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Biomedical subjects

S Hellström

Publications and source records attributed to S Hellström.

At least 55 records · Page 3Linked to original sources
PubMed1996

Healing of tympanic membrane after myringotomy during Streptococcus pneumoniae otitis media. An otomicroscopic and histologic study in the rat.

The purpose of our study was to elucidate the course of healing of the tympanic membrane (TM) when myringotomy was performed during acute otitis media. The early and long-lasting structural changes of the TM were studied in an animal model. Rats were inoculated with Streptococcus pneumoniae (PnC) type 3 in the bulla. When the infection was manifest, myringotomy was performed. On days 4 and 12, and 3 and 6 months after myringotomy, the TM status was checked by otomicroscopy and TMs were prepared for light and electron microscopy. Comparison was made with PnC-infected TMs that were not perforated, as well as myringotomized noninfected TMs. The infection resolved more slowly in myringotomized ears compared to PnC-infected ears that were left untouched. After 6 months, the pars tensa of the myringotomized infected ears was thickened and showed a disorganized collagen structure, compared with myringotomized noninfected ears, in which TMs were normalized. The PnC-infected TMs without myringotomy were completely normalized after 2 months. We conclude that a combination of bacterial infection and myringotomy causes long-lasting changes in TM structure. This impaired structure of the connective tissue could be of importance in chronic middle ear disease as a presumptive site for retraction and perforation of the TM.

Acute Disease↗
PubMed1995

Structural changes in the rat tympanic membrane following repeated pressure loads.

Healthy adult laboratory rats were exposed to alternating negative pressure and atmospheric pressure to replicate the clinical situation found in patients with chronic sniffing habits and chronic middle ear disease. The rats were placed in a box in which the pressure changed at intervals of 30 s between atmospheric pressure and a negative pressure of -3 kPa. This was repeated continuously for periods of 3 and 7 days. At completion of the experimental period, all rats had a normal otomicroscopic status. However, histological studies demonstrated that the pars flaccida was wrinkled and the loose connective tissue contained large fibroblasts with their long axes lying in a disorganized manner. The cells of the keratinizing epithelium were thicker than normal and mitoses were seen. Epithelial crypts filled with keratin were numerous along the epithelium. In the pars tensa, all layers were thicker than normal. These findings demonstrate that repeated pressure loading can create structural changes in the tympanic membrane.

Animals↗
PubMed1995

Localization and quantity of hyaluronan in urogenital organs of male and female rats.

The histochemical distribution of hyaluronan was analysed in various urogenital organs of male and female (non-pregnant and pregnant) rats by use of a hyaluronan-binding protein and avidin biotin/peroxidase staining. Microwave-aided fixation was used to preserve the extracellular location of hyaluronan. The concentrations of hyaluronan in the different tissues were measured with a highly sensitive radio-assay. Hyaluronan accumulated predominantly in the connective tissue around smooth muscle fibres and in the subepithelial lamina propria. Abundant hyaluronan also occurred in perivascular and perineural connective tissue. In the female urogenital organs, hyaluronan content was high in the vagina and urinary bladder, and highest in the vagina during pregnancy. In the uterus, the surface epithelium of the endometrium stained intensely. In the ovary, the zona pellucida of the oocyte and the theca interna cell layer of the follicles and the follicular fluid of mature follicles exhibited prominent staining. The corpus luteum was devoid of hyaluronan, whereas enlarged corpora lutea of pregnancy exhibited weak, patchy staining. In male urogenital organs, staining for hyaluronan was absent from the testis and epididymis, whereas the erectile connective tissue of the penis stained intensely. The hyaluronan concentrations were high in penile tissue and urinary bladder, while testis, epididymis and the ductus deferens contained only little hyaluronan.

Animals↗
PubMed1995

Comparison of the repair of permanent tympanic membrane perforations by hydrocolloidal dressing and paper patch.

