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Other Mechanisms (other + mechanism)
Selected AbstractsGlucose-induced inhibition: how many ionic mechanisms?ACTA PHYSIOLOGICA, Issue 3 2010D. Burdakov Abstract Sensing of sugar by specialized ,glucose-inhibited' cells helps organisms to counteract swings in their internal energy levels. Evidence from several cell types in both vertebrates and invertebrates suggests that this process involves sugar-induced stimulation of plasma membrane K+ currents. However, the molecular composition and the mechanism of activation of the underlying channel(s) remain controversial. In mouse hypothalamic neurones and neurosecretory cells of the crab Cancer borealis, glucose stimulates K+ currents displaying leak-like properties. Yet knockout of some of the candidate ,leak' channel subunits encoded by the KCNK gene family so far failed to abolish glucose inhibition of hypothalamic cells. Moreover, in other tissues, such as the carotid body, glucose-stimulated K+ channels appear to be not leak-like but voltage-gated, suggesting that glucose-induced inhibition may engage multiple types of K+ channels. Other mechanisms of glucose-induced inhibition, such as hyperpolarization mediated by opening of Cl, channels and depolarization block caused by closure of KATP channels have also been proposed. Here we review known ionic and pharmacological features of glucose-induced inhibition in different cell types, which may help to identify its molecular correlates. [source] Ovalbumin-induced sensitization affects non-quantal acetylcholine release from motor nerve terminals and alters contractility of skeletal muscles in miceEXPERIMENTAL PHYSIOLOGY, Issue 2 2009Alexander Y. Teplov Skeletal muscles play key roles in the development of various pathologies, including bronchial asthma and several types of auto-immune disorders, e.g. polymyositis. Since most of these maladies have an immunological/allergic element, this paper is devoted to assessing the impact of immunobiological reorganization on the functional properties of isolated skeletal muscles in mice. A combination of two methods (myography and electrophysiology) was used to evaluate extensor digitorum longus (EDL) and diaphragmatic muscle (DM) in this regard. Conventional myographic technique showed that ovalbumin-induced sensitization (OS) produced different changes in the contractile properties of EDL and DM. The amplitudes of carbachol (CCh)-induced contractions increased in DM but decreased in EDL. Those changes were inversely related to OS-mediated changes of non-quantal acetylcholine (ACh) release intensity within the muscle endplate, as shown by the electrophysiologically measured H-effect. These results clearly show that OS-mediated changes of non-quantal ACh release alter the functional properties of postjunctional ACh receptors and therefore contribute to the disturbance of CCh-induced contractility of skeletal muscles. Other mechanisms of OS-mediated changes of skeletal muscle contractility are also proposed and discussed. [source] Near IR Sensitization of Organic Bulk Heterojunction Solar Cells: Towards Optimization of the Spectral Response of Organic Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Markus Koppe Abstract The spectroscopic response of a poly(3-hexylthiophene)/[6,6]-phenyl-C61 -butyric acid methyl ester (P3HT/PCBM)-based bulk heterojunction solar cell is extended into the near infrared region (NIR) of the spectrum by adding the low bandgap polymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H -cyclopenta[2,1- b;3,4- b´]-dithiophene)- alt -4,7-(2,1,3-benzothiadiazole)] [PCPDTBT] to the blend. The dominant mechanism behind the enhanced photosensitivity of the ternary blend is found to be a two-step process: first, an ultrafast and efficient photoinduced charge transfer generates positive charges on P3HT and PCPDTBT and a negative charge on PCBM. In a second step, the positive charge on PCPDTBT is transferred to P3HT. Thus, P3HT serves two purposes. On the one hand it is involved in the generation of charge carriers by the photoinduced electron transfer to PCBM, and, on the other hand, it forms the charge transport matrix for the positive carriers transferred from PCPDTBT. Other mechanisms, such as energy transfer or photoinduced charge transfer directly between the two polymers, are found to be absent or negligible. [source] Agency problems and audit fees: further tests of the free cash flow hypothesisACCOUNTING & FINANCE, Issue 2 2010Paul A. Griffin G34; G35; M41; M42 Abstract This study finds that the agency problems of companies with high free cash flow (FCF) and low growth opportunities induce auditors of companies in the US to raise audit fees to compensate for the additional effort. We also find that high FCF companies with high growth prospects have higher audit fees. In both cases, higher debt levels moderate the increased fees, consistent with the role of debt as a monitoring mechanism. Other mechanisms to mitigate the agency costs of FCF such as dividend payout and share repurchase (not studied earlier) do not moderate the higher audit fees. [source] The ,oestrogen hypothesis', where do we stand now?,INTERNATIONAL JOURNAL OF ANDROLOGY, Issue 1 2003Richard M. Sharpe Summary The original ,oestrogen hypothesis' postulated that the apparent increase in human male reproductive developmental disorders (testis cancer, cryptorchidism, hypospadias, low sperm counts) might have occurred because of increased oestrogen exposure of the human foetus/neonate; five potential routes of exposure were considered. This review revisits this hypothesis in the light of the data to have emerged since 1993. It addresses whether there is a secular increasing trend in the listed disorders and highlights the limitations of available data and how these are being addressed. It considers whether new data has emerged to support the suggestion that increased oestrogen exposure could cause these abnormalities and reviews new data on potential routes via which such increased exposure could have occurred. Secular trends: The disorders listed above are now considered to represent a syndrome of disorders (testicular dysgenesis syndrome, TDS) with a common origin in foetal life. Testicular cancer has increased in incidence in Caucasian men worldwide and lifetime risk is 0.3,0.8%. Secular trends in cryptorchidism are unclear but it is by far the commonest (2,4% at birth) congenital abnormality in either sex. Secular trends for hypospadias are not robust, although most studies suggest a progressive increase; registry data probably under-estimates incidence, but based on this data hypospadias is the second most common (0.3,0.7% at birth) congenital malformation. Retrospective analyses of sperm count data show a global downward