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A N Popper

Publications and source records attributed to A N Popper.

At least 55 records · Page 3Linked to original sources
PubMed1992

Central-peripheral and rostral-caudal organization of the innervation of the saccule in a cichlid fish.

Saccular eighth nerve arbors were examined in the cichlid fish Astronotus ocellatus to determine if their morphology varies with saccular location. The saccule was divided into four regions: rostral-central, rostral-peripheral, caudal-central, caudal-peripheral. Arbors were filled with cobaltous-lysine. Axon diameter, maximum arbor width, and number of terminal points were taken as quantitative measures. Differences in these measures among the four different saccular regions were evaluated using an analysis of variance. The results indicate two types of organization: central-peripheral and rostral-caudal. The central-peripheral differences involve all three quantitative measures. The central saccule is innervated by arbors with larger axon diameters, larger arbor widths, and more terminal points than the peripheral saccule. The rostral-caudal organization involves only two measures. The rostral saccule is innervated by arbors having larger axon diameters and smaller arbor widths than the caudal saccule. In the oscar, we know of no other parameters that are organized along the rostral-caudal dimension. These findings of a spatial organization of innervation suggest to us that the oscar saccule is not homogeneous in function.

Animals↗
PubMed1991

Sensory hair cells of a fish ear: evidence of multiple types based on ototoxicity sensitivity.

Sensory hair cells from the striolar region (striolar hair cells) of the utricle and the lagena of the ear of a teleost fish Astronotus ocellatus (Cuvier) ear are sensitive to gentamicin sulphate, an ototoxic drug. In contrast, sensory hair cells from outside the striolar region (extra-striolar hair cells) are not sensitive to gentamicin. These data, combined with results from studies showing different ultrastructural features and different immunoreactivity to a calcium binding protein, S-100, lead to the suggestion that there are distinguishable types of hair cells in these endorgans. These results add to the increasing evidence that classifying the sensory hair cells of fish ears only as the traditional 'vestibular type II' may be inadequate for properly understanding structure and function of the fish ear.

Animals↗
PubMed1990

Spatial and morphological differentiation of trigger zones in afferent fibers to the teleost utricle.

A morphological correlate of the trigger site (the locus of action potential initiation) was identified in afferent axons of the utricle in the ear of two species of teleost fish. These sites were identified by the ferric-ferrocyanide (Prussian blue) cytochemical procedure and they were correlated with the geometries of afferent intraepithelial arbors as visualized by means of a silver stain. The intraepithelial arbors of afferent fibers show regional distributions that correlate with axon diameter and Prussian blue staining. Afferent axons with diameters greater than 4-5 microns only innervate the striola regions of the epithelium and terminate as one of two distinct types of intraepithelial arbors. Afferent axons with diameters smaller than 4 microns are ubiquitously distributed throughout the epithelium. Arbors that stained by Prussian blue within the utricular epithelium are restricted to the striolar regions. These arbors possess nodal-like membrane in different branches as postsynaptic membrane. Afferents that innervate hair cells in the extrastriolar epithelial regions stained with Prussian blue only at the extraepithelial terminal heminode. The postsynaptic membrane of these afferents is passive or dendritic-like.

Afferent Pathways↗
PubMed1990

Variations in receptor cell innervation in the saccule of a teleost fish ear.

Using transmission electron microscopy, we quantitatively analyzed the afferent and efferent synapses on 67 sensory hair cells along the saccular epithelium of the oscar (Astronotus ocellatus), a cichild fish with a non-specialized ear. The synaptic profile (number of afferent and efferent synapses per cell) varied considerably among cells. The number of synapses per hair cell ranged from three to 24, and all but six of the 67 hair cells had both afferent and efferent synapses. Statistical analysis showed that the synaptic profiles did not significantly vary anywhere on the saccular epithelium except at the edges. There, hair cells had significantly fewer efferent synapses than hair cells in other epithelial regions. This statistical variation in efferent synapse distribution in different epithelial regions corresponds with the lengths of ciliary bundles in these regions. The synapses on hair cells showed a regional specificity in position. In all cells synapses were never located more apically than the top of the nucleus. On hair cells towards the periphery, the most apical synapse on the hair cells tended to be afferent. On more centrally located cells, the most apical synapse was efferent in 92% of the cells.

