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  • 1
    Electronic Resource
    Electronic Resource
    Physiology The ACE gene and muscle performance (2000)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 403 (2000), S. 614-614 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Angiotensin-converting enzyme in human skeletal muscle can be encoded by either of two variants of the ACE gene, one of which carries an insertion of 287 base pairs. This longer allele gives rise to lower enzyme activity, and is associated with enhanced endurance performance and an anabolic ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35001141
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrogen Production by Rumen Holotrich Protozoa: Effects of Oxygen and Implications for Metabolic Control by In Situ Conditions (1989)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 36 (1989), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Experiments with washed suspensions of holotrich protozoa (Isotricha spp. and Dasytricha ruminantium) showed that both organisms have an efficient 0,-scavenging capability (apparent Km values 2.3 and 0.3 μM, respectively). Reversible inhibition of H2, production increased almost linearly with increasing O2 up to 1.5 μM; higher levels of O2 gave irreversible inhibition. In situ determinations of H, CH4, O2, and CO2, in ovine rumen liquor, using a membrane inlet mass spectrometer probe, indicated that O2, was present before feeding at 1-1.5 μM and decreased to undetectable levels (〈0.25 μM) within 25 min after feeding. A transient increase in O2. concentration after feeding occurred only in defaunated animals and resulted in suppression of CH4 and CO2 production. The presence of washed holotrich protozoa decreases the O2 sensitivity of CH4 production by suspensions of a cultured methanogenic bacterium Methanosarcina barkeri. It is concluded that holotrich protozoa play a role in ruminal O2 utilization as well as in the production of fermentation end products (especially short-chain volatile fatty acids) utilized by the ruminant and H, utilized by methanogenic bacteria. These hydrogenosome-containing protozoa thus both control patterns of fermentation by influencing O2 levels, and are themselves regulated by the low ambient O2 concentrations they experience in the rumen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1989.tb01075.x
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  • 3
    Electronic Resource
    Electronic Resource
    Exocellular Carbohydrase Formation by Rumen Holotrich Ciliates (1979)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 26 (1979), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS Exocellular carbohydrase activity was detected, in the absence of cell lysis, in cell-free culture supernatant fluids of rumen holotrich ciliates after incubations in buffer systems of varying tonicity, from cell suspensions that were isolated by various technics, and in which bacterial activity had been suppressed by antibiotics. The kinetic characteristics of the holotrich invertases and β–glucosidase from Dasytricha, although having interspecies variations, were the same for the intra- and extracellular form of the enzyme. The properties of the invertase activity present in cell-free rumen contents resembled those of the exocellular enzymes formed by the holotrichs. Invertase activity in the in vitro culture supernatant fluid of Dasytricha ruminantium increased throughout the incubation period and was influenced by the initial pH, temperature, sucrose concentration, and inoculum size. Exocellular holotrich carbohydrase activity was increased when the incubation substrate was not readily utilized by the protozoa. Intracellular carbohydrase activity was also influenced by the carbohydrate substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1979.tb04217.x
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  • 4
    Electronic Resource
    Electronic Resource
    A mathematical model of the aerobic deterioration of silage (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 50 (1995), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A mathematical model of the aerobic deterioration of silage is described that includes the physical processes of gas and heat Rows, as well as an established model of microbial growth and the associated chemical changes. Yeasts and acetic acid bacteria are included in the growth model. The version of the model described relates to a cylinder of silage subject to forced aeration, a common experimental configuration. The model was very sensitive to variations in insulation thickness and yeast growth rate, and to initial pH, especially when maize was the forage. Great care is needed when selecting input data for use in the model to be sure that the physical and chemical properties are accurate. The model solution was sensitive to grid size, but with 361 cells, the maximum grid resolution that could be used on a 486 series PC, solutions were achieved with an acceptably small loss of accuracy. The model predicted the results of an experiment on silage deterioration quite accurately. However, the model also predicted that considerable spatial gradients of parameters, such as temperature, pH, and lactic acid, would occur. This indicates the need for care when taking samples or making temperature measurements in deterioration experiments. The model is potentially a useful tool in predicting the optimal time and position to take samples for analysis in a time-course experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.1995.tb02306.x
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of oxygen concentration on changes in the microbial population, temperature and dry-matter content in grass silage (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 49 (1994), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of transfusing cores of grass silage with mixtures of oxygen and nitrogen containing 0%, 0·2%, 2%, 5% and 20% oxygen were investigated. Changes in populations of yeasts, lactobacilli and streptococci were measured and the relationship between populations after 7 days' transfusion and oxygen concentration were tested against the predictions of two models, based on Monod and logistic growth functions. Yeasts were related to oxygen by the Monod model, while lactobacilli and streptococci were related by the logistic model. The differences were ascribed to yeasts initiating deterioration by growing aerobically, while lactobacilli and streptococci grew fermentatively once the environment had changed following yeast growth. Dry-matter losses were related to oxygen by the Monod model. Changes in temperature were related to dry matter loss (through measurements of CO2 evolution) using a simple heat balance model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.1994.tb01991.x
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  • 6
    Electronic Resource
    Electronic Resource
