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91.
The production and action of immunoregulatory cytokines, including interleukin-1 (IL-1), are inhibited by glucocorticoid hormones in vivo and in vitro. Conversely, glucocorticoid blood levels were increased by factors released by human leukocytes exposed to Newcastle disease virus preparations. This activity was neutralized by an antibody to IL-1. Therefore the capacity of IL-1 to stimulate the pituitary-adrenal axis was tested. Administration of subpyrogenic doses of homogeneous human monocyte-derived IL-1 or the pI 7 form of human recombinant IL-1 to mice and rats increased blood levels of adrenocorticotropic hormone (ACTH) and glucocorticoids. Another monokine, tumor necrosis factor, and the lymphokines IL-2 and gamma-interferon had no such effects when administered in doses equivalent to or higher than those of IL-1. The stimulatory effect of IL-1 on the pituitary-adrenal axis seemed not to be mediated by the secondary release of products from mature T lymphocytes since IL-1 was endocrinologically active when injected into athymic nude mice. These results strongly support the existence of an immunoregulatory feedback circuit in which IL-1 acts as an afferent and glucocorticoid as an efferent hormonal signal. 相似文献
92.
Hafezparast M Klocke R Ruhrberg C Marquardt A Ahmad-Annuar A Bowen S Lalli G Witherden AS Hummerich H Nicholson S Morgan PJ Oozageer R Priestley JV Averill S King VR Ball S Peters J Toda T Yamamoto A Hiraoka Y Augustin M Korthaus D Wattler S Wabnitz P Dickneite C Lampel S Boehme F Peraus G Popp A Rudelius M Schlegel J Fuchs H Hrabe de Angelis M Schiavo G Shima DT Russ AP Stumm G Martin JE Fisher EM 《Science (New York, N.Y.)》2003,300(5620):808-812
Degenerative disorders of motor neurons include a range of progressive fatal diseases such as amyotrophic lateral sclerosis (ALS), spinal-bulbar muscular atrophy (SBMA), and spinal muscular atrophy (SMA). Although the causative genetic alterations are known for some cases, the molecular basis of many SMA and SBMA-like syndromes and most ALS cases is unknown. Here we show that missense point mutations in the cytoplasmic dynein heavy chain result in progressive motor neuron degeneration in heterozygous mice, and in homozygotes this is accompanied by the formation of Lewy-like inclusion bodies, thus resembling key features of human pathology. These mutations exclusively perturb neuron-specific functions of dynein. 相似文献
93.
Terracciano A Abdel-Khalek AM Adám N Adamovová L Ahn CK Ahn HN Alansari BM Alcalay L Allik J Angleitner A Avia MD Ayearst LE Barbaranelli C Beer A Borg-Cunen MA Bratko D Brunner-Sciarra M Budzinski L Camart N Dahourou D De Fruyt F de Lima MP del Pilar GE Diener E Falzon R Fernando K Ficková E Fischer R Flores-Mendoza C Ghayur MA Gülgöz S Hagberg B Halberstadt J Halim MS Hrebícková M Humrichouse J Jensen HH Jocic DD Jónsson FH Khoury B Klinkosz W Knezević G Lauri MA Leibovich N Martin TA 《Science (New York, N.Y.)》2005,310(5745):96-100
Most people hold beliefs about personality characteristics typical of members of their own and others' cultures. These perceptions of national character may be generalizations from personal experience, stereotypes with a "kernel of truth," or inaccurate stereotypes. We obtained national character ratings of 3989 people from 49 cultures and compared them with the average personality scores of culture members assessed by observer ratings and self-reports. National character ratings were reliable but did not converge with assessed traits. Perceptions of national character thus appear to be unfounded stereotypes that may serve the function of maintaining a national identity. 相似文献
94.
Radio waves from the sun were detected 50 years ago, but the microwave detection of other single solar-type stars has remained a challenge. Here, the discovery of four solar-type radio stars is reported. These "solar twin" G stars are radio sources up to 3000 times stronger than the quiet sun. The microwaves most likely originate from a large number of relativistic electrons, possibly produced along with coronal heating, a process that is not understood. Two of the stars are younger than the sun and rotate more rapidly; the dynamo process in the stellar interior is therefore presumably more vigorous, resulting in enhanced coronal activity. One of the detections, however, is an old, metal-deficient G dwarf. 相似文献
95.
Carmen Diana Deere 《Agriculture and Human Values》1993,10(3):35-51
Cuba's National Food Program aims to assure its population a minimum degree of food security during the current period of transition from dependency upon the ex-Socialist trading bloc. A number of important elements of the Food Program, however, were conceived before the demise of COMECON in an effort to deepen food import substitution. This paper reviews the degree of Cuba's food import dependence before the breakup of the Socialist bloc, the initial targets of the National Food Program, and how these have been modified due to the severe reduction in Cuba's normal level of imports of petroleum and other agricultural inputs. It is argued that Cuba's reliance upon scientific advances combined with a return to traditional, ecologically-benign agricultural practices and large-scale labor mobilizations have allowed it to overcome a drastic shortfall in production as a result of the reduced level of imports of modern agricultural inputs. At the same time, it has been exceedingly difficult for the country to maintain production levels at the trend of the late 1980s or to continue to aspire to meet the ambitious targets of the initial Food Program plan.Carmen Diana Deere is Professor of Economics and Director of Latin American Studies at the University of Massachusetts, Amherst. The author has been carrying out field research in Cuba since the mid 1980s, in recent years, in a collaborative study with colleagues at the University of Havana. She is grateful to Carollee Bengelsdorf, Ernel Gonzales, Cristobal Kay, Mieke Meurs, Lupo Nuñez, Niurka Pérez, Brian Pollitt, and José Luís Rodríguez for their comments on earlier drafts. This article is an updated and condensed version of Institute of Social Studies Working Paper Series #124 (The Hague, 1992). 相似文献
96.
