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The isolate Aspergillus versicolor was obtained from an estuary, which is exposed to metal contamination. It was found to have a good metal tolerance and sorption capacity. Further studies revealed that the rate of metal removal from solution is very rapid in the first 5-10 min, and is favoured by a pH of 6.0. The biosorption data obtained was explained by the Freundlich adsorption isotherm model and followed a pseudo-second order kinetics reaction. The fungus showed a higher accumulation of fatty acids when grown in presence of metals as compared to the mycelium grown in absence of the metal; there was also an increase in the saturation index of fatty acids in presence of Cu(2+) which serves as a protective mechanism for the fungus. Fourier Transform Infrared, scanning electron microscopy and EDAX analysis indicated that metal removal from solution by A. versicolor occurred by a passive adsorption to the fungal cell surface, involving an ion exchange mechanism. 相似文献
54.
The didelphid marsupial, Didelphis aurita, is suggested as an intraguild predator and as key‐species in small mammal assemblages of the Atlantic Forest of Brazil. The field experiments required to test this hypothesis are complex to implement, but the recent revival of regression methods offers a viable alternative. Here we use the dynamic and static regression methods to determine the importance of D. aurita as a competitor and intraguild predator. Capture–recapture data from two localities in the Rio de Janeiro State were used, Garrafão (municipality of Guapimirim), a coastal forest of the Serra do Mar, and Barra de Maricá, a costal sand dune vegetation. Population and microhabitat variables were monitored from April 1997 to April 2003 in Garrafão, and from January 1986 to July 1990 in Barra de Maricá. Microhabitat variables were related to Canopy, Plant, Litter and Rock covers, Obstruction from 0 to 1.5 m, and Number of logs. Exploitation competition was tested by the dynamic method, which models the effects of D. aurita on the per capita growth rate of a species. Interference by predation or competition was tested by the static method, where the abundance of D. aurita at trap stations was regressed against the abundance of other small mammals, after removal of any variation associated with microhabitat factors. Exploitation competition was not detected, but the interference of D. aurita was pervasive, affecting all small mammals studied in the two localities. The clear avoidance of D. aurita by all small mammals tested in two localities of different physiognomies indicates that it functions as an intraguild predator, even if actual predation by D. aurita is an occasional event. 相似文献
55.
Andrade LO Galvão LM Meirelles Mde N Chiari E Pena SD Macedo AM 《Memórias do Instituto Oswaldo Cruz》2010,105(6):834-837
We have previously demonstrated selection favoring the JG strain of Trypanosoma cruzi in hearts of BALB/c mice that were chronically infected with an equal mixture of the monoclonal JG strain and a clone of the Colombian strain, Col1.7G2. To evaluate whether cell invasion efficiency drives this selection, we infected primary cultures of BALB/c cardiomyocytes using these same T. cruzi populations. Contrary to expectation, Col1.7G2 parasites invaded heart cell cultures in higher numbers than JG parasites; however, intracellular multiplication of JG parasites was more efficient than that of Col1.7G2 parasites. This phenomenon was only observed for cardiomyocytes and not for cultured Vero cells. Double infections (Col1.7G2 + JG) showed similar results. Even though invasion might influence tissue selection, our data strongly suggest that intracellular development is important to determine parasite tissue tropism. 相似文献
56.
Ana Paula D. N. de Barros Christina M. Takiya Luciana R. Garzoni Mona Lisa Leal-Ferreira Hélio S. Dutra Luciana B. Chiarini Maria Nazareth Meirelles Radovan Borojevic Maria Isabel D. Rossi 《PloS one》2010,5(2)
Background
Migration, proliferation, and differentiation of hematopoietic stem cells (HSCs) are dependent upon a complex three-dimensional (3D) bone marrow microenvironment. Although osteoblasts control the HSC pool, the subendosteal niche is complex and its cellular composition and the role of each cell population in HSC fate have not been established. In vivo models are complex and involve subtle species-specific differences, while bidimensional cultures do not reflect the 3D tissue organization. The aim of this study was to investigate in vitro the role of human bone marrow–derived mesenchymal stromal cells (BMSC) and active osteoblasts in control of migration, lodgment, and proliferation of HSCs.Methodology/Principal Findings
A complex mixed multicellular spheroid in vitro model was developed with human BMSC, undifferentiated or induced for one week into osteoblasts. A clear limit between the two stromal cells was established, and deposition of extracellular matrix proteins fibronectin, collagens I and IV, laminin, and osteopontin was similar to the observed in vivo. Noninduced BMSC cultured as spheroid expressed higher levels of mRNA for the chemokine CXCL12, and the growth factors Wnt5a and Kit ligand. Cord blood and bone marrow CD34+ cells moved in and out the spheroids, and some lodged at the interface of the two stromal cells. Myeloid colony-forming cells were maintained after seven days of coculture with mixed spheroids, and the frequency of cycling CD34+ cells was decreased.Conclusions/Significance
Undifferentiated and one-week osteo-induced BMSC self-assembled in a 3D spheroid and formed a microenvironment that is informative for hematopoietic progenitor cells, allowing their lodgment and controlling their proliferation. 相似文献57.
