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  • Springer  (138)
  • Elsevier  (72)
  • American Chemical Society (ACS)
  • American Meteorological Society (AMS)
  • 1990-1994  (119)
  • 1980-1984  (91)
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  • 11
    Electronic Resource
    Electronic Resource
    Density dependent interactions between VA mycorrhizal fungi and even-aged seedlings of two perennial Fabaceae species (1992)
    Springer
    Oecologia 91 (1992), S. 281-287 
    Details
    ISSN: 1432-1939
    Keywords: Vesicular-arbuscular mycorrhizas ; Densitydependence ; Plant population dynamics ; Resource depletion ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The interaction of density and mycorrhizal effects on the growth, mineral nutrition and size distribution of seedlings of two perennial members of the Fabaceae was investigated in pot culture. Seedlings of Otholobium hirtum and Aspalathus linearis were grown at densities of 1, 4, 8 and 16 plants per 13-cm pot with or without vesicular-arbuscular (VA) mycorrhizal inoculum for 120 days. Plant mass, relative growth rates, height and leaf number all decreased with increasing plant density. This was ascribed to the decreasing availability of phosphorus per plant as density increased. O. hirtum was highly dependent on mycorrhizas for P uptake but both mycorrhizal and non-mycorrhizal A. linearis seedlings were able to extract soil P with equal ease. Plant size distribution as measured by the coefficient of variation (CV) of shoot mass was greater at higher densities. CVs of mycorrhizal O. hirtum plants were higher than those of non-mycorrhizal plants. CVs of the facultatively mycorrhizal A. linearis were similar for both mycorrhizal and non-mycorrhizal plants. Higher CVs are attributed to resource preemption by larger individuals. Individuals in populations with high CVs will probably survive stress which would result in the extinction of populations with low CVs. Mass of mycorrhizal plants of both species decreased more rapidly with increasing density than did non-mycorrhizal plant mass. It is concluded that the cost of being mycorrhizal increases as plant density increases, while the benefit decreases. The results suggest that mycorrhizas will influence density-dependent population processes of faculative and obligate mycorrhizal species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317797
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  • 12
    Electronic Resource
    Electronic Resource
    Regrowth and tannin production in woody and succulent karoo shrubs in response to simulated browsing (1993)
    Springer
    Oecologia 96 (1993), S. 562-568 
    Details
    ISSN: 1432-1939
    Keywords: Induced defence ; Clipping ; Semi-arid shrubs ; Herbivore-deterrents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Allocation of carbon to chemical defences has often been suggested to be a direct response to browsing or grazing by herbivores. This study quantitatively compares total polyphenol and tannin production in response to simulated browsing of three karoo shrubs in order to test this induced defence hypothesis. The three species studied responded to browsing either by rapid regrowth or by increasing polyphenol production in the remaining tissues. The patterns did not follow any phylogenetic relationships but were weakly associated with the palatability of each species. The highly palatable deciduous species Osteospermum sinuatum, which is capable of rapid regrowth, showed no or very low levels of constitutive and browsing-induced total polyphenols, condensed tannins and protein-precipitating tannins. The evergreen sclerophyllous species Pteronia pallens showed a limited regrowth capacity and had intermediate levels of polyphenols, while the evergreen succulent species Ruschia spinosa showed almost no regrowth over the study period. R. spinosa contained the highest constitutive and browsing-induced levels of polyphenols, condensed tannins and protein-precipitating tannins. In two of the species more than one anti-herbivore defence feature co-occur. P. pallens foliage contains both hepatotoxins and polyphenols while R. spinosa has both structural (spines) and chemical defences. Responses of karoo shrubs to simulated browsing are interpreted as the result of passive alterations in plant chemistry rather than as an active defence response to herbivores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00320514
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  • 13
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of S(+)- and R(−)-ibuprofen in volunteers and first clinical experience of S(+)-ibuprofen in rheumatoid arthritis (1990)
    Springer
    European journal of clinical pharmacology 38 (1990), S. 493-497 
    Details
    ISSN: 1432-1041
