Variability of hair cells in the coronal organ of ascidians (Chordata, Tunicata)

2010 ◽  
Vol 88 (6) ◽  
pp. 567-578 ◽  
Author(s):  
Federico Caicci ◽  
Valentina Degasperi ◽  
Fabio Gasparini ◽  
Giovanna Zaniolo ◽  
Marcello Del Favero ◽  
...  
Keyword(s):  
Water Flow ◽  
Hair Cells ◽  
Sensory Cell ◽  
Secretory Activity ◽  
Sensory Cells ◽  
Sensory Organs ◽  
Supporting Cells ◽  
Embryonic Origin

The tunicate ascidians are nonvertebrate chordates that possess mechanoreceptor cells in the coronal organ in the oral siphon, which monitor the incoming water flow. Like vertebrate hair cells, the mechanoreceptor–coronal cells are secondary sensory (axonless) cells accompanied by supporting cells and they exhibit morphological diversities of apical specialisations: they are multiciliate in ascidians of the order Enterogona, whereas they are more complex and possess one or two cilia accompanied by stereovilli, also graded in length, in ascidians of the order Pleurogona. In morphology, embryonic origin, and arrangement, coronal sensory cells closely resemble vertebrate hair cells. We describe here the coronal organs of five ascidians ( Pyura haustor (Stimpson, 1864), Pyura stolonifera (Heller, 1878), Styela gibbsii (Stimpson, 1864), Styela montereyensis (Dall, 1872), and Polyandrocarpa zorritensis (Van Name, 1931)), belonging to Pleurogona, also comprising species of one family (Pyuridae), not yet considered, and thus completing our overview of the order. Each species possesses at least two kinds of secondary sensory cells, some of them characterized by stereovilli graded in length. In some species, the coronal sensory cells exhibit secretory activity; in P. haustor, a mitotic sensory cell has also been found. We compare the coronal organ in both ascidians and with other chordate sensory organs formed of secondary sensory cells, and discuss their possible homologies.

Delta-Notch signalling and the patterning of sensory cell differentiation in the zebrafish ear: evidence from the mind bomb mutant

Development ◽  
1998 ◽  
Vol 125 (23) ◽  
pp. 4637-4644 ◽  
Author(s):  
C. Haddon ◽  
Y.J. Jiang ◽  
L. Smithers ◽  
J. Lewis
Keyword(s):  
Cell Differentiation ◽  
Lateral Inhibition ◽  
Hair Cells ◽  
Sensory Cell ◽  
Cell Types ◽  
Notch Signalling ◽  
Supporting Cells ◽  
Fine Grained ◽  
Mechanosensory Hair Cells ◽  
The Mind

Mechanosensory hair cells in the sensory patches of the vertebrate ear are interspersed among supporting cells, forming a fine-grained pattern of alternating cell types. Analogies with Drosophila mechanosensory bristle development suggest that this pattern could be generated through lateral inhibition mediated by Notch signalling. In the zebrafish ear rudiment, homologues of Notch are widely expressed, while the Delta homologues deltaA, deltaB and deltaD, coding for Notch ligands, are expressed in small numbers of cells in regions where hair cells are soon to differentiate. This suggests that the delta-expressing cells are nascent hair cells, in agreement with findings for Delta1 in the chick. According to the lateral inhibition hypothesis, the nascent hair cells, by expressing Delta protein, would inhibit their neighbours from becoming hair cells, forcing them to be supporting cells instead. The zebrafish mind bomb mutant has abnormalities in the central nervous system, somites, and elsewhere, diagnostic of a failure of Delta-Notch signalling: in the CNS, it shows a neurogenic phenotype accompanied by misregulated delta gene expression. Similar misregulation of delta; genes is seen in the ear, along with misregulation of a Serrate homologue, serrateB, coding for an alternative Notch ligand. Most dramatically, the sensory patches in the mind bomb ear consist solely of hair cells, which are produced in great excess and prematurely; at 36 hours post fertilization, there are more than ten times as many as normal, while supporting cells are absent. A twofold increase is seen in the number of otic neurons also. The findings are strong evidence that lateral inhibition mediated by Delta-Notch signalling controls the pattern of sensory cell differentiation in the ear.

scholarly journals The Key Transcription Factor Expression in the Developing Vestibular and Auditory Sensory Organs: A Comprehensive Comparison of Spatial and Temporal Patterns

