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401.
Using rules extracted from experience to solve problems in novel situations involves cognitions such as analogical reasoning and language learning and is considered a keystone of humans' unique abilities. Nonprimates, it has been argued, lack such rule transfer. We report that Rattus norvegicus can learn simple rules and apply them to new situations. Rats learned that sequences of stimuli consistent with a rule (such as XYX) were different from other sequences (such as XXY or YXX). When novel stimuli were used to construct sequences that did or did not obey the previously learned rule, rats transferred their learning. Therefore, rats, like humans, can transfer structural knowledge from sequential experiences. 相似文献
402.
O'Doherty A Ruf S Mulligan C Hildreth V Errington ML Cooke S Sesay A Modino S Vanes L Hernandez D Linehan JM Sharpe PT Brandner S Bliss TV Henderson DJ Nizetic D Tybulewicz VL Fisher EM 《Science (New York, N.Y.)》2005,309(5743):2033-2037
Aneuploidies are common chromosomal defects that result in growth and developmental deficits and high levels of lethality in humans. To gain insight into the biology of aneuploidies, we manipulated mouse embryonic stem cells and generated a trans-species aneuploid mouse line that stably transmits a freely segregating, almost complete human chromosome 21 (Hsa21). This "transchromosomic" mouse line, Tc1, is a model of trisomy 21, which manifests as Down syndrome (DS) in humans, and has phenotypic alterations in behavior, synaptic plasticity, cerebellar neuronal number, heart development, and mandible size that relate to human DS. Transchromosomic mouse lines such as Tc1 may represent useful genetic tools for dissecting other human aneuploidies. 相似文献
403.
Himler AG Adachi-Hagimori T Bergen JE Kozuch A Kelly SE Tabashnik BE Chiel E Duckworth VE Dennehy TJ Zchori-Fein E Hunter MS 《Science (New York, N.Y.)》2011,332(6026):254-256
Maternally inherited bacterial symbionts of arthropods are common, yet symbiont invasions of host populations have rarely been observed. Here, we show that Rickettsia sp. nr. bellii swept into a population of an invasive agricultural pest, the sweet potato whitefly, Bemisia tabaci, in just 6 years. Compared with uninfected whiteflies, Rickettsia-infected whiteflies produced more offspring, had higher survival to adulthood, developed faster, and produced a higher proportion of daughters. The symbiont thus functions as both mutualist and reproductive manipulator. The observed increased performance and sex-ratio bias of infected whiteflies are sufficient to explain the spread of Rickettsia across the southwestern United States. Symbiont invasions such as this represent a sudden evolutionary shift for the host, with potentially large impacts on its ecology and invasiveness. 相似文献
404.
Bringa EM Caro A Wang Y Victoria M McNaney JM Remington BA Smith RF Torralva BR Van Swygenhoven H 《Science (New York, N.Y.)》2005,309(5742):1838-1841
Molecular dynamics simulations of nanocrystalline copper under shock loading show an unexpected ultrahigh strength behind the shock front, with values up to twice those at low pressure. Partial and perfect dislocations, twinning, and debris from dislocation interactions are found behind the shock front. Results are interpreted in terms of the pressure dependence of both deformation mechanisms active at these grain sizes, namely dislocation-based plasticity and grain boundary sliding. These simulations, together with new shock experiments on nanocrystalline nickel, raise the possibility of achieving ultrahard materials during and after shock loading. 相似文献
405.
Since the earliest examination of cellular structures, biologists have been fascinated by observing cells using light microscopy. The advent of fluorescent labeling technologies plus the plethora of sophisticated light microscope techniques now available make studying dynamic processes in living cells almost commonplace. For anyone new to this area, however, it can be daunting to decide which techniques or equipment to try. Here, we aim to give a brief overview of the main approaches to live cell imaging, with some mention of their pros and cons. 相似文献
406.
407.
An optimized index for cold tolerance assessment in rice during germination and early seedling stage
Monzón Daisy Leticia Ramirez Cantero Jorge Danielowski Rodrigo da Luz Viviane Kopp Venske Eduardo Mota Monalize Salete da Silva Raissa Martins de Oliveira Victoria Freitas de Oliveira Antonio Costa de Magalhães Júnior Ariano Martins da Maia Luciano Carlos 《Journal of Crop Science and Biotechnology》2023,26(2):243-253
Journal of Crop Science and Biotechnology - Cold tolerance at germination and seedling stage is one of the most seeked traits in Southern Brazilian rice (Oryza sativa L.) cultivars, thus, the... 相似文献
408.
