Technical pitfalls in middle ear gas studies: Errors introduced by the gas permeability of tubing and additional dead space

Conclusions We demonstrated errors introduced by the gas permeability of the tubing and additional dead space. Materials with practically no permeability, such as glass, must be used to overcome the loss or gain of gas through the walls of tubes used for studying ME gas variations. Experiments conducted at a constant volume (variable pressure) require the smallest possible tubing volume in order to obtain good sensitivity and improve the accuracy of the results.

Objectives Experimental studies that investigate middle ear (ME) gas exchanges, using either pressure measurements or volume changes, are conducted using various tubing connections between the ME and a measuring device. The aims of this study were to highlight experimental problems due to the errors introduced by (i) the gas permeability of the tubing used and (ii) additional dead space in experiments conducted at constant volume.

Material and methods The problem of the gas permeability of the tubing was addressed by comparing three types of tube (silicone, polyethylene, PVC) with a glass tube. Horizontally placed tubes were connected to a syringe filled with pure CO₂ via a gas-tight valve. The end of each tube tested was plunged into colored water (5% Coomassie Brilliant Blue R-250). The tube was washed out with CO₂ until gas bubbles were seen leaving it. The valve was then closed and the movement of water in the tube was observed. The same experiments were repeated for pure O₂. The problem of the error introduced by the additional dead space volume was addressed at a theoretical level using the well-known gas laws. Two conditions were studied: condition A, in which the experiment was conducted at constant pressure and the volume was measured; and condition B, in which the experiment was conducted at constant volume and the pressure was measured. The main outcome measure of each condition was the calculated variation in the final number of moles of gas involved.

Results No water movement was observed in glass tubes. In contrast, plastic tubes exhibited significant gas permeability effects for both CO₂ and O₂. The colored solution advanced at a faster rate with CO₂ than O₂ but differently for each type of tubing. For condition A, gas transfer was independent of the volume of the external tubing and was accurately measured by the displacement of the droplet in the lumen. In contrast, for condition B, the pressure variations were influenced by the volume of the tubing.     

Aquaporin-2 in the human endolymphatic sac

Objective To detect and localize aquaporin-2 (AQP-2), a water channel regulated by the antidiuretic hormone, in human endolymphatic sac.

Material and Methods Human endolymphatic sacs were sampled during removal of vestibular schwannomas via a translabyrinthine approach. Samples were immediately fixed in 10% formalin (24 h) and embedded in paraffin; in situ hybridization and immunohistochemistry were performed with an AQP-2-specific probe and a polyclonal antibody.

Results Both AQP-2 mRNA and protein were detected in the epithelium of the endolymphatic sac. AQP-2 immunostaining was mainly cytoplasmic, suggesting that most AQP-2 was located in intracellular pools.

Conclusion In the endolymphatic sac, AQP-2 probably participates in the homeostasis of endolymph; the possibility of reducing the volume of endolymph by inhibiting its expression and membranous insertion using an antidiuretic hormone inhibitor represents a new therapeutic approach for the treatment of Ménière's disease.     

Temporal reduction of LATS kinases in the early preimplantation embryo prevents ICM lineage differentiation

Cellular localization of the Yes-associated protein (YAP) is dependent on large tumor suppressor (LATS) kinase activity and initiates lineage specification in the preimplantation embryo. We temporally reduced LATS activity to disrupt this early event, allowing its reactivation at later stages. This interference resulted in an irreversible lineage misspecification and aberrant polarization of the inner cell mass (ICM). Complementation experiments revealed that neither epiblast nor primitive endoderm can be established from these ICMs. We therefore conclude that precisely timed YAP localization in early morulae is essential to prevent trophectoderm marker expression in, and lineage specification of, the ICM.     

Surgical anatomy and pathology of the middle ear

Middle ear surgery is strongly influenced by anatomical and functional characteristics of the middle ear. The complex anatomy means a challenge for the otosurgeon who moves between preservation or improvement of highly important functions (hearing, balance, facial motion) and eradication of diseases. Of these, perforations of the tympanic membrane, chronic otitis media, tympanosclerosis and cholesteatoma are encountered most often in clinical practice. Modern techniques for reconstruction of the ossicular chain aim for best possible hearing improvement using delicate alloplastic titanium prostheses, but a number of prosthesis‐unrelated factors work against this intent. Surgery is always individualized to the case and there is no one‐fits‐all strategy. Above all, both middle ear diseases and surgery can be associated with a number of complications; the most important ones being hearing deterioration or deafness, dizziness, facial palsy and life‐threatening intracranial complications. To minimize risks, a solid knowledge of and respect for neurootologic structures is essential for an otosurgeon who must train him‐ or herself intensively on temporal bones before performing surgery on a patient.     

