BACKGROUND AND OBJECTIVES: Cisplatin or radiation have been widely used in the treatment of patients with head and neck cancers. However, their adverse effects such as ototoxicity and nephrotoxicity are serious considerations. This study was aimed to establish a dose-dependent response in an animal model, with the hope of contributing to research for prevention of ototoxicity in cancer patients treated with radiation or chemotherapy. MATERIAL AND METHODS: Three different doses (4, 8, 12 mg/kg) of intraperitoneal cisplatin and radiation (17, 23, 33 Gy) were administered to guinea pigs. RESULTS: After 8 days, the temporal bones were prepared for scanning electron microscopic examination. The cochlear hair cells, especially outer hair cells in the third row, were severely damaged in the cisplatin groups and irradiation groups and these damages were related to the dose administered. The main abnormalities were the deletion or distortion of stereocilia of the hair cells and the loss of stiffness. CONCLUSION: A dose-dependent response relationship established in this study will provide as a useful reference for other researches for the prevention of ototoxicity by cisplatin and radiation.
Animals ; Cisplatin* ; Cochlea* ; Drug Therapy ; Guinea Pigs* ; Guinea* ; Hair ; Head ; Hope ; Humans ; Models, Animal ; Neck ; Stereocilia ; Temporal Bone

BACKGROUND AND OBJECTIVES: Mechanism of inner ear hair cell distortion after noise exposure has been well described. The present study was designed to determine the response to the auditory system of a genetically well-defined laboratory mouse in preparation for examining the effect of noise on mice with specific genetic mutations. So it is important to recognize the relationship between noise exposure duration and hair cell morphological changes. We try to reveal the hearing loss and inner ear hair cell morphological changes after applying the noise protocol. SUBJECTS AND METHOD: The mice were BALB/c hybrids and aged 8 weeks. Six mice served as non-noise-exposed controls and 8 mice were exposed for 3 hours per day to white band noise with a center frequency from 0.2 kHz to 70 kHz and a sound pressure level of 120 dB. And we divided the noise exposure group into 3 subgroups(1 day, 3 day, 5 day noise exposure group). We checked the photographs of FITC phalloidin stain and scanning electron microscopy of cochlea after noise exposure. RESULTS: The hearing level of mice decreased after noise exposure. We could see the stereocilia damage in cochlea after FITC phalloidin stain in cochlea and sterocilia loss was more severe in basal turn. In scanning electron microscopy, morphological changes of stereocilia were observed to be more severe in the cochlear basal turn than other area. Significant hair cell loss in the cochlear basal turn could be calculated using cochleocytogram. CONCLUSION: 120dB broad white band noise can damage the hair cell of cochlea in mice. These changes were especially severe in the cochlear basal turn. Noise exposure duration is the other important factor in damaging cochlear hair cells. Therefore, we can guess that harmful noise level and noise exposure duration are the main risk factors that injure the inner ear hair cell.
Animals ; Cochlea ; Ear, Inner* ; Fluorescein-5-isothiocyanate ; Hair* ; Hearing ; Hearing Loss ; Mice* ; Microscopy, Electron, Scanning ; Noise* ; Phalloidine ; Risk Factors ; Stereocilia

