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  • Springer  (65)
  • Blackwell Publishing Ltd  (2)
  • BioMed Central  (1)
  • American Meteorological Society (AMS)
  • 1985-1989  (68)
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  • 11
    Digitale Medien
    Digitale Medien
    The costs of leaving home: ants disperse myrmecochorous seeds to low nutrient sites (1989)
    Springer
    Oecologia 81 (1989), S. 412-417 
    Details
    ISSN: 1432-1939
    Schlagwort(e): Myrmecochory ; Fynbos ; Regeneration ; Fire ; Nutrient
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Leucospermum conocarpodendron (L.) Buek (Proteaceae) seedlings were excavated several months after a fire in Cape fynbos. Seedlings under burnt parental skeletons had short hypocotyls (mean 25 mm) indicating passive dispersal whereas seedlings in the open were more deeply buried (mean 48 mm) by ants. Soil nutrient concentrations at the site of germination were negatively related to depth of burial and distance from parent. Ant dispersal resulted in seedlings emerging in soils with lower nutrient concentrations than passively dispersed seeds. Tissue analysis supported the soil results with lower P content in seedlings from open (ant dispersed) sites. Seedling survival in the first year of establishment was also lower in open sites, but not significantly so. However seedlings were slightly taller in the open. The results of this study, the first on naturally occurring intraspecific variation in myrmecochory, strongly contradict current explanations for the high incidence of myrmecochory in nutrient poor environments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00377092
    Standort Signatur Erwartet Verfügbarkeit
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  • 12
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of 6-thiouric acid and 6-mercaptopurine in renal allograft recipients after oral administration of azathioprine (1989)
    Springer
    European journal of clinical pharmacology 36 (1989), S. 265-271 
    Details
    ISSN: 1432-1041
    Schlagwort(e): azathioprine ; 6-thiouric acid ; 6-mercaptopurine ; renal transplantation ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The immunosuppressive activity of azathioprine (AZA) is unpredictable and depends on the formation of intracellular thiopurine ribonucleotides. However, the quantification of these active thiopurines presents difficult analytical problems. It has recently been postulated that plasma concentrations of 6-thiouric acid (6-TU) and 6-mercaptopurine (6-MP), metabolites of AZA, may provide more readily measurable indices of the pharmacologic activity of AZA. In order to evaluate the utility of 6-TU and 6-MP plasma concentrations in monitoring AZA therapy, we studied their pharmacokinetics in 6 renal transplant patients, and their in vitro immunosuppressive potency in a mixed lymphocyte proliferation assay. A peak plasma 6-TU concentration of 710.7 ng/ml was observed at 3.8 h after oral dosing. Good correlation was observed between the elimination t1/2 of 6-TU and serum creatinine, and between AUC over 24 h and serum creatinine. However, we did not observe a second peak in plasma 6-TU concentration that could be attributed to the degradation of active AZA metabolites. 6-MP plasma concentrations in the patients were low (mean peak concentration 36.0 ng/ml) and rapidly disappeared within 8 h. In vitro immunosuppressive activity could not be demonstrated for 6-TU over a concentration range of 1.25 ng/ml to 0.25 mg/ml. We conclude that 6-TU is pharmacologically inert and is primarily eliminated by the kidneys. Our findings currently do not support the use of plasma concentrations of 6-TU or 6-MP to monitor AZA therapy. In order to optimize AZA therapy, analytical techniques that are technically feasible and that can directly quantify the active intracellular thiopurines are being explored.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00558158
    Standort Signatur Erwartet Verfügbarkeit
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  • 13
    Digitale Medien
    Digitale Medien
    A comparative study of respirable particulate microenvironmental concentrations and personal exposures (1988)
    Springer
    Environmental monitoring and assessment 10 (1988), S. 105-122 
    Details
    ISSN: 1573-2959