97.
A global overview of dam-based impacts on large river systems shows that over half (172 out of 292) are affected by dams, including the eight most biogeographically diverse. Dam-impacted catchments experience higher irrigation pressure and about 25 times more economic activity per unit of water than do unaffected catchments. In view of projected changes in climate and water resource use, these findings can be used to identify ecological risks associated with further impacts on large river systems. 相似文献
98.
Gustavo R. Rodríguez Javier H. Pereira da Costa Damian D. Tomat Guillermo R. Pratta Roxana Zorzoli Liliana A. Picardi 《Scientia Horticulturae》2011
The tomato fruit quality results of biochemical and physiological changes that occur during the ripening process. Although, the pericarp total protein profiles are less polymorphic than DNA-based markers the polymorphism in those could be directly associated with fruit quality traits. The aim of this work was to identify associations between polymorphic polypeptides from fruit pericarp at two ripening stages and fruit quality traits evaluated in two segregating populations of tomato. A cross between a normal ripening cultivar of Solanum lycopersicum (C, Caimanta) and a genotype carrying the nor (non ripening) gene (N) as well as a cross between Caimanta and a cherry type tomato of S. lycopersicum var. cerasiforme (Ce) showed genetic variance for several fruit quality traits such as fruit weight, shape, solids soluble content, acidity, color and fruit shelf life. The quantitative variations observed at phenotypic level had correspondence with the polymorphism detected in the protein profiles. Indeed, the polymophic polypeptides associated with quality fruit traits and fruit shelf life would be useful to assist tomato breeding programs as protein molecular markers. 相似文献
99.
Hans Jacquemyn Carmen Van Mechelen Rein Brys Olivier Honnay 《Biological conservation》2011,(1):416-422
Calcareous grasslands, most of which are man made and therefore depend on some kind of human interference for their maintenance, are among the most species-rich communities on Earth at a small scale. For many centuries, most of these grasslands have been used as extensive pasture. However, after 1900, and particularly from 1940 onwards, livestock grazing has declined throughout Europe leading to the abandonment of low intensity grasslands over large areas. To conserve the remaining grasslands or to restore recently abandoned grasslands, better insights about the effects of grassland management on above and belowground species diversity are needed. Here, we describe the results of an 11-year experiment to investigate the role of grassland management (grazing, mowing and abandonment) in determining species composition and diversity both in the aboveground vegetation and the seed bank of a calcareous grassland in Belgium. Species diversity declined by about 60% 11 years after abandonment, from 29 species m−2 to as few as 12 species m−2. Plots that were grazed remained constant in species richness, whereas mown sites lost about 20% of their original species. Abandoned plots were largely dominated by a few grass species, in particular Festuca rubra. Concomitant with changes in the aboveground vegetation, both the number of species found in the seed bank and seed density (number of seeds m−2) had changed significantly 11 years after abandonment. Species diversity and seed density were significantly lower in abandoned plots than in grazed or mown plots. We conclude that abandonment of calcareous grasslands may lead to rapid decline of plant species diversity both in the aboveground vegetation and in the seed bank. As a result, seed banks probably have a limited role to play in the restoration of recently abandoned grasslands. 相似文献
100.
Lara Vilar del Hoyo M. Pilar Martín Isabel F. Javier Martínez Vega 《European Journal of Forest Research》2011,130(6):983-996
About 90% of the wildland fires occurred in Southern Europe are caused by human activities. In spite of these figures, the
human factor hardly ever appears in the definition of operational fire risk systems due to the difficulty of characterising
it. This paper describes two spatially explicit models that predict the probability of fire occurrence due to human causes
for their integration into a comprehensive fire risk–mapping methodology. A logistic regression technique at 1 × 1 km grid
resolution has been used to obtain these models in the region of Madrid, a highly populated area in the centre of Spain. Socio-economic
data were used as predictive variables to spatially represent anthropogenic factors related to fire risk. Historical fire
occurrence from 2000 to 2005 was used as the response variable. In order to analyse the effects of the spatial accuracy of
the response variable on the model performance (significant variables and classification accuracy), two different models were
defined. In the first model, fire ignition points (x, y coordinates) were used as response variable. This model was compared with another one (Kernel model) where the response variable
was the density of ignition points and was obtained through a kernel density interpolation technique from fire ignition points
randomly located within a 10 × 10 km grid, which is the standard spatial reference unit established by the Spanish Ministry
of Environment, Rural and Marine Affairs to report fire location in the national official statistics. Validation of both models
was accomplished using an independent set of fire ignition points (years 2006–2007). For the validation, we used the area
under the curve (AUC) obtained by a receiver-operating system. The first model performs slightly better with a value of AUC
of 0.70 as opposed to 0.67 for the Kernel model. Wildland–urban interface was selected by both models with high relative importance. 相似文献