OBJECTIVES: Gentamicin (GM) is a commonly used aminoglycoside antibiotic that generates free oxygen radicals within the inner ear, which can cause vestibulo-cochlear toxicity and permanent damage to the sensory hair cells and neurons. Piper longum L. (PL) is a well-known spice and traditional medicine in Asia and Pacific islands, which has been reported to exhibit a wide spectrum of activity, including antioxidant activity. In this study, we evaluated the effect of hexane:ethanol (2:8) PL extract (subfraction of PL [SPL] extract) on GM-induced hair cell loss in basal, middle and apical regions in a neonatal cochlea cultures. METHODS: The protective effects of SPL extract were measured by phalloidin staining of cultures from postnatal day 2-3 mice with GM-induced hair cell loss. The anti-apoptosis activity of SPL extract was measured using double labeling by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and myosin-7a staining. The radical-scavenging activity of SPL extract was assessed using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. RESULTS: SPL extract at a concentration of 1 microg/mL significantly inhibited GM-induced hair cell loss at basal and middle region of cochlea, while 5 microg/mL was effective against apical region hair cell loss. The protective effect of SPL extract was concentration dependent and hair cells retained their stereocilia in explants treated with SPL extract prior to treatment with 0.3 mM GM. SPL extract decreased GM-induced apoptosis of hair cells as assessed by TUNEL staining. The outer hair and inner hair counts were not decreased in SPL extract treated groups in compare to GM treated explants. Additionally, SPL extract showed concentration dependent radical scavenging activity in a DPPH assay. CONCLUSION: An anti-apoptosis effect and potent radical scavenger activity of SPL extract protects from GM-induced hair cell loss at basal, middle and apical regions in neonatal cochlea cultures.
Animals ; Apoptosis ; Asia ; Cochlea ; DNA Nucleotidylexotransferase ; Ear, Inner ; Ethanol* ; Gentamicins ; Hair* ; In Situ Nick-End Labeling ; Medicine, Traditional ; Mice ; Neurons ; Pacific Islands ; Phalloidine ; Piper* ; Reactive Oxygen Species ; Spices ; Stereocilia

Smoking has been positively associated with hearing loss in human. However, its effect on the cochlea has not been previously evaluated. Aim of work is to investigate the effect of nicotine, which is the primary pharmacological component of tobacco, on the structure of the cochlea of adult male guinea pigs. Fifteen male guinea pigs were classified into two groups: group I (control) and group II (nicotine treated group). Group II was further subdivided into two subgroups; IIA and IIB according to the dose of nicotine (3 mg/kg and 6 mg/kg, respectively). The cochlea was harvested and processed for light microscopy, transmission electron microscopy and scanning electron microscopy. Nicotine administration induced damage of outer hair cells which were distorted in shape with vacuolated cytoplasm and heterochromatic nuclei. Topography revealed damage of the stereocilia which included disorganization, bent and limp or complete loss and expansion of the surrounding supporting cells. These changes were more pronounced in the basal turn of the cochlea and mainly involved the outer hair cells. High dose induced more damage and resulted in protrusion of the apical poles of hair cells (blebing), particularly the outer two rows. Nicotine is proved to be harmful to the cells of the cochlea, particularly the outer hair cells of the basal turn. High doses induce blebing of hair cells.
Adult ; Animals ; Cochlea* ; Cytoplasm ; Guinea Pigs* ; Hair ; Hearing Loss ; Humans ; Male ; Microscopy ; Microscopy, Electron, Scanning ; Microscopy, Electron, Transmission ; Nicotine* ; Smoke ; Smoking ; Stereocilia ; Tobacco

BACKGROUND AND OBJECTIVES: Organotypic culture of organ of Corti maintains the basic organization of the spiral lamina and can conserve several factors responsible for the neuronal growth of the nervous components. The explant culture technique has been widely used in organ culture system, however, the floating drop method using collagen gel was also developed as a simple and reliable method. In order to study the effect of growth factors on the regenerative and protective ability of cochlear hair cells, we first had to establish an in vitro model of the inner ear. MATERIALS AND METHODS: Organ of Corti was obtained from newborn rats and cultured with the floating drop method using collagen gel. Immunohistochemical staining was used to visualize the stereocilia and scanning electron microscopic study was also carried out. RESULTS: Explants were maintained up to 10 days without contamination. Morphologically, immunofluorescent staining with phalloidin showed well preserved outer and inner hair cells with stereocilia on the second day of culture. On the tenth day of culture, the staining result showed inner and outer hair cells, although the stereocilia were poorly stained. In scanning electron microscopic examination, an explant on the tenth day of culture showed preserved outer and inner hair cells and stereocilia, although damaged hair cells and stereocilia were also observed. CONCLUSION: The floating drop method was an appropriate method for maintaining the organ of Corti in vitro with the advantage being the easiness in its manual manipulation.
Animals ; Collagen ; Culture Techniques ; Ear, Inner ; Hair ; Humans ; Infant, Newborn* ; Intercellular Signaling Peptides and Proteins ; Neurons ; Organ Culture Techniques ; Organ of Corti* ; Phalloidine ; Rats* ; Spiral Lamina ; Stereocilia