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Shaofeng Liu ◽  
Yunfeng Wang ◽  
Yongtian Lu ◽  
Wen Li ◽  
Wenjing Liu ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Inner Ear ◽  
Hair Cells ◽  
Expression Patterns ◽  
Organ Of Corti ◽  
Sensory Organ ◽  
Sensory Organs ◽  
Supporting Cells ◽  
Cell Fate Decisions ◽  
Temporal And Spatial

Inner ear formation requires that a series of cell fate decisions and morphogenetic events occur in a precise temporal and spatial pattern. Previous studies have shown that transcription factors, including Pax2, Sox2, and Prox1, play important roles during the inner ear development. However, the temporospatial expression patterns among these transcription factors are poorly understood. In the current study, we present a comprehensive description of the temporal and spatial expression profiles of Pax2, Sox2, and Prox1 during auditory and vestibular sensory organ development in mice. Using immunohistochemical analyses, we show that Sox2 and Pax2 are both expressed in the prosensory cells (the developing hair cells), but Sox2 is later restricted to only the supporting cells of the organ of Corti. In the vestibular sensory organ, however, the Pax2 expression is localized in hair cells at postnatal day 7, while Sox2 is still expressed in both the hair cells and supporting cells at that time. Prox1 was transiently expressed in the presumptive hair cells and developing supporting cells, and lower Prox1 expression was observed in the vestibular sensory organ compared to the organ of Corti. The different expression patterns of these transcription factors in the developing auditory and vestibular sensory organs suggest that they play different roles in the development of the sensory epithelia and might help to shape the respective sensory structures.

scholarly journals Hair Cell Generation in Cochlear Culture Models Mediated by Novel γ-Secretase Inhibitors

2021 ◽  
Vol 9 ◽  
Author(s):  
Silvia T. Erni ◽  
John C. Gill ◽  
Carlotta Palaferri ◽  
Gabriella Fernandes ◽  
Michelle Buri ◽  
...  
Keyword(s):  
Hair Cell ◽  
Notch Signaling ◽  
Hair Cells ◽  
Round Window ◽  
Notch Pathway ◽  
Outer Hair Cells ◽  
Round Window Membrane ◽  
Sensory Cells ◽  
Supporting Cells

Sensorineural hearing loss is prevalent within society affecting the quality of life of 460 million worldwide. In the majority of cases, this is due to insult or degeneration of mechanosensory hair cells in the cochlea. In adult mammals, hair cell loss is irreversible as sensory cells are not replaced spontaneously. Genetic inhibition of Notch signaling had been shown to induce hair cell formation by transdifferentiation of supporting cells in young postnatal rodents and provided an impetus for targeting Notch pathway with small molecule inhibitors for hearing restoration. Here, the oto-regenerative potential of different γ-secretase inhibitors (GSIs) was evaluated in complementary assay models, including cell lines, organotypic cultures of the organ of Corti and cochlear organoids to characterize two novel GSIs (CPD3 and CPD8). GSI-treatment induced hair cell gene expression in all these models and was effective in increasing hair cell numbers, in particular outer hair cells, both in baseline conditions and in response to ototoxic damage. Hair cells were generated from transdifferentiation of supporting cells. Similar findings were obtained in cochlear organoid cultures, used for the first time to probe regeneration following sisomicin-induced damage. Finally, effective absorption of a novel GSI through the round window membrane and hair cell induction was attained in a whole cochlea culture model and in vivo pharmacokinetic comparisons of transtympanic delivery of GSIs and different vehicle formulations were successfully conducted in guinea pigs. This preclinical evaluation of targeting Notch signaling with novel GSIs illustrates methods of characterization for hearing restoration molecules, enabling translation to more complex animal studies and clinical research.

Regeneration of sensory hair cells after acoustic trauma

Science ◽  
1988 ◽  
Vol 240 (4860) ◽  
pp. 1772-1774 ◽  
Author(s):  
JT Corwin ◽  
DA Cotanche
Keyword(s):  
Hearing Loss ◽  
Hair Cells ◽  
Acoustic Trauma ◽  
Sensory Cells ◽  
Lesion Site ◽  
Supporting Cells ◽  
Profound Hearing Loss ◽  
Cochlear Hair Cells ◽  
Sensory Hair ◽  
Sensory Hair Cells

Any loss of cochlear hair cells has been presumed to result in a permanent hearing deficit because the production of these cells normally ceases before birth. However, after acoustic trauma, injured sensory cells in the mature cochlea of the chicken are replaced. New cells appear to be produced by mitosis of supporting cells that survive at the lesion site and do not divide in the absence of trauma. This trauma-induced division of normally postmitotic cells may lead to recovery from profound hearing loss.

