Biomedical subjects

K A Barrett

Publications and source records attributed to K A Barrett.

7 recordsLinked to original sources

PubMed1999

Reduced progesterone metabolites are not critical for plus-maze performance of lactating female rats.

Lactation has been associated with anxiolysis in several tests of anxiety. These observations, considered together with observations that progesterone and its 5alpha-reduced metabolites are anxiolytic in cycling, nonlactating females, raised the question of whether the changes in anxiety-related behaviors that accompany lactation are driven by reduced progesterone metabolites. Lactating female rats were tested on the plus-maze on postpartum days 2 or 7, and demonstrated enhanced open-arm performance relative to cycling, nonlactating females. Hormonal analysis indicated that while serum levels of both progesterone and its 3alpha,5alpha-reduced metabolite were increased in lactating females, the turnover of progesterone to the metabolite was markedly reduced during lactation. Furthermore, treatment with a 5alpha-reductase inhibitor for 3 days prior to testing potentiated the open-arm performance in lactating females, implying that enhanced open-arm performance was not mediated by the reduction of progesterone or other steroids. Additionally, analysis of GABA(A) receptor function indicated that parturition and lactation did not alter the sensitivity of the receptor to GABA or to modulation by reduced steroids. The mechanisms driving enhanced plus-maze behavior in lactating females appear to differ from mechanisms identified in nonlactating females.

5-alpha Reductase Inhibitors↗

PubMed1998

Effect of gender on the mismatch negativity auditory evoked potential.

Mismatch negativity (MMN) was measured on normal-hearing young adult women and men to determine the effect of gender on this auditory evoked potential (AEP). In the experimental condition, recordings were obtained for 1000-Hz tone bursts presented at 75 dB nHL (standard stimuli) and 60 dB nHL (deviant stimuli). AEPs also were obtained in a control condition in which all stimuli were presented at 60 dB nHL; however, 15 percent of these responses were averaged to represent a response analogous to the experimental deviant response. The MMN was derived by subtracting the analogous control waveform from the experimental deviant waveform. Measures of peak-to-peak amplitude, peak latency, and area-under-the-curve were obtained for each derived waveform. Analysis of these data indicated no significant gender differences in peak latency of the MMN response. However, peak-to-peak amplitude and area-under-the-curve were significantly larger for women than for men.

Adolescent↗

PubMed1991

Test-retest reliability in tympanometry.

Test-retest reliability for tympanometric measures was evaluated across five sessions in 20 subjects with normal hearing and normal middle-ear function. Tympanograms were obtained on each ear for probe frequencies of 226, 678, and 1000 Hz using both ascending and descending directions of pressure change. Across all conditions, the tympanometric measure that consistently demonstrated the highest test-retest reliability was compensated static acoustic admittance. Test-retest correlations for peak compensated static acoustic admittance measures were higher than those for ambient measures across all probe frequencies and both directions of pressure change; the differences in correlations for peak and ambient measures, however, reached significance only for 226-Hz conditions. Across-session correlations for tympanogram width did not differ significantly for measures referenced to the lowest tympanogram tail and those referenced to +200 daPa.

Acoustic Impedance Tests↗

PubMed1990

Statistical conclusion validity of rehabilitation research. A quantitative analysis.

The findings of 100 data-based studies exploring the effectiveness of rehabilitation procedures were reviewed and analyzed. The statistical conclusion validity was determined by computing post hoc power coefficients for the statistical hypotheses tests included in the review studies. The data analysis revealed that the median power to detect a small effect size in the studiesreviewed was 0.08. The median power to detect medium and large effect sizes was 0.26 and 0.56, respectively. The results suggest the possibility of a high rate of type II experimental errors in the rehabilitation research. A type II error represents a false-negative conclusion and occurs when a researcher supports a null hypothesis that was false and should have been rejected.

Bias↗

PubMed1989

Measures of effect size in the reporting of rehabilitation research.

Effect size measures were computed for a sample of 100 research studies published in four leading rehabilitation journals. The effect size measures were categorized as small, medium, or large according to established criteria. Analysis of the effect size measures revealed that the average treatment effect was in the medium range (0.69). Further data analysis exposed a statistically significant difference in mean effect size values across articles contained in the four rehabilitation journals. A regression analysis indicated that characteristics of the study design were not significant predictors of effect size values in the 100 studies. The interpretation of effect size measures in relation to statistical significance testing is discussed and the argument made that reporting measures of effect size will assist researchers in determining the sensitivity of experimental manipulations in rehabilitation research.

Analysis of Variance↗

PubMed1978

Effects of PCA and DMAE on the namatode Caenorhabditis briggsae.

Concentration of 6.8 mM DMAE did not retard age pigment accumulation in Caenorhabditis briggsae. However, when the nematodes were exposed to 6.8 mM PCA + 6.8 mM DMAE combined, the accumulation of age pigment was significantly retarded. A combination of 3.4 mM DMAE + 3.4 mM PCA had no effect on age pigment. It is concluded from this study that PCA and DMAE act in concert to produce the observed effect on age pigment. In respect to this parameter neither molecule was effective alone. The results indicate that the effect of centrophenoxine on age pigment might be enhanced by retarding the hydrolysis of centrophenoxine. The accumulation of electron dense aggregates, thought to be aggregates of cross-linked molecules, was reduced by 6.8 PCA + 6.8 DMAE. It is suggested that centrophenoxine be tested for its ability to remove random, unwanted cross-linkages in higher animals.

Animals↗

PubMedDate not supplied

Comparative anatomy of eustachian tube and middle ear cavity in animal models for otitis media.

The comparative anatomy of the normal eustachian tube (ET) and normal middle ear cavity of three animal species (rat, gerbil, and chinchilla) is described relating to the usefulness of these animals as models for otitis media (OM). Routine histological and anatomical techniques and procedures were used. The gerbil and chinchilla, although of different sizes, are quite similar, having hypertrophied middle ear bullae, nearly vertical ET, and similar histology including seromucous glands draining directly into the ET. In contrast, the rat has a small bulla, a nearly horizontal ET, and a large concentration of goblet cells but few mucous glands in the ET. It appears that the chinchilla and the gerbil may serve as alternative models for OM research. Chinchillas and gerbils are relatively free of naturally occurring OM, while the rat has a high incidence of naturally occurring OM.

Animals↗