Presence of HPV in head and neck tumours: high prevalence in tonsillar localization.

Human papillomavirus (HPV) seems to be involved in head and neck carcinogenesis. To investigate this association, viral presence and expression were analysed by polymerase chain reaction (PCR)-based methods and correlated to tumour localization, clinical-pathological aspects, and alcohol and tobacco exposure in 65 patients. HPV DNA was found in 16 cases (24.6%); the HPV types detected were: HPV16 (10 cases), HPV 6 (3 cases) HPV 33, 35, and 58 (one case each). The tonsil was the location with the highest HPV positivity (6/8, 75%). This percentage was significantly higher than that found in tumours from any other site (P<0.01). Viral transcripts of early regions were detected in all HPV16 positive tumours. HPV status was not related to age, gender, tumour stage or grade, and use of alcohol and/or tobacco. The results suggest that HPV16 is actively involved in the genesis of a subset of head and neck cancers and that the tonsillar localization may be considered a hot spot for viral transformation.

Laser Doppler measurement of cochlear blood flow changes during conditioning noise exposure.

Using laser Doppler flowmetry, cochlear blood flow was assessed in Mongolian gerbils exposed to noise. Anesthetized animals were surgically implanted with permanent electrodes and then exposed for 10 consecutive days (6 h on/18 h off) to an octave band noise centered at 4 kHz (85 dB SPL). The auditory brainstem responses and the blood flow in the basal turn of the cochlea were compared with those of gerbils not exposed to noise. The exposed animals developed an initial threshold shift, followed by a progressive reduction in threshold shift up to complete recovery at the end of the test. In the exposed animals, a reduction in the cochlear blood flow during the first 4 days of exposure was observed, which was then followed by a progressive increase up to the end of the test. The results of this study exclude a possible role of the microvasculature of the lateral cochlear wall in determining the resistance to 4 kHz frequency noise exposure.

[Protective effect of allopurinol in the exposure to noise pulses]. / Effetto protettivo dell'allopurinolo nell'esposizione a rumore impulsivo.

Free oxygen radicals cause particularly severe tissues and organ damage. They appear to play an important role in the cochlea, mediating noise-exposure damage. In the present study 16 guinea pigs were implanted with permanent electrodes to record cochlear action potential. Eight animals were exposed to a 2-3 kHz, 125 dB SPL noise pulse, at a rate of 4 stimulations per second for 1.8 hours. Prior to noise exposure four out of eight animals were treated with a known dose of allopurinol. The remaining eight animals were used as controls. Endolymphatic malondialdehyde concentration was used as indicator of the lipid peroxidization processes exerted by the free radicals. No significant difference was found between the variations in hearing threshold and malondialdehyde concentration in the animals treated with allopurinol and then exposed to noise vs. the control group. The electophysiological and biochemical results have, therefore, demonstrated that preventative administration of allopurinol can provide valid protection vs. noise impulse damage.

Protective effect of the cochlear efferent system during noise exposure.

The aim of the present study was to confirm the hypothesis that the cochlear efferent system is involved in the mechanisms underlying the "toughening" effect at high frequencies. The toughening effect is defined as a progressive threshold shift reduction when repeated exposures to the same noise are applied. Vestibular neurectomy was performed through a posterior cranial fossa approach in six healthy pigmented guinea pigs, and it assured the interruption of both crossed and uncrossed olivocochlear bundles to one ear only, before their entrance in the internal auditory meatus. The animals were then implanted with permanent electrodes for the electrocochleographic findings. Ten days after the operation the animals were exposed to octave-band toughening noise, centered at 4 kHz, at 85-dB SPL, for 10 consecutive days, 6 hours on/18 hours off. The hearing threshold was registered before and at the end of each exposure session. The behavior of the hearing threshold in the operated ears was then compared to that of the controlateral, nonoperated ears. Complete recovery from TS in the control ear began after four days of exposure, whereas in the operated ear hearing loss increased to day 7 (55 dB), with only a partial reduction (45 dB) beyond ten days of exposure. The results of the present study clearly demonstrated that sectioning of the OCB in guinea pigs causes persistent hearing loss during noise-exposure conditioning, in comparison to the contralateral, nonoperated ear. Thus, one can assume that the lack of decrease of TS during intermittent noise exposure could be due to the loss of the protective effect of the efferent fibers, perhaps mediated by the lateral OC neurons that synapse beneath the IHCs.

Osmotic drugs in the treatment of cochlear disorders: a clinical and experimental study.

On the grounds of positive results obtained with Meniere's patients, agents such as glycerol and mannitol have been included in the therapeutical protocol of other cochlear disorders presenting with hearing loss either of sudden onset, but not observed at an early stage, or accompanied by tinnitus and aural pressure. Intravenous infusions of either 10% glycerol or 18% mannitol were given to selected patients 3 to 6 times with a time interval of 1 to 3 days. Hearing loss, tinnitus and aural pressure were evaluated as improved, unchanged or worsened. In 33% of the glycerol group and 23.8% of the mannitol group we observed hearing threshold improvement, while aural fullness improved in 45% of the glycerol and 56.2% of the mannitol groups, and tinnitus was only relieved in 13.1% of the glycerol and 5.8% of the mannitol group. A parallel experimental study was carried out on guinea-pigs in order to shed light on the effects of mannitol and glycerol on the inner ear. Cochlear blood flow was measured with a laser Doppler flowmeter at the level of the basal turn of the cochlear lateral wall, both in normal and hydropic guinea-pigs, before and after osmotic intraperitoneal infusion. Basal values in the normal cochlea were much higher than in the hydropic one, and both mannitol and glycerol markedly influenced the local blood flow in the normal cochlea, giving few or no changes in the hydropic one.