SARS-CoV-2 and male infertility: from short- to long-term impacts

PURPOSE

The coronavirus 2019 (COVID-19) pandemic-caused by a new type of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-has posed severe impacts on public health worldwide and has resulted in a total of > 6 million deaths. Notably, male patients developed more complications and had mortality rates ~ 77% higher than those of female patients. The extensive expression of the SARS-CoV-2 receptor and related proteins in the male reproductive tract and the association of serum testosterone levels with viral entry and infection have brought attention to COVID-19's effects on male fertility.

METHODS

The peer-reviewed articles and reviews were obtained by searching for the keywords SARS-CoV-2, COVID-19, endocrine, spermatogenesis, epididymis, prostate, and vaccine in the databases of PubMed, Web of Science and Google Scholar from 2020-2022.

RESULTS

This review summarizes the effects of COVID-19 on the male reproductive system and investigates the impact of various types of SARS-CoV-2 vaccines on male reproductive health. We also present the underlying mechanisms by which SARS-CoV-2 affects male reproduction and discuss the potentially harmful effects of asymptomatic infections, as well as the long-term impact of COVID-19 on male reproductive health.

CONCLUSION

COVID-19 disrupted the HPG axis, which had negative impacts on spermatogenesis and the epididymis, albeit further investigations need to be performed. The development of vaccines against various SARS-CoV-2 variations is important to lower infection rates and long-term COVID risks.

[Differential diagnosis and surgical management in chondrosarcoma of the jugular foramen]

Objective: To explore the diagnosis, surgical management and outcome of jugular foramen chondrosarcoma (CSA). Methods: Fifteen patients with jugular foramen CSA hospitalized in the Department of Otorhinolaryngology Head and Neck Surgery of Chinese PLA General Hospital from December 2002 to February 2020 were retrospectively collected,of whom 2 were male and 13 were female, aging from 22 to 61 years old. The clinical symptoms and signs, imaging features, differential diagnosis, surgical approaches, function of facial nerve and cranial nerves IX to XII, and surgical outcomes were analyzed. Results: Patients with jugular foramen CSA mainly presented with facial paralysis, hearing loss, hoarseness, cough, tinnitus and local mass. Computed tomography (CT) and magnetic resonance (MR) could provide important information for diagnosis. CT showed irregular destruction on bone margin of the jugular foramen. MR demonstrated iso or hypointense on T1WI, hyperintense on T2WI and heterogeneous contrast-enhancement. Surgical approaches were chosen upon the sizes and scopes of the tumors. Inferior temporal fossa A approach was adopted in 12 cases, inferior temporal fossa B approach in 2 cases and mastoid combined parotid approach in 1 case. Five patients with facial nerve involved received great auricular nerve graft. The House Brackmann (H-B) grading scale was used to evaluate the facial nerve function. Preoperative facial nerve function ranked grade Ⅴ in 4 cases and grade Ⅵ in 1 case. Postoperative facial nerve function improved to grade Ⅲ in 2 cases and grade Ⅵ in 3 cases. Five patients presented with cranial nerves Ⅸ and Ⅹ palsies. Hoarseness and cough of 2 cases improved after operation, while the other 3 cases did not. All the patients were diagnosed CSA by histopathology and immunohistochemistry, with immunohistochemical staining showing vimentin and S-100 positive, but cytokeratin negative in tumor cells. All patients survived during 28 to 234 months' follow-up. Two patients suffered from tumor recurrence 7 years after surgery and received revision surgery. No complications such as cerebrospinal fluid leakage and intracranial infection occurred after operation. Conclusions: Jugular foramen CSA lacks characteristic symptoms or signs. Imaging is helpful to differential diagnosis. Surgery is the primary treatment of jugular foramen CSA. Patients with facial paralysis should receive surgery in time as to restore the facial nerve. Long-term follow-up is necessary after surgery in case of recurrence.

[Phenotype-genotype analysis of the autosomal recessive hereditary hearing loss caused by OTOA variations]

Objective: To analyze the phenotypic-genotypic characteristics of hereditary deafness caused by OTOA gene variations. Methods: Family histories, clinical phenotypes and gene variations of six pedigrees were analyzed, which were diagnosed with hearing loss caused by OTOA gene variations at the PLA General Hospital from September 2015 to January 2022. The sequence variations were verified by Sanger sequencing and the copy number variations were validated by multiplex ligation-dependent probe amplification (MLPA) in the family members. Results: The hearing loss phenotype caused by OTOA variations ranged from mild to moderate in the low frequencies, and from moderate to severe in the high frequencies in the probands, which came from six sporadic pedigrees, among which a proband was diagnosed as congenital deafness and five were diagnosed as postlingual deafness. One proband carried homozygous variations and five probands carried compound heterozygous variations in OTOA gene. Nine pathogenic variations (six copy number variations, two deletion variations and one missense variation) and two variations with uncertain significance in OTOA were identified in total, including six copy number variations and five single nucleotide variants, and three of the five single nucleotide variants were firstly reported [c.1265G>T(p.Gly422Val),c.1534delG(p.Ala513Leufs*11) and c.3292C>T(p.Gln1098fs*)]. Conclusions: OTOA gene variations can lead to autosomal recessive nonsyndromic hearing loss. In this study, the hearing loss caused by OTOA defects mostly presents as bilateral, symmetrical, and postlingual, and that of a few presents as congenital. The pathogenic variations of OTOA gene are mainly copy number variations followed by deletion variations and missense variations.

[Prevalence and related factors of visual disability, hearing disability and comorbidity of visual and hearing disability among the elderly in China]

