The cellular stress response protects organisms from damage resulting from exposure to a wide variety of stressors, including elevated temperatures, ultraviolet (UV) light, trace metals, and xenobiotics. The stress response entails the rapid synthesis of a suite of proteins referred to as stress proteins, or heat-shock proteins, upon exposure to adverse environmental conditions. These proteins are highly conserved and have been found in organisms as diverse as bacteria, molluscs, and humans. In this review, we discuss the stress response in aquatic organisms from an environmental perspective. Our current understanding of the cellular functions of stress proteins is examined within the context of their role in repair and protection from environmentally induced damage, acquired tolerance, and environmental adaptation. The tissue specificity of the response and its significance relative to target organ toxicity also are addressed. In addition, the usefulness of using the stress response as a diagnostic in environmental toxicology is evaluated. From the studies discussed in this review, it is apparent that stress proteins are involved in organismal adaptation to both natural and anthropogenic environmental stress, and that further research using this focus will make important contributions to both environmental physiology and ecotoxicology.

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1991. Tissue-specific patterns of synthesis of heat-shock proteins and thermal tolerance of the fathead minnow (Pimephales promelas). Can. J. Zool. 69: 2021-2027. Qualitative and quantitative differences in the heat-shock response in brain, gill, and striated muscle tissues of the fathead minnow (Pimephales promelas) were investigated. The maximum sublethal heat-shock temperature was 34°C. The heat-shock proteins (hsps) induced, their biosynthetic rates, minimum temperatures required for induction, and maximum temperatures at which each tissue synthesized hsps were tissue specific. Six hsps were induced in gill tissue (100,90,78,70,68, and 60 kDa), four in muscle tissue (100,90,78, and 70 m a ) , and three in brain tissue (90,70, and 68 m a ) . Minimum temperatures required for inducing the stress response in gill, muscle, and brain were 28, 31, and 32"C, respectively. Maximum hsp synthesis and accumulation occurred at 33°C for the brain and 34°C for muscle and gill. Synthesis and accumulation of hsps decreased to near pre-exposure levels in the brain at 34°C. The fact that brain tissue synthesized the fewest hsps and had the lowest capacity for synthesis at the upper thermal limits of the organism supports the hypothesis that the central nervous system governs the thermal limits to survival in poikilotherms. DYER, S. D., DICKSON, K. Lr, ZIMMERMAN, E. G., et SANDERS, B. M. 1991. Tissue-specific patterns of synthesis of heat-shock proteins and thermal tolerance of the fathead minnow (Pimephales promelas). Can. J. Zool. 69 : 2021-2027. Les diffdrences qualitatives et quantitatives de la rkaction protkinique aux chocs t e~i q u e s ont Ct C mesurCes dans le cerveau, les branchies et les muscles striCs chez le T2te-de-boule (Pimephales promelas). La tempkrature de choc sublCtale supkrieure a Ct C CvaluCe A 34°C. Les protCines de choc spicifiques (hsp) synthCtisCes, leur taux de biosynthkse, les tempCratures minimales nCcessaires A la synthkse, et les tempkratures maximales auxquelles chaque tissu synthCtisait les hsp Ctaient spCcifiques A chaque tissu. Six de ces protCines ont Ct C synthCtisCes dans les branchies (100,90, 78,70,68 et 60 m a ) , quatre dans les muscles (100, 90,78 et 70 kDa) et trois dans le cerveau (90,70 et 68 m a ) . Les tempkratures minimales requises pour provoquer un stress ont Ct C estimCes A 28°C dans le cas des branchies, 3 1°C dans le cas des muscles et 32°C dans le cas du cerveau. C'est A 33°C dans le cerveau et A 34°C dans les muscles et les branchies que se sont produites la synthkse la plus active et l'accumulation maximale des protCines. A 34"C, la synthkse et l'accumulation des protCines sont retombCes A des valeurs voisines des valeurs enregistrdes avant le choc dans le cerveau. Le fait que le tissue du cerveau synthCtise le moins grand nombre de protkines de choc therrnique et qu'il ait la plus faible capacitC de synthdtisation aux limites lCtales supCrieures de l'organisme semble indiquer que c'est le systkme nerveux central qui fixe les seuils thermiques de survie chez les,poikilot...

Crab zoeae (Rhithropanopeus harrisii) were exposed during their development opment to a range of free cupric ion activities regulated in seawater by use of a copper chelate buffer system. Most cytosolic copper was found to be associated with metallothionein. Copper-thionein could be related to free cupric ion activity, and a shift in copper-thionein accumulation was correlated with inhibition of larval growth. These data reveal predictable relations between cupric ion activity in seawater and processes at the cellular and organismic levels.

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We have examined the relationships between Cd ion activity [Cd2+], in seawater, Cd accumulation and subcellular distribution and growth in the polychaete Neanthes arenaceodentata. Organisms were exposed for 3 weeks to a range of [Cd2+] in a Cd-chelate buffer system. Cadmium accumulation and growth were monitored weekly for each exposure group and subcellular Cd distributions were determined at the end of the 3-week period. We found Cd associated with all of the subcellular fractions except the very low molecular weight ligands. Total Cd accumulation was greatest at day 7 and decreased over time in all but the highest [Cd2+] where it remained constant. For each point in time, however, there was a linear relationship between total Cd and [Cd2+] in seawater. Linear relationships were also observed between [Cd2+] and Cd loading in each subcellular ligand pool. Specific growth rates varied with both [Cd2+] and time in a nonlinear manner.

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