Perception of mistuned harmonics in complex sounds by the bullfrog (Rana catesbeiana).

The ability of 73 male bullfrogs (Rana catesbeiana) to detect single mistuned harmonics in an otherwise periodic signal was studied. Bullfrogs in their natural environment were presented with playbacks of synthetic signals, resembling their species advertisement calls, that differed in the frequency of 1 harmonic component (out of 22). There were significant differences in the number and latency of the males' evoked vocal responses to these stimuli, suggesting that males were sensitive to the differences between the sounds. Differences in envelope shape (rate and depth of amplitude modulation) produced by the harmonic mistunings may underlie the differences in response. Frogs, like birds and humans, can discriminate sounds on the basis of harmonic structure, indicating that this is a general perceptual trait shared among vertebrates.

Mycobacterium tuberculosis infection in foreign born adoptees.

Korean adoptees placed by Associated Catholic Charities of Baltimore between January, 1985, and December, 1988 (N = 873), underwent surveillance for tuberculosis (TB). Overall tuberculin reactivity or active TB was documented in nine placements. Two children had active disease; both were skin test-negative and one died of tuberculous meningitis. The median age of the seven asymptomatic tuberculin reactors, none of whom had received Bacillus Calmette-Guérin vaccination, was 1 year. This reactivity rate is approximately 50 times greater than that of age-matched United States-born children. We conclude that high risk pediatric groups for TB, in addition to refugees, displaced persons and black and Hispanic minorities, include children involved in international adoption. Total reliance cannot be placed on screening tuberculin skin tests, and TB must be included in the differential diagnosis of high risk children presenting with recurrent pneumonia, fever of unknown origin, failure to thrive and altered mental status.