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G San-Blas

Publications and source records attributed to G San-Blas.

At least 19 recordsLinked to original sources
PubMed2005

alpha-galf I -->6-alpha-mannopyranoside side chains in Paracoccidioides brasiliensis cell wall are shared by members of the Onygenales, but not by galactomannans of other fungal genera.

The water-soluble polysaccharide fraction of the cell wall alkali extract (F1SS) from the mycelial phase of the dimorphic fungus Paracoccidioides brasiliensis is compared with F1SS polysaccharides obtained from the Onygenalean mycelial fungi Ascocalvatia alveolata, Onygena equina and Aphanoascus terreus. These polymers were exclusively composed of mannose and galactose. Data from methylation and NMR analyses reveal that F1SS polysaccharides from the four fungi contain the same residues although in different proportions: [-->2,6)-alpha-D-Manp-(1 -->]; [2)-alpha-D-Manp-(1 -->]; [ -->6)-alpha-D-Manp-(1 -->]; and [alpha-D-Galf-(1 -->]. In P. brasiliensis, the repeating unit of the polysaccharide consists of a backbone of [(1 -->6)-alpha-D-Manp] substituted at the 0-2 position by the disaccharide [alpha-D-Galf-(1 -->6)-alpha-D-Manp-(1 -->], while the remaining 0-2 positions are substituted by single residues of mannose or short chains of (1 -->2)-mannose. The other species had a lower proportion of galactofuranose-containing side chains and higher proportion of mannose-containing side chains. The similarities found among the F1SS polysaccharides from P. brasiliensis and the Onygenalean A. alveolata, A. terreus and O. equina, reveal the close relatedness of all these fungi, show differences with polysaccharides from other fungal genera and agree with the molecular evidence provided in the scientific literature for the placement of P. brasiliensis within the Onygenales.

Carbohydrate Sequence↗
PubMed2005

Paracoccidioides brasiliensis, paracoccidioidomycosis, and antifungal antibiotics.

Paracoccidioides brasiliensis is the causative agent of paracoccidioidomycosis (PCM), a human systemic, chronic and progressive mycosis. Preferred antifungals are sulfamethoxazol-trimethoprim, itraconazole, amphotericin B. Treatment is lengthy, the drugs may have undesirable side effects, and some are costly. Occasional resistant strains have been reported. Therefore, the search for more selective and efficient antifungals to treat this and other mycoses continues. Ajoene, chemically derived from garlic, behaves as an antifungal agent against P. brasiliensis and other fungi. Its antiproliferative effects in P. brasiliensis are associated with a reduction of phosphatidyl choline, a concomitant increase in its precursor phosphatidyl ethanolamine, and a large increase in unsaturated fatty acids in the pathogenic yeast phase. The sterol biosynthetic pathway has been largely studied for the search of antifungals. Azoles and allilamines act on differents steps of this pathway. However, they may interfere with similar steps in the host. Hence, the search for drugs that may act on more specific steps is ongoing. One such step focuses on the sterol C-methylations catalyzed by the enzyme (S)-adenosyl-L-methionine: Delta(24) - sterol methyl transferase (SMT). SMT inhibitors such as azasterols and derivatives (AZA1, AZA2, AZA3) have proven highly effective as antiproliferative agents against protozoa and some fungi, among them, P. brasiliensis. Their chemical synthesis and structure, and their molecular electrostatic potential are discussed in order to understand their mechanism of action, and derive rationally designed improvements on these molecules, that would favour a higher efficacy and selectivity.

Antifungal Agents↗
PubMed2004

Isolation of the CHS4 gene of Paracoccidioides brasiliensis and its accommodation in a new class of chitin synthases.

The nucleotide sequence of a chitin synthase gene (PbrCHS4) of the dimorphic fungal human pathogen Paracoccidioides brasiliensis has been determined. A homology search with the deduced amino acid sequence of PbrChs4 (1744 aa) reveals the presence of two distinct domains, an N-terminal domain showing up to 30% homology to myosin motor-like domains and a C-terminal domain with up to 68% homology to chitin synthases, as has been reported for some class V chitin synthases. However, unlike class V chitin synthases with myosin motor-like domains, PbrChs4 does not present characteristic signatures of myosin motor-like domains. Also, although the Chs domain presents the closest homology to other fungal class V enzymes, it is low enough to consider PbrChs4 as belonging to a new class, which we propose as class VII.

