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Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The activity, synthetic rate and mRNA levels of pancreatic digestive enzymes adapt to changes in their respective dietary substrates. Previous studies in vivo implicate ketones and secretin in lipase adaptation and cholecystokinin (caerulein) in protease and, possibly, amylase adaptation. These studies were undertaken to determine the direct role(s) in vitro of these nutrient and hormonal factors on digestive enzymes in cultured rat pancreatic acinar cells. Ketones, intermediates of triglyceride metabolism, did not affect lipase activity in cells isolated from rats fed commercial non-purified diet, whether cultured in media containing high or low concentrations of glucose, a competitive energy substrate. Beta(OH)-butyrate also had no affect on lipase activity in cells from high-fat fed rats in which lipase was already elevated, but did increase lipase activity dose-dependently in cells isolated from rats fed a purified low-fat diet. Importantly, lipase levels were higher in cells from rats fed high fat diet, compared to those of low-fat fed rats, demonstrating that dietary adaptation persisted in culture. The role of ketones in lipase regulation appeared to be more complex than originally proposed, and they may not be the sole mediator. Direct effects of secretin and caerulein on the activity, secretion and relative synthesis of lipase were studied. Secretin significantly increased media lipase activity biphasically after 12 h, but had no effect on cellular lipase activity. After 24 h, secretin had no effect on lipase activity or relative synthesis of pancreatic enzymes (amylase, lipase, chymotrypsin, trypsin, elastase). In cultured cells, enzyme activities decreased over time, while media activities increased. Amylase relative synthesis decreased over time, while that of the proteases increased. Caerulein further decreased cellular content of all enzymes and increased media amylase and lipase activities. Caerulein, however, increased the relative synthesis of trypsin (p < 0.05) and chymotrypsin (p < 0.06), supporting its proposed role in protease, but not amylase, adaptation. These studies did not, however, support definitive roles of ketones or secretin in lipase regulation; perhaps they have interactive effects, or act in conjunction with other potential regulators, in the dietary adaptation of lipase.

This study investigates the postlarval development of Penaeus indicus. Particular emphasis is given to characterisation of developmental morphology, growth, ontogenetic change in digestive enzymes, and assessment of energy requirements for postlarval substages. The morphology of the Penaeus indicus postlarvae (PL) changes continuously as consecutive substages (PL1-14) were reached by daily moults. After 22 ecdyses (typically 35 days) the PL22 substage is succeeded by the adult form. Most of the morphological differentiation is observed after 2 weeks at substage PL14, but the branchiae only reach full development from substage PL16. The rostrum teeth, telson spines and ratio of body segments are important characters for identification of Penaeus indicus PL stage. Growth of PL1 postlarvae was significantly slower when fed artificial diets rather than Artemia nauplii. Similarly 14-day postlarvae which were slow developers (PL9) also grew slowly on artificial diets whereas postlarvae of the same age (substage PL14) did not show this suppression. Trypsin and amylase digestive activities increased with PL development (P<0.001) but did not change significantly (P>0.05) with diet fed. Trypsin was low during early PL stages of development and a sharp increase in tryptic activity was only observed at substage PL20 (24 mm). Amylase increased from PL1 and exceeded that of trypsin for 2-3 weeks after metamorphosis. It appears that during early stages of development postlarvae are unable to efficiently digest artificial diets due to low digestive activity. For smaller 14-day postlarvae, poor performance is possible related to a genetic regulated constraint and not to digestive capacity since enzyme levels were similar to those in larger PL14. PL1 fed for 15 days on commercially dried low-hatch decapsulated Artemia cysts showed comparable growth and survival to that of PLs fed on Artemia nauplii, but significantly higher (P<0.05) than that supported by commercial granulated and flake diets and low-hatch decapsulated cysts processed into a granulated diet or dried at 90°C. Leaching of soluble protein and carbohydrates was high for all artificial diets but low-hatch decapsulated cysts were highly stable in water. Commercially dried low-hatch cysts retain a living membrane capable of osmoregulation and retaining highly digestible nutrients important for fast growth and development of postlarvae. Survival of postlarvae was negatively correlated (P<0.05) with leaching of soluble protein, but no correlation was observed for loss of soluble carbohydrates. Daily food ingestion and routine metabolism of postlarvae increased with PL development. Food metabolism (SDA) was low for early PL stages, but increased steadily up to stage PL16 and remained the same from this substage onwards. Assimilation efficiency decreased for early PL substages and remained low up to PL13, and then increased steadily. Different energy strategies seem to be adopted during postlarval development to cope with ontogenetic modifications after metamorphosis. During early development little energy is lost in metabolism, and so more energy is converted to growth to support fast development, with increase in predatory behaviour and development of digestive system. Later more energy is lost in metabolism and committed for maintenance. The ontogenetic changes in digestive activity, energy trend and assimilation efficiency latter in PL development seems to reflect the adaptation to benthic carnivorous existence and migration of postlarvae and juveniles form inshore nursery to deeper waters. Stocking density above 20 PLs 1- reduced growth and survival but increased size variability above the inherent range, for postlarvae PL1-18 days old. However, Penaeus indicus postlarvae showed low agonistic behaviour and tolerated relatively high densities similar to that of other penaeid species, which further enhances the potential and advantages of the white prawn for culture.

Field and laboratory studies on the morphology, gut contents, ingestion rates and digestion efficiency of Pollicipes pollicipes were combined to obtain estimates of the likely range and quality of materials required to sustain this species . Orientation of P. pollicipes on the shores of south; west Portugal appeared to be determined by microtopography. Animals generally faced into the wave backwash. Orientation could be temporarily altered by torsion of the peduncle in response to changes in flow direction, permitting more efficient filter feeding. Cirral and mouthpart morphology suggested that P. pollicipes, Capitulum mitella and Lepas anatifera were omnivores. Size-related changes in cirral morphology made small juveniles better equipped than adults to feed on small particles. Cirral activity of P. pollicipes was investigated. Very slow rhythmic cirral extension (or 'beating') was observed in all P. pollicipes, J but only in relatively still water; once flow rates exceeded 14 cm s all barnacles exhibited prolonged cirral extension. The 'beat' rate was temperature dependent in most animals and larger animals exhibited a lower extension frequency than juveniles. It was concluded that 'beating' was primarily respiratory in function and not a feeding mechanism. The gut contents of wild P. pollicipes included animal and algal material but little inorganic matter, -.,. Small organic material predominated in small juveniles while large organic material predominated in adults. The rates of faecal production and growth were much higher in barnacles feeding on zooplankton than on algae and although algal cells were ingested in high numbers, the energy intake was so low that animals barely maintained their body weight. Digestive efficiencies varied with diet but little with barnacle size. A wide range of digestive enzymes were identified in P. pollicipes and L. anatifera suggesting that a variety of foods may be digested. Specific enzyme activity was low, characteristic of more carnivorous animals.

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This dissertation deals with a study of certain aspects of the physiology of digestion of Petromyzon marinus with emphasis on the localization of certain enzymes. It was found that the physiology of digestion adjusted to the drastic change in feeding habits at metamorphosis. / Thesis / Doctor of Philosophy (PhD)