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1.
Hermógenes Fernández-Marín David R. Nash Sarah Higginbotham Catalina Estrada Jelle S. van Zweden Patrizia d'Ettorre William T. Wcislo Jacobus J. Boomsma 《Proceedings. Biological sciences / The Royal Society》2015,282(1807)
Fungus-farming ant colonies vary four to five orders of magnitude in size. They employ compounds from actinomycete bacteria and exocrine glands as antimicrobial agents. Atta colonies have millions of ants and are particularly relevant for understanding hygienic strategies as they have abandoned their ancestors'' prime dependence on antibiotic-based biological control in favour of using metapleural gland (MG) chemical secretions. Atta MGs are unique in synthesizing large quantities of phenylacetic acid (PAA), a known but little investigated antimicrobial agent. We show that particularly the smallest workers greatly reduce germination rates of Escovopsis and Metarhizium spores after actively applying PAA to experimental infection targets in garden fragments and transferring the spores to the ants'' infrabuccal cavities. In vitro assays further indicated that Escovopsis strains isolated from evolutionarily derived leaf-cutting ants are less sensitive to PAA than strains from phylogenetically more basal fungus-farming ants, consistent with the dynamics of an evolutionary arms race between virulence and control for Escovopsis, but not Metarhizium. Atta ants form larger colonies with more extreme caste differentiation relative to other attines, in societies characterized by an almost complete absence of reproductive conflicts. We hypothesize that these changes are associated with unique evolutionary innovations in chemical pest management that appear robust against selection pressure for resistance by specialized mycopathogens. 相似文献
2.
Yi-Shiang Huang Virginie Bertrand Dimitriya Bozukova Christophe Pagnoulle Christine Labrugère Edwin De Pauw Marie-Claire De Pauw-Gillet Marie-Christine Durrieu 《PloS one》2014,9(12)
Posterior Capsular Opacification (PCO) is the capsule fibrosis developed on implanted IntraOcular Lens (IOL) by the de-differentiation of Lens Epithelial Cells (LECs) undergoing Epithelial Mesenchymal Transition (EMT). Literature has shown that the incidence of PCO is multifactorial including the patient''s age or disease, surgical technique, and IOL design and material. Reports comparing hydrophilic and hydrophobic acrylic IOLs have shown that the former has more severe PCO. On the other hand, we have previously demonstrated that the adhesion of LECs is favored on hydrophobic compared to hydrophilic materials. By combining these two facts and contemporary knowledge in PCO development via the EMT pathway, we propose a biomimetically inspired strategy to promote LEC adhesion without de-differentiation to reduce the risk of PCO development. By surface grafting of a cell adhesion molecule (RGD peptide) onto the conventional hydrophilic acrylic IOL material, the surface-functionalized IOL can be used to reconstitute a capsule-LEC-IOL sandwich structure, which has been considered to prevent PCO formation in literature. Our results show that the innovative biomaterial improves LEC adhesion, while also exhibiting similar optical (light transmittance, optical bench) and mechanical (haptic compression force, IOL injection force) properties compared to the starting material. In addition, compared to the hydrophobic IOL material, our bioactive biomaterial exhibits similar abilities in LEC adhesion, morphology maintenance, and EMT biomarker expression, which is the crucial pathway to induce PCO. The in vitro assays suggest that this biomaterial has the potential to reduce the risk factor of PCO development. 相似文献
3.
Anton Pauw Sunshine A. Van Bael Halton A. Peters Steven D. Allison José L. C. Camargo Miguel Cifuentes-Jara Aurlstela Conserva Teresa Garcia Restom Tamara Heartsill-Scalley Scott A. Mangan Gabriela Nunez-lturri Elsie Rivera-Ocasio Mark Rountree Susanne Vetter Carolina Volkmer de Castllho 《Biotropica》2004,36(3):410-413
4.
