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排序方式: 共有147条查询结果,搜索用时 62 毫秒
1.
W. J. Middelhoven Mieke C. Hoogkamer-Te Niet W. T. A. M. De Laat C. Weijers C. J. E. A. Bulder 《Antonie van Leeuwenhoek》1986,52(6):525-535
The maximum growth rate of Trichosporon cutaneum CBS 8111 in chemostat cultures was 0.185 h-1 on ethylamine and 0.21 h-1 on butylamine, that of Candida famata CBS 8109 was 0.32 h-1 on putrescine.The amine oxidation pattern of the ascomycetous strains studied, viz. Candida famata CBS 8109, Stephanoascus ciferrii CBS 4856 and Trichosporon adeninovorans CBS 8244 was independent of the amine that had been used as the growth substrate. It resembled that of benzylamine/putrescine oxidase found in other ascomycetous yeasts. However, differences in pH optimum and substrate specificity were observed between the amine-oxidizing systems of these three species.The amine oxidation pattern of cell-free extracts of Trichosporon cutaneum CBS 8111 varied with the amine that was used as growth substrate. The enzyme system produced by Cryptococcus laurentii CBS 7140 failed to oxidize isobutylamine and benzylamine, and showed a high pH optimum.The synthesis of amine oxidase in the four yeast strains studied was not repressed by ammonium chloride and was weakly repressed by glucose but was strongly repressed if both compounds were present in the growth medium. 相似文献
2.
Wouter J. Middelhoven Heleen de Kievit André L. Biesbroek 《Antonie van Leeuwenhoek》1985,51(3):289-301
Yeast strains utilizing uric acid, adenine, monoamines or diamines as sole source of carbon and energy were isolated from
several soil samples by the enrichment culture method. The most common species wasTrichosporon cutaneum. Strains ofCandida catenulata, C. famata, C. parapsilosis, C. rugosa, Cryptococcus laurentii, Stephanoascus ciferrii andTr. adeninovorans were also isolated. All strains utilizing uric acid as sole carbon source utilized some primaryn-alkyl-l-amines hydroxyamines or diamines as well. The ascomycetous yeast strains showing these characteristics all belonged
to species known to assimilate hydrocarbons. Type strains of hydrocarbon-positive yeast species which were not found in the
enrichment cultures generally assimilated putrescine, some type strains also butylamine or pentylamine, but none assimilated
uric acid. Methanol-positive species were not isolated. Type strains of methanol-positive and of hydrocarbon-negative species
did not assimilate uric acid, butylamine or putrescine. Assimilation of putrescine as sole source of carbon and energy may
be a valuable diagnostic criterion in yeast taxonomy. 相似文献
3.
Wouter J. Middelhoven Alex Coenen Bart Kraakman Maarten D. Sollewijn Gelpke 《Antonie van Leeuwenhoek》1992,62(3):181-187
The imperfect ascomycetous yeastsCandida parapsilosis andArxula adeninivorans degraded 3-hydroxybenzoic acid via gentisate which was the cleavage substrate. 4-Hydroxybenzoic acid was metabolized via protocatechuate. No cleavage enzyme for the latter was detected. In stead of this NADH- and NADPH-dependent monooxygenases were present. In cells grown at the expense of hydroquinone and 4-hydroxygenzoic acid, enzymes of the hydroxyhydroquinone variant of the 3-oxoadipate pathway were demonstrated, which also took part in the degradation of 2,4-dihydroxybenzoic acid byC. parapsilosis.Abbreviations HHQ
Hydroxyhydroquinone (1,2,4-trihydroxybenzene)
- GSH
reduced Glutathione 相似文献
4.
