Genotype by environment effects and selection for drought tolerance in tropical maize. II. Three-mode pattern analysis     

Scott C. Chapman  José Crossa  Kaye E. Basford  Pieter M. Kroonenberg 《Euphytica》1997,95(1):11-20

A selection program in three tropical maize populations aimed to improve tolerance of mid-season to late season drought environments while maintaining grain yield (GY) potential. The selection process employed other attributes that included maintaining a constant anthesis date (AD) and, under drought, shortening the anthesis-silking interval (ASI) and increasing ear number per plant (EPP). Three-mode (genotypes × environments × attributes) pattern analysis, which consists of clustering and ordination, should be able to collectively interpret these changes from ten evaluation trials. Mixture maximum likelihood clustering identified four groups that indicated the populations' performance had changed with selection. Groups containing the advanced cycles of selection were higher yielding in most environments and had lower ASI and higher EPP, particularly in drought environments. Check entries with no selection for drought tolerance remained grouped with the initial cycles of selection. A 3 × 2 × 3 (genotypes by environments by attributes) principal component model explained 70% of the variation. For the first environmental component, ASI was shown to be highly negatively correlated with both GY and EPP while anthesis date (AD) was virtually uncorrelated with other traits. The second environmental component (explaining 10% of the variation) contrasted droughted and well-watered environments and showed that EPP and GY were better indicators of this contrast (in terms of changes in population performance) than were AD or ASI. Three-mode analysis demonstrated that improvements with selection occurred in both droughted and well-watered environments and clearly summarised the overall success of the breeding program. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Bottom-up dependent gating of frontal signals in early visual cortex     

Ekstrom LB  Roelfsema PR  Arsenault JT  Bonmassar G  Vanduffel W 《Science (New York, N.Y.)》2008,321(5887):414-417

The frontal eye field (FEF) is one of several cortical regions thought to modulate sensory inputs. Moreover, several hypotheses suggest that the FEF can only modulate early visual areas in the presence of a visual stimulus. To test for bottom-up gating of frontal signals, we microstimulated subregions in the FEF of two monkeys and measured the effects throughout the brain with functional magnetic resonance imaging. The activity of higher-order visual areas was strongly modulated by FEF stimulation, independent of visual stimulation. In contrast, FEF stimulation induced a topographically specific pattern of enhancement and suppression in early visual areas, but only in the presence of a visual stimulus. Modulation strength depended on stimulus contrast and on the presence of distractors. We conclude that bottom-up activation is needed to enable top-down modulation of early visual cortex and that stimulus saliency determines the strength of this modulation.  相似文献   

Do neurons predict the future?     

Roelfsema PR 《Science (New York, N.Y.)》2002,295(5553):227

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Molecular biology. When a part is as good as the whole     

deHaseth PL  Nilsen TW 《Science (New York, N.Y.)》2004,303(5662):1307-1308

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The genomic sequence of the accidental pathogen Legionella pneumophila     

Chien M  Morozova I  Shi S  Sheng H  Chen J  Gomez SM  Asamani G  Hill K  Nuara J  Feder M  Rineer J  Greenberg JJ  Steshenko V  Park SH  Zhao B  Teplitskaya E  Edwards JR  Pampou S  Georghiou A  Chou IC  Iannuccilli W  Ulz ME  Kim DH  Geringer-Sameth A  Goldsberry C  Morozov P  Fischer SG  Segal G  Qu X  Rzhetsky A  Zhang P  Cayanis E  De Jong PJ  Ju J  Kalachikov S  Shuman HA  Russo JJ 《Science (New York, N.Y.)》2004,305(5692):1966-1968

We present the genomic sequence of Legionella pneumophila, the bacterial agent of Legionnaires' disease, a potentially fatal pneumonia acquired from aerosolized contaminated fresh water. The genome includes a 45-kilobase pair element that can exist in chromosomal and episomal forms, selective expansions of important gene families, genes for unexpected metabolic pathways, and previously unknown candidate virulence determinants. We highlight the genes that may account for Legionella's ability to survive in protozoa, mammalian macrophages, and inhospitable environmental niches and that may define new therapeutic targets.  相似文献   

Risk factors and clinical presentation of cats with feline idiopathic cystitis     

Defauw PA  Van de Maele I  Duchateau L  Polis IE  Saunders JH  Daminet S 《Journal of Feline Medicine and Surgery》2011,13(12):967-975

