Biomedical subjects

S Hellström

Publications and source records attributed to S Hellström.

At least 181 records · Page 10Linked to original sources

PubMedDate not supplied

Mechanisms in middle ear effusion production caused by irritation of the external auditory canal.

In an animal model, a stream of chilled air blown into the external auditory canal evoked an edematous pars flaccida and accumulation of a serous effusion in the attic. The degree of inflammatory changes depended on the temperature of the stimuli. The nervous system appears to mediate the observed changes, as the vagus nerve, representing the parasympathetic system, potentiates vascular leakage, and the sympathetic nerves inhibit leakage.

Animals↗

PubMedDate not supplied

Tympanic membrane changes resulting from different methods of transmyringeal middle ear ventilation.

This experimental study was designed to evaluate the morphologic changes of the tympanic membrane in the rat after different methods of transmyringeal ventilation. Artificial ventilation was obtained in two principal ways, either by making tympanic membrane perforations with delayed healing or by inserting a tympanostomy tube. Perforations occupying the upper rear quadrant of the tympanic membrane were made by diathermy or by a carbon dioxide laser with healing times of 12 to 15 days and 18 to 21 days, respectively. Compared with the healing times of perforations made by lancet (9 to 11 days), the healing pattern was considerably delayed. The structural changes of the healed tympanic membrane were minimal, but the connective tissue remained thickened for several months. Repeated insertion of tympanostomy tubes caused a remarkable thickening (30-fold) of the tubulated quadrants. The thickened tympanic membranes were characterized by a hyperplastic, dense connective tissue containing sclerotic plaques. Similar changes, though less pronounced, were also seen after reiterated myringotomies without tube insertion.

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PubMedDate not supplied

Hyaluronic acid reduces connective tissue formation in middle ears filled with absorbable gelatin sponge: an experimental study.

Absorbable gelatin sponge, commonly used in otosurgery, was mixed with high-molecular-weight, highly concentrated hyaluronic acid. The mixture was introduced into the middle ear cavities of rats. The postoperative changes were evaluated by morphologic techniques after two months and three months. The middle ear cavity contained a loose mass of connective tissue with few cells, forming sail-like bridles between air-filled spaces. The filling material was easily detached from the surroundings. The structure of the middle ear mucosa and the tympanic membrane was well preserved. Compared with the findings in a previous study, in which absorbable gelatin sponge alone was used, the combination of gelatin sponge and hyaluronic acid caused significantly less structural alterations in the middle ear cavity. It is concluded that hyaluronic acid, a natural component in most tissues, markedly reduces the formation of the fibrous connective tissue known to develop in middle ear cavities filled with absorbable gelatin sponge alone.

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PubMedDate not supplied

Fate of exogenous hyaluronic acid in the middle ear.

The fate of exogenous high-molecular-weight hyaluronic acid applied in the middle ear was studied in rats. Tritium-labelled hyaluronic acid was deposited, and its disappearance through the eustachian tube was followed by analysis of nasopharyngeal secretions. Radioactivity in the secretions reached a peak after three hours and approached zero after 12 hours, indicating that almost all hyaluronic acid had been removed. The middle ears were all empty when opened 24 hours after the deposition of hyaluronic acid. The fate of hyaluronic acid after obstruction of the eustachian tube was followed both with radioactive hyaluronic acid and subsequent autoradiography and by direct analysis of the hyaluronic acid concentration and the hyaluronic acid molecular weight distribution. Radioactive hyaluronic acid was confined to the obstructed middle ear, and no uptake into surrounding tissues could be detected between three hours and four days after the deposition. The amount of hyaluronic acid deposited could be recovered to about the same extent for up to six days. Analysis of the molecular weight distribution of the deposited material indicated only a slow degradation, if any, during the same time period.

Animals↗

PubMedDate not supplied

Late effects of local anesthetics on tympanic membrane structure.

With the rat tympanic membrane used as a model, various topical anesthetics in current clinical use (phenol, Bonain's liquid, and Xylocaine spray) were tested. Structural changes were observed for up to five months from the time of anesthetic application. The most protracted changes affect the lamina propria, which exhibits a pronounced thickening. The extent of the changes, however, differs according to the agent used; for example, phenol applied to discrete areas exhibited the least widespread changes. In the tympanic portion of the lamina propria, the connective tissue was loosely packed with less regularly arranged collagen fibers, while a tightly packed fiber bundle existed on the meatal side. It is inferred that the submucosal connective tissue layer is the portion of the connective tissue layer where the remodeling and reconstruction of the fibrous layer occur.

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PubMedDate not supplied

Paraganglia of the human recurrent laryngeal nerve.

Recurrent laryngeal nerves (RLNs) from human autopsy material were collected and prepared for light microscopy. Within five of eight investigated RLNs, paraganglia-like organs were found, the mean cross-sectional area of which was estimated to be 0.03 mm2. These organs were composed of cells resembling the type I and type II cells of the carotid body. The possible function of laryngeal nerve paraganglia is discussed.

