Literatura académica sobre el tema "Hemocyanin. Dungeness crab"

The in vivo oxygen-binding characteristics of Cancer magister whole hemolymph were compared across developmental stages with those of purified hemocyanin. When the 25S hemocyanins from first-instar juvenile and adult C. magister were dialyzed against first-instar juvenile saline, the P50 values at pH 7.8 differed by 54 %: 2.16 kPa for the adult and 4.68 kPa for the first-instar juvenile. Since both purified proteins were examined under identical conditions, this represents an intrinsic stage-specific difference in hemocyanin O2-affinity. When the two types of hemocyanin were dialyzed against their respective stage-specific salines, the oxygen affinities differed by only 28 %: 3.39 kPa for the adult and still 4.68 kPa for the first-instar juvenile. Thus, the intrinsic difference in hemocyanin O2-affinity was reduced by the stage-specific differences in hemolymph ion concentrations. Even more significant is the fact that the whole-hemolymph P50 values of the juvenile and adult were indistinguishable at in vivo pH and divalent cation levels specific for each stage. Thus, despite significant differences in the intrinsic oxygen affinity of the purified 25S hemocyanin during development, the whole-hemolymph oxygen-binding properties are conserved. In the juvenile crab, it appears that the low-affinity hemocyanin serves to modulate the effects of a weak renal regulation of [Mg2+]. As ion regulation is enhanced during development and divalent cation levels decrease, the crab synthesizes higher-affinity hemocyanin.

Calcium and magnesium ions raise the oxygen affinities of 25S hemocyanins of both first-instar juvenile and adult Cancer magister. A physiologically relevant change in magnesium concentration from 16 to 32 mmol l-1 changes first-instar juvenile hemocyanin affinity by 5.6 mmHg (0.7 kPa) but adult affinity by only 1.1 mmHg (0.15 kPa). In early juvenile crabs, the higher magnesium sensitivity of the hemocyanin may be compensated for by the lower oxygen affinity, which has been shown previously to be 50 % lower than that of the adult under identical experimental conditions. Furthermore, ontogeny of ionic and osmotic regulation occurs during the development of C. magister, with especially high concentrations of magnesium being found in the hemolymph of early juveniles. Intermediate-stage juveniles (fifth to eighth instars) have hemocyanins with subunit stoichiometries and P50 values approaching those of the adult. These findings are significant because they indicate that modulation of C. magister hemocyanin oxygen-affinity during development incorporates differences in intrinsic affinity and differences in divalent cation sensitivity of the stage-specific hemocyanins.

Thesis (Ph. D.)--University of Oregon, 2006.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 94-108). Also available for download via the World Wide Web; free to University of Oregon users.

Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 172-183).
Cancer magister, the Dungeness crab, occurs in different habitats during its life cycle, habitats which vary widely in the magnitude of salinity and temperature changes. Cancer magister hemocyanin also changes in structure and oxygenation properties during development. The following question was considered in this thesis: what are the effects of environmental salinity and temperature on metabolic rates, ionic and osmotic regulation and hemocyanin oxygen affinity in Q. magister during development. Metabolic rates and hemolYmph ionic and osmotic concentrations were measured in the megalopa, 1st juvenile, 5th juvenile and adult crab eight hours after acute exposure to 100% seawater (=32 ppt), 75% seawater and 50% seawater at both 10°C and 20°C. The oxygen binding properties of the whole hemolymph from these stages in 100% seawater at 10°C was determined. The effects of calcium and magnesium on the oxygen affinity of purified hemocyanin from different stages were also determined. In 100% seawater, routine metabolic rates of the four stages scale with body mass over the size range, 0.05 gm to 500 gm. The Q10 (10°C to 20°C) for the megalopa is higher in 75% seawater and 50% seawater than in 100% seawater. For the 1st juvenile, 5th juvenile and adult the Q10 values (10°C to 20°C) are independent of salinity. The megalopa, 1st juvenile and 5th juvenile are weaker regulators of hemolymph chloride, sodium and osmotic concentrations than the adult. The megalopa and adult, unlike the 1st juvenile and 5th juvenile, strongly regulate hemolymph calcium in reduced salinity. In 100% seawater hemolymph magnesium is significantly higher in the megalopa, 1st juvenile and 5th juvenile than in the adult. The oxygen affinities of whole hemolymph from the four stages are indistinguishable when adjusted for endogenous L-lactate concentrations; the Bohr coefficients are not significantly different among stages. The effect of magnesium on oxygen affinity of purified adult hemocyanin is influenced by proton concentration; the effect of calcium is independent of proton concentration. In 100% seawater, endogenous inorganic ion concentrations in the whole hemolymph of the various stages reduce the intrinsic stage specific differences in hemocyanin oxygen affinity.

Thesis (Ph. D.)--University of Oregon, 2007.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 179-196). Also available for download via the World Wide Web; free to University of Oregon users.