Thermotolerance of tomato plants grafted onto wild relative rootstocks.

Heat stress is a major environmental constraint limiting tomato production. Tomato wild relatives Solanum pennellii and S. peruvianum are known for their drought tolerance but their heat stress responses have been less investigated, especially when used as rootstocks for grafting. This study aimed to evaluate the physiological and biochemical heat stress responses of tomato seedlings grafted onto a commercial 'Maxifort' and wild relative S. pennellii and S. peruvianum rootstocks. 'Celebrity' and 'Arkansas Traveler' tomato scion cultivars, previously characterized as heat-tolerant and heat-sensitive, respectively, were grafted onto the rootstocks or self-grafted as controls. Grafted seedlings were transplanted into 10-cm pots and placed in growth chambers set at high (38/30°C, day/night) and optimal (26/19°C) temperatures for 21 days during the vegetative stage. Under heat stress, S. peruvianum-grafted tomato seedlings had an increased leaf proline content and total non-enzymatic antioxidant capacity in both leaves and roots. Additionally, S. peruvianum-grafted plants showed more heat-tolerant responses, evidenced by their increase in multiple leaf antioxidant enzyme activities (superoxide dismutase, catalase and peroxidase) compared to self-grafted and 'Maxifort'-grafted plants. S. pennellii-grafted plants had similar or higher activities in all antioxidant enzymes than other treatments at optimal temperature conditions but significantly lower activities under heat stress conditions, an indication of heat sensitivity. Both S. pennellii and S. peruvianum-grafted plants had higher leaf chlorophyll content, chlorophyll fluorescence and net photosynthetic rate under heat stress, while their plant growth was significantly lower than self-grafted and 'Maxifort'-grafted plants possibly from graft incompatibility. Root abscisic acid (ABA) contents were higher in 'Maxifort' and S. peruvianum rootstocks, but no ABA-induced antioxidant activities were detected in either leaves or roots. In conclusion, the wild relative rootstock S. peruvianum was effective in enhancing the thermotolerance of scion tomato seedlings, showing potential as a breeding material for the introgression of heat-tolerant traits in interspecific tomato rootstocks.

The 2023 wearable photoplethysmography roadmap.

Photoplethysmography is a key sensing technology which is used in wearable devices such as smartwatches and fitness trackers. Currently, photoplethysmography sensors are used to monitor physiological parameters including heart rate and heart rhythm, and to track activities like sleep and exercise. Yet, wearable photoplethysmography has potential to provide much more information on health and wellbeing, which could inform clinical decision making. This Roadmap outlines directions for research and development to realise the full potential of wearable photoplethysmography. Experts discuss key topics within the areas of sensor design, signal processing, clinical applications, and research directions. Their perspectives provide valuable guidance to researchers developing wearable photoplethysmography technology.

Digital therapeutics from bench to bedside.

As a new therapeutic technique based on digital technology, the commercialization and clinical application of digital therapeutics (DTx) are increasing, and the demand for expansion to new clinical fields is remarkably high. However, the use of DTx as a general medical component is still ambiguous, and this ambiguity may be owing to a lack of consensus on a definition, in addition to insufficiencies in research and development, clinical trials, standardization of regulatory frameworks, and technological maturity. In this study, we conduct an in-depth investigation and analysis of definitions, clinical trials, commercial products, and the regulatory status related to DTx using published literature, ClinicalTrials.gov, and web pages of regulatory and private organizations in several countries. Subsequently, we suggest the necessity and considerations for international agreements on the definition and characteristics of DTx, focusing on the commercialization characteristics. In addition, we discuss the status and considerations of clinical research, key technology factors, and the direction of regulatory developments. In conclusion, for the successful settlement of DTx, real-world evidence-based validation should be strengthened by establishing a cooperative system between researchers, manufacturers, and governments, and there should be effective technologies and regulatory systems for overcoming engagement barriers of DTx.

Early differentiation of long-standing persistent atrial fibrillation using the characteristics of fibrillatory waves in surface ECG multi-leads.

