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931.
Maran SK Sieling FH Demla K Prinz AA Canavier CC 《Journal of computational neuroscience》2011,31(2):419-440
Central pattern generators (CPGs) frequently include bursting neurons that serve as pacemakers for rhythm generation. Phase
resetting curves (PRCs) can provide insight into mechanisms underlying phase locking in such circuits. PRCs were constructed
for a pacemaker bursting complex in the pyloric circuit in the stomatogastric ganglion of the lobster and crab. This complex
is comprised of the Anterior Burster (AB) neuron and two Pyloric Dilator (PD) neurons that are all electrically coupled. Artificial
excitatory synaptic conductance pulses of different strengths and durations were injected into one of the AB or PD somata
using the Dynamic Clamp. Previously, we characterized the inhibitory PRCs by assuming a single slow process that enabled synaptic
inputs to trigger switches between an up state in which spiking occurs and a down state in which it does not. Excitation produced
five different PRC shapes, which could not be explained with such a simple model. A separate dendritic compartment was required
to separate the mechanism that generates the up and down phases of the bursting envelope (1) from synaptic inputs applied
at the soma, (2) from axonal spike generation and (3) from a slow process with a slower time scale than burst generation.
This study reveals that due to the nonlinear properties and compartmentalization of ionic channels, the response to excitation
is more complex than inhibition. 相似文献
932.
Biodegradation and biotransformation of explosives 总被引:1,自引:0,他引:1
Explosives now contaminate millions of hectares of land in the US alone, with global levels of contamination difficult to fully assess. Understanding the biology behind the metabolism of these toxic compounds by microorganisms and plants is imperative for managing these pollutants in the environment. Towards this aim, recent studies have identified, and are now characterizing, plant genes involved in 2,4,6-trinitrotoluene detoxification and the biochemical pathways of nitramine degradation in microorganisms. A key scientific goal continues to be identification of enzymes capable of degrading 2,4,6-trinitrotoluene and this still remains elusive, although recent reports give insights into the origin of nitrite released during biotransformation of this major contaminant. Promising phytoremediation research using transgenic model plant systems has now been transferred to poplar, a species with field applicability. 相似文献
933.
The present study deals with the phenomenon of insular speciation and discusses, as a case study, the debated taxonomical issue of the status of Onthophagus massai (Coleoptera, Sarabaeidae) as an endemic species vicarious to Onthophagus fracticornis in Sicily. The authors investigated the differentiation patterns between an insular population belonging to the supposed species O. massai (collected in its locus typicus, Piano Battaglia) and three Italian O. fracticornis populations (collected along a N–S latitudinal gradient). These patterns are described and analysed using multiple approaches: the qualitative inspection of the microsculpture of elytral surfaces, considered a diagnostic character for O. massai identification; the comparison of horn static allometries, known to be a good indicator of divergence processes between closely related species or isolated populations of the same species; the comparison of the patterns of shape and size difference of the head, epipharynx and genitalia attained with a combination of traditional and geometric (landmark and semilandmark) morphometric methods; and, finally, the estimation of the genetic relationships between Sicilian and continental populations obtained by analysing cytochrome oxidase subunit 1 mitochondrial gene sequences. The integration of the results of these approaches indicates that there is not sufficient evidence to vindicate the species status for O. massai, which should more likely be considered a small-sized version of O. fracticornis (a possible case of insular dwarfism). However, the complex pattern of shape, size and genetic variation observed between the populations analysed hinted at the possibility that a diversification process is ongoing, but not only between insular and continental populations; each population showed a tendency to evolve as an evolutionarily independent unit. 相似文献
934.
935.
936.
Toine F.H. Bovee Mario Thevis Astrid R.M. Hamers Ad A.C.M. Peijnenburg Michel W.F. Nielen Willem G.E.J. Schoonen 《The Journal of steroid biochemistry and molecular biology》2010,118(1-2):85-92
Selective estrogen receptor modulators (SERMs) and selective androgen receptor modulators (SARMs) are compounds that activate their cognate receptor in particular target tissues without affecting other organs. Many of these compounds will find their use in therapeutic treatments. However, they also will have a high potential for misuse in veterinary practice and the sporting world. Here we demonstrate that yeast estrogen and androgen bioassays can be used to detect SERMs and SARMs, and are also useful screening tools to investigate their mode of action. Six steroidal 11β-substituents of E2 (SERMs) and some arylpropionamide- and quinoline-based SARMs were tested. In addition, 7 compounds previously tested on AR agonism and determined as inactive in the yeast androgen bioassay, while QSAR modelling revealed strong binding to the human androgen receptor, are now shown to act as AR antagonists. 相似文献
937.