    A comparison of the ensilage, in an anaerobic cabinet, of grass, either fresh or when thawed after deep freezing (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 50 (1995), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The suitability of freezing a large amount of grass from a single harvest for use in a series of experiments to investigate silage fermentation and its manipulation was examined. Perennial ryegrass, harvested in late June, was ensiled in sterile polythene bags inside an anaerobic cabinet; some was also stored frozen at -20°C for up to nine months before ensiling in a similar manner. The course of fermentation was followed using not only conventional chemical and microbiological analyses, but also by measuring microbial metabolic activity in vitro. Freezing and thawing affected the chemical composition and the microbial populations on the grass, and there were differences in the changes occurring in thawed grass during ensilage, probably related to damage to plant cells and impaired microbial activity associated with freezing and thawing. For both the grasses and the silages made from them, it was clear that the number of microorganisms present was not a reliable guide to microbial metabolic activity. Although the fermentation of frozen-and-thawed grass did not simulate precisely the fermentation occurring with fresh grass, it is concluded that, when used judiciously, the ensilage of thawed grass can be a useful experimental tool, particularly in the initial screening of manipulants of fermentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.1995.tb02297.x
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  • 7
    Electronic Resource
    Electronic Resource
    The effects of pressure and stage of ensilage on the mechanical properties and effluent production potential of grass silage (1997)
    Oxford, UK : Blackwell Science Ltd
    Grass and forage science 52 (1997), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Direct-cut grass silage was ensiled without compression in laboratory silos for 0–75 d. On occasions during this period, the silage was subjected to creep compression tests at three pressure levels for a period of 5 h and effluent production was measured. Precision-chopped Italian ryegrass (Lolium multiflorum) was ensiled in the first experiment, whereas flail-harvested perennial ryegrass (Lolium perenne) was ensiled in the second. Pressure levels were 11·3, 16·9 and 22·5 kPa for Experiment 1 and 5·7, 11·3 and 16·9 kPa for Experiment 2. Moisture contents of the ensiled herbage were 815 and 856 g kg−1 for Experiments 1 and 2 respectively. The consolidation of the grass silage was described by a Burgers body model. Effluent production was more closely related to strain than to compressibility. Linear regression equations for the relationship between strain and effluent production are presented. There was a significant positive linear relationship between pressure and effluent production at each silo opening time in both experiments. The time course of effluent production was fitted to a negative exponential curve. The time that elapsed before effluent release in each experiment was a function of both pressure and time after ensilage. The results of the experiments were compared with the predictions of two models of effluent production. Reasonable agreement between predicted and actual effluent production could be obtained provided the measured material parameters were used and immediate saturation of the forage was assumed. Using the models highlighted the need for a better understanding of saturation development in the silage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2494.1997.00049.x
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  • 8
    Electronic Resource
    Electronic Resource
    The effects of temperature on the effluent production potential of grass silage (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 52 (1997), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of temperature on silage effluent production were examined. In the first experiment, samples of perennial ryegrass (Lolium perenne) underwent fermentation at 20°C for between 52 and 66 d. The samples were then transferred to rooms at temperatures between 5°C and 27°C. Effluent production during creep consolidation was measured. Increasing temperature resulted in a significant increase in effluent production. There was a strong linear relationship between the mechanical properties of the silage and the amount of effluent produced. In the second experiment, Italian ryegrass (Lolium multiflorum) samples were ensiled at temperatures between 5°C and 25°C. The higher temperature treatments had faster and more extensive fermentations, and produced more effluent than the cooler temperatures. Again, there was a strong linear relationship between the mechanical properties of the silage and the amount of effluent produced. Increasing the temperature at the end of the experiment resulted in no extra effluent production from any treatment except that at 5°C. This indicated that the effects of temperature were evident only while effluent was available for release. The effects of temperature will therefore be most evident in the early stages of ensilage. In both experiments, effluent was released from the higher temperature treatments earlier. This was probably due to the effects of temperature on the viscosity of the effluent and to fermentation effects in the second experiment. In both experiments, the increase in effluent production with temperature was equivalent to the effects to be expected from decreasing the herbage dry matter concentration by between 3% and 4%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.1997.tb02366.x
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  • 9
    Electronic Resource
    Electronic Resource
    Changes in temperature and silo gas composition during ensiling, storage and feeding-out grass silage (1997)
    Oxford, UK : Blackwell Science Ltd
    Grass and forage science 52 (1997), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: An experiment is reported in which two bunker silos were filled with about 12 t of ryegrass; one was compacted with a surface pressure of 4·1 kPa and the other was not. Both were instrumented to record temperatures and gas compositions during fermentation and feed-out. Cores of silage (100 mm diameter) were removed from the bunkers and subjected to forced aeration in insulated cylinders. Simple mathematical models were used to simulate CO2 leakage from the silos and the associated loss of dry matter, and temperature changes during the forced aeration of silage cores. The leakage of CO2 from the silos, as shown by the fall in CO2 concentration with time, could be described empirically by an exponential equation and could be simulated with a simple mathematical model. Experimental evidence supported the hypothesis that permeation was the main method of gaseous exchange during fermentation and feed-out, but gas mixing by diffusion and/or convection also occurred within the silos during fermentation. Dry-matter losses by aerobic activity during storage of 120–150 d were conservatively estimated to be about 0·3% and 0·9% for the uncompacted and compacted bunkers respectively. These were considered to be lower than those that could be expected in farm silos, because the sealing was likely to be more thorough. The silages were also more stable, when subject to aeration, than others examined in this laboratory, probably because of high contents of acetic, propionic and butyric acids. Simple mathematical models were of value, but greater sophistication is needed (e.g. multi-compartmental models) to deal comprehensively with the heat and gas flows found in the complex biophysical systems of silage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.1997.tb02348.x
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  • 10
    Electronic Resource
    Electronic Resource
    Multiple hotspots in extragalactic radio sources (1985)
    [s.l.] : Nature Publishing Group
    Nature 313 (1985), S. 34-36 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In the context of the now-accepted jet model of radio sources5,6, authors differ in their interpretation of where the jet first deposits its energy. Laing4 has suggested that the compact subcomponent is the current point of impact of the jet on the surrounding medium whereas the diffuse ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/313034a0
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