Pacific Science Volume 36, Number 3, 1982

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Pacific Science is a quarterly publication devoted to the biological and physical sciences of the Pacific Region.


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    36:3 Table of Contents - Pacific Science
    (University of Hawai'i Press, 1982-07)
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    On the Relationship between P50 and the Mode of Gas Exchange in Tropical Crustaceans
    (University of Hawai'i Press, 1982-07) Mangum, Charlotte P.
    In general, the oxygen affinity of hemocyanin does not decrease when tropical decapod crustaceans carryon gas exchange in air instead of water. Other oxygenation properties such as cooperativity and the Bohr shift also change very little, if at all. The generalization of a higher oxygen affinity in tropical than in temperate zone species appears to be true but has exceptions of unclear origins, emphasizing the crudity of correlations between respiratory properties of the blood and gross features of the environment.
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    The Influence of Symbiotic Dinoflagellates on Respiratory Processes in the Giant Clam Tridacna squamosa
    (University of Hawai'i Press, 1982-07) Mangum, C.P. ; Johansen, K.
    Several aspects of respiratory gas exchange are distinctive in the giant clam Tridacna squamosa, which obtains nutrients from symbiotic dinoflagellates found in the mantle. During the day, when more oxygen is produced than consumed by the host and its symbionts, oxygen extraction is negative. Exhalant water P02 is higher than inhalant water P02, and prebranchial blood P02 is higher than heart blood P02. Ventilation of the mantle cavity and the gills continues, which rids the system of much excess oxygen and, possibly, prevents the formation of gas bubbles in the blood, which is supersaturated. In the dark, when the oxygen balance shifts to a rate of uptake that is unexceptional among lamellibranchs, the ventilation rate remains low and oxygen extraction high relative to species that rely exclusively on an exogenous food source. On a 24-hr basis, the total oxygen uptake exceeded the total oxygen production.
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    The Properties and Functions of Alanopine Dehydogenase and Octopine Dehydrogenase from the Pedal Retractor Muscle of Strombidae (Class Gastropoda)
    (University of Hawai'i Press, 1982-07) Baldwin, J. ; England, W.R.
    The pedal retractor muscles of Strombidae contain high activities of both alanopine dehydrogenase and octopine dehydrogenase, raising questions as to the functions of these two enzymes during muscle anoxia associated with locomotion. Alanopine dehydrogenase and octopine dehydrogenase were isolated from the pedal retractor muscle of Strombus luhuanus, and their structural and kinetic properties investigated. Alanopine dehydrogenase occurs as a single electrophoretic form with a molecular weight of approx. 42,000. Octopine dehydrogenase was electrophoretically polymorphic, existing as three alleles in the population of animals studied. The major form of the enzyme had a molecular weight of approx. 39,000. Both enzymes displayed similar pH optima for the forward (pyruvate reduction) reaction and similar Km values for the common substrates pyruvate and NADH. During bursts of leaping, both octopine and strombine/alanopine accumulated in the pedal retractor muscles of Strombidae. However, during recovery from exercise, only strombine/alanopine accumulated. Octopine was a potent inhibitor of the forward reaction catalyzed by octopine dehydrogenase, and may act to prevent further octopine production during the recovery phase. The results of this study show that both alanopine dehydrogenase and octopine dehydrogenase are functioning to catalyze the terminal step of anaerobic glycolysis during muscle anoxia associated with locomotion.
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    Sperm Morphology and Development in Two Acoel Turbellarians from the Philippines
    (University of Hawai'i Press, 1982-07) Boyer, Barbara Conta ; Smith, George W.
    In this study we compare spermiogenesis and ultrastructure of the mature sperm in two species of acoel Turbellaria from the Philippines. Sperm development is divided into five stages: (1) the early undifferentiated state, with a large nucleus, sparse cytoplasm containing few organelles, and no inclusions; (2) spermiogenesis I, in which Golgi activity is prominent, dense bodies appear in the cytoplasm, and peripheral centrioles migrate toward the nucleus; (3) spermiogenesis II, in which a manchette of microrods forms around the nucleus, refractile bodies are produced by the Golgi, and free 9+0 flagella are seen between the cells; (4) spermiogenesis III, which is characterized by marked cell elongation, nuclear condensation, and flagellar elongation and incorporation into the developing spermatid shaft; and (5) the mature sperm, which has a proximal nucleus, a middle shaft region containing a central keel of microrods, laterally incorporated axonemes, and many inclusions such as refractile bodies, dense bodies, open vesicles, mitochondria, and a distal flagellar region containing the two 9+0 axonemes tapering to terminal basal bodies. We propose that the refractile bodies may function as acrosomes, that the central keel provides support, that the biflagellate condition is important in providing the motile force that moves the sperm through intercellular spaces, and that the 9+0 axonemes may contain some central structure. The microrods of the keel appear to be a previously undescribed cellular component. The peculiar morphology of these spermatozoa is probably an adaptation associated with locomotion through the interdigitated acoel parenchyma where an extremely elongate cell, propelled flagellar tip first by undulations, is particularly efficient.
