SummaryThe mechanism of the genetic control of wing form determination of the small brown planthopper Laodelphax striatellus was analyzed by selection and crossing experiments. The selection experiment for brachypterous and macropterous forms for 13 generations showed that the wing form is under some genetic control. The crossing experiment showed that the wing form polymorphism was not a simple Mendelian character but was under polygenic control. The data from the crossing experiment were applied to the liability method for the quantitative genetics by Falconer (1981). The analysis suggested that wing form determination was a threshold character under polygenic control, and the estimated minimum number of loci concerned was 2.07. The realized heritability estimated from the data of selection experiment was 0.36 for macroptery. On the other hand, the heritability in broad sense estimated on the basis of the variance of F1 and F2 in crossing experiment was 0.81.

Recent advances in wearable devices have enabled the evaluation of awake bruxism [14][15][16]; electromyographic recordings can be used to diagnose awake bruxism during wakefulness [10]. Although previous studies have evaluated the association between sleep bruxism and tooth wear using a portable electromyographic measurement system, the relationship between them remains unclear [8]. Additionally, no study has been conducted on the association between awake bruxism and tooth wear. This study aimed to assess masseter electromyographic activity during wakefulness and sleep in individuals with moderate or severe tooth wear compared to an age-and sex-matched control group with no or mild tooth wear. We hypothesized that there was no significant difference in masseter electromyographic activity during wakefulness and sleep between the two groups.

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Background: Masticatory movement occurs complicatedly and bilaterally. Although the tongue plays an important role in mastication, bilateral tongue function during mastication has not been clarified yet. Objective: To investigate the effect of food properties on posterior tongue activity and coordination of muscles bilaterally by electromyography (EMG). Methods: Twenty healthy adults (10 males and 10 females; mean age 28 years; range: 22-33 years) participated in this study. Three test foods, gummy jelly (hard food), sponge cake (soft food requiring crushing), and mashed potatoes (soft food not requiring crushing), were used. Bilateral masseter N-EMG (surface electromyography for measuring the muscle activity of posterior tongue) and submental EMG were carried out while the participants chewed three test foods. The participants were instructed to masticate three test foods only on the right side and only on the left side unilaterally. Results: In the case of gummy jelly, N-EMG activity on the mastication side was significantly larger than that on the non-mastication side (P < .01). Regarding temporal relationship between the masseter and N-EMG activity, in the case of gummy jelly, the percentage of cases where the N-EMG peak was observed during masseter muscle EMG bursts was significantly higher than those for sponge cake and mashed potatoes (P < .01). Conclusion: N-EMG activity on the mastication side was significantly larger than that on the non-mastication side in the mastication of hard foods. Tongue showed activity pattern changes and coordinated with the masseter muscle depending on food texture.

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