Geology. An uncertain future for soil carbon   总被引：1，自引：0，他引：1  

Trumbore SE  Czimczik CI 《Science (New York, N.Y.)》2008,321(5895):1455-1456

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Failure of bone marrow cells to transdifferentiate into neural cells in vivo     

Castro RF  Jackson KA  Goodell MA  Robertson CS  Liu H  Shine HD 《Science (New York, N.Y.)》2002,297(5585):1299

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Bypass of DNA lesions generated during anticancer treatment with cisplatin by DNA polymerase eta     

Alt A  Lammens K  Chiocchini C  Lammens A  Pieck JC  Kuch D  Hopfner KP  Carell T 《Science (New York, N.Y.)》2007,318(5852):967-970

DNA polymerase eta (Pol eta) is a eukaryotic lesion bypass polymerase that helps organisms to survive exposure to ultraviolet (UV) radiation, and tumor cells to gain resistance against cisplatin-based chemotherapy. It allows cells to replicate across cross-link lesions such as 1,2-d(GpG) cisplatin adducts (Pt-GG) and UV-induced cis-syn thymine dimers. We present structural and biochemical analysis of how Pol eta copies Pt-GG-containing DNA. The damaged DNA is bound in an open DNA binding rim. Nucleotidyl transfer requires the DNA to rotate into an active conformation, driven by hydrogen bonding of the templating base to the dNTP. For the 3'dG of the Pt-GG, this step is accomplished by a Watson-Crick base pair to dCTP and is biochemically efficient and accurate. In contrast, bypass of the 5'dG of the Pt-GG is less efficient and promiscuous for dCTP and dATP as a result of the presence of the rigid Pt cross-link. Our analysis reveals the set of structural features that enable Pol eta to replicate across strongly distorting DNA lesions.  相似文献   

Synchrony dynamics during initiation, failure, and rescue of the segmentation clock     

Riedel-Kruse IH  Müller C  Oates AC 《Science (New York, N.Y.)》2007,317(5846):1911-1915

The "segmentation clock" is thought to coordinate sequential segmentation of the body axis in vertebrate embryos. This clock comprises a multicellular genetic network of synchronized oscillators, coupled by intercellular Delta-Notch signaling. How this synchrony is established and how its loss determines the position of segmentation defects in Delta and Notch mutants are unknown. We analyzed the clock's synchrony dynamics by varying strength and timing of Notch coupling in zebra-fish embryos with techniques for quantitative perturbation of gene function. We developed a physical theory based on coupled phase oscillators explaining the observed onset and rescue of segmentation defects, the clock's robustness against developmental noise, and a critical point beyond which synchrony decays. We conclude that synchrony among these genetic oscillators can be established by simultaneous initiation and self-organization and that the segmentation defect position is determined by the difference between coupling strength and noise.  相似文献   

稻瘟菌株CH63和TH16杂交后代毒性变异及其无毒基因组成   总被引：1，自引：0，他引：1  

王艳丽  KAYE Claudia  ADREIT Henri  关小波  沈瑛  THARREAU Didier 《中国农业科学》2005,38(12):2428-2433

 报道了两个稻瘟菌株CH63和TH16的杂交后代在36个水稻品种上的致病性分离、遗传分析以及无毒基因组成的分析结果。78个子囊孢子菌株中呈现显著的致病性分离，共出现71种致病类型，在不同品种上分别出现1∶1、1∶3、3∶1、1∶7、1∶15和15∶1等的无毒性/毒性分离，表明供试菌株对不同品种的无毒性/毒性是一个或多个基因控制的。遗传学分析结果表明，亲本菌株对不同品种的无毒性/毒性控制存在多种类型。菌株CH63对品种K 59(Pi-t)、中98－18、特特普、T 641、C 102 TTP(Pi-4)、C 101 TTP 6、E No.11、农虎6号、C 101 PKT(Pi-4a)、C 105 TTP-1(Pi-4)、中156 和中98－19分别持有1个无毒基因；对品种1461选、6392选、麻谷泰引1号、Lemont、宫崎7号、Vandana、长香稻、青珍8号和珍优3号分别持有2个无毒基因；对于品种草笛（Pi-k）、品种20中－1 、C 104 LAC(Pi-1)、C 103 TTP(Pi-1+1b)、K 3(Pi-kh)、梅雨明 (Pi-km)和东农363分别持有2个以上无毒基因；亲本菌株对于品种四丰43、珍龙13、C101LAC和20中－2分别持有2个无毒基因，关东51、欧244持有2个以上的无毒基因，但因亲本菌株对品种的致病型一致，难以判断控制菌株对品种非亲和性的基因来源。  相似文献   

Glutamatergic and dopaminergic neurons mediate anxiogenic and anxiolytic effects of CRHR1     

Refojo D  Schweizer M  Kuehne C  Ehrenberg S  Thoeringer C  Vogl AM  Dedic N  Schumacher M  von Wolff G  Avrabos C  Touma C  Engblom D  Schütz G  Nave KA  Eder M  Wotjak CT  Sillaber I  Holsboer F  Wurst W  Deussing JM 《Science (New York, N.Y.)》2011,333(6051):1903-1907

