The mechanical reaction of the pars flaccida of the eardrum to rapid air pressure oscillations modeling different levels of atmospheric disturbances

Necessities, opportunities, and challenges for tympanic membrane perforation scaffolding-based bioengineering

Tympanic membrane (TM) perforation is a global clinical dilemma. It occurs as a consequence of object penetration, blast trauma, barotrauma, and middle ear diseases. TM perforation may lead to otitis media, retraction pockets, cholesteatoma, and conductive deafness. Molecular therapies may not be suitable to treat perforation because there is no underlying tissue matrix to support epithelium bridging. Chronic perforations are usually reconstructed with autologous grafts via surgical myringoplasty. Surgical treatment is uncomfortable for the patients. The grafting materials are not perfect because they produce an opaque membrane, fail in up to 20% of cases, and are suboptimal to restore acoustic function. Millions of patients from developing parts of the world have not got access to surgical grafting due to operational complexities, lack of surgical resources, and high cost. These shortcomings emphasize bioengineering to improve placement options, healing rate, hearing outcomes, and minimize surgical procedures. This review highlights cellular, structural, pathophysiological, and perforation specific determinants that affect healing, acoustic and surgical outcomes; and integrates necessities relevant to bioengineered scaffolds. This study further summarizes scaffolding components, progress in scaffolding strategies and design, and engenders limitations and challenges for optimal bioengineering of chronic perforation.

Environmental cue affects the hearing-related behaviors of Drosophila melanogaster by targeting the redox pathways

Environmental cues like noise, pressure, and circadian rhythm can affect the hearing ability of human beings. Nevertheless, the complex physiology of the human being does not allow us to understand how these factors can affect hearing and hearing-related behaviors. Conversely, these effects can be easily checked using the hearing organ of Drosophila melanogaster, the Johnston organ. In the current study, the Drosophila was exposed to challenging environments like noise, low pressure, and altered circadian rhythm. The hearing organ of larvae, as well as adults, was analyzed for hearing-related defects. In the third instar larva, the cell deaths were detected in the antenna imaginal disc, the precursor of Johnston's organ. Elevated levels of reactive oxygen species and antioxidant enzymes were also detected in the adult antennae of environmentally challenged flies. The ultrastructure of the antennae suggests the presence of abundant mitochondria in the scolopidia of control. Fewer amounts of mitochondria are found in the environmentally challenged adult antennae. In adults, various hearing-related behaviors were analyzed as a readout of functionality of the hearing organ. Analysis of climbing, aggressive, and courtship behaviors suggests abnormal behavior in environmentally challenged flies than the control. The current study suggests that the environmental cues can alter hearing-related behaviors in Drosophila. The methods used in this study can be used to monitor the environmental pollution or to study the effect of alteration of noise, pressure, and circadian rhythm on hearing-related behaviors taking Drosophila melanogaster as a model organism. Graphical abstract.

Applicability of vital staining and tissue clearing to vascular anatomy and melanocytes' evaluation of temporal bone in six laboratory species

The purpose of the present study was to define the applicability of tissue clearing to the field of otology. We combined tissue clearing with vital staining perfusion via a pumping system to examine the vascular anatomy of temporal bones in laboratory animals. We used six different types of species including Korean wild mouse, mouse, Mongolian gerbil, hamsters and Guinea pigs. A mixture of Alcian blue reagent and 4% paraformaldehyde was circulated throughout the entire circulatory system of the animal via a perfusion pump system. Transparency images were obtained from the temporal bones according to the protocol of the SunHyun 3D Imaging Kit. In examining the inner surface of the tympanic membrane, flaccid part (pars flaccida) was positioned along the entire marginal area in Guinea pig. In the Guinea pig, unlike the other species, the cortical bone of the mastoid (bullae) was easily removed using cold instruments, allowing a direct approach to the enclosed structures. The distribution and pattern of cochlea melanocytes were compared among the species. "Mobius strip"-like accumulated melanocytes in vestibules were shown in both the Korean wild mouse and mouse. The collateral blood supply to the cochlea in six different species was checked in various pattern. Combining dye infusion with tissue-clearing techniques, we documented the middle ear and transparent inner ear structures in six different species. The information and associated images will help other researchers to develop hypotheses and design experimental investigations.