Amino Acid Sequence↗
PubMed2003

Chitin synthesis as target for antifungal drugs.

Human mycoses have become a threat to health world-wide. Unfortunately there are only a limited number of antimycotic drugs in use. Promising targets for drugs specific against fungi are those affecting chitin synthesis. Chitin is absent in vertebrates, and is essential for fungal wall integrity. A thorough knowledge of the mechanism of chitin synthesis is required to design specific inhibitors. We review here our current understanding of the process, and the most promising drugs that inhibit it. Chitin is made by chitin synthases requiring specific microvesicles, the chitosomes, for intracellular transport. Fungi contain several chitin synthases, some of which may be essential at a certain stage. This phenomenon is important to take into account for drug design. The most widely studied chitin synthase inhibitors are polyoxins and nikkomycins that probably bind to the catalytic site of chitin synthases. These are not equally susceptible to the drugs. In Saccharomyces cerevisiae the order of sensitivity is: Chs3p>Chs1p>Chs2p. Main problems for their succesful use in vivo are: low permeability, and different susceptibility of fungal species, and variable responses in animal models. Chemical modifications have been proposed to make more potent derivatives. Other synthetic or natural compounds are also promising as possible inhibitors, but their properties are less well known. Rational drug design has proceeded only on the basis of existing inhibitors, because the structure of the active site of chitin synthase is unknown. Undoubtedly, determination of this, and the biosynthetic mechanism will reveal unexpected drug targets in the future.

Aminoglycosides↗
PubMed2001

Biogeographic range expansion into South America by Coccidioides immitis mirrors New World patterns of human migration.

Long-distance population dispersal leaves its characteristic signature in genomes, namely, reduced diversity and increased linkage between genetic markers. This signature enables historical patterns of range expansion to be traced. Herein, we use microsatellite loci from the human pathogen Coccidioides immitis to show that genetic diversity in this fungus is geographically partitioned throughout North America. In contrast, analyses of South American C. immitis show that this population is genetically depauperate and was founded from a single North American population centered in Texas. Variances of allele distributions show that South American C. immitis have undergone rapid population growth, consistent with an epidemic increase in postcolonization population size. Herein, we estimate the introduction into South America to have occurred within the last 9,000-140,000 years. This range increase parallels that of Homo sapiens. Because of known associations between Amerindians and this fungus, we suggest that the colonization of South America by C. immitis represents a relatively recent and rapid codispersal of a host and its pathogen.

Base Sequence↗
PubMed2000

Differential expression of chitin synthase genes during temperature-induced dimorphic transitions in Paracoccidioides brasiliensis.

Fragments of five genes encoding chitin synthase enzymes were identified in the dimorphic fungus Paracoccidioides brasiliensis by polymerase chain reaction (PCR) amplification of conserved CHS gene domains. These represent several classes of enzyme: PbrCHS1, class I; PbrCHS2, class II; PbrCHS3, class IV; and PbrCHS4 and PbrCHS5, class V. Expression of these genes during the temperature regulated dimorphic transition from yeast to mycelium and from mycelium to yeast was determined by Northern analysis. One gene (PbrCHS3) was not expressed at detectable levels. The others were regulated by morphology and/or by the growth phase of the organism. Despite the fact that yeast cells contain more chitin than hyphal cells, the levels of mRNA for PbrCHS1, PbrCHS2, PbrCHS4, and PbrCHS5 were higher in hyphal cells than in yeast cells. This supports observations in other fungi that transcript levels often do not correlate with chitin content and that post-transcriptional regulation of CHS gene expression is important for morphogenesis.

Amino Acid Sequence↗
PubMed2000

RFLP analysis reveals marked geographical isolation between strains of Paracoccidioides brasiliensis.

Restriction fragment length polymorphism (RFLP) was performed on 32 isolates of the pathogenic fungus Paracoccidioides brasiliensis from geographically separated regions of South America. The use of HinfI and HincII gave clear RFLP patterns, for which high discriminatory indices could be calculated. Computational analysis of the RFLP patterns for the 32 isolates suggested that at least five groups of strains existed, each of which was geographically distinct and corresponded closely with present country borders. These results underline the belief that P. brasiliensis infections are acquired from exogenous sources and that this fungus occupies specialist endemic niches within the natural environment.

