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排序方式: 共有234条查询结果,搜索用时 359 毫秒
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Michael D. Weiser Nathan J. Sanders Donat Agosti Alan N. Andersen Aaron M. Ellison Brian L. Fisher Heloise Gibb Nicholas J. Gotelli Aaron D. Gove Kevin Gross Benoit Guénard Milan Janda Michael Kaspari Jean-Philippe Lessard John T. Longino Jonathan D. Majer Sean B. Menke Terrence P. McGlynn Catherine L. Parr Stacy M. Philpott Javier Retana Andrew V. Suarez Heraldo L. Vasconcelos Stephen P. Yanoviak Robert R. Dunn 《Biology letters》2010,6(6):769-772
Tropical forest canopies house most of the globe''s diversity, yet little is known about global patterns and drivers of canopy diversity. Here, we present models of ant species density, using climate, abundance and habitat (i.e. canopy versus litter) as predictors. Ant species density is positively associated with temperature and precipitation, and negatively (or non-significantly) associated with two metrics of seasonality, precipitation seasonality and temperature range. Ant species density was significantly higher in canopy samples, but this difference disappeared once abundance was considered. Thus, apparent differences in species density between canopy and litter samples are probably owing to differences in abundance–diversity relationships, and not differences in climate–diversity relationships. Thus, it appears that canopy and litter ant assemblages share a common abundance–diversity relationship influenced by similar but not identical climatic drivers. 相似文献
54.
Sean B. Menke Warren Booth Robert R. Dunn Coby Schal Edward L. Vargo Jules Silverman 《PloS one》2010,5(2)
The most rapidly expanding habitat globally is the urban habitat, yet the origin and life histories of the populations of native species that inhabit this habitat remain poorly understood. We use DNA barcoding of the COI gene in the widespread native pest ant Tapinoma sessile to test two hypotheses regarding the origin of urban populations and traits associated with their success. First, we determine if urban samples of T. sessile have a single origin from natural populations by looking at patterns of haplotype clustering from across their range. Second, we examine whether polygynous colony structure – a trait associated with invasion success – is correlated with urban environments, by studying the lineage dependence of colony structure. Our phylogenetic analysis of 49 samples identified four well supported geographic clades. Within clades, Kimura-2 parameter pairwise genetic distances revealed <2.3% variation; however, between clade genetic distances were 7.5–10.0%, suggesting the possibility of the presence of cryptic species. Our results indicate that T. sessile has successfully colonized urban environments multiple times. Additionally, polygynous colony structure is a highly plastic trait across habitat, clade, and haplotype. In short, T. sessile has colonized urban habitats repeatedly and appears to do so using life history strategies already present in more natural populations. Whether similar results hold for other species found in urban habitats has scarcely begun to be considered. 相似文献
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M. Menke J. Fuchs I. Schubert 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(8):1314-1320
The resolution of the chromosomal positions of six high- and one low-copy sequences by oligonucleotide-primed in situ (PRINS)
labelling was compared with corresponding data obtained after fluorescent in situ hybridization (FISH) on field-bean and barley
chromosomes. While PRINS proved to be suitable for the rapid detection of high-copy tandem repeats at the same loci as those
revealed by FISH, no clear PRINS signal was obtained for the low-copy family of vicilin genes at their locus on field-bean
chromosome II. This indicates that localization of short target sequences by primer extension via Taq polymerase in situ does not yet provide a resolution equal, or superior, to FISH on plant chromosomes. Therefore, the use
of a cocktail of chromosome-specific single-copy sequences as primers for PRINS is no alternative for the not as yet feasible
chromosome painting in plants.
