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41.
Widespread occurrence of bacterial thiol methyltransferases and the biogenic emission of methylated sulfur gases. 总被引:5,自引:4,他引:1 下载免费PDF全文
A majority of heterotrophic bacteria isolated from soil, water, sediment, vegetation, and marine algae cultures methylated sulfide, producing methanethiol. This was demonstrated with intact cells by measuring the emission of methanethiol with a sulfur-selective chemiluminescence detector, and in cell extracts by detection of sulfide-dependent thiol methyltransferase activity. Extracts of two Pseudomonas isolates were fractionated by gel-filtration and ion-exchange chromatography, and with sulfide as the substrate a single peak of thiol methyltransferase activity was seen in each case. Extracts of several bacterial strains also contained thiol methyltransferase activity with organic thiols as substrates. Thus, S-adenosylmethionine-dependent thiol methyltransferase activities are widespread in bacteria and may contribute to biogenic emissions of methylated sulfur gases and to the production of methyl thioethers. 相似文献
42.
P.A. Fall F. Leroi M. Cardinal F. Chevalier M.F. Pilet 《Letters in applied microbiology》2010,50(4):357-361
Aims: To investigate the antimicrobial spectrum of Lactococcus piscium CNCM I‐4031 and its protective effect in cooked and peeled shrimp against Brochothrix thermosphacta. Methods and Results: Sixteen pathogenic and spoiling bacteria were inhibited in Elliker, but not in shrimp juice agar plates. In shrimp packed under modified atmosphere and stored at 8°C, B. thermosphacta (103 CFU g?1) was inhibited by 4·1 log CFU g?1 when co‐inoculated with L. piscium (106 CFU g?1). Brochothrix thermosphacta spoiled the product after 11 days, with the emission of strong butter/caramel off‐odours. In co‐culture with L. piscium, sensory shelf‐life was extended by at least 10 days. The inhibition was partially explained by a drop in pH from 6·6 to 5·6. The physicochemical composition of shrimp and shrimp juice was established to identify the inhibition mechanisms involved. Conclusion: Lactococcus piscium CNCM I‐4031 has a wide antimicrobial spectrum. The strain inhibits B. thermosphacta in shrimp and significantly prolongs sensory shelf‐life. Significance and Impact of the Study: Lactococcus piscium CNCM I‐4031 is shown to be a promising agent for improving shrimp quality and may be tested against pathogens and in other food matrices. Knowledge of the physicochemical composition of shrimp and shrimp juice will allow the development of a chemically defined model medium for determining the inhibition mechanisms involved. 相似文献
43.
Unicapsula marquesi n. sp. (Myxosporea) is described from gill filaments of Polydactylus quadrifilis (Pisces, Polynemidae) obtained from coats of Senegal. The cysts were elongated and their length was 1 to 3 mm. The spores were pyramidal and composed of three valves. Only one of theses valves contained a developed polar capsule measuring 3.01 +/- 0.09 microns in diameter. Length of spore was 6.13 +/- 0.21 microns and the width was 7.18 +/- 0.17. No filament like appendage at the extremity of shell valves. Data on ultrastructure of spores are presented. 相似文献
44.
Shaikh Mohammed J Caicedo H Fall CP Eddington DT 《Journal of visualized experiments : JoVE》2007,(8):302
We have demonstrated the fabrication of a two-level microfluidic device that can be easily integrated with existing electrophysiology setups. The two-level microfluidic device is fabricated using a two-step standard negative resist lithography process. The first level contains microchannels with inlet and outlet ports at each end. The second level contains microscale circular holes located midway of the channel length and centered along with channel width. Passive pumping method is used to pump fluids from the inlet port to the outlet port. The microfluidic device is integrated with off-the-shelf perfusion chambers and allows seamless integration with the electrophysiology setup. The fluids introduced at the inlet ports flow through the microchannels towards the outlet ports and also escape through the circular openings located on top of the microchannels into the bath of the perfusion. Thus the bottom surface of the brain slice placed in the perfusion chamber bath and above the microfluidic device can be exposed with different neurotransmitters. The microscale thickness of the microfluidic device and the transparent nature of the materials [glass coverslip and PDMS (polydimethylsiloxane)] used to make the microfluidic device allow microscopy of the brain slice. The microfluidic device allows modulation (both spatial and temporal) of the chemical stimuli introduced to the brain slice microenvironments. 相似文献
45.
