When signal meets noise: immunity of the frog ear to interference.

Sound stimulates the tympanic membrane (TM) of anuran amphibians through multiple, poorly understood pathways. It is conceivable that interactions between the internal and external inputs to the TM contribute to the nonlinear effects that noise is known to produce at higher levels of the auditory pathway. To explore this issue, we conducted measurements of TM vibration in response to tones in the presence of noise in the frog Eupsophus calcaratus. Laser vibrometry revealed that the power spectra (n = 16) of the TM velocity in response to pure tones at a constant level of 80 dB sound-pressure level (SPL) had a maximum centered at an average frequency of 2,344 Hz (range 1,700-2,990 Hz) and a maximum velocity of 61.1 dB re 1 microm/s (range 42.9-66.6 dB re 1 microm/s). These TM-vibration velocity response profiles in the presence of increasing levels of 4-kHz band-pass noise were unaltered up to noise levels of 90 dB SPL. For the relatively low spectral densities of the noise used, the TM remains in its linear range. Such vibration patterns facilitate the detection of tonal signals in noise at the tympanic membrane and may underlie the remarkable vocal responsiveness maintained by males of E. calcaratus under noise interference.

Urinary leukotrienes in patients with nasal polyposis.

OBJECTIVES: To compare urinary leukotriene E4 (ULT) level in patients with nasal polyposis (NP) with and without aspirin intolerance and allergic rhinitis (AR), and correlate it with disease severity. STUDY DESIGN AND SETTING: Prospective study from November 2005 to November 2006. Patients with NP (n = 30) and AR (n = 35) were included. The concentration of ULT was measured in both groups. Oral provocation test with aspirin was performed to patients with NP. ULT level between both groups was compared and correlated with NP disease severity. RESULTS: ULT concentration was elevated on NP and AR. The patients with NP and aspirin intolerance (n = 4) presented higher levels of ULT compared to aspirin-tolerant patients. Leukotriene concentration was not correlated with NP severity. CONCLUSIONS: Patients with NP and aspirin intolerance have increased ULT excretion; thus their measurement can be used as an indicator of arachidonic acid metabolism alteration.

[Effects of midodrine on symptomatic hypotension during hemodialysis]. / Efecto de la midodrina en la hipotensión sintomática en hemodiálisis.

BACKGROUND: Hypotension occurs in 20% of hemodialysis procedures. AIM: To study the effects of midodrine on hypotension during hemodialysis. PATIENTS AND METHODS: Ten patients on chronic hemodialysis and with a history of hypotension during the procedure, were studied. They received midodrine 10 mg per os or placebo during 5 dialytic procedures each, in a double blind cross over design. RESULTS: Blood pressure levels prior to dialysis were similar during the midodrine or placebo administration periods. During dialysis, systolic blood pressure fell 19.3 +/- 28 mmHg with midodrine and 23.4 +/- 28 mmHg with placebo. Diastolic blood pressure fell 7.3 +/- 11.5 mmHg with midodrine and 11.1 +/- 12 mmHg with placebo. The reduction in median arterial pressure was also less pronounced with midodrine. CONCLUSIONS: Midodrine lessens the fall in arterial pressure during hemodialysis, in patients with symptomatic hypotension.