Steroid sulfatase activity in a Peptococcus niger strain from the human intestinal microflora. 总被引:3,自引:3,他引:0
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A strictly anaerobic gram-positive coccus, identified as Peptococcus niger, that developed sulfatase activity towards steroid-3-sulfate esters was isolated from human fecal material. This strain desulfated the arylsulfate esters estrone-3-sulfate (100%) and beta-estradiol-3-sulfate (50%); only trace amounts of desulfated estriol-3-sulfate were found. In addition, alkylsulfatase activity was found towards the 3 alpha-sulfates of 5 alpha-androstane-17-one and 5 beta-androstane-17-one and towards the 3 beta-sulfates of 5 alpha-androstane-17-one, delta 5-androstene-17-one, 5 alpha-pregnane-20-one, and delta 5-pregnene-20-one, all of which were 100% desulfated. No sulfatase activity was found towards the 17-sulfate esters of beta-estradiol or delta 4-androstene-3-one-17 alpha-ol. The nonsteroid arylsulfate esters paranitrophenyl sulfate, paranitrocatechol sulfate, and phenolphthalein disulfate were desulfated 70, 40, and 40%, respectively. In addition to its sulfatase activity, this strain also developed C-17 oxidoreductase activity towards the estrogens and androsta(e)nes and C-3 oxidoreductase activity towards androsta(e)nes and pregna(e)nes. 相似文献
5.
Rainer Voigt Jelle Atema 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,171(5):673-683
1. | We determined the spectral tuning properties of 47 chemoreceptor cells of the antenna of Homarus americanus to amino acids and other compounds. Tests with 17 single compounds at 10-4 M showed 40 of 47 cells responded best to hydroxyproline, 4 cells to taurine and 3 cells to betaine. Mean tuning breadth (H-metric) doubled with 10 fold increase in concentration. |
2. | In hydroxyproline-best cells the mean threshold for hydroxyproline (Hyp) was found between 10-7 M and 10-8 M. An equimolar mixture of the 17 compounds generated a shallower stimulus-response function with thresholds similar to Hyp function (mixture suppression). Hyp-best cells were relatively narrowly tuned, often with arginine or leucine as second best stimuli. |
3. | Thus, physiologically the second antenna of H. americanus is a major chemoreceptor organ. It is more than any of the 5 chemoreceptor organs studied so far dominated by a single best-cell type (Hyp). Receptor cell composition of antennae resembles that of antennules more than legs or maxillipeds. Hyp-best cells in antennae and lateral antennules have similar tuning spectra. |
4. | Our cell tuning studies argue for independent receptors for all amino acids tested. We conclude that diversity of receptor cell tuning is created by cell-specific blends of receptors. At the organ level, differences in organ tuning result from different blends of receptor cells. |
6.
Fluid dynamics and microscale chemical movement in the chemosensory appendages of the lobster, Homarus americanus 总被引:2,自引:1,他引:1
Every chemosensory structure has a boundary layer surroundingit through which chemical signals must pass before contactingreceptor cells. Fluid motion in this boundary layer is slowand odor movement is mainly by diffusion. The boundary layerstructure depends upon external fluid velocities and the morphologyof the appendage. High-speed (10200 Hz) electrochemicalrecordings from microchemical electrodes were used to quantifychemical transport in the microscale environment of three morphologicallydifferent chemosensory appendages of the lobster, Homarus americanus:lateral antennule, medial antennule and walking legs. Controlledpulses of the odor tracer (dopamine) were delivered to the threeappendages at three different flow speeds (0, 3, 6 cm/s). Theamplitudes of the pulses increased with increasing flow speed,indicating that boundary layer thickness decreased with increasingflow speed. Larger pulse amplitudes were measured in the walkinglegs than in the lateral or medial antennules at all flow speeds.In addition, larger amplitudes were recorded in the medial antennulethan the lateral antennule. Changes in pulse amplitude withincreasing flow speed were larger than changes in pulse duration.These results demonstrate that pulse amplitude is affected morethan pulse duration by boundary layer thickness and that themorphology of the receptor strucure helps determine the structureof signals arriving at receptor cells. This may explain whyanimals have adopted sampling strategies that reduce boundarylayer thickness. 相似文献
7.
High resolution spatio-temporal analysis of aquatic chemical signals using microelectrochemical electrodes 总被引:2,自引:1,他引:1
Detailed understanding of chemoreceptor cell transduction andfiltering depends on precise control and thus measurement ofthe chemical stimulus. In contrast to vision and hearing, accuratestimulus measurement in chemoreception has not been possibleat biologically relevant spatial and temporal scales. In thispaper we introduce a new high-speed (200 hz) electrochemicalmethod for the direct measurement of odor signals at biologicallyrelevant space scales (10-100 µm). We tested this systemin three applications: (i) temporal and spatial features ofodor plumes, (ii) stimulus calibrations in physiological recordingchambers and (iii) boundary layer diffusion measurements withinreceptor structures. 相似文献
8.