trend but this is inconclusive , prospective studies using standardized methodology show significant differences between countries and very low sperm counts in the youngest cohort of men. For all disorders, other then testis cancer, standardized prospective studies are the best way forward and are in progress across Europe. Oestrogen effects: Evidence that foetal exposure to oestrogens can induce the above disorders has strengthened. New pathways via which such changes could be induced have been identified, including suppression of testosterone production by the foetal testis, suppression of androgen receptor expression and suppression of insulin-like factor-3 (InsL3) production by foetal Leydig cells. Other evidence suggests that the balance between androgen and oestrogen action may be important in induction of reproductive tract abnormalities. Oestrogen exposure: Although many new environmental oestrogens have been identified, their uniformly weak oestrogenicity excludes the possibility that they could induce the above disorders. However, emerging data implicates various environmental chemicals in being able to alter endogenous levels of androgens (certain phthalates) and oestrogens (polychlorinated biphenyls, polyhalogenated hydrocarbons), and the former have been shown to induce a similar collection of disorders to TDS. Other mechanisms via which increased fetal exposure to pregnancy oestrogens might occur (increasing trend in obesity, dietary changes) are also discussed. [source] Non-ablative laser treatment of facial rhytides: A comparison of 1450-nm diode laser treatment with dynamic cooling as opposed to treatment with dynamic cooling aloneLASERS IN SURGERY AND MEDICINE, Issue 2 2002David J. Goldberg MD Abstract Background and Objective Non-ablative dermal remodeling has been shown to create new dermal collagen. This is thought to occur secondary to a laser-induced injury to the skin. Other mechanisms of injury may lead to similar results. The aim of this study was to evaluate the efficacy and complication rate of a 1450-nm diode laser and compare clinical effect when the laser is used in conjunction with cryogen cooling as compared to the use of cryogen cooling alone. Study Design/Materials and Methods Twenty subjects, skin types I,IV, age range 42,70 years, with Class I and II rhytides were enrolled in the study. Subjects were treated with 2,4 laser treatments and cryogen cooling on one side of their face, while the contralateral side was treated with cryogen cooling alone. Subjects were evaluated six months after their final treatment. Results Thirteen subjects showed clinical improvement on the laser/cryogen treated side. No subjects were noted to have any improvement at the cryogen alone side. Conclusion The 1450-nm diode laser can lead to non-ablative improvement of rhytides. This effect appears to be a direct laser induced effect. Lasers Surg. Med. 30:79,81, 2002. © 2002 Wiley-Liss, Inc. [source] Recent advances in adaptive thermogenesis: potential implications for the treatment of obesityOBESITY REVIEWS, Issue 2 2009S. L. J. Wijers Summary Large inter-individual differences in cold-induced (non-shivering) and diet-induced adaptive thermogenesis exist in animals and humans. These differences in energy expenditure can have a large impact on long-term energy balance and thus body weight (when other factors remain stable). Therefore, the level of adaptive thermogenesis might relate to the susceptibility to obesity; efforts to increase adaptive thermogenesis might be used to treat obesity. In small mammals, the main process involved is mitochondrial uncoupling in brown adipose tissue (BAT), which is regulated by the sympathetic nervous system. For a long time, it was assumed that mitochondrial uncoupling is not a major physiological contributor to adaptive thermogenesis in adult humans. However, several studies conducted in recent years suggest that mitochondrial uncoupling in BAT and skeletal muscle tissue in adult humans can be physiologically significant. Other mechanisms besides mitochondrial uncoupling that might be involved are futile calcium cycling, protein turnover and substrate cycling. In conjunction with recent advances on signal transduction studies, this knowledge makes manipulation of adaptive thermogenesis a more realistic option and thus a pharmacologically interesting target to treat obesity. [source] Spatial association of photosynthesis and chemical defense in Arabidopsis thaliana following herbivory by Trichoplusia niPHYSIOLOGIA PLANTARUM, Issue 2 2009Jennie Tang Because they share common precursors and require significant amounts of energy, photosynthesis and defense against herbivores and pathogens may be inversely related. This relationship was examined in Arabidopsis thaliana exposed to herbivory by Trichoplusia ni neonates. The spatial pattern of photosynthesis was compared statistically with that of induction of the defense-related cinnamate-4-hydroxylase (C4H) gene across individual leaves exposed to herbivory in transgenic plants harboring a C4H:GUS gene fusion. In portions of the leaf where C4H:GUS expression was upregulated, photosynthesis was depressed, while non-photochemical quenching was increased, suggesting a trade-off between these two processes. However, photosynthetic damage spread further into surrounding areas than the induction of C4H:GUS expression. Photosynthetic depression was observed up to 1 mm from the edges of holes, whereas C4H:GUS induction typically was limited to about 0.5 mm or less from edges. Other mechanisms may be responsible for the spread of photosynthetic damage beyond where C4H-related defense was induced. Alternatively, C4H induction may reflect a subset of defensive responses more limited in their spatial distribution than the downregulation of photosynthesis. The suppression of photosynthesis in remaining leaf tissue represents a ,hidden cost' of herbivore damage. [source] Heat acclimation and cross-tolerance against anoxia in ArabidopsisPLANT CELL & ENVIRONMENT, Issue 7 2008VALERIA BANTI ABSTRACT Arabidopsis seedlings are highly sensitive to low oxygen and they die rapidly when exposed to anoxia. Tolerance to anoxia depends on the ability to efficiently use carbohydrates through the fermentative pathway, as highlighted by the lower tolerance displayed by a mutant devoid of alcohol dehydrogenase. Other mechanisms of tolerance are also possible and may include a role for heat-induced genes. In fact, heat shock proteins (HSPs) are induced by anoxia. This suggests that there may be a cross-adaptation mechanism between heat and anoxic stress, and in this work, we studied the acclimation of Arabidopsis seedlings both to low oxygen and heat. The results show that seedlings subjected to hypoxia or heat pretreatment survive anoxia