SLC26A4 p.Thr410Met homozygous mutation in a patient with a cystic cochlea and an enlarged vestibular aqueduct showing characteristic features of incomplete partition type I and II

Mutations of SLC26A4 are associated with incomplete partition type II (IP-II) and isolated enlargement of the vestibular aqueduct (EVA). We experienced a congenitally deaf 6-year-old boy with a rare p.Thr410Met homozygous mutation in SLC26A4 who underwent bilateral cochlear implantation. He had bilateral inner ear malformation, in which the dilated vestibule and EVA were identical to those in IP-II, but the cochlea lacking a bony modiolus resembled that in incomplete partition type I. These results suggest that homozygous mutations in SLC26A4 are always associated with EVA, while the severity of cochlear malformation may vary depending on the type of SLC26A4 mutation.     

针药结合治疗耳闭

将已知临床有效方法"中药治疗脾虚失运,湿浊困耳型耳闭"方案改为"针刺为主针药结合治疗脾虚失运,湿浊困耳型耳闭",并对其实效性进行探索性研究。以针刺为主针药结合治疗脾虚失运,湿浊困耳型耳闭,治疗共5个疗程,针刺治疗贯穿始终,前3个疗程联合参苓白术散,后2个疗程只实施针刺。耳闭症状得以有效缓解,最终听力恢复。     

Appearance benefits of skin moisturization

Background/purpose: Skin hydration is essential for skin health. Moisturized skin is generally regarded as healthy and healthy looking. It is thus speculated that there may be appearance benefits of skin moisturization. This means that there are corresponding changes in the optical properties when skin is moisturized. Methods: The appearance of the skin is the result of light reflection, scattering and absorption at various skin layers of the stratum corneum, epidermis, dermis and beyond. The appearance benefits of skin moisturization are likely primarily due to the changes in the optical properties of the stratum corneum. We hypothesize that the major optical effect of skin moisturization is the decrease of light scattering at the skin surface, i.e., the stratum corneum. This decrease of surface scattering corresponds to an increase of light penetration into the deeper layers of the skin. An experiment was conducted to measure the corresponding change in skin spectral reflectance, the skin scattering coefficient and skin translucency with a change in skin hydration. In the experiment, skin hydration was decreased with the topical application of acetone and alcohol and increased with the topical application of known moisturizers and occlusives such as PJ. Result and conclusion: It was found that both the skin spectral reflectance and the skin scattering coefficient increased when the skin was dehydrated and decreased when the skin was hydrated. Skin translucency increased as the skin became moisturized. The results agree with the hypothesis that there is less light scattering at the skin surface and more light penetration into the deeper skin layers when the skin is moisturized. As a result, the skin appears darker, more pinkish and more translucent.     

3D micro-CT images of ossicles destroyed by middle ear cholesteatoma

Objective To reconstruct the 3D structures of normal ossicles and ossicles destroyed by different cholesteatomas, and to compare the volume fractions of the two types of ossicles.

Material and Methods Thirteen pathological ossicles from four kinds of middle ear cholesteatoma obtained during surgery were used. Normal ossicles harvested from cadaveric temporal bone specimens were used as controls. The structures of the ossicles were analyzed using micro-CT by filming 2D cross-sectional images perpendicular to the long axis, from which 3D images were reconstructed. The volume fraction was measured using a CT-Analyzer? and Ant?.

Results The volume fraction, indicating the relative strength of normal ossicles, was lower in the portion close to the articular surface. As the four types of cholesteatoma were found to express their patterns of destruction at various sites in the ossicles, they revealed a different volume fraction in each ossicle.

Conclusion Our preliminary data on ossicular structure obtained using micro-CT will be helpful for elucidating the normal and pathological structure of ossicles and for the further development of artificial prostheses.     

Vestibular evoked myogenic potentials in middle ear effusion

Conclusion. The vestibular evoked myogenic potential (VEMP) responses were significantly affected by middle ear effusion (MEE). The VEMP was either non-responsive or significantly delayed. However, after the conductive hearing loss (CHL) was significantly reduced with tympanic aspiration, the VEMP latencies and asymmetry ratio returned to the range of healthy controls. In addition, the recovery of VEMP response was prompt and immediate. Objective. To evaluate the VEMP in various degrees of CHL resulting from MEE and to clarify the responses after the CHL was reduced. Materials and methods. VEMPs were collected from 21 unilateral subjects with MEE (8 male, 13 female, aged 21–79 years) using unilateral tone-burst stimulation. The pure tone audiograms and tympanograms were recorded. The effusion was then cleared with tympanocentesis. The VEMP responses were compared to those of the healthy volunteers and the responses after the MEE was reduced by tympanic aspiration. Results. The pure tone hearing thresholds decreased significantly with tympanic aspiration. Before tympanic aspiration, the VEMP response rate was 67% and increased significantly to 95% (p<0.05) after tympanic aspiration. The latencies of p13 and n23 were significantly prolonged before tympanic aspiration (p<0.01), and shortened to the normal range after tympanic aspiration. The VEMP asymmetry ratio was significantly decreased after tympanic aspiration (p<0.05).