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161.
Muroya Y Plante I Azzam EI Meesungnoen J Katsumura Y Jay-Gerin JP 《Radiation research》2006,165(4):485-491
Ionizing radiation-induced bystander effects, commonly observed in cell populations exposed to high-linear energy transfer (LET) radiations, are initiated by damage to a cellular molecule which then gives rise to a toxic signal exported to neighboring cells not directly hit by radiation. A major goal in studies of this phenomenon is the identification of this initial radiation-induced lesion. Liquid water being the main constituent of biological matter, reactive species produced by water radiolysis in the cellular environment are likely to be major contributors to the induction of this lesion. In this context, the radiation track structure is of crucial importance in specifying the precise location and identity of all the radiolytic species and their subsequent signaling or damaging effects. We report here Monte Carlo track structure simulations of the radiolysis of liquid water by four different impacting ions 1H+, 4He2+, 12C6+ and 20Ne10+, with the same LET ( approximately 70 keV/ microm). The initial radial distribution profiles of the various water decomposition products (eaq(-), *OH, H*, H2 and H2O2) for the different ions considered are presented and discussed briefly in the context of track structure theory. As an example, the formation and temporal evolution of simulated 24 MeV 4He2+ ion tracks (LET approximately 26 keV/microm) are reported for each radiolytic species from 1 ps to 10 micros. The calculations reveal that the ion track structure is completely lost by approximately 1 micros. 相似文献
162.
163.
164.
Summary Nucleolus-associated bodies (NABs) occur in interphase nuclei of many plant species. The present work shows that, inZea mays, NABs are present in dry seeds as well as in germinating tissues. The frequency of these nuclear bodies remains more or less constant during the first 24 h of imbibition but decreases significantly during the next 24 h. By the time the nucleolus reaches maturation and contains granular zones, these bodies are still found in close association with the surface of this organelle, as is the case in mature root meristematic cells. Immunocytochemical observations on both dry seeds and germinating tissues further revealed that NABs reacted positively with a monoclonal antibody (mAbK121) recognizing the m3G cap of sn(small nuclear)RNAs. It is, therefore, concluded that the NABs present in such tissues already contain components characterizing snRNPs (small nuclear ribonucleoproteins) in mature tissues. The possible function of NABs as storage deposits of snRNPs in dry seeds and early germinating tissues is discussed. In view of their many similarities with the coiled bodies described in both animal and plant cells, it is most likely that NABs correspond to those structures.Abbreviations BSA
bovine serum albumin
- DABCO
1,4-diazabicyclo (2.2.2)octane
- EDTA
ethylenediaminetetraacetic acid
- IgM
immunoglobulin M
- NAB
nucleolus-associated body
- AO
acridine orange
- NAC
nucleolus-associated chromatin
- PBS
phosphate-buffered saline
- snRNA
small nuclear ribonucleic acid
- snRNP
small nuclear ribonucleoprotein 相似文献
165.
Plante D Bélanger G Leblanc D Ward P Houde A Trottier YL 《Letters in applied microbiology》2011,52(3):239-244
Aims: To demonstrate that produce rinsates used for RT‐qPCR detection of foodborne viruses may cause significant PCR inhibition and propose a means to reduce its impact on sensitivity. Methods and Results: Here, it is shown that rinsing and concentration from spinach and precut lettuce have the potential to generate RNA extracts that are inhibitory to RT‐qPCRs assembled from commercial kits for the detection of norovirus GII (NoV GII), hepatitis A virus (HAV), hepatitis E virus (HEV), rotavirus (RV) and feline calicivirus (FCV) as sample process control. It is further shown that the addition of bovine serum albumin (BSA) to those reactions restored a positive signal in all cases. The effect of BSA was dependent upon the primer/probe combination. Moreover, two of the detection systems (FCV and HAV) strongly benefited from the addition of BSA even in the absence of PCR inhibitors. Conclusions: BSA was shown to restore positive signals in five different RT‐qPCR systems that were otherwise completely inhibited by produce rinsate extracts. It is therefore suggested to consider the addition of BSA to RT‐qPCRs for the detection of foodborne viruses when inhibition is observed. Significance and Impact of the Study: This study clearly demonstrates the potency of PCR inhibitors generated during routine virus concentration from produce and that it can be alleviated by the addition of BSA to the RT‐qPCRs. Although used elsewhere, the addition of BSA to PCRs is not a common practice in this growing field of research. 相似文献
166.
