Mitochondrial telomere-binding protein from Candida parapsilosis suggests an evolutionary adaptation of a nonspecific single-stranded DNA-binding protein.
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The mitochondrial genome in a number of organisms is represented by linear DNA molecules with defined terminal structures. The telomeres of linear mitochondrial DNA (mtDNA) of yeast Candida parapsilosis consist of tandem arrays of large repetitive units possessing single-stranded 5' extension of about 110 nucleotides. Recently we identified the first mitochondrial telomere-binding protein (mtTBP) that specifically binds a sequence derived from the extreme end of C. parapsilosis linear mtDNA and protects it from attack by various DNA-modifying enzymes (Tomaska, L'., Nosek, J., and Fukuhara, H. (1997) J. Biol. Chem. 272, 3049-3059). Here we report the isolation of MTP1, the gene encoding mtTBP of C. parapsilosis. Sequence analysis revealed that mtTBP shares homology with several bacterial and mitochondrial single-stranded DNA-binding proteins that nonspecifically bind to single-stranded DNA with high affinity. Recombinant mtTBP displays a preference for the telomeric 5' overhang of C. parapsilosis mtDNA. The heterologous expression of a mtTBP-GFP fusion protein resulted in its localization to the mitochondria but was unable to functionally substitute for the loss of the S. cerevisiae homologue Rimlp. Analysis of the MTP1 gene and its translation product mtTBP may provide an insight into the evolutionary origin of linear mitochondrial genomes and the role it plays in their replication and maintenance. (+info)
Echocardiographic diagnosis of large fungal verruca attached to mitral valve.
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In a patient with endocarditis due to Candida tropicalis echocardiograms from mitral valve vegetations were found to mimic the typical pattern of a left atrial myxoma. A mass was shown occupying the mitral orifice posterior to the anterior mitral leaflet; densities also appeared in the left atrium. Though these echocardiographic findings were consistent with the diagnosis of a left atrial myxoma, there were other distinctive differential diagnostic features. Other diagnostic possibilities must, therefore, be considered in the interpretation of echocardiograms which suggest left atrial tumour. (+info)
Dacryolith formation around an eyelash retained in the lacrimal sac.
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A dacryolith was discovered in the lacrimal sac during a dacryocystorhinostomy for chronic dacryocystitis in which there was mucocele formation. Morphological examination confirmed the presence of an eyelash at the centre of the stone and electron microscopy demonstrated the presence of fungi (Candida sp.) in a matrix which was of markedly vairable morphology. The mechanism by which a hair enters the punctum and passes along the canaliculus may be attributed to the step-like pattern of ridges on the surface of a hair. The directional nature of these ridges dictates preferential movement towards the root end of the hair and prevents movements in the opposite direction. (+info)
Antifungal susceptibility testing of Candida species by flow cytometry.
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The feasibility of flow cytometric antifungal susceptibility testing has been studied using the fluorescent anionic membrane potential probe, bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC4(3)]. The in vitro antifungal susceptibility testing of amphotericin B was performed on 8 Candida isolates from clinical specimens and 2 ATCC strains by flow cytometry with the results compared to those of the National Committee of Clinical Laboratory Standards (NCCLS) M27-T, broth macrodilution method. The flow cytometric method is based on an increase of fluorescence given out by DiBAC4(3) in fungi when they are killed by antifungal agents. Minimum inhibitory concentration (MIC) of amphotericin B ranged from 0.25 to 1 microg/mL. All results agreed within +/-2 dilution between the flow cytometric method and the M27-T method. MIC with ATCC strains were within recommended ranges of M27-T. The new flow cytometric method revealed a clear and distinct reproducible test end point. A four hr of incubation was sufficient for the test. In conclusion, flow cytometry using DiBAC4(3) is a rapid and accurate in vitro antifungal susceptibility testing method. (+info)
High-frequency, in vitro reversible switching of Candida lusitaniae clinical isolates from amphotericin B susceptibility to resistance.
