Twelve lactating Holstein dairy cows were randomly divided into four groups of three animals each. Group A served as the control, group B was dosed at 0.05ppm/day of DDE (2,2-bis(P-chlorophenyl-1, 1-dichloroethylene), cows in group C were dosed at 0.1ppm DDE/day, while group D cows were dosed at 1.0ppm DDE/day. DDE was administered in a residue free peanut oil solution for 32-consecutive days. Milk samples were taken daily during the 32 day dosing period and for an additional 32 days after the dosing period. Quantitative analysis of DDE residue in milk fat was determined by using a Tracor MT-220 gas chromatograph with a Tritium electron capture detector. The average increase in DDE milk fat concentration during the dosing period was directly related to intake levels. DDE was the only organochlorine compound detected in the milk fat. The general slope and shape of the curves of milk fat DDE levels were similar for all treatments. The levels of DDE increased rapidly after the onset of dosing. After 15 days of dosing and throughout the remaining 17 days of the dosing period, milk fat DDE increased at a relatively slow rate. The level of milk fat DDE declined rapidly as soon as the DDE residue source was withdrawn. At the end of the 32-day post-dosing period, one cow from each group was slaughtered and samples were taken from muscles, brain, lung, lymph, spleen, kidney fat, heart, gonad, placenta, udder, and kidney for DDE analysis. Considerable DDE was found in the muscle, lymph, kidney fat, and udder tissues.

Gong Jun. / "March 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 254-294) / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Bibliography: leaves 177-191.

1,1,1-trichloro-2,2-bis(4-chlorophenyl)-ethane (DDT) residues (DDTr) are widespread and persistent environmental contaminants, and have been classed as priority pollutants by the United Nations Environment Programme (UNEP). DDTr are potent endocrine disrupting molecules, and have been associated with reproductive abnormalities in juvenile alligators and rats. Microorganisms that metabolise DDTr both aerobically and anaerobically have been isolated and characterised. Bacteria that degrade DDTr aerobically typically utilise a dioxygenase to initiate degradative reactions through ring-hydroxylation, and convert DDTr to 4-chlorobenzoate without further degradation. Terrabacter sp. strain DDE-1 was isolated from DDTr-contaminated soil from Canterbury, New Zealand, and aerobically degrades 1,1-dichloro-2,2-bis-(4-chlorophenyl)-ethylene (DDE) to 4-chlorobenzoate, when grown in the presence of biphenyl (BP). The intermediates of degradation were inferred to be the end products of dioxygenase activity. Sequencing of a large linear plasmid, pBPH-1, from strain DDE-1 identified a cluster of genes with high levels of sequence similarity to BP-degradation genes from Rhodococcus spp. and Pseudomonas spp. This plasmid is lost at high frequency producing the plasmid-cured strain MJ-2, which has lost the ability to degrade BP or DDE. The aim of this study was to confirm that DDE-degradation in strain DDE-1 is encoded by the bph operon located on pBPH-1. No genetic systems to study gene function in either DDE-1 or MJ-2 could be developed using an array of broad-host range vectors. However, heterologous expression of the bph genes in Rhodococcus erythropolis strain TA422 was successful, with the recombinant strain TA425, obtaining the ability to utilise BP and DDE as a sole source of carbon and energy. DDE-1 was shown to convert indole to indigo, but MJ-2 could not, indicating that the biphenyl dioxygenase located on pBPH-1 is responsible for this activity. The bph genes from strain DDE-1 also conferred the ability to produce indigo from indole on strain TA425, confirming successful expression of the functional biphenyl dioxygenase in this strain. Despite several attempts to show quantitative degradation in strain TA425 using gas chromatography, the results were inconclusive Further analysis is needed to provide unequivocal evidence of DDE-degradation by strain TA425. Attempts to express the bph genes in rhizosphere-colonising bacteria, such a Rhizobium spp. or Pseudomonas spp., were unsuccessful, as evidenced by the inability to produce indigo, hence the lack of a functional biphenyl dioxygenase. However, RT-PCR did indeed indicate that P. aeruginosa strain Fin1 produced a bphA1 transcript, indicating that an error is occurring post-transcriptionally in these strains, to prevent production of the functional enzyme. New Zealand has recently been shown to contain hotspots of DDTr-contamination. The second aim of this study was to determine the prevalence of DDTr-degrading bacteria and to gain insight into the types of bacteria that inhabit sites contaminated with DDTr. To investigate this, culture-dependent and culture-independent techniques were employed. Enrichment for DDTr-degrading bacteria yielded species of Rhodococcus and Ralstonia using DDTr-overlayer plate assays. The polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) were used to amplify and analyse the 16S rDNA and 16S rRNA for the identification of dominant and active bacteria in soil samples. The results of this analysis identified bacteria such as Williamsia spp. and Gordonia spp. that degrade other types of pollutants. This analysis did not identify a predominance of Rhodococcus or Ralstonia spp., or other bacteria that have been shown to degrade DDTr. To identify ecologically relevant members of the bacterial communities in DDTr-contaminated soils, and potentially important metabolic pathways, identification of ring-hydroxylating dioxygenase (RHD) genes was performed. PCR and restriction fragment length polymorphism (RFLP) analysis were employed together with phylogenetic analyses. The results showed that the RHD genes identified, clustered separately to those genes previously characterised from cultivated bacteria. Among these genes, one phylogenetic group was most closely related to the dioxygenase genes from Ralstonia eutropha H850, which is potent PCB-degrading bacterium that possesses a dioxygenase with a wide substrate range for many types of heavily chlorinated, PCB congeners. The identification of a predominance of genes with similarity to phenyl-propionate dioxygenases has been not been recognised previously in soil studies.