J. Jelle Lever Egbert H. Van Nes Marten Scheffer Jordi Bascompte 《Ecology letters》2023,26(10):1765-1779
Theory suggests that increasingly long, negative feedback loops of many interacting species may destabilize food webs as complexity increases. Less attention has, however, been paid to the specific ways in which these ‘delayed negative feedbacks’ may affect the response of complex ecosystems to global environmental change. Here, we describe five fundamental ways in which these feedbacks might pave the way for abrupt, large-scale transitions and species losses. By combining topological and bioenergetic models, we then proceed by showing that the likelihood of such transitions increases with the number of interacting species and/or when the combined effects of stabilizing network patterns approach the minimum required for stable coexistence. Our findings thus shift the question from the classical question of what makes complex, unaltered ecosystems stable to whether the effects of, known and unknown, stabilizing food-web patterns are sufficient to prevent abrupt, large-scale transitions under global environmental change. 相似文献
9.
A Mycobacterium leprae-specific gene encoding an immunologically recognized 45 kDa protein 总被引:1,自引:0,他引:1
Tobias F. Rinke de Wit Josephine E. Clark-Curtiss Feseha Abebe Arend H. J. Kolk Anneke A. M. Janson Miranda van Agterveld Jelle E. R. Thole 《Molecular microbiology》1993,10(4):829-838
By screening a Mycobacterium leprae lambda gt11 expression library with a serum from an Ethiopian lepromatous leprosy (LL) patient a clone was isolated (LL4) belonging to hybridization group III of a panel of previously isolated M. leprae clones. Members of this hybridization group encode a serologically recognized 45 kDa protein. The complete DNA sequences of the partially overlapping clones LL4 and L1 (hybridization group III) are presented and these revealed the presence of an open reading frame (ORF) predicting a protein with a molecular size of 42 448 Da. Southern hybridizations on total genomic DNA of M. Ieprae, Mycobacterium tuberculosis and eight atypical mycobacteria showed that the LL4 DNA fragment is specific for M. Ieprae DNA even under low-stringency conditions. The M. Ieprae specificity of LL4 DNA was further confirmed by the polymerase chain reaction using four different sets of primers. Western blotting analyses showed that the M. Ieprae 45 kDa protein is frequently recognized by antibodies from leprosy patients and that this recognition is specific since no antibodies could be detected in sera of tuberculosis patients. T-cell proliferation assays also demonstrated T-cell recognition by leprosy patients and healthy contacts of the M. Ieprae 45 kDa protein. The specificity of the LL4 DNA region and the 45 kDa antigen that is encoded by hybridization group III could provide unique tools for the development of M. Ieprae-specific immunological and DNA reagents. 相似文献
10.
Isolation and characterization of the mycobacterial phagosome: segregation from the endosomal/lysosomal pathway 总被引:5,自引:0,他引:5
Zahra Hasan Claudia Schlax Lotte Kuhn Ivan Lefkovits Douglas Young Jelle Thole & Jean Pieters 《Molecular microbiology》1997,24(3):545-553
Mycobacteria have the ability to persist within host phagocytes, and their success as intracellular pathogens is thought to be related to the ability to modify their intracellular environment. After entry into phagocytes, mycobacteria-containing phagosomes acquire markers for the endosomal pathway, but do not fuse with lysosomes. The molecular machinery that is involved in the entry and survival of mycobacteria in host cells is poorly characterized. Here we describe the use of organelle electrophoresis to study the uptake of Mycobacterium bovis bacille Calmette Guerin (BCG) into murine macrophages. We demonstrate that live, but not dead, mycobacteria occupy a phagosome that can be physically separated from endosomal/lysosomal compartments. Biochemical analysis of purified mycobacterial phagosomes revealed the absence of endosomal/lysosomal markers LAMP-1 and β-hexosaminidase. Combining subcellular fractionation with two-dimensional gel electrophoresis, we found that a set of host proteins was present in phagosomes that were absent from endosomal/lysosomal compartments. The residence of mycobacteria in compartments outside the endosomal/lysosomal system may explain their persistence inside host cells and their sequestration from immune recognition. Furthermore, the approach described here may contribute to an improved understanding of the molecular mechanisms that determine the intracellular fate of mycobacteria during infection. 相似文献