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121.
Magdesian MH Nery AA Martins AH Juliano MA Juliano L Ulrich H Ferreira ST 《The Journal of biological chemistry》2005,280(35):31085-31090
Alzheimer disease (AD) is characterized by accumulation of the neurotoxic amyloid beta peptide (Abeta) and by the loss of cholinergic neurons and nicotinic acetylcholine receptors (nAChRs) throughout the brain. Direct inhibition of nAChRs by Abeta has also been suggested to contribute to cholinergic dysfunction in AD. In an effort to find ligands capable of blocking Abeta-induced inhibition of nAChRs, we have screened a phage display library to identify peptides that bind to Abeta. Using this approach, we identified a heptapeptide denoted IQ, which binds with nanomolar affinity to Abeta and is homologous to the acetylcholine-binding protein and to most subtypes of nAChRs. Rapid kinetic whole-cell current-recording measurements showed that Abeta inhibits nAChR function in a dose-dependent manner in neuronal differentiated PC12 cells and that nanomolar concentrations of IQ completely block the inhibition by Abeta. These results indicate that the Abeta binding site in nAChRs is homologous to the IQ peptide and that this is a relevant target for Abeta neurotoxicity in AD and, more generally, for the regulation of nAChR function by soluble Abeta in a physiological context. Furthermore, the results suggest that the IQ peptide may be a lead for the development of novel drugs to block the inhibition of nAChRs in AD. 相似文献
122.
Summary
Erythroxylum longisetulosum I. Loiola & M. F. Sales and E. timothei I. Loiola & M. F. Sales (sect. Rhabdophyllum) from north-eastern Brazil are described and illustrated, and their taxonomic and ecological relationships are discussed. 相似文献
123.
Three hundred and thirty nine lactic bacteria strains isolated from food samples were screened for antimicrobial activity.
Only one strain isolated from meat pie and identified as Enterococcus faecium produced a bacteriocin-like inhibitory substance (BLIS) showing activity against Enterococcus, Leuconostoc, Lactobacillus, Listeria, Corynebacterium and Staphylococcus aureus. The BLIS produced was resistant to acid and alkali treatment and 121oC for 15 min. The addition of BLIS in BHI contaminated
with Listeria monocytogenes decreased the contamination in 4.8 log cycles in 24 h. The inhibition of listeria was also obtained in milk. Forty multiresistant
enterococci strains were inhibited in the well-diffusion test. Two vancomycin resistant strains tested in liquid with BLIS
were also inhibited. The BLIS producer showed no pathogenicity marker. 相似文献
124.
Ana Luiza de Brito Portela-Castro Horácio Ferreira Júlio Júnior Patrícia Belini Nishiyama 《Genetica》2000,110(3):277-283
The Moenkhausia sanctaefilomenae specimens showed a karyotype consisting of 2n = 50 chromosomes with 12 metacentrics, 36 submetacentrics and two subtelocentrics. In addition to the basic karyotype, all
the males specimens have cells ranging from zero to two B microchromosomes in mitotic metaphases. These chromosomes were not
observed in the female specimens. C-band analysis showed a distribution pattern of characteristic heterochromatin with interstitial
and centromeric blocks. However, the B chromosomes were faintly stained with C-banding and were not fluorescent with CMA3 staining. The meiotic studies showed the formation of bivalents in metaphase I and in pachytene under an optical microscope.
Through synaptonemal complex analysis with an electron microscope, the pachytene showed 25 bivalents completely paired and
a small bivalent corresponding to the B chromosomes. In the same preparation, one of the B chromosomes was observed in a univalent
form. On the basis of pairing behavior and morphology it is assumed that B chromosomes of M. sanctaefilomenae show homology between them and their evolutionary aspects are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
125.
