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41.
Phosphoinositide breakdown and evidence for protein kinase C involvement during human NK killing 总被引:2,自引:0,他引:2
Conjugation between human NK cells and susceptible target cells (K562 and Jurkat) leads to breakdown of inositol lipids in the effector cells but not when conjugated with resistant target cells. Extracellular Ca2+ is required for this activation. Sphingosine inhibits NK killing in both normal and IL-2-activated NK cells. Phorbol esters, TPA, and PDBU enhanced NK killing at low concentrations, where 4-alpha-PDIDE did not. The diacylglycerol derivative OAG increased NK cell killing and activated PKC from human lymphocytes. These results strongly suggest that phosphoinositide breakdown and activation of PKC is involved in NK killing. 相似文献
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Summary Of 45 fermentative gram negative bacterial isolates examined from wheat roots, three were capable of fixing atmospheric nitrogen as determined by the acetylene reduction technique and by protein contents of cells. A gram negative non-motile facultatively anaerobic bacterial strain capable of N2 fixation was identified asKlebsiella oxytoca ZMK-2.Optimal growth and N2 fixation occurred at pH 6.5. The optimum temperatures for growth under anaerobic conditions ranged between 30°–37°C. Acetylene reduction by intact cells was strikingly inhibited by 0.1 atm. or greater partial pressure of O2. Furthermore, the accumulation of H2 in the gas phase over cultures ofKlebsiella oxytoca ZMK-2 at partial pressures greater than 0.02 atm. resulted in a striking inhibition in the rate of C2H2 reduction. The addition of suspensions of eitherKlebsiella oxytoca ZMK-2 orAzotobacter vinelandii or a mixed culture of these two organisms to axenic cultures of wheat plants produced no significant increase in plant growth as measured by plant dry weight or nitrogen content of plants. 相似文献
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S. Cakmakci E. Dagdemir A. A. Hayaloglu M. Gurses E. Gundogdu 《World journal of microbiology & biotechnology》2008,24(3):293-299
The objective of the present study was to investigate the influence of container material (plastic or goat-skin bag) on the
growth of lactic acid bacteria in Tulum cheese during 9 months of ripening. The lactic acid bacteria in Tulum cheeses were
periodically counted on MRS and M17 agars throughout ripening. Results showed that the highest counts of lactic acid bacteria
on MRS or M17 were observed at the beginning of ripening and their counts decreased during later stages of ripening. The cheese
samples ripened in plastic bags exhibited higher numbers of LAB on MRS and M-17 agars than those ripened in goat-skin bags.
A total of 112 strains of lactic acid bacteria were isolated from Tulum cheeses ripened in plastic or goat-skin bags during
ripening. The lactic acid bacteria present in the cheese were classified by Microbial Identification System (MIS) based on
a comparison of the fatty acid methyl ester profiles. Different species including Enteroccocus, Lactobacillus, Streptococcus, Lactococcus and Pediococcus genera were found in unripened cheese. As ripening proceeded, the species Streptococcus and Lactococcus disappeared and the percentages of the species Enterococcus was unchanged in both containers. There were slight differences between the cheeses ripened in plastic or goat-skin bags
in terms of the profiles of lactic acid bacteria isolated. Some species including L. brevis, L. mesenteroides subsp. dextranicum, P. damnosus and E. mundtii were isolated only in the cheeses ripened in plastic bags; however, L. coryniformis and L. malafermentans were isolated only in the cheeses ripened in goat-skin bags at 6 or 9 months of ripening. Also the numbers of E. faecalis isolates were higher in the cheeses ripened in plastic containers than cheeses ripened goat-skin bags at the 6 or 9 months
of ripening. The results showed that Lactobacillus and Enterococcus were the predominant species in matured Tulum cheeses in both ripening containers. It seemed possible to produce Tulum cheese
with similar characteristics from both the containers used. 相似文献
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短尾猴和日本猴雄性性行为的比较研究 总被引:1,自引:2,他引:1
本文比较研究了短尾猴和日本猴的雄性性行为。短尾猴属单次爬跨射精型种类,每次交配平均持续23.2秒,日本猴属多次爬跨射精型种类,每次交配平均持续8.2分,交配期间雄性平均爬跨雌性lO.6次才能达到射精。短尾猴第1顺位雄性是群中的主要交配者,它占有交配总数的70.9 %;而日本猴第5顺位以下的雄性占交配总数的64%。交配中,两种猴雄性间相互打搅行为的发生频率大致相当。短尾猴高顺位雄性的打搅行为能使低顺位雄性的交配中断,但日本猴高顺位的打搅行为只能使低顺位雄性交配的54.3%中断。 相似文献