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Biomedical subjects

S Hellström

Publications and source records attributed to S Hellström.

193 records · Page 11Linked to original sources
PubMedDate not supplied

Middle ear effusion induced by a stream of air in the external auditory canal. A temperature-related phenomenon.

The blowing of chilled (14 degrees C) air into the external auditory canal (EAC) resulted in a profuse middle ear fluid production. The stimulation caused marked changes in the pars flaccida of the tympanic membrane. A slight vasodilatation was noted in the oedematous loose connective tissue layer of the pars flaccida. The abundant mast cells showed no signs of degranulation. When stimulating animals with air at 22 degrees C, only minimal effusion production and tympanic membrane changes could be induced. At 34 degrees C, no changes occurred at all. Thus it was shown that temperature is an important factor when provoking middle ear effusion by stimulating the EAC. As fluid production is one of the major signs in OME, one may speculate whether temperature may be an overlooked etiologic agent in this disease.

Air Movements↗
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Different structural changes in membrana Shrapnelli in serous and purulent otitis media. An experimental study in the rat.

In an animal model, production of serous and purulent effusion material was induced by blocking the Eustachian tube and cleaving the soft palate, respectively. Two and 6 weeks after the different surgical procedures, animals were sacrificed and the membrana Shrapnelli was analysed by light- and electronmicroscopy. The two types of middle ear effusion were associated with various structural changes of the membrana Shrapnelli. In serous otitis media the pars flaccida appeared fibrotic, with large dilated vessels. Sometimes its inner layer, facing the attic space, was contiguous with the investing layer of the ossicles. In purulent otitis media the pars flaccida was thickened and the inner epithelial lining was replaced by a pseudostratified squamous epithelium containing ciliated and secretory cells. Ciliated cells lining the pars flaccida appeared pathognomonic for a longstanding middle ear infection. It is inferred that the structure of membrana Shrapnelli changes under the influence of inflammatory conditions in the middle ear cavity, changes which specifically reflect the different types of otitis media.

Animals↗
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Structural changes in the tympanic membrane after repeated tympanostomy tube insertion.

In an animal model (rat) a polyethylene tympanostomy tube was repeatedly inserted (four periods lasting 2 weeks) into the upper rear quadrant of the right tympanic membrane (TM). The intervals between the different tubulation periods (TPs) lasted 3 weeks. The corresponding quadrant of the left TM was subjected to repeated myringotomies (four times). The structural changes in the TMs were evaluated otomicroscopically and by histological techniques 3 weeks and 3 months after the final TP. Repeated tympanostomy tube insertion caused a dramatically thickened pars tensa. The thickened areas were characterized by a scar tissue exhibiting sclerotic plaques and a dense connective tissue with bone-like formations. Occasionally, islands of keratinizing stratified squamous epithelium were noted within the thickened pars tensa as well as interrupting the epithelial lining facing the tympanic cavity. Similar structural changes occurred after myringotomy without tube insertion, but they were not so pronounced as after repeated tympanostomy tube insertion. The changes were not restricted to the manipulated quadrants, but also affected the untouched anterior quadrants. Throughout the observation period the anterior quadrants improved, while the rear quadrants remained severely affected.

Animals↗
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An overlooked site of tissue mast cells--the human tympanic membrane. Implications for middle ear affections.

The tympanic membranes of 14 deceased, with no record of ear disease in their medical files, were investigated with respect to the presence of mast cells. The Shrapnell membrane (pars flaccida) had a rich content of mast cells, whereas the pars tensa had none except for a few located close to blood vessels along the handle of the malleus. The volume density of the pars flaccida mast cells was calculated as 3.9% and the number of mast cells/mm2 as 299 +/- 35 (mean +/- SE; n = 14). The possible role of these mast cells under both healthy and diseased middle ear conditions is discussed.

Cell Count↗
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Inner ear effects of exogenous hyaluronan in the middle ear of the rat.