Objective: To estimate the prevalence of visual disability, hearing disability and comorbidity of visual and hearing disability among the elderly in China, and explore the related factors of comorbidity of visual and hearing disability in the elderly. Methods: This was a cross-sectional study. Based on the Second China National Sample Survey on Disability in 2006, the data of the elderly with visual and hearing disability were extracted and combined for descriptive analysis. Meanwhile, multivariate logistic regression model was used to analyze the related factors of comorbidity of visual and hearing disability among the elderly. Results: A total of 250 752 cases were in the final analysis (119 120 males and 131 632 females), and there were 164 003, 74 156 and 12 593 cases with the age of 65-<75, 75-<85 and ≥ 85 years, respectively. The prevalence of visual disability and hearing disability of the elderly in China was 8.10% (95%CI: 8.00%-8.21%), 13.41% (95%CI: 13.29%-13.54%), respectively, while the prevalence of comorbidity of visual and hearing disability was 1.97% (95%CI: 1.92%-2.02%). The severity of disability of the elderly with comorbidity of visual and hearing disability was higher, and the percentage of mild disabilities (18.31%, 966/5 277) was lower than those with visual (53.06%, 11 208/21 123) or hearing disabilities (32.96%, 11 536/34 995). Moreover, 19.40% (1 024/5 277) of visual or hearing disability occurred in the same year. Multivariate logistic regression analysis showed that education level below primary school (OR=0.65, 95%CI: 0.61-0.70, P<0.001), having a spouse (OR=0.68, 95%CI: 0.64-0.72, P<0.001), living in an urban area (OR=0.77, 95%CI: 0.71-0.82, P<0.001) and having a per capita household income higher than the national average (OR=0.73, 95%CI: 0.68-0.78, P<0.001) were protective factors for comorbidity of visual and hearing disability among the elderly. Conclusions: Visual disability is correlated with hearing disability in the elderly. Attention should be paid to the prevention and control of associated disabilities such as visual and hearing co-disabilities in the elderly population, with emphasis on strengthening publicity and education on prevention and control of visual and hearing disabilities for the elderly who are economically disadvantaged, have no spouse and live in remote areas.

Alleviating effect of mulberry leaf 1-deoxynojirimycin on resistin-induced hepatic steatosis and insulin resistance in mice

Resistin is upregulated in obese humans and mice, and elevated serum resistin induces insulin resistance and hepatic steatosis. Previous studies have revealed that mulberry 1-deoxynojirimycin (DNJ) is important for a variety of physiological processes, especially carbohydrate and lipid metabolism. However, it remains unclear whether DNJ has a positive effect on insulin resistance and hepatic steatosis, and what the exact mechanism is. Male C57BL/6J mice were treated with resistin with or without DNJ. DNJ reversed the homeostasis model assessment of insulin resistance (HOMA-IR)-induced by resistin and significantly decreased triglyceride levels both in the serum and liver. A histological analysis demonstrated that lipid accumulation significantly decreased in the DNJ group compared to the resistin group. A mechanistic analysis showed that DNJ significantly inhibited the resistin-induced decline in enzyme activities of hormone-sensitive lipase (HSL) and hepatic lipase (HL) in serum and lipoprotein lipase (LPL) in liver. FAS and Acox13α were significantly altered by resistin but restored by DNJ. Furthermore, DNJ partially but significantly restored insulin-stimulated glucose uptake compared with the resistin group, suggesting that DNJ reversed the insulin sensitivity impaired by hyperresistinemia. Treatment of AML12 cells with DNJ significantly restored the expression level and phosphorylation of Akt. The transcriptional levels of InsR and IRS1, as well as the protein levels of InsR and Glut4 and phosphorylation of PI3K and GSK3β, were also normalized in the DNJ-treated group. In conclusion: mulberry DNJ significantly alleviated liver steatosis and insulin resistance in hyperresistinemia.

[Analysis of the factors influencing positive predictive value of noninvasive prenatal testing for chromosome aneuploidies]

Objective: To investigate the influence of Z-score and different risk factors on positive predictive value (PPV) of noninvasive prenatal testing (NIPT) for chromosome aneuploidies. Methods: A total of 81 838 NIPT samples from January 1, 2016 to May 31, 2021 in the First Affiliated Hospital of Zhengzhou University were retrospectively analyzed. Invasive prenatal diagnosis was applied to verify the diagnosis of NIPT-positive results and the corresponding PPV was calculated. The PPV of the samples with different Z-score were compared. The women were divided into high-risk group and non-high-risk group: high-risk group (n=39 114) included those with ultrasound soft index abnormalities, advanced maternal age or high risk for maternal serum screening, while non-high-risk group (n=42 724) included those with intermediate risk for maternal serum screening or no indications. The differences of the PPV between these two groups were compared. Finally, the comprehensive influence of Z-score and different risk factors on PPV were analyzed. Results: A total of 471 high-risk cases were detected by NIPT results, including 362 cases of trisomy 21, 77 cases of trisomy 18 and 32 cases of trisomy 13. For trisomy 21, trisomy 18 and trisomy 13, there were 226 cases, 46 cases and 6 cases which were confirmed via invasive prenatal diagnosis respectively. The corresponding PPV were 79.3% (226/285), 82.1% (46/56) and 27.3% (6/22), respectively. PPV of trisomy 21 and trisomy 18 were positively correlated with the corresponding Z-score (r=0.92, 0.62, all P<0.05), while trisomy 13 could not be analyzed due to the small sample size. The PPV of high-risk group was 85.2% (207/243), which was higher than that of the non-high-risk group with PPV of 59.2%(71/120, χ²=30.30, P<0.01). When the Z-score was between 3-<4 and 4-<5, the PPV of the high-risk group were 46.2%(12/26)and 62.5%(15/24) respectively, which were higher than those of the non-high-risk group [16.0%(4/25) and 14.3%(3/21), χ²=4.10, 8.90, all P<0.05]. With the increase of Z-score, there was no significant difference in PPV between the two groups (all P>0.05). Conclusions: The PPV of trisomy 21 and trisomy 18 are positively correlated with Z-score. The PPV of high-risk group is higher than that of non-high-risk group. The combination of Z-score and other risk factors may provide more accurate genetic counseling for those with NIPT positive results.

[A study on longitudinal changes in white matter microstructure of parents who have lost their only child based on diffusion tensor imaging and its relationship with symptoms of posttraumatic stress disorder]

