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Sample records for potential mechanisms linking

  1. Linking Pesticide Exposure with Pediatric Leukemia: Potential Underlying Mechanisms

    PubMed Central

    Hernández, Antonio F.; Menéndez, Pablo

    2016-01-01

    Leukemia is the most common cancer in children, representing 30% of all childhood cancers. The disease arises from recurrent genetic insults that block differentiation of hematopoietic stem and/or progenitor cells (HSPCs) and drives uncontrolled proliferation and survival of the differentiation-blocked clone. Pediatric leukemia is phenotypically and genetically heterogeneous with an obscure etiology. The interaction between genetic factors and environmental agents represents a potential etiological driver. Although information is limited, the principal toxic mechanisms of potential leukemogenic agents (e.g., etoposide, benzene metabolites, bioflavonoids and some pesticides) include topoisomerase II inhibition and/or excessive generation of free radicals, which may induce DNA single- and double-strand breaks (DNA-DSBs) in early HSPCs. Chromosomal rearrangements (duplications, deletions and translocations) may occur if these lesions are not properly repaired. The initiating hit usually occurs in utero and commonly leads to the expression of oncogenic fusion proteins. Subsequent cooperating hits define the disease latency and occur after birth and may be of a genetic, epigenetic or immune nature (i.e., delayed infection-mediated immune deregulation). Here, we review the available experimental and epidemiological evidence linking pesticide exposure to infant and childhood leukemia and provide a mechanistic basis to support the association, focusing on early initiating molecular events. PMID:27043530

  2. LINKING CARDIOMETABOLIC DISORDERS TO SPORADIC AD: A PERSPECTIVE ON POTENTIAL MECHANISMS AND MEDIATORS

    PubMed Central

    Bhat, Narayan R.

    2010-01-01

    There is increasing evidence that the incidence of Alzheimer's disease (AD) is significantly influenced by cardiovascular risk factors in association with a cluster of metabolic diseases including diabetes and atherosclerosis. The shared risk is also reflected in the dietary and lifestyle links to both metabolic disorders and AD-type cognitive dysfunction. Recent studies with genetic and diet-induced animal models have begun to illuminate convergent mechanisms and mediators between these two categories of disease conditions with distinct tissue-specific pathologies. While it is clear that peripheral inflammation and insulin resistance are central to the pathogenesis of the disorders of metabolic syndrome, it seems that the same mechanisms are also in play across the blood brain barrier (BBB) that lead to AD-like molecular and cognitive changes. This review will highlight these convergent mechanisms and discuss the role of cerebrovascular dysfunction as a conduit to brain emergence of these pathogenic processes that might also represent future therapeutic targets in AD in common with metabolic disorders. PMID:20807313

  3. Children's Attentional Biases and "5-HTTLPR" Genotype: Potential Mechanisms Linking Mother and Child Depression

    ERIC Educational Resources Information Center

    Gibb, Brandon E.; Benas, Jessica S.; Grassia, Marie; McGeary, John

    2009-01-01

    In this study, we examined the roles of specific cognitive (attentional bias) and genetic ("5-HTTLPR") risk factors in the intergenerational transmission of depression. Focusing first on the link between maternal history of major depressive disorder (MDD) and children's attentional biases, we found that children of mothers with a history of MDD…

  4. Tipping the Balance of Autism Risk: Potential Mechanisms Linking Pesticides and Autism

    PubMed Central

    Hertz-Picciotto, Irva; Pessah, Isaac N.

    2012-01-01

    Background: Autism spectrum disorders (ASDs) have been increasing in many parts of the world and a portion of cases are attributable to environmental exposures. Conclusive replicated findings have yet to appear on any specific exposure; however, mounting evidence suggests gestational pesticides exposures are strong candidates. Because multiple developmental processes are implicated in ASDs during gestation and early life, biological plausibility is more likely if these agents can be shown to affect core pathophysiological features. Objectives: Our objectives were to examine shared mechanisms between autism pathophysiology and the effects of pesticide exposures, focusing on neuroexcitability, oxidative stress, and immune functions and to outline the biological correlates between pesticide exposure and autism risk. Methods: We review and discuss previous research related to autism risk, developmental effects of early pesticide exposure, and basic biological mechanisms by which pesticides may induce or exacerbate pathophysiological features of autism. Discussion: On the basis of experimental and observational research, certain pesticides may be capable of inducing core features of autism, but little is known about the timing or dose, or which of various mechanisms is sufficient to induce this condition. Conclusions: In animal studies, we encourage more research on gene × environment interactions, as well as experimental exposure to mixtures of compounds. Similarly, epidemiologic studies in humans with exceptionally high exposures can identify which pesticide classes are of greatest concern, and studies focused on gene × environment are needed to determine if there are susceptible subpopulations at greater risk from pesticide exposures. PMID:22534084

  5. The Link between the Appendix and Ulcerative Colitis: Clinical Relevance and Potential Immunological Mechanisms.

    PubMed

    Sahami, S; Kooij, I A; Meijer, S L; Van den Brink, G R; Buskens, C J; Te Velde, A A

    2016-02-01

    The human appendix has long been considered as a vestigial organ, an organ that has lost its function during evolution. In recent years, however, reports have emerged that link the appendix to numerous immunological functions in humans. Evidence has been presented for an important role of the appendix in maintaining intestinal health. This theory suggests that the appendix may be a reservoir or 'safe house' from which the commensal gut flora can rapidly be reestablished if it is eradicated from the colon. However, the appendix may also have a role in the development of inflammatory bowel disease (IBD). Several large epidemiological cohort studies have demonstrated the preventive effect of appendectomy on the development of ulcerative colitis, a finding that has been confirmed in murine colitis models. In addition, current studies are examining the possible therapeutic effect of an appendectomy to modulate disease course in patients with ulcerative colitis. This literature review assesses the current knowledge about the clinical and immunological aspects of the vermiform appendix in IBD and suggests that the idea of the appendix as a vestigial remnant should be discarded. PMID:26416189

  6. Obstructive Sleep Apnea is Linked to Depression and Cognitive Impairment: Evidence and Potential Mechanisms.

    PubMed

    Kerner, Nancy A; Roose, Steven P

    2016-06-01

    Obstructive sleep apnea (OSA) is highly prevalent but very frequently undiagnosed. OSA is an independent risk factor for depression and cognitive impairment/dementia. Herein the authors review studies in the literature pertinent to the effects of OSA on the cerebral microvascular and neurovascular systems and present a model to describe the key pathophysiologic mechanisms that may underlie the associations, including hypoperfusion, endothelial dysfunction, and neuroinflammation. Intermittent hypoxia plays a critical role in initiating and amplifying these pathologic processes. Hypoperfusion and impaired cerebral vasomotor reactivity lead to the development or progression of cerebral small vessel disease (C-SVD). Hypoxemia exacerbates these processes, resulting in white matter lesions, white matter integrity abnormalities, and gray matter loss. Blood-brain barrier (BBB) hyperpermeability and neuroinflammation lead to altered synaptic plasticity, neuronal damage, and worsening C-SVD. Thus, OSA may initiate or amplify the pathologic processes of C-SVD and BBB dysfunction, resulting in the development or exacerbation of depressive symptoms and cognitive deficits. Given the evidence that adequate treatment of OSA with continuous positive airway pressure improves depression and neurocognitive functions, it is important to identify OSA when assessing patients with depression or cognitive impairment. Whether treatment of OSA changes the deteriorating trajectory of elderly patients with already-diagnosed vascular depression and cognitive impairment/dementia remains to be determined in randomized controlled trials. PMID:27139243

  7. Curcumin Cross-links Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Polypeptides and Potentiates CFTR Channel Activity by Distinct Mechanisms*

    PubMed Central

    Bernard, Karen; Wang, Wei; Narlawar, Rajeshwar; Schmidt, Boris; Kirk, Kevin L.

    2009-01-01

    Cystic fibrosis (CF) is caused by loss-of-function mutations in the CFTR chloride channel. Wild type and mutant CFTR channels can be activated by curcumin, a well tolerated dietary compound with some appeal as a prospective CF therapeutic. However, we show here that curcumin has the unexpected effect of cross-linking CFTR polypeptides into SDS-resistant oligomers. This effect occurred for CFTR channels in microsomes as well as in intact cells and at the same concentrations that are effective for promoting CFTR channel activity (5–50 μm). Both mature CFTR polypeptides at the cell surface and immature CFTR protein in the endoplasmic reticulum were cross-linked by curcumin, although the latter pool was more susceptible to this modification. Curcumin cross-linked two CF mutant channels (ΔF508 and G551D) as well as a variety of deletion constructs that lack the major cytoplasmic domains. In vitro cross-linking could be prevented by high concentrations of oxidant scavengers (i.e. reduced glutathione and sodium azide) indicating a possible oxidation reaction with the CFTR polypeptide. Importantly, cyclic derivatives of curcumin that lack the reactive β diketone moiety had no cross-linking activity. One of these cyclic derivatives stimulated the activities of wild type CFTR channels, Δ1198-CFTR channels, and G551D-CFTR channels in excised membrane patches. Like the parent compound, the cyclic derivative irreversibly activated CFTR channels in excised patches during prolonged exposure (>5 min). Our results raise a note of caution about secondary biochemical effects of reactive compounds like curcumin in the treatment of CF. Cyclic curcumin derivatives may have better therapeutic potential in this regard. PMID:19740743

  8. A Potential of Rail Vehicle Having Bolster with Side Bearers for Improving Curving Performance on Sharp Curves Employing Link-Type Forced Steering Mechanism

    NASA Astrophysics Data System (ADS)

    Tanifuji, Katsuya; Yaegashi, Naoki; Soma, Hitoshi

    The air spring of bolsterless bogie trucks, which have been widely employed in railway vehicles in recent years, undergoes a large distortion when the vehicles negotiate sharp curves in lines such as subway lines, and this can deteriorate the durability of air springs. Furthermore, bolsterless trucks tend to suffer from increased wheel lateral force around sharp curves with a radius of 100 m or less. In this paper we discuss the application of a link-type forced steering mechanism to bogie trucks with a bolster as a countermeasure against the above-mentioned situation. A numerical simulation is carried out using a MBS software, SIMPACK. As a result, under the condition of reduced longitudinal stiffness in the primary suspension, a bolster truck with the link-type steering mechanism exhibits the potential to suppress the wheel lateral force occurring around sharp curves. Also, the deterioration in running stability due to the application of the steering mechanism can be recovered by adding moderate lateral damping in the secondary suspension. In addition, the obtained wear index shows that the forced steering truck has decreased flange wear resulting from passing through sharp curves.

  9. Mammary gene expression profiles during an intramammary challenge reveal potential mechanisms linking negative energy balance with impaired immune response

    PubMed Central

    Moyes, Kasey M.; Drackley, James K.; Morin, Dawn E.; Rodriguez-Zas, Sandra L.; Everts, Robin E.; Lewin, Harris A.

    2010-01-01

    Our objective was to compare mammary tissue gene expression profiles during a Streptococcus uberis (S. uberis) mastitis challenge between lactating cows subjected to dietary-induced negative energy balance (NEB; n = 5) and cows fed ad libitum to maintain positive energy balance (PEB; n = 5) to better understand the mechanisms associated with NEB and risk of mastitis during the transition period. The NEB cows were feed-restricted to 60% of calculated net energy for lactation requirements for 7 days, and cows assigned to PEB were fed the same diet for ad libitum intake. Five days after feed restriction, one rear mammary quarter of each cow was inoculated with 5,000 cfu of S. uberis (O140J). At 20 h postinoculation, S. uberis-infected mammary quarters from all cows were biopsied for RNA extraction. Negative energy balance resulted in 287 differentially expressed genes (DEG; false discovery rate ≤ 0.05), with 86 DEG upregulated and 201 DEG downregulated in NEB vs. PEB. Canonical pathways most affected by NEB were IL-8 signaling (10 genes), glucocorticoid receptor signaling (13), and NRF2-mediated oxidative stress response (10). Among the genes differentially expressed by NEB, cell growth and proliferation (48) and cellular development (36) were the most enriched functions. Regarding immune response, HLA-A was upregulated due to NEB, whereas the majority of genes involved in immune response were downregulated (e.g., AKT1, IRAK1, MAPK9, and TRAF6). This study provided new avenues for investigation into the mechanisms relating NEB and susceptibility to mastitis in lactating dairy cows. PMID:20103698

  10. Mechanical and structural response of a hybrid hydrogel based on chitosan and poly(vinyl alcohol) cross-linked with epichlorohydrin for potential use in tissue engineering.

    PubMed

    Garnica-Palafox, I M; Sánchez-Arévalo, F M; Velasquillo, C; García-Carvajal, Z Y; García-López, J; Ortega-Sánchez, C; Ibarra, C; Luna-Bárcenas, G; Solís-Arrieta, L

    2014-01-01

    The development and characterization of a hybrid hydrogel based on chitosan (CS) and poly(vinyl alcohol) (PVA) chemically cross-linked with epichlorohydrin (ECH) is presented. The mechanical response of these hydrogels was evaluated by uniaxial tensile tests; in addition, their structural properties such as average molecular weight between cross-link points (Mcrl), mesh size (DN), and volume fraction (v(s)) were determined. This was done using the equivalent polymer network theory in combination with the obtained results from tensile and swelling tests. The films showed Young's modulus values of 11 ± 2 MPa and 9 ± 1 MPa for none irradiated and ultraviolet (UV) irradiated hydrogels, respectively. The cell viability was assessed using Calcein AM and Ethidium homodimer-1 assay and environmental scanning electron microscopy. The 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan thiazolyl blue formazan (MTT Formazan assay) results did not show cytotoxic effects; this was in good agreement with nuclear magnetic resonance and fourier transform infrared spectroscopies; their results did not show traces of ECH. This indicated that after the crosslinking process, there was no free ECH; furthermore, any possibility of ECH release in the construct during cell culture was discarded. The CS-PVA-ECH hybrid hydrogel allowed cell growth and extracellular matrix formation and showed adequate mechanical, structural, and biological properties for potential use in tissue engineering applications. PMID:24007370

  11. Regulatory mechanisms link phenotypic plasticity to evolvability.

    PubMed

    van Gestel, Jordi; Weissing, Franz J

    2016-01-01

    Organisms have a remarkable capacity to respond to environmental change. They can either respond directly, by means of phenotypic plasticity, or they can slowly adapt through evolution. Yet, how phenotypic plasticity links to evolutionary adaptability is largely unknown. Current studies of plasticity tend to adopt a phenomenological reaction norm (RN) approach, which neglects the mechanisms underlying plasticity. Focusing on a concrete question - the optimal timing of bacterial sporulation - we here also consider a mechanistic approach, the evolution of a gene regulatory network (GRN) underlying plasticity. Using individual-based simulations, we compare the RN and GRN approach and find a number of striking differences. Most importantly, the GRN model results in a much higher diversity of responsive strategies than the RN model. We show that each of the evolved strategies is pre-adapted to a unique set of unseen environmental conditions. The regulatory mechanisms that control plasticity therefore critically link phenotypic plasticity to the adaptive potential of biological populations. PMID:27087393

  12. Regulatory mechanisms link phenotypic plasticity to evolvability

    PubMed Central

    van Gestel, Jordi; Weissing, Franz J.

    2016-01-01

    Organisms have a remarkable capacity to respond to environmental change. They can either respond directly, by means of phenotypic plasticity, or they can slowly adapt through evolution. Yet, how phenotypic plasticity links to evolutionary adaptability is largely unknown. Current studies of plasticity tend to adopt a phenomenological reaction norm (RN) approach, which neglects the mechanisms underlying plasticity. Focusing on a concrete question – the optimal timing of bacterial sporulation – we here also consider a mechanistic approach, the evolution of a gene regulatory network (GRN) underlying plasticity. Using individual-based simulations, we compare the RN and GRN approach and find a number of striking differences. Most importantly, the GRN model results in a much higher diversity of responsive strategies than the RN model. We show that each of the evolved strategies is pre-adapted to a unique set of unseen environmental conditions. The regulatory mechanisms that control plasticity therefore critically link phenotypic plasticity to the adaptive potential of biological populations. PMID:27087393

  13. Molecular Mechanics of Tip-Link Cadherins

    NASA Astrophysics Data System (ADS)

    Sotomayor, Marcos; Weihofen, Wilhelm A.; Gaudet, Rachelle; Corey, David P.

    2011-11-01

    The hair-cell tip link, a fine filament directly conveying force to mechanosensitive transduction channels, is likely composed of two proteins, protocadherin-15 and cadherin-23, whose mutation causes deafness. However, their complete molecular structure, elasticity, and deafness-related structural defects remain largely unknown. We present crystal structures of extracellular (EC) tip-link cadherin repeats involved in hereditary deafness and tip link formation. In addition, we show that the deafness mutation D101G, in the linker region between the repeats EC1 and EC2 of cadherin-23, causes a slight bend between repeats and decreases Ca2+ affinity. Molecular dynamics simulations suggest that tip-link cadherin repeats are stiff and that either removing Ca2+ or mutating Ca2+-binding residues reduces rigidity and unfolding strength. The structures and simulations also suggest mechanisms underlying inherited deafness and how cadherin-23 may bind with protocadherin-15 to form the tip link.

  14. Mechanisms Linking Advanced Airway Management and Cardiac Arrest Outcomes

    PubMed Central

    Benoit, Justin L.; Prince, David K.; Wang, Henry E.

    2015-01-01

    Advanced airway management – such as endotracheal intubation (ETI) or supraglottic airway (SGA) insertion – is one of the most prominent interventions in out-of-hospital cardiac arrest (OHCA) resuscitation. While randomized controlled trials are currently in progress to identify the best advanced airway technique in OHCA, the mechanisms by which airway management may influence OHCA outcomes remain unknown. We provide a conceptual model describing potential mechanisms linking advanced airway management with OHCA outcomes. PMID:26073275

  15. Molecular mechanisms in deformation of cross-linked hydrogel nanocomposite.

    PubMed

    Mathesan, Santhosh; Rath, Amrita; Ghosh, Pijush

    2016-02-01

    The self-folding behavior in response to external stimuli observed in hydrogels is potentially used in biomedical applications. However, the use of hydrogels is limited because of its reduced mechanical properties. These properties are enhanced when the hydrogels are cross-linked and reinforced with nanoparticles. In this work, molecular dynamics (MD) simulation is applied to perform uniaxial tension and pull out tests to understand the mechanism contributing towards the enhanced mechanical properties. Also, nanomechanical characterization is performed using quasi static nanoindentation experiments to determine the Young's modulus of hydrogels in the presence of nanoparticles. The stress-strain responses for chitosan (CS), chitosan reinforced with hydroxyapatite (HAP) and cross-linked chitosan are obtained from uniaxial tension test. It is observed that the Young's modulus and maximum stress increase as the HAP content increases and also with cross-linking process. Load displacement plot from pullout test is compared for uncross-linked and cross-linked chitosan chains on hydroxyapatite surface. MD simulation reveals that the variation in the dihedral conformation of chitosan chains and the evolution of internal structural variables are associated with mechanical properties. Additional results reveal that the formation of hydrogen bonds and electrostatic interactions is responsible for the above variations in different systems. PMID:26652360

  16. Type 2 diabetes and cognitive impairment: linking mechanisms

    PubMed Central

    Luchsinger, José A.

    2012-01-01

    This manuscript provides a brief review of current concepts in the mechanisms potentially linking type-2-diabetes (T2D) with cognitive impairment. Existing epidemiologic studies, imaging studies, autopsy studies and clinical trials provide insights into the mechanisms linking T2D and cognitive impairment. There seems to be little dispute that T2D can cause cerebrovascular disease and thus cause vascular cognitive impairment (VCI). Whether T2D can cause late onset Alzheimer’s disease (LOAD) remains to be elucidated. Many epidemiologic studies show an association between T2D and cognitive impairment, but the association with VCI seems to be stronger compared to LOAD, suggesting that cerebrovascular disease may be the main mechanism linking T2D and cognitive impairment. Imaging studies show an association between T2D and imaging markers of LOAD, but these observations could still be explained by cerebrovascular mechanisms. Autopsy studies are few and conflicting, with some suggesting a predominantly cerebrovascular mechanism, and others providing support for a neurodegenerative mechanism. Thus far, the evidence from clinical trials is mixed in supporting a causal association between T2D and cognitive impairment, and most clinical trials that can answer this question are yet to be reported or finished. Given the epidemic of T2D in the world, it is important to elucidate whether the association between T2D and cognitive impairment, particularly LOAD, is causal, and if so, what are the mechanisms. PMID:22433668

  17. Linking Mechanics and Statistics in Epidermal Tissues

    NASA Astrophysics Data System (ADS)

    Kim, Sangwoo; Hilgenfeldt, Sascha

    2015-03-01

    Disordered cellular structures, such as foams, polycrystals, or living tissues, can be characterized by quantitative measurements of domain size and topology. In recent work, we showed that correlations between size and topology in 2D systems are sensitive to the shape (eccentricity) of the individual domains: From a local model of neighbor relations, we derived an analytical justification for the famous empirical Lewis law, confirming the theory with experimental data from cucumber epidermal tissue. Here, we go beyond this purely geometrical model and identify mechanical properties of the tissue as the root cause for the domain eccentricity and thus the statistics of tissue structure. The simple model approach is based on the minimization of an interfacial energy functional. Simulations with Surface Evolver show that the domain statistics depend on a single mechanical parameter, while parameter fluctuations from cell to cell play an important role in simultaneously explaining the shape distribution of cells. The simulations are in excellent agreement with experiments and analytical theory, and establish a general link between the mechanical properties of a tissue and its structure. The model is relevant to diagnostic applications in a variety of animal and plant tissues.

  18. Linking properties to microstructure through multiresolution mechanics

    NASA Astrophysics Data System (ADS)

    McVeigh, Cahal James

    The macroscale mechanical and physical properties of materials are inherently linked to the underlying microstructure. Traditional continuum mechanics theories have focused on approximating the heterogeneous microstructure as a continuum, which is conducive to a partial differential equation mathematical description. Although this makes large scale simulation of material much more efficient than modeling the detailed microstructure, the relationship between microstructure and macroscale properties becomes unclear. In order to perform computational materials design, material models must clearly relate the key underlying microstructural parameters (cause) to macroscale properties (effect). In this thesis, microstructure evolution and instability events are related to macroscale mechanical properties through a new multiresolution continuum analysis approach. The multiresolution nature of this theory allows prediction of the evolving magnitude and scale of deformation as a direct function of the changing microstructure. This is achieved via a two-pronged approach: (a) Constitutive models which track evolving microstructure are developed and calibrated to direct numerical simulations (DNS) of the microstructure. (b) The conventional homogenized continuum equations of motion are extended via a virtual power approach to include extra coupled microscale stresses and stress couples which are active at each characteristic length scale within the microstructure. The multiresolution approach is applied to model the fracture toughness of a cemented carbide, failure of a steel alloy under quasi-static loading conditions and the initiation and velocity of adiabatic shear bands under high speed dynamic loading. In each case the multiresolution analysis predicts the important scale effects which control the macroscale material response. The strain fields predicted in the multiresolution continuum analyses compare well to those observed in direct numerical simulations of the

  19. Oocyte activation and latent HIV-1 reactivation: AMPK as a common mechanism of action linking the beginnings of life and the potential eradication of HIV-1.

    PubMed

    Finley, Jahahreeh

    2016-08-01

    stress (e.g. increase in Ca(2+) concentration, reactive oxygen species generation, increase in AMP/ATP ratio) is essential for oocyte maturation, T cell activation, and mitochondrial function. In addition to the AMPK kinase LKB1, CaMKK2, a Ca(2+)/calmodulin-dependent kinase that also activates AMPK, is present in and activated on T cell activation and is also present in mouse oocytes and persists until the zygote and two-cell stages. It is our hypothesis that AMPK activation represents a central node linking T cell activation-induced latent HIV-1 reactivation and both physiological and artificial oocyte activation. We further propose the novel observation that various compounds that have been shown to reactivate latent HIV-1 (e.g. PMA, ionomycin, metformin, bryostatin, resveratrol, etc.) or activate oocytes (PMA, ionomycin, ethanol, puromycin, etc.) either alone or in combination likely do so via stress-induced activation of AMPK. PMID:27372854

  20. Immune Mechanisms Linking Obesity and Preeclampsia.

    PubMed

    Spradley, Frank T; Palei, Ana C; Granger, Joey P

    2015-01-01

    Preeclampsia (PE) is characterized by hypertension occurring after the twentieth week of pregnancy. It is a significant contributor to maternal and perinatal morbidity and mortality in developing countries and its pervasiveness is increasing within developed countries including the USA. However, the mechanisms mediating the pathogenesis of this maternal disorder and its rising prevalence are far from clear. A major theory with strong experimental evidence is that placental ischemia, resulting from inappropriate remodeling and widening of the maternal spiral arteries, stimulates the release of soluble factors from the ischemic placenta causing maternal endothelial dysfunction and hypertension. Aberrant maternal immune responses and inflammation have been implicated in each of these stages in the cascade leading to PE. Regarding the increased prevalence of this disease, it is becoming increasingly evident from epidemiological data that obesity, which is a state of chronic inflammation in itself, increases the risk for PE. Although the specific mechanisms whereby obesity increases the rate of PE are unclear, there are strong candidates including activated macrophages and natural killer cells within the uterus and placenta and activation in the periphery of T helper cells producing cytokines including TNF-α, IL-6 and IL-17 and the anti-angiogenic factor sFlt-1 and B cells producing the agonistic autoantibodies to the angiotensin type 1 receptor (AT1-aa). This review will focus on the immune mechanisms that have been implicated in the pathogenesis of hypertension in PE with an emphasis on the potential importance of inflammatory factors in the increased risk of developing PE in obese pregnancies. PMID:26569331

  1. Immune Mechanisms Linking Obesity and Preeclampsia

    PubMed Central

    Spradley, Frank T.; Palei, Ana C.; Granger, Joey P.

    2015-01-01

    Preeclampsia (PE) is characterized by hypertension occurring after the twentieth week of pregnancy. It is a significant contributor to maternal and perinatal morbidity and mortality in developing countries and its pervasiveness is increasing within developed countries including the USA. However, the mechanisms mediating the pathogenesis of this maternal disorder and its rising prevalence are far from clear. A major theory with strong experimental evidence is that placental ischemia, resulting from inappropriate remodeling and widening of the maternal spiral arteries, stimulates the release of soluble factors from the ischemic placenta causing maternal endothelial dysfunction and hypertension. Aberrant maternal immune responses and inflammation have been implicated in each of these stages in the cascade leading to PE. Regarding the increased prevalence of this disease, it is becoming increasingly evident from epidemiological data that obesity, which is a state of chronic inflammation in itself, increases the risk for PE. Although the specific mechanisms whereby obesity increases the rate of PE are unclear, there are strong candidates including activated macrophages and natural killer cells within the uterus and placenta and activation in the periphery of T helper cells producing cytokines including TNF-α, IL-6 and IL-17 and the anti-angiogenic factor sFlt-1 and B cells producing the agonistic autoantibodies to the angiotensin type 1 receptor (AT1-aa). This review will focus on the immune mechanisms that have been implicated in the pathogenesis of hypertension in PE with an emphasis on the potential importance of inflammatory factors in the increased risk of developing PE in obese pregnancies. PMID:26569331

  2. Quantum mechanics without potential function

    SciTech Connect

    Alhaidari, A. D.; Ismail, M. E. H.

    2015-07-15

    In the standard formulation of quantum mechanics, one starts by proposing a potential function that models the physical system. The potential is then inserted into the Schrödinger equation, which is solved for the wavefunction, bound states energy spectrum, and/or scattering phase shift. In this work, however, we propose an alternative formulation in which the potential function does not appear. The aim is to obtain a set of analytically realizable systems, which is larger than in the standard formulation and may or may not be associated with any given or previously known potential functions. We start with the wavefunction, which is written as a bounded infinite sum of elements of a complete basis with polynomial coefficients that are orthogonal on an appropriate domain in the energy space. Using the asymptotic properties of these polynomials, we obtain the scattering phase shift, bound states, and resonances. This formulation enables one to handle not only the well-known quantum systems but also previously untreated ones. Illustrative examples are given for two- and three-parameter systems.

  3. Pathophysiological mechanisms linking obesity and esophageal adenocarcinoma

    PubMed Central

    Alexandre, Leo; Long, Elizabeth; Beales, Ian LP

    2014-01-01

    In recent decades there has been a dramatic rise in the incidence of esophageal adenocarcinoma (EAC) in the developed world. Over approximately the same period there has also been an increase in the prevalence of obesity. Obesity, especially visceral obesity, is an important independent risk factor for the development of gastro-esophageal reflux disease, Barrett’s esophagus and EAC. Although the simplest explanation is that this mediated by the mechanical effects of abdominal obesity promoting gastro-esophageal reflux, the epidemiological data suggest that the EAC-promoting effects are independent of reflux. Several, not mutually exclusive, mechanisms have been implicated, which may have different effects at various points along the reflux-Barrett’s-cancer pathway. These mechanisms include a reduction in the prevalence of Helicobacter pylori infection enhancing gastric acidity and possibly appetite by increasing gastric ghrelin secretion, induction of both low-grade systemic inflammation by factors secreted by adipose tissue and the metabolic syndrome with insulin-resistance. Obesity is associated with enhanced secretion of leptin and decreased secretion of adiponectin from adipose tissue and both increased leptin and decreased adiponectin have been shown to be independent risk factors for progression to EAC. Leptin and adiponectin have a set of mutually antagonistic actions on Barrett’s cells which appear to influence the progression of malignant behaviour. At present no drugs are of proven benefit to prevent obesity associated EAC. Roux-en-Y reconstruction is the preferred bariatric surgical option for weight loss in patients with reflux. Statins and aspirin may have chemopreventative effects and are indicated for their circulatory benefits. PMID:25400997

  4. The Vascular Depression Hypothesis: Mechanisms Linking Vascular Disease with Depression

    PubMed Central

    Taylor, Warren D.; Aizenstein, Howard J.; Alexopoulos, George S.

    2013-01-01

    The ‘Vascular Depression’ hypothesis posits that cerebrovascular disease may predispose, precipitate, or perpetuate some geriatric depressive syndromes. This hypothesis stimulated much research that has improved our understanding of the complex relationships between late-life depression (LLD), vascular risk factors, and cognition. Succinctly, there are well-established relationships between late-life depression, vascular risk factors, and cerebral hyperintensities, the radiological hallmark of vascular depression. Cognitive dysfunction is common in late-life depression, particularly executive dysfunction, a finding predictive of poor antidepressant response. Over time, progression of hyperintensities and cognitive deficits predicts a poor course of depression and may reflect underlying worsening of vascular disease. This work laid the foundation for examining the mechanisms by which vascular disease influences brain circuits and influences the development and course of depression. We review data testing the vascular depression hypothesis with a focus on identifying potential underlying vascular mechanisms. We propose a disconnection hypothesis, wherein focal vascular damage and white matter lesion location is a crucial factor influencing neural connectivity that contributes to clinical symptomatology. We also propose inflammatory and hypoperfusion hypotheses, concepts that link underlying vascular processes with adverse effects on brain function that influence the development of depression. Testing such hypotheses will not only inform the relationship between vascular disease and depression but also provide guidance on the potential repurposing of pharmacological agents that may improve late-life depression outcomes. PMID:23439482

  5. Mechanisms Linking Excess Adiposity and Carcinogenesis Promotion

    PubMed Central

    Pérez-Hernández, Ana I.; Catalán, Victoria; Gómez-Ambrosi, Javier; Rodríguez, Amaia; Frühbeck, Gema

    2014-01-01

    Obesity constitutes one of the most important metabolic diseases being associated to insulin resistance development and increased cardiovascular risk. Association between obesity and cancer has also been well established for several tumor types, such as breast cancer in post-menopausal women, colorectal, and prostate cancer. Cancer is the first death cause in developed countries and the second one in developing countries, with high incidence rates around the world. Furthermore, it has been estimated that 15–20% of all cancer deaths may be attributable to obesity. Tumor growth is regulated by interactions between tumor cells and their tissue microenvironment. In this sense, obesity may lead to cancer development through dysfunctional adipose tissue and altered signaling pathways. In this review, three main pathways relating obesity and cancer development are examined: (i) inflammatory changes leading to macrophage polarization and altered adipokine profile; (ii) insulin resistance development; and (iii) adipose tissue hypoxia. Since obesity and cancer present a high prevalence, the association between these conditions is of great public health significance and studies showing mechanisms by which obesity lead to cancer development and progression are needed to improve prevention and management of these diseases. PMID:24829560

  6. Mechanisms linking excess adiposity and carcinogenesis promotion.

    PubMed

    Pérez-Hernández, Ana I; Catalán, Victoria; Gómez-Ambrosi, Javier; Rodríguez, Amaia; Frühbeck, Gema

    2014-01-01

    Obesity constitutes one of the most important metabolic diseases being associated to insulin resistance development and increased cardiovascular risk. Association between obesity and cancer has also been well established for several tumor types, such as breast cancer in post-menopausal women, colorectal, and prostate cancer. Cancer is the first death cause in developed countries and the second one in developing countries, with high incidence rates around the world. Furthermore, it has been estimated that 15-20% of all cancer deaths may be attributable to obesity. Tumor growth is regulated by interactions between tumor cells and their tissue microenvironment. In this sense, obesity may lead to cancer development through dysfunctional adipose tissue and altered signaling pathways. In this review, three main pathways relating obesity and cancer development are examined: (i) inflammatory changes leading to macrophage polarization and altered adipokine profile; (ii) insulin resistance development; and (iii) adipose tissue hypoxia. Since obesity and cancer present a high prevalence, the association between these conditions is of great public health significance and studies showing mechanisms by which obesity lead to cancer development and progression are needed to improve prevention and management of these diseases. PMID:24829560

  7. Parthanatos: mitochondrial-linked mechanisms and therapeutic opportunities

    PubMed Central

    Fatokun, Amos A; Dawson, Valina L; Dawson, Ted M

    2014-01-01

    Cells die by a variety of mechanisms. Terminally differentiated cells such as neurones die in a variety of disorders, in part, via parthanatos, a process dependent on the activity of poly (ADP-ribose)-polymerase (PARP). Parthanatos does not require the mediation of caspases for its execution, but is clearly mechanistically dependent on the nuclear translocation of the mitochondrial-associated apoptosis-inducing factor (AIF). The nuclear translocation of this otherwise beneficial mitochondrial protein, occasioned by poly (ADP-ribose) (PAR) produced through PARP overactivation, causes large-scale DNA fragmentation and chromatin condensation, leading to cell death. This review describes the multistep course of parthanatos and its dependence on PAR signalling and nuclear AIF translocation. The review also discusses potential targets in the parthanatos cascade as promising avenues for the development of novel, disease-modifying, therapeutic agents. LINKED ARTICLES This article is part of a themed issue on Mitochondrial Pharmacology: Energy, Injury & Beyond. To view the other articles in this issue visit http://dx.doi.org/10.1111/bph.2014.171.issue-8 PMID:24684389

  8. Linking Mechanisms of Work-Family Conflict and Segmentation

    ERIC Educational Resources Information Center

    Michel, Jesse S.; Hargis, Michael B.

    2008-01-01

    Despite the abundance of work and family research, few studies have compared the linking mechanisms specified in theoretical models of work-family conflict and segmentation. Accordingly, the current study provides a greater degree of empirical clarity concerning the interplay of work and family by directly examining the indirect effects of…

  9. Novel Solution for Leg Motion with 5-Link Belt Mechanism

    NASA Astrophysics Data System (ADS)

    E. Ch., Lovasz; Pop, C.; Pop, F.; Dolga, V.

    2014-11-01

    From the analysis of Theo Jansen walking mechanism and of the path curve that it describes the reduced capability for crossing over obstacles of the Jansen leg (1 DOF) is pointed out. By using a 5 link belt mechanism with 2 DOF can be adapted for generating similar Jansen mechanism path curve, where the step height of this path can be increased. For this purpose a mathematical model is conceived in order to analyse and determine the parameters for driving and control of the operation of the novel walking leg solution.

  10. Load transfer mechanisms in cross-linked DWNT fibers

    NASA Astrophysics Data System (ADS)

    Filleter, T.; Naraghi, M.; Moravsky, A.; Bernal, R.; Loutfy, R. O.; Espinosa, H. D.

    2011-03-01

    The application of carbon nanotubes (CNT) to macroscopic composite fibers has been limited by weak shear interfaces between adjacent CNT shells and composite matrix elements. A fundamental understanding of load transfer at multiple length-scales is needed to identify how the exceptional mechanical properties of CNTs can be scaled to produce high-performance fibers. Through in-situ electron microscopy tensile testing we have elucidated load transfer mechanisms across multiple scales of cross-linked double-walled nanotube (DWNT) fibers. A low density of polymer cross-links is found to increase the total energy dissipated at failure and ductility of fibers by 5 and 10X, respectively, without reducing strength. This mutiscale approach has identified a need to enhance shear interactions between individual DWNTs within the hierarchical DWNT fiber structures. Through in-situ TEM electron irradiation studies we have shown that load can be effectively transferred to inner DWNTs within bundles by covalently cross-linking the interfaces of adjacent DWNTs and shells. We have observed order of magnitude increases in strength and modulus and identified their dependence on irradiation dose. In future a combined approach of irradiation induced covalent and polymer cross-linking may lead to high-performance DWNT-based fibers and composites with tunable mechanical properties.

  11. Analysis of Links Positions in Landing Gear Mechanism

    NASA Astrophysics Data System (ADS)

    Brewczyński, D.; Tora, G.

    2014-08-01

    This article contains a kinematic analysis of an aircraft chassis mechanism in a range of positions. The mechanism of the chassis is made up of several smaller subsystems with different functions. The first mechanism is used to eject the chassis before landing (touchdown) and fold it to hatchway after the lift off. The second mechanism is designed to perform rotation of the crossover with the wheel, in order to adjust the position of the wheel to fit it in the limited space in the hold. The third mechanism allows movement of the chassis resulting from the change in length of the damper. To determine the position of the following links of the mechanism calculus of vectors was applied in which unit vectors were used to represent the angular position of the links. The aim of the analysis is to determine the angle of convergence and the angle of heel wheels as a function of the variable length of hydraulic cylinder, length of the shock absorber, length of the regulations rods

  12. Glutaraldehyde-cross-linked meniscal allografts: mechanical properties.

    PubMed

    Wisnewski, P J; Powers, D L; Kennedy, J M

    1988-01-01

    Removal of a severely damaged medial meniscus has been shown to lead to degradation of the articular cartilage and formation of degenerative arthritis. To counter this degenerative effect, meniscal prostheses, including glutaraldehyde-cross-linked allografts, have been evaluated in dogs. The purpose of this research was to quantify the mechanical properties of both fresh and glutaraldehyde-cross-linked canine medial menisci. Mechanical properties quantified were tensile strength, tensile modulus, and compressive stiffness. In addition, water content of compressive test samples was measured. Analysis of variance showed significantly lower tensile strength and tensile modulus and significantly higher compressive stiffness for the glutaraldehyde-cross-linked menisci, as compared to fresh specimens. Measurement of the weight percentage of water in fresh and cross-linked samples revealed no significant differences in water content. When implanted into a joint, the increased compressive stiffness could increase the peripheral tensile load. Due to the decreased tensile strength in this region, the prosthetic meniscus could be susceptible to peripheral tears. PMID:3155295

  13. Mechanisms Linking Violence Exposure to Health Risk Behavior in Adolescence: Motivation to Cope and Sensation Seeking

    ERIC Educational Resources Information Center

    Brady, Sonya S.; Donenberg, Geri R.

    2006-01-01

    Objective: This study examined two potential mechanisms linking violence exposure and health risk behavior among adolescents in psychiatric care: sensation seeking and coping with stress through escape behavior. Method: Male (59%) and female adolescents (N = 251), ages 12 to 19 years, from diverse ethnic backgrounds (61% African American, 19%…

  14. The Link between Suicide and Insomnia: Theoretical Mechanisms

    PubMed Central

    Black, Carmen G.

    2013-01-01

    Insomnia has been established as a risk factor for depression and mental illness for decades, but a growing body of evidence has recently exposed insomnia to be an independent risk factor for suicide that encompasses all age ranges. This discovery has invigorated investigation to elucidate the relationship between insomnia and suicide, and over 20 studies reinforcing this association in adults have been published since 2010 alone. This article analyzes relevant research and emphasizes studies published within the last three years with the intent of proposing theoretical mechanisms explaining the link between suicide and insomnia. These mechanisms may then be used as targets for future investigation of treatment. PMID:23949486

  15. Links between fluid mechanics and quantum mechanics: a model for information in economics?

    PubMed

    Haven, Emmanuel

    2016-05-28

    This paper tallies the links between fluid mechanics and quantum mechanics, and attempts to show whether those links can aid in beginning to build a formal template which is usable in economics models where time is (a)symmetric and memory is absent or present. An objective of this paper is to contemplate whether those formalisms can allow us to model information in economics in a novel way. PMID:27091173

  16. Pole assignment for control of flexible link mechanisms

    NASA Astrophysics Data System (ADS)

    Ouyang, H.; Richiedei, D.; Trevisani, A.

    2013-06-01

    Although the dynamics of flexible link mechanisms and manipulators is nonlinear, motion and vibration control often relies on linear or piecewise-linear controllers based on linearized models in order to ensure real-time implementability. Keeping such an objective in mind, this paper proposes a general receptance-based method for pole assignment in flexible link mechanisms with a single rigid-body degree of freedom (dof) using a single control force (i.e. rank-one control). A chief advantage of the approach proposed is that it makes use of the second-order system model representation through the receptance matrix of the symmetric part of the asymmetric model. The asymmetric terms in the stiffness and damping matrices arise from the coupling between rigid-body motion and elastic motion. The proposed receptance-based formulation ensures numerical reliability and efficiency also for large dimensional and ill-conditioned system models originating from the simultaneous presence of high-frequency and weakly controllable oscillating modes, and of rigid-body motion low-frequency dynamics, which may also be unstable. The validation of the proposed technique is carried out by performing pole assignment through position and velocity feedback or acceleration and velocity feedback on a mechanism. Integral control is also introduced to improve the steady state system response. Numerical results indicate that the proposed method is more accurate and robust than two popular established methods.

  17. Cell mechanics and immune system link up to fight infections

    NASA Astrophysics Data System (ADS)

    Ekpenyong, Andrew; Man, Si Ming; Tourlomousis, Panagiotis; Achouri, Sarra; Cammarota, Eugenia; Hughes, Katherine; Rizzo, Alessandro; Ng, Gilbert; Guck, Jochen; Bryant, Clare

    2015-03-01

    Infectious diseases, in which pathogens invade and colonize host cells, are responsible for one third of all mortality worldwide. Host cells use special proteins (immunoproteins) and other molecules to fight viral and bacterial invaders. The mechanisms by which immunoproteins enable cells to reduce bacterial loads and survive infections remain unclear. Moreover, during infections, some immunoproteins are known to alter the cytoskeleton, the structure that largely determines cellular mechanical properties. We therefore used an optical stretcher to measure the mechanical properties of primary immune cells (bone marrow derived macrophages) during bacterial infection. We found that macrophages become stiffer upon infection. Remarkably, macrophages lacking the immunoprotein, NLR-C4, lost the stiffening response to infection. This in vitro result correlates with our in vivo data whereby mice lacking NLR-C4 have more lesions and hence increased bacterial distribution and spread. Thus, the immune-protein-dependent increase in cell stiffness in response to bacterial infection (in vitro result) seems to have a functional role in the system level fight against pathogens (in vivo result). We will discuss how this functional link between cell mechanical properties and innate immunity, effected by actin polymerization, reduces the spread of infection.

  18. Linking transient storage parameters to exchange mechanisms and reach characteristics

    NASA Astrophysics Data System (ADS)

    Morén, Ida; Wörman, Anders; Riml, Joakim

    2015-04-01

    transient storage model. Important geomorphologic and hydraulic features used as classification parameters are those that that can be directly linked to specific management measures implemented in streams to increase natural remediation of nutrients and other contaminants. Only field data from reaches where measurements independent of the tracer tests have been done is included in this study in order to correctly analyse dominating mechanisms and combination of mechanisms and to be able to link the retention times to relevant and measurable reach characteristics.

  19. AIR POLLUTION, INFLAMMATION AND PRETERM BIRTH: A POTENTIAL MECHANISTIC LINK

    PubMed Central

    Vadillo-Ortega, Felipe; Osornio-Vargas, Alvaro; Buxton, Miatta A.; Sánchez, Brisa N.; Rojas-Bracho, Leonora; Viveros-Alcaráz, Martin; Castillo-Castrejón, Marisol; Beltrán-Montoya, Jorge; Brown, Daniel G.; O´Neill, Marie S.

    2014-01-01

    Preterm birth is a public health issue of global significance, which may result in mortality during the perinatal period or may lead to major health and financial consequences due to lifelong impacts. Even though several risk factors for preterm birth have been identified, prevention efforts have failed to halt the increasing rates of preterm birth. Epidemiological studies have identified air pollution as an emerging potential risk factor for preterm birth. However, many studies were limited by study design and inadequate exposure assessment. Due to the ubiquitous nature of ambient air pollution and the potential public health significance of any role in causing preterm birth, a novel focus investigating possible causal mechanisms influenced by air pollution is therefore a global health priority. We hypothesize that air pollution may act together with other biological factors to induce systemic inflammation and influence the duration of pregnancy. Evaluation and testing of this hypothesis is currently being conducted in a prospective cohort study in Mexico City and will provide an understanding of the pathways that mediate the effects of air pollution on preterm birth. The important public health implication is that crucial steps in this mechanistic pathway can potentially be acted on early in pregnancy to reduce the risk of preterm birth. PMID:24382337

  20. Environmentally induced autoimmune diseases: potential mechanisms.

    PubMed Central

    Rao, T; Richardson, B

    1999-01-01

    Environmental and other xenobiotic agents can cause autoimmunity. Examples include drug-induced lupus, toxic oil syndrome, and contaminated l-tryptophan ingestion. Numerous mechanisms, based on (italic)in vitro(/italic) evidence and animal models, have been proposed to explain how xenobiotics induce or accelerate autoimmunity. The majority of these can be divided into three general categories. The first is those inhibiting the processes involved in establishing tolerance by deletion. Inhibiting deletion can result in the release of newly generated autoreactive cells into the periphery. The second mechanism is the modification of gene expression in the cells participating in the immune response, permitting lymphocytes to respond to signals normally insufficient to initiate a response or allowing the antigen-presenting cells to abnormally stimulate a response. Abnormal gene expression can thus disrupt tolerance maintained by suppression or anergy, permitting activation of autoreactive cells. The third is the modification of self-molecules such that they are recognized by the immune system as foreign. Examples illustrating these concepts are presented, and related mechanisms that have the potential to similarly affect the immune system are noted. Some mechanisms appear to be common to a variety of agents, and different mechanisms appear to produce similar diseases. However, evidence that any of these mechanisms are actually responsible for xenobiotic-induced human autoimmune disease is still largely lacking, and the potential for numerous and as yet unidentified mechanisms also exists. PMID:10502539

  1. The CHAIN program: forging evolutionary links to underlying mechanisms.

    PubMed

    Neuwald, Andrew F

    2007-11-01

    Proteins evolve new functions by modifying and extending the molecular machinery of an ancestral protein. Such changes show up as divergent sequence patterns, which are conserved in descendent proteins that maintain the divergent function. After multiply-aligning a set of input sequences, the CHAIN program partitions the sequences into two functionally divergent groups and then outputs an alignment that is annotated to reveal the selective pressures imposed on divergent residue positions. If atomic coordinates are also provided, hydrogen bonds and other atomic interactions associated with various categories of divergent residues are graphically displayed. Such analyses establish links between protein evolutionary divergence and functionally crucial atomic features and, as a result, can suggest plausible molecular mechanisms for experimental testing. This is illustrated here by its application to bacterial clamp-loader ATPases. PMID:17962021

  2. Tariffs, Mechanisms and Equilibria at a Single Internet Link

    NASA Astrophysics Data System (ADS)

    Courcoubetis, Costas; Dimakis, Antonis

    We analyze the interplay between the demand for downloads, choice of congestion control mechanism, and tariff structure at a single link, when users have preferences in terms of average download delay and they are charged according to the number of ECN marked packets they receive. Our model involves a timescale separation approach, where in the fast timescales active flows compete for instantaneous bandwidth share by optimally tuning congestion control parameters in a noncooperative fashion. This is modeled by letting flows choose utility functions within the network utility maximization framework laid down by Kelly [1]. On a slower timescale, users selfishly change their otherwise unrestricted demand for downloads based on the average experienced download delay and charges incurred. We study the equilibrium of this loop of interactions from the point of view of social welfare.

  3. Lymphangioleiomyomatosis Biomarkers Linked to Lung Metastatic Potential and Cell Stemness

    PubMed Central

    Ruiz de Garibay, Gorka; Herranz, Carmen; Llorente, Alicia; Boni, Jacopo; Serra-Musach, Jordi; Mateo, Francesca; Aguilar, Helena; Gómez-Baldó, Laia; Petit, Anna; Vidal, August; Climent, Fina; Hernández-Losa, Javier; Cordero, Álex; González-Suárez, Eva; Sánchez-Mut, José Vicente; Esteller, Manel; Llatjós, Roger; Varela, Mar; López, José Ignacio; García, Nadia; Extremera, Ana I.; Gumà, Anna; Ortega, Raúl; Plà, María Jesús; Fernández, Adela; Pernas, Sònia; Falo, Catalina; Morilla, Idoia; Campos, Miriam; Gil, Miguel; Román, Antonio; Molina-Molina, María; Ussetti, Piedad; Laporta, Rosalía; Valenzuela, Claudia; Ancochea, Julio; Xaubet, Antoni; Casanova, Álvaro; Pujana, Miguel Angel

    2015-01-01

    Lymphangioleiomyomatosis (LAM) is a rare lung-metastasizing neoplasm caused by the proliferation of smooth muscle-like cells that commonly carry loss-of-function mutations in either the tuberous sclerosis complex 1 or 2 (TSC1 or TSC2) genes. While allosteric inhibition of the mechanistic target of rapamycin (mTOR) has shown substantial clinical benefit, complementary therapies are required to improve response and/or to treat specific patients. However, there is a lack of LAM biomarkers that could potentially be used to monitor the disease and to develop other targeted therapies. We hypothesized that the mediators of cancer metastasis to lung, particularly in breast cancer, also play a relevant role in LAM. Analyses across independent breast cancer datasets revealed associations between low TSC1/2 expression, altered mTOR complex 1 (mTORC1) pathway signaling, and metastasis to lung. Subsequently, immunohistochemical analyses of 23 LAM lesions revealed positivity in all cases for the lung metastasis mediators fascin 1 (FSCN1) and inhibitor of DNA binding 1 (ID1). Moreover, assessment of breast cancer stem or luminal progenitor cell biomarkers showed positivity in most LAM tissue for the aldehyde dehydrogenase 1 (ALDH1), integrin-ß3 (ITGB3/CD61), and/or the sex-determining region Y-box 9 (SOX9) proteins. The immunohistochemical analyses also provided evidence of heterogeneity between and within LAM cases. The analysis of Tsc2-deficient cells revealed relative over-expression of FSCN1 and ID1; however, Tsc2-deficient cells did not show higher sensitivity to ID1-based cancer inhibitors. Collectively, the results of this study reveal novel LAM biomarkers linked to breast cancer metastasis to lung and to cell stemness, which in turn might guide the assessment of additional or complementary therapeutic opportunities for LAM. PMID:26167915

  4. Lymphangioleiomyomatosis Biomarkers Linked to Lung Metastatic Potential and Cell Stemness.

    PubMed

    Ruiz de Garibay, Gorka; Herranz, Carmen; Llorente, Alicia; Boni, Jacopo; Serra-Musach, Jordi; Mateo, Francesca; Aguilar, Helena; Gómez-Baldó, Laia; Petit, Anna; Vidal, August; Climent, Fina; Hernández-Losa, Javier; Cordero, Álex; González-Suárez, Eva; Sánchez-Mut, José Vicente; Esteller, Manel; Llatjós, Roger; Varela, Mar; López, José Ignacio; García, Nadia; Extremera, Ana I; Gumà, Anna; Ortega, Raúl; Plà, María Jesús; Fernández, Adela; Pernas, Sònia; Falo, Catalina; Morilla, Idoia; Campos, Miriam; Gil, Miguel; Román, Antonio; Molina-Molina, María; Ussetti, Piedad; Laporta, Rosalía; Valenzuela, Claudia; Ancochea, Julio; Xaubet, Antoni; Casanova, Álvaro; Pujana, Miguel Angel

    2015-01-01

    Lymphangioleiomyomatosis (LAM) is a rare lung-metastasizing neoplasm caused by the proliferation of smooth muscle-like cells that commonly carry loss-of-function mutations in either the tuberous sclerosis complex 1 or 2 (TSC1 or TSC2) genes. While allosteric inhibition of the mechanistic target of rapamycin (mTOR) has shown substantial clinical benefit, complementary therapies are required to improve response and/or to treat specific patients. However, there is a lack of LAM biomarkers that could potentially be used to monitor the disease and to develop other targeted therapies. We hypothesized that the mediators of cancer metastasis to lung, particularly in breast cancer, also play a relevant role in LAM. Analyses across independent breast cancer datasets revealed associations between low TSC1/2 expression, altered mTOR complex 1 (mTORC1) pathway signaling, and metastasis to lung. Subsequently, immunohistochemical analyses of 23 LAM lesions revealed positivity in all cases for the lung metastasis mediators fascin 1 (FSCN1) and inhibitor of DNA binding 1 (ID1). Moreover, assessment of breast cancer stem or luminal progenitor cell biomarkers showed positivity in most LAM tissue for the aldehyde dehydrogenase 1 (ALDH1), integrin-ß3 (ITGB3/CD61), and/or the sex-determining region Y-box 9 (SOX9) proteins. The immunohistochemical analyses also provided evidence of heterogeneity between and within LAM cases. The analysis of Tsc2-deficient cells revealed relative over-expression of FSCN1 and ID1; however, Tsc2-deficient cells did not show higher sensitivity to ID1-based cancer inhibitors. Collectively, the results of this study reveal novel LAM biomarkers linked to breast cancer metastasis to lung and to cell stemness, which in turn might guide the assessment of additional or complementary therapeutic opportunities for LAM. PMID:26167915

  5. Mechanical surface waves accompany action potential propagation.

    PubMed

    El Hady, Ahmed; Machta, Benjamin B

    2015-01-01

    Many diverse studies have shown that a mechanical displacement of the axonal membrane accompanies the electrical pulse defining the action potential (AP). We present a model for these mechanical displacements as arising from the driving of surface wave modes in which potential energy is stored in elastic properties of the neuronal membrane and cytoskeleton while kinetic energy is carried by the axoplasmic fluid. In our model, these surface waves are driven by the travelling wave of electrical depolarization characterizing the AP, altering compressive electrostatic forces across the membrane. This driving leads to co-propagating mechanical displacements, which we term Action Waves (AWs). Our model allows us to estimate the shape of the AW that accompanies any travelling wave of voltage, making predictions that are in agreement with results from several experimental systems. Our model can serve as a framework for understanding the physical origins and possible functional roles of these AWs. PMID:25819404

  6. Mechanical surface waves accompany action potential propagation

    NASA Astrophysics Data System (ADS)

    El Hady, Ahmed; Machta, Benjamin B.

    2015-03-01

    Many diverse studies have shown that a mechanical displacement of the axonal membrane accompanies the electrical pulse defining the action potential (AP). We present a model for these mechanical displacements as arising from the driving of surface wave modes in which potential energy is stored in elastic properties of the neuronal membrane and cytoskeleton while kinetic energy is carried by the axoplasmic fluid. In our model, these surface waves are driven by the travelling wave of electrical depolarization characterizing the AP, altering compressive electrostatic forces across the membrane. This driving leads to co-propagating mechanical displacements, which we term Action Waves (AWs). Our model allows us to estimate the shape of the AW that accompanies any travelling wave of voltage, making predictions that are in agreement with results from several experimental systems. Our model can serve as a framework for understanding the physical origins and possible functional roles of these AWs.

  7. Quantum mechanical streamlines. I - Square potential barrier

    NASA Technical Reports Server (NTRS)

    Hirschfelder, J. O.; Christoph, A. C.; Palke, W. E.

    1974-01-01

    Exact numerical calculations are made for scattering of quantum mechanical particles hitting a square two-dimensional potential barrier (an exact analog of the Goos-Haenchen optical experiments). Quantum mechanical streamlines are plotted and found to be smooth and continuous, to have continuous first derivatives even through the classical forbidden region, and to form quantized vortices around each of the nodal points. A comparison is made between the present numerical calculations and the stationary wave approximation, and good agreement is found between both the Goos-Haenchen shifts and the reflection coefficients. The time-independent Schroedinger equation for real wavefunctions is reduced to solving a nonlinear first-order partial differential equation, leading to a generalization of the Prager-Hirschfelder perturbation scheme. Implications of the hydrodynamical formulation of quantum mechanics are discussed, and cases are cited where quantum and classical mechanical motions are identical.

  8. Mechanical characterization of cross-linked serum albumin microcapsules.

    PubMed

    de Loubens, Clément; Deschamps, Julien; Georgelin, Marc; Charrier, Anne; Edwards-Levy, Florence; Leonetti, Marc

    2014-07-01

    Controlling the deformation of microcapsules and capsules is essential in numerous biomedical applications. The mechanical properties of the membrane of microcapsules made of cross-linked human serum albumin (HSA) are revealed by two complementary experiments in the linear elastic regime. The first provides the surfacic shear elastic modulus Gs by the study of small deformations of a single capsule trapped in an elongational flow: Gs varies from 0.002 to 5 N m(-1). The second gives the volumic Young's modulus E of the membrane by shallow and local indentations of the membrane with an AFM probe: E varies from 20 kPa to 1 MPa. The surfacic and volumic elastic moduli increase with the size of the capsule up to three orders of magnitude and with the protein concentration of the membrane. The membrane thickness is evaluated from these two membrane mechanical characteristics and increases with the size and the initial HSA concentration from 2 to 20 μm. PMID:24817568

  9. Integrative modelling reveals mechanisms linking productivity and plant species richness

    NASA Astrophysics Data System (ADS)

    Grace, James B.; Anderson, T. Michael; Seabloom, Eric W.; Borer, Elizabeth T.; Adler, Peter B.; Harpole, W. Stanley; Hautier, Yann; Hillebrand, Helmut; Lind, Eric M.; Pärtel, Meelis; Bakker, Jonathan D.; Buckley, Yvonne M.; Crawley, Michael J.; Damschen, Ellen I.; Davies, Kendi F.; Fay, Philip A.; Firn, Jennifer; Gruner, Daniel S.; Hector, Andy; Knops, Johannes M. H.; MacDougall, Andrew S.; Melbourne, Brett A.; Morgan, John W.; Orrock, John L.; Prober, Suzanne M.; Smith, Melinda D.

    2016-01-01

    How ecosystem productivity and species richness are interrelated is one of the most debated subjects in the history of ecology. Decades of intensive study have yet to discern the actual mechanisms behind observed global patterns. Here, by integrating the predictions from multiple theories into a single model and using data from 1,126 grassland plots spanning five continents, we detect the clear signals of numerous underlying mechanisms linking productivity and richness. We find that an integrative model has substantially higher explanatory power than traditional bivariate analyses. In addition, the specific results unveil several surprising findings that conflict with classical models. These include the isolation of a strong and consistent enhancement of productivity by richness, an effect in striking contrast with superficial data patterns. Also revealed is a consistent importance of competition across the full range of productivity values, in direct conflict with some (but not all) proposed models. The promotion of local richness by macroecological gradients in climatic favourability, generally seen as a competing hypothesis, is also found to be important in our analysis. The results demonstrate that an integrative modelling approach leads to a major advance in our ability to discern the underlying processes operating in ecological systems.

  10. Integrative modelling reveals mechanisms linking productivity and plant species richness.

    PubMed

    Grace, James B; Anderson, T Michael; Seabloom, Eric W; Borer, Elizabeth T; Adler, Peter B; Harpole, W Stanley; Hautier, Yann; Hillebrand, Helmut; Lind, Eric M; Pärtel, Meelis; Bakker, Jonathan D; Buckley, Yvonne M; Crawley, Michael J; Damschen, Ellen I; Davies, Kendi F; Fay, Philip A; Firn, Jennifer; Gruner, Daniel S; Hector, Andy; Knops, Johannes M H; MacDougall, Andrew S; Melbourne, Brett A; Morgan, John W; Orrock, John L; Prober, Suzanne M; Smith, Melinda D

    2016-01-21

    How ecosystem productivity and species richness are interrelated is one of the most debated subjects in the history of ecology. Decades of intensive study have yet to discern the actual mechanisms behind observed global patterns. Here, by integrating the predictions from multiple theories into a single model and using data from 1,126 grassland plots spanning five continents, we detect the clear signals of numerous underlying mechanisms linking productivity and richness. We find that an integrative model has substantially higher explanatory power than traditional bivariate analyses. In addition, the specific results unveil several surprising findings that conflict with classical models. These include the isolation of a strong and consistent enhancement of productivity by richness, an effect in striking contrast with superficial data patterns. Also revealed is a consistent importance of competition across the full range of productivity values, in direct conflict with some (but not all) proposed models. The promotion of local richness by macroecological gradients in climatic favourability, generally seen as a competing hypothesis, is also found to be important in our analysis. The results demonstrate that an integrative modelling approach leads to a major advance in our ability to discern the underlying processes operating in ecological systems. PMID:26760203

  11. Mechanical Surface Waves Accompany Action Potential Propagation

    NASA Astrophysics Data System (ADS)

    Machta, Benjamin; El Hady, Ahmed

    2015-03-01

    The action potential (AP) is the basic mechanism by which information is transmitted along neuronal axons. Although the excitable nature of axons is understood to be primarily electrical, many experimental studies have shown that a mechanical displacement of the axonal membrane co-propagates with the electrical signal. While the experimental evidence for co-propagating mechanical waves is diverse and compelling, there is no consensus for their physical underpinnings. We present a model in which these mechanical displacements arise from the driving of mechanical surface waves, in which potential energy is stored in elastic deformations of the neuronal membrane and cytoskeleton while kinetic energy is stored in the movement of the axoplasmic fluid. In our model these surface waves are driven by the traveling wave of electrical depolarization that characterizes the AP, altering the electrostatic forces across the membrane as it passes. Our model allows us to predict the shape of the displacement that should accompany any traveling wave of voltage, including the well-characterized AP. We expect our model to serve as a framework for understanding the physical origins and possible functional roles of these AWs in neurobiology. See Arxiv/1407.7600

  12. Linking continuum mechanics and 3D discrete dislocation simulations

    SciTech Connect

    El-Azab, A. A.; Fivel, M.

    1998-10-18

    A technique is developed for linking the methods of discrete dislocation dynamics simulation and finite element to treat elasto-plasticity problems. The overall formulation views the plastically deforming crystal as an elastic crystal with continuously changing dislocation microstructure which is tracked by the numerical dynamics simulation. The FEM code needed in this regard is based on linear elasticity only. This formulation presented here is focused on a continuous updating of the outer shape of the crystal, for possible regeneration of the FEM mesh, and adjustment of the surface geometry, in particular the surface normal. The method is expected to be potentially applicable to the nano- indentation experiments, where the zone around the indenter-crystal contact undergoes significant permanent deformation, the rigorous determination of which is very important to the calculation of the indentation print area and in turn, the surface hardness. Furthermore, the technique is expected to account for the plastic history of the surface displacement under the indenter. Other potential applications are mentioned in the text.

  13. Linking traits based on their shared molecular mechanisms

    PubMed Central

    Oren, Yael; Nachshon, Aharon; Frishberg, Amit; Wilentzik, Roni; Gat-Viks, Irit

    2015-01-01

    There is growing recognition that co-morbidity and co-occurrence of disease traits are often determined by shared genetic and molecular mechanisms. In most cases, however, the specific mechanisms that lead to such trait–trait relationships are yet unknown. Here we present an analysis of a broad spectrum of behavioral and physiological traits together with gene-expression measurements across genetically diverse mouse strains. We develop an unbiased methodology that constructs potentially overlapping groups of traits and resolves their underlying combination of genetic loci and molecular mechanisms. For example, our method predicts that genetic variation in the Klf7 gene may influence gene transcripts in bone marrow-derived myeloid cells, which in turn affect 17 behavioral traits following morphine injection; this predicted effect of Klf7 is consistent with an in vitro perturbation of Klf7 in bone marrow cells. Our analysis demonstrates the utility of studying hidden causative mechanisms that lead to relationships between complex traits. DOI: http://dx.doi.org/10.7554/eLife.04346.001 PMID:25781485

  14. Electro-Mechanical Actuator. DC Resonant Link Controller

    NASA Technical Reports Server (NTRS)

    Schreiner, Kenneth E.

    1996-01-01

    This report summarizes the work performed on the 68 HP electro-mechanical actuator (EMA) system developed on NASA contract for the Electrical Actuation (ELA) Technology Bridging Program. The system was designed to demonstrate the capability of large, high power linear ELAs for applications such as Thrust Vector Control (TVC) on rocket engines. It consists of a motor controller, drive electronics and a linear actuator capable of up to 32,00 lbs loading at 7.4 inches/second. The drive electronics are based on the Resonant DC link concept and operate at a nominal frequency of 55 kHz. The induction motor is a specially designed high speed, low inertia motor capable of a 68 peak HP. The actuator was originally designed by MOOG Aerospace under an internal R & D program to meet Space Shuttle Main Engine (SSME) TVC requirements. The design was modified to meet this programs linear rate specification of 7.4 inches/second. The motor and driver were tested on a dynamometer at the Martin Marietta Space Systems facility. System frequency response, step response and force-velocity tests were conducted at the MOOG Aerospace facility. A complete description of the system and all test results can be found in the body of the report.

  15. Excess body weight during pregnancy and offspring obesity: potential mechanisms.

    PubMed

    Paliy, Oleg; Piyathilake, Chandrika J; Kozyrskyj, Anita; Celep, Gulcin; Marotta, Francesco; Rastmanesh, Reza

    2014-03-01

    The rates of child and adult obesity have increased in most developed countries over the past several decades. The health consequences of obesity affect both physical and mental health, and the excess body weight can be linked to an elevated risk for developing type 2 diabetes, cardiovascular problems, and depression. Among the factors that can influence the development of obesity are higher infant weights and increased weight gain, which are associated with higher risk for excess body weight later in life. In turn, mother's excess body weight during and after pregnancy can be linked to the risk for offspring overweight and obesity through dietary habits, mode of delivery and feeding, breast milk composition, and through the influence on infant gut microbiota. This review considers current knowledge of these potential mechanisms that threaten to create an intergenerational cycle of obesity. PMID:24103493

  16. Direct mechanical stimulation of tip links in hair cells through DNA tethers

    PubMed Central

    Basu, Aakash; Lagier, Samuel; Vologodskaia, Maria; Fabella, Brian A; Hudspeth, AJ

    2016-01-01

    Mechanoelectrical transduction by hair cells commences with hair-bundle deflection, which is postulated to tense filamentous tip links connected to transduction channels. Because direct mechanical stimulation of tip links has not been experimentally possible, this hypothesis has not been tested. We have engineered DNA tethers that link superparamagnetic beads to tip links and exert mechanical forces on the links when exposed to a magnetic-field gradient. By pulling directly on tip links of the bullfrog's sacculus we have evoked transduction currents from hair cells, confirming the hypothesis that tension in the tip links opens transduction channels. This demonstration of direct mechanical access to tip links additionally lays a foundation for experiments probing the mechanics of individual channels. DOI: http://dx.doi.org/10.7554/eLife.16041.001 PMID:27331611

  17. Neurocomputational mechanisms of prosocial learning and links to empathy.

    PubMed

    Lockwood, Patricia L; Apps, Matthew A J; Valton, Vincent; Viding, Essi; Roiser, Jonathan P

    2016-08-30

    Reinforcement learning theory powerfully characterizes how we learn to benefit ourselves. In this theory, prediction errors-the difference between a predicted and actual outcome of a choice-drive learning. However, we do not operate in a social vacuum. To behave prosocially we must learn the consequences of our actions for other people. Empathy, the ability to vicariously experience and understand the affect of others, is hypothesized to be a critical facilitator of prosocial behaviors, but the link between empathy and prosocial behavior is still unclear. During functional magnetic resonance imaging (fMRI) participants chose between different stimuli that were probabilistically associated with rewards for themselves (self), another person (prosocial), or no one (control). Using computational modeling, we show that people can learn to obtain rewards for others but do so more slowly than when learning to obtain rewards for themselves. fMRI revealed that activity in a posterior portion of the subgenual anterior cingulate cortex/basal forebrain (sgACC) drives learning only when we are acting in a prosocial context and signals a prosocial prediction error conforming to classical principles of reinforcement learning theory. However, there is also substantial variability in the neural and behavioral efficiency of prosocial learning, which is predicted by trait empathy. More empathic people learn more quickly when benefitting others, and their sgACC response is the most selective for prosocial learning. We thus reveal a computational mechanism driving prosocial learning in humans. This framework could provide insights into atypical prosocial behavior in those with disorders of social cognition. PMID:27528669

  18. Mechanically Stiff, Zinc Cross-Linked Nanocomposite Scaffolds with Improved Osteostimulation and Antibacterial Properties.

    PubMed

    Sehgal, Rekha R; Carvalho, Edmund; Banerjee, Rinti

    2016-06-01

    Nanocomposite scaffolds are studied widely due to their resemblance with the natural extracellular matrix of bone; but their use as a bone tissue engineered scaffold is clinically hampered due to low mechanical stiffness, inadequate osteoconduction, and graft associated infections. The purpose of the current study was the development of a mechanically stiff nanocomposite scaffold using biodegradable gellan and xanthan polymers reinforced with bioglass nanoparticles (nB) (Size: 20-120 nm). These nanocomposite scaffolds were cross-linked with zinc sulfate ions to improve their osteoconduction and antibacterial properties for the regeneration of a functional bone. The compressive strength and modulus of the optimized nanocomposite scaffold (1% w/v polymer reinforced with 4%w/v nB nanoparticles, cross-linked with 1.5 mM zinc sulfate) was 1.91 ± 0.31 MPa and 20.36 ± 1.08 MPa, respectively, which was comparable to the trabecular bone and very high compared to nanocomposite scaffolds reported in earlier studies. Further, in vitro simulated body fluid (SBF) study suggested deposition of biomimetic apatite on the surface of zinc cross-linked nanocomposite scaffolds confirming their bioactivity. MG 63 osteoblast-like cells cultured with the nanocomposite scaffolds responded to matrix stiffness with better adhesion, spreading and cellular interconnections compared to the polymeric gellan and xanthan scaffolds. Incorporation of bioglass nanoparticles and zinc cross-linker in nanocomposite scaffolds demonstrated 62% increment in expression of alkaline phosphatase activity (ALP) and 150% increment in calcium deposition of MG 63 osteoblast-like cells compared to just gellan and xanthan polymeric scaffolds. Furthermore, zinc cross-linked nanocomposite scaffolds significantly inhibited the growth of Gram-positive Bacillus subtilis (70% reduction) and Gram-negative Escherichia coli (81% reduction) bacteria. This study demonstrated a facile approach to tune the mechanical stiffness

  19. Molecular Mechanisms Linking High Dose Medroxyprogesterone with HIV-1 Risk

    PubMed Central

    Irvin, Susan C.; Herold, Betsy C.

    2015-01-01

    Background Epidemiological studies suggest that medroxyprogesterone acetate (MPA) may increase the risk of HIV-1. The current studies were designed to identify potential underlying biological mechanisms. Methods Human vaginal epithelial (VK2/E6E7), peripheral blood mononuclear (PBMC), and polarized endometrial (HEC-1-A) cells were treated with a range of concentrations of MPA (0.015-150 μg/ml) and the impact on gene expression, protein secretion, and HIV infection was evaluated. Results Treatment of VK2/E6E7 cells with high doses (>15μg/ml] of MPA significantly upregulated proinflammatory cytokines, which resulted in a significant increase in HIV p24 levels secreted by latently infected U1 cells following exposure to culture supernatants harvested from MPA compared to mock-treated cells. MPA also increased syndecan expression by VK2/E6E7 cells and cells treated with 15 μg/ml of MPA bound and transferred more HIV-1 to T cells compared to mock-treated cells. Moreover, MPA treatment of epithelial cells and PBMC significantly decreased cell proliferation resulting in disruption of the epithelial barrier and decreased cytokine responses to phytohaemagglutinin, respectively. Conclusion We identified several molecular mechanisms that could contribute to an association between DMPA and HIV including proinflammatory cytokine and chemokine responses that could activate the HIV promoter and recruit immune targets, increased expression of syndecans to facilitate the transfer of virus from epithelial to immune cells and decreased cell proliferation. The latter could impede the ability to maintain an effective epithelial barrier and adversely impact immune cell function. However, these responses were observed primarily following exposure to high (15-150 μg/ml) MPA concentrations. Clinical correlation is needed to determine whether the prolonged MPA exposure associated with contraception activates these mechanisms in vivo. PMID:25798593

  20. Mechanisms Linking Colorectal Cancer to the Consumption of (Processed) Red Meat: A Review.

    PubMed

    Demeyer, Daniel; Mertens, Birgit; De Smet, Stefaan; Ulens, Michèle

    2016-12-01

    Colorectal cancer (CRC) is the third most commonly diagnosed cancer in the world. The vast majority of CRC cases have been linked to environmental causes rather than to heritable genetic changes. Over the last decades, epidemiological evidence linking the consumption of red and, more convincingly, of processed red meat to CRC has accumulated. In parallel, hypotheses on carcinogenic mechanisms underlying an association between CRC and the intake of red and processed red meat have been proposed and investigated in biological studies. The hypotheses that have received most attention until now include (1) the presence of polycyclic aromatic hydrocarbons and heterocyclic aromatic amines, two groups of compounds recognized as carcinogenic, (2) the enhancing effect of (nitrosyl)heme on the formation of carcinogenic N-nitroso compounds and lipid peroxidation. However, none of these hypotheses completely explains the link between red and processed red meat intake and the CRC risk. Consequently, scientists have proposed additional mechanisms or refined their hypotheses. This review first briefly summarizes the development of CRC followed by an in-depth overview and critical discussion of the different potential carcinogenic mechanisms underlying the increased CRC risk associated with the consumption of red and processed red meat. PMID:25975275

  1. Nanofilm biomaterials: localized cross-linking to optimize mechanical rigidity and bioactivity.

    PubMed

    Phelps, Jennifer A; Morisse, Samuel; Hindié, Mathilde; Degat, Marie-Christelle; Pauthe, Emmanuel; Van Tassel, Paul R

    2011-02-01

    Nanofilm biomaterials, formed by the layer-by-layer assembly of charged macromolecules, are important systems for a variety of cell-contacting biomedical and biotechnological applications. Mechanical rigidity and bioactivity are two key film properties influencing the behavior of contacting cells. Increased rigidity tends to improve cells attachment, and films may be rendered bioactive through the incorporation of proteins, peptides, or drugs. A key challenge is to realize films that are simultaneously rigid and bioactive. Chemical cross-linking of the polymer framework--the standard means of increasing a film's rigidity--can diminish bioactivity through deactivation or isolation of embedded biomolecules or inhibition of film biodegradation. We present here a strategy to decouple mechanical rigidity and bioactivity, potentially enabling nanofilm biomaterials that are both mechanically rigid and bioactive. Our idea is to selectively cross-link the outer region of the film, resulting in a rigid outer skin to promote cell attachment, while leaving the film interior (with any embedded bioactive species) unaffected. We propose an approach whereby an N-hydroxysulfosuccinimide (sulfo-NHS) activated poly(L-glutamic acid) is added as the terminal layer of a multilayer film and forms (covalent) amide bonds with amino groups of poly(L-lysine) placed previously within the film. We characterize film assembly and cross-linking extent via quartz crystal microbalance with dissipation monitoring (QCMD), Fourier transform infrared spectroscopy in attenuated total reflection mode (FTIR-ATR), and laser scanning confocal microscopy (LSCM) and measure the attachment and metabolic activity of preosteoblastic MC3T3-E1 cells. We show cross-linking to occur primarily at the film surface and the subsequent cell attachment and metabolic activity to be enhanced compared to native films. Our method appears promising as a means to realize films that are simultaneously mechanically rigid and

  2. Exosomes: The Link between GPCR Activation and Metastatic Potential?

    PubMed Central

    Isola, Allison L.; Chen, Suzie

    2016-01-01

    The activation of G-Protein Coupled Receptors (GPCRs) by their respective ligands initiates a cascade of multiple signaling processes within the cell, regulating growth, metabolism and other essential cellular functions. Dysregulation and aberrant expression of these GPCRs and their subsequent signaling cascades are associated with many different types of pathologies, including cancer. The main life threatening complication in patients diagnosed with cancer is the dissemination of cells from the primary tumor to distant vital organs within the body, metastasis. Communication between the primary tumor, immune system, and the site of future metastasis are some of the key events in the early stages of metastasis. It has been postulated that the communication is mediated by nanovesicles that, under non-pathological conditions, are released by normal cells to relay signals to other cells in the body. These nanovesicles are called exosomes, and are utilized by the tumor cell to influence changes within the recipient cell, such as bone marrow progenitor cells, and cells within the site of future metastatic growth, in order to prepare the site for colonization. Tumor cells have been shown to release an increased number of exosomes when compared to their normal cell counterpart. Exosome production and release are regulated by proteins involved in localization, degradation and size of the multivesicular body, whose function may be altered within cancer cells, resulting in the release of an increased number of these vesicles. This review investigates the possibility of GPCR signaling cascades acting as the upstream activator of proteins involved in exosome production and release, linking a commonly targeted trans-membrane protein class with cellular communication utilized by tumor cells in early stages of metastasis. PMID:27092178

  3. Tank tread assemblies with track-linking mechanism

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr. (Inventor)

    1986-01-01

    The proposed tank tread assembly has adjacent tank tread segments joined by a link bearing tapered pins retained by clips inserted through the tread shells perpendicular to the axes of the pin. It also has highway pads attached by a release rod bearing tapered, grooved cams which interlockingly engage tabs inserted into the tread shells.

  4. Persistent organic pollutants & obesity: potential mechanisms for breast cancer promotion?

    PubMed Central

    Reaves, Denise K.; Ginsburg, Erika; Bang, John J.; Fleming, Jodie M.

