Biomedical subjects

L Lundman

Publications and source records attributed to L Lundman.

8 recordsLinked to original sources

PubMed1999

Hearing in patients operated unilaterally for otosclerosis. Self-assessment of hearing and audiometric results.

The objective of this study was to examine the outcome of unilateral stapes surgery in one patient group with bilateral hearing loss and one group with unilateral hearing loss. The patients' own estimations of improvement in hearing ability and the occurrence of other ear-related symptoms were examined retrospectively and in a follow-up study. Ninety-five of 123 patients operated for otosclerosis in only one ear between 1987 and 1992 responded to a follow-up examination. Observed audiometric findings and changes thereof, along with the patients' own estimations of their hearing handicap pre- and postoperatively, and the occurrence of other ear-related symptoms were studied. Despite good surgical results (closure of air-bone gap within 20 dB in 94%), 33% of the patients had severe hearing disabilities postoperatively, and many of these patients needed further amplification with a hearing aid. Mild dizziness occurred in 33% of the patients postoperatively and did not decrease over time. Discomfort in the operated ear due to strong sounds was reported in 20%. Change in sound quality occurred in 80% of the operated ears, but tended to disappear over time. From the results of this study it may be concluded that surgery in one ear only, leaving the other ear with poor hearing, is not an optimal hearing rehabilitation of patients with otosclerosis. It is important endevour to achieve bilateral hearing in order to give the patient good social hearing. Postoperative dizziness and unpleasant hearing quality do occur frequently, and the patients need to be informed about these problems preoperatively.

Audiometry, Pure-Tone↗

PubMed1997

Round window membrane. Structure function and permeability: a review.

The ultrastructure of the round window membrane of humans, monkeys, felines, and rodents discloses three basic layers: an outer epithelium, a middle core of connective tissue, and an inner epithelium. Interspecies variations are mainly in terms of thickness, being thinnest in rodents and thicker in humans. Morphologic evidence suggests that the layers of the round window participate in absorption and secretion of substances to and from the inner ear, and that the entire membrane could play a role in the defense system of the ear. Different substances, including antibiotics, local anesthetics, and tracers such as cationic ferritin, horseradish peroxidase, and 1 mu latex microspheres, are placed in the middle ear side traverse the membrane. Cationic ferritin and 1 micron microspheres placed in perilymph become incorporated by the inner epithelial cells of the membrane. Permeability is selective; factors include size, concentration, liposolubility, electrical charge, and thickness of the membrane. Passage of substances through the round window membrane is by different pathways, the nature of which is seemingly decided at the outer epithelium of the round window membrane.

Aged↗

PubMed1992

Ciprofloxacin and the inner ear--a morphological and round window membrane permeability study.

This study was conducted in order to evaluate ototoxic potential and passage through the round window membrane of ciprofloxacin, a newly developed antimicrobial drug with an antibacterial spectrum well suited for the treatment of suppurative otitis media. Ciprofloxacin was injected intraperitoneally in 40 guinea pigs in doses ranging from 25 to 150 mg/kg body weight for 14 consecutive days. Sixteen inner ears of chinchillas were exposed to ciprofloxacin at a concentration of 0.1 mg/ml applied directly to the intact round window membrane. Despite severe deterioration of the animals injected with the highest doses, no behavioral or definite morphological evidence of inner ear or vestibular damage could be seen. Ciprofloxacin concentrations in the perilymph were determined with high-performance liquid chromatography. Direct passage of ciprofloxacin, presumably via the round window membrane, was demonstrated. After 1 h and 15 min, an arithmetic mean concentration of 0.165 micrograms/ml (95% confidence interval +/- 0.053) could be demonstrated in the perilymph. It can be concluded that ciprofloxacin has no ototoxic effect when administered systemically. Furthermore, when locally applied into the middle ear, it has the capacity to pass into the inner ear.

Animals↗

PubMed1992

Inner ear damage and passage through the round window membrane of Pseudomonas aeruginosa exotoxin A in a chinchilla model.

By the use of computer-assisted morphometric analysis of the organ of Corti and/or measurements of action potential threshold changes, inner ear changes in chinchillas were evaluated 4 weeks after application on the round window membrane of a Pseudomonas aeruginosa exotoxin A solution. Severe inner ear damage was detected after application of 50 ng (5 microL at a concentration of 10 micrograms/mL) exotoxin A, whereas application of 5 ng exotoxin did not cause measurable inner ear damage. Perilymph concentrations of exotoxin A were measured with an enzyme-linked immunosorbent assay 1.5 to 19 hours after 50 ng, 0.5 micrograms, or 5 micrograms of exotoxin A was applied on the round window membrane. Only the highest concentration produced measurable levels of exotoxin in the inner ear fluids. It is concluded that exotoxin A present on the round window membrane of the chinchilla has the ability to penetrate into the inner ear and cause irreversible inner ear changes.

