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Biomedical subjects

G Bredberg

Publications and source records attributed to G Bredberg.

At least 37 records · Page 2Linked to original sources
PubMed1990

Electrophonic hearing and cochlear implants.

It has been difficult to explain the good speech understanding obtained by some cochlear implant patients fitted with a single-channel electrode and analog transmissions of the speech signal (Vienna/3M implant). It has also been difficult to explain the variation in results reported by different groups using the same implant. One hypothesis asserts that the above differences can be explained by the observation that electric stimulation with an implanted electrode might result in two different auditory sensations, the first resulting from the stimulation of the remaining hair cells (electrophonic component) and the second from the electric stimulation of the auditory nerve (electro-neural component). The two sensations are very different. As a result of different definitions of total deafness (functional or threshold definition), patients with remaining hair cells are operated on by some groups, but not by other groups. Some published results from different studies are discussed with reference to the above hypothesis and the possible consequences for the selection of the patients, the use of extra- or intracochlear electrodes, and the selection of the speech coding strategy are discussed.

Audiometry, Pure-Tone↗
PubMed1989

Brainstem response audiometry in chronic Lyme borreliosis.

Auditory brainstem responses (ABR) were investigated in 26 patients with acrodermatitis chronic atrophicans, which is a late manifestation of Lyme borreliosis. Nine of the patients showed pathological ABR, four of them unilaterally and five bilaterally. The main pathological findings were: 1) Poor reproducibility of waves IV-V or of wave V; 2) Increased latency of wave V. After antibiotic treatment, ABR was improved in eight of the nine patients, and in three of them it was normal. In the five patients who did not completely recover, the improvement consisted in better reproducibility and a tendency towards normal wave V latencies. The results of this study indicate that the central nervous system may become involved in patients with acrodermatitis chronica atrophicans.

Adult↗
PubMed1987

Ultrastructural evaluation of the microslicing method for the study of temporal bone pathology.

Microslices 3 mm thick from undecalcified human temporal bones were prepared with a special cutting machine and then processed for SEM and TEM in order to evaluate advantages and disadvantages of the microslicing technique for the study of the temporal bone pathology. In the examined microslices there was some mechanical distortion of the membranous labyrinth, detachment of soft tissues from bone and a considerable amount of contamination by bone dust and debris which are circulated during sectioning. For SEM the method therefore has limited value. For TEM a relatively contamination free area can be found some distance from the cutting surface of each microslice.

Cochlea↗
PubMed1987

Hair cell distributions in the normal human cochlea. A report of a European working group.

Cochlear hair cell counts from individuals who had clinically normal hearing prior to their death have been plotted for various age bands as a function of the number of hair cells per millimetre against their position in the cochlea. Position has been expressed as the distance of that observation of hair cell density from the base of the cochlea, divided by the total length of the cochlea, thereby giving a proportional representation of the cochlea in the range of 0.0 to 1.0 with 20 subdivisions of 0.05. There is an age-related decrease in the number of hair cells in the normal population, and this is more marked for the outer hair cells.

Adolescent↗
PubMed1987

Hair cell distributions in the normal human cochlea.

This supplement presents the results of a collaborative project between workers from several European nations. The study was started in order to provide data describing the distribution of the sensory hair cells in the normal human cochlea and to allow the evaluation of age-related changes in the hair cell density. Fifty-three cochleas (including nine from fetuses) were preserved by perilymphatic perfusion with fixative shortly after death. In the non-fetal material the hearing was clinically normal prior to death. Some subjects had audiograms available and these also had to be normal for their age for inclusion of the cochlea in the study. Dissection of cochleas permitted surface preparation techniques to be used to count the hair cells and allow the hair cell density to be described as inner or outer hair cells per mm. The total length in mm of each cochlea was also measured (Length). The location of each hair cell density count was defined as distance in mm from the base (Distance), distance in mm from the apex (Length minus Distance), or as a proportion of the total length of the cochlea when the location of that count was measured as distance from the base (Distance/Length). The material was allocated to one of six age bands. For each age band and at each point in the cochlea for which data existed the average hair cell density and its standard deviation were calculated. This allowed average cytocochleograms to be drawn for both inner and outer hair cells. The proportional method of representation of location within the cochlea gave the best fit of the available data and the proportional cytocochleograms are presented, although the data for all three methods are included in tabular form. The average cytocochleograms indicate a progressive age-related loss of outer hair cells. This loss was exacerbated at both the apical and basal ends of the cochlea. The overall loss was less marked for the inner hair cell population but was accentuated at the base, like that of the inner hair cells, although not at the apex. With the proportional datasets, and taking fetal age as zero, a model of hair cell loss was developed. A simple linear equation in the form: Hair cell density(i) = (Age in years X Age Coefficient(i)) + Constant(i) gave the best fit at each proportional location (i) for both inner and outer hair. The age coefficients and constants are given in tables for inner and outer hair cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Cell Count↗
PubMed1986

Ototoxicity of kanamycin in albino and pigmented guinea pigs. I. A morphologic and electrophysiologic study.