Patrick M. A. James Marie-Josée Fortin Andrew Fall Dan Kneeshaw Christian Messier 《Ecosystems》2007,10(8):1261-1277
Forest age structure and its spatial arrangement are important elements of sustainable forestry because of their effects on
biodiversity and timber availability. Forest management objectives that include specific forest age structure may not be easily
attained due to constraints imposed by the legacies of historical management and natural disturbance. We used a spatially
explicit stochastic model to explore the synergetic effects of forest management and fire on boreal forest age structure.
Specifically, we examined (1) the duration of spatial legacies of different management practices in the boreal forest, (2)
how multiple shifts in management practices affect legacy duration and the spatial trajectories of forest age structure, and
(3) how fire influences legacy duration and pattern development in combination with harvesting. Results based on 30 replicates
of 500 years for each scenario indicate that (1) spatial legacies persist over 200 years and the rate at which legacies are
overcome depends on whether new management targets are in synchrony with existing spatial pattern; (2) age specific goals
were met faster after multiple management shifts due to the similar spatial scale of the preceding management types; (3) because
large fires can erase the spatial pattern created by smaller disturbances, scenarios with fire had shorter lags than scenarios
without fire. These results suggest that forest management goals can be accelerated by applying management at a similar spatial
scale as existing spatial patterns. Also, management planning should include careful consideration of historical management
as well as current and likely future disturbances. 相似文献
46.
Network topology serves as a useful model for biological systems at various scales. Contrary to many biological systems, spatial reference is crucial for habitat networks. Boreal forest landscapes provide a wide gradient of spatial patterns and, thus, unique network structures. Assuming forest-dwelling organisms in general aim to minimize travel distances during foraging, dispersal, etc., linear links across the landscape matrix constitute expected movement routes among forested areas in boreal landscapes. We quantified the number and length of links in a set of 57 boreal forest landscapes for four hierarchically nested graphs in order to compare the incremental changes in characteristics of resulting graph measures. The forest cover graphs consisted of the same set of forest patches, and hierarchical link types extracted from real landscapes: nearest neighbour graph (NN), minimum spanning tree (MST), Gabriel graph (GG) and minimum planar graph (MPG). Most of the links in graphs were NN and GG links. Commonly links were 100–200?m in length, but link lengths particularly in the GG and MPG shorten when the proportion of forest in landscapes increased. Most nodes had 3–5 links each, but the number of links per node depended on node size and the proportion of forest cover. GG and MPG graphs retain the topology of the underlying node layout. Changes in node pattern alter the NN and MST graphs more than GG and MPG. Variation in regional network topologies is likely to affect connectivity patterns in a landscape and, thus, many ecological processes that occur at a local scale. An appropriate network analysis enables the discovery and comparison of distinctive network patterns. Understanding network topologies provide practical tools for land use planning and biodiversity management of broader areas that target functional habitat networks. 相似文献
47.
Fall AG Diaïté A Etter E Bouyer J Ndiaye TD Konaté L 《Medical and veterinary entomology》2012,26(1):106-111
Active catches of adult females of Aedes vexans arabiensis Patton, (Diptera: Culicidae) Patton by nets or aspirator, were conducted in 2003 and 2004 in the vegetation at the edge of temporary ponds in Barkedji, Senegalese Ferlo area. Two hundred and forty-one engorged females were captured, dissected and the gut content adsorbed on a Whatman filter paper and analysed using the enzyme-linked immunosorbent assay (ELISA) technique to determinate the bloodmeal origin. Results indicated that Ae v. arabiensis fed primarily on mammals, including horses (35.7% of the bloodmeals), but also on birds (10%). Moreover, associations between horses and birds accounted for 42% of the mixed bloodmeals. These results show an opportunistic feeding behaviour and suggest that Ae v. arabiensis is a probable vector bridging the West Nile virus between horses and birds hosts in the Ferlo area. 相似文献
48.