much better. Interestingly, we also observed an increased anoxia tolerance in heat-treated alcohol dehydrogenase (adh) mutant plants. On the other hand, anoxic pretreatment does not confer tolerance to heat stress. The success of the induction of HSPs by anoxia is in direct relation to the amount of sucrose available, and this in turn relates to how well seedlings will survive under anoxia. HSP transcripts were also detected during seed development and germination, two hypoxia-prone processes, suggesting that hypoxia-induced HSP expression is physiologically relevant. [source] Characterization of the impact of geostationary clear-sky radiances on wind analyses in a 4D-Var contextTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 644 2009C. Peubey The impact of geostationary clear-sky radiances (CSRs) on 4D-Var wind analyses has been investigated by running a set of observing system experiments. Analysis scores have been calculated to measure the ability of individual satellite datasets to improve the wind analysis, starting from a no-satellite baseline. In this context, the assimilation of CSRs from the two water-vapour channels on Meteosat-9 has been found to improve the wind analysis throughout the troposphere, with the strongest signal at 300 and 500 hPa. Indeed, for the Northern Hemisphere and the Tropics, the CSR impact at these levels exceeds that of the Meteosat-9 atmospheric motion vectors (AMVs), the sampling of the latter in the assimilation being rather limited. Conversely, the impact of AMVs exceeds that of CSRs in the lower troposphere, where the latter provide very little direct information. This demonstrates the complementarity of the two datasets in the operational 4D-Var wind analysis. The mechanisms through which the assimilation of CSRs can impact wind analyses have been isolated. The dominant effect is that of humidity-tracer advection, by which the wind field is adjusted in order to fit observed humidity features via the minimization of the 4D-Var cost function. Other mechanisms, such as balance constraints and the cycling of the forecast model that links the humidity and wind variables, have been found to play a minor role. The benefit of having frequent CSR images within the assimilation window has also been demonstrated. Copyright © 2009 Royal Meteorological Society [source] Iron Absorption: Biochemical and Molecular Insights into the Importance of Iron Species for Intestinal UptakeBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 3 2002Piero Cremonesi Redox chemistry of iron is particularly important in iron metabolism, both as a potential source of toxic intermediates and as an essential requirement for efficient iron transport. The initial step in iron absorption (uptake from lumen to mucosa) is particularly important and several pathways involving Fe(III) reduction or transport and Fe(II) transport have been identified. Novel genes associated with iron uptake include Dcytb, a putative iron-regulated reductase and DMT1, a Fe(II) carrier in the brush border membrane. Other mechanisms may also operate, however. We review the recent findings and apply this to understanding the absorption of Fe(III) pharmaceuticals. [source] Effect of obesity on airway inflammation: a cross-sectional analysis of body mass index and sputum cell countsCLINICAL & EXPERIMENTAL ALLERGY, Issue 7 2007D. C. Todd Summary Background Several observational studies have demonstrated an association between obesity and asthma. Studies evaluating exhaled nitric oxide levels and obesity have revealed that a higher body mass index (BMI) is associated with elevated exhaled nitric oxide levels. Airway inflammation using sputum cell counts has not been assessed in obese patients with airway diseases. Objective The primary aim of this study was to determine whether obesity (based on BMI) is associated with eosinophilic or neutrophilic bronchitis. Methods The results from a database of induced sputum cell counts were compared with BMI and analysed using correlation statistics, regression and parametric and non-parametric analysis. Results Seven-hundred and twenty-seven adult participants with an equal number of sputum samples were included in the analysis. BMI varied from 14.5 to 55 kg/m2. Sputum total cell count (mean±SD: 12.9 × 106 cell/g±21.5), eosinophil percent (median; min to max: 0.3%; 0,89.0), and neutrophil percent (mean±SD: 63.5±26.6%) were within normal limits. Participants with asthma had a higher percentage of sputum eosinophils than those without asthma (P=0.01). However, there was no difference in the total or differential cell counts among the obese and non-obese participants, when the data were analysed according to BMI category, gender, dose of inhaled corticosteroid, and presence or absence of asthma. Conclusion In this large sample of adult asthmatic and non-asthmatic participants, there was no association between BMI and airway inflammation measured by sputum cell counts. Other mechanisms to explain the relationship between obesity and asthma will need to be explored if this association is to be better understood. [source] The Scope of Criminal Law and Criminal Sanctions: An Economic View and Policy ImplicationsJOURNAL OF LAW AND SOCIETY, Issue 3 2008Roger Bowles This paper considers why some harm-generating activities are controlled by criminal law and criminal sanctions while others are subject to some other mechanism such as civil law, administrative law, regulation or the tax system. It looks at the question from the perspective of the law and economics approach. We seek to identify the comparative benefits of using the criminal law relative to other enforcement mechanisms and , more broadly , why certain specific behaviours are criminalized. The paper argues that an economic approach emphasizing the relative merits of alternative legal instruments for bringing about harm reduction can provide an explanation for a number of recent legal developments. It argues also that the willingness of legislators to combine the use of sanctions traditionally used in one area of the law with sanctions from other areas is more readily explicable in economic terms than in other terms. [source] Nature of Resistance to Methyl Benzimidazole Carbamate Fungicides in Fusarium oxysporum f.sp. lilii and F. oxysporum f.sp. gladioli in TaiwanJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2009Wen Hsin Chung Abstract Fusarium oxysporum f.sp. gladioli and F. oxysporum f.sp. lilii cause corm rot and yellowing of gladiolus and lilies respectively. Resistance among isolates of these two pathogens to two benzimidazole (methyl benzimidazole carbamate: MBC) fungicides, benomyl and thiabendazole, has been identified. However, sensitivity to other benzimidazole fungicides among isolates of F. oxysporum