Ototoxic drugs of the aminoglycoside type have been shown to accumulate to melanin, suggesting a possible mechanism for their ototoxicity. The present study was undertaken by combining electrophysiologic and morphologic methods to investigate whether the ototoxicity of kanamycin is different in pigmented and albino guinea pigs. In pigmented animals a kanamycin dose of 200 mg per kilogram of body weight per day resulted in hearing loss together with loss of both inner and outer hair cells. The albino animals in the same dose group showed significantly less hearing loss and hair cell degeneration. With daily doses of 20 and 60 mg/kg/day, no difference in ototoxicity was found between the pigmented and albino animals. The results support the hypothesis that affinity of kanamycin to inner ear melanin might be responsible for the difference in ototoxicity between albino and pigmented guinea pigs.

Animals↗
PubMed1986

Ototoxicity of kanamycin in albino and pigmented guinea pigs. II. A scanning electron microscopic study.

In a previous study we demonstrated an increased ototoxicity in pigmented compared with albino guinea pigs given high doses of kanamycin. In the present investigation using scanning electron microscopy we studied the fine structure of the surface preparation of the organ of Corti to examine whether a qualitative difference in lesion pattern exists between albino and pigmented guinea pigs. Kanamycin was given by daily subcutaneous injections in the amounts of 20, 60, and 200 mg per kilogram of body weight until hearing impairment was noted. No difference in the pattern of degeneration was observed in the albino and pigmented guinea pigs. No giant cilia were seen. The classic gradient of degeneration of the outer hair cells (OHCs), with the most pronounced damage in the first row of OHCs in the basal coil and progressively diminishing lesions in the second and third rows, as observed in both species.

Animals↗
PubMed1983

A case material with post lingual severe hearing loss and communication handicap.

The analyses have given some general clues to the therapeutic handling of these patient categories: 1. The A and B groups can be labelled "hearing" with clearly useful residual hearing. 2. The patients in the C group, as a rule, are utilizing very little from acoustic speech stimulation, mostly the prosodic information. Several patients in this group are possible implant candidates, and it is reasonable to expect that (with a suitable stimulus device and a suitable application of this) the patients could get an additional support during speech reading, so that they function as the B group. Tactile devices are also an alternative or a supplement for this group, and a pilot study on six patients is in progress in the department in cooperation with the Department of Speech Communication at the Royal Institute of Technology. 3. The patients within the A and B groups will in the first place be offered additional functional training programmes (prosodic training, audio-visual training and possibly vibration training) and, as an ultimate alternative a social activation in group therapy may be considered. Some patients in these groups might also be candidates in the future for an extra cochlear implant.

Hearing Aids↗
PubMed1980

Response properties of spiral ganglion neurons in cochleas damaged by direct mechanical trauma.

Electrical activity of single neurons in the spiral ganglion of the guinea pig cochlea was correlated with receptor hair cell damage produced by local mechanical lesions of the organ of Corti. Damage to or loss of hair cells was assessed using scanning electronmicroscopy. Principal finds were (1) neurons emanating from damaged regions showed changes in their tuning curves such as loss of sensitivity, broadening of tuning curves; (2) in some cases, the loss of sharp tuning tip resulted in an apparent shift of the tuning curve to lower frequencies; and (3) apparently pure outer hair cell lesions, of limited spatial extent, could result in the same effects as mixed inner and outer hair cell lesions.

Animals↗
PubMed1977

Scanning electron microscopy of the nerves within the organ of Corti.

A method of studying the innervation inside the organ of Corti is presented. Rabbits, guinea pigs and chinchillas were fixed with perfusion of the perilymphatic spaces. The cochleas were dissected according to the surface specimen technique and the specimens critical point dried, coated with gold and studied in the SEM. The final dissection into the planes of the fluid spaces of the organ of Corti was done in the dry state using especially sharpened watch makers forceps and razor blade knives. The course of the afferent and efferent innervation is described and differences between the species illustrated. Small high nerve endings on the outer hair cell degenerate after cutting the efferent nerve supply by dividing the vestibular nerve indicating their efferent nature.

Animals↗