracellular matrix remodeling in 3D collagen. PMID:26195589

Follow-the-leader cell migration requires biased cell-cell contact and local microenvironmental signals

NASA Astrophysics Data System (ADS)

Wynn, Michelle L.; Rupp, Paul; Trainor, Paul A.; Schnell, Santiago; Kulesa, Paul M.

2013-06-01

Directed cell migration often involves at least two types of cell motility that include multicellular streaming and chain migration. However, what is unclear is how cell contact dynamics and the distinct microenvironments through which cells travel influence the selection of one migratory mode or the other. The embryonic and highly invasive neural crest (NC) are an excellent model system to study this question since NC cells have been observed in vivo to display both of these types of cell motility. Here, we present data from tissue transplantation experiments in chick and in silico modeling that test our hypothesis that cell contact dynamics with each other and the microenvironment promote and sustain either multicellular stream or chain migration. We show that when premigratory cranial NC cells (at the pre-otic level) are transplanted into a more caudal region in the head (at the post-otic level), cells alter their characteristic stream behavior and migrate in chains. Similarly, post-otic NC cells migrate in streams after transplantation into the pre-otic hindbrain, suggesting that local microenvironmental signals dictate the mode of NC cell migration. Simulations of an agent-based model (ABM) that integrates the NC cell behavioral data predict that chain migration critically depends on the interplay of biased cell-cell contact and local microenvironment signals. Together, this integrated modeling and experimental approach suggests new experiments and offers a powerful tool to examine mechanisms that underlie complex cell migration patterns.

Electrostatic contribution to the persistence length of a semiflexible dipolar chain.

PubMed

Podgornik, Rudi

2004-09-01

We investigate the electrostatic contribution to the persistence length of a semiflexible polymer chain whose segments interact via a screened Debye-Hückel dipolar interaction potential. We derive the expressions for the renormalized persistence length on the level of a 1/D-expansion method already successfully used in other contexts of polyelectrolye physics. We investigate different limiting forms of the renormalized persistence length of the dipolar chain and show that, in, general, it depends less strongly on the screening length than in the context of a monopolar chain. We show that for a dipolar chain the electrostatic persistence length in the same regime of the parameter phase space as the original Odijk-Skolnick-Fixman (OSF) form for a monopolar chain depends logarithmically on the screening length rather than quadratically. This can be understood solely on the basis of a swifter decay of the dipolar interactions with separation compared to the monopolar electrostatic interactions. We comment also on the general contribution of higher multipoles to the electrostatic renormalization of the bending rigidity.

Phosphorylation of WAVE2 by MAP kinases regulates persistent cell migration and polarity

PubMed Central

Danson, Christopher M.; Pocha, Shirin M.; Bloomberg, Graham B.; Cory, Giles O.

2009-01-01

Summary The WAVE family of proteins has long been implicated in the stimulus-dependent generation of lamellipodia at the leading edge of migrating cells, with WAVE2 in particular implicated in the formation of peripheral ruffles and chemotactic migration. However, the lack of direct visualisation of cell migration in WAVE2 mutants or knockdowns has made defining the mechanisms of WAVE2 regulation during cell migration difficult. We have characterised three MAP kinase phosphorylation sites within WAVE2 and analysed fibroblast behaviour in a scratch-wound model following introduction of transgenes encoding phospho-defective WAVE2. The cells exhibited an increase in migration speed, a decrease in the persistence of migration, and disruption of polarisation of the Golgi apparatus. All these effects could be mimicked by acute knockdown of endogenous WAVE2 expression with RNAi, indicating that phosphorylation of WAVE2 by MAP kinases regulates cell polarity during migration. PMID:18032787

Phosphorylation of WAVE2 by MAP kinases regulates persistent cell migration and polarity.

PubMed

Danson, Christopher M; Pocha, Shirin M; Bloomberg, Graham B; Cory, Giles O

2007-12-01

The WAVE family of proteins has long been implicated in the stimulus-dependent generation of lamellipodia at the leading edge of migrating cells, with WAVE2 in particular implicated in the formation of peripheral ruffles and chemotactic migration. However, the lack of direct visualisation of cell migration in WAVE2 mutants or knockdowns has made defining the mechanisms of WAVE2 regulation during cell migration difficult. We have characterised three MAP kinase phosphorylation sites within WAVE2 and analysed fibroblast behaviour in a scratch-wound model following introduction of transgenes encoding phospho-defective WAVE2. The cells exhibited an increase in migration speed, a decrease in the persistence of migration, and disruption of polarisation of the Golgi apparatus. All these effects could be mimicked by acute knockdown of endogenous WAVE2 expression with RNAi, indicating that phosphorylation of WAVE2 by MAP kinases regulates cell polarity during migration.

Retinoic acid temporally orchestrates colonization of the gut by vagal neural crest cells.

PubMed

Uribe, Rosa A; Hong, Stephanie S; Bronner, Marianne E

2018-01-01

The enteric nervous system arises from neural crest cells that migrate as chains into and along the primitive gut, subsequently differentiating into enteric neurons and glia. Little is known about the mechanisms governing neural crest migration en route to and along the gut in vivo. Here, we report that Retinoic Acid (RA) temporally controls zebrafish enteric neural crest cell chain migration. In vivo imaging reveals that RA loss severely compromises the integrity and migration of the chain of neural crest cells during the window of time window when they are moving along the foregut. After loss of RA, enteric progenitors accumulate in the foregut and differentiate into enteric neurons, but subsequently undergo apoptosis resulting in a striking neuronal deficit. Moreover, ectopic expression of the transcription factor meis3 and/or the receptor ret, partially rescues enteric neuron colonization after RA attenuation. Collectively, our findings suggest that retinoic acid plays a critical temporal role in promoting enteric neural crest chain migration and neuronal survival upstream of Meis3 and RET in vivo. Copyright © 2017 Elsevier Inc. All rights reserved.

Chain decomposition of aqueous triethanolamine. [Gamma Radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwarz, H.A.

A radiation-induced chain decomposition of aqueous triethanolamine into acetaldehyde and diethanolamine is reported. Chain lengths over 1000 have been observed, depending on pH, concentration, and radiation intensity. The chain propagation steps include OH group migration in the 2-hydroxy-1-(diethanolamino)ethyl radical and NR/sub 2/ migration in 1-hydroxy-2(diethanolamine)ethyl radical, each producing a 2-hydroxy-2-(diethanolamine)ethyl radical. Free-radical spectra and rate constants are given. Studies of diethanolamine and diethylethanolamine solutions gave similar free-radical spectra but much shorter chains.

Rear-polarized Wnt5a-receptor-actin-myosin-polarity (WRAMP) structures promote the speed and persistence of directional cell migration

PubMed Central

Connacher, Mary Katherine; Tay, Jian Wei; Ahn, Natalie G.

2017-01-01

In contrast to events at the cell leading edge, rear-polarized mechanisms that control directional cell migration are poorly defined. Previous work described a new intracellular complex, the Wnt5a-receptor-actomyosin polarity (WRAMP) structure, which coordinates the polarized localization of MCAM, actin, and myosin IIB in a Wnt5a-induced manner. However, the polarity and function for the WRAMP structure during cell movement were not determined. Here we characterize WRAMP structures during extended cell migration using live-cell imaging. The results demonstrate that cells undergoing prolonged migration show WRAMP structures stably polarized at the rear, where they are strongly associated with enhanced speed and persistence of directional movement. Strikingly, WRAMP structures form transiently, with cells displaying directional persistence during periods when they are present and cells changing directions randomly when they are absent. Cells appear to pause locomotion when WRAMP structures disassemble and then migrate in new directions after reassembly at a different location, which forms the new rear. We conclude that WRAMP structures represent a rear-directed cellular mechanism to control directional migration and that their ability to form dynamically within cells may control changes in direction during extended migration. PMID:28592632

Don't Fence Me In: Free Meanders in a Confined River Valley

NASA Astrophysics Data System (ADS)

Eke, E. C.; Wilcock, P. R.

2015-12-01

The interaction between meandering river channels and inerodible valley walls provides a useful test of our ability to understand meander dynamics. In some cases, river meanders confined between valley walls display distinctive angular bends in a dynamic equilibrium such that their size and shape persist as the meander migrates. In other cases, meander geometry is more varied and changes as the meander migrates. The ratio of channel to valley width has been identified as a useful parameter for defining confined meanders, but is not sufficient to distinguish cases in which sharp angular bends are able to migrate with little change in geometry. Here, we examine the effect of water and sediment supply on the geometry of confined rivers in order to identify conditions under which meander geometry reaches a persistent dynamic equilibrium. Because channel width and meander geometry are closely related, we use a numerical meander model that allows for independent migration of both banks, thereby allowing channel width to vary in space and time. We hypothesize that confined meanders with persistent angular bends have smaller transport rates of bed material and that their migration is driven by erosion of the cutbank (bank-pull migration). When bed material supply is sufficiently large that point bar deposition drives meander migration (bar-push migration), confined meander bends have a larger radius of curvature and a geometry that varies as the meander migrates. We test this hypothesis using historical patterns of confined meander migration for rivers with different rates of sediment supply and bed material transport. Interpretation of the meander migration pattern is provided by the free-width meander migration model.

Persistence in Food Webs. I. Lotka-Volterra Food Chains,

DTIC Science & Technology

1978-07-01

0256 UNCLASSIFIED N i EE’hEZE *1 Al 1,1 IqI 0 - r ~PERSISTENCE IN FOOD WEBS.A I. LOTKA - VOLTERRA FOOD CHAINS Thomas C./Gard en9 Mt aisFEB 2 7 1980...2260n80 PERSISTENCE IN FOOD WEBS: \\’ ,.’ ’,-’ - 1. LOTKA - VOLTERRA FOOD CHAINS Thomas C. Gard and Thomas G. Hallam \\\\ . ’ \\7 INTRODUCTION bf numerous...modelled by Lotka - Volterra dynamics are determined. Here a simple food chain has a single species composing each trophic level with its dynamics

Drain tube migration into the anastomotic site of an esophagojejunostomy for gastric small cell carcinoma: short report

PubMed Central

2010-01-01

Background Intraluminal migration of a drain through an anastomotic site is a rare complication of gastric surgery. Case Presentation We herein report the intraluminal migration of a drain placed after a lower esophagectomy and total gastrectomy with Roux-en-Y anastomosis for gastric small cell carcinoma. Persistent drainage was noted 1 month after surgery, and radiographic studies were consistent with drain tube migration. Endoscopy revealed the drain had migrated into the esophagojejunostomy anastomotic site. The drain was removed from outside of abdominal wound while observing the anastomotic site endoscopically. The patient was treated with suction via a nasogastric tube drain for 5 days, and thereafter had an uneventful recovery. Conclusions Though drain tube migration is a rare occurrence, it should be considered in patients with persistent drainage who have undergone gastric surgery. PMID:20492665

Drain tube migration into the anastomotic site of an esophagojejunostomy for gastric small cell carcinoma: short report.

PubMed

Lai, Peng-Sheng; Lo, Chiao; Lin, Long-Wei; Lee, Po-Chu

2010-05-21

Intraluminal migration of a drain through an anastomotic site is a rare complication of gastric surgery. We herein report the intraluminal migration of a drain placed after a lower esophagectomy and total gastrectomy with Roux-en-Y anastomosis for gastric small cell carcinoma. Persistent drainage was noted 1 month after surgery, and radiographic studies were consistent with drain tube migration. Endoscopy revealed the drain had migrated into the esophagojejunostomy anastomotic site. The drain was removed from outside of abdominal wound while observing the anastomotic site endoscopically. The patient was treated with suction via a nasogastric tube drain for 5 days, and thereafter had an uneventful recovery. Though drain tube migration is a rare occurrence, it should be considered in patients with persistent drainage who have undergone gastric surgery.

Use of Electronic Tag Data and Associated Analytical Tools to Identify and Predict Habitat Utilization of Marine Mammals

DTIC Science & Technology

2011-09-30

B. P. Wallace, J. R. Spotila, F. V. Paladino, R. Piedra , S. A. Eckert, B. A. Block (2008). Persistent Leatherback Turtle Migrations Present...Swithenbank, P. Gaspar, B. P. Wallace, J. R. Spotila, F. V. Paladino, R. Piedra , S. A. Eckert, B. A. Block (2008). Persistent Leatherback Turtle Migrations

β-Globin gene sequencing of hemoglobin Austin revises the historically reported electrophoretic migration pattern.

PubMed

Racsa, Lori D; Luu, Hung S; Park, Jason Y; Mitui, Midori; Timmons, Charles F

2014-06-01

Hemoglobin (Hb) Austin was defined in 1977, using amino acid sequencing of samples from 3 unrelated Mexican-Americans, as a substitution of serine for arginine at position 40 of the β-globin chain (Arg40Ser). Its electrophoretic migration on both cellulose acetate (pH 8.4) and citrate agar (pH 6.2) was reported between Hb F and Hb A, and this description persists in reference literature. OBJECTIVES.-To review the clinical features and redefine the diagnostic characteristics of Hb Austin. Eight samples from 6 unrelated individuals and 2 siblings, all with Hispanic surnames, were submitted for abnormal Hb identification between June 2010 and September 2011. High-performance liquid chromatography, isoelectric focusing (IEF), citrate agar electrophoresis, and bidirectional DNA sequencing of the entire β-globin gene were performed. DNA sequencing confirmed all 8 individuals to be heterozygous for Hb Austin (Arg40Ser). Retention time on high-performance liquid chromatography and migration on citrate agar electrophoresis were consistent with that identification. Migration on IEF, however, was not between Hb F and Hb A, as predicted from the report of cellulose acetate electrophoresis. By IEF, Hb Austin migrated anodal to ("faster than") Hb A. Hemoglobin Austin (Arg40Ser) appears on IEF as a "fast," anodally migrating, Hb variant, just as would be expected from its amino acid substitution. The cited historic report is, at best, not applicable to IEF and is probably erroneous. Our observation of 8 cases in 16 months suggests that this variant may be relatively common in some Hispanic populations, making its recognition important. Furthermore, gene sequencing is proving itself a powerful and reliable tool for definitive identification of Hb variants.

Foamy Macrophages from Tuberculous Patients' Granulomas Constitute a Nutrient-Rich Reservoir for M. tuberculosis Persistence

PubMed Central

Poquet, Yannick; Levillain, Florence; Botanch, Catherine; Bardou, Fabienne; Daffé, Mamadou; Emile, Jean-François; Marchou, Bruno; Cardona, Pere-Joan; de Chastellier, Chantal; Altare, Frédéric

2008-01-01

Tuberculosis (TB) is characterized by a tight interplay between Mycobacterium tuberculosis and host cells within granulomas. These cellular aggregates restrict bacterial spreading, but do not kill all the bacilli, which can persist for years. In-depth investigation of M. tuberculosis interactions with granuloma-specific cell populations are needed to gain insight into mycobacterial persistence, and to better understand the physiopathology of the disease. We have analyzed the formation of foamy macrophages (FMs), a granuloma-specific cell population characterized by its high lipid content, and studied their interaction with the tubercle bacillus. Within our in vitro human granuloma model, M. tuberculosis long chain fatty acids, namely oxygenated mycolic acids (MA), triggered the differentiation of human monocyte-derived macrophages into FMs. In these cells, mycobacteria no longer replicated and switched to a dormant non-replicative state. Electron microscopy observation of M. tuberculosis–infected FMs showed that the mycobacteria-containing phagosomes migrate towards host cell lipid bodies (LB), a process which culminates with the engulfment of the bacillus into the lipid droplets and with the accumulation of lipids within the microbe. Altogether, our results suggest that oxygenated mycolic acids from M. tuberculosis play a crucial role in the differentiation of macrophages into FMs. These cells might constitute a reservoir used by the tubercle bacillus for long-term persistence within its human host, and could provide a relevant model for the screening of new antimicrobials against non-replicating persistent mycobacteria. PMID:19002241

Analytical model of multi-planetary resonant chains and constraints on migration scenarios

NASA Astrophysics Data System (ADS)

Delisle, J.-B.

2017-09-01

Resonant chains are groups of planets for which each pair is in resonance, with an orbital period ratio locked at a rational value (2/1, 3/2, etc.). Such chains naturally form as a result of convergent migration of the planets in the proto-planetary disk. In this article, I present an analytical model of resonant chains of any number of planets. Using this model, I show that a system captured in a resonant chain can librate around several possible equilibrium configurations. The probability of capture around each equilibrium depends on how the chain formed, and especially on the order in which the planets have been captured in the chain. Therefore, for an observed resonant chain, knowing around which equilibrium the chain is librating allows for constraints to be put on the formation and migration scenario of the system. I apply this reasoning to the four planets orbiting Kepler-223 in a 3:4:6:8 resonant chain. I show that the system is observed around one of the six equilibria predicted by the analytical model. Using N-body integrations, I show that the most favorable scenario to reproduce the observed configuration is to first capture the two intermediate planets, then the outermost, and finally the innermost.

Detachment of Chain-Forming Neuroblasts by Fyn-Mediated Control of cell-cell Adhesion in the Postnatal Brain.

PubMed

Fujikake, Kazuma; Sawada, Masato; Hikita, Takao; Seto, Yayoi; Kaneko, Naoko; Herranz-Pérez, Vicente; Dohi, Natsuki; Homma, Natsumi; Osaga, Satoshi; Yanagawa, Yuchio; Akaike, Toshihiro; García-Verdugo, Jose Manuel; Hattori, Mitsuharu; Sobue, Kazuya; Sawamoto, Kazunobu

2018-05-09

In the rodent olfactory system, neuroblasts produced in the ventricular-subventricular zone of the postnatal brain migrate tangentially in chain-like cell aggregates toward the olfactory bulb (OB) through the rostral migratory stream (RMS). After reaching the OB, the chains are dissociated and the neuroblasts migrate individually and radially toward their final destination. The cellular and molecular mechanisms controlling cell-cell adhesion during this detachment remain unclear. Here we report that Fyn, a nonreceptor tyrosine kinase, regulates the detachment of neuroblasts from chains in the male and female mouse OB. By performing chemical screening and in vivo loss-of-function and gain-of-function experiments, we found that Fyn promotes somal disengagement from the chains and is involved in neuronal migration from the RMS into the granule cell layer of the OB. Fyn knockdown or Dab1 (disabled-1) deficiency caused p120-catenin to accumulate and adherens junction-like structures to be sustained at the contact sites between neuroblasts. Moreover, a Fyn and N-cadherin double-knockdown experiment indicated that Fyn regulates the N-cadherin-mediated cell adhesion between neuroblasts. These results suggest that the Fyn-mediated control of cell-cell adhesion is critical for the detachment of chain-forming neuroblasts in the postnatal OB. SIGNIFICANCE STATEMENT In the postnatal brain, newly born neurons (neuroblasts) migrate in chain-like cell aggregates toward their destination, where they are dissociated into individual cells and mature. The cellular and molecular mechanisms controlling the detachment of neuroblasts from chains are not understood. Here we show that Fyn, a nonreceptor tyrosine kinase, promotes the somal detachment of neuroblasts from chains, and that this regulation is critical for the efficient migration of neuroblasts to their destination. We further show that Fyn and Dab1 (disabled-1) decrease the cell-cell adhesion between chain-forming neuroblasts, which involves adherens junction-like structures. Our results suggest that Fyn-mediated regulation of the cell-cell adhesion of neuroblasts is critical for their detachment from chains in the postnatal brain. Copyright © 2018 the authors 0270-6474/18/384599-12$15.00/0.

β1 integrin signaling promotes neuronal migration along vascular scaffolds in the post-stroke brain.

PubMed

Fujioka, Teppei; Kaneko, Naoko; Ajioka, Itsuki; Nakaguchi, Kanako; Omata, Taichi; Ohba, Honoka; Fässler, Reinhard; García-Verdugo, José Manuel; Sekiguchi, Kiyotoshi; Matsukawa, Noriyuki; Sawamoto, Kazunobu

2017-02-01

Cerebral ischemic stroke is a main cause of chronic disability. However, there is currently no effective treatment to promote recovery from stroke-induced neurological symptoms. Recent studies suggest that after stroke, immature neurons, referred to as neuroblasts, generated in a neurogenic niche, the ventricular-subventricular zone, migrate toward the injured area, where they differentiate into mature neurons. Interventions that increase the number of neuroblasts distributed at and around the lesion facilitate neuronal repair in rodent models for ischemic stroke, suggesting that promoting neuroblast migration in the post-stroke brain could improve efficient neuronal regeneration. To move toward the lesion, neuroblasts form chain-like aggregates and migrate along blood vessels, which are thought to increase their migration efficiency. However, the molecular mechanisms regulating these migration processes are largely unknown. Here we studied the role of β1-class integrins, transmembrane receptors for extracellular matrix proteins, in these migrating neuroblasts. We found that the neuroblast chain formation and blood vessel-guided migration critically depend on β1 integrin signaling. β1 integrin facilitated the adhesion of neuroblasts to laminin and the efficient translocation of their soma during migration. Moreover, artificial laminin-containing scaffolds promoted neuroblast chain formation and migration toward the injured area. These data suggest that laminin signaling via β1 integrin supports vasculature-guided neuronal migration to efficiently supply neuroblasts to injured areas. This study also highlights the importance of vascular scaffolds for cell migration in development and regeneration. Copyright © 2017 3-V Biosciences. Published by Elsevier B.V. All rights reserved.

DNA Molecules in Microfluidic Oscillatory Flow

PubMed Central

Chen, Y.-L.; Graham, M.D.; de Pablo, J.J.; Jo, K.; Schwartz, D.C.

2008-01-01

The conformation and dynamics of a single DNA molecule undergoing oscillatory pressure-driven flow in microfluidic channels is studied using Brownian dynamics simulations, accounting for hydrodynamic interactions between segments in the bulk and between the chain and the walls. Oscillatory flow provides a scenario under which the polymers may remain in the channel for an indefinite amount of time as they are stretched and migrate away from the channel walls. We show that by controlling the chain length, flow rate and oscillatory flow frequency, we are able to manipulate the chain extension and the chain migration from the channel walls. The chain stretch and the chain depletion layer thickness near the wall are found to increase as the Weissenberg number increases and as the oscillatory frequency decreases. PMID:19057656

Flow induced migration in polymer melts – Theory and simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dorgan, John Robert, E-mail: jdorgan@mines.edu; Rorrer, Nicholas Andrew, E-mail: nrorrer@mines.edu

2015-04-28

Flow induced migration, whereby polymer melts are fractionated by molecular weight across a flow field, represents a significant complication in the processing of polymer melts. Despite its long history, such phenomena remain relatively poorly understood. Here a simple analytical theory is presented which predicts the phenomena based on well-established principles of non-equilibrium thermodynamics. It is unambiguously shown that for purely viscous materials, a gradient in shear rate is needed to drive migration; for purely viscometric flows no migration is expected. Molecular scale simulations of flow migration effects in dense polymer melts are also presented. In shear flow the melts exhibitmore » similar behavior as the quiescent case; a constant shear rate across the gap does not induce chain length based migration. In comparison, parabolic flow causes profound migration for both unentangled and entangled melts. These findings are consistent with the analytical theory. The picture that emerges is consistent with flow induced migration mechanisms predominating over competing chain degradation mechanisms.« less

Lipid reserve dynamics and magnification of persistent organic pollutants in spawning sockeye salmon (Oncorhynchus nerka) from the Fraser River, British Columbia.

PubMed

Kelly, Barry C; Gray, Samantha L; Ikonomou, Michael G; Macdonald, J Steve; Bandiera, Stelvio M; Hrycay, Eugene G

2007-05-01

Pacific sockeye salmon (Oncorhynchus nerka) can travel several hundred kilometers to reach native spawning grounds and fulfill semelparous reproduction. The dramatic changes in lipid reserves during upstream migration can greatly affect internal toxicokinetics of persistent organic pollutants (POPs) such as PCBs, PCDDs, and PCDFs. We measured lipid content changes and contaminant concentrations in tissues (liver, muscle, roe/gonads) and biomarker responses (ethoxyresorufin O-deethylase or EROD activity and CYP1A levels) in two Pacific sockeye salmon stocks sampled at several locations along their spawning migration in the Fraser River, British Columbia. Muscle lipid contents declined significantly with increasing upstream migration distance and corresponded to elevated lipid normalized concentrations of PCBs and PCDD/Fs in spawning sockeye. Post-migration magnification factors (MFs) in spawning sockeye ranged between 3 and 12 and were comparable to model-predicted MFs. sigmaPCBs(150-500 ng x g(-1) lipid), sigmaPCDD/Fs (1-1000 pg x g(-1) lipid) and 2,3,7,8-TCDD toxic equivalent or TEQ levels (0.1-15 pg x g(-1) lipid) in spawning sockeye were relatively low and did not affect hepatic EROD activity/CYP1A induction. Despite a 3-fold magnification, TEQ levels in eggs of spawning Fraser River sockeye did not exceed 0.3 pg x g(-1) wet wt, a threshold level associated with 30% egg mortality in salmonids. PCBs in Fraser River sockeye are comparable to previous levels in Pacific sockeye. In contrast to Pacific sockeye from more remote coastal locations, PCDDs and PCDFs in Fraser River sockeye were generally minor components (<25%) of TEQ levels, compared to dioxin like PCB contributions (>75%). The data suggest that (i) the Fraser River is not a major contamination source of PCBs or PCDD/Fs and (ii) marine contaminant distribution, food-chain dynamics, and ocean-migration pathway are likely important factors controlling levels and patterns of POPs in returning Pacific sockeye. We estimate an annual chemical flux entering the Fraser River of up to 150 g for sigmaPCBs and 40 mg for sigmaPCDD/ Fs via returning sockeye. The results indicate that historical concentrations of PCBs and PCDD/Fs remain a potential threat to organism and ecosystem health on the west coast of Canada.

STEM Field Persistence: The Impact of Engagement on Postsecondary STEM Persistence for Underrepresented Minority Students

ERIC Educational Resources Information Center

Flynn, Daniel T.

2016-01-01

Persistence studies in science, technology, engineering, and math (STEM) fields indicate that the pipeline to degree attainment is "leaky" and underrepresented minorities are not persisting in the STEM fields. Those students who do not persist in the STEM fields either migrate to other fields of study or drop out of higher education…

Migration of lymphocytes on fibronectin-coated surfaces: temporal evolution of migratory parameters

NASA Technical Reports Server (NTRS)

Bergman, A. J.; Zygourakis, K.; McIntire, L. V. (Principal Investigator)

1999-01-01

Lymphocytes typically interact with implanted biomaterials through adsorbed exogenous proteins. To provide a more complete characterization of these interactions, analysis of lymphocyte migration on adsorbed extracellular matrix proteins must accompany the commonly performed adhesion studies. We report here a comparison of the migratory and adhesion behavior of Jurkat cells (a T lymphoblastoid cell line) on tissue culture treated and untreated polystyrene surfaces coated with various concentrations of fibronectin. The average speed of cell locomotion showed a biphasic response to substrate adhesiveness for cells migrating on untreated polystyrene and a monotonic decrease for cells migrating on tissue culture-treated polystyrene. A modified approach to the persistent random walk model was implemented to determine the time dependence of cell migration parameters. The random motility coefficient showed significant increases with time when cells migrated on tissue culture-treated polystyrene surfaces, while it remained relatively constant for experiments with untreated polystyrene plates. Finally, a cell migration computer model was developed to verify our modified persistent random walk analysis. Simulation results suggest that our experimental data were consistent with temporally increasing random motility coefficients.

Short-chain chlorinated paraffins in the soils of two different Chinese cities: Occurrence, homologue patterns and vertical migration.

PubMed

Huang, Yumei; Chen, Laiguo; Feng, Yongbin; Ye, Zhixiang; He, Qiusheng; Feng, Qianhua; Qing, Xian; Liu, Ming; Gao, Bo

2016-07-01

Short-chain chlorinated paraffins (SCCPs) are candidate persistent organic pollutants (POPs) that are under review by the Stockholm Convention. China is currently the largest producer and consumer of chlorinated paraffins (CPs). To study the environmental behavior and fate of SCCPs in the soils of urban and suburban regions, the SCCP concentrations in 88 topsoils and 15 soil columns from land of different use types (e.g., woodland, vegetable field, paddy field and greenbelt) from Guangzhou and Chengdu have been determined. The SCCP concentrations in topsoils from Guangzhou (range: 1.45-25.5ngg(-1) dry weight (dw), average: 10.3ngg(-1) dw) were much higher than those from Chengdu (range: 0.218-3.26ngg(-1) dw, average: 1.43ngg(-1) dw). When compared to previously reported SCCP levels for topsoils from other areas, the SCCP concentrations measured in the present work were quite low. Much higher SCCP concentrations were observed in the greenbelt topsoils from Chengdu relative to the values measured from woodlands and vegetable and paddy fields. The composition profiles suggest that C10Cl6-10 and C11-13Cl6-8 were the major groups of SCCPs in topsoils from the woodlands and vegetable and paddy fields in Guangzhou and Chengdu. Vertical variations of the SCCP concentrations in the soil columns suggest that less chlorinated SCCPs (Cl5-6-SCCPs) are more capable of migrating to the deeper-layer soils than more chlorinated ones (Cl9-10-SCCPs). The SCCP concentrations displayed little dependence on organic matter (OM) for most topsoils (p>0.05), indicating that OM is not the controlling factor in the distribution of SCCPs in the soils. This study analyzed the occurrence, homologue patterns and vertical migration of SCCPs in the topsoils of two Chinese cities with different industrial structures and climate conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

NMR (Nuclear Magnetic Resonance) and macromolecular migration in a melt or in concentrated solutions

NASA Technical Reports Server (NTRS)

Addad, J. P. C.

1983-01-01

The purpose of this paper is to analyze the migration process of long polymer molecules in a melt or in concentrated solutions as it may be observed from the dynamics of the transverse magnetization of nuclear spins linked to these chains. The low frequency viscoelastic relaxation of polymer systems is known to be mainly controlled by the mechanism of dissociation of topological constraints excited on chains and which are called entanglements. This mechanism exhibits a strong dependence upon the chain molecular weight. These topological constraints also govern the diffusion process of polymer chains. So, the accurate description of the diffusion motion of a chain may be a convenient way to characterize disentanglement processes necessarily involved in any model proposed to explain viscoelastic effects.

Roles of endothelial A-type lamins in migration of T cells on and under endothelial layers

NASA Astrophysics Data System (ADS)

Song, Kwang Hoon; Lee, Jaehyun; Park, Hyoungjun; Kim, Hye Mi; Park, Jeehun; Kwon, Keon Woo; Doh, Junsang

2016-03-01

Stiff nuclei in cell-dense microenvironments may serve as distinct biomechanical cues for cell migration, but such a possibility has not been tested experimentally. As a first step addressing this question, we altered nuclear stiffness of endothelial cells (ECs) by reducing the expression of A-type lamins using siRNA, and investigated the migration of T cells on and under EC layers. While most T cells crawling on control EC layers avoided crossing over EC nuclei, a significantly higher fraction of T cells on EC layers with reduced expression of A-type lamins crossed over EC nuclei. This result suggests that stiff EC nuclei underlying T cells may serve as “duro-repulsive” cues to direct T cell migration toward less stiff EC cytoplasm. During subendothelial migration under EC layers with reduced expression of A-type lamins, T cells made prolonged contact and substantially deformed EC nuclei, resulting in reduced speed and directional persistence. This result suggests that EC nuclear stiffness promotes fast and directionally persistent subendothelial migration of T cells by allowing minimum interaction between T cells and EC nuclei.

Microbial biosynthesis of wax esters during desiccation: an adaptation for colonization of the earliest terrestrial environments?

NASA Astrophysics Data System (ADS)

Finkelstein, D. B.; Brassell, S. C.; Pratt, L. M.

2008-12-01

Biosynthesis of wax esters (WE) by prokaryotes in natural systems, notably bacteria from hot springs and marine phytoplankton, is poorly documented, primarily because saponification is a routine step in the analysis of microbial mat lipids. Use of this preparative procedure, critical for characterization of the diagnostic distributions of carboxylic acids in phospholipids, precludes recovery of intact WE. Examination of non-saponified lipids in emergent and desiccated mats with comparable microbial communities from the Warner Lake region, Oregon, reveals increases in the relative abundance (18.6 to 59.9μg/g Corg) and average chain length (C38 to C46) of WE in the latter, combined with assimilation of phytol and tocopherol moieties. Prokaryotes can accumulate WE as storage lipids in vitro, notably at elevated temperature or under nitrogen limiting conditions, but we propose that biosynthesis of long-chain WE that have a low solubility and are resistant to degradation/oxidation may represent an evolutionary strategy to survive desiccation in evaporative environments. Moreover, aeolian transport of desiccated mat-rip-ups between lake flats allows for migration of microbial communities within and between lake flats and basins during arid conditions. Subsequent rehydration within an alkaline environment would naturally saponify WE, and thereby regenerate alcohol and acid moieties that could serve as membrane lipids for the next viable microbial generation. The evolutionary cradle of WE was likely abiotic generation under hydrothermal conditions, which is consistent with the antiquity of the ester linkage necessitated by its integral role in the membranes of Eubacteria (though not Archaea) and in bacteriochlorophyll. The subsequent capability of microbes to biosynthesize WE may have facilitated their survival when nutrients were limiting, and production of long-chain WE (>C40) may represent a further critical evolutionary threshold that enabled their persistence through and during dehydration or desiccation cycles. Thus, production of WE may have facilitated microbial migration to the lake environments that represented the earliest terrestrial ecosystems, and survival through the Great Oxygenation Event.

EndoAnchors to Resolve Persistent Type Ia Endoleak Secondary to Proximal Cuff With Parallel Graft Placement.

PubMed

Donselaar, Esmé J; van der Vijver-Coppen, Rozemarijn J; van den Ham, Leo H; Lardenoye, Jan Willem H P; Reijnen, Michel M P J

2016-02-01

To describe 2 patients with a distally migrated endograft causing a type Ia endoleak and treatment with a proximal cuff and chimney grafts that required EndoAnchors to finally seal the leak. Two men, ages 86 and 72 years, presented with stent-graft migration and type Ia endoleak at 5 and 15 years after endovascular repair, respectively. Both were treated with a proximal cuff in combination with a chimney graft to the left renal artery. In both cases, the type Ia endoleak persisted, likely due to gutter formation. Both patients were treated in the same setting with EndoAnchors that instantly resolved the endoleak. At 1-year follow-up, there was no recurrent endoleak or migration, with patent chimney grafts and renal arteries and stable renal function. EndoAnchors may effectively resolve a persistent type Ia endoleak arising from gutter formation after placement of a proximal cuff and chimney grafts. © The Author(s) 2015.

Bayesian Probabilistic Projection of International Migration.

PubMed

Azose, Jonathan J; Raftery, Adrian E

2015-10-01

We propose a method for obtaining joint probabilistic projections of migration for all countries, broken down by age and sex. Joint trajectories for all countries are constrained to satisfy the requirement of zero global net migration. We evaluate our model using out-of-sample validation and compare point projections to the projected migration rates from a persistence model similar to the method used in the United Nations' World Population Prospects, and also to a state-of-the-art gravity model.

Nanotopography guides and directs cell migration in amoeboid and epithelial cells

NASA Astrophysics Data System (ADS)

Lee, Rachel; Das, Satarupa; Hourwitz, Matthew; Sun, Xiaoyu; Parent, Carole; Fourkas, John; Losert, Wolfgang

Cell migration plays a critical role in development, angiogenesis, immune response, wound healing, and cancer metastasis. In many cases, cells also move in the context of a matrix of collagen fibers, and the alignment of these fibers can both affect the migration phenotype and guide cells. Here we show that both fast and slow migrating cells - amoeboid HL-60 and epithelial MCF10A - are affected in similar ways by micro/nanostructures with dimensions similar to those of collagen fibers. Cell alignment enhances the efficiency of migration by increasing directional persistence.

Cell migration without a lamellipodium: translation of actin dynamics into cell movement mediated by tropomyosin.

PubMed

Gupton, Stephanie L; Anderson, Karen L; Kole, Thomas P; Fischer, Robert S; Ponti, Aaron; Hitchcock-DeGregori, Sarah E; Danuser, Gaudenz; Fowler, Velia M; Wirtz, Denis; Hanein, Dorit; Waterman-Storer, Clare M

2005-02-14

The actin cytoskeleton is locally regulated for functional specializations for cell motility. Using quantitative fluorescent speckle microscopy (qFSM) of migrating epithelial cells, we previously defined two distinct F-actin networks based on their F-actin-binding proteins and distinct patterns of F-actin turnover and movement. The lamellipodium consists of a treadmilling F-actin array with rapid polymerization-dependent retrograde flow and contains high concentrations of Arp2/3 and ADF/cofilin, whereas the lamella exhibits spatially random punctae of F-actin assembly and disassembly with slow myosin-mediated retrograde flow and contains myosin II and tropomyosin (TM). In this paper, we microinjected skeletal muscle alphaTM into epithelial cells, and using qFSM, electron microscopy, and immunolocalization show that this inhibits functional lamellipodium formation. Cells with inhibited lamellipodia exhibit persistent leading edge protrusion and rapid cell migration. Inhibition of endogenous long TM isoforms alters protrusion persistence. Thus, cells can migrate with inhibited lamellipodia, and we suggest that TM is a major regulator of F-actin functional specialization in migrating cells.

Formation of Close-in Super-Earths in an Evolving Disk Due to Disk Winds

NASA Astrophysics Data System (ADS)

Ogihara, Masahiro; Kokubo, Eiichiro; Suzuki, Takeru; Morbidelli, Alessandro

2018-04-01

Planets with masses larger than Mars mass undergo rapid inward migration (type I migration) in a standard protoplanetary disk. Recent magnetohydrodynamical simulations revealed the presence of magnetically-driven disk winds, which would alter the disk profile and the type I migration in the close-in region (r<1 au). We investigate orbital evolution of planetary embryos in a disk that viscously evolves under effects of magnetically-driven disk winds. The aim is to examine whether observed distributions of close-in super-Earths can be reproduced by simulations. We find that the type I migration is significantly suppressed in a disk with flat surface density profile. After planetary embryos undergo slow inward migration, they are captured in a resonant chain. The resonant chain undergoes late orbital instability during the gas depletion, leading to a non-resonant configuration. We also find that observed distributions of close-in super-Earths (e.g., period ratio, mass ratio) can be reproduced by results of simulations.

Clathrin light chains are required for the gyrating-clathrin recycling pathway and thereby promote cell migration.

PubMed

Majeed, Sophia R; Vasudevan, Lavanya; Chen, Chih-Ying; Luo, Yi; Torres, Jorge A; Evans, Timothy M; Sharkey, Andrew; Foraker, Amy B; Wong, Nicole M L; Esk, Christopher; Freeman, Theresa A; Moffett, Ashley; Keen, James H; Brodsky, Frances M

2014-05-23

The clathrin light chain (CLC) subunits participate in several membrane traffic pathways involving both clathrin and actin, through binding the actin-organizing huntingtin-interacting proteins (Hip). However, CLCs are dispensable for clathrin-mediated endocytosis of many cargoes. Here we observe that CLC depletion affects cell migration through Hip binding and reduces surface expression of β1-integrin by interference with recycling following normal endocytosis of inactive β1-integrin. CLC depletion and expression of a modified CLC also inhibit the appearance of gyrating (G)-clathrin structures, known mediators of rapid recycling of transferrin receptor from endosomes. Expression of the modified CLC reduces β1-integrin and transferrin receptor recycling, as well as cell migration, implicating G-clathrin in these processes. Supporting a physiological role for CLC in migration, the CLCb isoform of CLC is upregulated in migratory human trophoblast cells during uterine invasion. Together, these studies establish CLCs as mediating clathrin-actin interactions needed for recycling by G-clathrin during migration.

Non-Brownian dynamics and strategy of amoeboid cell locomotion.

PubMed

Nishimura, Shin I; Ueda, Masahiro; Sasai, Masaki

2012-04-01

Amoeboid cells such as Dictyostelium discoideum and Madin-Darby canine kidney cells show the non-Brownian dynamics of migration characterized by the superdiffusive increase of mean-squared displacement. In order to elucidate the physical mechanism of this non-Brownian dynamics, a computational model is developed which highlights a group of inhibitory molecules for actin polymerization. Based on this model, we propose a hypothesis that inhibitory molecules are sent backward in the moving cell to accumulate at the rear of cell. The accumulated inhibitory molecules at the rear further promote cell locomotion to form a slow positive feedback loop of the whole-cell scale. The persistent straightforward migration is stabilized with this feedback mechanism, but the fluctuation in the distribution of inhibitory molecules and the cell shape deformation concurrently interrupt the persistent motion to turn the cell into a new direction. A sequence of switching behaviors between persistent motions and random turns gives rise to the superdiffusive migration in the absence of the external guidance signal. In the complex environment with obstacles, this combined process of persistent motions and random turns drives the simulated amoebae to solve the maze problem in a highly efficient way, which suggests the biological advantage for cells to bear the non-Brownian dynamics.

Chain Conformation near the Buried Interface in Nanoparticle-Stabilized Polymer Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barkley, Deborah A.; Jiang, Naisheng; Sen, Mani

It is known that when nanoparticles are added to polymer thin films, they often migrate to the film-substrate interface and form an “immobile interfacial layer”, which has been believed as the origin of suppression of dewetting. We here report an alternative mechanism of dewetting suppression from the structural aspect of a polymer. Dodecane thiol-functionalized gold (Au) nanoparticles embedded in PS thin films prepared on Si substrates were used as a model. It was found that thermal annealing promotes irreversible polymer adsorption onto the substrate surface along with the surface migration of the nanoparticles. We also revealed that the surface migrationmore » causes additional nanoconfined space for the adsorbed polymer chains. As a result, the self-organization process of the strongly adsorbed polymer chains on the solid surface was so hindered that the chain conformations were randomized and expanded in the film normal direction. Here, the resultant chain conformation allows the interpenetration between free chains and the adsorbed chains, promoting adhesion and hence stabilizing the thin film.« less

Chain Conformation near the Buried Interface in Nanoparticle-Stabilized Polymer Thin Films

DOE PAGES

Barkley, Deborah A.; Jiang, Naisheng; Sen, Mani; ...

2017-09-26

It is known that when nanoparticles are added to polymer thin films, they often migrate to the film-substrate interface and form an “immobile interfacial layer”, which has been believed as the origin of suppression of dewetting. We here report an alternative mechanism of dewetting suppression from the structural aspect of a polymer. Dodecane thiol-functionalized gold (Au) nanoparticles embedded in PS thin films prepared on Si substrates were used as a model. It was found that thermal annealing promotes irreversible polymer adsorption onto the substrate surface along with the surface migration of the nanoparticles. We also revealed that the surface migrationmore » causes additional nanoconfined space for the adsorbed polymer chains. As a result, the self-organization process of the strongly adsorbed polymer chains on the solid surface was so hindered that the chain conformations were randomized and expanded in the film normal direction. Here, the resultant chain conformation allows the interpenetration between free chains and the adsorbed chains, promoting adhesion and hence stabilizing the thin film.« less

Development of an ultralow-light-level luminescence image analysis system for dynamic measurements of transcriptional activity in living and migrating cells.

PubMed

Maire, E; Lelièvre, E; Brau, D; Lyons, A; Woodward, M; Fafeur, V; Vandenbunder, B

2000-04-10

We have developed an approach to study in single living epithelial cells both cell migration and transcriptional activation, which was evidenced by the detection of luminescence emission from cells transfected with luciferase reporter vectors. The image acquisition chain consists of an epifluorescence inverted microscope, connected to an ultralow-light-level photon-counting camera and an image-acquisition card associated to specialized image analysis software running on a PC computer. Using a simple method based on a thin calibrated light source, the image acquisition chain has been optimized following comparisons of the performance of microscopy objectives and photon-counting cameras designed to observe luminescence. This setup allows us to measure by image analysis the luminescent light emitted by individual cells stably expressing a luciferase reporter vector. The sensitivity of the camera was adjusted to a high value, which required the use of a segmentation algorithm to eliminate the background noise. Following mathematical morphology treatments, kinetic changes of luminescent sources were analyzed and then correlated with the distance and speed of migration. Our results highlight the usefulness of our image acquisition chain and mathematical morphology software to quantify the kinetics of luminescence changes in migrating cells.

An Emerging Allee Effect Is Critical for Tumor Initiation and Persistence

PubMed Central

Böttger, Katrin; Hatzikirou, Haralambos; Voss-Böhme, Anja; Cavalcanti-Adam, Elisabetta Ada; Herrero, Miguel A.; Deutsch, Andreas

2015-01-01

Tumor cells develop different strategies to cope with changing microenvironmental conditions. A prominent example is the adaptive phenotypic switching between cell migration and proliferation. While it has been shown that the migration-proliferation plasticity influences tumor spread, it remains unclear how this particular phenotypic plasticity affects overall tumor growth, in particular initiation and persistence. To address this problem, we formulate and study a mathematical model of spatio-temporal tumor dynamics which incorporates the microenvironmental influence through a local cell density dependence. Our analysis reveals that two dynamic regimes can be distinguished. If cell motility is allowed to increase with local cell density, any tumor cell population will persist in time, irrespective of its initial size. On the contrary, if cell motility is assumed to decrease with respect to local cell density, any tumor population below a certain size threshold will eventually extinguish, a fact usually termed as Allee effect in ecology. These results suggest that strategies aimed at modulating migration are worth to be explored as alternatives to those mainly focused at keeping tumor proliferation under control. PMID:26335202

Migrating Myeloid Cells Sense Temporal Dynamics of Chemoattractant Concentrations.

PubMed

Petrie Aronin, Caren E; Zhao, Yun M; Yoon, Justine S; Morgan, Nicole Y; Prüstel, Thorsten; Germain, Ronald N; Meier-Schellersheim, Martin

2017-11-21

Chemoattractant-mediated recruitment of hematopoietic cells to sites of pathogen growth or tissue damage is critical to host defense and organ homeostasis. Chemotaxis is typically considered to rely on spatial sensing, with cells following concentration gradients as long as these are present. Utilizing a microfluidic approach, we found that stable gradients of intermediate chemokines (CCL19 and CXCL12) failed to promote persistent directional migration of dendritic cells or neutrophils. Instead, rising chemokine concentrations were needed, implying that temporal sensing mechanisms controlled prolonged responses to these ligands. This behavior was found to depend on G-coupled receptor kinase-mediated negative regulation of receptor signaling and contrasted with responses to an end agonist chemoattractant (C5a), for which a stable gradient led to persistent migration. These findings identify temporal sensing as a key requirement for long-range myeloid cell migration to intermediate chemokines and provide insights into the mechanisms controlling immune cell motility in complex tissue environments. Published by Elsevier Inc.

Traces of business cycles in credit-rating migrations

PubMed Central

Boreiko, Dmitri; Kaniovski, Serguei; Pflug, Georg

2017-01-01

Using migration data of a rating agency, this paper attempts to quantify the impact of macroeconomic conditions on credit-rating migrations. The migrations are modeled as a coupled Markov chain, where the macroeconomic factors are represented by unobserved tendency variables. In the simplest case, these binary random variables are static and credit-class-specific. A generalization treats tendency variables evolving as a time-homogeneous Markov chain. A more detailed analysis assumes a tendency variable for every combination of a credit class and an industry. The models are tested on a Standard and Poor’s (S&P’s) dataset. Parameters are estimated by the maximum likelihood method. According to the estimates, the investment-grade financial institutions evolve independently of the rest of the economy represented by the data. This might be an evidence of implicit too-big-to-fail bail-out guarantee policies of the regulatory authorities. PMID:28426758

Traces of business cycles in credit-rating migrations.

PubMed

Boreiko, Dmitri; Kaniovski, Serguei; Kaniovski, Yuri; Pflug, Georg

2017-01-01

Using migration data of a rating agency, this paper attempts to quantify the impact of macroeconomic conditions on credit-rating migrations. The migrations are modeled as a coupled Markov chain, where the macroeconomic factors are represented by unobserved tendency variables. In the simplest case, these binary random variables are static and credit-class-specific. A generalization treats tendency variables evolving as a time-homogeneous Markov chain. A more detailed analysis assumes a tendency variable for every combination of a credit class and an industry. The models are tested on a Standard and Poor's (S&P's) dataset. Parameters are estimated by the maximum likelihood method. According to the estimates, the investment-grade financial institutions evolve independently of the rest of the economy represented by the data. This might be an evidence of implicit too-big-to-fail bail-out guarantee policies of the regulatory authorities.

EphrinB3 restricts endogenous neural stem cell migration after traumatic brain injury.

PubMed

Dixon, Kirsty J; Mier, Jose; Gajavelli, Shyam; Turbic, Alisa; Bullock, Ross; Turnley, Ann M; Liebl, Daniel J

2016-11-01

Traumatic brain injury (TBI) leads to a series of pathological events that can have profound influences on motor, sensory and cognitive functions. Conversely, TBI can also stimulate neural stem/progenitor cell proliferation leading to increased numbers of neuroblasts migrating outside their restrictive neurogenic zone to areas of damage in support of tissue integrity. Unfortunately, the factors that regulate migration are poorly understood. Here, we examine whether ephrinB3 functions to restrict neuroblasts from migrating outside the subventricular zone (SVZ) and rostral migratory stream (RMS). We have previously shown that ephrinB3 is expressed in tissues surrounding these regions, including the overlying corpus callosum (CC), and is reduced after controlled cortical impact (CCI) injury. Our current study takes advantage of ephrinB3 knockout mice to examine the influences of ephrinB3 on neuroblast migration into CC and cortex tissues after CCI injury. Both injury and/or ephrinB3 deficiency led to increased neuroblast numbers and enhanced migration outside the SVZ/RMS zones. Application of soluble ephrinB3-Fc molecules reduced neuroblast migration into the CC after injury and limited neuroblast chain migration in cultured SVZ explants. Our findings suggest that ephrinB3 expression in tissues surrounding neurogenic regions functions to restrict neuroblast migration outside the RMS by limiting chain migration. Copyright © 2016 Michael Boutros, German Cancer Research Center, Heidelberg, Germany. Published by Elsevier B.V. All rights reserved.

Consequences of resource supplementation for disease risk in a partially migratory population.

PubMed

Brown, Leone M; Hall, Richard J

2018-05-05

Anthropogenic landscape features such as urban parks and gardens, landfills and farmlands can provide novel, seasonally reliable food sources that impact wildlife ecology and distributions. In historically migratory species, food subsidies can cause individuals to forgo migration and form partially migratory or entirely sedentary populations, eroding a crucial benefit of migration: pathogen avoidance through seasonal abandonment of transmission sites and mortality of infected individuals during migration. Since many migratory taxa are declining, and wildlife populations in urban areas can harbour zoonotic pathogens, understanding the mechanisms by which anthropogenic resource subsidies influence infection dynamics and the persistence of migration is important for wildlife conservation and public health. We developed a mathematical model for a partially migratory population and a vector-borne pathogen transmitted at a shared breeding ground, where food subsidies increase the nonbreeding survival of residents. We found that higher resident nonbreeding survival increased infection prevalence in residents and migrants, and lowered the fraction of the population that migrated. The persistence of migration may be especially threatened if residency permits emergence of more virulent pathogens, if resource subsidies reduce costs of infection for residents, and if infection reduces individual migratory propensity.This article is part of the theme issue 'Anthropogenic resource subsidies and host-parasite dynamics in wildlife'. © 2018 The Author(s).

A resonant chain of four transiting, sub-Neptune planets.

PubMed

Mills, Sean M; Fabrycky, Daniel C; Migaszewski, Cezary; Ford, Eric B; Petigura, Erik; Isaacson, Howard

2016-05-26

Surveys have revealed many multi-planet systems containing super-Earths and Neptunes in orbits of a few days to a few months. There is debate whether in situ assembly or inward migration is the dominant mechanism of the formation of such planetary systems. Simulations suggest that migration creates tightly packed systems with planets whose orbital periods may be expressed as ratios of small integers (resonances), often in a many-planet series (chain). In the hundreds of multi-planet systems of sub-Neptunes, more planet pairs are observed near resonances than would generally be expected, but no individual system has hitherto been identified that must have been formed by migration. Proximity to resonance enables the detection of planets perturbing each other. Here we report transit timing variations of the four planets in the Kepler-223 system, model these variations as resonant-angle librations, and compute the long-term stability of the resonant chain. The architecture of Kepler-223 is too finely tuned to have been formed by scattering, and our numerical simulations demonstrate that its properties are natural outcomes of the migration hypothesis. Similar systems could be destabilized by any of several mechanisms, contributing to the observed orbital-period distribution, where many planets are not in resonances. Planetesimal interactions in particular are thought to be responsible for establishing the current orbits of the four giant planets in the Solar System by disrupting a theoretical initial resonant chain similar to that observed in Kepler-223.

Care workers, care drain, and care chains: reflections on care, migration, and citizenship.

PubMed

Lutz, Helma; Palenga-Möllenbeck, Ewa

2012-01-01

In this article, we discuss a case study that deals with the care chain phenomenon and focuses on the question of how Poland and the Ukraine as sending countries and Poland as a receiving country are affected and deal with female migrant domestic workers. We look at the ways in which these women organize care replacement for their families left behind and at those families’ care strategies. As public discourse in both countries is reacting to the feminization of migration in a form that specifically questions the social citizenship obligations of these women, we also look at the media portrayal of the situation of nonmigrating children. Finally, we explore how different aspects of citizenship matter in transnational care work migration movements.

Electrostatic stiffening and induced persistence length for coassembled molecular bottlebrushes

NASA Astrophysics Data System (ADS)

Storm, Ingeborg M.; Stuart, Martien A. Cohen; de Vries, Renko; Leermakers, Frans A. M.

2018-03-01

A self-consistent field analysis for tunable contributions to the persistence length of isolated semiflexible polymer chains including electrostatically driven coassembled deoxyribonucleic acid (DNA) bottlebrushes is presented. When a chain is charged, i.e., for polyelectrolytes, there is, in addition to an intrinsic rigidity, an electrostatic stiffening effect, because the electric double layer resists bending. For molecular bottlebrushes, there is an induced contribution due to the grafts. We explore cases beyond the classical phantom main-chain approximation and elaborate molecularly more realistic models where the backbone has a finite volume, which is necessary for treating coassembled bottlebrushes. We find that the way in which the linear charge density or the grafting density is regulated is important. Typically, the stiffening effect is reduced when there is freedom for these quantities to adapt to the curvature stresses. Electrostatically driven coassembled bottlebrushes, however, are relatively stiff because the chains have a low tendency to escape from the compressed regions and the electrostatic binding force is largest in the convex part. For coassembled bottlebrushes, the induced persistence length is a nonmonotonic function of the polymer concentration: For low polymer concentrations, the stiffening grows quadratically with coverage; for semidilute polymer concentrations, the brush chains retract and regain their Gaussian size. When doing so, they lose their induced persistence length contribution. Our results correlate well with observed physical characteristics of electrostatically driven coassembled DNA-bioengineered protein-polymer bottlebrushes.

The persistence and characteristics of Chinook salmon migrations to the Upper Klamath River prior to exclusion by dams

USGS Publications Warehouse

Hamilton, John B; Rondorf, Dennis W.; Tinniswood, William; Leary, Ryan J; Mayer, Tim; Gavette, Charleen; Casal, Lynne A.

2016-01-01

In this research article, John Hamilton and his co-authors present extensive new research and information gathered since a 2005 publication on the historical evidence of anadromomous fish distribution in the Upper Klamath River watershed. Using historical accounts from early explorers and ethnographers to early-twentieth-century photographs, newspaper accounts, and government reports, the authors provide a more complete record of past salmon migrations. The updated record “substantiate[s] the historical persistence of salmon, their migration characteristics, and the broad population baseline that will be key to future commercial, recreational, and Tribal fisheries in the Klamath River and beyond.” During a time when salmon restoration plans are being considered in the region, the historical record can serve as guidance to once again establish diverse and thriving populations.

Social networks in the migration process: empirical evidence on chain migration in India.

PubMed

Banerjee, B

1983-01-01

This study, based on interviews with 1615 migrant heads of household in Delhi, was concerned with interactions between labor migrants and their urban-based contacts. 86% of the rural migrants reported having relatives and/or covillagers living in Delhi at the time of their arrival, and virtually all received some form of assistance from their contacts. A preference for assistance from relatives rather than covillagers was noted, suggesting that migrants regarded kinship bonds as stronger than village and caste ties. However, covillagers tended to be contacted if relatives failed to secure a job for the new migrants within a reasonable time. The moves of only 17% of the sample could be classified under delayed family migration (relocation of family members in lagged stages). The tendency for traditional norms to be relaxed in an urban setting is reflected in the finding that the places of origin of migrants and their urban-based relatives differed in about half the cases that involved assistance from relatives. In addition, 13% of migrants violated traditional norms by seeking assistance from female agnates and kin affinally linked through these women. The most common pattern of assistance provided by both relatives and covillagers included room, food, and job search; however, new migrants tended to prefer to obtain board and lodging from relatives. Migrants helped by primary male agnates were twice as likely to receive money as those helped by other relatives. A consequence of chain migration is the concentration of persons from the same village or kinship network in particular occupations. 36% of the wage employees in the sample had relatives and/or covillagers working for the same employer. This suggests that migration induced by urban-based contacts (accounting for 42% of the migration in this sample) will be low if the sectors in which job opportunities are expanding are dominated by nonmigrants. Given the prevalence of chain migration, the contribution of migration to urban unemployment is likely to be fairly low.

The electrostatic persistence length of polymers beyond the OSF limit.

PubMed

Everaers, R; Milchev, A; Yamakov, V

2002-05-01

We use large-scale Monte Carlo simulations to test scaling theories for the electrostatic persistence length l(e) of isolated, uniformly charged polymers with Debye-Hückel intrachain interactions in the limit where the screening length kappa(-1) exceeds the intrinsic persistence length of the chains. Our simulations cover a significantly larger part of the parameter space than previous studies. We observe no significant deviations from the prediction l(e) proportional to kappa(-2) by Khokhlov and Khachaturian which is based on applying the Odijk-Skolnick-Fixman theories of electrostatic bending rigidity and electrostatically excluded volume to the stretched de Gennes-Pincus-Velasco-Brochard polyelectrolyte blob chain. A linear or sublinear dependence of the persistence length on the screening length can be ruled out. We show that previous results pointing into this direction are due to a combination of excluded-volume and finite chain length effects. The paper emphasizes the role of scaling arguments in the development of useful representations for experimental and simulation data.

"Becoming Somebody": Youth Transitions through Education and Migration in Peru

ERIC Educational Resources Information Center

Crivello, Gina

2011-01-01

The past few decades have witnessed international pressure to get more children in the world educated, for longer. The view that school education is core to definitions of good childhoods and successful youth transitions is increasingly widespread, globally and locally. However, structural inequalities persist and migration for education has…

Analysis of a Mouse α-Globin Gene Mutation Induced by Ethylnitrosourea

PubMed Central

Popp, R. A.; Bailiff, E. G.; Skow, L. C.; Johnson, F. M.; Lewis, Susan E.

1983-01-01

A DBA/2 mouse treated with ethylnitrosourea sired an offspring whose hemoglobin showed an extra band following starch gel electrophoresis. The variant hemoglobin migrated to a more cathodal position in starch gel. Isoelectric focusing indicated that chain 5 of the mutant hemoglobin migrated to a more cathodal position than the normal chain 5 from DBA/2 mice and that the other α-globin, chain 1, was not affected. On focusing gels the phenotype of the mutant allele, Hbay9, was expressed without dominance to normal chain 5, and Hbay9/Hbay9 homozygotes were fully viable in the laboratory. The molecular basis for the germinal mutation was investigated by analyzing the amino acid sequence of chain 5y9, the mutant form of α-chain 5. A single amino acid substitution (His → Leu) at position 89 was found in chain 5y9. We propose that ethylnitrosourea induced an A → T transversion in the histidine codon at position 89 (CAC → CTC). This mutation has apparently not been observed previously in humans, mice or other mammals, and its novel occurrence may be indicative of other unusual mutational events that do not ordinarily occur in the absence of specific mutagen exposure. PMID:6618166

PEG-protein interaction induced contraction of NalD chains.

PubMed

Yu, Jiyan; Chen, Weizhong; Wu, Chi; Chen, Hao

2014-01-01

In a recent attempt to crystallize a regulator of MexAB-OprM multi-drug efflux systems in Pseudomonas aeruginosa (NalD), we found that adding polyethylene glycol (PEG3350, Mw = 3,350 g/mol) into the protein solution increases the speed of NalD migration in gel electrophoresis, signaling a smaller hydrodynamic size. At first we conjectured that NalD was degraded unexpectedly by PEG; however, we found that there was no change in its molar mass by MALDI-TOF characterization. Moreover, we found that adding polyacrylic acid (PAA) into the solution mixture returned the NalD migration to its normal speed. Furthermore, our analytic ultracentrifugation and dynamic laser light scattering results directly reveal that NalD interacts with PEG so that individual NalD chains gradually shrink as more PEG chains are added in the range of 10-50 mg/mL. Size exclusion chromatography also confirms that the NalD chain shrinks in the presence of PEG. A combination of these results indicates that PEG3350 chains can complex with NalD to induce an intra-protein chain contraction, presumably via the formation of hydrogen bond between -C-O-C- on PEG and -COOH on NalD, resulting in a smaller hydrodynamic size (faster migration) and a higher apparent molar mass. Note that because the presence of PEG affects osmotic pressure, it is considered to be a precipitator of protein crystallization. Our current finding reveals that the interaction of PEG/protein may play a significant role in protein crystallization. The complexation potentially makes the protein chain segments less flexible, and consequently makes crystallization easier. Hopefully, our current results will stimulate further studies in this direction.

PEG-Protein Interaction Induced Contraction of NalD Chains

PubMed Central

Yu, Jiyan; Chen, Weizhong; Wu, Chi; Chen, Hao

2014-01-01

In a recent attempt to crystallize a regulator of MexAB-OprM multi-drug efflux systems in Pseudomonas aeruginosa (NalD), we found that adding polyethylene glycol (PEG3350, Mw = 3,350 g/mol) into the protein solution increases the speed of NalD migration in gel electrophoresis, signaling a smaller hydrodynamic size. At first we conjectured that NalD was degraded unexpectedly by PEG; however, we found that there was no change in its molar mass by MALDI-TOF characterization. Moreover, we found that adding polyacrylic acid (PAA) into the solution mixture returned the NalD migration to its normal speed. Furthermore, our analytic ultracentrifugation and dynamic laser light scattering results directly reveal that NalD interacts with PEG so that individual NalD chains gradually shrink as more PEG chains are added in the range of 10–50 mg/mL. Size exclusion chromatography also confirms that the NalD chain shrinks in the presence of PEG. A combination of these results indicates that PEG3350 chains can complex with NalD to induce an intra-protein chain contraction, presumably via the formation of hydrogen bond between –C-O-C– on PEG and –COOH on NalD, resulting in a smaller hydrodynamic size (faster migration) and a higher apparent molar mass. Note that because the presence of PEG affects osmotic pressure, it is considered to be a precipitator of protein crystallization. Our current finding reveals that the interaction of PEG/protein may play a significant role in protein crystallization. The complexation potentially makes the protein chain segments less flexible, and consequently makes crystallization easier. Hopefully, our current results will stimulate further studies in this direction. PMID:24810951

Hot super-Earths and giant planet cores from different migration histories

NASA Astrophysics Data System (ADS)

Cossou, Christophe; Raymond, Sean N.; Hersant, Franck; Pierens, Arnaud

2014-09-01

Planetary embryos embedded in gaseous protoplanetary disks undergo Type I orbital migration. Migration can be inward or outward depending on the local disk properties but, in general, only planets more massive than several M⊕ can migrate outward. Here we propose that an embryo's migration history determines whether it becomes a hot super-Earth or the core of a giant planet. Systems of hot super-Earths (or mini-Neptunes) form when embryos migrate inward and pile up at the inner edge of the disk. Giant planet cores form when inward-migrating embryos become massive enough to switch direction and migrate outward. We present simulations of this process using a modified N-body code, starting from a swarm of planetary embryos. Systems of hot super-Earths form in resonant chains with the innermost planet at or interior to the disk inner edge. Resonant chains are disrupted by late dynamical instabilities triggered by the dispersal of the gaseous disk. Giant planet cores migrate outward toward zero-torque zones, which move inward and eventually disappear as the disk disperses. Giant planet cores migrate inward with these zones and are stranded at ~1-5 AU. Our model reproduces several properties of the observed extra-solar planet populations. The frequency of giant planet cores increases strongly when the mass in solids is increased, consistent with the observed giant exoplanet - stellar metallicity correlation. The frequency of hot super-Earths is not a function of stellar metallicity, also in agreement with observations. Our simulations can reproduce the broad characteristics of the observed super-Earth population.

California forests show early indications of both range shifts and local persistence under climate change

Treesearch

Josep M. Serra-Diaz; Janet Franklin; Whalen W. Dillon; Alexandra D. Syphard; Frank W. Davis; Ross K. Meentemeyer

2015-01-01

Aim Forest regeneration data provide an early signal of the persistence and migration of tree species, so we investigated whether species shifts due to climate change exhibit a common signal of response or whether changes vary by species. Location California Floristic Province, United...

Ecological carryover effects associated with partial migration in white perch (Morone americana) within the Hudson River Estuary

NASA Astrophysics Data System (ADS)

Gallagher, Brian K.; Piccoli, Philip M.; Secor, David H.

2018-01-01

Partial migration in complex life cycles allows environmental conditions experienced during one life-stage to interact with genetic thresholds and produce divergent spatial behaviors in the next stage. We evaluated partial migration over the entire life cycle of white perch, (Morone americana) within the Hudson River Estuary, combining otolith microchemistry, population demographics and environmental data analysis. Ecological carryover effects were used as a framework to test how environmental variation during the larval period influenced migration behaviors and growth characteristics in subsequent life-stages. Two annual cohorts of juveniles were classified based on whether they persisted in natal habitats (freshwater resident contingent) or dispersed into non-natal habitats (brackish water migratory contingent) as juveniles. The migratory contingent tended to hatch earlier and experience cooler temperatures as larvae, while the availability of zooplankton prey during the larval period appeared to influence growth dynamics before and after metamorphosis. Juvenile migration behaviors were reversible but usually persisted into adulthood. As juveniles, the consequences of partial migration on growth appeared to be modified by river flow, as demonstrated by the influence of a large storm event on feeding conditions in one of the study years. Migratory adults grew faster and attained larger maximum sizes, but may also experience higher rates of mortality. The interplay uncovered between life-stage transitions, conditional migration behaviors and habitat productivity throughout the life cycle shapes white perch population dynamics and will likely play an important role in responses to long-term environmental change.

Gender and Migration Background in Intergenerational Educational Mobility

ERIC Educational Resources Information Center

Schneebaum, Alyssa; Rumplmaier, Bernhard; Altzinger, Wilfried

2016-01-01

We employ 2011 European Union Statistics on Income and Living Conditions survey data for Austria to perform uni- and multivariate econometric analyses to study the role of gender and migration background (MB) in intergenerational educational mobility. We find that there is more persistence in the educational attainment of girls relative to their…

Magnolol Inhibits Human Glioblastoma Cell Migration by Regulating N-Cadherin.

PubMed

Cheng, Yu-Chen; Tsao, Min-Jen; Chiu, Chen-Yang; Kan, Po-Chieh; Chen, Ying

2018-06-01

Glioblastoma is a primary malignant brain tumor with a poor prognosis. An effective treatment for glioblastoma is needed. Magnolol is a natural compound from Magnolia officinalis suggested to have antiproliferative activity. The aim of this research was to investigate the anticancer effects of magnolol in glioma, with an emphasis on migration and the underlying mechanism. Magnolol decreased the expression of focal adhesion-related proteins and inhibited LN229 and U87MG glioma cell migration. The levels of phosphorylated myosin light chain (p-MLC), phosphorylated myosin light chain kinase and myosin phosphatase target subunit 1 were reduced in response to magnolol treatment. In addition, immunostaining and membrane fractionation showed that the distribution of N-cadherin at the glioma cell membrane was decreased by magnolol. In an orthotropic xenograft animal model, magnolol treatment not only inhibited tumor progression but also reduced p-MLC and N-cadherin protein expression. In conclusion, magnolol reduces cell migration, potentially through regulating focal adhesions and N-cadherin in glioma cells. Magnolol is a potential candidate for glioma treatment.

Phosphatidic acid inhibits ceramide 1-phosphate-stimulated macrophage migration.

PubMed

Ouro, Alberto; Arana, Lide; Rivera, Io-Guané; Ordoñez, Marta; Gomez-Larrauri, Ana; Presa, Natalia; Simón, Jorge; Trueba, Miguel; Gangoiti, Patricia; Bittman, Robert; Gomez-Muñoz, Antonio

2014-12-15

Ceramide 1-phosphate (C1P) was recently demonstrated to potently induce cell migration. This action could only be observed when C1P was applied exogenously to cells in culture, and was inhibited by pertussis toxin. However, the mechanisms involved in this process are poorly understood. In this work, we found that phosphatidic acid (PA), which is structurally related to C1P, displaced radiolabeled C1P from its membrane-binding site and inhibited C1P-stimulated macrophage migration. This effect was independent of the saturated fatty acid chain length or the presence of a double bond in each of the fatty acyl chains of PA. Treatment of RAW264.7 macrophages with exogenous phospholipase D (PLD), an enzyme that produces PA from membrane phospholipids, also inhibited C1P-stimulated cell migration. Likewise, PA or exogenous PLD inhibited C1P-stimulated extracellularly regulated kinases (ERK) 1 and 2 phosphorylation, leading to inhibition of cell migration. However, PA did not inhibit C1P-stimulated Akt phosphorylation. It is concluded that PA is a physiological regulator of C1P-stimulated macrophage migration. These actions of PA may have important implications in the control of pathophysiological functions that are regulated by C1P, including inflammation and various cellular processes associated with cell migration such as organogenesis or tumor metastasis. Copyright © 2014 Elsevier Inc. All rights reserved.

DNA compaction by poly (amido amine) dendrimers of ammonia cored and ethylene diamine cored

NASA Astrophysics Data System (ADS)

Qamhieh, K.; Al-Shawwa, J.

2017-06-01

The complexes build-up of DNA and soft particles poly amidoamine (PAMAM) dendrimers of ammonia cored of generations (G1-G6) and ethylenediamine cored of generations (G1-G10) have been studied, using a new theoretical model developed by Qamhieh and coworkers. The model describes the interaction between linear polyelectrolyte (LPE) chain and ion-penetrable spheres. Many factors affecting LPE/dendrimer complex have been investigated such as dendrimer generation, the Bjerrum length, salt concentration, and rigidity of the LPE chain represented by the persistence length. It is found that the wrapping chain length around dendrimer increases by increasing dendrimer`s generation, Bjerrum length, and salt concentration, while decreases by increasing the persistence length of the LPE chain. Also we can conclude that the wrapping length of LPE chain around ethylenediamine cored dendrimers is larger than its length around ammonia cored dendrimers.

Action-derived molecular dynamics simulations for the migration and coalescence of vacancies in graphene and carbon nanotubes.

PubMed

Lee, Alex Taekyung; Ryu, Byungki; Lee, In-Ho; Chang, K J

2014-03-19

We report the results of action-derived molecular dynamics simulations for the migration and coalescence processes of monovacancies in graphene and carbon nanotubes with different chiralities. In carbon nanotubes, the migration pathways and barriers of a monovacancy depend on the tube chirality, while there is no preferential pathway in graphene due to the lattice symmetry and the absence of the curvature effect. The probable pathway changes from the axial to circumferential direction as the chirality varies from armchair to zigzag. The chirality dependence is attributed to the preferential orientation of the reconstructed bond formed around each vacancy site. It is energetically more favourable for two monovacancies to coalesce into a divacancy via alternative movements rather than simultaneous movements. The energy barriers for coalescence are generally determined by the migration barrier for the monovacancy, although there are some variations due to interactions between two diffusing vacancies. In graphene and armchair nanotubes, two monovacancies prefer to migrate along different zigzag atomic chains rather than a single atomic chain connecting these vacancies. On the other hand, in zigzag tubes, the energy barrier for coalescence increases significantly unless monovacancies lie on the same circumference.

The downward occupational mobility of internationally educated nurses to domestic workers.

PubMed

Salami, Bukola; Nelson, Sioban

2014-06-01

Despite the fact that there is unmet demand for nurses in health services around the world, some nurses migrate to destination countries to work as domestic workers. According to the literature, these nurses experience contradictions in class mobility and are at increased risk of exploitation and abuse. This article presents a critical discussion of the migration of nurses as domestic workers using the concept of 'global care chain'. Although several scholars have used the concept of global care chains to illustrate south to north migration of domestic workers and nurses, there is a paucity of literature on the migration of nurses to destination countries as domestic workers. The migration of nurses to destination countries as domestic workers involves the extraction of reproductive and skilled care labor without adequate compensatory mechanisms to such skilled nurses. Using the case of the Canadian Live-in Caregiver Program, the study illustrates how the global movement of internationally educated nurses as migrant domestic workers reinforces inequities that are structured along the power gradient of gender, class, race, nationality, and ethnicity, especially within an era of global nursing shortage. © 2013 John Wiley & Sons Ltd.

Selective deuteration for molecular insights into the digestion of medium chain triglycerides.

PubMed

Salentinig, Stefan; Yepuri, Nageshwar Rao; Hawley, Adrian; Boyd, Ben J; Gilbert, Elliot; Darwish, Tamim A

2015-09-01

Medium chain triglycerides (MCTs) are a unique form of dietary fat that have a wide range of health benefits. They are molecules with a glycerol backbone esterified with medium chain (6-12 carbon atoms) fatty acids on the two outer (sn-1 and sn-3) and the middle (sn-2) positions. During lipid digestion in the gastrointestinal tract, pancreatic lipase stereoselectively hydrolyses the ester bonds of these triglycerides on the sn-1 and sn-3 positions resulting in sn-2 monoglyceride and fatty acids as major products. However, the sn-2 monoglycerides are thermodynamically less stable than their sn-1/3 counterparts. Isomerization or fatty acid migration from the sn-2 monoglyceride to sn-1/3 monoglyceride may occur spontaneously and would lead to glycerol and fatty acid as final products. Here, tricaprin (C10) with selectively deuterated fatty acid chains was used for the first time to monitor chain migration and the stereoselectivity of the pancreatic lipase-catalyzed hydrolysis of ester bonds. The intermediate and final digestion products were studied using NMR and mass spectrometry under biologically relevant conditions. The hydrolysis of the sn-2 monocaprin to glycerol and capric acid did not occur within biologically relevant timescales and fatty acid migration occurs only in limited amounts as a result of the presence of undigested diglyceride species over long periods of time in the digestion medium. The slow kinetics for the exchange of the sn-2 fatty acid chain and the stereoselectivity of pancreatic lipase on MCTs is relevant for industrial processes that involve enzymatic interesterification and the production of high-value products such as specific structured triacylglycerols, confectionery fats and nutritional products. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Modeling Caribou Movements: Seasonal Ranges and Migration Routes of the Central Arctic Herd

PubMed Central

Nicholson, Kerry L.; Arthur, Stephen M.; Horne, Jon S.; Garton, Edward O.; Del Vecchio, Patricia A.

2016-01-01

Migration is an important component of the life history of many animals, but persistence of large-scale terrestrial migrations is being challenged by environmental changes that fragment habitats and create obstacles to animal movements. In northern Alaska, the Central Arctic herd (CAH) of barren-ground caribou (Rangifer tarandus granti) is known to migrate over large distances, but the herd’s seasonal distributions and migratory movements are not well documented. From 2003–2007, we used GPS radio-collars to determine seasonal ranges and migration routes of 54 female caribou from the CAH. We calculated Brownian bridges to model fall and spring migrations for each year and used the mean of these over all 4 years to identify areas that were used repeatedly. Annual estimates of sizes of seasonal ranges determined by 90% fixed kernel utilization distributions were similar between summer and winter (X̅ = 27,929 SE = 1,064 and X̅ = 26,585 SE = 4912 km2, respectively). Overlap between consecutive summer and winter ranges varied from 3.3–18.3%. Percent overlap between summer ranges used during consecutive years (X̅ = 62.4% SE = 3.7%) was higher than for winter ranges (X̅ = 42.8% SE = 5.9%). Caribou used multiple migration routes each year, but some areas were used by caribou during all years, suggesting that these areas should be managed to allow for continued utilization by caribou. Restoring migration routes after they have been disturbed or fragmented is challenging. However, prior knowledge of movements and threats may facilitate maintenance of migratory paths and seasonal ranges necessary for long-term persistence of migratory species. PMID:27045587

CHANGES IN HIPPOCAMPAL SPINE DENSITY AND PROTEIN KINASE C ISOFORMS FOLLOWING DEVELOPMENTAL EXPOSURE TO A MIXTURE OF PERSISTENT CHEMICALS.

