PubMed Health⌕ Search

Biomedical subjects

I Polacheck

Publications and source records attributed to I Polacheck.

At least 19 recordsLinked to original sources
PubMed1995

Adherence of Candida albicans to epithelial cells: studies using fluorescently labelled yeasts and flow cytometry.

Candida albicans adherence to epithelial cells is the first step in the infectious process, but in spite of its importance, current methods for the quantitative measurement of adherence of C. albicans to epithelial cells in vitro have some serious limitations. They are based on filtration assays and either microscopic or radiometric analysis. The adherence reaction is usually carried out with a large excess of yeasts (100-fold) over epithelial cells in order to perform the microscopic analysis, which is slow, subjective and limited to 100-200 cells and thus lacks statistical power. The radiometric analysis fails to measure individual cells. A method for measuring yeast adherence that overcomes these problems has been developed. It is based on labelling the yeasts with the fluorogenic marker 2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester (BCECF) prior to the adherence reaction, and analysing 10(4) epithelial cells by flow cytometry, while nonbound yeasts are excluded by gating. Two subpopulations of buccal epithelial cells (BECs) which differ in their mean fluorescence intensities per cell (MFIs) were observed: one with MFI which did not exceed nonspecific fluorescence, and the other with MFI as high or higher than the MFI of labelled yeasts. The two subpopulations represent yeast-free and yeast-binding epithelial cells, respectively, and the MFI increment of the BECs is a quantitative measure of the extent of yeast adherence. Control experiments confirming previously described basic features of adherence, such as enhanced adherence at increasing yeast excess, diminished adherence of trypsin-treated or heat-inactivated yeasts, and the differential adherence of various Candida species, supported the validity of the assay. The possibility of studying adherence reliably at low yeast:epithelial cell ratios, which better mimic adhesion as it occurs in vivo, is an important advantage of the assay. New findings, using this method, included the observation that exfoliated BECs from diabetic patients exhibited the same capacity for C. albicans adherence as cells from healthy controls, and that epithelial cells from early human ontogenic stages had a significantly lower adherence level than those from later stages.

Adult↗
PubMed1992

Aspergillus quadrilineatus, a new causative agent of fungal sinusitis.

Aspergillus quadrilineatus was found to be the etiologic agent of pansinusitis in a patient suffering from acute nonlymphoblastic leukemia and who had undergone allogeneic bone marrow transplantation. A. quadrilineatus was cultured from biopsy specimens of the maxillary sinus, and tissue sections with fungal stains showed a necrotic area containing dichotomously branching septate hyphae, which is morphologically consistent with Aspergillus species. The patient was successfully treated with a combination of surgical debridement, granulocyte transfusions, and intravenous administration of amphotericin B-cholesterol sulfate colloidal dispersion. This is the first report of an infection caused by A. quadrilineatus.

Adult↗
PubMed1992

Development of DNA probes for early diagnosis and epidemiological study of cryptococcosis in AIDS patients.

We report the isolation of middle-repetitive DNA sequences from Cryptococcus neoformans that are species and variety specific. These probes were used for assessing strain relatedness among cryptococcal isolates from patients with and without AIDS who were from Zaire and the United States. Five distinct hybridization patterns were observed for the 60 isolates examined, regardless of the restriction enzyme used for digestion. The most common pattern among the isolates from the patients without AIDS was also the most common among the isolates from the patients with AIDS who were from the United States and was the only pattern observed for all isolates tested from patients with AIDS who were from Zaire. On the basis of the high specificity and sensitivity of the signals observed by hybridization, we suggest that these sequences provide a means for both biotyping and early diagnosis of C. neoformans.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Endocarditis caused by Blastoschizomyces capitatus and taxonomic review of the genus.

Blastoschizomyces capitatus Salkin, Gordon, Samsonoff et Rieder was found to be the etiologic agent of endocarditis in a patient with a prosthetic mitral valve. Cultures inoculated with peripheral blood and portions of the valve yielded B. capitatus. Examination of stained tissue sections revealed the presence of fungal filaments morphologically consistent with this organism. The salient characteristics of B. capitatus and the factors contributing to its recognition as a distinct taxon are described.

Aged↗
PubMed1992

The identification and tracking of Candida albicans isolates from oral lesions in HIV-seropositive individuals.

