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21.
Mycobacterium tuberculosis H37Ra,M. smegmatisATCC 607,M. smegmatis MC2155,M. aurum A +,M. aurum A11, and one representative strain ofM. flavescens were transformed by electroporation with plasmid pMY10 and cosmid pDC100. Plasmid pMY 10 contained the origin of replication of pAL5000, the origin of replication of pBR322, a kanamycin resistance gene, and the origin of transfer of the Inc plasmid RK2; the cosmid pDC100 contained the pHC79 SS cosmid, the origin of replication of pAL5000, and a kanamycin resistance gene. The efficiency of transformation varied with the recipient cells used and was in decreasing order: 7×105 forM. smegmatis MC2155, 6×103 forM. tuberculosis H37Ra, 103 forM. aurum, 50 forM. smegmatis ATCC 607, and 5 forM. flavescens. A rapid protocol for plasmid extraction from mycobacteria was developed.The satisfactory transformation of the nonvirulentM. tuberculosis strain H37Ra was of interest for future studies on cloning of virulence genes, while the satisfactory transformation ofM. aurum was of interest for future studies on the genetics of drug resistance because these bacteria are sensitive to drugs specifically used in the treatment of tuberculosis and leprosy. However, neither vector was stably maintained inM. smegmatis, indicating that further investigations are still necessary to resolve this difficulty. 相似文献
22.
Françoise Lagardère Rachid Amara Lucette Joassard 《Environmental Biology of Fishes》1999,56(1-2):213-228
To evaluate the impact of metamorphosis on the vertical distribution and feeding activity of sole, Solea solea, larvae passing from offshore spawning grounds to the Bay of Vilaine, sampling series at fixed stations were carried out in April 1991 and April 1993 at depths from 50 to 30 m. Comparisons between plankton and bottom samplin series indicated differences in vertical distribution of larvae in pre-metamorphic and metamorphic steps. Metamorphosing larvae displayed a tendency to concentrate in the lower part of the water column, mainly during the day. Gut contents, analysed for prey identification, fullness index and carbon content, indicated that metamorphosing larvae fed mostly on plankton. Variations in fullness index were observed not only during the day, but also depended on tide and wind-induced mixing conditions. Larvae sampled in mixed spring-tide waters had highly variable carbon estimates, resulting in unclear diel activity. More larvae fed actively at neap-tide, which allowed the observation of a diurnal feeding activity through hourly changes in carbon estimates. It is concluded that immigrating sole were not yet able to settle but prepared themselves for demersal life (i) without undergoing starvation and (ii) by modifying the patterns of vertical distributions. The presence of a larval swimbladder suggests they can adjust their vertical movements, depending on tidal cycles, which could in turn favour coastal accumulation of metamorphosing larvae and pulses of new settlers entering the nursery grounds. 相似文献
23.
El Abdllaoui A Auger P Kooi BW Bravo de la Parra R Mchich R 《Mathematical biosciences》2007,210(1):335-354
We consider a predator-prey model in a two-patch environment and assume that migration between patches is faster than prey growth, predator mortality and predator-prey interactions. Prey (resp. predator) migration rates are considered to be predator (resp. prey) density-dependent. Prey leave a patch at a migration rate proportional to the local predator density. Predators leave a patch at a migration rate inversely proportional to local prey population density. Taking advantage of the two different time scales, we use aggregation methods to obtain a reduced (aggregated) model governing the total prey and predator densities. First, we show that for a large class of density-dependent migration rules for predators and prey there exists a unique and stable equilibrium for migration. Second, a numerical bifurcation analysis is presented. We show that bifurcation diagrams obtained from the complete and aggregated models are consistent with each other for reasonable values of the ratio between the two time scales, fast for migration and slow for local demography. Our results show that, under some particular conditions, the density dependence of migrations can generate a limit cycle. Also a co-dim two Bautin bifurcation point is observed in some range of migration parameters and this implies that bistability of an equilibrium and limit cycle is possible. 相似文献
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25.
