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排序方式: 共有410条查询结果,搜索用时 15 毫秒
91.
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Janet Dvonch Kelly John A. McNulty Gary B. Schneider 《Biotechnic & histochemistry》1991,66(5):228-235
Tartrate resistant acid phosphatase (TRAP) has been accepted as a marker for identification of osteoclasts. A method is reported here for quantitating TRAP using an image analysis system. The amount of the enzyme specific to osteoclasts can be used to differentiate osteoclasts from other cells capable of TRAP expression. TRAP expression characteristic of the osteoclast was compared with that of multinucleated giant cells (MNGC)s recruited to the site of subcutaneously implanted mineralized bone matrix. Two weeks post-implantation, the pellets were removed and processed for the demonstration of TRAP along with rat proximal tibiae. A large amount of TRAP was consistently expressed by the in situ osteoclasts. The MNGCs associated with the mineralized bone implants expressed little if any TRAP reaction product. Using this system, the amount of TRAP reaction product or any other enzyme reaction product expressed can be objectively and reproducibly quantitated. 相似文献
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Recognizing the forest for the trees: testing temporal patterns of cladogenesis using a null model of stochastic diversification 总被引:2,自引:1,他引:1
Computer simulations are developed and employed to examine the expected
temporal distributions of nodes under a null model of stochastic lineage
bifurcation and extinction. These Markovian models of phylogenetic process
were constructed so as to permit direct comparisons against empirical
phylogenetic trees generated from molecular or other information available
solely from extant species. For replicate simulated phylads with n extant
species, cumulative distribution functions (cdf's) of branching times were
calculated, and compared (using the Kolmogorov-Smirnov test statistic D) to
those from three published empirical trees. Molecular phylogenies for
columbine plants and avian cranes showed statistically significant
departures from the null expectations, in directions indicating recent and
ancient species' radiations, respectively, whereas a molecular phylogeny
for the Drosophila virilis species group showed no apparent historical
clustering of branching events. Effects of outgroup choice and phylogenetic
frame of reference were investigated for the columbines and found to have a
predictable influence on the types of conclusions to be drawn from such
analyses. To enable other investigators to statistically test for
nonrandomness in temporal cladogenetic pattern in empirical trees generated
from data on extant species, we present tables of mean cdf's and associated
probabilities under the null model for expected branching times in phylads
of varying size. The approaches developed in this report complement and
extend those of other recent methods for employing null models to assess
the statistical significance of pattern in evolutionary trees.
相似文献
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Paoletti E Bytnerowicz A Andersen C Augustaitis A Ferretti M Grulke N Günthardt-Goerg MS Innes J Johnson D Karnosky D Luangjame J Matyssek R McNulty S Müller-Starck G Musselman R Percy K 《TheScientificWorldJournal》2007,7(Z1):1-8
Outcomes from the 22nd meeting for Specialists in Air Pollution Effects on Forest Ecosystems "Forests under Anthropogenic Pressure--Effects of Air Pollution, Climate Change and Urban Development", September 10-16, 2006, Riverside, CA, are summarized. Tropospheric or ground-level ozone (O3) is still the phytotoxic air pollutant of major interest. Challenging issues are how to make O3 standards or critical levels more biologically based and at the same time practical for wide use; quantification of plant detoxification processes in flux modeling; inclusion of multiple environmental stresses in critical load determinations; new concept development for nitrogen saturation; interactions between air pollution, climate, and forest pests; effects of forest fire on air quality; the capacity of forests to sequester carbon under changing climatic conditions and coexposure to elevated levels of air pollutants; enhanced linkage between molecular biology, biochemistry, physiology, and morphological traits. 相似文献
99.
Luo L Parrish CA Nevins N McNulty DE Chaudhari AM Carson JD Sudakin V Shaw AN Lehr R Zhao H Sweitzer S Lad L Wood KW Sakowicz R Annan RS Huang PS Jackson JR Dhanak D Copeland RA Auger KR 《Nature chemical biology》2007,3(11):722-726
The mitotic kinesin KSP (kinesin spindle protein, or Eg5) has an essential role in centrosome separation and formation of the bipolar mitotic spindle. Its exclusive involvement in the mitotic spindle of proliferating cells presents an opportunity for developing new anticancer agents with reduced side effects relative to antimitotics that target tubulin. Ispinesib is an allosteric small-molecule KSP inhibitor in phase 2 clinical trials. Mutations that attenuate ispinesib binding to KSP have been identified, which highlights the need for inhibitors that target different binding sites. We describe a new class of selective KSP inhibitors that are active against ispinesib-resistant forms of KSP. These ATP-competitive KSP inhibitors do not bind in the nucleotide binding pocket. Cumulative data from generation of resistant cells, site-directed mutagenesis and photo-affinity labeling suggest that they compete with ATP binding via a novel allosteric mechanism. 相似文献
100.
McNulty SN Fischer K Mehus JO Vaughan JA Tkach VV Weil GJ Fischer PU 《The Journal of parasitology》2012,98(2):382-387
Chandlerella quiscali is a filarial nematode parasite of the common grackle (Quiscalus quiscula), a widespread bird species found throughout most of North America. Worms collected from wild-caught birds were morphologically identified as C. quiscali and tested for the presence of Wolbachia, an alphaproteobacterial endosymbiont required for reproduction and maturation by many filarial species. Although various methods, including polymerase chain reaction, in situ hybridization, and immunohistology, were used, we were unable to detect evidence of colonization with Wolbachia. Due to the widespread distribution of the grackle host, localization within the host, and high prevalence, C. quiscali may be among the most easily obtainable of Wolbachia-free filarial species. Further studies of C. quiscali and other Wolbachia-free filarial species may help to clarify the reason(s) that some filarial species require Wolbachia but others do not. 相似文献