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91.
Kashif Mahfooz Mahendra Singh Robert Renden John F. Wesseling 《PLoS computational biology》2016,12(4)
The readily releasable pool (RRP) of vesicles is a core concept in studies of presynaptic function. However, operating principles lack consensus definition and the utility for quantitative analysis has been questioned. Here we confirm that RRPs at calyces of Held from 14 to 21 day old mice have a fixed capacity for storing vesicles that is not modulated by Ca2+. Discrepancies with previous studies are explained by a dynamic flow-through pool, established during heavy use, containing vesicles that are released with low probability despite being immediately releasable. Quantitative analysis ruled out a posteriori explanations for the vesicles with low release probability, such as Ca2+-channel inactivation, and established unexpected boundary conditions for remaining alternatives. Vesicles in the flow-through pool could be incompletely primed, in which case the full sequence of priming steps downstream of recruitment to the RRP would have an average unitary rate of at least 9/s during heavy use. Alternatively, vesicles with low and high release probability could be recruited to distinct types of release sites; in this case the timing of recruitment would be similar at the two types, and the downstream transition from recruited to fully primed would be much faster. In either case, further analysis showed that activity accelerates the upstream step where vesicles are initially recruited to the RRP. Overall, our results show that the RRP can be well defined in the mathematical sense, and support the concept that the defining mechanism is a stable group of autonomous release sites. 相似文献
92.
93.
Anjana Bagchi Partha Neogi Mahendra Sahai Anil B. Ray Yoshiteru Oshima Hiroshi Hikino 《Phytochemistry》1984,23(4):853-855
Novel withanolides, withaperuvin E and nicandrin B, isolated respectively, from Physalis peruviana and Nicandra physaloides, were fully characterized by chemical and spectroscopic means. 相似文献
94.
Magdalena Wypij Joanna Czarnecka Magdalena Świecimska Hanna Dahm Mahendra Rai Patrycja Golinska 《World journal of microbiology & biotechnology》2018,34(2):23
We report synthesis of silver nanoparticles (AgNPs) from Streptomyces xinghaiensis OF1 strain, which were characterised by UV–Vis and Fourier transform infrared spectroscopy, Zeta sizer, Nano tracking analyser, and Transmission electron microscopy. The antimicrobial activity of AgNPs alone, and in combination with antibiotics was evaluated against bacteria, namely Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis, and yeasts viz., Candida albicans and Malassezia furfur by using micro-dilution method. The minimum inhibitory concentration (MIC) and minimum biocidal concentration of AgNPs against bacterial and yeast strains were determined. Synergistic effect of AgNPs in combination with antibacterial and antifungal antibiotics was determined by FIC index. In addition, MTT assay was performed to study cytotoxicity of AgNPs alone and in combination with antibiotics against mouse fibroblasts and HeLa cell line. Biogenic AgNPs were stable, spherical, small, polydispersed and capped with organic compounds. The variable antimicrobial activity of AgNPs was observed against tested bacteria and yeasts. The lowest MIC (16 µg ml?1) of AgNPs was found against P. aeruginosa, followed by C. albicans and M. furfur (both 32 µg ml?1), B. subtilis and E. coli (both 64 µg ml?1), and then S. aureus and Klebsiella pneumoniae (256 µg ml?1). The high synergistic effect of antibiotics in combination with AgNPs against tested strains was found. The in vitro cytotoxicity of AgNPs against mouse fibroblasts and cancer HeLa cell lines revealed a dose dependent potential. The IC50 value of AgNPs was found in concentrations of 4 and 3.8 µg ml?1, respectively. Combination of AgNPs and antibiotics significantly decreased concentrations of both antimicrobials used and retained their high antibacterial and antifungal activity. The synthesis of AgNPs using S. xinghaiensis OF1 strain is an eco-friendly, cheap and nontoxic method. The antimicrobial activity of AgNPs could result from their small size. Remarkable synergistic effect of antibiotics and AgNPs offer their valuable potential in nanomedicine for clinical application as a combined therapy in the future. 相似文献
95.