Afferent Pathways↗
PubMed1990

Possible precursors to new hair cells, support cells, and Schwann cells in the ear of a post-embryonic fish.

The sources of new hair cells, support cells, and Schwann cells were identified in the statoacoustic end organs of normal post-embryonic fish (Astronotus ocellatus). S-phase cells, defined as cells that take up 3H-thymidine in preparation for mitosis, and their progeny were visualized using autoradiography. Two types of S-phase cells were found: 'embryonic-like neuroepithelial' (NE) cells and 'basally located S-phase' (BLS) cell. The NE cells had elongated nuclei and processes extending basally and apically. Thirty minutes after the thymidine injection labeled NE cell nuclei were found between hair cell nuclei and support cell nuclei. After two and four hours survival some labeled NE nuclei were closer to the lumen, where they divided. One labeled support cell was seen after four hours survival and one labeled hair cell after nine hours survival. Significant numbers of labeled support and hair cells were not seen until 24 h survival. These results led us to identify NE cells as the immediate source of new hair cells and support cells. The BLS cells had small nuclei with little surrounding cytoplasm. Shortly after the thymidine injection BLS cells were found between the hair cell nuclei and the basement membrane, and they underwent mitosis in this position. The BLS cells resemble intra-epithelial Schwann cells, except that they are not curved around axonal profiles. We suggest that the BLS cells are Schwann cell precursors.

Animals↗
PubMed1990

A ganglionic source of new eighth nerve neurons in a post-embryonic fish.

In the post-embryonic fish Astronotus ocellatus (the oscar) sensory hair cells and eighth nerve neurons are added to the peripheral statoacoustic system all during adulthood. Here we use 3H-thymidine to label S-phase precursors to new neurons in the statoacoustic ganglion. The neuronal precursor cells have small nuclei with little surrounding cytoplasm. They are surrounded by cells that appear to be part of a developmental sequence ending with mature eighth nerve neurons. Taken with our previous studies, these results demonstrate that hair cell and neuronal precursors in post-embryonic oscars are spatially segregated and morphologically distinct from one another.

Animals↗
PubMed1990

Growth of a fish ear. II. Locations of newly proliferated sensory hair cells in the saccular epithelium of Astronotus ocellatus.

Tritiated thymidine was used to investigate the sites of postembryonic hair cell addition in adult fish Astonotus ocellatus (oscar), a species known to add large numbers of hair cells for several years after hatching. Several types of labeled cells, including newly proliferated sensory hair cells, were found throughout the saccular epithelium, with the majority of the cells some distance away from the edges of the epithelium. There was no evidence for an 'annular' addition of sensory hair cells in Astronotus.

Animals↗
PubMed1988

Transmission electron microscopic study of the saccule in the embryonic, larval, and adult toadfish Opsanus tau.