Histological identification of nasopharyngeal mechanoreceptors

The auditory tube plays a fundamental role in regulating middle ear pressure. A "system" sensitive to a pressure gradient between the middle ear and the ambient environment is necessary. The presence of mechanoreceptors in the middle ear and the tympanic membrane has been studied, but the presence of these receptors in the nasopharyngeal region remains unclear. The aim of this study is to confirm the presence of pressure sensitive corpuscles in the nasopharynx. An experimental study was conducted on five fresh and unembalded human cadavers. The pharyngeal ostium of the auditory tube and its periphery was removed in one piece by video-assisted endonasal endoscopy. Samples were fixed in formaldehyde solution, embedded in paraffin, and cut. Slides were analyzed by HES (Hematoxyline Eosine Safran) coloration, by S100 protein and neurofilament protein immunostaining. Encapsulated nerve endings were researched and identified by slides analysis. Eight samples were included in our study. On seven samples, Ruffini corpuscles were identified in the mucosa of the posterior area of the pharyngeal ostium, with a higher concentration in the pharyngeal recess and in the posterior nasopharyngeal wall. Our study identified nasopharyngeal mechanoreceptors that could detect the nasopharyngeal pressure and, by extension, the atmospheric pressure. These findings support the theory of the neuronal reflex arc of isobaric system of the middle ear, based on the existence of a "system" sensitive to a pressure gradient between the middle ear and the ambient environment. Understanding of this system has been helpful in the diagnosis and management of middle ear diseases.

Atmospheric Pressure and Onset of Episodes of Menière's Disease - A Repeated Measures Study

Background

External changes of air pressure are transmitted to the middle and inner ear and may be used therapeutically in Menière’s disease, one of the most common vertigo disorders. We analyzed the possible relationship of atmospheric pressure and other meteorological parameters with the onset of MD vertigo episodes in order to determine whether atmospheric pressure changes play a role in the occurrence of MD episodes.

Methods

Patients of a tertiary outpatient dizziness clinic diagnosed with MD were asked to keep a daily vertigo diary to document MD episodes (2004–2009). Local air pressure, absolute temperature and dew point temperature were acquired on an hourly basis. Change in meteorological parameters was conceptualized as the maximum difference in a 24 hour time frame preceding each day. Effects were estimated using additive mixed models with a random participant effect. We included lagged air parameters, age, sex, weekday and season in the model.

Results

A total of 56 persons (59% female) with mean age 54 years were included. Mean follow-up time was 267 days. Persons experienced on average 10.3 episodes during the observation period (median 8). Age and change in air pressure were significantly associated with vertigo onset risk (Odds Ratio = 0.979 and 1.010). We could not show an effect of sex, weekday, season, air temperature, and dew point temperature.

Conclusions

Change in air pressure was significantly associated with onset of MD episodes, suggesting a potential triggering mechanism in the inner ear. MD patients may possibly use air pressure changes as an early warning system for vertigo attacks in the future.

Anatomical boundary of the tympanic membrane pars flaccida of the Meriones unguiculatus (Mongolian gerbil)

The pars flaccida of the Meriones unguiculatus (Mongolian gerbil) was in previous studies shown to bulge almost spherically when pressurized, a behavior suggesting that it is suspended by a fixed circular boundary. The question arises whether this "functional" boundary is based on an underlying circular anatomical boundary, an important issue for modeling the middle-ear mechanics. In this article, the boundaries of the Mongolian gerbil pars flaccida were visualized in situ with otomicroscopy and in slides with light microscopy and by micro-CT radiology. For the major part of its circumference, the pars flaccida was found to be suspended by rigid bone, that is, the tympanic legs. The remaining boundary is made up of the terminal portion of the handle of the malleus and the soft tissue of the terminal arches. The attachment to these structures is simple and uncomplicated, and the geometry is regular and symmetric: deviating by only 3.5% from a perfect circular shape. The findings justify the use of a fixed circular boundary as a good approximation for the modeling of pars flaccida deformation in the Mongolian gerbil.