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91.
Using long-term culture techniques, it has been shown that stromal cells in the marrow microenvironment are essential for the continued production and self-renewal of hematopoietic stem cells. We previously reported the development of a methylcellulose colony assay for a population of marrow stromal progenitors called CFU-RF. In this paper, a method is described for subculturing cells from individual CFU-RF-derived colonies to allow conditioned medium production (StCM). StCM, prepared in this way, was found to possess an erythroid lineage-specific activity that stimulated the formation of macroscopic erythroid colonies in cultures containing erythropoietin (epo). Using dose-response curves, the KG1 colony assay, and antibody neutralization, it was shown that the activity could not be attributed to interleukin 3 (IL3) or granulocyte-macrophage colony-stimulating factor (GM-CSF). However, it was further shown that a monolayer of stromal cells, which had earlier been producing the erythroid activity, could be stimulated by IL1 to produce granulocytic colony-stimulating activity, but only as long as IL1 was present in the culture medium. These findings indicate a mechanism whereby the same stromal population could be modulated to promote growth and differentiation of different hematopoietic lineages. 相似文献
92.
The mutualistic association between ants and hemipterans is often facultative and can be affected by the availability of other food sources. In the present study we tested whether the tending behavior of the big-headed ant, Pheidole megacephala (Fabricius), had a negative impact on the pink pineapple mealybug, Dysmicoccus brevipes (Cockerell), when alternative food sources: (1) sugar solution, (2) purified water + mealworms and (3) sugar solution + mealworms versus with purified water (control) were provided to the ant colonies. We found that the frequency of ant tending on D. brevipes decreased when ants were provided with alternative food sources. However, we did not see any aggressive behaviors and predation of ants on D. brevipes. Also, the survival of D. brevipes was not different among food condition treatments. These results suggest that the decreased tending frequency of ants can lead to the decline in ant protection service to mealybugs. 相似文献
93.
Aye T. Win Yuto Machida Yoshihiro Miyamoto Shigeto Dobata Kazuki Tsuji 《Journal of Ethology》2018,36(3):277-282
We investigated colony-level foraging activities of Diacamma sp., a queenless ponerine ant, in the field. Our aim was to elucidate the presence of any pattern in foraging activity in field colonies in relation to: (1) circadian rhythm, (2) physical environmental conditions such as extreme temperatures, (3) seasonality, and (4) short-term foraging efficiency (i.e. the success ratio in obtaining food per foraging trip). Colony-level foraging activity tended to be diurnal throughout the year, as more foraging trips were observed in the daytime. Although temperature had no linear effect on overall foraging activity, lower temperature precluded foraging at night. Overall, foraging was more frequent at times of day when foraging efficiency was high, but this relationship was weak and varied seasonally. Interestingly, we found that hourly foraging efficiency and hourly foraging activity were negatively correlated in autumn, the season when the average foraging efficiency peaked, whereas they were positively correlated in winter and spring. 相似文献
94.
Nutritional cues control Pseudomonas aeruginosa multicellular behavior in cystic fibrosis sputum 下载免费PDF全文
The sputum (mucus) layer of the cystic fibrosis (CF) lung is a complex substrate that provides Pseudomonas aeruginosa with carbon and energy to support high-density growth during chronic colonization. Unfortunately, the CF lung sputum layer has been difficult to mimic in animal models of CF disease, and mechanistic studies of P. aeruginosa physiology during growth in CF sputum are hampered by its complexity. In this study, we performed chromatographic and enzymatic analyses of CF sputum to develop a defined, synthetic CF sputum medium (SCFM) that mimics the nutritional composition of CF sputum. Importantly, P. aeruginosa displays similar phenotypes during growth in CF sputum and in SCFM, including similar growth rates, gene expression profiles, carbon substrate preferences, and cell-cell signaling profiles. Using SCFM, we provide evidence that aromatic amino acids serve as nutritional cues that influence cell-cell signaling and antimicrobial activity of P. aeruginosa during growth in CF sputum. 相似文献
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96.
Ali Koohang Nathan D. Majewski Erika L. Szotek Aye Aye Mar David A. Eiznhamer Michael T. Flavin Ze-Qi Xu 《Bioorganic & medicinal chemistry letters》2009,19(8):2168-2171
New A-ring modified betulin and dihydrobetulin derivatives possessing the 2-cyano-1-en-3-one moiety were prepared and tested for cytotoxicity in seven cancer cell lines. The most active agent 9a synthesized in this account was further demonstrated to induce apoptosis and to activate caspases in malignant melanoma cells. 相似文献
97.