Feline idiopathic cystitis (FIC) is the most common cause of feline lower urinary tract disease (FLUTD). This retrospective, case-controlled study evaluated possible risk factors associated with FIC and compared different clinical presentations in 64 cats with FIC. Several risk factors known to be involved in FLUTD were identified as playing a role in FIC. Of the stressful situations considered, most did not occur with increased frequency in cats with FIC compared to controls, except for a house move. The presence of pyuria, haematuria and an increased urine protein:creatinine ratio were significantly higher in obstructed males compared with non-obstructed males. An obstruction was significantly more likely in cats with struvite crystalluria compared with cats without struvite crystalluria. These findings suggest that urethral plugs might be an important cause or contributing factor of obstruction in FIC. Episodes of FIC seem to occur mainly in susceptible cats in combination with a deficient environment.  相似文献   

Modulation of hepatic drug metabolizing enzymes and oxidative status by rooibos (Aspalathus linearis) and Honeybush (Cyclopia intermedia), green and black (Camellia sinensis) teas in rats   总被引：1，自引：0，他引：1  

Marnewick JL  Joubert E  Swart P  Van Der Westhuizen F  Gelderblom WC 《Journal of agricultural and food chemistry》2003,51(27):8113-8119

Rooibos and honeybush teas significantly (P < 0.05) enhanced the activity of cytosolic glutathione S-transferase alpha. A significant (P < 0.05) to marginal (P < 0.1) increase in the activity of the microsomal UDP-glucuronosyl transferase was obtained with unprocessed rooibos and honeybush teas, respectively. Oxidized glutathione (GSSG) levels were significantly (P < 0.05) reduced in the liver of all tea treated rats while reduced glutathione (GSH) was markedly increased in the liver of the herbal tea treated rats. These changes resulted in a significant (P < 0.05) increase in the GSH/GSSG ratio by the unprocessed, processed rooibos and unprocessed honeybush teas. Green and black teas markedly to significantly decreased the oxygen radical absorbance capacity in liver homogenates, respectively. Modulation of phase II drug metabolizing enzymes and oxidative status in the liver may be important events in the protection against adverse effects related to mutagenesis and oxidative damage.  相似文献   

A rapid quantitative bioassay for the determination of biologically available bromacil in soils     

Paul H. Bennett  Pieter R. De Beer 《Pest management science》1984,15(5):425-430

A simple rapid bioassay is described for the determination of biologically available bromacil residues in soils. A clear aqueous extract was made from a soil fortified with a known amount of the herbicide, and similar extracts were made from samples of soil taken from plots that had been sprayed with a bromacil formulation at a rate of 4 kg ha⁻¹. Samples of these extracts were added to a suspension of the unicellular green alga Selenastrum capricornutum. The net photosynthetic oxygen production by the alga was then measured using an oxygen electrode. The results were expressed as a percentage of the oxygen production by a control suspension. The concentration of biologically available bromacil was determined by reference to a previously established dose-response curve of the percentage reduction in oxygen production against bromacil concentration. The accuracy of this bioassay was determined by comparing the results with those obtained using capillary gas-liquid chromatography. The results obtained by the two different methods showed good agreement.  相似文献   

A study of the epidermal structures of the miracidia of Calicophoron calicophorum (Fischoeder, 1901) N?smark, 1937 and Paramphistomum microbothrium (Fischoeder, 1901)     

P J Swart 《The Onderstepoort journal of veterinary research》1967,34(1):129-136

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Parasites in sheep grazing on Kikuyu (Pennisetum clandestinum) pastures in the winter rainfall region     

R K Reinecke  R Kirkpatrick  L Swart  A M Kriel  F Frank 《The Onderstepoort journal of veterinary research》1987,54(1):27-38

Regular worm counts were done post-mortem on sheep that had grazed on Kikuyu pastures at the Elsenburg Research Station near Stellenbosch, a winter rainfall region. Major species were Trichostrongylus colubriformis, Trichostrongylus axei, while Ostertagia circumcincta was usually present in large numbers. Minor species were Haemonchus contortus, Nematodirus spathiger, Dictyocaulus filaria, Oesophagostomum venulosum, Trichuris spp., Chabertia ovina and larvae of the arthropod Oestrus ovis. Muellerius capillaris caused the formation of nodules in the lungs but were not counted. The trial started in April 1982 and was concluded in March 1984. One hundred and four sheep died or were slaughtered and 99 were examined post-mortem during this period. Total worm burdens rose to a peak of 88,763 (range 67,281-124,735) worms in March 1983, i.e. sheep mortality was such that the flock had to be treated with an anthelmintic in April 1983 to prevent further losses. Kikuyu pastures provide shade, form an excellent mat, the humus layer under the grass retains moisture and is an excellent incubator for preinfective larvae and a protector for infective larvae. If these qualities are combined with more than 100 mm of rain in spring and summer, Kikuyu pastures are a paradise for the free-living stages.  相似文献