Objective: To investigate the longitudinal changes of white matter microstructural based on diffusion tensor imaging in parents who lost their only child without psychiatric disorders and its relationship with symptoms of posttraumatic stress disorder (PTSD). Methods: Parents who had who lost their only child and without psychiatric disorders in Jiangsu Province, from September 2016 to March 2017, were retrospectively collected (TENP group, 32). MRI scans were performed at baseline and at the end of 5-year follow-up, and the Clinician Administered PTSD Scales (CAPS) were used for assessing the severity of symptoms. Additionally, sex, age and education level matched healthy subjects were recruited as healthy controls (control group, 27) and underwent MRI scanning using the same protocol. The differences of fractional anisotropy (FA) values between TENP group and control group at baseline were analyzed by using Tract-based spatial statistics method, and the brain areas of lateral differences were used as the regions of interest for longitudinal follow-up analysis of TENP group. Partial correlation analysis was used to evaluate the relationship between FA values changes in longitudinal differences in brain regions and CAPS scores. Results: Compared with the control group, FA values of the right cingulate gyrus, Uncinate fasciculus, superior longitudinal fasciculus, corticospinal tract, Inferior fronto-occipital fasciculus, Inferior longitudinal fasciculus and forceps major in TENP group were decreased at baseline ((0.613±0.032) vs (0.631±0.034), (0.539±0.048) vs (0.563±0.045), (0.534±0.033) vs (0.558±0.039), (0.560±0.038) vs (0.580±0.030), (0.519±0.023) vs(0.549±0.024), (0.489±0.038) vs (0.518±0.027), (0.499±0.027) vs (0.533±0.032); all P<0.05). From baseline to follow-up, scores of trauma reexperience symptoms and avoidance/numbness symptoms were decreased ((5.2±2.8) vs (8.1±4.9), (4.0±3.2) vs (6.6±5.4); all P<0.05); FA values of the right corticospinal tract, Inferior fronto-occipital fasciculus, Inferior longitudinal fasciculus and forceps major were decreased ((0.523±0.049) vs (0.537±0.049), (0.568±0.052) vs (0.590±0.050), (0.540±0.063) vs (0.559±0.059), (0.520±0.059) vs (0.547±0.059); all P<0.05); The decrease of FA values of the right Inferior fronto-occipital fasciculus and right Inferior longitudinal fasciculus was negatively correlated with the decrease of avoidance/numbness symptoms scores (r=-0.458, -0.374, respectively, all P<0.05). Conclusions: The trauma of parents who lost their only child can result in impaired microstructural integrity of white matter. As the post-traumatic time goes by, parents who have lost their only child do not develop to PTSD and other psychiatric disorders, and the clinical symptoms are alleviated, the damage of the white matter microstructure continued to progress.

[Analysis of COL1A1 gene variation and clinical prevention and treatment in patients with Van der Hoeve syndrome]

Objective: To investigate the clinical phenotype, treatment and prevention of Van der Hoeve syndrome, and analyze the variation characteristics of its related gene COL1A1. Methods: Hearing and sequencing data of syndromic deafness patients who had undergone genetic testing for deafness at the Chinese People's Liberation Army General Hospital since January 2008 to October 2020 were retrospectively reviewed. The variation of the COL1A1 gene and return visits to traceable patients and families were summarized, the disease progress and clinical treatment effects were analyzed, and the prevention strategies were discussed. Results: A total of 7 patients with COL1A1 gene mutation underwent clinical intervention. The mutation sites were c.1342A>T (p.Lys448*), c.124C>T (p.Gln42*), c.249insG(p.Ala84*), c.668insC(p.Gly224*), c.2829+1G>C, c.1081C>T (p.Arg361*), c.1792C>T (p.Arg598*), of which c.1081C>T and c.1792C>T had been previously reported, and the remaining 5 were novo mutations that have not been reported. All the 7 probands underwent stapes implantation and received genetic counseling and prevention guidance. Conclusions: Van der Hoeve syndrome belongs to osteogenesis imperfecta type Ⅰ. The disease has high penetrance. Timely surgical intervention for hearing loss can improve the life quality in patients. Accurate genetic counseling and preimplantation genetic diagnosis can achieve the primary prevention for the disease.

[Reconstruction of complex tissue defects in temporal region: report of 3 cases]

Objective: To discuss the techniques and repairing methods of various degree of compound tissue defects in the auriculotemporal region. Methods: Retrospective analysis was conducted on three cases of different repairing methods for huge compound tissue defects in different degrees in the auriculotemporal region after the resection of the malignant tumor or sinus tract due to repeated infection in our hospital. Results: Following total removal of the tumors or sinus tract in all patients, we applied retroauricular lingual flap transfer repairing, latissimus dorsi flap free transfer repairing and vascular anastomosis, scalp tissue expansion in stage Ⅰ, then repairing the lesion with expanded scalp and filling the huge mastoid cavity with abdominal fat in stage Ⅱ, respectively, according to the characteristics of compound tissue defects in the auriculotemporal region. All free flaps survived well. Conclusions: The anatomy of the auricular-temporal area is complex and involves important vascular and neural structures of head and neck and lateral skull base. The huge composite tissue defect following auriculotemporal region surgery, which is composed of skin, muscle and bone tissue, needs to be repaired in one stage. Therefore, flexible repairing methods should be chosen based on different situations, for attaining the goal of completely removing tumor and lesions, and then, covering the operation cavity.

[Surgical strategy of minimally invasive cochlear implantation]

Cochlear implantation is currently the most effective treatment for patients with severe-to-profound sensorineural hearing loss. How to achieve minimally invasive treatment, preserve the residual hearing, and further improve curative effect and reduce surgical complications is the goal of cochlear implantation practice. This article introduces the minimally invasive cochlear implantation technique in terms of the idea of minimally invasive operation, the advantages of electric acoustic stimulation, the key points of electrode implantation technique, the design of surgical incision, and the precise processing of perioperative period. This technique not only has the merits of less operative damage and better hearing and speech rehabilitation after surgery, but also reserves favorable structures and function for the future application of gene therapy and hair cell regeneration technique. Therefore, it is strongly recommended for further promotion in clinical practice.

[Confirmation and analysis of 2 398 positive results of cell-free fetal DNA]

Objective: To explore the clinical application value and accuracy of cell-free fetal DNA (cff-DNA) technique in prenatal screening. Methods: The results of quantitative fluorescent PCR (QF-PCR) and karyotype of amniotic fluid cells were analyzed retrospectively in 2 398 monocyesis pregnant women who had been amniocentesis at the First Affiliated Hospital of Zhengzhou University from May 2013 to December 2019, and the results of 359 cases who had been examined by single-nucleotide polymorphism array (SNP array). Results: Cff-DNA test of 2, 398 cases indicated 987 cases of trisomy 21, 351 cases of trisomy 18, 135 cases of trisomy 13, 566 cases of sex chromosome abnormality, and 359 cases of other chromosome abnormality. Chromosome karyotype analysis detected 826 cases of trisomy 21, 213 cases of trisomy 18, 17 cases of trisomy 13, 221 cases of sex chromosome abnormality, and 26 cases of other chromosome abnormality. The detection rate were 83.69% (826/987), 60.68% (213/351), 12.59% (17/135), 39.04% (221/566) and 7.24% (26/359), respectively. QF-PCR detected 1 046 cases of trisomy and 188 cases of sex chromosomes abnormality, and the detection rate was 99.05% (1 046/1 056) and 85.07% (188/221), respectively. Compared with the abnormal number detected by chromosome karyotype analysis, 10 cases of trisomeric chimerism and 24 cases of sex chromosome were missed by QF-PCR. Among the 359 other chromosomal abnormalities detected by SNP array, 64 cases were consistent with the results of cff-DNA, and the detection rate was 17.83% (64/359), which was 10.59% higher than the karyotype result. Conclusions: Karyotype analysis is the gold standard for diagnosing chromosomal abnormalities. QF-PCR could diagnose common chromosome aneuploidy rapidly and accurately, and it could be used as an auxiliary detection technique for karyotype analysis. The incidence of sex chromosome chimerism is high, so missed diagnosis should be warned. SNP array could be given priority to verify chromosome microdeletion or microduplication detected by cff-DNA.