Alexey A. Morozov Grigorii M. Chuiko Victoria V. Yurchenko 《International Aquatic Research》2017,9(3):249-257
Alternation of physiological states during the annual cycle (pre-spawning mobilization, spawning energy loss, post-spawning accumulation of energy reserve, declined metabolic activity during the wintering) occurring in the wide temperature range requires high plasticity of fish defense systems. The article presents a 2-year study of hepatic antioxidant defenses and lipid peroxidation in the temperate cyprinid fish, common bream Abramis brama (L.), in relation to basic annual rhythms, such as photoperiodic and temperature cycling, reproduction and feeding activity. The objective of the study was to evaluate the plasticity of antioxidant defenses in bream under normal conditions throughout the annual cycle, by measuring hepatic antioxidants (superoxide dismutase, catalase, glutathione-S-transferase activities and reduced glutathione concentrations) and products of lipid peroxidation (thiobarbituric acid reactive substances concentrations). The results suggested that hepatic levels of antioxidants in bream varied dramatically during the annual cycle allowing bream to develop necessary adaptation and implement reproduction program. The lowest values of all studied antioxidants were witnessed in the middle of winter. In early spring, antioxidant enzyme activities increased rapidly reaching their maxima in late spring and summer. Toward the end of autumn, enzyme activities were declining toward the levels observed before the ice breakup. Spring–summer up-regulation of antioxidant defenses along with increased lipid peroxidation indicated bream to be experiencing mild oxidative stress. 相似文献
409.
Aleksandra Kvetkina Elena Kostina Irina Gladkikh Victoria Chausova Ekaterina Yurchenko Irina Bakunina Mikhail Pivkin Stanislav Anastyuk Roman Popov Margarita Monastyrnaya Emma Kozlovskaya Marina Isaeva Pavel Dmitrenok Elena Leychenko 《Marine drugs》2021,19(12)
The peculiarities of the survival and adaptation of deep-sea organisms raise interest in the study of their metabolites as promising drugs. In this work, the hemolytic, cytotoxic, antimicrobial, and enzyme-inhibitory activities of tentacle extracts from five species of sea anemones (Cnidaria, orders Actiniaria and Corallimorpharia) collected near the Kuril and Commander Islands of the Far East of Russia were evaluated for the first time. The extracts of Liponema brevicorne and Actinostola callosa demonstrated maximal hemolytic activity, while high cytotoxic activity against murine splenocytes and Ehrlich carcinoma cells was found in the extract of Actinostola faeculenta. The extracts of Corallimorphus cf. pilatus demonstrated the greatest activity against Ehrlich carcinoma cells but were not toxic to mouse spleen cells. Sea anemones C. cf. pilatus and Stomphia coccinea are promising sources of antimicrobial and antifungal compounds, being active against Gram-positive bacteria Bacillus subtilis, Staphylococcus aureus, and yeast Candida albicans. Moreover, all sea anemones contain α-galactosidase inhibitors. Peptide mass fingerprinting of L. brevicorne and C. cf. pilatus extracts provided a wide range of peptides, predominantly with molecular masses of 4000–5900 Da, which may belong to a known or new structural class of toxins. The obtained data allow concluding that deep-sea anemones are a promising source of compounds for drug discovery. 相似文献
410.
Fetters Kyle Rosen Gunther Kirtay Victoria Chadwick Bart Conder Jason Sacks Victoria Paris Grover Melissa Magar Victor 《Journal of Soils and Sediments》2020,20(1):204-219
Purpose
Monitored natural recovery (MNR) combined with a thin-layer cap (TLC), often referred to as enhanced monitored natural recovery (EMNR), has the potential to accelerate and improve the effectiveness of MNR as a remedial strategy while minimizing widespread disturbance to the existing habitat. This study evaluated the effectiveness of a nominal 15-cm thin-layer sand cap as an EMNR remedial strategy to address sediments that were moderately contaminated with the chlorinated pesticide dichlorodiphenyltrichloroethane and its derivatives, collectively DDX.
Materials and methodsPhysical, chemical, and biological measurements were conducted pre-remedy placement and 2, 14, and 25 months post-placement. Measurements were used to evaluate (1) TLC stability; (2) bottom-up mixing of the TLC; (3) advection through the TLC; (4) characteristics of newly deposited sediment atop the EMNR layer compared to pre-remedy surface sediment conditions; (5) changes in contaminant bioavailability; and (6) physical impacts to the benthic community.
Results and discussionSignificant reductions were observed from measurements conducted pre- and post-placement in surface sediment (84–97%), porewater (33–75%), and tissue concentrations (Lumbriculus variegatus deployed in situ) (72–82%). A 63 to 72% decrease in DDX depositional mass flux also was observed. Multiple lines of evidence indicated that the TLC material remained stable. Deposition of suspended material with low concentrations of DDX influenced low concentrations in the surface sediments. No adverse effects were observed on the benthic invertebrate community after TLC placement, and ecological metrics indicated increases in benthic community health, even in the short time period (2 months) following TLC placement.
ConclusionsThis demonstration showed that EMNR can be effective at reducing biological exposure in surface sediments while minimizing short-term disturbances to benthic communities at sites where MNR is a remedy option, but natural deposition rates are inadequate to achieve cleanup goals within a reasonable timeframe.
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