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Biomedical subjects

E Montoya

Publications and source records attributed to E Montoya.

At least 55 records · Page 3Linked to original sources
PubMed1984

Production and properties of a bacteriocin from Myxococcus coralloides D.

Myxococcus coralloides D was found to produce a substance with a narrow range of antibacterial activity. This substance was produced during the exponential growth phase and was not inducible by ultraviolet light or mitomycin C treatment. The bacteriocin was precipitable by ammonium sulphate, and showed resistance to heat (100 degrees C for 10 min), trypsin, lysozyme, beta-glucuronidase, DNase, RNase, acetone, ethyl ether, urea and mercaptoethanol; it was partially destroyed by pronase and inactivated at extreme pH values. Electron microscopy did not reveal any phage-like particles associated with bacteriocin activity.

Bacteria↗
PubMed1984

Cytoplasmic transformation of Saccharomyces cerevisiae using purified mtDNA.

Transformation of cytoplasmic mutants of Saccharomyces cerevisiae proved to be successful using plasmid or intact mitochondria, but not when mtDNA was used as the transforming principle. The sphaeroplasts of two cytoplasmic mutants, respiratory deficient and erythromycin sensitive cells, were transformed using purified mtDNA from respiratory competent or erythromycin resistant donor strains.

Cytoplasm↗
PubMed1983

Control of catalase and peroxidase biosynthesis by carbon source and oxygen in the yeast Saccharomyces cerevisiae.

The effect of carbon source and oxygen tension on catalase and peroxidase levels and on the intermediates of the biosynthesis of the prosthetic group of both enzymes has been studied. Oxygen produces an increase of both enzymatic activities, even in presence of glucose. On the other hand it seems probable that glucose does not have a direct inhibitory effect on the biosynthesis of 5-aminolevulinic acid (ALA) and porphyrins.

Aerobiosis↗
PubMed1983

Pigments with antibiotic activity from Myxococcus coralloides.

A strain of Myxococcus coralloides produces pigments with antibiotic activity. The pigments are non-diffusible and become detectable at the beginning of the autolytic phase. Red pigments produced by vegetatively growing cells were extracted by acetone treatment. The crude extract when chromatographed yielded several fractions, two of which were active against certain Gram-positive bacteria. Both fractions were partial purified in thin layer chromatography and can be differentiated according to colour, polarity and absorption spectrum. Production of active pigments is increased by nicotine and inhibited by diphenylamine. The pigments are also compared with the antibiotic produced by this bacterium.

Anti-Bacterial Agents↗
PubMed1982

Thyrotrophin-releasing hormone responsiveness and degradation in children with chronic renal failure: effect of time of evolution.

In order to study the hypothalamic-pituitary-thyroid function in children with chronic renal failure (CRF), the serum levels of L-thyroxine (L-T4), L-triiodothyronine (L-T3), reverse T3 (rT3), thyrotrophin (TSH) and prolactin (Prl) were measured by radioimmunoassay (RIA). Values were compared with those of normal subjects. Low levels of L-T4 were present in CRF patients as compared to controls. L-T3 was also found to be low but less than L-T4, and rT3 was lower in patients with long evolution. No alterations were observed in TSH basal levels, whereas Prl values in patients were high. After thyrotrophin-releasing hormone (TRH) administration, TSH and Prl rose to similar levels in both groups, but high values were maintained throughout (120 min) in CRF. A significant negative correlation was found between the peak rise of the TSH response and the CRF evolution time. The L-T3 response to TRH administration (120 min) was similar in both CRF and controls. The rate of in vivo and in vitro exogenous TRH degradation was decreased in patients with CRF or by their sera, respectively. Our data seem to confirm that the hypothyroid syndrome described in CRF patients is of hypothalamic origin, and the low in vivo and in vitro TRH degradation rates are a consequence of this state.

Adolescent↗
PubMed1981

Regulation of catalase biosynthesis in Saccharomyces cerevisiae: factor repressing catalase biosynthesis.

A factor which represses the catalase biosynthesis in yeast has been demonstrated in Saccharomyces cerevisiae. This factor can be obtained from yeast cells having both low and normal catalase levels, and is unable to enter the intact cytoplasmic membrane. Moreover, the factor-containing cell extracts obtained either from acatalasemic mutants or normal strains grown in catalase repressive conditions showed higher activity than those obtained from normal strains after being cultured in permissive conditions.

Catalase↗
PubMed1980

Effect of streptozotocin diabetes on the hypothalamic-pituitary-thyroid axis in the rat.

