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991.
Traditional methods for the enumeration of airborne fungi are slow, tedious, and rather imprecise. In this study, the possibility of using flow cytometry (FCM) for the assessment of exposure to the fungus aerosol was evaluated. Epifluorescence microscopy direct counting was adopted as the standard for comparison. Setting up of the method was achieved with pure suspensions of Aspergillus fumigatus and Penicillium brevicompactum conidia at different concentrations, and then analyses were extended to field samples collected by an impinger device. Detection and quantification of airborne fungi by FCM was obtained combining light scatter and propidium iodide red fluorescence parameters. Since inorganic debris are unstainable with propidium iodide, the biotic component could be recognized, whereas the preanalysis of pure conidia suspensions of some species allowed us to select the area corresponding to the expected fungal population. A close agreement between FCM and epifluorescence microscopy counts was found. Moreover, data processing showed that FCM can be considered more precise and reliable at any of the tested concentrations. 相似文献
992.
993.
The spores and conidia of most fungi have very thick and resistant cell walls that severely impede the staining with fluorescent dyes to allow epifluorescence microscopy to be employed for their direct detection and quantification in natural habitats. In this study, oxidation by sodium hypochlorite and microwave irradiation (MWI) were used to enhance the staining of Aspergillus fumigatus and Penicillium brevicompactum conidia with six fluorescent dyes. Sodium hypochlorite resulted in high percentages of stained conidia (up to 98.8% with 4',6-diamidino-2-phenylindole [DAPI]), but had to be removed prior to staining with consequent heavy conidia losses. By contrast, MWI gave very high percentages, while its enhancement of fluorescence intensity facilitated observation by epifluorescence microscopy. 相似文献
994.
Rossi V Picco R Vacca M D'Esposito M D'Urso M Galli T Filippini F 《Biology of the cell / under the auspices of the European Cell Biology Organization》2004,96(4):251-256
In eukaryotes, interactions among the alpha-helical coiled-coil domains (CCDs) of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) play a pivotal role in mediating the fusion among vesicles and target membranes. Surface residues of such CCDs are major candidates to regulate the specificity of membrane fusion, as they may alter local charge at the interaction layers and surface of the fusion complex, possibly modulating its formation and/or the binding of non-SNARE regulatory factors. Based on alternate patterns in surface residues, we have identified two motifs which group vesicular SNAREs in two novel subfamilies: RG-SNAREs and RD-SNAREs. The RG-SNARE CCD is common to all members of the widely conserved family of long VAMPs or longins and to yeast and non-neuronal VAMPs, possibly mediating "basic" fusion mechanisms; instead, only synaptobrevins from Bilateria share an RD-SNARE CCD, which is likely to mediate interactions to specific, yet unknown, regulatory factors and/or be the landmark of rapid fusion reactions like that mediating the release of neurotransmitters. 相似文献
995.
996.
Commercial crab populations off the Kamchatka coasts are infested to a considerable degree by the rhizocephalan parasite Briarosaccus callosus: of 769 Lithodes aequispina males examined, 43 (5.7%) were parasitized. Infestations result in the feminization of the crabs, a significant decrease in the cheliped length, and a significant decrease in the carapace length and width. We suggest that commercial selection of healthy males, and the returning of unsuitable crabs, including infested ones, back into the sea, results in an increase of the proportion of infested crabs in the population, their elimination from reproduction, and, eventually, the gradual degradation of a whole population. To minimize as far as possible the negative effects of commercial crab harvesting, all infested crab specimens caught must be destroyed, either aboard or elsewhere, instead of throwing them back into the sea. 相似文献
997.
