Univ., Diss. 2004--Lund, 2004. / Enth. 4 Beitr.

WHU Otto Beisheim School of Management, Diss.--Vallendar, 2006.

Univ., Diss--Bonn, 2008.

Recent research has suggested that individual specialization within populations could be substantial and more common than previously acknowledged. Eurasian perch is one of many species of fish in lakes of postglacial origin that displays a morphological and dietary variation tightly coupled to the littoral and pelagic habitats of the lake. The occurrence of such resource polymorphisms might have important consequences for local adaptation and might also be an important initial step in speciation. I have investigated the importance of a number of factors for the development of resource polymorphisms using perch as a study organism. I found a weak genetic basis for morphological differences, and the environmental influence on morphology was of such a magnitude that an induced morphology could be reversed. The results nevertheless suggested that genetic differentiation could be substantial at small spatial and temporal scales, even within habitats. Several environmental factors were shown to influence the morphological development, and the results also suggest that behavioral differences could mediate a morphological response. I also found evidence for that competition-driven divergence might only occur when divergence in resource use is favoured at the same time as growth rates are kept sufficiently high for character divergence to be effective. The results finally indicate that divergence in the gut length of individuals might co-vary with habitat and diet use in resource polymorphic populations. This might enhance habitat fidelity and possibly also facilitate the persistence of resource polymorphisms since individuals should experience a cost of switching diets due to a too specific digestive system. Based on these findings I conclude that small scaled genetic differentiation might be more common than currently acknowledged, that more multi-factorial studies are needed if we are to fully understand the mechanisms behind trait diversity, and that competition not always favors divergence.

Die Besiedlung des kindlichen Darms beginnt unmittelbar mit der Geburt. Hier findet der erste Kontakt mit verschiedensten Bakterien statt. Deshalb war die zentrale Fragestellung unserer Untersuchung, wie sich die Bakterienarten bei den Geburtsmodi unterscheiden und wie sich die bakterielle Zusammensetzung im Stuhl von Neugeborenen im Laufe der Jahre verändert hat. Wir untersuchten die Stuhlproben von 42 Neugeborenen, wovon 22 vaginal und 20 per Sectio entbunden wurden, am ersten, zweiten und dritten Lebenstag auf Bakterienwachstum. Es wurden die aufgetretenen Bakteriengattungen mittels Kultur bestimmt und von den aufgetretenen Staphylokokken und Enterokokken die Arten und deren Resistenzen mittels des Phönix-Vollautomaten untersucht. Wir konnten zeigen, dass im Gegensatz zu früheren Untersuchungen heutzutage vermehrt Staphylokokken den Darm von Neugeborenen besiedeln. Außerdem fiel auf, dass per Sectio entbundene Kinder eine verminderte Heterogenität in ihrer Stuhlflora haben und erst später besiedelt werden als vaginal entbundene Kinder.

From animal experimentation, and studies using in vitro models, there was evidence in the literature to suggest that dietary fibre may influence contractility and motility of the gastrointestinal tract and long chain (LC) n-3 polyunsaturated fatty acids (PUFAs) from marine sources may influence contractility of smooth muscle cells in blood vessels. The hypothesis of this thesis was that dietary fish oil and/or fibre influence the contractility of isolated intact sections of gut smooth muscle tissue from small animal models. Methodology was established to measure in vitro contractility of intact pieces of guinea pig ileum with the serosal side isolated from the lumen. It was demonstrated that four amino acid peptides from κ-casein (casoxins) applied to the lumen overcame morphine-induced inhibition of contraction. Using this established technology, the guinea pig was used to investigate the effects of dietary fibre and fish oil supplementation on gut in vitro contractility. In separate experiments, changes in sensitivity to electrically-driven and 8-iso-prostanglandin (PG)E₂-induced contractility were demonstrated for dietary fibre and fish oil. A modified, isolated gut super-perfusion system was then established for the rat to validate these findings. It was subsequently shown that LC n-3 PUFA from dietary fish oil significantly increased maximal contraction in response to the G-protein coupled receptor modulators, acetylcholine and the eicosanoids PGE₂, PGF₂α, 8-iso-PGE₂ and U-46619 in ileum but not colon, without changes in sensitivity (EC₅₀), when n-3 PUFA as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) had been incorporated to a similar degree into the gut total phospholipid membrane pool. It was further established that the spontaneously hypertensive rat (SHR) had a depressed prostanoid (PGE₂and PGF₂α) response in the gut that could be restored by dietary fish oil supplementation (5% w/w of total diet) in the ileum but not the colon. Importantly, the muscarinic response in the colon of the SHR was increased by fish oil supplementation with DHA likely to be the active agent. Dietary fish oil dose experiments deduced differential increases in response occurred at fish oil concentrations of 1% for muscarinic and 2.5% (w/w) for prostanoid stimulators of the ileum with no difference in receptor-independent KCl-induced depolarization-driven contractility. Studies combining high amylose resistant starch (HAMS, 10% w/w) and fish oil (10% w/w) fed to young rats demonstrated a low prostanoid response that was enhanced by dietary fish oil but not resistant starch. There was however, an interactive effect of the HAMS and fish oil noted for the muscarinic-mimetic, carbachol. Generally, resistant starch increased the large bowel short chain fatty acid pool with a subsequent lower pH. Binding studies determined that while the total muscarinic receptor binding properties of an isolated ileal membrane fraction were not affected in mature rats by dietary fish oil, young rats had a different order of muscarinic receptor subtype response with a rank order potency of M₃ > M₁ > M₂ compared to mature animals of M₃ > M₂ > M₁ with fish oil altering the sensitivity of the M₁ receptor subtype in isolated carbachol-precontracted ileal tissue. In conclusion, experiments using the guinea pig and rat gut models demonstrated that dietary fish oil supplementation, and to a lesser degree fibre, increased receptor-driven contractility in normal and compromised SHR ileum and colon. Further, changes in responsiveness were demonstrated in the developing rat gut prostanoid and muscarinic receptor populations that could be altered by dietary fish oil. Preliminary evidence suggested that fish oil as DHA may alter receptor-driven gut contractility by mechanisms involving smooth muscle calcium modulation. Defining the role that dietary fibre and fish oil, and other nutrients, play in normal and diseased states of bowel health such as inflammatory bowel disease (IBD), where contractility is compromised, are among the ongoing challenges. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1316907 / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2008

Universiẗat, Diss.--Frankfurt a.M., 2007. / Includes bibliographical references (p. 279-293).

Calif., Univ., Dep. of Economics, Diss.--Stanford, 2002. / Kopie, ersch. im Verl. UMI, Ann Arbor, Mich.

Calif., Univ. of California, Diss.--Los Angeles, 2002. / Kopie, ersch. im Verl. UMI, Ann Arbor, Mich. - Enth. 3 Beitr.

Univ., Diss.--Osnabrück, 1999.