A unified theory of calcium alternans in ventricular myocytes.

Intracellular calcium (Ca2+) alternans is a dynamical phenomenon in ventricular myocytes, which is linked to the genesis of lethal arrhythmias. Iterated map models of intracellular Ca2+ cycling dynamics in ventricular myocytes under periodic pacing have been developed to study the mechanisms of Ca2+ alternans. Two mechanisms of Ca2+ alternans have been demonstrated in these models: one relies mainly on fractional sarcoplasmic reticulum Ca2+ release and uptake, and the other on refractoriness and other properties of Ca2+ sparks. Each of the two mechanisms can partially explain the experimental observations, but both have their inconsistencies with the experimental results. Here we developed an iterated map model that is composed of two coupled iterated maps, which unifies the two mechanisms into a single cohesive mathematical framework. The unified theory can consistently explain the seemingly contradictory experimental observations and shows that the two mechanisms work synergistically to promote Ca2+ alternans. Predictions of the theory were examined in a physiologically-detailed spatial Ca2+ cycling model of ventricular myocytes

Compression via Compressive Sensing : A Low-Power Framework for the Telemonitoring of Multi-Channel Physiological Signals

Telehealth and wearable equipment can deliver personal healthcare and necessary treatment remotely. One major challenge is transmitting large amount of biosignals through wireless networks. The limited battery life calls for low-power data compressors. Compressive Sensing (CS) has proved to be a low-power compressor. In this study, we apply CS on the compression of multichannel biosignals. We firstly develop an efficient CS algorithm from the Block Sparse Bayesian Learning (BSBL) framework. It is based on a combination of the block sparse model and multiple measurement vector model. Experiments on real-life Fetal ECGs showed that the proposed algorithm has high fidelity and efficiency. Implemented in hardware, the proposed algorithm was compared to a Discrete Wavelet Transform (DWT) based algorithm, verifying the proposed one has low power consumption and occupies less computational resources.Comment: 2013 International Workshop on Biomedical and Health Informatic

R-from-T as a common mechanism of arrhythmia initiation in long QT syndromes

Background: Long QT syndromes (LQTS) arise from many genetic and nongenetic causes with certain characteristic ECG features preceding polymorphic ventricular tachyarrhythmias (PVTs). However, how the many molecular causes result in these characteristic ECG patterns and how these patterns are mechanistically linked to the spontaneous initiation of PVT remain poorly understood. Methods: Anatomic human ventricle and simplified tissue models were used to investigate the mechanisms of spontaneous initiation of PVT in LQTS. Results: Spontaneous initiation of PVT was elicited by gradually ramping up I-Ca,I-L to simulate the initial phase of a sympathetic surge or by changing the heart rate, reproducing the different genotype-dependent clinical ECG features. In LQTS type 2 (LQT2) and LQTS type 3 (LQT3), T-wave alternans was observed followed by premature ventricular complexes (PVCs). Compensatory pauses occurred resulting in short-long-short sequences. As I-Ca,I-L increased further, PVT episodes occurred, always preceded by a short-long-short sequence. However, in LQTS type 1 (LQT1), once a PVC occurred, it always immediately led to an episode of PVT. Arrhythmias in LQT2 and LQT3 were bradycardia dependent, whereas those in LQT1 were not. In all 3 genotypes, PVCs always originated spontaneously from the steep repolarization gradient region and manifested on ECG as R-on-T. We call this mechanism R-from-T, to distinguish it from the classic explanation of R-on-T arrhythmogenesis in which an exogenous PVC coincidentally encounters a repolarizing region. In R-from-T, the PVC and the T wave are causally related, where steep repolarization gradients combined with enhanced I-Ca,I-L lead to PVCs emerging from the T wave. Since enhanced I-Ca,I-L was required for R-from-T to occur, suppressing window I-Ca,I-L effectively prevented arrhythmias in all 3 genotypes. Conclusions: Despite the complex molecular causes, these results suggest that R-from-T is likely a common mechanism for PVT initiation in LQTS. Targeting I-Ca,I-L properties, such as suppressing window I-Ca,I-L or preventing excessive I-Ca,I-L increase, could be an effective unified therapy for arrhythmia prevention in LQTS

Gene expression profiling of bovine ovarian follicular selection

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on May 6, 2009)Vita.Thesis (Ph.D.) University of Missouri-Columbia 2006.Lack of, or abnormal, ovarian follicular development is a major factor associated with impaired fertility in mammals. However, development of new treatments is limited by our poor understanding of ovarian follicular development. Understanding the mechanisms by which a cohort of follicles is recruited and a single follicle is selected for further development to a dominant follicle is the key to understanding pyre-ovulatory follicular development. The objectives of this study are to identify changes in gene expression profiles during the selection stage of bovine follicular waves. Follicles of different sizes (8 mm to 12 mm) were collected and intra follicular concentrations of proastraddle, eststenedione were measured. Gene expression profiles were obtained using bovine c dna microarrays. Of the 17,692 probes on the arrays, 606 unique genes and 32 sequences not matching any known genes were identified as differentially expressed with a cut off false discovery rate (FDR) of 0.05. Seventeen gene expression profiles were confirmed using quantitative RT-PCR. Five.Includes bibliographical reference

Current Situation and Measures of Environment Affected by Mine Water in Hunan Limin Coal Mine

The pump drainage of mine water in Hunan Limin Coal Mine has caused various problems including huge depression cone and collapse of goaf roof, resulting in serious leakage of surface water. Therefore, a great need of measures should be conducted. In this paper, the mine water properties and the hydrogeological characteristics were studied. The results indicate that the PH value of main shaft water of Limin Well is 2.21-3.81 (average: 2.90), Fe2+ is 178-1,308 mg/L, Mn2+ is 3.93-8.65 mg/L; the PH value of auxiliary shaft water is 3.45-4.08, Fe2+ is 876-1,264 mg/L, Mn2+ is 6.27-8.71 mg/L; the PH value of Shuikoushan old pithead water is 2.33-3.91, Fe2+ is 1,059-2,207 mg/L and Mn2+ is 23.00-34.00 mg/L, which indicates that the mine water in the area is strongly acidic, and Fe2+ and Mn2+ exceed the standard seriously. Based on the characteristics of mining tunnel in the area, the wellhead of artesian water in Limin Well should be closed with shaft without pressure so as to ensure that the mine water can be discharged out in a concentrated and orderly way. The sewage treatment facilities at the main shaft of Limin Well need to be expanded, and new sewage treatment facilities should be built at Shuikoushan old pithead. Through hydrologic survey and water balance analysis, Zhoutou Reservoir can be used as a water source to construct drinking water project, which can completely solve the problem of drinking water safety in the area. The study would solve the bad situation of Limin Coal mine by providing the corresponding measures, which could provide the references for the similar mines when facing these problems