Birgitta Jansson

Subcellular changes in the endolymphatic sac after administration of hyperosmolar substances

The effects of hyperosmolar substances on the ultrastructure of the endolymphatic sac were studied in mice. Fifteen minutes after intravenous injection of urea or glycerol, subcellular changes in the endolymphatic sac were observed. These consisted of the occurrence of abundant cytoplasmic granules with a floccular or lamellar material, or both, in the light epithelial cells. Similar material was also present in the lumen of the endolymphatic sac, suggesting a common source and increased secretory activity. Mannitol caused similar changes, though less pronounced. The possibility that the alterations in the fine structure of the endolymphatic sac may be associated with a reduction in the hydrostatic fluid pressure in the rest of the labyrinth is discussed.

Effects of Glycerol on the Endolymphatic Sac

A time sequence study was performed on experimental animals to investigate long-term effects of intravenously administered glycerol on the epithelial cell activity in the endolymphatic sac (ES) and on the ES volume. Fifteen to 60 min after systemic glycerol administration, the ES volume decreased. During this time, the ES lumen was often obliterated. Subsequently, the lumen dilated. Meanwhile, many light epithelial cells showed granules with floccular and/or lamellar contents. Concomitant deposition of floccular material into the luminal space suggested secretion of macromolecular substances, presumably from these transformed light cells. The number of granule-containing cells was significantly increased 2 h (p < 0.01) and 4 h (p < 0.01) after glycerol administration. The ES was significantly dilated after 4 h (p < 0.01) and 6 h (p < 0.05). Thus systemic alterations in osmotic pressure led to a reversible change in ES volume, with initial collapse followed by dilation and normalization after 8 h. The secretory response of the ES preceded the volume increase. A great variability in ES volume indicated high compliance of this organ system. A secretion/degradation system or turnover of osmotically active macromolecular complexes in the epithelial lining and ES lumen seems to be linked to the ability of the ES to hold fluid volumes within a wide range. This may serve as a micromechanical pressure-volume-regulating device for monitoring endolymph fluid homeostasis.

Correlations between Serum Osmolality and Endolymphatic Sac Response Using Hypertonic Glycerol

This study, using mice, correlated serum osmotic pressure, experimentally elevated with an intravenous injection of glycerol of varying tonicity (1.3, 2.6 and 5.2 g glycerol/kg body weight) with endolymphatic sac (ES) response. The injection produced a rise in serum osmotic pressure that was measured after 15 min (from 308 +/- 12.9 mosm/kg b.w. to 320 +/- 1.9, 353 +/- 19.3, 427 +/- 9.4 mosm/kg b.w., respectively). Normal levels were noted about 60 min after the injection. The ES was graphically displayed at 0 min, 1, 2 and 4 h using as a basis composite electron micrographs. The ES responded with signs of active secretion and degradation of macromolecular substances which appeared to be related to the rise in serum osmotic pressure. The study showed that the ES responds to glycerol injection with fine structural changes indicative of increased intra-epithelial synthesis of sugar/protein residues which are secreted and degraded within its lumen. The technique used made it possible to characterize the ultrastructural secretory pathways from the epithelial cells into the sac lumen. The results indicate that the ES may sense and respond to dynamic changes of the micro-osmotic environment probably via alterations in inner ear fluid homeostasis.

The Autogenous Mucosal Cyst Procedure: Experimental Reconstructive Surgery of the Airway with a New Composite Graft Technique

Autogenous buccal mucosa was transplanted to the pretracheal region in five beagles. Subsequently a cyst developed in which the graft constituted the main part of the cyst wall. After 4 to 13 weeks the cyst was explored and a perforated autogenous cortical bone plate was sutured to its vertex. After a further 5 to 7 weeks the resulting composite graft was sutured to an anterior tracheal window defect. All dogs survived. They did not lose weight. One dog had moderate breathing difficulties during exertion. At bronchoscopy, which was performed in all dogs, no contractions or granulations were seen but the stability of the airway wall in the grafted areas was reduced. These areas were removed after 8 to 15 months and studied by light microscopy, scanning electron microscopy and transmission electron microscopy. The mucosa survived in all cases. Total resorption of the bone graft occurred in all but two cases, in which remnants were found.

Reconstruction of the Airway with a Composite Alloplastic and Autogenous Graft An Experimental Study

A method by which an alloplast can be lined with mucosa and thereafter used as a composite pedicled graft is described and discussed. Autogenous buccal mucosa was transplanted to the pretracheal region in five beagles. Subsequently a cyst developed in which the graft constituted the main part of the cyst wall. After 5 to 6 weeks the cyst was explored and a Proplast sheet was sutured to its exterior. After another 3-9 weeks the area was explored again. A composite graft had then formed comprising buccal mucosa on the outside, stabilized by Proplast and supplied by blood vessels arising from the strap muscles and their fascia. After opening of the cyst, the composite graft was used to repair a tracheal defect in the same dog. All of the dogs survived and they did not lose any weight. The graft areas were removed 5 1/2-9 months after the tracheal window repair. Tracheoscopy was performed at least twice on each dog. The grafted areas were also studied by light microscopy, scanning electron microscopy and transmission electron microscopy. The grafts survived in all cases. There was no tendency towards graft extrusion. Connective tissue cells predominated in the pores of the Proplast framework, in which small foci of metaplastic bone formation were also seen.