BACKGROUND AND OBJECTIVES: Injection of endotoxin into the middle ear of experimental animals results in otitis media with effusion and transient reversible hearing loss, which occurs in the higher concentration of endotoxin than the concentration found in human middle ear effusion. The purpose of this study was to investigate the histopathologic changes of the cochlea in guinea pigs with experimental otitis media with effusion induced by E.coli endotoxin. MATERIALS AND METHODS: Concentrations of lipopolysaccharides (LPS) from E.coli, such as 0.1 mg/ml, 1 mg/ml, and 10 mg/ml, were instillated into the middle ear cavity of 30 normal guinea pigs. Histopathologic changes of the cochlea were observed at 1 week after endotoxin instillation, using both light and electron microscope. Six normal guinea pigs were used as a control group whose middle ears were instillated with the physiologically sterile saline. RESULTS: There were deformation in the organ of Corti, partial loss of stereocilia in the hair cells, and vacuolation in stria vascularis at a concentration of 10 mg/ml lipopolysaccharides from E. coli. Mild morphologic abnormality of the cochlea was observed at the concentrations of 1 mg/ml and 0.1 mg/ml. CONCLUSION: A higher concentration of LPS in the middle ear cavity may produce severe inner ear damage, possibly resulting in the sensorineural hearing loss.
Animals ; Cochlea ; Ear, Inner ; Ear, Middle ; Guinea Pigs ; Hair ; Hearing Loss ; Hearing Loss, Sensorineural ; Humans ; Lipopolysaccharides ; Organ of Corti ; Otitis Media with Effusion* ; Otitis Media* ; Otitis* ; Pathology* ; Stereocilia ; Stria Vascularis

BACKGROUND: Despite numerous investigations, the pathogenesis of Meniere's disease is uncertain. Endolymphatic hydrops (ELH) has been the main histologic finding of Meniere's disease. Experimentally induced ELH in animal model has been developed in order to understand better the consequences of this morphopathology on inner ear structure and function. OBJECTIVES: The aim of this study is to develope the animal model of ELH. MATERIAL AND METHODS: We made an animal endolymphatic hydrops model on giunea pigs by mechanically obliterating the right endolympatic sac and duct. The left ears were used as a controls. RESULTS: After twelve weeks, the temporal bones were prepared for light and electron microscopic examination. The light microscopic study showed the distension and folding of Reissner's membrane, however other pathologic changes were uncertain in hydropic aminal. Under scanning electron microscopic examination, the cellular population of Reissner membrane remained normal but the microvilli of Reissner membrane were significantly decreased in hydrops group. The damage pattern of stereocilia were most severe in the apical turns, followed by the middle and the basal turns, in the order of severeity. The outer hair cell third row was most severely damaged in the entire cochlea, whereas the outer hair cell first row was relatively spared. On the single hair cell examination, abnormal distensions of the tip of stereocilia started from longer stereocilia. The number of microvilli on marginal cell was reduced in stria vascularis, but atrophic change was not observed.
Animals ; Cochlea ; Ear ; Ear, Inner ; Edema ; Endolymphatic Hydrops* ; Guinea Pigs* ; Guinea* ; Hair ; Membranes ; Meniere Disease ; Microvilli ; Models, Animal ; Stereocilia ; Stria Vascularis ; Swine ; Temporal Bone

