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931.
Patrice Savadogo Mulualem Tigabu Louis Sawadogo Per Christer Odén 《African Journal of Ecology》2009,47(4):699-710
Fire is an integral ecological factor in African savanna ecosystems, but its effects on savanna productivity are highly variable and less understood. We conducted a field experiment to quantify changes in herbaceous phytomass and nutrient composition in a Sudanian savanna woodland subjected to annual early fire from 1993 to 2004. Fire effects were also assessed on two perennial and two annual grass species during the following growing season. Early fire significantly reduced above‐ground phytomass of the studied species (P = 0.03), their crude protein (P = 0.022), neutral detergent insoluble crude protein (P = 0.016) and concentrations of Ca, Fe and Mn (P < 0.05). Perennial grasses had higher above‐ground phytomass but lower total crude protein and fat than annual grasses. Nonstructural carbohydrates tended to be higher for annuals, while fibre and lignin contents were high for perennials. Except Na and Fe, the concentration of mineral elements varied between species. Fire did not affect measures of digestibility and metabolizable energy, but its effect differed significantly among species. In conclusion, the results illustrate that long‐term frequent fire will counterbalance the short‐term increase in soil fertility and plant nutrient concentrations claimed to be accrued from single or less frequent fire. 相似文献
932.
Starch from the fruits of sweetsop (Anonna squamosa) and soursop (Anonna muricata) were isolated and purified and the fat, ash, phosphorus and protein contents measured. The amount of amylose present was determined spectrophotometrically and found to be very similar (19%) for both starches. Scanning electron microscopy showed very small indented and spherical granules from both with an average granule size of 4.84 μm and 4.72 μm, respectively. The physicochemical properties, namely the swelling power, solubility, pasting characteristics, paste clarity and freeze–thaw stability were studied to assess the functionality of the starch pastes as hydrocolloids. The sweetsop starch showed higher swelling power and solubility compared to soursop starch and had a lower gelatinization temperature indicating a weaker granular structure. Sweetsop starch exhibited a lower pasting temperature, higher viscosity peak, higher viscosity breakdown and lower setback, higher paste clarity and freeze–thaw stability compared to soursop starch. The low gelatinization temperature and high freeze thaw stability of sweetsop starch are comparable to that of waxy corn. The properties of sweetsop indicate that it has potential for application as a thickener in frozen foods. 相似文献
933.
Starch obtained from yellow and white plantain varieties were subjected to proximate analysis, physicochemical and rheological characterization in order to evaluate their properties. Yellow plantain variety gave higher yield of starch than the white variety. The two varieties differed in the purity of starch extract; white plantain starch contained: ash (1.09%), protein (0.640%) and fat (0.276%) while yellow plantain starch contained: ash (0.95%), protein (0.325%) and fat (0.403%). The amylose content of yellow plantain starch (24.36% (apparent), 26.13% (total)) was similar to that of white plantain starch (24.24% (apparent), 26.01% (total)). Scanning electron microscopy revealed bimodal irregular shaped granules (3.74–7.00 and 10.00–33.00 μm) in white plantain starch and elliptical granules (11.22–41.00 μm) in yellow plantain starch. Both starches differed markedly in their physicochemical properties. Their differences in gelatinization temperature (yellow plantain, 64.99–73.90 °C; white plantain, 68.08–77.15 °C), swelling and solubility patterns, and pasting characteristics indicated that yellow plantain starch had weaker granule architecture compared with white plantain starch. Further evidence of differences in properties was obtained from flow and viscoelastic properties of the starch gels, paste clarity and freeze–thaw stability. 相似文献
934.