    Keywords: ibuprofen ; rheumatoid arthritis ; enantiomer ; stereoselectivity ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary S(+)-, R(−)- or racemic ibuprofen was administered orally to volunteers in doses of 150 mg, 300 mg and 500 mg pure S(+)-, 300 mg pure R(−)- and 600 mg racemic ibuprofen. The pharmacokinetic parameters in humans showed that S(+)-ibuprofen was not inverted to R(−)-ibuprofen, whereas R(−)-ibuprofen was inverted to S(+)-ibuprofen to a variable degree. S(+)-ibuprofen and R(−)-ibuprofen given alone more rapidly reached significantly higher maximal plasma concentrations than after the same doses of the racemic compound. The elimination half-lives and clearance values for all three forms of ibuprofen were comparable. The mean residence time of S(+)-ibuprofen after R(−)- and racemic ibuprofen was significantly longer than after administration of the pure S(+)-enantiomer. Judged by the AUC, the bioavailability of S(+)-ibuprofen was independent of the dose within the range tested. Administration of S(+)-ibuprofen to 6 rheumatic patients showed that the pharmacokinetic behaviour of S(+)-ibuprofen in patients was similar to that found in volunteers. S(+)-ibuprofen proved to be an effective analgesic antirheumatic drug in the dose range 1 to 1.5 g/day.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02336690
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  • 14
    Electronic Resource
    Electronic Resource
    Physiological aspects of glyphosate degradation in Alcaligenes spec. strain GL (1990)
    Springer
    Archives of microbiology 153 (1990), S. 146-150 
    Details
    ISSN: 1432-072X
    Keywords: Alcaligenes spec. GL ; Phosphonate metabolism ; Glyphosate ; Sarcosine ; Phosphate starvation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Alcaligenes spec. strain GL (IMET 11314) is able to grow on glyphosate (N-[phosphonomethyl]glycine) and other phosphonates as sole source of phosphorus. Degradation of glyphosate to inorganic phosphate and sarcosine by this strain is subject to several regulatory principles. While uptake and dephosphonation of glyphosate are regulated by Pi starvation, the intensity of glyphosate degradation is also controlled by the cellular ability to utilize the C-skeleton derived from glyphosate. Depending on the external concentration of glyphosate, the liberated sarcosine is differentially metabolised. Utilization of the sarcosine moiety and complete incorporation of 3-[14C]-label of glyphosate into cellular material occur only in cultures adapted to higher concentrations (5 mM) of the herbicide. At low concentrations of glyphosate (1 mM) only the Pi required by the growing cultures is utilized but not the sarcosine. Initially high rates of glyphosate uptake obtained after Pi-starvation decrease in the presence of low glyphosate concentrations. It is suggested that uptake and metabolism of glyphosate are connected with the expression of the sarcosine metabolizing capacity of the Alcaligenes cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00247812
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  • 15
    Electronic Resource
    Electronic Resource
    Rat major histocompatibility RT1.C antigens of restricted tissue distribution consist of two polypeptide chains with molecular weights of about 42 000 and 12 500 (1982)
    Springer
    Immunogenetics 15 (1982), S. 271-277 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The RT1.C region has recently been defined genetically as a third region of the rat major histocompatibility system, RT1, and has been shown to code for cell-surface antigens with restricted tissue distribution (present on lymphocytes and absent from red blood cells and liver) and for target antigens of unrestricted cytotoxic T lymphocytes. Immunoprecipitation with C-antigen-specific alioantisera and SDS-PAGE analysis, reveal that C-region products are glycoproteins composed of molecules of 40 500–43 000 and 12 500 molecular weight, respectively. Thus, the RT1.B region, which codes for class II molecules, is flanked by RT1 regions which determine class I molecules (as defined biochemically), which are either expressed ubiquitously (RT1.A antigens) or in a restricted manner (RT1.C products). The homology to H-2Qa antigens is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00364335
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  • 16
    Electronic Resource
    Electronic Resource
    Internal structure rebuilding reactions of crystalline and amorphous solids (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 131-139 
    Details
    ISSN: 1572-8943
    Keywords: amorphous solids ; crystalline ; structural mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es werden Strukturmechanismen von internen thermischen Reaktionen von Dehydratation und Dehydroxylierung sowie der Kristallisierung der entstehenden amorphen Reaktionsprodukte betrachtet. Dabei handelt es sich um mehrstufige Prozesse, die über kleine translative Verschiebungen von polimerisierten Elementen des Anionennetzwerkes und durch Diffusionsverschiebung von Kationen ablaufen. Dies ist der Weg zum Gleichgewichtszustand mit dem geringsten Energieverbrauch und der niedrigsten, zu überwindenden Energiebarriere.