A comparative study of surface preparations of the organ of Corti of the harp seal (Pagophilus groenlandicus Erxleben 1777) and the ringed seal (Pusa hispida). 1. Sensory cell population and density

1976 ◽  
Vol 54 (1) ◽  
pp. 1-9 ◽  
Author(s):  
F. Ramprashad ◽  
K. Ronald ◽  
J. Geraci ◽  
T. G. Smith
Keyword(s):  
Cell Population ◽  
Hair Cells ◽  
Sensory Cell ◽  
Organ Of Corti ◽  
Ringed Seal ◽  
Outer Hair Cells ◽  
Harp Seal ◽  
Sensory Cells ◽  
Unit Surface Area ◽  
Inner Hair Cells

The surface preparation technique was used to estimate the sensory cell population and density in the organ of Corti of seven harp seals and four ringed seals. The average total of inner hair cells for the harp seal was 3654 (3078–263) as compared with an average total of 3232 (3120–3354) in the ringed seal. The average total number of outer hair cells in the harp seal was 14 318 (12 173 – 15 709) as compared with an average total of 13 497 (12 903 – 14 894).The distribution of outer and inner hair cells showed an increase in density from base to apex. An increase in density of about 21% and 29% was observed in the inner hair cells of the ringed and harp seal. The increase in density for each row of outer hair cells was 21% in the harp seal and 17% in the ringed seal. The density of outer hair cells per unit surface area decreased from a maximum value at the base to about half its value at the apex.The average total sensory cells of seals exceeded the average total sensory cells of both man and dolphin but were within the range of variation of the human.

The fine structure of the lateral-line sense organs of dogfish

1971 ◽  
Vol 179 (1055) ◽  
pp. 157-169 ◽  
Keyword(s):  
Hair Cell ◽  
Lateral Line ◽  
Hair Cells ◽  
Sensory Cell ◽  
Sensory Nerve ◽  
The Body ◽  
Apical Surface ◽  
Sense Organs ◽  
Supporting Cells ◽  
Efferent Nerve

The sense organs of the body lateral-line canals of Scyliorhinus were examined with the electron microscope and shown to consist of supporting cells and two kinds of sensory cell. One type of sensory cell has the well-known structure of hair cells, bearing on its apical surface a group of stereocilia (6 to 25) associated with a single kinocilium. Each hair cell is innervated by a sensory nerve fibre and some also receive an efferent nerve supply. The second kind of sensory cell is similar in appearance, but differs at the apex in containing many vacuoles and in lacking stereocilia. There are many long microvilli and a single cilium which arises from a shallow pit. The internal structure of this cilium is variable, with the number of tubules in the outer ring ranging between 7 and 9 and with the inner pair consisting of double elements. This type of sensory cell is innervated by sensory nerve fibres and possibly by efferent fibres. The situation of the kinocilium of a hair cell in relation to the stereocilia is more variable than has been described in other hair cells while the cilium of the second sensory cell appears to bear no special relation to the microvilli. The accessory cells of the neuromast include basal and peripheral supporting cells, many of which produce a secretion, and a large secretory cell which is found at intervals at the edge of the organ. This cell has a convoluted surface and is full of vesicles.

Fluorocitrate Neural Dystrophy of the Guinea Pig Cochlea

1975 ◽  
Vol 33 ◽  
pp. 368-369
Author(s):  
G.J. Spector ◽  
C.D. Carr ◽  
I. Kaufman Arenberg ◽  
R.H. Maisel
Keyword(s):  
Hearing Loss ◽  
Hair Cells ◽  
Sodium Phosphate ◽  
Sensory Cells ◽  
Barium Salt ◽  
Perfusion Medium ◽  
Cochlear Hair Cells ◽  
Neural Degeneration ◽  
Sodium Phosphate Buffer ◽  
Cochlear Neurons

