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81.
Laboratory experiments were used to examine the degassing of CH4 from a muddy sediment. Sediment containing dissolved CH4 showed a hyperbolic time course of CH4 release when allowed to degas in stoppered 20-ml vials. Equilibration required ca. 24 h for 5 ml of sediment. The rate of CH4 release was found to be dependent on the ratio of exposed sediment surface area to sediment volume. The water content of the sediment was a factor in the total amount of CH4 released but did not affect the rate of degassing. Addition of water to sediment samples (to form a slurry) accelerated CH4 release, with a 1:1 dilution giving ca. 80% of maximum release after only 2 min. Shaking (vortexing) the sediments also facilitated CH4 exchange, with 2 min of vigorous agitation giving 77% of maximum release. The organic content of the sediment did not affect either the amount or the rate of CH4 degassing. Rubber stoppers exposed to CH4 were found to absorb CH4 rapidly and to subsequently release it in proportion to the concentration to which they were exposed. Artifacts may be associated with CH4 production measurements if sediment and stopper degassing are not considered. It is recommended that any study of methane production or distribution include preliminary experiments to determine the degassing kinetics for the specific sediment system being used. 相似文献
82.
Bruno Golosio Chiara De Luca Cristiano Capone Elena Pastorelli Giovanni Stegel Gianmarco Tiddia Giulia De Bonis Pier Stanislao Paolucci 《PLoS computational biology》2021,17(6)
The brain exhibits capabilities of fast incremental learning from few noisy examples, as well as the ability to associate similar memories in autonomously-created categories and to combine contextual hints with sensory perceptions. Together with sleep, these mechanisms are thought to be key components of many high-level cognitive functions. Yet, little is known about the underlying processes and the specific roles of different brain states. In this work, we exploited the combination of context and perception in a thalamo-cortical model based on a soft winner-take-all circuit of excitatory and inhibitory spiking neurons. After calibrating this model to express awake and deep-sleep states with features comparable with biological measures, we demonstrate the model capability of fast incremental learning from few examples, its resilience when proposed with noisy perceptions and contextual signals, and an improvement in visual classification after sleep due to induced synaptic homeostasis and association of similar memories. 相似文献
83.
Ricci I Damiani C Scuppa P Mosca M Crotti E Rossi P Rizzi A Capone A Gonella E Ballarini P Chouaia B Sagnon N Esposito F Alma A Mandrioli M Sacchi L Bandi C Daffonchio D Favia G 《Environmental microbiology》2011,13(4):911-921
While symbiosis between bacteria and insects has been thoroughly investigated in the last two decades, investments on the study of yeasts associated with insects have been limited. Insect-associated yeasts are placed on different branches of the phylogenetic tree of fungi, indicating that these associations evolved independently on several occasions. Isolation of yeasts is frequently reported from insect habitats, and in some cases yeasts have been detected in the insect gut and in other organs/tissues. Here we show that the yeast Wickerhamomyces anomalus, previously known as Pichia anomala, is stably associated with the mosquito Anopheles stephensi, a main vector of malaria in Asia. Wickerhamomyces anomalus colonized pre-adult stages (larvae L(1)-L(4) and pupae) and adults of different sex and age and could be isolated in pure culture. By a combination of transmission electron microscopy and fluorescent in situ hybridization techniques, W. anomalus was shown to localize in the midgut and in both the male and female reproductive systems, suggesting multiple transmission patterns. 相似文献
84.
On the mechanism of eukaryotic cell penetration by α- and β-oligoarginines--targeting infected erythrocytes 总被引:1,自引:0,他引:1
Fluorescein-labeled α- and β-octaarginine amides were synthesized. The route, by which these oligoarginine (OA) derivatives enter cells (hepatocytes, fibroblasts, macrophages), was investigated by confocal fluorescence microscopy. Comparisons (by co-localization experiments) with compounds of known penetration modes revealed that the β-octaarginine amide also uses multiple pathways to enter cells. There was no difference between the α- and the β-OAs. Like other cell-penetrating peptides (CPPs), the β-octaarginine eventually winds up in the nucleoli of the cell nuclei (cf. Chem. Biodiversity, 2004, 1, 65). Surprisingly, there was no entry of α- or β-OA into intact and healthy human erythrocytes (which do not possess a nucleus). Blood cells infected by Plasmodium falciparum (malaria parasite) were, however, entered readily, and the OAs went all the way through a couple of membranes into the parasite. The potential of these results for delivering specific antimalarial drugs directly into the parasite is discussed. 相似文献
85.
