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  • 1
    ISSN: 1573-6881
    Keywords: Matrix calcium ; BAT mitochondria ; membrane permeability transition ; adenine nucleotide translocase ; calcium transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The role of the adenine nucleotide translocase on Ca2+ homeostasis in mitochondria from brown adipose tissue was examined. It was found that in mitochondria incubated with 50 μM Ca2+, ADP was not needed to retain the cation, but it was required for strengthening the inhibitory effect of cyclosporin on membrane permeability transition as induced by menadione. In addition, carboxyatractyloside was unable to promote matrix Ca2+ release, even though it inhibits the ADP exchange reaction. However, when the Ca2+ concentration was increased to 150 μM, carboxyatractyloside did induce Ca2+ release, and ADP favored Ca2+ retention. Determination of cardiolipin content in the inner membrane vesicles showed a greater concentration in brown adipose tissue mitochondria than that found in kidney mitochondria. It is suggested that the failure of the adenine nucleotide translocase to influence membrane permeability transition depends on the lipid composition of the inner membrane.
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  • 2
    ISSN: 1573-2568
    Keywords: CIRRHOSIS ; ASCITES ; OCTREOTIDE ; PLASMA RENIN ACTIVITY ; GLUCAGON ; NITRIC OXIDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Splanchnic and systemic arteriolar vasodilationplays an important role in ascites formation incirrhosis. Octreotide produces splanchnicvasoconstriction, but the effects on systemichemodynamics and renal function are controversial. This studyevaluated the effect of subcutaneous octreotideadministration on systemic hemodynamics, endogenousvasoactive systems, and renal function in cirrhoticpatients with ascites. Twenty patients were included: 10received octreotide 250 μg/12 hr subcutaneously (forfive days), and 10 did not. No statistically significantchanges were found in mean arterial pressure and cardiac rate. Octreotide induced astatistically significant decrease in plasma reninactivity (P 〈 0.01), plasma aldosterone (P = 0.01)and plasma glucagon (P 〈 0.05). No significantvariations were observed in other systemic vasoactivesubstances (nitric oxide and prostacyclin). Renalfunction was not modified in either group. Inconclusion, in cirrhotic patients with ascites,subcutaneous octreotide administration decreases plasma glucagon, reninactivity, and aldosterone without changing in systemichemodynamics or renal function.
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  • 3
    ISSN: 1572-879X
    Keywords: S poisoning ; Pt sulfidation ; Cu/Pt and Zn/Pt catalysts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The interaction of sulfur with Pt(111), Zn/Pt(111) and Cu/Pt(111) has been examined using X-ray photoelectron spectroscopy (XPS), X-ray excited Auger electron spectroscopy (XAES), and thermal desorption mass spectroscopy (TDS). At temperatures between 300 and 600 K, the exposure of Pt(111) to S2 gas produces a chemisorbed layer of sulfurwithout the formation of bulk sulfides. Exposure of S2 to a Zn/Pt(111) alloy, at room temperature, results in a breakdown of the alloy and formation of a zinc-sulfide film on Pt(111). Further S2 exposure at 550 K sulfidizes the remaining metallic zincwithout affecting platinum. For the Cu/Pt(111) surface alloy, on the other hand, exposure to S22 at 550 K leads to sulfidation of the platinum. Platinum can effectively compete for sulfur atoms bonded to copper but not for those bonded to zinc. The reaction of S2 gas with Cu/Pt(111) surfaces produces copper sulfides that promote the sulfidation of Pt by providing surface sites for the dissociation of S2, and by favoring the diffusion of S into the bulk of the system.
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  • 4
    ISSN: 1573-0832
    Keywords: Candida albicans ; antigenic variability ; blastospores ; germ tubes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effect of germ tube induction on the antigenic variability in C. albicans was studied in strains from blood cultures (Group I) and superficial candidiasis (Group II). When compared by immunoblotting with a rabbit antiserum, antigenic extracts from Group I strains grown as blastospores showed a higher reactivity than that of Group II strains. Major bands in Group I strains (45–47, 33, 30 kDa) were continuously expressed through the subcultures in vitro but, with the exception of the 45 kDa band, the reactivity of all of them decreased or disappeared after the tenth subculture in Group II strains. The induction of the germ tubes produced the re-expression of the antigens lost during subculture in the yeast form, the effect being very clear in Group II strains. The re-expression by C. albicans germ tubes of antigens lost during subculture of blastospores in vitro and the higher reactivity shown by Group I strains grown in mycelial phase should be taken into consideration when a test to detect anti-C. albicans antibodies is to be developed.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 14 (1961), S. 31-38 
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This work deals with some observations on Piedra in the Republic of Ecuador and it is a part of a general review about superficial mycoses which is now carried out in Guayaquil. This study comprises the two varieties, black and white. Beside the description of the nodules, with its microscopic characteristics, the cultures are also described in both aspects: macroscopic and micromorphologic. In black Piedra details of the asci are presented along with ascospores ofP. hortai (Brumpt)Fonseca &Leao, 1928. The A. found certain resemblance between the ascospores described and those ofP. javanica Boedijn &Verbunt, 1938. Typical black colonies were obtained beside otherTrichosporon type about which some interpretations are made. In white Piedra its rarity is mentioned. The isolated organism is identified withT. giganteum Behrend, 1890 and its microscopic and cultural characteristics are described.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 26 (1994), S. 393-399 
    ISSN: 1572-879X
    Keywords: Zn oxidation ; Cs catalysis ; Cs/ZnO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract On zinc films, the adsorption probability of O2 is extremely low (10−3–10−2), and O2 exposures in the range of 103–104 langmuir are necessary to produce a significant transformation of metallic zinc into zinc oxide. The presence of submonolayer coverages of cesium enhances the oxidation rate of zinc by 2–3 orders of magnitude. The cesium adatoms interact with O2 molecules, producing a reservoir of reactive oxygen species that oxidize zinc.