The RNA-binding protein fragile X-related 1 regulates somite formation in Xenopus laevis 总被引:5,自引:0,他引:5 下载免费PDF全文
Huot ME Bisson N Davidovic L Mazroui R Labelle Y Moss T Khandjian EW 《Molecular biology of the cell》2005,16(9):4350-4361
Fragile X-related 1 protein (FXR1P) is a member of a small family of RNA-binding proteins that includes the Fragile X mental retardation 1 protein (FMR1P) and the Fragile X-related 2 protein (FXR2P). These proteins are thought to transport mRNA and to control their translation. While FMR1P is highly expressed in neurons, substantial levels of FXR1P are found in striated muscles and heart, which are devoid of FMRP and FXR2P. However, little is known about the functions of FXR1P. We have isolated cDNAs for Xenopus Fxr1 and found that two specific splice variants are conserved in evolution. Knockdown of xFxr1p in Xenopus had highly muscle-specific effects, normal MyoD expression being disrupted, somitic myotomal cell rotation and segmentation being inhibited, and dermatome formation being abnormal. Consistent with the absence of the long muscle-specific xFxr1p isoform during early somite formation, these effects could be rescued by both the long and short mRNA variants. Microarray analyses showed that xFxr1p depletion affected the expression of 129 known genes of which 50% were implicated in muscle and nervous system formation. These studies shed significant new light on Fxr1p function(s). 相似文献
26.
Guerrero K Wuyam B Mezin P Vivodtzev I Vendelin M Borel JC Hacini R Chavanon O Imbeaud S Saks V Pison C 《American journal of physiology. Regulatory, integrative and comparative physiology》2005,289(4):R1144-R1154
Mechanisms responsible for limitation of exercise capacity in lung transplant recipients (LR) and benefits gained by exercise training were studied. Mitochondrial respiration parameters, energy transfer, and cell structure were assessed in vastus lateralis biopsies using the permeabilized fiber technique with histochemical and morphometric measurements. Twelve male controls (C) and 12 LR performed exercise training over 12 wk. Before exercise training, there were strong correlations between exercise capacity (maximal O(2) consumption and endurance time at 70% maximal power output) and cellular events, as assessed by percentage of type I fibers and apparent K(m) for exogenous ADP. Anticalcineurins were not involved in LR exercise limitation, since there were no differences in maximal mitochondrial rate of respiration before exercise training and no abnormalities in respiratory chain complexes compared with C. Training resulted in a significant increase in physiological parameters both at the cellular (apparent K(m) for exogenous ADP and stimulating effect of creatine) and integrated (maximal O(2) consumption, power output at ventilatory threshold, maximal power output, and endurance time at 70% maximal power output) levels in LR and C. After the training period, improvements in maximal O(2) consumption and in maximal mitochondrial rate of respiration were noted, as well as changes in endurance time and percentage of type I fibers. Because there were no changes in diameters and fiber types, baseline alteration of apparent K(m) for exogenous ADP and its improvement after training might be related to changes within the intracellular energetic units. After the training period, intracellular energetic units exhibited a higher control of mitochondrial respiration by creatine linked to a more efficient functional coupling adenine nucleotide translocase-mitochondrial creatine kinase, resulting in better exercise performances in C and LR. 相似文献
27.
Costa VV Fagundes CT Valadão DF Cisalpino D Dias AC Silveira KD Kangussu LM Ávila TV Bonfim MR Bonaventura D Silva TA Sousa LP Rachid MA Vieira LQ Menezes GB de Paula AM Atrasheuskaya A Ignatyev G Teixeira MM Souza DG 《PLoS neglected tropical diseases》2012,6(5):e1663
There are few animal models of dengue infection, especially in immunocompetent mice. Here, we describe alterations found in adult immunocompetent mice inoculated with an adapted Dengue virus (DENV-3) strain. Infection of mice with the adapted DENV-3 caused inoculum-dependent lethality that was preceded by several hematological and biochemical changes and increased virus dissemination, features consistent with severe disease manifestation in humans. IFN-γ expression increased after DENV-3 infection of WT mice and this was preceded by increase in expression of IL-12 and IL-18. In DENV-3-inoculated IFN-γ(-/-) mice, there was enhanced lethality, which was preceded by severe disease manifestation and virus replication. Lack of IFN-γ production was associated with diminished NO-synthase 2 (NOS2) expression and higher susceptibility of NOS2(-/-) mice to DENV-3 infection. Therefore, mechanisms of protection to DENV-3 infection rely on IFN-γ-NOS2-NO-dependent control of viral replication and of disease severity, a pathway showed to be relevant for resistance to DENV infection in other experimental and clinical settings. Thus, the model of DENV-3 infection in immunocompetent mice described here represents a significant advance in animal models of severe dengue disease and may provide an important tool to the elucidation of immunopathogenesis of disease and of protective mechanisms associated with infection. 相似文献
28.
