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1.
Mobbs D Petrovic P Marchant JL Hassabis D Weiskopf N Seymour B Dolan RJ Frith CD 《Science (New York, N.Y.)》2007,317(5841):1079-1083
Humans, like other animals, alter their behavior depending on whether a threat is close or distant. We investigated spatial imminence of threat by developing an active avoidance paradigm in which volunteers were pursued through a maze by a virtual predator endowed with an ability to chase, capture, and inflict pain. Using functional magnetic resonance imaging, we found that as the virtual predator grew closer, brain activity shifted from the ventromedial prefrontal cortex to the periaqueductal gray. This shift showed maximal expression when a high degree of pain was anticipated. Moreover, imminence-driven periaqueductal gray activity correlated with increased subjective degree of dread and decreased confidence of escape. Our findings cast light on the neural dynamics of threat anticipation and have implications for the neurobiology of human anxiety-related disorders. 相似文献
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Carolina M. Malgarin Javier B. Zarate Predrag Novakovic Susan E. Detmer Daniel J. MacPhee John C. S. Harding 《Journal of veterinary diagnostic investigation》2021,33(2):322
Porcine reproductive and respiratory syndrome virus (PRRSV) is transmitted vertically, causing fetal death in late gestation. Spatiotemporal distribution of virus at the maternal–fetal interface (MFI) is variable, and accurate assessment of viral concentration and lesions is thus subject to sampling error. Our objectives were: 1) to assess whether viral load and lesion severity in a single sample of endometrium (END) and placenta (PLC), collected near the base of the umbilical cord (the current standard), are representative of the entire organ; and 2) to compare sampling strategies and evaluate if spatial variation in viral load can be overcome by pooling of like-tissues. Spatially distinct pieces of END and PLC of 24 fetuses from PRRSV-2–infected dams were collected. PRRSV RNA quantified by RT-qPCR was compared in 5 individual pieces per fetus and in respective pools of tissue and extracted RNA. Three distinct pieces of MFI were assessed for histologic severity. Concordance correlation and kappa inter-rater agreement were used to characterize agreement among individual samples and pools. The viral load of individual samples and pools of END had greater concordance to a referent standard than did samples of PLC. Larger pool sizes had greater concordance than smaller pool sizes. Average viral load and lesion severity did not differ by location sampled, and no technical advantages of pooling tissues versus RNA extracts were found. We conclude that multiple pieces of MFI tissues must be evaluated to accurately assess lesion severity and viral load. Three pieces per fetus provided a reasonable balance of cost and logistic feasibility. 相似文献
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Gagnon E Ranitovic P Tong XM Cocke CL Murnane MM Kapteyn HC Sandhu AS 《Science (New York, N.Y.)》2007,317(5843):1374-1378
The direct observation of molecular dynamics initiated by x-rays has been hindered to date by the lack of bright femtosecond sources of short-wavelength light. We used soft x-ray beams generated by high-harmonic upconversion of a femtosecond laser to photoionize a nitrogen molecule, creating highly excited molecular cations. A strong infrared pulse was then used to probe the ultrafast electronic and nuclear dynamics as the molecule exploded. We found that substantial fragmentation occurs through an electron-shakeup process, in which a second electron is simultaneously excited during the soft x-ray photoionization process. During fragmentation, the molecular potential seen by the electron changes rapidly from nearly spherically symmetric to a two-center molecular potential. Our approach can capture in real time and with angstrom resolution the influence of ionizing radiation on a range of molecular systems, probing dynamics that are inaccessible with the use of other techniques. 相似文献
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Both calcium (Ca2+) and silicon (Si) improve plant performance under salt (NaCl) stress. Although these two mineral elements share numerous similarities, the information on how their extracellular interactions in the root apoplast affect uptake of sodium (Na+) is still lacking. Here, we investigated the effect of high Si supply in the bioavailable form of monosilicic acid (H4SiO4) on the activity of Ca2+ in the external root solution, and subsequent root uptake and compartmentation of Na in maize (Zea mays L.). In the short‐term experiments (6 h), 14‐d‐old maize plants were exposed to various concentrations of Ca2+ at three different pH‐values (6.5, 7.5, and 8.5) and two Si