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53.
Pablo M. Vergara Ingo J. Hahn Horacio Zeballos Juan J. Armesto 《Ecological Research》2010,25(3):683-690
Conservation of forest birds in fragmented landscapes requires not only determining the critical patch characteristics influencing
local population persistence but also identifying patch networks providing connectivity and suitable habitat conditions necessary
to ensure regional persistence. In this study, we assessed the importance of patch attributes, patch connectivity, and network
components (i.e., groups of interconnected patches) in explaining the occupancy pattern of the Thorn-tailed Rayadito (Aphrastura spinicauda), a forest bird species of central Chile. Using a daily movement threshold distance, we identified a total of 16 network
components of sclerophyllous forest within the study area. Among those components, patch area and vegetation structure-composition
were important predictors of patch occupancy. However, the inclusion of patch connectivity and component size (i.e., the area
of a network component) into the models greatly increases the models’ accuracy and parsimony. Using the best-fitted model,
a total of 33 patches were predicted to be occupied by rayaditos within the study area, but such occupied patches were distributed
in only six network components. These results suggest that persistence of rayaditos in central Chile requires the maintenance
of large single patches and patch networks providing habitat and connectivity. 相似文献
54.
Horacio Gómez-Acevedo Michael Y. Li Steven Jacobson 《Bulletin of mathematical biology》2010,72(3):681-696
Human T-cell leukaemia/lymphoma virus type I (HTLV-I) is a retrovirus that has been identified as the causative agent of HTLV-I-associated
myelopathy/tropical spastic paraparesis (HAM/TSP) and other illnesses. HTLV-I infects primarily CD4+ T cells and the transmission occurs through direct cell-to-cell contact. HAM/TSP patients harbor higher proviral loads in
peripheral blood lymphocytes than asymptomatic carriers. Also, HAM/TSP patients exhibit a remarkably high number of circulating
HTLV-I-specific CD8+ cytotoxic T lymphocytes (CTLs) in the peripheral blood. While CTLs have a protective role by killing the infected cells and
lowering the proviral load, a high level of CTLs and their cytotoxicity are believed to be a main cause of the development
of HAM/TSP. A mathematical model for HTLV-I infection of CD4+ T cells that incorporates the CD8+ cytotoxic T-cell (CTL) response is investigated. Our mathematical analysis reveals that the system can stabilize at a carrier
steady-state with persistent viral infection but no CTL response, or at a HAM/TSP steady-state at which both the viral infection
and CTL response are persistent. We also establish two threshold parameters R
0 and R
1, the basic reproduction numbers for viral persistence and for CTL response, respectively. We show that the parameter R
1 can be used to distinguish asymptomatic carriers from HAM/TSP patients, and as an important control parameter for preventing
the development of HAM/TSP. 相似文献
55.
Jennifer L. Belsky Alyssa J. Ashley Premal A. Bhatt Karen V. Gilbert Heather R. Joyce Chunhua Pan Horacio Pappa Samir Z. Wahab 《AAPS PharmSciTech》2010,11(2):994-1004
The water-insoluble procedures in US Pharmacopeia (USP) General Chapter Residual Solvents <467>, which are based on European Pharmacopoeia procedures, were optimized and modified before their inclusion in the chapter to improve their scope, performance, and ruggedness.
The optimized procedures use a static headspace introduction system with a gas chromatograph equipped with a flame ionization
detector. This article describes some of the key changes made to the USP published procedures, including use of dimethyl sulfoxide
(DMSO) or dimethylformamide (DMF) as the solvent, addition of 5 mL of water and 1 mL of sample (dissolved in DMSO or DMF)
to the headspace vial, use of a 3:1 GC split ratio, and use of new matrix-matched system suitability solutions. These procedures
were verified with two different active pharmaceutical ingredients—hydroxyzine pamoate and prednisone. In the investigation,
the more polar material (hydroxyzine pamoate) showed greater recoveries for the optimized procedures when prepared in DMSO.
The less polar material (prednisone) typically had greater recoveries in DMF for the optimized procedures. During experimentation,
insights into sample preparation, additional types of headspace instrumentation, solvent purity, and other parameters were
also gained. 相似文献
56.
Varela Eduardo Sousa; Beasley Colin Robert; Schneider Horacio; Sampaio Iracilda; Marques-Silva Nelane Do Socorro; Tagliaro Claudia Helena 《Journal of Molluscan Studies》2007,73(3):229-234
As a result of phenotypic plasticity, the cupped oysters (Crassostrea)are difficult to identify by means of their morphology. However,molecular DNA markers are a useful means of discriminating amongthese species. Cupped oysters are one of the most widely culturedmarine invertebrates and correct species identification is importantin aquaculture. Moreover, the molecular phylogeny of the genusCrassostrea and the subfamily Crassostreinae is still not clear.In order to identify the Brazilian cupped oysters and to clarifythe phylogenetic relationships of these species, we sequenceda fragment of mitochondrial DNA (16S rRNA gene) from 120 specimenscollected at nine different sites distributed along the Braziliancoast. The results identified two native species of oyster:Crassostrea gasar, from the Amazon to the Parnaíba delta;and Crassostrea rhizophorae, from the northeast (Fortim) tothe south of Brazil. An exotic Crassostrea species, closelyrelated to Indo-Pacific Crassostrea, was found in one locationin the north of Brazil. Crassostrea showed monophyly and theAtlantic oysters are clearly separated from the Indo-Pacificcluster. (Received 30 May 2006; accepted 12 April 2007) 相似文献
57.
