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The aim of the present study was to investigate the influence of microwave irradiation on fatiguing activity of isolated frog skeletal muscle fibres. The changes in the electrical and mechanical activity were used as criteria for the exposure effects. Repetitive suprathreshold stimulation with interstimulus interval of 200 ms for 3 min was applied. Intracellular (ICAP) and extracellular (ECAP) action potentials and twitch contractions (Tw) of muscle fibres after 1 hour microwave exposure (2.45 GHz, 20 mW/cm( 2) power density) were compared with those recorded after one hour sham exposure (control). The duration of uninterrupted activity in the trial (endurance time; ET) was not significantly affected by microwave field exposure. After microwave irradiation, the ICAP amplitude was higher, the rising time was shorter, and the resting membrane potential was more negative compared to controls. There was a slower rate of parameters changes during ET in potentials obtained from irradiated fibres. Microwave exposure increased the propagation velocity of excitation, the ECAP and Tw amplitudes, as well as shortened their time parameters. We concluded that a 2.45 GHz microwave field possesses a stimulating effect on muscle fibre activity, which is in part due to its specific, non-thermal properties. The microwave induced-changes in muscle fibre activity may reduce development of skeletal muscle fatigue.

Abstract. The present study was assigned to compare the applicability and sensitivity of three different methods (discrete wavelet transforms (DWT), median frequency (MDF) -calculated on the basis of fast Fourier transform, and spectral indices) for analysis of frequency content changes in potentials produced by repetitive stimulation from isolated slow (SMFs)-and fast (FMFs)-fatigable muscle fibers during uninterrupted activity. In order to affect fatigue, prior to starting the fatiguing stimulation (5 Hz), some of the fibres were exposed to microwave electromagnetic field and others were sham exposed. All the methods studied demonstrated that during a long-lasting fibre activity, the shift of the potential frequency content to lower frequencies was a consequence of lowering in higher frequency components and increasing in low frequency ones. The changes were faster in FMFs than SMFs and stronger in sham exposed fibres vs. microwave exposed. The MDF alterations in both fibre types and protocols were quite similar to other methods characterizing either individual changes in low and high frequency scales of the signal (discrete wavelet transform -DWT) or changes in their spectral ratio (spectral indices). The spectral indices showed sensitivity to fatigue effect at the final stages that made their changes considerably non-linear. DWT allowed processing the temporal occurrence of frequency content changes that corresponded to the alterations in the separate potential phases as well as earlier detection and precise evaluation of fatigue onset and progressing.All methods are applicable but DWT is a preferable for study of muscle fibre fatigue in clinical and experimental neurophysiology.

Objective:Rare disease Background:Gastrointestinal tract melanomas are usually of metastatic origin, with primary melanomas being relatively rare. Controversy arises about the existence of primary melanoma in the gastrointestinal tract except in areas where melanocytes exist. The appearance of primary colon melanoma is rare due to the embryological absence of melanocytes in the large intestine, with some authors denying its existence at all. Case Report:We present a clinical case of a female patient with a primary melanoma of the descending colon. The patient came to the clinic with nausea without vomiting, abdominal swelling and pain, difficult and irregular defecation, and data on a tumor process of the left colon from the performed colonoscopy. Laparoscopic left hemicolectomy with lymphatic dissection was performed. The conclusion to be drawn from histological results was that the malignancy is poorly-differentiated adenocarcinoma. However, the immunohistochemical examination showed colon melanoma. Postoperative complete dermatological and ophthalmic examinations showed no evidence of a cutaneous or an ocular primary lesion, so we decided that this could be a primary colon melanoma. Conclusions:Because of the colonoscopy we were able to make a detailed histological examination of the tumor, which allowed us to differentiate it from common colon adenocarcinomas. Surgical treatment is important in the removal of the primary tumor. The method of choice, with excellent postoperative results, is laparoscopic left hemicolectomy with selective cut-off of the colic vessels at the site of separation and removal of the affected segment together with the mesentery-bearing regional lymphatic basin.