All-optical closed-loop voltage clamp for precise control of muscles and neurons in live animals.

Excitable cells can be stimulated or inhibited by optogenetics. Since optogenetic actuation regimes are often static, neurons and circuits can quickly adapt, allowing perturbation, but not true control. Hence, we established an optogenetic voltage-clamp (OVC). The voltage-indicator QuasAr2 provides information for fast, closed-loop optical feedback to the bidirectional optogenetic actuator BiPOLES. Voltage-dependent fluorescence is held within tight margins, thus clamping the cell to distinct potentials. We established the OVC in muscles and neurons of Caenorhabditis elegans, and transferred it to rat hippocampal neurons in slice culture. Fluorescence signals were calibrated to electrically measured potentials, and wavelengths to currents, enabling to determine optical I/V-relationships. The OVC reports on homeostatically altered cellular physiology in mutants and on Ca2+-channel properties, and can dynamically clamp spiking in C. elegans. Combining non-invasive imaging with control capabilities of electrophysiology, the OVC facilitates high-throughput, contact-less electrophysiology in individual cells and paves the way for true optogenetic control in behaving animals.

QT interval evaluation associated with the use of hydroxychloroquine with combined use of azithromycin among hospitalised children positive for coronavirus disease 2019.

INTRODUCTION AND AIM: Hydroxychloroquine alone or in combination with azithromycin has been increasingly used for patients with coronavirus disease 2019, in both children and adults. Drugs are generally well tolerated in clinical practice; however, both can cause corrected QT prolongation. We aimed to report our experience of QT interval evaluation associated with the use of hydroxychloroquine with concurrent azithromycin among children testing positive for coronavirus disease 2019. METHODS: Our single-centre; retrospective, study evaluated children with coronavirus disease 2019 disease admitted to the Pediatric Department at Sancaktepe Training and Research Hospital Istanbul, Turkey from 10 March, 2020 to 10 April, 2020. The data including demographics, clinical symptoms, co-morbid diseases, laboratory, radiological findings as well as electrocardiographs of the patients were obtained from our records. Electrocardiograms were evaluated before, one day after and at the termination of the treatment. RESULTS: 21 patients aged 9 to 18 years were evaluated. The median age was 170 months (range 112-214), 51.1% of them were girls and 48.9% were boys. Their laboratory results did not reveal any abnormalities. None of them needed intensive care. We did not detect QT prolongation during or at the termination of the treatment. CONCLUSION: We did not detect QT prolongation during or at the termination of the treatment in our patients due to the fact that they were not severely affected by the disease. Patients were treated in our inpatient clinic and none of them required intensive care. Laboratory results were also insignificant. Furthermore, they did not need other medications.