concentrations, i.e., low (1 mM) and high (4 mM) supply of H4SiO4. The activity of Ca2+ and Na+ in the external solution as well as the root concentrations of total and cell sap and BaCl2‐exchangeble apoplastic fractions of both elements were analyzed. The pH of the nutrient solution affected neither the ion activities nor the root accumulation of both Ca2+ and Na+. At higher pH values (7.5 and 8.5) the interactions of Ca2+ and Si at high Si supply led to a decrease of Ca2+ activity and, hence, an increase of Na+ : Ca2+ activity ratio in the external root solution. Concomitantly, despite the elevated exchangeable apoplastic fraction of both Ca2+ and Na+, the total and cell sap concentrations were remarkably decreased for Ca2+ and increased for Na+ by the addition of 4 mM H4SiO4. This work demonstrates that at high Si supply extracellular Ca‐Si interactions leading to lowered activity of Ca2+ might rapidly compromise the ameliorative effect of Ca2+ on Na+ accumulation in roots. Practically, Si over‐fertilization of saline and, in particular, sodic soils may further promote the accumulation of Na+ in root tissues hours after Si application and, hence, increase a potential risk of Na+ toxicity. 相似文献
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Predrag Novakovic Yanyun Y. Huang Betty Lockerbie Farshid Shahriar John Kelly John R. Gordon Dorothy M. Middleton Matthew E. Loewen Beverly A. Kidney Elemir Simko 《Canadian journal of veterinary research》2015,79(2):120-128
F4ac-positive enterotoxigenic Escherichia coli (ETEC) must attach to the intestinal mucosa to cause diarrhea in piglets. Prevention of bacterial attachment to the intestinal mucosa is the most effective defense against ETEC-induced diarrhea. Porcine milk fat globule membranes (MFGM) were shown to be able to inhibit attachment of ETEC to the intestinal brush border; however, the specific components of porcine MFGM that inhibited attachment of ETEC to enterocytes were not identified. Accordingly, the purpose of this study was to identify F4ac-binding MFGM proteins by overlay Western blot and affinity chromatography. The proteome of porcine MFGM was characterized and the following F4ac-binding proteins were detected by overlay Western blot and affinity chromatography: lactadherin, butyrophilin, adipophilin, acyl-CoA synthetase 3, and fatty acid-binding protein 3. The biological function of these proteins was not investigated but it is possible that their interaction with F4ac fimbria interferes with bacterial attachment and colonization. 相似文献
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While there appear to be costs to farmers of over-applying nitrogen, there is evidence in many regions that farmers are applying nitrogen at levels that exceed those suggested by government extension services. A major reason why farmers would apparently waste money by applying more fertilizer than a crop can use is a perception that the general recommendations are not appropriate for their individual situations. In this paper we estimate the economically optimal rates for 7 Ontario sites over multiple years using four yield response functional forms to examine whether the profit-maximizing rates as determined at the end of the growing season (ex post optimal rates) are generally higher than recommended rates due to site, year, or yield response functional form differences. There was no statistical or economic basis for selecting one response model over another suggesting functional form choice or perception is not a reason for over-application. However, there was a great deal of variability found between the actual optimal rate for the season and the ex ante recommended rate, which is constant across seasons for a given site. While the recommended rate is higher than the maximum economic rate of nitrogen (MERN) on the majority of sites examined, the distribution is skewed due to a few large differences. When the recommended rate is lower than the ex post MERN in a given year, it tends to occur on less productive sites and is much lower. The pay-off function to alternative nitrogen rates is generally flat as the difference between the MERN and recommended was less than $10/ha on approximately one-third of the trials but there are large differences in the good years on less productive sites. Thus, the decision to apply more than average to take advantage of the good years is appropriate since the cost of over-application is low compared to the cost of under-application. While the pay off to soil testing for nitrogen and consequently variable rate application technology is brought into question, there appears to be significant value to information on the growing conditions for the upcoming season particularly on less productive sites. Another implication of the study is the need to have a sufficient range of application rates in nitrogen field trials for accurate estimation of the underlying response function. 相似文献