BACKGROUND AND OBJECTIVES: The study was designed to investigate the changes in the expression of hypoxia inducible factor-1alpha (HIF-1alpha) according to time after being exposed to noise trauma and find out the effect of HIF-1 alpha in the prevention of noiseinduced hearing loss by pre-treatment with cobalt chloride (CoCl2). SUBJECTS AND METHOD: BALB/c hybrid mice with 25 dB HL or less ABR were used in this study. In the study group, subjects were exposed to 120 dB SPL broad white band noise for 3 hours per day for 3 days. The changes in their hearing were documented before and after 1, 2, 3, 4, and 9 days of the first noise exposure. CoCl2 was injected into the peritoneum 2 hours prior to each noise exposure to see the effect of induced HIF-1alpha on noise-induced hearing loss. For the control, injection with distilled water was performed and hearing thresholds were measured in the same manner. Cochlea from each group was obtained in order to observe the morphological changes in the inner ear and the expression of the HIF-1alpha using immunohistochemial staining and immuno-fluorescein staining along with quantification of the hair cell loss. RESULTS: Mice exposed to the noise for 3 days, showed permanent threshold shift and the expression of HIF-1alpha was increased. When HIF-1alpha was induced by pre-treatment of CoCl2 prior to the noise exposure, however, hearing recovery was observed to some degree. And hair cell survival rate was also higher when treated with CoCl2 compared to the distilled water treated group. CONCLUSION: When pre-treated with CoCl2, inducing HIF-1alpha before the noise trauma, it allowed for a less stereocilia loss in the hair cells in the organ of Corti. HIF-1alpha may play an important role in the prevention of noise-induced hearing loss.
Animals ; Anoxia ; Cell Survival ; Cobalt ; Cochlea ; Ear, Inner ; Hair ; Hearing ; Hearing Loss ; Hearing Loss, Noise-Induced* ; Hypoxia-Inducible Factor 1 ; Mice ; Noise ; Organ of Corti ; Peritoneum ; Stereocilia ; Water

BACKGROUND AND OBJECTIVES: The mechanism of the noise damage to the cochlea is not fully understood in spite of many studies. The morphological changes in a noise stimulated model show various features relating to the duration of the exposure and sound intensity. Until now there had been a lot of the morphological studies on noise induced hearing loss models, but only a few reports of single blast injury of more than 150 dB. MATERIALS AND METHOD: We observed with a transmission electron microscope by using the microslicing technique for minimizing the tissue injury and successful hair cell counting in resin embedded cochlea of the guinea pig, stimulated by a 178 dB single blast wave. RESULTS: The area of hair cell damage in L.M. showed stereocilia bending at 24 hours, proliferation of Hensen's body, subsurface cistern in outer hair cell and mitochondria proliferation in inner hair cell within 2wks. The area of no hair cell damage in L.M. showed minimal changes in E.M., as well. CONCLUSION: These results suggest that the 178 dB single blast wave injury may not cause severe distortion of the organ of Corti in the guinea pig and thus the compensation process can be advanced gradually.
Animals ; Blast Injuries ; Cell Count ; Cochlea* ; Compensation and Redress ; Guinea Pigs* ; Guinea* ; Hair ; Hearing Loss ; Microscopy, Electron ; Mitochondria ; Noise ; Organ of Corti ; Stereocilia

BACKGROUND AND OBJECTIVES: Endolymphatic hydrops has been considered as an important histologic substrate of Meniere's disease. A permanent displacement of basilar membrane (BM) by increased endolymphatic pressure has been thought to be an explanation for hearing change. Direct observation of histological sections of temporal bones, however, suggested that stereocilia and tectorial membrane decoupling is more associated with pressure induced by mechanical deformation of the organ of Corti rather than with the displacement of BM. METERIALS AND METHOD: 26 cochleae from 13 female pigmented ginea pigs were harvested. One cochlea per each animal was injected with artificial perilymph. The other one was used as control. After fixation, followed by embedding and mid-modiolar sectionning, specimens were observed with a microscope. Morphometric parameters of each row and turn of the organ of Corti were measured and quantified. RESULTS: The average area and height of the organ of Corti were significantly smaller in the apical turn of the experimental group (p<0.05). The lengths of outer hair cell and Deiters cell in the apical turn were also significantly reduced in the experimental group (p<0.05). The angle between the outer hair cell and Deiters cell was smaller in the apex and in the 3rd turn of the experimental group (p<0.05). CONCLUSION: Results show that compression and deformation of the organ of Corti, especially in the apical turn, is a prominent feature in the acute endolymphatic hydrops model. We suggest that the deformation of organ of Corti is the primary cause of hydrops that induce the decoupling of tectorial membrane and stereocilia rather than the displacement of BM.
Animals ; Basilar Membrane ; Cochlea ; Edema ; Endolymphatic Hydrops* ; Female ; Guinea Pigs ; Hair ; Hearing ; Humans ; Meniere Disease ; Organ of Corti* ; Perilymph ; Stereocilia ; Swine ; Tectorial Membrane ; Temporal Bone