Cell Nucleolus↗

PubMedDate not supplied

A rat model for pneumococcal otitis media.

The middle ears of 29 male Sprague-Dawley rats were injected with viable pneumococci, type 3 or 6A, and changes were monitored by otomicroscopy and analysis of bacterial samples from middle ear effusions, blood, and the nasopharynx. Depending on the type of pneumococci and its concentration, three responses were noted: otitis media with purulent effusion, otitis media with serous effusion, or no reaction. The mortality rate was low and the animals recovered without permanent deterioration or otomicroscopically discernable change. The results of this study show the rat to be a suitable animal model for the study of bacterial otitis media.

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PubMedDate not supplied

Myringosclerosis develops within 9h of myringotomy.

The aim of the present experimental study was to elucidate the temporal development of myringosclerosis. Twenty-four Sprague-Dawley rats were myringotomized bilaterally. At 3, 6, 9, 12, 18, 24, 30, 36, 48, 60, 72 and 84 h after the myringotomy, 2 animals at each time were examined otomicroscopically and thereafter sacrificed. The pars flaccida and pars tensa were excised and prepared for light- and electron-microscopic studies. Otomicroscopically, myringosclerosis was visible in the pars tensa 24 h after myringotomy, whereas no sclerotic lesions were noted in the pars flaccida. Histologically, sclerotic lesions were present in the pars tensa and pars flaccida 9 and 12 h, respectively, after myringotomy. The pars flaccida responds promptly with an inflammatory reaction characterized by abundant macrophages. Myringosclerosis develops promptly after myringotomy and its establishment is related to an inflammatory reaction.

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PubMedDate not supplied

Distribution of hyaluronan in the middle and inner ear. A light microscopical study in the rat using a hyaluronan-binding protein as a specific probe.

The histochemical distribution of hyaluronan (hyaluronic acid, HYA) was analyzed in middle and inner ear tissues from rats by use of microwave-aided fixation, a hyaluronan-binding protein and the avidin-biotin/peroxidase staining procedure. In the middle ear HYA was mainly localized in the pars flaccida, the ossicles, the round window membrane and in the endomysium of the middle ear muscles. The subepithelial stroma of the Eustachian tube was strongly HYA-positive. In the inner ear, the spiral ligament of the cochlea and the connective tissue surrounding the nerve fibers emerging from the crista ampullaris stained intensely for HYA. Except for a weak staining of the basilar membrane, the Corti organ was devoid of HYA. The heterogenous distribution of HYA may indicate its specific involvement in middle and inner ear physiology and pathology.

Animals↗

PubMedDate not supplied

Middle ear mucosa in rats and humans.

The purposes of the study were to review thoroughly the literature and summarize it in a standardized fashion; to study the mucosa, including the distribution of mast cells, in all parts of the middle ear cavity in rats; and to compare the experimental findings with those known in humans. Adult, healthy rats were studied by light, scanning electron, and transmission electron microscopic techniques. The ciliated and secretory cells of the rat tympanic cavity are confined to two tracts, one anterior and one inferoposterior to the promontory. The tracts connect the epitympanum with the eustachian tube. The pars flaccida exhibits the highest density of mast cells, but mast cells are also distributed in the subepithelial layer of the tracts and in the floor of the tympanic bulla. The structure of the rat mucosa shows striking similarities to that of humans. Thus, from a morphological point of view, the rat seems to be a suitable model for middle ear studies. However, to be able to compare results obtained in different species and/or different laboratories, the areas of the middle ear from which the specimens have been taken must be carefully defined and presented in a standardized manner.

Adult↗

PubMedDate not supplied

The release of histamine from the pars flaccida mast cells one cause of otitis media with effusion?

In this experimental study in the rat, compound 48/80--a potent degranulating drug of mast cells--was instilled in the external auditory meatus towards the tympanic membrane. Moreover, effusion material was produced in the attic space by blocking the tympanic isthmus with a piece of Gelfoam applied through the tympanic bulla. Both these procedures caused a degranulation of the pars flaccida mast cells and subsequently histamine was detected in the rinsing fluid collected from the middle ear cavity. A possible direct cause of the effusion material in the middle ear cavity may be a degranulation of the pars flaccida mast cells, thus resembling an allergic reaction Type I.

Animals↗

PubMedDate not supplied

The site of initial production and transport of effusion materials in otitis media serosa. A study on rat middle ear cavity.

The aim of this experimental study was to localize the site of the initial production of effusion in the middle ear cavity. Via the tympanic bulla the passage between the lateral attic compartment and the rest of the middle ear (isthmus tympanicus) was blocked with Gelfoam and/or the Eustachian tube likewise with a polyethylene tube in both normal and sympathectomized rats. Effusion was thus produced in the attic, while concomitantly dilated vessels were seen in the pars flaccida, which after a couple of days gradually withdrew in a medial direction to form a retraction pocket. Sympathectomy did not prevent the production of effusion. The stream of effusion was nasal to the promontorium and the tensor tympani muscle. Its transport seems to be influenced by the ventilation through the tympanic tube.