EPA Science Inventory

Polychlorinated biphenyls (PCBs) offer a unique model to understand the major issues related to complex environmental mixtures of persistent chemicals. These pollutants are ubiquitous, persistent, bioaccumulate in human body through the food chain, and exist as mixtures of severa...

Kinetics of interior loop formation in semiflexible chains.

PubMed

Hyeon, Changbong; Thirumalai, D

2006-03-14

Loop formation between monomers in the interior of semiflexible chains describes elementary events in biomolecular folding and DNA bending. We calculate analytically the interior distance distribution function for semiflexible chains using a mean field approach. Using the potential of mean force derived from the distance distribution function we present a simple expression for the kinetics of interior looping by adopting Kramers theory. For the parameters, that are appropriate for DNA, the theoretical predictions in comparison with the case are in excellent agreement with explicit Brownian dynamics simulations of wormlike chain (WLC) model. The interior looping times (tauIC) can be greatly altered in the cases when the stiffness of the loop differs from that of the dangling ends. If the dangling end is stiffer than the loop then tauIC increases for the case of the WLC with uniform persistence length. In contrast, attachment of flexible dangling ends enhances rate of interior loop formation. The theory also shows that if the monomers are charged and interact via screened Coulomb potential then both the cyclization (tauc) and interior looping (tauIC) times greatly increase at low ionic concentration. Because both tauc and tauIC are determined essentially by the effective persistence length [lp(R)] we computed lp(R) by varying the range of the repulsive interaction between the monomers. For short range interactions lp(R) nearly coincides with the bare persistence length which is determined largely by the backbone chain connectivity. This finding rationalizes the efficacy of describing a number of experimental observations (response of biopolymers to force and cyclization kinetics) in biomolecules using WLC model with an effective persistence length.

Increasing the persistence of a heterogeneous behavior chain: Studies of extinction in a rat model of search behavior of working dogs

PubMed Central

Thrailkill, Eric A.; Kacelnik, Alex; Porritt, Fay; Bouton, Mark E.

2016-01-01

Dogs trained to search for contraband perform a chain of behavior in which they first search for a target and then make a separate response that indicates to the trainer that they have found one. The dogs often conduct multiple searches without encountering a target and receiving the reinforcer (i.e., no contraband is present). Understanding extinction (i.e., the decline in work rate when reinforcers are no longer encountered) may assist in training dogs to work in conditions where targets are rare. We therefore trained rats on a search-target behavior chain modeled on the search behavior of working dogs. A discriminative stimulus signaled that a search response (e.g., chain pull) led to a second stimulus that set the occasion for a target response (e.g., lever press) that was reinforced by a food pellet. In Experiment 1 training with longer search durations and intermittent (partial) reinforcement of searching (i.e. some trials had no target present) both led to more persistent search responding in extinction. The loss of search behavior in extinction was primarily dependent on the number of non-reinforced searches rather than time searching without reinforcement. In Experiments 2 and 3, delivery of non-contingent reinforcers during extinction increased search persistence provided they had also been presented during training. Thus, results with rats suggest that the persistence of working dog performance (or chained behavior generally) may be improved by training with partial reinforcement of searching and non-contingent reinforcement during both training and work (extinction). PMID:27306694

Softening of the stiffness of bottle-brush polymers by mutual interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolisetty, S.; Airaud, C.; Rosenfeldt, S.

2007-04-15

We study bottle-brush macromolecules in a good solvent by small-angle neutron scattering (SANS), static light scattering (SLS), and dynamic light scattering (DLS). These polymers consist of a linear backbone to which long side chains are chemically grafted. The backbone contains about 1600 monomer units (weight average) and every second monomer unit carries side chains with approximately 60 monomer units. The SLS and SANS data extrapolated to infinite dilution lead to the form factor of the polymer that can be described in terms of a wormlike chain with a contour length of 380 nm and a persistence length of 17.5 nm.more » An analysis of the DLS data confirms these model parameters. The scattering intensities taken at finite concentration can be modeled using the polymer reference interaction site model. It reveals a softening of the bottle-brush polymers caused by their mutual interaction. We demonstrate that the persistence decreases from 17.5 nm down to 5 nm upon increasing the concentration from dilute solution to the highest concentration (40.59 g/l) under consideration. The observed softening of the chains is comparable to the theoretically predicted decrease of the electrostatic persistence length of linear polyelectrolyte chains at finite concentrations.« less

Facilitation among plants in alpine environments in the face of climate change.

PubMed

Anthelme, Fabien; Cavieres, Lohengrin A; Dangles, Olivier

2014-01-01

While there is a large consensus that plant-plant interactions are a crucial component of the response of plant communities to the effects of climate change, available data remain scarce, particularly in alpine systems. This represents an important obstacle to making consistent predictions about the future of plant communities. Here, we review current knowledge on the effects of climate change on facilitation among alpine plant communities and propose directions for future research. In established alpine communities, while warming seemingly generates a net facilitation release, earlier snowmelt may increase facilitation. Some nurse plants are able to buffer microenvironmental changes in the long term and may ensure the persistence of other alpine plants through local migration events. For communities migrating to higher elevations, facilitation should play an important role in their reorganization because of the harsher environmental conditions. In particular, the absence of efficient nurse plants might slow down upward migration, possibly generating chains of extinction. Facilitation-climate change relationships are expected to shift along latitudinal gradients because (1) the magnitude of warming is predicted to vary along these gradients, and (2) alpine environments are significantly different at low vs. high latitudes. Data on these expected patterns are preliminary and thus need to be tested with further studies on facilitation among plants in alpine environments that have thus far not been considered. From a methodological standpoint, future studies will benefit from the spatial representation of the microclimatic environment of plants to predict their response to climate change. Moreover, the acquisition of long-term data on the dynamics of plant-plant interactions, either through permanent plots or chronosequences of glacial recession, may represent powerful approaches to clarify the relationship between plant interactions and climate change.

Facilitation among plants in alpine environments in the face of climate change

PubMed Central

Anthelme, Fabien; Cavieres, Lohengrin A.; Dangles, Olivier

2014-01-01

While there is a large consensus that plant–plant interactions are a crucial component of the response of plant communities to the effects of climate change, available data remain scarce, particularly in alpine systems. This represents an important obstacle to making consistent predictions about the future of plant communities. Here, we review current knowledge on the effects of climate change on facilitation among alpine plant communities and propose directions for future research. In established alpine communities, while warming seemingly generates a net facilitation release, earlier snowmelt may increase facilitation. Some nurse plants are able to buffer microenvironmental changes in the long term and may ensure the persistence of other alpine plants through local migration events. For communities migrating to higher elevations, facilitation should play an important role in their reorganization because of the harsher environmental conditions. In particular, the absence of efficient nurse plants might slow down upward migration, possibly generating chains of extinction. Facilitation–climate change relationships are expected to shift along latitudinal gradients because (1) the magnitude of warming is predicted to vary along these gradients, and (2) alpine environments are significantly different at low vs. high latitudes. Data on these expected patterns are preliminary and thus need to be tested with further studies on facilitation among plants in alpine environments that have thus far not been considered. From a methodological standpoint, future studies will benefit from the spatial representation of the microclimatic environment of plants to predict their response to climate change. Moreover, the acquisition of long-term data on the dynamics of plant–plant interactions, either through permanent plots or chronosequences of glacial recession, may represent powerful approaches to clarify the relationship between plant interactions and climate change. PMID:25161660

Airway structural alterations selectively associated with severe asthma.

PubMed

Benayoun, Laurent; Druilhe, Anne; Dombret, Marie-Christine; Aubier, Michel; Pretolani, Marina

2003-05-15

To identify airway pathologic abnormalities selectively associated with severe asthma, we examined 10 control subjects, 10 patients with intermittent asthma, 15 patients with mild-to-moderate persistent asthma, 15 patients with severe persistent asthma, and 10 patients with chronic obstructive pulmonary disease. Bronchial biopsies were assessed for epithelial integrity; subepithelial basement membrane (SBM) thickness; collagen type III deposition; eosinophil, neutrophil, and fibroblast numbers; mucous gland and airway smooth muscle (ASM) areas; SBM-ASM distance; ASM hypertrophy (increased cell size); and the expression of the contractile proteins alpha-actin, smooth muscle myosin heavy-chain isoforms, myosin light-chain kinase, and the phosphorylated form of the regulatory light chain of myosin. Neither mucosal eosinophilia nor neutrophilia, epithelial damage, or SBM thickness reflected asthma severity. In contrast, higher numbers of fibroblasts (p < 0.001), an increase in collagen type III deposition (p < 0.020), larger mucous gland (p < 0.040) and ASM (p < 0.001) areas, augmented ASM cell size (p < 0.001), and myosin light-chain kinase expression (p < 0.005) distinguished patients with severe persistent asthma from patients with milder disease or with chronic obstructive pulmonary disease. Stepwise multivariate regression analysis established that fibroblast numbers and ASM cell size were negatively associated with prebronchodilator and postbronchodilator FEV1 values in patients with asthma. We conclude that fibroblast accumulation and ASM hypertrophy in proximal airways are selective determinants of severe persistent asthma.

Time to Evolve? Potential Evolutionary Responses of Fraser River Sockeye Salmon to Climate Change and Effects on Persistence

PubMed Central

Reed, Thomas E.; Schindler, Daniel E.; Hague, Merran J.; Patterson, David A.; Meir, Eli; Waples, Robin S.; Hinch, Scott G.

2011-01-01

Evolutionary adaptation affects demographic resilience to climate change but few studies have attempted to project changes in selective pressures or quantify impacts of trait responses on population dynamics and extinction risk. We used a novel individual-based model to explore potential evolutionary changes in migration timing and the consequences for population persistence in sockeye salmon Oncorhynchus nerka in the Fraser River, Canada, under scenarios of future climate warming. Adult sockeye salmon are highly sensitive to increases in water temperature during their arduous upriver migration, raising concerns about the fate of these ecologically, culturally, and commercially important fish in a warmer future. Our results suggest that evolution of upriver migration timing could allow these salmon to avoid increasingly frequent stressful temperatures, with the odds of population persistence increasing in proportion to the trait heritability and phenotypic variance. With a simulated 2°C increase in average summer river temperatures by 2100, adult migration timing from the ocean to the river advanced by ∼10 days when the heritability was 0.5, while the risk of quasi-extinction was only 17% of that faced by populations with zero evolutionary potential (i.e., heritability fixed at zero). The rates of evolution required to maintain persistence under simulated scenarios of moderate to rapid warming are plausible based on estimated heritabilities and rates of microevolution of timing traits in salmon and related species, although further empirical work is required to assess potential genetic and ecophysiological constraints on phenological adaptation. These results highlight the benefits to salmon management of maintaining evolutionary potential within populations, in addition to conserving key habitats and minimizing additional stressors where possible, as a means to build resilience to ongoing climate change. More generally, they demonstrate the importance and feasibility of considering evolutionary processes, in addition to ecology and demography, when projecting population responses to environmental change. PMID:21738573

Global Migration Dynamics Underlie Evolution and Persistence of Human Influenza A (H3N2)

PubMed Central

Bedford, Trevor; Cobey, Sarah; Beerli, Peter; Pascual, Mercedes

2010-01-01

The global migration patterns of influenza viruses have profound implications for the evolutionary and epidemiological dynamics of the disease. We developed a novel approach to reconstruct the genetic history of human influenza A (H3N2) collected worldwide over 1998 to 2009 and used it to infer the global network of influenza transmission. Consistent with previous models, we find that China and Southeast Asia lie at the center of this global network. However, we also find that strains of influenza circulate outside of Asia for multiple seasons, persisting through dynamic migration between northern and southern regions. The USA acts as the primary hub of temperate transmission and, together with China and Southeast Asia, forms the trunk of influenza's evolutionary tree. These findings suggest that antiviral use outside of China and Southeast Asia may lead to the evolution of long-term local and potentially global antiviral resistance. Our results might also aid the design of surveillance efforts and of vaccines better tailored to different geographic regions. PMID:20523898

Efficiency of photochemical stages of photosynthesis in purple bacteria (a critical survey).

PubMed

Borisov, A Yu

2014-03-01

Based on currently available data, the energy transfer efficiency in the successive photophysical and photochemical stages has been analyzed for purple bacteria. This analysis covers the stages starting from migration of the light-induced electronic excitations from the bulk antenna pigments to the reaction centers up to irreversible stage of the electron transport along the transmembrane chain of cofactors-carriers. Some natural factors are revealed that significantly increase the rates of efficient processes in these stages. The influence on their efficiency by the "bottleneck" in the energy migration chain is established. The overall quantum yield of photosynthesis in these stages is determined.

Analysis of charge transport in gels containing polyoxometallates using methods of different sensitivity to migration.

PubMed

Caban, Karolina; Lewera, Adam; Zukowska, Grazyna Z; Kulesza, Pawel J; Stojek, Zbigniew; Jeffrey, Kenneth R

2006-08-04

Two methods have been used for examination of transport of charge in gels soaked with DMF and containing dissolved polyoxometallates. The first method is based on the analysis of both Cottrellian and steady-state currents and therefore is capable of giving the concentration of the electroactive redox centres and their transport (diffusion-type) coefficient. The second method provides the real diffusion coefficients, i.e. transport coefficients free of migrational influence, for both the substrate and the product of the electrode reaction. Several gels based on poly(methyl methacrylate), with charged (addition of 1-acrylamido-2-methyl-2-propanesulphonic acid to the polymerization mixture) and uncharged chains, have been used in the investigation. The ratio obtained for the diffusion coefficient (second method) and transport coefficient (first method) was smaller for the gels containing charged polymer chains than for the gels with uncharged chains. In part these changes could be explained by the contribution of migration to the transport of polyoxomatallates in the gels. However, the impact of the changes in the polymer-channel capacity at the electrode surface while the electrode process proceeds was also considered. These structural changes should affect differently the methods based on different time domains.

Nonmuscle myosin IIA and IIB differentially contribute to intrinsic and directed migration of human embryonic lung fibroblasts.

PubMed

Kuragano, Masahiro; Murakami, Yota; Takahashi, Masayuki

2018-03-25

Nonmuscle myosin II (NMII) plays an essential role in directional cell migration. In this study, we investigated the roles of NMII isoforms (NMIIA and NMIIB) in the migration of human embryonic lung fibroblasts, which exhibit directionally persistent migration in an intrinsic manner. NMIIA-knockdown (KD) cells migrated unsteadily, but their direction of migration was approximately maintained. By contrast, NMIIB-KD cells occasionally reversed their direction of migration. Lamellipodium-like protrusions formed in the posterior region of NMIIB-KD cells prior to reversal of the migration direction. Moreover, NMIIB KD led to elongation of the posterior region in migrating cells, probably due to the lack of load-bearing stress fibers in this area. These results suggest that NMIIA plays a role in steering migration by maintaining stable protrusions in the anterior region, whereas NMIIB plays a role in maintenance of front-rear polarity by preventing aberrant protrusion formation in the posterior region. These distinct functions of NMIIA and NMIIB might promote intrinsic and directed migration of normal human fibroblasts. Copyright © 2018 Elsevier Inc. All rights reserved.

The role of long distance migration in the rural renaissance, in gentrification, and in growth of the Sunbelt.

PubMed

Serow, W J

1980-01-01

The author "has examined trends in interstate migration during the 1970s for the four regions of the United States and, in particular, explored the relationship of this migration with nonmetropolitan expansion and the return to the city movement. The data show that the former trend is a very real one which has persisted throughout the decade and that population growth through interstate migration in nonmetropolitan America is, on balance, the result of nonblacks moving to the South from elsewhere in the nation. Except in the West, central cities continue to experience substantial losses of population through interstate migration. Interstate migration continues to be directed toward suburbs, and is especially vigorous in the West." Data are from the March 1975 and March 1979 Current Population Surveys. excerpt

Divergent migration within lake sturgeon (Acipenser fulvescens) populations: Multiple distinct patterns exist across an unrestricted migration corridor

USGS Publications Warehouse

Kessel, Steven T.; Hondorp, Darryl W.; Holbrook, Christopher; Boase, James C.; Chiotti, Justin A.; Thomas, Michael V.; Wills, Todd C.; Roseman, Edward; Drouin, Richard; Krueger, Charles C.

2018-01-01

Population structure, distribution, abundance, and dispersal arguably underpin the entire field of animal ecology, with consequences for regional species persistence, and provision of ecosystem services. Divergent migration behaviours among individuals or among populations is an important aspect of the ecology of highly-mobile animals, allowing populations to exploit spatially- or temporally-distributed food and space resources.This study investigated the spatial ecology of lake sturgeon (Acipenser fulvescens) within the barrier free Huron-Erie Corridor (HEC), which connects Lake Huron and Lake Erie of the North American Laurentian Great Lakes.Over six years (2011 – 2016), movements of 268 lake sturgeon in the HEC were continuously monitored across the Great Lakes using acoustic telemetry (10 yr battery life acoustic transmitters). Five distinct migration behaviours were identified with hierarchical cluster analysis, based on the phenology and duration of river and lake use.Lake sturgeon in the HEC were found to contain a high level of intraspecific divergent migration, including partial migration with the existence of residents. Specific behaviours included year-round river residency and multiple lake-migrant behaviours that involved movements between lakes and rivers. Over 85% of individuals were assign to migration behaviours as movements were consistently repeated over the study, which suggested migration behaviours were consistent and persistent in lake sturgeon. Differential use of specific rivers or lakes by acoustic-tagged lake sturgeon further subdivided individuals into 14 “contingents” (spatiotemporally segregated subgroups).Contingents associated with one river (Detroit or St. Clair) were rarely detected in the other river, which confirmed that lake sturgeon in the Detroit and St. Clair represent two semi-independent populations that could require separate management consideration for their conservation. The distribution of migration behaviours did not vary between populations, sexes, body size, or among release locations, which indicated that intrapopulation variability in migratory behaviour is a general feature of the spatial ecology of lake sturgeon in un-fragmented landscapes.

Transnational nurse migration: future directions for medical anthropological research.

PubMed

Prescott, Megan; Nichter, Mark

2014-04-01

Transnational nurse migration is a serious global health issue in which inequitably distributed shortages hinder health and development goals. This article selectively reviews the literature on nurse migration that has emerged from nursing, health planning, and the social sciences and offers productive directions for future anthropological research. The literature on global nurse migration has largely focused on push/pull economic logic and the concept of brain drain to understand the causes and effects of nurse migration. These concepts obscure political-economic, historical, and cultural factors that pattern nurse migration and influence the complex effects of nurse migration. Global nurse care chain analysis helps illuminate the numerous nodes in the production and migration of nurses, and management of this transnational process. Examples are provided from the Philippines and India to illustrate ways in which this analysis may be deepened, refined and rendered more critical by anthropological research. Copyright © 2014 Elsevier Ltd. All rights reserved.

Increasing the persistence of a heterogeneous behavior chain: Studies of extinction in a rat model of search behavior of working dogs.

PubMed

Thrailkill, Eric A; Kacelnik, Alex; Porritt, Fay; Bouton, Mark E

2016-08-01

Dogs trained to search for contraband perform a chain of behavior in which they first search for a target and then make a separate response that indicates to the trainer that they have found one. The dogs often conduct multiple searches without encountering a target and receiving the reinforcer (i.e., no contraband is present). Understanding extinction (i.e., the decline in work rate when reinforcers are no longer encountered) may assist in training dogs to work in conditions where targets are rare. We therefore trained rats on a search-target behavior chain modeled on the search behavior of working dogs. A discriminative stimulus signaled that a search response (e.g., chain pull) led to a second stimulus that set the occasion for a target response (e.g., lever press) that was reinforced by a food pellet. In Experiment 1 training with longer search durations and intermittent (partial) reinforcement of searching (i.e. some trials had no target present) both led to more persistent search responding in extinction. The loss of search behavior in extinction was primarily dependent on the number of non-reinforced searches rather than time searching without reinforcement. In Experiments 2 and 3, delivery of non-contingent reinforcers during extinction increased search persistence provided they had also been presented during training. Thus, results with rats suggest that the persistence of working dog performance (or chained behavior generally) may be improved by training with partial reinforcement of searching and non-contingent reinforcement during both training and work (extinction). Copyright © 2016 Elsevier B.V. All rights reserved.

Contact guidance is cell cycle-dependent.

PubMed

Pourfarhangi, Kamyar Esmaeili; De La Hoz, Edgar Cardenas; Cohen, Andrew R; Gligorijevic, Bojana

2018-09-01

Cancer cell migration is essential for metastasis, during which cancer cells move through the tumor and reach the blood vessels. In vivo , cancer cells are exposed to contact guidance and chemotactic cues. Depending on the strength of such cues, cells will migrate in a random or directed manner. While similar cues may also stimulate cell proliferation, it is not clear whether cell cycle progression affects migration of cancer cells and whether this effect is different in random versus directed migration. In this study, we tested the effect of cell cycle progression on contact guided migration in 2D and 3D environments, in the breast carcinoma cell line, FUCCI-MDA-MB-231. The results were quantified from live cell microscopy images using the open source lineage editing and validation image analysis tools (LEVER). In 2D, cells were placed inside 10 μ m-wide microchannels to stimulate contact guidance, with or without an additional chemotactic gradient of the soluble epidermal growth factor. In 3D, contact guidance was modeled by aligned collagen fibers. In both 2D and 3D, contact guidance was cell cycle-dependent, while the addition of the chemo-attractant gradient in 2D increased cell velocity and persistence in directionally migrating cells, regardless of their cell cycle phases. In both 2D and 3D contact guidance, cells in the G1 phase of the cell cycle outperformed cells in the S/G2 phase in terms of migration persistence and instantaneous velocity. These data suggest that in the presence of contact guidance cues in vivo , breast carcinoma cells in the G1 phase of the cell cycle may be more efficient in reaching the neighboring vasculature.

Infrared microscopic imaging of cutaneous wound healing: lipid conformation in the migrating epithelial tongue

NASA Astrophysics Data System (ADS)

Yu, Guo; Stojadinovic, Olivera; Tomic-Canic, Marjana; Flach, Carol R.; Mendelsohn, Richard

2012-09-01

Infrared microscopic imaging has been utilized to analyze for the first time the spatial distribution of lipid structure in an ex vivo human organ culture skin wound healing model. Infrared images were collected at zero, two, four, and six days following wounding. Analysis of lipid infrared spectral properties revealed the presence of a lipid class with disordered chains within and in the vicinity of the migrating epithelial tongue. The presence of lipid ester C=O bands colocalized with the disordered chains provided evidence for the presence of carbonyl-containing lipid species. Gene array data complemented the biophysical studies and provided a biological rationale for the generation of the disordered chain species. This is the first clear observation, to our knowledge, of disordered lipid involvement in cutaneous wound healing. Several possibilities are discussed for the biological relevance of these observations.

Immunomodulation by Persistent Organic Pollutants

EPA Science Inventory

Persistent organic pollutants (POPs) are widely distnbuted in the environment, are resistant to degradation, and increase in concentration (biomagnify) in the food chain. Concentrations in apical predators may be tens to hundreds of times greater than concentrations in their pref...

Raf-1 levels determine the migration rate of primary endometrial stromal cells of patients with endometriosis

PubMed Central

Yotova, Iveta; Quan, Ping; Gaba, Aulona; Leditznig, Nadja; Pateisky, Petra; Kurz, Christine; Tschugguel, Walter

2012-01-01

Endometriosis is a disease characterized by the localization of endometrial tissue outside the uterine cavity. The differences observed in migration of human endometrial stromal cells (hESC) obtained from patients with endometriosis versus healthy controls were proposed to correlate with the abnormal activation of Raf-1/ROCKII signalling pathway. To evaluate the mechanism by which Raf-1 regulates cytoskeleton reorganization and motility, we used primary eutopic (Eu-, n = 16) and ectopic (Ec-, n = 8; isolated from ovarian cysts) hESC of patients with endometriosis and endometriosis-free controls (Co-hESC, n = 14). Raf-1 siRNA knockdown in Co- and Eu-hESC resulted in contraction and decreased migration versus siRNA controls. This phenotype was reversed following the re-expression of Raf-1 in these cells. Lowest Raf-1 levels in Ec-hESC were associated with hyperactivated ROCKII and ezrin/radixin/moesin (E/R/M), impaired migration and a contracted phenotype similar to Raf-1 knockdown in Co- and Eu-hESC. We further show that the mechanism by which Raf-1 mediates migration in hESC includes direct myosin light chain phosphatase (MYPT1) phosphorylation and regulation of the levels of E/R/M, paxillin, MYPT1 and myosin light chain (MLC) phosphorylation indirectly via the hyperactivation of ROCKII kinase. Furthermore, we suggest that in contrast to Co-and Eu-hESC, where the cellular Raf-1 levels regulate the rate of migration, the low cellular Raf-1 content in Ec-hESC, might ensure their restricted migration by preserving the contracted cellular phenotype. In conclusion, our findings suggest that cellular levels of Raf-1 adjust the threshold of hESC migration in endometriosis. PMID:22225925

The continuous and persistent periodical growth induced by substrate accommodation in In2O3 nanostructure chains and their photoluminescence properties

NASA Astrophysics Data System (ADS)

Shariati, Mohsen

2015-03-01

The growth of pyramidal and triangular beaded In2O3 nanocrystal chains by using oxygen-assisted thermal evaporation, substrate accommodation and condensation method has been articulated. Self-assembled In2O3 nanocrystal chains have been synthesized by the vapor-solid (VS) and vapor-liquid-solid (VLS) growth mechanism and also through controlling the kinetics factors (saturation ratio). A periodical one-dimensional (1-D) and persistent (0-D) growth was proposed to explain the formation of lateral nanostructures, and this formation aspect was ascribed to the alternate 1-D and 0-D growth. Preparing the needed growth factor, the In2O3 nanocrystal chains extended to several micrometers. The growth mechanism analysis was useful to realize the relation between the kinetics factors and the complex nanostructure. The morphology and size of nanocrystals intensively were changed by oxygen concentration and led to interesting photoluminescence property.

PERSISTENT, BIOACCUMULATIVE, AND TOXIC POLLUTANTS (PBTS)

EPA Science Inventory

Article describes the class of compounds known as persistent, bioaccumulative, and toxic pollutants (known as PBTs), including the mechanisms responsible for ability to build up the food chain and for causing adverse health effects and ecosystem damage. Exposure to numerous PBTs ...

Ultrafast exciton migration in an HJ-aggregate: Potential surfaces and quantum dynamics

NASA Astrophysics Data System (ADS)

Binder, Robert; Polkehn, Matthias; Ma, Tianji; Burghardt, Irene

2017-01-01

Quantum dynamical and electronic structure calculations are combined to investigate the mechanism of exciton migration in an oligothiophene HJ aggregate, i.e., a combination of oligomer chains (J-type aggregates) and stacked aggregates of such chains (H-type aggregates). To this end, a Frenkel exciton model is parametrized by a recently introduced procedure [Binder et al., J. Chem. Phys. 141, 014101 (2014)] which uses oligomer excited-state calculations to perform an exact, point-wise mapping of coupled potential energy surfaces to an effective Frenkel model. Based upon this parametrization, the Multi-Layer Multi-Configuration Time-Dependent Hartree (ML-MCTDH) method is employed to investigate ultrafast dynamics of exciton transfer in a small, asymmetric HJ aggregate model composed of 30 sites and 30 active modes. For a partially delocalized initial condition, it is shown that a torsional defect confines the trapped initial exciton, and planarization induces an ultrafast resonant transition between an HJ-aggregated segment and a covalently bound "dangling chain" end. This model is a minimal realization of experimentally investigated mixed systems exhibiting ultrafast exciton transfer between aggregated, highly planarized chains and neighboring disordered segments.

Invasion and Persistence of Infectious Agents in Fragmented Host Populations

PubMed Central

Jesse, Marieke; Mazzucco, Rupert; Dieckmann, Ulf; Heesterbeek, Hans; Metz, Johan A. J.

2011-01-01

One of the important questions in understanding infectious diseases and their prevention and control is how infectious agents can invade and become endemic in a host population. A ubiquitous feature of natural populations is that they are spatially fragmented, resulting in relatively homogeneous local populations inhabiting patches connected by the migration of hosts. Such fragmented population structures are studied extensively with metapopulation models. Being able to define and calculate an indicator for the success of invasion and persistence of an infectious agent is essential for obtaining general qualitative insights into infection dynamics, for the comparison of prevention and control scenarios, and for quantitative insights into specific systems. For homogeneous populations, the basic reproduction ratio plays this role. For metapopulations, defining such an ‘invasion indicator’ is not straightforward. Some indicators have been defined for specific situations, e.g., the household reproduction number . However, these existing indicators often fail to account for host demography and especially host migration. Here we show how to calculate a more broadly applicable indicator for the invasion and persistence of infectious agents in a host metapopulation of equally connected patches, for a wide range of possible epidemiological models. A strong feature of our method is that it explicitly accounts for host demography and host migration. Using a simple compartmental system as an example, we illustrate how can be calculated and expressed in terms of the key determinants of epidemiological dynamics. PMID:21980339

Persistence of the single lineage of transmissible 'social cancer' in an asexual ant.

PubMed

Dobata, S; Sasaki, T; Mori, H; Hasegawa, E; Shimada, M; Tsuji, K

2011-02-01

How cooperation can arise and persist, given the threat of cheating phenotypes, is a central problem in evolutionary biology, but the actual significance of cheating in natural populations is still poorly understood. Theories of social evolution predict that cheater lineages are evolutionarily short-lived. However, an exception comes from obligate socially parasitic species, some of which thought to have arisen as cheaters within cooperator colonies and then diverged through sympatric speciation. This process requires the cheater lineage to persist by avoiding rapid extinction that would result from the fact that the cheaters inflict fitness cost on their host. We examined whether this prerequisite is fulfilled, by estimating the persistence time of cheaters in a field population of the parthenogenetic ant Pristomyrmex punctatus. Population genetic analysis found that the cheaters belong to one monophyletic lineage which we infer has persisted for 200-9200 generations. We show that the cheaters migrate and are thus horizontally transmitted between colonies, a trait allowing the lineage to avoid rapid extinction with its host colony. Although horizontal transmission of disruptive cheaters has the potential to induce extinction of the entire population, such collapse is likely averted when there is spatially restricted migration in a structured population, a scenario that matches the observed isolation by distance pattern that we found. We compare our result with other examples of disruptive and horizontally transmissible cheater lineages in nature. © 2010 Blackwell Publishing Ltd.

Complex coacervation in charge complementary biopolymers: Electrostatic versus surface patch binding.

PubMed

Pathak, Jyotsana; Priyadarshini, Eepsita; Rawat, Kamla; Bohidar, H B

2017-12-01

In this review, a number of systems are described to demonstrate the effect of polyelectrolyte chain stiffness (persistence length) on the coacervation phenomena, after we briefly review the field. We consider two specific types of complexation/coacervation: in the first type, DNA is used as a fixed substrate binding to flexible polyions such as gelatin A, bovine serum albumin and chitosan (large persistence length polyelectrolyte binding to low persistence length biopolymer), and in the second case, different substrates such as gelatin A, bovine serum albumin, and chitosan were made to bind to a polyion gelatin B (low persistence length substrate binding to comparable persistence length polyion). Polyelectrolyte chain flexibility was found to have remarkable effect on the polyelectrolyte-protein complex coacervation. The competitive interplay of electrostatic versus surface patch binding (SPB) leading to associative interaction followed by complex coacervation between these biopolymers is elucidated. We modelled the SPB interaction in terms of linear combination of attractive and repulsive Coulombic forces with respect to the solution ionic strength. The aforesaid interactions were established via a universal phase diagram, considering the persistence length of polyion as the sole independent variable. Copyright © 2017 Elsevier B.V. All rights reserved.

Heavy metal loss from agricultural watershed to aquatic system: A scientometrics review.

PubMed

Ouyang, Wei; Wang, Yidi; Lin, Chunye; He, Mengchang; Hao, Fanghua; Liu, Hongbin; Zhu, Weihong

2018-05-08

Heavy metal pollution in soil and aquatic environments has attracted widespread attention due to its persistence, accumulation in the food chain and negative effects on ecological and human health. However, analyses of the watershed-scale migration mechanisms of heavy metal loss from agricultural systems to aquatic systems have seldom been studied systematically. Therefore, this review summarizes the available data in the literature (2003-2017) using CiteSpace software to provide insights into the specific characteristics of heavy metal loss from agricultural watersheds to aquatic systems and consequently shows global development trends that scientists can use for establishing future research directions. As opposed to traditional review articles by experts, this study provides a new method for quantitatively visualizing information about the development of this field over the past decade. The results indicate that among all countries, China was the most active contributor with the most publications and cooperated the most with other countries. In addition, most articles were classified as environmental sciences and ecology, environmental sciences or agricultural studies. Furthermore, based on a keyword co-word analysis by CiteSpace, it was concluded that erosion-linked transport of heavy metals was the most influencing factor of mitigation mechanism. Additionally, the migration characteristics of heavy metals in farmland soils and water under the complex environment impacts of various factors such as climate change and land-use changes were of great significance that future studies should focus on. Copyright © 2018 Elsevier B.V. All rights reserved.

Prevention of polydimethylsiloxane microsphere migration using a mussel-inspired polydopamine coating for potential application in injection therapy.

PubMed

Chung, Eun-Jae; Jun, Dae-Ryong; Kim, Dong-Wook; Han, Mi-Jung; Kwon, Tack-Kyun; Choi, Sung-Wook; Kwon, Seong Keun

2017-01-01

The use of injectable bulking agents is a feasible alternative procedure for conventional surgical therapy. In this study, poly(dimethylsiloxane) (PDMS) microspheres coated with polydopamine (PDA) were developed as a potential injection agent to prevent migration in vocal fold. Uniform PDMS microspheres are fabricated using a simple fluidic device and then coated with PDA. Cell attachment test reveals that the PDA-coated PDMS (PDA-PDMS) substrate favors cell adhesion and attachment. The injected PDA-PDMS microspheres persist without migration on reconstructed axial CT images, whereas, pristine PDMS locally migrates over a period of 12 weeks. The gross appearance of the implants retrieved at 4, 8, 12 and 34 weeks indicates that the PDA-PDMS group maintained their original position without significant migration until 34 weeks after injection. By contrast, there is diffuse local migration of the pristine PDMS group from 4 weeks after injection. The PDA-coated PDMS microspheres can potentially be used as easily injectable, non-absorbable filler without migration.

Prevention of polydimethylsiloxane microsphere migration using a mussel-inspired polydopamine coating for potential application in injection therapy

PubMed Central

Kim, Dong-Wook; Han, Mi-Jung; Kwon, Tack-Kyun; Choi, Sung-Wook

2017-01-01

The use of injectable bulking agents is a feasible alternative procedure for conventional surgical therapy. In this study, poly(dimethylsiloxane) (PDMS) microspheres coated with polydopamine (PDA) were developed as a potential injection agent to prevent migration in vocal fold. Uniform PDMS microspheres are fabricated using a simple fluidic device and then coated with PDA. Cell attachment test reveals that the PDA-coated PDMS (PDA-PDMS) substrate favors cell adhesion and attachment. The injected PDA-PDMS microspheres persist without migration on reconstructed axial CT images, whereas, pristine PDMS locally migrates over a period of 12 weeks. The gross appearance of the implants retrieved at 4, 8, 12 and 34 weeks indicates that the PDA-PDMS group maintained their original position without significant migration until 34 weeks after injection. By contrast, there is diffuse local migration of the pristine PDMS group from 4 weeks after injection. The PDA-coated PDMS microspheres can potentially be used as easily injectable, non-absorbable filler without migration. PMID:29095854

Use of NEXRAD to study shorebird migration in the Prairie Pothole region: A feasibility study

USGS Publications Warehouse

Melcher, Cynthia P.; Skagen, Susan K.; Randall, Lori

2006-01-01

An essential component of shorebird conservation is identifying, protecting, and managing high-priority stopover sites and migration habitats crucial to the long-term persistence of migrating shorebirds. Because of the tremendous variability in migrant shorebird occurrence patterns in the Prairie Pothole Region of the U.S. (Skagen 1997), it is labor- and cost-intensive to locate the majority of sites used heavily by shorebirds in any one migration period. Because WSR-88D (Weather Surveillance Radar – 1988 Doppler) or NEXRAD (NEXt generation weather RADar) has been useful for locating migrating birds and revealing migration patterns and important roosting sites of some species (e.g., Diehl and others 2003, Gauthreaux and Belser 2003), we undertook a pilot field study to determine wheTHER it also might be feasible to use NEXRAD for locating important stopover sites used by migrating shorebirds in the prairie potholes landscape. Coordinated efforts to advance the applicability of radar technology to bird conservation are underway (Ruth and others 2005).

Detection of egg drop syndrome 1976 virus by polymerase chain reaction and study of its persistence in experimentally infected layer birds.

PubMed

Kumar, N S; Kataria, J M; Koti, M; Dhama, K; Toroghi, R

2003-01-01

Polymerase chain reaction (PCR) assay was developed for the detection of Egg drop syndrome 1976 (EDS-76) virus in tissues, namely in the uterus, spleen and buffy coat. It was also used to study the persistence of the virus in tissues of experimentally infected layer birds. The PCR assay could detect as little as 10 fg of purified EDS-76 viral DNA. It also amplified the DNA of Fowl adenovirus serotypes 4 (FAV-4) and 8 (FAV-8). The virus persisted in the uterus up to day 21 post infection (p.i.). Detection of EDS-76 viral DNA in the buffy coat could be useful for studying the occurrence of the respective disease in layer bird flocks.

Finding the Missing Physics: Simulating Polydisperse Polymer Melts

NASA Astrophysics Data System (ADS)

Rorrer, Nichoals; Dorgan, John

2014-03-01

A Monte Carlo algorithm has been developed to model polydisperse polymer melts. For the first time, this enables the specification of a predetermined molecular weight distribution for lattice based simulations. It is demonstrated how to map an arbitrary probability distributions onto a discrete number of chains residing on an fcc lattice. The resulting algorithm is able to simulate a wide variety of behaviors for polydisperse systems including confinement effects, shear flow, and parabolic flow. The dynamic version of the algorithm accurately captures Rouse dynamics for short polymer chains, and reptation-like dynamics for longer chain lengths.1 When polydispersity is introduced, smaller Rouse times and broadened the transition between different scaling regimes are observed. Rouse times also decrease under confinement for both polydisperse and monodisperse systems and chain length dependent migration effects are observed. The steady-state version of the algorithm enables the simulation of flow and when polydisperse systems are subject to parabolic (Poiseulle) flow, a migration phenomenon based on chain length is again present. These and other phenomena highlight the importance of including polydispersity in obtaining physically realistic simulations of polymeric melts. 1. Dorgan, J.R.; Rorrer, N.A.; Maupin, C.M., Macromolecules 2012, 45(21), 8833-8840. Work funded by the Fluid Dynamics program of the National Science Foundation under grant CBET-1067707.

Lamellipodin and the Scar/WAVE complex cooperate to promote cell migration in vivo

PubMed Central

Law, Ah-Lai; Vehlow, Anne; Kotini, Maria; Dodgson, Lauren; Soong, Daniel; Theveneau, Eric; Bodo, Cristian; Taylor, Eleanor; Navarro, Christel; Perera, Upamali; Michael, Magdalene; Dunn, Graham A.; Bennett, Daimark; Mayor, Roberto

2013-01-01

Cell migration is essential for development, but its deregulation causes metastasis. The Scar/WAVE complex is absolutely required for lamellipodia and is a key effector in cell migration, but its regulation in vivo is enigmatic. Lamellipodin (Lpd) controls lamellipodium formation through an unknown mechanism. Here, we report that Lpd directly binds active Rac, which regulates a direct interaction between Lpd and the Scar/WAVE complex via Abi. Consequently, Lpd controls lamellipodium size, cell migration speed, and persistence via Scar/WAVE in vitro. Moreover, Lpd knockout mice display defective pigmentation because fewer migrating neural crest-derived melanoblasts reach their target during development. Consistently, Lpd regulates mesenchymal neural crest cell migration cell autonomously in Xenopus laevis via the Scar/WAVE complex. Further, Lpd’s Drosophila melanogaster orthologue Pico binds Scar, and both regulate collective epithelial border cell migration. Pico also controls directed cell protrusions of border cell clusters in a Scar-dependent manner. Taken together, Lpd is an essential, evolutionary conserved regulator of the Scar/WAVE complex during cell migration in vivo. PMID:24247431

Rice production systems and avian influenza: Interactions between mixed-farming systems, poultry and wild birds

USGS Publications Warehouse

Muzaffar, S.B.; Takekawa, John Y.; Prosser, D.J.; Newman, S.H.; Xiao, X.

2010-01-01

Wild waterfowl are the reservoir for avian influenza viruses (AIVs), a family of RNA viruses that may cause mild sickness in waterbirds. Emergence of H5N1, a highly pathogenic avian influenza (HPAI) strain, causing severe disease and mortality in wild birds, poultry and humans, had raised concerns about the role of wild birds in possible transmission of the disease. In this review, the link between rice production systems, poultry production systems, and wild bird ecology is examined to assess the extent to which these interactions could contribute towards the persistence and evolution of HPAI H5N1. The rice (Oryza sativa) and poultry production systems in Asia described, and then migration and movements of wild birds discussed. Mixed farming systems in Asia and wild bird movement and migration patterns create opportunities for the persistence of low pathogenic AIVs in these systems. Nonetheless, there is no evidence of long-term persistence of HPAI viruses (including the H5N1 subtype) in the wild. There are still significant gaps in the understanding of how AIVs circulate in rice systems. A better understanding of persistence of AIVs in rice farms, particularly of poultry origins, is essential in limiting exchange of AIVs between mixed-farming systems, poultry and wild birds.

Genetic Structure and Diversity of the Endangered Fir Tree of Lebanon (Abies cilicica Carr.): Implications for Conservation

PubMed Central

Awad, Lara; Fady, Bruno; Khater, Carla; Roig, Anne; Cheddadi, Rachid

2014-01-01

The threatened conifer Abies cilicica currently persists in Lebanon in geographically isolated forest patches. The impact of demographic and evolutionary processes on population genetic diversity and structure were assessed using 10 nuclear microsatellite loci. All remnant 15 local populations revealed a low genetic variation but a high recent effective population size. FST-based measures of population genetic differentiation revealed a low spatial genetic structure, but Bayesian analysis of population structure identified a significant Northeast-Southwest population structure. Populations showed significant but weak isolation-by-distance, indicating non-equilibrium conditions between dispersal and genetic drift. Bayesian assignment tests detected an asymmetric Northeast-Southwest migration involving some long-distance dispersal events. We suggest that the persistence and Northeast-Southwest geographic structure of Abies cilicica in Lebanon is the result of at least two demographic processes during its recent evolutionary history: (1) recent migration to currently marginal populations and (2) local persistence through altitudinal shifts along a mountainous topography. These results might help us better understand the mechanisms involved in the species response to expected climate change. PMID:24587219

QUANTIFICATION OF TRANSGENIC PLANT MARKER GENE PERSISTENCE IN THE FIELD

EPA Science Inventory

Methods were developed to monitor persistence of genomic DNA in decaying plants in the field. As a model, we used recombinant neomycin phosphotransferase II (rNPT-II) marker genes present in genetically engineered plants. Polymerase chain reaction (PCR) primers were designed, com...

Divergent migration within lake sturgeon (Acipenser fulvescens) populations: Multiple distinct patterns exist across an unrestricted migration corridor.

PubMed

Kessel, Steven T; Hondorp, Darryl W; Holbrook, Christopher M; Boase, James C; Chiotti, Justin A; Thomas, Michael V; Wills, Todd C; Roseman, Edward F; Drouin, Richard; Krueger, Charles C

2018-01-01

Population structure, distribution, abundance and dispersal arguably underpin the entire field of animal ecology, with consequences for regional species persistence, and provision of ecosystem services. Divergent migration behaviours among individuals or among populations are an important aspect of the ecology of highly mobile animals, allowing populations to exploit spatially or temporally distributed food and space resources. This study investigated the spatial ecology of lake sturgeon (Acipenser fulvescens) within the barrier free Huron-Erie Corridor (HEC), which connects Lake Huron and Lake Erie of the North American Laurentian Great Lakes. Over 6 years (2011-2016), movements of 268 lake sturgeon in the HEC were continuously monitored across the Great Lakes using acoustic telemetry (10 years battery life acoustic transmitters). Five distinct migration behaviours were identified with hierarchical cluster analysis, based on the phenology and duration of river and lake use. Lake sturgeon in the HEC were found to contain a high level of intraspecific divergent migration, including partial migration with the existence of residents. Specific behaviours included year-round river residency and multiple lake-migrant behaviours that involved movements between lakes and rivers. Over 85% of individuals were assigned to migration behaviours as movements were consistently repeated over the study, which suggested migration behaviours were consistent and persistent in lake sturgeon. Differential use of specific rivers or lakes by acoustic-tagged lake sturgeon further subdivided individuals into 14 "contingents" (spatiotemporally segregated subgroups). Contingents associated with one river (Detroit or St. Clair) were rarely detected in the other river, which confirmed that lake sturgeon in the Detroit and St. Clair represent two semi-independent populations that could require separate management consideration for their conservation. The distribution of migration behaviours did not vary between populations, sexes, body size or among release locations, which indicated that intrapopulation variability in migratory behaviour is a general feature of the spatial ecology of lake sturgeon in unfragmented landscapes. 2017 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.

The effect of lipid monolayer in-plane rigidity on in vivo microbubble circulation persistence

PubMed Central

Garg, Sumit; Thomas, Alex A.; Borden, Mark A.

2013-01-01

The goal of this study was to increase in vivo microbubble circulation persistence for applications in medical imaging and targeted drug delivery. Our approach was to investigate the effect of lipid monolayer in-plane rigidity to reduce the rate of microbubble dissolution, while holding constant the microbubble size, concentration and surface architecture. We first estimated the impact of acyl chain length of the main diacyl phosphatidyl-choline (PC) lipid and inter-lipid distance on the cohesive surface energy and, based on these results, we hypothesized that microbubble stability and in vivo ultrasound contrast persistence would increase monotonically with increasing acyl chain length. We therefore measured microbubble in vitro stability to dilution with and without ultrasound exposure, as well as in vivo ultrasound contrast persistence. All measurements showed a sharp rise in stability between DPPC (C16:0) and DSPC (C18:0), which correlates to the wrinkling transition, which signals the onset of significant surface shear and gas permeation resistance, observed in prior single-bubble dissolution studies. Further evidence for the effect of the wrinkling transition came from an in vitro and in vivo stability comparison of microbubbles coated with pure DPPC with those of lung surfactant extract. Microbubble stability against dilution without ultrasound and in vivo ultrasound contrast persistence showed a monotonic increase with acyl chain length from DSPC to DBPC (C22:0). However, we also observed that stability dropped precipitously for all measurements on further increasing lipid acyl chain length from DBPC to DLiPC (C24:0). This result suggests that hydrophobic mismatch between the main PC lipid and the lipopolymer emulsifier, DSPE-PEG5000, may drive a less stable surface microstructure. Overall, these results support our general hypothesis of the role of in-plane rigidity for increasing the lifetime of microbubble circulation. PMID:23787108

Ab initio study of chain branching reactions involving second generation products in hydrocarbon combustion mechanisms.

PubMed

Davis, Alexander C; Francisco, Joseph S

2012-01-28

sec-Alkyl radicals are key reactive intermediates in the hydrocarbon combustion and atmospheric decomposition mechanisms that are formed by the abstraction of hydrogen from an alkane, or as a second generation product of n-alkyl H-migrations, C-C bond scissions in branched alkyl radicals, or the bimolecular reaction between olefins and n-alkyl radicals. Since alkanes and branched alkanes, which the sec-alkyl radicals are derived from, make up roughly 40-50% of traditional fuels an understanding of their chemistry is essential to improving combustion systems. The present work investigates all H-migration reactions initiated from an sec-alkyl radical that involve the movement of a secondary hydrogen, for the 2-butyl through 4-octyl radicals, using the CBS-Q, G2, and G4 composite methods. The resulting thermodynamic and kinetic parameters are compared to similar reactions in n-alkyl radicals in order to determine underlying trends. Particular attention is paid to the effect of cis/trans and 1,3-diaxial interactions on activation energies and rate coefficients. When combined with our previous work on n-alkyl radical H-migrations, a complete picture of H-migrations in unbranched alkyl radicals is obtained. This full data set suggests that the directionality of the remaining branched chains has a minimal effect on the rate coefficients for all but the largest viable transition states, which is in stark contrast to the differences predicted by the structurally similar dimethylcycloalkanes. In fact the initial location of the secondary radical site has a greater effect on the rate than does the directionality of the remaining alkyl chains. The activation energies for secondary to secondary reactions are much closer to those of the secondary to primary H-migrations. However, the rate coefficients are found to be closer to the corresponding primary to primary reaction values. A significant ramification of these results is that there will be multiple viable reaction pathways for these reactions instead of only one dominant pathway as previously believed.

Disruption, not displacement: Environmental variability and temporary migration in Bangladesh

PubMed Central

Gray, Clark; Yunus, Mohammad; Emch, Michael

2018-01-01

Mass migration is one of the most concerning potential outcomes of global climate change. Recent research into environmentally induced migration suggests that relationship is much more complicated than originally posited by the ‘environmental refugee’ hypothesis. Climate change is likely to increase migration in some cases and reduce it in others, and these movements will more often be temporary and short term than permanent and long term. However, few large-sample studies have examined the evolution of temporary migration under changing environmental conditions. To address this gap, we measure the extent to which temperature, precipitation, and flooding can predict temporary migration in Matlab, Bangladesh. Our analysis incorporates high-frequency demographic surveillance data, a discrete time event history approach, and a range of sociodemographic and contextual controls. This approach reveals that migration declines immediately after flooding but quickly returns to normal. In contrast, optimal precipitation and high temperatures have sustained positive effects on temporary migration that persist over one to two year periods. Building on previous studies of long-term migration, these results challenge the common assumption that flooding, precipitation extremes and high temperatures will consistently increase temporary migration. Instead, our results are consistent with a livelihoods interpretation of environmental migration in which households draw on a range of strategies to cope with environmental variability. PMID:29375196

Disruption, not displacement: Environmental variability and temporary migration in Bangladesh.

PubMed

Call, Maia A; Gray, Clark; Yunus, Mohammad; Emch, Michael

2017-09-01

Mass migration is one of the most concerning potential outcomes of global climate change. Recent research into environmentally induced migration suggests that relationship is much more complicated than originally posited by the 'environmental refugee' hypothesis. Climate change is likely to increase migration in some cases and reduce it in others, and these movements will more often be temporary and short term than permanent and long term. However, few large-sample studies have examined the evolution of temporary migration under changing environmental conditions. To address this gap, we measure the extent to which temperature, precipitation, and flooding can predict temporary migration in Matlab, Bangladesh. Our analysis incorporates high-frequency demographic surveillance data, a discrete time event history approach, and a range of sociodemographic and contextual controls. This approach reveals that migration declines immediately after flooding but quickly returns to normal. In contrast, optimal precipitation and high temperatures have sustained positive effects on temporary migration that persist over one to two year periods. Building on previous studies of long-term migration, these results challenge the common assumption that flooding, precipitation extremes and high temperatures will consistently increase temporary migration. Instead, our results are consistent with a livelihoods interpretation of environmental migration in which households draw on a range of strategies to cope with environmental variability.

Dynamics of neutrophil migration in lymph nodes during infection.

PubMed

Chtanova, Tatyana; Schaeffer, Marie; Han, Seong-Ji; van Dooren, Giel G; Nollmann, Marcelo; Herzmark, Paul; Chan, Shiao Wei; Satija, Harshita; Camfield, Kristin; Aaron, Holly; Striepen, Boris; Robey, Ellen A

2008-09-19

Although the signals that control neutrophil migration from the blood to sites of infection have been well characterized, little is known about their migration patterns within lymph nodes or the strategies that neutrophils use to find their local sites of action. To address these questions, we used two-photon scanning-laser microscopy to examine neutrophil migration in intact lymph nodes during infection with an intracellular parasite, Toxoplasma gondii. We found that neutrophils formed both small, transient and large, persistent swarms via a coordinated migration pattern. We provided evidence that cooperative action of neutrophils and parasite egress from host cells could trigger swarm formation. Neutrophil swarm formation coincided in space and time with the removal of macrophages that line the subcapsular sinus of the lymph node. Our data provide insights into the cellular mechanisms underlying neutrophil swarming and suggest new roles for neutrophils in shaping immune responses.

Dynamics of neutrophil migration in lymph nodes during infection

PubMed Central

Chtanova, Tatyana; Schaeffer, Marie; Han, Seong-Ji; van Dooren, Giel G.; Nollmann, Marcelo; Herzmark, Paul; Chan, Shiao Wei; Satija, Harshita; Camfield, Kristin; Aaron, Holly; Striepen, Boris; Robey, Ellen A.

2008-01-01

Summary While the signals that control neutrophil migration from the blood to sites of infection have been well characterized, little is known about their migration patterns within lymph nodes, or the strategies that neutrophils use to find their local sites of action. To address these questions, we used two-photon scanning laser microscopy (TPSLM) to examine neutrophil migration in intact lymph nodes during infection with an intracellular parasite, Toxoplasma gondii. We find that neutrophils form both small, transient or large, persistent swarms via a strikingly coordinated migration pattern. We provide evidence that cooperative action of neutrophils and parasite egress from host cells can trigger swarm formation. Neutrophil swarm formation coincides in space and time with the removal of macrophages that line the subcapsular sinus of the lymph node. Our data provide insights into the cellular mechanisms underlying neutrophil swarming and suggest new roles for neutrophils in shaping immune responses. PMID:18718768

Inter-Provincial Migration Intentions of Family Physicians in Canada: The Roles of Income and Community Characteristics

PubMed Central

Olfert, M. Rose

2015-01-01

The inter-provincial migration patterns of family physicians in Canada show that some provinces like Newfoundland and Saskatchewan experience persistent net out-migration, while others, including Ontario and British Columbia, are destinations more often than origins of migrants. Governments in provinces exhibiting net out-migration have responded with a number of incentive and recruitment programs. In this study, we investigate the determinants of the stated interprovincial migration intentions of 3,995 rural and urban family physicians in the 2010 wave of the National Physician Survey. We consider a range of physician characteristics, community attributes and working conditions. We find that in the intention to move, higher compensation has a modest effect, while the community characteristics have a consistently important influence. Our results suggest that policy and program designers should acknowledge the critical role of community-level living and working conditions in their family physician recruitment and retention efforts. PMID:26742116

Reduced evolutionary rate in reemerged Ebola virus transmission chains.

PubMed

Blackley, David J; Wiley, Michael R; Ladner, Jason T; Fallah, Mosoka; Lo, Terrence; Gilbert, Merle L; Gregory, Christopher; D'ambrozio, Jonathan; Coulter, Stewart; Mate, Suzanne; Balogun, Zephaniah; Kugelman, Jeffrey; Nwachukwu, William; Prieto, Karla; Yeiah, Adolphus; Amegashie, Fred; Kearney, Brian; Wisniewski, Meagan; Saindon, John; Schroth, Gary; Fakoli, Lawrence; Diclaro, Joseph W; Kuhn, Jens H; Hensley, Lisa E; Jahrling, Peter B; Ströher, Ute; Nichol, Stuart T; Massaquoi, Moses; Kateh, Francis; Clement, Peter; Gasasira, Alex; Bolay, Fatorma; Monroe, Stephan S; Rambaut, Andrew; Sanchez-Lockhart, Mariano; Scott Laney, A; Nyenswah, Tolbert; Christie, Athalia; Palacios, Gustavo

2016-04-01

On 29 June 2015, Liberia's respite from Ebola virus disease (EVD) was interrupted for the second time by a renewed outbreak ("flare-up") of seven confirmed cases. We demonstrate that, similar to the March 2015 flare-up associated with sexual transmission, this new flare-up was a reemergence of a Liberian transmission chain originating from a persistently infected source rather than a reintroduction from a reservoir or a neighboring country with active transmission. Although distinct, Ebola virus (EBOV) genomes from both flare-ups exhibit significantly low genetic divergence, indicating a reduced rate of EBOV evolution during persistent infection. Using this rate of change as a signature, we identified two additional EVD clusters that possibly arose from persistently infected sources. These findings highlight the risk of EVD flare-ups even after an outbreak is declared over.

Reduced evolutionary rate in reemerged Ebola virus transmission chains

PubMed Central

Blackley, David J.; Wiley, Michael R.; Ladner, Jason T.; Fallah, Mosoka; Lo, Terrence; Gilbert, Merle L.; Gregory, Christopher; D’ambrozio, Jonathan; Coulter, Stewart; Mate, Suzanne; Balogun, Zephaniah; Kugelman, Jeffrey; Nwachukwu, William; Prieto, Karla; Yeiah, Adolphus; Amegashie, Fred; Kearney, Brian; Wisniewski, Meagan; Saindon, John; Schroth, Gary; Fakoli, Lawrence; Diclaro, Joseph W.; Kuhn, Jens H.; Hensley, Lisa E.; Jahrling, Peter B.; Ströher, Ute; Nichol, Stuart T.; Massaquoi, Moses; Kateh, Francis; Clement, Peter; Gasasira, Alex; Bolay, Fatorma; Monroe, Stephan S.; Rambaut, Andrew; Sanchez-Lockhart, Mariano; Scott Laney, A.; Nyenswah, Tolbert; Christie, Athalia; Palacios, Gustavo

2016-01-01

On 29 June 2015, Liberia’s respite from Ebola virus disease (EVD) was interrupted for the second time by a renewed outbreak (“flare-up”) of seven confirmed cases. We demonstrate that, similar to the March 2015 flare-up associated with sexual transmission, this new flare-up was a reemergence of a Liberian transmission chain originating from a persistently infected source rather than a reintroduction from a reservoir or a neighboring country with active transmission. Although distinct, Ebola virus (EBOV) genomes from both flare-ups exhibit significantly low genetic divergence, indicating a reduced rate of EBOV evolution during persistent infection. Using this rate of change as a signature, we identified two additional EVD clusters that possibly arose from persistently infected sources. These findings highlight the risk of EVD flare-ups even after an outbreak is declared over. PMID:27386513

Time-lapse imaging of neuroblast migration in acute slices of the adult mouse forebrain.

PubMed

Khlghatyan, Jivan; Saghatelyan, Armen

2012-09-12

There is a substantial body of evidence indicating that new functional neurons are constitutively generated from an endogenous pool of neural stem cells in restricted areas of the adult mammalian brain. Newborn neuroblasts from the subventricular zone (SVZ) migrate along the rostral migratory stream (RMS) to their final destination in the olfactory bulb (OB). In the RMS, neuroblasts migrate tangentially in chains ensheathed by astrocytic processes using blood vessels as a structural support and a source of molecular factors required for migration. In the OB, neuroblasts detach from the chains and migrate radially into the different bulbar layers where they differentiate into interneurons and integrate into the existing network. In this manuscript we describe the procedure for monitoring cell migration in acute slices of the rodent brain. The use of acute slices allows the assessment of cell migration in the microenvironment that closely resembling to in vivo conditions and in brain regions that are difficult to access for in vivo imaging. In addition, it avoids long culturing condition as in the case of organotypic and cell cultures that may eventually alter the migration properties of the cells. Neuronal precursors in acute slices can be visualized using DIC optics or fluorescent proteins. Viral labeling of neuronal precursors in the SVZ, grafting neuroblasts from reporter mice into the SVZ of wild-type mice, and using transgenic mice that express fluorescent protein in neuroblasts are all suitable methods for visualizing neuroblasts and following their migration. The later method, however, does not allow individual cells to be tracked for long periods of time because of the high density of labeled cells. We used a wide-field fluorescent upright microscope equipped with a CCD camera to achieve a relatively rapid acquisition interval (one image every 15 or 30 sec) to reliably identify the stationary and migratory phases. A precise identification of the duration of the stationary and migratory phases is crucial for the unambiguous interpretation of results. We also performed multiple z-step acquisitions to monitor neuroblasts migration in 3D. Wide-field fluorescent imaging has been used extensively to visualize neuronal migration. Here, we describe detailed protocol for labeling neuroblasts, performing real-time video-imaging of neuroblast migration in acute slices of the adult mouse forebrain, and analyzing cell migration. While the described protocol exemplified the migration of neuroblasts in the adult RMS, it can also be used to follow cell migration in embryonic and early postnatal brains.

Migration ecology and stopover population size of Red Knots Calidris canutus rufa at Mingan Archipelago after exiting the breeding grounds

USGS Publications Warehouse

Lyons, James E.; Baker, Allan J.; González, Patricia M.; Aubry, Yves; Buidin, Christophe; Rochepault, Yann

2018-01-01

Populations of migratory birds present unique conservation challenges given the often vast distances separating critical resources throughout the annual cycle. Migration areas close to the breeding grounds represent a link between two key stages of the annual cycle, and understanding migration ecology as birds exit the breeding grounds may be particularly informative for successful conservation. We studied migration phenology and stopover ecology of an endangered subspecies of the Red Knot Calidris canutus rufa at a migration area relatively close to its breeding range. Using mark-recapture/resight data and a Jolly-Seber model for open populations, we described the arrival and departure schedules, stopover duration, and passage population size at the Mingan Archipelago, Quebec, Canada. Red Knots arrived at the study area in two distinct waves of birds separated by approximately 22 days. Nearly 30% of the passage population arrived in the first wave of arrivals during 15–18 July, and approximately 22% arrived in a second wave during 8–11 August. The sex-ratio in the stopover population at the time of the first wave was slightly skewed toward females, whereas the second wave was heavily skewed toward males. Because males remain on the breeding grounds to care for young, this may reflect successfulbreeding in the year of our study. The estimated stopover duration (population mean) was 11 days (95% credible interval: 10.3–11.7 days), but stopover persistence was variable throughout the season. We estimated a passage population size of 9,450 birds (8,355–10,710), a minimum estimate for reasons related to the duration of our sampling. Mingan Archipelago is thus an important migration area for this endangered subspecies and could be a priority in conservation planning. Our results also emphasize the advantages of mark-recapture/resight approaches for estimating migration phenology and stopover persistence.

Effects of TNF-alpha on Endothelial Cell Collective Migration

NASA Astrophysics Data System (ADS)

Chen, Desu; Wu, Di; Helim Aranda-Espinoza, Jose; Losert, Wolfgang

2013-03-01

Tumor necrosis factor (TNF-alpha) is a small cell-signaling protein usually released by monocytes and macrophages during an inflammatory response. Previous work had shown the effects of TNF-alpha on single cell morphology, migration, and biomechanical properties. However, the effect on collective migrations remains unexplored. In this work, we have created scratches on monolayers of human umbilical endothelial cells (HUVECs) treated with 25ng/mL TNF-alpha on glass substrates. The wound healing like processes were imaged with phase contrast microscopy. Quantitative analysis of the collective migration of cells treated with TNF-alpha indicates that these cells maintain their persistent motion and alignment better than untreated cells. In addition, the collective migration was characterized by measuring the amount of non-affine deformations of the wound healing monolayer. We found a lower mean non-affinity and narrower distribution of non-affinities upon TNF-alpha stimulation. These results suggest that TNF-alpha introduces a higher degree of organized cell collective migration.

Differential gene expression in migratory streams of cortical interneurons

PubMed Central

Antypa, Mary; Faux, Clare; Eichele, Gregor; Parnavelas, John G; Andrews, William D

2011-01-01

Cortical interneurons originate in the ganglionic eminences of the subpallium and migrate into the cortex in well-defined tangential streams. At the start of corticogenesis, two streams of migrating neurons are evident: a superficial one at the level of the preplate (PPL), and a deeper one at the level of the intermediate zone (IZ). Currently, little is known about the signalling mechanisms that regulate interneuron migration, and almost nothing is known about the molecules that may be involved in their choice of migratory stream. Here, we performed a microarray analysis, comparing the changes in gene expression between cells migrating in the PPL and those migrating in the IZ at embryonic day 13.5. This analysis identified genes, many of them novel, that were upregulated in one of the two streams. Moreover, polymerase chain reaction, in situ hybridization experiments and immunohistochemistry showed the expression of these genes in interneurons migrating within the PPL or IZ, suggesting that they play a role in their migration and choice of stream. PMID:22103416

Persistent leatherback turtle migrations present opportunities for conservation.

PubMed

Shillinger, George L; Palacios, Daniel M; Bailey, Helen; Bograd, Steven J; Swithenbank, Alan M; Gaspar, Philippe; Wallace, Bryan P; Spotila, James R; Paladino, Frank V; Piedra, Rotney; Eckert, Scott A; Block, Barbara A

2008-07-15

Effective transboundary conservation of highly migratory marine animals requires international management cooperation as well as clear scientific information about habitat use by these species. Populations of leatherback turtles (Dermochelys coriacea) in the eastern Pacific have declined by >90% during the past two decades, primarily due to unsustainable egg harvest and fisheries bycatch mortality. While research and conservation efforts on nesting beaches are ongoing, relatively little is known about this population of leatherbacks' oceanic habitat use and migration pathways. We present the largest multi-year (2004-2005, 2005-2006, and 2007) satellite tracking dataset (12,095 cumulative satellite tracking days) collected for leatherback turtles. Forty-six females were electronically tagged during three field seasons at Playa Grande, Costa Rica, the largest extant nesting colony in the eastern Pacific. After completing nesting, the turtles headed southward, traversing the dynamic equatorial currents with rapid, directed movements. In contrast to the highly varied dispersal patterns seen in many other sea turtle populations, leatherbacks from Playa Grande traveled within a persistent migration corridor from Costa Rica, past the equator, and into the South Pacific Gyre, a vast, low-energy, low-productivity region. We describe the predictable effects of ocean currents on a leatherback migration corridor and characterize long-distance movements by the turtles in the eastern South Pacific. These data from high seas habitats will also elucidate potential areas for mitigating fisheries bycatch interactions. These findings directly inform existing multinational conservation frameworks and provide immediate regions in the migration corridor where conservation can be implemented. We identify high seas locations for focusing future conservation efforts within the leatherback dispersal zone in the South Pacific Gyre.

Optimal chemotaxis in intermittent migration of animal cells

NASA Astrophysics Data System (ADS)

Romanczuk, P.; Salbreux, G.

2015-04-01

Animal cells can sense chemical gradients without moving and are faced with the challenge of migrating towards a target despite noisy information on the target position. Here we discuss optimal search strategies for a chaser that moves by switching between two phases of motion ("run" and "tumble"), reorienting itself towards the target during tumble phases, and performing persistent migration during run phases. We show that the chaser average run time can be adjusted to minimize the target catching time or the spatial dispersion of the chasers. We obtain analytical results for the catching time and for the spatial dispersion in the limits of small and large ratios of run time to tumble time and scaling laws for the optimal run times. Our findings have implications for optimal chemotactic strategies in animal cell migration.

No evidence of persisting measles virus in peripheral blood mononuclear cells from children with autism spectrum disorder.

PubMed

D'Souza, Yasmin; Fombonne, Eric; Ward, Brian J

2006-10-01

Despite epidemiologic evidence to the contrary, claims of an association between measles-mumps-rubella vaccination and the development of autism have persisted. Such claims are based primarily on the identification of measles virus nucleic acids in tissues and body fluids by polymerase chain reaction. We sought to determine whether measles virus nucleic acids persist in children with autism spectrum disorder compared with control children. Peripheral blood mononuclear cells were isolated from 54 children with autism spectrum disorder and 34 developmentally normal children, and up to 4 real-time polymerase chain reaction assays and 2 nested polymerase chain reaction assays were performed. These assays targeted the nucleoprotein, fusion, and hemagglutinin genes of measles virus using previously published primer pairs with detection by SYBR green I. Our own real-time assay targeted the fusion gene using novel primers and an internal fluorescent probe. Positive reactions were evaluated rigorously, and amplicons were sequenced. Finally, anti-measles antibody titers were measured by enzyme immunoassay. The real-time assays based on previously published primers gave rise to a large number of positive reactions in both autism spectrum disorder and control samples. Almost all of the positive reactions in these assays were eliminated by evaluation of melting curves and amplicon band size. The amplicons for the remaining positive reactions were cloned and sequenced. No sample from either autism spectrum disorder or control groups was found to contain nucleic acids from any measles virus gene. In the nested polymerase chain reaction and in-house assays, none of the samples yielded positive results. Furthermore, there was no difference in anti-measles antibody titers between the autism and control groups. There is no evidence of measles virus persistence in the peripheral blood mononuclear cells of children with autism spectrum disorder.

Explaining Australian immigration.

PubMed

Betts, K

1996-11-01

"This article reviews the post-Second World War literature on explanations for Australia's immigration program. It discovers three main schools of thought based on net pull factors: the official explanation and two unofficial explanations which focus on migrants as workers and on migrants as consumers. However the growing importance of net push factors after 1974 means that some of this work is less relevant today. Explanations focusing on net push factors have yet to cohere into a distinct perspective (or perspectives) but some research has been done on chain migration and family-based migration strategies, asylum seekers, temporary movement, and migration and the law." excerpt

A model to resolve organochlorine pharmacokinetics in migrating humpback whales.

PubMed

Cropp, Roger; Nash, Susan Bengtson; Hawker, Darryl

2014-07-01

Humpback whales are iconic mammals at the top of the Antarctic food chain. Their large reserves of lipid-rich tissues such as blubber predispose them to accumulation of lipophilic contaminants throughout their lifetime. Changes in the volume and distribution of lipids in humpback whales, particularly during migration, could play an important role in the pharmacokinetics of lipophilic contaminants such as the organochlorine pesticide hexachlorobenzene (HCB). Previous models have examined constant feeding and nonmigratory scenarios. In the present study, the authors develop a novel heuristic model to investigate HCB dynamics in a humpback whale and its environment by coupling an ecosystem nutrient-phytoplankton-zooplankton-detritus (NPZD) model, a dynamic energy budget (DEB) model, and a physiologically based pharmacokinetic (PBPK) model. The model takes into account the seasonal feeding pattern of whales, their energy requirements, and fluctuating contaminant burdens in the supporting plankton food chain. It is applied to a male whale from weaning to maturity, spanning 20 migration and feeding cycles. The model is initialized with environmental HCB burdens similar to those measured in the Southern Ocean and predicts blubber HCB concentrations consistent with empirical concentrations observed in a southern hemisphere population of male, migrating humpback whales. Results show for the first time some important details of the relationship between energy budgets and organochlorine pharmacokinetics. © 2014 SETAC.

Changes in leucocyte migration after renal transplantation

PubMed Central

Smith, M. G. M.; Eddleston, A. L. W. F.; Dominguez, J. A.; Evans, D. B.; Bewick, M.; Williams, Roger

1969-01-01

The leucocyte migration test, an in-vitro measure of cellular immunity, has been used to follow the changes in cell-mediated hypersensitivity to kidney and histocompatibility antigens in three patients after renal transplantation. Inhibition of leucocyte migration, indicating strong sensitization to the antigens used, occurred in each patient, starting five to seven days after transplantation. Satisfactory renal function had not been established in any of the patients at this time. In one case inhibition of leucocyte migration persisted almost continuously until the 24th day and was associated with poor renal function proved histologically to be due to rejection. Treatment with increased dosage of prednisone was associated with a rapid reversion to normal of the migration index and improvement in renal function. Later, inhibition of migration occurred again, and shortly afterwards the graft ceased to function. In the other two cases the migration index became normal without alteration in immunosuppressive therapy and a satisfactory diuresis followed. It is suggested that this simple test should prove useful in the specific diagnosis of rejection and in control of immunosuppressive therapy. ImagesFig. 3Fig. 4 PMID:4899455

Innate control of actin nucleation determines two distinct migration behaviours in dendritic cells

PubMed Central

Vargas, Pablo; Maiuri, Paolo; Bretou, Marine; Sáez, Pablo J.; Pierobon, Paolo; Maurin, Mathieu; Chabaud, Mélanie; Lankar, Danielle; Obino, Dorian; Terriac, Emmanuel; Raab, Matthew; Thiam, Hawa-Racine; Brocker, Thomas; Kitchen-Goosen, Susan M.; Alberts, Arthur S.; Sunareni, Praveen; Xia, Sheng; Li, Rong; Voituriez, Raphael; Piel, Matthieu; Lennon-Duménil, Ana-Maria

2018-01-01

Dendritic cell (DC) migration in peripheral tissues serves two main functions: antigen sampling by immature DCs, and chemokine-guided migration towards lymphatic vessels (LVs) on maturation. These migratory events determine the efficiency of the adaptive immune response. Their regulation by the core cell locomotion machinery has not been determined. Here, we show that the migration of immature DCs depends on two main actin pools: a RhoA–mDia1-dependent actin pool located at their rear, which facilitates forward locomotion; and a Cdc42–Arp2/3-dependent actin pool present at their front, which limits migration but promotes antigen capture. Following TLR4–MyD88-induced maturation, Arp2/3-dependent actin enrichment at the cell front is markedly reduced. Consequently, mature DCs switch to a faster and more persistent mDia1-dependent locomotion mode that facilitates chemotactic migration to LVs and lymph nodes. Thus, the differential use of actin-nucleating machineries optimizes the migration of immature and mature DCs according to their specific function. PMID:26641718

SCM: A method to improve network service layout efficiency with network evolution.

PubMed

Zhao, Qi; Zhang, Chuanhao; Zhao, Zheng

2017-01-01

Network services are an important component of the Internet, which are used to expand network functions for third-party developers. Network function virtualization (NFV) can improve the speed and flexibility of network service deployment. However, with the evolution of the network, network service layout may become inefficient. Regarding this problem, this paper proposes a service chain migration (SCM) method with the framework of "software defined network + network function virtualization" (SDN+NFV), which migrates service chains to adapt to network evolution and improves the efficiency of the network service layout. SCM is modeled as an integer linear programming problem and resolved via particle swarm optimization. An SCM prototype system is designed based on an SDN controller. Experiments demonstrate that SCM could reduce the network traffic cost and energy consumption efficiently.

The future scenario for international labour migration.

PubMed

Tassello, G

1989-01-01

The study of migration helps us to grasp the social evolution and the political and economic strategies required to meet the new economic trends. The issue of permanent or temporary migration, long debated in the 1960s, now tends to disappear. Migrants are compared more to commuters on the international labor markets. Besides the economic out-migration flows, there are also the refugee migrations or the ever present phenomenon of persons uprooted from their home country as a result of natural disasters and famine. The worldwide economic crisis in the 1970s, the recession affecting some industrialized countries which used to be traditional labor-importing countries have barred many potential immigrant workers from entering these countries. If, on 1 hand, the persistent high rate of unemployment due to the transformation of industry and the computerization process has caused the dismissal of numerous unskilled--mainly immigrants--on the other hand, it has created the exigency of highly qualified personnel. The children of the indigenous population are therefore favored because of their better scholastic training. A 2nd generation is now condemned to remain marginal even though they have been brought up to the ideals of social improvement and integration into higher standards of living. A highly dissatisfied category of young people is now an integral part of many labor-importing countries. Many industrial countries are flirting with zero population growth. Considering the demographic, economic, social, and political imbalances which exist and tend to grow, the world now has all the prerequisites for huge and prolonged migration flows originating from the South and moving almost exclusively toward the megacities and the industrial countries in the North. As long as technological as well as social inequalities persist, inner and international migration flows will continue. It is evident that the aim of many highly industrialized countries is the total ceasing of all forced migration flows. A more intense, productive, and efficacious cooperation between North and South seems to be the only possible option available, but the cooperation must not solely be bases on aid and must include financial and organizational cooperative ventures.