Vasconcelos MA Royo VA Ferreira DS Crotti AE Andrade e Silva ML Carvalho JC Bastos JK Cunha WR 《Zeitschrift für Naturforschung. C, Journal of biosciences》2006,61(7-8):477-482
The aim of this work was to use in vivo models to evaluate the analgesic and anti-inflammatory activities of ursolic acid (UA) and oleanoic acid (OA), the major compounds isolated as an isomeric mixture from the crude methylene chloride extract of Miconia albicans aerial parts in an attempt to clarify if these compounds are responsible for the analgesic properties displayed by this plant. Ursolic acid inhibited abdominal constriction in a dose-dependent manner, and the result obtained at a content of 40 mg kg(-1) was similar to that produced by administration of acetylsalicylic acid at a content of 100 mg kg(-1). Both acids reduced the number of paw licks in the second phase of the formalin test, and both of them displayed a significant anti-inflammatory effect at a content of 40 mg kg(-1). It is noteworthy that the administration of the isolated mixture, containing 65% ursolic acid/35% oleanolic acid, did not display significant analgesic and anti-inflammatory activities. On the basis of the obtained results, considering that the mixture of UA and OA was poorly active, it is suggested that other compounds, rather than UA and OA, should be responsible for the evaluated activities in the crude extract, since the crude extract samples displayed good activities. 相似文献
126.
da Silveira VC Benezra H Luz JS Georg RC Oliveira CC Ferreira AM 《Journal of inorganic biochemistry》2011,105(12):1692-1703
Previous studies on copper(II) complexes with oxindole-Schiff base ligands have shown their potential antitumor activity towards different cells, inducing apoptosis through a preferential attack to DNA and/or mitochondria. Herein, we better characterize the interactions between some of these copper(II) complexes and DNA. Investigations on its binding ability to DNA were carried out by fluorescence measurements in competitive experiments with ethidium bromide, using plasmidial or calf-thymus DNA. These results indicated an efficient binding process similar to that observed with copper(II)-phenanthroline species, [Cu(o-phen)2]2+, with binding constants in the range 3 to 9 × 102 M− 1. DNA cleavage experiments in the presence and absence of distamycin, a recognized binder of DNA, indicated that this binding probably occurs at major or minor groove, leading to double-strand DNA cleavage, and being modulated by the imine ligand. Corroborating these data, discrete changes in EPR spectra of the studied complexes were observed in the presence of DNA, while more remarkable changes were observed in the presence of nucleotides (AMP, GMP, CMP or UMP). Additional evidence for preferential coordination of the copper centers to the bases guanine or cytosine was obtained from titrations of these complexes with each nucleotide, monitored by absorption spectral changes. Therefore, the obtained data point out to their action as groove binders to DNA bases, rather than as intercalators or covalent cross-linkers. Further investigations by SDS PAGE using 32P-ATP or 32P-oligonucleotides attested that no hydrolysis of phosphate linkage in DNA or RNA occurs, in the presence of such complexes, confirming their main oxidative mechanism of action. 相似文献
127.
Evidence is presented that although many proteins from the fronds of Lemna minor L. undergo enhanced degradation during osmotic stress, ribulose-1,5-bisphosphate carboxylase (RuBPCase) is not degraded. Instead RuBPCase is converted in a series of steps to a very high-molecular-weight form. The first step involves the induction of an oxidase system which after 24 h of stress converts RuBPCase to an acidic and catalytically inactive form. Subsequently, the oxidised RuBPCase protein is gradually polymerized to a number of very large aggregates (molecular weight of several million).The conversion of RuBPCase to a high-molecular-weight form appears to be correlated with (i) a reduction in the number of-SH residues and (ii) the susceptibility to in-vitro proteolysis. Indeed, the number of-SH groups per RuBPCase molecule decreases from 89 in the native enzyme to 54 and 22 in the oxidised and polymerized forms, respectively. On the other hand, the oxidised enzyme is more susceptible to in-vitro proteolysis than the native form. However, it is the polymerized form of RuBPCase which is particularly susceptible to in-vitro proteolysis.Western-blotting experiments and anti-ubiquitin antibodies were used to detect the presence of ubiquitin conjugates in extracts from osmotically stressed Lemna fronds. The possible involvement of ubiquitin in the formation of the aggregates is discussed.Abbreviations DTT
dithiothreitol
- EDTA
ethylenediamine-tetraacetic acid
- FPLC
fast protein liquid chromatography
- kDa
kilodaltons
- PAGE
polyacrylamide gel electrophoresis
- PMSF
phenylmethylsulphonyl fluoride
- RuBPCase
ribulose bisphosphate carboxylase
- SDS
sodium dodecyl sulphate
- Tris
2-amino-2-(hydroxymethyl)-1,3-propanediol 相似文献
128.