    Notes: Abstract Structural mechanism of the internal thermal reactions of dehydration and dehydroxylation as of solids well as crystallization of their amorphous products and glasses are considered. They are multi-stage processes, realized through small translative displacements of polymerized anion network elements and diffusional shift of cations. It is the way to equilibrium state of the lowest energy consumption and the least energetic barrier to overcome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02109113
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  • 17
    Electronic Resource
    Electronic Resource
    Explosive thermal dehydration of solids (1991)
    Springer
    Journal of thermal analysis and calorimetry 37 (1991), S. 1415-1429 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es werden ausgewählte Beispiele für die Dehydratation, begleitet von heftiger Zersetzung oder Aufblähen der zersetzten Feststoffe dargelegt. Diese Erscheinung wird als ein Spezialfall der internen Zersetzung von Feststoffen beschrieben. Als Modell für diesen Prozeß wird ein abgeschlossener Behälter mit unter Druck stehenden gasförmigen Produkten vorgeschlagen. Praktische Anwendungen dieser Erscheinung werden diskutiert.
    Notes: Abstract Selected examples of dehydration, accompanied by violent disintegration or bloating of the decomposing solid substance are presented. This phenomenon has been explained as a specific case of internal decomposition of solids. A sealed box with compressed gaseous products is proposed as a model of the process. The practical applications of this phenomenon are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01913478
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  • 18
    Electronic Resource
    Electronic Resource
    Protein synthesis in liver, skeletal muscle, and brown adipose tissue of rats fed a protein-deficient diet (1983)
    Springer
    Bioscience reports 3 (1983), S. 569-575 
    Details
    ISSN: 1573-4935
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Feeding protein-deficient diets to rats is known to stimulate diet-induced thermogenesis and activate brown adipose tissue (BAT). The fact that BAT protein content, unlike that of other tissues, is unnaffected by protein deficiency prompted us to measure tissue protein synthesis in vivo in animals maintained on normal- (18.8%) and low- (7.6%) protein (LP) diets. Protein synthesis was depressed in the liver of the LP rats due to a fall in RNA activity, with no change in RNA content, and synthesis was also reduced in skeletal muscle from the LP group, but this was due to decreased RNA c o n t e n t with no change in RNA activity. Conversely, protein synthesis, RNA, DNA, and protein content of interscapular BAT were all unaltered in protein-restricted animals. These data indicate that, unlike liver, skeletal muscle, and whole carcass, BAT protein synthesis is not reduced in protein-restricted rats, and this may be related to activation of thermo-genesis in the tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01120702
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  • 19
    Electronic Resource
    Electronic Resource
    Identification of two mitochondrial GDP-binding sites in rat brown adipose tissue (1983)
    Springer
    Bioscience reports 3 (1983), S. 589-598 
    Details
    ISSN: 1573-4935
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Scatchard analysis of specific guanosine-diphosphate-([3H]GDP-) binding to rat brown-adipose-tissue mitochondria revealed two distinct binding sites with apparent dissociation constants (Kd) of approximately 0.05 and 2.0 μM. Binding to both sites was insensitive to atractyloside. Reducing the pH of the binding medium from 7.1 to 6.6 caused marked reductions in the Kd of both sites, but at pH 7.6, the dissociation constants were increased about 3-fold. Acute treatment of rats with noradrenaline, 1 h before sacrifice, increased the maximum number of binding sites (Bmax, pmol/rng mitochondrial protein) of both sites and also increased the dissociation constants. The Bmax of the lower-affinity site was elevated in rats exposed to 5°C or fed a palatable cafeteria diet for 10 d, compared to control animals, with the greater changes occurring in the cold-adapted group. The high-affinity site was unaltered by cold adaptation or cafeteria feeding. These results indicate the presence of two distinct nucleotide-binding sites in brown-fat mitochondria, both of which may be involved in thermogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01172869
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  • 20
    Electronic Resource
    Electronic Resource
    Sympathetic activation of brown-adipose-tissue thermogenesis in cachexia (1981)
    Springer
    Bioscience reports 1 (1981), S. 509-517 
    Details
    ISSN: 1573-4935
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Tumour-bearing mice spontaneously lose weight 8–9 weeks after implantation of a human hypernephroma, in spite of a normal food intake. Resting oxygen consumption was up to 40% higher in these animals than in sham-operated controls, but was significantly reduced by 8-adrenergic blockade with propranolol in the former group. The injection of noradrenaline caused a marked stimulation of the metabolic rate in all the animals, but the greatest response was seen in the cachectic mice. The brown-adipose-tissue mass was similar for both groups, but guanosine diphosphate binding to brownadipose-tissue mitochondria (an index of thermogenic capacity) was significantly increased in turnout-bearing mice, and the injection of noradrenaline 1 h prior to sacrifice caused the greatest stimulation of binding in the cachectic group. These data suggest that the rapid weight loss of tumour-bearing animals may be due to a high metabolic rate which results from sympathetic stimulation of brown-adipose-tissue metabolism. The relevance of these results to cancer-induced cachexia in man is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01121584
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