Clostridial glutamate dehydrogenase mutants, designed to accommodate the 2'-phosphate of disfavoured NADPH, showed the expected large specificity shifts with NAD(P)H. Puzzlingly, similar assays with oxidized cofactors initially revealed little improvement with NADP(+) , although rates with NAD(+) were markedly diminished. This article reveals that the enzyme's discrimination in favour of NAD(+) and against NADP(+) had been greatly underestimated and has indeed been abated by a factor of >?16,000 by the mutagenesis. Initially, stopped-flow studies of the wild-type enzyme showed a burst increase of A(340) with NADP(+) but not NAD(+), with amplitude depending on the concentration of the coenzyme, rather than enzyme. Amplitude also varied with the commercial source of the NADP(+). FPLC, HPLC and mass spectrometry identified NAD(+) contamination ranging from 0.04 to 0.37% in different commercial samples. It is now clear that apparent rates of NADP(+) utilization mainly reflected the reduction of contaminating NAD(+), creating an entirely false view of the initial coenzyme specificity and also of the effects of mutagenesis. Purification of the NADP(+) eliminated the burst. With freshly purified NADP(+), the NAD(+) : NADP(+) activity ratio under standard conditions, previously estimated as 300 : 1, is 11,000. The catalytic efficiency ratio is even higher at 80,000. Retested with pure cofactor, mutants showed marked specificity shifts in the expected direction, for example, 16 200 fold change in catalytic efficiency ratio for the mutant F238S/P262S, confirming that the key structural determinants of specificity have been successfully identified. Of wider significance, these results underline that, without purification, even the best commercial coenzyme preparations are inadequate for such studies. 相似文献
86.
Christel Devaud Benoît Rousseau Sonia Netzer Vincent Pitard Christian Paroissin Camille Khairallah Pierre Costet Jean-François Moreau Franck Couillaud Julie Dechanet-Merville Myriam Capone 《Cancer immunology, immunotherapy : CII》2013,62(7):1199-1210
The role of human intraepithelial Vδ1+ γδ T cell cytotoxic effectors in the immune surveillance against metastatic colon cancer has never been addressed, despite their reported capacity to infiltrate colon carcinomas and to kill colonic cancer cells in vitro. We previously showed that Vδ1+ γδ T cells are enriched in blood in response to cytomegalovirus (CMV) infection, and that such increase may be protective against epithelial cancers. The objective of the present study was to investigate whether CMV-induced Vδ1+ γδ T lymphocytes could inhibit the propagation of human colon tumors in vivo, in order to evaluate their immunotherapeutic potential in this context. Even though metastases are an important cause of death in various cancers including colorectal cancer (CRC), the anti-metastatic effect of immune effectors has been poorly analyzed. To this purpose, we set up a reliable model of metastatic colon cancer through orthotopic implantation of luciferase-expressing human HT29 cells in immunodeficient mice. Using bioluminescence imaging to follow the outcome of colonic cancer cells, we showed that a systemic treatment with CMV-induced Vδ1+ γδ T cells could not only inhibit primary colon tumor growth but also the emergence of secondary tumor foci in the lungs and liver. Finally, our data lead to propose that Vδ1+ γδ T lymphocytes may directly influence the appearance of metastases independently from their control of primary tumor size. These findings, which extend our previous work, pave the road for the potential manipulation of Vδ1+ γδ T lymphocytes in novel anti-CRC immunotherapeutic protocols. 相似文献
87.
