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Sergio Schenkman Pedro S. Araujo Ruud Dukman Frank H. Quina Hernan Chaimovich 《生物化学与生物物理学报:生物膜》1981,649(3):633-641
Small unilamellar vesicles of egg phosphatidylcholine (PC) or dimyristoylphosphatidylcholine, mixed with small unilamellar vesicles labelled with 2-(10-(1-pyrene)decanoyl)phosphatidylcholine, exhibit a constant average size and excimer to monomer (E/M) ratio for several hours when incubated at pH 3.6 at a temperature higher than the phase transition temperature (Tc) of the lipids. Addition of bovine serum albumin to this system produces a transient turbidity increase, a fast decrease in the E/M ratio, a partial loss of vesicle-entrapped [14C]sucrose and a measurable leak-in of externally added sucrose. Sepharose 4B filtration of the system demonstrates that the E/M ratio decrease is strictly paralleled by the formation of liposomes which exhibit a low E/M ratio and a hydrodynamic radius larger than that of small unilamellar vesicles. These data demonstrate that the E/M ratio decrease can be unequivocally ascribed to a vesicle-vesicle fusion process induced by serum albumin. The rate of serum-albumin induced fusion of small unilamellar vesicles is: (a) maximal at a stoichiometric ratio of approx. 2 albumins per vesicle: (b) sensitive to the nature of the lipid and; (c) not altered when human serum albumin replaces bovine serum albumin. The rate of albumin-induced fusion of dimyristoylphosphatidylcholine small unilamellar vesicles is higher below the Tc of the lipid and increases with temperature above the Tc. The formation of protein-bound aggregates with defined stoichiometries and a high local vesicle concentration, as well as changes in the local degree of hydration, are proposed to be the driving forces for the protein-induced vesicle fusion in this system. 相似文献
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Gustavo de Rezende Corrêa Karinne Cristinne da Silva Cunha Aline Araujo dos Santos Elizabeth Giestal de Araujo 《Neurochemical research》2010,35(9):1343-1352
It was already shown that ouabain treatment can stimulate PKC isoenzymes leading to the activation of intracellular pathways
involved in cell survival, growth and proliferation. We have previously demonstrated that ouabain or PMA treatment increases
retinal ganglion cell survival, an effect mediated by PKC activation. The aim of this work was to investigate the role of
EGF receptors in the ouabain effect and also to study which PKC isoform is activated by treatment with ouabain and PMA. Our
results show that 2.5 μM tyrphostin, 1.0 μM PP1, 4.0 μM U73122, 1.0 μM JNK inhibitor V and 2.0 μM rottlerin blocked the ouabain
effect indicating an involvement of receptors for EGF, Src, PLC, JNK and PKC δ respectively. The effect of PMA was only abolished
when cultures were treated with rottlerin or with the JNK inhibitor suggesting the involvement of PKC δ and JNK. These results
indicate that PKC δ could be a key regulator of retinal ganglion cell survival. 相似文献
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The mechanical properties of the respiratory system are important determinants of its function and can be severely compromised in disease. The assessment of respiratory system mechanical properties is thus essential in the management of some disorders as well as in the evaluation of respiratory system adaptations in response to an acute or chronic process. Most often, lungs and chest wall are treated as a linear dynamic system that can be expressed with differential equations, allowing determination of the system’s parameters, which will reflect the mechanical properties. However, different models that encompass nonlinear characteristics and also multicompartments have been used in several approaches and most specifically in mechanically ventilated patients with acute lung injury. Additionally, the input impedance over a range of frequencies can be assessed with a convenient excitation method allowing the identification of the mechanical characteristics of the central and peripheral airways as well as lung periphery impedance. With the evolution of computational power, the airway pressure and flow can be recorded and stored for hours, and hence continuous monitoring of the respiratory system mechanical properties is already available in some mechanical ventilators. This review aims to describe some of the most frequently used models for the assessment of the respiratory system mechanical properties in both time and frequency domain. 相似文献
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Karl J. Reinhard Adauto Araújo Johnica J. Morrow 《The Korean journal of parasitology》2016,54(5):591-603
Investigations of Enterobius sp. infection in prehistory have produced a body of data that can be used to evaluate the geographic distribution of infection through time in the Americas. Regional variations in prevalence are evident. In North America, 119 pinworm positive samples were found in 1,112 samples from 28 sites with a prevalence of 10.7%. Almost all of the positive samples came from agricultural sites. From Brazil, 0 pinworm positive samples were found in 325 samples from 7 sites. For the Andes region, 22 pinworm positive samples were found in 411 samples from 26 sites for a prevalence of 5.3%. Detailed analyses of these data defined several trends. First, preagricultural sites less frequently show evidence of infection compared to agricultural populations. This is especially clear in the data from North America, but is also evident in the data from South America. Second, there is an apparent relationship between the commonality of pinworms in coprolites and the manner of constructing villages. These analyses show that ancient parasitism has substantial value in documenting the range of human behaviors that influence parasitic infections. 相似文献
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The effect of terrestrial effluents on the incidence of Aeromonas spp. in coastal waters 总被引:2,自引:0,他引:2
The numbers of Aeromonas species were monitored for one year at 18 stations on the Barcelona coast. Their concentrations exceed those of faecal coliforms and faecal streptococci in all samples, both on the shoreline and at 500 m from the coast. The mean values of the three bacterial counts reflected the proximity of the terrestrial effluents. There was a positive correlation between aeromonads and faecal indicators on the shoreline but not at 500 m offshore. This reflected their common origin and different survival rates in seawater. When sterile sea water was inoculated with A. hydrophila ATCC 7966, the numbers decreased initially by three orders of magnitude before they began to multiply. The final count was related to the concentration of organic matter in the water. 相似文献
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Fiddler crabs (Uca spp., Decapoda: Ocypodidae) are commonly found forming large aggregations in intertidal zones, where they perform rhythmic waving displays with their greatly enlarged claws. While performing these displays, fiddler crabs often synchronize their behavior with neighboring males, forming the only known synchronized visual courtship displays involving reflected light and moving body parts. Despite being one of the most conspicuous aspects of fiddler crab behavior, little is known about the mechanisms underlying synchronization of male displays. In this study we develop a spatially explicit model of fiddler crab waving displays using coupled logistic map equations. We explored two alternative models in which males either direct their attention at random angles or preferentially toward neighbors. Our results indicate that synchronization is possible over a fairly large region of parameter space. Moreover, our model was capable of generating local synchronization neighborhoods, as commonly observed in fiddler crabs under natural conditions. 相似文献
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