Emilie Roeder Christel Henrionnet Jean Christophe Goebel Nicolas Gambier Olivier Beuf Denis Grenier Bailiang Chen Pierre-André Vuissoz Pierre Gillet Astrid Pinzano 《PloS one》2014,9(5)
Aim
The aim of this work was the development of successful cell therapy techniques for cartilage engineering. This will depend on the ability to monitor non-invasively transplanted cells, especially mesenchymal stem cells (MSCs) that are promising candidates to regenerate damaged tissues.Methods
MSCs were labeled with superparamagnetic iron oxide particles (SPIO). We examined the effects of long-term labeling, possible toxicological consequences and the possible influence of progressive concentrations of SPIO on chondrogenic differentiation capacity.Results
No influence of various SPIO concentrations was noted on human bone marow MSC viability or proliferation. We demonstrated long-term (4 weeks) in vitro retention of SPIO by human bone marrow MSCs seeded in collagenic sponges under TGF-β1 chondrogenic conditions, detectable by Magnetic Resonance Imaging (MRI) and histology. Chondrogenic differentiation was demonstrated by molecular and histological analysis of labeled and unlabeled cells. Chondrogenic gene expression (COL2A2, ACAN, SOX9, COL10, COMP) was significantly altered in a dose-dependent manner in labeled cells, as were GAG and type II collagen staining. As expected, SPIO induced a dramatic decrease of MRI T2 values of sponges at 7T and 3T, even at low concentrations.Conclusions
This study clearly demonstrates (1) long-term in vitro MSC traceability using SPIO and MRI and (2) a deleterious dose-dependence of SPIO on TGF-β1 driven chondrogenesis in collagen sponges. Low concentrations (12.5–25 µg Fe/mL) seem the best compromise to optimize both chondrogenesis and MRI labeling. 相似文献938.
Salme Timmusk Islam A. Abd El-Daim Lucian Copolovici Triin Tanilas Astrid K?nnaste Lawrence Behers Eviatar Nevo Gulaim Seisenbaeva Elna Stenstr?m ülo Niinemets 《PloS one》2014,9(5)
Water is the key resource limiting world agricultural production. Although an impressive number of research reports have been published on plant drought tolerance enhancement via genetic modifications during the last few years, progress has been slower than expected. We suggest a feasible alternative strategy by application of rhizospheric bacteria coevolved with plant roots in harsh environments over millions of years, and harboring adaptive traits improving plant fitness under biotic and abiotic stresses. We show the effect of bacterial priming on wheat drought stress tolerance enhancement, resulting in up to 78% greater plant biomass and five-fold higher survivorship under severe drought. We monitored emissions of seven stress-related volatiles from bacterially-primed drought-stressed wheat seedlings, and demonstrated that three of these volatiles are likely promising candidates for a rapid non-invasive technique to assess crop drought stress and its mitigation in early phases of stress development. We conclude that gauging stress by elicited volatiles provides an effectual platform for rapid screening of potent bacterial strains and that priming with isolates of rhizospheric bacteria from harsh environments is a promising, novel way to improve plant water use efficiency. These new advancements importantly contribute towards solving food security issues in changing climates. 相似文献
939.
Thomas Reitz Andre Rossberg Astrid Barkleit Sonja Selenska-Pobell Mohamed L. Merroun 《PloS one》2014,9(8)
Interactions of a facultative anaerobic bacterial isolate named Paenibacillus sp. JG-TB8 with U(VI) were studied under oxic and anoxic conditions in order to assess the influence of the oxygen-dependent cell metabolism on microbial uranium mobilization and immobilization. We demonstrated that aerobically and anaerobically grown cells of Paenibacillus sp. JG-TB8 accumulate uranium from aqueous solutions under acidic conditions (pH 2 to 6), under oxic and anoxic conditions. A combination of spectroscopic and microscopic methods revealed that the speciation of U(VI) associated with the cells of the strain depend on the pH as well as on the aeration conditions. At pH 2 and pH 3, uranium was exclusively bound by organic phosphate groups provided by cellular components, independently on the aeration conditions. At higher pH values, a part (pH 4.5) or the total amount (pH 6) of the dissolved uranium was precipitated under oxic conditions in a meta-autunite-like uranyl phosphate mineral phase without supplying an additional organic phosphate substrate. In contrast to that, under anoxic conditions no mineral formation was observed at pH 4.5 and pH 6, which was clearly assigned to decreased orthophosphate release by the cells. This in turn was caused by a suppression of the indigenous phosphatase activity of the strain. The results demonstrate that changes in the metabolism of facultative anaerobic microorganisms caused by the presence or absence of oxygen can decisively influence U(VI) biomineralization. 相似文献
940.
Joel G. Ray Donald A. Redelmeier Marcelo L. Urquia Astrid Guttmann Sarah D. McDonald Marian J. Vermeulen 《PloS one》2014,9(7)