DNA, Fungal↗
PubMed2000

From magic to science: a journey throughout Latin American medical mycology.

The start of Latin America's love story with fungi may be placed in pre-Hispanic times when the use of fungi in both ritual ceremonies and daily life were common to the native civilizations. But the medical mycology discipline in Latin America started at the end of the 19th Century. At that time, scholars such as A. Posadas, R. Seeber, A. Lutz and P. Almeida, discovered agents of fungal diseases, the study of which has influenced the regional research ever since. Heirs to them are the researchers that today thrive in regional Universities and Research Institutes. Two current initiatives improve cooperation among Latin American medical mycologists. First, the periodical organization of International Paracoccidioidomycosis Meetings (seven so far, from 1979 to 1999); second, the creation of the Latin American Association for Mycology in 1991 (three Congresses, from 1993 to 1999). Latin American publications have increased in international specialized journals such as that from our Society (ISHAM) (from 8% in 1967 to 19% in 1999), and the Iberoamerican Journal of Mycology (Revista Iberoamericana de Micologia; > 40% from 1997 to 1999). In addition, Latin American participation at ISHAM International Congresses has risen from 6.9% in 1975 to 21.3% in 1997, and 43.2% at the 14th ISHAM Congress, held for the first time in a Latin American country, Argentina. A significant contribution of women to the scientific establishment of Latin American medical mycology (e.g., 45% of Latin American papers vs. 18% of other regions published in Journal of Medical and Veterinary Mycology in 1987, had women as authors or coauthors) suggests a better academic consideration of Latin American women against their counterparts in the developed world. Taken together, all these figures reflect the enthusiasm of our Latin American colleagues in the field, despite the difficulties that afflict our region, and affect our work.

Bibliometrics↗
PubMed2000

Fungal morphogenesis and virulence.

Phenotypic variability in pathogenic fungi has long been correlated with virulence, but specific genetic and molecular mechanisms are only recently being unraveled. Fungal morphogenesis, reflecting the expression of several regulated genes, and the capacity of the rising forms or phases to cause disease has been focused on at the XIVth Congress of the International Society for Human and Animal Mycology. Three experimental models of pathogenic fungi have been discussed. In Cryptococcus neoformans, phenotypic variability or switching represents controlled and programmed changes rather than random mutations. Evaluated phenotypic traits were the capsular polysaccharide, cell and colony morphology and virulence. In the dimorphic Paracoccidioides brasiliensis, the serine-thiol proteinase from the yeast phase cleaves the main components of the basal membrane, thus being potentially relevant in fungal dissemination. In Candida albicans, relationships between adhesion proteins and those of lymphocytes and neutrophils are related to fungal pathogenicity. Regulation of the directional growth of hyphae and its tropic responses are correlated with the invasive potential of C. albicans.

Candida albicans↗
PubMed1998

Molecular cloning and sequencing of a chitin synthase gene (CHS2) of Paracoccidioides brasiliensis.

The nucleotide sequence of a chitin synthase gene (CHS2) of the dimorphic fungal human pathogen Paracoccidioides brasiliensis has been determined. The deduced amino acid sequence of Chs2p consists of 1043 residues and is highly homologous to other class II fungal chitin synthases. Computational structural analyses suggest very high similarity to other fungal chitin synthases with a highly variable region at the cytosolic amino-terminal region which may be related to its possible zymogenic nature, and the putative catalytic region close to seven membrane-spanning regions at the carboxyl terminus.

Amino Acid Sequence↗
PubMed1998

Cytosolic neutral proteinases of Paracoccidioides brasiliensis.

Cytosolic proteinases were assayed in both morphological phases of Paracoccidioides brasiliensis. Preparations from the mycelial phase were more active in vitro than those from the yeast cells. Optimal proteinase activities for both phases occurred at pH's between 6.0 and 9.0, and at 45 degrees C. Gelatin-SDS-PAGE electrophoresis separated several bands (58-112 kDa) in mycelial preparations; a single band (70 kDa) was seen in yeast preparations. Enzymatic activities were inhibited by antipain, phenyl methyl sulfonyl fluoride (PMSF), and chymostatin, suggestive of serine proteinases. Partial inhibition of the mycelial enzymes by ethylene diamine tetraacetic acid (EDTA), 1,10-phenanthroline, and iodoacetamide, also suggested the presence of cysteine- and metallo-proteinases. The enzymatic activity increased in preparations extracted from yeast cells transforming to mycelia, and decreased in preparations obtained from the reverse process.

