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1.
Much of eastern Australia's coastal lowlands are underlain by Holocene sulfidic sediments. Large areas have been drained for agriculture. Drained, sulfidic sediments oxidize and produce highly acidic discharge (pH<4) with significant impacts on estuarine ecosystems. The rate of production of acid from drained floodplains is between 100 to 300 kg H2SO4 /ha/y and hundreds of tonnes of H2SO4 can be discharged in a single flood from the floodplain. Generation and export of acidity is controlled by the water balance of the floodplain, the characteristics of the drainage system and the distribution of sulfides. Evapotranspiration by native plants and crops plays a dominant role in the oxidation of sediments in dry periods. In wet periods, upland discharges to floodplains dominate the water balance. Drain spacing and drain depth are critical factors in the export of acidity into coastal streams. Amelioration of acidic outflows requires an understanding of the interaction between chemical and hydrological processes in sulfidic landscapes. Redesign of drainage systems to manage surface waters and reduce drain density with the treatment of drains with lime offer promise for treating acidic discharge and reducing impacts. Reflooding of drained, partially oxidized floodplains with freshwater may not be a panacea because of the large volumes of acid stored in the soil, a lack of labile organic matter in the sediments needed to reduce sulfate and irreversible changes to the soil due to oxidation. Tidal brackish water reflooding of unproductive acidified lowlands offers promise for rehabilitating wetlands. Sulfidic wetlands which are still undrained should remain so unless all acidic discharge can be treated. 相似文献
2.
Tobias I. Baskin Catherine H. Busby Larry C. Fowke Margaret Sammut Frank Gubler 《Planta》1992,187(3):405-413
Microtubules are important in plant growth and development. Localizing microtubules in sectioned material is advantageous because it allows any tissue of interest to be studied and it permits the positional relations of the cells within the organ to be known. We describe here a method that uses semi-thin (0.5–2 m) sections of material embedded in butyl-methylmethacrylate, to which 10 mM dithiothreitol was added. After removing the embedding material and using indirect immunofluorescence staining, we obtain clear images of microtubules, actin microfilaments, callose and pulse-fed bromodeoxyuridine. This method works on the root tissues of Arabidopsis thaliana(L.) Heynh, Pinus radiataD. Don, Zamia furfuraceaAit., Azolla pinnataR. Br. and on sporophytic tissues of Funaria hygrometricaHedw. In general, most of the cells in the organs studied are successfully stained. Using this method, we find that interphase meristematic cells in all of these species have microtubules not only in the usual cortical array but also throughout their cytoplasm. The presence of the calcium chelator ethylene glycol-bis(-aminoethyl ether)N,N,N,N-tetraacetic acid EGTA in fixation buffers led to some tissue damage, and did not enhance the preservation of microtubules. The common assumption that EGTA-containing buffers stabilize plant microtubules during fixation appears unwarranted.Abbreviations BrdU
5-bromodeoxyuridine
- DTT
dithiothreitol
- EGTA
ethylene glycol-bis(-aminoethyl ether)
- N,N,N,N
tetraacetic acid
We thank Ann Cork for technical assistance, Professor B.E.S. Gunning (Australian National University) and Drs. A.R. Hardham (A.N.U.) and R.E. Williamson (A.N.U.) for intellectual and material support, Dr D. McCurdy (A.N.U.) for the purified anti-actin antibody, and Professor B. Stone (La Trobe University, Melbourne, Australia) for generously providing the anti-callose antibody. We also thank the Electron Microscopy Unit of A.N.U. for the use of facilities. L.C.F. gratefully acknowledges financial support from the National Sciences and Engineering Research Council of Canada. 相似文献
3.
