11 research outputs found
Comparison of the Covalent Binding of Various Chloroethanes with Nucleic Acids
No full textChlorinated hydrocarbons are widely produced and utilized for various purposes (as solvents, chemical intermediates, fumigants, vapor-pressure depressants in aerosols, etc.
The covalent binding of 1, 1,2,2‐tetrachloroethane to macromolecules of rat and mouse organs
No full textThe in vivo interaction of the hepatocarcinogen 1,1,2,2‐tetrachloroethane (1,1,2,2‐TTCE) with DNA, RNA, and proteins of male Wistar rats and BALB/c mice was measured 22 hr after i.p. injection. Covalent binding index (CBI) to liver DNA was about 500 and was comparable to those of carcinogens classified as moderate initiators. It was higher than those of other chloroethanes, even than that of 1,2‐ dichloroethane (1,2‐DCE), a symmetrically substituted haloethane whose genotoxicity has been widely demonstrated. In in vitro cell‐free systems, 1,1,2,2‐tetrachloroethane was bioactivated by mixed‐function oxidase(s) and glutathione‐S‐transferase(s) (GSH‐T) from microsomal and cytosolic fractions of rat and mouse liver and, to a lesser extent, of mouse lung. The in vitro activation led to formation of reactive species capable of binding to exogenous DNA and to the subcellular constituents of enzymatic fractions. These data, along with previous literature reports, provide sufficient evidence of 1,1,2,2‐TTCE genotoxicity. Copyright © 1987 Wiley‐Liss, Inc., A Wiley Compan
Comparison Between Photo-Induction and Microsomal Activation of Polycyclic Hydrocarbons with Different Oncogenic Potency
No full textHolocene coral patch reef ecology and sedimentary architecture, northern Belize, Central America
No full textA pronounced coral zonation exists across Elmer Reef, with Montastrea annularis dominating on its crest and Acropora cervicornis occurring on its windward and leeward flanks. -from Author
Environmental setting of Holocene sabellariid worm reefs, northern Belize
No full textCommunities of sabellariid worms (Polychaeta) occur as areally discontinuous, unlithified reefs on an irregular depositional topography of Holocene and older sediments at the mouth of the Northern River Lagoon, Belize, Central America. Based upon radiocarbon dating of peat deposits, and analyses of sediment cores, the worm reefs have flourished in the study area of at least 5100 yr. This time span corresponds with sea level rise and transgression of the northern Belize coast. Initially, worms colonized drowned levees. Once established, the worm reefs stabilized these levees so that their original orientation normal to shore line is preserved today. -from Author
Seismic stratigraphic analysis of the Mississippi Fan
No full textTypescript (photocopy).Examination of extensive multichannel and single-channel data across the Mississippi Fan, Gulf of Mexico reveals that at least eight seismic sequences comprise the Pliocene/Pleistocene section (sequences I-VIII, oldest to youngest). The sequence boundaries are basin-wide unconformities identified on the basis of truncation and reflector terminations. In general, each sequence is lens-shaped in cross-section, thinning laterally from an area of maximum thickness. Isopach and structure maps compiled for each of the sequences indicates a seaward and eastward migration in the fan depocenter during its development. Mapping of the orientation of the axis of maximum thickness for each sequence indicates a major eastward shift in the depocenter during the Late Pleistocene. This shift suggests a major influx of sediment from sources other than the Mississippi River Embayment, possibly from the DeSoto Canyon. Seven seismic facies have been identified within the fan unit, each with one or more facies types. A depositional mechanism has been proposed for each based on the reflection pattern, position within each sequence, and lateral facies relationships. Channel, overbank, mass transport, and turbidity flow deposits have been interpreted within each sequence. Each facies occupies a unique position in the evolution of each sequence, reflecting a succession of depositional regimes. This succession may be related to cycles of sea level fluctuations. Analyses of facies distributions and interpreted depositional mechanisms suggest that the development of an individual sequence can be described in four stages. (1) Initial deposition is characterized by thick, mounded chaotic units, probably the result of mass transport depositional processes. Initiation of canyon development may occur during this stage. Major deposition is possibly triggered by a fall in sea level, when rapid progradation of the shelf edge occurs with associated failure of unstable sediment. (2) Stage 1 deposits are capped by higher amplitude, moderate continuity reflectors which fill across the irregular upper surface of the mass transport deposits. The reflection patterns suggest deposition from predominantly turbidity flows, possibly associated with the middle to late stages of a fall in sea level. Canyon development continues. (3) "Classic" channelized lobe deposition occurs during this stage. The canyon controls deposition, channelizing the flow of the material reaching the fan. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UM
