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51.
Pascale Guiraud Régine Steiman Françoise Seigle-Murandi Lucile Sage 《Antonie van Leeuwenhoek》1997,72(4):317-325
Exserohilum sodomii sp. nov., is described. This new species was isolated from a soil sample from the Dead Sea surroundings. Its main physiological properties, as well as the influence of temperature and salts concentration in the culture medium on growth and morphology of the fungus were investigated and discussed. 相似文献
52.
Range shifts are predicted for numerous species due to climate change, and therefore understanding species dispersal is more crucial than ever. For some species, their low dispersal capabilities may prevent them from reaching new, suitable habitats, thus threatening their survival. This is of particular concern for those ground beetles which are flightless and depend on a specific type of habitat. However, studies on ground beetle dispersal rates are rare. We investigated the shift in distribution range of Carabus hortensis in northwestern Germany over a span of 22 years. We found that this species disperses on average 127 m per year with low variation between years. Although C. hortensis’ movement (locomotory) activity is not different or lower than that found in similar ground beetles, its dispersal rate is rather low. We speculate that this slow range expansion may be due to a long individual development time from egg to teneral and suggest that in the face of climate change, conservation actions, like assisted migration, may be an option for such slow dispersing species. 相似文献
53.
- 1.
- 1. When oxidizable substrates are added to a starved suspension of Azotobacter vinelandii osmotically shrunken in 0.2 M KCl, a decrease in absorbance is observed which results from a change in light scattering as the cells increase in volume. 相似文献
54.
Many types of smear slides can be made permanent rapidly and effectively by substituting for the usual dehydration series a single-step process of freezing the slide on a block of dry ice, placing it immediately in 95% or absolute alcohol, and then mounting it. Advantages of the technic are its speed, the ease of separation of cover slip from slide with a minimum loss of cells, and the superiority of the resulting permanent slides. 相似文献
55.
Nicole Sibelet Lucile Chamayou Helen Newing Isabel Gutiérrez Montes 《Human ecology: an interdisciplinary journal》2017,45(4):499-511
Trees outside forests can play an important role in production and conservation and increase connectivity within agricultural landscapes. However, farmers’ perceptions of the trees and the values they place on them will determine the extent to which they will do so in the future. In a case study in Costa Rica, northwest of the Central Volcanic Talamanca Biological Corridor, we conducted 42 semi-structured interviews with farmers and other key informants. Results show that farmers maintain trees on their land and attribute to them diverse values (technical, economic, ecological, social, cultural, aesthetic, and heritage). Farmers reported limitations to the maintenance of trees (lack of financial capital, labour, land area, technical assistance, and adapted species). In addition to potentially unsustainable Payments for Environmental Services, there is scope for more collaborative approaches to conserving the trees built on existing farmer practices. 相似文献
56.
Adsorption of DNA on clay minerals: protection against DNaseI and influence on gene transfer 总被引:1,自引:0,他引:1
Abstract Numerous authors have investigated DNA relationships with sandy soil. A model composed of various DNAs adsorbed on montmorillonite clay was developed to assay enzyme (DNaseI) activity on clay-adsorbed nucleic acids. The extent of DNA adsorption was affected by the concentration and valency of the cations used (Mg2+ , Ca2+ , Na+ ), indicating a charge-dependent process. Calf thymus DNA was found to be highly adsorbed by smectite (up to 30 mg g−1 of dry clay). Adsorbed DNA was shown to be more resistant to degradation by DNaseI than free DNA. Experimental data with plasmid and short linear amplified (through polymerase chain reaction) DNA showed that protection against nucleases was only partial. Nevertheless, clay-adsorbed DNA was found to be still able, even after a strong DNaseI treatment, to artificially transform competent Escherichia coli cells. The results show that persistance of DNA and gene transfer by genetic transformation may occur in soil. 相似文献
57.