    2015-01-01

    Dietary ingestion of persistent organic pollutants (POPs) correlates with developing obesity. Obesity alters metabolism, induces an inflammatory tissue microenvironment, and is also linked with diabetes and breast cancer risk/promotion of the disease. However, no direct evidence exists exploring the correlation among all three of these factors (POPs, obesity, and breast cancer). Herein, we present current correlative studies suggesting a causal link between POPs exposure through diet and their bioaccumulation in adipose that promotes the development of obesity and ultimately influences breast cancer development and/or progression. Furthermore, as endocrine disruptors, POPs can potentially interfere with hormonally responsive tissue functions causing dysregulation in hormone signaling and cell function. This review highlights the critical need for advanced in vitro and in vivo model systems to understand the complex relationship between obesity, POPs, breast cancer, and, more importantly, to delineate their multifaceted molecular, cellular, and biochemical mechanisms. Comprehensive in vitro and in vivo studies directly testing the observed correlations as well as detailing their molecular mechanisms are vital to cancer research and, ultimately, public health. PMID:25624167

  5. 49 CFR 238.207 - Link between coupling mechanism and car body.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 4 2014-10-01 2014-10-01 false Link between coupling mechanism and car body. 238.207 Section 238.207 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL... Requirements for Tier I Passenger Equipment § 238.207 Link between coupling mechanism and car body....

  6. 49 CFR 238.207 - Link between coupling mechanism and car body.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 4 2012-10-01 2012-10-01 false Link between coupling mechanism and car body. 238.207 Section 238.207 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL... Requirements for Tier I Passenger Equipment § 238.207 Link between coupling mechanism and car body....

  7. 49 CFR 238.207 - Link between coupling mechanism and car body.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 4 2013-10-01 2013-10-01 false Link between coupling mechanism and car body. 238.207 Section 238.207 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL... Requirements for Tier I Passenger Equipment § 238.207 Link between coupling mechanism and car body....

  8. 49 CFR 238.207 - Link between coupling mechanism and car body.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 4 2011-10-01 2011-10-01 false Link between coupling mechanism and car body. 238.207 Section 238.207 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL... Requirements for Tier I Passenger Equipment § 238.207 Link between coupling mechanism and car body....

  9. 49 CFR 238.207 - Link between coupling mechanism and car body.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Link between coupling mechanism and car body. 238.207 Section 238.207 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL... Requirements for Tier I Passenger Equipment § 238.207 Link between coupling mechanism and car body....

  10. Modeling and Simulation of a Slider Crank Mechanism with a Flexible Extensible Link

    NASA Astrophysics Data System (ADS)

    Dupac, M.; Noroozi, S.

    In this paper the modelling of a slider-crank mechanism with an extensible flexible link is presented and its dynamical behaviour analyzed. The link flexibility is modelled using extensible rigid links and rotational springs. The equations of motion with and without slider clearance are written. Accurate simulation of the extensible mechanism is performed to study its possible performance and behaviour under the combined effect of different parameters. A dynamic analysis is carried out in order to understand its behaviour under motion reconfiguration.

  11. A Potential Link between Environmental Triggers and Autoimmunity.

    PubMed

    Vojdani, Aristo

    2014-01-01

    Autoimmune diseases have registered an alarming rise worldwide in recent years. Accumulated evidence indicates that the immune system's ability to distinguish self from nonself is negatively impacted by genetic factors and environmental triggers. Genetics is certainly a factor, but since it normally takes a very long time for the human genetic pattern to change enough to register on a worldwide scale, increasingly the attention of studies has been focused on the environmental factors of a rapidly changing and evolving civilization. New technology, new industries, new inventions, new chemicals and drugs, and new foods and diets are constantly and rapidly being introduced in this fast-paced ever-changing world. Toxicants, infections, epitope spreading, dysfunctions of immune homeostasis, and dietary components can all have an impact on the body's delicate immune recognition system. Although the precise etiology and pathogenesis of many autoimmune diseases are still unknown, it would appear from the collated studies that there are common mechanisms in the immunopathogenesis of multiple autoimmune reactivities. Of particular interest is the citrullination of host proteins and their conversion to autoantigens by the aforementioned environmental triggers. The identification of these specific triggers of autoimmune reactivity is essential then for the development of new therapies for autoimmune diseases. PMID:24688790

  12. The epidemiology and molecular mechanisms linking obesity, diabetes, and cancer.

    PubMed

    Ferguson, Rosalyn D; Gallagher, Emily J; Scheinman, Eyal J; Damouni, Rawan; LeRoith, Derek

    2013-01-01

    The worldwide epidemic of obesity is associated with increasing rates of the metabolic syndrome and type 2 diabetes. Epidemiological studies have reported that these conditions are linked to increased rates of cancer incidence and mortality. Obesity, particularly abdominal obesity, is associated with insulin resistance and the development of dyslipidemia, hyperglycemia, and ultimately type 2 diabetes. Although many metabolic abnormalities occur with obesity and type 2 diabetes, insulin resistance and hyperinsulinemia appear to be central to these conditions and may contribute to dyslipidemia and altered levels of circulating estrogens and androgens. In this review, we will discuss the epidemiological and molecular links between obesity, type 2 diabetes, and cancer, and how hyperinsulinemia and dyslipidemia may contribute to cancer development. We will discuss how these metabolic abnormalities may interact with estrogen signaling in breast cancer growth. Finally, we will discuss the effects of type 2 diabetes medications on cancer risk. PMID:23810003

  13. Chemical, Physical, and Mechanical Characterization of Isocyanate Cross-linked Amine-Modified Silica Aerogels

    NASA Technical Reports Server (NTRS)

    Katti, Atul; Shimpi, Nilesh; Roy, Samit; Lu, Hongbing; Fabrizio, Eve F.; Dass, Amala; Capadona, Lynn A.; Leventis, Nicholas

    2006-01-01

    We describe a new mechanically strong lightweight porous composite material obtained by encapsulating the skeletal framework of amine-modified silica aerogels with polyurea. The conformal polymer coating preserves the mesoporous structure of the underlying silica framework and the thermal conductivity remains low at 0.041 plus or minus 0.001 W m(sup -1 K(sup -1). The potential of the new cross-linked silica aerogels for load-carrying applications was determined through characterization of their mechanical behavior under compression, three-point bending, and dynamic mechanical analysis (DMA). A primary glass transition temperature of 130 C was identified through DMA. At room temperature, results indicate a hyperfoam behavior where in compression cross-linked aerogels are linearly elastic under small strains (less than 4%) and then exhibit yield behavior (until 40% strain), followed by densification and inelastic hardening. At room temperature the compressive Young's modulus and the Poisson's ratio were determined to be 129 plus or minus 8 MPa and 0.18, respectively, while the strain at ultimate failure is 77% and the average specific compressive stress at ultimate failure is 3.89 x 10(exp 5) N m kg(sup -1). The specific flexural strength is 2.16 x 10(exp 4) N m kg(sup -1). Effects on the compressive behavior of strain rate and low temperature were also evaluated.

  14. Opioid receptor desensitization: mechanisms and its link to tolerance

    PubMed Central

    Allouche, Stéphane; Noble, Florence; Marie, Nicolas

    2014-01-01

    Opioid receptors (OR) are part of the class A of G-protein coupled receptors and the target of the opiates, the most powerful analgesic molecules used in clinic. During a protracted use, a tolerance to analgesic effect develops resulting in a reduction of the effectiveness. So understanding mechanisms of tolerance is a great challenge and may help to find new strategies to tackle this side effect. This review will summarize receptor-related mechanisms that could underlie tolerance especially receptor desensitization. We will focus on the latest data obtained on molecular mechanisms involved in opioid receptor desensitization: phosphorylation, receptor uncoupling, internalization, and post-endocytic fate of the receptor. PMID:25566076

  15. Integrating Mechanisms for Insulin Resistance: Common Threads and Missing Links

    PubMed Central

    Samuel, Varman T.; Shulman, Gerald I.

    2012-01-01

    Insulin resistance is a complex metabolic disorder that defies a single etiological pathway. Accumulation of ectopic lipid metabolites, activation of the unfolded protein response (UPR) pathway and innate immune pathways have all been implicated in the pathogenesis of insulin resistance. However, these pathways are also closely linked to changes in fatty acid uptake, lipogenesis, and energy expenditure that can impact ectopic lipid deposition. Ultimately, accumulation of specific lipid metabolites (diacylglycerols and/or ceramides) in liver and skeletal muscle, may be a common pathway leading to impaired insulin signaling and insulin resistance. PMID:22385956

  16. Relationship between cross-linking conditions of ethylene vinyl acetate and potential induced degradation for crystalline silicon photovoltaic modules

    NASA Astrophysics Data System (ADS)

    Jonai, Sachiko; Hara, Kohjiro; Tsutsui, Yuji; Nakahama, Hidenari; Masuda, Atsushi

    2015-08-01

    In this study, we investigated the relationship in crystalline silicon (c-Si) photovoltaic (PV) modules between the cross-linking level of copolymer of ethylene and vinyl acetate (EVA) as the encapsulant and the degree of degradation due to potential induced degradation (PID) phenomenon. We used three methods for the determination of cross-linking level of EVA: xylene method, which is one of the solvent extraction methods (SEM), curing degree by differential scanning calorimetry (DSC), and viscoelastic properties by dynamic mechanical analysis (DMA). The results indicate that degradation of PV modules by PID test depends on the cross-linking level of EVA. The PV modules encapsulated by EVA with higher cross-linking level show lower degradation degree due to PID phenomenon. Also we showed that EVA with higher cross-linking level tended to be higher volume resistivity. This tendency is similar to that for electrical resistance value during the PID test. The PID test was also done by changing thickness of EVA between front cover glass and c-Si with the same cross-linking level. The PV modules encapsulated by thicker EVA between front cover glass and c-Si cell show lower degradation by PID. From these results, the PV modules encapsulated by EVA with higher cross-linking level, higher volume resistivity and increased thickness would be tolerant of PID phenomenon.

  17. Mechanisms linking the social environment to health in African Americans

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The social environment may influence health directly or indirectly through psychosocial factors, such as perceived stress, depressive symptoms and discrimination. This study explored potential psychosocial mediators of the associations between the social environment and physical and mental health in...

  18. Linking sleep and general anesthesia mechanisms: this is no walkover.

    PubMed

    Bonhomme, V; Boveroux, P; Vanhaudenhuyse, A; Hans, P; Brichant, J F; Jaquet, O; Boly, M; Laureys, S

    2011-01-01

    This review aims at defining the link between physiological sleep and general anesthesia. Despite common behavioral and electrophysiological characteristics between both states, current literature suggests that the transition process between waking and sleep or anesthesia-induced alteration of consciousness is not driven by the same sequence of events. On the one hand, sleep originates in sub-cortical structures with subsequent repercussions on thalamo-cortical interactions and cortical activity. On the other hand, anesthesia seems to primarily affect the cortex with subsequent repercussions on the activity of sub-cortical networks. This discrepancy has yet to be confirmed by further functional brain imaging and electrophysiological experiments. The relationship between the observed functional modifications of brain activity during anesthesia and the known biochemical targets of hypnotic anesthetic agents also remains to be determined. PMID:22145259

  19. Influence of cross-link structure, density and mechanical properties in the mesoscale deformation mechanisms of collagen fibrils

    PubMed Central

    Depalle, Baptiste; Qin, Zhao; Shefelbine, Sandra J.; Buehler, Markus J.

    2015-01-01

    Collagen is a ubiquitous protein with remarkable mechanical properties. It is highly elastic, shows large fracture strength and enables substantial energy dissipation during deformation. Most of the connective tissue in humans consists of collagen fibrils composed of a staggered array of tropocollagen molecules, which are connected by intermolecular cross-links. In this study, we report a three-dimensional coarse-grained model of collagen and analyze the influence of enzymatic cross-links on the mechanics of collagen fibrils. Two representatives immature and mature cross-links are implemented in the mesoscale model using a bottom-up approach. By varying the number, type and mechanical properties of cross-links in the fibrils and performing tensile test on the models, we systematically investigate the deformation mechanisms of cross-linked collagen fibrils. We find that cross-linked fibrils exhibit a three phase behavior, which agrees closer with experimental results than what was obtained using previous models. The fibril mechanical response is characterized by: (i) an initial elastic deformation corresponding to the collagen molecule uncoiling, (ii) a linear regime dominated by molecule sliding and (iii) the second stiffer elastic regime related to the stretching of the backbone of the tropocollagen molecules until the fibril ruptures. Our results suggest that both cross-link density and type dictate the stiffness of large deformation regime by increasing the number of interconnected molecules while cross-links mechanical properties determine the failure strain and strength of the fibril. These findings reveal that cross-links play an essential role in creating an interconnected fibrillar material of tunable toughness and strength. PMID:25153614

  20. Mechanisms linking dietary fiber, gut microbiota and colon cancer prevention

    PubMed Central

    Zeng, Huawei; Lazarova, Darina L; Bordonaro, Michael

    2014-01-01

    Many epidemiological and experimental studies have suggested that dietary fiber plays an important role in colon cancer prevention. These findings may relate to the ability of fiber to reduce the contact time of carcinogens within the intestinal lumen and to promote healthy gut microbiota, which modifies the host’s metabolism in various ways. Elucidation of the mechanisms by which dietary fiber-dependent changes in gut microbiota enhance bile acid deconjugation, produce short chain fatty acids, and modulate inflammatory bioactive substances can lead to a better understanding of the beneficial role of dietary fiber. This article reviews the current knowledge concerning the mechanisms via which dietary fiber protects against colon cancer. PMID:24567795

  1. Mechanisms linking obesity to altered metabolism in mice colon carcinogenesis

    PubMed Central

    Nimri, Lili; Saadi, Janan; Peri, Irena; Yehuda-Shnaidman, Einav; Schwartz, Betty

    2015-01-01

    There are an increasing number of reports on obesity being a key risk factor for the development of colon cancer. Our goal in this study was to explore the metabolic networks and molecular signaling pathways linking obesity, adipose tissue and colon cancer. Using in-vivo experiments, we found that mice fed a high-fat diet (HFD) and injected with MC38 colon cancer cells develop significantly larger tumors than their counterparts fed a control diet. In ex-vivo experiments, MC38 and CT26 colon cancer cells exposed to conditioned media (CM) from the adipose tissue of HFD-fed mice demonstrated significantly lower oxygen consumption rate as well as lower maximal oxygen consumption rate after carbonyl cyanide-4-trifluoromethoxy-phenylhydrazone treatment. In addition, in-vitro assays showed downregulated expression of mitochondrial genes in colon cancer cells exposed to CM prepared from the visceral fat of HFD-fed mice or to leptin. Interestingly, leptin levels detected in the media of adipose tissue explants co-cultured with MC38 cancer cells were higher than in adipose tissue explants cultures, indicating cross talk between the adipose tissue and the cancer cells. Salient findings of the present study demonstrate that this crosstalk is mediated at least partially by the JNK/STAT3-signaling pathway. PMID:26472027

  2. Mechanisms linking obesity to altered metabolism in mice colon carcinogenesis.

    PubMed

    Nimri, Lili; Saadi, Janan; Peri, Irena; Yehuda-Shnaidman, Einav; Schwartz, Betty

    2015-11-10

    There are an increasing number of reports on obesity being a key risk factor for the development of colon cancer. Our goal in this study was to explore the metabolic networks and molecular signaling pathways linking obesity, adipose tissue and colon cancer. Using in-vivo experiments, we found that mice fed a high-fat diet (HFD) and injected with MC38 colon cancer cells develop significantly larger tumors than their counterparts fed a control diet. In ex-vivo experiments, MC38 and CT26 colon cancer cells exposed to conditioned media (CM) from the adipose tissue of HFD-fed mice demonstrated significantly lower oxygen consumption rate as well as lower maximal oxygen consumption rate after carbonyl cyanide-4-trifluoromethoxy-phenylhydrazone treatment. In addition, in-vitro assays showed downregulated expression of mitochondrial genes in colon cancer cells exposed to CM prepared from the visceral fat of HFD-fed mice or to leptin. Interestingly, leptin levels detected in the media of adipose tissue explants co-cultured with MC38 cancer cells were higher than in adipose tissue explants cultures, indicating cross talk between the adipose tissue and the cancer cells. Salient findings of the present study demonstrate that this crosstalk is mediated at least partially by the JNK/STAT3-signaling pathway. PMID:26472027

  3. Cross Linking and Degradation Mechanisms in Model Sealant Candidates

    NASA Technical Reports Server (NTRS)

    Paciorek, K. L.; Kaufman, J.; Ito, T. I.; Nakahara, J. H.; Kratzer, R. H.

    1977-01-01

    Model compounds were investigated as to which type of heterocyclic ring is the most advantageous for curing sealants based on perfluoroalkylether chains. The relative thermal, thermal oxidative, hydrolytic, and fuel stability of potential crosslinks were determined. Specifically substituted materials were synthesized and evaluation of their stabilities in air, inert atmosphere, water, and Jet-A fuel at 235 and 325 C was made. Three heterocyclic ring systems were considered, namely, triazine, 1,2,4- and 1,3,4-oxadiazoles.

  4. Nonextensive Statistical Mechanics: Some Links with Astronomical Phenomena

    NASA Astrophysics Data System (ADS)

    Tsallis, Constantino; Tsallis, Constantino; Prato, Domingo; Plastino, Angel R.; Plastino, Angel R.

    2004-04-01

    A variety of astronomical phenomena appear to not satisfy the ergodic hypothesis in the relevant stationary state, if any. As such, there is no reason for expecting the applicability of Boltzmann Gibbs (BG) statistical mechanics. Some of these phenomena appear to follow, instead, nonextensive statistical mechanics. In the same manner that the BG formalism is based on the entropy S BG=-k∑ i p i ln p i, the nonextensive one is based on the form S q=k(1 -∑ i p i q)/(q- 1) (with S 1=S BG). The stationary states of the former are characterized by an exponential dependence on the energy, whereas those of the latter are characterized by an (asymptotic) power law. A brief review of this theory is given here, as well as of some of its applications, such as the solar neutrino problem, polytropic self-gravitating systems, galactic peculiar velocities, cosmic rays and some cosmological aspects. In addition to these, an analogy with the Keplerian elliptic orbits versus the Ptolemaic epicycles is developed, where we show that optimizing S q with a few constraints is equivalent to optimizing S BG with an infinite number of constraints.

  5. White speck potential for mechanically harvested cottons

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This paper examines the white speck phenomena as seen in mechanically picked cottons based on HVI, AFIS and white speck fabric data. White specks are dye defects that can be inherent from the variety or can be caused by weather or other field conditions, and the fabric manufacturer is often caught ...

  6. Cognitive aspects of frailty: mechanisms behind the link between frailty and cognitive impairment.

    PubMed

    Halil, M; Cemal Kizilarslanoglu, M; Emin Kuyumcu, M; Yesil, Y; Cruz Jentoft, A J

    2015-03-01

    Whereas physical impairment is the main hallmark of frailty, evidence suggests that other dimensions, such as psychological, cognitive and social factors also contribute to this multidimensional condition. Cognition is now considered a relevant domain of frailty. Cognitive and physical frailty interact: cognitive problems and dementia are more prevalent in physically frail individuals, and those with cognitive impairment are more prone to become frail. Disentangling the relationship between cognition and frailty may lead to new intervention strategies for the prevention and treatment of both conditions. Both frailty and cognitive decline share common potential mechanisms. This review examines the relationship between frailty and cognitive decline and explores the role of vascular changes, hormones, vitamin D, inflammation, insulin resistance, and nutrition in the development of physical frailty and cognitive problems, as potential underlying mechanisms behind this link. Dual tasking studies may be a useful way to explore and understand the relation between cognitive and physical frailty. Further studies are needed to elucidate this complex relation to improve the outcomes of frailty. PMID:25732212

  7. A Link between Quantum Logic and Categorical Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Harding, John

    2009-03-01

    Abramsky and Coecke (Proceedings of the 19th Annual IEEE Symposium on Logic in Computer Science, pp. 415-425, IEEE Comput. Soc., New York, 2004) have recently introduced an approach to finite dimensional quantum mechanics based on strongly compact closed categories with biproducts. In this note it is shown that the projections of any object A in such a category form an orthoalgebra Proj A. Sufficient conditions are given to ensure this orthoalgebra is an orthomodular poset. A notion of a preparation for such an object is given by Abramsky and Coecke, and it is shown that each preparation induces a finitely additive map from Proj A to the unit interval of the semiring of scalars for this category. The tensor product for the category is shown to induce an orthoalgebra bimorphism Proj A× Proj B→ Proj ( A ⊗ B) that shares some of the properties required of a tensor product of orthoalgebras. These results are established in a setting more general than that of strongly compact closed categories. Many are valid in dagger biproduct categories, others require also a symmetric monoidal tensor compatible with the dagger and biproducts. Examples are considered for several familiar strongly compact closed categories.

  8. Mechanically Strong, Polymer Cross-linked Aerogels (X-Aerogels)

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas

    2006-01-01

    Aerogels comprise a class of low-density, high porous solid objects consisting of dimensionally quasi-stable self-supported three-dimensional assemblies of nanoparticles. Aerogels are pursued because of properties above and beyond those of the individual nanoparticles, including low thermal conductivity, low dielectric constant and high acoustic impedance. Possible applications include thermal and vibration insulation, dielectrics for fast electronics, and hosting of functional guests for a wide variety of optical, chemical and electronic applications. Aerogels, however, are extremely fragile materials, hence they have found only limited application in some very specialized environments, for example as Cerenkov radiation detectors in certain types of nuclear reactors, aboard spacecraft as collectors of hypervelocity particles (refer to NASA's Stardust program) and as thermal insulators on planetary vehicles on Mars (refer to Sojourner Rover in 1997 and Spirit and Opportunity in 2004). Along these lines, the X-Aerogel is a new NASA-developed strong lightweight material that has resolved the fragility problem of traditional (native) aerogels. X-Aerogels are made by applying a conformal polymer coating on the surfaces of the skeletal nanoparticles of native aerogels (see Scanning Electron Micrographs). Since the relative amounts of the polymeric crosslinker and the backbone are comparable, X-Aerogels can be viewed either as aerogels modified by the templated accumulation of polymer on the skeletal nanoparticles, or as nanoporous polymers made by remplated casting of polymer on a nanostructured framework. The most striking feature of X-Aerogels is that for a nominal 3-fold increase in density (still a ultralighweight material), the mechanical strength can be up to 300 times higher than the strength of the underlying native aerogel. Thus, X-Aerogels combine a multiple of the specific compressive strength of steel, with the the thermal conductivity of styrofoam. X

  9. Time with friends and physical activity as mechanisms linking obesity and television viewing among youth

    PubMed Central

    2015-01-01

    Background Though bivariate relationships between childhood obesity, physical activity, friendships and television viewing are well documented, empirical assessment of the extent to which links between obesity and television may be mediated by these factors is scarce. This study examines the possibility that time with friends and physical activity are potential mechanisms linking overweight/obesity to television viewing in youth. Methods Data were drawn from children ages 10-18 years old (M = 13.81, SD = 2.55) participating in the 2002 wave of Child Development Supplement (CDS) to the Panel Study of Income Dynamics (PSID) (n = 1,545). Data were collected both directly and via self-report from children and their parents. Path analysis was employed to examine a model whereby the relationships between youth overweight/obesity and television viewing were mediated by time spent with friends and moderate-to-vigorous physical activity (MVPA). Results Overweight/obesity was directly related to less time spent with friends, but not to MVPA. Time spent with friends was directly and positively related to MVPA, and directly and negatively related to time spent watching television without friends. In turn, MVPA was directly and negatively related to watching television without friends. There were significant indirect effects of both overweight/obesity and time with friends on television viewing through MVPA, and of overweight/obesity on MVPA through time with friends. Net of any indirect effects, the direct effect of overweight/obesity on television viewing remained. The final model fit the data extremely well (χ2 = 5.77, df = 5, p<0.0001, RMSEA = 0.01, CFI = 0.99, TLI =0.99). Conclusions We found good evidence that the positive relationships between time with friends and physical activity are important mediators of links between overweight/obesity and television viewing in youth. These findings highlight the importance of moving from examinations of bivariate relationships

  10. Platelet Activation: The Mechanisms and Potential Biomarkers

    PubMed Central

    Yun, Seong-Hoon; Sim, Eun-Hye; Goh, Ri-Young; Park, Joo-In

    2016-01-01

    Beyond hemostasis and thrombosis, an increasing number of studies indicate that platelets play an integral role in intercellular communication, mediating inflammatory and immunomodulatory activities. Our knowledge about how platelets modulate inflammatory and immunity has greatly improved in recent years. In this review, we discuss recent advances in the pathways of platelet activation and potential application of platelet activation biomarkers to diagnosis and prediction of disease states. PMID:27403440

  11. Vasectomy: potential links to an increased risk of aggressive prostate cancer?

    PubMed

    Gaines, Alexis R; Vidal, Adriana C; Freedland, Stephen J

    2015-01-01

    Several studies have found associations between aggressive prostate cancer (PC) and having a vasectomy. However, findings from two very recent meta-analyses have found that this is not the case. Therefore, the data are mixed. Herein, we detail the controversy between vasectomy and PC risk, particularly aggressive PC, by shedding some light on the molecular pathways, potential risk factors and suggested links for those considering vasectomy and medical professionals who perform it. We conclude by supporting the American Urological Association's position that there is no need to discuss potential prostate cancer risks with patients considering vasectomy given reasonably strong data finding no link between vasectomy and prostate cancer risk. PMID:26402245

  12. Potential Mechanisms of Progranulin-deficient FTLD

    PubMed Central

    Ward, Michael Emmerson

    2013-01-01

    Frontotemporal lobar dementia (FTLD) is the most common cause of dementia in patients younger than 60 years of age, and causes progressive neurodegeneration of the frontal and temporal lobes usually accompanied by devastating changes in language or behavior in affected individuals. Mutations in the progranulin (GRN) gene account for a significant fraction of familial FTLD, and in the vast majority of cases, these mutations lead to reduced expression of progranulin via nonsense-mediated mRNA decay. Progranulin is a secreted glycoprotein that regulates a diverse range of cellular functions including cell proliferation, cell migration, and inflammation. Recent fundamental discoveries about progranulin biology, including the findings that sortilin and tumor necrosis factor receptor (TNFR) are high affinity progranulin receptors, are beginning to shed light on the mechanism(s) by which progranulin deficiency causes FTLD. This review will explore how alterations in basic cellular functions due to PGRN deficiency, both intrinsic and extrinsic to neurons, might lead to the development of FTLD. PMID:21892758

  13. Vitamin D and Bone Health; Potential Mechanisms

    PubMed Central

    Laird, Eamon; Ward, Mary; McSorley, Emeir; Strain, J.J.; Wallace, Julie

    2010-01-01

    Osteoporosis is associated with increased morbidity, mortality and significant economic and health costs. Vitamin D is a secosteriod hormone essential for calcium absorption and bone mineralization which is positively associated with bone mineral density [BMD]. It is well-established that prolonged and severe vitamin D deficiency leads to rickets in children and osteomalacia in adults. Sub-optimal vitamin D status has been reported in many populations but it is a particular concern in older people; thus there is clearly a need for effective strategies to optimise bone health. A number of recent studies have suggested that the role of vitamin D in preventing fractures may be via its mediating effects on muscle function (a defect in muscle function is one of the classical signs of rickets) and inflammation. Studies have demonstrated that vitamin D supplementation can improve muscle strength which in turn contributes to a decrease in incidence of falls, one of the largest contributors to fracture incidence. Osteoporosis is often considered to be an inflammatory condition and pro-inflammatory cytokines have been associated with increased bone metabolism. The immunoregulatory mechanisms of vitamin D may thus modulate the effect of these cytokines on bone health and subsequent fracture risk. Vitamin D, therefore, may influence fracture risk via a number of different mechanisms. PMID:22254049

  14. Glycation Cross-Linking Induced Mechanical-Enzymatic Cleavage of Microscale Tendon Fibers

    PubMed Central

    Bourne, Jonathan W.; Lippell, Jared M.; Torzilli, Peter A.

    2014-01-01

    Recent molecular modeling data using collagen peptides predicted that mechanical force transmitted through intermolecular cross-links resulted in collagen triple helix unwinding. These simulations further predicted that this unwinding, referred to as triple helical microunfolding, occurred at forces well below canonical collagen damage mechanisms. Based in large part on these data, we hypothesized that mechanical loading of glycation cross-linked tendon microfibers would result in accelerated collagenolytic enzyme damage. This hypothesis is in stark contrast to reports in literature that indicated that individually mechanical loading or cross-linking each retards enzymatic degradation of collagen substrates. Using our Collagen Enzyme Mechano-Kinetic Automated Testing (CEMKAT) System we mechanically loaded collagen-rich tendon microfibers that had been chemically cross-linked with sugar and tested for degrading enzyme susceptibility. Our results indicated that cross-linked fibers were >5 times more resistant to enzymatic degradation while unloaded but became highly susceptible to enzyme cleavage when they were stretched by an applied mechanical deformation. PMID:24316373

  15. Complex Classical Mechanics of a QES Potential

    NASA Astrophysics Data System (ADS)

    Bhabani Prasad, Mandal; Sushant, S. Mahajan

    2015-10-01

    We study a combined parity (P) and time reversal (T) invariant non-Hermitian quasi-exactly solvable (QES) potential, which exhibits PT phase transition, in the complex plane classically to demonstrate different quantum effects. The particle with real energy makes closed orbits around one of the periodic wells of the complex potential depending on the initial condition. However interestingly the particle escapes to an open orbits even with real energy if it is placed beyond a certain distance from the center of the well. On the other hand when the particle energy is complex the trajectory is open and the particle tunnels back and forth between two wells which are separated by a classically forbidden path. The tunneling time is calculated for different pair of wells and is shown to vary inversely with the imaginary component of energy. Our study reveals that spontaneous PT symmetry breaking does not affect the qualitative features of the particle trajectories in the analogous complex classical model. Support from Department of Science and Technology (DST), Govt. of India under SERC Project Sanction Grant No. SR/S2/HEP-0009/2012

  16. Killing mechanism of stable N-halamine cross-linked polymethacrylamide nanoparticles that selectively target bacteria.

    PubMed

    Natan, Michal; Gutman, Ori; Lavi, Ronit; Margel, Shlomo; Banin, Ehud

    2015-02-24

    Increased resistance of bacteria to disinfection and antimicrobial treatment poses a serious public health threat worldwide. This has prompted the search for agents that can inhibit both bacterial growth and withstand harsh conditions (e.g., high organic loads). In the current study, N-halamine-derivatized cross-linked polymethacrylamide nanoparticles (NPs) were synthesized by copolymerization of the monomer methacrylamide (MAA) and the cross-linker monomer N,N-methylenebis(acrylamide) (MBAA) and were subsequently loaded with oxidative chlorine using sodium hypochlorite (NaOCl). The chlorinated NPs demonstrated remarkable stability and durability to organic reagents and to repetitive bacterial loading cycles as compared with the common disinfectant NaOCl (bleach), which was extremely labile under these conditions. The antibacterial mechanism of the cross-linked P(MAA-MBAA)-Cl NPs was found to involve generation of reactive oxygen species (ROS) only upon exposure to organic media. Importantly, ROS were not generated upon suspension in water, revealing that the mode of action is target-specific. Further, a unique and specific interaction of the chlorinated NPs with Staphylococcus aureus was discovered, whereby these microorganisms were all specifically targeted and marked for destruction. This bacterial encircling was achieved without using a targeting module (e.g., an antibody or a ligand) and represents a highly beneficial, natural property of the P(MAA-MBAA)-Cl nanostructures. Our findings provide insights into the mechanism of action of P(MAA-MBAA)-Cl NPs and demonstrate the superior efficacy of the NPs over bleach (i.e., stability, specificity, and targeting). This work underscores the potential of developing sustainable P(MAA-MBAA)-Cl NP-based devices for inhibiting bacterial colonization and growth. PMID:25602279

  17. Dynamic analysis and control of lightweight manipulators with flexible parallel link mechanisms

    NASA Technical Reports Server (NTRS)

    Lee, Jeh Won

    1991-01-01

    The flexible parallel link mechanism is designed for increased rigidity to sustain the buckling when it carries a heavy payload. Compared to a one link flexible manipulator, a two link flexible manipulator, especially the flexible parallel mechanism, has more complicated characteristics in dynamics and control. The objective of this research is the theoretical analysis and the experimental verification of dynamics and control of a two link flexible manipulator with a flexible parallel link mechanism. Nonlinear equations of motion of the lightweight manipulator are derived by the Lagrangian method in symbolic form to better understand the structure of the dynamic model. A manipulator with a flexible parallel link mechanism is a constrained dynamic system whose equations are sensitive to numerical integration error. This constrained system is solved using singular value decomposition of the constraint Jacobian matrix. The discrepancies between the analytical model and the experiment are explained using a simplified and a detailed finite element model. The step response of the analytical model and the TREETOPS model match each other well. The nonlinear dynamics is studied using a sinusoidal excitation. The actuator dynamic effect on a flexible robot was investigated. The effects are explained by the root loci and the Bode plot theoretically and experimentally. For the base performance for the advanced control scheme, a simple decoupled feedback scheme is applied.

  18. NAAG peptidase as a therapeutic target: Potential for regulating the link between glucose metabolism and cognition.

    PubMed

    Baslow, Morris H

    2006-04-01

    There is a new class of CNS drugs, N-acetylaspartylglutamate (NAAG) peptidase inhibitors, that can affect a two-step, neuron-astrocyte/astrocyte-vascular endothelium, signaling mechanism. Using this homeostatic mechanism, activated neurons continuously interact with the vascular system to indicate ongoing requirements for supplies of glucose (Glc) and oxygen needed to maintain cognitive functions. These new drugs impact the first step by inhibiting NAAG peptidase, located on the astrocyte surface, that cleaves glutamate (Glu) from the neuropeptide NAAG after it has docked with the astrocyte surface metabotropic Glu receptor 3 (mGluR3). As a result, this interferes with initiation of the second step, the astrocyte-vascular endothelium signal, activation of which results in a rapid hyperemic response that increases focal availability of energy supplies. Since NAAG is liberated upon each neuron depolarization, its release is linked to the level of neuronal spiking. This insures that its mGluR3 signal function reflects current levels of neuronal stimulation, so that Glc and oxygen can be supplied in a timely manner for metabolic replacement of ATP stocks depleted during the repolarization process. The metabolism of NAAG is very complex, being a component of the only metabolic sequence in the brain requiring three major brain cell types--neurons, astrocytes and oligodendrocytes--for its successful completion. In this review, we describe the unique NAAG tricellular metabolic cycle and survey some reported actions of these new and novel drugs. We also consider their probable site and mode of action and speculate upon their therapeutic potential. PMID:16804566

  19. Psychosocial Mechanisms Linking the Social Environment to Mental Health in African Americans.

    PubMed

    Mama, Scherezade K; Li, Yisheng; Basen-Engquist, Karen; Lee, Rebecca E; Thompson, Deborah; Wetter, David W; Nguyen, Nga T; Reitzel, Lorraine R; McNeill, Lorna H

    2016-01-01

    Resource-poor social environments predict poor health, but the mechanisms and processes linking the social environment to psychological health and well-being remain unclear. This study explored psychosocial mediators of the association between the social environment and mental health in African American adults. African American men and women (n = 1467) completed questionnaires on the social environment, psychosocial factors (stress, depressive symptoms, and racial discrimination), and mental health. Multiple-mediator models were used to assess direct and indirect effects of the social environment on mental health. Low social status in the community (p < .001) and U.S. (p < .001) and low social support (p < .001) were associated with poor mental health. Psychosocial factors significantly jointly mediated the relationship between the social environment and mental health in multiple-mediator models. Low social status and social support were associated with greater perceived stress, depressive symptoms, and perceived racial discrimination, which were associated with poor mental health. Results suggest the relationship between the social environment and mental health is mediated by psychosocial factors and revealed potential mechanisms through which social status and social support influence the mental health of African American men and women. Findings from this study provide insight into the differential effects of stress, depression and discrimination on mental health. Ecological approaches that aim to improve the social environment and psychosocial mediators may enhance health-related quality of life and reduce health disparities in African Americans. PMID:27119366

  20. Psychosocial Mechanisms Linking the Social Environment to Mental Health in African Americans

    PubMed Central

    Basen-Engquist, Karen; Lee, Rebecca E.; Thompson, Deborah; Wetter, David W.; Reitzel, Lorraine R.

    2016-01-01

    Resource-poor social environments predict poor health, but the mechanisms and processes linking the social environment to psychological health and well-being remain unclear. This study explored psychosocial mediators of the association between the social environment and mental health in African American adults. African American men and women (n = 1467) completed questionnaires on the social environment, psychosocial factors (stress, depressive symptoms, and racial discrimination), and mental health. Multiple-mediator models were used to assess direct and indirect effects of the social environment on mental health. Low social status in the community (p < .001) and U.S. (p < .001) and low social support (p < .001) were associated with poor mental health. Psychosocial factors significantly jointly mediated the relationship between the social environment and mental health in multiple-mediator models. Low social status and social support were associated with greater perceived stress, depressive symptoms, and perceived racial discrimination, which were associated with poor mental health. Results suggest the relationship between the social environment and mental health is mediated by psychosocial factors and revealed potential mechanisms through which social status and social support influence the mental health of African American men and women. Findings from this study provide insight into the differential effects of stress, depression and discrimination on mental health. Ecological approaches that aim to improve the social environment and psychosocial mediators may enhance health-related quality of life and reduce health disparities in African Americans. PMID:27119366

  1. Emotion dysregulation as a mechanism linking stress exposure to adolescent aggressive behavior.

    PubMed

    Herts, Kate L; McLaughlin, Katie A; Hatzenbuehler, Mark L

    2012-10-01

    Exposure to stress is associated with a wide range of internalizing and externalizing problems in adolescents, including aggressive behavior. Extant research examining mechanisms underlying the associations between stress and youth aggression has consistently identified social information processing pathways that are disrupted by exposure to violence and increase risk of aggressive behavior. In the current study, we use longitudinal data to examine emotion dysregulation as a potential mechanism linking a broader range of stressful experiences to aggressive behavior in a diverse sample of early adolescents (N = 1065). Specifically, we examined the longitudinal associations of peer victimization and stressful life events with emotion dysregulation and aggressive behavior. Structural equation modeling was used to create latent constructs of emotion dysregulation and aggression. Both stressful life events and peer victimization predicted subsequent increases in emotion dysregulation over a 4-month period. These increases in emotion dysregulation, in turn, were associated with increases in aggression over the subsequent 3 months. Longitudinal mediation models showed that emotion dysregulation mediated the relationship of both peer victimization (z = 2.35, p = 0.019) and stressful life events (z = 2.32, p = 0.020) with aggressive behavior. Increasing the use of adaptive emotion regulation strategies is an important target for interventions aimed at preventing the onset of adolescent aggressive behavior. PMID:22466516

  2. Dynamic Analysis and Control of Lightweight Manipulators with Flexible Parallel Link Mechanisms. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Lee, Jeh Won

    1990-01-01

    The objective is the theoretical analysis and the experimental verification of dynamics and control of a two link flexible manipulator with a flexible parallel link mechanism. Nonlinear equations of motion of the lightweight manipulator are derived by the Lagrangian method in symbolic form to better understand the structure of the dynamic model. The resulting equation of motion have a structure which is useful to reduce the number of terms calculated, to check correctness, or to extend the model to higher order. A manipulator with a flexible parallel link mechanism is a constrained dynamic system whose equations are sensitive to numerical integration error. This constrained system is solved using singular value decomposition of the constraint Jacobian matrix. Elastic motion is expressed by the assumed mode method. Mode shape functions of each link are chosen using the load interfaced component mode synthesis. The discrepancies between the analytical model and the experiment are explained using a simplified and a detailed finite element model.

  3. Imaging Mitochondrial Redox Potential and Its Possible Link to Tumor Metastatic Potential

    PubMed Central

    Li, Lin Z.

    2012-01-01

    Cellular redox states can regulate cell metabolism, growth, differentiation, motility, apoptosis, signaling pathways, and gene expressions etc. Growing body of literature suggest importance of redox status for cancer progression. While most studies on redox state were done on cells and tissue lysates, it is important to understand the role of redox state in tissue in vivo/ex vivo and image its heterogeneity. Redox scanning is a clinically-translatable method for imaging tissue mitochondrial redox potential with a submillimeter resolution. Redox scanning data in mouse models of human cancers demonstrate a correlation between mitochondrial redox state and tumor metastatic potential. I will discuss the significance of this correlation and possible directions for future research. PMID:22895837

  4. Link between the potentially hazardous Asteroid (86039) 1999 NC43 and the Chelyabinsk meteoroid tenuous

    NASA Astrophysics Data System (ADS)

    Reddy, Vishnu; Vokrouhlický, David; Bottke, William F.; Pravec, Petr; Sanchez, Juan A.; Gary, Bruce L.; Klima, Rachel; Cloutis, Edward A.; Galád, Adrián; Guan, Tan Thiam; Hornoch, Kamil; Izawa, Matthew R. M.; Kušnirák, Peter; Le Corre, Lucille; Mann, Paul; Moskovitz, Nicholas; Skiff, Brian; Vraštil, Jan

    2015-05-01

    We explored the statistical and compositional link between Chelyabinsk meteoroid and potentially hazardous Asteroid (86039) 1999 NC43 to investigate their proposed relation proposed by Borovička et al. (Borovička, J., et al. [2013]. Nature 503, 235-237). First, using a slightly more detailed computation we confirm that the orbit of the Chelyabinsk impactor is anomalously close to the Asteroid 1999 NC43. We find ∼(1-3) × 10-4 likelihood of that to happen by chance. Taking the standpoint that the Chelyabinsk impactor indeed separated from 1999 NC43 by a cratering or rotational fission event, we run a forward probability calculation, which is an independent statistical test. However, we find this scenario is unlikely at the ∼(10-3-10-2) level. Secondly, we note that efforts to conclusively prove separation of the Chelyabinsk meteoroid from (86039) 1999 NC43 in the past needs to meet severe criteria: relative velocity ≃1-10 m/s or smaller, and ≃100 km distance (i.e. about the Hill sphere distance from the parent body). We conclude that, unless the separation event was an extremely recent event, these criteria present an insurmountable difficulty due to the combination of strong orbital chaoticity, orbit uncertainty and incompleteness of the dynamical model with respect to thermal accelerations. This situation leaves the link of the two bodies unresolved and calls for additional analyses. With that goal, we revisit the presumed compositional link between (86039) 1999 NC43 and the Chelyabinsk body. Borovička et al. (Borovička, J., et al. [2013]. Nature 503, 235-237) noted that given its Q-type taxonomic classification, 1999 NC43 may pass this test. However, here we find that while the Q-type classification of 1999 NC43 is accurate, assuming that all Q-types are LL chondrites is not. Our experiment shows that not all ordinary chondrites fall under Q-taxonomic type and not all LL chondrites are Q-types. Spectral curve matching between laboratory spectra of

  5. Computational exploration of polymer nanocomposite mechanical property modification via cross-linking topology

    SciTech Connect

    Lacevic, N; Gee, R; Saab, A; Maxwell, R

    2008-04-24

    Molecular dynamics simulations have been performed in order to study the effects of nanoscale filler cross-linking topologies and loading levels on the mechanical properties of a model elastomeric nanocomposite. The model system considered here is constructed from octa-functional polyhedral oligomeric silsesquioxane (POSS) dispersed in a poly(dimethylsiloxane) (PDMS) matrix. Shear moduli, G, have been computed for pure and for filled and unfilled PDMS as a function of cross-linking density, POSS fill loading level, and polymer network topology. The results reported here show that G increases as the cross-linking (covalent bonds formed between the POSS and the PDMS network) density increases. Further, G is found to have a strong dependence on cross-linking topology. The increase in shear modulus, G, for POSS filled PDMS is significantly higher than that for unfilled PDMS cross-linked with standard molecular species, suggesting an enhanced reinforcement mechanism for POSS. In contrast, in blended systems (POSS/PDMS mixture with no cross-linking) G was not observed to significantly increase with POSS loading. Finally, we find intriguing differences in the structural arrangement of bond strains between the cross-linked and the blended systems. In the unfilled PDMS the distribution of highly strained bonds appears to be random, while in the POSS filled system, the strained bonds form a net-like distribution that spans the network. Such a distribution may form a structural network 'holding' the composite together and resulting in increases in G compared to an unfilled, cross-linked system. These results are of importance for engineering of new POSS-based multifunctional materials with tailor-made mechanical properties.

  6. Cystatin A, a Potential Common Link for Mutant Myocilin Causative Glaucoma

    PubMed Central

    Kennedy, K. David; AnithaChristy, S. A.; Buie, LaKisha K.; Borrás, Teresa

    2012-01-01

    Myocilin (MYOC) is a 504 aa secreted glycoprotein induced by stress factors in the trabecular meshwork tissue of the eye, where it was discovered. Mutations in MYOC are linked to glaucoma. The glaucoma phenotype of each of the different MYOC mutation varies, but all of them cause elevated intraocular pressure (IOP). In cells, forty percent of wild-type MYOC is cleaved by calpain II, a cysteine protease. This proteolytic process is inhibited by MYOC mutants. In this study, we investigated the molecular mechanisms by which MYOC mutants cause glaucoma. We constructed adenoviral vectors with variants Q368X, R342K, D380N, K423E, and overexpressed them in human trabecular meshwork cells. We analyzed expression profiles with Affymetrix U133Plus2 GeneChips using wild-type and null viruses as controls. Analysis of trabecular meshwork relevant mechanisms showed that the unfolded protein response (UPR) was the most affected. Search for individual candidate genes revealed that genes that have been historically connected to trabecular meshwork physiology and pathology were altered by the MYOC mutants. Some of those had known MYOC associations (MMP1, PDIA4, CALR, SFPR1) while others did not (EDN1, MGP, IGF1, TAC1). Some, were top-changed in only one mutant (LOXL1, CYP1B1, FBN1), others followed a mutant group pattern. Some of the genes were new (RAB39B, STC1, CXCL12, CSTA). In particular, one selected gene, the cysteine protease inhibitor cystatin A (CSTA), was commonly induced by all mutants and not by the wild-type. Subsequent functional analysis of the selected gene showed that CSTA was able to reduce wild-type MYOC cleavage in primary trabecular meshwork cells while an inactive mutated CSTA was not. These findings provide a new molecular understanding of the mechanisms of MYOC-causative glaucoma and reveal CSTA, a serum biomarker for cancer, as a potential biomarker and drug for the treatment of MYOC-induced glaucoma. PMID:22615763

  7. Flight tests show potential benefits of data link as primary communication medium

    NASA Technical Reports Server (NTRS)

    Scanlon, Charles H.; Knox, Charles E.

    1991-01-01

    Message exchange for air traffic control (ATC) purposes via data link offers the potential benefits of increasing the airspace system safety and efficiency. This is accomplished by reducing communication errors and relieving the overloaded ATC radio frequencies, which hamper efficient message exchanges during peak traffic periods in many busy terminal areas. However, the many uses and advantages of data link create additional questions concerning the interface among the human-users and the cockpit and ground systems. A flight test was conducted in the NASA Langley B-737 airplane to contrast flight operations using current voice communications with the use of data link for transmitting both strategic and tactical ATC clearances during a typical commercial airline flight from takeoff to landing. Commercial airplane pilots were used as test subjects.

  8. A novel strategy for preparing mechanically robust ionically cross-linked alginate hydrogels.

    PubMed

    Jejurikar, Aparna; Lawrie, Gwen; Martin, Darren; Grøndahl, Lisbeth

    2011-04-01

    The properties of alginate films modified using two cross-linker ions (Ca(2+) and Ba(2+)), comparing two separate cross-linking techniques (the traditional immersion (IM) method and a new strategy in a pressure-assisted diffusion (PD) method), are evaluated. This was achieved through measuring metal ion content, water uptake and film stability in an ionic solution ([Ca(2+)] = 2 mM). Characterization of the internal structure and mechanical properties of hydrated films were established by cryogenic scanning electron microscopy and tensile testing, respectively. It was found that gels formed by the PD technique possessed greater stability and did not exhibit any delamination after 21 day immersion as compared to gels formed by the IM technique. The Ba(2+) cross-linked gels possessed significantly higher cross-linking density as reflected in lower water content, a more dense internal structure and higher Young's modulus compared to Ca(2+) cross-linked gels. For the Ca(2+) cross-linked gels, a large improvement in the mechanical properties was observed in gels produced by the PD technique and this was attributed to thicker pore walls observed within the hydrogel structure. In contrast, for the Ba(2+) cross-linked gels, the PD technique resulted in gels that had lower tensile strength and strain energy density and this was attributed to phase separation and larger macropores in this gel. PMID:21436510

  9. Effects of interatomic potentials on mechanical deformation of glasses

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Ren; Iwashita, Takuya; Egami, Takeshi

    2013-03-01

    Apparently glasses behave like an elastic solid, which shows a linear relationship between stress and strain in mechanical deformation. However the understanding of the mechanical response of glasses remains elusive because of structural disorder. Mechanical deformation of monatomic model glasses was studied using athermal quasi-static shear (AQS) simulation and with three different potentials. As the interatomic potentials we employed the 12-6 Lennard-Jones (LJ) potential, modified Johnson (mJ) potential, and Dzugutov (Dz) potential, respectively. For mJ and Dz glasses the shear modulus keeps constant below a critical strain, below which it decreases rapidly or discontinuously with strain. Such changes in shear modulus were mostly related to the change in local topology of atomic connectivity or anelasticity. In contrast LJ glass shows a gradual decrease in shear modulus in a continuous manner. The results indicated that the difference arises from the nature of the potentials if the topology of atomic connectivity can be clearly defined.

  10. Tuning of cross-linking and mechanical properties of laser-deposited poly (methyl methacrylate) films

    NASA Astrophysics Data System (ADS)

    Süske, Erik; Scharf, Thorsten; Krebs, Hans-Ulrich; Panchenko, Elena; Junkers, Thomas; Egorov, Mark; Buback, Michael; Kijewski, Harald

    2005-03-01

    The chemical composition, amount of cross-linking and its influence on the mechanical properties of poly(methyl methacrylate) (PMMA) thin films produced by pulsed laser deposition (PLD) at a wavelength of 248nm under ultrahigh vacuum were investigated by infrared spectroscopy, scanning electron microscopy, size-exclusion chromatography, thermogravimetric analysis, and nanoindentation experiments. The films consist of two components, one fraction with a molecular weight well below that of the target material and a second fraction, which is cross-linked. Compared to bulk material, the Young's modulus of the film is increased. The amount of cross-linking in the film can be tuned by the applied laser fluence leading to changes of the mechanical properties.

  11. Tuning of cross-linking and mechanical properties of laser-deposited poly (methyl methacrylate) films

    SciTech Connect

    Sueske, Erik; Scharf, Thorsten; Krebs, Hans-Ulrich; Panchenko, Elena; Junkers, Thomas; Egorov, Mark; Buback, Michael; Kijewski, Harald

    2005-03-15

    The chemical composition, amount of cross-linking and its influence on the mechanical properties of poly(methyl methacrylate) (PMMA) thin films produced by pulsed laser deposition (PLD) at a wavelength of 248 nm under ultrahigh vacuum were investigated by infrared spectroscopy, scanning electron microscopy, size-exclusion chromatography, thermogravimetric analysis, and nanoindentation experiments. The films consist of two components, one fraction with a molecular weight well below that of the target material and a second fraction, which is cross-linked. Compared to bulk material, the Young's modulus of the film is increased. The amount of cross-linking in the film can be tuned by the applied laser fluence leading to changes of the mechanical properties.

  12. Insect mandibles—comparative mechanical properties and links with metal incorporation

    NASA Astrophysics Data System (ADS)

    Cribb, Bronwen W.; Stewart, Aaron; Huang, Han; Truss, Rowan; Noller, Barry; Rasch, Ronald; Zalucki, Myron P.

    2008-01-01

    A number of arthropod taxa contain metals in their mandibles (jaws), such as zinc, manganese, iron, and calcium. The occurrence of zinc and its co-located halogen chlorine have been studied in relation to the mechanical properties and shown to be linked in a direct fashion with increasing concentration. Hardness along with elastic modulus (stiffness) has also been linked to zinc and halogen concentration in some marine polychaete worms. The metal appears to be incorporated within the biological matrix, possibly bonding with proteins. However, the comparative advantage of metal inclusion has not been tested. It is possible that without metals, alternative mechanisms are used to achieve hardness of equal value in similar ‘tools’ such as mandibles. This question has direct bearing on the significance of metal hardening. In the present article, we compare across mandibles from six termite species, including samples with major zinc concentration, minor manganese, and no metals. Nanoindentation, electron microscopy, and electron microanalysis are used to assess metal concentration, form, and mechanical properties. The data demonstrate that termite mandibles lacking metals when fully developed have lower values for hardness and elastic modulus. Zinc is linked to a relative 20% increase in hardness when compared with mandibles devoid of metals. The similar transition metal, manganese, found in minor concentrations, is not linked to any significant increase in these mechanical properties. This raises the question of the function of manganese, which is as commonly found in insect mandibles as zinc and often located in the same mandibles.

  13. A New Realistic Evaluation Analysis Method: Linked Coding of Context, Mechanism, and Outcome Relationships

    ERIC Educational Resources Information Center

    Jackson, Suzanne F.; Kolla, Gillian

    2012-01-01

    In attempting to use a realistic evaluation approach to explore the role of Community Parents in early parenting programs in Toronto, a novel technique was developed to analyze the links between contexts (C), mechanisms (M) and outcomes (O) directly from experienced practitioner interviews. Rather than coding the interviews into themes in terms of…

  14. Psychosocial mechanisms linking the social environment to mental health in African Americans

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Resource-poor social environments predict poor health, but the mechanisms and processes linking the social environment to psychological health and well-being remain unclear. This study explored psychosocial mediators of the association between the social environment and mental health in African Amer...

  15. Insect mandibles--comparative mechanical properties and links with metal incorporation.

    PubMed

    Cribb, Bronwen W; Stewart, Aaron; Huang, Han; Truss, Rowan; Noller, Barry; Rasch, Ronald; Zalucki, Myron P

    2008-01-01

    A number of arthropod taxa contain metals in their mandibles (jaws), such as zinc, manganese, iron, and calcium. The occurrence of zinc and its co-located halogen chlorine have been studied in relation to the mechanical properties and shown to be linked in a direct fashion with increasing concentration. Hardness along with elastic modulus (stiffness) has also been linked to zinc and halogen concentration in some marine polychaete worms. The metal appears to be incorporated within the biological matrix, possibly bonding with proteins. However, the comparative advantage of metal inclusion has not been tested. It is possible that without metals, alternative mechanisms are used to achieve hardness of equal value in similar 'tools' such as mandibles. This question has direct bearing on the significance of metal hardening. In the present article, we compare across mandibles from six termite species, including samples with major zinc concentration, minor manganese, and no metals. Nanoindentation, electron microscopy, and electron microanalysis are used to assess metal concentration, form, and mechanical properties. The data demonstrate that termite mandibles lacking metals when fully developed have lower values for hardness and elastic modulus. Zinc is linked to a relative 20% increase in hardness when compared with mandibles devoid of metals. The similar transition metal, manganese, found in minor concentrations, is not linked to any significant increase in these mechanical properties. This raises the question of the function of manganese, which is as commonly found in insect mandibles as zinc and often located in the same mandibles. PMID:17646951

  16. Interpersonal Stress Generation as a Mechanism Linking Rumination to Internalizing Symptoms in Early Adolescents

    ERIC Educational Resources Information Center

    McLaughlin, Katie A.; Nolen-Hoeksema, Susan

    2012-01-01

    Rumination is a risk factor for depressive and anxiety symptoms in adolescents. Previous investigations of the mechanisms linking rumination to internalizing problems have focused primarily on cognitive factors. We investigated whether interpersonal stress generation plays a role in the longitudinal relationship between rumination and…

  17. Students' Conceptual Difficulties in Quantum Mechanics: Potential Well Problems

    ERIC Educational Resources Information Center

    Ozcan, Ozgur; Didis, Nilufer; Tasar, Mehmet Fatih

    2009-01-01

    In this study, students' conceptual difficulties about some basic concepts in quantum mechanics like one-dimensional potential well problems and probability density of tunneling particles were identified. For this aim, a multiple choice instrument named Quantum Mechanics Conceptual Test has been developed by one of the researchers of this study…

  18. Fracture Mechanics of Collagen Fibrils: Influence of Natural Cross-Links

    PubMed Central

    Svensson, Rene B.; Mulder, Hindrik; Kovanen, Vuokko; Magnusson, S. Peter

    2013-01-01

    Tendons are important load-bearing structures, which are frequently injured in both sports and work. Type I collagen fibrils are the primary components of tendons and carry most of the mechanical loads experienced by the tissue, however, knowledge of how load is transmitted between and within fibrils is limited. The presence of covalent enzymatic cross-links between collagen molecules is an important factor that has been shown to influence mechanical behavior of the tendons. To improve our understanding of how molecular bonds translate into tendon mechanics, we used an atomic force microscopy technique to measure the mechanical behavior of individual collagen fibrils loaded to failure. Fibrils from human patellar tendons, rat-tail tendons (RTTs), NaBH4 reduced RTTs, and tail tendons of Zucker diabetic fat rats were tested. We found a characteristic three-phase stress-strain behavior in the human collagen fibrils. There was an initial rise in modulus followed by a plateau with reduced modulus, which was finally followed by an even greater increase in stress and modulus before failure. The RTTs also displayed the initial increase and plateau phase, but the third region was virtually absent and the plateau continued until failure. The importance of cross-link lability was investigated by NaBH4 reduction of the rat-tail fibrils, which did not alter their behavior. These findings shed light on the function of cross-links at the fibril level, but further studies will be required to establish the underlying mechanisms. PMID:23746520

  19. Exactly Solvable Quantum Mechanical Potentials: An Alternative Approach.

    ERIC Educational Resources Information Center

    Pronchik, Jeremy N.; Williams, Brian W.

    2003-01-01

    Describes an alternative approach to finding exactly solvable, one-dimensional quantum mechanical potentials. Differs from the usual approach in that instead of starting with a particular potential and seeking solutions to the related Schrodinger equations, it begins with known solutions to second-order ordinary differential equations and seeks to…

  20. Can interactive educational technologies support the link between ultrasound theory and practice via feedback mechanisms?

    PubMed Central

    2014-01-01

    Linking theory to practice is an area of concern for ultrasound students, clinical mentors and academic staff. The link between theory and practice requires a robust clinical mentorship scheme in addition to careful curricula design considerations to improve student outcomes. The introduction of interactive technology in education provides ripe opportunity to improve feedback to students to support the link between theory and practice. A series of three interactive learning and teaching activities were designed and delivered to a PostGraduate Ultrasound cohort, after which, evaluation was performed to answer the research question: Which interactive technologies support the link between theory and practice through improved feedback mechanisms? An action research methodology was adopted involving an enquiry based literature review, planning, design and action process. Data were collected following action of three interactive teaching and learning sessions within the Medical Ultrasound cohort of 2013/2014 at Glasgow Caledonian University via a paper based questionnaire. A 100% response rate was achieved (n = 14). All three interactive learning and teaching sessions were considered with 100% highest point agreement to support the link between ultrasound theory and practice via feedback. Students found all three designed and facilitated sessions valuable and relevant to their learning, which in turn provided positive experiences which were perceived to support the link between theory and practice through feedback. These activities can be considered valuable in Postgraduate Ultrasound education. PMID:27433244

  1. Optical mechanical refinement of human amniotic membrane by dehydration and cross-linking.

    PubMed

    Tanaka, Yuji; Kubota, Akira; Yokokura, Shunji; Uematsu, Masafumi; Shi, Dong; Yamato, Masayuki; Okano, Teruo; Quantock, Andrew J; Nishida, Kohji

    2012-10-01

    The aim of this study was to develop a method for refining the optical and mechanical properties of human amniotic membrane (AM) to provide ophthalmic transparent implants for use during severe donor cornea shortages. AM was allowed to gradually dehydrate at 4-8 °C with and without chemical cross-linking. To improve the transparency of AM, a simple dehydration process using a refrigerator at 4-8 °C overnight was examined. For further improvements, dehydrated AM was then cross-linked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxy-succimide before rehydration. Light transmittance and tensile strength of individual specimens were evaluated. Light transmittance of AM improved from 50.9-77.7% at 550 nm by this simple low temperature dehydration process. Its high light transmittance was partially maintained at 70.1%, even after rehydration with normal saline. Interestingly, chemically cross-linked AM showed a significantly greater light transmittance of 81.5% under wet conditions. In addition, tensile strength was significantly increased after cross-linking from 2.32 N/mm(2) (native tissue) to 11.78 N/mm(2) (cross-linked specimens). Light transmittance and tensile strength were successfully improved by these approaches, including low temperature dehydration with and without chemical cross-linking. The use of refined AM could be feasible for use in current and future ophthalmic treatments. PMID:22489071

  2. Laser Communications Airborne Testbed: Potential For An Air-To-Satellite Laser Communications Link

    NASA Astrophysics Data System (ADS)

    Feldmann, Robert J.

    1988-05-01

    The Laser Communications Airborne Testbed (LCAT) offers an excellent opportunity for testing of an air-to-satellite laser communications link with the NASA Advanced Communications Technology Satellite (ACTS). The direct detection laser portion of the ACTS is suitable for examining the feasibility of an airborne terminal. Development of an airborne laser communications terminal is not currently part of the ACTS program; however, an air-to-satellite link is of interest. The Air Force performs airborne laser communications experiments to examine the potential usefulness of this technology to future aircraft. Lasers could be used, for example, by future airborne command posts and reconnaissance aircraft to communicate via satellite over long distances and transmit large quantities of data in the fastest way possible from one aircraft to another or to ground sites. Lasers are potentially secure, jam resistant and hard to detect and in this regard increase the survivability of the users. Under a contract awarded by Aeronautical Systems Division's Avionics Laboratory, a C-135E testbed aircraft belonging to ASD's 4950th Test Wing will be modified to create a Laser Communications Airborne Testbed. The contract is for development and fabrication of laser testbed equipment and support of the aircraft modification effort by the Test Wing. The plane to be modified is already in use as a testbed for other satellite communications projects and the LCAT effort will expand those capabilities. This analysis examines the characteristics of an LCAT to ACTS direct detection communications link. The link analysis provides a measure of the feasibility of developing an airborne laser terminal which will interface directly to the LCAT. Through the existence of the LCAT, the potential for development of an air-to-satellite laser communications terminal for the experimentation with the ACTS system is greatly enhanced.

  3. The Potential Link between Gut Microbiota and IgE-Mediated Food Allergy in Early Life

    PubMed Central

    Molloy, John; Allen, Katrina; Collier, Fiona; Tang, Mimi L. K.; Ward, Alister C.; Vuillermin, Peter

    2013-01-01

    There has been a dramatic rise in the prevalence of IgE-mediated food allergy over recent decades, particularly among infants and young children. The cause of this increase is unknown but one putative factor is a change in the composition, richness and balance of the microbiota that colonize the human gut during early infancy. The coevolution of the human gastrointestinal tract and commensal microbiota has resulted in a symbiotic relationship in which gut microbiota play a vital role in early life immune development and function, as well as maintenance of gut wall epithelial integrity. Since IgE mediated food allergy is associated with immune dysregulation and impaired gut epithelial integrity there is substantial interest in the potential link between gut microbiota and food allergy. Although the exact link between gut microbiota and food allergy is yet to be established in humans, recent experimental evidence suggests that specific patterns of gut microbiota colonization may influence the risk and manifestations of food allergy. An understanding of the relationship between gut microbiota and food allergy has the potential to inform both the prevention and treatment of food allergy. In this paper we review the theory and evidence linking gut microbiota and IgE-mediated food allergy in early life. We then consider the implications and challenges for future research, including the techniques of measuring and analyzing gut microbiota, and the types of studies required to advance knowledge in the field. PMID:24351744

  4. Numerical simulation of mechanisms and manipulator robots with flexible links and flexible joints

    NASA Astrophysics Data System (ADS)

    Gong, D.

    1995-01-01

    This thesis deals with numerical simulation of mechanical systems like mechanisms and manipulator robots. The mechanical system may be considered in a two or three dimensional space, may have electrical machines, and may contain flexible links and flexible joints. Methods and algorithms to perform static analysis, kinematic analysis, dynamic analysis, linearization of nonlinear systems, periodic solution of periodically forced systems and control simulation of robots have been applied. A finite element method is used to get the mathematical model for a mechanical system. Friendly interfaces for pre- and post-processing have been designed by using X Window on Sun workstations. An integrated program network and data base has been applied in the software system SPACAR. For the simulation of robots with flexible links and flexible joints, two linearization methods have been studied: the variational linearization method and the feedback linearization method. Numerical examples for simulation of robots with flexible links and flexible joints have been presented to show the elegance and powerfulness of the introduced methods and the designed software system.

  5. Vegetation and erosion: comments on the linking mechanisms from the perspective of the Australian drylands.

    NASA Astrophysics Data System (ADS)

    Dunkerley, D.

    2009-04-01

    John Thorne's wide-ranging research included an emphasis on the diverse roles of vegetation in modifying erosion processes under Mediterranean conditions, with primary field studies in Spain. Different global drylands reflect some differences in the nature or strength of the mechanisms linking vegetation and erosion. In Australia, low topographic gradients and plants adapted to water scarcity have facilitated the widespread development of contour-aligned vegetation groves. In these landscapes, the role of individual plants in modifying raindrop impact energy or overland flow erosivity is secondary to the community-level effects of the grove structures. Erosion in common rain events is limited to quite local redistribution of soil materials on metre scales. This highlights one of the unresolved issues that warrants more attention in drylands globally: under what range of rain events does the protective role of individual plants (or of groves) operate, and what is the threshold event size beyond which their effect is swamped by integrated overland flow arriving from upslope? In contrast with, for example, the well-understood role of bankfull flows in river architecture, general principles underlying dryland hillslope and channel responses to events of various magnitudes remain obscure. Clearly, however, there is no single role for plant cover; rather, that role varies with event magnitude and related properties such as the time since the last rain event. An important conclusion is therefore that context is important when evaluating the links between vegetation and erosion. The developing view of overland flow generally, but particularly relevant in drylands where plant cover is sparse, is that the connectedness of runoff flowpaths is a key parameter. It partly determines the extent to which the downslope movement of resources (soil, water, organic matter) is free or constrained, and this conception has the potential to support the formulation of some general models

  6. Aberrant bispecific antibody pharmacokinetics linked to liver sinusoidal endothelium clearance mechanism in cynomolgus monkeys.

    PubMed

    Datta-Mannan, Amita; Croy, Johnny E; Schirtzinger, Linda; Torgerson, Stacy; Breyer, Matthew; Wroblewski, Victor J

    2016-07-01

    Bispecific antibodies (BsAbs) can affect multiple disease pathways, thus these types of constructs potentially provide promising approaches to improve efficacy in complex disease indications. The specific and non-specific clearance mechanisms/biology that affect monoclonal antibody (mAb) pharmacokinetics are likely involved in the disposition of BsAbs. Despite these similarities, there are a paucity of studies on the in vivo biology that influences the biodistribution and pharmacokinetics of BsAbs. The present case study evaluated the in vivo disposition of 2 IgG-fusion BsAb formats deemed IgG-ECD (extracellular domain) and IgG-scFv (single-chain Fv) in cynomolgus monkeys. These BsAb molecules displayed inferior in vivo pharmacokinetic properties, including a rapid clearance (> 0.5 mL/hr/kg) and short half-life relative to their mAb counterparts. The current work evaluated factors in vivo that result in the aberrant clearance of these BsAb constructs. Results showed the rapid clearance of the BsAbs that was not attributable to target binding, reduced neonatal Fc receptor (FcRn) interactions or poor molecular/biochemical properties. Evaluation of the cellular distribution of the constructs suggested that the major clearance mechanism was linked to binding/association with liver sinusoidal endothelial cells (LSECs) versus liver macrophages. The role of LSECs in facilitating the clearance of the IgG-ECD and IgG-scFv BsAb constructs described in these studies was consistent with the minimal influence of clodronate-mediated macrophage depletion on the pharmacokinetics of the constructs in cynomolgus monkeys The findings in this report are an important demonstration that the elucidation of clearance mechanisms for some IgG-ECD and IgG-scFv BsAb molecules can be unique and complicated, and may require increased attention due to the proliferation of these more complex mAb-like structures. PMID:27111637

  7. Computational modeling of mechanical response of dual cross-linked polymer grafted nanoparticle networks

    NASA Astrophysics Data System (ADS)

    v S, Balaji; Yashin, Victor; Salib, Isaac; Kowalewski, Tomasz; Matyjaszewski, Krzystof; Balazs, Anna; Anna Balazs Collaboration; Krzystof Matyjaszewski Collaboration

    2013-03-01

    We develop a hybrid computational model for the behavior of a network of cross-linked polymer-grafted nanoparticles (PGNs). The individual nanoparticles are composed of a rigid core and a corona of grafted polymers that encompass reactive end groups. With the overlap of the coronas on adjacent particles, the reactive end groups can form permanent or labile bonds, which lead to the formation of a ``dual cross-linked'' network. To capture these multi-scale interactions, our approach integrates the essential structural features of the polymer grafted nanoparticles, the interactions between the overlapping coronas, and the kinetics of bond formation and rupture between the reactive groups on the chain ends. We investigate the mechanical response of the dual-cross linked network to an applied tensile deformation. We find that the response depends on the bond energies of the labile bonds, the fraction of permanent bonds in the network, and thickness of the corona. This model provides a powerful tool for the computational design of dual cross-linked PGN's by predicting how the structural features of the system affect the mechanical performance.

  8. Modification mechanism of sesbania gum, and preparation, property, adsorption of dialdehyde cross-linked sesbania gum.

    PubMed

    Tang, Hongbo; Gao, Shiqi; Li, Yanping; Dong, Siqing

    2016-09-20

    This paper studied the modification mechanism of Sesbania gum (SG) by means of the variations in the numbers of surface hydroxyl groups on the granules, Schiff's agent coloration of aldehyde groups, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), energy dispersive spectrum (EDS), etc., and also examined the preparation, property and adsorption of dialdehyde cross-linked sesbania gum (DCLSG). The results showed that the surface hydroxyl numbers of cross-linked sesbania gum (CLSG) decreased with increasing the cross-linking degree. The distribution of the aldehyde groups on the DCLSG particles was nonuniform because most of aldehyde groups mainly located on the edge of particles. The cross-linking occurred only on the surface of SG particles. The oxidization occurred not only on the surface of SG particles, but also in the interior of particles. The cross-linking or oxidization changed the thermal properties, and reduced the swelling power, viscosity, alkali and acid resistance of SG. PMID:27261740

  9. Organically linked iron oxide nanoparticle supercrystals with exceptional isotropic mechanical properties

    NASA Astrophysics Data System (ADS)

    Dreyer, Axel; Feld, Artur; Kornowski, Andreas; Yilmaz, Ezgi D.; Noei, Heshmat; Meyer, Andreas; Krekeler, Tobias; Jiao, Chengge; Stierle, Andreas; Abetz, Volker; Weller, Horst; Schneider, Gerold A.

    2016-05-01

    It is commonly accepted that the combination of the anisotropic shape and nanoscale dimensions of the mineral constituents of natural biological composites underlies their superior mechanical properties when compared to those of their rather weak mineral and organic constituents. Here, we show that the self-assembly of nearly spherical iron oxide nanoparticles in supercrystals linked together by a thermally induced crosslinking reaction of oleic acid molecules leads to a nanocomposite with exceptional bending modulus of 114 GPa, hardness of up to 4 GPa and strength of up to 630 MPa. By using a nanomechanical model, we determined that these exceptional mechanical properties are dominated by the covalent backbone of the linked organic molecules. Because oleic acid has been broadly used as nanoparticle ligand, our crosslinking approach should be applicable to a large variety of nanoparticle systems.

  10. Enhanced Mechanical Properties of Nanoparticle Networks Cross-Linked by Biomimetic Catch Bonds

    NASA Astrophysics Data System (ADS)

    Mbanga, Badel L.; Iyer, Balaji V. S.; Yashin, Victor V.; Balazs, Anna C.

    2015-03-01

    The tunable behavior of cross-linked networks of Polymer-Grafted Nanoparticles (PGNs) makes them excellent candidates for designing novel materials with enhanced mechanical properties. The building block of a PGN network is a nanoparticle with grafted polymer chains whose free ends' reactive groups can form bonds with the end chains on the nearby particles. We use computer modeling to study the tensile behavior of 3D samples, in which some fraction of cross-links is formed through the biomimetic ``catch'' bonds. In contrast to conventional ``slip'' bonds, the catch bonds might become stronger under an applied force due to transitions between two conformational states. The mechanical properties of the PGN networks are shown to exhibit a drastic improvement upon introduction of the catch bonds into the network. We discuss how ductility, toughness, and rate of strain recovery of the network depend on the catch bond content.

  11. Rheology and nonlinear mechanics of transiently cross linked semiflexible networks: Bundling, ripping, healing, and mechnomemory

    NASA Astrophysics Data System (ADS)

    Levine, Alex

    Transiently cross linked networks of semiflexible filaments make up the principal structural component of the cell -- the cytoskeleton. This intracellular network, along with molecular motors, forms the basis for cellular control of morphology and force generation. In this talk, I report on investigations of the effect of transiently bound cross linkers on the structure and mechanics of semiflexible networks. Specifically, I address the role of Casimir or fluctuation-induced interactions between cross linkers in the formation of filament bundles. I report on the linear viscoelasticity of transiently cross-linked networks of bundles. Finally, I discuss the nonlinear mechanical response of such networks, where applied stress induces a persistent structural rearrangement of the network that can dramatically alter its nonlinear response to stresses subsequently applied.

  12. Rapid chain generation of interpostsynaptic functional LINKs can trigger seizure generation: Evidence for potential interconnections from pathology to behavior.

    PubMed

    Vadakkan, Kunjumon I

    2016-06-01

    The experimental finding that a paroxysmal depolarizing shift (PDS), an electrophysiological correlate of seizure activity, is a giant excitatory postsynaptic potential (EPSP) necessitates a mechanism for spatially summating several EPSPs at the level of the postsynaptic terminals (dendritic spines). In this context, we will examine reversible interpostsynaptic functional LINKs (IPLs), a proposed mechanism for inducing first-person virtual internal sensations of higher brain functions concurrent with triggering behavioral motor activity for possible pathological changes that may contribute to seizures. Pathological conditions can trigger a rapid chain generation and propagation of different forms of IPLs leading to seizure generation. A large number of observations made at different levels during both ictal and interictal periods are explained by this mechanism, including the tonic and clonic motor activity, different types of hallucinations, loss of consciousness, gradual worsening of cognitive abilities, a relationship with kindling (which uses an augmented stimulation protocol than that used for inducing long-term potentiation (LTP), which is an electrophysiological correlate of behavioral makers of internal sensation of memory), effect of a ketogenic diet on seizure prevention, dendritic spine loss in seizure disorders, neurodegenerative changes, and associated behavioral changes. The interconnectable nature of these findings is explained as loss of function states of a proposed normal functioning of the nervous system. PMID:27085478

  13. Monogenic mouse models of autism spectrum disorders: Common mechanisms and missing links.

    PubMed

    Hulbert, S W; Jiang, Y-H

    2016-05-01

    Autism spectrum disorders (ASDs) present unique challenges in the fields of genetics and neurobiology because of the clinical and molecular heterogeneity underlying these disorders. Genetic mutations found in ASD patients provide opportunities to dissect the molecular and circuit mechanisms underlying autistic behaviors using animal models. Ongoing studies of genetically modified models have offered critical insight into possible common mechanisms arising from different mutations, but links between molecular abnormalities and behavioral phenotypes remain elusive. The challenges encountered in modeling autism in mice demand a new analytic paradigm that integrates behavioral assessment with circuit-level analysis in genetically modified models with strong construct validity. PMID:26733386

  14. An Investigation of Siloxane Cross-linked Hydroxyapatite-Gelatin/Copolymer Composites for Potential Orthopedic Applications().

    PubMed

    Dyke, Jason Christopher; Knight, Kelly Jane; Zhou, Huaxing; Chiu, Chi-Kai; Ko, Ching-Chang; You, Wei

    2012-01-01

    Causes of bone deficiency are numerous, but biomimetic alloplastic grafts provide an alternative to repair tissue naturally. Previously, a hydroxyapatite-gelatin modified siloxane (HAp-Gemosil) composite was prepared by cross-linking (N, N'-bis[(3-trimethoxysilyl)propyl]ethylene diamine (enTMOS) around the HAp-Gel nanocomposite particles, to mimic the natural composition and properties of bone. However, the tensile strength remained too low for many orthopedic applications. It was hypothesized that incorporating a polymer chain into the composite could help improve long range interaction. Furthermore, designing this polymer to interact with the enTMOS siloxane cross-linked matrix would provide improved adhesion between the polymer and the ceramic composite, and improve mechanical properties. To this end, copolymers of L-Lactide (LLA), and a novel alkyne derivatized trimethylene carbonate, propargyl carbonate (PC), were synthesized. Incorporation of PC during copolymerization affects properties of copolymers such as molecular weight, T(g), and % PC incorporation. More importantly, PC monomers bear a synthetic handle, allowing copolymers to undergo post-polymerization functionalization with graft monomers to specifically tailor the properties of the final composite. For our investigation, P(LLA-co-PC) copolymers were functionalized by an azido-silane (AS) via copper catalyzed azide-alkyne cycloaddition (CuAAC) through terminal alkyne on PC monomers. The new functionalized polymer, P(LLA-co-PC)(AS) was blended with HAp-Gemosil, with the azido-silane linking the copolymer to the silsesquioxane matrix within the final composite.These HAp-Gemosil/P(LLA-co-PC)(AS) composites were subjected to mechanical and biological testing, and the results were compared with those from the HAp-Gemosil composites. This study revealed that incorporating a cross-linkable polymer served to increase the flexural strength of the composite by 50%, while maintaining the biocompatibility of HAp

  15. An Investigation of Siloxane Cross-linked Hydroxyapatite-Gelatin/Copolymer Composites for Potential Orthopedic Applications†

    PubMed Central

    Dyke, Jason Christopher; Knight, Kelly Jane; Zhou, Huaxing; Chiu, Chi-Kai; Ko, Ching-Chang; You, Wei

    2012-01-01

    Causes of bone deficiency are numerous, but biomimetic alloplastic grafts provide an alternative to repair tissue naturally. Previously, a hydroxyapatite-gelatin modified siloxane (HAp-Gemosil) composite was prepared by cross-linking (N, N′-bis[(3-trimethoxysilyl)propyl]ethylene diamine (enTMOS) around the HAp-Gel nanocomposite particles, to mimic the natural composition and properties of bone. However, the tensile strength remained too low for many orthopedic applications. It was hypothesized that incorporating a polymer chain into the composite could help improve long range interaction. Furthermore, designing this polymer to interact with the enTMOS siloxane cross-linked matrix would provide improved adhesion between the polymer and the ceramic composite, and improve mechanical properties. To this end, copolymers of L-Lactide (LLA), and a novel alkyne derivatized trimethylene carbonate, propargyl carbonate (PC), were synthesized. Incorporation of PC during copolymerization affects properties of copolymers such as molecular weight, Tg, and % PC incorporation. More importantly, PC monomers bear a synthetic handle, allowing copolymers to undergo post-polymerization functionalization with graft monomers to specifically tailor the properties of the final composite. For our investigation, P(LLA-co-PC) copolymers were functionalized by an azido-silane (AS) via copper catalyzed azide-alkyne cycloaddition (CuAAC) through terminal alkyne on PC monomers. The new functionalized polymer, P(LLA-co-PC)(AS) was blended with HAp-Gemosil, with the azido-silane linking the copolymer to the silsesquioxane matrix within the final composite. These HAp-Gemosil/P(LLA-co-PC)(AS) composites were subjected to mechanical and biological testing, and the results were compared with those from the HAp-Gemosil composites. This study revealed that incorporating a cross-linkable polymer served to increase the flexural strength of the composite by 50%, while maintaining the biocompatibility of

  16. Links between the mechanical, seismic and thermal thickness, rheological structure and mechanical stability of the continental lithosphere.

