No description available.

Gonadotrophin surge attenuating factor (GnSAF) is a non-steroidal ovarian factor which reduces pituitary responsiveness to GnRH both <I>in vitro</I> and <I>in vivo</I>. GnSAF is present in serum from superovulated women in a 141 kDa molecular weight form. GnSAF bioactivity (suppression of GnRH-induced LH secretion from cultured rat pituitary cells) in serum from superovulated women is not overcome by incubation with an inhibin antibody, demonstrating that it is distinct from inhibin. Under the culture conditions used, the ovarian steroids had no significant suppressive effects on GnRH-induced LH secretion, showing that GnSAF bioactivity is not due oestradiol or progesterone. GnSAF is also present in serum from the follicular phase of spontaneously cycling women with maximal levels being produced during the mid follicular phase. It has been suggested that GnSAF production during the follicular phase suppresses LH release from the pituitary until the levels of oestradiol produced by the developing follicle are high enough to overcome the effects of GnSAF and the LH surge occurs. However, suppression of LH secretion by an enriched GnSAF preparation is potentiated by oestradiol and progesterone, both individually and in combination. This suggests that it is not a rise in steroid positive feedback but a decrease in GnSAF negative feedback which enables the LH surge to occur. Follistatin and GnSAF in combination have additive effects on the suppression of GnRH-induced LH secretion, whereas GnSAF and inhibin in combination cause no greater suppression than they do individually. GnSAF present in inhibin-stripped human follicular fluid is also able to reduce both the GnRH self-priming response, and its augmentation by progesterone, by rat pituitary cells in culture after only 90 minutes exposure. Inhibin and follistatin have no such effects under the same conditions.

No description available.

Chapter I contains a brief introduction to the applications of dioxirane chemistry and outlines the mechanistic investigations carried out to date. Chapter 2 describes investigations into the dimethyldioxirane oxidation of para-substituted N,N-dimethylanilines in acetone. The N-oxides were found to be the only products. Relative rates were determined and compared with those of reactions with methyl iodide and other oxidants. The dimethyldioxirane reactions followed the Hammett relationship with a p value of -1.0. The reaction rates are strongly accelerated in the presence of water and the overall reaction mechanism is electrophilic in nature and does not involve free radical species or electron transfer. Chapter 3 looks at the regioselectivity of dimethyldioxirane when used to oxidise several polyfunctionalised nitrogenous drugs with a view to developing a system for use in oxidative degradation studies. The regioselectivity of dimethyldioxirane in the oxidation of polyhydroxy steroids, namely a series of bile acid methyl esters, is discussed in chapter 4. No evidence for preferential oxidation of axial over equatorial hydroxyls or vice versa was seen. Instead the least hindered hydroxyl at C3 was oxidised preferentially with some oxidation also occurring at C6 and C7. Hydroxyls at the sterically hindered C 12 were not oxidised. This provides further evidence for the proposed butterfly transition state. Finally, chapter 5 discusses the use of novel trifluoromethyl aryl ketones as promoters for Oxone®mediated epoxidations. 4-(trifluoroacetyl)benzoic acid was used succesfully and can be readily isolated for re-use by simple base extraction.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 5 uppsatser.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 54-60).

Thesis (doctoral)--Lund University, 1995. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1995. / Added t.p. with thesis statement inserted.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Vita. Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1957.