scholarly journals Neuroprotective activation of astrocytes by methylmercury exposure in the inferior colliculus

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yasuhiro Ishihara ◽  
Kouichi Itoh ◽  
Ami Oguro ◽  
Yoichi Chiba ◽  
Masaki Ueno ◽  
...  
Keyword(s):  
Inferior Colliculus ◽  
Neurotrophic Factor ◽  
Auditory Brainstem Response ◽  
Global Analysis ◽  
Protein A ◽  
Auditory Pathway ◽  
Brain Derived Neurotrophic Factor ◽  
Auditory Brainstem ◽  
Protective Role ◽  
Brainstem Response

Abstract Methylmercury (MeHg) is well known to induce auditory disorders such as dysarthria. When we performed a global analysis on the brains of mice exposed to MeHg by magnetic resonance imaging, an increase in the T1 signal in the inferior colliculus (IC), which is localized in the auditory pathway, was observed. Therefore, the purpose of this study is to examine the pathophysiology and auditory dysfunction induced by MeHg, focusing on the IC. Measurement of the auditory brainstem response revealed increases in latency and decreases in threshold in the IC of mice exposed to MeHg for 4 weeks compared with vehicle mice. Incoordination in MeHg-exposed mice was noted after 6 weeks of exposure, indicating that IC dysfunction occurs earlier than incoordination. There was no change in the number of neurons or microglial activity, while the expression of glial fibrillary acidic protein, a marker for astrocytic activity, was elevated in the IC of MeHg-exposed mice after 4 weeks of exposure, indicating that astrogliosis occurs in the IC. Suppression of astrogliosis by treatment with fluorocitrate exacerbated the latency and threshold in the IC evaluated by the auditory brainstem response. Therefore, astrocytes in the IC are considered to play a protective role in the auditory pathway. Astrocytes exposed to MeHg increased the expression of brain-derived neurotrophic factor in the IC, suggesting that astrocytic brain-derived neurotrophic factor is a potent protectant in the IC. This study showed that astrogliosis in the IC could be an adaptive response to MeHg toxicity. The overall toxicity of MeHg might be determined on the basis of the balance between MeHg-mediated injury to neurons and protective responses from astrocytes.

Protective effects of brain-derived neurotrophic factor on the noise-damaged cochlear spiral ganglion

2010 ◽  
Vol 125 (5) ◽  
pp. 449-454 ◽  
Author(s):  
S-Q Zhai ◽  
W Guo ◽  
Y-Y Hu ◽  
N Yu ◽  
Q Chen ◽  
...  
Keyword(s):  
Neurotrophic Factor ◽  
Auditory Brainstem Response ◽  
Noise Exposure ◽  
Recombinant Adenovirus ◽  
Spiral Ganglion ◽  
Brain Derived Neurotrophic Factor ◽  
Auditory Brainstem ◽  
Response Threshold ◽  
Protective Effects ◽  
Brainstem Response

AbstractObjective:To explore the protective effects of brain-derived neurotrophic factor on the noise-damaged cochlear spiral ganglion.Methods:Recombinant adenovirus brain-derived neurotrophic factor vector, recombinant adenovirus LacZ and artificial perilymph were prepared. Guinea pigs with audiometric auditory brainstem response thresholds of more than 75 dB SPL, measured seven days after four hours of noise exposure at 135 dB SPL, were divided into three groups. Adenovirus brain-derived neurotrophic factor vector, adenovirus LacZ and perilymph were infused into the cochleae of the three groups, variously. Eight weeks later, the cochleae were stained immunohistochemically and the spiral ganglion cells counted.Results:The auditory brainstem response threshold recorded before and seven days after noise exposure did not differ significantly between the three groups. However, eight weeks after cochlear perfusion, the group receiving brain-derived neurotrophic factor had a significantly decreased auditory brainstem response threshold and increased spiral ganglion cell count, compared with the adenovirus LacZ and perilymph groups.Conclusion:When administered via cochlear infusion following noise damage, brain-derived neurotrophic factor appears to improve the auditory threshold, and to have a protective effect on the spiral ganglion cells.

Auditory pathway and auditory brainstem response in mice lacking NMDA receptor ϵ1 and ϵ4 subunits

1998 ◽  
Vol 251 (2) ◽  
pp. 101-104 ◽  
Author(s):  
Yumi Munemoto ◽  
Hiromichi Kuriyama ◽  
Tadashi Doi ◽  
Kazuo Sato ◽  
Ayumi Matsumoto ◽  
...  
Keyword(s):  
Nmda Receptor ◽  
Auditory Brainstem Response ◽  
Auditory Pathway ◽  
Auditory Brainstem ◽  
Brainstem Response

Diffusion Tensor Imaging of Auditory Pathway in Patients With Crigler-Najjar Syndrome Type I: Correlation With Auditory Brainstem Response

2021 ◽  
pp. 088307382110258
Author(s):  
Ahmed Abdel Khalek Abdel Razek ◽  
Mohamed Ezz El Regal ◽  
Mortada El-Shabrawi ◽  
Mohamed Moustafa Abdeltawwab ◽  
Ahmed Megahed ◽  
...  
Keyword(s):  
Diffusion Tensor Imaging ◽  
Inferior Colliculus ◽  
Cochlear Nucleus ◽  
Auditory Brainstem Response ◽  
Diffusion Tensor ◽  
Auditory Brainstem ◽  
Type I ◽  
Syndrome Type ◽  
Brainstem Response ◽  
Olivary Nucleus