HIV-1 pathogenesis is intimately linked with microbial infections and innate immunity during all stages of the disease. While the impact of microbial-derived products in transmission of R5-using virus to CD4+ T cells by dendritic cells (DCs) has been addressed before, very limited data are available on the effect of such compounds on DC-mediated dissemination of X4-tropic variant. Here, we provide evidence that treatment of DCs with dectin-1/TLR2 and NOD2 ligands increases cis-infection of autologous CD4+ T cells by X4-using virus. This phenomenon is most likely associated with an enhanced permissiveness of DCs to productive infection with X4 virus, which is linked to increased surface expression of CXCR4 and the acquisition of a maturation profile by DCs. The ensuing DC maturation enhances susceptibility of CD4+ T cells to productive infection with HIV-1. This study highlights the crucial role of DCs at different stages of HIV-1 infection and particularly in spreading of viral strains displaying a X4 phenotype. 相似文献
167.
Plante I 《Radiation and environmental biophysics》2011,50(3):405-415
The importance of the radiolysis of water in the initial events following irradiation of biological systems has motivated
considerable theoretical and experimental work in the field of radiation chemistry of water and aqueous systems. These studies
include Monte-Carlo simulations of the radiation track structure and of the non-homogeneous chemical stage, which have been
successfully used to calculate the yields of radiolytic species (H·, ·OH, H2, H2O2, eaq−, …). Most techniques used for the simulation of the non-homogeneous chemical stage such as the independent reaction time
(IRT) technique and diffusion kinetics methods do not calculate the time evolution of the positions of the radiolytic species.
This is a major limitation to their extension to the simulation of the irradiation of radiobiological systems. Step-by-step
(SBS) simulation programs provide such information, but they are very demanding in term of computer power and storage capacity.
Recent improvements in computer performance now allow the regular use of the SBS method in radiation chemistry simulations.
In the first of a series of two papers, the SBS method has been reviewed in details and the implementation of a SBS code has
been discussed. In this second paper, the results of several studies are presented: (1) the time evolution of the radiolytic
yields from the formation of the radiation track to 10−6 s; (2) the effect of pH on yields (pH ~ 0.4–7.0); (3) the effect of proton energy (and LET) on yields (300 MeV-0.1 MeV),
and iv) the effect of the ion type (1H+, 4He2+, 12C6+) on yields. Nonbiological applications, i.e., the study of the temperature on the yields (about 25–300°C) and the simulation
of the time evolution of G(Fe3+) in the Fricke dosimeter are also discussed. 相似文献
168.
Aims
Extracellular enzymes mediate the decomposition of organic matter and the release of plant-available nutrients. Current theory predicts that enzyme production by soil microbes is regulated by the stoichiometric demands of microbial biomass and the complexity of environmental resources, but most experiments ignore the potential effect of alleviated carbon limitation in the rhizosphere. Our objective was to investigate linkages between enzyme activities, soil nutrient availability and plant roots in a tropical Oxisol.Methods
We conducted a greenhouse experiment using soils from the Luquillo Experimental Forest and seedlings of Tabebuia heterophylla. Planted and unplanted pots were fertilized with different combinations of phosphorus and either mineral nitrogen (ammonia chloride) or a nitrogen-rich organic compound (casein). We measured changes in plant and soil nutrients and five extracellular enzyme activities.Results
Phosphatase activity declined by 28% in the P and 40% in the complex nitrogen treatment, while N-acetyl glucosaminidase increased 162% in the complex nitrogen treatment. Beta-glucosidase, beta-xylosidase, cellobiohydrolase and N-acetyl glucosaminidase all increased significantly over time in the simple nitrogen treatment (P?<?0.05).Conclusions
Enzymatic responses support microbial resource allocation theory, that is, the concept that soil microbes regulate enzyme production based on scarcity of resources. However, we did not observe any additional effect of roots on extracellular enzyme activities. Enzymatic C:N, C:P and N:P ratios further support the notion that shifts in microbial stoichiometric demand drive responses to nutrients. 相似文献169.