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  • 7
    ISSN: 1572-879X
    Keywords: nickel molybdate ; HDS catalysts ; sulfur poisoning ; X-ray absorption spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This study aims at characterizing the properties of pure and sulfided NiMoO4 catalysts using synchrotron-based near-edge X-ray absorption fine structure (NEXAFS) and temperature-programmed reduction (TPR). Mo LII-edge and MIII-edge NEXAFS spectra indicate that on reaction with H2S, the Mo component of NiMoO4 gets partially reduced with the formation of MoS2 type species. For the β-phase of NiMoO4, the sulfidation of Mo is more extensive than for the α-phase, making the former a better precursor for catalysts of hydrodesulfurization (HDS) reactions. The Ni LII-edge features are relatively insensitive to the changes accompanying the partial sulfidation of NiMoO4. The sulfidation of the Ni component is confirmed by analysis of the Ni K-edge extended X-ray absorption fine structure (EXAFS) spectra which show the formation of Ni–S bonds (bond length ∼2.48 Å) and a NiMoSx phase. The S K-edge NEXAFS spectra show the presence of at least two types of sulfur species, one associated with a formal oxidation state of 2- and another associated with a formal oxidation state of 6+. We attribute the former to the presence of metal–sulfur bonds (MoSx and NiSy). The latter is associated with the formation of S–O bonds (SO 4 2- ). The formation of sulfates is also supported by the O K-edge NEXAFS spectra. The partially sulfided NiMoO4 catalysts (both α- and β-isomorphs) have a much lower thermal stability in a reducing environment than pure NiMoO4 and MoS2. The sulfided molybdates react with H2 in TPR producing H2O and H2S at temperatures above 400 K.
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  • 8
    ISSN: 1573-6881
    Keywords: Matrix calcium ; BAT mitochondria ; membrane permeability transition ; adenine nucleotide translocase ; calcium transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The role of the adenine nucleotide translocase on Ca2+ homeostasis in mitochondria from brown adipose tissue was examined. It was found that in mitochondria incubated with 50 μM Ca2+, ADP was not needed to retain the cation, but it was required for strengthening the inhibitory effect of cyclosporin on membrane permeability transition as induced by menadione. In addition, carboxyatractyloside was unable to promote matrix Ca2+ release, even though it inhibits the ADP exchange reaction. However, when the Ca2+ concentration was increased to 150 μM, carboxyatractyloside did induce Ca2+ release, and ADP favored Ca2+ retention. Determination of cardiolipin content in the inner membrane vesicles showed a greater concentration in brown adipose tissue mitochondria than that found in kidney mitochondria. It is suggested that the failure of the adenine nucleotide translocase to influence membrane permeability transition depends on the lipid composition of the inner membrane.
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  • 9
    ISSN: 1573-6881
    Keywords: Mitochondrial calcium ; inorganic phosphate ; membrane permeability transition ; calcium transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The role of inorganic phosphate as inhibitor of mitochondrial membrane permeability transition was studied. It is shown that in mitochondria containing a high phosphate concentration, i.e., 68 nmol/mg, Ca2+ did not activate the pore opening. Conversely, at lower levels of matrix phosphate, i.e., 38 nmol/mg, Ca2+ was able to induce subsequent pore opening. The inhibitory effect of phosphate was apparent in sucrose-based media, but it was not achieved in KCl media. The matrix free Ca2+ concentration and matrix pH were lowered by phosphate, but they were always higher in K+-media. In the absence of ADP, phosphate strengthened the inhibitory effect of cyclosporin A on carboxyatractyloside-induced Ca2+ efflux. Acetate was unable to replace phosphate in the induction of the aforementioned effects. It is concluded that phosphate preserves selective membrane permeability by diminishing the matrix free Ca2+ concentration.
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  • 10
    ISSN: 1573-6903
    Keywords: Astrocyte cultures ; development ; histamine ; ornithine decarboxylase ; glutamine synthetase ; astrocyte proliferation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of histamine on different aspects of the growth of astrocytes was studied using primary cultures derived either from forebrain or from cerebellum of the rat. The influence on general growth and differentiation was monitored in terms of the activities of ornithine decarboxylase and glutamine synthetase enzymes, whereas [3H]thymidine incorporation into DNA was used as a specific index of cell proliferation. Treatment with 500 nM histamine of cells grown for 6 days in vitro, caused a time-dependent significant increase in ornithine decarboxylase activity of astrocytes from both sources. The maximum increase was observed at 4 h after histamine treatment, at that time the elevation in ornithine decarboxylase activity being about 80% and 300% over control values in the forebrain and the cerebellar astrocytes, respectively. Under similar experimental conditions, addition of histamine (500 nM) to medium resulted in a significant increase in [3H]thymidine incorporation into DNA in both types of cultures: in comparison with control, the elevation was about 45% at 48 h in forebrain astrocytes and at 24 h in cerebellar astrocytes. On the other hand, the specific activity of glutamine synthetase in cerebellar astrocytes was markedly enhanced (about 100%) by treatment with histamine (500 nM) for 4 days, but forebrain astrocytes were little affected. Addition of histamine to the culture medium produced no significant alteration in the activity of lactate dehydrogenase and protein content of either type of astroglial cells. The present findings, which support our earlier proposal that the biochemical properties of astrocytes differ between various brain regions, provide direct evidence for the involvement of histamine in the regulation of growth and development of astrocytes.
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