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  • 1
    ISSN: 1432-1041
    Keywords: Lithium clearance ; furosemide ; circadian variations ; sodium ; potassium ; creatinine clearance ; electrolyte excretion ; renal tubular physiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of chronic furosemide treatment on the circadian cycle of lithium clearance (CLLi) and electrolyte excretion has been examined in 8 young, male volunteers, by performing two 24 h clearance experiments, before and after one week of treatment with furosemide 80 mg once daily. After 8 days on furosemide there was a significant decrease in creatinine clearance (−21%), plasma Na (−8.4 mM) and plasma K (−0.58 mM). At that time, however, there were no changes in 24 h-values of CLLi or Na excretion, although the magnitude of the circadian variation in CLLi and other renal parameters was increased. Both CLLi and CLNa were increased in the first 3 h following furosemide administration and thereafter they fell below the control level in the remaining hours of the experiment. From the absolute and fractional changes in CLLi it is suggested that compensatory Na conservation in response to chronic furosemide treatment occurs between doses, and that it involves decreased output from the proximal tubules combined with increased fractional Na reabsorption in the distal nephron.
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  • 2
    ISSN: 1430-3418
    Keywords: Concanavalin A receptors ; Recognition ; Chemosensory behaviour ; Tetrahymena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between concanavalin A (ConA) receptors and the chemosensory behaviour of the ciliated protozoan Tetrahymena thermophila was studied using the peptide chemoattractants proteose peptone and fibroblast growth factor. Studies on the chemosensory behaviour in semisolid methylcellulose showed that 50 μg/ml ConA selectively inhibited the persistent element of swimming behaviour by reducing time runs of cells responding to proteose peptone from 12.2±4.5 min to 0.8±0.3 min. Methyl-alpha-D-mannoside, but not methyl-alpha-D-galactoside, abolished the inhibitory effect of ConA, suggesting that mannoside-containing ConA receptors are involved in maintaining a persistent swimming behaviour. Control experiments, carried out in liquids where persistent swimming is less important for cellular behaviour, showed that ConA did not affect proteose-peptone-induced chemoattraction under these conditions as measured by a two-phase assay for chemoattraction. Also, no inhibitory effect of ConA could be found on swimming rates when individual velocities of ConA-treated cells were determined. When tested in liquid chemoattraction assays, ConA was found to be a weak but significant chemoattractant. Studies of the cellular location of ConA receptors on the plasma membrane of starved cells showed an unequal distribution. A preferential clustering of receptors at the anterior end of the cell was observed when determined at high concentrations (100 μg/ml) of fluorescent ConA. Methyl-alpha-D-mannoside but not methyl-alpha-D-galactoside abolished the fluorescent ConA labelling, indicating a preferential clustering of these mannoside-containing receptors at the anterior part of the plasma membrane and cilia. At lower concentrations (25 μg/ml), FITC-ConA produced more general labelling of the entire cell membrane. The results suggest that ConA receptors are necessary for the persistent element of swimming and that binding of ConA to its receptors interferes with processes related to signal transduction rather than by limiting the free movement of cilia required for locomotion. The gradient of receptors seen at high FITC-ConA concentrations may be important for a putative spatial chemosensory mechanism, i.e. chemotaxis.
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  • 3
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract   Reductive dechlorination of tetrachloroethene was studied in a mesophilic upflow anaerobic sludge blanket reactor. Operating the reactor in batch mode the dynamic transformation of tetrachloroethene, trichloroethene and dichloroethene (DCE) was monitored. Tetrachloroethene was reductively dechlorinated to trichloroethene, which again was dechlorinated at the same rate as DCE was produced. DCE showed a lag period of 40 h before transformation was observed. During normal reactor operation trans-1,2-DCE was the major DCE isomer, followed by cis-1,2-DCE. Small amounts of 1,1-DCE but no vinyl chloride were detected. When the influent tetrachloroethene concentration was increased from 4.6 μM to 27 μM, the transformation rate increased, indicating that the system was not saturated with tetrachloroethene. The main organic component in the effluent was acetate, indicating that the aceticlastic methane-producing bacteria were inhibited by the chlorinated ethenes.
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  • 4
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This two-part paper is devoted to problems of structural-acoustic coupling with emphasis on analysis, design sensitivity analysis and optimization. Part II of the paper aims to (i) present consistent numerical techniques commonly used for treatment of coupled structural and acoustic dynamics, (ii) use the structural optimization tool ODESSY for solution of several coupled problems, and (iii) compare the numerical efficiency of alternative techniques and the relevance of selected objective functions.