    NASA Astrophysics Data System (ADS)

    Burov, E.; Watts, A. B.; Francois, T.; Tesauro, M.

    2012-04-01

    To fulfill its plate-tectonics functions, the lithosphere has to remain mechanically strong over geological time spans and be capable to support important geological loads while transferring horizontal tectonic stresses at global scales. We use thermo-mechanically and thermo-dynamically coupled numerical models accounting for brittle-elastic-plastic rheology and petrologically and seismologically consistent pressure-temperature dependent density and elastic structure to obtain more robust insights on thickness of the mechanical lithosphere (Hm) and its links to the LAB depth and its seismic (Hs) and thermal thickness (Ht). Testing the mechanical stability of lithospheres with different thermo-rheological structures allows us to constrain rheological parameters needed for long-term survival of lithospheric plates and establish links between LAB,Hm,Hs and Ht. Mechanical lithosphere appears to be 1.5-2 times thinner than Hs and Ht and its mechanical thickness, Hm, is strongly dependent on thermal and rheological structure. The important contribution of inelastic components (brittle and ductile behavior) to the mechanical strength of the lithosphere suggests that Hm is also stress and strain dependent: within the same plate, it might drop by 30-50% in the areas of high strain or stress, and remain much higher in the areas where tectonic deformation is moderate. In some cases it is possible to establish direct links between the laterally variable mechanical, seismic and thermal lithosphere thickness. This is of special importance since tracking the mechanical thickness of the lithosphere allows us to put better constraints on its stress/strain dependent rheological properties. We explored relationships between Hs,Ht and Hm of the lithosphere in oceans and in more complex continental lithospheres. In oceanic plates, Hm corresponds to the observed equivalent elastic thickness (EET) multiplied by a factor of 1.2-1.5, and correlates well with Ht and Hs. In continents, the

  17. The induction of reentry in cardiac tissue. The missing link: How electric fields alter transmembrane potential

    NASA Astrophysics Data System (ADS)

    Roth, Bradley J.; Krassowska, Wanda

    1998-03-01

    This review examines the initiation of reentry in cardiac muscle by strong electric shocks. Specifically, it concentrates on the mechanisms by which electric shocks change the transmembrane potential of the cardiac membrane and create the physiological substrate required by the critical point theory for the initiation of rotors. The mechanisms examined include (1) direct polarization of the tissue by the stimulating current, as described by the one-dimensional cable model and its two- and three-dimensional extensions, (2) the presence of virtual anodes and cathodes, as described by the bidomain model with unequal anisotropy ratios of the intra- and extracellular spaces, (3) polarization of the tissue due to changing orientation of cardiac fibers, and (4) polarization of individual cells or groups of cells by the electric field ("sawtooth potential"). The importance of these mechanisms in the initiation of reentry is examined in two case studies: the induction of rotors using successive stimulation with a unipolar electrode, and the induction of rotors using cross-field stimulation. These cases reveal that the mechanism by which a unipolar stimulation induces arrhythmias can be explained in the framework of the bidomain model with unequal anisotropy ratios. In contrast, none of the examined mechanisms provide an adequate explanation for the induction of rotors by cross-field stimulation. Hence, this study emphasizes the need for further experimental and theoretical work directed toward explaining the mechanism of field stimulation.

  18. Modulation of mechanical resonance by chemical potential oscillation in graphene

    NASA Astrophysics Data System (ADS)

    Chen, Changyao; Deshpande, Vikram V.; Koshino, Mikito; Lee, Sunwoo; Gondarenko, Alexander; MacDonald, Allan H.; Kim, Philip; Hone, James

    2016-03-01

    The classical picture of the force on a capacitor assumes a large density of electronic states, such that the electrochemical potential of charges added to the capacitor is given by the external electrostatic potential and the capacitance is determined purely by geometry. Here we consider capacitively driven motion of a nano-mechanical resonator with a low density of states, in which these assumptions can break down. We find three leading-order corrections to the classical picture: the first of which is a modulation in the static force due to variation in the internal chemical potential; the second and third are changes in the static force and dynamic spring constant due to the rate of change of chemical potential, expressed as the quantum (density of states) capacitance. As a demonstration, we study capacitively driven graphene mechanical resonators, where the chemical potential is modulated independently of the gate voltage using an applied magnetic field to manipulate the energy of electrons residing in discrete Landau levels. In these devices, we observe large periodic frequency shifts consistent with the three corrections to the classical picture. In devices with extremely low strain and disorder, the first correction term dominates and the resonant frequency closely follows the chemical potential. The theoretical model fits the data with only one adjustable parameter representing disorder-broadening of the Landau levels. The underlying electromechanical coupling mechanism is not limited by the particular choice of material, geometry, or mechanism for variation in the chemical potential, and can thus be extended to other low-dimensional systems.

  19. New Potentials for Old: The Darboux Transformation in Quantum Mechanics

    ERIC Educational Resources Information Center

    Williams, Brian Wesley; Celius, Tevye C.

    2008-01-01

    The Darboux transformation in quantum mechanics is reviewed at a basic level. Examples of how this transformation leads to exactly solvable potentials related to the "particle in a box" and the harmonic oscillator are shown in detail. The connection between the Darboux transformation and some modern operator based approaches to quantum mechanics…

  20. The Potential Neural Mechanisms of Acute Indirect Vibration

    PubMed Central

    2011-01-01

    There is strong evidence to suggest that acute indirect vibration acts on muscle to enhance force, power, flexibility, balance and proprioception suggesting neural enhancement. Nevertheless, the neural mechanism(s) of vibration and its potentiating effect have received little attention. One proposal suggests that spinal reflexes enhance muscle contraction through a reflex activity known as tonic vibration stretch reflex (TVR), which increases muscle activation. However, TVR is based on direct, brief, and high frequency vibration (>100 Hz) which differs to indirect vibration, which is applied to the whole body or body parts at lower vibration frequency (5-45 Hz). Likewise, muscle tuning and neuromuscular aspects are other candidate mechanisms used to explain the vibration phenomenon. But there is much debate in terms of identifying which neural mechanism(s) are responsible for acute vibration; due to a number of studies using various vibration testing protocols. These protocols include: different methods of application, vibration variables, training duration, exercise types and a range of population groups. Therefore, the neural mechanism of acute vibration remain equivocal, but spinal reflexes, muscle tuning and neuromuscular aspects are all viable factors that may contribute in different ways to increasing muscular performance. Additional research is encouraged to determine which neural mechanism(s) and their contributions are responsible for acute vibration. Testing variables and vibration applications need to be standardised before reaching a consensus on which neural mechanism(s) occur during and post-vibration. Key points There is strong evidence to suggest that acute indirect vibration acts on muscle to enhance force, power, flexibility, balance and proprioception, but little attention has been given to the neural mechanism(s) of acute indirect vibration. Current findings suggest that acute vibration exposure may cause a neural response, but there is little

  1. Beyond Failure: Potentially Mitigating Failed Author Searches in the Online Library Catalog through the Use of Linked Data

    ERIC Educational Resources Information Center

    Moulaison, Heather Lea; Stanley, Susan Nicole

    2013-01-01

    Linked data stores house vetted content that can supplement the information available through online library catalogs, potentially mitigating failed author searches if information about the author exists in linked data formats. In this case study, a total of 689 failed author index queries from a large Midwestern academic library's online library…

  2. Complex mechanisms linking neurocognitive dysfunction to insulin resistance and other metabolic dysfunction

    PubMed Central

    Stoeckel, Luke E.; Arvanitakis, Zoe; Gandy, Sam; Small, Dana; Kahn, C. Ronald; Pascual-Leone, Alvaro; Pawlyk, Aaron; Sherwin, Robert; Smith, Philip

    2016-01-01

    Scientific evidence has established several links between metabolic and neurocognitive dysfunction, and epidemiologic evidence has revealed an increased risk of Alzheimer’s disease and vascular dementia in patients with diabetes. In July 2015, the National Institute of Diabetes, Digestive, and Kidney Diseases gathered experts from multiple clinical and scientific disciplines, in a workshop entitled “The Intersection of Metabolic and Neurocognitive Dysfunction”, to clarify the state-of-the-science on the mechanisms linking metabolic dysfunction, and insulin resistance and diabetes in particular, to neurocognitive impairment and dementia. This perspective is intended to serve as a summary of the opinions expressed at this meeting, which focused on identifying gaps and opportunities to advance research in this emerging area with important public health relevance. PMID:27303627

  3. Dynamic modelling and link mechanism design of four-legged mobile robot

    NASA Astrophysics Data System (ADS)

    Park, Sung-Ho

    In order to apply the advanced biological phenomena to the leg design of mobile robots, the structural and locomotive characteristics of several selected animals and insects are studied, and the four-legged mobile robot which can cover all existing leg arrangements and locomotion patterns is modeled by a rigid multibody system consisting of links and joints. The model is simulated to prove that the given structure or locomotive conditions satisfy the requirement of minimum energy expenditure. According to the first simulation, there exist ideal forward and backward stroke distances for each pair leg. Therefore, the walking volume and link lengths of existing legged mobile robots should be modified. Also, for other structural and locomotive characteristics which have been used by living creatures, the model is simulated to determine whether or not the actual or possible biological phenomena can be applied to the leg mechanism design of mobile robot.

  4. A Systems Biology Approach Reveals Converging Molecular Mechanisms that Link Different POPs to Common Metabolic Diseases

    PubMed Central

    Ruiz, Patricia; Perlina, Ally; Mumtaz, Moiz; Fowler, Bruce A.

    2015-01-01

    Background: A number of epidemiological studies have identified statistical associations between persistent organic pollutants (POPs) and metabolic diseases, but testable hypotheses regarding underlying molecular mechanisms to explain these linkages have not been published. Objectives: We assessed the underlying mechanisms of POPs that have been associated with metabolic diseases; three well-known POPs [2,3,7,8-tetrachlorodibenzodioxin (TCDD), 2,2´,4,4´,5,5´-hexachlorobiphenyl (PCB 153), and 4,4´-dichlorodiphenyldichloroethylene (p,p´-DDE)] were studied. We used advanced database search tools to delineate testable hypotheses and to guide laboratory-based research studies into underlying mechanisms by which this POP mixture could produce or exacerbate metabolic diseases. Methods: For our searches, we used proprietary systems biology software (MetaCore™/MetaDrug™) to conduct advanced search queries for the underlying interactions database, followed by directional network construction to identify common mechanisms for these POPs within two or fewer interaction steps downstream of their primary targets. These common downstream pathways belong to various cytokine and chemokine families with experimentally well-documented causal associations with type 2 diabetes. Conclusions: Our systems biology approach allowed identification of converging pathways leading to activation of common downstream targets. To our knowledge, this is the first study to propose an integrated global set of step-by-step molecular mechanisms for a combination of three common POPs using a systems biology approach, which may link POP exposure to diseases. Experimental evaluation of the proposed pathways may lead to development of predictive biomarkers of the effects of POPs, which could translate into disease prevention and effective clinical treatment strategies. Citation: Ruiz P, Perlina A, Mumtaz M, Fowler BA. 2016. A systems biology approach reveals converging molecular mechanisms that

  5. Aliphatic β-Nitroalcohols for Therapeutic Corneoscleral Cross-linking: Chemical Mechanisms and Higher Order Nitroalcohols

    PubMed Central

    Solomon, Marissa R.; Wen, Quan; Turro, Nicholas J.; Trokel, Stephen L.

    2010-01-01

    Purpose. The recent tissue cross-linking studies indicate that aliphatic β-nitroalcohols (BNAs) may be useful as pharmacologic corneoscleral cross-linking agents. The present study was performed to identify the specific chemistry involved under physiologic conditions, with the intent of identifying more effective agents. Methods. The mechanism of chemical cross-linking at pH 7.4 and 37°C was studied using three techniques. The colorimetric Griess assay was used to follow the release of nitrite from three mono-nitroalcohols (2-nitroethanol [2ne], 2-nitro-1-propanol [2nprop]), and 3-nitro-2-pentanol [3n2pent]). Second, the evolution of 2nprop in 0.2 M NaH2PO4/Na2HPO4/D2O was studied using 1H-NMR. Third, thermal shrinkage temperature analysis (Ts), a measure of tissue cross-linking, was used to support information from 1the H-NMR studies. Results. A time-dependent release of nitrite was observed for all three mono-nitroalcohols studied. The maximum levels were comparable using either 2ne or 2nprop (∼30%). However, much less (∼10%) was observed from 3n2pent. Using 1H-NMR, 2nprop evolved into a unique splitting pattern. No match was observed with reference spectra from three possible products of denitration. In contrast, 2-methyl-2-nitro-1,3-propanediol (MNPD), a nitro-diol, was identified, implying the formation of formaldehyde from a retro-nitroaldol (i.e., reverse Henry) reaction. In support of this mechanism, Ts shifts induced by the nitro-triol 2-hydroxymethyl-2-nitro-1,3-propanediol (HNPD) were superior to the nitro-diol MNPD which were superior to the mono nitroalcohol 2nprop. Conclusions. BNAs function as both formaldehyde and nitrite donors under physiologic conditions to cross-link collagenous tissue. Higher order BNAs are more effective than mono nitroalcohols, raising the possibility of using these agents for therapeutic corneoscleral cross-linking. PMID:19797229

  6. Post-extrasystolic Potentiation: Link between Ca2+ Homeostasis and Heart Failure?

    PubMed Central

    Sprenkeler, David J; Vos, Marc A

    2016-01-01

    Post-extrasystolic potentiation (PESP) describes the phenomenon of increased contractility of the beat following an extrasystole and has been attributed to changes in Ca2+ homeostasis. While this effect has long been regarded to be a normal physiological phenomenon, a number of reports describe an enhanced potentiation of the post-extrasystolic beat in heart failure patients. The exact mechanism of this increased PESP is unknown, but disruption of normal Ca2+ handling in heart failure may be the underlying cause. The use of PESP as a prognostic marker or therapeutic intervention have recently regained new attention, however, the value of the application of PESP in the clinic is still under debate. In this review, the mechanism of PESP with regard to Ca2+ in the normal and failing heart will be discussed and the possible diagnostic and therapeutic role of this phenomenon will be explored. PMID:27403289

  7. Expression of myotubularins in blood platelets: Characterization and potential diagnostic of X-linked myotubular myopathy.

    PubMed

    Mansour, Rana; Severin, Sonia; Xuereb, Jean-Marie; Gratacap, Marie-Pierre; Laporte, Jocelyn; Buj-Bello, Ana; Tronchère, Hélène; Payrastre, Bernard

    2016-07-29

    Phosphoinositides play a key role in the spatiotemporal control of central intracellular processes and several specific kinases and phosphatases regulating the level of these lipids are implicated in human diseases. Myotubularins are a family of 3-phosphatases acting specifically on phosphatidylinositol 3-monophosphate and phosphatidylinositol 3,5 bisphosphate. Members of this family are mutated in genetic diseases including myotubularin 1 (MTM1) and myotubularin-related protein 2 (MTMR2) which mutations are responsible of X-linked centronuclear myopathy and Charcot-Marie-Tooth neuropathy, respectively. Here we show that MTM1 is expressed in blood platelets and that hundred microliters of blood is sufficient to detect the protein by western blotting. Since the most severe cases of pathogenic mutations of MTM1 lead to loss of expression of the protein, we propose that a minimal amount of blood can allow a rapid diagnostic test of X-linked myotubular myopathy, which is currently based on histopathology of muscle biopsy and molecular genetic testing. In platelets, MTM1 is a highly active 3-phosphatase mainly associated to membranes and found on the dense granules and to a lesser extent on alpha-granules. However, deletion of MTM1 in mouse had no significant effect on platelet count and on platelet secretion and aggregation induced by thrombin or collagen stimulation. Potential compensation by other members of the myotubularin family is conceivable since MTMR2 was easily detectable by western blotting and the mRNA of several members of the family increased during in vitro differentiation of human megakaryocytes and MEG-01 cells. In conclusion, we show the presence of several myotubularins in platelets and propose that minimal amounts of blood can be used to develop a rapid diagnostic test for genetic pathologies linked to loss of expression of these phosphatases. PMID:27155155

  8. Variation potential in higher plants: Mechanisms of generation and propagation

    PubMed Central

    Vodeneev, Vladimir; Akinchits, Elena; Sukhov, Vladimir

    2015-01-01

    Long-distance intercellular electrical signals, including variation potential (VP) in higher plants, are a potential mechanism of coordinate functional responses in different plant cells under action of stressors. VP, which is caused by damaging factors (e.g., heating, crushing), is transient depolarization with an irregular shape. It can include a long-term depolarization and fast impulse depolarization (‘AP-like’ spikes). Mechanisms of VP generation and propagation are still under investigation. It is probable that VP is a local electrical response induced by propagation of hydraulic wave and (or) chemical agent. Both hypotheses are based on numerous experimental results but they predict VP velocities which are not in a good accordance with speed of variation potential propagation. Thus combination of hydraulic and chemical signals is the probable mechanism of VP propagation. VP generation is traditionally connected with transient H+-ATPase inactivation, but AP-like spikes are also connected with passive ions fluxes. Ca2+ influx is a probable mechanism which triggers H+-ATPase inactivation and ions channels activation at VP. PMID:26313506

  9. Self-affirmation breaks the link between the behavioral inhibition system and the threat-potentiated startle response.

    PubMed

    Crowell, Adrienne; Page-Gould, Elizabeth; Schmeichel, Brandon J

    2015-04-01

    Reflecting on core personal values is a common means of self-affirmation that can change how a person responds to threatening events. Specifically, self-affirmation has been found to reduce psychological defenses against self-esteem threats. The current research examined the effects of self-affirmation on more basic reflexive mechanisms of motivation and emotion. The startle-eyeblink response is a defensive reflex that can be elicited by loud bursts of noise and is potentiated in the presence of threatening stimuli. Individual differences in anxiety-related traits, including behavioral inhibition-system (BIS) sensitivity, predict the magnitude of threat-potentiated startle responses, such that higher BIS sensitivity corresponds with more intense responses to threatening stimuli. The current experiment (N = 100) tested the hypothesis that affirming a core personal value breaks the link between BIS sensitivity and threat responsiveness. We measured individual differences in BIS, manipulated the opportunity for self-affirmation, and assessed eyeblink responses to startle probes during negative, neutral, and positive emotional picture viewing. In the no-affirmation condition, BIS sensitivity predicted the magnitude of startle-eyeblink responses during negative pictures, consistent with previous research. In the self-affirmation condition, the relationship between BIS sensitivity and threat-potentiated startle responding was eliminated. This finding suggests that self-affirmation's effects extend beyond self-esteem defenses to influence basic defensive reflexes in threat-prone individuals. (PsycINFO Database Record PMID:25603136

  10. Nonlinear optical collagen cross-linking and mechanical stiffening: a possible photodynamic therapeutic approach to treating corneal ectasia

    NASA Astrophysics Data System (ADS)

    Chai, Dongyul; Juhasz, Tibor; Brown, Donald J.; Jester, James V.

    2013-03-01

    In this study we test the hypothesis that nonlinear optical (NLO) multiphoton photoactivation of riboflavin using a focused femtosecond (FS) laser light can be used to induce cross-linking (CXL) and mechanically stiffen collagen as a potential clinical therapy for the treatment of keratoconus and corneal ectasia. Riboflavin-soaked, compressed collagen hydrogels are cross-linked using a FS laser tuned to 760 nm and set to either 100 mW (NLO CXL I) or 150 mW (NLO CXL II) of laser power. FS pulses are focused into the hydrogel using a 0.75 NA objective lens, and the hydrogel is three-dimensionally scanned. Measurement of hydrogel stiffness by indentation testing show that the calculated elastic modulus (E) values are significantly increased over twofold following NLO CXL I and II compared with baseline values (P<0.05). Additionally, no significant differences are detected between NLO CXL and single photon, UVA CXL (P>0.05). This data suggests that NLO CXL has a comparable effect to conventional UVA CXL in mechanically stiffening collagen and may provide a safe and effective approach to localize CXL at different regions and depths within the cornea.

  11. Risk factors for pancreatic cancer: underlying mechanisms and potential targets

    PubMed Central

    Kolodecik, Thomas; Shugrue, Christine; Ashat, Munish; Thrower, Edwin C.

    2014-01-01

    Purpose of the review: Pancreatic cancer is extremely aggressive, forming highly chemo-resistant tumors, and has one of the worst prognoses. The evolution of this cancer is multi-factorial. Repeated acute pancreatic injury and inflammation are important contributing factors in the development of pancreatic cancer. This article attempts to understand the common pathways linking pancreatitis to pancreatic cancer. Recent findings: Intracellular activation of both pancreatic enzymes and the transcription factor NF-κB are important mechanisms that induce acute pancreatitis (AP). Recurrent pancreatic injury due to genetic susceptibility, environmental factors such as smoking, alcohol intake, and conditions such as obesity lead to increases in oxidative stress, impaired autophagy and constitutive activation of inflammatory pathways. These processes can stimulate pancreatic stellate cells, thereby increasing fibrosis and encouraging chronic disease development. Activation of oncogenic Kras mutations through inflammation, coupled with altered levels of tumor suppressor proteins (p53 and p16) can ultimately lead to development of pancreatic cancer. Summary: Although our understanding of pancreatitis and pancreatic cancer has tremendously increased over many years, much remains to be elucidated in terms of common pathways linking these conditions. PMID:24474939

  12. Simple relations for different stomatal control mechanisms link partially drying soil and transpiration

    NASA Astrophysics Data System (ADS)

    Huber, Katrin; Vanderborght, Jan; Javaux, Mathieu; Vereecken, Harry

    2015-04-01

    Stomata can close to regulate plant water loss under unfavourable water availability. This closure can be triggered by hydraulic ('H') and/or chemical signals ('C', 'H+C'). By combining plant hydraulic relations with a model for stomatal conductance, including chemical signalling, our aim was to derive a simple relation that links soil water availability, expressed as the fraction of roots in dry soil, to transpiration. We used the detailed mechanistic soil-root water flow model R-SWMS to verify this relation. Virtual split root experiments were simulated, comparing horizontally and vertically split domains with varying fractions of roots in dry soil and comparing different strengths of stomatal regulation by chemical and hydraulic signals. Transpiration predicted by the relation was in good agreement with numerical simulations. Under certain conditions H+C control leads to isohydric plant behaviour, which means that stomata close to keep leaf water potential constant after reaching a certain level. C control on the other hand exerts anisohydric behaviour, meaning that stomata remain fully open during changes in leaf water potential. For C control the relation between transpiration reduction and fraction of roots in dry soil becomes independent of transpiration rate whereas H+C control results in stronger reduction for higher transpiration rates. Simple relations that link effective soil and leaf water potential can describe different stomatal control resulting in contrasting behaviour.

  13. Explicating the Social Mechanisms Linking Alcohol Use Behaviors and Ecology to Child Maltreatment

    PubMed Central

    Freisthler, Bridget; Holmes, Megan R.

    2013-01-01

    This paper begins to describe and explicate the specific mechanisms by which alcohol use and the alcohol use environment contribute to specific types of child maltreatment. These mechanisms relating alcohol outlet densities to child maltreatment described here include effects on social disorganization, parent’s drinking behaviors, and parental supervision. By investigating potential mechanisms, new information could be obtained on the importance and role of alcohol and their availability in the etiology of child maltreatment. This knowledge can be used to further tailor interventions to those conditions most likely to prevent and reduce maltreatment. PMID:25284922

  14. Explicating the Social Mechanisms Linking Alcohol Use Behaviors and Ecology to Child Maltreatment.

    PubMed

    Freisthler, Bridget; Holmes, Megan R

    2012-12-01

    This paper begins to describe and explicate the specific mechanisms by which alcohol use and the alcohol use environment contribute to specific types of child maltreatment. These mechanisms relating alcohol outlet densities to child maltreatment described here include effects on social disorganization, parent's drinking behaviors, and parental supervision. By investigating potential mechanisms, new information could be obtained on the importance and role of alcohol and their availability in the etiology of child maltreatment. This knowledge can be used to further tailor interventions to those conditions most likely to prevent and reduce maltreatment. PMID:25284922

  15. Structural Analysis and Mechanical Characterization of Hyaluronic Acid-Based Doubly Cross-Linked Networks

    PubMed Central

    Jha, Amit K.; Hule, Rohan A.; Jiao, Tong; Teller, Sean S.; Clifton, Rodney J.; Duncan, Randall L.; Pochan, Darrin J.; Jia, Xinqiao

    2009-01-01

    We have created a new class of hyaluronic acid (HA)-based hydrogel materials with HA hydrogel particles (HGPs) embedded in and covalently cross-linked to a secondary network. HA HGPs with an average diameter of ∼900 nm and narrow particle size distribution were synthesized using a refined reverse micelle polymerization technique. The average mesh size of the HGPs was estimated to be approximately 5.5 to 7.0 nm by a protein uptake experiment. Sodium periodate oxidation not only introduced aldehyde groups to the particles but also reduced the average particle size. The aldehyde groups generated were used as reactive handles for subsequent cross-linking with an HA derivative containing hydrazide groups. The resulting macroscopic gels contain two distinct hierarchical networks (doubly cross-linked networks, DXNs): one within individual particles and another among different particles. Bulk gels (BGs) formed by direct mixing of HA derivatives with mutually reactive groups were included for comparison. The hydrogel microstructures were collectively characterized by microscopy and neutron scattering techniques. Their viscoelasticity was quantified at low frequencies (0.1−10 Hz) using a controlled stress rheometer and at high frequencies (up to 200 Hz) with a home-built torsional wave apparatus. Both BGs and DXNs are stable elastic gels that become stiffer at higher frequencies. The HA-based DXN offers unique structural hierarchy and mechanical properties that are suitable for soft tissue regeneration. PMID:20046226

  16. Neural mechanisms linking social status and inflammatory responses to social stress.

    PubMed

    Muscatell, Keely A; Dedovic, Katarina; Slavich, George M; Jarcho, Michael R; Breen, Elizabeth C; Bower, Julienne E; Irwin, Michael R; Eisenberger, Naomi I

    2016-06-01

    Social stratification has important implications for health and well-being, with individuals lower in standing in a hierarchy experiencing worse outcomes than those higher up the social ladder. Separate lines of past research suggest that alterations in inflammatory processes and neural responses to threat may link lower social status with poorer outcomes. This study was designed to bridge these literatures to investigate the neurocognitive mechanisms linking subjective social status and inflammation. Thirty-one participants reported their subjective social status, and underwent a functional magnetic resonance imaging scan while they were socially evaluated. Participants also provided blood samples before and after the stressor, which were analysed for changes in inflammation. Results showed that lower subjective social status was associated with greater increases in inflammation. Neuroimaging data revealed lower subjective social status was associated with greater neural activity in the dorsomedial prefrontal cortex (DMPFC) in response to negative feedback. Finally, results indicated that activation in the DMPFC in response to negative feedback mediated the relation between social status and increases in inflammatory activity. This study provides the first evidence of a neurocognitive pathway linking subjective social status and inflammation, thus furthering our understanding of how social hierarchies shape neural and physiological responses to social interactions. PMID:26979965

  17. Structural Analysis and Mechanical Characterization of Hyaluronic Acid-Based Doubly Cross-Linked Networks.

    PubMed

    Jha, Amit K; Hule, Rohan A; Jiao, Tong; Teller, Sean S; Clifton, Rodney J; Duncan, Randall L; Pochan, Darrin J; Jia, Xinqiao

    2009-01-01

    We have created a new class of hyaluronic acid (HA)-based hydrogel materials with HA hydrogel particles (HGPs) embedded in and covalently cross-linked to a secondary network. HA HGPs with an average diameter of ∼900 nm and narrow particle size distribution were synthesized using a refined reverse micelle polymerization technique. The average mesh size of the HGPs was estimated to be approximately 5.5 to 7.0 nm by a protein uptake experiment. Sodium periodate oxidation not only introduced aldehyde groups to the particles but also reduced the average particle size. The aldehyde groups generated were used as reactive handles for subsequent cross-linking with an HA derivative containing hydrazide groups. The resulting macroscopic gels contain two distinct hierarchical networks (doubly cross-linked networks, DXNs): one within individual particles and another among different particles. Bulk gels (BGs) formed by direct mixing of HA derivatives with mutually reactive groups were included for comparison. The hydrogel microstructures were collectively characterized by microscopy and neutron scattering techniques. Their viscoelasticity was quantified at low frequencies (0.1-10 Hz) using a controlled stress rheometer and at high frequencies (up to 200 Hz) with a home-built torsional wave apparatus. Both BGs and DXNs are stable elastic gels that become stiffer at higher frequencies. The HA-based DXN offers unique structural hierarchy and mechanical properties that are suitable for soft tissue regeneration. PMID:20046226

  18. Mechanics of semiflexible chains formed by poly(ethylene glycol)-linked paramagnetic particles.

    PubMed

    Biswal, Sibani Lisa; Gast, Alice P

    2003-08-01

    Magnetorheological particles, permanently linked into chains, provide a magnetically actuated means to manipulate microscopic fluid flow. Paramagnetic colloidal particles form reversible chains by acquiring dipole moments in the presence of an external magnetic field. By chemically connecting paramagnetic colloidal particles, flexible magnetoresponsive chains can be created. We link the paramagnetic microspheres using streptavidin-biotin binding. Streptavidin coated microspheres are placed in a flow cell and a magnetic field is applied, causing the particles to form chains. Then a solution of polymeric linkers of bis-biotin-poly(ethylene glycol) molecules is added in the presence of the field. These linked chains remain responsive to a magnetic field; however, in the absence of an external magnetic field these chains bend and flex due to thermal motion. The chain flexibility is determined by the length of the spacer molecule between particles and is quantified by the flexural rigidity or bending stiffness. To understand the mechanical properties of the chains, we use a variety of optical trapping experiments to measure the flexural rigidity. Increasing the length of the poly(ethylene glycol) chain in the linker increases the flexibility of the chains. PMID:14524968

  19. Interplay between the mechanics of bacteriophage fibers and the strength of virus-host links

    NASA Astrophysics Data System (ADS)

    Ares, P.; Garcia-Doval, C.; Llauró, A.; Gómez-Herrero, J.; van Raaij, M. J.; de Pablo, P. J.

    2014-05-01

    Viral fibers play a central role in many virus infection mechanisms since they recognize the corresponding host and establish a mechanical link to its surface. Specifically, bacteriophages have to anchor to bacteria through the fibers surrounding the tail before starting the viral DNA translocation into the host. The protein gene product (gp) 37 from bacteriophage T4 long tail fibers forms a fibrous parallel homotrimer located at the distal end of the long tail fibers. Biochemical data indicate that, at least, three of these fibers are required for initial host cell interaction but do not reveal why three and no other numbers are required. By using atomic force microscopy, we obtained high-resolution images of gp37 fibers adsorbed on a mica substrate in buffer conditions and probed their local mechanical properties. Our experiments of radial indentation at the nanometer scale provided a radial stiffness of ˜0.08 N/m and a breaking force of ˜120 pN. In addition, we performed finite element analysis and determined a Young's modulus of ˜20 MPa. From these mechanical parameters, we hypothesize that three viral fibers provide enough mechanical strength to prevent a T4 virus from being detached from the bacteria by the viral particle Brownian motion, delivering a biophysical justification for the previous biochemical data.

  20. Interplay between the mechanics of bacteriophage fibers and the strength of virus-host links.

    PubMed

    Ares, P; Garcia-Doval, C; Llauró, A; Gómez-Herrero, J; van Raaij, M J; de Pablo, P J

    2014-05-01

    Viral fibers play a central role in many virus infection mechanisms since they recognize the corresponding host and establish a mechanical link to its surface. Specifically, bacteriophages have to anchor to bacteria through the fibers surrounding the tail before starting the viral DNA translocation into the host. The protein gene product (gp) 37 from bacteriophage T4 long tail fibers forms a fibrous parallel homotrimer located at the distal end of the long tail fibers. Biochemical data indicate that, at least, three of these fibers are required for initial host cell interaction but do not reveal why three and no other numbers are required. By using atomic force microscopy, we obtained high-resolution images of gp37 fibers adsorbed on a mica substrate in buffer conditions and probed their local mechanical properties. Our experiments of radial indentation at the nanometer scale provided a radial stiffness of ∼ 0.08 N/m and a breaking force of ∼ 120 pN. In addition, we performed finite element analysis and determined a Young's modulus of ∼ 20 MPa. From these mechanical parameters, we hypothesize that three viral fibers provide enough mechanical strength to prevent a T4 virus from being detached from the bacteria by the viral particle Brownian motion, delivering a biophysical justification for the previous biochemical data. PMID:25353832

  1. Impaired Aβ clearance: a potential link between atherosclerosis and Alzheimer’s disease

    PubMed Central

    Gupta, Ajay; Iadecola, Costantino

    2015-01-01

    Alzheimer’s Disease (AD) and atherosclerosis remain two of the largest public health burdens in the world today. Although traditionally considered distinct pathological entities, mounting epidemiologic, clinical and experimental evidence suggests that cerebrovascular atherosclerosis and AD interact reciprocally to disrupt brain structure and function. Whereas the hypoperfusion and hypoxia caused by atherosclerosis of cerebral vessels may enhance the production of amyloid-β peptide (Aβ), a peptide central to AD pathology, Aβ, in turn, may promote formation of atherosclerotic lesions through vascular oxidative stress and endothelial dysfunction leading to additional vascular damage. Here, we briefly review evidence suggesting that impaired clearance of Aβ is an additional, simultaneously occurring mechanism by which AD and cerebrovascular disease may be causally linked. We examine the literature supporting mechanisms by which flow-limiting large-artery stenosis, arterial stiffening and microvascular dysfunction could contribute to AD pathophysiology by impairing Aβ clearance and elevating brain levels of Aβ. Finally, we highlight the need for further research to improve our understanding of the complex interactions of AD and atherosclerosis with Aβ clearance, which may ultimately serve to guide the development of novel diagnostic and therapeutic approaches for this devastating and highly prevalent condition. PMID:26136682

  2. Apoptotic Pathways Linked to Endocrine System as Potential Therapeutic Targets for Benign Prostatic Hyperplasia

    PubMed Central

    Minutoli, Letteria; Rinaldi, Mariagrazia; Marini, Herbert; Irrera, Natasha; Crea, Giovanni; Lorenzini, Cesare; Puzzolo, Domenico; Valenti, Andrea; Pisani, Antonina; Adamo, Elena B.; Altavilla, Domenica; Squadrito, Francesco; Micali, Antonio

    2016-01-01

    Benign prostatic hyperplasia (BPH) is a chronic condition common in older men that can result in bothersome lower urinary tract symptoms. The molecular mechanisms and networks underlying the development and the progression of the disease are still far from being fully understood. BPH results from smooth muscle cell and epithelial cell proliferation, primarily within the transition zone of the prostate. Apoptosis and inflammation play important roles in the control of cell growth and in the maintenance of tissue homeostasis. Disturbances in molecular mechanisms of apoptosis machinery have been linked to BPH. Increased levels of the glycoprotein Dickkopf-related protein 3 in BPH cause an inhibition of the apoptosis machinery through a reduction in B cell lymphoma (Bcl)-2 associated X protein (Bax) expression. Inhibitors of apoptosis proteins influence cell death by direct inhibition of caspases and modulation of the transcription factor nuclear factor-κB. Current pharmacotherapy targets either the static component of BPH, including finasteride and dutasteride, or the dynamic component of BPH, including α-adrenoceptor antagonists such as tamsulosin and alfuzosin. Both these classes of drugs significantly interfere with the apoptosis machinery. Furthermore, phytotherapic supplements and new drugs may also modulate several molecular steps of apoptosis. PMID:27529214

  3. Apoptotic Pathways Linked to Endocrine System as Potential Therapeutic Targets for Benign Prostatic Hyperplasia.

    PubMed

    Minutoli, Letteria; Rinaldi, Mariagrazia; Marini, Herbert; Irrera, Natasha; Crea, Giovanni; Lorenzini, Cesare; Puzzolo, Domenico; Valenti, Andrea; Pisani, Antonina; Adamo, Elena B; Altavilla, Domenica; Squadrito, Francesco; Micali, Antonio

    2016-01-01

    Benign prostatic hyperplasia (BPH) is a chronic condition common in older men that can result in bothersome lower urinary tract symptoms. The molecular mechanisms and networks underlying the development and the progression of the disease are still far from being fully understood. BPH results from smooth muscle cell and epithelial cell proliferation, primarily within the transition zone of the prostate. Apoptosis and inflammation play important roles in the control of cell growth and in the maintenance of tissue homeostasis. Disturbances in molecular mechanisms of apoptosis machinery have been linked to BPH. Increased levels of the glycoprotein Dickkopf-related protein 3 in BPH cause an inhibition of the apoptosis machinery through a reduction in B cell lymphoma (Bcl)-2 associated X protein (Bax) expression. Inhibitors of apoptosis proteins influence cell death by direct inhibition of caspases and modulation of the transcription factor nuclear factor-κB. Current pharmacotherapy targets either the static component of BPH, including finasteride and dutasteride, or the dynamic component of BPH, including α-adrenoceptor antagonists such as tamsulosin and alfuzosin. Both these classes of drugs significantly interfere with the apoptosis machinery. Furthermore, phytotherapic supplements and new drugs may also modulate several molecular steps of apoptosis. PMID:27529214

  4. Mitophagy: Basic Mechanism and Potential Role in Kidney Diseases

    PubMed Central

    Tang, Chengyuan; He, Liyu; Liu, Jing; Dong, Zheng

    2015-01-01

    Background Mitochondria play fundamental roles in cellular metabolism, signaling, and viability. Disruption of mitochondria not only leads to dysfunction of the organelles but also activates mechanisms of cell injury and death, contributing to the pathogenesis of various diseases. Summary Removal of damaged mitochondria is therefore crucial for cellular homeostasis and survival. Mitophagy, the selective elimination of mitochondria via autophagy, is an important mechanism of mitochondrial quality control in physiological and pathological conditions. Defects in mitophagy have been implicated in a variety of human disorders, including both acute and chronic kidney diseases. However, the role and regulatory mechanisms of mitophagy in kidney cells and tissues remain largely unknown. Key Message This review provides updated information on mitophagy and suggests a potential role of mitophagy in renal pathophysiology.

  5. Unexpected reactivity and mechanism of carboxamide activation in bacterial N-linked protein glycosylation.

    PubMed

    Lizak, Christian; Gerber, Sabina; Michaud, Gaëlle; Schubert, Mario; Fan, Yao-Yun; Bucher, Monika; Darbre, Tamis; Aebi, Markus; Reymond, Jean-Louis; Locher, Kaspar P

    2013-01-01

    The initial glycan transfer in asparagine-linked protein glycosylation is catalysed by the integral membrane enzyme oligosaccharyltransferase (OST). Here we study the mechanism of the bacterial PglB protein, a single-subunit OST, using chemically synthesized acceptor peptide analogues. We find that PglB can glycosylate not only asparagine but also glutamine, homoserine and the hydroxamate Asp(NHOH), although at much lower rates. In contrast, N-methylated asparagine or 2,4-diaminobutanoic acid (Dab) are not glycosylated. We find that of the various peptide analogues, only asparagine- or Dab-containing peptides bind tightly to PglB. Glycopeptide products are unable to bind, providing the driving force of product release. We find no suitably positioned residues near the active site of PglB that can activate the acceptor asparagine by deprotonation, making a general base mechanism unlikely and leaving carboxamide twisting as the most likely mechanistic proposal for asparagine activation. PMID:24149797

  6. Prestressed F-actin networks cross-linked by hinged filamins replicate mechanical properties of cells

    NASA Astrophysics Data System (ADS)

    Gardel, M. L.; Nakamura, F.; Hartwig, J. H.; Crocker, J. C.; Stossel, T. P.; Weitz, D. A.

    2006-02-01

    We show that actin filaments, shortened to physiological lengths by gelsolin and cross-linked with recombinant human filamins (FLNs), exhibit dynamic elastic properties similar to those reported for live cells. To achieve elasticity values of comparable magnitude to those of cells, the in vitro network must be subjected to external prestress, which directly controls network elasticity. A molecular requirement for the strain-related behavior at physiological conditionsis a flexible hinge found in FLNa and some FLNb molecules. Basic physical properties of the in vitro filamin-F-actin network replicate the essential mechanical properties of living cells. This physical behavior could accommodate passive deformation and internal organelle trafficking at low strains yet resist externally or internally generated high shear forces. cytoskeleton | cell mechanics | nonlinear rheology

  7. A mechanical wave system to show waveforms similar to quantum mechanical wavefunctions in a potential

    NASA Astrophysics Data System (ADS)

    Faletič, Sergej

    2015-05-01

    Interviews with students suggest that even though they understand the formalism and the formal nature of quantum theory, they still often desire a mental picture of what the equations describe and some tangible experience with the wavefunctions. Here we discuss a mechanical wave system capable of reproducing correctly a mechanical equivalent of a quantum system in a potential, and the resulting waveforms in principle of any form. We have successfully reproduced the finite potential well, the potential barrier and the parabolic potential. We believe that these mechanical waveforms can provide a valuable experience base for introductory students to start from. We aim to show that mechanical systems that are described with the same mathematics as quantum mechanical, indeed behave in the same way. We believe that even if treated purely as a wave phenomenon, the system provides much insight into wave mechanics. This can be especially useful for physics teachers and others who often need to resort to concepts and experience rather than mathematics when explaining physical phenomena.

  8. Immune dysregulation mediated by the oral microbiome: potential link to chronic inflammation and atherosclerosis.

    PubMed

    Slocum, C; Kramer, C; Genco, C A

    2016-07-01

    Cardiovascular disease is an inflammatory disorder characterized by the progressive formation of plaque in coronary arteries, termed atherosclerosis. It is a multifactorial disease that is one of the leading causes of death worldwide. Although a number of risk factors have been associated with disease progression, the underlying inflammatory mechanisms contributing to atherosclerosis remain to be fully delineated. Within the last decade, the potential role for infection in inflammatory plaque progression has received considerable interest. Microbial pathogens associated with periodontal disease have been of particular interest due to the high levels of bacteremia that are observed after routine dental procedures and every day oral activities, such as tooth brushing. Here, we explore the potential mechanisms that may explain how periodontal pathogens either directly or indirectly elicit immune dysregulation and consequently progressive inflammation manifested as atherosclerosis. Periodontal pathogens have been shown to contribute directly to atherosclerosis by disrupting endothelial cell function, one of the earliest indicators of cardiovascular disease. Oral infection is thought to indirectly induce elevated production of inflammatory mediators in the systemic circulation. Recently, a number of studies have been conducted focusing on how disruption of the gut microbiome influences the systemic production of proinflammatory cytokines and consequently exacerbation of inflammatory diseases such as atherosclerosis. It is clear that the immune mechanisms leading to atherosclerotic plaque progression, by oral infection, are complex. Understanding the immune pathways leading to disease progression is essential for the future development of anti-inflammatory therapies for this chronic disease. PMID:26791914

  9. Comparing Chemical Mechanisms using Tagged Ozone Production Potentials

    NASA Astrophysics Data System (ADS)

    Coates, J.; Butler, T. M.

    2013-12-01

    Tropospheric ozone (O3) is a short-lived climate forcing pollutant that is detrimental to human health and crop growth. It is produced by reactions of volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the presence of sunlight [Atkinson,2000]. The chemistry of intermediate species formed during VOC degradation show a time dependence and impacts the amount of O3 produced by the VOC [Butler et al., 2011]. Representing the intricacies of these reactions is not viable for chemical mechanisms used in global and regional models due to the computational resources available. Thus, chemical mechanisms reduce the amount of reactions either by lumping chemical species together as a model species, reducing the number of reaction pathways or both. As different chemical mechanisms use varying reduction techniques and assumptions especially with respect to the intermediate degradation species, it is important to compare the temporal evolution of ozone production obtained from differing chemical mechanisms. In this study, chemical mechanisms are compared using Tagged Ozone Production Potentials (TOPP) [Butler et al.,2011]. TOPPs measure the effect of a VOC on the odd oxygen family (Ox), which includes O3, nitrogen dioxide (NO2) and other species whose cycling effect O3 and NO2 production. TOPP values are obtained via a boxmodel run lasting seven diurnal cycles and tagging all species produced during VOC degradation; this enables the Ox production to be attributed to the VOC. This technique enables the temporal evolution of a VOCs' Ox production to be compared between the mechanisms. Comparing the TOPP profiles of the VOCs obtained using different mechanisms shows the effect of reduction techniques implemented by the mechanism and also allows a comparison of the tropospheric chemistry represented in the mechanisms. [Atkinson,2000] Atkinson, R. (2000). Atmospheric chemistry of VOCs and NOx. Atmospheric Environment, 34:2063-2101 [Butler et al., 2011] Butler, T. M

  10. The carboxy-terminus of p63 links cell cycle control and the proliferative potential of epidermal progenitor cells

    PubMed Central

    Suzuki, Daisuke; Sahu, Raju; Leu, N. Adrian; Senoo, Makoto

    2015-01-01

    The transcription factor p63 (Trp63) plays a key role in homeostasis and regeneration of the skin. The p63 gene is transcribed from dual promoters, generating TAp63 isoforms with growth suppressive functions and dominant-negative ΔNp63 isoforms with opposing properties. p63 also encodes multiple carboxy (C)-terminal variants. Although mutations of C-terminal variants have been linked to the pathogenesis of p63-associated ectodermal disorders, the physiological role of the p63 C-terminus is poorly understood. We report here that deletion of the p63 C-terminus in mice leads to ectodermal malformation and hypoplasia, accompanied by a reduced proliferative capacity of epidermal progenitor cells. Notably, unlike the p63-null condition, we find that p63 C-terminus deficiency promotes expression of the cyclin-dependent kinase inhibitor p21Waf1/Cip1 (Cdkn1a), a factor associated with reduced proliferative capacity of both hematopoietic and neuronal stem cells. These data suggest that the p63 C-terminus plays a key role in the cell cycle progression required to maintain the proliferative potential of stem cells of many different lineages. Mechanistically, we show that loss of Cα, the predominant C-terminal p63 variant in epithelia, promotes the transcriptional activity of TAp63 and also impairs the dominant-negative activity of ΔNp63, thereby controlling p21Waf1/Cip1 expression. We propose that the p63 C-terminus links cell cycle control and the proliferative potential of epidermal progenitor cells via mechanisms that equilibrate TAp63 and ΔNp63 isoform function. PMID:25503409

  11. From Fragmented Knowledge to a Knowledge Structure: Linking the Domains of Mechanics and Electromagnetism.

    ERIC Educational Resources Information Center

    Bagno, Esther; Eylon, Bat-Sheva; Ganiel, Uri

    2000-01-01

    Describes the MAOF physics education program which is designed to relate large parts of mechanics and electromagnetism to each other via the key concepts of field and potential, while at the same time treat students' conceptual difficulties. Finds that students who studied with the MAOF program significantly improved their physics knowledge…

  12. Synthesis and biological evaluation of oxindole linked indolyl-pyrimidine derivatives as potential cytotoxic agents.

    PubMed

    Prajapti, Santosh Kumar; Nagarsenkar, Atulya; Guggilapu, Sravanthi Devi; Gupta, Keshav Kumar; Allakonda, Lingesh; Jeengar, Manish Kumar; Naidu, V G M; Babu, Bathini Nagendra

    2016-07-01

    In our endeavor towards the development of effective cytotoxic agents, a series of oxindole linked indolyl-pyrimidine derivatives were synthesized and characterized by IR, (1)H NMR, (13)C NMR and Mass spectral analysis. All the newly synthesized target compounds were assessed against PA-1 (ovarian), U-87MG (glioblastoma), LnCaP (prostate), and MCF-7 (Breast) cancer cell lines for their cytotoxic potential, with majority of them showing inhibitory activity at low micro-molar concentrations. Significantly, compound 8e was found to be most potent amongst all the tested compounds with an IC50 value of (2.43±0.29μM) on PA-1 cells. The influence of the most active cytotoxic compound 8e on the cell cycle distribution was assessed on the PA-1 cell line, exhibiting a cell cycle arrest at the G2/M phase. Moreover, acridine orange/ethidium bromide staining and annexin V binding assay confirmed that compound 8e can induce cell apoptosis in PA-1 cells. These preliminary results persuade further investigation on the synthesized compounds aiming to the development of potential cytotoxic agents. PMID:27210438

  13. The Potential of School-Linked Centers To Promote Adolescent Health and Development. Working Paper.

    ERIC Educational Resources Information Center

    Millstein, Susan G.

    The future of school-linked adolescent health centers cannot be determined without further evaluation. The recent development of school-linked health centers stems from concerns about the special health needs of adolescents. Currently there are 125 school-based and school-linked centers in operation. Characteristics include the following: (1) most…

  14. Mechanochromism and Mechanical-Force-Triggered Cross-Linking from a Single Reactive Moiety Incorporated into Polymer Chains.

    PubMed

    Zhang, Huan; Gao, Fei; Cao, Xiaodong; Li, Yanqun; Xu, Yuanze; Weng, Wengui; Boulatov, Roman

    2016-02-01

    Incorporation of small reactive moieties, the reactivity of which depends on externally imposed load (so-called mechanophores) into polymer chains offers access to a broad range of stress-responsive materials. Here, we report that polymers incorporating spirothiopyran (STP) manifest both green mechanochromism and load-induced addition reactions in solution and solid. Stretching a macromolecule containing colorless STP converts it into green thiomerocyanine (TMC), the mechanically activated thiolate moiety of which undergoes rapid thiol-ene click reactions with certain reactive C=C bonds to form a graft or a cross-link. The unique dual mechanochemical response of STP makes it of potentially great utility both for the design of new stress-responsive materials and for fundamental studies in polymer physics, for example, the dynamics of physical and mechanochemical remodeling of loaded materials. PMID:26805709

  15. Potential of isotope analysis (C, Cl) to identify dechlorination mechanisms

    NASA Astrophysics Data System (ADS)

    Cretnik, Stefan; Thoreson, Kristen; Bernstein, Anat; Ebert, Karin; Buchner, Daniel; Laskov, Christine; Haderlein, Stefan; Shouakar-Stash, Orfan; Kliegman, Sarah; McNeill, Kristopher; Elsner, Martin

    2013-04-01

    Chloroethenes are commonly used in industrial applications, and detected as carcinogenic contaminants in the environment. Their dehalogenation is of environmental importance in remediation processes. However, a detailed understanding frequently accounted problem is the accumulation of toxic degradation products such as cis-dichloroethylene (cis-DCE) at contaminated sites. Several studies have addressed the reductive dehalogenation reactions using biotic and abiotic model systems, but a crucial question in this context has remained open: Do environmental transformations occur by the same mechanism as in their corresponding in vitro model systems? The presented study shows the potential to close this research gap using the latest developments in compound specific chlorine isotope analysis, which make it possible to routinely measure chlorine isotope fractionation of chloroethenes in environmental samples and complex reaction mixtures.1,2 In particular, such chlorine isotope analysis enables the measurement of isotope fractionation for two elements (i.e., C and Cl) in chloroethenes. When isotope values of both elements are plotted against each other, different slopes reflect different underlying mechanisms and are remarkably insensitive towards masking. Our results suggest that different microbial strains (G. lovleyi strain SZ, D. hafniense Y51) and the isolated cofactor cobalamin employ similar mechanisms of reductive dechlorination of TCE. In contrast, evidence for a different mechanism was obtained with cobaloxime cautioning its use as a model for biodegradation. The study shows the potential of the dual isotope approach as a tool to directly compare transformation mechanisms of environmental scenarios, biotic transformations, and their putative chemical lab scale systems. Furthermore, it serves as an essential reference when using the dual isotope approach to assess the fate of chlorinated compounds in the environment.

  16. Photo-cross-linked hydrogels from thermoresponsive PEGMEMA-PPGMA-EGDMA copolymers containing multiple methacrylate groups: mechanical property, swelling, protein release, and cytotoxicity.

    PubMed

    Tai, Hongyun; Howard, Daniel; Takae, Seiji; Wang, Wenxin; Vermonden, Tina; Hennink, Wim E; Stayton, Patrick S; Hoffman, Allan S; Endruweit, Andreas; Alexander, Cameron; Howdle, Steven M; Shakesheff, Kevin M

    2009-10-12

    Photo-cross-linked hydrogels from thermoresponsive polymers can be used as advanced injectable biomaterials via a combination of physical interaction (in situ thermal gelation) and covalent cross-links (in situ photopolymerization). This can lead to gels with significantly enhanced mechanical properties compared to non-photo-cross-linked thermoresponsive hydrogels. Moreover, the thermally phase-separated gels have attractive advantages over non-thermoresponsive gels because thermal gelation upon injection allows easy handling and holds the shape of the gels prior to photopolymerization. In this study, water-soluble thermoresponsive copolymers containing multiple methacrylate groups were synthesized via one-step deactivation enhanced atom transfer radical polymerization (ATRP) of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA, M(n) = 475), poly(propylene glycol) methacrylate (PPGMA, M(n) = 375), and ethylene glycol dimethacrylate (EGDMA) and were used to form covalent cross-linked hydrogels by photopolymerization. The cross-linking density was found to have a significant influence on the mechanical and swelling properties of the photo-cross-linked gels. Release studies using lysozyme as a model protein demonstrated a sustained release profile that varied dependent on the copolymer composition, cross-linking density, and the temperature. Mouse C2C12 myoblast cells were cultured in the presence of the copolymers at concentrations up to 1 mg/mL. It was found that the majority of the cells remained viable, as assessed by Alamar Blue, lactate dehydrogenase (LDH), and Live/Dead cell viability/cytotoxicity assays. These studies demonstrate that thermoresponsive PEGMEMA-PPGMA-EGDMA copolymers offer potential as in situ photopolymerizable materials for tissue engineering and drug delivery applications through a combination of facile synthesis, enhanced mechanical properties, tunable cross-linking density, low cytotoxicity, and accessible functionality for further

  17. Linking acoustic emission signatures with grain-scale mechanical interactions during granular shearing

    NASA Astrophysics Data System (ADS)

    Michlmayr, G.; Cohen, D.; Or, D.

    2012-04-01

    Acoustic Emissions (AE) are high frequency (kHz range) elastic body waves, generated in deforming granular material during particle collisions, frictional slip, or other types of abrupt grain-scale mechanical interactions. The direct link with particle micro-mechanics makes AE a useful tool for gaining insights into mechanical aspects of progressive shear failure in granular material and slow granular flows. The formation of shear plane in granular matter involves numerous internal restructuring and failure events with distinct dynamics resembling features of critical phase transition. Following establishment of a shear plane, subsequent deformation involves episodic slip events interrupted by arrested flow (stick-slip behavior). We developed a model for interpreting measured AE signatures in terms of micro-failures during progressive granular shear a considering AE generation mechanisms and propagation of acoustic signals within granular material. Results from shear frame experiments include information on strains, stresses and acoustic emissions during deformation controlled tests on glass beads and sand. The number of failure associated AE event rates peaks with maximum shear resistance of the granular material. Intermittent slip events during stick-slip deformation are found to be closely related to low frequency AE events (~1kHz). Statistics of AE events and their temporal development are reproduced using a simple fiber-bundle model. A conceptual AE generation and propagation model accounts for conversion of mechanical events into elastic waves. In addition to gaining insights concerning grain-scale mechanical interactions, the AE method offers a useful tool for monitoring hazardous geologic mass movements, such as landslides, rock avalanches or debris flows.

  18. The potential mechanistic link between allergy and obesity development and infant formula feeding

    PubMed Central

    2014-01-01

    This article provides a new view of the cellular mechanisms that have been proposed to explain the links between infant formula feeding and the development of atopy and obesity. Epidemiological evidence points to an allergy- and obesity-preventive effect of breastfeeding. Both allergy and obesity development have been traced back to accelerated growth early in life. The nutrient-sensitive kinase mTORC1 is the master regulator of cell growth, which is predominantly activated by amino acids. In contrast to breastfeeding, artificial infant formula feeding bears the risk of uncontrolled excessive protein intake overactivating the infant’s mTORC1 signalling pathways. Overactivated mTORC1 enhances S6K1-mediated adipocyte differentiation, but negatively regulates growth and differentiation of FoxP3+ regulatory T-cells (Tregs), which are deficient in atopic individuals. Thus, the “early protein hypothesis” not only explains increased mTORC1-mediated infant growth but also the development of mTORC1-driven diseases such as allergy and obesity due to a postnatal deviation from the appropriate axis of mTORC1-driven metabolic and immunologic programming. Remarkably, intake of fresh unpasteurized cow’s milk exhibits an allergy-preventive effect in farm children associated with increased FoxP3+ Treg numbers. In contrast to unprocessed cow’s milk, formula lacks bioactive immune-regulatory microRNAs, such as microRNA-155, which plays a major role in FoxP3 expression. Uncontrolled excessive protein supply by formula feeding associated with the absence of bioactive microRNAs and bifidobacteria in formula apparently in a synergistic way result in insufficient Treg maturation. Treg deficiency allows Th2-cell differentiation promoting the development of allergic diseases. Formula-induced mTORC1 overactivation is thus the critical mechanism that explains accelerated postnatal growth, allergy and obesity development on one aberrant pathway. PMID:25071855

  19. The potential mechanistic link between allergy and obesity development and infant formula feeding.

    PubMed

    Melnik, Bodo C

    2014-01-01

    This article provides a new view of the cellular mechanisms that have been proposed to explain the links between infant formula feeding and the development of atopy and obesity. Epidemiological evidence points to an allergy- and obesity-preventive effect of breastfeeding. Both allergy and obesity development have been traced back to accelerated growth early in life. The nutrient-sensitive kinase mTORC1 is the master regulator of cell growth, which is predominantly activated by amino acids. In contrast to breastfeeding, artificial infant formula feeding bears the risk of uncontrolled excessive protein intake overactivating the infant's mTORC1 signalling pathways. Overactivated mTORC1 enhances S6K1-mediated adipocyte differentiation, but negatively regulates growth and differentiation of FoxP3(+) regulatory T-cells (Tregs), which are deficient in atopic individuals. Thus, the "early protein hypothesis" not only explains increased mTORC1-mediated infant growth but also the development of mTORC1-driven diseases such as allergy and obesity due to a postnatal deviation from the appropriate axis of mTORC1-driven metabolic and immunologic programming. Remarkably, intake of fresh unpasteurized cow's milk exhibits an allergy-preventive effect in farm children associated with increased FoxP3(+) Treg numbers. In contrast to unprocessed cow's milk, formula lacks bioactive immune-regulatory microRNAs, such as microRNA-155, which plays a major role in FoxP3 expression. Uncontrolled excessive protein supply by formula feeding associated with the absence of bioactive microRNAs and bifidobacteria in formula apparently in a synergistic way result in insufficient Treg maturation. Treg deficiency allows Th2-cell differentiation promoting the development of allergic diseases. Formula-induced mTORC1 overactivation is thus the critical mechanism that explains accelerated postnatal growth, allergy and obesity development on one aberrant pathway. PMID:25071855

  20. Unconventional Mechanics of Lipid Membranes: A Potential Role for Mechanotransduction of Hair Cell Stereocilia

    PubMed Central

    Kim, Jichul

    2015-01-01

    A force-conveying role of the lipid membrane across various mechanoreceptors is now an accepted hypothesis. However, such a mechanism is still not fully understood for mechanotransduction in the hair bundle of auditory sensory hair cells. A major goal of this theoretical assessment was to investigate the role of the lipid membrane in auditory mechanotransduction, especially in generating nonlinear bundle force versus displacement measurements, one of the main features of auditory mechanotransduction. To this end, a hair bundle model that generates lipid membrane tented deformation in the stereocilia was developed. A computational analysis of the model not only reproduced nonlinear bundle force measurements but also generated membrane energy that is potentially sufficient to activate the mechanosensitive ion channel of the hair cell. In addition, the model provides biophysical insight into 1) the likelihood that the channel must be linked in some way to the tip link; 2) how the interplay of the bending and stretching of the lipid bilayer may be responsible for the nonlinear force versus displacement response; 3) how measurements of negative stiffness may be a function of the rotational stiffness of the rootlets; and 4) how the standing tension of the tip link is required to interpret migration of the nonlinear force versus displacement and activation curves. These are all features of hair cell mechanotransduction, but the underlying biophysical mechanism has proved elusive for the last three decades. PMID:25650928

  1. Ballistocardiogram: Mechanism and Potential for Unobtrusive Cardiovascular Health Monitoring

    PubMed Central

    Kim, Chang-Sei; Ober, Stephanie L.; McMurtry, M. Sean; Finegan, Barry A.; Inan, Omer T.; Mukkamala, Ramakrishna; Hahn, Jin-Oh

    2016-01-01

    For more than a century, it has been known that the body recoils each time the heart ejects blood into the arteries. These subtle cardiogenic body movements have been measured with increasingly convenient ballistocardiography (BCG) instruments over the years. A typical BCG measurement shows several waves, most notably the “I”, “J”, and “K” waves. However, the mechanism for the genesis of these waves has remained elusive. We formulated a simple mathematical model of the BCG waveform. We showed that the model could predict the BCG waves as well as physiologic timings and amplitudes of the major waves. The validated model reveals that the principal mechanism for the genesis of the BCG waves is blood pressure gradients in the ascending and descending aorta. This new mechanistic insight may be exploited to allow BCG to realize its potential for unobtrusive monitoring and diagnosis of cardiovascular health and disease. PMID:27503664

  2. Dually cross-linked single network poly(acrylic acid) hydrogels with superior mechanical properties and water absorbency.

    PubMed

    Zhong, Ming; Liu, Yi-Tao; Liu, Xiao-Ying; Shi, Fu-Kuan; Zhang, Li-Qin; Zhu, Mei-Fang; Xie, Xu-Ming

    2016-06-28

    Poly(acrylic acid) (PAA) hydrogels with superior mechanical properties, based on a single network structure with dual cross-linking, are prepared by one-pot free radical polymerization. The network structure of the PAA hydrogels is composed of dual cross-linking: a dynamic and reversible ionic cross-linking among the PAA chains enabled by Fe(3+) ions, and a sparse covalent cross-linking enabled by a covalent cross-linker (Bis). Under deformation, the covalently cross-linked PAA chains remain intact to maintain their original configuration, while the Fe(3+)-enabled ionic cross-linking among the PAA chains is broken to dissipate energy and then recombined. It is found that the mechanical properties of the PAA hydrogels are significantly influenced by the contents of covalent cross-linkers, Fe(3+) ions and water, which can be adjusted within a substantial range and thus broaden the applications of the hydrogels. Meanwhile, the PAA hydrogels have excellent recoverability based on the dynamic and reversible ionic cross-linking enabled by Fe(3+) ions. Moreover, the swelling capacity of the PAA hydrogels is as high as 1800 times in deionized water due to the synergistic effects of ionic and covalent cross-linkings. The combination of balanced mechanical properties, efficient recoverability, high swelling capacity and facile preparation provides a new method to obtain high-performance hydrogels. PMID:27230478

  3. Neural mechanisms and potential treatment of epilepsy and its complications

    PubMed Central

    Liu, Tao-Tao; He, Zhi-Gang; Tian, Xue-Bi; Xiang, Hong-Bing

    2014-01-01

    The factors underlying epilepsy are multifaceted, but recent research suggests that the brain’s neural circuits, which play a key role in controlling the balance between epileptic and antiepileptic factors, may lie at the heart of epilepsy. This article provides a comprehensive review of the neural mechanisms and potential treatment of intractable epilepsy from neural inflammatory responses, melanocortin circuits in brain and pedunculopontine tegmental nucleus. Further studies should be undertaken to elucidate the nature of neural circuits so that we may more effectively apply these new preventive and symptomatic therapies to the patient suffering from medically refractory seizures and its complications. PMID:25628775

  4. Probiotics and Alcoholic Liver Disease: Treatment and Potential Mechanisms

    PubMed Central

    Li, Fengyuan; Duan, Kangmin; Wang, Cuiling; McClain, Craig; Feng, Wenke

    2016-01-01

    Despite extensive research, alcohol remains one of the most common causes of liver disease in the United States. Alcoholic liver disease (ALD) encompasses a broad spectrum of disorders, including steatosis, steatohepatitis, and cirrhosis. Although many agents and approaches have been tested in patients with ALD and in animals with experimental ALD in the past, there is still no FDA (Food and Drug Administration) approved therapy for any stage of ALD. With the increasing recognition of the importance of gut microbiota in the onset and development of a variety of diseases, the potential use of probiotics in ALD is receiving increasing investigative and clinical attention. In this review, we summarize recent studies on probiotic intervention in the prevention and treatment of ALD in experimental animal models and patients. Potential mechanisms underlying the probiotic function are also discussed. PMID:26839540

  5. Possibility and potential of clean development mechanisms in China

    NASA Astrophysics Data System (ADS)

    Gao, Weijun; Zhou, Nan; Li, Haifeng; Kammen, Daniel M.

    2007-10-01

    China has become the world's second largest greenhouse gas (GHG) emitter behind the United States. It emits approximately three billion tons of CO2 equivalents every year. Its growing economy and large population are making a wealthier, more consumption-oriented country. Energy demand is expected to grow 5 10% per year through 2030. Therefore, a large potential of GHG emission reduction in China can be expected. The clean development mechanism (CDM) put forward in the Kyoto Protocol for reductions of GHGs can support the sustainable development of developing countries and help developed countries to achieve their emission reduction targets at low cost. However, there are still many disagreements to be resolved between developing and developed countries. In this letter, we try to introduce the current development of CDM projects in China and discuss its potential and opportunities in the future decades.

  6. Uncertainty Propagation in Nerve Impulses Through the Action Potential Mechanism.

    PubMed

    Torres Valderrama, Aldemar; Witteveen, Jeroen; Navarro, Maria; Blom, Joke

    2015-12-01

    We investigate the propagation of probabilistic uncertainty through the action potential mechanism in nerve cells. Using the Hodgkin-Huxley (H-H) model and Stochastic Collocation on Sparse Grids, we obtain an accurate probabilistic interpretation of the deterministic dynamics of the transmembrane potential and gating variables. Using Sobol indices, out of the 11 uncertain parameters in the H-H model, we unravel two main uncertainty sources, which account for more than 90 % of the fluctuations in neuronal responses, and have a direct biophysical interpretation. We discuss how this interesting feature of the H-H model allows one to reduce greatly the probabilistic degrees of freedom in uncertainty quantification analyses, saving CPU time in numerical simulations and opening possibilities for probabilistic generalisation of other deterministic models of great importance in physiology and mathematical neuroscience. PMID:26458902

  7. Possibility and potential of clean development mechanisms inChina

    SciTech Connect

    Gao, Weijun; Zhou, Nan; Li, Haifeng; Kammen, Daniel

    2007-10-30

    China has become the world's second largest greenhouse gas(GHG) emitter behind the United States. It emits approximately threebillion tons of CO2 equivalents every year. Its growing economy and largepopulation are making a wealthier, more consumption-oriented country.Energy demand is expected to grow 5?10 percent per year through 2030.Therefore, a large potential of GHG emission reduction in Chinacan beexpected. The clean development mechanism (CDM) put forward in the KyotoProtocol for reductions of GHGs can support the sustainable developmentof developing countries and help developed countries to achieve theiremission reduction targets at low cost. However, there are still manydisagreements to be resolved between developing and developed countries.In this letter, we try to introduce the current development of CDMprojects in China and discuss its potential and opportunities in thefuture decades.

  8. Link between the relativistic canonical quantum mechanics of arbitrary spin and the corresponding field theory

    NASA Astrophysics Data System (ADS)

    Simulik, Volodimir

    2016-01-01

    The new relativistic equations of motion for the particles with arbitrary spin and nonzero mass have been introduced. The axiomatic level description of the relativistic canonical quantum mechanics of the arbitrary mass and spin has been given. The 64-dimensional ClR(0,6) algebra in terms of Dirac gamma matrices has been suggested. The link between the relativistic canonical quantum mechanics of the arbitrary spin and the covariant local field theory has been found. Different methods of the Dirac equation derivation have been reviewed. The manifestly covariant field equations for an arbitrary spin that follow from the quantum mechanical equations have been considered. The covariant local field theory equations for spin s = (1,1) particle-antiparticle doublet, spin s = (1,0,1,0) particle antiparticle multiplet, spin s = (3/2,3/2) particle-antiparticle doublet, spin s = (2,2) particle-antiparticle doublet, spin s = (2,0,2,0) particle-antiparticle multiplet and spin s = (2,1,2,1) particle-antiparticle multiplet have been introduced. The Maxwell-like equations for the boson with spin s = 1 and nonzero mass have been introduced as well.

  9. Radiation-induced genomic instability: Are epigenetic mechanisms the missing link?

    SciTech Connect

    Aypar, Umut; Morgan, William F.; Baulch, Janet E.

    2011-02-01

    Purpose: This review examines the evidence for the hypothesis that epigenetics are involved in the initiation and perpetuation of radiation-induced genomic instability (RIGI). Conclusion: In addition to the extensively studied targeted effects of radiation, it is now apparent that non-targeted delayed effects such as RIGI are also important post-irradiation outcomes. In RIGI, unirradiated progeny cells display phenotypic changes at delayed times after radiation of the parental cell. RIGI is thought to be important in the process of carcinogenesis, however, the mechanism by which this occurs remains to be elucidated. In the genomically unstable clones developed by Morgan and colleagues, radiation-induced mutations, double-strand breaks, or changes in mRNA levels alone could not account for the initiation or perpetuation of RIGI. Since changes in the DNA sequence could not fully explain the mechanism of RIGI, inherited epigenetic changes may be involved. Epigenetics are known to play an important role in many cellular processes and epigenetic aberrations can lead to carcinogenesis. Recent studies in the field of radiation biology suggest that the changes in methylation patterns may be involved in RIGI. Together these clues have led us to hypothesize that epigenetics may be the missing link in understanding the mechanism behind RIGI.

  10. Vitamin D receptor expression is linked to potential markers of human thyroid papillary carcinoma.

    PubMed

    Izkhakov, Elena; Somjen, Dalia; Sharon, Orli; Knoll, Esther; Aizic, Asaf; Fliss, Dan M; Limor, Rona; Stern, Naftali

    2016-05-01

    Genes regulated cell-cell and cell-matrix adhesion and degradation of the extracellular matrix (ECM) have been screened as potential markers of malignant thyroid nodules. The mRNA expression levels of two of them, the ECM protein-1 (ECM1) and the type II transmembrane serine protease-4 (TMPRSS4), were shown to be an independent predictor of an existing thyroid carcinoma. The vitamin D receptor (VDR) is expressed in epithelial cells of the normal thyroid gland, as well as in malignant dividing cells, which respond to the active metabolite of vitamin D by decreased proliferative activity in vitro. We evaluated the relationship between mRNA gene expressions of TMPRSS4, ECM1 and VDR in 21 papillary thyroid carcinoma samples and compared it to 21 normal thyroid tissues from the same patients. Gene expression was considered as up- or down-regulated if it varied by more or less than 2-fold in the cancer tissue relative to the normal thyroid tissue (Ca/N) from the same patient. We found an overall significant adjusted correlation between the mRNA expression ratio (ExR) of VDR and that of ECM1 in Ca/N thyroid tissue (R=0.648, P<0.001). There was a high ExR of VDR between Ca/N thyroid tissue from the same patient (3.06±2.9), which also exhibited a high Ca/N ExR of ECM1 and/or of TMPRSS4 (>2, P=0.05).The finding that increased VDR expression in human thyroid cancer cells is often linked to increased ECM1 and/or TPMRSS4 expression warrants further investigation into the potential role of vitamin D analogs in thyroid carcinoma. PMID:26907966

  11. Star/linear polymer topology transformation facilitated by mechanical linking of polymer chains.

    PubMed

    Aoki, Daisuke; Uchida, Satoshi; Takata, Toshikazu

    2015-06-01

    Topology transformation of a star polymer to a linear polymer is demonstrated for the first time. A three-armed star polymer possessing a mechanical linking of two polymer chains was synthesized by the living ring-opening polymerization of δ-valerolactone initiated by a pseudo[2]rotaxane having three hydroxy groups as the initiator sites on the wheel component and at both axle termini. The polymerization was followed by the propagation end-capping reaction with a bulky isocyanate not only to prevent the wheel component deslippage but also to introduce the urethane moiety at the axle terminal. The resulting rotaxane-linked star polymer with a fixed rotaxane linkage based on the ammonium/crown ether interaction was subjected to N-acetylation of the ammonium moiety, which liberated the components from the interaction to move the wheel component to the urethane terminal as the interaction site, eventually affording the linear polymer. The physical property change caused by the present topology transformation was confirmed by the hydrodynamic volume and viscosity. PMID:25892579

  12. Theoretical and empirical qualification of a mechanical-optical interface for parallel optics links

    NASA Astrophysics Data System (ADS)

    Chuang, S.; Schoellner, D.; Ugolini, A.; Wakjira, J.; Wolf, G.; Gandhi, P.; Persaud, A.

    2015-03-01

    As the implementation of parallel optics continues to evolve, development of a universal coupling interface between VCSEL/PD arrays and the corresponding photonic turn connector is necessary. A newly developed monolithic mechanical-optical interface efficiently couples optical transmit/receive arrays to the accompanying fiber optic connector. This paper describes the optical model behind the coupling interface and validates the model using empirical measurements. Optical modeling will address how the interface is adaptable to the broad range of VCSEL/PD optical parameters from commercially available VCSEL hardware manufacturers; the optical model will illustrate coupling efficiencies versus launch specifications. Theoretical modeling will examine system sensitivity through Monte Carlo simulations and provide alignment tolerance requirements. Empirical results will be presented to validate the optical model predictions and subsequent system performance. Functionality will be demonstrated through optical loss and coupling efficiency measurements. System metrics will include characterizations such as eye diagram results and link loss measurements.

  13. The influence of sex-linked genetic mechanisms on attention and impulsivity

    PubMed Central

    Trent, Simon; Davies, William

    2012-01-01

    It is now generally agreed that there are inherent sex differences in healthy individuals across a number of neurobiological domains (including brain structure, neurochemistry, and cognition). Moreover, there is a burgeoning body of evidence highlighting sex differences within neuropsychiatric populations (in terms of the rates of incidence, clinical features/progression, neurobiology and pathology). Here, we consider the extent to which attention and impulsivity are sexually dimorphic in healthy populations and the extent to which sex might modulate the expression of disorders characterised by abnormalities in attention and/or impulsivity such as attention deficit hyperactivity disorder (ADHD), autism and addiction. We then discuss general genetic mechanisms that might underlie sex differences in attention and impulsivity before focussing on specific positional and functional candidate sex-linked genes that are likely to influence these cognitive processes. Identifying novel sex-modulated molecular targets should ultimately enable us to develop more effective therapies in disorders associated with attentional/impulsive dysfunction. PMID:21983394

  14. Lamellipodial actin mechanically links myosin activity with adhesion-site formation.

    PubMed

    Giannone, Grégory; Dubin-Thaler, Benjamin J; Rossier, Olivier; Cai, Yunfei; Chaga, Oleg; Jiang, Guoying; Beaver, William; Döbereiner, Hans-Günther; Freund, Yoav; Borisy, Gary; Sheetz, Michael P

    2007-02-01

    Cell motility proceeds by cycles of edge protrusion, adhesion, and retraction. Whether these functions are coordinated by biochemical or biomechanical processes is unknown. We find that myosin II pulls the rear of the lamellipodial actin network, causing upward bending, edge retraction, and initiation of new adhesion sites. The network then separates from the edge and condenses over the myosin. Protrusion resumes as lamellipodial actin regenerates from the front and extends rearward until it reaches newly assembled myosin, initiating the next cycle. Upward bending, observed by evanescence and electron microscopy, results in ruffle formation when adhesion strength is low. Correlative fluorescence and electron microscopy shows that the regenerating lamellipodium forms a cohesive, separable layer of actin above the lamellum. Thus, actin polymerization periodically builds a mechanical link, the lamellipodium, connecting myosin motors with the initiation of adhesion sites, suggesting that the major functions driving motility are coordinated by a biomechanical process. PMID:17289574

  15. Interpersonal Stress Generation as a Mechanism Linking Rumination to Internalizing Symptoms in Early Adolescents

    PubMed Central

    McLaughlin, Katie A.; Nolen-Hoeksema, Susan

    2012-01-01

    Rumination is a risk factor for depressive and anxiety symptoms in adolescents. Previous investigations of the mechanisms linking rumination to internalizing problems have focused primarily on cognitive factors. We investigated whether interpersonal stress generation plays a role in the longitudinal relationship between rumination and internalizing symptoms in young adolescents. Adolescents (Grades 6–8, N =1,065) from an ethnically diverse community completed measures of depressive and anxiety symptoms, perceived friendship quality, and peer victimization at two assessments, 7 months apart. We determined whether rumination predicted increased exposure to peer victimization and whether changes in perceived friendship quality mediated this relationship. We also evaluated whether peer victimization mediated the association between rumination and internalizing symptoms. Adolescents who engaged in high levels of rumination at baseline were more likely to experience overt, relational, and reputational victimization at a subsequent time point 7 months later, controlling for baseline internalizing symptoms and victimization. Increased communication with peers was a significant partial mediator of this association for relational (z =1.98, p =.048) and reputational (z =2.52, p =.024) victimization. Exposure to overt (z = 3.37, p =.014), relational (z =3.67, p <.001), and reputational (z = 3.78, p < .001) victimization fully mediated the association between baseline rumination and increases in internalizing symptoms over the study period. These findings suggest that interpersonal stress generation is a mechanism linking rumination to internalizing problems in adolescents and highlight the importance of targeting interpersonal factors in treatment and preventive interventions for adolescents who engage in rumination. PMID:22867280

  16. Sexual intercourse and cerebral aneurysmal rupture: potential mechanisms and precipitants.

    PubMed

    Reynolds, Matthew R; Willie, Jon T; Zipfel, Gregory J; Dacey, Ralph G

    2011-04-01

    Aneurysmal subarachnoid hemorrhage (SAH) is a significant cause of death in young and middle-aged individuals and causes tremendous morbidity in affected patients. Despite the identification of various risk factors, the series of events leading to the formation, growth, and rupture of intracranial aneurysms is poorly understood. Cerebral aneurysm rupture has been associated with sexual intercourse and other forms of physical exercise. In fact, multiple case series reported that coitus was the immediate preceding activity in 3.8-14.5% of patients suffering from aneurysmal SAH. This may be related to the large elevations in mean arterial blood pressure that occur in both males and females during sexual intercourse (130-175 and 125-160 mm Hg, respectively). While coitus and physical exercise share important physiological similarities, each may differentially affect the probability that a preformed aneurysm will rupture. In this literature review and synthesis, the authors analyze the physiological human response to sexual intercourse in an effort to delineate those factors that may precipitate aneurysmal rupture. The authors' analysis is based on the original data collected by Masters and Johnson. To the authors' knowledge, this is the first review to address the link between sexual intercourse and intracranial aneurysmal rupture. While actual measurements of the physiological variables relevant to SAH were not performed in this article, the authors make reasonable assumptions based on the available data to help elucidate the mechanism of sexually induced aneurysmal rupture. PMID:20540599

  17. DNA methylation: a mechanism linking environmental chemical exposures to risk of autism spectrum disorders?

    PubMed Central

    Keil, Kimberly P.; Lein, Pamela J.