Essure Microinsert Abdominal Migration after Hysteroscopic Tubal Sterilization of an Appropriately Placed Essure Device: Dual Case Reports and Review of the Literature

PubMed Central

Rezai, Shadi; LaBine, Meghan; Gomez Roberts, Hunter Azdel; Lora Alcantara, Isamarie; Henderson, Cassandra E.; Elmadjian, Malvina; Nuritdinova, Dilfuza

2015-01-01

Background. The Essure device is a method of permanent sterilization widely used in the US that has proven to be safe and effective in most cases. However, there have been reports of device migration that have led to failed tubal occlusion as well as several other serious complications resulting from the presence of the device in the abdominal cavity. Case. This paper represents two cases of failed tubal occlusion by an appropriately placed Essure device without signs or symptoms of further complications related to device migration. Conclusion. Although there have only been 13 reported cases of abdominal device migration since November 2014, this case indicates that the actual number may be higher than reported since it is possible for migration to occur without additional complications. In the majority of reported cases of abdominal migration a major complication requiring surgical correction occurred, such as adhesions, small bowel obstruction, bowel perforation, or persistent pelvic pain. To avoid these complications it is recommended that migrating implants be removed; however, this case also represents an example of when a migrating device may remain in situ in an asymptomatic patient. PMID:26664781

On the formation of suspended noble-metal monatomic chains

NASA Astrophysics Data System (ADS)

Hasmy, A.; Rincón, L.; Hernández, R.; Mujica, V.; Márquez, M.; González, C.

2008-09-01

We present a tight-binding molecular-dynamics investigation of the geometrical and the electronic structure of suspended monatomic noble-metal chains. We show that linear monatomic chains are formed at temperatures equal to or smaller than 500 K for Au, 200 K for Ag, and 4 K for Cu and that they are stable for at least 10 ns. We also evidence that such stability is associated with the persisting sd orbital hybridization along the chains. The study highlights fundamental limitations of conductance measurement experiments to detect these chains in the breaking process of nanowires.

Adaptation, migration or extirpation: climate change outcomes for tree populations

PubMed Central

Aitken, Sally N; Yeaman, Sam; Holliday, Jason A; Wang, Tongli; Curtis-McLane, Sierra

2008-01-01

Abstract Species distribution models predict a wholesale redistribution of trees in the next century, yet migratory responses necessary to spatially track climates far exceed maximum post-glacial rates. The extent to which populations will adapt will depend upon phenotypic variation, strength of selection, fecundity, interspecific competition, and biotic interactions. Populations of temperate and boreal trees show moderate to strong clines in phenology and growth along temperature gradients, indicating substantial local adaptation. Traits involved in local adaptation appear to be the product of small effects of many genes, and the resulting genotypic redundancy combined with high fecundity may facilitate rapid local adaptation despite high gene flow. Gene flow with preadapted alleles from warmer climates may promote adaptation and migration at the leading edge, while populations at the rear will likely face extirpation. Widespread species with large populations and high fecundity are likely to persist and adapt, but will likely suffer adaptational lag for a few generations. As all tree species will be suffering lags, interspecific competition may weaken, facilitating persistence under suboptimal conditions. Species with small populations, fragmented ranges, low fecundity, or suffering declines due to introduced insects or diseases should be candidates for facilitated migration. PMID:25567494

Exact Calculation of the Joint Allele Frequency Spectrum for Isolation with Migration Models.

PubMed

Kern, Andrew D; Hey, Jody

2017-09-01

Population genomic datasets collected over the past decade have spurred interest in developing methods that can utilize massive numbers of loci for inference of demographic and selective histories of populations. The allele frequency spectrum (AFS) provides a convenient statistic for such analysis, and, accordingly, much attention has been paid to predicting theoretical expectations of the AFS under a number of different models. However, to date, exact solutions for the joint AFS of two or more populations under models of migration and divergence have not been found. Here, we present a novel Markov chain representation of the coalescent on the state space of the joint AFS that allows for rapid, exact calculation of the joint AFS under isolation with migration (IM) models. In turn, we show how our Markov chain method, in the context of composite likelihood estimation, can be used for accurate inference of parameters of the IM model using SNP data. Lastly, we apply our method to recent whole genome datasets from African Drosophila melanogaster . Copyright © 2017 Kern and Hey.

Attrition and performance of community college transfers

PubMed Central

Aulck, Lovenoor; West, Jevin

2017-01-01

Community colleges are an important part of the US higher education landscape, yet the aptitude and preparedness of student transfers to baccalaureate institutions is often called into question. Examining transcript records and demographic information of nearly 70,000 students across over 15 years of registrar records at a public university, this study performed a descriptive analysis of the persistence, performance, and academic migration patterns of community college transfers, transfers from four-year institutions, and freshmen entrants. We found little difference between community college transfers and freshmen entrants in terms of post-transfer grades and persistence. Transfers from four-year institutions had higher grades but also had higher attrition rates than their peers. This study also found no strong evidence of transfer shock on students’ post-transfer grades. When examining the tendencies of students to shift fields of study during their educational pursuits, the academic migration patterns of transfer students were more concentrated than those of freshmen entrants. PMID:28407002

Intercontinental reassortment and genomic variation of low pathogenic avian influenza viruses isolated from northern pintails (Anas acuta) in Alaska: examining the evidence through space and time

USGS Publications Warehouse

Ramey, Andrew M.; Pearce, John M.; Flint, Paul L.; Ip, Hon S.; Derksen, Dirk V.; Franson, J. Christian; Petrula, Michael J.; Scotton, Bradley D.; Sowl, Kristine M.; Wege, Michael L.; Trust, Kimberly A.

2010-01-01

Migration and population genetic data for northern pintails (Anas acuta) and phylogenetic analysis of low pathogenic avian influenza (LPAI) viruses from this host in Alaska suggest that northern pintails are involved in ongoing intercontinental transmission of avian influenza. Here, we further refine this conclusion through phylogenetic analyses which demonstrate that detection of foreign lineage gene segments is spatially dependent and consistent through time. Our results show detection of foreign lineage gene segments to be most likely at sample locations on the Alaska Peninsula and least likely along the Southern Alaska Coast. Asian lineages detected at four gene segments persisted across years, suggesting maintenance in avian hosts that migrate to Alaska each year from Asia or in hosts that remain in Alaska throughout the year. Alternatively, live viruses may persist in the environment and re-infect birds in subsequent seasons.

Migrated Essure permanent birth control device: sonographic findings.

PubMed

Khati, Nadia Juliet; Gorodenker, Joseph; Brindle, Kathleen Ann

2014-05-01

We report a case of a migrated Essure permanent birth control device. The correct diagnosis was made on conventional two-dimensional and three-dimensional pelvic sonography 7 years after placement of the device when the patient presented with persistent right-sided pain. The 3-month post placement hysterosalpingogram had shown an appropriately occluded right fallopian tube but had overlooked the abnormal position of the right Essure device, which was too proximal and extending slightly in the uterine cavity. Copyright © 2013 Wiley Periodicals, Inc.

Fractures, not Plumes, Have Controlled Major Seamount Volcanism in the Pacific over 170 Million Years

NASA Astrophysics Data System (ADS)

Natland, J. H.; Winterer, E. L.

2003-12-01

The distribution of guyots and atolls and large volcanic islands on the Pacific plate can be used to outline the likely connection between stresses acting on the plate and the gradual development of large, linear volcanic chains over the past 170 Ma. We construe three general periods with different stress regimes in the history of the Pacific plate. 1) During the Jurassic and Early Cretaceous, the Pacific plate was surrounded by ridge segments and there were no major stress alignments within it. Within-plate volcanism thus assumed the scattered arrangement for the condition of no tectonic stress (1), and the large Magellan and Wake seamount clusters formed. Near the eastern boundaries of the plate, complex and shifting patterns of ridge reorganization dictated formation of very long, splayed, near-axis ridges such as Horizon Guyot and Necker Ridge. 2) At about 90 Ma, the growing middle-aged Pacific plate achieved its first persistent stress regime with the formation of subduction boundaries along its western or northwestern margin. The plate was no longer static but began to move over the asthenosphere and into the mantle. Subduction boundaries and the overall direction of subduction are uncertain, but this imparted a general yet not fully stable component of tension across the plate, producing the NNW Gilbert-Marshall, Line and Emperor Seamount ridges, generally orthogonal to the overall direction of least principal stress. The Line Island seamount chain, being near ridge axes, sustained a variable stress regime. It thus has no age progression of rocks dated between 70-90 Ma (2), great width, and a dual orientations of ridges. 3) By 47 Ma, nearly half of the boundaries of the Pacific plate now were trenches spanning from the Aleutians to New Zealand. In addition, northward migration of the Indian plate and Australia caught a major portion of the westerly moving Pacific plate between the northeast corner of the Tonga Trench and the Aleutians. The plate could not shift laterally in response to whatever was occurring along its eastern spreading boundaries. A very consistent and strong stress regime therefore developed across the Pacific plate with a NNE direction of least principal stress. The change in stress orientation may have taken up to 10 million years, during an interval marked by little or no volcanic productivity at the western end of the Hawaiian chain. Since that time, the predominant alignment of both linear island chains and Puka Puka-type ridges, from the Kodiak-Bowie chain in the Gulf of Alaska to the Louisville Ridge south of the Antarctic convergence, has been orthogonal to this direction. Development of large-volume persistent chains and shorter small-volume chains indicates patterns of differential stress in the plate, variable fertility and geochemistry of the asthenosphere and/or shallow convective overturn of the asthenosphere rather than the action of mantle plumes of different sizes and depths of origin. Tapping of enriched mantle by widespread volcano clusters during the Mesozoic suggests the presence of a shallow asthenospheric source layer rather than multiple narrow conduits. (1) Hieronymus, C.F., and Bercovici, D. 2000. Earth Planet. Sci. Lett. 181, 539-554. (2) Davis, A.S., Gray, L.B., Clague, D.A., and Hein, J.R., 2002 Geochem. Geophys. Geosyst. 3: 10.1029/2001GC0000190, 1-28.

Identifying impediments to long-distance mammal migrations.

PubMed

Seidler, Renee G; Long, Ryan A; Berger, Joel; Bergen, Scott; Beckmann, Jon P

2015-02-01

In much of the world, the persistence of long-distance migrations by mammals is threatened by development. Even where human population density is relatively low, there are roads, fencing, and energy development that present barriers to animal movement. If we are to conserve species that rely on long-distance migration, then it is critical that we identify existing migration impediments. To delineate stopover sites associated with anthropogenic development, we applied Brownian bridge movement models to high-frequency locations of pronghorn (Antilocapra americana) in the Greater Yellowstone Ecosystem. We then used resource utilization functions to assess the threats to long-distance migration of pronghorn that were due to fences and highways. Migrating pronghorn avoided dense developments of natural gas fields. Highways with relatively high volumes of traffic and woven-wire sheep fence acted as complete barriers. At crossings with known migration bottlenecks, use of high-quality forage and shrub habitat by pronghorn as they approached the highway was lower than expected based on availability of those resources. In contrast, pronghorn consistently utilized high-quality forage close to the highway at crossings with no known migration bottlenecks. Our findings demonstrate the importance of minimizing development in migration corridors in the future and of mitigating existing pressure on migratory animals by removing barriers, reducing the development footprint, or installing crossing structures. © 2014 Society for Conservation Biology.

Treatment of esophagopleural fistulas using covered retrievable expandable metallic stents.

PubMed

Kim, Tae-Hyung; Shin, Ji Hoon; Kim, Kyung Rae; Park, Jung-Hoon; Kim, Jin Hyoung; Song, Ho-Young

2014-04-01

To evaluate the clinical efficacy of placement of covered retrievable expandable metallic stents for esophagopleural fistulas (EPFs). During the period 1997-2013, nine patients with EPF were treated using covered retrievable expandable metallic stents. The underlying causes of EPF were esophageal carcinoma (n = 6), lung cancer (n = 2), and postoperative empyema for Boerhaave syndrome (n = 1). Technical success was achieved in eight patients (88.9%). In one patient, incomplete EPF closure was due to incomplete stent expansion. Clinical success, defined as complete EPF closure within 7 days, was achieved in five patients (55.6%). Overall fistula persistence (n = 1) or reopening (n = 4) occurred in five patients (55.6%) 0-15 days after stent placement. The causes of reopening were due to the gap between the stent and the esophagus (n = 3) or stent migration (n = 1). For fistula persistence or reopening, additional interventional management, such as gastrostomy, stent removal, or stent reinsertion, was performed. Stent migration occurred as a complication in one patient with EPF from a benign cause secondary to postoperative empyema. In the eight patients who died during the follow-up period, the mean and median survival times were 78.8 days and 46 days, respectively. Placement of a covered expandable metallic esophageal stent for the palliative treatment of EPF is technically feasible, although the rate of clinical success was poor secondary to fistula persistence or reopening. Fistula reopening was caused by the gap between the stent and the esophagus or by stent migration, and additional interventional treatment was useful to ensure enteral nutritional support. Copyright © 2014 SIR. Published by Elsevier Inc. All rights reserved.

Mobility and persistence of methane in groundwater in a controlled-release field experiment

NASA Astrophysics Data System (ADS)

Cahill, Aaron G.; Steelman, Colby M.; Forde, Olenka; Kuloyo, Olukayode; Emil Ruff, S.; Mayer, Bernhard; Ulrich Mayer, K.; Strous, Marc; Cathryn Ryan, M.; Cherry, John A.; Parker, Beth L.

2017-03-01

Expansion of shale gas extraction has fuelled global concern about the potential impact of fugitive methane on groundwater and climate. Although methane leakage from wells is well documented, the consequences on groundwater remain sparsely studied and are thought by some to be minor. Here we present the results of a 72-day methane gas injection experiment into a shallow, flat-lying sand aquifer. In our experiment, although a significant fraction of methane vented to the atmosphere, an equal portion remained in the groundwater. We find that methane migration in the aquifer was governed by subtle grain-scale bedding that impeded buoyant free-phase gas flow and led to episodic releases of free-phase gas. The result was lateral migration of gas beyond that expected by groundwater advection alone. Methane persisted in the groundwater zone despite active growth of methanotrophic bacteria, although much of the methane that vented into the vadose zone was oxidized. Our findings demonstrate that even small-volume releases of methane gas can cause extensive and persistent free phase and solute plumes emanating from leaks that are detectable only by contaminant hydrogeology monitoring at high resolution.

On the polarization of the green emission of polyfluorenes

NASA Astrophysics Data System (ADS)

Yang, X. H.; Neher, D.; Spitz, C.; Zojer, E.; Brédas, J. L.; Güntner, R.; Scherf, U.

2003-10-01

An experimental and theoretical study of the anisotropic optical properties of polyfluorenes (PFs) bearing ketonic defects is presented. Polarized emission experiments performed on photooxidized aligned PF layers indicate that the transition dipole of the "green" CT π-π* transition of the keto-defect is oriented parallel to the chain direction. It is further observed that the polarization ratio of the green emission is slightly smaller than that of the blue emission component originating from undisturbed chains. Quantum mechanical calculations have been performed to support these observations. It is shown that the transition dipole moment of the CT π-π* transition of the defect is slightly misaligned with respect to the π-π* transition of the undisturbed PF chain, and that the angle between both depends on the chain conformation. For the most probably 5/2 helical conformation, this angle is, however, smaller than 5°. Further, polarized PL spectroscopy with polarized excitation has been performed to determine the extent of energy migration prior to emission from the keto-defect. For excitation at 380 nm, the polarization ratio of the green emission is essentially independent of the excitation polarization, indicating almost complete depolarization of the excitation before it is captured at a defect site. In contrast to this, energy migration after direct excitation of the keto-defect is inefficient or even absent.

Persistent Leatherback Turtle Migrations Present Opportunities for Conservation

PubMed Central

Shillinger, George L; Palacios, Daniel M; Bailey, Helen; Bograd, Steven J; Swithenbank, Alan M; Gaspar, Philippe; Wallace, Bryan P; Spotila, James R; Paladino, Frank V; Piedra, Rotney; Eckert, Scott A; Block, Barbara A

2008-01-01

Effective transboundary conservation of highly migratory marine animals requires international management cooperation as well as clear scientific information about habitat use by these species. Populations of leatherback turtles (Dermochelys coriacea) in the eastern Pacific have declined by >90% during the past two decades, primarily due to unsustainable egg harvest and fisheries bycatch mortality. While research and conservation efforts on nesting beaches are ongoing, relatively little is known about this population of leatherbacks' oceanic habitat use and migration pathways. We present the largest multi-year (2004–2005, 2005–2006, and 2007) satellite tracking dataset (12,095 cumulative satellite tracking days) collected for leatherback turtles. Forty-six females were electronically tagged during three field seasons at Playa Grande, Costa Rica, the largest extant nesting colony in the eastern Pacific. After completing nesting, the turtles headed southward, traversing the dynamic equatorial currents with rapid, directed movements. In contrast to the highly varied dispersal patterns seen in many other sea turtle populations, leatherbacks from Playa Grande traveled within a persistent migration corridor from Costa Rica, past the equator, and into the South Pacific Gyre, a vast, low-energy, low-productivity region. We describe the predictable effects of ocean currents on a leatherback migration corridor and characterize long-distance movements by the turtles in the eastern South Pacific. These data from high seas habitats will also elucidate potential areas for mitigating fisheries bycatch interactions. These findings directly inform existing multinational conservation frameworks and provide immediate regions in the migration corridor where conservation can be implemented. We identify high seas locations for focusing future conservation efforts within the leatherback dispersal zone in the South Pacific Gyre. PMID:18630987

SCM: A method to improve network service layout efficiency with network evolution

PubMed Central

Zhao, Qi; Zhang, Chuanhao

2017-01-01

Network services are an important component of the Internet, which are used to expand network functions for third-party developers. Network function virtualization (NFV) can improve the speed and flexibility of network service deployment. However, with the evolution of the network, network service layout may become inefficient. Regarding this problem, this paper proposes a service chain migration (SCM) method with the framework of “software defined network + network function virtualization” (SDN+NFV), which migrates service chains to adapt to network evolution and improves the efficiency of the network service layout. SCM is modeled as an integer linear programming problem and resolved via particle swarm optimization. An SCM prototype system is designed based on an SDN controller. Experiments demonstrate that SCM could reduce the network traffic cost and energy consumption efficiently. PMID:29267299

Semiflexible macromolecules in quasi-one-dimensional confinement: Discrete versus continuous bond angles.

PubMed

Huang, Aiqun; Hsu, Hsiao-Ping; Bhattacharya, Aniket; Binder, Kurt

2015-12-28

The conformations of semiflexible polymers in two dimensions confined in a strip of width D are studied by computer simulations, investigating two different models for the mechanism by which chain stiffness is realized. One model (studied by molecular dynamics) is a bead-spring model in the continuum, where stiffness is controlled by a bond angle potential allowing for arbitrary bond angles. The other model (studied by Monte Carlo) is a self-avoiding walk chain on the square lattice, where only discrete bond angles (0° and ±90°) are possible, and the bond angle potential then controls the density of kinks along the chain contour. The first model is a crude description of DNA-like biopolymers, while the second model (roughly) describes synthetic polymers like alkane chains. It is first demonstrated that in the bulk the crossover from rods to self-avoiding walks for both models is very similar, when one studies average chain linear dimensions, transverse fluctuations, etc., despite their differences in local conformations. However, in quasi-one-dimensional confinement two significant differences between both models occur: (i) The persistence length (extracted from the average cosine of the bond angle) gets renormalized for the lattice model when D gets less than the bulk persistence length, while in the continuum model it stays unchanged. (ii) The monomer density near the repulsive walls for semiflexible polymers is compatible with a power law predicted for the Kratky-Porod model in the case of the bead-spring model, while for the lattice case it tends to a nonzero constant across the strip. However, for the density of chain ends, such a constant behavior seems to occur for both models, unlike the power law observed for flexible polymers. In the regime where the bulk persistence length ℓp is comparable to D, hairpin conformations are detected, and the chain linear dimensions are discussed in terms of a crossover from the Daoud/De Gennes "string of blobs"-picture to the flexible rod picture when D decreases and/or the chain stiffness increases. Introducing a suitable further coarse-graining of the chain contours of the continuum model, direct estimates for the deflection length and its distribution could be obtained.

Thermal Stress Limit Rafting Migration of Seahorses: Prediction Based on Physiological and Behavioral Responses to Thermal Stress

NASA Astrophysics Data System (ADS)

Qin, G.; Li, C.; Lin, Q.

2017-12-01

Marine fish species escape from harmful environment by migration. Seahorses, with upright posture and low mobility, could migrate from unfavorable environment by rafting with their prehensile tail. The present study was designed to examine the tolerance of lined seahorse Hippocampus erectus to thermal stress and evaluate the effects of temperature on seahorse migration. The results figured that seahorses' tolerance to thermal stress was time dependent. Acute thermal stress (30°C) increased breathing rate and HSP genes expression significantly, but didn't affect seahorse feeding behavior. Chronic thermal treatment lead to persistent high expression of HSP genes, higher breathing rate, and decreasing feeding, and final higher mortality, suggesting that seahorse cannot adapt to thermal stress by acclimation. No significant negative effects were found in seahorse reproduction in response to chronic thermal stress. Given that seahorses make much slower migration by rafting on sea surface compared to other fishes, we suggest that thermal stress might limit seahorse migration range. and the influence might be magnified by global warming in future.

Automated Tracking of Cell Migration with Rapid Data Analysis.

PubMed

DuChez, Brian J

2017-09-01

Cell migration is essential for many biological processes including development, wound healing, and metastasis. However, studying cell migration often requires the time-consuming and labor-intensive task of manually tracking cells. To accelerate the task of obtaining coordinate positions of migrating cells, we have developed a graphical user interface (GUI) capable of automating the tracking of fluorescently labeled nuclei. This GUI provides an intuitive user interface that makes automated tracking accessible to researchers with no image-processing experience or familiarity with particle-tracking approaches. Using this GUI, users can interactively determine a minimum of four parameters to identify fluorescently labeled cells and automate acquisition of cell trajectories. Additional features allow for batch processing of numerous time-lapse images, curation of unwanted tracks, and subsequent statistical analysis of tracked cells. Statistical outputs allow users to evaluate migratory phenotypes, including cell speed, distance, displacement, and persistence, as well as measures of directional movement, such as forward migration index (FMI) and angular displacement. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

Avian influenza H5N1 viral and bird migration networks in Asia

USGS Publications Warehouse

Tian, Huaivu; Zhou, Sen; Dong, Lu; Van Boeckel, Thomas P.; Cui, Yujun; Newman, Scott H.; Takekawa, John Y.; Prosser, Diann J.; Xiao, Xiangming; Wu, Yarong; Cazelles, Bernard; Huang, Shanqian; Yang, Ruifu; Grenfell, Bryan T.; Xu, Bing

2015-01-01

The spatial spread of the highly pathogenic avian influenza virus H5N1 and its long-term persistence in Asia have resulted in avian influenza panzootics and enormous economic losses in the poultry sector. However, an understanding of the regional long-distance transmission and seasonal patterns of the virus is still lacking. In this study, we present a phylogeographic approach to reconstruct the viral migration network. We show that within each wild fowl migratory flyway, the timing of H5N1 outbreaks and viral migrations are closely associated, but little viral transmission was observed between the flyways. The bird migration network is shown to better reflect the observed viral gene sequence data than other networks and contributes to seasonal H5N1 epidemics in local regions and its large-scale transmission along flyways. These findings have potentially far-reaching consequences, improving our understanding of how bird migration drives the periodic reemergence of H5N1 in Asia.

Avian influenza H5N1 viral and bird migration networks in Asia

PubMed Central

Tian, Huaiyu; Zhou, Sen; Dong, Lu; Van Boeckel, Thomas P.; Cui, Yujun; Newman, Scott H.; Takekawa, John Y.; Prosser, Diann J.; Xiao, Xiangming; Wu, Yarong; Cazelles, Bernard; Huang, Shanqian; Yang, Ruifu; Grenfell, Bryan T.; Xu, Bing

2015-01-01

The spatial spread of the highly pathogenic avian influenza virus H5N1 and its long-term persistence in Asia have resulted in avian influenza panzootics and enormous economic losses in the poultry sector. However, an understanding of the regional long-distance transmission and seasonal patterns of the virus is still lacking. In this study, we present a phylogeographic approach to reconstruct the viral migration network. We show that within each wild fowl migratory flyway, the timing of H5N1 outbreaks and viral migrations are closely associated, but little viral transmission was observed between the flyways. The bird migration network is shown to better reflect the observed viral gene sequence data than other networks and contributes to seasonal H5N1 epidemics in local regions and its large-scale transmission along flyways. These findings have potentially far-reaching consequences, improving our understanding of how bird migration drives the periodic reemergence of H5N1 in Asia. PMID:25535385

Inter-Provincial Migration Intentions of Family Physicians in Canada: The Roles of Income and Community Characteristics.

PubMed

Mou, Haizhen; Olfert, M Rose

2015-11-01

The inter-provincial migration patterns of family physicians in canada show that some provinces like newfoundland and saskatchewan experience persistent net out-migration, while others, including ontario and british columbia, are destinations more often than origins of migrants. Governments in provinces exhibiting net out-migration have responded with a number of incentive and recruitment programs. In this study, we investigate the determinants of the stated interprovincial migration intentions of 3,995 rural and urban family physicians in the 2010 wave of the national physician survey. We consider a range of physician characteristics, community attributes and working conditions. We find that in the intention to move, higher compensation has a modest effect, while the community characteristics have a consistently important influence. Our results suggest that policy and program designers should acknowledge the critical role of community-level living and working conditions in their family physician recruitment and retention efforts. Copyright © 2015 Longwoods Publishing.

The blocking of aquaporin-3 (AQP3) impairs extravillous trophoblast cell migration.

PubMed

Alejandra, Reca; Natalia, Szpilbarg; Alicia E, Damiano

2018-05-05

Several aquaporins (AQPs) are expressed in extravillous (EVT) and villous trophoblast cells. Among them, AQP3 is the most abundant AQP expressed in chorionic villi samples from first trimester, followed by AQP1 and AQP9. Although AQP3 expression persists in term placentas, it is significantly decreased in placentas from preeclamptic pregnancies. AQP3 is involved in the migration of different cell types, however its role in human placenta is still unknown. Here, we evaluated the role of AQP3 in the migration of EVT cells during early gestation. Our results showed that Swan 71 cells expressed AQP1, AQP3 and AQP9 but only the blocking of AQP3 by CuSO 4 or the silencing of its expression by siRNA significantly attenuates EVT cell migration. Our work provides evidence that AQP3 is required for EVT cell migration and suggests that an altered expression of placental AQP3 may produce failures in placentation such as in preeclampsia. Copyright © 2018 Elsevier Inc. All rights reserved.

Substrate stiffness regulates cadherin-dependent collective migration through myosin-II contractility

PubMed Central

Ng, Mei Rosa; Besser, Achim

2012-01-01

The mechanical microenvironment is known to influence single-cell migration; however, the extent to which mechanical cues affect collective migration of adherent cells is not well understood. We measured the effects of varying substrate compliance on individual cell migratory properties in an epithelial wound-healing assay. Increasing substrate stiffness increased collective cell migration speed, persistence, and directionality as well as the coordination of cell movements. Dynamic analysis revealed that wounding initiated a wave of motion coordination from the wound edge into the sheet. This was accompanied by a front-to-back gradient of myosin-II activation and establishment of cell polarity. The propagation was faster and farther reaching on stiff substrates, indicating that substrate stiffness affects the transmission of directional cues. Manipulation of myosin-II activity and cadherin–catenin complexes revealed that this transmission is mediated by coupling of contractile forces between neighboring cells. Thus, our findings suggest that the mechanical environment integrates in a feedback with cell contractility and cell–cell adhesion to regulate collective migration. PMID:23091067

Lenalidomide enhances the function of chimeric antigen receptor T cells against the epidermal growth factor receptor variant III by enhancing immune synapses.

PubMed

Kuramitsu, S; Ohno, M; Ohka, F; Shiina, S; Yamamichi, A; Kato, A; Tanahashi, K; Motomura, K; Kondo, G; Kurimoto, M; Senga, T; Wakabayashi, T; Natsume, A

2015-10-01

The epidermal growth factor receptor variant III (EGFRvIII) is exclusively expressed on the cell surface in ~50% of glioblastoma multiforme (GBM). This variant strongly and persistently activates the phosphatidylinositol 3-kinase-Akt signaling pathway in a ligand-independent manner resulting in enhanced tumorigenicity, cellular motility and resistance to chemoradiotherapy. Our group generated a recombinant single-chain variable fragment (scFv) antibody specific to the EGFRvIII, referred to as 3C10-scFv. In the current study, we constructed a lentiviral vector transducing the chimeric antigen receptor (CAR) that consisted of 3C10-scFv, CD3ζ, CD28 and 4-1BB (3C10-CAR). The 3C10-CAR-transduced peripheral blood mononuclear cells (PBMCs) and CD3(+) T cells specifically lysed the glioma cells that express EGFRvIII. Moreover, we demonstrated that CAR CD3(+) T cells migrated to the intracranial xenograft of GBM in the mice treated with 3C10-CAR PBMCs. An important and novel finding of our study was that a thalidomide derivative lenalidomide induced 3C10-CAR PBMC proliferation and enhanced the persistent antitumor effect of the cells in vivo. Lenalidomide also exhibited enhanced immunological synapses between the effector cells and the target cells as determined by CD11a and F-actin polymerization. Collectively, lentiviral-mediated transduction of CAR effectors targeting the EGFRvIII showed specific efficacy, and lenalidomide even intensified CAR cell therapy by enhanced formation of immunological synapses.

Semi-flexible polymer engendered aggregation/dispersion of fullerene (C60) nano-particles: An atomistic investigation

NASA Astrophysics Data System (ADS)

Kumar, Sunil; Pattanayek, Sudip K.

2018-06-01

Semi flexible polymer chain has been modeled by choosing various values of persistent length (stiffness). As the polymer chain stiffness increases, the shape of polymer chain changes from globule to extended cigar to toroid like structure during cooling from a high temperature. The aggregation of fullerene nano-particles is found to depend on the morphology of polymer chain. To maximize, the number of polymer bead-nanoparticle contacts, all nano-particle have positioned inside the polymer globule. To minimize, the energy penalty, due to bending of the polymer chain, all nano-particle have positioned on the surface of the polymer's cigar and toroid morphology.

Insight into fast ion migration kinetics of a new hybrid single Li-ion conductor based on aluminate complexes for solid-state Li-ion batteries.

PubMed

Feng, Yancong; Tan, Rui; Zhao, Yan; Gao, Rongtan; Yang, Luyi; Yang, Jinlong; Li, Hao; Zhou, Guofu; Chen, Haibiao; Pan, Feng

2018-03-29

A novel hybrid single Li-ion conductor (SLIC) for a Li-ion solid electrolyte was prepared by mixing aluminate complexes-polyethylene glycol (LiAl-PEG) and polyethylene oxide (PEO) for solid-state Li-ion batteries. The LiAl-PEG/PEO blend possesses high thermal stability and electrochemical stability with an oxidation decomposition voltage up to 4.8 V. Notably, this hybrid SLIC exhibits not only excellent Li-ion migration kinetics, but also good ionic conductivity as high as 4.0 × 10-5 and 2.6 × 10-4 S cm-1 at 30 and 100 °C, respectively, which is much higher than previously reported SLICs. Importantly, by the combination of molecular dynamics simulations and experiment measurements, the mechanisms of Li-ion migration across the SLIC (LiAl-PEG), the salt-in-polymer (LiClO4/PEO) and the optimized SLIC (LiAl-PEG/PEO) were systematically investigated for the first time. The new hopping transport mechanism was verified for the SLIC system at the nanoscale. As for the hybrid SLIC, PEO chains enhance the segmental mobility of the ether-chains bonded with Al atoms, improve the ionicity, and provide extra ionic paths for Li transfer, resulting in the optimized Li-ion migration kinetics of LiAl-PEG/PEO.

The Quiet Migration Redux: International Adoption, Race, and Difference

PubMed Central

Leinaweaver, Jessaca B.

2014-01-01

Demographers frame international adoption primarily as an unusual kind of migration. This insight offers anthropologists new ways to think about kinship. Drawing on demographic scholarship and anthropological kinship and migration studies, this article develops a new and hybrid approach to international adoption as a complex social process that is both migratory and productive of kinship. Viewing international adoption as a form of migration reveals how the stated “push factors” and actual “pull factors” of international adoption do not align perfectly. Using an anthropological life course perspective, the article then explores how the experiences of these “migrants” and those close to them, over time, are better understood as racialization than solely the product of migration. Looking at adoptees’ lives through a migration lens reveals some of the persistent discomforts that prevent open conversations about racial difference and minority status in an adoptive context, that is, one where children have been caused to migrate, recruited into families. This article draws on data from ethnographic fieldwork with Spanish parents who have adopted Peruvian children to argue that international adoption is a unique form of immigration that produces a minority category within a majority population. PMID:25598546

The Quiet Migration Redux: International Adoption, Race, and Difference.

PubMed

Leinaweaver, Jessaca B

2014-01-01

Demographers frame international adoption primarily as an unusual kind of migration. This insight offers anthropologists new ways to think about kinship. Drawing on demographic scholarship and anthropological kinship and migration studies, this article develops a new and hybrid approach to international adoption as a complex social process that is both migratory and productive of kinship. Viewing international adoption as a form of migration reveals how the stated "push factors" and actual "pull factors" of international adoption do not align perfectly. Using an anthropological life course perspective, the article then explores how the experiences of these "migrants" and those close to them, over time, are better understood as racialization than solely the product of migration. Looking at adoptees' lives through a migration lens reveals some of the persistent discomforts that prevent open conversations about racial difference and minority status in an adoptive context, that is, one where children have been caused to migrate, recruited into families. This article draws on data from ethnographic fieldwork with Spanish parents who have adopted Peruvian children to argue that international adoption is a unique form of immigration that produces a minority category within a majority population.

Supply chain optimization: a practitioner's perspective on the next logistics breakthrough.

PubMed

Schlegel, G L

2000-08-01

The objective of this paper is to profile a practitioner's perspective on supply chain optimization and highlight the critical elements of this potential new logistics breakthrough idea. The introduction will briefly describe the existing distribution network, and business environment. This will include operational statistics, manufacturing software, and hardware configurations. The first segment will cover the critical success factors or foundations elements that are prerequisites for success. The second segment will give you a glimpse of a "working game plan" for successful migration to supply chain optimization. The final segment will briefly profile "bottom-line" benefits to be derived from the use of supply chain optimization as a strategy, tactical tool, and competitive advantage.

The cutoff phenomenon in finite Markov chains.

PubMed Central

Diaconis, P

1996-01-01

Natural mixing processes modeled by Markov chains often show a sharp cutoff in their convergence to long-time behavior. This paper presents problems where the cutoff can be proved (card shuffling, the Ehrenfests' urn). It shows that chains with polynomial growth (drunkard's walk) do not show cutoffs. The best general understanding of such cutoffs (high multiplicity of second eigenvalues due to symmetry) is explored. Examples are given where the symmetry is broken but the cutoff phenomenon persists. PMID:11607633

Sequence-Dependent Persistence Length of Long DNA

NASA Astrophysics Data System (ADS)

Chuang, Hui-Min; Reifenberger, Jeffrey G.; Cao, Han; Dorfman, Kevin D.

2017-12-01

Using a high-throughput genome-mapping approach, we obtained circa 50 million measurements of the extension of internal human DNA segments in a 41 nm ×41 nm nanochannel. The underlying DNA sequences, obtained by mapping to the reference human genome, are 2.5-393 kilobase pairs long and contain percent GC contents between 32.5% and 60%. Using Odijk's theory for a channel-confined wormlike chain, these data reveal that the DNA persistence length increases by almost 20% as the percent GC content increases. The increased persistence length is rationalized by a model, containing no adjustable parameters, that treats the DNA as a statistical terpolymer with a sequence-dependent intrinsic persistence length and a sequence-independent electrostatic persistence length.

Directional Collective Cell Migration Emerges as a Property of Cell Interactions

PubMed Central

Woods, Mae L.; Carmona-Fontaine, Carlos; Barnes, Chris P.; Couzin, Iain D.; Mayor, Roberto; Page, Karen M.

2014-01-01

Collective cell migration is a fundamental process, occurring during embryogenesis and cancer metastasis. Neural crest cells exhibit such coordinated migration, where aberrant motion can lead to fatality or dysfunction of the embryo. Migration involves at least two complementary mechanisms: contact inhibition of locomotion (a repulsive interaction corresponding to a directional change of migration upon contact with a reciprocating cell), and co-attraction (a mutual chemoattraction mechanism). Here, we develop and employ a parameterized discrete element model of neural crest cells, to investigate how these mechanisms contribute to long-range directional migration during development. Motion is characterized using a coherence parameter and the time taken to reach, collectively, a target location. The simulated cell group is shown to switch from a diffusive to a persistent state as the response-rate to co-attraction is increased. Furthermore, the model predicts that when co-attraction is inhibited, neural crest cells can migrate into restrictive regions. Indeed, inhibition of co-attraction in vivo and in vitro leads to cell invasion into restrictive areas, confirming the prediction of the model. This suggests that the interplay between the complementary mechanisms may contribute to guidance of the neural crest. We conclude that directional migration is a system property and does not require action of external chemoattractants. PMID:25181349

Four Decades of Andean Timberline Migration and Implications for Biodiversity Loss with Climate Change

PubMed Central

Lutz, David A.; Powell, Rebecca L.; Silman, Miles R.

2013-01-01

Rapid 21st-century climate change may lead to large population decreases and extinction in tropical montane cloud forest species in the Andes. While prior research has focused on species migrations per se, ecotones may respond to different environmental factors than species. Even if species can migrate in response to climate change, if ecotones do not they can function as hard barriers to species migrations, making ecotone migrations central to understanding species persistence under scenarios of climate change. We examined a 42-year span of aerial photographs and high resolution satellite imagery to calculate migration rates of timberline–the grassland-forest ecotone–inside and outside of protected areas in the high Peruvian Andes. We found that timberline in protected areas was more likely to migrate upward in elevation than in areas with frequent cattle grazing and fire. However, rates in both protected (0.24 m yr−1) and unprotected (0.05 m yr−1) areas are only 0.5–2.3% of the rates needed to stay in equilibrium with projected climate by 2100. These ecotone migration rates are 12.5 to 110 times slower than the observed species migration rates within the same forest, suggesting a barrier to migration for mid- and high-elevation species. We anticipate that the ecotone will be a hard barrier to migration under future climate change, leading to drastic population and biodiversity losses in the region unless intensive management steps are taken. PMID:24040260

Four decades of Andean timberline migration and implications for biodiversity loss with climate change.

PubMed

Lutz, David A; Powell, Rebecca L; Silman, Miles R

2013-01-01

Rapid 21st-century climate change may lead to large population decreases and extinction in tropical montane cloud forest species in the Andes. While prior research has focused on species migrations per se, ecotones may respond to different environmental factors than species. Even if species can migrate in response to climate change, if ecotones do not they can function as hard barriers to species migrations, making ecotone migrations central to understanding species persistence under scenarios of climate change. We examined a 42-year span of aerial photographs and high resolution satellite imagery to calculate migration rates of timberline--the grassland-forest ecotone-inside and outside of protected areas in the high Peruvian Andes. We found that timberline in protected areas was more likely to migrate upward in elevation than in areas with frequent cattle grazing and fire. However, rates in both protected (0.24 m yr(-1)) and unprotected (0.05 m yr(-1)) areas are only 0.5-2.3% of the rates needed to stay in equilibrium with projected climate by 2100. These ecotone migration rates are 12.5 to 110 times slower than the observed species migration rates within the same forest, suggesting a barrier to migration for mid- and high-elevation species. We anticipate that the ecotone will be a hard barrier to migration under future climate change, leading to drastic population and biodiversity losses in the region unless intensive management steps are taken.

Expression of macrophage migration inhibitory factor in footpad skin lesions with diabetic neuropathy.

PubMed

Up Noh, Sun; Lee, Won-Young; Kim, Won-Serk; Lee, Yong-Taek; Jae Yoon, Kyung

2018-01-01

Background Diabetic neuropathy originating in distal lower extremities is associated with pain early in the disease course, overwhelming in the feet. However, the pathogenesis of diabetic neuropathy remains unclear. Macrophage migration inhibitory factor has been implicated in the onset of neuropathic pain and the development of diabetes. Objective of this study was to observe pain syndromes elicited in the footpad of diabetic neuropathy rat model and to assess the contributory role of migration inhibitory factor in the pathogenesis of diabetic neuropathy. Methods Diabetic neuropathy was made in Sprague Dawley rats by streptozotocin. Pain threshold was evaluated using von Frey monofilaments for 24 weeks. On comparable experiment time after streptozotocin injection, all footpads were prepared for following procedures; glutathione assay, terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling staining, immunohistochemistry staining, real-time reverse transcription polymerase chain reaction, and Western blot. Additionally, human HaCaT skin keratinocytes were treated with methylglyoxal, transfected with migration inhibitory factor/control small interfering RNA, and prepared for real-time reverse transcription polymerase chain reaction and Western blot. Results As compared to sham group, pain threshold was significantly reduced in diabetic neuropathy group, and glutathione was decreased in footpad skin, simultaneously, cell death was increased. Over-expression of migration inhibitory factor, accompanied by low expression of glyoxalase-I and intraepidermal nerve fibers, was shown on the footpad skin lesions of diabetic neuropathy. But, there was no significance in expression of neurotransmitters and inflammatory mediators such as transient receptor potential vanilloid 1, mas-related G protein coupled receptor D, nuclear factor kappa B, tumor necrosis factor-alpha, and interleukin-6 between diabetic neuropathy group and sham group. Intriguingly, small interfering RNA-transfected knockdown of the migration inhibitory factor gene in methylglyoxal-treated skin keratinocytes increased expression of glyoxalase-I and intraepidermal nerve fibers in comparison with control small interfering RNA-transfected cells, which was decreased by induction of methylglyoxal. Conclusions Our findings suggest that migration inhibitory factor can aggravate diabetic neuropathy by suppressing glyoxalase-I and intraepidermal nerve fibers on the footpad skin lesions and provoke pain. Taken together, migration inhibitory factor might offer a pharmacological approach to alleviate pain syndromes in diabetic neuropathy.

Mobilization of human mesenchymal stem cells through different cytokines and growth factors after their immobilization by sulfur mustard.

PubMed

Schreier, Cassandra; Rothmiller, Simone; Scherer, Michael A; Rummel, Christoph; Steinritz, Dirk; Thiermann, Horst; Schmidt, Annette

2018-09-01

The chemical warfare agent sulfur mustard (SM), also known as mustard gas, was first used in World War I. Although prohibited by the chemical warfare convention, significant amounts of SM still exist and have still to be regarded as a threat for military personnel and civilians. After SM exposure, the most prominent clinical symptom is the development of extensive non-healing skin wounds. This chronic wound healing dysfunction is persisting over long time. Mesenchymal stem cells (MSC) are known to play an important role in wound healing. Moreover, it is also known that patients with chronic wound healing diseases have compromised mesenchymal stem cell functionality. Based on these observations and the known relationship between wound healing dysfunction and MSC function we investigated the impact of sulfur mustard on human MSC. Mesenchymal stem cells (MSC) were isolated from femoral heads of healthy donors. They were cultured for less than four passages. MSC were exposed towards different sulfur mustard concentrations. After exposure we analyzed the secretome and the migration capacity. The migration capacity under influence of SM was analyzed after treatment with various cytokines. SM exposure (even at very low concentrations) showed negative effects on the migration capability. Many cytokines that are necessary for MSC migration were secreted in a reduced manner. The reduced migratory capacity can be compensated in part by the addition of cytokines. Here especially IL-8 (e and m) and IL-6 significantly compensated the SM induced migration reduction. The effect of sulfur mustard on MSC might play an important role in the persistence of long-term adverse effects; here the reduced migration could particularly be important. The compensation of the SM-induced migration reduction by addition of cytokines could possibly solve this problem. Moreover, our current results will help to understand the relationship between alkylating agents and MSC and thus will also give guidance in the future perspective for the therapeutic use of MSC in patients suffering from sulfur mustard induced chronic skin wounds. Copyright © 2018 Elsevier B.V. All rights reserved.

Timing of the formation and migration of giant planets as constrained by CB chondrites

PubMed Central

Johnson, Brandon C.; Walsh, Kevin J.; Minton, David A.; Krot, Alexander N.; Levison, Harold F.

2016-01-01

The presence, formation, and migration of giant planets fundamentally shape planetary systems. However, the timing of the formation and migration of giant planets in our solar system remains largely unconstrained. Simulating planetary accretion, we find that giant planet migration produces a relatively short-lived spike in impact velocities lasting ~0.5 My. These high-impact velocities are required to vaporize a significant fraction of Fe,Ni metal and silicates and produce the CB (Bencubbin-like) metal-rich carbonaceous chondrites, a unique class of meteorites that were created in an impact vapor-melt plume ~5 My after the first solar system solids. This indicates that the region where the CB chondrites formed was dynamically excited at this early time by the direct interference of the giant planets. Furthermore, this suggests that the formation of the giant planet cores was protracted and the solar nebula persisted until ~5 My. PMID:27957541

Internal Migration and Sexual Initiation among Never Married Youths in Nigeria

PubMed Central

Mberu, Blessing Uchenna; White, Michael J

2013-01-01

The high rates of youth migration to urban and economic centers, in the context of persistent poverty and devastating HIV/AIDS burden, raises intricate social policy challenges in developing countries. This study examines patterns of internal migration and sexual initiation among Nigerian youths, using the 2003 Nigeria DHS data, descriptive statistics, Kaplan-Meier survival curves and discrete-time hazard regression models. Migrants generally show stronger association than non-migrants, and urban-urban migrants show the strongest independent association to early sexual initiation. These outcomes underscore that loss of social capital and exposure to sexually lenient urban environment increase youth's propensity to sexual engagement. Other significant covariates are age, gender, ethnic origin, education, independent living arrangement and formal employment. The findings highlight the inadequacy of policy perspectives that neglect complex contextual nuances across groups and the need to address limited livelihood opportunities that fuel youth migration to urban destinations. PMID:21435767

Timing of the formation and migration of giant planets as constrained by CB chondrites.

PubMed

Johnson, Brandon C; Walsh, Kevin J; Minton, David A; Krot, Alexander N; Levison, Harold F

2016-12-01

The presence, formation, and migration of giant planets fundamentally shape planetary systems. However, the timing of the formation and migration of giant planets in our solar system remains largely unconstrained. Simulating planetary accretion, we find that giant planet migration produces a relatively short-lived spike in impact velocities lasting ~0.5 My. These high-impact velocities are required to vaporize a significant fraction of Fe,Ni metal and silicates and produce the CB (Bencubbin-like) metal-rich carbonaceous chondrites, a unique class of meteorites that were created in an impact vapor-melt plume ~5 My after the first solar system solids. This indicates that the region where the CB chondrites formed was dynamically excited at this early time by the direct interference of the giant planets. Furthermore, this suggests that the formation of the giant planet cores was protracted and the solar nebula persisted until ~5 My.

Diverging patterns with endogenous labor migration.

PubMed

Reichlin, P; Rustichini, A

1998-05-05

"The standard neoclassical model cannot explain persistent migration flows and lack of cross-country convergence when capital and labor are mobile. Here we present a model where both phenomena may take place.... Our model is based on the Arrow-Romer approach to endogenous growth theory. We single out the importance of a (however weak) scale effect from the size of the workforce.... The main conclusion of this simple model is that lack of convergence, or even divergence, among countries is possible, even with perfect capital mobility and labor mobility." excerpt

Cell-cell interactions mediate cytoskeleton organization and collective endothelial cell chemotaxis.

PubMed

Shamloo, Amir

2014-09-01

This study investigates the role of cell-cell and cell-ligand interactions in cytoskeleton organization of endothelial cells (ECs) and their directional migration within a microfluidic device. The migration of ECs in response to a biochemical factor was studied. Mathematical analysis of the cell migration pathways and cellular cytoskeleton revealed that directional migration, migration persistence length, migration speed, and cytoskeletal stress fiber alignment can be mediated by the level of cell contacts as well as the presence or absence of a biochemical polarizing factor. It was shown that in the presence of a biochemical polarizing factor, higher cell density and more frequent cell contacts has a reinforcing effect on collective cell chemotaxis. In contrast, in the absence of a polarizing factor, high cell density can decrease or suppress the ability of the cells to migrate. Also, the correlation of actin stress fiber organization and alignment with directional migration of ECs was investigated. It was shown that in the presence of a biochemical polarizing factor, stress fibers within the cytoskeleton of ECs can be significantly aligned parallel to the gradient direction when the cells have higher level of contacts. The results also show that the organization and alignment of actin stress fibers is mediated by cell adhesion junctions during collective cell migration and introduce cell-cell interactions as a key factor during collective cell chemotaxis. © 2014 Wiley Periodicals, Inc.

Emigration from China in Comparative Perspective*

PubMed Central

Lu, Yao; Liang, Zai; Chunyu, Miao David

2014-01-01

Comparative research on international migration has increasingly focused on immigrant integration rather than the process of emigration. By investigating the different streams of Chinese migration to the United States and Europe, as well as the different stages of Chinese migration to the U.S., this study examines the way in which both receiving and sending contexts combine to shape the process of emigration. Using data from a 2002–2003 survey of emigration from China’s Fujian Province, we demonstrate that under restrictive exit and entry policies and high barriers to migration (i.e., clandestine migration from Fuzhou to the U.S.), resources such as migrant social capital, political capital (cadre resources), and human capital all play a crucial role in the emigration process. However, the roles of these resources in the migration process are limited when migration barriers are sufficiently low and when local governments adopt proactive policies promoting emigration (i.e., legal migration from Mingxi to Europe). Comparisons over time suggest that the importance of migrant social capital, political capital, and human capital has strongly persisted for Fuzhou-US emigration, as a result of tightening exit and entry policies. Despite these marked differences between Fuzhou and Mingxi emigration, the results also point to two general processes that are highly consistent across settings and over time—the cumulative causation of migration and the advantage conferred by traditional positional power (cadre status). PMID:26146414

Plasmon-Polariton Properties in Metallic Nanosphere Chains

PubMed Central

Jacak, Witold Aleksander; Krasnyj, Jurij; Chepok, Andrej

2015-01-01

The propagation of collective wave type plasmonic excitations along infinite chains of metallic nanospheres has been analyzed, including near-, medium- and far-field contributions to the plasmon dipole interaction with all retardation effects taken into account. It is proven that there exist weakly-damped self-modes of plasmon-polaritons in the chain for which the propagation range is limited by relatively small Ohmic losses only. In this regime, the Lorentz friction irradiation losses on each nanosphere in the chain are ideally compensated by the energy income from the rest of the chain. The completely undamped collective waves were identified in the case of the presence of persistent external excitation of some fragment of the chain. The obtained characteristics of these excitations fit the experimental observations well. PMID:28793415

aPKCζ affects directed cell migration through the regulation of myosin light chain phosphorylation

PubMed Central

Petrov, Daria; Dahan, Inbal; Cohen-Kfir, Einav; Ravid, Shoshana

2017-01-01

ABSTRACT Cell motility is an essential cellular process for a variety of biological events. It requires cross-talk between the signaling and the cytoskeletal systems. Despite the recognized importance of aPKCζ for cell motility, there is little understanding of the mechanism by which aPKCζ mediates extracellular signals to the cytoskeleton. In the present study, we report that aPKCζ is required for the cellular organization of acto-non-muscle myosin II (NMII) cytoskeleton, for proper cell adhesion and directed cell migration. We show that aPKCζ mediates EGF-dependent RhoA activation and recruitment to the cell membrane. We also show that aPKCζ mediates EGF-dependent myosin light chain (MRLC) phosphorylation that is carried out by Rho-associated protein kinase (ROCK), and that aPKCζ is required for EGF-dependent phosphorylation and inhibition of the myosin phosphatase targeting subunit (MYPT). Finally, we show that aPKCζ mediates the spatial organization of the acto-NMII cytoskeleton in response to EGF stimulation. Our data suggest that aPKCζ is an essential component regulator of acto-NMII cytoskeleton organization leading to directed cell migration, and is a mediator of the EGF signal to the cytoskeleton. PMID:27541056

Low Elevation Riparian Environments: Warm-Climate Refugia for Conifers in the Great Basin, USA?

NASA Astrophysics Data System (ADS)

Millar, C.; Charlet, D. A.; Westfall, R. D.; Delany, D.

2015-12-01

The Great Basin, USA, contains hundreds of small to large mountain ranges. Many reach alpine elevations, which are separated from each other by low-elevation basins currently inhospitable to conifer growth. Many of these ranges support montane and subalpine conifer species that have affinities to the Sierra Nevada or Rocky Mountains, and from which these conifers migrated during cool periods of the Pleistocene. Under Holocene climates, the Great Basin geography became a terrestrial island-archipelago, wherein conifer populations are isolated among ranges, and inter-range migration is highly limited. During warm intervals of the Holocene, conifers would be expected to have migrated upslope following favorable conditions, and extirpation would be assumed to result from continued warming. Independent patterns, repeating across multiple species' distributions, however, suggest that refugia were present in these ranges during warm periods, and that low elevation environments below the current main distributions acted as climatic refugia. We hypothesize that cool, narrow, and north-aspect ravines, which during cool climates support persistent or seasonal creeks and deciduous riparian communities, become available as conifer habitat when warming climates desiccate creeks and deplete riparian species. We further speculate that cold-air drainage, reduced solar insolation, lower wind exposure, and higher water tables in these topographic positions support populations of montane and subalpine conifers even during warm climate intervals when high elevations are unfavorable for conifer persistence. On return to cool climates, low elevation refugia become sources for recolonizing higher slopes, and/or continue to persist as relictual populations. We present several lines of evidence supporting this hypothesis, and speculate that low-elevation, extramarginal riparian environments might act as climate refugia for Great Basin conifers in the future as well.

[AntiEGFRnano inhibites proliferation and migration of estrogen-dependent Ishikawa cells of human endometrial cancer cell line].

PubMed

Diao, Zhen-yu; Lu, Wu-guang; Cao, Peng; Hu, Yun-long; Zhou, Xing; Xue, Ping-ping; Shen, Li; Sun, Hai-xiang

2012-10-01

Nanobody is a kind of antibody from camel, which misses light chain. Nanobody has the same antigen binding specificity and affinity as mAb. Moreover, because of its small molecular weight, high stability and easy preparation, nanobody has great value of biomedical applications. In this study, we successfully prepared highly pure antiEGFR nanobody in E.coli using genetic engineering techniques. Cell proliferation assay (CCK-8 assay) and migration experiments (cell scratch test and Transwell assay) indicated that the recombinant antiEGFRnano can significantly inhibit the proliferation and migration of endometrial cancer cells. These results provide a new way of thinking and methods for EGFR-targeted therapy of endometrial cancer.

Understanding the factors affecting the activation of alkane by Cp′Rh(CO)2 (Cp′ = Cp or Cp*)

PubMed Central

George, Michael W.; Hall, Michael B.; Jina, Omar S.; Portius, Peter; Sun, Xue-Zhong; Towrie, Michael; Wu, Hong; Yang, Xinzheng; Zarić, Snežana D.

2010-01-01

Fast time-resolved infrared spectroscopic measurements have allowed precise determination of the rates of activation of alkanes by Cp′Rh(CO) (Cp′ = η5-C5H5 or η5-C5Me5). We have monitored the kinetics of C─H activation in solution at room temperature and determined how the change in rate of oxidative cleavage varies from methane to decane. The lifetime of CpRh(CO)(alkane) shows a nearly linear behavior with respect to the length of the alkane chain, whereas the related Cp*Rh(CO)(alkane) has clear oscillatory behavior upon changing the alkane. Coupled cluster and density functional theory calculations on these complexes, transition states, and intermediates provide the insight into the mechanism and barriers in order to develop a kinetic simulation of the experimental results. The observed behavior is a subtle interplay between the rates of activation and migration. Unexpectedly, the calculations predict that the most rapid process in these Cp′Rh(CO)(alkane) systems is the 1,3-migration along the alkane chain. The linear behavior in the observed lifetime of CpRh(CO)(alkane) results from a mechanism in which the next most rapid process is the activation of primary C─H bonds (─CH3 groups), while the third key step in this system is 1,2-migration with a slightly slower rate. The oscillatory behavior in the lifetime of Cp*Rh(CO)(alkane) with respect to the alkane’s chain length follows from subtle interplay between more rapid migrations and less rapid primary C─H activation, with respect to CpRh(CO)(alkane), especially when the CH3 group is near a gauche turn. This interplay results in the activation being controlled by the percentage of alkane conformers. PMID:21048088

Capillary sample introduction of polymerase chain reaction (PCR) products separated in ultrathin slab gels.

PubMed

Bullard, K M; Hietpas, P B; Ewing, A G

1998-01-01

Polymerase chain reaction (PCR) amplified short tandem repeat (STR) samples from the HUMVWF locus have been analyzed using a unique sample introduction and separation technique. A single capillary is used to transfer samples onto an ultrathin slab gel (57 microm thin). This ultrathin nondenaturing polyacrylamide gel is used to separate the amplified fragments, and laser-induced fluorescence with ethidium bromide is used for detection. The feasibility of performing STR analysis using this system has been investigated by examining the reproducibility for repeated samples. Reproducibility is examined by comparing the migration of the 14 and 17 HUMVWF alleles on three consecutive separations on the ultrathin slab gel. Using one locus, separations match in migration time with the two alleles 42 s apart for each of the three consecutive separations. This technique shows potential to increase sample throughput in STR analysis techniques although separation resolution still needs to be improved.

Electrostatic persistence length.

PubMed

Fixman, Marshall

2010-03-11

The persistence length is calculated for polyelectrolyte chains with fixed bond lengths and bond angles (pi-theta), and a potential energy consisting of the screened Coulomb interaction between beads, potential wells alpha phi(i)2 for the dihedral angles phi(i), and coupling terms beta phi(i) phi(i+/-1). This model defines a librating chain that reduces in appropriate limits to the freely rotating or wormlike chains, it can accommodate local crumpling or extreme stiffness, and it is easy to simulate. A planar-quadratic (pq), analytic approximation is based on an expansion of the electrostatic energy in eigenfunctions of the quadratic form that describes the backbone energy, and on the assumption that the quadratic form not only is positive but also adequately confines the chain in an infinite phase space of dihedral angles to the physically unique part with all |phi(i)| < pi. The pq approximation is available under these weak constraints, but the simulations confirm its quantitative accuracy only under the expected condition that alpha is large, that is, for very stiff chains. Stiff chains can also be simulated with small alpha and small theta and compared to an OSF approximation suitably generalized to chains with finite rather than vanishing theta, and increasing agreement with OSF is found the smaller is theta. The two approximations, one becoming exact as alpha --> infinity with fixed theta, the other as theta --> 0 with fixed alpha, are quantitatively similar in behavior, both giving a persistence length P = P0 + aD2 for stiff chains, where D is the Debye length. However, the coefficient apq is about twice the value of aOSF. Under other conditions the simulations show that P may or not be linear in D2 at small or moderate D, depending on the magnitudes of alpha, beta, theta, and the charge density but always becomes linear at large D. Even at a moderately low charge density, corresponding to fewer than 20% of the beads being charged, and with strong crumpling induced by large beta, increasing D dissolves blobs and recovers a linear dependence of P on D2, although a lower power of D gives an adequate fit at moderate D. For the class of models considered, it is concluded that the only universal feature is the asymptotic linearity of P in D2, regardless of flexibility or stiffness.

Efforts to estimate pesticide degradation rates in subsurface ...

EPA Pesticide Factsheets

When pesticides are used in real-world settings, the objective is to be effective in pest eradication at the site of application, but also it is desired that the pesticide have minimal persistence and mobility as it migrates away from the application site. At the site of application, sorption on soil and surface-soil degradation rates both factor into the pesticides' persistence. But once it migrates to the subsurface vadose zone and/or aquifers, subsurface degradation rate is a factor as well. Unfortunately, numerous soil properties that might affect pesticide degradation rate vary by orders of magnitude in the subsurface environment, both spatially and temporally, e.g., organic-carbon concentration, oxygen concentration, redox conditions, pH and soil mineralogy. Consequently, estimation of subsurface pesticide degradation rates and, in tum, pesticide persistence and mobility in the environment, has remained a challenge. To address this intransigent uncertainty, we surveyed peer-reviewed literature to identify > 100 data pairs in which investigators reported pesticide degradation rates in both surface and subsurface soils, using internally consistent experimental methods. These > 100 data pairs represented >30 separate pesticides. When the > 100 subsurface half-lives were plotted against surface half-lives, a limiting line could be defined for which all subsurface half-lives but three fe ll below the line. Of the three data points plotting above the limiting li

Transient nature of cooperation by pay-it-forward reciprocity

PubMed Central

Horita, Yutaka; Takezawa, Masanori; Kinjo, Takuji; Nakawake, Yo; Masuda, Naoki

2016-01-01

Humans often forward kindness received from others to strangers, a phenomenon called the upstream or pay-it-forward indirect reciprocity. Some field observations and laboratory experiments found evidence of pay-it-forward reciprocity in which chains of cooperative acts persist in social dilemma situations. Theoretically, however, cooperation based on pay-it-forward reciprocity is not sustainable. We carried out laboratory experiments of a pay-it-forward indirect reciprocity game (i.e., chained gift-giving game) on a large scale in terms of group size and time. We found that cooperation consistent with pay-it-forward reciprocity occurred only in a first few decisions per participant and that cooperation originated from inherent pro-sociality of individuals. In contrast, the same groups of participants showed persisting chains of cooperation in a different indirect reciprocity game in which participants earned reputation by cooperating. Our experimental results suggest that pay-it-forward reciprocity is transient and disappears when a person makes decisions repeatedly, whereas the reputation-based reciprocity is stable in the same situation. PMID:26786178

Transient nature of cooperation by pay-it-forward reciprocity.

PubMed

Horita, Yutaka; Takezawa, Masanori; Kinjo, Takuji; Nakawake, Yo; Masuda, Naoki

2016-01-20

Humans often forward kindness received from others to strangers, a phenomenon called the upstream or pay-it-forward indirect reciprocity. Some field observations and laboratory experiments found evidence of pay-it-forward reciprocity in which chains of cooperative acts persist in social dilemma situations. Theoretically, however, cooperation based on pay-it-forward reciprocity is not sustainable. We carried out laboratory experiments of a pay-it-forward indirect reciprocity game (i.e., chained gift-giving game) on a large scale in terms of group size and time. We found that cooperation consistent with pay-it-forward reciprocity occurred only in a first few decisions per participant and that cooperation originated from inherent pro-sociality of individuals. In contrast, the same groups of participants showed persisting chains of cooperation in a different indirect reciprocity game in which participants earned reputation by cooperating. Our experimental results suggest that pay-it-forward reciprocity is transient and disappears when a person makes decisions repeatedly, whereas the reputation-based reciprocity is stable in the same situation.

Persistence length of collagen molecules based on nonlocal viscoelastic model.

PubMed

Ghavanloo, Esmaeal

2017-12-01

Persistence length is one of the most interesting properties of a molecular chain, which is used to describe the stiffness of a molecule. The experimentally measured values of the persistence length of the collagen molecule are widely scattered from 14 to 180 nm. Therefore, an alternative approach is highly desirable to predict the persistence length of a molecule and also to explain the experimental results. In this paper, a nonlocal viscoelastic model is developed to obtain the persistence length of the collagen molecules in solvent. A new explicit formula is proposed for the persistence length of the molecule with the consideration of the small-scale effect, viscoelastic properties of the molecule, loading frequency, and viscosity of the solvent. The presented model indicates that there exists a range of molecule lengths in which the persistence length strongly depends on the frequency and spatial mode of applied loads, small-scale effect, and viscoelastic properties of the collagen.

From single Debye-Hückel chains to polyelectrolyte solutions: Simulation results

NASA Astrophysics Data System (ADS)

Kremer, Kurt

1996-03-01

This lecture will present results from simulations of single weakly charged flexible chains, where the electrostatic part of the interaction is modeled by a Debye-Hückel potential,( with U. Micka, IFF, Forschungszentrum Jülich, 52425 Jülich, Germany) as well as simulations of polyelectrolyte solutions, where the counterions are explicitly taken into account( with M. J. Stevens, Sandia Nat. Lab., Albuquerque, NM 87185-1111) ( M. J. Stevens, K. Kremer, JCP 103), 1669 (1995). The first set of the simulations is meant to clear a recent contoversy on the dependency of the persistence length LP on the screening length Γ. While the analytic theories give Lp ~ Γ^x with either x=1 or x=2, the simulations find for all experimentally accessible chain lengths a varying exponent, which is significantly smaller than 1. This causes serious doubts on the applicability of this model for weakly charged polyelectrolytes in general. The second part deals with strongly charged flexible polyelectrolytes in salt free solution. These simulations are performed for multichain systems. The full Coulomb interactions of the monomers and counterions are treated explicitly. Experimental measurements of the osmotic pressure and the structure factor are reproduced and extended. The simulations reveal a new picture of the chain structure based on calculations of the structure factor, persistence length, end-to-end distance, etc. Even at very low density, the chains show significant bending. Furthermore, the chains contract significantly before they start to overlap. We also show that counterion condensation dramatically alters the chain structure, even for a good solvent backbone.

Control of barrier island shape by inlet sediment bypassing: East Frisian Islands, West Germany

USGS Publications Warehouse

FitzGerald, D.M.; Penland, S.; Nummedal, D.

1984-01-01

A study of the East Frisian Islands has shown that the plan form of these islands can be explained by processes of inlet sediment bypassing. This island chain is located on a high wave energy, high tide range shoreline where the average deep-water significant wave height exceeds 1.0 m and the spring tidal range varies from 2.7 m at Juist to 2.9 m at Wangerooge. An abundant sediment supply and a strong eastward component of wave power (4.4 ?? 103 W m-1) have caused a persistent eastward growth of the barrier islands. The eastward extension of the barriers has been accommodated more by inlet narrowing, than by inlet migration. It is estimated from morphological evidence that a minimum of 2.7 ?? 105 m3 of sand is delivered to the inlets each year via the easterly longshore transport system. Much of this sand ultimately bypasses the inlets in the form of large, migrating swash bars. The location where the swash bars attach to the beach is controlled by the amount of overlap of the ebb-tidal delta along the downdrift inlet shoreline. The configuration of the ebbtidal delta, in turn, is a function of inlet size and position of the main ebb channel. The swash bar welding process has caused preferential beach nourishment and historical shoreline progradation. Along the East Frisian Islands this process has produced barrier islands with humpbacked, bulbous updrift and bulbous downdrift shapes. The model of barrier island development presented in this paper not only explains well the configuration of the German barriers but also the morphology of barriers along many other mixed energy coasts. ?? 1984.

Migration of nanoparticles from plastic packaging materials containing carbon black into foodstuffs

PubMed Central

Bott, Johannes; Störmer, Angela; Franz, Roland

2014-01-01

Carbon black was investigated to assess and quantify the possibility that nanoparticles might migrate out of plastic materials used in the food packaging industry. Two types of carbon black were incorporated in low-density polyethylene (LDPE) and polystyrene (PS) at 2.5% and 5.0% loading (w/w), and then subjected to migration studies. The samples were exposed to different food simulants according to European Union Plastics Regulation 10/2011, simulating long-term storage with aqueous and fatty foodstuffs. Asymmetric flow field-flow fractionation (AF4) coupled to a multi-angle laser light-scattering (MALLS) detector was used to separate, characterise and quantify the potential release of nanoparticles. The AF4 method was successful in differentiating carbon black from other matrix components, such as extracted polymer chains, in the migration solution. At a detection limit of 12 µg kg−1, carbon black did not migrate from the packaging material into food simulants. The experimental findings are in agreement with theoretical considerations based on migration modelling. From both the experimental findings and theoretical considerations, it can be concluded that carbon black does not migrate into food once it is incorporated into a plastics food contact material. PMID:25105506

Migration of nanoparticles from plastic packaging materials containing carbon black into foodstuffs.

PubMed

Bott, Johannes; Störmer, Angela; Franz, Roland

2014-01-01

Carbon black was investigated to assess and quantify the possibility that nanoparticles might migrate out of plastic materials used in the food packaging industry. Two types of carbon black were incorporated in low-density polyethylene (LDPE) and polystyrene (PS) at 2.5% and 5.0% loading (w/w), and then subjected to migration studies. The samples were exposed to different food simulants according to European Union Plastics Regulation 10/2011, simulating long-term storage with aqueous and fatty foodstuffs. Asymmetric flow field-flow fractionation (AF4) coupled to a multi-angle laser light-scattering (MALLS) detector was used to separate, characterise and quantify the potential release of nanoparticles. The AF4 method was successful in differentiating carbon black from other matrix components, such as extracted polymer chains, in the migration solution. At a detection limit of 12 µg kg⁻¹, carbon black did not migrate from the packaging material into food simulants. The experimental findings are in agreement with theoretical considerations based on migration modelling. From both the experimental findings and theoretical considerations, it can be concluded that carbon black does not migrate into food once it is incorporated into a plastics food contact material.

The heparan sulfate-modifying enzyme glucuronyl C5-epimerase HSE-5 controls Caenorhabditis elegans Q neuroblast polarization during migration.

PubMed

Wang, Xiangming; Liu, Jianhong; Zhu, Zhiwen; Ou, Guangshuo

2015-03-15

Directional cell migration is fundamental for neural development, and extracellular factors are pivotal for this process. Heparan sulfate proteoglycans (HSPGs) that carry long chains of differentially modified sugar residues contribute to extracellular matrix; however, the functions of HSPG in guiding cell migration remain elusive. Here, we used the Caenorhabditis elegans mutant pool from the Million Mutation Project and isolated a mutant allele of the heparan sulfate-modifying enzyme glucuronyl C5-epimerase HSE-5. Loss-of-function of this enzyme resulted in defective Q neuroblast migration. We showed that hse-5 controlled Q cell migration in a cell non-autonomous manner. By performing live cell imaging in hse-5 mutant animals, we found that hse-5 controlled initial polarization during Q neuroblast migration. Furthermore, our genetic epistasis analysis demonstrated that lon-2 might act downstream of hse-5. Finally, rescue of the hse-5 mutant phenotype by expression of human and mouse hse-5 homologs suggested a conserved function for this gene in neural development. Taken together, our results indicated that proper HSPG modification in the extracellular matrix by HSE-5 is essential for neuroblast polarity during migration. Copyright © 2015 Elsevier Inc. All rights reserved.

Structural changes and triacetin migration of starch acetate film contacting with distilled water as food simulant.

PubMed

Zhu, Jie; Li, Xiaoxi; Huang, Chen; Chen, Ling; Li, Lin

2014-04-15

This work studied the structural changes and the migration of triacetin plasticizer in starch acetate films in the presence of distilled water as food simulant. Fourier-transform infrared spectroscopy result showed that the macromolecular interaction was enhanced to form compact aggregation of amorphous chains. The characterization of aggregation structures via wide and small angle X-ray scattering techniques indicated that the orderly microregion was compressed and the crystallites inside were "squeezed" to form interference and further aggregation. The compact aggregation structures restricted the mobility of macromolecules, triacetin and water molecules. The overall kinetic and the diffusion model analysis manifested that Fick's second law was the predominant mechanism for the short-term migration of triacetin. The increasing relaxation within film matrix caused the subsequent migration to deviate from Fick's law. The safe and reasonable application of the starch-based materials with restrained plasticizer migration could be accomplished by controlling the molecular interaction and aggregation structures. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

Cell migration and antigen capture are antagonistic processes coupled by myosin II in dendritic cells

PubMed Central

Chabaud, Mélanie; Heuzé, Mélina L.; Bretou, Marine; Vargas, Pablo; Maiuri, Paolo; Solanes, Paola; Maurin, Mathieu; Terriac, Emmanuel; Le Berre, Maël; Lankar, Danielle; Piolot, Tristan; Adelstein, Robert S.; Zhang, Yingfan; Sixt, Michael; Jacobelli, Jordan; Bénichou, Olivier; Voituriez, Raphaël; Piel, Matthieu; Lennon-Duménil, Ana-Maria

2015-01-01

The immune response relies on the migration of leukocytes and on their ability to stop in precise anatomical locations to fulfil their task. How leukocyte migration and function are coordinated is unknown. Here we show that in immature dendritic cells, which patrol their environment by engulfing extracellular material, cell migration and antigen capture are antagonistic. This antagonism results from transient enrichment of myosin IIA at the cell front, which disrupts the back-to-front gradient of the motor protein, slowing down locomotion but promoting antigen capture. We further highlight that myosin IIA enrichment at the cell front requires the MHC class II-associated invariant chain (Ii). Thus, by controlling myosin IIA localization, Ii imposes on dendritic cells an intermittent antigen capture behaviour that might facilitate environment patrolling. We propose that the requirement for myosin II in both cell migration and specific cell functions may provide a general mechanism for their coordination in time and space. PMID:26109323

Management strategies for persistent epithelial defects of the cornea

PubMed Central

Katzman, Lee R.; Jeng, Bennie H.

2014-01-01

Management of patients with persistent epithelial defects of the cornea can be challenging to even the seasoned ophthalmologist. It is essential that one understands not only the pathophysiology of the failure of the epithelium to migrate and close a wound appropriately, but also the mechanism of action of the available treatment modalities at one’s disposal. This article serves as a review of current standard therapies, recently introduced alternative therapies gaining in popularity, and a look into the newest developments that may change the way we manage corneal surface disease. PMID:25278792

Calculation of Physicochemical Properties for Short- and Medium-Chain Chlorinated Paraffins

NASA Astrophysics Data System (ADS)

Glüge, Juliane; Bogdal, Christian; Scheringer, Martin; Buser, Andreas M.; Hungerbühler, Konrad

2013-06-01

Short- and medium-chain chlorinated paraffins are potential PBT chemicals (persistent, bioaccumulative, toxic) and short-chain chlorinated paraffins are under review for inclusion in the UNEP Stockholm Convention on Persistent Organic Pollutants. Despite their high production volume of more than one million metric tonnes per year, only few data on their physicochemical properties are available. We calculated subcooled-liquid vapor pressure, subcooled-liquid solubility in water and octanol, Henry's law constant for water and octanol, as well as the octanol-water partition coefficient with the property calculation methods COSMOtherm, SPARC, and EPI Suite™, and compared the results to experimental data from the literature. For all properties, good or very good agreement between calculated and measured data was obtained for COSMOtherm; results from SPARC were in good agreement with the measured data except for subcooled-liquid water solubility, whereas EPI Suite™ showed the largest discrepancies for all properties. After critical evaluation of the three property calculation methods, a final set of recommended property data for short- and medium-chain chlorinated paraffins was derived. The calculated property data show interesting relationships with chlorine content and carbon chain length. Increasing chlorine content does not cause pronounced changes in water solubility and octanol-water partition coefficient (KOW) as long as it is below 55%. Increasing carbon chain length leads to strong increases in KOW and corresponding decreases in subcooled-liquid water solubility. The present data set can be used in further studies to assess the environmental fate and human exposure of this relevant compound class.

Supercurrent as a probe for topological superconductivity in magnetic adatom chains

NASA Astrophysics Data System (ADS)

Mohanta, Narayan; Kampf, Arno P.; Kopp, Thilo

2018-06-01

A magnetic adatom chain, proximity coupled to a conventional superconductor with spin-orbit coupling, exhibits locally an odd-parity, spin-triplet pairing amplitude. We show that the singlet-triplet junction, thus formed, leads to a net spin accumulation in the near vicinity of the chain. The accumulated spins are polarized along the direction of the local d vector for triplet pairing and generate an enhanced persistent current flowing around the chain. The spin polarization and the "supercurrent" reverse their directions beyond a critical exchange coupling strength at which the singlet superconducting order changes its sign on the chain. The current is strongly enhanced in the topological superconducting regime where Majorana bound states appear at the chain ends. The current and the spin profile offer alternative routes to characterize the topological superconducting state in adatom chains and islands.