We have developed a firing rate network model for working memory that combines Mexican-hat-like synaptic coupling with intrinsic
or cellular dynamics that are conditionally bistable. While our approach is in the spirit of Camperi and Wang (1998) we include
a specific and plausible mechanism for the cellular bistability. Modulatory neurotransmitters are known to activate second
messenger signaling systems, and our model includes an intracellular Ca2+ handling subsystem whose dynamics depend upon the level of the second messenger inositol 1,4,5 trisphosphate (IP3). This
Ca2+ subsystem endows individual units with conditional intrinsic bistability for a range of IP3. The full “hybrid” network sustains
IP3-dependent persistent (“bump”) activity in response to a brief transient stimulus. The bump response in our hybrid model,
like that of Camperi-Wang, is resistant to noise – its position does not drift with time.
Action Editor: Upinder Bhalla 相似文献
49.
B. Fall P. A. Fall B. Diao M. R. Kpatcha Y. Sow F. A. Kabore M. Ali A. K. Ndoye M. Ba B. A. Diagne 《Andrologie》2009,19(1):45-49
Objectives
To describe the epidemiological, clinical, biological and therapeutic features of Fournier’s gangrene and identify the prognostic factors.Patients and methods
We conducted a retrospective study on 102 cases of Fournier’s gangrene treated at the urology department of the university teaching hospital Aristide- Le-Dantec (Dakar) between January 2001 and December 2007.Results
The mean age of the patients was 50.0 ± 15.7 years (range: 20–93 years). The mean duration of hospital stay was 8.0 ± 7.1 days (range: 1–33 days). The lesions were located on the scrotum in 61.7% of cases, on the scrotum and penis in 17.6% of cases and on the penis alone in 3.9% of the cases. Perineal involvement was found in 14.7% of the cases. No etiologic factors (idiopathic) were found in 26 cases (25.5%) and 70 patients (68.6%) had Fournier’s gangrene secondary to urethral stricture. The most common predisposing factors were diabetes mellitus (13.7%), hypertension (5.9%), and renal failure (5.9%). Biological examination revealed that 79.4% of patients had a leukocytosis higher than 12,000/ml and the mean rate of haemoglobin was 9.8 ± 2.8 g/dl (range: 3.3–13.9 g/dl). The most common antibiotherapy associated a third generation cephalosporin, aminoside and metronidazole (46.1%). Twenty-one patients (20.6%) underwent extensive debridement only and eighty-one (79.4%) underwent extensive debridement and cystostomy. The death rate was 15.7%. Among the patients whose Fournier’s gangrene was idiopathic or secondary to urethral stricture, the statistically significant factors for a poor outcome were age, the secondary character of the gangrene, the extent of the lesions, and association with diabetes mellitus and/or hypertension.Conclusion
Fournier’s gangrene is still a frequent and lethal disease. Its good management requires a multidisciplinary approach. 相似文献50.
A. Sarr C. Dial Y. Sow M. Gaye A. Thiam B. Fall B. Diao M. Ba B.A. Diagne 《Andrologie》2010,20(4):279-281
The authors report the first case of pseudotumor of the spermatic cord in a patient presenting with an ectopic testis. On surgical exploration, a funicular mass overriding the testis was found, and histologic study of the specimen showed a pseudotumoral funiculitis. Through the analysis of this case and a review of the literature, we shall discuss the diagnostic and therapeutic features of rare paratesticular tumors. 相似文献