    2016-01-01

    There is now compelling evidence that gene by environment interactions are important in the etiology of autism spectrum disorders (ASDs). However, the mechanisms by which environmental factors interact with genetic susceptibilities to confer individual risk for ASD remain a significant knowledge gap in the field. The epigenome, and in particular DNA methylation, is a critical gene expression regulatory mechanism in normal and pathogenic brain development. DNA methylation can be influenced by environmental factors such as diet, hormones, stress, drugs, or exposure to environmental chemicals, suggesting that environmental factors may contribute to adverse neurodevelopmental outcomes of relevance to ASD via effects on DNA methylation in the developing brain. In this review, we describe epidemiological and experimental evidence implicating altered DNA methylation as a potential mechanism by which environmental chemicals confer risk for ASD, using polychlorinated biphenyls (PCBs), lead, and bisphenol A (BPA) as examples. Understanding how environmental chemical exposures influence DNA methylation and how these epigenetic changes modulate the risk and/or severity of ASD will not only provide mechanistic insight regarding gene-environment interactions of relevance to ASD but may also suggest potential intervention strategies for these and potentially other neurodevelopmental disorders. PMID:27158529

  18. Oxidation potentials of N-modified derivatives of the analgesic flupirtine linked to potassium KV 7 channel opening activity but not hepatocyte toxicity.

    PubMed

    Lemmerhirt, Christian J; Rombach, Mirko; Bodtke, Anja; Bednarski, Patrick J; Link, Andreas

    2015-02-01

    Openers of neuronal voltage-gated potassium channels (KV ) are of interest as therapeutic agents for treating pain (flupirtine) and epilepsy (retigabine). In an effort to better understand the mechanisms of action and toxicity of flupirtine, we synthesized nine novel analogues with varying redox behavior. Flupirtine can be oxidatively metabolized into azaquinone diimines; thus, the oxidation potentials of flupirtine and its analogues were measured by cyclic voltammetry. KV 7.2/3 (KCNQ2/3) opening activity was determined by an established assay with HEK293 cells overexpressing these channels. A link was found between the oxidation potentials of the compounds and their EC50 values for potassium channel opening activity. On the other hand, no correlation was observed between oxidation potentials and cytotoxicity in cultures of transgenic mouse hepatocytes (TAMH). These results support the idea that oxidative metabolites of flupirtine contribute to the mechanism of action, similar to what was recently proposed for acetaminophen (paracetamol), but not to hepatotoxicity. PMID:25392984

  19. Potential Mechanisms of Cancer Prevention by Weight Control

    NASA Astrophysics Data System (ADS)

    Jiang, Yu; Wang, Weiqun

    Weight control via dietary caloric restriction and/or physical activity has been demonstrated in animal models for cancer prevention. However, the underlying mechanisms are not fully understood. Body weight loss due to negative energy balance significantly reduces some metabolic growth factors and endocrinal hormones such as IGF-1, leptin, and adiponectin, but enhances glucocorticoids, that may be associated with anti-cancer mechanisms. In this review, we summarized the recent studies related to weight control and growth factors. The potential molecular targets focused on those growth factors- and hormones-dependent cellular signaling pathways are further discussed. It appears that multiple factors and multiple signaling cascades, especially for Ras-MAPK-proliferation and PI3K-Akt-anti-apoptosis, could be involved in response to weight change by dietary calorie restriction and/or exercise training. Considering prevalence of obesity or overweight that becomes apparent over the world, understanding the underlying mechanisms among weight control, endocrine change and cancer risk is critically important. Future studies using "-omics" technologies will be warrant for a broader and deeper mechanistic information regarding cancer prevention by weight control.

  20. Potential Role of Epigenetic Mechanism in Manganese Induced Neurotoxicity

    PubMed Central

    Tarale, Prashant; Chakrabarti, Tapan; Sivanesan, Saravanadevi; Naoghare, Pravin; Bafana, Amit; Krishnamurthi, Kannan

    2016-01-01

    Manganese is a vital nutrient and is maintained at an optimal level (2.5–5 mg/day) in human body. Chronic exposure to manganese is associated with neurotoxicity and correlated with the development of various neurological disorders such as Parkinson's disease. Oxidative stress mediated apoptotic cell death has been well established mechanism in manganese induced toxicity. Oxidative stress has a potential to alter the epigenetic mechanism of gene regulation. Epigenetic insight of manganese neurotoxicity in context of its correlation with the development of parkinsonism is poorly understood. Parkinson's disease is characterized by the α-synuclein aggregation in the form of Lewy bodies in neuronal cells. Recent findings illustrate that manganese can cause overexpression of α-synuclein. α-Synuclein acts epigenetically via interaction with histone proteins in regulating apoptosis. α-Synuclein also causes global DNA hypomethylation through sequestration of DNA methyltransferase in cytoplasm. An individual genetic difference may also have an influence on epigenetic susceptibility to manganese neurotoxicity and the development of Parkinson's disease. This review presents the current state of findings in relation to role of epigenetic mechanism in manganese induced neurotoxicity, with a special emphasis on the development of Parkinson's disease. PMID:27314012

  1. Increased rhythmicity in hypertensive arterial smooth muscle is linked to transient receptor potential canonical channels.

    PubMed

    Chen, Xiaoping; Yang, Dachun; Ma, Shuangtao; He, Hongbo; Luo, Zhidan; Feng, Xiaoli; Cao, Tingbing; Ma, Liqun; Yan, Zhencheng; Liu, Daoyan; Tepel, Martin; Zhu, Zhiming

    2010-10-01

    Vasomotion describes oscillations of arterial vascular tone due to synchronized changes of intracellular calcium concentrations. Since increased calcium influx into vascular smooth muscle cells from spontaneously hypertensive rats (SHR) has been associated with variances of transient receptor potential canonical (TRPC) channels, in the present study we tested the hypothesis that increased vasomotion in hypertension is directly linked to increased TRPC expression. Using a small vessel myograph we observed significantly increased norepinephrine-induced vasomotion in mesenteric arterioles from SHR compared to normotensive Wistar-Kyoto (WKY) rats. Using immunoblottings we obtained significantly increased expression of TRPC1, TRPC3 and TRPC5 in mesenteric arterioles from SHR compared to WKY, whereas TRPC4 and TRPC6 showed no differences. Norepinephrine-induced vasomotion from SHR was significantly reduced in the presence of verapamil, SKF96365, 2-aminoethoxydiphenylborane (2-APB) or gadolinium. Pre-incubation of mesenteric arterioles with anti-TRPC1 and anti-TRPC3 antibodies significantly reduced norepinephrine-induced vasomotion and calcium influx. Control experiments with pre-incubation of TRPC antibodies plus their respective antigenic peptide or in the presence of anti-β-actin antibodies or random immunoglobulins not related to TRPC channels showed no inhibitory effects of norepinephrine-induced vasomotion and calcium influx. Administration of candesartan or telmisartan, but not amlodipine to SHR for 16 weeks significantly reduced either the expression of TRPC1, TRPC3 and TRPC5 as well as norepinephrine-induced vasomotion in mesenteric arterioles. In conclusion we gave experimental evidence that the increased TRPC1, TRPC3 and TRPC5 expression in mesenteric arterioles from SHR causes increased vasomotion in hypertension. PMID:19725917

  2. Understanding the Mechanism of Hepatic Fibrosis and Potential Therapeutic Approaches

    PubMed Central

    Ahmad, Areeba; Ahmad, Riaz

    2012-01-01

    Hepatic fibrosis (HF) is a progressive condition with serious clinical complications arising from abnormal proliferation and amassing of tough fibrous scar tissue. This defiance of collagen fibers becomes fatal due to ultimate failure of liver functions. Participation of various cell types, interlinked cellular events, and large number of mediator molecules make the fibrotic process enormously complex and dynamic. However, with better appreciation of underlying cellular and molecular mechanisms of fibrosis, the assumption that HF cannot be cured is gradually changing. Recent findings have underlined the therapeutic potential of a number of synthetic compounds as well as plant derivatives for cessation or even the reversal of the processes that transforms the liver into fibrotic tissue. It is expected that future inputs will provide a conceptual framework to develop more specific strategies that would facilitate the assessment of risk factors, shortlist early diagnosis biomarkers, and eventually guide development of effective therapeutic alternatives. PMID:22626794

  3. Potential therapeutic mechanism of K(+) channel block for MS.

    PubMed

    Baker, Mark D

    2013-10-01

    While the potential use of K(+) channel blockers in MS has been explored over many years, the approval in the US, and more recently in the UK, of fampyra (fampridine, 4-aminopyridine, 4-AP) as a symptomatic treatment for walking disability, has reawakened interest. Recent years have seen a real improvement in the treatment options for relapsing remitting MS, but the disease remains inadequately treated, with the progressive phase (characterised by irreversible functional loss) lacking any effective therapy. Whether the symptomatic relief afforded by 4-AP translates into neuroprotection, remains poorly investigated, although there is no clear reason why this would be expected. Importantly, future clinical studies may shed light on this question. This review includes an overview of axonal K(+) channel expression and pharmacology, and the logic of the use of K(+) channel blockers derived from observations in experimental studies of demyelination and synaptic transmission. It provides an insight into the probable biophysical actions of 4-AP, and how its action may aid in the symptomatic treatment of MS. The key message of this review is that 4-AP is a blocker of neuronal K(+) channels, and its administration is known to be of value in the symptomatic treatment of some patients. The details of the mechanism underlying the beneficial effects remain somewhat vague, and the molecular target has not been properly defined. The useful mechanism is likely to include an action on synaptic function, but whether it is the presynaptic terminal or the presynaptic axon that is the primary target is unknown. It is argued that because of the apparent inability of 4-AP to increase safety factor in experimental demyelination when clinically relevant concentrations are used, it cannot be the ideal pharmacological agent for treating demyelination by the widening of axonal action potentials. That said, it remains a possibility that the useful therapeutic effect of 4-AP may involve subtle

  4. Artificial Bee Colony Optimization of Capping Potentials for Hybrid Quantum Mechanical/Molecular Mechanical Calculations.

    PubMed

    Schiffmann, Christoph; Sebastiani, Daniel

    2011-05-10

    We present an algorithmic extension of a numerical optimization scheme for analytic capping potentials for use in mixed quantum-classical (quantum mechanical/molecular mechanical, QM/MM) ab initio calculations. Our goal is to minimize bond-cleavage-induced perturbations in the electronic structure, measured by means of a suitable penalty functional. The optimization algorithm-a variant of the artificial bee colony (ABC) algorithm, which relies on swarm intelligence-couples deterministic (downhill gradient) and stochastic elements to avoid local minimum trapping. The ABC algorithm outperforms the conventional downhill gradient approach, if the penalty hypersurface exhibits wiggles that prevent a straight minimization pathway. We characterize the optimized capping potentials by computing NMR chemical shifts. This approach will increase the accuracy of QM/MM calculations of complex biomolecules. PMID:26610125

  5. Evaluation of underlying mechanisms in the link between childhood ADHD symptoms and risk for early initiation of substance use.

    PubMed

    Vitulano, Michael L; Fite, Paula J; Hopko, Derek R; Lochman, John; Wells, Karen; Asif, Irfan

    2014-09-01

    Although there has been support for attention-deficit/hyperactivity disorder (ADHD) as a risk for early substance use, this link is not fully established or understood. Furthermore, the potential mechanisms explaining these associations are unclear. The current study examined peer rejection, school bonding, and internalizing problems as potential mediators of the association between childhood ADHD symptoms and risk for early initiation of substance use. The sample included a control group of 126 students with problematic aggression (79% African American, 66% male) from an intervention study following children from fourth to ninth grade. Results suggested that ADHD symptoms follow a path to early initiation of tobacco use through the combined effects of peer rejection and internalizing problems as well as through internalizing problems alone. ADHD symptoms were also associated with the cubic slope of marijuana use initiation, such that increased ADHD symptoms were associated with a strong cubic trend (e.g., a more rapid acceleration of risk for initiation). ADHD symptoms were not associated with risk for early initiation of alcohol use. Identification of important vulnerability factors in children with ADHD symptoms highlight the need for primary prevention and psychological interventions that target these factors and decrease the likelihood of early tobacco and marijuana use initiation. PMID:25222174

  6. Potential mechanisms for low uric acid in Parkinson disease.

    PubMed

    Sampat, Radhika; Young, Sarah; Rosen, Ami; Bernhard, Douglas; Millington, David; Factor, Stewart; Jinnah, H A

    2016-04-01

    Several epidemiologic studies have described an association between low serum uric acid (UA) and Parkinson disease (PD). Uric acid is a known antioxidant, and one proposed mechanism of neurodegeneration in PD is oxidative damage of dopamine neurons. However, other complex metabolic pathways may contribute. The purpose of this study is to elucidate potential mechanisms of low serum UA in PD. Subjects who met diagnostic criteria for definite or probable PD (n = 20) and controls (n = 20) aged 55-80 years were recruited. Twenty-four hour urine samples were collected from all participants, and both uric acid and allantoin were measured and corrected for body mass index (BMI). Urinary metabolites were compared using a twoway ANOVA with diagnosis and sex as the explanatory variables. There were no significant differences between PD and controls for total UA (p = 0.60), UA corrected for BMI (p = 0.37), or in the interaction of diagnosis and sex on UA (p = 0.24). Similarly, there were no significant differences between PD and controls for allantoin (p = 0.47), allantoin corrected for BMI (p = 0.57), or in the interaction of diagnosis and sex on allantoin (p = 0.78). Allantoin/UA ratios also did not significantly differ by diagnosis (p = 0.99). Our results imply that low serum UA in PD may be due to an intrinsic mechanism that alters the homeostatic set point for serum UA in PD, and may contribute to relatively lower protection against oxidative damage. These findings provide indirect support for neuroprotection trials aimed at raising serum UA. PMID:26747026

  7. Androgen deprivation therapy and cardiovascular disease: what is the linking mechanism?

    PubMed Central

    Zareba, Piotr; Duivenvoorden, Wilhelmina; Leong, Darryl P.; Pinthus, Jehonathan H.

    2015-01-01

    The past decade has brought increased awareness of the potential adverse effects of androgen deprivation therapy (ADT) in men with prostate cancer. Arguably the most important and controversial of these is the increased risk of cardiovascular morbidity and mortality. Although multiple observational studies have shown that men treated with ADT are at increased risk of developing atherosclerotic cardiovascular disease, our understanding of the biological mechanisms that might underlie this phenomenon is still evolving. In this review, we discuss some of the mechanisms that have been proposed to date, including ADT-induced metabolic changes that promote the development and progression of atherosclerotic plaques as well as direct local effects of hormonal factors on plaque growth, rupture and thrombosis. PMID:27034724

  8. Zeroing in on LRRK2-Linked Pathogenic Mechanisms in Parkinson’s Disease

    PubMed Central

    Biskup, Saskia; West, Andrew B.

    2009-01-01

    Summary The frequency and potency of mutations in the LRRK2 gene redefine the role of genetic susceptibility in Parkinson’s disease. Dominant missense mutations that fulfill initial criteria for potential gain of function mechanisms coupled with enzymatic activity likely amenable to small molecule inhibition position LRRK2 as a promising therapeutic target. Herein, key observations from the clinic to the test tube are highlighted together with points of contention and outstanding critical issues. Resolution of the critical issues will expedite the development of therapies that exploit LRRK2 activity for neuroprotection strategies. PMID:18973807

  9. Alveolar bone loss: mechanisms, potential therapeutic targets, and interventions.

    PubMed

    Intini, G; Katsuragi, Y; Kirkwood, K L; Yang, S

    2014-05-01

    This article reviews recent research into mechanisms underlying bone resorption and highlights avenues of investigation that may generate new therapies to combat alveolar bone loss in periodontitis. Several proteins, signaling pathways, stem cells, and dietary supplements are discussed as they relate to periodontal bone loss and regeneration. RGS12 is a crucial protein that mediates osteoclastogenesis and bone destruction, and a potential therapeutic target. RGS12 likely regulates osteoclast differentiation through regulating calcium influx to control the calcium oscillation-NFATc1 pathway. A working model for RGS10 and RGS12 in the regulation of Ca(2+) oscillations during osteoclast differentiation is proposed. Initiation of inflammation depends on host cell-microbe interactions, including the p38 mitogen-activated protein kinase (MAPK) signaling pathway. Oral p38 inhibitors reduced lipopolysaccharide (LPS)-induced bone destruction in a rat periodontitis model but showed unsatisfactory safety profiles. The p38 substrate MK2 is a more specific therapeutic target with potentially superior tolerability. Furthermore, MKP-1 shows anti-inflammatory activity, reducing inflammatory cytokine biosynthesis and bone resorption. Multipotent skeletal stem cell (SSC) populations exist within the bone marrow and periosteum of long bones. These bone-marrow-derived SSCs and periosteum-derived SSCs have shown therapeutic potential in several applications, including bone and periodontal regeneration. The existence of craniofacial bone-specific SSCs is suggested based on existing studies. The effects of calcium, vitamin D, and soy isoflavone supplementation on alveolar and skeletal bone loss in post-menopausal women were investigated. Supplementation resulted in stabilization of forearm bone mass density and a reduced rate of alveolar bone loss over 1 yr, compared with placebo. Periodontal attachment levels were also well-maintained and alveolar bone loss suppressed during 24 wk of

  10. Early-Late Heterobimetallic Complexes Linked by Phosphinoamide Ligands. Tuning Redox Potentials and Small Molecule Activation

    SciTech Connect

    Thomas, Christine M.

    2015-08-01

    Recent attention in the chemical community has been focused on the energy efficient and environmentally benign conversion of abundant small molecules (CO2, H2O, etc.) to useful liquid fuels. This project addresses these goals by examining fundamental aspects of catalyst design to ultimately access small molecule activation processes under mild conditions. Specifically, Thomas and coworkers have targetted heterobimetallic complexes that feature metal centers with vastly different electronic properties, dictated both by their respective positions on the periodic table and their coordination environment. Unlike homobimetallic complexes featuring identical or similar metals, the bonds between metals in early/late heterobimetallics are more polarized, with the more electron-rich late metal center donating electron density to the more electron-deficient early metal center. While metal-metal bonds pose an interesting strategy for storing redox equivalents and stabilizing reactive metal fragments, the polar character of metal-metal bonds in heterobimetallic complexes renders these molecules ideally poised to react with small molecule substrates via cleavage of energy-rich single and double bonds. In addition, metal-metal interactions have been shown to dramatically affect redox potentials and promote multielectron redox activity, suggesting that metal-metal interactions may provide a mechanism to tune redox potentials and access substrate reduction/activation at mild overpotentials. This research project has provided a better fundamental understanding of how interactions between transition metals can be used as a strategy to promote and/or control chemical transformations related to the clean production of fuels. While this project focused on the study of homogeneous systems, it is anticipated that the broad conclusions drawn from these investigations will be applicable to heterogeneous catalysis as well, particularly on heterogeneous processes that occur at interfaces in

  11. Deletions linked to TP53 loss drive cancer through p53–independent mechanisms

    PubMed Central

    Xu, Zhengmin; Scuoppo, Claudio; Rillahan, Cory D.; Gao, Jianjiong; Spitzer, Barbara; Bosbach, Benedikt; Kastenhuber, Edward R.; Baslan, Timour; Ackermann, Sarah; Cheng, Lihua; Wang, Qingguo; Niu, Ting; Schultz, Nikolaus; Levine, Ross L.; Mills, Alea A.; Lowe, Scott W.

    2016-01-01

    Mutations disabling the TP53 tumour suppressor gene represent the most frequent events in human cancer and typically occur through a two-hit mechanism involving a missense mutation in one allele and a ‘loss of heterozygosity’ deletion encompassing the other. While TP53 missense mutations can also contribute gain-of-function activities that impact tumour progression, it remains unclear whether the deletion event, which frequently includes many genes, impacts tumorigenesis beyond TP53 loss alone. Here we show that somatic heterozygous deletion of mouse chromosome 11B3, a 4-megabase region syntenic to human 17p13.1, produces a greater effect on lymphoma and leukaemia development than Trp53 deletion. Mechanistically, the effect of 11B3 loss on tumorigenesis involves co-deleted genes such as Eif5a and Alox15b (also known as Alox8), the suppression of which cooperates with Trp53 loss to produce more aggressive disease. Our results imply that the selective advantage produced by human chromosome 17p deletion reflects the combined impact of TP53 loss and the reduced dosage of linked tumour suppressor genes. PMID:26982726

  12. ATRX ADD domain links an atypical histone methylation recognition mechanism to human mental-retardation syndrome

    SciTech Connect

    Iwase, Shigeki; Xiang, Bin; Ghosh, Sharmistha; Ren, Ting; Lewis, Peter W.; Cochrane, Jesse C.; Allis, C. David; Picketts, David J.; Patel, Dinshaw J.; Li, Haitao; Shi, Yang

    2011-07-19

    ATR-X (alpha-thalassemia/mental retardation, X-linked) syndrome is a human congenital disorder that causes severe intellectual disabilities. Mutations in the ATRX gene, which encodes an ATP-dependent chromatin-remodeler, are responsible for the syndrome. Approximately 50% of the missense mutations in affected persons are clustered in a cysteine-rich domain termed ADD (ATRX-DNMT3-DNMT3L, ADD{sub ATRX}), whose function has remained elusive. Here we identify ADD{sub ATRX} as a previously unknown histone H3-binding module, whose binding is promoted by lysine 9 trimethylation (H3K9me3) but inhibited by lysine 4 trimethylation (H3K4me3). The cocrystal structure of ADD{sub ATRX} bound to H3{sub 1-15}K9me3 peptide reveals an atypical composite H3K9me3-binding pocket, which is distinct from the conventional trimethyllysine-binding aromatic cage. Notably, H3K9me3-pocket mutants and ATR-X syndrome mutants are defective in both H3K9me3 binding and localization at pericentromeric heterochromatin; thus, we have discovered a unique histone-recognition mechanism underlying the ATR-X etiology.

  13. ATRX ADD Domain Links an Atypical Histone Methylation Recognition Mechanism to Human Mental-Retardation Syndrome

    SciTech Connect

    S Iwase; B Xiang; S Ghosh; T Ren; P Lewis; J Cochrane; C Allis; D Picketts; D Patel; et al.

    2011-12-31

    ATR-X (alpha-thalassemia/mental retardation, X-linked) syndrome is a human congenital disorder that causes severe intellectual disabilities. Mutations in the ATRX gene, which encodes an ATP-dependent chromatin-remodeler, are responsible for the syndrome. Approximately 50% of the missense mutations in affected persons are clustered in a cysteine-rich domain termed ADD (ATRX-DNMT3-DNMT3L, ADD{sub ATRX}), whose function has remained elusive. Here we identify ADD{sub ATRX} as a previously unknown histone H3-binding module, whose binding is promoted by lysine 9 trimethylation (H3K9me3) but inhibited by lysine 4 trimethylation (H3K4me3). The cocrystal structure of ADD{sub ATRX} bound to H3{sub 1-15}K9me3 peptide reveals an atypical composite H3K9me3-binding pocket, which is distinct from the conventional trimethyllysine-binding aromatic cage. Notably, H3K9me3-pocket mutants and ATR-X syndrome mutants are defective in both H3K9me3 binding and localization at pericentromeric heterochromatin; thus, we have discovered a unique histone-recognition mechanism underlying the ATR-X etiology.

  14. Macromolecular Transport between the Nucleus and the Cytoplasm: Advances in Mechanism and Emerging Links to Disease

    PubMed Central

    Tran, Elizabeth J.; King, Megan C.; Corbett, Anita H.

    2014-01-01

    Transport of macromolecules between the cytoplasm and the nucleus is critical for the function of all eukaryotic cells. Large macromolecular channels termed nuclear pore complexes that span the nuclear envelope mediate the bidirectional transport of cargoes between the nucleus and cytoplasm. However, the influence of macromolecular trafficking extends past the nuclear pore complex to transcription and RNA processing within the nucleus and signaling pathways that reach into the cytoplasm and beyond. At the Mechanisms of Nuclear Transport biennial meeting held from October 18-23, 2013 in Woods Hole, MA, researchers in the field met to report on their recent findings. The work presented highlighted significant advances in understanding nucleocytoplasmic trafficking including how transport receptors and cargoes pass through the nuclear pore complex, the many signaling pathways that impinge on transport pathways, interplay between the nuclear envelope, nuclear pore complexes, and transport pathways, and numerous links between transport pathways and human disease. The goal of this review is to highlight newly emerging themes in nuclear transport and underscore the major questions that are likely to be the focus of future research in the field. PMID:25116306

  15. Deletions linked to TP53 loss drive cancer through p53-independent mechanisms.

    PubMed

    Liu, Yu; Chen, Chong; Xu, Zhengmin; Scuoppo, Claudio; Rillahan, Cory D; Gao, Jianjiong; Spitzer, Barbara; Bosbach, Benedikt; Kastenhuber, Edward R; Baslan, Timour; Ackermann, Sarah; Cheng, Lihua; Wang, Qingguo; Niu, Ting; Schultz, Nikolaus; Levine, Ross L; Mills, Alea A; Lowe, Scott W

    2016-03-24

    Mutations disabling the TP53 tumour suppressor gene represent the most frequent events in human cancer and typically occur through a two-hit mechanism involving a missense mutation in one allele and a 'loss of heterozygosity' deletion encompassing the other. While TP53 missense mutations can also contribute gain-of-function activities that impact tumour progression, it remains unclear whether the deletion event, which frequently includes many genes, impacts tumorigenesis beyond TP53 loss alone. Here we show that somatic heterozygous deletion of mouse chromosome 11B3, a 4-megabase region syntenic to human 17p13.1, produces a greater effect on lymphoma and leukaemia development than Trp53 deletion. Mechanistically, the effect of 11B3 loss on tumorigenesis involves co-deleted genes such as Eif5a and Alox15b (also known as Alox8), the suppression of which cooperates with Trp53 loss to produce more aggressive disease. Our results imply that the selective advantage produced by human chromosome 17p deletion reflects the combined impact of TP53 loss and the reduced dosage of linked tumour suppressor genes. PMID:26982726

  16. Nuclear reorganisation and chromatin decondensation are conserved, but distinct, mechanisms linked to Hox gene activation.

    PubMed

    Morey, Céline; Da Silva, Nelly R; Perry, Paul; Bickmore, Wendy A

    2007-03-01

    The relocalisation of some genes to positions outside chromosome territories, and the visible decondensation or unfolding of interphase chromatin, are two striking facets of nuclear reorganisation linked to gene activation that have been assumed to be related to each other. Here, in a study of nuclear reorganisation around the Hoxd cluster, we suggest that this may not be the case. Despite its very different genomic environment from Hoxb, Hoxd also loops out from its chromosome territory, and unfolds, upon activation in differentiating embryonic stem (ES) cells and in the tailbud of the embryo. However, looping out and decondensation are not simply two different manifestations of the same underlying change in chromatin structure. We show that, in the limb bud of the embryonic day 9.5 embryo, where Hoxd is also activated, there is visible decondensation of chromatin but no detectable movement of the region out from the chromosome territory. During ES cell differentiation, decondensed alleles can also be found inside of chromosome territories, and loci that have looped out of the territories can appear to still be condensed. We conclude that evolutionarily conserved chromosome remodelling mechanisms, predating the duplication of mammalian Hox loci, underlie Hox regulation along the rostrocaudal embryonic axis. However, we suggest that separate modes of regulation can modify Hoxd chromatin in different ways in different developmental contexts. PMID:17251268

  17. Molecular Mechanisms of Vascular Calcification in Chronic Kidney Disease: The Link between Bone and the Vasculature

    PubMed Central

    Byon, Chang Hyun

    2015-01-01

    Vascular calcification is highly prevalent in patients with chronic kidney disease (CKD) and increases mortality in those patients. Impaired calcium and phosphate homeostasis, increased oxidative stress, and loss of calcification inhibitors have been linked to vascular calcification in CKD. Additionally, impaired bone may perturb serum calcium/phosphate and their key regulator, parathyroid hormone, thus contributing to increased vascular calcification in CKD. Therapeutic approaches for CKD, such as phosphate binders and bisphosphonates, have been shown to ameliorate bone loss as well as vascular calcification. The precise mechanisms responsible for vascular calcification in CKD and the contribution of bone metabolism to vascular calcification have not been elucidated. This review discusses the role of systemic uremic factors and impaired bone metabolism in the pathogenesis of vascular calcification in CKD. The regulation of the key osteogenic transcription factor Runt-related transcription factor 2 (Runx2) and the emerging role of Runx2-dependent receptor activator of nuclear factor kappa-B ligand (RANKL) in vascular calcification of CKD are emphasized. PMID:25947259

  18. Classifying compound mechanism of action for linking whole cell phenotypes to molecular targets

    PubMed Central

    Bourne, Christina R.; Wakeham, Nancy; Bunce, Richard A.; Berlin, K. Darrell; Barrow, William W.

    2013-01-01

    Drug development programs have proven successful when performed at a whole cell level, thus incorporating solubility and permeability into the primary screen. However, linking those results to the target within the cell has been a major set-back. The Phenotype Microarray system, marketed and sold by Biolog, seeks to address this need by assessing the phenotype in combination with a variety of chemicals with known mechanism of action (MOA). We have evaluated this system for usefulness in deducing the MOA for three test compounds. To achieve this, we constructed a database with 21 known antimicrobials, which served as a comparison for grouping our unknown MOA compounds. Pearson correlation and Ward linkage calculations were used to generate a dendrogram that produced clustering largely by known MOA, although there were exceptions. Of the three unknown compounds, one was definitively placed as an anti-folate. The second and third compounds’ MOA were not clearly identified, likely due to unique MOA not represented within the commercial database. The availability of the database generated in this report for S. aureus ATCC 29213 will increase the accessibility of this technique to other investigators. From our analysis, the Phenotype Microarray system can group compounds with clear MOA, but distinction of unique or broadly acting MOA at this time is less clear. PMID:22434711

  19. Positive extreme responding after cognitive therapy for depression: Correlates and potential mechanisms.

    PubMed

    Forand, Nicholas R; Strunk, Daniel R; DeRubeis, Robert J

    2016-08-01

    "Extreme responding" is the tendency to endorse extreme responses on self-report measures (e.g., 1s and 7s on a 7-point scale). It has been linked to depressive relapse after cognitive therapy (CT), but the mechanisms are unknown. Moreover, findings of positive extreme responding (PER) predicting depressive relapse do not support the original hypothesis of "extreme" negative thinking leading to extreme negative emotional reactions. We assessed the relationships between post-treatment PER on the Dysfunctional Attitudes Scale (DAS) and Attributional Style Questionnaire (ASQ) and these constructs: coping skills, in-session performance of cognitive therapy skills, age, and estimated IQ. Significant correlates were entered into a model predicting rate of relapse to determine whether these constructs explained the relationship between PER and relapse. The sample consisted of 60 individuals who participated in CT for moderate to severe depression. Results indicated the following relationships: a negative correlation between ASQ PER and IQ, negative correlations between DAS PER and performance of CT skills and planning coping, and a positive correlation between DAS PER and behavioral disengagement coping. IQ scores fully accounted for the relationship between ASQ PER and relapse. These results suggest two potential mechanisms linking PER to relapse: cognitive limitations and coping deficits/cognitive avoidance. PMID:27236074

  20. Motivation by potential gains and losses affects control processes via different mechanisms in the attentional network.

    PubMed

    Paschke, Lena M; Walter, Henrik; Steimke, Rosa; Ludwig, Vera U; Gaschler, Robert; Schubert, Torsten; Stelzel, Christine

    2015-05-01

    Attentional control in demanding cognitive tasks can be improved by manipulating the motivational state. Motivation to obtain gains and motivation to avoid losses both usually result in faster reaction times and stronger activation in relevant brain areas such as the prefrontal cortex, but little is known about differences in the underlying neurocognitive mechanisms of these types of motivation in an attentional control context. In the present functional magnetic resonance imaging (fMRI) study, we tested whether potential gain and loss as motivating incentives lead to overlapping or distinct neural effects in the attentional network, and whether one of these conditions is more effective than the other. A Flanker task with word stimuli as targets and distracters was performed by 115 healthy participants. Using a mixed blocked and event-related design allowed us to investigate transient and sustained motivation-related effects. Participants could either gain money (potential gain) or avoid losing money (potential loss) in different task blocks. Participants showed a congruency effect with increased reaction times for incongruent compared to congruent trials. Potential gain led to generally faster responses compared to the neutral condition and to stronger improvements than potential loss. Potential loss also led to shorter response times compared to the neutral condition, but participants improved mainly during incongruent and not during congruent trials. The event-related fMRI data revealed a main effect of congruency with increased activity in the left inferior frontal gyrus (IFG) and inferior frontal junction area (IFJ), the pre-supplementary motor area (pre-SMA), bilateral insula, intraparietal sulcus (IPS) and visual word form area (VWFA). While potential gain led to increased activity in a cluster of the IFJ and the VWFA only during incongruent trials, potential loss was linked to activity increases in these regions during incongruent and congruent trials. The

  1. Mechanical properties and potential commercial applications of agricultural composites

    SciTech Connect

    Asadi, M.; Farokhi, S.; McCabe, S.L.

    1995-11-01

    This paper reveals information on the mechanical properties of the agricultural composites and their commercial potential as a substitute for plastics and woods leading to a lower cost for these products. Chopped and particulate agricultural co-products (hereafter referred to agro-fibers) such as wheat, brome hay, switchgrass, and corn were mixed at a ratio of 66:34 fiber/epoxy by volume to manufacture agricultural composites (hereafter referred to agrocomposites) using the hand lay-up molding technique. The manufactured composite samples were tested for their mechanical properties such as tensile stress, compressive stress, moisture absorption, and thermal expansion. According to results, chopped switchgrass agro-composite samples showed the highest tensile strength, yet less than that of soft woods and slightly higher than that of plastics (high density polyethylene known as HDPE). As a result, a second set of agro-composite samples using only chopped switchgrass was manufactured at 10%, 20%, 30%, 40%, and 50% agro-fiber content to obtain the optimal fiber/epoxy ratio for which agro-composite samples show the maximum tensile stress. The same procedure was followed for comprehensive strength, thermal expansion, and moisture absorption measurements. According to the obtained results, at 50:50, agro-composite samples showed the highest tensile stress at 2,925 psi compared to that of plastic at 2,000 psi and of soft wood at 6,600 psi. At 10:90 agro-fiber/epoxy, compressive strength of the agro-composite samples were 60% higher than that of plastic and 80% higher than that of soft woods. Thermal expansion and moisture absorption of the manufactured agro-composite samples showed better performances than both woods and plastics. Optimized agro-composite samples, due to their cost competitiveness and low weight, could replace woods and plastics in some applications. A small fraction of plastic and wood market wood lead to new source of revenues for farmers.

  2. Actin cross-link assembly and disassembly mechanics for alpha-Actinin and fascin.

    PubMed

    Courson, David S; Rock, Ronald S

    2010-08-20

    Self-assembly of complex structures is commonplace in biology but often poorly understood. In the case of the actin cytoskeleton, a great deal is known about the components that include higher order structures, such as lamellar meshes, filopodial bundles, and stress fibers. Each of these cytoskeletal structures contains actin filaments and cross-linking proteins, but the role of cross-linking proteins in the initial steps of structure formation has not been clearly elucidated. We employ an optical trapping assay to investigate the behaviors of two actin cross-linking proteins, fascin and alpha-actinin, during the first steps of structure assembly. Here, we show that these proteins have distinct binding characteristics that cause them to recognize and cross-link filaments that are arranged with specific geometries. alpha-Actinin is a promiscuous cross-linker, linking filaments over all angles. It retains this flexibility after cross-links are formed, maintaining a connection even when the link is rotated. Conversely, fascin is extremely selective, only cross-linking filaments in a parallel orientation. Surprisingly, bundles formed by either protein are extremely stable, persisting for over 0.5 h in a continuous wash. However, using fluorescence recovery after photobleaching and fluorescence decay experiments, we find that the stable fascin population can be rapidly competed away by free fascin. We present a simple avidity model for this cross-link dissociation behavior. Together, these results place constraints on how cytoskeletal structures assemble, organize, and disassemble in vivo. PMID:20551315

  3. Innate inflammatory responses in stroke: mechanisms and potential therapeutic targets

    PubMed Central

    Kim, Jong Youl; Kawabori, Masahito; Yenari, Midori A.

    2014-01-01

    Stroke is a frequent cause of long-term disability and death worldwide. Ischemic stroke is more commonly encountered compared to hemorrhagic stroke, and leads to tissue death by ischemia due to occlusion of a cerebral artery. Inflammation is known to result as a result of ischemic injury, long thought to be involved in initiating the recovery and repair process. However, work over the past few decades indicates that aspects of this inflammatory response may in fact be detrimental to stroke outcome. Acutely, inflammation appears to have a detrimental effect, and anti-inflammatory treatments have been been studied as a potential therapeutic target. Chronically, reports suggest that post-ischemic inflammation is also essential for the tissue repairing and remodeling. The majority of the work in this area has centered around innate immune mechanisms, which will be the focus of this review. This review describes the different key players in neuroinflammation and their possible detrimental and protective effects in stroke. A better understanding of the roles of the different immune cells and their temporal profile of damage versus repair will help to clarify more effective modulation of inflammation post stroke. Introduction Stroke refers to conditions caused by occlusion and/or rupture of blood vessels in the brain, and is a leading cause of death and disability in the industrialized world. PMID:24372209

  4. Potential mechanisms of hepatitis B virus induced liver injury.

    PubMed

    Suhail, Mohd; Abdel-Hafiz, Hany; Ali, Ashraf; Fatima, Kaneez; Damanhouri, Ghazi A; Azhar, Esam; Chaudhary, Adeel Ga; Qadri, Ishtiaq

    2014-09-21

    Chronic active hepatitis (CAH) is acknowledged as an imperative risk factor for the development of liver injury and hepatocellular carcinoma. The histological end points of CAH are chronic inflammation, fibrosis and cirrhosis which are coupled with increased DNA synthesis in cirrhotic vs healthy normal livers. The potential mechanism involved in CAH includes a combination of processes leading to liver cell necrosis, inflammation and cytokine production and liver scaring (fibrosis). The severity of liver damage is regulated by Hepatitis B virus genotypes and viral components. The viral and cellular factors that contribute to liver injury are discussed in this article. Liver injury caused by the viral infection affects many cellular processes such as cell signaling, apoptosis, transcription, DNA repair which in turn induce radical effects on cell survival, growth, transformation and maintenance. The consequence of such perturbations is resulted in the alteration of bile secretion, gluconeogenesis, glycolysis, detoxification and metabolism of carbohydrates, proteins, fat and balance of nutrients. The identification and elucidation of the molecular pathways perturbed by the viral proteins are important in order to design effective strategy to minimize and/or restore the hepatocytes injury. PMID:25253946

  5. Potential mechanisms of hepatitis B virus induced liver injury

    PubMed Central

    Suhail, Mohd; Abdel-Hafiz, Hany; Ali, Ashraf; Fatima, Kaneez; Damanhouri, Ghazi A; Azhar, Esam; Chaudhary, Adeel GA; Qadri, Ishtiaq

    2014-01-01

    Chronic active hepatitis (CAH) is acknowledged as an imperative risk factor for the development of liver injury and hepatocellular carcinoma. The histological end points of CAH are chronic inflammation, fibrosis and cirrhosis which are coupled with increased DNA synthesis in cirrhotic vs healthy normal livers. The potential mechanism involved in CAH includes a combination of processes leading to liver cell necrosis, inflammation and cytokine production and liver scaring (fibrosis). The severity of liver damage is regulated by Hepatitis B virus genotypes and viral components. The viral and cellular factors that contribute to liver injury are discussed in this article. Liver injury caused by the viral infection affects many cellular processes such as cell signaling, apoptosis, transcription, DNA repair which in turn induce radical effects on cell survival, growth, transformation and maintenance. The consequence of such perturbations is resulted in the alteration of bile secretion, gluconeogenesis, glycolysis, detoxification and metabolism of carbohydrates, proteins, fat and balance of nutrients. The identification and elucidation of the molecular pathways perturbed by the viral proteins are important in order to design effective strategy to minimize and/or restore the hepatocytes injury. PMID:25253946

  6. Aldehydes: occurrence, carcinogenic potential, mechanism of action and risk assessment.

    PubMed

    Feron, V J; Til, H P; de Vrijer, F; Woutersen, R A; Cassee, F R; van Bladeren, P J

    1991-01-01

    Aldehydes constitute a group of relatively reactive organic compounds. They occur as natural (flavoring) constituents in a wide variety of foods and food components, often in relatively small, but occasionally in very large concentrations, and are also widely used as food additives. Evidence of carcinogenic potential in experimental animals is convincing for formaldehyde and acetaldehyde, limited for crotonaldehyde, furfural and glycidaldehyde, doubtful for malondialdehyde, very weak for acrolein and absent for vanillin. Formaldehyde carcinogenesis is a high-dose phenomenon in which the cytotoxicity plays a crucial role. Cytotoxicity may also be of major importance in acetaldehyde carcinogenesis but further studies are needed to prove or disprove this assumption. For a large number of aldehydes (relevant) data on neither carcinogenicity nor genotoxicity are available. From epidemiological studies there is no convincing evidence of aldehyde exposure being related to cancer in humans. Overall assessment of the cancer risk of aldehydes in the diet leads to the conclusion that formaldehyde, acrolein, citral and vanillin are no dietary risk factors, and that the opposite may be true for acetaldehyde, crotonaldehyde and furfural. Malondialdehyde, glycidaldehyde, benzaldehyde, cinnamaldehyde and anisaldehyde cannot be evaluated on the basis of the available data. A series of aldehydes should be subjected to at least mutagenicity, cytogenicity and cytotoxicity tests. Priority setting for testing should be based on expected mechanism of action and degree of human exposure. PMID:2017217

  7. Calcium signalling in pancreatic stellate cells: Mechanisms and potential roles.

    PubMed

    Gryshchenko, Oleksiy; Gerasimenko, Julia V; Gerasimenko, Oleg V; Petersen, Ole H

    2016-03-01

    Hepatic and pancreatic stellate cells may or may not be regarded as stem cells, but they are capable of remarkable transformations. There is less information about stellate cells in the pancreas than in the liver, where they were discovered much earlier and therefore have been studied longer and more intensively than in the pancreas. Most of the work on pancreatic stellate cells has been carried out in studies on cell cultures, but in this review we focus attention on Ca(2+) signalling in stellate cells in their real pancreatic environment. We review current knowledge on patho-physiologically relevant Ca(2+) signalling events and their underlying mechanisms. We focus on the effects of bradykinin in the initial stages of acute pancreatitis, an often fatal disease in which the pancreas digests itself and its surroundings. Ca(2+) signals, elicited in the stellate cells by the action of bradykinin, may have a negative effect on the outcome of the acute disease process and promote the development of chronic pancreatitis. The bradykinin-elicited Ca(2+) signals can be inhibited by blockade of type 2 receptors and also by blockade of Ca(2+)-release activated Ca(2+) channels. The potential benefits of such pharmacological inhibition for the treatment of pancreatitis are reviewed. PMID:26960936

  8. Building Student Networks with LinkedIn: The Potential for Connections, Internships, and Jobs

    ERIC Educational Resources Information Center

    Peterson, Robert M.; Dover, Howard F.

    2014-01-01

    Networking is a chance to interact with people, build friendships or business partners, identify opportunities, and create value. Technology has made this process easier, since individuals can readily contact others who were previously unknown. In the professional world, LinkedIn has become the standard way to build virtual and personal networks.…

  9. The effect of cross linking density on the mechanical properties and structure of the epoxy polymers: molecular dynamics simulation.

    PubMed

    Shokuhfar, Ali; Arab, Behrouz

    2013-09-01

    Recently, great attention has been focused on using epoxy polymers in different fields such as aerospace, automotive, biotechnology, and electronics, owing to their superior properties. In this study, the classical molecular dynamics (MD) was used to simulate the cross linking of diglycidyl ether of bisphenol-A (DGEBA) with diethylenetriamine (DETA) curing agent, and to study the behavior of resulted epoxy polymer with different conversion rates. The constant-strain (static) approach was then applied to calculate the mechanical properties (Bulk, shear and Young's moduli, elastic stiffness constants, and Poisson's ratio) of the uncured and cross-linked systems. Estimated material properties were found to be in good agreement with experimental observations. Moreover, the dependency of mechanical properties on the cross linking density was investigated and revealed improvements in the mechanical properties with increasing the cross linking density. The radial distribution function (RDF) was also used to study the evolution of local structures of the simulated systems as a function of cross linking density. PMID:23793720

  10. “Young at heart”: Regenerative potential linked to immature cardiac phenotypes

    PubMed Central

    Gomes, Renata S.M.; Skroblin, Philipp; Munster, Alex B.; Tomlins, Hannah; Langley, Sarah R.; Zampetaki, Anna; Yin, Xiaoke; Wardle, Fiona C.; Mayr, Manuel

    2016-01-01

    The adult human myocardium is incapable of regeneration; yet, the zebrafish (Danio rerio) can regenerate damaged myocardium. Similar to the zebrafish heart, hearts of neonatal, but not adult mice are capable of myocardial regeneration. We performed a proteomics analysis of adult zebrafish hearts and compared their protein expression profile to hearts from neonatal and adult mice. Using difference in-gel electrophoresis (DIGE), there was little overlap between the proteome from adult mouse (> 8 weeks old) and adult zebrafish (18 months old) hearts. Similarly, there was a significant degree of mismatch between the protein expression in neonatal and adult mouse hearts. Enrichment analysis of the selected proteins revealed over-expression of DNA synthesis-related proteins in the cardiac proteome of the adult zebrafish heart similar to neonatal and 4 days old mice, whereas in hearts of adult mice there was a mitochondria-related predominance in protein expression. Importantly, we noted pronounced differences in the myofilament composition: the adult zebrafish heart lacks many of the myofilament proteins of differentiated adult cardiomyocytes such as the ventricular isoforms of myosin light chains and nebulette. Instead, troponin I and myozenin 1 were expressed as skeletal isoforms rather than cardiac isoforms. The relative immaturity of the adult zebrafish heart was further supported by cardiac microRNA data. Our assessment of zebrafish and mammalian hearts challenges the assertions on the translational potential of cardiac regeneration in the zebrafish model. The immature myofilament composition of the fish heart may explain why adult mouse and human cardiomyocytes lack this endogenous repair mechanism. PMID:26827899

  11. Functional consequences of prolactin signalling in endothelial cells: a potential link with angiogenesis in pathophysiology?

    PubMed Central

    Reuwer, Anne Q; Nowak-Sliwinska, Patrycja; Mans, Laurie A; van der Loos, Chris M; von der Thüsen, Jan H; Twickler, Marcel Th B; Spek, C Arnold; Goffin, Vincent; Griffioen, Arjan W; Borensztajn, Keren S

    2012-01-01

    Prolactin is best known as the polypeptide anterior pituitary hormone, which regulates the development of the mammary gland. However, it became clear over the last decade that prolactin contributes to a broad range of pathologies, including breast cancer. Prolactin is also involved in angiogenesis via the release of pro-angiogenic factors by leukocytes and epithelial cells. However, whether prolactin also influences endothelial cells, and whether there are functional consequences of prolactin-induced signalling in the perspective of angiogenesis, remains so far elusive. In the present study, we show that prolactin induces phosphorylation of ERK1/2 and STAT5 and induces tube formation of endothelial cells on Matrigel. These effects are blocked by a specific prolactin receptor antagonist, del1-9-G129R-hPRL. Moreover, in an in vivo model of the chorioallantoic membrane of the chicken embryo, prolactin enhances vessel density and the tortuosity of the vasculature and pillar formation, which are hallmarks of intussusceptive angiogenesis. Interestingly, while prolactin has only little effect on endothelial cell proliferation, it markedly stimulates endothelial cell migration. Again, migration was reverted by del1-9-G129R-hPRL, indicating a direct effect of prolactin on its receptor. Immunohistochemistry and spectral imaging revealed that the prolactin receptor is present in the microvasculature of human breast carcinoma tissue. Altogether, these results suggest that prolactin may directly stimulate angiogenesis, which could be one of the mechanisms by which prolactin contributes to breast cancer progression, thereby providing a potential tool for intervention. PMID:22128761

  12. Galectin-3 enhances angiogenic and migratory potential of microglial cells via modulation of integrin linked kinase signaling

    PubMed Central

    Wesley, Umadevi V.; Vemuganti, Raghu; Ayvaci, Rabia; Dempsey, Robert J.

    2013-01-01

    Focal cerebral ischemia initiates self-repair mechanisms that include the production of neurotrophic factors and cytokines. Galectin-3 is an important angiogenic cytokine. We have previously demonstrated that expression of galectin 3 (Gal-3), a carbohydrate binding protein is significantly upregulated in activated microglia in the brains of rats subjected to focal ischemia. Further blocking of Gal-3 function with Gal-3 neutralizing antibody decreased the microvessel density in ischemic brain. We currently show that Gal-3 significantly increases the viability of microglia BV2 cells subjected to oxygen glucose deprivation (OGD) and re-oxygenation. Exogenous Gal-3 promoted the formation of pro-angiogenic structures in an in vitro human umbilical vein endothelial (HUVEC) and BV2 cell co-culture model. Gal-3 induced angiogenesis was associated with increased expression of vascular endothelial growth factor. The conditioned medium of BV2 cells exposed to OGD contained increased Gal-3 levels, and promoted the formation of pro-angiogenic structures in an in vitro HUVEC culture model. Gal-3 also augmented the in vitro migratory potential of BV2 microglia. Gal-3 mediated functions were associated with increased levels of integrin-linked kinase (ILK) signaling as demonstrated by the impaired angiogenesis and migration of BV2 cells following targeted silencing of ILK expression by SiRNA. Furthermore, we show that ILK levels correlate with the levels of phos-AKT and ERK1/2 that are downstream effectors of ILK pathway. Taken together, our studies indicate that Gal-3 contributes to angiogenesis and microglia migration that may have implications in post stroke repair. PMID:23246924

  13. Parenting practices as potential mechanisms for child adjustment following mass trauma.

    PubMed

    Gewirtz, Abigail; Forgatch, Marion; Wieling, Elizabeth

    2008-04-01

    Trauma research has identified a link between parental adjustment and children's functioning and the sometimes ensuing intergenerational impact of traumatic events. The effects of traumatic events on children have been demonstrated to be mediated through their impact on children's parents. However, until now, little consideration has been given to the separate and more proximal mechanism of parenting practices as potential mediators between children's adjustment and traumatic events. To shed some light in this arena, we review literature on trauma, adversity, and resilience, and discuss how parenting practices may mediate trauma and adverse environmental contexts. Using a social interaction learning perspective (Forgatch & Knutson, 2002; Patterson, 2005), we propose a prevention research framework to examine the role that parenting practices may play in influencing children's adjustment in the wake of trauma exposure. The article concludes by providing a specific model and role for evidence-based parenting interventions for children exposed to mass trauma. PMID:18412825

  14. Smoking and increased Alzheimer’s disease risk: A review of potential mechanisms

    PubMed Central

    Durazzo, Timothy C.; Mattsson, Niklas; Weiner, Michael W.

    2014-01-01

    Background Cigarette smoking has been linked with both increased and decreased risk for Alzheimer’s disease (AD). This is relevant for the US military because the prevalence of smoking in the military is approximately 11% higher than in civilians. Methods Systematic review of published studies on the association between smoking and increased risk for AD, and preclinical and human literature on the relationships between smoking, nicotine exposure and AD-related neuropathology. Original data from comparisons of smoking and never-smoking cognitively normal elders on in vivo amyloid imaging are also presented. Results Overall, the literature indicates that former/active smoking is related to a significantly increased risk for AD. Cigarette smoke/smoking is associated with AD neuropathology in preclinical models and humans. Smoking-related cerebral oxidative stress is a potential mechanism promoting AD pathophysiology and increased risk for AD. Conclusions A reduction in the incidence of smoking will likely reduce the future prevalence of AD. PMID:24924665

  15. Mechanisms That Link Parenting Practices to Adolescents' Risky Sexual Behavior: A Test of Six Competing Theories.

    PubMed

    Simons, Leslie Gordon; Sutton, Tara E; Simons, Ronald L; Gibbons, Frederick X; Murry, Velma McBride

    2016-02-01

    Risky sexual behavior, particularly among adolescents, continues to be a major source of concern. In order to develop effective education and prevention programs, there is a need for research that identifies the antecedents of such behavior. This study investigated the mediators that link parenting experiences during early adolescence to subsequent risky sexual behaviors among a diverse sample of African American youth (N = 629, 55 % female). While there is ample evidence that parenting practices (e.g., supportive parenting, harsh parenting, parental management) are antecedent to risky sexual behavior, few studies have examined whether one approach to parenting is more strongly related to risky sex than others. Using a developmental approach, the current study focused on factors associated with six theories of risky sexual behavior. While past research has provided support for all of the theories, few studies have assessed the relative contribution of each while controlling for the processes proposed by the others. The current study addresses these gaps in the literature and reports results separately by gender. Longitudinal analyses using structural equation modeling revealed that the mediating mechanisms associated with social learning and attachment theories were significantly related to the risky sexual behavior of males and females. Additionally, there was support for social control and self-control theories only for females and for life history theory only for males. We did not find support for problem behavior theory, a perspective that dominates the risky sex literature, after controlling for the factors associated with the other theories. Finally, supportive parenting emerged as the parenting behavior most influential with regard to adolescents' risky sexual behavior. These results provide insight regarding efficacious approaches to education and preventative programs designed to reduce risky sexual behaviors among adolescents. PMID:26718543

  16. Family Socioeconomic Status and Academic Achievement among Korean Adolescents: Linking Mechanisms of Family Processes and Adolescents' Time Use

    ERIC Educational Resources Information Center

    Bae, Dayoung; Wickrama, K. A. S.

    2015-01-01

    This study examined pathways through which family socioeconomic status may influence adolescents' academic achievement. We focused on parental monitoring and adolescents' after-school time-use patterns as linking mechanisms. Participants were 441 twelve- to fourteen-year-old Korean adolescents who participated in the Korea Welfare Panel Study.…

  17. Compulsive Eating: The Emotional Link of Its Use as a Coping Mechanism for Resident Freshman Female College Students.

    ERIC Educational Resources Information Center

    Beylerian, Nvair Kadian

    An 18-year old's freshman year in college is not only a test of his or her intellect, but also a test in social skills, adaptability to new living situations, and other conditions. This study examined the link of emotions to compulsive eating and its use as a coping mechanism for female college students. It explores the stresses of the transition…

  18. Androgen dependence in hamsters: overdose, tolerance, and potential opioidergic mechanisms.

    PubMed

    Peters, K D; Wood, R I

    2005-01-01

    Anabolic steroids are drugs of abuse. However, the potential for steroid reward and addiction remains largely unexplored. This study used i.c.v. testosterone self-administration and controlled infusions of testosterone or vehicle in hamsters to explore central mechanisms of androgen overdose. Forty-two hamsters used nose-pokes to self-administer 1 microg/microl testosterone i.c.v. 4 h/day in an operant chamber. During 1-56 days of androgen self-administration, 10 (24%) hamsters died. Deaths correlated with peak daily intake of testosterone. Of the hamsters that self-administered a peak intake of <20 microg/day, there was 100% survival (10/10). Survival decreased to 86% (19/22) when daily testosterone intake peaked at 20-60 microg/day. Only 30% (three of 10) survived when daily testosterone intake exceeded 60 microg/day. Deaths are not due to volume or vehicle because i.c.v. infusions of 80 mul vehicle had no effect. Testosterone overdose resembles opiate intoxication. When male hamsters received infusions of 40 microg testosterone, locomotion (25.1+/-18.8 grid-crossings/10 min), respiration (72.7+/-5.4 breaths/min) and body temperature (33.5+/-0.4 degrees C) were significantly reduced, compared with males receiving vehicle infusions (186.1+/-8.1 crossings/10 min, 117.6+/-1.0 breaths/min, 35.9+/-0.1 degrees C, P<0.05). However, males developed tolerance to continued daily testosterone infusion. After 15 days, locomotion (170.2+/-6.3 crossings), respiration (118.4+/-1.3 breaths/min), and body temperature (35.3+/-0.3 degrees C) in testosterone-infused males were equivalent to that in vehicle controls (P>0.05). The depressive effects of testosterone infusion are blocked by the opioid antagonist, naltrexone. With naltrexone pre-treatment (10 mg/kg s.c.), locomotion (183.7+/-1.8 crossings/10 min), respiration (116.9+/-0.3 breaths/min), and body temperature (36.1+/-0.4 degrees C) during testosterone infusion were equivalent to vehicle controls. Likewise, naltrexone

  19. Biochar Mechanisms of Heavy Metal Sorption and Potential Utility

    NASA Astrophysics Data System (ADS)

    Ippolito, J.

    2015-12-01

    Mining-affected lands are a global issue; in the USA alone there are an estimated 500,000 abandoned mines encompassing hundreds of thousands of hectares. Many of these sites generate acidic mine drainage that causes release of heavy metals, and subsequently degradation in environmental quality. Because of its potential liming characteristics, biochar may play a pivotal role as a soil amendment in future mine land reclamation. However, to date, most studies have focused on the use of biochar to sorb metals from solution. Previous studies suggest that metals are complexed by biochar surface function groups (leading to ion exchange, complexation), coordination with Pi electrons (C=C) of carbon, and precipitation of inorganic mineral phases. Several recent studies have focused on the use of biochar for amending mine land soils, showing that biochar can indeed reduce heavy metal lability, yet the mechanism(s) behind labile metal reduction have yet to be established. In a proof-of-concept study, we added lodgepole pine, tamarisk, and switchgrass biochar (0, 5, 10, 15% by weight; 500 oC) to four different western US mine land soils affected by various heavy metals (Cd, Cu, Mn, Pb, Zn). Extraction with 0.01M CaCl2 showed that increasing biochar application rate significantly decreased 'bioaccessible' metals in almost all instances. A concomitant increase in solution pH was observed, suggesting that metals may be rendered bio-inaccessible through precipitation as carbonate or (hydr)oxide phases, or sorbed onto mineral surfaces. However, this was only supposition and required further research. Thus, following the 0.01M CaCl2 extraction, biochar-soil mixtures were air-dried and metals were further extracted using the four-step BCR sequential removal procedure. Results from selective extraction suggest that, as compared to the controls, most metals in the biochar-amended mine land soils were associated with exchange sites, carbonate, and oxide phases. Biochar may play a

  20. Corneal Cross-Linking: Evaluating the Potential for a Lower Power, Shorter Duration Treatment

    PubMed Central

    Caruso, Ciro; Barbaro, Gaetano; Tronino, Diana; Ostacolo, Carmine; Sacchi, Antonia; Pacente, Luigi; Del Prete, Antonio; Sala, Marina; Troisi, Salvatore

    2016-01-01

    Purpose: To determine the cross-linking effect of a riboflavin ultraviolet-A (UV-A) corneal cross-linking treatment that is both shorter and has lower energy than the Dresden protocol. Methods: In a first experiment, 12 human corneas were presoaked with riboflavin and then irradiated with UV-A at 3 mW/cm2 after clearing the surface of riboflavin, with no added riboflavin during irradiation. Percent UV-A transmission through the corneas was measured at intervals up to 30 minutes. A second experiment involved 24 porcine corneas. Eight were de-epithelialized, presoaked in riboflavin for 30 minutes, and irradiated at 1.5 mW/cm2 for 10 minutes. An additional 8 were riboflavin treated and similarly irradiated, but with epithelium intact and a final 8 corneas were not treated. Young modulus was measured in all 24 corneas at the end of the experiment. Results: The first experiment showed essentially complete riboflavin oxidation after only 10 minutes. Based on these results, a shortened UV-A exposure cross-linking experiment was designed using a reduced UV-A fluence of 1.5 mW/cm2, an endothelial exposure within safety limits in humans. With this protocol Young modulus was the same in the irradiated porcine corneas but with epithelium intact as in the untreated corneas. In contrast, Young modulus increased by a factor of 1.99 in the UV-A cross-linked corneas at 1.5 mW/cm2 for 10 minutes with the epithelium removed. Conclusions: A shorter, lower energy protocol than the Dresden protocol seems to provide a significant increase in Young modulus, similar to published results with higher energy, longer exposure protocols. PMID:26989958

  1. Fractionation of the β-Linked Glucans of Bradyrhizobium japonicum and Their Response to Osmotic Potential

    PubMed Central

    Tully, Raymond E.; Keister, Donald L.; Gross, Kenneth C.

    1990-01-01

    Bradyrhizobium japonicum USDA 110 synthesized both extracellular and periplasmic polysaccharides when grown on mannitol minimal medium. The extracellular polysaccharides were separated into a high-molecular-weight acidic capsular extracellular polysaccharide fraction (90% of total hexose) and three lower-molecular-weight glucan fractions by liquid chromatography. Periplasmic glucans, extracted from washed cells with 1% trichloroacetic acid, gave a similar pattern on liquid chromatography. Linkage analysis of the major periplasmic glucan fractions demonstrated mainly 6-linked glucose (63 to 68%), along with some 3,6- (8 to 18%), 3- (9 to 11%), and terminal (7 to 8%) linkages. The glucose residues were β-linked as shown by 1H-nuclear magnetic resonance analysis. Glucan synthesis by B. japonicum cells grown on mannitol medium with 0 to 350 mM fructose as osmolyte was measured. Fructose at 150 mM or higher inhibited synthesis of periplasmic and extracellular 3- and 6-linked glucans but had no effect on the synthesis of capsular acidic extracellular polysaccharides. PMID:16348201

  2. Dendritic cells provide a potential link between smoking and inflammation in rheumatoid arthritis

    PubMed Central

    2012-01-01

    Introduction Smoking increases the risk of developing rheumatoid arthritis (RA) and affects the severity of established RA. Smoking can impact on Th17 lymphocyte differentiation and function through activation of the aryl hydrocarbon receptor (AHR), a process with implications for the pathogenic mechanisms in RA that involve the cytokine, interleukin (IL)-17A. The objective of this study was to establish any effect of smoking on the inflammatory tissue lesions of rheumatoid arthritis via the AHR and IL-17A. Methods Twenty synovial and eighteen subcutaneous nodule tissue samples from 31 patients with RA were studied. Patient smoking status at the time of tissue collection was established. Expression of AHR, CYP1A1, AHRR, IL6, IL17A, IL17F, IL22, IL23, IL23R, IFNG, TBX21, IDO1 and FOXP3 genes were assessed in tissues and cultured cells using real-time PCR. Two-colour immunofluorescence was used to co-localise AHR and CYP1A1 protein in synovial tissues. The response of monocytes and monocyte-derived dendritic cells (mo-DCs) to the AHR agonist, benzo(a)pyrene (BaP) was compared in vitro. Results AHR gene expression was demonstrated in rheumatoid synovial tissues and nodules with significantly greater expression in synovia. Expression was not influenced by smoking in either tissue. Evidence of AHR activation, indicated by CYP1A1 and AHRR gene expression, was found only in synovia from patients who smoked. However, IL17A gene expression was lower in synovia from smokers. TBX21 and FOXP3 expression was not affected by smoking. Within the synovial tissues of smokers the principal cell type with evidence of AHR activation was a subset of synovial DCs. This observation was consistent with the sensitivity of human mo-DCs to BaP stimulation demonstrated in vitro. Exposure to BaP affected mo-DC function as demonstrated by decreased IL6 expression induced by PolyI:C, without affecting indoleamine 2,3 dioxygenase (IDO)1 expression. Conclusion Our findings show that one effect of

  3. Quantum mechanics of graphene with a one-dimensional potential

    SciTech Connect

    Miserev, D. S.; Entin, M. V.

    2012-10-15

    Electron states in graphene with a one-dimensional potential have been studied. An approximate solution has been obtained for a small angle between vectors of the incident electron momentum and potential gradient. Exactly solvable problems with a potential of the smoothened step type U(x) Utanh(x/a) and a potential with a singularity U(x) = -U/(|x| + d) are considered. The transmission/reflection coefficients and phases for various potential barriers are determined. A quasi-classical solution is obtained.

  4. The potentiality of cross-linked fungal chitosan to control water contamination through bioactive filtration.

    PubMed

    Tayel, Ahmed A; El-Tras, Wael F; Elguindy, Nihal M

    2016-07-01

    Water contamination, with heavy metals and microbial pathogens, is among the most dangerous challenges that confront human health worldwide. Chitosan is a bioactive biopolymer that could be produced from fungal mycelia to be utilized in various applied fields. An attempt to apply fungal chitosan for heavy metals chelation and microbial pathogens inhibition, in contaminated water, was performed in current study. Chitosan was produced from the mycelia of Aspergillus niger, Cunninghamella elegans, Mucor rouxii and from shrimp shells, using unified production conditions. The FT-IR spectra of produced chitosans were closely comparable. M. rouxii chitosan had the highest deacetylation degree (91.3%) and the lowest molecular weight (33.2kDa). All chitosan types had potent antibacterial activities against Escherichia coli and Staphylococcus aureus; the most forceful type was C. elegans chitosan. Chitosan beads were cross-linked with glutaraldehyde (GLA) and ethylene-glycol-diglycidyl ether (EGDE); linked beads became insoluble in water, acidic and alkaline solutions and could effectively adsorb heavy metals ions, e.g. copper, lead and zinc, in aqueous solution. The bioactive filter, loaded with EGDE- A. niger chitosan beads, was able to reduce heavy metals' concentration with >68%, and microbial load with >81%, after 6h of continuous water flow in the experimentally designed filter. PMID:26995612

  5. The identification of factors linked to the potential acceptance of transgenic biopharmaceuticals: an exploratory study.

    PubMed

    Duguay, Francois; Katsanis, Lea Prevel; Thakor, Mrugank V

    2003-01-01

    In this exploratory study, Rogers' diffusion of innovation theory was used to identify which factors are likely to contribute to the potential acceptance of transgenic biopharmaceuticals (TG-Bs). These products are not yet available to the general public. A scale was designed to assess three of five core attributes related to the potential adoption rate of innovations (Rogers 1995), as well as to measure potential acceptance characteristics for biotechnology products. These attributes were relative advantage, compatibility with existing values, and complexity. In addition, two other characteristics were included: knowledge (Gartrell and Gartrell 1979) and perceived risks (Bauer 1960). The survey was completed by 74 consumers (78% response rate) using convenience sampling. The research findings show that Rogers' three core attributes are supported, but that knowledge andperceived risks were excluded from the model. The model for transgenic biopharmaceuticals consists of: 1. Consumer-related benefits (positively correlated to potential adoption). 2. New types of animals (negatively correlated to potential 3. Perceived complexity (negatively correlated to potential adoption). All the scaled items developed for this study were highly significant, which indicates that they can be used successfully by other researchers working in this field. As TG-Bs are a discontinuous innovation, biotechnology companies may need to present the benefits of these products, as well as the ease of their use prior to their launch, in order to increase their potential acceptance by consumers. PMID:15271632

  6. The third exactly solvable hypergeometric quantum-mechanical potential

    NASA Astrophysics Data System (ADS)

    Ishkhanyan, Artur

    2016-07-01

    We introduce the third independent exactly solvable hypergeometric potential, after the Eckart and the Pöschl-Teller potentials, which is proportional to an energy-independent parameter and has a shape that is independent of this parameter. The general solution of the Schrödinger equation for this potential is written through fundamental solutions each of which presents an irreducible combination of two Gauss hypergeometric functions. The potential is an asymmetric step-barrier with variable height and steepness. Discussing the transmission above such a barrier, we derive a compact formula for the reflection coefficient.

  7. Potentiated Hsp104 variants suppress toxicity of diverse neurodegenerative disease-linked proteins.

    PubMed

    Jackrel, Meredith E; Shorter, James

    2014-10-01

    Protein misfolding is implicated in numerous lethal neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS) and Parkinson disease (PD). There are no therapies that reverse these protein-misfolding events. We aim to apply Hsp104, a hexameric AAA+ protein from yeast, to target misfolded conformers for reactivation. Hsp104 solubilizes disordered aggregates and amyloid, but has limited activity against human neurodegenerative disease proteins. Thus, we have previously engineered potentiated Hsp104 variants that suppress aggregation, proteotoxicity and restore proper protein localization of ALS and PD proteins in Saccharomyces cerevisiae, and mitigate neurodegeneration in an animal PD model. Here, we establish that potentiated Hsp104 variants possess broad substrate specificity and, in yeast, suppress toxicity and aggregation induced by wild-type TDP-43, FUS and α-synuclein, as well as missense mutant versions of these proteins that cause neurodegenerative disease. Potentiated Hsp104 variants also rescue toxicity and aggregation of TAF15 but not EWSR1, two RNA-binding proteins with a prion-like domain that are connected with the development of ALS and frontotemporal dementia. Thus, potentiated Hsp104 variants are not entirely non-specific. Indeed, they do not unfold just any natively folded protein. Rather, potentiated Hsp104 variants are finely tuned to unfold proteins bearing short unstructured tracts that are not recognized by wild-type Hsp104. Our studies establish the broad utility of potentiated Hsp104 variants. PMID:25062688

  8. Behavioral differences in aggressive children linked with neural mechanisms of emotion regulation.

    PubMed

    Lewis, Marc D; Granic, Isabela; Lamm, Connie

    2006-12-01

    Children with aggressive behavior problems may have difficulties regulating negative emotions, resulting in harmful patterns of interpersonal behavior at home and in the schoolyard. Ventral and dorsal regions of the prefrontal cortex (PFC) have been associated with response inhibition and self-control-key components of emotion regulation. Our research program aims to explore differences among aggressive and normal children in the activation of these cortical regions during emotional episodes, to the extent possible using electrophysiological techniques, to identify diagnostic subtypes, gain insights into their interpersonal difficulties, and help develop effective treatment strategies. This report reviews several recent studies investigating individual and developmental differences in cortical mechanisms of emotion regulation, corresponding with different patterns of interpersonal behavior. Our methods include event-related potentials (ERPs) and cortical source modeling, using dense-array electroencephalography (EEG) technology, as well as videotaped observations of parent-child interactions, with both normal and aggressive children. By relating patterns of brain activation to observed behavioral differences, we find (i) a steady decrease in cortical activation subserving self-regulation across childhood and adolescence, (ii) different cortical activation patterns as well as behavioral constellations distinguishing subtypes of aggressive children, and (iii) robust correlations between the activation of cortical mediators of emotion regulation and flexibility in parent-child emotional communication in children referred for aggressive behavior problems. These findings point toward models of developmental psychopathology based on the interplay among biological, psychological, and social factors. PMID:17347349

  9. The effect of transient proanthocyanidins preconditioning on the cross-linking and mechanical properties of demineralized dentin.

    PubMed

    Liu, Ruirui; Fang, Ming; Xiao, Yuhong; Li, Fang; Yu, Lan; Zhao, Sanjun; Shen, Lijuan; Chen, Jihua

    2011-11-01

    Proanthocyanidin-based preconditioners were prepared by adding powdered proanthocyanidins-rich grape seed extract to various solvents at different concentrations. Demineralized dentin specimens were preconditioned for 20, 30, 60 or 120 s, followed by the evaluation of their cross-linking degree, mechanical properties and micromorphology. The cross-linking degree of the demineralized dentin collagen exhibited concentration- and time- dependent increase after preconditioning treatment, irrespective of the preconditioner and the solvent. When treated for the same exposure time, specimens after 15% proanthocyanidins preconditioning resulted in the highest mean ultimate tensile strength compared with all the other groups tested. Five percent glutaraldehyde control group produced the highest cross-linking degree, but the ultimate tensile strength was lower than that of 15% proanthocyanidins group. The field emission scanning electron microscopy confirmed that the demineralized dentin collagen was in a homogeneous and regular arrangement after preconditioning and maintained expanding, regardless of the surface moisture conditions. PMID:21979164

  10. Investigations into the Mechanisms of Cell Death: The Common Link between Anticancer Nanotherapeutics and Nanotoxicology

    NASA Astrophysics Data System (ADS)

    Minocha, Shalini

    Nanotoxicology and anticancer nanotherapeutics are essentially two sides of the same coin. The nanotoxicology discipline deals with the nanoparticle (NP)-induced toxicity and mechanisms of cell death in healthy cells, whereas anticancer agents delivered via nano-based approaches aim to induce cell death in abnormally proliferating cancer cells. The objectives of the studies presented herein were two-fold; to (a) systematically study the physico-chemical properties and cell death mechanisms of model NPs and (b) utilize the knowledge gained from cell death-nanotoxicity studies in developing a potentially novel anticancer nanotherapeutic agent. For the first objective, the effect of a distinguishing characteristic, i.e., surface carbon coating on the matched pairs of carbon-coated and non-coated copper and nickel NPs (Cu, C-Cu, Ni and C-Ni) on the physico-chemical properties and toxicity in A549 alveolar epithelial cells were evaluated. The effect of carbon coating on particle size, zeta potential, oxidation state, cellular uptake, release of soluble metal and concentration dependent toxicity of Cu and Ni NPs was systematically evaluated. A significant effect of carbon coating was observed on the physico-chemical properties, interaction with cellular membranes, and overall toxicity of the NPs. C-Cu NPs, compared to Cu NPs, showed four-fold lower release of soluble copper, ten-fold higher cellular uptake and protection against surface oxidation. In toxicity assays, C-Cu NPs induced higher mitochondrial damage than Cu NPs whereas Cu NPs were associated with a significant damage to plasma membrane integrity. Nickel and carbon coated nickel NPs were less toxic compared to Cu and C-Cu NPs. Thus, by studying the effect of carbon coating, correlations between physico-chemical properties and toxicity of NPs were established. The second objective was focused on utilizing nano-based approaches for the intracellular delivery of an anticancer agent, Cytochrome c (Cyt c), to

  11. Astrocytes and Microglia and Their Potential Link with Autism Spectrum Disorders.

    PubMed

    Petrelli, Francesco; Pucci, Luca; Bezzi, Paola

    2016-01-01

    The cellular mechanism(s) underlying autism spectrum disorders (ASDs) are not fully understood although it has been shown that various genetic and environmental factors contribute to their etiology. As increasing evidence indicates that astrocytes and microglial cells play a major role in synapse maturation and function, and there is evidence of deficits in glial cell functions in ASDs, one current hypothesis is that glial dysfunctions directly contribute to their pathophysiology. The aim of this review is to summarize microglia and astrocyte functions in synapse development and their contributions to ASDs. PMID:26903806

  12. Astrocytes and Microglia and Their Potential Link with Autism Spectrum Disorders

    PubMed Central

    Petrelli, Francesco; Pucci, Luca; Bezzi, Paola

    2016-01-01

    The cellular mechanism(s) underlying autism spectrum disorders (ASDs) are not fully understood although it has been shown that various genetic and environmental factors contribute to their etiology. As increasing evidence indicates that astrocytes and microglial cells play a major role in synapse maturation and function, and there is evidence of deficits in glial cell functions in ASDs, one current hypothesis is that glial dysfunctions directly contribute to their pathophysiology. The aim of this review is to summarize microglia and astrocyte functions in synapse development and their contributions to ASDs. PMID:26903806

  13. Design and Development of a Linked Open Data-Based Health Information Representation and Visualization System: Potentials and Preliminary Evaluation

    PubMed Central

    Kauppinen, Tomi; Keßler, Carsten; Fritz, Fleur

    2014-01-01

    Background Healthcare organizations around the world are challenged by pressures to reduce cost, improve coordination and outcome, and provide more with less. This requires effective planning and evidence-based practice by generating important information from available data. Thus, flexible and user-friendly ways to represent, query, and visualize health data becomes increasingly important. International organizations such as the World Health Organization (WHO) regularly publish vital data on priority health topics that can be utilized for public health policy and health service development. However, the data in most portals is displayed in either Excel or PDF formats, which makes information discovery and reuse difficult. Linked Open Data (LOD)—a new Semantic Web set of best practice of standards to publish and link heterogeneous data—can be applied to the representation and management of public level health data to alleviate such challenges. However, the technologies behind building LOD systems and their effectiveness for health data are yet to be assessed. Objective The objective of this study is to evaluate whether Linked Data technologies are potential options for health information representation, visualization, and retrieval systems development and to identify the available tools and methodologies to build Linked Data-based health information systems. Methods We used the Resource Description Framework (RDF) for data representation, Fuseki triple store for data storage, and Sgvizler for information visualization. Additionally, we integrated SPARQL query interface for interacting with the data. We primarily use the WHO health observatory dataset to test the system. All the data were represented using RDF and interlinked with other related datasets on the Web of Data using Silk—a link discovery framework for Web of Data. A preliminary usability assessment was conducted following the System Usability Scale (SUS) method. Results We developed an LOD

  14. The Perception of Time: Basic Research and Some Potential Links to the Study of Language

    ERIC Educational Resources Information Center

    Wearden, J. H.