Development of seawater tolerance and subsequent downstream migration in wild and stocked young-of-the-year derived Atlantic salmon Salmo salar smolts.

PubMed

Urke, H A; Arnekleiv, J V; Nilsen, T O; Nilssen, K J

2014-01-01

This study investigated the development of hypo-osmoregulatory capacity and timing of downstream migration in wild Atlantic salmon Salmo salar smolts from the River Stjørdalselva and stocked young-of-the-year (YOY), derived S. salar smolts from the tributary River Dalåa. Both wild and stocked S. salar smolts developed seawater (SW) tolerance in early May, persisting through June, measured as their ability to regulate plasma osmolality and chloride following 24 h SW (salinity = 35) exposure. Although the majority of downstream migration among the stocked S. salar smolts occurred later than observed in their wild counterparts, the development of SW tolerance occurred concurrently. The wild S. salar from Stjørdalselva and stocked YOY smolts from the River Dalåa started to migrate on the same cumulative day-degrees (D°). The study revealed no downstream migration before development of SW tolerance. This emphasizes the importance of incorporating physiological status when studying environmental triggers for downstream migration of S. salar smolts. Overall, these findings suggest that the onset of smolt migration in stocked S. salar smolts was within the smolt window from an osmoregulatory point of view. © 2014 The Fisheries Society of the British Isles.

Past matrix stiffness primes epithelial cells and regulates their future collective migration through a mechanical memory.

PubMed

Nasrollahi, Samila; Walter, Christopher; Loza, Andrew J; Schimizzi, Gregory V; Longmore, Gregory D; Pathak, Amit

2017-11-01

During morphogenesis and cancer metastasis, grouped cells migrate through tissues of dissimilar stiffness. Although the influence of matrix stiffness on cellular mechanosensitivity and motility are well-recognized, it remains unknown whether these matrix-dependent cellular features persist after cells move to a new microenvironment. Here, we interrogate whether priming of epithelial cells by a given matrix stiffness influences their future collective migration on a different matrix - a property we refer to as the 'mechanical memory' of migratory cells. To prime cells on a defined matrix and track their collective migration onto an adjoining secondary matrix of dissimilar stiffness, we develop a modular polyacrylamide substrate through step-by-step polymerization of different PA compositions. We report that epithelial cells primed on a stiff matrix migrate faster, display higher actomyosin expression, form larger focal adhesions, and retain nuclear YAP even after arriving onto a soft secondary matrix, as compared to their control behavior on a homogeneously soft matrix. Priming on a soft ECM causes a reverse effect. The depletion of YAP dramatically reduces this memory-dependent migration. Our results present a previously unidentified regulation of mechanosensitive collective cell migration by past matrix stiffness, in which mechanical memory depends on YAP activity. Copyright © 2017 Elsevier Ltd. All rights reserved.

Intercontinental migratory connectivity and population structuring of Dunlins from western Alaska

USGS Publications Warehouse

Gill, Robert E.; Handel, Colleen M.; Ruthrauff, Daniel R.

2013-01-01

The Dunlin (Calidris alpina) is a polytypic shorebird with complex patterns of distribution and migration throughout its holarctic range. We analyzed mark-re sighting data obtained between 1977 and 2010 from birds captured at two major staging areas in western Alaska to test the hypothesis that the migration patterns of Alaskan populations are a mixture of parallel and chain, similar to those of Dunlin populations in the western Palearctic. Birds marked on the Yukon—Kuskokwim Delta were found wintering in both Asia and North America, which documented the unexpected mixing of C. a. arcticola from northern Alaska and C. a. pacifica from western Alaska and contradicted our initial prediction of parallel migration pathways for these two subspecies. In its North American winter range C. a. pacifica segregated according to location of marking, confirming our prediction of a chain migration pattern within this population. Individuals of C. a. pacifica marked on the delta were resighted significantly farther north, mostly in southern British Columbia and Washington, than birds marked on the second, more southerly staging area on the Alaska Peninsula, which were resighted primarily in the San Francisco Bay area of northern California. We recommend additional studies use a combination of intrinsic and extrinsic markers to quantify the strength of migratory connectivity between breeding, staging, and wintering areas. Such information is needed to guide conservation efforts because the Dunlin and other waterbirds are losing intertidal habitats at an unprecedented rate and scale, particularly in the Yellow Sea and other parts of Asia.

Functional Requirements for Heparan Sulfate Biosynthesis in Morphogenesis and Nervous System Development in C. elegans.

PubMed

Blanchette, Cassandra R; Thackeray, Andrea; Perrat, Paola N; Hekimi, Siegfried; Bénard, Claire Y

2017-01-01

The regulation of cell migration is essential to animal development and physiology. Heparan sulfate proteoglycans shape the interactions of morphogens and guidance cues with their respective receptors to elicit appropriate cellular responses. Heparan sulfate proteoglycans consist of a protein core with attached heparan sulfate glycosaminoglycan chains, which are synthesized by glycosyltransferases of the exostosin (EXT) family. Abnormal HS chain synthesis results in pleiotropic consequences, including abnormal development and tumor formation. In humans, mutations in either of the exostosin genes EXT1 and EXT2 lead to osteosarcomas or multiple exostoses. Complete loss of any of the exostosin glycosyltransferases in mouse, fish, flies and worms leads to drastic morphogenetic defects and embryonic lethality. Here we identify and study previously unavailable viable hypomorphic mutations in the two C. elegans exostosin glycosyltransferases genes, rib-1 and rib-2. These partial loss-of-function mutations lead to a severe reduction of HS levels and result in profound but specific developmental defects, including abnormal cell and axonal migrations. We find that the expression pattern of the HS copolymerase is dynamic during embryonic and larval morphogenesis, and is sustained throughout life in specific cell types, consistent with HSPGs playing both developmental and post-developmental roles. Cell-type specific expression of the HS copolymerase shows that HS elongation is required in both the migrating neuron and neighboring cells to coordinate migration guidance. Our findings provide insights into general principles underlying HSPG function in development.

Spontaneous Isomerization of Peptide Cation Radicals Following Electron Transfer Dissociation Revealed by UV-Vis Photodissociation Action Spectroscopy.

PubMed

Imaoka, Naruaki; Houferak, Camille; Murphy, Megan P; Nguyen, Huong T H; Dang, Andy; Tureček, František

2018-01-16

Peptide cation radicals of the z-type were produced by electron transfer dissociation (ETD) of peptide dications and studied by UV-Vis photodissociation (UVPD) action spectroscopy. Cation radicals containing the Asp (D), Asn (N), Glu (E), and Gln (Q) residues were found to spontaneously isomerize by hydrogen atom migrations upon ETD. Canonical N-terminal [z 4 + H] +● fragment ion-radicals of the R-C ● H-CONH- type, initially formed by N-C α bond cleavage, were found to be minor components of the stable ion fraction. Vibronically broadened UV-Vis absorption spectra were calculated by time-dependent density functional theory for several [ ● DAAR + H] + isomers and used to assign structures to the action spectra. The potential energy surface of [ ● DAAR + H] + isomers was mapped by ab initio and density functional theory calculations that revealed multiple isomerization pathways by hydrogen atom migrations. The transition-state energies for the isomerizations were found to be lower than the dissociation thresholds, accounting for the isomerization in non-dissociating ions. The facile isomerization in [ ● XAAR + H] + ions (X = D, N, E, and Q) was attributed to low-energy intermediates having the radical defect in the side chain that can promote hydrogen migration along backbone C α positions. A similar side-chain mediated mechanism is suggested for the facile intermolecular hydrogen migration between the c- and [z + H] ● -ETD fragments containing Asp, Asn, Glu, and Gln residues. Graphical Abstract ᅟ.

Spontaneous Isomerization of Peptide Cation Radicals Following Electron Transfer Dissociation Revealed by UV-Vis Photodissociation Action Spectroscopy

NASA Astrophysics Data System (ADS)

Imaoka, Naruaki; Houferak, Camille; Murphy, Megan P.; Nguyen, Huong T. H.; Dang, Andy; Tureček, František

2018-01-01

Peptide cation radicals of the z-type were produced by electron transfer dissociation (ETD) of peptide dications and studied by UV-Vis photodissociation (UVPD) action spectroscopy. Cation radicals containing the Asp (D), Asn (N), Glu (E), and Gln (Q) residues were found to spontaneously isomerize by hydrogen atom migrations upon ETD. Canonical N-terminal [z4 + H]+● fragment ion-radicals of the R-C●H-CONH- type, initially formed by N-Cα bond cleavage, were found to be minor components of the stable ion fraction. Vibronically broadened UV-Vis absorption spectra were calculated by time-dependent density functional theory for several [●DAAR + H]+ isomers and used to assign structures to the action spectra. The potential energy surface of [●DAAR + H]+ isomers was mapped by ab initio and density functional theory calculations that revealed multiple isomerization pathways by hydrogen atom migrations. The transition-state energies for the isomerizations were found to be lower than the dissociation thresholds, accounting for the isomerization in non-dissociating ions. The facile isomerization in [●XAAR + H]+ ions (X = D, N, E, and Q) was attributed to low-energy intermediates having the radical defect in the side chain that can promote hydrogen migration along backbone Cα positions. A similar side-chain mediated mechanism is suggested for the facile intermolecular hydrogen migration between the c- and [z + H]●-ETD fragments containing Asp, Asn, Glu, and Gln residues. [Figure not available: see fulltext.

Substrate Topography Induces a Crossover from 2D to 3D Behavior in Fibroblast Migration

PubMed Central

Ghibaudo, Marion; Trichet, Léa; Le Digabel, Jimmy; Richert, Alain; Hersen, Pascal; Ladoux, Benoît

2009-01-01

Abstract In a three-dimensional environment, cells migrate through complex topographical features. Using microstructured substrates, we investigate the role of substrate topography in cell adhesion and migration. To do so, fibroblasts are plated on chemically identical substrates composed of microfabricated pillars. When the dimensions of the pillars (i.e., the diameter, length, and spacing) are varied, migrating cells encounter alternating flat and rough surfaces that depend on the spacing between the pillars. Consequently, we show that substrate topography affects cell shape and migration by modifying cell-to-substrate interactions. Cells on micropillar substrates exhibit more elongated and branched shapes with fewer actin stress fibers compared with cells on flat surfaces. By analyzing the migration paths in various environments, we observe different mechanisms of cell migration, including a persistent type of migration, that depend on the organization of the topographical features. These responses can be attributed to a spatial reorganization of the actin cytoskeleton due to physical constraints and a preferential formation of focal adhesions on the micropillars, with an increased lifetime compared to that observed on flat surfaces. By changing myosin II activity, we show that actomyosin contractility is essential in the cellular response to micron-scale topographic signals. Finally, the analysis of cell movements at the frontier between flat and micropillar substrates shows that cell transmigration through the micropillar substrates depends on the spacing between the pillars. PMID:19580774

Tumor cell migration screen identifies SRPK1 as breast cancer metastasis determinant.

PubMed

van Roosmalen, Wies; Le Dévédec, Sylvia E; Golani, Ofra; Smid, Marcel; Pulyakhina, Irina; Timmermans, Annemieke M; Look, Maxime P; Zi, Di; Pont, Chantal; de Graauw, Marjo; Naffar-Abu-Amara, Suha; Kirsanova, Catherine; Rustici, Gabriella; Hoen, Peter A C 't; Martens, John W M; Foekens, John A; Geiger, Benjamin; van de Water, Bob

2015-04-01

Tumor cell migration is a key process for cancer cell dissemination and metastasis that is controlled by signal-mediated cytoskeletal and cell matrix adhesion remodeling. Using a phagokinetic track assay with migratory H1299 cells, we performed an siRNA screen of almost 1,500 genes encoding kinases/phosphatases and adhesome- and migration-related proteins to identify genes that affect tumor cell migration speed and persistence. Thirty candidate genes that altered cell migration were validated in live tumor cell migration assays. Eight were associated with metastasis-free survival in breast cancer patients, with integrin β3-binding protein (ITGB3BP), MAP3K8, NIMA-related kinase (NEK2), and SHC-transforming protein 1 (SHC1) being the most predictive. Examination of genes that modulate migration indicated that SRPK1, encoding the splicing factor kinase SRSF protein kinase 1, is relevant to breast cancer outcomes, as it was highly expressed in basal breast cancer. Furthermore, high SRPK1 expression correlated with poor breast cancer disease outcome and preferential metastasis to the lungs and brain. In 2 independent murine models of breast tumor metastasis, stable shRNA-based SRPK1 knockdown suppressed metastasis to distant organs, including lung, liver, and spleen, and inhibited focal adhesion reorganization. Our study provides comprehensive information on the molecular determinants of tumor cell migration and suggests that SRPK1 has potential as a drug target for limiting breast cancer metastasis.

Persistence, Engagement, and Migration in Engineering Programs. Research Brief

ERIC Educational Resources Information Center

Ohland, Matthew W.; Sheppard, Sheri D.; Lichtenstein, Gary; Eris, Ozgur; Chachra, Debbie; Layton, Richard A.

2008-01-01

Those responsible for designing, maintaining, and delivering engineering education are asking questions to understand the outcomes of undergraduate engineering programs. These questions have been motivated by concerns about the declining interest in studying engineering, the continued lack of gender and ethnic diversity in the engineering…

Environmental Constraints Guide Migration of Malaria Parasites during Transmission

PubMed Central

Hellmann, Janina Kristin; Münter, Sylvia; Kudryashev, Mikhail; Schulz, Simon; Heiss, Kirsten; Müller, Ann-Kristin; Matuschewski, Kai; Spatz, Joachim P.; Schwarz, Ulrich S.; Frischknecht, Friedrich

2011-01-01

Migrating cells are guided in complex environments mainly by chemotaxis or structural cues presented by the surrounding tissue. During transmission of malaria, parasite motility in the skin is important for Plasmodium sporozoites to reach the blood circulation. Here we show that sporozoite migration varies in different skin environments the parasite encounters at the arbitrary sites of the mosquito bite. In order to systematically examine how sporozoite migration depends on the structure of the environment, we studied it in micro-fabricated obstacle arrays. The trajectories observed in vivo and in vitro closely resemble each other suggesting that structural constraints can be sufficient to guide Plasmodium sporozoites in complex environments. Sporozoite speed in different environments is optimized for migration and correlates with persistence length and dispersal. However, this correlation breaks down in mutant sporozoites that show adhesion impairment due to the lack of TRAP-like protein (TLP) on their surfaces. This may explain their delay in infecting the host. The flexibility of sporozoite adaption to different environments and a favorable speed for optimal dispersal ensures efficient host switching during malaria transmission. PMID:21698220

SDN-1/Syndecan Acts in Parallel to the Transmembrane Molecule MIG-13 to Promote Anterior Neuroblast Migration.

PubMed

Sundararajan, Lakshmi; Norris, Megan L; Lundquist, Erik A

2015-05-28

The Q neuroblasts in Caenorhabditis elegans display left-right asymmetry in their migration, with QR and descendants on the right migrating anteriorly, and QL and descendants on the left migrating posteriorly. Initial QR and QL migration is controlled by the transmembrane receptors UNC-40/DCC, PTP-3/LAR, and the Fat-like cadherin CDH-4. After initial migration, QL responds to an EGL-20/Wnt signal that drives continued posterior migration by activating MAB-5/Hox activity in QL but not QR. QR expresses the transmembrane protein MIG-13, which is repressed by MAB-5 in QL and which drives anterior migration of QR descendants. A screen for new Q descendant AQR and PQR migration mutations identified mig-13 as well as hse-5, the gene encoding the glucuronyl C5-epimerase enzyme, which catalyzes epimerization of glucuronic acid to iduronic acid in the heparan sulfate side chains of heparan sulfate proteoglycans (HSPGs). Of five C. elegans HSPGs, we found that only SDN-1/Syndecan affected Q migrations. sdn-1 mutants showed QR descendant AQR anterior migration defects, and weaker QL descendant PQR migration defects. hse-5 affected initial Q migration, whereas sdn-1 did not. sdn-1 and hse-5 acted redundantly in AQR and PQR migration, but not initial Q migration, suggesting the involvement of other HSPGs in Q migration. Cell-specific expression studies indicated that SDN-1 can act in QR to promote anterior migration. Genetic interactions between sdn-1, mig-13, and mab-5 suggest that MIG-13 and SDN-1 act in parallel to promote anterior AQR migration and that SDN-1 also controls posterior migration. Together, our results indicate previously unappreciated complexity in the role of multiple signaling pathways and inherent left-right asymmetry in the control of Q neuroblast descendant migration. Copyright © 2015 Sundararajan et al.

SDN-1/Syndecan Acts in Parallel to the Transmembrane Molecule MIG-13 to Promote Anterior Neuroblast Migration

PubMed Central

Sundararajan, Lakshmi; Norris, Megan L.; Lundquist, Erik A.

2015-01-01

The Q neuroblasts in Caenorhabditis elegans display left-right asymmetry in their migration, with QR and descendants on the right migrating anteriorly, and QL and descendants on the left migrating posteriorly. Initial QR and QL migration is controlled by the transmembrane receptors UNC-40/DCC, PTP-3/LAR, and the Fat-like cadherin CDH-4. After initial migration, QL responds to an EGL-20/Wnt signal that drives continued posterior migration by activating MAB-5/Hox activity in QL but not QR. QR expresses the transmembrane protein MIG-13, which is repressed by MAB-5 in QL and which drives anterior migration of QR descendants. A screen for new Q descendant AQR and PQR migration mutations identified mig-13 as well as hse-5, the gene encoding the glucuronyl C5-epimerase enzyme, which catalyzes epimerization of glucuronic acid to iduronic acid in the heparan sulfate side chains of heparan sulfate proteoglycans (HSPGs). Of five C. elegans HSPGs, we found that only SDN-1/Syndecan affected Q migrations. sdn-1 mutants showed QR descendant AQR anterior migration defects, and weaker QL descendant PQR migration defects. hse-5 affected initial Q migration, whereas sdn-1 did not. sdn-1 and hse-5 acted redundantly in AQR and PQR migration, but not initial Q migration, suggesting the involvement of other HSPGs in Q migration. Cell-specific expression studies indicated that SDN-1 can act in QR to promote anterior migration. Genetic interactions between sdn-1, mig-13, and mab-5 suggest that MIG-13 and SDN-1 act in parallel to promote anterior AQR migration and that SDN-1 also controls posterior migration. Together, our results indicate previously unappreciated complexity in the role of multiple signaling pathways and inherent left-right asymmetry in the control of Q neuroblast descendant migration. PMID:26022293

Soluble guanylate cyclase generation of cGMP regulates migration of MGE neurons.

PubMed

Mandal, Shyamali; Stanco, Amelia; Buys, Emmanuel S; Enikolopov, Grigori; Rubenstein, John L R

2013-10-23

Here we have provided evidence that nitric oxide-cyclic GMP (NO-cGMP) signaling regulates neurite length and migration of immature neurons derived from the medial ganglionic eminence (MGE). Dlx1/2(-/-) and Lhx6(-/-) mouse mutants, which exhibit MGE interneuron migration defects, have reduced expression of the gene encoding the α subunit of a soluble guanylate cyclase (Gucy1A3). Furthermore, Dlx1/2(-/-) mouse mutants have reduced expression of NO synthase 1 (NOS1). Gucy1A3(-/-) mice have a transient reduction in cortical interneuron number. Pharmacological inhibition of soluble guanylate cyclase and NOS activity rapidly induces neurite retraction of MGE cells in vitro and in slice culture and robustly inhibits cell migration from the MGE and caudal ganglionic eminence. We provide evidence that these cellular phenotypes are mediated by activation of the Rho signaling pathway and inhibition of myosin light chain phosphatase activity.

Conformational Dynamics Guides Coherent Exciton Migration in Conjugated Polymer Materials: First-Principles Quantum Dynamical Study

NASA Astrophysics Data System (ADS)

Binder, Robert; Lauvergnat, David; Burghardt, Irene

2018-06-01

We report on high-dimensional quantum dynamical simulations of photoinduced exciton migration in a single-chain oligothiophene segment, in view of elucidating the controversial nature of the elementary exciton transport steps in semiconducting polymers. A novel first-principles parametrized Frenkel J aggregate Hamiltonian is employed that goes significantly beyond the standard Frenkel-Holstein Hamiltonian. Departing from a nonequilibrium state created by photoexcitation, these simulations provide evidence of an ultrafast two-timescale process at low temperatures, involving exciton-polaron formation within tens of femtoseconds (fs), followed by torsional relaxation on an ˜400 fs timescale. The second step is the driving force for exciton migration, as initial conjugation breaks are removed by dynamical planarization. The quantum coherent nature of the elementary exciton migration step is consistent with experimental observations highlighting the correlated and vibrationally coherent nature of the dynamics on ultrafast timescales.

Conformational Dynamics Guides Coherent Exciton Migration in Conjugated Polymer Materials: First-Principles Quantum Dynamical Study.

PubMed

Binder, Robert; Lauvergnat, David; Burghardt, Irene

2018-06-01

We report on high-dimensional quantum dynamical simulations of photoinduced exciton migration in a single-chain oligothiophene segment, in view of elucidating the controversial nature of the elementary exciton transport steps in semiconducting polymers. A novel first-principles parametrized Frenkel J aggregate Hamiltonian is employed that goes significantly beyond the standard Frenkel-Holstein Hamiltonian. Departing from a nonequilibrium state created by photoexcitation, these simulations provide evidence of an ultrafast two-timescale process at low temperatures, involving exciton-polaron formation within tens of femtoseconds (fs), followed by torsional relaxation on an ∼400  fs timescale. The second step is the driving force for exciton migration, as initial conjugation breaks are removed by dynamical planarization. The quantum coherent nature of the elementary exciton migration step is consistent with experimental observations highlighting the correlated and vibrationally coherent nature of the dynamics on ultrafast timescales.

Conservation physiology of animal migration

PubMed Central

Lennox, Robert J.; Chapman, Jacqueline M.; Souliere, Christopher M.; Tudorache, Christian; Wikelski, Martin; Metcalfe, Julian D.; Cooke, Steven J.

2016-01-01

Migration is a widespread phenomenon among many taxa. This complex behaviour enables animals to exploit many temporally productive and spatially discrete habitats to accrue various fitness benefits (e.g. growth, reproduction, predator avoidance). Human activities and global environmental change represent potential threats to migrating animals (from individuals to species), and research is underway to understand mechanisms that control migration and how migration responds to modern challenges. Focusing on behavioural and physiological aspects of migration can help to provide better understanding, management and conservation of migratory populations. Here, we highlight different physiological, behavioural and biomechanical aspects of animal migration that will help us to understand how migratory animals interact with current and future anthropogenic threats. We are in the early stages of a changing planet, and our understanding of how physiology is linked to the persistence of migratory animals is still developing; therefore, we regard the following questions as being central to the conservation physiology of animal migrations. Will climate change influence the energetic costs of migration? Will shifting temperatures change the annual clocks of migrating animals? Will anthropogenic influences have an effect on orientation during migration? Will increased anthropogenic alteration of migration stopover sites/migration corridors affect the stress physiology of migrating animals? Can physiological knowledge be used to identify strategies for facilitating the movement of animals? Our synthesis reveals that given the inherent challenges of migration, additional stressors derived from altered environments (e.g. climate change, physical habitat alteration, light pollution) or interaction with human infrastructure (e.g. wind or hydrokinetic turbines, dams) or activities (e.g. fisheries) could lead to long-term changes to migratory phenotypes. However, uncertainty remains because of the complexity of biological systems, the inherently dynamic nature of the environment and the scale at which many migrations occur and associated threats operate, necessitating improved integration of physiological approaches to the conservation of migratory animals. PMID:27293751

Conservation physiology of animal migration.

PubMed

Lennox, Robert J; Chapman, Jacqueline M; Souliere, Christopher M; Tudorache, Christian; Wikelski, Martin; Metcalfe, Julian D; Cooke, Steven J

2016-01-01

Migration is a widespread phenomenon among many taxa. This complex behaviour enables animals to exploit many temporally productive and spatially discrete habitats to accrue various fitness benefits (e.g. growth, reproduction, predator avoidance). Human activities and global environmental change represent potential threats to migrating animals (from individuals to species), and research is underway to understand mechanisms that control migration and how migration responds to modern challenges. Focusing on behavioural and physiological aspects of migration can help to provide better understanding, management and conservation of migratory populations. Here, we highlight different physiological, behavioural and biomechanical aspects of animal migration that will help us to understand how migratory animals interact with current and future anthropogenic threats. We are in the early stages of a changing planet, and our understanding of how physiology is linked to the persistence of migratory animals is still developing; therefore, we regard the following questions as being central to the conservation physiology of animal migrations. Will climate change influence the energetic costs of migration? Will shifting temperatures change the annual clocks of migrating animals? Will anthropogenic influences have an effect on orientation during migration? Will increased anthropogenic alteration of migration stopover sites/migration corridors affect the stress physiology of migrating animals? Can physiological knowledge be used to identify strategies for facilitating the movement of animals? Our synthesis reveals that given the inherent challenges of migration, additional stressors derived from altered environments (e.g. climate change, physical habitat alteration, light pollution) or interaction with human infrastructure (e.g. wind or hydrokinetic turbines, dams) or activities (e.g. fisheries) could lead to long-term changes to migratory phenotypes. However, uncertainty remains because of the complexity of biological systems, the inherently dynamic nature of the environment and the scale at which many migrations occur and associated threats operate, necessitating improved integration of physiological approaches to the conservation of migratory animals.

Predicting gaseous reaction rates of short chain chlorinated paraffins with ·OH: overcoming the difficulty in experimental determination.

PubMed

Li, Chao; Xie, Hong-Bin; Chen, Jingwen; Yang, Xianhai; Zhang, Yifei; Qiao, Xianliang

2014-12-02

Short chain chlorinated paraffins (SCCPs) are under evaluation for inclusion in the Stockholm Convention on persistent organic pollutants. However, information on their reaction rate constants with gaseous ·OH (kOH) is unavailable, limiting the evaluation of their persistence in the atmosphere. Experimental determination of kOH is confined by the unavailability of authentic chemical standards for some SCCP congeners. In this study, we evaluated and selected density functional theory (DFT) methods to predict kOH of SCCPs, by comparing the experimental kOH values of six polychlorinated alkanes (PCAs) with those calculated by the different theoretical methods. We found that the M06-2X/6-311+G(3df,2pd)//B3LYP/6-311 +G(d,p) method is time-effective and can be used to predict kOH of PCAs. Moreover, based on the calculated kOH of nine SCCPs and available experimental kOH values of 22 PCAs with low carbon chain, a quantitative structure-activity relationship (QSAR) model was developed. The molecular structural characteristics determining the ·OH reaction rate were discussed. logkOH was found to negatively correlate with the percentage of chlorine substitutions (Cl%). The DFT calculation method and the QSAR model are important alternatives to the conventional experimental determination of kOH for SCCPs, and are prospective in predicting their persistence in the atmosphere.

A modeling assessment of the physicochemical properties and environmental fate of emerging and novel per- and polyfluoroalkyl substances.

PubMed

Gomis, Melissa Ines; Wang, Zhanyun; Scheringer, Martin; Cousins, Ian T

2015-02-01

Long-chain perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkane sulfonic acids (PFSAs) are persistent, bioaccumulative, and toxic contaminants that are globally present in the environment, wildlife and humans. Phase-out actions and use restrictions to reduce the environmental release of long-chain PFCAs, PFSAs and their precursors have been taken since 2000. In particular, long-chain poly- and perfluoroalkyl substances (PFASs) are being replaced with shorter-chain homologues or other fluorinated or non-fluorinated alternatives. A key question is: are these alternatives, particularly the structurally similar fluorinated alternatives, less hazardous to humans and the environment than the substances they replace? Several fluorinated alternatives including perfluoroether carboxylic acids (PFECAs) and perfluoroether sulfonic acids (PFESAs) have been recently identified. However, the scarcity of experimental data prevents hazard and risk assessments for these substances. In this study, we use state-of-the-art in silico tools to estimate key properties of these newly identified fluorinated alternatives. [i] COSMOtherm and SPARC are used to estimate physicochemical properties. The US EPA EPISuite software package is used to predict degradation half-lives in air, water and soil. [ii] In combination with estimated chemical properties, a fugacity-based multimedia mass-balance unit-world model - the OECD Overall Persistence (POV) and Long-Range Transport Potential (LRTP) Screening Tool - is used to assess the likely environmental fate of these alternatives. Even though the fluorinated alternatives contain some structural differences, their physicochemical properties are not significantly different from those of their predecessors. Furthermore, most of the alternatives are estimated to be similarly persistent and mobile in the environment as the long-chain PFASs. The models therefore predict that the fluorinated alternatives will become globally distributed in the environment similar to their predecessors. Although such in silico methods are coupled with uncertainties, this preliminary assessment provides enough cause for concern to warrant experimental work to better determine the properties of these fluorinated alternatives. Copyright © 2014 Elsevier B.V. All rights reserved.

[Italian immigration into Imperial Germany up to World War I].

PubMed

Trincia, L

1996-09-01

"A rapid growth, both economic and industrial, of the German Empire during the last decade of the nineteenth century...produced a major switch in Germany's status from that of a country of emigration to a country of immigration.... The essay gives a concise description of the characteristics of Italian migration flows towards Germany, integration processes and chain migration patterns. The impact of immigration on the receiving country is...analyzed, both in terms of economic development and from a social, political and legal point of view." (SUMMARY IN ENG AND FRE) excerpt

Tracking in vivo migration and distribution of antigen-specific cytotoxic T lymphocytes by 5,6-carboxyfluorescein diacetate succinimidyl ester staining during cancer immunotherapy.

PubMed

Xu, Wei-li; Li, Suo-lin; Wen, Ming; Wen, Jun-ye; Han, Jie; Zhang, Hong-zhen; Gao, Fei; Cai, Jian-hui

2013-08-01

Killing of targeted tumors during adoptive cell transfer therapy is associated with cytotoxic T lymphocyte (CTL) numbers, immunophenotype, tumor-specificity, and in vivo residence time, migration, and distribution. Therefore, tracing in vivo persistence, migration, and distribution of CTLs is important for cancer immunotherapy. Optimal staining concentration for CTL proliferation was determined by cell counting kit-8 (CCK-8) assay and killing efficiencies of CTLs or carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled melanoma antigen-specific cytotoxic T lymphocytes (CFSE-CTLs) for malignant melanoma cells in vitro were compared. Additionally, CFSE-CTLs were intravenously transfused to mice receiving B16 melanoma, and their residence time, migration, and distribution in vivo were observed by measuring fluorescence intensities of CFSE-CTLs per gram of tissue (%FI/g) in various tissues and analyzing tumor/non-tumor (T/NT) values. Anti-tumor effects of transferred CTLs and correlation between %FI/g and D-value of tumor size were analyzed. Five-micromolar CFSE was optimal for labeling CTLs with minimal cytotoxicity. No significant difference occurred between CTLs and CFSE-CTLs for tumor cell killing (P = 0.849) or interleukin-2 (P = 0.318) and interferon-γ (P = 0.201) levels. Distribution of CTLs in vivo varied with time. A negative correlation between %FI/g in tumors and D-value of tumor sizes by Spearman correlation analysis was observed. CTLs were recruited to and killed tumors from 6 hours to 3 days after cell infusion. CTLs were observed up to three weeks later in the tumor, liver, kidneys, and spleen; this was related to the abundant blood supply or the nature of immune organs. CCK-8 assay is a novel method to select optimal CFSE staining concentrations. Fluorescence intensity of transferred CTLs reflects their killing efficiency of tumors. CFSE fluorescent markers can trace in vivo CTL persistence, migration, and distribution because of its stability, long half-life, and low toxicity.

Universal aspects of conformations and transverse fluctuations of a two-dimensional semi-flexible chain

NASA Astrophysics Data System (ADS)

Hsu, Hsiao-Ping; Huang, Aiqun; Bhattacharya, Aniket; Binder, Kurt

2015-03-01

In this talk we compare the results obtained from Monte Carlo (MC) and Brownian dynamics (BD) simulation for the universal properties of a semi-flexible chain. Specifically we compare MC results obtained using pruned-enriched Rosenbluth method (PERM) with those obtained from BD simulation. We find that the scaled plot of root-mean-square (RMS) end-to-end distance / 2 Llp and RMS transverse transverse fluctuations √{ } /lp as a function of L /lp (where L and lp are the contour length, and the persistence length respectively) are universal and independent of the definition of the persistence length used in MC and BD schemes. We further investigate to what extent these results agree for a semi-flexible polymer confined in a quasi one dimensional channel.

Nonequilibrium spin transport in integrable spin chains: Persistent currents and emergence of magnetic domains

NASA Astrophysics Data System (ADS)

De Luca, Andrea; Collura, Mario; De Nardis, Jacopo

2017-07-01

We construct exact steady states of unitary nonequilibrium time evolution in the gapless XXZ spin-1/2 chain where integrability preserves ballistic spin transport at long times. We characterize the quasilocal conserved quantities responsible for this feature and introduce a computationally effective way to evaluate their expectation values on generic matrix product initial states. We employ this approach to reproduce the long-time limit of local observables in all quantum quenches which explicitly break particle-hole or time-reversal symmetry. We focus on a class of initial states supporting persistent spin currents and our predictions remarkably agree with numerical simulations at long times. Furthermore, we propose a protocol for this model where interactions, even when antiferromagnetic, are responsible for the unbounded growth of a macroscopic magnetic domain.

Transport and fate of organic wastes in groundwater at the Stringfellow hazardous waste disposal site, southern California

USGS Publications Warehouse

Leenheer, J.A.; Hsu, J.; Barber, L.B.

2001-01-01

In January 1999, wastewater influent and effluent from the pretreatment plant at the Stringfellow hazardous waste disposal site were sampled along with groundwater at six locations along the groundwater contaminant plume. The objectives of this sampling and study were to identify at the compound class level the unidentified 40-60% of wastewater organic contaminants, and to determine what organic compound classes were being removed by the wastewater pretreatment plant, and what organic compound classes persisted during subsurface waste migration. The unidentified organic wastes are primarily chlorinated aromatic sulfonic acids derived from wastes from DDT manufacture. Trace amounts of EDTA and NTA organic complexing agents were discovered along with carboxylate metabolites of the common alkylphenolpolyethoxylate plasticizers and nonionic surfactants. The wastewater pretreatment plant removed most of the aromatic chlorinated sulfonic acids that have hydrophobic neutral properties, but the p-chlorobenzenesulfonic acid which is the primary waste constituent passed through the pretreatment plant and was discharged in the treated wastewaters transported to an industrial sewer. During migration in groundwater, p-chlorobenzenesulfonic acid is removed by natural remediation processes. Wastewater organic contaminants have decreased 3- to 45-fold in the groundwater from 1985 to 1999 as a result of site remediation and natural remediation processes. The chlorinated aromatic sulfonic acids with hydrophobic neutral properties persist and have migrated into groundwater that underlies the adjacent residential community. Copyright ?? 2001 .

Navigator-3, a modulator of cell migration, may act as a suppressor of breast cancer progression

PubMed Central

Cohen-Dvashi, Hadas; Ben-Chetrit, Nir; Russell, Roslin; Carvalho, Silvia; Lauriola, Mattia; Nisani, Sophia; Mancini, Maicol; Nataraj, Nishanth; Kedmi, Merav; Roth, Lee; Köstler, Wolfgang; Zeisel, Amit; Yitzhaky, Assif; Zylberg, Jacques; Tarcic, Gabi; Eilam, Raya; Wigelman, Yoav; Will, Rainer; Lavi, Sara; Porat, Ziv; Wiemann, Stefan; Ricardo, Sara; Schmitt, Fernando; Caldas, Carlos; Yarden, Yosef

2015-01-01

Dissemination of primary tumor cells depends on migratory and invasive attributes. Here, we identify Navigator-3 (NAV3), a gene frequently mutated or deleted in human tumors, as a regulator of epithelial migration and invasion. Following induction by growth factors, NAV3 localizes to the plus ends of microtubules and enhances their polarized growth. Accordingly, NAV3 depletion trimmed microtubule growth, prolonged growth factor signaling, prevented apoptosis and enhanced random cell migration. Mathematical modeling suggested that NAV3-depleted cells acquire an advantage in terms of the way they explore their environment. In animal models, silencing NAV3 increased metastasis, whereas ectopic expression of the wild-type form, unlike expression of two, relatively unstable oncogenic mutants from human tumors, inhibited metastasis. Congruently, analyses of > 2,500 breast and lung cancer patients associated low NAV3 with shorter survival. We propose that NAV3 inhibits breast cancer progression by regulating microtubule dynamics, biasing directionally persistent rather than random migration, and inhibiting locomotion of initiated cells. PMID:25678558

Cell directional migration and oriented division on three-dimensional laser-induced periodic surface structures on polystyrene.

PubMed

Wang, Xuefeng; Ohlin, Christian A; Lu, Qinghua; Hu, Jun

2008-05-01

The extracellular matrix in animal tissues usually provides a three-dimensional structural support to cells in addition to performing various other important functions. In the present study, wavy submicrometer laser-irradiated periodic surface structures (LIPSS) were produced on a smooth polystyrene film by polarized laser irradiation with a wavelength of 266 nm. Rat C6 glioma cells exhibited directional migration and oriented division on laser-irradiated polystyrene, which was parallel to the direction of LIPSS. However, rat C6 glioma cells on smooth polystyrene moved in a three-step invasion cycle, with faster migration speed than that on laser-irradiated polystyrene. In addition, focal adhesions examined by immunostaining focal adhesion kinase in human epithelial carcinoma HeLa cells were punctuated on smooth polystyrene, whereas dash-like on laser-irradiated polystyrene. We hypothesized that LIPSS on laser-irradiated polystyrene acted as an anisotropic and persistent mechanical stimulus to guide cell anisotropic spreading, migration and division through focal adhesions.

Structure of flexible and semiflexible polyelectrolyte chains in confined spaces of slit micro/nanochannels.

PubMed

Jeon, Jonggu; Chun, Myung-Suk

2007-04-21

Understanding the behavior of a polyelectrolyte in confined spaces has direct relevance in design and manipulation of microfluidic devices, as well as transport in living organisms. In this paper, a coarse-grained model of anionic semiflexible polyelectrolyte is applied, and its structure and dynamics are fully examined with Brownian dynamics (BD) simulations both in bulk solution and under confinement between two negatively charged parallel plates. The modeling is based on the nonlinear bead-spring discretization of a continuous chain with additional long-range electrostatic, Lennard-Jones, and hydrodynamic interactions between pairs of beads. The authors also consider the steric and electrostatic interactions between the bead and the confining wall. Relevant model parameters are determined from experimental rheology data on the anionic polysaccharide xanthan reported previously. For comparison, both flexible and semiflexible models are developed accompanying zero and finite intrinsic persistence lengths, respectively. The conformational changes of the polyelectrolyte chain induced by confinements and their dependence on the screening effect of the electrolyte solution are faithfully characterized with BD simulations. Depending on the intrinsic rigidity and the medium ionic strength, the polyelectrolyte can be classified as flexible, semiflexible, or rigid. Confined flexible and semiflexible chains exhibit a nonmonotonic variation in size, as measured by the radius of gyration and end-to-end distance, with changing slit width. For the semiflexible chain, this is coupled to the variations in long-range bond vector correlation. The rigid chain, realized at low ionic strength, does not have minima in size but exhibits a sigmoidal transition. The size of confined semiflexible and rigid polyelectrolytes can be well described by the wormlike chain model once the electrostatic effects are taken into account by the persistence length measured at long length scale.

Absence of γ-Chain in Keratinocytes Alters Chemokine Secretion, Resulting in Reduced Immune Cell Recruitment.

PubMed

Nowak, Karolin; Linzner, Daniela; Thrasher, Adrian J; Lambert, Paul F; Di, Wei-Li; Burns, Siobhan O

2017-10-01

Loss-of-function mutations in the common gamma (γc) chain cytokine receptor subunit give rise to severe combined immunodeficiency characterized by lack of T and natural killer cells and infant death from infection. Hematopoietic stem cell transplantation or gene therapy offer a cure, but despite successful replacement of lymphoid immune lineages, a long-term risk of severe cutaneous human papilloma virus infections persists, possibly related to persistent γc-deficiency in other cell types. Here we show that keratinocytes, the only cell type directly infected by human papilloma virus, express functional γc and its co-receptors. After stimulation with the γc-ligand IL-15, γc-deficient keratinocytes show significantly impaired secretion of specific chemokines including CXCL1, CXCL8, and CCL20, resulting in reduced chemotaxis of dendritic cells and CD4 + T cells. Furthermore, γc-deficient keratinocytes also exhibit defective induction of T-cell chemotaxis in a model of stable human papilloma virus-18 infection. These findings suggest that persistent γc-deficiency in keratinocytes alters immune cell recruitment to the skin, which may contribute to the development and persistence of warts in this condition and would require different treatment approaches. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

DNA methyltransferase inhibitor CDA-II inhibits myogenic differentiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Zirong; Department of Molecular Genetics and Microbiology, Shands Cancer Center, University of Florida, Gainesville, FL 32610; Jin, Guorong

2012-06-08

Highlights: Black-Right-Pointing-Pointer CDA-II inhibits myogenic differentiation in a dose-dependent manner. Black-Right-Pointing-Pointer CDA-II repressed expression of muscle transcription factors and structural proteins. Black-Right-Pointing-Pointer CDA-II inhibited proliferation and migration of C2C12 myoblasts. -- Abstract: CDA-II (cell differentiation agent II), isolated from healthy human urine, is a DNA methyltransferase inhibitor. Previous studies indicated that CDA-II played important roles in the regulation of cell growth and certain differentiation processes. However, it has not been determined whether CDA-II affects skeletal myogenesis. In this study, we investigated effects of CDA-II treatment on skeletal muscle progenitor cell differentiation, migration and proliferation. We found that CDA-II blocked differentiationmore » of murine myoblasts C2C12 in a dose-dependent manner. CDA-II repressed expression of muscle transcription factors, such as Myogenin and Mef2c, and structural proteins, such as myosin heavy chain (Myh3), light chain (Mylpf) and MCK. Moreover, CDA-II inhibited C1C12 cell migration and proliferation. Thus, our data provide the first evidence that CDA-II inhibits growth and differentiation of muscle progenitor cells, suggesting that the use of CDA-II might affect skeletal muscle functions.« less

DIM SUM: demography and individual migration simulated using a Markov chain.

PubMed

Brown, Jeremy M; Savidge, Kevin; McTavish, Emily Jane B

2011-03-01

An increasing number of studies seek to infer demographic history, often jointly with genetic relationships. Despite numerous analytical methods for such data, few simulations have investigated the methods' power and robustness, especially when underlying assumptions have been violated. DIM SUM (Demography and Individual Migration Simulated Using a Markov chain) is a stand-alone Java program for the simulation of population demography and individual migration while recording ancestor-descendant relationships. It does not employ coalescent assumptions or discrete population boundaries. It is extremely flexible, allowing the user to specify border positions, reactions of organisms to borders, local and global carrying capacities, individual dispersal kernels, rates of reproduction and strategies for sampling individuals. Spatial variables may be specified using image files (e.g., as exported from gis software) and may vary through time. In combination with software for genetic marker simulation, DIM SUM will be useful for testing phylogeographic (e.g., nested clade phylogeographic analysis, coalescent-based tests and continuous-landscape frameworks) and landscape-genetic methods, specifically regarding violations of coalescent assumptions. It can also be used to explore the qualitative features of proposed demographic scenarios (e.g. regarding biological invasions) and as a pedagogical tool. DIM SUM (with user's manual) can be downloaded from http://code.google.com/p/bio-dimsum. © 2010 Blackwell Publishing Ltd.

Aligned fibers direct collective cell migration to engineer closing and nonclosing wound gaps

PubMed Central

Sharma, Puja; Ng, Colin; Jana, Aniket; Padhi, Abinash; Szymanski, Paige; Lee, Jerry S. H.; Behkam, Bahareh; Nain, Amrinder S.

2017-01-01

Cell emergence onto damaged or organized fibrous extracellular matrix (ECM) is a crucial precursor to collective cell migration in wound closure and cancer metastasis, respectively. However, there is a fundamental gap in our quantitative understanding of the role of local ECM size and arrangement in cell emergence–based migration and local gap closure. Here, using ECM-mimicking nanofibers bridging cell monolayers, we describe a method to recapitulate and quantitatively describe these in vivo behaviors over multispatial (single cell to cell sheets) and temporal (minutes to weeks) scales. On fiber arrays with large interfiber spacing, cells emerge (invade) either singularly by breaking cell–cell junctions analogous to release of a stretched rubber band (recoil), or in groups of few cells (chains), whereas on closely spaced fibers, multiple chains emerge collectively. Advancing cells on fibers form cell streams, which support suspended cell sheets (SCS) of various sizes and curvatures. SCS converge to form local gaps that close based on both the gap size and shape. We document that cell stream spacing of 375 µm and larger hinders SCS advancement, thus providing abilities to engineer closing and nonclosing gaps. Altogether we highlight the importance of studying cell-fiber interactions and matrix structural remodeling in fundamental and translational cell biology. PMID:28747440

40 CFR 227.18 - Factors considered.

Code of Federal Regulations, 2012 CFR

2012-07-01

... persistent and may have an adverse effect on humans directly or through food chain interactions; (h) Presence... standards; (d) Visible characteristics of the materials (e.g., color, suspended particulates) which result...

40 CFR 227.18 - Factors considered.

Code of Federal Regulations, 2011 CFR

2011-07-01

... persistent and may have an adverse effect on humans directly or through food chain interactions; (h) Presence... standards; (d) Visible characteristics of the materials (e.g., color, suspended particulates) which result...

40 CFR 227.18 - Factors considered.

Code of Federal Regulations, 2013 CFR

2013-07-01

... persistent and may have an adverse effect on humans directly or through food chain interactions; (h) Presence... standards; (d) Visible characteristics of the materials (e.g., color, suspended particulates) which result...

40 CFR 227.18 - Factors considered.

Code of Federal Regulations, 2014 CFR

2014-07-01

... persistent and may have an adverse effect on humans directly or through food chain interactions; (h) Presence... standards; (d) Visible characteristics of the materials (e.g., color, suspended particulates) which result...

Balancing Cell Migration with Matrix Degradation Enhances Gene Delivery to Cells Cultured Three-Dimensionally Within Hydrogels

PubMed Central

Shepard, Jaclyn A.; Huang, Alyssa; Shikanova, Ariella; Shea, Lonnie D.

2010-01-01

In regenerative medicine, hydrogels are employed to fill defects and support the infiltration of cells that can ultimately regenerate tissue. Gene delivery within hydrogels targeting infiltrating cells has the potential to promote tissue formation, but the delivery efficiency of nonviral vectors within hydrogels is low hindering their applicability in tissue regeneration. To improve their functionality, we have conducted a mechanistic study to investigate the contribution of cell migration and matrix degradation on gene delivery. In this report, lipoplexes were entrapped within hydrogels based on poly(ethylene glycol) (PEG) crosslinked with peptides containing matrix metalloproteinase degradable sequences. The mesh size of these hydrogels is substantially less than the size of the entrapped lipoplexes, which can function to retain vectors. Cell migration and transfection were simultaneously measured within hydrogels with varying density of cell adhesion sites (Arg-Gly-Asp peptides) and solids content. Increasing RGD density increased expression levels up to 100-fold, while greater solids content sustained expression levels for 16 days. Increasing RGD density and decreasing solids content increased cell migration, which indicates expression levels increase with increased cell migration. Initially exposing cells to vector resulted in transient expression that declined after 2 days, verifying the requirement of migration to sustain expression. Transfected cells were predominantly located within the population of migrating cells for hydrogels that supported cell migration. Although the small mesh size retained at least 70% of the lipoplexes in the absence of cells after 32 days, the presence of cells decreased retention to 10% after 16 days. These results indicate that vectors retained within hydrogels contact migrating cells, and that persistent cell migration can maintain elevated expression levels. Thus matrix degradation and cell migration are fundamental design parameters for maximizing gene delivery from hydrogels. PMID:20450944

Life history diversity of Snake River finespotted cutthroat trout: managing for persistence in a rapidly changing environment

USGS Publications Warehouse

Homel, Kristen M.; Gresswell, Robert E.; Kershner, Jeffrey L.

2015-01-01

Over the last century, native trout have experienced dramatic population declines, particularly in larger river systems where habitats associated with different spawning life history forms have been lost through habitat degradation and fragmentation. The resulting decrease in life history diversity has affected the capacity of populations to respond to environmental variability and disturbance. Unfortunately, because few large rivers are intact enough to permit full expression of life history diversity, it is unclear what patterns of diversity should be a conservation target. In this study, radiotelemetry was used to identify spawning and migration patterns of Snake River Finespotted Cutthroat Trout Oncorhynchus clarkii behnkei in the upper Snake River. Individuals were implanted with radio tags in October 2007 and 2008, and monitored through October 2009. Radio-tagged cutthroat trout in the upper Snake River exhibited variation in spawning habitat type and location, migration distance, spawn timing, postspawning behavior, and susceptibility to mortality sources. Between May and July, Cutthroat Trout spawned in runoff-dominated tributaries, groundwater-dominated spring creeks, and side channels of the Snake River. Individuals migrated up to 101 km from tagging locations in the upper Snake River to access spawning habitats, indicating that the upper Snake River provided seasonal habitat for spawners originating throughout the watershed. Postspawning behavior also varied; by August each year, 28% of spring-creek spawners remained in their spawning location, compared with 0% of side-channel spawners and 7% of tributary spawners. These spawning and migration patterns reflect the connectivity, habitat diversity, and dynamic template of the Snake River. Ultimately, promoting life history diversity through restoration of complex habitats may provide the most opportunities for cutthroat trout persistence in an environment likely to experience increased variability from climate change and disturbance from invasive species.

Cellular Composition and Organization of the Subventricular Zone and Rostral Migratory Stream in the Adult and Neonatal Common Marmoset Brain

PubMed Central

Sawamoto, Kazunobu; Hirota, Yuki; Alfaro-Cervello, Clara; Soriano-Navarro, Mario; He, Xiaoping; Hayakawa-Yano, Yoshika; Yamada, Masayuki; Hikishima, Keigo; Tabata, Hidenori; Iwanami, Akio; Nakajima, Kazunori; Toyama, Yoshiaki; Itoh, Toshio; Alvarez-Buylla, Arturo; Garcia-Verdugo, Jose Manuel; Okano, Hideyuki

2014-01-01

The adult subventricular zone (SVZ) of the lateral ventricle contains neural stem cells. In rodents, these cells generate neuroblasts that migrate as chains toward the olfactory bulb along the rostral migratory stream (RMS). The neural-stem-cell niche at the ventricular wall is conserved in various animal species, including primates. However, it is unclear how the SVZ and RMS organization in nonhuman primates relates to that of rodents and humans. Here we studied the SVZ and RMS of the adult and neonatal common marmoset (Callithrix jacchus), a New World primate used widely in neuroscience, by electron microscopy, and immunohistochemical detection of cell-type-specific markers. The marmoset SVZ contained cells similar to type B, C, and A cells of the rodent SVZ in their marker expression and morphology. The adult marmoset SVZ had a three-layer organization, as in the human brain, with ependymal, hypocellular, and astro-cyte-ribbon layers. However, the hypocellular layer was very thin or absent in the adult-anterior and neonatal SVZ. Anti-PSA-NCAM staining of the anterior SVZ in whole-mount ventricular wall preparations of adult marmosets revealed an extensive network of elongated cell aggregates similar to the neuroblast chains in rodents. Time-lapse recordings of marmoset SVZ explants cultured in Matrigel showed the neuroblasts migrating in chains, like rodent type A cells. These results suggest that some features of neurogenesis and neuronal migration in the SVZ are common to marmosets, humans, and rodents. This basic description of the adult and neonatal marmoset SVZ will be useful for future studies on adult neurogenesis in primates. PMID:21246550

Innate and adaptive immune responses in migrating spring-run adult chinook salmon, Oncorhynchus tshawytscha

USGS Publications Warehouse

Dolan, Brian P.; Fisher, Kathleen M.; Colvin, Michael E.; Benda, Susan E.; Peterson, James T.; Kent, Michael L.; Schreck, Carl B.

2016-01-01

Adult Chinook salmon (Oncorhynchus tshawytscha) migrate from salt water to freshwater streams to spawn. Immune responses in migrating adult salmon are thought to diminish in the run up to spawning, though the exact mechanisms for diminished immune responses remain unknown. Here we examine both adaptive and innate immune responses as well as pathogen burdens in migrating adult Chinook salmon in the Upper Willamette River basin. Messenger RNA transcripts encoding antibody heavy chain molecules slightly diminish as a function of time, but are still present even after fish have successfully spawned. In contrast, the innate anti-bacterial effector proteins present in fish plasma rapidly decrease as spawning approaches. Fish also were examined for the presence and severity of eight different pathogens in different organs. While pathogen burden tended to increase during the migration, no specific pathogen signature was associated with diminished immune responses. Transcript levels of the immunosuppressive cytokines IL-10 and TGF beta were measured and did not change during the migration. These results suggest that loss of immune functions in adult migrating salmon are not due to pathogen infection or cytokine-mediated immune suppression, but is rather part of the life history of Chinook salmon likely induced by diminished energy reserves or hormonal changes which accompany spawning.

A Unique Role for Endothelial Cell Kinesin Light Chain 1, Variant 1 in Leukocyte Transendothelial Migration

PubMed Central

Cyrus, Bita F.; Muller, William A.

2017-01-01

A reservoir of parajunctional membrane in endothelial cells, the lateral border recycling compartment (LBRC), is critical for transendothelial migration (TEM). We have previously shown that targeted recycling of the LBRC to the site of TEM requires microtubules and a kinesin molecular motor. However, the identity of the kinesin and mechanism of cargo binding were not known. We show that microinjection of endothelial cells with a monoclonal antibody specific for kinesin-1 significantly blocked LBRC-targeted recycling and TEM. In complementary experiments, knocking down KIF5B, a ubiquitous kinesin-1 isoform, in endothelial cells significantly decreased targeted recycling of the LBRC and leukocyte TEM. Kinesin heavy chains move cargo along microtubules by one of many kinesin light chains (KLCs), which directly bind the cargo. Knocking down KLC 1 isoform variant 1 (KLC1C) significantly decreased LBRC-targeted recycling and TEM, whereas knocking down other isoforms of KLC1 had no effect. Re-expression of KLC1C resistant to the knockdown shRNA restored targeted recycling and TEM. Thus kinesin-1 and KLC1C are specifically required for targeted recycling and TEM. These data suggest that of the many potential combinations of the 45 kinesin family members and multiple associated light chains, KLC1C links the LBRC to kinesin-1 (KIF5B) during targeted recycling and TEM. Thus, KLC1C can potentially be used as a target for anti-inflammatory therapy. PMID:26994343

Persistence of fan-shaped keratocytes is a matrix-rigidity-dependent mechanism that requires α5β1 integrin engagement.

PubMed

Riaz, Maryam; Versaevel, Marie; Mohammed, Danahe; Glinel, Karine; Gabriele, Sylvain

2016-09-28

Despite the importance of matrix rigidity on cell functions, many aspects of the mechanosensing process in highly migratory cells remain elusive. Here, we studied the migration of highly motile keratocytes on culture substrates with similar biochemical properties and rigidities spanning the range between soft tissues (~kPa) and stiff culture substrates (~GPa). We show that morphology, polarization and persistence of motile keratocytes are regulated by the matrix stiffness over seven orders of magnitude, without changing the cell spreading area. Increasing the matrix rigidity leads to more F-actin in the lamellipodia and to the formation of mature contractile actomyosin fibers that control the cell rear retraction. Keratocytes remain rounded and form nascent adhesions on compliant substrates, whereas large and uniformly distributed focal adhesions are formed on fan-shaped keratocytes migrating on rigid surfaces. By combining poly-L-lysine, fibronectin and vitronectin coatings with selective blocking of α v β 3 or α 5 β 1 integrins, we show that α V β 3 integrins permit the spreading of keratocytes but are not sufficient for polarization and rigidity sensing that require the engagement of α 5 β 1 integrins. Our study demonstrates a matrix rigidity-dependent regulation of the directional persistence in motile keratocytes and refines the role of α v β 3 and α 5 β 1 integrins in the molecular clutch model.

Influence of RNA Strand Rigidity on Polyion Complex Formation with Block Catiomers.

PubMed

Hayashi, Kotaro; Chaya, Hiroyuki; Fukushima, Shigeto; Watanabe, Sumiyo; Takemoto, Hiroyasu; Osada, Kensuke; Nishiyama, Nobuhiro; Miyata, Kanjiro; Kataoka, Kazunori

2016-03-01

Polyion complexes (b-PICs) are prepared by mixing single- or double-stranded oligo RNA (aniomer) with poly(ethylene glycol)-b-poly(L-lysine) (PEG-PLL) (block catiomer) to clarify the effect of aniomer chain rigidity on association behaviors at varying concentrations. Here, a 21-mer single-stranded RNA (ssRNA) (persistence length: 1.0 nm) and a 21-mer double-stranded RNA (small interfering RNA, siRNA) (persistence length: 62 nm) are compared. Both oligo RNAs form a minimal charge-neutralized ionomer pair with a single PEG-PLL chain, termed unit b-PIC (uPIC), at low concentrations (<≈ 0.01 mg mL(-1)). Above the critical association concentration (≈ 0.01 mg mL(-1)), ssRNA b-PICs form secondary associates, PIC micelles, with sizes up to 30-70 nm, while no such multimolecular assembly is observed for siRNA b-PICs. The entropy gain associated with the formation of a segregated PIC phase in the multimolecular PIC micelles may not be large enough for rigid siRNA strands to compensate with appreciably high steric repulsion derived from PEG chains. Chain rigidity appears to be a critical parameter in polyion complex association. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tumor cell migration screen identifies SRPK1 as breast cancer metastasis determinant

PubMed Central

van Roosmalen, Wies; Le Dévédec, Sylvia E.; Golani, Ofra; Smid, Marcel; Pulyakhina, Irina; Timmermans, Annemieke M.; Look, Maxime P.; Zi, Di; Pont, Chantal; de Graauw, Marjo; Naffar-Abu-Amara, Suha; Kirsanova, Catherine; Rustici, Gabriella; Hoen, Peter A.C. ‘t; Martens, John W.M.; Foekens, John A.; Geiger, Benjamin; van de Water, Bob

2015-01-01

Tumor cell migration is a key process for cancer cell dissemination and metastasis that is controlled by signal-mediated cytoskeletal and cell matrix adhesion remodeling. Using a phagokinetic track assay with migratory H1299 cells, we performed an siRNA screen of almost 1,500 genes encoding kinases/phosphatases and adhesome- and migration-related proteins to identify genes that affect tumor cell migration speed and persistence. Thirty candidate genes that altered cell migration were validated in live tumor cell migration assays. Eight were associated with metastasis-free survival in breast cancer patients, with integrin β3–binding protein (ITGB3BP), MAP3K8, NIMA-related kinase (NEK2), and SHC-transforming protein 1 (SHC1) being the most predictive. Examination of genes that modulate migration indicated that SRPK1, encoding the splicing factor kinase SRSF protein kinase 1, is relevant to breast cancer outcomes, as it was highly expressed in basal breast cancer. Furthermore, high SRPK1 expression correlated with poor breast cancer disease outcome and preferential metastasis to the lungs and brain. In 2 independent murine models of breast tumor metastasis, stable shRNA-based SRPK1 knockdown suppressed metastasis to distant organs, including lung, liver, and spleen, and inhibited focal adhesion reorganization. Our study provides comprehensive information on the molecular determinants of tumor cell migration and suggests that SRPK1 has potential as a drug target for limiting breast cancer metastasis. PMID:25774502

Ring-Shaped Microlanes and Chemical Barriers as a Platform for Probing Single-Cell Migration.

PubMed

Schreiber, Christoph; Segerer, Felix J; Wagner, Ernst; Roidl, Andreas; Rädler, Joachim O

2016-05-31

Quantification and discrimination of pharmaceutical and disease-related effects on cell migration requires detailed characterization of single-cell motility. In this context, micropatterned substrates that constrain cells within defined geometries facilitate quantitative readout of locomotion. Here, we study quasi-one-dimensional cell migration in ring-shaped microlanes. We observe bimodal behavior in form of alternating states of directional migration (run state) and reorientation (rest state). Both states show exponential lifetime distributions with characteristic persistence times, which, together with the cell velocity in the run state, provide a set of parameters that succinctly describe cell motion. By introducing PEGylated barriers of different widths into the lane, we extend this description by quantifying the effects of abrupt changes in substrate chemistry on migrating cells. The transit probability decreases exponentially as a function of barrier width, thus specifying a characteristic penetration depth of the leading lamellipodia. Applying this fingerprint-like characterization of cell motion, we compare different cell lines, and demonstrate that the cancer drug candidate salinomycin affects transit probability and resting time, but not run time or run velocity. Hence, the presented assay allows to assess multiple migration-related parameters, permits detailed characterization of cell motility, and has potential applications in cell biology and advanced drug screening.

Displacement correlations between a single mesenchymal-like cell and its nucleus effectively link subcellular activities and motility in cell migration analysis

NASA Astrophysics Data System (ADS)

Lan, Tian; Cheng, Kai; Ren, Tina; Arce, Stephen Hugo; Tseng, Yiider

2016-09-01

Cell migration is an essential process in organism development and physiological maintenance. Although current methods permit accurate comparisons of the effects of molecular manipulations and drug applications on cell motility, effects of alterations in subcellular activities on motility cannot be fully elucidated from those methods. Here, we develop a strategy termed cell-nuclear (CN) correlation to parameterize represented dynamic subcellular activities and to quantify their contributions in mesenchymal-like migration. Based on the biophysical meaning of the CN correlation, we propose a cell migration potential index (CMPI) to measure cell motility. When the effectiveness of CMPI was evaluated with respect to one of the most popular cell migration analysis methods, Persistent Random Walk, we found that the cell motility estimates among six cell lines used in this study were highly consistent between these two approaches. Further evaluations indicated that CMPI can be determined using a shorter time period and smaller cell sample size, and it possesses excellent reliability and applicability, even in the presence of a wide range of noise, as might be generated from individual imaging acquisition systems. The novel approach outlined here introduces a robust strategy through an analysis of subcellular locomotion activities for single cell migration assessment.

Migration, Remittances, and Educational Stratification among Blacks in Apartheid and Post-Apartheid South Africa.

PubMed

Lu, Yao; Treiman, Donald J

2011-06-01

This paper extends previous work on family structure and children's education by conceptualizing migration as a distinct form of family disruption that reduces parental input but brings substantial economic benefits through remittances. It examines the multiple and countervailing effects of migration on schooling in the context of substantial migration and limited educational opportunities for Blacks in South Africa. The receipt of remittances substantially increases Black children's school attendance, but has no such effect for Whites. The effect for Blacks is in part attributable to improved household economic conditions that increase household educational spending and reduce the demand for child labor. We also find a negative effect of parental absence due to migration, but it is largely cushioned by inflows of remittances. Sensitivity analyses using propensity score methods and contextual fixed-effect modeling suggest that the beneficial effect of remittances is relatively robust. We find further that remittances help ameliorate inter-familial socioeconomic inequality in schooling. Finally, we evaluate possible temporal changes and show that the positive and equalizing effects of remittances persisted during and after the apartheid regime. We conclude that labor migration and remittances, as institutionalized family strategies adopted by many Blacks, help reconfigure structural opportunities in the educational stratification process in South Africa.

The Water Suitcase of Migrants: Assessing Virtual Water Fluxes Associated to Human Migration

PubMed Central

Metulini, Rodolfo; Tamea, Stefania; Laio, Francesco; Riccaboni, Massimo

2016-01-01

Disentangling the relations between human migrations and water resources is relevant for food security and trade policy in water-scarce countries. It is commonly believed that human migrations are beneficial to the water endowments of origin countries for reducing the pressure on local resources. We show here that such belief is over-simplistic. We reframe the problem by considering the international food trade and the corresponding virtual water fluxes, which quantify the water used for the production of traded agricultural commodities. By means of robust analytical tools, we show that migrants strengthen the commercial links between countries, triggering trade fluxes caused by food consumption habits persisting after migration. Thus migrants significantly increase the virtual water fluxes and the use of water in the countries of origin. The flux ascribable to each migrant, i.e. the “water suitcase”, is found to have increased from 321 m3/y in 1990 to 1367 m3/y in 2010. A comparison with the water footprint of individuals shows that where the water suitcase exceeds the water footprint of inhabitants, migrations turn out to be detrimental to the water endowments of origin countries, challenging the common perception that migrations tend to relieve the pressure on the local (water) resources of origin countries. PMID:27124488

The Water Suitcase of Migrants: Assessing Virtual Water Fluxes Associated to Human Migration.

PubMed

Metulini, Rodolfo; Tamea, Stefania; Laio, Francesco; Riccaboni, Massimo

2016-01-01

Disentangling the relations between human migrations and water resources is relevant for food security and trade policy in water-scarce countries. It is commonly believed that human migrations are beneficial to the water endowments of origin countries for reducing the pressure on local resources. We show here that such belief is over-simplistic. We reframe the problem by considering the international food trade and the corresponding virtual water fluxes, which quantify the water used for the production of traded agricultural commodities. By means of robust analytical tools, we show that migrants strengthen the commercial links between countries, triggering trade fluxes caused by food consumption habits persisting after migration. Thus migrants significantly increase the virtual water fluxes and the use of water in the countries of origin. The flux ascribable to each migrant, i.e. the "water suitcase", is found to have increased from 321 m3/y in 1990 to 1367 m3/y in 2010. A comparison with the water footprint of individuals shows that where the water suitcase exceeds the water footprint of inhabitants, migrations turn out to be detrimental to the water endowments of origin countries, challenging the common perception that migrations tend to relieve the pressure on the local (water) resources of origin countries.

Migration, Remittances, and Educational Stratification among Blacks in Apartheid and Post-Apartheid South Africa

PubMed Central

Lu, Yao; Treiman, Donald J.

2013-01-01

This paper extends previous work on family structure and children’s education by conceptualizing migration as a distinct form of family disruption that reduces parental input but brings substantial economic benefits through remittances. It examines the multiple and countervailing effects of migration on schooling in the context of substantial migration and limited educational opportunities for Blacks in South Africa. The receipt of remittances substantially increases Black children’s school attendance, but has no such effect for Whites. The effect for Blacks is in part attributable to improved household economic conditions that increase household educational spending and reduce the demand for child labor. We also find a negative effect of parental absence due to migration, but it is largely cushioned by inflows of remittances. Sensitivity analyses using propensity score methods and contextual fixed-effect modeling suggest that the beneficial effect of remittances is relatively robust. We find further that remittances help ameliorate inter-familial socioeconomic inequality in schooling. Finally, we evaluate possible temporal changes and show that the positive and equalizing effects of remittances persisted during and after the apartheid regime. We conclude that labor migration and remittances, as institutionalized family strategies adopted by many Blacks, help reconfigure structural opportunities in the educational stratification process in South Africa. PMID:23935219

CHARACTERIZATION OF SEVEN POLYMORPHIC MICROSATELLITE LOCI IN THE COMMON LOON (GAVIA IMMER)

EPA Science Inventory

We describe polymerase chain reaction (PCR) primers and conditions to amplify seven microsatellite DNA loci isolated from the Common Loon (Gavia immer). The PCR primers were tested on 83 individuals from ten locations in North America, including breeding, migration stopover, and...

Identifying future directions for subsurface hydrocarbon migration research

NASA Astrophysics Data System (ADS)

Leifer, I.; Clark, J. F.; Luyendyk, B.; Valentine, D.

Subsurface hydrocarbon migration is important for understanding the input and impacts of natural hydrocarbon seepage on the environment. Great uncertainties remain in most aspects of hydrocarbon migration, including some basic mechanisms of this four-phase flow of tar, oil, water, and gas through the complex fracture-network geometry particularly since the phases span a wide range of properties. Academic, government, and industry representatives recently attended a workshop to identify the areas of greatest need for future research in shallow hydrocarbon migration.Novel approaches such as studying temporal and spatial seepage variations and analogous geofluid systems (e.g., geysers and trickle beds) allow deductions of subsurface processes and structures that remain largely unclear. Unique complexities exist in hydrocarbon migration due to its multiphase flow and complex geometry, including in-situ biological weathering. Furthermore, many aspects of the role of hydrocarbons (positive and negative) in the environment are poorly understood, including how they enter the food chain (respiration, consumption, etc.) and “percolate” to higher trophic levels. But understanding these ecological impacts requires knowledge of the emissions' temporal and spatial variability and trajectories.

Temporal migration patterns between natal locations of ruby-throated hummingbirds (Archilochus colubris) and their Gulf Coast stopover site.

PubMed

Zenzal, Theodore J; Contina, Andrea J; Kelly, Jeffrey F; Moore, Frank R

2018-01-01

Autumn latitudinal migrations generally exhibit one of two different temporal migration patterns: type 1 where southern populations migrate south before northern populations, or type 2 where northern populations overtake southern populations en route . The ruby-throated hummingbird ( Archilochus colubris ) is a species with an expansive breeding range, which allows opportunities to examine variation in the timing of migration. Our objective was to determine a relationship between natal origin of ruby-throated hummingbirds and arrival at a Gulf coast stopover site; and if so, what factors, such as differences in body size across the range as well as the cost of migration, might drive such a pattern. To carry out our objectives, we captured hummingbirds at a coastal stopover site during autumn migration, at which time we collected feathers from juveniles for analysis of hydrogen stable isotopes. Using the hydrogen stable isotope gradient of precipitation across North America and published hydrogen isotope values of feathers from populations of breeding ruby-throated hummingbirds, we assigned migrants to probable natal latitudes. Our results confirm that individuals from across the range (30-50° N) stopover along the Gulf of Mexico and there is a positive relationship between arrival day and latitude, suggesting a type 1 migration pattern. We also found no relationship between fuel load (proxy for migration cost) or fat-free body mass (proxy for body size) and natal latitude. Our results, coupled with previous work on the spatial migration patterns of hummingbirds, show a type 1 chain migration pattern. While the mechanisms we tested do not seem to influence the evolution of migratory patterns, other factors such as resource availability may play a prominent role in the evolution of this migration system.

Inertial and viscoelastic forces on rigid colloids in microfluidic channels.

PubMed

Howard, Michael P; Panagiotopoulos, Athanassios Z; Nikoubashman, Arash

2015-06-14

We perform hybrid molecular dynamics simulations to study the flow behavior of rigid colloids dispersed in a dilute polymer solution. The underlying Newtonian solvent and the ensuing hydrodynamic interactions are incorporated through multiparticle collision dynamics, while the constituent polymers are modeled as bead-spring chains, maintaining a description consistent with the colloidal nature of our system. We study the cross-stream migration of the solute particles in slit-like channels for various polymer lengths and colloid sizes and find a distinct focusing onto the channel center under specific solvent and flow conditions. To better understand this phenomenon, we systematically measure the effective forces exerted on the colloids. We find that the migration originates from a competition between viscoelastic forces from the polymer solution and hydrodynamically induced inertial forces. Our simulations reveal a significantly stronger fluctuation of the lateral colloid position than expected from thermal motion alone, which originates from the complex interplay between the colloid and polymer chains.

Feasibility study on the use of probabilistic migration modeling in support of exposure assessment from food contact materials.

PubMed

Poças, Maria F; Oliveira, Jorge C; Brandsch, Rainer; Hogg, Timothy

2010-07-01

The use of probabilistic approaches in exposure assessments of contaminants migrating from food packages is of increasing interest but the lack of concentration or migration data is often referred as a limitation. Data accounting for the variability and uncertainty that can be expected in migration, for example, due to heterogeneity in the packaging system, variation of the temperature along the distribution chain, and different time of consumption of each individual package, are required for probabilistic analysis. The objective of this work was to characterize quantitatively the uncertainty and variability in estimates of migration. A Monte Carlo simulation was applied to a typical solution of the Fick's law with given variability in the input parameters. The analysis was performed based on experimental data of a model system (migration of Irgafos 168 from polyethylene into isooctane) and illustrates how important sources of variability and uncertainty can be identified in order to refine analyses. For long migration times and controlled conditions of temperature the affinity of the migrant to the food can be the major factor determining the variability in the migration values (more than 70% of variance). In situations where both the time of consumption and temperature can vary, these factors can be responsible, respectively, for more than 60% and 20% of the variance in the migration estimates. The approach presented can be used with databases from consumption surveys to yield a true probabilistic estimate of exposure.

Molecular oxygen migration through the xenon docking sites of human hemoglobin in the R-state.

PubMed

Lepeshkevich, Sergei V; Gilevich, Syargey N; Parkhats, Marina V; Dzhagarov, Boris M

2016-09-01

A nanosecond laser flash-photolysis technique was used to study bimolecular and geminate molecular oxygen (O2) rebinding to tetrameric human hemoglobin and its isolated α and β chains in buffer solutions equilibrated with 1atm of air and up to 25atm of xenon. Xenon binding to the isolated α chains and to the α subunits within tetrameric hemoglobin was found to cause a decrease in the efficiency of O2 escape by a factor of ~1.30 and 3.3, respectively. A kinetic model for O2 dissociation, rebinding, and migration through two alternative pathways in the hemoglobin subunits was introduced and discussed. It was shown that, in the isolated α chains and α subunits within tetrameric hemoglobin, nearly one- and two-third escaping molecules of O2 leave the protein via xenon docking sites, respectively. The present experimental data support the idea that O2 molecule escapes from the β subunits mainly through the His(E7) gate, and show unambiguously that, in the α subunits, in addition to the direct E7 channel, there is at least one alternative escape route leading to the exterior via the xenon docking sites. Copyright © 2016 Elsevier B.V. All rights reserved.

Derivation of persistent time for anisotropic migration of cells

NASA Astrophysics Data System (ADS)

Liu, Yan-Ping; Zhang, Xiao-Cui; Wu, Yu-Ling; Liu, Wen; Li, Xiang; Liu, Ru-Chuan; Liu, Li-Yu; Shuai, Jian-Wei

2017-12-01

Not Available Project supported by the National Natural Science Foundation of China (Grant Nos. 31370830, 11675134, 11474345, and 11604030), the State Key Development Program for Basic Research of China (Grant No. 2013CB837200), the 111 Project, China (Grant No. B16029), and the China Postdoctoral Science Foundation (Grant No. 2016M602071).

Efforts to estimate pesticide degradation rates in subsurface vadose and aquifer materials

EPA Science Inventory

When pesticides are used in real-world settings, the objective is to be effective in pest eradication at the site of application, but also it is desired that the pesticide have minimal persistence and mobility as it migrates away from the application site. At the site of applicat...

A Bond-Fluctuation Model of Translational Dynamics of Chain-like Particles through Mucosal Scaffolds.

PubMed

Bajd, Franci; Serša, Igor

2018-06-05

Mucus scaffolds represent one of the most common barriers in targeted drug delivery and can remarkably reduce the outcome of pharmacological therapies. An efficient transport of drug particles through a mucus barrier is a precondition for an efficient drug delivery. Understanding the transport mechanism is particularly important for treatment of disorders such as cystic fibrosis. These are characterized by an onset of high-density mucus scaffolds imposing an increased steric filtering. In this study, we employed the bond-fluctuation model to analyze the effect of steric interactions on slowing the translational dynamics of compound chain-like particles traversing through scaffolds of different configurations (regular isotropic and anisotropic versus irregular random). The model, which accounts for both the geometry-imposed steric interaction as well as the intrachain steric interaction between the chain subunits, yields a transient subdiffusive motional pattern persists between the short-time and long-time Gaussian diffusion limits. The motion is analyzed in terms of a mean-squared displacement, diffusion coefficient, and radius of gyration. With higher levels of restriction or larger particles, the subdiffusive motional regime persists longer. The study also demonstrates that an important feature of the motion is also geometry-induced chain accommodation. The presented model is generic and could also be applied to studying the translational dynamics of other particles with more complex architecture such as dendrites or chain-decorated nanoparticles. Copyright © 2018 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Decadal shifts in autumn migration timing by Pacific Arctic beluga whales are related to delayed annual sea ice formation.