Bibliography: leaves 177-191. / xxi, 191 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil and Water, 2001

<p>Persistent environmental pollutants were examined for their interaction with the glucocorticoid hormone system. The focus was placed on interference with the glucocorticoid synthesis and the glucocorticoid-signalling pathway in various <i>in vitro</i> test systems.</p><p>Several aryl methyl sulphones competitively inhibited CYP11B1 activity in mouse adrenocortical Y1 cells. The DDT metabolite, 3-methylsulphonyl-2,2’-bis(4-chlorophenyl)-1,1’-dichloroethene (3-MeSO₂-DDE) had a higher affinity to the enzyme than the endogenous substrate, 11-deoxycorticosterone. In fact, 3-MeSO₂-DDE (K_i 1.6 μM) was almost as potent as the drug metyrapone (K_i 0.8 μM), a well-known inhibitor of the enzyme. 3-MeSO₂-DDE inhibited CYP11B1 activity in human adrenocortical H295R carcinoma cells, and at higher concentrations the CYP21 activity. The human H295R cell line seems to be a useful test system for studies of enzyme activities and could be used to screen endocrine disrupting chemicals interfering with the glucocorticoid hormone synthesis.</p><p>Several chiral PCB methyl sulphones and the fungicide tolylfluanid proved to be antagonists to the glucocorticoid receptor (GR) in rat hepatoma cells and/or Chinese hamster ovary cells stable transformed with a human GR and a responsive reporter vector. The 4-methylsulphonyl-2,3,6,2’,4’,5’-hexachlorobiphenyl (4-MeSO₂-CB149) enantiomers had similar antagonistic effect on the GR. Co-exposure of substances led to additive inhibitory effects on glucocorticoid-regulated protein synthesis in rat hepatoma cells. In general, 4-substituted but not 3-substituted methylsulphonyl-PCBs interacted with the glucocorticoid hormone system.</p><p>In the environment, humans and wildlife are constantly exposed to a wide range of chemicals. Considering the effects of these substances via mechanisms of actions described in this thesis, interference of xenobiotics with the glucocorticoid hormone system deserves further attention. In conclusion, environmental pollutants can interact with the glucocorticoid hormone system <i>in vitro</i>, yet the effects of the tested substances on this hormone system remain to be established <i>in vivo.</i></p>

Humans are continuously exposed to complex mixtures of anthropogenic chemicals. This thesis focus on human exposure to persistent organic pollutants (POPs). POPs ability to bioaccumulate and biomagnify together with the extensive historical use of POPs in e.g. agriculture and industry have resulted in detection of these compounds in humans and animals from all over the world. Adverse health effects caused by POPs are of particular concern for newborns and young individuals. The objective of this thesis is to assess human exposure to a selected set of POPs and their metabolites. More specifically, one aim of my thesis is to determine the exposure to polychlorinated biphenyls (PCBs) and in particular their methylsulfonyl and hydroxylated metabolites in humans from a “hot-spot” area of PCB contamination in eastern Slovakia. The maternal transfer of these chemicals is studied. Further, another specific aim is to determine occurrence, levels and, when possible, temporal trends of POPs in children and adults from three developing countries, Nicaragua, Guinea-Bissau and Bangladesh. High concentrations of PCBs and their metabolites are shown in men and women from Michalovce in eastern Slovakia. Placental transfer of methylsulfonyl-metabolites of PCBs and 4,4’-DDE was observed for the first time. Decreasing temporal trends of the majority of POPs are shown in serum from a cohort of policemen from Guinea-Bissau. In contrast, the levels of polybrominated diphenyl ethers (PBDEs) show an increasing time trend. Within five years, decreasing levels of POPs were also shown in children working and living at a waste disposal site in Nicaragua. Children working and living at waste disposal sites in Bangladesh have considerably lower levels of POPs compared to the children from Nicaragua except for 4,4’-DDT and 4,4’-DDE that are present at very high concentrations, indicating ongoing use of technical DDT. There are many studies on levels and trends of environmental pollutants from the developed industrial countries in the world, whereas data from developing countries is still scarce. This thesis contributes to partly fill this data gap since it includes assessments of POPs in children and adults from four countries on four continents. / At the time of doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Manuscript. Paper 6: Manuscript.

