Biomedical subjects

A Flock

Publications and source records attributed to A Flock.

114 records · Page 7Linked to original sources

PubMedDate not supplied

Ultrastructure of synapses in the lateral line canal organ.

The ultrastructure of afferent and efferent synapses on hair cells in the lateral line canal organ of hair cells in the lateral line canal organ of the fish Lota lota was studied, utilizing various fixation and staining techniques. New information was obtained about membrane-associated material, such as the presynaptic body and postsynaptic densities, by examining glutaral-dehyde-fixed material not subjected to osmication. Contrast was instead obtained either by section staining with uranyl acetate and lead citrate or by block impregnation with phosphotungstic acid (PTA). PTA-staining enhances the postsynaptic membrane of both the afferent and efferent synapses. It also stains the presynaptic dense projections at the efferent synapse and in a differential fashion, the afferent synaptic body. Secretion staining reveals a substructure in the feed of the afferent synaptic body, faintly seen but masked in osmicated tissue.

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PubMedDate not supplied

Sensory hairs and filaments rods in vestibular hair cells of the waltzing guinea pig. Organization and identification of actin.

The waltzing guinea pig suffers from hereditary deafness and vestibular disorder. In vestibular organs, hair cells of Type I develop pathologically and will eventually degenerate. They show fusion of sensory hairs, protrusion of the cuticular plate and contain a rod-shaped inclusion body. With fixation techniques designed to preserve proteins it is shown that this rod has a filamentous substructure reminding one of stereocilia. The packing density of the filaments is similar and circular packing patterns are seen within both structures. However, the rod has an irregular cross-section, as opposed to the circular circumference of stereocilia. The filaments in the rod were identified as containing the protein actin (as those in the stereocilia) by decoration with sub-fragment S-1 of myosin. All filaments in the rod have an identical functional polarity, pointing up from the nucleus towards the cuticular plate. This is contrary to that seen in stereocilia, which have filaments pointing down towards the cuticular plate. It is concluded that the rod is not developed by random polymerization of actin but is the result of co-ordinated assembly reminiscent of that which gives rise to stereocilia. The genetic defect appears to be related to mechanisms which determine the site of nucleation and the functional orientation of actin filaments during development.

Actins↗

PubMedDate not supplied

Immunohistochemical identification and localization of actin and fimbrin in vestibular hair cells in the normal guinea pig and in a strain of the waltzing guinea pig.

Using immunohistochemical methods, actin and fimbrin were identified and localized in vestibular epithelia iin the normal guinea pig and in the waltzing guinea pig. In the normal guinea pig, actin was found in the stereocilia and in the cuticular plate. Fimbrin was detected in the stereocilia but surprisingly not in the cuticular plate. As fimbrin was found in the cuticular plates in cochlear hair cells it is suggested that the hair cells in the two organs have different mechanoreceptor properties which can demand different cuticular plate stability. In the waltzing guinea pig, actin was found in the stereocilia, in the rod and n the cuticular plate. Fimbrin was seen in the stereocilia and in the rod, but could not be detected in the cuticular plate. These results emphasize the resemblance between the rod and the stereocilia. It is suggested that the rod is a genetically induced pathological intracellular type of stereocilium which grows in an uncontrolled manner.

Actins↗

PubMedDate not supplied

Freeze-fracturing of vestibular sensory epithelia in a strain of the waltzing guinea pig.

The waltzing guinea pig exhibits genetically induced inner ear disease which develops into deafness and vestibular disorder. The type I hair cell in vestibular end organs shows specific pathology, featuring protrusion of the hair cell apex, sensory hair fusion and an intracellular actin filament rod. With the freeze-fracturing technique, consecutive stages of degeneration of the apical part of the type I hair cell are shown. Different possible mechanisms underlying these changes are discussed. It is probable that the genetically induced prenatally developed hair cell pathology is related to a pathological development of actin filaments and their connections in the apical cytoskeleton.

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PubMedDate not supplied

Ultrastructural and electrophysiological changes in the olfactory epithelium following exposure to organic solvents.

The present study describes some effects on frog olfactory mucosa following acute exposure to styrene and toluene, two organic solvents. The olfactory summed receptor potential (EOG) was recorded in order to monitor the functional effect. The olfactory epithelium was examined with transmission electron microscopy, using both thin section and freeze-fracture technique. The ultrastructural changes in the olfactory epithelium following exposure to the solvents were mainly of two types: (1) an increased secretion from the sustentacular cells, (2) membrane fusion of the cilia, sometimes with a loosening of the ciliary membrane. The tight junctional complex between the receptor and sustentacular cells at the epithelial surface remained intact. The EOG amplitude generally showed some degree of reduction following exposure, with a gradual recovery towards pre-exposure values.

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PubMedDate not supplied

Ultrastructural morphology of enzyme-dissociated cochlear sensory cells.

Enzyme-dissociated chinchilla cochlear sensory cells maintained excellent cellular integrity for two hours or more when kept in the tissue culture medium. The healthy appearing sensory cells maintained their refractile characteristics. Early signs of cell stress were shown by the aggregation of nuclear chromatin, clustering of cytoplasmic contents in the central portion of the supranuclear region of the outer hair cells, and Brownian motion of the mitochondria. The ultrastructural morphology of the enzyme-dissociated outer hair cells was generally well maintained, but with such subtle changes as increased vesicle formation, condensation of mitochondrial matrix, nuclear chromatin aggregation, and vacuole formation. Some of the vesicles present in the infranuclear region are interpreted to be neural synaptic vesicles that have accumulated in the cell, or they may be dilated microsomes or vesicles formed from the degenerating cytoplasmic membrane system (ER system) as a sign of cell stress or degeneration.

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