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1.
Auxotrophic mutants of Candida albicans FC18 were induced by a combination of treatments with nitrous acid and UV irradiation. Arginine (Arg-), histidine (His-) and methionine/cysteine (MetA-) auxotrophs were recovered by this means. The Arg- auxotrophs lacked active argininosuccinate lyase (EC 4.3.2.1), the enzyme catalysing the final step in arginine biosynthesis. Thus the locus may be designated arg-4. The mutant strains bearing this mutation did not form germ tubes unless the germination medium contained arginine. 相似文献
2.
Maria Rebelo Claudia Sousa Howard M. Shapiro Maria M. Mota Martin P. Grobusch Thomas H?nscheid 《PloS one》2013,8(4)
Resistance of Plasmodium falciparum to almost all antimalarial drugs, including the first-line treatment with artemisinins, has been described, representing an obvious threat to malaria control. In vitro antimalarial sensitivity testing is crucial to detect and monitor drug resistance. Current assays have been successfully used to detect drug effects on parasites. However, they have some limitations, such as the use of radioactive or expensive reagents or long incubation times. Here we describe a novel assay to detect antimalarial drug effects, based on flow cytometric detection of hemozoin (Hz), which is rapid and does not require any additional reagents. Hz is an optimal parasite maturation indicator since its amount increases as the parasite matures. Due to its physical property of birefringence, Hz depolarizes light, hence it can be detected using optical methods such as flow cytometry. A common flow cytometer was adapted to detect light depolarization caused by Hz. Synchronized in vitro cultures of P. falciparum were incubated for 48 hours with several antimalarial drugs. Analysis of depolarizing events, corresponding to parasitized red blood cells containing Hz, allowed the detection of parasite maturation. Moreover, chloroquine resistance and the inhibitory effect of all antimalarial drugs tested, except for pyrimethamine, could be determined as early as 18 to 24 hours of incubation. At 24 hours incubation, 50% inhibitory concentrations (IC50) were comparable to previously reported values. These results indicate that the reagent-free, real-time Hz detection assay could become a novel assay for the detection of drug effects on Plasmodium falciparum. 相似文献
3.
We have used a quantitative titration assay for mixed lymphocyte interactions to determine the additivity of responses of rat lymphocyte populations to simultaneous stimulation with major histocompatibility complex alloantigens from pairs of apparently unrelated rat strains. Our inability to detect strict additive stimulation led us to investigate inclusion among allo-reactive lymphocyte populations. After specific depletion of reactivity to PVG by negative selection through an AO × PVG F1 hybrid rat, AO thoracic duct lymphocytes showed an asymmetrical loss of reactivity to the unrelated strains DA and F344. We suggest that this differential loss of reactivity probably reflects alloantigen sharing among rat strains which had been previously undetected using other less sensitive techniques for the quantitation of lymphocyte reactivity after specific depletion of allo-reactive cells. 相似文献
4.
Serological comparison of bovine T-mycoplasmas 总被引:1,自引:0,他引:1
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The Devonian cemented brachiopod Schuchertellopsis durbutensis has proved difficult to classify and its possible taxonomic relationships are unknown. Morphologically Schuchertellopsis resembles more closely members of the Orthotetidina than the Davidsoniidina. Examination of the shell structure, a key diagnostic feature of the Orthotetidina, shows that Schuchertellopsis has the cross laminar secondary shell typical of all orthotetidines. However, the presence of both pseudopunctate and incipient an extropunctate fabric within the ventral valve is unique amongst orthotetidine brachiopods and is thought to represent a phase of shell fabric experimentation. Schuchertellopsis probably fits most comfortably within the Schuchertellidae, and is the earliest representative of that family. 相似文献
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Relationship Between Solute Permeability and Osmotic Remediability in a Galactose-Negative Strain of Saccharomyces cerevisiae 总被引:3,自引:1,他引:2 下载免费PDF全文
An osmotic remedial allele, gal 7-1, in the galactose pathway of Saccharomyces cerevisiae responds to either penetrating (ethylene glycol and diethylene glycol) or nonpenetrating (KCl, NaCl, and sorbitol) solutes in the growth medium. Extracts from cells grown under restrictive conditions gave no increase in enzyme activity (gal-1-phosphate, uridylyl transferase) when exposed to the penetrating solutes; thus protein synthesis or possibly polymer assembly is proposed as the critical step remedied by the addition of the solutes. 相似文献
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