Aquatic intact

Most of the reactions carried out by fish and higher aquatic organisms are relatively limited transformation reactions in which the skeletal structure of the contaminants remains intact. The following three widely distributed reactions are of greatest significance ... 

Investigation of Xenobiotic Metabolism in Intact Aquatic Animals... 

Standardized techniques and equipment for such investigations are in widespread use. Unfortunately, the same cannot be said for metabolism investigations in aquatic animals. Most of the world s animals exclusive of the insects —over 200,000 known species -- live at least a part of their lives in water over 100 species have major economic importance and they form the populations most often at risk of exposure to a growing number of chemical pollutants, but science remains largely ignorant of the disposition of xenobiotics by intact, living specimens of even the most common of the aquatic animals. 

Metals, nonmetals, and acids/bases released by human activities severely deteriorate water quality, since they are toxic even at concentrations of parts per million. It has to be noted that heavy metals are extremely dangerous to human health and aquatic life. But what is worse is that there is nocycle of natural treatment of these substances. Inevitably, heavy metals remain intact in the environment and finally, they are accumulated in the food chain (bioaccumulation). 

Aquatic Pseudomonas sp. B13 (degrades 3-chlorobenzene) 28 Intact sediment cores with overlaid water column GEM survived in sediment throughout the length of study. Microcosm was healthy, and presence of GEM did not affect total numbers of bacteria present. GEM enhanced the rate of 3-chlorobenzoate and 4-methylbenzoate added to sediment. Pipke et al. (1992)... 

Morse, D. E., Tegner, M., Duncan, H., Hooker, N., Trevelyan, G., and Cameron, A., Induction of settling and metamorphosis of planktonic molluscan (Haliotis) larvae. Ill Signalling by metabolites of intact algae is dependent on contact, in Chemical Signals in Vertebrate and Aquatic Animals, Miiller-Schwarze, D. and Silverstein, R. M., Eds., Plenum Press, New York, 1980, 67. 

Schistosomiasis (bilharziasis) (see also p. 292). The causative organisms are trema-todes with a complex life cycle that need (aquatic) snails as intermediate hosts. Free-swimming larval cercariae penetrate the intact skin of humans. The adult worms (Schistosoma mansoni, D) live in the venous vasculature. Occurrence tropical countries rich in aquatic habitats. About 200 million humans are af icted. Therapy praziquantel, 10-40 mg/kg, single dose, is highly effective with minimal adverse effects. Substances released from decaying worms may cause problems. 

Chiysotile asbestos may undergo some dissolution in the aquatic environment, especially at low pH. Magnesium hydroxide leaches from the outer bmcite layer, but the basic silicate structure of the liber remains intact. Amphibole asbestos is much more resistant to attack in acidic media (Chissick 1985 Choi and Smith 1972 Morgan and Holmes 1986 WHO 1998). 

Connell, E. L., Colmer, T. D., and Walker, D. I. (1999). Radial oxygen loss from intact roots of Halophila ovalis as a function of distance behind the root tip and shoot illumination. Aquat. Bot. 63, 219-228. 

Similar transplasmamembrane reductases are present in other algae and aquatic macrophytes, and probably aquatic bacteria. As in the preceding example, evidence for their existence comes from the observation that a variety of membrane-impermeable solutes are oxidized and reduced by intact cells. Distinct from these enzymes are other redox enzymes present on the inside and outside surfaces of the plasmamembrane that may somehow be linked to the transplasmamembrane redox system. 

Although complex chemical transformations — mainly photochemical — take place in the atmosphere, many chemically stable compounds may be transported intact via the atmosphere and subsequently enter the aquatic and terrestrial environments in the form of precipitation. Although the whole issue of chemical reactions in the troposphere lies outside the scope of this account, some comments are given in Chapter 4, Section 4.1.2, and reference should be made to the comprehensive account of principles given by Finlay-son-Pitts and Pitts (1986). The persistence in the troposphere of xenobiotics — even those of moderate or low volatility — is determined by the rates of transformation processes. These involve reactions with hydroxyl radicals, nitrate radicals, and ozone, or direct photolysis. Reactions with hydroxyl radicals are generally the most important. Illustrative values are given for the rates of reaction (cm3 s 1 molecule1) with hydroxyl radicals, nitrate radicals, and ozone (Atkinson 1990). 

The fate and distribution of the pyrethroid insecticide deltamethrin was studied in small outdoor ponds over a period of 306 days (Muir et al. 1985). The compound rapidly partitioned into suspended solids, plants, sediment, and the atmosphere, and at the termination of the experiment, the major sink for the intact compound was the sediment phase. Although fathead minnows (P. promelas) concentrated the compound from the aquatic phase, no mortality was observed. 

Schirmer K, Herbrick JS, Greenberg BM, et al. 1997. An evaluation of the cytotoxicity and photocytotoxicity of intact and photomodified creosote through the use of a rainbow trout gill cell line, TRGILL-W1, and two flourescent indicator dyes, alamar blue and 5-carboxyfluorescein diacetate acetoxymethyleste. Can Tech Rep Fish Aquat Sci 2192 4. 

Introduction of pharmaceuticals into environment is rapidly becoming an emerging issue in aquatic and wetland ecosystems. Pharmaceuticals due to their amount and application for human and veterinary cares are entering streams and water bodies. Pharmaceutically active compounds are complex molecules with various physicochemical and biological properties. The molecular weights of these compounds range from 300 to 1,000. Some pharmaceuticals are largely metabolized whereas others are only moderately or poorly metabolized and others are excreted intact. 

Fig. 21.4 Effects of eyestalk ablation on lobster growth. The larger animal (upper) had both of its eyestalks removed 2 months after hatching. The intact control animal (lower) was its full sibling. Both lobsters were kept in the same aquatic system for 1 year and fed excess amounts of food. From Conklin and Chang (1983)...

Neverthless, some guiding Interpretations for further experimental work are necessary, even If these be, admittedly, simple minded. We will assume that upon Injection of the clsplatln into the extracellular fluid of an animal the high chloride concentration (on the order of 100 milliequivalents per liter) limits any aquation reaction, and the drug remains intact as It courses through the body. Additional reactions of clsplatln with molecules in the blood will have to be left to the pharmacokinetlclsts to sort out. There is evidence to suggest that the Intact drug passively permeates cell membranes (viz, no active carrier is necessary). Usually, the intracellular chloride concentration Is lower than the extracellular value. 

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