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21.
Arpigny C Jehin E Manfroid J Hutsemékers D Schulz R Stüwe JA Zucconi JM Ilyin I 《Science (New York, N.Y.)》2003,301(5639):1522-1524
High-resolution spectra of the CN B2 summation operator +-X2 summation operator + (0,0) band at 390 nanometers yield isotopic ratios for comets C/1995 O1 (Hale-Bopp) and C/2000 WM1 (LINEAR) as follows: 165 +/- 40 and 115 +/- 20 for 12C/13C, 140 +/- 35 and 140 +/- 30 for 14N/15N. Our N isotopic measurements are lower than the terrestrial 14N/15N = 272 and the ratio for Hale-Bopp from measurements of HCN, the presumed parent species of CN. This isotopic anomaly suggests the existence of other parent(s) of CN, with an even lower N isotopic ratio. Organic compounds like those found in interplanetary dust particles are good candidates. 相似文献
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The effects of soil pH, different levels of nitrogen (N), phosphoras (P), and potassium (K), alone and in combination on cadmium (Cd) uptake by Indian mustard [Brassica juncea (L.) Czen., cv ‘426308'] were studied under greenhouse conditions. Results showed that Cd concentration in aboveground biomass at soil pH 5.5 was three times more than at pH 6.5 and 7.5. Treatments without N application at pH 5.5 had the highest Cd concentrations in the aboveground biomass. Dry weight of aboveground biomass was significantly lower atpH 5.5 compared to pH 6.5 and 7.5. Total Cd uptake at pH 6.5 increased by 2 to 2.5 times compared to uptake at soil pH 5.5. Those conditions for maximum Cd accumulation by the aboveground biomass of Indian mustard from Cd‐contaminated soil occurs at soil pH 6.5 and when the application rates of N, P, and K are at 200, 100, and 66 kg ha‐1, respectively. 相似文献
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Surface ion equilibrium is hypothesized to play an important role in defining the interactions between foreign materials and biological systems. In this study, we compare two surfaces with respect to their ability to activate adhering platelets. One is a commonly used implant material TiO(2), which binds Ca(2+), and the other one is glass, which does not. We show, that in the presence of Ca(2+), TiO(2) acts as an agonist, activating adhering platelets and causing the expression on their surface of two well-known activation markers, CD62P (P-selectin) and CD63. On the contrary, in the absence of Ca(2+), platelets adhering on TiO(2) express only one of the two markers, CD63. Platelets adhering on glass, as well as platelets challenged with soluble agonists in solution, express both markers independently of whether Ca(2+) is present or not. The expression of CD62P and CD63 is indicative of the exocytosis of the so-called α- and dense granules, respectively. It is a normal response of platelets to activation. Differences in the expression profiles of these two markers point to differential regulation of the exocytosis of the two kinds of granules, confirming the recent notion that platelets can tune their microenvironment in a trigger-specific fashion. 相似文献
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Aleksandra A. PANYUTINA Alexander N. KUZNETSOV Ilya A. VOLODIN Alexei V. ABRAMOV Irina B. SOLDATOVA 《Integrative zoology》2017,12(2):172-184
The means of orientation is studied in the Vietnamese pygmy dormouse Typhlomys chapensis, a poorly known enigmatic semi‐fossorial semi‐arboreal rodent. Data on eye structure are presented, which prove that Typhlomys (translated as “the blind mouse”) is incapable of object vision: the retina is folded and retains no more than 2500 ganglion cells in the focal plane, and the optic nerve is subject to gliosis. Hence, Typhlomys has no other means for rapid long‐range orientation among tree branches other than echolocation. Ultrasonic vocalization recordings at the frequency range of 50–100 kHz support this hypothesis. The vocalizations are represented by bouts of up to 7 more or less evenly‐spaced and uniform frequency‐modulated sweep‐like pulses in rapid succession. Structurally, these sweeps are similar to frequency‐modulated ultrasonic echolocation calls of some bat species, but they are too faint to be revealed with a common bat detector. When recording video simultaneously with the ultrasonic audio, a significantly greater pulse rate during locomotion compared to that of resting animals has been demonstrated. Our findings of locomotion‐associated ultrasonic vocalization in a fast‐climbing but weakly‐sighted small mammal ecotype add support to the “echolocation‐first theory” of pre‐flight origin of echolocation in bats. 相似文献
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Ilya Yevdokimov Andreas Gattinger Franz Buegger Jean Charles Munch Michael Schloter 《Biology and Fertility of Soils》2008,44(8):1103-1106
The changes in size, activity and structure of soil microbial community caused by N fertilization were studied in a laboratory
incubation experiment. The rates of N fertiliser applied (KNO3) were 0 (control), 100 and 2,000 μg N g−1 soil. Despite no extra C sources added, a high percentage of N was immobilized. Whereas no significant increase of microbial
