Thesis (M.S.)--Oregon State University, 1971. / Typescript (photocopy). Includes bibliographical references. Also available online.

Graduation date: 1975

Thesis (M.Sc.)--College of William and Mary. / Vita. Includes bibliographical references.

The ingestion, uptake, and metabolism of liposomes by juvenile Pacific oysters (Crassostrea gigas) were studied by several methods in an effort to assess their potential as encapsulating agents. Liposomes composed of egg phosphatidylcholine-cholesterol-stearylamine (7:1:2) formed readily and appeared stable in 20°/oo seawater. Radiotracer studies with liposomes made with ¹⁴C-labeled cholesterol or phosphatidylcholine showed uptake of up to 40% of the dose in 24 hrs, with the majority of uptake occurring in the visceral mass. Only slight amounts of label were observed in adductor muscle or mantle tissue. Absence of label in free fatty acids in oysters fed liposomes made with di[l-¹⁴C] palmitoyl phosphatidylcholine indicated a lack of significant amounts of fatty acid hydrolysis from phospholipid in the stomach or lumen of the digestive diverticula. However, radioactivity was observed in lipid other than phosphatidylcholine, including triglyceride, phosphatidylethanolamine, and an unidentified polar lipid. Radioactivity in these lipids resided exclusively in the fatty acids, indicating breakdown of the ¹⁴C-phosphatidylcholine via acyl transfer. To examine metabolism of liposome-encapsulated substances, [1-¹⁴C]glucose and [U-¹⁴C]amino acids were entrapped and fed to oysters. Label from glucose appeared largely in a choloroform-methanol-insoluble fraction, with little radioactivity recovered in the lipid or soluble aqueous fractions. Most label from amino acids was recovered in trichloroacetic acid-precipitable protein. Control oysters given the same amounts of non-encapsulated [1-¹⁴C] glucose or [U-¹⁴C]amino acids as in liposome trials showed (1) the same uptake of label from free amino acids in comparison with encapsulated glucose, and (2) increased uptake of free, amino acids in comparison with encapsulated amino acids. Label from free glucose or amino acids entered the same fractions as encapsulated label. Evidence for intracellular uptake of liposomes was obtained with fluorescence microscopy after feeding oysters with liposomes containing bovine serum albumin conjugated with fluorescein isothiocyante (FITC). The appearance of small fluorescent inclusions within the apical portions of many of the ducts and tubules of the digestive diverticula suggest phagocytosis of intact liposomes. Uptake was not observed in other parts of the alimentary canal. The feeding of liposomes in which the stearylamine had been conjugated with FITC resulted in generalized fluorescence in most of the digestive diverticula and stomach epithelium, perhaps due to extracellular hydrolysis of FITC and its subsequent diffusion into epithelial cells. No fluorescence occurred in tissues other than those of the digestive tract. Autoradiography studies with liposomes containing di[l-¹⁴C]palmitoyl phosphatidylcholine showed radioactivity dispersed throughout the epithelial cells of the ducts and tubules of the digestive diverticula. Only slight radioactivity was observed in the intertubular connective tissue or the lumen of the tubules or stomach. This distribution of liposomal materials resembled that of fluorescence from feeding trials with FITC-tagged liposomes, and indicated uptake of intact liposomes followed by intracellular breakdown and dispersal of the liposomal components. To investigate the process of particle selection in oysters, polyacrylamide beads (2 [plus or minus] 1μ) with aminoethyl side groups, and beads with FITC-conjugated side groups were fed to oysters. Large quantities of both types of beads were observed in the stomach and intestine, but not in the digestive diverticula, indicating recognition as non-food particles despite their organic nature. The ingestion of such derivitizable particles suggests their use in studies of acceptance-rejection processes in the stomach of bivalves. The ingestion, intracellular uptake, and breakdown of liposomes and their contents indicates a use for these particles in studies of nutrition or pollutant-food web relationships in bivalve molluscs or other filter-feeding organisms. / Graduation date: 1981

Thesis (M.S.)--Oregon State College, 1953. / Typescript. Includes bibliographical references (leaves 47-48). Also available online.

Thesis (Ph. D.)--Oregon State University, 1992. / Typescript (photocopy). Includes bibliographical references (leaves 96-103). Also available online.

Proefschrift--Amsterdam. / "Samenvatting": p. [xiii]-xvi. "Stellingen": [3] p. inserted. Bibliography: p. 237-249.

The objective was to design and evaluate a Suspension oyster tray unit to optimize conditions necessary for successful commercial culture of oysters in British Columbia for the half-shell market. The suspension system was tested against MacNicol and Nestier trays presently used by the industry. Units were located in two sites in Trevenen Bay. One location was sheltered and calm; the other a natural tidal raceway with intense current flow. The purpose was to test the ability of the design to provide more uniform growth, retard fouling, be easily handled and be commercially feasible to construct. Assessing tray performance was based on monitoring shell growth, condition index, fouling occurrence, materials handling and the capital costs of the systems. Field-experimentation began in June and terminated in October, 1979. The Nestier unit had the best shell growth in the calm environment but displayed variation in growth among trays in the stack, suffered retarded growth in the tidal raceway and had significant barnacle accumulation. The MacNicol performed on par with the Suspension system except for variations in growth due to vertical position, the accumulation of mussels and lowered performance at the tidal raceway site. Suspension tray units performed similarily at both sites, exhibited less variation in growth among trays in a stack, retarded fouling and proved the most economically feasible system for commercial use. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

The microbial composition of Pacific oysters (Crassostrea gigas) subjected to UV-treated seawater was determined by quantitative and qualitative means. A total of 2,779 microorganisms were identified from seawater and oysters during a 72 hour sampling period employing a computer assisted replica-plating technique. UV treatment effectively eliminated coliforms and Pseudomonas Type I from seawater but other gram-negative asporogenous rods were more resistant. The microogranisms commonly found in oysters, whether subjected to UV-treated seawater or not, were, in the order of predominance, Pseudomonas Type III or IV, Vibrio/Pseudomonas Type II, Flavobacterium/ Cytophaga and Acinetobacter /Moraxella. The composition of microbial flora in oysters remained relatively stable irrespective of the microorganisms present in the seawater. A total of 18 presumptive hemolytic vibrios were found in oysters but further confirmation revealed two isolates to be Vibrio parahaemolyticas and the remainder Aeromonas species. Approximately 10 percent of the microorganisms isolated from seawater and oysters were gram-positive cocci and 14 to 23 percent of these were coagulase positive, DNase positive, and (β-hemolytic on human blood agar. / Graduation date: 1971

Graduation date: 1953