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Recent studies have revealed an increase in the incidence of serious infections caused by non-albicans Candida species. Candida lusitaniae is of special interest because of its sporadic resistance to amphotericin B (AmB). The present in vitro study demonstrated that, unlike other Candida species, C. lusitaniae isolates frequently generated AmB-resistant lineages form previously susceptible colonies. Cells switching from a resistant colony to a susceptible phenotype were also detected after treatment with either UV light, heat shock, or exposure to whole blood, all of which increased the frequency of switching. In some C. lusitaniae lineages, after a cell switched to a resistant phenotype, the resistant phenotype was stable; in other lineages, colonies were composed primarily of AmB-susceptible cells. Although resistant and susceptible lineages were identical in many aspects, their cellular morphologies were dramatically different. Switching mechanisms that involve exposure to antifungals may have an impact on antifungal therapeutic strategies as well as on standardized susceptibility testing of clinical yeast specimens. (+info)
The aconitase of yeast. IV. Studies on iron and sulfur in yeast aconitase.
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Chemical analyses were carried out to determine the active components of the crystalline aconitase [EC 4.2.1.3] of Candida lipolytica. The enzyme contained 2 atoms of non-heme iron, 1 atom of labile sulfur, and 6 sulfhydryl groups per molecule. One atom of the non-heme iron was released by the addition of metal-chelating agents such as sodium citrate, sodium nitrilotriacetate (NTA) or sodium ethylenediaminetetraacetate (EDTA) without loss of the enzyme activity. The non-heme iron and labile sulfur were released by the addition of sulfhydryl reagents such as rho-chloromercuribenzoate (PCMB), sodium mersalyl or urea with loss of the enzyme activity. o-Phenanthroline reacted with the iron atoms in the enzyme at pH 6.0 with loss of the activity. These results show that yeast aconitase is an iron-sulfur protein and that only one of the two non-heme iron atoms is essential for enzyme activity. (+info)
The aconitase of yeast. V. The reconstitution of yeast aconitase.
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The apoenzyme of yeast aconitase [EC 4.2.1.3] was prepared by treatment of yeast aconitase with sodium mersalyl, followed by passage by passage of the reaction mixture through a column of Dowex A-1 and gel filtration on Sephadex G-25. The apoenzyme had no aconitase activity, but the active enzyme could be reconstituted by treatment of the apoenzyme with ferrous ions and sodium sulfide in the presence of 2-mercapto-ethanol. The reconstituted active enzyme was isolated by DEAE-Sephadex A-50 column chromatography and Sephadex G-100 gel filtration from the reaction mixture. The reconstituted enzyme was identical with the original untreated enzyme in terms of specific activity, iron content and spectral characteristics, but not in terms of labile sulfur content. A significant difference in visible spectra between the holo- and apoenzymes appeared to be due to the difference in iron and labile sulfur contents between the two proteins. (+info)
Liposomal amphotericin (AmBisome) in the prophylaxis of fungal infections in neutropenic patients: a randomised, double-blind, placebo-controlled study.
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Liposomal amphotericin (AmBisome) 2 mg/kg three times weekly was compared with placebo as prophylaxis against fungal infection in patients undergoing chemotherapy or bone marrow transplantation (BMT) for haematological malignancies. Prophylaxis began on day 1 of chemotherapy and continued until neutrophils regenerated or infection was suspected. Of 161 evaluable patients, 74 received AmBisome and 87 received placebo. Proven fungal infections developed in no patients on AmBisome and in three on placebo (3.4%) (P = NS). Suspected fungal infections requiring intervention with systemic antifungal therapy (usually amphotericin B) occurred in 31 patients on AmBisome (42%) and in 40 on placebo (46%) (P = NS). Suspected deep-seated infections developed in 21 (28.3%) and 31 (35.6%) patients, respectively (P = NS). Time to develop a suspected or proven deep-seated infection showed a trend in favour of AmBisome (P = 0.11). Fifty patients had fungal colonisation (48 with Candida spp, two with Aspergillus spp) of at least one body site during prophylaxis; 15 patients while receiving AmBisome (20%) and 35 while on placebo (40%) (P < 0.01). Time to colonisation was significantly delayed in the group receiving AmBisome (P < 0.05). Treatment-related toxicity was modest and no additional toxicity was observed in patients receiving AmBisome. AmBisome 2 mg/kg three times weekly is safe and reduces fungal colonisation in patients receiving intensive chemotherapy or BMT. However, despite encouraging trends, prophylactic AmBisome did not lead to a significant reduction in fungal infection or in requirement for systemic antifungal therapy. (+info)