Mutagenic Effect of Proton Beams Characterized by Phenotypic Analysis and Whole Genome Sequencing in Arabidopsis.

Protons may have contributed to the evolution of plants as a major component of cosmic-rays and also have been used for mutagenesis in plants. Although the mutagenic effect of protons has been well-characterized in animals, no comprehensive phenotypic and genomic analyses has been reported in plants. Here, we investigated the phenotypes and whole genome sequences of Arabidopsis M2 lines derived by irradiation with proton beams and gamma-rays, to determine unique characteristics of proton beams in mutagenesis. We found that mutation frequency was dependent on the irradiation doses of both proton beams and gamma-rays. On the basis of the relationship between survival and mutation rates, we hypothesized that there may be a mutation rate threshold for survived individuals after irradiation. There were no significant differences between the total mutation rates in groups derived using proton beam or gamma-ray irradiation at doses that had similar impacts on survival rate. However, proton beam irradiation resulted in a broader mutant phenotype spectrum than gamma-ray irradiation, and proton beams generated more DNA structural variations (SVs) than gamma-rays. The most frequent SV was inversion. Most of the inversion junctions contained sequences with microhomology and were associated with the deletion of only a few nucleotides, which implies that preferential use of microhomology in non-homologous end joining was likely to be responsible for the SVs. These results show that protons, as particles with low linear energy transfer (LET), have unique characteristics in mutagenesis that partially overlap with those of low-LET gamma-rays and high-LET heavy ions in different respects.

Influence of load and carrying method on gait, specifically pelvic movement.

[Purpose] The purpose of this study was to examine how carrying methods and load affects pelvic movement while walking. [Subjects and Methods] Sixteen healthy subjects (age 20.68 ± 1.95 years, height 167.56 ± 8.46 cm, weight 60.25 ± 9.37 kg) volunteered. The items carried included a hand bag, shoulder bag, cross bag, and a back pack. The load weights were 0%, 5%, 10% and 15% of body weight. G-Walk was used to record and analyze pelvic movement while the participants walked with different loads. [Results] In the case of hand bags and shoulder bags, pelvic tilt increased along with weight. In particular, when compared with the 0%, 5% and 10% load conditions, the 15% load of a hand bag induced a significant increase. Pelvic rotation showed a tendency to decrease as the weight increased. [Conclusion] Lateral pelvic tilt is thought to increase when the weight exceeds 15% of body weight, thereby resulting in decreased efficiency of gait. The pelvic rotation is thought to decrease as the weight increases, causing restricted upper limb movements.

Activation of back and lower limb muscles during squat exercises with different trunk flexion.

[Purpose] The purpose of this study was to investigate the activation of back and lower limb muscles in subjects who were performing a squat exercise at different angles of trunk flexion. [Subjects and Methods] Twenty healthy subjects (age 21.1± 1.8 years, height 168.7 ± 8.2 cm, weight 66.1 ± 12.3 kg) volunteered. The activation of the erector spinae muscle, rectus femoris muscle, gluteus maximus muscle and biceps femoris muscle was observed while the subjects performed squat exercises with a trunk flexion of 0°, 15°, and 30°. [Results] The erector spinae muscle, gluteus maximus muscle, and biceps femoris muscle were activated more during the squat exercise with the trunk flexion at 30° than the exercise with the trunk flexion at 0°. The rectus femoris muscle showed a tendency to decrease as the truck flexion increased. [Conclusion] Squat exercise be executed while maintaining an erect trunk posture if one wishes to strengthen the quadriceps muscle while reducing the load on the lower back.

The effect of simulating a leg-length discrepancy on pelvic position and spinal posture.

[Purpose] The purpose of this study was to examine how a leg-length discrepancy contributes to the pelvic position and spinal posture. [Subjects and Methods] A total of 20 subjects (10 males, 10 females) were examined during different artificially created leg-length inequalities (0-4 cm) using a platform. The pelvic tilt and torsion and the sagittal deviation of the spine were measured using the rasterstereographic device formetric 4D. [Results] Changes in platform height led to an increase in pelvic tilt and torsion, while no changes in the spinal posture were found with the different simulated leg-length inequalities. [Conclusion] Our study showed that a leg-length discrepancy may cause pelvic deviation and torsion, but may not lead to kyphosis and lordosis. Therefore, we consider that an artificially created leg-length discrepancy has a greater effect on pelvic position than spine position.

How different modes of child delivery influence abdominal muscle activities in the active straight leg raise.

[Purpose] The purpose of this study was to examine the activities of the abdominal muscles of women who had experienced vaginal delivery in comparison with those who had experienced Cesarean childbirth. [Subjects and Methods] A total of 14 subjects (7 vaginal delivery, 7 Cesarean section) performed an active straight leg raise to 20 cm above the ground, and we measured the activities of the internal oblique abdominal muscle, the external oblique abdominal muscle, and the rectus abdominal muscle on both sides using electromyography. The effort required to raise the leg was scored on a Likert scale. Then, the subjects conducted maximum isometric contraction for hip joint flexion with the leg raised at 20 cm, and maximum torque and abdominal muscle activities were measured using electromyography. [Results] During the active straight leg raise, abdominal muscle activities were higher in the Cesarean section subjects. The Likert scale did not show a significant difference. The activities of the abdominal muscles and the maximum torque of the hip joint flexion at maximum isometric contraction were higher in the vaginal delivery subjects. [Conclusion] The abdominal muscles of Cesarean section subjects showed greater recruitment for maintaining pelvic stability during the active straight leg raising, but were relatively weaker when powerful force was required. Therefore, we consider that more abdominal muscle training is necessary for maintaining pelvic stability of Cesarean section subjects.

How different knee flexion angles influence the hip extensor in the prone position.

[Purpose] The present study examined the effects of knee flexion angle on hip extensor muscle activity. [Subjects and Methods] Twenty healthy subjects maintained knee flexion angles of 0°, 30°, 60°, 90° and 110° in the prone position and performed maximal voluntary contraction in hip extension. Maximum torque in hip extension at the different angles was measured, and surface electromyogram activities of the gluteus maximus (GM), biceps femoris (BF) and semitendinosus (ST) were recorded and normalized by the maximum voluntary isometric contraction (MVIC). [Results] The maximum torque of the hip extensor showed significant decreases between 0°and 60°, 90° and 110° of knee flexion. The muscle activity of BF was significantly high at 0°, and GM showed a significantly higher activity than both BF and ST at 60°, 90°and 110° of knee flexion. [Conclusion] The maximum torque in hip extension and muscle activities of BF and ST were significantly high at 0° but they decreased at knee flexion angles of more than 60°. Therefore, we consider that more than 60° of knee joint flexion is required to increase GM activity, and to reduce the muscle activities of BF and ST.