Barth H Cerino R Arcuri M Hoffmann M Schürmann P Adah MI Gissler B Zhao X Ghisetti V Lavezzo B Blum HE von Weizsäcker F Vitelli A Scarselli E Baumert TF 《Journal of virology》2005,79(9):5774-5785
Hepatitis C virus (HCV) is a major cause of chronic hepatitis worldwide. The study of early steps during HCV infection has been hampered by the lack of suitable in vitro or in vivo models. Primary Tupaia hepatocytes (PTH) have been shown to be susceptible to HCV infection in vitro and in vivo. Human scavenger receptor class B type I (SR-BI) represents an HCV receptor candidate mediating the cellular binding of E2 glycoprotein to HepG2 hepatoma cells. However, the function of SR-BI for viral infection of hepatocytes is unknown. In this study, we used PTH to assess the functional role of SR-BI as a putative HCV receptor. Sequence analysis of cloned tupaia SR-BI revealed a high homology between tupaia and human SR-BI. Transfection of CHO cells with human or tupaia SR-BI but not mouse SR-BI cDNA resulted in cellular E2 binding, suggesting that E2-binding domains between human and tupaia SR-BI are highly conserved. Preincubation of PTH with anti-SR-BI antibodies resulted in marked inhibition of E2 or HCV-like particle binding. However, anti-SR-BI antibodies were not able to block HCV infection of PTH. In conclusion, our results demonstrate that SR-BI represents an important cell surface molecule for the binding of the HCV envelope to hepatocytes and suggest that other or additional cell surface molecules are required for the initiation of HCV infection. Furthermore, the structural and functional similarities between human and tupaia SR-BI indicate that PTH represent a useful model system to characterize the molecular interaction of the HCV envelope and SR-BI on primary hepatocytes. 相似文献
998.
999.
Two membrane-bound, ascorbate-dependent b-type cytochromes were identified in etiolated bean (Phaseolus vulgaris L.) hypocotyls. Following solubilization of microsomal membranes and anion-exchange chromatography at pH 8.0, two major cytochrome peaks (P-I and P-II) were separated. Both cytochromes were reduced by ascorbate and re-oxidized by monodehydroascorbate, but P-I reduction by ascorbate was higher and saturated at far lower concentrations of ascorbate with respect to P-II. The -band was symmetrically centered at 561 nm in P-I, but it was asymmetric in P-II with a maximum at 562 nm and shoulder at 557 nm. Ascorbate reduction of P-II, but not P-I, was inhibited by diethyl pyrocarbonate. Reduced P-II but not P-I was readily oxidized by certain ferric chelates, including FeEDTA and Fe-nitrilotriacetic acid. Purified P-I, associated with the plasma membrane, showed up as a 63-kDa glycosylated protein during sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) and behaved as a monomer of about 70 kDa during size-exclusion chromatography. P-I identified with a previously purified ascorbate-dependent b-type cytochrome of bean hypocotyl plasma membranes [P. Trost et al. (2000) Biochim Biophys Acta 1468:1–5]. Partially purified P-II, on the other hand, correlated with a heme-protein of 27 kDa in SDS–PAGE gels, was dimeric (60 kDa) during size-exclusion chromatography, and was associated with the tonoplast marker V-ATPase in sucrose gradients. The sequence of a peptide of 11 residues obtained by tryptic digestion of P-II was found to be identical to a segment of a putative cytochrome b561 of Zea mays and highly conserved in other related plant sequences, including that of Arabidopsis thaliana cytochrome b561-1 (CAA18169). The biochemical features fully support the assignment of P-II cytochrome to the family of cytochrome b561, ascorbate-dependent (CYBASC) cytochromes, which also includes cytochrome b561 of animal chromaffin granules. The presence of a cytochrome reducing ferric chelates on the tonoplast is consistent with the role of plant vacuoles in iron homeostasis. 相似文献
1000.
De Antoni A Pearson CG Cimini D Canman JC Sala V Nezi L Mapelli M Sironi L Faretta M Salmon ED Musacchio A 《Current biology : CB》2005,15(3):214-225
Background: The spindle assembly checkpoint (SAC) imparts fidelity to chromosome segregation by delaying anaphase until all sister chromatid pairs have become bipolarly attached. Mad2 is a component of the SAC effector complex that sequesters Cdc20 to halt anaphase. In prometaphase, Mad2 is recruited to kinetochores with the help of Mad1, and it is activated to bind Cdc20. These events are linked to the existence of two distinct conformers of Mad2: a closed conformer bound to its kinetochore receptor Mad1 or its target in the checkpoint Cdc20 and an open conformer unbound to these ligands. Results: We investigated the mechanism of Mad2 recruitment to the kinetochore during checkpoint activation and subsequent transfer to Cdc20. We report that a closed conformer of Mad2 constitutively bound to Mad1, rather than Mad1 itself, is the kinetochore receptor for cytosolic open Mad2 and show that the interaction of open and closed Mad2 conformers is essential to sustain the SAC. Conclusions: We propose that closed Mad2 bound to Mad1 represents a template for the conversion of open Mad2 into closed Mad2 bound to Cdc20. This simple model, which we have named the "Mad2 template" model, predicts a mechanism for cytosolic propagation of the spindle checkpoint signal away from kinetochores. 相似文献