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However, although we are currently lacking fully integrated explanatory frameworks
for evaluating complex environmental information and predicting harmful biological
effects and their subsequent consequences for environmental health, considerable prog-
ress has been achieved (Allen and Moore 2004; Moore et al. 2006a). And although it is
clearly recognized that stress-induced changes at the population/assemblage/ecosystem/
human health levels of biological organization are the ultimate concern, they are generally
too complex and far removed from the causative events to be of much use in developing
tools for the early detection and prediction of the consequences of environmental stress
(Depledge et al. 1993; Moore et al. 2004a, b).
Consequently, it is only at the lower levels of biological organization that we will have
the reasonable expectation of developing a basis of mechanistic understanding of how
different environmental conditions can modulate organismal function, which in turn will
ultimately help in linking causality with predictability of response (Livingstone et al. 2000;
Marigómez and Baybay-Villacorta 2003). This is partly attributable to our ability to make
certain generalizations about biological organization and function at the molecular and
cellular levels, which rapidly disappears as we ascend through the organizational hierar-
chy. Consequently, distress signals at the molecular, cellular, and physiological levels of
organisation should be capable of providing early warning biomarkers indicating reduced
performance, some of which may be prognostic for impending pathology and severe dam-
age to health of the animal (Depledge et al. 1993; Depledge 1994; Moore 2002; Galloway et
al. 2002, 2004; Moore et al. 2006a, b, 2007).
In consideration of these factors, the focus of this chapter is relating stress-induced
changes in processes at the subcellular level, specifically the intracellular lysosomal sys-
tem, to adverse effects at higher cellular physiological responses and pathological reactions.
5.1.1 Can Lysosomal Function Be Used to Assess Health of Aquatic Environment?
Responses of the lysosomal-vacuolar system may provide a solution to the question of
prognostic biomarkers, since injurious lysosomal reactions frequently precede cell and
tissue pathology. Lysosomal perturbations have been widely used as early indicators of
adverse effect to various factors, including pollutant exposure (Moore 2002; Galloway et
al. 2004; Moore et al. 2004a, b). Consequently, lysosomal function can be used across a
range of animals, including annelids, mollusks, crustaceans, and fish, to detect responses
to environmental stress (Köhler et al. 1992, 2002; Lowe et al. 1992, 1995a, b; Svendsen and
Weeks 1995; Wedderburn et al. 1998; Cajaraville et al. 2000; Lekube et al. 2000; Hwang et al.
2002; Galloway et al. 2004; Hankard et al. 2004).
Lysosomes are highly conserved multifunctional cellular organelles present in almost
all cells of eukaryotic organisms from yeast to humans (Figure 5.1). Their function in the
cellular economy includes the degradation of redundant or damaged organelles (e.g., mito-
chondria and endoplasmic reticulum) and longer-lived proteins as part of autophagic cel-
lular turnover (Klionsky and Emr 2000). Lysosomes are also involved in the digestion of
materials ingested by endocytosis and phagocytosis (i.e., intracellular digestion).
Lysosomes are involved in normal physiological responses as well as many cell injury
and disease processes; these include augmented sequestration and autophagy of organ-
elles and proteins (Figure 5.1; Moore 1990, 2002; Klionsky and Emr 2000; Cuervo 2004).
Stress-induced macroautophagy, such as that triggered by nutrient deprivation, is regu-
lated by the mTOR (mammalian target of rapamycin) kinase in eukaryotic cells from yeast
to mammals (Klionsky and Emr 2000). Such reactions have been widely documented for
many adaptive and developmental physiological and disease processes, and lysosomal
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