Studies of the hypothalamic-pituitary-thyroid axis have been performed in streptozotocin (STZ)-diabetic Wistar rats and their controls. Plasma PBI concentration, plasma and pituitary TSH, contents, and hypothalamic TRH content were measured by RIA in basal and stimulated conditions. Compared to controls, rats made diabetic by 6.0 or 7.5 mg STZ/100 g BW showed decreased plasma PBI and TSH and diminished pituitary TSH content, with greater alterations in rats receiving the highest STZ dose. Both diabetic groups showed an almost 50% reduction of hypothalamic TRH content in comparison with the mean control value. After thyroidectomy, pituitary TSH secretion increased in diabetic, ad libitum fed, and semistarved animals, but it was lower in the diabetic group in which the reduction in plasma PBI was similar or greater. To evaluate pituitary sensitivity to the inhibitory action of L-T4 on TSH secretion in diabetes, thyroidectomized control (Thx-C), thyroidectomized diabetic (Thx-D), and thyroidectomized semistarved (Thx-S) rats were injected twice daily for 7 days with either saline or a fractional L-T4 dose of 0.25, 0.50, or 1.00 microgram/100 microgram/100 g BW. In Thx-D rats, a daily dose of 1.00 microgram L-T4 was sufficient to normalize pituitary TSH secretion, while a dose of 2.00 microgram was required to induce a similar effect in the Thx-C and Thx-S animals. Pituitary TSH content was increased in the Thx-C group with increasing T4 doses. No modification in this parameter was seen in the Thx-D and Thx-S animals. The fact that diabetes caused a reduction in the hypothalamic TRH content indicates that the primary cause of pituitary-thyroid alterations in STZ-diabetic rats lies in the hypothalamus, although the metabolic imbalance induced by diabetes and, in less degree, by undernutrition could also be partly responsible for some of the described modifications.

Animals↗
PubMed1980

The partial purification, separation, and properties of yeast killer toxins.

Two different kinds of yeast killer toxins (YKT) have been partially concentrated and their properties and molecular behaviour comparatively studied. The toxin of the first system (YKT1) shows more sensitivity to several agents (temperature, pH, enzymes) than the toxin of the second system (YKT2). YKT1 shows only one chromatographic band on Sephadex G-200, while YKT2 shows two bands. The molecular weights of these bands have been estimated. Both toxins can be separated by isoelectrofocusing and show estimated isoelectrical points of 5.4 (YKT1) and 4.3 (YKT2).

Hydrogen-Ion Concentration↗
PubMed1979

Purification and partial characterization of an antibiotic produced by Myxococcus coralloides.

A strain of Myxococcus coralloides producing an antibiotic capable of inhibiting growth of Gram-positive bacteria was isolated. Antibiotic production occurred during vegetative growth but not during myxospore formation. The antibiotic was extracted from the growth medium with chloroform and purified by adsorption on silicic acid and by preparative silica gel thin-layer chromatography. The purified antibiotic showed a resistance to heat, acid, alkali and proteolytic enzymes. Chromatographic and electrophoretic behavior as well as infrared, ultraviolet and mass spectra are presented.

Anti-Bacterial Agents↗
PubMed1979

Two methods of large-scale extraction of an antibiotic produced by Myxococcus coralloides.

Two methods for the isolation of an antibiotic produced by Myxococcus coralloides have been developed: the chloroform extraction method and the charcoal adsorption method. The recovery of antibiotic in each case was 25% and 30%, respectively, by the two methods. Although the two methods yield a relative low recovery, the charcoal adsorption method seems more attractive and promising due to its simplicity and economic advantages.

Adsorption↗
PubMed1979

Biological activity of an antibiotic produced by Myxococcus coralloides.

A strain of Myxococcus coralloides was isolated which produced an antibiotic active against Gram-positive bacteria and also against Neisseria sp at high levels of antibiotic. The antibiotic was bactericidal on sensitive growing bacteria. It was inactive on non-growing cells and also on cells whose growth has been stopped by addition of chloramphenicol. Strains of S. aureus resistant to several antibiotics, including penicillin and ampicillin, were also sensitive to this antibiotic.

Anti-Bacterial Agents↗
PubMed1978

Induction of polygalacturonase production in legume roots as a consequence of extrachromosomal DNA carried by Rhizobium meliloti.

The ability of Rhizobium meliloti to induce polygalacturonase production in legume roots decreased during culture under laboratory conditions but was inducible with mitomycin C. This character was irreversibly lost after treatment with acridine orange. Extrachromosomal DNA of molecular weight 5.9 x 10(6) daltons was detectable in neutral sucrose gradient but was absent from cells 'cured' with acridine orange. Therefore, the ability to induce the enzyme production may be controlled by a plasmid.

Acridine Orange↗
PubMed1978

Quality and rate of extracellular polysaccharides produced by Rhizobium meliloti and their inducing effect on polygalacturonase production in legume roots as derived from the presence of extrachromosomal DNA.

The ability of extracellular polysaccharides of different strains of Rhizobium meliloti to induce the production of polygalacturonase by roots of Medicago sativa seedlings has been studied. Some strains showed a high inducing activity while those derived from them, after treatment with acridine orange and in which extrachromosomal DNA was absent, did not show this character. A comparative study of polysaccharide production and preliminary studies on the chemical composition of the active fractions obtained after Sephadex G-25 filtration indicated that the monomers which form the active fractions are qualitatively and quantitatively different according to their origin.

Acridine Orange↗