Figure 3.

Muscle function is impaired in ryanodine-treated and Ryr¹⁶ larvae. (A) The average BWC/min was determined for newly hatched larvae of the specified genotype. The wild type, Itp-r¹, Ryr^k04913/CyO-GFP^arm, and Ryr¹⁶/CyO-GFP^arm larvae performed identically in this assay. Ryr^k04913 larvae had a slight, reproducible reduction, Ryr¹⁶ a ≈50% reduction, and Ryr¹⁶/Df(2R)Np3 hemizygotes a 90% decrease in BWC/min. The BWC/min for each genotype was measured at least three times on separate collections of larvae (n = 30), and the error is the SEM. (B) Yeast paste freshly doped with 0.01–100 μM ryanodine was fed to newly hatched Ryr¹⁶/CyO-GFP^arm, and the effect on BWC rates was determined after 30 min. Concentrations of ryanodine 1 μM or less and the ethanol control (not shown) had no significant effect on BWC rates, and concentrations ≥100 μM completely inhibited BWC. For each concentration of ryanodine, the BWC measurement was performed on at least two separate larval samples (n = 30), and the error is the SEM. (C) Larvae scored positive for ingestion if they had a concentrated level of dye in the first section of the midgut. Representative curves are shown for Ryr¹⁶/CyO-GFP^arm (○) and Itp-r¹ (□). Ryr^k04913 larvae (◊) showed only a slight lag in reaching 100% positive compared with controls, but the delay was reproducible in multiple trials. In contrast, the percentage of positive Ryr¹⁶ larvae (▵) typically ranged from 40% to 60% at the end of a 6-h time course. (D) To assay excretion, larvae positive for ingestion after feeding blue yeast for 4 h were transferred to unadulterated yeast paste and scored for the complete loss of dye. Ryr¹⁶/CyO-GFP^arm (○), Itp-r¹ (□), and wild-type larvae (not shown) had nearly identical excretion time courses. The rate of excretion was significantly decreased in Ryr¹⁶ larvae (▵). For C and D, each larval genotype was assayed in at least three independent trials (n ≥ 30).