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This study investigated the relationship between 2-year-old children's exposure to TV and language delay. The subjects of this study were 1,778 toddlers (906 males and 872 females) who participated in the Panel Study on Korean Children conducted in 2010. The linguistic ability of the toddlers was measured with the K-ASQ (Korean-Ages and Stages Questionnaire). The relationship between the amount of young children's exposure to TV and language delay was analyzed with Poisson regression. The average daily TV watching time of 2-year-old Korean toddlers in this study was 1.21 hours. After all confounding variables were adjusted, toddlers with over 2 hours and less than 3 hours of TV watching time had 2.7 times more risk (RR = 2.74, 95% CI: 1.13-6.65) of language delay than those with less than 1 hour of TV watching time. Those with more than 3 hours of TV watching time had approximately 3 times (RR = 3.03, 95% CI: 1.12-8.21) more risk (p<0.05). In addition, the risk of language delay increased proportionately with the increase in toddlers' TV watching time (p = 0.004). Two-year-old Korean toddlers' average daily TV watching time of more than 2 hours was related with language delay.

Gentamicin-induced ototoxicity leads to irreversible sensorineural hearing loss due to structural and functional damage to inner ear hair cells. In this study, we identified (-)-butaclamol as a potent protective agent against gentamicin-induced cytotoxicity through high-content screening (HCS) of a natural compound library. (-)-Butaclamol significantly enhanced cell viability in both HEI-OC1 cells and zebrafish neuromasts, demonstrating robust protection against gentamicin toxicity. Mechanistically, (-)-butaclamol inhibited intrinsic apoptosis, as evidenced by reduced TUNEL-positive cell counts and the downregulation of BAX and caspase-3, alongside the upregulation of BCL-2. Moreover, (-)-butaclamol activated key survival signaling pathways, including AKT/mTOR and ERK, while suppressing the inflammatory regulator NF-κB. Additional analyses revealed that (-)-butaclamol effectively mitigated oxidative stress and restored autophagic activity, as confirmed by CellROX and LysoTracker assays. Notably, TMRE staining showed that (-)-butaclamol preserved mitochondrial membrane potential in zebrafish hair cells, indicating mitochondrial protection. Collectively, these findings suggest that (-)-butaclamol exerts comprehensive cytoprotective effects against gentamicin-induced ototoxicity by modulating apoptosis, enhancing survival signaling, and restoring mitochondrial and cellular homeostasis. These results highlight the therapeutic potential of (-)-butaclamol and provide a foundation for future studies aimed at its clinical application.

While cisplatin is an effective anti-tumor treatment, it induces ototoxicity through mechanisms involving DNA damage, oxidative stress, and programmed cell death. Rho-associated coiled-coil-containing protein kinase (ROCK) is essential for numerous cellular processes, including apoptosis regulation. Studies have suggested that ROCK inhibitors could prevent apoptosis and promote regeneration. We aimed to investigate the protective effects of the ROCK inhibitor fasudil against cisplatin-induced ototoxicity in a zebrafish model. The zebrafish larvae were exposed to 1 mM cisplatin alone or 1 mM cisplatin co-administered with varying concentrations of fasudil for 4 h. The surviving hair cell counts, apoptosis, reactive oxygen species (ROS) levels, mitochondrial membrane potential (ΔΨm), caspase 3 activity, and autophagy activation were assessed. Rheotaxis behavior was also examined. Cisplatin reduced hair cell counts; increased apoptosis, ROS production, and ΔΨm loss; and activated caspase 3 and autophagy. Fasudil (100 and 500 µM) mitigated cisplatin-induced hair cell loss, reduced apoptosis, and inhibited caspase 3 and autophagy activation. Rheotaxis in zebrafish was preserved by the co-administration of fasudil with cisplatin. Cisplatin induces hair cell apoptosis in zebrafish, whereas fasudil is a promising protective agent against cisplatin-induced ototoxicity.

Our study investigated the embryo-ototoxic effects of deodorant2 (DA2) on zebrafish embryos, which serve as valuable model organisms due to genetic and physiological similarities to humans. We focused on understanding DA2’s impact on zebrafish hair cells, which are vital for sensory perception and balance regulation. DA2, provided by the Ministry of Environment, Republic of Korea, was used at 460 μg/mL in dimethyl sulfoxide (DMSO), with a 0.43% DMSO solvent control group. Three experiments, each using 10 zebrafish specimens from each group, showed an initial 13% hair cell count reduction in the DA2-exposed group. Subsequent experiments demonstrated reductions of 37% and 22%, each with one mortality case. Statistical analysis revealed a significant 24% hair cell count reduction in the DA2-exposed group. We also assessed DA2’s impact on zebrafish behavior. Although not statistically significant, differences in distances traveled (0.33–0.39, 95% confidence interval: −0.46–1.1, p = 0.2033) and latencies (−0.016–0.018, 95% confidence interval: −0.052–0.021, p = 0.1917) hinted at negative effects. These results highlight DA2’s ototoxic properties affecting zebrafish auditory systems and behavior. Further investigation into DA2’s effects on aquatic organisms and potential mitigation strategies are essential. These findings contribute to understanding DA2’s safety profile, benefiting aquatic ecosystems and human health assessments.

One-sided vestibular disorders are common in clinical practice; however, their models have not been fully established. We investigated the effect of unilateral or bilateral deficits in the vestibular organs on the vestibulo-ocular reflex (VOR) and optokinetic reflex (OKR) of zebrafish using in-house equipment. For physical dislodgement of the otoliths in the utricles of zebrafish larvae, one or both utricles were separated from the surrounding tissue using glass capillaries. The video data from VOR and OKR tests with the larvae was collected and processed using digital signal processing techniques such as fast Fourier transform and low-pass filters. The results showed that unilateral and bilateral damage to the vestibular system significantly reduced VOR and OKR. In contrast, no significant difference was observed between unilateral and bilateral damage. This study confirmed that VOR and OKR were significantly reduced in zebrafish with unilateral and bilateral vestibular damage. Follow-up studies on unilateral vestibular disorders can be conducted using this tool.

This study aimed to devise a method for prioritizing hazardous chemicals for further regulatory action. To accomplish this objective, we chose appropriate indicators and algorithms. Nine indicators from the Globally Harmonized System of Classification and Labeling of Chemicals were used to identify categories to which the authors assigned numerical scores. Exposure indicators included handling volume, distribution, and exposure level. To test the method devised by this study, sixty-two harmful substances controlled by the Occupational Safety and Health Act in Korea, including acrylamide, acrylonitrile, and styrene were ranked using this proposed method. The correlation coefficients between total score and each indicator ranged from 0.160 to 0.641, and those between total score and hazard indicators ranged from 0.603 to 0.641. The latter were higher than the correlation coefficients between total score and exposure indicators, which ranged from 0.160 to 0.421. Correlations between individual indicators were low (−0.240 to 0.376), except for those between handling volume and distribution (0.613), suggesting that each indicator was not strongly correlated. The low correlations between each indicator mean that the indicators and independent and were well chosen for prioritizing harmful chemicals. This method proposed by this study can improve the cost efficiency of chemical management as utilized in occupational regulatory systems.