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Marina Piria Predrag Simonović Eleni Kalogianni Leonidas Vardakas Nicholas Koutsikos Davor Zanella Milica Ristovska Apostolos Apostolou Avdul Adrović Danilo Mrdak Ali Serhan Tarkan Dragana Milošević Linda N Zanella Rigers Bakiu F Güler Ekmekçi Metka Povž Kastriot Korro Vera Nikolić Rifat Škrijelj Vasil Kostov Andrej Gregori Michael K Joy 《Fish and Fisheries》2018,19(1):138-169
Fish introductions, particularly in areas of high biological diversity and endemism, represent a major threat for biodiversity. In the Balkan Peninsula, 60 fish species have been introduced to date, of which 36 have become naturalized in inland waters. Since the Balkans are one of the world's 35 biodiversity hot spots, this large presence of alien fish species poses a serious threat for the stability of freshwater ecosystems and the survival of the native ichthyofauna and of aquatic biodiversity in general. The motivation for the introductions, and the historical timeline, varies among the Balkan states. Despite recent attempts to implement and align legislation aimed at preventing the introduction of potentially invasive species, and the implementation of rigorous controls of introductions and increased protection of open waters, the majority of current introductions remain intentional, primarily via aquaculture. This review article provides a historical overview of freshwater fish introductions, the motivation behind them and the current distribution of alien freshwater fishes in the Balkans. The ecological implications and future perspectives concerning alien fish species in the region are also discussed. 相似文献
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Branko Glamuzina Pero Tutman Luka Glamuzina Zoran Vidović Predrag Simonović Lorenzo Vilizzi 《Fisheries Management and Ecology》2021,28(2):138-146
Biological invasions are a major driver of global environmental change as invasive non-native species can exert severe environmental impacts on invaded ecosystems. Estuaries are especially vulnerable to biological invasions, which in highly urbanised areas are further facilitated by introduction pathways linked to commercial activities. This study provides a risk screening of non-native invasive species for the highly urbanised River Neretva Estuary (Eastern Adriatic Sea: Croatia and Bosnia–Herzegovina). In total, 12 species of non-native aquatic organisms were identified and screened for their invasiveness with the Aquatic Species Invasiveness Screening Kit. Of these species, eight were classified as carrying a high risk of invasiveness under current climate conditions and nine under future climate conditions. Amongst the high-risk species, blue crab Callinectes sapidus has already caused impacts in the risk assessment area, where it also represents an important economic resource. The “horizon” species Pacific oyster Crassostrea gigas and Manila clam Ruditapes philippinarum also carried a high risk of invasiveness, which for the latter species applied under predicted global warming. The present findings will contribute towards preventative management and control measures for the conservation of the natural ecosystem of the River Neretva Estuary whilst accounting for aquatic farming demands. 相似文献
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The distributions of ammonium acetate — extracted (‘exchangeable’) Co, Ni, Cu, Zn, Cd and Pb were determined in alluvial sediments of the Sava River at Novi Beograd (Belgrade aquifer, Yugoslavia). Samples were taken from the river bottom and from three drill-holes in the alluvial formation (in increasing distance from the river-bed). The alluvial samples included the quaternary formation — humified surface layers, sands and clays, as well as some samples from the impervious tertiary layer at about 25 m depth. A combined method for the interpretation of results was introduced in order to obtain a clear insight into the factors of heavy metal distribution within the examined aquifer sequence, including elementary statistical methods, as well as factor analysis. There are no significant correlations between metal concentrations and burial depth, river distance, or lithologic type. The application of factor analysis on the exchangeable metal phase, however, reveals the existence of two sample populations and two dominant ecochemical factors, governing the distribution of heavy metals within the aquifer. One factor representssurface contamination, and the other representsriver water influence, accumulating exchangeable heavy metals within a sharply outlined zone. This zone spreads over most layers in the immediate vicinity of the river, as well as over a few, more distant layers which are at roughly the same level as the river-bed. 相似文献