Thirty consecutive patients with permanent perforations of their tympanic membranes (TM) present from 2.5 to 50 years (mean 18.7 years) were admitted to a prospective study using two alternative methods of dressings for closure of the perforations. An adhesive-coated hydrocolloid material was compared with a conventional dressing of vaseline impregnated rice paper patch after de-epithelialization of the perforation border. Nine of the permanent TM perforations (30 per cent), five with the hydrocolloidal dressing and four with the rice paper patch had healed when followed-up after one year. The size of eight of the central perforations that had healed was equal to or less than 25 per cent of the TM. Also one perforation with a size of 65 per cent had healed. Seven perforations were located in the posterior part of the TM: four in the posterior-superior quadrant, one in the inferior quadrant, one had engulfed the posterior half of the TM and one included the anterior-inferior quadrant. Only two perforations out of 14, with a size of 25 per cent or less, located in the anterior-inferior quadrant, healed. No significant difference was demonstrated between the two types of dressings. Both groups noted an immediate improvement in hearing of 10.8 and 9.3 dB, respectively, after application of the dressing. The study demonstrates that application of an occlusive dressing or paper patch in 30 per cent of patients can promote the healing of long-standing perforations. The chances for healing are better if the perforation is located in the posterior part of the TM. This simple technique immediately improved hearing and should be tried before a patient is referred for myringoplasty surgery.

Adolescent↗
PubMed1995

Myringosclerosis caused by increased oxygen concentration in traumatized tympanic membranes. Experimental study.

The purpose of this study was to elucidate possible relationships between the oxygen concentration of the middle ear cavity and the development of myringosclerosis. Three groups of rats with myringotomized tympanic membranes were exposed to different oxygen concentrations of 10%, 15%, and 40%, respectively, for 1 week. A fourth group was kept in ambient air. Two other groups of rats with myringotomized and intubated tympanic membranes were exposed to oxygen concentrations of 10% and 40%, respectively, for the same period of time. Otomicroscopically, all hyperoxic animals had more numerous myringosclerotic lesions compared with the ambient air group, and also displayed a pronounced hyperplasia of the keratinizing epithelium around the perforation border. By contrast, the hypoxic animals showed less pronounced myringosclerotic lesions or even completely lacked them. It is inferred that an increased oxygen concentration in the middle ear cavity will increase the likelihood of myringosclerotic deposits. The mechanism involved could be related to the formation of oxygen radicals.

Animals↗
PubMed1994

Early structural changes in the rat tympanic membrane during pneumococcal otitis media.

The early inflammatory reaction in the rat tympanic membrane was studied during the first 36h following inoculation of Streptococcus pneumoniae type 3 in the middle ear cavity. Otomicroscopic examination showed only minor signs of inflammation in the early stages although changes at the light microscopic level were pronounced. This reaction differed significantly between the pars flaccida and pars tensa of the tympanic membrane. Three hours after inoculation, edema and infiltration with polymorphonuclear leukocytes and macrophages were found in the pars flaccida whereas in the pars tensa no polymorphonuclear leukocytes were noted until after 12h. This reaction was most prominent after 36h. In the pars flaccida, mitoses occurred frequently among the cells of the simple squamous epithelium, which changed into a double-layered cuboidal epithelium. These findings demonstrate that an inflammatory reaction starts earlier in the pars flaccida than in the pars tensa of the tympanic membrane.

Acute Disease↗
PubMed1994

The distribution of hyaluronan in human skin and mature, hypertrophic and keloid scars.

A hyaluronan-binding protein (HABP) was used to locate the distribution of HA in normal skin and in various types of scar tissue: mature scar tissue, hypertrophic scar tissue and keloids. The study was intended to establish whether or not a deviant HA distribution could explain the different clinical features of these scar tissues. The distribution of HA was found to differ between the various scar tissues. In normal skin an intense HA-staining was observed in the papillary dermis. In mature scar tissue the distribution of HA resembled that of normal uninjured tissue, but the layer of HA was thinner. In hypertrophic scar tissue, HA occurred mainly as a narrow strip in the papillary dermis. Keloid tissue showed the least HA-staining of the papillary layer and resembled that of the bulging reticular dermis. In contrast, the thickened granular and spinous layer of the keloid epidermis exhibited an intense HA-staining. We suggest that the altered distribution and amount of HA in these different scar tissues may contribute to their different clinical characteristics. This histochemical technique for the demonstration of HA in scar tissue could be of use in clinical work to decide on therapeutic strategies.