The development of the sensory epithelium of the saccular macula of Opsanus tau was studied with transmission electron microscopy. In the 10-12 somite embryo all cells of the newly formed otocyst are morphologically undefined, having an apically placed cilium with an underlying basal body and parabasal body. Junctional complexes are characterized primarily by tight junctions and a few desmosomes. In the 17-somite embryo the sensory cells begin to differentiate and are definable by the development of microvilli, which lack a cuticular plate. When the embryo has approximately 25-30 somites, ganglion cells differentiate and send their nerve processes toward the thin, disrupted basal lamina and the developing rhombencephalon. Desmosomes are more definable in the sensory regions at this age. As the myotomes begin forming (approximately 5-8 days before hatching), the nerves invade the sensory epithelium, and the developing sensory cells contain dense bodies surrounded by clear, membrane-bound vesicles. Clear synapticlike vesicles are also found throughout the infranuclear region of the sensory cells. However, afferent fibers lack a postsynaptic density. Three to 6 days prior to hatching a cuticular plate begins forming under the ciliary bundles and support and peripheral cells begin to morphologically differentiate. Two to 4 days before hatching the cuticular plate is well formed, desmosomes are numerous, afferent synapses are complete, and the sensory cells are in the upper two-thirds of the epithelium. Seven to 10 days after hatching, sensory cells have efferent synapses and ganglion cells and nerves show a myelin coat. These results suggest that sensory cells begin their development prior to VIIIth nerve innervation, although the orientation and pattern development of these cells may be related to the formation of the cuticular plate, desmosomes, afferent innervation, and basal lamina formation.

Animals↗
PubMed1988

Processing of acoustic signals in the auditory system of bony fish.

In order to determine unambiguously the bearing of a sound source, a fish must be able to resolve acoustic pressure and the components of the acoustic displacement vector from the signals detected by the otolithic organs. A new hypothesis for the processing of acoustical information by bony fish is presented. It is demonstrated that much of the processing required to do this may be implicit in the structure of the ear and its associated neural innervation. Possible algorithms are presented that the central nervous system might use to further process the derived information to localize a sound source and discriminate frequency and range. The hypothesis is shown to be consistent with much of what is known of the morphology and physiology of the auditory system of bony fishes.

Algorithms↗
PubMed1987

The ultrastructure and innervation of the ear of the gar, Lepisosteus osseus.

The endorgans of the inner ear of the gar were examined using transmission and scanning electron microscopy as well as nerve staining. The ultrastructure of the sensory hair cells and supporting cells of the gar ear are similar to cells in other bony fishes, whereas there are significant differences between the gar and other bony fishes in the orientations patterns of the sensory hair cells on the saccular and lagenar sensory epithelia. The saccular sensory epithelium has two regions, a main region and a secondary region ventral to the main region. The ciliary bundles on the main region are divided into two groups, one oriented dorsally and the other ventrally. Furthermore, as a result of curvature of the saccular sensory epithelium, the dorsal and ventral ciliary bundles on the rostral portion of the epithelium are rotated ninety degrees and are thus oriented on the animal's rostro-caudal axis. Hair cells on the secondary region are generally oriented ventrally. The lagenar epithelium has three groups of sensory hair cells. The groups on the rostral and caudal ends of the macula are oriented dorsally, whereas the middle group is oriented ventrally. Hair cell orientations on the utricular epithelium and macula neglecta are similar to those in other bony fishes. Nerve fiber diameters can be divided into three size classes, 1-8 microns, 9-13 microns, and 14 microns or more, with the smallest size class containing the majority of fibers. The distribution of the various classes of fiber diameters is not the same in nerve branches to each of the end organs. Similarly, the ratio of hair cells to axons differs in each end organ. The highest hair cell to axon ratio is in the utricle (23:1) and the smallest is in the macula neglecta (7:1). The number of sensory hair cells far exceed the number of eighth nerve axons in all sensory epithelia.

Animals↗
PubMed1987

Gross and ultrastructural development of the saccule of the toadfish Opsanus tau.