Restriction fragment polymorphism analysis was used to investigate the identity and genotypic relatedness of Candida albicans strains isolated from human immunodeficiency virus (HIV)-infected patients with or without oral candidiasis and from some of their sexual partners. Use of the species-specific DNA probe Ca3 revealed that most subjects carried a single distinct C. albicans strain throughout the course of the study, during both symptomatic and asymptomatic periods. Sexual partners were more likely to carry the same or similar C. albicans isolates than unrelated subjects, raising the possibility of transmission via intimate contact. One patient appeared to acquire his partner's isolate, which then became predominant in both partners in subsequent isolations. These findings indicate that recurrent oral candidiasis is usually caused by a single persistent strain unique to each patient, but that in some cases transmission via intimate contact may occur between sexual partners.

AIDS-Related Opportunistic Infections↗
PubMed1992

Cytokine-induced resistance to microbial infections in normal, immunosuppressed and bone marrow transplanted mice.

We studied the efficacy of in vivo and in vitro treatments with IL-1, IL-2, IL-3, and GM-CSF in the protection against bacterial (Salmonella typhimurium), fungal (Candida albicans) and viral (influenza virus A/PR8) infections, of normal, sublethally irradiated and lethally irradiated, bone marrow (BM) reconstituted mice. In parallel, the cytokines were tested for their ability to potentiate hematopoietic activity in vitro and in vivo. We demonstrate that, under the experimental conditions employed, IL-1 had the best protective activity against the three micro-organisms in both normal and immunocompromised mice when administered in vivo. Administration of IL-2 led to increased resistance in normal but not in immunodeficient mice, whereas GM-CSF had no beneficial effects. In contrast, preincubation of BM cells in these cytokines, singly or combined, prior to transplantation to lethally irradiated mice, did not confer protection against subsequent infection, although it increased the number of BM derived CFU-GM in culture (except in the case of IL-2). Administration of IL-1 or GM-CSF to BM transplanted mice facilitated WBC recovery, whereas IL-2 delayed it. Collectively, the data suggest that IL-1, alone or combined with other cytokines, may be beneficial in the prevention or treatment of microbial infections in immunocompromised and BM transplanted patients. It can also be concluded that enhanced hematopoietic recovery may not always coincide with the development of resistance to micro-organisms.

Animals↗
PubMed1991

Mode of action of the antimycotic agent G2 isolated from alfalfa roots.

The mode of action of the antimycotic alfalfa root saponin, medicagenic acid 3-O-beta-D-glucopyranoside (compound G2), which possesses a pronounced antifungal activity against medically important yeasts and dermatophytes, was studied in Saccharomyces cerevisiae. Compound G2 caused lethal leakage of ions out of the yeast cells. Exposure of S. cerevisiae to compound G2 resulted in a disappearance of the main sterol, ergosterol, from the cell membranes, suggesting that compound G2 was highly specific for ergosterol. Independently, chemical data indicated that compound G2 forms stable complexes with both ergosterol and cholesterol. Addition of cholesterol or ergosterol protected the cells of S. cerevisiae and several pathogenic yeasts from the inhibitory activity of compound G2 by producing a higher ratio of sterols (mainly ergosterol) to phospholipids in the membranes. The fact that an amphotericin B-resistant Candida tropicalis was susceptible to G2 suggested that its mode of action was different from that described for polyene antibiotics. This was also confirmed by the finding that 0.2 M KCl did not protect S. cerevisiae cells against ion leakage with G2, but did so with amphotericin B.

Antifungal Agents↗
PubMed1990

Activity of compound G2 isolated from alfalfa roots in experimental dermatophyte infection.

Compound G2 isolated from alfalfa roots was applied topically to skin lesions of guinea pigs experimentally infected with the dermatophyte Trichophyton mentagrophytes var. granulare. After 12 to 15 applications, 80% of the infected lesions were cured, as judged by clinical and microbial criteria, compared with 20% of the untreated lesions which healed spontaneously (P less than 0.01).

Animals↗
PubMed1990

Catecholamines and virulence of Cryptococcus neoformans.

Cryptococcus neoformans was unable to utilize catecholamines (epinephrine, norepinephrine, or dopamine) as sole carbon or nitrogen sources. Therefore, catecholamines are not essential growth factors for this fungus and the brain is not a preferred nutritional niche for its growth with regard to catecholamines. To establish whether the brain is a survival niche for C. neoformans and to explain the role of phenoloxidase as a virulence factor, a wild-type strain that had phenoloxidase activity and mutants which lacked it were exposed to an epinephrine oxidative system, and the survival of both strains was tested. The oxidative system contained epinephrine as an electron donor, Fe3+ as the catalytic transition metal ion, and hydrogen peroxide as an electron acceptor. The wild-type strain was found to be resistant to this oxidative system, whereas under the same conditions the mutant strain was susceptible and its survival decreased at a rate of 4 logs per h. Damage to high-molecular-weight DNA seems to be a causative factor of cell death after exposure of the mutants to the oxidative system. These results suggest that C. neoformans may survive in the brain because of its ability to utilize catecholamines for melanogenesis and thus neutralize the harmful effects of catecholamines which are manifested in the presence of hydrogen peroxide and transition metal ions. The role of phenoloxidase in resistance to the epinephrine oxidative system is also discussed.

