In this study, a wearable multichannel human magnetocardiogram (MCG) system based on a spin exchange relaxation-free regime (SERF) magnetometer array is developed. The MCG system consists of a magnetically shielded device, a wearable SERF magnetometer array, and a computer for data acquisition and processing. Multichannel MCG signals from a healthy human are successfully recorded simultaneously. Independent component analysis (ICA) and empirical mode decomposition (EMD) are used to denoise MCG data. MCG imaging is realized to visualize the magnetic and current distribution around the heart. The validity of the MCG signals detected by the system is verified by electrocardiogram (ECG) signals obtained at the same position, and similar features and intervals of cardiac signal waveform appear on both MCG and ECG. Experiments show that our wearable MCG system is reliable for detecting MCG signals and can provide cardiac electromagnetic activity imaging.
Specific adipokines, such as adiponectin and resistin, are secreted from adipose tissue and are associated with the development of obesity. Supplementation of dietary SCFA can prevent and reverse high-fat-diet (HFD)-induced obesity. However, it is not clear whether SCFA ameliorate abnormal expression of adiponectin and resistin in the obese state. The aim of this study was to investigate the effects of SCFA on adiponectin and resistin's expressions in diet-induced obese mice, as well as the potential mechanisms associated with DNA methylation. C57BL/6J male mice were fed for 16 weeks with five types of HFD (34·9 % fat by wt., 60 % kJ) - a control HFD and four HFD with acetate (HFD-A), propionate (HFD-P), butyrate (HFD-B) and their admixture (HFD-SCFA). Meanwhile, a low-fat diet (4·3 % fat by wt., 10 % kJ) was used as the control group. The reduced mRNA levels of adiponectin and resistin in the adipose tissue of the HFD-fed mice were significantly reversed by dietary supplementation of acetate, propionate, butyrate or their admixture to the HFD. Moreover, the expressional changes of adiponectin and resistin induced by SCFA were associated with alterations in DNA methylation at their promoters, which was mediated by reducing the expressions of enzyme-catalysed DNA methyltransferase (DNMT1, 3a, 3b) and the methyl-CpG-binding domain protein 2 (MBD2) and suppressing the binding of these enzymes to the promoters of adiponectin and resistin. Our results indicate that SCFA may correct aberrant expressions of adiponectin and resistin in obesity by epigenetic regulation.
Summary In recent years, optically pumped magnetometer (OPM)-based magnetoencephalography (MEG) has shown potential for analyzing brain activity. It has a flexible sensor configuration and comparable sensitivity to conventional SQUID-MEG. We constructed a 32-channel OPM-MEG system and used it to measure cortical responses to median and ulnar nerve stimulations. Traditional magnetic source imaging methods tend to blur the spatial extent of sources. Accurate estimation of the spatial size of the source is important for studying the organization of brain somatotopy and for pre-surgical functional mapping. We proposed a new method called variational free energy-based spatial smoothing estimation (FESSE) to enhance the accuracy of mapping somatosensory cortex responses. A series of computer simulations based on the OPM-MEG showed better performance than the three types of competing methods under different levels of signal-to-noise ratios, source patch sizes, and co-registration errors. FESSE was then applied to the source imaging of the OPM-MEG experimental data.
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