The Different Genotoxicity of P-Dichlorobenzene in Mouse and Rat: Measurement of the in Vivo and in Vitro Covalent Interaction with Nucleic Acids
No full text Twenty-two hours after i.p. injection to male Wistar rats and BALB/c mice para-dichlorobenzene (p-DCB) is bound covalently to DNA from liver, kidney, lung and stomach of mice but not of rats. DNA adducts in mouse liver are repaired in seventy-two hours. The covalent binding index value, calculated on the labelling of mouse liver DNA, classifies p-DCB as a weak initiator with an oncogenic activity lower than that of chlorobenzene. The labelling of RNA and proteins from the different organs of both species is, however, low. In vitro interaction with calf thymus DNA mediated by mouse and rat microsomes from liver and lung did occur. Binding extent was strongly reduced by addition of 2-diethylaminoethyl-2,2-diphenylvalerate hydrochloride (SKF 525-A) to the microsomal standard incubation mixture, whereas it was enhanced by adding GSH. Cytosolic fractions from kidney and lung were able to induce binding of p-DCB to DNA to a lower extent with respect to microsome-mediated binding. These results indicate that microsomal mixed function oxidase system and microsomal GSH-transferases can be involved in overall activating metabolism whereas cytosolic GSH-transferases play a minor role. This study, which is a part of a structure-activity relationship approach on benzene and its haloderivatives, provides the first evidence of genotoxicity of p-DCB in mammalian cell. It allows to partly explain variations of susceptibility of different species to hepatocarcinogenesis and of hepatotoxicity of different isomers. </jats:p
Recent high-energy marine events in the sediments of the Lagoa de Óbidos and Martinhal (Portugal): Recognition, age and likely causes
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under the Creative Commons Attribution 3.0 License.This article has been made available through the Brunel Open Access Publishing Fund.A key issue in coastal hazards research is the need to distinguish sediments deposited by past extreme storms from those of past tsunamis. This study contributes to this aim by investigating patterns of sedimentation associated with extreme coastal flood events, in particular, within the Lagoa de Óbidos (Portugal). The recent stratigraphy of this coastal lagoon was studied using a wide range of techniques including visual description, grain-size analysis, digital and x-ray photography, magnetic susceptibility and geochemical analysis. The sequence was dated by 14C, 210Pb and Optically Stimulated Luminescence. Results disclose a distinctive coarser sedimentary unit, within the top of the sequence studied, and shown in quartz sand by the enrichment of elements with marine affinity (e.g., Ca and Na) and carbonates. The unit fines upwards and inland, thins inland and presents a sharp erosive basal contact. A noticeable post-event change in the sedimentary pattern was observed. The likely agent of sedimentation is discussed here and the conceivable association with the Great Lisbon tsunami of AD 1755 is debated, while a comparison is attempted with a possibly synchronous deposit from a tsunami in Martinhal (Algarve, Portugal). The possibility of a storm origin is also discussed in the context of the storminess of the western Portuguese coast and the North Atlantic Oscillation. This study highlights certain characteristics of the sedimentology of the deposits that may have a value in the recognition of extreme marine inundation signatures elsewhere in the world.This article is made available through the Brunel Open Access Publishing Fund
Chloroform Bioactivation Leading to Nucleic Acids Binding
No full text Chloroform was bound covalently to DNA, RNA and proteins of rat and mouse organs in vivo after i.p. injection. Covalent Binding Index values of rat and mouse liver DNA classify chloroform as a weak initiator. Labelings of RNA and proteins from various organs of both species were higher than that of DNA. In an in vitro cell-free system, chloroform was bioactivated by cytochrome P450-dependent microsomal fractions, by cytosolic GSH-transferases from rat and mouse liver, and particularly by the latter enzymes from mouse lung. This observation suggests that GSH plays a role In the binding of chloroform metabolites to DNA. The presence of both microsomal and cytosolic enzymatic systems in the standard incubation mixture generally led to an additive or synergistic bioactivating effect for rat and mouse, respectively. </jats:p
