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Biomedical subjects

J A Marquez

Publications and source records attributed to J A Marquez.

At least 19 recordsLinked to original sources
PubMed2001

Identification of Candida tropicalis HSR1, a gene of the heat-shock factor-related family, which confers salt tolerance in Saccharomyces cerevisiae.

A genomic library of Candida tropicalis in a yeast multicopy plasmid has been screened for clones conferring salt tolerance upon transformation into S. cerevisiae. The best halotolerance clone contained an open reading frame encoding a predicted protein of 728 amino acids with homology to transcription factors of the heat-shock family. This novel gene was named HSR1 and is present in single copy in the C. tropicalis genome. Upon transformation into S. cerevisiae it increases the expression of ENA1, a major determinant of salt tolerance encoding a cation-extrusion pump. The sequence of CtHSR1 has been deposited in the EMBL data library under Accession No. AJ296093.

Adenosine Triphosphatases↗
PubMed2000

A study of alternative metal particle structures and mixtures for dental amalgams based on mercury additions.

The perception that mercury in dental amalgam is toxic to the human organism has prompted worldwide efforts by the scientific community to develop alternative amalgam-like materials that utilize little or no mercury. In this investigation, an attempt is made to develop a new dental alloy system by adding liquid mercury to silver-coated Ag4Sn intermetallic particles in lesser amounts than are used in conventional amalgam alloys. An effort to precipitate the important eta-prime (Cu6Sn5) phase was made by adding pure Cu and Sn powders to the alloy formulation during trituration. Tytin a popular Ag-Sn-Cu single-composition, spray-atomized conventional dental alloy was used as the control to obtain baseline data for comparisons of microstructures and mechanical properties. Amalgamation of the coated particles with mercury, with or without the addition of Cu and Sn powders, mostly produced specimens with chemically non-coherent microstructures that were relatively weak in compression. These results were due, in part, to mercury's inability to chemically wet the Ag-coated particles and Cu and Sn powders because of naturally occurring surface oxide films. The strongest specimens tested had silver dendritic coatings, resulting in compression strength values up to 40% of the control's. Their higher strength is attributed to mechanical interlocking at the particle/matrix interfaces.

Journal Article↗
PubMed1987

A novel tetracycline from Actinomadura brunnea. Fermentation, isolation and structure elucidation.

A novel tetracycline antibiotic, Sch 33256, was isolated from a culture broth of a new species of Actinomadura. The antibiotic was isolated by solvent extraction, Sephadex G-25 column chromatography and crystallization. The structure was determined by comparison of the spectra with that of chlortetracycline. Spectroscopic analysis of the compound yielded 2'-N-methyl-8-methoxychlortetracycline as the proposed structure.

Bacteria↗
PubMed1987

A new tetracycline antibiotic from a Dactylosporangium species. Fermentation, isolation and structure elucidation.

An actinomycete identified as a Dactylosporangium sp. produces a new tetracycline, 4a-hydroxy-8-methoxychlortetracycline (Sch 34164). The addition of magnesium ions to complex fermentation media increased the antibiotic titers. Sch 34164 was isolated by solvent extraction and Sephadex G-25 column chromatography. The novel structure was proposed based on spectroscopic analysis. The shift of C-4a (35 to 77 ppm) and C-8 (140 to 163 ppm) in the 13C NMR as compared to chlortetracycline was indicative of the novel hydroxyl and methoxy substituents, respectively.

Actinomycetales↗
PubMed1984

A novel phenazine antifungal antibiotic, 1,6-dihydroxy-2-chlorophenazine. Fermentation, isolation, structure and biological properties.

A novel, solvent extractable, antibiotic complex has been purified from the fermentation broth of an unusual member of the genus Streptosporangium. Two of the major components were isolated from the complex by alumina column chromatography. One of the components was identified as a previously reported compound, 1,6-dihydroxyphenazine. The other component was a novel chlorine containing phenazine, 1,6-dihydroxy-2-chlorophenazine, which exhibited broad spectrum antifungal activity in vitro against dermatophytes and Candida.

Actinomycetales↗
PubMed1983

The hazimicins, a new class of antibiotics. Taxonomy, fermentation, isolation, characterization and biological properties.

The hazimicins, a new class of broad spectrum antibiotics with at least 2 active components (5 and 6), were isolated from the fermentation of Micromonospora echinospora var challisensis SCC 1411. The complex was separated from the broth by a solvent extraction procedure, and the individual components were separated by column chromatography. The two primary active components are isomers, with unique structures shown to be di-tyrosine analogs containing two isonitrile groups. The antibiotic has in vitro activity against Gram-positive and Gram-negative bacteria, and in vitro activity against yeasts and dermatophytes.