Sophie Daburon Christel Devaud Pierre Costet Aurore Morello Laure Garrigue-Antar Mike Maillasson Nathalie Hargous Delphine Lapaillerie Marc Bonneu Julie Dechanet-Merville Patrick Legembre Myriam Capone Jean-Fran?ois Moreau Jean-Luc Taupin 《PloS one》2013,8(1)
Binding of ligand FasL to its receptor Fas triggers apoptosis via the caspase cascade. FasL itself is homotrimeric, and a productive apoptotic signal requires that FasL be oligomerized beyond the homotrimeric state. We generated a series of FasL chimeras by fusing FasL to domains of the Leukemia Inhibitory Factor receptor gp190 which confer homotypic oligomerization, and analyzed the capacity of these soluble chimeras to trigger cell death. We observed that the most efficient FasL chimera, called pFasL, was also the most polymeric, as it reached the size of a dodecamer. Using a cellular model, we investigated the structure-function relationships of the FasL/Fas interactions for our chimeras, and we demonstrated that the Fas-mediated apoptotic signal did not solely rely on ligand-mediated receptor aggregation, but also required a conformational adaptation of the Fas receptor. When injected into mice, pFasL did not trigger liver injury at a dose which displayed anti-tumor activity in a model of human tumor transplanted to immunodeficient animals, suggesting a potential therapeutic use. Therefore, the optimization of the FasL conformation has to be considered for the development of efficient FasL-derived anti-cancer drugs targeting Fas. 相似文献
88.
Stephanie H. Capone Murielle Dufresne Mathias Rechel Marie-José Fleury Anne-Virginie Salsac Patrick Paullier Martine Daujat-Chavanieu Cecile Legallais 《PloS one》2013,8(4)
Recently, interest has focused on hepatocytes’ implantation to provide end stage liver failure patients with a temporary support until spontaneous recovery or a suitable donor becomes available. To avoid cell damage and use of an immunosuppressive treatment, hepatic cells could be implanted after encapsulation in a porous biomaterial of bead or capsule shape. The aim of this study was to compare the production and the physical properties of the beads, together with some hepatic cell functions, resulting from the use of different material combinations for cell microencapsulation: alginate alone or combined with type I collagen with or without poly-L-lysine and alginate coatings. Collagen and poly-L-lysine increased the bead mechanical resistance but lowered the mass transfer kinetics of vitamin B12. Proliferation of encapsulated HepG2/C3A cells was shown to be improved in alginate-collagen beads. Finally, when the beads were subcutaneously implanted in mice, the inflammatory response was reduced in the case of alginate mixed with collagen. This in vitro and in vivo study clearly outlines, based on a systematic comparison, the necessity of compromising between material physical properties (mechanical stability and porosity) and cell behavior (viability, proliferation, functionalities) to define optima hepatic cell microencapsulation conditions before implantation. 相似文献
89.
ABSTRACT The acoustic characteristics of an Amazonian lowland rain forest study site in southern Venezuela was analysed to determine environmental constraints upon acoustic communication. Signal degradation was measured by conducting transmission experiments at different heights above ground level. Measurements of ambient noise served to determine possible communication distances for various times of day, heights above ground level and frequencies. “Sound windows” for acoustic long-range communication were found for low frequencies, calling heights in the midstorey and calling in the morning or during the night. Sound attenuation was affected by height and frequency but not by time of day. Background noise varied remarkably with time of day and frequency and had a greater impact on communication distance than signal attenuation. 相似文献
90.
Alexander L. Ruchelman Hon-Wah Man Weihong Zhang Roger Chen Lori Capone Jian Kang Anastasia Parton Laura Corral Peter H. Schafer Darius Babusis Mehran F. Moghaddam Yang Tang Michael A. Shirley George W. Muller 《Bioorganic & medicinal chemistry letters》2013,23(1):360-365
A series of analogs of the immunomodulary drugs lenalidomide (1) and pomalidomide (2), in which the amino group is replaced with various isosteres, was prepared and assayed for immunomodulatory activity and activity against cancer cell lines. The 4-methyl and 4-chloro analogs 4 and 15, respectively, displayed potent inhibition of tumor necrosis factor-α (TNF-α) in LPS-stimulated hPBMC, potent stimulation of IL-2 in a human T cell co-stimulation assay, and anti-proliferative activity against the Namalwa lymphoma cell line. Both of these analogs displayed oral bioavailability in rat. 相似文献