f.sp. gladioli and F. oxysporum f.sp. lilii remains unclear. Sensitivity among isolates of these two pathogens to benomyl, thiophanate-methyl, carbendazim and thiabendazole were evaluated in this study. Results showed that among six F. oxysporum f.sp. gladioli isolates, one was highly resistant, four were moderately resistant and one was highly sensitive to benomyl, five were highly resistant to thiophanate-methyl, four were sensitive and one was highly sensitive to carbendazim and all six isolates were sensitive to thiabendazole. Among the 13 F. oxysporum f.sp. lilii isolates tested, three were moderately resistant and 10 were highly sensitive to benomyl, and five were highly resistant, three were moderately resistant and five were sensitive to thiophanate-methyl. While all isolates were highly sensitive or sensitive to carbendazim and thiabendazole. These results strongly suggest that the mode of fungicide resistance in these two pathogens varies among members of the benzimidazole fungicide group and that cross resistance does not always occur. Sequence analysis of the partially amplified , -tubulin gene indicated that mutation in codons 198 and 200 had not occurred in the benzimidazole resistant isolates. It was concluded that resistance found in Taiwan isolates of F. oxysporum f.sp. gladioli and F. oxysporum f.sp. lilii to these fungicides may be due to some other mechanism. [source] The clustering of narrow-line AGN in the local UniverseMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2006Cheng Li ABSTRACT We have analysed the clustering of ,90 000 narrow-line active galactic nuclei (AGN) drawn from the Data Release 4 (DR4) of the Sloan Digital Sky Survey. Our analysis addresses the following questions. (i) How do the locations of galaxies within the large-scale distribution of dark matter influence ongoing accretion on to their central black holes? (ii) Is AGN activity triggered by interactions or mergers between galaxies? We compute the cross-correlation between AGN and a reference sample of galaxies drawn from the DR4. We compare this to results for control samples of inactive galaxies matched simultaneously in redshift, stellar mass, concentration, velocity dispersion and mean stellar age, as measured by the 4000-Å break strength. We also compare near-neighbour counts around AGN and around the control galaxies. On scales larger than a few Mpc, AGN have almost the same clustering amplitude as the control sample. This demonstrates that AGN host galaxies and inactive control galaxies populate dark matter haloes of similar mass. On scales between 100 kpc and 1 Mpc, AGN are clustered more weakly than the control galaxies. We use mock catalogues constructed from high-resolution N -body simulations to interpret this antibias, showing that the observed effect is easily understood if AGN are preferentially located at the centres of their dark matter haloes. On scales less than 70 kpc, AGN cluster marginally more strongly than the control sample, but the effect is weak. When compared to the control sample, we find that only one in 100 AGN has an extra neighbour within a radius of 70 kpc. This excess increases as a function of the accretion rate on to the black hole, but it does not rise above the few per cent level. Although interactions between galaxies may be responsible for triggering nuclear activity in a minority of nearby AGN, some other mechanism is required to explain the activity seen in the majority of the objects in our sample. [source] Mannose-binding lectin gene polymorphism and resistance to therapy in women with recurrent vulvovaginal candidiasisBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 10 2008GGG Donders Precis, Women with recurrent vulvovaginal candidiasis (RVC) due to a polymorphism in codon 54 of the MBL2 gene respond better to fluconazole maintenance therapy than do women with other underlying causes. Objective, To explain differences in response rates to maintenance therapy with fluconazole in women suffering from RVC by evaluating associations with a polymorphism in the gene coding for mannose-binding lectin (MBL). Design, Follow-up study, neted case-control group. Setting, Women attending vulvoginitis clinic for RVC. Population, Women participating in a multicentric study in Belgium with a degressive dose of fluconazole for RVC (the ReCiDiF trial) were divided into good responders, intermediate responders and nonresponders according to the number of relapses they experienced during therapy. From 109 of these women with adequate follow-up data, vaginal lavage with 2 ml of saline were performed at the moment of a proven acute attack at inclusion in the study, before maintenance treatment was started. A buccal swab was obtained from 55 age-matched women without a history of Candida infections, serving as a control group. Methods, Extracted DNA from buccal or vaginal cells was tested for codon 54 MBL2 gene polymorphism by polymerase chain reaction and endonuclease digestion. Main outcome measures, Frequency of MBL2 condon 54 allele B in women with optimal or poor response to maintenance therapy in composition with controls. Results, Women (n = 109) suffering from RVC were more likely to carry the variant MBL2 codon 54 allele B than control women (20 versus 6.6%, OR 3.4 [95% CI 1.3,8.2], P = 0.01). B alleles were present in 25% of the 36 women not suffering from any recurrence during the maintenance therapy with decreasing doses of fluconazole (OR 4.9 [95% CI 1.9,12.5], P = 0.0007 versus controls), in 20% of the 43 women with sporadic recurrences (OR 3.6 [95% CI 1.4,9.2], P = 0.007 versus controls) and in 15% of the 30 women who had to interrupt the treatment regimen due to frequent relapses (P = 0.097 versus controls). Conclusions, The MBL2 codon 54 gene polymorphism is more frequent in Belgian women suffering from RVC than in controls. The presence of the B allele is associated with a superior response to fluconazole maintenance therapy as compared with RVC patients without this polymorphism. We conclude that RVC due to deficient MBL production is more easily helped with antifungal medication than is RVC due to some other mechanism. [source] Assessing the Risk of Introducing Exotic Species via the Live Marine Species TradeCONSERVATION BIOLOGY, Issue 1 2005SHANNON M. WEIGLE especies estuarinas; introducción de especies; mecanismos de transferencia de especies invasoras; prevención de especies invasoras; riesgo de invasiones Abstract:,Although the shipping industry has received considerable attention as a dispersal mechanism for aquatic nuisance species, many invasions have been linked to other mechanisms of transfer. The threat posed to coastal ecosystems by these alternative mechanisms, however, remains largely unquantified. We assessed the potential risks of introducing