The Autogenous Mucosal Cyst An Experimental Study with Special Reference to Reconstructive Surgery of the Airway

Autogenous buccal mucosa was transplanted to the pretracheal region in beagles. The result was studied by surgical exploration, light microscopy, transmission electron microscopy and scanning electron microscopy. The grafts were transformed into mucosal cysts after 4 weeks. There was no significant alteration of the epithelium of the cyst wall proper as compared with normal mucosa. After observation periods of 4 to 13 weeks a cyst adequate for further transplantation procedures had developed. There were no essential differences between cysts observed at four weeks and those observed at later periods up to 13 weeks. The possibilities of combining the mucosa with framework materials (bone, cartilage, alloplastic materials, etc) and flaps (e.g. deltopectoral & myocutaneous) are mentioned.

Osmotically induced macrophage activity in the endolymphatic sac

This study aimed to investigate the origin of the free cells in the lumen of the endolymphatic sac (ES). Activation of the cells was accomplished through osmotic induction using glycerol. The ES and the perisaccular tissue were analyzed with special reference to the activity of periaqueductal bone marrow cells after different time intervals following the injection of hyperosmotic agents. The results show that the perisaccular or periaqueductal bone marrow space may constitute a source of some of the free cells occurring in the ES. Osmotic challenging of the inner ear may cause activation of the periaqueductal bone marrow, initiating the locomotion and migration of cells (mostly monocytes, neutrophils and eosinophilic leukocytes) along bone marrow sinusoids that frequently anastomose with the ES vessels. The free cells show signs of transepithelial diapedesis and, in the lumen of the ES, cells may develop into phagocytes which initiate the ingestion and degradation of secreted macromolecular aggregates. It is thought that osmotic alterations in the inner ear may give rise to local changes in or around the ES, leading to the chemotactic attraction of bone marrow cells. The results verify the existence of a complex sugar/protein aggregate metabolism over the wall of the ES, which is linked to the turnover of free cells. The findings may indicate that ES macrophages are important in the regulation of inner ear fluid homeostasis.

Structure of the endolymphatic sac after instillation of hyaluronan in the middle ear

Hyaluronan (HA) 0.5, 1, 1.9 and 4% was instilled into the round window niche in mice. Six hours after the 1.9% HA and 4, 6 and 8 h after the 4% HA deposition there was a significant increase in the proportion of granule-containing light epithelial cells in the endolymphatic sac. This indicated an increase in secretory activity. This activity could be a response to lowered intralabyrinthine pressure due to the osmotic capacity of HA. Secretion of high molecular substances can serve to keep the sac lumen patent and/or to regulate labyrinthine volume and pressure.

Effects of Hyperosmolar Substances on the Endolymphatic Sac

The murine endolymphatic sac (ES) was studied 15 min to 8 hours after intravenous glycerol administration. Initially the ES showed varying degrees of obliteration and this was mostly pronounced at 15-60 min after the injection. After 2 hours the normal volume was regained and after 4 hours the lumen was dilated to 160% of its normal volume. After 6-8 hours the ES had almost regained its normal appearance. The epithelial lining showed an increase in the number of granular cells which, after two hours, reached a peak of 15.8% (p less than 0.01) compared to normal controls which showed 6.1% granular cells of total cell population in the ES. The increase of granular cells was accompanied by filling of the ES lumen with a stainable substance. The epithelial reaction may serve the purpose of counteracting decreases in endolymph pressure either in the ES or in the entire labyrinth.

Experimental Reconstruction of the Airway with Buccal Mucosa and Cortical Bone in a Single-stage Procedure

Autogenous buccal mucosa and cortical bone were transplanted in a one-stage procedure to an anterior tracheal defect in 5 beagles. The result was studied by endoscopy, light microscopy, scanning electron microscopy and transmission electron microscopy. The bone graft was shaped as an oval disc and perforated with large holes for vascular nutrition of the mucosal graft. Small holes were made along the periphery for suturing the buccal mucosa to the bone disc and for suturing the composite graft to the tracheal defect. The mucosa sloughed off from the framework during the first 2 weeks and the bone graft was subsequently expelled through the airway. The mucosal graft was replaced by ciliated columnar epithelium supported by firm connective tissue. Various surface structures were found in the regenerating epithelium. Although the animals did not suffocate or develop a stenosis, this procedure cannot in its present form be recommended for use in clinical practice.