Characterization of Arabidopsis fluoroacetate-resistant mutants reveals the principal mechanism of acetate activation for entry into the glyoxylate cycle.

The toxic acetate analogue monofluoroacetic acid was employed to isolate Arabidopsis tDNA-tagged plants deficient in their ability to utilize or sense acetate. Several tDNA-tagged lines were isolated, including two that were determined to be allelic to an EMS-mutagenized line denoted acn1 for ac non-utilizing. Following conventions, the tDNA-tagged mutants were designated acn1-2 and acn1-3.

Influence of acquisition parameters on the measurement of click evoked otoacoustic emissions in neonates in a hospital environment.

There is much interest in the introduction of a universal neonatal hearing screening programme. Screening programmes using high-risk criteria have been used for some time, but 50 per cent of deaf and hearing-impaired neonates are not identified because they are not classified as high risk for hearing impairment at birth. Otoacoustic emission (OAE) measurement is widely regarded as a technique likely to be suitable for universal hearing screening.

Frequency-specific auditory brainstem responses relationship to behavioural thresholds in cochlear-impaired adults.

Auditory brainstem response (ABR) thresholds to ipsilaterally masked tone pip stimuli were obtained from three groups of hearing-impaired subjects. Using high-pass (for 500-Hz tone pips) and notched noise (for 1-, 2- and 4-kHz tone pips), ABR thresholds in subjects with low-frequency, high-frequency or flat cochlear hearing losses were compared to conventional pure-tone audiometric thresholds. A strong positive relationship was found between ABR and behavioural threshold elevation.

Frequency-specific auditory brainstem responses. Effective masking levels and relationship to behavioural thresholds in normal hearing adults.

Ipsilateral masking levels and normal thresholds for tone pip auditory brainstem responses (ABRs) were investigated in normal subjects for the purpose of establishing recording parameters and norms for frequency-specific tone pip ABR testing. White noise was found to effectively mask ABRs to tone pips at mean signal-to-noise ratios of between -1 and -5.5 dB [dB peak-equivalent (pe) SPL/dB SPL] depending on the tone pip frequency.

Acoustic reflex amplitude and noise-induced hearing loss.

Acoustic reflex maximum amplitude measurements elicited both contralaterally and ipsilaterally were obtained from subjects with noise-induced hearing loss and compared with those obtained from normal-hearing subjects. The eliciting signal was a pure tone of 1 kHz presented for 1,000 ms. The groups were matched on age, sex, static immittance and ear canal volume.