The principle of the combined reversed-phase chromatographic electrochemical detection assay of the major serum thyroid hormones is demonstrated. The separation of 3,3',5-triiodothyronine (T(,3)), 3,3',5'-triiodothyronine (rT(,3)) and 3,5,3',5'-tetraiodothyronine (T(,4)) has been studied as a function of solvent strength, pH, temperature and ionic strength. Detection was carried out using a thin-layer electrochemical detection cell set at 1.500 V containing a new material, low temperature isotropic carbon, as a working electrode. This material was evaluated against carbon paste and using it, subnanogram detection limits were noted for the above analytes under defined conditions. Investigation of the feasibility of this analysis applied to 1.0 mL serum samples was carried out using a combined solvent extraction-cation exchange resin clean-up approach. The data indicate that under the defined conditions, elevated total T(,3) levels can be discerned and total T(,4) levels quantitated demonstrating the potential utility of this approach in screening thyrometabolic status.

Methods were established for the serum-free primary culture of rat and sheep hepatocytes. These were used to study the IGF-1 production by the cells. IGF-1 in media was separated by acid gel filtration or HPLC prior to RIA. IGF-1 production by both rat and sheep hepatocytes were time-dependent over 30 hours of culture. Production rates by rat cells in modified Eagle's medium, sheep cells modified Eagle's medium and Waymouth's medium were 13.1, 4.4 and 6.4 pmol/mg cell DNA/10 hours respectively. IGF-1 production by rat cells was very sensitive to altering concentrations of amino acids, glucose and both in the medium. IGF-1 production by sheep cells was also controlled by nutrients in modified Eagle's medium, but was not as sensitive as in rat cells. Growth hormone (GH), unlike insulin and T₃, had no effect on hepatic IGF-1 production in rat cells. In contrast, omitting GH from the medium for sheep cells decreased IGF-1 production by 20-60% in sheep cells. Insulin also controlled hepatic IGF-1 production in sheep. The results show the species difference in the hepatice IGF-1 production and control between rats and sheep. Data in this thesis are thought to provide the first published evidence of a direct nutritional control over IGF-1 production in rat hepatocytes and to give the first direct evidence that sheep hepatocytes produce IGF-1 and this is directly controlled by GH.

There is worldwide concern over the possible estrogenic effects of organic chemicals on a variety of wildlife and indeed on humankind. In the U.K., estrogenic compounds in sewage treatment works (STW) effluents have been implicated in causing the increases in egg yolk protein production observed in caged male trout and other fish species. At the initiation of the present study, few of the estrogenic compounds in STW effiuents had been recognised, although circumstantial evidence suggested that steroidal hormones were primary candidates. Cholesterol is abundant in STW effluents and is the precursor of all steroidal hormones biosynthesised in mammalian systems. Thus, the aim of the present study was to examine the hypothesis that cholesterol might undergo A-ring aromatisation, during sewage treatment, producing estrone and 17β-estradiol via, intermediates such as l9-norcholest-l,3,5(10)-trien-3-ol (NCT). To study this hypothesis NCT was first synthesised via a known route and several of its chromatographic and mass spectral properties established for the first time. NCT itself was found to possess some estrogenic potential determined using an established assay but this was rather weak compared to 17β-estradiol - about 200,000 times less active at the minimum concentration needed to invoke a response. NCT also proved to be a much more hydrophobic compound than, for example, 17β-estradiol with a computed log octanol-water partition coefficient (Kow) of over 9 compared with a log Kow of about 4 for l7β-estradiol. The established analytical properties of NCT were then used to investigate possible NCT formation in sewage. Radiolabelled 14C-cholesterol was incubated aerobically and anaerobically in Semi-Continuous Aaivated Sludge (SCAS), Die Away (DA) or simple stand alone STW simulation vessels. The products of incubation in both aqueous and solid fractions were examined by radio-high performance liquid chromatography (r-HPLC), radio-thin layer chromatography (r-TLC) and radio-gas chromatography (r-GC). Aerobic studies showed that side chain cleavage and A-ring rupture of cholesterol occurred rapidly (~25 % of added activity within 24 hrs) as measured by 14C02 evolution. Gaseous evolution was not monitored from the anaerobic experiments. Most remaining activity was associated with the solids fractions in all experiments. In the aqueous experiments both SCAS and DA systems, r-HPLC revealed rapid production of polar products which were not identified further. r-HPLC also revealed non-polar components of which choIest-3,5-diene, an unknown cholestadiene, a cholestadienol (other than 5,7-dienol), cholest-4-en-3-one and possibly NCT were identified by r-GC in the products of DA experiments. Whilst r-HPLC and r-TLC also revealed several products of anaerobic digestion of cholesterol, no compounds were detected by r-GC. STW effluents from two wastewater plants in the North London area were monitored over 7 months for A-ring steroids and other suspected estrogenic chemicals. Both effluents had previously proved estrogenic to caged fish. Liquid and SPM samples were taken, extracted and analysed by GC-MS. The two main estrogens, l7β-estradiol and estrone were identified from all liquid samples but not in SPM extracts. Generally the concentration of estrone (maximum ca 3 ng Lˉ¹) was significantly higher than that for 17β-estradiol (maximum 1 ng fˉ¹). The third natural estrogen, l6a,l7β-estriol, was identified in all Harpenden effluent samples analysed up to a concentration ca 0.5 ng Lˉ¹. However, estriol was not found in Deephams effluent extracts. The phytoestrogen, daidzein, found in soya based products was intermittently found in aqueous effluents samples from both sites >1 ng Lˉ¹. SPM made up <0.001 % of the effluent. Extracts showed that there was a high percentage of steroidal based material with coprostanol>cholesterol=β-sitosterol>>stigmasterol. NCT was twice identified from SPM taken from Deephams with a concentration of 39 and 136 ng 1ˉ¹ but <LOD in Harpenden SPM extracts. In conclusion this study showed that formation of NCT from cholesterol in STW treatment under conditions monitored herein is not a major process. However, estrone, 17β-estradiol and 16a, 17β-estriol are relatively abundant and widespread components of the STW effluents tested. The origins of the components undoubtedly include direct inputs from female urine and faeces but other metabolic sources should not be entirely ruled out.

No description available.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1994. / Includes bibliographical references (leaves 85-101). / Microfiche. / xvi, 101 leaves, bound ill. 29 cm

Thesis (Ph. D.)--University of Adelaide, Dept. of Animal Sciences, 1986. / Includes bibliographical references (leaves 191-207).

Thesis (M.Sc.) -- University of Adelaide, Depart of Anatomy and Histology, 1981.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.

Thesis (M.S.)--Texas State University--San Marcos, 2008. / Includes bibliographical references (leaves 72-77). Also available on microfilm.

Thesis (Ph. D.)--University of Sydney, 2008. / Title from title screen (viewed May 8, 2009) Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Discipline of Pharmacology, Faculty of Medicine. Degree awarded 2008; thesis submitted 2007. Includes bibliography. Also available in print form.