SQUID-detected FMR: Resonance in single crystalline and polycrystalline yttrium iron garnet.

Here two new techniques for the detection of broadband (100 MHz-20 GHz) ferromagnetic resonance (FMR)/ferrimagnetic resonance in single and poly-crystalline materials, which rely on SQUID-based gradiometry detection of small changes in the magnetisation, are developed. In the first method, small changes in the along-the-applied-field projection of the coupled magnetic moment (Δmz) are detected as the material is driven into resonance. Absolute measurement of the longitudinal component of the magnetisation and the resonance induced lowering of this moment makes estimation of the precession cone angle accessible, which is typically difficult to extract using conventional cavity or stripline based detection methods. The second method invokes the change in Δmz with the resonance-induced thermal heating dmzdT. Magnetisation dynamics in bulk Y3Fe5O12 are observed over a broad range of experimental temperatures (4 K-400 K) and fields (10-500 mT). The inhomogeneous microwave excitation allows for the observation of higher magnetostatic modes and the convenient tracking of very broad resonances. The two SQUID-detection techniques when combined with conventional broadband vector network analyser-FMR, low-frequency magnetic susceptibility, and DC magnetometry, all easily realised, essentially concurrently, using the same module, greatly expand the amount of static and dynamic information accessible.

Aromatase inhibition in JAr choriocarcinoma cells by 7alpha-arylaliphatic androgens.

The JAr choriocarcinoma cell cultures have demonstrated high levels of aromatase activity and have been useful for assaying a wide variety of aromatase inhibitors for aromatase inhibition in intact cells. Recently, several 7alpha-arylaliphatic androgens have shown effective inhibition of human placental microsomal aromatase in vitro, with apparent Ki values ranging from 10 to 20 nM. A series of 7alpha-arylaliphatic androst-4-ene-3,17-dione compounds demonstrated potent competitive inhibition, and 7alpha-arylaliphatic androsta-1,4-diene-3,17-diones were enzyme-activated irreversible inhibitors. Both series of these potent inhibitors were investigated for the ability to inhibit aromatase activity in JAr cells by measuring the conversion of [1beta-3H]-androstenedione to 3H2O and unlabelled estrone. JAr cell cultures were incubated for 2 h at 37 degrees C with the aromatase inhibitors at concentrations of 10 pM to 10 microM, the percentage of enzyme inhibition was determined, and IC50 values for inhibitors were calculated. Both series of synthetic compounds demonstrated good to excellent aromatase inhibition, and the most effective inhibitors in both series were those compounds with a phenylpropyl substituent at the 7alpha-position of the steroid nucleus. The 7alpha-arylaliphatic androst-4-ene-3,17-diones exhibited inhibition of JAr aromatase activity with IC50 values from 300 to 434 nM. More potent aromatase inhibition was observed with the 7alpha-arylaliphatic androsta-1,4-diene-3,17-diones, which exhibited IC50 values from 64 to 232 nM. Enhanced efficacy of steroidal enzyme-activated irreversible inhibitors compared to competitive inhibitors was observed in these studies and is consistent with previous reports. These results suggest that JAr choriocarcinoma cells with high levels of aromatase activity may be useful in differentiating steroidal aromatase inhibitors exhibiting different mechanisms of enzyme inhibition. In summary, the 7alpha-phenylpropyl androsta-1,4-diene-3,17-dione analogs, which are enzyme-activated irreversible inhibitors, demonstrated the most effective inhibition of aromatase activity present in the JAr cell cultures among the various 7alpha-arylaliphatic androgens.

Biochemistry and pharmacology of 7alpha-substituted androstenediones as aromatase inhibitors.

The inhibition of aromatase, the enzyme responsible for converting androgens to estrogens, is therapeutically useful for the endocrine treatment of hormone-dependent breast cancer. Research by our laboratory has focused on developing competitive and irreversible steroidal aromatase inhibitors, with an emphasis on synthesis and biochemistry of 7alpha-substituted androstenediones. Numerous 7alpha-thiosubstituted androst-4-ene-3,17-diones are potent competitive inhibitors, and several 1,4-diene analogs, such as 7alpha-(4'-aminophenylthio)-androsta-1,4-diene-3,17-di one (7alpha-APTADD), have demonstrated effective enzyme-activated irreversible inhibition of aromatase in microsomal enzyme assays. One focus of current research is to examine the effectiveness and biochemical pharmacology of 7alpha-APTADD in vivo. In the hormone-dependent 7,12-dimethylbenz(a)anthracene (DMBA)-induced rat mammary carcinoma model system, 7alpha-APTADD at a 50 mg/kg/day dose caused an initial decrease in mean tumor volume during the first week, and tumor volume remained unchanged throughout the remaining 5-week treatment period. This agent lowers serum estradiol levels and inhibits ovarian aromatase activity. A second research area has focused on the synthesis of more metabolically stable inhibitors by replacing the thioether linkage at the 7alpha position with a carbon-carbon linkage. Several 7alpha-arylaliphatic androst-4-ene-3,17-diones were synthesized by 1,6-conjugate additions of appropriate organocuprates to a protected androst-4,6-diene or by 1,4-conjugate additions to a seco-A-ring steroid intermediate. These compounds were all potent inhibitors of aromatase with apparent Kis ranging between 13 and 19 nM. Extension of the research on these 7alpha-arylaliphatic androgens includes the introduction of a C1-C2 double bond in the A-ring to provide enzyme-activated irreversible inhibitors. The desired 7alpha-arylaliphatic androsta-1,4-diene-3,17-diones were obtained from their corresponding 7alpha-arylaliphatic androst-4-ene-3,17-diones by oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). These inhibitors demonstrated enzyme-mediated inactivation of aromatase with apparent k(inact)s ranging from 4.4 x 10(-4) to 1.90 x 10(-3) s(-1). The best inactivator of the series was 7alpha-phenpropylandrosta-1,4-diene-3,17-dione, which exhibited a T(1/2) of 6.08 min. Aromatase inhibition was also observed in MCF-7 human mammary carcinoma cell cultures and in JAr human choriocarcinoma cell cultures, exhibiting IC50 values of 64-328 nM. The 7alpha-arylaliphatic androgens thus demonstrate potent inhibition of aromatase in both microsomal incubations and in choriocarcinoma cell lines expressing aromatase enzymatic activity. Additionally, the results from these studies provide further evidence for the presence of a hydrophobic binding pocket existing near the 7alpha-position of the steroid in the active site of aromatase. The size of the 7alpha-substituent influences optimal binding of steroidal inhibitors to the active site and affects the extent of enzyme-mediated inactivation observed with androsta-1,4-diene-3,17-dione analogs.