Received: 21 April 1998 / Accepted: 12 May 1998 相似文献
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Fibroadenomas are the most common benign lump in females. The study of gene alterations and/or deregulation in reproductive years may help explain hormonal physiological processes involved in nodule development and evolution. The objective was to compare ER-alpha, c-myc, and bcl-2 gene expression in breast fibroadenomas and in normal tissue and evaluate menstrual cycle, parity, and oral contraceptive influences. Fifty-seven premenopausal women (14-49 years) undergoing surgical removal of fibroadenomas were selected. Samples from fibroadenomas and circumjacent normal tissue were obtained for RT-PCR paired analysis. Patients were divided in groups according to menstrual cycle, use of contraceptives and parity. Tissue from 32 patients was adequate for RT-PCR. Paired analysis showed higher expression of ER-alpha (P=0.012) and bcl-2 (P=0.001) in fibroadenomas than in normal breast, while c-myc presented a similar expression (P=0.655). ER-alpha was higher in fibroadenomas of patients in follicular phase versus contraceptive users and normal tissue (P=0.003); bcl-2 was higher in fibroadenomas of patients in luteal phase than in the normal samples from all groups (P=0.007). c-myc did not differ according to menstrual cycle, but was higher in fibroadenomas>3 cm versus<3 cm (P=0.015) and in nulliparous women (P=0.04). A positive correlation between c-myc levels and fibroadenoma diameter was demonstrated (r=0.536; P=0.007). Nulliparous mean nodule diameter was superior than parous women (P=0.008). In conclusion, the expression of ER-alpha, bcl-2 and c-myc depends on hormonal and reproductive factors, with a possible contribution to lump formation and evolution. 相似文献
59.
DNA damage and repair in Arabidopsis thaliana as measured by the comet assay after treatment with different classes of genotoxins 总被引:5,自引:0,他引:5
We have studied the occurrence of the apoptosis phenomenon in the action of adriamycin (ADR) on human melanoma cells sensitive (ME18) and resistant (ME18/R) to ADR.
The study has shown that the intensity of apoptotic morphological changes noted in melanoma cells depended on the duration of the ADR treatment.
We have not observed any positive correlation between the induction of apoptosis and sensitivity to ADR.
We have used a fluorescence microscope and flow cytometer to evaluate apoptotic events in cells treated with ADR. 相似文献
60.
Goedkoop AY Kraan MC Picavet DI de Rie MA Teunissen MB Bos JD Tak PP 《Arthritis research & therapy》2004,6(4):R326-R334
Psoriasis and psoriatic arthritis are inflammatory diseases that respond well to anti-tumour necrosis factor-α therapy. To
evaluate the effects of anti-tumour necrosis factor-α treatment on expression of adhesion molecules and angiogenesis in psoriatic
lesional skin and synovial tissue, we performed a prospective single-centre study with infliximab therapy combined with stable
methotrexate therapy. Eleven patients with both active psoriasis and psoriatic arthritis received infusions of infliximab
(3 mg/kg) at baseline, and at weeks 2, 6, 14 and 22 in an open-label study. In addition, patients continued to receive stable
methotrexate therapy in dosages ranging from 5 to 20 mg/week. Clinical assessments, including Psoriasis Area and Severity
Index (PASI) and Disease Activity Score (DAS), were performed at baseline and every 2 weeks afterward. In addition, skin biopsies
from a target psoriatic plaque and synovial tissue biopsies from a target joint were taken before treatment and at week 4.
Immunohistochemical analysis was performed to detect the number of blood vessels, the expression of adhesion molecules and
the presence of vascular growth factors. Stained sections were evaluated by digital image analysis. At week 16, the mean PASI
was reduced from 12.3 ± 2.4 at baseline to 1.8 ± 0.4 (P ≤ 0.02). The mean DAS was reduced from 6.0 ± 0.5 to 3.6 ± 0.6 (P ≤ 0.02). We found some fluctuations in DAS response as compared with the change in PASI, with the latter exhibiting a steady
decrease over time. After 4 weeks the cell infiltrate was reduced in both skin and synovium. There was a significant reduction
in the number of blood vessels in dermis and synovium at week 4. A significant reduction in the expression of αvβ3 integrin, a marker of neovascularization, was also found in both skin and synovium at week 4. In addition, a significant
reduction in the expression of adhesion molecules was observed in both skin and synovium at week 4. We also observed a trend
toward reduced expression of vascular endothelial growth factor in both skin and synovium. In conclusion, low-dose infliximab
treatment leads to decreased neoangiogenesis and deactivation of the endothelium, resulting in decreased cell infiltration
and clinical improvement in psoriasis and psoriatic arthritis. 相似文献