David R. Livingstone

Tissue And Subcellular-Distribution Of Enzyme-Activities Of Mixed-Function Oxygenase And Benzo[A]Pyrene Metabolism In The Common Mussel Mytilus-Edulis-L

Abstract A survey of the tissue and subcellular distribution of some enzyme activities of mixed-function oxygenase (MFO) and benzo [a] pyrene (BP) metabolism in Mytilus edulis has been carried out. Subcellular fractions were characterized by marker enzymes (pyruvate kinase, β-N-acetylglucoseaminidase, succinic dehydrogenase and glycose-6-phosphatase) and electron microscopy. The tissues examined in male and female mussels were the digestive gland, gills, mantle, posterior adductor muscle, foot, ‘rest’ fraction and blood cells. Evidence was obtained that in the female digestive gland in particular a signifant fraction of the microsomes co-sedimented with the mitochondria at 12 000 × g and some solubilization of the endoplasmic reticulum also occurred during homogenization and extraction. MFO activities and cytochromes were localized in the microsomes. Cytochrome P-450 was present only in the digestive gland and the P-450-associated activities were highest in this tissue. In contrast cytochrome b5 was also present in the gills and mantle. The activities were higher in the digestive gland microsomes of female mussels than of males and were in females (means ± SEM, n = 4): 7.5 ± 0.7 (glucose-6-phosphate dehydrogenase), 930.2 ± 54.6 (NADH-ferricyanide reductase), 156.5 ± 9.5 (NADH-cytochrome c reductase) and 18.4 ± 4.6 (NADPH-cytochrome c reductase) (all in nmol min−1 mg−1 protein at 25°C); 31.0 ± 3.9 (BP hydroxylase, pmol min−1 mg−1 protein at 25°C); 75.5 ± 11.7 (b5) and 134 ± 64 (P-450) (in pmol mg−1 protein and both the pooled material of both sexes, n = 4). Digestive gland microsomal BP hydroxylase activity was partially inhibited by carbon monoxide, SKF-525A and α-naphtoflavone. Based on this evidence and an observed relationship between microsomal BP hydroxylase and NADPH-cytochrome c reductase activities, it is concluded that a cytochrome P-450 mediated MFO system is present in mussels.

Physiological and biochemical aspects of the valve snap and valve closure responses in the giant scallopPlacopecten magellanicus

Summary1.The giant scallopPlacopecten magellanicus responds to stimulation with starfish extract by snapping the valves in a series of rapid adductions. After approximately 25–35 adductions, the scallop does not respond to further stimulation, and usually closes the valves.2.Snapping of the valves results in an accelerated heart rate, increased stroke volume and enhanced cardiac output. The supply of oxygen to the adductor muscle will be increased but must be insufficient, as bloodn

Studies on the phylogenetic distribution of pyruvate oxidoreductases

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Responses of the cytochrome P-450 monooxygenase system to diesel oil in the common mussel mytilus edulis L., and the periwinkle, Littorina littorea L

n decreases to 15 mm Hg and energy-producing anaerobic pathways are invoked (de Zwaan et al., 1980). There is an increase in the total carbon dioxide content of the blood and a fall in blood pH. When the scallop reopens, there is a transient increase in oxygen uptake.3.The restoration of physiological functions to normal values takes several hours.4.During valve closure, then

Induction Of Enzymes As A Mechanism For The Seasonal Control Of Metabolism In Marine-Invertebrates - Glucose-6-Phosphate Dehydrogenases From The Mantle And Hepatopancreas Of The Common Mussel Mytilus-Edulis-L

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PHYLOGENETIC DISTRIBUTION OF PYRUVATE OXIDOREDUCTASES, ARGININE KINASE AND AMINOTRANSFERASES.

n of the mantle water decreases from 145 mm Hg to 80 mm Hg, bloodn