1.9% hyaluronan (HA) (mol. wt. 3 x 10(6] was applied repeatedly into the middle ear of rats through a myringotomy. The function and structure of the cochlea was analysed by auditory brainstem recordings (ABR) at 2-31.5 kHz and by light microscopy. The myringotomy significantly impaired the ABR thresholds at frequencies below 8 kHz. Five days after the last application of HA, the ABR thresholds showed minor improvements at 6-8 kHz but were impaired at 12 and 20 kHz, as compared with control levels. One month after the last administration of HA, ABR thresholds were significantly improved as compared with the initial level at 2-6 kHz but normal at all other frequencies. After 3 months, all ABR thresholds had returned to the pre-treatment (normal) level. Five days after the last application of HA, the latencies for almost all frequencies were significantly prolonged for waves II and IV at the ABR threshold. After 3 months all latencies had returned to their pre-treatment (normal) values. Highly concentrated hyaluronan (1.9%) is free from ototoxicity but does have transient functional effects on the inner ear.

Animals↗
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Autonomic nerves and middle ear fluid production. An experimental study in the rat.

The production of middle ear effusion by mechanical stimulation was studied in sympathectomized and vagotomized animals. Mechanical stimulation was obtained by a 14 degree C airstream in the external auditory canal. In sympathectomized animals this procedure caused effusion production and vasoconstriction of pars flaccida vessels. Mechanical stimulation in the vagotomized animals did not cause any production of effusion material. Degranulated mast cells were observed in all animals, including controls. The study indicates that the vagal nerve, in contrast to the sympathetic nerves, is involved in the mechanisms causing the leakage of fluid into the middle ear cavity, when cold air is blown into the external auditory canal.

Air↗
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Middle ear effusion induced by various inflammatory mediators and neuropeptides. An experimental study in the rat.

Vascular leakage in the middle ear cavity was studied after i.v. administration of various substances in rats and determined by the Evans blue technique. Bradykinin, histamine, serotonin, acetylcholine, substance P (SP) and vasoactive intestinal polypeptide (VIP) resulted in extravasation of Evans blue. In the case of bradykinin and histamine, the leakage was dose dependent. Calcitonin gene-related peptide (CGRP) did not affect vessel permeability. In other experiments the effect of histamine antagonists was tested on production of middle ear effusion, caused by blowing air at 14 degrees C into the external auditory canal (EAC). The increase in vessel permeability in this otitis media model was inhibited by the H2-receptor antagonist cimetidine, at doses 0.1 and 1.0 mg/ml. Diphenhydramine, an H1-receptor antagonist, arrested only partly middle ear fluid accumulation. Our study demonstrated that various inflammatory mediators and neuropeptides are capable of inducing vascular leakage in the middle ear cavity. It was also concluded that H2-receptors are involved in the regulation of middle ear vascular permeability.

Acute-Phase Proteins↗
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Motor and sensory fibers of the superior laryngeal nerve in the rat. A light and electron microscopic study.

A quantitative and qualitative study of the superior laryngeal nerve (SLN) and its branches was performed on the intact nerve and after experimental denervation procedures. The distribution patterns of the myelinated fibers of the intact internal (SLNI) and external (SLNE) branches in the rat were unimodal with a fiber diameter range of 0.5-12 microns and with peaks at 2-4 microns. Numerous unmyelinated fibers, ranging in diameter from 0.1-2.3 microns, were evenly distributed all over the nerve. The SLNI contained no degenerated myelinated fibers after intracranial vagotomy, but about 25% of the unmyelinated fibers showed degenerative features. In the SLNE 2-10% of the myelinated fibers and about 25% of the unmyelinated fibers were degenerated after the same procedure. Extracranial vagotomy caused degeneration of nearly all fibers in the SLNI and SLNE. Single unmyelinated fibers appeared normal after this procedure. Occasional myelinated and a few unmyelinated fibers were degenerated after excision of the superior cervical ganglion. It is inferred from the results that a majority of the myelinated fibers in the SLN (96-99%) are sensory, with the cell bodies in the extracranial vagal ganglia. The SLNE was also found to be predominantly sensory, as only 2-10% of the myelinated fibers and about 25% of the unmyelinated fibers had their cell bodies in the brainstem. Single myelinated and a few unmyelinated fibers in both the SLNI and SLNE had their origin in the superior cervical ganglion.