    2008-01-01

    The article first discusses some recent work in time perception--in particular the distinction among prospective timing, retrospective timing, and passage of time judgments. The history and application of an "internal clock" model as an explanation of prospective timing performance is reviewed and contrasted with the different mechanisms needed…

  15. Potential Link Between Contents of Fatty Acids and Soybean Seed Germination Rate Under Early Production System

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soybean seed produced from the Early Soybean Production System (ESPS) in the Midsouth often has low germination with poor seed quality. The mechanism of this phenomenon is not clear. A field study was conducted in 2008 and 2009 on a silt-loam -soil at the Delta Research and Extension Center, Stonevi...

  16. Abuse and Intellectual Disability: A Potential Link or an Inescapable Reality.

    ERIC Educational Resources Information Center

    Conway, Robert N. F.

    1994-01-01

    This discussion of abuse of people with intellectual disabilities notes the varieties of abusive actions found, including sexual abuse; the possible incidence of such abuse; and reasons why this population is especially vulnerable to abuse. A current study to examine the incidence of abuse and reporting mechanisms is briefly described. (Author/DB)

  17. Cylindrospermopsin: water-linked potential threat to human health in Europe.

    PubMed

    Poniedziałek, Barbara; Rzymski, Piotr; Kokociński, Mikołaj

    2012-11-01

    Cylindrospermopsin (CYN) is a secondary metabolite produced by several cyanobacteria species. Its potential effect on human health includes liver, kidneys, lungs, spleen and intestine injuries. CYN can be cyto- and genotoxic to a variety of cell types. Occurrence and expansion of species able to synthesize CYN in European water bodies has been recently reported and raised awareness of potential harm to human health. Therefore, surface water of different human use should be monitored for the presence of toxic species of blue-green algae. This paper aims to describe the distribution of CYN producers in Europe and the potential effects of the toxin on human health according to the current state of knowledge. PMID:22986102

  18. Hydroxyl radical-induced cross-linking of thymine and lysine: identification of the primary structure and mechanism.

    PubMed

    Morimoto, S; Hatta, H; Fujita, S; Matsuyama, T; Ueno, T; Nishimoto, S

    1998-04-01

    Hydroxyl radical-induced formation of a cross-link of thymine (Thy) and lysine (Lys) in the gamma-radiolysis of N2O-saturated aqueous solution was studied. A Thy-Lys cross-link (I) of the formal structure that OH radical and 4-carbon-centered Lys radical added respectively to C(5) and C(6) positions of Thy was isolated by a preparative HPLC and identified by a FAB-HRMS. The primary cross-link I was dehydrated by treatment with HCl at 120 degrees C to yield the secondary structure (II) possessing a C(5)-C(6) double bond in the Thy moiety: the latter structure II was reported previously (Dizdaroglu, M.; Gajewski, E. Cancer Res. 1989, 49, 3463-3467). A pulse radiolysis study with a redox titration method indicated that 4-carbon centered Lys radical intermediate was of neutral redox reactivity in contrast to reducing reactivity of 5-hydroxy-5,6-dihydrothymin-6-yl radical intermediate. The cross-link I could be formed by a conventional radical recombination mechanism, but not by an ionic recombination mechanism involving a redox reaction between the radical intermediates. PMID:9871556

  19. Exposure to Potentially Traumatic Events in Early Childhood: Differential Links to Emergent Psychopathology

    ERIC Educational Resources Information Center

    Briggs-Gowan, Margaret J.; Carter, Alice S.; Clark, Roseanne; Augustyn, Marilyn; McCarthy, Kimberly J.; Ford, Julian D.

    2010-01-01

    Research NeedsObjective: To examine associations between exposure to potentially traumatic events (PTEs) and clinical patterns of symptoms and disorders in preschool children. Method: Two hundred and thirteen referred and non-referred children, ages 24 to 48 months (MN = 34.9, SD = 6.7 months) were studied. Lifetime exposure to PTEs (family…

  20. Compassionate love as a mechanism linking sacred qualities of marriage to older couples' marital satisfaction.

    PubMed

    Sabey, Allen K; Rauer, Amy J; Jensen, Jakob F

    2014-10-01

    Previous work has underscored the robust links between sanctification of marriage and marital outcomes, and recent developments in the literature suggest that compassionate love, which is important for intimate relationships, may act as a mediator of that relationship. Accordingly, the current study used actor-partner interdependence models to examine the relationship between a spiritual cognition (i.e., perceived sacred qualities of marriage) and marital satisfaction, and to determine whether that relationship is mediated by compassionate love, in a sample of older married couples (N = 64). Results revealed that wives' greater sacred qualities of marriage were significantly and positively linked to marital satisfaction on the part of both spouses, and that these links were partially mediated by couples' reports of compassionate love. These findings highlight the importance of moving beyond simply establishing the existence of the link between global markers of involvement of religion and marriage to understanding how specific spiritual cognitions may foster better relationship quality, especially among older couples. PMID:24866728

  1. Mechanisms linking metabolism of Helicobacter pylori to 18O and 13C-isotopes of human breath CO2

    PubMed Central

    Som, Suman; De, Anulekha; Banik, Gourab Dutta; Maity, Abhijit; Ghosh, Chiranjit; Pal, Mithun; Daschakraborty, Sunil B.; Chaudhuri, Sujit; Jana, Subhra; Pradhan, Manik

    2015-01-01

    The gastric pathogen Helicobacter pylori utilize glucose during metabolism, but the underlying mechanisms linking to oxygen-18 (18O) and carbon-13 (13C)-isotopic fractionations of breath CO2 during glucose metabolism are poorly understood. Using the excretion dynamics of 18O/16O and 13C/12C-isotope ratios of breath CO2, we found that individuals with Helicobacter pylori infections exhibited significantly higher isotopic enrichments of 18O in breath CO2 during the 2h-glucose metabolism regardless of the isotopic nature of the substrate, while no significant enrichments of 18O in breath CO2 were manifested in individuals without the infections. In contrast, the 13C-isotopic enrichments of breath CO2 were significantly higher in individuals with Helicobacter pylori compared to individuals without infections in response to 13C-enriched glucose uptake, whereas a distinguishable change of breath 13C/12C-isotope ratios was also evident when Helicobacter pylori utilize natural glucose. Moreover, monitoring the 18O and 13C-isotopic exchange in breath CO2 successfully diagnosed the eradications of Helicobacter pylori infections following a standard therapy. Our findings suggest that breath 12C18O16O and 13C16O16O can be used as potential molecular biomarkers to distinctively track the pathogenesis of Helicobacter pylori and also for eradication purposes and thus may open new perspectives into the pathogen’s physiology along with isotope-specific non-invasive diagnosis of the infection. PMID:26039789

  2. System Voltage Potential-Induced Degradation Mechanisms in PV Modules and Methods for Test: Preprint

    SciTech Connect

    Hacke, P.; Terwilliger, K.; Smith, R.; Glick, S.; Pankow, J.; Kempe, M.; Kurtz, S.; Bennett, I.; Kloos, M.

    2011-07-01

    Over the past decade, degradation and power loss have been observed in PV modules resulting from the stress exerted by system voltage bias. This is due in part to qualification tests and standards that do not adequately evaluate for the durability of modules to the long-term effects of high voltage bias experienced in fielded arrays. High voltage can lead to module degradation by multiple mechanisms. The extent of the voltage bias degradation is linked to the leakage current or coulombs passed from the silicon active layer through the encapsulant and glass to the grounded module frame, which can be experimentally determined; however, competing processes make the effect non-linear and history-dependent. Appropriate testing methods and stress levels are described that demonstrate module durability to system voltage potential-induced degradation (PID) mechanisms. This information, along with outdoor testing that is in progress, is used to estimate the acceleration factors needed to evaluate the durability of modules to system voltage stress. Na-rich precipitates are observed on the cell surface after stressing the module to induce PID in damp heat with negative bias applied to the active layer.

  3. System Voltage Potential-Induced Degradation Mechanisms in PV Modules and Methods for Test

    SciTech Connect

    Hacke, P.; Terwilliger, K.; Smith, R.; Glick, S.; Pankow, J.; Kempe, M.; Kurtz, S.; Bennett, I.; Kloos, M.

    2011-01-01

    Over the past decade, degradation and power loss have been observed in PV modules resulting from the stress exerted by system voltage bias. This is due in part to qualification tests and standards that do not adequately evaluate for the durability of modules to the long-term effects of high voltage bias experienced in fielded arrays. High voltage can lead to module degradation by multiple mechanisms. The extent of the voltage bias degradation is linked to the leakage current or culombs passed from the silicon active layer through the encapsulant and glass to the grounded module frame, which can be experimentally determined; however, competing processes make the effect non-linear and history-dependent. Appropriate testing methods and stress levels are described that demonstrate module durability to system voltage potential-induced degradation (PID) mechanisms. This information, along with outdoor testing that is in progress, is used to estimate the acceleration factors needed to evaluate the durability of modules to system voltage stress. Na-rich precipitates are observed on the cell surface after stressing the module to induce PID in damp heat with negative bias applied to the active layer.

  4. Child Care Subsidy Use and Child Development: Potential Causal Mechanisms

    ERIC Educational Resources Information Center

    Hawkinson, Laura E.

    2011-01-01

    Research using an experimental design is needed to provide firm causal evidence on the impacts of child care subsidy use on child development, and on underlying causal mechanisms since subsidies can affect child development only indirectly via changes they cause in children's early experiences. However, before costly experimental research is…

  5. [Linking optical properties of dissolved organic matter with NDMA formation potential in the Huangpu River].

    PubMed

    Dong, Qian-Qian; Zhang, Ai; Li, Yong-Mei; Chen, Ling; Huang, Qing-Hui

    2014-03-01

    Surface water samples from the Huangpu River were filtered to measure the UV absorption and fluorescence spectrum. Dissolved organic carbon (DOC), N-nitrosodimethylamine (NDMA), and its formation potential (NDMA-FP) were also analyzed to explore relationships between the properties of dissolved organic matter (DOM) and the formation potential of disinfection byproducts-NDMA in the Huangpu River. The study found that: NDMA-FP concentration increased with the increasing of DOC concentration (r = 0.487, P < 0.01), but it had negative relationships with SUVA254 and HIX (r = -0.605, P < 0.01; r = -0.396, P < 0.01). NDMA-FP concentration had positive relationships with the fluorescence intensity of protein-like substances such as low-molecular-weight (LMW) tyrosine-like and tryptophan-like substances (r = 0.421, P < 0.01; r = 0.426, P < 0.01), but had a negative relationship with humic-like substance (r = -0.422, P < 0.01). Therefore, NDMA formation potential increases with the increasing DOM content in the Huangpu River, which is significantly related with the protein-like substances, but decreases with the increasing aromaticity and humification of DOM. PMID:24881383

  6. Mechanical properties of tough hydrogels synthesized with a facile simultaneous radiation polymerization and cross-linking method

    NASA Astrophysics Data System (ADS)

    Jiang, Fangzhi; Wang, Xuezhen; He, Changcheng; Saricilar, Sureyya; Wang, Huiliang

    2015-01-01

    Radiation-induced polymerization and cross-linking method has been applied to hydrogel preparations for decades, but less attention has been paid to the mechanical properties of the hydrogels. In this work, we provide a systematic study on the mechanical properties of hydrogels synthesized with the simultaneous radiation polymerization and cross-linking method. The prepared polyacrylamide (PAAm) had very good mechanical properties, namely high compressive strengths (several to more than 10 MPa), high tensile strengths (up to 260 kPa), high fracture strains (up to 12) and high fracture energies (10-160 J/m2). Absorbed dose and monomer concentration were the two important factors affecting the mechanical properties of the gels. The compressive strength and elastic modulus of the gels increased with increasing absorbed dose and monomer concentration, while the tensile strength, fracture strain and fracture energy of the gels decreased with increasing absorbed dose. The gels also showed excellent elastic recovery property, as indicated by the low stress-strain hysteresis ratios in cyclic tensile tests as well as the small loss factors measured with dynamic mechanical analysis (DMA).

  7. Polyextremotolerant black fungi: oligotrophism, adaptive potential, and a link to lichen symbioses

    PubMed Central

    Gostinčar, Cene; Muggia, Lucia; Grube, Martin

    2012-01-01

    Black meristematic fungi can survive high doses of radiation and are resistant to desiccation. These adaptations help them to colonize harsh oligotrophic habitats, e.g., on the surface and subsurface of rocks. One of their most characteristic stress-resistance mechanisms is the accumulation of melanin in the cell walls. This, production of other protective molecules and a plastic morphology further contribute to ecological flexibility of black fungi. Increased growth rates of some species after exposure to ionizing radiation even suggest yet unknown mechanisms of energy production. Other unusual metabolic strategies may include harvesting UV or visible light or gaining energy by forming facultative lichen-like associations with algae or cyanobacteria. The latter is not entirely surprising, since certain black fungal lineages are phylogenetically related to clades of lichen-forming fungi. Similar to black fungi, lichen-forming fungi are adapted to growth on exposed surfaces with low availability of nutrients. They also efficiently use protective molecules to tolerate frequent periods of extreme stress. Traits shared by both groups of fungi may have been important in facilitating the evolution and radiation of lichen-symbioses. PMID:23162543

  8. Potential Molecular and Cellular Mechanism of Psychotropic Drugs

    PubMed Central

    Seo, Myoung Suk; Scarr, Elizabeth; Lai, Chi-Yu

    2014-01-01

    Psychiatric disorders are among the most debilitating of all medical illnesses. Whilst there are drugs that can be used to treat these disorders, they give sub-optimal recovery in many people and a significant number of individuals do not respond to any treatments and remain treatment resistant. Surprisingly, the mechanism by which psychotropic drugs cause their therapeutic benefits remain unknown but likely involves the underlying molecular pathways affected by the drugs. Hence, in this review, we have focused on recent findings on the molecular mechanism affected by antipsychotic, mood stabilizing and antidepressant drugs at the levels of epigenetics, intracellular signalling cascades and microRNAs. We posit that understanding these important interactions will result in a better understanding of how these drugs act which in turn may aid in considering how to develop drugs with better efficacy or increased therapeutic reach. PMID:25191500

  9. Mental Imagery in Depression: Phenomenology, Potential Mechanisms, and Treatment Implications.

    PubMed

    Holmes, Emily A; Blackwell, Simon E; Burnett Heyes, Stephanie; Renner, Fritz; Raes, Filip

    2016-03-28

    Mental imagery is an experience like perception in the absence of a percept. It is a ubiquitous feature of human cognition, yet it has been relatively neglected in the etiology, maintenance, and treatment of depression. Imagery abnormalities in depression include an excess of intrusive negative mental imagery; impoverished positive imagery; bias for observer perspective imagery; and overgeneral memory, in which specific imagery is lacking. We consider the contribution of imagery dysfunctions to depressive psychopathology and implications for cognitive behavioral interventions. Treatment advances capitalizing on the representational format of imagery (as opposed to its content) are reviewed, including imagery rescripting, positive imagery generation, and memory specificity training. Consideration of mental imagery can contribute to clinical assessment and imagery-focused psychological therapeutic techniques and promote investigation of underlying mechanisms for treatment innovation. Research into mental imagery in depression is at an early stage. Work that bridges clinical psychology and neuroscience in the investigation of imagery-related mechanisms is recommended. PMID:26772205

  10. Inhibitory Potential of Turbinaria ornata against Key Metabolic Enzymes Linked to Diabetes

    PubMed Central

    Unnikrishnan, P. S.; Suthindhiran, K.; Jayasri, M. A.

    2014-01-01

    One of the therapeutic approaches in treating diabetes is to reduce postprandial hyperglycemia by inhibiting major carbohydrate hydrolyzing enzymes. In the present study, crude extracts of marine seaweed, Turbinaria ornata, were tested for their antidiabetic potential using enzyme inhibitory assays (α-amylase, α-glucosidase, and dipeptidyl peptidase-IV). Among the tested extracts, methanol and acetone extracts showed significant inhibitory effects on α-amylase (IC50 250.9 μg/mL), α-glucosidase (535.6 μg/mL), and dipeptidyl peptidase-4 (55.2 μg/mL), respectively. Free radical scavenging activity of these extracts was analyzed using DPPH assay (65%). Extracts were tested for in vitro toxicity using DNA fragmentation assay, haemolytic assay, and MTT assay. None of the extracts showed toxicity in tested models. Furthermore, GC-MS analysis of lead extracts showed the presence of major compounds, hentriacontane, z, z-6, 28-heptatriactontadien-2-one, 8-heptadecene, and 1-heptacosanol. Our findings suggest that Turbinaria ornata can be used as a potential source for further in vivo studies in controlling hyperglycemia. PMID:25050371

  11. Linking motor-related brain potentials and velocity profiles in multi-joint arm reaching movements.

    PubMed

    Amengual, Julià L; Marco-Pallarés, Josep; Grau, Carles; Münte, Thomas F; Rodríguez-Fornells, Antoni

    2014-01-01

    The study of the movement related brain potentials (MRPBs) needs accurate technical approaches to disentangle the specific patterns of bran activity during the preparation and execution of movements. During the last forty years, synchronizing the electromyographic activation (EMG) of the muscle with electrophysiological recordings (EEG) has been commonly ussed for these purposes. However, new clinical approaches in the study of motor diseases and rehabilitation suggest the demand of new paradigms that might go further into the study of the brain activity associated with the kinematics of movements. As a response to this call, we have used a 3-D hand-tracking system with the aim to record continuously the position of an ultrasonic sender attached to the hand during the performance of multi-joint self-paced movements. We synchronized time-series of position and velocity of the sender with the EEG recordings, obtaining specific patterns of brain activity as a function of the fluctuations of the kinematics during natural movement performance. Additionally, the distribution of the brain activity during the preparation and execution phases of movements was similar that reported previously using the EMG, suggesting the validity of our technique. We claim that this paradigm could be usable in patients because of its simplicity and the potential knowledge that can be extracted from clinical protocols. PMID:24808853

  12. TARANIS: a Tool to investigate Potential Links Between Sprites and Ionospheric and Magnetospheric Plasmas

    NASA Astrophysics Data System (ADS)

    Francois, L.; Elisabeth, B.; TARANIS Team

    2004-12-01

    TARANIS (Tool for the Analysis of RAdiations from lightNIngs and Sprites) is a CNES microsatellite project which will be in phase A in 2005. The main scientific objective is to compare observations of sprites and other optical emissions (blue jets, halos, elves,etc.) with observations of terrestrial gamma and X ray flashes, electromagnetic and electrostatic emissions, and energetic electrons, in order to investigate physical mechanisms allowing impulsive transfers of energy between the neutral atmosphere and the ionospheric and magnetospheric plasmas. The main questions to be addressed for a satellite mission are presented. They include : the triggering factor of the optical emissions, the quasi electrostatic field above thunderstorms, the modification of the electrodynamics of the ionosphere, the detection and the modeling of energetic runaways electron beams, the associated electromagnetic and electrostatic emissions, the presence of the generated electron beams within the magnetosphere and more specifically within the radiation belts. The adequation of the scientific payload to the scientific objectives is discussed.

  13. The activation of mechanisms linking judgements of work design and management with musculoskeletal pain.

    PubMed

    Randall, Raymond; Griffiths, Amanda; Cox, Tom; Welsh, Claire

    2002-01-15

    The report of work-related musculoskeletal pain may be related to worker evaluations of the design and management of work through two mechanisms: one biomechanical and the other stress-related. This study of engineering workers (n = 204) explored the validity of these mechanisms using sequential logistic regression. Analyses suggested that workers' ratings of the adequacy of the design and management of their work were related to their report of work-related musculoskeletal pain. However, the mechanisms appeared to be activated in certain conditions. The reporting of pain in the upper body was both biomechanically- and stress-related, whereas that in the lower body was only biomechanically-related. It is argued that the mechanism activated appeared to be determined by the anatomical location of the pain, and probably the variance shared between the different aspects of work design and management, on the one hand, and the mechanical load of the job, on the other. PMID:11964192

  14. (Metabolic mechanisms of plant growth at low-water potentials)

    SciTech Connect

    Boyer, J.S.

    1989-01-01

    For the year 1989, the progress made on this DOE sponsored research will be described by considering the questions presented in the original proposal and describing the work on each one. We used soybean seedlings grown in vermiculite in a dark, humid environment because they are convenient to grow, undergo most of the physiological changes induced by low water potentials in large plants, and have exposed growing regions on which molecular experiments can be done.

  15. Cap buckling as a potential mechanism of atherosclerotic plaque vulnerability.

    PubMed

    Abdelali, Maria; Reiter, Steven; Mongrain, Rosaire; Bertrand, Michel; L'Allier, Philippe L; Kritikou, Ekaterini A; Tardif, Jean-Claude

    2014-04-01

    Plaque rupture in atherosclerosis is the primary cause of potentially deadly coronary events, yet about 40% of ruptures occur away from the plaque cap shoulders and cannot be fully explained with the current biomechanical theories. Here, cap buckling is considered as a potential destabilizing factor which increases the propensity of the atherosclerotic plaque to rupture and which may also explain plaque failure away from the cap shoulders. To investigate this phenomenon, quasistatic 2D finite element simulations are performed, considering the salient geometrical and nonlinear material properties of diverse atherosclerotic plaques over the range of physiological loads. The numerical results indicate that buckling may displace the location of the peak von Mises stresses in the deflected caps. Plaque buckling, together with its deleterious effects is further observed experimentally in plaque caps using a physical model of deformable mock coronary arteries with fibroatheroma. Moreover, an analytical approach combining quasistatic equilibrium equations with the Navier-Bresse formulas is used to demonstrate the buckling potential of a simplified arched slender cap under intraluminal pressure and supported by foundations. This analysis shows that plaque caps - calcified, fibrotic or cellular - may buckle in specific undulated shapes once submitted to critical loads. Finally, a preliminary analysis of intravascular ultrasonography recordings of patients with atherosclerotic coronary arteries corroborates the numerical, experimental and theoretical findings and shows that various plaque caps buckle in vivo. By displacing the sites of high stresses in the plaque cap, buckling may explain the atherosclerotic plaque cap rupture at various locations, including cap shoulders. PMID:24491969

  16. [The significance of sex-linked differences for the assessment of somatosensory evoked potentials (author's transl)].

    PubMed

    Strenge, H; Hedderich, J; Tackmann, W

    1981-09-01

    In 45 healthy volunteers (22 males and 23 females with the same age structure) the peak latencies and inter-peak differences of the cervical and early cortical components of the somatosensory evoked potential were measured. The distribution of the values of the variables and their relationship with arm length were investigated both for the sample as a whole and for each sex separately. Significantly higher average values of the latencies and arm lengths were found in men. The correlations between arm length and latency had consistently higher values for the female sample. On the basis of these results it is concluded that a sufficient assessment of the latencies is only possible with the help of sex-specific normal values. PMID:6795015

  17. Spermidine-cross-linked hydrogels as novel potential platforms for pharmaceutical applications.

    PubMed

    López-Cebral, Rita; Paolicelli, Patrizia; Romero-Caamaño, Vanessa; Seijo, Begoña; Casadei, Maria Antonietta; Sanchez, Alejandro

    2013-08-01

    Endogen polyamines are known to be molecules of high biological value. Herein, a new generation of physical hydrogels was developed through the mild ionotropic gelantion technique, using the endogen polyamine spermidine as a physical cross-linker. The main negatively charged polymer of the hydrogel is the natural polysaccharide gellan gum. Optionally, interesting endogen molecules, such as chondroitin sulfate and albumin, can be included as part of the formulation. These new hydrogels were characterized and the influence of the different components on their final properties was carefully analyzed, ultimately demonstrating the possibility to modulate these properties as well as the system's versatility in terms of composition. On the contrary, in vitro cell studies showed the absence of cytotoxicity of these hydrogels. Finally, the in vitro-release profiles obtained for different model molecules evidenced the potential of these systems as novel drug delivery platforms. PMID:23757346

  18. Sodium arsenite potentiates the clastogenicity and mutagenicity of DNA cross linking agents

    SciTech Connect

    Lee, T.C.; Lee, K.C.; Tzeng, Y.J.; Huang, R.Y.; Jan, K.Y.

    1986-01-01

    To see if sodium arsenite enhances the clastogenicity and the mutagenicity of DNA crosslinking agents, Chinese hamster ovary (CHO) cells and human skin fibroblasts were exposed to cis-diamminedichloroplatinum (II) (cis-Pt(II)) or 8-methoxypsoralen (8-MOP) plus long-wave ultraviolet light (UVA) and then to sodium arsenite. The results indicate that the clastogenicity of cis-Pt(II) and 8-MOP pllus UVA are enhanced by the post-treatment with sodium arsenite. Chromatid breaks and exchanges are predominantly increased in doubly treated cells. Furthermore, the mutagenicity of cis-Pt(II) at the hypoxanthine-guanine phosphoribosyl transferase locus is also potentiated by sodium arsenite in CHO cells

  19. Links between Ammonia Oxidizer Community Structure, Abundance, and Nitrification Potential in Acidic Soils ▿ †

    PubMed Central

    Yao, Huaiying; Gao, Yangmei; Nicol, Graeme W.; Campbell, Colin D.; Prosser, James I.; Zhang, Limei; Han, Wenyan; Singh, Brajesh K.

    2011-01-01

    Ammonia oxidation is the first and rate-limiting step of nitrification and is performed by both ammonia-oxidizing archaea (AOA) and bacteria (AOB). However, the environmental drivers controlling the abundance, composition, and activity of AOA and AOB communities are not well characterized, and the relative importance of these two groups in soil nitrification is still debated. Chinese tea orchard soils provide an excellent system for investigating the long-term effects of low pH and nitrogen fertilization strategies. AOA and AOB abundance and community composition were therefore investigated in tea soils and adjacent pine forest soils, using quantitative PCR (qPCR), terminal restriction fragment length polymorphism (T-RFLP) and sequence analysis of respective ammonia monooxygenase (amoA) genes. There was strong evidence that soil pH was an important factor controlling AOB but not AOA abundance, and the ratio of AOA to AOB amoA gene abundance increased with decreasing soil pH in the tea orchard soils. In contrast, T-RFLP analysis suggested that soil pH was a key explanatory variable for both AOA and AOB community structure, but a significant relationship between community abundance and nitrification potential was observed only for AOA. High potential nitrification rates indicated that nitrification was mainly driven by AOA in these acidic soils. Dominant AOA amoA sequences in the highly acidic tea soils were all placed within a specific clade, and one AOA genotype appears to be well adapted to growth in highly acidic soils. Specific AOA and AOB populations dominated in soils at particular pH values and N content, suggesting adaptation to specific niches. PMID:21571885

  20. Is forebrain neurogenesis a potential repair mechanism after stroke?

    PubMed

    Inta, Dragos; Gass, Peter

    2015-07-01

    The use of adult subventricular zone (SVZ) neurogenesis as brain repair strategy after stroke represents a hot topic in neurologic research. Recent radiocarbon-14 dating has revealed a lack of poststroke neurogenesis in the adult human neocortex; however, adult neurogenesis has been shown to occur, even under physiologic conditions, in the human striatum. Here, these results are contrasted with experimental poststroke neurogenesis in the murine brain. Both in humans and in rodents, the SVZ generates predominantly calretinin (CR)-expressing GABAergic interneurons, which cannot replace the broad spectrum of neuronal subtypes damaged by stroke. Therefore, SVZ neurogenesis may represent a repair mechanism only after genetic manipulation redirecting its differentiation. PMID:25966955

  1. Structural and mechanical properties of UV-photo-cross-linked poly(N-vinyl-2-pyrrolidone) hydrogels.

    PubMed

    D'Errico, Gerardino; De Lellis, Marco; Mangiapia, Gaetano; Tedeschi, Annamaria; Ortona, Ornella; Fusco, Sabato; Borzacchiello, Assunta; Ambrosio, Luigi

    2008-01-01

    Biocompatible poly( N-vinyl-2-pyrrolidone) (PVP) hydrogels have been produced by UV irradiation of aqueous polymer mixtures, using a high-pressure mercury lamp. The resulting materials have been characterized by a combination of experimental techniques, including rheology, small-angle neutron scattering (SANS), electron paramagnetic resonance (EPR), and pulsed gradient spin-echo nuclear magnetic resonance (PGSE-NMR), to put in evidence the relationship between the microstructural properties and the macrofunctional behavior of the gels. Viscoelastic measurements showed that UV photo-cross-linked PVP hydrogels present a strong gel mechanical behavior and viscoelastic moduli values similar to those of biological gels. The average distance between the cross-linking points of the polymer network was estimated from the hydrogels elastic modulus. However, SANS measurements showed that the network microstructure is highly inhomogeneous, presenting polymer-rich regions more densely cross-linked, surrounded by a water-rich environment. EPR and PGSE-NMR data further support the existence of these water-rich domains. Inclusion of a third component, such as glycerol, in the PVP aqueous mixture to be irradiated has been also investigated. A small amount of glycerol (<3% w/w) can be added keeping satisfactory properties of the hydrogel, while higher amounts significantly affect the cross-linking process. PMID:18163572

  2. Mechanisms of cardiac radiation injury and potential preventive approaches.

    PubMed

    Slezak, Jan; Kura, Branislav; Ravingerová, Táňa; Tribulova, Narcisa; Okruhlicova, Ludmila; Barancik, Miroslav

    2015-09-01

    In addition to cytostatic treatment and surgery, the most common cancer treatment is gamma radiation. Despite sophisticated radiological techniques however, in addition to irradiation of the tumor, irradiation of the surrounding healthy tissue also takes place, which results in various side-effects, depending on the absorbed dose of radiation. Radiation either damages the cell DNA directly, or indirectly via the formation of oxygen radicals that in addition to the DNA damage, react with all cell organelles and interfere with their molecular mechanisms. The main features of radiation injury besides DNA damage is inflammation and increased expression of pro-inflammatory genes and cytokines. Endothelial damage and dysfunction of capillaries and small blood vessels plays a particularly important role in radiation injury. This review is focused on summarizing the currently available data concerning the mechanisms of radiation injury, as well as the effectiveness of various antioxidants, anti-inflammatory cytokines, and cytoprotective substances that may be utilized in preventing, mitigating, or treating the toxic effects of ionizing radiation on the heart. PMID:26030720

  3. [Mechanisms and potential of the therapeutic stimulation of arteriogenesis].

    PubMed

    Schirmer, S H; van Royen, N; Laufs, U; Böhm, M

    2009-02-01

    The stimulation of collateral artery growth (arteriogenesis) is a promising alternative approach to non-invasively treat arterial obstructive disease, such as coronary, peripheral or cerebral artery disease. Patients unable to undergo conventional revascularization strategies may benefit from adaptive arteriogenesis. Underlying mechanisms are experimentally validated and include an increase in shear stress after obstruction or occlusion of a major artery; monocyte adhesion, transmigration and perivascular accumulation, secretion of growth factors; and smooth muscle and endothelial cell proliferation and growth of pre-existent collateral arteries. Therapeutic stimulation of arteriogenesis with cytokines has been successfully performed in experimental models. Translation into clinical practice, however, has hitherto been problematic. Reasons for this include differences between the healthy laboratory animal and an often severely diseased patient, possible harmful effects of pro-arteriogenic therapies and unsuitable clinical endpoints for the detection of collateral artery growth. Recent investigations of human arteriogenesis demonstrate significant inter-individual differences and point towards the importance of anti-arteriogenic mechanisms in patients with impaired adaptive arteriogenesis and high cardiovascular risk factors. PMID:19197812

  4. Misfolded Protein Aggregates: Mechanisms, Structures and Potential for Disease Transmission

    PubMed Central

    Moreno-Gonzalez, Ines; Soto, Claudio

    2011-01-01

    Some of the most prevalent human degenerative diseases appear as a result of the misfolding and aggregation of proteins. Compelling evidence suggest that misfolded protein aggregates play an important role in cell dysfunction and tissue damage, leading to the disease. Prion protein (Prion diseases), amyloid-beta (Alzheimer’s disease), alpha-synuclein (Parkinson’s disease), Huntingtin (Huntington’s disease), serum amyloid A (AA amyloidosis) and islet amyloid polypeptide (Type 2 Diabetes) are some of the proteins that trigger disease when they get misfolded. The recent understanding of the crucial role of misfolded proteins as well as the structural requirements and mechanism of protein misfolding have raised the possibility that these diseases may be transmissible by self-propagation of the protein misfolding process in a similar way as the infamous prions transmit prion diseases. Future research in this field should aim to clarify this possibility and translate the knowledge of the basic disease mechanisms into development of novel strategies for early diagnosis and efficient treatment. PMID:21571086

  5. Challenging Mycobacterium tuberculosis dormancy mechanisms and their immunodiagnostic potential.

    PubMed

    Chaves, Alexandre Silva; Rodrigues, Michele Fernandes; Mattos, Ana Márcia Menezes; Teixeira, Henrique Couto

    2015-01-01

    Mycobacterium tuberculosis is the etiologic agent of tuberculosis, one of the world's greatest cause of morbidity and mortality due to infectious disease. Many evolutionary mechanisms have contributed to its high level of adaptation as a host pathogen. Prior to become dormant, a group of about 50 genes related to metabolic changes are transcribed by the DosR regulon, one of the most complex and important systems of host-pathogen interaction. This genetic mechanism allows the mycobacteria to persist during long time periods, establishing the so-called latent infection. Even in the presence of a competent immune response, the host cannot eliminate the pathogen, only managing to keep it surrounded by an unfavorable microenvironment for its growth. However, conditions such as immunosuppression may reestablish optimal conditions for bacterial growth, culminating in the onset of active disease. The interactions between the pathogen and its host are still not completely elucidated. Nonetheless, many studies are being carried out in order to clarify this complex relationship, thus creating new possibilities for patient approach and laboratory screening. PMID:26358744

  6. Elucidating the mechanisms linking early pubertal timing, sexual activity, and substance use for maltreated versus nonmaltreated adolescents

    PubMed Central

    Negriff, Sonya; Brensilver, Matthew; Trickett, Penelope K.

    2015-01-01

    Purpose To test models linking pubertal timing, peer substance use, sexual behavior, and substance use for maltreated versus comparison adolescents. Three theoretical mechanisms were tested: 1) peer influence links early pubertal timing to later sexual behavior and substance use, 2) early maturers engage in substance use on their own and then select substance-using friends, or 3) early maturers initiate sexual behaviors which leads them to substance-using peers. Methods The data came from a longitudinal study of the effects of child maltreatment on adolescent development (303 maltreated and 151 comparison adolescents; age: 9–13 years at initial wave). Multiple-group structural equation models tested the hypotheses across three timepoints including variables of pubertal timing, perception of peer substance use, sexual behavior, and self-reported substance use. Results Early pubertal timing was associated with substance-using peers only for maltreated adolescents, indicating the mediation path from early pubertal timing through substance-using peers to subsequent adolescent substance use and sexual behavior only holds for maltreated adolescents. Mediation via sexual behavior was significant for both maltreated and comparison adolescents. This indicates that sexual behavior may be a more universal mechanism linking early maturation with risky friends regardless of adverse life experiences. Conclusions The findings are a step toward elucidating the developmental pathways from early puberty to risk behavior and identifying early experiences that may alter mediation effects. PMID:26003577

  7. Linking potential denitrification rates to microbial gene abundances in multiple boreal ecosystems

    NASA Astrophysics Data System (ADS)

    Petersen, D. G.; Blazewicz, S.; Herman, D. J.; Firestone, M. K.; Waldrop, M. P.

    2010-12-01

    The composition and functioning of boreal ecosystems are vulnerable to changes in climate, leading to changes in season length, fire regimes, and soil moisture status. To investigate the influence of vegetation and soil moisture on microbial nitrogen cycling several disparate boreal ecosystems was studied. The two primary objectives were to: (1) determine whether process rates could be predicted solely from soil physical and chemical characteristics and (2) determine if the abundance of functional genes could be an additional explanatory variable. Surface soils were sampled along an elevation-driven hydrologic gradient at the Bonanza Creek LTER that corresponds with five plant communities typical of interior Alaska. The plant communities included a black spruce stand, a deciduous stand, a tussock grassland, an emergent fen, and a rich fen. We examined the chemical composition of the surface organic moss and soil, measured gross N-mineralization, potential rates of nitrification and denitrification (DEA), and abundances of several functional groups of microorganisms from soil cores collected in mid summer. We used quantitative PCR to assess the gene abundances of ammonia oxidizers and denitrifiers based on a functional gene approach. Here, we focus on potential denitrification rates (PDR), and abundance of denitrifyers carrying NirS and NirK genes (nitrate reductase) and NosZ genes (nitrous oxide reductase). PDR increased dramatically with increasing soil moisture along the gradient, from 1 mg N/m2/h at the dry black spruce site to 300 mg N/m2/h in the rich fen, which is very high compared to other poorly drained soil environments. PDR were linearly related to the abundance of functional genes from the microorganisms responsible for this process. Abundances of NirS, NirK and NosZ genes correlated significantly to PDR (r2 = 0.61 p < 0.0001, r2 = 0.45 p < 0.0003, r2 = 0.81 p < 0.0001, respectively). In addition, PDR were better explained by functional gene abundances

  8. Emplacement mechanisms and trapping potential of gravity-driven allochthons

    SciTech Connect

    Pinney, R.B.

    1985-02-01

    Gravity-slide blocks of Paleozoic carbonate detached from the Snake River Range show evidence of episodic emplacement into the Salt Lake group (Mio-Pliocene) in the Palisades reservoir area near Alpine, Wyoming. The allochthons lie in a large graben system created by the Grand Valley listric normal fault, a reactivated thrust that soles into a ramp in the underlying Absaroka thrust. In the Alpine 7 1/2-min quadrangle, one of the detached blocks is 2 1/2 mi (4 km) by 1 mi (1.6 km) in map view and contains the Ferry Peak thrust as well as other Laramide structures. Structures and formations of the Alpine allochthon may be matched to those in the range to restore approximate predetachment position. Very low-angle westward translation at or near the surface moved the blocks across the Grand Valley fault into the graben. The current location and attitude of these allochthons are due to subsequent movement and rotation on the Grand Valley fault. The allochthons occur at different stratigraphic levels in the Salt Lake group, each level corresponding to the time of a specific emplacement event. Catastrophic emplacement of a fractured allochthon, a potential reservoir, into a lacustrine or other source rock depocenter creates a unique and potentially predictable type of petroleum occurrence. Paleogeographic reconstruction may explain anomalous occurrence of discrete allochthons in structurally low areas where it can be shown that a gravitational potential existed for detachment and sliding. The resulting trap would consist of allochthons encased in autochthonous source rock.

  9. Metabolic Syndrome, Type 2 Diabetes, and Cancer: Epidemiology and Potential Mechanisms.

    PubMed

    Ben-Shmuel, Sarit; Rostoker, Ran; Scheinman, Eyal J; LeRoith, Derek

    2016-01-01

    Obesity is associated with multiple metabolic disorders that drive cardiovascular disease, T2D and cancer. The doubling in the number of obese adults over the past 3 decades led to the recognition of obesity as a "disease". With over 42 million children obese or overweight, this epidemic is rapidly growing worldwide. Obesity and T2D are both associated together and independently with an increased risk for cancer and a worse prognosis. Accumulating evidence from epidemiological studies revealed potential factors that may explain the association between obesity-linked metabolic disorders and cancer risk. Studies based on the insulin resistance MKR mice, highlighted the roe of the insulin receptor and its downstream signaling proteins in mediating hyperinsulinemia's mitogenic effects. Hypercholesterolemia was also shown to promote the formation of larger tumors and enhancement in metastasis. Furthermore, the conversion of cholesterol into 27-Hydroxycholesterol was found to link high fat diet-induced hypercholesterolemia with cancer pathophysiology. Alteration in circulating adipokines and cytokines are commonly found in obesity and T2D. Adipokines are involved in tumor growth through multiple mechanisms including mTOR, VEGF and cyclins. In addition, adipose tissues are known to recruit and alter macrophage phenotype; these macrophages can promote cancer progression by secreting inflammatory cytokines such as TNF-α and IL-6. Better characterization on the above factors and their downstream effects is required in order to translate the current knowledge into the clinic, but more importantly is to understand which are the key factors that drive cancer in each patient. Until we reach this point, policies and activities toward healthy diets and physical activities remain the best medicine. PMID:25903410

  10. Benzylpiperidine-Linked Diarylthiazoles as Potential Anti-Alzheimer's Agents: Synthesis and Biological Evaluation.

    PubMed

    Shidore, Mahesh; Machhi, Jatin; Shingala, Kaushik; Murumkar, Prashant; Sharma, Mayank Kumar; Agrawal, Neetesh; Tripathi, Ashutosh; Parikh, Zalak; Pillai, Prakash; Yadav, Mange Ram

    2016-06-23

    A novel series of hybrid molecules were designed and synthesized by fusing the pharmacophoric features of cholinesterase inhibitor donepezil and diarylthiazole as potential multitarget-directed ligands for the treatment of Alzheimer's disease (AD). The compounds showed significant in vitro anticholinesterase (anti-ChE) activity, the most potent compound (44) among them showing the highest activity (IC50 value of 0.30 ± 0.01 μM) for AChE and (1.84 ± 0.03 μM) for BuChE. Compound 44 showed mixed inhibition of AChE in the enzyme kinetic studies. Some compounds exhibited moderate to high inhibition of AChE-induced Aβ1-42 aggregation and noticeable in vitro antioxidant and antiapoptotic properties. Compound 44 showed significant in vivo anti-ChE and antioxidant activities. Furthermore, compound 44 demonstrated in vivo neuroprotection by decreasing Aβ1-42-induced toxicity by attenuating abnormal levels of Aβ1-42, p-Tau, cleaved caspase-3, and cleaved PARP proteins. Compound 44 exhibited good oral absorption and was well tolerated up to 2000 mg/kg, po, dose without showing toxic effects. PMID:27253679

  11. Bioreducible cross-linked polymers based on G1 peptide dendrimer as potential gene delivery vectors.

    PubMed

    Li, Chun-Yan; Wang, Hai-Jiao; Cao, Jing-Ming; Zhang, Ji; Yu, Xiao-Qi

    2014-11-24

    A series of cationic polymers based on low generation (G1) peptide dendrimer were synthesized with disulfide-containing linkages. The DNA binding abilities of the target polymers were studied by gel electrophoresis and fluorescence quenching assay. The bioreducible property of the disulfide-containing polymers P2 and P3 was also investigated in the presence of dithiothreitol (DTT). Results from dynamic light scattering (DLS) and transmission electron microscopy (TEM) assays reveal that these materials may condense DNA into nanoparticles with proper sizes and zeta-potentials. In vitro cell experiments show that compared to branched 25 KDa PEI, P2 and P3 may exhibit much higher gene transfection efficiency and lower cytotoxicity in both HEK293 and U-2OS cells. Additionally, polymer prepared from Michael addition gives better gene transfection ability, while polymer prepared from ring-opening reaction has better serum tolerance. Results indicate that these polymers might be promising non-viral gene vectors for their easy preparation, very low cytotoxicity, and good transfection efficiency. PMID:25282264

  12. A potential link among antioxidant enzymes, histopathology and trace elements in canine visceral leishmaniasis

    PubMed Central

    Souza, Carolina C; Barreto, Tatiane de O; da Silva, Sydnei M; Pinto, Aldair W J; Figueiredo, Maria M; Ferreira Rocha, Olguita G; Cangussú, Silvia D; Tafuri, Wagner L

    2014-01-01

    Canine visceral leishmaniasis (CVL) is a severe and fatal systemic chronic inflammatory disease. We investigated the alterations in, and potential associations among, antioxidant enzymes, trace elements and histopathology in CVL. Blood and tissue levels of Cu-Zn superoxide dismutase, catalase and glutathione peroxidase were measured in mixed-breed dogs naturally infected with Leishmania infantum chagasi, symptomatic (n = 19) and asymptomatic (n = 11). Serum levels of copper, iron, zinc, selenium and nitric oxide, and plasma lipid peroxidation were measured. Histological and morphometric analyses were conducted of lesions in liver, spleen and lymph nodes. We found lower blood catalase and glutathione peroxidase activity to be correlated with lower iron and selenium respectively. However, higher activity of Cu-Zn superoxide dismutase was not correlated with the increase in copper and decreased in zinc observed in infected animals compared to controls. Organ tissue was characterized by lower enzyme activity in infected dogs than in controls, but this was not correlated with trace elements. Lipid peroxidation was higher in symptomatic than in asymptomatic and control dogs and was associated with lesions such as chronic inflammatory reaction, congestion, haemosiderin and fibrosis. Systemic iron deposition was observed primarily in the symptomatic dogs showing a higher tissue parasite load. Dogs with symptomatic CVL displayed enhanced LPO and Fe tissue deposition associated with decreased levels of antioxidant enzymes. These results showed new points in the pathology of CVL and might open new treatment perspectives associated with antioxidants and the role of iron in the pathogenesis of CVL. PMID:24766461

  13. A potential link among antioxidant enzymes, histopathology and trace elements in canine visceral leishmaniasis.

    PubMed

    Souza, Carolina C; Barreto, Tatiane de O; da Silva, Sydnei M; Pinto, Aldair W J; Figueiredo, Maria M; Rocha, Olguita G Ferreira; Cangussú, Silvia D; Tafuri, Wagner L

    2014-08-01

    Canine visceral leishmaniasis (CVL) is a severe and fatal systemic chronic inflammatory disease. We investigated the alterations in, and potential associations among, antioxidant enzymes, trace elements and histopathology in CVL. Blood and tissue levels of Cu-Zn superoxide dismutase, catalase and glutathione peroxidase were measured in mixed-breed dogs naturally infected with Leishmania infantum chagasi, symptomatic (n = 19) and asymptomatic (n = 11). Serum levels of copper, iron, zinc, selenium and nitric oxide, and plasma lipid peroxidation were measured. Histological and morphometric analyses were conducted of lesions in liver, spleen and lymph nodes. We found lower blood catalase and glutathione peroxidase activity to be correlated with lower iron and selenium respectively. However, higher activity of Cu-Zn superoxide dismutase was not correlated with the increase in copper and decreased in zinc observed in infected animals compared to controls. Organ tissue was characterized by lower enzyme activity in infected dogs than in controls, but this was not correlated with trace elements. Lipid peroxidation was higher in symptomatic than in asymptomatic and control dogs and was associated with lesions such as chronic inflammatory reaction, congestion, haemosiderin and fibrosis. Systemic iron deposition was observed primarily in the symptomatic dogs showing a higher tissue parasite load. Dogs with symptomatic CVL displayed enhanced LPO and Fe tissue deposition associated with decreased levels of antioxidant enzymes. These results showed new points in the pathology of CVL and might open new treatment perspectives associated with antioxidants and the role of iron in the pathogenesis of CVL. PMID:24766461

  14. Rainbow-shift mechanism behind discrete optical-potential ambiguities

    SciTech Connect

    Brandan, M.E. ); McVoy, K.W. )

    1991-03-01

    Some years ago, Drisko {ital et} {ital al}. suggested that the discrete ambiguity often encountered for elastic scattering optical potentials could be understood as being due to the interior or small-{ital l} {ital S}-matrix elements for two equivalent'' potentials differing in phase by 2{pi}, {ital l}-by-{ital l}. We point out that the {ital absence} of this phase change for peripheral partial waves is equally essential, and suggest that a deeper understanding of the ambiguity may be achieved by viewing it as a consequence of a farside interference between interior and peripheral partial waves. It is this interference which produces the broad Airy maxima'' of a nuclear rainbow, and we show that a Drisko-type phase-shift increment {delta}{sub {ital l}}{r arrow}({delta}{sub {ital l}}+{pi}) for low-{ital l} phases relative to the high-{ital l} ones is exactly what is needed to shift a farside rainbow pattern by one Airy maximum, thus providing an equivalent rainbow-shift'' interpretation of the discrete ambiguity. The physical importance of both interpretations lies in the fact that the existence of discrete ambiguities (as well as of nuclear rainbows) is explicit evidence for low-{ital l} transparency in nucleus-nucleus collisions. The essential role played by low partial waves explains why peripheral reactions have generally not proven helpful in resolving this ambiguity.

  15. Comparing potential copper chelation mechanisms in Parkinson's disease protein

    NASA Astrophysics Data System (ADS)

    Rose, Frisco; Hodak, Miroslav; Bernholc, Jerry

    2011-03-01

    We have implemented the nudged elastic band (NEB) as a guided dynamics framework for our real-space multigrid method of DFT-based quantum simulations. This highly parallel approach resolves a minimum energy pathway (MEP) on the energy hypersurface by relaxing intermediates in a chain-of-states. As an initial application we present an investigation of chelating agents acting on copper ion bound to α -synuclein, whose misfolding is implicated in Parkinson's disease (PD). Copper ions are known to act as highly effective misfolding agents in a-synuclein and are thus an important target in understanding PD. Furthermore, chelation therapy has shown promise in the treatment of Alzheimer's and other neuro-degenerative diseases with similar metal-correlated pathologies. At present, our candidate chelating agents include nicotine, curcumin and clioquinol. We examine their MEP activation barriers in the context of a PD onset mechanism to assess the viability of various chelators for PD remediation.

  16. Gadd45α: A Novel Diabetes-Associated Gene Potentially Linking Diabetic Cardiomyopathy and Baroreflex Dysfunction

    PubMed Central

    Xie, Fang; Sun, Lihua; Su, Xiaolin; Wang, Ying; Wei, Ran; Zhang, Rong; Li, Xia; Yang, Baofeng; Ai, Jing

    2012-01-01

    Both diabetic cardiomyopathy (DCM) and baroreflex dysfunction independently contribute to sudden cardiac death (SCD), however the inherent connections between them under diabetic state remains unclear. As microRNAs (miRNAs) have been reported to participate in various physiological and pathological processes, we presume they may also be involved in DCM and DM-induced impairment of baroreflex sensitivity. Two sets of gene expression profiles data from streptozotocin (STZ)-induced diabetic heart and diabetic dorsal root ganglia (DDRG) were retrieved from GEO and ArrayExpress. Co-differentially-expressed genes in diabetic heart and DDRG were identified by t test and intersection analysis. Human Protein Reference Database (HPRD) was applied to find direct interacting proteins of Gadd45α. Differentially-expressed miRNAs in left ventricle from 4-week STZ-induced diabetic rats were screened by miRNA microarray. Expression of miR-499 and its regulating effect on Gadd45α were then verified by quantitative real-time PCR (qRT-PCR), western blot, computational predication, and dual-luciferase reporter analysis. Four co-differentially-expressed genes in DCM and DDRG were identified. Among these genes, Gadd45α has 16 direct interacting proteins and 11 of them are documentedly associated with DM. Accompanied with significantly increased miR-499 expression, Gadd45α expression was increased at mRNA level but decreased at protein level in both diabetic heart and nucleus ambiguous. Furthermore, miR-499 was confirmed negatively regulating Gadd45α by targeting its 3′UTR. Collectively, reduced Gadd45α protein expression by forced miR-499 expression indicated it's a diabetes-associated gene which might potentially be involved in both DCM and DM-induced baroreflex dysfunction. PMID:23227140

  17. Maladaptive perfectionism's link to aggression and self-harm: Emotion regulation as a mechanism.

    PubMed

    Chester, David S; Merwin, Lauren M; DeWall, C Nathan

    2015-01-01

    The negative affect that results from negative feedback is a substantial, proximal cause of aggression. People high in maladaptive perfectionism, the tendency to focus on the discrepancy between one's standards and performance, are characterized by an exaggerated negative affective response to negative feedback. This exacerbated affective response to failure may then dispose them to hurt others and themselves as aggression and self-harm are often perceived as a means to regulate negative affect. In Study 1, we demonstrated that maladaptive perfectionism was linked to greater aggressive behavior towards others after receiving negative feedback. Suggesting the presence of an emotion regulation strategy, this effect was mediated by the motivation to use aggression to improve mood. In Study 2, maladaptive perfectionism was linked to self-harm, an effect exacerbated by negative feedback and mediated by negative affect. These findings suggest that maladaptive perfectionists are at risk for greater harm towards others and the self because negative feedback has a stronger affective impact and harming others and the self is perceived a means to alleviate this aversive state. PMID:26918433

  18. Wind a potential mechanism of Mars gully formation

    NASA Astrophysics Data System (ADS)

    Yue, Z.; Xie, H.

    2007-12-01

    Since Mars gullies were first revealed with the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) in 2000, they rapidly became a hotspot in Mars studying in that some of them are very young features on Mars surface. The previous studies focused on their formation and erosion mechanisms. As a result, several mechanisms have been proposed. But none of them can interpret the formation of all gullies perfectly. High resolution HiRISE images give us a good opportunity to examine it. In this study, we propose that wind could play an important role in some of the gullies formation. Wind is the most important agent acting on Mars surface (Fenton, 2003) and produced many features on Mars surface, including ubiquitous dunes, yardangs, deflation pits, dust storms, and dust deposits. Similarly, wind can also affect the inner edge of craters and valleys, where the gullies have been found mostly. Under the erosion of wind, the small channel will turn to a big gully. Wind could be a major reason to explain (1) why gullies formed in one side of a crater wall, while small wind-blown sand deposits in the opposite side of the same crater, as found in the crater of this HiRISE image (PSP_001697_1390_RED.JP2) and (2) why two craters next to each other, but only the big one has gullies developed. The reason for this is that big crater can form a strong wind circulation. In another HiRISE image (PSP_001330_1395_RED.JP2), we found a rock in the lower end of a gully course in a crater wall, for which we explain this gully is in the process of formation. This rock could be moving down and carving in to form the course due to the wind force. Based on the common characteristics of wind abrasion mechanics (Greeley and Iversen, 1985), we propose the following processes of gully formation by wind: (1) Embryonic stage: one side of a crater wall or valley wall was "softened" by the wind storm and formed some irregular and V-shaped fractured channels. (2) Youthful stage: small impact pits formed

  19. Potential Mechanism Leading to Impaired Thermoregulation Following Microgravity Exposure

    NASA Technical Reports Server (NTRS)

    Crandall, C. G.; Etzel, R. A.

    1999-01-01

    Prolonged exposure to microgravity or its analogues impairs thermoregulation in humans evidenced by higher internal temperatures following the exposure during a thermal challenge. Although the mechanism leading to this response has not been clearly delineated, we identified that prolonged head-down tilt (HDT) markedly impairs thermoregulatory reflex control of skin blood flow, as demonstrated by an increased internal temperature threshold for cutaneous vasodilation, and by a reduced slope of the relationship between the elevation in skin blood flow relative to the elevation in internal temperature. Recently, Fortney et al. identified similar responses in two individuals following 115 days of microgravity exposure. One possible mechanism leading to altered cutaneous vasodilation during a thermal challenge following actual or simulated microgravity exposure may be associated with baroreflex-mediated attenuation in the elevation of skin blood flow. During a heat stress the elevation in skin blood flow is accomplished through a combination of increased cutaneous vascular conductance and cardiac output, both of which result in central venous pressure (CVP) decreasing 2-6 mmHg. Reductions in CVP of this magnitude in normothermia decrease muscle blood flow and skin blood flow presumably through unloading the cardiopulmonary baroreceptors. It is unclear whether the reduction in CVP, and accompanying cardiopulmonary baroreceptor unloading, during passive heating buffers the elevation in skin blood flow. That is, would the elevation in skin blood flow be greater if CVP did not decrease, or decreased to a lesser extent during the heat stress? Conversely, if CVP decreased to a greater extend during a thermal challenge following a perturbation such as prolonged HDT, would the elevation in skin blood flow be attenuated during that thermal challenge? Given that prolonged HDT decreases plasma volume and central venous pressure, such a finding would provide a plausible hypothesis

  20. Nonlinear Riccati equations as a unifying link between linear quantum mechanics and other fields of physics

    NASA Astrophysics Data System (ADS)

    Schuch, Dieter

    2014-04-01

    Theoretical physics seems to be in a kind of schizophrenic state. Many phenomena in the observable macroscopic world obey nonlinear evolution equations, whereas the microscopic world is governed by quantum mechanics, a fundamental theory that is supposedly linear. In order to combine these two worlds in a common formalism, at least one of them must sacrifice one of its dogmas. I claim that linearity in quantum mechanics is not as essential as it apparently seems since quantum mechanics can be reformulated in terms of nonlinear Riccati equations. In a first step, it will be shown where complex Riccati equations appear in time-dependent quantum mechanics and how they can be treated and compared with similar space-dependent Riccati equations in supersymmetric quantum mechanics. Furthermore, the time-independent Schrödinger equation can also be rewritten as a complex Riccati equation. Finally, it will be shown that (real and complex) Riccati equations also appear in many other fields of physics, like statistical thermodynamics and cosmology.

  1. Metabolic memory and diabetic nephropathy: potential role for epigenetic mechanisms.

    PubMed

    Tonna, Stephen; El-Osta, Assam; Cooper, Mark E; Tikellis, Chris

    2010-06-01

    Many clinical studies have shown that intensive glycemic control in patients with diabetes can reduce the incidence and progression of diabetic nephropathy and can also reduce the incidence of other complications. These beneficial effects persist after patients return to usual (often worse) glycemic control. The Diabetes Control and Complications Trial was the first to refer to this phenomenon as 'metabolic memory'. Many patients with diabetes, however, still develop diabetic nephropathy despite receiving intensified glycemic control. Preliminary work in endothelial cells has shown that transient episodes of hyperglycemia can induce changes in gene expression that are dependent on modifications to histone tails (for example, methylation), and that these changes persist after return to normoglycemia. The persistence of such modifications cannot yet be fully explained, but certain epigenetic changes, as well as biochemical mechanisms such as advanced glycation, may provide new and interesting clues towards explaining the pathogenesis of this phenomenon. Further elucidation of the molecular events that enable prior glycemic control to result in end-organ protection in diabetes may lead to the development of new approaches for reducing the burden of diabetic nephropathy. PMID:20421885

  2. Vascular remodeling after ischemic stroke: mechanisms and therapeutic potentials

    PubMed Central

    Liu, Jialing; Wang, Yongting; Akamatsu, Yosuke; Lee, Chih Cheng; Stetler, R Anne; Lawton, Michael T.; Yang, Guo-Yuan

    2014-01-01

    The brain vasculature has been increasingly recognized as a key player that directs brain development, regulates homeostasis, and contributes to pathological processes. Following ischemic stroke, the reduction of blood flow elicits a cascade of changes and leads to vascular remodeling. However, the temporal profile of vascular changes after stroke is not well understood. Growing evidence suggests that the early phase of cerebral blood volume (CBV) increase is likely due to the improvement in collateral flow, also known as arteriogenesis, whereas the late phase of CBV increase is attributed to the surge of angiogenesis. Arteriogenesis is triggered by shear fluid stress followed by activation of endothelium and inflammatory processes, while angiogenesis induces a number of pro-angiogenic factors and circulating endothelial progenitor cells (EPCs). The status of collaterals in acute stroke has been shown to have several prognostic implications, while the causal relationship between angiogenesis and improved functional recovery has yet to be established in patients. A number of interventions aimed at enhancing cerebral blood flow including increasing collateral recruitment are under clinical investigation. Transplantation of EPCs to improve angiogenesis is also underway. Knowledge in the underlying physiological mechanisms for improved arteriogenesis and angiogenesis shall lead to more effective therapies for ischemic stroke. PMID:24291532

  3. Drug release mechanisms of chemically cross-linked albumin microparticles: effect of the matrix erosion.

    PubMed

    Sitta, Danielly L A; Guilherme, Marcos R; da Silva, Elisangela P; Valente, Artur J M; Muniz, Edvani C; Rubira, Adley F

    2014-10-01

    Albumin (BSA) microparticles were developed as a biotechnological alternative for drug delivery. Vitamin B12 (Vit-B12) was used as a model drug. The microparticles were obtained from maleic anhydride-functionalized BSA and N',N'-dimethylacrylamide (DMAAm) in a W/O emulsion without and with PVA. The microparticles produced at 15min of stirring without PVA showed the best results in terms of size, homogeneity, and sphericity. In such a case, BSA played a role as a surface active agent, replacing PVA. For longer stirring times, BSA was unable to act as an emulsifier. These microparticles showed an uncommon release profile, consisting of a two-step release mechanism, at the pH range studied. Considering that a two-step release mechanism is occurring, the experimental data were adjusted by applying modified power law and Weibull equations in order to describe release mechanism n and release rate constant k, respectively. Each one of the release stages was related to a specific value of n and k. The second stage was driven by a super case II transport mechanism, as a result of diffusion, macromolecular relaxation, and erosion. A third model, described by Hixson-Crowell, confirmed the erosion mechanism. Vit-B12 diffusion kinetics in aqueous solutions (i.e., without the microparticles) follows a one-step process, being k dependent on the pH, confirming that the two-step release mechanism is a characteristic profile of the developed microparticles. The microparticles released only 2.70% of their initial drug load at pH 2, and 58.53% at pH 10. PMID:25087021

  4. Obesity and atrial fibrillation: A comprehensive review of the pathophysiological mechanisms and links.

    PubMed

    Goudis, Christos A; Korantzopoulos, Panagiotis; Ntalas, Ioannis V; Kallergis, Eleftherios M; Ketikoglou, Dimitrios G

    2015-11-01

    Obesity is a worldwide health problem with epidemic proportions that has been associated with atrial fibrillation (AF). Even though the underlying pathophysiological mechanisms have not been completely elucidated, several experimental and clinical studies implicate obesity in the initiation and perpetuation of AF. Of note, hypertension, diabetes mellitus, metabolic syndrome, coronary artery disease, and obstructive sleep apnea, represent clinical correlates between obesity and AF. In addition, ventricular adaptation, diastolic dysfunction, and epicardial adipose tissue appear to be implicated in atrial electrical and structural remodeling, thereby promoting the arrhythmia in obese subjects. The present article provides a concise overview of the association between obesity and AF, and highlights the underlying pathophysiological mechanisms. PMID:25959929

  5. Comorbidity Factors and Brain Mechanisms Linking Chronic Stress and Systemic Illness

    PubMed Central

    Duric, Vanja; Clayton, Sarah; Leong, Mai Lan; Yuan, Li-Lian

    2016-01-01

    Neuropsychiatric symptoms and mental illness are commonly present in patients with chronic systemic diseases. Mood disorders, such as depression, are present in up to 50% of these patients, resulting in impaired physical recovery and more intricate treatment regimen. Stress associated with both physical and emotional aspects of systemic illness is thought to elicit detrimental effects to initiate comorbid mental disorders. However, clinical reports also indicate that the relationship between systemic and psychiatric illnesses is bidirectional, further increasing the complexity of the underlying pathophysiological processes. In this review, we discuss the recent evidence linking chronic stress and systemic illness, such as activation of the immune response system and release of common proinflammatory mediators. Altogether, discovery of new targets is needed for development of better treatments for stress-related psychiatric illnesses as well as improvement of mental health aspects of different systemic diseases. PMID:26977323

  6. Linking susceptibility genes and pathogenesis mechanisms using mouse models of systemic lupus erythematosus

    PubMed Central

    Crampton, Steve P.; Morawski, Peter A.; Bolland, Silvia

    2014-01-01

    Systemic lupus erythematosus (SLE) represents a challenging autoimmune disease from a clinical perspective because of its varied forms of presentation. Although broad-spectrum steroids remain the standard treatment for SLE, they have many side effects and only provide temporary relief from the symptoms of the disease. Thus, gaining a deeper understanding of the genetic traits and biological pathways that confer susceptibility to SLE will help in the design of more targeted and effective therapeutics. Both human genome-wide association studies (GWAS) and investigations using a variety of mouse models of SLE have been valuable for the identification of the genes and pathways involved in pathogenesis. In this Review, we link human susceptibility genes for SLE with biological pathways characterized in mouse models of lupus, and discuss how the mechanistic insights gained could advance drug discovery for the disease. PMID:25147296

  7. The Effects of Calorie Restriction in Depression and Potential Mechanisms

    PubMed Central

    Zhang, Yifan; Liu, Changhong; Zhao, Yinghao; Zhang, Xingyi; Li, Bingjin; Cui, Ranji

    2015-01-01

    Depression, also called major depressive disorder, is a neuropsychiatric disorder jeopardizing an increasing number of the population worldwide. To date, a large number of studies have devoted great attention to this problematic condition and raised several hypotheses of depression. Based on these theories, many antidepressant drugs were developed for the treatment of depression. Yet, the depressed patients are often refractory to the antidepressant therapies. Recently, increasing experimental evidences demonstrated the effects of calorie restriction in neuroendocrine system and in depression. Both basic and clinical investigations indicated that short-term calorie restriction might induce an antidepressant efficacy in depression, providing a novel avenue for treatment. Molecular basis underlying the antidepressant actions of calorie restriction might involve multiple physiological processes, primarily including orexin signaling activation, increased CREB phosphorylation and neurotrophic effects, release of endorphin and ketone production. However, the effects of chronic calorie restriction were quite controversial, in the cases that it often resulted in the long-term detrimental effects via inhibiting the function of 5-HT system and decreasing leptin levels. Here we review such dual effects of calorie restriction in depression and potential molecular basis behind these effects, especially focusing on antidepressant effects. PMID:26412073

  8. Evaluating Molecular Mechanical Potentials for Helical Peptides and Proteins

    PubMed Central

    Thompson, Erik J.; DePaul, Allison J.; Patel, Sarav S.; Sorin, Eric J.

    2010-01-01

    Multiple variants of the AMBER all-atom force field were quantitatively evaluated with respect to their ability to accurately characterize helix-coil equilibria in explicit solvent simulations. Using a global distributed computing network, absolute conformational convergence was achieved for large ensembles of the capped A21 and Fs helical peptides. Further assessment of these AMBER variants was conducted via simulations of a flexible 164-residue five-helix-bundle protein, apolipophorin-III, on the 100 ns timescale. Of the contemporary potentials that had not been assessed previously, the AMBER-99SB force field showed significant helix-destabilizing tendencies, with beta bridge formation occurring in helical peptides, and unfolding of apolipophorin-III occurring on the tens of nanoseconds timescale. The AMBER-03 force field, while showing adequate helical propensities for both peptides and stabilizing apolipophorin-III, (i) predicts an unexpected decrease in helicity with ALA→ARG+ substitution, (ii) lacks experimentally observed 310 helical content, and (iii) deviates strongly from average apolipophorin-III NMR structural properties. As is observed for AMBER-99SB, AMBER-03 significantly overweighs the contribution of extended and polyproline backbone configurations to the conformational equilibrium. In contrast, the AMBER-99φ force field, which was previously shown to best reproduce experimental measurements of the helix-coil transition in model helical peptides, adequately stabilizes apolipophorin-III and yields both an average gyration radius and polar solvent exposed surface area that are in excellent agreement with the NMR ensemble. PMID:20418937

  9. Ambient particle inhalation and the cardiovascular system: potential mechanisms.

    PubMed Central

    Donaldson, K; Stone, V; Seaton, A; MacNee, W

    2001-01-01

    Well-documented air pollution episodes throughout recent history have led to deaths among individuals with cardiovascular and respiratory disease. Although the components of air pollution that cause the adverse health effects in these individuals are unknown, a small proportion by mass but a large proportion by number of the ambient air particles are ultrafine, i.e., less than 100 nm in diameter. This ultrafine component of particulate matter with a mass median aerodynamic diameter less than 10 microm (PM(10) may mediate some of the adverse health effects reported in epidemiologic studies and for which there is toxicologic evidence to support this contention. The exact mechanism by which ultrafine particles have adverse effects is unknown, but these particles have recently been shown to enhance calcium influx on contact with macrophages. Oxidative stress is also to be anticipated at the huge particle surface; this can be augmented by oxidants generated by recruited inflammatory leukocytes. Atheromatous plaques form in the coronary arteries and are major causes of morbidity and death associated epidemiologically with particulate air pollution. In populations exposed to air pollution episodes, blood viscosity, fibrinogen, and C-reactive protein (CRP) were higher. More recently, increases in heart rate in response to rising air pollution have been described and are most marked in individuals who have high blood viscosity. In our study of elderly individuals, there were significant rises in CRP, an index of inflammation. In this present review, we consider the likely interactions between the ultrafine particles the acute phase response and cardiovascular disease. PMID:11544157

  10. Potential self-regulatory mechanisms of yoga for psychological health

    PubMed Central

    Gard, Tim; Noggle, Jessica J.; Park, Crystal L.; Vago, David R.; Wilson, Angela

    2014-01-01

    Research suggesting the beneficial effects of yoga on myriad aspects of psychological health has proliferated in recent years, yet there is currently no overarching framework by which to understand yoga’s potential beneficial effects. Here we provide a theoretical framework and systems-based network model of yoga that focuses on integration of top-down and bottom-up forms of self-regulation. We begin by contextualizing yoga in historical and contemporary settings, and then detail how specific components of yoga practice may affect cognitive, emotional, behavioral, and autonomic output under stress through an emphasis on interoception and bottom-up input, resulting in physical and psychological health. The model describes yoga practice as a comprehensive skillset of synergistic process tools that facilitate bidirectional feedback and integration between high- and low-level brain networks, and afferent and re-afferent input from interoceptive processes (somatosensory, viscerosensory, chemosensory). From a predictive coding perspective we propose a shift to perceptual inference for stress modulation and optimal self-regulation. We describe how the processes that sub-serve self-regulation become more automatized and efficient over time and practice, requiring less effort to initiate when necessary and terminate more rapidly when no longer needed. To support our proposed model, we present the available evidence for yoga affecting self-regulatory pathways, integrating existing constructs from behavior theory and cognitive neuroscience with emerging yoga and meditation research. This paper is intended to guide future basic and clinical research, specifically targeting areas of development in the treatment of stress-mediated psychological disorders. PMID:25368562

  11. Links between mechanical behavior of cancellous bone and its microstructural properties under dynamic loading.

    PubMed

    Prot, M; Saletti, D; Pattofatto, S; Bousson, V; Laporte, S

    2015-02-01

    Previous studies show that in vivo assessment of fracture risk can be achieved by identifying the relationships between microarchitecture description from clinical imaging and mechanical properties. This study demonstrates that results obtained at low strain rates can be extrapolated to loadings with an order of magnitude similar to trauma such as car crashes. Cancellous bovine bone specimens were compressed under dynamic loadings (with and without confinement) and the mechanical response properties were identified, such as Young׳s modulus, ultimate stress, ultimate strain, and ultimate strain energy. Specimens were previously scanned with pQCT, and architectural and structural microstructure properties were identified, such as parameters of geometry, topology, connectivity and anisotropy. The usefulness of micro-architecture description studied was in agreement with statistics laws. Finally, the differences between dynamic confined and non-confined tests were assessed by the bone marrow influence and the cancellous bone response to different boundary conditions. Results indicate that architectural parameters, such as the bone volume fraction (BV/TV), are as strong determinants of mechanical response parameters as ultimate stress at high strain rates (p-value<0.001). This study reveals that cancellous bone response at high strain rates, under different boundary conditions, can be predicted from the architectural parameters, and that these relations with mechanical properties can be used to make fracture risk prediction at a determined magnitude. PMID:25577437

  12. Emotion Dysregulation as a Mechanism Linking Stress Exposure to Adolescent Aggressive Behavior

    ERIC Educational Resources Information Center

    Herts, Kate L.; McLaughlin, Katie A.; Hatzenbuehler, Mark L.

    2012-01-01

    Exposure to stress is associated with a wide range of internalizing and externalizing problems in adolescents, including aggressive behavior. Extant research examining mechanisms underlying the associations between stress and youth aggression has consistently identified social information processing pathways that are disrupted by exposure to…

  13. SSRIs and the female brain--potential for utilizing steroid-stimulating properties to treat menstrual cycle-linked dysphorias.

    PubMed

    Lovick, Thelma

    2013-12-01

    One unexpected property of selective serotonin reuptake inhibitors is their ability, at doses well below those that effect 5-HT systems, to raise brain concentrations of neuroactive steroids such as the progesterone metabolite allopregnanolone. In women, rapid withdrawal from allopregnanolone when progesterone secretion drops sharply in the late luteal phase precipitates menstrual cycle-linked disorders such as premenstrual syndrome and catamenial epilepsy. Short-term, low-dose fluoxetine during the late luteal phase has the potential to prevent the development of such disorders, by raising brain allopregnanolone concentration. In female rats, withdrawal from allopregnanolone, as ovarian progesterone secretion falls rapidly in the late diestrus phase (similar to late luteal phase in women), induces upregulation of extrasynaptic GABAA receptors on GABAergic neurons in brain regions involved in mediating anxiety-like behaviors. The functional consequence of this receptor plasticity is disinhibition of principal neurons, hyperexcitable neuronal circuitry and increased behavioral responsiveness to anxiogenic stress. These withdrawal responses were prevented by short-term treatment with fluoxetine during the late diestrus phase, which raised brain allopregnanolone concentration, so blunting the rapid physiological fall. The steroid-stimulating properties of fluoxetine offer untapped opportunities for developing new treatments for menstrual cycle-linked disorders in women, which are precipitated by abrupt falls in brain concentration of allopregnanolone. PMID:23704364

  14. pH-dependent cross-linking of catechols through oxidation via Fe(3+) and potential implications for mussel adhesion.

    PubMed

    Fullenkamp, Dominic E; Barrett, Devin G; Miller, Dusty R; Kurutz, Josh W; Messersmith, Phillip B

    2014-01-01

    The mussel byssus is a remarkable attachment structure that is formed by injection molding and rapid in-situ hardening of concentrated solutions of proteins enriched in the catecholic amino acid 3,4-dihydroxy-L-phenylalanine (DOPA). Fe(3+), found in high concentrations in the byssus, has been speculated to participate in redox reactions with DOPA that lead to protein polymerization, however direct evidence to support this hypothesis has been lacking. Using small molecule catechols, DOPA-containing peptides, and native mussel foot proteins, we report the first direct observation of catechol oxidation and polymerization accompanied by reduction of Fe(3+) to Fe(2+). In the case of the small molecule catechol, we identified two dominant dimer species and characterized their connectivities by nuclear magnetic resonance (NMR), with the C6-C6 and C5-C6 linked species as the major and minor products, respectively. For the DOPA-containing peptide, we studied the pH dependence of the reaction and demonstrated that catechol polymerization occurs readily at low pH, but is increasingly diminished in favor of metal-catechol coordination interactions at higher pH. Finally, we demonstrate that Fe(3+) can induce cross-links in native byssal mussel proteins mefp-1 and mcfp-1 at acidic pH. Based on these findings, we discuss the potential implications to the chemistry of mussel adhesion. PMID:25243062

  15. Potentially hazardous Asteroid 2007 LE: Compositional link to the black chondrite Rose City and Asteroid (6) Hebe

    NASA Astrophysics Data System (ADS)

    Fieber-Beyer, Sherry K.; Gaffey, Michael J.; Bottke, William F.; Hardersen, Paul S.

    2015-04-01

    The research is an integrated effort beginning with telescopic observations and extending through detailed mineralogical characterizations to provide constraints on the albedo, diameter, composition, and meteorite affinity of near-Earth object-potentially hazardous asteroid (NEO-PHA 2007 LE). Results of the analysis indicate a diameter of 0.56 kilometers (km) and an albedo of 0.08. 2007 LE exhibits a 1-μm absorption feature without a discernible Band II feature. Compositional analysis of 2007 LE reveal Fs17 and Fa19 values, which are consistent with the Fa and Fs values for the H-type ordinary chondrites (Fs14.5-18 and Fa16-20) and of Asteroid (6) Hebe (Fs17 and Fa15). Spectroscopically, 2007 LE does not appear like the average H-chondrite spectra, exhibiting a reddened spectrum and subdued absorption feature. Further investigation of the meteorite classes yielded a black chondrite, Rose City, which is both similar in mineralogy and spectrally to PHA 2007 LE. Dynamical analysis could not directly link the fall of the Rose City meteorite to 2007 LE. As it stands, 2007 LE and Rose City have a compositional link, and both could come from the same parent body/possible family, one known source of the H chondrites is (6) Hebe.

  16. pH-dependent cross-linking of catechols through oxidation via Fe3+ and potential implications for mussel adhesion

    PubMed Central

    Fullenkamp, Dominic E.; Barrett, Devin G.; Miller, Dusty R.; Kurutz, Josh W.; Messersmith, Phillip B.

    2014-01-01

    The mussel byssus is a remarkable attachment structure that is formed by injection molding and rapid in-situ hardening of concentrated solutions of proteins enriched in the catecholic amino acid 3,4-dihydroxy-L-phenylalanine (DOPA). Fe3+, found in high concentrations in the byssus, has been speculated to participate in redox reactions with DOPA that lead to protein polymerization, however direct evidence to support this hypothesis has been lacking. Using small molecule catechols, DOPA-containing peptides, and native mussel foot proteins, we report the first direct observation of catechol oxidation and polymerization accompanied by reduction of Fe3+ to Fe2+. In the case of the small molecule catechol, we identified two dominant dimer species and characterized their connectivities by nuclear magnetic resonance (NMR), with the C6-C6 and C5-C6 linked species as the major and minor products, respectively. For the DOPA-containing peptide, we studied the pH dependence of the reaction and demonstrated that catechol polymerization occurs readily at low pH, but is increasingly diminished in favor of metal-catechol coordination interactions at higher pH. Finally, we demonstrate that Fe3+ can induce cross-links in native byssal mussel proteins mefp-1 and mcfp-1 at acidic pH. Based on these findings, we discuss the potential implications to the chemistry of mussel adhesion. PMID:25243062

  17. Bacterial population and biodegradation potential in chronically crude oil-contaminated marine sediments are strongly linked to temperature.