We are currently in an interesting phase of plant biotechnology releases, both for the scientists responsible for these innovations who are beginning to see their ideas realized, and for the biotechnology companies that are starting to see a return on their investment. One of the most notable examples, is the introduction of transgenic crops that are engineered to express a Bacillus thuringiensis toxin that confers resistance to insect predation. However, the picture is not altogether positive - there is concern that the introduction of this technology was premature or should not have happened at all, and that the valuable insecticidal properties of Bacillus thuringiensis will be lost. 相似文献
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59.
Amoresano A; Andolfo A; Siciliano RA; Mele A; Coscarella A; De Santis R; Mauro S; Pucci P; Marino G 《Glycobiology》1998,8(8):779-790
MEN 11300 is a hybrid glycoprotein of 297 amino acids obtained by fusion of
the cDNA encoding GM-CSF with the cDNA encoding EPO followed by
transfection of the hybrid gene into CHO cells. The oligonucleotide
construct incorporated a spacing sequence between the two individual cDNAs
which encodes eight amino acids constituting a linker peptide intended to
separate the GM-CSF and EPO moieties. The recombinant MEN 11300 protein was
submitted to a detailed structural characterization including the
verification of the entire amino acid sequence, the assignment of the
disulfide bridges pattern, the identification of the glycosylation sites
and the definition of the glycosidic moiety, including site-specificity.
Partial processing of the C-terminal Arg residue and the occurrence of
N-glycosylation sites at Asn27, Asn155, Asn169, Asn214 were established.
Moreover, O-glycosylation at Ser257 and at the N-terminal region was also
detected. A large heterogeneity was observed in the N-glycans due to the
presence of differently sialylated and fucosylated branched complex type
oligosaccharides whereas O-linked glycans were constituted by GalGalNAc
chains with a different number of sialic acids. The disulfide bridges
pattern was established by direct FABMS analysis of the proteolytic digests
or by ESMS analysis of HPLC purified fractions. Pairing of the eight
cysteine residues resulted in Cys54-Cys96, Cys88-Cys121, Cys138-Cys292, and
Cys160-Cys164. This S-S bridges pattern is identical to that occurring in
the individual natural GM-CSF and EPO, thus showing that the two protein
moieties in MEN 11300 can independently acquire their native
three-dimensional structure.
相似文献
60.
Maria-Cristina Plotkowski Mario Bernardo Filho Maria de Nazareth Meirelles Jean Marie Tournier Edith Puchelle 《Current microbiology》1993,26(2):91-95
We have investigatedPseudomonas aeruginosa binding to plasma and cellular fibronectin (FN), in both their soluble and insoluble forms. Bacterial binding to insoluble FN was studied by exposing coverslips coated with FN to radiolabeled microorganisms.P. aeruginosa binding to soluble FN was investigated (1) by comparing radiolabeled bacteria treated with FN with PBS-treated bacteria in their adhesion to a collagen matrix; (2) by analyzing the reactivity ofP. aeruginosa with plasma or cellular FN adsorbed to gold particles with transmission electron microscopy (TEM).P. aeruginosa did not bind significantly to insoluble plasma or cellular FN, or to soluble plasma FN. In contrast, bacterial treatment with soluble cellular FN significantly increased the adhesion to the collagen matrix. With TEM, we confirmed the reactivity ofP. aeruginosa with soluble cellular FN. Because there is a marked secretion of cellular FN during wound repair, we speculate that this reactivity may account for the propensity ofP. aeruginosa to infect repairing tissues. 相似文献