Animals↗

PubMedDate not supplied

Middle ear effusion caused by mechanical stimulation of the external auditory canal. An experimental study in the rat.

Mechanical stimulation of the external auditory canal (EAC) in rat, either by scratching or exposure to a stream of air, caused effusion behind an intact ear-drum both in the experimental ear and in the contralateral one. Histologically the pars flaccida appeared oedematous, especially its lamina propria; and was infiltrated by inflammatory cells indicating a vascular leakage. Determination of the histamine level of the content of the middle ear cavity showed elevated levels, not only in the experimental ear but also in the contralateral. This increased level of histamine was recorded as long as 24 hours after stimulation. Though the mechanisms involved are not known, new ideas about the initiation of otitis media with effusion are inferred.

Animals↗

PubMedDate not supplied

Absorbable gelatin sponge (Gelfoam) in otosurgery: one cause of undesirable postoperative results?

Absorbable gelatin sponge (Gelfoam)--commonly used in otosurgery--was gently inserted or firmly packed into the middle ear cavities of rats. The postoperative changes were evaluated 2 to 3 months later when, apart from some air-filled canals leading from the tympanal orifice of the Eustachian tube towards the attic, the middle ear cavity had become filled with newly formed bone and an amorphous mass of adhesions and bridles. The mass consisted of loose connective tissue, with fibroblasts, vessels and inflammatory cells. The tympanic membrane was retracted and fixed to the promontory. There were no signs that any Gelfoam had been removed through the Eustachian tube. The authors proposed that similar tissue reactions may occur in tympano-plasties.

Animals↗

PubMedDate not supplied

Membrana shrapnelli of maturing rats. The occurrence of mast cells, and histamine content in relation to otitis media with effusion.

The membrana shrapnelli or pars flaccida of 12 day old rats is thick (84 micron) and almost completely fills the lateral attic compartment. Histologically it is characterized by a thickened layer of stratified squamous epithelium and a lamina propria whereas an inner epithelial lining is difficult to discern. Mast cells are numerous and distributed throughout the lamina propria. At day 21 and day 30 the thickness of the pars flaccida is reduced and histologically it resembles that of the adult. Mast cells are mainly located in the vicinity of blood vessels and in a layer just beneath the squamous epithelium. The number of mast cells per unit area of pars flaccida is considerably higher in young rats as compared to adults. At day 12 their number is roughly 2.1 times that of the adult and at day 21 and 30 about 1.5 times. Except for a slightly raised level of histamine at day 30 the concentration of histamine in the pars flaccida of young rats did not differ from values obtained in the adult. Previous experimental studies have indicated that mast cells in the pars flaccida may play an important role in the pathogenesis of OME. It is interesting to note that the pars flaccida of young rats contains more mast cells than that of the adult. Should this also be the case in the pars flaccida of young humans it is tempting to suggest that mast cells may play a role in the pathogenesis of OME in children too.

Animals↗

PubMedDate not supplied

Myringotomy made by CO2 laser--an alternative to the ventilation tube? An experimental study.

In order to examine whether a myringotomy made with a CO2-laser might be alternative to a ventilation tube, a perforation was made in the upper rear quadrant bilaterally, of 22 rats. The laser-made perforations showed a delayed healing pattern, about twice the closing time of a similar-sized perforation made with a myringotomy lancet. Serous effusion was constantly observed in the attic space during the first 9 days but only in one ear was there actual discharge through the perforation. The size of the perforation started to diminish when the hyperplastic keratinizing squamous epithelium reached the perforation border.

Animals↗

PubMedDate not supplied

Autonomic innervation of the tympanic membrane. An immunocytochemical and histofluorescence study.

The innervation of the tympanic membrane of the rat was investigated with respect to noradrenergic and peptide-containing nerve fibres. In sections, most of the nerves in both the flaccida portion and the tensa portion seemed to be of the small, unmyelinated types, though a few larger myelinated nerves were also found. Noradrenergic fibres, exhibiting specific catecholamine fluorescence (CA), were detected along the blood vessels in the pars flaccida and along the vascular network of the annulus fibrosus. In the pars flaccida, fibres exhibiting SP-like, VIP-like- and enkephalin-like immunoreactivity were noted. None of these peptides could be detected in the pars tensa. The exclusive localization of the oedema-provoking peptides, SP and VIP, to the pars flaccida may be of importance with regard to establishing pars flaccida as the initial site of effusion production in experimental secretory otitis media.

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PubMedDate not supplied

Fine structure of the rat tympanic membrane after treatment with local anaesthetics.

The tympanic membrane of the rat was studied ultrastructurally after application of a local anaesthetic--lidocaine spray. Already after 10 min, degenerative changes--or even necrosis--were observed on both epithelial surfaces of the eardrum. Later on, a marked hyperplasia of the epidermal layer was most characteristic, as was a proliferation of the fibroblasts of the subepithelial connective tissue. After 3 weeks the eardrum had not regained its normal appearance. No perforations were encountered and only minute substructural changes could be detected within the fibrous layer.

Aerosols↗