PubMed

Hauser, Donna D W; Laidre, Kristin L; Stafford, Kathleen M; Stern, Harry L; Suydam, Robert S; Richard, Pierre R

2017-06-01

Migrations are often influenced by seasonal environmental gradients that are increasingly being altered by climate change. The consequences of rapid changes in Arctic sea ice have the potential to affect migrations of a number of marine species whose timing is temporally matched to seasonal sea ice cover. This topic has not been investigated for Pacific Arctic beluga whales (Delphinapterus leucas) that follow matrilineally maintained autumn migrations in the waters around Alaska and Russia. For the sympatric Eastern Chukchi Sea ('Chukchi') and Eastern Beaufort Sea ('Beaufort') beluga populations, we examined changes in autumn migration timing as related to delayed regional sea ice freeze-up since the 1990s, using two independent data sources (satellite telemetry data and passive acoustics) for both populations. We compared dates of migration between 'early' (1993-2002) and 'late' (2004-2012) tagging periods. During the late tagging period, Chukchi belugas had significantly delayed migrations (by 2 to >4 weeks, depending on location) from the Beaufort and Chukchi seas. Spatial analyses also revealed that departure from Beaufort Sea foraging regions by Chukchi whales was postponed in the late period. Chukchi beluga autumn migration timing occurred significantly later as regional sea ice freeze-up timing became later in the Beaufort, Chukchi, and Bering seas. In contrast, Beaufort belugas did not shift migration timing between periods, nor was migration timing related to freeze-up timing, other than for southward migration at the Bering Strait. Passive acoustic data from 2008 to 2014 provided independent and supplementary support for delayed migration from the Beaufort Sea (4 day yr -1 ) by Chukchi belugas. Here, we report the first phenological study examining beluga whale migrations within the context of their rapidly transforming Pacific Arctic ecosystem, suggesting flexible responses that may enable their persistence yet also complicate predictions of how belugas may fare in the future. © 2016 John Wiley & Sons Ltd.

Migrations and swimming capabilities of endangered pallid sturgeon (Scaphirhynchus albus) to guide passage designs in the fragmented Yellowstone River

USGS Publications Warehouse

Braaten, P. J.; Elliott, Caroline M.; Rhoten, Jason C.; Fuller, D. B.; McElroy, Brandon J.

2015-01-01

Fragmentation of the Yellowstone River is hypothesized to preclude recruitment of endangered Scaphirhynchus albus (pallid sturgeon) by impeding upstream spawning migrations and access to upstream spawning areas, thereby limiting the length of free-flowing river required for survival of early life stages. Building on this hypothesis, the reach of the Yellowstone River affected by Intake Diversion Dam (IDD) is targeted for modification. Structures including a rock ramp and by-pass channel have been proposed as restoration alternatives to facilitate passage. Limited information on migrations and swimming capabilities of pallid sturgeon is available to guide engineering design specifications for the proposed structures. Migration behavior, pathways (channel routes used during migrations), and swimming capabilities of free-ranging wild adult pallid sturgeon were examined using radiotelemetry, and complemented with hydraulic data obtained along the migration pathways. Migrations of 12–26% of the telemetered pallid sturgeon population persisted to IDD, but upstream passage over the dam was not detected. Observed migration pathways occurred primarily through main channel habitats; however, migrations through side channels up to 3.9 km in length were documented. The majority of pallid sturgeon used depths of 2.2–3.4 m and mean water velocities of 0.89–1.83 m/s while migrating. Results provide inferences on depths, velocities, and habitat heterogeneity of reaches successfully negotiated by pallid sturgeon that may be used to guide designs for structures facilitating passage at IDD. Passage will provide connectivity to potential upstream spawning areas on the Yellowstone River, thereby increasing the likelihood of recruitment for this endangered species.

Infectious Agents As Markers of Human Migration toward the Amazon Region of Brazil

PubMed Central

Ishak, Ricardo; Machado, Luiz F. A.; Cayres-Vallinoto, Izaura; Guimarães Ishak, Marluísa de O.; Vallinoto, Antonio C. R.

2017-01-01

Infectious agents are common companions of humans and since ancient times they follow human migration on their search for a better place to live. The study of paleomicrobiology was significantly improved in its accuracy of measurement with the constant development of better methods to detect and analyze nucleic acids. Human tissues are constantly used to trace ancient infections and the association of anthropological evidences are important to confirm the microbiological information. Infectious agents which establish human persistent infections are particularly useful to trace human migrations. In the present article, the evidence of infection by viral agents such as human T-lymphotropic virus 1, human T-lymphotropic virus 2, human herpes virus-8, JC virus, and a bacterium, Chlamydia trachomatis, was described using different methodologies for their detection. Their presence was further used as biomarkers associated with anthropological and other relevant information to trace human migration into the Amazon region of Brazil. The approach also evidenced their microbiological origin, emergence, evolution, and spreading. The information obtained confirms much of the archeological information available tracing ancient and more recent human migration into this particular geographical region. In this article, the paleomicrobiological information on the subject was summarized and reviewed. PMID:28912770

The annealing helicase and branch migration activities of Drosophila HARP.

PubMed

Kassavetis, George A; Kadonaga, James T

2014-01-01

HARP (SMARCAL1, MARCAL1) is an annealing helicase that functions in the repair and restart of damaged DNA replication forks through its DNA branch migration and replication fork regression activities. HARP is conserved among metazoans. HARP from invertebrates differs by the absence of one of the two HARP-specific domain repeats found in vertebrates. The annealing helicase and branch migration activity of invertebrate HARP has not been documented. We found that HARP from Drosophila melanogaster retains the annealing helicase activity of human HARP, the ability to disrupt D-loops and to branch migrate Holliday junctions, but fails to regress model DNA replication fork structures. A comparison of human and Drosophila HARP on additional substrates revealed that both HARPs are competent in branch migrating a bidirectional replication bubble composed of either DNA:DNA or RNA:DNA hybrid. Human, but not Drosophila, HARP is also capable of regressing a replication fork structure containing a highly stable poly rG:dC hybrid. Persistent RNA:DNA hybrids in vivo can lead to replication fork arrest and genome instability. The ability of HARP to strand transfer hybrids may signify a hybrid removal function for this enzyme, in vivo.

International migration patterns of Red-throated Loons (Gavia stellata) from four breeding populations in Alaska

USGS Publications Warehouse

McCloskey, Sarah E.; Uher-Koch, Brian D.; Schmutz, Joel A.; Fondell, Thomas F.

2018-01-01

Identifying post-breeding migration and wintering distributions of migratory birds is important for understanding factors that may drive population dynamics. Red-throated Loons (Gavia stellata) are widely distributed across Alaska and currently have varying population trends, including some populations with recent periods of decline. To investigate population differentiation and the location of migration pathways and wintering areas, which may inform population trend patterns, we used satellite transmitters (n = 32) to describe migration patterns of four geographically separate breeding populations of Red-throated Loons in Alaska. On average (± SD) Red-throated Loons underwent long (6,288 ± 1,825 km) fall and spring migrations predominantly along coastlines. The most northern population (Arctic Coastal Plain) migrated westward to East Asia and traveled approximately 2,000 km farther to wintering sites than the three more southerly populations (Seward Peninsula, Yukon-Kuskokwim Delta, and Copper River Delta) which migrated south along the Pacific coast of North America. These migration paths are consistent with the hypothesis that Red-throated Loons from the Arctic Coastal Plain are exposed to contaminants in East Asia. The three more southerly breeding populations demonstrated a chain migration pattern in which the more northerly breeding populations generally wintered in more northerly latitudes. Collectively, the migration paths observed in this study demonstrate that some geographically distinct breeding populations overlap in wintering distribution while others use highly different wintering areas. Red-throated Loon population trends in Alaska may therefore be driven by a wide range of effects throughout the annual cycle.

A model for a spatially structured metapopulation accounting for within patch dynamics.

PubMed

Smith, Andrew G; McVinish, Ross; Pollett, Philip K

2014-01-01

We develop a stochastic metapopulation model that accounts for spatial structure as well as within patch dynamics. Using a deterministic approximation derived from a functional law of large numbers, we develop conditions for extinction and persistence of the metapopulation in terms of the birth, death and migration parameters. Interestingly, we observe the Allee effect in a metapopulation comprising two patches of greatly different sizes, despite there being decreasing patch specific per-capita birth rates. We show that the Allee effect is due to the way the migration rates depend on the population density of the patches. Copyright © 2013 Elsevier Inc. All rights reserved.

Synthetic Method for Oligonucleotide Block by Using Alkyl-Chain-Soluble Support.

PubMed

Matsuno, Yuki; Shoji, Takao; Kim, Shokaku; Chiba, Kazuhiro

2016-02-19

A straightforward method for the synthesis of oligonucleotide blocks using a Cbz-type alkyl-chain-soluble support (Z-ACSS) attached to the 3'-OH group of 3'-terminal nucleosides was developed. The Z-ACSS allowed for the preparation of fully protected deoxyribo- and ribo-oligonucleotides without chromatographic purification and released dimer- to tetramer-size oligonucleotide blocks via hydrogenation using a Pd/C catalyst without significant loss or migration of protective groups such as 5'-end 4,4'-dimethoxtrityl, 2-cyanoethyl on internucleotide bonds, or 2'-TBS.

The Outdoor Classroom. Experiencing Nature in the Elementary Curriculum.

ERIC Educational Resources Information Center

Alexander, Phyllis, Ed.; And Others

Through direct experience within natural settings, outdoor education allows students to learn about environmental concerns such as migration of birds, weather systems, wildlife habitats, watersheds, soil erosion, geological formations, food chains, and community resources. All subject areas in the present curriculum can be enriched through outdoor…

MOVEMENT OF STRONTIUM AND CAESIUM IN SOILS AND ITS SIGNIFICANCE IN STUDIES ON THE CONTAMINATION OF FOOD CHAINS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, R.S.; Shone, M.G.T.

ABS>Experimental results are given of a long term study on the migration and fixation of strontium and cesium in several types of soil The investigations were designed to approximate to field conditions in which the soil remained undisturbed by cultivation. The effects of the addition of nutrients and of a permanent crop of ryegrass grown on the artificially contaminated soils were also examined. The relevance of processes of migration and fixation to assessments of the uptake of strontium and cesium by crop plants is considered in the light of field experiments. (auth)

Interpretation Difficulties of Serum Immunofixation Test in Immunoglobulin D Multiple Myeloma with Hidden Lambda Light Chains.

PubMed

Biaz, A; Uwingabiye, J; Rachid, A; Dami, A; Bouhsain, S; Ouzzif, Z; Idrissi, S El Machtani

2018-06-01

We report a case of immunoglobulin (Ig) D myeloma with hidden lambda light chains in a patient whose immunofixation test was very difficult to interpret: the IgD reacts with the anti-δ heavy chain antiserum but does not react with anti-lambda antiserum. The band in the D heavy chain lane is unmatched in light chain lanes and the band in lambda light chain lane migrates higher. To distinguish between heavy chain disease and immunoglobulin with "hidden" light chains, the sample was exposed to a very high concentration of anti-lambda and anti-kappa antisera for 48 hours. The serum immunofixation test of the sample treated with anti-lambda showed a decrease in the intensity of the band corresponding to D heavy chain lane as well as the modification of its mobility confirming the presence of IgD with the hidden lambda light chains. The IgD myeloma with hidden light chains remains a rare entity, hence the interest of sensitizing health professionals to be vigilant and ensure a good diagnosis. The proposed technique is useful, simple, reliable, and less laborious than those previous reported in the literature. Medical laboratories using Sebia-Hydrasys® system should be aware of the described phenomenon in order to avoid identifying an IgD myeloma as a delta heavy chain disease.

Decorin-Mediated Inhibition of Human Trophoblast Cells Proliferation, Migration, and Invasion and Promotion of Apoptosis In Vitro

PubMed Central

Zou, Yanfen; Yu, Xiang; Lu, Jing; Jiang, Ziyan; Zuo, Qing; Fan, Mingsong; Huang, Shiyun

2015-01-01

Preeclampsia (PE) is a unique complication of pregnancy, the pathogenesis of which has been generally accepted to be associated with the dysfunctions of extravillous trophoblast (EVT) including proliferation, apoptosis, and migration and invasion. Decorin (DCN) has been proved to be a decidua-derived TGF-binding proteoglycan, which negatively regulates proliferation, migration, and invasiveness of human extravillous trophoblast cells. In this study, we identified a higher expression level of decorin in severe PE placentas by both real-time reverse transcription-polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC). And an inhibitory effect of decorin on proliferation, migration, and invasion and an enhanced effect on apoptosis in trophoblast cells HTR-8/SVneo and JEG-3 were validated in vitro. Also the modulations of decorin on trophoblast cells' metastasis and invasion functions were detected through regulating the matrix metalloproteinases (MMP2 and MMP9). Thus, we suggested that the contribution of decorin to the modulation of trophoblast cells might have implications for the pathogenesis of preeclampsia. PMID:26357650

International nurse recruitment in India.

PubMed

Khadria, Binod

2007-06-01

This paper describes the practice of international recruitment of Indian nurses in the model of a "business process outsourcing" of comprehensive training-cum-recruitment-cum-placement for popular destinations like the United Kingdom and United States through an agency system that has acquired growing intensity in India. Despite the extremely low nurse to population ratio in India, hospital managers in India are not concerned about the growing exodus of nurses to other countries. In fact, they are actively joining forces with profitable commercial ventures that operate as both training and recruiting agencies. Most of this activity is concentrated in Delhi, Bangalore, and Kochi. Gaps in data on nursing education, employment, and migration, as well as nonstandardization of definitions of "registered nurse," impair the analysis of international migration of nurses from India, making it difficult to assess the impact of migration on vacancy rates. One thing is clear, however, the chain of commercial interests that facilitate nurse migration is increasingly well organized and profitable, making the future growth of this business a certainty.

Labor migration, externalities and ethics: Theorizing the meso-level determinants of HIV vulnerability

PubMed Central

Hirsch, Jennifer S.

2013-01-01

This paper discusses labor migration as an example of how focusing on the meso-level highlights the social processes through which structural factors produce HIV risk. Situating that argument in relation to existing work on economic organization and HIV risk as well as research on labor migration and HIV vulnerabilities, the paper demonstrates how analyzing the processes through which labor migration creates vulnerability can shift attention away from the proximate behavioral determinants of HIV risk and towards the community and policy levels. Further, it presents the concepts of externalities and the ethics of consumption, which underline how both producers and consumers benefit from low-waged migrant labor, and thus are responsible for the externalization of HIV risk characteristic of supply chains that rely on migrant labor. These concepts point to strategies through which researchers and advocates could press the public and private sectors to improve the conditions in which migrants live and work, with implications for HIV as well as other health outcomes. PMID:24444837

Suppression of fructose-bisphosphate aldolase C expression as a predictor of advanced oral squamous cell carcinoma.

PubMed

Li, Yue-Ju; Huang, Tse-Hung; Hsiao, Michael; Lin, Been-Ren; Cheng, Shih-Jung; Yang, Cheng-Ning; Lai, Wei-Ting; Wu, Tai-Sheng; Fan, Jia-Ruei; Kuo, Mark Yen-Ping; Chang, Cheng-Chi

2016-04-01

Glycolysis machinery regulates cancer cell behavior. However, the roles of these glycolysis enzymes in oral squamous cell carcinoma (OSCC) progression remain unknown. Fructose-bisphosphate aldolase C (ALDOC) expression in OSCC patients and cell lines was detected using quantitative real-time polymerase chain reaction (PCR). The functions of ALDOC in migration and invasion were determined using gain and loss of function approaches. An orthotopic OSCC animal model was performed to investigate the effects of ALDOC on metastasis and tumorigenesis in vivo. ALDOC expression is negatively significantly correlated with clinical outcome and cell migration in vitro and in vivo. ALDOC blocks adenosine triphosphate generation and lactate production, and mutation constructs of Arg42 and Lys146 functionally restore ALDOC-inhibited cell migration and invasion. ALDOC functions as an OSCC prognosis marker clinically, and suppresses migration and invasion by its catalytic domain of Arg42 and Lys146. © 2015 Wiley Periodicals, Inc. Head Neck 38: E1075-E1085, 2016. © 2015 Wiley Periodicals, Inc.

Myosin II Motors and F-Actin Dynamics Drive the Coordinated Movement of the Centrosome and Soma during CNS Glial-Guided Neuronal Migration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solecki, Dr. David; Trivedi, Dr. Niraj; Govek, Eve-Ellen

2009-01-01

Lamination of cortical regions of the vertebrate brain depends on glial-guided neuronal migration. The conserved polarity protein Par6{alpha} localizes to the centrosome and coordinates forward movement of the centrosome and soma in migrating neurons. The cytoskeletal components that produce this unique form of cell polarity and their relationship to polarity signaling cascades are unknown. We show that F-actin and Myosin II motors are enriched in the neuronal leading process and that Myosin II activity is necessary for leading process actin dynamics. Inhibition of Myosin II decreased the speed of centrosome and somal movement, whereas Myosin II activation increased coordinated movement.more » Ectopic expression or silencing of Par6{alpha} inhibited Myosin II motors by decreasing Myosin light-chain phosphorylation. These findings suggest leading-process Myosin II may function to 'pull' the centrosome and soma forward during glial-guided migration by a mechanism involving the conserved polarity protein Par6{alpha}.« less

Regulating the migration of smooth muscle cells by a vertically distributed poly(2-hydroxyethyl methacrylate) gradient on polymer brushes covalently immobilized with RGD peptides.

PubMed

Wu, Sai; Du, Wang; Duan, Yiyuan; Zhang, Deteng; Liu, Yixiao; Wu, Bingbing; Zou, Xiaohui; Ouyang, Hongwei; Gao, Changyou

2018-05-30

The gradient localization of biological cues is of paramount importance to guide directional migration of cells. In this study, poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate)-block- poly(2-hydroxyethyl methacrylate) (P(HEMA-co-GMA)-b-PHEMA) brushes with a uniform underneath P(HEMA-co-GMA) layer and a gradient thickness of PHEMA blocks were prepared by using surface-initiated atom-transfer radical polymerization and a dynamically controlled polymerization process. The polymer chains were subsequently functionalized with the cell-adhesive arginine-glycine-aspartic acid (RGD) peptides by reaction with the glycidyl groups, and their structures and properties were characterized by X-ray photoelectron spectrometry (XPS), quartz crystal microbalance with dissipation (QCM-D) and air contact angle. Adhesion and migration processes of smooth muscle cells (SMCs) were then studied. Compared with those on the sufficiently exposed RGD surface, the cell adhesion and mobility were well maintained when the RGD peptides were localized at 18.9 nm depth, whereas the adhesion, spreading and migration rate of SMCs were significantly impaired when the RGD peptides were localized at a depth of 38.4 nm. On the RGD depth gradient surface, the SMCs exhibited preferential orientation and enhanced directional migration toward the direction of reduced thickness of the second PHEMA brushes. Half of the cells were oriented within ± 30° to the x-axis direction, and 72% of the cells moved directionally at the optimal conditions. Cell adhesion strength, arrangement of cytoskeleton, and gene and protein expression levels of adhesion-related proteins were studied to corroborate the mechanisms, demonstrating that the cell mobility is regulated by the complex and synergetic intracellular signals resulted from the difference in surface properties. Cell migration is of paramount importance for the processes of tissue repair and regeneration. So far, the gradient localization of biological cues perpendicular to the substrate, which is the usual case for the biological signaling molecules to locate in ECM in vivo, has been scarcely studied, and has not been used to guide the directional migration of cells. In this study, we prepare a depth gradient of RGD peptides along the polymer chains, which is used to guide the directional migration of SMCs after a second hydrophilic bock is prepared in a gradient manner. For the first time the directional migration of SMCs is achieved under the guidance of a depth gradient of RGD ligands. The mechanisms of different cell migration abilities are further discussed based on the results of cell adhesion, cell adhesion force, cytoskeleton alignment and expression of relative proteins and genes. This work paves a new strategy by fabricating a gradient polymer brushes with immobilized bioactive molecules to dominate the directional cell migration, and elucidates the mechanisms underlining the biased migration along RGD depth localization gradients, shedding a light for the design of novel biomaterials to control and guide cell migration and invasion. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The BSD2 ortholog in Chlamydomonas reinhardtii is a polysome-associated chaperone that co-migrates on sucrose gradients with the rbcL transcript encoding the Rubisco large subunit.

PubMed

Doron, Lior; Segal, Na'ama; Gibori, Hadas; Shapira, Michal

2014-10-01

The expression of the CO2 -fixation enzyme ribulose-bisphosphate carboxylase/oxygenase (Rubisco), which is affected by light, involves the cysteine-rich protein bundle-sheath defective-2 (BSD2) that was originally identified in maize bundle-sheath cells. We identified the BSD2 ortholog in Chlamydomonas reinhardtii as a small protein (17 kDa) localized to the chloroplast. The algal BSD2-ortholog contains four CXXCXGXG DnaJ-like elements, but lacks the other conserved domains of DnaJ. BSD2 co-migrated with the rbcL transcript on heavy polysomes, and both BSD2 and rbcL mRNA shifted to the lighter fractions under oxidizing conditions that repress the translation of the Rubisco large subunit (RbcL). This profile of co-migration supports the possibility that BSD2 is required for the de novo synthesis of RbcL. Furthermore, BSD2 co-migrated with the rbcL transcript in a C. reinhardtii premature-termination mutant that encodes the first 60 amino acids of RbcL. In both strains, BSD2 shared its migration profile with the rbcL transcript but not with psbA mRNA. The chaperone activity of BSD2 was exemplified by its ability to prevent the aggregation of both citrate synthase (CS) and RbcL in vitro following their chemical denaturation. This activity did not depend on the presence of the thiol groups on BSD2. In contrast, the activity of BSD2 in preventing the precipitation of reduced β-chains in vitro in the insulin turbidity assay was thiol-dependent. We conclude that BSD2 combines a chaperone 'holdase' function with the ability to interact with free thiols, with both activities being required to protect newly synthesized RbcL chains. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

Association of Wnt1-inducible signaling pathway protein-1 with the proliferation, migration and invasion in gastric cancer cells.

PubMed

Jia, Shuqin; Qu, Tingting; Feng, Mengmeng; Ji, Ke; Li, Ziyu; Jiang, Wenguo; Ji, Jiafu

2017-06-01

Wnt1-inducible signaling pathway protein-1 is a cysteine-rich protein that belongs to the CCN family, which has been implicated in mediating the occurrence and progression through distinct molecular mechanisms in several tumor types. However, the association of Wnt1-inducible signaling pathway protein-1 with gastric cancer and the related molecular mechanisms remain to be elucidated. Therefore, this study aimed to clarify the biological role of Wnt1-inducible signaling pathway protein-1 in the proliferation, migration, and invasion in gastric cancer cells and further investigated the associated molecular mechanism on these biological functions. We first detected the expression level of Wnt1-inducible signaling pathway protein-1 in gastric cancer, and the reverse transcription polymerase chain reaction have shown that Wnt1-inducible signaling pathway protein-1 expression levels were upregulated in gastric cancer tissues. The expression of Wnt1-inducible signaling pathway protein-1 in gastric cancer cell lines was also detected by quantitative real-time polymerase chain reaction and Western blotting. Furthermore, two gastric cancer cell lines with high expression of Wnt1-inducible signaling pathway protein-1 were selected to explore the biological function of Wnt1-inducible signaling pathway protein-1 in gastric cancer. Function assays indicated that knockdown of Wnt1-inducible signaling pathway protein-1 suppressed cell proliferation, migration, and invasion in BGC-823 and AGS gastric cancer cells. Further investigation of mechanisms suggested that cyclinD1 was identified as one of Wnt1-inducible signaling pathway protein-1 related genes to accelerate proliferation in gastric cancer cells. In addition, one pathway of Wnt1-inducible signaling pathway protein-1 induced migration and invasion was mainly through the enhancement of epithelial-to-mesenchymal transition progression. Taken together, our findings presented the first evidence that Wnt1-inducible signaling pathway protein-1 was upregulated in gastric cancer and acted as an oncogene by promoting proliferation, migration, and invasion in gastric cancer cells.

Upregulation of MiR-212 Inhibits Migration and Tumorigenicity and Inactivates Wnt/β-Catenin Signaling in Human Hepatocellular Carcinoma.

PubMed

Jia, Pengbo; Wei, Guangbing; Zhou, Cancan; Gao, Qi; Wu, Yunhua; Sun, Xuejun; Li, Xuqi

2018-01-01

MicroRNAs are involved in hepatocellular carcinoma metastasis, a principal cause of hepatocellular carcinoma-related death in patients worldwide. MiR-212 is a microRNA that has been identified in several types of cancers and is postulated to influence cell signaling and subsequent malignant pathogenesis. Despite emerging reports suggesting that miR-212 plays a significant role in the onset, progression, and migration of these types of malignant tumors, its involvement in the development of hepatocellular carcinoma has not been fully elucidated. Quantitative reverse transcription polymerase chain reaction, wound healing, transwell migration and invasion assays, Western blotting, and xenograft tumor growth models were performed to test the expression levels and functions of miR-212 in hepatocellular carcinoma. Luciferase reporter assay, quantitative reverse transcription polymerase chain reaction, Western blotting, and immunohistochemistry were used to identify and verify the target of miR-212. In this study, we identify significant repression of miR-212 in hepatocellular carcinoma and demonstrate that overexpression of miR-212 inhibits the migration of hepatocellular carcinoma cells in vitro and in vivo. Furthermore, we identify forkhead box M1, whose expression is inversely related to that of miR-212, as a direct target of miR-212. Additionally, reexpression of forkhead box M1 rescues the miR-212-mediated inhibition of cell migration. We observed that inhibition of miR-212 activates forkhead box M1 but inhibits the Wnt/β-catenin pathway by suppressing Wnt, LEF-1, c-Myc, and nuclear β-catenin. Finally, in vivo studies confirmed the inhibitory effect of miR-212 on hepatocellular carcinoma growth. Our present findings indicate that miR-212 is a potential prognostic biomarker of hepatocellular carcinoma and that the miR-212/forkhead box M1 regulatory axis may represent a new therapeutic objective for hepatocellular carcinoma treatment.

In Vivo Persistence of Human Rhinoviruses in Immunosuppressed Patients

PubMed Central

Engelmann, Ilka; Dewilde, Anny; Lazrek, Mouna; Batteux, Mathilde; Hamissi, Aminati; Yakoub-Agha, Ibrahim; Hober, Didier

2017-01-01

Several species of the genus Enterovirus cause persistent infections in humans. Human rhinovirus (HRV) infections are generally self-limiting but occasionally persistent infections have been described. This study aimed to identify persistent HRV infections and investigate the clinical and virologic characteristics of patients with persistent infections. From January 2012 to March 2015, 3714 respiratory specimens from 2608 patients were tested for respiratory viruses by using a multiplex reverse transcription–polymerase chain reaction. A retrospective study was performed. Patients with at least two specimens positive for HRV/enterovirus taken 45 days or longer apart were identified and the HRV/enteroviruses were typed. Patients with persistent infection were compared to patients with reinfection and patients with cleared infection. Phylogenetic analysis of the viral protein(VP)4/VP2 region was performed. 18 patients with persistent HRV/enterovirus infection were identified. Minimum median duration of persistence was 92 days (range 50–455 days). All but one patients with persistence were immunosuppressed. Immunosuppression and hematologic disorders were more frequent in patients with persistence (n = 18) than in patients with reinfection (n = 33) and with cleared infection (n = 25) (p = 0.003 and p = 0.001, respectively). In conclusion, this retrospective study identified HRV persistence in vivo which occurred mainly in immunosuppressed patients. PMID:28151988

The population ecology of despotism. Concessions and migration between central and peripheral habitats.

PubMed

Bell, Adrian Viliami; Winterhalder, Bruce

2014-03-01

Since despotism is a common evolutionary development in human history, we seek to understand the conditions under which it can originate, persist, and affect population trajectories. We describe a general system of population ecology equations representing the Ideal Free and Despotic Distributions for one and two habitats, one of which contains a despotic class that controls the distribution of resources. Using analytical and numerical solutions we derive the optimal concession strategy by despots with and without subordinate migration to an alternative habitat. We show that low concessions exponentially increase the time it takes for the despotic habitat to fill, and we discuss the trade-offs despots and subordinates confront at various levels of exploitation. Contrary to previous hypotheses, higher levels of despotism do not necessarily cause faster migration to alternative habitats. We further show how, during colonization, divergent population trajectories may arise if despotic systems experience Allee-type economies of scale.

Evaluation of strategies to control Fab light chain dimer during mammalian expression and purification: A universal one-step process for purification of correctly assembled Fab.

PubMed

Spooner, Jennifer; Keen, Jenny; Nayyar, Kalpana; Birkett, Neil; Bond, Nicholas; Bannister, David; Tigue, Natalie; Higazi, Daniel; Kemp, Benjamin; Vaughan, Tristan; Kippen, Alistair; Buchanan, Andrew

2015-07-01

Fabs are an important class of antibody fragment as both research reagents and therapeutic agents. There are a plethora of methods described for their recombinant expression and purification. However, these do not address the issue of excessive light chain production that forms light chain dimers nor do they describe a universal purification strategy. Light chain dimer impurities and the absence of a universal Fab purification strategy present persistent challenges for biotechnology applications using Fabs, particularly around the need for bespoke purification strategies. This study describes methods to address light chain dimer formation during Fab expression and identifies a novel CH 1 affinity resin as a simple and efficient one-step purification for correctly assembled Fab. © 2015 Wiley Periodicals, Inc.

Blockade of interferon Beta, but not interferon alpha, signaling controls persistent viral infection.

PubMed

Ng, Cherie T; Sullivan, Brian M; Teijaro, John R; Lee, Andrew M; Welch, Megan; Rice, Stephanie; Sheehan, Kathleen C F; Schreiber, Robert D; Oldstone, Michael B A

2015-05-13

Although type I interferon (IFN-I) is thought to be beneficial against microbial infections, persistent viral infections are characterized by high interferon signatures suggesting that IFN-I signaling may promote disease pathogenesis. During persistent lymphocytic choriomeningitis virus (LCMV) infection, IFNα and IFNβ are highly induced early after infection, and blocking IFN-I receptor (IFNAR) signaling promotes virus clearance. We assessed the specific roles of IFNβ versus IFNα in controlling LCMV infection. While blockade of IFNβ alone does not alter early viral dissemination, it is important in determining lymphoid structure, lymphocyte migration, and anti-viral T cell responses that lead to accelerated virus clearance, approximating what occurs during attenuation of IFNAR signaling. Comparatively, blockade of IFNα was not associated with improved viral control, but with early dissemination of virus. Thus, despite their use of the same receptor, IFNβ and IFNα have unique and distinguishable biologic functions, with IFNβ being mainly responsible for promoting viral persistence. Copyright © 2015 Elsevier Inc. All rights reserved.

Credible Immigration Policy Reform: A Response to Briggs

ERIC Educational Resources Information Center

Orrenius, Pia M.; Zavodny, Madeline

2012-01-01

The authors agree with Vernon M. Briggs, Jr., that U.S. immigration policy has had unexpected consequences. The 1965 immigration reforms led to unanticipated chain migration from developing countries whereas the 1986 Immigration Reform and Control Act failed to slow unauthorized immigration. The result is a large foreign-born population with…

Department of Defense Information Enterprise: Strategic Plan 2010-2012

DTIC Science & Technology

2010-04-01

migrate from circuit-based technology to a converged (voice, video , and data) IP network and UC services environment. Ensure the optimal...Kevin Coleman, “Cyber Attacks on Supply Chain Systems,” Defense Tech, April 15, 2009 8 Lolita C. Baldor, “Federal Web Sites Knocked Out by Cyber Attack

N-body simulations of terrestrial planet formation under the influence of a hot Jupiter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogihara, Masahiro; Kobayashi, Hiroshi; Inutsuka, Shu-ichiro, E-mail: omasahiro@oca.eu, E-mail: ogihara@nagoya-u.jp

We investigate the formation of multiple-planet systems in the presence of a hot Jupiter (HJ) using extended N-body simulations that are performed simultaneously with semianalytic calculations. Our primary aims are to describe the planet formation process starting from planetesimals using high-resolution simulations, and to examine the dependences of the architecture of planetary systems on input parameters (e.g., disk mass, disk viscosity). We observe that protoplanets that arise from oligarchic growth and undergo type I migration stop migrating when they join a chain of resonant planets outside the orbit of an HJ. The formation of a resonant chain is almost independentmore » of our model parameters, and is thus a robust process. At the end of our simulations, several terrestrial planets remain at around 0.1 AU. The formed planets are not equal mass; the largest planet constitutes more than 50% of the total mass in the close-in region, which is also less dependent on parameters. In the previous work of this paper, we have found a new physical mechanism of induced migration of the HJ, which is called a crowding-out. If the HJ opens up a wide gap in the disk (e.g., owing to low disk viscosity), crowding-out becomes less efficient and the HJ remains. We also discuss angular momentum transfer between the planets and disk.« less

Physical confinement alters tumor cell adhesion and migration phenotypes

PubMed Central

Balzer, Eric M.; Tong, Ziqiu; Paul, Colin D.; Hung, Wei-Chien; Stroka, Kimberly M.; Boggs, Amanda E.; Martin, Stuart S.; Konstantopoulos, Konstantinos

2012-01-01

Cell migration on planar surfaces is driven by cycles of actin protrusion, integrin-mediated adhesion, and myosin-mediated contraction; however, this mechanism may not accurately describe movement in 3-dimensional (3D) space. By subjecting cells to restrictive 3D environments, we demonstrate that physical confinement constitutes a biophysical stimulus that alters cell morphology and suppresses mesenchymal motility in human breast carcinoma (MDA-MB-231). Dorsoventral polarity, stress fibers, and focal adhesions are markedly attenuated by confinement. Inhibitors of myosin, Rho/ROCK, or β1-integrins do not impair migration through 3-μm-wide channels (confinement), even though these treatments repress motility in 50-μm-wide channels (unconfined migration) by ≥50%. Strikingly, confined migration persists even when F-actin is disrupted, but depends largely on microtubule (MT) dynamics. Interfering with MT polymerization/depolymerization causes confined cells to undergo frequent directional changes, thereby reducing the average net displacement by ≥80% relative to vehicle controls. Live-cell EB1-GFP imaging reveals that confinement redirects MT polymerization toward the leading edge, where MTs continuously impact during advancement of the cell front. These results demonstrate that physical confinement can induce cytoskeletal alterations that reduce the dependence of migrating cells on adhesion-contraction force coupling. This mechanism may explain why integrins can exhibit reduced or altered function during migration in 3D environments.—Balzer, E. M., Tong, Z., Paul, C. D., Hung, W.-C., Stroka, K. M., Boggs, A. E., Martin, S. S., Konstantopoulos, K. Physical confinement alters tumor cell adhesion and migration phenotypes. PMID:22707566

Geographical and Geodemographic Connections between Different Types of Small Area as the Origins and Destinations of Migrants to Mid-Wales

ERIC Educational Resources Information Center

Walford, Nigel

2007-01-01

Exchanges of population between supposedly "urban" and "rural" spaces have occurred throughout history as people migrate between areas with relatively, densely and sparsely settled populations. However, comparatively little is known about whether the same small areas persistently contribute to the flow and what types of…

[Population trends in Albania].

PubMed

Sivignon, M

1983-01-01

Recent demographic trends in Albania are reviewed. The author notes that rapid population growth persists due to continuing fertility, although the fertility rate has begun to decline during the past 20 years. Controls placed on internal migration have succeeded in restricting the growth of the urban population and have contributed to the sustained growth of the population in rural areas. (summary in ENG)

The allure of new immigrant destinations and the Great Recession in the United States.

PubMed

Ellis, Mark; Wright, Richard; Townley, Matthew

2014-01-01

In the 1990s, the immigrant population in the United States dispersed to non-traditional settlement locations (what have become known as "new immigrant destinations"). This paper examines whether the allure of new destinations persisted in the 2000s with a particular focus on the internal migration of the foreign born during the recent deep recessionary period and its aftermath. Three specific questions motivate the analysis. First, are immigrants, much like the US-born population, becoming less migratory within the country over time? Second, is immigrant dispersal from traditional gateways via internal migration continuing despite considerable economic contraction in many new destination metropolitan areas? Third, is immigration from aboard a substitute for what appears to be declining immigrant internal migration to new destinations? The findings reveal a close correlation between the declining internal migration propensity of the US-born and immigrants in the last two decades. We also observe parallels between the geographies of migration of native- and foreign-born populations with both groups moving to similar metropolitan areas in the 1990s. This redistributive association, however, weakened in the subsequent decade as new destination metropolitan areas lost their appeal for both groups, especially immigrants. There is no evidence to suggest that immigration from abroad is substituting for the decline in immigrant redistribution through internal migration to new destinations. Across destination types the relationship between immigration from abroad and the internal migration of the foreign born remained the same before, during, and after the Great Recession.

Optical control demonstrates switch-like PIP3 dynamics underlying the initiation of immune cell migration

PubMed Central

Karunarathne, W. K. Ajith; Giri, Lopamudra; Patel, Anilkumar K.; Venkatesh, Kareenhalli V.; Gautam, N.

2013-01-01

There is a dearth of approaches to experimentally direct cell migration by continuously varying signal input to a single cell, evoking all possible migratory responses and quantitatively monitoring the cellular and molecular response dynamics. Here we used a visual blue opsin to recruit the endogenous G-protein network that mediates immune cell migration. Specific optical inputs to this optical trigger of signaling helped steer migration in all possible directions with precision. Spectrally selective imaging was used to monitor cell-wide phosphatidylinositol (3,4,5)-triphosphate (PIP3), cytoskeletal, and cellular dynamics. A switch-like PIP3 increase at the cell front and a decrease at the back were identified, underlying the decisive migratory response. Migration was initiated at the rapidly increasing switch stage of PIP3 dynamics. This result explains how a migratory cell filters background fluctuations in the intensity of an extracellular signal but responds by initiating directionally sensitive migration to a persistent signal gradient across the cell. A two-compartment computational model incorporating a localized activator that is antagonistic to a diffusible inhibitor was able to simulate the switch-like PIP3 response. It was also able simulate the slow dissipation of PIP3 on signal termination. The ability to independently apply similar signaling inputs to single cells detected two cell populations with distinct thresholds for migration initiation. Overall the optical approach here can be applied to understand G-protein–coupled receptor network control of other cell behaviors. PMID:23569254

Optical control demonstrates switch-like PIP3 dynamics underlying the initiation of immune cell migration.

PubMed

Karunarathne, W K Ajith; Giri, Lopamudra; Patel, Anilkumar K; Venkatesh, Kareenhalli V; Gautam, N

2013-04-23

There is a dearth of approaches to experimentally direct cell migration by continuously varying signal input to a single cell, evoking all possible migratory responses and quantitatively monitoring the cellular and molecular response dynamics. Here we used a visual blue opsin to recruit the endogenous G-protein network that mediates immune cell migration. Specific optical inputs to this optical trigger of signaling helped steer migration in all possible directions with precision. Spectrally selective imaging was used to monitor cell-wide phosphatidylinositol (3,4,5)-triphosphate (PIP3), cytoskeletal, and cellular dynamics. A switch-like PIP3 increase at the cell front and a decrease at the back were identified, underlying the decisive migratory response. Migration was initiated at the rapidly increasing switch stage of PIP3 dynamics. This result explains how a migratory cell filters background fluctuations in the intensity of an extracellular signal but responds by initiating directionally sensitive migration to a persistent signal gradient across the cell. A two-compartment computational model incorporating a localized activator that is antagonistic to a diffusible inhibitor was able to simulate the switch-like PIP3 response. It was also able simulate the slow dissipation of PIP3 on signal termination. The ability to independently apply similar signaling inputs to single cells detected two cell populations with distinct thresholds for migration initiation. Overall the optical approach here can be applied to understand G-protein-coupled receptor network control of other cell behaviors.

Emergence of collective propulsion through cell-cell adhesion.

PubMed

Matsushita, Katsuyoshi

2018-04-01

The mechanisms driving the collective movement of cells remain poorly understood. To contribute toward resolving this mystery, a model was formulated to theoretically explore the possible functions of polarized cell-cell adhesion in collective cell migration. The model consists of an amoeba cell with polarized cell-cell adhesion, which is controlled by positive feedback with cell motion. This model cell has no persistent propulsion and therefore exhibits a simple random walk when in isolation. However, at high density, these cells acquire collective propulsion and form ordered movement. This result suggests that cell-cell adhesion has a potential function, which induces collective propulsion with persistence.

Emergence of collective propulsion through cell-cell adhesion

NASA Astrophysics Data System (ADS)

Matsushita, Katsuyoshi

2018-04-01

The mechanisms driving the collective movement of cells remain poorly understood. To contribute toward resolving this mystery, a model was formulated to theoretically explore the possible functions of polarized cell-cell adhesion in collective cell migration. The model consists of an amoeba cell with polarized cell-cell adhesion, which is controlled by positive feedback with cell motion. This model cell has no persistent propulsion and therefore exhibits a simple random walk when in isolation. However, at high density, these cells acquire collective propulsion and form ordered movement. This result suggests that cell-cell adhesion has a potential function, which induces collective propulsion with persistence.

Coupling between oxygen redox and cation migration explains unusual electrochemistry in lithium-rich layered oxides

DOE PAGES

Gent, William E.; Lim, Kipil; Liang, Yufeng; ...

2017-12-01

© 2017 The Author(s). Lithium-rich layered transition metal oxide positive electrodes offer access to anion redox at high potentials, thereby promising high energy densities for lithium-ion batteries. However, anion redox is also associated with several unfavorable electrochemical properties, such as open-circuit voltage hysteresis. Here we reveal that in Li 1.17-x Ni 0.21 Co 0.08 Mn 0.54 O 2 , these properties arise from a strong coupling between anion redox and cation migration. We combine various X-ray spectroscopic, microscopic, and structural probes to show that partially reversible transition metal migration decreases the potential of the bulk oxygen redox couple by >more » 1 V, leading to a reordering in the anionic and cationic redox potentials during cycling. First principles calculations show that this is due to the drastic change in the local oxygen coordination environments associated with the transition metal migration. We propose that this mechanism is involved in stabilizing the oxygen redox couple, which we observe spectroscopically to persist for 500 charge/discharge cycles.« less

HEPATOCYTE GROWTH FACTOR ACTS AS A MITOGEN AND CHEMOATTRACTANT FOR POSTNATAL SUBVENTRICULAR ZONE-OLFACTORY BULB NEUROGENESIS

PubMed Central

Wang, Tsu-Wei; Zhang, Huailin; Gyetko, Margaret R.; Parent, Jack M.

2011-01-01

Neural progenitor cells persist throughout life in the forebrain subventricular zone (SVZ). They generate neuroblasts that migrate to the olfactory bulb and differentiate into interneurons, but mechanisms underlying these processes are poorly understood. Hepatocyte growth factor/scatter factor (HGF/SF) is a pleiotropic factor that influences cell motility, proliferation and morphogenesis in neural and non-neural tissues. HGF and its receptor, c-Met, are present in the rodent SVZ-olfactory bulb pathway. Using in vitro neurogenesis assays and in vivo studies of partially HGF-deficient mice, we find that HGF promotes SVZ cell proliferation and progenitor cell maintenance, while slowing differentiation and possibly altering cell fate choices. HGF also acts as a chemoattractant for SVZ neuroblasts in co-culture assays. Decreased HGF signaling induces ectopic SVZ neuroblast migration and alters the timing of migration to the olfactory bulb. These results suggest that HGF influences multiple steps in postnatal forebrain neurogenesis. HGF is a mitogen for SVZ neural progenitors, and regulates their differentiation and olfactory bulb migration. PMID:21683144

The meningeal lymphatic system: a route for HIV brain migration?

PubMed

Lamers, Susanna L; Rose, Rebecca; Ndhlovu, Lishomwa C; Nolan, David J; Salemi, Marco; Maidji, Ekaterina; Stoddart, Cheryl A; McGrath, Michael S

2016-06-01

Two innovative studies recently identified functional lymphatic structures in the meninges that may influence the development of HIV-associated neurological disorders (HAND). Until now, blood vessels were assumed to be the sole transport system by which HIV-infected monocytes entered the brain by bypassing a potentially hostile blood-brain barrier through inflammatory-mediated semi-permeability. A cascade of specific chemokine signals promote monocyte migration from blood vessels to surrounding brain tissues via a well-supported endothelium, where the cells differentiate into tissue macrophages capable of productive HIV infection. Lymphatic vessels on the other hand are more loosely organized than blood vessels. They absorb interstitial fluid from bodily tissues where HIV may persist and exchange a variety of immune cells (CD4(+) T cells, monocytes, macrophages, and dendritic cells) with surrounding tissues through discontinuous endothelial junctions. We propose that the newly discovered meningeal lymphatics are key to HIV migration among viral reservoirs and brain tissue during periods of undetectable plasma viral loads due to suppressive combinational antiretroviral therapy, thus redefining the migration process in terms of a blood-lymphatic transport system.

Coupling between oxygen redox and cation migration explains unusual electrochemistry in lithium-rich layered oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gent, William E.; Lim, Kipil; Liang, Yufeng

© 2017 The Author(s). Lithium-rich layered transition metal oxide positive electrodes offer access to anion redox at high potentials, thereby promising high energy densities for lithium-ion batteries. However, anion redox is also associated with several unfavorable electrochemical properties, such as open-circuit voltage hysteresis. Here we reveal that in Li 1.17-x Ni 0.21 Co 0.08 Mn 0.54 O 2 , these properties arise from a strong coupling between anion redox and cation migration. We combine various X-ray spectroscopic, microscopic, and structural probes to show that partially reversible transition metal migration decreases the potential of the bulk oxygen redox couple by >more » 1 V, leading to a reordering in the anionic and cationic redox potentials during cycling. First principles calculations show that this is due to the drastic change in the local oxygen coordination environments associated with the transition metal migration. We propose that this mechanism is involved in stabilizing the oxygen redox couple, which we observe spectroscopically to persist for 500 charge/discharge cycles.« less

Foiled Aspirations: The Influence of Unauthorized Status on the Educational Expectations of Latino Immigrant Youth

PubMed Central

Perreira, Krista; Spees, Lisa

2015-01-01

Latino immigrant adolescents have the highest high school dropout rates of any race-ethnic or nativity group in the United States. One potential reason for high dropout rates among Latino immigrant youth is that many are unauthorized entrants. These unauthorized Latino immigrant youth have few opportunities to attend college, and, as they become aware of barriers to their educational progress and employment, they may lower their educational expectations. Using data from the Latino Adolescent Migration, Health, and Adaptation Project (N=275), we examine the association of unauthorized entry into the U.S. with the educational expectations of Latino immigrant youth. We find that adolescents entering the U.S. without authorization have lower educational expectations than those who enter with authorization. These differences in their expectations persist after controlling for differences in their pre-migration, migration, and post-migration experiences. Policies and programs that reduce barriers to higher education and labor market opportunities can potentially help to foster higher educational expectations among unauthorized immigrant youth and may promote their high school completion. PMID:26451064

Expression of macrophage migration inhibitory factor and CD74 in the inner ear and middle ear in lipopolysaccharide-induced otitis media.

PubMed

Ishihara, Hisashi; Kariya, Shin; Okano, Mitsuhiro; Zhao, Pengfei; Maeda, Yukihide; Nishizaki, Kazunori

2016-10-01

Significant expression of macrophage migration inhibitory factor and its receptor (CD74) was observed in both the middle ear and inner ear in experimental otitis media in mice. Modulation of macrophage migration inhibitory factor and its signaling pathway might be useful in the management of inner ear inflammation due to otitis media. Inner ear dysfunction secondary to otitis media has been reported. However, the specific mechanisms involved are not clearly understood. The aim of this study is to investigate the expression of macrophage migration inhibitory factor and CD74 in the middle ear and inner ear in lipopolysaccharide-induced otitis media. BALB/c mice received a transtympanic injection of either lipopolysaccharide or phosphate-buffered saline (PBS). The mice were sacrificed 24 h after injection, and temporal bones were processed for polymerase chain reaction (PCR) analysis, histologic examination, and immunohistochemistry. PCR examination revealed that the lipopolysaccharide-injected mice showed a significant up-regulation of macrophage migration inhibitory factor in both the middle ear and inner ear as compared with the PBS-injected control mice. The immunohistochemical study showed positive reactions for macrophage migration inhibitory factor and CD74 in infiltrating inflammatory cells, middle ear mucosa, and inner ear in the lipopolysaccharide-injected mice.

Increased migration of uncemented acetabular cups in female total hip arthroplasty patients with low systemic bone mineral density. A 2-year RSA and 8-year radiographic follow-up study of 34 patients.

PubMed

Finnilä, Sami; Moritz, Niko; SvedströM, Erkki; Alm, Jessica J; Aro, Hannu T

2016-02-01

Low bone mineral density (BMD) may jeopardize the initial component stability and delay osseointegration of uncemented acetabular cups in total hip arthroplasty (THA). We measured the migration of uncemented cups in women with low or normal BMD. We used radiostereometric analysis (RSA) to measure the migration of hydroxyapatite-coated titanium alloy cups with alumina-on-alumina bearings in THA of 34 female patients with a median age of 64 (41-78) years. 10 patients had normal BMD and 24 patients had low systemic BMD (T-score ≤ -1) based on dual-energy X-ray absorptiometry (DXA). Cup migration was followed with RSA for 2 years. Radiographic follow-up was done at a median of 8 (2-10) years. Patients with normal BMD did not show a statistically significant cup migration after the settling period of 3 months, while patients with low BMD had a continuous proximal migration between 3 and 12 months (p = 0.03). These differences in cup migration persisted at 24 months. Based on the perceived risk of cup revision, 14 of the 24 cases were "at risk" (proximal translation of 0.2 to 1.0 mm) in the low-BMD group and 2 of the 10 cases were "at risk" in the normal-BMD group (odds ratio (OR) = 8.0, 95% CI: 1.3-48). The radiographic follow-up showed no radiolucent lines or osteolysis. 2 cups have been revised for fractures of the ceramic bearings, but none for loosening. Low BMD contributed to cup migration beyond the settling period of 3 months, but the migrating cups appeared to osseointegrate eventually.

Visualizing Human Migration Trhough Space and Time

NASA Astrophysics Data System (ADS)

Zambotti, G.; Guan, W.; Gest, J.

2015-07-01

Human migration has been an important activity in human societies since antiquity. Since 1890, approximately three percent of the world's population has lived outside of their country of origin. As globalization intensifies in the modern era, human migration persists even as governments seek to more stringently regulate flows. Understanding this phenomenon, its causes, processes and impacts often starts from measuring and visualizing its spatiotemporal patterns. This study builds a generic online platform for users to interactively visualize human migration through space and time. This entails quickly ingesting human migration data in plain text or tabular format; matching the records with pre-established geographic features such as administrative polygons; symbolizing the migration flow by circular arcs of varying color and weight based on the flow attributes; connecting the centroids of the origin and destination polygons; and allowing the user to select either an origin or a destination feature to display all flows in or out of that feature through time. The method was first developed using ArcGIS Server for world-wide cross-country migration, and later applied to visualizing domestic migration patterns within China between provinces, and between states in the United States, all through multiple years. The technical challenges of this study include simplifying the shapes of features to enhance user interaction, rendering performance and application scalability; enabling the temporal renderers to provide time-based rendering of features and the flow among them; and developing a responsive web design (RWD) application to provide an optimal viewing experience. The platform is available online for the public to use, and the methodology is easily adoptable to visualizing any flow, not only human migration but also the flow of goods, capital, disease, ideology, etc., between multiple origins and destinations across space and time.

Oligoanilines as a suppressor of polysulfide shuttling in lithium–sulfur batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Chi-Hao; Chung, Sheng-Heng; Han, Pauline

The migration of small polysulfide (LiPS) chains through the porous polymeric separators seriously jeopardizes the cycle life and energy density of lithium–sulfur (Li–S) batteries. Herein, we present a new concept in which an organic oligoaniline, amine-capped aniline trimer (ACAT), serves as an effective suppressor of the LiPS migration in Li–S cells. The strong interaction between LiPS and ACAT facilitates the formation of bulky ACAT–LiPS complexes (organoLiPS complexes), which are then size-selectively sieved by the porous polymeric separators employed in Li–S cells. Thus, the addition of ACAT significantly ameliorates the electrochemical performances of Li–S batteries due to suppressed LiPS migration. Thismore » new concept offers a viable strategy to achieve practically viable Li–S batteries.« less

Markov Chains for Investigating and Predicting Migration: A Case from Southwestern China

NASA Astrophysics Data System (ADS)

Qin, Bo; Wang, Yiyu; Xu, Haoming

2018-03-01

In order to accurately predict the population’s happiness, this paper conducted two demographic surveys on a new district of a city in western China, and carried out a dynamic analysis using related mathematical methods. This paper argues that the migration of migrants in the city will change the pattern of spatial distribution of human resources in the city and thus affect the social and economic development in all districts. The migration status of the population will change randomly with the passage of time, so it can be predicted and analyzed through the Markov process. The Markov process provides the local government and decision-making bureau a valid basis for the dynamic analysis of the mobility of migrants in the city as well as the ways for promoting happiness of local people’s lives.

Oligoanilines as a suppressor of polysulfide shuttling in lithium–sulfur batteries

DOE PAGES

Chang, Chi-Hao; Chung, Sheng-Heng; Han, Pauline; ...

2017-07-25

The migration of small polysulfide (LiPS) chains through the porous polymeric separators seriously jeopardizes the cycle life and energy density of lithium–sulfur (Li–S) batteries. Herein, we present a new concept in which an organic oligoaniline, amine-capped aniline trimer (ACAT), serves as an effective suppressor of the LiPS migration in Li–S cells. The strong interaction between LiPS and ACAT facilitates the formation of bulky ACAT–LiPS complexes (organoLiPS complexes), which are then size-selectively sieved by the porous polymeric separators employed in Li–S cells. Thus, the addition of ACAT significantly ameliorates the electrochemical performances of Li–S batteries due to suppressed LiPS migration. Thismore » new concept offers a viable strategy to achieve practically viable Li–S batteries.« less

Fragmentation of alpha-Radical Cations of Arginine-Containing Peptides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laskin, Julia; Yang, Zhibo; Ng, Dominic C.

2010-04-01

Fragmentation pathways of peptide radical cations, M+, with well-defined initial location of the radical site were explored using collision-induced dissociation (CID) experiments. Peptide radical cations were produced by gas-phase fragmentation of CoIII(salen)-peptide complexes [salen = N,N´-ethylenebis (salicylideneaminato)]. Subsequent hydrogen abstraction from the -carbon of the side chain followed by Ca-C bond cleavage results in the loss of a neutral side chain and formation of an a-radical cation with the radical site localized on the a-carbon of the backbone. Similar CID spectra dominated by radical-driven dissociation products were obtained for a number of a-radicals when the basic arginine side chain wasmore » present in the sequence. In contrast, proton-driven fragmentation dominates CID spectra of a-radicals produced via the loss of the arginine side chain. Our results suggest that in most cases radical migration precedes fragmentation of large peptide radical cations.« less

Hb Molfetta [beta126(H4)Val-->Leu, GTG-->CTG]: a new, silent, neutral beta chain variant found in an Italian woman.

PubMed

Qualtieri, Antonio; Le, Pera Maria; Pedace, Vera; Magariello, Angela; Brancati, Carlo

2002-02-01

We have identified a new neutral hemoglobin variant in a pregnant Italian woman, that resulted from a GTG-->CTG replacement at codon 126 of the beta chain, corresponding to a Val-->Leu amino acid change at position beta126(H4). Thermal and isopropanol stability tests were normal and there were no abnormal clinical features. Routine electrophoretic and ion exchange chromatographic methods for hemoglobin separation failed to show this variant, but reversed phase high performance liquid chromatography revealed an abnormal peak eluting near the normal beta chain. No abnormal tryptic peptide was revealed on the high performance liquid chromatographic elution pattern of the total globin digest. The mutation was determined at the DNA level by amplification of the three beta exons by polymerase chain reaction and direct sequencing of one exon that showed an abnormal migration on single strand conformational polymorphism analysis.

Is DNA a worm-like chain in Couette flow? In search of persistence length, a critical review.

PubMed

Rittman, Martyn; Gilroy, Emma; Koohya, Hashem; Rodger, Alison; Richards, Adair

2009-01-01

Persistence length is the foremost measure of DNA flexibility. Its origins lie in polymer theory which was adapted for DNA following the determination of BDNA structure in 1953. There is no single definition of persistence length used, and the links between published definitions are based on assumptions which may, or may not be, clearly stated. DNA flexibility is affected by local ionic strength, solvent environment, bound ligands and intrinsic sequence-dependent flexibility. This article is a review of persistence length providing a mathematical treatment of the relationships between four definitions of persistence length, including: correlation, Kuhn length, bending, and curvature. Persistence length has been measured using various microscopy, force extension and solution methods such as linear dichroism and transient electric birefringence. For each experimental method a model of DNA is required to interpret the data. The importance of understanding the underlying models, along with the assumptions required by each definition to determine a value of persistence length, is highlighted for linear dichroism data, where it transpires that no model is currently available for long DNA or medium to high shear rate experiments.

Persistent Drought Social-Ecological Regime Shift and Migration among Agricultural Communities in Bundelkhand Region India

NASA Astrophysics Data System (ADS)

Alam, Parvej

2017-04-01

Drought is a hydro-meteorological syndrome of 'prolonged period of water scarcity affecting natural resources, environment and, thereby, the people'. Different parts of India suffer from drought incidences of varying periodicity, with all 13 districts of Bundelkhand region repeatedly declared as drought-prone. Spread over the states of Uttar Pradesh and Madhya Pradesh, Bundelkhand falls in the rain shadow, semi-arid zone of the northern extreme of Peninsular India. In recent years, because of changing pattern of monsoons across India, rainfall in Bundelkhand in addition to being deficient has also become unpredictable. Such unpredictability has made agriculture in Bundelkhand region a risky and less attractive proposition and farmers are increasingly forgoing agriculture in villages in favour of livelihood opportunities in urban areas. Thus, there has been a constant flow of rural to urban migration in towns and cities in Bundelkhand. The present study analyses the changing land use pattern of Bundelkhand with the help of land use classification and explores the trend of rural-urban migration in Bundelkhand in the light of Galor's Model of Migration. In the current work, Climate Change is taken as a major driver behind migration decision and with the help of primary survey, a two-generational, inter regional model based on Galor's model has been developed. Keywords: Bundelkhand, Drought, Migration, Galor's Model

Discrete persistent-chain model for protein binding on DNA.

PubMed

Lam, Pui-Man; Zhen, Yi

2011-04-01

We describe and solve a discrete persistent-chain model of protein binding on DNA, involving an extra σ(i) at a site i of the DNA. This variable takes the value 1 or 0, depending on whether or not the site is occupied by a protein. In addition, if the site is occupied by a protein, there is an extra energy cost ɛ. For a small force, we obtain analytic expressions for the force-extension curve and the fraction of bound protein on the DNA. For higher forces, the model can be solved numerically to obtain force-extension curves and the average fraction of bound proteins as a function of applied force. Our model can be used to analyze experimental force-extension curves of protein binding on DNA, and hence deduce the number of bound proteins in the case of nonspecific binding. ©2011 American Physical Society

DNA Motion Capture Reveals the Mechanical Properties of DNA at the Mesoscale

PubMed Central

Price, Allen C.; Pilkiewicz, Kevin R.; Graham, Thomas G.W.; Song, Dan; Eaves, Joel D.; Loparo, Joseph J.

2015-01-01

Single-molecule studies probing the end-to-end extension of long DNAs have established that the mechanical properties of DNA are well described by a wormlike chain force law, a polymer model where persistence length is the only adjustable parameter. We present a DNA motion-capture technique in which DNA molecules are labeled with fluorescent quantum dots at specific sites along the DNA contour and their positions are imaged. Tracking these positions in time allows us to characterize how segments within a long DNA are extended by flow and how fluctuations within the molecule are correlated. Utilizing a linear response theory of small fluctuations, we extract elastic forces for the different, ∼2-μm-long segments along the DNA backbone. We find that the average force-extension behavior of the segments can be well described by a wormlike chain force law with an anomalously small persistence length. PMID:25992731

Motivations of nurses who migrate to Canada as domestic workers.

PubMed

Salami, B; Nelson, S; Hawthorne, L; Muntaner, C; McGillis Hall, L

2014-12-01

While some trained nurses migrate to destination countries to work as domestic workers, little is known about their migration motivations. This study explores the motivations of Philippine educated nurses who migrated to Canada through the Live-in Caregiver Program from 2001 to 2011 (a Canadian domestic worker programme). A single case study qualitative methodology and the transnational feminist concept of global care chains were utilized for this study. Interviews of 15 Philippine educated nurses who migrated to Canada as domestic workers were conducted in the province of Ontario, Canada, between February to October 2012. All participants had a baccalaureate degree from the Philippines. Interviews were tape recorded, transcribed verbatim and analysed using critical discourse analysis, aided by NVIVO 10 data analysis software. Findings reveal a multi-step immigration process in which nurses migrate from the Philippines to the Middle East (especially Saudi Arabia) and finally to Canada. While emigration from the Philippines is mainly economically driven, migration from the Middle East to Canada is primarily motivated by the desire for Canadian citizenship for the family. Also, perceived social status and lifestyle in Canada as compared to the Middle East motivates this group of women to migrate to Canada. The major limitation of this study is the lack of input from nursing policy makers. Gender-based familial ideologies and perspective on social status influence the migration decision of this group of nurses. Implications for nursing and health policy makers include the provision of clear pre-migration information (including on the nursing registration process) to internationally educated nurses, advocacy for stronger immigration policies to ensure the integration of internationally educated nurses and a consideration of gender in all health human resource policies. © 2014 International Council of Nurses.

The dynamics of avian influenza in western Arctic snow geese: implications for annual and migratory infection patterns

USGS Publications Warehouse

Samuel, Michael D.; Hall, Jeffrey S.; Brown, Justin D.; Goldberg, Diana R.; Ip, Hon S.; Baranyuk, Vasily V.

2015-01-01

Wild water birds are the natural reservoir for low-pathogenic avian influenza viruses (AIV). However, our ability to investigate the epizootiology of AIV in these migratory populations is challenging, and despite intensive worldwide surveillance, remains poorly understood. We conducted a cross-sectional, retrospective analysis in Pacific Flyway lesser snow geese Chen caerulescens to investigate AIV serology and infection patterns. We collected nearly 3,000 sera samples from snow geese at 2 breeding colonies in Russia and Canada during 1993-1996 and swab samples from > 4,000 birds at wintering and migration areas in the United States during 2006-2011. We found seroprevalence and annual seroconversion varied considerably among years. Seroconversion and infection rates also differed between snow goose breeding colonies and wintering areas, suggesting that AIV exposure in this gregarious waterfowl species is likely occurring during several phases (migration, wintering and potentially breeding areas) of the annual cycle. We estimated AIV antibody persistence was longer (14 months) in female geese compared to males (6 months). This relatively long period of AIV antibody persistence suggests that subtype-specific serology may be an effective tool for detection of exposure to subtypes associated with highly-pathogenic AIV. Our study provides further evidence of high seroprevalence in Arctic goose populations, and estimates of annual AIV seroconversion and antibody persistence for North American waterfowl. We suggest future AIV studies include serology to help elucidate the epizootiological dynamics of AIV in wild bird populations.

Supply chain analysis of e-tailing versus retailing operation - a case study

NASA Astrophysics Data System (ADS)

Kumar, Sameer; Tiffany, Maryellen; Vaidya, Salil

2016-07-01

The swift growth of e-commerce or e-tailing as a consumer retail channel has made it a serious competitor to traditional retail channels and is changing consumers' purchasing behaviour. The purpose of this case study, based on Target and Amazon.com, is to analyse the attributes of traditional retailing, e-tailing, and hybrid supply chain models to form conclusions about the feasibility of an idealised supply chain model for the future. An integrated and generalised modelling framework is used that incorporates Six Sigma - define, measure, analyse, improve, control methodology leveraging various tools, including process flow maps, cause and effect diagram, performance efficiency metrics, failure mode and effects analysis (FMEA), and Monte Carlo simulation. Based on this analysis and research, the conclusion is that the idealised supply chain of the future may evolve into a hybrid supply chain, which includes both e-tail and retail channels. The main recommendations from this study include assessing the risks of migrating to such a hybrid supply chain and to leverage the recommended actions provided in the hybrid FMEA. To facilitate more effective and mature processes, this study can guide researchers in exhaustive empirical evaluations of hybrid supply chains, gather experiences and lessons learned for practitioners.

Persistence of opinion in the Sznajd consensus model: computer simulation

NASA Astrophysics Data System (ADS)

Stauffer, D.; de Oliveira, P. M. C.

2002-12-01

The density of never changed opinions during the Sznajd consensus-finding process decays with time t as 1/t^θ. We find θ simeq 3/8 for a chain, compatible with the exact Ising result of Derrida et al. In higher dimensions, however, the exponent differs from the Ising θ. With simultaneous updating of sublattices instead of the usual random sequential updating, the number of persistent opinions decays roughly exponentially. Some of the simulations used multi-spin coding.

A Nation of Immigrants: Assimilation and Economic Outcomes in the Age of Mass Migration

PubMed Central

Abramitzky, Ran; Boustan, Leah Platt; Eriksson, Katherine

2015-01-01

During the Age of Mass Migration (1850–1913), the United States maintained an open border, absorbing 30 million European immigrants. Prior cross-sectional work finds that immigrants initially held lower-paid occupations than natives but converged over time. In newly assembled panel data, we show that, in fact, the average immigrant did not face a substantial occupation-based earnings penalty upon first arrival and experienced occupational advancement at the same rate as natives. Cross-sectional patterns are driven by biases from declining arrival cohort skill level and departures of negatively selected return migrants. We show that assimilation patterns vary substantially across sending countries and persist in the second generation. PMID:26609186

Simulation modeling of population viability for the leopard darter (Percidae: Percina pantherina)

USGS Publications Warehouse

Williams, L.R.; Echelle, A.A.; Toepfer, C.S.; Williams, M.G.; Fisher, W.L.

1999-01-01

We used the computer program RAMAS to perform a population viability analysis for the leopard darter, Percina pantherina. This percid fish is a threatened species confined to five isolated rivers in the Ouachita Mountains of Oklahoma and Arkansas. A base model created from life history data indicated a 6% probability that the leopard darter would go extinct in 50 years. We performed sensitivity analyses to determine the effects of initial population size, variation in age structure, variation in severity and probability of catastrophe, and migration rate. Catastrophe (modeled as the probability and severity of drought) and migration had the greatest effects on persistence. Results of these simulations have implications for management of this species.

Fumarate-Mediated Persistence of Escherichia coli against Antibiotics

PubMed Central

Kim, Jun-Seob; Cho, Da-Hyeong; Heo, Paul; Jung, Suk-Chae; Park, Myungseo; Oh, Eun-Joong; Sung, Jaeyun; Kim, Pan-Jun; Lee, Suk-Chan; Lee, Dae-Hee; Lee, Sarah; Lee, Choong Hwan; Shin, Dongwoo

2016-01-01

Bacterial persisters are a small fraction of quiescent cells that survive in the presence of lethal concentrations of antibiotics. They can regrow to give rise to a new population that has the same vulnerability to the antibiotics as did the parental population. Although formation of bacterial persisters in the presence of various antibiotics has been documented, the molecular mechanisms by which these persisters tolerate the antibiotics are still controversial. We found that amplification of the fumarate reductase operon (FRD) in Escherichia coli led to a higher frequency of persister formation. The persister frequency of E. coli was increased when the cells contained elevated levels of intracellular fumarate. Genetic perturbations of the electron transport chain (ETC), a metabolite supplementation assay, and even the toxin-antitoxin-related hipA7 mutation indicated that surplus fumarate markedly elevated the E. coli persister frequency. An E. coli strain lacking succinate dehydrogenase (SDH), thereby showing a lower intracellular fumarate concentration, was killed ∼1,000-fold more effectively than the wild-type strain in the stationary phase. It appears that SDH and FRD represent a paired system that gives rise to and maintains E. coli persisters by producing and utilizing fumarate, respectively. PMID:26810657

Elasticity of short DNA molecules: theory and experiment for contour lengths of 0.6-7 microm.

PubMed

Seol, Yeonee; Li, Jinyu; Nelson, Philip C; Perkins, Thomas T; Betterton, M D

2007-12-15

The wormlike chain (WLC) model currently provides the best description of double-stranded DNA elasticity for micron-sized molecules. This theory requires two intrinsic material parameters-the contour length L and the persistence length p. We measured and then analyzed the elasticity of double-stranded DNA as a function of L (632 nm-7.03 microm) using the classic solution to the WLC model. When the elasticity data were analyzed using this solution, the resulting fitted value for the persistence length p(wlc) depended on L; even for moderately long DNA molecules (L = 1300 nm), this apparent persistence length was 10% smaller than its limiting value for long DNA. Because p is a material parameter, and cannot depend on length, we sought a new solution to the WLC model, which we call the "finite wormlike chain (FWLC)," to account for effects not considered in the classic solution. Specifically we accounted for the finite chain length, the chain-end boundary conditions, and the bead rotational fluctuations inherent in optical trapping assays where beads are used to apply the force. After incorporating these corrections, we used our FWLC solution to generate force-extension curves, and then fit those curves with the classic WLC solution, as done in the standard experimental analysis. These results qualitatively reproduced the apparent dependence of p(wlc) on L seen in experimental data when analyzed with the classic WLC solution. Directly fitting experimental data to the FWLC solution reduces the apparent dependence of p(fwlc) on L by a factor of 3. Thus, the FWLC solution provides a significantly improved theoretical framework in which to analyze single-molecule experiments over a broad range of experimentally accessible DNA lengths, including both short (a few hundred nanometers in contour length) and very long (microns in contour length) molecules.

Shape-Persistent, Thermoresponsive Polypeptide Brushes Prepared by Vapor Deposition Surface-Initiated Ring-Opening Polymerization of α-Amino Acid N -Carboxyanhydrides

DOE PAGES

Shen, Yong; Desseaux, Solenne; Aden, Bethany; ...

2015-04-20

We report that surface-grafting thermoresponsive polymers allows the preparation of thin polymer brush coatings with surface properties that can be manipulated by variation of temperature. In most instances, thermoresponsive polymer brushes are produced using polymers that dehydrate and collapse above a certain temperature. This report presents the preparation and properties of polymer brushes that show thermoresponsive surface properties, yet are shape-persistent in that they do not undergo main chain collapse. The polymer brushes presented here are obtained via vapor deposition surface-initiated ring-opening polymerization (SI-ROP) of γ-di- or tri(ethylene glycol)-modified glutamic acid N-carboxyanhydrides. Vapor deposition SI-ROP of γ-di- or tri(ethylene glycol)-modifiedmore » L- or D-glutamic acid N-carboxyanhydrides affords helical surface-tethered polymer chains that do not show any changes in secondary structure between 10 and 70 °C. QCM-D experiments, however, revealed significant dehydration of poly(γ-(2-(2-methoxyethoxy)ethyl)-l-glutamate) (poly(L-EG 2-Glu)) brushes upon heating from 10 to 40 °C. At the same time, AFM and ellipsometry studies did not reveal significant variations in film thickness over this temperature range, which is consistent with the shape-persistent nature of these polypeptide brushes and indicates that the thermoresponsiveness of the films is primarily due to hydration and dehydration of the oligo(ethylene glycol) side chains. The results we present here illustrate the potential of surface-initiated NCA ring-opening polymerization to generate densely grafted assemblies of polymer chains that possess well-defined secondary structures and tunable surface properties. These polypeptide brushes complement their conformationally unordered counterparts that can be generated via surface-initiated polymerization of vinyl-type monomers and represent another step forward to biomimetic surfaces and interfaces.« less

End-monomer Dynamics in Semiflexible Polymers

PubMed Central

Hinczewski, Michael; Schlagberger, Xaver; Rubinstein, Michael; Krichevsky, Oleg; Netz, Roland R.

2009-01-01

Spurred by an experimental controversy in the literature, we investigate the end-monomer dynamics of semiflexible polymers through Brownian hydrodynamic simulations and dynamic mean-field theory. Precise experimental observations over the last few years of end-monomer dynamics in the diffusion of double-stranded DNA have given conflicting results: one study indicated an unexpected Rouse-like scaling of the mean squared displacement (MSD) 〈r2(t)〉 ~ t1/2 at intermediate times, corresponding to fluctuations at length scales larger than the persistence length but smaller than the coil size; another study claimed the more conventional Zimm scaling 〈r2(t)〉 ~ t2/3 in the same time range. Using hydrodynamic simulations, analytical and scaling theories, we find a novel intermediate dynamical regime where the effective local exponent of the end-monomer MSD, α(t) = d log〈r2(t)〉/d log t, drops below the Zimm value of 2/3 for sufficiently long chains. The deviation from the Zimm prediction increases with chain length, though it does not reach the Rouse limit of 1/2. The qualitative features of this intermediate regime, found in simulations and in an improved mean-field theory for semiflexible polymers, in particular the variation of α(t) with chain and persistence lengths, can be reproduced through a heuristic scaling argument. Anomalously low values of the effective exponent α are explained by hydrodynamic effects related to the slow crossover from dynamics on length scales smaller than the persistence length to dynamics on larger length scales. PMID:21359118

Stromal laminin chain distribution in normal, hyperplastic and malignant oral mucosa: relation to myofibroblast occurrence and vessel formation.

PubMed

Franz, Marcus; Wolheim, Anke; Richter, Petra; Umbreit, Claudia; Dahse, Regine; Driemel, Oliver; Hyckel, Peter; Virtanen, Ismo; Kosmehl, Hartwig; Berndt, Alexander

2010-04-01

The contribution of stromal laminin chain expression to malignant potential, tumour stroma reorganization and vessel formation in oral squamous cell carcinoma (OSCC) is not fully understood. Therefore, the expression of the laminin chains alpha2, alpha3, alpha4, alpha5 and gamma2 in the stromal compartment/vascular structures in OSCC was analysed. Frozen tissue of OSCC (9x G1, 24x G2, 8x G3) and normal (2x)/hyperplastic (11x) oral mucosa was subjected to laminin chain and alpha-smooth muscle actin (ASMA) immunohistochemistry. Results were correlated to tumour grade. The relation of laminin chain positive vessels to total vessel number was assessed by immunofluorescence double labelling with CD31. Stromal laminin alpha2 chain significantly decreases and alpha3, alpha4, alpha5 and gamma2 chains and also ASMA significantly increase with rising grade. The amount of stromal alpha3, alpha4 and gamma2 chains significantly increased with rising ASMA positivity. There is a significant decrease in alpha3 chain positive vessels with neoplastic transformation. Mediated by myofibroblasts, OSCC development is associated with a stromal up-regulation of laminin isoforms possibly contributing to a migration promoting microenvironment. A vascular basement membrane reorganization concerning alpha3 and gamma2 chain laminins during tumour angioneogenesis is suggested.

Bi-parentally inherited species-specific markers identify hybridization between rainbow trout and cutthroat trout subspecies

USGS Publications Warehouse

Ostberg, C.O.; Rodriguez, R.J.

2004-01-01

Eight polymerase chain reaction primer sets amplifying bi-parentally inherited species-specific markers were developed that differentiate between rainbow trout (Oncorhynchus mykiss) and various cutthroat trout (O. clarki) subspecies. The primers were tested within known F1 and first generation hybrid backcrosses and were shown to amplify codominantly within hybrids. Heterozygous individuals also amplified a slower migrating band that was a heteroduplex, caused by the annealing of polymerase chain reaction products from both species. These primer sets have numerous advantages for native cutthroat trout conservation including statistical genetic analyses of known crosses and simple hybrid identification.

Reducing Supply Chain GHG Emissions from LCD Panel Manufacturing Webinar

EPA Pesticide Factsheets

Fluorinated greenhouse gases (F-GHGs) are among the most potent and persistent greenhouse gases contributing to global climate change. Learn about the manufacturing processes which release F-GHGs, and how LCD suppliers are working to reduce emissions.