The development of the saccule of the inner ear in the toadfish was studied using light and scanning electron microscopy. Development was studied from the early embryo (2-3 days postfertilization), when the otocyst first forms, to the early-aged juvenile when the development of the inner ear approximates that of the adult (4 weeks postfertilization). The ultrastructural features examined included the morphological sequence of ciliary bundle growth, the development of orientation patterns of the ciliary bundles, and the relation of the ultrastructural development to overall gross development. Gross development may be divided into four distinct morphological stages. Stage I encompasses the time from initial formation of the otocyst until the start of stage II, which is the stage when the pars inferior begins migrating ventrally. In stage III the pars inferior continues to elongate ventrally. Stage IV starts when the pars inferior elongates in a rostral and caudal direction. The ear attains its adult shape in stage IV. The differentiation of the sensory cells begins during stage I. During the early part of stage I, a small cilium is found on the apical surface of each cell throughout the otocyst. In the middle and late periods of stage I, a few microvillous buds add to the surface of the cells that already have a kinocilium. These early ciliary bundles are clustered on the rostral-ventral and caudal walls of the otocyst. There is no clear patterning to the orientation of these ciliary bundles. In stage II the ventral stretching of the labyrinth wall causes a spreading of the clustered bundles along the ventral and medial walls of the pars inferior. The orientation of the ciliary bundles has no distinct pattern. In stage III the orientations of the ciliary bundles appear adultlike, although there are so few ciliary bundles that it is difficult to make a definite determination. During stage IV, hair cells with an adultlike horizontal and vertical orientation pattern are found on the rostral and caudal sections of the saccular macula, respectively. The transition region lying between these areas has ciliary bundles with various orientations.

Animals↗
PubMed1987

Sound reception in two anabantid fishes.

1. Pure tone displacement sensitivity and bandwidth were measured from the saccule of the ear in two anabantid species (Trichogaster trichopterus and Helostoma temincki) using microphonic potentials with a 1 microV RMS threshold for the second harmonic of the stimulus frequency. 2. Saccular microphonics were recorded in both species from 80 to 1600 Hz, with lowest thresholds between 100 and 200 Hz. The overall microphonic response curves (sensitivity and bandwidth) of the two species were statistically similar to one another with an analysis of variance, although there were statistically different thresholds at 100 and 800 Hz. 3. The hair cell orientation patterns of the saccular epithelia differ in the two species. Consequently, the comparative sizes of the saccular sensory epithelium and numbers of sensory hair cells were examined. The saccular sensory epithelium of Helostoma is about 40% larger and contains nearly 50% more hair cells than the saccular epithelium of a comparably sized Trichogaster. 4. An extracranial air bubble, located in the suprabranchial chamber, is found in both species. The bubble has direct access to the saccular chamber in Trichogaster through a foramen which is absent in Helostoma. Despite the difference in morphology and the larger numbers of sensory hair cells in Helostoma, hearing sensitivity and bandwidth is similar in the two species. Although the structural differences in the auditory periphery do not affect pure tone sensitivity and bandwidth, other aspects of fish hearing such as frequency discrimination, discrimination of signals in the presence of noise, and/or sound localization ability may be affected by these structural differences.

Acoustic Stimulation↗
PubMed1987

Sensory and nonsensory ciliated cells in the ear of the sea lamprey, Petromyzon marinus.

The inner ear of the sea lamprey, Petromyzon marinus, was examined using scanning and transmission electron microscopy. Many of the nonsensory surfaces of the ear chamber are lined by numerous, noninnervated, multiciliated epithelial cells. Each multiciliated epithelial cell has 43-66 true cilia projecting from its apical surface into the lumen of the ear. Although the cilia leave the cell individually, all of the cilia from a single cell come together just above the apical cell surface and are held together by a cross-network of fibrillar material. The cell bodies of the multiciliated cells sit upon a basal lamina which overlies a collagen-filled matrix. Petromyzon has typical vertebrate sensory hair cells on the cristae of the two semicircular canals as well as on the main sensory epithelium, the macula communis. Cell bodies of the sensory hair cells are similar to hair cells of other vertebrates. However, unlike other fishes, the sensory hair cells in Petromyzon have striated organelles between the nucleus and the apical cell membrane. The hair cells are innervated by afferent and efferent nerve fibers.

Acoustic Maculae↗
PubMed1984

Growth of a fish ear: 1. Quantitative analysis of hair cell and ganglion cell proliferation.

