Cochlear ablation effects on amino acid levels in the chinchilla cochlear nucleus.

Inner ear damage can lead to hearing disorders, including tinnitus, hyperacusis, and hearing loss. We measured the effects of severe inner ear damage, produced by cochlear ablation, on the levels and distributions of amino acids in the first brain center of the auditory system, the cochlear nucleus. Measurements were also made for its projection pathways and the superior olivary nuclei. Cochlear ablation produces complete degeneration of the auditory nerve, which provides a baseline for interpreting the effects of partial damage to the inner ear, such as that from ototoxic drugs or intense sound. Amino acids play a critical role in neural function, including neurotransmission, neuromodulation, cellular metabolism, and protein construction. They include major neurotransmitters of the brain - glutamate, glycine, and γ-aminobutyrate (GABA) - as well as others closely related to their metabolism and/or functions - aspartate, glutamine, and taurine. Since the effects of inner ear damage develop over time, we measured the changes in amino acid levels at various survival times after cochlear ablation. Glutamate and aspartate levels decreased by 2weeks in the ipsilateral ventral cochlear nucleus and deep layer of the dorsal cochlear nucleus, with the largest decreases in the posteroventral cochlear nucleus (PVCN): 66% for glutamate and 63% for aspartate. Aspartate levels also decreased in the lateral part of the ipsilateral trapezoid body, by as much as 50%, suggesting a transneuronal effect. GABA and glycine levels showed some bilateral decreases, especially in the PVCN. These results may represent the state of amino acid metabolism in the cochlear nucleus of humans after removal of eighth nerve tumors, which may adversely result in destruction of the auditory nerve. Measurement of chemical changes following inner ear damage may increase understanding of the pathogenesis of hearing impairments and enable improvements in their diagnosis and treatment.

Cochlear implantation in cochlear otosclerosis.

OBJECTIVES/HYPOTHESIS: The objective was to correlate implant performance in cochlear otosclerosis to 1) matched control samples, 2) severity of otic capsule involvement, 3) prior ipsilateral surgery, and 4) programming issues. STUDY DESIGN: Retrospective case controlled study. METHODS: Study cohort comprised 30 individuals. Diagnosis was based on prior ear surgery (stapedectomy [n = 18] or fenestration [n = 2]) and/or pathognomonic radiological findings. High-resolution computed tomography images of the temporal bones were assessed by two radiologists and graded (range, 0-3) for the extent of otosclerosis. Operative records were reviewed. Performance, programming visits, and the number of electrode deactivations at 6 months and at 1 year after implantation were determined for the individuals with otosclerosis and compared with a group of matched control subjects. A within-group comparison correlating severity of otosclerosis to the above was carried out. RESULTS: Implant performance in individuals with cochlear otosclerosis was not significantly different from those without. Previous surgery on the side of implantation did not alter performance. Programming difficulty as reflected in the number of visits and electrode deactivation for sound quality reasons were comparable. Deactivation for facial nerve stimulation occurred exclusively in otosclerotics with the most severe radiological disease (grade 3) and was only with non-modiolar hugging electrodes (n = 5). There was no observed difference between the radiological extent of otosclerosis and implant performance. CONCLUSION: Individuals with severe otosclerosis considering cochlear implantation can be counseled to expect similar benefit to those without, regardless of whether prior surgery occurred on the side of implantation or of severity of otic capsule involvement. There is a significant risk of facial nerve stimulation in otosclerotics with grade 3 disease.

Intratympanic gentamicin for the treatment of unilateral Meniere's disease.