We characterized the f-waves in atrial fibrillation (AF) in the surface ECG by quantifying the amplitude, irregularity, and dominant rate of the f-waves in leads II, aVL, and V1, and investigated whether those parameters of the f-waves could discriminate long-standing persistent AF (LPeAF) from non-LPeAF. A total of 224 AF patients were enrolled: 112 with PAF (87 males), 48 with PeAF (38 males), and 64 with LPeAF (47 males). The f-waves in surface ECG leads V1, aVL, and II, which reflect well electrical activity in the right atrium (RA), the left atrium (LA), and both atria, respectively, were analyzed. The f-waves for LPeAF had lower amplitudes in II and aVL, increased irregularity and a higher dominant rate in II and V1 compared to PAF and PeAF (all p < 0.02). In a multivariate analysis, a low amplitude in lead II (<34.6 uV) and high dominant rate in lead V1 (≧390/min) (p < 0.001) independently discriminated LPeAF from the other AF types. The f-waves combined with both a low amplitude in lead II and high dominant rate in lead V1 were significantly associated with LPeAF (OR 6.27, p < 0.001). Characteristics of the f-waves on the surface ECG could discriminate LPeAF from other types of AF.

Electromechanical cardioplasty using a wrapped elasto-conductive epicardial mesh.

Heart failure remains a major public health concern with a 5-year mortality rate higher than that of most cancers. Myocardial disease in heart failure is frequently accompanied by impairment of the specialized electrical conduction system and myocardium. We introduce an epicardial mesh made of electrically conductive and mechanically elastic material, to resemble the innate cardiac tissue and confer cardiac conduction system function, to enable electromechanical cardioplasty. Our epicardium-like substrate mechanically integrated with the heart and acted as a structural element of cardiac chambers. The epicardial device was designed with elastic properties nearly identical to the epicardial tissue itself and was able to detect electrical signals reliably on the moving rat heart without impeding diastolic function 8 weeks after induced myocardial infarction. Synchronized electrical stimulation over the ventricles by the epicardial mesh with the high conductivity of 11,210 S/cm shortened total ventricular activation time, reduced inherent wall stress, and improved several measures of systolic function including increases of 51% in fractional shortening, ~90% in radial strain, and 42% in contractility. The epicardial mesh was also capable of delivering an electrical shock to terminate a ventricular tachyarrhythmia in rodents. Electromechanical cardioplasty using an epicardial mesh is a new pathway toward reconstruction of the cardiac tissue and its specialized functions.

Automatic lumen contour detection in intravascular OCT images using Otsu binarization and intensity curve.

This paper proposes an automatic method for the detection of lumen contours in intravascular OCT images with guide wire shadow artifacts. This algorithm is divided into five main procedures: pre-processing, an Otsu binarization approach, an intensity curve approach, a lumen contour position correction, and image reconstruction and contour extraction. The 30 IVOCT images from six anonymous patients were used to verify this method and we obtained 99.2% sensitivity and 99.7% specificity with this algorithm.

Relations between ac-dc components and optical path length in photoplethysmography.

Photoplethysmography is used in various areas such as vital sign measurement, vascular characteristics analysis, and autonomic nervous system assessment. Photoplethysmographic signals are composed of ac and dc, but it is difficult to find research about the interaction of photoplethysmographic components. This study suggested a model equation combining two Lambert-Beer equations at the onset and peak points of photoplethysmography to evaluate ac characteristics, and verified the model equation through simulation and experiment. In the suggested equation, ac was dependent on dc and optical path length. In the simulation, dc was inversely proportionate to ac sensitivity (slope), and ac and optical path length were proportionate. When dc increased from 10% to 90%, stabilized ac decreased from 1 to 0.89 ± 0.21, and when optical path length increased from 10% to 90%, stabilized ac increased from 1 to 1.53 ± 0.40.

Optimum conductive fabric sensor sites for evaluating the status of knee joint movements using bio-impedance.