Measurement of F(2)-isoprostanes (F(2)-IsoPs) has been independently verified as one of the most reliable approaches to assess oxidative stress in vivo. However, the rapid clearance of F(2)-IsoPs makes the timing of sample collection critical for short-lived oxidative insults. Isoketals (IsoKs) are gamma-ketoaldehydes formed via the IsoP pathway of lipid peroxidation that rapidly react with lysyl residues of proteins to form stable protein adducts. Oxidative stress can also activate cyclooxygenases to produce prostaglandin H(2), which can form two specific isomers of IsoK-levuglandin (LG) D(2) and E(2). Because adducted proteins are not rapidly cleared, IsoK/LG protein adduct levels can serve as a dosimeter of oxidative and inflammatory damage over prolonged periods of time as well as brief episodes of injury. Quantification of IsoK/LG protein adducts begins with liquid-phase extraction to separate proteins from lipid membranes, allowing measurement of both IsoK/LG protein adducts and F(2)-IsoP from the same sample if desired. IsoK/LG-lysyl-lactam adducts are measured by liquid chromatography tandem mass spectrometry after proteolytic digestion of extracted proteins, solid-phase extraction and preparative HPLC. 相似文献
58.
Miller JD Clabaugh SE Smith DR Stevens RB Wrenshall LE 《Immunology and cell biology》2012,90(2):159-167
Interleukin-2 (IL-2) is a multifaceted cytokine with immunostimulatory and immunosuppressive properties. Our laboratory recently demonstrated that the availability of IL-2 is regulated, in part, by association with perlecan, a heparan sulfate proteoglycan. Given the abundance of perlecan in blood vessels, we asked whether IL-2 is present in vessel walls. Our results indicate that IL-2 is associated with endothelial and smooth muscle cells within the human arterial wall. This IL-2 is released by heparanase, and promotes the proliferation of an IL-2-dependent cell line. Given the presence of IL-2 in human arteries, we asked whether the large vessels of IL-2-deficient mice were normal. The aortas of IL-2-deficient mice exhibited a loss of smooth muscle cells, suggesting that IL-2 may contribute to their survival. In their entirety, these results suggest a here-to-fore unrecognized role of IL-2 in vascular biology, and have significant implications for both the immune and cardiovascular systems. 相似文献
59.
Lucile Garidou Sara Heydari Phi Truong David G. Brooks Dorian B. McGavern 《Journal of virology》2009,83(17):8905-8915
Persistent viral infections are a major health concern worldwide. During persistent infection, overwhelming viral replication and the rapid loss of antiviral T-cell function can prevent immune-mediated clearance of the infection, and therapies to reanimate the immune response and purge persistent viruses have been largely unsuccessful. Adoptive immunotherapy using memory T cells is a highly successful therapeutic approach to eradicate a persistent viral infection. Understanding precisely how therapeutically administered memory T cells achieve clearance should improve our ability to terminate states of viral persistence in humans. Mice persistently infected from birth with lymphocytic choriomeningitis virus are tolerant to the pathogen at the T-cell level and thus provide an excellent model to evaluate immunotherapeutic regimens. Previously, we demonstrated that adoptively transferred memory T cells require recipient dendritic cells to effectively purge an established persistent viral infection. However, the mechanisms that reactivate and sustain memory T-cell responses during clearance of such an infection remain unclear. Here we establish that therapeutic memory T cells require CD80 and CD86 costimulatory signals to efficiently clear an established persistent viral infection in vivo. Early blockade of costimulatory pathways with CTLA-4-Fc decreased the secondary expansion of virus-specific CD8+ and CD4+ memory T cells as well as their ability to produce antiviral cytokines and purge the persistent infection. Late costimulation blockade also reduced virus-specific T-cell numbers, illustrating that sustained interactions with costimulatory molecules is required for efficient T-cell expansion. These findings indicate that antiviral memory T cells require costimulation to efficiently clear a persistent viral infection and that costimulatory pathways can be targeted to modulate the magnitude of an adoptive immunotherapeutic regimen.Persistent viruses, such as human immunodeficiency virus, hepatitis B virus, and hepatitis C virus, cause major health problems worldwide and are extraordinarily difficult to clear following the establishment of persistence. Given the challenges associated