Effects of open-top passive warming chambers on soil respiration in the semi-arid steppe to taiga forest transition zone in Northern Mongolia 总被引:1,自引:0,他引:1
Anarmaa Sharkhuu Alain F. Plante Orsoo Enkhmandal Brenda B. Casper Brent R. Helliker Bazartseren Boldgiv Peter S. Petraitis 《Biogeochemistry》2013,115(1-3):333-348
The response of soil respiration to warming has been poorly studied in regions at higher latitude with low precipitation. We manipulated air temperature, soil temperature and soil moisture using passive, open-top chambers (OTCs) in three different ecosystem settings in close proximity (boreal forest, riparian area, and semi-arid steppe) to investigate how environmental factors would affect soil respiration in these different ecosystems, anticipating that soil respiration would increase in response to the chamber treatment. The results indicated that OTCs significantly increased air and soil temperature in areas with open canopy and short-statured vegetation (i.e., steppe areas) but not in forest. OTCs also affected soil moisture, but the direction of change depended on the ecosystem, and the magnitude of change was highly variable. Generally, OTCs did not affect soil respiration in steppe and riparian areas. Although soil respiration was slightly greater in OTCs placed in the forest, the difference was not statistically significant. Analyses of relationships between soil respiration and environmental variables suggested that different factors controlled soil respiration in the different ecosystems. Competing effects analysis using a model selection approach and regression analyses (e.g., Q10) demonstrated that soil respiration in the forest was more sensitive to warming, while soil respiration in the steppe was more sensitive to soil moisture. The differing responses and controlling factors among these neighboring forest, riparian and steppe ecosystems in Northern Mongolia highlight the importance of taking into account potential biome shifts in C cycling modeling to generate more accurate predictions of landscape-scale responses to anticipated climate change. 相似文献
170.
We have expressed recombinant α-subunits of hH1 (human heart subtype 1), rSkM1 (rat skeletal muscle subtype 1) and hSkM1 (human
skeletal muscle) sodium channels in human embryonic kidney cell line, namely the tsA201 cells and compared the effects of
ATX II on these sodium channel subtypes. ATX II slows the inactivation phase of hH1 with little or no effect on activation.
At intermediate concentrations of ATX II the time course of inactivation is biexponential due to the mixture of free (fast
component, τfast
h
) and toxin-bound (slow component, τslow
h
) channels. The relative amplitude of τslow
h
allows an estimate of the IC50 values ∼11 nm. The slowing of inactivation in the presence of ATX II is consistent with destabilization of the inactivated state by toxin
binding. Further evidence for this conclusion is: (i) The voltage-dependence of the current decay time constants (τ
h
) is lost or possibly reversed (time constants plateau or increase at more positive voltages in contrast to these of untreated
channels). (ii) The single channel mean open times are increased by a factor of two in the presence of ATX II. (iii) The recovery
from inactivation is faster in the presence of ATX II.
Similar effects of ATX II on rSkM1 channel behavior occur, but only at higher concentrations of toxin (IC50= 51 nm). The slowing of inactivation on hSkM1 is comparable to the one seen with rSkM1.
A residual or window current appears in the presence of ATX II that is similar to that observed in channels containing mutations
associated with some of the familial periodic paralyses.
Received: 5 December 1995/Revised: 1 March 1996 相似文献