Isolation and characterization of plasma membrane-associated cortical granules from sea urchin eggs 总被引:9,自引:6,他引:3 下载免费PDF全文
Cortical granules, which are specialized secretory organelles found in ova of many organisms, have been isolated from the eggs of the sea urchins Arbacia punctulata and Strongylocentrtus pupuratus by a simple, rapid procedure. Electron micropscope examination of cortical granules prepared by this procedure reveals that they are tightly attached to large segments of the plasma membrane and its associated vitelline layer. Further evidence that he cortical granules were associated with these cell surface layers was obtained by (125)I-labeling techniques. The cortical granule preparations were found to be rich in proteoesterase, which was purified 32-fold over that detected in a crude homogenate. Similarly, the specific radioactivity of a (125)I-labeled, surface glycoprotein was increased 40-fold. These facts, coupled with electron microscope observations, indicate the isolation procedure yields a preparation in which both the cortical granules and the plasma membrane-vitelline layer are purified to the same extent. Gel electrophoresis of the membrane-associated cortical granule preparation reveals the presence of at least eight polypeptides. The major polypeptide, which is a glycotprotein of apparent mol wt of 100,000, contains most of the radioactivity introduced by (125)I-labeling of the intact eggs. Lysis of the cortical granules is observed under hypotonic conditions, or under isotonic conditions if Ca(2+) ion is present. When lysis is under isotonic conditions is induced by addition of Ca(2+) ion, the electron-dense contents of the granules remain insoluble. In contrast, hypotonic lysis results in release of the contents of the granule in a soluble form. However, in both cases the (125)I-labeled glycoprotein remains insoluble, presumably because it is a component of either the plasma membrane or the vitelline layer. All these findings indicate that, using this purified preparation, it should be possible to carry out in vitro studies to better define some of the initial, surface-related events observed in vivo upon fertilization. 相似文献
5.
Aggregation-dependent turnover of flagellar adhesion molecules in chlamydomonas gametes 总被引:8,自引:7,他引:1 下载免费PDF全文
Previous studies on flagellar adhesion in chlamydomonas (Snell, W. and S. Roseman. 1979. J. Biol. Chem. 254:10820-10829.) have shown that as gametes adhere to flagella isolated from gametes of the opposite mating type, the adhsiveness of the added flagella but not of the gametes is lost. The studies reported here show that the addition of protein synthesis inhibitors (cycloheximide [CH] or anisomycin) to the medium of such cell- flagella mixtures causes the cells to lose their adhesiveness. This loss, however, occurs only after the cells have interacted with 4-8 flagella/cell and does not occur if the cells are kept in CH (7 h) without aggregating. The availability of an impotent (imp) mating type plus (MT(+)) mutant (provided by U.W. Goodenough), which adheres but is unable to undergo the fusion that normally follows adhesion, made it possible to determine whether a similar loss of adhesiveness occurs in mixtures of matting type minus (mt(-)) and imp mt(+) gametes. In the absence of inhibitor, mt(-) and imp mt(+) gametes adhered to each other (without fusing) for several hours; however, in the presence of CH or anisomycin, the gametes began to de-adhere 35 min after mixing, and, by 90 min, 100 percent of the cells were single again. This effect was reversible, and the rapid turnover of cells were single again. This effect was reversible, and the rapid turnover of molecules involved in adhesion occurred only during adhesion inasmuch as gametes pretreated for 4 h with CH were able to aggregate in CH for the same length of time as nonpretreated cells aggregated in CH. By the addition of CH at various times after the mt(-) and imp mt(+) gametes were mixed, measurements were made of the “pool size” of the molecules involved in adhesion. The pool reached a minimum after 25 min of aggregation, rapidly increased for the next 25 min, and then leveled off at the premixing level. These results suggest that flagellar adhesion in chlamydomonas causes modification of surface molecules (receptors, ligands), which brings about their inactivation and stimulates their replacement. 相似文献
6.
7.
Diederik WJ Dippel Eric J van Breda H Bart van der Worp H Maarten A van Gemert Ron J Meijer L Jaap Kappelle Peter J Koudstaal 《BMC cardiovascular disorders》2003,3(1):1-8
Background
Body temperature is a strong predictor of outcome in acute stroke. In a previous randomized trial we observed that treatment with high-dose acetaminophen (paracetamol) led to a reduction of body temperature in patients with acute ischemic stroke, even when they had no fever. The purpose of the present trial was to study whether this effect of acetaminophen could be reproduced, and whether ibuprofen would have a similar, or even stronger effect.Methods
Seventy-five patients with acute ischemic stroke confined to the anterior circulation were randomized to treatment with either 1000 mg acetaminophen, 400 mg ibuprofen, or placebo, given 6 times daily during 5 days. Treatment was started within 24 hours from the onset of symptoms. Body temperatures were measured at 2-hour intervals during the first 24 hours, and at 6-hour intervals thereafter.Results
No difference in body temperature at 24 hours was observed between the three treatment groups. However, treatment with high-dose acetaminophen resulted in a 0.3°C larger reduction in body temperature from baseline than placebo treatment (95% CI: 0.0 to 0.6 °C). Acetaminophen had no significant effect on body temperature during the subsequent four days compared to placebo, and ibuprofen had no statistically significant effect on body temperature during the entire study period.Conclusions
Treatment with a daily dose of 6000 mg acetaminophen results in a small, but potentially worthwhile decrease in body temperature after acute ischemic stroke, even in normothermic and subfebrile patients. Further large randomized clinical trials are needed to study whether early reduction of body temperature leads to improved outcome. 相似文献8.