Self-made Salmonella Pullorum agglutination antigen development and its potential practical application

Pullorum disease caused by Salmonella Pullorum is one of the most important infectious diseases in the poultry industry worldwide, which leads to serious economic losses in many developing countries because of its high mortality rate in young chicks. The traditional slide agglutination test with low cost, fast reaction, and on-site detection has been widely used in the diagnosis of Pullorum disease. However, in practice, the test performance is with the disadvantages of false positive results and unstable detection results. In this paper, we developed self-made agglutination antigens prepared by local isolates in the poultry farm and compare the detection performance with commercial agglutination antigens (China Institute of Veterinary Drug Control) and Group D Salmonella ELISA kit (BioChek UK Ltd). The results of detecting 200 serum samples indicated that the consistency of commercial agglutination antigen detecting in 2 times was only 79.5%. Using the ELISA kit as the reference method, the commercial agglutination antigen detecting results of the Kappa test were only moderately consistent (0.58 ∼ 0.59). Meanwhile, positive and total coincidence rates of the self-made agglutination antigen test with more reliable repeat could reach 97.4 and 88%, respectively, and the result of Kappa test was highly consistent (0.75). The Receiver Operating Characteristic curve analysis clarified that the area under the receiver-operating-characteristic curve values of self-made and commercial agglutination antigen tests could reach 0.861 and 0.804, respectively. These results were coincident when detecting known positive serum from the infected chickens. It's worth mentioning that the visible positive reaction of self-made agglutination antigen test appeared faster and stronger than commercial antigen test. In conclusion, self-made Salmonella Pullorum agglutination antigen developed in this study was much better than commercial agglutination antigen and is expected to be a valuable tool in the diagnosis of the epidemiology of Salmonella Pullorum.

Computer-generated photorealistic hologram using ray-wavefront conversion based on the additive compressive light field approach

The conventional computer-generated hologram reconstructing photorealistic three-dimensional (3D) images based on ray-wavefront conversion has the disadvantage of spatio-angular resolution trade-off. In this Letter, we propose for the first time, to the best of our knowledge, a computer-generated photorealistic hologram without spatio-angular resolution trade-off based on the additive compressive light field (CLF) approach. The original light field is compressed into multiple layer images through numerical optimization based on the additive light field principle. Then, by independently calculating the wave propagation from each layer image to the hologram plane and adding them together, a CLF hologram is generated. Since the CLF information is presented through a holographic method, the advantage of high resolution in CLF is preserved while the limitation of the number of physically stacked layers (such as liquid crystal displays) is removed, leading to higher quality, larger depth of field, and higher brightness compared with a conventional CLF display. The proposed method is verified with a photorealistic optical experiment.

[PTPN11 and the deafness]

Summary PTPN11 gene encodes tyrosine phosphatase SHP-2 which locates on chromosome 12（12q24.1）, expresses in most embryonic and adult tissues, and plays pivotal roles in cell proliferation, differentiation, survival and cell death. SHP-2 apparently participates in signaling events downstream of RAS-MAPK and JAK/STAT. Diseases related to PTPN11 gene mutations include the Noonan syndrome（NS） and the NS with Multiple Lentigines（NSML）. Both NS and NSML contain the phenotypes of deafness, craniofacial anomalies, short stature, congenital heart defects, skin disorders, ophthalmologic abnormalities and cancer predisposition.

[Case report and diagnosis of Noonan syndrome with multiple lentigines with deafness as its main clinical feature]

Summary Noonan syndrome with multiple lentigines（NSML） is a disorder with syndromic hearing loss. Abnormalities of other systems in NSML have received increasing attention, but hearing loss is rarely concerned. And due to the incomplete phenotype, some patients with NSML maybe missed or maybe confused with other syndromic deafness such as Waardenburg syndrome. Our study will familiarize more otolaryngologists with Leopard syndrome. A 5-year-old boy with bilateral sensorineural hearing loss and numerous symmetrically distributed dark brown macules that had good effect of cochlear implantation was collected in this study. And his father had bilateral sensorineural hearing loss and numerous symmetrically distributed dark brown macules. Waardenburg syndrome was initially diagnosed by clinical phenotype and its molecular etiology was confirmed by gene diagnosis. Waardenburg syndrome-related deafness genes and 131 known deafness genes were not identified by second-generation sequencing. Whole-exon sequencing was performed for 4 individuals in the family and the results were confirmed by Sanger sequencing. This study confirmed the diagnosis by identifying a disease-causing mutation in the PTPN11 gene, which was a heterozygous missense mutation at p. Tyr279Cys（c. 836A>G）. The mutation co-segregated with hearing loss in the family. Our results demonstrated that hearing loss in this family was caused by heterozygous mutations in PTPN11. These cases will familiarize more otolaryngologists with NSML, and they emphasize the importance of considering NSML as a possible cause of hearing problems.