Induction of micronuclei by Zearalenone in Vero monkey kidney cells and in bone marrow cells of mice: protective effect of Vitamin E 总被引:7,自引:0,他引:7
Zearalenone (ZEN) is a non-steroidal estrogenic mycotoxin mainly produced by Fusarium graminaerum, found as a world-wide contaminant mainly of corn and wheat. Previous studies have demonstrated that among several other effects on animals and humans, ZEN also displays hepatotoxicity, immunotoxicity and nephrotoxicity. ZEN is mainly known as a hormonal disrupter due to its estrogenic activities and consequent toxicity for reproduction. Furthermore, mutagenic and genotoxic proprieties of ZEN were disclosed recently, the molecular mechanisms of which are not yet well understood. In the present study, the genotoxic potential of ZEN was evaluated using genotoxicity tests: the 'cytokinesis block micronucleus assay' in Vero monkey kidney cells and the 'in vivo mouse bone marrow micronucleus assay'. In cultured cells treated with 5, 10 and 20 microM ZEN, the frequency of binucleated micronucleated cells (BNMN) was assessed in 1000 binucleated cells and in mice given oral doses of 10, 20 and 40 mg/kg bw, the frequency of polychromatic erythrocytes micronucleated (PCEMN) in bone marrow cells was assessed in 2000 polychromatic erythrocytes (PCE). The potential prevention of ZEN-induced effects by 25 microM Vitamin E (Vit E) was also evaluated.In vivo, doses of 10, 20 and 40 mg/kg bw ZEN representing, respectively 2, 4 and 8% of the LD50 (LD50 of ZEN in mice is 500 mg/kg bw), were administered to animals either with or without pre-treatment with Vit E (216.6 mg/kg bw) in order to evaluate its preventive potential.ZEN was found to induce micronuclei (MN) in a dose-dependent manner in cultured Vero cells as well as in mouse bone marrow cells. The present data emphasise the likely clastogenic pathway among the molecular mechanisms that underlay the ZEN-induced genotoxicity. Vit E was found to prevent partially-from 30 to 50%-these toxic effects, most likely acting either as a structural analogue of ZEN or as an antioxidant. 相似文献
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30.
Désiré Gnanvossou J. Steve Yaninek Rachid Hanna Marcel Dicke 《Experimental & applied acarology》2003,30(3):265-278
The effects of prey mite suitability on several demographic characteristics of phytoseiid predators and the relationship of
these effects to the potential of phytoseiid predators to control herbivorous mite populations are well documented. Evidence
has also accumulated in the last 20 years demonstrating that phytoseiid predators utilize herbivorous prey mite-induced plant
volatiles as olfactory cues in locating their herbivorous mite prey, but less well established is the predictability of reproductive
success from the ability of the predators to utilize olfactory cues to locate their prey, and how these processes are related
to the success of the predators as biological control agents of the herbivorous mite. In this study, we determined in laboratory
no choice experiments, the development, survivorship and fecundity of the two neotropical phytoseiid predators Typhlodromalus manihoti Moraes and T. aripo DeLeon when feeding on three herbivorous mites, including the key prey species Mononychellus tanajoa (Bondar), and the two alternative prey species Oligonychus gossypii (Zacher) and Tetranychus urticae (Koch). Intrinsic rate of increase (rm) of T. aripo was 2.1 fold higher on M. tanajoa as prey compared with T. urticae as prey, while it was almost nil on O. gossypii. For T. manihoti, rm was 2.3 fold higher on M. tanajoa as prey compared with O. gossypii as prey, while reproduction was nil on T. urticae. An independent experiment on odor-related prey preference of the two predator species showed that T. manihoti and T. aripo preferred odors from M. tanajoa-infested leaves to odors from O. gossypii-infested leaves. Moreover, both predator species preferred odors from M. tanajoa-infested leaves over those from T. urticae-infested leaves. As reported here, life history of the two predatory mites matches odor-related prey preference if the key
prey species is compared to the two inferior prey species. The implications of our findings for the persistence of T. manihoti and T. aripo and biological control of M. tanajoa in the cassava agroecosystem in Africa are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献