Elizabeth?R?Unger Rosane?Nisenbaum Harvey?Moldofsky Angela?Cesta Christopher?Sammut Michele?Reyes William?C?ReevesEmail author 《BMC neurology》2004,4(1):6
Background
Chronic fatigue syndrome (CFS) is a disabling condition that affects approximately 800,000 adult Americans. The pathophysiology remains unknown and there are no diagnostic markers or characteristic physical signs or laboratory abnormalities. Most CFS patients complain of unrefreshing sleep and many of the postulated etiologies of CFS affect sleep. Conversely, many sleep disorders present similarly to CFS. Few studies characterizing sleep in unselected CFS subjects have been published and none have been performed in cases identified from population-based studies.Methods
The study included 339 subjects (mean age 45.8 years, 77% female, 94.1% white) identified through telephone screen in a previously described population-based study of CFS in Wichita, Kansas. They completed questionnaires to assess fatigue and wellness and 2 self-administered sleep questionnaires. Scores for five of the six sleep factors (insomnia/hypersomnia, non-restorative sleep, excessive daytime somnolence, sleep apnea, and restlessness) in the Centre for Sleep and Chronobiology's Sleep Assessment Questionnaire© (SAQ©) were dichotomized based on threshold. The Epworth Sleepiness Scale score was used as a continuous variable.Results
81.4% of subjects had an abnormality in at least one SAQ© sleep factor. Subjects with sleep factor abnormalities had significantly lower wellness scores but statistically unchanged fatigue severity scores compared to those without SAQ© abnormality. CFS subjects had significantly increased risk of abnormal scores in the non-restorative (adjusted odds ratio [OR] = 28.1; 95% confidence interval [CI]= 7.4–107.0) and restlessness (OR = 16.0; 95% CI = 4.2–61.6) SAQ© factors compared to non-fatigued, but not for factors of sleep apnea or excessive daytime somnolence. This is consistent with studies finding that, while fatigued, CFS subjects are not sleepy. A strong correlation (0.78) of Epworth score was found only for the excessive daytime somnolence factor.Conclusions
SAQ© factors describe sleep abnormalities associated with CFS and provide more information than the Epworth score. Validation of these promising results will require formal polysomnographic sleep studies.4.
Kenny S Duval C Sammut SJ Steele I Pritchard DM Atherton JC Argent RH Dimaline R Dockray GJ Varro A 《American journal of physiology. Gastrointestinal and liver physiology》2008,295(3):G431-G441
The gastric pathogen Helicobacter pylori (H. pylori) is linked to peptic ulcer and gastric cancer, but the relevant pathophysiological mechanisms are unclear. We now report that H. pylori stimulates the expression of plasminogen activator inhibitor (PAI)-1, urokinase plasminogen activator (uPA), and its receptor (uPAR) in gastric epithelial cells and the consequences for epithelial cell proliferation. Real-time PCR of biopsies from gastric corpus, but not antrum, showed significantly increased PAI-1, uPA, and uPAR in H. pylori-positive patients. Transfection of primary human gastric epithelial cells with uPA, PAI-1, or uPAR promoters in luciferase reporter constructs revealed expression of all three in H+/K+ATPase- and vesicular monoamine transporter 2-expressing cells; uPA was also expressed in pepsinogen- and uPAR-containing trefoil peptide-1-expressing cells. In each case expression was increased in response to H. pylori and for uPA, but not PAI-1 or uPAR, required the virulence factor CagE. H. pylori also stimulated soluble and cell surface-bound uPA activity, and both were further increased by PAI-1 knockdown, consistent with PAI-1 inhibition of endogenous uPA. H. pylori stimulated epithelial cell proliferation, which was inhibited by uPA immunoneutralization and uPAR knockdown; exogenous uPA also stimulated proliferation that was further increased after PAI-1 knockdown. The proliferative effects of uPA were inhibited by immunoneutralization of the EGF receptor and of heparin-binding EGF (HB-EGF) by the mutant diphtheria toxin CRM197 and an EGF receptor tyrosine kinase inhibitor. H. pylori induction of uPA therefore leads to epithelial proliferation through activation of HB-EGF and is normally inhibited by concomitant induction of PAI-1; treatments directed at inhibition of uPA may slow the progression to gastric cancer. 相似文献
5.
6.
