Dose response to a single injection of azoxymethane in rats. Induction of tumors in the gastrointestinal tract, auditory sebaceous glands, kidney, liver and preputial gland. (41/195)

Male Fischer rats, 6 weeks old, were injected once with one of five doses of azoxymethane. There was a dose response to the carcinogen as determined by weight gain and tumor induction. Rats given the three highest doses developed tumors of the gastrointestinal tract, auditory sebaceous glands, kidney, liver, and preputial gland, whereas rats receiving the lowest doses had tumors mainly of the intestine. Chronic liver lesions in high-dose rats were cirrhosis with megalocytosis, mild fibrosis, nodular hepatocellular hyperplasia, and hyperplasia of bile ductules.  (+info)

A rare case of synovial otorrhea of iatrogenic nature in dentistry. (42/195)

The authors describe a unique case of left synovial otorrhea in a masticatory phase, occurring in a 64-year-old patient after a long dental sitting. The otoscopic examination and the transverse CT of the ear revealed the fracture of the anterior wall of left external auditory canal and the presence of a small bone fragment on the external side of the glenoid fossa. This situation, at present, has been judged inoperable by otologists due to the close relationship between this area and the head of the left condyle, probably responsible for the fracture. The therapy used was based on the use of a masticatory bite plate, with the aim of increasing the vertical dimension of the jaws during mastication and, so, to keep the condyle in a forward position. The result obtained was the decrease and then the halting of the liquid exit in the auricle, through an increase of the bite plate height determined by the ex iuvantibus method. This temporary therapy could bring about a spontaneous healing of the fracture, thanks to the masticatory increase of the bite plate; but if this is not possible, a fixed prosthetic solution should then be provided for the patient. Research into the literature revealed no similar observations.  (+info)

Theory of forward and reverse middle-ear transmission applied to otoacoustic emissions in infant and adult ears. (43/195)

The purpose of this study is to understand why otoacoustic emission (OAE) levels are higher in normal-hearing human infants relative to adults. In a previous study, distortion product (DP) OAE input/output (I/O) functions were shown to differ at f2 = 6 kHz in adults compared to infants through 6 months of age. These DPOAE I/0 functions were used to noninvasively assess immaturities in forward/reverse transmission through the ear canal and middle ear [Abdala, C., and Keefe, D. H., (2006). J. Acoust Soc. Am. 120, 3832-3842]. In the present study, ear-canal reflectance and DPOAEs measured in the same ears were analyzed using a scattering-matrix model of forward and reverse transmission in the ear canal, middle ear, and cochlea. Reflectance measurements were sensitive to frequency-dependent effects of ear-canal and middle-ear transmission that differed across OAE type and subject age. Results indicated that DPOAE levels were larger in infants mainly because the reverse middle-ear transmittance level varied with ear-canal area, which differed by more than a factor of 7 between term infants and adults. The forward middle-ear transmittance level was -16 dB less in infants, so that the conductive efficiency was poorer in infants than adults.  (+info)

Testing a method for quantifying the output of implantable middle ear hearing devices. (44/195)

This report describes tests of a standard practice for quantifying the performance of implantable middle ear hearing devices (also known as implantable hearing aids). The standard and these tests were initiated by the Food and Drug Administration of the United States Government. The tests involved measurements on two hearing devices, one commercially available and the other home built, that were implanted into ears removed from human cadavers. The tests were conducted to investigate the utility of the practice and its outcome measures: the equivalent ear canal sound pressure transfer function that relates electrically driven middle ear velocities to the equivalent sound pressure needed to produce those velocities, and the maximum effective ear canal sound pressure. The practice calls for measurements in cadaveric ears in order to account for the varied anatomy and function of different human middle ears.  (+info)

Magnitude of impacted earwax in Oman, its impact on hearing impairment and economic burden of earwax on health services. (45/195)

BACKGROUND: Wax in ear canal causes a sizeable burden on resources of health services to a country. AIM: The magnitude of impacted wax, its effect in a survey and cost of managing this problem were reviewed in 2002. SETTINGS AND DESIGNS: A study was conducted during 1996 to estimate the magnitude and causes of hearing impairment and ear diseases in Oman. The authors further reviewed the data of community-based prevalence study to assess the role of impacted wax. MATERIALS AND METHODS: Trained physicians used portable audiometers to test the hearing status of each ear. They used otoscopes to examine the ear. Persons suspected to have hearing impairment or ear disease were reexamined by audiologists and otologists to determine the causes of hearing impairment. The resources for managing impacted wax were also calculated. RESULTS: In this survey, 11,402 subjects of all ages were examined. Prevalence of impacted wax was 11.7% (CI 95% 11.1-12.2). Impacted wax was significantly higher in females compared to males [RR = 1.22 (CI 95% 1.10-1.35)]. It was more common in residents of regions with humid environment than those of regions with less humidity [RR = 1.91 (CI 95% 1.67-2.18)]. Impacted wax in ear canal was associated with ear diseases. A total of 181,000 Omani people were estimated to have impacted wax in the ear canal. Managing impacted wax could cost 3.6 million US dollars to the ear care services. CONCLUSIONS: Impacted wax was a hindrance in the hearing survey and countries should plan to deal with earwax in such surveys. Its impact on hearing impairment and resource burden should be considered while formulating policies for ear care.  (+info)

A human case of otoacariasis involving a histiostomatid mite (Acari: Histiostomatidae). (46/195)

A 31-year-old Saudi man was seen at an ear, nose, and throat clinic at Riyadh, Saudi Arabia, with bilateral itching in the external auditory canal. On otoscopic examination, the skin lining the ear canal was thickened with whitish sheets of sloughed cells and thick discharge. Large numbers of mites of an undescribed species closely related to members of the genus Loxanoetus (Histiostomatidae) were present. The patient underwent successive washings of the ear canal with saline and 70% ethanol at intervals of 2-3 months and was treated with antibiotics. Treatment with Eurax (crotamiton) ear drops for one week cleared the mite infestation. This represents the first reported case of human otoacariasis involving a histiostomatid mite. Based on the known biology of histiostomatid mites and the associated hosts of Loxanoetus and related genera, there is reason to speculate that the patient acquired the infestation while swimming in a lake or pond where this mite was present.  (+info)

Cerumen impaction. (47/195)

Cerumen is a naturally occurring, normally extruded product of the external auditory canal. It is usually asymptomatic, but when it becomes impacted it can cause complications such as hearing loss, pain, or dizziness. It also can interfere with examination of the tympanic membrane. Depending on available equipment, physician skill, and patient circumstances, treatment options for cerumen impaction include watchful waiting, manual removal, the use of ceruminolytic agents, and irrigation with or without ceruminolytic pretreatment. The overall quality of the evidence on treatment is limited. Referral to an otolaryngologist for further evaluation is indicated if treatment with a ceruminolytic agent followed by irrigation is ineffective, if manual removal is not possible, if the patient develops severe pain or has vertigo during irrigation, or if hearing loss is still present after cerumen has been removed. The use of cotton swabs and ear candles should be avoided.  (+info)

The primate semicircular canal system and locomotion. (48/195)

The semicircular canal system of vertebrates helps coordinate body movements, including stabilization of gaze during locomotion. Quantitative phylogenetically informed analysis of the radius of curvature of the three semicircular canals in 91 extant and recently extinct primate species and 119 other mammalian taxa provide support for the hypothesis that canal size varies in relation to the jerkiness of head motion during locomotion. Primate and other mammalian species studied here that are agile and have fast, jerky locomotion have significantly larger canals relative to body mass than those that move more cautiously.  (+info)