Impacts of rising atmospheric carbon dioxide on model terrestrial ecosystems   总被引：2，自引：0，他引：2  

TH Jones  LJ Thompson  JH Lawton  TM Bezemer  RD Bardgett  TM Blackburn  KD Bruce  PF Cannon  GS Hall  SE Hartley  G Howson  CG Jones  C Kampichler  E Kandeler  DA Ritchie 《Science (New York, N.Y.)》1998,280(5362):441-443

In model terrestrial ecosystems maintained for three plant generations at elevated concentrations of atmospheric carbon dioxide, increases in photosynthetically fixed carbon were allocated below ground, raising concentrations of dissolved organic carbon in soil. These effects were then transmitted up the decomposer food chain. Soil microbial biomass was unaffected, but the composition of soil fungal species changed, with increases in rates of cellulose decomposition. There were also changes in the abundance and species composition of Collembola, fungal-feeding arthropods. These results have implications for long-term feedback processes in soil ecosystems that are subject to rising global atmospheric carbon dioxide concentrations.  相似文献   

Bodyweights and growth rates of spring- and autumn-born Thoroughbred horses raised on pasture     

CG Brown-Douglas  TJ Parkinson  EC Firth  PF Fennessy 《New Zealand veterinary journal》2013,61(5):326-331

AIM: To examine the growth of spring- and autumn-born Thoroughbred foals raised on pasture.

METHODS: Bodyweight and growth rates were measured in pasture-raised Thoroughbred horses, born in either spring (n=56) or autumn (n=7), from birth to approximately 13 and 17 months of age.

RESULTS: Birthweight tended to be lower in autumn- than spring-born foals (54.4, SD 7.92 kg vs 57.3, SD 5.90 kg; p=0.08). Between birth and 6 months of age, there was no difference in growth rate at equivalent ages between horses born in spring and autumn. Spring-born horses, which were weaned in the autumn, had lower post-weaning growth rates than autumn-born horses that were weaned in the spring. At time of the late yearling sales (March–April) in the Southern Hemisphere, unadjusted mean bodyweights of autumn-born horses (379.3, SD 24.8 kg) were lower (p=0.017) than those of the spring-born horses (437.2, SD 35.3 kg), although values in the autumn-born horses were all within two standard deviations (SD) of the mean of the spring-born animals. When adjusted for the covariates of birthweight and gender, the difference between spring- and autumn-born horses at that time was not significant (p=0.25).

CONCLUSIONS AND CLINICAL RELEVANCE: Some autumn-born foals could be marketed for late yearling sales in the Southern Hemisphere, on the basis of bodyweight. Furthermore, they might also be competitive in the Northern Hemisphere industry (sales or racing), as they would be competing against horses of the same official age.  相似文献   

Determination of membrane protein structure by rotational resonance NMR: bacteriorhodopsin   总被引：6，自引：0，他引：6  

F Creuzet  A McDermott  R Gebhard  K van der Hoef  M B Spijker-Assink  J Herzfeld  J Lugtenburg  M H Levitt  R G Griffin 《Science (New York, N.Y.)》1991,251(4995):783-786

Rotationally resonant magnetization exchange, a new nuclear magnetic resonance (NMR) technique for measuring internuclear distances between like spins in solids, was used to determine the distance between the C-8 and C-18 carbons of retinal in two model compounds and in the membrane protein bacteriorhodopsin. Magnetization transfer between inequivalent spins with an isotropic shift separation, delta, is driven by magic angle spinning at a speed omega r that matches the rotational resonance condition delta = n omega r, where n is a small integer. The distances measured in this way for both the 6-s-cis- and 6-s-trans-retinoic acid model compounds agreed well with crystallographically known distances. In bacteriorhodopsin the exchange trajectory between C-8 and C-18 was in good agreement with the internuclear distance for a 6-s-trans configuration [4.2 angstroms (A)] and inconsistent with that for a 6-s-cis configuration (3.1 A). The results illustrate that rotational resonance can be used for structural studies in membrane proteins and in other situations where diffraction and solution NMR techniques yield limited information.  相似文献   

Genetic polymorphism in CX3CR1 and risk of HIV disease     

McDermott DH  Colla JS  Kleeberger CA  Plankey M  Rosenberg PS  Smith ED  Zimmerman PA  Combadière C  Leitman SF  Kaslow RA  Goedert JJ  Berger EA  O'Brien TR  Murphy PM 《Science (New York, N.Y.)》2000,290(5499):2031

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1994 Kluwer Academic Publishers. Towards a marker assisted breeding for resistance against apple scab     

L. Gianfranceschi  J. M. McDermott  N. Seglias  B. Koller  M. Kellerhals  C. Gessler 《Euphytica》1994,77(1-2):93-96

Summary We present the first attempts to find molecular markers (RAPDs) in the apple genome linked to theVf gene conferring resistance to scab. The availability of genetic markers will allow selection of individuals with resistance genes in progeny. Moreover genetic markers allow us to recognise individuals with minimal linkage drag in back-crossing experiments with wild species. The feasibility of the bulk-segregant analysis to identify linked markers has been demonstrated on several occasions (Martin et al., 1991; Giovannoni et al., 1991; Michelmore et al., 1991). In this paper we report the preliminary results proving that the method could also be applied successfully in allogamous plants.  相似文献   

Introducing Modern Medicine in a Navajo Community     

McDermott W  Deuschle K  Adair J  Fulmer H  Loughlin B 《Science (New York, N.Y.)》1960,131(3396):280-287

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Post-breeding bird responses to canopy tree retention, stand size, and edge in regenerating Appalachian hardwood stands     