C was revealed during incubation period, microbial growth kinetics as determined by the substrate-induced growth-response
method demonstrated a significant decrease in the specific growth rate of microbial community in soil treated with 2,000 μg
N g−1 soil. Additionally, a shift in microbial community structure resulting in an increase in fungal biomarkers, mainly in the
treatment with 2,000 μg N g−1 soil was visible. 相似文献
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Vera A. MATROSOVA Anastasia D. IVANOVA Elena V. VOLODINA Ilya A. VOLODIN Dmitry Yu. ALEXANDROV Olga V. SIBIRYAKOVA Oleg A. ERMAKOV 《Integrative zoology》2019,14(4):341-353
Distribution area and taxonomic borders within the species complex Spermophilus erythrogenys sensu lato remain questionable. Early evidence suggests that red‐cheeked ground squirrels of Southeast Kazakhstan are remarkably different in terms of the acoustic structure of their alarm calls from the red‐cheeked ground squirrels of the Kurgan region in Russia. In this study, we analyzed the differences in the acoustic structure of the alarm call and mitochondrial DNA (complete control region, 1005–1006 bp and complete cytochrome b gene, 1140 bp) in 3 populations of red‐cheeked ground squirrels (Tara, Altyn‐Emel and Balkhash), all located within areas isolated by geographical barriers in Southeast Kazakhstan. We found that the alarm call variables were similar between the 3 study populations and differed by the maximum fundamental frequency (8.46 ± 0.75 kHz) from the values (5.62 ± 0.06 kHz) reported for the red‐cheeked ground squirrels from the Kurgan region of Russia. Variation in mtDNA control region was only 3% and variation in cytochrome b gene was only 2.5%. Phylogenetic trees based on cytochrome b gene polymorphism of 44 individuals from the study area and adjacent territories indicated 3 clades with high (98–100%) bootstrap support: “intermedius,” “brevicauda” and “iliensis”). We conclude that the 3 study populations in Southeast Kazakhstan belong to the clade intermedius and suggest a taxonomical revision of the species complex Spermophilus erythrogenys sensu lato, including analyses of nuclear DNA and alarm calls for populations of the brevicauda and iliensis clades. 相似文献
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To identify factors that influence the relatively high productivity of a semi-arid pine afforestation system in southern Israel, we investigated inorganic nitrogen deposition and mineralization for more than 2 years. To this end, we measured bulk and dry deposition, in situ N-mineralization over the seasonal cycle, and the potential activity of nitrifying microorganisms by soil slurry incubations. There was a small increase in bulk N deposition in the forest, compared with shrubland, but no change in dry deposition. An unexpected rapid increase in nitrite concentration in the forest soil was observed after soil rewetting by the first winter rains, which could not be explained by deposition. This was accompanied by a decrease in ammonium and only a slight increase in nitrate concentrations. Only a small increase in nitrite and a rapid increase in nitrate concentration in the mineral soil were observed in the surrounding shrubland. Soil slurry incubations from the forest sites exhibited significant delay in nitrite, compared with nitrate accumulation (up to 50 h under lab conditions) in samples taken in the dry season, but not in the wet season. This indicated different rates of ammonium and nitrite oxidation that are most likely linked to differential activation of different microbial populations after the summer stress. The initial oxidation process of ammonia to nitrate, upon soil rewetting in semi-arid environments, appears to occur as a partially uncoupled two-step process, as opposed to a rapid continuous one in wetter environments. This may have implications for the synchronization of nitrate availability to plants and therefore for high forest productivity and nitrogen use efficiency. Forest productivity in the semi-arid regions, in turn, is becoming increasingly more important with persistent predictions of warming and drying trends over the entire Mediterranean basin and other regions. 相似文献
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Gorelick-Feldman J Maclean D Ilic N Poulev A Lila MA Cheng D Raskin I 《Journal of agricultural and food chemistry》2008,56(10):3532-3537
Phytoecdysteroids, which are structurally similar or identical to insect molting hormones, produce a range of effects in mammals, including increasing growth and physical performance. To study the mechanism of action of phytoecdysteroids in mammalian tissue, an in vitro cellular assay of protein synthesis was developed. In C2C12 murine myotubes and human primary myotubes, phytoecdysteroids increased protein synthesis by up to 20%. In vivo, ecdysteroids increased rat grip strength. Ecdysteroid-containing plant extracts produced similar results. The effect was inhibited by a phosphoinositide kinase-3 inhibitor, which suggests a PI3K-mediated mechanism. 相似文献