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991.
Food limitation was tested in the laboratory by individual growth and reproduction of two cladoceran species, Ceriodaphnia richardi and Daphnia gessneri, from the shallow tropical Brazilian Lake Monte Alegre. The cladocerans were fed cultivated green alga Scenedesmus spinosus in concentrations of 0.20, 0.10, 0.05, and 0.025 mg C l−1. Higher biomass and growth rates occurred in the two highest-food concentrations; the two lowest ones negatively affected
clutch size and first reproduction. The threshold food concentration is lower than 0.025 mg C l−1 and the incipient limiting level is a value between 0.10 and 0.20 mg C l−1. The largest species, D. gessneri, was more sensitive to low food concentrations. The effects of low and high temperatures (19 and 27°C) were evaluated by
life table experiments with three cladocerans from the lake—Daphnia ambigua, D. gessneri, and Moina micrura—with no food limitation (1 mg C l−1 of S. spinosus). Higher population growth rates for the three species were found at 27°C; better performance in most life table parameters
was observed for the former two species at the highest temperature, D. gessneri being the most sensitive to the lowest temperature. There are indications that temperature is an important abiotic factor
that constrains populations of cladocerans for a short period in winter in the lake, when temperature decreases to 18–19°C.
However, its influence cannot be separated from a biotic factor such as food, whose effect is stronger in the cool season,
when concentrations are lower and contribution of inedible algae is relatively higher. 相似文献
992.
Correlated three-dimensional light and electron microscopy reveals transformation of mitochondria during apoptosis 总被引:4,自引:0,他引:4
Sun MG Williams J Munoz-Pinedo C Perkins GA Brown JM Ellisman MH Green DR Frey TG 《Nature cell biology》2007,9(9):1057-1065
In addition to their role in cellular bioenergetics, mitochondria also initiate common forms of programmed cell death (apoptosis) through the release of proteins such as cytochrome c from the intermembrane and intracristal spaces. The release of these proteins is studied in populations of cells by western blotting mitochondrial and cytoplasmic fractions of cellular extracts, and in single cells by fluorescence microscopy using fluorescent indicators and fusion proteins. However, studying the changes in ultrastructure associated with release of proteins requires the higher resolution provided by transmission electron microscopy. Here, we have used fluorescence microscopy to characterize the state of apoptosis in HeLa cells treated with etoposide followed by electron microscopy and three-dimensional electron microscope tomography of the identical cells to study the sequence of structural changes. We have identified a remodelling of the inner mitochondrial membrane into many separate vesicular matrix compartments that accompanies release of proteins; however, this remodelling is not required for efficient release of cytochrome c. Swelling occurs only late in apoptosis after release of cytochrome c and loss of the mitochondrial membrane potential. 相似文献
993.
Fibroblast-led collective invasion of carcinoma cells with differing roles for RhoGTPases in leading and following cells 总被引:5,自引:0,他引:5
Gaggioli C Hooper S Hidalgo-Carcedo C Grosse R Marshall JF Harrington K Sahai E 《Nature cell biology》2007,9(12):1392-1400
Imaging of collectively invading cocultures of carcinoma cells and stromal fibroblasts reveals that the leading cell is always a fibroblast and that carcinoma cells move within tracks in the extracellular matrix behind the fibroblast. The generation of these tracks by fibroblasts is sufficient to enable the collective invasion of the squamous cell carcinoma (SCC) cells and requires both protease- and force-mediated matrix remodelling. Force-mediated matrix remodelling depends on integrins alpha3 and alpha5, and Rho-mediated regulation of myosin light chain (MLC) activity in fibroblasts, but these factors are not required in carcinoma cells. Instead, carcinoma cells use Cdc42 and MRCK (myotonic dystrophy kinase-related CDC42-binding protein kinases) mediated regulation of MLC to follow the tracks generated by fibroblasts. 相似文献
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995.
996.
Randrianarison Rose Marie Lutz Meredith Torti Valeria Tan Chia Bonadonna Giovanna Randrianambinina Blanchard Rasoloharijaona Solofonirina Rabarison Harison Miaretsoa Longondraza Rarojoson Nianja Jemisa De Gregorio Chiara Valente Daria Gamba Marco Ratsimbazafy Jonah Giacoma Cristina 《International journal of primatology》2022,43(4):584-610
International Journal of Primatology - Deforestation around the world is a major threat to primates. Understanding primate species’ habitat and dietary requirements is critical in creating... 相似文献
997.
Castro-Cárdenas Nadia Vázquez-Santana Sonia Teixeira Simone P. Ibarra-Manríquez Guillermo 《Journal of plant research》2022,135(6):739-755
Journal of Plant Research - The syconium is the urn-shaped inflorescence shared by all species of the genus Ficus. The orifice at the apex of the syconium is called the ostiole, and it is covered... 相似文献
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999.
Cadavid Isabel Cristina Giraldo Carlos E. Balbinott Natalia González Mailyn Adriana Uribe Sandra Inés de Boer Hugo J. 《Journal of plant biochemistry and biotechnology.》2022,31(4):938-952
Journal of Plant Biochemistry and Biotechnology - Solanum is the largest and most diverse genus of the Solanaceae family. The genus includes around 1,400 species, and almost a third belong to... 相似文献
1000.
Evaluation of rapid screening techniques for detection of Salmonella spp. from produce samples after pre‐enrichment according to FDA BAM and a short secondary enrichment 下载免费PDF全文