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

1. Glucose-6-phosphate dehydrogenase from the hepatopancreas and mantle tissue of M. edulis was investigated over two years for changes in specific activity (crude enzyme preparations) and the apparent Michaelis constants for G6P and NADP+ (highly purified enzyme preparations). 2. The specific activity of the mantle enzyme was low in summer and autumn and increased in the winter during the time of lipid deposition. In contrast, the specific activity of the hepatopancreas enzyme was high in summer and declined during the autumn and winter. 3. The apparent values for G6P and NADP+ of the mantle enzymechange little during a year. Changes were observed for the hepatopancreas enzyme during the first year but not the second.

Mixed-Function Oxygenases And Xenobiotic Detoxication-Toxication Systems In Bivalve Mollusks

Components of a xenobiotic detoxication/toxication system involving mixed function oxygenases are present inMytilus edulis. Our paper critically reviews the recent literature on this topic which reported the apparent absence of such a system in bivalve molluscs and attempts to reconcile this viewpoint with our own findings on NADPH neotetrazolium reductase, glucose-6-phosphate dehydrogenase, aldrin epoxidation and other reports of the presence of mixed function oxygenases. New experimental data are presented which indicate that some elements of the detoxication/toxication system inM. edulis can be induced by aromatic hydrocarbons derived from crude oil. This includes a brief review of the results of long-term experiments in which mussels were exposed to low concentrations of the water accommodated fraction of North Sea crude oil (7.7–68 µg 1−1) in which general stress responses such as reduced physiological scope for growth, cytotoxic damage to lysosomal integrity and cellular damage are considered as characteristics of the general stress syndrome induced by the toxic action of the xenobiotics. In addition, induction in the blood cells of microsomal NADPH neotetrazolium reductase (associated with mixed function oxygenases) and the NADPH generating enzyme glucose-6-phosphate dehydrogenase are considered to be specific biological responses to the presence of aromatic hydrocarbons. The consequences of this detoxication/toxication system forMytilus edulis are discussed in terms of the formation of toxic electrophilic intermediate metabolites which are highly reactive and can combine with DNA, RNA and proteins with subsequent damage to these cellular constituents. Implications for neoplasms associated with the blood cells are also discussed. Finally, in view of the increased use of mussel species in pollutant monitoring programmes, the induction phenomenon which is associated with microsomal enzymes in the blood cells is considered as a possible tool for the detection of the biological effects of environmental contamination by low concentrations of certain groups of organic xenobiotics.

Laboratory Simulation Of Chemical Processes Induced By Estuarine Mixing - The Behavior Of Iron And Phosphate In Estuaries

A series of well stirred tank reactors has been shown to provide an adaptable laboratory analogue of a one-dimensional estuarine mixing profile which can be applied dynamically to the study of the chemistry of estuarine mixing. Simulations of the behaviour of iron and phosphate in the low salinity region of an estuary have been achieved with this system. The well documented general features of iron removal, involving rapid aggregation of river-borne colloids, were reproduced. Phosphate removal is attributable in part to the coagulation process, although specific adsorption of phosphate by colloids also appears to be significant.