Catechol Oxidase↗
PubMed1990

Isolation of the Candida albicans histidinol dehydrogenase (HIS4) gene and characterization of a histidine auxotroph.

Genetic studies were done with Candida albicans CBS 562. Various auxotrophs were isolated following mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. SAG5 (his4C), a stable histidine auxotroph defective in histidinol dehydrogenase activity, was characterized and chosen for further molecular studies. Therefore, the C. albicans HIS4 gene was isolated. The gene was obtained from a genomic library of the wild-type strain, which was constructed in plasmid YEp24. The HIS4 gene was isolated by transformation of a Saccharomyces cerevisiae strain that carried a his4 mutation. The isolated C. albicans HIS4 gene complemented S. cerevisiae his4A, his4B, his4C, and his4ABC mutant strains, which indicates that the clone contains the entire HIS4 gene. The gene was isolated on plasmid pSTC7, whose physical map was constructed with BamHI, SalI, and EcoRV restriction endonucleases, locating the HIS4 gene on a 14-kilobase-pair DNA fragment. Hybridization experiments with HIS4 and C. albicans genomic DNA showed correspondence between the restriction patterns of the gene with that of the chromosomal DNA, indicating that the gene originates from C. albicans and appears in a single copy. Chromosomes of C. albicans CBS562 and four other strains were resolved by orthogonal-field alteration gel electrophoresis. The electrokaryotyping results showed heterogeneity in chromosomal sizes. The electrokaryotyping of CBS 562 showed a resolution of six chromosomal bands, three of which seemed to be doublets. The C. albicans HIS4 gene was located on the largest resolvable chromosome in all of the strains.

Alcohol Oxidoreductases↗
PubMed1989

Electrophoretic karyotype of the pathogenic yeast Cryptococcus neoformans.

The electrokaryotype of the pathogenic yeast Cryptococcus neoformans is described for the first time. Three different patterns were seen: (a) serotypes B and C (variety gattii) are similar and consist of nine chromosome mobility groups of greater than 580 kb; (b) serotype A (variety neoformans) revealed eight chromosome-like groups greater than 700 kb; (c) serotype D (the second serotype of variety neoformans) not only differs from those described above, but each D isolate tested showed a different distribution of bands. The discrepancy, and the importance of electrokaryotyping as a taxonomic tool, are discussed.

Cryptococcus↗
PubMed1989

Fusarium oxysporum keratitis.

We describe herein a patient with a rare occurrence of mycotic keratitis caused by Fusarium oxysporum. The fungus destroyed the cornea, and a perforating corneal graft had to be performed. The drug of choice in such diagnosed cases is natamycin. A comparison between Fusarium oxysporum and Fusarium solani is discussed.

Adult↗
PubMed1988

Melanogenesis in Cryptococcus neoformans.

Melanogenesis in Cryptococcus neoformans begins with the oxidation of dihydroxyphenylalanine by the enzyme phenol oxidase. The succeeding steps are very rapid. Two intermediates, dopachrome and 5,6-dihydroxyindole, have been isolated and characterized by high performance liquid chromatography. A pathway of melanin formation in C. neoformans is proposed, based on the presence of these intermediates.

Chemical Phenomena↗
PubMed1988

Activities of compound G2 isolated from alfalfa roots against dermatophytes.

An antimycotic agent, compound G2, isolated from alfalfa roots exhibited considerable activity against the six most common dermatophytes. MICs in agar and broth dilutions ranged from 10 to 30 micrograms/ml and from 2 to 10 micrograms/ml, respectively. G2 was fungicidal at 5 to 22 micrograms/ml. Structure and toxicity relations are discussed.

Antifungal Agents↗
PubMed1988

In vitro synergistic activity of ketoconazole with trifluoperazine and with chlorpromazine against medically important yeasts.

Combination of ketoconazole and trifluoperazine or chlorpromazine yielded an in vitro synergistic effect on growth inhibition of Candida albicans, Torulopsis glabrata, Cryptococcus neoformans, Candida parapsilosis and Candida tropicalis. The optimal pH range for the synergistic effects was 7.0-7.6. At pH 5.0 the drug combination was antagonistic. (Application for patent protection has been filed).

Chlorpromazine↗