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Personal monitoring (PM) for respirable suspended particulate matter (RSP) of thirty subjects was performed as part of an air pollution health effects study conducted in Houston, Texas. Parallel RSP measurements were performed in the study subjects' homes and two fixed site monitoring stations. The participants' daytime activities were independently recorded by study techicians. These data were used to characterize RSP concentrations in each microenvironment visited by the participants. Four estimates of daytime exposure to RSP were calculated based on two different microenvironmental models, and home and fixed site mean daytime RSP concentrations. These estimates were compared to mean daytime personal exposure from PM. Hourly estimates of exposure were calculated from a microenvironmental model and mean hourly home RSP concentrations and compared to hourly PM data. The results of the study indicate that, as in the case of NO2, it is important to characterize indoor microenvironmental RSP concentrations according to location, sources, and concurrent activities, both qualitatively and quantitatively. Stratification of concentrations according to sources present and self-reported activity can lead to misclassification of exposures. For RSP and, probably, other pollutants with indoor sources and with short exposure integration times, adequate measures of exposure can only be obtained with very detailed and complex microenvironmental models or comprehensive personal monitoring.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00401776
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  • 14
    Digitale Medien
    Digitale Medien
    Whither brown fat? (1986)
    Springer
    Bioscience reports 6 (1986), S. 3-18 
    Details
    ISSN: 1573-4935
    Schlagwort(e): brown adipose tissue ; thermogenesis ; cold ; diet ; neural control ; hormonal control
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01145174
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  • 15
    Digitale Medien
    Digitale Medien
    Effect of a selectiveβ 2-adrenergic agonist (Cenbuterol) on energy balance and body composition in normal and protein deficient rats (1987)
    Springer
    Bioscience reports 7 (1987), S. 933-940 
    Details
    ISSN: 1573-4935
    Schlagwort(e): body composition ; protein deficiency ; adrenergic agonists
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract In rats fed a normal (22% protein) diet, injection of clenbuterol (1 mg/kg/d for 21 d) did not affect energy intake, energy expenditure or weight gain, but reduced energetic efficiency, and fat and energy gains and increased body protein content. Presenting a low-protein (8%) diet reduced energy intake, gain and efficiency, body protein content and the mass of the gastrocnemius muscle when compared to rats fed the control diet. Injection of the protein-deficient rats with clenbuterol (1 mg/kg/d for 21 d) caused hypophagia and reduced body weight and energy gains, energy expenditure and total body fat. However, the total body content of protein was not significantly reduced and the percentage of body protein in this protein deficient, clenbuterol-treated group was greater than that of untreated rats on both the high- and low-protein diets. The ratio of body protein to fat following clenbuterol treatment was increased by over 50% in both normal and protein-deficient rats. The results show that in protein deficient animals, clenbuterol treatment may help conserve body protein at the expense of fat, resulting in a smaller, but leaner body mass.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01122126
    Standort Signatur Erwartet Verfügbarkeit
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  • 16
    Digitale Medien
    Digitale Medien
    Book reviews (1985)
    Springer
    Chromatographia 20 (1985), S. 499-500 
    Details
    ISSN: 1612-1112
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02344793
    Standort Signatur Erwartet Verfügbarkeit
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  • 17
    Digitale Medien
    Digitale Medien
    Mofification of body composition by clenbuterol in normal and dystrophic (mdx) mice (1985)
    Springer
    Bioscience reports 5 (1985), S. 755-760 
    Details
    ISSN: 1573-4935
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Female dystrophic mice (mdx on C57 Black background) gained weight more rapidly than age-matched controls and had a higher body fat content (% body weight), a slightly lower protein content and a reduced mass of muscle. Chronic treatment (21 d) of the mice with theβ 2-agonist clenbuterol stimulated weight gain in both genotypes without affecting energy intake. Clenbuterol increased the mass of the gastrocnemius and soleus muscle by 13% and 29% in normal and dystrophic mice, respectively, and raised body protein but depressed body fat. Body water and energy content were unaffected by clenbuterol, but the ratio of protein to fat in the carcasses was enhanced by 17% in normal and 56% in dystrophic mice following clenbuterol treatment. Thus, theβ 2-agonist restored the body composition of dystrophic mice to normal and enhanced the protein to fat ratio in both these and normal mice.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01119873
