There is an increasing body of evidence that the bioaccumulation of sediment-associated hydrophobic organic compounds (HOCs) is strongly influenced by sequestration. At present, it is not known how equilibrium partitioning theory (EqP), the most commonly employed approach for describing sediment bioaccumulation can be applied to sediments with sequestered contaminants. In this paper, we present freely dissolved pore-water concentrations of HOCs. These data were employed to interpret sediment bioaccumulation and sequestration data in order to arrive at a process based evaluation of EqP. The data analysis suggests that sediment bioaccumulation of compounds up to log K(ow) 7.5 in Tubificidae can be described as bioconcentration from pore-water. In addition, the pore-water concentrations of HOCs (4.5 < log K(ow) < 7.5) are established by equilibrium partitioning between the rapidly desorbing HOCs fraction in the sediment and the pore-water. Taken together, these findings indicate that EqP is a conceptually correct representation of sediment bioaccumulation, provided that sequestration is accounted for. This implies that the risk assessment of sediment-associated HOCs can be significantly simplified: With a method at hand for measuring freely dissolved pore-water concentrations of HOCs, it appears that HOCs' body residues in sediment dwelling organisms can be estimated on the basis of concentrations in pore-water and bioconcentration factors.
It has been demonstrated that human placental alkaline phosphatase (HPLAP) attenuates the lipopolysaccharide (LPS)-mediated inflammatory response, likely through dephosphorylation of the lipid A moiety of LPS. In this study, it is demonstrated that also alkaline phosphatase derived from calf intestine (CIAP) is able to detoxify LPS. In mice administered CIAP, 80% of the animals survived a lethal Escherichia coli infection. In piglets, previous to LPS detoxification, the pharmacokinetic behavior of CIAP was studied. CIAP clearance was shown to be doseindependent and showed a biphasic pattern with an initial t 1/2 of 3 to 5 min and a second phase t 1/2 of 2 to 3 h. Although CIAP is cleared much faster than HPLAP, it attenuates LPS-mediated
Experimental data are presented on octanol/water partition coefficients for 70 hydrophobic organic chemicals that were determined with a "slow-stirring" method. With this method, log KO, values can be obtained relatively easily, with high reproducibility and low standard deviations. For compounds with log KO, values of less than 4.5, the experimental data agree well with literature data based on the classical shake-flask method. For more hydrophobic compounds, deviations occur because of the formation of octanol emulsions in the shake-flask procedure. In general, there is reasonable agreement with literature data obtained by reversed-phase HPLC or the generator-column method, although substantial deviations do occur for some individual compounds, especially the higher-chlorinated ortho-substituted polychlorinated biphenyl (PCB) congeners. For chlorobenzenes, chloroanilines and PCBs, substituent constants ( T ) are calculated. With these T values, partition coefficients for these compounds can be estimated simply by calculation.
Solid phase microextraction (SPME) is an extraction technique that uses a polymer-coated fiber as the extraction device. After extraction, the compound of interest can be desorbed from the fiber and subsequently analyzed by GC or HPLC. One of the properties of SPME is that only the freely dissolved fraction of a chemical is available for partitioning to the extraction device. The method can be applied in a way that small amounts are extracted from the sample, which allows negligible depletion extraction. These two properties make SPME devices particularly suitable for measurements of free concentrations. In toxicological studies the free concentration is considered to be a more relevant parameter, concerning toxic effects, than the nominal concentration that is used most frequently. In the current study, the usefulness of this method to measure phospholipid/water partition coefficients and free concentrations in three different in vitro test systems (rat hepatocytes in primary culture, 9000 g and 100,000 g homogenate fractions of rainbow trout liver) was demonstrated. Results show separate relationships between phospholipid/water and n-octanol/water partition coefficients for a set of polar and nonpolar organic chemicals, respectively. These observations suggest that phospholipid/water partition coefficients may be a more suitable parameter in modeling the kinetic behavior of organic chemicals. Additionally, differences between the nominal and the actual free concentration in in vitro systems are more pronounced for more hydrophobic compounds, as was expected based on theoretical considerations. To our knowledge, the approach presented here is the first analytical method to measure toxicologically relevant concentrations in in vitro test systems in a fast and efficient way.
As a consequence of the rapid expansion of the uses and applications of the organotin compounds, the concern about their environmental and health effects is increasing. The main subject of this overview is the current understanding of the mammalian toxicity of the organotin compounds. Four different types of target organ toxicity, namely neurotoxicity, hepatotoxicity, immunotoxicity, and cutaneous toxicity, are discussed in more detail. The effects of the organotin compounds on the mitochondfial and cellular level are summarized and discussed in relation to the mode of action of these compounds on the central nervous system, the liver and bile duct, the immune system, and the skin. © 1987 Academic Press, Inc. ORGANOTIN COMPOUNDS: APPLICATIONS AND TOXICITY Organotin CompoundsTin can be present as an element in a wide variety of both inorganic and organometallic compounds. Organometallic tin compounds or organotins are characterized by the presence of at least one covalent carbon-tin bond. Although tin may exist either in the Sn 2+ or in the Sn 4+ oxidation state, almost all organotins have a tetravalent structure. Depending on the number of organic moieties, the organotin compounds are classified as mono-, di-, tri-, and tetraorganotins. In compounds of industrial importance, methyl, butyl, octyl, and phenyl groups form the organic substituents, while the anion is usually chloride, fluoride, oxide, hydroxide, carboxylate, or thiolate. All alkyltin compounds refered to in this article contain unbranched saturated hydrocarbon side chains (n-alkyltins).
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