Increased Expression of MuRF1 Is Associated with Radiation-induced Laryngeal Muscle Atrophy.

BACKGROUND: Laryngeal muscles play an important role in breathing, sound production and trachea protection against food. Laryngeal dysfunctions during radiotherapy for head and neck cancers are common. In the present study, we aimed to investigate the early effect of radiation on the laryngeal muscles in vivo and possible mechanisms involved in this process. MATERIALS AND METHODS: Eight-week-old female C57bl/ mice received neck irradiation with a single dose of 25 Gy and bilateral thyroarytenoid (TA) muscles of mice were collected at day 3, 7 and 10 post-irradiation for evaluating muscle size, myosins, myosin heavy chain (MyHC) composition and MuRF1 protein levels. RESULTS: A significant reduction in the size of muscle fibers and myosins in the TA muscles were observed at days 3, 7, 10 after radiation (p<0.05). The loss of IIB myosin was more severe than that of IIA/X myosins at day 7 post-irradiation (75% vs. 64%). MuRF1 protein level was markedly increased at day 7 and 10 after radiation (p<0.05). CONCLUSION: Radiation induced an acute muscle fiber atrophy and myosin loss in the intrinsic laryngeal muscles. MuRF1 may play an important role in the radiation-induced protein degradation in the laryngeal muscles and warrants further investigation.

Protective effect of laser phototherapy on acetylcholine receptors and creatine kinase activity in denervated muscle.

OBJECTIVE: This study was designed to assess the status of skeletal muscles after laser treatment during long-term denervation processes, by investigating changes in the level of acetylcholine receptors (AChR) and creatine kinase (CK) activity in the denervated gastrocnemius muscle of the rat. BACKGROUND DATA: Progressive muscle atrophy is common in patients with severe peripheral nerve injury. Denervated muscles can account for significant differences in the extent of AChR and CK activity during the denervation period. MATERIAL AND METHODS: The study was conducted on 96 rats: 48 that received laser treatment and 48 untreated controls. The gastrocnemius muscle was denervated by removing a 10 mm segment of the sciatic nerve. Low power laser irradiation was delivered transcutaneously to the right gastrocnemius muscle (HeNe continuous wave [CW] laser, 632.8 nm, 35 mW, 30 min) for 14 consecutive days. Under general anesthesia, the rats were euthanized at seven time points: day 7 (n=10), day 14 (n=10), day 21 (n=10), day 30 (n=5), day 60 (n=4), day 120 (n=5), and day 210 (n=4), with and without laser treatment, respectively. AChR was quantified by the (125)I-α-bungarotoxin. CK activity was measured by a specific spectrophotometric method. RESULTS: Laser treatment had a significant therapeutic effect on the denervated muscle during the first 21 days for AChR and the first 30 days for CK activity. CONCLUSIONS: In the early stages of muscle atrophy, laser phototherapy may preserve the denervated muscle by maintaining CK activity and the amount of AChR.

Low-level laser irradiation promotes the recovery of atrophied gastrocnemius skeletal muscle in rats.

Low-level laser (LLL) irradiation promotes proliferation of muscle satellite cells, angiogenesis and expression of growth factors. Satellite cells, angiogenesis and growth factors play important roles in the regeneration of muscle. The objective of this study was to examine the effect of LLL irradiation on rat gastrocnemius muscle recovering from disuse muscle atrophy. Eight-week-old rats were subjected to hindlimb suspension for 2 weeks, after which they were released and recovered. During the recovery period, rats underwent daily LLL irradiation (Ga-Al-As laser; 830 nm; 60 mW; total, 180 s) to the right gastrocnemius muscle through the skin. The untreated left gastrocnemius muscle served as the control. In conjunction with LLL irradiation, 5-bromo-2-deoxyuridine (BrdU) was injected subcutaneously to label the nuclei of proliferating cells. After 2 weeks, myofibre diameters of irradiated muscle increased in comparison with those of untreated muscle, but did not recover back to normal levels. Additionally, in the superficial region of the irradiated muscle, the number of capillaries and fibroblast growth factor levels exhibited significant elevation relative to those of untreated muscle. In the deep region of irradiated muscle, BrdU-positive nuclei of satellite cells and/or myofibres increased significantly relative to those of the untreated muscle. The results of this study suggest that LLL irradiation can promote recovery from disuse muscle atrophy in association with proliferation of satellite cells and angiogenesis.

[Rationale for using helium-neon laser in medical rehabilitation of patients with atrophy]. / Obosnovanie primeneniia gelii- neonovogo lazera v meditsinskoi reabilitatsii bolnykh s atrofiiami.

High resolution measurements of helium-neon laser spectra have been conducted about 0.64 mm wavelength. The singlet oxygen photo-generation was demonstrated to be responsible for the bioeffects of this spectral interval. Helium-neon radiation with 0.633 mm wavelength was used for medical rehabilitation of 15 patients with muscular atrophy as a result of wearing immobilizing plaster arm-bends on lower extremity fractures. 50-day hypokinesia of a damaged extremity induced differences in functional indices between damaged and healthy extremities in the same patient. This difference was diminishing more rapidly after laser therapy than in the control group though all patients had adequate rehabilitative treatment. Due to the likelihood of hypokinesia- and weightlessness-induced atrophies, helium-neon laser may be recommended for atrophy prophylaxis and treatment in both cases.