Partial 25S rRNA sequencing of Cerinosterus cyanescens showed it to be a close relative of Microstroma juglandis, a member of the basidiomycetous order Microstromatales. It is unrelated to the generic type species, C. luteoalba, which is a member of the order Dacrymycetales. The clinical occurrence of C. cyanescens is possibly explained by its thermotolerance and lipolytic activity. The species' nutritional profile is established. Growth on n-hexadecane is rapid; it grows well on typical plant constituents like gallic, tannic, vanillic, quinic and p-coumaric acids, but not on 3-hydroxybenzoic acid, phenol and hydroquinone. The failure to assimilate D-galactose, L-sorbose and ethylamine, the presence of urease and sensitivity to cycloheximide are diagnostic for the species. 相似文献
9.
19F Nuclear Magnetic Resonance as a Tool To Investigate Microbial Degradation of Fluorophenols to Fluorocatechols and Fluoromuconates 总被引:1,自引:0,他引:1 下载免费PDF全文
Marelle G. Boersma Tatiana Y. Dinarieva Wouter J. Middelhoven Willem J. H. van Berkel Joel Doran Jacques Vervoort Ivonne M. C. M. Rietjens 《Applied microbiology》1998,64(4):1256-1263
A method was developed to study the biodegradation and oxidative biodehalogenation of fluorinated phenols by 19F nuclear magnetic resonance (NMR). Characterization of the 19F NMR spectra of metabolite profiles of a series of fluorophenols, converted by purified phenol hydroxylase, catechol 1,2-dioxygenase, and/or by the yeast-like fungus Exophiala jeanselmei, provided possibilities for identification of the 19F NMR chemical shift values of fluorinated catechol and muconate metabolites. As an example, the 19F NMR method thus defined was used to characterize the time-dependent metabolite profiles of various halophenols in either cell extracts or in incubations with whole cells of E. jeanselmei. The results obtained for these two systems are similar, except for the level of muconates observed. Altogether, the results of the present study describe a 19F NMR method which provides an efficient tool for elucidating the metabolic pathways for conversion of fluorine-containing phenols by microorganisms, with special emphasis on possibilities for biodehalogenation and detection of the type of fluorocatechols and fluoromuconates involved. In addition, the method provides possibilities for studying metabolic pathways in vivo in whole cells. 相似文献
10.
Evolutionary distances for protein-coding sequences: modeling site- specific residue frequencies 总被引:13,自引:8,他引:5
Estimation of evolutionary distances from coding sequences must take into
account protein-level selection to avoid relative underestimation of longer
evolutionary distances. Current modeling of selection via site-to-site rate
heterogeneity generally neglects another aspect of selection, namely
position-specific amino acid frequencies. These frequencies determine the
maximum dissimilarity expected for highly diverged but functionally and
structurally conserved sequences, and hence are crucial for estimating long
distances. We introduce a codon- level model of coding sequence evolution
in which position-specific amino acid frequencies are free parameters. In
our implementation, these are estimated from an alignment using methods
described previously. We use simulations to demonstrate the importance and
feasibility of modeling such behavior; our model produces linear distance
estimates over a wide range of distances, while several alternative models
underestimate long distances relative to short distances. Site-to-site
differences in rates, as well as synonymous/nonsynonymous and
first/second/third-codon-position differences, arise as a natural
consequence of the site-to-site differences in amino acid frequencies.
相似文献