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  • 5
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper is devoted to problems of structuralacoustic coupling with emphasis on analysis, design sensitivity analysis and optimization. The paper is divided into two parts, and it is the aim of Part I to (i) give a brief survey of recent developments in sensitivity analysis and sound emission and NVH (Noise, Vibration and Harshness) design of acoustically loaded structures, and (ii) discuss alternative objective functions and optimization formulations for structural acoustics. The aims of Part II are to (i) present consistent numerical techniques commonly used for treatment of coupled structural and acoustic dynamics, (ii) use the structural optimization tool ODESSY for solution of several coupled problems, and (iii) compare the numerical efficiency of alternative techniques and the relevance of selected objective functions.
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  • 6
    ISSN: 1432-136X
    Keywords: Synthetic nutrient medium ; Cell multiplication ; Hemin ; Phospholipids ; Tetrahymena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ciliate Tetrahymena thermophila was grown in a synthetic nutrient medium at various amino acid concentrations. Before the beginning of the experiments the cells were starved for 4 h in a pH buffer. They were inoculated at an initial density of only 250 cells per ml. Under these conditions the cells grew and multiplied at only the two highest amino acid concentrations used. Hemin or phospholipids were found to stimulate cell growth at the lower amino acid concentrations. The mechanism behind this stimulatory effect is unknown, but may be connected with the maintenance of an adequate energy flow under adverse conditions. These additions represent an improvement of the synthetic medium for Tetrahymena.
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  • 7
    ISSN: 1432-1424
    Keywords: Key words: Volume regulation — Phosphoinositidase C — Ins(1,4,5)P3— Ca2+signaling — K+ channels — Charybdotoxin — Clotrimazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. The putative role for Ca2+ entry and Ca2+ mobilization in the activation of the regulatory volume decrease (RVD) response has been assessed in Ehrlich cells. Following hypotonic exposure (50% osmolarity) there is: (i) no increase in cellular Ins(1,4,5)P3 content, as measured in extracts from [2-3H]myoinositol-labeled cells, a finding at variance with earlier reports from our group; (ii) no evidence of Ca2+-signaling recorded in a suspension of fura-2-loaded cells; (iii) Ca2+-signaling in only about 6% of the single, fura-2-loaded cells at 1-mm Ca2+ (1% only at 0.1-mm Ca2+ and in Ca2+-free medium), as monitored by fluorescence-ratio imaging; (iv) no effect of removing external Ca2+ upon the volume-induced K+ loss; (v) no significant inhibition of the RVD response in cells loaded with the Ca2+ chelator BAPTA when the BAPTA-loading is performed in K+ equilibrium medium; (vi) an inhibition of the swelling-induced K+ loss (about 50%) at 1-mm Ba2+, but almost no effect of charybdotoxin (100 nm) or of clotrimazole (10 μm), reported inhibitors of the K+ loss induced by Ca2+-mobilizing agonists. Thus, Ca2+signaling by Ca2+ release or Ca2+ entry appears to play no role in the activation mechanism for the RVD response in Ehrlich cells.
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  • 8
    ISSN: 1573-5036
    Keywords: ammonium ; nitrate ; split-roots ; root exudate ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of plant-root N-status on bacterial growth in the rhizosphere was studied with 5-week-old wheat plants grown in soil with low N content obtained by mixing 9:1 gravel:sandy loam. As a consequence of N limitation, significant increase in3Hthymidine (Tdr) incorporation rate occured 3 days after addition of 30 mM ammonium compared to controls without ammonium. Plants were grown with split-roots to separate the effect of soil N from effect of plant root derived organic matter-N on bacterial activity. The increase in nitrate concentration from 10 mM to 30 mM at one part of the root system led to significant increased3HT dr incorporation in the rhizosphere at the other part of root system after 4 days showing that the composition of root exudates became more favourable for bacterial growth when plants were fertilized with the higher level of nitrate.
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  • 9
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1436-6215
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Die Ergebnisse von Experimenten mit Tieren führen zu der Feststellung, daß ein Fütterungszusatz von entweder Psyllium-Samenkernen oder Lignin das Verhältnis von Desoxycholsäure zu Chenodesoxycholsäure in der Galle ändert. In dieser Untersuchung scheint bei Patienten mit Gallensteinen eine akzeptable Dosis von Psyllium-Samenkernen oder Lignin die relativen Mengen von in der Galle befindlichem Cholesterin oder den einzeln verschiedenen Gallensäuren nicht zu ändern.
    Notes: Summary Animal experiments suggest that supplementing the diet with either psyllium seed husk or lignin alters the ratio of deoxycholic acid to chenodeoxycholic in bile. In this study dosages of psyllium seed husk or lignin acceptable to patients with gallstones do not appear to alter the relative amounts of cholesterol, or individual bile acids in the bile.
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