Animals↗
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Inner ear disturbances following inoculation of endotoxin into the middle ear.

Inner ear function was assessed by a frequency-specific (+/-100 Hz) auditory brainstem response (ABR) technique after a single instillation of a suspension of purified E. coli lipopolysaccharide in sterile water into the round window (RW) niche in rats. Instillation of endotoxin caused a transient concentration and tonotopically dependent dysfunction of the inner ear. The largest threshold impairment occurred in the high-frequency region anatomically located close to the RW. At 31.5 kHz the threshold impairment persisted throughout the study. Morphologic damage to the inner ear was not detected at the light microscopic level when using serial sections from decalcified specimens. Our study supports the clinical hypothesis that remnants of non-viable bacteria such as endotoxins, when trapped in the middle ear, can promote middle ear effusion and dysfunction of the inner ear.

Animals↗
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Prevention of experimental acute otitis media with penicillin V.

The preventive effect of penicillin V (pcV) in pneumococcal otitis media in the rat has been studied. The pcV was administered either before bacterial challenge (prevention group) or after challenge but before the establishing of acute purulent otitis media (AOM) (early treatment group). In both cases a fulminant infection was avoided. Thus, in the prevention group no animal developed AOM and in the early treatment group the fulminant AOM was avoided in all cases. These results give further support to the idea of using long-term treatment with an antibiotic with a narrow spectrum to avoid recurrent AOM (rAOM). Furthermore the observation that early treatment might stop the development of fulminant AOM indicates another more restrictive possibility to use antibiotic as a prophylactic measure in otitis-prone children.

Acute Disease↗
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Bacteriological characterization of the effusion material in an animal model for serous and purulent otitis media.

By means of cleaving the soft palate and blocking the Eustachian tube, two otomicroscopically well defined types of otitis media, serous and purulent, were created in an animal model (rat). The microbiological pattern of these conditions were characterized at 1, 2, 3, 4 and 6 weeks after the onset. Samples were collected from the middle ear cavity via the bulla tympanica and cultured for aerobic as well as anaerobic bacteria. The serous effusion was culture-negative. The purulent effusion material was culture positive, and mixed with Gram-positive (S. aureus, S. epidermidis, Strept. faecalis) and Gram-negative (E. coli, Proteus mirabilis) bacteria of which the latter dominated. No anaerobic species were detected. The study shows that the two otomicroscopically different types of otitis media also differ with regard to the microbiological pattern. The rat thus provides the opportunity to study these two different inflammatory middle ear responses--infectious and noninfectious--during standardized conditions.

Animals↗
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Persistent structural changes in the middle ear mucosa of the rat, after an experimentally induced episode of pneumococcal otitis media.

To examine the effect of a transient episode of purulent AOM on the middle ear mucosa, an animal model was used. Histological examination was performed after inoculation of pneumococci into the rat middle ear. At 4, 8 and 12 days, and at 2 months after the inoculation, rats were sacrificed on each occasion and samples taken from specific areas of the middle ear mucosa. Structural alterations were noted at all mucosal sites. The normally flat epithelium had become more cuboidal or cylindrical, and numerous ciliated cells occurred in areas originally devoid of these cells. Epithelial cells penetrated the subepithelium forming gland-like structures. In the early phase, day 4 and day 8, inflammatory cells invaded the subepithelial layer except in the tympanic membrane. At 2 months, with the tympanic membrane otimicroscopically and histologically normalized, the structural changes of the mucosa still persisted indicating that a transient episode of pneumococcal otitis media can cause persisting mucosal changes.

Acute Disease↗