Morphological and physiological characteristics of the two major motor axons supplying the commonly studied ventral longitudinal muscle fibers (6 and 7) of third-instar Drosophila melanogaster larvae were investigated. The innervating terminals of the two motor axons differ in the size of their synapse-bearing varicosities. The terminal with the larger varicosities also fluoresces more brightly when stained with the vital fluorescent dye 4-(4-diethylaminostyryl)-N-methylpyridinium iodide (4-Di-2-Asp) and occupies a larger total contact area on the muscle fiber. Through selective simultaneous recording of synaptic currents from identified boutons in living preparations during elicitation of synaptic potentials, it was shown that the axon with the smaller varicosities generates a large excitatory junction potential (EJP) in muscle 6 and that the axon with the larger varicosities generates a smaller EJP. Short-term facilitation is more pronounced for the smaller EJP. In preparations treated with 4-Di-2-Asp, the fluorescence of smaller varicosities increases with stimulation that elicits the large EJPs, indicating an activity-dependent entry of calcium that enhances mitochondrial fluorescence. The differences in morphology and physiology of the two axons are similar to, though less pronounced than, those observed in "phasic" and "tonic" motor axons of crustaceans.

IMPORTANCEPublic health measures to reduce the spread of COVID-19 have heightened distress among children and adolescents and contributed to a shift in delivery of mental health care services.OBJECTIVES To measure and compare physician-based outpatient mental health care utilization before and during the COVID-19 pandemic and quantify the extent of uptake of virtual care delivery. DESIGN, SETTING, AND PARTICIPANTSPopulation-based repeated cross-sectional study using linked health and administrative databases in Ontario, Canada. All individuals aged 3 to 17

Anecdotal reports suggest a significant increase in acute presentations of eating disorders among children and adolescents. Our objective was to compare the rates of emergency department visits and hospitalizations for pediatric eating disorders before and during the first 10 months of the COVID-19 pandemic. Methods: Using linked health administrative databases, we conducted a population-based repeated cross-sectional study of emergency department visits and hospitalizations for eating disorders among all children and adolescents aged 3e17 years, residing in Ontario, Canada. We defined the pre