Persistent environmental pollutants were examined for their interaction with the glucocorticoid hormone system. The focus was placed on interference with the glucocorticoid synthesis and the glucocorticoid-signalling pathway in various in vitro test systems. Several aryl methyl sulphones competitively inhibited CYP11B1 activity in mouse adrenocortical Y1 cells. The DDT metabolite, 3-methylsulphonyl-2,2’-bis(4-chlorophenyl)-1,1’-dichloroethene (3-MeSO2-DDE) had a higher affinity to the enzyme than the endogenous substrate, 11-deoxycorticosterone. In fact, 3-MeSO2-DDE (Ki 1.6 μM) was almost as potent as the drug metyrapone (Ki 0.8 μM), a well-known inhibitor of the enzyme. 3-MeSO2-DDE inhibited CYP11B1 activity in human adrenocortical H295R carcinoma cells, and at higher concentrations the CYP21 activity. The human H295R cell line seems to be a useful test system for studies of enzyme activities and could be used to screen endocrine disrupting chemicals interfering with the glucocorticoid hormone synthesis. Several chiral PCB methyl sulphones and the fungicide tolylfluanid proved to be antagonists to the glucocorticoid receptor (GR) in rat hepatoma cells and/or Chinese hamster ovary cells stable transformed with a human GR and a responsive reporter vector. The 4-methylsulphonyl-2,3,6,2’,4’,5’-hexachlorobiphenyl (4-MeSO2-CB149) enantiomers had similar antagonistic effect on the GR. Co-exposure of substances led to additive inhibitory effects on glucocorticoid-regulated protein synthesis in rat hepatoma cells. In general, 4-substituted but not 3-substituted methylsulphonyl-PCBs interacted with the glucocorticoid hormone system. In the environment, humans and wildlife are constantly exposed to a wide range of chemicals. Considering the effects of these substances via mechanisms of actions described in this thesis, interference of xenobiotics with the glucocorticoid hormone system deserves further attention. In conclusion, environmental pollutants can interact with the glucocorticoid hormone system in vitro, yet the effects of the tested substances on this hormone system remain to be established in vivo.

Environmentalists, social scientists, and economists have long critiqued the enduring impacts of the Green Revolution’s diffusion of agricultural technologies throughout the Global South. However, largely missing from the myriad analyses is the relationship between those technologies, namely pesticides, and health outcomes. This thesis explores the social and biological mechanisms through which excessive pesticide use culminated into adverse reproductive health outcomes for rural women in the Global South. Drawing together the history of the Green Revolution’s use of DDT, its social and economic impacts, and the biology of pesticide contamination in women’s bodies exposes how the Green Revolution situated women in spaces of increased pesticide exposure. Together, the gendered nature women’s social and biological susceptibilities resulted in impaired reproductive functioning. The most common reproductive impacts of DDT contamination are breast milk contamination, spontaneous abortion, and preterm delivery. Analyzing an intricate web of social, economic, and biological factors through the theoretical lenses of ecofeminism, structural violence, and dialectics illustrates how women’s negative health outcomes are a new, and unacknowledged legacy of the Green Revolution.

DNA-damage tolerance (DDT) in yeast is composed of two parallel pathways and mediated by sequential ubiquitination of proliferating cell nuclear antigen (PCNA). While monoubiquitination of PCNA promotes translesion synthesis (TLS), which is dependent on low fidelity polymerase ζ (Pol ζ) composed of a catalytic subunit Rev3 and a regulatory subunit Rev7, polyubiquitination of PCNA by Mms2-Ubc13-Rad5 promotes error-free lesion bypass. Inactivation of these two pathways results in a synergistic effect on DNA-damage responses; however, this two-branch DDT model has not been reported in any multicellular organisms. In order to examine whether Arabidopsis thaliana possesses a two-branch DDT system, rad5a rev3 double mutant plants were created and compared with the corresponding single mutants. Arabidopsis rad5a and rev3 mutations are indeed synergistic with respect to growth inhibition induced by replication-blocking lesions, suggesting that AtRAD5a and AtREV3 are required for error-free and TLS branches of DDT, respectively. Unexpectedly this study reveals three modes of genetic interactions in response to different types of DNA damage, indicating that plant RAD5 and REV3are also involved in DNA damage responses independent of DDT. By comparing with yeast cells, it is apparent that plant TLS is a more frequently utilized means of lesion bypass than error-free DDT. In addition, it was also observed that treatments with the DNA damaging agent methylmethanesulfonate increased the nuclear ploidy level in the double mutant plants.