[Clinical diagnosis and surgical management of 110 cases of facial nerve schwannomas]

Objective: To elucidate the clinical behavior, causes of misdiagnosis, surgical management, and outcomes of facial nerve schwannomas (FNS). Methods: A retrospective review in Chinese People's Liberation Army General Hospital from January 1, 2002 to December 31, 2015 was carried out and evaluated 110 patients with FNS, including 50 males and 60 females, aged 16-67 years old. The appropriate surgical strategy was selected based on each patient's clinical manifestations, facial nerve function, and imaging characteristics. After surgery, patients received follow-up visits to assess their facial nerve functions, with the effect of treatment compared to the reality before surgery. The Kruskal-Wallis H test was used to distinguish between the pre- and post-operation facial nerve functions in patients who had different facial nerve functions before the operations. Results: 110 cases of FNS mainly presented with facial paralysis, hearing loss, tinnitus, otalgia, dizziness, and facial spasm. 20 of the cases were misdiagnosed as Bell's Palsy, 6 were mistaken for chronic otitis media/cholesteatoma with radical mastoidectomy, 3 were mistaken for Meniere's disease, 1 was misdiagnosed as petrous bone cholesteatoma, and 4 were mistaken for acoustic neuroma. 81.8 % (90/110) of the patients had multiple segments of the facial nerve, including the vertical segment of the facial nerve, accounting for 65.5% (72/110), followed by the labyrinthine/geniculate segment, for 61.8% (68/110), and the horizontal segment, for 55.5% (61/110). The appropriate surgical approaches were chosed based on the sizes and scopes of the tumors evaluated by imaging: transmastoid approach in 73 cases, translabyrinthe approach in 14 cases, middle cranial fossa approach in 13 cases, retrosigmoid approach in 3 cases, transmastoid-middle cranial fossa approach in 3 cases, and transmastoid-neck approach in 4 cases, with all the patients undergoing a total/subtotal resection of the tumor. Eighty-seven patients had their facial nerves reconstructed. Among them, 6 received facial nerve end-to-end anastomosis, 55 received great auricular nerve graft, and 26 were subjected to facial nerve-hypoglossal nerve anastomosis. Because of long histories, facial muscle atrophies, or other reasons, the remaining patients were not received facial nerve reconstruction. The House-Brackmann(H-B) grading scale was used to evaluate the facial nerve function pre- and post-operation. Patients with better facial nerve functions and shorter history of facial paralysis before operation would get relatively better facial nerve function. The before and after operation comparisons revealed that the recovery of the facial nerve functions in patients with H-B Ⅰ-Ⅲ was better than the improvement in patients with H-B Ⅳ-Ⅴ. The difference was statistically significant (Kruskal-Wallis H test, H=8.508, P<0.05). Conclusions: The diagnosis of patients with unknown facial paralysis, hearing loss, and tinnitus should take into account the possibility of FNS. CT and other imaging examinations of the temporal bone can avoid misdiagnosis and determine the tumor size and extent of lesions, as well as provide the basis for the choice of the surgical approach. After tumors have been completely resected, facial nerve reconstruction can be performed simultaneously, according to the defect of the nerve.

[The surgical treatment of middle ear cholesteatoma complicated with peripheral facial paralysis (with 22 cases)]

Objective:To summarize the clinical characteristics, the surgical methods and the recovery of facial nerve function outcomes in patients with the middle ear cholesteatoma complicated with peripheral facial paralysis.Method:Retrospective analysis method was used on patients treated for middle ear cholesteatoma associated with peripheral facial paralysis. Facial nerve decompression and great auricular nerve grafting were performed for restoration of facial nerve. Facial nerve function was assessed with the House-Brackmann (H-B) grade scale. Spearman test was employed for statistic analysis.Result:Surgical exploration revealed that the cholesteatoma was mainly located in epitympanic cavity, mastoid and sinus tympani, which mainly damaged the tympanic segment of facial nerve. Nineteen cases with facial nerve edema, including complete sheath (n=15) and sheath defect (n=4), were performed decompression. Among which 15 recovered to H-B Ⅰ, 3 recovered to H-B Ⅱ, 1 recovered to H-B Ⅳ. Three cases with facial nerve disrupt underwent great auricular nerve grafting, 1 recovered to H-B Ⅳ, 2 recovered to H-BⅤ. The rate of recovery to H-B Ⅰ or Ⅱ in patients underwent surgery within 2 weeks was 92.3%(12/13).Conclusion:When the middle ear cholesteatoma complicated with peripheral facial paralysis, surgery should be carried out as soon as possible. After removed the cholesteatoma completely, facial nerve decompression could acquire a better facial nerve function recovery compared to great auricular grafting.

[Petrous bone cholesteatoma: surgery approach and outcomes]

Objective: To investigate the choice of surgical approach of petrous bone cholesteatoma (PBC)and surgical outcomes. Methods: A retrospective study was performed on 90 patients diagnosed and treated for PBC from January 2000 to December 2014 by the Chinese People's Liberation Army General Hospital otolaryngologists. According to Sanna's classification, 40 out of the 90 cases were supralabyrinthine, five infralabyrinthine, four infralabyrinthine-apical, 25 massive and 16 apical. Five cases underwent transmastoid and retrolabyrinthine approach, translabyrinthine approach was performed on six patients, 19 cases underwent subtotal petrosectomy, seven cases underwent transotic approach, 41 cases underwent middle fossa approach, combined transmastoid/middle fossa approach was performed on 11 cases, translabyrinthine and sphenoid sinus approach were performed on one case. Supralabyrinthine cases mainly applied middle fossa approach (77.5%, 31/40) and combined transmastoid and middle-fossa approach(20.0%, 8/40). Combined transmastoid-retrolabyrinthine approach were applied for all the infralabyrinthine cases (100.0%, 5/5). Infralabyrinthine-apical cases mainly applied subtotal petrosectomy (75.0%, 3/4). Massive cases mainly applied subtotal petrosectomy (60.0%, 15/25), transcochlear approach (20.0%, 5/25), and translabyrinthine approach (16.0%, 4/25). Apical cases mainly applied middle fossa approach (62.5%, 10/16). Results: Ninty percent (18/20) of the patients who had preoperative grade Ⅰ facial nerve function maintained in the postoperative period. Out of 90 cases, only 11 cases received open cavity, and the rest cases received cavityobliteration. There were three cases of recurrence, four cases of cavity infection, three cases of cerebrospinal fluid leakage, and one case of epidural hematoma, who all received surgeries. Conclusions: Sanna's classification should be used to classify different kinds of PBC cases, choose the best surgical approach for different cases, and preserve or repair facial function during removal of PBC, and thus reduce recurrence and complications.

