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T Ovesen

Publications and source records attributed to T Ovesen.

33 records · Page 2Linked to original sources
PubMed1995

Culture of rabbit middle ear epithelial cells. A method for primary culture and subculture with identification, characterization and growth specification.

During the last decade middle ear epithelium has been cultured from various species. Until now, subcultivation has been achieved only with the use of a feeder-cell layer or conditioned medium. These factors are possible confounders in the in vitro model. On the other hand, subcultivation is necessary for exact quantitative studies. We present a reproducible culture method allowing subcultivation without feeder-cells or conditioned medium. The main features in our method are a low-serum, hormone-supplemented medium, an incubation temperature of 34 degrees C, fixation of explants, gentle trypsinization and replating with high cell density. Cells were identified by immunohistochemistry through a battery of monclonal antibodies. The percentage of epithelial cells in the subculture was 99.2%. To our knowledge, this is the first report describing subcultivation of middle ear epithelial cells exclusively in a completely controlled environment. These are optimal circumstances for future investigation and quantification of various factors influencing proliferation and differentiation of middle ear epithelium.

Animals↗
PubMed1994

Superoxide dismutase in in vitro cultures of middle ear fibroblasts from the rabbit.

The present study was undertaken to establish whether intra- and extracellular concentrations of the antioxidative enzyme superoxide dismutase (SOD) in cultures of rabbit middle ear and skin fibroblasts were affected by increasing normal oxygen tensions from 7% to 21% and cause structural damage. The DNA amount was measured fluorometrically and intra- and extracellular concentrations of SOD were determined spectrophotometrically by the inhibition of formazan absorbance. Results demonstrated that SOD was located primarily intracellularly in middle ear fibroblasts and that exposure to atmospheric air gave rise to a significant increase in the SOD concentration from the 6th day following altered oxygen tension (P < 0.0044). Extracellular SOD was sparse in cultures at 7% oxygen whereas atmospheric air induced a significant increase in formazan absorbance from 5% to 60% (P < 0.0163). Inhibition studies indicated that the latter was partly the result of compounds with reducing capabilities similar to superoxide anions. These findings suggest that exposure of middle ear fibroblasts to atmospheric air may involve generation of oxygen-derived free radicals in vitro as well as in vivo but the complexity and significance of these changes need further investigation.

Animals↗
PubMed1994

Immunohistochemical quantitation of collagen types I, II, IV and V in the ventilated and non-ventilated rabbit middle ear with otitis media with effusion.

Morphometric quantitation of the area fractions of collagen types I, II, IV and V was determined in the normal rabbit middle ear mucosa and in relation to otitis media with effusion (OME) using a three-layered peroxidase-antiperoxidase technique. The effects of substituting normal low-oxygen middle ear gas (non-ventilated) with atmospheric air (ventilated) were studied in both healthy ears and ears with OME. Based upon previous histological examinations in rabbits, only ears with OME for more than 8 weeks were included to ensure the presence of chronic inflammation (COME). Atmospheric air was introduced into the middle ears by insertion of ventilation tubes or by an enlarged myringotomy. Collagen type I was predominant in all groups studied. The area fractions of collagen types I, II and IV were increased significantly in COME, with collagen type II elevated in particular. Ventilation of the normal ears resulted in a significantly increased area fraction of cells, while the area fractions and distributions of the collagen types were unaffected. None of the ventilated ears in COME improved or healed spontaneously. The total fraction of collagen in COME was not changed significantly by the introduction of atmospheric air. However, the individual distribution of the collagen types was altered, with significantly larger area fractions of types II and V found in ventilated ears with COME. Possible explanations for the differences found are discussed, including the role of oxygen-derived free radicals.

Animals↗
PubMed1994

In vitro growth and collagen synthesis in fibroblasts from the rabbit middle ear mucosa.

The present methodological study was undertaken to introduce a model system in which individual cells of the middle ear mucosa could be studied under controlled conditions allowing standardized sampling and different manipulations using quantitative methods. The method is based upon isolation and culture of fibroblasts from normal rabbit middle ear mucosae. The growth pattern of the cells was determined by measurement of the total content of cell protein, DNA content and cell division activity. Collagen synthesis was also estimated and results compared with normal skin fibroblasts. Finally, fibroblasts derived from rabbit middle ear mucosae with otitis media were cultured under similar conditions. Results demonstrated the method to be valid and reproducible. Evaluated by any of the parameters applied, growth initially increased exponentially, followed by a stationary phase with a constant cell mass. The growth potentials in middle ear fibroblasts appeared to differ significantly from skin fibroblasts. Except for a decreased cell proliferation, fibroblasts from diseased mucosae did not demonstrate any major differences from the normal fibroblasts probably because the original inflammatory stimuli in vivo were lost in vitro. These findings suggest that future investigations of a model system of otitis media in vitro require the addition of inflammatory mediators.