with clearing persistent infections, it is important to develop and mechanistically understand therapeutic strategies that successfully achieve viral eradication without inducing permanent damage in the host. Studies using the lymphocytic choriomeningitis virus (LCMV) model system have convincingly demonstrated that a systemic persistent viral infection can be completely purged from a murine host by using a therapeutic approach referred to as adoptive immunotherapy (1, 15, 22, 29, 30). Remarkably, total body control of multiple persistent viral infections in both the mouse (1, 15, 22, 29, 30) and humans (8, 14, 24, 26, 31) can be achieved using adoptive immunotherapy. When mice are persistently infected at birth or in utero with LCMV (referred to as carrier mice), the virus establishes systemic persistence (6). Adult LCMV carrier mice are tolerant to the virus at the T-cell level and thus are unable to eradicate the pathogen (23), which provides an excellent model to study immunotherapeutic regimens. Immunocytotherapy relies on the adoptive transfer of virus-specific memory CD8 and CD4 T cells from LCMV-immune donor mice into recipient carrier mice (1, 15, 22, 29, 30). Following the therapeutic administration of memory cells, LCMV is purged from most peripheral tissues of carrier mice in 14 days, whereas more than 100 days are required to clear virus from the central nervous system (CNS) and kidneys (1, 15, 22). Furthermore, successful viral clearance requires antiviral “memory” but not “effector” T cells (11). Thus, in addition to its proven therapeutic relevance, this model also provides a paradigm to understand factors that regulate memory T cells following secondary exposure to pathogens in vivo.The mechanisms leading to activation of naïve T cells have been well described and involve recognition of major histocompatibility complex (MHC) peptide through the T-cell receptor (TCR) as well as costimulation (e.g., CD80 and CD86 interactions) (4, 25, 27). On the other hand, the factors that govern the activation and secondary expansion of memory CD8+ and CD4+ T cells are less clearly defined, particularly in an in vivo therapeutic setting. When memory T cells reencounter cognate antigen, they respond rapidly by producing cytokines and dividing. Previous studies indicated that there was no role for dendritic cells or costimulation (4, 27) in the reactivation of memory T cells; however, three recent studies have shown that dendritic cells (DCs) stimulate memory T-cell activity upon antigen rechallenge (2, 33) and during adoptive immunotherapy (15). Because MHC class I antigen (MHC-I) is expressed on nearly all cell types but costimulatory molecules are not, these three studies strongly suggested that DCs were influencing memory T cells with costimulatory pathways thought only to be required during priming. Indeed, when the issue was reexamined, it was revealed that memory CD8+ and CD4+ T cells require CD28-CD80/CD86 costimulation to be fully reactivated upon secondary exposure to antigen (3, 7, 21).Because therapeutically administered memory T cells require effective interactions with the host hematopoietic system (10), in particular dendritic cells (15), to achieve successful viral clearance, we set out to address several unanswered questions. First, is costimulation required for the immunotherapeutic clearance of an established persistent viral infection? This is a particularly important question because the requirements imposed on therapeutically administered memory T cells, which encounter immediate and overwhelmingly high levels of virus, heightened antigenic stimulation, and a unique inflammatory milieu, are likely to be different than those faced by endogenous memory T cells following pathogen rechallenge in an otherwise-quiescent environment. The second question we set out to address in this study was whether costimulation blockade could modulate the activities of an immunotherapeutic regimen consisting of memory T cells. This question is of great importance in a clinical setting where pathogen-specific memory T cells can induce severe tissue pathology through the release of effector molecules (12). Thus, it is critical to have a strategy to limit the magnitude of an undesirable response without impeding viral clearance. 相似文献
60.
Jevon Plunkett Scott Doniger Thomas Morgan Ritva Haataja Mikko Hallman Hilkka Puttonen Ramkumar Menon Edward Kuczynski Errol Norwitz Victoria Snegovskikh Aarno Palotie Leena Peltonen Vineta Fellman Emily A DeFranco Bimal P Chaudhari John Oates Olivier Boutaud Tracy L McGregor Jude J McElroy Kari Teramo Ingrid Borecki Justin C Fay Louis J Muglia 《BMC medical genomics》2010,3(1):1-9