BACKGROUND: There have been many studies that utilize the bio-impedance measurement method to analyze the movements of the upper and lower limbs. A fixed electrical current flows into the limbs through four standard disposable electrodes in this method. The current flows in the muscles and blood vessels, which have relatively low resistivity levels in the human body. This method is used to measure bio-impedance changes following volume changes of muscles and blood vessels around a knee joint. The result of the bio-impedance changes is used to evaluate the movements. However, the method using the standard disposable electrodes has a restriction related to its low bio-impedance changes: the standard disposable electrodes are only able to measure bio-impedance from a limited part of a muscle. Moreover, it is impossible to use continuously, as the electrodes are designed to be disposable. This paper describes a conductive fabric sensor (CFS) using a bio-impedance measurement method and determines the optimum configuration of the sensor for estimating knee joint movements. METHODS: The upper side of subjects' lower limbs was divided into two areas and the lower side of subjects' lower limbs was divided into three areas. The spots were matched and 6 pairs were selected. Subjects were composed of 15 males (age: 30.7 ± 5.3, weight: 69.8 ± 4.2 kg, and height: 173.5 ± 2.8 cm) with no known problems with their knee joints. Bio-impedance changes according to knee joint flexion/extension assessments were calculated and compared with bio-impedance changes by an ankle joint flexion/extension test (SNR I) and a hip joint flexion/extension test (SNR II). RESULTS: The bio-impedance changes of the knee joint flexion/extension assessment were 35.4 ± 20.0 Ω on the (1, 5) pair. SNR I was 3.8 ± 8.4 and SNR II was 6.6 ± 7.9 on the (1, 5) pair. CONCLUSIONS: The optimum conductive fabric sensor configuration for evaluating knee joint movements were represented by the (1, 5) pair.

Cardiomyocytes from phorbol myristate acetate-activated mesenchymal stem cells restore electromechanical function in infarcted rat hearts.

Despite the safety and feasibility of mesenchymal stem cell (MSC) therapy, an optimal cell type has not yet emerged in terms of electromechanical integration in infarcted myocardium. We found that poor to moderate survival benefits of MSC-implanted rats were caused by incomplete electromechanical integration induced by tissue heterogeneity between myocytes and engrafted MSCs in the infarcted myocardium. Here, we report the development of cardiogenic cells from rat MSCs activated by phorbol myristate acetate, a PKC activator, that exhibited high expressions of cardiac-specific markers and Ca(2+) homeostasis-related proteins and showed adrenergic receptor signaling by norepinephrine. Histological analysis showed high connexin 43 coupling, few inflammatory cells, and low fibrotic markers in myocardium implanted with these phorbol myristate acetate-activated MSCs. Infarct hearts implanted with these cells exhibited restoration of conduction velocity through decreased tissue heterogeneity and improved myocardial contractility. These findings have major implications for the development of better cell types for electromechanical integration of cell-based treatment for infarcted myocardium.

Ideal filtering approach on DCT domain for biomedical signals: index blocked DCT filtering method (IB-DCTFM).

We proposed Index-Blocked Discrete Cosine Transform Filtering Method (IB-DCTFM) to design ideal frequency range filter on DCT domain for biomedical signal which frequently exposed to specific frequency noise such as motion artifacts and 50/60 Hz powerline interference. IB-DCTFM removes unwanted frequency range signal on time domain by blocking specific DCT index on DCT domain. In simulation, electrocardiography, electromyography, photoplethysmography are used as a signal source and FIR, IIR and adaptive filter are used for comparison with proposed IB-DCTFM. To evaluate filter performance, we calculated signal-to-noise ratio and correlation coefficient to clean signal of each signal and filtering method respectively. As a result of filter simulation, average signal to noise ration and correlation coefficient of IB-DCTFM are improved about 75.8 dB/0.477, and FIR, IIR and adaptive filtering results are 24.8 dB/0.130, 54.3 dB/0.440 and 29.5 dB/0.200 respectively.

Adaptive threshold method for the peak detection of photoplethysmographic waveform.

Photoplethysmography (PPG)-based temporal analyses have been widely used as a useful analytical method in physiological and cardiovascular diagnosis. Most of temporal approaches of PPG are based on detected peak points, peak and foot of PPG. The aim of presented study is the development of improved peak detection algorithm of PPG waveform. The present study demonstrates a promising approach to overcome respiration effect and to detect PPG peak. More extensive investigation is necessary to adapt for the cardiovascular diseases, whose PPG morphology has different form.

Robust and real-time monitoring of nerve regeneration using implantable flexible microelectrode array.

