Browsing by Subject "Diurnaler Rhythmus"

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Abgabe von bodenbürtigem Lachgas über Pflanzen
(2003) Ferch, Norbert-Jakob; Römheld, Volker
The aim of this work was to explore and to rank the different ways and forms of transition of N2O through plants (dissolved in water and transported with the transpiration or gaseous through aerenchyma). To achieve this goal an experimental set-up had to be realized that allowed the determination of possible N2O emissions by plants, the determination of different ways of transition of N2O through the plant and the determination of different influencing factors (e.g. N2O concentration) on the N2O emissions. In the beginning experiments with closed chambers and with ?controlled opened chambers? were conducted in comparison to each other. In the experiments with closed chambers samples were drawn by means of molecular sieves and vacutainers. N2O concentrations of the samples were measured with a GC (gas chromatograph type HP 5890) equipped with an ECD (electron capture detector). Besides the two methods mentioned above in order to determine the N2O concentrations within the experiments with the ?controlled opened chambers? a third method was used for N2O measurement by means of a photo acoustic online measuring machine. The accuracy of the photo acoustic measurement was evaluated with the GC. For the questions of interest the photo acoustic measurement showed to be the best to determine differences of N2O emissions between different experimental treatments. The experiments that were taken in consideration were conducted in a ?controlled opened system? because in closed chambers CO2 concentration decreased rapidly. Additionally, the air in the closed chambers became saturated in water vapour within a few minutes. These two factors lead to inhibited growth of the plants and to undesired influences on the N2O measurements. The ?controlled opened system? consisted of a root and a shoot compartment. Both compartments were separated airtight from each other and from the surroundings. The root compartments were enriched with a definite amount of N2O. The N2O concentrations measured in the shoot compartments of the systems with N2O enrichment in the root compartment were compared with measurements of systems without N2O enrichment and measurements of ambient air. The necessity to divide the root compartment from the shoot compartment airtight was realised with a material on the basis of silicone that is usually used to make prints of teeth (Optosil, from Haereus) and a sealing mass (Prestik AE hellgrau, from Bostik GmbH). To determine the different factors potentially influencing the N2O emission through plants a hydroponical culture system was established that allowed controlling the following factors: concentration of nutrients, pH-factor, concentration of different water soluble gases (e. g. N2O, CO2) and the ratio between water and gas filled space in the root compartment. As experimental plants sunflower (Helianthus annuus cv. Frankasol), barley (Hordeum vulgare cv. Scarlet), rice (Oryza sativa cv. 94D-22) and corn (Zea mays cv. Helix) were used. For the experiment with sunflower (no aerenchyma, N2O dissolved in water available only) a relationship between N2O concentration in the root compartment, the emitted amount of N2O by the shoots and the intensity of transpiration in a diurnal pattern was found. In systems with gaseous availability of N2O in the root compartment the observed emissions were higher than in systems with availability of N2O dissolved only in water. From this it could be concluded, that gaseous N2O is better available for plants than N2O dissolved in water. Similar results were obtained from experiments with barley. The only difference was that the highest N2O emissions were observed in systems with availability of N2O dissolved in water only. The possible N2O emission through aerenchyma was checked with rice plants. In these experiments a pronounced diurnal pattern of the N2O emissions was also found. This lead to the conclusion that aerenchyma only have a small influence on the N2O emissions out of the root compartment through rice plants. Because the N2O emission in the three experiments described above followed the diurnal pattern of the transpiration, it was concluded that N2O was transported with the transpiration water flow from the root (compartment) to the shoot (compartment). The experiments with corn showed for all treatments (control and availability of N2O in gaseous form or dissolved in water) a net N2O depletion in the shoot compartment for night (darkness) and day (light) respectively, thus leading to the conclusion that N2O can be metabolised and used as a nitrogen source. All in all the experiments showed that the main way of transition of N2O through plants is water dissolved with the transpiration water flow and not gaseous (through aerenchyma).