[6 cases of temporal bone carcinoid clinical analysis]

Objective: This study is aimed at reporting 6 cases of temporal bone carcinoid and analyzing clinical and prognostic features of temporal bone carcinoid.Method: Clinical data from 6 cases of temporal bone carcinoid treated from July 2008 to July 2015 at the Chinese PLA General Hospital were reviewed. Based on temporal bone lesions row subtotal temporal bone resection or temporal bone extensive excision.Result: Six patients imaging data shows a different range of temporal bone lesions. Pathological both temporal bone carcinoid. The final diagnosis is unilateral primary temporal bone carcinoid. All of them received surgical partial resection of the temporal bone in our hospital,and there were no serious complications.Follow-up of 5 cases had no recurrence,and 1 case died spread to the liver.Conclusion:The diagnosis of temporal bone carcinoid relies mainly on pathology and immunohistochemistry. Temporal bone carcinoid could be treated by surgical.

Highly sensitive fluorescence detection of metastatic lymph nodes of gastric cancer with photo-oxidation of protoporphyrin IX

BACKGROUND

The establishment of a precise and rapid method to detect metastatic lymph nodes (LNs) is essential to perform less invasive surgery with reduced gastrectomy along with reduced lymph node dissection. We herein describe a novel imaging strategy to detect 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX) fluorescence in excised LNs specifically with reduced effects of tissue autofluorescence based on photo-oxidation of PpIX. We applied the method in a clinical setting, and evaluated its feasibility.

METHODS

To reduce the unfavorable effect of autofluorescence, we focused on photo-oxidation of PpIX: Following light irradiation, PpIX changes into another substance, photo-protoporphyrin, via an oxidative process, which has a different spectral peak, at 675 nm, whereas PpIX has its spectral peak at 635 nm. Based on the unique spectral alteration, fluorescence spectral imaging before and after light irradiation and subsequent originally-developed image processing was performed. Following in vitro study, we applied this method to a total of 662 excised LNs obtained from 30 gastric cancer patients administered 5-ALA preoperatively.

RESULTS

Specific visualization of PpIX was achieved in in vitro study. The method allowed highly sensitive detection of metastatic LNs, with sensitivity of 91.9% and specificity of 90.8% in the in vivo clinical trial. Receiver operating characteristic analysis indicated high diagnostic accuracy, with the area under the curve of 0.926.

CONCLUSIONS

We established a highly sensitive and specific 5-ALA-induced fluorescence imaging method applicable in clinical settings. The novel method has a potential to become a useful tool for intraoperative rapid diagnosis of LN metastasis.

A novel role for the apoptosis inhibitor ARC in suppressing TNFα-induced regulated necrosis

TNFα signaling can promote apoptosis or a regulated form of necrosis. ARC (apoptosis repressor with CARD (caspase recruitment domain)) is an endogenous inhibitor of apoptosis that antagonizes both the extrinsic (death receptor) and intrinsic (mitochondrial/ER) apoptosis pathways. We discovered that ARC blocks not only apoptosis but also necrosis. TNFα-induced necrosis was abrogated by overexpression of wild-type ARC but not by a CARD mutant that is also defective for inhibition of apoptosis. Conversely, knockdown of ARC exacerbated TNFα-induced necrosis, an effect that was rescued by reconstitution with wild-type, but not CARD-defective, ARC. Similarly, depletion of ARC in vivo exacerbated necrosis caused by infection with vaccinia virus, which elicits severe tissue damage through this pathway, and sensitized mice to TNFα-induced systemic inflammatory response syndrome. The mechanism underlying these effects is an interaction of ARC with TNF receptor 1 that interferes with recruitment of RIP1, a critical mediator of TNFα-induced regulated necrosis. These findings extend the role of ARC from an apoptosis inhibitor to a regulator of the TNFα pathway and an inhibitor of TNFα-mediated regulated necrosis.

Detection of common deafness mutation by maternal plasma cell-free DNA

OBJECTIVES

The aim is to investigate the use of the ligase detection reaction (LDR) microarray to examine the difference of the single nucleotide between the pregnant woman and the fetus by cell-free DNA in the maternal plasma in congenital deafness.

MATERIALS AND METHODS

The proband and the couples' venous blood samples and the amniotic fluid/ chorionic villi collected from seven deafness families for prenatal diagnosis were analyzed. The cell-free DNA from maternal plasma was examined to determine if they carried the mutations of GJB2 235delC.

RESULTS

Three samples were found to carry the mutation of GJB2 235delC. It is in agreement with the sequencing results. The affected fetuses were suggested to take invasive procedure for confirmation.

CONCLUSIONS

The chip may be a potential method to screen for congenital deafness based on maternal plasma DNA.

Effects of liver diseases on drug-metabolizing enzymes: implications for drug fate alterations and nano-therapeutic openings

Metabolizing and eliminating toxic chemicals in the liver are key processes in the body's defense system. Drug-metabolizing enzymes (DMEs) play central roles in such processes. The activity and expression of several key DMEs are changed in various liver diseases and thus lead to significantly altered drug disposition. This phenomenon severely affects the pharmacotherapy of clinical medications in terms of the safety and efficacy of drug responses. This review highlights liver physiological functions, altered DMEs, and altered drug disposition in liver diseases. Moreover, the implications of changes in DMEs on the fate of clinically relevant drugs are also discussed. Pregnane X receptor and constitutive androstane receptor are two liver-enriched nuclear receptors originally defined as xenobiotic sensors that affect regulation of DMEs. Altered regulation of DMEs in liver diseases contributes to the development of powerful in vitro and in vivo tools to predict drug responses and options for improved drug delivery and development. Although a number of treatment drugs are available for liver diseases, they are limited by their low drug concentration in the target site, presence of side effects, and instability in the human body. The nanoparticle drug delivery system has recently attracted research attention because of its potential to offer solutions to current obstacles that involve the use of therapeutic drugs for liver diseases. Conclusively, this review aims to improve understanding on the regulation of DMEs in liver diseases and on corresponding implications in drug disposition, including novel therapeutic medications.

Filled Skutterudite Antimonides: Validation of the Electron-Crystal Phonon-Glass Approach to New Thermoelectric Materials

After a brief review of the transport and thermoelectric properties of filled skutterudite antimonides, we present resonant ultrasound, specific heat, and inelastic neutron scattering results that establish the existence of two low-energy vibrational modes in the filled skutterudite LaFe3CoSb12. It is likely that at least one of these modes represents the localized, incoherent vibrations of the La ion in an oversized atomic “cage.” These results support the usefulness of weakly bound, “rattling” ions for the improvement of thermoelectric performance.