The corticotropin-releasing hormone receptor 1 (CRHR1) critically controls behavioral adaptation to stress and is causally linked to emotional disorders. Using neurochemical and genetic tools, we determined that CRHR1 is expressed in forebrain glutamatergic and γ-aminobutyric acid-containing (GABAergic) neurons as well as in midbrain dopaminergic neurons. Via specific CRHR1 deletions in glutamatergic, GABAergic, dopaminergic, and serotonergic cells, we found that the lack of CRHR1 in forebrain glutamatergic circuits reduces anxiety and impairs neurotransmission in the amygdala and hippocampus. Selective deletion of CRHR1 in midbrain dopaminergic neurons increases anxiety-like behavior and reduces dopamine release in the prefrontal cortex. These results define a bidirectional model for the role of CRHR1 in anxiety and suggest that an imbalance between CRHR1-controlled anxiogenic glutamatergic and anxiolytic dopaminergic systems might lead to emotional disorders.  相似文献   

Competencies: a cure for pre-med curriculum     

Anderson WA  Amasino RM  Ares M  Banerjee U  Bartel B  Corces VG  Drennan CL  Elgin SC  Epstein IR  Fanning E  Guillette LJ  Handelsman J  Hatfull GF  Hoy RR  Kelley D  Leinwand LA  Losick R  Lu Y  Lynn DG  Neuhauser C  O'Dowd DK  Olivera T  Pevzner P  Richards-Kortum RR  Rine J  Sah RL  Strobel SA  Walker GC  Walt DR  Warner IM  Wessler S  Willard HF  Zare RN 《Science (New York, N.Y.)》2011,334(6057):760-761

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Diabetes and hypertension increases in a society with abdominal obesity: results of the Mexican National Health Survey 2000   总被引：5，自引：0，他引：5  

Sánchez-Castillo CP  Velásquez-Monroy O  Lara-Esqueda A  Berber A  Sepulveda J  Tapia-Conyer R  James WP 《Public health nutrition》2005,8(1):53-60

OBJECTIVES: To determine the prevalences of overweight, obesity, type 2 diabetes mellitus (DM) and hypertension (HT) in the Mexican population and compare them with those of a previous Mexican urban survey and an American survey. DESIGN: A structured, randomised, nationally representative Mexican sample was compared with a 1993 Mexican urban survey and the US Third National Health and Nutrition Examination Survey (NHANES III) of non-Hispanic Whites. SETTING: The Mexican National Health Survey 2000.Subjects: Subjects were 12,856 men and 28,332 women, aged 20-69 years, who had their body weight, height, waist circumference (WC), blood pressure and fasting capillary blood glucose measured. RESULTS: Mexican adult men and women had a high prevalence of overweight (41.3 and 36.3%, respectively) and obesity (19.4 and 29.0%, respectively), similar to those in the USA in 1988-1992 and exceeding those of the 1993 Mexican survey. The prevalence of HT was 33.3% in men and 25.6% in women, with inferred DM rates of 5.6 and 9.7%, respectively. Abdominal obesity affected 46.3% of men (WC>or=94 cm) and 81.4% of women (WC>or=80 cm). There was a high prevalence of abdominal obesity in normal-weight women, with co-morbidities relating better to WC than to body mass index (BMI) in both sexes. Rates of DM and HT exceeded US rates on a comparable BMI or WC basis in adults aged <50 years. CONCLUSION: The high prevalence of obesity and abdominal obesity in Mexicans is associated with markedly increased prevalences of DM and HT to levels comparable with, or even higher than, those in NHANES III of non-Hispanic Whites.  相似文献   

Compositional and moisture content effects on the biodegradability of zein/ethylcellulose films     

Romero-Bastida CA  Flores-Huicochea E  Martin-Polo MO  Velazquez G  Torres JA 《Journal of agricultural and food chemistry》2004,52(8):2230-2235

The effect of moisture content and film composition on biodegradability is the focus of this study. Flexible films were first characterized for the effect on water sorption isotherms of relative humidity, temperature, zein content, and the addition of the plasticizers stearic acid, poly(ethylene glycol), or etoxylated ricine oil. Zein/ethylcellulose (EC) mixture films had a behavior between that for pure zein and EC films, which had the lowest water sorption. For films with plasticizer, the lowest water sorption at 25 degrees C was observed for those with stearic acid. Biodegradability of zein/EC films, evaluated using bacterial cultures selected for their zein proteolytic activity and isolated from a local solid waste landfill and a lagoon, showed no plasticizer effect even though its effect on moisture content was significant. Large differences were observed at different film zein concentration with the highest biodegradability for 100% zein. However, biodegradability did not mimic the water sorption behavior of zein/EC mixture films.  相似文献   

Characterization of selenium species in Brazil nuts by HPLC-ICP-MS and ES-MS     

Vonderheide AP  Wrobel K  Kannamkumarath SS  B'Hymer C  Montes-Bayón M  Ponce De León C  Caruso JA 《Journal of agricultural and food chemistry》2002,50(20):5722-5728

Brazil nuts have been classified as the foodstuffs that contain the highest level of unadulterated selenium, an essential trace element that appears to prevent cancer. To date, characterization of the selenium species in brazil nuts has not yet been investigated. In this work, various sample preparation approaches, including microwave extractions and enzymatic treatments, are examined with the goal of species preservation and subsequent selenium speciation; of these approaches, an enzymatic treatment with Proteinase K proved most effective. High-performance liquid chromatography (HPLC) separation strategies and inductively coupled plasma mass spectrometry (ICP-MS) detection schemes will also be presented. Extracts are evaluated against available standards for the commercially obtainable seleno-amino acids, selenomethionine (SeMet), selenoethionine (SeEt), and selenocystine (SeCys); selenomethionine was demonstrated to be the most abundant of these seleno-amino acids. Further characterization of unidentified selenium-containing peaks is attempted by the employment of several procedures, including electrospray-mass spectrometry (ES-MS). A peptide structure was identified; however, this was considered a tentative proposal due to the large background produced by the extremely complicated brazil nut matrix.  相似文献