Lasarte JJ Casares N Gorraiz M Hervás-Stubbs S Arribillaga L Mansilla C Durantez M Llopiz D Sarobe P Borrás-Cuesta F Prieto J Leclerc C 《Journal of immunology (Baltimore, Md. : 1950)》2007,178(2):748-756
Vaccination strategies based on the in vivo targeting of Ags to dendritic cells (DCs) are needed to improve the induction of specific T cell immunity against tumors and infectious agents. In this study, we have used a recombinant protein encompassing the extra domain A from fibronectin (EDA), an endogenous ligand for TLR4, to deliver Ags to TLR4-expressing DC. The purified EDA protein was shown to bind to TLR4-expressing HEK293 cells and to activate the TLR4 signaling pathway. EDA also stimulated the production by DC of proinflammatory cytokines such as IL-12 or TNF-alpha and induced their maturation in vitro and in vivo. A fusion protein between EDA and a cytotoxic T cell epitope from OVA efficiently presented this epitope to specific T cells and induced the in vivo activation of a strong and specific CTL response. Moreover, a fusion protein containing EDA and the full OVA also improved OVA presentation by DC and induced CTL responses in vivo. These EDA recombinant proteins protected mice from a challenge with tumor cells expressing OVA. These results strongly suggest that the fibronectin extra domain A may serve as a suitable Ag carrier for the development of antiviral or antitumoral vaccines. 相似文献
58.
Occupational exposure to airborne fungi and bacteria in a household recycled container sorting plant
Several studies have showed an association between the work in waste treatment plants and occupational health problems such as irritation of skin, eyes and mucous membranes, pulmonary diseases, gastrointestinal problems and symptoms of organic dust toxic syndrome (ODTS). These symptoms have been related to bioaerosol exposure. The aim of this study was to investigate the occupational exposure to biological agents in a plant sorting source-separated packages (plastics materials, ferric and non-ferric metals) household waste. Airborne samples were collected with M Air T Millipore sampler. The concentration of total fungi and bacteria and gram-negative bacteria were determined and the most abundant genera were identified. The results shown that the predominant airborne microorganisms were fungi, with counts greater than 12,000 cfu/m(3) and gram-negative bacteria, with a environmental concentration between 1,395 and 5,280 cfu/m(3). In both cases, these concentrations were higher than levels obtained outside of the sorting plant. Among the fungi, the predominant genera were Penicillium and Cladosporium, whereas the predominant genera of gram-negative bacteria were Escherichia, Enterobacter, Klebsiella and Serratia. The present study shows that the workers at sorting source-separated packages (plastics materials, ferric and non-ferric metals) domestic waste plant may be exposed to airborne biological agents, especially fungi and gram-negative bacteria. 相似文献
59.
Grigorios A. Papadakos Horacio Nastri Paul Riggs Cynthia M. Dupureur 《Journal of biological inorganic chemistry》2007,12(4):557-569
The hydrolysis of phosphodiester bonds by nucleases is critical to nucleic acid processing. Many nucleases utilize metal ion cofactors, and for a number of these enzymes two active-site metal ions have been detected. Testing proposed mechanistic roles for individual bound metal ions has been hampered by the similarity between the sites and cooperative behavior. In the homodimeric PvuII restriction endonuclease, the metal ion dependence of DNA binding is sigmoidal and consistent with two classes of coupled metal ion binding sites. We reasoned that a conservative active-site mutation would perturb the ligand field sufficiently to observe the titration of individual metal ion binding sites without significantly disturbing enzyme function. Indeed, mutation of a Tyr residue 5.5 A from both metal ions in the enzyme-substrate crystal structure (Y94F) renders the metal ion dependence of DNA binding biphasic: two classes of metal ion binding sites become distinct in the presence of DNA. The perturbation in metal ion coordination is supported by 1H-15N heteronuclear single quantum coherence spectra of enzyme-Ca(II) and enzyme-Ca(II)-DNA complexes. Metal ion binding by free Y94F is basically unperturbed: through multiple experiments with different metal ions, the data are consistent with two alkaline earth metal ion binding sites per subunit of low millimolar affinity, behavior which is very similar to that of the wild type. The results presented here indicate a role for the hydroxyl group of Tyr94 in the coupling of metal ion binding sites in the presence of DNA. Its removal causes the affinities for the two metal ion binding sites to be resolved in the presence of substrate. Such tuning of metal ion affinities will be invaluable to efforts to ascertain the contributions of individual bound metal ions to metallonuclease function. 相似文献
60.
Melissa Richard-Greenblatt Horacio Bach John Adamson Sandra Pe?a-Diaz Wu Li Adrie J. C. Steyn Yossef Av-Gay 《The Journal of biological chemistry》2015,290(38):23064-23076
Ergothioneine (EGT) is synthesized in mycobacteria, but limited knowledge exists regarding its synthesis, physiological role, and regulation. We have identified Rv3701c from Mycobacterium tuberculosis to encode for EgtD, a required histidine methyltransferase that catalyzes first biosynthesis step in EGT biosynthesis. EgtD was found to be phosphorylated by the serine/threonine protein kinase PknD. PknD phosphorylates EgtD both in vitro and in a cell-based system on Thr213. The phosphomimetic (T213E) but not the phosphoablative (T213A) mutant of EgtD failed to restore EGT synthesis in a ΔegtD mutant. The findings together with observed elevated levels of EGT in a pknD transposon mutant during in vitro growth suggests that EgtD phosphorylation by PknD negatively regulates EGT biosynthesis. We further showed that EGT is required in a nutrient-starved model of persistence and is needed for long term infection of murine macrophages. 相似文献