No description available.

<p>Ammonia accumulation is a regular process in live storage of Norway lobster in water. Three different filter methods are used to purify the water in water tanks.</p>

Thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1984. / Includes bibliographical references (p. 433-457).

Ammonia accumulation is a regular process in live storage of Norway lobster in water. Three different filter methods are used to purify the water in water tanks.

Polyphenoloxidases (EC 1.10.3.1) (PPO) were extracted from the skin layer between the muscle and exoskeleton, of lobster (Homarus americanus) by the successive steps of (NH$ sb4) sb2$SO$ sb4$ fractionation, ion-exchange chromatography and isoelectric focusing. The lobster 'PPO-fraction' recovered by the 40-80% (NH$ sb4) sb2$SO$ sb4$ fractionation step was found to exist in the inactive precursor form which required trypsin for activation and was inhibited by polyvinyl pyrrolidone (PVP). A comparative study of the lobster 'PPO-fraction' and the commercial tyrosinase from mushroom (EC 1.14.18.1) indicated that the two enzymes were similar with respect to substrate specificity, response to pH and selected inhibitors (cysteine, EDTA and PABA). However, both enzymes differed from one another in terms of their thermal and pH stabilities. Their catalytic efficiencies indicated that tyrosinase was better suited to catalyze oxidation of DOPA than lobster 'PPO-fraction'. Also, the activity of both enzymes were enhanced by copper. / Further purification of the 'PPO-fraction' by ion-exchange chromatography and preparative isoelectric focusing with a Rotofor unit yielded three isozymes designated PPO 1, PPO 11 and PPO 111. These isozymes had pI values of 3.89, 4.26 and 4.54 and molecular weights of 32,180, 35,480 and 39,300 respectively. The isozymes were similar with respect to their pH and temperature activity profiles but differed from one another (especially PPO 1 versus PPOs 11 and 111) in terms of their pH and thermal stabilities. They also exhibited varying degrees of differences in their catalytic efficiencies. All three isozymes were inhibited by PABA, EDTA and cysteine, with PABA being a competitive inhibitor, and EDTA or cysteine a noncompetitive inhibitor. Lower concentrations of ascorbate and mercaptoethanol had no effect on the isozymes. The free amino acid analysis suggested that melanosis might originate from the skin of the lobster.

A collagenolytic enzyme fraction was isolated from the hepatopancreas of the lobster (Homarus americanus) and semi-purified by the successive steps of acetone precipitation, ammonium sulfate fractionation, ion exchange chromatography on Mono Q column, followed by gel filtration on a Superdex 75 column or by preparative isoelectric focusing using a Rotofor cell. / Semi-purified collagenase fractions from the lobster hepatopancreas was electrophoresed in polyacrylamide gels both in the presence or absence of SDS, and shown to have molecular weights ranging from 15,000-66,000. The enzymatically active peak 1 fraction from the isoelectric focusing step in the Rotofor cell migrated as a single band in 12% polyacrylamide gel with few light protein bands. / The pH-activity data indicated that the collagenase fraction had two pH optima for the hydrolysis of native collagen, one at pH 4 and the other between pH 7-8. / The temperature-activity data for the hydrolysis of native collagen indicated the lobster enzyme exhibited two temperature optima--a minor one at 25$ sp circ$C and a more pronounced one between 40$ sp circ$C and 50$ sp circ$C.

The European lobster (<i>Homarus gammarus</i> L.) fishery in all coasts of Scotland records total annual landings of nearly 900 metric tonnes and total value of about £7 millions.  Two Scottish lobster populations were investigated, the Hebrides and Southeast with data from early 1960’s to late 1990’s. Diverse sources of information were used and when possible comparisons between the populations were carried out at varied spatial and temporal scales emphasising on two components, the sub-legal and legal lobsters.   The lack of accessibility to the Hebrides fishery limited the comparisons between the populations.  More studies on the southeast lobster population were possible. Varied methods and traditional and innovative techniques applied to the data showed dissimilarities between the populations. Differences in the size-structures, estimates of fecundity, size at the onset of sexual maturity (SOM), sex ratio, fishery duration, influence of environmental variables on the catch of undersized and legal size lobsters, and respective exploitation rates were found. The Southeast lobster population showed high historical exploitation levels but recruitment levels indicated strong resilience of this population to environmental or fisher-related processes.   Increasing landings with time might be related to an increase in temperature at large and small spatial scales. Habitat type and shelter availability affect the size-structure of this population.  Exploitation rate estimates indicated a relatively healthy state of this fishery but risks of growth over-fishing might be considered. Fluctuations of the Hebrides fishery were strongly related to density-independent processes.  The historical patterns of exploitation and the little evidence of good recruitment levels questioned the resilience of the population.  Assumptions of over-fishing risks and recruitment failure were weak.  The results contribute to the knowledge of the European lobster fishery in Scottish waters and for other commercially important lobster fisheries.

No description available.

Thesis (Ph.D.) in Marine Sciences--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 94-97).

Thesis (Ph.D.) - University of Glasgow, 2004. / Ph.D. thesis submitted to the Division of Environmental and Evolutionary Biology, Institute of Biomedical and Life Sciences, University of Glasgow, 2004. Includes bibliographical references. Print version also available.