Diurnal and photoperiodic effects on the immune system and glucocorticoid signaling in domestic pigs
(2019) Engert, Larissa; Stefanski, Volker
Physiology and behavior of humans and animals display pronounced diurnal and seasonal rhythmic variations. Diurnal rhythms are controlled by daylight and seasonal rhythms are adjusted by the photoperiod, i.e., the relative span of light per day. Modern human life and housing conditions of livestock are often directed against natural daylight conditions and thus, may entail circadian disruption causing misalignment between the central circadian pacemaker and peripheral tissues. Thereby, glucocorticoids are regarded as a main link between these compartments. Circadian disruption might be detrimental for health, in particular affecting immune function, which was mainly investigated in humans and nocturnal rodents but underlying mechanisms are not clearly defined yet. Therefore, the main objective of the present thesis was to investigate diurnal and photoperiodic effects on the immune system and glucocorticoid signaling as well as potential underlying endocrine, behavioral, and molecular mechanisms of these effects in domestic pigs. Adult male castrated pigs, held under specific lighting schedules, were surgically catheterized to enable blood collection without disturbance of the animals. Initially, domestic pigs were held under standard 12L:12D-lighting conditions and blood samples were taken every 2 hours over periods of up to 50 hours. Cosinor analyses revealed pronounced diurnal rhythmicity in peripheral leukocyte numbers of various immune cell populations. These rhythms were mainly comparable to results in humans and nocturnal rodents in relation to their respective rest-activity cycles, with the exception of porcine neutrophils differing from both species. Moreover, the investigated diurnal rhythms in activity behavior and plasma cortisol concentration confirmed that domestic pigs under the applied experimental conditions are diurnally active like humans. Linear mixed model analyses revealed associations of immune cell counts with plasma cortisol concentration, which also resembles results from humans and rodents. Subsequently, photoperiodic effects on diurnal rhythms in peripheral immune cell numbers were investigated for the first time in any species. Domestic pigs were held either under long day conditions (LD) or under short day conditions (SD) and were sampled every 2 hours over periods of 50 hours. Distinct photoperiodic differences in relative amplitudes and peak times of cell counts in various porcine leukocyte types were found, whereas mesor values did not differ. Moreover, photoperiodic effects on diurnal rhythms in plasma cortisol concentrations and activity behavior were found, which is in agreement with human and primate studies. Generalized linear mixed model analyses again revealed associations of leukocyte counts with plasma cortisol concentration and with activity behavior as well. In summary, the results imply stronger rhythmicity of peripheral immune cell numbers in general under SD than under LD. Common intrinsic mechanisms seem to regulate diurnal rhythms in peripheral leukocyte numbers in most immune cell types in domestic pigs, except for neutrophils again. Finally, to investigate potential molecular differences in diurnal regulation between different immune cell types, glucocorticoid receptor (GR) number and affinity were examined in peripheral blood mononuclear cells (PBMC) and granulocytes of domestic pigs. Thereby, a greater number of GR sites per cell and a higher GR binding affinity in PBMC compared to granulocytes were found, pointing to differences in the molecular mechanisms of glucocorticoid signaling between leukocyte populations. The results of the present thesis project are subsequently discussed in regard to specific implications for immune function and health as well as animal husbandry and welfare. Moreover, a methodological assessment of the approaches used within the thesis project was carried out and finally, suggestions for future research directions were given. In conclusion, the present thesis revealed for the first time diurnal and photoperiodic effects on the immune system as well as glucocorticoid signaling in domestic pigs and uncovered potential underlying mechanisms of these effects. Hence, an additional diurnally active model species in chronoimmunology research was established. Moreover, conducting chronoimmunology research in the porcine species represents an innovative approach in agricultural science and provides entirely new opportunities to improve animal health and welfare. Thereby, future studies might investigate diurnal differences in immune function, clarify the role of different zeitgebers on immune rhythms, and assess potential consequences of stressor exposure at different times of the day.