Presynaptic SNAP-25 regulates retinal waves and retinogeniculate projection via phosphorylation.

Patterned spontaneous activity periodically displays in developing retinas termed retinal waves, essential for visual circuit refinement. In neonatal rodents, retinal waves initiate in starburst amacrine cells (SACs), propagating across retinal ganglion cells (RGCs), further through visual centers. Although these waves are shown temporally synchronized with transiently high PKA activity, the downstream PKA target important for regulating the transmission from SACs remains unidentified. A t-SNARE, synaptosome-associated protein of 25 kDa (SNAP-25/SN25), serves as a PKA substrate, implying a potential role of SN25 in regulating retinal development. Here, we examined whether SN25 in SACs could regulate wave properties and retinogeniculate projection during development. In developing SACs, overexpression of wild-type SN25b, but not the PKA-phosphodeficient mutant (SN25b-T138A), decreased the frequency and spatial correlation of wave-associated calcium transients. Overexpressing SN25b, but not SN25b-T138A, in SACs dampened spontaneous, wave-associated, postsynaptic currents in RGCs and decreased the SAC release upon augmenting the cAMP-PKA signaling. These results suggest that SN25b overexpression may inhibit the strength of transmission from SACs via PKA-mediated phosphorylation at T138. Moreover, knockdown of endogenous SN25b increased the frequency of wave-associated calcium transients, supporting the role of SN25 in restraining wave periodicity. Finally, the eye-specific segregation of retinogeniculate projection was impaired by in vivo overexpression of SN25b, but not SN25b-T138A, in SACs. These results suggest that SN25 in developing SACs dampens the spatiotemporal properties of retinal waves and limits visual circuit refinement by phosphorylation at T138. Therefore, SN25 in SACs plays a profound role in regulating visual circuit refinement.

Development and validation of an analytical procedure for quantitation of surfactants in dishwashing detergents using ultra-performance liquid chromatography-mass spectrometry.

The detection of surfactants in dishwashing detergents is challenging because the detergents tend to create a lot of foam. The aim of this study was therefore to develop a simple and robust procedure for simultaneous identification and quantification of multiple surfactants in dishwashingdetergents using standard addition method and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). The results contain the method validation for 11 surfactants (linear alkylbenzene sulfonates, PPG-9-ethylhexeth-5, sodium lauryl polyoxyethylene ether sulfate, alkyl polyglucoside, sodium C14-16 olefin sulfonate, cocamide diethanolamine, cocamide monoethanolamine, lauryldimethylamine oxide, cocamidopropyl betaine, nonylphenol, and nonylphenol ethoxylate). The correlation coefficients of the linear calibration curves were larger than 0.98. The limits of detection and quantification were in the ranges of 0.43-8.0 µg/mL and 1.42-26.4 µg/mL, respectively. The precision ranged from 1.72% to 11.70%. The recoveries were within the range of 84-115%. The validation criteria were fulfilled for the 11 tested surfactants. The analytical procedure was applied to the analysis of 20 dishwashing detergent products collected from markets. The surfactants labeled on 13 out of the 20 products were consistent with the test results. Two surfactants, nonylphenol and nonylphenol ethoxylate, are relatively toxic to aquatic plants, fish, and aquatic invertebrates. These two surfactants were not detected among the 20 dishwashing detergent products, indicating that they were likely not added to the dishwashing detergent products. The developed UPLC-MS-based analytical procedure can be effectively applied to surfactant identification and quantification in dishwashing detergent products.