    PubMed

    Bargiela, Rafael; Mapelli, Francesca; Rojo, David; Chouaia, Bessem; Tornés, Jesús; Borin, Sara; Richter, Michael; Del Pozo, Mercedes V; Cappello, Simone; Gertler, Christoph; Genovese, María; Denaro, Renata; Martínez-Martínez, Mónica; Fodelianakis, Stilianos; Amer, Ranya A; Bigazzi, David; Han, Xifang; Chen, Jianwei; Chernikova, Tatyana N; Golyshina, Olga V; Mahjoubi, Mouna; Jaouanil, Atef; Benzha, Fatima; Magagnini, Mirko; Hussein, Emad; Al-Horani, Fuad; Cherif, Ameur; Blaghen, Mohamed; Abdel-Fattah, Yasser R; Kalogerakis, Nicolas; Barbas, Coral; Malkawi, Hanan I; Golyshin, Peter N; Yakimov, Michail M; Daffonchio, Daniele; Ferrer, Manuel

    2015-01-01

    Two of the largest crude oil-polluted areas in the world are the semi-enclosed Mediterranean and Red Seas, but the effect of chronic pollution remains incompletely understood on a large scale. We compared the influence of environmental and geographical constraints and anthropogenic forces (hydrocarbon input) on bacterial communities in eight geographically separated oil-polluted sites along the coastlines of the Mediterranean and Red Seas. The differences in community compositions and their biodegradation potential were primarily associated (P < 0.05) with both temperature and chemical diversity. Furthermore, we observed a link between temperature and chemical and biological diversity that was stronger in chronically polluted sites than in pristine ones where accidental oil spills occurred. We propose that low temperature increases bacterial richness while decreasing catabolic diversity and that chronic pollution promotes catabolic diversification. Our results further suggest that the bacterial populations in chronically polluted sites may respond more promptly in degrading petroleum after accidental oil spills. PMID:26119183

  18. An affine continuum mechanical model for cross-linked F-actin networks with compliant linker proteins.

    PubMed

    Holzapfel, Gerhard A; Unterberger, Michael J; Ogden, Ray W

    2014-10-01

    Cross-linked actin networks are important building blocks of the cytoskeleton. In order to gain deeper insight into the interpretation of experimental data on actin networks, adequate models are required. In this paper we introduce an affine constitutive network model for cross-linked F-actin networks based on nonlinear continuum mechanics, and specialize it in order to reproduce the experimental behavior of in vitro reconstituted model networks. The model is based on the elastic properties of single filaments embedded in an isotropic matrix such that the overall properties of the composite are described by a free-energy function. In particular, we are able to obtain the experimentally determined shear and normal stress responses of cross-linked actin networks typically observed in rheometer tests. In the present study an extensive analysis is performed by applying the proposed model network to a simple shear deformation. The single filament model is then extended by incorporating the compliance of cross-linker proteins and further extended by including viscoelasticity. All that is needed for the finite element implementation is the constitutive model for the filaments, the linkers and the matrix, and the associated elasticity tensor in either the Lagrangian or Eulerian formulation. The model facilitates parameter studies of experimental setups such as micropipette aspiration experiments and we present such studies to illustrate the efficacy of this modeling approach. PMID:25043658

  19. Graphene oxide papers modified by divalent ions-enhancing mechanical properties via chemical cross-linking.

    PubMed

    Park, Sungjin; Lee, Kyoung-Seok; Bozoklu, Gulay; Cai, Weiwei; Nguyen, Sonbinh T; Ruoff, Rodney S

    2008-03-01

    Significant enhancement in mechanical stiffness (10-200%) and fracture strength (approximately 50%) of graphene oxide paper, a novel paperlike material made from individual graphene oxide sheets, can be achieved upon modification with a small amount (less than 1 wt %) of Mg(2+) and Ca(2+). These results can be readily rationalized in terms of the chemical interactions between the functional groups of the graphene oxide sheets and the divalent metals ions. While oxygen functional groups on the basal planes of the sheets and the carboxylate groups on the edges can both bond to Mg(2+) and Ca(2+), the main contribution to mechanical enhancement of the paper comes from the latter. PMID:19206584

  20. Potential Mechanisms for Microbial Energy Acquisition in Oxic Deep-Sea Sediments

    PubMed Central

    Heidelberg, John F.

    2016-01-01

    ABSTRACT The South Pacific Gyre (SPG) possesses the lowest rates of sedimentation, surface chlorophyll concentration, and primary productivity in the global oceans. As a direct result, deep-sea sediments are thin and contain small amounts of labile organic carbon. It was recently shown that the entire SPG sediment column is oxygenated and may be representative of up to a third of the global marine environment. To understand the microbial processes that contribute to the removal of the labile organic matter at the water-sediment interface, a sediment sample was collected and subjected to metagenomic sequencing and analyses. Analysis of nine partially reconstructed environmental genomes, which represent approximately one-third of the microbial community, revealed that the members of the SPG surface sediment microbial community are phylogenetically distinct from surface/upper-ocean organisms. These genomes represent a wide distribution of novel organisms, including deep-branching Alphaproteobacteria, two novel organisms within the Proteobacteria, and new members of the Nitrospirae, Nitrospinae, and candidate phylum NC10. These genomes contain evidence for microbially mediated metal (iron/manganese) oxidation and carbon fixation linked to nitrification. Additionally, despite hypothesized energy limitation, members of the SPG microbial community had motility and chemotaxis genes and possessed mechanisms for the degradation of high-molecular-weight organic matter. This study contributes to our understanding of the metabolic potential of microorganisms in deep-sea oligotrophic sediments and their impact on local carbon geochemistry. IMPORTANCE This research provides insight into the microbial metabolic potential of organisms inhabiting oxygenated deep-sea marine sediments. Current estimates suggest that these environments account for up to a third of the global marine sediment habitat. Nine novel deep-sea microbial genomes were reconstructed from a metagenomic data set

  1. Development and qualification of a mechanical-optical interface for parallel optics links

    NASA Astrophysics Data System (ADS)

    Chuang, S.; Schoellner, D.; Ugolini, A.; Wakjira, J.; Wolf, G.

    2015-03-01

    As parallel optics applications continue to expand, there remains a need for an effective coupling interface between the board-level active components and the passive components of the network. While mid-board level photonic turn connectors are available, coupling interfaces are generally not available outside of proprietary solutions. Development of a general mechanical-optical coupling interface opens the door for broader parallel optics implementation. An interface for use between the optical transmitter and the photonic turn connector is introduced. The interface is a monolithic injection molded component with an array of collimating lenses to couple efficiently with common VCSEL/PD designs. The component has precise epoxy control features to manage epoxy bond-line thickness and strength. Suitable UV and thermal epoxies have been qualified for effective die bond placement of the component in the VCSEL/PD environment. Environmental and mechanical performance of the component to industry-standard qualification requirements are reviewed, and tensile force testing and durability results validate the mechanical characteristics of the interface.

  2. Mechanisms Linking Energy Substrate Metabolism to the Function of the Heart

    PubMed Central

    Carley, Andrew N.; Taegtmeyer, Heinrich; Lewandowski, E. Douglas

    2015-01-01

    Metabolic signaling mechanisms are increasingly recognized to mediate the cellular response to alterations in workload demand, as a consequence of physiological and pathophysiological challenges. Thus, an understanding of the metabolic mechanisms coordinating activity in the cytosol with the energy-providing pathways in the mitochondrial matrix becomes critical for deepening our insights into the pathogenic changes that occur in the stressed cardiomyocyte. Processes that exchange both metabolic intermediates and cations between the cytosol and mitochondria enable transduction of dynamic changes in contractile state to the mitochondrial compartment of the cell. Disruption of such metabolic transduction pathways has severe consequences for the energetic support of contractile function in the heart and is implicated in the pathogenesis of heart failure. Deficiencies in metabolic reserve and impaired metabolic transduction in the cardiomyocyte can result from inherent deficiencies in metabolic phenotype or maladaptive changes in metabolic enzyme expression and regulation in the response to pathogenic stress. This review examines both current and emerging concepts of the functional linkage between the cytosol and the mitochondrial matrix with a specific focus on metabolic reserve and energetic efficiency. These principles of exchange and transport mechanisms across the mitochondrial membrane are reviewed for the failing heart from the perspectives of chronic pressure overload and diabetes mellitus. PMID:24526677

  3. Mechanically strong, flexible polyimide aerogels cross-linked with aromatic triamine.

    PubMed

    Meador, Mary Ann B; Malow, Ericka J; Silva, Rebecca; Wright, Sarah; Quade, Derek; Vivod, Stephanie L; Guo, Haiquan; Guo, Jiao; Cakmak, Miko

    2012-02-01

    Polyimide gels are produced by cross-linking anhydride capped polyamic acid oligomers with aromatic triamine in solution and chemically imidizing. The gels are then supercritically dried to form nanoporous polyimide aerogels with densities as low as 0.14 g/cm(3) and surface areas as high as 512 m(2)/g. To understand the effect of the polyimide backbone on properties, aerogels from several combinations of diamine and dianhydride, and formulated oligomer chain length are examined. Formulations made from 2,2'-dimethylbenzidine as the diamine shrink the least but have among the highest compressive modulus. Formulations made using 4,4'-oxydianiline or 2,2'dimethylbenzidine can be fabricated into continuous thin films using a roll to roll casting process. The films are flexible enough to be rolled or folded back on themselves and recover completely without cracking or flaking, and have tensile strengths of 4-9 MPa. Finally, the highest onset of decomposition (above 600 °C) of the polyimide aerogels was obtained using p-phenylene diamine as the backbone diamine with either dianhydride studied. All of the aerogels are suitable candidates for high-temperature insulation with glass transition temperatures ranging from 270-340 °C and onsets of decomposition from 460-610 °C. PMID:22233638

  4. Neuroinflammatory mechanisms in Parkinson's disease: Potential environmental triggers, pathways, and targets for early therapeutic intervention

    PubMed Central

    Tansey, Malú G.; McCoy, Melissa K.; Frank-Cannon, Tamy C.

    2013-01-01

    Most acute and chronic neurodegenerative conditions are accompanied by neuroinflammation; yet the exact nature of the inflammatory processes and whether they modify disease progression is not well understood. In this review, we discuss the key epidemiological, clinical, and experimental evidence implicating inflammatory processes in the progressive degeneration of the dopaminergic (DA) nigrostriatal pathway and their potential contribution to the pathophysiology of Parkinson's disease (PD). Given that interplay between genetics and environment are likely to contribute to risk for development of idiopathic PD, recent data showing interactions between products of genes linked to heritable PD that function to protect DA neurons against oxidative or proteolytic stress and inflammation pathways will be discussed. Cellular mechanisms activated or enhanced by inflammatory processes that may contribute to mitochondrial dysfunction, oxidative stress, or apoptosis of dopaminergic (DA) neurons will be reviewed, with special emphasis on tumor necrosis factor (TNF) and interleukin-1-beta (IL-1β) signaling pathways. Epigenetic factors which have the potential to trigger neuroinflammation, including environmental exposures and age-associated chronic inflammatory conditions, will be discussed as possible ‘second-hit’ triggers that may affect disease onset or progression of idiopathic PD. If inflammatory processes have an active role in nigrostriatal pathway degeneration, then evidence should exist to indicate that such processes begin in the early stages of disease and that they contribute to neuronal dysfunction and/or hasten neurodegeneration of the nigrostriatal pathway. Therapeutically, if anti-inflammatory interventions can be shown to rescue nigral DA neurons from degeneration and lower PD risk, then timely use of anti-inflammatory therapies should be investigated further in well-designed clinical trials for their ability to prevent or delay the progressive loss of

  5. The role of hexokinase in cardioprotection – mechanism and potential for translation

    PubMed Central

    Pereira, Gonçalo C; Pasdois, Philippe

    2015-01-01

    Mitochondrial permeability transition pore (mPTP) opening plays a critical role in cardiac reperfusion injury and its prevention is cardioprotective. Tumour cell mitochondria usually have high levels of hexokinase isoform 2 (HK2) bound to their outer mitochondrial membranes (OMM) and HK2 binding to heart mitochondria has also been implicated in resistance to reperfusion injury. HK2 dissociates from heart mitochondria during ischaemia, and the extent of this correlates with the infarct size on reperfusion. Here we review the mechanisms and regulations of HK2 binding to mitochondria and how this inhibits mPTP opening and consequent reperfusion injury. Major determinants of HK2 dissociation are the elevated glucose‐6‐phosphate concentrations and decreased pH in ischaemia. These are modulated by the myriad of signalling pathways implicated in preconditioning protocols as a result of a decrease in pre‐ischaemic glycogen content. Loss of mitochondrial HK2 during ischaemia is associated with permeabilization of the OMM to cytochrome c, which leads to greater reactive oxygen species production and mPTP opening during reperfusion. Potential interactions between HK2 and OMM proteins associated with mitochondrial fission (e.g. Drp1) and apoptosis (B‐cell lymphoma 2 family members) in these processes are examined. Also considered is the role of HK2 binding in stabilizing contact sites between the OMM and the inner membrane. Breakage of these during ischaemia is proposed to facilitate cytochrome c loss during ischaemia while increasing mPTP opening and compromising cellular bioenergetics during reperfusion. We end by highlighting the many unanswered questions and discussing the potential of modulating mitochondrial HK2 binding as a pharmacological target. Linked Articles This article is part of a themed section on Conditioning the Heart – Pathways to Translation. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue‐8 PMID

  6. Evaluation of potential reaction mechanisms leading to the formation of coniferyl alcohol a-linkages in lignin: a density functional theory study

    SciTech Connect

    Watts, Heath D.; Mohamed, Mohamed Naseer Ali; Kubicki, James D.

    2011-01-01

    Five potential reaction mechanisms, each leading to the formation of an α-O-4-linked coniferyl alcohol dimer, and one scheme leading to the formation of a recently proposed free-radical coniferyl alcohol trimer were assessed using density functional theory (DFT) calculations. These potential reaction mechanisms were evaluated using both the calculated Gibbs free energies, to predict the spontaneity of the constituent reactions, and the electron-density mapped Fukui function, to determine the most reactive sites of each intermediate species. The results indicate that each reaction in one of the six mechanisms is thermodynamically favorable to those in the other mechanisms; what is more, the Fukui function for each free radical intermediate corroborates with the thermochemical results for this mechanism. This mechanism proceeds via the formation of two distinct free-radical intermediates, which then react to produce the four α-O-4 stereoisomers.

  7. Pathological relationships involving iron and myelin may constitute a shared mechanism linking various rare and common brain diseases

    PubMed Central

    Heidari, Moones; Gerami, Sam H.; Bassett, Brianna; Graham, Ross M.; Chua, Anita C.G.; Aryal, Ritambhara; House, Michael J.; Collingwood, Joanna F.; Bettencourt, Conceição; Houlden, Henry; Ryten, Mina; Olynyk, John K.; Trinder, Debbie; Johnstone, Daniel M.; Milward, Elizabeth A.

    2016-01-01

    ABSTRACT We previously demonstrated elevated brain iron levels in myelinated structures and associated cells in a hemochromatosis Hfe−/−xTfr2mut mouse model. This was accompanied by altered expression of a group of myelin-related genes, including a suite of genes causatively linked to the rare disease family ‘neurodegeneration with brain iron accumulation’ (NBIA). Expanded data mining and ontological analyses have now identified additional myelin-related transcriptome changes in response to brain iron loading. Concordance between the mouse transcriptome changes and human myelin-related gene expression networks in normal and NBIA basal ganglia testifies to potential clinical relevance. These analyses implicate, among others, genes linked to various rare central hypomyelinating leukodystrophies and peripheral neuropathies including Pelizaeus-Merzbacher-like disease and Charcot-Marie-Tooth disease as well as genes linked to other rare neurological diseases such as Niemann-Pick disease. The findings may help understand interrelationships of iron and myelin in more common conditions such as hemochromatosis, multiple sclerosis and various psychiatric disorders. PMID:27500074

  8. Pathological relationships involving iron and myelin may constitute a shared mechanism linking various rare and common brain diseases.

    PubMed

    Heidari, Moones; Gerami, Sam H; Bassett, Brianna; Graham, Ross M; Chua, Anita C G; Aryal, Ritambhara; House, Michael J; Collingwood, Joanna F; Bettencourt, Conceição; Houlden, Henry; Ryten, Mina; Olynyk, John K; Trinder, Debbie; Johnstone, Daniel M; Milward, Elizabeth A

    2016-01-01

    We previously demonstrated elevated brain iron levels in myelinated structures and associated cells in a hemochromatosis Hfe (-/-) xTfr2 (mut) mouse model. This was accompanied by altered expression of a group of myelin-related genes, including a suite of genes causatively linked to the rare disease family 'neurodegeneration with brain iron accumulation' (NBIA). Expanded data mining and ontological analyses have now identified additional myelin-related transcriptome changes in response to brain iron loading. Concordance between the mouse transcriptome changes and human myelin-related gene expression networks in normal and NBIA basal ganglia testifies to potential clinical relevance. These analyses implicate, among others, genes linked to various rare central hypomyelinating leukodystrophies and peripheral neuropathies including Pelizaeus-Merzbacher-like disease and Charcot-Marie-Tooth disease as well as genes linked to other rare neurological diseases such as Niemann-Pick disease. The findings may help understand interrelationships of iron and myelin in more common conditions such as hemochromatosis, multiple sclerosis and various psychiatric disorders. PMID:27500074

  9. Diminished swelling of cross-linked aromatic oligoamide surfaces revealing a new fouling mechanism of reverse-osmosis membranes.

    PubMed

    Ying, Wang; Kumar, Rajender; Herzberg, Moshe; Kasher, Roni

    2015-06-01

    Swelling of the active layer of reverse osmosis (RO) membranes has an important effect on permeate water flux. The effects of organic- and biofouling on the swelling of the RO membrane active layer and the consequent changes of permeate flux are examined here. A cross-linked aromatic oligoamide film that mimics the surface chemistry of an RO polyamide membrane was synthesized stepwise on gold-coated surfaces. Foulant adsorption to the oligoamide film and its swelling were measured with a quartz crystal microbalance, and the effects of fouling on the membrane's performance were evaluated. The foulants were extracellular polymeric substances (EPS) extracted from fouled RO membranes and organic compounds of ultrafiltration permeate (UFP) from a membrane bioreactor used to treat municipal wastewater. The adsorbed foulants affected the swelling of the cross-linked oligoamide film differently. EPS had little effect on the swelling of the oligoamide film, whereas UFP significantly impaired swelling. Permeate flux declined more rapidly under UFP fouling than it did under EPS. Foulant adsorption was shown to diminish swelling of the aromatic oligoamide surfaces. Among the already known RO membrane fouling mechanisms, a novel RO fouling mechanism is proposed, in which foulant-membrane interactions hinder membrane swelling and thus increase hydraulic resistance. PMID:25920584

  10. Link between pay for performance incentives and physician payment mechanisms: evidence from the diabetes management incentive in Ontario.

    PubMed

    Kantarevic, Jasmin; Kralj, Boris

    2013-12-01

    Pay for performance (P4P) incentives for physicians are generally designed as additional payments that can be paired with any existing payment mechanism such as a salary, fee-for-services and capitation. However, the link between the physician response to performance incentives and the existing payment mechanisms is still not well understood. In this article, we study this link using the recent primary care physician payment reform in Ontario as a natural experiment and the Diabetes Management Incentive as a case study. Using a comprehensive administrative data strategy and a difference-in-differences matching strategy, we find that physicians in a blended capitation model are more responsive to the Diabetes Management Incentive than physicians in an enhanced fee-for-service model. We show that this result implies that the optimal size of P4P incentives vary negatively with the degree of supply-side cost-sharing. These results have important implications for the design of P4P programs and the cost of their implementation. PMID:23203722

  11. Linking chlorophyll a fluorescence to photosynthesis for remote sensing applications: mechanisms and challenges.

    PubMed

    Porcar-Castell, Albert; Tyystjärvi, Esa; Atherton, Jon; van der Tol, Christiaan; Flexas, Jaume; Pfündel, Erhard E; Moreno, Jose; Frankenberg, Christian; Berry, Joseph A

    2014-08-01

    Chlorophyll a fluorescence (ChlF) has been used for decades to study the organization, functioning, and physiology of photosynthesis at the leaf and subcellular levels. ChlF is now measurable from remote sensing platforms. This provides a new optical means to track photosynthesis and gross primary productivity of terrestrial ecosystems. Importantly, the spatiotemporal and methodological context of the new applications is dramatically different compared with most of the available ChlF literature, which raises a number of important considerations. Although we have a good mechanistic understanding of the processes that control the ChlF signal over the short term, the seasonal link between ChlF and photosynthesis remains obscure. Additionally, while the current understanding of in vivo ChlF is based on pulse amplitude-modulated (PAM) measurements, remote sensing applications are based on the measurement of the passive solar-induced chlorophyll fluorescence (SIF), which entails important differences and new challenges that remain to be solved. In this review we introduce and revisit the physical, physiological, and methodological factors that control the leaf-level ChlF signal in the context of the new remote sensing applications. Specifically, we present the basis of photosynthetic acclimation and its optical signals, we introduce the physical and physiological basis of ChlF from the molecular to the leaf level and beyond, and we introduce and compare PAM and SIF methodology. Finally, we evaluate and identify the challenges that still remain to be answered in order to consolidate our mechanistic understanding of the remotely sensed SIF signal. PMID:24868038

  12. Water Vapor Feedback and Links to Mechanisms of Recent Tropical Climate Variations

    NASA Technical Reports Server (NTRS)

    Robertson, F. R.; Miller, Tim L.

    2008-01-01

    Recent variations of tropical climate on interannual to near-decadal scales have provided a useful target for studying feedback processes. A strong warm/cold ENSO couplet (e.g. 1997-2000) along with several subsequent weaker events are prominent interannual signals that are part of an apparent longer term strengthening of the Walker circulation during the mid to late1990 s with some weakening thereafter. Decadal scale changes in tropical SST structure during the 1990s are accompanied by focusing of precipitation over the Indo-Pacific warm pool and an increase in tropical ocean evaporation of order 1.0 %/decade. Here we use a number of diverse satellite measurements to explore connections between upper-tropospheric humidity (UTH) variations on these time scales and changes in other water and energy fluxes. Precipitation (GPCP, TRMM), turbulent fluxes (OAFlux), and radiative fluxes (ERBE / CERES, SRB) are use to analyze vertically-integrated divergence of moist static energy, divMSE, and its dry and moist components. Strong signatures of MSE flux transport linking ascending and descending regions of tropical circulations are found. Relative strengths of these transports compared to radiative flux changes are interpreted as a measure of efficiency in the overall process of heat rejection during episodes of warm or cold SST forcing. In conjunction with the diagnosed energy transports we explore frequency distributions of upper-tropospheric humidity as inferred from SSM/T-2 and AMSU-B passive microwave measurements. Relating these variations to SST changes suggests positive water vapor feedback, but at a level reduced from constant relative humidity.

  13. Parenting Mechanisms in Links between Parents’ and Adolescents’ Alcohol Use Behaviors

    PubMed Central

    Latendresse, Shawn J.; Rose, Richard J.; Viken, Richard J.; Pulkkinen, Lea; Kaprio, Jaakko; Dick, Danielle M.

    2008-01-01

    Background Adolescence has been identified as a critical period with regard to the initiation and early escalation of alcohol use. Moreover, research on familial risk and protective processes provides independent support for multiple domains of parental influence on adolescent drinking; including parents’ own drinking behaviors, as well as the practices they employ to socialize their children. Despite this prevalence of findings, whether and how these distinct associations are related to one another is still not entirely clear. Methods The present study used data from 4731 adolescents and their parents to test the nature of associations between (a) parents’ frequencies of alcohol use and intoxication, and lifetime alcohol-related problems, (b) adolescents’ perceptions of the parenting that they receive, and (c) adolescents’ prevalence of alcohol use and intoxication at ages 14 and 17½. As such, multiple mediation modeling was used to assess whether parental alcohol use behaviors influence adolescent alcohol use directly, or if they operate through indirect associations with various aspects of parenting that subsequently influence adolescent use. Results Examination of simple associations demonstrated that maternal and paternal alcohol use behaviors were positively linked with adolescent use behaviors at ages 14 and 17½. Likewise, several parenting behaviors were independently associated with both parental and adolescent drinking. Examined collectively, multivariate path analyses indicated that associations between parents’ and adolescents’ alcohol-related behaviors were mediated, in part, by adolescents’ perceptions of the parenting that they received, especially at age 14. Furthermore, perceived parental monitoring and discipline had unique mediating capabilities, net the effects of all other parenting behaviors. Conclusions This study demonstrates that parenting is an important mediator of the association between parental and adolescent drinking

  14. CAPS and Munc13 utilize distinct PIP2-linked mechanisms to promote vesicle exocytosis

    PubMed Central

    Kabachinski, Greg; Yamaga, Masaki; Kielar-Grevstad, D. Michelle; Bruinsma, Stephen; Martin, Thomas F. J.

    2014-01-01

    Phosphoinositides provide compartment-specific signals for membrane trafficking. Plasma membrane phosphatidylinositol 4,5-bisphosphate (PIP2) is required for Ca2+-triggered vesicle exocytosis, but whether vesicles fuse into PIP2-rich membrane domains in live cells and whether PIP2 is metabolized during Ca2+-triggered fusion were unknown. Ca2+-dependent activator protein in secretion 1 (CAPS-1; CADPS/UNC31) and ubMunc13-2 (UNC13B) are PIP2-binding proteins required for Ca2+-triggered vesicle exocytosis in neuroendocrine PC12 cells. These proteins are likely effectors for PIP2, but their localization during exocytosis had not been determined. Using total internal reflection fluorescence microscopy in live cells, we identify PIP2-rich membrane domains at sites of vesicle fusion. CAPS is found to reside on vesicles but depends on plasma membrane PIP2 for its activity. Munc13 is cytoplasmic, but Ca2+-dependent translocation to PIP2-rich plasma membrane domains is required for its activity. The results reveal that vesicle fusion into PIP2-rich membrane domains is facilitated by sequential PIP2-dependent activation of CAPS and PIP2-dependent recruitment of Munc13. PIP2 hydrolysis only occurs under strong Ca2+ influx conditions sufficient to activate phospholipase Cη2 (PLCη2). Such conditions reduce CAPS activity and enhance Munc13 activity, establishing PLCη2 as a Ca2+-dependent modulator of exocytosis. These studies provide a direct view of the spatial distribution of PIP2 linked to vesicle exocytosis via regulation of lipid-dependent protein effectors CAPS and Munc13. PMID:24356451

  15. Linking hydrologic, physical and chemical habitat environments for the potential assessment of fish community rehabilitation in a developing city

    NASA Astrophysics Data System (ADS)

    Zhao, C. S.; Yang, S. T.; Liu, C. M.; Dou, T. W.; Yang, Z. L.; Yang, Z. Y.; Liu, X. L.; Xiang, H.; Nie, S. Y.; Zhang, J. L.; Mitrovic, S. M.; Yu, Q.; Lim, R. P.

    2015-04-01

    Aquatic ecological rehabilitation is increasingly attracting considerable public and research attention. An effective method that requires less data and expertise would help in the assessment of rehabilitation potential and in the monitoring of rehabilitation activities as complicated theories and excessive data requirements on assemblage information make many current assessment models expensive and limit their wide use. This paper presents an assessment model for restoration potential which successfully links hydrologic, physical and chemical habitat factors to fish assemblage attributes drawn from monitoring datasets on hydrology, water quality and fish assemblages at a total of 144 sites, where 5084 fish were sampled and tested. In this model three newly developed sub-models, integrated habitat index (IHSI), integrated ecological niche breadth (INB) and integrated ecological niche overlap (INO), are established to study spatial heterogeneity of the restoration potential of fish assemblages based on gradient methods of habitat suitability index and ecological niche models. To reduce uncertainties in the model, as many fish species as possible, including important native fish, were selected as dominant species with monitoring occurring over several seasons to comprehensively select key habitat factors. Furthermore, a detrended correspondence analysis (DCA) was employed prior to a canonical correspondence analysis (CCA) of the data to avoid the "arc effect" in the selection of key habitat factors. Application of the model to data collected at Jinan City, China proved effective reveals that three lower potential regions that should be targeted in future aquatic ecosystem rehabilitation programs. They were well validated by the distribution of two habitat parameters: river width and transparency. River width positively influenced and transparency negatively influenced fish assemblages. The model can be applied for monitoring the effects of fish assemblage restoration

  16. A molecular mechanism that links Hippo signalling to the inhibition of Wnt/β-catenin signalling

    PubMed Central

    Imajo, Masamichi; Miyatake, Koichi; Iimura, Akira; Miyamoto, Atsumu; Nishida, Eisuke

    2012-01-01

    The Hippo signalling pathway has emerged as a key regulator of organ size, tissue homeostasis, and patterning. Recent studies have shown that two effectors in this pathway, YAP/TAZ, modulate Wnt/β-catenin signalling through their interaction with β-catenin or Dishevelled, depending on biological contexts. Here, we identify a novel mechanism through which Hippo signalling inhibits Wnt/β-catenin signalling. We show that YAP and TAZ, the transcriptional co-activators in the Hippo pathway, suppress Wnt signalling without suppressing the stability of β-catenin but through preventing its nuclear translocation. Our results show that YAP/TAZ binds to β-catenin, thereby suppressing Wnt-target gene expression, and that the Hippo pathway-stimulated phosphorylation of YAP, which induces cytoplasmic translocation of YAP, is required for the YAP-mediated inhibition of Wnt/β-catenin signalling. We also find that downregulation of Hippo signalling correlates with upregulation of β-catenin signalling in colorectal cancers. Remarkably, our analysis demonstrates that phosphorylated YAP suppresses nuclear translocation of β-catenin by directly binding to it in the cytoplasm. These results provide a novel mechanism, in which Hippo signalling antagonizes Wnt signalling by regulating nuclear translocation of β-catenin. PMID:22234184

  17. Intermediate strain rate behaviour of cancellous bone: Links between microstructural and mechanical properties

    NASA Astrophysics Data System (ADS)

    Prot, Marianne; Cloete, Trevor; Saletti, Dominique; Laporte, Sebastien

    2015-09-01

    Relationships between the micro-architecture description of cancellous bone, obtained from medical imaging, and its mechanical properties can be used to assess the compression fracture risk at high and low strain rate. This study extends the rupture prediction to the intermediate strain rate regime. The micro-architecture description was obtained with a CT-scan, for which geometry, topology, connectivity and anisotropy parameters were computed and compared to mechanical identified parameters in order to confirm their usefulness. Three strain rates were investigated: 1/s, 10/s and 100/s using two different devices: a Wedge-Bar apparatus and a conventional split Hopkinson pressure bar implemented with a Cone-in-Tube striker and a tandem momentum trap. This setup provides a constant strain rate loading with routine specimen recovery allowing the fracture zone to be investigated. This study reveals that a transition in the response behaviour occurred in the intermediate regime and confirms the significant porous organization influence through the regimes.

  18. A novel DAG-dependent mechanism links PKCa and Cyclin B1 regulating cell cycle progression

    PubMed Central

    Poli, Alessandro; Ramazzotti, Giulia; Matteucci, Alessandro; Manzoli, Lucia; Lonetti, Annalisa; Suh, Pann-Ghill; McCubrey, James A.; Cocco, Lucio

    2014-01-01

    Through the years, different studies showed the involvement of Protein Kinase C (PKC) in cell cycle control, in particular during G1/S transition. Little is known about their role at G2/M checkpoint. In this study, using K562 human erythroleukemia cell line, we found a novel and specific mechanism through which the conventional isoform PKC⍺ positively affects Cyclin B1 modulating G2/M progression of cell cycle. Since the kinase activity of this PKC isoform was not necessary in this process, we demonstrated that PKC⍺, physically interacting with Cyclin B1, avoided its degradation and stimulated its nuclear import at mitosis. Moreover, the process resulted to be strictly connected with the increase in nuclear diacylglycerol levels (DAG) at G2/M checkpoint, due to the activity of nuclear Phospholipase C β1 (PLCβ1), the only PLC isoform mainly localized in the nucleus of K562 cells. Taken together, our findings indicated a novel DAG dependent mechanism able to regulate the G2/M progression of the cell cycle. PMID:25362646

  19. From hypothesis to mechanism: uncovering nuclear pore complex links to gene expression.

    PubMed

    Burns, Laura T; Wente, Susan R

    2014-06-01

    The gene gating hypothesis put forth by Blobel in 1985 was an alluring proposal outlining functions for the nuclear pore complex (NPC) in transcription and nuclear architecture. Over the past several decades, collective studies have unveiled a full catalog of nucleoporins (Nups) that comprise the NPC, structural arrangements of Nups in the nuclear pore, and mechanisms of nucleocytoplasmic transport. With this foundation, investigations of the gene gating hypothesis have now become possible. Studies of several model organisms provide credence for Nup functions in transcription, mRNA export, and genome organization. Surprisingly, Nups are not only involved in transcriptional events that occur at the nuclear periphery, but there are also novel roles for dynamic Nups within the nucleoplasmic compartment. Several tenants of the original gene gating hypothesis have yet to be addressed. Knowledge of whether the NPC impacts the organization of the genome to control subsets of genes is limited, and the cooperating molecular machinery or specific genomic anchoring sequences are not fully resolved. This minireview summarizes the current evidence for gene gating in Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, and mammalian model systems. These examples highlight new and unpredicted mechanisms for Nup impacts on transcription and questions that are left to be explored. PMID:24615017

  20. Fast Prediction of HCCI Combustion with an Artificial Neural Network Linked to a Fluid Mechanics Code

    SciTech Connect

    Aceves, S M; Flowers, D L; Chen, J; Babaimopoulos, A

    2006-08-29

    We have developed an artificial neural network (ANN) based combustion model and have integrated it into a fluid mechanics code (KIVA3V) to produce a new analysis tool (titled KIVA3V-ANN) that can yield accurate HCCI predictions at very low computational cost. The neural network predicts ignition delay as a function of operating parameters (temperature, pressure, equivalence ratio and residual gas fraction). KIVA3V-ANN keeps track of the time history of the ignition delay during the engine cycle to evaluate the ignition integral and predict ignition for each computational cell. After a cell ignites, chemistry becomes active, and a two-step chemical kinetic mechanism predicts composition and heat generation in the ignited cells. KIVA3V-ANN has been validated by comparison with isooctane HCCI experiments in two different engines. The neural network provides reasonable predictions for HCCI combustion and emissions that, although typically not as good as obtained with the more physically representative multi-zone model, are obtained at a much reduced computational cost. KIVA3V-ANN can perform reasonably accurate HCCI calculations while requiring only 10% more computational effort than a motored KIVA3V run. It is therefore considered a valuable tool for evaluation of engine maps or other performance analysis tasks requiring multiple individual runs.

  1. Statistical Analysis of Crystallization Database Links Protein Physico-Chemical Features with Crystallization Mechanisms

    PubMed Central

    Fusco, Diana; Barnum, Timothy J.; Bruno, Andrew E.; Luft, Joseph R.; Snell, Edward H.; Mukherjee, Sayan; Charbonneau, Patrick

    2014-01-01

    X-ray crystallography is the predominant method for obtaining atomic-scale information about biological macromolecules. Despite the success of the technique, obtaining well diffracting crystals still critically limits going from protein to structure. In practice, the crystallization process proceeds through knowledge-informed empiricism. Better physico-chemical understanding remains elusive because of the large number of variables involved, hence little guidance is available to systematically identify solution conditions that promote crystallization. To help determine relationships between macromolecular properties and their crystallization propensity, we have trained statistical models on samples for 182 proteins supplied by the Northeast Structural Genomics consortium. Gaussian processes, which capture trends beyond the reach of linear statistical models, distinguish between two main physico-chemical mechanisms driving crystallization. One is characterized by low levels of side chain entropy and has been extensively reported in the literature. The other identifies specific electrostatic interactions not previously described in the crystallization context. Because evidence for two distinct mechanisms can be gleaned both from crystal contacts and from solution conditions leading to successful crystallization, the model offers future avenues for optimizing crystallization screens based on partial structural information. The availability of crystallization data coupled with structural outcomes analyzed through state-of-the-art statistical models may thus guide macromolecular crystallization toward a more rational basis. PMID:24988076

  2. Linking the mechanics and energetics of hopping with elastic ankle exoskeletons.

    PubMed

    Farris, Dominic James; Sawicki, Gregory S

    2012-12-15

    The springlike mechanics of the human leg during bouncing gaits has inspired the design of passive assistive devices that use springs to aid locomotion. The purpose of this study was to test whether a passive spring-loaded ankle exoskeleton could reduce the mechanical and energetic demands of bilateral hopping on the musculoskeletal system. Joint level kinematics and kinetics were collected with electromyographic and metabolic energy consumption data for seven participants hopping at four frequencies (2.2, 2.5, 2.8, and 3.2 Hz). Hopping was performed without an exoskeleton; with an springless exoskeleton; and with a spring-loaded exoskeleton. Spring-loaded ankle exoskeletons reduced plantar flexor muscle activity and the biological contribution to ankle joint moment (15-25%) and average positive power (20-40%). They also facilitated reductions in metabolic power (15-20%) across frequencies from 2.2 to 2.8 Hz compared with hopping with a springless exoskeleton. Reductions in metabolic power compared with hopping with no exoskeleton were restricted to hopping at 2.5 Hz only (12%). These results highlighted the importance of reducing the rate of muscular force production and work to achieve metabolic reductions. They also highlighted the importance of assisting muscles acting at the knee joint. Exoskeleton designs may need to be tuned to optimize exoskeleton mass, spring stiffness, and spring slack length to achieve greater metabolic reductions. PMID:23065760

  3. Linking governance mechanisms to health outcomes: a review of the literature in low- and middle-income countries.

    PubMed

    Ciccone, Dana Karen; Vian, Taryn; Maurer, Lydia; Bradley, Elizabeth H

    2014-09-01

    We conducted a synthesis of peer-reviewed literature to shed light on links between governance mechanisms and health outcomes in low- and middle-income countries. Our review yielded 30 studies, highlighting four key governance mechanisms by which governance may influence health outcomes in these settings: Health system decentralization that enables responsiveness to local needs and values; health policymaking that aligns and empowers diverse stakeholders; enhanced community engagement; and strengthened social capital. Most, but not all, studies found a positive association between governance and health. Additionally, the nature of the association between governance mechanisms and health differed across studies. In some studies (N = 9), the governance effect was direct and positive, while in others (N = 5), the effect was indirect or modified by contextual factors. In still other studies (N = 4), governance was found to have a moderating effect, indicating that governance mechanisms influenced other system processes or structures that improved health. The remaining studies reported mixed findings about the association between governance and health (N = 6), no association between governance and health (N = 4), or had inconclusive results (N = 2). Further exploration is needed to fully understand the relationship between governance and health and to inform the design and delivery of evidence-based, effective governance interventions around the world. PMID:25054281

  4. Remarkable Improvement in the Mechanical Properties and CO2 Uptake of MOFs Brought About by Covalent Linking to Graphene.

    PubMed

    Kumar, Ram; Raut, Devaraj; Ramamurty, Upadrasta; Rao, C N R

    2016-06-27

    Metal-organic frameworks (MOFs) are exceptional as gas adsorbents but their mechanical properties are poor. We present a successful strategy to improve the mechanical properties along with gas adsorption characteristics, wherein graphene (Gr) is covalently bonded with M/DOBDC (M=Mg(2+) , Ni(2+) , or Co(2+) , DOBDC=2,5-dioxido-1,4-benzene dicarboxylate) MOFs. The surface area of the graphene-MOF composites increases up to 200-300 m(2)  g(-1) whereas the CO2 uptake increases by ca. 3-5 wt % at 0.15 atm and by 6-10 wt % at 1 atm. What is significant is that the composites exhibit improved mechanical properties. In the case of Mg/DOBDC, a three-fold increase in both the elastic modulus and hardness with 5 wt % graphene reinforcement is observed. Improvement in both the mechanical properties and gas adsorption characteristics of porous MOFs on linking them to graphene is a novel observation and suggests a new avenue for the design and synthesis of porous materials. PMID:27282430

  5. Unexpected behavior of irradiated spider silk links conformational freedom to mechanical performance.

    PubMed

    Perea, G Belén; Solanas, Concepción; Plaza, Gustavo R; Guinea, Gustavo V; Jorge, Inmaculada; Vázquez, Jesús; Pérez Mateos, Jorge M; Marí-Buyé, Núria; Elices, Manuel; Pérez-Rigueiro, José

    2015-06-28

    Silk fibers from Argiope trifasciata and Nephila inaurata orb-web weaving spiders were UV irradiated to modify the molecular weight of the constituent proteins. Fibers were characterized either as forcibly silked or after being subjected to maximum supercontraction. The effect of irradiation on supercontraction was also studied, both in terms of the percentage of supercontraction and the tensile properties exhibited by irradiated and subsequently supercontracted fibers. The effects of UV exposure at the molecular level were assessed by polyacrylamide gel electrophoresis and mass spectrometry. It is shown that UV-irradiated fibers show a steady decrease in their main tensile parameters, most notably, tensile strength and strain. The combination of the mechanical and biochemical data suggests that the restricted conformational freedom of the proteins after UV irradiation is critical in the reduction of these properties. Consequently, an adequate topological organization of the protein chains emerges as a critical design principle in the performance of spider silk. PMID:25994594

  6. An evaluation and force gradient determination of mechanically linked reversible sidestick controllers for General Aviation aircraft

    NASA Technical Reports Server (NTRS)

    Bergeron, H. P.

    1984-01-01

    In connection with the increase in air traffic, IFR (Instrument Flight Rules) flight in the air traffic control system has become very demanding. It has, therefore, become imperative to optimize the pilot's skills in his management of the various aircraft systems. The present investigation is concerned with the human factors aspects of the use of sidesticks in direct mechanical linkage (reversible) control systems in a production General Aviation (G.A.) aircraft. A total of 140 fifteen to twenty minute flight tasks were flown on the NASA Langley G.A. motion base simulator. The study involved a comparison of three locations of the sidestick, left side, center, and right side, and the standard yoke. It was found that the sidestick is preferable to the standard yoke. However, some of the design and installation features of the sidestick are critical for pilot acceptance.

  7. Linking Pathogenic Mechanisms of Alcoholic Liver Disease With Clinical Phenotypes.

    PubMed

    Nagy, Laura E; Ding, Wen-Xing; Cresci, Gail; Saikia, Paramananda; Shah, Vijay H

    2016-06-01

    Alcoholic liver disease (ALD) develops in approximately 20% of alcoholic patients, with a higher prevalence in females. ALD progression is marked by fatty liver and hepatocyte necrosis, as well as apoptosis, inflammation, regenerating nodules, fibrosis, and cirrhosis.(1) ALD develops via a complex process involving parenchymal and nonparenchymal cells, as well as recruitment of other cell types to the liver in response to damage and inflammation. Hepatocytes are damaged by ethanol, via generation of reactive oxygen species and induction of endoplasmic reticulum stress and mitochondrial dysfunction. Hepatocyte cell death via apoptosis and necrosis are markers of ethanol-induced liver injury. We review the mechanisms by which alcohol injures hepatocytes and the response of hepatic sinusoidal cells to alcohol-induced injury. We also discuss how recent insights into the pathogenesis of ALD will affect the treatment and management of patients. PMID:26919968

  8. Photoinduced electron transfer and fluorescence mechanisms in covalently linked polynuclear aromatic-nucleotide complexes

    SciTech Connect

    Geacintov, N.E.; Mao, Bing; Zhao, Rushen; Chen, Junxin; Liu, Tong Ming; Ya, Nai-Qi; France, L.L.; Sutherland, J.D.

    1992-04-01

    The fluorescence of polycyclic aromatic hydrocarbon-nucleic acid complexes is quenched by photoinduced electron transfer mechanisms in aqueous solutions at ambient temperatures. These effects are illustrated with the biologically important compound benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE), a mutagenic and carcinogenic metabolite of the environmental pollutant benzo[a]pyrene, which forms covalent mutagenic lesions with 2{prime}-deoxyguanosine (dG) residues in DNA. The dependence of the fluroescence yeild and fluorescence decay times of the covalent model adduct (+)-trans-BPDE-N{sup 2}-dG as a function of temperature and methanol/water composition are described. Because of the sensitivity of the fluorescence of the pyrenyl residue to the polarity of the microenvironment, the magnitude of the fluorescence yield can be used to distinguish between highly hydrophobic (e.g. intercalation) and other more solvent-exposed BPDE-nucleic acid binding sites.

  9. Photoinduced electron transfer and fluorescence mechanisms in covalently linked polynuclear aromatic-nucleotide complexes

    SciTech Connect

    Geacintov, N.E.; Mao, Bing; Zhao, Rushen; Chen, Junxin; Liu, Tong Ming; Ya, Nai-Qi . Dept. of Chemistry); France, L.L.; Sutherland, J.D. )

    1992-01-01

    The fluorescence of polycyclic aromatic hydrocarbon-nucleic acid complexes is quenched by photoinduced electron transfer mechanisms in aqueous solutions at ambient temperatures. These effects are illustrated with the biologically important compound benzo(a)pyrene-7,8-diol-9,10-epoxide (BPDE), a mutagenic and carcinogenic metabolite of the environmental pollutant benzo(a)pyrene, which forms covalent mutagenic lesions with 2{prime}-deoxyguanosine (dG) residues in DNA. The dependence of the fluroescence yeild and fluorescence decay times of the covalent model adduct (+)-trans-BPDE-N{sup 2}-dG as a function of temperature and methanol/water composition are described. Because of the sensitivity of the fluorescence of the pyrenyl residue to the polarity of the microenvironment, the magnitude of the fluorescence yield can be used to distinguish between highly hydrophobic (e.g. intercalation) and other more solvent-exposed BPDE-nucleic acid binding sites.

  10. Linking Ventilation Heterogeneity Quantified via Hyperpolarized 3He MRI to Dynamic Lung Mechanics and Airway Hyperresponsiveness

    PubMed Central

    Lui, Justin K.; Parameswaran, Harikrishnan; Albert, Mitchell S.; Lutchen, Kenneth R.

    2015-01-01

    Advancements in hyperpolarized helium-3 MRI (HP 3He-MRI) have introduced the ability to render and quantify ventilation patterns throughout the anatomic regions of the lung. The goal of this study was to establish how ventilation heterogeneity relates to the dynamic changes in mechanical lung function and airway hyperresponsiveness in asthmatic subjects. In four healthy and nine mild-to-moderate asthmatic subjects, we measured dynamic lung resistance and lung elastance from 0.1 to 8 Hz via a broadband ventilation waveform technique. We quantified ventilation heterogeneity using a recently developed coefficient of variation method from HP 3He-MRI imaging. Dynamic lung mechanics and imaging were performed at baseline, post-challenge, and after a series of five deep inspirations. AHR was measured via the concentration of agonist that elicits a 20% decrease in the subject’s forced expiratory volume in one second compared to baseline (PC20) dose. The ventilation coefficient of variation was correlated to low-frequency lung resistance (R = 0.647, P < 0.0001), the difference between high and low frequency lung resistance (R = 0.668, P < 0.0001), and low-frequency lung elastance (R = 0.547, P = 0.0003). In asthmatic subjects with PC20 values <25 mg/mL, the coefficient of variation at baseline exhibited a strong negative trend (R = -0.798, P = 0.02) to PC20 dose. Our findings were consistent with the notion of peripheral rather than central involvement of ventilation heterogeneity. Also, the degree of AHR appears to be dependent on the degree to which baseline airway constriction creates baseline ventilation heterogeneity. HP 3He-MRI imaging may be a powerful predictor of the degree of AHR and in tracking the efficacy of therapy. PMID:26569412

  11. Linking lipid architecture to bilayer structure and mechanics using self-consistent field modelling

    NASA Astrophysics Data System (ADS)

    Pera, H.; Kleijn, J. M.; Leermakers, F. A. M.

    2014-02-01

    To understand how lipid architecture determines the lipid bilayer structure and its mechanics, we implement a molecularly detailed model that uses the self-consistent field theory. This numerical model accurately predicts parameters such as Helfrichs mean and Gaussian bending modulus kc and bar{k} and the preferred monolayer curvature J_0^m, and also delivers structural membrane properties like the core thickness, and head group position and orientation. We studied how these mechanical parameters vary with system variations, such as lipid tail length, membrane composition, and those parameters that control the lipid tail and head group solvent quality. For the membrane composition, negatively charged phosphatidylglycerol (PG) or zwitterionic, phosphatidylcholine (PC), and -ethanolamine (PE) lipids were used. In line with experimental findings, we find that the values of kc and the area compression modulus kA are always positive. They respond similarly to parameters that affect the core thickness, but differently to parameters that affect the head group properties. We found that the trends for bar{k} and J_0^m can be rationalised by the concept of Israelachivili's surfactant packing parameter, and that both bar{k} and J_0^m change sign with relevant parameter changes. Although typically bar{k}<0, membranes can form stable cubic phases when the Gaussian bending modulus becomes positive, which occurs with membranes composed of PC lipids with long tails. Similarly, negative monolayer curvatures appear when a small head group such as PE is combined with long lipid tails, which hints towards the stability of inverse hexagonal phases at the cost of the bilayer topology. To prevent the destabilisation of bilayers, PG lipids can be mixed into these PC or PE lipid membranes. Progressive loading of bilayers with PG lipids lead to highly charged membranes, resulting in J_0^m ≫ 0, especially at low ionic strengths. We anticipate that these changes lead to unstable membranes

  12. Quantum mechanical elucidation of reaction mechanisms of heavy-light-heavy systems: Role of potential ridge

    NASA Astrophysics Data System (ADS)

    Nobusada, Katsuyuki; Tolstikhin, Oleg I.; Nakamura, Hiroki

    1998-06-01

    A new idea to elucidate quantum reaction dynamics of heavy-light-heavy (HLH) systems is proposed on the basis of the hyperspherical elliptic coordinate approach. This coordinate system has a big advantage of nicely expressing good vibrational adiabaticity in the HLH systems. Taking this advantage, the concept of potential ridge is introduced, for the first time, in three-dimensional reactions. The potential ridge is proved to be very useful to extract some important avoided crossings which dominate the reaction dynamics. In fact, qualitative features of the reaction dynamics can be interpreted in terms of nonadiabatic transitions at those important avoided crossings near the potential ridge. Examples are: (i) onset of reaction for a specified initial rotational state, and (ii) major reactive transition for a specified initial rotational state. Avoided crossings to the left of the potential ridge are also useful to interpret certain aspects of reactions accompanying vibrational transitions. The new idea mentioned above is applied to a typical HLH reaction O(3P)+HCl→OH+Cl with the use of two types of potential energy surfaces.

  13. A lost link between a flightless parrot and a parasitic plant and the potential role of coprolites in conservation paleobiology.

    PubMed

    Wood, Jamie R; Wilmshurst, Janet M; Worthy, Trevor H; Holzapfel, Avi S; Cooper, Alan

    2012-12-01

    approach of linking paleobiology with neoecology offers significant untapped potential to help inform conservation and restoration plans. PMID:23025275

  14. Tomographic, kinematic and gravitational evidence for a slab under Greenland and its potential links to Arctic magmatism.

    NASA Astrophysics Data System (ADS)

    Shephard, Grace; Spakman, Wim; Panet, Isabelle; Gaina, Carmen; Trønnes, Reidar

    2015-04-01

    Seismic tomography and recent satellite gravity data reveal regions of anomalous structure within Earth's present-day mantle. On scales of some tens to hundreds of kilometers in wavelength, individual subducted slabs and mantle plumes can be resolved. When linked with global plate reconstructions and models of mantle convection, subducted slabs of lithosphere can be related to distinct periods of ocean basin closure. Here we explore the origins for a distinct fast seismic feature under present-day Greenland that is apparent across several P and S-wave tomography models. The sub-rounded seismic anomaly of interest is distinct from the more westerly "Farallon" slab, and is located in the mid mantle between ~1000-1600 km depth. We include a discussion of mantle sinking rates, showing that taking 1600 km slab base depth and applying sinking rate of 1.2 cm/yr implies a subduction age of ~133 Ma. We supplement the tomographic evidence for this slab with independent, satellite-derived vertical gravity gradients. Preliminary analysis of the gravity reveals a possible mantle anomaly in the SW Greenland region, complementary in spatial extent to that inferred from tomography. Considering absolute and relative plate reference frames, we suggest that palaeo-Arctic subduction related to the opening of the Amerasia Basin in the Jurassic, may account for this mantle feature. We finally investigate potential geochemical links of this slab feature with high arctic magmatism in the Cretaceous, showing that a time-dependent consideration of surface kinematics and mantle dynamics may reveal new insights into the geodynamic evolution of the Arctic.

  15. Colony Failure Linked to Low Sperm Viability in Honey Bee (Apis mellifera) Queens and an Exploration of Potential Causative Factors.

    PubMed

    Pettis, Jeffery S; Rice, Nathan; Joselow, Katie; vanEngelsdorp, Dennis; Chaimanee, Veeranan

    2016-01-01

    Queen health is closely linked to colony performance in honey bees as a single queen is normally responsible for all egg laying and brood production within the colony. In the U. S. in recent years, queens have been failing at a high rate; with 50% or greater of queens replaced in colonies within 6 months when historically a queen might live one to two years. This high rate of queen failure coincides with the high mortality rates of colonies in the US, some years with >50% of colonies dying. In the current study, surveys of sperm viability in US queens were made to determine if sperm viability plays a role in queen or colony failure. Wide variation was observed in sperm viability from four sets of queens removed from colonies that beekeepers rated as in good health (n = 12; average viability = 92%), were replacing as part of normal management (n = 28; 57%), or where rated as failing (n = 18 and 19; 54% and 55%). Two additional paired set of queens showed a statistically significant difference in viability between colonies rated by the beekeeper as failing or in good health from the same apiaries. Queens removed from colonies rated in good health averaged high viability (ca. 85%) while those rated as failing or in poor health had significantly lower viability (ca. 50%). Thus low sperm viability was indicative of, or linked to, colony performance. To explore the source of low sperm viability, six commercial queen breeders were surveyed and wide variation in viability (range 60-90%) was documented between breeders. This variability could originate from the drones the queens mate with or temperature extremes that queens are exposed to during shipment. The role of shipping temperature as a possible explanation for low sperm viability was explored. We documented that during shipment queens are exposed to temperature spikes (<8 and > 40°C) and these spikes can kill 50% or more of the sperm stored in queen spermathecae in live queens. Clearly low sperm viability is linked

  16. Colony Failure Linked to Low Sperm Viability in Honey Bee (Apis mellifera) Queens and an Exploration of Potential Causative Factors

    PubMed Central

    Pettis, Jeffery S.; Rice, Nathan; Joselow, Katie; vanEngelsdorp, Dennis; Chaimanee, Veeranan

    2016-01-01

    linked to colony performance and laboratory and field data provide evidence that temperature extremes are a potential causative factor. PMID:26863438

  17. Linking lipid architecture to bilayer structure and mechanics using self-consistent field modelling

    SciTech Connect

    Pera, H.; Kleijn, J. M.; Leermakers, F. A. M.

    2014-02-14

    To understand how lipid architecture determines the lipid bilayer structure and its mechanics, we implement a molecularly detailed model that uses the self-consistent field theory. This numerical model accurately predicts parameters such as Helfrichs mean and Gaussian bending modulus k{sub c} and k{sup ¯} and the preferred monolayer curvature J{sub 0}{sup m}, and also delivers structural membrane properties like the core thickness, and head group position and orientation. We studied how these mechanical parameters vary with system variations, such as lipid tail length, membrane composition, and those parameters that control the lipid tail and head group solvent quality. For the membrane composition, negatively charged phosphatidylglycerol (PG) or zwitterionic, phosphatidylcholine (PC), and -ethanolamine (PE) lipids were used. In line with experimental findings, we find that the values of k{sub c} and the area compression modulus k{sub A} are always positive. They respond similarly to parameters that affect the core thickness, but differently to parameters that affect the head group properties. We found that the trends for k{sup ¯} and J{sub 0}{sup m} can be rationalised by the concept of Israelachivili's surfactant packing parameter, and that both k{sup ¯} and J{sub 0}{sup m} change sign with relevant parameter changes. Although typically k{sup ¯}<0, membranes can form stable cubic phases when the Gaussian bending modulus becomes positive, which occurs with membranes composed of PC lipids with long tails. Similarly, negative monolayer curvatures appear when a small head group such as PE is combined with long lipid tails, which hints towards the stability of inverse hexagonal phases at the cost of the bilayer topology. To prevent the destabilisation of bilayers, PG lipids can be mixed into these PC or PE lipid membranes. Progressive loading of bilayers with PG lipids lead to highly charged membranes, resulting in J{sub 0}{sup m}≫0, especially at low ionic

  18. A Summary of Pathways or Mechanisms Linking Preconception Maternal Nutrition with Birth Outcomes.

    PubMed

    King, Janet C

    2016-07-01

    Population, human, animal, tissue, and molecular studies show collectively and consistently that maternal nutrition in the pre- or periconception period influences fetal growth and development, which subsequently affects the individual's long-term health. It is known that nutrition during pregnancy is an important determinant of the offspring's growth and health. However, now there is evidence that the mother's nutritional status at conception also influences pregnancy outcome and long-term health. For example, the mother's nutritional status at conception influences the way energy is partitioned between maternal and fetal needs. Furthermore, placental development during the first weeks of gestation reflects maternal nutrition and establishes mechanisms for balancing maternal and fetal nutritional needs. Also, maternal nutritional signals at fertilization influence epigenetic remodeling of fetal genes. These findings all indicate that maternal parenting begins before conception. The following papers from a symposium on preconception nutrition presented at the 2015 Scientific Sessions and Annual Meeting of the ASN emphasize the importance of maternal nutrition at conception on the growth and long-term health of the child. PMID:27281808

  19. Broken English, broken bones? Mechanisms linking language proficiency and occupational health in a Montreal garment factory.

    PubMed

    Premji, Stéphanie; Messing, Karen; Lippel, Katherine

    2008-01-01

    Language barriers are often cited as a factor contributing to ethnic inequalities in occupational health; however, little information is available about the mechanisms at play. The authors describe the multiple ways in which language influences occupational health in a large garment factory employing many immigrants in Montreal. Between 2004 and 2006, individual, semi-structured interviews were conducted with 15 women and 10 men from 14 countries of birth. Interviews were conducted in French and English, Canada's official languages, as well as in non-official languages with the help of colleague-interpreters. Observation within the workplace was also carried out at various times during the project. The authors describe how proficiency in the official languages influences occupational health by affecting workers' ability to understand and communicate information, and supporting relationships that can affect work-related health. They also describe workers' strategies to address communication barriers and discuss the implications of these strategies from an occupational health standpoint. Along with the longer-term objectives of integrating immigrants into the linguistic majority and addressing structural conditions that can affect health, policies and practices need to be put in place to protect the health and well-being of those who face language barriers in the short term. PMID:18341120

  20. Mechanisms linking bacterial infections of the bovine endometrium to disease and infertility.

    PubMed

    Carneiro, Luísa Cunha; Cronin, James Graham; Sheldon, Iain Martin

    2016-03-01

    Bacterial infections of the endometrium after parturition commonly cause metritis and endometritis in dairy cattle, and these diseases are important because they compromise animal welfare and incur economic costs, as well as delaying or preventing conception. Here we highlight that uterine infections cause infertility, discuss which bacteria cause uterine disease, and review the evidence for mechanisms of inflammation and tissue damage in the endometrium. Bacteria cultured from the uterus of diseased animals include Escherichia coli, Trueperella pyogenes, and several anaerobic species, but their causative role in disease is challenged by the discovery of many other bacteria in the uterine disease microbiome. Irrespective of the species of bacteria, endometrial cell inflammatory responses to infection initially depend on innate immunity, with Toll-like receptors binding pathogen-associated molecular patterns, such as lipopolysaccharide and bacterial lipopeptides. In addition to tissue damage associated with parturition and inflammation, endometrial cell death is caused by a cholesterol-dependent cytolysin secreted by T. pyogenes, called pyolysin, which forms pores in plasma membranes of endometrial cells. However, endometrial cells surprisingly do not sense damage-associated molecular patterns, but a combination of infections followed by cell damage leads to release of the intracellular cytokine interleukin (IL)-1 alpha from endometrial cells, which then acts to scale inflammatory responses. To develop strategies to limit the impact of uterine disease on fertility, future work should focus on determining which bacteria and virulence factors cause endometritis, and understanding how the host response to infection is regulated in the endometrium. PMID:26952747

  1. Transcriptional mechanisms link epithelial plasticity to adhesion and differentiation of epidermal progenitor cells

    PubMed Central

    Lee, Briana; Villarreal-Ponce, Alvaro; Fallahi, Magid; Ovadia, Jeremy; Sun, Peng; Yu, Qian-Chun; Ito, Seiji; Sinha, Satrajit; Nie, Qing; Dai, Xing

    2014-01-01

    During epithelial tissue morphogenesis, developmental progenitor cells undergo dynamic adhesive and cytoskeletal remodeling to trigger proliferation and migration. Transcriptional mechanisms that restrict such mild form of epithelial plasticity to maintain lineage-restricted differentiation in committed epithelial tissues are poorly understood. Here we report that simultaneous ablation of transcriptional repressor-encoding Ovol1 and Ovol2 results in expansion and blocked terminal differentiation of embryonic epidermal progenitor cells. Conversely, mice overexpressing Ovol2 in their skin epithelia exhibit precocious differentiation accompanied by smaller progenitor cell compartments. We show that Ovol1/2-deficient epidermal cells fail to undertake α-catenin–driven actin cytoskeletal reorganization and adhesive maturation, and exhibit changes that resemble epithelial-to-mesenchymal transition (EMT). Remarkably, these alterations as well as defective terminal differentiation are reversed upon depletion of EMT-promoting transcriptional factor Zeb1. Collectively, our findings reveal Ovol-Zeb1-α-catenin sequential repression and highlight functions of Ovol as gatekeepers of epithelial adhesion and differentiation by inhibiting progenitor-like traits and epithelial plasticity. PMID:24735878

  2. Mammalian cell-transforming potential of traffic-linked ultrafine particulate matter PM0.056 in urban roadside atmosphere.

    PubMed

    Verma, Mukesh K; Poojan, Shiv; Sultana, Sarwat; Kumar, Sushil

    2014-09-01

    We examined the clastogenic and cell-transforming potential of ultrafine particulate matter fraction PM0.056 of urban ambient aerosol using mammalian cells. PM1.0, PM0.56 and PM0.056 fractions were sampled from roadside atmosphere of an urban area using the cascade impactor MOUDI-NR-110. The potential to induce cytotoxicity, DNA damage and micronuclei formation was examined at the test concentrations of 3, 6, 12.5, 25, 50 and 100 μg/ml using the 3-4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, the plasmid relaxation assay and the C3H10T1/2 (10T1/2) cells. The cell-transforming potential was investigated in vitro using 10T1/2 cell transformation assay and the soft agar assay. PM1, PM0.56 and PM0.056 fractions were found to be toxic in dose-dependent manner. These induced cytotoxicity at five test concentrations, the ultrafine particle fraction PM0.056 showed greater cytotoxic potential. PM0.056 induced micronucleus formation in 10T1/2 cells. The effect was statistically significant. The DNA-damaging potential was measured in a plasmid relaxation assay. Both fine and ultrafine particle fraction PM0.56 and PM0.056 displayed greater effect as compared to larger PM1 fraction. DNA damage was found to be dependent on particulate matter intrinsic pro-oxidant chemicals. The ability of the ultrafine particle fraction PM0.056 to induce morphological cell transformation was demonstrated by significant and dose-dependent increases in type III focus formation by morphologically transformed cells in culture flasks and their clonal expansion in soft agar. It is concluded that the traffic-linked ultrafine particle fraction PM0.056 in the atmosphere by the roadside of an urban area is clastogenic and able to induce morphological transformation of mammalian cells. PMID:24895420

  3. A Prospective Examination of the Mechanisms Linking Childhood Physical Abuse to Body Mass Index in Adulthood

    PubMed Central

    Francis, Melville M.; Nikulina, Valentina; Widom, Cathy Spatz

    2016-01-01

    Previous research has reported associations between childhood physical abuse and Body Mass Index (BMI) in adulthood. This paper examined the role of four potential mediators (anxiety, depression, posttraumatic stress, and coping) hypothesized to explain this relationship. Using data from a prospective cohort design, court-substantiated cases of childhood physical abuse (N = 78) and non-maltreated comparisons (N = 349) were followed-up and assessed in adulthood at three time points (1989-1995, 2000-2002, and 2003-2005) when participants were ages 29.2, 39.5, and 41.2, respectively. At age 41, average BMI of the current sample was 29.97, falling between overweight and obese categories. Meditation analyses were conducted, controlling for age, sex, race, smoking, and self-reported weight. Childhood physical abuse was positively associated with subsequent generalized anxiety, major depression and posttraumatic stress disorder symptoms at age 29.2 and higher levels of depression and posttraumatic stress predicted higher BMI at age 41.2. In contrast, higher levels of anxiety predicted lower BMI. Coping did not mediate between physical abuse and BMI. Anxiety symptoms mediated the relationship between physical abuse and BMI for women, but not men. These findings illustrate the complexity of studying the consequences of physical abuse, particularly the relationship between psychiatric symptoms and adult health outcomes. PMID:25648448

  4. PSYCHIATRIC DISORDERS AND LEUKOCYTE TELOMERE LENGTH: UNDERLYING MECHANISMS LINKING MENTAL ILLNESS WITH CELLULAR AGING

    PubMed Central

    Lindqvist, Daniel; Epel, Elissa S.; Mellon, Synthia H.; Penninx, Brenda W.; Révész, Dóra; Verhoeven, Josine E.; Reus, Victor I.; Lin, Jue; Mahan, Laura; Hough, Christina M.; Rosser, Rebecca; Bersani, F. Saverio; Blackburn, Elizabeth H.; Wolkowitz, Owen M.

    2015-01-01

    Many psychiatric illnesses are associated with early mortality and with an increased risk of developing physical diseases that are more typically seen in the elderly. Moreover, certain psychiatric illnesses may be associated with accelerated cellular aging, evidenced by shortened leukocyte telomere length (LTL), which could underlie this association. Shortened LTL reflects a cell’s mitotic history and cumulative exposure to inflammation and oxidation as well as the availability of telomerase, a telomere-lengthening enzyme. Critically short telomeres can cause cells to undergo senescence, apoptosis or genomic instability, and shorter LTL correlates with poorer health and predicts mortality. Emerging data suggest that LTL may be reduced in certain psychiatric illnesses, perhaps in proportion to exposure to the psychiatric illnesses, although conflicting data exist. Telomerase has been less well characterized in psychiatric illnesses, but a role in depression and in antidepressant and neurotrophic effects has been suggested by preclinical and clinical studies. In this article, studies on LTL and telomerase activity in psychiatric illnesses are critically reviewed, potential mediators are discussed, and future directions are suggested. A deeper understanding of cellular aging in psychiatric illnesses could lead to re-conceptualizing them as systemic illnesses with manifestations inside and outside the brain and could identify new treatment targets. PMID:25999120

  5. A Prospective Examination of the Mechanisms Linking Childhood Physical Abuse to Body Mass Index in Adulthood.

    PubMed

    Francis, Melville M; Nikulina, Valentina; Widom, Cathy Spatz

    2015-08-01

    Previous research has reported associations between childhood physical abuse and body mass index (BMI) in adulthood. This article examined the role of four potential mediators (anxiety, depression, posttraumatic stress, and coping) hypothesized to explain this relationship. Using data from a prospective cohort design, court-substantiated cases of childhood physical abuse (N = 78) and nonmaltreated comparisons (N = 349) were followed up and assessed in adulthood at three time points (1989-1995, 2000-2002, and 2003-2005) when participants were of age 29.2, 39.5, and 41.2, respectively. At age 41, average BMI of the current sample was 29.97, falling between overweight and obese categories. Meditation analyses were conducted, controlling for age, sex, race, smoking, and self-reported weight. Childhood physical abuse was positively associated with subsequent generalized anxiety, major depression, and post-traumatic stress disorder symptoms at age 29.2 and higher levels of depression and posttraumatic stress predicted higher BMI at age 41.2. In contrast, higher levels of anxiety predicted lower BMI. Coping did not mediate between physical abuse and BMI. Anxiety symptoms mediated the relationship between physical abuse and BMI for women, but not for men. These findings illustrate the complexity of studying the consequences of physical abuse, particularly the relationship between psychiatric symptoms and adult health outcomes. PMID:25648448

  6. Psychiatric disorders and leukocyte telomere length: Underlying mechanisms linking mental illness with cellular aging.

    PubMed

    Lindqvist, Daniel; Epel, Elissa S; Mellon, Synthia H; Penninx, Brenda W; Révész, Dóra; Verhoeven, Josine E; Reus, Victor I; Lin, Jue; Mahan, Laura; Hough, Christina M; Rosser, Rebecca; Bersani, F Saverio; Blackburn, Elizabeth H; Wolkowitz, Owen M

    2015-08-01

    Many psychiatric illnesses are associated with early mortality and with an increased risk of developing physical diseases that are more typically seen in the elderly. Moreover, certain psychiatric illnesses may be associated with accelerated cellular aging, evidenced by shortened leukocyte telomere length (LTL), which could underlie this association. Shortened LTL reflects a cell's mitotic history and cumulative exposure to inflammation and oxidation as well as the availability of telomerase, a telomere-lengthening enzyme. Critically short telomeres can cause cells to undergo senescence, apoptosis or genomic instability, and shorter LTL correlates with poorer health and predicts mortality. Emerging data suggest that LTL may be reduced in certain psychiatric illnesses, perhaps in proportion to exposure to the psychiatric illnesses, although conflicting data exist. Telomerase has been less well characterized in psychiatric illnesses, but a role in depression and in antidepressant and neurotrophic effects has been suggested by preclinical and clinical studies. In this article, studies on LTL and telomerase activity in psychiatric illnesses are critically reviewed, potential mediators are discussed, and future directions are suggested. A deeper understanding of cellular aging in psychiatric illnesses could lead to re-conceptualizing them as systemic illnesses with manifestations inside and outside the brain and could identify new treatment targets. PMID:25999120

  7. The evolutionary ecology of complex lifecycle parasites: linking phenomena with mechanisms

    PubMed Central

    Auld, S KJR; Tinsley, M C

    2015-01-01

    Many parasitic infections, including those of humans, are caused by complex lifecycle parasites (CLPs): parasites that sequentially infect different hosts over the course of their lifecycle. CLPs come from a wide range of taxonomic groups—from single-celled bacteria to multicellular flatworms—yet share many common features in their life histories. Theory tells us when CLPs should be favoured by selection, but more empirical studies are required in order to quantify the costs and benefits of having a complex lifecycle, especially in parasites that facultatively vary their lifecycle complexity. In this article, we identify ecological conditions that favour CLPs over their simple lifecycle counterparts and highlight how a complex lifecycle can alter transmission rate and trade-offs between growth and reproduction. We show that CLPs participate in dynamic host–parasite coevolution, as more mobile hosts can fuel CLP adaptation to less mobile hosts. Then, we argue that a more general understanding of the evolutionary ecology of CLPs is essential for the development of effective frameworks to manage the many diseases they cause. More research is needed identifying the genetics of infection mechanisms used by CLPs, particularly into the role of gene duplication and neofunctionalisation in lifecycle evolution. We propose that testing for signatures of selection in infection genes will reveal much about how and when complex lifecycles evolved, and will help quantify complex patterns of coevolution between CLPs and their various hosts. Finally, we emphasise four key areas where new research approaches will provide fertile opportunities to advance this field. PMID:25227255

  8. The evolutionary ecology of complex lifecycle parasites: linking phenomena with mechanisms.

    PubMed

    Auld, S K J R; Tinsley, M C

    2015-02-01

    Many parasitic infections, including those of humans, are caused by complex lifecycle parasites (CLPs): parasites that sequentially infect different hosts over the course of their lifecycle. CLPs come from a wide range of taxonomic groups-from single-celled bacteria to multicellular flatworms-yet share many common features in their life histories. Theory tells us when CLPs should be favoured by selection, but more empirical studies are required in order to quantify the costs and benefits of having a complex lifecycle, especially in parasites that facultatively vary their lifecycle complexity. In this article, we identify ecological conditions that favour CLPs over their simple lifecycle counterparts and highlight how a complex lifecycle can alter transmission rate and trade-offs between growth and reproduction. We show that CLPs participate in dynamic host-parasite coevolution, as more mobile hosts can fuel CLP adaptation to less mobile hosts. Then, we argue that a more general understanding of the evolutionary ecology of CLPs is essential for the development of effective frameworks to manage the many diseases they cause. More research is needed identifying the genetics of infection mechanisms used by CLPs, particularly into the role of gene duplication and neofunctionalisation in lifecycle evolution. We propose that testing for signatures of selection in infection genes will reveal much about how and when complex lifecycles evolved, and will help quantify complex patterns of coevolution between CLPs and their various hosts. Finally, we emphasise four key areas where new research approaches will provide fertile opportunities to advance this field. PMID:25227255

  9. Mechanisms of proximal tubule sodium transport regulation that link extracellular fluid volume and blood pressure.

    PubMed

    McDonough, Alicia A

    2010-04-01

    One-hundred years ago, Starling articulated the interdependence of renal control of circulating blood volume and effective cardiac performance. During the past 25 years, the molecular mechanisms responsible for the interdependence of blood pressure (BP), extracellular fluid volume (ECFV), the renin-angiotensin system (RAS), and sympathetic nervous system (SNS) have begun to be revealed. These variables all converge on regulation of renal proximal tubule (PT) sodium transport. The PT reabsorbs two-thirds of the filtered Na(+) and volume at baseline. This fraction is decreased when BP or perfusion pressure is increased, during a high-salt diet (elevated ECFV), and during inhibition of the production of ANG II; conversely, this fraction is increased by ANG II, SNS activation, and a low-salt diet. These variables all regulate the distribution of the Na(+)/H(+) exchanger isoform 3 (NHE3) and the Na(+)-phosphate cotransporter (NaPi2), along the apical microvilli of the PT. Natriuretic stimuli provoke the dynamic redistribution of these transporters along with associated regulators, molecular motors, and cytoskeleton-associated proteins to the base of the microvilli. The lipid raft-associated NHE3 remains at the base, and the nonraft-associated NaPi2 is endocytosed, culminating in decreased Na(+) transport and increased PT flow rate. Antinatriuretic stimuli return the same transporters and regulators to the body of the microvilli associated with an increase in transport activity and decrease in PT flow rate. In summary, ECFV and BP homeostasis are, at least in part, maintained by continuous and acute redistribution of transporter complexes up and down the PT microvilli, which affect regulation of PT sodium reabsorption in response to fluctuations in ECFV, BP, SNS, and RAS. PMID:20106993

  10. Linking rapid magma reservoir assembly and eruption trigger mechanisms at evolved Yellowstone-type supervolcanoes

    USGS Publications Warehouse

    Wotzlaw, J.F.; Bindeman, I.N.; Watts, Kathryn E.; Schmitt, A.K.; Caricchi, L.; Schaltegger, U.

    2014-01-01

    reservoir configurations inferred from seismic data at active supervolcanoes. The connection of magma batches vertically distributed over several kilometers in the upper crust would cause a substantial increase of buoyancy overpressure, providing an eruption trigger mechanism that is the direct consequence of the reservoir assembly process.

  11. Mammary blood flow and metabolic activity are linked by a feedback mechanism involving nitric oxide synthesis.

    PubMed

    Cieslar, S R L; Madsen, T G; Purdie, N G; Trout, D R; Osborne, V R; Cant, J P

    2014-01-01

    To test which, if any, of the major milk precursors can elicit a rapid change in the rate of mammary blood flow (MBF) and to define the time course and magnitude of such changes, 4 lactating cows were infused with glucose, amino acids, or triacylglycerol into the external iliac artery feeding one udder half while iliac plasma flow (IPF) was monitored continuously by dye dilution. Adenosine and saline were infused as positive and negative controls, respectively, and insulin was infused to characterize the response to a centrally produced anabolic hormone. To test the roles of cyclooxygenase, NO synthase and ATP-sensitive K (KATP) channels in nutrient-mediated changes in blood flow, their respective inhibitors-indomethacin, Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME), and glibenclamide-were infused simultaneously with glucose. Each day, 1 infusate was given twice to each cow, over a 20-min period each time, separated by a 20-min washout period. In addition, each treatment protocol was administered on 2 separate days. A 73% increase in IPF during adenosine infusion showed that the mammary vasodilatory response was quadratic in time, with most changes occurring in the first 5min. Glucose infusion decreased IPF by 9% in a quadratic manner, most rapidly in the first 5min, indicating that a feedback mechanism of local blood flow control, likely through adenosine release, was operative in the mammary vasculature. Amino acid infusion increased IPF 9% in a linear manner, suggesting that mammary ATP utilization was stimulated more than ATP production. This could reflect a stimulation of protein synthesis. Triacylglycerol only tended to decrease IPF and insulin did not affect IPF. A lack of IPF response to glibenclamide indicates that KATP channels are not involved in MBF regulation. Indomethacin and L-NAME both depressed IPF. In the presence of indomethacin, glucose infusion caused a quadratic 9% increase in IPF. Indomethacin is an inhibitor of mitochondrial

  12. Mechanisms of Staphylococcus epidermidis adhesion to model biomaterial surfaces: Establising a link between thrombosis and infection

    NASA Astrophysics Data System (ADS)

    Higashi, Julie Miyo

    Infections involving Staphylococcus epidermidis remain a life threatening complication associated with the use of polymer based cardiovascular devices. One of the critical steps in infection pathogenesis is the adhesion of the bacteria to the device surface. Currently, mechanisms of S. epidermidis adhesion are incompletely understood, but are thought to involve interactions between bacteria, device surface, and host blood elements in the form of adsorbed plasma proteins and surface adherent platelets. Our central hypothesis is that elements participating in thrombosis also promote S. epidermidis adhesion by specifically binding to the bacterial surface. The adhesion kinetics of S. epidermidis RP62A to host modified model biomaterial surface octadecyltrichlorosilane (OTS) under hydrodynamic shear conditions were characterized. Steady state adhesion to adsorbed proteins and surface adherent platelets was achieved at 90-120 minutes and 60-90 minutes, respectively. A dose response curve of S. epidermidis adhesion in the concentration range of 10sp7{-}10sp9 bac/mL resembled a multilayer adsorption isotherm. Increasing shear stress was found to LTA, and other LTA blocking agents significantly decreased S. epidermidis adhesion to the fibrin-platelet clots, suggesting that this interaction between S. epidermidis and fibrin-platelet clots is specific. Studies evaluated the adhesion of S. epidermidis to polymer immobilized heparin report conflicting results. Paulsson et al., showed that coagulase negative staphylococci adhered in comparable numbers to both immobilized heparin and nonheparinized surfaces, while exhibiting significantly greater adhesion to both surfaces than S. aureus. Preadsorption of the surfaces with specific heparin binding plasma proteins vitronectin, fibronectin, laminin, and collagen significantly increased adhesion. It was postulated that immobilized heparin contained binding sites for the plasma proteins, exposing bacteria binding domains of the

  13. Does the Concept of “Sensitization” Provide a Plausible Mechanism for the Putative Link Between the Environment and Schizophrenia?