Matthew W. Breed Samra E. Elser Workineh Torben Andrea P. O. Jordan Pyone P. Aye Cecily Midkiff Faith Schiro Chie Sugimoto Xavier Alvarez-Hernandez Robert V. Blair Anoma Somasunderam Netanya S. Utay Marcelo J. Kuroda Bapi Pahar Roger W. Wiseman David H. O'Connor Celia C. LaBranche David C. Montefiori Mark Marsh Yuan Li Michael Piatak Jr. Jeffrey D. Lifson Brandon F. Keele Patricia N. Fultz Andrew A. Lackner James A. Hoxie 《Journal of virology》2015,89(20):10156-10175
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Irving L.M.H. Aye Brendan J. Waddell Peter J. Mark Jeffrey A. Keelan 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2010,1801(9):1013-1024
ATP-binding cassette (ABC) transporters ABCA1 and ABCG1 mediate the efflux of cholesterol and other sterols. Both transporters are expressed on the fetal capillaries of the placenta and are involved in maternal-to-fetal cholesterol delivery. In this study, we report that ABCA1 and ABCG1 are also present on the syncytiotrophoblast, the maternal facing placental membrane. Syncytial ABCA1 expression is apical, suggesting a role in cholesterol efflux to the mother, while ABCG1 is expressed basolaterally indicating transport to the fetus. Silencing of ABCA1 expression in primary trophoblasts in culture, or pharmacological antagonism by glyburide, decreased cholesterol efflux to apolipoprotein A-I (apoA-I) compared to controls, while ABCG1-silencing decreased cholesterol efflux to high density lipoproteins (HDL). In contrast, treatment with endogenous or synthetic LXR α/β ligands such as T0901317 increased ABCA1 and ABCG1 expression and enhanced cholesterol efflux to apoA-I and HDL, respectively, while treatment with pharmacological PPAR-α or -γ ligands was without effect. Trophoblasts transfected with ABCA1 or ABCG1 siRNA were more sensitive to toxic oxysterols substrates (25-hydroxycholesterol and 7-ketocholesterol) compared to mock-transfected cells, while prior treatment with T0901317 reduced oxysterol-mediated toxicity. These results identify syncytial ABCA1 and ABCG1 as important, inducible cholesterol transporters which also prevent placental accumulation of cytotoxic oxysterols. 相似文献
100.
Htay Htay Shwe Mye Aye Myint Myint Sein Khin Than Htay Peter Kreitmeier Jürg Gertsch Oliver Reiser Jörg Heilmann 《化学与生物多样性》2010,7(3):610-622
Three new steroid saponins (3β,25R)‐spirost‐5‐en‐3‐yl 6‐deoxy‐α‐L ‐mannopyranosyl‐(1→2)‐[β‐D ‐glucopyranosyl‐(1→4)‐6‐deoxy‐α‐L ‐mannopyranosyl‐(1→3)]‐β‐D ‐glucopyranoside ( 1 ), (3β,22R,25R)‐26‐(β‐D ‐glucopyranosyloxy)‐22‐hydroxyfurost‐5‐en‐3‐yl 6‐deoxy‐α‐L ‐mannopyranosyl‐(1→2)‐[6‐deoxy‐α‐L ‐mannopyranosyl‐(1→3)]‐β‐D ‐glucopyranoside ( 3 ), and (3β,22R,25R)‐26‐(β‐D ‐glucopyranosyloxy)‐22‐hydroxyfurost‐5‐en‐3‐yl 6‐deoxy‐α‐L ‐mannopyranosyl‐(1→2)‐[β‐D ‐glucopyranosyl‐(1→4)‐6‐deoxy‐α‐L ‐mannopyranosyl‐(1→3)]‐β‐D ‐glucopyranoside ( 5 ), as well as the new pregnane glycoside (3β,16β)‐3‐{[6‐deoxy‐α‐L ‐mannopyranosyl‐(1→2)‐[6‐deoxy‐α‐L ‐mannopyranosyl‐(1→3)]‐β‐D ‐glucopyranosyl]oxy}‐20‐oxopregn‐5‐en‐16‐yl (4R)‐5‐(β‐D ‐glucopyranosyloxy)‐4‐methylpentanoate ( 6 ), were isolated from the rhizomes of Tacca integrifolia together with two known (25R) configurated steroid saponins (3β,25R)‐spirost‐5‐en‐3‐yl 6‐deoxy‐α‐L ‐mannopyranosyl‐(1→2)‐[6‐deoxy‐α‐L ‐mannopyranosyl‐(1→3)]‐β‐D ‐glucopyranoside ( 2 ) and (3β,22R,25R)‐26‐(β‐D ‐glucopyranosyloxy)‐22‐methoxyfurost‐5‐en‐3‐yl 6‐deoxy‐α‐L ‐mannopyranosyl‐(1→2)‐[6‐deoxy‐α‐L ‐mannopyranosyl‐(1→3)]‐β‐D ‐glucopyranoside ( 4 ). The cytotoxic activity of the isolated compounds was evaluated in HeLa cells and showed the highest cytotoxicity value for compound 2 with an IC50 of 1.2±0.4 μM . Intriguingly, while compounds 1 – 5 exhibited similar cytotoxic properties between 1.2±0.4 ( 2 ) and 4.0±0.6 μM ( 5 ), only compound 2 showed a significant microtubule‐stabilizing activity in vitro. 相似文献