Gyöngyi Cinege Sandrine Louis Robert Hänsch Jörg-Peter Schnitzler 《Plant molecular biology》2009,69(5):593-604
Isoprene synthase (ISPS) catalyzes the formation of isoprene, an important volatile terpenoid with strong effects on global atmospheric chemistry and protective physiological functions in plant leaves. Many terpene synthase genes including isoprene synthase, a member of the TPS-b cluster of this numerous gene family, were already functionally analysed but much less is known about regulation of their promoters. To study regulation of the PcISPS gene in detail we developed transgenic Grey poplar (Populus × canescens) and Arabidopsis thaliana plants in which the PcISPS promoter is fused to enhanced green fluorescent protein (E-GFP) and β-glucuronidase (GUS) reporter genes. We analysed these reporters during plant development, for organ specificity and in plants subjected to different light and temperature regimes. We observed low promoter activity in non-isoprene emitting tissue like roots where ISPS gene is transcribed but no active enzyme is detectable. In leaves we demonstrate that light and temperature directly modulate ISPS promoter activity. Moreover, with confocal laser scanning microscopy we show a cell specific gradient of ISPS promoter activity within the leaf parenchyma depending on light direction. Our results indicate that ISPS promoter activity, which correlates with basal isoprene emission capacity, is not uniformly distributed within leaf tissue and that it can adapt rapidly towards internal as well as external environmental stimuli. 相似文献
935.
Christian Laflamme Louis Gendron Nathalie Turgeon Geneviève Filion Jim Ho Caroline Duchaine 《Systematic and applied microbiology》2009
Rapid detection of Bacillus spores is a challenging task in food and defense industries. In situ labeling of spores would be advantageous for detection by automated systems based on single-cell analysis. Determination of antibiotic-resistance genes in bacterial spores using in situ labeling has never been developed. Most of the in situ detection schemes employ techniques such as fluorescence in situ hybridization (FISH) that target the naturally amplified ribosomal RNA (rRNA). However, the majority of antibiotic-resistance genes has a plasmidic or chromosomal origin and is present in low copy numbers in the cell. The main challenge in the development of low-target in situ detection in spores is the permeabilization procedure and the signal amplification required for detection. This study presents permeabilization and in situ signal amplification protocols, using Bacillus cereus spores as a model, in order to detect antibiotic-resistance genes. The permeabilization protocol was designed based on the different layers of the Bacillus spore. Catalyzed reporter deposition (CARD)–FISH and in situ polymerase chain reaction (PCR) were used as signal amplification techniques. B. cereus was transformed with the high copy number pC194 and low copy number pMTL500Eres plasmids in order to induce resistance to chloramphenicol and erythromycin, respectively. In addition, a rifampicin-resistant B. cereus strain, conferred by a single-nucleotide polymorphism (SNP) in the chromosome, was used. Using CARD–FISH, only the high copy number plasmid pC194 was detected. On the other hand, in situ PCR gave positive results in all tested instances. This study demonstrated that it was feasible to detect antibiotic-resistance genes in Bacillus spores using in situ techniques. In addition, in situ PCR has been shown to be more sensitive and more applicable than CARD–FISH in detecting low copy targets. 相似文献
936.
Sven H. Hausner David Alagille Andrei O. Koren Louis Amici Julie K. Staley Kelly P. Cosgrove Ronald M. Baldwin Gilles D. Tamagnan 《Bioorganic & medicinal chemistry letters》2009,19(2):543-545
A series of novel 5- and 6-substituted 2-(4-dimethylaminophenyl)-1,3-benzoxazoles was synthesized and their potential as imaging probes for Alzheimer’s Disease (AD)-related amyloid plaque was evaluated in vitro and in vivo. In vitro binding affinities for Aβ1–40 peptide of several of these compounds were in the low-nanomolar range . The lowest Ki of 9.3 nM was found for N-(2-(4-(dimethylamino)phenyl)-1,3-benzoxazol-5-yl)-4-iodobenzamide (1e). Its 123I-radiolabeled form ([123I]1e) was subsequently prepared by iododestannylation of the corresponding tributylstannyl precursor and evaluated in vivo in a baboon model using SPECT imaging. Contrary to our expectations, 1e did not cross the blood–brain barrier (BBB) to any significant extent. 相似文献
937.