OBJECTIVE: To determine the efficacy of intratympanic gentamicin instillation as treatment of incapacitating unilateral Meniere's disease, using a predetermined regimen with a fixed dose. STUDY DESIGN: A prospective study from a single institution between 1988 and 1998. METHODS: One hundred fourteen patients were enrolled in this study. Gentamicin (26.7 mg/mL) was administered three times daily for 4 consecutive days. The Committee on Hearing and Equilibrium Guidelines for Reporting Treatment Results in Meniere's Disease of the American Academy of Otolaryngology and Head and Neck Surgery (1985) were used. RESULTS: Comprehensive data were available for 90 individuals. Complete control of vertigo was achieved in 76 (84.4%), substantial control in 8 (9.0%), limited control in 2 (2.2%), and insignificant control in 4 (4.4%) patients. Disability scores at the end of 2 years were as follows: 76 patients (84.4%) had no disability, 5 (5.6%) had mild disability, 2 (22%) had moderate disability, and 7(7.8%) had severe disability. Caloric testing responses, as determined using electronystagmography, were as follows: 71% of the patients had an absent ice-water response, 16% had a positive ice-water response, and in 13% there continued to be present a bithermal response. Hearing was worse in 22 patients (25.6%), unchanged in 41 (48.2%), and improved in 22 (25.6%). CONCLUSIONS: Intratympanic gentamicin administration using this particular protocol is an effective treatment option for patients with disabling unilateral Meniere's disease. Hearing loss is a distinct possibility, and patients should be advised accordingly.

Delayed onset and decreased incidence of diabetes in BB rats fed free radical scavengers.

We tested the hypothesis that free radicals play a role in the selective destruction of pancreatic beta-cells in BB/Wor rats. Diabetes-prone BB rats of both sexes and 40 days of age were divided into three groups. The control group was fed ad libitum Purina rat chow powder, while the experimental group was fed ad libitum the rat chow powder blended with a mixture of four known free radical scavengers: allopurinol, mercaptopropionylglycine, dimethylthiourea and Vitamin E. A third group was pair-fed 10 g chow powder/rat/day, since in earlier experiments we observed that rats on the experimental diet consumed only about 10 g/rat/day. All rats were studied up to age 120 days. Body weight and food intake were measured daily. Urine was tested for glucose beginning at age 60 days. When glucosuria appeared, blood glucose and urinary ketones were measured. Body weight gain in the experimental and pair-fed groups was similar, but lower than the control group. Life table analysis of the data showed a decreased and a delayed onset of diabetes in the rats fed free radical scavengers. Thus, the results of this study demonstrated that calorie restriction and the related impaired growth did not affect the incidence of diabetes in the BB rat. In addition, the results suggested a role for free radicals in the spontaneous destruction of pancreatic beta-cells in the BB rat.

Manpower for obstetrics-gynecology. III. Contributions to total female medical care.

This final report from the cooperative manpower study of the University of Southern California and The American College of Obstetricians and Gynecologists describes the development of a female data file that outlines the care of women patients by all specialties. Obstetrician-gynecologists are compared to other specialists; they see 300,000 women per day in the United States and provide a wide range of care. Preventive care plays a larger role than in other major specialties, patient counseling and education are emphasized, and obstetric care is a major commitment. Nonetheless, acute and serious surgical and medical diagnoses are an important component of the practices of obstetrician-gynecologists.

PIP: This paper, a report from the comparative manpower study of the University of Southern California and the American College of Obstetrics and Gynecologists compares the contribution of obstetricians-gynecologists (ob-gyns) to that of other specialists in providing medical care to the total female population. 24 allopathic medical and surgical specialities were studied, accounting for 2/3 of the nation's physicians. Patient-physician encounters in the female data file total 211,780. Obstetrics-gynecology and general internal medicine each account for 1 of 7 visits by female patients. The chief types of problems addressed by ob-gyns are preventive, medical and surgical. Ob-gyns have about 1/5 of their encounters in the latter 3 groups in the younger and postmenopausal age groups, contrasting with care provided by other specialists where the percentage drops from 13.9% at 20-24 years of age to 2.8% for those 65 and older. For patients of all ages ob-gyns obtain samples for cervical cytologic examinations at 32.9% of all visits. Twice as much preventive care is provided by ob-gyns as by the other leading generalist specialities. Almost 40% of the ob-gyns' primary patient problems are classed as obstetric, whereas 2/3 of the generalists' are medical and less than 20% of the ob-gyns' are exclusively medical. Care of special conditions and examinations without sickness accounts for over 60% of the ob-gyns work compared to 12% for the other generalists. Most of the neoplasms seen by ob-gyns are benign whereas the opposite is true for other generalists. It is clear from this data that women do make choices in regard to which physician in which specialty they see and under what conditions.