All studies on primary neural degeneration in the cochlea have evaluated the end stages of degeneration or the indiscriminate destruction of both sensory cells and cochlear neurons. We have developed a model which selectively simulates the dystrophic changes denoting cochlear neural degeneration while sparing the cochlear hair cells. Such a model can be used to define more precisely the mechanism of presbycusis or the hearing loss in aging man.Twenty-two pigmented guinea pigs (200-250 gm) were perfused by the perilymphatic route as live preparations using fluorocitrate in various concentrations (15-250 ug/cc) and at different incubation times (5-150 minutes). The barium salt of DL fluorocitrate, (C6H4O7F)2Ba3, was reacted with 1.0N sulfuric acid to precipitate the barium as a sulfate. The perfusion medium was prepared, just prior to use, as follows: sodium phosphate buffer 0.2M, pH 7.4 = 9cc; fluorocitrate = 15-200 mg/cc; and sucrose = 0.2M.

Electron Microscopic Findings in Presbycusic Degeneration of the Basal Turn of the Human Cochlea

1979 ◽  
Vol 87 (6) ◽  
pp. 818-836 ◽  
Author(s):  
Joseph B. Nadol
Keyword(s):  
Light Microscopy ◽  
Hair Cells ◽  
Basilar Membrane ◽  
Ganglion Cells ◽  
Nerve Fibers ◽  
Degenerative Changes ◽  
Supporting Cells ◽  
Neural Degeneration ◽  
Basal Turn ◽  
Temporal Bones

Three human temporal bones with presbycusis affecting the basal turn of the cochlea were studied by light and electron microscopy. Conditions in two ears examined by light microscopy were typical of primary neural degeneration, with a descending audiometric pattern, loss of cochlear neurons in the basal turn, and preservation of the organ of Corti. Ultrastructural analysis revealed normal hair cells and marked degenerative changes of the remaining neural fibers, especially in the basal turn. These changes included a decrease in the number of synapses at the base of hair cells, accumulation of cellular debris in the spiral bundles, abnormalities of the dendritic fibers and their sheaths in the osseous spiral lamina, and degenerative changes in the spiral ganglion cells and axons. These changes were interpreted as an intermediate stage of degeneration prior to total loss of nerve fibers and ganglion cells as visualized by light microscopy. In the third ear the changes observed were typical of primary degeneration of hair and supporting cells in the basal turn with secondary neural degeneration. Additional observations at an ultrastructural level included maintenance of the tight junctions of the scala media despite loss of both hair and supporting cells, suggesting a capacity for cellular “healing” in the inner ear. Degenerative changes were found in the remaining neural fibers in the osseous spiral lamina. In addition, there was marked thickening of the basilar membrane in the basal turn, which consisted of an increased number of fibrils and an accumulation of amorphous osmiophilic material in the basilar membrane. This finding supports the concept that mechanical alterations may occur in presbycusis of the basal turn.

Ultrastructure of the lophophoral tentacles in the genus Phoronis (Phoronida, Lophophorata)

1993 ◽  
Vol 71 (9) ◽  
pp. 1861-1868 ◽  
Author(s):  
F. Pardos ◽  
C. Roldán ◽  
J. Benito ◽  
A. Aguirre ◽  
I. Fernández
Keyword(s):  
Cell Types ◽  
Point Of View ◽  
Sensory Cells ◽  
Blood Capillary ◽  
Supporting Cells ◽  
Connective Tissue Layer ◽  
Hollow Structures ◽  
Building Activities ◽  
Abundance And Distribution ◽  
Epidermal Gland

The lophophoral tentacles of two phoronids, Phoronis psammophila and Phoronis hippocrepia, are described from an ultrastructural point of view. The tentacles are hollow structures, with an epidermis exhibiting supporting cells, sensory cells, and four types of gland cells, A, B1, B2, B3. The epidermis rests on a connective tissue layer, tubular in shape, enclosing a coelomic space lined by myoepithelial mesothelium (peritoneum). There is a single blood capillary in the tentacular coelomic cavity, attached to the frontal face of the tentacle, with contractile walls derived from the peritoneum. Both erythrocytes and amoebocyte-like cells occur inside the capillary. Differences between the tentacles of these two species and those of Phoronis australis, whose structure is already known, mainly concern the abundance and distribution of the epidermal gland cell types and are related to the burrowing and tube-building activities of these animals in different substrata.

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