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1.
The uniform distribution of nuclei, mitochondria, lipid material,protein, and RNA in the hyphae and haustoria of Peronosporaparasitica was demonstrated by staining techniques. Glycogenwas not detected, the only insoluble carbohydrate material detectedby the periodic acid-Schiff reaction being in the fungal wall.The host cell walls reacted more intensely to this stain thanthe hyphal walls. The reaction of haustorial walls varied betweenthe slight staining reaction characteristic of the fungal walls,and the strong reaction of the host cell wall. Callose sheathswere occasionally seen. Fine structure was found to be similar to that of other Oomycetes.Welldeveloped sheaths of a vesicular nature, possibly synonymouswith callose sheaths, were occasionally seen partly surroundinghaustoria. 相似文献
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Effects of aluminium on fluoride uptake by plants 总被引:8,自引:1,他引:7
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Interactive effects of ozone and soil volume on Plantago major 总被引:4,自引:2,他引:2
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Mediation of pinocytosis in cultured arterial smooth muscle and endothelial cells by platelet-derived growth factor 总被引:23,自引:10,他引:13 下载免费PDF全文
Pinocytosis was measured in monkey aortic smooth muscle cells (SMC), bovine aortic endothelial cells, and Swiss 3T3 cells in culture as cellular uptake of [U-(14)C]sucrose and horseradish peroxidase (HRP) from the tissue culture medium. Monkey arterial SMC and Swiss 3T3 cells were maintained in a quiescent state of growth at low cells density in medium containing 5 percent monkey plasma-derived serum (PDS). Replacement of PDS with 5 percent monkey whole blood serum (WBS) from the same donor, or addition to PDS of partially purified platelet-derived growth factor(s) (PF), resulted in a marked stimulation of pinocytosis as well as of cellular proliferation. In SMC, enhancement of the rate of pinocytosis occurred 4-6 h after exposure to WBS or PF, and the rate was up to twofold higher than the rate in medium containing PDS. In contrast, [(3)H]thymidine uptake by SMC did not increase until 12-16 h after exposure to PF. In endothelial cells the presence of PF or WBS did not enhance either the rate of pinocytosis or the rate of proliferation over that in PDS. Thus, endothelial cells did not become quiescent at subconfluent densities in PDS but maintained rates of proliferation and pinocytosis that were equivalent to those in WBS. By autoradiography, the fraction of labeled nuclei in SMC cultures 24 h after change of medium increased from 0.061 +/- 0.004 in quiescent cultures to 0.313 +/- 0.028 after exposure to WBS or PF. In contrast, labeling indices of endothelial cells were similar for cultures grown in PDS, WBS, or PF at any single time point after change of medium. These findings suggest that the rate of pinocytosis maybe be coupled in some fashion to growth regulation, which may be mediated in part by specific growth factors, such as that derived from the thrombocyte. 相似文献
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ANGUS DAVISON 《Biological journal of the Linnean Society. Linnean Society of London》2000,70(4):697-706
Some continental European populations of the land snail Cepaea nemoralis have mitochondrial haplotypes that differ by up to 20% at the 16S rRNA locus. I mapped the distribution of different lineages in populations from 36 different sites in Britain and Ireland. In 93% of individuals, one of two mitochondrial lineages was found, A or. N , which differ from each other by about 6% using a 16S rRNA fragment {approximately 300 base pairs). The distribution of these two types is very striking–one is confined to Wales, West and central England, and Scotland, while the other is found mainly in East and central England. The two types meet in a transition zone. The most likely explanation for the distribution is that it reflects two routes of colonization after the last ice age. Cepaea dispersal is leptokurtic, and only limited gene flow occurs between established populations, so that the original pattern could have been retained since the post-glacial colonization. However, many environmental gradients are orientated East-West, so alternative selective explanations are possible. A distinct mitochondrial lineage, as well as fossil evidence, suggests that Ireland was colonized separately from Britain. The implications of these distributions for the origins of the puzzling geographical patterns of shell types known as 'area effects' is discussed. 相似文献
9.
Michelle F Griffin Peter E Butler Alexander M Seifalian Deepak M Kalaskar 《World journal of stem cells》2015,7(1):37-50
Stem cells are capable of long-term self-renewal and differentiation into specialised cell types, making them an ideal candidate for a cell source for regenerative medicine. The control of stem cell fate has become a major area of interest in the field of regenerative medicine and therapeutic intervention. Conventional methods of chemically inducing stem cells into specific lineages is being challenged by the advances in biomaterial technology, with evidence highlighting that material properties are capable of driving stem cell fate. Materials are being designed to mimic the clues stem cells receive in their in vivo stem cell niche including topographical and chemical instructions. Nanotopographical clues that mimic the extracellular matrix(ECM) in vivo have shown to regulate stem cell differentiation. The delivery of ECM components on biomaterials in the form of short peptides sequences has also proved successful in directing stem cell lineage. Growth factors responsible for controlling stem cell fate in vivo have also been delivered via biomaterials to provide clues to determine stem cell differentiation. An alternative approach to guide stem cells fate is to provide genetic clues including delivering DNA plasmids and small interfering RNAs via scaffolds. This review, aims to provide an overview of the topographical, chemical and molecular clues that biomaterials can provide to guide stem cell fate. The promising features and challenges of such approaches will be highlighted, to provide directions for future advancements in this exciting area of stem cell translation for regenerative medicine. 相似文献
10.
SHAWN W. MEYER SHANNON S. BADZINSKI SCOTT A. PETRIE C. DAVISON ANKNEY 《The Journal of wildlife management》2010,74(7):1559-1566
Abstract: Common reed (Phragmites australis) forms dense stands with deep layers of residual organic matter that negatively affects plant diversity and possibly habitat use by wetland birds. We sought to determine whether seasonal relative abundance and species richness of birds varied among 3 habitat types in Great Lakes coastal wetland complexes recently invaded by common reed. We used fixed-distance point counts to determine species relative abundances and species richness in edge and interior locales within common reed, cattail (Typha spp.), and meadow marsh habitats of various sizes during 2 summers (2001 and 2002) and 1 autumn (2001) at Long Point, Lake Erie, Ontario, Canada. We found that total relative abundance and species richness of birds were greater in common reed habitat compared to cattail or meadow marsh habitats. However, we also found that relative abundance of marsh-nesting birds was greater in meadow marsh habitat than in cattail and common reed during summer. Lastly, we found that, irrespective of habitat type, habitat edges had higher total relative abundance and species richness of birds than did habitat interiors. Our results show that common reed provides suitable habitat for a diversity of landbirds during summer and autumn but only limited habitat for many marsh-nesting birds during summer. Based on these results, we recommend restoration of meadow marsh habitat through reduction of common reed in Great Lakes wetlands where providing habitat for breeding marsh-nesting birds is an objective. Managers also might consider reducing the size of nonnative common reed stands to increase edge effect and use by birds, possibly including wetland birds. 相似文献