Objective:To observe the effects of Yiyuan moxibustion on bladder function and antioxidant level of spinal cord tissues in rats with urinary retention after spinal cord injury (SCI); To explore the mechanism of inhibition of ferroptosis in spinal cord neurons after SCI by Yiyuan moxibustion.Methods:Wistar female rats were divided into sham-operation group, model group, and Yiyuan moxibustion group according to random number table method, with 12 rats in each group. The modified Allen′s vertical percussion method was used to construct the model of urinary retention after SCI in T10 segment. The rats in the Yiyuan moxibustion group were moxibued at the Zhongji acupoint, Guanyuan acupoint, and Shenque acupoint for 20 min per day, and the intervention was continued for 2 weeks. Urodynamic test was used to observe the degree of urinary retention in rats; HE staining was used to observe the morphological changes of the injured spinal cord tissues; transmission electron microscopy was used to observe the mitochondrial ultrastructure of the spinal cord tissues; ferric ion kit was used to detect the ferric ion content of the spinal cord tissues; ELISA was used to detect the GSH and MDA contents of the spinal cord tissues of the rats; Western blot was used to measure the relative expressions of glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11 (SLC7A11) proteins in rat spinal cord tissue.Results:Compared with the model group, the basal and leakage point pressures of the bladder, and bladder compliance were significantly reduced in the Yiyuan moxibustion group ( P<0.05); the spinal cord tissue structure was restored and mitochondrial morphology improved; the levels of iron ions and MDA in spinal cord tissue decreased ( P<0.05), while the level of GSH increased ( P<0.05), and the relative expressions of GPX4 and SLC7A11 proteins increased ( P<0.05). Conclusion:Yiyuan moxibustion can improve bladder function in rats with urinary retention after SCI, and the mechanism may involve the initiation of antioxidant defense and reduction of lipid peroxidation in spinal cord neuronal cells, thus preventing the occurrence of ferroptosis and achieving the protection of neuronal cells.

In order to eliminate the influence of motion artifacts, high-frequency noise and baseline drift on photoplethysmographic (PPG), and to obtain the accurate value of heart rate in motion state, this paper proposed a de-noising method of PPG signal based on normalized least mean square (NLMS) adaptive filtering combining ensemble empirical mode decomposition(EEMD). Firstly, the PPG signal containing noise is passed through an adaptive filter with a 3-axis acceleration sensor as a reference signal to filter out motion artifacts. Secondly, the PPG signal is decomposed by EEMD to obtain a series of intrinsic modal function (IMF) according to the frequency from high to low. The threshold range of the signal is judged by the permutation entropy (PE) criterion, thereby filtering out the high frequency noise and the baseline drift. The experimental results show that the Pearson correlation coefficient between the calculated heart rate of PPG signal and the standard heart rate based on electrocardiogram (ECG) signal is 0.731 and the average absolute error percentage is 6.10% under different motion states, which indicates that the method can accurately calculate the heart rate in moving state and is beneficial to the physiological monitoring under the state of human motion.