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Digitale Medien

Colonization and degradation of oxidized bituminous and lignite coals by fungi (1990)

Stewart, D. L. ; Thomas, B. L. ; Bean, R. M. ; [weitere]

Springer

Journal of industrial microbiology and biotechnology 6 (1990), S. 53-59

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ISSN: 1476-5535

Schlagwort(e): Bituminous coal ; Biosolubilization ; Penicillium sp. ; Surface colonization

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: Summary APenicillium sp. previously shown to grow on lignite coals degraded an air-oxidized bituminous coal (Illinois #6) to a material that was more than 80% soluble in 0.5 N NaOH. Scanning electron microscopy of the oxidized Illinois #6 revealed colonization of the surface by thePenicillium sp., production of conidia, and erosion of the coal surface. The average molecular weight (MW) of Illinois #6 degraded by the fungus and base-solubilized was approximately 1000 Da. The average MW for base-solubilized Illinois #6 that was not exposed to the fungus was 6000 Da, suggesting solubilizing mechanisms other than base catalysis. A spectrophotometric assay to quantify the microbial conversion of biosolubilized coal was developed. Standard curves were constructed based on the absorbance at 450 nm of different quantities of microbe-solubilized coal. An acid precipitation step was necessary to remove medium and/or microbial metabolites from solubilized coal to prevent overestimation of the extent of coal biosolubilization. Furthermore, the absorption spectra for different coal products varied, necessitating construction of standard curves for individual coals.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01576177

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Digitale Medien

Post-receptor defect accounts for phosphorylase hypersensitivity in cultured diabetic cardiomyocytes (1992)

Buczek-Thomas, Jo Ann ; Jaspers, Stephen R. ; Miller, Thomas B.

Springer

Molecular and cellular biochemistry 117 (1992), S. 63-70

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ISSN: 1573-4919

Schlagwort(e): glycogen phosphorylase ; alloxan-diabetes ; cardiomyocytes ; G-protein

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie , Medizin

Notizen: Abstract The basis for the hypersensitive response of glycogen phosphorylase to epinephrine stimulation was investigated in adult rat cardiomyocytes isolated from normal and alloxan-diabetic animals. To assess potential G-protein involvement in the response, normal and diabetic derived myocytes were incubated with either cholera or pertussis toxin prior to hormonal stimulation. Pretreatment of cardiomyocytes with cholera toxin resulted in a potentiated response to epinephrine stimulation whereas pertussis toxin did not affect the activation of this signaling pathway. To determine if the enhanced response of phosphorylase activation resulted from an alteration in adenylate cyclase activation, the cells were challenged with forskolin. After 3 hr in primary culture, diabetic cardiomyocytes exhibited a hypersensitive response to forskolin stimulation relative to normal cells. However, after 24 hr in culture, both normal and diabetic myocytes responded identically to forskolin challenge. The present data suggest that a cholera toxin sensitive G-protein mediates the hypersensitive response of glycogen phosphorylase to catecholamine stimulation in diabetic cardiomyocytes and this response which is present in alloxan-diabetic cells and is induced in vitro in normal cardiomyocytes is primarily due to a defect at a post-receptor site.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00230411

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Digitale Medien

Identification of the molecular basis for phosphorylase hypersensitivity in cultured diabetic cardiomyocytes (1995)

Buczek-Thomas, Jo Ann ; Miller, Thomas B.

Springer

Molecular and cellular biochemistry 145 (1995), S. 131-139

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ISSN: 1573-4919

Schlagwort(e): glycogen phosphorylase ; alloxan-diabetes ; cardiomyocytes ; cGMP ; phosphodiesterase

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie , Medizin

Notizen: Abstract The focus of this study was to identify the molecular basis for the hypersensitive response of glycogen phosphorylase activation to epinephrine stimulation in alloxan diabetic-derived cardiomyocytes. Cyclic AMP levels were found not to be significantly different between normal and diabetic-derived cells while cGMP concentrations were found consistently to be significantly lower in diabetic-derived cells than in normal cells. Treatment with cyclic GMP analogues did not affect phosphorylase activation by epinephrine in normal cardiomyocytes whereas, IBMX, a nonselective phosphodiesterase inhibitor, had a significant effect on basal and agonist-stimulated phosphorylase activity in both normal and diabetic-derived cardiomyocytes. Differences in the time course for the rate of decay of phosphorylasea from agonist-stimulated to basal levels were observed between normal and diabetic cells. After 3 h in primary culture, phosphorylasea activity returned to basal levels more quickly in normal than in diabetic-derived cells while after 24 h in culture, the time for phosphorylasea decay was not significantly different between normal and diabetic myocytes and was longer than the 3 h response. After 3 h in primary culture, no significant difference in phosphorylase kinase activity was observed between normal and diabetic-derived cells exposed to epinephrine whereas, after 24 h in culture, phosphorylase kinase activity was significantly decreased in diabetic cells under basal and agonist-stimulated conditions. These data collectively suggest that the hypersensitive response of glycogen phosphorylase to epinephrine stimulation in diabetic-derived cardiomyocytes is not due to a defect present at the level of phosphorylase kinase but may, in part, result from an alteration in cardiac phosphodiesterase activity resulting from diminished intracellular cyclic GMP concentrations.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00935485

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Digitale Medien

Al3+-Ca2+ interactions in aluminum rhizotoxicity (1993)

Ryan, Peter R. ; Kinraide, Thomas B. ; Kochian, Leon V.

Springer

Planta 192 (1993), S. 98-103

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ISSN: 1432-2048

Schlagwort(e): Aluminum toxicity ; Calcium uptake ; Growth inhibition ; Root ; Triticum

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract The cation Al3+ is toxic to plants at micromolar concentrations and can severely inhibit root growth in solution experiments. Trivalent aluminum hydrolyzes in solution, and, apart from the Al3+ ion, which dominates speciation below pH 5.0, various mononuclear and polynuclear hydroxy-Al species can also occur (Kinraide 1991). Accumulating evidence suggests that Al3+ is the rhizotoxic species under the experimental conditions used in the present study (Kinraide 1991; Kinraide et al. 1992). The inhibition of Ca2+ uptake in roots by Al3+ has been proposed as a possible mechanism for Al3+ toxicity, and in this study the hypothesis was tested directly. Root growth and Ca2+ uptake were measured in 5-d-old seedlings of wheat (Triticum aestivum L. Thell) during exposure to Al3+ in a low-Ca2+ basal medium, and to Al3+ in the presence of added cations. Uptake of Ca2+ in whole roots and translocation to the shoot were measured using 45Ca2+, and localized measurements of net Ca2+ flux were also made at the root apex using the technique of microelectrode ion-flux estimation. Treatment with 2.64 μM AlCl3 in 226 μM CaCl2, at pH 4.5, severely inhibited root growth without affecting Ca2+ uptake. Addition of 30 mM Na2+, 3 mM Mg2+ or 50 μM tris(ethylenediamine)cobalt(III) to this Al3+ treatment restored root growth but significantly reduced Ca2+ uptake measured over the entire root system and at the root apex. The Al3+ and Ca2+ concentrations were adjusted so that the activities of the Al3+ and Ca2+ ions were constant in all solutions (1.5 μM and 200 μM, respectively). Root growth can be severely inhibited by Al3+ concentrations that do not affect Ca2+ uptake, while the addition of ameliorating cations depresses Ca2+ uptake. These results argue against the hypothesis that Al3+ inhibits root growth by reducing Ca2+ uptake.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00198698

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