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71.
Hasna Ahyayauch Jesús Sot M.?Isabel Collado Nerea Huarte José Requejo-Isidro Alicia Alonso Félix?M. Go?i 《Biophysical journal》2015,108(7):1672-1682
Diacylglycerol (DAG)-induced activation of phosphatidylinositol-phospholipase C (PI-PLC) was studied with vesicles containing PI, either pure or in mixtures with dimyristoyl phosphatidylcholine, distearoyl phosphatidylcholine, sphingomyelin, or galactosylceramide, used as substrates. At 22°C, DAG at 33 mol % increased PI-PLC activity in all of the mixtures, but not in pure PI bilayers. DAG also caused an overall decrease in diphenylhexatriene fluorescence polarization (decreased molecular order) in all samples, and increased overall enzyme binding. Confocal fluorescence microscopy of giant unilamellar vesicles of all of the compositions under study, with or without DAG, and quantitative evaluation of the phase behavior using Laurdan generalized polarization, and of enzyme binding to the various domains, indicated that DAG activates PI-PLC whenever it can generate fluid domains to which the enzyme can bind with high affinity. In the specific case of PI/dimyristoyl phosphatidylcholine bilayers at 22°C, DAG induced/increased enzyme binding and activation, but no microscopic domain separation was observed. The presence of DAG-generated nanodomains, or of DAG-induced lipid packing defects, is proposed instead for this system. In PI/galactosylceramide mixtures, DAG may exert its activation role through the generation of small vesicles, which PI-PLC is known to degrade at higher rates. In general, our results indicate that global measurements obtained using fluorescent probes in vesicle suspensions in a cuvette are not sufficient to elucidate DAG effects that take place at the domain level. The above data reinforce the idea that DAG functions as an important physical agent in regulating membrane and cell properties. 相似文献
72.
Noemi Jiménez-Rojo Jesús Sot Ana R. Viguera M. Isabel Collado Alejandro Torrecillas J.C. Gómez-Fernández Félix M. Goñi Alicia Alonso 《Biophysical journal》2014
Sphingosine [(2S, 3R, 4E)-2-amino-4-octadecen-1, 3-diol] is the most common sphingoid long chain base in sphingolipids. It is the precursor of important cell signaling molecules, such as ceramides. In the last decade it has been shown to act itself as a potent metabolic signaling molecule, by activating a number of protein kinases. Moreover, sphingosine has been found to permeabilize phospholipid bilayers, giving rise to vesicle leakage. The present contribution intends to analyze the mechanism by which this bioactive lipid induces vesicle contents release, and the effect of negatively charged bilayers in the release process. Fluorescence lifetime measurements and confocal fluorescence microscopy have been applied to observe the mechanism of sphingosine efflux from large and giant unilamellar vesicles; a graded-release efflux has been detected. Additionally, stopped-flow measurements have shown that the rate of vesicle permeabilization increases with sphingosine concentration. Because at the physiological pH sphingosine has a net positive charge, its interaction with negatively charged phospholipids (e.g., bilayers containing phosphatidic acid together with sphingomyelins, phosphatidylethanolamine, and cholesterol) gives rise to a release of vesicular contents, faster than with electrically neutral bilayers. Furthermore, phosphorous 31-NMR and x-ray data show the capacity of sphingosine to facilitate the formation of nonbilayer (cubic phase) intermediates in negatively charged membranes. The data might explain the pathogenesis of Niemann-Pick type C1 disease. 相似文献
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74.
A method for direct selection of acid-resistant Bifidobacterium strains was developed by prolonged exposure of human feces to homologous lethal stress conditions. The recovered strains were intrinsically resistant to acidic gastric conditions (pH 2.0) and also showed good tolerance to high concentrations of bile salts and NaCl. Bifidobacterium breve and Bifidobacterium adolescentis were, respectively, the infant- and adult-type bifidobacterial species showing the highest ability to develop an acid-tolerant phenotype. Therefore, this procedure could be applicable to the direct selection of Bifidobacterium strains with improved stability in adverse environments and, probably, contribute to expand the spectra of probiotic species of human origin currently marketed. 相似文献
75.
Enterobacter sakazakii is an opportunistic pathogen and an occasional contaminant in powdered infant formula. Interaction between specific probiotics and E. sakazakii may reduce the risk of infection. The aim of this study was to characterize in vitro the ability of probiotics (alone and in combinations) to inhibit, compete with and displace the adhesion of E. sakazakii to immobilized human mucus and to assess their capacity to aggregate with pathogen. Specific probiotic strains have proved to aggregate E. sakazakii cells and, through competitive exclusion, inhibition and displacement of the adhered pathogen, were able to inhibit E. sakazakii action on intestinal mucus. The ability to inhibit and to displace adhered pathogen depended on both the probiotic and the pathogen, suggesting that several complementary mechanisms are involved in the processes. We suggest that the selection of specific probiotic strains and their combinations may be a useful means of counteracting E. sakazakii contamination in infant formula and thus to reduce the risk of emerging infection. This approach may also allow the development of new probiotic combinations to counteract the risks associated with other pathogens by improving the intestinal barrier against pathogens. 相似文献
76.
