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Glomeruli isolated from rat and human kidneys were studied using the freeze-fracture technique. Discontinuous zonulae occludentes and gap junctions were found in the replicas of the split plasma membrane of the endothelial cells. A diaphragm across the endothelial pores was not demonstrated. The central layer of the basement membrane, corresponding to the lamina densa described in thin sections, revealed a coarse substructure. A slit membrane between the pedicles of the podocytes was not detectable; however, its position was indicated by the different texture of the replica, which abruptly changed at the transition of the basement membrane to the primary urinary space. Furthermore, at the level of the slit membrane arrays of particles were present within the cleaved membrane of the pedicles, probably representing the attachment points of the slit membrane. Isolated strands of a zonula occludens as well as gap junctions were seen on the split plasma membrane of the podocytes. The mesangial cells could be identified by their contiguity to the endothelial cells and by their numerous gap junctions. 相似文献
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Effects of long term CO2 enrichment on microbial community structure in calcareous grassland 总被引:1,自引:0,他引:1
Diana Ebersberger Nicola Wermbter Pascal A. Niklaus Ellen Kandeler 《Plant and Soil》2004,264(1-2):313-323
Elevated CO2 generally increases plant productivity, and has been found to alter plant community composition in many ecosystems. Because soil microbes depend on plant-derived C and are often associated with specific plant species, elevated CO2 has the potential to alter structure and functioning of soil microbial communities. We investigated soil microbial community structure of a species-rich semi-natural calcareous grassland that had been exposed to elevated CO2 (600 μL L?1) for 6 growing seasons. We analysed microbial community structure using phospholipid fatty acid (PLFA) profiles and DNA fingerprints obtained by Denaturing Gradient Gel Electrophoresis (DGGE) of 16S rDNA fragments amplified by the Polymerase Chain Reaction (PCR). PLFA profiles were not affected by CO2 enrichment and the ratio of fungal and bacterial PLFA did not change. Ordination analysis of DNA fingerprints revealed a significant relation between CO2 enrichment and variation in DNA fingerprints in summer (P=0.01), but not in spring. This variation was due to changes in low-intensity bands, while dominant bands did not differ between CO2 treatments. Diversity of the bacterial community, as assessed by number of bands in DNA fingerprints and calculation of Shannon diversity indices, was not affected by elevated CO2. Overall, only minor effects on microbial community structure were detected, corroborating earlier findings that soil carbon inputs did probably change much less than suggested by plant photosynthetic responses. 相似文献
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Reiter Birgit Wermbter Nicola Gyamfi Stephen Schwab Helmut Sessitsch Angela 《Plant and Soil》2003,257(2):397-405
The diversity of abundant and metabolically active pseudomonads in potato plants was analysed using a culture-independent approach. The effect of two plant varieties, Agria and Bionta, as well as the presence of a plant pathogen Erwinia carotovora ssp. atroseptica on this bacterial group was tested. A combination of Pseudomonas-specific PCR, DGGE analysis, cloning and sequencing of partial 16S rDNA genes was performed using DNA and RNA extracted from potato stem tissue. Sequence analysis revealed a high species diversity, with the most prominent ones being Pseudomonas stutzeri and Pseudomonas gingeri. Some species showed high rRNA contents indicating high metabolic activity. Both, highly abundant and metabolically active Pseudomonaspopulations were more affected by the plant genotype than by the presence of E. carotovora. 相似文献
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