Aim: To evaluate the role of diffusion tensor imaging of the auditory pathway in patients with Crigler Najjar syndrome type I and its relation to auditory brainstem response. Methods: Prospective study was done including 12 patients with Crigler Najjar syndrome type I and 10 age- and sex-matched controls that underwent diffusion tensor imaging of brain. Mean diffusivity and fractional anisotropy at 4 regions of the brain and brainstem on each side were measured and correlated with the results of auditory brainstem response for patients. Results: There was significantly higher mean diffusivity of cochlear nucleus, superior olivary nucleus, inferior colliculus, and auditory cortex of patients versus controls on both sides for all regions ( P = .001). The fractional anisotropy of cochlear nucleus, superior olivary nucleus, inferior colliculus, and auditory cortex of patients versus controls was significantly lower, with P values of, respectively, .001, .001, .003, and .001 on the right side and .001, .001, .003, and .001 on left side, respectively. Also, a negative correlation was found between the maximum bilirubin level and fractional anisotropy of the left superior olivary nucleus and inferior colliculus of both sides. A positive correlation was found between the mean diffusivity and auditory brainstem response wave latency of the right inferior colliculus and left cochlear nucleus. The fractional anisotropy and auditory brainstem response wave latency of the right superior olivary nucleus, left cochlear nucleus, and inferior colliculus of both sides were negatively correlated. Conclusion: Diffusion tensor imaging can detect microstructural changes in the auditory pathway in Crigler Najjar syndrome type I that can be correlated with auditory brainstem response.

scholarly journals Ipsilateral and Contralateral Auditory Brainstem Response Reorganization in Hemispherectomized Patients

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Ning Yao ◽  
Hui Qiao ◽  
Ping Li ◽  
Yang Liu ◽  
Liang Wu ◽  
...  
Keyword(s):  
Auditory Brainstem Response ◽  
Auditory Pathway ◽  
Auditory Brainstem ◽  
Subcortical Structures ◽  
Auditory Pathways ◽  
Control Subjects ◽  
Monaural Stimulation ◽  
Brainstem Response ◽  
Magnetic Resonance Imaging Mri

Background. Cortical hemispherectomy leads to degeneration of ipsilateral subcortical structures, which can be observed long term after the operation. Therefore, reorganization of the brainstem auditory pathway might occur. The aim of this study was to assess reorganization of brainstem auditory pathways by measuring the auditory brainstem response (ABR) in long-term hemispherectomized patients.Methods. We performed bilateral monaural stimulation and measured bilateral ABR in 8 patients~20 years after hemispherectomy and 10 control subjects. Magnetic resonance imaging (MRI) was performed in patients to assess structural degeneration.Results. All patients showed degenerated ipsilateral brainstem structures by MRI but no significant differences in bilateral recording ABR wave latencies. However, nonsurgical-side stimulation elicited significantly longer wave V latencies compared to surgical-side stimulation. Differences in bilateral ABR were observed between hemispherectomized patients and control subjects. Waves III and V latencies elicited by nonsurgical-side stimulation were significantly longer than those in control subjects; surgical-side stimulation showed no significant differences.Conclusions. (1) Differences in ABR latency elicited by unilateral stimulation are predominantly due to bilateral brainstem auditory pathway activity rather than to changes in brainstem volume; (2) ABR Waves III and V originate predominantly in the contralateral brainstem; and (3) subcortical auditory pathways appear to reorganize after long term hemispherectomy.

scholarly journals Brainstem auditory pathway of children with acute lymphoid leukemia on chemotherapy with methotrexate

2020 ◽  
Vol 78 (2) ◽  
pp. 63-69 ◽  
Author(s):  
Renata Aparecida LEITE ◽  
Jéssica Sales VOSGRAU ◽  
Leticia CORTEZ NETO ◽  
Nayara Pereira SANTOS ◽  
Sandro Luiz de Andrade MATAS ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
Auditory Brainstem Response ◽  
Otoacoustic Emissions ◽  
Lymphoblastic Leukemia ◽  
Auditory Pathway ◽  
Auditory Brainstem ◽  
Intrathecal Methotrexate ◽  
Lymphoid Leukemia ◽  
Acute Lymphoid Leukemia ◽  
Brainstem Response

Abstract Objective: Investigate the auditory pathway in the brainstem of children with acute lymphoblastic leukemia submitted to chemotherapy (by intravenous or intrathecal infusion). Methods: Fourteen children aged between 2 and 12 years with diagnosis of acute lymphoid leukemia were evaluated. The following procedures were used: meatoscopy, acoustic immitance measurements, tonal audiometry, vocal audiometry, transient otoacoustic emissions, and auditory brainstem response. Results: From the 14 children with normal auditory thresholds, 35.71% showed an alteration in auditory brainstem response, with a predominance of hearing impairment in the lower brainstem. It was found that 80% of the children with alteration had used intrathecal methotrexate less than 30 days and that 40% had the highest cumulative intravenous methotrexate doses. Conclusion: Children with acute lymphoblastic leukemia submitted to chemotherapy, present auditory pathway impairment in the brainstem, with a predominance of a low brainstem.

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