Amar S. Prashad Daniel Wang Joan Subrath Biqi Wu Melissa Lin Mei-Yi Zhang Natasha Kagan Julie Lee Xiaoke Yang Agnes Brennan Divya Chaudhary Xin Xu Louis Leung Jack Wang Diane H. Boschelli 《Bioorganic & medicinal chemistry letters》2009,19(19):5799-5802
We previously reported that a 3-pyridinecarbonitrile analog with a furan substituent at C-5 and a 4-methylindol-5-ylamino substituent at C-4, 1, was a potent inhibitor of PKCθ (IC50 = 4.5 nM). Replacement of the C-5 furan ring of 1 with bicyclic heteroaryl rings, led to compounds with significantly improved potency against PKCθ. Analog 6b with a 4-methylindol-5-ylamino group at C-4 and a 5-[(4-methylpiperazin-1-yl)methyl]-1-benzofuran-2-yl group at C-5 had an IC50 value of 0.28 nM for the inhibition of PKCθ. 相似文献
938.
Louis G. Zachos 《Journal of theoretical biology》2009,259(3):646-125
A new computational model has been developed to simulate growth of regular sea urchin skeletons. The model incorporates the processes of plate addition and individual plate growth into a composite model of whole-body (somatic) growth. A simple developmental model based on hypothetical morphogens underlies the assumptions used to define the simulated growth processes. The data model is based on a Delaunay triangulation of plate growth center points, using the dual Voronoi polygons to define plate topologies. A spherical frame of reference is used for growth calculations, with affine deformation of the sphere (based on a Young-Laplace membrane model) to result in an urchin-like three-dimensional form. The model verifies that the patterns of coronal plates in general meet the criteria of Voronoi polygonalization, that a morphogen/threshold inhibition model for plate addition results in the alternating plate addition pattern characteristic of sea urchins, and that application of the Bertalanffy growth model to individual plates results in simulated somatic growth that approximates that seen in living urchins. The model suggests avenues of research that could explain some of the distinctions between modern sea urchins and the much more disparate groups of forms that characterized the Paleozoic Era. 相似文献
939.
Cooperia oncophora is an important parasitic nematode of cattle with a wide distribution in temperate areas. Twenty Holstein nematode-naïve bull calves were experimentally infected with approximately 100,000 infective L3s and infection was allowed to progress for 7, 14, 28, 42 days, respectively. This experiment was conducted to identify putative recognition and inflammatory pathways in the host-parasite relationship. Gene expression profiles of the small intestine were compared using a high-density bovine 60 mer oligo microarray. A total of 310 genes were differentially expressed during the course of infection. The pathways and regulatory networks significantly impacted by the infection were analysed. A total of 22 canonical pathways and nine regulatory networks were significantly affected during infection. During the early phase of the infection (7 days p.i.), parasites suppressed the acute phase response and the complement system of the host. At 14 days p.i., three out of the six pathways impacted were related with retinoid X receptor (RXR) functions. At 28 days p.i., the effects on RXR were less evident. The host response shifted to lipid metabolism and signalling, especially eicosanoid production and signalling, suggesting that eicosanoid-mediated inflammation might be a major host defence mechanism. By 42 days p.i., the pathways impacted involved glycosphingolipid biosynthesis and transforming growth factor β (TGFβ signalling. The expression of cadherin-like 26 (CDH26) was strongly up-regulated starting at 14 days p.i. and peaked at 28 days p.i. The extent of its expression is positively correlated with the infiltration of eosinophils (R = 0.82) and coincides with the number of adult parasites in the tissue. CDH26 demonstrated an expression profile similar to two other cell adhesion molecules involved in recognition of carbohydrates on foreign organisms, collectin and galectin, suggesting that it may serve as a pattern recognition molecule for C. oncophora. These results provide a potential molecular roadmap for future studies aimed at defining host immune responses and understanding protective immunity against gastrointestinal nematodes. 相似文献
940.