    Standort Signatur Erwartet Verfügbarkeit
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  • 18
    Digitale Medien
    Digitale Medien
    Changes in thermogenesis and brown fat activity in response to tumour necrosis factor in the rat (1987)
    Springer
    Bioscience reports 7 (1987), S. 791-799 
    Details
    ISSN: 1573-4935
    Schlagwort(e): tumour necrosing factor ; brown fat ; thermogenesis ; GDP-binding ; food intake ; body weight ; rats
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract A single intravenous injection of recombinant human tumour necrosis factor (TNF) resulted in significant, but transient (24–48 hr) reductions in food intake and body weight, and increases in rectal temperature, resting oxygen consumption (VO2) and brown adipose tissue (BAT) thermogenic activity (mitochondrial GDP-binding). The increased VO2 was inhibited by β-adrenergic blockade (propranolol), and activation of BAT was prevented by denervation of the tissue. In adult (4-month old) animals, TNF induced greater reductions in food intake and body weight, caused general malaise and some fatalities, but did not significantly alter VO2 or BAT activity. However, the reduction in VO2 following β-adrenergic blockade was greater in TNF-treated rats and BAT activity was enhanced when compared to pair-fed controls. Injection of adult rats with gamma-interferon induced small changes in body weight and temperature which were slightly potentiated when injected with a low dose of TNF. The results indicate that TNF stimulates sympathetic outflow to BAT. This effect may be partly responsible for the increases in body temperature and metabolic rate associated with TNF treatment and with cancer cachexia.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01116752
    Standort Signatur Erwartet Verfügbarkeit
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  • 19
    Digitale Medien
    Digitale Medien
    Electrophilic aromatic substitution on poly-(4-N,N-dimethylaminostyrene-co-styrene) copolymers (1989)
    Springer
    Polymer bulletin 21 (1989), S. 319-326 
    Details
    ISSN: 1436-2449
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Summary Poly-[-4-(N,N-dimethylamino)styrene and its copolymers are prepared by standard radical polymerization proceeding and modified using 4-phenyl-1, 2,4-triazoline-3,5-dione (PTD). From IR- and NMR-spectroscopy and the intrinsic viscosity [η] it can be deduced that hydrogen bonds mainly are formed between the dimethylamino group and the proton of the urazole ring, contrary to the formation of dimeric hydrogen bond complexes in modified polydienes. The basicity of the dimethylamino group is too small to abstract the urazole proton completely, which would generate a zwitterionic species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00955925
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  • 20
    Digitale Medien
    Digitale Medien
    Soil nitrogen mineralization in a coastal fynbos succession (1988)
    Springer
    Plant and soil 106 (1988), S. 295-298 
    Details
    ISSN: 1573-5036
    Schlagwort(e): fynbos ; fire ; mineralization ; nitrification ; succession
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Patterns of net nitrogen mineralization and nitrification in 0–7.5 cm deep mineral soils of different stages (seral ages 1, 6 and 20 years) of a post-fire coastal fynbos succession were assayed using laboratory andin situ incubations. No evidence of increasing allelopathic inhibition of nitrification with successional development was found as NO3−N was the predominant product at all seral stages and the NO3−N∶NH4−N ratio remained constant. Rather the results of field incubations of soils beneathProtea repens stands of different successional ages showed that increased mineralization and nitrification appeared to be associated with increased soil total N content rather than with successional age. Further, the incubation of soilsin situ during the dry summer months showed that NO3−N production appears to be closely related to temperature and soil moisture content, both of which are variables that vary throughout succession due to the changing structure of the vegetation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02371229
    Standort Signatur Erwartet Verfügbarkeit
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