marine and estuarine species associated with seven mechanisms of transfer: seafood companies, aquaculture operations, bait shops, stores that sell marine ornamental species, research and educational organizations, public aquariums, and coastal restoration projects. For each, we compiled a comprehensive database of organizations in coastal Massachusetts. We then designed and administered a survey to a subset of organizations that inquired about (1) their proximity to saltwater and methods of handling live imports; (2) the type and quantity of marine species being imported; and (3) the organization's familiarity with marine invasions. Respondents in five of the seven categories acknowledged importing nonlocal live marine species to the area. Seafood companies handled the majority of individuals but relatively few taxa. This mechanism of transfer also had the most complex trade patterns and the greatest number of operations located near saltwater. In contrast, the other transfer mechanisms each had simpler trade pathways and fewer operations but varied in the quantity and taxonomic diversity of their imports. Significantly, no single mechanism of transfer stood out as presenting a primary risk. Rather, each had characteristics or used handling practices at different points in the importation process that could facilitate introductions. To prevent future marine invasions, better reporting requirements for live species imports are needed, and best-management practices and outreach strategies specific to the transfer mechanism should be developed and implemented. Resumen:,Aunque la industria de transportación marítima ha recibido considerable atención como un mecanismo de dispersión de especies acuáticas molestas, muchas invasiones han sido relacionadas con otros mecanismos de transferencia. Sin embargo, la amenaza de estos mecanismos alternativos a los ecosistemas costeros permanece en gran parte sin cuantificar. Evaluamos los potenciales riesgos para especies marinas y estuarinas asociados con siete mecanismos de transferencia: compañías de mariscos, operaciones acuaculturales, tiendas de especies marinas ornamentales, organizaciones de investigación y educativas, acuarios públicos y proyectos de restauración costera. Para cada uno, compilamos una amplia base de datos de organizaciones en la costa de Massachussetts. Luego diseñamos y aplicamos una encuesta a un subconjunto de organizaciones para obtener información sobre (1) su proximidad al agua marina y sus métodos para el manejo de importaciones vivas, (2) el tipo y cantidad de especies marinas importadas y (3) la familiaridad de la organización con invasiones marinas. Evaluamos los potenciales riesgos de introducciones de especies marinas y estuarinas. Los encuestados en cinco de siete categorías reconocieron importar especies marinas vivas no locales al área. Las compañías de mariscos manejaron a la mayoría de los individuos pero relativamente pocos taxa. Este mecanismo de transferencia también tuvo los patrones comerciales más complejos y el mayor número de operaciones localizadas cerca de agua marina. En contraste, cada uno de los demás mecanismos de transferencia tuvo canales de comercialización más simples y menos operaciones, pero variaron en la cantidad y diversidad taxonómica de sus importaciones. Significativamente, ningún mecanismo individual resaltó como un riesgo primario. Más bien, cada uno tenía características o utilizaba prácticas de manejo en diferentes etapas del proceso de importación que podían facilitar las introducciones. Para prevenir futuras invasiones marinas, se necesitan mejores requerimientos para reportar la importación de especies vivas, y se deben desarrollar e implementar prácticas de manejo óptimo y estrategias de extensión específicas para el mecanismo de transferencia. [source] Chronic inhibition of standing behaviour alters baroreceptor reflex function in ratsACTA PHYSIOLOGICA, Issue 3 2009H. Waki Abstract Aim:, To investigate whether daily orthostatic stress during development is an important factor affecting arterial baroreceptor reflex function, we examined the effect of chronic inhibition of upright standing behaviour on the baroreceptor reflex function in rats. Methods:, Upright standing behaviour was chronically inhibited during the developmental period between 3 and 8 weeks of age in Sprague,Dawley rats and heart rate (HR) and aortic nerve activity in response to increased and decreased mean arterial pressure (MAP) was measured after the treatment period. Results:, The baroreceptor cardiac gain in the rats grown without standing behaviour was significantly lower than the control rats grown in a normal commercial cage (1.0 ± 0.1 beats min,1 mmHg,1 vs. 1.6 ± 0.2 beatsmin,1 mmHg,1, P < 0.05). The range of HR change in the MAP,HR functional curve was also lowered by chronic inhibition of orthostatic behaviour (56.2 ± 5.9 beats min,1) compared with that of the control rats (76.8 ± 6.9 beats min,1, P < 0.05). However the aortic afferent function remained normal after the treatment period, indicating that the attenuated baroreceptor reflex function may be due to other mechanisms involving functional alterations in the cardiovascular centres, efferents and/or peripheral organs. Body weight and adrenal weight were not affected by the inhibition of orthostatic behaviour, suggesting that the animals were not exposed to specific stress by this treatment. Conclusion:, These results indicate that active haemodynamic changes induced by orthostatic behaviour are an important factor for setting the basal level of reflex function during development. Moreover, our experimental model may be useful for studying mechanisms of attenuated baroreceptor reflex observed after exposure to a chronic inactive condition. [source] Long-term effects of botulinum toxin A in children with cerebral palsyDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 2 2009KRISTINA TEDROFF MD The long-term effects of botulinum toxin A (BoNT-A) treatment in children with cerebral palsy (CP) are still elusive. We studied a prospective clinical cohort of 94 children with different subtypes (50% spastic diplegic CP, 22% hemiplegic CP, 25% tetraplegic CP, 3% dyskinetic CP), sex (55% male, 45% female), severity according to Gross Motor Function Classification System (29% Level I, 15% Level II, 16% Level III, 17% Level IV, 23% Level V), and age (median 5y 4mo, range 11mo,17y 8mo). The longest follow-up time was 3 years 7 months (median 1y 6mo) and included a maximum of eight injections per muscle (median two injections to a specific muscle). Outcome measurements were muscle tone (Modified Ashworth Scale) and joint range of motion (ROM). Assessments were made at a minimum before and 3 months after each injection. Ninety-five per cent confidence intervals for