Ferreira LQ Avelar KE Vieira JM de Paula GR Colombo AP Domingues RM Ferreira MC 《Current microbiology》2007,54(5):348-353
The Bacteroides genus, the most prevalent anaerobic bacteria of the intestinal tract, carries a plethora of the mobile elements, such as
plasmids and conjugative and mobilizable transposons, which are probably responsible for the spreading of resistance genes.
Production of β-lactamases is the most important resistance mechanism including cephalosporin resistance to β-lactam agents
in species of the Bacteroides fragilis group. In our previous study, the cfxA gene was detected in B. distasonis species, which encodes a clinically significant broad-spectrum β-lactamase responsible for widespread resistance to cefoxitin
and other β-lactams. Such gene has been associated with the mobilizable transposon Tn4555. Therefore, the aim of this study was to detect the association between the cfxA gene and the presence of transposon Tn4555 in 53 Bacteroides strains isolated in Rio de Janeiro, Brazil, by PCR assay. The cfxA gene was detected in 11 strains and the Tn4555 in 15. The transposon sequence revealed similarities of approximately 96% with the B. vulgatus sequence which has been deposited in GenBank. Hybridization assay was performed in attempt to detect the cfxA gene in the transposon. It was possible to associate the cfxA gene in 11 of 15 strains that harbored Tn4555. Among such strains, 9 presented the cfxA gene as well as Tn4555, but in 2 strains the cfxA gene was not detected by PCR assay. Our results confirm the involvement of Tn4555 in spreading the cfxA gene in Bacteroides species. 相似文献
129.
PAULO R. GUIMARES UMBERTO KUBOTA BRUNO ZACARIAS GOMES RAFAEL LUÍS FONSECA CLUDIA BOTTCHER MAURO GALETTI 《Austral ecology》2006,31(1):95-98
Abstract: Red‐rumped agoutis (Dasyprocta leporina) are important seed dispersers/predators of Neotropical large‐seeded plants. Several species of seeds cached by agoutis have an edible reward, in contrast to temperate rodent‐dispersed diaspores. The quick meal hypothesis states that the presence of a reward such as edible pulp will enhance the efficiency of rodents as seed disperses by satiating the animal and, consequently, reducing seed predation and enhancing hoarding. In this study, this hypothesis was tested using as the reference system the pulp and seeds of Hymenaea courbaril. Seeds with and without pulp were offered to agoutis and the behaviour of each individual was recorded. Since the probability of predation and hoarding were complementary, we used the probability of predation. The proportion of agoutis that preyed on at least one seed was similar for seeds with (42.8% of individuals) and without (40.0% of individuals) pulp. In agoutis that preyed upon at least one seed, the probability that they killed a seed did not differ between seeds with (0.17 ± 0.03) and without (0.20 ± 0.08) pulp. Hence, these results do not support the ‘quick meal hypothesis’. 相似文献
130.
De Sousa LP Brasil BS Silva BM Freitas MH Nogueira SV Ferreira PC Kroon EG Bonjardim CA 《Biochemical and biophysical research communications》2005,329(1):237-245
In this study, we showed that plasminogen (Plg) and plasmin (Pla) bind to lysine-binding sites on cell surface and trigger a signaling pathway that activates the mitogen-activated protein kinase (MAPK) MEK and ERK1/2, which in turn leads to the expression of the primary response genes c-fos and early growth response gene egr-1. Our data show that the Plg/Pla-stimulated steady-state mRNA levels of both genes reached a maximum by 30 min and then returned to basal levels by 1h. The gene induction was sensitive to both pharmacological and genetic inhibition of MEK. Leupeptin, a serine protease inhibitor, suppressed Pla but not Plg-induced c-fos and egr-1 expression, emphasizing the role played by the serine protease activity associated with Pla. Pre-incubation with cholera toxin completely blocked the Plg/Pla-induced gene expression, suggesting that another signaling pathway, which recruits G protein-coupled receptors, may also be involved. Furthermore, Plg/Pla also stimulated AP-1 and EGR-1 DNA-binding activities, which were abrogated by pharmacological inhibition of MEK. Altogether, these results suggest that Plg/Pla stimulates c-fos and egr-1 expression via activation of the MEK/ERK pathway. 相似文献