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    An Immunochemical Study of Structural and Evolutionary Relationships among Molluscan Octopine Dehydrogenases
    (University of Hawai'i Press, 1982-07) Baldwin, John
    Antisera produced against octopine dehydrogenases isolated from a gastropod and a cephalopod were used to investigate structural and evolutionary relationships of this enzyme in a range of mollusks. Antisera against octopine dehydrogenase of the blue-ringed octopus Hapalochlaena maculosa was most effective in inhibiting the enzyme from other octopods, followed by the enzymes of squids and cuttlefishes. Limited inhibition also occurred with octopine dehydrogenase of Nautilus pompilius, a representative of the most ancient group of living cephalopods. This antisera did not inhibit octopine dehydrogenases ofgastropods or bivalves. Antisera against the enzyme of the gastropod Strombus luhuanus inhibited octopine dehydrogenases from other genera of the family Strombidae, but did not inhibit the enzyme from other families of gastropods or the enzymes from cephalopods or bivalves. It is concluded that the octopine dehydrogenases of cephalopods possess structural similarities and have diverged from a common ancestral gene. The structural and evolutionary relationships among gastropod octopine dehydrogenases and the relationships among octopine dehydrogenases from different molluscan classes remain unresolved.
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    Correlations between Enzyme Profiles in Cephalopod Muscle and Swimming Behavior
    (University of Hawai'i Press, 1982-07) Baldwin, John
    The maximum activities of octopine dehydrogenase, lactate dehydrogenase, alanopine dehydrogenase, citrate synthetase, a-glycerophosphate dehydrogenase, malate dehydrogenase, and glutamate oxaloacetate transaminase were measured in a range of muscles used in swimming by octopods, squids, cuttlefishes, and a nautiloid. The high activities of octopine dehydrogenase and the positive correlation between the activities of Krebs cycle enzymes and enzymes used in the cytoplasmic reoxidation of NADH during aerobic glycolysis indicate the importance of carbohydrates as a major fuel during both anaerobic and aerobic muscle work. The maximum activities of enzymes associated with anaerobic and aerobic carbohydrate catabolism correlate well with the ways in which cephalopod muscles are used in providing propulsion during swimming.
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    The Fate of Arginine and Proline Carbon in Squid Tissues
    (University of Hawai'i Press, 1982-07) Mommsen, T.P. ; French, C.J. ; Emmett, B. ; Hochachka, P.W.
    The metabolism of proline and arginine was investigated in kidney, gill, and heart of the pelagic squid, Symplectoteuthis. The rates of CO2 release from 14C-proline exceeded the rates from 14C-arginine. The metabolic rate of arginine and proline was assessed by monitoring the incorporation of arginine-derived carbon into various intermediates. Arginine was metabolized, through ornithine, to proline as well as to glutamate and various subsequent derivatives (alanine, octopine, aspartate, and carboxylic acids). The same components became labeled using 14C-proline as the starting substrate, but only the gill was capable of converting proline to arginine via the urea cycle. In addition, 14C-proline oxidation rates were high enough to exceed those of 14C-glucose in at least three tissues, kidney, heart, and inner mantle muscle.
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    Glucose and Proline Metabolism in Nautilus
    (University of Hawai'i Press, 1982-07) Fields, JHA ; Hochachka, P.W.
    The rates of incorporation of [U-14C]proline and [U-14C]glucose into CO2 and glycogen were assessed in Nautilus pompilius under both in vitro and in vivo conditions. Both substrates exhibited tissue-specific rates of metabolism. However, overall higher rates of incorporation into CO2 and glycogen were observed with glucose, both with tissue slices and in the intact, catheterized organism.
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    Arginine, Glutamate, and Proline as Substrates for Oxidation and for Glycogenesis in Cephalopod Tissues
    (University of Hawai'i Press, 1982-07) Hochachka, P.W. ; Fields, JHA
    In addition to the usual metabolic roles for arginine and proline in cephalopod metabolism (the first serving in anaerobic metabolism and the second in augmenting the Krebs cycle pool of intermediates), we found that arginine and proline were vigorously oxidized and that their catabolism appeared to proceed through two common intermediates, glutamate and ornithine. In addition, we found that glutamate and proline were both capable of supplying precursors for the gluconeogenic pathway. On a unit mass basis, highest rates of 14C-glutamate and 14C-proline incorporation into glycogen occurred in the kidney, but when overall organ and tissue mass were considered, muscle, kidney, and gill displayed comparable rates of glycogen formation from these amino acids. The possibility was considered that these interactions between arginine, proline, and glycogen metabolism may be utilized during replenishment of all three substrate stores during recovery from exhaustive exercise.
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