Adolescent↗
PubMed1994

Exogenous heparin, topically administered, aids the remodelling of connective tissue in the healing of experimental tympanic membrane perforations.

Heparin, in concentrations of 250, 2,500 and 25,000 IU, was applied topically to the edge of tympanic membrane (TM) perforations, standardized in size, once daily until the perforation had closed. At 2 months, the animals were killed and the TMs subjected to otomicroscopic and light microscopic studies. The day that closure of the TM perforations was complete (median 8 days) was the same for the various heparin groups as for the sterile water-treated controls. However, regarding opacity of the healed TM area, heparin affected the TM in a dose-dependent manner. The TMs that had been subjected to the highest concentration of heparin were the most transparent and showed the least sclerosis. When compared for thickness, the TMs treated with the higher concentration of heparin were considerably thinner than those treated with the lower concentration. The sterile water-treated controls were all thicker than the heparin-treated TMs. It is inferred that glycosaminoglycan heparin improves the quality of the healed area of TM perforations.

Administration, Topical↗
PubMed1994

Localization of hyaluronan in the human endolymphatic sac. A study using the affinity hyaluronan binding protein.

This study was undertaken with the aim of localizing hyaluronan (hyaluronic acid, HYA) in tissue sections of the human endolymphatic sac by use of a hyaluronan-binding affinity protein and the avidin-biotin/peroxidase staining procedure. Five human endolymphatic sacs were removed during surgery for acoustic neuroma. After microwave-aided fixation and decalcification, paraffin-embedded sections were prepared by routine histological methods. HYA was detected in some of the intraluminal substance as well as in parts of the epithelial lining, mainly in the rugose portions of the endolymphatic sac. HYA was observed intracellularly in epithelial cells. It was also found in the subepithelial tissue near the epithelia and close to the bony aqueduct. The distribution of HYA was uneven at all locations. The finding of HYA within the human endolymphatic sac may imply that this substance has important functions in the control of inner ear fluid homeostasis.

Affinity Labels↗
PubMed1994

Experimental cholesteatoma in the rat.

The etiology of cholesteatoma is still enigmatic. Of the current theories, none has been confirmed with adequately convincing evidence. A completely suitable animal model has not hitherto been available and there is still a need for further experimental studies of this entity. As a possible experimental model we suggest dimethyl-benzanthracene induced cholesteatoma in the rat.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1994

Pharmacologic labyrinthectomy.

Pharmacologic labyrinthectomy has become an alternative to surgery for treatment of severe Ménièr's disease. The use of systemic streptomycin has been replaced by intratympanal instillations of gentamicin that are administered once daily for a limited number of days. Gentamicin provides a high success rate for ablation of vertigo without causing any unnecessary negative effects on hearing. Future development of more selective vestibulotoxic chemicals could mean that pharmacologic labyrinthectomy will become a simple and ultimate treatment for disabling Ménière's disease.

Aminoglycosides↗
PubMed1993

Phenol anesthesia of the tympanic membrane in purulent otitis media: a structural analysis in the rat.

In the present study, local anesthetics were applied to the tympanic membrane (TM) of rats following experimentally evoked purulent otitis media (POM). The structure of the TM was evaluated 24 h, 2 weeks and 3 months after application of phenol to a discrete are of the right TM. The left ear was used as a control. POM induced swelling of all tissue layers of the pears tensa. The tissues were invaded by inflammatory cells and disintegrated. The fibrous layer also dissolved, leaving spontaneous perforations. However, phenol on inflamed TMs did not further alter the TM structure. These findings infer that the injurious effect of topical anesthesia on the intact TM is more or less negligible when applied to diseased TMs.