Sequence divergence derives from either point substitution or indel (insertion or deletion) processes. We investigated the
rates of these two processes both in protein and non-protein coding DNA. We aligned sequence pairs using two pair-hidden Markov
models (PHMMs) conjoined by one silent state. The two PHMMs had their own set of parameters to model rates in their respective
regions. The aim was to test the hypothesis that the indel mutation rate mimics the point mutation rate. That is, indels are
found less often in conserved regions (slow point substitution rate) and more often in non-conserved regions (fast point substitution
rate). Both polypeptides and rRNA molecules in our data exhibited a clear distinction between slow and fast rates of the two
processes. These two rates served as surrogates to conserved and non-conserved secondary structure components, respectively.
With polypeptides we found both the fast indel rate and the fast replacement rate were co-located with hydrophilic residues.
We also found that the average concordance, of our alignments with corresponding curated alignments, improves markedly when
the model allows either of the two fast rates to colocate with hydrophilic residues. With rRNA molecules, our model did not
detect colocation between the fast indel rate and the fast substitution rate. Nevertheless, coupling the indel rates with
the point substitution rates across the two regions markedly increased model fit. This result suggests that rRNA pairwise
alignments should be modeled after allowing for the two processes to vary simultaneously and independently in the two regions. 相似文献
7.
Class I major histocompatibility complex (Mhc) cDNA clones were isolated from axolotl mRNA by polymerase chain reaction (PCR) and by screening a cDNA phage library. The
nucleotide and predicted amino acid sequences show definite similarities to the Mhc class Iα molecules of higher vertebrates.
Most of the amino acids in the peptide binding region that dock peptides at their N and C termini in mammals are conserved.
Several amino acids considered to be important for the interaction of β2-microglobulin with the Mhc α chain are also conserved in the axolotl sequence. The fact that axolotl class I A cDNAs are
ubiquitously expressed and highly polymorphic in the α1 and α2 domains suggests the classical nature of axolotl class I A
genes.
Received: 3 June 1996 / Revised: 14 October 1996 相似文献
8.
Knight R Maxwell P Birmingham A Carnes J Caporaso JG Easton BC Eaton M Hamady M Lindsay H Liu Z Lozupone C McDonald D Robeson M Sammut R Smit S Wakefield MJ Widmann J Wikman S Wilson S Ying H Huttley GA 《Genome biology》2007,8(8):R171-16
We have implemented in Python the COmparative GENomic Toolkit, a fully integrated and thoroughly tested framework for novel probabilistic analyses of biological sequences, devising workflows, and generating publication quality graphics. PyCogent includes connectors to remote databases, built-in generalized probabilistic techniques for working with biological sequences, and controllers for third-party applications. The toolkit takes advantage of parallel architectures and runs on a range of hardware and operating systems, and is available under the general public license from http://sourceforge.net/projects/pycogent. 相似文献
9.
Summary Calcofluor White ST is a fluorescent brightener that has previously been shown to alter cellulose ribbon assembly in the bacteriumAcetobacter xylinum. In this report, we demonstrate that Calcofluor also disrupts cell wall assembly in the eukaryotic algaOocystis apiculata. When observed with polarization microscopy, walls altered by Calcofluor show reduced birefringence relative to controls. Electron microscopy has shown that these altered walls contain regions which consist primarily of amorphous material and which generally lack organized microfibrils. We propose that wall alteration occurs because Calcofluor binds with the glucan chains polymerized by the cellulose synthesizing enzymes as they are produced. As a consequence, the glucan chains are prevented from co-crystallizing to form microfibrils. Synthesis of normal walls resumes when Calcofluor is removed, which is consistent with our proposal that Calcofluor acts by direct physical interaction with newly synthesized wall components.Several types of fluorescent patterns at the cell wall/plasmalemma interface have also been observed following Calcofluor treatment. Fluorescent spots, striations; helical bands, and lens-shaped thickenings have been documented. Each of these patterns may be the result of the interaction of Calcofluor with cellulose at different spatial or temporal levels or from varying concentrations of the brightener itself. Helical bands and lens-shaped thickenings also have been examined with the electron microscope. Like other regions of wall alteration, they are found to contain primarily amorphous material. Finally, we note that cells with severely disrupted walls are unable to complete their normal life cycle. 相似文献
10.
Tseng KY Caballero A Dec A Cass DK Simak N Sunu E Park MJ Blume SR Sammut S Park DJ West AR 《PloS one》2011,6(11):e27187