Persistent PlatformsThe DDG 51 Case

DTIC Science & Technology

2015-09-30

Retrieved from http://insidedefense.com Biernacki, P., & Waldorf, D. (1981). Snowball sampling : Problems and techniques of chain referral sampling ...indicators of successful shipbuilding practices (Government Accountability Office [GAO], 2009). This paper uses the “ snowball ” technique of data gathering

Markov model of the loan portfolio dynamics considering influence of management and external economic factors

NASA Astrophysics Data System (ADS)

Bozhalkina, Yana; Timofeeva, Galina

2016-12-01

Mathematical model of loan portfolio in the form of a controlled Markov chain with discrete time is considered. It is assumed that coefficients of migration matrix depend on corrective actions and external factors. Corrective actions include process of receiving applications, interaction with existing solvent and insolvent clients. External factors are macroeconomic indicators, such as inflation and unemployment rates, exchange rates, consumer price indices, etc. Changes in corrective actions adjust the intensity of transitions in the migration matrix. The mathematical model for forecasting the credit portfolio structure taking into account a cumulative impact of internal and external changes is obtained.

Irreversible Heavy Chain Transfer to Chondroitin*

PubMed Central

Lauer, Mark E.; Hascall, Vincent C.; Green, Dixy E.; DeAngelis, Paul L.; Calabro, Anthony

2014-01-01

We have recently demonstrated that the transfer of heavy chains (HCs) from inter-α-inhibitor, via the enzyme TSG-6 (tumor necrosis factor-stimulated gene 6), to hyaluronan (HA) oligosaccharides is an irreversible event in which subsequent swapping of HCs between HA molecules does not occur. We now describe our results of HC transfer experiments to chondroitin sulfate A, chemically desulfated chondroitin, chemoenzymatically synthesized chondroitin, unsulfated heparosan, heparan sulfate, and alginate. Of these potential HC acceptors, only chemically desulfated chondroitin and chemoenzymatically synthesized chondroitin were HC acceptors. The kinetics of HC transfer to chondroitin was similar to HA. At earlier time points, HCs were more widely distributed among the different sizes of chondroitin chains. As time progressed, the HCs migrated to lower molecular weight chains of chondroitin. Our interpretation is that TSG-6 swaps the HCs from the larger, reversible sites on chondroitin chains, which function as HC acceptors, onto smaller chondroitin chains, which function as irreversible HC acceptors. HCs transferred to smaller chondroitin chains were unable to be swapped off the smaller chondroitin chains and transferred to HA. HCs transferred to high molecular weight HA were unable to be swapped onto chondroitin. We also present data that although chondroitin was a HC acceptor, HA was the preferred acceptor when chondroitin and HA were in the same reaction mixture. PMID:25135638

Polymeric Selectin Ligands Mimicking Complex Carbohydrates: From Selectin Binders to Modifiers of Macrophage Migration.

PubMed

Moog, Kai E; Barz, Matthias; Bartneck, Matthias; Beceren-Braun, Figen; Mohr, Nicole; Wu, Zhuojun; Braun, Lydia; Dernedde, Jens; Liehn, Elisa A; Tacke, Frank; Lammers, Twan; Kunz, Horst; Zentel, Rudolf

2017-01-24

Novel polymeric cell adhesion inhibitors were developed in which the selectin tetrasaccharide sialyl-Lewis X (SLe X ) is multivalently presented on a biocompatible poly(2-hydroxypropyl)methacrylamide (PHPMA) backbone either alone (P1) or in combination with O-sulfated tyramine side chains (P2). For comparison, corresponding polymeric glycomimetics were prepared in which the crucial "single carbohydrate" substructures fucose, galactose, and sialic acid side chains were randomly linked to the PHPMA backbone (P3 or P4 (O-sulfated tyramine)). All polymers have an identical degree of polymerization, as they are derived from the same precursor polymer. Binding assays to selectins, to activated endothelial cells, and to macrophages show that polyHPMA with SLe X is an excellent binder to E-, L-, and P-selectins. However, mimetic P4 can also achieve close to comparable binding affinities in in vitro measurements and surprisingly, it also significantly inhibits the migration of macrophages; this provides new perspectives for the therapy of severe inflammatory diseases. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Children of Mexican Immigrants in U.S. Schools: Exploring Their Parents' and Teachers' Perception and Knowledge Gaps

ERIC Educational Resources Information Center

Janecek, Uvaldina

2012-01-01

The influx of Mexican immigrants has posed enormous challenges to the nation's public school systems where migration is rapidly increasing. The high Hispanic dropout rate points to a failure in educating Latinos and has received ample attention from researchers, educators, and policymakers; but the achievement disparities persist. Using the lens…

Schooling for Newcomers: Variation in Educational Persistence in the Northern United States in 1920

ERIC Educational Resources Information Center

Tolnay, Stewart E.; Bailey, Amy Kate

2006-01-01

Early in the 20th century, high rates of international migration from Europe and an increasing number of migrants from the South were rapidly changing the composition of cities in the northern United States. Within this dynamic environment, families faced a more complex set of decisions for the preferred economic roles of their members. For…

Loose, Falling Characters and Sentences: The Persistence of the OCR Problem in Digital Repository E-Books

ERIC Educational Resources Information Center

Kichuk, Diana

2015-01-01

The electronic conversion of scanned image files to readable text using optical character recognition (OCR) software and the subsequent migration of raw OCR text to e-book text file formats are key remediation or media conversion technologies used in digital repository e-book production. Despite real progress, the OCR problem of reliability and…

Knowing Where They Went: Six Years of Online Access Statistics via the Online Catalog for Federal Government Information

ERIC Educational Resources Information Center

Brown, Christopher C.

2011-01-01

As federal government information is increasingly migrating to online formats, libraries are providing links to this content via URLs or persistent URLs (PURLs) in their online public access catalogs (OPACs). Clickthrough statistics that accumulated as users visited links to online content in the University of Denver's library OPAC were gathered…

Connectivity, passability and heterogeneity interact to determine fish population persistence in river networks

PubMed Central

Samia, Yasmine; Lutscher, Frithjof; Hastings, Alan

2015-01-01

The movement of fish in watersheds is frequently inhibited by human-made migration barriers such as dams or culverts. The resulting lack of connectivity of spatial subpopulations is often cited as a cause for observed population decline. We formulate a matrix model for a spatially distributed fish population in a watershed, and we investigate how location and other characteristics of a single movement barrier impact the asymptotic growth rate of the population. We find that while population growth rate often decreases with the introduction of a movement obstacle, it may also increase due to a ‘retention effect’. Furthermore, obstacle mortality greatly affects population growth rate. In practice, different connectivity indices are used to predict population effects of migration barriers, but the relation of these indices to population growth rates in demographic models is often unclear. When comparing our results with the dentritic connectivity index, we see that the index captures neither the retention effect nor the influences of obstacle mortality. We argue that structural indices cannot entirely replace more detailed demographic models to understand questions of persistence and extinction. We advocate the development of novel functional indices and characteristics. PMID:26311313

Connectivity, passability and heterogeneity interact to determine fish population persistence in river networks.

PubMed

Samia, Yasmine; Lutscher, Frithjof; Hastings, Alan

2015-09-06

The movement of fish in watersheds is frequently inhibited by human-made migration barriers such as dams or culverts. The resulting lack of connectivity of spatial subpopulations is often cited as a cause for observed population decline. We formulate a matrix model for a spatially distributed fish population in a watershed, and we investigate how location and other characteristics of a single movement barrier impact the asymptotic growth rate of the population. We find that while population growth rate often decreases with the introduction of a movement obstacle, it may also increase due to a 'retention effect'. Furthermore, obstacle mortality greatly affects population growth rate. In practice, different connectivity indices are used to predict population effects of migration barriers, but the relation of these indices to population growth rates in demographic models is often unclear. When comparing our results with the dentritic connectivity index, we see that the index captures neither the retention effect nor the influences of obstacle mortality. We argue that structural indices cannot entirely replace more detailed demographic models to understand questions of persistence and extinction. We advocate the development of novel functional indices and characteristics. © 2015 The Author(s).

Aging with HIV infection: a journey to the center of inflammAIDS, immunosenescence and neuroHIV.

PubMed

Nasi, Milena; Pinti, Marcello; De Biasi, Sara; Gibellini, Lara; Ferraro, Diana; Mussini, Cristina; Cossarizza, Andrea

2014-11-01

In the last years, a significant improvement in life expectancy of HIV+ patients has been observed in Western countries. The parallel increase in the mean age of these patients causes a parallel increase in the frequency of non-AIDS related complications (i.e., neurocognitive, cardiovascular, liver and kidney diseases, metabolic syndrome, osteoporosis, non-HIV associated cancers, among others), even when antiviral treatment is successful. Immune activation and persistent inflammation characterizes both HIV infection and physiological aging, and both conditions share common detrimental pathways that lead to early immunosenescence. Furthermore, HIV-associated neurocognitive disorders represent important consequences of the infection. The persistent systemic immune activation, the continuous migration of activated monocytes to the central nervous system and progressive patients' aging contribute to develop neuronal injuries, that are in turn linked to HIV-associated neurocognitive disorders, which can persist despite successful antiretroviral treatment. Copyright © 2014 Elsevier B.V. All rights reserved.

Prevalence of persistent blood eosinophilia: relation to outcomes in patients with COPD.

PubMed

Casanova, Ciro; Celli, Bartolome R; de-Torres, Juan P; Martínez-Gonzalez, Cristina; Cosio, Borja G; Pinto-Plata, Victor; de Lucas-Ramos, Pilar; Divo, Miguel; Fuster, Antonia; Peces-Barba, Germán; Calle-Rubio, Myriam; Solanes, Ingrid; Aguero, Ramón; Feu-Collado, Nuria; Alfageme, Inmaculada; De Diego, Alfredo; Romero, Amparo; Balcells, Eva; Llunell, Antonia; Galdiz, Juan B; Marin, Margarita; Moreno, Amalia; Cabrera, Carlos; Golpe, Rafael; Lacarcel, Celia; Soriano, Joan B; López-Campos, José Luis; Soler-Cataluña, Juan J; Marin, José M

2017-11-01

The impact of blood eosinophilia in chronic obstructive pulmonary disease (COPD) remains controversial.To evaluate the prevalence and stability of a high level of blood eosinophils (≥300 cells·μL -1 ) and its relationship to outcomes, we determined blood eosinophils at baseline and over 2 years in 424 COPD patients (forced expiratory volume in 1 s (FEV 1 ) 60% predicted) and 67 smokers without COPD from the CHAIN cohort, and in 308 COPD patients (FEV 1 60% predicted) in the BODE cohort. We related eosinophil levels to exacerbations and survival using Cox hazard analysis.In COPD patients, 15.8% in the CHAIN cohort and 12.3% in the BODE cohort had persistently elevated blood eosinophils at all three visits. A significant proportion (43.8%) of patients had counts that oscillated above and below the cut-off points, while the rest had persistent eosinophil levels <300 cells·μL -1 A similar eosinophil blood pattern was observed in controls. Exacerbation rates did not differ in patients with and without eosinophilia. All-cause mortality was lower in patients with high eosinophils compared with those with values <300 cells·μL -1 (15.8% versus 33.7%; p=0.026).In patients with COPD, blood eosinophils ≥300 cells·μL -1 persisting over 2 years was not a risk factor for COPD exacerbations. High eosinophil count was associated with better survival. Copyright ©ERS 2017.

Intractable duodenal ulcer caused by transmural migration of gossypiboma into the duodenum--a case report and literature review.

PubMed

Lv, Yun-Xiao; Yu, Cheng-Chan; Tung, Chun-Fang; Wu, Cheng-Chung

2014-06-10

Gossypiboma is a term used to describe a mass that forms around a cotton sponge or abdominal compress accidentally left in a patient during surgery. Transmural migration of an intra-abdominal gossypiboma has been reported to occur in the digestive tract, bladder, vagina and diaphragm. Open surgery is the most common approach in the treatment of gossypiboma. However, gossypibomas can be extracted by endoscopy while migrating into the digestive tract. We report a case of intractable duodenal ulcer caused by transmural migration of gossypiboma successfully treated by duodenorrhaphy. A systemic literature review is provided and a scheme of the therapeutic approach is proposed. A 61-year-old Han Chinese man presented with intermittent epigastric pain for the last 10 months. He had undergone laparoscopic cholecystectomy conversion to open cholecystectomy for acute gangrenous cholecystitis 10 months ago at another hospital. Transmural migration of gossypiboma into the duodenum was found. Endoscopic intervention failed to remove the entire gauze, and duodenal ulcer caused by the gauze persisted. Surgical intervention was performed and the gauze was removed successfully. The penetrated ulcer was repaired with duodenorrhaphy. The postoperative period was uneventful.We systematically reviewed the literature on transmural migration of gossypiboma into duodenum and present an overview of published cases. Our PubMed search yielded seven reports of transmural migration of retained surgical sponge into the duodenum. Surgical interventions were necessary in two patients. Transmural migration of gossypiboma into the duodenum is a rare surgical complication. The treatment strategies include endoscopic extraction and surgical intervention. Prompt surgical intervention should be considered for emergent conditions such as active bleeding, gastrointestinal obstruction, or intra-abdominal sepsis. For non-emergent conditions, surgical intervention could be considered for intractable cases in which endoscopic extraction failed.

A 184-year record of river meander migration from tree rings, aerial imagery, and cross sections

NASA Astrophysics Data System (ADS)

Schook, Derek M.; Rathburn, Sara L.; Friedman, Jonathan M.; Wolf, J. Marshall

2017-09-01

Channel migration is the primary mechanism of floodplain turnover in meandering rivers and is essential to the persistence of riparian ecosystems. Channel migration is driven by river flows, but short-term records cannot disentangle the effects of land use, flow diversion, past floods, and climate change. We used three data sets to quantify nearly two centuries of channel migration on the Powder River in Montana. The most precise data set came from channel cross sections measured an average of 21 times from 1975 to 2014. We then extended spatial and temporal scales of analysis using aerial photographs (1939-2013) and by aging plains cottonwoods along transects (1830-2014). Migration rates calculated from overlapping periods across data sets mostly revealed cross-method consistency. Data set integration revealed that migration rates have declined since peaking at 5 m/year in the two decades after the extreme 1923 flood (3000 m3/s). Averaged over the duration of each data set, cross section channel migration occurred at 0.81 m/year, compared to 1.52 m/year for the medium-length air photo record and 1.62 m/year for the lengthy cottonwood record. Powder River peak annual flows decreased by 48% (201 vs. 104 m3/s) after the largest flood of the post-1930 gaged record (930 m3/s in 1978). Declining peak discharges led to a 53% reduction in channel width and a 29% increase in sinuosity over the 1939-2013 air photo record. Changes in planform geometry and reductions in channel migration make calculations of floodplain turnover rates dependent on the period of analysis. We found that the intensively studied last four decades do not represent the past two centuries.

A 184-year record of river meander migration from tree rings, aerial imagery, and cross sections

USGS Publications Warehouse

Schook, Derek M.; Rathburn, Sara L.; Friedman, Jonathan M.; Wolf, J. Marshall

2017-01-01

Channel migration is the primary mechanism of floodplain turnover in meandering rivers and is essential to the persistence of riparian ecosystems. Channel migration is driven by river flows, but short-term records cannot disentangle the effects of land use, flow diversion, past floods, and climate change. We used three data sets to quantify nearly two centuries of channel migration on the Powder River in Montana. The most precise data set came from channel cross sections measured an average of 21 times from 1975 to 2014. We then extended spatial and temporal scales of analysis using aerial photographs (1939–2013) and by aging plains cottonwoods along transects (1830–2014). Migration rates calculated from overlapping periods across data sets mostly revealed cross-method consistency. Data set integration revealed that migration rates have declined since peaking at 5 m/year in the two decades after the extreme 1923 flood (3000 m3/s). Averaged over the duration of each data set, cross section channel migration occurred at 0.81 m/year, compared to 1.52 m/year for the medium-length air photo record and 1.62 m/year for the lengthy cottonwood record. Powder River peak annual flows decreased by 48% (201 vs. 104 m3/s) after the largest flood of the post-1930 gaged record (930 m3/s in 1978). Declining peak discharges led to a 53% reduction in channel width and a 29% increase in sinuosity over the 1939–2013 air photo record. Changes in planform geometry and reductions in channel migration make calculations of floodplain turnover rates dependent on the period of analysis. We found that the intensively studied last four decades do not represent the past two centuries

S-Fms signalobody enhances myeloid cell growth and migration.

PubMed

Kawahara, Masahiro; Hitomi, Azusa; Nagamune, Teruyuki

2014-07-01

Since receptor tyrosine kinases (RTKs) control various cell fates in many types of cells, mimicry of RTK functions is promising for artificial control of cell fates. We have previously developed single-chain Fv (scFv)/receptor chimeras named signalobodies that can mimic receptor signaling in response to a specific antigen. While the RTK-based signalobodies enabled us to control cell growth and migration, further extension of applicability in another cell type would underlie the impact of the RTK-based signalobodies. In this study, we applied the scFv-c-Fms (S-Fms) signalobody in a murine myeloid progenitor cell line, FDC-P1. S-Fms transduced a fluorescein-conjugated BSA (BSA-FL)-dependent growth signal and activated downstream signaling molecules including MEK, ERK, Akt, and STAT3, which are major constituents of Ras/MAPK, PI3K/Akt, and JAK/STAT signaling pathways. In addition, S-Fms transduced a migration signal as demonstrated by the transwell-based migration assay. Direct real-time observation of the cells further confirmed that FDC/S-Fms cells underwent directional cell migration toward a positive gradient of BSA-FL. These results demonstrated the utility of the S-Fms signalobody for controlling growth and migration of myeloid cells. Further extension of our approach includes economical large-scale production of practically relevant blood cells as well as artificial control of cell migration for tissue regeneration and immune response. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nectin-like molecule 1 inhibits the migration and invasion of U251 glioma cells by regulating the expression of an extracellular matrix protein osteopontin.

PubMed

Yin, Bin; Li, Ke-han; An, Tai; Chen, Tao; Peng, Xiao-zhong

2010-06-01

To investigate the molecular mechanism of nectin-like molecule 1 (NECL1) inhibiting the migration and invasion of U251 glioma cells. We infected U251 glioma cells with adeno-nectin-like molecule 1 (Ad-NECL1) or empty adenovirus (Ad). Transwell and wound healing assays were performed to observe the migration of U251 cells incubated with the cell supernatant from Ad-NECL1 or Ad infected U251 cells. DNA microarray was applied to screen the gene expression profile after the restoration of NECL1 in U251 glioma cell lines. The differential expression of osteopontin (OPN), a gene related to migration and invasion, was further analyzed with semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR), Western blot, and immunohistochemistry. The restoration of NECL1 inhibited migration of U251 cells significantly (P<0.05). Altogether 195 genes were found differentially expressed by microarray, in which 175 were up-regulated and 20 down-regulated, including 9 extracellular matrix proteins involved in the migration of cells. Both mRNA and protein expressions of OPN, the most markedly reduced extracellular matrix protein, were found decreased in U251 cells after restoration of NECL1. Immunohistochemical assay also detected an increase of OPN in glioma tissues, related with the progressing of malignant grade. A link might exist between NECL1 and the extracellular matrix protein OPN in inhibiting the migration and invasion of U251 glioma cells.

Tuning the probe location on zwitterionic micellar system with variation of pH and addition of surfactants with different alkyl chains: solvent and rotational relaxation studies.

PubMed

Banerjee, Chiranjib; Mandal, Sarthak; Ghosh, Surajit; Rao, Vishal Govind; Sarkar, Nilmoni

2012-09-13

In this manuscript, we have modulated the location of an anionic probe, Coumarin-343 (C-343) in a zwitterionic (N-hexadecyl-N,N-dimethylammonio-1-propanesulfonate (SB-16)) micellar system by three different approaches. The effect of addition of the surfactant sodium dodecyl sulfate (SDS) and the room temperature ionic liquid (RTIL), 1-ethyl-3-methylimidazolium octylsulfate (EmimOs) and N,N-dimethylethanol hexanoate (DAH), to the micellar solution has been studied. The effect of pH variation has been studied as well using solvent and rotational measurements. Migration of the anionic probe, C-343, from the palisade layer of SB-16 micelle to the bulk water has been observed to varying extents with the addition of SDS and EmimOs. The effect is much more pronounced in the presence of SDS and can be ascribed to the presence of the long alkyl (dodecyl) chain on SDS which can easily orient itself and fuse inside the SB-16 micelle and facilitate the observed migration of the probe molecule. This phenomenon is confirmed by faster solvation and rotational relaxation of the investigated probe molecule. The analogous fusion process is difficult in case of EmimOs and DAH because of their comparatively smaller alkyl (octyl and hexanoate) chain. However, the direction of C-343 migration is reversed with the decrease of pH of the SB-16 micellar medium. An increase in the average solvation and rotational relaxation time of the probe in acidic medium has been observed. Since experimental conditions are maintained such that the probe molecules and the zwitterionic SB-16 micelles remain oppositely charged, the observed results can be attributed to the increased electrostatic interaction (attractive) between them. Temperature dependent study also supports this finding.

Focal adhesion kinase is involved in mechanosensing during fibroblast migration

NASA Technical Reports Server (NTRS)

Wang, H. B.; Dembo, M.; Hanks, S. K.; Wang, Y.

2001-01-01

Focal adhesion kinase (FAK) is a non-receptor protein tyrosine kinase localized at focal adhesions and is believed to mediate adhesion-stimulated effects. Although ablation of FAK impairs cell movement, it is not clear whether FAK might be involved in the guidance of cell migration, a role consistent with its putative regulatory function. We have transfected FAK-null fibroblasts with FAK gene under the control of the tetracycline repression system. Cells were cultured on flexible polyacrylamide substrates for the detection of traction forces and the application of mechanical stimulation. Compared with control cells expressing wild-type FAK, FAK-null cells showed a decrease in migration speed and directional persistence. In addition, whereas FAK-expressing cells responded to exerted forces by reorienting their movements and forming prominent focal adhesions, FAK-null cells failed to show such responses. Furthermore, FAK-null cells showed impaired responses to decreases in substrate flexibility, which causes control cells to generate weaker traction forces and migrate away from soft substrates. Cells expressing Y397F FAK, which cannot be phosphorylated at a key tyrosine site, showed similar defects in migration pattern and force-induced reorientation as did FAK-null cells. However, other aspects of F397-FAK cells, including the responses to substrate flexibility and the amplification of focal adhesions upon mechanical stimulation, were similar to that of control cells. Our results suggest that FAK plays an important role in the response of migrating cells to mechanical input. In addition, phosphorylation at Tyr-397 is required for some, but not all, of the functions of FAK in cell migration.

Influence of chain rigidity on the conformation of model lipid membranes in the presence of cylindrical nanoparticle inclusions

NASA Astrophysics Data System (ADS)

Diloreto, Chris; Wickham, Robert

2012-02-01

We employ real-space self-consistent field theory to study the conformation of model lipid membranes in the presence of solvent and cylindrical nanoparticle inclusions (''peptides''). Whereas it is common to employ a polymeric Gaussian chain model for the lipids, here we model the lipids as persistent, worm-like chains. Our motivation is to develop a more realistic field theory to describe the action of pore-forming anti-microbial peptides that disrupt the bacterial cell membrane. We employ operator-splitting and a pseudo-spectral algorithm, using SpharmonicKit for the chain tangent degrees of freedom, to solve for the worm-like chain propagator. The peptides, modelled using a mask function, have a surface patterned with hydrophobic and hydrophillic patches, but no charge. We examine the role chain rigidity plays in the hydrophobic mismatch, the membrane-mediated interaction between two peptides, the size and structure of pores formed by peptide aggregates, and the free-energy barrier for peptide insertion into the membrane. Our results suggest that chain rigidity influences both the pore structure and the mechanism of pore formation.

The Longevity of Water Ice on Ganymedes and Europas around Migrated Giant Planets

NASA Astrophysics Data System (ADS)

Lehmer, Owen R.; Catling, David C.; Zahnle, Kevin J.

2017-04-01

The gas giant planets in the Solar System have a retinue of icy moons, and we expect giant exoplanets to have similar satellite systems. If a Jupiter-like planet were to migrate toward its parent star the icy moons orbiting it would evaporate, creating atmospheres and possible habitable surface oceans. Here, we examine how long the surface ice and possible oceans would last before being hydrodynamically lost to space. The hydrodynamic loss rate from the moons is determined, in large part, by the stellar flux available for absorption, which increases as the giant planet and icy moons migrate closer to the star. At some planet-star distance the stellar flux incident on the icy moons becomes so great that they enter a runaway greenhouse state. This runaway greenhouse state rapidly transfers all available surface water to the atmosphere as vapor, where it is easily lost from the small moons. However, for icy moons of Ganymede’s size around a Sun-like star we found that surface water (either ice or liquid) can persist indefinitely outside the runaway greenhouse orbital distance. In contrast, the surface water on smaller moons of Europa’s size will only persist on timescales greater than 1 Gyr at distances ranging 1.49-0.74 au around a Sun-like star for Bond albedos of 0.2 and 0.8, where the lower albedo becomes relevant if ice melts. Consequently, small moons can lose their icy shells, which would create a torus of H atoms around their host planet that might be detectable in future observations.

The Longevity of Water Ice on Ganymedes and Europas around Migrated Giant Planets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lehmer, Owen R.; Catling, David C.; Zahnle, Kevin J., E-mail: olehmer@gmail.com

The gas giant planets in the Solar System have a retinue of icy moons, and we expect giant exoplanets to have similar satellite systems. If a Jupiter-like planet were to migrate toward its parent star the icy moons orbiting it would evaporate, creating atmospheres and possible habitable surface oceans. Here, we examine how long the surface ice and possible oceans would last before being hydrodynamically lost to space. The hydrodynamic loss rate from the moons is determined, in large part, by the stellar flux available for absorption, which increases as the giant planet and icy moons migrate closer to themore » star. At some planet–star distance the stellar flux incident on the icy moons becomes so great that they enter a runaway greenhouse state. This runaway greenhouse state rapidly transfers all available surface water to the atmosphere as vapor, where it is easily lost from the small moons. However, for icy moons of Ganymede’s size around a Sun-like star we found that surface water (either ice or liquid) can persist indefinitely outside the runaway greenhouse orbital distance. In contrast, the surface water on smaller moons of Europa’s size will only persist on timescales greater than 1 Gyr at distances ranging 1.49–0.74 au around a Sun-like star for Bond albedos of 0.2 and 0.8, where the lower albedo becomes relevant if ice melts. Consequently, small moons can lose their icy shells, which would create a torus of H atoms around their host planet that might be detectable in future observations.« less

Labor migration, externalities and ethics: theorizing the meso-level determinants of HIV vulnerability.

PubMed

Hirsch, Jennifer S

2014-01-01

This paper discusses labor migration as an example of how focusing on the meso-level highlights the social processes through which structural factors produce HIV risk. Situating that argument in relation to existing work on economic organization and HIV risk as well as research on labor migration and HIV vulnerabilities, the paper demonstrates how analyzing the processes through which labor migration creates vulnerability can shift attention away from the proximate behavioral determinants of HIV risk and toward the community and policy levels. Further, it presents the concepts of externalities and the ethics of consumption, which underline how both producers and consumers benefit from low-waged migrant labor, and thus are responsible for the externalization of HIV risk characteristic of supply chains that rely on migrant labor. These concepts point to strategies through which researchers and advocates could press the public and private sectors to improve the conditions in which migrants live and work, with implications for HIV as well as other health outcomes. Copyright © 2013 Elsevier Ltd. All rights reserved.

International Nurse Recruitment in India

PubMed Central

Khadria, Binod

2007-01-01

Objective This paper describes the practice of international recruitment of Indian nurses in the model of a “business process outsourcing” of comprehensive training-cum-recruitment-cum-placement for popular destinations like the United Kingdom and United States through an agency system that has acquired growing intensity in India. Findings Despite the extremely low nurse to population ratio in India, hospital managers in India are not concerned about the growing exodus of nurses to other countries. In fact, they are actively joining forces with profitable commercial ventures that operate as both training and recruiting agencies. Most of this activity is concentrated in Delhi, Bangalore, and Kochi. Conclusions Gaps in data on nursing education, employment, and migration, as well as nonstandardization of definitions of “registered nurse,” impair the analysis of international migration of nurses from India, making it difficult to assess the impact of migration on vacancy rates. One thing is clear, however, the chain of commercial interests that facilitate nurse migration is increasingly well organized and profitable, making the future growth of this business a certainty. PMID:17489924

DOT1L histone methyltransferase regulates the expression of BCAT1 and is involved in sphere formation and cell migration of breast cancer cell lines.

PubMed

Oktyabri, Dulamsuren; Ishimura, Akihiko; Tange, Shoichiro; Terashima, Minoru; Suzuki, Takeshi

2016-04-01

DOT1L is a histone H3 lysine 79 (H3K79) methyltransferase mainly implicated in leukemia. Here we analyzed the function of DOT1L in breast cancer cells. The expression of DOT1L was up-regulated in malignant breast cancer tissues. Over-expression of DOT1L significantly increased the sphere formation and the cell migration activities of MCF7 breast cancer cell line. In contrast, knockdown of DOT1L reduced the cell migration activity of MDA-MB-231 breast cancer cell line. BCAT1, which encodes a branched-chain amino acid transaminase, was identified as one of the target genes controlled by DOT1L through the regulation of H3K79 methylation. Mechanistic investigation revealed that BCAT1 might be an important regulator responsible for DOT1L-mediated sphere formation and cell migration in breast cancer cells. Copyright © 2016 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

Interactions between Therapeutic Proteins and Acrylic Acid Leachable.

PubMed

Liu, Dengfeng; Nashed-Samuel, Yasser; Bondarenko, Pavel V; Brems, David N; Ren, Da

2012-01-01

Leachables are chemical compounds that migrate from manufacturing equipment, primary containers and closure systems, and packaging components into biopharmaceutical and pharmaceutical products. Acrylic acid (at concentration around 5 μg/mL) was detected as leachable in syringes from one of the potential vendors (X syringes). In order to evaluate the potential impact of acrylic acid on therapeutic proteins, an IgG 2 molecule was filled into a sterilized X syringe and then incubated at 45 °C for 45 days in a pH 5 acetate buffer. We discovered that acrylic acid can interact with proteins at three different sites: (1) the lysine side chain, (2) the N-terminus, and (3) the histidine side chain, by the Michael reaction. In this report, the direct interactions between acrylic acid leachable and a biopharmaceutical product were demonstrated and the reaction mechanism was proposed. Even thought a small amount (from 0.02% to 0.3%) of protein was found to be modified by acrylic acid, the modified protein can potentially be harmful due to the toxicity of acrylic acid. After being modified by acrylic acid, the properties of the therapeutic protein may change due to charge and hydrophobicity variations. Acrylic acid was detected to migrate from syringes (Vendor X) into a therapeutic protein solution (at a concentration around 5 μg/mL). In this study, we discovered that acrylic acid can modify proteins at three different sites: (1) the lysine side chain, 2) the N-terminus, and 3) the histidine side chain, by the Michael reaction. In this report, the direct interactions between acrylic acid leachable and a biopharmaceutical product were demonstrated and the reaction mechanism was proposed.

Photophysics of conjugated polymers: interplay between Förster energy migration and defect concentration in shaping a photochemical funnel in PPV.

PubMed

Saini, Sangeeta; Bagchi, Biman

2010-07-21

Recent single molecule experiments have suggested the existence of a photochemical funnel in the photophysics of conjugated polymers, like poly[2-methoxy-5-(2'-ethylhexyl)oxy-1,4-phenylenevinylene] (MEH-PPV). The funnel is believed to be a consequence of the presence of conformational or chemical defects along the polymer chain and efficient non-radiative energy transfer among different chromophore segments. Here we address the effect of the excitation energy dynamics on the photophysics of PPV. The PPV chain is modeled as a polymer with the length distribution of chromophores given either by a Gaussian or by a Poisson distribution. We observe that the Poisson distribution of the segment lengths explains the photophysics of PPV better than the Gaussian distribution. A recently proposed version of an extended 'particle-in-a-box' model is used to calculate the exciton energies and the transition dipole moments of the chromophores, and a master equation to describe the excitation energy transfer among different chromophores. The rate of energy transfer is assumed to be given here, as a first approximation, by the well-known Förster expression. The observed excitation population dynamics confirms the photochemical funneling of excitation energy from shorter to longer chromophores of the polymer chain. The time scale of spectral shift and energy transfer for our model polymer, with realistic values of optical parameters, is in the range of 200-300 ps. We find that the excitation energy may not always migrate towards the longest chromophore segments in the polymer chain as the efficiency of energy transfer between chromophores depends on the separation distance between the two and their relative orientation.

[Study of migration and distribution of bone marrow cells transplanted animals with B16 melanoma ].

PubMed

Poveshchenko, A F; Solovieva, A O; Zubareva, K E; Strunkin, D N; Gricyk, O B; Poveshchenko, O V; Shurlygina, A V; Konenkov, V I

2017-01-01

Purpose. Reveal features migration and distribution of syngeneic bone marrow cells (BMC) and subpopulations (MSC) after transplantation into the recipient carrier B16 melanoma bodies. Methods. We used mouse male and female C57BL/6 mice. Induction of Tumor Growth: B16 melanoma cells implanted subcutaneously into right hind paw of female C57BL/6 mice at a dose of 2.5 x 105 cells / mouse. migration study in vivo distribution and BMC and MSC was performed using genetic markers - Y-chromosome specific sequence line male C57Bl/6 syngeneic intravenous transplantation in females using the polymerase chain reaction (PCR) in real time on Authorized Termal Cycler - Light Cycler 480 II / 96 (Roche). Introduction suspension of unseparated bone marrow cells, mesenchymal stem cells from donor to recipient male mice (syngeneic recipient female C57BL/6), followed by isolation of recipients of organs was performed at regular intervals, then of organ recipients isolated DNA. Results. It was shown that bone marrow cells positive for Y-chromosome in migrate lymphoid (lymph nodes, spleen, bone marrow) or in non-lymphoid organs (liver, heart, brain, skin) syngeneic recipients. In addition to the migration of cells from the bone marrow to other organs, there is a way back migration of cells from the circulation to the bone marrow. B16 melanoma stimulates the migration of transplanted MSCs and BMC in bone marrow. It is found that tumor growth enhanced migration of transplanted bone marrow cells, including populations of MSCs in the bone marrow. In the early stages of tumor formation MSC migration activity higher than the BMC. In the later stages of tumor formation undivided population of bone marrow cells migrate to the intense swelling compared with a population of MSCs. Conclusion. The possibility of using bone marrow MSCs for targeted therapy of tumor diseases, because migration of MSCs in tumor tissue can be used to effectively deliver anticancer drugs.

Migration of Lebanese nurses: a questionnaire survey and secondary data analysis.

PubMed

El-Jardali, Fadi; Dumit, Nuhad; Jamal, Diana; Mouro, Gladys

2008-10-01

Nursing is becoming a mobile profession. Nurse migration is multifactorial and not limited to financial incentives. Non-economic factors that might lead to migration include poor recruitment and retention strategies, poor job satisfaction and working conditions, socio-political and economic stability, and the poor social image of the nursing profession. Lebanon is facing a problem of excessive nurse migration to countries of the Gulf, North America and Europe. No study has been conducted to understand the determinants and magnitude of the problem. The objective of this study is to provide an evidence base for understanding the incidence of nurse migration out of Lebanon, its magnitude and reasons. A cross-sectional research design comprising both quantitative and qualitative methods was employed to achieve the stated objectives. This includes a survey of nursing schools in Lebanon, survey of nurse recruitment agencies, secondary data analysis and survey of migrant nurses. An estimated one in five nurses that receive a bachelors of science in nursing migrates out of Lebanon within 1 or 2 years of graduation. The majority of nurses migrate to countries of the Gulf. The main reasons for migration included: shift work, high patient/nurse ratios, lack of autonomy in decision-making, lack of a supportive environment, and poor commitment to excellent nursing care. Further, nurses reported that combinations of financial and non-financial incentives can encourage them to return to practice in Lebanon. The most recurring incentives (pull factors) to encourage nurses to return to practice in Lebanon included educational support, managerial support, better working conditions, utilization of best nursing practices and autonomy. Nurse migration and retention have become major health workforce issues confronting many health systems in the East Mediterranean Region. Our study demonstrated that nurse migration is a product of poor management and lack of effective retention strategies and sufficient knowledge about the context, needs and challenges facing nurses. Nurse migration in Lebanon underscores the importance of developing a monitoring system that would identify implications and help implement innovative retention strategies. Nurse migration out of Lebanon is likely to persist and even increase if underlying factors are not properly resolved.

The persistence of bifidobacteria populations in a river measured by molecular and culture techniques.

PubMed

Bonjoch, X; Lucena, F; Blanch, A R

2009-10-01

To determine relative to faecal coliforms (FC) and sulfite-reducing clostridia (SRC), the environmental persistence of natural populations of Bifidobacterium spp. enumerated by culturing and quantitative polymerase chain reaction (q-PCR). Dialysis tubing containing river supplemented with overnight cultures of Bifidobacterium adolescentis (BA) and Bifidobacterium dentium (BD) or urban wastewater were suspended in a river for up to 10 days. At intervals, the contents of each dialysis tube were assayed using q-PCR assays for BA and BD, and selective culture media for FC, SRC, total bifidobacteria (TB), sorbitol-fermenting bifidobacteria (SFB) and cultivable BA. Mean summer T(90) values were 251 h for SRC, 92 h for FC, 48 h for BA and BD by q-PCR, and 9 h for TB. Bifidobacterium spp. was the population with the lowest persistence, showing seasonal differences in T(90) when measured by culture techniques or by q-PCR. This difference in relative persistence is because of a longer persistence of molecular targets than cultivable cells. The persistence of a viable bifidobacteria cells is shorter, but the longest persistence of molecular targets. This factor could be used for origin the faecal pollution in water for the development of microbial source tracking (MST).

Endothelial cell-derived GABA signaling modulates neuronal migration and postnatal behavior

PubMed Central

Li, Suyan; Kumar T, Peeyush; Joshee, Sampada; Kirschstein, Timo; Subburaju, Sivan; Khalili, Jahan S; Kloepper, Jonas; Du, Chuang; Elkhal, Abdallah; Szabó, Gábor; Jain, Rakesh K; Köhling, Rüdiger; Vasudevan, Anju

2018-01-01

The cerebral cortex is essential for integration and processing of information that is required for most behaviors. The exquisitely precise laminar organization of the cerebral cortex arises during embryonic development when neurons migrate successively from ventricular zones to coalesce into specific cortical layers. While radial glia act as guide rails for projection neuron migration, pre-formed vascular networks provide support and guidance cues for GABAergic interneuron migration. This study provides novel conceptual and mechanistic insights into this paradigm of vascular-neuronal interactions, revealing new mechanisms of GABA and its receptor-mediated signaling via embryonic forebrain endothelial cells. With the use of two new endothelial cell specific conditional mouse models of the GABA pathway (Gabrb3ΔTie2-Cre and VgatΔTie2-Cre), we show that partial or complete loss of GABA release from endothelial cells during embryogenesis results in vascular defects and impairs long-distance migration and positioning of cortical interneurons. The downstream effects of perturbed endothelial cell-derived GABA signaling are critical, leading to lasting changes to cortical circuits and persistent behavioral deficits. Furthermore, we illustrate new mechanisms of activation of GABA signaling in forebrain endothelial cells that promotes their migration, angiogenesis and acquisition of blood-brain barrier properties. Our findings uncover and elucidate a novel endothelial GABA signaling pathway in the CNS that is distinct from the classical neuronal GABA signaling pathway and shed new light on the etiology and pathophysiology of neuropsychiatric diseases, such as autism spectrum disorders, epilepsy, anxiety, depression and schizophrenia. PMID:29086765

Katrina in Historical Context: Environment and Migration in the U.S.

PubMed

Gutmann, Myron P; Field, Vincenzo

2010-01-01

The massive publicity surrounding the exodus of residents from New Orleans spurred by Hurricane Katrina has encouraged interest in the ways that past migration in the U.S. has been shaped by environmental factors. So has Timothy Egan's exciting book, The Worst Hard Time: The Untold Story of those who survived the Great American Dust Bowl. This paper places those dramatic stories into a much less exciting context, demonstrating that the kinds of environmental factors exemplified by Katrina and the Dust Bowl are dwarfed in importance and frequency by the other ways that environment has both impeded and assisted the forces of migration. We accomplish this goal by enumerating four types of environmental influence on migration in the U.S.: 1) environmental calamities, including floods, hurricanes, earthquakes, and tornadoes, 2) environmental hardships and their obverse, short-term environmental benefits, including both drought and short periods of favorable weather, 3) environmental amenities, including warmth, sun, and proximity to water or mountains, and 4) environmental barriers and their management, including heat, air conditioning, flood control, drainage, and irrigation. In U.S. history, all four of these have driven migration flows in one direction or another. Placing Katrina into this historical context is an important task, both because the environmental calamities of which Katrina is an example are relatively rare and have not had a wide impact, and because focusing on them defers interest from the other kinds of environmental impacts, whose effect on migration may have been stronger and more persistent, though less dramatic.

Biomagnification of persistent organic pollutants along a high-altitude aquatic food chain in the Tibetan Plateau: Processes and mechanisms.

PubMed

Ren, Jiao; Wang, Xiaoping; Wang, Chuanfei; Gong, Ping; Wang, Xiruo; Yao, Tandong

2017-01-01

Biomagnification of some persistent organic pollutants (POPs) has been found in marine and freshwater food chains; however, due to the relatively short food chains in high-altitude alpine lakes, whether trophic transfer would result in the biomagnification of POPs is not clear. The transfer of various POPs, including organochlorine pesticides and polychlorinated biphenyls (PCBs), along the aquatic food chain in Nam Co Lake (4700 m), in the central Tibetan Plateau, was studied. The POPs levels in the water, sediment and biota [plankton, invertebrates and fish (Gymnocypris namensis)] of Nam Co were generally low, with concentrations comparable to those reported for the remote Arctic. The composition profiles of POPs in the fish were different from that in the water, but similar to their food. DDEs, DDDs, PCB 138, 153 and 180 displayed significant positive correlations with trophic levels, with trophic magnification factors (TMFs) ranged between 1.5 and 4.2, implying these chemicals can undergo final biomagnification along food chain. A fugacity-based dynamic bioaccumulation model was applied to the fish with localized parameters, by which the simulated concentrations were comparable to the measured data. Modeling results showed that most compounds underwent net gill loss and net gut uptake; only when the net result of the combined gut and gill fluxes would be positive, bioaccumulation could eventually occur. The net accumulation flux increased with fish age, which was caused by the continuous increase of gut uptake by aged fish. Due to the oligotrophic condition, efficient food absorption is likely the key factor that influences the gut POPs uptake. Long residence times with half-lives up to two decades were found for the higher chlorinated PCBs in Gymnocypris namensis. Copyright © 2016 Elsevier Ltd. All rights reserved.

QUANTIFICATION OF FLUOROTELOMER-BASED CHEMICALS IN MAMMALIAN MATRICES BY MONITORING PERFLUOROALKYL CHAIN FRAGMENTS WITH GC/MS

EPA Science Inventory

Perfluorocarboxylic acids (PFCAs), namely perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA), have been identified as persistent, bioaccurnulative and potentially toxic compounds. The structural analog, 8-2 fluorotelomer alcohol (8-2 FTOH) is considered the probable ...

Optimization and Persistence

DTIC Science & Technology

1997-09-01

and Ronen 1987], capital budget- ing [Brown, Clemence, Teufert, and Wood 1991], and global supply chain manage- ment [ Arntzen , Brown, Harrison, and...crew-pairing opti- mization at American Airlines," Interfaces, Vol. 21, No. 1 Oanuary- February), pp. 62-74. Arntzen , B. C.; Brown, G. G.; Harrison, T

Partial migration: growth varies between resident and migratory fish.

PubMed

Gillanders, Bronwyn M; Izzo, Christopher; Doubleday, Zoë A; Ye, Qifeng

2015-03-01

Partial migration occurs in many taxa and ecosystems and may confer survival benefits. Here, we use otolith chemistry data to determine whether fish from a large estuarine system were resident or migratory, and then examine whether contingents display differences in modelled growth based on changes in width of otolith growth increments. Sixty-three per cent of fish were resident based on Ba : Ca of otoliths, with the remainder categorized as migratory, with both contingents distributed across most age/size classes and both sexes, suggesting population-level bet hedging. Migrant fish were in slightly better condition than resident fish based on Fulton's K condition index. Migration type (resident versus migratory) was 56 times more likely to explain variation in growth than a model just incorporating year- and age-related growth trends. While average growth only varied slightly between resident and migratory fish, year-to-year variation was significant. Such dynamism in growth rates likely drives persistence of both life-history types. The complex relationships in growth between contingents suggest that management of species exhibiting partial migration is challenging, especially in a world subject to a changing climate. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Endogenous electric fields as guiding cue for cell migration

PubMed Central

Funk, Richard H. W.

2015-01-01

This review covers two topics: (1) “membrane potential of low magnitude and related electric fields (bioelectricity)” and (2) “cell migration under the guiding cue of electric fields (EF).”Membrane potentials for this “bioelectricity” arise from the segregation of charges by special molecular machines (pumps, transporters, ion channels) situated within the plasma membrane of each cell type (including eukaryotic non-neural animal cells). The arising patterns of ion gradients direct many cell- and molecular biological processes such as embryogenesis, wound healing, regeneration. Furthermore, EF are important as guiding cues for cell migration and are often overriding chemical or topographic cues. In osteoblasts, for instance, the directional information of EF is captured by charged transporters on the cell membrane and transferred into signaling mechanisms that modulate the cytoskeleton and motor proteins. This results in a persistent directional migration along an EF guiding cue. As an outlook, we discuss questions concerning the fluctuation of EF and the frequencies and mapping of the “electric” interior of the cell. Another exciting topic for further research is the modeling of field concepts for such distant, non-chemical cellular interactions. PMID:26029113

Seasonal migration to high latitudes results in major reproductive benefits in an insect

PubMed Central

Chapman, Jason W.; Bell, James R.; Burgin, Laura E.; Reynolds, Donald R.; Pettersson, Lars B.; Hill, Jane K.; Bonsall, Michael B.; Thomas, Jeremy A.

2012-01-01

Little is known of the population dynamics of long-range insect migrants, and it has been suggested that the annual journeys of billions of nonhardy insects to exploit temperate zones during summer represent a sink from which future generations seldom return (the “Pied Piper” effect). We combine data from entomological radars and ground-based light traps to show that annual migrations are highly adaptive in the noctuid moth Autographa gamma (silver Y), a major agricultural pest. We estimate that 10–240 million immigrants reach the United Kingdom each spring, but that summer breeding results in a fourfold increase in the abundance of the subsequent generation of adults, all of which emigrate southward in the fall. Trajectory simulations show that 80% of emigrants will reach regions suitable for winter breeding in the Mediterranean Basin, for which our population dynamics model predicts a winter carrying capacity only 20% of that of northern Europe during the summer. We conclude not only that poleward insect migrations in spring result in major population increases, but also that the persistence of such species is dependent on summer breeding in high-latitude regions, which requires a fundamental change in our understanding of insect migration. PMID:22927392

Migrant Nurses and Federal Caregiver Programs in Canada: Migration and Health Human Resources Paradox.

PubMed

Salami, Bukola

2016-06-01

Despite the links between health human resources policy, immigration policy, and education policy, silos persist in the policy-making process that complicate the professional integration of internationally educated nurses in Canada. Drawing on the literature on nurse migration to Canada through the Live-in Caregiver Program, this paper sheds light on the contradictions between immigration and health human resources policy and their effect on the integration of internationally educated nurses in Canada. The analysis reveals a series of paradoxes within and across immigration and health human resources policy that affect the process of professional integration of this group of health professionals into the nursing workforce in Canada. I will further link the discussion to the recently implemented Caregiver Program, which provides a unique pathway for healthcare workers, including nurses, to migrate to Canada. Given recent introduction of the Canadian Caregiver Program, major policy implications include the need to bridge the gap between health human resources policy and immigration policy to ensure the maximum integration of migrant nurses in Canada.

Spatial extent and dynamics of dam impacts on tropical island freshwater fish assemblages

USGS Publications Warehouse

Cooney, Patrick B.; Kwak, Thomas J.

2013-01-01

Habitat connectivity is vital to the persistence of migratory fishes. Native tropical island stream fish assemblages composed of diadromous species require intact corridors between ocean and riverine habitats. High dams block fish migration, but low-head artificial barriers are more widespread and are rarely assessed for impacts. Among all 46 drainages in Puerto Rico, we identified and surveyed 335 artificial barriers that hinder fish migration to 74.5% of the upstream habitat. We also surveyed occupancy of native diadromous fishes (Anguillidae, Eleotridae, Gobiidae, and Mugilidae) in 118 river reaches. Occupancy models demonstrated that barriers 2 meters (m) high restricted nongoby fish migration and extirpated those fish upstream of 4-m barriers. Gobies are adapted to climbing and are restricted by 12-m barriers and extirpated upstream of 32-m barriers. Our findings quantitatively illustrate the extensive impact of low-head structures on island stream fauna and provide guidance for natural resource management, habitat restoration, and water development strategies.

Force transmission in migrating cells

PubMed Central

Sauser, Roger; Ambrosi, Davide; Meister, Jean-Jacques; Verkhovsky, Alexander B.

2010-01-01

During cell migration, forces generated by the actin cytoskeleton are transmitted through adhesion complexes to the substrate. To investigate the mechanism of force generation and transmission, we analyzed the relationship between actin network velocity and traction forces at the substrate in a model system of persistently migrating fish epidermal keratocytes. Front and lateral sides of the cell exhibited much stronger coupling between actin motion and traction forces than the trailing cell body. Further analysis of the traction–velocity relationship suggested that the force transmission mechanisms were different in different cell regions: at the front, traction was generated by a gripping of the actin network to the substrate, whereas at the sides and back, it was produced by the network’s slipping over the substrate. Treatment with inhibitors of the actin–myosin system demonstrated that the cell body translocation could be powered by either of the two different processes, actomyosin contraction or actin assembly, with the former associated with significantly larger traction forces than the latter. PMID:20100912

Migration of cells in a social context

PubMed Central

Vedel, Søren; Tay, Savaş; Johnston, Darius M.; Bruus, Henrik; Quake, Stephen R.

2013-01-01

In multicellular organisms and complex ecosystems, cells migrate in a social context. Whereas this is essential for the basic processes of life, the influence of neighboring cells on the individual remains poorly understood. Previous work on isolated cells has observed a stereotypical migratory behavior characterized by short-time directional persistence with long-time random movement. We discovered a much richer dynamic in the social context, with significant variations in directionality, displacement, and speed, which are all modulated by local cell density. We developed a mathematical model based on the experimentally identified “cellular traffic rules” and basic physics that revealed that these emergent behaviors are caused by the interplay of single-cell properties and intercellular interactions, the latter being dominated by a pseudopod formation bias mediated by secreted chemicals and pseudopod collapse following collisions. The model demonstrates how aspects of complex biology can be explained by simple rules of physics and constitutes a rapid test bed for future studies of collective migration of individual cells. PMID:23251032

Migration of cells in a social context.

PubMed

Vedel, Søren; Tay, Savaş; Johnston, Darius M; Bruus, Henrik; Quake, Stephen R

2013-01-02

In multicellular organisms and complex ecosystems, cells migrate in a social context. Whereas this is essential for the basic processes of life, the influence of neighboring cells on the individual remains poorly understood. Previous work on isolated cells has observed a stereotypical migratory behavior characterized by short-time directional persistence with long-time random movement. We discovered a much richer dynamic in the social context, with significant variations in directionality, displacement, and speed, which are all modulated by local cell density. We developed a mathematical model based on the experimentally identified "cellular traffic rules" and basic physics that revealed that these emergent behaviors are caused by the interplay of single-cell properties and intercellular interactions, the latter being dominated by a pseudopod formation bias mediated by secreted chemicals and pseudopod collapse following collisions. The model demonstrates how aspects of complex biology can be explained by simple rules of physics and constitutes a rapid test bed for future studies of collective migration of individual cells.

Global Skills and Mobility Challenges and Possibilities for VET: A Crossborder Cross-Sectoral Case Study

ERIC Educational Resources Information Center

Cameron, Roslyn; O'Hanlon-Rose, Terry

2011-01-01

The complex interplay of technological advances, global demographic trends and macroeconomic forces has seen the emergence of global markets, economies, supply chains and labour markets. The use of skilled migration policy and initiatives for many countries feeling the effects of aging populations and skill shortages adds another dimension to this…

[Migration, urbanization, and development policy in Senegal].

PubMed

Dione, D

1992-01-01

"The various studies focussing on human settlements in Senegal show that the share of population living in cities is ever increasing because of the massive and continuous flow from rural areas. The persistance of such migration trends from the country to cities deepens regional disparities, compounds the difficulties and cost of city management and development, specially in the case of Dakar, and runs counter to the goals of social and economic development plans.... The growing importance of such phenomena calls for the designing of corrective measures in favour of rural areas and small towns in order to settle rural populations and halt the inordinate and chaotic geographical growth of large cities. Failing this, development efforts may well be compromised." (SUMMARY IN ENG) excerpt

Impact of Pathogen Population Heterogeneity and Stress-Resistant Variants on Food Safety.

PubMed

Abee, T; Koomen, J; Metselaar, K I; Zwietering, M H; den Besten, H M W

2016-01-01

This review elucidates the state-of-the-art knowledge about pathogen population heterogeneity and describes the genotypic and phenotypic analyses of persister subpopulations and stress-resistant variants. The molecular mechanisms underlying the generation of persister phenotypes and genetic variants are identified. Zooming in on Listeria monocytogenes, a comparative whole-genome sequence analysis of wild types and variants that enabled the identification of mutations in variants obtained after a single exposure to lethal food-relevant stresses is described. Genotypic and phenotypic features are compared to those for persistent strains isolated from food processing environments. Inactivation kinetics, models used for fitting, and the concept of kinetic modeling-based schemes for detection of variants are presented. Furthermore, robustness and fitness parameters of L. monocytogenes wild type and variants are used to model their performance in food chains. Finally, the impact of stress-resistant variants and persistence in food processing environments on food safety is discussed.

Pertussis Prevalence in Korean Adolescents and Adults with Persistent Cough.

PubMed

Lee, Soo Young; Han, Seung Beom; Kang, Jin Han; Kim, Ju Sang

2015-07-01

We investigated the prevalence of pertussis in Korean adolescents and adults with persistent cough. Study population was adolescents (aged 11-20 yr) and adults (≥ 21 yr old) who showed persistent cough of 1-8 weeks' duration. Pertussis was diagnosed by culture, polymerase chain reaction (PCR), and serology. A total of 310 subjects participated in this study, and 76 cases (24.5%) met the criteria for laboratory-confirmed pertussis. The majority of the pertussis cases (66/76) were confirmed by serology, while 3 cases (1.0%) were diagnosed with culture, and 10 cases (3.2%) were detected with PCR. Of the 76 subjects diagnosed with pertussis, 20/86 cases were adolescents and 56/224 cases were adults. Neither adolescents nor adults received adolescent-adult booster against pertussis within the previous 5 yr. Pertussis can be a primary cause of persistent cough in Korean adolescents and adults.

Characterization of increased persistence and intensity of precipitation in the northeastern United States

NASA Astrophysics Data System (ADS)

Guilbert, Justin; Betts, Alan K.; Rizzo, Donna M.; Beckage, Brian; Bomblies, Arne

2015-03-01

We present evidence of increasing persistence in daily precipitation in the northeastern United States that suggests that global circulation changes are affecting regional precipitation patterns. Meteorological data from 222 stations in 10 northeastern states are analyzed using Markov chain parameter estimates to demonstrate that a significant mode of precipitation variability is the persistence of precipitation events. We find that the largest region-wide trend in wet persistence (i.e., the probability of precipitation in 1 day and given precipitation in the preceding day) occurs in June (+0.9% probability per decade over all stations). We also find that the study region is experiencing an increase in the magnitude of high-intensity precipitation events. The largest increases in the 95th percentile of daily precipitation occurred in April with a trend of +0.7 mm/d/decade. We discuss the implications of the observed precipitation signals for watershed hydrology and flood risk.

Senescence-Induced Alterations of Laminin Chain Expression Modulate Tumorigenicity of Prostate Cancer Cells1

PubMed Central

Sprenger, Cynthia C T; Drivdahl, Rolf H; Woodke, Lillie B; Eyman, Daniel; Reed, May J; Carter, William G; Plymate, Stephen R

2008-01-01

Prostate cancer is an age-associated epithelial cancer, and as such, it contributes significantly to the mortality of the elderly. Senescence is one possible mechanism by which the body defends itself against various epithelial cancers. Senescent cells alter the microenvironment, in part, through changes to the extracellular matrix. Laminins (LMs) are extracellular proteins important to both the structure and function of the microenvironment. Overexpression of the senescence-associated gene mac25 in human prostate cancer cells resulted in increased mRNA levels of the LM α4 and β2 chains compared to empty vector control cells. The purpose of this study was to examine the effects of these senescence-induced LM chains on tumorigenicity of prostate cancer cells. We created stable M12 human prostate cancer lines overexpressing either the LM α4 or β2 chain or both chains. Increased expression of either the LM α4 or β2 chain resulted in increased in vitro migration and in vivo tumorigenicity of those cells, whereas high expression of both chains led to decreased in vitro proliferation and in vivo tumorigenicity compared to M12 control cells. This study demonstrates that senescent prostate epithelial cells can alter the microenvironment and that these changes modulate progression of prostate cancer. PMID:19048114

Ankle bipolar fresh osteochondral allograft survivorship and integration: transplanted tissue genetic typing and phenotypic characteristics.

PubMed

Neri, Simona; Vannini, Francesca; Desando, Giovanna; Grigolo, Brunella; Ruffilli, Alberto; Buda, Roberto; Facchini, Andrea; Giannini, Sandro

2013-10-16

Fresh osteochondral allografts represent a treatment option for early ankle posttraumatic arthritis. Transplanted cartilage survivorship, integration, and colonization by recipient cells have not been fully investigated. The aim of this study was to evaluate the ability of recipient cells to colonize the allograft cartilage and to assess allograft cell phenotype. Seventeen ankle allograft samples were studied. Retrieved allograft cartilage DNA from fifteen cases was compared with recipient and donor constitutional DNA by genotyping. In addition, gene expression was evaluated on six allograft cartilage samples by means of real-time reverse transcription-polymerase chain reaction. Histology and immunohistochemistry were performed to support molecular observations. Of fifteen genotyped allografts, ten completely matched to the host, three matched to the donor, and two showed a mixed profile. Gene expression analysis showed that grafted cartilage expressed cartilage-specific markers. The rare persistence of donor cells and the prevailing presence of host DNA in retrieved ankle allografts suggest the ingrowth of recipient cells into the allograft cartilage, presumably migrating from the subchondral bone, in accordance with morphological findings. The expression of chondrogenic markers in some of the samples argues for the acquisition of a chondrocyte-like phenotype by these cells. To our knowledge, this is the first report describing the colonization of ankle allograft cartilage by host cells showing the acquisition of a chondrocyte-like phenotype.

Accuracy of actuarial procedures for assessment of sexual offender recidivism risk may vary across ethnicity.

PubMed

Långström, Niklas

2004-04-01

Little is known about whether the accuracy of tools for assessment of sexual offender recidivism risk holds across ethnic minority offenders. I investigated the predictive validity across ethnicity for the RRASOR and the Static-99 actuarial risk assessment procedures in a national cohort of all adult male sex offenders released from prison in Sweden 1993-1997. Subjects ordered out of Sweden upon release from prison were excluded and remaining subjects (N = 1303) divided into three subgroups based on citizenship. Eighty-three percent of the subjects were of Nordic ethnicity, and non-Nordic citizens were either of non-Nordic European (n = 49, hereafter called European) or African Asian descent (n = 128). The two tools were equally accurate among Nordic and European sexual offenders for the prediction of any sexual and any violent nonsexual recidivism. In contrast, neither measure could differentiate African Asian sexual or violent recidivists from nonrecidivists. Compared to European offenders, AfricanAsian offenders had more often sexually victimized a nonrelative or stranger, had higher Static-99 scores, were younger, more often single, and more often homeless. The results require replication, but suggest that the promising predictive validity seen with some risk assessment tools may not generalize across offender ethnicity or migration status. More speculatively, different risk factors or causal chains might be involved in the development or persistence of offending among minority or immigrant sexual abusers.

Influence of local capillary trapping on containment system effectiveness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bryant, Steven

2014-03-31

Immobilization of CO 2 injected into deep subsurface storage reservoirs is a critical component of risk assessment for geologic CO 2 storage (GCS). Local capillary trapping (LCT) is a recently established mode of immobilization that arises when CO 2 migrates due to buoyancy through heterogeneous storage reservoirs. This project sought to assess the amount and extent of LCT expected in storage formations under a range of injection conditions, and to confirm the persistence of LCT if the seal overlying the reservoir were to lose its integrity. Numerical simulation using commercial reservoir simulation software was conducted to assess the influence ofmore » injection. Laboratory experiments, modeling and numerical simulation were conducted to assess the effect of compromised seal integrity. Bench-scale (0.6 m by 0.6 m by 0.03 m) experiments with surrogate fluids provided the first empirical confirmation of the key concepts underlying LCT: accumulation of buoyant nonwetting phase at above residual saturations beneath capillary barriers in a variety of structures, which remains immobile under normal capillary pressure gradients. Immobilization of above-residual saturations is a critical distinction between LCT and the more familiar “residual saturation trapping.” To estimate the possible extent of LCT in a storage reservoir an algorithm was developed to identify all potential local traps, given the spatial distribution of capillary entry pressure in the reservoir. The algorithm assumes that the driving force for CO 2 migration can be represented as a single value of “critical capillary entry pressure” P c,entry crit, such that cells with capillary entry pressure greater/less than P c,entry crit act as barriers/potential traps during CO 2 migration. At intermediate values of P c,entry crit, the barrier regions become more laterally extensive in the reservoir, approaching a percolation threshold while non-barrier regions remain numerous. The maximum possible extent of LCT thus occurs at P c,entry crit near this threshold. Testing predictions of this simple algorithm against full-physics simulations of buoyancy-driven CO 2 migration support the concept of critical capillary entry pressure. However, further research is needed to determine whether a single value of critical capillary entry pressure always applies and how that value can be determined a priori. Simulations of injection into high-resolution (cells 0.3 m on a side) 2D and 3D heterogeneous domains show two characteristic behaviors. At small gravity numbers (vertical flow velocity much less than horizontal flow velocity) the CO 2 fills local traps as well as regions that would act as local barriers if CO 2 were moving only due to buoyancy. When injection ceases, the CO 2 migrates vertically to establish large saturations within local traps and residual saturation elsewhere. At large gravity numbers, the CO 2 invades a smaller portion of the perforated interval. Within this smaller swept zone the local barriers are not invaded, but local traps are filled to large saturation during injection and remain during post-injection gravity-driven migration. The small gravity number behavior is expected in the region within 100 m of a vertical injection well at anticipated rates of injection for commercial GCS. Simulations of leakage scenarios (through-going region of large permeability imposed in overlying seal) indicate that LCT persists (i.e. CO 2 remains held in a large fraction of the local iv traps) and the persistence is independent of injection rate during storage. Simulations of leakage for the limiting case of CO 2 migrating vertically from an areally extensive emplacement in the lower portion of a reservoir showed similar strong persistence of LCT. This research has two broad implications for GCS. The first is that LCT can retain a significant fraction of the CO 2 stored in a reservoir – above and beyond the residual saturation -- if the overlying seal were to fail. Thus frameworks for risk assessment should be extended to account for LCT. The second implication is that compared to pressure driven flow in reservoirs, CO 2 migration and trapping behave in a qualitatively different manner in heterogeneous reservoirs when buoyancy is the dominant driving force for flow. Thus simulations of GCS that neglect capillary heterogeneity will fail to capture important features of the CO 2 plume. While commercial reservoir simulation software can account for fine scale capillary heterogeneity, it has not been designed to work efficiently with such domains, and no simulators can handle fine-scale resolution throughout the reservoir. A possible way to upscale the migration and trapping is to apply an “effective residual saturation” to coarse-scale grids. While the extent of overall immobilization can be correlated in this way, all coarser grids failed to capture the distance traveled by the migrating CO 2 for large gravity number. Thus it remains unclear how best to account for LCT in the routine simulation work-flow that will be needed for large-scale GCS. Alternatives meriting investigation include streamline methods, reduced-physics proxies (e.g. particle tracking), and biased invasion percolation algorithms, which are based on precisely the capillary heterogeneity essential for LCT.« less

Pirfenidone inhibits migration, differentiation, and proliferation of human retinal pigment epithelial cells in vitro

PubMed Central

Wang, Jing; Yang, Yangfan; Xu, Jiangang; Lin, Xianchai; Wu, Kaili

2013-01-01

Purpose To investigate the effects of pirfenidone (PFD) on the migration, differentiation, and proliferation of retinal pigment epithelial (RPE) cells and demonstrate whether the drug induces cytotoxicity. Methods Human RPE cells (line D407) were treated with various concentrations of PFD. Cell migration was measured with scratch assay. The protein levels of fibronectin (FN), connective tissue growth factor (CTGF), α-smooth muscle actin (α-SMA), transforming growth factor beta (TGFβS), and Smads were assessed with western blot analyses. Levels of mRNA of TGFβS, FN, and Snail1 were analyzed using reverse transcriptase–polymerase chain reaction. Cell apoptosis was detected with flow cytometry using the Annexin V/PI apoptosis kit, and the percentages of cells labeled in different apoptotic stage were compared. A Trypan Blue assay was used to assess cell viability. Results PFD inhibited RPE cell migration. Western blot analyses showed that PFD inhibited the expression of FN, α-SMA, CTGF, TGFβ1, TGFβ2, Smad2/3, and Smad4. Similarly, PFD also downregulated mRNA levels of Snail1, FN, TGFβ1, and TGFβ2. No significant differences in cell apoptosis or viability were observed between the control and PFD-treated groups. Conclusions PFD inhibited RPE cell migration, differentiation, and proliferation in vitro and caused no significant cytotoxicity. PMID:24415895

Glycosaminoglycan Chain of Dentin Sialoprotein Proteoglycan

PubMed Central

Zhu, Q.; Sun, Y.; Prasad, M.; Wang, X.; Yamoah, A.K.; Li, Y.; Feng, J.; Qin, C.

2010-01-01

Dentin sialophosphoprotein (DSPP) is processed into dentin sialoprotein (DSP) and dentin phosphoprotein. A molecular variant of rat DSP, referred to as “HMW-DSP”, has been speculated to be a proteoglycan form of DSP. To determine if HMW-DSP is the proteoglycan form of DSP and to identify the glycosaminoglycan side-chain attachment site(s), we further characterized HMW-DSP. Chondroitinase ABC treatment reduced the migration rate for portions of rat HMW-DSP to the level of DSP. Disaccharide analysis showed that rat HMW-DSP contains glycosaminoglycan chains made of chondroitin-4-sulfate and has an average of 31-32 disaccharides/mol. These observations confirmed that HMW-DSP is the proteoglycan form of DSP (renamed “DSP-PG”). Edman degradation and mass spectrometric analyses of tryptic peptides from rat DSP-PG, along with substitution analyses of candidate Ser residues in mouse DSPP, confirmed that 2 glycosaminoglycan chains are attached to Ser241 and Ser253 in the rat, or Ser242 and Ser254 in the mouse DSPP sequence. PMID:20400719

Glycosaminoglycan chain of dentin sialoprotein proteoglycan.

PubMed

Zhu, Q; Sun, Y; Prasad, M; Wang, X; Yamoah, A K; Li, Y; Feng, J; Qin, C

2010-08-01

Dentin sialophosphoprotein (DSPP) is processed into dentin sialoprotein (DSP) and dentin phosphoprotein. A molecular variant of rat DSP, referred to as "HMW-DSP", has been speculated to be a proteoglycan form of DSP. To determine if HMW-DSP is the proteoglycan form of DSP and to identify the glycosaminoglycan side-chain attachment site(s), we further characterized HMW-DSP. Chondroitinase ABC treatment reduced the migration rate for portions of rat HMW-DSP to the level of DSP. Disaccharide analysis showed that rat HMW-DSP contains glycosaminoglycan chains made of chondroitin-4-sulfate and has an average of 31-32 disaccharides/mol. These observations confirmed that HMW-DSP is the proteoglycan form of DSP (renamed "DSP-PG"). Edman degradation and mass spectrometric analyses of tryptic peptides from rat DSP-PG, along with substitution analyses of candidate Ser residues in mouse DSPP, confirmed that 2 glycosaminoglycan chains are attached to Ser(241) and Ser(253) in the rat, or Ser(242) and Ser(254) in the mouse DSPP sequence.

Controlling photophysical properties of ultrasmall conjugated polymer nanoparticles through polymer chain packing

PubMed Central

Piwoński, Hubert; Michinobu, Tsuyoshi; Habuchi, Satoshi

2017-01-01

Applications of conjugated polymer nanoparticles (Pdots) for imaging and sensing depend on their size, fluorescence brightness and intraparticle energy transfer. The molecular design of conjugated polymers (CPs) has been the main focus of the development of Pdots. Here we demonstrate that proper control of the physical interactions between the chains is as critical as the molecular design. The unique design of twisted CPs and fine-tuning of the reprecipitation conditions allow us to fabricate ultrasmall (3.0–4.5 nm) Pdots with excellent photostability. Extensive photophysical and structural characterization reveals the essential role played by the packing of the polymer chains in the particles in the intraparticle spatial alignment of the emitting sites, which regulate the fluorescence brightness and the intraparticle energy migration efficiency. Our findings enhance understanding of the relationship between chain interactions and the photophysical properties of CP nanomaterials, providing a framework for designing and fabricating functional Pdots for imaging applications. PMID:28508857

50-Ma Initiation of Hawaiian-Emperor Bend Records Major Change in Pacific Plate Motion

NASA Astrophysics Data System (ADS)

Sharp, Warren D.; Clague, David A.

2006-09-01

The Hawaiian-Emperor bend has played a prominent yet controversial role in deciphering past Pacific plate motions and the tempo of plate motion change. New ages for volcanoes of the central and southern Emperor chain define large changes in volcanic migration rate with little associated change in the chain's trend, which suggests that the bend did not form by slowing of the Hawaiian hot spot. Initiation of the bend near Kimmei seamount about 50 million years ago (MA) was coincident with realignment of Pacific spreading centers and early magmatism in western Pacific arcs, consistent with formation of the bend by changed Pacific plate motion.

The diel migrations and distributions within a mesopelagic community in the North East Atlantic. 7. Siphonophores

NASA Astrophysics Data System (ADS)

Pugh, P. R.

Siphonophores are by far the dominant macroplanktonic-micronektonic taxon of animals present in the 48 hr series of samples as a whole. A total of 35 species were identified, with four of these making up over 90% of the total numbers. Details of how the siphonophore population was estimated are discussed, but few species underwent clear cut diel vertical migration although there was considerable variability in their distributions over the sampling periods. The hydrography of the sampling area was investigated in relation to its possible effects on the faunal assemblages, and the important role of siphonophores as carnivores in the planktonic food chain was discussed.

Salmonella and Campylobacter biofilm formation: a comparative assessment from farm to fork.

PubMed

Lamas, Alexandre; Regal, Patricia; Vázquez, Beatriz; Miranda, José M; Cepeda, Alberto; Franco, Carlos M

2018-02-09

It takes several steps to bring food from the farm to the fork (dining table), and contamination with food-borne pathogens can occur at any point in the process. Campylobacter spp. and Salmonella spp. are the main microorganisms responsible for foodborne disease in the EU. These two pathogens are able to persist throughout the food supply chain thanks to their ability to form biofilms. Owing to the high prevalence of Salmonella and especially of Campylobacter in the food supply chain and the huge efforts of food authorities to reduce these levels, it is of great importance to fully understand their mechanisms of persistence. Diverse studies have evaluated the biofilm-forming capacity of foodborne pathogens isolated at different steps of food production. Nonetheless, the principal obstacle of these studies is to reproduce the real conditions that microorganisms encounter in the food supply chain. While there are a wide number of Salmonella biofilm studies, information on Campylobacter biofilms is still limited. A comparison between the two microorganisms could help to develop new research in the field of Campylobacter biofilms. Therefore, this review evaluates relevant work in the field of Salmonella and Campylobacter biofilms and the applicability of the data obtained from these studies to real working conditions. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry.

Evidence of Partial Migration in a Large Coastal Predator: Opportunistic Foraging and Reproduction as Key Drivers?

PubMed Central

Espinoza, Mario; Heupel, Michelle R.; Tobin, Andrew J.; Simpfendorfer, Colin A.

2016-01-01

Understanding animal movement decisions that involve migration is critical for evaluating population connectivity, and thus persistence. Recent work on sharks has shown that often only a portion of the adult population will undertake migrations, while the rest may be resident in an area for long periods. Defining the extent to which adult sharks use specific habitats and their migratory behaviour is essential for assessing their risk of exposure to threats such as fishing and habitat degradation. The present study used acoustic telemetry to examine residency patterns and migratory behaviour of adult bull sharks (Carcharhinus leucas) along the East coast of Australia. Fifty-six VR2W acoustic receivers were used to monitor the movements of 33 bull sharks in the central Great Barrier Reef (GBR). Both males and females were detected year-round, but their abundance and residency peaked between September and December across years (2012–2014). High individual variability in reef use patterns was apparent, with some individuals leaving the array for long periods, whereas others (36%) exhibited medium (0.20–0.40) or high residency (> 0.50). A large portion of the population (51%) undertook migrations of up to 1,400 km to other coral reefs and/or inshore coastal habitats in Queensland and New South Wales. Most of these individuals (76%) were mature females, and the timing of migrations coincided with the austral summer (Dec-Feb). All migrating individuals (except one) returned to the central GBR, highlighting its importance as a potential foraging ground. Our findings suggest that adult bull sharks appear to be highly dependent on coral reef resources and provide evidence of partial migration, where only a portion of the female population undertook seasonal migrations potentially to give birth. Given that estuarine habitats face constant anthropogenic pressures, understanding partial migration and habitat connectivity of large coastal predators should be a priority for their management. PMID:26841110

Cell Migration in 1D and 2D Nanofiber Microenvironments.

PubMed

Estabridis, Horacio M; Jana, Aniket; Nain, Amrinder; Odde, David J

2018-03-01

Understanding how cells migrate in fibrous environments is important in wound healing, immune function, and cancer progression. A key question is how fiber orientation and network geometry influence cell movement. Here we describe a quantitative, modeling-based approach toward identifying the mechanisms by which cells migrate in fibrous geometries having well controlled orientation. Specifically, U251 glioblastoma cells were seeded onto non-electrospinning Spinneret based tunable engineering parameters fiber substrates that consist of networks of suspended 400 nm diameter nanofibers. Cells were classified based on the local fiber geometry and cell migration dynamics observed by light microscopy. Cells were found in three distinct geometries: adhering two a single fiber, adhering to two parallel fibers, and adhering to a network of orthogonal fibers. Cells adhering to a single fiber or two parallel fibers can only move in one dimension along the fiber axis, whereas cells on a network of orthogonal fibers can move in two dimensions. We found that cells move faster and more persistently in 1D geometries than in 2D, with cell migration being faster on parallel fibers than on single fibers. To explain these behaviors mechanistically, we simulated cell migration in the three different geometries using a motor-clutch based model for cell traction forces. Using nearly identical parameter sets for each of the three cases, we found that the simulated cells naturally replicated the reduced migration in 2D relative to 1D geometries. In addition, the modestly faster 1D migration on parallel fibers relative to single fibers was captured using a correspondingly modest increase in the number of clutches to reflect increased surface area of adhesion on parallel fibers. Overall, the integrated modeling and experimental analysis shows that cell migration in response to varying fibrous geometries can be explained by a simple mechanical readout of geometry via a motor-clutch mechanism.

Expression of laminin-5 and integrins in actinic cheilitis and superficially invasive squamous cell carcinomas of the lip.