Anisotropic structure of the order parameter in FeSe(0.45)Te(0.55) revealed by angle-resolved specific heat

The central issues for understanding iron (Fe)-based superconductors are the symmetry and structure of the superconducting gap. So far the experimental data and theoretical models have been highly controversial. Some experiments favor two or more constant or nearly constant gaps, others indicate strong anisotropy and yet others suggest gap zeros ('nodes'). A unique method for addressing this issue, and one of very few methods that are bulk and angle resolved, is measuring the electronic-specific heat in a rotating magnetic field. In this study, we present the first such measurement for an Fe-based high-T(c) superconductor. We observed a fourfold oscillation of the specific heat as a function of the in-plane magnetic field direction. Our results are consistent with the expectations for an extended s-wave model, with a significant gap anisotropy on the electron pockets and the gap minima along the ΓM (Fe-Fe bond) direction.

A novel DFNA5 mutation, IVS8+4 A>G, in the splice donor site of intron 8 causes late-onset non-syndromic hearing loss in a Chinese family

We report here the clinical, genetic, and molecular characteristics of a large Chinese family exhibiting non-syndromic, late-onset autosomal dominant sensorineural hearing loss. Clinical evaluation revealed variable phenotypes of hearing loss in terms of severity and age-at-onset of disease in these subjects. Genome-wide linkage analysis mapped the disease gene to the DFNA5 locus with a maximum two-point log odds score of 5.39 at [theta] = 0 for marker D7S2457. DNA sequencing of DFNA5 revealed a novel heterozygous IVS8+4 A>G substitution in the splice donor site of intron 8. Reverse transcriptase-polymerase chain reaction (RT-PCR) showed skipping of exon 8 in the mutant transcript. This mutation faithfully cosegregated with hearing loss in the family. In addition, the mutation was absent in 100 unrelated control DNA samples of Chinese origin. The IVS8+4 A>G mutation is predicted to create a shift in the reading frame and introduce a stop codon at position 372, thereby resulting in a prematurely truncated DFNA5 protein. Up to date, a total of four mutations in DFNA5 have been reported to lead to hearing impairment, all of them result in skipping of exon 8 at the mRNA level. Our findings provide further support for the hypothesis that DFNA5-associated hearing loss is caused by a very specific gain-of-function mutation.

Somatic instability of the DNA sequences encoding the polymorphic polyglutamine tract of the AIB1 gene

BACKGROUND

AIB1 contains a polymorphic polyglutamine tract (poly Q) that is encoded by a trinucleotide CAG repeat. Previously there have been conflicting results regarding the effect of the poly Q tract length on breast cancer. Since poly Q is not encoded by a perfect CAG repeat, the heterozygous polymorphic alleles need to be resolved, to understand the exact DNA sequences encoding poly Q.

METHODS

Poly Q encoding sequences of AIB1 from 107 DNA samples, including breast cancer cell lines, sporadic primary breast tumours, and blood samples from BRCA1/BRCA2 mutation carriers and the general population, were resolved by PCR/cloning followed by sequencing of each individual clone.

RESULTS

25 distinct poly Q encoding sequence patterns were found. More than two distinct sequence patterns were found in a significantly higher proportion of tumours and cell lines than that of the general population, suggesting somatic instability. A significantly higher proportion of cancer cell lines or primary breast tumours than that of the general population contained rare sequence patterns. The proportion of sporadic breast tumours having at least one allele < or =27 repeats is significantly higher than that in the blood of BRCA1/BRCA2 mutation carrier breast cancer patients or the general population.

CONCLUSION

The poly Q encoding DNA sequences are somatically unstable in tumour tissues and cell lines. A missense mutation and a very short glutamine repeat in primary tumours suggests that AIB1 activity may be modulated through poly Q, which in turn plays a role in the cotransactivation of gene expressions in breast cancers.

In-plane thermal conductivity of Nd2CuO4: evidence for magnon heat transport

We report the temperature and magnetic field dependence of the in-plane thermal conductivity (kappa(ab)) of high-quality monocrystalline Nd2CuO4. Isothermal measurements of the field dependence of kappa(ab) at low temperatures (2 K<or=T<or=5 K) show no change in kappa(ab) below a critical magnetic field H(c) (H(c) approximately 4.5 T for H parallel [100]) and H(c) approximately 2.5 T for H approximately parallel [110]). Above H(c), kappa(ab) more than doubles as H is increased to 9 T. At H(c), there is a transition from a noncollinear to a collinear arrangement of the Nd and Cu spins and a collapse of the gap, Delta, in an acoustic magnon branch at k=0. Closure of this gap appears to allow the conduction of substantial amounts of heat by acoustic magnons.

[Rat hearing loss and hearing organs mitochondrial DNA4834 deletions associated with hypercholesteremia]

OBJECTIVE

To determine whether or not the rat hypercholesteremia contributes to hearing organs mtDNA4834 deletion and involves in the development of hearing loss.

METHODS

The rat hypercholesteremia model (n = 38) was established by feeding with high cholesterol diet and the control group (n = 22) with common diet for 6 months. The rats were tested for auditory sensitivity using auditory brainstem response (ABR). Twenty-one left cochleae and 27 left cochlear nuclei from experimental group and 10 left cochleae and 13 left cochlear nuclei from control group were harvested. The total DNA of them was extracted. mtDNA was amplified by nest PCR to examine the presence of mtDNA4834 deletion.

RESULTS

Our result showed: (1) There is a significant increase in serum cholesterol level and ABR threshold in the experimental group. (2) The mitochondrially-encoded tRNA and ND1 segments were amplified from all samples, as well as mtDNA4834 deletions. (3) The incidence of mtDNA4834 deletions in hearing organs of hypercholesteremia rats was significantly higher than that of the control group (P < 0.05).

CONCLUSION

Extended hypercholesteremia can induce hearing loss, and mtDNA4834 deletion in hearing organs may be one of the pathogenic mechanisms.

