A gene cadre orchestrates the normal development of sensory and non-sensory cells in the inner ear, segregating the cochlea with a distinct tonotopic sound frequency map, similar brain projection, and five vestibular end-organs. However, the role of genes driving the ear development is largely unknown. Here, we show double deletion of the Iroquois homeobox 3 and 5 transcription factors (Irx3/5 DKO) leads to the fusion of the saccule and the cochlear base. The overlying otoconia and tectorial membranes are absent in the Irx3/5 DKO inner ear, and the primary auditory neurons project fibers to both the saccule and cochlear hair cells. The central neuronal projections from the cochlear apex-base contour are not fully segregated into a dorsal and ventral innervation in the Irx3/5 DKO cochlear nucleus, obliterating the characteristic tonotopic auditory map. Additionally, Irx3/5 deletion reveals a pronounced cochlear-apex-vestibular "vestibular-cochlear" nerve (VCN) bilateral connection that is less noticeable in wild-type control mice. Moreover, the incomplete segregation of apex and base projections that expands fibers to connect with vestibular nuclei. The results suggest the mammalian cochlear apex is a derived lagena reminiscent of sarcopterygians. Thus, Irx3 and 5 are potential evolutionary branch-point genes necessary for balance-sound segregation, which fused into a saccule-cochlea organization.

• MeSH
• homeodoménové proteiny * genetika   metabolismus   MeSH
• kochlea * fyziologie   MeSH
• myši knockoutované * MeSH
• myši MeSH
• sakulus a utrikulus * fyziologie   MeSH
• sluchová dráha fyziologie   MeSH
• transkripční faktory * genetika   metabolismus   nedostatek   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

• MeSH
• aminoglykosidy MeSH
• kochlea embryologie   MeSH

• Konspekt
• Lékařské vědy. Lékařství
• NLK Obory
• otorinolaryngologie
• farmacie a farmakologie

Všeobecně je přijat názor, že Carhartův zub u otosklerózy vzniká absencí středoušníosteotympanální složky kostního vedení následkem blokády oválného okénka. V článku jsou shrnu-ty důvody, které tento názor zpochybňují. Autoři se domnívají, že Carhartův zub vzniká následkemzměněných mechanických a hydrodynamických změn uvnitř kochley.

It is generally accepted that Carhart's “dip” in otosclerosis develops as a result of the absence of the middle ear osteotympanic component of the bone conduction due to a block of the oval window. In the submitted article the authors summarize reasons which cast doubts on this view. The authors assume that Carhart's “dip” oceurs as a result of the mechanical and hydrodyna- mic changes in the cochlea.

• MeSH
• kochlea patologie   MeSH
• kostní vedení zvuku MeSH
• lidé MeSH
• otoskleróza MeSH
• poruchy sluchu etiologie   MeSH
• sluchový práh MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• srovnávací studie MeSH

• MeSH
• evokované potenciály MeSH
• kochlea embryologie   fyziologie   MeSH
• krysa rodu rattus MeSH
• vývojová biologie MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• zvířata MeSH

Even brief acoustic trauma during the critical period of development that results in no permanent hearing threshold shift may lead to altered auditory processing in adulthood. By monitoring the acoustic startle response (ASR), we examined the development of auditory function in control rats and in rats exposed to intense noise at the 14th postnatal day (P14). First ASRs appeared on P10-P11 to intense low-frequency tones. By P14, the range of sound intensities and frequencies eliciting ASRs extended considerably, the ASR reactivity being similar at all frequencies (4-32 kHz). During the subsequent two weeks, ASR amplitudes to low-frequency stimuli (4-8 kHz) increased, whereas the ASRs to high-frequency tones were maintained (16 kHz) or even decreased (32 kHz). Compared to controls, noise exposure on P14 (125 dB SPL for 8, 12, or 25 min) produced transient hyper-reactivity to startle stimuli, manifested by a decrease of ASR thresholds and an increase of ASR amplitudes. ASR enhancement occurred regardless of permanent hearing loss and was more pronounced at high frequencies. The hyper-reactivity of ASRs declined by P30; the ASR amplitudes in adult exposed rats were lower than in controls. The histological control did not reveal loss of hair cells in adult exposed rats, however, the number of inner hair cell ribbon synapses was significantly decreased, especially in the high-frequency part of the cochlea. The results indicate that early acoustic trauma may result in complex changes of ASRs during development.