Sexual differentiation and lateralization of neurone number in a discrete forebrain nucleus (SDApc) related to masculine vocal emission, occur contemporaneously in postnatal (P0–P15) gerbils. Stereological estimates of cell proliferation and death during SDApc organization were made by BrdU labelling and pyknosis, respectively. Results confirmed that rates of apoptosis were greater in females and lateralized in males. Immunoreactive BrdU cells, located in the SDApc at P0–P6, with low levels at P15, were not numerically different between the sexes. Only at one age, P0, in males, was a left‐right difference seen in BrdU‐immunoreactive cell numbers. Microglia, identified by isolectin immunostaining, were numerically similar to BrdU cells. We suggest that apoptosis, rather than neurogenesis, differentiates and lateralizes SDApc organization, and proliferating cells are microglia, phagocytosing debris. © 2001 John Wiley & Sons, Inc. J Neurobiol 47: 150–158, 2001 相似文献
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78.
Background
Microbial communities are influenced by environmental factors including host genetics. We investigated the relationship between host bitter taste receptor genotype hTAS2R38 and oral microbiota, together with the influence of geographical location.Methods
hTAS2R38 polymorphisms and 16S bacterial gene sequencing from oral samples were analyzed from a total of 45 healthy volunteers from different geographical locations.Results
Genetic variation in the bitter taste receptor TAS2R38 reflected in the microbial composition of oral mucosa in Finnish and Spanish subjects. Multivariate analysis showed significant differences in the microbial composition between country and also dependent on taste genotype. Oral microbiota was shown to be more stable to the geographical location impact among AVI-homozygotes than PAV-homozygotes or heterozygotes (PAV/AVI).Conclusion
Geographical location and genetic variation in the hTAS2R38 taste receptor impact oral mucosa microbial composition. These findings provide an advance in the knowledge regarding the interactions between taste receptor genes and oral microbiota. This study suggests the role of host-microbiota interactions on the food taste perception in food choices, nutrition, and eating behavior.79.
Summary Grafting regions of the blastodisc of the chick, labeled with H3-thymidine at Stages 5 and 6 ofHamilton andHamburger, is a very useful technique for following the morphogenetic movements of the grafted material. Areas (E-M) of the blastodisc of 2.75 by 0.55 mm, grafted in the homologous region of an embryo, participate in its morphogenetic movements. The labeled reversed cardiac area can sometimes be incorporated into the host, and a tubular heart can develop which includes some of the graft tissue, Figs. 3, 4, 5, and 6. The morphogenetic movements shaping the anterior intesinal portal and early foregut can occur despite the reversal of a large rectangle of the endomesoderm, Fig. 6. The coelomic epithelium lining the operated side, a part of the myoepicardium of this side, as well as the endoderm of the ventral portion of the foregut, and, more caudally, half of the anterior intestinal portal are derived from the graft as shown by strong radioactive labeling of the cells, Figs. 3, 4 and 6. The morphogenetic movements of the graft endoderm and mesoderm are independent, the pre-heart mesoderm moving in a cranial direction, while the endoderm extends caudally, Figs. 3 and 4.This study raises an interesting question: Can the original cephalic preconal cardiogenic mesoderm regulate to form sinoatrial tissue (and vice versa) ? The evidence obtained in the present investigation is not extensive enough to warrant conclusions as to the important question of regulation; for this a considerable number of operated embryos is required in which a recognizable normal heart has developed (up to Stage 12–13).This research was supported by a grant from the Association for the Aid of Crippled Children, New York. 相似文献
80.
We sampled 30 lakes in Costa Rica in the wet season (July–August) of 1991 for phytoplankton (with integrated and whole water samples), and 17 for zooplankton (with net tows). Taxa of plankton and community richness were poorly related to geography, morphology, chemistry, and other biota. Neither the zooplankton nor the phytoplankton appeared to influence the composition of the other, and neither were apparently influenced by the presence of fish.Phytoplankton richness reflected primarily sampling method, but also tended to decrease with elevation and with Secchi disk depth, and tended to increase with pH and alkalinity. Chlorophytes were the most abundant division in 14 lakes; these lakes tended to be unstratified, turbid, and located at higher elevation. Diatoms were common in 4 of the 7 lakes with elevated silica (over 30 ppm). Each lake showed at least a 3 : 1 dominance by copepods, cladocera, or insect larvae. Copepods dominated 7 of the 17 lakes, most of which were shallow, turbid, and had low alkalinity. Cladocera dominated 7 lakes that were typically deeper and located at low-to mid-elevations. Insect larvae dominated two small, turbid lakes. 相似文献