    PubMed Central

    Collip, Dina; Myin-Germeys, Inez; Van Os, Jim

    2008-01-01

    Previous evidence reviewed in Schizophrenia Bulletin suggests the importance of a range of different environmental factors in the development of psychotic illness. It is unlikely, however, that the diversity of environmental influences associated with schizophrenia can be linked to as many different underlying mechanisms. There is evidence that environmental exposures may induce, in interaction with (epi)genetic factors, psychological or physiological alterations that can be traced to a final common pathway of cognitive biases and/or altered dopamine neurotransmission, broadly referred to as “sensitization,” facilitating the onset and persistence of psychotic symptoms. At the population level, the behavioral phenotype for sensitization may be examined by quantifying, in populations exposed to environmental risk factors associated with stress or dopamine-agonist drugs, (1) the increased rate of persistence (indicating lasting sensitization) of normally transient developmental expressions of subclinical psychotic experiences and (2) the subsequent increased rate of transition to clinical psychotic disorder. PMID:18203757

  14. Effect of modified starch and nanoclay particles on biodegradability and mechanical properties of cross-linked poly lactic acid.

    PubMed

    Shayan, M; Azizi, H; Ghasemi, I; Karrabi, M

    2015-06-25

    Mechanical properties and biodegradation of cross-linked poly(lactic acid) (PLA)/maleated thermoplastic starch (MTPS)/montmorillonite (MMT) nanocomposite were studied. Crosslinking was carried out by adding di-cumyl peroxide (DCP) in the presence of triallyl isocyanurate (TAIC) as coagent. At first, MTPS was prepared by grafting maleic anhydride (MA) to thermoplastic starch in internal mixer. Experimental design was performed by using Box-Behnken method at three variables: MTPS, nanoclay and TAIC at three levels. Results showed that increasing TAIC amount substantially increased the gel fraction, enhanced tensile strength, and caused a decrease in elongation at break. Biodegradation was prevented by increasing TAIC amount in nanocomposite. Increasing MTPS amount caused a slight increase in gel fraction and decreased the tensile strength of nanocomposite. Also, MTPS could increase the elongation at break of nanocomposite and improve the biodegradation. Nanoclay had no effect on the gel fraction, but it improved tensile strength. PMID:25839817

  15. Linking Genomo- and Pathotype: Exploiting the Zebrafish Embryo Model to Investigate the Divergent Virulence Potential among Cronobacter spp.

    PubMed Central

    Eshwar, Athmanya K.; Tall, Ben D.; Gangiredla, Jayanthi; Gopinath, Gopal R.; Patel, Isha R.; Neuhauss, Stephan C. F.; Stephan, Roger; Lehner, Angelika

    2016-01-01

    Bacteria belonging to the genus Cronobacter have been recognized as causative agents of life-threatening systemic infections primarily in premature, low-birth weight and immune-compromised neonates. Apparently not all Cronobacter species are linked to infantile infections and it has been proposed that virulence varies among strains. Whole genome comparisons and in silico analysis have proven to be powerful tools in elucidating potential virulence determinants, the presence/absence of which may explain the differential virulence behaviour of strains. However, validation of these factors has in the past been hampered by the availability of a suitable neonatal animal model. In the present study we have used zebrafish embryos to model Cronobacter infections in vivo using wild type and genetically engineered strains. Our experiments confirmed the role of the RepF1B-like plasmids as “virulence plasmids” in Cronobacter and underpinned the importantce of two putative virulence factors—cpa and zpx—in in vivo pathogenesis. We propose that by using this model in vivo infection studies are now possible on a large scale level which will boost the understanding on the virulence strategies employed by these pathogens. PMID:27355472

  16. Bacterial population and biodegradation potential in chronically crude oil-contaminated marine sediments are strongly linked to temperature

    PubMed Central

    Bargiela, Rafael; Mapelli, Francesca; Rojo, David; Chouaia, Bessem; Tornés, Jesús; Borin, Sara; Richter, Michael; Del Pozo, Mercedes V.; Cappello, Simone; Gertler, Christoph; Genovese, María; Denaro, Renata; Martínez-Martínez, Mónica; Fodelianakis, Stilianos; Amer, Ranya A.; Bigazzi, David; Han, Xifang; Chen, Jianwei; Chernikova, Tatyana N.; Golyshina, Olga V.; Mahjoubi, Mouna; Jaouanil, Atef; Benzha, Fatima; Magagnini, Mirko; Hussein, Emad; Al-Horani, Fuad; Cherif, Ameur; Blaghen, Mohamed; Abdel-Fattah, Yasser R.; Kalogerakis, Nicolas; Barbas, Coral; Malkawi, Hanan I.; Golyshin, Peter N.; Yakimov, Michail M.; Daffonchio, Daniele; Ferrer, Manuel

    2015-01-01

    Two of the largest crude oil-polluted areas in the world are the semi-enclosed Mediterranean and Red Seas, but the effect of chronic pollution remains incompletely understood on a large scale. We compared the influence of environmental and geographical constraints and anthropogenic forces (hydrocarbon input) on bacterial communities in eight geographically separated oil-polluted sites along the coastlines of the Mediterranean and Red Seas. The differences in community compositions and their biodegradation potential were primarily associated (P < 0.05) with both temperature and chemical diversity. Furthermore, we observed a link between temperature and chemical and biological diversity that was stronger in chronically polluted sites than in pristine ones where accidental oil spills occurred. We propose that low temperature increases bacterial richness while decreasing catabolic diversity and that chronic pollution promotes catabolic diversification. Our results further suggest that the bacterial populations in chronically polluted sites may respond more promptly in degrading petroleum after accidental oil spills. PMID:26119183

  17. Linking Genomo- and Pathotype: Exploiting the Zebrafish Embryo Model to Investigate the Divergent Virulence Potential among Cronobacter spp.

    PubMed

    Eshwar, Athmanya K; Tall, Ben D; Gangiredla, Jayanthi; Gopinath, Gopal R; Patel, Isha R; Neuhauss, Stephan C F; Stephan, Roger; Lehner, Angelika

    2016-01-01

    Bacteria belonging to the genus Cronobacter have been recognized as causative agents of life-threatening systemic infections primarily in premature, low-birth weight and immune-compromised neonates. Apparently not all Cronobacter species are linked to infantile infections and it has been proposed that virulence varies among strains. Whole genome comparisons and in silico analysis have proven to be powerful tools in elucidating potential virulence determinants, the presence/absence of which may explain the differential virulence behaviour of strains. However, validation of these factors has in the past been hampered by the availability of a suitable neonatal animal model. In the present study we have used zebrafish embryos to model Cronobacter infections in vivo using wild type and genetically engineered strains. Our experiments confirmed the role of the RepF1B-like plasmids as "virulence plasmids" in Cronobacter and underpinned the importantce of two putative virulence factors-cpa and zpx-in in vivo pathogenesis. We propose that by using this model in vivo infection studies are now possible on a large scale level which will boost the understanding on the virulence strategies employed by these pathogens. PMID:27355472

  18. A potential mechanism for a singular solution of the Euler Equations

    NASA Astrophysics Data System (ADS)

    Brenner, Michael; Hormoz, Sahand; Pumir, Alain

    We describe a potential mechanism for a singular solution of the Euler equation. The mechanism involves the interaction of vortex filaments, but occurs sufficiently quickly and at small enough scales that it could have plausibly evaded experimental and computational detection. Scaling estimates for the characteristics of this solution will be presented, as well as numerical simulations of the initial stages.

  19. A potential mechanism for a singular solution of the Euler Equations

    NASA Astrophysics Data System (ADS)

    Brenner, Michael; Hormoz, Sahand; Pumir, Alain

    2015-11-01

    We describe a potential mechanism for a singular solution of the Euler equation. The mechanism involves the interaction of vortex filaments, but occurs sufficiently quickly and at small enough scales that it could have plausibly evaded experimental and computational detection. Scaling estimates for the characteristics of this solution will be presented, as well as numerical simulations of the initial stages.

  20. The Double-Well Potential in Quantum Mechanics: A Simple, Numerically Exact Formulation

    ERIC Educational Resources Information Center

    Jelic, V.; Marsiglio, F.

    2012-01-01

    The double-well potential is arguably one of the most important potentials in quantum mechanics, because the solution contains the notion of a state as a linear superposition of "classical" states, a concept which has become very important in quantum information theory. It is therefore desirable to have solutions to simple double-well potentials…

  1. Exaggerated neurobiological sensitivity to threat as a mechanism linking anxiety with increased risk for diseases of aging

    PubMed Central

    O’Donovan, Aoife; Slavich, George M; Epel, Elissa S.; Neylan, Thomas C

    2015-01-01

    Anxiety disorders increase risk for the early development of several diseases of aging. Elevated inflammation, a common risk factor across diseases of aging, may play a key role in the relationship between anxiety and physical disease. However, the neurobiological mechanisms linking anxiety with elevated inflammation remain unclear. In this review, we present a neurobiological model of the mechanisms by which anxiety promotes inflammation. Specifically we propose that exaggerated neurobiological sensitivity to threat in anxious individuals may lead to sustained threat perception, which is accompanied by prolonged activation of threat-related neural circuitry and threat-responsive biological systems including the hypothalamic-pituitary-adrenal (HPA) axis, autonomic nervous system (ANS), and inflammatory response. Over time, this pattern of responding can promote chronic inflammation through structural and functional brain changes, altered sensitivity of immune cell receptors, dysregulation of the HPA axis and ANS, and accelerated cellular aging. Chronic inflammation, in turn, increases risk for diseases of aging. Exaggerated neurobiological sensitivity to threat may thus be a treatment target for reducing disease risk in anxious individuals. PMID:23127296

  2. The cytotoxicity of the α1-adrenoceptor antagonist prazosin is linked to an endocytotic mechanism equivalent to transport-P.

    PubMed

    Fuchs, Robert; Stracke, Anika; Ebner, Nadine; Zeller, Christian Wolfgang; Raninger, Anna Maria; Schittmayer, Matthias; Kueznik, Tatjana; Absenger-Novak, Markus; Birner-Gruenberger, Ruth

    2015-12-01

    Since the α1-adrenergic antagonist prazosin (PRZ) was introduced into medicine as a treatment for hypertension and benign prostate hyperplasia, several studies have shown that PRZ induces apoptosis in various cell types and interferes with endocytotic trafficking. Because PRZ is also able to induce apoptosis in malignant cells, its cytotoxicity is a focus of interest in cancer research. Besides inducing apoptosis, PRZ was shown to serve as a substrate for an amine uptake mechanism originally discovered in neurones called transport-P. In line with our hypothesis that transport-P is an endocytotic mechanism also present in non-neuronal tissue and linked to the cytotoxicity of PRZ, we tested the uptake of QAPB, a fluorescent derivative of PRZ, in cancer cell lines in the presence of inhibitors of transport-P and endocytosis. Early endosomes and lysosomes were visualised by expression of RAB5-RFP and LAMP1-RFP, respectively; growth and viability of cells in the presence of PRZ and uptake inhibitors were also tested. Cancer cells showed co-localisation of QAPB with RAB5 and LAMP1 positive vesicles as well as tubulation of lysosomes. The uptake of QAPB was sensitive to transport-P inhibitors bafilomycin A1 (inhibits v-ATPase) and the antidepressant desipramine. Endocytosis inhibitors pitstop(®) 2 (general inhibitor of endocytosis), dynasore (dynamin inhibitor) and methyl-β-cyclodextrin (cholesterol chelator) inhibited the uptake of QAPB. Bafilomycin A1 and methyl-β-cyclodextrin but not desipramine were able to preserve growth and viability of cells in the presence of PRZ. In summary, we confirmed the hypothesis that the cellular uptake of QAPB/PRZ represents an endocytotic mechanism equivalent to transport-P. Endocytosis of QAPB/PRZ depends on a proton gradient, dynamin and cholesterol, and results in reorganisation of the LAMP1 positive endolysosomal system. Finally, the link seen between the cellular uptake of PRZ and cell death implies a still unknown pro

  3. Wear, debris, and biologic activity of cross-linked polyethylene in the knee: benefits and potential concerns.

    PubMed

    Fisher, John; McEwen, Hannah M J; Tipper, Joanne L; Galvin, Alison L; Ingram, Jo; Kamali, Amir; Stone, Martin H; Ingham, Eileen

    2004-11-01

    Cross-linked polyethylene currently is being introduced in knee prostheses. The wear rates, wear debris, and biologic reactivity of non cross-linked, moderately cross-linked, and highly cross-linked polyethylene have been compared in multidirectional wear tests and knee simulators. Multidirectional pin-on-plate wear studies of noncross-linked, moderately cross-linked (5 Mrad), and highly cross-linked (10 Mrad) polyethylene showed a 75% reduction in wear with the highly cross-linked material under kinematics found in the hip, but only a 33% reduction under wear in kinematics representative of the knee. In knee simulator studies, with the fixed-bearing press-fit, condylar Sigma cruciate-retaining knee under high kinematic input conditions, the wear of 5 Mrad moderately cross-linked polyethylene was 13 +/- 4 mm per 1 million cycles, which was lower (p < 0.05) than the wear of clinically used, gamma vacuum foil GUR 1020 polyethylene (23 +/- 6 mm/1 million cycles). For the low-contact stress mobile-bearing knee, the wear of moderately cross-linked polyethylene was 2 +/- 1 mm per 1 million cycles, which was lower (p < 0.05) than GVF GUR 1020 polyethylene (5 +/- 2 mm/1 million cycles). The wear debris isolated from the fixed-bearing knees showed the moderately cross-linked material had a larger percentage volume of particles smaller than 1 mum in size, compared with GVF GUR 1020 polyethylene. Direct cell culture studies of wear debris generated in sterile wear simulators using multidirectional motion showed a increase (p < 0.05) in tumor necrosis factor-alpha levels and reactivity for GUR 1050 cross-linked polyethylene debris compared with an equivalent volume of noncross-linked GUR 1050 polyethylene. The use of cross-linked polyethylene in the knee reduces the volumetric wear rate. However, the clinical significance of reduced fracture toughness, elevated wear in abrasive conditions, and the elevated tumor necrosis factor-alpha release from smaller more reactive

  4. CD40L induces inflammation and adipogenesis in adipose cells--a potential link between metabolic and cardiovascular disease.

    PubMed

    Missiou, Anna; Wolf, Dennis; Platzer, Isabel; Ernst, Sandra; Walter, Carina; Rudolf, Philipp; Zirlik, Katja; Köstlin, Natascha; Willecke, Florian K; Münkel, Christian; Schönbeck, Uwe; Libby, Peter; Bode, Christoph; Varo, Nerea; Zirlik, Andreas

    2010-04-01

    CD40L figures prominently in atherogenesis. Recent data demonstrate elevated levels of sCD40L in the serum of patients with the metabolic syndrome (MS). This study investigated the role of CD40L in pro-inflammatory gene expression and cellular differentiation in adipose tissue to obtain insight into mechanisms linking the MS with atherosclerosis. Human adipocytes and preadipocytes expressed CD40 but not CD40L. Stimulation with recombinant CD40L or membranes over-expressing CD40L induced a time- and dose-dependent expression of IL-6, MCP-1, IL-8, and PAI-1. Supernatants of CD40L-stimulated adipose cells activated endothelial cells, suggesting a systemic functional relevance of our findings. Neutralising antibodies against CD40L attenuated these effects substantially. Signalling studies revealed the involvement of mitogen-activated protein kinases and NFkB. Furthermore, stimulation with CD40L resulted in enhanced activation of C/EBPa and PPARg and promoted adipogenesis of preadipose cells in the presence and absence of standard adipogenic conditions. Finally, patients suffering from the metabolic syndrome with high levels of sCD40L also displayed high levels of IL-6, in line with the concept that CD40L may induce the expression of inflammatory cytokines in vivo in this population. Our data reveal potent metabolic functions of CD40L aside from its known pivotal pro-inflammatory role within plaques. Our data suggest that CD40L may mediate risk at the interface of metabolic and atherothrombotic disease. PMID:20174757

  5. DEHP exposure in utero disturbs sex determination and is potentially linked with precocious puberty in female mice.

    PubMed

    Wang, Yongan; Yang, Qing; Liu, Wei; Yu, Mingxi; Zhang, Zhou; Cui, Xiaoyu

    2016-09-15

    Human's ubiquitous exposure to di (2-ethylhexyl) phthalate (DEHP) is thought to be associated with female reproductive toxicity. Previous studies found that DEHP inhibited follicle growth and decreased estradiol levels in adult female mice. However, limited information is available on the link between in utero DEHP exposure and ovarian development in female mouse offspring. The present study evaluates the disturbances in regulatory genes involved in female sex determination and the ovarian outcomes in fetal and postnatal female mice treated with in utero DEHP exposure. Pregnant mice were exposed to DEHP by gavage, with the dosage regime beginning at human relevant exposure levels. After in utero DEHP exposure, increased follicular atresia was observed in the female pups at postnatal days (PND) 21. Foxl2 expression was significantly upregulated, and Fst was significantly downregulated by DEHP above 2mg/kg/d at PND 1 and 21. This suggests that lesion of granulosa cell differentiation and disturbance of follicle development in postnatal female mice. The expression of Cyp11a1 and Star were significantly downregulated by in utero DEHP exposure, indicating effects on estradiol biosynthesis. The female sex determination pathway was disturbed in fetus by DEHP at 2mg/kg/d and above during the critical time window of sex determination causing significant upregulation of Foxl2, Wnt4, β-catenin and Fst. Furthermore, the increased expression of Wnt4 was supported by whole-mount in situ hybridization (WISH). These results suggest a possible association between in utero DEHP exposure and precocious puberty in the postnatal life of mice offspring, where disturbance of the sex determination regulating pathway acted as an important mechanism. PMID:27495896

  6. ASC provides a potential link between depression and inflammatory disorders: A clinical study of depressed Iranian medical students.

    PubMed

    Momeni, Mohammad; Ghorban, Khodayar; Dadmanesh, Maryam; Khodadadi, Hassan; Bidaki, Reza; Kazemi Arababadi, Mohammad; Kennedy, Derek

    2016-05-01

    Background and aims AIM2 is a component of inflammasomes which can activate caspase-1 via an adaptor protein (ASC) after pathogen-associated molecular pattern (PAMP) or danger-associated molecular pattern (DAMP) recognition. Activation of caspase-1 is a trigger for the induction of IL-1 and IL-18 which are important pro-inflammatory cytokines. Furthermore, IL-1β, which can regulate inflammatory responses, has also been associated with depression. Previous studies revealed that patients suffering from depression may also have altered immune responses, but the mechanisms underlying this correlation are unclear. Thus, the aim of this study was to determine the mRNA levels of AIM2 and ASC in the peripheral blood mononuclear cells (PBMCs) isolated from Iranian medical students suffering from depression. Materials and methods The participants used for the study included 38 Iranian medical students diagnosed with depression and 43 non-depressed students as a control group. The mRNA levels of AIM2 and ASC were evaluated by quantitative real-time polymerase chain reaction (PCR) using β-actin as a housekeeping gene for the normalization of expression. Results The results showed that mRNA levels of AIM2 were similar in both groups. However, ASC levels were significantly increased in PBMCs isolated from individuals with elevated depressive symptoms when compared to non-depressed participants. Conclusions Based on the current results, it appears that ASC transcript expression may be a surrogate marker for depression and may represent a link between depression and the altered immune responses observed in these categories of individuals with elevated depressive symptoms. PMID:26750863

  7. Genetic analysis of repair and damage tolerance mechanisms for DNA-protein cross-links in Escherichia coli.

    PubMed

    Salem, Amir M H; Nakano, Toshiaki; Takuwa, Minako; Matoba, Nagisa; Tsuboi, Tomohiro; Terato, Hiroaki; Yamamoto, Kazuo; Yamada, Masami; Nohmi, Takehiko; Ide, Hiroshi

    2009-09-01

    DNA-protein cross-links (DPCs) are unique among DNA lesions in their unusually bulky nature. We have recently shown that nucleotide excision repair (NER) and RecBCD-dependent homologous recombination (HR) collaboratively alleviate the lethal effect of DPCs in Escherichia coli. In this study, to gain further insight into the damage-processing mechanism for DPCs, we assessed the sensitivities of a panel of repair-deficient E. coli mutants to DPC-inducing agents, including formaldehyde (FA) and 5-azacytidine (azaC). We show here that the damage tolerance mechanism involving HR and subsequent replication restart (RR) provides the most effective means of cell survival against DPCs. Translesion synthesis does not serve as an alternative damage tolerance mechanism for DPCs in cell survival. Elimination of DPCs from the genome relies primarily on NER, which provides a second and moderately effective means of cell survival against DPCs. Interestingly, Cho rather than UvrC seems to be an effective nuclease for the NER of DPCs. Together with the genes responsible for HR, RR, and NER, the mutation of genes involved in several aspects of DNA repair and transactions, such as recQ, xth nfo, dksA, and topA, rendered cells slightly but significantly sensitive to FA but not azaC, possibly reflecting the complexity of DPCs or cryptic lesions induced by FA. UvrD may have an additional role outside NER, since the uvrD mutation conferred a slight azaC sensitivity on cells. Finally, DNA glycosylases mitigate azaC toxicity, independently of the repair of DPCs, presumably by removing 5-azacytosine or its degradation product from the chromosome. PMID:19617358

  8. Supramolecular Cross-Links in Poly(alkyl methacrylate) Copolymers and Their Impact on the Mechanical and Reversible Adhesive Properties.

    PubMed

    Heinzmann, Christian; Salz, Ulrich; Moszner, Norbert; Fiore, Gina L; Weder, Christoph

    2015-06-24

    Hydrogen-bonded, side-chain-functionalized supramolecular poly(alkyl methacrylate)s were investigated as light- and temperature-responsive reversible adhesives that are useful for bonding and debonding on demand applications. Here, 2-hydroxyethyl methacrylate (HEMA) was functionalized with 2-ureido-4[1H]pyrimidinone (UPy) via a hexamethylenediisocyanate (HMDI) linker, to create a monomer (UPy-HMDI-HEMA) that serves to form supramolecular cross-links by way of forming quadruple hydrogen bonded dimers. UPy-HMDI-HEMA was copolymerized with either hexyl methacrylate or butyl methacrylate to create copolymers comprising 2.5, 5, or 10 mol % of the cross-linker. The mechanical properties of all (co)polymers were investigated with stress-strain experiments and dynamic mechanical analysis. Furthermore, the adhesive properties were studied at temperatures between 20 and 60 °C by testing single lap joints formed with stainless steel substrates. It was found that increasing the concentration of the UPy-HMDI-HEMA cross-linker leads to improved mechanical and adhesive properties at elevated temperatures. Concurrently, the reversibility of the bond formation remained unaffected, where rebonded samples displayed the same adhesive strength as regularly bonded samples. Debonding on demand abilities were also tested exemplarily for one copolymer, which for light-induced debonding experiments was blended with a UV-absorber that served as light-heat converter. Single lap joints were subjected to a constant force and heated or irradiated with UV light until debonding occurred. The necessary debonding temperature was comparable for direct heating and UV irradiation and varied between 28 and 82 °C, depending on the applied force. The latter also influenced the debonding time, which under the chosen conditions ranged from 30 s to 12 min. PMID:26043809

  9. Juvenile flatfish in the northern Baltic Sea - long-term decline and potential links to habitat characteristics

    NASA Astrophysics Data System (ADS)

    Jokinen, Henri; Wennhage, Håkan; Ollus, Victoria; Aro, Eero; Norkko, Alf

    2016-01-01

    Flatfish in the northern Baltic Sea are facing multiple environmental pressures due to on-going large-scale ecosystem changes linked to eutrophication and climate change. Shallow juvenile habitats of flatfishes are expected to be especially susceptible to these environmental pressures. Using previously unpublished historical and present-state data on juvenile flatfish in nursery areas along the Finnish coast we demonstrate a drastic (up to 40 ×) decline in 1-Y-O flounder densities since the 1980s and a particularly low current occurrence of both flounders and turbots in several known juvenile habitats. As a consequence of ongoing coastal eutrophication vegetation coverage and filamentous algae have generally increased in shallow areas. We examined the predicted negative effect of vegetation/algae by exploring quantitative relationships between juvenile flatfish (flounder and turbot) occurrence and vegetation/algae among other environmental factors in shallow juvenile habitats. Despite sparse occurrence of juveniles we found a significant negative relationship between flatfish abundance and vegetation cover, implicating eutrophication as a potential major driver affecting the value of juvenile habitat. Shallow littoral habitats play a particularly central role for flatfish due to the spatial concentration of fish in these areas during the critical juvenile stage. Despite their importance, these areas have been relatively poorly studied in the northern Baltic Sea, which makes it difficult to quantify overall changes in environmental conditions and to relate these changes to flatfish recruitment. The low present-state flatfish densities recorded preclude strong inferences of the role of habitat quality to be drawn. Our study does, however, provide a baseline for future assessment. Based on existing evidence, we cannot thus establish any bottlenecks but hypothesize that the current low occurrence of juvenile flatfish, and the population decline of flounder on the

  10. Insights into mRNA export-linked molecular mechanisms of human disease through a Gle1 structure-function analysis

    PubMed Central

    Folkmann, Andrew W.; Dawson, T. Renee; Wente, Susan R.

    2013-01-01

    A critical step during gene expression is the directional export of nuclear messenger (m)RNA through nuclear pore complexes (NPCs) to the cytoplasm. During export, Gle1 in conjunction with inositol hexakisphosphate (IP6) spatially regulates the activity of the DEAD-box protein Dbp5 at the NPC cytoplasmic face. GLE1 mutations are causally linked to the human diseases lethal congenital contracture syndrome 1 (LCCS1) and lethal arthrogryposis with anterior horn cell disease (LAAHD). Here, structure prediction and functional analysis provide strong evidence to suggest that the LCCS1 and LAAHD disease mutations disrupt the function of Gle1 in mRNA export. Strikingly, direct fluorescence microscopy in living cells reveals a dramatic loss of steady-state NPC localization for GFP-gle1 proteins expressed from human gle1 genes harboring LAAHD and LCCS1 mutations. The potential significance of these residues is further clarified by analyses of sequence and predicted structural conservation. This work offers insights into the perturbed mechanisms underlying human LCCS-1 and LAAHD disease states and emphasizes the potential impact of altered mRNA transport and gene expression in human disease. PMID:24275432

  11. Ambient-Potential Composite Ewald Method for ab Initio Quantum Mechanical/Molecular Mechanical Molecular Dynamics Simulation.

    PubMed

    Giese, Timothy J; York, Darrin M

    2016-06-14

    A new approach for performing Particle Mesh Ewald in ab initio quantum mechanical/molecular mechanical (QM/MM) simulations with extended atomic orbital basis sets is presented. The new approach, the Ambient-Potential Composite Ewald (CEw) method, does not perform the QM/MM interaction with Mulliken charges nor electrostatically fit charges. Instead the nuclei and electron density interact directly with the MM environment, but in a manner that avoids the use of dense Fourier transform grids. By performing the electrostatics with the underlying QM density, the CEw method avoids self-consistent field instabilities that have been encountered with simple charge mapping procedures. Potential of mean force (PMF) profiles of the p-nitrophenyl phosphate dissociation reaction in explicit solvent are computed from PBE0/6-31G* QM/MM molecular dynamics simulations with various electrostatic protocols. The CEw profiles are shown to be stable with respect to real-space Ewald cutoff, whereas the PMFs computed from truncated and switched electrostatics produce artifacts. PBE0/6-311G**, AM1/d-PhoT, and DFTB2 QM/MM simulations are performed to generate two-dimensional PMF profiles of the phosphoryl transesterification reactions with ethoxide and phenoxide leaving groups. The semiempirical models incorrectly produce a concerted ethoxide mechanism, whereas PBE0 correctly produces a stepwise mechanism. The ab initio reaction barriers agree more closely to experiment than the semiempirical models. The failure of Mulliken-charge QM/MM-Ewald is analyzed. PMID:27171914

  12. Mechanisms of optical response in superconducting YBa2Cu3O7-delta thin films and grain-boundary weak links

    NASA Technical Reports Server (NTRS)

    Bhattacharya, S.; Rajeswari, M.; Takeuchi, I.; Trajanovic, Z.; Li, QI; Xi, X. X.; Venkatesan, T.

    1994-01-01

    The optical response of single grain-boundary weak links in superconducting YBCO thin films has been investigated. At temperatures well below the transition temperature, the grain boundary exhibits an optical response which is qualitatively different from transition edge response. Using a resistively shunted-junction model for the grain-boundary weak link, we find that the optical response below the transition temperature can be described by radiation induced thermal modulation of the critical currents of the weak links. The dependence on the bias current and the temperature distinguishes the weak-link optical response from the transition edge optical response. We discuss novel aspects of a potential radiation detector based on grain-boundary weak-link junctions.

  13. The costly filtering of potential distraction: evidence for a supramodal mechanism.

    PubMed

    Marini, Francesco; Chelazzi, Leonardo; Maravita, Angelo

    2013-08-01

    When dealing with significant sensory stimuli, performance can be hampered by distracting events. Attention mechanisms lessen such negative effects, enabling selection of relevant information while blocking potential distraction. Recent work shows that preparatory brain activity, occurring before a critical stimulus, may reflect mechanisms of attentional control aimed to filter upcoming distracters. However, it is unknown whether the engagement of these filtering mechanisms to counteract distraction in itself taxes cognitive-brain systems, leading to performance costs. Here we address this question and, specifically, seek the behavioral signature of a mechanism for the filtering of potential distraction within and between sensory modalities. We show that, in potentially distracting contexts, a filtering mechanism is engaged to cope with forthcoming distraction, causing a dramatic behavioral cost in no-distracter trials during a speeded tactile discrimination task. We thus demonstrate an impaired processing caused by a potential, yet absent, distracter. This effect generalizes across different sensory modalities, such as vision and audition, and across different manipulations of the context, such as the distracter's sensory modality and pertinence to the task. Moreover, activation of the filtering mechanism relies on both strategic and reactive processes, as shown by its dynamic dependence on probabilistic and cross-trial contingencies. Crucially, across participants, the observed strategic cost is inversely related to the interference exerted by a distracter on distracter-present trials. These results attest to a mechanism for the monitoring and filtering of potential distraction in the human brain. Although its activation is indisputably beneficial when distraction occurs, it leads to robust costs when distraction is actually expected but currently absent. PMID:22984954

  14. Enhancement of Runx2 expression is potentially linked to β-catenin accumulation in canine intervertebral disc degeneration.

    PubMed

    Iwata, Munetaka; Aikawa, Takeshi; Hakozaki, Takaharu; Arai, Kiyotaka; Ochi, Hiroki; Haro, Hirotaka; Tagawa, Masahiro; Asou, Yoshinori; Hara, Yasushi

    2015-01-01

    Intervertebral disc degeneration (IVDD) greatly affects the quality of life. The nucleus pulposus (NP) of chondrodystrophic dog breeds (CDBs) is similar to the human NP because the cells disappear with age and are replaced by fibrochondrocyte-like cells. Because IVDD develops as early as within the first year of life, we used canines as a model to investigate the in vitro mechanisms underlying IVDD. The mechanism underlying age-related IVDD, however, is poorly understood. Several research groups have suggested that Wnt/β-catenin signaling plays an important role in IVDD. However, the role of Wnt/β-catenin signals in IVD cells is not yet well understood. Here, we demonstrate that Wnt/β-catenin signaling could enhance Runx2 expression in IVDD and lead to IVD calcification. Nucleus pulposus (NP) tissue was obtained from Beagle dogs after evaluation of the degeneration based on magnetic resonance imaging (MRI). Histological analysis showed that lack of Safranin-O staining, calcified area, and matrix metalloproteinase (MMP) 13-positive cells increased with progression of the degeneration. Furthermore, the levels of β-catenin- and Runx2-positive cells also increased. Real-time reverse-transcription polymerase chain reaction analysis showed that the MRI signal intensity and mRNA expression levels of β-catenin and Runx2 are correlated in NP tissues. Moreover, supplementation of LiCl induced β-catenin accumulation and Runx2 expression. In contrast, FH535 inhibited LiCl-induced upregulation. These results suggest that Runx2 transcript and protein expression, potentially in combination with β-catenin accumulation, are enhanced in degenerated and calcified intervertebral discs of CDBs. PMID:24916026

  15. SO2 photoexcitation mechanism links mass-independent sulfur isotopic fractionation in cryospheric sulfate to climate impacting volcanism

    PubMed Central

    Hattori, Shohei; Schmidt, Johan A.; Johnson, Matthew S.; Danielache, Sebastian O.; Yamada, Akinori; Ueno, Yuichiro; Yoshida, Naohiro

    2013-01-01

    Natural climate variation, such as that caused by volcanoes, is the basis for identifying anthropogenic climate change. However, knowledge of the history of volcanic activity is inadequate, particularly concerning the explosivity of specific events. Some material is deposited in ice cores, but the concentration of glacial sulfate does not distinguish between tropospheric and stratospheric eruptions. Stable sulfur isotope abundances contain additional information, and recent studies show a correlation between volcanic plumes that reach the stratosphere and mass-independent anomalies in sulfur isotopes in glacial sulfate. We describe a mechanism, photoexcitation of SO2, that links the two, yielding a useful metric of the explosivity of historic volcanic events. A plume model of S(IV) to S(VI) conversion was constructed including photochemistry, entrainment of background air, and sulfate deposition. Isotopologue-specific photoexcitation rates were calculated based on the UV absorption cross-sections of 32SO2, 33SO2, 34SO2, and 36SO2 from 250 to 320 nm. The model shows that UV photoexcitation is enhanced with altitude, whereas mass-dependent oxidation, such as SO2 + OH, is suppressed by in situ plume chemistry, allowing the production and preservation of a mass-independent sulfur isotope anomaly in the sulfate product. The model accounts for the amplitude, phases, and time development of Δ33S/δ34S and Δ36S/Δ33S found in glacial samples. We are able to identify the process controlling mass-independent sulfur isotope anomalies in the modern atmosphere. This mechanism is the basis of identifying the magnitude of historic volcanic events. PMID:23417298

  16. SO2 photoexcitation mechanism links mass-independent sulfur isotopic fractionation in cryospheric sulfate to climate impacting volcanism.

    PubMed

    Hattori, Shohei; Schmidt, Johan A; Johnson, Matthew S; Danielache, Sebastian O; Yamada, Akinori; Ueno, Yuichiro; Yoshida, Naohiro

    2013-10-29

    Natural climate variation, such as that caused by volcanoes, is the basis for identifying anthropogenic climate change. However, knowledge of the history of volcanic activity is inadequate, particularly concerning the explosivity of specific events. Some material is deposited in ice cores, but the concentration of glacial sulfate does not distinguish between tropospheric and stratospheric eruptions. Stable sulfur isotope abundances contain additional information, and recent studies show a correlation between volcanic plumes that reach the stratosphere and mass-independent anomalies in sulfur isotopes in glacial sulfate. We describe a mechanism, photoexcitation of SO2, that links the two, yielding a useful metric of the explosivity of historic volcanic events. A plume model of S(IV) to S(VI) conversion was constructed including photochemistry, entrainment of background air, and sulfate deposition. Isotopologue-specific photoexcitation rates were calculated based on the UV absorption cross-sections of (32)SO2, (33)SO2, (34)SO2, and (36)SO2 from 250 to 320 nm. The model shows that UV photoexcitation is enhanced with altitude, whereas mass-dependent oxidation, such as SO2 + OH, is suppressed by in situ plume chemistry, allowing the production and preservation of a mass-independent sulfur isotope anomaly in the sulfate product. The model accounts for the amplitude, phases, and time development of Δ(33)S/δ(34)S and Δ(36)S/Δ(33)S found in glacial samples. We are able to identify the process controlling mass-independent sulfur isotope anomalies in the modern atmosphere. This mechanism is the basis of identifying the magnitude of historic volcanic events. PMID:23417298

  17. Biomass Carbon in the South Mexican Pacific Coast: Exploring Mangrove Potential to REDD+ Mechanisms

    NASA Astrophysics Data System (ADS)

    Bejarano, M.; Amezcua-Torrijos, I.

    2014-12-01

    Mangroves have the highest carbon stocks amongst tropical forests. In Mexico, however, little is known about their potential to mitigate climate change. In this work, we estimated biomass carbon stocks in the Southern Mexican Pacific Coast (~69,000 ha). We quantified above and belowground biomass carbon stocks at (1) the regional scale along two environmental strata (i.e. dry and wet), and (2) at the local scale along three geomorphological types of mangroves (i.e. fringe, estuarine and basin). Regional strata were defined using intensity and influence of rivers and, the mean annual precipitation and evapotranspiration ratio (i.e., wet < 1 > dry). By lowering the stressing environmental conditions (e.g., low salinity and high sediment accumulation), we expected the highest stocks in mangroves growing in wet and estuarine strata at the regional scale and local scale, respectively. Quantifications were carried out in sixty-six sites chosen through stratified randomized design in which six strata were obtained by a full combination of regional and local strata. In all strata, aboveground carbon represents 64-67% of total carbon. Total biomass carbon was higher in wet than dry stratum (W: 87.3 ± 6.9, D: 47.0 ± 5.0, p<0.001). While at local scale, total biomass carbon was high in estuarine mangroves of both wet and dry regions (W: 91.6 ± 7.8, D: 77.6 ± 14.8, p<0.001), and these were statistically similar to fringe wet mangroves (110.9 ± 24.2, p<0.001), the stratum with the highest total carbon. Following a conservative approach, the Mexican Southern Pacific Coast is storing near 20,344 Gg CO2e. If the historical annual deforestation rate of 0.54% continues, this region could emit between 0.03 and 14.4 Gg of CO2e ha/year, out of which wet estuarine mangroves would have the highest emission values. Evidence suggests that these mangroves are the most important strata in which REDD+ mechanisms could be implemented due to (1) their carbon stocks, and (2) their highest

  18. Correlation of fragility with mechanical moduli in double-well potential for glass-forming liquid

    NASA Astrophysics Data System (ADS)

    Cao, Wan Qiang

    2012-02-01

    The shoving model and the Vogel-Fulcher relation are employed to derive correlation of the fragility with the mechanical moduli for glass-forming simple liquids. The result shows that a liquid with smaller fragility will have larger ratio of K∞/G∞ in dilute liquid system. Based on radial distribution function with the Lennard-Jones potential modified by the Gaussian potential with a second minimum, fragility of the supercooled simple liquid is derived from the correlation between viscosity and shear modulus via configurational entropy. The results demonstrate that the fragility is determined by two parts: thermodynamic components and mechanical moduli. For a weak Gaussian potential liquid, the fragility is proportional to the Tg, while for a strong one, the fragility is inversely proportional to the Tg, and the Gaussian potential will increase fragility.

  19. The role of shape invariance potentials in the relativistic quantum mechanics

    NASA Astrophysics Data System (ADS)

    Bakhshi, Z.; Panahi, H.

    2016-05-01

    The point canonical transformation in non-relativistic quantum mechanics is applied as an algebraic method to obtain the solutions of the Dirac equation with spherical symmetry electromagnetic potentials. We want to show that some of the non-relativistic solvable potentials with shape-invariant symmetry can be related to the radial Dirac equation. Using this method, the idea of supersymmetry and shape invariance can be expanded to the relativistic quantum mechanics. The spinor wave functions for some of the obtained four-component electromagnetic potential are given in terms of special functions such as Jacobi, generalized Laguerre and Hermite polynomials. The relativistic bound-states spectrum for each case is also calculated in terms of the bound-states spectrum of the solvable potentials.

  20. Mutations in the X-linked intellectual disability gene, zDHHC9, alter autopalmitoylation activity by distinct mechanisms.

    PubMed

    Mitchell, David A; Hamel, Laura D; Reddy, Krishna D; Farh, Lynn; Rettew, Logan M; Sanchez, Phillip R; Deschenes, Robert J

    2014-06-27

    Early onset intellectual disabilities result in significant societal and economic costs and affect 1-3% of the population. The underlying genetic determinants are beginning to emerge and are interpreted in the context of years of work characterizing postsynaptic receptor and signaling functions of learning and memory. DNA sequence analysis of intellectual disability patients has revealed greater than 80 loci on the X-chromosome that are potentially linked to disease. One of the loci is zDHHC9, a gene encoding a Ras protein acyltransferase. Protein palmitoylation is a reversible modification that controls the subcellular localization and distribution of membrane receptors, scaffolds, and signaling proteins required for neuronal plasticity. Palmitoylation occurs in two steps. In the first step, autopalmitoylation, an enzyme-palmitoyl intermediate is formed. During the second step, the palmitoyl moiety is transferred to a protein substrate, or if no substrate is available, hydrolysis of the thioester linkage produces the enzyme and free palmitate. In this study, we demonstrate that two naturally occurring variants of zDHHC9, encoding R148W and P150S, affect the autopalmitoylation step of the reaction by lowering the steady state amount of the palmitoyl-zDHHC9 intermediate. PMID:24811172

  1. The health effects of ambient PM2.5 and potential mechanisms.

    PubMed

    Feng, Shaolong; Gao, Dan; Liao, Fen; Zhou, Furong; Wang, Xinming

    2016-06-01

    The impacts of ambient PM2.5 on public health have become great concerns worldwide, especially in the developing countries. Epidemiological and toxicological studies have shown that PM2.5 does not only induce cardiopulmonary disorders and/or impairments, but also contributes to a variety of other adverse health effects, such as driving the initiation and progression of diabetes mellitus and eliciting adverse birth outcomes. Of note, recent findings have demonstrated that PM2.5 may still pose a hazard to public health even at very low levels (far below national standards) of exposure. The proposed underlying mechanisms whereby PM2.5 causes adverse effects to public health include inducing intracellular oxidative stress, mutagenicity/genotoxicity and inflammatory responses. The present review aims to provide an brief overview of new insights into the molecular mechanisms linking ambient PM2.5 exposure and health effects, which were explored with new technologies in recent years. PMID:26896893

  2. Non-Hermitian quantum mechanics: wave packet propagation on autoionizing potential energy surfaces.

    PubMed

    Moiseyev, N; Scheit, S; Cederbaum, L S

    2004-07-01

    The correspondence between the time-dependent and time-independent molecular dynamic formalisms is shown for autoionizing processes. We demonstrate that the definition of the inner product in non-Hermitian quantum mechanics plays a key role in the proof. When the final state of the process is dissociative, it is technically favorable to introduce a complex absorbing potential into the calculations. The conditions which this potential should fulfill are briefly discussed. An illustrative numerical example is presented involving three potential energy surfaces. PMID:15260598

  3. Enzyme mechanism-based, oxidative DNA-protein cross-links formed with DNA polymerase β in vivo.

    PubMed

    Quiñones, Jason L; Thapar, Upasna; Yu, Kefei; Fang, Qingming; Sobol, Robert William; Demple, Bruce

    2015-07-14

    Free radical attack on the C1' position of DNA deoxyribose generates the oxidized abasic (AP) site 2-deoxyribonolactone (dL). Upon encountering dL, AP lyase enzymes such as DNA polymerase β (Polβ) form dead-end, covalent intermediates in vitro during attempted DNA repair. However, the conditions that lead to the in vivo formation of such DNA-protein cross-links (DPC), and their impact on cellular functions, have remained unknown. We adapted an immuno-slot blot approach to detect oxidative Polβ-DPC in vivo. Treatment of mammalian cells with genotoxic oxidants that generate dL in DNA led to the formation of Polβ-DPC in vivo. In a dose-dependent fashion, Polβ-DPC were detected in MDA-MB-231 human cells treated with the antitumor drug tirapazamine (TPZ; much more Polβ-DPC under 1% O2 than under 21% O2) and even more robustly with the "chemical nuclease" 1,10-copper-ortho-phenanthroline, Cu(OP)2. Mouse embryonic fibroblasts challenged with TPZ or Cu(OP)2 also incurred Polβ-DPC. Nonoxidative agents did not generate Polβ-DPC. The cross-linking in vivo was clearly a result of the base excision DNA repair pathway: oxidative Polβ-DPC depended on the Ape1 AP endonuclease, which generates the Polβ lyase substrate, and they required the essential lysine-72 in the Polβ lyase active site. Oxidative Polβ-DPC had an unexpectedly short half-life (∼ 30 min) in both human and mouse cells, and their removal was dependent on the proteasome. Proteasome inhibition under Cu(OP)2 treatment was significantly more cytotoxic to cells expressing wild-type Polβ than to cells with the lyase-defective form. That observation underscores the genotoxic potential of oxidative Polβ-DPC and the biological pressure to repair them. PMID:26124145

  4. Enzyme mechanism-based, oxidative DNA–protein cross-links formed with DNA polymerase β in vivo

    PubMed Central

    Quiñones, Jason L.; Thapar, Upasna; Yu, Kefei; Fang, Qingming; Sobol, Robert William; Demple, Bruce

    2015-01-01

    Free radical attack on the C1′ position of DNA deoxyribose generates the oxidized abasic (AP) site 2-deoxyribonolactone (dL). Upon encountering dL, AP lyase enzymes such as DNA polymerase β (Polβ) form dead-end, covalent intermediates in vitro during attempted DNA repair. However, the conditions that lead to the in vivo formation of such DNA–protein cross-links (DPC), and their impact on cellular functions, have remained unknown. We adapted an immuno-slot blot approach to detect oxidative Polβ-DPC in vivo. Treatment of mammalian cells with genotoxic oxidants that generate dL in DNA led to the formation of Polβ-DPC in vivo. In a dose-dependent fashion, Polβ-DPC were detected in MDA-MB-231 human cells treated with the antitumor drug tirapazamine (TPZ; much more Polβ-DPC under 1% O2 than under 21% O2) and even more robustly with the “chemical nuclease” 1,10-copper-ortho-phenanthroline, Cu(OP)2. Mouse embryonic fibroblasts challenged with TPZ or Cu(OP)2 also incurred Polβ-DPC. Nonoxidative agents did not generate Polβ-DPC. The cross-linking in vivo was clearly a result of the base excision DNA repair pathway: oxidative Polβ-DPC depended on the Ape1 AP endonuclease, which generates the Polβ lyase substrate, and they required the essential lysine-72 in the Polβ lyase active site. Oxidative Polβ-DPC had an unexpectedly short half-life (∼30 min) in both human and mouse cells, and their removal was dependent on the proteasome. Proteasome inhibition under Cu(OP)2 treatment was significantly more cytotoxic to cells expressing wild-type Polβ than to cells with the lyase-defective form. That observation underscores the genotoxic potential of oxidative Polβ-DPC and the biological pressure to repair them. PMID:26124145

  5. Atypical Gaze Following in Autism: A Comparison of Three Potential Mechanisms

    ERIC Educational Resources Information Center

    Gillespie-Lynch, K.; Elias, R.; Escudero, P.; Hutman, T.; Johnson, S. P.

    2013-01-01

    In order to evaluate the following potential mechanisms underlying atypical gaze following in autism, impaired reflexive gaze following, difficulty integrating gaze and affect, or reduced understanding of the referential significance of gaze, we administered three paradigms to young children with autism (N = 21) and chronological (N = 21) and…

  6. An Introductory Organic Chemistry Review Homework Exercise: Deriving Potential Mechanisms for Glucose Ring Opening in Mutarotation

    ERIC Educational Resources Information Center

    Murdock, Margaret; Holman, R. W.; Slade, Tyler; Clark, Shelley L. D.; Rodnick, Kenneth J.

    2014-01-01

    A unique homework assignment has been designed as a review exercise to be implemented near the end of the one-year undergraduate organic chemistry sequence. Within the framework of the exercise, students derive potential mechanisms for glucose ring opening in the aqueous mutarotation process. In this endeavor, 21 general review principles are…

  7. POTENTIAL MECHANISMS RESPONSIBLE FOR CHLOROTRIAZINE-INDUCED ALTERATIONS IN CATECHOLAMINES IN PHEOCHROMOCYTOMA (PC12) CELLS

    EPA Science Inventory

    ABSTRACT

    Potential Mechanisms Responsible for Chlorotriazine-induced Changes in Catecholamine Metabolism in Pheochromocytoma (PC12) Cells*
    PARIKSHIT C. DAS1, WILLIAM K. McELROY2 , AND RALPH L. COOPER2+
    1Curriculum in Toxicology, University of North Carolina, Chape...

  8. Lifelong bilingualism and neural reserve against Alzheimer's disease: a review of findings and potential mechanisms.

    PubMed

    Gold, Brian T

    2015-03-15

    Alzheimer's disease (AD) is a progressive brain disorder that initially affects medial temporal lobe circuitry and memory functions. Current drug treatments have only modest effects on the symptomatic course of the disease. In contrast, a growing body of evidence suggests that lifelong bilingualism may delay the onset of clinical AD symptoms by several years. The purpose of the present review is to summarize evidence for bilingualism as a reserve variable against AD and discuss potential underlying neurocognitive mechanisms. Evidence is reviewed suggesting that bilingualism may delay clinical AD symptoms by protecting frontostriatal and frontoparietal executive control circuitry rather than medial temporal lobe memory circuitry. Cellular and molecular mechanisms that may contribute to bilingual cognitive reserve effects are discussed, including those that may affect neuronal metabolic functions, dynamic neuronal-glial interactions, vascular factors, myelin structure and neurochemical signaling. Future studies that may test some of these potential mechanisms of bilingual CR effects are proposed. PMID:25496781

  9. Colony failure linked to low sperm viability in honey bee (Apis mellifera) queens and an exploration of potential causative factors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Queen health is closely linked to colony performance in honey bees as a single queen is normally responsible for all egg laying and brood production within the colony. In the U. S. in recent years, queens have been failing at a high rate; with 50% or greater of queens replaced in colonies within 6 m...

  10. Sequestosome 1/p62 links familial ALS mutant SOD1 to LC3 via an ubiquitin-independent mechanism

    PubMed Central

    Gal, Jozsef; Strom, Anna-Lena; Kwinter, David M.; Kilty, Renee; Zhang, Jiayu; Shi, Ping; Fu, Weisi; Wooten, Marie W.; Zhu, Haining

    2009-01-01

    The p62/sequestosome 1 protein has been identified as a component of pathological protein inclusions in neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). P62 has also been implicated in autophagy, a process of mass degradation of intracellular proteins and organelles. Autophagy is a critical pathway for degrading misfolded and/or damaged proteins, including the copper-zinc superoxide dismutase (SOD1) mutants linked to familial ALS. We previously reported that p62 interacted with ALS mutants of SOD1 and that the ubiquitin-association (UBA) domain of p62 was dispensable for the interaction. In this study, we identified two distinct regions of p62 that were essential to its binding to mutant SOD1: the N-terminal PB1 domain (residues 1-104) and a separate internal region (residues 178–224) termed here as SOD1 mutant interaction region (SMIR). The PB1 domain is required for appropriate oligomeric status of p62 and the SMIR is the actual region interacting with mutant SOD1. Within the SMIR, the conserved W184, H190 and positively charged R183, R186, K187 and K189 residues are critical to the p62-mutant SOD1 interaction since substitution of these residues with alanine resulted in significantly abolished binding. In addition, SMIR and the p62 sequence responsible for the interaction with LC3, a protein essential for autophagy activation, are independent of each other. In cells lacking p62, the existence of mutant SOD1 in acidic autolysosomes decreased, suggesting that p62 can function as an adaptor between mutant SOD1 and the autophagy machinery. This study provides a novel molecular mechanism by which mutant SOD1 can be recognized by p62 in an ubiquitin-independent fashion and targeted for the autophagy-lysosome degradation pathway. PMID:19765191

  11. Acute stress evokes selective mobilization of T cells that differ in chemokine receptor expression: a potential pathway linking immunologic reactivity to cardiovascular disease.

    PubMed

    Bosch, Jos A; Berntson, Gary G; Cacioppo, John T; Dhabhar, Firdaus S; Marucha, Phillip T

    2003-08-01

    T lymphocytes and monocytes/macrophages are the most abundant cells found in the atherosclerotic plaque. These cells can migrate towards the activated endothelium through the local release of chemotactic cytokines, or chemokines. Given the important role of leukocyte migration in atherosclerosis and the role of stress in mediating leukocyte trafficking, the present study examined the effects of an acute stressor on the redistribution of T cells (CD3+) and monocytes that express the chemokine receptors CCR5, CCR6, CXCR1, CXCR2, CXCR3, and CXCR4. Forty-four undergraduate students underwent a public speaking task. The acute stressor induced sympathetic cardiac activation, parasympathetic cardiac withdrawal, lymphocytosis, and monocytosis (all p<.001). Although the total number of T lymphocytes did not change, there was a selective increase in the number of circulating T cells expressing CXCR2, CXCR3, and CCR5. The ligands of these receptors are chemokines known to be secreted by activated endothelial cells. Analyses of individual differences in stress-induced responses demonstrated a positive relationship between sympathetic cardiac reactivity and mobilization of the various T cell subsets (.35potentially contribute to the complications that follow acute stressful events. This mechanism may help explain the link between stress, reactivity, and cardiovascular disease. PMID:12831827

  12. Early life stress interactions with the epigenome: potential mechanisms driving vulnerability towards psychiatric illness

    PubMed Central

    Olive, Michael Foster

    2014-01-01

    Throughout the 20th century a body of literature concerning the long lasting effects of early environment was produced. Adverse experiences in early life, or early life stress (ELS), is associated with a higher risk for developing various psychiatric illnesses. The mechanisms driving the complex interplay between ELS and adult phenotype has baffled many investigators for decades. Over the last decade, the new field of neuroepigenetics has emerged as one possible mechanism by which ELS can have far reaching effects on adult phenotype, behavior, and risk for psychiatric illness. Here we review two commonly investigated epigenetic mechanisms, histone modifications and DNA methylation, and the emerging field of neuroepigenetics as they relate to ELS. We discuss the current animal literature demonstrating ELS induced epigenetic modulation of gene expression that results in altered adult phenotypes. We also briefly discuss other areas in which neuroepigenetics has emerged as a potential mechanism underlying environmental and genetic interactions. PMID:25003947

  13. Electrical stimulation alleviates depressive-like behaviors of rats: investigation of brain targets and potential mechanisms

    PubMed Central

    Lim, L W; Prickaerts, J; Huguet, G; Kadar, E; Hartung, H; Sharp, T; Temel, Y

    2015-01-01

    Deep brain stimulation (DBS) is a promising therapy for patients with refractory depression. However, key questions remain with regard to which brain target(s) should be used for stimulation, and which mechanisms underlie the therapeutic effects. Here, we investigated the effect of DBS, with low- and high-frequency stimulation (LFS, HFS), in different brain regions (ventromedial prefrontal cortex, vmPFC; cingulate cortex, Cg; nucleus accumbens (NAc) core or shell; lateral habenula, LHb; and ventral tegmental area) on a variety of depressive-like behaviors using rat models. In the naive animal study, we found that HFS of the Cg, vmPFC, NAc core and LHb reduced anxiety levels and increased motivation for food. In the chronic unpredictable stress model, there was a robust depressive-like behavioral phenotype. Moreover, vmPFC HFS, in a comparison of all stimulated targets, produced the most profound antidepressant effects with enhanced hedonia, reduced anxiety and decreased forced-swim immobility. In the following set of electrophysiological and histochemical experiments designed to unravel some of the underlying mechanisms, we found that vmPFC HFS evoked a specific modulation of the serotonergic neurons in the dorsal raphe nucleus (DRN), which have long been linked to mood. Finally, using a neuronal mapping approach by means of c-Fos expression, we found that vmPFC HFS modulated a brain circuit linked to the DRN and known to be involved in affect. In conclusion, HFS of the vmPFC produced the most potent antidepressant effects in naive rats and rats subjected to stress by mechanisms also including the DRN. PMID:25826110

  14. Electrical stimulation alleviates depressive-like behaviors of rats: investigation of brain targets and potential mechanisms.

    PubMed

    Lim, L W; Prickaerts, J; Huguet, G; Kadar, E; Hartung, H; Sharp, T; Temel, Y

    2015-01-01

    Deep brain stimulation (DBS) is a promising therapy for patients with refractory depression. However, key questions remain with regard to which brain target(s) should be used for stimulation, and which mechanisms underlie the therapeutic effects. Here, we investigated the effect of DBS, with low- and high-frequency stimulation (LFS, HFS), in different brain regions (ventromedial prefrontal cortex, vmPFC; cingulate cortex, Cg; nucleus accumbens (NAc) core or shell; lateral habenula, LHb; and ventral tegmental area) on a variety of depressive-like behaviors using rat models. In the naive animal study, we found that HFS of the Cg, vmPFC, NAc core and LHb reduced anxiety levels and increased motivation for food. In the chronic unpredictable stress model, there was a robust depressive-like behavioral phenotype. Moreover, vmPFC HFS, in a comparison of all stimulated targets, produced the most profound antidepressant effects with enhanced hedonia, reduced anxiety and decreased forced-swim immobility. In the following set of electrophysiological and histochemical experiments designed to unravel some of the underlying mechanisms, we found that vmPFC HFS evoked a specific modulation of the serotonergic neurons in the dorsal raphe nucleus (DRN), which have long been linked to mood. Finally, using a neuronal mapping approach by means of c-Fos expression, we found that vmPFC HFS modulated a brain circuit linked to the DRN and known to be involved in affect. In conclusion, HFS of the vmPFC produced the most potent antidepressant effects in naive rats and rats subjected to stress by mechanisms also including the DRN. PMID:25826110

  15. Magnetic particle-linked anti hCG β antibody for immunoassay of human chorionic gonadotropin (hCG), potential application to early pregnancy diagnosis.

    PubMed

    Kuo, Hsiao-Ting; Yeh, Jay Z; Jiang, Chi-Ming; Wu, Ming-Chang

    2012-07-31

    The objective of this study was to develop a magnetic particle-linked monoclonal antibody to hCG β for immunosorbent assay of human chorionic gonadotropin (hCG) with improved detection sensitivity. Monoclonal antibody against hCG β was found to be optimally cross-linked to the superparamagnetic particles (SPIO) using EDC and NHS as cross-linking reagents. This superparamagnetic particle-linked monoclonal antibody was able to concentrate hCG from a tested solution for further ELISA assay using horse radish peroxidase-labeled monoclonal antibody against hCG β. This hybrid technique had greatly decreased the detection limit to 0.1 mIU/mL, making an early detection of pregnancy possible. With an improved sensitivity and simple operation, the magnetic particle-linked anti hCG β antibody for immunoassay of human chorionic gonadotropin (hCG) has a great potential to supersede the traditional ELISA for pregnancy diagnosis. PMID:22542932

  16. Formulation of wide-ranging embedded-atom-type potentials: the role of mechanical stability

    NASA Astrophysics Data System (ADS)

    Pechenik, Eugene; Kelson, Itzhak; Makov, Guy

    2013-01-01

    Wide-ranging inter-atomic potentials are necessary for modeling many problems in material physics that involve multiple atomic environments and phases. The domains of thermodynamic and mechanical stability of embedded-atom-type potentials are examined for the cubic phases. It is shown that the choice of the pair potential is critical in determining the domain of stability of embedded-atom-type potentials. In particular, the Lennard-Jones embedded-atom potential is shown not to stabilize the bcc phase. A simple four-parameter universal equation of state-based embedded-atom potential is shown to have a domain of stability for all the cubic phases and to reproduce the high-pressure equation of state. A model phase diagram for the three cubic phases is presented. This potential is fitted to 17 elemental systems and found to be able to reproduce both the elastic constants and the ground state crystalline structure. For elements with a low degree of elastic anisotropy, this potential can also reproduce the high-pressure behavior.

  17. Despair-associated memory requires a slow-onset CA1 long-term potentiation with unique underlying mechanisms

    PubMed Central

    Jing, Liang; Duan, Ting-Ting; Tian, Meng; Yuan, Qiang; Tan, Ji-Wei; Zhu, Yong-Yong; Ding, Ze-Yang; Cao, Jun; Yang, Yue-Xiong; Zhang, Xia; Mao, Rong-Rong; Richter-levin, Gal; Zhou, Qi-Xin; Xu, Lin

    2015-01-01

    The emotion of despair that occurs with uncontrollable stressful event is probably retained by memory, termed despair-associated memory, although little is known about the underlying mechanisms. Here, we report that forced swimming (FS) with no hope to escape, but not hopefully escapable swimming (ES), enhances hippocampal α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-dependent GluA1 Ser831 phosphorylation (S831-P), induces a slow-onset CA1 long-term potentiation (LTP) in freely moving rats and leads to increased test immobility 24-h later. Before FS application of the antagonists to block S831-P or N-methyl-D-aspartic acid receptor (NMDAR) or glucocorticoid receptor (GR) disrupts LTP and reduces test immobility, to levels similar to those of the ES group. Because these mechanisms are specifically linked with the hopeless of escape from FS, we suggest that despair-associated memory occurs with an endogenous CA1 LTP that is intriguingly mediated by a unique combination of rapid S831-P with NMDAR and GR activation to shape subsequent behavioral despair. PMID:26449319

  18. Despair-associated memory requires a slow-onset CA1 long-term potentiation with unique underlying mechanisms.

    PubMed

    Jing, Liang; Duan, Ting-Ting; Tian, Meng; Yuan, Qiang; Tan, Ji-Wei; Zhu, Yong-Yong; Ding, Ze-Yang; Cao, Jun; Yang, Yue-Xiong; Zhang, Xia; Mao, Rong-Rong; Richter-Levin, Gal; Zhou, Qi-Xin; Xu, Lin

    2015-01-01

    The emotion of despair that occurs with uncontrollable stressful event is probably retained by memory, termed despair-associated memory, although little is known about the underlying mechanisms. Here, we report that forced swimming (FS) with no hope to escape, but not hopefully escapable swimming (ES), enhances hippocampal α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-dependent GluA1 Ser831 phosphorylation (S831-P), induces a slow-onset CA1 long-term potentiation (LTP) in freely moving rats and leads to increased test immobility 24-h later. Before FS application of the antagonists to block S831-P or N-methyl-D-aspartic acid receptor (NMDAR) or glucocorticoid receptor (GR) disrupts LTP and reduces test immobility, to levels similar to those of the ES group. Because these mechanisms are specifically linked with the hopeless of escape from FS, we suggest that despair-associated memory occurs with an endogenous CA1 LTP that is intriguingly mediated by a unique combination of rapid S831-P with NMDAR and GR activation to shape subsequent behavioral despair. PMID:26449319

  19. Methicillin-Resistant Staphylococcus aureus Ocular Infection after Corneal Cross-Linking for Keratoconus: Potential Association with Atopic Dermatitis

    PubMed Central

    Fasciani, Romina; Agresta, Antonio; Caristia, Alice; Mosca, Luigi; Scupola, Andrea; Caporossi, Aldo

    2015-01-01

    Purpose. To report the risk of methicillin-resistant Staphylococcus aureus (MRSA) ocular infection after UVA-riboflavin corneal collagen cross-linking in a patient with atopic dermatitis. Methods. A 22-year-old man, with bilateral evolutive keratoconus and atopic dermatitis, underwent UVA-riboflavin corneal cross-linking and presented with rapidly progressive corneal abscesses and cyclitis in the treated eye five days after surgery. The patient was admitted to the hospital and treated with broad-spectrum antimicrobic therapy. Results. The patient had positive cultures for MRSA, exhibiting a strong resistance to antibiotics. Antibiotic therapy was modified and targeted accordingly. The intravitreal reaction is extinguished, but severe damage of ocular structures was unavoidable. Conclusion. Riboflavin/UVA corneal cross-linking is considered a safe procedure and is extremely effective in halting keratoconus' progression. However, this procedure is not devoid of infectious complications, due to known risk factors and/or poor patients' hygiene compliance in the postoperative period. Atopic dermatitis is a common disease among patients with keratoconus and Staphylococcus aureus colonization is commonly found in patients with atopic dermatitis. Therefore, comorbidity with atopic dermatitis should be thoroughly assessed through clinical history before surgery. A clinical evaluation within three days after surgery and the imposition of strict personal hygiene rules are strongly recommended. PMID:25866692

  20. Simultaneous Measurement of [Ca2+]i and Membrane Potential under Mechanical or Biochemical Stimulation

    NASA Astrophysics Data System (ADS)

    Sano, Minoru; Imura, Katsuaki; Ushida, Takashi; Tateishi, Tetsuya

    In human umbilical endothelial cells (HUVEC), mechanical stress is known to induce transients of [Ca2+]i that lead to the regulation of vascular functions in vivo. The transmembraneous influx of Ca2+ is thought to be mediated by voltage-dependent ion channels or stretch-activated ion channels. In order to elucidate the correlation of [Ca2+]i and membrane potential under mechanical stress, the influences of mechanical or biochemical stimulation on endothelial cells stained with both fura-2 and DiBAC4(3) were studied in vitro, by constructing an imaging system that could capture four kinds of fluorescence images simultaneously at real-time. In the application of thrombin, [Ca2+]i transients were accompanied with preceding depolarization, while mechanical stress that were loaded on a single cell with a micropipette did not evoke dramatic changes of membrane potential. These results indicate that the signaling pathway initiated by mechanical stress could be independent of electrochemical activation, and different from that by biochemical stimulation in HUVEC.

  1. Potential molecular, cellular and microenvironmental mechanism of sorafenib resistance in hepatocellular carcinoma.

    PubMed

    Chen, Jiang; Jin, Renan; Zhao, Jie; Liu, Jinghua; Ying, Hanning; Yan, Han; Zhou, Senjun; Liang, Yuelong; Huang, Diyu; Liang, Xiao; Yu, Hong; Lin, Hui; Cai, Xiujun

    2015-10-10

    Sorafenib, an orally-available kinase inhibitor, is the only standard clinical treatment against advanced hepatocellular carcinoma. However, development of resistance to sorafenib has raised concern in recent years due to the high-level heterogeneity of individual response to sorafenib treatment. The resistance mechanism underlying the impaired sensitivity to sorafenib is still elusive though some researchers have made great efforts. Here, we provide a systemic insight into the potential molecular, cellular and microenvironmental mechanism of sorafenib resistance in hepatocellular carcinoma depending on abundant previous studies and reports. PMID:26170167

  2. Potential Mechanisms for IgG4 Inhibition of Immediate Hypersensitivity Reactions.

    PubMed

    James, Louisa K; Till, Stephen J

    2016-03-01

    IgG4 is the least abundant IgG subclass in human serum, representing less than 5 % of all IgG. Increases in IgG4 occur following chronic exposure to antigen and are generally associated with states of immune tolerance. In line with this, IgG4 is regarded as an anti-inflammatory antibody with a limited ability to elicit effective immune responses. Furthermore, IgG4 attenuates allergic responses by inhibiting the activity of IgE. The mechanism by which IgG4 inhibits IgE-mediated hypersensitivity has been investigated using a variety of model systems leading to two proposed mechanisms. First by sequestering antigen, IgG4 can function as a blocking antibody, preventing cross-linking of receptor bound IgE. Second IgG4 has been proposed to co-stimulate the inhibitory IgG receptor FcγRIIb, which can negatively regulate FcεRI signaling and in turn inhibit effector cell activation. Recent advances in our understanding of the structural features of human IgG4 have shed light on the unique functional and immunologic properties of IgG4. The aim of this review is to evaluate our current understanding of IgG4 biology and reassess the mechanisms by which IgG4 functions to inhibit IgE-mediated allergic responses. PMID:26892721

  3. The Electrokinetic Mechanism of Hydrothermal-Circulation-Related and Production-Induced Self-Potentials

    SciTech Connect

    Ishido, T.; Kikuchi, T.; Sugihara, M.

    1987-01-20

    Self-potential (SP) surveys were carried out on a number of geothermal areas in Japan during the last decade. In most cases SP anomalies of positive polarity are found to overlie high temperature upflow zones. Streaming potential generated by hydrothermal circulation (Ishido, 1981) is considered to be the most likely cause of the observed positive anomalies. Repeated surveys conducted on the Nigorikawa caldera in Japan detected a change in SP induced by production of geothermal fluids. The observed change is dipolar in waveform and can also be attributed to an electrokinetic mechanism. 6 figs., 14 refs.

  4. Molecular Mechanism Linking BRCA1 Dysfunction to High Grade Serous Epithelial Ovarian Cancers with Peritoneal Permeability and Ascites

    PubMed Central

    Desai, A; Xu, J; Aysola, K; Akinbobuyi, O; White, M; Reddy, VE; Okoli, J; Clark, C; Partridge, EE; Childs, Ed; Beech, DJ; Rice, MV; Reddy, ESP; Rao, VN

    2015-01-01

    Ovarian cancer constitutes the second most common gynecological cancer with a five-year survival rate of 40%. Among the various histotypes associated with hereditary ovarian cancer, high-grade serous epithelial ovarian carcinoma (HGSEOC) is the most predominant and women with inherited mutations in BRCA1 have a lifetime risk of 40–60%. HGSEOC is a challenge for clinical oncologists, due to late presentation of patient, diagnosis and high rate of relapse. Ovarian tumors have a wide range of clinical presentations including development of ascites as a result of deregulated endothelial function thereby causing increased vascular permeability of peritoneal vessels. The molecular mechanisms remain elusive. Studies have shown that fallopian tube cancers develop in women with BRCA1 gene mutations more often than previously suspected. Recent studies suggest that many primary peritoneal cancers and some high-grade serous epithelial ovarian carcinomas actually start in the fallopian tubes. In this article we have addressed the molecular pathway of a recently identified potential biomarker Ubc9 whose deregulated expression due to BRCA1 dysfunction can result in HGSEOC with peritoneal permeability and formation of ascites. We also discuss the role of downstream targets Caveolin-1 and Vascular Endothelial Growth Factor (VEGF) in the pathogenesis of ascites in ovarian carcinomas. Finally we hypothesize a signaling axis between Ubc9 over expression, loss of Caveolin-1 and induction of VEGF in BRCA1 mutant HGSEOC cells. We suggest that Ubc9-mediated stimulation of VEGF as a novel mechanism underlying ovarian cancer aggressiveness and ascites formation. Agents that target Ubc9 and VEGF signaling may represent a novel therapeutic strategy to impede peritoneal growth and spread of HGSEOC. PMID:26665166

  5. Music and Memory in Alzheimer's Disease and The Potential Underlying Mechanisms.

    PubMed

    Peck, Katlyn J; Girard, Todd A; Russo, Frank A; Fiocco, Alexandra J

    2016-01-01

    With population aging and a projected exponential expansion of persons diagnosed with Alzheimer's disease (AD), the development of treatment and prevention programs has become a fervent area of research and discovery. A growing body of evidence suggests that music exposure can enhance memory and emotional function in persons with AD. However, there is a paucity of research that aims to identify specific underlying neural mechanisms associated with music's beneficial effects in this particular population. As such, this paper reviews existing anecdotal and empirical evidence related to the enhancing effects of music exposure on cognitive function and further provides a discussion on the potential underlying mechanisms that may explain music's beneficial effect. Specifically, this paper will outline the potential role of the dopaminergic system, the autonomic nervous system, and the default network in explaining how music may enhance memory function in persons with AD. PMID:26967216

  6. Archaeal Ubiquitin-like SAMP3 is Isopeptide-linked to Proteins via a UbaA-dependent Mechanism*

    PubMed Central

    Miranda, Hugo V.; Antelmann, Haike; Hepowit, Nathaniel; Chavarria, Nikita E.; Krause, David J.; Pritz, Jonathan R.; Bäsell, Katrin; Becher, Dörte; Humbard, Matthew A.; Brocchieri, Luciano; Maupin-Furlow, Julie A.

    2014-01-01

    SAMP1 and SAMP2 are ubiquitin-like proteins that function as protein modifiers and are required for the production of sulfur-containing biomolecules in the archaeon Haloferax volcanii. Here we report a novel small archaeal modifier protein (named SAMP3) with a β-grasp fold and C-terminal diglycine motif characteristic of ubiquitin that is functional in protein conjugation in Hfx. volcanii. SAMP3 conjugates were dependent on the ubiquitin-activating E1 enzyme homolog of archaea (UbaA) for synthesis and were cleaved by the JAMM/MPN+ domain metalloprotease HvJAMM1. Twenty-three proteins (28 lysine residues) were found to be isopeptide-linked to the C-terminal carboxylate of SAMP3, and 331 proteins were reproducibly found associated with SAMP3 in a UbaA-dependent manner based on tandem mass spectrometry (MS/MS) analysis. The molybdopterin (MPT) synthase large subunit homolog MoaE, found samp3ylated at conserved active site lysine residues in MS/MS analysis, was also shown to be covalently bound to SAMP3 by immunoprecipitation and tandem affinity purifications. HvJAMM1 was demonstrated to catalyze the cleavage of SAMP3 from MoaE, suggesting a mechanism of controlling MPT synthase activity. The levels of samp3ylated proteins and samp3 transcripts were found to be increased by the addition of dimethyl sulfoxide to aerobically growing cells. Thus, we propose a model in which samp3ylation is covalent and reversible and controls the activity of enzymes such as MPT synthase. Sampylation of MPT synthase may govern the levels of molybdenum cofactor available and thus facilitate the scavenging of oxygen prior to the transition to respiration with molybdenum-cofactor-containing terminal reductases that use alternative electron acceptors such as dimethyl sulfoxide. Overall, our study of SAMP3 provides new insight into the diversity of functional ubiquitin-like protein modifiers and the network of ubiquitin-like protein targets in Archaea. PMID:24097257

  7. Rupture of giant vertebrobasilar aneurysm following flow diversion: mechanical stretch as a potential mechanism for early aneurysm rupture.

    PubMed

    Fox, Benjamin; Humphries, William Edward; Doss, Vinodh T; Hoit, Daniel; Elijovich, Lucas; Arthur, Adam S

    2014-01-01

    A patient with a giant symptomatic vertebrobasilar aneurysm was treated by endoscopic third ventriculostomy for obstructive hydrocephalus followed by treatment of the aneurysm by flow diversion using a Pipeline Embolization Device. After an uneventful procedure and initial periprocedural period, the patient experienced an unexpected fatal subarachnoid hemorrhage 1 week later. Autopsy demonstrated extensive subarachnoid hemorrhage and aneurysm rupture (linear whole wall rupture). The patent Pipeline Embolization Device was in its intended location, as was the persistent coil occlusion of the distal left vertebral artery. The aneurysm appeared to rupture in a linear manner and contained a thick large expansile clot that seemed to disrupt or rupture the thin aneurysm wall directly opposite the basilar artery/Pipeline Embolization Device. We feel the pattern of aneurysm rupture in our patient supports the idea that the combination of flow diversion and the resulting growing intra-aneurysmal thrombus can create a mechanical force with the potential to cause aneurysm rupture. PMID:25355741

  8. Rupture of giant vertebrobasilar aneurysm following flow diversion: mechanical stretch as a potential mechanism for early aneurysm rupture.

    PubMed

    Fox, Benjamin; Humphries, William Edward; Doss, Vinodh T; Hoit, Daniel; Elijovich, Lucas; Arthur, Adam S

    2015-11-01

    A patient with a giant symptomatic vertebrobasilar aneurysm was treated by endoscopic third ventriculostomy for obstructive hydrocephalus followed by treatment of the aneurysm by flow diversion using a Pipeline Embolization Device. After an uneventful procedure and initial periprocedural period, the patient experienced an unexpected fatal subarachnoid hemorrhage 1 week later. Autopsy demonstrated extensive subarachnoid hemorrhage and aneurysm rupture (linear whole wall rupture). The patent Pipeline Embolization Device was in its intended location, as was the persistent coil occlusion of the distal left vertebral artery. The aneurysm appeared to rupture in a linear manner and contained a thick large expansile clot that seemed to disrupt or rupture the thin aneurysm wall directly opposite the basilar artery/Pipeline Embolization Device. We feel the pattern of aneurysm rupture in our patient supports the idea that the combination of flow diversion and the resulting growing intra-aneurysmal thrombus can create a mechanical force with the potential to cause aneurysm rupture. PMID:25361560

  9. Potential effects of the introduction of the discrete address beacon system data link on air/ground information transfer problems

    NASA Technical Reports Server (NTRS)

    Grayson, R. L.

    1981-01-01

    This study of Aviation Safety Reporting System reports suggests that benefits should accure from implementation of discrete address beacon system data link. The phase enhanced terminal information system service is expected to provide better terminal information than present systems by improving currency and accuracy. In the exchange of air traffic control messages, discrete address insures that only the intended recipient receives and acts on a specific message. Visual displays and printer copy of messages should mitigate many of the reported problems associated with voice communications. The problems that remain unaffected include error in addressing the intended recipient and messages whose content is wrong but are otherwise correct as to format and reasonableness.

  10. A review of potential neurotoxic mechanisms among three chlorinated organic solvents

    SciTech Connect

    Bale, Ambuja S. Barone, Stan; Scott, Cheryl Siegel; Cooper, Glinda S.

    2011-08-15

    The potential for central nervous system depressant effects from three widely used chlorinated solvents, trichloroethylene (TCE), perchloroethylene (PERC), and dichloromethane (DCM), has been shown in human and animal studies. Commonalities of neurobehavioral and neurophysiological changes for the chlorinated solvents in in vivo studies suggest that there is a common mechanism(s) of action in producing resultant neurotoxicological consequences. The purpose of this review is to examine the mechanistic studies conducted with these chlorinated solvents and to propose potential mechanisms of action for the different neurological effects observed. Mechanistic studies indicate that this solvent class has several molecular targets in the brain. Additionally, there are several pieces of evidence from animal studies indicating this solvent class alters neurochemical functions in the brain. Although earlier evidence indicated that these three chlorinated solvents perturb the lipid bilayer, more recent data suggest an interaction between several specific neuronal receptors produces the resultant neurobehavioral effects. Collectively, TCE, PERC, and DCM have been reported to interact directly with several different classes of neuronal receptors by generally inhibiting excitatory receptors/channels and potentiating the function of inhibitory receptors/channels. Given this mechanistic information and available studies for TCE, DCM, and PERC, we provide hypotheses on primary targets (e.g. ion channel targets) that appear to be most influential in producing the resultant neurological effects. - Research Highlights: > Comparison of neurological effects among TCE, PERC, and DCM. > Correlation of mechanistic findings to neurological effects. > Data support that TCE, PERC, and DCM interact with several ion channels to produce neurological changes.

