A spin-column procedure for estrogen receptor equilibrium and competition binding analysis.

Estrogen receptors, members of the nuclear hormone receptor family, are not only able to bind their endogenous hormone, 17beta-estradiol, but can also accommodate other naturally-occuring, non-steroidal molecules. Here, we describe a spin-column procedure to determine accurately equilibrium dissociation constants (Kds) and IC50 concentrations for estrogenic compounds. The human wild-type ERalpha was used to validate the protocol. We expressed the full-length ERalpha protein in an eukaryotic system to ensure all possible post-transcriptional modifications. The gel filtration-based assay revealed a temperature-dependent Kd shift for ERalpha. At physiological conditions (150 mM salt, 37 degrees C) we determined the 17beta-estradiol Kd for ERalpha to be 281 +/- 13 pmol/L. Positive cooperativity was only apparent at low temperatures and diminished to zero at 37 degrees C. In homologous competition binding experiments using 17beta-estradiol, we observed fifty fold higher IC50 values than the respective Kd. This paper presents a reliable and sensitive protocol to generate saturation binding curves and heterologous competition curves to test estrogenic compounds.

Comparison of linear gain and wide dynamic range compression hearing aid circuits: aided speech perception measures.

OBJECTIVES: The goal of this study was to test the theoretical advantages of a single-channel wide dynamic range compression (WDRC) circuit for speech intelligibility and loudness comfort for five speech spectra. DESIGN: Twelve adolescents and young adults with moderate to severe hearing loss were fitted with the Siemens Viva 2 Pro behind-the-ear instrument set to DSL 4.0 targets for both linear gain and WDRC processing. Speech intelligibility was measured in the unaided, linear gain and WDRC conditions using two tasks in quiet: nonsense words and sentences. The items were digitally filtered to represent five speech spectra: average speech at 4 m, average speech at 1 m, own voice at ear level, classroom at 1 m, and shouted speech at 1 m. The subjects also rated the loudness of each hearing aid/speech spectrum combination using a categorical rating scale. RESULTS: Both the linear gain and WDRC settings provided improved speech recognition relative to the unaided condition, and the two circuits resulted in equivalent performance for average speech input levels. On average, the WDRC aid resulted in high and uniform speech recognition scores across the five spectra. In contrast, the linear gain aid resulted in a lower recognition score for soft speech and shouted speech relative to that obtained with an average speech level. Analysis of individual speech recognition benefit scores revealed that 11 out of 12 subjects had equal or greater performance with the WDRC processing than the linear processing. Subjective loudness ratings in the linear gain condition were compatible with decreased sensation level for soft speech and loudness discomfort for shouted speech. CONCLUSIONS: WDRC processing has potential applications in hearing aid fittings for listeners with moderate to severe hearing loss because it provides a consistently audible and comfortable signal across a wide range of listening conditions in quiet without the need for volume control adjustments.

An alternating treatments comparison of two intensive interventions for food refusal.

We compared two treatment packages involving negative reinforcement contingencies for 3 children with chronic food refusal. One involved physically guiding the child to accept food contingent on noncompliance, whereas the other involved nonremoval of the spoon until the child accepted the presented food. Subsequent to baseline, an alternating treatments comparison was implemented in a multiple baseline design across subjects. After each child had been exposed to at least nine sessions of each treatment condition and percentage of bites accepted had increased to at least 80%, the child's caregivers selected the preferred treatment package. The results indicated that both treatments were effective in establishing food acceptance. However, physical guidance was associated with fewer corollary behaviors, shorter meal durations, and parental preference.