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Large Zone (large + zone)
Selected AbstractsBarrier to gene flow between two ecologically divergent Populus species, P. alba (white poplar) and P. tremula (European aspen): the role of ecology and life history in gene introgressionMOLECULAR ECOLOGY, Issue 4 2005C. LEXER Abstract The renewed interest in the use of hybrid zones for studying speciation calls for the identification and study of hybrid zones across a wide range of organisms, especially in long-lived taxa for which it is often difficult to generate interpopulation variation through controlled crosses. Here, we report on the extent and direction of introgression between two members of the ,model tree' genus Populus: Populus alba (white poplar) and Populus tremula (European aspen), across a large zone of sympatry located in the Danube valley. We genotyped 93 hybrid morphotypes and samples from four parental reference populations from within and outside the zone of sympatry for a genome-wide set of 20 nuclear microsatellites and eight plastid DNA restriction site polymorphisms. Our results indicate that introgression occurs preferentially from P. tremula to P. alba via P. tremula pollen. This unidirectional pattern is facilitated by high levels of pollen vs. seed dispersal in P. tremula (pollen/seed flow = 23.9) and by great ecological opportunity in the lowland floodplain forest in proximity to P. alba seed parents, which maintains gene flow in the direction of P. alba despite smaller effective population sizes (Ne) in this species (P. alba Nec. 500,550; P. tremula Nec. 550,700). Our results indicate that hybrid zones will be valuable tools for studying the genetic architecture of the barrier to gene flow between these two ecologically divergent Populus species. [source] Optimization of medium composition for the production of antimicrobial activity by Bacillus subtilis B38BIOTECHNOLOGY PROGRESS, Issue 5 2009Olfa Tabbene Abstract An antimicrobial activity produced by Bacillus subtilis B38 was found to be effective against several bacteria, including pathogenic and spoilage microorganisms such as, Listeria monocytogenes, Salmonella enteridis, and clinical isolates of methicillin-resistant Staphylococcus species. Nutrients such as carbon, nitrogen sources, and inorganic salts enhanced the production level of the antibacterial activity by B. subtilis B38. A first screening step showed that lactose, ammonium succinate, and manganese most influenced both cell growth and antibacterial activity production. These three factors varied at two levels in eight experiments using full factorial design. Results indicated that maximum cell growth (OD = 10.2) and maximum production of antibacterial activity (360 AU/mL) were obtained in a modified medium containing 1.5% (w/v) lactose, 0.15% (w/v) ammonium succinate, and 0.3 mg/L manganese. Depending on the indicator strain used, the antibacterial activity was 2- to 4-fold higher in the modified culture medium than in TSB medium under the same conditions. Thin layer chromatography-bioautography assay showed the presence of three active spots with Rf values of 0.47, 0.7, and 0.82 in TSB medium. However, the inhibition zone of two spots (Rf values of 0.7 and 0.82) was slightly larger in the modified medium. Moreover, a large zone of inhibition with an Rf value of 0.3, was observed in this modified medium, instead of the spot having an Rf value of 0.47. These results suggest that the nutrients act as environmental factors, quantitatively and qualitatively affecting the production of antibacterial compounds by B. subtilis B38. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Are long subglacial bedforms indicative of fast ice flow?BOREAS, Issue 3 2002CHRIS R. STOKES It has been suggested that extremely long subglacial bedforms (e.g. attenuated drumlins and mega-scale glacial lineations) record former areas of fast-flowing ice and that bedform elongation ratio is a useful proxy for ice velocity. Despite the availability of much data pertaining to the measurement and analysis of subglacial bed-forms, these assumptions have rarely been explicitly addressed in detail. In this paper, we demonstrate that long subglacial bedforms (length:width ratios 10:1) are indicative of fast ice flow. Using satellite imagery, we mapped over 8000 lineaments associated with a highly convergent flow pattern near Dubawnt Lake, District of Keewatin, Canada. This flow pattern is unusual in that it displays a large zone of convergence feeding into a main ,trunk' and then diverging towards the inferred ice margin. The ,bottleneck' pattern is taken to record an increase and subsequent decrease in ice velocity and we analysed transverse and longitudinal variations in bedform morphometry. The main trunk of the flow pattern (down-ice of the convergent zone) is characterized by mega-scale glacial lineations of great length (up to 13 km) and high elongation ratios (up to 43:1). The down-ice variations in elongation ratio reflect exactly what we would expect from a terrestrial ice stream whose velocity increases in the onset zone passes through a maximum in the main trunk and slows down as the ice diverges at the terminus. It is suggested that any unifying theory of drumlin formation must be able to account for the association between long subglacial bedforms and fast ice flow, although it is not assumed that fast ice flow always produces attenuated bedforms. A further implication of this work is that many more ice streams may be identified on the basis of attenuated subglacial bedforms, radically altering our views on the flow dynamics of former ice sheets. [source] Pyoderma gangrenosum of the scalp treated with cyclosporine AINTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 12 2002Pasquale Patrone MD A 56-year-old woman presented with an ulcer, with a depth of 9 mm, on the vertex and frontal parietal regions of the scalp. The lesion had a round shape (diameter, 7 cm), with clear-cut margins and vertical borders sinking vertically to a bottom that was entirely covered with purulent fibrinous yellowish matter and greenish colored necrotic tissue. Other numerous small roundish ulcers were present next to the large ulcer. These had irregular margins with a yellowish fibrinous bottom (Fig. 1). The patient reported the appearance of two small ulcers on the left and on the right frontal parietal regions about 1 year earlier. These had been treated locally with antimicrobials and antiseptics with no result. During the 2 months prior to our evaluation, a few small round-shaped ulcers had appeared on the scalp. These had progressively increased in size and number. Figure Figure 1 . Large ulcer with clear-cut margins, covered by purulent fibrinous matter, and other small roundish ulcers The patient had been an insulin-dependent diabetic for 23 years. Hematochemical examinations showed no significant alterations, except for a rise in glycemia. Urine examination gave normal results. Carcinoembryonic antigen and lymphocytic phenotyping indices were normal. Echographic, endoscopic, and radiocontrast studies of the abdomen did not reveal the presence of lesions either in the gastrointestinal tract or in other organs. Samples of ulcerous tissue were collected from the scalp to perform histologic and microbiologic analysis in search of fungi and bacteria. This last examination revealed the presence of Staphylococcus aureus and Candida parapsylosis. Direct search for mycobacteria was negative. Histology indicated the presence of dermal granulomatous inflammation with giant multinucleate cells, associated with large zones of suppuration and colliquative necrosis. While waiting to complete the diagnostic course, topical antiseptic, antimicrobial, and fibrinolytic therapy was administered; subsequently, as this did not lead to any improvement, systemic treatment with cyclosporine A (5 mg/kg/day) was started. Rapid improvement of the clinical picture occurred. The ulcers appeared cleaner from the first 2 weeks of treatment, radial growth stopped, and the margins were slightly more superficial. The patient continued with immunomodulating therapy at home over a period of 7 months. The dose was progressively reduced until, over a period of about 3 months, complete re-epithelialization of the lesion, with subsequent partial regrowth of the hair, was obtained (Figs 2 and 3). No relapses were observed 1 year after treatment was suspended. Figure 2. Partial re-epithelialization of the lesion with partial regrowth of the hair Figure 3. Scar and hair regrowth [source] | ||||||||||