Bibliography: leaves 142-147 / x, 147 leaves, [17] leaves of plates : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Entomology, 1987

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

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

No description available.

Thesis (Ph. D.)--University of Nevada, Reno, 1998. / Includes bibliographical references. Online version available on the World Wide Web.

Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 38-39.

Thesis (doctoral)--Rijksuniversiteit te Groningen.

Thesis--University of Copenhagen. / Bibliography: p 205-227.

The objective of this thesis was to delineate aspects of the control mechanisms of mammalian pepsinogen secretion. In order to accomplish this goal, a comprehensive study was undertaken which would establish an historical perspective of the subject, validate appropriate methodology and then seek to answer specific questions regarding the physiology and pathophysiology of pepsinogen secretion. More specifically, the objectives of this thesis were: 1. To review the historical background of the subject of pepsinogen in the context of the physiology of digestion with specific emphasis on the work and lives of the two major initial proponents of pepsinogen research (Schwann and Langley). 2. To provide a contemporary overview and evaluation of the current status of pepsinogen pathophysiology. 3. To modify and adapt experimental models necessary for the study of pepsinogen and acid secretion in mammalian gastric mucosa and cells. 4. To establish and validate a pepsinogen assay sensitive and reproducible enough for use in mammalian mucosa! and cellular secretory systems. 5. To delineate the fundamental (second messenger) control mechanisms (cyclic AMP and calcium calmodulin) of pepsinogen secretion in the isolated gastric gland model. 6. To define whether the process of pepsinogen secretion is independent of acid secretion in intact mucosa! preparations. 7. To identify different classes of pharmacological agents which would inhibit pepsinogen secretion and/or release. 8. To identify whether conditions present in critically ill patients liable to mucosal "stress ulceration" might influence the release of pepsinogen.

No description available.