differences from baseline were used to identify significant changes. BoNT-A injections induced reduction of long-term spasticity in all muscle-groups examined: the gastrocnemius, hamstring, and adductor muscles. The reduction in tone was most distinct in the gastrocnemius muscle, and each repeated injection produced an immediate reduction in muscle tone. However, improvement in ROM was brief and measured only after the first injections, whereupon the ROM declined. Thus, the results suggest that BoNT-A can be effective in reducing muscle tone over a longer period, but not in preventing development of contractures in spastic muscles. The dissociation between the effects on muscle tone and ROM indicates that development of contractures is not coupled to increased muscle tone only, but might be caused by other mechanisms. [source] Temporal association between food distribution and human caregiver presence and the development of affinity to humans in lambsDEVELOPMENTAL PSYCHOBIOLOGY, Issue 2 2008Céline Tallet Abstract The presence of the caregiver around feeding favors the development of a human,animal relationship. To understand the underlying mechanism, we tested various temporal associations between food distribution and human presence: from an early age, a person was repeatedly present for 2 min just before milk distribution ("Forward"), during milk distribution ("Simultaneous"), and 20 min afterwards ("Delayed"). The "Control" group received no human contacts. During the treatments, "Forward" and "Delayed" lambs had more physical contacts with the person than "Simultaneous" lambs. When tested in unfamiliar environments, they stood longer near the person than did "Control" or "Simultaneous" lambs, which did not differ. Only "Forward" and "Delayed" lambs bleated when separated from the person. Fasting before testing had no effect. "Forward" and "Delayed" seemed to produce the same human,animal relationship, showing that this did not rely only on a conditioning process associating the caregiver with food. The caregiver may acquire properties for social support through other mechanisms (attachment and/or postingestive effects). © 2008 Wiley Periodicals, Inc. Dev Psychobiol 50: 147,159, 2008. [source] Maternal transmission of diabetesDIABETIC MEDICINE, Issue 2 2002J. C. Alcolado Abstract Type 2 diabetes mellitus represents a heterogeneous group of conditions characterized by impaired glucose homeostasis. The disorder runs in families but the mechanism underlying this is unknown. Many, but not all, studies have suggested that mothers are excessively implicated in the transmission of the disorder. A number of possible genetic phenomena could explain this observation, including the exclusively maternal transmission of mitochondrial DNA (mtDNA). It is now apparent that mutations in mtDNA can indeed result in maternally inherited diabetes. Although several mutations have been implicated, the strongest evidence relates to a point substitution at nucleotide position 3243 (A to G) in the mitochondrial tRNAleu(UUR) gene. Mitochondrial diabetes is commonly associated with nerve deafness and often presents with progressive non-autoimmune ,-cell failure. Specific treatment with Coenzyme Q10 or L-carnitine may be beneficial. Several rodent models of mitochondrial diabetes have been developed, including one in which mtDNA is specifically depleted in the pancreatic islets. Apart from severe, pathogenic mtDNA mutations, common polymorphisms in mtDNA may contribute to variations of insulin secretory capacity in normal individuals. Mitochondrial diabetes accounts for less than 1% of all diabetes and other mechanisms must underlie the maternal transmission of Type 2 diabetes. Possibilities include the role of maternally controlled environments, imprinted genes and epigenetic phenomena. [source] "Supranormal" Cardiac Function in Athletes Related to Better Arterial and Endothelial FunctionECHOCARDIOGRAPHY, Issue 6 2010Maria Florescu M.D. Objective: Athlete's heart is associated with left ventricular (LV) hypertrophy (LVH), and "supranormal" cardiac function, suggesting that this is a physiological process. Hypertrophy alone cannot explain increase in cardiac function, therefore, other mechanisms, such as better ventriculo-arterial coupling might be involved. Methods: We studied 60 male (21 ± 3 years) subjects: 27 endurance athletes, and a control group of 33 age-matched sedentary subjects. We assessed global systolic and diastolic LV function, short- and long-axis myocardial velocities, arterial structure and function and ventriculo-arterial coupling, endothelial function by flow-mediated dilatation, and amino-terminal pro-brain natriuretic peptide (NT-proBNP) and biological markers of myocardial fibrosis and of oxidative stress. Results: Athletes had "supranormal" LV longitudinal function (12.4 ± 1.0 vs 10.1 ± 1.4 cm/s for longitudinal systolic velocity, and 17.4 ± 2.6 vs 15.1 ± 2.4 cm/s for longitudinal early diastolic velocity, both P < 0.01), whereas ejection fraction and short-axis function were similar to controls. Meanwhile, they had better endothelial function (16.7 ± 7.0 vs 13.3 ± 5.3%, P < 0.05) and lower arterial stiffness (pulse wave velocity 7.1 ± 0.6 vs 8.8 ± 1.1 m/s, P = 0.0001), related to lower oxidative stress (0.259 ± 0.71 vs 0.428 ± 0.88 nmol/mL, P = 0.0001), with improved ventriculo-arterial coupling (37.1 ± 21.5 vs 15.5 ± 13.4 mmHg.m/s3× 103, P = 0.0001). NT-proBNP and markers of myocardial fibrosis were not different from controls. LV longitudinal function was directly related to ventriculo-arterial coupling, and inversely related to arterial stiffness and to oxidative stress. Conclusions: "Supranormal" cardiac function in athletes is due to better endothelial and arterial function, related to lower oxidative stress, with optimized ventriculo-arterial coupling; athlete's heart is purely a physiological phenomenon, associated with "supranormal" cardiac function, and there are no markers of myocardial fibrosis. (Echocardiography 2010;27:659-667) [source] Density-dependent growth of young-of-the-year Atlantic salmon (Salmo salar) revisitedECOLOGY OF FRESHWATER FISH, Issue 1 2010I. Imre Imre I, Grant JWA, Cunjak RA. Density-dependent growth of young-of-the-year Atlantic salmon (Salmo salar) revisited. Ecology of Freshwater Fish 2010: 19: 1,6. © 2009 John Wiley & Sons A/S Abstract,,, The length of individual young-of-the-year (YOY) Atlantic salmon (Salmo salar) in Catamaran Brook decreases with increasing population density following a negative power curve. Because most of this decrease in growth rate occurs at low densities (<1 fish·m,2), (Imre et al. 2005; Journal of Animal Ecology, 74: 508,516) suggested that exploitation competition for drifting prey rather than space limitation might be responsible for