Novel SNP at the common primer site of exon IIIa of FGFR2 gene causes error in molecular diagnosis of craniosynostosis syndrome

Most mutations in Crouzon, Pfeiffer, and Apert syndromes are in the extracellular, third immunoglobulin-like domain and adjacent linker regions (exons IIIa and IIIc) of the fibroblast growth factor receptor 2 (FGFR2) gene. Using the published primers for PCR, a patient with Crouzon syndrome was found to be homozygous for a mutation that results in a Q289P amino acid substitution in FGFR2. Two additional patients; one with Apert syndrome and P253R mutation, the other with Pfeiffer syndrome and S267P mutation, also appeared to be homozygous. Using a new primer located 146 bp 5' of exon IIIa for PCR followed by sequencing revealed an A to G polymorphism at -62 [corrected] position of exon IIIa. All three patients were heterozygous for both the mutation and the polymorphism. These results indicate that the polymorphism and the mutation are not on the same chromosome. The single nucleotide polymorphism is located at the second to the last base of the 3' end of the published primer. This primer mismatch caused the failure of amplification of the normal chromosome and thus, the apparent homozygosity. The frequency of this novel polymorphism was determined to be 0.03 by studying 326 chromosomes from the general population. We propose that a new primer should be used for mutational analysis of exon IIIa of FGFR2 to avoid misdiagnosis caused by primer mismatch.

Severe lactic acidosis caused by a novel frame-shift mutation in mitochondrial-encoded cytochrome c oxidase subunit II

We report the first frame-shift truncation mutation in a mitochondrial DNA (mtDNA)-encoded subunit II of cytochrome c oxidase (COXII). The mutation was identified by temporal temperature gradient gel electrophoresis (TTGE) followed by direct DNA sequencing in an infant who died at 12 days of age following a course of apnea, bradycardia, and severe lactic acidosis. The patient had a twin brother who died at two days of age of similar course. The mutation, 8042delAT, produced a truncated protein that was 72 amino acids shorter than the wild type protein. The mutant protein, missing one third of the amino acid residues at the C-terminal essential for hydrophilic interaction with cytochrome c, ligand binding to CuA and Mg, and the formation of proton and water channels, apparently has devastating effects on mitochondrial respiratory function.

Jahn-Teller phonon anomaly and dynamic phase fluctuations in La0.7Ca0.3MnO3

Inelastic neutron scattering was used to study the temperature (T) dependence of the lattice excitations in La 0.7Ca 0.3MnO (3). An optical Jahn-Teller phonon exhibits continuous but anomalous damping with increasing temperature in the ferromagnetic-metallic phase and collapses above the Curie temperature T(C) (240 K). We attribute this anomaly to the growing dynamic phase segregation as T-->T(C), thus providing evidence of local fluctuations associated with the short-range polaron or charge/orbital ordering in the ferromagnetic-metallic state.

Molecular genetics of glycogen-storage disease type 1a in Chinese patients of Taiwan

The mutation spectrum of the glucose 6-phosphatase (G6Pase) gene in Chinese patients with type 1a glycogen-storage disease of Taiwan was studied by PCR/RFLP, temporal temperature gradient gel electrophoresis, and direct DNA sequencing methods. In addition to the two most prevalent mutations, 727G --> T (44.4%) and R83H (36.1%), that were detected by RFLP analysis, five other mutations, 341delG, 933insAA, Q104X, I341N, and H119L were identified. The frameshift mutations (341delG and 933insAA) and the nonsense mutation (Q104X) that produce truncated proteins are predicted to be disease-causing. The missense mutation, I341N, occurring in the last transmembrane domain of the ER-bound enzyme, retains a small amount of residual activity of approximately 10%. Except for R83H, the mutations have been described only in Asians. H119L, however, is of particular interest because of the essential role of the catalytic histidine of phosphohydrolase. This amino acid is believed to be involved in the formation of the phosphoryl-enzyme intermediate during catalysis. The patient who was compound heterozygous for 727G --> T and H119L mutations had essentially no G6Pase activity in her liver biopsy. This observation is consistent with the importance of H119L in catalysis.

A family of depsi-peptide fungal metabolites, as selective and competitive human tachykinin receptor (NK2) antagonists: fermentation, isolation, physico-chemical properties, and biological activity

Four tachykinin (NK2) receptor inhibitors, SCH 378161 (1), SCH 217048 (2), SCH 378199 (3), and SCH 378167 (4) were isolated from the fermentation broth of a taxonomically unidentified fungus. These compounds were separated from the fermentation broth by ethyl acetate extraction. Purification and separation of the individual compounds were achieved by NK2 assay-guided fractionation using gel filtration, reverse phase chromatography and HPLC. They were identified to be a family of depsipeptides by spectroscopic and degradation studies. Compounds 1 and 3 contain proline and differ as an amide and acid whereas 2 and 4 contain pipecolic acid and differ in being an amide and acid. All of these compounds contain an identical hydroxy acid. They are selective NK2 inhibitors with Ki values ranging from 27-982 nM and demonstrate no activity at 10 microM in the NK1 and NK3 assays. In addition, compounds 1 and 2 inhibited NKA-induced increases in the concentration of intracellular Ca2+, [Ca2+]i, in a CHO cell expressing the human NK2 receptor; this inhibition was competitive in nature with pA2 values of 7.2 and 7.5, respectively. These data demonstrate that these natural products are selective and competitive receptor antagonists of the human NK2 receptor.

[Cochlear hypoxia and mtDNA deletion: possible correlated factors to cause presbycusis]

OBJECTIVE

To find the relationship among the most common mitochondrial DNA (mtDNA) 4,977 bp deletion, aging and deterioration of acoustic organ and determine the pathologic factors causing mtDNA 4,977 bp deletion.

METHODS

Sixty-seven temporal bones from a presbycusis group, an age-matched control group and a young control group were evaluated. The nested PCR and tri-nested PCR techniques were used to test the presence of mtDNA 4,977 deletion. Computer imaging processing was used to measure the parameters of blood vessels in the internal acoustic meatus.

RESULTS

Temporal bones from patients aged 50 years or over frequently showed mtDNA 4,977 deletions. In presbycusis patients, 17 of 34 ears showed mtDNA 4,977 deletion, whereas only 4 of 19 ears from the age-matched control group showed mtDNA 4,977 deletions. mtDNA 4,977 deletions were often seen in the spiral ganglion and vestibular ganglion neurons. In the presbycusis group, the lumen of the vasa nervosum of the internal auditory meatus showed a more severe reduction in patients with mtDNA 4,977 deletion than in those without deletion.

CONCLUSION

There is a strong correlation between presbycusis and mtDNA 4,977 deletion. We hypothesize that cochlear hypoxia may cause mtDNA 4,977 deletions and other mtDNA mutants which in turn may cause a reduction of mitochondrial oxidative phosphorylation and decreased auditory nerve function. The symptoms of neural presbycusis, however, may appear only after mtDNA metabolism decreases below a specific threshold.