Fluorescence scanning near-field optical microscopy of polyfluorene composites.

Fluorescence scanning near-field optical microscopy (SNOM) is used to investigate binary polyfluorene-based composites of varying composition. The samples investigated contain blends of the polymer poly(9,9'-dioctylfluorene-cobenzothiadiazole), F8BT, with similar polyfluorenes of wider band gap. Images acquired from a film containing 50% by weight F8BT exhibit a high degree of correlation between the topography and fluorescence, with an F8BT-rich phase which protrudes from the surface of the film forming isolated regions with sizes from hundreds of nanometres to several micrometres. A film containing 10% by weight F8BT also has micrometre-size F8BT-rich regions, but also present are small and locally varying proportions of F8BT in the other polyfluorene component phase, indicating a hierarchy of phases within this sample. The fluorescence and topographic images of a third sample studied, containing 90% by weight F8BT, display no correlation, demonstrating that it is not always appropriate to use topographic information to determine the phase structure within polymer blends. The fluorescence SNOM images acquired from these samples are able to assist our understanding of the photovoltaic efficiency of devices fabricated from these films, which are governed by the extent of the interfacial area between these two constituent polymers.

Strategies for screening for colorectal carcinoma.

Four tests commonly used in screening strategies to detect colorectal cancer were examined from a cost-effectiveness perspective. Thirteen combinations of the tests were evaluated. Evaluating a positive fecal occult blood test with a double-contrast barium enema study, followed, if necessary, by colonoscopy, is the most cost-effective strategy for individuals at average risk. An alternative screening strategy for higher-risk individuals or for populations in which the frequency of adenomatous polyps is higher is to follow a positive fecal occult blood test directly with colonoscopy. Sensitivity analysis demonstrated that the superior cost-effectiveness of these two strategies compared with the other 11 modeled strategies is almost independent for reasonable alterations in test cost and for the sensitivities and specificities of the procedures. The major contributing factor to the diagnostic cost is the frequency of adenomatous polyps. The major contributing factor to the marginal cost per year of extended life is the frequency of cancer.

The effects of neurotransmitters and other cellular modulators and factors on hypothalamic and anterior pituitary delta 4-steroid (progesterone) 5 alpha-reductase activity.

A number of diverse biological compounds involved in the regulation of the hypothalamo-hypophyseal-ovarian axis have been examined for effects on the conversion of 3H-progesterone to 3H-5 alpha-dihydro-progesterone and 3H-3 alpha-hydroxy-5 alpha-pregnan-20-one by female rat hypothalamus and/or anterior pituitary. Broken cell preparations were incubated with 3H-progesterone and NADPH, and product 5 alpha-reduced progestins were quantitated by reverse isotopic dilution analysis. Progesterone 5 alpha-reductase activity was reduced up to 50% in the presence of 10(-2) to 10(-3) M serotonin in both preparations. At 10(-3) M, various indoles including n-acetylserotonin, melatonin, 5-methoxytryptamine, 5-methoxytryptophol, and 5-hydroxyindole acetic acid decreased by 10 to 30% 5 alpha-reduced product formation. At 10(-2) M, carbamylcholine and norepinephrine were without effect, while 10(-2) M dopamine reduced by 20% the 5 alpha-reduction of progesterone only in pituitary homogenates. The LHRH protease inhibitor bacitracin (2 X 10(-3) M) decreased by 10 to 40% progesterone 5 alpha-reductase activity in both tissues. By itself, LHRH did not affect the 5 alpha-reduction of progesterone nor did it potentiate the bacitracin effect. In the presence of 1 mM ATP, 100 micronM cAMP and 100 micronM cGMP increased 5 alpha-reduced product formation in the hypothalamus by 19 and 14%. The gonadotropins LH and FSH and the prostaglandins E1, E2, F1 alpha, and F2 alpha were without effect. Thus, these results and others indicate that a number of cellular components and other factors can affect the in vitro 5 alpha-reduction of progesterone in broken cell preparations.