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排序方式: 共有1220条查询结果,搜索用时 15 毫秒
1.
Ivonne J. Garzn‐Ordua Shaun L. Winterton Yunlan Jiang Laura C.V. Breitkreuz Peter Duelli Michael S. Engel Norman D. Penny Catherine A. Tauber Atsushi Mochizuki Xingyue Liu 《Systematic Entomology》2019,44(3):499-513
We present a time‐calibrated phylogeny of the charismatic green lacewings (Neuroptera: Chrysopidae). Previous phylogenetic studies on the family using DNA sequences have suffered from sparse taxon sampling and/or limited amounts of data. Here we combine all available previously published DNA sequence data and add to it new DNA sequences generated for this study. We analysed these data in a supermatrix using Bayesian and maximum likelihood methods and provide a phylogenetic hypothesis for the family that recovers strong support for the monophyly of all subfamilies and resolves relationships among a large proportion of chrysopine genera. Chrysopinae tribes Leucochrysini and Belonopterygini were recovered as monophyletic sister clades, while the species‐rich tribe Chrysopini was rendered paraphyletic by Ankylopterygini. Relationships among the subfamilies were resolved, although with relatively low statistical support, and the topology varied based on the method of analysis. Greatest support was found for Apochrysinae as sister to Nothochrysinae and Chrysopinae, which is in contrast to traditional concepts that place Nothochrysinae as sister to the rest of the family. Divergence estimates suggest that the stem groups to the various subfamilies diverged during the Triassic‐Jurassic, and that stem groups of the chrysopine tribes diverged during the Cretaceous. 相似文献
2.
Fire has historically been an important ecological component of forests in the Intermountain Region of the northwestern United States. This study is set in a small biogeographically disjunct mountain range. Our research objectives were to (1) investigate the historical frequency, severity, size, and spatial pattern of fire; (2) determine if and how fire regimes have changed since Euro-American settlement; and (3) compare how fire regimes of a small isolated range compare to nearby, but considerably larger, mountain agglomerations. Our findings suggest that this mountain range has historically supported fires typified by small size and high frequency, resulting in a high degree of spatial pattern complexity compared to mountain agglomerations. We also found disparity in size and burn severity solely within the study area based on the bisecting Continental Divide. Since the advent of Euro-American settlement in the 1870s, fire frequency and sizes of individual fires in the West Big Hole Range have significantly decreased resulting in an estimated 87% reduction in area burned. We discuss potential relationships of mountain range isolation and fire regimes in the Intermountain Region. Furthermore, we suggest that the relative small size of this mountain range predisposes it to greater anthropogenic effects upon fire occurrence. 相似文献
3.
A method is described for the subcellular fractionation of goldfish xanthophores. The procedure produces relatively pure fractions of caroteniod droplets, pterinosomes, cytosol and what appears to be plasma membrane. The presence of a distinct pattern of proteins is shown to be associated with the carotenoid droplets. Treatment of the xanthophores with ACTH affects the buoyant density of some carotenoid droplets and stimulates the phosphorylation of a polypeptide associated with the carotenoid droplets. 相似文献
4.
Utilizing horseradish peroxidase as a tracer protein, it is shown that trichogen and tormogen cells have a secretory function. Protein tracer from the haemolymph enters these cells by endocytosis and is transported to the sensillum liquor cavity by transport vacuoles and multivesicular bodies. It is also suggested that closely associated pigment cells may be involved in macromolecular transport. 相似文献
5.
The met proto-oncogene was mapped in the mouse and cat genomes with the use of mouse X hamster and cat X rodent somatic cell hybrid DNA panels. Based on these analyses we assigned the met gene to mouse chromosome 6 and to cat chromosome A2. We also assigned the cat raf-1 proto-oncogene to the A2 chromosome; met and raf-1 are the first cloned DNAs mapped to this linkage group. Using an interspecies backcross we further localized met on mouse chromosome 6 to a position proximal to the beta chain of the T-cell receptor. This places met near the obese locus in a region of mouse chromosome 6 that appears to be homologous with the long arm of human chromosome 7. The close linkage of met to the gene responsible for cystic fibrosis in humans suggests that further genetic analysis of mouse chromosome 6 may be useful in developing a mouse model for the disease. 相似文献
6.