Rai Mahendra Ingle Avinash P. Paralikar Priti Anasane Netravati Gade Rajendra Ingle Pramod 《Applied microbiology and biotechnology》2018,102(16):6827-6839
Applied Microbiology and Biotechnology - Ginger (Zingiber officinale Rosc.) is a tropical plant cultivated all over the world due to its culinary and medicinal properties. It is one of the most... 相似文献
96.
Rates of weight loss and release of nutrients during different phases of decomposition in young water hyacinth leaves were
determined under laboratory conditions. The leaves decomposed solely by physical leaching during the initial 4-day phase and
later by microbial processes. The largest part of weight loss and nutrient release by physical leaching took place within
the first 4 h of incubation and thereafter the decomposition rate declined. Microbial processes decayed leaves at a significantly
higher rate than that by physical leaching. The overall decay rate constants were related inversely and the release of nutrients
directly to the levels of leaf additions in the lake water. The dissolved inorganic and organic nutrients were released chiefly
by abiotic processes during the initial as well as later phases of decay. The release was significantly higher during the
initial phase in comparison with that during the later phase. Microbes utilized only a small amount of nutrients that were
released during decomposition of water hyacinth leaves. The % release of various elements from the decaying leaves was in
the order of K > P > C > Na > N. 相似文献
97.
98.
A corn (Zea mays L.) mutant, blue fluorescent-1 (bf), is described that shows ultraviolet light induced blue fluorescence in young seedling leaves if homozygous for the mutant gene, and in anthers if either homozygous or heterozygous. The blue fluorescent compounds were extracted with acetone and separated by paper chromatography. Anthranilic acid was present and the beta-glucoside was also identified by paper chromatography and beta-glucosdase and acid treatment. A third major fluorescent compound was not identified, but it was convertible to anthranilic acid by acid treatment. Anthranilate synthetase from mutant plants was 3-40 times more active and was also more resistant to feedback inhibition by tryptophan than was the enzyme from normal plants. The high activity and feedback resistance would both lead to anthranilate accumulation. Anthranilate-phosphoribosylpyrophosphate phosphoribosyltransferase (PR transferase), the enzyme which usually utilizes anthranilate in the tryptophan pathway, was inhibited by the beta-glucoside of anthranilic acid in a noncompetitive manner and showed very little activity in the mutant plant extract. This inhibition of the enzyme which utilizes anthranilate would also lead to accumulation. Apparently the oversynthesis of anthranilate leads to the formation of the beta-glucoside, which inhibits anthranilate utilization. The fluorescent compounds are absent in seed, but form on germination. The levels decrease with age after 35 days postgermination, but are still present in leaves during grain filling. 相似文献
99.
Summary The transformation of urea and ammonium sulphate in Ladwa sandy loam and Balsamand sand was studied in laboratory. Urea took
at least one week in sandy loam and 2 weeks in sandy soils to hydrolyse completely. The process of hydrolysis was faster in
finer soil with high organic matter than in coarse soil having low organic matter. There was no nitrification upto 3 days
in sandy loam and upto 7 days in sandy soils, respectively, but there was immobilization of NO3-N during these initial periods. The NO3-N content at the end of incubation period (35 days) was more in case of urea than in case of ammonium sulphate treated samples
in sandy loam soil and reverse was true in sandy soil. The hydrolysis of urea did not follow zero or first order kinetics
as proposed in previous studies. 相似文献
100.
Summary The rate of hydrolysis of unsonicated liposomes of egg lecithin by phospholipase A (from bee venom and Russell viper venom) and phospholipase C (fromBacillus cereus andClostridium welchii) is markedly dependent on the nature and concentration of a variety of added alcohols. Typical plots of rate against alcohol concentration are bell-shaped. The maximum rate and the alcohol concentration at which it is achieved are alcohol-specific. In a homologous series ofn-alkanols, the maximal rates increase and the optimal concentrations decrease as the chain length is increased from C4 to C8. For longer alcohols (C9 to C12), progressively higher concentrations are required to elicit maximal activation. The optimal activating concentrationsC for C4 to C8
n-alkanols obey the relationshipp C=a logP
octanol+constant [cf. Hansch & Dunn,J. Pharm. Sci.
61:1 (1972)], suggesting that the alcohol-activating effect is a consequence of their incorporation into the liposomes with resultant modification of liposomal structure. 相似文献