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It is current opinion that the intercellular spaces of the stria vascularis represent a closed compartment isolated from the endolymph by the tight junctions of the marginal cells and from the perilymph by the junctional complexes of the basel cells. However, it has not yet been investigated whether these two barriers meet at the stria margins toward Reissner's membrane and the spiral prominence. Possible candidates for this sealing could be junctions between the spindle-shaped cells. In the present study freeze-fracture replicas of guinea pig specimens fixed in the presence of filipin were used in order to investigate the junctions of the spindle-shaped cells and to localize the cholesterol in their plasma membrane. Replicas reveal that, below the belt-like apical zonula occludens, the basolateral plasma membranes of the spindle-shaped cells adjacent to each other and to the basal cells are joined over their entire extension by a large number of junctional strands intermingled with numerous filipin-cholesterol-complexes. Gap junctions are present in the meshes formed by these junctional strands. Thus, the plasma membrane of the spindle-shaped cells shows morphological and cytochemical characteristics which indicate that they are the anatomical components completing the barrier isolating the intrastrial compartment from the surrounding fluids.

Owing to its position, shape and prominence, the auricle is at risk of sharp and blunt trauma, lacerations, bite wounds, burns and damage from extreme cold.

A multicentre study of the inner ears of an 88-year-old patient with vertiginous spells and severe hearing loss in the left ear was performed, employing regular and block surface preparations, light and electron microscopy with qualitative and quantitative evaluation of the cochlear and vestibular nerves. There was severe hydrops of the left cochlea and saccule. Reissner's membrane extended into the vestibule and herniated into the perilymphatic space of the non-ampullated end of the horizontal canal. Furthermore, the short canal connecting the posterior ampulla with the utricle had a small, exceedingly thin balloon-like expansion. Only slight hydrops limited to the cochlea was found in the right ear. Sensorineural degeneration was much more pronounced in the left cochlea than in the right. The number of cochlear and vestibular nerve fibres was greatly reduced in the left ear where more fibres with degenerative changes were present. In both specimens the number of myelinated nerve fibres in osseous spiral lamina was smaller than that in the cochlear nerve in the internal auditory canal. Changes occurred in the endolymphatic sacs but were considered non-specific. In this case severe, apparently progressive hydrops and sensorineural degeneration, characteristic of Menière's disease, were associated with atypical onset of clinical symptoms at a late age.

Middle ear ossicles removed during ear surgery in 40 patients were examined in order to compare the histopathologic changes in children with those observed in adults. Bone resorption, mainly localized at the level of the periosteum and haversian canals in adults, was much more extensive in children. Replacement of bone by fibrous granulation tissue was observed in 60% of children's ossicles and in 27% of those belonging to adults. In children, extensive active resorptive osteitis of the ossicles was frequently associated with intensive round cell infiltration, which seems to play an important role in bone absorption and in the aggressiveness of cholesteatoma.

The Reissner membrane of the chinchilla inner ear was studied with the freeze-fracture method. Zonulae occludentes, composed of 2 to 8 strands, seal the intercellular space close to the endolymphatic surface. They are morphologically simialr to those seen between the marginal cells of the stri vascularis, but much less developed than those between the basal strial cells.

The maculae sacculi and utriculi of the chinchilla vestibular labyrinth have been studied by freeze-fracture method. In the replicas extensive zonulae oc-cludentes have been found between sensory and supporting cells at the endolymphatic surface. Gap junctions are located between the supporting cells. Some intramem-branous specializations of the synoptic regions are described in both types of the sensory cells.

Cochlear hair cell counts from individuals who had clinically normal hearing prior to their death have been plotted for various age bands as a function of the number of hair cells per millimetre against their position in the cochlea. Position has been expressed as the distance of that observation of hair cell density from the base of the cochlea, divided by the total length of the cochlea, thereby giving a proportional representation of the cochlea in the range of 0.0 to 1.0 with 20 subdivisions of 0.05. There is an age-related decrease in the number of hair cells in the normal population, and this is more marked for the outer hair cells.

The junctional complexes in the reticular membrane of the organ of Corti have been investigated in chinchilla inner ear by the freeze-fracture method. Extremely developed zonulae occludentes were observed where the supporting cells contact each other and the sensory cells. These junctions can be considered “very tight” and completely seal off the tunnel of Corti, Nuel's space and the outer tunnel from the endolymph, as observed by investigations carried out by using tracers. The zonulae occludentes between Hensen's cells are always uninterrupted but considerably lower than among supporting and sensory cells.

The localization of AChE activity was investigated in the cochlear and vestibular ganglion cells of the chinchilla inner ear with the electron microscope by Karnovsky's method. The reaction product was localized within the rough-surfaced cisterns of the E. R., including the perinuclear cistern, and in some cisterns of the Golgi complex. In a few myelinated nerve fibres and in most of the unmyelinated ones the reaction product was present along the axolemma. The reaction product was absent in the satellite and Schwann cells. The controls indicated that the reaction was due to AChE activity.