Mode of interview and reporting of sensitive issues: design and implementation of audio computer-assisted self-interviewing.

Substantial underreporting is typical in interviewing respondents on their drug use and other sensitive behaviors. This chapter reviews established strategies, self-administered questionnaires and indirect questioning techniques, for increasing the willingness of respondents to report stigmatizing behaviors. While these methods improve reporting, each has shortcomings and burdens which limit their effectiveness. A new computer-based self-interviewing approach which incorporates recorded audio playback of questions offers improved self-administered interviewing. The chapter discusses this technology, audio computer-assisted self-interviewing (audio-CASI), describing its features and positive results from the early research tests of the method.

7alpha-Arylaliphatic androsta-1,4-diene-3,17-diones as enzyme-activated irreversible inhibitors of aromatase.

Inhibition of aromatase, the enzyme responsible for converting androgens to estrogens, may be therapeutically useful for the endocrine treatment of hormone-dependent breast cancer. Previous research on 7alpha-thiosubstituted androgens, especially 7alpha-(4'-aminophenylthio)-androsta-1,4-diene-3,17-di one, has shown that these compounds are potent enzyme-activated irreversible inhibitors of aromatase. Research on the synthesis of more metabolically stable inhibitors has focused on replacing the thioether linkage at the 7alpha position with a carbon-carbon linkage. Several 7alpha-arylaliphatic androst-4-ene-3,17-diones were previously shown to be potent competitive inhibitors of aromatase. The extension of the research on these 7alpha-arylaliphatic androgens includes the introduction of a C1-C2 double bond in the A-ring to provide enzyme-activated irreversible inhibitors. The desired 7alpha-arylaliphatic androsta-1,4-diene-3,17-diones were obtained from their corresponding 7alpha-arylaliphatic androst-4-ene-3,17-diones by oxidation using DDQ. A new improved synthesis of the 7alpha-arylaliphatic androst-4-ene-3,17-diones using an in situ preparation of the CuI-(n-Bu3)P complex was employed. The aryl ring of the 7alpha-phenethyl and 7alpha-phenpropyl derivatives were functionalized to their corresponding p-nitro and p-amino derivatives. These compounds were all potent inhibitors of aromatase with apparent K(i)s ranging between 7 and 19 nM. These inhibitors demonstrated enzyme-mediated inactivation of aromatase with apparent k(inact)s ranging from 4.4 x 10(-4) to 1.90 x 10(-3)/s. The best inactivator of the series was the 7alpha-phenpropylandrosta-1,4-diene-3,17-dione, which exhibited a T(1/2) of 6.08 min.

Synthesis, structure elucidation, and biochemical evaluation of 7 alpha- and 7 beta-arylaliphatic-substituted androst-4-ene-3,17-diones as inhibitors of aromatase.

The inhibition of aromatase, the cytochrome P450 enzyme complex responsible for the conversion of androgens to estrogens, may be useful for the endocrine treatment of breast cancer. Previously, several 7 alpha-thio-substituted androstenediones have been shown to be potent inhibitors of aromatase. Recent research has focused on producing a more metabolically stable aromatase inhibitor by replacing the carbon-sulfur bond at the 7 alpha-position with a carbon-carbon bond. The new inhibitors, 7 alpha-arylaliphatic-substituted androst-4-ene-3,17-diones (2-4), have alkyl chains of varying length between the steroid and the aryl ring at the 7 alpha-position. The desired targets were synthesized via a 1,6-conjugate addition of the appropriate cuprate to 17 beta-(tert-butyldimethylsiloxy)androsta-4,6-dien-3-one (7). The synthesis also resulted in the formation of the 7 beta-substituted diastereomers (10-11 and 13) as minor products. Initial assignments of the 7 alpha-phenethyl and 7 beta-phenethyl diastereomers were made using highfield 1-D and 2-D NMR studies. The assignment of the diastereomers was confirmed using X-ray crystallography. These compounds were all good inhibitors of aromatase in vitro when assayed using microsomes isolated from human placenta. The 7 alpha-substituted androst-4-ene-3,17-diones (2-4) were effective inhibitors with apparent Kis of 13-19 nM. The corresponding 17 beta-hydroxy analogs (8 and 14) and the 7 beta-substituted androstenediones (13 and 16) were less effective inhibitors with apparent Kis of 36-44 nM. Thus, a new series of 7 alpha-arylaliphatic-substituted androst-4-ene-3,17-diones has been synthesized, and the compounds are potent competitive inhibitors of aromatase.