Proliferation (or addition) of inner ear sensory hair cells continues for a long time postembryonically in cartilaginous and bony fishes, and in amphibians. In contrast, proliferation only occurs during embryonic development in birds and mammals. However, detailed quantitative data on hair cell addition are not available for bony fishes. In order to quantify the extent of proliferation, we determined the number of sensory hair cells on the saccular sensory epithelium in specimens of the cichlid fish Astronotus ocellatus (the oscar) ranging from 2.0 to 19.0 cm in standard length (0.9-343 g). Ganglion cells were counted using serial sections of the saccular branch of the eighth nerve in animals of the same size range. The saccular macula of a 2.0 cm long (0.9 g) Astronotus contains approximately 5500 sensory hair cells; fish from 16 to 19 cm long have over 170 000 hair cells. The increase in number of sensory cells and the increase in both length and weight of the animals studied were statistically correlated (r2 = 0.8). The relative densities of saccular sensory cells in different epithelial regions remained constant in animals from 2.0 to 17 cm; in larger animals the cell density decreased somewhat. Based upon very conservative estimates of the rate of growth of Astronotus, we calculate that an average of 167 hair cells/day are added during the time when the cell population of the saccule increases. Ganglion cell number also increased approximately 4.8 times in the range of fish studied. The smallest animals in our study had about 150 ganglion cells per saccular epithelium, while the largest fish had over 600 ganglion cells. We estimate that the average ratio of hair cells to afferent fibers increases from about 30:1 in the smallest fish to over 300:1 in the largest animals.

Animals↗
PubMed1984

Variation in lengths of ciliary bundles on hair cells along the macula of the sacculus in two species of teleost fishes.

The sacculus is one of the end-organs of the inner ear. In many teleost fishes the sacculus is considered the major auditory organ. We have used scanning electron microscopy to examine the lengths of the ciliary bundles on hair cells in the sensory macula of the sacculus in two diverse species of teleosts. The data are presented in a form allowing direct comparison with recent data on a wide range of tetrapod auditory organs. In goldfish, the ciliary bundles are significantly longer in the caudal part of the macula than in the rostral part, but the kissing gourami shows nearly uniform ciliary bundle heights along its entire length. Based on limited data from the literature, the part of the macula responsive to lower frequencies is the part containing these taller bundles in goldfish, suggesting a parallel with the gradient of ciliary bundles and frequency response found in tetrapods.

Animals↗
PubMed1983

Spatial organization in the saccule and lagena of a teleost: hair cell pattern and innervation.

The relationship between the hair cell orientation pattern and innervation in the saccule and lagena of the teleost Helostoma temmincki (the kissing gourami) was investigated with scanning electron microscopy and the Winkelmann-Schmitt silver impregnation technique. The hair cell pattern in the saccule consists of four orthogonally oriented groups. The anterior two groups are oriented along the animal's rostrocaudal axis, and the posterior two are oriented along its dorsoventral axis. The pattern of hair cell orientations in the lagena is a typical bidirectional one. Two divisions of the eighth nerve innervate the saccule. The anterior division innervates the horizontally oriented hair cell groups, and the posterior division innervates the dorsoventrally oriented groups. A single nerve innervates the lagena, with the majority of fibers innervating one or the other of the two lagenar hair cell groups. The segregated pattern of innervation according to hair cell orientation groups in the saccule was confirmed in other species. Individual types of axonal terminations appear to innervate hair cells of specific ciliary bundle types.

Animals↗
PubMed1983

The saccule may be the transducer for directional hearing of nonostariophysine teleosts.

The hearing of fishes is transduced by the otolithic end-organs of the eighth nerve. In several nonostariophysine fish, the nerve innervation and hair cell orientation in the saccule, one otolithic organ, suggest that directionality is encoded by a set of mutually perpendicular sensory epithelia. The anterior saccular branch innervates only the hair cell groups oriented along the rostrocaudal body axis which are located at the anterior of the saccule. The posterior saccular branches innervate the hair cell groups oriented along the dorsoventral body axis and are found at the posterior of the saccule.

Animals↗