Molly E. McDermott  Petra Bohall Wood 《Forest Ecology and Management》2011,262(3):547-554

Avian use of even-aged timber harvests is likely affected by stand attributes such as size, amount of edge, and retained basal area, all characteristics that can easily be manipulated in timber harvesting plans. However, few studies have examined their effects during the post-breeding period. We studied the impacts of clearcut, low-leave two-age, and high-leave two-age harvesting on post-breeding birds using transect sampling and mist-netting in north-central West Virginia. In our approach, we studied the effects of these harvest types as well as stand size and edge on species characteristic of both early-successional and mature forest habitats. In 2005-2006, 13 stands ranging from 4 to 10 years post-harvest and 4-21 ha in size were sampled from late June through mid-August. Capture rates and relative abundance were similar among treatments for generalist birds. Early-successional birds had the lowest capture rates and fewer species (∼30% lower), and late-successional birds reached their highest abundance and species totals (double the other treatments) in high-leave two-age stands. Area sensitivity was evident for all breeding habitat groups. Both generalist and late-successional bird captures were negatively related to stand size, but these groups showed no clear edge effects. Mean relative abundance decreased to nearly zero for the latter group in the largest stands. In contrast, early-successional species tended to use stand interiors more often and responded positively to stand size. Capture rates for this group tripled as stand size increased from 4 to 21 ha. Few birds in the forest periphery responded to harvest edge types despite within-stand edge effects evident for several species. To create suitable habitat for early-successional birds, large, non-linear openings with a low retained basal area are ideal, while smaller harvests and increased residual tree retention would provide habitat for more late-successional birds post-breeding. Although our study has identified habitat use patterns for different species in timber harvests, understanding habitat-specific bird survival is needed to help determine the quality of silvicultural harvests for post-breeding birds.  相似文献   

Potato glycoalkaloids: Increases and variations of ratios in aged slices over prolonged storage     

T. J. Fitzpatrick  S. F. Herb  S. F. Osman  J. A. McDermott  Eastern Regional Research Center 《American Journal of Potato Research》1977,54(11):539-544

Four commercial cultivars of potatoes were maintained under normal storage conditions at 44 F for 34 weeks. Except for a final 10 week interval tubers were withdrawn at 6 week intervals. After slicing, a portion of the slices was immediately analyzed for total glycoalkaloid content. The remaining slices were aged for four days in the dark at room temperature, then similarly analyzed. The total glycoalkaloid content of the aged slices increased dramatically on aging. This increase on aging of slices reached a maximum early in storage then decreased gradually over the storage period. In determining the individual glycoalkaloids, α-solanine and α-chaconine both increased in these slices, but the greatest increase was in the former. Appearing solely in the aged slices of the Kennebec variety, α-and β-solamarine appeared early in the storage period and gradually decreased over the storage period. Analyses of the unaged slices indicated that the glycoalkaloid content and composition of the potato tubers was little affected by storage. Aging of potato sprouts did not change their glycoalkaloid content.  相似文献   

Excitotoxicity can be mediated through an interaction within the optic nerve; activation of cell body NMDA receptors is not required     

Christian K. Vorwerk  ‡  Rita Naskar  Frank Schuettauf  David Zurakowski  †  Luann M. McDermott  Kristine M. Quinto  Evan B. Dreyer 《Veterinary ophthalmology》2001,4(3):201-204

Axonal trauma leads to a series of pathologic events that can culminate in neuronal death. Although the precise mechanisms of retinal ganglion cell death after optic nerve crush in the rat model have not been elucidated, glutamate antagonists can protect retinal ganglion cells after optic nerve axotomy. We therefore explored whether a glutamate congener was toxic if applied directly within the optic nerve, or if toxicity depended upon an interaction at the cell body level. NMDA reduced retinal ganglion cell survival when applied directly into the rat optic nerve. Glutamate can be toxic if administered within the optic nerve; a direct effect at the cell body is not necessary. Future work will help to additionally unravel the steps by which axotomy induces excitotoxic damage to ganglion cells, and perhaps indicate protective interventions.  相似文献   

Barley mildew in Europe: population biology and host resistance   总被引：5，自引：0，他引：5  

M. S. Wolfe  U. Brändle  B. Koller  E. Limpert  J. M. McDermott  K. Müller  D. Schaffner 《Euphytica》1992,63(1-2):125-139

Summary Isolates of the barley mildew pathogen from the air spora over a large part of Europe and from fields of variety mixtures, were tested for virulence against 12 host resistance alleles. Subsamples were tested for their response to triadimenol fungicide and analyzed for 10 DNA loci using RAPD markers and PCR. There was a large range of haplotypes spread over Europe; irregularity in the distribution was probably due mainly to non-uniform use of the corresponding host resistances and fungicides. A large range of variation was also detectable within individual fields. Positive gametic disequilibria distorted the distribution of virulence alleles among haplotypes and reduced the number of haplotypes detectable in the sample. Analysis of the spread of the newly selectedVal3 allele into different European sub-populations indicated that gene flow throughout the population may be rapid for alleles that have a selective advantage.Fungicide resistance was widespread in areas known for intensive use of fungicides for mildew control. Four classes of fungicide response were detectable and particular virulence haplotypes were found to be characteristic for each class.Variety mixtures used in the former German Democratic Republic (GDR) reduced mildew infection, and thus fungicide use, during the years 1984–1991 despite the limited variation in host resistance among the mixtures. A tendency for complex pathogen races to increase in mixture crops was reversed by the large-scale re-introduction of fungicides for mildew control in 1991. The mixture strategy appeared to be more successful than using the same resistance alleles in pure monoculture or combining them in a single host genotype.  相似文献