Animals↗
PubMed1994

Atmospheric air vs. normal middle ear gas: effects on in vitro growth and collagen synthesis in normal middle ear fibroblasts.

The present study was undertaken to quantitate the effects of atmospheric air and normal middle ear gas on cultured fibroblasts obtained from normal rabbit middle ear mucosa. The cells were exposed to three different gas compositions: 7% O2:5% CO2:88% N2, 21% O2:5% CO2:74% N2, and 75% O2:5% CO2:20% N2. The growth was monitored by measuring the total content of cell protein, the amount of DNA, and the cell division activity. The activity of the synthetic apparatus was determined by the collagen synthesis. For comparison, rabbit skin fibroblasts were grown under identical conditions. The results demonstrated significantly higher replication rate of middle ear fibroblasts at 7% oxygen than at atmospheric air whereas the collagen synthesis was significantly lower at 7%. Furthermore, the responses varied significantly between rabbit middle ear and rabbit skin fibroblasts. Thus the present study substantiates the hypothesis of an influence of atmospheric air on the middle ear mucosa which might be of importance, e.g., in relation to insertion of ventilation tubes or longstanding perforations of the tympanic membrane in otitis media.

Animals↗
PubMed1994

The influence of endotoxin upon middle ear fibroblasts cultured in normal middle ear gas and atmospheric air.

Otitis media represents a continuum of inflammatory stages frequently in association with bacteria and/or endotoxin. Furthermore, the disease is often treated with insertion of ventilation tubes, which causes hyperoxia relative to the physiological state in the tympanic cavity. The present study was undertaken to quantitate the interaction between endotoxin and relative hyperoxia in cultures of rabbit middle ear fibroblasts incubated in normal middle ear gas and atmospheric air, respectively. Growth was monitored by determination of DNA, cell protein and cell division. The synthetic activity was estimated by collagen production. The antioxidant defense was determined by measuring the intra-and extracellular concentrations of superoxide dismutase (SOD). The results demonstrated that hyperoxia significantly impaired the growth of middle ear fibroblasts, which was compensated for by addition of endotoxin stimulating the growth. The collagen synthesis increased significantly in atmospheric air with a synergistic effect of endotoxin. Hyperoxia induced intracellular SOD formation, while endotoxin tended to reduce the synthesis. Finally, exposure to atmospheric air caused significantly larger amounts of reducing agents extracellularly in cultures without endotoxin compared to endotoxin incubated cultures. It is suggested that endotoxin possess both synergistic and antagonistic potential as regards the effects of relative hyperoxia, and that the interaction between endotoxin and hyperoxia may be an important factor in otitis media.

Animals↗
PubMed1993

The effect of N-acetylcysteine on the in vitro growth of normal rabbit middle ear fibroblasts.

In the present study the effect of N-acetylcysteine on the growth pattern and collagen synthesis of cultures of rabbit middle ear fibroblasts was determined. The growth pattern was evaluated by cell counting, measurements of the total content of cell protein and mitotic activity by incorporation of 3H-thymidine. Collagen synthesis was estimated by incorporation of 3H-proline. The results demonstrate a dose-dependent reduction in both normal cell proliferation and collagen production. Thus, N-acetylcysteine seems to possess properties desirable and useful in the treatment of secretory otitis media.

Acetylcysteine↗
PubMed1992

Local application of N-acetylcysteine in secretory otitis media in rabbits.

The middle ears of patients with secretory otitis media treated by ventilation tubes are exposed to two abnormal conditions: an inflammatory process and a hyperoxic condition. Both are known to cause changes in the mucosa, fibrosis in particular. N-acetylcysteine has been demonstrated to exhibit anti-inflammatory effects as well as being an oxygen radical scavenger. In an attempt to elucidate if N-acetylcysteine is capable of preventing the changes caused by secretory otitis media and ventilation tubes we administered different doses of the substance locally to the middle ear of an animal model. The results showed that N-acetylcysteine reduced the extent of the inflammation in the middle-ear mucosa and prevented the long-term fibrotic changes associated with secretory otitis media.

Acetylcysteine↗
PubMed1992

Bacteria and endotoxin in middle ear fluid and the course of secretory otitis media.

To determine the influence of bacteria and bacterial products on the course of secretory otitis media (SOM) following ventilation tube insertion we examined 68 middle ear effusions from 57 children with SOM. Swabs were taken for bacteriological examination and the content of endotoxin was measured. The children were followed up for one year and relapse of SOM was recorded. Bacteria were present in 38% of effusions and endotoxin was detectable in 96%. Relapse occurred in 26% of the patients and was related to the presence of bacteria in the original effusion (P < 0.01). The concentration of endotoxin, however, did not correlate with the course of SOM.

Adolescent↗
PubMed1992

Alterations in tympanic membrane appearance and middle ear function in 11-year-old children with complete unilateral cleft lip and palate compared with healthy age-matched subjects.