  11. Shifts in a single muscle's control potential of body dynamics are determined by mechanical feedback

    PubMed Central

    Sponberg, Simon; Libby, Thomas; Mullens, Chris H.; Full, Robert J.

    2011-01-01

    Muscles are multi-functional structures that interface neural and mechanical systems. Muscle work depends on a large multi-dimensional space of stimulus (neural) and strain (mechanical) parameters. In our companion paper, we rewrote activation to individual muscles in intact, behaving cockroaches (Blaberus discoidalis L.), revealing a specific muscle's potential to control body dynamics in different behaviours. Here, we use those results to provide the biologically relevant parameters for in situ work measurements. We test four hypotheses about how muscle function changes to provide mechanisms for the observed control responses. Under isometric conditions, a graded increase in muscle stress underlies its linear actuation during standing behaviours. Despite typically absorbing energy, this muscle can recruit two separate periods of positive work when controlling running. This functional change arises from mechanical feedback filtering a linear increase in neural activation into nonlinear work output. Changing activation phase again led to positive work recruitment, but at different times, consistent with the muscle's ability to also produce a turn. Changes in muscle work required considering the natural sequence of strides and separating swing and stance contributions of work. Both in vivo control potentials and in situ work loops were necessary to discover the neuromechanical coupling enabling control. PMID:21502130

  12. Cadmium transfer and detoxification mechanisms in a soil-mulberry-silkworm system: phytoremediation potential.

    PubMed

    Zhou, Lingyun; Zhao, Ye; Wang, Shuifeng

    2015-11-01

    Phytoremediation has been proven to be an environmentally sound alternative for the recovery of contaminated soils, and the economic profit that comes along with the process might stimulate its field use. This study investigated cadmium (Cd) transfer and detoxification mechanisms in a soil-mulberry-silkworm system to estimate the suitability of the mulberry and silkworm as an alternative method for the remediation of Cd-polluted soil; it also explored the underlying mechanisms regulating the trophic transfer of Cd. The results show that both the mulberry and silkworm have high Cd tolerance. The transfer factor suggests that the mulberry has high potential for Cd extraction from polluted soil. The subcellular distribution and chemical forms of Cd in mulberry leaves show that cell wall deposition and vacuolar compartmentalization play important role in Cd tolerance. In the presence of increasing Cd concentrations in silkworm food, detoxification mechanisms (excretion and homeostasis) were activated so that excess Cd was excreted in fecal balls, and metallothionein levels in the mid-gut, the posterior of the silk gland, and the fat body of silkworms were enhanced. And, the Cd concentrations in silk are at a low level, ranging from 0.02 to 0.21 mg kg(-1). Therefore, these mechanisms of detoxification can regulate Cd trophic transfer, and mulberry planting and silkworm breeding has high phytoremediation potential for Cd-contaminated soil. PMID:26169822

  13. Potential mechanisms mediating improved glycemic control after bariatric/metabolic surgery.

    PubMed

    Yamamoto, Hiroshi; Kaida, Sachiko; Yamaguchi, Tsuyoshi; Murata, Satoshi; Tani, Masaji; Tani, Tohru

    2016-03-01

    Conservative medical treatment for morbid obesity generally fails to sustain weight loss. On the other hand, surgical operations, so-called bariatric surgery, have evolved due to their long-term effects. The global increase in the overweight population and the introduction of laparoscopic surgery have resulted in the use of bariatric surgery spreading quickly worldwide in recent years. Recent clinical evidence suggests that bariatric surgery not only reduces body weight, but also improves secondary serious diseases, including type 2 diabetes mellitus, in so-called metabolic surgery. Moreover, several potential mechanisms mediating the improvement in glycemic control after bariatric/metabolic surgery have been proposed based on the animal and human studies. These mechanisms include changes in the levels of gastrointestinal hormones, bacterial flora, bile acids, intestinal gluconeogenesis and gastrointestinal motility as well as adipose tissue and inflammatory mediators after surgery. The mechanisms underlying improved glycemic control are expected to accelerate the promotion of both metabolic and bariatric surgery. This article describes the current status of bariatric surgery worldwide and in Japan, reviews the accumulated data for weight loss and diabetic improvements after surgery and discusses the potential mechanisms mediating improved glycemic control. PMID:25700844

  14. An exploration of the potential mechanisms and translational potential of five medicinal plants for applications in Alzheimer’s disease

    PubMed Central

    Shakir, Taner; Coulibaly, Ahmed Y; Kehoe, Patrick G

    2013-01-01

    Alzheimer’s disease (AD) is the most common type of dementia, and represents a vast worldwide socio-economic burden, and in the absence of a current cure, effective therapeutic strategies are still needed. Cholinergic and cerebral blood flow deficits, excessive levels of oxidative stress, neuroinflammation and glutamate excitatory mechanisms are all believed to contribute to the development and progression of the disease. Scoparia dulcis, Catharanthus roseus, Sesamum indicum, Erythrina senegalensis and Vigna unguiculata represent five plants that have been used as traditional medicines for the treatment of AD in certain cultures. Review of the scientific literature was conducted to explore the properties of these plants that might be beneficial and explain what would be perceived by many to be largely anecdotal evidence of their benefit. All plants were found to possess varying levels of anti-oxidant capability. Scoparia dulcis was also found to potentiate nerve growth factor-like effects upon cell lines. Catharanthus roseus appears to inhibit acetylcholinesterase with relatively high potency, while Sesamum indicum demonstrated the strongest antioxidant ability. Comparisons with currently used plant derived therapeutics illustrate how these plants may be likely to have some therapeutic benefits in AD. The evidence presented also highlights how appropriate dietary supplementation with some of these plants in various cultural settings might have effects analogous or complementary to the so-called protective Mediterranean diet. However, prior to embarking on making any formal recommendations to this end, further rigorous evaluation is needed to better elucidate the breadth and potential toxicological aspects of medicinal properties harboured by these plants. This would be vital to ensuring a more informed and safe delivery of preparations of these plants if they were to be considered as a form of dietary supplementation and where appropriate, how these might

  15. An exploration of the potential mechanisms and translational potential of five medicinal plants for applications in Alzheimer's disease.

    PubMed

    Shakir, Taner; Coulibaly, Ahmed Y; Kehoe, Patrick G

    2013-01-01

    Alzheimer's disease (AD) is the most common type of dementia, and represents a vast worldwide socio-economic burden, and in the absence of a current cure, effective therapeutic strategies are still needed. Cholinergic and cerebral blood flow deficits, excessive levels of oxidative stress, neuroinflammation and glutamate excitatory mechanisms are all believed to contribute to the development and progression of the disease. Scoparia dulcis, Catharanthus roseus, Sesamum indicum, Erythrina senegalensis and Vigna unguiculata represent five plants that have been used as traditional medicines for the treatment of AD in certain cultures. Review of the scientific literature was conducted to explore the properties of these plants that might be beneficial and explain what would be perceived by many to be largely anecdotal evidence of their benefit. All plants were found to possess varying levels of anti-oxidant capability. Scoparia dulcis was also found to potentiate nerve growth factor-like effects upon cell lines. Catharanthus roseus appears to inhibit acetylcholinesterase with relatively high potency, while Sesamum indicum demonstrated the strongest antioxidant ability. Comparisons with currently used plant derived therapeutics illustrate how these plants may be likely to have some therapeutic benefits in AD. The evidence presented also highlights how appropriate dietary supplementation with some of these plants in various cultural settings might have effects analogous or complementary to the so-called protective Mediterranean diet. However, prior to embarking on making any formal recommendations to this end, further rigorous evaluation is needed to better elucidate the breadth and potential toxicological aspects of medicinal properties harboured by these plants. This would be vital to ensuring a more informed and safe delivery of preparations of these plants if they were to be considered as a form of dietary supplementation and where appropriate, how these might interact

  16. Identifying Potential Mechanisms Enabling Acidophily in the Ammonia-Oxidizing Archaeon “Candidatus Nitrosotalea devanaterra”

    PubMed Central

    Sayavedra-Soto, Luis A.; Gallois, Nicolas; Schouten, Stefan; Stein, Lisa Y.; Prosser, James I.; Nicol, Graeme W.

    2016-01-01

    Ammonia oxidation is the first and rate-limiting step in nitrification and is dominated by two distinct groups of microorganisms in soil: ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). AOA are often more abundant than AOB and dominate activity in acid soils. The mechanism of ammonia oxidation under acidic conditions has been a long-standing paradox. While high rates of ammonia oxidation are frequently measured in acid soils, cultivated ammonia oxidizers grew only at near-neutral pH when grown in standard laboratory culture. Although a number of mechanisms have been demonstrated to enable neutrophilic AOB growth at low pH in the laboratory, these have not been demonstrated in soil, and the recent cultivation of the obligately acidophilic ammonia oxidizer “Candidatus Nitrosotalea devanaterra” provides a more parsimonious explanation for the observed high rates of activity. Analysis of the sequenced genome, transcriptional activity, and lipid content of “Ca. Nitrosotalea devanaterra” reveals that previously proposed mechanisms used by AOB for growth at low pH are not essential for archaeal ammonia oxidation in acidic environments. Instead, the genome indicates that “Ca. Nitrosotalea devanaterra” contains genes encoding both a predicted high-affinity substrate acquisition system and potential pH homeostasis mechanisms absent in neutrophilic AOA. Analysis of mRNA revealed that candidate genes encoding the proposed homeostasis mechanisms were all expressed during acidophilic growth, and lipid profiling by high-performance liquid chromatography–mass spectrometry (HPLC-MS) demonstrated that the membrane lipids of “Ca. Nitrosotalea devanaterra” were not dominated by crenarchaeol, as found in neutrophilic AOA. This study for the first time describes a genome of an obligately acidophilic ammonia oxidizer and identifies potential mechanisms enabling this unique phenotype for future biochemical characterization. PMID:26896134

  17. Identifying Potential Mechanisms Enabling Acidophily in the Ammonia-Oxidizing Archaeon "Candidatus Nitrosotalea devanaterra".

    PubMed

    Lehtovirta-Morley, Laura E; Sayavedra-Soto, Luis A; Gallois, Nicolas; Schouten, Stefan; Stein, Lisa Y; Prosser, James I; Nicol, Graeme W

    2016-05-01

    Ammonia oxidation is the first and rate-limiting step in nitrification and is dominated by two distinct groups of microorganisms in soil: ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). AOA are often more abundant than AOB and dominate activity in acid soils. The mechanism of ammonia oxidation under acidic conditions has been a long-standing paradox. While high rates of ammonia oxidation are frequently measured in acid soils, cultivated ammonia oxidizers grew only at near-neutral pH when grown in standard laboratory culture. Although a number of mechanisms have been demonstrated to enable neutrophilic AOB growth at low pH in the laboratory, these have not been demonstrated in soil, and the recent cultivation of the obligately acidophilic ammonia oxidizer "Candidatus Nitrosotalea devanaterra" provides a more parsimonious explanation for the observed high rates of activity. Analysis of the sequenced genome, transcriptional activity, and lipid content of "Ca Nitrosotalea devanaterra" reveals that previously proposed mechanisms used by AOB for growth at low pH are not essential for archaeal ammonia oxidation in acidic environments. Instead, the genome indicates that "Ca Nitrosotalea devanaterra" contains genes encoding both a predicted high-affinity substrate acquisition system and potential pH homeostasis mechanisms absent in neutrophilic AOA. Analysis of mRNA revealed that candidate genes encoding the proposed homeostasis mechanisms were all expressed during acidophilic growth, and lipid profiling by high-performance liquid chromatography-mass spectrometry (HPLC-MS) demonstrated that the membrane lipids of "Ca Nitrosotalea devanaterra" were not dominated by crenarchaeol, as found in neutrophilic AOA. This study for the first time describes a genome of an obligately acidophilic ammonia oxidizer and identifies potential mechanisms enabling this unique phenotype for future biochemical characterization. PMID:26896134

  18. A model of the mechanism of cooperativity and associativity of long-term potentiation in the hippocampus: a fundamental mechanism of associative memory and learning.

    PubMed

    Kitajima, T; Hara, K

    1991-01-01

    Long-Term Potentiation (LTP) has three properties: (1) input specificity, (2) cooperativity and (3) associativity. In a previous paper, we proposed an integrated model of the mechanisms of the induction and maintenance of LTP with input specificity. In this paper, a model of the mechanism of cooperative and associative LTP is described. According to computer simulations of the model, its mechanism is based on the spread of synaptic potentials. PMID:2049412

  19. Chemical compounds from anthropogenic environment and immune evasion mechanisms: potential interactions

    PubMed Central

    Kravchenko, Julia; Corsini, Emanuela; Williams, Marc A.; Decker, William; Manjili, Masoud H.; Otsuki, Takemi; Singh, Neetu; Al-Mulla, Faha; Al-Temaimi, Rabeah; Amedei, Amedeo; Colacci, Anna Maria; Vaccari, Monica; Mondello, Chiara; Scovassi, A. Ivana; Raju, Jayadev; Hamid, Roslida A.; Memeo, Lorenzo; Forte, Stefano; Roy, Rabindra; Woodrick, Jordan; Salem, Hosni K.; Ryan, Elizabeth P.; Brown, Dustin G.; Lowe, Leroy; Lyerly, H.Kim

    2015-01-01

    An increasing number of studies suggest an important role of host immunity as a barrier to tumor formation and progression. Complex mechanisms and multiple pathways are involved in evading innate and adaptive immune responses, with a broad spectrum of chemicals displaying the potential to adversely influence immunosurveillance. The evaluation of the cumulative effects of low-dose exposures from the occupational and natural environment, especially if multiple chemicals target the same gene(s) or pathway(s), is a challenge. We reviewed common environmental chemicals and discussed their potential effects on immunosurveillance. Our overarching objective was to review related signaling pathways influencing immune surveillance such as the pathways involving PI3K/Akt, chemokines, TGF-β, FAK, IGF-1, HIF-1α, IL-6, IL-1α, CTLA-4 and PD-1/PDL-1 could individually or collectively impact immunosurveillance. A number of chemicals that are common in the anthropogenic environment such as fungicides (maneb, fluoxastrobin and pyroclostrobin), herbicides (atrazine), insecticides (pyridaben and azamethiphos), the components of personal care products (triclosan and bisphenol A) and diethylhexylphthalate with pathways critical to tumor immunosurveillance. At this time, these chemicals are not recognized as human carcinogens; however, it is known that they these chemicalscan simultaneously persist in the environment and appear to have some potential interfere with the host immune response, therefore potentially contributing to promotion interacting with of immune evasion mechanisms, and promoting subsequent tumor growth and progression. PMID:26002081

  20. Spinal mechanisms underlying potentiation of hindpaw responses observed after transient hindpaw ischemia in mice

    PubMed Central

    Watanabe, Tatsunori; Sasaki, Mika; Komagata, Seiji; Tsukano, Hiroaki; Hishida, Ryuichi; Kohno, Tatsuro; Baba, Hiroshi; Shibuki, Katsuei

    2015-01-01

    Transient ischemia produces postischemic tingling sensation. Ischemia also produces nerve conduction block that may modulate spinal neural circuits. In the present study, reduced mechanical thresholds for hindpaw-withdrawal reflex were found in mice after transient hindpaw ischemia, which was produced by a high pressure applied around the hindpaw for 30 min. The reduction in the threshold was blocked by spinal application of LY354740, a specific agonist of group II metabotropic glutamate receptors. Neural activities in the spinal cord and the primary somatosensory cortex (S1) were investigated using activity-dependent changes in endogenous fluorescence derived from mitochondrial flavoproteins. Ischemic treatment induced potentiation of the ipsilateral spinal and contralateral S1 responses to hindpaw stimulation. Both types of potentiation were blocked by spinal application of LY354740. The contralateral S1 responses, abolished by lesioning the ipsilateral dorsal column, reappeared after ischemic treatment, indicating that postischemic tingling sensation reflects a sensory modality shift from tactile sensation to nociception in the spinal cord. Changes in neural responses were investigated during ischemic treatment in the contralateral spinal cord and the ipsilateral S1. Potentiation already appeared during ischemic treatment for 30 min. The present findings suggest that the postischemic potentiation shares spinal mechanisms, at least in part, with neuropathic pain. PMID:26165560

  1. Pulsed magnetic stimulation modifies amplitude of action potentials in vitro via ionic channels-dependent mechanism.

    PubMed

    Ahmed, Zaghloul; Wieraszko, Andrzej

    2015-07-01

    This paper investigates the influence of pulsed magnetic fields (PMFs) on amplitude of evoked, compound action potential (CAP) recorded from the segments of sciatic nerve in vitro. PMFs were applied for 30 min at frequency of 0.16 Hz and intensity of 15 mT. In confirmation of our previous reports, PMF exposure enhanced amplitude of CAPs. The effect persisted beyond PMF activation period. As expected, CAP amplitude was attenuated by antagonists of sodium channel, lidocaine, and tetrodotoxin. Depression of the potential by sodium channels antagonists was reversed by subsequent exposure to PMFs. The effect of elevated potassium concentration and veratridine on the action potential was modified by exposure to PMFs as well. Neither inhibitors of protein kinase C and protein kinase A, nor known free radicals scavengers had any effects on PMF action. Possible mechanisms of PMF action are discussed. PMID:25884360

  2. Newtonian mechanics of a many-particle assembly coupled to an external body potential

    NASA Technical Reports Server (NTRS)

    Salvino, R. E.

    1990-01-01

    The Newtonian mechanics of a many-particle system evolving in time under the influence of an external body potential, that is, an external potential that couples to the center of mass only, is examined. The lack of any other external fields allows the complete separation of the center-of-mass (or external-field-dependent) equations from the internal (or external-field-independent) dynamics. The complete solution of the center-of-mass motion then allows an analytical evaluation of the external body potential contributions to the thermophysical properties of the system. The phenomena of field-induced heating, Taylor-Aris hydrodynamic form for the diffusion tensor, and an analogous hydrodynamic form for the viscosity tensor are derived from microscopic principles. A brief and model-dependent description of equilibrium phenomena is also presented.

  3. Enhancement of mechanical properties, microstructure, and antimicrobial activities of zein films cross-linked using succinic anhydride, eugenol, and citric Acid.

    PubMed

    Khalil, Ashraf A; Deraz, Sahar F; Elrahman, Somia Abd; El-Fawal, Gomaa

    2015-08-18

    Zein constitutes about half of the endosperm proteins in corn. Recently, attempts have been made to utilize zein for food coatings and biodegradable materials, which require better physical properties, using chemical modification of zein. In this study, zein proteins were modified using citric acid, succinic anhydride, and eugenol as natural cross-linking agents in the wet state. The cross-linkers were added either separately or combined in increment concentrations (0.1, 0.2, 0.3, and 0.4%). The effects of those agents on the mechanical properties, microstructure, optical properties, infrared (IR) spectroscopy, and antibacterial activities of zein were investigated. The addition of cross-linking agents promoted changes in the arrangement of groups in zein film-forming particles. Regarding the film properties, incorporation of cross-linking agents into zein films prepared in ethanol resulted in two- to three-fold increases in tensile strength (TS) values. According to the Fourier-transform infrared (FTIR) spectra and Hunter parameters there were no remarkable changes in the structure and color of zein films. Transparency of zein films was decreased differentially according to the type and cross-linker concentration. The mechanical and optical properties of zein films were closely related to their microstructure. All cross-linked films showed remarkable antibacterial activities against Bacillus cereus ATCC 49064 and Salmonella enterica ATCC 25566. Food spoilage and pathogenic bacteria were affected in a film-dependent manner. Our experimental results show that even with partial cross-linking the mechanical properties and antipathogen activities of zein films were significantly improved, which would be useful for various industrial applications. PMID:25036665

  4. Transplant Tolerance Induction in Newborn Infants: Mechanisms, Advantages, and Potential Strategies

    PubMed Central

    Pan, Hua; Gazarian, Aram; Dubernard, Jean-Michel; Belot, Alexandre; Michallet, Marie-Cécile; Michallet, Mauricette

    2016-01-01

    Although several tolerance induction protocols have been successfully implemented in adult renal transplantation, no tolerance induction approach has, as yet, been defined for solid organ transplantations in young infants. Pediatric transplant recipients have a pressing demand for the elaboration of tolerance induction regimens. Indeed, since they display a longer survival time, they are exposed to a higher level of risks linked to long-term immunosuppression (IS) and to chronic rejection. Interestingly, central tolerance induction may be of great interest in newborns, because of their immunological immaturity and the important role of the thymus at this early stage in life. The present review aims to clarify mechanisms and strategies of tolerance induction in these immunologically premature recipients. We first introduce the discovery and mechanisms of neonatal tolerance in murine experimental models and subsequently analyze tolerance induction in human newborn infants. Hematopoietic mixed chimerism in neonates is also discussed based on in utero hematopoietic stem cell (HSC) transplant studies. Then, we review the recent advances in tolerance induction approaches in adults, including the infusion of HSCs associated with less toxic conditioning regimens, regulatory T cells/facilitating cells/mesenchymal stem cells transplantation, costimulatory blockade, and thymus manipulation. Finally, IS withdrawal in pediatric solid organ transplant is discussed. In conclusion, the establishment of transplant tolerance induction in infants is promising and deserves further investigations. Future studies could focus on the selection of patients, on less toxic conditioning regimens, and on biomarkers for IS minimization or withdrawal. PMID:27092138

  5. Transplant Tolerance Induction in Newborn Infants: Mechanisms, Advantages, and Potential Strategies.

    PubMed

    Pan, Hua; Gazarian, Aram; Dubernard, Jean-Michel; Belot, Alexandre; Michallet, Marie-Cécile; Michallet, Mauricette

    2016-01-01

    Although several tolerance induction protocols have been successfully implemented in adult renal transplantation, no tolerance induction approach has, as yet, been defined for solid organ transplantations in young infants. Pediatric transplant recipients have a pressing demand for the elaboration of tolerance induction regimens. Indeed, since they display a longer survival time, they are exposed to a higher level of risks linked to long-term immunosuppression (IS) and to chronic rejection. Interestingly, central tolerance induction may be of great interest in newborns, because of their immunological immaturity and the important role of the thymus at this early stage in life. The present review aims to clarify mechanisms and strategies of tolerance induction in these immunologically premature recipients. We first introduce the discovery and mechanisms of neonatal tolerance in murine experimental models and subsequently analyze tolerance induction in human newborn infants. Hematopoietic mixed chimerism in neonates is also discussed based on in utero hematopoietic stem cell (HSC) transplant studies. Then, we review the recent advances in tolerance induction approaches in adults, including the infusion of HSCs associated with less toxic conditioning regimens, regulatory T cells/facilitating cells/mesenchymal stem cells transplantation, costimulatory blockade, and thymus manipulation. Finally, IS withdrawal in pediatric solid organ transplant is discussed. In conclusion, the establishment of transplant tolerance induction in infants is promising and deserves further investigations. Future studies could focus on the selection of patients, on less toxic conditioning regimens, and on biomarkers for IS minimization or withdrawal. PMID:27092138

  6. Immature articular cartilage and subchondral bone covered by menisci are potentially susceptive to mechanical load

    PubMed Central

    2014-01-01

    Background The differences of mechanical and histological properties between cartilage covered by menisci and uncovered by menisci may contribute to the osteoarthritis after meniscectomy and these differences are not fully understood. The purpose of this study is to investigate potential differences in the mechanical and histological properties, and in particular the collagen architecture, of the superficial cartilage layer and subchondral bone between regions covered and uncovered by menisci using immature knee. Methods Osteochondral plugs were obtained from porcine tibial cartilage that was either covered or uncovered by menisci. Investigation of the thickness, mechanical properties, histology, and water content of the cartilage as well as micro-computed tomography analysis of the subchondral bone was performed to compare these regions. Collagen architecture was also assessed by using scanning electron microscopy. Results Compared to the cartilage uncovered by menisci, that covered by menisci was thinner and showed a higher deformity to compression loading and higher water content. In the superficial layer of cartilage in the uncovered regions, collagen fibers showed high density, whereas they showed low density in covered regions. Furthermore, subchondral bone architecture varied between the 2 regions, and showed low bone density in covered regions. Conclusions Cartilage covered by menisci differed from that uncovered in both its mechanical and histological properties, especially with regards to the density of the superficial collagen layer. These regional differences may be related to local mechanical environment in normal condition and indicate that cartilage covered by menisci is tightly guarded by menisci from extreme mechanical loading. Our results indicate that immature cartilage degeneration and subchondral microfracture may occur easily to extreme direct mechanical loading in covered region after meniscectomy. PMID:24669849

  7. Multiple mechanisms involved in the large-spectrum therapeutic potential of cannabidiol in psychiatric disorders.

    PubMed

    Campos, Alline Cristina; Moreira, Fabricio Araújo; Gomes, Felipe Villela; Del Bel, Elaine Aparecida; Guimarães, Francisco Silveira

    2012-12-01

    Cannabidiol (CBD) is a major phytocannabinoid present in the Cannabis sativa plant. It lacks the psychotomimetic and other psychotropic effects that the main plant compound Δ(9)-tetrahydrocannabinol (THC) being able, on the contrary, to antagonize these effects. This property, together with its safety profile, was an initial stimulus for the investigation of CBD pharmacological properties. It is now clear that CBD has therapeutic potential over a wide range of non-psychiatric and psychiatric disorders such as anxiety, depression and psychosis. Although the pharmacological effects of CBD in different biological systems have been extensively investigated by in vitro studies, the mechanisms responsible for its therapeutic potential are still not clear. Here, we review recent in vivo studies indicating that these mechanisms are not unitary but rather depend on the behavioural response being measured. Acute anxiolytic and antidepressant-like effects seem to rely mainly on facilitation of 5-HT1A-mediated neurotransmission in key brain areas related to defensive responses, including the dorsal periaqueductal grey, bed nucleus of the stria terminalis and medial prefrontal cortex. Other effects, such as anti-compulsive, increased extinction and impaired reconsolidation of aversive memories, and facilitation of adult hippocampal neurogenesis could depend on potentiation of anandamide-mediated neurotransmission. Finally, activation of TRPV1 channels may help us to explain the antipsychotic effect and the bell-shaped dose-response curves commonly observed with CBD. Considering its safety profile and wide range of therapeutic potential, however, further studies are needed to investigate the involvement of other possible mechanisms (e.g. inhibition of adenosine uptake, inverse agonism at CB2 receptor, CB1 receptor antagonism, GPR55 antagonism, PPARγ receptors agonism, intracellular (Ca(2+)) increase, etc.), on CBD behavioural effects. PMID:23108553

  8. Multiple mechanisms involved in the large-spectrum therapeutic potential of cannabidiol in psychiatric disorders

    PubMed Central

    Campos, Alline Cristina; Moreira, Fabricio Araújo; Gomes, Felipe Villela; Del Bel, Elaine Aparecida; Guimarães, Francisco Silveira

    2012-01-01

    Cannabidiol (CBD) is a major phytocannabinoid present in the Cannabis sativa plant. It lacks the psychotomimetic and other psychotropic effects that the main plant compound Δ9-tetrahydrocannabinol (THC) being able, on the contrary, to antagonize these effects. This property, together with its safety profile, was an initial stimulus for the investigation of CBD pharmacological properties. It is now clear that CBD has therapeutic potential over a wide range of non-psychiatric and psychiatric disorders such as anxiety, depression and psychosis. Although the pharmacological effects of CBD in different biological systems have been extensively investigated by in vitro studies, the mechanisms responsible for its therapeutic potential are still not clear. Here, we review recent in vivo studies indicating that these mechanisms are not unitary but rather depend on the behavioural response being measured. Acute anxiolytic and antidepressant-like effects seem to rely mainly on facilitation of 5-HT1A-mediated neurotransmission in key brain areas related to defensive responses, including the dorsal periaqueductal grey, bed nucleus of the stria terminalis and medial prefrontal cortex. Other effects, such as anti-compulsive, increased extinction and impaired reconsolidation of aversive memories, and facilitation of adult hippocampal neurogenesis could depend on potentiation of anandamide-mediated neurotransmission. Finally, activation of TRPV1 channels may help us to explain the antipsychotic effect and the bell-shaped dose-response curves commonly observed with CBD. Considering its safety profile and wide range of therapeutic potential, however, further studies are needed to investigate the involvement of other possible mechanisms (e.g. inhibition of adenosine uptake, inverse agonism at CB2 receptor, CB1 receptor antagonism, GPR55 antagonism, PPARγ receptors agonism, intracellular (Ca2+) increase, etc.), on CBD behavioural effects. PMID:23108553

  9. The effect of cross-linking on the microstructure, mechanical properties and biocompatibility of electrospun polycaprolactone-gelatin/PLGA-gelatin/PLGA-chitosan hybrid composite

    NASA Astrophysics Data System (ADS)

    Nguyen, Thi-Hiep; Lee, Byong-Taek

    2012-06-01

    In this study, multilayered scaffolds composed of polycaprolactone (PCL)-gelatin/poly(lactic-co-glycolic acid) (PLGA)-gelatin/PLGA-chitosan artificial blood vessels were fabricated using a double-ejection electrospinning system. The mixed fibers from individual materials were observed by scanning electron microscopy. The effects of the cross-linking process on the microstructure, mechanical properties and biocompatibility of the fibers were examined. The tensile stress and liquid strength of the cross-linked artificial blood vessels were 2.3 MPa and 340 mmHg, respectively, and were significantly higher than for the non-cross-linked vessel (2.0 MPa and 120 mmHg). The biocompatibility of the cross-linked artificial blood vessel scaffold was examined using the MTT assay and by evaluating cell attachment and cell proliferation. The cross-linked PCL-gelatin/PLGA-gelatin/PLGA-chitosan artificial blood vessel scaffold displayed excellent flexibility, was able to withstand high pressures and promoted cell growth; thus, this novel material holds great promise for eventual use in artificial blood vessels.

  10. Amide Link Scission in the Polyamide Active Layers of Thin-Film Composite Membranes upon Exposure to Free Chlorine: Kinetics and Mechanisms.

    PubMed

    Powell, Joshua; Luh, Jeanne; Coronell, Orlando

    2015-10-20

    The volume-averaged amide link scission in the aromatic polyamide active layer of a reverse osmosis membrane upon exposure to free chlorine was quantified at a variety of free chlorine exposure times, concentrations, and pH and rinsing conditions. The results showed that (i) hydroxyl ions are needed for scission to occur, (ii) hydroxide-induced amide link scission is a strong function of exposure to hypochlorous acid, (iii) the ratio between amide links broken and chlorine atoms taken up increased with the chlorination pH and reached a maximum of ∼25%, (iv) polyamide disintegration occurs when high free chlorine concentrations, alkaline conditions, and high exposure times are combined, (v) amide link scission promotes further chlorine uptake, and (vi) scission at the membrane surface is unrepresentative of volume-averaged scission in the active layer. Our observations are consistent with previously proposed mechanisms describing amide link scission as a result of the hydrolysis of the N-chlorinated amidic N-C bond due to nucleophilic attack by hydroxyl ions. This study increases the understanding of the physicochemical changes that could occur for membranes in treatment plants using chlorine as an upstream disinfectant and the extent and rate at which those changes would occur. PMID:26394532

  11. Potential Role of Epigenetic Mechanisms in the Regulation of Drug Metabolism and Transport

    PubMed Central

    Ingelman-Sundberg, Magnus; Zhong, Xiao-Bo; Hankinson, Oliver; Beedanagari, Sudheer; Yu, Ai-Ming; Peng, Lai

    2013-01-01

    This is a report of a symposium on the potential role of epigenetic mechanisms in the control of drug disposition sponsored by the American Society for Pharmacology and Experimental Therapeutics and held at the Experimental Biology 2013 meeting in Boston, MA, April 21, 2013. Epigenetics is a rapidly evolving area, and recent studies have revealed that expression of drug-metabolizing enzymes and transporters is regulated by epigenetic factors, including histone modification, DNA methylation, and noncoding RNAs. The symposium speakers provided an overview of genetic and epigenetic mechanisms underlying variable drug metabolism and drug response, as well as the implications for personalized medicine. Considerable insight into the epigenetic mechanisms in differential regulation of the dioxin-inducible drug and carcinogen-metabolizing enzymes CYP1A1 and 1B1 was provided. The role of noncoding microRNAs in the control of drug metabolism and disposition through targeting of cytochrome P450 (P450) enzymes and ATP-binding cassette membrane transporters was discussed. In addition, potential effects of xenobiotics on chromatin interactions and epigenomics, as well as the possible role of long noncoding RNAs in regulation of P450s during liver maturation were presented. PMID:23918665

  12. A novel role for integrin-linked kinase in periodic mechanical stress-mediated ERK1/2 mitogenic signaling in rat chondrocytes.

    PubMed

    Song, Huanghe; Liang, Wenwei; Xu, Shun; Li, Zeng; Chen, Zhefeng; Cui, Weiding; Zhou, Jinchun; Wang, Qing; Liu, Feng; Fan, Weimin

    2016-07-01

    In recent years, a variety of studies have been performed to investigate the cellular responses of periodic mechanical stress on chondrocytes. Integrin β1-mediated ERK1/2 activation was proven to be indispensable in periodic mechanical stress-induced chondrocyte proliferation and matrix synthesis. However, other signal proteins responsible for the mitogenesis of chondrocytes under periodic mechanical stress remain incompletely understood. In the current investigation, we probed the roles of integrin-linked kinase (ILK) signaling in periodic mechanical stress-induced chondrocyte proliferation and matrix synthesis. We found that upon periodic mechanical stress induction, ILK activity increased significantly. Depletion of ILK with targeted shRNA strongly inhibited periodic mechanical stress-induced chondrocyte proliferation and matrix synthesis. In addition, pretreatment with a blocking antibody against integrin β1 resulted in a remarkable decrease in ILK activity in cells exposed to periodic mechanical stress. Furthermore, inhibition of ILK with its target shRNA significantly suppressed ERK1/2 activation in relation to periodic mechanical stress. Based on the above results, we identified ILK as a crucial regulator involved in the integrin β1-ERK1/2 signal cascade responsible for periodic mechanical stress-induced chondrocyte proliferation and matrix synthesis. PMID:27154044

  13. Supersymmetric quantum mechanics: Engineered hierarchies of integrable potentials and related orthogonal polynomials

    SciTech Connect

    Balondo Iyela, Daddy; Govaerts, Jan; Hounkonnou, M. Norbert

    2013-09-15

    Within the context of supersymmetric quantum mechanics and its related hierarchies of integrable quantum Hamiltonians and potentials, a general programme is outlined and applied to its first two simplest illustrations. Going beyond the usual restriction of shape invariance for intertwined potentials, it is suggested to require a similar relation for Hamiltonians in the hierarchy separated by an arbitrary number of levels, N. By requiring further that these two Hamiltonians be in fact identical up to an overall shift in energy, a periodic structure is installed in the hierarchy which should allow for its resolution. Specific classes of orthogonal polynomials characteristic of such periodic hierarchies are thereby generated, while the methods of supersymmetric quantum mechanics then lead to generalised Rodrigues formulae and recursion relations for such polynomials. The approach also offers the practical prospect of quantum modelling through the engineering of quantum potentials from experimental energy spectra. In this paper, these ideas are presented and solved explicitly for the cases N= 1 and N= 2. The latter case is related to the generalised Laguerre polynomials, for which indeed new results are thereby obtained. In the context of dressing chains and deformed polynomial Heisenberg algebras, some partial results for N⩾ 3 also exist in the literature, which should be relevant to a complete study of the N⩾ 3 general periodic hierarchies.

  14. Proton cellular influx as a probable mechanism of variation potential influence on photosynthesis in pea.

    PubMed

    Sukhov, Vladimir; Sherstneva, Oksana; Surova, Lyubov; Katicheva, Lyubov; Vodeneev, Vladimir

    2014-11-01

    Electrical signals (action potential and variation potential, VP) caused by environmental stimuli are known to induce various physiological responses in plants, including changes in photosynthesis; however, their functional mechanisms remain unclear. In this study, the influence of VP on photosynthesis in pea (Pisum sativum L.) was investigated and the proton participation in this process analysed. VP, induced by local heating, inactivated photosynthesis and activated respiration, with the initiation of the photosynthetic response connected with inactivation of the photosynthetic dark stage; however, direct VP influence on the light stage was also probable. VP generation was accompanied with pH increases in apoplasts (0.17-0.30 pH unit) and decreases in cytoplasm (0.18-0.60 pH unit), which probably reflected H(+) -ATPase inactivation and H(+) influx during this electrical event. Imitation of H(+) influx using the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) induced a photosynthetic response that was similar with a VP-induced response. Experiments on chloroplast suspensions showed that decreased external pH also induced an analogous response and that its magnitude depended on the magnitude of pH change. Thus, the present results showed that proton cellular influx was the probable mechanism of VP's influence on photosynthesis in pea. Potential means of action for this influence are discussed. PMID:24635649

  15. Coagulation-flocculation mechanisms in wastewater treatment plants through zeta potential measurements.

    PubMed

    López-Maldonado, E A; Oropeza-Guzman, M T; Jurado-Baizaval, J L; Ochoa-Terán, A

    2014-08-30

    Based on the polyelectrolyte-contaminant physical and chemical interactions at the molecular level, this article analyzed and discussed the coagulation-flocculation and chemical precipitation processes in order to improve their efficiency. Bench experiments indicate that water pH, polyelectrolyte (PE) dosing strategy and cationic polyelectrolyte addition are key parameters for the stability of metal-PE complexes. The coagulation-flocculation mechanism is proposed based on zeta potential (ζ) measurement as the criteria to define the electrostatic interaction between pollutants and coagulant-flocculant agents. Polyelectrolyte and wastewater dispersions are exposed to an electrophoretic effect to determine ζ. Finally, zeta potential values are compared at pH 9, suggesting the optimum coagulant dose at 162mg/L polydadmac and 67mg/L of flocculant, since a complete removal of TSS and turbidity is achieved. Based on the concentration of heavy metals (0.931mg/L Sn, 0.7mg/L Fe and 0.63mg/L Pb), treated water met the Mexican maximum permissible limits. In addition, the treated water has 45mg O2/L chemical oxygen demand (COD) and 45mg C/L total organic carbon (TOC). The coagulation-flocculation mechanism is proposed taking into account both: zeta potential (ζ)-pH measurement and chemical affinity, as the criteria to define the electrostatic and chemical interaction between pollutants and polyelectrolytes. PMID:25036994

  16. Pentoxifylline decreases oxidized lipid products in nonalcoholic steatohepatitis: New evidence on the potential therapeutic mechanism

    PubMed Central

    Zein, Claudia O.; Lopez, Rocio; Fu, Xiaoming; Kirwan, John P.; Yerian, Lisa M.; McCullough, Arthur J.; Hazen, Stanley L.; Feldstein, Ariel E.

    2012-01-01

    Background Pentoxifylline (PTX) improved histological features of nonalcoholic steatohepatitis (NASH) in a recent randomized placebo-controlled trial. However, the underlying mechanism responsible for the beneficial effects of PTX in NASH remains unidentified. A key role of lipid oxidation in the pathogenesis and progression of NASH has been established. PTX is known to decrease free-radical mediated oxidative stress and inhibit lipid oxidation. The primary aim of this study was to evaluate the effects of PTX on levels of lipid oxidation products in patients with NASH. Methods Levels of multiple structurally specific oxidized fatty acids including hydroxy-octadecadenoic acids (HODEs), oxo-octadecadenoic acids (oxoODEs), and hydroxy-eicosatetraenoic acids (HETEs) were quantified by mass spectrometry in plasma obtained at baseline and at study completion in patients who completed 1 year of therapy with PTX or placebo in a randomized controlled trial. Results Therapy with PTX resulted in significant decreases on 9-HODE and 13-oxoODE, oxidized lipid products of linoleic acid (LA) linked to histological severity in NAFLD. Similarly, PTX therapy was associated with significant decreases in 8-HETE, 9-HETE, and 11-HETE compared to placebo. Statistically significant correlations were demonstrated between the decrease in HODEs and oxoODEs and improved histological scores of fibrosis; and between the decrease in HETEs and improved lobular inflammation. Conclusion Therapy with PTX compared to placebo was associated with a significant reduction of oxidized fatty acids. This novel evidence supports that the beneficial effects of PTX in patients with NASH are likely partly mediated through decreasing lipid oxidation, largely free-radical mediated lipid oxidation. Additionally, this is the first report on the link between decreased oxidized lipid products and improved histological disease in the setting of a therapeutic trial in NASH. PMID:22505276

  17. Theoretical studies on models of lysine-arginine cross-links derived from α-oxoaldehydes: a new mechanism for glucosepane formation.

    PubMed

    Nasiri, Rasoul; Zahedi, Mansour; Jamet, Hélène; Moosavi-Movahedi, Ali Akbar

    2012-04-01

    Availability and high reactivity of α-oxoaldehydes have been approved by experimental techniques not only in vivo systems but also in foodstuffs. In this article we re-examine the mechanism of glucosepane formation by using computational model chemistry. Density functional theory has been applied to propose a new mechanism for glucosepane formation through reaction of α-oxoaldehydes with methyl amine (MA) and methyl guanidine (MGU) models of lysine and arginine residues respectively. This non enzymatic process can be described in three main steps: (1) Schiff base formation from methyl amine, methyl glyoxal (MGO) (2) addition of methyl guanidine and (3) addition of glyceraldehyde. We show that this process is thermodynamically possible and presents a rate-determining step with a reasonable free energy barrier equal to 37.8 kcal mol(-1) in water solvent. Comparisons were done with the mechanism formation of GODIC (glyoxal-derived imidazolium cross-link) and MODIC (methyl glyoxal-derived imidazolium cross-link), two other important cross-links in vivo. PMID:21811778

  18. Potential Link between the Sphingosine-1-Phosphate (S1P) System and Defective Alveolar Macrophage Phagocytic Function in Chronic Obstructive Pulmonary Disease (COPD)

    PubMed Central

    Barnawi, Jameel; Tran, Hai; Jersmann, Hubertus; Pitson, Stuart; Roscioli, Eugene; Hodge, Greg; Meech, Robyn; Haberberger, Rainer; Hodge, Sandra

    2015-01-01

    patient-derived macrophages. Antagonising SIPR5 significantly improved phagocytosis. Conclusion Our results suggest a potential link between the S1P signalling system and defective macrophage phagocytic function in COPD and advise therapeutic targets. PMID:26485657

  19. POTENTIAL EFFECTS OF A FOREST MANAGEMENT PLAN ON BACHMAN'S SPARROWS (AIMOPHILA AESTIVALIS): LINKING A SPATIALLY EXPLICIT MODEL WITH GIS

    EPA Science Inventory

    By combining a spatially explicit, individual-based population simulation model with a geographic information system, this study simulated the potential effects of a U.S. Forest management plan on the population dynamics of Bachman's Sparrow at the Savannah River Site, South Caro...

  20. Potential link between excess added sugar intake and ectopic fat: a systematic review of randomized controlled trials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Context: The effect of added sugar intake on ectopic fat accumulation is a subject of debate. Objective: A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to examine the potential effect of added sugar intake on ectopic fat depots. Data Sources: MEDLINE, CA...

  1. Linking Climate Suitability, Spread Rates and Host-Impact When Estimating the Potential Costs of Invasive Pests

    PubMed Central

    Kriticos, Darren J.; Leriche, Agathe; Palmer, David J.; Cook, David C.; Brockerhoff, Eckehard G.; Stephens, Andréa E. A.; Watt, Michael S.

    2013-01-01

    Biosecurity agencies need robust bioeconomic tools to help inform policy and allocate scarce management resources. They need to estimate the potential for each invasive alien species (IAS) to create negative impacts, so that relative and absolute comparisons can be made. Using pine processionary moth (Thaumetopoea pityocampa sensu lato) as an example, these needs were met by combining species niche modelling, dispersal modelling, host impact and economic modelling. Within its native range (the Mediterranean Basin and adjacent areas), T. pityocampa causes significant defoliation of pines and serious urticating injuries to humans. Such severe impacts overseas have fuelled concerns about its potential impacts, should it be introduced to New Zealand. A stochastic bioeconomic model was used to estimate the impact of PPM invasion in terms of pine production value lost due to a hypothetical invasion of New Zealand by T. pityocampa. The bioeconomic model combines a semi-mechanistic niche model to develop a climate-related damage function, a climate-related forest growth model, and a stochastic spread model to estimate the present value (PV) of an invasion. Simulated invasions indicate that Thaumetopoea pityocampa could reduce New Zealand’s merchantable and total pine stem volume production by 30%, reducing forest production by between NZ$1,550 M to NZ$2,560 M if left untreated. Where T. pityocampa is controlled using aerial application of an insecticide, projected losses in PV were reduced, but still significant (NZ$30 M to NZ$2,210 M). The PV estimates were more sensitive to the efficacy of the spray program than the potential rate of spread of the moth. Our novel bioeconomic method provides a refined means of estimating potential impacts of invasive alien species, taking into account climatic effects on asset values, the potential for pest impacts, and pest spread rates. PMID:23405097

  2. Linking climate suitability, spread rates and host-impact when estimating the potential costs of invasive pests.

    PubMed

    Kriticos, Darren J; Leriche, Agathe; Palmer, David J; Cook, David C; Brockerhoff, Eckehard G; Stephens, Andréa E A; Watt, Michael S

    2013-01-01

    Biosecurity agencies need robust bioeconomic tools to help inform policy and allocate scarce management resources. They need to estimate the potential for each invasive alien species (IAS) to create negative impacts, so that relative and absolute comparisons can be made. Using pine processionary moth (Thaumetopoea pityocampa sensu lato) as an example, these needs were met by combining species niche modelling, dispersal modelling, host impact and economic modelling. Within its native range (the Mediterranean Basin and adjacent areas), T. pityocampa causes significant defoliation of pines and serious urticating injuries to humans. Such severe impacts overseas have fuelled concerns about its potential impacts, should it be introduced to New Zealand. A stochastic bioeconomic model was used to estimate the impact of PPM invasion in terms of pine production value lost due to a hypothetical invasion of New Zealand by T. pityocampa. The bioeconomic model combines a semi-mechanistic niche model to develop a climate-related damage function, a climate-related forest growth model, and a stochastic spread model to estimate the present value (PV) of an invasion. Simulated invasions indicate that Thaumetopoea pityocampa could reduce New Zealand's merchantable and total pine stem volume production by 30%, reducing forest production by between NZ$1,550 M to NZ$2,560 M if left untreated. Where T. pityocampa is controlled using aerial application of an insecticide, projected losses in PV were reduced, but still significant (NZ$30 M to NZ$2,210 M). The PV estimates were more sensitive to the efficacy of the spray program than the potential rate of spread of the moth. Our novel bioeconomic method provides a refined means of estimating potential impacts of invasive alien species, taking into account climatic effects on asset values, the potential for pest impacts, and pest spread rates. PMID:23405097

  3. Meditation as a Therapeutic Intervention for Adults at Risk for Alzheimer’s Disease – Potential Benefits and Underlying Mechanisms

    PubMed Central

    Innes, Kim E.; Selfe, Terry Kit

    2014-01-01

    Alzheimer’s disease (AD) is a chronic, progressive, brain disorder that affects at least 5.3 million Americans at an estimated cost of $148 billion, figures that are expected to rise steeply in coming years. Despite decades of research, there is still no cure for AD, and effective therapies for preventing or slowing progression of cognitive decline in at-risk populations remain elusive. Although the etiology of AD remains uncertain, chronic stress, sleep deficits, and mood disturbance, conditions common in those with cognitive impairment, have been prospectively linked to the development and progression of both chronic illness and memory loss and are significant predictors of AD. Therapies such as meditation that specifically target these risk factors may thus hold promise for slowing and possibly preventing cognitive decline in those at risk. In this study, we briefly review the existing evidence regarding the potential utility of meditation as a therapeutic intervention for those with and at risk for AD, discuss possible mechanisms underlying the observed benefits of meditation, and outline directions for future research. PMID:24795656

  4. Serotonin Receptor 2B Mediates Mechanical Hyperalgesia by Regulating Transient Receptor Potential Vanilloid 1.

    PubMed

    Su, Yeu-Shiuan; Chiu, Yuan-Yi; Lin, Shih-Yuan; Chen, Chih-Cheng; Sun, Wei-Hsin

    2016-05-01

    Serotonin [5-hydroxytryptamine (5-HT)], an inflammatory mediator, contributes to inflammatory pain. The presence of multiple 5-HT subtype receptors on peripheral and central nociceptors complicates the role of 5-HT in pain. Previously, we found that 5-HT2B/2C antagonist could block 5-HT-induced mechanical hyperalgesia. However, the types of neurons or circuits underlying this effect remained unsolved. Here, we demonstrate that the Gq/11-phospholipase Cβ-protein kinase Cε (PKCε) pathway mediated by 5-HT2B is involved in 5-HT-induced mechanical hyperalgesia in mice. Administration of a transient receptor potential vanilloid 1 (TRPV1) antagonist inhibited the 5-HT-induced mechanical hyperalgesia. 5-HT injection enhanced 5-HT- and capsaicin-evoked calcium signals specifically in isolectin B4 (IB4)-negative neurons; signals were inhibited by a 5-HT2B/2C antagonist and PKCε blocker. Thus, 5-HT2B mediates 5-HT-induced mechanical hyperalgesia by regulating TRPV1 function. PMID:26635025

  5. The Cardioprotective Effects of Hydrogen Sulfide in Heart Diseases: From Molecular Mechanisms to Therapeutic Potential

    PubMed Central

    Shen, Yaqi; Shen, Zhuqing; Luo, Shanshan; Guo, Wei; Zhu, Yi Zhun

    2015-01-01

    Hydrogen sulfide (H2S) is now recognized as a third gaseous mediator along with nitric oxide (NO) and carbon monoxide (CO), though it was originally considered as a malodorous and toxic gas. H2S is produced endogenously from cysteine by three enzymes in mammalian tissues. An increasing body of evidence suggests the involvement of H2S in different physiological and pathological processes. Recent studies have shown that H2S has the potential to protect the heart against myocardial infarction, arrhythmia, hypertrophy, fibrosis, ischemia-reperfusion injury, and heart failure. Some mechanisms, such as antioxidative action, preservation of mitochondrial function, reduction of apoptosis, anti-inflammatory responses, angiogenic actions, regulation of ion channel, and interaction with NO, could be responsible for the cardioprotective effect of H2S. Although several mechanisms have been identified, there is a need for further research to identify the specific molecular mechanism of cardioprotection in different cardiac diseases. Therefore, insight into the molecular mechanisms underlying H2S action in the heart may promote the understanding of pathophysiology of cardiac diseases and lead to new therapeutic targets based on modulation of H2S production. PMID:26078822

  6. The absence of a dense potential core in supercritical injection: A thermal break-up mechanism

    NASA Astrophysics Data System (ADS)

    Banuti, Daniel T.; Hannemann, Klaus

    2016-03-01

    Certain experiments in quasi-isobaric supercritical injection remain unexplained by the current state of theory: Without developing a constant value potential core as expected from the mechanical view of break-up, density is observed to drop immediately upon entering the chamber. Furthermore, this phenomenon has never been captured in computational fluid dynamics (CFD) despite having become a de facto standard case for real fluid CFD validation. In this paper, we present strong evidence for a thermal jet disintegration mechanism (in addition to classical mechanical break-up) which resolves both the theoretical and the computational discrepancies. A new interpretation of supercritical jet disintegration is introduced, based on pseudo-boiling, a nonlinear supercritical transition from gas-like to liquid-like states. We show that thermal disintegration may dominate classical mechanical break-up when heat transfer takes place in the injector and when the fluid state is sufficiently close to the pseudo-boiling point. A procedure which allows to capture subsided cores with standard CFD is provided and demonstrated.

  7. Mechanisms of radiation interaction with DNA: Potential implications for radiation protection

    SciTech Connect

    Sinclair, W.K.; Fry, R.J.M.

    1987-01-01

    An overview of presentations and discussions which took place at the US Department of Energy/Commission of European Communities (DOE/CEC) workshop on ''Mechanisms of Radiation Interaction with DNA: Potential Implications for Radiation Protection,'' held at San Diego, California, January 21-22, 1987, is provided. The Department has traditionally supported fundamental research on interactions of ionizing radiation with different biological systems and at all levels of biological organization. The aim of this workshop was to review the base of knowledge in the area of mechanisms of radiation action at the DNA level, and to explore ways in which this information can be applied to the development of scientifically sound concepts and procedures for use in the field of radiation protection.

  8. Potential Anti-Cancer Activities and Mechanisms of Costunolide and Dehydrocostuslactone

    PubMed Central

    Lin, Xuejing; Peng, Zhangxiao; Su, Changqing

    2015-01-01

    Costunolide (CE) and dehydrocostuslactone (DE) are derived from many species of medicinal plants, such as Saussurea lappa Decne and Laurus nobilis L. They have been reported for their wide spectrum of biological effects, including anti-inflammatory, anticancer, antiviral, antimicrobial, antifungal, antioxidant, antidiabetic, antiulcer, and anthelmintic activities. In recent years, they have caused extensive interest in researchers due to their potential anti-cancer activities for various types of cancer, and their anti-cancer mechanisms, including causing cell cycle arrest, inducing apoptosis and differentiation, promoting the aggregation of microtubule protein, inhibiting the activity of telomerase, inhibiting metastasis and invasion, reversing multidrug resistance, restraining angiogenesis has been studied. This review will summarize anti-cancer activities and associated molecular mechanisms of these two compounds for the purpose of promoting their research and application. PMID:25984608

  9. Mechanism of Action and Clinical Potential of Fingolimod for the Treatment of Stroke

    PubMed Central

    Li, Wentao; Xu, Haoliang; Testai, Fernando D.

    2016-01-01

    Fingolimod (FTY720) is an orally bio-available immunomodulatory drug currently approved by the FDA for the treatment of multiple sclerosis. Currently, there is a significant interest in the potential benefits of FTY720 on stroke outcomes. FTY720 and the sphingolipid signaling pathway it modulates has a ubiquitous presence in the central nervous system and both rodent models and pilot clinical trials seem to indicate that the drug may improve overall functional recovery in different stroke subtypes. Although the precise mechanisms behind these beneficial effects are yet unclear, there is evidence that FTY720 has a role in regulating cerebrovascular responses, blood–brain barrier permeability, and cell survival in the event of cerebrovascular insult. In this article, we critically review the data obtained from the latest laboratory findings and clinical trials involving both ischemic and hemorrhagic stroke, and attempt to form a cohesive picture of FTY720’s mechanisms of action in stroke. PMID:27617002

  10. Autophagy in Alcohol-Induced Multiorgan Injury: Mechanisms and Potential Therapeutic Targets

    PubMed Central

    Wang, Shaogui; Ni, Hong-Min; Huang, Heqing

    2014-01-01

    Autophagy is a genetically programmed, evolutionarily conserved intracellular degradation pathway involved in the trafficking of long-lived proteins and cellular organelles to the lysosome for degradation to maintain cellular homeostasis. Alcohol consumption leads to injury in various tissues and organs including liver, pancreas, heart, brain, and muscle. Emerging evidence suggests that autophagy is involved in alcohol-induced tissue injury. Autophagy serves as a cellular protective mechanism against alcohol-induced tissue injury in most tissues but could be detrimental in heart and muscle. This review summarizes current knowledge about the role of autophagy in alcohol-induced injury in different tissues/organs and its potential molecular mechanisms as well as possible therapeutic targets based on modulation of autophagy. PMID:25140315

  11. Mechanism of Action and Clinical Potential of Fingolimod for the Treatment of Stroke.

    PubMed

    Li, Wentao; Xu, Haoliang; Testai, Fernando D

    2016-01-01

    Fingolimod (FTY720) is an orally bio-available immunomodulatory drug currently approved by the FDA for the treatment of multiple sclerosis. Currently, there is a significant interest in the potential benefits of FTY720 on stroke outcomes. FTY720 and the sphingolipid signaling pathway it modulates has a ubiquitous presence in the central nervous system and both rodent models and pilot clinical trials seem to indicate that the drug may improve overall functional recovery in different stroke subtypes. Although the precise mechanisms behind these beneficial effects are yet unclear, there is evidence that FTY720 has a role in regulating cerebrovascular responses, blood-brain barrier permeability, and cell survival in the event of cerebrovascular insult. In this article, we critically review the data obtained from the latest laboratory findings and clinical trials involving both ischemic and hemorrhagic stroke, and attempt to form a cohesive picture of FTY720's mechanisms of action in stroke. PMID:27617002

  12. Cytotoxic T Cells Use Mechanical Force to Potentiate Target Cell Killing.

    PubMed

    Basu, Roshni; Whitlock, Benjamin M; Husson, Julien; Le Floc'h, Audrey; Jin, Weiyang; Oyler-Yaniv, Alon; Dotiwala, Farokh; Giannone, Gregory; Hivroz, Claire; Biais, Nicolas; Lieberman, Judy; Kam, Lance C; Huse, Morgan

    2016-03-24

    The immunological synapse formed between a cytotoxic T lymphocyte (CTL) and an infected or transformed target cell is a physically active structure capable of exerting mechanical force. Here, we investigated whether synaptic forces promote the destruction of target cells. CTLs kill by secreting toxic proteases and the pore forming protein perforin into the synapse. Biophysical experiments revealed a striking correlation between the magnitude of force exertion across the synapse and the speed of perforin pore formation on the target cell, implying that force potentiates cytotoxicity by enhancing perforin activity. Consistent with this interpretation, we found that increasing target cell tension augmented pore formation by perforin and killing by CTLs. Our data also indicate that CTLs coordinate perforin release and force exertion in space and time. These results reveal an unappreciated physical dimension to lymphocyte function and demonstrate that cells use mechanical forces to control the activity of outgoing chemical signals. PMID:26924577

  13. Expression mechanisms underlying long-term potentiation: a postsynaptic view, 10 years on

    PubMed Central

    Granger, Adam J.; Nicoll, Roger A.

    2014-01-01

    This review focuses on the research that has occurred over the past decade which has solidified a postsynaptic expression mechanism for long-term potentiation (LTP). However, experiments that have suggested a presynaptic component are also summarized. It is argued that the pairing of glutamate uncaging onto single spines with postsynaptic depolarization provides the final and most elegant demonstration of a postsynaptic expression mechanism for NMDA receptor-dependent LTP. The fact that the magnitude of this LTP is similar to that evoked by pairing synaptic stimulation and depolarization leaves little room for a substantial presynaptic component. Finally, recent data also require a revision in our thinking about the way AMPA receptors (AMPARs) are recruited to the postsynaptic density during LTP. This recruitment is independent of subunit type, but does require an adequate reserve pool of extrasynaptic receptors. PMID:24298139

  14. Dimethylacetamide-induced Hepatic Injury in Vitro: Mechanism and Potential Preventive Strategy.

    PubMed

    Liu, Xin; Gong, Wei; Xu, Yan Qiong; Zhu, Bao Li

    2016-02-01

    N,N-Dimethylacetamide (DMAc) is a widely used organic solvent in modern chemical industry with low to moderate hepatotoxicity to occupational health of employees. But so far, there are fewer and less conclusive data concerning its pathogenic mechanism in detail. In current study, the toxicity of DMAc was firstly investigated on human normal hepatocytes (LO-2), using a series of molecular biology measurements to ananlyze the effect and mechanism of DMAc-induced hepatic cell injury and explore effective prophylactic measures. We found that DMAc triggered LO-2 apoptosis in a obviously dose-dependent manner, caused by increased ROS generation and activation of Bcl-2 pathway. Significantly, glutathione (GSH) rather than vitamin C (Vit C) could partially inhibit DMAc-induced apoptosis thus showing potential as a effective precaution for workers. PMID:27003174

  15. Physicochemical Control of Adult Stem Cell Differentiation: Shedding Light on Potential Molecular Mechanisms

    PubMed Central

    Titushkin, Igor; Sun, Shan; Shin, Jennifer; Cho, Michael

    2010-01-01

    Realization of the exciting potential for stem-cell-based biomedical and therapeutic applications, including tissue engineering, requires an understanding of the cell-cell and cell-environment interactions. To this end, recent efforts have been focused on the manipulation of adult stem cell differentiation using inductive soluble factors, designing suitable mechanical environments, and applying noninvasive physical forces. Although each of these different approaches has been successfully applied to regulate stem cell differentiation, it would be of great interest and importance to integrate and optimally combine a few or all of the physicochemical differentiation cues to induce synergistic stem cell differentiation. Furthermore, elucidation of molecular mechanisms that mediate the effects of multiple differentiation cues will enable the researcher to better manipulate stem cell behavior and response. PMID:20379388

  16. Human oocyte developmental potential is predicted by mechanical properties within hours after fertilization

    PubMed Central

    Yanez, Livia Z.; Han, Jinnuo; Behr, Barry B.; Pera, Renee A. Reijo; Camarillo, David B.

    2016-01-01

    The causes of embryonic arrest during pre-implantation development are poorly understood. Attempts to correlate patterns of oocyte gene expression with successful embryo development have been hampered by the lack of reliable and nondestructive predictors of viability at such an early stage. Here we report that zygote viscoelastic properties can predict blastocyst formation in humans and mice within hours after fertilization, with >90% precision, 95% specificity and 75% sensitivity. We demonstrate that there are significant differences between the transcriptomes of viable and non-viable zygotes, especially in expression of genes important for oocyte maturation. In addition, we show that low-quality oocytes may undergo insufficient cortical granule release and zona-hardening, causing altered mechanics after fertilization. Our results suggest that embryo potential is largely determined by the quality and maturation of the oocyte before fertilization, and can be predicted through a minimally invasive mechanical measurement at the zygote stage. PMID:26904963

  17. Human oocyte developmental potential is predicted by mechanical properties within hours after fertilization.

    PubMed

    Yanez, Livia Z; Han, Jinnuo; Behr, Barry B; Reijo Pera, Renee A; Camarillo, David B

    2016-01-01

    The causes of embryonic arrest during pre-implantation development are poorly understood. Attempts to correlate patterns of oocyte gene expression with successful embryo development have been hampered by the lack of reliable and nondestructive predictors of viability at such an early stage. Here we report that zygote viscoelastic properties can predict blastocyst formation in humans and mice within hours after fertilization, with >90% precision, 95% specificity and 75% sensitivity. We demonstrate that there are significant differences between the transcriptomes of viable and non-viable zygotes, especially in expression of genes important for oocyte maturation. In addition, we show that low-quality oocytes may undergo insufficient cortical granule release and zona-hardening, causing altered mechanics after fertilization. Our results suggest that embryo potential is largely determined by the quality and maturation of the oocyte before fertilization, and can be predicted through a minimally invasive mechanical measurement at the zygote stage. PMID:26904963

  18. Potential mechanisms underlying ectodermal differentiation of Wharton's jelly mesenchymal stem cells.

    PubMed

    Jadalannagari, Sushma; Berry, Abigale M; Hopkins, Richard A; Bhavsar, Dhaval; Aljitawi, Omar S

    2016-09-16

    Wharton's jelly mesenchymal stem cells (WJMSCs) are being increasingly recognized for their ectodermal differentiation potential. Previously, we demonstrated that when WJMSC were seeded onto an acellular matrix material derived from Wharton's jelly and cultured in osteogenic induction media, generated CK19 positive cells and hair-like structures indicative of ectodermal differentiation of WJMSCs. In this manuscript, we examine the underlying mechanism behind this observation using a variety of microscopy and molecular biology techniques such as western blotting and qPCR. We demonstrate that these hair-like structures are associated with live cells that are positive for epithelial and mesenchymal markers such as cytokeratin-19 and α-smooth muscle actin, respectively. We also show that up-regulation of β-catenin and noggin, along with the expression of TGF-β and SMAD and inhibition of BMP4 could be the mechanism behind this ectodermal differentiation and hair-like structure formation. PMID:27501759

  19. Mechanical stress altered electron gate tunneling current and extraction of conduction band deformation potentials for germanium

    NASA Astrophysics Data System (ADS)

    Choi, Youn Sung; Lim, Ji-Song; Numata, Toshinori; Nishida, Toshikazu; Thompson, Scott E.

    2007-11-01

    Strain altered electron gate tunneling current is measured for germanium (Ge) metal-oxide-semiconductor devices with HfO2 gate dielectric. Uniaxial mechanical stress is applied using four-point wafer bending along [100] and [110] directions to extract both dilation and shear deformation potential constants of Ge. Least-squares fit to the experimental data results in Ξd and Ξu of -4.3±0.3 and 16.5±0.5 eV, respectively, which agree with theoretical calculations. The dominant mechanism for the strain altered electron gate tunneling current is a strain-induced change in the conduction band offset between Ge and HfO2. Tensile stress reduces the offset and increases the gate tunneling current for Ge while the opposite occurs for Si.

  20. Evolutionary constraints over microsatellite abundance in larger mammals as a potential mechanism against carcinogenic burden

    PubMed Central

    Park, Jung Youn; An, Yong-Rock; An, Chul-Min; Kang, Jung-Ha; Kim, Eun Mi; Kim, Heebal; Cho, Seoae; Kim, Jaemin

    2016-01-01

    Larger organisms tend to live longer, have more potentially carcinogenic cells, and undergo more cell divisions. While one might intuitively expect cancer incidence to scale with body size, this assertion does not hold over the range of different mammals. Explaining this lack of correlation, so-called ‘Peto’s paradox’ can likely increase our understanding of how cancer defense mechanisms are shaped by natural selection. Here, we study the occurrence of microsatellite in mammal genomes and observe that animals with expanded body size restrain the number of microsatellite. To take into account of higher mutation rate in the microsatellite region compared to that of genome, limiting the abundance of somatic mutations might explain how larger organisms could overcome the burden of cancer. These observations may serve as the basis to better understand how evolution has modeled protective mechanisms against cancer development. PMID:27125812

  1. Evolutionary constraints over microsatellite abundance in larger mammals as a potential mechanism against carcinogenic burden.

    PubMed

    Park, Jung Youn; An, Yong-Rock; An, Chul-Min; Kang, Jung-Ha; Kim, Eun Mi; Kim, Heebal; Cho, Seoae; Kim, Jaemin

    2016-01-01

    Larger organisms tend to live longer, have more potentially carcinogenic cells, and undergo more cell divisions. While one might intuitively expect cancer incidence to scale with body size, this assertion does not hold over the range of different mammals. Explaining this lack of correlation, so-called 'Peto's paradox' can likely increase our understanding of how cancer defense mechanisms are shaped by natural selection. Here, we study the occurrence of microsatellite in mammal genomes and observe that animals with expanded body size restrain the number of microsatellite. To take into account of higher mutation rate in the microsatellite region compared to that of genome, limiting the abundance of somatic mutations might explain how larger organisms could overcome the burden of cancer. These observations may serve as the basis to better understand how evolution has modeled protective mechanisms against cancer development. PMID:27125812

  2. Effect of biochar on nitrous oxide emission and its potential mechanisms.

    PubMed

    Liu, Liang; Shen, Guoqing; Sun, Mingxing; Cao, Xinde; Shang, Guofeng; Chen, Ping

    2014-08-01

    Extensive use of biochar to mitigate nitrous oxide (N2O) emission is limited by the lack of understanding on the exact mechanisms altering N2O emission from biochar-amended soil. Biochars produced from rice straw and dairy manure at 350 and 500 degrees C by oxygen-limited pyrolysis were used to investigate their influence on N2O emission. A quadratic effect of biochar levels was observed on the N2O emissions. The potential mechanisms were explored by terminal restriction fragment length polymorphism (T-RFLP) and real-time polymerase chain reaction (qPCR). A lower relative abundance of bacteria, which included ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), was observed at 4% biochar application rate. Reduced copy numbers of the ammonia monooxygenase gene amoA and the nitrite reductase gene nirS coincided with decreased N2O emissions. Therefore, biochar may potentially alter N2O emission by affecting ammonia-oxidizing and denitrification bacteria, which is determined by the application rate of biochar in soil. Implications: Biochar research has received increased interest in recent years because of the potential beneficial effects of biochar on soil properties. Recent research shows that biochar can alter the rates of nitrogen cycling in soil systems by influencing nitrification and denitrification, which are key sources of the greenhouse gas nitrous oxide (N2O). However, there are still some controversial data. The purpose of this research was to (1) examine how applications of different dose of biochar to soil affect emission of N2O and (2) improve the understanding of the underlying mechanisms. PMID:25185392

  3. Expression of the erythropoietin receptor by germline-derived cells - further support for a potential developmental link between the germline and hematopoiesis

    PubMed Central

    2014-01-01

    Background Expressing several markers of migrating primordial germ cells (PGCs), the rare population of quiescent, bone marrow (BM)-residing very small embryonic-like stem cells (VSELs) can be specified like PGCs into hematopoietic stem/progenitor cells (HSPCs). These two properties of VSELs support the possibility of a developmental origin of HSPCs from migrating PGCs. Methods To address a potential link between VSELs and germ line cells we analyzed by RT-PCR and FACS expression of erythropoietin receptor (EpoR) on murine bone marrow- and human umbilical cord blood-derived VSELs, murine and human teratocarcinoma cell lines and human ovarian cancer cells. A proper gating strategy and immunostaining excluded from FACS analysis potential contamination by erythroblasts. Furthermore, the transwell chemotaxis assays as well as adhesion and signaling studies were performed to demonstrate functionality of erythropoietin - EpoR axes on these cells. Results We report here that murine and human VSELs as well as murine and human teratocarcinoma cell lines and ovarian cancer cell lines share a functional EpoR. Conclusions Our data provide more evidence of a potential developmental link between germline cells, VSELs, and HSCs and sheds more light on the developmental hierarchy of the stem cell compartment in adult tissues. PMID:24982693

  4. Semiclassical stochastic mechanics for the Coulomb potential with applications to modelling dark matter

    NASA Astrophysics Data System (ADS)

    Neate, Andrew; Truman, Aubrey

    2016-05-01

    Little is known about dark matter particles save that their most important interactions with ordinary matter are gravitational and that, if they exist, they are stable, slow moving and relatively massive. Based on these assumptions, a semiclassical approximation to the Schrödinger equation under the action of a Coulomb potential should be relevant for modelling their behaviour. We investigate the semiclassical limit of the Schrödinger equation for a particle of mass M under a Coulomb potential in the context of Nelson's stochastic mechanics. This is done using a Freidlin-Wentzell asymptotic series expansion in the parameter ɛ = √{ ħ / M } for the Nelson diffusion. It is shown that for wave functions ψ ˜ exp((R + iS)/ɛ2) where R and S are real valued, the ɛ = 0 behaviour is governed by a constrained Hamiltonian system with Hamiltonian Hr and constraint Hi = 0 where the superscripts r and i denote the real and imaginary parts of the Bohr correspondence limit of the quantum mechanical Hamiltonian, independent of Nelson's ideas. Nelson's stochastic mechanics is restored in dealing with the nodal surface singularities and by computing (correct to first order in ɛ) the relevant diffusion process in terms of Jacobi fields thereby revealing Kepler's laws in a new light. The key here is that the constrained Hamiltonian system has just two solutions corresponding to the forward and backward drifts in Nelson's stochastic mechanics. We discuss the application of this theory to modelling dark matter particles under the influence of a large gravitating point mass.

  5. Inverted xerographic depletion discharge mechanism for the dark decay of electrostatic surface potential on amorphous semiconductors

    SciTech Connect

    Kasap, S.O.

    1988-07-01

    Recently, the xerographic depletion discharge (XDD) model has been applied extensively to chemically modified a-Se, a-Se/sub 1/..sqrt../sub x/Te/sub x/ alloys, and a-As/sub 2/Se/sub 3/ as well as to a-Si:H films to study the nature of charge carrier generation from deep mobility gap states which control the dark decay of the electrostatic surface potential on a corona charged amorphous semiconductor. In the normal XDD model, the dark discharge involves bulk thermal generation of a mobile carrier of the same sign as the surface charge and its subsequent sweep out from the sample leaving behind an ionized center of opposite charge. It is shown that an ''inverted depletion discharge'' mechanism, which involves the thermal generation of a mobile charge carrier of the opposite sign to the surface charge and its subsequent drift to the surface and the resulting surface charge neutralization there, results in a dark discharge rate which has identical features as the normal XDD mechanism. In the normal XDD mechanism, the neutral region develops after the depletion time from the grounded electrode, whereas in the inverted XDD mechanism the neutral region grows from the surface. Furthermore, during inverted depletion discharge the surface charge is actually dissipated by neutralization, whereas in the normal depletion discharge model there is no such requirement over the time scale of the experiment. It is concluded that xerographic dark decay experiments alone cannot determine the sign of the thermally generated mobile carrier and that of the bulk space charge. Chemically modified amorphous selenium case is discussed as an example of surface potential decay resulting from bulk space-charge buildup.

  6. Molecular Mechanism and Potential Targets for Blocking HPV-Induced Lesion Development

    PubMed Central

    Guzmán-Olea, E.; Bermúdez-Morales, V. H.; Peralta-Zaragoza, O.; Torres-Poveda, K.; Madrid-Marina, V.

    2012-01-01

    Persistent infection with high-risk HPV is the etiologic agent associated with the development of cervical cancer (CC) development. However, environmental, social, epidemiological, genetic, and host factors may have a joint influence on the risk of disease progression. Cervical lesions caused by HPV infection can be removed naturally by the host immune response and only a small percentage may progress to cancer; thus, the immune response is essential for the control of precursor lesions and CC. We present a review of recent research on the molecular mechanisms that allow HPV-infected cells to evade immune surveillance and potential targets of molecular therapy to inhibit tumor immune escape. PMID:22220169

  7. Molecular Mechanism and Potential Targets for Blocking HPV-Induced Lesion Development.

    PubMed

    Guzmán-Olea, E; Bermúdez-Morales, V H; Peralta-Zaragoza, O; Torres-Poveda, K; Madrid-Marina, V

    2012-01-01

    Persistent infection with high-risk HPV is the etiologic agent associated with the development of cervical cancer (CC) development. However, environmental, social, epidemiological, genetic, and host factors may have a joint influence on the risk of disease progression. Cervical lesions caused by HPV infection can be removed naturally by the host immune response and only a small percentage may progress to cancer; thus, the immune response is essential for the control of precursor lesions and CC. We present a review of recent research on the molecular mechanisms that allow HPV-infected cells to evade immune surveillance and potential targets of molecular therapy to inhibit tumor immune escape. PMID:22220169

  8. Wavelet analysis of corneal endothelial electrical potential difference reveals cyclic operation of the secretory mechanism

    NASA Astrophysics Data System (ADS)

    Cacace, V. I.; Montalbetti, N.; Kusnier, C.; Gomez, M. P.; Fischbarg, J.

    2011-09-01

    The corneal endothelium is a fluid-transporting epithelium. As other similar tissues, it displays an electrical potential of ˜1 mV (aqueous side negative) across the entire layer [transendothelial potential difference (TEPD)]. It appears that this electrical potential is mainly the result of the transport of anions across the cell layer (from stroma to aqueous). There is substantial evidence that the TEPD is related linearly to fluid transport; hence, under proper conditions, its measure could serve as a measure of fluid transport. Furthermore, the TEPD is not steady; instead, it displays a spectrum of frequency components (0-15 Hz) recognized recently using Fourier transforms. Such frequency components appear due to charge-separating (electrogenic) processes mediated by epithelial plasma membrane proteins (both ionic channels and ionic cotransporters). In particular, the endothelial TEPD oscillations of the highest amplitude (1-2 Hz) were linked to the operation of so-called sodium bicarbonate cotransporters. However, no time localization of that activity could be obtained with the Fourier methodology utilized. For that reason we now characterize the TEPD using wavelet analysis with the aim to localize in time the variations in TEPD. We find that the mentioned high-amplitude oscillatory components of the TEPD appear cyclically during the several hours that an endothelial preparation survives in vitro. They have a period of 4.6 ± 0.4 s on average (n=4). The wavelet power value at the peak of such oscillations is 1.5 ± 0.1 mV2 Hz on average (n = 4), and is remarkably narrow in its distribution.

  9. Potential molecular mechanisms underlying muscle fatigue mediated by reactive oxygen and nitrogen species

    PubMed Central

    Debold, Edward P.

    2015-01-01

    Intense contractile activity causes a dramatic decline in the force and velocity generating capacity of skeletal muscle within a few minutes, a phenomenon that characterizes fatigue. Much of the research effort has focused on how elevated levels of the metabolites of ATP hydrolysis might inhibit the function of the contractile proteins. However, there is now growing evidence that elevated levels of reactive oxygen and nitrogen species (ROS/RNS), which also accumulate in the myoplasm during fatigue, also play a causative role in this type of fatigue. The most compelling evidence comes from observations demonstrating that pre-treatment of intact muscle with a ROS scavenger can significantly attenuate the development of fatigue. A clear advantage of this line of inquiry is that the molecular targets and protein modifications of some of the ROS scavengers are well-characterized enabling researchers to begin to identify potential regions and even specific amino acid residues modified during fatigue. Combining this knowledge with assessments of contractile properties from the whole muscle level down to the dynamic motions within specific contractile proteins enable the linking of the structural modifications to the functional impacts, using advanced chemical and biophysical techniques. Based on this approach at least two areas are beginning emerge as potentially important sites, the regulatory protein troponin and the actin binding region of myosin. This review highlights some of these recent efforts which have the potential to offer uniquely precise information on the underlying molecular basis of fatigue. This work may also have implications beyond muscle fatigue as ROS/RNS mediated protein modifications are also thought to play a role in the loss of muscle function with aging and in some acute pathologies like cardiac arrest and ischemia. PMID:26388779

  10. Interplay of waves and eddies in rotating stratified turbulence and the link with kinetic-potential energy partition

    NASA Astrophysics Data System (ADS)

    Marino, Raffaele; Rosenberg, Duane; Herbert, Corentin; Pouquet, Annick

    2015-11-01

    The interplay between waves and eddies in stably stratified rotating flows is investigated by means of world-class direct numerical simulations using up to 30723 grid points. Strikingly, we find that the shift from vortex- to wave-dominated dynamics occurs at a wave number k R which does not depend on the Reynolds number, suggesting that the partition of energy between wave and vortical modes is not sensitive to the development of turbulence at the smaller scales. We also show that k R is comparable to the wave number at which exchanges between kinetic and potential modes stabilize at close to equipartition, emphasizing the role of potential energy, as conjectured in the atmosphere and the oceans. Moreover, k R varies as the inverse of the Froude number as explained by the scaling prediction proposed, consistently with recent observations and modeling of the Mesosphere-Lower Thermosphere and of the ocean.

  11. Is eating behavior manipulated by the gastrointestinal microbiota? Evolutionary pressures and