Isolation and culture of cells derived from human cerebral microvessels 总被引:10,自引:0,他引:10
Harry V. Vinters Susan Reave Penny Costello John P. Girvin Steven A. Moore 《Cell and tissue research》1987,249(3):657-667
Summary Microvessels were isolated from non-neoplastic human cerebral cortical fragments resected for treatment of intractable seizure disorder. The microvessels were incubated in modified Lewis medium with 20 or 30% fetal bovine serum. Within 1–2 weeks, two cell populations emerged from the isolates. One type of cells had polygonal morphology, showed density-dependent contact inhibition at confluence in vitro, showed lectin-binding characteristics of endothelium (but only moderate positivity for factor VIII antigen), demonstrated induction of -glutamyl trans-peptidase when exposed to astrocyte-conditioned media, and responded to insulin by a pronounced increase in DNA synthesis. The other variety of cells grew in vitro more slowly in irregular strands separated by clear zones, showed ultrastructural features of smooth muscle, and isoelectric focusing of cell proteins revealed the presence of smooth-musclespecific -isoactin. Both types of cells could be serially subcultured. The ability to isolate and grow the two cell types, tentatively identified as human cerebral microvascular endothelium and smooth muscle, may facilitate studies of human blood-brain barrier function as well as the pathogenesis of cerebral microangiopathies unique to the human brain.Funded by Canadian Heart Foundation, Heart and Stroke Foundation of Ontario and UCLA Biomedical Research Support Grant 相似文献
7.
Helen L. Henry Chhanda Dutta Noreen Cunningham Raymond Blanchard Robert Penny Chilung Tang Gail Marchetto Shu-Yin Chou 《The Journal of steroid biochemistry and molecular biology》1992,41(3-8)
The synthesis of 1,25(OH)2D3 is a critical control point in the regulation of calcium metabolism, and possibly in the growth and differentiation of a number of cell types. This paper reviews our current understanding of the regulation of this process at the cellular and molecular levels, with the emphasis on the mechanisms of feedback control 1,25(OH)2D3 itself, control of parathyroid hormone, the roles of cyclic AMP dependent protein kinase and protein kinase C, and the interaction between the various intracellular regulators of 1,25(OH)2D3 production. 相似文献
8.
Aerial Dispersal and Epiphytic Survival of Pseudomonas syringae during a Pretest for the Release of Genetically Engineered Strains into the Environment 总被引:15,自引:15,他引:0
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Steven E. Lindow Guy R. Knudsen Ramon J. Seidler Michael V. Walter Victor W. Lambou Penny S. Amy David Schmedding Valerie Prince Stephen Hern 《Applied microbiology》1988,54(6):1557-1563
Prospective experimental field evaluation of genetically engineered microorganisms, such as microbial pest control agents, raises issues of how to properly ascertain their fate and survival in the environment. Field trials with recombinant organisms must reflect requirements for sampling and monitoring. Field trials were conducted at Tulelake, Calif., to monitor the numbers of viable cells of a nonrecombinant strain of Pseudomonas syringae that entered the atmosphere and landed on plants and soil during and after an aerosol spray application. An exponential decrease in numbers of viable cells deposited at increasing distances from three sprayed plots was observed. The relative rate of survival of cells sprayed directly on plants was more than 10 times higher than that of cells dispersed through the air to similar adjacent plants. Results are being used to gain experience with the characteristics of a release site that influence containment or dispersal and to develop appropriate sampling methodologies for evaluating survival and dispersal characteristics of genetically engineered bacteria released into the environment. The ability to make predictions about microbial dispersal and survival will reduce the uncertainties associated with environmental releases of recombinant organisms. 相似文献
9.
We studied the frequencies and types of excision events which can occur with a retroviral shuttle vector containing the simian virus 40 origin of DNA replication. Analysis of the recloned vector plasmids by size and restriction enzyme mapping indicated that most contain one long terminal repeat. By hybridizing the plasmids to a mouse genomic repetitive DNA probe, we also determined that approximately 1 to 3% contain transduced cellular DNA sequences. 相似文献
10.
Summary Cultures generated from tissues consisting of multiple types of cells are often heterogeneous. Unless the cell type of interest
has or can be given some selective growth advantage it may be overgrown by other cells. While developing techniques for the
tissue culture of microvascular endothelial cells we evaluated an electrosurgical generator (diathermy) to selectively kill
nonendothelail cells. Primary cell cultures were observed at ×100 magnification under phase contrast microscopy and a needle
electrode apposed to the cell to be destroyed. A return electrode was constructed by placing a sterile clip in contact with
the culture medium. The diathermy power setting controlled the area of lysis. Use of this technique allowed weeding of unwanted
cells without damage to endothelial cells, which were able to grow to confluence in pure culture.
Dr. Marks receives a Medical Postgraduate Research Scholarship from the National Health and Medical Research Council of Australia.
Financial support was received from the Leo Leukaemia and Cancer Research Trust and the Scleroderma Association of New South
Wales. 相似文献