Forty-four 11-year-old children born with a complete unilateral cleft lip and palate were examined to determine the frequency and the extent of changes in the tympanic membrane and the middle ear function and compared with 16 healthy children of the same age. The incidence of hearing impairment, abnormal middle ear pressure, retraction of the pars flaccida and abnormal tympanic membrane appearance were 24, 44, 23 and 67% respectively among the patients while the same parameters in the control group were 0, 12.5, 6 and 12%. Previous grommet insertion in the patient group was statistically correlated to both tympanic membrane abnormality and abnormal middle ear pressure but, remarkably, no association was found between grommet insertion and hearing impairment. The poor middle ear function in the children with cleft lip and palate was probably a result of reduced Eustachian tube function.

Acoustic Impedance Tests↗
PubMed1992

Histological examination of the rabbit middle ear in secretory otitis media with and without a ventilation tube.

To study the time-related histopathological lesions in secretory otitis media as it develops into the chronic stage, including the influence of ventilation of the middle ear, we examined the middle ear mucosa in a rabbit model. The observation period was from two weeks until 18 months. The histological method applied included haematoxylin-eosin and Sirius red staining for morphometric quantification of the goblet cells, the thickness of the connective tissue layer, the area fractions of blood vessels, inflammatory cells, fibroblasts and collagen fibres. In conclusion, the middle ear mucosa in secretory otitis media exhibited inflammatory changes correlating with the duration of the disease. Ventilation of the middle ear in secretory otitis media did not improve the changes.

Animals↗
PubMed1992

Superoxide dismutase in middle ear fluid from children with secretory otitis media.

Superoxide dismutase (SOD) constitutes an important enzymatic defense against the destructive biochemical events associated with inflammation. To examine the presence of SOD in the middle ear fluid (MEF) in secretory otitis media (SOM) the content of SOD was measured in the MEF from 66 children with SOM. The applied method was based on light emission associated with reduction of the chemiluminescence of luminol reacting with superoxide anions (O2-). From the inhibition exerted by the addition of standard SOD the concentration of SOD in the samples was extrapolated. The findings divided the MEF's into two significantly different groups: 48% with undetectable SOD, 52% with a SOD range of 200-12,000 ng/ml, median: 3,333 ng/ml, 95% confidence limits: 2,000-5,000 ng/ml (p < 0.0005). It is suggested that the concentration of superoxide dismutase in the middle ear may play an essential role for the outcome of secretory otitis media and the effect of insertion of ventilation tubes.

Adolescent↗
PubMedDate not supplied

Accuracy of an automatic impedance apparatus in a population with secretory otitis media: principles in the evaluation of tympanometrical findings.

INTRODUCTION: The primary demand for a screening procedure for secretory otitis media (SOM) is to identify an objective test with sufficient sensitivity and specificity to meet the needs of the screening program. This study was designed to estimate the value of a portable automatic impedance apparatus to meet these needs. SUBJECTS AND METHODS: Two hundred twenty children with unilateral or bilateral SOM were evaluated in a double-blind, cross-sectional study. All have fulfilled two of the following three criteria for surgical intervention: (1) SOM by physical examination, (2) greater than 20 dB hearing impairment, and/or (3) adenoid symptoms. All ears were evaluated using tympanometry, following which myringotomy was performed. RESULTS: Otomicroscopy showed fluid behind the tympanic membrane in 393 ears. All underwent myringotomy. Thirteen percent (51 ears) were empty. Of the otomicroscopic findings consistent with SOM, 82% had B curves, 6% had C2 curves, 8% had C1 curves, and 4% had A curves. Both C2 and B curves were considered abnormal. Sensitivity of the apparatus is 94.4% and of the specificity is 52.9%. There was no statistical correlation between tympanometrical findings and fluid viscosity. RESULTS: A test intended for screening has to be simple, easy, and quick to perform. Furthermore, the test should have high sensitivity. The automatic impedance apparatus is able to meet these demands; however, the individual results have to be confirmed by another method, eg, otomicroscopy, pure-tone audiometry, and/or manual tympanometry.

Acoustic Impedance Tests↗
PubMedDate not supplied

Cortical centres underlying auditory temporal processing in humans: a PET study.

We have used positron emission tomography (PET) to test a specific hypothesis of a neural system subserving auditory temporal processing (acoustical stimulus duration discrimination). Maps of the cerebral blood flow distribution during specific stimulations were obtained from five normally-hearing and otherwise healthy subjects. The auditory stimuli consisted of sounds of varying duration and of auditorily presented words in which the duration of the initial phoneme was manipulated. All stimuli alternated with conditions of silence in a subtraction paradigm. The blood flow distribution was mapped with O-15-labelled water. The results demonstrated that stimuli requiring recognizing, memorizing, or attending to specific target sounds during temporal processing generally resulted in significant activation of both frontal lobes and the parietal lobe in the right hemisphere. Based on these results, we hypothesise that a network consisting of anterior and posterior auditory attention and short-term memory sites subserves acoustical stimulus duration perception and analysis (auditory temporal processing).

Adult↗