Increased APN/CD13 and acid aminopeptidase activities in head and neck squamous cell carcinoma.

BACKGROUND: Involvement of peptidases in carcinogenic processes of several tumor types has been investigated in recent years. Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancers worldwide and accounts for more than 90% of all head and neck cancers. Increased understanding of its pathophysiology has led to implication of several proteinases, specially matrix metalloproteinases, in its genesis, growth, and dissemination. However, very little is known about involvement of peptidases in this neoplasm. METHODS: Seventeen HNSCC tissue samples were selected for the study. Tumor and normal tissue samples were frozen for enzymatic study. The catalytic activity for a pool of peptidases (PSA, APN/CD13, APB, APA, Asp-AP, CAP, DPPIV/CD26, NEP/CD10, and PGI) was measured fluorometrically. RESULTS: The activity of 2 cell surface aminopeptidases (APN/CD13 and APA) and a cytosolic aminopeptidase (Asp-AP) was significantly increased in HNSCC tissues. CONCLUSIONS: These data show the involvement of cell surface and cytosolic peptidases in the mechanisms underlying HNSCC.

Evaluation of the frequency selectivity of contralateral acoustic stimulation on the active mechanisms of the organ of corti by analyzing the changes in the amplitude of transitory evoked otoacoustic emissions and distortion products.

INTRODUCTION: The central nervous system can regulate the input of acoustic information to the cochlea by means of the olivocochlear efferent system's action on the organ of Corti. The aim of this study was to determine whether the suppressor effect of contralateral acoustic stimulation shows frequency selectivity in active cochlear mechanisms by recording transient evoked otoacoustic emissions (TEOAEs) and distortion product otoacoustic emissions (DPOAEs). MATERIAL AND METHOD: We conducted a prospective study of 56 subjects with normal-hearing ears aged 20 to 22 years (mean 5 20.9 years); 50% were male and 50% were female. We studied the amplitude of each TEOAE and DPOAE frequency band before and after contralateral acoustic stimulation with broadband white noise, 0 to 20,000 Hz frequency range, and pure tones of 700, 1000, 1500, 2000, 3000, 4000, 5000, and 6000 Hz, at an intensity of 60 dB HL. RESULTS: TEOAE recording amplitudes decreased 84% after contralateral acoustic stimulation. White noise and pure tones of 1000, 1500, and 2000 Hz had the greatest suppressor effects on the TEOAEs. The suppressor effect was higher in 1000 to 4000 Hz frequency bands, with a statistically significant decrease in amplitudes of 0.5 to 2.5 dB. Distortion product amplitude decreased 75%. Stimulation with white noise and pure-tone contralateral stimulation at 1000 and 1500 Hz showed the highest decrease in DPOAE amplitude. Suppression was concentrated in DPOAEs obtained with F2 of 1500 and 2000 Hz. CONCLUSION: Contralateral acoustic stimulation causes selective frequency modulation of the cochlear micromechanisms, which can be assessed by recording TEOAEs and DPOAEs.

Evaluation of the influence of visual stimulation in the active mechanisms of the organ of Corti by analyzing the changes in the amplitude of distortion products.

INTRODUCTION: The central nervous system can regulate the input of information to the cochlea by means of the activity of the olivocochlear efferent system on the active micromechanisms of the organ of Corti. This article discusses a quantitative study of the inhibitory phenomenon that visual tasks exert on active cochlear micromechanisms. MATERIAL AND METHOD: We studied prospectively the characteristics of distortion products (DPs) in 80 normal ears, with and without visual stimulation. RESULTS: The results showed a decrease in the amplitude of DPs (2F1-F2), which was significant in frequencies between 1500 and 6000 Hz. CONCLUSION: Visual stimulation causes a modulation of the cochlear micromechanisms from the central nervous system from the medial olivocochlear bundle of the efferent auditory pathway.

Evaluation of cochlear function in normal-hearing young adults exposed to MP3 player noise by analyzing transient evoked otoacoustic emissions and distortion products.

OBJECTIVE: Exposure to recreational noise may cause injuries to the inner ear, and transient evoked (TEOAEs) and distortion product otoacoustic emissions (DPOAEs) may identify these cochlear alterations. The goal of this study was to evaluate TEOAEs and DPOAEs as a method to diagnose early cochlear alterations in young adults exposed to MP3 player noise. MATERIAL AND METHODS: We performed a prospective study of the cochlear function in normal-hearing MP3 player users by analyzing TEOAE and DPOAE incidence, amplitude, and spectral content. We gathered a sample of 40 ears from patients between 19 and 29 years old (mean age 24.09 years, SD 3.9 years). We compared the results with those of a control group of 232 ears not exposed to MP3 noise from patients aged 18 to 32 years (mean age 23.35 years, SD 2.7 years). Fifty percent of ears were from females and 50% were from males. RESULTS: Subjects who had used MP3 players for most years and for more hours each week exhibited a reduction in TEOAE and DPOAE incidence and amplitudes and an increase in DPOAE thresholds. TEOAEs showed a statistically significant lower incidence and amplitudes for normal-hearing subjects using MP3 players at frequencies of 2000, 3000, and 4000 Hz. DPOAE incidence was lower at 700, 1000, 1500, and 2000 Hz; the amplitudes were lower at frequencies between 1500 and 6000 Hz; and the thresholds were higher for all frequency bands, statistically significant at frequencies from 1500 to 6000 Hz, p < .05. CONCLUSIONS: Cochlear impairment caused by MP3 player noise exposure may be detectable by analyzing TEOAEs and DPOAEs before the impairment becomes clinically apparent.

Evaluation of cochlear function in patients with tinnitus using spontaneous and transitory evoked otoacoustic emissions.

OBJECTIVE: The aim of this paper has been to investigate the cochlear function and the basic properties of otoacoustic emissions (OAEs) in patients with tinnitus using Spontaneous Otoacoustic Emissions (SOAEs) and Transitory Evoked Otoacoustic Emissions (TEOAEs). MATERIALS AND METHODS: We have analyzed the incidence, amplitude and spectral content of hearing thresholds, SOAEs and TEOAEs in a sample of 44 ears. We have measured incidence, intensity, frequency, number of peaks and amplitude of emission and their variability across frequency range from 500 to 5000 Hz. A correlation was determined between the OAEs results and the results obtained using hearing thresholds. RESULTS: We have not found statistically significant differences at 500, 1000, 2000, 4000 and 8000 Hz frequencies neither at mean hearing thresholds between the sample of ears with tinnitus and the sample of ears without tinnitus. SOAEs were only present in 1 of the 44 ears tested (2.27%) and it was a 17 dB SPL amplitude peak at 2770 Hz frequency. TEOAEs, however, were displayed in some frequency in all the ears. We have compared TEOAEs parameters between the sample of ears with tinnitus and the sample of ears without tinnitus in 500, 1000, 2000, 4000 and 5000 Hz frequencies, and we have only found statistically significant differences at 4000 Hz, p = 0.02. Comparison of TEOAEs parameters between ears with tinnitus and ears without tinnitus in the same patient have only found statistically significant differences at 4000 Hz frequency, p = 0.011. In both cases there were not statistically significant differences at 500, 1000, 2000 and 5000 Hz frequencies nor at mean TEOAEs amplitudes for every group. CONCLUSIONS: We have not found significant relations between tinnitus and OAEs registration.