This paper presents a robust and quasi-real-time monitoring method for examining the degree of regeneration of peripheral nerves using a polymer-based implantable microelectrode array (IMA). The IMA was implanted in the sciatic nerves of rats using two different approaches: (1) direct implantation which was achieved by directly suturing to nerve stumps for short-term regeneration and (2) assembly implantation which was achieved by implanting the IMA assembled with a resorbable conduit that cross a 4-mm nerve defect. The regeneration of the injury was evaluated by measuring the nerve signals following foot pricking and impulse stimulating to the proximal stump. The direct implantation produced a peak voltage of 3.43 mV before amplification and a conduction velocity of 19.8m/s. The assembly implantation produced a peak voltage of 1.51 mV and a conduction velocity of 18 m/s. The degree of regeneration was also examined using gait and morphological analyses. The sciatic function index was -38.5+/-12.5 for direct implantation and -64.9+/-7.5 for assembly implantation. The morphologies of the regenerated nerves were examined using toluidine blue, transmission electron microscopy images, and pilot tests. Te regeneration ratios after the direct and assembly implantation were 45% and 21%, respectively.

Wavelet-based multi-resolution deformation for medical endoscopic image segmentation.

Image segmentation is an essential technique in image analysis. In spite of issues in contour initialization, boundary concavities and high-level computation, active contour models (snakes) are popular and successful method for segmentation among researchers. Segmentation process in snakes consists of calculation of energy and deformation of contour. In this paper, we present a new deformation method for active contour model, multi-resolution deformation based on wavelet ensuring powerful time reduction, high accuracy supported by stable results in convergence of an initial contour to target boundary in medical image segmentation.

Development of arrhythmia diagnosis algorithm for effective control of antitachycardia pacing and high energy shock of ICD.

In this paper, we propose a modified arrhythmia diagnosis and therapy control algorithm based on VENTAK PRIZM 2 algorithm of the Guidant corp. Existing arrhythmia detection and therapy control algorithms control arrhythmia through two steps. First step is event detection using peak-to-peak interval detection, and the second step is duration detection. We modify these stages to improve diagnosis time delay and treatment efficiency.

The measurement of compound neural action potential in sciatic nerve using microelectrode array.

As a method of observing regeneration of damaged nerves, research is being conducted on analyzing the electric signals of nerve fibers that are damaged and regenerating by implanting a microelectrode array between those nerves. Microelectrode arrays possess high impedance and a unique phase characteristic according to their structural features, thus it requires a phase linearity test and an impedance test to prevent neural signal distortion. Therefore, this paper analyzes the features of microelectrode array and designs a bioamplifier. We also measured signals from sciatic nerves in rats with microelectrode array.

The measurement of compound neural action potential in sciatic nerve using microelectrode array.

As a method of observing regeneration of damaged nerves, research is being conducted on analyzing the electric signals of nerve fibers that are damaged and regenerating by implanting a microelectrode array between those nerves. Microelectrode arrays possess high impedance and a unique phase characteristic according to their structural features,thus it requires a phase linearity test and an impedance test to prevent neural signal distortion.Therefore, this paper analyzes the features of microelectrode array and designs a bioamplifier. We also measured signals from sciatic nerves in rats with microelectrode array.

Time-frequency analysis for arrhythmia discrimination using human atrium electrogram.

Detection methods for atrial tachycardia and fibrillation on the time axis have the advantages of light operational load and are easy to apply to various applications. Despite these advantages, arrhythmia detection algorithm on the time axis cannot stand much noise such as motion artifacts, moreover the peak detection algorithm has high complexity. In this paper, we use a spectrum analysis method for the detection of atrial tachycardia and fibrillation. By applying spectrum analysis and digital filtering on obtained electrogram signals, we can diagnose cardiac arrhythmia without using peak detection algorithm.

Frequency-hopping optical orthogonal codes with arbitrary time-blank patterns.

We investigate a general scheme of frequency-hopping optical orthogonal codes with a specified distance between adjacent frequency symbols and propose a novel code that allows time blanks between adjacent frequency symbols in code sequences. A time blank represents the absence of frequency symbols in code sequences and makes no interference with frequency components. The insertion of time-blank patterns can provide ample scope to generate much more code sequences than the conventional codes lacking in time-blank patterns, and we show this by constructing an algorithm to generate the proposed code. The performance analysis demonstrates that its performance is superior to that of the conventional codes in terms of the bit error rate. We also derive the upper bound on the proposed code set.