Anesthesia, Local↗
PubMed1993

Structural changes in the middle ear tissues of the rat after fractionated irradiation.

Chronic suppurative otitis media often ensues in patients treated with irradiation against a head and neck tumor. In an experimental study, rats were exposed to irradiation to evaluate the sensitivity of the middle ear to an accumulated irradiation dose of 20-45 Gy. Observed otomicroscopically, all animals appeared to have normal tympanic membranes and no fluid developed in the middle ear space. Ten days after the irradiation, minor structural changes had occurred in the pars flaccida. The keratinizing epithelium had thickened and mitoses were seen histologically. The lamina propria was edematous and contained polymorphonuclear cells and macrophages. The middle ear mucosa from all other tissue sites appeared normal. Six months after irradiation only minor changes in the pars flaccida were evident: the lamina propria was thin and inelastic and macrophages were present in the stroma. It is inferred from this study that the middle ear of the rat is relatively resistant to irradiation.

Animals↗
PubMed1993

Bronchial mucosal structure after histamine inhalation.

Previous studies have shown an increased number of inflammatory cells and an increased level of hyaluronan in the bronchoalveolar lavage (BAL) fluid, 24 h after the inhalation of histamine. In the present report, the influence of histamine inhalation on the bronchial mucosa was, therefore, investigated in 20 subjects. Scanning electron microscopy (SEM) revealed that small areas of the mucosal surface were altered or lacked cilia more frequently in the bronchial biopsies taken 24 h after the inhalation of histamine than in the control biopsies. In contrast, light and transmission electron microscopy revealed no increase in epithelial damage and no changes in the subepithelial morphology. The results indicate that inhalation of histamine does not significantly alter the structure of the bronchial mucosa, which means that bronchial biopsies can be taken for routine morphological examination within 24 h after a histamine test. When using the biopsies in research, one should consider the possible influence of the histamine test.

Adult↗
PubMed1993

Round window membrane in serous and purulent otitis media. Structural study in the rat.

The rat was used as an animal model to reveal structural alterations in the round window membrane (RWM) during serous otitis media (SOM) and purulent otitis media (POM) over a 6-week period. Comparison of POM animals and control animals showed that the RWM in the former became almost six times as thick as that in controls, whereas that of SOM animals was twice as thick. The structural changes in the RWM in POM animals were confined mainly to the epithelium facing the middle ear cavity and the subepithelial space, which was invaded by inflammatory cells and exhibited dilated vessels. The normal flat epithelium was transformed via cuboidal cells to a cylindric epithelium containing both ciliated and goblet cells. In SOM animals, light microscopy revealed only minor changes in the RWM structure. Ultrastructurally, however, the connective tissue layer exhibited dense aggregations of collagen, increased numbers of fibroblasts, and, in one case, elastic fibers. This last phenomenon was not observed in either POM ears or normal ears. The study showed that various inflammatory conditions of the middle ear, both noninfectious (SOM) and infectious (POM), can cause different structural alterations of the RWM. These structural changes may influence passage through the RWM differently.

Animals↗
PubMed1993

Animal model for persistent tympanic membrane perforations.

Topically applied hydrocortisone was used to develop an animal model for persistent tympanic membrane (TM) perforations. Hydrocortisone suspension was applied on the margins of TM perforations of standardized size in rats once daily for 10 days. The healing patterns of the TMs were mapped weekly and, when the perforations were about to close, daily. After 50 days, all hydrocortisone-treated perforations were open, whereas the controls closed within 9 to 12 days. At 3 months, when one third of the perforations still were open, the TMs were studied by otomicroscopy and light microscopy. All TMs were thickened and covered by keratin and wax. The thickened epidermal layer at the border of the TM perforations that remained open also draped the surface of the perforation facing the middle ear cavity. The thickened connective tissue layer contained abundant fibroblasts with their axes of length oriented at random. Both application of 1.4% hyaluronan and wounding of the perforation border enhanced the healing rate of the hydrocortisone-induced chronic TM perforation.

Animals↗