• MeSH
• akustická stimulace škodlivé účinky   MeSH
• kochlea cytologie   růst a vývoj   MeSH
• potkani Long-Evans MeSH
• senzorické prahy fyziologie   MeSH
• sluchová percepce fyziologie   MeSH
• sluchové kmenové evokované potenciály fyziologie   MeSH
• sluchové testy MeSH
• synapse fyziologie   MeSH
• úleková reakce fyziologie   MeSH
• zvířata MeSH
• Check Tag
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

• MeSH
• evokované potenciály MeSH
• kochlea fyziologie   MeSH
• myši MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH

• MeSH
• audiologie MeSH
• elektrofyziologie MeSH
• kochlea MeSH
• králíci MeSH
• otorinolaryngologie MeSH
• vnitřní ucho MeSH
• Check Tag
• králíci MeSH

• Konspekt
• Patologie. Klinická medicína
• NLK Obory
• otorinolaryngologie
• otorinolaryngologie

• MeSH
• evokované potenciály MeSH
• kochlea fyziologie   MeSH
• myši MeSH
• percepce MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH

We review the molecular basis of several transcription factors (Eya1, Sox2), including the three related genes coding basic helix-loop-helix (bHLH; see abbreviations) proteins (Neurog1, Neurod1, Atoh1) during the development of spiral ganglia, cochlear nuclei, and cochlear hair cells. Neuronal development requires Neurog1, followed by its downstream target Neurod1, to cross-regulate Atoh1 expression. In contrast, hair cells and cochlear nuclei critically depend on Atoh1 and require Neurod1 expression for interactions with Atoh1. Upregulation of Atoh1 following Neurod1 loss changes some vestibular neurons' fate into "hair cells", highlighting the significant interplay between the bHLH genes. Further work showed that replacing Atoh1 by Neurog1 rescues some hair cells from complete absence observed in Atoh1 null mutants, suggesting that bHLH genes can partially replace one another. The inhibition of Atoh1 by Neurod1 is essential for proper neuronal cell fate, and in the absence of Neurod1, Atoh1 is upregulated, resulting in the formation of "intraganglionic" HCs. Additional genes, such as Eya1/Six1, Sox2, Pax2, Gata3, Fgfr2b, Foxg1, and Lmx1a/b, play a role in the auditory system. Finally, both Lmx1a and Lmx1b genes are essential for the cochlear organ of Corti, spiral ganglion neuron, and cochlear nuclei formation. We integrate the mammalian auditory system development to provide comprehensive insights beyond the limited perception driven by singular investigations of cochlear neurons, cochlear hair cells, and cochlear nuclei. A detailed analysis of gene expression is needed to understand better how upstream regulators facilitate gene interactions and mammalian auditory system development.

• MeSH
• kochlea cytologie   metabolismus   MeSH
• lidé MeSH
• neurogeneze genetika   fyziologie   MeSH
• transkripční faktory bHLH genetika   metabolismus   MeSH
• transkripční faktory genetika   metabolismus   MeSH
• vláskové buňky metabolismus   MeSH
• vývojová regulace genové exprese MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

• MeSH
• ductus cochlearis embryologie   MeSH
• kochlea embryologie   MeSH
• králíci MeSH
• vnitřní ucho embryologie   MeSH
• Check Tag
• králíci MeSH

• Konspekt
• Lékařské vědy. Lékařství
• NLK Obory
• otorinolaryngologie
• embryologie a teratologie