PubMed

Peixoto da-Silva, Janaína; Lourenço, Silvia; Nico, Marcello; Silva, Filomena H; Martins, Marília Trierveiler; Costa-Neves, Adriana

2012-10-15

The progression of carcinogenesis entails the detachment of cells, invasion and migration of neoplastic cells. Alterations in epithelial adhesion and basement membrane proteins might mediate the early stages of carcinogenesis. This study investigated the expression of adhesion molecules and the basement membrane protein laminin-5 in actinic cheilitis (AC) and incipient squamous cell carcinoma of the lower lip to understand early photocarcinogenesis. Ln-5γ2 chain as well as α3, β1 subunits of α3β1 heterodimer and β4 subunit of integrin α6β4 were evaluated by immunohistochemistry in 16 cases of AC and 16 cases of superficially invasive squamous cell carcinoma (SISCC). Most AC cases showed reduced expression of β1, β4 and α3 integrins, and SISCCs lacked β1, β4 and α3 integrins in the invasive front. AC cases were negative for the Ln-5γ2 chain. Five cases of SISCC (31%) showed heterogeneous Ln-5γ2 chain expression in the invasive front of the tumor. Integrin β1, β4 and α3 expression is lost during the early stages of lip carcinogenesis. Expression of Ln-5γ2 in the invasive front in cases and its correlation with tumor progression suggest that it mediates the acquisition of the migrating and invading epithelial cell phenotype. Copyright © 2012 Elsevier GmbH. All rights reserved.

SELECTIVE CHANGES IN BRAIN PROTEIN KINASE C ISOFORMS FOLLOWING DEVELOPMENTAL EXPOSURE TO A PCB MIXTURE.

EPA Science Inventory

Introduction
Polychlorinated biphenyls (PCBs) offer a unique model to understand the major issues related to complex environmental mixtures. These environmental pollutants are ubiquitous, persistent, bioaccumulate in human body through the food chain, and exist as mixtures of ...

Effects of silencing S100A8 and S100A9 with small interfering RNA on the migration of CNE1 nasopharyngeal carcinoma cells.

PubMed

Yan, Lin-Lin; Huang, Yuan-Jiao; Yi, Xiang; Yan, Xue-Min; Cai, Yan; He, Qin; Han, Zi-Jian

2015-06-01

The calcium-binding S100 proteins are involved in functions such as cell growth, differentiation, migration, adhesion and signal transduction. S100A8 and S100A9 are highly expressed in a variety of tumor cells, and are implicated in tumor development and progression. However, the role of S100A8 and S100A9 in nasopharyngeal carcinoma (NPC) cell migration is unclear. The present study investigated the effect of S100A8 and S100A9 on migration using a NPC cell line, CNE1. The CNE1 cells were transfected with S100A8 or S100A9 small interfering RNA (siRNA). Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect S100A8 and S100A9 gene expression. Following the downregulation of S100A8 or S100A9, the effects on cell migration were determined using wound-healing assays. The expression of matrix metalloproteinase-7 (MMP7), a member of the MMP family that is associated with tumor cell invasion and migration, was also detected by RT-qPCR. S100A8 and S100A9 siRNAs effectively suppressed S100A8 and S100A9 gene expression, and substantially inhibited the migration of the CNE1 cells. In addition, MMP7 expression was reduced to varying extents in S100A8 and S100A9 siRNA-treated cells compared with controls. Thus, S100A8 and S100A9 promoted the migration of CNE1 NPC cells.

Effects of silencing S100A8 and S100A9 with small interfering RNA on the migration of CNE1 nasopharyngeal carcinoma cells

PubMed Central

YAN, LIN-LIN; HUANG, YUAN-JIAO; YI, XIANG; YAN, XUE-MIN; CAI, YAN; HE, QIN; HAN, ZI-JIAN

2015-01-01

The calcium-binding S100 proteins are involved in functions such as cell growth, differentiation, migration, adhesion and signal transduction. S100A8 and S100A9 are highly expressed in a variety of tumor cells, and are implicated in tumor development and progression. However, the role of S100A8 and S100A9 in nasopharyngeal carcinoma (NPC) cell migration is unclear. The present study investigated the effect of S100A8 and S100A9 on migration using a NPC cell line, CNE1. The CNE1 cells were transfected with S100A8 or S100A9 small interfering RNA (siRNA). Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect S100A8 and S100A9 gene expression. Following the downregulation of S100A8 or S100A9, the effects on cell migration were determined using wound-healing assays. The expression of matrix metalloproteinase-7 (MMP7), a member of the MMP family that is associated with tumor cell invasion and migration, was also detected by RT-qPCR. S100A8 and S100A9 siRNAs effectively suppressed S100A8 and S100A9 gene expression, and substantially inhibited the migration of the CNE1 cells. In addition, MMP7 expression was reduced to varying extents in S100A8 and S100A9 siRNA-treated cells compared with controls. Thus, S100A8 and S100A9 promoted the migration of CNE1 NPC cells. PMID:26137102

Ginkgolide K promotes astrocyte proliferation and migration after oxygen-glucose deprivation via inducing protective autophagy through the AMPK/mTOR/ULK1 signaling pathway.

PubMed

Zhang, Ying; Miao, Ju-Mei

2018-05-19

Ischemic stroke is the leading cause of death around the world. Ginkgolide K (GK) has been used to treat ischemic stroke due to its neuroprotective potential. However, the molecular mechanism underlying the neuroprotective effect of GK in ischemic stroke is still almost blank. In this study, astrocytes were divided into four groups: control group, oxygen-glucose deprivation (OGD) group, OGD + GK group and OGD + GK + Compound C (CC) group. The viability and proliferation of astrocytes were examined by Cell Counting Kit-8 assay and 5-ethynyl-20-deoxyuridine (EdU) assay, respectively. Transwell migration and wound scratch assays were conducted to evaluate astrocyte migration. The protein expression in astrocytes were determined by western blot assay. We found that GK pretreatment promoted astrocyte proliferation and migration after OGD as shown by the increase in the viability of astrocytes, glial fibrillary acidic protein level, the number of EdU positive cells and migrated cells, and the migration distance. GK pretreatment induced autophagy after OGD, as indicated by upregulation of autophagy-related protein 7, Beclin-1 protein and increase of microtubule-associated protein 1 light chain 3 (LC3)-II/LC3-I, and downregulation of p62 protein. Moreover, GK pretreatment activated the AMP activated protein kinase (AMPK)/mammalian target of rapamycin (m-TOR)/ULK1 pathway in astrocytes following OGD. Notably, CC treatment blocked the promotory effect of GK on astrocyte proliferation and migration after OGD. Collectively, GK promoted astrocyte proliferation and migration after OGD via inducing protective autophagy through the AMPK/mTOR/ULK1 signaling pathway. Our findings suggested that GK might be a potential agent for cerebral ischemia/reperfusion injury. Copyright © 2018. Published by Elsevier B.V.

Doxycycline inhibits leukemic cell migration via inhibition of matrix metalloproteinases and phosphorylation of focal adhesion kinase

PubMed Central

WANG, CHUNHUAI; XIANG, RU; ZHANG, XIANGZHONG; CHEN, YUNXIAN

2015-01-01

Doxycycline, a tetracycline-based antibiotic, has been reported to attenuate melanoma cell migration through inhibiting the focal adhesion kinase (FAK) signaling pathway. However, it remains to be elucidated whether doxycycline exerts this effect on leukemia cell migration. The present study aimed to examine the role of doxycycline in leukemia cell migration. The invasion capacities of the human leukemia cell lines KG1a (acute myelogenous leukemia) and K562 (chronic myelogenous leukemia) were evaluated using Matrigel® matrix-coated Transwell® chamber assays; leukemic cell lines treated with doxycycline (1 µg/ml) or anti-β1-integrin antibodies were added to the upper chamber, while untreated cells were included as controls. Reverse transcription quantitative polymerase chain reaction was performed in order to further understand the influence of doxycycline treatment on the expression of FAK and gelatinases in the KG1a and K562 leukemic cell lines. In addition, FAK protein expression and phosphorylation were determined using western blot analysis in order to investigate the mechanism by which doxycycline inhibited leukemic cell migration. The results revealed that doxycycline treatment significantly attenuated the migration of KG1a and K562 cells, which was demonstrated to be associated with inhibition of the expression and phosphorylation of FAK. In addition, doxycycline treatment inhibited matrix metalloproteinase (MMP)-2 and MMP-9 expression. Furthermore, incubation with blocking anti-β1-integrin antibodies had an analogous inhibitory effect on leukemic cell migration to that of doxycycline. In conclusion, the results of the present study suggested that doxycycline attenuated leukemic cell migration through inhibiting the FAK signaling pathway. Therefore, doxycycline may have potential for use as a novel strategy for the treatment of leukemia. PMID:26004127

Evidence of a Cell Surface Role for Hsp90 Complex Proteins Mediating Neuroblast Migration in the Subventricular Zone.

PubMed

Miyakoshi, Leo M; Marques-Coelho, Diego; De Souza, Luiz E R; Lima, Flavia R S; Martins, Vilma R; Zanata, Silvio M; Hedin-Pereira, Cecilia

2017-01-01

In most mammalian brains, the subventricular zone (SVZ) is a germinative layer that maintains neurogenic activity throughout adulthood. Neuronal precursors arising from this region migrate through the rostral migratory stream (RMS) and reach the olfactory bulbs where they differentiate and integrate into the local circuitry. Recently, studies have shown that heat shock proteins have an important role in cancer cell migration and blocking Hsp90 function was shown to hinder cell migration in the developing cerebellum. In this work, we hypothesize that chaperone complexes may have an important function regulating migration of neuronal precursors from the subventricular zone. Proteins from the Hsp90 complex are present in the postnatal SVZ as well as in the RMS. Using an in vitro SVZ explant model, we have demonstrated the expression of Hsp90 and Hop/STI1 by migrating neuroblasts. Treatment with antibodies against Hsp90 and co-chaperone Hop/STI1, as well as Hsp90 and Hsp70 inhibitors hinder neuroblast chain migration. Time-lapse videomicroscopy analysis revealed that cell motility and average migratory speed was decreased after exposure to both antibodies and inhibitors. Antibodies recognizing Hsp90, Hsp70, and Hop/STI1 were found bound to the membranes of cells from primary SVZ cultures and biotinylation assays demonstrated that Hsp70 and Hop/STI1 could be found on the external leaflet of neuroblast membranes. The latter could also be detected in conditioned medium samples obtained from cultivated SVZ cells. Our results suggest that chaperones Hsp90, Hsp70, and co-chaperone Hop/STI1, components of the Hsp90 complex, regulate SVZ neuroblast migration in a concerted manner through an extracellular mechanism.

DNA motion capture reveals the mechanical properties of DNA at the mesoscale.

PubMed

Price, Allen C; Pilkiewicz, Kevin R; Graham, Thomas G W; Song, Dan; Eaves, Joel D; Loparo, Joseph J

2015-05-19

Single-molecule studies probing the end-to-end extension of long DNAs have established that the mechanical properties of DNA are well described by a wormlike chain force law, a polymer model where persistence length is the only adjustable parameter. We present a DNA motion-capture technique in which DNA molecules are labeled with fluorescent quantum dots at specific sites along the DNA contour and their positions are imaged. Tracking these positions in time allows us to characterize how segments within a long DNA are extended by flow and how fluctuations within the molecule are correlated. Utilizing a linear response theory of small fluctuations, we extract elastic forces for the different, ∼2-μm-long segments along the DNA backbone. We find that the average force-extension behavior of the segments can be well described by a wormlike chain force law with an anomalously small persistence length. Copyright © 2015 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Hydrologically driven ecosystem processes determine the distribution and persistence of ecosystem-specialist predators under climate change.

PubMed

Carroll, Matthew J; Heinemeyer, Andreas; Pearce-Higgins, James W; Dennis, Peter; West, Chris; Holden, Joseph; Wallage, Zoe E; Thomas, Chris D

2015-07-31

Climate change has the capacity to alter physical and biological ecosystem processes, jeopardizing the survival of associated species. This is a particular concern in cool, wet northern peatlands that could experience warmer, drier conditions. Here we show that climate, ecosystem processes and food chains combine to influence the population performance of species in British blanket bogs. Our peatland process model accurately predicts water-table depth, which predicts abundance of craneflies (keystone invertebrates), which in turn predicts observed abundances and population persistence of three ecosystem-specialist bird species that feed on craneflies during the breeding season. Climate change projections suggest that falling water tables could cause 56-81% declines in cranefly abundance and, hence, 15-51% reductions in the abundances of these birds by 2051-2080. We conclude that physical (precipitation, temperature and topography), biophysical (evapotranspiration and desiccation of invertebrates) and ecological (food chains) processes combine to determine the distributions and survival of ecosystem-specialist predators.

Hydrologically driven ecosystem processes determine the distribution and persistence of ecosystem-specialist predators under climate change

PubMed Central

Carroll, Matthew J.; Heinemeyer, Andreas; Pearce-Higgins, James W.; Dennis, Peter; West, Chris; Holden, Joseph; Wallage, Zoe E.; Thomas, Chris D.

2015-01-01

Climate change has the capacity to alter physical and biological ecosystem processes, jeopardizing the survival of associated species. This is a particular concern in cool, wet northern peatlands that could experience warmer, drier conditions. Here we show that climate, ecosystem processes and food chains combine to influence the population performance of species in British blanket bogs. Our peatland process model accurately predicts water-table depth, which predicts abundance of craneflies (keystone invertebrates), which in turn predicts observed abundances and population persistence of three ecosystem-specialist bird species that feed on craneflies during the breeding season. Climate change projections suggest that falling water tables could cause 56–81% declines in cranefly abundance and, hence, 15–51% reductions in the abundances of these birds by 2051–2080. We conclude that physical (precipitation, temperature and topography), biophysical (evapotranspiration and desiccation of invertebrates) and ecological (food chains) processes combine to determine the distributions and survival of ecosystem-specialist predators. PMID:26227623

Migration Pathways of Thalamic Neurons and Development of Thalamocortical Connections in Humans Revealed by Diffusion MR Tractography.

PubMed

Wilkinson, Molly; Kane, Tara; Wang, Rongpin; Takahashi, Emi

2017-12-01

The thalamus plays an important role in signal relays in the brain, with thalamocortical (TC) neuronal pathways linked to various sensory/cognitive functions. In this study, we aimed to see fetal and postnatal development of the thalamus including neuronal migration to the thalamus and the emergence/maturation of the TC pathways. Pathways from/to the thalami of human postmortem fetuses and in vivo subjects ranging from newborns to adults with no neurological histories were studied using high angular resolution diffusion MR imaging (HARDI) tractography. Pathways likely linked to neuronal migration from the ventricular zone and ganglionic eminence (GE) to the thalami were both successfully detected. Between the ventricular zone and thalami, more tractography pathways were found in anterior compared with posterior regions, which was well in agreement with postnatal observations that the anterior TC segment had more tract count and volume than the posterior segment. Three different pathways likely linked to neuronal migration from the GE to the thalami were detected. No hemispheric asymmetry of the TC pathways was quantitatively observed during development. These results suggest that HARDI tractography is useful to identify multiple differential neuronal migration pathways in human brains, and regional differences in brain development in fetal ages persisted in postnatal development. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Pre-Treatment of Human Mesenchymal Stem Cells With Inflammatory Factors or Hypoxia Does Not Influence Migration to Osteoarthritic Cartilage and Synovium.

PubMed

Leijs, Maarten J C; van Buul, Gerben M; Verhaar, Jan A N; Hoogduijn, Martin J; Bos, Pieter K; van Osch, Gerjo J V M

2017-04-01

Mesenchymal stem cells (MSCs) are promising candidates as a cell-based therapy for osteoarthritis (OA), although current results are modest. Pre-treatment of MSCs before application might improve their therapeutic efficacy. Pre-treatment of MSCs with inflammatory factors or hypoxia will improve their migration and adhesion capacities toward OA-affected tissues. Controlled laboratory study. We used real-time polymerase chain reaction to determine the effects of different fetal calf serum (FCS) batches, platelet lysate (PL), hypoxia, inflammatory factors, factors secreted by OA tissues, and OA synovial fluid (SF) on the expression of 12 genes encoding chemokine or adhesion receptors. Migration of MSCs toward factors secreted by OA tissues was studied in vitro, and attachment of injected MSCs was evaluated in vivo in healthy and OA knees of male Wistar rats. Different FCS batches, PL, or hypoxia did not influence the expression of the migration and adhesion receptor genes. Exposure to inflammatory factors altered the expression of CCR1, CCR4, CD44, PDGFRα, and PDGFRβ. MSCs migrated toward factors secreted by OA tissues in vitro. Neither pre-treatment with inflammatory factors nor the presence of OA influenced MSC migration in vitro or adhesion in vivo. Factors secreted by OA tissues increase MSC migration in vitro. In vivo, no difference in MSC adhesion was found between OA and healthy knees. Pre-treatment with inflammatory factors influenced the expression of migration and adhesion receptors of MSCs but not their migration in vitro or adhesion in vivo. To improve the therapeutic capacity of intra-articular injection of MSCs, they need to remain intra-articular for a longer period of time. Pre-treatment of MSCs with hypoxia or inflammatory factors did not increase the migration or adhesion capacity of MSCs and will therefore not likely prolong their intra-articular longevity. Alternative approaches to prolong the intra-articular presence of MSCs should be developed to increase the therapeutic effect of MSCs in OA.

Correlation functions of main-chain polymer nematics constrained by tensorial and vectorial conservation laws

NASA Astrophysics Data System (ADS)

Svenšek, Daniel; Podgornik, Rudolf

2015-09-01

We present and analyze correlation functions of a main-chain polymer nematic in a continuum worm-like chain description for two types of constraints formalized by the tensorial and vectorial conservation laws, both originating in the microscopic chain integrity, i.e., the connectivity of the polymer chains. In particular, our aim is to identify the features of the correlation functions that are most susceptible to the differences between the two constraints. Besides the density and director autocorrelations in both the tensorial and vectorial cases, we calculate also the density-director correlation functions, the latter being a direct signature of the presence of a specific constraint. Its amplitude is connected to the strength of the constraint and is zero if none of the constraints are present, i.e., for a standard non-polymeric nematic. Generally, the correlation functions with the constraints differ substantially from the correlation functions in the non-polymeric case, if the constraints are strong which in practice requires long chains. Moreover, for the tensorial conservation law to be well distinguishable from the vectorial one, the chain persistence length should be much smaller than the total length of the chain, so that hairpins (chain backfolding) are numerous and the polar order is small.

A framework for understanding semi-permeable barrier effects on migratory ungulates

USGS Publications Warehouse

Sawyer, Hall; Kauffman, Matthew J.; Middleton, Arthur D.; Morrison, Thomas A.; Nielson, Ryan M.; Wyckoff, Teal B.

2013-01-01

1. Impermeable barriers to migration can greatly constrain the set of possible routes and ranges used by migrating animals. For ungulates, however, many forms of development are semi-permeable, and making informed management decisions about their potential impacts to the persistence of migration routes is difficult because our knowledge of how semi-permeable barriers affect migratory behaviour and function is limited. 2. Here, we propose a general framework to advance the understanding of barrier effects on ungulate migration by emphasizing the need to (i) quantify potential barriers in terms that allow behavioural thresholds to be considered, (ii) identify and measure behavioural responses to semi-permeable barriers and (iii) consider the functional attributes of the migratory landscape (e.g. stopovers) and how the benefits of migration might be reduced by behavioural changes. 3. We used global position system (GPS) data collected from two subpopulations of mule deer Odocoileus hemionus to evaluate how different levels of gas development influenced migratory behaviour, including movement rates and stopover use at the individual level, and intensity of use and width of migration route at the population level. We then characterized the functional landscape of migration routes as either stopover habitat or movement corridors and examined how the observed behavioural changes affected the functionality of the migration route in terms of stopover use. 4. We found migratory behaviour to vary with development intensity. Our results suggest that mule deer can migrate through moderate levels of development without any noticeable effects on migratory behaviour. However, in areas with more intensive development, animals often detoured from established routes, increased their rate of movement and reduced stopover use, while the overall use and width of migration routes decreased. 5. Synthesis and applications. In contrast to impermeable barriers that impede animal movement, semi-permeable barriers allow animals to maintain connectivity between their seasonal ranges. Our results identify the mechanisms (e.g. detouring, increased movement rates, reduced stopover use) by which semi-permeable barriers affect the functionality of ungulate migration routes and emphasize that the management of semi-permeable barriers may play a key role in the conservation of migratory ungulate populations.

Increased expression of TLR9 associated with pro-inflammatory S100A8 and IL-8 in diabetic wounds could lead to unresolved inflammation in type 2 diabetes mellitus (T2DM) cases with impaired wound healing.

PubMed

Singh, Kanhaiya; Agrawal, Neeraj K; Gupta, Sanjeev K; Sinha, Pratima; Singh, Kiran

2016-01-01

Type 2 diabetes mellitus (T2DM) is characterized by persistent hyperglycemia which causes a chain of abrupt biochemical and physiological changes. Immune dys-regulation is the hallmark of T2DM that could contribute to prolonged inflammation causing transformation of wounds into non-healing chronic ulcers. Toll like receptor -9 (TLR9) is a major receptor involved in innate immune regulation. TLR9 activation induces release of pro-inflammatory molecules like S100A8 and interleukin-8 (IL-8) by myeloid cells causing migration of myeloid cells to the site of inflammation. We hypothesized that pro-inflammatory S100A8 and IL-8 proteins could cause persistent inflammation in chronic wounds like diabetic foot ulcer (DFU) and may contribute to impaired wound healing in T2DM patients. Expression of TLR9 and its downstream effector molecules S100A8, and IL-8 were analyzed in chronic diabetic wound and non-diabetic control wound tissue samples by semiquantitative reverse transcriptase - polymerase chain reaction (RT-PCR), quantitative RT-PCR, western blot and immunofluorescence. CD11b(+)CD33(+) myeloid cells were analyzed by flow cytometry. TLR9 message and protein were higher in diabetic wounds compared to control wounds (p=0.03, t=2.21 for TLR9 mRNA; p=<0.001, t=4.21 for TLR9 protein). TLR9 down-stream effector molecules S100A8 and IL-8 were also increased in diabetic wounds (p=0.003, t=3.1 for S100A8 mRNA; p=0.04, t=2.04 for IL-8). CD11b(+) CD33(+) myeloid cells were decreased in T2DM as compared to non-diabetic controls (p=0.001, t=3.6). DFU subjects had higher levels of CD11b(+) CD33(+) myeloid cells as compared to non-DFU T2DM control (p=0.003, t=2.8). Infection in the wound microenvironment could be the cause of increase in CD11b(+)CD33(+) myeloid cells in DFU (p=0.03, t=2.5). The up-regulation of myeloid cell-derived pro-inflammatory molecules S100A8 and IL-8 in combination with lower levels of CD11b(+) CD33(+) myeloid cells may cause the impairment of wound healing in T2DM subjects leading to chronic ulcers. Copyright © 2016 Elsevier Inc. All rights reserved.

An in vitro correlation of mechanical forces and metastatic capacity

NASA Astrophysics Data System (ADS)

Indra, Indrajyoti; Undyala, Vishnu; Kandow, Casey; Thirumurthi, Umadevi; Dembo, Micah; Beningo, Karen A.

2011-02-01

Mechanical forces have a major influence on cell migration and are predicted to significantly impact cancer metastasis, yet this idea is currently poorly defined. In this study we have asked if changes in traction stress and migratory properties correlate with the metastatic progression of tumor cells. For this purpose, four murine breast cancer cell lines derived from the same primary tumor, but possessing increasing metastatic capacity, were tested for adhesion strength, traction stress, focal adhesion organization and for differential migration rates in two-dimensional and three-dimensional environments. Using traction force microscopy (TFM), we were surprised to find an inverse relationship between traction stress and metastatic capacity, such that force production decreased as the metastatic capacity increased. Consistent with this observation, adhesion strength exhibited an identical profile to the traction data. A count of adhesions indicated a general reduction in the number as metastatic capacity increased but no difference in the maturation as determined by the ratio of nascent to mature adhesions. These changes correlated well with a reduction in active beta-1 integrin with increasing metastatic ability. Finally, in two dimensions, wound healing, migration and persistence were relatively low in the entire panel, maintaining a downward trend with increasing metastatic capacity. Why metastatic cells would migrate so poorly prompted us to ask if the loss of adhesive parameters in the most metastatic cells indicated a switch to a less adhesive mode of migration that would only be detected in a three-dimensional environment. Indeed, in three-dimensional migration assays, the most metastatic cells now showed the greatest linear speed. We conclude that traction stress, adhesion strength and rate of migration do indeed change as tumor cells progress in metastatic capacity and do so in a dimension-sensitive manner.

Electron transport chains in organohalide-respiring bacteria and bioremediation implications.

PubMed

Wang, Shanquan; Qiu, Lan; Liu, Xiaowei; Xu, Guofang; Siegert, Michael; Lu, Qihong; Juneau, Philippe; Yu, Ling; Liang, Dawei; He, Zhili; Qiu, Rongliang

In situ remediation employing organohalide-respiring bacteria represents a promising solution for cleanup of persistent organohalide pollutants. The organohalide-respiring bacteria conserve energy by utilizing H 2 or organic compounds as electron donors and organohalides as electron acceptors. Reductive dehalogenase (RDase), a terminal reductase of the electron transport chain in organohalide-respiring bacteria, is the key enzyme that catalyzes halogen removal. Accumulating experimental evidence thus far suggests that there are distinct models for respiratory electron transfer in organohalide-respirers of different lineages, e.g., Dehalococcoides, Dehalobacter, Desulfitobacterium and Sulfurospirillum. In this review, to connect the knowledge in organohalide-respiratory electron transport chains to bioremediation applications, we first comprehensively review molecular components and their organization, together with energetics of the organohalide-respiratory electron transport chains, as well as recent elucidation of intramolecular electron shuttling and halogen elimination mechanisms of RDases. We then highlight the implications of organohalide-respiratory electron transport chains in stimulated bioremediation. In addition, major challenges and further developments toward understanding the organohalide-respiratory electron transport chains and their bioremediation applications are identified and discussed. Copyright © 2018 Elsevier Inc. All rights reserved.

Specific Function of the Met-Tyr-Trp Adduct Radical and Residues Arg-418 and Asp-137 in the Atypical Catalase Reaction of Catalase-Peroxidase KatG*

PubMed Central

Zhao, Xiangbo; Khajo, Abdelahad; Jarrett, Sanchez; Suarez, Javier; Levitsky, Yan; Burger, Richard M.; Jarzecki, Andrzej A.; Magliozzo, Richard S.

2012-01-01

Catalase activity of the dual-function heme enzyme catalase-peroxidase (KatG) depends on several structural elements, including a unique adduct formed from covalently linked side chains of three conserved amino acids (Met-255, Tyr-229, and Trp-107, Mycobacterium tuberculosis KatG numbering) (MYW). Mutagenesis, electron paramagnetic resonance, and optical stopped-flow experiments, along with calculations using density functional theory (DFT) methods revealed the basis of the requirement for a radical on the MYW-adduct, for oxyferrous heme, and for conserved residues Arg-418 and Asp-137 in the rapid catalase reaction. The participation of an oxyferrous heme intermediate (dioxyheme) throughout the pH range of catalase activity is suggested from our finding that carbon monoxide inhibits the activity at both acidic and alkaline pH. In the presence of H2O2, the MYW-adduct radical is formed normally in KatG[D137S] but this mutant is defective in forming dioxyheme and lacks catalase activity. KatG[R418L] is also catalase deficient but exhibits normal formation of the adduct radical and dioxyheme. Both mutants exhibit a coincidence between MYW-adduct radical persistence and H2O2 consumption as a function of time, and enhanced subunit oligomerization during turnover, suggesting that the two mutations disrupting catalase turnover allow increased migration of the MYW-adduct radical to protein surface residues. DFT calculations showed that an interaction between the side chain of residue Arg-418 and Tyr-229 in the MYW-adduct radical favors reaction of the radical with the adjacent dioxyheme intermediate present throughout turnover in WT KatG. Release of molecular oxygen and regeneration of resting enzyme are thereby catalyzed in the last step of a proposed catalase reaction. PMID:22918833

Hydrodynamic radius fluctuations in model DNA-grafted nanoparticles

NASA Astrophysics Data System (ADS)

Vargas-Lara, Fernando; Starr, Francis W.; Douglas, Jack F.

2016-05-01

We utilize molecular dynamics simulations (MD) and the path-integration program ZENO to quantify hydrodynamic radius (Rh) fluctuations of spherical symmetric gold nanoparticles (NPs) decorated with single-stranded DNA chains (ssDNA). These results are relevant to understanding fluctuation-induced interactions among these NPs and macromolecules such as proteins. In particular, we explore the effect of varying the ssDNA-grafted NPs structural parameters, such as the chain length (L), chain persistence length (lp), NP core size (R), and the number of chains (N) attached to the nanoparticle core. We determine Rh fluctuations by calculating its standard deviation (σRh) of an ensemble of ssDNA-grafted NPs configurations generated by MD. For the parameter space explored in this manuscript, σR h shows a peak value as a function of N, the amplitude of which depends on L, lp and R, while the broadness depends on R.

Poliomyelitis: immunoglobulin-containing cells in the central nervous system in acute and convalescent phases of the human disease.

PubMed Central

Esiri, M M

1980-01-01

The immunoperoxidase method has been used to demonstrate the presence of immunoglobulin-containing cells in the central nervous system in acute and convalescent phases of poliomyelitis. These cells were found in considerable numbers in the areas of damage during the acute phase, and persisted at the same sites, though in smaller numbers, during the convalescent phase for at least 8 months. Most of the positively stained cells were plasma cells. IgA was the commonest heavy chain type demonstrated, with lesser amounts also of IgG and, during the acute phase, IgM. In the acute phase more lambda than kappa light chain was demonstrated but in the convalescent phase this ratio was reversed. More light chain than heavy chain was demonstrable during the acute phase. The significance of these results is briefly discussed. Images Fig. 2 PMID:6771081

40 CFR 227.18 - Factors considered.

Code of Federal Regulations, 2010 CFR

2010-07-01

... biochemical degradation during movement of the materials from a disposal site to an area of significant... humans directly; (g) Presence in the material of chemical constituents which may be bioaccumulated or persistent and may have an adverse effect on humans directly or through food chain interactions; (h) Presence...

The effects of gypsy moth defoliation on soil water chemistry

Treesearch

Thomas R., Jr. Eagle; Ray R., Jr. Hicks

1993-01-01

Twenty-eight plots were established in oak stands along the leading edge of gypsy moth migration into north-central West Virginia. Plots were arranged in a 3-chain square grid pattern in areas of varying aspect, percent slope, elevation, site index and species composition. Soft water, gypsy moth frass and leaf fragments generated by larval feeding were collected weekly...

Modification of apparent fission yields by Chemical Fractionation following Fission (CFF)

NASA Astrophysics Data System (ADS)

Hohenberg, Charles; Meshik, Alex

2008-04-01

Grain-by-grain studies of the 2 billion year old Oklo natural reactor, using laser micro-extraction^1,2, yield detailed information about Oklo, a water-moderated pulsed reactor, cycle times, total neutron fluence and duration, but it also demonstrates Chemical Fractionation following Fission. In the CFF process, members of an isobaric yield chain with long half-lives are subject to migration before decay can occur. Of particular interest is the 129 isobar where 17 million ^129I can migrate out of the host grain before decay, and iodine compounds are water soluble. This is amply demonstated by the variation of Xe spectra between micron-sized uranium-bearing minerals and adjacent uranium-free minerals. Fission 129 yields for the spontaneous fission of ^238U generally come from measured ^129Xe in pitchblend^2, ores emplaced by aqueous activity, and are incorrect due to the CFF process. ^238U yields for the 131 and 129 chains, reported in Hyde^3, as 0.455 +- .02 and < 0.012, respectively, the latter being anomalously low. ^1A Meshik, C Hohenberg and O Pravdivtesva, PRL 93, 182302 (2004); A Meshik Sci. Am. Nov (2005), 55; ^2E K Hyde, Nucl Prop of Heavy Elements III (1964).

Surface immunoglobulin on cultured foetal mouse thymocytes

PubMed Central

Haustein, D.; Mandel, T. E.

1979-01-01

Organ cultures of 14–15 day foetal mouse thymus were used as a source of non-neoplastic differentiating T cells, free of contaminating B cells. Viable cells obtained from such cultured thymuses were radio-iodinated and immunoglobulins (Ig) were isolated by co-precipitation from the 125I-labelled cell-surface proteins released during 1 h of incubation at 37°. The precipitates, both reduced and unreduced, were then analysed by polyacrylamide gel electrophoresis. The unreduced material migrated in a 5% gel as a single peak with a mobility slightly faster than that of mouse IgG. After reduction, however, two peaks were obtained (in a 10% gel), one corresponding in migration to mouse light chain and the other which moved slightly faster than mouse μ chain. This pattern was identical with that previously seen for both surface Ig of normal mouse thymocytes and neoplastic T lymphoma cells. Uncultured, 15 day foetal thymocytes did not produce any detectable co-precipitated cell surface material. Ig detected in these experiments was therefore produced during in vitro culture by non-neoplastic T cells in a system free of contaminating B cells and mouse serum proteins. PMID:315364

Turning behaviors of T cells climbing up ramp-like structures are regulated by myosin light chain kinase activity and lamellipodia formation.

PubMed

Song, Kwang Hoon; Lee, Jaehyun; Jung, Hong-Ryul; Park, HyoungJun; Doh, Junsang

2017-09-14

T cells navigate diverse microenvironments to perform immune responses. Micro-scale topographical structures within the tissues, which may inherently exist in normal tissues or may be formed by inflammation or injury, can influence T cell migration, but how T cell migration is affected by such topographical structures have not been investigated. In this study, we fabricated ramp-like structures with a 5 μm height and various slopes, and observed T cells climbing up the ramp-like structures. T cells encountering the ramp-like structures exhibited MLC accumulation near head-tail junctions contacting the ramp-like structures, and made turns to the direction perpendicular to the ramp-like structures. Pharmacological study revealed that lamellipodia formation mediated by arp2/3 and contractility regulated by myosin light chain kinase (MLCK) were responsible for the intriguing turning behavior of T cells climbing the ramp-like structures. Arp2/3 or MLCK inhibition substantially reduced probability of T cells climbing sharp-edged ramp-like structures, indicating intriguing turning behavior of T cells mediated by lamellipodia formation and MLCK activity may be important for T cells to access inflamed or injured tissues with abrupt topographical changes.

Corridors of migrating neurons in the human brain and their decline during infancy.

PubMed

Sanai, Nader; Nguyen, Thuhien; Ihrie, Rebecca A; Mirzadeh, Zaman; Tsai, Hui-Hsin; Wong, Michael; Gupta, Nalin; Berger, Mitchel S; Huang, Eric; Garcia-Verdugo, Jose-Manuel; Rowitch, David H; Alvarez-Buylla, Arturo

2011-09-28

The subventricular zone of many adult non-human mammals generates large numbers of new neurons destined for the olfactory bulb. Along the walls of the lateral ventricles, immature neuronal progeny migrate in tangentially oriented chains that coalesce into a rostral migratory stream (RMS) connecting the subventricular zone to the olfactory bulb. The adult human subventricular zone, in contrast, contains a hypocellular gap layer separating the ependymal lining from a periventricular ribbon of astrocytes. Some of these subventricular zone astrocytes can function as neural stem cells in vitro, but their function in vivo remains controversial. An initial report found few subventricular zone proliferating cells and rare migrating immature neurons in the RMS of adult humans. In contrast, a subsequent study indicated robust proliferation and migration in the human subventricular zone and RMS. Here we find that the infant human subventricular zone and RMS contain an extensive corridor of migrating immature neurons before 18 months of age but, contrary to previous reports, this germinal activity subsides in older children and is nearly extinct by adulthood. Surprisingly, during this limited window of neurogenesis, not all new neurons in the human subventricular zone are destined for the olfactory bulb--we describe a major migratory pathway that targets the prefrontal cortex in humans. Together, these findings reveal robust streams of tangentially migrating immature neurons in human early postnatal subventricular zone and cortex. These pathways represent potential targets of neurological injuries affecting neonates.

Silencing heat shock protein 27 (HSP27) inhibits the proliferation and migration of vascular smooth muscle cells in vitro.

PubMed

Huang, Jie; Xie, Liang-di; Luo, Li; Zheng, Su-Li; Wang, Hua-Jun; Xu, Chang-Sheng

2014-05-01

The objective of this study was to examine the role of heat shock protein 27 (HSP27) in proliferation and migration of vascular smooth muscle cells (VSMCs). Three complementary DNA sequences targeting rat HSP27 gene were designed, synthesized, and subcloned into lentiviral vector. The interfering efficiency was detected by reverse transcriptase-polymerase chain reaction and Western blot. Methyl thiazolyl tetrazolium bromide assay was used for examining cell proliferation. F-actin polymerization was detected by FITC-Phalloidin staining using confocal microscopy. Modified Boyden chamber technique was used to assess VSMCs migration. The recombinant lentivirus containing RNAi targeting HSP27 gene significantly inhibited expression of HSP27 at both mRNA and protein levels. The interfering efficiencies of pNL-HSP27-EGFP-1, pNL-HSP27-EGFP-2, and pNL-HSP27-EGFP-3 were 71 %, 77 %, and 43 %, respectively. Reorganization of actin stimulated by PDGF-BB was markedly blocked by pretreatment with pNL-HSP27-EGFP-2. Proliferation and migration rates of VSMCs induced by PDGF-BB were inhibited by 30.8 % and 45.6 %, respectively, by pNL-HSP27-EGFP-2 (all P < 0.01). To conclude, these data indicate that HSP27 may regulate the proliferation, actin reorganization, and the migration of VSMCs. RNAi targeting at HSP27 may be a potential approach for inhibition of cell migration involved in pathogenesis of proliferative vascular diseases.

Epidermal growth factor receptor expression is related to post-mitotic events in cerebellar development: regulation by thyroid hormone.

PubMed

Carrasco, Emilce; Blum, Mariann; Weickert, Cynthia Shannon; Casper, Diana

2003-01-10

It has been established that thyroid hormone and neurotrophic factors both orchestrate developmental events in the brain. However, it is not clear how these two influences are related. In this study, we investigated the effects of thyroid hormone on cerebellar development and the coincident expression of transforming growth factor-alpha (TGF-alpha), a ligand in the epidermal growth factor (EGF) family, and the epidermal growth factor receptor (EGFR). Profiles of thyroid hormone expression were measured in postnatal animals and were found to peak at postnatal day 15 (P15). These levels dropped below detectable levels when mice were made hypothyroid with propylthiouracil (PTU). TGF-alpha and EGFR expression, as determined by RNAse protection assay, was maximal at P6 in normal animals, but remained low in hypothyroid animals, suggesting that thyroid hormone was responsible for their induction. In situ hybridization and immunohistochemical analysis of EGFR expression revealed that this receptor was present on granule cells within the inner zone of the external granule cell layer (EGL), suggesting that EGFR-ligands were not inducing granule cell proliferation. The persistence of EGFR expression on migrating granule cells and subsequent down-regulation of expression in the internal granule cell layer (IGL) implicates a role for EGFR-ligands in differentiation and/or migration. In hypothyroid animals, we observed a delayed progression of granule cell migration, consistent with the persistence of EGFR labeling in the EGL, and in the 'pile-up' of labeled cells at the interface between the molecular layer and the Purkinje cell layer. Taken together, these results implicate thyroid hormone in the coordinated expression of TGF-alpha and EGFR, which are positioned to play a role in post-mitotic developmental events in the cerebellum.

Reoccurrence of Avian Influenza A(H5N2) Virus Clade 2.3.4.4 in Wild Birds, Alaska, USA, 2016.

PubMed

Lee, Dong-Hun; Torchetti, Mia K; Killian, Mary Lea; DeLiberto, Thomas J; Swayne, David E

2017-02-01

We report reoccurrence of highly pathogenic avian influenza A(H5N2) virus clade 2.3.4.4 in a wild mallard in Alaska, USA, in August 2016. Identification of this virus in a migratory species confirms low-frequency persistence in North America and the potential for re-dissemination of the virus during the 2016 fall migration.

Human papillomavirus-exposed Langerhans cells are activated by stabilized Poly-I:C.

PubMed

Da Silva, Diane M; Woodham, Andrew W; Rijkee, Laurie K; Skeate, Joseph G; Taylor, Julia R; Koopman, Maaike E; Brand, Heike E; Wong, Michael K; McKee, Greg M; Salazar, Andres M; Kast, W Martin

2015-12-01

Human papillomaviruses (HPV) establish persistent infections because of evolved immune evasion mechanisms, particularly HPV-mediated suppression of the immune functions of Langerhans cells (LC), the antigen presenting cells of the epithelium. Polyinosinic-polycytidilic acid (Poly-I:C) is broadly immunostimulatory with the ability to enhance APC expression of costimulatory molecules and inflammatory cytokines resulting in T cell activation. Here we investigated the activation of primary human LC derived from peripheral blood monocytes after exposure to HPV16 virus like particles followed by treatment with stabilized Poly-I:C compounds (s-Poly-I:C), and their subsequent induction of HPV16-specific T cells. Our results indicate that HPV16 particles alone were incapable of inducing LC activation as demonstrated by the lack of costimulatory molecules, inflammatory cytokines, chemokine-directed migration, and HPV16-specific CD8 + T cells in vitro . Conversely, s-Poly-I:C caused significant upregulation of costimulatory molecules and induction of chemokine-directed migration of LC that were pre-exposed to HPV16. In HLA-A*0201-positive donors, s-Poly-I:C treatment was able to induce CD8 + T cell immune responses against HPV16-derived peptides. Thus, s-Poly-I:C compounds are attractive for translation into therapeutics in which they could potentially mediate clearance of persistent HPV infection.

Katrina in Historical Context: Environment and Migration in the U.S

PubMed Central

Gutmann, Myron P.; Field, Vincenzo

2010-01-01

The massive publicity surrounding the exodus of residents from New Orleans spurred by Hurricane Katrina has encouraged interest in the ways that past migration in the U.S. has been shaped by environmental factors. So has Timothy Egan’s exciting book, The Worst Hard Time: The Untold Story of those who survived the Great American Dust Bowl. This paper places those dramatic stories into a much less exciting context, demonstrating that the kinds of environmental factors exemplified by Katrina and the Dust Bowl are dwarfed in importance and frequency by the other ways that environment has both impeded and assisted the forces of migration. We accomplish this goal by enumerating four types of environmental influence on migration in the U.S.: 1) environmental calamities, including floods, hurricanes, earthquakes, and tornadoes, 2) environmental hardships and their obverse, short-term environmental benefits, including both drought and short periods of favorable weather, 3) environmental amenities, including warmth, sun, and proximity to water or mountains, and 4) environmental barriers and their management, including heat, air conditioning, flood control, drainage, and irrigation. In U.S. history, all four of these have driven migration flows in one direction or another. Placing Katrina into this historical context is an important task, both because the environmental calamities of which Katrina is an example are relatively rare and have not had a wide impact, and because focusing on them defers interest from the other kinds of environmental impacts, whose effect on migration may have been stronger and more persistent, though less dramatic. PMID:20436951

Ireland's medical brain drain: migration intentions of Irish medical students.

PubMed

Gouda, Pishoy; Kitt, Kevin; Evans, David S; Goggin, Deirdre; McGrath, Deirdre; Last, Jason; Hennessy, Martina; Arnett, Richard; O'Flynn, Siun; Dunne, Fidelma; O'Donovan, Diarmuid

2015-03-12

To provide the optimum level of healthcare, it is important that the supply of well-trained doctors meets the demand. However, despite many initiatives, Ireland continues to have a shortfall of physicians, which has been projected to persist. Our study aimed to investigate the migration intentions of Irish medical students and identify the factors that influence their decisions in order to design appropriate interventions to sustain the supply of trained doctors in order to maintain a viable medical system. An online cross-sectional survey was undertaken of all Irish medical students studying in the Republic of Ireland. The survey included nominal, ordinal, and scale items to determine migration intentions, factors influencing their decisions, and understanding of the Irish healthcare system. A total of 2 273 medical students responded (37% response rate), of whom 1 519 were classified as Irish medical students (having completed secondary school in Ireland). Of these, 88% indicated they were either definitely migrating or contemplating migrating following graduation or completion of the pre-registration intern year. Forty percent expressed an intention of returning to Ireland within 5 years. The factors most influencing their decision to leave were career opportunities (85%), working conditions (83%), and lifestyle (80%). The migration intentions expressed in this study predict an immediate and severe threat to the sustainability of the Irish healthcare service. Urgent interventions such as providing information about career options and specialty training pathways are required. These must begin in the undergraduate phase and continue in postgraduate training and are needed to retain medical school graduates.

A dual-docking microfluidic cell migration assay (D2-Chip) for testing neutrophil chemotaxis and the memory effect.

PubMed

Yang, Ke; Wu, Jiandong; Xu, Guoqing; Xie, Dongxue; Peretz-Soroka, Hagit; Santos, Susy; Alexander, Murray; Zhu, Ling; Zhang, Michael; Liu, Yong; Lin, Francis

2017-04-18

Chemotaxis is a classic mechanism for guiding cell migration and an important topic in both fundamental cell biology and health sciences. Neutrophils are a widely used model to study eukaryotic cell migration and neutrophil chemotaxis itself can lead to protective or harmful immune actions to the body. While much has been learnt from past research about how neutrophils effectively navigate through a chemoattractant gradient, many interesting questions remain unclear. For example, while it is tempting to model neutrophil chemotaxis using the well-established biased random walk theory, the experimental proof was challenged by the cell's highly persistent migrating nature. A special experimental design is required to test the key predictions from the random walk model. Another question that has interested the cell migration community for decades concerns the existence of chemotactic memory and its underlying mechanism. Although chemotactic memory has been suggested in various studies, a clear quantitative experimental demonstration will improve our understanding of the migratory memory effect. Motivated by these questions, we developed a microfluidic cell migration assay (so-called dual-docking chip or D 2 -Chip) that can test both the biased random walk model and the memory effect for neutrophil chemotaxis on a single chip enabled by multi-region gradient generation and dual-region cell alignment. Our results provide experimental support for the biased random walk model and chemotactic memory for neutrophil chemotaxis. Quantitative data analyses provide new insights into neutrophil chemotaxis and memory by making connections to entropic disorder, cell morphology and oscillating migratory response.

Dominant frequency increase rate predicts transition from paroxysmal to long-term persistent atrial fibrillation.

PubMed

Martins, Raphael P; Kaur, Kuljeet; Hwang, Elliot; Ramirez, Rafael J; Willis, B Cicero; Filgueiras-Rama, David; Ennis, Steven R; Takemoto, Yoshio; Ponce-Balbuena, Daniela; Zarzoso, Manuel; O'Connell, Ryan P; Musa, Hassan; Guerrero-Serna, Guadalupe; Avula, Uma Mahesh R; Swartz, Michael F; Bhushal, Sandesh; Deo, Makarand; Pandit, Sandeep V; Berenfeld, Omer; Jalife, José

2014-04-08

Little is known about the mechanisms underlying the transition from paroxysmal to persistent atrial fibrillation (AF). In an ovine model of long-standing persistent AF we tested the hypothesis that the rate of electric and structural remodeling, assessed by dominant frequency (DF) changes, determines the time at which AF becomes persistent. Self-sustained AF was induced by atrial tachypacing. Seven sheep were euthanized 11.5±2.3 days after the transition to persistent AF and without reversal to sinus rhythm; 7 sheep were euthanized after 341.3±16.7 days of long-standing persistent AF. Seven sham-operated animals were in sinus rhythm for 1 year. DF was monitored continuously in each group. Real-time polymerase chain reaction, Western blotting, patch clamping, and histological analyses were used to determine the changes in functional ion channel expression and structural remodeling. Atrial dilatation, mitral valve regurgitation, myocyte hypertrophy, and atrial fibrosis occurred progressively and became statistically significant after the transition to persistent AF, with no evidence for left ventricular dysfunction. DF increased progressively during the paroxysmal-to-persistent AF transition and stabilized when AF became persistent. Importantly, the rate of DF increase correlated strongly with the time to persistent AF. Significant action potential duration abbreviation, secondary to functional ion channel protein expression changes (CaV1.2, NaV1.5, and KV4.2 decrease; Kir2.3 increase), was already present at the transition and persisted for 1 year of follow up. In the sheep model of long-standing persistent AF, the rate of DF increase predicts the time at which AF stabilizes and becomes persistent, reflecting changes in action potential duration and densities of sodium, L-type calcium, and inward rectifier currents.

Genome-wide-analyses of Listeria monocytogenes from food-processing plants reveal clonal diversity and date the emergence of persisting sequence types.

PubMed

Knudsen, Gitte M; Nielsen, Jesper Boye; Marvig, Rasmus L; Ng, Yin; Worning, Peder; Westh, Henrik; Gram, Lone

2017-08-01

Whole genome sequencing is increasing used in epidemiology, e.g. for tracing outbreaks of food-borne diseases. This requires in-depth understanding of pathogen emergence, persistence and genomic diversity along the food production chain including in food processing plants. We sequenced the genomes of 80 isolates of Listeria monocytogenes sampled from Danish food processing plants over a time-period of 20 years, and analysed the sequences together with 10 public available reference genomes to advance our understanding of interplant and intraplant genomic diversity of L. monocytogenes. Except for three persisting sequence types (ST) based on Multi Locus Sequence Typing being ST7, ST8 and ST121, long-term persistence of clonal groups was limited, and new clones were introduced continuously, potentially from raw materials. No particular gene could be linked to the persistence phenotype. Using time-based phylogenetic analyses of the persistent STs, we estimate the L. monocytogenes evolutionary rate to be 0.18-0.35 single nucleotide polymorphisms/year, suggesting that the persistent STs emerged approximately 100 years ago, which correlates with the onset of industrialization and globalization of the food market. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

Increased mitochondrial functions in human glioblastoma cells persistently infected with measles virus.

PubMed

Takahashi, Megumi; Wolf, Alexander M; Watari, Eiji; Norose, Yoshihiko; Ohta, Shigeo; Takahashi, Hidemi

2013-09-01

Measles virus (MV) is known for its ability to cause an acute infection with a potential of development of persistent infection. However, knowledge of how viral genes and cellular factors interact to cause or maintain the persistent infection has remained unclear. We have previously reported the possible involvement of mitochondrial short chain enoyl-CoA hydratase (ECHS), which is localized at mitochondria, in the regulation of MV replication. In this study we found increased functions of mitochondria in MV-persistently infected cells compared with uninfected or acutely infected cells. Furthermore, impairment of mitochondrial functions by treatment with mitochondrial inhibitors such as ethidium bromide (EtBr) or carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) induced the cytopathic effects of extensive syncytial formation in persistently infected cells. These findings suggest that mitochondria are one of the subcellular organelles contributing to regulate persistent infection of MV. Recent studies showed mitochondria provide an integral platform for retinoic acid-inducible protein (RIG-I)-like cytosolic receptors (RLRs) signaling and participate in cellular innate antiviral immunity. Our findings not only reveal a role of mitochondria in RLR mediated antiviral signaling but also suggest that mitochondria contribute to the regulation of persistent viral infection. Copyright © 2013 Elsevier B.V. All rights reserved.

The snakelike chain character of unstructured RNA.

PubMed

Jacobson, David R; McIntosh, Dustin B; Saleh, Omar A

2013-12-03

In the absence of base-pairing and tertiary structure, ribonucleic acid (RNA) assumes a random-walk conformation, modulated by the electrostatic self-repulsion of the charged, flexible backbone. This behavior is often modeled as a Kratky-Porod "wormlike chain" (WLC) with a Barrat-Joanny scale-dependent persistence length. In this study we report measurements of the end-to-end extension of poly(U) RNA under 0.1 to 10 pN applied force and observe two distinct elastic-response regimes: a low-force, power-law regime characteristic of a chain of swollen blobs on long length scales and a high-force, salt-valence-dependent regime consistent with ion-stabilized crumpling on short length scales. This short-scale structure is additionally supported by force- and salt-dependent quantification of the RNA ion atmosphere composition, which shows that ions are liberated under stretching; the number of ions liberated increases with increasing bulk salt concentration. Both this result and the observation of two elastic-response regimes directly contradict the WLC model, which predicts a single elastic regime across all forces and, when accounting for scale-dependent persistence length, the opposite trend in ion release with salt concentration. We conclude that RNA is better described as a "snakelike chain," characterized by smooth bending on long length scales and ion-stabilized crumpling on short length scales. In monovalent salt, these two regimes are separated by a characteristic length that scales with the Debye screening length, highlighting the determining importance of electrostatics in RNA conformation. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Spindle pole body-anchored Kar3 drives the nucleus along microtubules from another nucleus in preparation for nuclear fusion during yeast karyogamy.

PubMed

Gibeaux, Romain; Politi, Antonio Z; Nédélec, François; Antony, Claude; Knop, Michael

2013-02-01

Nuclear migration during yeast karyogamy, termed nuclear congression, is required to initiate nuclear fusion. Congression involves a specific regulation of the microtubule minus end-directed kinesin-14 motor Kar3 and a rearrangement of the cytoplasmic microtubule attachment sites at the spindle pole bodies (SPBs). However, how these elements interact to produce the forces necessary for nuclear migration is less clear. We used electron tomography, molecular genetics, quantitative imaging, and first principles modeling to investigate how cytoplasmic microtubules are organized during nuclear congression. We found that Kar3, with the help of its light chain, Cik1, is anchored during mating to the SPB component Spc72 that also serves as a nucleator and anchor for microtubules via their minus ends. Moreover, we show that no direct microtubule-microtubule interactions are required for nuclear migration. Instead, SPB-anchored Kar3 exerts the necessary pulling forces laterally on microtubules emanating from the SPB of the mating partner nucleus. Therefore, a twofold symmetrical application of the core principle that drives nuclear migration in higher cells is used in yeast to drive nuclei toward each other before nuclear fusion.

Spindle pole body-anchored Kar3 drives the nucleus along microtubules from another nucleus in preparation for nuclear fusion during yeast karyogamy

PubMed Central

Gibeaux, Romain; Politi, Antonio Z.; Nédélec, François; Antony, Claude; Knop, Michael

2013-01-01

Nuclear migration during yeast karyogamy, termed nuclear congression, is required to initiate nuclear fusion. Congression involves a specific regulation of the microtubule minus end-directed kinesin-14 motor Kar3 and a rearrangement of the cytoplasmic microtubule attachment sites at the spindle pole bodies (SPBs). However, how these elements interact to produce the forces necessary for nuclear migration is less clear. We used electron tomography, molecular genetics, quantitative imaging, and first principles modeling to investigate how cytoplasmic microtubules are organized during nuclear congression. We found that Kar3, with the help of its light chain, Cik1, is anchored during mating to the SPB component Spc72 that also serves as a nucleator and anchor for microtubules via their minus ends. Moreover, we show that no direct microtubule–microtubule interactions are required for nuclear migration. Instead, SPB-anchored Kar3 exerts the necessary pulling forces laterally on microtubules emanating from the SPB of the mating partner nucleus. Therefore, a twofold symmetrical application of the core principle that drives nuclear migration in higher cells is used in yeast to drive nuclei toward each other before nuclear fusion. PMID:23388829

Epac1 increases migration of endothelial cells and melanoma cells via FGF2-mediated paracrine signaling

PubMed Central

Baljinnyam, Erdene; Umemura, Masanari; Chuang, Christine; De Lorenzo, Mariana S; Iwatsubo, Mizuka; Chen, Suzie; Goydos, James S; Ishikawa, Yoshihiro; Whitelock, John M; Iwatsubo, Kousaku

2014-01-01

Fibroblast growth factor (FGF2) regulates endothelial and melanoma cell migration. The binding of FGF2 to its receptor requires N-sulfated heparan sulfate (HS) glycosamine. We have previously reported that Epac1, an exchange protein activated by cAMP, increases N-sulfation of HS in melanoma. Therefore, we examined whether Epac1 regulates FGF2-mediated cell–cell communication. Conditioned medium (CM) of melanoma cells with abundant expression of Epac1 increased migration of human umbilical endothelial cells (HUVEC) and melanoma cells with poor expression of Epac1. CM-induced increase in migration was inhibited by antagonizing FGF2, by the removal of HS and by the knockdown of Epac1. In addition, knockdown of Epac1 suppressed the binding of FGF2 to FGF receptor in HUVEC, and in vivo angiogenesis in melanoma. Furthermore, knockdown of Epac1 reduced N-sulfation of HS chains attached to perlecan, a major secreted type of HS proteoglycan that mediates the binding of FGF2 to FGF receptor. These data suggested that Epac1 in melanoma cells regulates melanoma progression via the HS–FGF2-mediated cell–cell communication. PMID:24725364

From cell differentiation to cell collectives: Bacillus subtilis uses division of labor to migrate.

PubMed

van Gestel, Jordi; Vlamakis, Hera; Kolter, Roberto

2015-04-01

The organization of cells, emerging from cell-cell interactions, can give rise to collective properties. These properties are adaptive when together cells can face environmental challenges that they separately cannot. One particular challenge that is important for microorganisms is migration. In this study, we show how flagellum-independent migration is driven by the division of labor of two cell types that appear during Bacillus subtilis sliding motility. Cell collectives organize themselves into bundles (called "van Gogh bundles") of tightly aligned cell chains that form filamentous loops at the colony edge. We show, by time-course microscopy, that these loops migrate by pushing themselves away from the colony. The formation of van Gogh bundles depends critically on the synergistic interaction of surfactin-producing and matrix-producing cells. We propose that surfactin-producing cells reduce the friction between cells and their substrate, thereby facilitating matrix-producing cells to form bundles. The folding properties of these bundles determine the rate of colony expansion. Our study illustrates how the simple organization of cells within a community can yield a strong ecological advantage. This is a key factor underlying the diverse origins of multicellularity.

From Cell Differentiation to Cell Collectives: Bacillus subtilis Uses Division of Labor to Migrate

PubMed Central

van Gestel, Jordi; Vlamakis, Hera; Kolter, Roberto

2015-01-01

The organization of cells, emerging from cell–cell interactions, can give rise to collective properties. These properties are adaptive when together cells can face environmental challenges that they separately cannot. One particular challenge that is important for microorganisms is migration. In this study, we show how flagellum-independent migration is driven by the division of labor of two cell types that appear during Bacillus subtilis sliding motility. Cell collectives organize themselves into bundles (called “van Gogh bundles”) of tightly aligned cell chains that form filamentous loops at the colony edge. We show, by time-course microscopy, that these loops migrate by pushing themselves away from the colony. The formation of van Gogh bundles depends critically on the synergistic interaction of surfactin-producing and matrix-producing cells. We propose that surfactin-producing cells reduce the friction between cells and their substrate, thereby facilitating matrix-producing cells to form bundles. The folding properties of these bundles determine the rate of colony expansion. Our study illustrates how the simple organization of cells within a community can yield a strong ecological advantage. This is a key factor underlying the diverse origins of multicellularity. PMID:25894589

Mesenchymal chemotaxis requires selective inactivation of Myosin II at the leading edge via a non-canonical PLCγ/PKCα pathway

PubMed Central

Asokan, Sreeja B.; Johnson, Heath E.; Rahman, Anisur; King, Samantha J.; Rotty, Jeremy D.; Lebedeva, Irina P.; Haugh, Jason M.; Bear, James E.

2014-01-01

Summary Chemotaxis, migration towards soluble chemical cues, is critical for processes such as wound healing and immune surveillance, and is exhibited by various cell types from rapidly-migrating leukocytes to slow-moving mesenchymal cells. To interrogate the mechanisms involved in mesenchymal chemotaxis, we observed cell migration in microfluidic chambers that generate stable gradients of the chemoattractant PDGF. Surprisingly, we found that pathways implicated in amoeboid chemotaxis, such as PI3K and mTOR signaling, are dispensable for chemotaxis to PDGF. Instead, we find that local inactivation of Myosin IIA, through a non-canonical Ser1/2 phosphorylation of the regulatory light chain, is essential. This site is phosphorylated by PKCα, which is activated by an intracellular gradient of diacylglycerol generated by PLCγ. Using a combination of TIRF imaging and gradients of activators/inhibitors in the microfluidic chambers, we demonstrate that this signaling pathway and subsequent inhibition of Myosin II activity at the leading edge is required for mesenchymal chemotaxis. PMID:25482883

Preparation of a cell line persistently infected with maedi/visna virus and production of viral antigens.

PubMed

Suzuki, Kazuya; Oguma, Keisuke; Sentsui, Hiroshi

2017-01-20

We attempted to prepare a cell line that produces maedi/visna virus (MVV) and is free of contamination by other viruses and mycoplasmas. Three cell lines, which originated from a sheep, goat and bat, were infected with MVV and passaged approximately every 5 days. The cultured cells were then subjected to polymerase chain reaction analysis for MVV provirus. As a result, a cell line persistently infected with MVV was established from ZZ-R cells, which originated from the fetal goat tongue. The 50-fold concentrated culture fluid formed a precipitation line against reference antiserum.

Coastal-change impacts during hurricane katrina: an overview

USGS Publications Warehouse

Sallenger, Asbury; Wright, C. Wayne; Lillycrop, Jeff

2007-01-01

As part of an ongoing cooperative effort between USGS, NASA and USACE, the barrier islands within the right-front quadrant of Hurricane Katrina were surveyed with airborne lidar both before and after landfall. Dauphin Island, AL was located the farthest from landfall and wave runup intermittently overtopped its central and western sections. The Gulf-side of the island experienced severe erosion, leaving the first row of houses in the sea, while the bayside accreted. In contrast, the Chandeleur Islands, LA did not experience, this classic `rollover'. Rather, the island chain was completely stripped of sand, transforming a 40-km-long sandy island chain into a discontinuous series of muddy marsh islets. Models indicate that storm surge likely submerged the entire Chandeleur Island chain, at least during the latter part of the storm. The net result was destructive coastal change for the Chandeleur Islands, while Dauphin Island tended to maintain its form through landward migration.

ONE FISH, TWO FISH, RED FISH, BLUE FISH: THE FISH QUALITY INDEX AS A RISK COMMUNICATION TOOL

EPA Science Inventory

Many people are at high risk for methyl mercury toxicity because of their consumption of contaminated fish. Often health risks of Persistent Bioaccumulative Toxicants (PT) such as methyl mercury, PCBs or Dioxins are underestimated because of their amplification in the food chain ...

Non-Leaching, Benign, Fouling Control, Multilayer Polymer Coatings for Marine Applications: PP-1274 Findings

DTIC Science & Technology

2003-09-01

transition temperature TBT tributyltin THF tetrahydrofuran TPE thermoplastic elastomer 4 EXECUTIVE SUMMARY The goal of this research is to...compounds that are environmentally persistant cause damage to the ecosystem, and enter the food chain. The ban on tributyltin ( TBT ) antifoulants by the

MONITORING ASPERGILLUS SPECIES BY QUANTITATIVE PCR DURING CONSTRUCTION OF A MULTI-STORY HOSPITAL BUILDING

EPA Science Inventory

Noscomial fungal infections represent a persistent threat in hospitals. One of the major issues in fungal control has been monitoring these fungi in a timely manner. Quantitative polymerase chain reaction (QPCR) allows for the rapid (2 to 4 h), sensitive (often down to a single...

Nitric oxide donor up-regulation of SDF1/CXCR4 and Ang1/Tie2 promotes neuroblast cell migration after stroke.

PubMed

Cui, Xu; Chen, Jieli; Zacharek, Alex; Roberts, Cynthia; Yang, Yuping; Chopp, Michael

2009-01-01

We tested the hypothesis that a nitric oxide donor, DETA-NONOate, up-regulates stromal cell-derived factor-1 (SDF1) and angiopoietin 1 (Ang1) in the ischemic brain and their respective receptors chemokine CXC motif receptor 4 (CXCR4) and Tie2 in the subventricular zone (SVZ) and thereby promote SVZ neuroblast cell migration after stroke. C57BL/6J mice were subjected to middle cerebral artery occlusion (MCAo), and 24 hr later DETA-NONOate (0.4 mg/kg) or phosphate-buffered solution was intravenously administered. Mice were sacrificed at 14 days for histological assessment or sacrificed at 3 days for analysis by real-time polymerase chain reaction and migration after MCAo. To elucidate whether SDF1/CXCR4 and Ang1/Tie2 pathways mediate DETA-NONOate-induced SVZ migration after stroke, SDF1alpha, Ang1 peptide, a specific antagonist of CXCR4 (AMD3100), and a neutralizing antibody of Tie2 (anti-Tie2) were used in vitro. DETA-NONOate significantly increased the percentage area of doublecortin (DCX, a marker of migrating neuroblasts)-immunoreactive cells in the SVZ and ischemic boundary zone. DETA-NONOate significantly increased the expression of SDF1 and Ang1 in the ischemic border and up-regulated CXCR4 and Tie2 in the SVZ compared with MCAo control. DCX-positive cell migration from SVZ explants was significantly increased in the DETA-NONOate treatment group compared with MCAo-alone animals. In vitro, SDF1alpha and Ang1 significantly increased SVZ explants cell migration. In addition, inhibition of CXCR4 or Tie2 significantly attenuated DETA-NONOate-induced SVZ cell migration. Our data indicate that treatment of stroke with a nitric oxide donor up-regulates SDF1/CXCR4 and Ang1/Tie2 pathways and thereby likely increases SVZ neuroblast cell migration. 2008 Wiley-Liss, Inc.

Nitric Oxide Donor Upregulation of SDF1/CXCR4 and Ang1/Tie2 Promotes Neuroblast Cell Migration After Stroke

PubMed Central

Cui, Xu; Chen, Jieli; Zacharek, Alex; Roberts, Cynthia; Yang, Yuping; Chopp, Michael

2008-01-01

We tested the hypothesis that a nitric oxide donor, DETA-NONOate upregulates Stromal cell-Derived Factor-1 (SDF1) and Angiopoietin 1 (Ang1) in the ischemic brain and their, respective, receptors chemokine CXC motif receptor 4 (CXCR4) and Tie2 in the subventricular zone (SVZ) and thereby promote SVZ neuroblast cell migration after stroke. C57BL/6J mice were subjected to middle cerebral artery occlusion (MCAo) and 24 hours later DETA-NONOate (0.4 mg/kg) or phosphate buffered solution were intravenously administered. Mice were sacrificed at 14 days for histological assessment or sacrificed at 3 days for analysis real-time polymerase chain reaction and migration after MCAo. To elucidate whether SDF1/CXCR4 and Ang1/Tie2 pathways mediate DETA-NONOate induced SVZ migration after stroke, SDF1α, Ang1 peptide and a specific antagonist of CXCR4 (AMD3100) and a neutralizing antibody of Tie2 (anti-Tie2) were used in vitro. DETA-NONOate significantly increased the percent area of doublecortin (a marker of migrating neuroblasts) immunoreactive-cells in the SVZ and ischemic boundary zone. DETA-NONOate significantly increased the expression of SDF1 and Ang1 in the ischemic border and upregulated CXCR4 and Tie2 in the SVZ compared with MCAo control. DCX-positive cell migration from SVZ explants was significantly increased in the DETA-NONOate treatment group compared with MCAo alone animals. In vitro, SDF1α and Ang1 significantly increased SVZ explants cell migration. In addition, inhibition of CXCR4 or Tie2 significantly attenuated DETA-NONOate induced SVZ cell migration. Our data indicated that treatment of stroke with a nitric oxide donor upregulates SDF1/CXCR4 and Ang1/Tie2 pathways and thereby likely increases SVZ neuroblast cell migration. PMID:18711749

The costs and benefits of nurse migration on families: A Lesotho experience.

PubMed

Ntlale, Matsola E; Duma, Sinegugu E

2012-02-22

The present day migration of nurses from developing countries, to more developed countries,depletes these countries of this vital human resource, which is necessary to provide optimum quality nursing care to their populations. If nurse migration persists, the health systems of these countries face collapse.It is important that a nurse understands the costs and benefits of migration to their families, whom they leave behind. This is not only to curb the problems that may occur, but to help the migrant nurses to realise how migration affects their families, especially their children and spouses, before they decide to leave their home countries to work in foreign lands.The purpose of this study, which was exploratory, descriptive and qualitative, was to investigate and describe the experiences of family members, of migrant nurses, from the Maseru district of Lesotho, about the costs and benefits of nurse migration. The objectives were to explore and describe the disadvantageous costs and the benefits gained by the families of migrant nurses. These were explored through the research question 'What are the experiences of family members of migrating nurses with regard to the costs and benefits of nurse migration?'The target population of the study was families of migrant nurses from Lesotho. Using purposive sampling the families of two migrant nurses, who were colleagues of the researcher, were identified and approached to participate in the study. Snowball sampling was next utilised to recruit the remainder of the participants. In total, six families were identified and included in the study.The semi-structured interviews and field notes were the two data collection methods that were implemented. The Giorgi's (1970) steps for data analysis, as outlined in (Burns & Grove 2001:610), were followed and seven themes were discovered as findings. The themes that relate to the costs of nurse migration are: emotional instability, weaker family connections and increased responsibility. The themes that relate to the benefits of nurse migration for their families are: better household income, improved quality of life, essential skills development and travelling opportunities.The use of communication technology is recommended to increase contact across borders in order to reduce the emotional costs of nurse migration on the families of migrant nurses. The article provides a balanced view of the costs and benefits of nurse migration on their families.

Intractable duodenal ulcer caused by transmural migration of gossypiboma into the duodenum - a case report and literature review

PubMed Central

2014-01-01

Background Gossypiboma is a term used to describe a mass that forms around a cotton sponge or abdominal compress accidentally left in a patient during surgery. Transmural migration of an intra-abdominal gossypiboma has been reported to occur in the digestive tract, bladder, vagina and diaphragm. Open surgery is the most common approach in the treatment of gossypiboma. However, gossypibomas can be extracted by endoscopy while migrating into the digestive tract. We report a case of intractable duodenal ulcer caused by transmural migration of gossypiboma successfully treated by duodenorrhaphy. A systemic literature review is provided and a scheme of the therapeutic approach is proposed. Case presentation A 61-year-old Han Chinese man presented with intermittent epigastric pain for the last 10 months. He had undergone laparoscopic cholecystectomy conversion to open cholecystectomy for acute gangrenous cholecystitis 10 months ago at another hospital. Transmural migration of gossypiboma into the duodenum was found. Endoscopic intervention failed to remove the entire gauze, and duodenal ulcer caused by the gauze persisted. Surgical intervention was performed and the gauze was removed successfully. The penetrated ulcer was repaired with duodenorrhaphy. The postoperative period was uneventful. We systematically reviewed the literature on transmural migration of gossypiboma into duodenum and present an overview of published cases. Our PubMed search yielded seven reports of transmural migration of retained surgical sponge into the duodenum. Surgical interventions were necessary in two patients. Conclusion Transmural migration of gossypiboma into the duodenum is a rare surgical complication. The treatment strategies include endoscopic extraction and surgical intervention. Prompt surgical intervention should be considered for emergent conditions such as active bleeding, gastrointestinal obstruction, or intra-abdominal sepsis. For non-emergent conditions, surgical intervention could be considered for intractable cases in which endoscopic extraction failed. PMID:24917191

Compositional shifts in Costa Rican forests due to climate-driven species migrations.

PubMed

Feeley, Kenneth J; Hurtado, Johanna; Saatchi, Sassan; Silman, Miles R; Clark, David B

2013-11-01

Species are predicted to shift their distributions upslope or poleward in response to global warming. This prediction is supported by a growing number of studies documenting species migrations in temperate systems but remains poorly tested for tropical species, and especially for tropical plant species. We analyzed changes in tree species composition in a network of 10 annually censused 1-ha plots spanning an altitudinal gradient of 70-2800 m elevation in Costa Rica. Specifically, we combined plot data with herbarium records (accessed through GBIF) to test if the plots' community temperature scores (CTS, average thermal mean of constituent species weighted by basal area) have increased over the past decade as is predicted by climate-driven species migrations. In addition, we quantified the contributions of stem growth, recruitment, and mortality to the observed patterns. Supporting our a priori hypothesis of upward species migrations, we found that there have been consistent directional shifts in the composition of the plots, such that the relative abundance of lowland species, and hence CTS, increased in 90% of plots. The rate of the observed compositional shifts corresponds to a mean thermal migration rate (TMR) of 0.0065 °C yr(-1) (95% CI = 0.0005-0.0132 °C yr(-1) ). While the overall TMR is slower than predicted based on concurrent regional warming of 0.0167 °C yr(-1) , migrations were on pace with warming in 4 of the 10 plots. The observed shifts in composition were driven primarily by mortality events (i.e., the disproportionate death of highland vs. lowland species), suggesting that individuals of many tropical tree species will not be able to tolerate future warming and thus their persistence in the face of climate change will depend on successful migrations. Unfortunately, in Costa Rica and elsewhere, land area inevitably decreases at higher elevations; hence, even species that are able to migrate successfully will face heightened risks of extinction. © 2013 John Wiley & Sons Ltd.

Chain migration through the social network: experience of labour migrants in Kuwait.

PubMed

Shah, N M; Menon, I

1999-01-01

"Labour migration to the Gulf countries is predominantly contract based and a majority of workers fall below the salary ceiling necessary for sponsoring family members. Despite this, social networks have expanded in Kuwait, primarily in the form of sponsorship of additional labour migrants by those already in the country. The objectives of the article are to describe how the process of arranging sponsorship works, to delineate the predictors of moving through a friend or relative, or arranging sponsorship for a subsequent labour migrant, and to assess the ¿multiplier' effect of the above process. The article is based on a survey among 800 South Asian skilled and unskilled male migrants, 200 each from Bangladesh, India, Pakistan and Sri Lanka." (EXCERPT)

Analytical cell adhesion chromatography reveals impaired persistence of metastatic cell rolling adhesion to P-selectin

PubMed Central

Oh, Jaeho; Edwards, Erin E.; McClatchey, P. Mason; Thomas, Susan N.

2015-01-01

ABSTRACT Selectins facilitate the recruitment of circulating cells from the bloodstream by mediating rolling adhesion, which initiates the cell–cell signaling that directs extravasation into surrounding tissues. To measure the relative efficiency of cell adhesion in shear flow for in vitro drug screening, we designed and implemented a microfluidic-based analytical cell adhesion chromatography system. The juxtaposition of instantaneous rolling velocities with elution times revealed that human metastatic cancer cells, but not human leukocytes, had a reduced capacity to sustain rolling adhesion with P-selectin. We define a new parameter, termed adhesion persistence, which is conceptually similar to migration persistence in the context of chemotaxis, but instead describes the capacity of cells to resist the influence of shear flow and sustain rolling interactions with an adhesive substrate that might modulate the probability of extravasation. Among cell types assayed, adhesion persistence to P-selectin was specifically reduced in metastatic but not leukocyte-like cells in response to a low dose of heparin. In conclusion, we demonstrate this as an effective methodology to identify selectin adhesion antagonist doses that modulate homing cell adhesion and engraftment in a cell-subtype-selective manner. PMID:26349809

[The new migratory deal in Southern Europe].