A review is given of the methods employed in human temporal bone pathology, from the camera lucida drawings of the last century to the sophisticated techniques of today.

The junctional complexes in the vascular stria and spiral ligament of the chinchilla inner ear have been studied using the electron microscope with freeze-fracture technique. The intercellular spaces of the vascular stria are sealed towards the endolymph by the zonulae occludentes “intermediate to tight” of the marginal cells and towards the perilymph by the zonulae occludentes “very tight” of the basal cells. All the cells of the vascular stria and spiral ligament have their cytoplasms in direct communication, which is mediated by numerous gap junctions. The significance of the junctional complexes of the vascular stria probably is connected with the unique ionic composition of the cochlear endolymph and with the maintenance of steep solute gradients by active transport in the stria.

Two different tissues have been observed in specimens of tympanosclerotic material studied under light and electron microscopy. The first. devoid of cells and blood vessels, is a dense fibrous tissue similar to that already described in fibrous tympanosclerosis. The sec ond resembles a bone tissue, containing osteocytes and vascular channels: it is laid down by metaplasic fibro-blasts following the invasion of the first tissue by osteo-clasts and blood vessels after its calcification.

Microslices 3 mm thick from undecalcified human temporal bones were prepared with a special cutting machine and then processed for SEM and TEM in order to evaluate advantages and disadvantages of the microslicing technique for the study of the temporal bone pathology. In the examined microslices there was some mechanical distortion of the membranous labyrinth, detachment of soft tissues from bone and a considerable amount of contamination by bone dust and debris which are circulated during sectioning. For SEM the method therefore has limited value. For TEM a relatively contamination free area can be found some distance from the cutting surface of each microslice.

The relation between organ of Corti degeneration and radial nerve fibre degeneration in the osseous spiral lamina was studied in two human cochleas.

Intercellular junctions and other membrane specializations of neuroblasts and satellite cells were studied in spinal ganglia of chick embryos at the 4th, 10th, and 16th incubation days using the freeze-fracture technique. At the 4th day neuroblasts are closely arranged and connected by gap junctions. At the 10th day, instead, satellite cells appear interposed between neuroblasts so the gap junctions previously joining the latter are no longer evident. These temporary junctions probably play a role in cell differentiation and intercellular adhesion. Together with adhering junctions, gap junctions might maintain the cell organization of the ganglionic rudiment, which at the 4th day still lacks connective tissue. At the 10th day adjacent satellite cells display on their split plasma membrane small gap junctions, short, usually isolated strands recalling those composing zonulae occludentes, and orthogonal particle assemblies. These two latter specializations are still evident at the 16th day. The possible significance of these specializations is briefly discussed.

The distribution of mineral salts was studied in 58 normal and 80 otosclerotic stapedes of different degree of activity. By means of soft roentgen micro-radiography it was possible to compare the distribution of mineral salts in otosclerotic foci and normal stapedes. In the otosclerotic stapedes it was found that the active and quiescent foci are less mineralized than the parts not affected by the disease; the foci are also less mineralized than the normal stapedes. The active foci showed a lower X-ray absorption than the quiescent ones; this means that the otosclerotic foci increase their mineral content in the course of their evolution.

Publisher Summary In the past fifteen years, several researchers have shown the existence in the vestibular sensory areas of two morphologically different systems of nerve fibers and endings, afferent and efferent, suggesting a dual innervation of these organs. This chapter deals with the origin, course, peripheral distribution, and histochemical properties of the efferent vestibular fibers in mammals. Knowledge on the efferent control of the vestibular receptors has increased. Currently, it is known that there is a descending system of myelinated nerve fibers, which end in the vestibular sensory areas making synapses with the nerve chalices, afferent fibers, and hair cells of type II. These synapses are similar in appearance to those in the central nervous system. The acetylcholinesterase (AChE) activity found in the vestibular sensory areas seems to be an exclusive property of the efferent elements. Some comments on the possible neurohumoral transmitter of these fibers and on their physiological significance are also included here.

The area of the vestibulary apparatus called “Planum semilunatum” consists of an epithelium clearly distinguished by the presence of a highly developed system of double membranes in the basal portion of the cells and by the accumulation, in the apical portion, of material in vesicular systems. The authors hold that the epithelium performs a function of filtration from basal membrane towards the endolymphatic lumen and hence that this zone is also producing endolymph.

The spiral limbus of the chinchilla inner ear was investigated using the freeze-fracture method.

Investigation carried out on the inner ears of ten chinchillas by use of the freeze-fracture-method.

The Reissner membrane of the chinchilla inner ear was studied with the freeze-fracture method. Zonulae occludentes, composed of 2 to 8 strands, seal the intercellular space close to the endolymphatic surface. They are morphologically simialr to those seen between the marginal cells of the stri vascularis, but much less developed than those between the basal strial cells.