Anti-Bacterial Agents↗
PubMed1981

Kijanimicin (Sch 25663), a novel antibiotic produced by Actinomadura kijaniata SCC 1256. Fermentation, isolation, characterization and biological properties.

A novel antibiotic complex has been isolated form the fermentation broth of a new species of Actinomadura, A. kijaniata SCC 1256. The complex was separated form the broth by a solvent extraction procedure and consists of 1 major component, designated kijanimicin, and 3 minor components. Kijanimicin was isolated form the complex by column chromatography and/or preparative high pressure liquid chromatography. Structurally the compound is a unique, large acid enol antibiotic and possesses an unusual in vitro spectrum of activity against some Gram-positive and anaerobic microorganisms. In vivo it has also shown interesting activity against malaria.

Aminoglycosides↗
PubMed1977

Separation of gentamicin C-complex into five components by Craig distribution.

A gentamicin C-complex preparation was separated preparatively into five components by Craig distribution. Gentamicins C1, C2, and C1a were the major components, whereas components C2a and C2b represented only 4% of the total C-complex mixture. Paper chromatographic analysis showed that the gentamicin C2b separated by Craig distribution was identical with a gentamicin isolated from Micromonospora purpurea var. JI-33 fermentation broth and identified as 6'-N-methylgentamicin C1a. Similarly, component C2a was identical with a previously separated gentamicin component tentatively identified as the 6'-C epimer of gentamicin C2.

Biological Assay↗
PubMed1977

Biotransformation of sisomicin to gentamicin C2b.

Sisomicin was transformed to gentamicin C(2b) by Micromonospora rhodorangea NRRL 5326. The mechanisms involved in the biotransformation are the 6'-N-methylation and the (4'-5')-reduction. The progression of the methylation was followed by the isotope technique, but the reduction reaction was not monitored.

Gentamicins↗
PubMed1976

A new actinomycin complex produced by a Micromonospora species: fermentation, isolation, and characterization.

A species of Micromonospora, Micromonospora floridensis NRRL 8020, has been found to produce an actinomycin complex consisting of at least 25 active components. After solvent extraction of the complex, separation of the individual components was carried out by preparative thin-layer chromatography. Hydrolysis and subsequent electrophoretic and chromatographic identification of the amino acid content of each of the isolated components have shown differences from known actinomycins, and the probability exists that these contain a number of amino or imino acids not previously found in other members of this group of antibiotics.

Amino Acids↗
PubMed1976

A new broad spectrum aminoglycoside antibiotic, G-52, produced by Micromonospora zionensis.

G-52 is a new broad spectrum aminoglycoside produced by a species of the genus Micromonospora, Micromonospora zionensis. It has been differentiated from other known related antibiotics by a variety of chemical and biological methods. Its in vitro and in vivo spectrum of activity appears to be quite similar to that of verdamicin and gentamicin but is differentiated from them by its increased activity against 6'-N-acetylating strains.

Animals↗
PubMed1975

Verdamicin, a new broad spectrum aminoglycoside antibiotic.

Verdamicin is a new aminoglycoside antibiotic isolated from fermentation broths of a species of the genus Micromonospora, M. grisea. It has been differentiated from other known related antibiotics by a variety of chemical and biological methods. Its in vitro and in vivo spectrum of activity appears to be similar to those of gentamicin and sisomicin.

Aminoglycosides↗
PubMed1975

New polyene antifungal antibiotic produced by a species of Actinoplanes.

A new species of Actinoplanes, which has been deposited with the designation NRRL 5325 at the Northern Utilization Research and Development Division of the U. S. Department of Agriculture, produces a polyene antifungal complex designated as Sch 16656. The complex, consisting of one major and three minor components, is isolated from the fermentation broth by a solvent extraction procedure and purified by precipitation methods. The major component is a heptaene and is highly active in vitro and in vivo against Candida albicans. It is active also against strains of Torulopsis and is significantly more potent orally than candicidin in mice against Candida infections.

Actinomycetales↗
PubMed1974

Antibiotic G-418, a new Micromonospora-produced aminoglycoside with activity against protozoa and helminths: fermentation, isolation, and preliminary characterization.

Antibiotic G-418 is a new aminoglycoside produced as the major component by a new species of Micromonospora, M. rhodorangea NRRL 5326. The antibiotic is prepared by submerged fermentation in a soybean-dextrin medium. Antibiotic G-418 is adsorbed on a cationic-exchange resin and separated from other impurities by passing it down a Dowex (1 x 2) resin column. The antibiotic, which contains 2-deoxystreptamine, has broad-spectrum antibacterial activity and is highly active against protozoa, amoebae, tapeworm, and pinworm infections in mice. This report describes the taxonomy of the organism, and fermentation, isolation, and preliminary characterization of antibiotic G-418.

Aminoglycosides↗