PubMed

Simon, G

1986-09-01

The author examines migration patterns in Southern Europe during the 1970s and early 1980s, noting particularly the reduction in migration northward from this region. It is noted that "departure potential remains sizable in certain areas of Portugal, Spain, Southern Italy, and most particularly, of Turkey and Yugoslavia. Transoceanic migrations have by no means ceased, as new flows of skilled labor have, since 1974, gone towards Arab states endowed with petrol (oil) revenues. And yet, the paramount fact is most surely the emergence and the proliferation in Greece, Spain, and (especially) in Italy, of basically clandestine (illegal) immigration. This movement is due to the convergence of several factors: economic and demographic disparities between northern and southern shores of the Mediterranean Sea, the sealing-off of borders in Northwestern Europe and the 'carry-over' effect upon nations of 'transit', the extent of the flow of refugees, and--most particularly--the appeal provided by the development, in these new employer countries, of an underground economy accompanied by the extension into industry of the practice of 'undeclared' work. And notwithstanding the series of rules lastly drawn up in Spain and in Greece, such forms of clandestine (unauthorized) migration appear highly likely--to say the least--to persist." (SUMMARY IN ENG AND SPA) excerpt

Integrin activation by a cold atmospheric plasma jet

NASA Astrophysics Data System (ADS)

Volotskova, Olga; Stepp, Mary Ann; Keidar, Michael

2012-05-01

Current breakthrough research on cold atmospheric plasma (CAP) demonstrates that CAP has great potential in various areas, including medicine and biology, thus providing a new tool for living tissue treatment. In this paper, we explore potential mechanisms by which CAP alters cell migration and influences cell adhesion. We focus on the study of CAP interaction with fibroblasts and corneal epithelial cells. The data show that fibroblasts and corneal epithelial cells have different thresholds (treatment times) required to achieve maximum inhibition of cell migration. Both cell types reduced their migration rates by ˜30-40% after CAP compared to control cells. Also, the impact of CAP treatment on cell migration and persistence of fibroblasts after integrin activation by MnCl2, serum starvation or replating cells onto surfaces coated with integrin ligands is assessed; the results show that activation by MnCl2 or starvation attenuates cells’ responses to plasma. Studies carried out to assess the impact of CAP treatment on the activation state of β1 integrin and focal adhesion size by using immunofluorescence show that fibroblasts have more active β1 integrin on their surface and large focal adhesions after CAP treatment. Based on these data, a thermodynamic model is presented to explain how CAP leads to integrin activation and focal adhesion assembly.

The Role of Astrocytes in the Generation, Migration, and Integration of New Neurons in the Adult Olfactory Bulb

PubMed Central

Gengatharan, Archana; Bammann, Rodrigo R.; Saghatelyan, Armen

2016-01-01

In mammals, new neurons in the adult olfactory bulb originate from a pool of neural stem cells in the subventricular zone of the lateral ventricles. Adult-born cells play an important role in odor information processing by adjusting the neuronal network to changing environmental conditions. Olfactory bulb neurogenesis is supported by several non-neuronal cells. In this review, we focus on the role of astroglial cells in the generation, migration, integration, and survival of new neurons in the adult forebrain. In the subventricular zone, neural stem cells with astrocytic properties display regional and temporal specificity when generating different neuronal subtypes. Non-neurogenic astrocytes contribute to the establishment and maintenance of the neurogenic niche. Neuroblast chains migrate through the rostral migratory stream ensheathed by astrocytic processes. Astrocytes play an important regulatory role in neuroblast migration and also assist in the development of a vasculature scaffold in the migratory stream that is essential for neuroblast migration in the postnatal brain. In the olfactory bulb, astrocytes help to modulate the network through a complex release of cytokines, regulate blood flow, and provide metabolic support, which may promote the integration and survival of new neurons. Astrocytes thus play a pivotal role in various processes of adult olfactory bulb neurogenesis, and it is likely that many other functions of these glial cells will emerge in the near future. PMID:27092050

Population genomics reveals seahorses (Hippocampus erectus) of the western mid-Atlantic coast to be residents rather than vagrants.

PubMed

Boehm, J T; Waldman, John; Robinson, John D; Hickerson, Michael J

2015-01-01

Understanding population structure and areas of demographic persistence and transients is critical for effective species management. However, direct observational evidence to address the geographic scale and delineation of ephemeral or persistent populations for many marine fishes is limited. The Lined seahorse (Hippocampus erectus) can be commonly found in three western Atlantic zoogeographic provinces, though inhabitants of the temperate northern Virginia Province are often considered tropical vagrants that only arrive during warm seasons from the southern provinces and perish as temperatures decline. Although genetics can locate regions of historical population persistence and isolation, previous evidence of Virginia Province persistence is only provisional due to limited genetic sampling (i.e., mitochondrial DNA and five nuclear loci). To test alternative hypotheses of historical persistence versus the ephemerality of a northern Virginia Province population we used a RADseq generated dataset consisting of 11,708 single nucleotide polymorphisms (SNP) sampled from individuals collected from the eastern Gulf of Mexico to Long Island, NY. Concordant results from genomic analyses all infer three genetically divergent subpopulations, and strongly support Virginia Province inhabitants as a genetically diverged and a historically persistent ancestral gene pool. These results suggest that individuals that emerge in coastal areas during the warm season can be considered "local" and supports offshore migration during the colder months. This research demonstrates how a large number of genes sampled across a geographical range can capture the diversity of coalescent histories (across loci) while inferring population history. Moreover, these results clearly demonstrate the utility of population genomic data to infer peripheral subpopulation persistence in difficult-to-observe species.

Locostatin, a disrupter of Raf kinase inhibitor protein, inhibits extracellular matrix production, proliferation, and migration in human uterine leiomyoma and myometrial cells.

PubMed

Janjusevic, Milijana; Greco, Stefania; Islam, Md Soriful; Castellucci, Clara; Ciavattini, Andrea; Toti, Paolo; Petraglia, Felice; Ciarmela, Pasquapina

2016-11-01

To investigate the presence of Raf kinase inhibitor protein (RKIP) in human myometrium and leiomyoma as well as to determine the effect of locostatin (RKIP inhibitor) on extracellular matrix (ECM) production, proliferation, and migration in human myometrial and leiomyoma cells. Laboratory study. Human myometrium and leiomyoma. Thirty premenopausal women who were admitted to the hospital for myomectomy or hysterectomy. Myometrial and leiomyoma tissues were used to investigate the localization and the expression level of RKIP through immunohistochemistry and Western blotting. Myometrial and leiomyoma cells were treated with locostatin (10 μM) to measure ECM expression by real-time polymerase chain reaction, GSK3β expression by Western blotting, cell migration by wound-healing assay, and cell proliferation by MTT assay and immunocytochemistry. The expression of RKIP in human myometrial and leiomyoma tissue; ECM components and GSK3β expression, migration, and proliferation in myometrial and leiomyoma cells. RKIP is expressed in human myometrial and leiomyoma tissue. Locostatin treatment resulted in the activation of the mitogen-activated protein kinase (MAPK) signal pathway (ERK phosphorylation), providing a powerful validation of our targeting protocol. Further, RKIP inhibition by locostatin reduces ECM components. Moreover, the inhibition of RKIP by locostatin impaired cell proliferation and migration in both leiomyoma and myometrial cells. Finally, locostatin treatment reduced GSK3β expression. Therefore, even if the activation of MAPK pathway should increase proliferation and migration, the destabilization of GSK3β leads to the reduction of proliferation and migration of myometrial and leiomyoma cells. Our results indicate that RKIP may be involved in leiomyoma pathophysiology. Copyright © 2016 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

Geodynamic modeling of the capture and release of a plume conduit by a migrating mid-ocean ridge

NASA Astrophysics Data System (ADS)

Hall, P. S.

2011-12-01

plates over the relatively stationary, long-lived conduits of mantle plumes. However, paleomagnetic data from the Hawaii-Emperor Seamount Chain suggests that the Hawaiian hotspot moved rapidly (~40 mm/yr) between 81 - 47 Ma [Tarduno et al., 2003]. Recently, Tarduno et al. [2009] suggested that this period of rapid motion might be the surface expression of a plume conduit returning to a largely vertical orientation after having been captured and tilted as the result of being "run over" by migrating mid-ocean ridge. I report on a series of analog geodynamic experiments designed to characterize the evolution of a plume conduit as a mid-ocean ridge migrates over. Experiments were conducted in a clear acrylic tank (100 cm x 70 cm x 50 cm) filled with commercial grade high-fructose corn syrup. Plate-driven flow is modeled by dragging two sheets of Mylar film (driven by independent DC motors) in opposite directions over the surface of the fluid. Ridge migration is achieved by moving the point at which the mylar sheets diverge using a separate motor drive. Buoyant plume flow is generated using a small electrical heater placed at the bottom of the tank. Plate velocities and ridge migration rate are controlled and plume temperature monitored using LabView software. Experiments are recorded using digital video which is then analyzed using digital image analysis software to track the position and shape of the plume conduit throughout the course of the experiment. The intersection of the plume conduit with the surface of the fluid is taken as an analog for the locus of hotspot volcanism and tracked as a function of time to obtain a hotspot migration rate. Results show that the plume conduit experiences significant tilting immediately following the passage of the migrating ridge.

The effect of growth hormone on fibroblast proliferation and keratinocyte migration.

PubMed

Lee, Sang Woo; Kim, Suk Hwa; Kim, Ji Youn; Lee, Yoonho

2010-04-01

The beneficial effects of growth hormones (GHs) on wound healing have been reported. Although the mechanism of how GH promotes wound healing is unclear, there are reports showing that the principal factor lies in the GH-stimulated production of IGF-1 in topical wounds. In this study, a human primary cell model was devised to examine how the topical application of GHs affects fibroblast proliferation and keratinocyte migration, which play fundamental roles in wound healing. The fibroblasts were cultured in media with different concentrations of GH. The amount of fibroblast proliferation was assessed using a tetrazolium-based colourimetric assay (MTT assay). The amount of newly formed IGF-I mRNA was measured by reverse transcription and polymerase chain reaction (RT-PCR). Keratinocyte migration was compared using a migration assay. Fibroblast proliferation was significantly higher in the experimental group than in the control group (the absorbance of 2.5IU L(-1) GH applied group: 0.3954+/-0.056, control group: 0.2943+/-0.0554, P<0.05), and the promotion of IGF-I formation by fibroblasts was observed. There was more keratinocyte migration in the experimental group than in the control group (the remaining gap in the 2.5IU L(-1) GH applied group after keratinocyte migration: 46.57+/-2.22% of the primary gap, control group: 75.14+/-3.44%, P<0.05). GH enhances the local formation of IGF-1, which activates fibroblast proliferation and keratinocyte migration. These results highlight the potential of the topical application of GHs in the treatment of wounds. Copyright 2009 British Association of Plastic, Reconstructive and Aesthetic Surgeons. All rights reserved.

Simulating the Oceanic Migration of Silver Japanese Eels

PubMed Central

Chang, Yu-Lin; Miyazawa, Yasumasa; Béguer-Pon, Mélanie

2016-01-01

The oceanic migration of silver Japanese eels starts from their continental growth habitats in East Asia and ends at the spawning area near the West Mariana Ridge seamount chain. However, the actual migration routes remain unknown. In this study, we examined the possible oceanic migration routes and strategies of silver Japanese eels using a particle tracking method in which virtual eels (v-eels) were programmed to move vertically and horizontally in an ocean circulation model (Japan Coastal Ocean Predictability Experiment 2, JCOPE2). Four horizontal swimming strategies were tested: random heading, true navigation (readjusted heading), orientation toward the spawning area (fixed heading), and swimming against the Kuroshio. We found that all strategies, except random swimming, allowed v-eels swimming at 0.65 m s−1 to reach the spawning area within eight months after their departure from the south coast of Japan (end of the spawning season). The estimated minimum swimming speed required to reach the area spawning within eight months was 0.1 m s−1 for true navigation, 0.12 m s−1 for constant compass heading, and 0.35 m s−1 for swimming against the Kuroshio. The lowest swimming speed estimated from tracked Japanese eels at sea was 0.03 m.s−1, which would not allow them to reach the spawning area within eight months, through any of the tested orientation strategies. Our numerical experiments also showed that ocean circulation significantly affected the migration of Japanese v-eels. A strong Kuroshio could advect v-eels further eastward. In addition, western Pacific ocean currents accelerated the migration of navigating v-eels. The migration duration was shortened in years with a stronger southward flow, contributed by a stronger recirculation south of Japan, an enhanced subtropical gyre, or a higher southward Kuroshio velocity. PMID:26982484

Simulating the Oceanic Migration of Silver Japanese Eels.

PubMed

Chang, Yu-Lin; Miyazawa, Yasumasa; Béguer-Pon, Mélanie

2016-01-01

The oceanic migration of silver Japanese eels starts from their continental growth habitats in East Asia and ends at the spawning area near the West Mariana Ridge seamount chain. However, the actual migration routes remain unknown. In this study, we examined the possible oceanic migration routes and strategies of silver Japanese eels using a particle tracking method in which virtual eels (v-eels) were programmed to move vertically and horizontally in an ocean circulation model (Japan Coastal Ocean Predictability Experiment 2, JCOPE2). Four horizontal swimming strategies were tested: random heading, true navigation (readjusted heading), orientation toward the spawning area (fixed heading), and swimming against the Kuroshio. We found that all strategies, except random swimming, allowed v-eels swimming at 0.65 m s-1 to reach the spawning area within eight months after their departure from the south coast of Japan (end of the spawning season). The estimated minimum swimming speed required to reach the area spawning within eight months was 0.1 m s-1 for true navigation, 0.12 m s-1 for constant compass heading, and 0.35 m s-1 for swimming against the Kuroshio. The lowest swimming speed estimated from tracked Japanese eels at sea was 0.03 m.s-1, which would not allow them to reach the spawning area within eight months, through any of the tested orientation strategies. Our numerical experiments also showed that ocean circulation significantly affected the migration of Japanese v-eels. A strong Kuroshio could advect v-eels further eastward. In addition, western Pacific ocean currents accelerated the migration of navigating v-eels. The migration duration was shortened in years with a stronger southward flow, contributed by a stronger recirculation south of Japan, an enhanced subtropical gyre, or a higher southward Kuroshio velocity.

[Trans-uranium elements in food products (review)].

PubMed

Vasilenko, I Ia

1994-01-01

The data of Russian and foreign authors concerning of level environmental contamination and migration of transuranic elements in food chains, metabolism and biological danger of nuclides entering in human body with foods are reviewed. A level of radionuclide load of population and doses of radiation are discussed and the danger is estimated. The doses of radiation from radionuclide ingestion are lower than level of allowed radiation safety standards.

Changes in the Management of Information in Audio-Visual Archives following Digitization: Current and Future Outlook

ERIC Educational Resources Information Center

Caldera-Serrano, Jorge

2008-01-01

This article attempts to offer an overview of the current changes that are being experienced in the management of audio-visual documentation and those that can be forecast in the future as a result of the migration from analogue to digital information. For this purpose the documentary chain will be used as a basis to analyse individually the tasks…

Persistently high Epstein-Barr virus (EBV) loads in peripheral blood lymphocytes from patients with chronic active EBV infection.

PubMed

Maeda, A; Wakiguchi, H; Yokoyama, W; Hisakawa, H; Tomoda, T; Kurashige, T

1999-04-01

Chronic active Epstein-Barr virus infection (CAEBV) is a severe illness with unusual EBV activation that persists for years, and its pathogenesis is largely unknown. After the creation of an accurate and reproducible polymerase chain reaction system to quantify EBV DNA, virus loads in peripheral blood lymphocytes (PBL) were determined in 54 children: 15 with CAEBV, 16 with infectious mononucleosis (IM), and 23 healthy children. Children with CAEBV and those with IM had high virus loads. Lower loads were detected in 47% of seropositive healthy donors. There were two distinct differences between children with CAEBV and those with IM: The former had greater viral replication (10(3)-10(7) copies/2.5x10(5) PBL) than those with IM, and viral replication declined in children with IM whereas active replication persisted for years in subjects with CAEBV. Persisting high virus loads are a possible diagnostic criterion for CAEBV. EBV loads may enable classification and prognosis of EBV infections.

Inhibitors of type II NADH:menaquinone oxidoreductase represent a class of antitubercular drugs

PubMed Central

Weinstein, Edward A.; Yano, Takahiro; Li, Lin-Sheng; Avarbock, David; Avarbock, Andrew; Helm, Douglas; McColm, Andrew A.; Duncan, Ken; Lonsdale, John T.; Rubin, Harvey

2005-01-01

Mycobacterium tuberculosis (Mtb) is an obligate aerobe that is capable of long-term persistence under conditions of low oxygen tension. Analysis of the Mtb genome predicts the existence of a branched aerobic respiratory chain terminating in a cytochrome bd system and a cytochrome aa3 system. Both chains can be initiated with type II NADH:menaquinone oxidoreductase. We present a detailed biochemical characterization of the aerobic respiratory chains from Mtb and show that phenothiazine analogs specifically inhibit NADH:menaquinone oxidoreductase activity. The emergence of drug-resistant strains of Mtb has prompted a search for antimycobacterial agents. Several phenothiazines analogs are highly tuberculocidal in vitro, suppress Mtb growth in a mouse model of acute infection, and represent lead compounds that may give rise to a class of selective antibiotics. PMID:15767566

Gender, migration and urban development in Costa Rica: the case of Guanacaste.

PubMed

Chant, S

1991-01-01

Factors fueling urbanization in Guanacaste province, Costa Rica are explored and how the pattern of urban growth reflects gender divisions of labor is considered. Urbanization in Latin America has been due largely to the expansion of economic activities in urban centers, but in Guanacaste, rural employment persists among the poor. Towns in this peripheral province have witnessed no major expansion in urban-based employment opportunities. On the basis of an in-depth survey of urban dwellers in the province's 3 leading towns (Liberia, Canas, and Santa Cruz), an attempt is made to explain Guanacaste's urbanization. The 1st section discusses the migration, urbanization, and economic development in Costa Rica, as well as Guanacaste. The 2nd section provides the findings of the survey of 350 low-income, urban households in Guanacaste, focusing on the households' reported reasons for moving. Section 3 examines household survival strategies in the areas surveyed, paying close attention to gender and age selectivity of short-term out-migration to external labor markets. Section 4 interprets the apparent connection between gender-differentiated labor migration and the dominance of reproductive factors in household decisions to move to urban centers. Section 5 considers the implications of the migration patterns on women, while section 6 discusses the wider implications of the study. The study reveals that in Guanacaste, urbanization is more strongly linked to the reproductive (e.g., housing and welfare) needs of household survival than to productive (employment and income) needs.

Cellular Contraction Can Drive Rapid Epithelial Flows.

PubMed

Vig, Dhruv K; Hamby, Alex E; Wolgemuth, Charles W

2017-10-03

Single, isolated epithelial cells move randomly; however, during wound healing, organism development, cancer metastasis, and many other multicellular phenomena, motile cells group into a collective and migrate persistently in a directed manner. Recent work has examined the physics and biochemistry that coordinates the motions of these groups of cells. Of late, two mechanisms have been touted as being crucial to the physics of these systems: leader cells and jamming. However, the actual importance of these to collective migration remains circumstantial. Fundamentally, collective behavior must arise from the actions of individual cells. Here, we show how biophysical activity of an isolated cell impacts collective dynamics in epithelial layers. Although many reports suggest that wound closure rates depend on isolated cell speed and/or leader cells, we find that these correlations are not universally true, nor do collective dynamics follow the trends suggested by models for jamming. Instead, our experimental data, when coupled with a mathematical model for collective migration, shows that intracellular contractile stress, isolated cell speed, and adhesion all play a substantial role in influencing epithelial dynamics, and that alterations in contraction and/or substrate adhesion can cause confluent epithelial monolayers to exhibit an increase in motility, a feature reminiscent of cancer metastasis. These results directly question the validity of wound-healing assays as a general means for measuring cell migration, and provide further insight into the salient physics of collective migration. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Soluble Factors from Biofilms of Wound Pathogens Modulate Human Bone Marrow-derived Stromal Cell Differentiation, Migration, Angiogenesis, and Cytokine Secretion

DTIC Science & Technology

2015-03-28

Becerra, Christopher R Rathbone and Joseph C Wenke Abstract Background: Chronic, non- healing wounds are often characterized by the persistence of bacteria...within biofilms - aggregations of cells encased within a self -produced polysaccharide matrix. Biofilm bacteria exhibit unique characteristics from...modulation of host-immune responses by secreting factors that promote wound healing . While these characteristics make MSCs an attractive therapeutic

A novel role of HLA class I in the pathology of medulloblastoma.

PubMed

Smith, Courtney; Santi, Mariarita; Rajan, Bhargavi; Rushing, Elisabeth J; Choi, Mi Rim; Rood, Brian R; Cornelison, Robert; MacDonald, Tobey J; Vukmanovic, Stanislav

2009-07-12

MHC class I expression by cancer cells enables specific antigen recognition by the immune system and protection of the host. However, in some cancer types MHC class I expression is associated with an unfavorable outcome. We explored the basis of MHC class I association with unfavorable prognostic marker expression in the case of medulloblastoma. We investigated expression of four essential components of MHC class I (heavy chain, beta2m, TAP1 and TAP2) in 10 medulloblastoma mRNA samples, a tissue microarray containing 139 medulloblastoma tissues and 3 medulloblastoma cell lines. Further, in medulloblastoma cell lines we evaluated the effects of HLA class I engagement on activation of ERK1/2 and migration in vitro. The majority of specimens displayed undetectable or low levels of the heavy chains. Medulloblastomas expressing high levels of HLA class I displayed significantly higher levels of anaplasia and c-myc expression, markers of poor prognosis. Binding of beta2m or a specific antibody to open forms of HLA class I promoted phosphorylation of ERK1/2 in medulloblastoma cell line with high levels, but not in the cell line with low levels of HLA heavy chain. This treatment also promoted ERK1/2 activation dependent migration of medulloblastoma cells. MHC class I expression in medulloblastoma is associated with anaplasia and c-myc expression, markers of poor prognosis. Peptide- and/or beta2m-free forms of MHC class I may contribute to a more malignant phenotype of medulloblastoma by modulating activation of signaling molecules such as ERK1/2 that stimulates cell mobility.

A novel role of HLA class I in the pathology of medulloblastoma

PubMed Central

Smith, Courtney; Santi, Mariarita; Rajan, Bhargavi; Rushing, Elisabeth J; Choi, Mi Rim; Rood, Brian R; Cornelison, Robert; MacDonald, Tobey J; Vukmanovic, Stanislav

2009-01-01

Background MHC class I expression by cancer cells enables specific antigen recognition by the immune system and protection of the host. However, in some cancer types MHC class I expression is associated with an unfavorable outcome. We explored the basis of MHC class I association with unfavorable prognostic marker expression in the case of medulloblastoma. Methods We investigated expression of four essential components of MHC class I (heavy chain, β2m, TAP1 and TAP2) in 10 medulloblastoma mRNA samples, a tissue microarray containing 139 medulloblastoma tissues and 3 medulloblastoma cell lines. Further, in medulloblastoma cell lines we evaluated the effects of HLA class I engagement on activation of ERK1/2 and migration in vitro. Results The majority of specimens displayed undetectable or low levels of the heavy chains. Medulloblastomas expressing high levels of HLA class I displayed significantly higher levels of anaplasia and c-myc expression, markers of poor prognosis. Binding of β2m or a specific antibody to open forms of HLA class I promoted phosphorylation of ERK1/2 in medulloblastoma cell line with high levels, but not in the cell line with low levels of HLA heavy chain. This treatment also promoted ERK1/2 activation dependent migration of medulloblastoma cells. Conclusion MHC class I expression in medulloblastoma is associated with anaplasia and c-myc expression, markers of poor prognosis. Peptide- and/or β2m-free forms of MHC class I may contribute to a more malignant phenotype of medulloblastoma by modulating activation of signaling molecules such as ERK1/2 that stimulates cell mobility. PMID:19594892

Multivalent conjugates of basic fibroblast growth factor enhance in vitro proliferation and migration of endothelial cells.

PubMed

Zbinden, Aline; Browne, Shane; Altiok, Eda I; Svedlund, Felicia L; Jackson, Wesley M; Healy, Kevin E

2018-05-01

Growth factors hold great promise for regenerative therapies. However, their clinical use has been halted by poor efficacy and rapid clearance from tissue, necessitating the delivery of extremely high doses to achieve clinical effectiveness which has raised safety concerns. Thus, strategies to either enhance growth factor activity at low doses or to increase their residence time within target tissues are necessary for clinical success. In this study, we generated multivalent conjugates (MVCs) of basic fibroblast growth factor (bFGF), a key growth factor involved in angiogenesis and wound healing, to hyaluronic acid (HyA) polymer chains. Multivalent bFGF conjugates (mvbFGF) were fabricated with minimal non-specific interaction observed between bFGF and the HyA chain. The hydrodynamic radii of mvbFGF ranged from ∼50 to ∼75 nm for conjugation ratios of bFGF to HyA chains at low (10 : 1) and high (30 : 1) feed ratios, respectively. The mvbFGF demonstrated enhanced bioactivity compared to unconjugated bFGF in assays of cell proliferation and migration, processes critical to angiogenesis and tissue regeneration. The 30 : 1 mvbFGF outperformed the 10 : 1 conjugate, which could be due to either FGF receptor clustering or interference with receptor mediated internalization and signal deactivation. This study simultaneously investigated the role of both protein to polymer ratio and multivalent conjugate size on their bioactivity, and determined that increasing the protein-to-polymer ratio and conjugate size resulted in greater cell bioactivity.

Headaches secondary to intraventricular silicone oil successfully managed with ventriculoperitoneal shunt.

PubMed

Hruby, Paul M; Poley, Preeti R; Terp, Patricia A; Thorell, William E; Margalit, Eyal

2013-01-01

To describe a case of intravitreal silicone oil (SO) migration into the cerebral ventricles with secondary chronic headaches. Retrospective case report. Chart review. Single patient. A 51-year-old man with a history of proliferative diabetic retinopathy underwent surgery for traction retinal detachment using SO. Postoperatively, he developed elevated intraocular pressure, headaches, and a blind painful eye, which was enucleated. Neuroimaging revealed SO within the cerebral ventricles. Five years after the initial retinal detachment surgery, the patient developed chronic headaches. Lumbar puncture revealed an elevated opening pressure. The headaches were initially managed medically. A ventriculoperitoneal shunt was placed after the headaches persisted, which resulted in their complete resolution at 6 weeks after shunt placement. Ocular hypertension after intravitreal SO placement may play a role in SO intracranial migration. In the case presented, intraventricular SO was the apparent cause of elevated intracranial pressure and headaches. As all published cases of intraventricular SO migration reporting intraocular pressure to this point have described ocular hypertension, careful monitoring of intraocular pressure and aggressive control of ocular hypertension in the presence of intravitreal SO is recommended.

Integrin-mediated human glioblastoma cells adhesion, migration and invasion by native and recombinant phospholipases of Scorpio maurus venom glands.

PubMed

Krayem, Najeh; Abdelkefi-Koubaa, Zaineb; Gargouri, Youssef; Luis, José

2018-05-01

Integrins are a large family of cell surface receptors mediating the interaction of cells with their microenvironment and they play an important role in glioma biology. In the present work, we reported the anti-tumor effect of Sm-PLGV a phospholipase A 2 from Tunisian scorpion venom glands-as well as its recombinant forms expressed in Escherichia coli-through interference with integrin receptor function in malignant glioma cells U87. These phospholipases inhibited in a dose dependent manner the adhesion, migration and invasion onto fibrinogen and fibronectin without any cytotoxicity. We showed that Sm-PLGV and its recombinant constructs blocked U87 migration by reducing their velocity and directional persistence. The inhibitory effect was related to a blockage of the integrins αvβ3 and α5β1 function. Inactivation of the enzymatic activity of Sm-PLGV by chemical modification with p-bromophenacyl bromide did not affect its anti-tumor properties, suggesting the presence of 'pharmacological sites' distinct from the catalytic site in scorpion venom phospholipases A 2 . Copyright © 2018 Elsevier Inc. All rights reserved.

GABAergic excitation after febrile seizures induces ectopic granule cells and adult epilepsy.

PubMed

Koyama, Ryuta; Tao, Kentaro; Sasaki, Takuya; Ichikawa, Junya; Miyamoto, Daisuke; Muramatsu, Rieko; Matsuki, Norio; Ikegaya, Yuji

2012-08-01

Temporal lobe epilepsy (TLE) is accompanied by an abnormal location of granule cells in the dentate gyrus. Using a rat model of complex febrile seizures, which are thought to be a precipitating insult of TLE later in life, we report that aberrant migration of neonatal-generated granule cells results in granule cell ectopia that persists into adulthood. Febrile seizures induced an upregulation of GABA(A) receptors (GABA(A)-Rs) in neonatally generated granule cells, and hyperactivation of excitatory GABA(A)-Rs caused a reversal in the direction of granule cell migration. This abnormal migration was prevented by RNAi-mediated knockdown of the Na(+)K(+)2Cl(-) co-transporter (NKCC1), which regulates the excitatory action of GABA. NKCC1 inhibition with bumetanide after febrile seizures rescued the granule cell ectopia, susceptibility to limbic seizures and development of epilepsy. Thus, this work identifies a previously unknown pathogenic role of excitatory GABA(A)-R signaling and highlights NKCC1 as a potential therapeutic target for preventing granule cell ectopia and the development of epilepsy after febrile seizures.

Comparative Diagnosis of Human Bocavirus 1 Respiratory Infection With Messenger RNA Reverse-Transcription Polymerase Chain Reaction (PCR), DNA Quantitative PCR, and Serology.

PubMed

Xu, Man; Arku, Benedict; Jartti, Tuomas; Koskinen, Janne; Peltola, Ville; Hedman, Klaus; Söderlund-Venermo, Maria

2017-05-15

Human bocavirus (HBoV) 1 can cause life-threatening respiratory tract infection in children. Diagnosing acute HBoV1 infection is challenging owing to long-term airway persistence. We assessed whether messenger RNA (mRNA) detection would correlate better than DNA detection with acute HBoV1 infection. Paired serum samples from 121 children with acute wheezing were analyzed by means of serology. Quantitative polymerase chain reaction (PCR) and reverse-transcription (RT) PCR were applied to nasopharyngeal swab (NPS) samples from all acutely HBoV1-infected children and from controls with nonacute infection. By serology, 16 of 121 children (13.2%) had acute HBoV1 infection, all of whom had HBoV1 DNA in NPS samples, and 12 of 16 (75%) had HBoV1 mRNA. Among 25 children with nondiagnostic results, 6 had HBoV1 DNA in NPS samples, and 1 had mRNA. All 13 mRNA-positive samples exhibited high DNA loads (≥106 copies/mL). No mRNA persisted for 2 weeks, whereas HBoV1 DNA persisted for 2 months in 4 children; 1 year later all 15 samples were DNA negative. Compared with serology, DNA PCR had high clinical sensitivity (100%) but, because of viral persistence, low specificity (76%). In contrast, mRNA RT-PCR had low clinical sensitivity (75%) but high specificity (96%). A combination of HBoV1 serology and nasopharyngeal DNA quantitative PCR and mRNA RT-PCR should be used for accurate diagnosis of HBoV1 infection. © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail journals.permissions@oup.com.

Climate change and avian influenza

PubMed Central

Slingenbergh, J.; Xiao, X.

2009-01-01

Summary This paper discusses impacts of climate change on the ecology of avian influenza viruses (AI viruses), which presumably co-evolved with migratory water birds, with virus also persisting outside the host in subarctic water bodies. Climate change would almost certainly alter bird migration, influence the AI virus transmission cycle and directly affect virus survival outside the host. The joint, net effects of these changes are rather unpredictable, but it is likely that AI virus circulation in water bird populations will continue with endless adaptation and evolution. In domestic poultry, too little is known about the direct effect of environmental factors on highly pathogenic avian influenza transmission and persistence to allow inference about the possible effect of climate change. However, possible indirect links through changes in the distribution of duck-crop farming are discussed. PMID:18819672

Chain Conformation and Dynamics in Spin-Assisted Weak Polyelectrolyte Multilayers

DOE PAGES

Zhuk, Aliaksandr; Selin, Victor; Zhuk, Iryna; ...

2015-03-13

In this paper, we report on the effect of the deposition technique on film layering, stability, and chain mobility in weak polyelectrolyte layer-by-layer (LbL) films. Ellipsometry and neutron reflectometry (NR) showed that shear forces arising during spin-assisted assembly lead to smaller amounts of adsorbed polyelectrolytes within LbL films, result in a higher degree of internal film order, and dramatically improve stability of assemblies in salt solutions as compared to dip-assisted LbL assemblies. The underlying flattening of polyelectrolyte chains in spin-assisted LbL films was also revealed as an increase in ionization degree of the assembled weak polyelectrolytes. As demonstrated by fluorescencemore » recovery after photobleaching (FRAP), strong binding between spin-deposited polyelectrolytes results in a significant slowdown of chain diffusion in salt solutions as compared to dip-deposited films. Moreover, salt-induced chain intermixing in the direction perpendicular to the substrate is largely inhibited in spin-deposited films, resulting in only subdiffusional (<2 Å) chain displacements even after 200 h exposure to 1 M NaCl solutions. Finally, this persistence of polyelectrolyte layering has important ramifications for multistage drug delivery and optical applications of LbL assemblies.« less

Data-driven backward chaining

NASA Technical Reports Server (NTRS)

Haley, Paul

1991-01-01

The C Language Integrated Production System (CLIPS) cannot effectively perform sound and complete logical inference in most real-world contexts. The problem facing CLIPS is its lack of goal generation. Without automatic goal generation and maintenance, forward chaining can only deduce all instances of a relationship. Backward chaining, which requires goal generation, allows deduction of only that subset of what is logically true which is also relevant to ongoing problem solving. Goal generation can be mimicked in simple cases using forward chaining. However, such mimicry requires manual coding of additional rules which can assert an inadequate goal representation for every condition in every rule that can have corresponding facts derived by backward chaining. In general, for N rules with an average of M conditions per rule the number of goal generation rules required is on the order of N*M. This is clearly intractable from a program maintenance perspective. We describe the support in Eclipse for backward chaining which it automatically asserts as it checks rule conditions. Important characteristics of this extension are that it does not assert goals which cannot match any rule conditions, that 2 equivalent goals are never asserted, and that goals persist as long as, but no longer than, they remain relevant.

Twist-writhe partitioning in a coarse-grained DNA minicircle model

NASA Astrophysics Data System (ADS)

Sayar, Mehmet; Avşaroǧlu, Barış; Kabakçıoǧlu, Alkan

2010-04-01

Here we present a systematic study of supercoil formation in DNA minicircles under varying linking number by using molecular-dynamics simulations of a two-bead coarse-grained model. Our model is designed with the purpose of simulating long chains without sacrificing the characteristic structural properties of the DNA molecule, such as its helicity, backbone directionality, and the presence of major and minor grooves. The model parameters are extracted directly from full-atomistic simulations of DNA oligomers via Boltzmann inversion; therefore, our results can be interpreted as an extrapolation of those simulations to presently inaccessible chain lengths and simulation times. Using this model, we measure the twist/writhe partitioning in DNA minicircles, in particular its dependence on the chain length and excess linking number. We observe an asymmetric supercoiling transition consistent with experiments. Our results suggest that the fraction of the linking number absorbed as twist and writhe is nontrivially dependent on chain length and excess linking number. Beyond the supercoiling transition, chains of the order of one persistence length carry equal amounts of twist and writhe. For longer chains, an increasing fraction of the linking number is absorbed by the writhe.

Persistence of polyomavirus in mice infected as adults differs from that observed in mice infected as newborns.

PubMed Central

Berke, Z; Dalianis, T

1993-01-01

By using the polymerase chain reaction (PCR) technique, a technique more sensitive than Southern analysis, which allows detection of polyomavirus DNA only in newborn and nude adult mice, it has now been possible to monitor the persistence pattern of polyomavirus DNA after infection of normal adult CBA mice for the first time. Viral signs appeared gradually, showing variations in time course and organ distribution between mice, and reached a peak activity after 2 to 3 weeks, when they could be found in bone, heart, gonads, lymph node, and skin, but disappeared by 2 to 5 months. No virus DNA was detected in the kidneys or lungs, which is in contrast to what is observed after infection of newborn mice. This finding suggests that the persistence pattern of polyomavirus is age dependent. PMID:8389934

Barrier island evolution and reworking by inlet migration along the Mississippi-Alabama gulf coast

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rucker, J.B.; Snowden, J.O.

1990-09-01

The five barrier islands along the Mississippi-Alabama coast are located 10 to 14 mi (16 to 23 km) offshore and separate Mississippi Sound from the Gulf of Mexico. The barrier islands in the chain are, from east to west: Dauphin Island, Petit Bois Island, Horn Island, Ship Island, and Cat Island. The islands are low sand bodies situated on a relatively broad Holocene sand platform that extends 70 mi (113 km) from Dauphin Island on the east to Cat Island on the west. The platform varies in thickness from 25 to 75 ft (7.6 to 23 m) and rests onmore » Holocene marine clays or on Pleistocene sediments. The barrier island chain predates the St. Bernard lobe of the Mississippi delta complex, which began to prograde about 3,000 years ago, and continued until it was abandoned approximately 1,500 years ago. In contrast to the other islands, Cat Island at the western down-drift end of the Mississippi-Alabama barrier island chain is characterized by more than 12 prominent east west-oriented progradational linear ridges. The ridge system of Cat Island is interpreted as a relict of an earlier stage in the life cycle of the barrier platform when there was a more robust littoral drift system and an abundant sediment supply During the Pre-St. Bernard Delta period of vigorous sedimentation, all of the islands in the barrier chain probably exhibited progradational ridges similar to those now found only on Cat Island. Presently, only vestigial traces of these progradational features remain on the islands to the east of Cat Island. Unlike Cat Island, which has been protected and preserved by the St. Bernard Delta, the other barrier islands have been modified and reworked during the past 1,500 years by processes of island and tidal inlet migration, accompanied by a general weakening of the littoral drift and a reduction of the available sediment supply.« less

Magnolol inhibits migration of vascular smooth muscle cells via cytoskeletal remodeling pathway to attenuate neointima formation.

PubMed

Karki, Rajendra; Kim, Seong-Bin; Kim, Dong-Wook

2013-12-10

Increased proliferation and migration of vascular smooth muscle cells (VSMCs) contribute importantly to the formation of both atherosclerotic and restenotic lesions. The objective of this study was to investigate the effect of magnolol on VSMC migration. The proteolytic activity of matrix metalloproteinases (MMPs) in tumor necrosis factor alpha (TNF-α) stimulated VSMCs was performed by gelatin zymography. VSMC migration was assessed by wound healing and Boyden chamber methods. Collagen induced VSMC adhesion was determined by spectrofluorimeter and stress fibers formation was evaluated by fluorescence microscope. The expression of signaling molecules involved in stress fibers formation was determined by western blot. The phosphorylation of myosin light chain (MLC20) was determined by urea-glycerol polyacrylamide gel electrophoresis. Immunohistochemistry was performed to determine the expression of β1-integrin and collagen type I in the injured carotid arteries of rats on day 35 after vascular injury. VSMC migration was strongly inhibited by magnolol without affecting MMPs expression. Also, magnolol inhibited β1-integrin expression, FAK phosphorylation and RhoA and Cdc42 activation to inhibit the collagen induced stress fibers formation. Moreover, magnolol inhibited the phosphorylation of MLC20. Our in vivo results showed that magnolol inhibited β1-integrin expression, collagen type I deposition and FAK phosphorylation in injured carotid arteries without affecting MMP-2 activity. Magnolol inhibited VSMC migration via inhibition of cytoskeletal remodeling pathway to attenuate neointima formation. This study provides a rationale for further evaluation of magnolol for the management of atherosclerosis and restenosis. Crown Copyright © 2013. Published by Elsevier Inc. All rights reserved.

Examining speed versus selection in connectivity models using elk migration as an example

USGS Publications Warehouse

Brennan, Angela; Hanks, Ephraim M.; Merkle, Jerod A.; Cole, Eric K.; Dewey, Sarah R.; Courtemanch, Alyson B.; Cross, Paul C.

2018-01-01

ContextLandscape resistance is vital to connectivity modeling and frequently derived from resource selection functions (RSFs). RSFs estimate relative probability of use and tend to focus on understanding habitat preferences during slow, routine animal movements (e.g., foraging). Dispersal and migration, however, can produce rarer, faster movements, in which case models of movement speed rather than resource selection may be more realistic for identifying habitats that facilitate connectivity.ObjectiveTo compare two connectivity modeling approaches applied to resistance estimated from models of movement rate and resource selection.MethodsUsing movement data from migrating elk, we evaluated continuous time Markov chain (CTMC) and movement-based RSF models (i.e., step selection functions [SSFs]). We applied circuit theory and shortest random path (SRP) algorithms to CTMC, SSF and null (i.e., flat) resistance surfaces to predict corridors between elk seasonal ranges. We evaluated prediction accuracy by comparing model predictions to empirical elk movements.ResultsAll connectivity models predicted elk movements well, but models applied to CTMC resistance were more accurate than models applied to SSF and null resistance. Circuit theory models were more accurate on average than SRP models.ConclusionsCTMC can be more realistic than SSFs for estimating resistance for fast movements, though SSFs may demonstrate some predictive ability when animals also move slowly through corridors (e.g., stopover use during migration). High null model accuracy suggests seasonal range data may also be critical for predicting direct migration routes. For animals that migrate or disperse across large landscapes, we recommend incorporating CTMC into the connectivity modeling toolkit.

Examining speed versus selection in connectivity models using elk migration as an example

USGS Publications Warehouse

Brennan, Angela; Hanks, EM; Merkle, JA; Cole, EK; Dewey, SR; Courtemanch, AB; Cross, Paul C.

2018-01-01

Context: Landscape resistance is vital to connectivity modeling and frequently derived from resource selection functions (RSFs). RSFs estimate relative probability of use and tend to focus on understanding habitat preferences during slow, routine animal movements (e.g., foraging). Dispersal and migration, however, can produce rarer, faster movements, in which case models of movement speed rather than resource selection may be more realistic for identifying habitats that facilitate connectivity. Objective: To compare two connectivity modeling approaches applied to resistance estimated from models of movement rate and resource selection. Methods: Using movement data from migrating elk, we evaluated continuous time Markov chain (CTMC) and movement-based RSF models (i.e., step selection functions [SSFs]). We applied circuit theory and shortest random path (SRP) algorithms to CTMC, SSF and null (i.e., flat) resistance surfaces to predict corridors between elk seasonal ranges. We evaluated prediction accuracy by comparing model predictions to empirical elk movements. Results: All models predicted elk movements well, but models applied to CTMC resistance were more accurate than models applied to SSF and null resistance. Circuit theory models were more accurate on average than SRP algorithms. Conclusions: CTMC can be more realistic than SSFs for estimating resistance for fast movements, though SSFs may demonstrate some predictive ability when animals also move slowly through corridors (e.g., stopover use during migration). High null model accuracy suggests seasonal range data may also be critical for predicting direct migration routes. For animals that migrate or disperse across large landscapes, we recommend incorporating CTMC into the connectivity modeling toolkit.

Enhanced photocatalytic activity of degrading short chain chlorinated paraffins over reduced graphene oxide/CoFe2O4/Ag nanocomposite.

PubMed

Chen, Xin; Zhao, Qidong; Li, Xinyong; Wang, Dong

2016-10-01

Short chain chlorinated paraffins have recently attracted great attention because of their environmental persistence and biological toxicity as an important organic pollutant. In this work, reduced graphene oxide/CoFe2O4/Ag (RGO/CoFe2O4/Ag) nanocomposite was prepared and employed for photocatalytic degradation of short chain chlorinated paraffins. The process of photocatalytic degradation of short chain chlorinated paraffins over RGO/CoFe2O4/Ag under visible light (λ>400nm) was investigated by in situ Fourier transform infrared spectroscopy and the related mechanisms were proposed. An apparent degradation ratio of 91.9% over RGO/CoFe2O4/Ag could be obtained under visible light illumination of 12h, while only about 21.7% was obtained with commercial P25 TiO2 under the same experimental conditions, which demonstrates that the RGO/CoFe2O4/Ag nanocomposite is a potential candidate for effective photocatalytic removal of short chain chlorinated paraffins. Copyright © 2016 Elsevier Inc. All rights reserved.

Maximum Likelihood Implementation of an Isolation-with-Migration Model for Three Species.

PubMed

Dalquen, Daniel A; Zhu, Tianqi; Yang, Ziheng

2017-05-01

We develop a maximum likelihood (ML) method for estimating migration rates between species using genomic sequence data. A species tree is used to accommodate the phylogenetic relationships among three species, allowing for migration between the two sister species, while the third species is used as an out-group. A Markov chain characterization of the genealogical process of coalescence and migration is used to integrate out the migration histories at each locus analytically, whereas Gaussian quadrature is used to integrate over the coalescent times on each genealogical tree numerically. This is an extension of our early implementation of the symmetrical isolation-with-migration model for three species to accommodate arbitrary loci with two or three sequences per locus and to allow asymmetrical migration rates. Our implementation can accommodate tens of thousands of loci, making it feasible to analyze genome-scale data sets to test for gene flow. We calculate the posterior probabilities of gene trees at individual loci to identify genomic regions that are likely to have been transferred between species due to gene flow. We conduct a simulation study to examine the statistical properties of the likelihood ratio test for gene flow between the two in-group species and of the ML estimates of model parameters such as the migration rate. Inclusion of data from a third out-group species is found to increase dramatically the power of the test and the precision of parameter estimation. We compiled and analyzed several genomic data sets from the Drosophila fruit flies. Our analyses suggest no migration from D. melanogaster to D. simulans, and a significant amount of gene flow from D. simulans to D. melanogaster, at the rate of ~0.02 migrant individuals per generation. We discuss the utility of the multispecies coalescent model for species tree estimation, accounting for incomplete lineage sorting and migration. © The Author(s) 2016. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Monte Carlo simulations of lattice models for single polymer systems

NASA Astrophysics Data System (ADS)

Hsu, Hsiao-Ping

2014-10-01

Single linear polymer chains in dilute solutions under good solvent conditions are studied by Monte Carlo simulations with the pruned-enriched Rosenbluth method up to the chain length N ˜ O(10^4). Based on the standard simple cubic lattice model (SCLM) with fixed bond length and the bond fluctuation model (BFM) with bond lengths in a range between 2 and sqrt{10}, we investigate the conformations of polymer chains described by self-avoiding walks on the simple cubic lattice, and by random walks and non-reversible random walks in the absence of excluded volume interactions. In addition to flexible chains, we also extend our study to semiflexible chains for different stiffness controlled by a bending potential. The persistence lengths of chains extracted from the orientational correlations are estimated for all cases. We show that chains based on the BFM are more flexible than those based on the SCLM for a fixed bending energy. The microscopic differences between these two lattice models are discussed and the theoretical predictions of scaling laws given in the literature are checked and verified. Our simulations clarify that a different mapping ratio between the coarse-grained models and the atomistically realistic description of polymers is required in a coarse-graining approach due to the different crossovers to the asymptotic behavior.

WESTERN AIRBORNE CONTAMINANTS ASSESSMENT PROJECT (WACAP): ASSESSING DEPOSITION AND IMPACTS OF PERSISTENT ORGANIC POLLUTANTS AND METALS IN SEVEN NATIONAL PARKS IN THE WESTERN UNITED STATES

EPA Science Inventory

Airborne contaminants, especially those that biomagnify in the food chain, can pose serious health threats to wildlife and humans. Biological effects of airborne contaminants include impacts on reproductive success, growth, behavior, disease, and survival. In response to concer...

Finding and testing network communities by lumped Markov chains.

PubMed

Piccardi, Carlo

2011-01-01

Identifying communities (or clusters), namely groups of nodes with comparatively strong internal connectivity, is a fundamental task for deeply understanding the structure and function of a network. Yet, there is a lack of formal criteria for defining communities and for testing their significance. We propose a sharp definition that is based on a quality threshold. By means of a lumped Markov chain model of a random walker, a quality measure called "persistence probability" is associated to a cluster, which is then defined as an "α-community" if such a probability is not smaller than α. Consistently, a partition composed of α-communities is an "α-partition." These definitions turn out to be very effective for finding and testing communities. If a set of candidate partitions is available, setting the desired α-level allows one to immediately select the α-partition with the finest decomposition. Simultaneously, the persistence probabilities quantify the quality of each single community. Given its ability in individually assessing each single cluster, this approach can also disclose single well-defined communities even in networks that overall do not possess a definite clusterized structure.

Paradox of Migration in Kolkata: A Megacity in GBM Delta

NASA Astrophysics Data System (ADS)

Das, S.; Hazra, S.; Ghosh, T.

2015-12-01

Contrary to other coastal cities (Mumbai, Chennai, Bhubaneswar etc.) in India, Kolkata, the largest city of India until 1990, has been showing a persistent trend of out-migration over the last decade. The situation is more paradoxical when compared to Dhaka in Bangladesh, the other coastal city in Ganga-Brahmaputra-Meghna (GBM) delta. Exacerbating impacts of Climate Change like accelerated sea level rise, impact of cyclones, rising temperature and high rainfall events and waterlogging, vis-à-vis the density of poor population in slums, Kolkata has been assessed as one of the most vulnerable cities of the world. However, Kolkata has long been a preferred destination for migrants for its port based economy, existence of industrial belt with labour intensive industries. The city and its surrounding districts attracted a massive influx of trans-border migrants when India and Bangladesh gained Independence in 1947 and 1971 respectively. The paper attempts to explore reasons behind the present trend of depopulation in the erstwhile preferred migration destination. This paper distinguishes between 'Kolkata City' (census district) with 4.5 million residents and 'Kolkata Megacity' which encompasses also the peri-urban areas and home to almost 14.1 million people according to Census 2011. Analysing migration as an ongoing research activity under DECCMA project, an overall 'in-migration' pattern can be deciphered in Kolkata 'megacity'. On the contrary, the Kolkata 'city' located right in the heart of the megacity exhibits negative net migration (-5.11%) i.e. high 'out-migration'. Plausible causes can be movement of people from Kolkata 'city' to peri-urban areas and satellite towns (urban to urban migration) probably due to closure of labour intensive industries, comparatively lower land prices, availability of space and accommodation, lower costs of living, development of different modes of commutation and communication. Further growth of population in the Kolkata Megacity area is accomplished by rural to urban migration from vulnerable areas of Sundarban. Thus in spite of the declining population in Kolkata city, Kolkata megacity is emerging as a 'major setting of human habitation' in a 21st century world stressed by climate change.

Health worker migration from South Africa: causes, consequences and policy responses.

PubMed

Labonté, Ronald; Sanders, David; Mathole, Thubelihle; Crush, Jonathan; Chikanda, Abel; Dambisya, Yoswa; Runnels, Vivien; Packer, Corinne; MacKenzie, Adrian; Murphy, Gail Tomblin; Bourgeault, Ivy Lynn

2015-12-03

This paper arises from a four-country study that sought to better understand the drivers of skilled health worker migration, its consequences, and the strategies countries have employed to mitigate negative impacts. The four countries-Jamaica, India, the Philippines, and South Africa-have historically been "sources" of skilled health workers (SHWs) migrating to other countries. This paper presents the findings from South Africa. The study began with a scoping review of the literature on health worker migration from South Africa, followed by empirical data collected from skilled health workers and stakeholders. Surveys were conducted with physicians, nurses, pharmacists, and dentists. Interviews were conducted with key informants representing educators, regulators, national and local governments, private and public sector health facilities, recruitment agencies, and professional associations and councils. Survey data were analyzed using descriptive statistics and regression models. Interview data were analyzed thematically. There has been an overall decrease in out-migration of skilled health workers from South Africa since the early 2000s largely attributed to a reduced need for foreign-trained skilled health workers in destination countries, limitations on recruitment, and tighter migration rules. Low levels of worker satisfaction persist, although the Occupation Specific Dispensation (OSD) policy (2007), which increased wages for health workers, has been described as critical in retaining South African nurses. Return migration was reportedly a common occurrence. The consequences attributed to SHW migration are mixed, but shortages appear to have declined. Most promising initiatives are those designed to reinforce the South African health system and undertaken within South Africa itself. In the near past, South Africa's health worker shortages as a result of emigration were viewed as significant and harmful. Currently, domestic policies to improve health care and the health workforce including innovations such as new skilled health worker cadres and OSD policies appear to have served to decrease SHW shortages to some extent. Decreased global demand for health workers and indications that South African SHWs primarily use migratory routes for professional development suggest that health worker shortages as a result of permanent migration no longer pertains to South Africa.

Wild waterfowl migration and domestic duck density shape the epidemiology of highly pathogenic H5N8 influenza in the Republic of Korea

PubMed Central

Hill, Sarah C.; Lee, Youn-Jeong; Song, Byung-Min; Kang, Hyun-Mi; Lee, Eun-Kyoung; Hanna, Amanda; Gilbert, Marius; Brown, Ian H.; Pybus, Oliver G.

2015-01-01

Highly pathogenic avian influenza (HPAI) viruses threaten human and animal health yet their emergence is poorly understood, partly because sampling of the HPAI Asian-origin H5N1 lineage immediately after its identification in 1996 was comparatively sparse. The discovery of a novel H5N8 virus in 2013 provides a new opportunity to investigate HPAI emergence in greater detail. Here we investigate the origin and transmission of H5N8 in the Republic of Korea, the second country to report the new strain. We reconstruct viral spread using phylogeographic methods and interpret the results in the context of ecological data on poultry density, overwintering wild bird numbers, and bird migration patterns. Our results indicate that wild waterfowl migration and domestic duck density were important to H5N8 epidemiology. Specifically, we infer that H5N8 entered the Republic of Korea via Jeonbuk province, then spread rapidly among western provinces where densities of overwintering waterfowl and domestic ducks are higher, yet rarely persisted in eastern regions. The common ancestor of H5N8 in the Republic of Korea was estimated to have arrived during the peak of inward migration of overwintering birds. Recent virus isolations likely represent re-introductions via bird migration from an as-yet unsampled reservoir. Based on the limited data from outside the Republic of Korea, our data suggest that H5N8 may have entered Europe at least twice, and Asia at least three times from this reservoir, most likely carried by wild migrating birds. PMID:26079277

CCL26/eotaxin-3 is more effective to induce the migration of eosinophils of asthmatics than CCL11/eotaxin-1 and CCL24/eotaxin-2.

PubMed

Provost, Véronique; Larose, Marie-Chantal; Langlois, Anick; Rola-Pleszczynski, Marek; Flamand, Nicolas; Laviolette, Michel

2013-08-01

CCL11, CCL24, and CCL26 are chemokines involved in the recruitment of eosinophils into tissues and mainly activate CCR3. Whereas the genomic or pharmacological inhibition of CCR3 prevents the development of experimental asthma in rodents, it only impairs the recruitment of eosinophils by ∼40% in humans. As humans, but not rodents, express CCL26, we investigated the impact of CCL11, CCL24, and CCL26 on human eosinophils recruitment and evaluated the involvement of CCR3. The migration of eosinophils of healthy volunteers was similar for the three eotaxins. Eosinophils of mild asthmatics had a greater response to CCL11 and a much greater response to CCL26. Whereas all eotaxins induced the migration of eosinophil of asthmatics from 0 to 6 h, CCL26 triggered a second phase of migration between 12 and 18 h. Given that the CCR3 antagonists SB 328437 and SB 297006 inhibited the 5-oxo-eicosatetraenoate-induced migration of eosinophils and that the CCR3 antagonist UCB 35625 was not specific for CCR3, CCR3 blockade was performed with the CCR3 mAb. This antibody completely blocked the effect of all eotaxins on eosinophils of healthy subjects and the effect of CCL24 on the eosinophils of asthmatics. Interestingly, CCR3 blockade did not affect the second migration phase induced by CCL26 on eosinophils of asthmatics. In conclusion, CCL26 is a more effective chemoattractant than CCL11 and CCL24 for eosinophils of asthmatics. The mechanism of this greater efficiency is not yet defined. However, these results suggest that CCL26 may play a unique and important role in the recruitment of eosinophils in persistent asthma.

Wild waterfowl migration and domestic duck density shape the epidemiology of highly pathogenic H5N8 influenza in the Republic of Korea.

PubMed

Hill, Sarah C; Lee, Youn-Jeong; Song, Byung-Min; Kang, Hyun-Mi; Lee, Eun-Kyoung; Hanna, Amanda; Gilbert, Marius; Brown, Ian H; Pybus, Oliver G

2015-08-01

Highly pathogenic avian influenza (HPAI) viruses threaten human and animal health yet their emergence is poorly understood, partly because sampling of the HPAI Asian-origin H5N1 lineage immediately after its identification in 1996 was comparatively sparse. The discovery of a novel H5N8 virus in 2013 provides a new opportunity to investigate HPAI emergence in greater detail. Here we investigate the origin and transmission of H5N8 in the Republic of Korea, the second country to report the new strain. We reconstruct viral spread using phylogeographic methods and interpret the results in the context of ecological data on poultry density, overwintering wild bird numbers, and bird migration patterns. Our results indicate that wild waterfowl migration and domestic duck density were important to H5N8 epidemiology. Specifically, we infer that H5N8 entered the Republic of Korea via Jeonbuk province, then spread rapidly among western provinces where densities of overwintering waterfowl and domestic ducks are higher, yet rarely persisted in eastern regions. The common ancestor of H5N8 in the Republic of Korea was estimated to have arrived during the peak of inward migration of overwintering birds. Recent virus isolations likely represent re-introductions via bird migration from an as-yet unsampled reservoir. Based on the limited data from outside the Republic of Korea, our data suggest that H5N8 may have entered Europe at least twice, and Asia at least three times from this reservoir, most likely carried by wild migrating birds. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Kaposi's Sarcoma-Associated Herpesvirus Interleukin-6 Modulates Endothelial Cell Movement by Upregulating Cellular Genes Involved in Migration.

PubMed

Giffin, Louise; West, John A; Damania, Blossom

2015-12-08

Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of human Kaposi's sarcoma, a tumor that arises from endothelial cells, as well as two B cell lymphoproliferative diseases, primary effusion lymphoma and multicentric Castleman's disease. KSHV utilizes a variety of mechanisms to evade host immune responses and promote cellular transformation and growth in order to persist for the life of the host. A viral homolog of human interleukin-6 (hIL-6) named viral interleukin-6 (vIL-6) is encoded by KSHV and expressed in KSHV-associated cancers. Similar to hIL-6, vIL-6 is secreted, but the majority of vIL-6 is retained within the endoplasmic reticulum, where it can initiate functional signaling through part of the interleukin-6 receptor complex. We sought to determine how intracellular vIL-6 modulates the host endothelial cell environment by analyzing vIL-6's impact on the endothelial cell transcriptome. vIL-6 significantly altered the expression of many cellular genes associated with cell migration. In particular, vIL-6 upregulated the host factor carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) at the protein and message levels. CEACAM1 has been implicated in tumor invasion and metastasis and promotes migration and vascular remodeling in endothelial cells. We report that vIL-6 upregulates CEACAM1 by a STAT3-dependent mechanism and that CEACAM1 promotes vIL-6-mediated migration. Furthermore, latent and de novo KSHV infections of endothelial cells also induce CEACAM1 expression. Collectively, our data suggest that vIL-6 modulates endothelial cell migration by upregulating the expression of cellular factors, including CEACAM1. Kaposi's sarcoma-associated herpesvirus (KSHV) is linked with the development of three human malignancies, Kaposi's sarcoma, multicentric Castleman's disease, and primary effusion lymphoma. KSHV expresses many factors that enable the virus to manipulate the host environment in order to persist and induce disease. The viral interleukin-6 (vIL-6) produced by KSHV is structurally and functionally homologous to the human cytokine interleukin-6, except that vIL-6 is secreted slowly and functions primarily from inside the host cell. To investigate the unique intracellular role of vIL-6, we analyzed the impact of vIL-6 on endothelial cell gene expression. We report that vIL-6 significantly alters the expression of genes associated with cell movement, including that for CEACAM1. The gene for CEACAM1 was upregulated by vIL-6 and by latent and primary KSHV infection and promotes vIL-6-mediated endothelial cell migration. This work advances the field's understanding of vIL-6 function and its contribution to KSHV pathogenesis. Copyright © 2015 Giffin et al.

[Women in labor and migration. The female labor market between 1950 and 1990 and migration of women to Santiago, Chile].

PubMed

Szasz, I

1994-06-01

Changes in the volume of female migration to Santiago and in the employment patterns of migrant women are analyzed in relationship to changes in the female labor market from 1950 onward, with special emphasis on the years 1970-90. Data sources include published works, the censuses of 1952 to 1982, a 1962 survey on in-migration to Santiago, employment surveys conducted by the University of Chile and the National Institute of Statistics, special tabulations for subsamples of the 1970 and 1982 censuses, and household employment survey information from the fourth quarter of 1993. In 1973 Chile embarked on a process of structural adjustments that affected social expenditures and employment, profoundly modifying urban labor markets. The Chilean economy is currently in a phase of consolidating its productive transformation, with positive results for economic growth and recuperation of employment, but with no reduction of poverty. The explanation of the growth in poverty should be sought in modifications in the conditions of employment of the Chilean population during the productive transformation. Modernization processes such as increased education and access to fertility control contributed to an increase in the number of highly educated women in nonmanual occupations in Santiago, but have not significantly influenced the volume or direction of female migration or modified the disadvantageous occupational profile of migrant women. Gender considerations including cultural norms governing female sexual behavior and nuptiality appear to exercise a decisive influence on the occupational status of migrant women in Santiago. Low status, single women migrating to Santiago have been concentrated in domestic service in part because of their need to find work providing safe living quarters. After 1975, migrant women encountered an increasing proportion of urban women working and looking for work and a structural transformation of domestic service marked by massive absorption of low status nonmigrant women. The disadvantages of migrant women related to their lower age, education, and urban experience have declined or disappeared, but disadvantages related to lack of family and housing in the city have persisted. Continuing high rates of urban poverty in Santiago and substitution of precarious employment for open unemployment have resulted in continuing high rates of female employment. The lack of dynamism in the expansion of female employment, the persistence of gender segmentation of the labor market, continuing tertiarization of female employment, and new trends to precarious employment and increased economic participation of nonmigrant women suggest that occupational patterns of migrant women will not change greatly in the 1990s. Although they have become better educated and prefer to avoid live-in domestic service, their employment options appear limited.

Long-range hot-carrier transport in hybrid perovskites visualized by ultrafast microscopy

NASA Astrophysics Data System (ADS)

Guo, Zhi; Wan, Yan; Yang, Mengjin; Snaider, Jordan; Zhu, Kai; Huang, Libai

2017-04-01

The Shockley-Queisser limit for solar cell efficiency can be overcome if hot carriers can be harvested before they thermalize. Recently, carrier cooling time up to 100 picoseconds was observed in hybrid perovskites, but it is unclear whether these long-lived hot carriers can migrate long distance for efficient collection. We report direct visualization of hot-carrier migration in methylammonium lead iodide (CH3NH3PbI3) thin films by ultrafast transient absorption microscopy, demonstrating three distinct transport regimes. Quasiballistic transport was observed to correlate with excess kinetic energy, resulting in up to 230 nanometers transport distance that could overcome grain boundaries. The nonequilibrium transport persisted over tens of picoseconds and ~600 nanometers before reaching the diffusive transport limit. These results suggest potential applications of hot-carrier devices based on hybrid perovskites.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Yong; Desseaux, Solenne; Aden, Bethany

We report that surface-grafting thermoresponsive polymers allows the preparation of thin polymer brush coatings with surface properties that can be manipulated by variation of temperature. In most instances, thermoresponsive polymer brushes are produced using polymers that dehydrate and collapse above a certain temperature. This report presents the preparation and properties of polymer brushes that show thermoresponsive surface properties, yet are shape-persistent in that they do not undergo main chain collapse. The polymer brushes presented here are obtained via vapor deposition surface-initiated ring-opening polymerization (SI-ROP) of γ-di- or tri(ethylene glycol)-modified glutamic acid N-carboxyanhydrides. Vapor deposition SI-ROP of γ-di- or tri(ethylene glycol)-modifiedmore » L- or D-glutamic acid N-carboxyanhydrides affords helical surface-tethered polymer chains that do not show any changes in secondary structure between 10 and 70 °C. QCM-D experiments, however, revealed significant dehydration of poly(γ-(2-(2-methoxyethoxy)ethyl)-l-glutamate) (poly(L-EG 2-Glu)) brushes upon heating from 10 to 40 °C. At the same time, AFM and ellipsometry studies did not reveal significant variations in film thickness over this temperature range, which is consistent with the shape-persistent nature of these polypeptide brushes and indicates that the thermoresponsiveness of the films is primarily due to hydration and dehydration of the oligo(ethylene glycol) side chains. The results we present here illustrate the potential of surface-initiated NCA ring-opening polymerization to generate densely grafted assemblies of polymer chains that possess well-defined secondary structures and tunable surface properties. These polypeptide brushes complement their conformationally unordered counterparts that can be generated via surface-initiated polymerization of vinyl-type monomers and represent another step forward to biomimetic surfaces and interfaces.« less

Separation and screening of short-chain chlorinated paraffins in environmental samples using comprehensive two-dimensional gas chromatography with micro electron capture detection.

PubMed

Xia, Dan; Gao, Lirong; Zhu, Shuai; Zheng, Minghui

2014-11-01

Short-chain chlorinated paraffins (SCCPs) are highly complex technical mixtures with thousands of isomers and numerous homologs. They are classified as priority candidate persistent organic pollutants under the Stockholm Convention for their persistence, bioaccumulation, and toxicity. Analyzing SCCPs is challenging because of the complexity of the mixtures. Chromatograms of SCCPs acquired using one-dimensional (1D) gas chromatography (GC) contain a large characteristic "peak" with a broad and unresolved profile. Comprehensive two-dimensional GC (GC×GC) shows excellent potential for separating complex mixtures. In this study, GC×GC coupled with micro electron capture detection (μECD) was used to separate and screen SCCPs. The chromatographic parameters, including the GC column types, oven temperature program, and modulation period, were systematically optimized. The SCCP congeners were separated into groups using a DM-1 column connected to a BPX-50 column. The SCCP congeners in technical mixtures were separated according to the number of chlorine substituents for a given carbon chain length and according to the number of carbon atoms plus chlorine atoms for different carbon chain lengths. A fish tissue sample was analyzed to illustrate the feasibility of the GC×GC-μECD method in analyzing biological samples. Over 1,500 compounds were identified in the fish extract, significantly more than were identified using 1D GC. The detection limits for five selected SCCP congeners were between 1 and 5 pg/L using the GC×GC method, and these were significantly lower than those achieved using 1D GC. This method is a good choice for analysis of SCCPs in environmental samples, exhibiting good separation and good sensitivity.

Climate of migration? How climate triggered migration from southwest Germany to North America during the 19th century

NASA Astrophysics Data System (ADS)

Glaser, Rüdiger; Himmelsbach, Iso; Bösmeier, Annette

2017-11-01

This paper contributes to the ongoing debate on the extent to which climate and climatic change can have a negative impact on societies by triggering migration, or even contribute to conflict. It summarizes results from the transdisciplinary project Climate of migration (funded 2010-2014), whose innovative title was created by Franz Mauelshagen and Uwe Lübken. The overall goal of this project was to analyze the relation between climatic and socioeconomic parameters and major migration waves from southwest Germany to North America during the 19th century. The article assesses the extent to which climatic conditions triggered these migration waves. The century investigated was in general characterized by the Little Ice Age with three distinct cooling periods, causing major glacier advances in the alpine regions and numerous climatic extremes such as major floods, droughts and severe winter. Societal changes were tremendous, marked by the warfare during the Napoleonic era (until 1815), the abolition of serfdom (1817), the bourgeois revolution (1847/48), economic freedom (1862), the beginning of industrialization accompanied by large-scale rural-urban migration resulting in urban poverty, and finally by the foundation of the German Empire in 1871.

The presented study is based on quantitative data and a qualitative, information-based discourse analysis. It considers climatic conditions as well as socioeconomic and political issues, leading to the hypothesis of a chain of effects ranging from unfavorable climatic conditions to a decrease in crop yields to rising cereal prices and finally to emigration. These circumstances were investigated extensively for the peak emigration years identified with each migration wave. Furthermore, the long-term relations between emigration and the prevailing climatic conditions, crop yields and cereal prices were statistically evaluated with a sequence of linear models which were significant with explanatory power between 22 and 38 %.

Ubiquitous Occurrence of Fluorotelomer Alcohols in Eco-Friendly Paper-Made Food-Contact Materials and Their Implication for Human Exposure.

PubMed

Yuan, Guanxiang; Peng, Hui; Huang, Chong; Hu, Jianying

2016-01-19

The occurrence of fluorotelomer alcohols (FTOHs) was investigated in 94 food-contact materials (FCMs). We detected 6:2 FTOH (<0.60-1110 ng/g), 8:2 FTOH (<0.40-8490 ng/g), and 10:2 FTOH (<0.02-9350 ng/g) in most FCM samples, and four longer-chain C14-20 FTOHs were, for the first time, identified in FCMs with relatively high concentrations (<0.02-8450 ng/g for 12:2 FTOH, <0.02-1640 ng/g for 14:2 FTOH, <0.02-372 ng/g for 16:2 FTOH, and <0.02-130 ng/g for 18:2 FTOH). There were three typical profiles of FTOHs that were dominated by 6:2 FTOH (95.6 ± 8.1% in 9 FCMs), 8:2 FTOH (50.9 ± 20.8% in 22 FCMs), and 10:2 FTOH (44.5 ± 20.9% in 30 FCMs), indicating the congener-specific usage of FTOHs for different commercial purposes. All nine detectable FCMs produced in the United States were dominated by 6:2 FTOH, which was significantly different from those produced in China. The median concentration of total FTOHs in eco-friendly paper tableware was 2990 ng/g, which was lower than in popcorn bags (18 200 ng/g) but much higher than other FCMs (<0.55-38.7 ng/g). FTOHs could migrate from paper bowls, with migration efficiencies of 0.004-0.24% into water, 0.004-0.24% into 10% ethanol, 0.009-2.79% into 30% ethanol, 0.06-13.0% into 50% ethanol (v/v) simulants, and 0.04-2.28% into oil. Migration efficiencies decreased with increasing carbon chain lengths of FTOHs.

African Female Physicians and Nurses in the Global Care Chain: Qualitative Explorations from Five Destination Countries.

PubMed

Wojczewski, Silvia; Pentz, Stephen; Blacklock, Claire; Hoffmann, Kathryn; Peersman, Wim; Nkomazana, Oathokwa; Kutalek, Ruth

2015-01-01

Migration of health professionals is an important policy issue for both source and destination countries around the world. The majority of migrant care workers in industrialized countries today are women. However, the dimension of mobility of highly skilled females from countries of the global south has been almost entirely neglected for many years. This paper explores the experiences of high-skilled female African migrant health-workers (MHW) utilising the framework of Global Care Chain (GCC) research. In the frame of the EU-project HURAPRIM (Human Resources for Primary Health Care in Africa), the research team conducted 88 semi-structured interviews with female and male African MHWs in five countries (Botswana, South Africa, Belgium, Austria, UK) from July 2011 until April 2012. For this paper we analysed the 34 interviews with female physicians and nurses using the qualitative framework analysis approach and the software atlas.ti. In terms of the effect of the migration on their career, almost all of the respondents experienced short-term, long-term or permanent inability to work as health-care professionals; few however also reported a positive career development post-migration. Discrimination based on a foreign nationality, race or gender was reported by many of our respondents, physicians and nurses alike, whether they worked in an African or a European country. Our study shows that in addition to the phenomenon of deskilling often reported in GCC research, many female MHW are unable to work according to their qualifications due to the fact that their diplomas are not recognized in the country of destination. Policy strategies are needed regarding integration of migrants in the labour market and working against discrimination based on race and gender.

African Female Physicians and Nurses in the Global Care Chain: Qualitative Explorations from Five Destination Countries

PubMed Central

Wojczewski, Silvia; Pentz, Stephen; Blacklock, Claire; Hoffmann, Kathryn; Peersman, Wim; Nkomazana, Oathokwa; Kutalek, Ruth

2015-01-01

Migration of health professionals is an important policy issue for both source and destination countries around the world. The majority of migrant care workers in industrialized countries today are women. However, the dimension of mobility of highly skilled females from countries of the global south has been almost entirely neglected for many years. This paper explores the experiences of high-skilled female African migrant health-workers (MHW) utilising the framework of Global Care Chain (GCC) research. In the frame of the EU-project HURAPRIM (Human Resources for Primary Health Care in Africa), the research team conducted 88 semi-structured interviews with female and male African MHWs in five countries (Botswana, South Africa, Belgium, Austria, UK) from July 2011 until April 2012. For this paper we analysed the 34 interviews with female physicians and nurses using the qualitative framework analysis approach and the software atlas.ti. In terms of the effect of the migration on their career, almost all of the respondents experienced short-term, long-term or permanent inability to work as health-care professionals; few however also reported a positive career development post-migration. Discrimination based on a foreign nationality, race or gender was reported by many of our respondents, physicians and nurses alike, whether they worked in an African or a European country. Our study shows that in addition to the phenomenon of deskilling often reported in GCC research, many female MHW are unable to work according to their qualifications due to the fact that their diplomas are not recognized in the country of destination. Policy strategies are needed regarding integration of migrants in the labour market and working against discrimination based on race and gender. PMID:26068218

Source and migration of short-chain chlorinated paraffins in the coastal East China Sea using multiproxies of marine organic geochemistry.

PubMed

Zhao, Zongshan; Li, Huijuan; Wang, Yawei; Li, Guoliang; Cao, Yali; Zeng, Lixi; Lan, Jing; Wang, Thanh; Jiang, Guibin

2013-05-21

Multiple proxies of terrestrial organic matters (TOM) were introduced to study the migration behaviors of short-chain chlorinated paraffins (SCCPs) in the coastal East China Sea (ECS). The contents of SCCPs in the surface sediment collected from Changjiang (Yangtze) River Delta (CRD) and along the Zhejiang-Fujian coastline ranged from 9.0 to 37.2 ng/g (dry weight, d.w.), displaying a "band-style" distribution trend. Spatial distribution patterns of SCCP congeners presented an increasing trend seaward and southward along the coastline for shorter carbon length (C₁₀ + C₁₁) and lower chlorinated (Cl₅ + Cl₆ + Cl₇) congeners, suggesting a spreading tendency seaward and southward from the CRD and the north of the inner shelf. The significant relationship between ΣSCCPs and total organic carbons (TOC) (r(2) = 0.402, p < 0.05) indicated that the migration of SCCPs in sediments was markedly affected by TOC. The spatial patterns of the TOM proxies of TOC δ(13)C, the contents of ΣC₂₇ + C₂₉ + C₃₁ n-alkanes, terrestrial marine biomarker ratio (TMBR), and terrestrial TOC (T-TOC) were all similar to that of ΣSCCPs. Linear relationships between SCCP contents and both the contents of ΣC₂₇ + C₂₉ + C₃₁ n-alkanes (r(2) = 0.537, p < 0.05) and T-TOC (r(2) = 0.495, p < 0.05) were also observed. The consistence demonstrated that a major portion of sedimentary SCCPs in the coastal ECS should be from the river input of Changjiang River and deposited in the CRD and along the inner shelf of the ECS, but only a minor fraction was transported to the offshore areas.

Natural flows of H2-rich fluids in the ophiolites of Oman and the Philippines: Tectonic control of migration pathways and associated diagenetic processes

NASA Astrophysics Data System (ADS)

Deville, E. P.; Prinzhofer, A.; Vacquand, C.; Chavagnac, V.; Monnin, C.; Ceuleneer, G.; Arcilla, C. A.

2009-12-01

We compare the geological environments of sites of emission of natural hydrogen in the Oman ophiolite and the Zambales ophiolite (Luzon, Philippines). The genesis of natural H2 results from the interaction between ultrabasic rocks and aqueous solutions circulating in deep fracture networks, by oxidation of metals (Fe2+, Mn2+) and reduction of water, probably under high temperature conditions. This process generates very reducing conditions capable of destabilizing other molecules (notably reduction of deep CO2 being transformed into CH4 by Fisher-Tropsch type reactions). Nitrogen is also commonly associated to the H2-rich fluids. H2 flows are associated with the expulsion of hyperalkaline waters rich in ions OH- and Ca2+ and characterized by high pH (between 11 and 12). Most alkaline springs are found in the vicinity of major faults and/or lithological discontinuities like the basal thrust plane of the ophiolites and the peridotite-gabbro contact (Moho). Within the fracture networks, gas and water separate probably at shallow depth, i.e. close to the top of the upper aquifer level. Locally high flows of gas migrate vertically through fracture pathways and they are able to inflame spontaneously on the surface. Aqueous fluids tends to migrate laterally in the fracture network toward the creeks where most of the hyperalkaline springs are found. This water circulation induces a chain of diagenetic reactions starting in the fracture systems and continuing at the surface where it leads to the precipitation of calcite, aragonite, brucite and more rarely portlandite. This chain of diagenetic reactions is associated with the capture of the atmospheric CO2 during the precipitation of carbonates.