Managing cattle to disseminate seeds of desirable plants, or alternatively, to restrict weed seed contamination on rangelands is of interest to managers. Four experiments were conducted to determine effects of ruminant digestion on germination of ingested seeds. A number of plant species representing a variety of seed size and seed coat hardness were subjected to in vitro digestion. Experiment one was conducted to determine effect of varying lengths of digestion time on seed germination. Seed germination varied by plant species in response to length of digestion. Germination of large soft-coated seeds, such as bluebunch wheatgrass (Agropyron spicatum (Pursh) Scribn. & Smith Goldar) and basin wildrye (Elymus cinereus Scribn & Merril Magnar), was reduced to 0%. Smaller grass seeds, such as Sherman big bluegrass (Poa secunda Presl. Sherman), survived but germination declined following 24-hour, 48-hour, and 72-hour digestion. Experiment two examined effect of different stages of ruminant digestion on seed germination. The combination of Stage I (rumen-simulated digestion) and Stage II (abomasal-simulated digestion) resulted in greatest seed mortality. Two water treatments were included to evaluate the effects of high temperatures (39��C), moisture uptake, and lack of oxygen. Water + O��� and Water + CO��� reduced germination, however not as much as Stage I and Stage II treatments. The third experiment determined effects of diet quality on seed germination. Seeds digested in rumen fluid collected from steers fed a 72% corn concentrate diet resulted in 0% germination for all species. Grass seed germination was low for seeds digested in rumen fluid collected from steers fed a forage diet. Whitetop (Cardaria draba (L.) Hand.) germination was 24% and 28% for 35-hour and 59-hour roughage treatment, respectively, and germination was 0% for 35-hour and 59-hour concentrate treatments. Germination of water-only treatments for most species was reduced in comparison to the control treatment, but was greater than remaining treatments. Experiment four evaluated germination of seeds exposed to in situ versus in vitro digestion. In situ digestion resulted in lower seed germination than in vitro digestion for all species examined. Large, soft grass seeds may not be suitable candidates for reseeding rangelands. However, it is important for managers to recognize that cattle may distribute viable weed seeds in feces. Confining cattle or supplementing with high concentrate diets may help prevent spread of weedy species. / Graduation date: 1997

This thesis explores the feasibility of using melanophore-based biosensors from Oreochromis niloticus. Melanophores are one type of pigmented cell of the scales and fins of fish that respond in a motile fashion to a diverse range of stimuli. Fish scales were employed as the first step in determining the utility of melanophores as biosensors. Responsiveness of melanophores in scales was quantitated with several bioactive agents. Experiments with depolarizing potassium ion, guanethidine, yohimbine (an adrenergic antagonist), and capsaicin (a sensory stimulant) provided evidence that melanophores are under nervous regulation. Conditions were developed to allow simplification of intact scale preparations, entailing epidermal removal and dennervation of scales. This simplification resulted in increased sensitivity and responsiveness to a larger array of bioactive agents, including a cyclic AMP analog. The simplified preparation was successfully tested for its ability to function as a biosensor using pharmaceutical eye drops; the response observed was determined to be due to naphazoline, an adrenergic agonist. Methods were developed that enabled culturing of chromatophores independent from scales. Cultured chromatophores were found to be responsive to bioactive agents with a comparable degree of sensitivity as simplified scale preparations. Attempts were undertaken to develop co-cultures of chromatophores with other cell types and with further development melanophore-based biosensors can be exploited. / Graduation date: 1997

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 96-113).

Universiẗat, Diss.--Bochum, 2007. / Literaturverz. S. XIII - XXVII.

Thesis (Ph. D.)--University of Chicago, Committee on Human Development, Dept. of Psychology, June 2001. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Michigan, 1940. / Cover title. "Contribution from the Department of zoology, University of Michigan." "Reprinted from Transactions of the American microscopical society, vol. LX, no. 2, April, 1941." Bibliography: p. 258-260.

Thesis (Ph. D.)--York University, 2001. Graduate Programme in Philosophy. / Typescript. Includes bibliographical references (leaves 365-382). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ66368.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

published_or_final_version / Obstetrics and Gynaecology / Master / Master of Philosophy