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J M Langlois

Publications and source records attributed to J M Langlois.

8 recordsLinked to original sources
PubMed1985

Permanent defects in rat peripheral auditory function following perinatal hypothyroidism: determination of a critical period.

Rats were treated with propylthiouracil (PTU) for 10-day periods beginning at different ages. Daily injections of L-thyroxine (T4) were administered concurrently with PTU to a group of rats which served as one control group. Peripheral auditory function was evaluated by the brainstem response audiometry (BSRA) technique performed at 12, 16, 25 and 120 days of age. PTU treatment significantly increased wave I latency (cochlear nerve compound action potential) in adult rats when administered from 3 days before delivery through 6 days of age, but was without permanent effect (wave I latencies and thresholds) when administered for 10 days starting at 10 days after birth. T4 replacement during the first 10 postnatal days prevented permanent abnormalities. These data suggest that the period of greatest vulnerability to thyroid hormone depletion in the peripheral auditory system extends from at least 3 days before delivery through between 5 and 10 days of age.

Animals↗
PubMed1985

Effect of graded periods of congenital hypothyroidism on the peripheral auditory evoked activity of rats.

Rats were treated with a goitrogen, propylthiouracil (PTU), from 3 days before delivery up to different ages postnatally. Peripheral auditory function was evaluated with the auditory brain-stem response (ABR) technique performed at 200 days of age. All groups of rats exposed consecutively pre- and postnatally to PTU displayed permanent auditory impairment for each stimulus modality used, as revealed by significantly prolonged wave I latencies and elevated thresholds, and the severity of these abnormalities was directly related to the duration of PTU treatment. The only congenitally hypothyroid animals not affected were those treated from 3 days before parturition up to birth and those treated for 10 days beginning at 35 days of age. These data underline the susceptibility of the developing auditory system since, while very brief perinatal PTU exposure resulted in permanent evoked response abnormalities, longer exposure in later life had no effect.

Animals↗