Rule learning by rats     

Murphy RA  Mondragón E  Murphy VA 《Science (New York, N.Y.)》2008,319(5871):1849-1851

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   

An aneuploid mouse strain carrying human chromosome 21 with Down syndrome phenotypes     

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   

Rapid spread of a bacterial symbiont in an invasive whitefly is driven by fitness benefits and female bias     

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   

Ultrahigh strength in nanocrystalline materials under shock loading     

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   

Light microscopy techniques for live cell imaging     

Stephens DJ  Allan VJ 《Science (New York, N.Y.)》2003,300(5616):82-86

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   

Observing others: multiple action representation in the frontal lobe     

Nelissen K  Luppino G  Vanduffel W  Rizzolatti G  Orban GA 《Science (New York, N.Y.)》2005,310(5746):332-336

Observation of actions performed by others activates monkey ventral premotor cortex, where action meaning, but not object identity, is coded. In a functional MRI (fMRI) study, we investigated whether other monkey frontal areas respond to actions performed by others. Observation of a hand grasping objects activated four frontal areas: rostral F5 and areas 45B, 45A, and 46. Observation of an individual grasping an object also activated caudal F5, which indicates different degrees of action abstraction in F5. Observation of shapes activated area 45, but not premotor F5. Convergence of object and action information in area 45 may be important for full comprehension of actions.  相似文献   

Annual variations in hepatic antioxidant defenses and lipid peroxidation in a temperate fish,common bream Abramis brama (L.)     

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   

Contemporary climate infuence on variability patterns of Anadenanthera colubrina var. cebil,a key species in seasonally dry tropical forestsOA     

María Victoria García  María Eugenia Barrandeguy  Kathleen Prinz 《林业研究》2022,33(1):89-101

The distribution of many plant species has been shaped by climate changes, and their current phenotypic and genetic variability refect microclimatically suitable habitats. This study relates contemporary climate to variability patterns of phenotypic traits and molecular markers in the Argentinean distribution of Anadenanthera colubrina var.cebil, as well as to identify the most relevant phenotypic trait or molecular marker associated with those patterns.Individuals from four populations in both ...  相似文献   

Modelling relative abundance of Oligoryzomys flavescens,an Orthohantavirus reservoir,in an endemic hantavirus pulmonary syndrome zone     

María Victoria Vadell  Carlos González Fischer  Mariano Codesido  Aníbal Carbajo  David Bilenca  Isabel E. Gómez Villafañe 《Zoonoses and public health》2023,70(1):13-21

Hantavirus pulmonary syndrome (HPS) is a zoonotic emerging infectious disease caused by New World orthohantaviruses (family Hantaviridae) hosted by rodents of the family Cricetidae. In Argentina, one of its main hosts is the sigmodontine rodent Oligoryzomys flavescens, a widely distributed mouse of the Pampas, Delta and Espinal ecoregions of central-east Argentina. Because the abundance of the reservoir and its proportion in the rodent community affects both virus prevalence and human exposure risk, its estimation throughout its known geographical distribution is of key importance for the design of public health strategies to prevent HPS. The aim of this study was therefore to model the relative abundance of O. flavescens in most of the Pampas ecoregion within Buenos Aires Province, Argentina, where hantavirus pulmonary syndrome is endemic. To do this we used owl-pellet samples collected between 2006 and 2008 from 51 sites distributed throughout most of Buenos Aires province. Mammalian prey in each pellet was identified to the lowest possible taxonomic level by examination of the skulls, dentaries and molars. We modelled the frequency of O. flavescens found in each sample as a function of climatic, environmental, and topographic data of each site. The two best models were applied to a Geo referential Information System to build maps of estimated frequency (as a proxy of relative abundance) within Buenos Aires province. Estimated relative abundance of O. flavescens in Buenos Aires province was significantly associated with annual mean temperature, annual precipitation and presence of freshwater bodies, and varied among sub-regions, with the Inland and Rolling Pampas being the regions with highest frequencies. Knowing in which areas O. flavescens abundance is expected to be higher can be used to concentrate limited sanitary efforts in those areas that are most needed in order to reduce transmission and increase detection.  相似文献   

Comparative Studies on Composition and Distribution of Phenolic Acids in Cereal Grain Botanical Fractions     

Victoria U. Ndolo  Trust Beta 《Cereal Chemistry》2014,91(5):522-530

The phenolic acid composition and concentration of four manually separated fractions (pericarp, aleurone layer, germ, and endosperm fractions) as well as whole grains of yellow corn, wheat, barley, and oats were analyzed by HPLC‐MS/MS following microwave‐assisted alkaline aqueous extraction. Phenolic acid compositions in whole grains and their fractions were similar, with minor differences among the grain fractions. Significant differences (P < 0.05), however, were observed in phenolic acid concentrations among cereal types, within cereal varieties, and among grain fractions, with yellow corn exhibiting the highest values. The concentrations of p‐coumaric and syringic acid in the pericarp were 10‐ to 15‐fold and 6‐ to 10‐fold higher, respectively, in yellow corn than in wheat, barley, and oats. In the aleurone layer, sinapic and vanillic acids in yellow corn were about 8‐ and 30‐fold more than in wheat. The germ fraction of wheat had 1.8 times more syringic acid than yellow corn germ. Grain fractions, excluding endosperm, had enhanced levels of phenolic acids compared with whole grain. Sinapic acid was more concentrated in the pericarp and germ of wheat, whereas isoferulic acid was concentrated in the germ of purple barley. Syringic and vanillic acids were concentrated in the pericarp and sinapic acid in the aleurone layer of yellow corn. These findings are important in understanding the composition and distribution of phenolic acids, and they act as a guide in identification of grain fractions for use as food ingredients. In addition, yellow corn fractions (aleurone and pericarp) may be potential alternative phenolic‐rich functional food ingredients in grain‐based food products.  相似文献