this pattern. Recently, (Ward et al. 2007; Journal of Animal Ecology, 76: 135,138) showed that the negative power curve of growth rate versus density can be caused by other mechanisms and suggested that Imre et al.'s evidence for density-dependent growth would have been stronger if we had analysed final size versus initial density rather than final density. We examined (i) whether the negative power curve of size versus density was also apparent in an analysis of final size versus initial density and tested two predictions that emerge from Ward et al.'s model, (ii) the variance in body size increases with population density, and (iii) the maximum fish size at a site is density-independent. The final size of YOY salmon decreased with increasing initial density following a negative power curve. Our data did not provide strong support for the above predictions emerging from Ward et al.'s model. Our analyses of different years, sites and seasons were consistent with the hypothesis of density-dependent growth of YOY salmon. [source] Impact of chemical elicitor applications on greenhouse tomato plants and population growth of the green peach aphid, Myzus persicaeENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2006Anthony J. Boughton Abstract Recent advances in the understanding of plant signaling pathways have opened the way for using elicitor-induced plant resistance as a tactic for protecting plants against arthropod pests. Four common elicitors of induced responses in tomato, Lycopersicon esculentum Mill. (Solanaceae), were evaluated with regard to phytotoxicity, induction of plant defensive proteins, and effects on population growth and fecundity of a common pest, the green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae). Ethephon and methyl jasmonate (MJ) treatments caused varying degrees of phytotoxicity. Ethephon caused pronounced changes in plant growth form and severe, dose-dependent negative impacts on plant growth and flowering. Effects with MJ were milder, but still caused temporary inhibition of development, leading to smaller plants and delayed flowering. The commercial elicitors benzothiadiazole (BTH) and harpin did not cause detectable phytotoxicity. The highest doses of ethephon and MJ significantly increased leaf peroxidase (POD) levels but only MJ treatments significantly increased polyphenol oxidase (PPO) levels. BTH and harpin had no detectable effects on POD and PPO. Populations of green peach aphids grew significantly more slowly on plants treated with BTH or MJ than on control plants or plants treated with harpin or ethephon. Slowed aphid population growth on BTH-treated plants was due to significant reductions in aphid fecundity, although this was independent of changes in time to onset of reproduction or time to death. Aphid fecundity was also reduced on MJ-treated plants relative to controls, but this difference was not statistically significant, suggesting that other mechanisms are involved in slowing aphid population growth on MJ-treated plants. Growth of aphid populations on plants treated with a MJ,BTH mixture was reduced almost as much as with treatments of MJ alone, suggesting that antagonism between JA-dependant and SA-dependent plant signaling pathways is only mild with regard to induced defenses against aphids. [source] Monitoring pyrethroid resistance in field collected Blattella germanica Linn. (Dictyoptera: Blattellidae) in IndonesiaENTOMOLOGICAL RESEARCH, Issue 2 2009Intan AHMAD Abstract The German cockroach, Blattella germanica, is a major and the most common pest in public areas in Indonesia. Although intensive control measures have been carried out to control the populations of this pest, results have been far from successful, which is believed to be because of its resistance to insecticides. A standard World Health Organization (WHO) glass jar test was carried out to determine the resistance level of this insect to pyrethroid insecticides, the most commonly used insecticides for cockroach control in Indonesia. A susceptible S1 strain collected from Tembagapura Papua was compared with four strains collected from Bandung, West Java: strain S2, from a local restaurant; strain S3, from the Bandung train station; and strains S4 and S5, from two different hotels. All strains showed low resistance to the pyrethroid, except the S5 strain, which had a Resistance Ratio (RR)50 of 95 for permethrin. The addition of piperonyl butoxide (PBO) suggests that the detoxifying enzyme mixed function oxidases (MFO) played an important role in the development of resistance to permethrin in the S5 strain, suggested by the high Synergist Ratio (SR) of 70.4. However, the low level of resistance to cypermethrin was not affected by PBO, suggesting that other mechanisms of pyrethroid resistance are involved. Our study is the first report of German cockroach resistance to permethrin in Indonesia, and the findings can be used in formulating potential strategies for cockroach resistance management. [source] Use of freshwater rotifer Brachionus calyciflorus in screening assay for potential endocrine disruptorsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2000Benjamin L. Preston Abstract eports of the effectsofendocrinedisruptorsonaquatic invertebrates arebecoming increasingly common. However, little is known about the endocrine systems of most aquatic invertebrates, limiting the development of assays based on endocrine mechanisms. As a result, endocrine disruption is often inferred through the effects caused by the chemical of interest, making it difficult to rule out other mechanisms of toxicity. To be a good candidate for an endocrine disruptor, effects should be observed in processes known to be under endocrine control, at life stages where endocrine signals are known to be active, and at concentrations below acute and chronic toxic effects. We developed a 96-h reproductive assay using the freshwater rotifer Brachionus calyciflorus to screen for potential endocrine disruptors and examined cadmium, chlorpyrifos, naphthol, pentachlorophenol, estradiol, methoprene, precocene, nonylphenol, flutamide, and testosterone for effects on asexual and sexual reproduction. Flutamide, testosterone, and nonylphenol inhibited fertilization of sexual females at concentrations of 1, 10, and 50 ,g/L, respectively. The fertilization no-observable-effect concentrations (NOECs) for these compounds were 5 to 200 times lower than previously described reproduction NOECs for B. calyciflorus. Sexual reproduction was inhibited with no effects on asexual reproduction, increasing the likelihood that these specific reproductive effects occurred through an endocrine mechanism. Rotifer reproduction assays may be a useful, rapid, and inexpensive method for screening compounds suspected to have endocrine