ADP Ribose Transferases↗

PubMed1992

Permeability of the normal round window membrane to Haemophilus influenzae type b endotoxin.

Sensorineural hearing loss associated with otitis media may be due to passage of ototoxic substances such as bacterial toxins and antibiotics, from the middle ear into the inner ear. The round window membrane is the most likely route for such transport. The aim of this study was to analyze the extent of endotoxin passage through the normal round window membrane. The round window membranes of 19 chinchillas were exposed in vivo to Gelfoam soaked in purified Haemophilus influenzae type b endotoxin at a concentration of 45,000 endotoxin units per ml (EU/ml) during 3 to 24 h. Endotoxin levels in the perilymph were measured with Limulus Amaebocyte Lysate or Quantitative Chromogenic Limulus Amaebocyte Lysate. Endotoxin was detected in half of the inner ears at concentrations close to the detection limit (approximately 4 EU/ml). The results suggest that the normal round window membrane efficiently protects the inner ear against the passage of bacterial endotoxins from the middle ear cavity. It is unlikely that endotoxin at concentrations found in the middle ear secretion during otitis media can traverse the round window membrane in sufficient amount to cause inner ear deterioration.

Animals↗

PubMed1992

Pseudomonas aeruginosa exotoxin A and Haemophilus influenzae type b endotoxin. Effect on the inner ear and passage through the round window membrane of the chinchilla.

Pseudomonas aeruginosa exotoxin A was applied to the round window membrane of the chinchilla in concentrations ranging from 1 microgram/ml to 1 mg/ml. Haemophilus influenzae type b endotoxin (45,000 endotoxin units/ml) was applied in the same way. Five animals were also subjected to blocking of the Eustachian tube, 3 to 8 months earlier, resulting in serous otitis media and exotoxin A (1 mg/ml) was applied into the round window niche of these animals. Effects on the inner ear was recorded with quantitative morphology (hair cell counting) and electrophysiologically (action potential threshold measurements) 4 weeks after application of exotoxin A. Concentrations of exotoxin A in perilymph was measured with ELISA and concentration of endotoxin in perilymph was measured with Limulus Amoebocyte Lysate and Quantitative Chromogenic Limulus Amebocyte Lysate. Four weeks after application of exotoxin A at a concentration of 10 micrograms/ml severe inner ear damage could be demonstrated. No inner ear damage was demonstrated when lower concentrations were used. Passage into the inner ear could only be demonstrated after exposure of the round window membrane to an exotoxin A concentration of 1 mg/ml. Round window membranes affected by chronic inflammation were shown to be less permeable to exotoxin A, thus indicating that thickening of the round window membrane may have a protective effect on the inner ear. A low passage rate into the inner ear was demonstrated after endotoxin exposure. It may be concluded that small amounts of exotoxin A passing through the round window membrane may cause inner ear damage. The passage rates, however, for both exotoxin A and endotoxins are low.

Animals↗

PubMed1989

Round window membrane permeability. An in vitro model.

The round window membrane of the mongolian gerbil was dissected out, together with its bony niche. The preparation was mounted between two glass chambers representing the middle ear cavity and the perilymphatic space respectively. Passage through the round window membrane did not occur within 3 h when testing high-density lipoprotein with a molecular weight 115-350 kD. Horse-radish peroxidase, with a molecular weight of 48 kD, passed the round window membrane at a mean rate of 6 micrograms/h when the concentration of the protein was 10 g/l in the middle ear chamber. The present in vitro model is considered to be free from leakage artifacts between the chambers. Passage rates for different substances through the round window membrane can be calculated under controlled conditions using this type of in vitro model.

Albumins↗

PubMed1987

Round window membrane permeability. An in vitro model.

The round window membrane is regarded to be the main route for passage of potentially ototoxic substances from the middle ear cavity into the inner ear. This is of clinical importance in acute otitis media and chronic otitis media, where sensorineural hearing impairments sometimes develop. The accuracy and reliability of an in vitro round window membrane permeability model was studied. The round window membrane of the mongolian gerbil was resected, together with its bone niche. The preparation was mounted between two glass chambers, representing the middle ear cavity and the perilymphatic space respectively. Passage through the round window membrane did not occur within 3 h for low-density lipoprotein with a molecular weight of 2,300 kD and high-density lipoprotein with a molecular weight of 115-350 kD. Horseradish peroxidase, with a molecular weight of 40 kD, passed the round window membrane at a mean rate of 6 micrograms/h when the concentration of the protein was 10 g/l in the middle ear chamber. The present in vitro model is considered to be free of leakage artifacts between the chambers. Passage rates for different substances through the round window membrane can be calculated under controlled conditions using this type of in vitro model.

Animals↗