Antipain↗
PubMed1998

Geographic discrimination of Paracoccidioides brasiliensis strains by randomly amplified polymorphic DNA analysis.

Randomly amplified polymorphic DNA (RAPD) analysis of 33 Paracoccidioides brasiliensis strains from Argentina, Brazil, Colombia, Peru, and Venezuela produced reproducible amplification products which were sufficiently polymorphic to allow differentiation of the strains. Types generated with five primers (OPG 03, OPG 05, OPG 14, OPG 16, and OPG 18) resulted in a high discriminatory index (0.956). The discriminatory index was slightly reduced (0.940) when only two primers (OPG 3 and OPG 14) were used. A dendrogram based on these results showed a high degree of similarity among the strains, and genetic differences were expressed in clusters related to geographical regions but not to pathological features of the disease. With a few exceptions, strains were sorted into five groups by geographical origin as follows: group I, Venezuelan strains; group II, Brazilian strains; group III, Peruvian strains; group IV, Colombian strains; and group V, Argentinian strains. The group containing the most disparate strains was group V (discriminatory index, 0.633); the discriminatory index for the other four groups was 0.824. The use of primer OPG 18 by itself was sufficient to discriminate species specificity, and the use of primer OPG 14 by itself was sufficient to discriminate among the geographical locations of the strains in the sample. This method may be helpful for epidemiological studies of P. brasiliensis.

DNA, Fungal↗
PubMed1998

Lysis of Paracoccidioides brasiliensis by Zygosporium geminatum.

Zygosporium geminatum, isolated as a contaminant in a culture of the mycelial phase of Paracoccidioides brasiliensis, was lethal to the latter organism. Its lytic action was due to exocellular alpha-1,3- and beta-1,3-glucanases which degraded the P. brasiliensis cell wall. The alpha-1,3-glucanase was more active at 30 degrees C and the beta-1,3-glucanase at 23 degrees C, each having pH 6.0 as its optimum.

Cell Wall↗
PubMed1996

Polyamines in growth and dimorphism of Paracoccidioides brasiliensis.

Putrescine and spermidine were the only polyamines found in Paracoccidioides brasiliensis, a dimorphic fungus pathogenic for humans. Free polyamines (putrescine > spermidine) increased during the first 24 h of yeast growth, with a second peak at 42 h, and also during the first 12 h of mycelium-to-yeast transition (spermidine > putrescine). Conjugated and bound polyamines were also quantified. 1, 4-Diamino-2-butanone decreased free putrescine and spermidine accumulation by inhibiting the activity of ornithine decarboxylase. The increase in free polyamines corresponds to bud emergence in yeast growth and to the mycelium-to-yeast transition of P. brasiliensis.

Ornithine Decarboxylase Inhibitors↗
PubMed1996

Ornithine decarboxylase in Paracoccidioides brasiliensis.

Ornithine decarboxylase in Paracoccidioides brasiliensis, a dimorphic human pathogenic fungus, was more active at 37 degrees C in the yeast phase and at 30 degrees C in the mycelial phase. In contrast to other fungal systems, yeast growth and mycelium-to-yeast transition in P. brasiliensis were accompanied by a high activity of ornithine decarboxylase at the onset of the budding process, the activity of which was inhibited by 1,4-diamino-2-butanone. The activity of ornithine decarboxylase remained at a basal level during vegetative growth of both the mycelial phase and the late stage of yeast phase, and also through the yeast-to-mycelium transition.

Enzyme Inhibitors↗
PubMed1996

Cladosporium carrionii and Hormoconis resinae (C. resinae): cell wall and melanin studies.

Two phaeoid strains of the fungus Cladosporium carrionii (SR3 from a xerophyte species and PP8201 from a patient), and one strain of Hormoconis resinae (Cladosporium resinae), isolated from oil-impregnated soil, were analyzed for their cell wall composition by colorimetric methods, X-ray diffraction, infrared spectroscopy, and solid-state 13C-nuclear magnetic resonance. Results suggested that the cell walls were composed mainly of hexoses (34%-47%) as beta-1,3-glucan (some galactose and mannose were also present) and melanin, chitin being absent. Electron microscopic observations suggested that melanin was found not only in the cell wall but also in intracellular bodies resembling melanosomes.

Cell Wall↗