disrupting activity in aquatic invertebrates. [source] Neurological manifestations of antiphospholipid syndromeEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 4 2010Carlos E. M. Rodrigues Eur J Clin Invest 2010; 40 (4): 350,359 Abstract Background, Neurologic disorders are among the most common and important clinical manifestations associated with the antiphospholipid syndrome (APS). It is characterized by diverse neurological manifestations. These include stroke, transient ischaemic attack, Sneddon's syndrome, convulsions/epilepsy, dementia, cognitive deficits, headaches/migraine, chorea, multiple sclerosis-like, transverse myelitis, ocular symptoms and Guillain,Barré syndrome. Material and methods, We review the latest data about neurologic disorders and APS. Results, In patients under 45 years of age, 20% of strokes are potentially associated with APS. Our study group recently reported a correlation between primary APS and peripheral neuropathy. Only one study investigated the occurrence of peripheral neuropathy in patients diagnosed with PAPS through electrophysiological study and showed alterations in 35% of patients. The mechanism of nervous system involvement in APS is considered to be primarily thrombotic. However, other mechanisms have been described, such as antiphospholipid antibodies that bind to the neural tissue, deregulating their functions and having an immediate pathogenic effect. Conclusions, This review summarizes the latest data regarding the clinical aspects, radiological and therapeutic of major neurologic manifestations associated with antiphospholipid antibodies. [source] Different pathophysiological mechanisms of intramitochondrial iron accumulation in acquired and congenital sideroblastic anemia caused by mitochondrial DNA deletionEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 2 2006Thomas Matthes Abstract:, Sideroblastic anemias (SA) are characterized by iron accumulation in the mitochondria of erythroblasts. Although we have evidence of mitochondrial gene alterations in sporadic congenital cases, the origin of acquired forms [refractory anemia with ring sideroblasts (RARS)], is still largely unknown. Here, we report the analysis of respiratory chain function in a patient with a large mitochondrial deletion and in patients with RARS. A young boy with SA showed symptoms typical of a mitochondrial disease with metabolic acidosis, muscle weakness and cerebral involvement. His bone marrow DNA was analyzed for the presence of mitochondrial deletions. We found a new mitochondrial (mt)DNA deletion spanning 3614 bp and including all the mt genes encoding complex IV, plus ATPase 6 and 8, and several transfer (t)RNAs. All tissues analyzed (liver, skeletal muscle, brain, pancreas) showed a heteroplasmic distribution of this mutant DNA. Bone marrow homogenates were obtained from five patients with RARS and from three patients with normal bone marrow and respiratory chain function assayed by spectrophotometric analysis. Cytochrome c oxidase (CCO) activity was greatly reduced in the patient's bone marrow. In contrast, CCO activity and global respiratory chain function were conserved in patients with RARS. We conclude that deficient CCO activity secondary to mtDNA deletions is related to intramitochondrial iron accumulation, as in our patient or in those with Pearson's syndrome, whereas other mechanisms, e.g. nuclear DNA mutations, have to be proposed to be involved in the acquired forms of SA. [source] Nigrostriatal lesion induces D2-modulated phase-locked activity in the basal ganglia of ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2007Camila L. Zold Abstract There is a debate as to what modifications of neuronal activity underlie the clinical manifestations of Parkinson's disease and the efficacy of antiparkinsonian pharmacotherapy. Previous studies suggest that release of GABAergic striatopallidal neurons from D2 receptor-mediated inhibition allows spreading of cortical rhythms to the globus pallidus (GP) in rats with 6-hydroxydopamine-induced nigrostriatal lesions. Here this abnormal spreading was thoroughly investigated. In control urethane-anaesthetized rats most GP neurons were excited during the active part of cortical slow waves (,direct-phase' neurons). Two neuronal populations having opposite phase relationships with cortical and striatal activity coexisted in the GP of 6-hydroxydopamine-lesioned rats. ,Inverse-phase' GP units exhibited reduced firing coupled to striatal activation during slow waves, suggesting that this GP oscillation was driven by striatopallidal hyperactivity. Half of the pallidonigral neurons identified by antidromic stimulation exhibited inverse-phase activity. Therefore, spreading of inverse-phase oscillations through pallidonigral axons might contribute to the abnormal direct-phase cortical entrainment of basal ganglia output described previously. Systemic administration of the D2 agonist quinpirole to 6-hydroxydopamine-lesioned rats reduced GP inverse-phase coupling with slow waves, and this effect was reversed by the D2 antagonist eticlopride. Because striatopallidal hyperactivity was only slightly reduced by quinpirole, other mechanisms might have contributed to the effect of quinpirole on GP oscillations. These results suggest that antiparkinsonian efficacy may rely on other actions of D2 agonists on basal ganglia activity. However, abnormal slow rhythms may promote enduring changes in functional connectivity along the striatopallidal axis, contributing to D2 agonist-resistant clinical signs of parkinsonism. [source] Environmental and frequency effects on fatigue crack growth rate and paths in aluminium alloyFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 1-2 2005S. A. MICHEL ABSTRACT The environmental and frequency effects on fatigue crack growth in aluminium alloys are studied theoretically and experimentally. 2024-T351 and 7075-T651 tested in corrosive environments (humid air or technically purified nitrogen) show a constant crack growth rate (da/dN) at low values of the effective stress intensity range (,Keff). Typical well-known fits of this curve (da/dN vs ,Keff) do not reflect the plateau-like region. A new model of crack growth is presented, which physically attributes this region to the formation and subsequent fracture of a crack tip oxide layer. The thickness of this layer is measured with X-ray photon electron spectroscopy. At higher loads, other mechanisms are understood to be active. The model parameters are determined from constant amplitude tests, and are valid for a given material and environment. In 7075-T651 tested in nitrogen, with R= 0.1 and 83 Hz, unexpected macroscopical crack branching is observed when ,Keff reaches approximately 3.0 MPa ,m. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||